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x86/umip: Add emulation (spoofing) for UMIP covered instructions in 64-bit processes as well
Add emulation (spoofing) of the SGDT, SIDT, and SMSW instructions for 64-bit processes. Wine users have encountered a number of 64-bit Windows games that use these instructions (particularly SGDT), and were crashing when run on UMIP-enabled systems. Originally-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Signed-off-by: Brendan Shanks <bshanks@codeweavers.com> Reviewed-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Reviewed-by: H. Peter Anvin (Intel) <hpa@zytor.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20190905232222.14900-1-bshanks@codeweavers.com [ Minor edits: capitalization, added 'spoofing' wording. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
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1 changed files with 38 additions and 27 deletions
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@ -19,7 +19,7 @@
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/** DOC: Emulation for User-Mode Instruction Prevention (UMIP)
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*
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* The feature User-Mode Instruction Prevention present in recent Intel
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* processor prevents a group of instructions (sgdt, sidt, sldt, smsw, and str)
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* processor prevents a group of instructions (SGDT, SIDT, SLDT, SMSW and STR)
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* from being executed with CPL > 0. Otherwise, a general protection fault is
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* issued.
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*
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@ -36,8 +36,8 @@
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* DOSEMU2) rely on this subset of instructions to function.
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*
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* The instructions protected by UMIP can be split in two groups. Those which
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* return a kernel memory address (sgdt and sidt) and those which return a
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* value (sldt, str and smsw).
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* return a kernel memory address (SGDT and SIDT) and those which return a
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* value (SLDT, STR and SMSW).
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*
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* For the instructions that return a kernel memory address, applications
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* such as WineHQ rely on the result being located in the kernel memory space,
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@ -45,15 +45,13 @@
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* value that, lies close to the top of the kernel memory. The limit for the GDT
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* and the IDT are set to zero.
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*
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* Given that sldt and str are not commonly used in programs that run on WineHQ
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* Given that SLDT and STR are not commonly used in programs that run on WineHQ
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* or DOSEMU2, they are not emulated.
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*
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* The instruction smsw is emulated to return the value that the register CR0
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* has at boot time as set in the head_32.
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*
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* Also, emulation is provided only for 32-bit processes; 64-bit processes
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* that attempt to use the instructions that UMIP protects will receive the
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* SIGSEGV signal issued as a consequence of the general protection fault.
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* Emulation is provided for both 32-bit and 64-bit processes.
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*
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* Care is taken to appropriately emulate the results when segmentation is
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* used. That is, rather than relying on USER_DS and USER_CS, the function
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@ -63,17 +61,18 @@
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* application uses a local descriptor table.
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*/
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#define UMIP_DUMMY_GDT_BASE 0xfffe0000
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#define UMIP_DUMMY_IDT_BASE 0xffff0000
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#define UMIP_DUMMY_GDT_BASE 0xfffffffffffe0000ULL
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#define UMIP_DUMMY_IDT_BASE 0xffffffffffff0000ULL
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/*
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* The SGDT and SIDT instructions store the contents of the global descriptor
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* table and interrupt table registers, respectively. The destination is a
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* memory operand of X+2 bytes. X bytes are used to store the base address of
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* the table and 2 bytes are used to store the limit. In 32-bit processes, the
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* only processes for which emulation is provided, X has a value of 4.
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* the table and 2 bytes are used to store the limit. In 32-bit processes X
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* has a value of 4, in 64-bit processes X has a value of 8.
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*/
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#define UMIP_GDT_IDT_BASE_SIZE 4
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#define UMIP_GDT_IDT_BASE_SIZE_64BIT 8
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#define UMIP_GDT_IDT_BASE_SIZE_32BIT 4
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#define UMIP_GDT_IDT_LIMIT_SIZE 2
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#define UMIP_INST_SGDT 0 /* 0F 01 /0 */
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@ -189,6 +188,7 @@ static int identify_insn(struct insn *insn)
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* @umip_inst: A constant indicating the instruction to emulate
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* @data: Buffer into which the dummy result is stored
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* @data_size: Size of the emulated result
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* @x86_64: true if process is 64-bit, false otherwise
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*
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* Emulate an instruction protected by UMIP and provide a dummy result. The
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* result of the emulation is saved in @data. The size of the results depends
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@ -202,11 +202,8 @@ static int identify_insn(struct insn *insn)
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* 0 on success, -EINVAL on error while emulating.
