kernel-hardening - Re: [PATCH v4 03/17] arm64: kvm: stop treating register x18 as caller save

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Message-ID: <79e8f958cbde52a3d90aec24dd4638d9@www.loen.fr>
Date: Mon, 04 Nov 2019 12:13:00 +0109
From: Marc Zyngier <maz@...nel.org>
To: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Will Deacon <will@...nel.org>, Catalin Marinas
 <catalin.marinas@....com>, Steven Rostedt <rostedt@...dmis.org>, Masami
 Hiramatsu <mhiramat@...nel.org>, Ard Biesheuvel <ard.biesheuvel@...aro.org>,
 Dave Martin <dave.martin@....com>, Kees Cook <keescook@...omium.org>, Laura
 Abbott <labbott@...hat.com>, Mark Rutland <mark.rutland@....com>, Nick
 Desaulniers <ndesaulniers@...gle.com>, Jann Horn <jannh@...gle.com>, Miguel
 Ojeda <miguel.ojeda.sandonis@...il.com>, Masahiro Yamada
 <yamada.masahiro@...ionext.com>, <clang-built-linux@...glegroups.com>,
 <kernel-hardening@...ts.openwall.com>,
 <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 03/17] arm64: kvm: stop treating register x18 as  caller save

Hi Sami,

On 2019-11-01 23:20, Sami Tolvanen wrote:
> From: Ard Biesheuvel <ard.biesheuvel@...aro.org>
>
> In preparation of reserving x18, stop treating it as caller save in
> the KVM guest entry/exit code. Currently, the code assumes there is
> no need to preserve it for the host, given that it would have been
> assumed clobbered anyway by the function call to __guest_enter().
> Instead, preserve its value and restore it upon return.
>
> Link: https://patchwork.kernel.org/patch/9836891/
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> [Sami: updated commit message, switched from x18 to x29 for the guest
> context]
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> Reviewed-by: Kees Cook <keescook@...omium.org>

If you intend for this to be merged via the arm64 tree, please add my

Reviewed-by: Marc Zyngier <marc.zyngier@....com>

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...

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