// Copyright (c) 2014 GitHub, Inc.
// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by the MIT license that can be
// found in the LICENSE file.

// For linux_syscall_support.h. This makes it safe to call embedded system
// calls when in seccomp mode.

#include "shell/common/crash_reporter/linux/crash_dump_handler.h"

#include <poll.h>

#include <algorithm>

#include "base/posix/eintr_wrapper.h"
#include "breakpad/src/client/linux/minidump_writer/directory_reader.h"
#include "breakpad/src/common/linux/linux_libc_support.h"
#include "breakpad/src/common/memory_allocator.h"

#include "third_party/lss/linux_syscall_support.h"

// Some versions of gcc are prone to warn about unused return values. In cases
// where we either a) know the call cannot fail, or b) there is nothing we
// can do when a call fails, we mark the return code as ignored. This avoids
// spurious compiler warnings.
#define IGNORE_RET(x) \
  do {                \
    if (x)            \
      ;               \
  } while (0)

namespace crash_reporter {

namespace {

// String buffer size to use to convert a uint64_t to string.
const size_t kUint64StringSize = 21;

// Writes the value |v| as 16 hex characters to the memory pointed at by
// |output|.
void write_uint64_hex(char* output, uint64_t v) {
  static const char hextable[] = "0123456789abcdef";

  for (int i = 15; i >= 0; --i) {
    output[i] = hextable[v & 15];
    v >>= 4;
  }
}

// uint64_t version of my_int_len() from
// breakpad/src/common/linux/linux_libc_support.h. Return the length of the
// given, non-negative integer when expressed in base 10.
unsigned my_uint64_len(uint64_t i) {
  if (!i)
    return 1;

  unsigned len = 0;
  while (i) {
    len++;
    i /= 10;
  }

  return len;
}

// uint64_t version of my_uitos() from
// breakpad/src/common/linux/linux_libc_support.h. Convert a non-negative
// integer to a string (not null-terminated).
void my_uint64tos(char* output, uint64_t i, unsigned i_len) {
  for (unsigned index = i_len; index; --index, i /= 10)
    output[index - 1] = '0' + (i % 10);
}

// Converts a struct timeval to milliseconds.
uint64_t kernel_timeval_to_ms(struct kernel_timeval* tv) {
  uint64_t ret = tv->tv_sec;  // Avoid overflow by explicitly using a uint64_t.
  ret *= 1000;
  ret += tv->tv_usec / 1000;
  return ret;
}

bool my_isxdigit(char c) {
  return (c >= '0' && c <= '9') || ((c | 0x20) >= 'a' && (c | 0x20) <= 'f');
}

size_t LengthWithoutTrailingSpaces(const char* str, size_t len) {
  while (len > 0 && str[len - 1] == ' ') {
    len--;
  }
  return len;
}

// MIME substrings.
const char g_rn[] = "\r\n";
const char g_form_data_msg[] = "Content-Disposition: form-data; name=\"";
const char g_quote_msg[] = "\"";
const char g_dashdash_msg[] = "--";
const char g_dump_msg[] = "upload_file_minidump\"; filename=\"dump\"";
const char g_content_type_msg[] = "Content-Type: application/octet-stream";

// MimeWriter manages an iovec for writing MIMEs to a file.
class MimeWriter {
 public:
  static const int kIovCapacity = 30;
  static const size_t kMaxCrashChunkSize = 64;

  MimeWriter(int fd, const char* const mime_boundary);
  ~MimeWriter();

  // Append boundary.
  virtual void AddBoundary();

  // Append end of file boundary.
  virtual void AddEnd();

  // Append key/value pair with specified sizes.
  virtual void AddPairData(const char* msg_type,
                           size_t msg_type_size,
                           const char* msg_data,
                           size_t msg_data_size);

  // Append key/value pair.
  void AddPairString(const char* msg_type, const char* msg_data) {
    AddPairData(msg_type, my_strlen(msg_type), msg_data, my_strlen(msg_data));
  }

  // Append key/value pair, splitting value into chunks no larger than
  // |chunk_size|. |chunk_size| cannot be greater than |kMaxCrashChunkSize|.
  // The msg_type string will have a counter suffix to distinguish each chunk.
  virtual void AddPairDataInChunks(const char* msg_type,
                                   size_t msg_type_size,
                                   const char* msg_data,
                                   size_t msg_data_size,
                                   size_t chunk_size,
                                   bool strip_trailing_spaces);

