linux-yocto/Makefile

SPDX-License-Identifier: GPL-2.0

VERSION = 5 PATCHLEVEL = 13 SUBLEVEL = 15 EXTRAVERSION = NAME = Opossums on Parade

DOCUMENTATION

To see a list of typical targets execute "make help"

More info can be located in ./README

Comments in this file are targeted only to the developer, do not

expect to learn how to build the kernel reading this file.

$(if $(filter %, $(MAKECMDGOALS)),
$(error targets prefixed with '' are only for internal use))

That's our default target when none is given on the command line

PHONY := __all __all:

We are using a recursive build, so we need to do a little thinking

to get the ordering right.

Most importantly: sub-Makefiles should only ever modify files in

their own directory. If in some directory we have a dependency on

a file in another dir (which doesn't happen often, but it's often

unavoidable when linking the built-in.a targets which finally

turn into vmlinux), we will call a sub make in that other dir, and

after that we are sure that everything which is in that other dir

is now up to date.

The only cases where we need to modify files which have global

effects are thus separated out and done before the recursive

descending is started. They are now explicitly listed as the

prepare rule.

ifneq ($(sub_make_done),1)

Do not use make's built-in rules and variables

(this increases performance and avoids hard-to-debug behaviour)

MAKEFLAGS += -rR

Avoid funny character set dependencies

unexport LC_ALL LC_COLLATE=C LC_NUMERIC=C export LC_COLLATE LC_NUMERIC

Avoid interference with shell env settings

unexport GREP_OPTIONS

Beautify output

---------------------------------------------------------------------------

Normally, we echo the whole command before executing it. By making

that echo $($(quiet)$(cmd)), we now have the possibility to set

$(quiet) to choose other forms of output instead, e.g.

quiet_cmd_cc_o_c = Compiling $(RELDIR)/$@

cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<

If $(quiet) is empty, the whole command will be printed.

If it is set to "quiet_", only the short version will be printed.

If it is set to "silent_", nothing will be printed at all, since

the variable $(silent_cmd_cc_o_c) doesn't exist.

A simple variant is to prefix commands with $(Q) - that's useful

for commands that shall be hidden in non-verbose mode.

$(Q)ln $@ :<

If KBUILD_VERBOSE equals 0 then the above command will be hidden.

If KBUILD_VERBOSE equals 1 then the above command is displayed.

If KBUILD_VERBOSE equals 2 then give the reason why each target is rebuilt.

To put more focus on warnings, be less verbose as default

Use 'make V=1' to see the full commands

ifeq ("$(origin V)", "command line") KBUILD_VERBOSE = $(V) endif ifndef KBUILD_VERBOSE KBUILD_VERBOSE = 0 endif

ifeq ($(KBUILD_VERBOSE),1) quiet = Q = else quiet=quiet_ Q = @ endif

If the user is running make -s (silent mode), suppress echoing of

commands

ifneq ($(findstring s,$(filter-out --%,$(MAKEFLAGS))),) quiet=silent_ KBUILD_VERBOSE = 0 endif

export quiet Q KBUILD_VERBOSE

Call a source code checker (by default, "sparse") as part of the

C compilation.

Use 'make C=1' to enable checking of only re-compiled files.

Use 'make C=2' to enable checking of all source files, regardless

of whether they are re-compiled or not.

See the file "Documentation/dev-tools/sparse.rst" for more details,

including where to get the "sparse" utility.

ifeq ("$(origin C)", "command line") KBUILD_CHECKSRC = $(C) endif ifndef KBUILD_CHECKSRC KBUILD_CHECKSRC = 0 endif

export KBUILD_CHECKSRC

Use make M=dir or set the environment variable KBUILD_EXTMOD to specify the

directory of external module to build. Setting M= takes precedence.

ifeq ("$(origin M)", "command line") KBUILD_EXTMOD := $(M) endif

$(if $(word 2, $(KBUILD_EXTMOD)),
$(error building multiple external modules is not supported))

Remove trailing slashes

ifneq ($(filter %/, $(KBUILD_EXTMOD)),) KBUILD_EXTMOD := $(shell dirname $(KBUILD_EXTMOD).) endif

export KBUILD_EXTMOD

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 output directory.

export KBUILD_OUTPUT=dir/to/store/output/files/; make

The O= assignment takes precedence over the KBUILD_OUTPUT environment

variable.

Do we want to change the working directory?

ifeq ("$(origin O)", "command line") KBUILD_OUTPUT := $(O) endif

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

this-makefile := $(lastword $(MAKEFILE_LIST)) abs_srctree := $(realpath $(dir $(this-makefile)))

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. We need to invoke sub-make.

MAKEFLAGS += --include-dir=$(abs_srctree) need-sub-make := 1 endif

ifneq ($(filter 3.%,$(MAKE_VERSION)),)

'MAKEFLAGS += -rR' does not immediately become effective for GNU Make 3.x

We need to invoke sub-make to avoid implicit rules in the top Makefile.

need-sub-make := 1

Cancel implicit rules for this Makefile.

$(this-makefile): ; endif

export abs_srctree abs_objtree export sub_make_done := 1

ifeq ($(need-sub-make),1)

PHONY += $(MAKECMDGOALS) __sub-make

$(filter-out $(this-makefile), $(MAKECMDGOALS)) __all: __sub-make @:

Invoke a second make in the output directory, passing relevant variables

__sub-make: $(Q)$(MAKE) -C $(abs_objtree) -f $(abs_srctree)/Makefile $(MAKECMDGOALS)

endif # need-sub-make endif # sub_make_done

We process the rest of the Makefile if this is the final invocation of make

ifeq ($(need-sub-make),)

Do not print "Entering directory ...",

but we want to display it when entering to the output directory

so that IDEs/editors are able to understand relative filenames.

MAKEFLAGS += --no-print-directory

ifeq ($(abs_srctree),$(abs_objtree)) # building in the source tree srctree := . building_out_of_srctree := else ifeq ($(abs_srctree)/,$(dir $(abs_objtree))) # building in a subdirectory of the source tree srctree := .. else srctree := $(abs_srctree) endif building_out_of_srctree := 1 endif

ifneq ($(KBUILD_ABS_SRCTREE),) srctree := $(abs_srctree) endif

objtree := . VPATH := $(srctree)

export building_out_of_srctree 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

clean-targets := %clean mrproper cleandocs no-dot-config-targets := $(clean-targets)
cscope gtags TAGS tags help% %docs check% coccicheck
$(version_h) headers headers_% archheaders archscripts
%asm-generic kernelversion %src-pkg dt_binding_check
outputmakefile

Installation targets should not require compiler. Unfortunately, vdso_install

is an exception where build artifacts may be updated. This must be fixed.

no-compiler-targets := $(no-dot-config-targets) install dtbs_install
headers_install modules_install kernelrelease image_name no-sync-config-targets := $(no-dot-config-targets) %install kernelrelease
image_name single-targets := %.a %.i %.ko %.lds %.ll %.lst %.mod %.o %.s %.symtypes %/

config-build := mixed-build := need-config := 1 need-compiler := 1 may-sync-config := 1 single-build :=

ifneq ($(filter $(no-dot-config-targets), $(MAKECMDGOALS)),) ifeq ($(filter-out $(no-dot-config-targets), $(MAKECMDGOALS)),) need-config := endif endif

ifneq ($(filter $(no-compiler-targets), $(MAKECMDGOALS)),) ifeq ($(filter-out $(no-compiler-targets), $(MAKECMDGOALS)),) need-compiler := endif endif

ifneq ($(filter $(no-sync-config-targets), $(MAKECMDGOALS)),) ifeq ($(filter-out $(no-sync-config-targets), $(MAKECMDGOALS)),) may-sync-config := endif endif

ifneq ($(KBUILD_EXTMOD),) may-sync-config := endif

ifeq ($(KBUILD_EXTMOD),) ifneq ($(filter %config,$(MAKECMDGOALS)),) config-build := 1 ifneq ($(words $(MAKECMDGOALS)),1) mixed-build := 1 endif endif endif

We cannot build single targets and the others at the same time

ifneq ($(filter $(single-targets), $(MAKECMDGOALS)),) single-build := 1 ifneq ($(filter-out $(single-targets), $(MAKECMDGOALS)),) mixed-build := 1 endif endif

For "make -j clean all", "make -j mrproper defconfig all", etc.

ifneq ($(filter $(clean-targets),$(MAKECMDGOALS)),) ifneq ($(filter-out $(clean-targets),$(MAKECMDGOALS)),) mixed-build := 1 endif endif

install and modules_install need also be processed one by one

ifneq ($(filter install,$(MAKECMDGOALS)),) ifneq ($(filter modules_install,$(MAKECMDGOALS)),) mixed-build := 1 endif endif

ifdef mixed-build

===========================================================================

We're called with mixed targets (*config and build targets).

