This is a note to let you know that I've just added the patch titled
Disable "frame-address" warning
to the 4.4-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:
disable-frame-address-warning.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 124a3d88fa20e1869fc229d7d8c740cc81944264 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Date: Wed, 27 Jul 2016 19:03:04 -0700
Subject: Disable "frame-address" warning
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From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
commit 124a3d88fa20e1869fc229d7d8c740cc81944264 upstream.
Newer versions of gcc warn about the use of __builtin_return_address()
with a non-zero argument when "-Wall" is specified:
kernel/trace/trace_irqsoff.c: In function ‘stop_critical_timings’:
kernel/trace/trace_irqsoff.c:433:86: warning: calling ‘__builtin_return_address’ with a nonzero argument is unsafe [-Wframe-address]
stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
[ .. repeats a few times for other similar cases .. ]
It is true that a non-zero argument is somewhat dangerous, and we do not
actually have very many uses of that in the kernel - but the ftrace code
does use it, and as Stephen Rostedt says:
"We are well aware of the danger of using __builtin_return_address() of
> 0. In fact that's part of the reason for having the "thunk" code in
x86 (See arch/x86/entry/thunk_{64,32}.S). [..] it adds extra frames
when tracking irqs off sections, to prevent __builtin_return_address()
from accessing bad areas. In fact the thunk_32.S states: 'Trampoline to
trace irqs off. (otherwise CALLER_ADDR1 might crash)'."
For now, __builtin_return_address() with a non-zero argument is the best
we can do, and the warning is not helpful and can end up making people
miss other warnings for real problems.
So disable the frame-address warning on compilers that need it.
Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
Makefile | 1 +
1 file changed, 1 insertion(+)
--- a/Makefile
+++ b/Makefile
@@ -617,6 +617,7 @@ include arch/$(SRCARCH)/Makefile
KBUILD_CFLAGS += $(call cc-option,-fno-delete-null-pointer-checks,)
KBUILD_CFLAGS += $(call cc-disable-warning,maybe-uninitialized,)
+KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,)
ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
KBUILD_CFLAGS += -Os
Patches currently in stable-queue which might be from torvalds@xxxxxxxxxxxxxxxxxxxx are
queue-4.4/disable-maybe-uninitialized-warning-globally.patch
queue-4.4/include-linux-kernel.h-change-abs-macro-so-it-uses-consistent-return-type.patch
queue-4.4/makefile-mute-warning-for-__builtin_return_address-0-for-tracing-only.patch
queue-4.4/add-braces-to-avoid-ambiguous-else-compiler-warnings.patch
queue-4.4/ocfs2-fix-start-offset-to-ocfs2_zero_range_for_truncate.patch
queue-4.4/tools-support-relative-directory-path-for-o.patch
queue-4.4/disable-frame-address-warning.patch
queue-4.4/ocfs2-dlm-fix-race-between-convert-and-migration.patch
queue-4.4/reiserfs-fix-new_insert_key-may-be-used-uninitialized.patch
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