linux_util.cc revision ddb351dbec246cf1fab5ec20d2d5520909041de1 
1// Copyright (c) 2011 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "base/linux_util.h"
6
7#include <dirent.h>
8#include <errno.h>
9#include <fcntl.h>
10#include <glib.h>
11#include <stdlib.h>
12#include <sys/stat.h>
13#include <sys/types.h>
14#include <unistd.h>
15
16#include <vector>
17
18#include "base/command_line.h"
19#include "base/file_util.h"
20#include "base/memory/scoped_ptr.h"
21#include "base/memory/singleton.h"
22#include "base/path_service.h"
23#include "base/process_util.h"
24#include "base/string_util.h"
25#include "base/synchronization/lock.h"
26
27namespace {
28
29// Not needed for OS_CHROMEOS.
30#if defined(OS_LINUX)
31enum LinuxDistroState {
32  STATE_DID_NOT_CHECK  = 0,
33  STATE_CHECK_STARTED  = 1,
34  STATE_CHECK_FINISHED = 2,
35};
36
37// Helper class for GetLinuxDistro().
38class LinuxDistroHelper {
39 public:
40  // Retrieves the Singleton.
41  static LinuxDistroHelper* GetInstance() {
42    return Singleton<LinuxDistroHelper>::get();
43  }
44
45  // The simple state machine goes from:
46  // STATE_DID_NOT_CHECK -> STATE_CHECK_STARTED -> STATE_CHECK_FINISHED.
47  LinuxDistroHelper() : state_(STATE_DID_NOT_CHECK) {}
48  ~LinuxDistroHelper() {}
49
50  // Retrieve the current state, if we're in STATE_DID_NOT_CHECK,
51  // we automatically move to STATE_CHECK_STARTED so nobody else will
52  // do the check.
53  LinuxDistroState State() {
54    base::AutoLock scoped_lock(lock_);
55    if (STATE_DID_NOT_CHECK == state_) {
56      state_ = STATE_CHECK_STARTED;
57      return STATE_DID_NOT_CHECK;
58    }
59    return state_;
60  }
61
62  // Indicate the check finished, move to STATE_CHECK_FINISHED.
63  void CheckFinished() {
64    base::AutoLock scoped_lock(lock_);
65    DCHECK_EQ(STATE_CHECK_STARTED, state_);
66    state_ = STATE_CHECK_FINISHED;
67  }
68
69 private:
70  base::Lock lock_;
71  LinuxDistroState state_;
72};
73#endif  // if defined(OS_LINUX)
74
75// expected prefix of the target of the /proc/self/fd/%d link for a socket
76static const char kSocketLinkPrefix[] = "socket:[";
77
78// Parse a symlink in /proc/pid/fd/$x and return the inode number of the
79// socket.
80//   inode_out: (output) set to the inode number on success
81//   path: e.g. /proc/1234/fd/5 (must be a UNIX domain socket descriptor)
82//   log: if true, log messages about failure details
83bool ProcPathGetInode(ino_t* inode_out, const char* path, bool log = false) {
84  DCHECK(inode_out);
85  DCHECK(path);
86
87  char buf[256];
88  const ssize_t n = readlink(path, buf, sizeof(buf) - 1);
89  if (n == -1) {
90    if (log) {
91      LOG(WARNING) << "Failed to read the inode number for a socket from /proc"
92                      "(" << errno << ")";
93    }
94    return false;
95  }
96  buf[n] = 0;
97
98  if (memcmp(kSocketLinkPrefix, buf, sizeof(kSocketLinkPrefix) - 1)) {
99    if (log) {
100      LOG(WARNING) << "The descriptor passed from the crashing process wasn't a"
101                      " UNIX domain socket.";
102    }
103    return false;
104  }
105
106  char *endptr;
107  const unsigned long long int inode_ul =
108      strtoull(buf + sizeof(kSocketLinkPrefix) - 1, &endptr, 10);
109  if (*endptr != ']')
110    return false;
111
112  if (inode_ul == ULLONG_MAX) {
113    if (log) {
114      LOG(WARNING) << "Failed to parse a socket's inode number: the number was "
115                      "too large. Please report this bug: " << buf;
116    }
117    return false;
118  }
119
120  *inode_out = inode_ul;
121  return true;
122}
123
124}  // namespace
125
126namespace base {
127
128// Account for the terminating null character.
129static const int kDistroSize = 128 + 1;
130
131// We use this static string to hold the Linux distro info. If we
132// crash, the crash handler code will send this in the crash dump.
133char g_linux_distro[kDistroSize] =
134#if defined(OS_CHROMEOS)
135    "CrOS";
136#else  // if defined(OS_LINUX)
137    "Unknown";
138#endif
139
140std::string GetLinuxDistro() {
141#if defined(OS_CHROMEOS)
142  return g_linux_distro;
143#elif defined(OS_LINUX)
144  LinuxDistroHelper* distro_state_singleton = LinuxDistroHelper::GetInstance();
145  LinuxDistroState state = distro_state_singleton->State();
146  if (STATE_DID_NOT_CHECK == state) {
147    // We do this check only once per process. If it fails, there's
148    // little reason to believe it will work if we attempt to run
149    // lsb_release again.
