opcodes/s390-dis.c

   1 /* s390-dis.c -- Disassemble S390 instructions
   2    Copyright (C) 2000-2017 Free Software Foundation, Inc.
   3    Contributed by Martin Schwidefsky (schwidefsky@de.ibm.com).
   4
   5    This file is part of the GNU opcodes library.
   6
   7    This library is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3, or (at your option)
  10    any later version.
  11
  12    It is distributed in the hope that it will be useful, but WITHOUT
  13    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  14    or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
  15    License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this file; see the file COPYING.  If not, write to the
  19    Free Software Foundation, 51 Franklin Street - Fifth Floor, Boston,
  20    MA 02110-1301, USA.  */
  21
  22 #include "sysdep.h"
  23 #include <stdio.h>
  24 #include "ansidecl.h"
  25 #include "dis-asm.h"
  26 #include "opintl.h"
  27 #include "opcode/s390.h"
  28
  29 static int init_flag = 0;
  30 static int opc_index[256];
  31 static int current_arch_mask = 0;
  32 static int option_use_insn_len_bits_p = 0;
  33
  34 /* Set up index table for first opcode byte.  */
  35
  36 static void
  37 init_disasm (struct disassemble_info *info)
  38 {
  39   int i;
  40   const char *p;
  41
  42   memset (opc_index, 0, sizeof (opc_index));
  43
  44   /* Reverse order, such that each opc_index ends up pointing to the
  45      first matching entry instead of the last.  */
  46   for (i = s390_num_opcodes; i--; )
  47     opc_index[s390_opcodes[i].opcode[0]] = i;
  48
  49   for (p = info->disassembler_options; p != NULL; )
  50     {
  51       if (CONST_STRNEQ (p, "esa"))
  52         current_arch_mask = 1 << S390_OPCODE_ESA;
  53       else if (CONST_STRNEQ (p, "zarch"))
  54         current_arch_mask = 1 << S390_OPCODE_ZARCH;
  55       else if (CONST_STRNEQ (p, "insnlength"))
  56         option_use_insn_len_bits_p = 1;
  57       else
  58         fprintf (stderr, "Unknown S/390 disassembler option: %s\n", p);
  59
  60       p = strchr (p, ',');
  61       if (p != NULL)
  62         p++;
  63     }
  64
  65   if (!current_arch_mask)
  66     current_arch_mask = 1 << S390_OPCODE_ZARCH;
  67
  68   init_flag = 1;
  69 }
  70
  71 /* Derive the length of an instruction from its first byte.  */
  72
  73 static inline int
  74 s390_insn_length (const bfd_byte *buffer)
  75 {
  76   /* 00xxxxxx -> 2, 01xxxxxx/10xxxxxx -> 4, 11xxxxxx -> 6.  */
  77   return ((buffer[0] >> 6) + 3) & ~1U;
  78 }
  79
  80 /* Match the instruction in BUFFER against the given OPCODE, excluding
  81    the first byte.  */
  82
  83 static inline int
  84 s390_insn_matches_opcode (const bfd_byte *buffer,
  85                           const struct s390_opcode *opcode)
  86 {
  87   return (buffer[1] & opcode->mask[1]) == opcode->opcode[1]
  88     && (buffer[2] & opcode->mask[2]) == opcode->opcode[2]
  89     && (buffer[3] & opcode->mask[3]) == opcode->opcode[3]
  90     && (buffer[4] & opcode->mask[4]) == opcode->opcode[4]
  91     && (buffer[5] & opcode->mask[5]) == opcode->opcode[5];
  92 }
  93
  94 union operand_value
  95 {
  96   int i;
  97   unsigned int u;
  98 };
  99
 100 /* Extracts an operand value from an instruction.  */
 101 /* We do not perform the shift operation for larl-type address
 102    operands here since that would lead to an overflow of the 32 bit
 103    integer value.  Instead the shift operation is done when printing
 104    the operand.  */
 105
 106 static inline union operand_value
 107 s390_extract_operand (const bfd_byte *insn,
 108                       const struct s390_operand *operand)
 109 {
 110   union operand_value ret;
 111   unsigned int val;
 112   int bits;
 113   const bfd_byte *orig_insn = insn;
 114
 115   /* Extract fragments of the operand byte for byte.  */
 116   insn += operand->shift / 8;
 117   bits = (operand->shift & 7) + operand->bits;
 118   val = 0;
 119   do
 120     {
 121       val <<= 8;
 122       val |= (unsigned int) *insn++;
 123       bits -= 8;
 124     }
 125   while (bits > 0);
 126   val >>= -bits;
 127   val &= ((1U << (operand->bits - 1)) << 1) - 1;
 128
 129   /* Check for special long displacement case.  */
 130   if (operand->bits == 20 && operand->shift == 20)
 131     val = (val & 0xff) << 12 | (val & 0xfff00) >> 8;
 132
