diff mbox

[3/4] kbuild: re-order the code to not parse unnecessary variables

Message ID 1507089367-10402-3-git-send-email-yamada.masahiro@socionext.com (mailing list archive)
State New, archived
Headers show

Commit Message

Masahiro Yamada Oct. 4, 2017, 3:56 a.m. UTC 
The top Makefile is divided into some sections such as mixed targets,
config targets, build targets, etc.

When we build mixed targets, Kbuild just invokes submake to process
them one by one.  In this case, compiler-related variables like CC,
KBUILD_CFLAGS, etc. are unneeded.

Check what kind of targets we are building first, then parse necessary
variables for building them.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

 Makefile | 233 ++++++++++++++++++++++++++++++++-------------------------------
 1 file changed, 118 insertions(+), 115 deletions(-)

Comments

Doug Anderson Oct. 9, 2017, 10:03 p.m. UTC | #1 
Hi,

On Tue, Oct 3, 2017 at 8:56 PM, Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
> The top Makefile is divided into some sections such as mixed targets,
> config targets, build targets, etc.
>
> When we build mixed targets, Kbuild just invokes submake to process
> them one by one.  In this case, compiler-related variables like CC,
> KBUILD_CFLAGS, etc. are unneeded.
>
> Check what kind of targets we are building first, then parse necessary
> variables for building them.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---
>
>  Makefile | 233 ++++++++++++++++++++++++++++++++-------------------------------
>  1 file changed, 118 insertions(+), 115 deletions(-)

I'm even further outside my comfort zone with this big of a change,
but I will say that as far as I can tell this seems like a good
change.  If it were me I'd have probably broken it up into several
tinier changes that were each massively easy to check/verify, but
presumably for those who know the Makefile better then rolling them
together is fine.  ;)

I're spent some time reviewing this (not tons--maybe an hour or so),
but IMHO I don't know this well enough to add a Reviewed-by tag.


> diff --git a/Makefile b/Makefile
> index 39a7c03..a4fd682 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -186,15 +186,6 @@ ifeq ("$(origin M)", "command line")
>    KBUILD_EXTMOD := $(M)
>  endif
>
> -# If building an external module we do not care about the all: rule
> -# but instead _all depend on modules
> -PHONY += all
> -ifeq ($(KBUILD_EXTMOD),)
> -_all: all
> -else
> -_all: modules
> -endif
> -
>  ifeq ($(KBUILD_SRC),)
>          # building in the source tree
>          srctree := .
> @@ -206,6 +197,9 @@ else
>                  srctree := $(KBUILD_SRC)
>          endif
>  endif
> +
> +export KBUILD_CHECKSRC KBUILD_EXTMOD KBUILD_SRC

The old Makefile also used to export KBUILD_SRC, but I'm not sure why.
Shouldn't this be implicit because KBUILD_SRC always comes from a
command line parameter or environment variable?


-Doug
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Masahiro Yamada Oct. 10, 2017, 12:08 a.m. UTC | #2 
2017-10-10 7:03 GMT+09:00 Doug Anderson <dianders@chromium.org>:
> Hi,
>
> On Tue, Oct 3, 2017 at 8:56 PM, Masahiro Yamada
> <yamada.masahiro@socionext.com> wrote:
>> The top Makefile is divided into some sections such as mixed targets,
>> config targets, build targets, etc.
>>
>> When we build mixed targets, Kbuild just invokes submake to process
>> them one by one.  In this case, compiler-related variables like CC,
>> KBUILD_CFLAGS, etc. are unneeded.
>>
>> Check what kind of targets we are building first, then parse necessary
>> variables for building them.
>>
>> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
>> ---
>>
>>  Makefile | 233 ++++++++++++++++++++++++++++++++-------------------------------
>>  1 file changed, 118 insertions(+), 115 deletions(-)
>
> I'm even further outside my comfort zone with this big of a change,
> but I will say that as far as I can tell this seems like a good
> change.  If it were me I'd have probably broken it up into several
> tinier changes that were each massively easy to check/verify, but
> presumably for those who know the Makefile better then rolling them
> together is fine.  ;)
>
> I're spent some time reviewing this (not tons--maybe an hour or so),
> but IMHO I don't know this well enough to add a Reviewed-by tag.
>
>
>> diff --git a/Makefile b/Makefile
>> index 39a7c03..a4fd682 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -186,15 +186,6 @@ ifeq ("$(origin M)", "command line")
>>    KBUILD_EXTMOD := $(M)
>>  endif
>>
>> -# If building an external module we do not care about the all: rule
>> -# but instead _all depend on modules
>> -PHONY += all
>> -ifeq ($(KBUILD_EXTMOD),)
>> -_all: all
>> -else
>> -_all: modules
>> -endif
>> -
>>  ifeq ($(KBUILD_SRC),)
>>          # building in the source tree
>>          srctree := .
>> @@ -206,6 +197,9 @@ else
>>                  srctree := $(KBUILD_SRC)
>>          endif
>>  endif
>> +
>> +export KBUILD_CHECKSRC KBUILD_EXTMOD KBUILD_SRC
>
> The old Makefile also used to export KBUILD_SRC, but I'm not sure why.
> Shouldn't this be implicit because KBUILD_SRC always comes from a
> command line parameter or environment variable?