  // Add binary file contents to be uploaded with the specified filename.
  virtual void AddFileContents(const char* filename_msg,
                               uint8_t* file_data,
                               size_t file_size);

  // Flush any pending iovecs to the output file.
  void Flush() {
    IGNORE_RET(sys_writev(fd_, iov_, iov_index_));
    iov_index_ = 0;
  }

 protected:
  void AddItem(const void* base, size_t size);
  // Minor performance trade-off for easier-to-maintain code.
  void AddString(const char* str) { AddItem(str, my_strlen(str)); }
  void AddItemWithoutTrailingSpaces(const void* base, size_t size);

  struct kernel_iovec iov_[kIovCapacity];
  int iov_index_ = 0;

  // Output file descriptor.
  int fd_ = -1;

  const char* const mime_boundary_;

 private:
  DISALLOW_COPY_AND_ASSIGN(MimeWriter);
};

MimeWriter::MimeWriter(int fd, const char* const mime_boundary)
    : fd_(fd), mime_boundary_(mime_boundary) {}

MimeWriter::~MimeWriter() {}

void MimeWriter::AddBoundary() {
  AddString(mime_boundary_);
  AddString(g_rn);
}

void MimeWriter::AddEnd() {
  AddString(mime_boundary_);
  AddString(g_dashdash_msg);
  AddString(g_rn);
}

void MimeWriter::AddPairData(const char* msg_type,
                             size_t msg_type_size,
                             const char* msg_data,
                             size_t msg_data_size) {
  AddString(g_form_data_msg);
  AddItem(msg_type, msg_type_size);
  AddString(g_quote_msg);
  AddString(g_rn);
  AddString(g_rn);
  AddItem(msg_data, msg_data_size);
  AddString(g_rn);
}

void MimeWriter::AddPairDataInChunks(const char* msg_type,
                                     size_t msg_type_size,
                                     const char* msg_data,
                                     size_t msg_data_size,
                                     size_t chunk_size,
                                     bool strip_trailing_spaces) {
  if (chunk_size > kMaxCrashChunkSize)
    return;

  unsigned i = 0;
  size_t done = 0, msg_length = msg_data_size;

  while (msg_length) {
    char num[kUint64StringSize];
    const unsigned num_len = my_uint_len(++i);
    my_uitos(num, i, num_len);

    size_t chunk_len = std::min(chunk_size, msg_length);

    AddString(g_form_data_msg);
    AddItem(msg_type, msg_type_size);
    AddItem(num, num_len);
    AddString(g_quote_msg);
    AddString(g_rn);
    AddString(g_rn);
    if (strip_trailing_spaces) {
      AddItemWithoutTrailingSpaces(msg_data + done, chunk_len);
    } else {
      AddItem(msg_data + done, chunk_len);
    }
    AddString(g_rn);
    AddBoundary();
    Flush();

    done += chunk_len;
    msg_length -= chunk_len;
  }
}

void MimeWriter::AddFileContents(const char* filename_msg,
                                 uint8_t* file_data,
                                 size_t file_size) {
  AddString(g_form_data_msg);
  AddString(filename_msg);
  AddString(g_rn);
  AddString(g_content_type_msg);
  AddString(g_rn);
  AddString(g_rn);
  AddItem(file_data, file_size);
  AddString(g_rn);
}

void MimeWriter::AddItem(const void* base, size_t size) {
  // Check if the iovec is full and needs to be flushed to output file.
  if (iov_index_ == kIovCapacity) {
    Flush();
  }
  iov_[iov_index_].iov_base = const_cast<void*>(base);
  iov_[iov_index_].iov_len = size;
  ++iov_index_;
}

void MimeWriter::AddItemWithoutTrailingSpaces(const void* base, size_t size) {
  AddItem(base,
          LengthWithoutTrailingSpaces(static_cast<const char*>(base), size));
}

void LoadDataFromFD(google_breakpad::PageAllocator* allocator,
                    int fd,
                    bool close_fd,
                    uint8_t** file_data,
                    size_t* size) {
  struct kernel_stat st;
  if (sys_fstat(fd, &st) != 0) {
    static const char msg[] = "Cannot upload crash dump: stat failed\n";
    WriteLog(msg, sizeof(msg) - 1);
    if (close_fd)
      IGNORE_RET(sys_close(fd));
    return;
  }

