checksyscalls: move instance functionality into generic code

On MIPS the checksyscalls.sh script may be executed multiple times.
Currently these multiple executions are executed on each build as kbu

checksyscalls: move instance functionality into generic code

On MIPS the checksyscalls.sh script may be executed multiple times.
Currently these multiple executions are executed on each build as kbuild
see that the commands have changed each time.

Use a dedicated stamp file for each different invocation to avoid the
spurious executions.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Link: https://patch.msgid.link/20260402-kbuild-missing-syscalls-v3-3-6641be1de2db@weissschuh.net
Signed-off-by: Nicolas Schier <nsc@kernel.org>

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checksyscalls: only run when necessary

Currently checksyscalls.sh is unconditionally executed during each build.
Most of these executions are unnecessary.

Only run checksyscalls.sh if one of its in

checksyscalls: only run when necessary

Currently checksyscalls.sh is unconditionally executed during each build.
Most of these executions are unnecessary.

Only run checksyscalls.sh if one of its inputs have changed.

This new logic does not work for the multiple invocations done for MIPS.
The effect is that checksyscalls.sh is still executed unconditionally.
However this is not worse than before.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Link: https://patch.msgid.link/20260402-kbuild-missing-syscalls-v3-2-6641be1de2db@weissschuh.net
Signed-off-by: Nicolas Schier <nsc@kernel.org>

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sched: Make migrate_{en,dis}able() inline

For now, migrate_enable and migrate_disable are global, which makes them
become hotspots in some case. Take BPF for example, the function calling
to migrate

sched: Make migrate_{en,dis}able() inline

For now, migrate_enable and migrate_disable are global, which makes them
become hotspots in some case. Take BPF for example, the function calling
to migrate_enable and migrate_disable in BPF trampoline can introduce
significant overhead, and following is the 'perf top' of FENTRY's
benchmark (./tools/testing/selftests/bpf/bench trig-fentry):

54.63% bpf_prog_2dcccf652aac1793_bench_trigger_fentry [k]
bpf_prog_2dcccf652aac1793_bench_trigger_fentry
10.43% [kernel] [k] migrate_enable
10.07% bpf_trampoline_6442517037 [k] bpf_trampoline_6442517037
8.06% [kernel] [k] __bpf_prog_exit_recur
4.11% libc.so.6 [.] syscall
2.15% [kernel] [k] entry_SYSCALL_64
1.48% [kernel] [k] memchr_inv
1.32% [kernel] [k] fput
1.16% [kernel] [k] _copy_to_user
0.73% [kernel] [k] bpf_prog_test_run_raw_tp

So in this commit, we make migrate_enable/migrate_disable inline to obtain
better performance. The struct rq is defined internally in
kernel/sched/sched.h, and the field "nr_pinned" is accessed in
migrate_enable/migrate_disable, which makes it hard to make them inline.

Alexei Starovoitov suggests to generate the offset of "nr_pinned" in [1],
so we can define the migrate_enable/migrate_disable in
include/linux/sched.h and access "this_rq()->nr_pinned" with
"(void *)this_rq() + RQ_nr_pinned".

The offset of "nr_pinned" is generated in include/generated/rq-offsets.h
by kernel/sched/rq-offsets.c.

Generally speaking, we move the definition of migrate_enable and
migrate_disable to include/linux/sched.h from kernel/sched/core.c. The
calling to __set_cpus_allowed_ptr() is leaved in ___migrate_enable().

The "struct rq" is not available in include/linux/sched.h, so we can't
access the "runqueues" with this_cpu_ptr(), as the compilation will fail
in this_cpu_ptr() -> raw_cpu_ptr() -> __verify_pcpu_ptr():
typeof((ptr) + 0)

So we introduce the this_rq_raw() and access the runqueues with
arch_raw_cpu_ptr/PERCPU_PTR directly.

The variable "runqueues" is not visible in the kernel modules, and export
it is not a good idea. As Peter Zijlstra advised in [2], we define and
export migrate_enable/migrate_disable in kernel/sched/core.c too, and use
them for the modules.