As the comment line around line 109 says,
"KBUILD_SRC is not intended to be used by the regular user (for now)"


It is set by "sub-make" around line 143:

sub-make:
         $(Q)$(MAKE) -C $(KBUILD_OUTPUT) KBUILD_SRC=$(CURDIR) \
         -f $(CURDIR)/Makefile $(filter-out _all sub-make,$(MAKECMDGOALS))



I'd like to improve it in the future,
but currently KBUILD_SRC works like that.

But, you are right.
I also thought "export KBUILD_SRC" is redundant.
KBUILD_SRC=$(CURDIR) implies exporting it.


I see some more redundant exporting
for variables we know they only come from command line or environment.


I think cleaning-up is OK, but should be
separated to another patch just in case.
(my commit claims I am just changing the code order...)
Masahiro Yamada Oct. 12, 2017, 12:59 a.m. UTC | #3 
2017-10-04 12:56 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>:
> The top Makefile is divided into some sections such as mixed targets,
> config targets, build targets, etc.
>
> When we build mixed targets, Kbuild just invokes submake to process
> them one by one.  In this case, compiler-related variables like CC,
> KBUILD_CFLAGS, etc. are unneeded.
>
> Check what kind of targets we are building first, then parse necessary
> variables for building them.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---
>
>  Makefile | 233 ++++++++++++++++++++++++++++++++-------------------------------
>  1 file changed, 118 insertions(+), 115 deletions(-)


Applied to linux-kbuild/kbuild.  Thanks.
diff mbox

Patch

diff --git a/Makefile b/Makefile
index 39a7c03..a4fd682 100644
--- a/Makefile
+++ b/Makefile
@@ -186,15 +186,6 @@  ifeq ("$(origin M)", "command line")
   KBUILD_EXTMOD := $(M)
 endif
 
-# If building an external module we do not care about the all: rule
-# but instead _all depend on modules
-PHONY += all
-ifeq ($(KBUILD_EXTMOD),)
-_all: all
-else
-_all: modules
-endif
-
 ifeq ($(KBUILD_SRC),)
         # building in the source tree
         srctree := .
@@ -206,6 +197,9 @@  else
                 srctree := $(KBUILD_SRC)
         endif
 endif
+
+export KBUILD_CHECKSRC KBUILD_EXTMOD KBUILD_SRC
+
 objtree		:= .
 src		:= $(srctree)
 obj		:= $(objtree)
@@ -214,6 +208,74 @@  VPATH		:= $(srctree)$(if $(KBUILD_EXTMOD),:$(KBUILD_EXTMOD))
 
