aboutsummaryrefslogtreecommitdiff
path: root/src/common/linux/dump_symbols.cc
blob: 74bf86708669cf75b26ed3c6a42aeef9ce9acd74 (plain)
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
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
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
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
// 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.

#include <elf.h>
#include <fcntl.h>
#include <link.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>

#include <cassert>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>

#include "common/dwarf/dwarf2diehandler.h"
#include "common/linux/dump_stabs.h"
#include "common/linux/dump_symbols.h"
#include "common/linux/dwarf_cu_to_module.h"
#include "common/linux/dwarf_line_to_module.h"
#include "common/linux/file_id.h"
#include "common/linux/module.h"
#include "common/linux/stabs_reader.h"

// This namespace contains helper functions.
namespace {

using google_breakpad::DumpStabsHandler;
using google_breakpad::DwarfCUToModule;
using google_breakpad::DwarfLineToModule;
using google_breakpad::Module;

// Fix offset into virtual address by adding the mapped base into offsets.
// Make life easier when want to find something by offset.
static void FixAddress(void *obj_base) {
  ElfW(Addr) base = reinterpret_cast<ElfW(Addr)>(obj_base);
  ElfW(Ehdr) *elf_header = static_cast<ElfW(Ehdr) *>(obj_base);
  elf_header->e_phoff += base;
  elf_header->e_shoff += base;
  ElfW(Shdr) *sections = reinterpret_cast<ElfW(Shdr) *>(elf_header->e_shoff);
  for (int i = 0; i < elf_header->e_shnum; ++i)
    sections[i].sh_offset += base;
}

// Find the prefered loading address of the binary.
static ElfW(Addr) GetLoadingAddress(const ElfW(Phdr) *program_headers,
                                    int nheader) {
  for (int i = 0; i < nheader; ++i) {
    const ElfW(Phdr) &header = program_headers[i];
    // For executable, it is the PT_LOAD segment with offset to zero.
    if (header.p_type == PT_LOAD &&
        header.p_offset == 0)
      return header.p_vaddr;
  }
  // For other types of ELF, return 0.
  return 0;
}

static bool IsValidElf(const ElfW(Ehdr) *elf_header) {
  return memcmp(elf_header, ELFMAG, SELFMAG) == 0;
}

static const ElfW(Shdr) *FindSectionByName(const char *name,
                                           const ElfW(Shdr) *sections,
                                           const ElfW(Shdr) *section_names,
                                           int nsection) {
  assert(name != NULL);
  assert(sections != NULL);
  assert(nsection > 0);

  int name_len = strlen(name);
  if (name_len == 0)
    return NULL;

  for (int i = 0; i < nsection; ++i) {
    const char *section_name =
      reinterpret_cast<char*>(section_names->sh_offset + sections[i].sh_name);
    if (!strncmp(name, section_name, name_len))
      return sections + i;
  }
  return NULL;
}

static bool LoadStabs(const ElfW(Shdr) *stab_section,
                      const ElfW(Shdr) *stabstr_section,
                      Module *module) {
  // A callback object to handle data from the STABS reader.
  DumpStabsHandler handler(module);
  // Find the addresses of the STABS data, and create a STABS reader object.
  uint8_t *stabs = reinterpret_cast<uint8_t *>(stab_section->sh_offset);
  uint8_t *stabstr = reinterpret_cast<uint8_t *>(stabstr_section->sh_offset);
  google_breakpad::StabsReader reader(stabs, stab_section->sh_size,
                                      stabstr, stabstr_section->sh_size,
                                      &handler);
  // Read the STABS data, and do post-processing.
  if (!reader.Process())
    return false;
  handler.Finalize();
  return true;
}

