linux-kernel - Re: [BUG FIX] Make x86_32 uni-processor Atomic ops, Atomic

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Message-ID: <4A1C2320.1030704@zytor.com>
Date:	Tue, 26 May 2009 10:13:04 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	lkml@...ethan.org
CC:	Harald Welte <HaraldWelte@...tech.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [BUG FIX] Make x86_32 uni-processor Atomic ops, Atomic

Michael S. Zick wrote:
> 
> Disassembly of section .text:
> 
> 00000000 <diff_umask>:
>    0:   8b 44 24 0c             mov    0xc(%esp),%eax
>    4:   8b 4c 24 04             mov    0x4(%esp),%ecx
>    8:   8b 10                   mov    (%eax),%edx
>    a:   8d 04 11                lea    (%ecx,%edx,1),%eax
>    d:   8b 54 24 08             mov    0x8(%esp),%edx
>   11:   2b 02                   sub    (%edx),%eax
>   13:   21 c8                   and    %ecx,%eax
>   15:   c3                      ret
> 
> = = = =
> 
> Checking the byte string 0x8d, 0x04, 0x11 against the Intel
> documentation shows that the disassembly output of objdump
> is incorrect - that bit string does not have an offset field.
> That is the byte encoding for the gcc assembly input.
> 
> What's a person to do when the tool-chain lies?
> 

The ,1 isn't an offset field... it's a scale factor.

	-hpa

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