opcodes/wasm32-dis.c

   1 /* Opcode printing code for the WebAssembly target
   2    Copyright (C) 2017-2020 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 "bfd_stdint.h"
  31
  32 /* Type names for blocks and signatures.  */
  33 #define BLOCK_TYPE_NONE              0x40
  34 #define BLOCK_TYPE_I32               0x7f
  35 #define BLOCK_TYPE_I64               0x7e
  36 #define BLOCK_TYPE_F32               0x7d
  37 #define BLOCK_TYPE_F64               0x7c
  38
  39 enum wasm_class
  40 {
  41   wasm_typed,
  42   wasm_special,
  43   wasm_break,
  44   wasm_break_if,
  45   wasm_break_table,
  46   wasm_return,
  47   wasm_call,
  48   wasm_call_import,
  49   wasm_call_indirect,
  50   wasm_get_local,
  51   wasm_set_local,
  52   wasm_tee_local,
  53   wasm_drop,
  54   wasm_constant_i32,
  55   wasm_constant_i64,
  56   wasm_constant_f32,
  57   wasm_constant_f64,
  58   wasm_unary,
  59   wasm_binary,
  60   wasm_conv,
  61   wasm_load,
  62   wasm_store,
  63   wasm_select,
  64   wasm_relational,
  65   wasm_eqz,
  66   wasm_current_memory,
  67   wasm_grow_memory,
  68   wasm_signature
  69 };
  70
  71 struct wasm32_private_data
  72 {
  73   bfd_boolean print_registers;
  74   bfd_boolean print_well_known_globals;
  75
  76   /* Limit valid symbols to those with a given prefix.  */
  77   const char *section_prefix;
  78 };
  79
  80 typedef struct
  81 {
  82   const char *name;
  83   const char *description;
  84 } wasm32_options_t;
  85
  86 static const wasm32_options_t options[] =
  87 {
  88   { "registers", N_("Disassemble \"register\" names") },
  89   { "globals",   N_("Name well-known globals") },
  90 };
  91
  92 #define WASM_OPCODE(opcode, name, intype, outtype, clas, signedness)     \
  93   { name, wasm_ ## clas, opcode },
  94
  95 struct wasm32_opcode_s
  96 {
  97   const char *name;
  98   enum wasm_class clas;
  99   unsigned char opcode;
 100 } wasm32_opcodes[] =
 101 {
 102 #include "opcode/wasm.h"
 103   { NULL, 0, 0 }
 104 };
 105
 106 /* Parse the disassembler options in OPTS and initialize INFO.  */
 107
 108 static void
 109 parse_wasm32_disassembler_options (struct disassemble_info *info,
 110                                    const char *opts)
 111 {
 112   struct wasm32_private_data *private = info->private_data;
 113
 114   while (opts != NULL)
 115     {
 116       if (CONST_STRNEQ (opts, "registers"))
 117         private->print_registers = TRUE;
 118       else if (CONST_STRNEQ (opts, "globals"))
 119         private->print_well_known_globals = TRUE;
 120
 121       opts = strchr (opts, ',');
 122       if (opts)
 123         opts++;
 124     }
 125 }
 126
 127 /* Check whether SYM is valid.  Special-case absolute symbols, which
 128    are unhelpful to print, and arguments to a "call" insn, which we
 129    want to be in a section matching a given prefix.  */
 130
 131 static bfd_boolean
 132 wasm32_symbol_is_valid (asymbol *sym,
 133                         struct disassemble_info *info)
 134 {
 135   struct wasm32_private_data *private_data = info->private_data;
 136
 137   if (sym == NULL)
 138     return FALSE;
 139
 140   if (strcmp(sym->section->name, "*ABS*") == 0)
 141     return FALSE;
 142
 143   if (private_data && private_data->section_prefix != NULL
 144       && strncmp (sym->section->name, private_data->section_prefix,
 145                   strlen (private_data->section_prefix)))
 146     return FALSE;
 147
 148   return TRUE;
 149 }
 150
 151 /* Initialize the disassembler structures for INFO.  */
 152
 153 void
 154 disassemble_init_wasm32 (struct disassemble_info *info)
 155 {
 156   if (info->private_data == NULL)
 157     {
 158       static struct wasm32_private_data private;
 159
 160       private.print_registers = FALSE;
 161       private.print_well_known_globals = FALSE;
 162       private.section_prefix = NULL;
