Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
[linux-3.10.git] / arch / arm / kernel / opcodes.c
1 /*
2  *  linux/arch/arm/kernel/opcodes.c
3  *
4  *  A32 condition code lookup feature moved from nwfpe/fpopcode.c
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 as
8  * published by the Free Software Foundation.
9  */
10
11 #include <linux/module.h>
12 #include <asm/opcodes.h>
13
14 #define ARM_OPCODE_CONDITION_UNCOND 0xf
15
16 /*
17  * condition code lookup table
18  * index into the table is test code: EQ, NE, ... LT, GT, AL, NV
19  *
20  * bit position in short is condition code: NZCV
21  */
22 static const unsigned short cc_map[16] = {
23         0xF0F0,                 /* EQ == Z set            */
24         0x0F0F,                 /* NE                     */
25         0xCCCC,                 /* CS == C set            */
26         0x3333,                 /* CC                     */
27         0xFF00,                 /* MI == N set            */
28         0x00FF,                 /* PL                     */
29         0xAAAA,                 /* VS == V set            */
30         0x5555,                 /* VC                     */
31         0x0C0C,                 /* HI == C set && Z clear */
32         0xF3F3,                 /* LS == C clear || Z set */
33         0xAA55,                 /* GE == (N==V)           */
34         0x55AA,                 /* LT == (N!=V)           */
35         0x0A05,                 /* GT == (!Z && (N==V))   */
36         0xF5FA,                 /* LE == (Z || (N!=V))    */
37         0xFFFF,                 /* AL always              */
38         0                       /* NV                     */
39 };
40
41 /*
42  * Returns:
43  * ARM_OPCODE_CONDTEST_FAIL   - if condition fails
44  * ARM_OPCODE_CONDTEST_PASS   - if condition passes (including AL)
45  * ARM_OPCODE_CONDTEST_UNCOND - if NV condition, or separate unconditional
46  *                              opcode space from v5 onwards
47  *
48  * Code that tests whether a conditional instruction would pass its condition
49  * check should check that return value == ARM_OPCODE_CONDTEST_PASS.
50  *
51  * Code that tests if a condition means that the instruction would be executed
52  * (regardless of conditional or unconditional) should instead check that the
53  * return value != ARM_OPCODE_CONDTEST_FAIL.
54  */
55 asmlinkage unsigned int arm_check_condition(u32 opcode, u32 psr)
56 {
57         u32 cc_bits  = opcode >> 28;
58         u32 psr_cond = psr >> 28;
59         unsigned int ret;
60
61         if (cc_bits != ARM_OPCODE_CONDITION_UNCOND) {
62                 if ((cc_map[cc_bits] >> (psr_cond)) & 1)
63                         ret = ARM_OPCODE_CONDTEST_PASS;
64                 else
65                         ret = ARM_OPCODE_CONDTEST_FAIL;
66         } else {
67                 ret = ARM_OPCODE_CONDTEST_UNCOND;
68         }
69
70         return ret;
71 }
72 EXPORT_SYMBOL_GPL(arm_check_condition);