linux-kernel - Re: [PATCH 9/19] UML - Tidy ptrace interface

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Message-ID: <alpine.LFD.1.00.0804291613570.2548@localhost.localdomain>
Date:	Tue, 29 Apr 2008 16:14:25 +0800 (CST)
From:	WANG Cong <xiyou.wangcong@...il.com>
To:	Jeff Dike <jdike@...toit.com>
cc:	WANG Cong <xiyou.wangcong@...il.com>, akpm@...l.org,
	linux-kernel@...r.kernel.org,
	user-mode-linux-devel@...ts.sourceforge.net
Subject: Re: [PATCH 9/19] UML - Tidy ptrace interface

On Mon, 28 Apr 2008, Jeff Dike wrote:

> On Sat, Apr 26, 2008 at 05:35:38PM +0800, WANG Cong wrote:
>> From: Jeff Dike <jdike@...toit.com>
>> Date: Fri, 25 Apr 2008 13:56:10 -0400
>> > Tidy the ptrace interface code.  Removed a bunch of unused macros.
>> > Started converting register sets from arrays of longs to structures.
>> 
>> Could you please explain a bit why do this? I think long arrary is OK.
>
> It's wrong on x86_64.  There, FRAME_SIZE is 168 -
>     #define FRAME_SIZE 
> and SS is the last register defined -
>    #define SS 160
> but there are a number of registers beyond that in the user_regs_struct:
> 	unsigned long	ss;
> 	unsigned long	fs_base;
> 	unsigned long	gs_base;
> 	unsigned long	ds;
> 	unsigned long	es;
> 	unsigned long	fs;
> 	unsigned long	gs;
>
> The effect of GETREGS into a long[FRAME_SIZE] will be stack corruption.
>

Thanks for teaching this. ;-)

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