libbacktrace/pecoff.c

   1 /* pecoff.c -- Get debug data from a PE/COFFF file for backtraces.
   2    Copyright (C) 2015-2017 Free Software Foundation, Inc.
   3    Adapted from elf.c by Tristan Gingold, AdaCore.
   4
   5 Redistribution and use in source and binary forms, with or without
   6 modification, are permitted provided that the following conditions are
   7 met:
   8
   9     (1) Redistributions of source code must retain the above copyright
  10     notice, this list of conditions and the following disclaimer.
  11
  12     (2) Redistributions in binary form must reproduce the above copyright
  13     notice, this list of conditions and the following disclaimer in
  14     the documentation and/or other materials provided with the
  15     distribution.
  16
  17     (3) The name of the author may not be used to
  18     endorse or promote products derived from this software without
  19     specific prior written permission.
  20
  21 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  22 IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  23 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  24 DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
  25 INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  26 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  27 SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28 HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  29 STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
  30 IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  31 POSSIBILITY OF SUCH DAMAGE.  */
  32
  33 #include "config.h"
  34
  35 #include <stdlib.h>
  36 #include <string.h>
  37 #include <sys/types.h>
  38
  39 #include "backtrace.h"
  40 #include "internal.h"
  41
  42 /* Coff file header.  */
  43
  44 typedef struct {
  45   uint16_t machine;
  46   uint16_t number_of_sections;
  47   uint32_t time_date_stamp;
  48   uint32_t pointer_to_symbol_table;
  49   uint32_t number_of_symbols;
  50   uint16_t size_of_optional_header;
  51   uint16_t characteristics;
  52 } b_coff_file_header;
  53
  54 /* Coff optional header.  */
  55
  56 typedef struct {
  57   uint16_t magic;
  58   uint8_t  major_linker_version;
  59   uint8_t  minor_linker_version;
  60   uint32_t size_of_code;
  61   uint32_t size_of_initialized_data;
  62   uint32_t size_of_uninitialized_data;
  63   uint32_t address_of_entry_point;
  64   uint32_t base_of_code;
  65   union {
  66     struct {
  67       uint32_t base_of_data;
  68       uint32_t image_base;
  69     } pe;
  70     struct {
  71       uint64_t image_base;
  72     } pep;
  73   } u;
  74 } b_coff_optional_header;
  75
  76 /* Values of magic in optional header.  */
  77
  78 #define PE_MAGIC 0x10b          /* PE32 executable.  */
  79 #define PEP_MAGIC 0x20b         /* PE32+ executable (for 64bit targets).  */
  80
  81 /* Coff section header.  */
  82
  83 typedef struct {
  84   char name[8];
  85   uint32_t virtual_size;
  86   uint32_t virtual_address;
  87   uint32_t size_of_raw_data;
  88   uint32_t pointer_to_raw_data;
  89   uint32_t pointer_to_relocations;
  90   uint32_t pointer_to_line_numbers;
  91   uint16_t number_of_relocations;
  92   uint16_t number_of_line_numbers;
  93   uint32_t characteristics;
  94 } b_coff_section_header;
  95
  96 /* Coff symbol name.  */
  97
  98 typedef union {
  99   char short_name[8];
 100   struct {
 101     unsigned char zeroes[4];
 102     unsigned char off[4];
