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Subject[PATCH] x86: Get bp from the IRQ regs instead of directly from the CPU
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Date
Passing 0 for bp causes dump_trace() to get bp directly from the
hardware register. This leads to the IRQ stack being included in the
generated call chains, which means the stack looks something like
this:

[ ip ] [ IRQ stack ] [ rest of stack trace ]

which is incorrect and confusing to user space.

Getting bp from the IRQ regs instead makes the tracing start after the
IRQ stack:

[ ip ] [ rest of stack trace ]

Signed-off-by: Søren Sandmann Pedersen <sandmann@redhat.com>
---
arch/x86/kernel/cpu/perf_event.c | 10 +++++++++-
1 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index b5801c3..39b1d0c 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -2177,10 +2177,18 @@ static const struct stacktrace_ops backtrace_ops = {
static void
perf_callchain_kernel(struct pt_regs *regs, struct perf_callchain_entry *entry)
{
+ unsigned long bp;
+
callchain_store(entry, PERF_CONTEXT_KERNEL);
callchain_store(entry, regs->ip);

- dump_trace(NULL, regs, NULL, 0, &backtrace_ops, entry);
+#ifdef CONFIG_FRAME_POINTER
+ bp = regs->bp;
+#else
+ bp = 0;
+#endif
+
+ dump_trace(NULL, regs, NULL, bp, &backtrace_ops, entry);
}

/*
--
1.6.5.rc2
--
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