From: Arjan van de Ven <arjan@infradead.org>
To: Albert Cahalan <acahalan@gmail.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: JIT emulator needs
Date: Fri, 22 Jun 2007 06:43:41 -0700 [thread overview]
Message-ID: <1182519821.2672.1.camel@laptopd505.fenrus.org> (raw)
In-Reply-To: <787b0d920706212256u7e78ba6n15ef41bcea99aff0@mail.gmail.com>
On Fri, 2007-06-22 at 01:56 -0400, Albert Cahalan wrote:
> On 6/21/07, Arjan van de Ven <arjan@infradead.org> wrote:
> > On Fri, 2007-06-08 at 02:35 -0400, Albert Cahalan wrote:
> > > Right now, Linux isn't all that friendly to JIT emulators.
> > > Here are the problems and suggestions to improve the situation.
> > >
> > > There is an SE Linux execmem restriction that enforces W^X.
> > > Assuming you don't wish to just disable SE Linux, there are
> > > two ugly ways around the problem. You can mmap a file twice,
> > > or you can abuse SysV shared memory. The mmap method requires
> > > that you know of a filesystem mounted rw,exec where you can
> > > write a very large temporary file. This arbitrary filesystem,
> > > rather than swap space, will be the backing store. The SysV
> > > shared memory method requires an undocumented flag and is
> > > subject to some annoying size limits. Both methods create
> > > objects that will fail to be deleted if the program dies
> > > before marking the objects for deletion.
> >
> > and these methods also destroy yourself on any machine with a looser
> > cache coherency between I and D-cache....
> >
> > for all but x86 you pretty much have to do the mprotect() between the
> > two states to deal with the cache flushing properly...
>
> If the instructions to force data write-back and/or to
> invalidate the instruction cache are priveleged, yes.
> AFAIK, only ARM is that lame.
and your program executes this on all the cpus in the system?
--
if you want to mail me at work (you don't), use arjan (at) linux.intel.com
Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org
next prev parent reply other threads:[~2007-06-22 13:47 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-06-08 6:35 JIT emulator needs Albert Cahalan
2007-06-08 7:09 ` Eric Dumazet
2007-06-09 4:12 ` Albert Cahalan
2007-06-08 11:10 ` Alan Cox
2007-06-08 16:35 ` Nicholas Miell
2007-06-09 5:17 ` Albert Cahalan
2007-06-09 20:00 ` H. Peter Anvin
2007-06-19 15:08 ` William Lee Irwin III
2007-06-20 3:16 ` Albert Cahalan
2007-06-20 16:01 ` William Lee Irwin III
2007-06-20 16:37 ` H. Peter Anvin
2007-06-20 17:54 ` William Lee Irwin III
2007-06-20 18:23 ` H. Peter Anvin
2007-06-20 18:25 ` Albert Cahalan
2007-06-20 18:51 ` H. Peter Anvin
2007-06-21 3:21 ` Albert Cahalan
2007-06-21 3:32 ` H. Peter Anvin
2007-06-21 7:38 ` Albert Cahalan
2007-06-20 18:43 ` Albert Cahalan
2007-06-23 3:52 ` Kyle Moffett
2007-06-24 4:14 ` William Lee Irwin III
2007-06-21 17:44 ` Arjan van de Ven
2007-06-22 5:56 ` Albert Cahalan
2007-06-22 13:43 ` Arjan van de Ven [this message]
2007-06-22 14:32 ` Albert Cahalan
2007-06-22 14:42 ` Arjan van de Ven
2007-06-23 2:30 ` Albert Cahalan
[not found] <8tGiE-2Hv-1@gated-at.bofh.it>
[not found] ` <8xNvm-2Tw-29@gated-at.bofh.it>
[not found] ` <8xYTM-3So-13@gated-at.bofh.it>
2007-06-21 11:08 ` Bodo Eggert
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