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x86/umip: Add emulation (spoofing) for UMIP covered instructions in 64-bit processes as well

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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>
This commit is contained in:
Brendan Shanks 2019-09-05 16:22:21 -07:00 committed by Ingo Molnar
parent 98ededb61f
commit e86c2c8b93
1 changed files with 38 additions and 27 deletions
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65
arch/x86/kernel/umip.c
View File

@ -19,7 +19,7 @@
/** DOC: Emulation for User-Mode Instruction Prevention (UMIP) /** DOC: Emulation for User-Mode Instruction Prevention (UMIP)
* *
* The feature User-Mode Instruction Prevention present in recent Intel * The feature User-Mode Instruction Prevention present in recent Intel
* processor prevents a group of instructions (sgdt, sidt, sldt, smsw, and str) * processor prevents a group of instructions (SGDT, SIDT, SLDT, SMSW and STR)
* from being executed with CPL > 0. Otherwise, a general protection fault is * from being executed with CPL > 0. Otherwise, a general protection fault is
* issued. * issued.
* *
@ -36,8 +36,8 @@
* DOSEMU2) rely on this subset of instructions to function. * DOSEMU2) rely on this subset of instructions to function.
* *
* The instructions protected by UMIP can be split in two groups. Those which * The instructions protected by UMIP can be split in two groups. Those which
* return a kernel memory address (sgdt and sidt) and those which return a * return a kernel memory address (SGDT and SIDT) and those which return a
* value (sldt, str and smsw). * value (SLDT, STR and SMSW).
* *
* For the instructions that return a kernel memory address, applications * For the instructions that return a kernel memory address, applications
* such as WineHQ rely on the result being located in the kernel memory space, * such as WineHQ rely on the result being located in the kernel memory space,
@ -45,15 +45,13 @@
* value that, lies close to the top of the kernel memory. The limit for the GDT * value that, lies close to the top of the kernel memory. The limit for the GDT
* and the IDT are set to zero. * and the IDT are set to zero.
* *
* Given that sldt and str are not commonly used in programs that run on WineHQ * Given that SLDT and STR are not commonly used in programs that run on WineHQ
* or DOSEMU2, they are not emulated. * 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. * has at boot time as set in the head_32.
* *
* Also, emulation is provided only for 32-bit processes; 64-bit processes * Emulation is provided for both 32-bit and 64-bit processes.
* that attempt to use the instructions that UMIP protects will receive the
* SIGSEGV signal issued as a consequence of the general protection fault.
* *
* Care is taken to appropriately emulate the results when segmentation is * Care is taken to appropriately emulate the results when segmentation is
* used. That is, rather than relying on USER_DS and USER_CS, the function * used. That is, rather than relying on USER_DS and USER_CS, the function
@ -63,17 +61,18 @@
* application uses a local descriptor table. * application uses a local descriptor table.
*/ */
#define UMIP_DUMMY_GDT_BASE 0xfffe0000 #define UMIP_DUMMY_GDT_BASE 0xfffffffffffe0000ULL
#define UMIP_DUMMY_IDT_BASE 0xffff0000 #define UMIP_DUMMY_IDT_BASE 0xffffffffffff0000ULL
/* /*
* The SGDT and SIDT instructions store the contents of the global descriptor * The SGDT and SIDT instructions store the contents of the global descriptor
* table and interrupt table registers, respectively. The destination is a * table and interrupt table registers, respectively. The destination is a
* memory operand of X+2 bytes. X bytes are used to store the base address of * memory operand of X+2 bytes. X bytes are used to store the base address of
* the table and 2 bytes are used to store the limit. In 32-bit processes, the * the table and 2 bytes are used to store the limit. In 32-bit processes X
* only processes for which emulation is provided, X has a value of 4. * has a value of 4, in 64-bit processes X has a value of 8.
*/ */
#define UMIP_GDT_IDT_BASE_SIZE 4 #define UMIP_GDT_IDT_BASE_SIZE_64BIT 8
#define UMIP_GDT_IDT_BASE_SIZE_32BIT 4
#define UMIP_GDT_IDT_LIMIT_SIZE 2 #define UMIP_GDT_IDT_LIMIT_SIZE 2
#define UMIP_INST_SGDT 0 /* 0F 01 /0 */ #define UMIP_INST_SGDT 0 /* 0F 01 /0 */
@ -189,6 +188,7 @@ static int identify_insn(struct insn *insn)
* @umip_inst: A constant indicating the instruction to emulate * @umip_inst: A constant indicating the instruction to emulate
* @data: Buffer into which the dummy result is stored * @data: Buffer into which the dummy result is stored
* @data_size: Size of the emulated result * @data_size: Size of the emulated result
* @x86_64: true if process is 64-bit, false otherwise
* *
* Emulate an instruction protected by UMIP and provide a dummy result. The * Emulate an instruction protected by UMIP and provide a dummy result. The
* result of the emulation is saved in @data. The size of the results depends * result of the emulation is saved in @data. The size of the results depends
@ -202,11 +202,8 @@ static int identify_insn(struct insn *insn)
* 0 on success, -EINVAL on error while emulating. * 0 on success, -EINVAL on error while emulating.
