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Subject[PATCH 0/2] perf-probe: Improve warning message for buildid mismatch
Date
Hello,

This series ensure the build-ids for target binary and debuginfo
are matched. If there is a mismatch, it warns user to check the
package versions.

To reproduce the problematic environment (on Fedora26),
I did following operations;

=====
# rpm -q glibc glibc-debuginfo
glibc-2.25-12.fc26.x86_64
package glibc-debuginfo is not installed

# dnf debuginfo-install glibc
[...]
Installed:
glibc-debuginfo.x86_64 2.25-12.fc26
glibc-debuginfo-common.x86_64 2.25-12.fc26

Complete!

# dnf downgrade glibc
[...]
Downgraded:
glibc.x86_64 2.25-6.fc26 glibc-common.x86_64 2.25-6.fc26
glibc-devel.x86_64 2.25-6.fc26 glibc-headers.x86_64 2.25-6.fc26
glibc-langpack-en.x86_64 2.25-6.fc26 libcrypt-nss.x86_64 2.25-6.fc26

Complete!

# rpm -q glibc glibc-debuginfo
glibc-2.25-6.fc26.x86_64
glibc-debuginfo-2.25-12.fc26.x86_64
=====

OK, so you can see now we have different versions of glibc and
glibc-debuginfo. Each debuginfo must be different.

With this series, defining new events also warns :)

=====
# perf probe -x /usr/lib64/libc-2.25.so -a malloc_get_state\\@GLIBC_2.2.5
WARN: There is a build-id mismatch between
/usr/lib/debug/usr/lib64/libc-2.25.so.debug
and
/usr/lib64/libc-2.25.so
Please check your system's debuginfo files for mismatches, e.g. check the versions for the target package and debuginfo package.
Added new event:
probe_libc:malloc_get_state (on malloc_get_state@GLIBC_2.2.5 in /usr/lib64/libc-2.25.so)

You can now use it in all perf tools, such as:

perf record -e probe_libc:malloc_get_state -aR sleep 1

=====

And listing up events warns.

=====
# perf probe -l | more
WARN: There is a build-id mismatch between
/usr/lib/debug/usr/lib64/libc-2.25.so.debug
and
/usr/lib64/libc-2.25.so
Please check your system's debuginfo files for mismatches, e.g. check the versions for the target package and debuginfo package.
probe_libc:malloc_get_state (on malloc_get_state@GLIBC_2.2.5 in /usr/lib64/libc-2.25.so)
=====

With [1/2], this warning messages repeated on same target (glibc). To suppress
this, [2/2] introduces no-debuginfo blacklist to skip it 2nd time as below.

=====
# perf probe -l | more
WARN: There is a build-id mismatch between
/usr/lib/debug/usr/lib64/libc-2.25.so.debug
and
/usr/lib64/libc-2.25.so
Please check your system's debuginfo files for mismatches, e.g. check the versions for the target package and debuginfo package.
probe_libc:malloc_get_state (on malloc_get_state@GLIBC_2.2.5 in /usr/lib64/libc-2.25.so)
probe_libc:malloc_get_state_1 (on malloc_get_state@GLIBC_2.2.5 in /usr/lib64/libc-2.25.so)
probe_libc:malloc_get_state_2 (on malloc_get_state@GLIBC_2.2.5 in /usr/lib64/libc-2.25.so)
=====

Arnaldo, would this match to your request?


Thank you,
---

Masami Hiramatsu (2):
perf-probe: Ensure debuginfo's build-id is correct
perf-probe: Skip searching debuginfo if we know no debuginfo


tools/perf/util/probe-finder.c | 34 +++++++++++++++++++++++++++++++++-
1 file changed, 33 insertions(+), 1 deletion(-)

--
Masami Hiramatsu (Linaro Ltd.) <mhiramat@kernel.org>

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