From 124a3d88fa20e1869fc229d7d8c740cc81944264 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Wed, 27 Jul 2016 19:03:04 -0700 Subject: [PATCH] Disable "frame-address" warning MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Linus Torvalds --- Makefile | 1 + 1 file changed, 1 insertion(+) diff --git a/Makefile b/Makefile index d384848478b9..393b6159ae92 100644 --- a/Makefile +++ b/Makefile @@ -620,6 +620,7 @@ 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 -- 2.20.1