// A line-to-module loader that accepts line number info parsed by
// dwarf2reader::LineInfo and populates a Module and a line vector
// with the results.
class DumperLineToModule: public DwarfCUToModule::LineToModuleFunctor {
 public:
  // Create a line-to-module converter using BYTE_READER.
  DumperLineToModule(dwarf2reader::ByteReader *byte_reader)
      : byte_reader_(byte_reader) { }
  void operator()(const char *program, uint64 length,
                  Module *module, vector<Module::Line> *lines) {
    DwarfLineToModule handler(module, lines);
    dwarf2reader::LineInfo parser(program, length, byte_reader_, &handler);
    parser.Start();
  }
 private:
  dwarf2reader::ByteReader *byte_reader_;
};

static bool LoadDwarf(const string &dwarf_filename,
                      const ElfW(Ehdr) *elf_header,
                      Module *module) {
  // Figure out what endianness this file is.
  dwarf2reader::Endianness endianness;
  if (elf_header->e_ident[EI_DATA] == ELFDATA2LSB)
    endianness = dwarf2reader::ENDIANNESS_LITTLE;
  else if (elf_header->e_ident[EI_DATA] == ELFDATA2MSB)
    endianness = dwarf2reader::ENDIANNESS_BIG;
  else {
    fprintf(stderr, "bad data encoding in ELF header: %d\n",
            elf_header->e_ident[EI_DATA]);
    return false;
  }
  dwarf2reader::ByteReader byte_reader(endianness);

  // Construct a context for this file.
  DwarfCUToModule::FileContext file_context(dwarf_filename, module);

  // Build a map of the ELF file's sections.
  const ElfW(Shdr) *sections
      = reinterpret_cast<ElfW(Shdr) *>(elf_header->e_shoff);
  int num_sections = elf_header->e_shnum;
  const ElfW(Shdr) *section_names = sections + elf_header->e_shstrndx;
  for (int i = 0; i < num_sections; i++) {
    const ElfW(Shdr) *section = &sections[i];
    string name = reinterpret_cast<const char *>(section_names->sh_offset
                                                 + section->sh_name);
    const char *contents = reinterpret_cast<const char *>(section->sh_offset);
    uint64 length = section->sh_size;
    file_context.section_map[name] = std::make_pair(contents, length);
  }

  // Parse all the compilation units in the .debug_info section.
  DumperLineToModule line_to_module(&byte_reader);
  std::pair<const char *, uint64> debug_info_section
      = file_context.section_map[".debug_info"];
  // We should never have been called if the file doesn't have a
  // .debug_info section.
  assert(debug_info_section.first);
  uint64 debug_info_length = debug_info_section.second;
  for (uint64 offset = 0; offset < debug_info_length;) {
    // Make a handler for the root DIE that populates MODULE with the
    // data we find.
    DwarfCUToModule::WarningReporter reporter(dwarf_filename, offset);
    DwarfCUToModule root_handler(&file_context, &line_to_module, &reporter);
    // Make a Dwarf2Handler that drives our DIEHandler.
    dwarf2reader::DIEDispatcher die_dispatcher(&root_handler);
    // Make a DWARF parser for the compilation unit at OFFSET.
    dwarf2reader::CompilationUnit reader(file_context.section_map,
                                         offset,
                                         &byte_reader,
                                         &die_dispatcher);
    // Process the entire compilation unit; get the offset of the next.
    offset += reader.Start();
  }
  return true;
}

static bool LoadSymbols(const std::string &obj_file, ElfW(Ehdr) *elf_header,
                        Module *module) {
  // Translate all offsets in section headers into address.
  FixAddress(elf_header);
  ElfW(Addr) loading_addr = GetLoadingAddress(
      reinterpret_cast<ElfW(Phdr) *>(elf_header->e_phoff),
      elf_header->e_phnum);
  module->SetLoadAddress(loading_addr);

  const ElfW(Shdr) *sections =
      reinterpret_cast<ElfW(Shdr) *>(elf_header->e_shoff);
  const ElfW(Shdr) *section_names = sections + elf_header->e_shstrndx;
  bool found_debug_info_section = false;
  const ElfW(Shdr) *stab_section
      = FindSectionByName(".stab", sections, section_names,
                          elf_header->e_shnum);
  if (stab_section) {
    const ElfW(Shdr) *stabstr_section = stab_section->sh_link + sections;
    if (stabstr_section) {
      found_debug_info_section = true;
      if (!LoadStabs(stab_section, stabstr_section, module))
        fprintf(stderr, "\".stab\" section found, but failed to load STABS"
                " debugging information\n");
    }
  }
  const ElfW(Shdr) *dwarf_section
      = FindSectionByName(".debug_info", sections, section_names,
                          elf_header->e_shnum);
  if (dwarf_section) {
    found_debug_info_section = true;
    if (!LoadDwarf(obj_file, elf_header, module))
      fprintf(stderr, "\".debug_info\" section found, but failed to load "
              "DWARF debugging information\n");
  }
  if (!found_debug_info_section) {
    fprintf(stderr, "file contains no debugging information"
            " (no \".stab\" or \".debug_info\" sections)\n");
    return false;
  }
  return true;
}

