608 Commits

Author	SHA1	Message	Date
Linus Torvalds	8bf722c684	ring-buffer changes for v6.16: ... - Allow the persistent ring buffer to be memory mapped In the last merge window there was issues with the implementation of mapping the persistent ring buffer because it was assumed that the persistent memory was just physical memory without being part of the kernel virtual address space. But this was incorrect and the persistent ring buffer can be mapped the same way as the allocated ring buffer is mapped. The meta data for the persistent ring buffer is different than the normal ring buffer and the organization of mapping it to user space is a little different. Make the updates needed to the meta data to allow the persistent ring buffer to be mapped to user space. - Fix cpus_read_lock() with buffer->mutex and cpu_buffer->mapping_lock Mapping the ring buffer to user space uses the cpu_buffer->mapping_lock. The buffer->mutex can be taken when the mapping_lock is held, giving the locking order of: cpu_buffer->mapping_lock -->> buffer->mutex. But there also exists the ordering: buffer->mutex -->> cpus_read_lock() mm->mmap_lock -->> cpu_buffer->mapping_lock cpus_read_lock() -->> mm->mmap_lock causing a circular chain of: cpu_buffer->mapping_lock -> buffer->mutex -->> cpus_read_lock() -->> mm->mmap_lock -->> cpu_buffer->mapping_lock By moving the cpus_read_lock() outside the buffer->mutex where: cpus_read_lock() -->> buffer->mutex, breaks the deadlock chain. - Do not trigger WARN_ON() for commit overrun When the ring buffer is user space mapped and there's a "commit overrun" (where an interrupt preempted an event, and then added so many events it filled the buffer having to drop events when it hit the preempted event) a WARN_ON() was triggered if this was read via a memory mapped buffer. This is due to "missed events" being non zero when the reader page ended up with the commit page. The idea was, if the writer is on the reader page, there's only one page that has been written to and there should be no missed events. But if a commit overrun is done where the writer is off the commit page and looped around to the commit page causing missed events, it is possible that the reader page is the commit page with missed events. Instead of triggering a WARN_ON() when the reader page is the commit page with missed events, trigger it when the reader page is the tail_page with missed events. That's because the writer is always on the tail_page if an event was interrupted (which holds the commit event) and continues off the commit page. - Reset the persistent buffer if it is fully consumed On boot up, if the user fully consumes the last boot buffer of the persistent buffer, if it reboots without enabling it, there will still be events in the buffer which can cause confusion. Instead, reset the buffer when it is fully consumed, so that the data is not read again. - Clean up some goto out jumps There's a few cases that the code jumps to the "out:" label that simply returns a value. There used to be more work done at those labels but now that they simply return a value use a return instead of jumping to a label. - Use guard() to simplify some of the code Add guard() around some locking instead of jumping to a label to do the unlocking. - Use free() to simplify some of the code Use free(kfree) on variables that will get freed on error and use return_ptr() to return the variable when its not freed. There's one instance where free(kfree) simplifies the code on a temp variable that was allocated just for the function use. -----BEGIN PGP SIGNATURE----- iIoEABYKADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCaDjJMxQccm9zdGVkdEBn b29kbWlzLm9yZwAKCRAp5XQQmuv6qkDzAP468AZOnjIxezfzYEmtcDl8ZUgf2U3I XtXjn7aKH/gZiwD/dCCZX2IY2gddqAb6s9Bo4/AWgtYbjacLPL+pWYbTJwQ= =DOfF -----END PGP SIGNATURE----- Merge tag 'trace-ringbuffer-v6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull ring-buffer updates from Steven Rostedt: - Allow the persistent ring buffer to be memory mapped In the last merge window there was issues with the implementation of mapping the persistent ring buffer because it was assumed that the persistent memory was just physical memory without being part of the kernel virtual address space. But this was incorrect and the persistent ring buffer can be mapped the same way as the allocated ring buffer is mapped. The metadata for the persistent ring buffer is different than the normal ring buffer and the organization of mapping it to user space is a little different. Make the updates needed to the meta data to allow the persistent ring buffer to be mapped to user space. - Fix cpus_read_lock() with buffer->mutex and cpu_buffer->mapping_lock Mapping the ring buffer to user space uses the cpu_buffer->mapping_lock. The buffer->mutex can be taken when the mapping_lock is held, giving the locking order of: cpu_buffer->mapping_lock -->> buffer->mutex. But there also exists the ordering: buffer->mutex -->> cpus_read_lock() mm->mmap_lock -->> cpu_buffer->mapping_lock cpus_read_lock() -->> mm->mmap_lock causing a circular chain of: cpu_buffer->mapping_lock -> buffer->mutex -->> cpus_read_lock() -->> mm->mmap_lock -->> cpu_buffer->mapping_lock By moving the cpus_read_lock() outside the buffer->mutex where: cpus_read_lock() -->> buffer->mutex, breaks the deadlock chain. - Do not trigger WARN_ON() for commit overrun When the ring buffer is user space mapped and there's a "commit overrun" (where an interrupt preempted an event, and then added so many events it filled the buffer having to drop events when it hit the preempted event) a WARN_ON() was triggered if this was read via a memory mapped buffer. This is due to "missed events" being non zero when the reader page ended up with the commit page. The idea was, if the writer is on the reader page, there's only one page that has been written to and there should be no missed events. But if a commit overrun is done where the writer is off the commit page and looped around to the commit page causing missed events, it is possible that the reader page is the commit page with missed events. Instead of triggering a WARN_ON() when the reader page is the commit page with missed events, trigger it when the reader page is the tail_page with missed events. That's because the writer is always on the tail_page if an event was interrupted (which holds the commit event) and continues off the commit page. - Reset the persistent buffer if it is fully consumed On boot up, if the user fully consumes the last boot buffer of the persistent buffer, if it reboots without enabling it, there will still be events in the buffer which can cause confusion. Instead, reset the buffer when it is fully consumed, so that the data is not read again. - Clean up some goto out jumps There's a few cases that the code jumps to the "out:" label that simply returns a value. There used to be more work done at those labels but now that they simply return a value use a return instead of jumping to a label. - Use guard() to simplify some of the code Add guard() around some locking instead of jumping to a label to do the unlocking. - Use free() to simplify some of the code Use free(kfree) on variables that will get freed on error and use return_ptr() to return the variable when its not freed. There's one instance where free(kfree) simplifies the code on a temp variable that was allocated just for the function use. * tag 'trace-ringbuffer-v6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ring-buffer: Simplify functions with __free(kfree) to free allocations ring-buffer: Make ring_buffer_{un}map() simpler with guard(mutex) ring-buffer: Simplify ring_buffer_read_page() with guard() ring-buffer: Simplify reset_disabled_cpu_buffer() with use of guard() ring-buffer: Remove jump to out label in ring_buffer_swap_cpu() ring-buffer: Removed unnecessary if() goto out where out is the next line tracing: Reset last-boot buffers when reading out all cpu buffers ring-buffer: Allow reserve_mem persistent ring buffers to be mmapped ring-buffer: Do not trigger WARN_ON() due to a commit_overrun ring-buffer: Move cpus_read_lock() outside of buffer->mutex	2025-05-30 21:20:11 -07:00
Linus Torvalds	b78f1293f9	tracing updates for v6.16: ... - Have module addresses get updated in the persistent ring buffer The addresses of the modules from the previous boot are saved in the persistent ring buffer. If the same modules are loaded and an address is in the old buffer points to an address that was both saved in the persistent ring buffer and is loaded in memory, shift the address to point to the address that is loaded in memory in the trace event. - Print function names for irqs off and preempt off callsites When ignoring the print fmt of a trace event and just printing the fields directly, have the fields for preempt off and irqs off events still show the function name (via kallsyms) instead of just showing the raw address. - Clean ups of the histogram code The histogram functions saved over 800 bytes on the stack to process events as they come in. Instead, create per-cpu buffers that can hold this information and have a separate location for each context level (thread, softirq, IRQ and NMI). Also add some more comments to the code. - Add "common_comm" field for histograms Add "common_comm" that uses the current->comm as a field in an event histogram and acts like any of the other fields of the event. - Show "subops" in the enabled_functions file When the function graph infrastructure is used, a subsystem has a "subops" that it attaches its callback function to. Instead of the enabled_functions just showing a function calling the function that calls the subops functions, also show the subops functions that will get called for that function too. - Add "copy_trace_marker" option to instances There are cases where an instance is created for tooling to write into, but the old tooling has the top level instance hardcoded into the application. New tools want to consume the data from an instance and not the top level buffer. By adding a copy_trace_marker option, whenever the top instance trace_marker is written into, a copy of it is also written into the instance with this option set. This allows new tools to read what old tools are writing into the top buffer. If this option is cleared by the top instance, then what is written into the trace_marker is not written into the top instance. This is a way to redirect the trace_marker writes into another instance. - Have tracepoints created by DECLARE_TRACE() use trace_<name>_tp() If a tracepoint is created by DECLARE_TRACE() instead of TRACE_EVENT(), then it will not be exposed via tracefs. Currently there's no way to differentiate in the kernel the tracepoint functions between those that are exposed via tracefs or not. A calling convention has been made manually to append a "_tp" prefix for events created by DECLARE_TRACE(). Instead of doing this manually, force it so that all DECLARE_TRACE() events have this notation. - Use __string() for task->comm in some sched events Instead of hardcoding the comm to be TASK_COMM_LEN in some of the scheduler events use __string() which makes it dynamic. Note, if these events are parsed by user space it they may break, and the event may have to be converted back to the hardcoded size. - Have function graph "depth" be unsigned to the user Internally to the kernel, the "depth" field of the function graph event is signed due to -1 being used for end of boundary. What actually gets recorded in the event itself is zero or positive. Reflect this to user space by showing "depth" as unsigned int and be consistent across all events. - Allow an arbitrary long CPU string to osnoise_cpus_write() The filtering of which CPUs to write to can exceed 256 bytes. If a machine has 256 CPUs, and the filter is to filter every other CPU, the write would take a string larger than 256 bytes. Instead of using a fixed size buffer on the stack that is 256 bytes, allocate it to handle what is passed in. - Stop having ftrace check the per-cpu data "disabled" flag The "disabled" flag in the data structure passed to most ftrace functions is checked to know if tracing has been disabled or not. This flag was added back in 2008 before the ring buffer had its own way to disable tracing. The "disable" flag is now not always set when needed, and the ring buffer flag should be used in all locations where the disabled is needed. Since the "disable" flag is redundant and incorrect, stop using it. Fix up some locations that use the "disable" flag to use the ring buffer info. - Use a new tracer_tracing_disable/enable() instead of data->disable flag There's a few cases that set the data->disable flag to stop tracing, but this flag is not consistently used. It is also an on/off switch where if a function set it and calls another function that sets it, the called function may incorrectly enable it. Use a new trace_tracing_disable() and tracer_tracing_enable() that uses a counter and can be nested. These use the ring buffer flags which are always checked making the disabling more consistent. - Save the trace clock in the persistent ring buffer Save what clock was used for tracing in the persistent ring buffer and set it back to that clock after a reboot. - Remove unused reference to a per CPU data pointer in mmiotrace functions - Remove unused buffer_page field from trace_array_cpu structure - Remove more strncpy() instances - Other minor clean ups and fixes -----BEGIN PGP SIGNATURE----- iIoEABYKADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCaDhiqRQccm9zdGVkdEBn b29kbWlzLm9yZwAKCRAp5XQQmuv6qkheAQDpyRHoXF1AIoEqyahDax8f3vpZQeCH B/mn+YJmU1wuVgEA7AFALov5SHKv4IzoARz68GXtR0jGhP5D8uebUhUqDAQ= =WmFG -----END PGP SIGNATURE----- Merge tag 'trace-v6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing updates from Steven Rostedt: - Have module addresses get updated in the persistent ring buffer The addresses of the modules from the previous boot are saved in the persistent ring buffer. If the same modules are loaded and an address is in the old buffer points to an address that was both saved in the persistent ring buffer and is loaded in memory, shift the address to point to the address that is loaded in memory in the trace event. - Print function names for irqs off and preempt off callsites When ignoring the print fmt of a trace event and just printing the fields directly, have the fields for preempt off and irqs off events still show the function name (via kallsyms) instead of just showing the raw address. - Clean ups of the histogram code The histogram functions saved over 800 bytes on the stack to process events as they come in. Instead, create per-cpu buffers that can hold this information and have a separate location for each context level (thread, softirq, IRQ and NMI). Also add some more comments to the code. - Add "common_comm" field for histograms Add "common_comm" that uses the current->comm as a field in an event histogram and acts like any of the other fields of the event. - Show "subops" in the enabled_functions file When the function graph infrastructure is used, a subsystem has a "subops" that it attaches its callback function to. Instead of the enabled_functions just showing a function calling the function that calls the subops functions, also show the subops functions that will get called for that function too. - Add "copy_trace_marker" option to instances There are cases where an instance is created for tooling to write into, but the old tooling has the top level instance hardcoded into the application. New tools want to consume the data from an instance and not the top level buffer. By adding a copy_trace_marker option, whenever the top instance trace_marker is written into, a copy of it is also written into the instance with this option set. This allows new tools to read what old tools are writing into the top buffer. If this option is cleared by the top instance, then what is written into the trace_marker is not written into the top instance. This is a way to redirect the trace_marker writes into another instance. - Have tracepoints created by DECLARE_TRACE() use trace_<name>_tp() If a tracepoint is created by DECLARE_TRACE() instead of TRACE_EVENT(), then it will not be exposed via tracefs. Currently there's no way to differentiate in the kernel the tracepoint functions between those that are exposed via tracefs or not. A calling convention has been made manually to append a "_tp" prefix for events created by DECLARE_TRACE(). Instead of doing this manually, force it so that all DECLARE_TRACE() events have this notation. - Use __string() for task->comm in some sched events Instead of hardcoding the comm to be TASK_COMM_LEN in some of the scheduler events use __string() which makes it dynamic. Note, if these events are parsed by user space it they may break, and the event may have to be converted back to the hardcoded size. - Have function graph "depth" be unsigned to the user Internally to the kernel, the "depth" field of the function graph event is signed due to -1 being used for end of boundary. What actually gets recorded in the event itself is zero or positive. Reflect this to user space by showing "depth" as unsigned int and be consistent across all events. - Allow an arbitrary long CPU string to osnoise_cpus_write() The filtering of which CPUs to write to can exceed 256 bytes. If a machine has 256 CPUs, and the filter is to filter every other CPU, the write would take a string larger than 256 bytes. Instead of using a fixed size buffer on the stack that is 256 bytes, allocate it to handle what is passed in. - Stop having ftrace check the per-cpu data "disabled" flag The "disabled" flag in the data structure passed to most ftrace functions is checked to know if tracing has been disabled or not. This flag was added back in 2008 before the ring buffer had its own way to disable tracing. The "disable" flag is now not always set when needed, and the ring buffer flag should be used in all locations where the disabled is needed. Since the "disable" flag is redundant and incorrect, stop using it. Fix up some locations that use the "disable" flag to use the ring buffer info. - Use a new tracer_tracing_disable/enable() instead of data->disable flag There's a few cases that set the data->disable flag to stop tracing, but this flag is not consistently used. It is also an on/off switch where if a function set it and calls another function that sets it, the called function may incorrectly enable it. Use a new trace_tracing_disable() and tracer_tracing_enable() that uses a counter and can be nested. These use the ring buffer flags which are always checked making the disabling more consistent. - Save the trace clock in the persistent ring buffer Save what clock was used for tracing in the persistent ring buffer and set it back to that clock after a reboot. - Remove unused reference to a per CPU data pointer in mmiotrace functions - Remove unused buffer_page field from trace_array_cpu structure - Remove more strncpy() instances - Other minor clean ups and fixes * tag 'trace-v6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (36 commits) tracing: Fix compilation warning on arm32 tracing: Record trace_clock and recover when reboot tracing/sched: Use __string() instead of fixed lengths for task->comm tracepoint: Have tracepoints created with DECLARE_TRACE() have _tp suffix tracing: Cleanup upper_empty() in pid_list tracing: Allow the top level trace_marker to write into another instances tracing: Add a helper function to handle the dereference arg in verifier tracing: Remove unnecessary "goto out" that simply returns ret is trigger code tracing: Fix error handling in event_trigger_parse() tracing: Rename event_trigger_alloc() to trigger_data_alloc() tracing: Replace deprecated strncpy() with strscpy() for stack_trace_filter_buf tracing: Remove unused buffer_page field from trace_array_cpu structure tracing: Use atomic_inc_return() for updating "disabled" counter in irqsoff tracer tracing: Convert the per CPU "disabled" counter to local from atomic tracing: branch: Use trace_tracing_is_on_cpu() instead of "disabled" field ring-buffer: Add ring_buffer_record_is_on_cpu() tracing: Do not use per CPU array_buffer.data->disabled for cpumask ftrace: Do not disabled function graph based on "disabled" field tracing: kdb: Use tracer_tracing_on/off() instead of setting per CPU disabled tracing: Use tracer_tracing_disable() instead of "disabled" field for ftrace_dump_one() ...	2025-05-29 21:04:36 -07:00
