Utils.cpp - SHIFTPHONES/android_system_vold - Gitiles

 /*
  * Copyright (C) 2015 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include "Utils.h"

 #include "Process.h"
 #include "sehandle.h"

 #include <android-base/file.h>
 #include <android-base/logging.h>
 #include <android-base/properties.h>
 #include <android-base/stringprintf.h>
 #include <android-base/strings.h>
 #include <android-base/unique_fd.h>
 #include <cutils/fs.h>
 #include <logwrap/logwrap.h>
 #include <private/android_filesystem_config.h>

 #include <dirent.h>
 #include <fcntl.h>
 #include <linux/fs.h>
 #include <mntent.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/mount.h>
 #include <sys/stat.h>
 #include <sys/statvfs.h>
 #include <sys/sysmacros.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <list>
 #include <mutex>

 #ifndef UMOUNT_NOFOLLOW
 #define UMOUNT_NOFOLLOW 0x00000008 /* Don't follow symlink on umount */
 #endif

 using android::base::ReadFileToString;
 using android::base::StringPrintf;

 namespace android {
 namespace vold {

 security_context_t sBlkidContext = nullptr;
 security_context_t sBlkidUntrustedContext = nullptr;
 security_context_t sFsckContext = nullptr;
 security_context_t sFsckUntrustedContext = nullptr;

 bool sSleepOnUnmount = true;

 static const char* kBlkidPath = "/system/bin/blkid";
 static const char* kKeyPath = "/data/misc/vold";

 static const char* kProcFilesystems = "/proc/filesystems";

 // Lock used to protect process-level SELinux changes from racing with each
 // other between multiple threads.
 static std::mutex kSecurityLock;

 status_t CreateDeviceNode(const std::string& path, dev_t dev) {
     std::lock_guard<std::mutex> lock(kSecurityLock);
     const char* cpath = path.c_str();
     status_t res = 0;

     char* secontext = nullptr;
     if (sehandle) {
         if (!selabel_lookup(sehandle, &secontext, cpath, S_IFBLK)) {
             setfscreatecon(secontext);
         }
     }

     mode_t mode = 0660 | S_IFBLK;
     if (mknod(cpath, mode, dev) < 0) {
         if (errno != EEXIST) {
             PLOG(ERROR) << "Failed to create device node for " << major(dev) << ":" << minor(dev)
                         << " at " << path;
             res = -errno;
         }
     }

     if (secontext) {
         setfscreatecon(nullptr);
         freecon(secontext);
     }

     return res;
 }

 status_t DestroyDeviceNode(const std::string& path) {
     const char* cpath = path.c_str();
     if (TEMP_FAILURE_RETRY(unlink(cpath))) {
         return -errno;
     } else {
         return OK;
     }
 }

 status_t PrepareDir(const std::string& path, mode_t mode, uid_t uid, gid_t gid) {
     std::lock_guard<std::mutex> lock(kSecurityLock);
     const char* cpath = path.c_str();

     char* secontext = nullptr;
     if (sehandle) {
         if (!selabel_lookup(sehandle, &secontext, cpath, S_IFDIR)) {
             setfscreatecon(secontext);
         }
     }

     int res = fs_prepare_dir(cpath, mode, uid, gid);

     if (secontext) {
         setfscreatecon(nullptr);
         freecon(secontext);
     }

     if (res == 0) {
         return OK;
     } else {
         return -errno;
     }
 }

 status_t ForceUnmount(const std::string& path) {
     const char* cpath = path.c_str();
     if (!umount2(cpath, UMOUNT_NOFOLLOW) || errno == EINVAL || errno == ENOENT) {
         return OK;
     }
     // Apps might still be handling eject request, so wait before
     // we start sending signals
     if (sSleepOnUnmount) sleep(5);

     KillProcessesWithOpenFiles(path, SIGINT);
     if (sSleepOnUnmount) sleep(5);
     if (!umount2(cpath, UMOUNT_NOFOLLOW) || errno == EINVAL || errno == ENOENT) {
         return OK;
     }

     KillProcessesWithOpenFiles(path, SIGTERM);
     if (sSleepOnUnmount) sleep(5);
     if (!umount2(cpath, UMOUNT_NOFOLLOW) || errno == EINVAL || errno == ENOENT) {
         return OK;
     }

     KillProcessesWithOpenFiles(path, SIGKILL);
     if (sSleepOnUnmount) sleep(5);
     if (!umount2(cpath, UMOUNT_NOFOLLOW) || errno == EINVAL || errno == ENOENT) {
         return OK;
     }

     return -errno;
 }

 status_t KillProcessesUsingPath(const std::string& path) {
     if (KillProcessesWithOpenFiles(path, SIGINT) == 0) {
         return OK;
     }
     if (sSleepOnUnmount) sleep(5);

     if (KillProcessesWithOpenFiles(path, SIGTERM) == 0) {
         return OK;
     }
     if (sSleepOnUnmount) sleep(5);

     if (KillProcessesWithOpenFiles(path, SIGKILL) == 0) {
         return OK;
     }
     if (sSleepOnUnmount) sleep(5);

     // Send SIGKILL a second time to determine if we've
     // actually killed everyone with open files
     if (KillProcessesWithOpenFiles(path, SIGKILL) == 0) {
         return OK;
     }
     PLOG(ERROR) << "Failed to kill processes using " << path;
     return -EBUSY;
 }

 status_t BindMount(const std::string& source, const std::string& target) {
     if (::mount(source.c_str(), target.c_str(), "", MS_BIND, NULL)) {
         PLOG(ERROR) << "Failed to bind mount " << source << " to " << target;
         return -errno;
     }
     return OK;
 }

 bool FindValue(const std::string& raw, const std::string& key, std::string* value) {
     auto qual = key + "=\"";
     auto start = raw.find(qual);
     if (start > 0 && raw[start - 1] != ' ') {
         start = raw.find(qual, start + 1);
     }

     if (start == std::string::npos) return false;
     start += qual.length();

     auto end = raw.find("\"", start);
     if (end == std::string::npos) return false;