 export srctree objtree VPATH
 
+# To make sure we do not include .config for any of the *config targets
+# catch them early, and hand them over to scripts/kconfig/Makefile
+# It is allowed to specify more targets when calling make, including
+# mixing *config targets and build targets.
+# For example 'make oldconfig all'.
+# Detect when mixed targets is specified, and make a second invocation
+# of make so .config is not included in this case either (for *config).
+
+version_h := include/generated/uapi/linux/version.h
+old_version_h := include/linux/version.h
+
+no-dot-config-targets := clean mrproper distclean \
+			 cscope gtags TAGS tags help% %docs check% coccicheck \
+			 $(version_h) headers_% archheaders archscripts \
+			 kernelversion %src-pkg
+
+config-targets := 0
+mixed-targets  := 0
+dot-config     := 1
+
+ifneq ($(filter $(no-dot-config-targets), $(MAKECMDGOALS)),)
+	ifeq ($(filter-out $(no-dot-config-targets), $(MAKECMDGOALS)),)
+		dot-config := 0
+	endif
+endif
+
+ifeq ($(KBUILD_EXTMOD),)
+        ifneq ($(filter config %config,$(MAKECMDGOALS)),)
+                config-targets := 1
+                ifneq ($(words $(MAKECMDGOALS)),1)
+                        mixed-targets := 1
+                endif
+        endif
+endif
+# install and modules_install need also be processed one by one
+ifneq ($(filter install,$(MAKECMDGOALS)),)
+        ifneq ($(filter modules_install,$(MAKECMDGOALS)),)
+	        mixed-targets := 1
+        endif
+endif
+
+ifeq ($(mixed-targets),1)
+# ===========================================================================
+# We're called with mixed targets (*config and build targets).
+# Handle them one by one.
+
+PHONY += $(MAKECMDGOALS) __build_one_by_one
+
+$(filter-out __build_one_by_one, $(MAKECMDGOALS)): __build_one_by_one
+	@:
+
+__build_one_by_one:
+	$(Q)set -e; \
+	for i in $(MAKECMDGOALS); do \
+		$(MAKE) -f $(srctree)/Makefile $$i; \
+	done
+
+else
+
+# We need some generic definitions (do not try to remake the file).
+scripts/Kbuild.include: ;
+include scripts/Kbuild.include
+
+# Read KERNELRELEASE from include/config/kernel.release (if it exists)
+KERNELRELEASE = $(shell cat include/config/kernel.release 2> /dev/null)
+KERNELVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)
+export VERSION PATCHLEVEL SUBLEVEL KERNELRELEASE KERNELVERSION
+
 # SUBARCH tells the usermode build what the underlying arch is.  That is set
 # first, and if a usermode build is happening, the "ARCH=um" on the command
 # line overrides the setting of ARCH below.  If a native build is happening,
@@ -308,40 +370,6 @@  HOSTCFLAGS  += -Wno-unused-value -Wno-unused-parameter \
 		-Wno-missing-field-initializers -fno-delete-null-pointer-checks
 endif
 
-# Decide whether to build built-in, modular, or both.
-# Normally, just do built-in.
-
-KBUILD_MODULES :=
-KBUILD_BUILTIN := 1
-
-# If we have only "make modules", don't compile built-in objects.
-# When we're building modules with modversions, we need to consider
-# the built-in objects during the descend as well, in order to
-# make sure the checksums are up to date before we record them.
-
-ifeq ($(MAKECMDGOALS),modules)
-  KBUILD_BUILTIN := $(if $(CONFIG_MODVERSIONS),1)
-endif
-
-# If we have "make <whatever> modules", compile modules
-# in addition to whatever we do anyway.
-# Just "make" or "make all" shall build modules as well
-
-ifneq ($(filter all _all modules,$(MAKECMDGOALS)),)
-  KBUILD_MODULES := 1
-endif
-
-ifeq ($(MAKECMDGOALS),)
-  KBUILD_MODULES := 1
-endif
-
-export KBUILD_MODULES KBUILD_BUILTIN
-export KBUILD_CHECKSRC KBUILD_SRC KBUILD_EXTMOD
-
-# We need some generic definitions (do not try to remake the file).
-scripts/Kbuild.include: ;
-include scripts/Kbuild.include
-
 # Make variables (CC, etc...)
 AS		= $(CROSS_COMPILE)as
 LD		= $(CROSS_COMPILE)ld
@@ -406,11 +434,6 @@  KBUILD_AFLAGS_MODULE  := -DMODULE
 KBUILD_CFLAGS_MODULE  := -DMODULE
 KBUILD_LDFLAGS_MODULE := -T $(srctree)/scripts/module-common.lds
 
-# Read KERNELRELEASE from include/config/kernel.release (if it exists)
-KERNELRELEASE = $(shell cat include/config/kernel.release 2> /dev/null)
-KERNELVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)
-
-export VERSION PATCHLEVEL SUBLEVEL KERNELRELEASE KERNELVERSION
 export ARCH SRCARCH CONFIG_SHELL HOSTCC HOSTCFLAGS CROSS_COMPILE AS LD CC
 export CPP AR NM STRIP OBJCOPY OBJDUMP HOSTLDFLAGS HOST_LOADLIBES
 export MAKE AWK GENKSYMS INSTALLKERNEL PERL PYTHON UTS_MACHINE
@@ -459,73 +482,6 @@  ifneq ($(KBUILD_SRC),)
 	    $(srctree) $(objtree) $(VERSION) $(PATCHLEVEL)
 endif
 
