kbuild: enable 'make AFLAGS=...' to add additional options to AS

The variable AFLAGS 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 AFLAGS with KBUILD_AFLAGS all over
the tree.

Patch was tested on following architectures:
alpha, arm, i386, x86_64, mips, sparc, sparc64, ia64, m68k, s390

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

Documentation/kbuild/makefiles.txt

@@ -424,6 +424,7 @@ more details, with real examples.
 	as-instr checks if the assembler reports a specific instruction
 	and then outputs either option1 or option2
 	C escapes are supported in the test instruction
+	Note: as-instr-option uses KBUILD_AFLAGS for $(AS) options
 
     cc-option
 	cc-option is used to check if $(CC) supports a given option, and not
@@ -819,14 +820,14 @@ When kbuild executes, the following steps are followed (roughly):
 	In this example, the binary $(obj)/image is a binary version of
 	vmlinux. The usage of $(call if_changed,xxx) will be described later.
 
-    AFLAGS		$(AS) assembler flags
+    KBUILD_AFLAGS		$(AS) assembler flags
 
 	Default value - see top level Makefile
 	Append or modify as required per architecture.
 
 	Example:
 		#arch/sparc64/Makefile
-		AFLAGS += -m64 -mcpu=ultrasparc
+		KBUILD_AFLAGS += -m64 -mcpu=ultrasparc
 
     KBUILD_CFLAGS		$(CC) compiler flags
 

Makefile

@@ -323,7 +323,7 @@ CPPFLAGS        := -D__KERNEL__ $(LINUXINCLUDE)
 KBUILD_CFLAGS   := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
 		   -fno-strict-aliasing -fno-common \
 		   -Werror-implicit-function-declaration
-AFLAGS          := -D__ASSEMBLY__
+KBUILD_AFLAGS   := -D__ASSEMBLY__
 
 # Read KERNELRELEASE from include/config/kernel.release (if it exists)
 KERNELRELEASE = $(shell cat include/config/kernel.release 2> /dev/null)
@@ -336,7 +336,7 @@ export HOSTCXX HOSTCXXFLAGS LDFLAGS_MODULE CHECK CHECKFLAGS
 
 export CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS LDFLAGS
 export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE
-export AFLAGS AFLAGS_KERNEL AFLAGS_MODULE
+export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE
 
 # When compiling out-of-tree modules, put MODVERDIR in the module
 # tree rather than in the kernel tree. The kernel tree might
@@ -507,7 +507,7 @@ endif
 
 ifdef CONFIG_DEBUG_INFO
 KBUILD_CFLAGS	+= -g
-AFLAGS		+= -gdwarf-2
+KBUILD_AFLAGS	+= -gdwarf-2
 endif
 
 # Force gcc to behave correct even for buggy distributions
@@ -1502,7 +1502,7 @@ quiet_cmd_rmfiles = $(if $(wildcard $(rm-files)),CLEAN   $(wildcard $(rm-files))
       cmd_rmfiles = rm -f $(rm-files)
 
 
-a_flags = -Wp,-MD,$(depfile) $(AFLAGS) $(AFLAGS_KERNEL) \
+a_flags = -Wp,-MD,$(depfile) $(KBUILD_AFLAGS) $(AFLAGS_KERNEL) \
 	  $(NOSTDINC_FLAGS) $(CPPFLAGS) \
 	  $(modkern_aflags) $(EXTRA_AFLAGS) $(AFLAGS_$(basetarget).o)
 

arch/arm/Makefile

@@ -86,7 +86,7 @@ endif
 
 # Need -Uarm for gcc < 3.x
 KBUILD_CFLAGS	+=$(CFLAGS_ABI) $(arch-y) $(tune-y) $(call cc-option,-mshort-load-bytes,$(call cc-option,-malignment-traps,)) -msoft-float -Uarm
-AFLAGS		+=$(CFLAGS_ABI) $(arch-y) $(tune-y) -msoft-float
+KBUILD_AFLAGS	+=$(CFLAGS_ABI) $(arch-y) $(tune-y) -msoft-float
 
 CHECKFLAGS	+= -D__arm__
 

arch/arm/vfp/Makefile

@@ -7,7 +7,7 @@
 # EXTRA_CFLAGS := -DDEBUG
 # EXTRA_AFLAGS := -DDEBUG
 
-AFLAGS		:=$(AFLAGS:-msoft-float=-Wa,-mfpu=softvfp+vfp)
+KBUILD_AFLAGS	:=$(KBUILD_AFLAGS:-msoft-float=-Wa,-mfpu=softvfp+vfp)
 LDFLAGS		+=--no-warn-mismatch
 
 obj-y			+= vfp.o

arch/avr32/Makefile

@@ -12,14 +12,14 @@ all: uImage vmlinux.elf
 KBUILD_DEFCONFIG	:= atstk1002_defconfig
 