     *value = raw.substr(start, end - start);
     return true;
 }

 static status_t readMetadata(const std::string& path, std::string* fsType, std::string* fsUuid,
                              std::string* fsLabel, bool untrusted) {
     fsType->clear();
     fsUuid->clear();
     fsLabel->clear();

     std::vector<std::string> cmd;
     cmd.push_back(kBlkidPath);
     cmd.push_back("-c");
     cmd.push_back("/dev/null");
     cmd.push_back("-s");
     cmd.push_back("TYPE");
     cmd.push_back("-s");
     cmd.push_back("UUID");
     cmd.push_back("-s");
     cmd.push_back("LABEL");
     cmd.push_back(path);

     std::vector<std::string> output;
     status_t res = ForkExecvp(cmd, output, untrusted ? sBlkidUntrustedContext : sBlkidContext);
     if (res != OK) {
         LOG(WARNING) << "blkid failed to identify " << path;
         return res;
     }

     for (const auto& line : output) {
         // Extract values from blkid output, if defined
         FindValue(line, "TYPE", fsType);
         FindValue(line, "UUID", fsUuid);
         FindValue(line, "LABEL", fsLabel);
     }

     return OK;
 }

 status_t ReadMetadata(const std::string& path, std::string* fsType, std::string* fsUuid,
                       std::string* fsLabel) {
     return readMetadata(path, fsType, fsUuid, fsLabel, false);
 }

 status_t ReadMetadataUntrusted(const std::string& path, std::string* fsType, std::string* fsUuid,
                                std::string* fsLabel) {
     return readMetadata(path, fsType, fsUuid, fsLabel, true);
 }

 status_t ForkExecvp(const std::vector<std::string>& args) {
     return ForkExecvp(args, nullptr);
 }

 status_t ForkExecvp(const std::vector<std::string>& args, security_context_t context) {
     std::lock_guard<std::mutex> lock(kSecurityLock);
     size_t argc = args.size();
     char** argv = (char**)calloc(argc, sizeof(char*));
     for (size_t i = 0; i < argc; i++) {
         argv[i] = (char*)args[i].c_str();
         if (i == 0) {
             LOG(DEBUG) << args[i];
         } else {
             LOG(DEBUG) << "    " << args[i];
         }
     }

     if (context) {
         if (setexeccon(context)) {
             LOG(ERROR) << "Failed to setexeccon";
             abort();
         }
     }
     status_t res = android_fork_execvp(argc, argv, NULL, false, true);
     if (context) {
         if (setexeccon(nullptr)) {
             LOG(ERROR) << "Failed to setexeccon";
             abort();
         }
     }

     free(argv);
     return res;
 }

 status_t ForkExecvp(const std::vector<std::string>& args, std::vector<std::string>& output) {
     return ForkExecvp(args, output, nullptr);
 }

 status_t ForkExecvp(const std::vector<std::string>& args, std::vector<std::string>& output,
                     security_context_t context) {
     std::lock_guard<std::mutex> lock(kSecurityLock);
     std::string cmd;
     for (size_t i = 0; i < args.size(); i++) {
         cmd += args[i] + " ";
         if (i == 0) {
             LOG(DEBUG) << args[i];
         } else {
             LOG(DEBUG) << "    " << args[i];
         }
     }
     output.clear();

     if (context) {
         if (setexeccon(context)) {
             LOG(ERROR) << "Failed to setexeccon";
             abort();
         }
     }
     FILE* fp = popen(cmd.c_str(), "r");  // NOLINT
     if (context) {
         if (setexeccon(nullptr)) {
             LOG(ERROR) << "Failed to setexeccon";
             abort();
         }
     }

     if (!fp) {
         PLOG(ERROR) << "Failed to popen " << cmd;
         return -errno;
     }
     char line[1024];
     while (fgets(line, sizeof(line), fp) != nullptr) {
         LOG(DEBUG) << line;
         output.push_back(std::string(line));
     }
     if (pclose(fp) != 0) {
         PLOG(ERROR) << "Failed to pclose " << cmd;
         return -errno;
     }

     return OK;
 }

 pid_t ForkExecvpAsync(const std::vector<std::string>& args) {
     size_t argc = args.size();
     char** argv = (char**)calloc(argc + 1, sizeof(char*));
     for (size_t i = 0; i < argc; i++) {
         argv[i] = (char*)args[i].c_str();
         if (i == 0) {
             LOG(DEBUG) << args[i];
         } else {
             LOG(DEBUG) << "    " << args[i];
         }
     }

     pid_t pid = fork();
     if (pid == 0) {
         close(STDIN_FILENO);
         close(STDOUT_FILENO);
         close(STDERR_FILENO);

         if (execvp(argv[0], argv)) {
             PLOG(ERROR) << "Failed to exec";
         }

         _exit(1);
     }

     if (pid == -1) {
         PLOG(ERROR) << "Failed to exec";
     }

     free(argv);
     return pid;
 }

 status_t ReadRandomBytes(size_t bytes, std::string& out) {
     out.resize(bytes);
     return ReadRandomBytes(bytes, &out[0]);
 }

 status_t ReadRandomBytes(size_t bytes, char* buf) {
     int fd = TEMP_FAILURE_RETRY(open("/dev/urandom", O_RDONLY | O_CLOEXEC | O_NOFOLLOW));
     if (fd == -1) {
         return -errno;
     }

     size_t n;
     while ((n = TEMP_FAILURE_RETRY(read(fd, &buf[0], bytes))) > 0) {
         bytes -= n;
         buf += n;
     }
     close(fd);

     if (bytes == 0) {
         return OK;
     } else {
         return -EIO;
     }
 }

 status_t GenerateRandomUuid(std::string& out) {
     status_t res = ReadRandomBytes(16, out);
     if (res == OK) {
         out[6] &= 0x0f; /* clear version        */
         out[6] |= 0x40; /* set to version 4     */
         out[8] &= 0x3f; /* clear variant        */
         out[8] |= 0x80; /* set to IETF variant  */
     }
     return res;
 }

 status_t HexToStr(const std::string& hex, std::string& str) {
     str.clear();
     bool even = true;
     char cur = 0;
     for (size_t i = 0; i < hex.size(); i++) {
         int val = 0;
         switch (hex[i]) {
             // clang-format off
             case ' ': case '-': case ':': continue;
             case 'f': case 'F': val = 15; break;
             case 'e': case 'E': val = 14; break;
             case 'd': case 'D': val = 13; break;
             case 'c': case 'C': val = 12; break;
             case 'b': case 'B': val = 11; break;
             case 'a': case 'A': val = 10; break;
             case '9': val = 9; break;
             case '8': val = 8; break;
             case '7': val = 7; break;
             case '6': val = 6; break;
             case '5': val = 5; break;
             case '4': val = 4; break;
             case '3': val = 3; break;
             case '2': val = 2; break;
             case '1': val = 1; break;
             case '0': val = 0; break;
             default: return -EINVAL;
                 // clang-format on
         }

         if (even) {
             cur = val << 4;
         } else {
             cur += val;
             str.push_back(cur);
             cur = 0;
         }
         even = !even;
     }
     return even ? OK : -EINVAL;
 }

 static const char* kLookup = "0123456789abcdef";

