linux-kernel - Re: [PATCH 3/3] powerpc: enable support for GCC plugins

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Message-ID: <CAGXu5jKQf4ReBkGC85+r_j1rVUFTZoeWk9A_mjhjnFHq1PAr8Q@mail.gmail.com>
Date:   Tue, 6 Dec 2016 12:40:50 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Andrew Donnellan <andrew.donnellan@....ibm.com>
Cc:     "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        Emese Revfy <re.emese@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-kbuild <linux-kbuild@...r.kernel.org>,
        PaX Team <pageexec@...email.hu>,
        Brad Spengler <spender@...ecurity.net>,
        Michal Marek <mmarek@...e.com>
Subject: Re: [PATCH 3/3] powerpc: enable support for GCC plugins

On Mon, Dec 5, 2016 at 10:28 PM, Andrew Donnellan
<andrew.donnellan@....ibm.com> wrote:
> Enable support for GCC plugins on powerpc.
>
> Add an additional version check in gcc-plugins-check to advise users to
> upgrade to gcc 5.2+ on powerpc to avoid issues with header files (gcc <=
> 4.6) or missing copies of rs6000-cpus.def (4.8 to 5.1 on 64-bit targets).
>
> Signed-off-by: Andrew Donnellan <andrew.donnellan@....ibm.com>
>
> ---
>
> Open to bikeshedding on the gcc version check.

I think this looks fine. Anyone wanting to use gcc plugins on ppc with
an earlier gcc can send patches if they find a sane way to make it
work. :)

> Compile tested with all plugins enabled on gcc 4.6-6.2,
> x86->ppc{32,64,64le} and 4.8-6.2 ppc64le->ppc{32,64,64le}. Thanks to
> Chris Smart for help with this.

I assume also tested on 5.2? :)

> I think it's best to take this through powerpc#next with an ACK from
> Kees/Emese?

That would be fine by me. Please consider the whole series:

Acked-by: Kees Cook <keescook@...omium.org>

Thanks!

-Kees

> ---
>  arch/powerpc/Kconfig         | 1 +
>  scripts/Makefile.gcc-plugins | 8 ++++++++
>  2 files changed, 9 insertions(+)
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 65fba4c..6efbc08 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -92,6 +92,7 @@ config PPC
>         select HAVE_DYNAMIC_FTRACE_WITH_REGS if MPROFILE_KERNEL
>         select HAVE_FUNCTION_TRACER
>         select HAVE_FUNCTION_GRAPH_TRACER
> +       select HAVE_GCC_PLUGINS
>         select SYSCTL_EXCEPTION_TRACE
>         select VIRT_TO_BUS if !PPC64
>         select HAVE_IDE
> diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
> index 26c67b7..9835a75 100644
> --- a/scripts/Makefile.gcc-plugins
> +++ b/scripts/Makefile.gcc-plugins
> @@ -47,6 +47,14 @@ 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
> +        endif
> +      endif
>        ifeq ($(call cc-ifversion, -ge, 0405, y), y)
>         $(Q)$(srctree)/scripts/gcc-plugin.sh --show-error "$(__PLUGINCC)" "$(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
> --
> Andrew Donnellan              OzLabs, ADL Canberra
> andrew.donnellan@....ibm.com  IBM Australia Limited
>



-- 
Kees Cook
Nexus Security