Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Mon, 2 Mar 2020 20:58:00 -0800
From:   Kees Cook <keescook@chromium.org>
To:     Thomas Garnier <thgarnie@chromium.org>
Cc:     kernel-hardening@lists.openwall.com, kristen@linux.intel.com,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        Andy Lutomirski <luto@kernel.org>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Len Brown <len.brown@intel.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v11 06/11] x86/CPU: Adapt assembly for PIE support
Message-ID: <202003022057.D84B66E042@keescook>
References: <20200228000105.165012-1-thgarnie@chromium.org>
 <20200228000105.165012-7-thgarnie@chromium.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200228000105.165012-7-thgarnie@chromium.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Feb 27, 2020 at 04:00:51PM -0800, Thomas Garnier wrote:
> Change the assembly code to use only relative references of symbols for the
> kernel to be PIE compatible.
> 
> Signed-off-by: Thomas Garnier <thgarnie@chromium.org>

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

-Kees

> ---
>  arch/x86/include/asm/processor.h | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index 09705ccc393c..fdf6366c482d 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -746,11 +746,13 @@ static inline void sync_core(void)
>  		"pushfq\n\t"
>  		"mov %%cs, %0\n\t"
>  		"pushq %q0\n\t"
> -		"pushq $1f\n\t"
> +		"leaq 1f(%%rip), %q0\n\t"
> +		"pushq %q0\n\t"
>  		"iretq\n\t"
>  		UNWIND_HINT_RESTORE
>  		"1:"
> -		: "=&r" (tmp), ASM_CALL_CONSTRAINT : : "cc", "memory");
> +		: "=&r" (tmp), ASM_CALL_CONSTRAINT
> +		: : "cc", "memory");
>  #endif
>  }
>  
> -- 
> 2.25.1.481.gfbce0eb801-goog
> 

-- 
Kees Cook