 103   } long_name;
 104 } b_coff_name;
 105
 106 /* Coff symbol (external representation which is unaligned).  */
 107
 108 typedef struct {
 109   b_coff_name name;
 110   unsigned char value[4];
 111   unsigned char section_number[2];
 112   unsigned char type[2];
 113   unsigned char storage_class;
 114   unsigned char number_of_aux_symbols;
 115 } b_coff_external_symbol;
 116
 117 /* Symbol types.  */
 118
 119 #define N_TBSHFT 4                      /* Shift for the derived type.  */
 120 #define IMAGE_SYM_DTYPE_FUNCTION 2      /* Function derived type.  */
 121
 122 /* Size of a coff symbol.  */
 123
 124 #define SYM_SZ 18
 125
 126 /* Coff symbol, internal representation (aligned).  */
 127
 128 typedef struct {
 129   const char *name;
 130   uint32_t value;
 131   int16_t sec;
 132   uint16_t type;
 133   uint16_t sc;
 134 } b_coff_internal_symbol;
 135
 136 /* An index of sections we care about.  */
 137
 138 enum debug_section
 139 {
 140   DEBUG_INFO,
 141   DEBUG_LINE,
 142   DEBUG_ABBREV,
 143   DEBUG_RANGES,
 144   DEBUG_STR,
 145   DEBUG_MAX
 146 };
 147
 148 /* Names of sections, indexed by enum debug_section.  */
 149
 150 static const char * const debug_section_names[DEBUG_MAX] =
 151 {
 152   ".debug_info",
 153   ".debug_line",
 154   ".debug_abbrev",
 155   ".debug_ranges",
 156   ".debug_str"
 157 };
 158
 159 /* Information we gather for the sections we care about.  */
 160
 161 struct debug_section_info
 162 {
 163   /* Section file offset.  */
 164   off_t offset;
 165   /* Section size.  */
 166   size_t size;
 167   /* Section contents, after read from file.  */
 168   const unsigned char *data;
 169 };
 170
 171 /* Information we keep for an coff symbol.  */
 172
 173 struct coff_symbol
 174 {
 175   /* The name of the symbol.  */
 176   const char *name;
 177   /* The address of the symbol.  */
 178   uintptr_t address;
 179 };
 180
 181 /* Information to pass to coff_syminfo.  */
 182
 183 struct coff_syminfo_data
 184 {
 185   /* Symbols for the next module.  */
 186   struct coff_syminfo_data *next;
 187   /* The COFF symbols, sorted by address.  */
 188   struct coff_symbol *symbols;
 189   /* The number of symbols.  */
 190   size_t count;
 191 };
 192
 193 /* A dummy callback function used when we can't find any debug info.  */
 194
 195 static int
 196 coff_nodebug (struct backtrace_state *state ATTRIBUTE_UNUSED,
 197               uintptr_t pc ATTRIBUTE_UNUSED,
 198               backtrace_full_callback callback ATTRIBUTE_UNUSED,
 199               backtrace_error_callback error_callback, void *data)
 200 {
 201   error_callback (data, "no debug info in PE/COFF executable", -1);
 202   return 0;
 203 }
 204
 205 /* A dummy callback function used when we can't find a symbol
 206    table.  */
 207
 208 static void
 209 coff_nosyms (struct backtrace_state *state ATTRIBUTE_UNUSED,
 210              uintptr_t addr ATTRIBUTE_UNUSED,
 211              backtrace_syminfo_callback callback ATTRIBUTE_UNUSED,
 212              backtrace_error_callback error_callback, void *data)
 213 {
 214   error_callback (data, "no symbol table in PE/COFF executable", -1);
 215 }
 216
 217 /* Read a potentially unaligned 4 byte word at P, using native endianness.  */
 218
 219 static uint32_t
 220 coff_read4 (const unsigned char *p)
 221 {
 222   uint32_t res;
 223
 224   memcpy (&res, p, 4);
 225   return res;
 226 }
 227
 228 /* Read a potentially unaligned 2 byte word at P, using native endianness.