 KBUILD_CFLAGS	+= -pipe -fno-builtin -mno-pic
-AFLAGS		+= -mrelax -mno-pic
+KBUILD_AFLAGS	+= -mrelax -mno-pic
 CFLAGS_MODULE	+= -mno-relax
 LDFLAGS_vmlinux	+= --relax
 
 cpuflags-$(CONFIG_CPU_AT32AP7000)	+= -mcpu=ap7000
 
 KBUILD_CFLAGS	+= $(cpuflags-y)
-AFLAGS		+= $(cpuflags-y)
+KBUILD_AFLAGS	+= $(cpuflags-y)
 
 CHECKFLAGS	+= -D__avr32__ -D__BIG_ENDIAN
 

arch/blackfin/Makefile

@@ -54,7 +54,7 @@ rev-$(CONFIG_BF_REV_NONE) := none
 rev-$(CONFIG_BF_REV_ANY)  := any
 
 KBUILD_CFLAGS += -mcpu=$(cpu-y)-$(rev-y)
-AFLAGS += -mcpu=$(cpu-y)-$(rev-y)
+KBUILD_AFLAGS += -mcpu=$(cpu-y)-$(rev-y)
 
 head-y   := arch/$(ARCH)/mach-$(MACHINE)/head.o arch/$(ARCH)/kernel/init_task.o
 

arch/cris/Makefile

@@ -29,7 +29,7 @@ LD = $(CROSS_COMPILE)ld -mcrislinux
 OBJCOPYFLAGS := -O binary -R .note -R .comment -S
 
 CPPFLAGS_vmlinux.lds = -DDRAM_VIRTUAL_BASE=0x$(CONFIG_ETRAX_DRAM_VIRTUAL_BASE)
-AFLAGS += -mlinux
+KBUILD_AFLAGS += -mlinux
 
 KBUILD_CFLAGS += -mlinux -march=$(arch-y) -pipe
 

arch/frv/Makefile

@@ -63,16 +63,16 @@ endif
 
 ifdef CONFIG_CPU_FR451_COMPILE
 KBUILD_CFLAGS	+= -mcpu=fr450
-AFLAGS		+= -mcpu=fr450
+KBUILD_AFLAGS	+= -mcpu=fr450
 ASFLAGS		+= -mcpu=fr450
 else
 ifdef CONFIG_CPU_FR551_COMPILE
 KBUILD_CFLAGS	+= -mcpu=fr550
-AFLAGS		+= -mcpu=fr550
+KBUILD_AFLAGS	+= -mcpu=fr550
 ASFLAGS		+= -mcpu=fr550
 else
 KBUILD_CFLAGS	+= -mcpu=fr400
-AFLAGS		+= -mcpu=fr400
+KBUILD_AFLAGS	+= -mcpu=fr400
 ASFLAGS		+= -mcpu=fr400
 endif
 endif
@@ -82,14 +82,14 @@ endif
 # - all the extra registers are dealt with only at context switch time
 KBUILD_CFLAGS	+= -mno-fdpic -mgpr-32 -msoft-float -mno-media
 KBUILD_CFLAGS	+= -ffixed-fcc3 -ffixed-cc3 -ffixed-gr15 -ffixed-icc2
-AFLAGS		+= -mno-fdpic
+KBUILD_AFLAGS	+= -mno-fdpic
 ASFLAGS		+= -mno-fdpic
 
 # make sure the .S files get compiled with debug info
 # and disable optimisations that are unhelpful whilst debugging
 ifdef CONFIG_DEBUG_INFO
 #KBUILD_CFLAGS	+= -O1
-AFLAGS		+= -Wa,--gdwarf2
+KBUILD_AFLAGS	+= -Wa,--gdwarf2
 ASFLAGS		+= -Wa,--gdwarf2
 endif
 

arch/h8300/Makefile

@@ -35,7 +35,7 @@ KBUILD_CFLAGS += -mint32 -fno-builtin
 KBUILD_CFLAGS += -g
 KBUILD_CFLAGS += -D__linux__
 KBUILD_CFLAGS += -DUTS_SYSNAME=\"uClinux\"
-AFLAGS += -DPLATFORM=$(PLATFORM) -DMODEL=$(MODEL) $(cflags-y)
+KBUILD_AFLAGS += -DPLATFORM=$(PLATFORM) -DMODEL=$(MODEL) $(cflags-y)
 LDFLAGS += $(ldflags-y)
 
