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Currently, there is a problem with tracex2, as it doesn't print the
histogram properly and the results are misleading. (all results report
as 0)
The problem is caused by a change in arguments of the function to which
the kprobe connects. This tracex2 bpf program uses kprobe (attached
to __x64_sys_write) to figure out the size of the write system call. In
order to achieve this, the third argument 'count' must be intact.
The following is a prototype of the sys_write variant. (checked with
pfunct)
~/git/linux$ pfunct -P fs/read_write.o | grep sys_write
ssize_t ksys_write(unsigned int fd, const char * buf, size_t count);
long int __x64_sys_write(const struct pt_regs * regs);
... cross compile with s390x ...
long int __s390_sys_write(struct pt_regs * regs);
Since the nature of SYSCALL_WRAPPER function wraps the argument once,
additional process of argument extraction is required to properly parse
the argument.
#define BPF_KSYSCALL(name, args...)
... snip ...
struct pt_regs *regs = LINUX_HAS_SYSCALL_WRAPPER \
? (struct pt_regs *)PT_REGS_PARM1(ctx) \
: ctx; \
In order to fix this problem, the BPF_SYSCALL macro has been used. This
reduces the hassle of parsing arguments from pt_regs. Since the macro
uses the CORE version of argument extraction, additional portability
comes too.
Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221224071527.2292-5-danieltimlee@gmail.com
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
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| MAINTAINERS | ||
| Makefile | ||
| 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 Restructured Text 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.