 133   /* Sign extend value if the operand is signed or pc relative.  Avoid
 134      integer overflows.  */
 135   if (operand->flags & (S390_OPERAND_SIGNED | S390_OPERAND_PCREL))
 136     {
 137       unsigned int m = 1U << (operand->bits - 1);
 138
 139       if (val >= m)
 140         ret.i = (int) (val - m) - 1 - (int) (m - 1U);
 141       else
 142         ret.i = (int) val;
 143     }
 144   else if (operand->flags & S390_OPERAND_LENGTH)
 145     /* Length x in an instruction has real length x + 1.  */
 146     ret.u = val + 1;
 147
 148   else if (operand->flags & S390_OPERAND_VR)
 149     {
 150       /* Extract the extra bits for a vector register operand stored
 151          in the RXB field.  */
 152       unsigned vr = operand->shift == 32 ? 3
 153         : (unsigned) operand->shift / 4 - 2;
 154
 155       ret.u = val | ((orig_insn[4] & (1 << (3 - vr))) << (vr + 1));
 156     }
 157   else
 158     ret.u = val;
 159
 160   return ret;
 161 }
 162
 163 /* Print the S390 instruction in BUFFER, assuming that it matches the
 164    given OPCODE.  */
 165
 166 static void
 167 s390_print_insn_with_opcode (bfd_vma memaddr,
 168                              struct disassemble_info *info,
 169                              const bfd_byte *buffer,
 170                              const struct s390_opcode *opcode)
 171 {
 172   const unsigned char *opindex;
 173   char separator;
 174
 175   /* Mnemonic.  */
 176   info->fprintf_func (info->stream, "%s", opcode->name);
 177
 178   /* Operands.  */
 179   separator = '\t';
 180   for (opindex = opcode->operands; *opindex != 0; opindex++)
 181     {
 182       const struct s390_operand *operand = s390_operands + *opindex;
 183       union operand_value val = s390_extract_operand (buffer, operand);
 184       unsigned long flags = operand->flags;
 185
 186       if ((flags & S390_OPERAND_INDEX) && val.u == 0)
 187         continue;
 188       if ((flags & S390_OPERAND_BASE) &&
 189           val.u == 0 && separator == '(')
 190         {
 191           separator = ',';
 192           continue;
 193         }
 194
 195       /* For instructions with a last optional operand don't print it
 196          if zero.  */
 197       if ((opcode->flags & S390_INSTR_FLAG_OPTPARM)
 198           && val.u == 0
 199           && opindex[1] == 0)
 200         break;
 201
 202       if (flags & S390_OPERAND_GPR)
 203         info->fprintf_func (info->stream, "%c%%r%u", separator, val.u);
 204       else if (flags & S390_OPERAND_FPR)
 205         info->fprintf_func (info->stream, "%c%%f%u", separator, val.u);
 206       else if (flags & S390_OPERAND_VR)
 207         info->fprintf_func (info->stream, "%c%%v%i", separator, val.u);
 208       else if (flags & S390_OPERAND_AR)
 209         info->fprintf_func (info->stream, "%c%%a%u", separator, val.u);
 210       else if (flags & S390_OPERAND_CR)
 211         info->fprintf_func (info->stream, "%c%%c%u", separator, val.u);
 212       else if (flags & S390_OPERAND_PCREL)
 213         {
 214           info->fprintf_func (info->stream, "%c", separator);
 215           info->print_address_func (memaddr + val.i + val.i, info);
 216         }
 217       else if (flags & S390_OPERAND_SIGNED)
 218         info->fprintf_func (info->stream, "%c%i", separator, val.i);
 219       else
 220         {
 221           if (flags & S390_OPERAND_OR1)
 222             val.u &= ~1;
 223           if (flags & S390_OPERAND_OR2)
 224             val.u &= ~2;
 225           if (flags & S390_OPERAND_OR8)
 226             val.u &= ~8;
 227
 228           if ((opcode->flags & S390_INSTR_FLAG_OPTPARM)
 229               && val.u == 0
 230               && opindex[1] == 0)
 231             break;
 232           info->fprintf_func (info->stream, "%c%u", separator, val.u);
 233         }
 234
 235       if (flags & S390_OPERAND_DISP)
 236         separator = '(';
 237       else if (flags & S390_OPERAND_BASE)
 238         {
 239           info->fprintf_func (info->stream, ")");
 240           separator = ',';
 241         }
 242       else
 243         separator = ',';
 244     }
 245 }
 246
 247 /* Check whether opcode A's mask is more specific than that of B.  */
 248
 249 static int
 250 opcode_mask_more_specific (const struct s390_opcode *a,
 251                            const struct s390_opcode *b)
 252 {
 253   return (((int) a->mask[0] + a->mask[1] + a->mask[2]