  *file_data = reinterpret_cast<uint8_t*>(allocator->Alloc(st.st_size));
  if (!(*file_data)) {
    static const char msg[] = "Cannot upload crash dump: cannot alloc\n";
    WriteLog(msg, sizeof(msg) - 1);
    if (close_fd)
      IGNORE_RET(sys_close(fd));
    return;
  }
  my_memset(*file_data, 0xf, st.st_size);

  *size = st.st_size;
  int byte_read = sys_read(fd, *file_data, *size);
  if (byte_read == -1) {
    static const char msg[] = "Cannot upload crash dump: read failed\n";
    WriteLog(msg, sizeof(msg) - 1);
    if (close_fd)
      IGNORE_RET(sys_close(fd));
    return;
  }

  if (close_fd)
    IGNORE_RET(sys_close(fd));
}

void LoadDataFromFile(google_breakpad::PageAllocator* allocator,
                      const char* filename,
                      int* fd,
                      uint8_t** file_data,
                      size_t* size) {
  // WARNING: this code runs in a compromised context. It may not call into
  // libc nor allocate memory normally.
  *fd = sys_open(filename, O_RDONLY, 0);
  *size = 0;

  if (*fd < 0) {
    static const char msg[] = "Cannot upload crash dump: failed to open\n";
    WriteLog(msg, sizeof(msg) - 1);
    return;
  }

  LoadDataFromFD(allocator, *fd, true, file_data, size);
}

// Spawn the appropriate upload process for the current OS:
// - generic Linux invokes wget.
// - ChromeOS invokes crash_reporter.
// |dumpfile| is the path to the dump data file.
// |mime_boundary| is only used on Linux.
// |exe_buf| is only used on CrOS and is the crashing process' name.
void ExecUploadProcessOrTerminate(const BreakpadInfo& info,
                                  const char* dumpfile,
                                  const char* mime_boundary,
                                  const char* exe_buf,
                                  google_breakpad::PageAllocator* allocator) {
  // The --header argument to wget looks like:
  //   --header=Content-Type: multipart/form-data; boundary=XYZ
  // where the boundary has two fewer leading '-' chars
  static const char header_msg[] =
      "--header=Content-Type: multipart/form-data; boundary=";
  char* const header = reinterpret_cast<char*>(
      allocator->Alloc(sizeof(header_msg) - 1 + strlen(mime_boundary) - 2 + 1));
  memcpy(header, header_msg, sizeof(header_msg) - 1);
  memcpy(header + sizeof(header_msg) - 1, mime_boundary + 2,
         strlen(mime_boundary) - 2);
  // We grab the NUL byte from the end of |mime_boundary|.

  // The --post-file argument to wget looks like:
  //   --post-file=/tmp/...
  static const char post_file_msg[] = "--post-file=";
  char* const post_file = reinterpret_cast<char*>(
      allocator->Alloc(sizeof(post_file_msg) - 1 + strlen(dumpfile) + 1));
  memcpy(post_file, post_file_msg, sizeof(post_file_msg) - 1);
  memcpy(post_file + sizeof(post_file_msg) - 1, dumpfile, strlen(dumpfile));

  static const char kWgetBinary[] = "/usr/bin/wget";
  const char* args[] = {
      kWgetBinary,    header, post_file, info.upload_url,
      "--timeout=60",  // Set a timeout so we don't hang forever.
      "--tries=1",     // Don't retry if the upload fails.
      "--quiet",       // Be silent.
      "-O",            // output reply to /dev/null.
      "/dev/fd/3",    NULL,
  };
  static const char msg[] =
      "Cannot upload crash dump: cannot exec "
      "/usr/bin/wget\n";
  execve(args[0], const_cast<char**>(args), environ);
  WriteLog(msg, sizeof(msg) - 1);
  sys__exit(1);
}

// Runs in the helper process to wait for the upload process running
// ExecUploadProcessOrTerminate() to finish. Returns the number of bytes written
// to |fd| and save the written contents to |buf|.
// |buf| needs to be big enough to hold |bytes_to_read| + 1 characters.
size_t WaitForCrashReportUploadProcess(int fd,
                                       size_t bytes_to_read,
                                       char* buf) {
  size_t bytes_read = 0;