 status_t StrToHex(const std::string& str, std::string& hex) {
     hex.clear();
     for (size_t i = 0; i < str.size(); i++) {
         hex.push_back(kLookup[(str[i] & 0xF0) >> 4]);
         hex.push_back(kLookup[str[i] & 0x0F]);
     }
     return OK;
 }

 status_t StrToHex(const KeyBuffer& str, KeyBuffer& hex) {
     hex.clear();
     for (size_t i = 0; i < str.size(); i++) {
         hex.push_back(kLookup[(str.data()[i] & 0xF0) >> 4]);
         hex.push_back(kLookup[str.data()[i] & 0x0F]);
     }
     return OK;
 }

 status_t NormalizeHex(const std::string& in, std::string& out) {
     std::string tmp;
     if (HexToStr(in, tmp)) {
         return -EINVAL;
     }
     return StrToHex(tmp, out);
 }

 status_t GetBlockDevSize(int fd, uint64_t* size) {
     if (ioctl(fd, BLKGETSIZE64, size)) {
         return -errno;
     }

     return OK;
 }

 status_t GetBlockDevSize(const std::string& path, uint64_t* size) {
     int fd = open(path.c_str(), O_RDONLY | O_CLOEXEC);
     status_t res = OK;

     if (fd < 0) {
         return -errno;
     }

     res = GetBlockDevSize(fd, size);

     close(fd);

     return res;
 }

 status_t GetBlockDev512Sectors(const std::string& path, uint64_t* nr_sec) {
     uint64_t size;
     status_t res = GetBlockDevSize(path, &size);

     if (res != OK) {
         return res;
     }

     *nr_sec = size / 512;

     return OK;
 }

 uint64_t GetFreeBytes(const std::string& path) {
     struct statvfs sb;
     if (statvfs(path.c_str(), &sb) == 0) {
         return (uint64_t)sb.f_bavail * sb.f_frsize;
     } else {
         return -1;
     }
 }

 // TODO: borrowed from frameworks/native/libs/diskusage/ which should
 // eventually be migrated into system/
 static int64_t stat_size(struct stat* s) {
     int64_t blksize = s->st_blksize;
     // count actual blocks used instead of nominal file size
     int64_t size = s->st_blocks * 512;

     if (blksize) {
         /* round up to filesystem block size */
         size = (size + blksize - 1) & (~(blksize - 1));
     }

     return size;
 }

 // TODO: borrowed from frameworks/native/libs/diskusage/ which should
 // eventually be migrated into system/
 int64_t calculate_dir_size(int dfd) {
     int64_t size = 0;
     struct stat s;
     DIR* d;
     struct dirent* de;

     d = fdopendir(dfd);
     if (d == NULL) {
         close(dfd);
         return 0;
     }

     while ((de = readdir(d))) {
         const char* name = de->d_name;
         if (fstatat(dfd, name, &s, AT_SYMLINK_NOFOLLOW) == 0) {
             size += stat_size(&s);
         }
         if (de->d_type == DT_DIR) {
             int subfd;

             /* always skip "." and ".." */
             if (name[0] == '.') {
                 if (name[1] == 0) continue;
                 if ((name[1] == '.') && (name[2] == 0)) continue;
             }

             subfd = openat(dfd, name, O_RDONLY | O_DIRECTORY | O_CLOEXEC);
             if (subfd >= 0) {
                 size += calculate_dir_size(subfd);
             }
         }
     }
     closedir(d);
     return size;
 }

 uint64_t GetTreeBytes(const std::string& path) {
     int dirfd = open(path.c_str(), O_RDONLY | O_DIRECTORY | O_CLOEXEC);
     if (dirfd < 0) {
         PLOG(WARNING) << "Failed to open " << path;
         return -1;
     } else {
         return calculate_dir_size(dirfd);
     }
 }

 bool IsFilesystemSupported(const std::string& fsType) {
     std::string supported;
     if (!ReadFileToString(kProcFilesystems, &supported)) {
         PLOG(ERROR) << "Failed to read supported filesystems";
         return false;
     }
     return supported.find(fsType + "\n") != std::string::npos;
 }

 status_t WipeBlockDevice(const std::string& path) {
     status_t res = -1;
     const char* c_path = path.c_str();
     uint64_t range[2] = {0, 0};

     int fd = TEMP_FAILURE_RETRY(open(c_path, O_RDWR | O_CLOEXEC));
     if (fd == -1) {
         PLOG(ERROR) << "Failed to open " << path;
         goto done;
     }

     if (GetBlockDevSize(fd, &range[1]) != OK) {
         PLOG(ERROR) << "Failed to determine size of " << path;
         goto done;
     }

     LOG(INFO) << "About to discard " << range[1] << " on " << path;
     if (ioctl(fd, BLKDISCARD, &range) == 0) {
         LOG(INFO) << "Discard success on " << path;
         res = 0;
     } else {
         PLOG(ERROR) << "Discard failure on " << path;
     }

 done:
     close(fd);
     return res;
 }

 static bool isValidFilename(const std::string& name) {
     if (name.empty() || (name == ".") || (name == "..") || (name.find('/') != std::string::npos)) {
         return false;
     } else {
         return true;
     }
 }

 std::string BuildKeyPath(const std::string& partGuid) {
     return StringPrintf("%s/expand_%s.key", kKeyPath, partGuid.c_str());
 }

 std::string BuildDataSystemLegacyPath(userid_t userId) {
     return StringPrintf("%s/system/users/%u", BuildDataPath("").c_str(), userId);
 }

 std::string BuildDataSystemCePath(userid_t userId) {
     return StringPrintf("%s/system_ce/%u", BuildDataPath("").c_str(), userId);
 }

 std::string BuildDataSystemDePath(userid_t userId) {
     return StringPrintf("%s/system_de/%u", BuildDataPath("").c_str(), userId);
 }

 std::string BuildDataMiscLegacyPath(userid_t userId) {
     return StringPrintf("%s/misc/user/%u", BuildDataPath("").c_str(), userId);
 }

 std::string BuildDataMiscCePath(userid_t userId) {
     return StringPrintf("%s/misc_ce/%u", BuildDataPath("").c_str(), userId);
 }

 std::string BuildDataMiscDePath(userid_t userId) {
     return StringPrintf("%s/misc_de/%u", BuildDataPath("").c_str(), userId);
 }

