lib/3rdparty/softx86/softx86/jumpy.c

   1 /*
   2  * jumpy.c
   3  *
   4  * Copyright (C) 2003, 2004 Jonathan Campbell <jcampbell@mdjk.com>
   5  *
   6  * Decompiler and executioneer for CALL/J<condition> instructions.
   7  *
   8  ***********************************************************************************
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU General Public License
  11  * as published by the Free Software Foundation; either version 2
  12  * of the License, or (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License
  20  * along with this program; if not, write to the Free Software
  21  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  22  ************************************************************************************/
  23
  24 #include <softx86.h>
  25 #include <memory.h>
  26 #include <stdio.h>
  27 #include <string.h>
  28 #include "optable.h"
  29 #include "jumpy.h"
  30
  31 int Sfx86OpcodeExec_jc(sx86_ubyte opcode,softx86_ctx* ctx)
  32 {
  33         int tf;
  34         sx86_udword rel;
  35
  36 /* Intel's tendancy to sort the instructions in their documentation alphabetically
  37    by name instead of by opcode tends to distort the fact that all of these
  38    opcodes (except for JCXZ) lie between 0x70 and 0x7F. */
  39         if (!(opcode == 0xE3 || ((opcode&0xF0) == 0x70))) return 0;
  40
  41         rel = (sx86_udword)softx86_fetch_exec_byte(ctx);
  42         if (rel & 0x80) rel |= 0xFFFFFF00;
  43         rel += ctx->state->reg_ip;
  44         rel &= 0xFFFF;
  45
  46 /* JCXZ */
  47         if (opcode == 0xE3)
  48                 tf = (ctx->state->general_reg[SX86_REG_CX].w.lo == 0);
  49 /* JO */
  50         else if (opcode == 0x70)
  51                 tf = (ctx->state->reg_flags.val & SX86_CPUFLAG_OVERFLOW);
  52 /* JNO */
  53         else if (opcode == 0x71)
  54                 tf = !(ctx->state->reg_flags.val & SX86_CPUFLAG_OVERFLOW);
  55 /* JC */
  56         else if (opcode == 0x72)
  57                 tf = (ctx->state->reg_flags.val & SX86_CPUFLAG_CARRY);
  58 /* JNC */
  59         else if (opcode == 0x73)
  60                 tf = !(ctx->state->reg_flags.val & SX86_CPUFLAG_CARRY);
  61 /* JZ */
  62         else if (opcode == 0x74)
  63                 tf = (ctx->state->reg_flags.val & SX86_CPUFLAG_ZERO);
  64 /* JNZ */
  65         else if (opcode == 0x75)
  66                 tf = !(ctx->state->reg_flags.val & SX86_CPUFLAG_ZERO);
  67 /* JBE */
  68         else if (opcode == 0x76)
  69                 tf =    (ctx->state->reg_flags.val & SX86_CPUFLAG_ZERO) ||
  70                         (ctx->state->reg_flags.val & SX86_CPUFLAG_CARRY);
  71 /* JA */
  72         else if (opcode == 0x77)
  73                 tf =    (!(ctx->state->reg_flags.val & SX86_CPUFLAG_ZERO)) &&
  74                         (!(ctx->state->reg_flags.val & SX86_CPUFLAG_CARRY));
  75 /* JS */
  76         else if (opcode == 0x78)
  77                 tf = (ctx->state->reg_flags.val & SX86_CPUFLAG_SIGN);
  78 /* JNS */
  79         else if (opcode == 0x79)
  80                 tf = !(ctx->state->reg_flags.val & SX86_CPUFLAG_SIGN);
  81 /* JP */
  82         else if (opcode == 0x7A)
  83                 tf = (ctx->state->reg_flags.val & SX86_CPUFLAG_PARITY);
  84 /* JNP */
  85         else if (opcode == 0x7B)
  86                 tf = !(ctx->state->reg_flags.val & SX86_CPUFLAG_PARITY);
  87 /* JL */
  88         else if (opcode == 0x7C)
  89                 tf =     (((ctx->state->reg_flags.val & SX86_CPUFLAG_SIGN) ? 1 : 0) !=
  90                           ((ctx->state->reg_flags.val & SX86_CPUFLAG_OVERFLOW) ? 1 : 0));
