On 25/07/2013 15:25, Ludwig Nussel wrote: > Dominic Fandrey wrote: >> On 23/07/2013 01:36, Tim Angus wrote: >>> On Mon, 22 Jul 2013 14:36:18 -0500 Harley wrote: >>>> It looks like the culprit is the range check (MASK_REG in the new vm) >>>> for OP_STORE4. Commenting out MASK_REG under that case seems to make >>>> UrbanTerror 4.2 load up. I haven't actually tried a real game though. >>> >>> This is probably indicative of a bug in Urban Terror. We have hacks in >>> sound backends to work around UrT's misuse of the API, but in that case >>> it's not harmful. Removing a range check would mean compromising >>> security for the sake of UrT. Hmmm. >> >> Well, given the issue I think that the VM should be fixed rather >> than changing ioq3. I build standalone binaries for UT, where I can >> remove the alignment enforcement without affecting the general ioq3 >> packages. >> >> I wonder how much overhead would be produced by reporting unaligned >> data access (OP_LOAD* and OP_STORE*) instead of just force-aligning >> stuff. > > If the analysis by Harley is correct issue is not about alignment. If > removing the mask fixes the issue then UrT tries to write outside it's > allocated memory area. That leads to unpredictable behavior or > crashes in any case.
You can leave the mask in place and just remove the &~3 from the mask that enforces alignment. > The issue should be reproducible with the interpreter in idq3 as > well as that one always had the masking in OP_STORE4 AFAICS. Nope, it really is the alignment. Someone on the UT side with access to the qvm confirmed it and started working on it. But someone else muscled in and locked the thread because: > UrbanTerror is a mod of Q3 and as such it does not have to be > compatible with any other version of the Q3 engine like ioQ3. I'd have expected that failing so hard with a commercial idtech-3 partnership should have clued them in on the advantages of working with an open source project. -- A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing on usenet and in e-mail?
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