 // Keep in sync with installd (frameworks/native/cmds/installd/utils.h)
 std::string BuildDataProfilesDePath(userid_t userId) {
     return StringPrintf("%s/misc/profiles/cur/%u", BuildDataPath("").c_str(), userId);
 }

 std::string BuildDataVendorCePath(userid_t userId) {
     return StringPrintf("%s/vendor_ce/%u", BuildDataPath("").c_str(), userId);
 }

 std::string BuildDataVendorDePath(userid_t userId) {
     return StringPrintf("%s/vendor_de/%u", BuildDataPath("").c_str(), userId);
 }

 std::string BuildDataPath(const std::string& volumeUuid) {
     // TODO: unify with installd path generation logic
     if (volumeUuid.empty()) {
         return "/data";
     } else {
         CHECK(isValidFilename(volumeUuid));
         return StringPrintf("/mnt/expand/%s", volumeUuid.c_str());
     }
 }

 std::string BuildDataMediaCePath(const std::string& volumeUuid, userid_t userId) {
     // TODO: unify with installd path generation logic
     std::string data(BuildDataPath(volumeUuid));
     return StringPrintf("%s/media/%u", data.c_str(), userId);
 }

 std::string BuildDataUserCePath(const std::string& volumeUuid, userid_t userId) {
     // TODO: unify with installd path generation logic
     std::string data(BuildDataPath(volumeUuid));
     if (volumeUuid.empty() && userId == 0) {
         std::string legacy = StringPrintf("%s/data", data.c_str());
         struct stat sb;
         if (lstat(legacy.c_str(), &sb) == 0 && S_ISDIR(sb.st_mode)) {
             /* /data/data is dir, return /data/data for legacy system */
             return legacy;
         }
     }
     return StringPrintf("%s/user/%u", data.c_str(), userId);
 }

 std::string BuildDataUserDePath(const std::string& volumeUuid, userid_t userId) {
     // TODO: unify with installd path generation logic
     std::string data(BuildDataPath(volumeUuid));
     return StringPrintf("%s/user_de/%u", data.c_str(), userId);
 }

 dev_t GetDevice(const std::string& path) {
     struct stat sb;
     if (stat(path.c_str(), &sb)) {
         PLOG(WARNING) << "Failed to stat " << path;
         return 0;
     } else {
         return sb.st_dev;
     }
 }

 status_t RestoreconRecursive(const std::string& path) {
     LOG(DEBUG) << "Starting restorecon of " << path;

     static constexpr const char* kRestoreconString = "selinux.restorecon_recursive";

     android::base::SetProperty(kRestoreconString, "");
     android::base::SetProperty(kRestoreconString, path);

     android::base::WaitForProperty(kRestoreconString, path);

     LOG(DEBUG) << "Finished restorecon of " << path;
     return OK;
 }

 bool Readlinkat(int dirfd, const std::string& path, std::string* result) {
     // Shamelessly borrowed from android::base::Readlink()
     result->clear();

     // Most Linux file systems (ext2 and ext4, say) limit symbolic links to
     // 4095 bytes. Since we'll copy out into the string anyway, it doesn't
     // waste memory to just start there. We add 1 so that we can recognize
     // whether it actually fit (rather than being truncated to 4095).
     std::vector<char> buf(4095 + 1);
     while (true) {
         ssize_t size = readlinkat(dirfd, path.c_str(), &buf[0], buf.size());
         // Unrecoverable error?
         if (size == -1) return false;
         // It fit! (If size == buf.size(), it may have been truncated.)
         if (static_cast<size_t>(size) < buf.size()) {
             result->assign(&buf[0], size);
             return true;
         }
         // Double our buffer and try again.
         buf.resize(buf.size() * 2);
     }
 }

 bool IsRunningInEmulator() {
     return android::base::GetBoolProperty("ro.kernel.qemu", false);
 }

 status_t UnmountTree(const std::string& prefix) {
     FILE* fp = setmntent("/proc/mounts", "r");
     if (fp == NULL) {
         PLOG(ERROR) << "Failed to open /proc/mounts";
         return -errno;
     }

     // Some volumes can be stacked on each other, so force unmount in
     // reverse order to give us the best chance of success.
     std::list<std::string> toUnmount;
     mntent* mentry;
     while ((mentry = getmntent(fp)) != NULL) {
         auto test = std::string(mentry->mnt_dir) + "/";
         if (android::base::StartsWith(test, prefix)) {
             toUnmount.push_front(test);
         }
     }
     endmntent(fp);

     for (const auto& path : toUnmount) {
         if (umount2(path.c_str(), MNT_DETACH)) {
             PLOG(ERROR) << "Failed to unmount " << path;
         }
     }
     return OK;
 }

 static status_t delete_dir_contents(DIR* dir) {
     // Shamelessly borrowed from android::installd
     int dfd = dirfd(dir);
     if (dfd < 0) {
         return -errno;
     }

     status_t result;
     struct dirent* de;
     while ((de = readdir(dir))) {
         const char* name = de->d_name;
         if (de->d_type == DT_DIR) {
             /* always skip "." and ".." */
             if (name[0] == '.') {
                 if (name[1] == 0) continue;
                 if ((name[1] == '.') && (name[2] == 0)) continue;
             }

             android::base::unique_fd subfd(
                 openat(dfd, name, O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC));
             if (subfd.get() == -1) {
                 PLOG(ERROR) << "Couldn't openat " << name;
                 result = -errno;
                 continue;
             }
             std::unique_ptr<DIR, decltype(&closedir)> subdirp(fdopendir(subfd), closedir);
             if (!subdirp) {
                 PLOG(ERROR) << "Couldn't fdopendir " << name;
                 result = -errno;
                 continue;
             }
             result = delete_dir_contents(subdirp.get());
             if (unlinkat(dfd, name, AT_REMOVEDIR) < 0) {
                 PLOG(ERROR) << "Couldn't unlinkat " << name;
                 result = -errno;
             }
         } else {
             if (unlinkat(dfd, name, 0) < 0) {
                 PLOG(ERROR) << "Couldn't unlinkat " << name;
                 result = -errno;
             }
         }
     }
     return result;
 }

 status_t DeleteDirContentsAndDir(const std::string& pathname) {
     // Shamelessly borrowed from android::installd
     std::unique_ptr<DIR, decltype(&closedir)> dirp(opendir(pathname.c_str()), closedir);
     if (!dirp) {
         if (errno == ENOENT) {
             return OK;
         }
         PLOG(ERROR) << "Failed to opendir " << pathname;
         return -errno;
     }
     status_t res = delete_dir_contents(dirp.get());
     if (res < 0) {
         return res;
     }
     dirp.reset(nullptr);
     if (rmdir(pathname.c_str()) != 0) {
         PLOG(ERROR) << "rmdir failed on " << pathname;
         return -errno;
     }
     LOG(VERBOSE) << "Success: rmdir on " << pathname;
     return OK;
 }

 }  // namespace vold
 }  // namespace android
	/*
	* Copyright (C) 2015 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include "Utils.h"

