base/linux_util.cc

   1 // Copyright (c) 2010 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/stat.h>
  14 #include <sys/types.h>
  15 #include <unistd.h>
  16
  17 #include <vector>
  18
  19 #include "base/command_line.h"
  20 #include "base/file_util.h"
  21 #include "base/lock.h"
  22 #include "base/path_service.h"
  23 #include "base/process_util.h"
  24 #include "base/singleton.h"
  25 #include "base/scoped_ptr.h"
  26 #include "base/string_util.h"
  27
  28 namespace {
  29
  30 // Not needed for OS_CHROMEOS.
  31 #if defined(OS_LINUX)
  32 enum LinuxDistroState {
  33   STATE_DID_NOT_CHECK  = 0,
  34   STATE_CHECK_STARTED  = 1,
  35   STATE_CHECK_FINISHED = 2,
  36 };
  37
  38 // Helper class for GetLinuxDistro().
  39 class LinuxDistroHelper {
  40  public:
  41   // Retrieves the Singleton.
  42   static LinuxDistroHelper* Get() {
  43     return Singleton<LinuxDistroHelper>::get();
  44   }
  45
  46   // The simple state machine goes from:
  47   // STATE_DID_NOT_CHECK -> STATE_CHECK_STARTED -> STATE_CHECK_FINISHED.
  48   LinuxDistroHelper() : state_(STATE_DID_NOT_CHECK) {}
  49   ~LinuxDistroHelper() {}
  50
  51   // Retrieve the current state, if we're in STATE_DID_NOT_CHECK,
  52   // we automatically move to STATE_CHECK_STARTED so nobody else will
  53   // do the check.
  54   LinuxDistroState State() {
  55     AutoLock scoped_lock(lock_);
  56     if (STATE_DID_NOT_CHECK == state_) {
  57       state_ = STATE_CHECK_STARTED;
  58       return STATE_DID_NOT_CHECK;
  59     }
  60     return state_;
  61   }
  62
  63   // Indicate the check finished, move to STATE_CHECK_FINISHED.
  64   void CheckFinished() {
  65     AutoLock scoped_lock(lock_);
  66     DCHECK(state_ == STATE_CHECK_STARTED);
  67     state_ = STATE_CHECK_FINISHED;
  68   }
  69
  70  private:
  71   Lock lock_;
  72   LinuxDistroState state_;
  73 };
  74 #endif  // if defined(OS_LINUX)
  75
  76 // expected prefix of the target of the /proc/self/fd/%d link for a socket
  77 static const char kSocketLinkPrefix[] = "socket:[";
  78
  79 // Parse a symlink in /proc/pid/fd/$x and return the inode number of the
  80 // socket.
  81 //   inode_out: (output) set to the inode number on success
  82 //   path: e.g. /proc/1234/fd/5 (must be a UNIX domain socket descriptor)
  83 //   log: if true, log messages about failure details
  84 bool ProcPathGetInode(ino_t* inode_out, const char* path, bool log = false) {
  85   DCHECK(inode_out);
  86   DCHECK(path);
  87
  88   char buf[256];
  89   const ssize_t n = readlink(path, buf, sizeof(buf) - 1);
  90   if (n == -1) {
  91     if (log) {
  92       LOG(WARNING) << "Failed to read the inode number for a socket from /proc"
  93                       "(" << errno << ")";
  94     }
  95     return false;
  96   }
  97   buf[n] = 0;
  98
  99   if (memcmp(kSocketLinkPrefix, buf, sizeof(kSocketLinkPrefix) - 1)) {
 100     if (log) {
 101       LOG(WARNING) << "The descriptor passed from the crashing process wasn't a"
 102                       " UNIX domain socket.";
 103     }
 104     return false;
 105   }
 106
 107   char *endptr;
 108   const unsigned long long int inode_ul =
 109       strtoull(buf + sizeof(kSocketLinkPrefix) - 1, &endptr, 10);
 110   if (*endptr != ']')
 111     return false;
 112
 113   if (inode_ul == ULLONG_MAX) {
 114     if (log) {
 115       LOG(WARNING) << "Failed to parse a socket's inode number: the number was "
 116                       "too large. Please report this bug: " << buf;
 117     }
 118     return false;
 119   }
 120
 121   *inode_out = inode_ul;
 122   return true;
 123 }
 124
 125 }  // namespace
 126
 127 namespace base {
 128
 129 // We use this static string to hold the Linux distro info. If we
 130 // crash, the crash handler code will send this in the crash dump.
 131 std::string linux_distro =
 132 #if defined(OS_CHROMEOS)
 133     "CrOS";
 134 #else  // if defined(OS_LINUX)
 135     "Unknown";
 136 #endif
 137
 138 std::string GetLinuxDistro() {
 139 #if defined(OS_CHROMEOS)
 140   return linux_distro;
 141 #elif defined(OS_LINUX)
 142   LinuxDistroHelper* distro_state_singleton = LinuxDistroHelper::Get();
 143   LinuxDistroState state = distro_state_singleton->State();
 144   if (STATE_DID_NOT_CHECK == state) {
 145     // We do this check only once per process. If it fails, there's
 146     // little reason to believe it will work if we attempt to run
 147     // lsb_release again.
