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

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Message-ID: <20110822011939.GN2203@ZenIV.linux.org.uk>
Date:	Mon, 22 Aug 2011 02:19:39 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andrew Lutomirski <luto@....edu>, "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 06:09:00PM -0700, Linus Torvalds wrote:
> On Sun, Aug 21, 2011 at 5:44 PM, Andrew Lutomirski <luto@....edu> wrote:
> >
> > Which suggests an easy-ish fix: if sysenter is used or if syscall is
> > entered from the EIP is is supposed to be entered from, then just
> > change ip in the argument save to point to the int 0x80 instruction.
> 
> Indeed. Just add an "int 0x80" instruction to the vsyscall thing, and
> you'd be done.
> 
> In fact, just replace the
> 
>   jmp .Lenter_kernel
> 
> with
> 
>   int 0x80
> 
> and you'd be pretty much all done, no?

In case of sysenter - almost, in case of syscall - nope...
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