| From 124a3d88fa20e1869fc229d7d8c740cc81944264 Mon Sep 17 00:00:00 2001 |
| From: Linus Torvalds <torvalds@linux-foundation.org> |
| Date: Wed, 27 Jul 2016 19:03:04 -0700 |
| Subject: Disable "frame-address" warning |
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| |
| From: Linus Torvalds <torvalds@linux-foundation.org> |
| |
| 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@goodmis.org> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| 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 |
