symbolize.cc 21.9 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
// Copyright (c) 2006, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
's avatar
committed
30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
// Author: Satoru Takabayashi
// Stack-footprint reduction work done by Raksit Ashok
//
// Implementation note:
//
// We don't use heaps but only use stacks.  We want to reduce the
// stack consumption so that the symbolizer can run on small stacks.
//
// Here are some numbers collected with GCC 4.1.0 on x86:
// - sizeof(Elf32_Sym)  = 16
// - sizeof(Elf32_Shdr) = 40
// - sizeof(Elf64_Sym)  = 24
// - sizeof(Elf64_Shdr) = 64
//
// This implementation is intended to be async-signal-safe but uses
// some functions which are not guaranteed to be so, such as memchr()
// and memmove().  We assume they are async-signal-safe.
//

49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93
#include "utilities.h"

#if defined(HAVE_SYMBOLIZE)

#include "symbolize.h"
#include "demangle.h"

_START_GOOGLE_NAMESPACE_

// We don't use assert() since it's not guaranteed to be
// async-signal-safe.  Instead we define a minimal assertion
// macro. So far, we don't need pretty printing for __FILE__, etc.

// A wrapper for abort() to make it callable in ? :.
static int AssertFail() {
  abort();
  return 0;  // Should not reach.
}

#define SAFE_ASSERT(expr) ((expr) ? 0 : AssertFail())

static SymbolizeCallback g_symbolize_callback = NULL;
void InstallSymbolizeCallback(SymbolizeCallback callback) {
  g_symbolize_callback = callback;
}

// This function wraps the Demangle function to provide an interface
// where the input symbol is demangled in-place.
// To keep stack consumption low, we would like this function to not
// get inlined.
static ATTRIBUTE_NOINLINE void DemangleInplace(char *out, int out_size) {
  char demangled[256];  // Big enough for sane demangled symbols.
  if (Demangle(out, demangled, sizeof(demangled))) {
    // Demangling succeeded. Copy to out if the space allows.
    int len = strlen(demangled);
    if (len + 1 <= out_size) {  // +1 for '\0'.
      SAFE_ASSERT(len < sizeof(demangled));
      memmove(out, demangled, len + 1);
    }
  }
}

_END_GOOGLE_NAMESPACE_

#if defined(__ELF__)
's avatar
committed
94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443

#include <dlfcn.h>
#include <elf.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <link.h>  // For ElfW() macro.
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#include "symbolize.h"
#include "config.h"
#include "glog/raw_logging.h"

// Re-runs fn until it doesn't cause EINTR.
#define NO_INTR(fn)   do {} while ((fn) < 0 && errno == EINTR)

_START_GOOGLE_NAMESPACE_

// Read up to "count" bytes from file descriptor "fd" into the buffer
// starting at "buf" while handling short reads and EINTR.  On
// success, return the number of bytes read.  Otherwise, return -1.
static ssize_t ReadPersistent(const int fd, void *buf, const size_t count) {
  SAFE_ASSERT(fd >= 0);
  SAFE_ASSERT(count >= 0 && count <= SSIZE_MAX);
  char *buf0 = reinterpret_cast<char *>(buf);
  ssize_t num_bytes = 0;
  while (num_bytes < count) {
    ssize_t len;
    NO_INTR(len = read(fd, buf0 + num_bytes, count - num_bytes));
    if (len < 0) {  // There was an error other than EINTR.
      return -1;
    }
    if (len == 0) {  // Reached EOF.
      break;
    }
    num_bytes += len;
  }
  SAFE_ASSERT(num_bytes <= count);
  return num_bytes;
}

// Read up to "count" bytes from "offset" in the file pointed by file
// descriptor "fd" into the buffer starting at "buf".  On success,
// return the number of bytes read.  Otherwise, return -1.
static ssize_t ReadFromOffset(const int fd, void *buf,
                              const size_t count, const off_t offset) {
  off_t off = lseek(fd, offset, SEEK_SET);
  if (off == (off_t)-1) {
    return -1;
  }
  return ReadPersistent(fd, buf, count);
}