Handle them one by one.

PHONY += $(MAKECMDGOALS) __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 # !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) KERNELVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION) export VERSION PATCHLEVEL SUBLEVEL KERNELRELEASE KERNELVERSION

include $(srctree)/scripts/subarch.include

Cross compiling and selecting different set of gcc/bin-utils

---------------------------------------------------------------------------

When performing cross compilation for other architectures ARCH shall be set

to the target architecture. (See arch/* for the possibilities).

ARCH can be set during invocation of make:

make ARCH=ia64

Another way is to have ARCH set in the environment.

The default ARCH is the host where make is executed.

CROSS_COMPILE specify the prefix used for all executables used

during compilation. Only gcc and related bin-utils executables

are prefixed with $(CROSS_COMPILE).

CROSS_COMPILE can be set on the command line

make CROSS_COMPILE=ia64-linux-

Alternatively CROSS_COMPILE can be set in the environment.

Default value for CROSS_COMPILE is not to prefix executables

Note: Some architectures assign CROSS_COMPILE in their arch/*/Makefile

ARCH ?= $(SUBARCH)

Architecture as present in compile.h

UTS_MACHINE := $(ARCH) SRCARCH := $(ARCH)

Additional ARCH settings for x86

ifeq ($(ARCH),i386) SRCARCH := x86 endif ifeq ($(ARCH),x86_64) SRCARCH := x86 endif

Additional ARCH settings for sparc

ifeq ($(ARCH),sparc32) SRCARCH := sparc endif ifeq ($(ARCH),sparc64) SRCARCH := sparc endif

export cross_compiling := ifneq ($(SRCARCH),$(SUBARCH)) cross_compiling := 1 endif

KCONFIG_CONFIG ?= .config export KCONFIG_CONFIG

SHELL used by kbuild

CONFIG_SHELL := sh

HOST_LFS_CFLAGS := $(shell getconf LFS_CFLAGS 2>/dev/null) HOST_LFS_LDFLAGS := $(shell getconf LFS_LDFLAGS 2>/dev/null) HOST_LFS_LIBS := $(shell getconf LFS_LIBS 2>/dev/null)

ifneq ($(LLVM),) HOSTCC = clang HOSTCXX = clang++ else HOSTCC = gcc HOSTCXX = g++ endif

export KBUILD_USERCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes
-O2 -fomit-frame-pointer -std=gnu89 export KBUILD_USERLDFLAGS :=

KBUILD_HOSTCFLAGS := $(KBUILD_USERCFLAGS) $(HOST_LFS_CFLAGS) $(HOSTCFLAGS) KBUILD_HOSTCXXFLAGS := -Wall -O2 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS) KBUILD_HOSTLDFLAGS := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS) KBUILD_HOSTLDLIBS := $(HOST_LFS_LIBS) $(HOSTLDLIBS)

Make variables (CC, etc...)

CPP = $(CC) -E ifneq ($(LLVM),) CC = clang LD = ld.lld AR = llvm-ar NM = llvm-nm OBJCOPY = llvm-objcopy OBJDUMP = llvm-objdump READELF = llvm-readelf STRIP = llvm-strip else CC = $(CROSS_COMPILE)gcc LD = $(CROSS_COMPILE)ld AR = $(CROSS_COMPILE)ar NM = $(CROSS_COMPILE)nm OBJCOPY = $(CROSS_COMPILE)objcopy OBJDUMP = $(CROSS_COMPILE)objdump READELF = $(CROSS_COMPILE)readelf STRIP = $(CROSS_COMPILE)strip endif PAHOLE = pahole RESOLVE_BTFIDS = $(objtree)/tools/bpf/resolve_btfids/resolve_btfids LEX = flex YACC = bison AWK = awk INSTALLKERNEL := installkernel DEPMOD = depmod PERL = perl PYTHON3 = python3 CHECK = sparse BASH = bash KGZIP = gzip KBZIP2 = bzip2 KLZOP = lzop LZMA = lzma LZ4 = lz4c XZ = xz ZSTD = zstd

CHECKFLAGS := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__
-Wbitwise -Wno-return-void -Wno-unknown-attribute $(CF) NOSTDINC_FLAGS := CFLAGS_MODULE = AFLAGS_MODULE = LDFLAGS_MODULE = CFLAGS_KERNEL = AFLAGS_KERNEL = LDFLAGS_vmlinux =

Use USERINCLUDE when you must reference the UAPI directories only.

USERINCLUDE :=
-I$(srctree)/arch/$(SRCARCH)/include/uapi
-I$(objtree)/arch/$(SRCARCH)/include/generated/uapi
-I$(srctree)/include/uapi
-I$(objtree)/include/generated/uapi
-include $(srctree)/include/linux/compiler-version.h
-include $(srctree)/include/linux/kconfig.h

Use LINUXINCLUDE when you must reference the include/ directory.

Needed to be compatible with the O= option

LINUXINCLUDE :=
-I$(srctree)/arch/$(SRCARCH)/include
-I$(objtree)/arch/$(SRCARCH)/include/generated
$(if $(building_out_of_srctree),-I$(srctree)/include)
-I$(objtree)/include
$(USERINCLUDE)

KBUILD_AFLAGS := -D__ASSEMBLY__ -fno-PIE KBUILD_CFLAGS := -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs
-fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE
-Werror=implicit-function-declaration -Werror=implicit-int
-Werror=return-type -Wno-format-security
-std=gnu89 KBUILD_CPPFLAGS := -D__KERNEL__ KBUILD_AFLAGS_KERNEL := KBUILD_CFLAGS_KERNEL := KBUILD_AFLAGS_MODULE := -DMODULE KBUILD_CFLAGS_MODULE := -DMODULE KBUILD_LDFLAGS_MODULE := KBUILD_LDFLAGS := CLANG_FLAGS :=

export ARCH SRCARCH CONFIG_SHELL BASH HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE LD CC export CPP AR NM STRIP OBJCOPY OBJDUMP READELF PAHOLE RESOLVE_BTFIDS LEX YACC AWK INSTALLKERNEL export PERL PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX export KGZIP KBZIP2 KLZOP LZMA LZ4 XZ ZSTD export KBUILD_HOSTCXXFLAGS KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS LDFLAGS_MODULE

export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS KBUILD_LDFLAGS export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL

Files to ignore in find ... statements

export RCS_FIND_IGNORE := ( -name SCCS -o -name BitKeeper -o -name .svn -o
-name CVS -o -name .pc -o -name .hg -o -name .git -o -name meta )
-prune -o export RCS_TAR_IGNORE := --exclude SCCS --exclude BitKeeper --exclude .svn
--exclude CVS --exclude .pc --exclude .hg --exclude .git

===========================================================================

Rules shared between *config targets and build targets

Basic helpers built in scripts/basic/

PHONY += scripts_basic scripts_basic: $(Q)$(MAKE) $(build)=scripts/basic $(Q)rm -f .tmp_quiet_recordmcount

PHONY += outputmakefile

Before starting out-of-tree build, make sure the source tree is clean.

outputmakefile generates a Makefile in the output directory, if using a

separate output directory. This allows convenient use of make in the

output directory.

At the same time when output Makefile generated, generate .gitignore to

ignore whole output directory

outputmakefile: ifdef building_out_of_srctree $(Q)if [ -f $(srctree)/.config -o
-d $(srctree)/include/config -o
-d $(srctree)/arch/$(SRCARCH)/include/generated ]; then
echo >&2 "";
echo >&2 " The source tree is not clean, please run 'make$(if $(findstring command line, $(origin ARCH)), ARCH=$(ARCH)) mrproper'";
echo >&2 "*** in $(abs_srctree)";
echo >&2 "**";
false;
fi $(Q)ln -fsn $(srctree) source $(Q)$(CONFIG_SHELL) $(srctree)/scripts/mkmakefile $(srctree) $(Q)test -e .gitignore ||
{ echo "# this is build directory, ignore it"; echo ""; } > .gitignore endif

The expansion should be delayed until arch/$(SRCARCH)/Makefile is included.

Some architectures define CROSS_COMPILE in arch/$(SRCARCH)/Makefile.

CC_VERSION_TEXT is referenced from Kconfig (so it needs export),

and from include/config/auto.conf.cmd to detect the compiler upgrade.

