linux-kernel - Re: [PATCH -tip] x86: acpi/sleep.c saved

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Date:	Fri, 10 Apr 2009 21:13:34 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	Pavel Machek <pavel@....cz>
Cc:	Jaswinder Singh Rajput <jaswinder@...nel.org>,
	Ingo Molnar <mingo@...e.hu>, x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -tip] x86: acpi/sleep.c saved_magic fix overflow

On Fri, Apr 10, 2009 at 07:55:45PM +0200, Pavel Machek wrote:
> On Fri 2009-04-10 23:06:55, Jaswinder Singh Rajput wrote:
> > Impact: fix overflow
> 
> > Constant 0x123456789abcdef0 is so big for a long.
> > So using saved_magic 0x12345678 for both 32 and 64 bit.
> 
> Have you tested the patch? I have feeling that this is tested from
> assembly... Plus it is only set to long constant on 64-bit, so I don't
> think you are fixing anything. And if your code is correct the
> variable is write only...

$ git grep saved_magic
kernel/acpi/sleep.c:    saved_magic = 0x12345678;
kernel/acpi/sleep.c:    saved_magic = 0x123456789abcdef0;
kernel/acpi/sleep.h:extern long saved_magic;
kernel/acpi/wakeup_32.S:        movl    %cs:saved_magic, %eax
kernel/acpi/wakeup_32.S:ENTRY(saved_magic)      .long   0
kernel/acpi/wakeup_64.S:        movq    saved_magic, %rax
kernel/acpi/wakeup_64.S:ENTRY(saved_magic)      .quad   0


wakeup_32.S:
        movl    %cs:saved_magic, %eax
        cmpl    $0x12345678, %eax

wakeup_64.S:
        movq    saved_magic, %rax
        movq    $0x123456789abcdef0, %rdx

So patch is obviously bogus.

	Sam
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