text: /*
   * Copyright (C) 2008 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.
   */
  
  /*
   * Disable optimization of this file if we are compiling with the address
   * sanitizer.  This is a mitigation for b/122921367 and can be removed once the
   * bug is fixed.
   */
  #if __has_feature(address_sanitizer)
  #pragma clang optimize off
  #endif
  
  #define LOG_TAG "Zygote"
  #define ATRACE_TAG ATRACE_TAG_DALVIK
  
  #include <async_safe/log.h>
  
  // sys/mount.h has to come before linux/fs.h due to redefinition of MS_RDONLY, MS_BIND, etc
  #include <sys/mount.h>
  #include <linux/fs.h>
  
  #include <array>
  #include <atomic>
  #include <functional>
  #include <list>
  #include <optional>
  #include <sstream>
  #include <string>
  #include <string_view>
  
  #include <android/fdsan.h>
  #include <arpa/inet.h>
  #include <fcntl.h>
  #include <grp.h>
  #include <inttypes.h>
  #include <link.h>
  #include <malloc.h>
  #include <mntent.h>
  #include <paths.h>
  #include <signal.h>
  #include <stdlib.h>
  #include <sys/capability.h>
  #include <sys/cdefs.h>
  #include <sys/eventfd.h>
  #include <sys/mman.h>
  #include <sys/personality.h>
  #include <sys/prctl.h>
  #include <sys/resource.h>
  #include <sys/socket.h>
  #include <sys/stat.h>
  #include <sys/time.h>
  #include <sys/types.h>
  #include <sys/utsname.h>
  #include <sys/wait.h>
  #include <unistd.h>
  
  #include <android-base/logging.h>
  #include <android-base/properties.h>
  #include <android-base/file.h>
  #include <android-base/stringprintf.h>
  #include <android-base/strings.h>
  #include <android-base/unique_fd.h>
  #include <bionic_malloc.h>
  #include <cutils/ashmem.h>
  #include <cutils/fs.h>
  #include <cutils/multiuser.h>
  #include <private/android_filesystem_config.h>
  #include <utils/String8.h>
  #include <utils/Trace.h>
  #include <selinux/android.h>
  #include <seccomp_policy.h>
  #include <stats_event_list.h>
  #include <processgroup/processgroup.h>
  #include <processgroup/sched_policy.h>
  
  #include "core_jni_helpers.h"
  #include <nativehelper/JNIHelp.h>
  #include <nativehelper/ScopedLocalRef.h>
  #include <nativehelper/ScopedPrimitiveArray.h>
  #include <nativehelper/ScopedUtfChars.h>
  #include "fd_utils.h"
  
  #include "nativebridge/native_bridge.h"
  
  namespace {
  
  // TODO (chriswailes): Add a function to initialize native Zygote data.
  // TODO (chriswailes): Fix mixed indentation style (2 and 4 spaces).
  
  using namespace std::placeholders;
  
  using android::String8;
  using android::base::StringAppendF;
  using android::base::StringPrintf;
  using android::base::WriteStringToFile;
  using android::base::GetBoolProperty;
  
  #define CREATE_ERROR(...) StringPrintf("%s:%d: ", __FILE__, __LINE__). \
                                append(StringPrintf(__VA_ARGS__))
  
  // This type is duplicated in fd_utils.h
  typedef const std::function<void(std::string)>& fail_fn_t;
  
  static pid_t gSystemServerPid = 0;
  
  static constexpr const char* kZygoteClassName = "com/android/internal/os/Zygote";
  static jclass gZygoteClass;
  static jmethodID gCallPostForkSystemServerHooks;
  static jmethodID gCallPostForkChildHooks;
  
  static constexpr const char* kZygoteInitClassName = "com/android/internal/os/ZygoteInit";
  static jclass gZygoteInitClass;
  static jmethodID gCreateSystemServerClassLoader;
  
  static bool gIsSecurityEnforced = true;
  
  /**
   * The maximum number of characters (not including a null terminator) that a
   * process name may contain.
   */
  static constexpr size_t MAX_NAME_LENGTH = 15;
  
  /**
   * The prefix string for environmental variables storing socket FDs created by
   * init.
   */
  
  static constexpr std::string_view ANDROID_SOCKET_PREFIX("ANDROID_SOCKET_");
  
  /**
   * The file descriptor for the Zygote socket opened by init.
   */
  
  static int gZygoteSocketFD = -1;
  
  /**
   * The file descriptor for the unspecialized app process (USAP) pool socket opened by init.
   */
  
  static int gUsapPoolSocketFD = -1;
  
  /**
   * The number of USAPs currently in this Zygote's pool.
   */
  static std::atomic_uint32_t gUsapPoolCount = 0;
  
  /**
   * Event file descriptor used to communicate reaped USAPs to the
   * ZygoteServer.
   */
  static int gUsapPoolEventFD = -1;
  
  /**
   * The maximum value that the gUSAPPoolSizeMax variable may take.  This value
   * is a mirror of ZygoteServer.USAP_POOL_SIZE_MAX_LIMIT
   */
  static constexpr int USAP_POOL_SIZE_MAX_LIMIT = 100;
  
