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

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Message-Id: <20100215194123.96D49FC3@magilla.sf.frob.com>
Date:	Mon, 15 Feb 2010 11:41:23 -0800 (PST)
From:	Roland McGrath <roland@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: x86: get rid of the insane TIF_ABI_PENDING bit

> 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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