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Date: Thu, 12 Apr 2018 00:55:05 +0900
From: Masahiro Yamada <yamada.masahiro@...ionext.com>
To: Kees Cook <keescook@...omium.org>
Cc: linux-kbuild <linux-kbuild@...r.kernel.org>,
Sam Ravnborg <sam@...nborg.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Arnd Bergmann <arnd@...db.de>, Ulf Magnusson <ulfalizer@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Randy Dunlap <rdunlap@...radead.org>,
"Luis R . Rodriguez" <mcgrof@...nel.org>,
Nicolas Pitre <nico@...aro.org>, LKML <linux-kernel@...r.kernel.org>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>,
Emese Revfy <re.emese@...il.com>
Subject: Re: [PATCH v2 19/21] gcc-plugins: test GCC plugin support in Kconfig
2018-03-28 20:44 GMT+09:00 Kees Cook <keescook@...omium.org>:
> On Mon, Mar 26, 2018 at 10:29 PM, Masahiro Yamada
> <yamada.masahiro@...ionext.com> wrote:
>> Run scripts/gcc-plugin.sh from Kconfig. Users can enable GCC_PLUGINS
>> only when it is supported.
>>
>> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
>> ---
>>
>> Changes in v2: None
>>
>> arch/Kconfig | 4 +++
>> scripts/Makefile.gcc-plugins | 82 ++++++++++++++++----------------------------
>> scripts/gcc-plugin.sh | 1 -
>> 3 files changed, 33 insertions(+), 54 deletions(-)
>>
>> diff --git a/arch/Kconfig b/arch/Kconfig
>> index b42378d..88cc925 100644
>> --- a/arch/Kconfig
>> +++ b/arch/Kconfig
>> @@ -407,9 +407,13 @@ config HAVE_GCC_PLUGINS
>> An arch should select this symbol if it supports building with
>> GCC plugins.
>>
>> +config CC_HAS_GCC_PLUGINS
>> + bool
>> +
>
> This doesn't seem used anywhere?
>
>> menuconfig GCC_PLUGINS
>> bool "GCC plugins"
>> depends on HAVE_GCC_PLUGINS
>> + depends on $(success $srctree/scripts/gcc-plugin.sh $HOSTCXX $CC)
>> depends on !COMPILE_TEST
>> help
>> GCC plugins are loadable modules that provide extra features to the
>> diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
>> index 25da4c0..19d0d5b 100644
>> --- a/scripts/Makefile.gcc-plugins
>> +++ b/scripts/Makefile.gcc-plugins
>> [...]
>> -# If plugins aren't supported, abort the build before hard-to-read compiler
>> -# errors start getting spewed by the main build.
>> -PHONY += gcc-plugins-check
>> -gcc-plugins-check: FORCE
>> -ifdef CONFIG_GCC_PLUGINS
>> - ifeq ($(PLUGINCC),)
>> - ifneq ($(GCC_PLUGINS_CFLAGS),)
>> - $(Q)$(srctree)/scripts/gcc-plugin.sh --show-error $(HOSTCXX) $(CC) || true
>> - @echo "Cannot use CONFIG_GCC_PLUGINS: your gcc installation does not support plugins, perhaps the necessary headers are missing?" >&2 && exit 1
>
> As mentioned in the other email, we lose the error reporting. Now the
> lack of plugins is just a silent =n in menuconfig.
This is the right thing to do.
Features unsupported by the compiler should be silently disable.
> Keeping
> --show-error in the Kconfig call and retaining stderr would be nice.
No.
There is no problem to use a compiler without plugin support.
If a user does not want to use plugin in the first place,
why does he/she need to be bothered by such information in stderr?
> I need to do some further testing with SANCOV, but otherwise this all
> looks correct, and my testing shows it behaving correctly.
>
> -Kees
>
> --
> Kees Cook
> Pixel Security
> --
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--
Best Regards
Masahiro Yamada
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