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#include <linux/types.h>
#include "opcode.h"
static bool opcode_is_prefix(uint8_t b)
{
return
/* Group 1 */
b == 0xf0 || b == 0xf2 || b == 0xf3
/* Group 2 */
|| b == 0x2e || b == 0x36 || b == 0x3e || b == 0x26
|| b == 0x64 || b == 0x65 || b == 0x2e || b == 0x3e
/* Group 3 */
|| b == 0x66
/* Group 4 */
|| b == 0x67;
}
static bool opcode_is_rex_prefix(uint8_t b)
{
return (b & 0xf0) == 0x40;
}
/*
* This is a VERY crude opcode decoder. We only need to find the size of the
* load/store that caused our #PF and this should work for all the opcodes
* that we care about. Moreover, the ones who invented this instruction set
* should be shot.
*/
void kmemcheck_opcode_decode(const uint8_t *op,
const uint8_t **rep_prefix, const uint8_t **rex_prefix,
unsigned int *size)
{
/* Default operand size */
int operand_size_override = 4;
*rep_prefix = NULL;
/* prefixes */
for (; opcode_is_prefix(*op); ++op) {
if (*op == 0xf2 || *op == 0xf3)
*rep_prefix = op;
if (*op == 0x66)
operand_size_override = 2;
}
*rex_prefix = NULL;
#ifdef CONFIG_X86_64
/* REX prefix */
if (opcode_is_rex_prefix(*op)) {
*rex_prefix = op;
if (*op & 0x08) {
*size = 8;
return;
}
++op;
}
#endif
/* escape opcode */
if (*op == 0x0f) {
++op;
if (*op == 0xb6) {
*size = 1;
return;
}
if (*op == 0xb7) {
*size = 2;
return;
}
}
*size = (*op & 1) ? operand_size_override : 1;
}
const uint8_t *kmemcheck_opcode_get_primary(const uint8_t *op)
{
/* skip prefixes */
while (opcode_is_prefix(*op))
++op;
if (opcode_is_rex_prefix(*op))
++op;
return op;
}
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