// Try reading exactly "count" bytes from "offset" bytes in a file
// pointed by "fd" into the buffer starting at "buf" while handling
// short reads and EINTR.  On success, return true. Otherwise, return
// false.
static bool ReadFromOffsetExact(const int fd, void *buf,
                                const size_t count, const off_t offset) {
  ssize_t len = ReadFromOffset(fd, buf, count, offset);
  return len == count;
}

// Returns elf_header.e_type if the file pointed by fd is an ELF binary.
static int FileGetElfType(const int fd) {
  ElfW(Ehdr) elf_header;
  if (!ReadFromOffsetExact(fd, &elf_header, sizeof(elf_header), 0)) {
    return -1;
  }
  if (memcmp(elf_header.e_ident, ELFMAG, SELFMAG) != 0) {
    return -1;
  }
  return elf_header.e_type;
}

// Read the section headers in the given ELF binary, and if a section
// of the specified type is found, set the output to this section header
// and return true.  Otherwise, return false.
// To keep stack consumption low, we would like this function to not get
// inlined.
static ATTRIBUTE_NOINLINE bool
GetSectionHeaderByType(const int fd, ElfW(Half) sh_num, const off_t sh_offset,
                       ElfW(Word) type, ElfW(Shdr) *out) {
  // Read at most 16 section headers at a time to save read calls.
  ElfW(Shdr) buf[16];
  for (int i = 0; i < sh_num;) {
    const ssize_t num_bytes_left = (sh_num - i) * sizeof(buf[0]);
    const ssize_t num_bytes_to_read =
        (sizeof(buf) > num_bytes_left) ? num_bytes_left : sizeof(buf);
    const ssize_t len = ReadFromOffset(fd, buf, num_bytes_to_read,
                                       sh_offset + i * sizeof(buf[0]));
    SAFE_ASSERT(len % sizeof(buf[0]) == 0);
    const ssize_t num_headers_in_buf = len / sizeof(buf[0]);
    SAFE_ASSERT(num_headers_in_buf <= sizeof(buf) / sizeof(buf[0]));
    for (int j = 0; j < num_headers_in_buf; ++j) {
      if (buf[j].sh_type == type) {
        *out = buf[j];
        return true;
      }
    }
    i += num_headers_in_buf;
  }
  return false;
}

// There is no particular reason to limit section name to 63 characters,
// but there has (as yet) been no need for anything longer either.
const int kMaxSectionNameLen = 64;

// name_len should include terminating '\0'.
bool GetSectionHeaderByName(int fd, const char *name, size_t name_len,
                            ElfW(Shdr) *out) {
  ElfW(Ehdr) elf_header;
  if (!ReadFromOffsetExact(fd, &elf_header, sizeof(elf_header), 0)) {
    return false;
  }

  ElfW(Shdr) shstrtab;
  off_t shstrtab_offset = (elf_header.e_shoff +
                           elf_header.e_shentsize * elf_header.e_shstrndx);
  if (!ReadFromOffsetExact(fd, &shstrtab, sizeof(shstrtab), shstrtab_offset)) {
    return false;
  }

  for (int i = 0; i < elf_header.e_shnum; ++i) {
    off_t section_header_offset = (elf_header.e_shoff +
                                   elf_header.e_shentsize * i);
    if (!ReadFromOffsetExact(fd, out, sizeof(*out), section_header_offset)) {
      return false;
    }
    char header_name[kMaxSectionNameLen];
    if (sizeof(header_name) < name_len) {
      RAW_LOG(WARNING, "Section name '%s' is too long (%"PRIuS"); "
              "section will not be found (even if present).", name, name_len);
      // No point in even trying.
      return false;
    }
    off_t name_offset = shstrtab.sh_offset + out->sh_name;
    ssize_t n_read = ReadFromOffset(fd, &header_name, name_len, name_offset);
    if (n_read == -1) {
      return false;
    } else if (n_read != name_len) {
      // Short read -- name could be at end of file.
      continue;
    }
    if (memcmp(header_name, name, name_len) == 0) {
      return true;
    }
  }
  return false;
}

