lkml.org 
[lkml]   [2007]   [Jun]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: JIT emulator needs
    From
    Date
    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@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2007-06-21 19:51    [from the cache]
    ©2003-2014 Jasper Spaans. hosted at Digital Ocean