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 <[email protected]>
Originally-by: Ricardo Neri <[email protected]>
Signed-off-by: Brendan Shanks <[email protected]>
---
v3: Use (GDT_ENTRY_TSS * 8) for task register selector instead of
harcoding 0x40.
arch/x86/kernel/umip.c | 32 +++++++++++++++++++++++---------
1 file changed, 23 insertions(+), 9 deletions(-)
diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c
index 8d5cbe1bbb3b..166c579b0273 100644
--- a/arch/x86/kernel/umip.c
+++ b/arch/x86/kernel/umip.c
@@ -244,16 +244,35 @@ 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 = GDT_ENTRY_TSS * 8;
+ else if (umip_inst == UMIP_INST_SLDT)
+ {
+#ifdef CONFIG_MODIFY_LDT_SYSCALL
+ down_read(¤t->mm->context.ldt_usr_sem);
+ if (current->mm->context.ldt)
+ dummy_value = GDT_ENTRY_LDT * 8;
+ else
+ dummy_value = 0;
+ up_read(¤t->mm->context.ldt_usr_sem);
+#else
+ dummy_value = 0;
+#endif
+ }
/*
- * 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 +280,6 @@ 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 +401,6 @@ 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
On Mon, Jun 08, 2020 at 03:44:24PM -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 <[email protected]>
> Originally-by: Ricardo Neri <[email protected]>
> Signed-off-by: Brendan Shanks <[email protected]>
> ---
>
> v3: Use (GDT_ENTRY_TSS * 8) for task register selector instead of
> harcoding 0x40.
>
> arch/x86/kernel/umip.c | 32 +++++++++++++++++++++++---------
> 1 file changed, 23 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c
> index 8d5cbe1bbb3b..166c579b0273 100644
> --- a/arch/x86/kernel/umip.c
> +++ b/arch/x86/kernel/umip.c
> @@ -244,16 +244,35 @@ 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 = GDT_ENTRY_TSS * 8;
> + else if (umip_inst == UMIP_INST_SLDT)
> + {
This brace should go in the previous line. Also, if you use braces in
the last part of the conditional you should probably use them in the
previous ones. I guess in this case it woudln't improve readability.
Instead, you can probably have a switch instead of the three ifs. That
probably does improve readability and solves the dilemma of needing to
put braces in all the one-line conditionals.
BTW, you should also delete the comment at the top of the file saying
that str and sldt will not be emulated:
diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c
index 166c579b0273..0984a55eb8c0 100644
--- a/arch/x86/kernel/umip.c
+++ b/arch/x86/kernel/umip.c
@@ -45,9 +45,6 @@
* value that, lies close to the top of the kernel memory. The limit for the GDT
* and the IDT are set to zero.
*
- * Given that SLDT and STR are not commonly used in programs that run on WineHQ
- * or DOSEMU2, they are not emulated.
- *
* The instruction smsw is emulated to return the value that the register CR0
* has at boot time as set in the head_32.
*
Thanks and BR,
Ricardo
On Mon, Jun 08, 2020 at 05:38:12PM -0700, Ricardo Neri wrote:
> On Mon, Jun 08, 2020 at 03:44:24PM -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 <[email protected]>
> > Originally-by: Ricardo Neri <[email protected]>
> > Signed-off-by: Brendan Shanks <[email protected]>
> > ---
> >
> > v3: Use (GDT_ENTRY_TSS * 8) for task register selector instead of
> > harcoding 0x40.
> >
> > arch/x86/kernel/umip.c | 32 +++++++++++++++++++++++---------
> > 1 file changed, 23 insertions(+), 9 deletions(-)
> >
> > diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c
> > index 8d5cbe1bbb3b..166c579b0273 100644
> > --- a/arch/x86/kernel/umip.c
> > +++ b/arch/x86/kernel/umip.c
> > @@ -244,16 +244,35 @@ 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 = GDT_ENTRY_TSS * 8;
> > + else if (umip_inst == UMIP_INST_SLDT)
> > + {
>
> This brace should go in the previous line. Also, if you use braces in
> the last part of the conditional you should probably use them in the
> previous ones. I guess in this case it woudln't improve readability.
> Instead, you can probably have a switch instead of the three ifs. That
> probably does improve readability and solves the dilemma of needing to
> put braces in all the one-line conditionals.
>
> BTW, you should also delete the comment at the top of the file saying
> that str and sldt will not be emulated:
>
> diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c
> index 166c579b0273..0984a55eb8c0 100644
> --- a/arch/x86/kernel/umip.c
> +++ b/arch/x86/kernel/umip.c
> @@ -45,9 +45,6 @@
> * value that, lies close to the top of the kernel memory. The limit for the GDT
> * and the IDT are set to zero.
> *
> - * Given that SLDT and STR are not commonly used in programs that run on WineHQ
> - * or DOSEMU2, they are not emulated.
> - *
> * The instruction smsw is emulated to return the value that the register CR0
> * has at boot time as set in the head_32.
... And also explain that the emulated values for str and sldt are the
simply the values that Linux assigns programatically.
Thanks and BR,
Ricardo