// Read a symbol table and look for the symbol containing the
// pc. Iterate over symbols in a symbol table and look for the symbol
// containing "pc".  On success, return true and write the symbol name
// to out.  Otherwise, return false.
// To keep stack consumption low, we would like this function to not get
// inlined.
static ATTRIBUTE_NOINLINE bool
FindSymbol(uint64_t pc, const int fd, char *out, int out_size,
           uint64_t symbol_offset, const ElfW(Shdr) *strtab,
           const ElfW(Shdr) *symtab) {
  if (symtab == NULL) {
    return false;
  }
  const int num_symbols = symtab->sh_size / symtab->sh_entsize;
  for (int i = 0; i < num_symbols;) {
    off_t offset = symtab->sh_offset + i * symtab->sh_entsize;

    // If we are reading Elf64_Sym's, we want to limit this array to
    // 32 elements (to keep stack consumption low), otherwise we can
    // have a 64 element Elf32_Sym array.
#if __WORDSIZE == 64
#define NUM_SYMBOLS 32
#else
#define NUM_SYMBOLS 64
#endif

    // Read at most NUM_SYMBOLS symbols at once to save read() calls.
    ElfW(Sym) buf[NUM_SYMBOLS];
    const ssize_t len = ReadFromOffset(fd, &buf, sizeof(buf), offset);
    SAFE_ASSERT(len % sizeof(buf[0]) == 0);
    const ssize_t num_symbols_in_buf = len / sizeof(buf[0]);
    SAFE_ASSERT(num_symbols_in_buf <= sizeof(buf)/sizeof(buf[0]));
    for (int j = 0; j < num_symbols_in_buf; ++j) {
      const ElfW(Sym)& symbol = buf[j];
      uint64_t start_address = symbol.st_value;
      start_address += symbol_offset;
      uint64_t end_address = start_address + symbol.st_size;
      if (symbol.st_value != 0 &&  // Skip null value symbols.
          symbol.st_shndx != 0 &&  // Skip undefined symbols.
          start_address <= pc && pc < end_address) {
        ssize_t len1 = ReadFromOffset(fd, out, out_size,
                                      strtab->sh_offset + symbol.st_name);
        if (len1 <= 0 || memchr(out, '\0', out_size) == NULL) {
          return false;
        }
        return true;  // Obtained the symbol name.
      }
    }
    i += num_symbols_in_buf;
  }
  return false;
}

// Get the symbol name of "pc" from the file pointed by "fd".  Process
// both regular and dynamic symbol tables if necessary.  On success,
// write the symbol name to "out" and return true.  Otherwise, return
// false.
static bool GetSymbolFromObjectFile(const int fd, uint64_t pc,
                                    char *out, int out_size,
                                    uint64_t map_start_address) {
  // Read the ELF header.
  ElfW(Ehdr) elf_header;
  if (!ReadFromOffsetExact(fd, &elf_header, sizeof(elf_header), 0)) {
    return false;
  }

  uint64_t symbol_offset = 0;
  if (elf_header.e_type == ET_DYN) {  // DSO needs offset adjustment.
    symbol_offset = map_start_address;
  }

  ElfW(Shdr) symtab, strtab;

  // Consult a regular symbol table first.
  if (!GetSectionHeaderByType(fd, elf_header.e_shnum, elf_header.e_shoff,
                              SHT_SYMTAB, &symtab)) {
    return false;
  }
  if (!ReadFromOffsetExact(fd, &strtab, sizeof(strtab), elf_header.e_shoff +
                           symtab.sh_link * sizeof(symtab))) {
    return false;
  }
  if (FindSymbol(pc, fd, out, out_size, symbol_offset,
                 &strtab, &symtab)) {
    return true;  // Found the symbol in a regular symbol table.
  }

