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  */
arm_check_condition(u32 opcode,u32 psr)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);
70