Before this patch, the performance of BPF FENTRY is:

fentry : 113.030 ± 0.149M/s
fentry : 112.501 ± 0.187M/s
fentry : 112.828 ± 0.267M/s
fentry : 115.287 ± 0.241M/s

After this patch, the performance of BPF FENTRY increases to:

fentry : 143.644 ± 0.670M/s
fentry : 149.764 ± 0.362M/s
fentry : 149.642 ± 0.156M/s
fentry : 145.263 ± 0.221M/s

Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/bpf/CAADnVQ+5sEDKHdsJY5ZsfGDO_1SEhhQWHrt2SMBG5SYyQ+jt7w@mail.gmail.com/ [1]
Link: https://lore.kernel.org/all/20250819123214.GH4067720@noisy.programming.kicks-ass.net/ [2]

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drm: ensure drm headers are self-contained and pass kernel-doc

Ensure drm headers build, are self-contained, have header guards, and
have no kernel-doc warnings, when CONFIG_DRM_HEADER_TEST=y.

The

drm: ensure drm headers are self-contained and pass kernel-doc

Ensure drm headers build, are self-contained, have header guards, and
have no kernel-doc warnings, when CONFIG_DRM_HEADER_TEST=y.

The mechanism follows similar patters used in i915, xe, and usr/include.

To cover include/drm, we need to recurse there using the top level
Kbuild and the new include/Kbuild files.

v4: check for CONFIG_WERROR in addition to CONFIG_DRM_WERROR

v3: adapt to upstream build changes

v2: make DRM_HEADER_TEST depend on DRM

Suggested-by: Daniel Vetter <daniel@ffwll.ch>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Simona Vetter <simona.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/d8ad1c6d707f38a55987f616cb9650aef30b84e1.1737556766.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

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Merge tag 'kbuild-v6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

- Remove potentially incomplete targets when Kbuid is inte

Merge tag 'kbuild-v6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

- Remove potentially incomplete targets when Kbuid is interrupted by
SIGINT etc in case GNU Make may miss to do that when stderr is piped
to another program.

- Rewrite the single target build so it works more correctly.

- Fix rpm-pkg builds with V=1.

- List top-level subdirectories in ./Kbuild.

- Ignore auto-generated __kstrtab_* and __kstrtabns_* symbols in
kallsyms.

- Avoid two different modules in lib/zstd/ having shared code, which
potentially causes building the common code as build-in and modular
back-and-forth.

- Unify two modpost invocations to optimize the build process.

- Remove head-y syntax in favor of linker scripts for placing
particular sections in the head of vmlinux.

- Bump the minimal GNU Make version to 3.82.

- Clean up misc Makefiles and scripts.

* tag 'kbuild-v6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (41 commits)
docs: bump minimal GNU Make version to 3.82
ia64: simplify esi object addition in Makefile
Revert "kbuild: Check if linker supports the -X option"
kbuild: rebuild .vmlinux.export.o when its prerequisite is updated
kbuild: move modules.builtin(.modinfo) rules to Makefile.vmlinux_o
zstd: Fixing mixed module-builtin objects
kallsyms: ignore __kstrtab_* and __kstrtabns_* symbols
kallsyms: take the input file instead of reading stdin
kallsyms: drop duplicated ignore patterns from kallsyms.c
kbuild: reuse mksysmap output for kallsyms
mksysmap: update comment about __crc_*
kbuild: remove head-y syntax
kbuild: use obj-y instead extra-y for objects placed at the head
kbuild: hide error checker logs for V=1 builds
kbuild: re-run modpost when it is updated
kbuild: unify two modpost invocations
kbuild: move vmlinux.o rule to the top Makefile
kbuild: move .vmlinux.objs rule to Makefile.modpost
kbuild: list sub-directories in ./Kbuild
Makefile.compiler: replace cc-ifversion with compiler-specific macros
...

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kbuild: list sub-directories in ./Kbuild

Use the ordinary obj-y syntax to list subdirectories.

Note1:
Previously, the link order of lib-y depended on CONFIG_MODULES; lib-y
was linked before drivers

kbuild: list sub-directories in ./Kbuild

Use the ordinary obj-y syntax to list subdirectories.

Note1:
Previously, the link order of lib-y depended on CONFIG_MODULES; lib-y
was linked before drivers-y when CONFIG_MODULES=y, otherwise after
drivers-y. This was a bug of commit 7273ad2b08f8 ("kbuild: link lib-y
objects to vmlinux forcibly when CONFIG_MODULES=y"), but it was not a
big deal after all. Now, all objects listed in lib-y are linked last,
irrespective of CONFIG_MODULES.