 229    All 2 byte word in symbols are always aligned, but for coherency all
 230    fields are declared as char arrays.  */
 231
 232 static uint16_t
 233 coff_read2 (const unsigned char *p)
 234 {
 235   uint16_t res;
 236
 237   memcpy (&res, p, sizeof (res));
 238   return res;
 239 }
 240
 241 /* Return the length (without the trailing 0) of a COFF short name.  */
 242
 243 static size_t
 244 coff_short_name_len (const char *name)
 245 {
 246   int i;
 247
 248   for (i = 0; i < 8; i++)
 249     if (name[i] == 0)
 250       return i;
 251   return 8;
 252 }
 253
 254 /* Return true iff COFF short name CNAME is the same as NAME (a NUL-terminated
 255    string).  */
 256
 257 static int
 258 coff_short_name_eq (const char *name, const char *cname)
 259 {
 260   int i;
 261
 262   for (i = 0; i < 8; i++)
 263     {
 264       if (name[i] != cname[i])
 265         return 0;
 266       if (name[i] == 0)
 267         return 1;
 268     }
 269   return name[8] == 0;
 270 }
 271
 272 /* Return true iff NAME is the same as string at offset OFF.  */
 273
 274 static int
 275 coff_long_name_eq (const char *name, unsigned int off,
 276                    struct backtrace_view *str_view)
 277 {
 278   if (off >= str_view->len)
 279     return 0;
 280   return strcmp (name, (const char *)str_view->data + off) == 0;
 281 }
 282
 283 /* Compare struct coff_symbol for qsort.  */
 284
 285 static int
 286 coff_symbol_compare (const void *v1, const void *v2)
 287 {
 288   const struct coff_symbol *e1 = (const struct coff_symbol *) v1;
 289   const struct coff_symbol *e2 = (const struct coff_symbol *) v2;
 290
 291   if (e1->address < e2->address)
 292     return -1;
 293   else if (e1->address > e2->address)
 294     return 1;
 295   else
 296     return 0;
 297 }
 298
 299 /* Convert SYM to internal (and aligned) format ISYM, using string table
 300    from STRTAB and STRTAB_SIZE, and number of sections SECTS_NUM.
 301    Return -1 in case of error (invalid section number or string index).  */
 302
 303 static int
 304 coff_expand_symbol (b_coff_internal_symbol *isym,
 305                     const b_coff_external_symbol *sym,
 306                     uint16_t sects_num,
 307                     const unsigned char *strtab, size_t strtab_size)
 308 {
 309   isym->type = coff_read2 (sym->type);
 310   isym->sec = coff_read2 (sym->section_number);
 311   isym->sc = sym->storage_class;
 312
 313   if (isym->sec > 0 && (uint16_t) isym->sec > sects_num)
 314     return -1;
 315   if (sym->name.short_name[0] != 0)
 316     isym->name = sym->name.short_name;
 317   else
 318     {
 319       uint32_t off = coff_read4 (sym->name.long_name.off);
 320
 321       if (off >= strtab_size)
 322         return -1;
 323       isym->name = (const char *) strtab + off;
 324     }
 325   return 0;
 326 }
 327
 328 /* Return true iff SYM is a defined symbol for a function.  Data symbols
 329    aren't considered because they aren't easily identified (same type as
 330    section names, presence of symbols defined by the linker script).  */
 331
 332 static int
 333 coff_is_function_symbol (const b_coff_internal_symbol *isym)
 334 {
 335   return (isym->type >> N_TBSHFT) == IMAGE_SYM_DTYPE_FUNCTION
 336     && isym->sec > 0;
 337 }
 338
 339 /* Initialize the symbol table info for coff_syminfo.  */
 340
 341 static int
 342 coff_initialize_syminfo (struct backtrace_state *state,
 343                          uintptr_t base_address,
 344                          const b_coff_section_header *sects, size_t sects_num,
 345                          const b_coff_external_symbol *syms, size_t syms_size,
 346                          const unsigned char *strtab, size_t strtab_size,
 347                          backtrace_error_callback error_callback,
 348                          void *data, struct coff_syminfo_data *sdata)
 349 {
 350   size_t syms_count;
 351   char *coff_symstr;
 352   size_t coff_symstr_len;
