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-calde...@linux.intel.com>
> Signed-off-by: Brendan Shanks <bsha...@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
