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authorOlof Johansson <olof@lixom.net>2014-02-14 19:35:15 +0000
committerCatalin Marinas <catalin.marinas@arm.com>2014-02-17 09:16:33 +0000
commite306dfd06fcb44d21c80acb8e5a88d55f3d1cf63 (patch)
tree27dea73b0449bd5790e5897a55d3c64fe0063393 /arch/arm64/kernel
parent6d0abeca3242a88cab8232e4acd7e2bf088f3bc2 (diff)
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ARM64: unwind: Fix PC calculation
The frame PC value in the unwind code used to just take the saved LR value and use that. That's incorrect as a stack trace, since it shows the return path stack, not the call path stack. In particular, it shows faulty information in case the bl is done as the very last instruction of one label, since the return point will be in the next label. That can easily be seen with tail calls to panic(), which is marked __noreturn and thus doesn't have anything useful after it. Easiest here is to just correct the unwind code and do a -4, to get the actual call site for the backtrace instead of the return site. Signed-off-by: Olof Johansson <olof@lixom.net> Cc: stable@vger.kernel.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/kernel')
-rw-r--r--arch/arm64/kernel/stacktrace.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index c3b6c63ea5fb..38f0558f0c0a 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -48,7 +48,11 @@ int unwind_frame(struct stackframe *frame)
frame->sp = fp + 0x10;
frame->fp = *(unsigned long *)(fp);
- frame->pc = *(unsigned long *)(fp + 8);
+ /*
+ * -4 here because we care about the PC at time of bl,
+ * not where the return will go.
+ */
+ frame->pc = *(unsigned long *)(fp + 8) - 4;
return 0;
}