opcodes/wasm32-dis.c

   1 /* Opcode printing code for the WebAssembly target
   2    Copyright (C) 2017-2024 Free Software Foundation, Inc.
   3
   4    This file is part of libopcodes.
   5
   6    This library is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    It is distributed in the hope that it will be useful, but WITHOUT
  12    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  13    or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
  14    License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software
  18    Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  19    MA 02110-1301, USA.  */
  20
  21 #include "sysdep.h"
  22 #include "disassemble.h"
  23 #include "opintl.h"
  24 #include "safe-ctype.h"
  25 #include "floatformat.h"
  26 #include "libiberty.h"
  27 #include "elf-bfd.h"
  28 #include "elf/internal.h"
  29 #include "elf/wasm32.h"
  30 #include <stdint.h>
  31
  32 #include <limits.h>
  33 #ifndef CHAR_BIT
  34 #define CHAR_BIT 8
  35 #endif
  36
  37 /* Type names for blocks and signatures.  */
  38 #define BLOCK_TYPE_NONE              0x40
  39 #define BLOCK_TYPE_I32               0x7f
  40 #define BLOCK_TYPE_I64               0x7e
  41 #define BLOCK_TYPE_F32               0x7d
  42 #define BLOCK_TYPE_F64               0x7c
  43
  44 enum wasm_class
  45 {
  46   wasm_typed,
  47   wasm_special,
  48   wasm_break,
  49   wasm_break_if,
  50   wasm_break_table,
  51   wasm_return,
  52   wasm_call,
  53   wasm_call_import,
  54   wasm_call_indirect,
  55   wasm_get_local,
  56   wasm_set_local,
  57   wasm_tee_local,
  58   wasm_drop,
  59   wasm_constant_i32,
  60   wasm_constant_i64,
  61   wasm_constant_f32,
  62   wasm_constant_f64,
  63   wasm_unary,
  64   wasm_binary,
  65   wasm_conv,
  66   wasm_load,
  67   wasm_store,
  68   wasm_select,
  69   wasm_relational,
  70   wasm_eqz,
  71   wasm_current_memory,
  72   wasm_grow_memory,
  73   wasm_signature
  74 };
  75
  76 struct wasm32_private_data
  77 {
  78   bool print_registers;
  79   bool print_well_known_globals;
  80
  81   /* Limit valid symbols to those with a given prefix.  */
  82   const char *section_prefix;
  83 };
  84
  85 typedef struct
  86 {
  87   const char *name;
  88   const char *description;
  89 } wasm32_options_t;
  90
  91 static const wasm32_options_t options[] =
  92 {
  93   { "registers", N_("Disassemble \"register\" names") },
  94   { "globals",   N_("Name well-known globals") },
  95 };
  96
  97 #define WASM_OPCODE(opcode, name, intype, outtype, clas, signedness)     \
  98   { name, wasm_ ## clas, opcode },
  99
 100 struct wasm32_opcode_s
 101 {
 102   const char *name;
 103   enum wasm_class clas;
 104   unsigned char opcode;
 105 } wasm32_opcodes[] =
 106 {
 107 #include "opcode/wasm.h"
 108   { NULL, 0, 0 }
 109 };
 110
 111 /* Parse the disassembler options in OPTS and initialize INFO.  */
 112
 113 static void
 114 parse_wasm32_disassembler_options (struct disassemble_info *info,
 115                                    const char *opts)
 116 {
 117   struct wasm32_private_data *private = info->private_data;
 118
 119   while (opts != NULL)
 120     {
 121       if (startswith (opts, "registers"))
 122         private->print_registers = true;
 123       else if (startswith (opts, "globals"))
 124         private->print_well_known_globals = true;
 125
 126       opts = strchr (opts, ',');
 127       if (opts)
 128         opts++;
 129     }
 130 }
 131
 132 /* Check whether SYM is valid.  Special-case absolute symbols, which
 133    are unhelpful to print, and arguments to a "call" insn, which we
 134    want to be in a section matching a given prefix.  */
 135
 136 static bool
 137 wasm32_symbol_is_valid (asymbol *sym,
 138                         struct disassemble_info *info)
 139 {
 140   struct wasm32_private_data *private_data = info->private_data;
 141
 142   if (sym == NULL)
 143     return false;
 144
 145   if (strcmp(sym->section->name, "*ABS*") == 0)
 146     return false;
 147
 148   if (private_data && private_data->section_prefix != NULL
 149       && strncmp (sym->section->name, private_data->section_prefix,
 150                   strlen (private_data->section_prefix)))
 151     return false;
 152
 153   return true;
 154 }
 155
 156 /* Initialize the disassembler structures for INFO.  */