 353   size_t coff_symbol_count;
 354   size_t coff_symbol_size;
 355   struct coff_symbol *coff_symbols;
 356   struct coff_symbol *coff_sym;
 357   char *coff_str;
 358   size_t i;
 359
 360   syms_count = syms_size / SYM_SZ;
 361
 362   /* We only care about function symbols.  Count them.  Also count size of
 363      strings for in-symbol names.  */
 364   coff_symbol_count = 0;
 365   coff_symstr_len = 0;
 366   for (i = 0; i < syms_count; ++i)
 367     {
 368       const b_coff_external_symbol *asym = &syms[i];
 369       b_coff_internal_symbol isym;
 370
 371       if (coff_expand_symbol (&isym, asym, sects_num, strtab, strtab_size) < 0)
 372         {
 373           error_callback (data, "invalid section or offset in coff symbol", 0);
 374           return 0;
 375         }
 376       if (coff_is_function_symbol (&isym))
 377         {
 378           ++coff_symbol_count;
 379           if (asym->name.short_name[0] != 0)
 380             coff_symstr_len += coff_short_name_len (asym->name.short_name) + 1;
 381         }
 382
 383       i += asym->number_of_aux_symbols;
 384     }
 385
 386   coff_symbol_size = (coff_symbol_count + 1) * sizeof (struct coff_symbol);
 387   coff_symbols = ((struct coff_symbol *)
 388                   backtrace_alloc (state, coff_symbol_size, error_callback,
 389                                    data));
 390   if (coff_symbols == NULL)
 391     return 0;
 392
 393   /* Allocate memory for symbols strings.  */
 394   if (coff_symstr_len > 0)
 395     {
 396       coff_symstr = ((char *)
 397                      backtrace_alloc (state, coff_symstr_len, error_callback,
 398                                       data));
 399       if (coff_symstr == NULL)
 400         {
 401           backtrace_free (state, coff_symbols, coff_symbol_size,
 402                           error_callback, data);
 403           return 0;
 404         }
 405     }
 406   else
 407     coff_symstr = NULL;
 408
 409   /* Copy symbols.  */
 410   coff_sym = coff_symbols;
 411   coff_str = coff_symstr;
 412   for (i = 0; i < syms_count; ++i)
 413     {
 414       const b_coff_external_symbol *asym = &syms[i];
 415       b_coff_internal_symbol isym;
 416
 417       if (coff_expand_symbol (&isym, asym, sects_num, strtab, strtab_size))
 418         {
 419           /* Should not fail, as it was already tested in the previous
 420              loop.  */
 421           abort ();
 422         }
 423       if (coff_is_function_symbol (&isym))
 424         {
 425           const char *name;
 426           int16_t secnum;
 427
 428           if (asym->name.short_name[0] != 0)
 429             {
 430               size_t len = coff_short_name_len (isym.name);
 431               name = coff_str;
 432               memcpy (coff_str, isym.name, len);
 433               coff_str[len] = 0;
 434               coff_str += len + 1;
 435             }
 436           else
 437             name = isym.name;
 438
 439           /* Strip leading '_'.  */
 440           if (name[0] == '_')
 441             name++;
 442
 443           /* Symbol value is section relative, so we need to read the address
 444              of its section.  */
 445           secnum = coff_read2 (asym->section_number);
 446
 447           coff_sym->name = name;
 448           coff_sym->address = (coff_read4 (asym->value)
 449                                + sects[secnum - 1].virtual_address
 450                                + base_address);
 451           coff_sym++;
 452         }
 453
 454       i += asym->number_of_aux_symbols;
 455     }
 456
 457   /* End of symbols marker.  */
 458   coff_sym->name = NULL;
 459   coff_sym->address = -1;
 460
 461   backtrace_qsort (coff_symbols, coff_symbol_count,
 462                    sizeof (struct coff_symbol), coff_symbol_compare);
 463
 464   sdata->next = NULL;
 465   sdata->symbols = coff_symbols;
 466   sdata->count = coff_symbol_count;
 467
 468   return 1;
 469 }
 470