CC_VERSION_TEXT = $(subst $(pound),,$(shell $(CC) --version 2>/dev/null | head -n 1))

ifneq ($(findstring clang,$(CC_VERSION_TEXT)),) ifneq ($(CROSS_COMPILE),) CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) endif ifeq ($(LLVM_IAS),1) CLANG_FLAGS += -integrated-as else CLANG_FLAGS += -no-integrated-as GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit)) CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE)) endif CLANG_FLAGS += -Werror=unknown-warning-option KBUILD_CFLAGS += $(CLANG_FLAGS) KBUILD_AFLAGS += $(CLANG_FLAGS) export CLANG_FLAGS endif

Include this also for config targets because some architectures need

cc-cross-prefix to determine CROSS_COMPILE.

ifdef need-compiler include $(srctree)/scripts/Makefile.compiler endif

ifdef config-build

===========================================================================

*config targets only - make sure prerequisites are updated, and descend

in scripts/kconfig to make the *config target

Read arch specific Makefile to set KBUILD_DEFCONFIG as needed.

KBUILD_DEFCONFIG may point out an alternative default configuration

used for 'make defconfig'

include $(srctree)/arch/$(SRCARCH)/Makefile export KBUILD_DEFCONFIG KBUILD_KCONFIG CC_VERSION_TEXT

config: outputmakefile scripts_basic FORCE $(Q)$(MAKE) $(build)=scripts/kconfig $@

%config: outputmakefile scripts_basic FORCE $(Q)$(MAKE) $(build)=scripts/kconfig $@

else #!config-build

===========================================================================

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.

ifeq ($(MAKECMDGOALS),modules) KBUILD_BUILTIN := endif

If we have "make modules", compile modules

in addition to whatever we do anyway.

Just "make" or "make all" shall build modules as well

ifneq ($(filter all modules nsdeps %compile_commands.json clang-%,$(MAKECMDGOALS)),) KBUILD_MODULES := 1 endif

ifeq ($(MAKECMDGOALS),) KBUILD_MODULES := 1 endif

export KBUILD_MODULES KBUILD_BUILTIN

ifdef need-config include include/config/auto.conf endif

ifeq ($(KBUILD_EXTMOD),)

Objects we will link into vmlinux / subdirs we need to visit

core-y := init/ usr/ drivers-y := drivers/ sound/ drivers-$(CONFIG_SAMPLES) += samples/ drivers-$(CONFIG_NET) += net/ drivers-y += virt/ libs-y := lib/ endif # KBUILD_EXTMOD

The all: target is the default when no target is given on the

command line.

This allow a user to issue only 'make' to build a kernel including modules

Defaults to vmlinux, but the arch makefile usually adds further targets

all: vmlinux

CFLAGS_GCOV := -fprofile-arcs -ftest-coverage
$(call cc-option,-fno-tree-loop-im)
$(call cc-disable-warning,maybe-uninitialized,) export CFLAGS_GCOV

The arch Makefiles can override CC_FLAGS_FTRACE. We may also append it later.

ifdef CONFIG_FUNCTION_TRACER CC_FLAGS_FTRACE := -pg endif

RETPOLINE_CFLAGS_GCC := -mindirect-branch=thunk-extern -mindirect-branch-register RETPOLINE_VDSO_CFLAGS_GCC := -mindirect-branch=thunk-inline -mindirect-branch-register RETPOLINE_CFLAGS_CLANG := -mretpoline-external-thunk RETPOLINE_VDSO_CFLAGS_CLANG := -mretpoline RETPOLINE_CFLAGS := $(call cc-option,$(RETPOLINE_CFLAGS_GCC),$(call cc-option,$(RETPOLINE_CFLAGS_CLANG))) RETPOLINE_VDSO_CFLAGS := $(call cc-option,$(RETPOLINE_VDSO_CFLAGS_GCC),$(call cc-option,$(RETPOLINE_VDSO_CFLAGS_CLANG))) export RETPOLINE_CFLAGS export RETPOLINE_VDSO_CFLAGS

include $(srctree)/arch/$(SRCARCH)/Makefile

ifdef need-config ifdef may-sync-config

Read in dependencies to all Kconfig* files, make sure to run syncconfig if

changes are detected. This should be included after arch/$(SRCARCH)/Makefile

because some architectures define CROSS_COMPILE there.

include include/config/auto.conf.cmd

$(KCONFIG_CONFIG): @echo >&2 '' @echo >&2 ' Configuration file "$@" not found!' @echo >&2 '' @echo >&2 ' Please run some configurator (e.g. "make oldconfig" or' @echo >&2 '*** "make menuconfig" or "make xconfig").' @echo >&2 '***' @/bin/false

The actual configuration files used during the build are stored in

include/generated/ and include/config/. Update them if .config is newer than

include/config/auto.conf (which mirrors .config).

This exploits the 'multi-target pattern rule' trick.

The syncconfig should be executed only once to make all the targets.

(Note: use the grouped target '&:' when we bump to GNU Make 4.3)

Do not use $(call cmd,...) here. That would suppress prompts from syncconfig,

so you cannot notice that Kconfig is waiting for the user input.

%/config/auto.conf %/config/auto.conf.cmd %/generated/autoconf.h: $(KCONFIG_CONFIG) $(Q)$(kecho) " SYNC $@" $(Q)$(MAKE) -f $(srctree)/Makefile syncconfig else # !may-sync-config

External modules and some install targets need include/generated/autoconf.h

and include/config/auto.conf but do not care if they are up-to-date.

Use auto.conf to trigger the test

PHONY += include/config/auto.conf

include/config/auto.conf: $(Q)test -e include/generated/autoconf.h -a -e $@ || (
echo >&2;
echo >&2 " ERROR: Kernel configuration is invalid.";
echo >&2 " include/generated/autoconf.h or $@ are missing.";
echo >&2 " Run 'make oldconfig && make prepare' on kernel src to fix it.";
echo >&2 ;
/bin/false)

endif # may-sync-config endif # need-config

KBUILD_CFLAGS += $(call cc-option,-fno-delete-null-pointer-checks,) KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,) KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation) KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow) KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)

ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE KBUILD_CFLAGS += -O2 else ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3 KBUILD_CFLAGS += -O3 else ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE KBUILD_CFLAGS += -Os endif

Tell gcc to never replace conditional load with a non-conditional one

KBUILD_CFLAGS += $(call cc-option,--param=allow-store-data-races=0) KBUILD_CFLAGS += $(call cc-option,-fno-allow-store-data-races)

ifdef CONFIG_READABLE_ASM

Disable optimizations that make assembler listings hard to read.

reorder blocks reorders the control in the function

ipa clone creates specialized cloned functions

partial inlining inlines only parts of functions

KBUILD_CFLAGS += $(call cc-option,-fno-reorder-blocks,)
$(call cc-option,-fno-ipa-cp-clone,)
$(call cc-option,-fno-partial-inlining) endif

ifneq ($(CONFIG_FRAME_WARN),0) KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN) endif

stackp-flags-y := -fno-stack-protector stackp-flags-$(CONFIG_STACKPROTECTOR) := -fstack-protector stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG) := -fstack-protector-strong

KBUILD_CFLAGS += $(stackp-flags-y)

ifdef CONFIG_CC_IS_CLANG KBUILD_CPPFLAGS += -Qunused-arguments KBUILD_CFLAGS += -Wno-format-invalid-specifier KBUILD_CFLAGS += -Wno-gnu

CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the

source of a reference will be _MergedGlobals and not on of the whitelisted names.

See modpost pattern 2

KBUILD_CFLAGS += -mno-global-merge else

Warn about unmarked fall-throughs in switch statement.

Disabled for clang while comment to attribute conversion happens and

https://github.com/ClangBuiltLinux/linux/issues/636 is discussed.

KBUILD_CFLAGS += $(call cc-option,-Wimplicit-fallthrough,) endif

These warnings generated too much noise in a regular build.

Use make W=1 to enable them (see scripts/Makefile.extrawarn)

KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)

KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) ifdef CONFIG_FRAME_POINTER KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls else

Some targets (ARM with Thumb2, for example), can't be built with frame

pointers. For those, we don't have FUNCTION_TRACER automatically

select FRAME_POINTER. However, FUNCTION_TRACER adds -pg, and this is

incompatible with -fomit-frame-pointer with current GCC, so we don't use

-fomit-frame-pointer with FUNCTION_TRACER.

ifndef CONFIG_FUNCTION_TRACER KBUILD_CFLAGS += -fomit-frame-pointer endif endif

Initialize all stack variables with a 0xAA pattern.

ifdef CONFIG_INIT_STACK_ALL_PATTERN KBUILD_CFLAGS += -ftrivial-auto-var-init=pattern endif

Initialize all stack variables with a zero value.

ifdef CONFIG_INIT_STACK_ALL_ZERO

Future support for zero initialization is still being debated, see

https://bugs.llvm.org/show_bug.cgi?id=45497. These flags are subject to being

renamed or dropped.