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*/
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static int emulate_umip_insn(struct insn *insn, int umip_inst,
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unsigned char *data, int *data_size)
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unsigned char *data, int *data_size, bool x86_64)
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{
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unsigned long dummy_base_addr, dummy_value;
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unsigned short dummy_limit = 0;
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if (!data || !data_size || !insn)
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return -EINVAL;
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/*
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@ -219,6 +216,9 @@ static int emulate_umip_insn(struct insn *insn, int umip_inst,
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* is always returned irrespective of the operand size.
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*/
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if (umip_inst == UMIP_INST_SGDT || umip_inst == UMIP_INST_SIDT) {
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u64 dummy_base_addr;
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u16 dummy_limit = 0;
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/* SGDT and SIDT do not use registers operands. */
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if (X86_MODRM_MOD(insn->modrm.value) == 3)
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return -EINVAL;
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@ -228,13 +228,24 @@ static int emulate_umip_insn(struct insn *insn, int umip_inst,
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else
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dummy_base_addr = UMIP_DUMMY_IDT_BASE;
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*data_size = UMIP_GDT_IDT_LIMIT_SIZE + UMIP_GDT_IDT_BASE_SIZE;
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/*
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* 64-bit processes use the entire dummy base address.
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* 32-bit processes use the lower 32 bits of the base address.
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* dummy_base_addr is always 64 bits, but we memcpy the correct
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* number of bytes from it to the destination.
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*/
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if (x86_64)
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*data_size = UMIP_GDT_IDT_BASE_SIZE_64BIT;
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else
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*data_size = UMIP_GDT_IDT_BASE_SIZE_32BIT;
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memcpy(data + 2, &dummy_base_addr, UMIP_GDT_IDT_BASE_SIZE);
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memcpy(data + 2, &dummy_base_addr, *data_size);
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*data_size += UMIP_GDT_IDT_LIMIT_SIZE;
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memcpy(data, &dummy_limit, UMIP_GDT_IDT_LIMIT_SIZE);
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} else if (umip_inst == UMIP_INST_SMSW) {
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dummy_value = CR0_STATE;
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unsigned long dummy_value = CR0_STATE;
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/*
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* Even though the CR0 register has 4 bytes, the number
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@ -290,11 +301,10 @@ static void force_sig_info_umip_fault(void __user *addr, struct pt_regs *regs)
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* fixup_umip_exception() - Fixup a general protection fault caused by UMIP
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* @regs: Registers as saved when entering the #GP handler
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*
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* The instructions sgdt, sidt, str, smsw, sldt cause a general protection
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* fault if executed with CPL > 0 (i.e., from user space). If the offending
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* user-space process is not in long mode, this function fixes the exception
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* up and provides dummy results for sgdt, sidt and smsw; str and sldt are not
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* fixed up. Also long mode user-space processes are not fixed up.
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* The instructions SGDT, SIDT, STR, SMSW and SLDT cause a general protection
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* fault if executed with CPL > 0 (i.e., from user space). This function fixes
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* the exception up and provides dummy results for SGDT, SIDT and SMSW; STR
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* and SLDT are not fixed up.
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*
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* If operands are memory addresses, results are copied to user-space memory as
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* indicated by the instruction pointed by eIP using the registers indicated in
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@ -373,13 +383,14 @@ bool fixup_umip_exception(struct pt_regs *regs)
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umip_pr_warning(regs, "%s instruction cannot be used by applications.\n",
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umip_insns[umip_inst]);
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/* Do not emulate SLDT, STR or user long mode processes. */
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if (umip_inst == UMIP_INST_STR || umip_inst == UMIP_INST_SLDT || user_64bit_mode(regs))
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/* Do not emulate (spoof) SLDT or STR. */
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if (umip_inst == UMIP_INST_STR || umip_inst == UMIP_INST_SLDT)
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return false;
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umip_pr_warning(regs, "For now, expensive software emulation returns the result.\n");
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if (emulate_umip_insn(&insn, umip_inst, dummy_data, &dummy_data_size))
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if (emulate_umip_insn(&insn, umip_inst, dummy_data, &dummy_data_size,
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user_64bit_mode(regs)))
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return false;
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/*
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