Steven Rostedt	99d2328044	ring-buffer: Simplify functions with __free(kfree) to free allocations ... The function rb_allocate_pages() allocates cpu_buffer and on error needs to free it. It has a single return. Use __free(kfree) and return directly on errors and have the return use return_ptr(cpu_buffer). The function alloc_buffer() allocates buffer and on error needs to free it. It has a single return. Use __free(kfree) and return directly on errors and have the return use return_ptr(buffer). The function __rb_map_vma() allocates a temporary array "pages". Have it use __free() and not worry about freeing it when returning. Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Link: https://lore.kernel.org/20250527143144.6edc4625@gandalf.local.home Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-05-29 08:24:08 -04:00
Steven Rostedt	60bc720e10	ring-buffer: Make ring_buffer_{un}map() simpler with guard(mutex) ... Convert the taking of the buffer->mutex and the cpu_buffer->mapping_lock over to guard(mutex) and simplify the ring_buffer_map() and ring_buffer_unmap() functions. Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Vincent Donnefort <vdonnefort@google.com> Link: https://lore.kernel.org/20250527122009.267efb72@gandalf.local.home Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-05-29 08:24:08 -04:00
Steven Rostedt	b2e7c6ed26	ring-buffer: Simplify ring_buffer_read_page() with guard() ... The function ring_buffer_read_page() had two gotos. One was simply returning "ret" and the other was unlocking the reader_lock. There's no reason to use goto to simply return the "ret" variable. Instead just return the value. The jump to the unlocking of the reader_lock can be replaced by guard(raw_spinlock_irqsave)(&cpu_buffer->reader_lock). With these two changes the "ret" variable is no longer used and can be removed. The return value on non-error is what was read and is stored in the "read" variable. Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Link: https://lore.kernel.org/20250527145216.0187cf36@gandalf.local.home Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-05-29 08:24:07 -04:00
Steven Rostedt	f0d8cbc8cc	ring-buffer: Simplify reset_disabled_cpu_buffer() with use of guard() ... Use guard(raw_spinlock_irqsave)() in reset_disabled_cpu_buffer() to simplify the locking. Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Link: https://lore.kernel.org/20250527144623.77a9cc47@gandalf.local.home Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-05-29 08:24:07 -04:00
Steven Rostedt	f115d2b70b	ring-buffer: Remove jump to out label in ring_buffer_swap_cpu() ... The function ring_buffer_swap_cpu() has a bunch of jumps to the label out that simply returns "ret". There's no reason to jump to a label that simply returns a value. Just return directly from there. This goes back to almost the beginning when commit 8aabee573d ("ring-buffer: remove unneeded get_online_cpus") was introduced. That commit removed a put_online_cpus() from that label, but never updated all the jumps to it that now no longer needed to do anything but return a value. Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Link: https://lore.kernel.org/20250527145753.6b45d840@gandalf.local.home Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-05-29 08:24:07 -04:00
Steven Rostedt	2d22216521	ring-buffer: Removed unnecessary if() goto out where out is the next line ... In the function ring_buffer_discard_commit() there's an if statement that jumps to the next line: if (rb_try_to_discard(cpu_buffer, event)) goto out; out: This was caused by the change that modified the way timestamps were taken in interrupt context, and removed the code between the if statement and the goto, but failed to update the conditional logic. Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Link: https://lore.kernel.org/20250527155116.227f35be@gandalf.local.home Fixes: a389d86f7f ("ring-buffer: Have nested events still record running time stamp") Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-05-29 08:24:07 -04:00
Steven Rostedt	c2a0831142	ring-buffer: Allow reserve_mem persistent ring buffers to be mmapped ... When the persistent ring buffer is created from the memory returned by reserve_mem there is nothing prohibiting it to be memory mapped to user space. The memory is the same as the pages allocated by alloc_page(). The way the memory is managed by the ring buffer code is slightly different though and needs to be addressed. The persistent memory uses the page->id for its own purpose where as the user mmap buffer currently uses that for the subbuf array mapped to user space. If the buffer is a persistent buffer, use the page index into that buffer as the identifier instead of the page->id. That is, the page->id for a persistent buffer, represents the order of the buffer is in the link list. ->id == 0 means it is the reader page. When a reader page is swapped, the new reader page's ->id gets zero, and the old reader page gets the ->id of the page that it swapped with. The user space mapping has the ->id is the index of where it was mapped in user space and does not change while it is mapped. Since the persistent buffer is fixed in its location, the index of where a page is in the memory range can be used as the "id" to put in the meta page array, and it can be mapped in the same order to user space as it is in the persistent memory. A new rb_page_id() helper function is used to get and set the id depending on if the page is a normal memory allocated buffer or a physical memory mapped buffer. Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Mike Rapoport <rppt@kernel.org> Cc: Jann Horn <jannh@google.com> Link: https://lore.kernel.org/20250401203332.246646011@goodmis.org Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-05-29 08:24:07 -04:00
Steven Rostedt	4fc78a7c9c	ring-buffer: Do not trigger WARN_ON() due to a commit_overrun ... When reading a memory mapped buffer the reader page is just swapped out with the last page written in the write buffer. If the reader page is the same as the commit buffer (the buffer that is currently being written to) it was assumed that it should never have missed events. If it does, it triggers a WARN_ON_ONCE(). But there just happens to be one scenario where this can legitimately happen. That is on a commit_overrun. A commit overrun is when an interrupt preempts an event being written to the buffer and then the interrupt adds so many new events that it fills and wraps the buffer back to the commit. Any new events would then be dropped and be reported as "missed_events". In this case, the next page to read is the commit buffer and after the swap of the reader page, the reader page will be the commit buffer, but this time there will be missed events and this triggers the following warning: ------------[ cut here ]------------ WARNING: CPU: 2 PID: 1127 at kernel/trace/ring_buffer.c:7357 ring_buffer_map_get_reader+0x49a/0x780 Modules linked in: kvm_intel kvm irqbypass CPU: 2 UID: 0 PID: 1127 Comm: trace-cmd Not tainted 6.15.0-rc7-test-00004-g478bc2824b45-dirty #564 PREEMPT Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:ring_buffer_map_get_reader+0x49a/0x780 Code: 00 00 00 48 89 fe 48 c1 ee 03 80 3c 2e 00 0f 85 ec 01 00 00 4d 3b a6 a8 00 00 00 0f 85 8a fd ff ff 48 85 c0 0f 84 55 fe ff ff <0f> 0b e9 4e fe ff ff be 08 00 00 00 4c 89 54 24 58 48 89 54 24 50 RSP: 0018:ffff888121787dc0 EFLAGS: 00010002 RAX: 00000000000006a2 RBX: ffff888100062800 RCX: ffffffff8190cb49 RDX: ffff888126934c00 RSI: 1ffff11020200a15 RDI: ffff8881010050a8 RBP: dffffc0000000000 R08: 0000000000000000 R09: ffffed1024d26982 R10: ffff888126934c17 R11: ffff8881010050a8 R12: ffff888126934c00 R13: ffff8881010050b8 R14: ffff888101005000 R15: ffff888126930008 FS: 00007f95c8cd7540(0000) GS:ffff8882b576e000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f95c8de4dc0 CR3: 0000000128452002 CR4: 0000000000172ef0 Call Trace: <TASK> ? __pfx_ring_buffer_map_get_reader+0x10/0x10 tracing_buffers_ioctl+0x283/0x370 __x64_sys_ioctl+0x134/0x190 do_syscall_64+0x79/0x1c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0033:0x7f95c8de48db Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00 RSP: 002b:00007ffe037ba110 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007ffe037bb2b0 RCX: 00007f95c8de48db RDX: 0000000000000000 RSI: 0000000000005220 RDI: 0000000000000006 RBP: 00007ffe037ba180 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffe037bb6f8 R14: 00007f95c9065000 R15: 00005575c7492c90 </TASK> irq event stamp: 5080 hardirqs last enabled at (5079): [<ffffffff83e0adb0>] _raw_spin_unlock_irqrestore+0x50/0x70 hardirqs last disabled at (5080): [<ffffffff83e0aa83>] _raw_spin_lock_irqsave+0x63/0x70 softirqs last enabled at (4182): [<ffffffff81516122>] handle_softirqs+0x552/0x710 softirqs last disabled at (4159): [<ffffffff815163f7>] __irq_exit_rcu+0x107/0x210 ---[ end trace 0000000000000000 ]--- The above was triggered by running on a kernel with both lockdep and KASAN as well as kmemleak enabled and executing the following command: # perf record -o perf-test.dat -a -- trace-cmd record --nosplice -e all -p function hackbench 50 With perf interjecting a lot of interrupts and trace-cmd enabling all events as well as function tracing, with lockdep, KASAN and kmemleak enabled, it could cause an interrupt preempting an event being written to add enough events to wrap the buffer. trace-cmd was modified to have --nosplice use mmap instead of reading the buffer. The way to differentiate this case from the normal case of there only being one page written to where the swap of the reader page received that one page (which is the commit page), check if the tail page is on the reader page. The difference between the commit page and the tail page is that the tail page is where new writes go to, and the commit page holds the first write that hasn't been committed yet. In the case of an interrupt preempting the write of an event and filling the buffer, it would move the tail page but not the commit page. Have the warning only trigger if the tail page is also on the reader page, and also print out the number of events dropped by a commit overrun as that can not yet be safely added to the page so that the reader can see there were events dropped. Cc: stable@vger.kernel.org Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Vincent Donnefort <vdonnefort@google.com> Link: https://lore.kernel.org/20250528121555.2066527e@gandalf.local.home Fixes: fe832be05a ("ring-buffer: Have mmapped ring buffer keep track of missed events") Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-05-29 08:23:48 -04:00
Steven Rostedt	c98cc9797b	ring-buffer: Move cpus_read_lock() outside of buffer->mutex ... Running a modified trace-cmd record --nosplice where it does a mmap of the ring buffer when '--nosplice' is set, caused the following lockdep splat: ====================================================== WARNING: possible circular locking dependency detected 6.15.0-rc7-test-00002-gfb7d03d8a82f #551 Not tainted ------------------------------------------------------ trace-cmd/1113 is trying to acquire lock: ffff888100062888 (&buffer->mutex){+.+.}-{4:4}, at: ring_buffer_map+0x11c/0xe70 but task is already holding lock: ffff888100a5f9f8 (&cpu_buffer->mapping_lock){+.+.}-{4:4}, at: ring_buffer_map+0xcf/0xe70 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #5 (&cpu_buffer->mapping_lock){+.+.}-{4:4}: __mutex_lock+0x192/0x18c0 ring_buffer_map+0xcf/0xe70 tracing_buffers_mmap+0x1c4/0x3b0 __mmap_region+0xd8d/0x1f70 do_mmap+0x9d7/0x1010 vm_mmap_pgoff+0x20b/0x390 ksys_mmap_pgoff+0x2e9/0x440 do_syscall_64+0x79/0x1c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #4 (&mm->mmap_lock){++++}-{4:4}: __might_fault+0xa5/0x110 _copy_to_user+0x22/0x80 _perf_ioctl+0x61b/0x1b70 perf_ioctl+0x62/0x90 __x64_sys_ioctl+0x134/0x190 do_syscall_64+0x79/0x1c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #3 (&cpuctx_mutex){+.+.}-{4:4}: __mutex_lock+0x192/0x18c0 perf_event_init_cpu+0x325/0x7c0 perf_event_init+0x52a/0x5b0 start_kernel+0x263/0x3e0 x86_64_start_reservations+0x24/0x30 x86_64_start_kernel+0x95/0xa0 common_startup_64+0x13e/0x141 -> #2 (pmus_lock){+.+.}-{4:4}: __mutex_lock+0x192/0x18c0 perf_event_init_cpu+0xb7/0x7c0 cpuhp_invoke_callback+0x2c0/0x1030 __cpuhp_invoke_callback_range+0xbf/0x1f0 _cpu_up+0x2e7/0x690 cpu_up+0x117/0x170 cpuhp_bringup_mask+0xd5/0x120 bringup_nonboot_cpus+0x13d/0x170 smp_init+0x2b/0xf0 kernel_init_freeable+0x441/0x6d0 kernel_init+0x1e/0x160 ret_from_fork+0x34/0x70 ret_from_fork_asm+0x1a/0x30 -> #1 (cpu_hotplug_lock){++++}-{0:0}: cpus_read_lock+0x2a/0xd0 ring_buffer_resize+0x610/0x14e0 __tracing_resize_ring_buffer.part.0+0x42/0x120 tracing_set_tracer+0x7bd/0xa80 tracing_set_trace_write+0x132/0x1e0 vfs_write+0x21c/0xe80 ksys_write+0xf9/0x1c0 do_syscall_64+0x79/0x1c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #0 (&buffer->mutex){+.+.}-{4:4}: __lock_acquire+0x1405/0x2210 lock_acquire+0x174/0x310 __mutex_lock+0x192/0x18c0 ring_buffer_map+0x11c/0xe70 tracing_buffers_mmap+0x1c4/0x3b0 __mmap_region+0xd8d/0x1f70 do_mmap+0x9d7/0x1010 vm_mmap_pgoff+0x20b/0x390 ksys_mmap_pgoff+0x2e9/0x440 do_syscall_64+0x79/0x1c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e other info that might help us debug this: Chain exists of: &buffer->mutex --> &mm->mmap_lock --> &cpu_buffer->mapping_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&cpu_buffer->mapping_lock); lock(&mm->mmap_lock); lock(&cpu_buffer->mapping_lock); lock(&buffer->mutex); *** DEADLOCK *** 2 locks held by trace-cmd/1113: #0: ffff888106b847e0 (&mm->mmap_lock){++++}-{4:4}, at: vm_mmap_pgoff+0x192/0x390 #1: ffff888100a5f9f8 (&cpu_buffer->mapping_lock){+.+.}-{4:4}, at: ring_buffer_map+0xcf/0xe70 stack backtrace: CPU: 5 UID: 0 PID: 1113 Comm: trace-cmd Not tainted 6.15.0-rc7-test-00002-gfb7d03d8a82f #551 PREEMPT Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x6e/0xa0 print_circular_bug.cold+0x178/0x1be check_noncircular+0x146/0x160 __lock_acquire+0x1405/0x2210 lock_acquire+0x174/0x310 ? ring_buffer_map+0x11c/0xe70 ? ring_buffer_map+0x11c/0xe70 ? __mutex_lock+0x169/0x18c0 __mutex_lock+0x192/0x18c0 ? ring_buffer_map+0x11c/0xe70 ? ring_buffer_map+0x11c/0xe70 ? function_trace_call+0x296/0x370 ? __pfx___mutex_lock+0x10/0x10 ? __pfx_function_trace_call+0x10/0x10 ? __pfx___mutex_lock+0x10/0x10 ? _raw_spin_unlock+0x2d/0x50 ? ring_buffer_map+0x11c/0xe70 ? ring_buffer_map+0x11c/0xe70 ? __mutex_lock+0x5/0x18c0 ring_buffer_map+0x11c/0xe70 ? do_raw_spin_lock+0x12d/0x270 ? find_held_lock+0x2b/0x80 ? _raw_spin_unlock+0x2d/0x50 ? rcu_is_watching+0x15/0xb0 ? _raw_spin_unlock+0x2d/0x50 ? trace_preempt_on+0xd0/0x110 tracing_buffers_mmap+0x1c4/0x3b0 __mmap_region+0xd8d/0x1f70 ? ring_buffer_lock_reserve+0x99/0xff0 ? __pfx___mmap_region+0x10/0x10 ? ring_buffer_lock_reserve+0x99/0xff0 ? __pfx_ring_buffer_lock_reserve+0x10/0x10 ? __pfx_ring_buffer_lock_reserve+0x10/0x10 ? bpf_lsm_mmap_addr+0x4/0x10 ? security_mmap_addr+0x46/0xd0 ? lock_is_held_type+0xd9/0x130 do_mmap+0x9d7/0x1010 ? 0xffffffffc0370095 ? __pfx_do_mmap+0x10/0x10 vm_mmap_pgoff+0x20b/0x390 ? __pfx_vm_mmap_pgoff+0x10/0x10 ? 0xffffffffc0370095 ksys_mmap_pgoff+0x2e9/0x440 do_syscall_64+0x79/0x1c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0033:0x7fb0963a7de2 Code: 00 00 00 0f 1f 44 00 00 41 f7 c1 ff 0f 00 00 75 27 55 89 cd 53 48 89 fb 48 85 ff 74 3b 41 89 ea 48 89 df b8 09 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 76 5b 5d c3 0f 1f 00 48 8b 05 e1 9f 0d 00 64 RSP: 002b:00007ffdcc8fb878 EFLAGS: 00000246 ORIG_RAX: 0000000000000009 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fb0963a7de2 RDX: 0000000000000001 RSI: 0000000000001000 RDI: 0000000000000000 RBP: 0000000000000001 R08: 0000000000000006 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffdcc8fbe68 R14: 00007fb096628000 R15: 00005633e01a5c90 </TASK> The issue is that cpus_read_lock() is taken within buffer->mutex. The memory mapped pages are taken with the mmap_lock held. The buffer->mutex is taken within the cpu_buffer->mapping_lock. There's quite a chain with all these locks, where the deadlock can be fixed by moving the cpus_read_lock() outside the taking of the buffer->mutex. Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Vincent Donnefort <vdonnefort@google.com> Link: https://lore.kernel.org/20250527105820.0f45d045@gandalf.local.home Fixes: 117c39200d ("ring-buffer: Introducing ring-buffer mapping functions") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-05-27 15:46:39 -04:00
Steven Rostedt	1d6c39c89f	ring-buffer: Fix persistent buffer when commit page is the reader page ... The ring buffer is made up of sub buffers (sometimes called pages as they are by default PAGE_SIZE). It has the following "pages": "tail page" - this is the page that the next write will write to "head page" - this is the page that the reader will swap the reader page with. "reader page" - This belongs to the reader, where it will swap the head page from the ring buffer so that the reader does not race with the writer. The writer may end up on the "reader page" if the ring buffer hasn't written more than one page, where the "tail page" and the "head page" are the same. The persistent ring buffer has meta data that points to where these pages exist so on reboot it can re-create the pointers to the cpu_buffer descriptor. But when the commit page is on the reader page, the logic is incorrect. The check to see if the commit page is on the reader page checked if the head page was the reader page, which would never happen, as the head page is always in the ring buffer. The correct check would be to test if the commit page is on the reader page. If that's the case, then it can exit out early as the commit page is only on the reader page when there's only one page of data in the buffer. There's no reason to iterate the ring buffer pages to find the "commit page" as it is already found. To trigger this bug: # echo 1 > /sys/kernel/tracing/instances/boot_mapped/events/syscalls/sys_enter_fchownat/enable # touch /tmp/x # chown sshd /tmp/x # reboot On boot up, the dmesg will have: Ring buffer meta [0] is from previous boot! Ring buffer meta [1] is from previous boot! Ring buffer meta [2] is from previous boot! Ring buffer meta [3] is from previous boot! Ring buffer meta [4] commit page not found Ring buffer meta [5] is from previous boot! Ring buffer meta [6] is from previous boot! Ring buffer meta [7] is from previous boot! Where the buffer on CPU 4 had a "commit page not found" error and that buffer is cleared and reset causing the output to be empty and the data lost. When it works correctly, it has: # cat /sys/kernel/tracing/instances/boot_mapped/trace_pipe <...>-1137 [004] ..... 998.205323: sys_enter_fchownat: __syscall_nr=0x104 (260) dfd=0xffffff9c (4294967196) filename=(0xffffc90000a0002c) user=0x3e8 (1000) group=0xffffffff (4294967295) flag=0x0 (0 Cc: stable@vger.kernel.org Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Link: https://lore.kernel.org/20250513115032.3e0b97f7@gandalf.local.home Fixes: 5f3b6e839f ("ring-buffer: Validate boot range memory events") Reported-by: Tasos Sahanidis <tasos@tasossah.com> Tested-by: Tasos Sahanidis <tasos@tasossah.com> Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-05-14 13:53:23 -04:00
Steven Rostedt	092a38565e	ring-buffer: Add ring_buffer_record_is_on_cpu() ... Add the function ring_buffer_record_is_on_cpu() that returns true if the ring buffer for a give CPU is writable and false otherwise. Also add tracer_tracing_is_on_cpu() to return if the ring buffer for a given CPU is writeable for a given trace_array. Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Link: https://lore.kernel.org/20250505212236.059853898@goodmis.org Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-05-09 15:19:10 -04:00