	#include "Process.h"
	#include "sehandle.h"

	#include <android-base/file.h>
	#include <android-base/logging.h>
	#include <android-base/properties.h>
	#include <android-base/stringprintf.h>
	#include <android-base/strings.h>
	#include <android-base/unique_fd.h>
	#include <cutils/fs.h>
	#include <logwrap/logwrap.h>
	#include <private/android_filesystem_config.h>

	#include <dirent.h>
	#include <fcntl.h>
	#include <linux/fs.h>
	#include <mntent.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <sys/mount.h>
	#include <sys/stat.h>
	#include <sys/statvfs.h>
	#include <sys/sysmacros.h>
	#include <sys/types.h>
	#include <sys/wait.h>
	#include <list>
	#include <mutex>

	#ifndef UMOUNT_NOFOLLOW
	#define UMOUNT_NOFOLLOW 0x00000008 /* Don't follow symlink on umount */
	#endif

	using android::base::ReadFileToString;
	using android::base::StringPrintf;

	namespace android {
	namespace vold {

	security_context_t sBlkidContext = nullptr;
	security_context_t sBlkidUntrustedContext = nullptr;
	security_context_t sFsckContext = nullptr;
	security_context_t sFsckUntrustedContext = nullptr;

	bool sSleepOnUnmount = true;

	static const char* kBlkidPath = "/system/bin/blkid";
	static const char* kKeyPath = "/data/misc/vold";

	static const char* kProcFilesystems = "/proc/filesystems";

	// Lock used to protect process-level SELinux changes from racing with each
	// other between multiple threads.
	static std::mutex kSecurityLock;

	status_t CreateDeviceNode(const std::string& path, dev_t dev) {
	std::lock_guard<std::mutex> lock(kSecurityLock);
	const char* cpath = path.c_str();
	status_t res = 0;

	char* secontext = nullptr;
	if (sehandle) {
	if (!selabel_lookup(sehandle, &secontext, cpath, S_IFBLK)) {
	setfscreatecon(secontext);
	}
	}

	mode_t mode = 0660 \| S_IFBLK;
	if (mknod(cpath, mode, dev) < 0) {
	if (errno != EEXIST) {
	PLOG(ERROR) << "Failed to create device node for " << major(dev) << ":" << minor(dev)
	<< " at " << path;
	res = -errno;
	}
	}

	if (secontext) {
	setfscreatecon(nullptr);
	freecon(secontext);
	}

	return res;
	}

	status_t DestroyDeviceNode(const std::string& path) {
	const char* cpath = path.c_str();
	if (TEMP_FAILURE_RETRY(unlink(cpath))) {
	return -errno;
	} else {
	return OK;
	}
	}

	status_t PrepareDir(const std::string& path, mode_t mode, uid_t uid, gid_t gid) {
	std::lock_guard<std::mutex> lock(kSecurityLock);
	const char* cpath = path.c_str();

	char* secontext = nullptr;
	if (sehandle) {
	if (!selabel_lookup(sehandle, &secontext, cpath, S_IFDIR)) {
	setfscreatecon(secontext);
	}
	}

	int res = fs_prepare_dir(cpath, mode, uid, gid);

	if (secontext) {
	setfscreatecon(nullptr);
	freecon(secontext);
	}

	if (res == 0) {
	return OK;
	} else {
	return -errno;
	}
	}

	status_t ForceUnmount(const std::string& path) {
	const char* cpath = path.c_str();
	if (!umount2(cpath, UMOUNT_NOFOLLOW) \|\| errno == EINVAL \|\| errno == ENOENT) {
	return OK;
	}
	// Apps might still be handling eject request, so wait before
	// we start sending signals
	if (sSleepOnUnmount) sleep(5);

	KillProcessesWithOpenFiles(path, SIGINT);
	if (sSleepOnUnmount) sleep(5);
	if (!umount2(cpath, UMOUNT_NOFOLLOW) \|\| errno == EINVAL \|\| errno == ENOENT) {
	return OK;
	}

	KillProcessesWithOpenFiles(path, SIGTERM);
	if (sSleepOnUnmount) sleep(5);
	if (!umount2(cpath, UMOUNT_NOFOLLOW) \|\| errno == EINVAL \|\| errno == ENOENT) {
	return OK;
	}

	KillProcessesWithOpenFiles(path, SIGKILL);
	if (sSleepOnUnmount) sleep(5);
	if (!umount2(cpath, UMOUNT_NOFOLLOW) \|\| errno == EINVAL \|\| errno == ENOENT) {
	return OK;
	}

	return -errno;
	}

	status_t KillProcessesUsingPath(const std::string& path) {
	if (KillProcessesWithOpenFiles(path, SIGINT) == 0) {
	return OK;
	}
	if (sSleepOnUnmount) sleep(5);

	if (KillProcessesWithOpenFiles(path, SIGTERM) == 0) {
	return OK;
	}
	if (sSleepOnUnmount) sleep(5);

	if (KillProcessesWithOpenFiles(path, SIGKILL) == 0) {
	return OK;
	}
	if (sSleepOnUnmount) sleep(5);

	// Send SIGKILL a second time to determine if we've
	// actually killed everyone with open files
	if (KillProcessesWithOpenFiles(path, SIGKILL) == 0) {
	return OK;
	}
	PLOG(ERROR) << "Failed to kill processes using " << path;
	return -EBUSY;
	}

	status_t BindMount(const std::string& source, const std::string& target) {
	if (::mount(source.c_str(), target.c_str(), "", MS_BIND, NULL)) {
	PLOG(ERROR) << "Failed to bind mount " << source << " to " << target;
	return -errno;
	}
	return OK;
	}

	bool FindValue(const std::string& raw, const std::string& key, std::string* value) {
	auto qual = key + "=\"";
	auto start = raw.find(qual);
	if (start > 0 && raw[start - 1] != ' ') {
	start = raw.find(qual, start + 1);
	}

	if (start == std::string::npos) return false;
	start += qual.length();

	auto end = raw.find("\"", start);
	if (end == std::string::npos) return false;

