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James Clark 4194744602 perf cs-etm: Output 0 instead of 0xdeadbeef when exception packets are flushed 
Normally exception packets don't directly output a branch sample, but
if they're the last record in a buffer then they will. Because they
don't have addresses set we'll see the placeholder value
CS_ETM_INVAL_ADDR (0xdeadbeef) in the output.

Since commit 6035b6804b ("perf cs-etm: Support dummy address value for
CS_ETM_TRACE_ON packet") we've used 0 as an externally visible "not set"
address value. For consistency reasons and to not make exceptions look
like an error, change them to use 0 too.

This is particularly visible when doing userspace only tracing because
trace is disabled when jumping to the kernel, causing the flush and then
forcing the last exception packet to be emitted as a branch. With kernel
trace included, there is no flush so exception packets don't generate
samples until the next range packet and they'll pick up the correct
address.

Before:

  $ perf record -e cs_etm//u -- stress -i 1 -t 1
  $ perf script -F comm,ip,addr,flags

  stress   syscall                    ffffb7eedbc0 => deadbeefdeadbeef
  stress   syscall                    ffffb7f14a14 => deadbeefdeadbeef
  stress   syscall                    ffffb7eedbc0 => deadbeefdeadbeef

After:

  stress   syscall                    ffffb7eedbc0 =>                0
  stress   syscall                    ffffb7f14a14 =>                0
  stress   syscall                    ffffb7eedbc0 =>                0

Reviewed-by: Mike Leach <mike.leach@linaro.org>
Signed-off-by: James Clark <james.clark@linaro.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Leo Yan <leo.yan@arm.com>
Cc: Leo Yan <leo.yan@linux.dev>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: coresight@lists.linaro.org
Cc: gankulkarni@os.amperecomputing.com
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lore.kernel.org/r/20240722152756.59453-2-james.clark@linaro.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2024-07-31 16:58:18 -03:00
arch ARM updates for v6.11-rc1 2024-07-29 10:33:51 -07:00
block block: fix deadlock between sd_remove & sd_release 2024-07-24 09:51:21 -06:00
certs kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
crypto crypto: testmgr - generate power-of-2 lengths more often 2024-07-13 11:50:28 +12:00
Documentation CXL for v6.11 merge window 2024-07-28 09:33:28 -07:00
drivers chrome-platform fixes for v6.11-rc2 2024-07-30 12:53:52 -07:00
fs for-6.11-rc1-tag 2024-07-30 19:28:36 -07:00
include for-6.11-rc1-tag 2024-07-30 19:28:36 -07:00
init Rust changes for v6.11 2024-07-27 13:44:54 -07:00
io_uring io_uring/napi: pass ktime to io_napi_adjust_timeout 2024-07-26 08:31:59 -06:00
ipc sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
kernel profiling: remove stale percpu flip buffer variables 2024-07-29 16:34:17 -07:00
lib minmax: don't use max() in situations that want a C constant expression 2024-07-28 20:23:27 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm minmax: make generic MIN() and MAX() macros available everywhere 2024-07-28 15:49:18 -07:00
net minmax: add a few more MIN_T/MAX_T users 2024-07-28 13:41:14 -07:00
rust Rust changes for v6.11 2024-07-27 13:44:54 -07:00
samples Driver core changes for 6.11-rc1 2024-07-25 10:42:22 -07:00
scripts Kbuild fixes for v6.11 2024-07-28 14:02:48 -07:00
security apparmor-pr-2024-07-24 PR 2024-07-25 2024-07-27 13:28:39 -07:00
sound Devicetree fixes for 6.11, part 1 2024-07-27 12:46:16 -07:00
tools perf cs-etm: Output 0 instead of 0xdeadbeef when exception packets are flushed 2024-07-31 16:58:18 -03:00
usr initramfs: shorten cmd_initfs in usr/Makefile 2024-07-16 01:07:52 +09:00
virt KVM generic changes for 6.11 2024-07-16 09:51:36 -04:00
.clang-format Docs: Move clang-format from process/ to dev-tools/ 2024-06-26 16:36:00 -06:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: add script and target to generate pacman package 2024-07-22 01:24:22 +09:00
.mailmap MAINTAINERS: mailmap: update James Clark's email address 2024-07-26 14:32:35 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING
CREDITS tracing: Update of MAINTAINERS and CREDITS file 2024-07-18 14:08:42 -07:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig
MAINTAINERS CXL for v6.11 merge window 2024-07-28 09:33:28 -07:00
Makefile Linux 6.11-rc1 2024-07-28 14:19:55 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.