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

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Date:	Tue, 16 Feb 2010 10:43:33 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Oleg Nesterov <oleg@...hat.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] x86: set_personality_ia32() abuses TS_COMPAT

On Tue, 16 Feb 2010, Oleg Nesterov wrote:
> 
> and, following this logic, shouldn't set_personality_64bit() clear
> TS_COMPAT ?

Yes, I think it should. If we come from a 32-bit environment, and execute 
a 64-bit binary, I think the execve() environment of the new 64-bit binary 
should be _exactly_ the same as if it was executed from a 64-bit one.

Of course, it's entirely possible that TS_COMPAT simply doesn't matter at 
all in either context, but I do think that we should strive for "the 
binary does exactly the same regardless of whether it was started from 
a 32-bit or a 64-bit binary".

And the best way to guarantee that is to make sure that we really do set 
the environment to the same thing. So yes, set_personality_64bit() should 
clear all the 32-bit compat bits.

		Linus
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