	*value = raw.substr(start, end - start);
	return true;
	}

	static status_t readMetadata(const std::string& path, std::string* fsType, std::string* fsUuid,
	std::string* fsLabel, bool untrusted) {
	fsType->clear();
	fsUuid->clear();
	fsLabel->clear();

	std::vector<std::string> cmd;
	cmd.push_back(kBlkidPath);
	cmd.push_back("-c");
	cmd.push_back("/dev/null");
	cmd.push_back("-s");
	cmd.push_back("TYPE");
	cmd.push_back("-s");
	cmd.push_back("UUID");
	cmd.push_back("-s");
	cmd.push_back("LABEL");
	cmd.push_back(path);

	std::vector<std::string> output;
	status_t res = ForkExecvp(cmd, output, untrusted ? sBlkidUntrustedContext : sBlkidContext);
	if (res != OK) {
	LOG(WARNING) << "blkid failed to identify " << path;
	return res;
	}

	for (const auto& line : output) {
	// Extract values from blkid output, if defined
	FindValue(line, "TYPE", fsType);
	FindValue(line, "UUID", fsUuid);
	FindValue(line, "LABEL", fsLabel);
	}

	return OK;
	}

	status_t ReadMetadata(const std::string& path, std::string* fsType, std::string* fsUuid,
	std::string* fsLabel) {
	return readMetadata(path, fsType, fsUuid, fsLabel, false);
	}

	status_t ReadMetadataUntrusted(const std::string& path, std::string* fsType, std::string* fsUuid,
	std::string* fsLabel) {
	return readMetadata(path, fsType, fsUuid, fsLabel, true);
	}

	status_t ForkExecvp(const std::vector<std::string>& args) {
	return ForkExecvp(args, nullptr);
	}

	status_t ForkExecvp(const std::vector<std::string>& args, security_context_t context) {
	std::lock_guard<std::mutex> lock(kSecurityLock);
	size_t argc = args.size();
	char argv = (char)calloc(argc, sizeof(char*));
	for (size_t i = 0; i < argc; i++) {
	argv[i] = (char*)args[i].c_str();
	if (i == 0) {
	LOG(DEBUG) << args[i];
	} else {
	LOG(DEBUG) << " " << args[i];
	}
	}

	if (context) {
	if (setexeccon(context)) {
	LOG(ERROR) << "Failed to setexeccon";
	abort();
	}
	}
	status_t res = android_fork_execvp(argc, argv, NULL, false, true);
	if (context) {
	if (setexeccon(nullptr)) {
	LOG(ERROR) << "Failed to setexeccon";
	abort();
	}
	}

	free(argv);
	return res;
	}

	status_t ForkExecvp(const std::vector<std::string>& args, std::vector<std::string>& output) {
	return ForkExecvp(args, output, nullptr);
	}

	status_t ForkExecvp(const std::vector<std::string>& args, std::vector<std::string>& output,
	security_context_t context) {
	std::lock_guard<std::mutex> lock(kSecurityLock);
	std::string cmd;
	for (size_t i = 0; i < args.size(); i++) {
	cmd += args[i] + " ";
	if (i == 0) {
	LOG(DEBUG) << args[i];
	} else {
	LOG(DEBUG) << " " << args[i];
	}
	}
	output.clear();

	if (context) {
	if (setexeccon(context)) {
	LOG(ERROR) << "Failed to setexeccon";
	abort();
	}
	}
	FILE* fp = popen(cmd.c_str(), "r"); // NOLINT
	if (context) {
	if (setexeccon(nullptr)) {
	LOG(ERROR) << "Failed to setexeccon";
	abort();
	}
	}

	if (!fp) {
	PLOG(ERROR) << "Failed to popen " << cmd;
	return -errno;
	}
	char line[1024];
	while (fgets(line, sizeof(line), fp) != nullptr) {
	LOG(DEBUG) << line;
	output.push_back(std::string(line));
	}
	if (pclose(fp) != 0) {
	PLOG(ERROR) << "Failed to pclose " << cmd;
	return -errno;
	}

	return OK;
	}

	pid_t ForkExecvpAsync(const std::vector<std::string>& args) {
	size_t argc = args.size();
	char argv = (char)calloc(argc + 1, sizeof(char*));
	for (size_t i = 0; i < argc; i++) {
	argv[i] = (char*)args[i].c_str();
	if (i == 0) {
	LOG(DEBUG) << args[i];
	} else {
	LOG(DEBUG) << " " << args[i];
	}
	}

	pid_t pid = fork();
	if (pid == 0) {
	close(STDIN_FILENO);
	close(STDOUT_FILENO);
	close(STDERR_FILENO);

	if (execvp(argv[0], argv)) {
	PLOG(ERROR) << "Failed to exec";
	}

	_exit(1);
	}

	if (pid == -1) {
	PLOG(ERROR) << "Failed to exec";
	}

	free(argv);
	return pid;
	}

	status_t ReadRandomBytes(size_t bytes, std::string& out) {
	out.resize(bytes);
	return ReadRandomBytes(bytes, &out[0]);
	}

	status_t ReadRandomBytes(size_t bytes, char* buf) {
	int fd = TEMP_FAILURE_RETRY(open("/dev/urandom", O_RDONLY \| O_CLOEXEC \| O_NOFOLLOW));
	if (fd == -1) {
	return -errno;
	}

	size_t n;
	while ((n = TEMP_FAILURE_RETRY(read(fd, &buf[0], bytes))) > 0) {
	bytes -= n;
	buf += n;
	}
	close(fd);

	if (bytes == 0) {
	return OK;
	} else {
	return -EIO;
	}
	}

	status_t GenerateRandomUuid(std::string& out) {
	status_t res = ReadRandomBytes(16, out);
	if (res == OK) {
	out[6] &= 0x0f; /* clear version */
	out[6] \|= 0x40; /* set to version 4 */
	out[8] &= 0x3f; /* clear variant */
	out[8] \|= 0x80; /* set to IETF variant */
	}
	return res;
	}

	status_t HexToStr(const std::string& hex, std::string& str) {
	str.clear();
	bool even = true;
	char cur = 0;
	for (size_t i = 0; i < hex.size(); i++) {
	int val = 0;
	switch (hex[i]) {
	// clang-format off
	case ' ': case '-': case ':': continue;
	case 'f': case 'F': val = 15; break;
	case 'e': case 'E': val = 14; break;
	case 'd': case 'D': val = 13; break;
	case 'c': case 'C': val = 12; break;
	case 'b': case 'B': val = 11; break;
	case 'a': case 'A': val = 10; break;
	case '9': val = 9; break;
	case '8': val = 8; break;
	case '7': val = 7; break;
	case '6': val = 6; break;
	case '5': val = 5; break;
	case '4': val = 4; break;
	case '3': val = 3; break;
	case '2': val = 2; break;
	case '1': val = 1; break;
	case '0': val = 0; break;
	default: return -EINVAL;
	// clang-format on
	}

	if (even) {
	cur = val << 4;
	} else {
	cur += val;
	str.push_back(cur);
	cur = 0;
	}
	even = !even;
	}
	return even ? OK : -EINVAL;
	}

	static const char* kLookup = "0123456789abcdef";