  /**
   * A helper class containing accounting information for USAPs.
   */
  class UsapTableEntry {
   public:
    struct EntryStorage {
      int32_t pid;
      int32_t read_pipe_fd;
  
      bool operator!=(const EntryStorage& other) {
        return pid != other.pid || read_pipe_fd != other.read_pipe_fd;
      }
    };
  
   private:
    static constexpr EntryStorage INVALID_ENTRY_VALUE = {-1, -1};
  
    std::atomic<EntryStorage> mStorage;
    static_assert(decltype(mStorage)::is_always_lock_free);
  
   public:
    constexpr UsapTableEntry() : mStorage(INVALID_ENTRY_VALUE) {}
  
    /**
     * If the provided PID matches the one stored in this entry, the entry will
     * be invalidated and the associated file descriptor will be closed.  If the
     * PIDs don't match nothing will happen.
     *
     * @param pid The ID of the process who's entry we want to clear.
     * @return True if the entry was cleared by this call; false otherwise
     */
    bool ClearForPID(int32_t pid) {
      EntryStorage storage = mStorage.load();
  
      if (storage.pid == pid) {
        /*
         * There are three possible outcomes from this compare-and-exchange:
         *   1) It succeeds, in which case we close the FD
         *   2) It fails and the new value is INVALID_ENTRY_VALUE, in which case
         *      the entry has already been cleared.
         *   3) It fails and the new value isn't INVALID_ENTRY_VALUE, in which
         *      case the entry has already been cleared and re-used.
         *
         * In all three cases the goal of the caller has been met, but only in
         * the first case do we need to decrement the pool count.
         */
        if (mStorage.compare_exchange_strong(storage, INVALID_ENTRY_VALUE)) {
          close(storage.read_pipe_fd);
          return true;
        } else {
          return false;
        }
  
      } else {
        return false;
      }
    }
  
    void Clear() {
      EntryStorage storage = mStorage.load();
  
      if (storage != INVALID_ENTRY_VALUE) {
        close(storage.read_pipe_fd);
        mStorage.store(INVALID_ENTRY_VALUE);
      }
    }
  
    void Invalidate() {
      mStorage.store(INVALID_ENTRY_VALUE);
    }
  
    /**
     * @return A copy of the data stored in this entry.
     */
    std::optional<EntryStorage> GetValues() {
      EntryStorage storage = mStorage.load();
  
      if (storage != INVALID_ENTRY_VALUE) {
        return storage;
      } else {
        return std::nullopt;
      }
    }
  
    /**
     * Sets the entry to the given values if it is currently invalid.
     *
     * @param pid  The process ID for the new entry.
     * @param read_pipe_fd  The read end of the USAP control pipe for this
     * process.
     * @return True if the entry was set; false otherwise.
     */
    bool SetIfInvalid(int32_t pid, int32_t read_pipe_fd) {
      EntryStorage new_value_storage;
  
      new_value_storage.pid = pid;
      new_value_storage.read_pipe_fd = read_pipe_fd;
  
      EntryStorage expected = INVALID_ENTRY_VALUE;
  
      return mStorage.compare_exchange_strong(expected, new_value_storage);
    }
  };
  
  /**
   * A table containing information about the USAPs currently in the pool.
   *
   * Multiple threads may be attempting to modify the table, either from the
   * signal handler or from the ZygoteServer poll loop.  Atomic loads/stores in
   * the USAPTableEntry class prevent data races during these concurrent
   * operations.
   */
  static std::array<UsapTableEntry, USAP_POOL_SIZE_MAX_LIMIT> gUsapTable;
  
  /**
   * The list of open zygote file descriptors.
   */
  static FileDescriptorTable* gOpenFdTable = nullptr;
  
  // Must match values in com.android.internal.os.Zygote.
  enum MountExternalKind {
    MOUNT_EXTERNAL_NONE = 0,
    MOUNT_EXTERNAL_DEFAULT = 1,
    MOUNT_EXTERNAL_READ = 2,
    MOUNT_EXTERNAL_WRITE = 3,
    MOUNT_EXTERNAL_LEGACY = 4,
    MOUNT_EXTERNAL_INSTALLER = 5,
    MOUNT_EXTERNAL_FULL = 6,
  };
  
  // Must match values in com.android.internal.os.Zygote.
  enum RuntimeFlags : uint32_t {
    DEBUG_ENABLE_JDWP = 1,
    PROFILE_FROM_SHELL = 1 << 15,
  };
  
  // Forward declaration so we don't have to move the signal handler.
  static bool RemoveUsapTableEntry(pid_t usap_pid);
  
  static void RuntimeAbort(JNIEnv* env, int line, const char* msg) {
    std::ostringstream oss;
    oss << __FILE__ << ":" << line << ": " << msg;
    env->FatalError(oss.str().c_str());
  }
  
  // This signal handler is for zygote mode, since the zygote must reap its children
  static void SigChldHandler(int /*signal_number*/) {
    pid_t pid;
    int status;
    int64_t usaps_removed = 0;
  
    // It's necessary to save and restore the errno during this function.
    // Since errno is stored per thread, changing it here modifies the errno
    // on the thread on which this signal handler executes. If a signal occurs
    // between a call and an errno check, it's possible to get the errno set
    // here.
    // See b/23572286 for extra information.
    int saved_errno = errno;
  
    while ((pid = waitpid(-1, &status, WNOHANG)) > 0) {
       // Log process-death status that we care about.
      if (WIFEXITED(status)) {
        async_safe_format_log(ANDROID_LOG_INFO, LOG_TAG,
                              "Process %d exited cleanly (%d)", pid, WEXITSTATUS(status));
  
        // Check to see if the PID is in the USAP pool and remove it if it is.
        if (RemoveUsapTableEntry(pid)) {
          ++usaps_removed;
        }
      } else if (WIFSIGNALED(status)) {
        async_safe_format_log(ANDROID_LOG_INFO, LOG_TAG,
                              "Process %d exited due to signal %d (%s)%s", pid,
                              WTERMSIG(status), strsignal(WTERMSIG(status)),
                              WCOREDUMP(status) ? "; core dumped" : "");
  
        // If the process exited due to a signal other than SIGTERM, check to see
        // if the PID is in the USAP pool and remove it if it is.  If the process
        // was closed by the Zygote using SIGTERM then the USAP pool entry will
        // have already been removed (see nativeEmptyUsapPool()).
        if (WTERMSIG(status) != SIGTERM && RemoveUsapTableEntry(pid)) {
          ++usaps_removed;
        }
      }
  
      // If the just-crashed process is the system_server, bring down zygote
      // so that it is restarted by init and system server will be restarted
      // from there.
      if (pid == gSystemServerPid) {
        async_safe_format_log(ANDROID_LOG_ERROR, LOG_TAG,
                              "Exit zygote because system server (pid %d) has terminated", pid);
        kill(getpid(), SIGKILL);
      }
    }
  
