From 0e48026ae7abf871e51eaa9183c81ab5bef4c267 Mon Sep 17 00:00:00 2001 From: Stephane Eranian Date: Tue, 19 Mar 2013 16:10:38 +0100 Subject: [PATCH] perf/x86: Fix uninitialized pt_regs in intel_pmu_drain_bts_buffer() This patch fixes an uninitialized pt_regs struct in drain BTS function. The pt_regs struct is propagated all the way to the code_get_segment() function from perf_instruction_pointer() and may get garbage. We cannot simply inherit the actual pt_regs from the interrupt because BTS must be flushed on context-switch or when the associated event is disabled. And there we do not have a pt_regs handy. Setting pt_regs to all zeroes may not be the best option but it is not clear what else to do given where the drain_bts_buffer() is called from. In V2, we move the memset() later in the code to avoid doing it when we end up returning early without doing the actual BTS processing. Also dropped the reg.val initialization because it is redundant with the memset() as suggested by PeterZ. Signed-off-by: Stephane Eranian Acked-by: Peter Zijlstra Cc: peterz@infradead.org Cc: sqazi@google.com Cc: ak@linux.intel.com Cc: jolsa@redhat.com Link: http://lkml.kernel.org/r/20130319151038.GA25439@quad Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_event_intel_ds.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c index 826054a4f2ee..f71c9f09fd4b 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_ds.c +++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c @@ -314,10 +314,11 @@ int intel_pmu_drain_bts_buffer(void) if (top <= at) return 0; + memset(®s, 0, sizeof(regs)); + ds->bts_index = ds->bts_buffer_base; perf_sample_data_init(&data, 0, event->hw.last_period); - regs.ip = 0; /* * Prepare a generic sample, i.e. fill in the invariant fields.