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Date:   Tue, 18 Feb 2020 16:58:25 -0800
From:   Kees Cook <keescook@chromium.org>
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>,
        Mark Rutland <mark.rutland@arm.com>, james.morse@arm.com,
        Dave Martin <Dave.Martin@arm.com>,
        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 v8 09/12] arm64: disable SCS for hypervisor code
Message-ID: <202002181658.41FA7C514E@keescook>
References: <20191018161033.261971-1-samitolvanen@google.com>
 <20200219000817.195049-1-samitolvanen@google.com>
 <20200219000817.195049-10-samitolvanen@google.com>
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On Tue, Feb 18, 2020 at 04:08:14PM -0800, Sami Tolvanen wrote:
> Disable SCS for code that runs at a different exception level by
> adding __noscs to __hyp_text.
> 
> Suggested-by: James Morse <james.morse@arm.com>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> ---
>  arch/arm64/include/asm/kvm_hyp.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
> index a3a6a2ba9a63..0f0603f55ea0 100644
> --- a/arch/arm64/include/asm/kvm_hyp.h
> +++ b/arch/arm64/include/asm/kvm_hyp.h
> @@ -13,7 +13,7 @@
>  #include <asm/kvm_mmu.h>
>  #include <asm/sysreg.h>
>  
> -#define __hyp_text __section(.hyp.text) notrace
> +#define __hyp_text __section(.hyp.text) notrace __noscs
>  
>  #define read_sysreg_elx(r,nvh,vh)					\
>  	({								\
> -- 
> 2.25.0.265.gbab2e86ba0-goog
> 

-- 
Kees Cook