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>

7 files changed, 12 insertions, 12 deletions

diff --git a/arch/um/Makefile b/arch/um/Makefile
index 989224f2134..18123bf7b64 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -58,14 +58,14 @@ SYS_DIR		:= $(ARCH_DIR)/include/sysdep-$(SUBARCH)
 #
 # These apply to USER_CFLAGS to.
 
-CFLAGS += $(CFLAGS-y) -D__arch_um__ -DSUBARCH=\"$(SUBARCH)\"	\
+KBUILD_CFLAGS += $(CFLAGS-y) -D__arch_um__ -DSUBARCH=\"$(SUBARCH)\"	\
 	$(ARCH_INCLUDE) $(MODE_INCLUDE) -Dvmap=kernel_vmap	\
 	-Din6addr_loopback=kernel_in6addr_loopback
 
 AFLAGS += $(ARCH_INCLUDE)
 
 USER_CFLAGS = $(patsubst $(KERNEL_DEFINES),,$(patsubst -D__KERNEL__,,\
-	$(patsubst -I%,,$(CFLAGS)))) $(ARCH_INCLUDE) $(MODE_INCLUDE) \
+	$(patsubst -I%,,$(KBUILD_CFLAGS)))) $(ARCH_INCLUDE) $(MODE_INCLUDE) \
 	-D_FILE_OFFSET_BITS=64
 
 include $(srctree)/$(ARCH_DIR)/Makefile-$(SUBARCH)
@@ -75,14 +75,14 @@ include $(srctree)/$(ARCH_DIR)/Makefile-os-$(OS)
 
 # -Derrno=kernel_errno - This turns all kernel references to errno into
 # kernel_errno to separate them from the libc errno.  This allows -fno-common
-# in CFLAGS.  Otherwise, it would cause ld to complain about the two different
+# in KBUILD_CFLAGS.  Otherwise, it would cause ld to complain about the two different
 # errnos.
 # These apply to kernelspace only.
 
 KERNEL_DEFINES = -Derrno=kernel_errno -Dsigprocmask=kernel_sigprocmask \
 	-Dmktime=kernel_mktime $(ARCH_KERNEL_DEFINES)
-CFLAGS += $(KERNEL_DEFINES)
-CFLAGS += $(call cc-option,-fno-unit-at-a-time,)
+KBUILD_CFLAGS += $(KERNEL_DEFINES)
+KBUILD_CFLAGS += $(call cc-option,-fno-unit-at-a-time,)
 
 # These are needed for clean and mrproper, since in that case .config is not
 # included; the values here are meaningless
diff --git a/arch/um/Makefile-i386 b/arch/um/Makefile-i386
index c9f1c5b24c9..26bc786fc61 100644
--- a/arch/um/Makefile-i386
+++ b/arch/um/Makefile-i386
@@ -15,7 +15,7 @@ OBJCOPYFLAGS  		:= -O binary -R .note -R .comment -S
 
 ifeq ("$(origin SUBARCH)", "command line")
 ifneq ("$(shell uname -m | sed -e s/i.86/i386/)", "$(SUBARCH)")
-CFLAGS			+= $(call cc-option,-m32)
+KBUILD_CFLAGS		+= $(call cc-option,-m32)
 AFLAGS			+= $(call cc-option,-m32)
 LINK-y			+= $(call cc-option,-m32)
 UML_OBJCOPYFLAGS	+= -F $(ELF_FORMAT)
@@ -36,4 +36,4 @@ cflags-y += $(call cc-option,-mpreferred-stack-boundary=2)
 # an unresolved reference.
 cflags-y += -ffreestanding
 
-CFLAGS += $(cflags-y)
+KBUILD_CFLAGS += $(cflags-y)
diff --git a/arch/um/Makefile-os-Linux b/arch/um/Makefile-os-Linux
index 0c0f9a1cbba..52859487c95 100644
--- a/arch/um/Makefile-os-Linux
+++ b/arch/um/Makefile-os-Linux
@@ -5,4 +5,4 @@
 
 # To get a definition of F_SETSIG
 USER_CFLAGS += -D_GNU_SOURCE -D_LARGEFILE64_SOURCE
-CFLAGS += -D_LARGEFILE64_SOURCE
+KBUILD_CFLAGS += -D_LARGEFILE64_SOURCE
diff --git a/arch/um/Makefile-x86_64 b/arch/um/Makefile-x86_64
index 69ecea63fda..36d2bb5e419 100644
--- a/arch/um/Makefile-x86_64
+++ b/arch/um/Makefile-x86_64
@@ -9,7 +9,7 @@ _extra_flags_ = -fno-builtin -m64
 #We #undef __x86_64__ for kernelspace, not for userspace where
 #it's needed for headers to work!
 ARCH_KERNEL_DEFINES = -U__$(SUBARCH)__
-CFLAGS += $(_extra_flags_)
+KBUILD_CFLAGS += $(_extra_flags_)
 
 CHECKFLAGS  += -m64
 AFLAGS += -m64
diff --git a/arch/um/drivers/Makefile b/arch/um/drivers/Makefile
index de17d4c6e02..0f780dd0d4c 100644
--- a/arch/um/drivers/Makefile
+++ b/arch/um/drivers/Makefile
@@ -17,7 +17,7 @@ ubd-objs := ubd_kern.o ubd_user.o
 port-objs := port_kern.o port_user.o
 harddog-objs := harddog_kern.o harddog_user.o
 
-LDFLAGS_pcap.o := -r $(shell $(CC) $(CFLAGS) -print-file-name=libpcap.a)
+LDFLAGS_pcap.o := -r $(shell $(CC) $(KBUILD_CFLAGS) -print-file-name=libpcap.a)
 
 targets := pcap_kern.o pcap_user.o
 
diff --git a/arch/um/sys-i386/Makefile b/arch/um/sys-i386/Makefile
index d6b3ecd4b77..8909b07d9ee 100644
--- a/arch/um/sys-i386/Makefile
+++ b/arch/um/sys-i386/Makefile
@@ -20,4 +20,4 @@ CFLAGS_stub_segv.o := $(CFLAGS_NO_HARDENING)
 
 include arch/um/scripts/Makefile.rules
 
-$(obj)/unmap.%: _c_flags = $(call unprofile,$(CFLAGS))
+$(obj)/unmap.%: _c_flags = $(call unprofile,$(KBUILD_CFLAGS))
diff --git a/arch/um/sys-x86_64/Makefile b/arch/um/sys-x86_64/Makefile
index 4d9e5efa6fb..e446a9916fd 100644
--- a/arch/um/sys-x86_64/Makefile
+++ b/arch/um/sys-x86_64/Makefile
@@ -28,4 +28,4 @@ CFLAGS_stub_segv.o := $(CFLAGS_NO_HARDENING)
 
 include arch/um/scripts/Makefile.rules
 
-$(obj)/unmap.%: _c_flags = $(call unprofile,$(CFLAGS))
+$(obj)/unmap.%: _c_flags = $(call unprofile,$(KBUILD_CFLAGS))