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 e8de12fb7c ("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>
- detect missing include guard in UAPI headers
- do not create orphan built-in.a or obj-y objects
- generate modules.builtin more simply, and drop tristate.conf
- simplify built-in initramfs creation
- make linux-headers deb package thinner
- optimize the deb package build script
- misc cleanups
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Merge tag 'kbuild-v5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull Kbuild updates from Masahiro Yamada:
- detect missing include guard in UAPI headers
- do not create orphan built-in.a or obj-y objects
- generate modules.builtin more simply, and drop tristate.conf
- simplify built-in initramfs creation
- make linux-headers deb package thinner
- optimize the deb package build script
- misc cleanups
* tag 'kbuild-v5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (34 commits)
builddeb: split libc headers deployment out into a function
builddeb: split kernel headers deployment out into a function
builddeb: remove redundant make for ARCH=um
builddeb: avoid invoking sub-shells where possible
builddeb: remove redundant $objtree/
builddeb: match temporary directory name to the package name
builddeb: remove unneeded files in hdrobjfiles for headers package
kbuild: use -S instead of -E for precise cc-option test in Kconfig
builddeb: allow selection of .deb compressor
kbuild: remove 'Building modules, stage 2.' log
kbuild: remove *.tmp file when filechk fails
kbuild: remove PYTHON2 variable
modpost: assume STT_SPARC_REGISTER is defined
gen_initramfs.sh: remove intermediate cpio_list on errors
initramfs: refactor the initramfs build rules
gen_initramfs.sh: always output cpio even without -o option
initramfs: add default_cpio_list, and delete -d option support
initramfs: generate dependency list and cpio at the same time
initramfs: specify $(src)/gen_initramfs.sh as a prerequisite in Makefile
initramfs: make initramfs compression choice non-optional
...
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>
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>
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>
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
589834b3a0 ("kbuild: Add -Werror=unknown-warning-option to
CLANG_FLAGS") was applied on top of commit b303c6df80 ("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 589834b3a0 ("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>
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>
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>
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>
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 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>