 163
 164       info->private_data = &private;
 165     }
 166
 167   if (info->disassembler_options)
 168     {
 169       parse_wasm32_disassembler_options (info, info->disassembler_options);
 170
 171       info->disassembler_options = NULL;
 172     }
 173
 174   info->symbol_is_valid = wasm32_symbol_is_valid;
 175 }
 176
 177 /* Read an LEB128-encoded integer from INFO at address PC, reading one
 178    byte at a time.  Set ERROR_RETURN if no complete integer could be
 179    read, LENGTH_RETURN to the number oof bytes read (including bytes
 180    in incomplete numbers).  SIGN means interpret the number as
 181    SLEB128.  Unfortunately, this is a duplicate of wasm-module.c's
 182    wasm_read_leb128 ().  */
 183
 184 static uint64_t
 185 wasm_read_leb128 (bfd_vma                   pc,
 186                   struct disassemble_info * info,
 187                   bfd_boolean *             error_return,
 188                   unsigned int *            length_return,
 189                   bfd_boolean               sign)
 190 {
 191   uint64_t result = 0;
 192   unsigned int num_read = 0;
 193   unsigned int shift = 0;
 194   unsigned char byte = 0;
 195   int status = 1;
 196
 197   while (info->read_memory_func (pc + num_read, &byte, 1, info) == 0)
 198     {
 199       num_read++;
 200
 201       if (shift < sizeof (result) * 8)
 202         {
 203           result |= ((uint64_t) (byte & 0x7f)) << shift;
 204           if ((result >> shift) != (byte & 0x7f))
 205             /* Overflow.  */
 206             status |= 2;
 207           shift += 7;
 208         }
 209       else if ((byte & 0x7f) != 0)
 210         status |= 2;
 211
 212       if ((byte & 0x80) == 0)
 213         {
 214           status &= ~1;
 215           if (sign && (shift < 8 * sizeof (result)) && (byte & 0x40))
 216             result |= -((uint64_t) 1 << shift);
 217           break;
 218         }
 219     }
 220
 221   if (length_return != NULL)
 222     *length_return = num_read;
 223   if (error_return != NULL)
 224     *error_return = status != 0;
 225
 226   return result;
 227 }
 228
 229 /* Read a 32-bit IEEE float from PC using INFO, convert it to a host
 230    double, and store it at VALUE.  */
 231
 232 static int
 233 read_f32 (double *value, bfd_vma pc, struct disassemble_info *info)
 234 {
 235   bfd_byte buf[4];
 236
 237   if (info->read_memory_func (pc, buf, sizeof (buf), info))
 238     return -1;
 239
 240   floatformat_to_double (&floatformat_ieee_single_little, buf,
 241                          value);
 242
 243   return sizeof (buf);
 244 }
 245
 246 /* Read a 64-bit IEEE float from PC using INFO, convert it to a host
 247    double, and store it at VALUE.  */
 248
 249 static int
 250 read_f64 (double *value, bfd_vma pc, struct disassemble_info *info)
 251 {
 252   bfd_byte buf[8];
 253
 254   if (info->read_memory_func (pc, buf, sizeof (buf), info))
 255     return -1;
 256
 257   floatformat_to_double (&floatformat_ieee_double_little, buf,
 258                          value);
 259
 260   return sizeof (buf);
 261 }
 262
 263 /* Main disassembly routine.  Disassemble insn at PC using INFO.  */
 264
 265 int
 266 print_insn_wasm32 (bfd_vma pc, struct disassemble_info *info)
 267 {
 268   unsigned char opcode;
 269   struct wasm32_opcode_s *op;
 270   bfd_byte buffer[16];
 271   void *stream = info->stream;
 272   fprintf_ftype prin = info->fprintf_func;
 273   struct wasm32_private_data *private_data = info->private_data;
 274   long long constant = 0;
 275   double fconstant = 0.0;
 276   long flags = 0;
 277   long offset = 0;
 278   long depth = 0;
 279   long function_index = 0;
 280   long target_count = 0;
 281   long block_type = 0;
 282   int len = 1;
 283   int ret = 0;
 284   unsigned int bytes_read = 0;
 285   int i;
 286   const char *locals[] =
