Re: warning: calling â__builtin_return_addressâ with a nonzero argument is unsafe

From: Steven Rostedt
Date: Thu Jul 28 2016 - 22:30:53 EST


On Thu, 28 Jul 2016 18:25:33 -0700
Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> I tried something like that, but the CFLAGS games the tracing code
> does made my thing result in
>
> kernel/trace/Makefile:20: *** Recursive variable 'KBUILD_CFLAGS'
> references itself (eventually). Stop.
>
> but yes, if you have the magic fingers to make it work, limiting the
> -Wno-frame-address to just the tracing code sounds like the
> RightThing(tm).

Take 2:

It compiles for me, but I don't have a compiler that has that warning
to test with. See if this works. BTW, it looks like that last comma
before the ending parenthesis is not needed.

Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
diff --git a/Makefile b/Makefile
index 393b615..d384848 100644
--- a/Makefile
+++ b/Makefile
@@ -620,7 +620,6 @@ 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
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index 979e7bf..d0a1617 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -1,4 +1,8 @@

+# We are fully aware of the dangers of __builtin_return_address()
+FRAME_CFLAGS := $(call cc-disable-warning,frame-address)
+KBUILD_CFLAGS += $(FRAME_CFLAGS)
+
# Do not instrument the tracer itself:

ifdef CONFIG_FUNCTION_TRACER