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// SPDX-License-Identifier: GPL-2.0
#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
/* Group 3 */
|| b == 0x66
/* Group 4 */
|| b == 0x67;
}
#ifdef CONFIG_X86_64
static bool opcode_is_rex_prefix(uint8_t b)
{
return (b & 0xf0) == 0x40;
}
#else
static bool opcode_is_rex_prefix(uint8_t b)
{
return false;
}
#endif
#define REX_W (1 << 3)
/*
* 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, unsigned int *size)
{
/* Default operand size */
int operand_size_override = 4;
/* prefixes */
for (; opcode_is_prefix(*op); ++op) {
if (*op == 0x66)
operand_size_override = 2;
}
/* REX prefix */
if (opcode_is_rex_prefix(*op)) {
uint8_t rex = *op;
++op;
if (rex & REX_W) {
switch (*op) {
case 0x63:
*size = 4;
return;
case 0x0f:
++op;
switch (*op) {
case 0xb6:
case 0xbe:
*size = 1;
return;
case 0xb7:
case 0xbf:
*size = 2;
return;
}
break;
}
*size = 8;
return;
}
}
/* escape opcode */
if (*op == 0x0f) {
++op;
/*
* This is move with zero-extend and sign-extend, respectively;
* we don't have to think about 0xb6/0xbe, because this is
* already handled in the conditional below.
*/
if (*op == 0xb7 || *op == 0xbf)
operand_size_override = 2;
}
*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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