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

[Masami Hiramatsu]

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@xxxxxxxxxxx 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@xxxxxxxxxxx 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@xxxxxxxxxxx in /usr/lib64/libc-2.25.so)
    probe_libc:malloc_get_state_1 (on malloc_get_state@xxxxxxxxxxx in /usr/lib64/libc-2.25.so)
    probe_libc:malloc_get_state_2 (on malloc_get_state@xxxxxxxxxxx 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@xxxxxxxxxx>