*/ */
static int emulate_umip_insn(struct insn *insn, int umip_inst, static int emulate_umip_insn(struct insn *insn, int umip_inst,
unsigned char *data, int *data_size) unsigned char *data, int *data_size, bool x86_64)
{ {
unsigned long dummy_base_addr, dummy_value;
unsigned short dummy_limit = 0;
if (!data || !data_size || !insn) if (!data || !data_size || !insn)
return -EINVAL; return -EINVAL;
/* /*
@ -219,6 +216,9 @@ static int emulate_umip_insn(struct insn *insn, int umip_inst,
* is always returned irrespective of the operand size. * is always returned irrespective of the operand size.
*/ */
if (umip_inst == UMIP_INST_SGDT || umip_inst == UMIP_INST_SIDT) { if (umip_inst == UMIP_INST_SGDT || umip_inst == UMIP_INST_SIDT) {
u64 dummy_base_addr;
u16 dummy_limit = 0;
/* SGDT and SIDT do not use registers operands. */ /* SGDT and SIDT do not use registers operands. */
if (X86_MODRM_MOD(insn->modrm.value) == 3) if (X86_MODRM_MOD(insn->modrm.value) == 3)
return -EINVAL; return -EINVAL;
@ -228,13 +228,24 @@ static int emulate_umip_insn(struct insn *insn, int umip_inst,
else else
dummy_base_addr = UMIP_DUMMY_IDT_BASE; dummy_base_addr = UMIP_DUMMY_IDT_BASE;
*data_size = UMIP_GDT_IDT_LIMIT_SIZE + UMIP_GDT_IDT_BASE_SIZE; /*
* 64-bit processes use the entire dummy base address.
* 32-bit processes use the lower 32 bits of the base address.
* dummy_base_addr is always 64 bits, but we memcpy the correct
* number of bytes from it to the destination.
*/
if (x86_64)
*data_size = UMIP_GDT_IDT_BASE_SIZE_64BIT;
else
*data_size = UMIP_GDT_IDT_BASE_SIZE_32BIT;
memcpy(data + 2, &dummy_base_addr, UMIP_GDT_IDT_BASE_SIZE); memcpy(data + 2, &dummy_base_addr, *data_size);
*data_size += UMIP_GDT_IDT_LIMIT_SIZE;
memcpy(data, &dummy_limit, UMIP_GDT_IDT_LIMIT_SIZE); memcpy(data, &dummy_limit, UMIP_GDT_IDT_LIMIT_SIZE);
} else if (umip_inst == UMIP_INST_SMSW) { } else if (umip_inst == UMIP_INST_SMSW) {
dummy_value = CR0_STATE; unsigned long dummy_value = CR0_STATE;
/* /*
* Even though the CR0 register has 4 bytes, the number * Even though the CR0 register has 4 bytes, the number
@ -290,11 +301,10 @@ static void force_sig_info_umip_fault(void __user *addr, struct pt_regs *regs)
* fixup_umip_exception() - Fixup a general protection fault caused by UMIP * fixup_umip_exception() - Fixup a general protection fault caused by UMIP
* @regs: Registers as saved when entering the #GP handler * @regs: Registers as saved when entering the #GP handler
* *
* The instructions sgdt, sidt, str, smsw, sldt cause a general protection * The instructions SGDT, SIDT, STR, SMSW and SLDT cause a general protection
* fault if executed with CPL > 0 (i.e., from user space). If the offending * fault if executed with CPL > 0 (i.e., from user space). This function fixes
* user-space process is not in long mode, this function fixes the exception * the exception up and provides dummy results for SGDT, SIDT and SMSW; STR
* up and provides dummy results for sgdt, sidt and smsw; str and sldt are not * and SLDT are not fixed up.
* fixed up. Also long mode user-space processes are not fixed up.
* *
* If operands are memory addresses, results are copied to user-space memory as * If operands are memory addresses, results are copied to user-space memory as
* indicated by the instruction pointed by eIP using the registers indicated in * indicated by the instruction pointed by eIP using the registers indicated in
@ -373,13 +383,14 @@ bool fixup_umip_exception(struct pt_regs *regs)
umip_pr_warning(regs, "%s instruction cannot be used by applications.\n", umip_pr_warning(regs, "%s instruction cannot be used by applications.\n",
umip_insns[umip_inst]); umip_insns[umip_inst]);
/* Do not emulate SLDT, STR or user long mode processes. */ /* Do not emulate (spoof) SLDT or STR. */
if (umip_inst == UMIP_INST_STR || umip_inst == UMIP_INST_SLDT || user_64bit_mode(regs)) if (umip_inst == UMIP_INST_STR || umip_inst == UMIP_INST_SLDT)
return false; return false;
umip_pr_warning(regs, "For now, expensive software emulation returns the result.\n"); umip_pr_warning(regs, "For now, expensive software emulation returns the result.\n");
if (emulate_umip_insn(&insn, umip_inst, dummy_data, &dummy_data_size)) if (emulate_umip_insn(&insn, umip_inst, dummy_data, &dummy_data_size,
user_64bit_mode(regs)))
return false; return false;
/* /*