  // If the symbol is not found, then consult a dynamic symbol table.
  if (!GetSectionHeaderByType(fd, elf_header.e_shnum, elf_header.e_shoff,
                              SHT_DYNSYM, &symtab)) {
    return false;
  }
  if (!ReadFromOffsetExact(fd, &strtab, sizeof(strtab), elf_header.e_shoff +
                           symtab.sh_link * sizeof(symtab))) {
    return false;
  }
  if (FindSymbol(pc, fd, out, out_size, symbol_offset,
                 &strtab, &symtab)) {
    return true;  // Found the symbol in a dynamic symbol table.
  }

  return false;
}

namespace {
// Thin wrapper around a file descriptor so that the file descriptor
// gets closed for sure.
struct FileDescriptor {
  const int fd_;
  explicit FileDescriptor(int fd) : fd_(fd) {}
  ~FileDescriptor() {
    if (fd_ >= 0) {
      NO_INTR(close(fd_));
    }
  }
  int get() { return fd_; }

 private:
  explicit FileDescriptor(const FileDescriptor&);
  void operator=(const FileDescriptor&);
};

// Helper class for reading lines from file.
//
// Note: we don't use ProcMapsIterator since the object is big (it has
// a 5k array member) and uses async-unsafe functions such as sscanf()
// and snprintf().
class LineReader {
 public:
  explicit LineReader(int fd, char *buf, int buf_len) : fd_(fd),
    buf_(buf), buf_len_(buf_len), bol_(buf), eol_(buf), eod_(buf) {
  }

  // Read '\n'-terminated line from file.  On success, modify "bol"
  // and "eol", then return true.  Otherwise, return false.
  //
  // Note: if the last line doesn't end with '\n', the line will be
  // dropped.  It's an intentional behavior to make the code simple.
  bool ReadLine(const char **bol, const char **eol) {
    if (BufferIsEmpty()) {  // First time.
      const ssize_t num_bytes = ReadPersistent(fd_, buf_, buf_len_);
      if (num_bytes <= 0) {  // EOF or error.
        return false;
      }
      eod_ = buf_ + num_bytes;
      bol_ = buf_;
    } else {
      bol_ = eol_ + 1;  // Advance to the next line in the buffer.
      SAFE_ASSERT(bol_ <= eod_);  // "bol_" can point to "eod_".
      if (!HasCompleteLine()) {
        const int incomplete_line_length = eod_ - bol_;
        // Move the trailing incomplete line to the beginning.
        memmove(buf_, bol_, incomplete_line_length);
        // Read text from file and append it.
        char * const append_pos = buf_ + incomplete_line_length;
        const int capacity_left = buf_len_ - incomplete_line_length;
        const ssize_t num_bytes = ReadPersistent(fd_, append_pos,
                                                 capacity_left);
        if (num_bytes <= 0) {  // EOF or error.
          return false;
        }
        eod_ = append_pos + num_bytes;
        bol_ = buf_;
      }
    }
    eol_ = FindLineFeed();
    if (eol_ == NULL) {  // '\n' not found.  Malformed line.
      return false;
    }
    *eol_ = '\0';  // Replace '\n' with '\0'.