 287     {
 288       "$dpc", "$sp1", "$r0", "$r1", "$rpc", "$pc0",
 289       "$rp", "$fp", "$sp",
 290       "$r2", "$r3", "$r4", "$r5", "$r6", "$r7",
 291       "$i0", "$i1", "$i2", "$i3", "$i4", "$i5", "$i6", "$i7",
 292       "$f0", "$f1", "$f2", "$f3", "$f4", "$f5", "$f6", "$f7",
 293     };
 294   int nlocals = ARRAY_SIZE (locals);
 295   const char *globals[] =
 296     {
 297       "$got", "$plt", "$gpo"
 298     };
 299   int nglobals = ARRAY_SIZE (globals);
 300   bfd_boolean error = FALSE;
 301
 302   if (info->read_memory_func (pc, buffer, 1, info))
 303     return -1;
 304
 305   opcode = buffer[0];
 306
 307   for (op = wasm32_opcodes; op->name; op++)
 308     if (op->opcode == opcode)
 309       break;
 310
 311   if (!op->name)
 312     {
 313       prin (stream, "\t.byte 0x%02x\n", buffer[0]);
 314       return 1;
 315     }
 316   else
 317     {
 318       len = 1;
 319
 320       prin (stream, "\t");
 321       prin (stream, "%s", op->name);
 322
 323       if (op->clas == wasm_typed)
 324         {
 325           block_type = wasm_read_leb128
 326             (pc + len, info, &error, &bytes_read, FALSE);
 327           if (error)
 328             return -1;
 329           len += bytes_read;
 330           switch (block_type)
 331             {
 332             case BLOCK_TYPE_NONE:
 333               prin (stream, "[]");
 334               break;
 335             case BLOCK_TYPE_I32:
 336               prin (stream, "[i]");
 337               break;
 338             case BLOCK_TYPE_I64:
 339               prin (stream, "[l]");
 340               break;
 341             case BLOCK_TYPE_F32:
 342               prin (stream, "[f]");
 343               break;
 344             case BLOCK_TYPE_F64:
 345               prin (stream, "[d]");
 346               break;
 347             }
 348         }
 349
 350       switch (op->clas)
 351         {
 352         case wasm_special:
 353         case wasm_eqz:
 354         case wasm_binary:
 355         case wasm_unary:
 356         case wasm_conv:
 357         case wasm_relational:
 358         case wasm_drop:
 359         case wasm_signature:
 360         case wasm_call_import:
 361         case wasm_typed:
 362         case wasm_select:
 363           break;
 364
 365         case wasm_break_table:
 366           target_count = wasm_read_leb128
 367             (pc + len, info, &error, &bytes_read, FALSE);
 368           if (error)
 369             return -1;
 370           len += bytes_read;
 371           prin (stream, " %ld", target_count);
 372           for (i = 0; i < target_count + 1; i++)
 373             {
 374               long target = 0;
 375               target = wasm_read_leb128
 376                 (pc + len, info, &error, &bytes_read, FALSE);
 377               if (error)
 378                 return -1;
 379               len += bytes_read;
 380               prin (stream, " %ld", target);
 381             }
 382           break;
 383
 384         case wasm_break:
 385         case wasm_break_if:
 386           depth = wasm_read_leb128
 387             (pc + len, info, &error, &bytes_read, FALSE);
 388           if (error)
 389             return -1;
 390           len += bytes_read;
 391           prin (stream, " %ld", depth);
 392           break;
 393
 394         case wasm_return:
 395           break;
 396
 397         case wasm_constant_i32:
 398         case wasm_constant_i64:
 399           constant = wasm_read_leb128
 400             (pc + len, info, &error, &bytes_read, TRUE);
 401           if (error)
 402             return -1;
 403           len += bytes_read;
 404           prin (stream, " %lld", constant);
 405           break;
 406
 407         case wasm_constant_f32:
 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           break;
 416
 417         case wasm_constant_f64:
