This is a note to let you know that I've just added the patch titled
ARM64: unwind: Fix PC calculation
to the 3.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm64-unwind-fix-pc-calculation.patch
and it can be found in the queue-3.13 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e306dfd06fcb44d21c80acb8e5a88d55f3d1cf63 Mon Sep 17 00:00:00 2001
From: Olof Johansson <olof@xxxxxxxxx>
Date: Fri, 14 Feb 2014 19:35:15 +0000
Subject: ARM64: unwind: Fix PC calculation
From: Olof Johansson <olof@xxxxxxxxx>
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@xxxxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/kernel/stacktrace.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -48,7 +48,11 @@ int unwind_frame(struct stackframe *fram
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;
}
Patches currently in stable-queue which might be from olof@xxxxxxxxx are
queue-3.13/arm-imx6-build-pm-imx6q.c-independently-of-config_pm.patch
queue-3.13/arm-tegra-only-run-pl310-init-on-systems-with-one.patch
queue-3.13/arm64-unwind-fix-pc-calculation.patch
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