    *bol = bol_;
    *eol = eol_;
    return true;
  }

  // Beginning of line.
  const char *bol() {
    return bol_;
  }

  // End of line.
  const char *eol() {
    return eol_;
  }

 private:
  explicit LineReader(const LineReader&);
  void operator=(const LineReader&);

  char *FindLineFeed() {
444
    return reinterpret_cast<char *>(memchr(bol_, '\n', eod_ - bol_));
's avatar
committed
445 446 447 448 449 450 451 452 453 454 455 456 457
  }

  bool BufferIsEmpty() {
    return buf_ == eod_;
  }

  bool HasCompleteLine() {
    return !BufferIsEmpty() && FindLineFeed() != NULL;
  }

  const int fd_;
  char * const buf_;
  const int buf_len_;
458
  char *bol_;
's avatar
committed
459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618
  char *eol_;
  const char *eod_;  // End of data in "buf_".
};
}  // namespace

// Place the hex number read from "start" into "*hex".  The pointer to
// the first non-hex character or "end" is returned.
static char *GetHex(const char *start, const char *end, uint64_t *hex) {
  *hex = 0;
  const char *p;
  for (p = start; p < end; ++p) {
    int ch = *p;
    if ((ch >= '0' && ch <= '9') ||
        (ch >= 'A' && ch <= 'F') || (ch >= 'a' && ch <= 'f')) {
      *hex = (*hex << 4) | (ch < 'A' ? ch - '0' : (ch & 0xF) + 9);
    } else {  // Encountered the first non-hex character.
      break;
    }
  }
  SAFE_ASSERT(p <= end);
  return const_cast<char *>(p);
}

// Search for the object file (from /proc/self/maps) that contains
// the specified pc. If found, open this file and return the file handle,
// and also set start_address to the start address of where this object
// file is mapped to in memory. Otherwise, return -1.
static ATTRIBUTE_NOINLINE int
OpenObjectFileContainingPcAndGetStartAddress(uint64_t pc,
                                             uint64_t &start_address) {
  int object_fd;

  // Open /proc/self/maps.
  int maps_fd;
  NO_INTR(maps_fd = open("/proc/self/maps", O_RDONLY));
  FileDescriptor wrapped_maps_fd(maps_fd);
  if (wrapped_maps_fd.get() < 0) {
    return -1;
  }

  // Iterate over maps and look for the map containing the pc.  Then
  // look into the symbol tables inside.
  char buf[1024];  // Big enough for line of sane /proc/self/maps
  LineReader reader(wrapped_maps_fd.get(), buf, sizeof(buf));
  while (true) {
    const char *cursor;
    const char *eol;
    if (!reader.ReadLine(&cursor, &eol)) {  // EOF or malformed line.
      return -1;
    }

    // Start parsing line in /proc/self/maps.  Here is an example:
    //
    // 08048000-0804c000 r-xp 00000000 08:01 2142121    /bin/cat
    //
    // We want start address (08048000), end address (0804c000), flags
    // (r-xp) and file name (/bin/cat).

    // Read start address.
    cursor = GetHex(cursor, eol, &start_address);
    if (cursor == eol || *cursor != '-') {
      return -1;  // Malformed line.
    }
    ++cursor;  // Skip '-'.

    // Read end address.
    uint64_t end_address;
    cursor = GetHex(cursor, eol, &end_address);
    if (cursor == eol || *cursor != ' ') {
      return -1;  // Malformed line.
    }
    ++cursor;  // Skip ' '.

    // Check start and end addresses.
    if (!(start_address <= pc && pc < end_address)) {
      continue;  // We skip this map.  PC isn't in this map.
    }

    // Read flags.  Skip flags until we encounter a space or eol.
    const char * const flags_start = cursor;
    while (cursor < eol && *cursor != ' ') {
      ++cursor;
    }
    // We expect at least four letters for flags (ex. "r-xp").
    if (cursor == eol || cursor < flags_start + 4) {
      return -1;  // Malformed line.
    }

    // Check flags.  We are only interested in "r-x" maps.
    if (memcmp(flags_start, "r-x", 3) != 0) {  // Not a "r-x" map.
      continue;  // We skip this map.
    }
    ++cursor;  // Skip ' '.

