decoder.c

   1 /**
   2  * Author: Humberto Naves (hsnaves@gmail.com)
   3  */
   4
   5 #include <string.h>
   6
   7 #include "code.h"
   8 #include "utils.h"
   9
  10 int decode_instructions (struct code *c)
  11 {
  12   struct location *base;
  13   uint32 i, numopc, size, address;
  14   const uint8 *code;
  15   int slot = FALSE;
  16
  17   address = c->file->programs->vaddr;
  18   size = c->file->modinfo->expvaddr - 4;
  19   code = c->file->programs->data;
  20
  21   numopc = size >> 2;
  22
  23   if ((size & 0x03) || (address & 0x03)) {
  24     error (__FILE__ ": size/address is not multiple of 4");
  25     return 0;
  26   }
  27
  28   base = (struct location *) xmalloc ((numopc) * sizeof (struct location));
  29   memset (base, 0, (numopc) * sizeof (struct location));
  30
  31   c->base = base;
  32   c->end = &base[numopc - 1];
  33   c->baddr = address;
  34   c->numopc = numopc;
  35
  36   for (i = 0; i < numopc; i++) {
  37     struct location *loc = &base[i];
  38     uint32 tgt;
  39
  40
  41     loc->opc = code[i << 2];
  42     loc->opc |= code[(i << 2) + 1] << 8;
  43     loc->opc |= code[(i << 2) + 2] << 16;
  44     loc->opc |= code[(i << 2) + 3] << 24;
  45     loc->insn = allegrex_decode (loc->opc, FALSE);
  46     loc->address = address + (i << 2);
  47
  48     if (loc->insn == NULL) {
  49       loc->error = ERROR_INVALID_OPCODE;
  50       slot = FALSE;
  51       continue;
  52     }
  53
  54     /*
  55     if (INSN_TYPE (loc->insn->flags) != INSN_ALLEGREX) {
  56       slot = FALSE;
  57       continue;
  58     }
  59     */
  60
  61     if (loc->insn->flags & (INSN_BRANCH | INSN_JUMP)) {
  62       if (slot) c->base[i - 1].error = ERROR_DELAY_SLOT;
  63       slot = TRUE;
  64     } else {
  65       slot = FALSE;
  66     }
  67
  68     if (loc->insn->flags & INSN_BRANCH) {
  69       tgt = loc->opc & 0xFFFF;
  70       if (tgt & 0x8000) { tgt |= ~0xFFFF;  }
  71       tgt += i + 1;
  72       if (tgt < numopc) {
  73         loc->target = &base[tgt];
  74       } else {
  75         loc->error = ERROR_TARGET_OUTSIDE_FILE;
  76       }
  77
  78       if (location_gpr_used (loc) == 0 ||
  79           ((loc->insn->flags & INSN_READ_GPR_T) && RS (loc->opc) == RT (loc->opc))) {
  80         switch (loc->insn->insn) {
  81         case I_BEQ:
  82         case I_BEQL:
  83         case I_BGEZ:
  84         case I_BGEZAL:
  85         case I_BGEZL:
  86         case I_BLEZ:
  87         case I_BLEZL:
  88           loc->branchalways = TRUE;
  89           break;
  90         case I_BGTZ:
  91         case I_BGTZL:
  92         case I_BLTZ:
  93         case I_BLTZAL:
  94         case I_BLTZALL:
  95         case I_BLTZL:
  96         case I_BNE:
  97         case I_BNEL:
  98           loc->error = ERROR_ILLEGAL_BRANCH;
  99           break;
 100         default:
 101           loc->branchalways = FALSE;
 102         }
 103       }
 104
 105     } else if (loc->insn->insn == I_J || loc->insn->insn == I_JAL) {
 106       uint32 target_addr = (loc->opc & 0x3FFFFFF) << 2;;
 107       target_addr |= ((loc->address) & 0xF0000000);
 108       tgt = (target_addr - address) >> 2;
 109       if (tgt < numopc) {
 110         loc->target = &base[tgt];
 111       } else {
 112         loc->error = ERROR_TARGET_OUTSIDE_FILE;
 113       }
 114     }
 115   }
 116
 117   if (slot) {
 118     c->base[i - 1].error = ERROR_TARGET_OUTSIDE_FILE;
 119   }
 120
 121   return 1;
 122 }
 123
 124 uint32 location_gpr_used (struct location *loc)
 125 {
 126   uint32 result = 0;
 127
 128   if (loc->insn->flags & INSN_READ_GPR_S) {
 129     if (RS (loc->opc) != 0)
 130       result |= 1 << (RS (loc->opc));
 131   }
 132
 133   if (loc->insn->flags & INSN_READ_GPR_T) {
 134     if (RT (loc->opc) != 0)
 135       result |= 1 << (RT (loc->opc));
 136   }
 137
 138   if (loc->insn->flags & INSN_READ_GPR_D) {
 139     if (RD (loc->opc) != 0)
 140       result |= 1 << (RD (loc->opc));
 141   }
 142
 143   return result;
 144 }
 145
 146 uint32 location_gpr_defined (struct location *loc)
 147 {
 148   uint32 result = 0;
 149
 150   if (loc->insn->flags & INSN_LINK) {
 151     result |= 1 << 31;
 152   }
 153
 154   if (loc->insn->flags & INSN_WRITE_GPR_D) {
 155     if (RD (loc->opc) != 0)
 156       result |= 1 << (RD (loc->opc));
 157   }
 158
 159   if (loc->insn->flags & INSN_WRITE_GPR_T) {
 160     if (RT (loc->opc) != 0)
 161       result |= 1 << (RT (loc->opc));
 162   }
 163   return result;
 164 }
 165
 166 int location_branch_may_swap (struct location *branch)
 167 {
 168   int gpr_used, gpr_defined;
 169
 170   gpr_used = location_gpr_used (branch);
 171   gpr_defined = location_gpr_defined (&branch[1]);
 172   return  (!(gpr_used & gpr_defined));
 173 }