1  // Copyright 2011 Google LLC
  2  //
  3  // Redistribution and use in source and binary forms, with or without
  4  // modification, are permitted provided that the following conditions are
  5  // met:
  6  //
  7  //     * Redistributions of source code must retain the above copyright
  8  // notice, this list of conditions and the following disclaimer.
  9  //     * Redistributions in binary form must reproduce the above
 10  // copyright notice, this list of conditions and the following disclaimer
 11  // in the documentation and/or other materials provided with the
 12  // distribution.
 13  //     * Neither the name of Google LLC nor the names of its
 14  // contributors may be used to endorse or promote products derived from
 15  // this software without specific prior written permission.
 16  //
 17  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 18  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 19  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 20  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 21  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 22  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 23  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 24  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 25  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 26  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 27  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 28  
 29  // elf_core_dump.cc: Implement google_breakpad::ElfCoreDump.
 30  // See elf_core_dump.h for details.
 31  
 32  #ifdef HAVE_CONFIG_H
 33  #include <config.h>  // Must come first
 34  #endif
 35  
 36  #include "common/linux/elf_core_dump.h"
 37  
 38  #include <stddef.h>
 39  #include <string.h>
 40  #include <unistd.h>
 41  
 42  namespace google_breakpad {
 43  
 44  // Implementation of ElfCoreDump::Note.
 45  
 46  ElfCoreDump::Note::Note() {}
 47  
 48  ElfCoreDump::Note::Note(const MemoryRange& content) : content_(content) {}
 49  
 50  bool ElfCoreDump::Note::IsValid() const {
 51    return GetHeader() != NULL;
 52  }
 53  
 54  const ElfCoreDump::Nhdr* ElfCoreDump::Note::GetHeader() const {
 55    return content_.GetData<Nhdr>(0);
 56  }
 57  
 58  ElfCoreDump::Word ElfCoreDump::Note::GetType() const {
 59    const Nhdr* header = GetHeader();
 60    // 0 is not being used as a NOTE type.
 61    return header ? header->n_type : 0;
 62  }
 63  
 64  MemoryRange ElfCoreDump::Note::GetName() const {
 65    const Nhdr* header = GetHeader();
 66    if (header) {
 67        return content_.Subrange(sizeof(Nhdr), header->n_namesz);
 68    }
 69    return MemoryRange();
 70  }
 71  
 72  MemoryRange ElfCoreDump::Note::GetDescription() const {
 73    const Nhdr* header = GetHeader();
 74    if (header) {
 75      return content_.Subrange(AlignedSize(sizeof(Nhdr) + header->n_namesz),
 76                               header->n_descsz);
 77    }
 78    return MemoryRange();
 79  }
 80  
 81  ElfCoreDump::Note ElfCoreDump::Note::GetNextNote() const {
 82    MemoryRange next_content;
 83    const Nhdr* header = GetHeader();
 84    if (header) {
 85      size_t next_offset = AlignedSize(sizeof(Nhdr) + header->n_namesz);
 86      next_offset = AlignedSize(next_offset + header->n_descsz);
 87      next_content =
 88          content_.Subrange(next_offset, content_.length() - next_offset);
 89    }
 90    return Note(next_content);
 91  }
 92  
 93  // static
 94  size_t ElfCoreDump::Note::AlignedSize(size_t size) {
 95    size_t mask = sizeof(Word) - 1;
 96    return (size + mask) & ~mask;
 97  }
 98  
 99  
100  // Implementation of ElfCoreDump.
101  
102  ElfCoreDump::ElfCoreDump() : proc_mem_fd_(-1) {}
103  
104  ElfCoreDump::ElfCoreDump(const MemoryRange& content)
105      : content_(content), proc_mem_fd_(-1) {}
106  
107  ElfCoreDump::~ElfCoreDump() {
108    if (proc_mem_fd_ != -1) {
109      close(proc_mem_fd_);
110      proc_mem_fd_ = -1;
111    }
112  }
113  
114  void ElfCoreDump::SetContent(const MemoryRange& content) {
115    content_ = content;
116  }
117  
118  void ElfCoreDump::SetProcMem(int fd) {
119    if (proc_mem_fd_ != -1) {
120      close(proc_mem_fd_);
121    }
122    proc_mem_fd_ = fd;
123  }
124  
125  bool ElfCoreDump::IsValid() const {
126    const Ehdr* header = GetHeader();
127    return (header &&
128            header->e_ident[0] == ELFMAG0 &&
129            header->e_ident[1] == ELFMAG1 &&
130            header->e_ident[2] == ELFMAG2 &&
131            header->e_ident[3] == ELFMAG3 &&
132            header->e_ident[4] == kClass &&
133            header->e_version == EV_CURRENT &&
134            header->e_type == ET_CORE);
135  }
136  
137  const ElfCoreDump::Ehdr* ElfCoreDump::GetHeader() const {
138    return content_.GetData<Ehdr>(0);
139  }
140  
141  const ElfCoreDump::Phdr* ElfCoreDump::GetProgramHeader(unsigned index) const {
142    const Ehdr* header = GetHeader();
143    if (header) {
144      return reinterpret_cast<const Phdr*>(content_.GetArrayElement(
145          header->e_phoff, header->e_phentsize, index));
146    }
147    return NULL;
148  }
149  
150  const ElfCoreDump::Phdr* ElfCoreDump::GetFirstProgramHeaderOfType(
151      Word type) const {
152    for (unsigned i = 0, n = GetProgramHeaderCount(); i < n; ++i) {
153      const Phdr* program = GetProgramHeader(i);
154      if (program->p_type == type) {
155        return program;
156      }
157    }
158    return NULL;
159  }
160  
161  unsigned ElfCoreDump::GetProgramHeaderCount() const {
162    const Ehdr* header = GetHeader();
163    return header ? header->e_phnum : 0;
164  }
165  
166  bool ElfCoreDump::CopyData(void* buffer, Addr virtual_address, size_t length) {
167    for (unsigned i = 0, n = GetProgramHeaderCount(); i < n; ++i) {
168      const Phdr* program = GetProgramHeader(i);
169      if (program->p_type != PT_LOAD)
170        continue;
171  
172      size_t offset_in_segment = virtual_address - program->p_vaddr;
173      if (virtual_address >= program->p_vaddr &&
174          offset_in_segment < program->p_filesz) {
175        const void* data =
176            content_.GetData(program->p_offset + offset_in_segment, length);
177        if (data) {
178          memcpy(buffer, data, length);
179          return true;
180        }
181      }
182    }
183  
184    /* fallback: if available, read from /proc/<pid>/mem */
185    if (proc_mem_fd_ != -1) {
186      off_t offset = virtual_address;
187      ssize_t r = pread(proc_mem_fd_, buffer, length, offset);
188      if (r < ssize_t(length)) {
189        return false;
190      }
191      return true;
192    }
193    return false;
194  }
195  
196  ElfCoreDump::Note ElfCoreDump::GetFirstNote() const {
197    MemoryRange note_content;
198    const Phdr* program_header = GetFirstProgramHeaderOfType(PT_NOTE);
199    if (program_header) {
200      note_content = content_.Subrange(program_header->p_offset,
201                                       program_header->p_filesz);
202    }
203    return Note(note_content);
204  }
205  
206  }  // namespace google_breakpad