opcodes/wasm32-dis.c

   1 /* Opcode printing code for the WebAssembly target
   2    Copyright (C) 2017-2018 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 /* 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   bfd_boolean success = FALSE;
 196
 197   while (info->read_memory_func (pc + num_read, &byte, 1, info) == 0)
 198     {
 199       num_read++;
 200
 201       result |= ((bfd_vma) (byte & 0x7f)) << shift;
 202
 203       shift += 7;
 204       if ((byte & 0x80) == 0)
 205         {
 206           success = TRUE;
 207           break;
 208         }
 209     }
 210
 211   if (length_return != NULL)
 212     *length_return = num_read;
 213   if (error_return != NULL)
 214     *error_return = ! success;
 215
 216   if (sign && (shift < 8 * sizeof (result)) && (byte & 0x40))
 217     result |= -((uint64_t) 1 << shift);
 218
 219   return result;
 220 }
 221
 222 /* Read a 32-bit IEEE float from PC using INFO, convert it to a host
 223    double, and store it at VALUE.  */
 224
 225 static int
 226 read_f32 (double *value, bfd_vma pc, struct disassemble_info *info)
 227 {
 228   bfd_byte buf[4];
 229
 230   if (info->read_memory_func (pc, buf, sizeof (buf), info))
 231     return -1;
 232
 233   floatformat_to_double (&floatformat_ieee_single_little, buf,
 234                          value);
 235
 236   return sizeof (buf);
 237 }
 238
 239 /* Read a 64-bit IEEE float from PC using INFO, convert it to a host
 240    double, and store it at VALUE.  */
 241
 242 static int
 243 read_f64 (double *value, bfd_vma pc, struct disassemble_info *info)
 244 {
 245   bfd_byte buf[8];
 246
 247   if (info->read_memory_func (pc, buf, sizeof (buf), info))
 248     return -1;
 249
 250   floatformat_to_double (&floatformat_ieee_double_little, buf,
 251                          value);
 252
 253   return sizeof (buf);
 254 }
 255
 256 /* Main disassembly routine.  Disassemble insn at PC using INFO.  */
 257
 258 int
 259 print_insn_wasm32 (bfd_vma pc, struct disassemble_info *info)
 260 {
 261   unsigned char opcode;
 262   struct wasm32_opcode_s *op;
 263   bfd_byte buffer[16];
 264   void *stream = info->stream;
 265   fprintf_ftype prin = info->fprintf_func;
 266   struct wasm32_private_data *private_data = info->private_data;
 267   long long constant = 0;
 268   double fconstant = 0.0;
 269   long flags = 0;
 270   long offset = 0;
 271   long depth = 0;
 272   long function_index = 0;
 273   long target_count = 0;
 274   long block_type = 0;
 275   int len = 1;
 276   int ret = 0;
 277   unsigned int bytes_read = 0;
 278   int i;
 279   const char *locals[] =
 280     {
 281       "$dpc", "$sp1", "$r0", "$r1", "$rpc", "$pc0",
 282       "$rp", "$fp", "$sp",
 283       "$r2", "$r3", "$r4", "$r5", "$r6", "$r7",
 284       "$i0", "$i1", "$i2", "$i3", "$i4", "$i5", "$i6", "$i7",
 285       "$f0", "$f1", "$f2", "$f3", "$f4", "$f5", "$f6", "$f7",
 286     };
 287   int nlocals = ARRAY_SIZE (locals);
 288   const char *globals[] =
 289     {
 290       "$got", "$plt", "$gpo"
 291     };
 292   int nglobals = ARRAY_SIZE (globals);
 293   bfd_boolean error = FALSE;
 294
 295   if (info->read_memory_func (pc, buffer, 1, info))
 296     return -1;
 297
 298   opcode = buffer[0];
 299
 300   for (op = wasm32_opcodes; op->name; op++)
 301     if (op->opcode == opcode)
 302       break;
 303
 304   if (!op->name)
 305     {
 306       prin (stream, "\t.byte 0x%02x\n", buffer[0]);
 307       return 1;
 308     }
 309   else
 310     {
 311       len = 1;
 312
 313       prin (stream, "\t");
 314       prin (stream, "%s", op->name);
 315
 316       if (op->clas == wasm_typed)
 317         {
 318           block_type = wasm_read_leb128
 319             (pc + len, info, &error, &bytes_read, FALSE);
 320           if (error)
 321             return -1;
 322           len += bytes_read;
 323           switch (block_type)
 324             {
 325             case BLOCK_TYPE_NONE:
 326               prin (stream, "[]");
 327               break;
 328             case BLOCK_TYPE_I32:
 329               prin (stream, "[i]");
 330               break;
 331             case BLOCK_TYPE_I64:
 332               prin (stream, "[l]");
 333               break;
 334             case BLOCK_TYPE_F32:
 335               prin (stream, "[f]");
 336               break;
 337             case BLOCK_TYPE_F64:
 338               prin (stream, "[d]");
 339               break;
 340             }
 341         }
 342
 343       switch (op->clas)
 344         {
 345         case wasm_special:
 346         case wasm_eqz:
 347         case wasm_binary:
 348         case wasm_unary:
 349         case wasm_conv:
 350         case wasm_relational:
 351         case wasm_drop:
 352         case wasm_signature:
 353         case wasm_call_import:
 354         case wasm_typed:
 355         case wasm_select:
 356           break;
 357
 358         case wasm_break_table:
 359           target_count = wasm_read_leb128
 360             (pc + len, info, &error, &bytes_read, FALSE);
 361           if (error)
 362             return -1;
 363           len += bytes_read;
 364           prin (stream, " %ld", target_count);
 365           for (i = 0; i < target_count + 1; i++)
 366             {
 367               long target = 0;
