Re: [PATCH v7 08/12] x86/acpi: Adapt assembly for PIE support

From: Kees Cook <keescook@chromium.org>
To: Thomas Garnier <thgarnie@chromium.org>
Cc: kernel-hardening@lists.openwall.com, kristen@linux.intel.com,
	Thomas Garnier <thgarnie@google.com>, Pavel Machek <pavel@ucw.cz>,
	"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Len Brown <len.brown@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, linux-pm@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v7 08/12] x86/acpi: Adapt assembly for PIE support
Date: Mon, 10 Jun 2019 16:52:02 -0700	[thread overview]
Message-ID: <201906101652.CA88F8F@keescook> (raw)
In-Reply-To: <20190520231948.49693-9-thgarnie@chromium.org>

On Mon, May 20, 2019 at 04:19:33PM -0700, Thomas Garnier wrote:
> From: Thomas Garnier <thgarnie@google.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@google.com>

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

-Kees

> Acked-by: Pavel Machek <pavel@ucw.cz>
> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
>  arch/x86/kernel/acpi/wakeup_64.S | 31 ++++++++++++++++---------------
>  1 file changed, 16 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S
> index 510fa12aab73..e080e943e295 100644
> --- a/arch/x86/kernel/acpi/wakeup_64.S
> +++ b/arch/x86/kernel/acpi/wakeup_64.S
> @@ -14,7 +14,7 @@
>  	 * Hooray, we are in Long 64-bit mode (but still running in low memory)
>  	 */
>  ENTRY(wakeup_long64)
> -	movq	saved_magic, %rax
> +	movq	saved_magic(%rip), %rax
>  	movq	$0x123456789abcdef0, %rdx
>  	cmpq	%rdx, %rax
>  	jne	bogus_64_magic
> @@ -25,14 +25,14 @@ ENTRY(wakeup_long64)
>  	movw	%ax, %es
>  	movw	%ax, %fs
>  	movw	%ax, %gs
> -	movq	saved_rsp, %rsp
> +	movq	saved_rsp(%rip), %rsp
>  
> -	movq	saved_rbx, %rbx
> -	movq	saved_rdi, %rdi
> -	movq	saved_rsi, %rsi
> -	movq	saved_rbp, %rbp
> +	movq	saved_rbx(%rip), %rbx
> +	movq	saved_rdi(%rip), %rdi
> +	movq	saved_rsi(%rip), %rsi
> +	movq	saved_rbp(%rip), %rbp
>  
> -	movq	saved_rip, %rax
> +	movq	saved_rip(%rip), %rax
>  	jmp	*%rax
>  ENDPROC(wakeup_long64)
>  
> @@ -45,7 +45,7 @@ ENTRY(do_suspend_lowlevel)
>  	xorl	%eax, %eax
>  	call	save_processor_state
>  
> -	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)
> @@ -64,13 +64,14 @@ ENTRY(do_suspend_lowlevel)
>  	pushfq
>  	popq	pt_regs_flags(%rax)
>  
> -	movq	$.Lresume_point, saved_rip(%rip)
> +	leaq	.Lresume_point(%rip), %rax
> +	movq	%rax, saved_rip(%rip)
>  
> -	movq	%rsp, saved_rsp
> -	movq	%rbp, saved_rbp
> -	movq	%rbx, saved_rbx
> -	movq	%rdi, saved_rdi
> -	movq	%rsi, saved_rsi
> +	movq	%rsp, saved_rsp(%rip)
> +	movq	%rbp, saved_rbp(%rip)
> +	movq	%rbx, saved_rbx(%rip)
> +	movq	%rdi, saved_rdi(%rip)
> +	movq	%rsi, saved_rsi(%rip)
>  
>  	addq	$8, %rsp
>  	movl	$3, %edi
> @@ -82,7 +83,7 @@ ENTRY(do_suspend_lowlevel)
>  	.align 4
>  .Lresume_point:
>  	/* We don't restore %rax, it must be 0 anyway */
> -	movq	$saved_context, %rax
> +	leaq	saved_context(%rip), %rax
>  	movq	saved_context_cr4(%rax), %rbx
>  	movq	%rbx, %cr4
>  	movq	saved_context_cr3(%rax), %rbx
> -- 
> 2.21.0.1020.gf2820cf01a-goog
> 

-- 
Kees Cook