Linus Torvalds	6cb0bd94c0	Persistent buffer cleanups and simplifications for v6.15: ... It was mistaken that the physical memory returned from "reserve_mem" had to be vmap()'d to get to it from a virtual address. But reserve_mem already maps the memory to the virtual address of the kernel so a simple phys_to_virt() can be used to get to the virtual address from the physical memory returned by "reserve_mem". With this new found knowledge, the code can be cleaned up and simplified. - Enforce that the persistent memory is page aligned As the buffers using the persistent memory are all going to be mapped via pages, make sure that the memory given to the tracing infrastructure is page aligned. If it is not, it will print a warning and fail to map the buffer. - Use phys_to_virt() to get the virtual address from reserve_mem Instead of calling vmap() on the physical memory returned from "reserve_mem", use phys_to_virt() instead. As the memory returned by "memmap" or any other means where a physical address is given to the tracing infrastructure, it still needs to be vmap(). Since this memory can never be returned back to the buddy allocator nor should it ever be memmory mapped to user space, flag this buffer and up the ref count. The ref count will keep it from ever being freed, and the flag will prevent it from ever being memory mapped to user space. - Use vmap_page_range() for memmap virtual address mapping For the memmap buffer, instead of allocating an array of struct pages, assigning them to the contiguous phsycial memory and then passing that to vmap(), use vmap_page_range() instead - Replace flush_dcache_folio() with flush_kernel_vmap_range() Instead of calling virt_to_folio() and passing that to flush_dcache_folio(), just call flush_kernel_vmap_range() directly. This also fixes a bug where if a subbuffer was bigger than PAGE_SIZE only the PAGE_SIZE portion would be flushed. -----BEGIN PGP SIGNATURE----- iIoEABYIADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCZ+6oZRQccm9zdGVkdEBn b29kbWlzLm9yZwAKCRAp5XQQmuv6qhq6AP481KHAgaowQCg7zrKPkMlbYBIigYoU 7aqoAg2rSLBRSQEAl8fViHZgZ9Q+O7xdozQWiIR7/KQW8VIaTcP/V7cHkAU= =+5JB -----END PGP SIGNATURE----- Merge tag 'trace-ringbuffer-v6.15-3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull ring-buffer updates from Steven Rostedt: "Persistent buffer cleanups and simplifications. It was mistaken that the physical memory returned from "reserve_mem" had to be vmap()'d to get to it from a virtual address. But reserve_mem already maps the memory to the virtual address of the kernel so a simple phys_to_virt() can be used to get to the virtual address from the physical memory returned by "reserve_mem". With this new found knowledge, the code can be cleaned up and simplified. - Enforce that the persistent memory is page aligned As the buffers using the persistent memory are all going to be mapped via pages, make sure that the memory given to the tracing infrastructure is page aligned. If it is not, it will print a warning and fail to map the buffer. - Use phys_to_virt() to get the virtual address from reserve_mem Instead of calling vmap() on the physical memory returned from "reserve_mem", use phys_to_virt() instead. As the memory returned by "memmap" or any other means where a physical address is given to the tracing infrastructure, it still needs to be vmap(). Since this memory can never be returned back to the buddy allocator nor should it ever be memmory mapped to user space, flag this buffer and up the ref count. The ref count will keep it from ever being freed, and the flag will prevent it from ever being memory mapped to user space. - Use vmap_page_range() for memmap virtual address mapping For the memmap buffer, instead of allocating an array of struct pages, assigning them to the contiguous phsycial memory and then passing that to vmap(), use vmap_page_range() instead - Replace flush_dcache_folio() with flush_kernel_vmap_range() Instead of calling virt_to_folio() and passing that to flush_dcache_folio(), just call flush_kernel_vmap_range() directly. This also fixes a bug where if a subbuffer was bigger than PAGE_SIZE only the PAGE_SIZE portion would be flushed" * tag 'trace-ringbuffer-v6.15-3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ring-buffer: Use flush_kernel_vmap_range() over flush_dcache_folio() tracing: Use vmap_page_range() to map memmap ring buffer tracing: Have reserve_mem use phys_to_virt() and separate from memmap buffer tracing: Enforce the persistent ring buffer to be page aligned	2025-04-03 16:09:29 -07:00
Steven Rostedt	e4d4b8670c	ring-buffer: Use flush_kernel_vmap_range() over flush_dcache_folio() ... Some architectures do not have data cache coherency between user and kernel space. For these architectures, the cache needs to be flushed on both the kernel and user addresses so that user space can see the updates the kernel has made. Instead of using flush_dcache_folio() and playing with virt_to_folio() within the call to that function, use flush_kernel_vmap_range() which takes the virtual address and does the work for those architectures that need it. This also fixes a bug where the flush of the reader page only flushed one page. If the sub-buffer order is 1 or more, where the sub-buffer size would be greater than a page, it would miss the rest of the sub-buffer content, as the "reader page" is not just a page, but the size of a sub-buffer. Link: https://lore.kernel.org/all/CAG48ez3w0my4Rwttbc5tEbNsme6tc0mrSN95thjXUFaJ3aQ6SA@mail.gmail.com/ Cc: stable@vger.kernel.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Mike Rapoport <rppt@kernel.org> Link: https://lore.kernel.org/20250402144953.920792197@goodmis.org Fixes: 117c39200d ("ring-buffer: Introducing ring-buffer mapping functions"); Suggested-by: Jann Horn <jannh@google.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-04-02 11:02:27 -04:00
Linus Torvalds	46d29f23a7	ring-buffer updates for v6.15 ... - Restructure the persistent memory to have a "scratch" area Instead of hard coding the KASLR offset in the persistent memory by the ring buffer, push that work up to the callers of the persistent memory as they are the ones that need this information. The offsets and such is not important to the ring buffer logic and it should not be part of that. A scratch pad is now created when the caller allocates a ring buffer from persistent memory by stating how much memory it needs to save. - Allow where modules are loaded to be saved in the new scratch pad Save the addresses of modules when they are loaded into the persistent memory scratch pad. - A new module_for_each_mod() helper function was created With the acknowledgement of the module maintainers a new module helper function was created to iterate over all the currently loaded modules. This has a callback to be called for each module. This is needed for when tracing is started in the persistent buffer and the currently loaded modules need to be saved in the scratch area. - Expose the last boot information where the kernel and modules were loaded The last_boot_info file is updated to print out the addresses of where the kernel "_text" location was loaded from a previous boot, as well as where the modules are loaded. If the buffer is recording the current boot, it only prints "# Current" so that it does not expose the KASLR offset of the currently running kernel. - Allow the persistent ring buffer to be released (freed) To have this in production environments, where the kernel command line can not be changed easily, the ring buffer needs to be freed when it is not going to be used. The memory for the buffer will always be allocated at boot up, but if the system isn't going to enable tracing, the memory needs to be freed. Allow it to be freed and added back to the kernel memory pool. - Allow stack traces to print the function names in the persistent buffer Now that the modules are saved in the persistent ring buffer, if the same modules are loaded, the printing of the function names will examine the saved modules. If the module is found in the scratch area and is also loaded, then it will do the offset shift and use kallsyms to display the function name. If the address is not found, it simply displays the address from the previous boot in hex. -----BEGIN PGP SIGNATURE----- iIoEABYIADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCZ+cUERQccm9zdGVkdEBn b29kbWlzLm9yZwAKCRAp5XQQmuv6qrAsAQCFt2nfzxoe3wtF5EqIT1VHp/8bQVjG gBe8B6ouboreogD/dS7yK8MRy24ZAmObGwYG0RbVicd50S7P8Rf7+823ng8= =OJKk -----END PGP SIGNATURE----- Merge tag 'trace-ringbuffer-v6.15-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull ring-buffer updates from Steven Rostedt: - Restructure the persistent memory to have a "scratch" area Instead of hard coding the KASLR offset in the persistent memory by the ring buffer, push that work up to the callers of the persistent memory as they are the ones that need this information. The offsets and such is not important to the ring buffer logic and it should not be part of that. A scratch pad is now created when the caller allocates a ring buffer from persistent memory by stating how much memory it needs to save. - Allow where modules are loaded to be saved in the new scratch pad Save the addresses of modules when they are loaded into the persistent memory scratch pad. - A new module_for_each_mod() helper function was created With the acknowledgement of the module maintainers a new module helper function was created to iterate over all the currently loaded modules. This has a callback to be called for each module. This is needed for when tracing is started in the persistent buffer and the currently loaded modules need to be saved in the scratch area. - Expose the last boot information where the kernel and modules were loaded The last_boot_info file is updated to print out the addresses of where the kernel "_text" location was loaded from a previous boot, as well as where the modules are loaded. If the buffer is recording the current boot, it only prints "# Current" so that it does not expose the KASLR offset of the currently running kernel. - Allow the persistent ring buffer to be released (freed) To have this in production environments, where the kernel command line can not be changed easily, the ring buffer needs to be freed when it is not going to be used. The memory for the buffer will always be allocated at boot up, but if the system isn't going to enable tracing, the memory needs to be freed. Allow it to be freed and added back to the kernel memory pool. - Allow stack traces to print the function names in the persistent buffer Now that the modules are saved in the persistent ring buffer, if the same modules are loaded, the printing of the function names will examine the saved modules. If the module is found in the scratch area and is also loaded, then it will do the offset shift and use kallsyms to display the function name. If the address is not found, it simply displays the address from the previous boot in hex. * tag 'trace-ringbuffer-v6.15-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: tracing: Use _text and the kernel offset in last_boot_info tracing: Show last module text symbols in the stacktrace ring-buffer: Remove the unused variable bmeta tracing: Skip update_last_data() if cleared and remove active check for save_mod() tracing: Initialize scratch_size to zero to prevent UB tracing: Fix a compilation error without CONFIG_MODULES tracing: Freeable reserved ring buffer mm/memblock: Add reserved memory release function tracing: Update modules to persistent instances when loaded tracing: Show module names and addresses of last boot tracing: Have persistent trace instances save module addresses module: Add module_for_each_mod() function tracing: Have persistent trace instances save KASLR offset ring-buffer: Add ring_buffer_meta_scratch() ring-buffer: Add buffer meta data for persistent ring buffer ring-buffer: Use kaslr address instead of text delta ring-buffer: Fix bytes_dropped calculation issue	2025-03-31 13:37:22 -07:00
Jiapeng Chong	de48d7fff7	ring-buffer: Remove the unused variable bmeta ... Variable bmeta is not effectively used, so delete it. kernel/trace/ring_buffer.c:1952:27: warning: variable ‘bmeta’ set but not used. Link: https://lore.kernel.org/20250317015524.3902-1-jiapeng.chong@linux.alibaba.com Reported-by: Abaci Robot <abaci@linux.alibaba.com> Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=19524 Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-03-28 08:39:56 -04:00
Steven Rostedt	b65334825f	tracing: Have persistent trace instances save KASLR offset ... There's no reason to save the KASLR offset for the ring buffer itself. That is used by the tracer. Now that the tracer has a way to save data in the persistent memory of the ring buffer, have the tracing infrastructure take care of the saving of the KASLR offset. Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Link: https://lore.kernel.org/20250305164608.792722274@goodmis.org Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-03-28 08:39:27 -04:00
Steven Rostedt	4af0a9c518	ring-buffer: Add ring_buffer_meta_scratch() ... Now that there's one meta data at the start of the persistent memory used by the ring buffer, allow the caller to request some memory right after that data that it can use as its own persistent memory. Also fix some white space issues with ring_buffer_alloc(). Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Link: https://lore.kernel.org/20250305164608.619631731@goodmis.org Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-03-28 08:39:27 -04:00
Steven Rostedt	4009cc31e7	ring-buffer: Add buffer meta data for persistent ring buffer ... Instead of just having a meta data at the first page of each sub buffer that has duplicate data, add a new meta page to the entire block of memory that holds the duplicate data and remove it from the sub buffer meta data. This will open up the extra memory in this first page to be used by the tracer for its own persistent data. Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Link: https://lore.kernel.org/20250305164608.446351513@goodmis.org Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-03-28 08:39:26 -04:00
Steven Rostedt	bcba8d4dbe	ring-buffer: Use kaslr address instead of text delta ... Instead of saving off the text and data pointers and using them to compare with the current boot's text and data pointers, just save off the KASLR offset. Then that can be used to figure out how to read the previous boots buffer. The last_boot_info will now show this offset, but only if it is for a previous boot: ~# cat instances/boot_mapped/last_boot_info 39000000 [kernel] ~# echo function > instances/boot_mapped/current_tracer ~# cat instances/boot_mapped/last_boot_info # Current If the KASLR offset saved is for the current boot, the last_boot_info will show the value of "current". Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Link: https://lore.kernel.org/20250305164608.274956504@goodmis.org Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-03-28 08:39:26 -04:00
Feng Yang	c73f0b6964	ring-buffer: Fix bytes_dropped calculation issue ... The calculation of bytes-dropped and bytes_dropped_nested is reversed. Although it does not affect the final calculation of total_dropped, it should still be modified. Link: https://lore.kernel.org/20250223070106.6781-1-yangfeng59949@163.com Fixes: 6c43e554a2 ("ring-buffer: Add ring buffer startup selftest") Signed-off-by: Feng Yang <yangfeng@kylinos.cn> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-03-28 08:39:26 -04:00
Zhouyi Zhou	3ca4d7af35	ring-buffer: Fix typo in comment about header page pointer ... Fix typo in comment about header page pointer in function rb_get_reader_page. Link: https://lore.kernel.org/20250118012352.3430519-1-zhouzhouyi@gmail.com Signed-off-by: Zhouyi Zhou <zhouzhouyi@gmail.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-03-06 13:35:26 -05:00
Steven Rostedt	97937834ae	ring-buffer: Update pages_touched to reflect persistent buffer content ... The pages_touched field represents the number of subbuffers in the ring buffer that have content that can be read. This is used in accounting of "dirty_pages" and "buffer_percent" to allow the user to wait for the buffer to be filled to a certain amount before it reads the buffer in blocking mode. The persistent buffer never updated this value so it was set to zero, and this accounting would take it as it had no content. This would cause user space to wait for content even though there's enough content in the ring buffer that satisfies the buffer_percent. Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Vincent Donnefort <vdonnefort@google.com> Link: https://lore.kernel.org/20250214123512.0631436e@gandalf.local.home Fixes: 5f3b6e839f ("ring-buffer: Validate boot range memory events") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-02-15 14:00:59 -05:00
Steven Rostedt	f5b95f1fa2	ring-buffer: Validate the persistent meta data subbuf array ... The meta data for a mapped ring buffer contains an array of indexes of all the subbuffers. The first entry is the reader page, and the rest of the entries lay out the order of the subbuffers in how the ring buffer link list is to be created. The validator currently makes sure that all the entries are within the range of 0 and nr_subbufs. But it does not check if there are any duplicates. While working on the ring buffer, I corrupted this array, where I added duplicates. The validator did not catch it and created the ring buffer link list on top of it. Luckily, the corruption was only that the reader page was also in the writer path and only presented corrupted data but did not crash the kernel. But if there were duplicates in the writer side, then it could corrupt the ring buffer link list and cause a crash. Create a bitmask array with the size of the number of subbuffers. Then clear it. When walking through the subbuf array checking to see if the entries are within the range, test if its bit is already set in the subbuf_mask. If it is, then there is duplicates and fail the validation. If not, set the corresponding bit and continue. Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Vincent Donnefort <vdonnefort@google.com> Link: https://lore.kernel.org/20250214102820.7509ddea@gandalf.local.home Fixes: c76883f18e ("ring-buffer: Add test if range of boot buffer is valid") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-02-14 12:50:51 -05:00
Steven Rostedt	9ba0e1755a	ring-buffer: Unlock resize on mmap error ... Memory mapping the tracing ring buffer will disable resizing the buffer. But if there's an error in the memory mapping like an invalid parameter, the function exits out without re-enabling the resizing of the ring buffer, preventing the ring buffer from being resized after that. Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Vincent Donnefort <vdonnefort@google.com> Link: https://lore.kernel.org/20250213131957.530ec3c5@gandalf.local.home Fixes: 117c39200d ("ring-buffer: Introducing ring-buffer mapping functions") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-02-14 12:50:05 -05:00
Steven Rostedt	cd2375a356	ring-buffer: Do not allow events in NMI with generic atomic64 cmpxchg() ... Some architectures can not safely do atomic64 operations in NMI context. Since the ring buffer relies on atomic64 operations to do its time keeping, if an event is requested in NMI context, reject it for these architectures. Cc: stable@vger.kernel.org Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andreas Larsson <andreas@gaisler.com> Link: https://lore.kernel.org/20250120235721.407068250@goodmis.org Fixes: c84897c0ff ("ring-buffer: Remove 32bit timestamp logic") Closes: https://lore.kernel.org/all/86fb4f86-a0e4-45a2-a2df-3154acc4f086@gaisler.com/ Reported-by: Ludwig Rydberg <ludwig.rydberg@gaisler.com> Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-01-21 15:19:00 -05:00