 157
 158 void
 159 disassemble_init_wasm32 (struct disassemble_info *info)
 160 {
 161   if (info->private_data == NULL)
 162     {
 163       static struct wasm32_private_data private;
 164
 165       private.print_registers = false;
 166       private.print_well_known_globals = false;
 167       private.section_prefix = NULL;
 168
 169       info->private_data = &private;
 170     }
 171
 172   if (info->disassembler_options)
 173     {
 174       parse_wasm32_disassembler_options (info, info->disassembler_options);
 175
 176       info->disassembler_options = NULL;
 177     }
 178
 179   info->symbol_is_valid = wasm32_symbol_is_valid;
 180 }
 181
 182 /* Read an LEB128-encoded integer from INFO at address PC, reading one
 183    byte at a time.  Set ERROR_RETURN if no complete integer could be
 184    read, LENGTH_RETURN to the number oof bytes read (including bytes
 185    in incomplete numbers).  SIGN means interpret the number as
 186    SLEB128.  Unfortunately, this is a duplicate of wasm-module.c's
 187    wasm_read_leb128 ().  */
 188
 189 static uint64_t
 190 wasm_read_leb128 (bfd_vma pc,
 191                   struct disassemble_info *info,
 192                   bool *error_return,
 193                   unsigned int *length_return,
 194                   bool sign)
 195 {
 196   uint64_t result = 0;
 197   unsigned int num_read = 0;
 198   unsigned int shift = 0;
 199   unsigned char byte = 0;
 200   unsigned char lost, mask;
 201   int status = 1;
 202
 203   while (info->read_memory_func (pc + num_read, &byte, 1, info) == 0)
 204     {
 205       num_read++;
 206
 207       if (shift < CHAR_BIT * sizeof (result))
 208         {
 209           result |= ((uint64_t) (byte & 0x7f)) << shift;
 210           /* These bits overflowed.  */
 211           lost = byte ^ (result >> shift);
 212           /* And this is the mask of possible overflow bits.  */
 213           mask = 0x7f ^ ((uint64_t) 0x7f << shift >> shift);
 214           shift += 7;
 215         }
 216       else
 217         {
 218           lost = byte;
 219           mask = 0x7f;
 220         }
 221       if ((lost & mask) != (sign && (int64_t) result < 0 ? mask : 0))
 222         status |= 2;
 223
 224       if ((byte & 0x80) == 0)
 225         {
 226           status &= ~1;
 227           if (sign && shift < CHAR_BIT * sizeof (result) && (byte & 0x40))
 228             result |= -((uint64_t) 1 << shift);
 229           break;
 230         }
 231     }
 232
 233   if (length_return != NULL)
 234     *length_return = num_read;
 235   if (error_return != NULL)
 236     *error_return = status != 0;
 237
 238   return result;
 239 }
 240
 241 /* Read a 32-bit IEEE float from PC using INFO, convert it to a host
 242    double, and store it at VALUE.  */
 243
 244 static int
 245 read_f32 (double *value, bfd_vma pc, struct disassemble_info *info)
 246 {
 247   bfd_byte buf[4];
 248
 249   if (info->read_memory_func (pc, buf, sizeof (buf), info))
 250     return -1;
 251
 252   floatformat_to_double (&floatformat_ieee_single_little, buf,
 253                          value);
 254
 255   return sizeof (buf);
 256 }
 257
 258 /* Read a 64-bit IEEE float from PC using INFO, convert it to a host
 259    double, and store it at VALUE.  */
 260
 261 static int
 262 read_f64 (double *value, bfd_vma pc, struct disassemble_info *info)
 263 {
 264   bfd_byte buf[8];
 265
 266   if (info->read_memory_func (pc, buf, sizeof (buf), info))
 267     return -1;
 268
 269   floatformat_to_double (&floatformat_ieee_double_little, buf,
 270                          value);
 271
 272   return sizeof (buf);
 273 }
 274
 275 /* Main disassembly routine.  Disassemble insn at PC using INFO.  */
 276
 277 int
 278 print_insn_wasm32 (bfd_vma pc, struct disassemble_info *info)
 279 {
 280   unsigned char opcode;
 281   struct wasm32_opcode_s *op;
 282   bfd_byte buffer[16];
 283   void *stream = info->stream;
 284   fprintf_ftype prin = info->fprintf_func;
 285   struct wasm32_private_data *private_data = info->private_data;
 286   uint64_t val;
 287   int len;
 288   unsigned int bytes_read;
 289   bool error;
 290
 291   if (info->read_memory_func (pc, buffer, 1, info))
 292     return -1;
 293
 294   opcode = buffer[0];
 295
 296   for (op = wasm32_opcodes; op->name; op++)