KBUILD_CFLAGS += -ftrivial-auto-var-init=zero KBUILD_CFLAGS += -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang endif

While VLAs have been removed, GCC produces unreachable stack probes

for the randomize_kstack_offset feature. Disable it for all compilers.

KBUILD_CFLAGS += $(call cc-option, -fno-stack-clash-protection)

DEBUG_CFLAGS :=

Workaround for GCC versions < 5.0

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61801

ifdef CONFIG_CC_IS_GCC DEBUG_CFLAGS += $(call cc-ifversion, -lt, 0500, $(call cc-option, -fno-var-tracking-assignments)) endif

ifdef CONFIG_DEBUG_INFO

ifdef CONFIG_DEBUG_INFO_SPLIT DEBUG_CFLAGS += -gsplit-dwarf else DEBUG_CFLAGS += -g endif

ifneq ($(LLVM_IAS),1) KBUILD_AFLAGS += -Wa,-gdwarf-2 endif

ifndef CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT dwarf-version-$(CONFIG_DEBUG_INFO_DWARF4) := 4 dwarf-version-$(CONFIG_DEBUG_INFO_DWARF5) := 5 DEBUG_CFLAGS += -gdwarf-$(dwarf-version-y) endif

ifdef CONFIG_DEBUG_INFO_REDUCED DEBUG_CFLAGS += $(call cc-option, -femit-struct-debug-baseonly)
$(call cc-option,-fno-var-tracking) endif

ifdef CONFIG_DEBUG_INFO_COMPRESSED DEBUG_CFLAGS += -gz=zlib KBUILD_AFLAGS += -gz=zlib KBUILD_LDFLAGS += --compress-debug-sections=zlib endif

endif # CONFIG_DEBUG_INFO

KBUILD_CFLAGS += $(DEBUG_CFLAGS) export DEBUG_CFLAGS

ifdef CONFIG_FUNCTION_TRACER ifdef CONFIG_FTRACE_MCOUNT_USE_CC CC_FLAGS_FTRACE += -mrecord-mcount ifdef CONFIG_HAVE_NOP_MCOUNT ifeq ($(call cc-option-yn, -mnop-mcount),y) CC_FLAGS_FTRACE += -mnop-mcount CC_FLAGS_USING += -DCC_USING_NOP_MCOUNT endif endif endif ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL CC_FLAGS_USING += -DCC_USING_NOP_MCOUNT endif ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT ifdef CONFIG_HAVE_C_RECORDMCOUNT BUILD_C_RECORDMCOUNT := y export BUILD_C_RECORDMCOUNT endif endif ifdef CONFIG_HAVE_FENTRY ifeq ($(call cc-option-yn, -mfentry),y) CC_FLAGS_FTRACE += -mfentry CC_FLAGS_USING += -DCC_USING_FENTRY endif endif export CC_FLAGS_FTRACE KBUILD_CFLAGS += $(CC_FLAGS_FTRACE) $(CC_FLAGS_USING) KBUILD_AFLAGS += $(CC_FLAGS_USING) endif

We trigger additional mismatches with less inlining

ifdef CONFIG_DEBUG_SECTION_MISMATCH KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once) endif

ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections LDFLAGS_vmlinux += --gc-sections endif

ifdef CONFIG_SHADOW_CALL_STACK CC_FLAGS_SCS := -fsanitize=shadow-call-stack KBUILD_CFLAGS += $(CC_FLAGS_SCS) export CC_FLAGS_SCS endif

ifdef CONFIG_LTO_CLANG ifdef CONFIG_LTO_CLANG_THIN CC_FLAGS_LTO := -flto=thin -fsplit-lto-unit KBUILD_LDFLAGS += --thinlto-cache-dir=$(extmod_prefix).thinlto-cache else CC_FLAGS_LTO := -flto endif CC_FLAGS_LTO += -fvisibility=hidden

Limit inlining across translation units to reduce binary size

KBUILD_LDFLAGS += -mllvm -import-instr-limit=5

Check for frame size exceeding threshold during prolog/epilog insertion

when using lld < 13.0.0.

ifneq ($(CONFIG_FRAME_WARN),0) ifeq ($(shell test $(CONFIG_LLD_VERSION) -lt 130000; echo ?),0) KBUILD_LDFLAGS += -plugin-opt=-warn-stack-size=$(CONFIG_FRAME_WARN) endif endif endif

ifdef CONFIG_LTO KBUILD_CFLAGS += -fno-lto $(CC_FLAGS_LTO) KBUILD_AFLAGS += -fno-lto export CC_FLAGS_LTO endif

ifdef CONFIG_CFI_CLANG CC_FLAGS_CFI := -fsanitize=cfi
-fsanitize-cfi-cross-dso
-fno-sanitize-cfi-canonical-jump-tables
-fno-sanitize-trap=cfi
-fno-sanitize-blacklist

ifdef CONFIG_CFI_PERMISSIVE CC_FLAGS_CFI += -fsanitize-recover=cfi endif

If LTO flags are filtered out, we must also filter out CFI.

CC_FLAGS_LTO += $(CC_FLAGS_CFI) KBUILD_CFLAGS += $(CC_FLAGS_CFI) export CC_FLAGS_CFI endif

ifdef CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_32B KBUILD_CFLAGS += -falign-functions=32 endif

arch Makefile may override CC so keep this after arch Makefile is included

NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)

warn about C99 declaration after statement

KBUILD_CFLAGS += -Wdeclaration-after-statement

Variable Length Arrays (VLAs) should not be used anywhere in the kernel

KBUILD_CFLAGS += -Wvla

disable pointer signed / unsigned warnings in gcc 4.0

KBUILD_CFLAGS += -Wno-pointer-sign

disable stringop warnings in gcc 8+

KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation)

We'll want to enable this eventually, but it's not going away for 5.7 at least

KBUILD_CFLAGS += $(call cc-disable-warning, zero-length-bounds) KBUILD_CFLAGS += $(call cc-disable-warning, array-bounds) KBUILD_CFLAGS += $(call cc-disable-warning, stringop-overflow)

Another good warning that we'll want to enable eventually

KBUILD_CFLAGS += $(call cc-disable-warning, restrict)

Enabled with W=2, disabled by default as noisy

KBUILD_CFLAGS += $(call cc-disable-warning, maybe-uninitialized)

disable invalid "can't wrap" optimizations for signed / pointers

KBUILD_CFLAGS += -fno-strict-overflow

Make sure -fstack-check isn't enabled (like gentoo apparently did)

KBUILD_CFLAGS += -fno-stack-check

conserve stack if available

KBUILD_CFLAGS += $(call cc-option,-fconserve-stack)

Prohibit date/time macros, which would make the build non-deterministic

KBUILD_CFLAGS += -Werror=date-time

enforce correct pointer usage

KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types)

Require designated initializers for all marked structures

KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)

change FILE to the relative path from the srctree

KBUILD_CPPFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)

include additional Makefiles when needed

include-y := scripts/Makefile.extrawarn include-$(CONFIG_KASAN) += scripts/Makefile.kasan include-$(CONFIG_KCSAN) += scripts/Makefile.kcsan include-$(CONFIG_UBSAN) += scripts/Makefile.ubsan include-$(CONFIG_KCOV) += scripts/Makefile.kcov include-$(CONFIG_GCC_PLUGINS) += scripts/Makefile.gcc-plugins

include $(addprefix $(srctree)/, $(include-y))

scripts/Makefile.gcc-plugins is intentionally included last.

Do not add $(call cc-option,...) below this line. When you build the kernel

from the clean source tree, the GCC plugins do not exist at this point.

Add user supplied CPPFLAGS, AFLAGS and CFLAGS as the last assignments

KBUILD_CPPFLAGS += $(KCPPFLAGS) KBUILD_AFLAGS += $(KAFLAGS) KBUILD_CFLAGS += $(KCFLAGS)

KBUILD_LDFLAGS_MODULE += --build-id=sha1 LDFLAGS_vmlinux += --build-id=sha1

ifeq ($(CONFIG_STRIP_ASM_SYMS),y) LDFLAGS_vmlinux += $(call ld-option, -X,) endif

ifeq ($(CONFIG_RELR),y) LDFLAGS_vmlinux += --pack-dyn-relocs=relr --use-android-relr-tags endif

We never want expected sections to be placed heuristically by the

linker. All sections should be explicitly named in the linker script.

ifdef CONFIG_LD_ORPHAN_WARN LDFLAGS_vmlinux += --orphan-handling=warn endif

Align the bit size of userspace programs with the kernel

KBUILD_USERCFLAGS += $(filter -m32 -m64 --target=%, $(KBUILD_CFLAGS)) KBUILD_USERLDFLAGS += $(filter -m32 -m64 --target=%, $(KBUILD_CFLAGS))

make the checker run with the right architecture

CHECKFLAGS += --arch=$(ARCH)

insure the checker run with the right endianness

CHECKFLAGS += $(if $(CONFIG_CPU_BIG_ENDIAN),-mbig-endian,-mlittle-endian)

the checker needs the correct machine size

CHECKFLAGS += $(if $(CONFIG_64BIT),-m64,-m32)

Default kernel image to build when no specific target is given.