Jeongjun Park	6e31b759b0	ring-buffer: Make reading page consistent with the code logic ... In the loop of __rb_map_vma(), the 's' variable is calculated from the same logic that nr_pages is and they both come from nr_subbufs. But the relationship is not obvious and there's a WARN_ON_ONCE() around the 's' variable to make sure it never becomes equal to nr_subbufs within the loop. If that happens, then the code is buggy and needs to be fixed. The 'page' variable is calculated from cpu_buffer->subbuf_ids[s] which is an array of 'nr_subbufs' entries. If the code becomes buggy and 's' becomes equal to or greater than 'nr_subbufs' then this will be an out of bounds hit before the WARN_ON() is triggered and the code exiting safely. Make the 'page' initialization consistent with the code logic and assign it after the out of bounds check. Link: https://lore.kernel.org/20250110162612.13983-1-aha310510@gmail.com Signed-off-by: Jeongjun Park <aha310510@gmail.com> [ sdr: rewrote change log ] Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-01-13 16:05:43 -05:00
Vincent Donnefort	0568c6ebf0	ring-buffer: Check for empty ring-buffer with rb_num_of_entries() ... Currently there are two ways of identifying an empty ring-buffer. One relying on the current status of the commit / reader page (rb_per_cpu_empty()) and the other on the write and read counters (rb_num_of_entries() used in rb_get_reader_page()). with rb_num_of_entries(). This intends to ease later introduction of ring-buffer writers which are out of the kernel control and with whom, the only information available is through the meta-page counters. Link: https://lore.kernel.org/20250108114536.627715-2-vdonnefort@google.com Signed-off-by: Vincent Donnefort <vdonnefort@google.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2025-01-13 15:39:50 -05:00
Edward Adam Davis	c58a812c8e	ring-buffer: Fix overflow in __rb_map_vma ... An overflow occurred when performing the following calculation: nr_pages = ((nr_subbufs + 1) << subbuf_order) - pgoff; Add a check before the calculation to avoid this problem. syzbot reported this as a slab-out-of-bounds in __rb_map_vma: BUG: KASAN: slab-out-of-bounds in __rb_map_vma+0x9ab/0xae0 kernel/trace/ring_buffer.c:7058 Read of size 8 at addr ffff8880767dd2b8 by task syz-executor187/5836 CPU: 0 UID: 0 PID: 5836 Comm: syz-executor187 Not tainted 6.13.0-rc2-syzkaller-00159-gf932fb9b4074 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024 Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xc3/0x620 mm/kasan/report.c:489 kasan_report+0xd9/0x110 mm/kasan/report.c:602 __rb_map_vma+0x9ab/0xae0 kernel/trace/ring_buffer.c:7058 ring_buffer_map+0x56e/0x9b0 kernel/trace/ring_buffer.c:7138 tracing_buffers_mmap+0xa6/0x120 kernel/trace/trace.c:8482 call_mmap include/linux/fs.h:2183 [inline] mmap_file mm/internal.h:124 [inline] __mmap_new_file_vma mm/vma.c:2291 [inline] __mmap_new_vma mm/vma.c:2355 [inline] __mmap_region+0x1786/0x2670 mm/vma.c:2456 mmap_region+0x127/0x320 mm/mmap.c:1348 do_mmap+0xc00/0xfc0 mm/mmap.c:496 vm_mmap_pgoff+0x1ba/0x360 mm/util.c:580 ksys_mmap_pgoff+0x32c/0x5c0 mm/mmap.c:542 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:89 [inline] __se_sys_mmap arch/x86/kernel/sys_x86_64.c:82 [inline] __x64_sys_mmap+0x125/0x190 arch/x86/kernel/sys_x86_64.c:82 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f The reproducer for this bug is: ------------------------8<------------------------- #include <fcntl.h> #include <stdlib.h> #include <unistd.h> #include <asm/types.h> #include <sys/mman.h> int main(int argc, char **argv) { int page_size = getpagesize(); int fd; void *meta; system("echo 1 > /sys/kernel/tracing/buffer_size_kb"); fd = open("/sys/kernel/tracing/per_cpu/cpu0/trace_pipe_raw", O_RDONLY); meta = mmap(NULL, page_size, PROT_READ, MAP_SHARED, fd, page_size * 5); } ------------------------>8------------------------- Cc: stable@vger.kernel.org Fixes: 117c39200d ("ring-buffer: Introducing ring-buffer mapping functions") Link: https://lore.kernel.org/tencent_06924B6674ED771167C23CC336C097223609@qq.com Reported-by: syzbot+345e4443a21200874b18@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=345e4443a21200874b18 Signed-off-by: Edward Adam Davis <eadavis@qq.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-12-18 14:15:10 -05:00
Linus Torvalds	f1db825805	trace ring-buffer updates for v6.13 ... - Limit time interrupts are disabled in rb_check_pages() The rb_check_pages() is called after the ring buffer size is updated to make sure that the ring buffer has not been corrupted. Commit c2274b908d ("ring-buffer: Fix a race between readers and resize checks") fixed a race with the check pages and simultaneous resizes to the ring buffer by adding a raw_spin_lock_irqsave() around the check operation. Although this was a simple fix, it would hold interrupts disabled for non determinative amount of time. This could harm PREEMPT_RT operations. Instead, modify the logic by adding a counter when the buffer is modified and to release the raw_spin_lock() at each iteration. It checks the counter under the lock to see if a modification happened during the loop, and if it did, it would restart the loop up to 3 times. After 3 times, it will simply exit the check, as it is unlikely that would ever happen as buffer resizes are rare occurrences. - Replace some open coded str_low_high() with the helper - Fix some documentation/comments -----BEGIN PGP SIGNATURE----- iIoEABYIADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCZz5KNxQccm9zdGVkdEBn b29kbWlzLm9yZwAKCRAp5XQQmuv6qiANAP4/6cSGOhQgIkaN8UsKmWTfBqU89JK2 a4tqAZWKsQormgEAkDLPD0Lda0drmu/Dwnr/klS21yyLcQBzyX1CYw9G4gY= =jkLz -----END PGP SIGNATURE----- Merge tag 'trace-ring-buffer-v6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull trace ring-buffer updates from Steven Rostedt: - Limit time interrupts are disabled in rb_check_pages() rb_check_pages() is called after the ring buffer size is updated to make sure that the ring buffer has not been corrupted. Commit c2274b908d ("ring-buffer: Fix a race between readers and resize checks") fixed a race with the check pages and simultaneous resizes to the ring buffer by adding a raw_spin_lock_irqsave() around the check operation. Although this was a simple fix, it would hold interrupts disabled for non determinative amount of time. This could harm PREEMPT_RT operations. Instead, modify the logic by adding a counter when the buffer is modified and to release the raw_spin_lock() at each iteration. It checks the counter under the lock to see if a modification happened during the loop, and if it did, it would restart the loop up to 3 times. After 3 times, it will simply exit the check, as it is unlikely that would ever happen as buffer resizes are rare occurrences. - Replace some open coded str_low_high() with the helper - Fix some documentation/comments * tag 'trace-ring-buffer-v6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ring-buffer: Correct a grammatical error in a comment ring-buffer: Use str_low_high() helper in ring_buffer_producer() ring-buffer: Reorganize kerneldoc parameter names ring-buffer: Limit time with disabled interrupts in rb_check_pages()	2024-11-22 13:11:17 -08:00
liujing	537affea16	ring-buffer: Correct a grammatical error in a comment ... The word "trace" begins with a consonant sound, so "a" should be used instead of "an". Link: https://lore.kernel.org/20241107095327.6390-1-liujing@cmss.chinamobile.com Signed-off-by: liujing <liujing@cmss.chinamobile.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-11-18 09:40:17 -05:00
Steven Rostedt	580bb355bc	Revert: "ring-buffer: Do not have boot mapped buffers hook to CPU hotplug" ... A crash happened when testing cpu hotplug with respect to the memory mapped ring buffers. It was assumed that the hot plug code was adding a per CPU buffer that was already created that caused the crash. The real problem was due to ref counting and was fixed by commit 2cf9733891 ("ring-buffer: Fix refcount setting of boot mapped buffers"). When a per CPU buffer is created, it will not be created again even with CPU hotplug, so the fix to not use CPU hotplug was a red herring. In fact, it caused only the boot CPU buffer to be created, leaving the other CPU per CPU buffers disabled. Revert that change as it was not the culprit of the fix it was intended to be. Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Link: https://lore.kernel.org/20241113230839.6c03640f@gandalf.local.home Fixes: 912da2c384 ("ring-buffer: Do not have boot mapped buffers hook to CPU hotplug") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-11-14 10:01:00 -05:00
Julia Lawall	0b60a7fb60	ring-buffer: Reorganize kerneldoc parameter names ... Reorganize kerneldoc parameter names to match the parameter order in the function header. Problems identified using Coccinelle. Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Link: https://lore.kernel.org/20240930112121.95324-22-Julia.Lawall@inria.fr Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-10-19 11:12:25 -04:00
Petr Pavlu	b237e1f7d2	ring-buffer: Limit time with disabled interrupts in rb_check_pages() ... The function rb_check_pages() validates the integrity of a specified per-CPU tracing ring buffer. It does so by traversing the underlying linked list and checking its next and prev links. To guarantee that the list isn't modified during the check, a caller typically needs to take cpu_buffer->reader_lock. This prevents the check from running concurrently, for example, with a potential reader which can make the list temporarily inconsistent when swapping its old reader page into the buffer. A problem with this approach is that the time when interrupts are disabled is non-deterministic, dependent on the ring buffer size. This particularly affects PREEMPT_RT because the reader_lock is a raw spinlock which doesn't become sleepable on PREEMPT_RT kernels. Modify the check so it still attempts to traverse the entire list, but gives up the reader_lock between checking individual pages. Introduce for this purpose a new variable ring_buffer_per_cpu.cnt which is bumped any time the list is modified. The value is used by rb_check_pages() to detect such a change and restart the check. Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Link: https://lore.kernel.org/20241015112810.27203-1-petr.pavlu@suse.com Signed-off-by: Petr Pavlu <petr.pavlu@suse.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-10-19 11:12:01 -04:00
Petr Pavlu	09661f75e7	ring-buffer: Fix reader locking when changing the sub buffer order ... The function ring_buffer_subbuf_order_set() updates each ring_buffer_per_cpu and installs new sub buffers that match the requested page order. This operation may be invoked concurrently with readers that rely on some of the modified data, such as the head bit (RB_PAGE_HEAD), or the ring_buffer_per_cpu.pages and reader_page pointers. However, no exclusive access is acquired by ring_buffer_subbuf_order_set(). Modifying the mentioned data while a reader also operates on them can then result in incorrect memory access and various crashes. Fix the problem by taking the reader_lock when updating a specific ring_buffer_per_cpu in ring_buffer_subbuf_order_set(). Link: https://lore.kernel.org/linux-trace-kernel/20240715145141.5528-1-petr.pavlu@suse.com/ Link: https://lore.kernel.org/linux-trace-kernel/20241010195849.2f77cc3f@gandalf.local.home/ Link: https://lore.kernel.org/linux-trace-kernel/20241011112850.17212b25@gandalf.local.home/ Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Link: https://lore.kernel.org/20241015112440.26987-1-petr.pavlu@suse.com Fixes: 8e7b58c27b ("ring-buffer: Just update the subbuffers when changing their allocation order") Signed-off-by: Petr Pavlu <petr.pavlu@suse.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-10-15 11:18:51 -04:00
Steven Rostedt	912da2c384	ring-buffer: Do not have boot mapped buffers hook to CPU hotplug ... The boot mapped ring buffer has its buffer mapped at a fixed location found at boot up. It is not dynamic. It cannot grow or be expanded when new CPUs come online. Do not hook fixed memory mapped ring buffers to the CPU hotplug callback, otherwise it can cause a crash when it tries to add the buffer to the memory that is already fully occupied. Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Link: https://lore.kernel.org/20241008143242.25e20801@gandalf.local.home Fixes: be68d63a13 ("ring-buffer: Add ring_buffer_alloc_range()") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-10-09 09:24:35 -04:00
Vincent Donnefort	eb2dcde9f9	ring-buffer: Align meta-page to sub-buffers for improved TLB usage ... Previously, the mapped ring-buffer layout caused misalignment between the meta-page and sub-buffers when the sub-buffer size was not a multiple of PAGE_SIZE. This prevented hardware with larger TLB entries from utilizing them effectively. Add a padding with the zero-page between the meta-page and sub-buffers. Also update the ring-buffer map_test to verify that padding. Link: https://lore.kernel.org/20240628104611.1443542-1-vdonnefort@google.com Signed-off-by: Vincent Donnefort <vdonnefort@google.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-08-26 13:42:23 -04:00
Steven Rostedt	d0f2d6e951	ring-buffer: Add magic and struct size to boot up meta data ... Add a magic number as well as save the struct size of the ring_buffer_meta structure in the meta data to also use as validation. Updating the magic number could be used to force a invalidation between kernel versions, and saving the structure size is also a good method to make sure the content is what is expected. Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Vincent Donnefort <vdonnefort@google.com> Link: https://lore.kernel.org/20240815115032.0c197b32@rorschach.local.home Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-08-26 13:34:22 -04:00
Steven Rostedt	bca704f62d	ring-buffer: Don't reset persistent ring-buffer meta saved addresses ... The text and data address is saved in the meta data so that it can be used to know the delta of the text and data addresses of the last boot compared to the text and data addresses of the current boot. The delta is used to convert function pointer entries in the ring buffer to something that can be used by kallsyms (note this only works for built-in functions). But the saved addresses get reset on boot up. If the buffer is not used and there's another reboot, then the saved text and data addresses will be of the last boot and not that of the boot that created the content in the ring buffer. To get an idea of the issue: # trace-cmd start -B boot_mapped -p function # reboot # trace-cmd show -B boot_mapped | tail <...>-1 [000] d..1. 461.983243: native_apic_msr_write <-native_kick_ap <...>-1 [000] d..1. 461.983244: __pfx_native_apic_msr_eoi <-native_kick_ap <...>-1 [000] d..1. 461.983244: reserve_irq_vector_locked <-native_kick_ap <...>-1 [000] d..1. 461.983262: branch_emulate_op <-native_kick_ap <...>-1 [000] d..1. 461.983262: __ia32_sys_ia32_pread64 <-native_kick_ap <...>-1 [000] d..1. 461.983263: native_kick_ap <-__smpboot_create_thread <...>-1 [000] d..1. 461.983263: store_cache_disable <-native_kick_ap <...>-1 [000] d..1. 461.983279: acpi_power_off_prepare <-native_kick_ap <...>-1 [000] d..1. 461.983280: __pfx_acpi_ns_delete_node <-acpi_suspend_enter <...>-1 [000] d..1. 461.983280: __pfx_acpi_os_release_lock <-acpi_suspend_enter # reboot # trace-cmd show -B boot_mapped |tail <...>-1 [000] d..1. 461.983243: 0xffffffffa9669220 <-0xffffffffa965f3db <...>-1 [000] d..1. 461.983244: 0xffffffffa96690f0 <-0xffffffffa965f3db <...>-1 [000] d..1. 461.983244: 0xffffffffa9663fa0 <-0xffffffffa965f3db <...>-1 [000] d..1. 461.983262: 0xffffffffa9672e80 <-0xffffffffa965f3e0 <...>-1 [000] d..1. 461.983262: 0xffffffffa962b940 <-0xffffffffa965f3ec <...>-1 [000] d..1. 461.983263: 0xffffffffa965f540 <-0xffffffffa96e1362 <...>-1 [000] d..1. 461.983263: 0xffffffffa963c940 <-0xffffffffa965f55b <...>-1 [000] d..1. 461.983279: 0xffffffffa9ee30c0 <-0xffffffffa965f59b <...>-1 [000] d..1. 461.983280: 0xffffffffa9f16c10 <-0xffffffffa9ee3157 <...>-1 [000] d..1. 461.983280: 0xffffffffa9ee02e0 <-0xffffffffa9ee3157 By not updating the saved text and data addresses in the meta data at every boot up and only updating them when the buffer is reset, it allows multiple boots to see the same data. Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Vincent Donnefort <vdonnefort@google.com> Link: https://lore.kernel.org/20240815113629.0dc90af8@rorschach.local.home Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-08-26 13:33:53 -04:00
Steven Rostedt	ee057c8c19	Linux 6.11-rc3 ... -----BEGIN PGP SIGNATURE----- iQFSBAABCAA8FiEEq68RxlopcLEwq+PEeb4+QwBBGIYFAma5LLIeHHRvcnZhbGRz QGxpbnV4LWZvdW5kYXRpb24ub3JnAAoJEHm+PkMAQRiGwUAIAJNwbkdgTIqEsyBU wsFcXGaFSsGJNbTulINJb34jl2gD2yr4pmnnrA0NePW1TUKOnx169hNMF8NWbr/A 0cHIREV9cyfnm/kzAcnHn7cWLSmsKd+x3TnCbCyodDZQDJzdLmw3LQG+4dTNJbw1 WtJO/EoaU4qaydW2VxtApw54sirq5bopZz7rpcRapA1afzbA2TUDbnnuEWjm9KCF 5K+RZTJZA/xI9gqEwJB+/p5FglW4n/T3xcDwaQp5uFsDskgV5e1AUrRLM+icTsem 0Egrs8Ca2Vp4oBM+r9miCSwjRu04jLKyuu20p7AN8zXLyN7WGAjduS15Dv+aHRZ/ 9XABZs0= =/T17 -----END PGP SIGNATURE----- Merge tag 'v6.11-rc3' into trace/ring-buffer/core The "reserve_mem" kernel command line parameter has been pulled into v6.11. Merge the latest -rc3 to allow the persistent ring buffer memory to be able to be mapped at the address specified by the "reserve_mem" command line parameter. Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-08-14 16:59:28 -04:00
Jianhui Zhou	58f7e4d7ba	ring-buffer: Remove unused function ring_buffer_nr_pages() ... Because ring_buffer_nr_pages() is not an inline function and user accesses buffer->buffers[cpu]->nr_pages directly, the function ring_buffer_nr_pages is removed. Signed-off-by: Jianhui Zhou <912460177@qq.com> Link: https://lore.kernel.org/tencent_F4A7E9AB337F44E0F4B858D07D19EF460708@qq.com Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-08-07 20:26:44 -04:00
Thorsten Blum	b96c312551	ring-buffer: Use vma_pages() helper function ... Use the vma_pages() helper function and fix the following Coccinelle/coccicheck warning reported by vma_pages.cocci: WARNING: Consider using vma_pages helper on vma Rename the local variable vma_pages accordingly. Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com> Link: https://lore.kernel.org/20240709215657.322071-2-thorsten.blum@toblux.com Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-07-15 15:09:06 -04:00
Steven Rostedt (Google)	7a1d1e4b96	tracing/ring-buffer: Add last_boot_info file to boot instance ... If an instance is mapped to memory on boot up, create a new file called "last_boot_info" that will hold information that can be used to properly parse the raw data in the ring buffer. It will export the delta of the addresses for text and data from what it was from the last boot. It does not expose actually addresses (unless you knew what the actual address was from the last boot). The output will look like: # cat last_boot_info text delta: -268435456 data delta: -268435456 The text and data are kept separate in case they are ever made different. Link: https://lkml.kernel.org/r/20240612232026.658680738@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vineeth Pillai <vineeth@bitbyteword.org> Cc: Youssef Esmat <youssefesmat@google.com> Cc: Beau Belgrave <beaub@linux.microsoft.com> Cc: Alexander Graf <graf@amazon.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: David Howells <dhowells@redhat.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Ross Zwisler <zwisler@google.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-06-14 12:28:22 -04:00
Steven Rostedt (Google)	8f3e665965	ring-buffer: Save text and data locations in mapped meta data ... When a ring buffer is mapped to a specific address, save the address of a text function and some data. This will be used to determine the delta between the last boot and the current boot for pointers to functions as well as to data. Link: https://lkml.kernel.org/r/20240612232026.496176678@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vineeth Pillai <vineeth@bitbyteword.org> Cc: Youssef Esmat <youssefesmat@google.com> Cc: Beau Belgrave <beaub@linux.microsoft.com> Cc: Alexander Graf <graf@amazon.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: David Howells <dhowells@redhat.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Ross Zwisler <zwisler@google.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-06-14 12:28:21 -04:00
