dom/system/gonk/OpenFileFinder.cpp

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
   3  * You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #include "OpenFileFinder.h"
   6
   7 #include "mozilla/FileUtils.h"
   8 #include "nsPrintfCString.h"
   9
  10 #include <sys/stat.h>
  11 #include <errno.h>
  12
  13 #define USE_DEBUG 0
  14
  15 #undef LOG
  16 #define LOG(args...)  __android_log_print(ANDROID_LOG_INFO,  "OpenFileFinder", ## args)
  17 #define LOGW(args...) __android_log_print(ANDROID_LOG_WARN,  "OpenFileFinder", ## args)
  18 #define ERR(args...)  __android_log_print(ANDROID_LOG_ERROR, "OpenFileFinder", ## args)
  19
  20 #if USE_DEBUG
  21 #define DBG(args...)  __android_log_print(ANDROID_LOG_DEBUG, "OpenFileFinder" , ## args)
  22 #else
  23 #define DBG(args...)
  24 #endif
  25
  26 namespace mozilla {
  27 namespace system {
  28
  29 OpenFileFinder::OpenFileFinder(const nsACString& aPath,
  30                                bool aCheckIsB2gOrDescendant /* = true */)
  31   : mPath(aPath),
  32     mProcDir(nullptr),
  33     mFdDir(nullptr),
  34     mPid(0),
  35     mCheckIsB2gOrDescendant(aCheckIsB2gOrDescendant)
  36 {
  37   // We assume that we're running in the parent process
  38   mMyPid = getpid();
  39 }
  40
  41 OpenFileFinder::~OpenFileFinder()
  42 {
  43   Close();
  44 }
  45
  46 bool
  47 OpenFileFinder::First(OpenFileFinder::Info* aInfo)
  48 {
  49   Close();
  50
  51   mProcDir = opendir("/proc");
  52   if (!mProcDir) {
  53     return false;
  54   }
  55   mState = NEXT_PID;
  56   return Next(aInfo);
  57 }
  58
  59 bool
  60 OpenFileFinder::Next(OpenFileFinder::Info* aInfo)
  61 {
  62   // NOTE: This function calls readdir and readlink, neither of which should
  63   //       block since we're using the proc filesystem, which is a purely
  64   // kernel in-memory filesystem and doesn't depend on external driver
  65   // behaviour.
  66   while (mState != DONE) {
  67     switch (mState) {
  68       case NEXT_PID: {
  69         struct dirent *pidEntry;
  70         pidEntry = readdir(mProcDir);
  71         if (!pidEntry) {
  72           mState = DONE;
  73           break;
  74         }
  75         char *endPtr;
  76         mPid = strtol(pidEntry->d_name, &endPtr, 10);
  77         if (mPid == 0 || *endPtr != '\0') {
  78           // Not a +ve number - ignore
  79           continue;
  80         }
  81         // We've found a /proc/PID directory. Scan open file descriptors.
  82         if (mFdDir) {
  83           closedir(mFdDir);
  84         }
  85         nsPrintfCString fdDirPath("/proc/%d/fd", mPid);
  86         mFdDir = opendir(fdDirPath.get());
  87         if (!mFdDir) {
  88           continue;
  89         }
  90         mState = CHECK_FDS;
  91       }
  92       // Fall through
  93       case CHECK_FDS: {
  94         struct dirent *fdEntry;
  95         while((fdEntry = readdir(mFdDir))) {
  96           if (!strcmp(fdEntry->d_name, ".") ||
  97               !strcmp(fdEntry->d_name, "..")) {
  98             continue;
  99           }
 100           nsPrintfCString fdSymLink("/proc/%d/fd/%s", mPid, fdEntry->d_name);
 101           nsCString resolvedPath;
 102           if (ReadSymLink(fdSymLink, resolvedPath) && PathMatches(resolvedPath)) {
 103             // We found an open file contained within the directory tree passed
 104             // into the constructor.
 105             FillInfo(aInfo, resolvedPath);
 106             // If sCheckIsB2gOrDescendant is set false, the caller cares about
 107             // all processes which have open files. If sCheckIsB2gOrDescendant
 108             // is set false, we only care about the b2g proccess or its descendants.
 109             if (!mCheckIsB2gOrDescendant || aInfo->mIsB2gOrDescendant) {
 110               return true;
 111             }
 112             LOG("Ignore process(%d), not a b2g process or its descendant.",
 113                 aInfo->mPid);
 114           }
 115         }
 116         // We've checked all of the files for this pid, move onto the next one.
