Re: [PATCH -tip v5 2/5] perf: set correct value to perf_event_header.miscfor BTS

[Akihiro Nagai]

(2012/01/30 18:35), Peter Zijlstra wrote:
> On Mon, 2012-01-30 at 13:43 +0900, Akihiro Nagai wrote:
> > @@ -330,6 +342,14 @@ int intel_pmu_drain_bts_buffer(void)
> >                  return 1;
> >
> >          for (; at<  top; at++) {
> > +               /*
> > +                * To resolve user space symbols and DSOs correctly, set
> > +                * PERF_RECORD_MISC_USER if from_addr or to_addr is user space.
> > +                */
> > +               if (!kernel_ip(data.ip) || !kernel_ip(data.addr)) {
> > +                       header.misc&= ~PERF_RECORD_MISC_CPUMODE_MASK;
> > +                       header.misc |= PERF_RECORD_MISC_USER;
> > +               }
> >                  data.ip         = at->from;
> >                  data.addr       = at->to;
>
> Why not key off of the from? If its a jump from userspace its a user
> event, its a jump from kernel space its a kernel event?

Of course, originally, perf does that. And, in those cases,
BTS records the both addresses of kernel and user in one
perf_sample on branches from kernel to user. Current perf
sets PERF_RECORD_MISC_KERNEL to all BTS events, and
perf-script doesn't resolve symbols and DSOs about the
user-space address, because it is a kernel event. So, to
solve both kernel and user symbols on an event, I had to
add this change.

Thank you,
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