Steven Rostedt (Google)	5f3b6e839f	ring-buffer: Validate boot range memory events ... Make sure all the events in each of the sub-buffers that were mapped in a memory region are valid. This moves the code that walks the buffers for time-stamp validation out of the CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS ifdef block and is used to validate the content. Only the ring buffer event meta data and time stamps are checked and not the data load. This also has a second purpose. The buffer_page structure that points to the data sub-buffers has accounting that keeps track of the number of events that are on the sub-buffer. This updates that counter as well. That counter is used in reading the buffer and knowing if the ring buffer is empty or not. Link: https://lkml.kernel.org/r/20240612232026.172503570@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vineeth Pillai <vineeth@bitbyteword.org> Cc: Youssef Esmat <youssefesmat@google.com> Cc: Beau Belgrave <beaub@linux.microsoft.com> Cc: Alexander Graf <graf@amazon.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: David Howells <dhowells@redhat.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Ross Zwisler <zwisler@google.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-06-14 12:28:21 -04:00
Steven Rostedt (Google)	c76883f18e	ring-buffer: Add test if range of boot buffer is valid ... Add a test against the ring buffer memory range to see if it has valid data. The ring_buffer_meta structure is given a new field called "first_buffer" which holds the address of the first sub-buffer. This is used to both determine if the other fields are valid as well as finding the offset between the old addresses of the sub-buffer from the previous boot to the new addresses of the current boot. Since the values for nr_subbufs and subbuf_size is to be the same, check if the values in the meta page match the values calculated. Take the range of the first_buffer and the total size of all the buffers and make sure the saved head_buffer and commit_buffer fall in the range. Iterate through all the sub-buffers to make sure that the values in the sub-buffer "commit" field (the field that holds the amount of data on the sub-buffer) is within the end of the sub-buffer. Also check the index array to make sure that all the indexes are within nr_subbufs. Link: https://lkml.kernel.org/r/20240612232026.013843655@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vineeth Pillai <vineeth@bitbyteword.org> Cc: Youssef Esmat <youssefesmat@google.com> Cc: Beau Belgrave <beaub@linux.microsoft.com> Cc: Alexander Graf <graf@amazon.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: David Howells <dhowells@redhat.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Ross Zwisler <zwisler@google.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-06-14 12:28:21 -04:00
Steven Rostedt (Google)	950032ffce	ring-buffer: Add output of ring buffer meta page ... Add a buffer_meta per-cpu file for the trace instance that is mapped to boot memory. This shows the current meta-data and can be used by user space tools to record off the current mappings to help reconstruct the ring buffer after a reboot. It does not expose any virtual addresses, just indexes into the sub-buffer pages. Link: https://lkml.kernel.org/r/20240612232025.854471446@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vineeth Pillai <vineeth@bitbyteword.org> Cc: Youssef Esmat <youssefesmat@google.com> Cc: Beau Belgrave <beaub@linux.microsoft.com> Cc: Alexander Graf <graf@amazon.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: David Howells <dhowells@redhat.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Ross Zwisler <zwisler@google.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-06-14 12:28:21 -04:00
Steven Rostedt (Google)	b14d032973	ring-buffer: Add ring_buffer_meta data ... Populate the ring_buffer_meta array. It holds the pointer to the head_buffer (next to read), the commit_buffer (next to write) the size of the sub-buffers, number of sub-buffers and an array that keeps track of the order of the sub-buffers. This information will be stored in the persistent memory to help on reboot to reconstruct the ring buffer. Link: https://lkml.kernel.org/r/20240612232025.530733577@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vineeth Pillai <vineeth@bitbyteword.org> Cc: Youssef Esmat <youssefesmat@google.com> Cc: Beau Belgrave <beaub@linux.microsoft.com> Cc: Alexander Graf <graf@amazon.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: David Howells <dhowells@redhat.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Ross Zwisler <zwisler@google.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-06-14 12:28:20 -04:00
Steven Rostedt (Google)	be68d63a13	ring-buffer: Add ring_buffer_alloc_range() ... In preparation to allowing the trace ring buffer to be allocated in a range of memory that is persistent across reboots, add ring_buffer_alloc_range(). It takes a contiguous range of memory and will split it up evenly for the per CPU ring buffers. If there's not enough memory to handle all CPUs with the minimum size, it will fail to allocate the ring buffer. Link: https://lkml.kernel.org/r/20240612232025.363998725@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vineeth Pillai <vineeth@bitbyteword.org> Cc: Youssef Esmat <youssefesmat@google.com> Cc: Beau Belgrave <beaub@linux.microsoft.com> Cc: Alexander Graf <graf@amazon.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: David Howells <dhowells@redhat.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Ross Zwisler <zwisler@google.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-06-14 12:28:20 -04:00
Steven Rostedt (Google)	dd4900d94f	ring-buffer: Allow mapped field to be set without mapping ... In preparation for having the ring buffer mapped to a dedicated location, which will have the same restrictions as user space memory mapped buffers, allow it to use the "mapped" field of the ring_buffer_per_cpu structure without having the user space meta page mapping. When this starts using the mapped field, it will need to handle adding a user space mapping (and removing it) from a ring buffer that is using a dedicated memory range. Link: https://lkml.kernel.org/r/20240612232025.190908567@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vineeth Pillai <vineeth@bitbyteword.org> Cc: Youssef Esmat <youssefesmat@google.com> Cc: Beau Belgrave <beaub@linux.microsoft.com> Cc: Alexander Graf <graf@amazon.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: David Howells <dhowells@redhat.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Ross Zwisler <zwisler@google.com> Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-06-14 12:28:20 -04:00
Petr Pavlu	c2274b908d	ring-buffer: Fix a race between readers and resize checks ... The reader code in rb_get_reader_page() swaps a new reader page into the ring buffer by doing cmpxchg on old->list.prev->next to point it to the new page. Following that, if the operation is successful, old->list.next->prev gets updated too. This means the underlying doubly-linked list is temporarily inconsistent, page->prev->next or page->next->prev might not be equal back to page for some page in the ring buffer. The resize operation in ring_buffer_resize() can be invoked in parallel. It calls rb_check_pages() which can detect the described inconsistency and stop further tracing: [ 190.271762] ------------[ cut here ]------------ [ 190.271771] WARNING: CPU: 1 PID: 6186 at kernel/trace/ring_buffer.c:1467 rb_check_pages.isra.0+0x6a/0xa0 [ 190.271789] Modules linked in: [...] [ 190.271991] Unloaded tainted modules: intel_uncore_frequency(E):1 skx_edac(E):1 [ 190.272002] CPU: 1 PID: 6186 Comm: cmd.sh Kdump: loaded Tainted: G E 6.9.0-rc6-default #5 158d3e1e6d0b091c34c3b96bfd99a1c58306d79f [ 190.272011] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552c-rebuilt.opensuse.org 04/01/2014 [ 190.272015] RIP: 0010:rb_check_pages.isra.0+0x6a/0xa0 [ 190.272023] Code: [...] [ 190.272028] RSP: 0018:ffff9c37463abb70 EFLAGS: 00010206 [ 190.272034] RAX: ffff8eba04b6cb80 RBX: 0000000000000007 RCX: ffff8eba01f13d80 [ 190.272038] RDX: ffff8eba01f130c0 RSI: ffff8eba04b6cd00 RDI: ffff8eba0004c700 [ 190.272042] RBP: ffff8eba0004c700 R08: 0000000000010002 R09: 0000000000000000 [ 190.272045] R10: 00000000ffff7f52 R11: ffff8eba7f600000 R12: ffff8eba0004c720 [ 190.272049] R13: ffff8eba00223a00 R14: 0000000000000008 R15: ffff8eba067a8000 [ 190.272053] FS: 00007f1bd64752c0(0000) GS:ffff8eba7f680000(0000) knlGS:0000000000000000 [ 190.272057] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 190.272061] CR2: 00007f1bd6662590 CR3: 000000010291e001 CR4: 0000000000370ef0 [ 190.272070] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 190.272073] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 190.272077] Call Trace: [ 190.272098] <TASK> [ 190.272189] ring_buffer_resize+0x2ab/0x460 [ 190.272199] __tracing_resize_ring_buffer.part.0+0x23/0xa0 [ 190.272206] tracing_resize_ring_buffer+0x65/0x90 [ 190.272216] tracing_entries_write+0x74/0xc0 [ 190.272225] vfs_write+0xf5/0x420 [ 190.272248] ksys_write+0x67/0xe0 [ 190.272256] do_syscall_64+0x82/0x170 [ 190.272363] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 190.272373] RIP: 0033:0x7f1bd657d263 [ 190.272381] Code: [...] [ 190.272385] RSP: 002b:00007ffe72b643f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 [ 190.272391] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f1bd657d263 [ 190.272395] RDX: 0000000000000002 RSI: 0000555a6eb538e0 RDI: 0000000000000001 [ 190.272398] RBP: 0000555a6eb538e0 R08: 000000000000000a R09: 0000000000000000 [ 190.272401] R10: 0000555a6eb55190 R11: 0000000000000246 R12: 00007f1bd6662500 [ 190.272404] R13: 0000000000000002 R14: 00007f1bd6667c00 R15: 0000000000000002 [ 190.272412] </TASK> [ 190.272414] ---[ end trace 0000000000000000 ]--- Note that ring_buffer_resize() calls rb_check_pages() only if the parent trace_buffer has recording disabled. Recent commit d78ab79270 ("tracing: Stop current tracer when resizing buffer") causes that it is now always the case which makes it more likely to experience this issue. The window to hit this race is nonetheless very small. To help reproducing it, one can add a delay loop in rb_get_reader_page(): ret = rb_head_page_replace(reader, cpu_buffer->reader_page); if (!ret) goto spin; for (unsigned i = 0; i < 1U << 26; i++) /* inserted delay loop */ __asm__ __volatile__ ("" : : : "memory"); rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list; .. and then run the following commands on the target system: echo 1 > /sys/kernel/tracing/events/sched/sched_switch/enable while true; do echo 16 > /sys/kernel/tracing/buffer_size_kb; sleep 0.1 echo 8 > /sys/kernel/tracing/buffer_size_kb; sleep 0.1 done & while true; do for i in /sys/kernel/tracing/per_cpu/*; do timeout 0.1 cat $i/trace_pipe; sleep 0.2 done done To fix the problem, make sure ring_buffer_resize() doesn't invoke rb_check_pages() concurrently with a reader operating on the same ring_buffer_per_cpu by taking its cpu_buffer->reader_lock. Link: https://lore.kernel.org/linux-trace-kernel/20240517134008.24529-3-petr.pavlu@suse.com Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Fixes: 659f451ff2 ("ring-buffer: Add integrity check at end of iter read") Signed-off-by: Petr Pavlu <petr.pavlu@suse.com> [ Fixed whitespace ] Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-05-21 19:03:35 -04:00
Petr Pavlu	ea70a9628e	ring-buffer: Correct stale comments related to non-consuming readers ... Adjust the following code documentation: * Kernel-doc comments for ring_buffer_read_prepare() and ring_buffer_read_finish() mention that recording to the ring buffer is disabled when the read is active. Remove mention of this restriction because it was already lifted in commit 1039221cc2 ("ring-buffer: Do not disable recording when there is an iterator"). * Function ring_buffer_read_finish() performs a self-check of the ring-buffer by locking cpu_buffer->reader_lock and then calling rb_check_pages(). The preceding comment explains that the lock is needed because rb_check_pages() clears the HEAD flag required by readers which might be running in parallel. Remove this explanation because commit 8843e06f67 ("ring-buffer: Handle race between rb_move_tail and rb_check_pages") simplified the function so it no longer resets the mentioned flag. Nonetheless, the lock is still needed because a reader swapping a page into the ring buffer can make the underlying doubly-linked list temporarily inconsistent. This is a non-functional change. Link: https://lore.kernel.org/linux-trace-kernel/20240517134008.24529-2-petr.pavlu@suse.com Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Petr Pavlu <petr.pavlu@suse.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-05-21 19:03:35 -04:00
Steven Rostedt (Google)	b9c6820f02	ring-buffer: Add cast to unsigned long addr passed to virt_to_page() ... The sub-buffer pages are held in an unsigned long array, and when it is passed to virt_to_page() a cast is needed. Link: https://lore.kernel.org/all/20240515124808.06279d04@canb.auug.org.au/ Link: https://lore.kernel.org/linux-trace-kernel/20240515010558.4abaefdd@rorschach.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Fixes: 117c39200d ("ring-buffer: Introducing ring-buffer mapping functions") Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-05-15 01:28:42 -04:00
Steven Rostedt (Google)	fe832be05a	ring-buffer: Have mmapped ring buffer keep track of missed events ... While testing libtracefs on the mmapped ring buffer, the test that checks if missed events are accounted for failed when using the mapped buffer. This is because the mapped page does not update the missed events that were dropped because the writer filled up the ring buffer before the reader could catch it. Add the missed events to the reader page/sub-buffer when the IOCTL is done and a new reader page is acquired. Note that all accesses to the reader_page via rb_page_commit() had to be switched to rb_page_size(), and rb_page_size() which was just a copy of rb_page_commit() but now it masks out the RB_MISSED bits. This is needed as the mapped reader page is still active in the ring buffer code and where it reads the commit field of the bpage for the size, it now must mask it otherwise the missed bits that are now set will corrupt the size returned. Link: https://lore.kernel.org/linux-trace-kernel/20240312175405.12fb6726@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Vincent Donnefort <vdonnefort@google.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-05-13 19:55:22 -04:00
Vincent Donnefort	117c39200d	ring-buffer: Introducing ring-buffer mapping functions ... In preparation for allowing the user-space to map a ring-buffer, add a set of mapping functions: ring_buffer_{map,unmap}() And controls on the ring-buffer: ring_buffer_map_get_reader() /* swap reader and head */ Mapping the ring-buffer also involves: A unique ID for each subbuf of the ring-buffer, currently they are only identified through their in-kernel VA. A meta-page, where are stored ring-buffer statistics and a description for the current reader The linear mapping exposes the meta-page, and each subbuf of the ring-buffer, ordered following their unique ID, assigned during the first mapping. Once mapped, no subbuf can get in or out of the ring-buffer: the buffer size will remain unmodified and the splice enabling functions will in reality simply memcpy the data instead of swapping subbufs. Link: https://lore.kernel.org/linux-trace-kernel/20240510140435.3550353-3-vdonnefort@google.com CC: <linux-mm@kvack.org> Signed-off-by: Vincent Donnefort <vdonnefort@google.com> Acked-by: David Hildenbrand <david@redhat.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-05-13 18:09:56 -04:00
Vincent Donnefort	c09d4167b5	ring-buffer: Allocate sub-buffers with __GFP_COMP ... In preparation for the ring-buffer memory mapping, allocate compound pages for the ring-buffer sub-buffers to enable us to map them to user-space with vm_insert_pages(). Link: https://lore.kernel.org/linux-trace-kernel/20240510140435.3550353-2-vdonnefort@google.com Acked-by: David Hildenbrand <david@redhat.com> Signed-off-by: Vincent Donnefort <vdonnefort@google.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-05-13 18:09:55 -04:00
Steven Rostedt (Google)	ffe3986fec	ring-buffer: Only update pages_touched when a new page is touched ... The "buffer_percent" logic that is used by the ring buffer splice code to only wake up the tasks when there's no data after the buffer is filled to the percentage of the "buffer_percent" file is dependent on three variables that determine the amount of data that is in the ring buffer: 1) pages_read - incremented whenever a new sub-buffer is consumed 2) pages_lost - incremented every time a writer overwrites a sub-buffer 3) pages_touched - incremented when a write goes to a new sub-buffer The percentage is the calculation of: (pages_touched - (pages_lost + pages_read)) / nr_pages Basically, the amount of data is the total number of sub-bufs that have been touched, minus the number of sub-bufs lost and sub-bufs consumed. This is divided by the total count to give the buffer percentage. When the percentage is greater than the value in the "buffer_percent" file, it wakes up splice readers waiting for that amount. It was observed that over time, the amount read from the splice was constantly decreasing the longer the trace was running. That is, if one asked for 60%, it would read over 60% when it first starts tracing, but then it would be woken up at under 60% and would slowly decrease the amount of data read after being woken up, where the amount becomes much less than the buffer percent. This was due to an accounting of the pages_touched incrementation. This value is incremented whenever a writer transfers to a new sub-buffer. But the place where it was incremented was incorrect. If a writer overflowed the current sub-buffer it would go to the next one. If it gets preempted by an interrupt at that time, and the interrupt performs a trace, it too will end up going to the next sub-buffer. But only one should increment the counter. Unfortunately, that was not the case. Change the cmpxchg() that does the real switch of the tail-page into a try_cmpxchg(), and on success, perform the increment of pages_touched. This will only increment the counter once for when the writer moves to a new sub-buffer, and not when there's a race and is incremented for when a writer and its preempting writer both move to the same new sub-buffer. Link: https://lore.kernel.org/linux-trace-kernel/20240409151309.0d0e5056@gandalf.local.home Cc: stable@vger.kernel.org Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Fixes: 2c2b0a78b3 ("ring-buffer: Add percentage of ring buffer full to wake up reader") Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-04-11 17:49:57 -04:00
Steven Rostedt (Google)	b70f293824	ring-buffer: Make wake once of ring_buffer_wait() more robust ... The default behavior of ring_buffer_wait() when passed a NULL "cond" parameter is to exit the function the first time it is woken up. The current implementation uses a counter that starts at zero and when it is greater than one it exits the wait_event_interruptible(). But this relies on the internal working of wait_event_interruptible() as that code basically has: if (cond) return; prepare_to_wait(); if (!cond) schedule(); finish_wait(); That is, cond is called twice before it sleeps. The default cond of ring_buffer_wait() needs to account for that and wait for its counter to increment twice before exiting. Instead, use the seq/atomic_inc logic that is used by the tracing code that calls this function. Add an atomic_t seq to rb_irq_work and when cond is NULL, have the default callback take a descriptor as its data that holds the rbwork and the value of the seq when it started. The wakeups will now increment the rbwork->seq and the cond callback will simply check if that number is different, and no longer have to rely on the implementation of wait_event_interruptible(). Link: https://lore.kernel.org/linux-trace-kernel/20240315063115.6cb5d205@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Fixes: 7af9ded0c2 ("ring-buffer: Use wait_event_interruptible() in ring_buffer_wait()") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-03-18 10:11:43 -04:00
