kbuild: Add -Wa,--fatal-warnings to as-instr invocation

Certain assembler instruction tests may only induce warnings from the
assembler on an unsupported instruction or option, which causes as-instr
to succeed when it was expected to fail. Some tests workaround this
limitation by additionally testing that invalid input fails as expected.
However, this is fragile if the assembler is changed to accept the
invalid input, as it will cause the instruction/option to be unavailable
like it was unsupported even when it is.

Use '-Wa,--fatal-warnings' in the as-instr macro to turn these warnings
into hard errors, which avoids this fragility and makes tests more
robust and well formed.

Cc: stable@vger.kernel.org
Suggested-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Eric Biggers <ebiggers@google.com>
Tested-by: Andy Chiu <andybnac@gmail.com>
Reviewed-by: Andy Chiu <andybnac@gmail.com>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Masahiro Yamada <masahiroy@kernel.org>
Link: https://lore.kernel.org/r/20240125-fix-riscv-option-arch-llvm-18-v1-1-390ac9cc3cd0@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

kbuild: Update assembler calls to use proper flags and language target

as-instr uses KBUILD_AFLAGS, but as-option uses KBUILD_CFLAGS. This can
cause as-option to fail unexpectedly when CONFIG_WERROR is set, because
clang will emit -Werror,-Wunused-command-line-argument for various -m
and -f flags in KBUILD_CFLAGS for assembler sources.

Callers of as-option and as-instr should be adding flags to
KBUILD_AFLAGS / aflags-y, not KBUILD_CFLAGS / cflags-y. Use
KBUILD_AFLAGS in all macros to clear up the initial problem.

Unfortunately, -Wunused-command-line-argument can still be triggered
with clang by the presence of warning flags or macro definitions because
'-x assembler' is used, instead of '-x assembler-with-cpp', which will
consume these flags. Switch to '-x assembler-with-cpp' in places where
'-x assembler' is used, as the compiler is always used as the driver for
out of line assembler sources in the kernel.

Finally, add -Werror to these macros so that they behave consistently
whether or not CONFIG_WERROR is set.

[nathan: Reworded and expanded on problems in commit message
Use '-x assembler-with-cpp' in a couple more places]

Link: https://github.com/ClangBuiltLinux/linux/issues/1699
Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Tested-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Kbuild: add Rust support

Having most of the new files in place, we now enable Rust support
in the build system, including `Kconfig` entries related to Rust,
the Rust configuration printer and a few other bits.

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Co-developed-by: Alex Gaynor <alex.gaynor@gmail.com>
Signed-off-by: Alex Gaynor <alex.gaynor@gmail.com>
Co-developed-by: Finn Behrens <me@kloenk.de>
Signed-off-by: Finn Behrens <me@kloenk.de>
Co-developed-by: Adam Bratschi-Kaye <ark.email@gmail.com>
Signed-off-by: Adam Bratschi-Kaye <ark.email@gmail.com>
Co-developed-by: Wedson Almeida Filho <wedsonaf@google.com>
Signed-off-by: Wedson Almeida Filho <wedsonaf@google.com>
Co-developed-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Co-developed-by: Sven Van Asbroeck <thesven73@gmail.com>
Signed-off-by: Sven Van Asbroeck <thesven73@gmail.com>
Co-developed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Gary Guo <gary@garyguo.net>
Co-developed-by: Boris-Chengbiao Zhou <bobo1239@web.de>
Signed-off-by: Boris-Chengbiao Zhou <bobo1239@web.de>
Co-developed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Co-developed-by: Douglas Su <d0u9.su@outlook.com>
Signed-off-by: Douglas Su <d0u9.su@outlook.com>
Co-developed-by: Dariusz Sosnowski <dsosnowski@dsosnowski.pl>
Signed-off-by: Dariusz Sosnowski <dsosnowski@dsosnowski.pl>
Co-developed-by: Antonio Terceiro <antonio.terceiro@linaro.org>
Signed-off-by: Antonio Terceiro <antonio.terceiro@linaro.org>
Co-developed-by: Daniel Xu <dxu@dxuuu.xyz>
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Co-developed-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Signed-off-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Co-developed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Signed-off-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

kbuild: set EXIT trap before creating temporary directory

Swap the order of 'mkdir' and 'trap' just in case the subshell is
interrupted between 'mkdir' and 'trap' although the effect might be
subtle.

