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 <andi@notmuch.email>
> Originally-by: Ricardo Neri <ricardo.neri-calde...@linux.intel.com>
> Signed-off-by: Brendan Shanks <bsha...@codeweavers.com>
> ---
>
> 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
