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From: Roland McGrath <roland@redhat.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Oleg Nesterov <oleg@redhat.com>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       linux-kernel@vger.kernel.org
Subject: Re: x86: get rid of the insane TIF_ABI_PENDING bit
In-Reply-To: H. Peter Anvin's message of  Monday, 15 February 2010 11:10:55 -0800 <4B799C3F.7010308@zytor.com>
References: <20100215161752.GA19962@redhat.com>
	<4B799C3F.7010308@zytor.com>
Message-Id: <20100215194123.96D49FC3@magilla.sf.frob.com>
Date: Mon, 15 Feb 2010 11:41:23 -0800 (PST)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 965
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> I suspect the purpose of TS_COMPAT is actually so you can ptrace() the
> newly exec'd process (and see it as a 32-bit process!) before it returns
> to userspace.  The comment, obviously, is wrong -- that again refers to
> TIF_IA32.

I don't follow you.  TS_COMPAT does not affect ptrace.
It affects syscall-audit, but only at syscall entry time.
It affects asm/syscall.h accessors, but ptrace does not use those.
It affects whatever uses is_compat_task(), but I can't see anything
where that matters except inside some particular syscall or for
syscall restart after signals.

TS_COMPAT does not affect the syscall return machinery itself.
The return path just follows from the particular entry path.


Thanks,
Roland
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