Re: [PATCH v2 12/21] kconfig: show compiler version text in the top comment

From: Kees Cook <keescook@chromium.org>
To: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: linux-kbuild <linux-kbuild@vger.kernel.org>,
	Sam Ravnborg <sam@ravnborg.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Arnd Bergmann <arnd@arndb.de>,
	Ulf Magnusson <ulfalizer@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	"Luis R . Rodriguez" <mcgrof@kernel.org>,
	Nicolas Pitre <nico@linaro.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 12/21] kconfig: show compiler version text in the top comment
Date: Tue, 27 Mar 2018 20:26:11 -0700	[thread overview]
Message-ID: <CAGXu5j+runDn9cZ8SCMYQzWr3twBvQPt=sRP+UNJfjxv19a4Yw@mail.gmail.com> (raw)
In-Reply-To: <1522128575-5326-13-git-send-email-yamada.masahiro@socionext.com>

On Mon, Mar 26, 2018 at 10:29 PM, Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
> The kernel configuration phase is now tightly coupled with the compiler
> in use.  It will be nice to show the compiler information in Kconfig.
>
> The compiler information will be displayed like this:
>
>   $ make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- config
>   scripts/kconfig/conf  --oldaskconfig Kconfig
>   *
>   * Linux/arm64 4.16.0-rc1 Kernel Configuration
>   *
>   *
>   * Compiler: aarch64-linux-gnu-gcc (Linaro GCC 7.2-2017.11) 7.2.1 20171011
>   *
>   *
>   * General setup
>   *
>   Compile also drivers which will not load (COMPILE_TEST) [N/y/?]
>
> If you use GUI methods such as menuconfig, it will be displayed in the
> top menu.
>
> This is simply implemented by using 'comment'.  So, it will be saved
> into the .config file as well.
>
> This commit has a very important meaning.  If the compiler is upgraded,
> Kconfig must be re-run since different compilers have different sets
> of supported options.
>
> All referenced environments are written to include/config/auto.conf.cmd
> so that any environment change triggers syncconfig, and prompt the user
> to input new values if needed.
>
> With this commit, something like follows will be added to
> include/config/auto.conf.cmd
>
>   ifneq "$(CC_VERSION_TEXT)" "aarch64-linux-gnu-gcc (Linaro GCC 7.2-2017.11) 7.2.1 20171011"
>   include/config/auto.conf: FORCE
>   endif
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

I like seeing this in the config. Good idea!

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> ---
>
> Changes in v2: None
>
>  Kconfig  | 2 ++
>  Makefile | 2 ++
>  2 files changed, 4 insertions(+)
>
> diff --git a/Kconfig b/Kconfig
> index e6ece5b..99ed4b8 100644
> --- a/Kconfig
> +++ b/Kconfig
> @@ -5,4 +5,6 @@
>  #
>  mainmenu "Linux/$ARCH $KERNELVERSION Kernel Configuration"
>
> +comment "Compiler: $CC_VERSION_TEXT"
> +
>  source "arch/$SRCARCH/Kconfig"
> diff --git a/Makefile b/Makefile
> index 5cadffa..3dc9eb8 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -450,6 +450,8 @@ export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE
>  export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL
>  export KBUILD_ARFLAGS
>
> +export CC_VERSION_TEXT := $(shell $(CC) --version | head -n 1)
> +
>  # When compiling out-of-tree modules, put MODVERDIR in the module
>  # tree rather than in the kernel tree. The kernel tree might
>  # even be read-only.
> --
> 2.7.4
>

-- 
Kees Cook
Pixel Security