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-rw-r--r--arch/x86/mm/kmemcheck/opcode.c106
1 files changed, 106 insertions, 0 deletions
diff --git a/arch/x86/mm/kmemcheck/opcode.c b/arch/x86/mm/kmemcheck/opcode.c
new file mode 100644
index 000000000000..63c19e27aa6f
--- /dev/null
+++ b/arch/x86/mm/kmemcheck/opcode.c
@@ -0,0 +1,106 @@
1#include <linux/types.h>
2
3#include "opcode.h"
4
5static bool opcode_is_prefix(uint8_t b)
6{
7 return
8 /* Group 1 */
9 b == 0xf0 || b == 0xf2 || b == 0xf3
10 /* Group 2 */
11 || b == 0x2e || b == 0x36 || b == 0x3e || b == 0x26
12 || b == 0x64 || b == 0x65 || b == 0x2e || b == 0x3e
13 /* Group 3 */
14 || b == 0x66
15 /* Group 4 */
16 || b == 0x67;
17}
18
19#ifdef CONFIG_X86_64
20static bool opcode_is_rex_prefix(uint8_t b)
21{
22 return (b & 0xf0) == 0x40;
23}
24#else
25static bool opcode_is_rex_prefix(uint8_t b)
26{
27 return false;
28}
29#endif
30
31#define REX_W (1 << 3)
32
33/*
34 * This is a VERY crude opcode decoder. We only need to find the size of the
35 * load/store that caused our #PF and this should work for all the opcodes
36 * that we care about. Moreover, the ones who invented this instruction set
37 * should be shot.
38 */
39void kmemcheck_opcode_decode(const uint8_t *op, unsigned int *size)
40{
41 /* Default operand size */
42 int operand_size_override = 4;
43
44 /* prefixes */
45 for (; opcode_is_prefix(*op); ++op) {
46 if (*op == 0x66)
47 operand_size_override = 2;
48 }
49
50 /* REX prefix */
51 if (opcode_is_rex_prefix(*op)) {
52 uint8_t rex = *op;
53
54 ++op;
55 if (rex & REX_W) {
56 switch (*op) {
57 case 0x63:
58 *size = 4;
59 return;
60 case 0x0f:
61 ++op;
62
63 switch (*op) {
64 case 0xb6:
65 case 0xbe:
66 *size = 1;
67 return;
68 case 0xb7:
69 case 0xbf:
70 *size = 2;
71 return;
72 }
73
74 break;
75 }
76
77 *size = 8;
78 return;
79 }
80 }
81
82 /* escape opcode */
83 if (*op == 0x0f) {
84 ++op;
85
86 /*
87 * This is move with zero-extend and sign-extend, respectively;
88 * we don't have to think about 0xb6/0xbe, because this is
89 * already handled in the conditional below.
90 */
91 if (*op == 0xb7 || *op == 0xbf)
92 operand_size_override = 2;
93 }
94
95 *size = (*op & 1) ? operand_size_override : 1;
96}
97
98const uint8_t *kmemcheck_opcode_get_primary(const uint8_t *op)
99{
100 /* skip prefixes */
101 while (opcode_is_prefix(*op))
102 ++op;
103 if (opcode_is_rex_prefix(*op))
104 ++op;
105 return op;
106}