linke li	f1e30cb636	ring-buffer: use READ_ONCE() to read cpu_buffer->commit_page in concurrent environment ... In function ring_buffer_iter_empty(), cpu_buffer->commit_page is read while other threads may change it. It may cause the time_stamp that read in the next line come from a different page. Use READ_ONCE() to avoid having to reason about compiler optimizations now and in future. Link: https://lore.kernel.org/linux-trace-kernel/tencent_DFF7D3561A0686B5E8FC079150A02505180A@qq.com Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: linke li <lilinke99@qq.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-03-17 07:58:53 -04:00
Vincent Donnefort	6b76323e5a	ring-buffer: Zero ring-buffer sub-buffers ... In preparation for the ring-buffer memory mapping where each subbuf will be accessible to user-space, zero all the page allocations. Link: https://lore.kernel.org/linux-trace-kernel/20240220202310.2489614-2-vdonnefort@google.com Signed-off-by: Vincent Donnefort <vdonnefort@google.com> Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-03-17 07:58:53 -04:00
Linus Torvalds	63bd30f249	Tracing/ring-buffer fixes for 6.8 (to be applied in 6.9-rc): ... - Do not update shortest_full in rb_watermark_hit() if the watermark is hit. The shortest_full field was being updated regardless if the task was going to wait or not. If the watermark is hit, then the task is not going to wait, so do not update the shortest_full field (used by the waker). - Update shortest_full field before setting the full_waiters_pending flag In the poll logic, the full_waiters_pending flag was being set before the shortest_full field was set. If the full_waiters_pending flag is set, writers will check the shortest_full field which has the least percentage of data that the ring buffer needs to be filled before waking up. The writer will check shortest_full if full_waiters_pending is set, and if the ring buffer percentage filled is greater than shortest full, then it will call the irq_work to wake up the waiters. The problem was that the poll logic set the full_waiters_pending flag before updating shortest_full, which when zero will always trigger the writer to call the irq_work to wake up the waiters. The irq_work will reset the shortest_full field back to zero as the woken waiters is suppose to reset it. - There's some optimized logic in the rb_watermark_hit() that is used in ring_buffer_wait(). Use that helper function in the poll logic as well. - Restructure ring_buffer_wait() to use wait_event_interruptible() The logic to wake up pending readers when the file descriptor is closed is racy. Restructure ring_buffer_wait() to allow callers to pass in conditions besides the ring buffer having enough data in it by using wait_event_interruptible(). - Update the tracing_wait_on_pipe() to call ring_buffer_wait() with its own conditions to exit the wait loop. -----BEGIN PGP SIGNATURE----- iIoEABYIADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCZfH6MRQccm9zdGVkdEBn b29kbWlzLm9yZwAKCRAp5XQQmuv6qtlwAP9ZoSIkvw2MVu7FclgAguaX2CaylGEw sv0wZaCy1kgAPgD8CFhezZcHrt/RwJibpMxVnUs+DDqYnGdJsHYLihlbWgg= =99FG -----END PGP SIGNATURE----- Merge tag 'trace-ring-buffer-v6.8-rc7-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing updates from Steven Rostedt: - Do not update shortest_full in rb_watermark_hit() if the watermark is hit. The shortest_full field was being updated regardless if the task was going to wait or not. If the watermark is hit, then the task is not going to wait, so do not update the shortest_full field (used by the waker). - Update shortest_full field before setting the full_waiters_pending flag In the poll logic, the full_waiters_pending flag was being set before the shortest_full field was set. If the full_waiters_pending flag is set, writers will check the shortest_full field which has the least percentage of data that the ring buffer needs to be filled before waking up. The writer will check shortest_full if full_waiters_pending is set, and if the ring buffer percentage filled is greater than shortest full, then it will call the irq_work to wake up the waiters. The problem was that the poll logic set the full_waiters_pending flag before updating shortest_full, which when zero will always trigger the writer to call the irq_work to wake up the waiters. The irq_work will reset the shortest_full field back to zero as the woken waiters is suppose to reset it. - There's some optimized logic in the rb_watermark_hit() that is used in ring_buffer_wait(). Use that helper function in the poll logic as well. - Restructure ring_buffer_wait() to use wait_event_interruptible() The logic to wake up pending readers when the file descriptor is closed is racy. Restructure ring_buffer_wait() to allow callers to pass in conditions besides the ring buffer having enough data in it by using wait_event_interruptible(). - Update the tracing_wait_on_pipe() to call ring_buffer_wait() with its own conditions to exit the wait loop. * tag 'trace-ring-buffer-v6.8-rc7-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: tracing/ring-buffer: Fix wait_on_pipe() race ring-buffer: Use wait_event_interruptible() in ring_buffer_wait() ring-buffer: Reuse rb_watermark_hit() for the poll logic ring-buffer: Fix full_waiters_pending in poll ring-buffer: Do not set shortest_full when full target is hit	2024-03-14 16:25:01 -07:00
Steven Rostedt (Google)	2aa043a55b	tracing/ring-buffer: Fix wait_on_pipe() race ... When the trace_pipe_raw file is closed, there should be no new readers on the file descriptor. This is mostly handled with the waking and wait_index fields of the iterator. But there's still a slight race. CPU 0 CPU 1 ----- ----- wait_index++; index = wait_index; ring_buffer_wake_waiters(); wait_on_pipe() ring_buffer_wait(); The ring_buffer_wait() will miss the wakeup from CPU 1. The problem is that the ring_buffer_wait() needs the logic of: prepare_to_wait(); if (!condition) schedule(); Where the missing condition check is the iter->wait_index update. Have the ring_buffer_wait() take a conditional callback function and a data parameter that can be used within the wait_event_interruptible() of the ring_buffer_wait() function. In wait_on_pipe(), pass a condition function that will check if the wait_index has been updated, if it has, it will return true to break out of the wait_event_interruptible() loop. Create a new field "closed" in the trace_iterator and set it in the .flush() callback before calling ring_buffer_wake_waiters(). This will keep any new readers from waiting on a closed file descriptor. Have the wait_on_pipe() condition callback also check the closed field. Change the wait_index field of the trace_iterator to atomic_t. There's no reason it needs to be 'long' and making it atomic and using atomic_read_acquire() and atomic_fetch_inc_release() will provide the necessary memory barriers. Add a "woken" flag to tracing_buffers_splice_read() to exit the loop after one more try to fetch data. That is, if it waited for data and something woke it up, it should try to collect any new data and then exit back to user space. Link: https://lore.kernel.org/linux-trace-kernel/CAHk-=wgsNgewHFxZAJiAQznwPMqEtQmi1waeS2O1v6L4c_Um5A@mail.gmail.com/ Link: https://lore.kernel.org/linux-trace-kernel/20240312121703.557950713@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: linke li <lilinke99@qq.com> Cc: Rabin Vincent <rabin@rab.in> Fixes: f3ddb74ad0 ("tracing: Wake up ring buffer waiters on closing of the file") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-03-12 12:44:48 -04:00
Steven Rostedt (Google)	7af9ded0c2	ring-buffer: Use wait_event_interruptible() in ring_buffer_wait() ... Convert ring_buffer_wait() over to wait_event_interruptible(). The default condition is to execute the wait loop inside __wait_event() just once. This does not change the ring_buffer_wait() prototype yet, but restructures the code so that it can take a "cond" and "data" parameter and will call wait_event_interruptible() with a helper function as the condition. The helper function (rb_wait_cond) takes the cond function and data parameters. It will first check if the buffer hit the watermark defined by the "full" parameter and then call the passed in condition parameter. If either are true, it returns true. If rb_wait_cond() does not return true, it will set the appropriate "waiters_pending" flag and returns false. Link: https://lore.kernel.org/linux-trace-kernel/CAHk-=wgsNgewHFxZAJiAQznwPMqEtQmi1waeS2O1v6L4c_Um5A@mail.gmail.com/ Link: https://lore.kernel.org/linux-trace-kernel/20240312121703.399598519@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: linke li <lilinke99@qq.com> Cc: Rabin Vincent <rabin@rab.in> Fixes: f3ddb74ad0 ("tracing: Wake up ring buffer waiters on closing of the file") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-03-12 12:44:35 -04:00
Steven Rostedt (Google)	e36f19a645	ring-buffer: Reuse rb_watermark_hit() for the poll logic ... The check for knowing if the poll should wait or not is basically the exact same logic as rb_watermark_hit(). The only difference is that rb_watermark_hit() also handles the !full case. But for the full case, the logic is the same. Just call that instead of duplicating the code in ring_buffer_poll_wait(). Link: https://lore.kernel.org/linux-trace-kernel/20240312131952.802267543@goodmis.org Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-03-12 12:44:07 -04:00
Steven Rostedt (Google)	8145f1c35f	ring-buffer: Fix full_waiters_pending in poll ... If a reader of the ring buffer is doing a poll, and waiting for the ring buffer to hit a specific watermark, there could be a case where it gets into an infinite ping-pong loop. The poll code has: rbwork->full_waiters_pending = true; if (!cpu_buffer->shortest_full || cpu_buffer->shortest_full > full) cpu_buffer->shortest_full = full; The writer will see full_waiters_pending and check if the ring buffer is filled over the percentage of the shortest_full value. If it is, it calls an irq_work to wake up all the waiters. But the code could get into a circular loop: CPU 0 CPU 1 ----- ----- [ Poll ] [ shortest_full = 0 ] rbwork->full_waiters_pending = true; if (rbwork->full_waiters_pending && [ buffer percent ] > shortest_full) { rbwork->wakeup_full = true; [ queue_irqwork ] cpu_buffer->shortest_full = full; [ IRQ work ] if (rbwork->wakeup_full) { cpu_buffer->shortest_full = 0; wakeup poll waiters; [woken] if ([ buffer percent ] > full) break; rbwork->full_waiters_pending = true; if (rbwork->full_waiters_pending && [ buffer percent ] > shortest_full) { rbwork->wakeup_full = true; [ queue_irqwork ] cpu_buffer->shortest_full = full; [ IRQ work ] if (rbwork->wakeup_full) { cpu_buffer->shortest_full = 0; wakeup poll waiters; [woken] [ Wash, rinse, repeat! ] In the poll, the shortest_full needs to be set before the full_pending_waiters, as once that is set, the writer will compare the current shortest_full (which is incorrect) to decide to call the irq_work, which will reset the shortest_full (expecting the readers to update it). Also move the setting of full_waiters_pending after the check if the ring buffer has the required percentage filled. There's no reason to tell the writer to wake up waiters if there are no waiters. Link: https://lore.kernel.org/linux-trace-kernel/20240312131952.630922155@goodmis.org Cc: stable@vger.kernel.org Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Fixes: 42fb0a1e84 ("tracing/ring-buffer: Have polling block on watermark") Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-03-12 12:43:30 -04:00
Steven Rostedt (Google)	761d9473e2	ring-buffer: Do not set shortest_full when full target is hit ... The rb_watermark_hit() checks if the amount of data in the ring buffer is above the percentage level passed in by the "full" variable. If it is, it returns true. But it also sets the "shortest_full" field of the cpu_buffer that informs writers that it needs to call the irq_work if the amount of data on the ring buffer is above the requested amount. The rb_watermark_hit() always sets the shortest_full even if the amount in the ring buffer is what it wants. As it is not going to wait, because it has what it wants, there's no reason to set shortest_full. Link: https://lore.kernel.org/linux-trace-kernel/20240312115641.6aa8ba08@gandalf.local.home Cc: stable@vger.kernel.org Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Fixes: 42fb0a1e84 ("tracing/ring-buffer: Have polling block on watermark") Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-03-12 12:40:28 -04:00
Linus Torvalds	685d982112	Core x86 changes for v6.9: ... - The biggest change is the rework of the percpu code, to support the 'Named Address Spaces' GCC feature, by Uros Bizjak: - This allows C code to access GS and FS segment relative memory via variables declared with such attributes, which allows the compiler to better optimize those accesses than the previous inline assembly code. - The series also includes a number of micro-optimizations for various percpu access methods, plus a number of cleanups of %gs accesses in assembly code. - These changes have been exposed to linux-next testing for the last ~5 months, with no known regressions in this area. - Fix/clean up __switch_to()'s broken but accidentally working handling of FPU switching - which also generates better code. - Propagate more RIP-relative addressing in assembly code, to generate slightly better code. - Rework the CPU mitigations Kconfig space to be less idiosyncratic, to make it easier for distros to follow & maintain these options. - Rework the x86 idle code to cure RCU violations and to clean up the logic. - Clean up the vDSO Makefile logic. - Misc cleanups and fixes. [ Please note that there's a higher number of merge commits in this branch (three) than is usual in x86 topic trees. This happened due to the long testing lifecycle of the percpu changes that involved 3 merge windows, which generated a longer history and various interactions with other core x86 changes that we felt better about to carry in a single branch. ] Signed-off-by: Ingo Molnar <mingo@kernel.org> -----BEGIN PGP SIGNATURE----- iQJFBAABCgAvFiEEBpT5eoXrXCwVQwEKEnMQ0APhK1gFAmXvB0gRHG1pbmdvQGtl cm5lbC5vcmcACgkQEnMQ0APhK1jUqRAAqnEQPiabF5acQlHrwviX+cjSobDlqtH5 9q2AQy9qaEHapzD0XMOxvFye6XIvehGOGxSPvk6CoviSxBND8rb56lvnsEZuLeBV Bo5QSIL2x42Zrvo11iPHwgXZfTIusU90sBuKDRFkYBAxY3HK2naMDZe8MAsYCUE9 nwgHF8DDc/NYiSOXV8kosWoWpNIkoK/STyH5bvTQZMqZcwyZ49AIeP1jGZb/prbC e/rbnlrq5Eu6brpM7xo9kELO0Vhd34urV14KrrIpdkmUKytW2KIsyvW8D6fqgDBj NSaQLLcz0pCXbhF+8Nqvdh/1coR4L7Ymt08P1rfEjCsQgb/2WnSAGUQuC5JoGzaj ngkbFcZllIbD9gNzMQ1n4Aw5TiO+l9zxCqPC/r58Uuvstr+K9QKlwnp2+B3Q73Ft rojIJ04NJL6lCHdDgwAjTTks+TD2PT/eBWsDfJ/1pnUWttmv9IjMpnXD5sbHxoiU 2RGGKnYbxXczYdq/ALYDWM6JXpfnJZcXL3jJi0IDcCSsb92xRvTANYFHnTfyzGfw EHkhbF4e4Vy9f6QOkSP3CvW5H26BmZS9DKG0J9Il5R3u2lKdfbb5vmtUmVTqHmAD Ulo5cWZjEznlWCAYSI/aIidmBsp9OAEvYd+X7Z5SBIgTfSqV7VWHGt0BfA1heiVv F/mednG0gGc= =3v4F -----END PGP SIGNATURE----- Merge tag 'x86-core-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull core x86 updates from Ingo Molnar: - The biggest change is the rework of the percpu code, to support the 'Named Address Spaces' GCC feature, by Uros Bizjak: - This allows C code to access GS and FS segment relative memory via variables declared with such attributes, which allows the compiler to better optimize those accesses than the previous inline assembly code. - The series also includes a number of micro-optimizations for various percpu access methods, plus a number of cleanups of %gs accesses in assembly code. - These changes have been exposed to linux-next testing for the last ~5 months, with no known regressions in this area. - Fix/clean up __switch_to()'s broken but accidentally working handling of FPU switching - which also generates better code - Propagate more RIP-relative addressing in assembly code, to generate slightly better code - Rework the CPU mitigations Kconfig space to be less idiosyncratic, to make it easier for distros to follow & maintain these options - Rework the x86 idle code to cure RCU violations and to clean up the logic - Clean up the vDSO Makefile logic - Misc cleanups and fixes * tag 'x86-core-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (52 commits) x86/idle: Select idle routine only once x86/idle: Let prefer_mwait_c1_over_halt() return bool x86/idle: Cleanup idle_setup() x86/idle: Clean up idle selection x86/idle: Sanitize X86_BUG_AMD_E400 handling sched/idle: Conditionally handle tick broadcast in default_idle_call() x86: Increase brk randomness entropy for 64-bit systems x86/vdso: Move vDSO to mmap region x86/vdso/kbuild: Group non-standard build attributes and primary object file rules together x86/vdso: Fix rethunk patching for vdso-image-{32,64}.o x86/retpoline: Ensure default return thunk isn't used at runtime x86/vdso: Use CONFIG_COMPAT_32 to specify vdso32 x86/vdso: Use $(addprefix ) instead of $(foreach ) x86/vdso: Simplify obj-y addition x86/vdso: Consolidate targets and clean-files x86/bugs: Rename CONFIG_RETHUNK => CONFIG_MITIGATION_RETHUNK x86/bugs: Rename CONFIG_CPU_SRSO => CONFIG_MITIGATION_SRSO x86/bugs: Rename CONFIG_CPU_IBRS_ENTRY => CONFIG_MITIGATION_IBRS_ENTRY x86/bugs: Rename CONFIG_CPU_UNRET_ENTRY => CONFIG_MITIGATION_UNRET_ENTRY x86/bugs: Rename CONFIG_SLS => CONFIG_MITIGATION_SLS ...	2024-03-11 19:53:15 -07:00
Steven Rostedt (Google)	68282dd930	ring-buffer: Fix resetting of shortest_full ... The "shortest_full" variable is used to keep track of the waiter that is waiting for the smallest amount on the ring buffer before being woken up. When a tasks waits on the ring buffer, it passes in a "full" value that is a percentage. 0 means wake up on any data. 1-100 means wake up from 1% to 100% full buffer. As all waiters are on the same wait queue, the wake up happens for the waiter with the smallest percentage. The problem is that the smallest_full on the cpu_buffer that stores the smallest amount doesn't get reset when all the waiters are woken up. It does get reset when the ring buffer is reset (echo > /sys/kernel/tracing/trace). This means that tasks may be woken up more often then when they want to be. Instead, have the shortest_full field get reset just before waking up all the tasks. If the tasks wait again, they will update the shortest_full before sleeping. Also add locking around setting of shortest_full in the poll logic, and change "work" to "rbwork" to match the variable name for rb_irq_work structures that are used in other places. Link: https://lore.kernel.org/linux-trace-kernel/20240308202431.948914369@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: linke li <lilinke99@qq.com> Cc: Rabin Vincent <rabin@rab.in> Fixes: 2c2b0a78b3 ("ring-buffer: Add percentage of ring buffer full to wake up reader") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-03-10 12:27:40 -04:00
