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Message-Id: <1313800642-32418-1-git-send-email-lacombar@gmail.com>
Date: Fri, 19 Aug 2011 20:37:22 -0400
From: Arnaud Lacombe <lacombar@...il.com>
To: linux-kbuild@...r.kernel.org
Cc: Arnaud Lacombe <lacombar@...il.com>, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org
Subject: [RFC] Kbuild: allow code re-use across different directories
Hi folks,
The attached patch modify Kbuild to allow to directly re-use code in multiple
directory without having to go through a copy. Technically, it changes Kbuild to
use by default the VPATH feature of GNU make and provides accessors for Makefile
to change it indirectly.
Considering:
arch/foo/lib:
fancy.c
We want to be able to build it with -DPANTS=32 in the kernel, but the
bootloader requires -DPANTS_SIZE=30.
Currently we would do, either:
arch/foo/lib/Makefile
LDFLAGS_fancy.o := -DPANTS=32
obj-y += fancy.o
and, either:
arch/foo/boot/Makefile:
LDFLAGS_fancy.o := -DPANTS=30
obj-y += fancy.o
$(obj)/fancy.c: $(srctree)/arch/foo/lib/fancy.c
$(call cmd,shipped)
or
arch/foo/boot/Makefile:
LDFLAGS_fancy.o := -DPANTS=30
obj-y += fancy.o
$(obj)/fancy.o: $(srctree)/arch/foo/lib/fancy.c
$(call cmd,cc_c_o)
The former implies an extra copy of the source file, the latter expose Kbuild
internal function.
With the attached patch, we would do:
arch/foo/boot/Makefile:
LDFLAGS_fancy.o := -DPANTS=30
obj-y += fancy.o
vpath-y += $(srctree)/arch/foo/lib
and let GNU make do the job.
Comments welcome,
- Arnaud
Cc: linux-kernel@...r.kernel.org
Cc: linux-arm-kernel@...ts.infradead.org
---
Makefile | 5 +++--
scripts/Makefile.build | 24 +++++++++++++++---------
scripts/Makefile.lib | 17 ++++++++++++-----
3 files changed, 30 insertions(+), 16 deletions(-)
diff --git a/Makefile b/Makefile
index b4ca4e1..db7f7f5 100644
--- a/Makefile
+++ b/Makefile
@@ -154,9 +154,10 @@ objtree := $(CURDIR)
src := $(srctree)
obj := $(objtree)
-VPATH := $(srctree)$(if $(KBUILD_EXTMOD),:$(KBUILD_EXTMOD))
+KBUILD_VPATH := $(srctree)$(if $(KBUILD_EXTMOD),:$(KBUILD_EXTMOD))
+VPATH := $(KBUILD_VPATH)
-export srctree objtree VPATH
+export srctree objtree KBUILD_VPATH
# SUBARCH tells the usermode build what the underlying arch is. That is set
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index a0fd502..ac539d7 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -18,6 +18,8 @@ always :=
targets :=
subdir-y :=
subdir-m :=
+vpath-y :=
+vpath-m :=
EXTRA_AFLAGS :=
EXTRA_CFLAGS :=
EXTRA_CPPFLAGS :=
@@ -37,6 +39,7 @@ include scripts/Kbuild.include
# For backward compatibility check that these variables do not change
save-cflags := $(CFLAGS)
+save-vpath := $(VPATH)
# The filename Kbuild has precedence over Makefile
kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
@@ -48,6 +51,9 @@ ifeq ($(KBUILD_NOPEDANTIC),)
ifneq ("$(save-cflags)","$(CFLAGS)")
$(error CFLAGS was changed in "$(kbuild-file)". Fix it to use EXTRA_CFLAGS)
endif
+ ifneq ("$(save-vpath)","$(VPATH)")
+ $(error VPATH was changed in "$(kbuild-file)". Please uses vpath-y)
+ endif
endif
#
@@ -198,13 +204,13 @@ $(multi-objs-y:.o=.lst) : modname = $(modname-multi)
quiet_cmd_cc_s_c = CC $(quiet_modtag) $@
cmd_cc_s_c = $(CC) $(c_flags) -fverbose-asm -S -o $@ $<
-$(obj)/%.s: $(src)/%.c FORCE
+$(obj)/%.s: %.c FORCE
$(call if_changed_dep,cc_s_c)
quiet_cmd_cc_i_c = CPP $(quiet_modtag) $@
cmd_cc_i_c = $(CPP) $(c_flags) -o $@ $<
-$(obj)/%.i: $(src)/%.c FORCE
+$(obj)/%.i: %.c FORCE
$(call if_changed_dep,cc_i_c)
cmd_gensymtypes = \
@@ -219,7 +225,7 @@ cmd_cc_symtypes_c = \
$(call cmd_gensymtypes,true,$@) >/dev/null; \