KBUILD_IMAGE may be overruled on the command line or

set in the environment

Also any assignments in arch/$(ARCH)/Makefile take precedence over

this default value

export KBUILD_IMAGE ?= vmlinux

INSTALL_PATH specifies where to place the updated kernel and system map

images. Default is /boot, but you can set it to other values

export INSTALL_PATH ?= /boot

INSTALL_DTBS_PATH specifies a prefix for relocations required by build roots.

Like INSTALL_MOD_PATH, it isn't defined in the Makefile, but can be passed as

an argument if needed. Otherwise it defaults to the kernel install path

export INSTALL_DTBS_PATH ?= $(INSTALL_PATH)/dtbs/$(KERNELRELEASE)

INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory

relocations required by build roots. This is not defined in the

makefile but the argument can be passed to make if needed.

MODLIB = $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE) export MODLIB

HOST_LIBELF_LIBS = $(shell pkg-config libelf --libs 2>/dev/null || echo -lelf)

has_libelf = $(call try-run,
echo "int main() {}" | $(HOSTCC) $(KBUILD_HOSTLDFLAGS) -xc -o /dev/null $(HOST_LIBELF_LIBS) -,1,0)

ifdef CONFIG_STACK_VALIDATION ifeq ($(has_libelf),1) objtool_target := tools/objtool FORCE else SKIP_STACK_VALIDATION := 1 export SKIP_STACK_VALIDATION endif endif

PHONY += resolve_btfids_clean

resolve_btfids_O = $(abspath $(objtree))/tools/bpf/resolve_btfids

tools/bpf/resolve_btfids directory might not exist

in output directory, skip its clean in that case

resolve_btfids_clean: ifneq ($(wildcard $(resolve_btfids_O)),) $(Q)$(MAKE) -sC $(srctree)/tools/bpf/resolve_btfids O=$(resolve_btfids_O) clean endif

ifdef CONFIG_BPF ifdef CONFIG_DEBUG_INFO_BTF ifeq ($(has_libelf),1) resolve_btfids_target := tools/bpf/resolve_btfids FORCE else ERROR_RESOLVE_BTFIDS := 1 endif endif # CONFIG_DEBUG_INFO_BTF endif # CONFIG_BPF

PHONY += prepare0

export extmod_prefix = $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/) export MODORDER := $(extmod_prefix)modules.order export MODULES_NSDEPS := $(extmod_prefix)modules.nsdeps

ifeq ($(KBUILD_EXTMOD),) core-y += kernel/ certs/ mm/ fs/ ipc/ security/ crypto/ block/

vmlinux-dirs := $(patsubst %/,%,$(filter %/,
$(core-y) $(core-m) $(drivers-y) $(drivers-m)
$(libs-y) $(libs-m)))

vmlinux-alldirs := $(sort $(vmlinux-dirs) Documentation
$(patsubst %/,%,$(filter %/, $(core-)
$(drivers-) $(libs-))))

subdir-modorder := $(addsuffix modules.order,$(filter %/,
$(core-y) $(core-m) $(libs-y) $(libs-m)
$(drivers-y) $(drivers-m)))

build-dirs := $(vmlinux-dirs) clean-dirs := $(vmlinux-alldirs)

Externally visible symbols (used by link-vmlinux.sh)

KBUILD_VMLINUX_OBJS := $(head-y) $(patsubst %/,%/built-in.a, $(core-y)) KBUILD_VMLINUX_OBJS += $(addsuffix built-in.a, $(filter %/, $(libs-y))) ifdef CONFIG_MODULES KBUILD_VMLINUX_OBJS += $(patsubst %/, %/lib.a, $(filter %/, $(libs-y))) KBUILD_VMLINUX_LIBS := $(filter-out %/, $(libs-y)) else KBUILD_VMLINUX_LIBS := $(patsubst %/,%/lib.a, $(libs-y)) endif KBUILD_VMLINUX_OBJS += $(patsubst %/,%/built-in.a, $(drivers-y))

export KBUILD_VMLINUX_OBJS KBUILD_VMLINUX_LIBS export KBUILD_LDS := arch/$(SRCARCH)/kernel/vmlinux.lds

used by scripts/Makefile.package

export KBUILD_ALLDIRS := $(sort $(filter-out arch/%,$(vmlinux-alldirs)) LICENSES arch include scripts tools)

vmlinux-deps := $(KBUILD_LDS) $(KBUILD_VMLINUX_OBJS) $(KBUILD_VMLINUX_LIBS)

Recurse until adjust_autoksyms.sh is satisfied

PHONY += autoksyms_recursive ifdef CONFIG_TRIM_UNUSED_KSYMS

For the kernel to actually contain only the needed exported symbols,

we have to build modules as well to determine what those symbols are.

(this can be evaluated only once include/config/auto.conf has been included)

KBUILD_MODULES := 1

autoksyms_recursive: descend modules.order $(Q)$(CONFIG_SHELL) $(srctree)/scripts/adjust_autoksyms.sh
"$(MAKE) -f $(srctree)/Makefile vmlinux" endif

autoksyms_h := $(if $(CONFIG_TRIM_UNUSED_KSYMS), include/generated/autoksyms.h)

quiet_cmd_autoksyms_h = GEN $@ cmd_autoksyms_h = mkdir -p $(dir $@);
$(CONFIG_SHELL) $(srctree)/scripts/gen_autoksyms.sh $@

$(autoksyms_h): $(call cmd,autoksyms_h)

ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)

Final link of vmlinux with optional arch pass after final link

cmd_link-vmlinux =
$(CONFIG_SHELL) $< "$(LD)" "$(KBUILD_LDFLAGS)" "$(LDFLAGS_vmlinux)";
$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)

vmlinux: scripts/link-vmlinux.sh autoksyms_recursive $(vmlinux-deps) FORCE +$(call if_changed_dep,link-vmlinux)

targets := vmlinux

The actual objects are generated when descending,

make sure no implicit rule kicks in

$(sort $(vmlinux-deps) $(subdir-modorder)): descend ;

filechk_kernel.release =
echo "$(KERNELVERSION)$$($(CONFIG_SHELL) $(srctree)/scripts/setlocalversion $(srctree))"

Store (new) KERNELRELEASE string in include/config/kernel.release

include/config/kernel.release: FORCE $(call filechk,kernel.release)

Additional helpers built in scripts/

Carefully list dependencies so we do not try to build scripts twice

in parallel

PHONY += scripts scripts: scripts_basic scripts_dtc $(Q)$(MAKE) $(build)=$(@)

Things we need to do before we recursively start building the kernel

or the modules are listed in "prepare".

A multi level approach is used. prepareN is processed before prepareN-1.

archprepare is used in arch Makefiles and when processed asm symlink,

version.h and scripts_basic is processed / created.

PHONY += prepare archprepare

archprepare: outputmakefile archheaders archscripts scripts include/config/kernel.release
asm-generic $(version_h) $(autoksyms_h) include/generated/utsrelease.h
include/generated/autoconf.h remove-stale-files

prepare0: archprepare $(Q)$(MAKE) $(build)=scripts/mod $(Q)$(MAKE) $(build)=.