  // Upload should finish in about 10 seconds. Add a few more 500 ms
  // internals to account for process startup time.
  for (size_t wait_count = 0; wait_count < 24; ++wait_count) {
    struct kernel_pollfd poll_fd;
    poll_fd.fd = fd;
    poll_fd.events = POLLIN | POLLPRI | POLLERR;
    int ret = sys_poll(&poll_fd, 1, 500);
    if (ret < 0) {
      // Error
      break;
    } else if (ret > 0) {
      // There is data to read.
      ssize_t len = HANDLE_EINTR(
          sys_read(fd, buf + bytes_read, bytes_to_read - bytes_read));
      if (len < 0)
        break;
      bytes_read += len;
      if (bytes_read == bytes_to_read)
        break;
    }
    // |ret| == 0 -> timed out, continue waiting.
    // or |bytes_read| < |bytes_to_read| still, keep reading.
  }
  buf[bytes_to_read] = 0;  // Always NUL terminate the buffer.
  return bytes_read;
}

// |buf| should be |expected_len| + 1 characters in size and NULL terminated.
bool IsValidCrashReportId(const char* buf,
                          size_t bytes_read,
                          size_t expected_len) {
  if (bytes_read != expected_len)
    return false;
  for (size_t i = 0; i < bytes_read; ++i) {
    if (!my_isxdigit(buf[i]) && buf[i] != '-')
      return false;
  }
  return true;
}

// |buf| should be |expected_len| + 1 characters in size and NULL terminated.
void HandleCrashReportId(const char* buf,
                         size_t bytes_read,
                         size_t expected_len) {
  if (!IsValidCrashReportId(buf, bytes_read, expected_len)) {
    static const char msg[] = "Failed to get crash dump id.";
    WriteLog(msg, sizeof(msg) - 1);
    WriteNewline();

    static const char id_msg[] = "Report Id: ";
    WriteLog(id_msg, sizeof(id_msg) - 1);
    WriteLog(buf, bytes_read);
    WriteNewline();
    return;
  }

  // Write crash dump id to stderr.
  static const char msg[] = "Crash dump id: ";
  WriteLog(msg, sizeof(msg) - 1);
  WriteLog(buf, my_strlen(buf));
  WriteNewline();

  // Write crash dump id to crash log as: seconds_since_epoch,crash_id
  struct kernel_timeval tv;
  if (!sys_gettimeofday(&tv, NULL)) {
    uint64_t time = kernel_timeval_to_ms(&tv) / 1000;
    char time_str[kUint64StringSize];
    const unsigned time_len = my_uint64_len(time);
    my_uint64tos(time_str, time, time_len);

    const int kLogOpenFlags = O_CREAT | O_WRONLY | O_APPEND | O_CLOEXEC;
    int log_fd = sys_open(g_crash_log_path, kLogOpenFlags, 0600);
    if (log_fd > 0) {
      sys_write(log_fd, time_str, time_len);
      sys_write(log_fd, ",", 1);
      sys_write(log_fd, buf, my_strlen(buf));
      sys_write(log_fd, "\n", 1);
      IGNORE_RET(sys_close(log_fd));
    }
  }
}

}  // namespace

char g_crash_log_path[256];

void HandleCrashDump(const BreakpadInfo& info) {
  int dumpfd;
  bool keep_fd = false;
  size_t dump_size;
  uint8_t* dump_data;
  google_breakpad::PageAllocator allocator;
  const char* exe_buf = NULL;

  if (info.fd != -1) {
    // Dump is provided with an open FD.
    keep_fd = true;
    dumpfd = info.fd;

    // The FD is pointing to the end of the file.
    // Rewind, we'll read the data next.
    if (lseek(dumpfd, 0, SEEK_SET) == -1) {
      static const char msg[] =
          "Cannot upload crash dump: failed to "
          "reposition minidump FD\n";
      WriteLog(msg, sizeof(msg) - 1);
      IGNORE_RET(sys_close(dumpfd));
      return;
    }
    LoadDataFromFD(&allocator, info.fd, false, &dump_data, &dump_size);
  } else {
    // Dump is provided with a path.
    keep_fd = false;
    LoadDataFromFile(&allocator, info.filename, &dumpfd, &dump_data,
                     &dump_size);
  }

