107 lines
1.9 KiB
C
107 lines
1.9 KiB
C
#include <linux/types.h>
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#include "opcode.h"
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static bool opcode_is_prefix(uint8_t b)
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{
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return
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/* Group 1 */
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b == 0xf0 || b == 0xf2 || b == 0xf3
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/* Group 2 */
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|| b == 0x2e || b == 0x36 || b == 0x3e || b == 0x26
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|| b == 0x64 || b == 0x65
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/* Group 3 */
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|| b == 0x66
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/* Group 4 */
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|| b == 0x67;
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}
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#ifdef CONFIG_X86_64
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static bool opcode_is_rex_prefix(uint8_t b)
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{
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return (b & 0xf0) == 0x40;
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}
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#else
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static bool opcode_is_rex_prefix(uint8_t b)
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{
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return false;
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}
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#endif
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#define REX_W (1 << 3)
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/*
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* This is a VERY crude opcode decoder. We only need to find the size of the
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* load/store that caused our #PF and this should work for all the opcodes
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* that we care about. Moreover, the ones who invented this instruction set
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* should be shot.
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*/
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void kmemcheck_opcode_decode(const uint8_t *op, unsigned int *size)
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{
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/* Default operand size */
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int operand_size_override = 4;
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/* prefixes */
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for (; opcode_is_prefix(*op); ++op) {
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if (*op == 0x66)
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operand_size_override = 2;
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}
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/* REX prefix */
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if (opcode_is_rex_prefix(*op)) {
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uint8_t rex = *op;
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++op;
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if (rex & REX_W) {
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switch (*op) {
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case 0x63:
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*size = 4;
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return;
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case 0x0f:
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++op;
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switch (*op) {
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case 0xb6:
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case 0xbe:
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*size = 1;
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return;
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case 0xb7:
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case 0xbf:
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*size = 2;
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return;
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}
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break;
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}
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*size = 8;
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return;
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}
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}
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/* escape opcode */
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if (*op == 0x0f) {
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++op;
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/*
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* This is move with zero-extend and sign-extend, respectively;
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* we don't have to think about 0xb6/0xbe, because this is
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* already handled in the conditional below.
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*/
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if (*op == 0xb7 || *op == 0xbf)
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operand_size_override = 2;
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}
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*size = (*op & 1) ? operand_size_override : 1;
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}
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const uint8_t *kmemcheck_opcode_get_primary(const uint8_t *op)
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{
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/* skip prefixes */
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while (opcode_is_prefix(*op))
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++op;
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if (opcode_is_rex_prefix(*op))
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++op;
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return op;
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}
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