kbuild: allow assignment to {A,C}FLAGS_KERNEL on the command line

It is now possible to assign options to AS and CC
on the command line - which is only used for built-in code.

{A,C}FLAGS_KERNEL was used both in the top-level Makefile
in the arch makefiles, thus users had no way to specify
additional options to AS, CC without overriding
the original value.

Introduce a new set of variables KBUILD_{A,C}FLAGS_KERNEL
that is used by arch specific files and free up
{A,C}FLAGS_KERNEL so they can be assigned on
the command line.

All arch Makefiles that used the old variables has been updated.

Signed-off-by: Sam Ravnborg <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Hirokazu Takata <[email protected]>
Signed-off-by: Michal Marek <[email protected]>

Documentation/kbuild/kbuild.txt

@@ -28,10 +28,20 @@ AFLAGS_MODULE
 --------------------------------------------------
 Addtional module specific options to use for $(AS).
 
+AFLAGS_KERNEL
+--------------------------------------------------
+Addtional options for $(AS) when used for assembler
+code for code that is compiled as built-in.
+
 KCFLAGS
 --------------------------------------------------
 Additional options to the C compiler (for built-in and modules).
 
+CFLAGS_KERNEL
+--------------------------------------------------
+Addtional options for $(CC) when used to compile
+code that is compiled as built-in.
+
 CFLAGS_MODULE
 --------------------------------------------------
 Addtional module specific options to use for $(CC).

Documentation/kbuild/makefiles.txt

@@ -923,9 +923,9 @@ When kbuild executes, the following steps are followed (roughly):
 	The first example utilises the trick that a config option expands
 	to 'y' when selected.
 
-    CFLAGS_KERNEL	$(CC) options specific for built-in
+    KBUILD_AFLAGS_KERNEL	$(AS) options specific for built-in
 
-	$(CFLAGS_KERNEL) contains extra C compiler flags used to compile
+	$(KBUILD_AFLAGS_KERNEL) contains extra C compiler flags used to compile
 	resident kernel code.
 
     KBUILD_AFLAGS_MODULE   Options for $(AS) when building modules
@@ -934,6 +934,11 @@ When kbuild executes, the following steps are followed (roughly):
 	are used for $(AS).
 	From commandline AFLAGS_MODULE shall be used (see kbuild.txt).
 
+    KBUILD_CFLAGS_KERNEL	$(CC) options specific for built-in
+
+	$(KBUILD_CFLAGS_KERNEL) contains extra C compiler flags used to compile
+	resident kernel code.
+
     KBUILD_CFLAGS_MODULE   Options for $(CC) when building modules
 
 	$(KBUILD_CFLAGS_MODULE) is used to add arch specific options that

Makefile

@@ -353,6 +353,8 @@ KBUILD_CFLAGS   := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
 		   -Werror-implicit-function-declaration \
 		   -Wno-format-security \
 		   -fno-delete-null-pointer-checks
+KBUILD_AFLAGS_KERNEL :=
+KBUILD_CFLAGS_KERNEL :=
 KBUILD_AFLAGS   := -D__ASSEMBLY__
 KBUILD_AFLAGS_MODULE  := -DMODULE
 KBUILD_CFLAGS_MODULE  := -DMODULE
@@ -372,6 +374,7 @@ export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS LDFLAGS
 export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE CFLAGS_GCOV
 export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE
 export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE
+export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL
 
 # When compiling out-of-tree modules, put MODVERDIR in the module
 # tree rather than in the kernel tree. The kernel tree might
@@ -1481,6 +1484,7 @@ cmd_crmodverdir = $(Q)mkdir -p $(MODVERDIR) \
                   $(if $(KBUILD_MODULES),; rm -f $(MODVERDIR)/*)
 
 a_flags = -Wp,-MD,$(depfile) $(KBUILD_AFLAGS) $(AFLAGS_KERNEL) \
+	  $(KBUILD_AFLAGS_KERNEL)                              \
 	  $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(KBUILD_CPPFLAGS) \
 	  $(modkern_aflags) $(EXTRA_AFLAGS) $(AFLAGS_$(basetarget).o)
 

arch/ia64/Makefile

@@ -23,12 +23,12 @@ CHECKFLAGS	+= -m64 -D__ia64=1 -D__ia64__=1 -D_LP64 -D__LP64__
 OBJCOPYFLAGS	:= --strip-all
 LDFLAGS_vmlinux	:= -static
 KBUILD_LDFLAGS_MODULE += -T $(srctree)/arch/ia64/module.lds
-AFLAGS_KERNEL	:= -mconstant-gp
+KBUILD_AFLAGS_KERNEL := -mconstant-gp
 EXTRA		:=
 
 cflags-y	:= -pipe $(EXTRA) -ffixed-r13 -mfixed-range=f12-f15,f32-f127 \
 		   -falign-functions=32 -frename-registers -fno-optimize-sibling-calls
-CFLAGS_KERNEL	:= -mconstant-gp
+KBUILD_CFLAGS_KERNEL := -mconstant-gp
 
 GAS_STATUS	= $(shell $(srctree)/arch/ia64/scripts/check-gas "$(CC)" "$(OBJDUMP)")
 KBUILD_CPPFLAGS += $(shell $(srctree)/arch/ia64/scripts/toolchain-flags "$(CC)" "$(OBJDUMP)" "$(READELF)")

arch/m32r/Makefile

@@ -12,7 +12,7 @@ OBJCOPYFLAGS	:= -O binary -R .note -R .comment -S
 LDFLAGS_vmlinux	:=
 
 KBUILD_CFLAGS += -pipe -fno-schedule-insns
-CFLAGS_KERNEL += -mmodel=medium
+KBUILD_CFLAGS_KERNEL += -mmodel=medium
 KBUILD_CFLAGS_MODULE += -mmodel=large
 
 ifdef CONFIG_CHIP_VDEC2

scripts/Makefile.build

@@ -118,7 +118,7 @@ endif
 modkern_cflags =                                          \
 	$(if $(part-of-module),                           \
 		$(KBUILD_CFLAGS_MODULE) $(CFLAGS_MODULE), \
-		$(CFLAGS_KERNEL))
+		$(KBUILD_CFLAGS_KERNEL) $(CFLAGS_KERNEL))
 quiet_modtag := $(empty)   $(empty)
 
 $(real-objs-m)        : part-of-module := y
@@ -251,7 +251,7 @@ $(obj)/%.lst: $(src)/%.c FORCE
 # Compile assembler sources (.S)
 # ---------------------------------------------------------------------------
 
-modkern_aflags := $(AFLAGS_KERNEL)
+modkern_aflags := $(KBUILD_AFLAGS_KERNEL) $(AFLAGS_KERNEL)
 
 $(real-objs-m)      : modkern_aflags := $(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE)
 $(real-objs-m:.o=.s): modkern_aflags := $(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE)