From: Yan, Zheng <zheng.z....@intel.com>
"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....@intel.com>
Signed-off-by: Kan Liang <kan.li...@intel.com>
---
arch/x86/kernel/cpu/perf_event_intel_lbr.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c
b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
index 45a63a4..7ed04f8 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
@@ -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)
@@ -689,6 +692,12 @@ 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;
--
1.8.3.2
--
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