Messages in this thread | | | From | Vince Weaver <> | Date | Fri, 6 Mar 2015 13:37:03 -0500 (EST) | Subject | Re: [patch] perf_event_open.2: 3.19 PERF_SAMPLE_REGS_INTR support |
| |
On Mon, 2 Mar 2015, Andi Kleen wrote:
> > do not enable REGS_USER and REG_INTR at the same time > > as REGS_USER will have REG_INTR values and > > cannot be used for user stack unwinding > > If that's true it would be a bug. But I doubt it. > > The PEBS handler sets up its own pt_regs, so they should > be independent.
I could be wrong here, but was tracing through the code.
If you trigger a PEBS interrupt (because you have precise_ip set) and you have both REGS_USER and REGS_INTR set, then __intel_pmu_pebs_event() is called from arch/x86/kernel/cpu/perf_event_intel_ds.c
and in there it sets the regs values based solely on
if (sample_type & PERF_SAMPLE_REGS_INTR) { }
with those values copies into regs and then passed upstream through perf_event_overflow()
so if the sample_type has *both* PERF_SAMPLE_REGS_INTR and PERF_SAMPLE_REGS_USER set, then the PERF_SAMPLE_REGS_USER values will have the same register values as the PERF_SAMPLE_REGS_INTR values.
Maybe this is the expected behavior, or maybe I am missing something still.
Vince
| |