    // Note that we shouldn't consider ECHILD an error because
    // the secondary zygote might have no children left to wait for.
    if (pid < 0 && errno != ECHILD) {
      async_safe_format_log(ANDROID_LOG_WARN, LOG_TAG,
                            "Zygote SIGCHLD error in waitpid: %s", strerror(errno));
    }
  
    if (usaps_removed > 0) {
      if (TEMP_FAILURE_RETRY(write(gUsapPoolEventFD, &usaps_removed, sizeof(usaps_removed))) == -1) {
        // If this write fails something went terribly wrong.  We will now kill
        // the zygote and let the system bring it back up.
        async_safe_format_log(ANDROID_LOG_ERROR, LOG_TAG,
                              "Zygote failed to write to USAP pool event FD: %s",
                              strerror(errno));
        kill(getpid(), SIGKILL);
      }
    }
  
    errno = saved_errno;
  }
  
  // Configures the SIGCHLD/SIGHUP handlers for the zygote process. This is
  // configured very late, because earlier in the runtime we may fork() and
  // exec() other processes, and we want to waitpid() for those rather than
  // have them be harvested immediately.
  //
  // Ignore SIGHUP because all processes forked by the zygote are in the same
  // process group as the zygote and we don't want to be notified if we become
  // an orphaned group and have one or more stopped processes. This is not a
  // theoretical concern :
  // - we can become an orphaned group if one of our direct descendants forks
  //   and is subsequently killed before its children.
  // - crash_dump routinely STOPs the process it's tracing.
  //
  // See issues b/71965619 and b/25567761 for further details.
  //
  // This ends up being called repeatedly before each fork(), but there's
  // no real harm in that.
  static void SetSignalHandlers() {
    struct sigaction sig_chld = {};
    sig_chld.sa_handler = SigChldHandler;
  
    if (sigaction(SIGCHLD, &sig_chld, nullptr) < 0) {
      ALOGW("Error setting SIGCHLD handler: %s", strerror(errno));
    }
  
    struct sigaction sig_hup = {};
    sig_hup.sa_handler = SIG_IGN;
    if (sigaction(SIGHUP, &sig_hup, nullptr) < 0) {
      ALOGW("Error setting SIGHUP handler: %s", strerror(errno));
    }
  }
  
  // Sets the SIGCHLD handler back to default behavior in zygote children.
  static void UnsetChldSignalHandler() {
    struct sigaction sa;
    memset(&sa, 0, sizeof(sa));
    sa.sa_handler = SIG_DFL;
  
    if (sigaction(SIGCHLD, &sa, nullptr) < 0) {
      ALOGW("Error unsetting SIGCHLD handler: %s", strerror(errno));
    }
  }
  
  // Calls POSIX setgroups() using the int[] object as an argument.
  // A nullptr argument is tolerated.
  static void SetGids(JNIEnv* env, jintArray managed_gids, fail_fn_t fail_fn) {
    if (managed_gids == nullptr) {
      return;
    }
  
    ScopedIntArrayRO gids(env, managed_gids);
    if (gids.get() == nullptr) {
      fail_fn(CREATE_ERROR("Getting gids int array failed"));
    }
  
    if (setgroups(gids.size(), reinterpret_cast<const gid_t*>(&gids[0])) == -1) {
      fail_fn(CREATE_ERROR("setgroups failed: %s, gids.size=%zu", strerror(errno), gids.size()));
    }
  }
  
  // Sets the resource limits via setrlimit(2) for the values in the
  // two-dimensional array of integers that's passed in. The second dimension
  // contains a tuple of length 3: (resource, rlim_cur, rlim_max). nullptr is
  // treated as an empty array.
  static void SetRLimits(JNIEnv* env, jobjectArray managed_rlimits, fail_fn_t fail_fn) {
    if (managed_rlimits == nullptr) {
      return;
    }
  
    rlimit rlim;
    memset(&rlim, 0, sizeof(rlim));
  
    for (int i = 0; i < env->GetArrayLength(managed_rlimits); ++i) {
      ScopedLocalRef<jobject>
          managed_rlimit_object(env, env->GetObjectArrayElement(managed_rlimits, i));
      ScopedIntArrayRO rlimit_handle(env, reinterpret_cast<jintArray>(managed_rlimit_object.get()));
  
      if (rlimit_handle.size() != 3) {
        fail_fn(CREATE_ERROR("rlimits array must have a second dimension of size 3"));
      }
  
      rlim.rlim_cur = rlimit_handle[1];
      rlim.rlim_max = rlimit_handle[2];
  
      if (setrlimit(rlimit_handle[0], &rlim) == -1) {
        fail_fn(CREATE_ERROR("setrlimit(%d, {%ld, %ld}) failed",
                             rlimit_handle[0], rlim.rlim_cur, rlim.rlim_max));
      }
    }
  }
  
  static void EnableDebugger() {
    // To let a non-privileged gdbserver attach to this
    // process, we must set our dumpable flag.
    if (prctl(PR_SET_DUMPABLE, 1, 0, 0, 0) == -1) {
      ALOGE("prctl(PR_SET_DUMPABLE) failed");
    }
  
    // A non-privileged native debugger should be able to attach to the debuggable app, even if Yama
    // is enabled (see kernel/Documentation/security/Yama.txt).
    if (prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY, 0, 0, 0) == -1) {
      // if Yama is off prctl(PR_SET_PTRACER) returns EINVAL - don't log in this
      // case since it's expected behaviour.
      if (errno != EINVAL) {
        ALOGE("prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY) failed");
      }
    }
  
    // Set the core dump size to zero unless wanted (see also coredump_setup in build/envsetup.sh).
    if (!GetBoolProperty("persist.zygote.core_dump", false)) {
      // Set the soft limit on core dump size to 0 without changing the hard limit.
      rlimit rl;
      if (getrlimit(RLIMIT_CORE, &rl) == -1) {
        ALOGE("getrlimit(RLIMIT_CORE) failed");
      } else {
        rl.rlim_cur = 0;
        if (setrlimit(RLIMIT_CORE, &rl) == -1) {
          ALOGE("setrlimit(RLIMIT_CORE) failed");
        }
      }
    }
  }
  
  static void PreApplicationInit() {
    // The child process sets this to indicate it's not the zygote.
    android_mallopt(M_SET_ZYGOTE_CHILD, nullptr, 0);
  
