kbuild: enable 'make CFLAGS=...' to add additional options to CC

The variable CFLAGS is a wellknown variable and the usage by
kbuild may result in unexpected behaviour.
On top of that several people over time has asked for a way to
pass in additional flags to gcc.

This patch replace use of CFLAGS with KBUILD_CFLAGS all over the
tree and enabling one to use:
make CFLAGS=...
to specify additional gcc commandline options.

One usecase is when trying to find gcc bugs but other
use cases has been requested too.

Patch was tested on following architectures:
alpha, arm, i386, x86_64, mips, sparc, sparc64, ia64, m68k

Test was simple to do a defconfig build, apply the patch and check
that nothing got rebuild.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

1 files changed, 12 insertions, 12 deletions

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 643839a3f5d..51309848c11 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -77,8 +77,8 @@ CFLAGS-$(CONFIG_PPC64)	:= -mminimal-toc -mtraceback=none  -mcall-aixdesc
 CFLAGS-$(CONFIG_PPC32)  := -Iarch/$(ARCH) -ffixed-r2 -mmultiple
 CPPFLAGS        += $(CPPFLAGS-y)
 AFLAGS          += $(AFLAGS-y)
-CFLAGS          += -msoft-float -pipe $(CFLAGS-y)
-CPP             = $(CC) -E $(CFLAGS)
+KBUILD_CFLAGS   += -msoft-float -pipe $(CFLAGS-y)
+CPP             = $(CC) -E $(KBUILD_CFLAGS)
 
 CHECKFLAGS      += -m$(CONFIG_WORD_SIZE) -D__powerpc__ -D__powerpc$(CONFIG_WORD_SIZE)__
 
@@ -88,35 +88,35 @@ GCC_BROKEN_VEC	:= $(shell if [ $(call cc-version) -lt 0400 ] ; then echo "y"; fi
 ifeq ($(CONFIG_POWER4_ONLY),y)
 ifeq ($(CONFIG_ALTIVEC),y)
 ifeq ($(GCC_BROKEN_VEC),y)
-        CFLAGS += $(call cc-option,-mcpu=970)
+        KBUILD_CFLAGS += $(call cc-option,-mcpu=970)
 else
-        CFLAGS += $(call cc-option,-mcpu=power4)
+        KBUILD_CFLAGS += $(call cc-option,-mcpu=power4)
 endif
 else
-        CFLAGS += $(call cc-option,-mcpu=power4)
+        KBUILD_CFLAGS += $(call cc-option,-mcpu=power4)
 endif
 else
-        CFLAGS += $(call cc-option,-mtune=power4)
+        KBUILD_CFLAGS += $(call cc-option,-mtune=power4)
 endif
 endif
 
 ifeq ($(CONFIG_TUNE_CELL),y)
-        CFLAGS += $(call cc-option,-mtune=cell)
+        KBUILD_CFLAGS += $(call cc-option,-mtune=cell)
 endif
 
 # No AltiVec instruction when building kernel
-CFLAGS += $(call cc-option,-mno-altivec)
+KBUILD_CFLAGS += $(call cc-option,-mno-altivec)
 
 # Enable unit-at-a-time mode when possible. It shrinks the
 # kernel considerably.
-CFLAGS += $(call cc-option,-funit-at-a-time)
+KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
 
 # Never use string load/store instructions as they are
 # often slow when they are implemented at all
-CFLAGS          += -mno-string
+KBUILD_CFLAGS           += -mno-string
 
 ifeq ($(CONFIG_6xx),y)
-CFLAGS          += -mcpu=powerpc
+KBUILD_CFLAGS           += -mcpu=powerpc
 endif
 
 cpu-as-$(CONFIG_4xx)            += -Wa,-m405
@@ -126,7 +126,7 @@ cpu-as-$(CONFIG_E500)		+= -Wa,-me500
 cpu-as-$(CONFIG_E200)           += -Wa,-me200
 
 AFLAGS += $(cpu-as-y)
-CFLAGS += $(cpu-as-y)
+KBUILD_CFLAGS += $(cpu-as-y)
 
 head-y                          := arch/powerpc/kernel/head_$(CONFIG_WORD_SIZE).o
 head-$(CONFIG_8xx)              := arch/powerpc/kernel/head_8xx.o