-# Support for using generic headers in asm-generic
-PHONY += asm-generic uapi-asm-generic
-asm-generic: uapi-asm-generic
-	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.asm-generic \
-	            src=asm obj=arch/$(SRCARCH)/include/generated/asm
-uapi-asm-generic:
-	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.asm-generic \
-	            src=uapi/asm obj=arch/$(SRCARCH)/include/generated/uapi/asm
-
-# To make sure we do not include .config for any of the *config targets
-# catch them early, and hand them over to scripts/kconfig/Makefile
-# It is allowed to specify more targets when calling make, including
-# mixing *config targets and build targets.
-# For example 'make oldconfig all'.
-# Detect when mixed targets is specified, and make a second invocation
-# of make so .config is not included in this case either (for *config).
-
-version_h := include/generated/uapi/linux/version.h
-old_version_h := include/linux/version.h
-
-no-dot-config-targets := clean mrproper distclean \
-			 cscope gtags TAGS tags help% %docs check% coccicheck \
-			 $(version_h) headers_% archheaders archscripts \
-			 kernelversion %src-pkg
-
-config-targets := 0
-mixed-targets  := 0
-dot-config     := 1
-
-ifneq ($(filter $(no-dot-config-targets), $(MAKECMDGOALS)),)
-	ifeq ($(filter-out $(no-dot-config-targets), $(MAKECMDGOALS)),)
-		dot-config := 0
-	endif
-endif
-
-ifeq ($(KBUILD_EXTMOD),)
-        ifneq ($(filter config %config,$(MAKECMDGOALS)),)
-                config-targets := 1
-                ifneq ($(words $(MAKECMDGOALS)),1)
-                        mixed-targets := 1
-                endif
-        endif
-endif
-# install and modules_install need also be processed one by one
-ifneq ($(filter install,$(MAKECMDGOALS)),)
-        ifneq ($(filter modules_install,$(MAKECMDGOALS)),)
-	        mixed-targets := 1
-        endif
-endif
-
-ifeq ($(mixed-targets),1)
-# ===========================================================================
-# We're called with mixed targets (*config and build targets).
-# Handle them one by one.
-
-PHONY += $(MAKECMDGOALS) __build_one_by_one
-
-$(filter-out __build_one_by_one, $(MAKECMDGOALS)): __build_one_by_one
-	@:
-
-__build_one_by_one:
-	$(Q)set -e; \
-	for i in $(MAKECMDGOALS); do \
-		$(MAKE) -f $(srctree)/Makefile $$i; \
-	done
-
-else
 ifeq ($(config-targets),1)
 # ===========================================================================
 # *config targets only - make sure prerequisites are updated, and descend
@@ -548,6 +504,44 @@  else
 # Build targets only - this includes vmlinux, arch specific targets, clean
 # targets and others. In general all targets except *config targets.
 
+# If building an external module we do not care about the all: rule
+# but instead _all depend on modules
+PHONY += all
+ifeq ($(KBUILD_EXTMOD),)
+_all: all
+else
+_all: modules
+endif
+
+# Decide whether to build built-in, modular, or both.
+# Normally, just do built-in.
+
+KBUILD_MODULES :=
+KBUILD_BUILTIN := 1
+
+# If we have only "make modules", don't compile built-in objects.
+# When we're building modules with modversions, we need to consider
+# the built-in objects during the descend as well, in order to
+# make sure the checksums are up to date before we record them.
+
+ifeq ($(MAKECMDGOALS),modules)
+  KBUILD_BUILTIN := $(if $(CONFIG_MODVERSIONS),1)
+endif
+
+# If we have "make <whatever> modules", compile modules
+# in addition to whatever we do anyway.
+# Just "make" or "make all" shall build modules as well
+
+ifneq ($(filter all _all modules,$(MAKECMDGOALS)),)
+  KBUILD_MODULES := 1
+endif
+
+ifeq ($(MAKECMDGOALS),)
+  KBUILD_MODULES := 1
+endif
+
+export KBUILD_MODULES KBUILD_BUILTIN
+
 ifeq ($(KBUILD_EXTMOD),)
 # Additional helpers built in scripts/
 # Carefully list dependencies so we do not try to build scripts twice
@@ -1063,6 +1057,15 @@  prepare0: archprepare gcc-plugins
 # All the preparing..
 prepare: prepare0 prepare-objtool
 
+# Support for using generic headers in asm-generic
+PHONY += asm-generic uapi-asm-generic
+asm-generic: uapi-asm-generic
+	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.asm-generic \
+	            src=asm obj=arch/$(SRCARCH)/include/generated/asm
+uapi-asm-generic:
+	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.asm-generic \
+	            src=uapi/asm obj=arch/$(SRCARCH)/include/generated/uapi/asm
+
 PHONY += prepare-objtool
 prepare-objtool: $(objtool_target)