	status_t StrToHex(const std::string& str, std::string& hex) {
	hex.clear();
	for (size_t i = 0; i < str.size(); i++) {
	hex.push_back(kLookup[(str[i] & 0xF0) >> 4]);
	hex.push_back(kLookup[str[i] & 0x0F]);
	}
	return OK;
	}

	status_t StrToHex(const KeyBuffer& str, KeyBuffer& hex) {
	hex.clear();
	for (size_t i = 0; i < str.size(); i++) {
	hex.push_back(kLookup[(str.data()[i] & 0xF0) >> 4]);
	hex.push_back(kLookup[str.data()[i] & 0x0F]);
	}
	return OK;
	}

	status_t NormalizeHex(const std::string& in, std::string& out) {
	std::string tmp;
	if (HexToStr(in, tmp)) {
	return -EINVAL;
	}
	return StrToHex(tmp, out);
	}

	status_t GetBlockDevSize(int fd, uint64_t* size) {
	if (ioctl(fd, BLKGETSIZE64, size)) {
	return -errno;
	}

	return OK;
	}

	status_t GetBlockDevSize(const std::string& path, uint64_t* size) {
	int fd = open(path.c_str(), O_RDONLY \| O_CLOEXEC);
	status_t res = OK;

	if (fd < 0) {
	return -errno;
	}

	res = GetBlockDevSize(fd, size);

	close(fd);

	return res;
	}

	status_t GetBlockDev512Sectors(const std::string& path, uint64_t* nr_sec) {
	uint64_t size;
	status_t res = GetBlockDevSize(path, &size);

	if (res != OK) {
	return res;
	}

	*nr_sec = size / 512;

	return OK;
	}

	uint64_t GetFreeBytes(const std::string& path) {
	struct statvfs sb;
	if (statvfs(path.c_str(), &sb) == 0) {
	return (uint64_t)sb.f_bavail * sb.f_frsize;
	} else {
	return -1;
	}
	}

	// TODO: borrowed from frameworks/native/libs/diskusage/ which should
	// eventually be migrated into system/
	static int64_t stat_size(struct stat* s) {
	int64_t blksize = s->st_blksize;
	// count actual blocks used instead of nominal file size
	int64_t size = s->st_blocks * 512;

	if (blksize) {
	/* round up to filesystem block size */
	size = (size + blksize - 1) & (~(blksize - 1));
	}

	return size;
	}

	// TODO: borrowed from frameworks/native/libs/diskusage/ which should
	// eventually be migrated into system/
	int64_t calculate_dir_size(int dfd) {
	int64_t size = 0;
	struct stat s;
	DIR* d;
	struct dirent* de;

	d = fdopendir(dfd);
	if (d == NULL) {
	close(dfd);
	return 0;
	}

	while ((de = readdir(d))) {
	const char* name = de->d_name;
	if (fstatat(dfd, name, &s, AT_SYMLINK_NOFOLLOW) == 0) {
	size += stat_size(&s);
	}
	if (de->d_type == DT_DIR) {
	int subfd;

	/* always skip "." and ".." */
	if (name[0] == '.') {
	if (name[1] == 0) continue;
	if ((name[1] == '.') && (name[2] == 0)) continue;
	}

	subfd = openat(dfd, name, O_RDONLY \| O_DIRECTORY \| O_CLOEXEC);
	if (subfd >= 0) {
	size += calculate_dir_size(subfd);
	}
	}
	}
	closedir(d);
	return size;
	}

	uint64_t GetTreeBytes(const std::string& path) {
	int dirfd = open(path.c_str(), O_RDONLY \| O_DIRECTORY \| O_CLOEXEC);
	if (dirfd < 0) {
	PLOG(WARNING) << "Failed to open " << path;
	return -1;
	} else {
	return calculate_dir_size(dirfd);
	}
	}

	bool IsFilesystemSupported(const std::string& fsType) {
	std::string supported;
	if (!ReadFileToString(kProcFilesystems, &supported)) {
	PLOG(ERROR) << "Failed to read supported filesystems";
	return false;
	}
	return supported.find(fsType + "\n") != std::string::npos;
	}

	status_t WipeBlockDevice(const std::string& path) {
	status_t res = -1;
	const char* c_path = path.c_str();
	uint64_t range[2] = {0, 0};

	int fd = TEMP_FAILURE_RETRY(open(c_path, O_RDWR \| O_CLOEXEC));
	if (fd == -1) {
	PLOG(ERROR) << "Failed to open " << path;
	goto done;
	}

	if (GetBlockDevSize(fd, &range[1]) != OK) {
	PLOG(ERROR) << "Failed to determine size of " << path;
	goto done;
	}

	LOG(INFO) << "About to discard " << range[1] << " on " << path;
	if (ioctl(fd, BLKDISCARD, &range) == 0) {
	LOG(INFO) << "Discard success on " << path;
	res = 0;
	} else {
	PLOG(ERROR) << "Discard failure on " << path;
	}

	done:
	close(fd);
	return res;
	}

	static bool isValidFilename(const std::string& name) {
	if (name.empty() \|\| (name == ".") \|\| (name == "..") \|\| (name.find('/') != std::string::npos)) {
	return false;
	} else {
	return true;
	}
	}

	std::string BuildKeyPath(const std::string& partGuid) {
	return StringPrintf("%s/expand_%s.key", kKeyPath, partGuid.c_str());
	}

	std::string BuildDataSystemLegacyPath(userid_t userId) {
	return StringPrintf("%s/system/users/%u", BuildDataPath("").c_str(), userId);
	}

	std::string BuildDataSystemCePath(userid_t userId) {
	return StringPrintf("%s/system_ce/%u", BuildDataPath("").c_str(), userId);
	}

	std::string BuildDataSystemDePath(userid_t userId) {
	return StringPrintf("%s/system_de/%u", BuildDataPath("").c_str(), userId);
	}

	std::string BuildDataMiscLegacyPath(userid_t userId) {
	return StringPrintf("%s/misc/user/%u", BuildDataPath("").c_str(), userId);
	}

	std::string BuildDataMiscCePath(userid_t userId) {
	return StringPrintf("%s/misc_ce/%u", BuildDataPath("").c_str(), userId);
	}

	std::string BuildDataMiscDePath(userid_t userId) {
	return StringPrintf("%s/misc_de/%u", BuildDataPath("").c_str(), userId);
	}

