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Date:   Thu, 16 Jan 2020 17:37:40 +0000
From:   Will Deacon <will@kernel.org>
To:     Sami Tolvanen <samitolvanen@google.com>
Cc:     Catalin Marinas <catalin.marinas@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Dave Martin <Dave.Martin@arm.com>,
        Kees Cook <keescook@chromium.org>,
        Laura Abbott <labbott@redhat.com>,
        Marc Zyngier <maz@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Jann Horn <jannh@google.com>,
        Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        clang-built-linux@googlegroups.com,
        kernel-hardening@lists.openwall.com,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 09/15] arm64: reserve x18 from general allocation with
 SCS
Message-ID: <20200116173739.GA21396@willie-the-truck>
References: <20191018161033.261971-1-samitolvanen@google.com>
 <20191206221351.38241-1-samitolvanen@google.com>
 <20191206221351.38241-10-samitolvanen@google.com>
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On Fri, Dec 06, 2019 at 02:13:45PM -0800, Sami Tolvanen wrote:
> Reserve the x18 register from general allocation when SCS is enabled,
> because the compiler uses the register to store the current task's
> shadow stack pointer. Note that all external kernel modules must also be
> compiled with -ffixed-x18 if the kernel has SCS enabled.
> 
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> ---
>  arch/arm64/Makefile | 4 ++++
>  1 file changed, 4 insertions(+)

Acked-by: Will Deacon <will@kernel.org>

Will