On 12:43 19.05.20, Ricardo Neri wrote: > > > Running the same executable on the exact same kernel (and userland) but > > > on a Intel i7-8565U doesn't crash at this point. I am guessing the > > > emulation is supposed to do something different on AMD CPUs? > > I am surprised you don't see it on the Intel processor. Maybe it does > not have UMIP. Do you see umip when you do > > $ grep umip /proc/cpuinfo
Indeed it doesn't ahve the feature. I would have assumed that it is recent enough. Apparently not. > > > On the Ryzen the code executes successfully after setting > > > CONFIG_X86_UMIP=n. > > > > Hi Andreas, > > > > The problem is that the kernel does not emulate/spoof the SLDT instruction, > > only SGDT, SIDT, and SMSW. > > SLDT and STR weren't thought to be commonly used, so emulation/spoofing > > wasn’t added. > > In the last few months I have seen reports of one or two (32-bit) Windows > > games that use SLDT though. > > Can you share more information about the application you’re running? > > > > Maybe the best path is to add kernel emulation/spoofing for SLDT and STR on > > 32 and 64-bit, just to cover all the cases. It should be a pretty simple > > patch, I’ll start working on it. > > I have a patch for this already that I wrote for testing purposes: > > https://github.com/ricardon/tip/commit/1692889cb3f8accb523d44b682458e234b93be50 > > Perhaps it can be used as a starting point? Not sure what the spoofing > value should be, though. Perhaps 0? I am not entirely sure what it should return in the general case. My assumption is that 0 might work. Maybe making it configurable like with the other UMIP constants that I saw? I'll give the patch a shot and try to figure out what the authors of the code have to say about it.