 368               target = wasm_read_leb128
 369                 (pc + len, info, &error, &bytes_read, FALSE);
 370               if (error)
 371                 return -1;
 372               len += bytes_read;
 373               prin (stream, " %ld", target);
 374             }
 375           break;
 376
 377         case wasm_break:
 378         case wasm_break_if:
 379           depth = wasm_read_leb128
 380             (pc + len, info, &error, &bytes_read, FALSE);
 381           if (error)
 382             return -1;
 383           len += bytes_read;
 384           prin (stream, " %ld", depth);
 385           break;
 386
 387         case wasm_return:
 388           break;
 389
 390         case wasm_constant_i32:
 391         case wasm_constant_i64:
 392           constant = wasm_read_leb128
 393             (pc + len, info, &error, &bytes_read, TRUE);
 394           if (error)
 395             return -1;
 396           len += bytes_read;
 397           prin (stream, " %lld", constant);
 398           break;
 399
 400         case wasm_constant_f32:
 401           /* This appears to be the best we can do, even though we're
 402              using host doubles for WebAssembly floats.  */
 403           ret = read_f32 (&fconstant, pc + len, info);
 404           if (ret < 0)
 405             return -1;
 406           len += ret;
 407           prin (stream, " %.9g", fconstant);
 408           break;
 409
 410         case wasm_constant_f64:
 411           ret = read_f64 (&fconstant, pc + len, info);
 412           if (ret < 0)
 413             return -1;
 414           len += ret;
 415           prin (stream, " %.17g", fconstant);
 416           break;
 417
 418         case wasm_call:
 419           function_index = wasm_read_leb128
 420             (pc + len, info, &error, &bytes_read, FALSE);
 421           if (error)
 422             return -1;
 423           len += bytes_read;
 424           prin (stream, " ");
 425           private_data->section_prefix = ".space.function_index";
 426           (*info->print_address_func) ((bfd_vma) function_index, info);
 427           private_data->section_prefix = NULL;
 428           break;
 429
 430         case wasm_call_indirect:
 431           constant = wasm_read_leb128
 432             (pc + len, info, &error, &bytes_read, FALSE);
 433           if (error)
 434             return -1;
 435           len += bytes_read;
 436           prin (stream, " %lld", constant);
 437           constant = wasm_read_leb128
 438             (pc + len, info, &error, &bytes_read, FALSE);
 439           if (error)
 440             return -1;
 441           len += bytes_read;
 442           prin (stream, " %lld", constant);
 443           break;
 444
 445         case wasm_get_local:
 446         case wasm_set_local:
 447         case wasm_tee_local:
 448           constant = wasm_read_leb128
 449             (pc + len, info, &error, &bytes_read, FALSE);
 450           if (error)
 451             return -1;
 452           len += bytes_read;
 453           prin (stream, " %lld", constant);
 454           if (strcmp (op->name + 4, "local") == 0)
 455             {
 456               if (private_data->print_registers
 457                   && constant >= 0 && constant < nlocals)
 458                 prin (stream, " <%s>", locals[constant]);
 459             }
 460           else
 461             {
 462               if (private_data->print_well_known_globals
 463                   && constant >= 0 && constant < nglobals)
 464                 prin (stream, " <%s>", globals[constant]);
 465             }
 466           break;
 467
 468         case wasm_grow_memory:
 469         case wasm_current_memory:
 470           constant = wasm_read_leb128
 471             (pc + len, info, &error, &bytes_read, FALSE);
 472           if (error)
 473             return -1;
 474           len += bytes_read;
 475           prin (stream, " %lld", constant);
 476           break;
 477
 478         case wasm_load:
 479         case wasm_store:
 480           flags = wasm_read_leb128
 481             (pc + len, info, &error, &bytes_read, FALSE);
 482           if (error)
 483             return -1;
 484           len += bytes_read;
 485           offset = wasm_read_leb128
 486             (pc + len, info, &error, &bytes_read, FALSE);
 487           if (error)
 488             return -1;
 489           len += bytes_read;
 490           prin (stream, " a=%ld %ld", flags, offset);
 491         }
 492     }
 493   return len;
 494 }
 495
 496 /* Print valid disassembler options to STREAM.  */
 497
 498 void
 499 print_wasm32_disassembler_options (FILE *stream)
 500 {
 501   unsigned int i, max_len = 0;
 502
 503   fprintf (stream, _("\
 504 The following WebAssembly-specific disassembler options are supported for use\n\
 505 with the -M switch:\n"));
 506
 507   for (i = 0; i < ARRAY_SIZE (options); i++)
 508     {
 509       unsigned int len = strlen (options[i].name);
 510
 511       if (max_len < len)
 512         max_len = len;
 513     }
 514
 515   for (i = 0, max_len++; i < ARRAY_SIZE (options); i++)
 516     fprintf (stream, "  %s%*c %s\n",
 517              options[i].name,
 518              (int)(max_len - strlen (options[i].name)), ' ',
 519              _(options[i].description));
 520 }