 CROSS_COMPILE = h8300-elf-

arch/i386/Makefile

@@ -55,11 +55,11 @@ KBUILD_CFLAGS += $(shell if [ $(call cc-version) -lt 0400 ] ; then echo $(call c
 
 # do binutils support CFI?
 cflags-y += $(call as-instr,.cfi_startproc\n.cfi_rel_offset esp${comma}0\n.cfi_endproc,-DCONFIG_AS_CFI=1,)
-AFLAGS += $(call as-instr,.cfi_startproc\n.cfi_rel_offset esp${comma}0\n.cfi_endproc,-DCONFIG_AS_CFI=1,)
+KBUILD_AFLAGS += $(call as-instr,.cfi_startproc\n.cfi_rel_offset esp${comma}0\n.cfi_endproc,-DCONFIG_AS_CFI=1,)
 
 # is .cfi_signal_frame supported too?
 cflags-y += $(call as-instr,.cfi_startproc\n.cfi_signal_frame\n.cfi_endproc,-DCONFIG_AS_CFI_SIGNAL_FRAME=1,)
-AFLAGS += $(call as-instr,.cfi_startproc\n.cfi_signal_frame\n.cfi_endproc,-DCONFIG_AS_CFI_SIGNAL_FRAME=1,)
+KBUILD_AFLAGS += $(call as-instr,.cfi_startproc\n.cfi_signal_frame\n.cfi_endproc,-DCONFIG_AS_CFI_SIGNAL_FRAME=1,)
 
 KBUILD_CFLAGS += $(cflags-y)
 
@@ -117,7 +117,7 @@ drivers-$(CONFIG_PM)			+= arch/x86/power/
 drivers-$(CONFIG_FB)                    += arch/x86/video/
 
 KBUILD_CFLAGS += $(mflags-y)
-AFLAGS += $(mflags-y)
+KBUILD_AFLAGS += $(mflags-y)
 
 boot := arch/x86/boot
 

arch/m32r/Makefile

@@ -25,7 +25,7 @@ cflags-$(CONFIG_ISA_M32R)	+= -DNO_FPU
 aflags-$(CONFIG_ISA_M32R)	+= -DNO_FPU -O2 -Wa,-no-bitinst
 
 KBUILD_CFLAGS += $(cflags-y)
-AFLAGS += $(aflags-y)
+KBUILD_AFLAGS += $(aflags-y)
 
 CHECKFLAGS	+= -D__m32r__ -D__BIG_ENDIAN__=1
 

arch/m68knommu/Makefile

@@ -102,7 +102,7 @@ cflags-$(CONFIG_M68EZ328)	:= -m68000
 cflags-$(CONFIG_M68VZ328)	:= -m68000
 cflags-$(CONFIG_M68360)		:= -m68332
 
-AFLAGS += $(cflags-y)
+KBUILD_AFLAGS += $(cflags-y)
 
 KBUILD_CFLAGS += $(cflags-y)
 KBUILD_CFLAGS += -D__linux__

arch/mips/Makefile

@@ -608,7 +608,7 @@ ifdef CONFIG_64BIT
   endif
 endif
 
-AFLAGS		+= $(cflags-y)
+KBUILD_AFLAGS	+= $(cflags-y)
 KBUILD_CFLAGS	+= $(cflags-y) \
 			-D"VMLINUX_LOAD_ADDRESS=$(load-y)"
 

arch/powerpc/Makefile

@@ -76,7 +76,7 @@ AFLAGS-$(CONFIG_PPC32)	:= -Iarch/$(ARCH)
 CFLAGS-$(CONFIG_PPC64)	:= -mminimal-toc -mtraceback=none  -mcall-aixdesc
 CFLAGS-$(CONFIG_PPC32)	:= -Iarch/$(ARCH) -ffixed-r2 -mmultiple
 CPPFLAGS	+= $(CPPFLAGS-y)
-AFLAGS		+= $(AFLAGS-y)
+KBUILD_AFLAGS	+= $(AFLAGS-y)
 KBUILD_CFLAGS	+= -msoft-float -pipe $(CFLAGS-y)
 CPP		= $(CC) -E $(KBUILD_CFLAGS)
 
