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perf/x86/intel: Discard zero length call entries in LBR call stack

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"Zero length call" uses the attribute of the call instruction to push
the immediate instruction pointer on to the stack and then pops off
that address into a register. This is accomplished without any matching
return instruction. It confuses the hardware and make the recorded call
stack incorrect.

We can partially resolve this issue by: decode call instructions and
discard any zero length call entry in the LBR stack.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: eranian@google.com
Cc: jolsa@redhat.com
Link: http://lkml.kernel.org/r/1415156173-10035-16-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Yan, Zheng 2014-11-04 21:56:11 -05:00 committed by Ingo Molnar
parent 2c70d0086e
commit aa54ae9b87
1 changed files with 11 additions and 2 deletions
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13
arch/x86/kernel/cpu/perf_event_intel_lbr.c
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@ -94,7 +94,8 @@ enum {
X86_BR_ABORT = 1 << 12,/* transaction abort */
X86_BR_IN_TX = 1 << 13,/* in transaction */
X86_BR_NO_TX = 1 << 14,/* not in transaction */
X86_BR_CALL_STACK = 1 << 15,/* call stack */
X86_BR_ZERO_CALL = 1 << 15,/* zero length call */
X86_BR_CALL_STACK = 1 << 16,/* call stack */
};
#define X86_BR_PLM (X86_BR_USER | X86_BR_KERNEL)
@ -111,13 +112,15 @@ enum {
X86_BR_JMP |\
X86_BR_IRQ |\
X86_BR_ABORT |\
X86_BR_IND_CALL)
X86_BR_IND_CALL |\
X86_BR_ZERO_CALL)
#define X86_BR_ALL (X86_BR_PLM | X86_BR_ANY)
#define X86_BR_ANY_CALL \
(X86_BR_CALL |\
X86_BR_IND_CALL |\
X86_BR_ZERO_CALL |\
X86_BR_SYSCALL |\
X86_BR_IRQ |\
X86_BR_INT)
@ -702,6 +705,12 @@ static int branch_type(unsigned long from, unsigned long to, int abort)
ret = X86_BR_INT;
break;
case 0xe8: /* call near rel */
insn_get_immediate(&insn);
if (insn.immediate1.value == 0) {
/* zero length call */
ret = X86_BR_ZERO_CALL;
break;
}
case 0x9a: /* call far absolute */
ret = X86_BR_CALL;
break;