  91 /* JGE */
  92         else if (opcode == 0x7D)
  93                 tf =    ((ctx->state->reg_flags.val & SX86_CPUFLAG_SIGN) ? 1 : 0) ==
  94                         ((ctx->state->reg_flags.val & SX86_CPUFLAG_OVERFLOW) ? 1 : 0);
  95 /* JLE */
  96         else if (opcode == 0x7E)
  97                 tf =    (((ctx->state->reg_flags.val & SX86_CPUFLAG_SIGN) ? 1 : 0) !=
  98                          ((ctx->state->reg_flags.val & SX86_CPUFLAG_OVERFLOW) ? 1 : 0) ||
  99                          (ctx->state->reg_flags.val & SX86_CPUFLAG_ZERO));
 100 /* JG */
 101         else if (opcode == 0x7F)
 102                 tf =     (((ctx->state->reg_flags.val & SX86_CPUFLAG_SIGN) ? 1 : 0) ==
 103                           ((ctx->state->reg_flags.val & SX86_CPUFLAG_OVERFLOW) ? 1 : 0) &&
 104                         (!(ctx->state->reg_flags.val & SX86_CPUFLAG_ZERO)));
 105 /* should NOT be here !*/
 106         else
 107                 return 0;
 108
 109 /* if condition met, go! */
 110         if (tf)
 111                 softx86_set_instruction_ptr(ctx,ctx->state->segment_reg[SX86_SREG_CS].val,rel);
 112
 113         return 1;
 114 }
 115
 116 int Sfx86OpcodeDec_jc(sx86_ubyte opcode,softx86_ctx* ctx,char buf[128])
 117 {
 118         sx86_udword rel;
 119
 120 /* Intel's tendancy to sort the instructions in their documentation alphabetically
 121    by name instead of by opcode tends to distort the fact that all of these
 122    opcodes (except for JCXZ) lie between 0x70 and 0x7F. */
 123         if (!(opcode == 0xE3 || ((opcode&0xF0) == 0x70))) return 0;
 124
 125         rel = (sx86_udword)softx86_fetch_dec_byte(ctx);
 126         if (rel & 0x80) rel |= 0xFFFFFF00;
 127         rel += ctx->state->reg_ip_decompiler;
 128         rel &= 0xFFFF;
 129
 130         if (opcode == 0xE3)
 131                 sprintf(buf,"JCXZ %04Xh",rel);
 132         else if (opcode == 0x70)
 133                 sprintf(buf,"JO %04Xh",rel);
 134         else if (opcode == 0x71)
 135                 sprintf(buf,"JNO %04Xh",rel);
 136         else if (opcode == 0x72)
 137                 sprintf(buf,"JC %04Xh",rel);
 138         else if (opcode == 0x73)
 139                 sprintf(buf,"JNC %04Xh",rel);
 140         else if (opcode == 0x74)
 141                 sprintf(buf,"JZ %04Xh",rel);
 142         else if (opcode == 0x75)
 143                 sprintf(buf,"JNZ %04Xh",rel);
 144         else if (opcode == 0x76)
 145                 sprintf(buf,"JBE %04Xh",rel);
 146         else if (opcode == 0x77)
 147                 sprintf(buf,"JA %04Xh",rel);
 148         else if (opcode == 0x78)
 149                 sprintf(buf,"JS %04Xh",rel);
 150         else if (opcode == 0x79)
 151                 sprintf(buf,"JNS %04Xh",rel);
 152         else if (opcode == 0x7A)
 153                 sprintf(buf,"JP %04Xh",rel);
 154         else if (opcode == 0x7B)
 155                 sprintf(buf,"JNP %04Xh",rel);
 156         else if (opcode == 0x7C)
 157                 sprintf(buf,"JL %04Xh",rel);
 158         else if (opcode == 0x7D)
 159                 sprintf(buf,"JGE %04Xh",rel);
 160         else if (opcode == 0x7E)
 161                 sprintf(buf,"JLE %04Xh",rel);
 162         else if (opcode == 0x7F)
 163                 sprintf(buf,"JG %04Xh",rel);
 164 /* should NOT be here !*/
 165         else
 166                 return 0;
 167
 168         return 1;
 169 }
 170
 171 int Sfx86OpcodeExec_call(sx86_ubyte opcode,softx86_ctx* ctx)
 172 {
 173         if (opcode == 0x9A) {           // CALL FAR seg:offs
 174                 sx86_uword seg,ofs;
 175