@@ -125,7 +125,7 @@ cpu-as-$(CONFIG_POWER4)		+= -Wa,-maltivec
 cpu-as-$(CONFIG_E500)		+= -Wa,-me500
 cpu-as-$(CONFIG_E200)		+= -Wa,-me200
 
-AFLAGS += $(cpu-as-y)
+KBUILD_AFLAGS += $(cpu-as-y)
 KBUILD_CFLAGS += $(cpu-as-y)
 
 head-y				:= arch/powerpc/kernel/head_$(CONFIG_WORD_SIZE).o

arch/ppc/Makefile

@@ -23,7 +23,7 @@ endif
 LDFLAGS_vmlinux	:= -Ttext $(KERNELLOAD) -Bstatic
 # The -Iarch/$(ARCH)/include is temporary while we are merging
 CPPFLAGS	+= -Iarch/$(ARCH) -Iarch/$(ARCH)/include
-AFLAGS		+= -Iarch/$(ARCH)
+KBUILD_AFLAGS	+= -Iarch/$(ARCH)
 KBUILD_CFLAGS	+= -Iarch/$(ARCH) -msoft-float -pipe \
 		-ffixed-r2 -mmultiple
 
@@ -45,7 +45,7 @@ cpu-as-$(CONFIG_6xx)		+= -Wa,-maltivec
 cpu-as-$(CONFIG_E500)		+= -Wa,-me500
 cpu-as-$(CONFIG_E200)		+= -Wa,-me200
 
-AFLAGS += $(cpu-as-y)
+KBUILD_AFLAGS += $(cpu-as-y)
 KBUILD_CFLAGS += $(cpu-as-y)
 
 # Default to the common case.

arch/s390/Makefile

@@ -16,7 +16,7 @@
 ifndef CONFIG_64BIT
 LDFLAGS		:= -m elf_s390
 KBUILD_CFLAGS	+= -m31
-AFLAGS		+= -m31
+KBUILD_AFLAGS	+= -m31
 UTS_MACHINE	:= s390
 STACK_SIZE	:= 8192
 CHECKFLAGS	+= -D__s390__ -msize-long
@@ -24,7 +24,7 @@ else
 LDFLAGS		:= -m elf64_s390
 MODFLAGS	+= -fpic -D__PIC__
 KBUILD_CFLAGS	+= -m64
-AFLAGS		+= -m64
+KBUILD_AFLAGS	+= -m64
 UTS_MACHINE	:= s390x
 STACK_SIZE	:= 16384
 CHECKFLAGS	+= -D__s390__ -D__s390x__
@@ -79,7 +79,7 @@ endif
 
 KBUILD_CFLAGS	+= -mbackchain -msoft-float $(cflags-y)
 KBUILD_CFLAGS	+= -pipe -fno-strength-reduce -Wno-sign-compare
-AFLAGS		+= $(aflags-y)
+KBUILD_AFLAGS	+= $(aflags-y)
 
 OBJCOPYFLAGS	:= -O binary
 LDFLAGS_vmlinux := -e start

arch/sh/Makefile

@@ -92,7 +92,7 @@ LDFLAGS			+= -EB
 endif
 
 KBUILD_CFLAGS		+= -pipe $(cflags-y)
-AFLAGS		+= $(cflags-y)
+KBUILD_AFLAGS		+= $(cflags-y)
 
 head-y := arch/sh/kernel/head.o arch/sh/kernel/init_task.o
 

arch/sparc/Makefile

@@ -17,7 +17,7 @@ CHECKFLAGS	+= -D__sparc__
 
 #KBUILD_CFLAGS += -g -pipe -fcall-used-g5 -fcall-used-g7
 KBUILD_CFLAGS += -m32 -pipe -mno-fpu -fcall-used-g5 -fcall-used-g7
-AFLAGS := $(AFLAGS) -m32
+KBUILD_AFLAGS += -m32
 
 #LDFLAGS_vmlinux = -N -Ttext 0xf0004000
 #  Since 2.5.40, the first stage is left not btfix-ed.