Note2:
Finally, the single target build in arch/*/lib/ works correctly. There was
a bug report about this. [1]

$ make ARCH=arm arch/arm/lib/findbit.o
CALL scripts/checksyscalls.sh
AS arch/arm/lib/findbit.o

[1]: https://lore.kernel.org/linux-kbuild/YvUQOwL6lD4%2F5%2FU6@shell.armlinux.org.uk/

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

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kbuild: check sha1sum just once for each atomic header

It is unneeded to check the sha1sum every time.

Create the timestamp files to manage it.

Add '.' to clean-dirs because 'make clean' must visi

kbuild: check sha1sum just once for each atomic header

It is unneeded to check the sha1sum every time.

Create the timestamp files to manage it.

Add '.' to clean-dirs because 'make clean' must visit ./Kbuild to
clean up the timestamp files.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

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kbuild: add phony targets to ./Kbuild

missing-syscalls and old-atomics are meant to be phony targets.
Adding them to always-y is odd. (always-y should generate something).

Add a new phony target 'p

kbuild: add phony targets to ./Kbuild

missing-syscalls and old-atomics are meant to be phony targets.
Adding them to always-y is odd. (always-y should generate something).

Add a new phony target 'prepare', which depends on all the other.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

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kbuild: rename hostprogs-y/always to hostprogs/always-y

In old days, the "host-progs" syntax was used for specifying host
programs. It was renamed to the current "hostprogs-y" in 2004.

It is typica

kbuild: rename hostprogs-y/always to hostprogs/always-y

In old days, the "host-progs" syntax was used for specifying host
programs. It was renamed to the current "hostprogs-y" in 2004.

It is typically useful in scripts/Makefile because it allows Kbuild to
selectively compile host programs based on the kernel configuration.

This commit renames like follows:

always -> always-y
hostprogs-y -> hostprogs

So, scripts/Makefile will look like this:

always-$(CONFIG_BUILD_BIN2C) += ...
always-$(CONFIG_KALLSYMS) += ...
...
hostprogs := $(always-y) $(always-m)

I think this makes more sense because a host program is always a host
program, irrespective of the kernel configuration. We want to specify
which ones to compile by CONFIG options, so always-y will be handier.

The "always", "hostprogs-y", "hostprogs-m" will be kept for backward
compatibility for a while.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

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kbuild: do not descend to ./Kbuild when cleaning

'make clean' descends into ./Kbuild, but does not clean anything
since everything is added to no-clean-files.

There is no need to descend to ./Kbuil

kbuild: do not descend to ./Kbuild when cleaning

'make clean' descends into ./Kbuild, but does not clean anything
since everything is added to no-clean-files.

There is no need to descend to ./Kbuild in the first place.
We can drop the no-clean-files assignment.

With this, there is no more user of no-clean-files. I will keep it
for a while to see whether a new user will appear.

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

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kbuild: remove meaningless 'targets' in ./Kbuild

timeconst.h is generated by $(call filechk,...), missing-syscalls and
old-atomics are invoked by $(call cmd,...)

None of them needs to be added to '

kbuild: remove meaningless 'targets' in ./Kbuild

timeconst.h is generated by $(call filechk,...), missing-syscalls and
old-atomics are invoked by $(call cmd,...)

None of them needs to be added to 'targets'.

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

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Merge tag 'kbuild-v5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

