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Message-Id: <1182447884.2704.7.camel@laptopd505.fenrus.org> Date: Thu, 21 Jun 2007 10:44:44 -0700 From: Arjan van de Ven <arjan@...radead.org> To: Albert Cahalan <acahalan@...il.com> Cc: linux-kernel <linux-kernel@...r.kernel.org> Subject: Re: JIT emulator needs 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... - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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