 418           ret = read_f64 (&fconstant, pc + len, info);
 419           if (ret < 0)
 420             return -1;
 421           len += ret;
 422           prin (stream, " %.17g", fconstant);
 423           break;
 424
 425         case wasm_call:
 426           function_index = wasm_read_leb128
 427             (pc + len, info, &error, &bytes_read, FALSE);
 428           if (error)
 429             return -1;
 430           len += bytes_read;
 431           prin (stream, " ");
 432           private_data->section_prefix = ".space.function_index";
 433           (*info->print_address_func) ((bfd_vma) function_index, info);
 434           private_data->section_prefix = NULL;
 435           break;
 436
 437         case wasm_call_indirect:
 438           constant = wasm_read_leb128
 439             (pc + len, info, &error, &bytes_read, FALSE);
 440           if (error)
 441             return -1;
 442           len += bytes_read;
 443           prin (stream, " %lld", constant);
 444           constant = wasm_read_leb128
 445             (pc + len, info, &error, &bytes_read, FALSE);
 446           if (error)
 447             return -1;
 448           len += bytes_read;
 449           prin (stream, " %lld", constant);
 450           break;
 451
 452         case wasm_get_local:
 453         case wasm_set_local:
 454         case wasm_tee_local:
 455           constant = wasm_read_leb128
 456             (pc + len, info, &error, &bytes_read, FALSE);
 457           if (error)
 458             return -1;
 459           len += bytes_read;
 460           prin (stream, " %lld", constant);
 461           if (strcmp (op->name + 4, "local") == 0)
 462             {
 463               if (private_data->print_registers
 464                   && constant >= 0 && constant < nlocals)
 465                 prin (stream, " <%s>", locals[constant]);
 466             }
 467           else
 468             {
 469               if (private_data->print_well_known_globals
 470                   && constant >= 0 && constant < nglobals)
 471                 prin (stream, " <%s>", globals[constant]);
 472             }
 473           break;
 474
 475         case wasm_grow_memory:
 476         case wasm_current_memory:
 477           constant = wasm_read_leb128
 478             (pc + len, info, &error, &bytes_read, FALSE);
 479           if (error)
 480             return -1;
 481           len += bytes_read;
 482           prin (stream, " %lld", constant);
 483           break;
 484
 485         case wasm_load:
 486         case wasm_store:
 487           flags = wasm_read_leb128
 488             (pc + len, info, &error, &bytes_read, FALSE);
 489           if (error)
 490             return -1;
 491           len += bytes_read;
 492           offset = wasm_read_leb128
 493             (pc + len, info, &error, &bytes_read, FALSE);
 494           if (error)
 495             return -1;
 496           len += bytes_read;
 497           prin (stream, " a=%ld %ld", flags, offset);
 498         }
 499     }
 500   return len;
 501 }
 502
 503 /* Print valid disassembler options to STREAM.  */
 504
 505 void
 506 print_wasm32_disassembler_options (FILE *stream)
 507 {
 508   unsigned int i, max_len = 0;
 509
 510   fprintf (stream, _("\
 511 The following WebAssembly-specific disassembler options are supported for use\n\
 512 with the -M switch:\n"));
 513
 514   for (i = 0; i < ARRAY_SIZE (options); i++)
 515     {
 516       unsigned int len = strlen (options[i].name);
 517
 518       if (max_len < len)
 519         max_len = len;
 520     }
 521
 522   for (i = 0, max_len++; i < ARRAY_SIZE (options); i++)
 523     fprintf (stream, "  %s%*c %s\n",
 524              options[i].name,
 525              (int)(max_len - strlen (options[i].name)), ' ',
 526              _(options[i].description));
 527 }