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

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Date:   Mon, 13 Aug 2018 13:18:22 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Stefan Agner <stefan@...er.ch>,
        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

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.


-Kees

-- 
Kees Cook
Pixel Security