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authorOlof Johansson <olof@lixom.net>2014-02-14 19:35:15 +0000
committerJiri Slaby <jslaby@suse.cz>2014-03-05 17:13:54 +0100
commitb9cac36b22d4a4c4dca3a42b63931702bd4cc4c8 (patch)
treeb45370ee51a254e8a4daa76c9e30bc62a0b3f04d
parent23c0ac16e67d6583d4ca1fa1e1bbf4e66d019bb2 (diff)
downloadlinux-linaro-stable-b9cac36b22d4a4c4dca3a42b63931702bd4cc4c8.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: Jiri Slaby <jslaby@suse.cz>
-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;
}