Add option to enable -Wframe-larger-than= on gcc 4.4

Add option to enable -Wframe-larger-than= on gcc 4.4

gcc mainline (upcoming 4.4) added a new -Wframe-larger-than=...
option to warn at build time about too large stack frames. Add a config
option to enable this warning, since this very useful for the kernel.

I choose (somewhat arbitarily) 2048 as default warning threshold for 64bit
and 1024 as default for 32bit architectures.  With some research and
fixing all the code for smaller values these defaults should be probably
lowered.

With the default allyesconfigs have some new warnings, but I think
that is all code that should be just fixed.

At some point (when gcc 4.4 is released and widely used) this should
obsolete make checkstack

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index 6ae7fd4475b8..c6d331ba140b 100644
--- a/Makefile
+++ b/Makefile
@@ -507,6 +507,10 @@ else
 KBUILD_CFLAGS	+= -O2
 endif
 
+ifneq (CONFIG_FRAME_WARN,0)
+KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
+endif
+
 # Force gcc to behave correct even for buggy distributions
 # Arch Makefiles may override this setting
 KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)