 471 /* Add EDATA to the list in STATE.  */
 472
 473 static void
 474 coff_add_syminfo_data (struct backtrace_state *state,
 475                        struct coff_syminfo_data *sdata)
 476 {
 477   if (!state->threaded)
 478     {
 479       struct coff_syminfo_data **pp;
 480
 481       for (pp = (struct coff_syminfo_data **) (void *) &state->syminfo_data;
 482            *pp != NULL;
 483            pp = &(*pp)->next)
 484         ;
 485       *pp = sdata;
 486     }
 487   else
 488     {
 489       while (1)
 490         {
 491           struct coff_syminfo_data **pp;
 492
 493           pp = (struct coff_syminfo_data **) (void *) &state->syminfo_data;
 494
 495           while (1)
 496             {
 497               struct coff_syminfo_data *p;
 498
 499               p = backtrace_atomic_load_pointer (pp);
 500
 501               if (p == NULL)
 502                 break;
 503
 504               pp = &p->next;
 505             }
 506
 507           if (__sync_bool_compare_and_swap (pp, NULL, sdata))
 508             break;
 509         }
 510     }
 511 }
 512
 513 /* Compare an ADDR against an elf_symbol for bsearch.  We allocate one
 514    extra entry in the array so that this can look safely at the next
 515    entry.  */
 516
 517 static int
 518 coff_symbol_search (const void *vkey, const void *ventry)
 519 {
 520   const uintptr_t *key = (const uintptr_t *) vkey;
 521   const struct coff_symbol *entry = (const struct coff_symbol *) ventry;
 522   uintptr_t addr;
 523
 524   addr = *key;
 525   if (addr < entry->address)
 526     return -1;
 527   else if (addr >= entry[1].address)
 528     return 1;
 529   else
 530     return 0;
 531 }
 532
 533 /* Return the symbol name and value for an ADDR.  */
 534
 535 static void
 536 coff_syminfo (struct backtrace_state *state, uintptr_t addr,
 537               backtrace_syminfo_callback callback,
 538               backtrace_error_callback error_callback ATTRIBUTE_UNUSED,
 539               void *data)
 540 {
 541   struct coff_syminfo_data *sdata;
 542   struct coff_symbol *sym = NULL;
 543
 544   if (!state->threaded)
 545     {
 546       for (sdata = (struct coff_syminfo_data *) state->syminfo_data;
 547            sdata != NULL;
 548            sdata = sdata->next)
 549         {
 550           sym = ((struct coff_symbol *)
 551                  bsearch (&addr, sdata->symbols, sdata->count,
 552                           sizeof (struct coff_symbol), coff_symbol_search));
 553           if (sym != NULL)
 554             break;
 555         }
 556     }
 557   else
 558     {
 559       struct coff_syminfo_data **pp;
 560
 561       pp = (struct coff_syminfo_data **) (void *) &state->syminfo_data;
 562       while (1)
 563         {
 564           sdata = backtrace_atomic_load_pointer (pp);
 565           if (sdata == NULL)
 566             break;
 567
 568           sym = ((struct coff_symbol *)
 569                  bsearch (&addr, sdata->symbols, sdata->count,
 570                           sizeof (struct coff_symbol), coff_symbol_search));
 571           if (sym != NULL)
 572             break;
 573
 574           pp = &sdata->next;
 575         }
 576     }
 577
 578   if (sym == NULL)
 579     callback (data, addr, NULL, 0, 0);
 580   else
 581     callback (data, addr, sym->name, sym->address, 0);
 582 }
 583
 584 /* Add the backtrace data for one PE/COFF file.  Returns 1 on success,
 585    0 on failure (in both cases descriptor is closed).  */
 586
 587 static int
 588 coff_add (struct backtrace_state *state, int descriptor,
 589           backtrace_error_callback error_callback, void *data,
 590           fileline *fileline_fn, int *found_sym, int *found_dwarf)
 591 {
 592   struct backtrace_view fhdr_view;
 593   off_t fhdr_off;
 594   int magic_ok;
 595   b_coff_file_header fhdr;
 596   off_t opt_sects_off;
 597   size_t opt_sects_size;
 598   unsigned int sects_num;
 599   struct backtrace_view sects_view;
 600   int sects_view_valid;
