perf record: Handle restrictive permissions in /proc/{kallsyms,modules}
authorArnaldo Carvalho de Melo <acme@redhat.com>
Mon, 22 Nov 2010 16:01:55 +0000 (14:01 -0200)
committerArnaldo Carvalho de Melo <acme@redhat.com>
Mon, 22 Nov 2010 16:01:55 +0000 (14:01 -0200)
commitc1a3a4b90a5a47adcca0e587f5d7e9ea61329b26
treec756520ea4e1eaa007bba3c32c9eab154d13a1a6
parentde31ec8a31046111befd16a7083e3bdda2ff42cf
perf record: Handle restrictive permissions in /proc/{kallsyms,modules}

The 59365d1 commit, even being reverted by 33e0d57, showed a non robust
behavior in 'perf record': it really should just warn the user that some
functionality will not be available.

The new behavior then becomes:

[acme@felicio linux]$ ls -la /proc/{kallsyms,modules}
-r-------- 1 root root 0 Nov 22 12:19 /proc/kallsyms
-r-------- 1 root root 0 Nov 22 12:19 /proc/modules
[acme@felicio linux]$ perf record ls -R > /dev/null
Couldn't record kernel reference relocation symbol
Symbol resolution may be skewed if relocation was used (e.g. kexec).
Check /proc/kallsyms permission or run as root.
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.004 MB perf.data (~161 samples) ]
[acme@felicio linux]$ perf report --stdio
[kernel.kallsyms] with build id 77b05e00e64e4de1c9347d83879779b540d69f00 not found, continuing without symbols
# Events: 98  cycles
#
# Overhead  Command    Shared Object                Symbol
# ........  .......  ...............  ....................
#
    48.26%       ls  [kernel]         [k] ffffffff8102b92b
    22.49%       ls  libc-2.12.90.so  [.] __strlen_sse2
     8.35%       ls  libc-2.12.90.so  [.] __GI___strcoll_l
     8.17%       ls  ls               [.]            11580
     3.35%       ls  libc-2.12.90.so  [.] _IO_new_file_xsputn
     3.33%       ls  libc-2.12.90.so  [.] _int_malloc
     1.88%       ls  libc-2.12.90.so  [.] _int_free
     0.84%       ls  libc-2.12.90.so  [.] malloc_consolidate
     0.84%       ls  libc-2.12.90.so  [.] __readdir64
     0.83%       ls  ls               [.] strlen@plt
     0.83%       ls  libc-2.12.90.so  [.] __GI_fwrite_unlocked
     0.83%       ls  libc-2.12.90.so  [.] __memcpy_sse2

#
# (For a higher level overview, try: perf report --sort comm,dso)
#
[acme@felicio linux]$

It still has the build-ids for DSOs in the maps with hits:

[acme@felicio linux]$ perf buildid-list
77b05e00e64e4de1c9347d83879779b540d69f00 [kernel.kallsyms]
09c4a431a4a8b648fcfc2c2bdda70f56050ddff1 /bin/ls
af75ea9ad951d25e0f038901a11b3846dccb29a4 /lib64/libc-2.12.90.so
[acme@felicio linux]$

That can be used in another machine to resolve kernel symbols.

Cc: Eugene Teo <eugeneteo@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jesper Juhl <jj@chaosbits.net>
Cc: Marcus Meissner <meissner@suse.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
tools/perf/builtin-record.c