    // Set the jemalloc decay time to 1.
    mallopt(M_DECAY_TIME, 1);
  }
  
  static void SetUpSeccompFilter(uid_t uid, bool is_child_zygote) {
    if (!gIsSecurityEnforced) {
      ALOGI("seccomp disabled by setenforce 0");
      return;
    }
  
    // Apply system or app filter based on uid.
    if (uid >= AID_APP_START) {
      if (is_child_zygote) {
        set_app_zygote_seccomp_filter();
      } else {
        set_app_seccomp_filter();
      }
    } else {
      set_system_seccomp_filter();
    }
  }
  
  static void EnableKeepCapabilities(fail_fn_t fail_fn) {
    if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) == -1) {
      fail_fn(CREATE_ERROR("prctl(PR_SET_KEEPCAPS) failed: %s", strerror(errno)));
    }
  }
  
  static void DropCapabilitiesBoundingSet(fail_fn_t fail_fn) {
    for (int i = 0; prctl(PR_CAPBSET_READ, i, 0, 0, 0) >= 0; i++) {;
      if (prctl(PR_CAPBSET_DROP, i, 0, 0, 0) == -1) {
        if (errno == EINVAL) {
          ALOGE("prctl(PR_CAPBSET_DROP) failed with EINVAL. Please verify "
                "your kernel is compiled with file capabilities support");
        } else {
          fail_fn(CREATE_ERROR("prctl(PR_CAPBSET_DROP, %d) failed: %s", i, strerror(errno)));
        }
      }
    }
  }
  
  static void SetInheritable(uint64_t inheritable, fail_fn_t fail_fn) {
    __user_cap_header_struct capheader;
    memset(&capheader, 0, sizeof(capheader));
    capheader.version = _LINUX_CAPABILITY_VERSION_3;
    capheader.pid = 0;
  
    __user_cap_data_struct capdata[2];
    if (capget(&capheader, &capdata[0]) == -1) {
      fail_fn(CREATE_ERROR("capget failed: %s", strerror(errno)));
    }
  
    capdata[0].inheritable = inheritable;
    capdata[1].inheritable = inheritable >> 32;
  
    if (capset(&capheader, &capdata[0]) == -1) {
      fail_fn(CREATE_ERROR("capset(inh=%" PRIx64 ") failed: %s", inheritable, strerror(errno)));
    }
  }
  
  static void SetCapabilities(uint64_t permitted, uint64_t effective, uint64_t inheritable,
                              fail_fn_t fail_fn) {
    __user_cap_header_struct capheader;
    memset(&capheader, 0, sizeof(capheader));
    capheader.version = _LINUX_CAPABILITY_VERSION_3;
    capheader.pid = 0;
  
    __user_cap_data_struct capdata[2];
    memset(&capdata, 0, sizeof(capdata));
    capdata[0].effective = effective;
    capdata[1].effective = effective >> 32;
    capdata[0].permitted = permitted;
    capdata[1].permitted = permitted >> 32;
    capdata[0].inheritable = inheritable;
    capdata[1].inheritable = inheritable >> 32;
  
    if (capset(&capheader, &capdata[0]) == -1) {
      fail_fn(CREATE_ERROR("capset(perm=%" PRIx64 ", eff=%" PRIx64 ", inh=%" PRIx64 ") "
                           "failed: %s", permitted, effective, inheritable, strerror(errno)));
    }
  }
  
  static void SetSchedulerPolicy(fail_fn_t fail_fn) {
    errno = -set_sched_policy(0, SP_DEFAULT);
    if (errno != 0) {
      fail_fn(CREATE_ERROR("set_sched_policy(0, SP_DEFAULT) failed: %s", strerror(errno)));
    }
  }
  
  static int UnmountTree(const char* path) {
    ATRACE_CALL();
  
    size_t path_len = strlen(path);
  
    FILE* fp = setmntent("/proc/mounts", "r");
    if (fp == nullptr) {
      ALOGE("Error opening /proc/mounts: %s", strerror(errno));
      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> to_unmount;
    mntent* mentry;
    while ((mentry = getmntent(fp)) != nullptr) {
      if (strncmp(mentry->mnt_dir, path, path_len) == 0) {
        to_unmount.push_front(std::string(mentry->mnt_dir));
      }
    }
    endmntent(fp);
  
    for (const auto& path : to_unmount) {
      if (umount2(path.c_str(), MNT_DETACH)) {
        ALOGW("Failed to unmount %s: %s", path.c_str(), strerror(errno));
      }
    }
    return 0;
  }
  
  // Create a private mount namespace and bind mount appropriate emulated
  // storage for the given user.
  static void MountEmulatedStorage(uid_t uid, jint mount_mode,
          bool force_mount_namespace,
          fail_fn_t fail_fn) {
    // See storage config details at http://source.android.com/tech/storage/
    ATRACE_CALL();
  
    String8 storage_source;
    if (mount_mode == MOUNT_EXTERNAL_DEFAULT) {
      storage_source = "/mnt/runtime/default";
    } else if (mount_mode == MOUNT_EXTERNAL_READ) {
      storage_source = "/mnt/runtime/read";
    } else if (mount_mode == MOUNT_EXTERNAL_WRITE
        || mount_mode == MOUNT_EXTERNAL_LEGACY
        || mount_mode == MOUNT_EXTERNAL_INSTALLER) {
      storage_source = "/mnt/runtime/write";
    } else if (mount_mode == MOUNT_EXTERNAL_FULL) {
      storage_source = "/mnt/runtime/full";
    } else if (mount_mode == MOUNT_EXTERNAL_NONE && !force_mount_namespace) {
      // Sane default of no storage visible
      return;
    }
  