150    std::vector<std::string> argv;
151    argv.push_back("lsb_release");
152    argv.push_back("-d");
153    std::string output;
154    base::GetAppOutput(CommandLine(argv), &output);
155    if (output.length() > 0) {
156      // lsb_release -d should return: Description:<tab>Distro Info
157      static const std::string field = "Description:\t";
158      if (output.compare(0, field.length(), field) == 0) {
159        SetLinuxDistro(output.substr(field.length()));
160      }
161    }
162    distro_state_singleton->CheckFinished();
163    return g_linux_distro;
164  } else if (STATE_CHECK_STARTED == state) {
165    // If the distro check above is in progress in some other thread, we're
166    // not going to wait for the results.
167    return "Unknown";
168  } else {
169    // In STATE_CHECK_FINISHED, no more writing to |linux_distro|.
170    return g_linux_distro;
171  }
172#else
173  NOTIMPLEMENTED();
174#endif
175}
176
177void SetLinuxDistro(const std::string& distro) {
178  std::string trimmed_distro;
179  TrimWhitespaceASCII(distro, TRIM_ALL, &trimmed_distro);
180  base::strlcpy(g_linux_distro, trimmed_distro.c_str(), kDistroSize);
181}
182
183bool FileDescriptorGetInode(ino_t* inode_out, int fd) {
184  DCHECK(inode_out);
185
186  struct stat buf;
187  if (fstat(fd, &buf) < 0)
188    return false;
189
190  if (!S_ISSOCK(buf.st_mode))
191    return false;
192
193  *inode_out = buf.st_ino;
194  return true;
195}
196
197bool FindProcessHoldingSocket(pid_t* pid_out, ino_t socket_inode) {
198  DCHECK(pid_out);
199  bool already_found = false;
200
201  DIR* proc = opendir("/proc");
202  if (!proc) {
203    LOG(WARNING) << "Cannot open /proc";
204    return false;
205  }
206
207  std::vector<pid_t> pids;
208
209  struct dirent* dent;
210  while ((dent = readdir(proc))) {
211    char *endptr;
212    const unsigned long int pid_ul = strtoul(dent->d_name, &endptr, 10);
213    if (pid_ul == ULONG_MAX || *endptr)
214      continue;
215    pids.push_back(pid_ul);
216  }
217  closedir(proc);
218
219  for (std::vector<pid_t>::const_iterator
220       i = pids.begin(); i != pids.end(); ++i) {
221    const pid_t current_pid = *i;
222    char buf[256];
223    snprintf(buf, sizeof(buf), "/proc/%d/fd", current_pid);
224    DIR* fd = opendir(buf);
225    if (!fd)
226      continue;
227
228    while ((dent = readdir(fd))) {
229      if (snprintf(buf, sizeof(buf), "/proc/%d/fd/%s", current_pid,
230                   dent->d_name) >= static_cast<int>(sizeof(buf))) {
231        continue;
232      }
233
234      ino_t fd_inode;
235      if (ProcPathGetInode(&fd_inode, buf)) {
236        if (fd_inode == socket_inode) {
237          if (already_found) {
238            closedir(fd);
239            return false;
240          }
241
242          already_found = true;
243          *pid_out = current_pid;
244          break;
245        }
246      }
247    }
248
249    closedir(fd);
250  }
251
252  return already_found;
253}
254
255pid_t FindThreadIDWithSyscall(pid_t pid, const std::string& expected_data) {
256  char buf[256];
257  snprintf(buf, sizeof(buf), "/proc/%d/task", pid);
258  DIR* task = opendir(buf);
259  if (!task) {
260    LOG(WARNING) << "Cannot open " << buf;
261    return -1;
262  }
263
264  std::vector<pid_t> tids;
265  struct dirent* dent;
266  while ((dent = readdir(task))) {
267    char *endptr;
268    const unsigned long int tid_ul = strtoul(dent->d_name, &endptr, 10);
269    if (tid_ul == ULONG_MAX || *endptr)
270      continue;
271    tids.push_back(tid_ul);
272  }
273  closedir(task);
274
275  scoped_array<char> syscall_data(new char[expected_data.length()]);
276  for (std::vector<pid_t>::const_iterator
277       i = tids.begin(); i != tids.end(); ++i) {
278    const pid_t current_tid = *i;
279    snprintf(buf, sizeof(buf), "/proc/%d/task/%d/syscall", pid, current_tid);
280    int fd = open(buf, O_RDONLY);
281    if (fd < 0)
282      continue;
283    bool read_ret =
284        file_util::ReadFromFD(fd, syscall_data.get(), expected_data.length());
285    close(fd);
286    if (!read_ret)
287      continue;
288
289    if (0 == strncmp(expected_data.c_str(), syscall_data.get(),
290                     expected_data.length())) {
291      return current_tid;
292    }
293  }
294  return -1;
295}
296
297}  // namespace base
298