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authorOlof Johansson <olof@lixom.net>2014-02-14 19:35:15 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-03-06 21:30:12 -0800
commitc56e0dc1b70f1537659acffc6ac8d8d615be2dae (patch)
tree605f3703b082f82b88445c8806dc62eee1cab2d9
parentb500c0d3edf6c54e34a65c766a7a657b8ca88952 (diff)
downloadlinux-linaro-stable-c56e0dc1b70f1537659acffc6ac8d8d615be2dae.tar.gz
ARM64: unwind: Fix PC calculation
commit e306dfd06fcb44d21c80acb8e5a88d55f3d1cf63 upstream. 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> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-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 d25459ff57fc..048334bb2651 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;
}