Commit 25b146c5 authored by Masahiro Yamada's avatar Masahiro Yamada
Browse files

kbuild: allow Kbuild to start from any directory 



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: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: default avatarKieran Bingham <kbingham@kernel.org>
parent 6b1a9a02

Makefile

+50 −37
Original line number Diff line number Diff line
@@ -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

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