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>

2 files changed, 4 insertions, 4 deletions

diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index ebd5d02a7d78..64512abef61d 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -609,13 +609,13 @@ ifdef CONFIG_64BIT
 endif
 
 AFLAGS          += $(cflags-y)
-CFLAGS          += $(cflags-y) \
+KBUILD_CFLAGS   += $(cflags-y) \
                         -D"VMLINUX_LOAD_ADDRESS=$(load-y)"
 
 LDFLAGS                 += -m $(ld-emul)
 
 ifdef CONFIG_MIPS
-CHECKFLAGS += $(shell $(CC) $(CFLAGS) -dM -E -xc /dev/null | \
+CHECKFLAGS += $(shell $(CC) $(KBUILD_CFLAGS) -dM -E -xc /dev/null | \
         egrep -vw '__GNUC_(|MINOR_|PATCHLEVEL_)_' | \
         sed -e 's/^\#define /-D/' -e "s/ /='/" -e "s/$$/'/")
 ifdef CONFIG_64BIT
@@ -632,7 +632,7 @@ OBJCOPYFLAGS		+= --remove-section=.reginfo
 #
 
 CPPFLAGS_vmlinux.lds := \
-        $(CFLAGS) \
+        $(KBUILD_CFLAGS) \
         -D"LOADADDR=$(load-y)" \
         -D"JIFFIES=$(JIFFIES)" \
         -D"DATAOFFSET=$(if $(dataoffset-y),$(dataoffset-y),0)"
diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index a2689f93c160..95a356ef3910 100644
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@@ -71,7 +71,7 @@ obj-$(CONFIG_PCSPEAKER)		+= pcspeaker.o
 obj-$(CONFIG_KEXEC)             += machine_kexec.o relocate_kernel.o
 obj-$(CONFIG_EARLY_PRINTK)      += early_printk.o
 
-CFLAGS_cpu-bugs64.o     = $(shell if $(CC) $(CFLAGS) -Wa,-mdaddi -c -o /dev/null -xc /dev/null >/dev/null 2>&1; then echo "-DHAVE_AS_SET_DADDI"; fi)
+CFLAGS_cpu-bugs64.o     = $(shell if $(CC) $(KBUILD_CFLAGS) -Wa,-mdaddi -c -o /dev/null -xc /dev/null >/dev/null 2>&1; then echo "-DHAVE_AS_SET_DADDI"; fi)
 
 obj-$(CONFIG_HAVE_STD_PC_SERIAL_PORT)   += 8250-platform.o