 297     if (op->opcode == opcode)
 298       break;
 299
 300   if (!op->name)
 301     {
 302       prin (stream, "\t.byte 0x%02x\n", buffer[0]);
 303       return 1;
 304     }
 305
 306   len = 1;
 307
 308   prin (stream, "\t");
 309   prin (stream, "%s", op->name);
 310
 311   if (op->clas == wasm_typed)
 312     {
 313       val = wasm_read_leb128 (pc + len, info, &error, &bytes_read, false);
 314       if (error)
 315         return -1;
 316       len += bytes_read;
 317       switch (val)
 318         {
 319         case BLOCK_TYPE_NONE:
 320           prin (stream, "[]");
 321           break;
 322         case BLOCK_TYPE_I32:
 323           prin (stream, "[i]");
 324           break;
 325         case BLOCK_TYPE_I64:
 326           prin (stream, "[l]");
 327           break;
 328         case BLOCK_TYPE_F32:
 329           prin (stream, "[f]");
 330           break;
 331         case BLOCK_TYPE_F64:
 332           prin (stream, "[d]");
 333           break;
 334         default:
 335           return -1;
 336         }
 337     }
 338
 339   switch (op->clas)
 340     {
 341     case wasm_special:
 342     case wasm_eqz:
 343     case wasm_binary:
 344     case wasm_unary:
 345     case wasm_conv:
 346     case wasm_relational:
 347     case wasm_drop:
 348     case wasm_signature:
 349     case wasm_call_import:
 350     case wasm_typed:
 351     case wasm_select:
 352       break;
 353
 354     case wasm_break_table:
 355       {
 356         uint32_t target_count, i;
 357         val = wasm_read_leb128 (pc + len, info, &error, &bytes_read,
 358                                 false);
 359         target_count = val;
 360         if (error || target_count != val || target_count == (uint32_t) -1)
 361           return -1;
 362         len += bytes_read;
 363         prin (stream, " %u", target_count);
 364         for (i = 0; i < target_count + 1; i++)
 365           {
 366             uint32_t target;
 367             val = wasm_read_leb128 (pc + len, info, &error, &bytes_read,
 368                                     false);
 369             target = val;
 370             if (error || target != val)
 371               return -1;
 372             len += bytes_read;
 373             prin (stream, " %u", target);
 374           }
 375       }
 376       break;
 377
 378     case wasm_break:
 379     case wasm_break_if:
 380       {
 381         uint32_t depth;
 382         val = wasm_read_leb128 (pc + len, info, &error, &bytes_read,
 383                                 false);
 384         depth = val;
 385         if (error || depth != val)
 386           return -1;
 387         len += bytes_read;
 388         prin (stream, " %u", depth);
 389       }
 390       break;
 391
 392     case wasm_return:
 393       break;
 394
 395     case wasm_constant_i32:
 396     case wasm_constant_i64:
 397       val = wasm_read_leb128 (pc + len, info, &error, &bytes_read, true);
 398       if (error)
 399         return -1;
 400       len += bytes_read;
 401       prin (stream, " %" PRId64, val);
 402       break;
 403
 404     case wasm_constant_f32:
 405       {
 406         double fconstant;
 407         int ret;
 408         /* This appears to be the best we can do, even though we're
 409            using host doubles for WebAssembly floats.  */
 410         ret = read_f32 (&fconstant, pc + len, info);
 411         if (ret < 0)
 412           return -1;
 413         len += ret;
 414         prin (stream, " %.9g", fconstant);
 415       }
 416       break;
 417
 418     case wasm_constant_f64:
 419       {
 420         double fconstant;
 421         int ret;
 422         ret = read_f64 (&fconstant, pc + len, info);
 423         if (ret < 0)
 424           return -1;
 425         len += ret;
 426         prin (stream, " %.17g", fconstant);
 427       }
 428       break;
 429
 430     case wasm_call:
 431       {
 432         uint32_t function_index;
 433         val = wasm_read_leb128 (pc + len, info, &error, &bytes_read,
 434                                 false);
 435         function_index = val;
 436         if (error || function_index != val)
 437           return -1;
 438         len += bytes_read;
 439         prin (stream, " ");
 440         private_data->section_prefix = ".space.function_index";
 441         (*info->print_address_func) ((bfd_vma) function_index, info);
