linux-kernel - Re: SYSCALL, ptrace and syscall restart breakages (Re: [RFC] weird crap with vdso on uml/i386)

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Message-ID: <20110821145126.GK2203@ZenIV.linux.org.uk>
Date:	Sun, 21 Aug 2011 15:51:26 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Andrew Lutomirski <luto@....edu>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>, mingo@...hat.com,
	Richard Weinberger <richard@....at>,
	user-mode-linux-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: Re: SYSCALL, ptrace and syscall restart breakages (Re: [RFC] weird
 crap with vdso on uml/i386)

On Sun, Aug 21, 2011 at 09:37:18AM -0400, Andrew Lutomirski wrote:

> Gack.  Is this a holdover from the 32-bit code that shares the
> argument save area with the parameters passed on the C stack?  If so,
> we could just set up the argument save area honestly and pass the real
> parameters in registers like 64-bit C code expects.
> 
> If the tracing and restart cases use iret to return to userspace, this
> should all just work.  ptrace users shouldn't notice the overhead, and
> syscall restart is presumably slow enough anyway that it wouldn't
> matter.  The userspace entry code would be as simple as:
> 
> sysenter
> ret
> 
> or
> 
> sysexit
> ret

You are making no sense at all...
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