linux-kernel - Re: [PATCH 2/3] x86, acpi: On S3 failure, just fall through

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Date:	Mon, 15 Jun 2015 12:35:25 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Denys Vlasenko <dvlasenk@...hat.com>
Cc:	Ingo Molnar <mingo@...nel.org>, Pavel Machek <pavel@....cz>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...capital.net>,
	Oleg Nesterov <oleg@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] x86, acpi: On S3 failure, just fall through

On Sun, Jun 14, 2015 at 03:23:09PM +0200, Denys Vlasenko wrote:
> Th "jmp" deleted by this patch in fact compiles to "jmp to next insn",
> since ".p2align 4,,7" happens to not do any alignment -
> aligning to 2^4 would require more than 7 bytes of padding:
> 
> 000000b0 <do_suspend_lowlevel>:
>   b0:   e8 fc ff ff ff          call   <save_processor_state>
>   b5:   e8 8d ff ff ff          call   47 <save_registers>
>   ba:   6a 03                   push   $0x3
>   bc:   e8 fc ff ff ff          call   <x86_acpi_enter_sleep_state>
>   c1:   83 c4 04                add    $0x4,%esp
>   c4:   eb 00                   jmp    c6 <ret_point>   <============ THIS
> 000000c6 <ret_point>:
>   c6:   e8 c4 ff ff ff          call   8f <restore_registers>
> 
> Run-tested.
> 
> Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
> CC: Pavel Machek <pavel@....cz>
> CC: Linus Torvalds <torvalds@...ux-foundation.org>
> CC: Steven Rostedt <rostedt@...dmis.org>
> CC: Ingo Molnar <mingo@...nel.org>
> CC: Borislav Petkov <bp@...en8.de>
> CC: "H. Peter Anvin" <hpa@...or.com>
> CC: Andy Lutomirski <luto@...capital.net>
> CC: Oleg Nesterov <oleg@...hat.com>
> CC: Frederic Weisbecker <fweisbec@...il.com>
> CC: Alexei Starovoitov <ast@...mgrid.com>
> CC: Will Drewry <wad@...omium.org>
> CC: Kees Cook <keescook@...omium.org>
> CC: x86@...nel.org
> CC: linux-kernel@...r.kernel.org
> ---
>  arch/x86/kernel/acpi/wakeup_32.S | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/acpi/wakeup_32.S b/arch/x86/kernel/acpi/wakeup_32.S
> index eef2bd3..5fec9b0 100644
> --- a/arch/x86/kernel/acpi/wakeup_32.S
> +++ b/arch/x86/kernel/acpi/wakeup_32.S
> @@ -68,11 +68,8 @@ ENTRY(do_suspend_lowlevel)
>  	pushl	$3
>  	call	x86_acpi_enter_sleep_state
>  	addl	$4, %esp
> +# If S3 fails, we simply fall through to S3 wakeup code:
>  
> -#	In case of S3 failure, we'll emerge here.  Jump
> -# 	to ret_point to recover
> -	jmp	ret_point
> -	.p2align 4,,7
>  ret_point:
>  	call	restore_registers
>  	call	restore_processor_state

Reviewed-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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