    // Create a second private mount namespace for our process
    if (unshare(CLONE_NEWNS) == -1) {
      fail_fn(CREATE_ERROR("Failed to unshare(): %s", strerror(errno)));
    }
  
    // Handle force_mount_namespace with MOUNT_EXTERNAL_NONE.
    if (mount_mode == MOUNT_EXTERNAL_NONE) {
      return;
    }
  
    if (TEMP_FAILURE_RETRY(mount(storage_source.string(), "/storage", nullptr,
                                 MS_BIND | MS_REC | MS_SLAVE, nullptr)) == -1) {
      fail_fn(CREATE_ERROR("Failed to mount %s to /storage: %s",
                           storage_source.string(),
                           strerror(errno)));
    }
  
    // Mount user-specific symlink helper into place
    userid_t user_id = multiuser_get_user_id(uid);
    const String8 user_source(String8::format("/mnt/user/%d", user_id));
    if (fs_prepare_dir(user_source.string(), 0751, 0, 0) == -1) {
      fail_fn(CREATE_ERROR("fs_prepare_dir failed on %s",
                           user_source.string()));
    }
  
    if (TEMP_FAILURE_RETRY(mount(user_source.string(), "/storage/self",
                                 nullptr, MS_BIND, nullptr)) == -1) {
      fail_fn(CREATE_ERROR("Failed to mount %s to /storage/self: %s",
                           user_source.string(), strerror(errno)));
    }
  }
  
  static bool NeedsNoRandomizeWorkaround() {
  #if !defined(__arm__)
      return false;
  #else
      int major;
      int minor;
      struct utsname uts;
      if (uname(&uts) == -1) {
          return false;
      }
  
      if (sscanf(uts.release, "%d.%d", &major, &minor) != 2) {
          return false;
      }
  
      // Kernels before 3.4.* need the workaround.
      return (major < 3) || ((major == 3) && (minor < 4));
  #endif
  }
  
  // Utility to close down the Zygote socket file descriptors while
  // the child is still running as root with Zygote's privileges.  Each
  // descriptor (if any) is closed via dup3(), replacing it with a valid
  // (open) descriptor to /dev/null.
  
  static void DetachDescriptors(JNIEnv* env,
                                const std::vector<int>& fds_to_close,
                                fail_fn_t fail_fn) {
  
    if (fds_to_close.size() > 0) {
      android::base::unique_fd devnull_fd(open("/dev/null", O_RDWR | O_CLOEXEC));
      if (devnull_fd == -1) {
        fail_fn(std::string("Failed to open /dev/null: ").append(strerror(errno)));
      }
  
      for (int fd : fds_to_close) {
        ALOGV("Switching descriptor %d to /dev/null", fd);
        if (dup3(devnull_fd, fd, O_CLOEXEC) == -1) {
          fail_fn(StringPrintf("Failed dup3() on descriptor %d: %s", fd, strerror(errno)));
        }
      }
    }
  }
  
  void SetThreadName(const std::string& thread_name) {
    bool hasAt = false;
    bool hasDot = false;
  
    for (const char str_el : thread_name) {
      if (str_el == '.') {
        hasDot = true;
      } else if (str_el == '@') {
        hasAt = true;
      }
    }
  
    const char* name_start_ptr = thread_name.c_str();
    if (thread_name.length() >= MAX_NAME_LENGTH && !hasAt && hasDot) {
      name_start_ptr += thread_name.length() - MAX_NAME_LENGTH;
    }
  
    // pthread_setname_np fails rather than truncating long strings.
    char buf[16];       // MAX_TASK_COMM_LEN=16 is hard-coded into bionic
    strlcpy(buf, name_start_ptr, sizeof(buf) - 1);
    errno = pthread_setname_np(pthread_self(), buf);
    if (errno != 0) {
      ALOGW("Unable to set the name of current thread to '%s': %s", buf, strerror(errno));
    }
    // Update base::logging default tag.
    android::base::SetDefaultTag(buf);
  }
  
  /**
   * A failure function used to report fatal errors to the managed runtime.  This
   * function is often curried with the process name information and then passed
   * to called functions.
   *
   * @param env  Managed runtime environment
   * @param process_name  A native representation of the process name
   * @param managed_process_name  A managed representation of the process name
   * @param msg  The error message to be reported
   */
  [[noreturn]]
  static void ZygoteFailure(JNIEnv* env,
                            const char* process_name,
                            jstring managed_process_name,
                            const std::string& msg) {
    std::unique_ptr<ScopedUtfChars> scoped_managed_process_name_ptr = nullptr;
    if (managed_process_name != nullptr) {
      scoped_managed_process_name_ptr.reset(new ScopedUtfChars(env, managed_process_name));
      if (scoped_managed_process_name_ptr->c_str() != nullptr) {
        process_name = scoped_managed_process_name_ptr->c_str();
      }
    }
  
    const std::string& error_msg =
        (process_name == nullptr) ? msg : StringPrintf("(%s) %s", process_name, msg.c_str());
  
    env->FatalError(error_msg.c_str());
    __builtin_unreachable();
  }
  
  /**
   * A helper method for converting managed strings to native strings.  A fatal
   * error is generated if a problem is encountered in extracting a non-null
   * string.
   *
   * @param env  Managed runtime environment
   * @param process_name  A native representation of the process name
   * @param managed_process_name  A managed representation of the process name
   * @param managed_string  The managed string to extract
   *
   * @return An empty option if the managed string is null.  A optional-wrapped
   * string otherwise.
   */
  static std::optional<std::string> ExtractJString(JNIEnv* env,
                                                   const char* process_name,
                                                   jstring managed_process_name,
                                                   jstring managed_string) {
    if (managed_string == nullptr) {
      return std::nullopt;
    } else {
      ScopedUtfChars scoped_string_chars(env, managed_string);
  
      if (scoped_string_chars.c_str() != nullptr) {
        return std::optional<std::string>(scoped_string_chars.c_str());
      } else {
        ZygoteFailure(env, process_name, managed_process_name, "Failed to extract JString.");
      }
    }
  }
  