arch/sparc64/Makefile

@@ -45,7 +45,7 @@ else
   KBUILD_CFLAGS += -m64 -pipe -mno-fpu -mcpu=ultrasparc -mcmodel=medlow \
 	    -ffixed-g4 -ffixed-g5 -fcall-used-g7 -Wno-sign-compare \
 	    $(CC_UNDECL)
-  AFLAGS += -m64 -mcpu=ultrasparc $(CC_UNDECL)
+  KBUILD_AFLAGS += -m64 -mcpu=ultrasparc $(CC_UNDECL)
 endif
 
 ifeq ($(CONFIG_MCOUNT),y)

arch/um/Makefile

@@ -62,7 +62,7 @@ KBUILD_CFLAGS += $(CFLAGS-y) -D__arch_um__ -DSUBARCH=\"$(SUBARCH)\"	\
 	$(ARCH_INCLUDE) $(MODE_INCLUDE) -Dvmap=kernel_vmap	\
 	-Din6addr_loopback=kernel_in6addr_loopback
 
-AFLAGS += $(ARCH_INCLUDE)
+KBUILD_AFLAGS += $(ARCH_INCLUDE)
 
 USER_CFLAGS = $(patsubst $(KERNEL_DEFINES),,$(patsubst -D__KERNEL__,,\
 	$(patsubst -I%,,$(KBUILD_CFLAGS)))) $(ARCH_INCLUDE) $(MODE_INCLUDE) \

arch/um/Makefile-i386

@@ -16,7 +16,7 @@ OBJCOPYFLAGS  		:= -O binary -R .note -R .comment -S
 ifeq ("$(origin SUBARCH)", "command line")
 ifneq ("$(shell uname -m | sed -e s/i.86/i386/)", "$(SUBARCH)")
 KBUILD_CFLAGS		+= $(call cc-option,-m32)
-AFLAGS			+= $(call cc-option,-m32)
+KBUILD_AFLAGS		+= $(call cc-option,-m32)
 LINK-y			+= $(call cc-option,-m32)
 UML_OBJCOPYFLAGS	+= -F $(ELF_FORMAT)
 

arch/um/Makefile-x86_64

@@ -12,7 +12,7 @@ ARCH_KERNEL_DEFINES = -U__$(SUBARCH)__
 KBUILD_CFLAGS += $(_extra_flags_)
 
 CHECKFLAGS  += -m64
-AFLAGS += -m64
+KBUILD_AFLAGS += -m64
 LDFLAGS += -m elf_x86_64
 CPPFLAGS += -m64
 

arch/um/sys-ppc/Makefile

@@ -1,7 +1,7 @@
 OBJ = built-in.o
 
 .S.o:
-	$(CC) $(AFLAGS) -D__ASSEMBLY__ -D__UM_PPC__ -c $< -o $*.o
+	$(CC) $(KBUILD_AFLAGS) -D__ASSEMBLY__ -D__UM_PPC__ -c $< -o $*.o
 
 OBJS = ptrace.o sigcontext.o semaphore.o checksum.o miscthings.o misc.o \
 	ptrace_user.o sysrq.o
@@ -57,13 +57,13 @@ ppc_defs.h: mk_defs.c ppc_defs.head \
 checksum.o: checksum.S
 	rm -f asm
 	ln -s $(TOPDIR)/include/asm-ppc asm
-	$(CC) $(EXTRA_AFLAGS) $(AFLAGS) -D__ASSEMBLY__ -D__UM_PPC__ -c $< -o $*.o
+	$(CC) $(EXTRA_AFLAGS) $(KBUILD_AFLAGS) -D__ASSEMBLY__ -D__UM_PPC__ -c $< -o $*.o
 	rm -f asm
 
 misc.o: misc.S ppc_defs.h
 	rm -f asm
 	ln -s $(TOPDIR)/include/asm-ppc asm
-	$(CC) $(EXTRA_AFLAGS) $(AFLAGS) -D__ASSEMBLY__ -D__UM_PPC__ -c $< -o $*.o
+	$(CC) $(EXTRA_AFLAGS) $(KBUILD_AFLAGS) -D__ASSEMBLY__ -D__UM_PPC__ -c $< -o $*.o
 	rm -f asm
 
 clean-files := $(OBJS) ppc_defs.h checksum.S semaphore.c mk_defs.c

arch/x86/boot/Makefile

@@ -61,7 +61,7 @@ KBUILD_CFLAGS	:= $(LINUXINCLUDE) -g -Os -D_SETUP -D__KERNEL__ \
 			$(call cc-option, -fno-unit-at-a-time)) \
 		   $(call cc-option, -fno-stack-protector) \
 		   $(call cc-option, -mpreferred-stack-boundary=2)
-AFLAGS		:= $(KBUILD_CFLAGS) -D__ASSEMBLY__
+KBUILD_AFLAGS	:= $(KBUILD_CFLAGS) -D__ASSEMBLY__
 