All the preparing..

prepare: prepare0 prepare-objtool prepare-resolve_btfids

PHONY += remove-stale-files remove-stale-files: $(Q)$(srctree)/scripts/remove-stale-files

Support for using generic headers in asm-generic

asm-generic := -f $(srctree)/scripts/Makefile.asm-generic obj

PHONY += asm-generic uapi-asm-generic asm-generic: uapi-asm-generic $(Q)$(MAKE) $(asm-generic)=arch/$(SRCARCH)/include/generated/asm
generic=include/asm-generic uapi-asm-generic: $(Q)$(MAKE) $(asm-generic)=arch/$(SRCARCH)/include/generated/uapi/asm
generic=include/uapi/asm-generic

PHONY += prepare-objtool prepare-resolve_btfids prepare-objtool: $(objtool_target) ifeq ($(SKIP_STACK_VALIDATION),1) ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL @echo "error: Cannot generate __mcount_loc for CONFIG_DYNAMIC_FTRACE=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2 @false endif ifdef CONFIG_UNWINDER_ORC @echo "error: Cannot generate ORC metadata for CONFIG_UNWINDER_ORC=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2 @false else @echo "warning: Cannot use CONFIG_STACK_VALIDATION=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2 endif endif

prepare-resolve_btfids: $(resolve_btfids_target) ifeq ($(ERROR_RESOLVE_BTFIDS),1) @echo "error: Cannot resolve BTF IDs for CONFIG_DEBUG_INFO_BTF, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2 @false endif

Generate some files

---------------------------------------------------------------------------

KERNELRELEASE can change from a few different places, meaning version.h

needs to be updated, so this check is forced on all builds

uts_len := 64 define filechk_utsrelease.h if [ echo -n "$(KERNELRELEASE)" | wc -c -gt $(uts_len) ]; then
echo '"$(KERNELRELEASE)" exceeds $(uts_len) characters' >&2;
exit 1;
fi;
echo #define UTS_RELEASE "$(KERNELRELEASE)" endef

define filechk_version.h if [ $(SUBLEVEL) -gt 255 ]; then
echo #define LINUX_VERSION_CODE $(shell
expr $(VERSION) * 65536 + $(PATCHLEVEL) * 256 + 255);
else
echo #define LINUX_VERSION_CODE $(shell
expr $(VERSION) * 65536 + $(PATCHLEVEL) * 256 + $(SUBLEVEL));
fi;
echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) +
((c) > 255 ? 255 : (c)))';
echo #define LINUX_VERSION_MAJOR $(VERSION);
echo #define LINUX_VERSION_PATCHLEVEL $(PATCHLEVEL);
echo #define LINUX_VERSION_SUBLEVEL $(SUBLEVEL) endef

$(version_h): PATCHLEVEL := $(if $(PATCHLEVEL), $(PATCHLEVEL), 0) $(version_h): SUBLEVEL := $(if $(SUBLEVEL), $(SUBLEVEL), 0) $(version_h): FORCE $(call filechk,version.h)

include/generated/utsrelease.h: include/config/kernel.release FORCE $(call filechk,utsrelease.h)

PHONY += headerdep headerdep: $(Q)find $(srctree)/include/ -name '*.h' | xargs --max-args 1
$(srctree)/scripts/headerdep.pl -I$(srctree)/include

---------------------------------------------------------------------------

Kernel headers

#Default location for installed headers export INSTALL_HDR_PATH = $(objtree)/usr

quiet_cmd_headers_install = INSTALL $(INSTALL_HDR_PATH)/include cmd_headers_install =
mkdir -p $(INSTALL_HDR_PATH);
rsync -mrl --include='/' --include='.h' --exclude='*'
usr/include $(INSTALL_HDR_PATH)

PHONY += headers_install headers_install: headers $(call cmd,headers_install)

PHONY += archheaders archscripts

hdr-inst := -f $(srctree)/scripts/Makefile.headersinst obj

PHONY += headers headers: $(version_h) scripts_unifdef uapi-asm-generic archheaders archscripts $(if $(wildcard $(srctree)/arch/$(SRCARCH)/include/uapi/asm/Kbuild),,
$(error Headers not exportable for the $(SRCARCH) architecture)) $(Q)$(MAKE) $(hdr-inst)=include/uapi $(Q)$(MAKE) $(hdr-inst)=arch/$(SRCARCH)/include/uapi

Deprecated. It is no-op now.

PHONY += headers_check headers_check: @echo >&2 "=================== WARNING ===================" @echo >&2 "Since Linux 5.5, 'make headers_check' is no-op," @echo >&2 "and will be removed after Linux 5.15 release." @echo >&2 "Please remove headers_check from your scripts." @echo >&2 "==============================================="

ifdef CONFIG_HEADERS_INSTALL prepare: headers endif

PHONY += scripts_unifdef scripts_unifdef: scripts_basic $(Q)$(MAKE) $(build)=scripts scripts/unifdef

---------------------------------------------------------------------------

Install

Many distributions have the custom install script, /sbin/installkernel.

If DKMS is installed, 'make install' will eventually recuses back

to the this Makefile to build and install external modules.

Cancel sub_make_done so that options such as M=, V=, etc. are parsed.

install: sub_make_done :=

Kernel selftest

PHONY += kselftest kselftest: $(Q)$(MAKE) -C $(srctree)/tools/testing/selftests run_tests

kselftest-%: FORCE $(Q)$(MAKE) -C $(srctree)/tools/testing/selftests $*

PHONY += kselftest-merge kselftest-merge: $(if $(wildcard $(objtree)/.config),, $(error No .config exists, config your kernel first!)) $(Q)find $(srctree)/tools/testing/selftests -name config |
xargs $(srctree)/scripts/kconfig/merge_config.sh -m $(objtree)/.config $(Q)$(MAKE) -f $(srctree)/Makefile olddefconfig

---------------------------------------------------------------------------

Devicetree files

ifneq ($(wildcard $(srctree)/arch/$(SRCARCH)/boot/dts/),) dtstree := arch/$(SRCARCH)/boot/dts endif

ifneq ($(dtstree),)

%.dtb: include/config/kernel.release scripts_dtc $(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@

%.dtbo: include/config/kernel.release scripts_dtc $(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@

PHONY += dtbs dtbs_install dtbs_check dtbs: include/config/kernel.release scripts_dtc $(Q)$(MAKE) $(build)=$(dtstree)

ifneq ($(filter dtbs_check, $(MAKECMDGOALS)),) export CHECK_DTBS=y dtbs: dt_binding_check endif

dtbs_check: dtbs

dtbs_install: $(Q)$(MAKE) $(dtbinst)=$(dtstree) dst=$(INSTALL_DTBS_PATH)

ifdef CONFIG_OF_EARLY_FLATTREE all: dtbs endif

endif

PHONY += scripts_dtc scripts_dtc: scripts_basic $(Q)$(MAKE) $(build)=scripts/dtc

ifneq ($(filter dt_binding_check, $(MAKECMDGOALS)),) export CHECK_DT_BINDING=y endif

PHONY += dt_binding_check dt_binding_check: scripts_dtc $(Q)$(MAKE) $(build)=Documentation/devicetree/bindings

---------------------------------------------------------------------------

Modules

ifdef CONFIG_MODULES

By default, build modules as well

all: modules

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.

ifdef CONFIG_MODVERSIONS KBUILD_BUILTIN := 1 endif

Build modules

A module can be listed more than once in obj-m resulting in

duplicate lines in modules.order files. Those are removed

using awk while concatenating to the final file.

PHONY += modules modules: $(if $(KBUILD_BUILTIN),vmlinux) modules_check modules_prepare

cmd_modules_order = $(AWK) '!x[$$0]++' $(real-prereqs) > $@

modules.order: $(subdir-modorder) FORCE $(call if_changed,modules_order)

targets += modules.order

Target to prepare building external modules

PHONY += modules_prepare modules_prepare: prepare $(Q)$(MAKE) $(build)=scripts scripts/module.lds

export modules_sign_only :=

ifeq ($(CONFIG_MODULE_SIG),y) PHONY += modules_sign modules_sign: modules_install @:

modules_sign is a subset of modules_install.

'make modules_install modules_sign' is equivalent to 'make modules_install'.

ifeq ($(filter modules_install,$(MAKECMDGOALS)),) modules_sign_only := y endif endif

modinst_pre := ifneq ($(filter modules_install,$(MAKECMDGOALS)),) modinst_pre := __modinst_pre endif

modules_install: $(modinst_pre) PHONY += __modinst_pre __modinst_pre: @rm -rf $(MODLIB)/kernel @rm -f $(MODLIB)/source @mkdir -p $(MODLIB)/kernel @ln -s $(abspath $(srctree)) $(MODLIB)/source @if [ ! $(objtree) -ef $(MODLIB)/build ]; then
rm -f $(MODLIB)/build ;
ln -s $(CURDIR) $(MODLIB)/build ;
fi @sed 's:^:kernel/:' modules.order > $(MODLIB)/modules.order @cp -f modules.builtin $(MODLIB)/ @cp -f $(objtree)/modules.builtin.modinfo $(MODLIB)/

endif # CONFIG_MODULES

Cleaning is done on three levels.

make clean Delete most generated files

Leave enough to build external modules

make mrproper Delete the current configuration, and all generated files

make distclean Remove editor backup files, patch leftover files and the like

Directories & files removed with 'make clean'

CLEAN_FILES += include/ksym vmlinux.symvers modules-only.symvers
modules.builtin modules.builtin.modinfo modules.nsdeps
compile_commands.json .thinlto-cache

Directories & files removed with 'make mrproper'

