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);