linux-kernel - Re: [PATCH] gcc-plugins: require GCC

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Date:   Tue, 14 Aug 2018 11:28:25 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Stefan Agner <stefan@...er.ch>
Cc:     Kees Cook <keescook@...omium.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Josef Bacik <jbacik@...com>, Emese Revfy <re.emese@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gcc-plugins: require GCC

2018-08-14 6:29 GMT+09:00 Stefan Agner <stefan@...er.ch>:
> On 13.08.2018 22:18, Kees Cook wrote:
>> On Mon, Aug 13, 2018 at 1:10 PM, Kees Cook <keescook@...omium.org> wrote:
>>> On Mon, Aug 13, 2018 at 12:38 AM, Masahiro Yamada
>>> <yamada.masahiro@...ionext.com> wrote:
>>>> 2018-08-11 18:48 GMT+09:00 Stefan Agner <stefan@...er.ch>:
>>>>> Unsurprisingly GCC plugins require GCC as a compiler. This avoids
>>>>> GCC plugins being selectable when using clang.
>>>>>
>>>>> Signed-off-by: Stefan Agner <stefan@...er.ch>
>>>>> ---
>>>>>  arch/Kconfig | 2 +-
>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/arch/Kconfig b/arch/Kconfig
>>>>> index 1aa59063f1fd..8c693a837ed7 100644
>>>>> --- a/arch/Kconfig
>>>>> +++ b/arch/Kconfig
>>>>> @@ -422,7 +422,7 @@ config HAVE_GCC_PLUGINS
>>>>>
>>>>>  menuconfig GCC_PLUGINS
>>>>>         bool "GCC plugins"
>>>>> -       depends on HAVE_GCC_PLUGINS
>>>>> +       depends on HAVE_GCC_PLUGINS && CC_IS_GCC
>>>>>         depends on PLUGIN_HOSTCC != ""
>>>>>         help
>>>>>           GCC plugins are loadable modules that provide extra features to the
>>>>> --
>>>>> 2.18.0
>>>>>
>>>>
>>>> I guess the more correct way is to fix
>>>> scripts/gcc-plugin.sh
>>>>
>>>> This shell script should exit 0
>>>> only when GCC plugin is supported.
>>>
>>> I'm of two minds: we already have the gcc test in Kconfig so we might
>>> want to avoid redundant checks, but maybe the script should be a
>>> "complete" test. I guess the latter. I will send a patch.
>>
>> Actually, how about we do the test in Kconfig, but ahead of the
>> script? That will reduce redundancy:
>>
>> diff --git a/arch/Kconfig b/arch/Kconfig
>> index 1aa59063f1fd..18f518624e41 100644
>> --- a/arch/Kconfig
>> +++ b/arch/Kconfig
>> @@ -409,7 +409,7 @@ preferred-plugin-hostcc := $(if-success,[
>> $(gcc-version) -ge 40800 ],$(HOSTCXX),
>>
>>  config PLUGIN_HOSTCC
>>         string
>> -       default "$(shell,$(srctree)/scripts/gcc-plugin.sh
>> "$(preferred-plugin-hostcc)" "$(HOSTCXX)" "$(CC)")"
>> +       default "$(shell,$(srctree)/scripts/gcc-plugin.sh
>> "$(preferred-plugin-hostcc)" "$(HOSTCXX)" "$(CC)")" if CC_IS_GCC
>>         help
>>           Host compiler used to build GCC plugins.  This can be $(HOSTCXX),
>>           $(HOSTCC), or a null string if GCC plugin is unsupported.
>
> I like this better. A script which is called gcc-plugin.sh should only
> be called if gcc is used...
>

This does not work like that.

$(shell,$(srctree)/scripts/gcc-plugin.sh "$(preferred-plugin-hostcc)"
"$(HOSTCXX)" "$(CC)")

is expanded in the parse stage regardless of CC_IS_GCC.




If nobody comes up with a better way, I am fine with this.

Reviewed-by: Masahiro Yamada <yamada.masahiro@...ionext.com>




> --
> Stefan
>
>>
>>
>> -Kees



-- 
Best Regards
Masahiro Yamada