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14b7d43c5c
- Update more header copies with the kernel sources, including const.h, msr-index.h, arm64's cputype.h, kvm's, bits.h and unaligned.h - The return from 'write' isn't a pid, fix cut'n'paste error in 'perf trace'. - Fix up the python binding build on architectures without HAVE_KVM_STAT_SUPPORT. - Add some more bounds checks to augmented_raw_syscalls.bpf.c (used to collect syscall pointer arguments in 'perf trace') to make the resulting bytecode to pass the kernel BPF verifier, allowing us to go back accepting clang 12.0.1 as the minimum version required for compiling BPF sources. - Add __NR_capget for x86 to fix a regression on running perf + intel PT (hw tracing) as non-root setting up the capabilities as described in https://www.kernel.org/doc/html/latest/admin-guide/perf-security.html. - Fix missing syscalltbl in non-explicitly listed architectures, noticed on ARM 32-bit, that still needs a .tbl generator for the syscall id<->name tables, should be added for v6.13. - Handle 'perf test' failure when handling broken DWARF for ASM files. Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQR2GiIUctdOfX2qHhGyPKLppCJ+JwUCZyKQVQAKCRCyPKLppCJ+ JxZKAQCOU0YgvvQ0LH6PfB9uGqRC/zOEHp9CnXxTK17rpKD/iAD/YYvH97Rrfx2V H5FdoyK7OtFrkV8WhNcKMKHFfBMl8Ac= =XDkJ -----END PGP SIGNATURE----- Merge tag 'perf-tools-fixes-for-v6.12-2-2024-10-30' of git://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools Pull perf tools fixes from Arnaldo Carvalho de Melo: - Update more header copies with the kernel sources, including const.h, msr-index.h, arm64's cputype.h, kvm's, bits.h and unaligned.h - The return from 'write' isn't a pid, fix cut'n'paste error in 'perf trace' - Fix up the python binding build on architectures without HAVE_KVM_STAT_SUPPORT - Add some more bounds checks to augmented_raw_syscalls.bpf.c (used to collect syscall pointer arguments in 'perf trace') to make the resulting bytecode to pass the kernel BPF verifier, allowing us to go back accepting clang 12.0.1 as the minimum version required for compiling BPF sources - Add __NR_capget for x86 to fix a regression on running perf + intel PT (hw tracing) as non-root setting up the capabilities as described in https://www.kernel.org/doc/html/latest/admin-guide/perf-security.html - Fix missing syscalltbl in non-explicitly listed architectures, noticed on ARM 32-bit, that still needs a .tbl generator for the syscall id<->name tables, should be added for v6.13 - Handle 'perf test' failure when handling broken DWARF for ASM files * tag 'perf-tools-fixes-for-v6.12-2-2024-10-30' of git://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools: perf cap: Add __NR_capget to arch/x86 unistd tools headers: Update the linux/unaligned.h copy with the kernel sources tools headers arm64: Sync arm64's cputype.h with the kernel sources tools headers: Synchronize {uapi/}linux/bits.h with the kernel sources tools arch x86: Sync the msr-index.h copy with the kernel sources perf python: Fix up the build on architectures without HAVE_KVM_STAT_SUPPORT perf test: Handle perftool-testsuite_probe failure due to broken DWARF tools headers UAPI: Sync kvm headers with the kernel sources perf trace: Fix non-listed archs in the syscalltbl routines perf build: Change the clang check back to 12.0.1 perf trace augmented_raw_syscalls: Add more checks to pass the verifier perf trace augmented_raw_syscalls: Add extra array index bounds checking to satisfy some BPF verifiers perf trace: The return from 'write' isn't a pid tools headers UAPI: Sync linux/const.h with the kernel headers |
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| README | ||
Why we want a copy of kernel headers in tools?
==============================================
There used to be no copies, with tools/ code using kernel headers
directly. From time to time tools/perf/ broke due to legitimate kernel
hacking. At some point Linus complained about such direct usage. Then we
adopted the current model.
The way these headers are used in perf are not restricted to just
including them to compile something.
There are sometimes used in scripts that convert defines into string
tables, etc, so some change may break one of these scripts, or new MSRs
may use some different #define pattern, etc.
E.g.:
$ ls -1 tools/perf/trace/beauty/*.sh | head -5
tools/perf/trace/beauty/arch_errno_names.sh
tools/perf/trace/beauty/drm_ioctl.sh
tools/perf/trace/beauty/fadvise.sh
tools/perf/trace/beauty/fsconfig.sh
tools/perf/trace/beauty/fsmount.sh
$
$ tools/perf/trace/beauty/fadvise.sh
static const char *fadvise_advices[] = {
[0] = "NORMAL",
[1] = "RANDOM",
[2] = "SEQUENTIAL",
[3] = "WILLNEED",
[4] = "DONTNEED",
[5] = "NOREUSE",
};
$
The tools/perf/check-headers.sh script, part of the tools/ build
process, points out changes in the original files.
So its important not to touch the copies in tools/ when doing changes in
the original kernel headers, that will be done later, when
check-headers.sh inform about the change to the perf tools hackers.
Another explanation from Ingo Molnar:
It's better than all the alternatives we tried so far:
- Symbolic links and direct #includes: this was the original approach but
was pushed back on from the kernel side, when tooling modified the
headers and broke them accidentally for kernel builds.
- Duplicate self-defined ABI headers like glibc: double the maintenance
burden, double the chance for mistakes, plus there's no tech-driven
notification mechanism to look at new kernel side changes.
What we are doing now is a third option:
- A software-enforced copy-on-write mechanism of kernel headers to
tooling, driven by non-fatal warnings on the tooling side build when
kernel headers get modified:
Warning: Kernel ABI header differences:
diff -u tools/include/uapi/drm/i915_drm.h include/uapi/drm/i915_drm.h
diff -u tools/include/uapi/linux/fs.h include/uapi/linux/fs.h
diff -u tools/include/uapi/linux/kvm.h include/uapi/linux/kvm.h
...
The tooling policy is to always pick up the kernel side headers as-is,
and integate them into the tooling build. The warnings above serve as a
notification to tooling maintainers that there's changes on the kernel
side.
We've been using this for many years now, and it might seem hacky, but
works surprisingly well.