 601   const b_coff_optional_header *opt_hdr;
 602   const b_coff_section_header *sects;
 603   struct backtrace_view str_view;
 604   int str_view_valid;
 605   size_t str_size;
 606   off_t str_off;
 607   struct backtrace_view syms_view;
 608   off_t syms_off;
 609   size_t syms_size;
 610   int syms_view_valid;
 611   unsigned int syms_num;
 612   unsigned int i;
 613   struct debug_section_info sections[DEBUG_MAX];
 614   off_t min_offset;
 615   off_t max_offset;
 616   struct backtrace_view debug_view;
 617   int debug_view_valid;
 618   uintptr_t image_base;
 619
 620   *found_sym = 0;
 621   *found_dwarf = 0;
 622
 623   sects_view_valid = 0;
 624   syms_view_valid = 0;
 625   str_view_valid = 0;
 626   debug_view_valid = 0;
 627
 628   /* Map the MS-DOS stub (if any) and extract file header offset.  */
 629   if (!backtrace_get_view (state, descriptor, 0, 0x40, error_callback,
 630                            data, &fhdr_view))
 631     goto fail;
 632
 633   {
 634     const char *vptr = (const char *)fhdr_view.data;
 635
 636     if (vptr[0] == 'M' && vptr[1] == 'Z')
 637       memcpy (&fhdr_off, vptr + 0x3c, 4);
 638     else
 639       fhdr_off = 0;
 640   }
 641
 642   backtrace_release_view (state, &fhdr_view, error_callback, data);
 643
 644   /* Map the coff file header.  */
 645   if (!backtrace_get_view (state, descriptor, fhdr_off,
 646                            sizeof (b_coff_file_header) + 4,
 647                            error_callback, data, &fhdr_view))
 648     goto fail;
 649
 650   if (fhdr_off != 0)
 651     {
 652       const char *magic = (const char *) fhdr_view.data;
 653       magic_ok = memcmp (magic, "PE\0", 4) == 0;
 654       fhdr_off += 4;
 655
 656       memcpy (&fhdr, fhdr_view.data + 4, sizeof fhdr);
 657     }
 658   else
 659     {
 660       memcpy (&fhdr, fhdr_view.data, sizeof fhdr);
 661       /* TODO: test fhdr.machine for coff but non-PE platforms.  */
 662       magic_ok = 0;
 663     }
 664   backtrace_release_view (state, &fhdr_view, error_callback, data);
 665
 666   if (!magic_ok)
 667     {
 668       error_callback (data, "executable file is not COFF", 0);
 669       goto fail;
 670     }
 671
 672   sects_num = fhdr.number_of_sections;
 673   syms_num = fhdr.number_of_symbols;
 674
 675   opt_sects_off = fhdr_off + sizeof (fhdr);
 676   opt_sects_size = (fhdr.size_of_optional_header
 677                     + sects_num * sizeof (b_coff_section_header));
 678
 679   /* To translate PC to file/line when using DWARF, we need to find
 680      the .debug_info and .debug_line sections.  */
 681
 682   /* Read the optional header and the section headers.  */
 683
 684   if (!backtrace_get_view (state, descriptor, opt_sects_off, opt_sects_size,
 685                            error_callback, data, &sects_view))
 686     goto fail;
 687   sects_view_valid = 1;
 688   opt_hdr = (const b_coff_optional_header *) sects_view.data;
 689   sects = (const b_coff_section_header *)
 690     (sects_view.data + fhdr.size_of_optional_header);
 691
 692   if (fhdr.size_of_optional_header > sizeof (*opt_hdr))
 693     {
 694       if (opt_hdr->magic == PE_MAGIC)
 695         image_base = opt_hdr->u.pe.image_base;
 696       else if (opt_hdr->magic == PEP_MAGIC)
 697         image_base = opt_hdr->u.pep.image_base;
 698       else
 699         {
 700           error_callback (data, "bad magic in PE optional header", 0);
 701           goto fail;
 702         }
 703     }
 704   else
 705     image_base = 0;
 706
 707   /* Read the symbol table and the string table.  */
 708
 709   if (fhdr.pointer_to_symbol_table == 0)
 710     {
 711       /* No symbol table, no string table.  */
 712       str_off = 0;
 713       str_size = 0;
 714       syms_num = 0;
 715       syms_size = 0;
 716     }
 717   else
 718     {
 719       /* Symbol table is followed by the string table.  The string table
 720          starts with its length (on 4 bytes).