	// Keep in sync with installd (frameworks/native/cmds/installd/utils.h)
	std::string BuildDataProfilesDePath(userid_t userId) {
	return StringPrintf("%s/misc/profiles/cur/%u", BuildDataPath("").c_str(), userId);
	}

	std::string BuildDataVendorCePath(userid_t userId) {
	return StringPrintf("%s/vendor_ce/%u", BuildDataPath("").c_str(), userId);
	}

	std::string BuildDataVendorDePath(userid_t userId) {
	return StringPrintf("%s/vendor_de/%u", BuildDataPath("").c_str(), userId);
	}

	std::string BuildDataPath(const std::string& volumeUuid) {
	// TODO: unify with installd path generation logic
	if (volumeUuid.empty()) {
	return "/data";
	} else {
	CHECK(isValidFilename(volumeUuid));
	return StringPrintf("/mnt/expand/%s", volumeUuid.c_str());
	}
	}

	std::string BuildDataMediaCePath(const std::string& volumeUuid, userid_t userId) {
	// TODO: unify with installd path generation logic
	std::string data(BuildDataPath(volumeUuid));
	return StringPrintf("%s/media/%u", data.c_str(), userId);
	}

	std::string BuildDataUserCePath(const std::string& volumeUuid, userid_t userId) {
	// TODO: unify with installd path generation logic
	std::string data(BuildDataPath(volumeUuid));
	if (volumeUuid.empty() && userId == 0) {
	std::string legacy = StringPrintf("%s/data", data.c_str());
	struct stat sb;
	if (lstat(legacy.c_str(), &sb) == 0 && S_ISDIR(sb.st_mode)) {
	/* /data/data is dir, return /data/data for legacy system */
	return legacy;
	}
	}
	return StringPrintf("%s/user/%u", data.c_str(), userId);
	}

	std::string BuildDataUserDePath(const std::string& volumeUuid, userid_t userId) {
	// TODO: unify with installd path generation logic
	std::string data(BuildDataPath(volumeUuid));
	return StringPrintf("%s/user_de/%u", data.c_str(), userId);
	}

	dev_t GetDevice(const std::string& path) {
	struct stat sb;
	if (stat(path.c_str(), &sb)) {
	PLOG(WARNING) << "Failed to stat " << path;
	return 0;
	} else {
	return sb.st_dev;
	}
	}

	status_t RestoreconRecursive(const std::string& path) {
	LOG(DEBUG) << "Starting restorecon of " << path;

	static constexpr const char* kRestoreconString = "selinux.restorecon_recursive";

	android::base::SetProperty(kRestoreconString, "");
	android::base::SetProperty(kRestoreconString, path);

	android::base::WaitForProperty(kRestoreconString, path);

	LOG(DEBUG) << "Finished restorecon of " << path;
	return OK;
	}

	bool Readlinkat(int dirfd, const std::string& path, std::string* result) {
	// Shamelessly borrowed from android::base::Readlink()
	result->clear();

	// Most Linux file systems (ext2 and ext4, say) limit symbolic links to
	// 4095 bytes. Since we'll copy out into the string anyway, it doesn't
	// waste memory to just start there. We add 1 so that we can recognize
	// whether it actually fit (rather than being truncated to 4095).
	std::vector<char> buf(4095 + 1);
	while (true) {
	ssize_t size = readlinkat(dirfd, path.c_str(), &buf[0], buf.size());
	// Unrecoverable error?
	if (size == -1) return false;
	// It fit! (If size == buf.size(), it may have been truncated.)
	if (static_cast<size_t>(size) < buf.size()) {
	result->assign(&buf[0], size);
	return true;
	}
	// Double our buffer and try again.
	buf.resize(buf.size() * 2);
	}
	}

	bool IsRunningInEmulator() {
	return android::base::GetBoolProperty("ro.kernel.qemu", false);
	}

	status_t UnmountTree(const std::string& prefix) {
	FILE* fp = setmntent("/proc/mounts", "r");
	if (fp == NULL) {
	PLOG(ERROR) << "Failed to open /proc/mounts";
	return -errno;
	}

	// Some volumes can be stacked on each other, so force unmount in
	// reverse order to give us the best chance of success.
	std::list<std::string> toUnmount;
	mntent* mentry;
	while ((mentry = getmntent(fp)) != NULL) {
	auto test = std::string(mentry->mnt_dir) + "/";
	if (android::base::StartsWith(test, prefix)) {
	toUnmount.push_front(test);
	}
	}
	endmntent(fp);

	for (const auto& path : toUnmount) {
	if (umount2(path.c_str(), MNT_DETACH)) {
	PLOG(ERROR) << "Failed to unmount " << path;
	}
	}
	return OK;
	}

	static status_t delete_dir_contents(DIR* dir) {
	// Shamelessly borrowed from android::installd
	int dfd = dirfd(dir);
	if (dfd < 0) {
	return -errno;
	}

	status_t result;
	struct dirent* de;
	while ((de = readdir(dir))) {
	const char* name = de->d_name;
	if (de->d_type == DT_DIR) {
	/* always skip "." and ".." */
	if (name[0] == '.') {
	if (name[1] == 0) continue;
	if ((name[1] == '.') && (name[2] == 0)) continue;
	}

	android::base::unique_fd subfd(
	openat(dfd, name, O_RDONLY \| O_DIRECTORY \| O_NOFOLLOW \| O_CLOEXEC));
	if (subfd.get() == -1) {
	PLOG(ERROR) << "Couldn't openat " << name;
	result = -errno;
	continue;
	}
	std::unique_ptr<DIR, decltype(&closedir)> subdirp(fdopendir(subfd), closedir);
	if (!subdirp) {
	PLOG(ERROR) << "Couldn't fdopendir " << name;
	result = -errno;
	continue;
	}
	result = delete_dir_contents(subdirp.get());
	if (unlinkat(dfd, name, AT_REMOVEDIR) < 0) {
	PLOG(ERROR) << "Couldn't unlinkat " << name;
	result = -errno;
	}
	} else {
	if (unlinkat(dfd, name, 0) < 0) {
	PLOG(ERROR) << "Couldn't unlinkat " << name;
	result = -errno;
	}
	}
	}
	return result;
	}

	status_t DeleteDirContentsAndDir(const std::string& pathname) {
	// Shamelessly borrowed from android::installd
	std::unique_ptr<DIR, decltype(&closedir)> dirp(opendir(pathname.c_str()), closedir);
	if (!dirp) {
	if (errno == ENOENT) {
	return OK;
	}
	PLOG(ERROR) << "Failed to opendir " << pathname;
	return -errno;
	}
	status_t res = delete_dir_contents(dirp.get());
	if (res < 0) {
	return res;
	}
	dirp.reset(nullptr);
	if (rmdir(pathname.c_str()) != 0) {
	PLOG(ERROR) << "rmdir failed on " << pathname;
	return -errno;
	}
	LOG(VERBOSE) << "Success: rmdir on " << pathname;
	return OK;
	}

	} // namespace vold
	} // namespace android