test -s $@ || rm -f $@
-$(obj)/%.symtypes : $(src)/%.c FORCE
+$(obj)/%.symtypes : %.c FORCE
$(call cmd,cc_symtypes_c)
# C (.c) files
@@ -301,13 +307,13 @@ define rule_cc_o_c
endef
# Built-in and composite module parts
-$(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE
+$(obj)/%.o: %.c $(recordmcount_source) FORCE
$(call cmd,force_checksrc)
$(call if_changed_rule,cc_o_c)
# Single-part modules are special since we need to mark them in $(MODVERDIR)
-$(single-used-m): $(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE
+$(single-used-m): %.o: %.c $(recordmcount_source) FORCE
$(call cmd,force_checksrc)
$(call if_changed_rule,cc_o_c)
@{ echo $(@:.o=.ko); echo $@; } > $(MODVERDIR)/$(@F:.o=.mod)
@@ -317,7 +323,7 @@ quiet_cmd_cc_lst_c = MKLST $@
$(CONFIG_SHELL) $(srctree)/scripts/makelst $*.o \
System.map $(OBJDUMP) > $@
-$(obj)/%.lst: $(src)/%.c FORCE
+$(obj)/%.lst: %.c FORCE
$(call if_changed_dep,cc_lst_c)
# Compile assembler sources (.S)
@@ -331,13 +337,13 @@ $(real-objs-m:.o=.s): modkern_aflags := $(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE)
quiet_cmd_as_s_S = CPP $(quiet_modtag) $@
cmd_as_s_S = $(CPP) $(a_flags) -o $@ $<
-$(obj)/%.s: $(src)/%.S FORCE
+$(obj)/%.s: %.S FORCE
$(call if_changed_dep,as_s_S)
quiet_cmd_as_o_S = AS $(quiet_modtag) $@
cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<
-$(obj)/%.o: $(src)/%.S FORCE
+$(obj)/%.o: %.S FORCE
$(call if_changed_dep,as_o_S)
targets += $(real-objs-y) $(real-objs-m) $(lib-y)
@@ -349,7 +355,7 @@ quiet_cmd_cpp_lds_S = LDS $@
cmd_cpp_lds_S = $(CPP) $(cpp_flags) -P -C -U$(ARCH) \
-D__ASSEMBLY__ -DLINKER_SCRIPT -o $@ $<
-$(obj)/%.lds: $(src)/%.lds.S FORCE
+$(obj)/%.lds: %.lds.S FORCE
$(call if_changed_dep,cpp_lds_S)
# Build the compiled-in targets
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index aeea84a..b57b621 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -46,6 +46,13 @@ obj-m := $(filter-out %/, $(obj-m))
subdir-ym := $(sort $(subdir-y) $(subdir-m))
+#
+vpath-ym := $(vpath-y) $(vpath-m)
+VPATH := $(KBUILD_VPATH)
+VPATH += $(srctree)/$(src)
+VPATH += $(obj)
+VPATH += $(vpath-ym)
+
# if $(foo-objs) exists, foo.o is a composite object
multi-used-y := $(sort $(foreach m,$(obj-y), $(if $(strip $($(m:.o=-objs)) $($(m:.o=-y))), $(m))))
multi-used-m := $(sort $(foreach m,$(obj-m), $(if $(strip $($(m:.o=-objs)) $($(m:.o=-y))), $(m))))
@@ -167,7 +174,7 @@ ifdef REGENERATE_PARSERS
quiet_cmd_gperf = GPERF $@
cmd_gperf = gperf -t --output-file $@ -a -C -E -g -k 1,3,$$ -p -t $<
-$(src)/%.hash.c_shipped: $(src)/%.gperf
+$(src)/%.hash.c_shipped: %.gperf
$(call cmd,gperf)
# LEX
@@ -177,7 +184,7 @@ LEX_PREFIX = $(if $(LEX_PREFIX_${baseprereq}),$(LEX_PREFIX_${baseprereq}),yy)
quiet_cmd_flex = LEX $@
cmd_flex = flex -o$@ -L -P $(LEX_PREFIX) $<
-$(src)/%.lex.c_shipped: $(src)/%.l
+$(src)/%.lex.c_shipped: %.l
$(call cmd,flex)
# YACC
@@ -187,13 +194,13 @@ YACC_PREFIX = $(if $(YACC_PREFIX_${baseprereq}),$(YACC_PREFIX_${baseprereq}),yy)
quiet_cmd_bison = YACC $@
cmd_bison = bison -o$@ -t -l -p $(YACC_PREFIX) $<
-$(src)/%.tab.c_shipped: $(src)/%.y
+$(src)/%.tab.c_shipped: %.y
$(call cmd,bison)
quiet_cmd_bison_h = YACC $@
cmd_bison_h = bison -o/dev/null --defines=$@ -t -l -p $(YACC_PREFIX) $<
-$(src)/%.tab.h_shipped: $(src)/%.y
+$(src)/%.tab.h_shipped: %.y
$(call cmd,bison_h)
endif
@@ -204,7 +211,7 @@ endif
quiet_cmd_shipped = SHIPPED $@
cmd_shipped = cat $< > $@
-$(obj)/%: $(src)/%_shipped
+$(obj)/%: %_shipped
$(call cmd,shipped)
# Commands useful for building a boot image
--
1.7.6.153.g78432
--
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