[PATCH] x86/umip: Add emulation for 64-bit processes
From: Brendan Shanks
Date: Thu Sep 05 2019 - 19:44:22 EST
Add emulation 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@xxxxxxxxxxxxxxx>
Signed-off-by: Brendan Shanks <bshanks@xxxxxxxxxxxxxxx>
---
arch/x86/kernel/umip.c | 55 +++++++++++++++++++++++++-----------------
1 file changed, 33 insertions(+), 22 deletions(-)
diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c
index 5b345add550f..1812e95d2f55 100644
--- a/arch/x86/kernel/umip.c
+++ b/arch/x86/kernel/umip.c
@@ -51,9 +51,7 @@
* The instruction smsw is emulated to return the value that the register CR0
* has at boot time as set in the head_32.
*
- * Also, emulation is provided only for 32-bit processes; 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.
+ * Emulation is provided for both 32-bit and 64-bit processes.
*
* 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
@@ -63,17 +61,18 @@
* application uses a local descriptor table.
*/
-#define UMIP_DUMMY_GDT_BASE 0xfffe0000
-#define UMIP_DUMMY_IDT_BASE 0xffff0000
+#define UMIP_DUMMY_GDT_BASE 0xfffffffffffe0000ULL
+#define UMIP_DUMMY_IDT_BASE 0xffffffffffff0000ULL
/*
* The SGDT and SIDT instructions store the contents of the global descriptor
* 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
- * the table and 2 bytes are used to store the limit. In 32-bit processes, the
- * only processes for which emulation is provided, X has a value of 4.
+ * the table and 2 bytes are used to store the limit. In 32-bit processes X
+ * 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_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
* @data: Buffer into which the dummy result is stored
* @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
* 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.
*/
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)
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.
*/
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. */
if (X86_MODRM_MOD(insn->modrm.value) == 3)
return -EINVAL;
@@ -228,13 +228,24 @@ static int emulate_umip_insn(struct insn *insn, int umip_inst,
else
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, *data_size);
- memcpy(data + 2, &dummy_base_addr, UMIP_GDT_IDT_BASE_SIZE);
+ *data_size += UMIP_GDT_IDT_LIMIT_SIZE;
memcpy(data, &dummy_limit, UMIP_GDT_IDT_LIMIT_SIZE);
} 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
@@ -291,10 +302,9 @@ static void force_sig_info_umip_fault(void __user *addr, struct pt_regs *regs)
* @regs: Registers as saved when entering the #GP handler
*
* The instructions sgdt, sidt, str, smsw, sldt cause a general protection
- * fault if executed with CPL > 0 (i.e., from user space). If the offending
- * user-space process is not in long mode, this function fixes the exception
- * up and provides dummy results for sgdt, sidt and smsw; str and sldt are not
- * fixed up. Also long mode user-space processes are not fixed up.
+ * fault if executed with CPL > 0 (i.e., from user space). This function fixes
+ * the exception up and provides dummy results for sgdt, sidt and smsw; str
+ * and sldt are not fixed up.
*
* 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
@@ -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_insns[umip_inst]);
- /* Do not emulate SLDT, STR or user long mode processes. */
- if (umip_inst == UMIP_INST_STR || umip_inst == UMIP_INST_SLDT || user_64bit_mode(regs))
+ /* Do not emulate SLDT or STR. */
+ if (umip_inst == UMIP_INST_STR || umip_inst == UMIP_INST_SLDT)
return false;
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;
/*
--
2.17.1