On Mon, 14 Oct 2013 22:45:09 +0400 Eugene Shatokhin <euspectre@xxxxxxxxx> wrote: > Hi, > > There is an interesting TODO item on MmioTraceDeveloper page: > "kprobes has a generic instruction decoding facility, use that instead of > homebrewn (or KVM), and use emulation instead of page faulting" > > Actually, I have done something similar in one of my systems, KernelStrider > (http://code.google.com/p/kernel-strider/). The system instruments a kernel > module when that module is being loaded. The instrumented code executes > instead of the original one and provides information about the memory > accesses it makes and the functions it calls. These data are sent to user > space for further analysis. > > Currently, I use this system to detect data races in the Linux kernel (and > have found some). I suppose, it could probably be useful to MmioTrace as > well. > > KernelStrider uses an enhanced version of the x86 instruction decoder that > Kprobes use and relies on binary instrumentation rather than on page > faults. So, it can track: > - memory accesses (address and size of the accessed memory as well as the > access type are recorded) > - function calls (exported functions and callbacks, one can setup pre- and > post- handlers for these) > > Is there any interest in trying this approach to the task of MmioTrace? > > If so, we can discuss it. When I have time, I could try to create a > prototype based on KernelStrider's core that tracks the memory accesses > Mmiotrace needs. > What do you think? Hi Eugene, that is very interesting! I assume emulating the instructions is not only cleaner, but also faster than page-faulting, right? Maybe even more reliable, perhaps up to the point where we would not need to disable all but one CPU. Unfortunately, my job exhausts my coding energy, and I haven't even touched mmiotrace in years. However, let's see if there are interested people on the mailing lists. I'm CC'ing nouveau, since that is where mmiotrace started, and dri-devel in the hopes to catch other drivers' reverse engineers. Thanks, pq _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