This does not intend to make the cleanup perfect. There are more cases
that miss to remove the tmp directory, for example:

- When interrupted, dash does not invoke the EXIT trap (bash does)

- 'rm' command might be interrupted before removing the directory

I am not addressing all the cases since the tmp directory is harmless
after all.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

kconfig: shorten the temporary directory name for cc-option

The cc-option macro creates the temporary directory, .tmp_$$$$.
Shell expands '$$' into its process ID. '$$$$' results in repeated PID.

In Makefile, '$$$$' is correct (see TMPOUT in scripts/Malefile.compiler)
because '$$' is an escape sequence of '$'. Make expands '$$$$' into '$$',
then shell expands it into the process ID.

This does not apply to Kconfig because Kconfig requires variable
references to be enclosed by curly braces, like ${variable}.
The '$' that is not followed by '{' loses its effect.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Nicolas Schier <nicolas@fjasle.eu>

kbuild: check the minimum assembler version in Kconfig

Documentation/process/changes.rst defines the minimum assembler version
(binutils version), but we have never checked it in the build time.

Kbuild never invokes 'as' directly because all assembly files in the
kernel tree are *.S, hence must be preprocessed. I do not expect
raw assembly source files (*.s) would be added to the kernel tree.

Therefore, we always use $(CC) as the assembler driver, and commit
aa824e0c962b ("kbuild: remove AS variable") removed 'AS'. However,
we are still interested in the version of the assembler acting behind.

As usual, the --version option prints the version string.

$ as --version | head -n 1
GNU assembler (GNU Binutils for Ubuntu) 2.35.1

But, we do not have $(AS). So, we can add the -Wa prefix so that
$(CC) passes --version down to the backing assembler.

$ gcc -Wa,--version | head -n 1
gcc: fatal error: no input files
compilation terminated.

OK, we need to input something to satisfy gcc.

$ gcc -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
GNU assembler (GNU Binutils for Ubuntu) 2.35.1

The combination of Clang and GNU assembler works in the same way:

$ clang -no-integrated-as -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
GNU assembler (GNU Binutils for Ubuntu) 2.35.1

Clang with the integrated assembler fails like this:

$ clang -integrated-as -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
clang: error: unsupported argument '--version' to option 'Wa,'

For the last case, checking the error message is fragile. If the
proposal for -Wa,--version support [1] is accepted, this may not be
even an error in the future.

One easy way is to check if -integrated-as is present in the passed
arguments. We did not pass -integrated-as to CLANG_FLAGS before, but
we can make it explicit.

Nathan pointed out -integrated-as is the default for all of the
architectures/targets that the kernel cares about, but it goes
along with "explicit is better than implicit" policy. [2]

With all this in my mind, I implemented scripts/as-version.sh to
check the assembler version in Kconfig time.

$ scripts/as-version.sh gcc
GNU 23501
$ scripts/as-version.sh clang -no-integrated-as
GNU 23501
$ scripts/as-version.sh clang -integrated-as
LLVM 0

[1]: https://github.com/ClangBuiltLinux/linux/issues/1320
[2]: https://lore.kernel.org/linux-kbuild/20210307044253.v3h47ucq6ng25iay@archlinux-ax161/

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>

kbuild: check the minimum linker version in Kconfig

Unify the two scripts/ld-version.sh and scripts/lld-version.sh, and
check the minimum linker version like scripts/cc-version.sh did.

I tested this script for some corner cases reported in the past:

- GNU ld version 2.25-15.fc23
as reported by commit 8083013fc320 ("ld-version: Fix it on Fedora")

- GNU ld (GNU Binutils) 2.20.1.20100303
as reported by commit 0d61ed17dd30 ("ld-version: Drop the 4th and
5th version components")

This script show an error message if the linker is too old:

$ make LD=ld.lld-9
SYNC include/config/auto.conf
***
*** Linker is too old.
*** Your LLD version: 9.0.1
*** Minimum LLD version: 10.0.1
***
scripts/Kconfig.include:50: Sorry, this linker is not supported.
make[2]: *** [scripts/kconfig/Makefile:71: syncconfig] Error 1
make[1]: *** [Makefile:600: syncconfig] Error 2
make: *** [Makefile:708: include/config/auto.conf] Error 2

I also moved the check for gold to this script, so gold is still rejected:

$ make LD=gold
SYNC include/config/auto.conf
gold linker is not supported as it is not capable of linking the kernel proper.
scripts/Kconfig.include:50: Sorry, this linker is not supported.
make[2]: *** [scripts/kconfig/Makefile:71: syncconfig] Error 1
make[1]: *** [Makefile:600: syncconfig] Error 2
make: *** [Makefile:708: include/config/auto.conf] Error 2

Thanks to David Laight for suggesting shell script improvements.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>

kbuild: check the minimum compiler version in Kconfig

Paul Gortmaker reported a regression in the GCC version check. [1]
If you use GCC 4.8, the build breaks before showing the error message
"error Sorry, your version of GCC is too old - please use 4.9 or newer."

