Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx> writes: > On Thu, 2017-03-30 at 13:10 +0300, Stas Sergeev wrote: >> 30.03.2017 08:14, Ricardo Neri пишет: >> >>>> But at least dosemu implements it, so probably it is needed. >> >>> Right. >> >>> >> >>>> Of course if it is used by one of 100 DOS progs, then there >> >>>> is an option to just add its support to dosemu2 and pretend >> >>>> the compatibility problems did not exist. :) >> >>> Do you mean relaying the GP fault to dosemu instead of trapping it and >> >>> emulating it in the kernel? >> >> Yes, that would be optimal if this does not severely break >> >> the current setups. If we can find out that smsw is not in >> >> the real use, we can probably do exactly that. >> >> But other >> >> instructions are not in real use in v86 for sure, so I >> >> wouldn't be adding the explicit test-cases to the kernel >> >> that will make you depend on some particular behaviour >> >> that no one may need. >> >> My objection was that we shouldn't >> >> write tests before we know exactly how we want this to work. >> > OK, if only SMSW is used then I'll keep the emulation for SMSW only. >> In fact, smsw has an interesting property, which is that >> no one will ever want to disable its in-kernel emulation >> to provide its own. >> So while I'll try to estimate its usage, emulating it in kernel >> will not be that problematic in either case. > > Ah good to know! > >> As for protected mode, if wine only needs sgdt/sidt, then >> again, no one will want to disable its emulation. Not the >> case with sldt, but AFAICS wine doesn't need sldt, and so >> we can leave sldt without a fixups. Is my understanding >> correct? > > This is my understanding as well. I could not find any use of sldt in > wine. Alexandre, would you mind confirming? Some versions of the Themida software protection are known to use sldt as part of the virtual machine detection code [1]. The check currently fails because it expects the LDT to be zero, so the app is already broken, but sldt segfaulting would still cause a crash where there wasn't one before. However, I'm only aware of one application using this, and being able to catch and emulate sldt ourselves would actually give us a chance to fix this app in newer Wine versions, so I'm not opposed to having it segfault. In fact it would be nice to be able to make sidt/sgdt/etc. segfault too. I know a new syscall is a pain, but as far as Wine is concerned, being able to opt out from any emulation would be potentially useful. [1] https://www.winehq.org/pipermail/wine-bugs/2008-February/094470.html -- Alexandre Julliard julliard@xxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-msdos" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