Steven Rostedt (Google)	b359457368	ring-buffer: Fix waking up ring buffer readers ... A task can wait on a ring buffer for when it fills up to a specific watermark. The writer will check the minimum watermark that waiters are waiting for and if the ring buffer is past that, it will wake up all the waiters. The waiters are in a wait loop, and will first check if a signal is pending and then check if the ring buffer is at the desired level where it should break out of the loop. If a file that uses a ring buffer closes, and there's threads waiting on the ring buffer, it needs to wake up those threads. To do this, a "wait_index" was used. Before entering the wait loop, the waiter will read the wait_index. On wakeup, it will check if the wait_index is different than when it entered the loop, and will exit the loop if it is. The waker will only need to update the wait_index before waking up the waiters. This had a couple of bugs. One trivial one and one broken by design. The trivial bug was that the waiter checked the wait_index after the schedule() call. It had to be checked between the prepare_to_wait() and the schedule() which it was not. The main bug is that the first check to set the default wait_index will always be outside the prepare_to_wait() and the schedule(). That's because the ring_buffer_wait() doesn't have enough context to know if it should break out of the loop. The loop itself is not needed, because all the callers to the ring_buffer_wait() also has their own loop, as the callers have a better sense of what the context is to decide whether to break out of the loop or not. Just have the ring_buffer_wait() block once, and if it gets woken up, exit the function and let the callers decide what to do next. Link: https://lore.kernel.org/all/CAHk-=whs5MdtNjzFkTyaUy=vHi=qwWgPi0JgTe6OYUYMNSRZfg@mail.gmail.com/ Link: https://lore.kernel.org/linux-trace-kernel/20240308202431.792933613@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: linke li <lilinke99@qq.com> Cc: Rabin Vincent <rabin@rab.in> Fixes: e30f53aad2 ("tracing: Do not busy wait in buffer splice") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-03-10 12:24:59 -04:00
Steven Rostedt (Google)	e78fb4eac8	ring-buffer: Do not let subbuf be bigger than write mask ... The data on the subbuffer is measured by a write variable that also contains status flags. The counter is just 20 bits in length. If the subbuffer is bigger than then counter, it will fail. Make sure that the subbuffer can not be set to greater than the counter that keeps track of the data on the subbuffer. Link: https://lore.kernel.org/linux-trace-kernel/20240220095112.77e9cb81@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Fixes: 2808e31ec1 ("ring-buffer: Add interface for configuring trace sub buffer size") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-02-21 09:15:23 -05:00
Ingo Molnar	4589f199eb	Merge branch 'x86/bugs' into x86/core, to pick up pending changes before dependent patches ... Merge in pending alternatives patching infrastructure changes, before applying more patches. Signed-off-by: Ingo Molnar <mingo@kernel.org>	2024-02-14 10:49:37 +01:00
Vincent Donnefort	66bbea9ed6	ring-buffer: Clean ring_buffer_poll_wait() error return ... The return type for ring_buffer_poll_wait() is __poll_t. This is behind the scenes an unsigned where we can set event bits. In case of a non-allocated CPU, we do return instead -EINVAL (0xffffffea). Lucky us, this ends up setting few error bits (EPOLLERR | EPOLLHUP | EPOLLNVAL), so user-space at least is aware something went wrong. Nonetheless, this is an incorrect code. Replace that -EINVAL with a proper EPOLLERR to clean that output. As this doesn't change the behaviour, there's no need to treat this change as a bug fix. Link: https://lore.kernel.org/linux-trace-kernel/20240131140955.3322792-1-vdonnefort@google.com Cc: stable@vger.kernel.org Fixes: 6721cb6002 ("ring-buffer: Do not poll non allocated cpu buffers") Signed-off-by: Vincent Donnefort <vdonnefort@google.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2024-01-31 14:10:24 -05:00
Linus Torvalds	a2ded784cd	tracing updates for 6.8: ... - Allow kernel trace instance creation to specify what events are created Inside the kernel, a subsystem may create a tracing instance that it can use to send events to user space. This sub-system may not care about the thousands of events that exist in eventfs. Allow the sub-system to specify what sub-systems of events it cares about, and only those events are exposed to this instance. - Allow the ring buffer to be broken up into bigger sub-buffers than just the architecture page size. A new tracefs file called "buffer_subbuf_size_kb" is created. The user can now specify a minimum size the sub-buffer may be in kilobytes. Note, that the implementation currently make the sub-buffer size a power of 2 pages (1, 2, 4, 8, 16, ...) but the user only writes in kilobyte size, and the sub-buffer will be updated to the next size that it will can accommodate it. If the user writes in 10, it will change the size to be 4 pages on x86 (16K), as that is the next available size that can hold 10K pages. - Update the debug output when a corrupt time is detected in the ring buffer. If the ring buffer detects inconsistent timestamps, there's a debug config options that will dump the contents of the meta data of the sub-buffer that is used for debugging. Add some more information to this dump that helps with debugging. - Add more timestamp debugging checks (only triggers when the config is enabled) - Increase the trace_seq iterator to 2 page sizes. - Allow strings written into tracefs_marker to be larger. Up to just under 2 page sizes (based on what trace_seq can hold). - Increase the trace_maker_raw write to be as big as a sub-buffer can hold. - Remove 32 bit time stamp logic, now that the rb_time_cmpxchg() has been removed. - More selftests were added. - Some code clean ups as well. -----BEGIN PGP SIGNATURE----- iIoEABYIADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCZZ8p3BQccm9zdGVkdEBn b29kbWlzLm9yZwAKCRAp5XQQmuv6ql2GAQDZg/zlFEiJHyTfWbCIE8pA3T5xbzKo 26TNxIZAxJJZpQEAvGFU5Smy14pG6soEoVMp8B6ZOANbqU8VVamhOL+r+Qw= =0OYG -----END PGP SIGNATURE----- Merge tag 'trace-v6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing updates from Steven Rostedt: - Allow kernel trace instance creation to specify what events are created Inside the kernel, a subsystem may create a tracing instance that it can use to send events to user space. This sub-system may not care about the thousands of events that exist in eventfs. Allow the sub-system to specify what sub-systems of events it cares about, and only those events are exposed to this instance. - Allow the ring buffer to be broken up into bigger sub-buffers than just the architecture page size. A new tracefs file called "buffer_subbuf_size_kb" is created. The user can now specify a minimum size the sub-buffer may be in kilobytes. Note, that the implementation currently make the sub-buffer size a power of 2 pages (1, 2, 4, 8, 16, ...) but the user only writes in kilobyte size, and the sub-buffer will be updated to the next size that it will can accommodate it. If the user writes in 10, it will change the size to be 4 pages on x86 (16K), as that is the next available size that can hold 10K pages. - Update the debug output when a corrupt time is detected in the ring buffer. If the ring buffer detects inconsistent timestamps, there's a debug config options that will dump the contents of the meta data of the sub-buffer that is used for debugging. Add some more information to this dump that helps with debugging. - Add more timestamp debugging checks (only triggers when the config is enabled) - Increase the trace_seq iterator to 2 page sizes. - Allow strings written into tracefs_marker to be larger. Up to just under 2 page sizes (based on what trace_seq can hold). - Increase the trace_maker_raw write to be as big as a sub-buffer can hold. - Remove 32 bit time stamp logic, now that the rb_time_cmpxchg() has been removed. - More selftests were added. - Some code clean ups as well. * tag 'trace-v6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (29 commits) ring-buffer: Remove stale comment from ring_buffer_size() tracing histograms: Simplify parse_actions() function tracing/selftests: Remove exec permissions from trace_marker.tc test ring-buffer: Use subbuf_order for buffer page masking tracing: Update subbuffer with kilobytes not page order ringbuffer/selftest: Add basic selftest to test changing subbuf order ring-buffer: Add documentation on the buffer_subbuf_order file ring-buffer: Just update the subbuffers when changing their allocation order ring-buffer: Keep the same size when updating the order tracing: Stop the tracing while changing the ring buffer subbuf size tracing: Update snapshot order along with main buffer order ring-buffer: Make sure the spare sub buffer used for reads has same size ring-buffer: Do no swap cpu buffers if order is different ring-buffer: Clear pages on error in ring_buffer_subbuf_order_set() failure ring-buffer: Read and write to ring buffers with custom sub buffer size ring-buffer: Set new size of the ring buffer sub page ring-buffer: Add interface for configuring trace sub buffer size ring-buffer: Page size per ring buffer ring-buffer: Have ring_buffer_print_page_header() be able to access ring_buffer_iter ring-buffer: Check if absolute timestamp goes backwards ...	2024-01-18 14:35:29 -08:00
Breno Leitao	aefb2f2e61	x86/bugs: Rename CONFIG_RETPOLINE => CONFIG_MITIGATION_RETPOLINE ... Step 5/10 of the namespace unification of CPU mitigations related Kconfig options. [ mingo: Converted a few more uses in comments/messages as well. ] Suggested-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Breno Leitao <leitao@debian.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Ariel Miculas <amiculas@cisco.com> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20231121160740.1249350-6-leitao@debian.org	2024-01-10 10:52:28 +01:00
Steven Rostedt (Google)	25742aeb13	ring-buffer: Remove stale comment from ring_buffer_size() ... It's been 11 years since the ring_buffer_size() function was updated to use the nr_pages from the buffer->buffers[cpu] structure instead of using the buffer->nr_pages that no longer exists. The comment in the code is more of what a change log should have and is pretty much useless for development. It's saying how things worked back in 2012 that bares no purpose on today's code. Remove it. Link: https://lore.kernel.org/linux-trace-kernel/84d3b41a72bd43dbb9d44921ef535c92@AcuMS.aculab.com/ Link: https://lore.kernel.org/linux-trace-kernel/20231220081028.7cd7e8e2@gandalf.local.home Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Reported-by: David Laight <David.Laight@ACULAB.COM> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>	2024-01-09 22:54:37 -05:00
Steven Rostedt (Google)	39a7dc23a1	tracing: Fix blocked reader of snapshot buffer ... If an application blocks on the snapshot or snapshot_raw files, expecting to be woken up when a snapshot occurs, it will not happen. Or it may happen with an unexpected result. That result is that the application will be reading the main buffer instead of the snapshot buffer. That is because when the snapshot occurs, the main and snapshot buffers are swapped. But the reader has a descriptor still pointing to the buffer that it originally connected to. This is fine for the main buffer readers, as they may be blocked waiting for a watermark to be hit, and when a snapshot occurs, the data that the main readers want is now on the snapshot buffer. But for waiters of the snapshot buffer, they are waiting for an event to occur that will trigger the snapshot and they can then consume it quickly to save the snapshot before the next snapshot occurs. But to do this, they need to read the new snapshot buffer, not the old one that is now receiving new data. Also, it does not make sense to have a watermark "buffer_percent" on the snapshot buffer, as the snapshot buffer is static and does not receive new data except all at once. Link: https://lore.kernel.org/linux-trace-kernel/20231228095149.77f5b45d@gandalf.local.home Cc: stable@vger.kernel.org Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Mark Rutland <mark.rutland@arm.com> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Fixes: debdd57f51 ("tracing: Make a snapshot feature available from userspace") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-29 09:18:49 -05:00
Steven Rostedt (Google)	623b1f896f	ring-buffer: Fix wake ups when buffer_percent is set to 100 ... The tracefs file "buffer_percent" is to allow user space to set a water-mark on how much of the tracing ring buffer needs to be filled in order to wake up a blocked reader. 0 - is to wait until any data is in the buffer 1 - is to wait for 1% of the sub buffers to be filled 50 - would be half of the sub buffers are filled with data 100 - is not to wake the waiter until the ring buffer is completely full Unfortunately the test for being full was: dirty = ring_buffer_nr_dirty_pages(buffer, cpu); return (dirty * 100) > (full * nr_pages); Where "full" is the value for "buffer_percent". There is two issues with the above when full == 100. 1. dirty * 100 > 100 * nr_pages will never be true That is, the above is basically saying that if the user sets buffer_percent to 100, more pages need to be dirty than exist in the ring buffer! 2. The page that the writer is on is never considered dirty, as dirty pages are only those that are full. When the writer goes to a new sub-buffer, it clears the contents of that sub-buffer. That is, even if the check was ">=" it would still not be equal as the most pages that can be considered "dirty" is nr_pages - 1. To fix this, add one to dirty and use ">=" in the compare. Link: https://lore.kernel.org/linux-trace-kernel/20231226125902.4a057f1d@gandalf.local.home Cc: stable@vger.kernel.org Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Fixes: 03329f9939 ("tracing: Add tracefs file buffer_percentage") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-29 09:18:30 -05:00
Steven Rostedt (Google)	3cb3091138	ring-buffer: Use subbuf_order for buffer page masking ... The comparisons to PAGE_SIZE were all converted to use the buffer->subbuf_order, but the use of PAGE_MASK was missed. Convert all the PAGE_MASK usages over to: (PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1 Link: https://lore.kernel.org/linux-trace-kernel/20231219173800.66eefb7a@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Fixes: 139f840021 ("ring-buffer: Page size per ring buffer") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-21 11:04:48 -05:00
Steven Rostedt (Google)	8e7b58c27b	ring-buffer: Just update the subbuffers when changing their allocation order ... The ring_buffer_subbuf_order_set() was creating ring_buffer_per_cpu cpu_buffers with the new subbuffers with the updated order, and if they all successfully were created, then they the ring_buffer's per_cpu buffers would be freed and replaced by them. The problem is that the freed per_cpu buffers contains state that would be lost. Running the following commands: 1. # echo 3 > /sys/kernel/tracing/buffer_subbuf_order 2. # echo 0 > /sys/kernel/tracing/tracing_cpumask 3. # echo 1 > /sys/kernel/tracing/snapshot 4. # echo ff > /sys/kernel/tracing/tracing_cpumask 5. # echo test > /sys/kernel/tracing/trace_marker Would result in: -bash: echo: write error: Bad file descriptor That's because the state of the per_cpu buffers of the snapshot buffer is lost when the order is changed (the order of a freed snapshot buffer goes to 0 to save memory, and when the snapshot buffer is allocated again, it goes back to what the main buffer is). In operation 2, the snapshot buffers were set to "disable" (as all the ring buffers CPUs were disabled). In operation 3, the snapshot is allocated and a call to ring_buffer_subbuf_order_set() replaced the per_cpu buffers losing the "record_disable" count. When it was enabled again, the atomic_dec(&cpu_buffer->record_disable) was decrementing a zero, setting it to -1. Writing 1 into the snapshot would swap the snapshot buffer with the main buffer, so now the main buffer is "disabled", and nothing can write to the ring buffer anymore. Instead of creating new per_cpu buffers and losing the state of the old buffers, basically do what the resize does and just allocate new subbuf pages into the new_pages link list of the per_cpu buffer and if they all succeed, then replace the old sub buffers with the new ones. This keeps the per_cpu buffer descriptor in tact and by doing so, keeps its state. Link: https://lore.kernel.org/linux-trace-kernel/20231219185630.944104939@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Fixes: f9b94daa54 ("ring-buffer: Set new size of the ring buffer sub page") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-21 11:02:52 -05:00
Steven Rostedt (Google)	353cc21937	ring-buffer: Keep the same size when updating the order ... The function ring_buffer_subbuf_order_set() just updated the sub-buffers to the new size, but this also changes the size of the buffer in doing so. As the size is determined by nr_pages * subbuf_size. If the subbuf_size is increased without decreasing the nr_pages, this causes the total size of the buffer to increase. This broke the latency tracers as the snapshot needs to be the same size as the main buffer. The size of the snapshot buffer is only expanded when needed, and because the order is still the same, the size becomes out of sync with the main buffer, as the main buffer increased in size without the tracing system knowing. Calculate the nr_pages to allocate with the new subbuf_size to be buffer_size / new_subbuf_size. Link: https://lore.kernel.org/linux-trace-kernel/20231219185630.649397785@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Fixes: f9b94daa54 ("ring-buffer: Set new size of the ring buffer sub page") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-21 11:02:01 -05:00
Steven Rostedt (Google)	b81e03a249	ring-buffer: Do no swap cpu buffers if order is different ... As all the subbuffer order (subbuffer sizes) must be the same throughout the ring buffer, check the order of the buffers that are doing a CPU buffer swap in ring_buffer_swap_cpu() to make sure they are the same. If the are not the same, then fail to do the swap, otherwise the ring buffer will think the CPU buffer has a specific subbuffer size when it does not. Link: https://lore.kernel.org/linux-trace-kernel/20231219185629.467894710@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-21 10:54:50 -05:00
Steven Rostedt (Google)	22887dfba0	ring-buffer: Clear pages on error in ring_buffer_subbuf_order_set() failure ... On failure to allocate ring buffer pages, the pointer to the CPU buffer pages is freed, but the pages that were allocated previously were not. Make sure they are freed too. Link: https://lore.kernel.org/linux-trace-kernel/20231219185629.179352802@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Fixes: f9b94daa54 ("tracing: Set new size of the ring buffer sub page") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-21 10:53:59 -05:00
Tzvetomir Stoyanov (VMware)	bce761d757	ring-buffer: Read and write to ring buffers with custom sub buffer size ... As the size of the ring sub buffer page can be changed dynamically, the logic that reads and writes to the buffer should be fixed to take that into account. Some internal ring buffer APIs are changed: ring_buffer_alloc_read_page() ring_buffer_free_read_page() ring_buffer_read_page() A new API is introduced: ring_buffer_read_page_data() Link: https://lore.kernel.org/linux-trace-devel/20211213094825.61876-6-tz.stoyanov@gmail.com Link: https://lore.kernel.org/linux-trace-kernel/20231219185628.875145995@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com> [ Fixed kerneldoc on data_page parameter in ring_buffer_free_read_page() ] Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-20 07:54:56 -05:00
Tzvetomir Stoyanov (VMware)	f9b94daa54	ring-buffer: Set new size of the ring buffer sub page ... There are two approaches when changing the size of the ring buffer sub page: 1. Destroying all pages and allocating new pages with the new size. 2. Allocating new pages, copying the content of the old pages before destroying them. The first approach is easier, it is selected in the proposed implementation. Changing the ring buffer sub page size is supposed to not happen frequently. Usually, that size should be set only once, when the buffer is not in use yet and is supposed to be empty. Link: https://lore.kernel.org/linux-trace-devel/20211213094825.61876-5-tz.stoyanov@gmail.com Link: https://lore.kernel.org/linux-trace-kernel/20231219185628.588995543@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-20 07:54:56 -05:00