  // We need to build a MIME block for uploading to the server. Since we are
  // going to fork and run wget, it needs to be written to a temp file.
  const int ufd = sys_open("/dev/urandom", O_RDONLY, 0);
  if (ufd < 0) {
    static const char msg[] =
        "Cannot upload crash dump because /dev/urandom"
        " is missing\n";
    WriteLog(msg, sizeof(msg) - 1);
    return;
  }

  static const char temp_file_template[] =
      "/tmp/chromium-upload-XXXXXXXXXXXXXXXX";
  char temp_file[sizeof(temp_file_template)];
  int temp_file_fd = -1;
  if (keep_fd) {
    temp_file_fd = dumpfd;
    // Rewind the destination, we are going to overwrite it.
    if (lseek(dumpfd, 0, SEEK_SET) == -1) {
      static const char msg[] =
          "Cannot upload crash dump: failed to "
          "reposition minidump FD (2)\n";
      WriteLog(msg, sizeof(msg) - 1);
      IGNORE_RET(sys_close(dumpfd));
      return;
    }
  } else {
    if (info.upload) {
      memcpy(temp_file, temp_file_template, sizeof(temp_file_template));

      for (unsigned i = 0; i < 10; ++i) {
        uint64_t t;
        sys_read(ufd, &t, sizeof(t));
        write_uint64_hex(temp_file + sizeof(temp_file) - (16 + 1), t);

        temp_file_fd = sys_open(temp_file, O_WRONLY | O_CREAT | O_EXCL, 0600);
        if (temp_file_fd >= 0)
          break;
      }

      if (temp_file_fd < 0) {
        static const char msg[] =
            "Failed to create temporary file in /tmp: "
            "cannot upload crash dump\n";
        WriteLog(msg, sizeof(msg) - 1);
        IGNORE_RET(sys_close(ufd));
        return;
      }
    } else {
      temp_file_fd = sys_open(info.filename, O_WRONLY, 0600);
      if (temp_file_fd < 0) {
        static const char msg[] = "Failed to save crash dump: failed to open\n";
        WriteLog(msg, sizeof(msg) - 1);
        IGNORE_RET(sys_close(ufd));
        return;
      }
    }
  }

  // The MIME boundary is 28 hyphens, followed by a 64-bit nonce and a NUL.
  char mime_boundary[28 + 16 + 1];
  my_memset(mime_boundary, '-', 28);
  uint64_t boundary_rand;
  sys_read(ufd, &boundary_rand, sizeof(boundary_rand));
  write_uint64_hex(mime_boundary + 28, boundary_rand);
  mime_boundary[28 + 16] = 0;
  IGNORE_RET(sys_close(ufd));

  // The MIME block looks like this:
  //   BOUNDARY \r\n
  //   Content-Disposition: form-data; name="prod" \r\n \r\n
  //   Chrome_Linux \r\n
  //   BOUNDARY \r\n
  //   Content-Disposition: form-data; name="ver" \r\n \r\n
  //   1.2.3.4 \r\n
  //   BOUNDARY \r\n
  //
  //   zero or one:
  //   Content-Disposition: form-data; name="ptime" \r\n \r\n
  //   abcdef \r\n
  //   BOUNDARY \r\n
  //
  //   zero or one:
  //   Content-Disposition: form-data; name="ptype" \r\n \r\n
  //   abcdef \r\n
  //   BOUNDARY \r\n
  //
  //   zero or one:
  //   Content-Disposition: form-data; name="lsb-release" \r\n \r\n
  //   abcdef \r\n
  //   BOUNDARY \r\n
  //
  //   zero or one:
  //   Content-Disposition: form-data; name="oom-size" \r\n \r\n
  //   1234567890 \r\n
  //   BOUNDARY \r\n
  //
  //   zero or more (up to CrashKeyStorage::num_entries = 64):
  //   Content-Disposition: form-data; name=crash-key-name \r\n
  //   crash-key-value \r\n
  //   BOUNDARY \r\n
  //
  //   Content-Disposition: form-data; name="dump"; filename="dump" \r\n
  //   Content-Type: application/octet-stream \r\n \r\n
  //   <dump contents>
  //   \r\n BOUNDARY -- \r\n

  MimeWriter writer(temp_file_fd, mime_boundary);
  {
    writer.AddBoundary();
    if (info.pid > 0) {
      char pid_value_buf[kUint64StringSize];
      uint64_t pid_value_len = my_uint64_len(info.pid);
      my_uint64tos(pid_value_buf, info.pid, pid_value_len);
      static const char pid_key_name[] = "pid";
      writer.AddPairData(pid_key_name, sizeof(pid_key_name) - 1, pid_value_buf,
                         pid_value_len);
      writer.AddBoundary();
    }
    writer.Flush();
  }

