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

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Date:	Mon, 15 Feb 2010 19:52:06 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.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, H. Peter Anvin wrote:
>
> 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.

Yes, I understand we should set TIF_IA32, but my question was about
TS_COMPAT.

Oh. And ELF_PLAT_INIT() clears TIF_IA32... at this point it should
be already cleared by SET_PERSONALITY() ?

OK. If this is all really needed, please ignore me, I don't really
understand these details anyway.

> >> 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.

Indeed, not sure what I was thinking about, thanks.

Oleg.

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