* [PATCH] x86/umip: Add emulation/spoofing for SLDT and STR instructions
@ 2020-06-02 18:42 Brendan Shanks
2020-06-04 0:12 ` Ricardo Neri
0 siblings, 1 reply; 5+ messages in thread
From: Brendan Shanks @ 2020-06-02 18:42 UTC (permalink / raw)
To: linux-kernel
Cc: ricardo.neri-calderon, tglx, mingo, bp, hpa, x86, ebiederm, andi,
Babu.Moger, Brendan Shanks
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;
/*
- * Even though the CR0 register has 4 bytes, the number
+ * For these 3 instructions, the number
* of bytes to be copied in the result buffer is determined
* by whether the operand is a register or a memory location.
* If operand is a register, return as many bytes as the operand
* size. If operand is memory, return only the two least
- * siginificant bytes of CR0.
+ * siginificant bytes.
*/
if (X86_MODRM_MOD(insn->modrm.value) == 3)
*data_size = insn->opnd_bytes;
@@ -261,7 +271,6 @@ static int emulate_umip_insn(struct insn *insn, int umip_inst,
*data_size = 2;
memcpy(data, &dummy_value, *data_size);
- /* STR and SLDT are not emulated */
} else {
return -EINVAL;
}
@@ -383,10 +392,6 @@ bool fixup_umip_exception(struct pt_regs *regs)
umip_pr_warn(regs, "%s instruction cannot be used by applications.\n",
umip_insns[umip_inst]);
- /* Do not emulate (spoof) SLDT or STR. */
- if (umip_inst == UMIP_INST_STR || umip_inst == UMIP_INST_SLDT)
- return false;
-
umip_pr_warn(regs, "For now, expensive software emulation returns the result.\n");
if (emulate_umip_insn(&insn, umip_inst, dummy_data, &dummy_data_size,
--
2.26.2
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] x86/umip: Add emulation/spoofing for SLDT and STR instructions
2020-06-02 18:42 [PATCH] x86/umip: Add emulation/spoofing for SLDT and STR instructions Brendan Shanks
@ 2020-06-04 0:12 ` Ricardo Neri
2020-06-04 4:39 ` Andy Lutomirski
0 siblings, 1 reply; 5+ messages in thread
From: Ricardo Neri @ 2020-06-04 0:12 UTC (permalink / raw)
To: Brendan Shanks
Cc: linux-kernel, tglx, mingo, bp, hpa, x86, ebiederm, andi, Babu.Moger
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).
Thanks and BR,
Ricardo
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] x86/umip: Add emulation/spoofing for SLDT and STR instructions
2020-06-04 0:12 ` Ricardo Neri
@ 2020-06-04 4:39 ` Andy Lutomirski
[not found] ` <E32838F8-665E-488F-96E4-040DD7BDA284@codeweavers.com>
0 siblings, 1 reply; 5+ messages in thread
From: Andy Lutomirski @ 2020-06-04 4:39 UTC (permalink / raw)
To: Ricardo Neri
Cc: Brendan Shanks, LKML, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, H. Peter Anvin, X86 ML, Eric W. Biederman,
Andreas Rammhold, Moger, Babu
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
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2020-06-08 18:13 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2020-06-02 18:42 [PATCH] x86/umip: Add emulation/spoofing for SLDT and STR instructions Brendan Shanks
2020-06-04 0:12 ` Ricardo Neri
2020-06-04 4:39 ` Andy Lutomirski
[not found] ` <E32838F8-665E-488F-96E4-040DD7BDA284@codeweavers.com>
2020-06-05 22:42 ` Ricardo Neri
2020-06-08 18:13 ` Brendan Shanks
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