On Sat, 2017-03-11 at 02:58 +0300, Stas Sergeev wrote: > 11.03.2017 02:47, Ricardo Neri пишет: > >> > >>>> It doesn't need to be a matter of this particular > >>>> patch set, i.e. this proposal should not trigger a > >>>> v7 resend of all 21 patches. :) But it would be useful > >>>> for the future development of dosemu2. > >>> Would dosemu2 use 32-bit processes in order to keep segmentation? If it > >>> could use 64-bit processes, emulation is not used in this case and the > >>> SIGSEGV is delivered to user space. > >> It does use the mix: 64bit process but some segments > >> are 32bit for DOS code. > > Do you mean that dosemu2 will start as a 64-bit process and will jump to > > 32-bit code segments? > Yes, so the offending insns are executed only in 32bit > and 16bit segments, even if the process itself is 64bit. > I guess you handle 16bit segments same as 32bit ones. I have code to handle 16-bit and 32-bit address encodings differently. Segmentation is used if !user_64bit_mode(regs). In such a case, the emulation code will check the segment descriptor D flag and the address-size overrides prefix to determine the address size and use 16-bit or 32-bit address encodings as applicable. > > > My emulation code should work in this case as it > > will use segmentation in 32-bit code descriptors. Is there anything else > > needed? > If I understand you correctly, you are saying that SLDT > executed in 64bit code segment, will inevitably segfault > to userspace. Correct. > If this is the case and it makes your code > simpler, then its perfectly fine with me as dosemu does > not do this and the 64bit DOS progs are not anticipated. But if 32-bit or 16-bit code segments are used emulation will be used. Thanks and BR, Ricardo -- 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
