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