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SubjectRe: [PATCH 2/4] perf/x86: add support for sampling PEBS machine state registers
On Wed, Jul 09, 2014 at 12:15:57AM +0200, Stephane Eranian wrote:
> PEBS can capture machine state regs at retirement of the sampled
> instructions. When precise sampling is enabled on an event, PEBS
> is used, so substitute the interrupted state with the PEBS state.
> Note that not all registers are captured by PEBS. Those missing
> are replaced by the interrupt state counter-parts.
>
> Signed-off-by: Stephane Eranian <eranian@google.com>
> ---
> arch/x86/kernel/cpu/perf_event_intel_ds.c | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
> index 980970c..d612bcd 100644
> --- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
> +++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
> @@ -925,6 +925,25 @@ static void __intel_pmu_pebs_event(struct perf_event *event,
> regs.bp = pebs->bp;
> regs.sp = pebs->sp;
>
> + if (sample_type & PERF_SAMPLE_REGS_INTR) {
> + regs.ax = pebs->ax;
> + regs.bx = pebs->bx;
> + regs.cx = pebs->cx;
> + regs.si = pebs->si;
> + regs.di = pebs->di;
> +
> + regs.r8 = pebs->r8;
> + regs.r9 = pebs->r9;
> + regs.r10 = pebs->r10;
> + regs.r11 = pebs->r11;
> + regs.r12 = pebs->r12;
> + regs.r13 = pebs->r13;
> + regs.r14 = pebs->r14;
> + regs.r14 = pebs->r15;
> +
> + data.regs_intr.regs = &regs;

this assignement is not necessary, because you assign this regs pointer
again in perf_prepare_sample -> perf_sample_regs_intr later

jirka


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