I do not want to apply his fix-up since it implies we would not be able
to remove any cc-option test. Anyway, I admit checking the GCC version
in <linux/compiler-gcc.h> is too late.

Almost at the same time, Linus also suggested to move the compiler
version error to Kconfig time. [2]

I unified the two similar scripts, gcc-version.sh and clang-version.sh
into cc-version.sh. The old scripts invoked the compiler multiple times
(3 times for gcc-version.sh, 4 times for clang-version.sh). I refactored
the code so the new one invokes the compiler just once, and also tried
my best to use shell-builtin commands where possible.

The new script runs faster.

$ time ./scripts/clang-version.sh clang
120000

real 0m0.029s
user 0m0.012s
sys 0m0.021s

$ time ./scripts/cc-version.sh clang
Clang 120000

real 0m0.009s
user 0m0.006s
sys 0m0.004s

cc-version.sh also shows an error message if the compiler is too old:

$ make defconfig CC=clang-9
*** Default configuration is based on 'x86_64_defconfig'
***
*** Compiler is too old.
*** Your Clang version: 9.0.1
*** Minimum Clang version: 10.0.1
***
scripts/Kconfig.include:46: Sorry, this compiler is not supported.
make[1]: *** [scripts/kconfig/Makefile:81: defconfig] Error 1
make: *** [Makefile:602: defconfig] Error 2

The new script takes care of ICC because we have <linux/compiler-intel.h>
although I am not sure if building the kernel with ICC is well-supported.

[1]: https://lore.kernel.org/r/20210110190807.134996-1-paul.gortmaker@windriver.com
[2]: https://lore.kernel.org/r/CAHk-=wh-+TMHPTFo1qs-MYyK7tZh-OQovA=pP3=e06aCVp6_kA@mail.gmail.com

Fixes: 87de84c9140e ("kbuild: remove cc-option test of -Werror=date-time")
Reported-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Tested-by: Miguel Ojeda <ojeda@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

kconfig: unify cc-option and as-option

cc-option and as-option are almost the same; both pass the flag to
$(CC). The main difference is the cc-option stops before the assemble
stage (-S option) whereas as-option stops after (-c option).

I chose -S because it is slightly faster, but $(cc-option,-gz=zlib)
returns a wrong result (https://lkml.org/lkml/2020/6/9/1529).
It has been fixed by commit 7b16994437c7 ("Makefile: Improve compressed
debug info support detection"), but the assembler should always be
invoked for more reliable compiler option tests.

However, you cannot simply replace -S with -c because the following
code in lib/Kconfig.debug would break:

depends on $(cc-option,-gsplit-dwarf)

The combination of -c and -gsplit-dwarf does not accept /dev/null as
output.

$ cat /dev/null | gcc -gsplit-dwarf -S -x c - -o /dev/null
$ echo $?
0

$ cat /dev/null | gcc -gsplit-dwarf -c -x c - -o /dev/null
objcopy: Warning: '/dev/null' is not an ordinary file
$ echo $?
1

$ cat /dev/null | gcc -gsplit-dwarf -c -x c - -o tmp.o
$ echo $?
0

There is another flag that creates an separate file based on the
object file path:

$ cat /dev/null | gcc -ftest-coverage -c -x c - -o /dev/null
<stdin>:1: error: cannot open /dev/null.gcno

So, we cannot use /dev/null to sink the output.

Align the cc-option implementation with scripts/Kbuild.include.

With -c option used in cc-option, as-option is unneeded.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Will Deacon <will@kernel.org>

gcc-plugins: drop support for GCC <= 4.7

Nobody was opposed to raising minimum GCC version to 4.8 [1]
So, we will drop GCC <= 4.7 support sooner or later.

We always use C++ compiler for building plugins for GCC >= 4.8.

This commit drops the plugin support for GCC <= 4.7 a bit earlier,
which allows us to dump lots of code.

[1] https://lkml.org/lkml/2020/1/23/545

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>

kconfig: Add support for 'as-option'

Currently kconfig does not have a feature that allows to detect if the
used assembler supports a specific compilation option.

Introduce 'as-option' to serve this purpose in the context of Kconfig:

config X
def_bool $(as-option,...)

Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Acked-by: Masahiro Yamada <masahiroy@kernel.org>
Cc: linux-kbuild@vger.kernel.org
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

kconfig: introduce m32-flag and m64-flag

When a compiler supports multiple architectures, some compiler features
can be dependent on the target architecture.

This is typical for Clang, which supports multiple LLVM backends.
Even for GCC, we need to take care of biarch compiler cases.

It is not a problem when we evaluate cc-option in Makefiles because
cc-option is tested against the flag in question + $(KBUILD_CFLAGS).

The cc-option in Kconfig, on the other hand, does not accumulate
tested flags. Due to this simplification, it could potentially test
cc-option against a different target.

At first, Kconfig always evaluated cc-option against the host
architecture.

Since commit e8de12fb7cde ("kbuild: Check for unknown options with
cc-option usage in Kconfig and clang"), in case of cross-compiling
with Clang, the target triple is correctly passed to Kconfig.

The case with biarch GCC (and native build with Clang) is still not
handled properly. We need to pass some flags to specify the target
machine bit.

Due to the design, all the macros in Kconfig are expanded in the
parse stage, where we do not know the target bit size yet.

For example, arch/x86/Kconfig allows a user to toggle CONFIG_64BIT.
If a compiler flag -foo depends on the machine bit, it must be tested
twice, one with -m32 and the other with -m64.

However, -m32/-m64 are not always recognized. So, this commits adds
m64-flag and m32-flag macros. They expand to -m32, -m64, respectively
if supported. Or, they expand to an empty string if unsupported.

The typical usage is like this:

config FOO
bool
default $(cc-option,$(m64-flag) -foo) if 64BIT
default $(cc-option,$(m32-flag) -foo)

This is clumsy, but there is no elegant way to handle this in the
current static macro expansion.

There was discussion for static functions vs dynamic functions.
The consensus was to go as far as possible with the static functions.
(https://lkml.org/lkml/2018/3/2/22)

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: George Spelvin <lkml@sdf.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>

kbuild: use -S instead of -E for precise cc-option test in Kconfig

Currently, -E (stop after the preprocessing stage) is used to check
whether the given compiler flag is supported.

While it is faster than -S (or -c), it can be false-positive. You need
to run the compilation proper to check the flag more precisely.

For example, -E and -S disagree about the support of
"--param asan-instrument-allocas=1".

$ gcc -Werror --param asan-instrument-allocas=1 -E -x c /dev/null -o /dev/null
$ echo $?
0

$ gcc -Werror --param asan-instrument-allocas=1 -S -x c /dev/null -o /dev/null
cc1: error: invalid --param name ‘asan-instrument-allocas’; did you mean ‘asan-instrument-writes’?
$ echo $?
1

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

kbuild: Add support for 'as-instr' to be used in Kconfig files

Similar to 'cc-option' or 'ld-option', it is occasionally necessary to
check whether the assembler supports certain ISA extensions. In the
arm64 code we currently do this in Makefile with an additional define:

lseinstr := $(call as-instr,.arch_extension lse,-DCONFIG_AS_LSE=1)

Add the 'as-instr' option so that it can be used in Kconfig directly:

def_bool $(as-instr,.arch_extension lse)

Acked-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

kbuild: Fail if gold linker is detected

The gold linker has known issues of failing the build both in random and in
predictible ways:

- The x86/X32 VDSO build fails with:

arch/x86/entry/vdso/vclock_gettime-x32.o:vclock_gettime.c:function do_hres:
error: relocation overflow: reference to 'hvclock_page'

That's a known issue for years and the usual workaround is to disable
CONFIG_X86_32

- A recent build failure is caused by turning a relocation into an
absolute one for unknown reasons. See link below.

- There are a couple of gold workarounds applied already, but reports
about broken builds with ld.gold keep coming in on a regular base and in
most cases the root cause is unclear.

In context of the most recent fail H.J. stated:

"Since building a workable kernel for different kernel configurations
isn't a requirement for gold, I don't recommend gold for kernel."

So instead of dealing with attempts to duct tape gold support without
understanding the root cause and without support from the gold folks, fail
the build when gold is detected.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/CAMe9rOqMqkQ0LNpm25yE_Yt0FKp05WmHOrwc0aRDb53miFKM+w@mail.gmail.com
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

kbuild: Check for unknown options with cc-option usage in Kconfig and clang

If the particular version of clang a user has doesn't enable
-Werror=unknown-warning-option by default, even though it is the
default[1], then make sure to pass the option to the Kconfig cc-option
command so that testing options from Kconfig files works properly.
Otherwise, depending on the default values setup in the clang toolchain
we will silently assume options such as -Wmaybe-uninitialized are
supported by clang, when they really aren't.