- do not generate unneeded top-level built-in.a

- let gi

Merge tag 'kbuild-v5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

- do not generate unneeded top-level built-in.a

- let git ignore O= directory entirely

- optimize scripts/kallsyms slightly

- exclude DWARF info from *.s regardless of config options

- fix GCC toolchain search path for Clang to prepare ld.lld support

- do not generate modules.order when CONFIG_MODULES is disabled

- simplify single target rules and remove VPATH for external module
build

- allow to add optional flags to dpkg-buildpackage when building
deb-pkg

- move some compiler option tests from Makefile to Kconfig

- various Makefile cleanups

* tag 'kbuild-v5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (40 commits)
kbuild: remove scripts/basic/% build target
kbuild: use -Werror=implicit-... instead of -Werror-implicit-...
kbuild: clean up scripts/gcc-version.sh
kbuild: remove cc-version macro
kbuild: update comment block of scripts/clang-version.sh
kbuild: remove commented-out INITRD_COMPRESS
kbuild: move -gsplit-dwarf, -gdwarf-4 option tests to Kconfig
kbuild: [bin]deb-pkg: add DPKG_FLAGS variable
kbuild: move ".config not found!" message from Kconfig to Makefile
kbuild: invoke syncconfig if include/config/auto.conf.cmd is missing
kbuild: simplify single target rules
kbuild: remove empty rules for makefiles
kbuild: make -r/-R effective in top Makefile for old Make versions
kbuild: move tools_silent to a more relevant place
kbuild: compute false-positive -Wmaybe-uninitialized cases in Kconfig
kbuild: refactor cc-cross-prefix implementation
kbuild: hardcode genksyms path and remove GENKSYMS variable
scripts/gdb: refactor rules for symlink creation
kbuild: create symlink to vmlinux-gdb.py in scripts_gdb target
scripts/gdb: do not descend into scripts/gdb from scripts
...

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kbuild: remove unimportant comments from ./Kbuild

Every time we add/remove a target, we need to touch the header part,
including renumbering. This is not so important information.

Numbering targets

kbuild: remove unimportant comments from ./Kbuild

Every time we add/remove a target, we need to touch the header part,
including renumbering. This is not so important information.

Numbering targets is rather misleading because they are not necessarily
generated in this order. For example, 1) and 2) can be executed
simultaneously when the -j option is given.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

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scripts/gdb: delay generation of gdb constants.py

scripts/gdb/linux/constants.py is never used in the kernel build
process. There is no good reason to create it so early.

Get it out of the 'prepare

scripts/gdb: delay generation of gdb constants.py

scripts/gdb/linux/constants.py is never used in the kernel build
process. There is no good reason to create it so early.

Get it out of the 'prepare' stage.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

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Merge branch 'locking/atomics' into locking/core, to pick up WIP commits

Signed-off-by: Ingo Molnar <mingo@kernel.org>

kbuild: use assignment instead of define ... endef for filechk_* rules

You do not have to use define ... endef for filechk_* rules.

For simple cases, the use of assignment looks cleaner, IMHO.

I u

kbuild: use assignment instead of define ... endef for filechk_* rules

You do not have to use define ... endef for filechk_* rules.

For simple cases, the use of assignment looks cleaner, IMHO.

I updated the usage for scripts/Kbuild.include in case somebody
misunderstands the 'define ... endif' is the requirement.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>

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kbuild: change filechk to surround the given command with { }

filechk_* rules often consist of multiple 'echo' lines. They must be
surrounded with { } or ( ) to work correctly. Otherwise, only the
s

kbuild: change filechk to surround the given command with { }

filechk_* rules often consist of multiple 'echo' lines. They must be
surrounded with { } or ( ) to work correctly. Otherwise, only the
string from the last 'echo' would be written into the target.

Let's take care of that in the 'filechk' in scripts/Kbuild.include
to clean up filechk_* rules.

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

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kbuild: remove unused cmd_gentimeconst

filechk_gentimeconst is always used instead of cmd_gentimeconst.

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

kbuild: remove $(obj)/ prefixes in ./Kbuild

Adding $(obj)/ to file paths relative from the top objtree looks
a bit redundant to me. This commit has no functional change since
$(obj) is '.' in this f

kbuild: remove $(obj)/ prefixes in ./Kbuild

Adding $(obj)/ to file paths relative from the top objtree looks
a bit redundant to me. This commit has no functional change since
$(obj) is '.' in this file.

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

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treewide: remove explicit rules for *offsets.s

These explicit rules are unneeded because scripts/Makefile.build
provides a pattern rule to create %.s from %.c

Signed-off-by: Masahiro Yamada <yamada

treewide: remove explicit rules for *offsets.s

These explicit rules are unneeded because scripts/Makefile.build
provides a pattern rule to create %.s from %.c

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

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locking/atomics: Fix out-of-tree build

Building a kernel out of tree with:

make O=/tmp/b oldconfig
cd /tmp/b
make

gives this error:

CALL /mnt/kernel/kernel/linux/scripts/atomic/check

locking/atomics: Fix out-of-tree build

Building a kernel out of tree with:

make O=/tmp/b oldconfig
cd /tmp/b
make

gives this error:

CALL /mnt/kernel/kernel/linux/scripts/atomic/check-atomics.sh
/bin/bash: scripts/atomic/check-atomics.sh: No such file or directory
make[3]: *** [/mnt/kernel/kernel/linux/./Kbuild:86: old-atomics] Error 127
make[3]: *** Waiting for unfinished jobs....