 254            + a->mask[3] + a->mask[4] + a->mask[5])
 255           > ((int) b->mask[0] + b->mask[1] + b->mask[2]
 256              + b->mask[3] + b->mask[4] + b->mask[5]));
 257 }
 258
 259 /* Print a S390 instruction.  */
 260
 261 int
 262 print_insn_s390 (bfd_vma memaddr, struct disassemble_info *info)
 263 {
 264   bfd_byte buffer[6];
 265   const struct s390_opcode *opcode = NULL;
 266   unsigned int value;
 267   int status, opsize, bufsize, bytes_to_dump, i;
 268
 269   if (init_flag == 0)
 270     init_disasm (info);
 271
 272   /* The output looks better if we put 6 bytes on a line.  */
 273   info->bytes_per_line = 6;
 274
 275   /* Every S390 instruction is max 6 bytes long.  */
 276   memset (buffer, 0, 6);
 277   status = info->read_memory_func (memaddr, buffer, 6, info);
 278   if (status != 0)
 279     {
 280       for (bufsize = 0; bufsize < 6; bufsize++)
 281         if (info->read_memory_func (memaddr, buffer, bufsize + 1, info) != 0)
 282           break;
 283       if (bufsize <= 0)
 284         {
 285           info->memory_error_func (status, memaddr, info);
 286           return -1;
 287         }
 288       opsize = s390_insn_length (buffer);
 289       status = opsize > bufsize;
 290     }
 291   else
 292     {
 293       bufsize = 6;
 294       opsize = s390_insn_length (buffer);
 295     }
 296
 297   if (status == 0)
 298     {
 299       const struct s390_opcode *op;
 300
 301       /* Find the "best match" in the opcode table.  */
 302       for (op = s390_opcodes + opc_index[buffer[0]];
 303            op != s390_opcodes + s390_num_opcodes
 304              && op->opcode[0] == buffer[0];
 305            op++)
 306         {
 307           if ((op->modes & current_arch_mask)
 308               && s390_insn_matches_opcode (buffer, op)
 309               && (opcode == NULL
 310                   || opcode_mask_more_specific (op, opcode)))
 311             opcode = op;
 312         }
 313
 314       if (opcode != NULL)
 315         {
 316           /* The instruction is valid.  Print it and return its size.  */
 317           s390_print_insn_with_opcode (memaddr, info, buffer, opcode);
 318           return opsize;
 319         }
 320     }
 321
 322   /* For code sections it makes sense to skip unknown instructions
 323      according to their length bits.  */
 324   if (status == 0
 325       && option_use_insn_len_bits_p
 326       && info->section != NULL
 327       && (info->section->flags & SEC_CODE))
 328     bytes_to_dump = opsize;
 329   else
 330     /* By default unknown instructions are printed as .long's/.short'
 331        depending on how many bytes are available.  */
 332     bytes_to_dump = bufsize >= 4 ? 4 : bufsize;
 333
 334   if (bytes_to_dump == 0)
 335     return 0;
 336
 337   /* Fall back to hex print.  */
 338   switch (bytes_to_dump)
 339     {
 340     case 4:
 341       value = (unsigned int) buffer[0];
 342       value = (value << 8) + (unsigned int) buffer[1];
 343       value = (value << 8) + (unsigned int) buffer[2];
 344       value = (value << 8) + (unsigned int) buffer[3];
 345       info->fprintf_func (info->stream, ".long\t0x%08x", value);
 346       return 4;
 347     case 2:
 348       value = (unsigned int) buffer[0];
 349       value = (value << 8) + (unsigned int) buffer[1];
 350       info->fprintf_func (info->stream, ".short\t0x%04x", value);
 351       return 2;
 352     default:
 353       info->fprintf_func (info->stream, ".byte\t0x%02x",
 354                           (unsigned int) buffer[0]);
 355       for (i = 1; i < bytes_to_dump; i++)
 356         info->fprintf_func (info->stream, ",0x%02x",
 357                           (unsigned int) buffer[i]);
 358       return bytes_to_dump;
 359     }
 360   return 0;
 361 }
 362
 363 void
 364 print_s390_disassembler_options (FILE *stream)
 365 {
 366   fprintf (stream, _("\n\
 367 The following S/390 specific disassembler options are supported for use\n\
 368 with the -M switch (multiple options should be separated by commas):\n"));
 369
 370   fprintf (stream, _("  esa         Disassemble in ESA architecture mode\n"));
 371   fprintf (stream, _("  zarch       Disassemble in z/Architecture mode\n"));
 372   fprintf (stream, _("  insnlength  Print unknown instructions according "
 373                      "to length from first two bits\n"));
 374 }