    // Skip to file name.  "cursor" now points to file offset.  We need to
    // skip at least three spaces for file offset, dev, and inode.
    int num_spaces = 0;
    while (cursor < eol) {
      if (*cursor == ' ') {
        ++num_spaces;
      } else if (num_spaces >= 3) {
        // The first non-space character after  skipping three spaces
        // is the beginning of the file name.
        break;
      }
      ++cursor;
    }
    if (cursor == eol) {
      return -1;  // Malformed line.
    }

    // Finally, "cursor" now points to file name of our interest.
    NO_INTR(object_fd = open(cursor, O_RDONLY));
    if (object_fd < 0) {
      return -1;
    }
    return object_fd;
  }
}

// The implementation of our symbolization routine.  If it
// successfully finds the symbol containing "pc" and obtains the
// symbol name, returns true and write the symbol name to "out".
// Otherwise, returns false. If Callback function is installed via
// InstallSymbolizeCallback(), the function is also called in this function,
// and "out" is used as its output.
// To keep stack consumption low, we would like this function to not
// get inlined.
static ATTRIBUTE_NOINLINE bool SymbolizeAndDemangle(void *pc, char *out,
                                                    int out_size) {
  uint64_t pc0 = reinterpret_cast<uintptr_t>(pc);
  uint64_t start_address = 0;

  int object_fd = OpenObjectFileContainingPcAndGetStartAddress(pc0,
                                                               start_address);
  if (object_fd == -1) {
    return false;
  }
  FileDescriptor wrapped_object_fd(object_fd);
  int elf_type = FileGetElfType(wrapped_object_fd.get());
  if (elf_type == -1) {
    return false;
  }
  if (g_symbolize_callback) {
    // Run the call back if it's installed.
    // Note: relocation (and much of the rest of this code) will be
    // wrong for prelinked shared libraries and PIE executables.
    uint64 relocation = (elf_type == ET_DYN) ? start_address : 0;
    int num_bytes_written = g_symbolize_callback(wrapped_object_fd.get(),
                                                 pc, out, out_size,
                                                 relocation);
    if (num_bytes_written > 0) {
      out += num_bytes_written;
      out_size -= num_bytes_written;
    }
  }
  if (!GetSymbolFromObjectFile(wrapped_object_fd.get(), pc0,
                               out, out_size, start_address)) {
    return false;
  }
619

's avatar
committed
620 621 622 623 624
  // Symbolization succeeded.  Now we try to demangle the symbol.
  DemangleInplace(out, out_size);
  return true;
}

625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655
_END_GOOGLE_NAMESPACE_

#elif defined(OS_MACOSX) && defined(HAVE_DLADDR)

#include <dlfcn.h>
#include <string.h>

_START_GOOGLE_NAMESPACE_

static ATTRIBUTE_NOINLINE bool SymbolizeAndDemangle(void *pc, char *out,
                                                    int out_size) {
  Dl_info info;
  if (dladdr(pc, &info)) {
    if (strlen(info.dli_sname) < out_size) {
      strcpy(out, info.dli_sname);
      // Symbolization succeeded.  Now we try to demangle the symbol.
      DemangleInplace(out, out_size);
      return true;
    }
  }
  return false;
}

_END_GOOGLE_NAMESPACE_

#else
# error BUG: HAVE_SYMBOLIZE was wrongly set
#endif

_START_GOOGLE_NAMESPACE_

's avatar
committed
656 657 658 659 660 661 662
bool Symbolize(void *pc, char *out, int out_size) {
  SAFE_ASSERT(out_size >= 0);
  return SymbolizeAndDemangle(pc, out, out_size);
}

_END_GOOGLE_NAMESPACE_

663
#else  /* HAVE_SYMBOLIZE */
's avatar
committed
664 665 666 667 668 669 670

#include <assert.h>

#include "config.h"

_START_GOOGLE_NAMESPACE_

671
// TODO: Support other environments.
's avatar
committed
672 673 674 675 676 677 678 679
bool Symbolize(void *pc, char *out, int out_size) {
  assert(0);
  return false;
}

_END_GOOGLE_NAMESPACE_

#endif