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From:   Kees Cook <keescook@chromium.org>
Date:   Wed, 28 Mar 2018 04:30:59 -0700
Message-ID: <CAGXu5jJrd2w5ys6tfwH6zd6dpep65XuV3wCZs=hUi=p5nbjDHw@mail.gmail.com>
Subject: Re: [PATCH v2 18/21] gcc-plugins: move GCC version check for PowerPC
 to Kconfig
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>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>,
        Emese Revfy <re.emese@gmail.com>
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Sender: linux-kernel-owner@vger.kernel.org
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On Mon, Mar 26, 2018 at 10:29 PM, Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
> For PowerPC, GCC 5.2 is the requirement for GCC plugins.  Move the
> version check to Kconfig so that the GCC plugin menus will be hidden
> if an older compiler is in use.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> Acked-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
> ---
>
> Changes in v2: None
>
>  arch/powerpc/Kconfig         | 2 +-
>  scripts/Makefile.gcc-plugins | 8 --------
>  2 files changed, 1 insertion(+), 9 deletions(-)
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 73ce5dd..b8474c2 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -195,7 +195,7 @@ config PPC
>         select HAVE_FTRACE_MCOUNT_RECORD
>         select HAVE_FUNCTION_GRAPH_TRACER
>         select HAVE_FUNCTION_TRACER
> -       select HAVE_GCC_PLUGINS
> +       select HAVE_GCC_PLUGINS                 if GCC_VERSION >= 50200
>         select HAVE_GENERIC_GUP
>         select HAVE_HW_BREAKPOINT               if PERF_EVENTS && (PPC_BOOK3S || PPC_8xx)
>         select HAVE_IDE
> diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
> index b0f9108..25da4c0 100644
> --- a/scripts/Makefile.gcc-plugins
> +++ b/scripts/Makefile.gcc-plugins
> @@ -56,14 +56,6 @@ gcc-plugins-check: FORCE
>  ifdef CONFIG_GCC_PLUGINS
>    ifeq ($(PLUGINCC),)
>      ifneq ($(GCC_PLUGINS_CFLAGS),)
> -      # Various gccs between 4.5 and 5.1 have bugs on powerpc due to missing
> -      # header files. gcc <= 4.6 doesn't work at all, gccs from 4.8 to 5.1 have
> -      # issues with 64-bit targets.
> -      ifeq ($(ARCH),powerpc)
> -        ifeq ($(call cc-ifversion, -le, 0501, y), y)
> -         @echo "Cannot use CONFIG_GCC_PLUGINS: plugin support on gcc <= 5.1 is buggy on powerpc, please upgrade to gcc 5.2 or newer" >&2 && exit 1

I think we should retain the "buggy" note as a comment in Kconfig
since that knowledge isn't obvious just from the GCC_VERSION test.

> -        endif
> -      endif
>        $(Q)$(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
>      endif
> --
> 2.7.4
>

-Kees

-- 
Kees Cook
Pixel Security