MRPROPER_FILES += include/config include/generated
arch/$(SRCARCH)/include/generated .tmp_objdiff
debian snap tar-install
.config .config.old .version
Module.symvers
certs/signing_key.pem certs/signing_key.x509
certs/x509.genkey
vmlinux-gdb.py
*.spec

clean - Delete most, but leave enough to build external modules

clean: rm-files := $(CLEAN_FILES)

PHONY += archclean vmlinuxclean

vmlinuxclean: $(Q)$(CONFIG_SHELL) $(srctree)/scripts/link-vmlinux.sh clean $(Q)$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) clean)

clean: archclean vmlinuxclean resolve_btfids_clean

mrproper - Delete all generated files, including .config

mrproper: rm-files := $(wildcard $(MRPROPER_FILES)) mrproper-dirs := $(addprefix mrproper,scripts)

PHONY += $(mrproper-dirs) mrproper $(mrproper-dirs): $(Q)$(MAKE) $(clean)=$(patsubst mrproper%,%,$@)

mrproper: clean $(mrproper-dirs) $(call cmd,rmfiles)

distclean

PHONY += distclean

distclean: mrproper @find . $(RCS_FIND_IGNORE)
( -name '.orig' -o -name '.rej' -o -name '~'
-o -name '.bak' -o -name '##' -o -name '%'
-o -name 'core' -o -name tags -o -name TAGS -o -name 'cscope*'
-o -name GPATH -o -name GRTAGS -o -name GSYMS -o -name GTAGS )
-type f -print | xargs rm -f

Packaging of the kernel to various formats

---------------------------------------------------------------------------

%src-pkg: FORCE $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.package $@ %pkg: include/config/kernel.release FORCE $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.package $@

Brief documentation of the typical targets used

---------------------------------------------------------------------------

boards := $(wildcard $(srctree)/arch/$(SRCARCH)/configs/_defconfig) boards := $(sort $(notdir $(boards))) board-dirs := $(dir $(wildcard $(srctree)/arch/$(SRCARCH)/configs//*_defconfig)) board-dirs := $(sort $(notdir $(board-dirs:/=)))

PHONY += help help: @echo 'Cleaning targets:' @echo ' clean - Remove most generated files but keep the config and' @echo ' enough build support to build external modules' @echo ' mrproper - Remove all generated files + config + various backup files' @echo ' distclean - mrproper + remove editor backup and patch files' @echo '' @echo 'Configuration targets:' @$(MAKE) -f $(srctree)/scripts/kconfig/Makefile help @echo '' @echo 'Other generic targets:' @echo ' all - Build all targets marked with []' @echo ' vmlinux - Build the bare kernel' @echo '* modules - Build all modules' @echo ' modules_install - Install all modules to INSTALL_MOD_PATH (default: /)' @echo ' dir/ - Build all files in dir and below' @echo ' dir/file.[ois] - Build specified target only' @echo ' dir/file.ll - Build the LLVM assembly file' @echo ' (requires compiler support for LLVM assembly generation)' @echo ' dir/file.lst - Build specified mixed source/assembly target only' @echo ' (requires a recent binutils and recent build (System.map))' @echo ' dir/file.ko - Build module including final link' @echo ' modules_prepare - Set up for building external modules' @echo ' tags/TAGS - Generate tags file for editors' @echo ' cscope - Generate cscope index' @echo ' gtags - Generate GNU GLOBAL index' @echo ' kernelrelease - Output the release version string (use with make -s)' @echo ' kernelversion - Output the version stored in Makefile (use with make -s)' @echo ' image_name - Output the image name (use with make -s)' @echo ' headers_install - Install sanitised kernel headers to INSTALL_HDR_PATH';
echo ' (default: $(INSTALL_HDR_PATH))';
echo '' @echo 'Static analysers:' @echo ' checkstack - Generate a list of stack hogs' @echo ' versioncheck - Sanity check on version.h usage' @echo ' includecheck - Check for duplicate included header files' @echo ' export_report - List the usages of all exported symbols' @echo ' headerdep - Detect inclusion cycles in headers' @echo ' coccicheck - Check with Coccinelle' @echo ' clang-analyzer - Check with clang static analyzer' @echo ' clang-tidy - Check with clang-tidy' @echo '' @echo 'Tools:' @echo ' nsdeps - Generate missing symbol namespace dependencies' @echo '' @echo 'Kernel selftest:' @echo ' kselftest - Build and run kernel selftest' @echo ' Build, install, and boot kernel before' @echo ' running kselftest on it' @echo ' Run as root for full coverage' @echo ' kselftest-all - Build kernel selftest' @echo ' kselftest-install - Build and install kernel selftest' @echo ' kselftest-clean - Remove all generated kselftest files' @echo ' kselftest-merge - Merge all the config dependencies of' @echo ' kselftest to existing .config.' @echo '' @$(if $(dtstree),
echo 'Devicetree:';
echo '* dtbs - Build device tree blobs for enabled boards';
echo ' dtbs_install - Install dtbs to $(INSTALL_DTBS_PATH)';
echo ' dt_binding_check - Validate device tree binding documents';
echo ' dtbs_check - Validate device tree source files';
echo '')

@echo 'Userspace tools targets:'
@echo '  use "make tools/help"'
@echo '  or  "cd tools; make help"'
@echo  ''
@echo  'Kernel packaging:'
@$(MAKE) -f $(srctree)/scripts/Makefile.package help
@echo  ''
@echo  'Documentation targets:'
@$(MAKE) -f $(srctree)/Documentation/Makefile dochelp
@echo  ''
@echo  'Architecture specific targets ($(SRCARCH)):'
@$(if $(archhelp),$(archhelp),\
	echo '  No architecture specific help defined for $(SRCARCH)')
@echo  ''
@$(if $(boards), \
	$(foreach b, $(boards), \
	printf "  %-27s - Build for %s\\n" $(b) $(subst _defconfig,,$(b));) \
	echo '')
@$(if $(board-dirs), \
	$(foreach b, $(board-dirs), \
	printf "  %-16s - Show %s-specific targets\\n" help-$(b) $(b);) \
	printf "  %-16s - Show all of the above\\n" help-boards; \
	echo '')

@echo  '  make V=0|1 [targets] 0 => quiet build (default), 1 => verbose build'
@echo  '  make V=2   [targets] 2 => give reason for rebuild of target'
@echo  '  make O=dir [targets] Locate all output files in "dir", including .config'
@echo  '  make C=1   [targets] Check re-compiled c source with $$CHECK'
@echo  '                       (sparse by default)'
@echo  '  make C=2   [targets] Force check of all c source with $$CHECK'
@echo  '  make RECORDMCOUNT_WARN=1 [targets] Warn about ignored mcount sections'
@echo  '  make W=n   [targets] Enable extra build checks, n=1,2,3 where'
@echo  '		1: warnings which may be relevant and do not occur too often'
@echo  '		2: warnings which occur quite often but may still be relevant'
@echo  '		3: more obscure warnings, can most likely be ignored'
@echo  '		Multiple levels can be combined with W=12 or W=123'
@echo  ''
@echo  'Execute "make" or "make all" to build all targets marked with [*] '
@echo  'For further info see the ./README file'

help-board-dirs := $(addprefix help-,$(board-dirs))

help-boards: $(help-board-dirs)

boards-per-dir = $(sort $(notdir $(wildcard $(srctree)/arch/$(SRCARCH)/configs/$/_defconfig)))

$(help-board-dirs): help-%: @echo 'Architecture specific targets ($(SRCARCH) $):' @$(if $(boards-per-dir),
$(foreach b, $(boards-per-dir),
printf " %-24s - Build for %s\n" $/$(b) $(subst _defconfig,,$(b));)
echo '')

Documentation targets

---------------------------------------------------------------------------

DOC_TARGETS := xmldocs latexdocs pdfdocs htmldocs epubdocs cleandocs
linkcheckdocs dochelp refcheckdocs PHONY += $(DOC_TARGETS) $(DOC_TARGETS): $(Q)$(MAKE) $(build)=Documentation $@

Misc

---------------------------------------------------------------------------

PHONY += scripts_gdb scripts_gdb: prepare0 $(Q)$(MAKE) $(build)=scripts/gdb $(Q)ln -fsn $(abspath $(srctree)/scripts/gdb/vmlinux-gdb.py)

ifdef CONFIG_GDB_SCRIPTS all: scripts_gdb endif

else # KBUILD_EXTMOD

External module support.

When building external modules the kernel used as basis is considered

read-only, and no consistency checks are made and the make

system is not used on the basis kernel. If updates are required

in the basis kernel ordinary make commands (without M=...) must be used.

We are always building only modules.