  /**
   * A helper method for converting managed string arrays to native vectors.  A
   * fatal error is generated if a problem is encountered in extracting a non-null array.
   *
   * @param env  Managed runtime environment
   * @param process_name  A native representation of the process name
   * @param managed_process_name  A managed representation of the process name
   * @param managed_array  The managed integer array to extract
   *
   * @return An empty option if the managed array is null.  A optional-wrapped
   * vector otherwise.
   */
  static std::optional<std::vector<int>> ExtractJIntArray(JNIEnv* env,
                                                          const char* process_name,
                                                          jstring managed_process_name,
                                                          jintArray managed_array) {
    if (managed_array == nullptr) {
      return std::nullopt;
    } else {
      ScopedIntArrayRO managed_array_handle(env, managed_array);
  
      if (managed_array_handle.get() != nullptr) {
        std::vector<int> native_array;
        native_array.reserve(managed_array_handle.size());
  
        for (size_t array_index = 0; array_index < managed_array_handle.size(); ++array_index) {
          native_array.push_back(managed_array_handle[array_index]);
        }
  
        return std::move(native_array);
  
      } else {
        ZygoteFailure(env, process_name, managed_process_name, "Failed to extract JIntArray.");
      }
    }
  }
  
  /**
   * A utility function for blocking signals.
   *
   * @param signum  Signal number to block
   * @param fail_fn  Fatal error reporting function
   *
   * @see ZygoteFailure
   */
  static void BlockSignal(int signum, fail_fn_t fail_fn) {
    sigset_t sigs;
    sigemptyset(&sigs);
    sigaddset(&sigs, signum);
  
    if (sigprocmask(SIG_BLOCK, &sigs, nullptr) == -1) {
      fail_fn(CREATE_ERROR("Failed to block signal %s: %s", strsignal(signum), strerror(errno)));
    }
  }
  
  
  /**
   * A utility function for unblocking signals.
   *
   * @param signum  Signal number to unblock
   * @param fail_fn  Fatal error reporting function
   *
   * @see ZygoteFailure
   */
  static void UnblockSignal(int signum, fail_fn_t fail_fn) {
    sigset_t sigs;
    sigemptyset(&sigs);
    sigaddset(&sigs, signum);
  
    if (sigprocmask(SIG_UNBLOCK, &sigs, nullptr) == -1) {
      fail_fn(CREATE_ERROR("Failed to un-block signal %s: %s", strsignal(signum), strerror(errno)));
    }
  }
  
  static void ClearUsapTable() {
    for (UsapTableEntry& entry : gUsapTable) {
      entry.Clear();
    }
  
    gUsapPoolCount = 0;
  }
  
  // Utility routine to fork a process from the zygote.
  static pid_t ForkCommon(JNIEnv* env, bool is_system_server,
                          const std::vector<int>& fds_to_close,
                          const std::vector<int>& fds_to_ignore) {
    SetSignalHandlers();
  
    // Curry a failure function.
    auto fail_fn = std::bind(ZygoteFailure, env, is_system_server ? "system_server" : "zygote",
                             nullptr, _1);
  
    // Temporarily block SIGCHLD during forks. The SIGCHLD handler might
    // log, which would result in the logging FDs we close being reopened.
    // This would cause failures because the FDs are not whitelisted.
    //
    // Note that the zygote process is single threaded at this point.
    BlockSignal(SIGCHLD, fail_fn);
  
    // Close any logging related FDs before we start evaluating the list of
    // file descriptors.
    __android_log_close();
    stats_log_close();
  
    // If this is the first fork for this zygote, create the open FD table.  If
    // it isn't, we just need to check whether the list of open files has changed
    // (and it shouldn't in the normal case).
    if (gOpenFdTable == nullptr) {
      gOpenFdTable = FileDescriptorTable::Create(fds_to_ignore, fail_fn);
    } else {
      gOpenFdTable->Restat(fds_to_ignore, fail_fn);
    }
  
    android_fdsan_error_level fdsan_error_level = android_fdsan_get_error_level();
  
    pid_t pid = fork();
  
    if (pid == 0) {
      // The child process.
      PreApplicationInit();
  
      // Clean up any descriptors which must be closed immediately
      DetachDescriptors(env, fds_to_close, fail_fn);
  
      // Invalidate the entries in the USAP table.
      ClearUsapTable();
  
      // Re-open all remaining open file descriptors so that they aren't shared
      // with the zygote across a fork.
      gOpenFdTable->ReopenOrDetach(fail_fn);
  
      // Turn fdsan back on.
      android_fdsan_set_error_level(fdsan_error_level);
    } else {
      ALOGD("Forked child process %d", pid);
    }
  
    // We blocked SIGCHLD prior to a fork, we unblock it here.
    UnblockSignal(SIGCHLD, fail_fn);
  
    return pid;
  }
  
  // Utility routine to specialize a zygote child process.
  static void SpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArray gids,
                               jint runtime_flags, jobjectArray rlimits,
                               jlong permitted_capabilities, jlong effective_capabilities,
                               jint mount_external, jstring managed_se_info,
                               jstring managed_nice_name, bool is_system_server,
                               bool is_child_zygote, jstring managed_instruction_set,
                               jstring managed_app_data_dir) {
    const char* process_name = is_system_server ? "system_server" : "zygote";
    auto fail_fn = std::bind(ZygoteFailure, env, process_name, managed_nice_name, _1);
    auto extract_fn = std::bind(ExtractJString, env, process_name, managed_nice_name, _1);
  
    auto se_info = extract_fn(managed_se_info);
    auto nice_name = extract_fn(managed_nice_name);
    auto instruction_set = extract_fn(managed_instruction_set);
    auto app_data_dir = extract_fn(managed_app_data_dir);
  
    // Keep capabilities across UID change, unless we're staying root.
    if (uid != 0) {
      EnableKeepCapabilities(fail_fn);
    }
  