 176                 ofs  =  (sx86_uword)softx86_fetch_exec_byte(ctx);
 177                 ofs |= ((sx86_uword)softx86_fetch_exec_byte(ctx))<<8;
 178                 seg  =  (sx86_uword)softx86_fetch_exec_byte(ctx);
 179                 seg |= ((sx86_uword)softx86_fetch_exec_byte(ctx))<<8;
 180                 softx86_stack_pushw(ctx,ctx->state->segment_reg[SX86_SREG_CS].val);
 181                 softx86_stack_pushw(ctx,ctx->state->reg_ip);
 182                 softx86_set_instruction_ptr(ctx,seg,ofs);
 183                 return 1;
 184         }
 185         else if (opcode == 0xE8) {      // CALL rel16
 186                 int ofs;
 187
 188                 ofs  =  (int)softx86_fetch_exec_byte(ctx);
 189                 ofs |= ((int)softx86_fetch_exec_byte(ctx))<<8;
 190                 if (ofs & 0x8000) ofs -= 0x10000;
 191                 ofs +=  ctx->state->reg_ip;
 192                 ofs &=  0xFFFF;
 193                 softx86_stack_pushw(ctx,ctx->state->reg_ip);
 194                 softx86_set_near_instruction_ptr(ctx,(sx86_udword)ofs);
 195                 return 1;
 196         }
 197
 198         return 0;
 199 }
 200
 201 int Sfx86OpcodeDec_call(sx86_ubyte opcode,softx86_ctx* ctx,char buf[128])
 202 {
 203         if (opcode == 0x9A) {           // CALL FAR seg:offs
 204                 sx86_uword seg,ofs;
 205
 206                 ofs  =  (sx86_uword)softx86_fetch_dec_byte(ctx);
 207                 ofs |= ((sx86_uword)softx86_fetch_dec_byte(ctx))<<8;
 208                 seg  =  (sx86_uword)softx86_fetch_dec_byte(ctx);
 209                 seg |= ((sx86_uword)softx86_fetch_dec_byte(ctx))<<8;
 210                 sprintf(buf,"CALL FAR %04X:%04X",seg,ofs);
 211                 return 1;
 212         }
 213         else if (opcode == 0xE8) {      // CALL rel16
 214                 int ofs;
 215
 216                 ofs  =  (int)softx86_fetch_dec_byte(ctx);
 217                 ofs |= ((int)softx86_fetch_dec_byte(ctx))<<8;
 218                 if (ofs & 0x8000) ofs -= 0x10000;
 219                 ofs +=  ctx->state->reg_ip_decompiler;
 220                 ofs &=  0xFFFF;
 221                 sprintf(buf,"CALL %04X",ofs);
 222                 return 1;
 223         }
 224
 225         return 0;
 226 }
 227
 228 int Sfx86OpcodeExec_jmp(sx86_ubyte opcode,softx86_ctx* ctx)
 229 {
 230         if (opcode == 0xE9) {           // JMP rel16
 231                 int ofs;
 232
 233                 ofs  =  (int)softx86_fetch_exec_byte(ctx);
 234                 ofs |= ((int)softx86_fetch_exec_byte(ctx))<<8;
 235                 if (ofs & 0x8000) ofs -= 0x10000;
 236                 ofs +=  ctx->state->reg_ip;
 237                 ofs &=  0xFFFF;
 238                 softx86_set_near_instruction_ptr(ctx,(sx86_udword)ofs);
 239                 return 1;
 240         }
 241         else if (opcode == 0xEA) {      // JMP FAR seg:offs
 242                 sx86_uword seg,ofs;
 243
 244                 ofs  =  (sx86_uword)softx86_fetch_exec_byte(ctx);
 245                 ofs |= ((sx86_uword)softx86_fetch_exec_byte(ctx))<<8;
 246                 seg  =  (sx86_uword)softx86_fetch_exec_byte(ctx);
 247                 seg |= ((sx86_uword)softx86_fetch_exec_byte(ctx))<<8;
 248                 softx86_set_instruction_ptr(ctx,seg,ofs);
 249                 return 1;
 250         }
 251         else if (opcode == 0xEB) {      // JMP rel8
 252                 int ofs;
 253
 254                 ofs  =  (int)softx86_fetch_exec_byte(ctx);
 255                 if (ofs & 0x80) ofs -= 0x100;
 256                 ofs +=  ctx->state->reg_ip;
 257                 ofs &=  0xFFFF;
