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

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Message-ID: <20080428154240.GD7334@c2.user-mode-linux.org>
Date:	Mon, 28 Apr 2008 11:42:40 -0400
From:	Jeff Dike <jdike@...toit.com>
To:	WANG Cong <xiyou.wangcong@...il.com>
Cc:	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 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.

    	      	      Jeff

-- 
Work email - jdike at linux dot intel dot com
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