On 10:54 09.06.20, 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]> > --- > > v4: Use braces for every clause of the conditional. I tried a switch(), > but it takes more lines and looks more cluttered (especially with the > #ifdef). > Also replace out-of-date comment at top of file. > > arch/x86/kernel/umip.c | 38 ++++++++++++++++++++++++++------------ > 1 file changed, 26 insertions(+), 12 deletions(-) > > diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c > index 8d5cbe1bbb3b..62f4f0afb979 100644 > --- a/arch/x86/kernel/umip.c > +++ b/arch/x86/kernel/umip.c > @@ -45,11 +45,12 @@ > * 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. > + * sldt and str are emulated to return the values that the kernel > programmatically > + * assigns: > + * - sldt returns (GDT_ENTRY_LDT * 8) if an LDT has been set, 0 if not. > + * - str returns (GDT_ENTRY_TSS * 8). > * > * Emulation is provided for both 32-bit and 64-bit processes. > * > @@ -244,16 +245,34 @@ 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 >
A bit late but I was able to test my workload with the above patch applied on 5.7.2. Tested-by: Andreas Rammhold <[email protected]>