 117         mState = NEXT_PID;
 118         continue;
 119       }
 120       case DONE:
 121       default:
 122         mState = DONE;  // covers the default case
 123         break;
 124     }
 125   }
 126   return false;
 127 }
 128
 129 void
 130 OpenFileFinder::Close()
 131 {
 132   if (mFdDir) {
 133     closedir(mFdDir);
 134   }
 135   if (mProcDir) {
 136     closedir(mProcDir);
 137   }
 138 }
 139
 140 void
 141 OpenFileFinder::FillInfo(OpenFileFinder::Info* aInfo, const nsACString& aPath)
 142 {
 143   aInfo->mFileName = aPath;
 144   aInfo->mPid = mPid;
 145   nsPrintfCString exePath("/proc/%d/exe", mPid);
 146   ReadSymLink(exePath, aInfo->mExe);
 147   aInfo->mComm.Truncate();
 148   aInfo->mAppName.Truncate();
 149   nsPrintfCString statPath("/proc/%d/stat", mPid);
 150   nsCString statString;
 151   statString.SetLength(200);
 152   char *stat = statString.BeginWriting();
 153   if (!stat) {
 154     return;
 155   }
 156   ReadSysFile(statPath.get(), stat, statString.Length());
 157   // The stat line includes the comm field, surrounded by parenthesis.
 158   // However, the contents of the comm field itself is arbitrary and
 159   // and can include ')', so we search for the rightmost ) as being
 160   // the end of the comm field.
 161   char *closeParen = strrchr(stat, ')');
 162   if (!closeParen) {
 163     return;
 164   }
 165   char *openParen = strchr(stat, '(');
 166   if (!openParen) {
 167     return;
 168   }
 169   if (openParen >= closeParen) {
 170     return;
 171   }
 172   nsDependentCSubstring comm(&openParen[1], closeParen - openParen - 1);
 173   aInfo->mComm = comm;
 174   // There is a single character field after the comm and then
 175   // the parent pid (the field we're interested in).
 176   // ) X ppid
 177   // 01234
 178   int ppid = atoi(&closeParen[4]);
 179
 180   if (mPid == mMyPid) {
 181     // This is chrome process
 182     aInfo->mIsB2gOrDescendant = true;
 183     DBG("Chrome process has open file(s)");
 184     return;
 185   }
 186   // For the rest (non-chrome process), we recursively check the ppid to know
 187   // it is a descendant of b2g or not. See bug 931456.
 188   while (ppid != mMyPid && ppid != 1) {
 189     DBG("Process(%d) is not forked from b2g(%d) or Init(1), keep looking",
 190         ppid, mMyPid);
 191     nsPrintfCString ppStatPath("/proc/%d/stat", ppid);
 192     ReadSysFile(ppStatPath.get(), stat, statString.Length());
 193     closeParen = strrchr(stat, ')');
 194     if (!closeParen) {
 195       return;
 196     }
 197     ppid = atoi(&closeParen[4]);
 198   }
 199   if (ppid == 1) {
 200     // This is a not a b2g process.
 201     DBG("Non-b2g process has open file(s)");
 202     aInfo->mIsB2gOrDescendant = false;
 203     return;
 204   }
 205   if (ppid == mMyPid) {
 206     // This is a descendant of b2g.
 207     DBG("Child process of chrome process has open file(s)");
 208     aInfo->mIsB2gOrDescendant = true;
 209   }
 210
 211   // This looks like a content process. The comm field will be the
 212   // app name.
 213   aInfo->mAppName = aInfo->mComm;
 214 }
 215
 216 bool
 217 OpenFileFinder::ReadSymLink(const nsACString& aSymLink, nsACString& aOutPath)
 218 {
 219   aOutPath.Truncate();
 220   const char *symLink = aSymLink.BeginReading();
 221
 222   // Verify that we actually have a symlink.
 223   struct stat st;
 224   if (lstat(symLink, &st)) {
 225       return false;
 226   }
 227   if ((st.st_mode & S_IFMT) != S_IFLNK) {
 228       return false;
 229   }
 230
 231   // Contrary to the documentation st.st_size doesn't seem to be a reliable
 232   // indication of the length when reading from /proc, so we use a fixed
 233   // size buffer instead.
 234
 235   char resolvedSymLink[PATH_MAX];
 236   ssize_t pathLength = readlink(symLink, resolvedSymLink,
 237                                 sizeof(resolvedSymLink) - 1);
 238   if (pathLength <= 0) {
 239       return false;
 240   }
 241   resolvedSymLink[pathLength] = '\0';
 242   aOutPath.Assign(resolvedSymLink);
 243   return true;
 244 }
 245
 246 } // system
 247 } // mozilla