kbuild: add read-file macro

Since GNU Make 4.2, $(file ...) supports the read operater '<', which
is useful to read a file without forking a new process. No warning is
shown even if the input file is missing.

For older Make versions, it falls back to the cat command.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Reviewed-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Tested-by: Alexander Lobakin <alexandr.lobakin@intel.com>
This commit is contained in:
Masahiro Yamada 2022-12-11 11:54:47 +09:00
parent a5db80c65d
commit 6768fa4bcb
4 changed files with 17 additions and 3 deletions

View File

@ -376,7 +376,7 @@ else # !mixed-build
include $(srctree)/scripts/Kbuild.include
# Read KERNELRELEASE from include/config/kernel.release (if it exists)
KERNELRELEASE = $(shell cat include/config/kernel.release 2> /dev/null)
KERNELRELEASE = $(call read-file, include/config/kernel.release)
KERNELVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)
export VERSION PATCHLEVEL SUBLEVEL KERNELRELEASE KERNELVERSION

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@ -10,6 +10,10 @@ empty :=
space := $(empty) $(empty)
space_escape := _-_SPACE_-_
pound := \#
define newline
endef
###
# Comparison macros.
@ -61,6 +65,16 @@ stringify = $(squote)$(quote)$1$(quote)$(squote)
kbuild-dir = $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
kbuild-file = $(or $(wildcard $(kbuild-dir)/Kbuild),$(kbuild-dir)/Makefile)
###
# Read a file, replacing newlines with spaces
#
# Make 4.2 or later can read a file by using its builtin function.
ifneq ($(filter-out 3.% 4.0 4.1, $(MAKE_VERSION)),)
read-file = $(subst $(newline),$(space),$(file < $1))
else
read-file = $(shell cat $1 2>/dev/null)
endif
###
# Easy method for doing a status message
kecho := :

View File

@ -13,7 +13,7 @@ include $(srctree)/scripts/Kbuild.include
include $(srctree)/scripts/Makefile.lib
# find all modules listed in modules.order
modules := $(shell cat $(MODORDER))
modules := $(call read-file, $(MODORDER))
__modfinal: $(modules)
@:

View File

@ -9,7 +9,7 @@ __modinst:
include include/config/auto.conf
include $(srctree)/scripts/Kbuild.include
modules := $(shell cat $(MODORDER))
modules := $(call read-file, $(MODORDER))
ifeq ($(KBUILD_EXTMOD),)
dst := $(MODLIB)/kernel