 148     std::vector<std::string> argv;
 149     argv.push_back("lsb_release");
 150     argv.push_back("-d");
 151     std::string output;
 152     base::GetAppOutput(CommandLine(argv), &output);
 153     if (output.length() > 0) {
 154       // lsb_release -d should return: Description:<tab>Distro Info
 155       static const std::string field = "Description:\t";
 156       if (output.compare(0, field.length(), field) == 0) {
 157         linux_distro = output.substr(field.length());
 158         TrimWhitespaceASCII(linux_distro, TRIM_ALL, &linux_distro);
 159       }
 160     }
 161     distro_state_singleton->CheckFinished();
 162     return linux_distro;
 163   } else if (STATE_CHECK_STARTED == state) {
 164     // If the distro check above is in progress in some other thread, we're
 165     // not going to wait for the results.
 166     return "Unknown";
 167   } else {
 168     // In STATE_CHECK_FINISHED, no more writing to |linux_distro|.
 169     return linux_distro;
 170   }
 171 #else
 172   NOTIMPLEMENTED();
 173 #endif
 174 }
 175
 176 bool FileDescriptorGetInode(ino_t* inode_out, int fd) {
 177   DCHECK(inode_out);
 178
 179   struct stat buf;
 180   if (fstat(fd, &buf) < 0)
 181     return false;
 182
 183   if (!S_ISSOCK(buf.st_mode))
 184     return false;
 185
 186   *inode_out = buf.st_ino;
 187   return true;
 188 }
 189
 190 bool FindProcessHoldingSocket(pid_t* pid_out, ino_t socket_inode) {
 191   DCHECK(pid_out);
 192   bool already_found = false;
 193
 194   DIR* proc = opendir("/proc");
 195   if (!proc) {
 196     LOG(WARNING) << "Cannot open /proc";
 197     return false;
 198   }
 199
 200   std::vector<pid_t> pids;
 201
 202   struct dirent* dent;
 203   while ((dent = readdir(proc))) {
 204     char *endptr;
 205     const unsigned long int pid_ul = strtoul(dent->d_name, &endptr, 10);
 206     if (pid_ul == ULONG_MAX || *endptr)
 207       continue;
 208     pids.push_back(pid_ul);
 209   }
 210   closedir(proc);
 211
 212   for (std::vector<pid_t>::const_iterator
 213        i = pids.begin(); i != pids.end(); ++i) {
 214     const pid_t current_pid = *i;
 215     char buf[256];
 216     snprintf(buf, sizeof(buf), "/proc/%d/fd", current_pid);
 217     DIR* fd = opendir(buf);
 218     if (!fd)
 219       continue;
 220
 221     while ((dent = readdir(fd))) {
 222       if (snprintf(buf, sizeof(buf), "/proc/%d/fd/%s", current_pid,
 223                    dent->d_name) >= static_cast<int>(sizeof(buf))) {
 224         continue;
 225       }
 226
 227       ino_t fd_inode;
 228       if (ProcPathGetInode(&fd_inode, buf)) {
 229         if (fd_inode == socket_inode) {
 230           if (already_found) {
 231             closedir(fd);
 232             return false;
 233           }
 234
 235           already_found = true;
 236           *pid_out = current_pid;
 237           break;
 238         }
 239       }
 240     }
 241
 242     closedir(fd);
 243   }
 244
 245   return already_found;
 246 }
 247
 248 pid_t FindThreadIDWithSyscall(pid_t pid, const std::string& expected_data) {
 249   char buf[256];
 250   snprintf(buf, sizeof(buf), "/proc/%d/task", pid);
 251   DIR* task = opendir(buf);
 252   if (!task) {
 253     LOG(WARNING) << "Cannot open " << buf;
 254     return -1;
 255   }
 256
 257   std::vector<pid_t> tids;
 258   struct dirent* dent;
 259   while ((dent = readdir(task))) {
 260     char *endptr;
 261     const unsigned long int tid_ul = strtoul(dent->d_name, &endptr, 10);
 262     if (tid_ul == ULONG_MAX || *endptr)
 263       continue;
 264     tids.push_back(tid_ul);
 265   }
 266   closedir(task);
 267
 268   scoped_array<char> syscall_data(new char[expected_data.length()]);
 269   for (std::vector<pid_t>::const_iterator
 270        i = tids.begin(); i != tids.end(); ++i) {
 271     const pid_t current_tid = *i;
 272     snprintf(buf, sizeof(buf), "/proc/%d/task/%d/syscall", pid, current_tid);
 273     int fd = open(buf, O_RDONLY);
 274     if (fd < 0)
 275       continue;
 276     bool read_ret =
 277         file_util::ReadFromFD(fd, syscall_data.get(), expected_data.length());
 278     close(fd);
 279     if (!read_ret)
 280       continue;
 281
 282     if (0 == strncmp(expected_data.c_str(), syscall_data.get(),
 283                      expected_data.length())) {
 284       return current_tid;
 285     }
 286   }
 287   return -1;
 288 }
 289
 290 }  // namespace base