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kbuild: allow Kbuild to start from any directory

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Kbuild always runs in the top of the output directory.

If Make starts in the source directory with O=, it relocates the
working directory to the location specified by O=.

Also, users can start build from the output directory by using the
Makefile generated by scripts/mkmakefile.

With a little more effort, Kbuild will be able to start from any
directory path.

This commit allows to specify the source directory by using
the -f option.

For example, you can do:

  $ cd path/to/output/dir
  $ make -f path/to/source/dir/Makefile

Or, for the equivalent behavior, you can do:

  $ make O=path/to/output/dir -f path/to/source/dir/Makefile

KBUILD_SRC is now deprecated.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kieran Bingham <kbingham@kernel.org>
This commit is contained in:
Masahiro Yamada 2019-03-30 21:04:14 +09:00
parent 6b1a9a02c7
commit 25b146c5b8
1 changed files with 50 additions and 37 deletions
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87
Makefile
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@ -96,56 +96,65 @@ endif
export quiet Q KBUILD_VERBOSE
# kbuild supports saving output files in a separate directory.
# To locate output files in a separate directory two syntaxes are supported.
# In both cases the working directory must be the root of the kernel src.
# Kbuild will save output files in the current working directory.
# This does not need to match to the root of the kernel source tree.
#
# For example, you can do this:
#
# cd /dir/to/store/output/files; make -f /dir/to/kernel/source/Makefile
#
# If you want to save output files in a different location, there are
# two syntaxes to specify it.
#
# 1) O=
# Use "make O=dir/to/store/output/files/"
#
# 2) Set KBUILD_OUTPUT
# Set the environment variable KBUILD_OUTPUT to point to the directory
# where the output files shall be placed.
# export KBUILD_OUTPUT=dir/to/store/output/files/
# make
# Set the environment variable KBUILD_OUTPUT to point to the output directory.
# export KBUILD_OUTPUT=dir/to/store/output/files/; make
#
# The O= assignment takes precedence over the KBUILD_OUTPUT environment
# variable.
# KBUILD_SRC is not intended to be used by the regular user (for now),
# it is set on invocation of make with KBUILD_OUTPUT or O= specified.
# OK, Make called in directory where kernel src resides
# Do we want to locate output files in a separate directory?
# Do we want to change the working directory?
ifeq ("$(origin O)", "command line")
KBUILD_OUTPUT := $(O)
endif
ifneq ($(words $(subst :, ,$(CURDIR))), 1)
$(error main directory cannot contain spaces nor colons)
ifneq ($(KBUILD_OUTPUT),)
# Make's built-in functions such as $(abspath ...), $(realpath ...) cannot
# expand a shell special character '~'. We use a somewhat tedious way here.
abs_objtree := $(shell mkdir -p $(KBUILD_OUTPUT) && cd $(KBUILD_OUTPUT) && pwd)
$(if $(abs_objtree),, \
$(error failed to create output directory "$(KBUILD_OUTPUT)"))
# $(realpath ...) resolves symlinks
abs_objtree := $(realpath $(abs_objtree))
else
abs_objtree := $(CURDIR)
endif # ifneq ($(KBUILD_OUTPUT),)
ifeq ($(abs_objtree),$(CURDIR))
# Suppress "Entering directory ..." unless we are changing the work directory.
MAKEFLAGS += --no-print-directory
else
need-sub-make := 1
endif
ifneq ($(KBUILD_OUTPUT),)
# check that the output directory actually exists
saved-output := $(KBUILD_OUTPUT)
KBUILD_OUTPUT := $(shell mkdir -p $(KBUILD_OUTPUT) && cd $(KBUILD_OUTPUT) \
&& pwd)
$(if $(KBUILD_OUTPUT),, \
$(error failed to create output directory "$(saved-output)"))
abs_srctree := $(realpath $(dir $(lastword $(MAKEFILE_LIST))))
ifneq ($(words $(subst :, ,$(abs_srctree))), 1)
$(error source directory cannot contain spaces or colons)
endif
ifneq ($(abs_srctree),$(abs_objtree))
# Look for make include files relative to root of kernel src
#
# This does not become effective immediately because MAKEFLAGS is re-parsed
# once after the Makefile is read. It is OK since we are going to invoke
# 'sub-make' below.
MAKEFLAGS += --include-dir=$(CURDIR)
# once after the Makefile is read. We need to invoke sub-make.
MAKEFLAGS += --include-dir=$(abs_srctree)
need-sub-make := 1
else
# Do not print "Entering directory ..." at all for in-tree build.
MAKEFLAGS += --no-print-directory
endif # ifneq ($(KBUILD_OUTPUT),)
endif
ifneq ($(filter 3.%,$(MAKE_VERSION)),)
# 'MAKEFLAGS += -rR' does not immediately become effective for GNU Make 3.x
@ -155,6 +164,7 @@ need-sub-make := 1
$(lastword $(MAKEFILE_LIST)): ;
endif
export abs_srctree abs_objtree
export sub_make_done := 1
ifeq ($(need-sub-make),1)
@ -166,9 +176,7 @@ $(filter-out _all sub-make $(lastword $(MAKEFILE_LIST)), $(MAKECMDGOALS)) _all:
# Invoke a second make in the output directory, passing relevant variables
sub-make:
$(Q)$(MAKE) \
$(if $(KBUILD_OUTPUT),-C $(KBUILD_OUTPUT) KBUILD_SRC=$(CURDIR)) \
-f $(CURDIR)/Makefile $(MAKECMDGOALS)
$(Q)$(MAKE) -C $(abs_objtree) -f $(abs_srctree)/Makefile $(MAKECMDGOALS)
endif # need-sub-make
endif # sub_make_done
@ -213,16 +221,21 @@ ifeq ("$(origin M)", "command line")
KBUILD_EXTMOD := $(M)
endif
ifeq ($(KBUILD_SRC),)
ifeq ($(abs_srctree),$(abs_objtree))
# building in the source tree
srctree := .
else
ifeq ($(KBUILD_SRC)/,$(dir $(CURDIR)))
ifeq ($(abs_srctree)/,$(dir $(abs_objtree)))
# building in a subdirectory of the source tree
srctree := ..
else
srctree := $(KBUILD_SRC)
srctree := $(abs_srctree)
endif
# TODO:
# KBUILD_SRC is only used to distinguish in-tree/out-of-tree build.
# Replace it with $(srctree) or something.
KBUILD_SRC := $(abs_srctree)
endif
export KBUILD_CHECKSRC KBUILD_EXTMOD KBUILD_SRC