 258                 softx86_set_near_instruction_ptr(ctx,(sx86_udword)ofs);
 259                 return 1;
 260         }
 261
 262         return 0;
 263 }
 264
 265 int Sfx86OpcodeDec_jmp(sx86_ubyte opcode,softx86_ctx* ctx,char buf[128])
 266 {
 267         if (opcode == 0xE9) {           // JMP rel16
 268                 int ofs;
 269
 270                 ofs  =  (int)softx86_fetch_dec_byte(ctx);
 271                 ofs |= ((int)softx86_fetch_dec_byte(ctx))<<8;
 272                 if (ofs & 0x8000) ofs -= 0x10000;
 273                 ofs +=  ctx->state->reg_ip_decompiler;
 274                 ofs &=  0xFFFF;
 275                 sprintf(buf,"JMP %04X",ofs);
 276                 return 1;
 277         }
 278         else if (opcode == 0xEA) {      // JMP FAR seg:offs
 279                 sx86_uword seg,ofs;
 280
 281                 ofs  =  (sx86_uword)softx86_fetch_dec_byte(ctx);
 282                 ofs |= ((sx86_uword)softx86_fetch_dec_byte(ctx))<<8;
 283                 seg  =  (sx86_uword)softx86_fetch_dec_byte(ctx);
 284                 seg |= ((sx86_uword)softx86_fetch_dec_byte(ctx))<<8;
 285                 sprintf(buf,"JMP FAR %04X:%04X",seg,ofs);
 286                 return 1;
 287         }
 288         else if (opcode == 0xEB) {      // JMP rel8
 289                 int ofs;
 290
 291                 ofs  =  (int)softx86_fetch_dec_byte(ctx);
 292                 if (ofs & 0x80) ofs -= 0x100;
 293                 ofs +=  ctx->state->reg_ip_decompiler;
 294                 ofs &=  0xFFFF;
 295                 sprintf(buf,"JMP %04X",ofs);
 296                 return 1;
 297         }
 298
 299         return 0;
 300 }
 301
 302 int Sfx86OpcodeExec_loop(sx86_ubyte opcode,softx86_ctx* ctx)
 303 {
 304         int tf;
 305         sx86_udword rel;
 306
 307         if (opcode < 0xE0 || opcode > 0xE2) return 0;
 308         rel = (sx86_udword)softx86_fetch_exec_byte(ctx);
 309         if (rel & 0x80) rel |= 0xFFFFFF00;
 310         rel += ctx->state->reg_ip;
 311         rel &= 0xFFFF;
 312
 313         ctx->state->general_reg[SX86_REG_CX].w.lo--;
 314
 315 /* LOOP */
 316         if (opcode == 0xE2)
 317                 tf =    (ctx->state->general_reg[SX86_REG_CX].w.lo != 0);
 318 /* LOOPZ */
 319         else if (opcode == 0xE1)
 320                 tf =    (ctx->state->reg_flags.val & SX86_CPUFLAG_ZERO) &&
 321                         (ctx->state->general_reg[SX86_REG_CX].w.lo != 0);
 322 /* LOOPNZ */
 323         else if (opcode == 0xE0)
 324                 tf =    ((ctx->state->reg_flags.val & SX86_CPUFLAG_ZERO) == 0) &&
 325                         (ctx->state->general_reg[SX86_REG_CX].w.lo != 0);
 326 /* should NOT be here !*/
 327         else
 328                 return 0;
 329
 330 /* if condition met, go! */
 331         if (tf)
 332                 softx86_set_instruction_ptr(ctx,ctx->state->segment_reg[SX86_SREG_CS].val,rel);
 333
 334         return 1;
 335 }
 336
 337 int Sfx86OpcodeDec_loop(sx86_ubyte opcode,softx86_ctx* ctx,char buf[128])
 338 {
 339         sx86_udword rel;
 340
 341         rel = (sx86_udword)softx86_fetch_dec_byte(ctx);
 342         if (rel & 0x80) rel |= 0xFFFFFF00;
 343         rel += ctx->state->reg_ip_decompiler;
 344         rel &= 0xFFFF;
 345
 346         if (opcode == 0xE2)
 347                 sprintf(buf,"LOOP %04Xh",rel);
 348         else if (opcode == 0xE1)
 349                 sprintf(buf,"LOOPZ %04Xh",rel);
 350         else if (opcode == 0xE0)
 351                 sprintf(buf,"LOOPNZ %04Xh",rel);
 352 /* should NOT be here !*/
 353         else
 354                 return 0;
 355
 356         return 1;
 357 }
 358