x86/umip: Add emulation/spoofing for SLDT and STR instructions (b91e7089) · Commits · 戴 / test

arch/x86/kernel/umip.c

+27 −13

Original line number	Diff line number	Diff line
		@@ -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,

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