On Thu, 2017-03-09 at 18:39 -0800, Andy Lutomirski wrote:
On Thu, Mar 9, 2017 at 2:10 PM, Stas Sergeev stsp@list.ru wrote:
09.03.2017 04:15, Ricardo Neri пишет:
On Wed, 2017-03-08 at 08:46 -0800, Andy Lutomirski wrote:
On Wed, Mar 8, 2017 at 8:29 AM, Stas Sergeev stsp@list.ru wrote:
08.03.2017 19:06, Andy Lutomirski пишет:
On Wed, Mar 8, 2017 at 6:08 AM, Stas Sergeev stsp@list.ru 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.
Initially my patches disabled UMIP on virtual-8086 instructions, without regards of protected mode (i.e., UMIP was always enabled). I didn't have emulation at the time. Then, I added emulation code that now covers protected and virtual-8086 modes. I guess it is not special anymore.
But isn't SLDT&friends just throw UD in v86? How does UMIP affect this? How does your patch affect this?
Er, right. Ricardo, your code may need fixing. But don't you have a test case for this? The behavior should be the same with and without your patches applied. The exception is #UD, not #GP, so maybe your code just never executes in the vm86 case.
Ouch! Yes, I am afraid my code will attempt to emulate sldt in vm86 mode. The test cases that I have for vm86 are only for the instructions that are valid in vm86: smsw, sidt and sgdt.
I will add test cases for str and sldt and make sure that a #UD is issued.
Would this trigger a v7 series?
Thanks and BR, Ricardo
--Andy