 721          Map the symbol table and the length of the string table.  */
 722       syms_off = fhdr.pointer_to_symbol_table;
 723       syms_size = syms_num * SYM_SZ;
 724
 725       if (!backtrace_get_view (state, descriptor, syms_off, syms_size + 4,
 726                                error_callback, data, &syms_view))
 727         goto fail;
 728       syms_view_valid = 1;
 729
 730       memcpy (&str_size, syms_view.data + syms_size, 4);
 731
 732       str_off = syms_off + syms_size;
 733
 734       if (str_size > 4)
 735         {
 736           /* Map string table (including the length word).  */
 737
 738           if (!backtrace_get_view (state, descriptor, str_off, str_size,
 739                                    error_callback, data, &str_view))
 740             goto fail;
 741           str_view_valid = 1;
 742         }
 743     }
 744
 745   memset (sections, 0, sizeof sections);
 746
 747   /* Look for the symbol table.  */
 748   for (i = 0; i < sects_num; ++i)
 749     {
 750       const b_coff_section_header *s = sects + i;
 751       unsigned int str_off;
 752       int j;
 753
 754       if (s->name[0] == '/')
 755         {
 756           /* Extended section name.  */
 757           str_off = atoi (s->name + 1);
 758         }
 759       else
 760         str_off = 0;
 761
 762       for (j = 0; j < (int) DEBUG_MAX; ++j)
 763         {
 764           const char *dbg_name = debug_section_names[j];
 765           int match;
 766
 767           if (str_off != 0)
 768             match = coff_long_name_eq (dbg_name, str_off, &str_view);
 769           else
 770             match = coff_short_name_eq (dbg_name, s->name);
 771           if (match)
 772             {
 773               sections[j].offset = s->pointer_to_raw_data;
 774               sections[j].size = s->virtual_size <= s->size_of_raw_data ?
 775                 s->virtual_size : s->size_of_raw_data;
 776               break;
 777             }
 778         }
 779     }
 780
 781   if (syms_num != 0)
 782     {
 783       struct coff_syminfo_data *sdata;
 784
 785       sdata = ((struct coff_syminfo_data *)
 786                backtrace_alloc (state, sizeof *sdata, error_callback, data));
 787       if (sdata == NULL)
 788         goto fail;
 789
 790       if (!coff_initialize_syminfo (state, image_base,
 791                                     sects, sects_num,
 792                                     syms_view.data, syms_size,
 793                                     str_view.data, str_size,
 794                                     error_callback, data, sdata))
 795         {
 796           backtrace_free (state, sdata, sizeof *sdata, error_callback, data);
 797           goto fail;
 798         }
 799
 800       *found_sym = 1;
 801
 802       coff_add_syminfo_data (state, sdata);
 803     }
 804
 805   backtrace_release_view (state, &sects_view, error_callback, data);
 806   sects_view_valid = 0;
 807   backtrace_release_view (state, &syms_view, error_callback, data);
 808   syms_view_valid = 0;
 809
 810   /* Read all the debug sections in a single view, since they are
 811      probably adjacent in the file.  We never release this view.  */
 812
 813   min_offset = 0;
 814   max_offset = 0;
 815   for (i = 0; i < (int) DEBUG_MAX; ++i)
 816     {
 817       off_t end;
 818
 819       if (sections[i].size == 0)
 820         continue;
 821       if (min_offset == 0 || sections[i].offset < min_offset)
 822         min_offset = sections[i].offset;
 823       end = sections[i].offset + sections[i].size;
 824       if (end > max_offset)
 825         max_offset = end;
 826     }
 827   if (min_offset == 0 || max_offset == 0)
 828     {
 829       if (!backtrace_close (descriptor, error_callback, data))
 830         goto fail;
 831       *fileline_fn = coff_nodebug;