    SetInheritable(permitted_capabilities, fail_fn);
  
    DropCapabilitiesBoundingSet(fail_fn);
  
    bool use_native_bridge = !is_system_server &&
                             instruction_set.has_value() &&
                             android::NativeBridgeAvailable() &&
                             android::NeedsNativeBridge(instruction_set.value().c_str());
  
    if (use_native_bridge && !app_data_dir.has_value()) {
      // The app_data_dir variable should never be empty if we need to use a
      // native bridge.  In general, app_data_dir will never be empty for normal
      // applications.  It can only happen in special cases (for isolated
      // processes which are not associated with any app).  These are launched by
      // the framework and should not be emulated anyway.
      use_native_bridge = false;
      ALOGW("Native bridge will not be used because managed_app_data_dir == nullptr.");
    }
  
    MountEmulatedStorage(uid, mount_external, use_native_bridge, fail_fn);
  
    // If this zygote isn't root, it won't be able to create a process group,
    // since the directory is owned by root.
    if (!is_system_server && getuid() == 0) {
      const int rc = createProcessGroup(uid, getpid());
      if (rc == -EROFS) {
        ALOGW("createProcessGroup failed, kernel missing CONFIG_CGROUP_CPUACCT?");
      } else if (rc != 0) {
        ALOGE("createProcessGroup(%d, %d) failed: %s", uid, /* pid= */ 0, strerror(-rc));
      }
    }
  
    SetGids(env, gids, fail_fn);
    SetRLimits(env, rlimits, fail_fn);
  
    if (use_native_bridge) {
      // Due to the logic behind use_native_bridge we know that both app_data_dir
      // and instruction_set contain values.
      android::PreInitializeNativeBridge(app_data_dir.value().c_str(),
                                         instruction_set.value().c_str());
    }
  
    if (setresgid(gid, gid, gid) == -1) {
      fail_fn(CREATE_ERROR("setresgid(%d) failed: %s", gid, strerror(errno)));
    }
  
    // Must be called when the new process still has CAP_SYS_ADMIN, in this case,
    // before changing uid from 0, which clears capabilities.  The other
    // alternative is to call prctl(PR_SET_NO_NEW_PRIVS, 1) afterward, but that
    // breaks SELinux domain transition (see b/71859146).  As the result,
    // privileged syscalls used below still need to be accessible in app process.
    SetUpSeccompFilter(uid, is_child_zygote);
  
    if (setresuid(uid, uid, uid) == -1) {
      fail_fn(CREATE_ERROR("setresuid(%d) failed: %s", uid, strerror(errno)));
    }
  
    // The "dumpable" flag of a process, which controls core dump generation, is
    // overwritten by the value in /proc/sys/fs/suid_dumpable when the effective
    // user or group ID changes. See proc(5) for possible values. In most cases,
    // the value is 0, so core dumps are disabled for zygote children. However,
    // when running in a Chrome OS container, the value is already set to 2,
    // which allows the external crash reporter to collect all core dumps. Since
    // only system crashes are interested, core dump is disabled for app
    // processes. This also ensures compliance with CTS.
    int dumpable = prctl(PR_GET_DUMPABLE);
    if (dumpable == -1) {
      ALOGE("prctl(PR_GET_DUMPABLE) failed: %s", strerror(errno));
      RuntimeAbort(env, __LINE__, "prctl(PR_GET_DUMPABLE) failed");
    }
  
    if (dumpable == 2 && uid >= AID_APP) {
      if (prctl(PR_SET_DUMPABLE, 0, 0, 0, 0) == -1) {
        ALOGE("prctl(PR_SET_DUMPABLE, 0) failed: %s", strerror(errno));
        RuntimeAbort(env, __LINE__, "prctl(PR_SET_DUMPABLE, 0) failed");
      }
    }
  
    // Set process properties to enable debugging if required.
    if ((runtime_flags & RuntimeFlags::DEBUG_ENABLE_JDWP) != 0) {
      EnableDebugger();
    }
    if ((runtime_flags & RuntimeFlags::PROFILE_FROM_SHELL) != 0) {
      // simpleperf needs the process to be dumpable to profile it.
      if (prctl(PR_SET_DUMPABLE, 1, 0, 0, 0) == -1) {
        ALOGE("prctl(PR_SET_DUMPABLE) failed: %s", strerror(errno));
        RuntimeAbort(env, __LINE__, "prctl(PR_SET_DUMPABLE, 1) failed");
      }
    }
  
    if (NeedsNoRandomizeWorkaround()) {
      // Work around ARM kernel ASLR lossage (http://b/5817320).
      int old_personality = personality(0xffffffff);
      int new_personality = personality(old_personality | ADDR_NO_RANDOMIZE);
      if (new_personality == -1) {
        ALOGW("personality(%d) failed: %s", new_personality, strerror(errno));
      }
    }
  
    SetCapabilities(permitted_capabilities, effective_capabilities, permitted_capabilities, fail_fn);
  
    SetSchedulerPolicy(fail_fn);
  
    __android_log_close();
    stats_log_close();
  
    const char* se_info_ptr = se_info.has_value() ? se_info.value().c_str() : nullptr;
    const char* nice_name_ptr = nice_name.has_value() ? nice_name.value().c_str() : nullptr;
  
    if (selinux_android_setcontext(uid, is_system_server, se_info_ptr, nice_name_ptr) == -1) {
      fail_fn(CREATE_ERROR("selinux_android_setcontext(%d, %d, \"%s\", \"%s\") failed",
                           uid, is_system_server, se_info_ptr, nice_name_ptr));
    }
  
    // Make it easier to debug audit logs by setting the main thread's name to the
    // nice name rather than "app_process".
    if (nice_name.has_value()) {
      SetThreadName(nice_name.value());
    } else if (is_system_server) {
      SetThreadName("system_server");
    }
  