Make the command use the proper build prerequisite which is the absolute
path to the script.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: arnd@arndb.de
Cc: aryabinin@virtuozzo.com
Cc: catalin.marinas@arm.com
Cc: dvyukov@google.com
Cc: glider@google.com
Cc: linux-arm-kernel@lists.infradead.org
Cc: linuxdrivers@attotech.com
Fixes: 8d32588077bd ("locking/atomics: Check generated headers are up-to-date")
Link: http://lkml.kernel.org/r/20181108194128.13368-1-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

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locking/atomics: Check generated headers are up-to-date

Now that all the generated atomic headers are in place, it would be good
to ensure that:

a) the headers are up-to-date when scripting changes

locking/atomics: Check generated headers are up-to-date

Now that all the generated atomic headers are in place, it would be good
to ensure that:

a) the headers are up-to-date when scripting changes.

b) developers don't directly modify the generated headers.

To ensure both of these properties, let's add a Kbuild step to check
that the generated headers are up-to-date.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: catalin.marinas@arm.com
Cc: Will Deacon <will.deacon@arm.com>
Cc: linuxdrivers@attotech.com
Cc: dvyukov@google.com
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: arnd@arndb.de
Cc: aryabinin@virtuozzo.com
Cc: glider@google.com
Link: http://lkml.kernel.org/r/20180904104830.2975-6-mark.rutland@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

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Merge tag 'kbuild-v4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:
"One of the most remarkable improvements in this cycle is,

Merge tag 'kbuild-v4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:
"One of the most remarkable improvements in this cycle is, Kbuild is
now able to cache the result of shell commands. Some variables are
expensive to compute, for example, $(call cc-option,...) invokes the
compiler. It is not efficient to redo this computation every time,
even when we are not actually building anything. Kbuild creates a
hidden file ".cache.mk" that contains invoked shell commands and their
results. The speed-up should be noticeable.

Summary:

- Fix arch build issues (hexagon, sh)

- Clean up various Makefiles and scripts

- Fix wrong usage of {CFLAGS,LDFLAGS}_MODULE in arch Makefiles

- Cache variables that are expensive to compute

- Improve cc-ldopton and ld-option for Clang

- Optimize output directory creation"

* tag 'kbuild-v4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (30 commits)
kbuild: move coccicheck help from scripts/Makefile.help to top Makefile
sh: decompressor: add shipped files to .gitignore
frv: .gitignore: ignore vmlinux.lds
selinux: remove unnecessary assignment to subdir-
kbuild: specify FORCE in Makefile.headersinst as .PHONY target
kbuild: remove redundant mkdir from ./Kbuild
kbuild: optimize object directory creation for incremental build
kbuild: create object directories simpler and faster
kbuild: filter-out PHONY targets from "targets"
kbuild: remove redundant $(wildcard ...) for cmd_files calculation
kbuild: create directory for make cache only when necessary
sh: select KBUILD_DEFCONFIG depending on ARCH
kbuild: fix linker feature test macros when cross compiling with Clang
kbuild: shrink .cache.mk when it exceeds 1000 lines
kbuild: do not call cc-option before KBUILD_CFLAGS initialization
kbuild: Cache a few more calls to the compiler
kbuild: Add a cache for generated variables
kbuild: add forward declaration of default target to Makefile.asm-generic
kbuild: remove KBUILD_SUBDIR_ASFLAGS and KBUILD_SUBDIR_CCFLAGS
hexagon/kbuild: replace CFLAGS_MODULE with KBUILD_CFLAGS_MODULE
...

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kbuild: remove redundant mkdir from ./Kbuild

These two targets are added to "targets". Their directories are
automatically created.

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

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.

For non */uapi/* files that summary was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139

and resulted in the first patch in this series.

If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930

and resulted in the second patch in this series.

- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:

SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1

and that resulted in the third patch in this series.

- when the two scanners agreed on the detected license(s), that became
the concluded license(s).

- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.

- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).

- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.

- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct

This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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