A compilation issue only started happening for me once commit
589834b3a009 ("kbuild: Add -Werror=unknown-warning-option to
CLANG_FLAGS") was applied on top of commit b303c6df80c9 ("kbuild:
compute false-positive -Wmaybe-uninitialized cases in Kconfig"). This
leads kbuild to try and test for the existence of the
-Wmaybe-uninitialized flag with the cc-option command in
scripts/Kconfig.include, and it doesn't see an error returned from the
option test so it sets the config value to Y. Then the Makefile tries to
pass the unknown option on the command line and
-Werror=unknown-warning-option catches the invalid option and breaks the
build. Before commit 589834b3a009 ("kbuild: Add
-Werror=unknown-warning-option to CLANG_FLAGS") the build works fine,
but any cc-option test of a warning option in Kconfig files silently
evaluates to true, even if the warning option flag isn't supported on
clang.

Note: This doesn't change cc-option usages in Makefiles because those
use a different rule that includes KBUILD_CFLAGS by default (see the
__cc-option command in scripts/Kbuild.incluide). The KBUILD_CFLAGS
variable already has the -Werror=unknown-warning-option flag set. Thanks
to Doug for pointing out the different rule.

[1] https://clang.llvm.org/docs/DiagnosticsReference.html#wunknown-warning-option
Cc: Peter Smith <peter.smith@linaro.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

treewide: Add SPDX license identifier - Makefile/Kconfig

Add SPDX license identifiers to all Make/Kconfig files which:

- Have no license information of any form

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

GPL-2.0-only

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

kbuild: terminate Kconfig when $(CC) or $(LD) is missing

If the compiler specified by $(CC) is not present, the Kconfig stage
sprinkles 'not found' messages, then succeeds.

$ make CROSS_COMPILE=foo defconfig
/bin/sh: 1: foogcc: not found
/bin/sh: 1: foogcc: not found
*** Default configuration is based on 'x86_64_defconfig'
./scripts/gcc-version.sh: 17: ./scripts/gcc-version.sh: foogcc: not found
./scripts/gcc-version.sh: 18: ./scripts/gcc-version.sh: foogcc: not found
./scripts/gcc-version.sh: 19: ./scripts/gcc-version.sh: foogcc: not found
./scripts/gcc-version.sh: 17: ./scripts/gcc-version.sh: foogcc: not found
./scripts/gcc-version.sh: 18: ./scripts/gcc-version.sh: foogcc: not found
./scripts/gcc-version.sh: 19: ./scripts/gcc-version.sh: foogcc: not found
./scripts/clang-version.sh: 11: ./scripts/clang-version.sh: foogcc: not found
./scripts/gcc-plugin.sh: 11: ./scripts/gcc-plugin.sh: foogcc: not found
init/Kconfig:16:warning: 'GCC_VERSION': number is invalid
#
# configuration written to .config
#

Terminate parsing files immediately if $(CC) or $(LD) is not found.
"make *config" will fail more nicely.

$ make CROSS_COMPILE=foo defconfig
*** Default configuration is based on 'x86_64_defconfig'
scripts/Kconfig.include:34: compiler 'foogcc' not found
make[1]: *** [scripts/kconfig/Makefile;82: defconfig] Error 1
make: *** [Makefile;557: defconfig] Error 2

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

kbuild: clean up scripts/gcc-version.sh

Now that the Kconfig is the only user of this script, we can drop
unneeded code.

Remove the -p option, and stop prepending the output with zero,
so that Kconfig can directly use the output from this script.

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

gcc-plugins: test plugin support in Kconfig and clean up Makefile

Run scripts/gcc-plugin.sh from Kconfig so that users can enable
GCC_PLUGINS only when the compiler supports building plugins.

Kconfig defines a new symbol, PLUGIN_HOSTCC. This will contain
the compiler (g++ or gcc) used for building plugins, or empty
if the plugin can not be supported at all.

This allows us to remove all ugly testing in Makefile.gcc-plugins.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Kees Cook <keescook@chromium.org>

kconfig: add basic helper macros to scripts/Kconfig.include

Kconfig got text processing tools like we see in Make. Add Kconfig
helper macros to scripts/Kconfig.include like we collect Makefile
macros in scripts/Kbuild.include.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Ulf Magnusson <ulfalizer@gmail.com>