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From: Roland McGrath <roland@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Chuck Ebbert <cebbert@redhat.com>,
       Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org,
       Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
       "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH x86/mm 6/6] x86-64 ia32 ptrace get/putreg32 current
 task
In-Reply-To: Linus Torvalds's message of  Thursday, 29 November 2007 10:09:00 -0800 <alpine.LFD.0.9999.0711290958110.8458@woody.linux-foundation.org>
References: <20071129003849.428E026F8E7@magilla.localdomain>
	<20071129004222.E49AD26F8E7@magilla.localdomain>
	<474EF824.3020806@redhat.com>
	<alpine.LFD.0.9999.0711290958110.8458@woody.linux-foundation.org>
Message-Id: <20071129222531.EFEA826F8E7@magilla.localdomain>
Date: Thu, 29 Nov 2007 14:25:31 -0800 (PST)
Sender: linux-kernel-owner@vger.kernel.org
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> But the ones that do the same thing for fs/es/ds are *not*. Those three 
> registers are kernel mode registers (ds/es are the regular kernel data 
> segment, fs is the per-cpu data segment), and restored on return to user 
> space from the stack.

Um, really?  This is x86-64 code.  AIUI those values don't have any effect
at all in 64-bit mode (as the kernel is).  I haven't found any code in
entry_64.S or ia32entry.S that touches them.  __switch_to uses direct
access to the segment registers just as I've done.


Thanks,
Roland
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