linux-kernel - Re: [PATCH v7 10/12] x86/power/64: Adapt assembly for PIE support

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Message-ID: <201906101652.94483CD@keescook>
Date:   Mon, 10 Jun 2019 16:52:32 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Thomas Garnier <thgarnie@...omium.org>
Cc:     kernel-hardening@...ts.openwall.com, kristen@...ux.intel.com,
        Thomas Garnier <thgarnie@...gle.com>,
        Pavel Machek <pavel@....cz>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 10/12] x86/power/64: Adapt assembly for PIE support

On Mon, May 20, 2019 at 04:19:35PM -0700, Thomas Garnier wrote:
> From: Thomas Garnier <thgarnie@...gle.com>
> 
> Change the assembly code to use only relative references of symbols for the
> kernel to be PIE compatible.
> 
> Position Independent Executable (PIE) support will allow to extend the
> KASLR randomization range below 0xffffffff80000000.
> 
> Signed-off-by: Thomas Garnier <thgarnie@...gle.com>

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

-Kees

> Acked-by: Pavel Machek <pavel@....cz>
> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  arch/x86/power/hibernate_asm_64.S | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/power/hibernate_asm_64.S b/arch/x86/power/hibernate_asm_64.S
> index 3008baa2fa95..9ed980efef72 100644
> --- a/arch/x86/power/hibernate_asm_64.S
> +++ b/arch/x86/power/hibernate_asm_64.S
> @@ -24,7 +24,7 @@
>  #include <asm/frame.h>
>  
>  ENTRY(swsusp_arch_suspend)
> -	movq	$saved_context, %rax
> +	leaq	saved_context(%rip), %rax
>  	movq	%rsp, pt_regs_sp(%rax)
>  	movq	%rbp, pt_regs_bp(%rax)
>  	movq	%rsi, pt_regs_si(%rax)
> @@ -115,7 +115,7 @@ ENTRY(restore_registers)
>  	movq	%rax, %cr4;  # turn PGE back on
>  
>  	/* We don't restore %rax, it must be 0 anyway */
> -	movq	$saved_context, %rax
> +	leaq	saved_context(%rip), %rax
>  	movq	pt_regs_sp(%rax), %rsp
>  	movq	pt_regs_bp(%rax), %rbp
>  	movq	pt_regs_si(%rax), %rsi
> -- 
> 2.21.0.1020.gf2820cf01a-goog
> 

-- 
Kees Cook