 832       return 1;
 833     }
 834
 835   if (!backtrace_get_view (state, descriptor, min_offset,
 836                            max_offset - min_offset,
 837                            error_callback, data, &debug_view))
 838     goto fail;
 839   debug_view_valid = 1;
 840
 841   /* We've read all we need from the executable.  */
 842   if (!backtrace_close (descriptor, error_callback, data))
 843     goto fail;
 844   descriptor = -1;
 845
 846   for (i = 0; i < (int) DEBUG_MAX; ++i)
 847     {
 848       if (sections[i].size == 0)
 849         sections[i].data = NULL;
 850       else
 851         sections[i].data = ((const unsigned char *) debug_view.data
 852                             + (sections[i].offset - min_offset));
 853     }
 854
 855   if (!backtrace_dwarf_add (state, /* base_address */ 0,
 856                             sections[DEBUG_INFO].data,
 857                             sections[DEBUG_INFO].size,
 858                             sections[DEBUG_LINE].data,
 859                             sections[DEBUG_LINE].size,
 860                             sections[DEBUG_ABBREV].data,
 861                             sections[DEBUG_ABBREV].size,
 862                             sections[DEBUG_RANGES].data,
 863                             sections[DEBUG_RANGES].size,
 864                             sections[DEBUG_STR].data,
 865                             sections[DEBUG_STR].size,
 866                             0, /* FIXME */
 867                             error_callback, data, fileline_fn))
 868     goto fail;
 869
 870   *found_dwarf = 1;
 871
 872   return 1;
 873
 874  fail:
 875   if (sects_view_valid)
 876     backtrace_release_view (state, &sects_view, error_callback, data);
 877   if (str_view_valid)
 878     backtrace_release_view (state, &str_view, error_callback, data);
 879   if (syms_view_valid)
 880     backtrace_release_view (state, &syms_view, error_callback, data);
 881   if (debug_view_valid)
 882     backtrace_release_view (state, &debug_view, error_callback, data);
 883   if (descriptor != -1)
 884     backtrace_close (descriptor, error_callback, data);
 885   return 0;
 886 }
 887
 888 /* Initialize the backtrace data we need from an ELF executable.  At
 889    the ELF level, all we need to do is find the debug info
 890    sections.  */
 891
 892 int
 893 backtrace_initialize (struct backtrace_state *state,
 894                       const char *filename ATTRIBUTE_UNUSED, int descriptor,
 895                       backtrace_error_callback error_callback,
 896                       void *data, fileline *fileline_fn)
 897 {
 898   int ret;
 899   int found_sym;
 900   int found_dwarf;
 901   fileline coff_fileline_fn;
 902
 903   ret = coff_add (state, descriptor, error_callback, data,
 904                   &coff_fileline_fn, &found_sym, &found_dwarf);
 905   if (!ret)
 906     return 0;
 907
 908   if (!state->threaded)
 909     {
 910       if (found_sym)
 911         state->syminfo_fn = coff_syminfo;
 912       else if (state->syminfo_fn == NULL)
 913         state->syminfo_fn = coff_nosyms;
 914     }
 915   else
 916     {
 917       if (found_sym)
 918         backtrace_atomic_store_pointer (&state->syminfo_fn, coff_syminfo);
 919       else
 920         __sync_bool_compare_and_swap (&state->syminfo_fn, NULL, coff_nosyms);
 921     }
 922
 923   if (!state->threaded)
 924     {
 925       if (state->fileline_fn == NULL || state->fileline_fn == coff_nodebug)
 926         *fileline_fn = coff_fileline_fn;
 927     }
 928   else
 929     {
 930       fileline current_fn;
 931
 932       current_fn = backtrace_atomic_load_pointer (&state->fileline_fn);
 933       if (current_fn == NULL || current_fn == coff_nodebug)
 934         *fileline_fn = coff_fileline_fn;
 935     }
 936
 937   return 1;
 938 }