Messages in this thread | | | From | Andy Lutomirski <> | Date | Wed, 3 Jun 2020 21:39:59 -0700 | Subject | Re: [PATCH] x86/umip: Add emulation/spoofing for SLDT and STR instructions |
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On Wed, Jun 3, 2020 at 5:12 PM Ricardo Neri <ricardo.neri-calderon@linux.intel.com> wrote: > > On Tue, Jun 02, 2020 at 11:42:12AM -0700, Brendan Shanks wrote: > > Add emulation/spoofing of SLDT and STR for both 32- and 64-bit > > processes. > > > > Wine users have found a small number of Windows apps using SLDT that > > were crashing when run on UMIP-enabled systems. > > > > Reported-by: Andreas Rammhold <andi@notmuch.email> > > Originally-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> > > Signed-off-by: Brendan Shanks <bshanks@codeweavers.com> > > --- > > arch/x86/kernel/umip.c | 23 ++++++++++++++--------- > > 1 file changed, 14 insertions(+), 9 deletions(-) > > > > diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c > > index 8d5cbe1bbb3b..59dfceac5cc0 100644 > > --- a/arch/x86/kernel/umip.c > > +++ b/arch/x86/kernel/umip.c > > @@ -64,6 +64,8 @@ > > #define UMIP_DUMMY_GDT_BASE 0xfffffffffffe0000ULL > > #define UMIP_DUMMY_IDT_BASE 0xffffffffffff0000ULL > > > > +#define UMIP_DUMMY_TASK_REGISTER_SELECTOR 0x40 > > + > > /* > > * The SGDT and SIDT instructions store the contents of the global descriptor > > * table and interrupt table registers, respectively. The destination is a > > @@ -244,16 +246,24 @@ static int emulate_umip_insn(struct insn *insn, int umip_inst, > > *data_size += UMIP_GDT_IDT_LIMIT_SIZE; > > memcpy(data, &dummy_limit, UMIP_GDT_IDT_LIMIT_SIZE); > > > > - } else if (umip_inst == UMIP_INST_SMSW) { > > - unsigned long dummy_value = CR0_STATE; > > + } else if (umip_inst == UMIP_INST_SMSW || umip_inst == UMIP_INST_SLDT || > > + umip_inst == UMIP_INST_STR) { > > + unsigned long dummy_value; > > + > > + if (umip_inst == UMIP_INST_SMSW) > > + dummy_value = CR0_STATE; > > + else if (umip_inst == UMIP_INST_STR) > > + dummy_value = UMIP_DUMMY_TASK_REGISTER_SELECTOR; > > + else > > + dummy_value = 0; > > Perhaps you can return a non-zero value for SLDT if it has an LDT, as > Andy had suggested. Maybe this can be implemented by looking at > current->mm->context.ldt > > I guess the non-zero value can be (GDT_ENTRY_LDT*8).
You could probably even get away with always returning a nonzero value. After all, an empty LDT is quite similar to no LDT.
--Andy
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