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From: Pavel Machek <pavel@ucw.cz>
To: Andy Lutomirski <luto@MIT.EDU>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
	Andi Kleen <andi@firstfloor.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	torvalds@linux-foundation.org, lueckintel@yahoo.com,
	kimwooyoung@gmail.com, Suresh Siddha <suresh.b.siddha@intel.com>
Subject: Re: [RFC v2] x86-64: Allow emulated vsyscalls from user addresses
Date: Thu, 11 Aug 2011 15:16:10 +0200	[thread overview]
Message-ID: <20110811131610.GA21916@ucw.cz> (raw)
In-Reply-To: <44eea096d708c5c3273e41ced354073ebd62a1d6.1312599769.git.luto@mit.edu>

Hi!

> They trace control flow through the vsyscall page and recompile that
> code somewhere else.  Then they expect it to work.  DynamoRIO
> (http://dynamorio.org/) and Pin (http://www.pintool.org/) are
> affected.  They crash when tracing programs that use vsyscalls.
> Valgrind is smart enough not to cause problems.  It crashes on the
> getcpu vsyscall, but that has nothing to do with emulation.
> 
> This patch makes each of the three vsyscall entries use a different
> vector so that they can work when relocated.  It assumes that the
> code that relocates them is okay with the int instruction acting
> like ret.  DynamoRIO at least appears to work.

int acting as ret is seriously weird semantics. And no, invalid
syscall parameters will not cause segfault, just return of -EFAULT. So
... can this be changed?

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

  parent reply	other threads:[~2011-08-11 13:16 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-08-05 20:09 New vsyscall emulation breaks JITs Andi Kleen
2011-08-05 20:23 ` H. Peter Anvin
2011-08-05 20:26   ` Andi Kleen
2011-08-05 20:36     ` H. Peter Anvin
2011-08-05 20:47       ` Andi Kleen
2011-08-05 20:45   ` Andrew Lutomirski
2011-08-05 20:48     ` H. Peter Anvin
2011-08-05 20:52       ` Andi Kleen
2011-08-05 21:00         ` Andrew Lutomirski
2011-08-05 21:21           ` Andi Kleen
2011-08-05 21:26             ` Andrew Lutomirski
2011-08-05 22:06               ` H. Peter Anvin
2011-08-05 22:11                 ` Andrew Lutomirski
2011-08-06  0:20                   ` Andrew Lutomirski
2011-08-06  0:32                     ` H. Peter Anvin
2011-08-06  3:01                       ` [RFC] x86-64: Allow emulated vsyscalls from user addresses Andy Lutomirski
2011-08-06  3:04                       ` [RFC v2] " Andy Lutomirski
2011-08-06  6:45                         ` Ingo Molnar
2011-08-07 12:19                           ` Borislav Petkov
2011-08-07 12:58                             ` Andrew Lutomirski
2011-08-07 15:44                               ` Borislav Petkov
2011-08-07 16:14                                 ` Andrew Lutomirski
2011-08-11 13:16                         ` Pavel Machek [this message]
2011-08-11 13:27                           ` Andrew Lutomirski
2011-08-09 22:27                       ` New vsyscall emulation breaks JITs Suresh Siddha
2011-08-09 13:26             ` Andrew Lutomirski
2011-08-09 15:04               ` Andi Kleen
2011-08-09 15:22                 ` Andrew Lutomirski
2011-08-09 16:47                   ` [RFC] x86-64: Add vsyscall=emulate|native|none option Andy Lutomirski
2011-08-09 19:54                     ` Linus Torvalds
2011-08-09 16:57                   ` New vsyscall emulation breaks JITs H. Peter Anvin
2011-08-09 17:05                     ` Andrew Lutomirski
     [not found]                       ` <1312919938.17118.YahooMailNeo@web120010.mail.ne1.yahoo.com>
2011-08-09 20:59                         ` H. Peter Anvin
2011-08-09 21:04                         ` Andrew Lutomirski
2011-08-09 22:36                           ` Linus Torvalds
2011-08-10  0:56                             ` H. Peter Anvin
     [not found]                             ` <1312934493.45753.YahooMailNeo@web120015.mail.ne1.yahoo.com>
2011-08-10  1:49                               ` H. Peter Anvin

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