KBUILD_BUILTIN := KBUILD_MODULES := 1

build-dirs := $(KBUILD_EXTMOD) $(MODORDER): descend @:

compile_commands.json: $(extmod_prefix)compile_commands.json PHONY += compile_commands.json

clean-dirs := $(KBUILD_EXTMOD) clean: rm-files := $(KBUILD_EXTMOD)/Module.symvers $(KBUILD_EXTMOD)/modules.nsdeps
$(KBUILD_EXTMOD)/compile_commands.json $(KBUILD_EXTMOD)/.thinlto-cache

PHONY += help help: @echo ' Building external modules.' @echo ' Syntax: make -C path/to/kernel/src M=$$PWD target' @echo '' @echo ' modules - default target, build the module(s)' @echo ' modules_install - install the module' @echo ' clean - remove generated files in module directory only' @echo ''

no-op for external module builds

PHONY += prepare modules_prepare

endif # KBUILD_EXTMOD

---------------------------------------------------------------------------

Modules

PHONY += modules modules_install

ifdef CONFIG_MODULES

modules: modules_check $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost

PHONY += modules_check modules_check: $(MODORDER) $(Q)$(CONFIG_SHELL) $(srctree)/scripts/modules-check.sh $<

quiet_cmd_depmod = DEPMOD $(MODLIB) cmd_depmod = $(CONFIG_SHELL) $(srctree)/scripts/depmod.sh $(DEPMOD)
$(KERNELRELEASE)

modules_install: $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modinst $(call cmd,depmod)

else # CONFIG_MODULES

Modules not configured

---------------------------------------------------------------------------

modules modules_install: @echo >&2 '' @echo >&2 ' The present kernel configuration has modules disabled.' @echo >&2 '*** To use the module feature, please run "make menuconfig" etc.' @echo >&2 '*** to enable CONFIG_MODULES.' @echo >&2 '***' @exit 1

endif # CONFIG_MODULES

Single targets

---------------------------------------------------------------------------

To build individual files in subdirectories, you can do like this:

make foo/bar/baz.s

The supported suffixes for single-target are listed in 'single-targets'

To build only under specific subdirectories, you can do like this:

make foo/bar/baz/

ifdef single-build

.ko is special because modpost is needed

single-ko := $(sort $(filter %.ko, $(MAKECMDGOALS))) single-no-ko := $(sort $(patsubst %.ko,%.mod, $(MAKECMDGOALS)))

$(single-ko): single_modpost @: $(single-no-ko): descend @:

ifeq ($(KBUILD_EXTMOD),)

For the single build of in-tree modules, use a temporary file to avoid

the situation of modules_install installing an invalid modules.order.

MODORDER := .modules.tmp endif

PHONY += single_modpost single_modpost: $(single-no-ko) modules_prepare $(Q){ $(foreach m, $(single-ko), echo $(extmod_prefix)$m;) } > $(MODORDER) $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost

KBUILD_MODULES := 1

export KBUILD_SINGLE_TARGETS := $(addprefix $(extmod_prefix), $(single-no-ko))

trim unrelated directories

build-dirs := $(foreach d, $(build-dirs),
$(if $(filter $(d)/%, $(KBUILD_SINGLE_TARGETS)), $(d)))

endif

ifndef CONFIG_MODULES KBUILD_MODULES := endif

Handle descending into subdirectories listed in $(build-dirs)

Preset locale variables to speed up the build process. Limit locale

tweaks to this spot to avoid wrong language settings when running

make menuconfig etc.

Error messages still appears in the original language

PHONY += descend $(build-dirs) descend: $(build-dirs) $(build-dirs): prepare $(Q)$(MAKE) $(build)=$@
single-build=$(if $(filter-out $@/, $(filter $@/%, $(KBUILD_SINGLE_TARGETS))),1)
need-builtin=1 need-modorder=1

clean-dirs := $(addprefix clean, $(clean-dirs)) PHONY += $(clean-dirs) clean $(clean-dirs): $(Q)$(MAKE) $(clean)=$(patsubst clean%,%,$@)

clean: $(clean-dirs) $(call cmd,rmfiles) @find $(if $(KBUILD_EXTMOD), $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE)
( -name '.[aios]' -o -name '.ko' -o -name '..cmd'
-o -name '.ko.'
-o -name '.dtb' -o -name '.dtbo' -o -name '.dtb.S' -o -name '.dt.yaml'
-o -name '.dwo' -o -name '.lst'
-o -name '.su' -o -name '.mod'
-o -name '..d' -o -name '..tmp' -o -name '.mod.c'
-o -name '.lex.c' -o -name '.tab.[ch]'
-o -name '.asn1.[ch]'
-o -name '.symtypes' -o -name 'modules.order'
-o -name '.tmp_.o.'
-o -name '.c.[012].'
-o -name '.ll'
-o -name '.gcno'
-o -name '.*.symversions' ) -type f -print | xargs rm -f

Generate tags for editors

---------------------------------------------------------------------------

quiet_cmd_tags = GEN $@ cmd_tags = $(BASH) $(srctree)/scripts/tags.sh $@

tags TAGS cscope gtags: FORCE $(call cmd,tags)

Script to generate missing namespace dependencies

---------------------------------------------------------------------------

PHONY += nsdeps nsdeps: export KBUILD_NSDEPS=1 nsdeps: modules $(Q)$(CONFIG_SHELL) $(srctree)/scripts/nsdeps

Clang Tooling

---------------------------------------------------------------------------

quiet_cmd_gen_compile_commands = GEN $@ cmd_gen_compile_commands = $(PYTHON3) $< -a $(AR) -o $@ $(filter-out $<, $(real-prereqs))

$(extmod_prefix)compile_commands.json: scripts/clang-tools/gen_compile_commands.py
$(if $(KBUILD_EXTMOD),,$(KBUILD_VMLINUX_OBJS) $(KBUILD_VMLINUX_LIBS))
$(if $(CONFIG_MODULES), $(MODORDER)) FORCE $(call if_changed,gen_compile_commands)

targets += $(extmod_prefix)compile_commands.json

PHONY += clang-tidy clang-analyzer

ifdef CONFIG_CC_IS_CLANG quiet_cmd_clang_tools = CHECK $< cmd_clang_tools = $(PYTHON3) $(srctree)/scripts/clang-tools/run-clang-tools.py $@ $<

clang-tidy clang-analyzer: $(extmod_prefix)compile_commands.json $(call cmd,clang_tools) else clang-tidy clang-analyzer: @echo "$@ requires CC=clang" >&2 @false endif

Scripts to check various things for consistency

---------------------------------------------------------------------------

PHONY += includecheck versioncheck coccicheck export_report

includecheck: find $(srctree)/* $(RCS_FIND_IGNORE)
-name '*.[hcS]' -type f -print | sort
| xargs $(PERL) -w $(srctree)/scripts/checkincludes.pl

versioncheck: find $(srctree)/* $(RCS_FIND_IGNORE)
-name '*.[hcS]' -type f -print | sort
| xargs $(PERL) -w $(srctree)/scripts/checkversion.pl

coccicheck: $(Q)$(BASH) $(srctree)/scripts/$@

export_report: $(PERL) $(srctree)/scripts/export_report.pl

PHONY += checkstack kernelrelease kernelversion image_name

UML needs a little special treatment here. It wants to use the host

toolchain, so needs $(SUBARCH) passed to checkstack.pl. Everyone

else wants $(ARCH), including people doing cross-builds, which means

that $(SUBARCH) doesn't work here.

ifeq ($(ARCH), um) CHECKSTACK_ARCH := $(SUBARCH) else CHECKSTACK_ARCH := $(ARCH) endif checkstack: $(OBJDUMP) -d vmlinux $$(find . -name '*.ko') |
$(PERL) $(srctree)/scripts/checkstack.pl $(CHECKSTACK_ARCH)

kernelrelease: @echo "$(KERNELVERSION)$$($(CONFIG_SHELL) $(srctree)/scripts/setlocalversion $(srctree))"

kernelversion: @echo $(KERNELVERSION)

image_name: @echo $(KBUILD_IMAGE)

Clear a bunch of variables before executing the submake

ifeq ($(quiet),silent_) tools_silent=s endif

tools/: FORCE $(Q)mkdir -p $(objtree)/tools $(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/

tools/%: FORCE $(Q)mkdir -p $(objtree)/tools $(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/ $*

quiet_cmd_rmfiles = $(if $(wildcard $(rm-files)),CLEAN $(wildcard $(rm-files))) cmd_rmfiles = rm -rf $(rm-files)

read saved command lines for existing targets

existing-targets := $(wildcard $(sort $(targets)))

-include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)

endif # config-build endif # mixed-build endif # need-sub-make

PHONY += FORCE FORCE:

Declare the contents of the PHONY variable as phony. We keep that

information in a variable so we can use it in if_changed and friends.

.PHONY: $(PHONY)