  if (info.process_start_time > 0) {
    struct kernel_timeval tv;
    if (!sys_gettimeofday(&tv, NULL)) {
      uint64_t time = kernel_timeval_to_ms(&tv);
      if (time > info.process_start_time) {
        time -= info.process_start_time;
        char time_str[kUint64StringSize];
        const unsigned time_len = my_uint64_len(time);
        my_uint64tos(time_str, time, time_len);

        static const char process_time_msg[] = "ptime";
        writer.AddPairData(process_time_msg, sizeof(process_time_msg) - 1,
                           time_str, time_len);
        writer.AddBoundary();
        writer.Flush();
      }
    }
  }

  if (info.distro_length) {
    static const char distro_msg[] = "lsb-release";
    writer.AddPairString(distro_msg, info.distro);
    writer.AddBoundary();
    writer.Flush();
  }

  if (info.oom_size) {
    char oom_size_str[kUint64StringSize];
    const unsigned oom_size_len = my_uint64_len(info.oom_size);
    my_uint64tos(oom_size_str, info.oom_size, oom_size_len);
    static const char oom_size_msg[] = "oom-size";
    writer.AddPairData(oom_size_msg, sizeof(oom_size_msg) - 1, oom_size_str,
                       oom_size_len);
    writer.AddBoundary();
    writer.Flush();
  }

  if (info.crash_keys) {
    CrashKeyStorage::Iterator crash_key_iterator(*info.crash_keys);
    const CrashKeyStorage::Entry* entry;
    while ((entry = crash_key_iterator.Next())) {
      writer.AddPairString(entry->key, entry->value);
      writer.AddBoundary();
      writer.Flush();
    }
  }

  writer.AddFileContents(g_dump_msg, dump_data, dump_size);
  writer.AddEnd();
  writer.Flush();

  IGNORE_RET(sys_close(temp_file_fd));

  if (!info.upload)
    return;

  const pid_t child = sys_fork();
  if (!child) {
    // Spawned helper process.
    //
    // This code is called both when a browser is crashing (in which case,
    // nothing really matters any more) and when a renderer/plugin crashes, in
    // which case we need to continue.
    //
    // Since we are a multithreaded app, if we were just to fork(), we might
    // grab file descriptors which have just been created in another thread and
    // hold them open for too long.
    //
    // Thus, we have to loop and try and close everything.
    const int fd = sys_open("/proc/self/fd", O_DIRECTORY | O_RDONLY, 0);
    if (fd < 0) {
      for (unsigned i = 3; i < 8192; ++i)
        IGNORE_RET(sys_close(i));
    } else {
      google_breakpad::DirectoryReader reader(fd);
      const char* name;
      while (reader.GetNextEntry(&name)) {
        int i;
        if (my_strtoui(&i, name) && i > 2 && i != fd)
          IGNORE_RET(sys_close(i));
        reader.PopEntry();
      }

      IGNORE_RET(sys_close(fd));
    }

    IGNORE_RET(sys_setsid());

    // Leave one end of a pipe in the upload process and watch for it getting
    // closed by the upload process exiting.
    int fds[2];
    if (sys_pipe(fds) >= 0) {
      const pid_t upload_child = sys_fork();
      if (!upload_child) {
        // Upload process.
        IGNORE_RET(sys_close(fds[0]));
        IGNORE_RET(sys_dup2(fds[1], 3));
        ExecUploadProcessOrTerminate(info, temp_file, mime_boundary, exe_buf,
                                     &allocator);
      }

      // Helper process.
      if (upload_child > 0) {
        IGNORE_RET(sys_close(fds[1]));

        const size_t kCrashIdLength = 36;
        char id_buf[kCrashIdLength + 1];
        size_t bytes_read =
            WaitForCrashReportUploadProcess(fds[0], kCrashIdLength, id_buf);
        HandleCrashReportId(id_buf, bytes_read, kCrashIdLength);

        if (sys_waitpid(upload_child, NULL, WNOHANG) == 0) {
          // Upload process is still around, kill it.
          sys_kill(upload_child, SIGKILL);
        }
      }
    }

    // Helper process.
    IGNORE_RET(sys_unlink(info.filename));
    IGNORE_RET(sys_unlink(temp_file));
    sys__exit(0);
  }

  // Main browser process.
  if (child <= 0)
    return;
  (void)HANDLE_EINTR(sys_waitpid(child, NULL, 0));
}

size_t WriteLog(const char* buf, size_t nbytes) {
  return sys_write(2, buf, nbytes);
}

size_t WriteNewline() {
  return WriteLog("\n", 1);
}

}  // namespace crash_reporter
