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  // memory_mapped_file.cc: Implement google_breakpad::MemoryMappedFile.
 30  // See memory_mapped_file.h for details.
 31  
 32  #ifdef HAVE_CONFIG_H
 33  #include <config.h>  // Must come first
 34  #endif
 35  
 36  #include "common/linux/memory_mapped_file.h"
 37  
 38  #include <fcntl.h>
 39  #include <sys/mman.h>
 40  #if defined(__ANDROID__)
 41  #include <sys/stat.h>
 42  #endif
 43  #include <unistd.h>
 44  
 45  #include "common/memory_range.h"
 46  #include "third_party/lss/linux_syscall_support.h"
 47  
 48  namespace google_breakpad {
 49  
 50  MemoryMappedFile::MemoryMappedFile() {}
 51  
 52  MemoryMappedFile::MemoryMappedFile(const char* path, size_t offset) {
 53    Map(path, offset);
 54  }
 55  
 56  MemoryMappedFile::~MemoryMappedFile() {
 57    Unmap();
 58  }
 59  
 60  #include <unistd.h>
 61  
 62  bool MemoryMappedFile::Map(const char* path, size_t offset) {
 63    Unmap();
 64    // Based on https://pubs.opengroup.org/onlinepubs/7908799/xsh/open.html
 65    // If O_NONBLOCK is set: The open() function will return without blocking
 66    // for the device to be ready or available. Setting this value will provent
 67    // hanging if file is not avilable.
 68    int fd = sys_open(path, O_RDONLY | O_NONBLOCK, 0);
 69    if (fd == -1) {
 70      return false;
 71    }
 72  
 73  #if defined(__x86_64__) || defined(__aarch64__) || \
 74     (defined(__mips__) && _MIPS_SIM == _ABI64) || \
 75     (defined(__riscv) && __riscv_xlen == 64)
 76  
 77    struct kernel_stat st;
 78    if (sys_fstat(fd, &st) == -1 || st.st_size < 0) {
 79  #else
 80    struct kernel_stat64 st;
 81    if (sys_fstat64(fd, &st) == -1 || st.st_size < 0) {
 82  #endif
 83      sys_close(fd);
 84      return false;
 85    }
 86  
 87    // Strangely file size can be negative, but we check above that it is not.
 88    size_t file_len = static_cast<size_t>(st.st_size);
 89    // If the file does not extend beyond the offset, simply use an empty
 90    // MemoryRange and return true. Don't bother to call mmap()
 91    // even though mmap() can handle an empty file on some platforms.
 92    if (offset >= file_len) {
 93      sys_close(fd);
 94      return true;
 95    }
 96  
 97    size_t content_len = file_len - offset;
 98    void* data = sys_mmap(NULL, content_len, PROT_READ, MAP_PRIVATE, fd, offset);
 99    sys_close(fd);
100    if (data == MAP_FAILED) {
101      return false;
102    }
103  
104    content_.Set(data, content_len);
105    return true;
106  }
107  
108  void MemoryMappedFile::Unmap() {
109    if (content_.data()) {
110      sys_munmap(const_cast<uint8_t*>(content_.data()), content_.length());
111      content_.Set(NULL, 0);
112    }
113  }
114  
115  }  // namespace google_breakpad