linux-kernel - Re: [PATCH 2/3] x86: set_personality_ia32() abuses TS

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Message-ID: <4B7ADB07.1050500@zytor.com>
Date:	Tue, 16 Feb 2010 09:51:03 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Oleg Nesterov <oleg@...hat.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] x86: set_personality_ia32() abuses TS_COMPAT

On 02/16/2010 09:44 AM, Oleg Nesterov wrote:
> On 02/16, Linus Torvalds wrote:
>>
>> And after we have switched to 32-bit mode, we _are_ inside a 32-bit system
>> call: the execve has "changed" from a 64-bit one to a 32-bit one.
>>
>> So I really don't understand why you dislike TS_COMPAT here.
> 
> and, following this logic, shouldn't set_personality_64bit() clear
> TS_COMPAT ?
> 

It's quite possible it should... I haven't dug into if that isn't either
done elsewhere or isn't done for some other reason.  This would be worth
looking into.

> OK, in any case I do not claim we need fixes. Just I am confused.

Trying to understand the code is good.  However, you seem to have
started out with a point of view that we should have the minimal set of
state changes possible instead of keeping state as self-consistent as
possible.  Invariants are a Very Good Thing.  Documented invariants are
even better ;)

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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