//
// FDWrapper
//
// Wrapper class to make sure opened file is closed.
//
class FDWrapper {
 public:
  explicit FDWrapper(int fd) :
    fd_(fd) {
    }
  ~FDWrapper() {
    if (fd_ != -1)
      close(fd_);
  }
  int get() {
    return fd_;
  }
  int release() {
    int fd = fd_;
    fd_ = -1;
    return fd;
  }
 private:
  int fd_;
};

//
// MmapWrapper
//
// Wrapper class to make sure mapped regions are unmapped.
//
class MmapWrapper {
  public:
   MmapWrapper(void *mapped_address, size_t mapped_size) :
     base_(mapped_address), size_(mapped_size) {
   }
   ~MmapWrapper() {
     if (base_ != NULL) {
       assert(size_ > 0);
       munmap(base_, size_);
     }
   }
   void release() {
     base_ = NULL;
     size_ = 0;
   }

  private:
   void *base_;
   size_t size_;
};

// Return the breakpad symbol file identifier for the architecture of
// ELF_HEADER.
const char *ElfArchitecture(const ElfW(Ehdr) *elf_header) {
  ElfW(Half) arch = elf_header->e_machine;
  if (arch == EM_386)
    return "x86";
  else if (arch == EM_X86_64)
    return "x86_64";
  else
    return NULL;
}

// Format the Elf file identifier in IDENTIFIER as a UUID with the
// dashes removed.
std::string FormatIdentifier(unsigned char identifier[16]) {
  char identifier_str[40];
  google_breakpad::FileID::ConvertIdentifierToString(
      identifier,
      identifier_str,
      sizeof(identifier_str));
  std::string id_no_dash;
  for (int i = 0; identifier_str[i] != '\0'; ++i)
    if (identifier_str[i] != '-')
      id_no_dash += identifier_str[i];
  // Add an extra "0" by the end.  PDB files on Windows have an 'age'
  // number appended to the end of the file identifier; this isn't
  // really used or necessary on other platforms, but let's preserve
  // the pattern.
  id_no_dash += '0';
  return id_no_dash;
}

// Return the non-directory portion of FILENAME: the portion after the
// last slash, or the whole filename if there are no slashes.
std::string BaseFileName(const std::string &filename) {
  // Lots of copies!  basename's behavior is less than ideal.
  char *c_filename = strdup(filename.c_str());
  std::string base = basename(c_filename);
  free(c_filename);
  return base;
}

}  // namespace

namespace google_breakpad {

bool DumpSymbols::WriteSymbolFile(const std::string &obj_file,
                                  FILE *sym_file) {
  int obj_fd = open(obj_file.c_str(), O_RDONLY);
  if (obj_fd < 0)
    return false;
  FDWrapper obj_fd_wrapper(obj_fd);
  struct stat st;
  if (fstat(obj_fd, &st) != 0 && st.st_size <= 0)
    return false;
  void *obj_base = mmap(NULL, st.st_size,
                        PROT_READ | PROT_WRITE, MAP_PRIVATE, obj_fd, 0);
  if (obj_base == MAP_FAILED)
    return false;
  MmapWrapper map_wrapper(obj_base, st.st_size);
  ElfW(Ehdr) *elf_header = reinterpret_cast<ElfW(Ehdr) *>(obj_base);
  if (!IsValidElf(elf_header))
    return false;

  unsigned char identifier[16];
  google_breakpad::FileID file_id(obj_file.c_str());
  if (!file_id.ElfFileIdentifier(identifier))
    return false;

  const char *architecture = ElfArchitecture(elf_header);
  if (!architecture)
    return false;

  std::string name = BaseFileName(obj_file);
  std::string os = "Linux";
  std::string id = FormatIdentifier(identifier);

  Module module(name, os, architecture, id);
  if (!LoadSymbols(obj_file, elf_header, &module))
    return false;
  if (!module.Write(sym_file))
    return false;

  return true;
}

}  // namespace google_breakpad