UbiquitousOS
/
OpenCloudOS-Kernel
mirror of https://gitee.com/OpenCloudOS/OpenCloudOS-Kernel.git
11
0
Fork 0
Code Issues Projects Releases Wiki Activity

x86/umip: Add emulation/spoofing for SLDT and STR instructions 

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.

Originally-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Reported-by: Andreas Rammhold <andi@notmuch.email>
Signed-off-by: Brendan Shanks <bshanks@codeweavers.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Tested-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Link: https://lkml.kernel.org/r/20200710224525.21966-1-bshanks@codeweavers.com
This commit is contained in:
Brendan Shanks 2020-07-10 15:45:25 -07:00 committed by Borislav Petkov
parent 40eb0cb493
commit b91e7089ae
1 changed files with 27 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
arch/x86/kernel/umip.c
View File

@ -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
* 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(&current->mm->context.ldt_usr_sem);
if (current->mm->context.ldt)
dummy_value = GDT_ENTRY_LDT * 8;
else
dummy_value = 0;
up_read(&current->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,