Re: [RFC] perf: probe_finder: continue if atleast one probe point found

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Sun, Feb 28, 2016 at 03:49:44AM -0800, Joel Fernandes escreveu:
> Taeung,
> 
> Thanks for that. As this is an RFC, I have added them now to this email
> thread and when I post the final patch, I'll include them in CC.
> 
> All,
> Please provide your comments on my patch.

Masami, are you ok with this patch?

- Arnaldo
 
> Thanks,
> Joel
> 
> On Sun, Feb 28, 2016 at 3:35 AM, Taeung Song <treeze.taeung@gmail.com>
> wrote:
> 
> > Hi, Joel
> >
> > perf subsystem's maintainers are
> > Arnaldo Carvalho de Melo <acme@kernel.org>
> > Peter Zijlstra <peterz@infradead.org>
> > Ingo Molnar <mingo@redhat.com>
> >
> > (or Namhyung Kim <namhyung@kernel.org>, Jiri Olsa <jolsa@kernel.org>)
> >
> > AFAIK,
> > When sending some patches, it would be better to add them into To: or Cc:
> >
> >
> > Thanks,
> > Taeung
> >
> >
> > On 02/28/2016 08:14 PM, Joel Fernandes wrote:
> >
> >> Sometimes for inline functions, perf probe can fail such as if an
> >> arguments are
> >> requested at probe points. This is probably because when the compiler
> >> inlines,
> >> for some instances it optimizes away arguments. Either way, the DWARF has
> >> missing arguments for certain probe points of inline functions causing
> >> 'perf
> >> probe' to fail. I noticed this when probing the C library that ships with
> >> my
> >> distribution. With the following patch I am successfully able to record
> >> kprobe
> >> events with arguments.
> >>
> >> Test
> >> ----
> >>   ./perf probe \
> >>     -k ./vmlinux -s ./ -x /lib/x86_64-linux-gnu/libc.so.6 -a 'malloc
> >> bytes' -v
> >>
> >> Without the patch
> >> -----------------
> >> Matched function: __libc_malloc
> >> found inline addr: 0x831a6
> >> Probe point found: malloc_atfork+150
> >> Searching 'bytes' variable in context.
> >> Converting variable bytes into trace event.
> >> bytes type is long unsigned int.
> >> found inline addr: 0x844a0
> >> Probe point found: __libc_malloc+0
> >> Searching 'bytes' variable in context.
> >> Converting variable bytes into trace event.
> >> bytes type is long unsigned int.
> >> found inline addr: 0x8463b
> >> Probe point found: __malloc_get_state+11
> >> Searching 'bytes' variable in context.
> >> Failed to find 'bytes' in this function.
> >> An error occurred in debuginfo analysis (-2).
> >>    Error: Failed to add events. Reason: No such file or directory (Code:
> >> -2)
> >>
> >> With the patch
> >> --------------
> >> Open Debuginfo file: /usr/lib/debug/lib/x86_64-linux-gnu/libc-2.21.so
> >> Try to find probe point from debuginfo.
> >> Symbol malloc address found : 844a0
> >> Matched function: __libc_malloc
> >> found inline addr: 0x831a6
> >> Probe point found: malloc_atfork+150
> >> Searching 'bytes' variable in context.
> >> Converting variable bytes into trace event.
> >> bytes type is long unsigned int.
> >> found inline addr: 0x844a0
> >> Probe point found: __libc_malloc+0
> >> Searching 'bytes' variable in context.
> >> Converting variable bytes into trace event.
> >> bytes type is long unsigned int.
> >> found inline addr: 0x8463b
> >> Probe point found: __malloc_get_state+11
> >> Searching 'bytes' variable in context.
> >> Failed to find 'bytes' in this function.
> >> Probe point error, ignoring. Atleast one probe point found
> >> found inline addr: 0x84bba
> >> Probe point found: __libc_realloc+410
> >> Searching 'bytes' variable in context.
> >> Failed to find 'bytes' in this function.
> >> Probe point error, ignoring. Atleast one probe point found
> >> found inline addr: 0x84d08
> >> ...
> >> Probe point error, ignoring. Atleast one probe point found
> >> Found 3 probe_trace_events.
> >> Opening /sys/kernel/debug/tracing//uprobe_events write=1
> >> Writing event: p:probe_libc/malloc /lib/x86_64-linux-gnu/libc-2.21.so:0x831a6
> >> bytes=%bp:u64
> >> Writing event: p:probe_libc/malloc_1 /lib/x86_64-linux-gnu/libc-2.21.so:0x844a0
> >> bytes=%di:u64
> >> Writing event: p:probe_libc/malloc_2 /lib/x86_64-linux-gnu/libc-2.21.so:0x85af7
> >> bytes=%di:u64
> >> Added new events:
> >>    probe_libc:malloc    (on malloc in /lib/x86_64-linux-gnu/libc-2.21.so
> >> with bytes)
> >>    probe_libc:malloc_1  (on malloc in /lib/x86_64-linux-gnu/libc-2.21.so
> >> with bytes)
> >>    probe_libc:malloc_2  (on malloc in /lib/x86_64-linux-gnu/libc-2.21.so
> >> with bytes)
> >>
> >> Signed-off-by: Joel Fernandes <agnel.joel@gmail.com>
> >> ---
> >>   tools/perf/util/probe-finder.c | 4 ++++
> >>   1 file changed, 4 insertions(+)
> >>
> >> diff --git a/tools/perf/util/probe-finder.c
> >> b/tools/perf/util/probe-finder.c
> >> index 4ce5c5e..3ac9481 100644
> >> --- a/tools/perf/util/probe-finder.c
> >> +++ b/tools/perf/util/probe-finder.c
> >> @@ -1255,6 +1255,10 @@ end:
> >>         if (ret) {
> >>                 clear_probe_trace_event(tev);
> >>                 tf->ntevs--;
> >> +               if (tf->ntevs != 0) {
> >> +                       pr_debug("Ignoring error as atleast one probe
> >> point found.\n");
> >> +                       ret = 0;
> >> +               }
> >>         }
> >>         free(args);
> >>         return ret;
> >>
> >>