On Sat, Aug 30, 2003 at 09:59:01PM +0100, Pedro F. Giffuni wrote: > --- Tim Kientzle <[EMAIL PROTECTED]> wrote: >... >> >> The OpenBSD work on tightening up read/write/exec memory permissions >> looks interesting, but I wonder what impact it has on >> JIT technologies; do the current Java VMs or other incremental >> compilation engines require write+exec? > >I haven't ever seen the source code for Java but I wouldn't think there is any >problem. Bytecode is not really executable, and the java program doesn't need >to modify itself either.
JIT is on-the-fly compilation to native code. Whilst the Java bytecode is not natively executable, a JIT JVM needs to be able to write and immediately execute native code. The OpenBSD W^X approach would require system calls between the compilation and execution steps. My understanding of current JIT is that the compilation is done is very small pieces and adding the overhead of a pair of system calls would basically kill it. >The OpenBSD people reported only Emacs got broken due to things they shouldn't >do, and they found a workaround anyways. Does OpenBSD support any JIT JVM? > If perl didn't break, I think Java will survive too. Emacs and perl both use traditional bytecode interpreters, as does the Classic JVM. I agree they will be unaffected. This change will only impact JIT JVMs. Peter _______________________________________________ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"
