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Date:   Mon, 4 Nov 2019 11:39:30 +0000
From:   Mark Rutland <mark.rutland@arm.com>
To:     Sami Tolvanen <samitolvanen@google.com>
Cc:     Will Deacon <will@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        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 v4 04/17] arm64: kernel: avoid x18 __cpu_soft_restart
Message-ID: <20191104113929.GA45140@lakrids.cambridge.arm.com>
References: <20191018161033.261971-1-samitolvanen@google.com>
 <20191101221150.116536-1-samitolvanen@google.com>
 <20191101221150.116536-5-samitolvanen@google.com>
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On Fri, Nov 01, 2019 at 03:11:37PM -0700, Sami Tolvanen wrote:
> From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> 
> The code in __cpu_soft_restart() uses x18 as an arbitrary temp register,
> which will shortly be disallowed. So use x8 instead.
> 
> Link: https://patchwork.kernel.org/patch/9836877/
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> [Sami: updated commit message]
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> Reviewed-by: Mark Rutland <mark.rutland@arm.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>

Trivial nit, but the commit title is missing "in" between x18 and
__cpu_soft_restart.

Mark.

> ---
>  arch/arm64/kernel/cpu-reset.S | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kernel/cpu-reset.S b/arch/arm64/kernel/cpu-reset.S
> index 6ea337d464c4..32c7bf858dd9 100644
> --- a/arch/arm64/kernel/cpu-reset.S
> +++ b/arch/arm64/kernel/cpu-reset.S
> @@ -42,11 +42,11 @@ ENTRY(__cpu_soft_restart)
>  	mov	x0, #HVC_SOFT_RESTART
>  	hvc	#0				// no return
>  
> -1:	mov	x18, x1				// entry
> +1:	mov	x8, x1				// entry
>  	mov	x0, x2				// arg0
>  	mov	x1, x3				// arg1
>  	mov	x2, x4				// arg2
> -	br	x18
> +	br	x8
>  ENDPROC(__cpu_soft_restart)
>  
>  .popsection
> -- 
> 2.24.0.rc1.363.gb1bccd3e3d-goog
>