 442         private_data->section_prefix = NULL;
 443       }
 444       break;
 445
 446     case wasm_call_indirect:
 447       {
 448         uint32_t type_index, xtra_index;
 449         val = wasm_read_leb128 (pc + len, info, &error, &bytes_read,
 450                                 false);
 451         type_index = val;
 452         if (error || type_index != val)
 453           return -1;
 454         len += bytes_read;
 455         prin (stream, " %u", type_index);
 456         val = wasm_read_leb128 (pc + len, info, &error, &bytes_read,
 457                                 false);
 458         xtra_index = val;
 459         if (error || xtra_index != val)
 460           return -1;
 461         len += bytes_read;
 462         prin (stream, " %u", xtra_index);
 463       }
 464       break;
 465
 466     case wasm_get_local:
 467     case wasm_set_local:
 468     case wasm_tee_local:
 469       {
 470         uint32_t local_index;
 471         val = wasm_read_leb128 (pc + len, info, &error, &bytes_read,
 472                                 false);
 473         local_index = val;
 474         if (error || local_index != val)
 475           return -1;
 476         len += bytes_read;
 477         prin (stream, " %u", local_index);
 478         if (strcmp (op->name + 4, "local") == 0)
 479           {
 480             static const char *locals[] =
 481               {
 482                 "$dpc", "$sp1", "$r0", "$r1", "$rpc", "$pc0",
 483                 "$rp", "$fp", "$sp",
 484                 "$r2", "$r3", "$r4", "$r5", "$r6", "$r7",
 485                 "$i0", "$i1", "$i2", "$i3", "$i4", "$i5", "$i6", "$i7",
 486                 "$f0", "$f1", "$f2", "$f3", "$f4", "$f5", "$f6", "$f7",
 487               };
 488             if (private_data->print_registers
 489                 && local_index < ARRAY_SIZE (locals))
 490               prin (stream, " <%s>", locals[local_index]);
 491           }
 492         else
 493           {
 494             static const char *globals[] =
 495               {
 496                 "$got", "$plt", "$gpo"
 497               };
 498             if (private_data->print_well_known_globals
 499                 && local_index < ARRAY_SIZE (globals))
 500               prin (stream, " <%s>", globals[local_index]);
 501           }
 502       }
 503       break;
 504
 505     case wasm_grow_memory:
 506     case wasm_current_memory:
 507       {
 508         uint32_t reserved_size;
 509         val = wasm_read_leb128 (pc + len, info, &error, &bytes_read,
 510                                 false);
 511         reserved_size = val;
 512         if (error || reserved_size != val)
 513           return -1;
 514         len += bytes_read;
 515         prin (stream, " %u", reserved_size);
 516       }
 517       break;
 518
 519     case wasm_load:
 520     case wasm_store:
 521       {
 522         uint32_t flags, offset;
 523         val = wasm_read_leb128 (pc + len, info, &error, &bytes_read,
 524                                 false);
 525         flags = val;
 526         if (error || flags != val)
 527           return -1;
 528         len += bytes_read;
 529         val = wasm_read_leb128 (pc + len, info, &error, &bytes_read,
 530                                 false);
 531         offset = val;
 532         if (error || offset != val)
 533           return -1;
 534         len += bytes_read;
 535         prin (stream, " a=%u %u", flags, offset);
 536       }
 537       break;
 538     }
 539   return len;
 540 }
 541
 542 /* Print valid disassembler options to STREAM.  */
 543
 544 void
 545 print_wasm32_disassembler_options (FILE *stream)
 546 {
 547   unsigned int i, max_len = 0;
 548
 549   fprintf (stream, _("\
 550 The following WebAssembly-specific disassembler options are supported for use\n\
 551 with the -M switch:\n"));
 552
 553   for (i = 0; i < ARRAY_SIZE (options); i++)
 554     {
 555       unsigned int len = strlen (options[i].name);
 556
 557       if (max_len < len)
 558         max_len = len;
 559     }
 560
 561   for (i = 0, max_len++; i < ARRAY_SIZE (options); i++)
 562     fprintf (stream, "  %s%*c %s\n",
 563              options[i].name,
 564              (int)(max_len - strlen (options[i].name)), ' ',
 565              _(options[i].description));
 566 }