Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757254AbXFVNrs (ORCPT ); Fri, 22 Jun 2007 09:47:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753871AbXFVNrl (ORCPT ); Fri, 22 Jun 2007 09:47:41 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:45421 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752218AbXFVNrk (ORCPT ); Fri, 22 Jun 2007 09:47:40 -0400 Subject: Re: JIT emulator needs From: Arjan van de Ven To: Albert Cahalan Cc: linux-kernel In-Reply-To: <787b0d920706212256u7e78ba6n15ef41bcea99aff0@mail.gmail.com> References: <787b0d920706072335v10d6025cwe1437194b6c60d84@mail.gmail.com> <1182447884.2704.7.camel@laptopd505.fenrus.org> <787b0d920706212256u7e78ba6n15ef41bcea99aff0@mail.gmail.com> Content-Type: text/plain Organization: Intel International BV Date: Fri, 22 Jun 2007 06:43:41 -0700 Message-Id: <1182519821.2672.1.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.10.2 (2.10.2-2.fc7) Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1905 Lines: 39 On Fri, 2007-06-22 at 01:56 -0400, Albert Cahalan wrote: > On 6/21/07, Arjan van de Ven 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 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/