From c1a3a4b90a5a47adcca0e587f5d7e9ea61329b26 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Mon, 22 Nov 2010 14:01:55 -0200 Subject: [PATCH] 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 Cc: Frederic Weisbecker Cc: Ingo Molnar Cc: Jesper Juhl Cc: Marcus Meissner Cc: Mike Galbraith Cc: Paul Mackerras Cc: Peter Zijlstra Cc: Sarah Sharp Cc: Stephane Eranian Cc: Tejun Heo Cc: Tom Zanussi LKML-Reference: Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-record.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index 93bd2ff001fb..e2c2de201eec 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -697,17 +697,18 @@ static int __cmd_record(int argc, const char **argv) if (err < 0) err = event__synthesize_kernel_mmap(process_synthesized_event, session, machine, "_stext"); - if (err < 0) { - pr_err("Couldn't record kernel reference relocation symbol.\n"); - return err; - } + if (err < 0) + pr_err("Couldn't record kernel reference relocation symbol\n" + "Symbol resolution may be skewed if relocation was used (e.g. kexec).\n" + "Check /proc/kallsyms permission or run as root.\n"); err = event__synthesize_modules(process_synthesized_event, session, machine); - if (err < 0) { - pr_err("Couldn't record kernel reference relocation symbol.\n"); - return err; - } + if (err < 0) + pr_err("Couldn't record kernel module information.\n" + "Symbol resolution may be skewed if relocation was used (e.g. kexec).\n" + "Check /proc/modules permission or run as root.\n"); + if (perf_guest) perf_session__process_machines(session, event__synthesize_guest_os); -- 2.20.1