linux-kernel - Re: x86: get rid of the insane TIF_ABI

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Date:	Mon, 15 Feb 2010 10:06:39 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Oleg Nesterov <oleg@...hat.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: x86: get rid of the insane TIF_ABI_PENDING bit

On 02/15/2010 08:50 AM, Oleg Nesterov wrote:
> 
> Could you please point me where do we check TS_COMPAT during return
> to user-mode?
> 

Sorry, I was thinking about TIF_IA32, which is examined on line 415 of
entry_64.S.

>>> If a 64bit task execs a 32bit app, can't this TS_COMPAT break, say,
>>> syscall_get_arguments() ?
>>
>> At that point (this is after the exec!) we don't get arguments anyway.
> 
> I meant /proc/pid/syscall, but even if I am right this probably
> doesn't matter.

What does getting the arguments from a process which has never done a
system call yet even mean?  Presumably we get some kind of "null answer"
which depends on the default register set; in that case the compat null
answer is the correct one.

	-hpa

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

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