1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * linux/arch/arm/kernel/opcodes.c
4 *
5 * A32 condition code lookup feature moved from nwfpe/fpopcode.c
6 */
7
8 #include <linux/module.h>
9 #include <asm/opcodes.h>
10
11 #define ARM_OPCODE_CONDITION_UNCOND 0xf
12
13 /*
14 * condition code lookup table
15 * index into the table is test code: EQ, NE, ... LT, GT, AL, NV
16 *
17 * bit position in short is condition code: NZCV
18 */
19 static const unsigned short cc_map[16] = {
20 0xF0F0, /* EQ == Z set */
21 0x0F0F, /* NE */
22 0xCCCC, /* CS == C set */
23 0x3333, /* CC */
24 0xFF00, /* MI == N set */
25 0x00FF, /* PL */
26 0xAAAA, /* VS == V set */
27 0x5555, /* VC */
28 0x0C0C, /* HI == C set && Z clear */
29 0xF3F3, /* LS == C clear || Z set */
30 0xAA55, /* GE == (N==V) */
31 0x55AA, /* LT == (N!=V) */
32 0x0A05, /* GT == (!Z && (N==V)) */
33 0xF5FA, /* LE == (Z || (N!=V)) */
34 0xFFFF, /* AL always */
35 0 /* NV */
36 };
37
38 /*
39 * Returns:
40 * ARM_OPCODE_CONDTEST_FAIL - if condition fails
41 * ARM_OPCODE_CONDTEST_PASS - if condition passes (including AL)
42 * ARM_OPCODE_CONDTEST_UNCOND - if NV condition, or separate unconditional
43 * opcode space from v5 onwards
44 *
45 * Code that tests whether a conditional instruction would pass its condition
46 * check should check that return value == ARM_OPCODE_CONDTEST_PASS.
47 *
48 * Code that tests if a condition means that the instruction would be executed
49 * (regardless of conditional or unconditional) should instead check that the
50 * return value != ARM_OPCODE_CONDTEST_FAIL.
51 */
52 asmlinkage unsigned int arm_check_condition(u32 opcode, u32 psr)
53 {
54 u32 cc_bits = opcode >> 28;
55 u32 psr_cond = psr >> 28;
56 unsigned int ret;
57
58 if (cc_bits != ARM_OPCODE_CONDITION_UNCOND) {
59 if ((cc_map[cc_bits] >> (psr_cond)) & 1)
60 ret = ARM_OPCODE_CONDTEST_PASS;
61 else
62 ret = ARM_OPCODE_CONDTEST_FAIL;
63 } else {
64 ret = ARM_OPCODE_CONDTEST_UNCOND;
65 }
66
67 return ret;
68 }
69 EXPORT_SYMBOL_GPL(arm_check_condition);