Tzvetomir Stoyanov (VMware)	2808e31ec1	ring-buffer: Add interface for configuring trace sub buffer size ... The trace ring buffer sub page size can be configured, per trace instance. A new ftrace file "buffer_subbuf_order" is added to get and set the size of the ring buffer sub page for current trace instance. The size must be an order of system page size, that's why the new interface works with system page order, instead of absolute page size: 0 means the ring buffer sub page is equal to 1 system page and so forth: 0 - 1 system page 1 - 2 system pages 2 - 4 system pages ... The ring buffer sub page size is limited between 1 and 128 system pages. The default value is 1 system page. New ring buffer APIs are introduced: ring_buffer_subbuf_order_set() ring_buffer_subbuf_order_get() ring_buffer_subbuf_size_get() Link: https://lore.kernel.org/linux-trace-devel/20211213094825.61876-4-tz.stoyanov@gmail.com Link: https://lore.kernel.org/linux-trace-kernel/20231219185628.298324722@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-20 07:54:55 -05:00
Tzvetomir Stoyanov (VMware)	139f840021	ring-buffer: Page size per ring buffer ... Currently the size of one sub buffer page is global for all buffers and it is hard coded to one system page. In order to introduce configurable ring buffer sub page size, the internal logic should be refactored to work with sub page size per ring buffer. Link: https://lore.kernel.org/linux-trace-devel/20211213094825.61876-3-tz.stoyanov@gmail.com Link: https://lore.kernel.org/linux-trace-kernel/20231219185628.009147038@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-20 07:54:55 -05:00
Tzvetomir Stoyanov (VMware)	d5cfbdfc96	ring-buffer: Have ring_buffer_print_page_header() be able to access ring_buffer_iter ... In order to introduce sub-buffer size per ring buffer, some internal refactoring is needed. As ring_buffer_print_page_header() will depend on the trace_buffer structure, it is moved after the structure definition. Link: https://lore.kernel.org/linux-trace-devel/20211213094825.61876-2-tz.stoyanov@gmail.com Link: https://lore.kernel.org/linux-trace-kernel/20231219185627.723857541@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-20 07:52:47 -05:00
Steven Rostedt (Google)	f50345b49b	ring-buffer: Check if absolute timestamp goes backwards ... The check_buffer() which checks the timestamps of the ring buffer sub-buffer page, when enabled, only checks if the adding of deltas of the events from the last absolute timestamp or the timestamp of the sub-buffer page adds up to the current event. What it does not check is if the absolute timestamp causes the time of the events to go backwards, as that can cause issues elsewhere. Test for the timestamp going backwards too. This also fixes a slight issue where if the warning triggers at boot up (because of the resetting of the tsc), it will disable all further checks, even those that are after boot Have it continue checking if the warning was ignored during boot up. Link: https://lore.kernel.org/linux-trace-kernel/20231219074732.18b092d4@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-19 07:49:47 -05:00
Steven Rostedt (Google)	d40dbb617a	ring-buffer: Add interrupt information to dump of data sub-buffer ... When the ring buffer timestamp verifier triggers, it dumps the content of the sub-buffer. But currently it only dumps the timestamps and the offset of the data as well as the deltas. It would be even more informative if the event data also showed the interrupt context level it was in. That is, if each event showed that the event was written in normal, softirq, irq or NMI context. Then a better idea about how the events may have been interrupted from each other. As the payload of the ring buffer is really a black box of the ring buffer, just assume that if the payload is larger than a trace entry, that it is a trace entry. As trace entries have the interrupt context information saved in a flags field, look at that location and report the output of the flags. If the payload is not a trace entry, there's no way to really know, and the information will be garbage. But that's OK, because this is for debugging only (this output is not used in production as the buffer check that calls it causes a huge overhead to the tracing). This information, when available, is crucial for debugging timestamp issues. If it's garbage, it will also be pretty obvious that its garbage too. As this output usually happens in kselftests of the tracing code, the user will know what the payload is at the time. Link: https://lore.kernel.org/linux-trace-kernel/20231219074542.6f304601@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Suggested-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-19 07:49:22 -05:00
Steven Rostedt (Google)	c84897c0ff	ring-buffer: Remove 32bit timestamp logic ... Each event has a 27 bit timestamp delta that is used to hold the delta from the last event. If the time between events is greater than 2^27, then a timestamp is added that holds a 59 bit absolute timestamp. Until a389d86f7f ("ring-buffer: Have nested events still record running time stamp"), if an interrupt interrupted an event in progress, all the events delta would be zero to not deal with the races that need to be handled. The commit a389d86f7f changed that to handle the races giving all events, even those that preempt other events, still have an accurate timestamp. To handle those races requires performing 64-bit cmpxchg on the timestamps. But doing 64-bit cmpxchg on 32-bit architectures is considered very slow. To try to deal with this the timestamp logic was broken into two and then three 32-bit cmpxchgs, with the thought that two (or three) 32-bit cmpxchgs are still faster than a single 64-bit cmpxchg on 32-bit architectures. Part of the problem with this is that I didn't have any 32-bit architectures to test on. After hitting several subtle bugs in this code, an effort was made to try and see if three 32-bit cmpxchgs are indeed faster than a single 64-bit. After a few people brushed off the dust of their old 32-bit machines, tests were done, and even though 32-bit cmpxchg was faster than a single 64-bit, it was in the order of 50% at best, not 300%. After some more refactoring of the code, all 4 64-bit cmpxchg were removed: https://lore.kernel.org/linux-trace-kernel/20231211114420.36dde01b@gandalf.local.home https://lore.kernel.org/linux-trace-kernel/20231214222921.193037a7@gandalf.local.home https://lore.kernel.org/linux-trace-kernel/20231215081810.1f4f38fe@rorschach.local.home https://lore.kernel.org/linux-trace-kernel/20231218230712.3a76b081@gandalf.local.home/ With all the 64-bit cmpxchg removed, the complex 32-bit workaround can also be removed. The 32-bit and 64-bit logic is now exactly the same. Link: https://lore.kernel.org/all/20231213214632.15047c40@gandalf.local.home/ Link: https://lore.kernel.org/linux-trace-kernel/20231219074303.28f9abda@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-19 07:47:04 -05:00
Steven Rostedt (Google)	8ec90be7f1	tracing: Allow for max buffer data size trace_marker writes ... Allow a trace write to be as big as the ring buffer tracing data will allow. Currently, it only allows writes of 1KB in size, but there's no reason that it cannot allow what the ring buffer can hold. Link: https://lore.kernel.org/linux-trace-kernel/20231212131901.5f501e72@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-18 23:14:16 -05:00
Steven Rostedt (Google)	0b9036efd8	ring-buffer: Add offset of events in dump on mismatch ... On bugs that have the ring buffer timestamp get out of sync, the config CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS, that checks for it and if it is detected it causes a dump of the bad sub buffer. It shows each event and their timestamp as well as the delta in the event. But it's also good to see the offset into the subbuffer for that event to know if how close to the end it is. Also print where the last event actually ended compared to where it was expected to end. Link: https://lore.kernel.org/linux-trace-kernel/20231211131623.59eaebd2@gandalf.local.home Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-18 23:14:16 -05:00
Steven Rostedt (Google)	b803d7c664	ring-buffer: Fix slowpath of interrupted event ... To synchronize the timestamps with the ring buffer reservation, there are two timestamps that are saved in the buffer meta data. 1. before_stamp 2. write_stamp When the two are equal, the write_stamp is considered valid, as in, it may be used to calculate the delta of the next event as the write_stamp is the timestamp of the previous reserved event on the buffer. This is done by the following: /*A*/ w = current position on the ring buffer before = before_stamp after = write_stamp ts = read current timestamp if (before != after) { write_stamp is not valid, force adding an absolute timestamp. } /*B*/ before_stamp = ts /*C*/ write = local_add_return(event length, position on ring buffer) if (w == write - event length) { /* Nothing interrupted between A and C */ /*E*/ write_stamp = ts; delta = ts - after /* * If nothing interrupted again, * before_stamp == write_stamp and write_stamp * can be used to calculate the delta for * events that come in after this one. */ } else { /* * The slow path! * Was interrupted between A and C. */ This is the place that there's a bug. We currently have: after = write_stamp ts = read current timestamp /*F*/ if (write == current position on the ring buffer && after < ts && cmpxchg(write_stamp, after, ts)) { delta = ts - after; } else { delta = 0; } The assumption is that if the current position on the ring buffer hasn't moved between C and F, then it also was not interrupted, and that the last event written has a timestamp that matches the write_stamp. That is the write_stamp is valid. But this may not be the case: If a task context event was interrupted by softirq between B and C. And the softirq wrote an event that got interrupted by a hard irq between C and E. and the hard irq wrote an event (does not need to be interrupted) We have: /*B*/ before_stamp = ts of normal context ---> interrupted by softirq /*B*/ before_stamp = ts of softirq context ---> interrupted by hardirq /*B*/ before_stamp = ts of hard irq context /*E*/ write_stamp = ts of hard irq context /* matches and write_stamp valid */ <---- /*E*/ write_stamp = ts of softirq context /* No longer matches before_stamp, write_stamp is not valid! */ <--- w != write - length, go to slow path // Right now the order of events in the ring buffer is: // // |-- softirq event --|-- hard irq event --|-- normal context event --| // after = write_stamp (this is the ts of softirq) ts = read current timestamp if (write == current position on the ring buffer [true] && after < ts [true] && cmpxchg(write_stamp, after, ts) [true]) { delta = ts - after [Wrong!] The delta is to be between the hard irq event and the normal context event, but the above logic made the delta between the softirq event and the normal context event, where the hard irq event is between the two. This will shift all the remaining event timestamps on the sub-buffer incorrectly. The write_stamp is only valid if it matches the before_stamp. The cmpxchg does nothing to help this. Instead, the following logic can be done to fix this: before = before_stamp ts = read current timestamp before_stamp = ts after = write_stamp if (write == current position on the ring buffer && after == before && after < ts) { delta = ts - after } else { delta = 0; } The above will only use the write_stamp if it still matches before_stamp and was tested to not have changed since C. As a bonus, with this logic we do not need any 64-bit cmpxchg() at all! This means the 32-bit rb_time_t workaround can finally be removed. But that's for a later time. Link: https://lore.kernel.org/linux-trace-kernel/20231218175229.58ec3daf@gandalf.local.home/ Link: https://lore.kernel.org/linux-trace-kernel/20231218230712.3a76b081@gandalf.local.home Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Fixes: dd93942570 ("ring-buffer: Do not try to put back write_stamp") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-18 23:12:22 -05:00
Steven Rostedt (Google)	712292308a	ring-buffer: Do not record in NMI if the arch does not support cmpxchg in NMI ... As the ring buffer recording requires cmpxchg() to work, if the architecture does not support cmpxchg in NMI, then do not do any recording within an NMI. Link: https://lore.kernel.org/linux-trace-kernel/20231213175403.6fc18540@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-15 08:54:26 -05:00
Steven Rostedt (Google)	0aa0e5289c	ring-buffer: Have rb_time_cmpxchg() set the msb counter too ... The rb_time_cmpxchg() on 32-bit architectures requires setting three 32-bit words to represent the 64-bit timestamp, with some salt for synchronization. Those are: msb, top, and bottom The issue is, the rb_time_cmpxchg() did not properly salt the msb portion, and the msb that was written was stale. Link: https://lore.kernel.org/linux-trace-kernel/20231215084114.20899342@rorschach.local.home Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Fixes: f03f2abce4 ("ring-buffer: Have 32 bit time stamps use all 64 bits") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-15 08:43:35 -05:00
Mathieu Desnoyers	dec890089b	ring-buffer: Fix 32-bit rb_time_read() race with rb_time_cmpxchg() ... The following race can cause rb_time_read() to observe a corrupted time stamp: rb_time_cmpxchg() [...] if (!rb_time_read_cmpxchg(&t->msb, msb, msb2)) return false; if (!rb_time_read_cmpxchg(&t->top, top, top2)) return false; <interrupted before updating bottom> __rb_time_read() [...] do { c = local_read(&t->cnt); top = local_read(&t->top); bottom = local_read(&t->bottom); msb = local_read(&t->msb); } while (c != local_read(&t->cnt)); *cnt = rb_time_cnt(top); /* If top and msb counts don't match, this interrupted a write */ if (*cnt != rb_time_cnt(msb)) return false; ^ this check fails to catch that "bottom" is still not updated. So the old "bottom" value is returned, which is wrong. Fix this by checking that all three of msb, top, and bottom 2-bit cnt values match. The reason to favor checking all three fields over requiring a specific update order for both rb_time_set() and rb_time_cmpxchg() is because checking all three fields is more robust to handle partial failures of rb_time_cmpxchg() when interrupted by nested rb_time_set(). Link: https://lore.kernel.org/lkml/20231211201324.652870-1-mathieu.desnoyers@efficios.com/ Link: https://lore.kernel.org/linux-trace-kernel/20231212193049.680122-1-mathieu.desnoyers@efficios.com Fixes: f458a14534 ("ring-buffer: Test last update in 32bit version of __rb_time_read()") Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-15 08:39:34 -05:00
Steven Rostedt (Google)	fff88fa0fb	ring-buffer: Fix a race in rb_time_cmpxchg() for 32 bit archs ... Mathieu Desnoyers pointed out an issue in the rb_time_cmpxchg() for 32 bit architectures. That is: static bool rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set) { unsigned long cnt, top, bottom, msb; unsigned long cnt2, top2, bottom2, msb2; u64 val; /* The cmpxchg always fails if it interrupted an update */ if (!__rb_time_read(t, &val, &cnt2)) return false; if (val != expect) return false; <<<< interrupted here! cnt = local_read(&t->cnt); The problem is that the synchronization counter in the rb_time_t is read *after* the value of the timestamp is read. That means if an interrupt were to come in between the value being read and the counter being read, it can change the value and the counter and the interrupted process would be clueless about it! The counter needs to be read first and then the value. That way it is easy to tell if the value is stale or not. If the counter hasn't been updated, then the value is still good. Link: https://lore.kernel.org/linux-trace-kernel/20231211201324.652870-1-mathieu.desnoyers@efficios.com/ Link: https://lore.kernel.org/linux-trace-kernel/20231212115301.7a9c9a64@gandalf.local.home Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Fixes: 10464b4aa6 ("ring-buffer: Add rb_time_t 64 bit operations for speeding up 32 bit") Reported-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-15 08:39:34 -05:00
Steven Rostedt (Google)	083e9f65bd	ring-buffer: Remove useless update to write_stamp in rb_try_to_discard() ... When filtering is enabled, a temporary buffer is created to place the content of the trace event output so that the filter logic can decide from the trace event output if the trace event should be filtered out or not. If it is to be filtered out, the content in the temporary buffer is simply discarded, otherwise it is written into the trace buffer. But if an interrupt were to come in while a previous event was using that temporary buffer, the event written by the interrupt would actually go into the ring buffer itself to prevent corrupting the data on the temporary buffer. If the event is to be filtered out, the event in the ring buffer is discarded, or if it fails to discard because another event were to have already come in, it is turned into padding. The update to the write_stamp in the rb_try_to_discard() happens after a fix was made to force the next event after the discard to use an absolute timestamp by setting the before_stamp to zero so it does not match the write_stamp (which causes an event to use the absolute timestamp). But there's an effort in rb_try_to_discard() to put back the write_stamp to what it was before the event was added. But this is useless and wasteful because nothing is going to be using that write_stamp for calculations as it still will not match the before_stamp. Remove this useless update, and in doing so, we remove another cmpxchg64()! Also update the comments to reflect this change as well as remove some extra white space in another comment. Link: https://lore.kernel.org/linux-trace-kernel/20231215081810.1f4f38fe@rorschach.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Vincent Donnefort <vdonnefort@google.com> Fixes: b2dd797543 ("ring-buffer: Force absolute timestamp on discard of event") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-15 08:38:11 -05:00
Steven Rostedt (Google)	dd93942570	ring-buffer: Do not try to put back write_stamp ... If an update to an event is interrupted by another event between the time the initial event allocated its buffer and where it wrote to the write_stamp, the code try to reset the write stamp back to the what it had just overwritten. It knows that it was overwritten via checking the before_stamp, and if it didn't match what it wrote to the before_stamp before it allocated its space, it knows it was overwritten. To put back the write_stamp, it uses the before_stamp it read. The problem here is that by writing the before_stamp to the write_stamp it makes the two equal again, which means that the write_stamp can be considered valid as the last timestamp written to the ring buffer. But this is not necessarily true. The event that interrupted the event could have been interrupted in a way that it was interrupted as well, and can end up leaving with an invalid write_stamp. But if this happens and returns to this context that uses the before_stamp to update the write_stamp again, it can possibly incorrectly make it valid, causing later events to have in correct time stamps. As it is OK to leave this function with an invalid write_stamp (one that doesn't match the before_stamp), there's no reason to try to make it valid again in this case. If this race happens, then just leave with the invalid write_stamp and the next event to come along will just add a absolute timestamp and validate everything again. Bonus points: This gets rid of another cmpxchg64! Link: https://lore.kernel.org/linux-trace-kernel/20231214222921.193037a7@gandalf.local.home Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Vincent Donnefort <vdonnefort@google.com> Fixes: a389d86f7f ("ring-buffer: Have nested events still record running time stamp") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>	2023-12-15 08:38:05 -05:00