 $(obj)/zImage:  IMAGE_OFFSET := 0x1000
 $(obj)/zImage:  EXTRA_AFLAGS := $(SVGA_MODE) $(RAMDISK)

arch/x86/boot/compressed/Makefile_64

@@ -10,7 +10,7 @@ KBUILD_CFLAGS := -m64 -D__KERNEL__ $(LINUXINCLUDE) -O2  \
 	  -fno-strict-aliasing -fPIC -mcmodel=small \
 	   $(call cc-option, -ffreestanding) \
 	   $(call cc-option, -fno-stack-protector)
-AFLAGS  := $(KBUILD_CFLAGS) -D__ASSEMBLY__
+KBUILD_AFLAGS  := $(KBUILD_CFLAGS) -D__ASSEMBLY__
 LDFLAGS := -m elf_x86_64
 
 LDFLAGS_vmlinux := -T

arch/x86_64/Makefile

@@ -61,18 +61,18 @@ cflags-y += -maccumulate-outgoing-args
 
 # do binutils support CFI?
 cflags-y += $(call as-instr,.cfi_startproc\n.cfi_rel_offset rsp${comma}0\n.cfi_endproc,-DCONFIG_AS_CFI=1,)
-AFLAGS += $(call as-instr,.cfi_startproc\n.cfi_rel_offset rsp${comma}0\n.cfi_endproc,-DCONFIG_AS_CFI=1,)
+KBUILD_AFLAGS += $(call as-instr,.cfi_startproc\n.cfi_rel_offset rsp${comma}0\n.cfi_endproc,-DCONFIG_AS_CFI=1,)
 
 # is .cfi_signal_frame supported too?
 cflags-y += $(call as-instr,.cfi_startproc\n.cfi_signal_frame\n.cfi_endproc,-DCONFIG_AS_CFI_SIGNAL_FRAME=1,)
-AFLAGS += $(call as-instr,.cfi_startproc\n.cfi_signal_frame\n.cfi_endproc,-DCONFIG_AS_CFI_SIGNAL_FRAME=1,)
+KBUILD_AFLAGS += $(call as-instr,.cfi_startproc\n.cfi_signal_frame\n.cfi_endproc,-DCONFIG_AS_CFI_SIGNAL_FRAME=1,)
 
 cflags-$(CONFIG_CC_STACKPROTECTOR) += $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-x86_64-has-stack-protector.sh "$(CC)" -fstack-protector )
 cflags-$(CONFIG_CC_STACKPROTECTOR_ALL) += $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-x86_64-has-stack-protector.sh "$(CC)" -fstack-protector-all )
 
 KBUILD_CFLAGS += $(cflags-y)
 CFLAGS_KERNEL += $(cflags-kernel-y)
-AFLAGS += -m64
+KBUILD_AFLAGS += -m64
 
 head-y := arch/x86/kernel/head_64.o arch/x86/kernel/head64.o arch/x86/kernel/init_task_64.o
 

scripts/Kbuild.include

@@ -81,7 +81,7 @@ as-option = $(call try-run,\
 # Usage: cflags-y += $(call as-instr,instr,option1,option2)
 
 as-instr = $(call try-run,\
-	echo -e "$(1)" | $(CC) $(AFLAGS) -c -xassembler -o "$$TMP" -,$(2),$(3))
+	echo -e "$(1)" | $(CC) $(KBUILD_AFLAGS) -c -xassembler -o "$$TMP" -,$(2),$(3))
 
 # cc-option
 # Usage: cflags-y += $(call cc-option,-march=winchip-c6,-march=i586)

scripts/Makefile.lib

@@ -85,7 +85,7 @@ modname_flags  = $(if $(filter 1,$(words $(modname))),\
                  -D"KBUILD_MODNAME=KBUILD_STR($(call name-fix,$(modname)))")
 
 _c_flags       = $(KBUILD_CFLAGS) $(EXTRA_CFLAGS) $(CFLAGS_$(basetarget).o)
-_a_flags       = $(AFLAGS) $(EXTRA_AFLAGS) $(AFLAGS_$(basetarget).o)
+_a_flags       = $(KBUILD_AFLAGS) $(EXTRA_AFLAGS) $(AFLAGS_$(basetarget).o)
 _cpp_flags     = $(CPPFLAGS) $(EXTRA_CPPFLAGS) $(CPPFLAGS_$(@F))
 
 # If building the kernel in a separate objtree expand all occurrences