On Wed, Mar 8, 2017 at 8:29 AM, Stas Sergeev <stsp@xxxxxxx> wrote: > 08.03.2017 19:06, Andy Lutomirski пишет: >> >> On Wed, Mar 8, 2017 at 6:08 AM, Stas Sergeev <stsp@xxxxxxx> wrote: >>> >>> 08.03.2017 03:32, Ricardo Neri пишет: >>>> >>>> These are the instructions covered by UMIP: >>>> * SGDT - Store Global Descriptor Table >>>> * SIDT - Store Interrupt Descriptor Table >>>> * SLDT - Store Local Descriptor Table >>>> * SMSW - Store Machine Status Word >>>> * STR - Store Task Register >>>> >>>> This patchset initially treated tasks running in virtual-8086 mode as a >>>> special case. However, I received clarification that DOSEMU[8] does not >>>> support applications that use these instructions. >> >> Can you remind me what was special about it? It looks like you still >> emulate them in v8086 mode. > > Indeed, sorry, I meant prot mode here. :) > So I wonder what was cited to be special about v86. Not sure. Ricardo? > >>> Yes, this is the case. >>> But at least in the past there was an attempt to >>> support SLDT as it is used by an ancient pharlap >>> DOS extender (currently unsupported by dosemu1/2). >>> So how difficult would it be to add an optional >>> possibility of delivering such SIGSEGV to userspace >>> so that the kernel's dummy emulation can be overridden? >>> 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. >> >> What I'd actually like to see is a totally separate patchset that adds >> an inheritable (but reset on exec) per-task mask of legacy >> compatibility features to disable. Maybe: >> >> sys_adjust_compat_mask(int op, int word, u32 mask); > > No no, since I meant prot mode, this is not what I need. > I would never need to disable UMIP as to allow the > prot mode apps to do SLDT. Instead it would be good > to have an ability to provide a replacement for the dummy > emulation that is currently being proposed for kernel. > All is needed for this, is just to deliver a SIGSEGV. That's what I meant. Turning off FIXUP_UMIP would leave UMIP on but turn off the fixup, so you'd get a SIGSEGV indicating #GP (or a vm86 GP exit). --Andy -- 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
