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Date:   Mon, 13 Aug 2018 23:29:26 +0200
From:   Stefan Agner <stefan@agner.ch>
To:     Kees Cook <keescook@chromium.org>
Cc:     Masahiro Yamada <yamada.masahiro@socionext.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Josef Bacik <jbacik@fb.com>, Emese Revfy <re.emese@gmail.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] gcc-plugins: require GCC
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On 13.08.2018 22:18, Kees Cook wrote:
> On Mon, Aug 13, 2018 at 1:10 PM, Kees Cook <keescook@chromium.org> wrote:
>> On Mon, Aug 13, 2018 at 12:38 AM, Masahiro Yamada
>> <yamada.masahiro@socionext.com> wrote:
>>> 2018-08-11 18:48 GMT+09:00 Stefan Agner <stefan@agner.ch>:
>>>> Unsurprisingly GCC plugins require GCC as a compiler. This avoids
>>>> GCC plugins being selectable when using clang.
>>>>
>>>> Signed-off-by: Stefan Agner <stefan@agner.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...

--
Stefan

> 
> 
> -Kees