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Date: Mon, 2 Mar 2020 20:58:00 -0800
From: Kees Cook <keescook@...omium.org>
To: Thomas Garnier <thgarnie@...omium.org>
Cc: kernel-hardening@...ts.openwall.com, kristen@...ux.intel.com,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
Andy Lutomirski <luto@...nel.org>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
Len Brown <len.brown@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v11 06/11] x86/CPU: Adapt assembly for PIE support
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@...omium.org>
Reviewed-by: Kees Cook <keescook@...omium.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
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