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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Mon, 11 Oct 2021 10:23:57 -0700
Message-ID: <CAKwvOd=D=UvGfHjEyeYPk3c=ksg9mF8nUX-9jyJhkX8QbugMSQ@mail.gmail.com>
Subject: Re: [PATCH] [PATCH V2]ARM64: SCS: Add gcc plugin to support Shadow
 Call Stack
To:     Dan Li <ashimida@linux.alibaba.com>
Cc:     Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Michal Marek <michal.lkml@markovi.net>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Sami Tolvanen <samitolvanen@google.com>, frederic@kernel.org,
        Mike Rapoport <rppt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>, yifeifz2@illinois.edu,
        Steven Rostedt <rostedt@goodmis.org>,
        Viresh Kumar <viresh.kumar@linaro.org>, andreyknvl@gmail.com,
        Colin King <colin.king@canonical.com>,
        Miguel Ojeda <ojeda@kernel.org>,
        Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
        Marco Elver <elver@google.com>,
        Arvind Sankar <nivedita@alum.mit.edu>,
        Ard Biesheuvel <ardb@kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        linux-hardening@vger.kernel.org,
        clang-built-linux <clang-built-linux@googlegroups.com>
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On Mon, Oct 11, 2021 at 8:42 AM Dan Li <ashimida@linux.alibaba.com> wrote:
>
>
>
> On 10/10/21 11:43 PM, Miguel Ojeda wrote:
> > On Sun, Oct 10, 2021 at 5:16 PM Dan Li <ashimida@linux.alibaba.com> wrote:
> >>
> >> -         This option enables Clang's Shadow Call Stack, which uses a
> >> -         shadow stack to protect function return addresses from being
> >> -         overwritten by an attacker. More information can be found in
> >> -         Clang's documentation:
> >> +         This option enables Clang/GCC plugin's Shadow Call Stack, which
> >> +         uses a shadow stack to protect function return addresses from
> >> +         being overwritten by an attacker. More information can be found
> >> +         in Clang's documentation:
> >
> > Perhaps it could be worded in a better way? It sounds like it is a
> > custom plugin for Clang as well, e.g.:
> >
> >      This option enables Shadow Call Stack (in the case of GCC, as a plugin),
> >
> > Cheers,
> > Miguel
> >
>
> Thanks Miguel.
>
> How about writing like this:
> This option enables Shadow Call Stack (supported as a compiler option in
> the case of clang, supported as a plugin in the case of gcc), which uses
> a shadow stack to ...

That sounds reasonable.

One question I have Dan, what is your sense for getting this feature
landed upstream in GCC proper?  It's neat to be able to use plugins to
support older versions of a compiler than when the feature initially
lands; I was curious if you're working to submit this into GCC as
well?  I didn't see anything in GCC's bug tracker for "shadow call
stack," but maybe there's a different feature bug tracking this?
-- 
Thanks,
~Nick Desaulniers