    // Unset the SIGCHLD handler, but keep ignoring SIGHUP (rationale in SetSignalHandlers).
    UnsetChldSignalHandler();
  
    if (is_system_server) {
      env->CallStaticVoidMethod(gZygoteClass, gCallPostForkSystemServerHooks);
      if (env->ExceptionCheck()) {
        fail_fn("Error calling post fork system server hooks.");
      }
  
      // Prefetch the classloader for the system server. This is done early to
      // allow a tie-down of the proper system server selinux domain.
      env->CallStaticVoidMethod(gZygoteInitClass, gCreateSystemServerClassLoader);
      if (env->ExceptionCheck()) {
        // Be robust here. The Java code will attempt to create the classloader
        // at a later point (but may not have rights to use AoT artifacts).
        env->ExceptionClear();
      }
  
      // TODO(oth): Remove hardcoded label here (b/117874058).
      static const char* kSystemServerLabel = "u:r:system_server:s0";
      if (selinux_android_setcon(kSystemServerLabel) != 0) {
        fail_fn(CREATE_ERROR("selinux_android_setcon(%s)", kSystemServerLabel));
      }
    }
  
    env->CallStaticVoidMethod(gZygoteClass, gCallPostForkChildHooks, runtime_flags,
                              is_system_server, is_child_zygote, managed_instruction_set);
  
    if (env->ExceptionCheck()) {
      fail_fn("Error calling post fork hooks.");
    }
  }
  
  static uint64_t GetEffectiveCapabilityMask(JNIEnv* env) {
      __user_cap_header_struct capheader;
      memset(&capheader, 0, sizeof(capheader));
      capheader.version = _LINUX_CAPABILITY_VERSION_3;
      capheader.pid = 0;
  
      __user_cap_data_struct capdata[2];
      if (capget(&capheader, &capdata[0]) == -1) {
          ALOGE("capget failed: %s", strerror(errno));
          RuntimeAbort(env, __LINE__, "capget failed");
      }
  
      return capdata[0].effective | (static_cast<uint64_t>(capdata[1].effective) << 32);
  }
  
  static jlong CalculateCapabilities(JNIEnv* env, jint uid, jint gid, jintArray gids,
                                     bool is_child_zygote) {
    jlong capabilities = 0;
  
    /*
     *  Grant the following capabilities to the Bluetooth user:
     *    - CAP_WAKE_ALARM
     *    - CAP_NET_ADMIN
     *    - CAP_NET_RAW
     *    - CAP_NET_BIND_SERVICE (for DHCP client functionality)
     *    - CAP_SYS_NICE (for setting RT priority for audio-related threads)
     */
  
    if (multiuser_get_app_id(uid) == AID_BLUETOOTH) {
      capabilities |= (1LL << CAP_WAKE_ALARM);
      capabilities |= (1LL << CAP_NET_ADMIN);
      capabilities |= (1LL << CAP_NET_RAW);
      capabilities |= (1LL << CAP_NET_BIND_SERVICE);
      capabilities |= (1LL << CAP_SYS_NICE);
    }
  
    if (multiuser_get_app_id(uid) == AID_NETWORK_STACK) {
      capabilities |= (1LL << CAP_NET_ADMIN);
      capabilities |= (1LL << CAP_NET_BROADCAST);
      capabilities |= (1LL << CAP_NET_BIND_SERVICE);
      capabilities |= (1LL << CAP_NET_RAW);
    }
  
    /*
     * Grant CAP_BLOCK_SUSPEND to processes that belong to GID "wakelock"
     */
  
    bool gid_wakelock_found = false;
    if (gid == AID_WAKELOCK) {
      gid_wakelock_found = true;
    } else if (gids != nullptr) {
      jsize gids_num = env->GetArrayLength(gids);
      ScopedIntArrayRO native_gid_proxy(env, gids);
  
      if (native_gid_proxy.get() == nullptr) {
        RuntimeAbort(env, __LINE__, "Bad gids array");
      }
  
      for (int gids_index = 0; gids_index < gids_num; ++gids_index) {
        if (native_gid_proxy[gids_index] == AID_WAKELOCK) {
          gid_wakelock_found = true;
          break;
        }
      }
    }
  
    if (gid_wakelock_found) {
      capabilities |= (1LL << CAP_BLOCK_SUSPEND);
    }
  
    /*
     * Grant child Zygote processes the following capabilities:
     *   - CAP_SETUID (change UID of child processes)
     *   - CAP_SETGID (change GID of child processes)
     *   - CAP_SETPCAP (change capabilities of child processes)
     */
  
    if (is_child_zygote) {
      capabilities |= (1LL << CAP_SETUID);
      capabilities |= (1LL << CAP_SETGID);
      capabilities |= (1LL << CAP_SETPCAP);
    }
  
    /*
     * Containers run without some capabilities, so drop any caps that are not
     * available.
     */
  
    return capabilities & GetEffectiveCapabilityMask(env);
  }
  
  /**
   * Adds the given information about a newly created unspecialized app
   * processes to the Zygote's USAP table.
   *
   * @param usap_pid  Process ID of the newly created USAP
   * @param read_pipe_fd  File descriptor for the read end of the USAP
   * reporting pipe.  Used in the ZygoteServer poll loop to track USAP
   * specialization.
   */
  static void AddUsapTableEntry(pid_t usap_pid, int read_pipe_fd) {
    static int sUsapTableInsertIndex = 0;
  
    int search_index = sUsapTableInsertIndex;
  
    do {
      if (gUsapTable[search_index].SetIfInvalid(usap_pid, read_pipe_fd)) {
        // Start our next search right after where we finished this one.
        sUsapTableInsertIndex = (search_index + 1) % gUsapTable.size();
  
        return;
      }
  
      search_index = (search_index + 1) % gUsapTable.size();
    } while (search_index != sUsapTableInsertIndex);
  
    // Much like money in the banana stand, there should always be an entry
    // in the USAP table.
    __builtin_unreachable();
  }
  
  /**
   * Invalidates the entry in the USAPTable corresponding to the provided
   * process ID if it is present.  If an entry was removed the USAP pool
   * count is decremented.
   *
   * @param usap_pid  Process ID of the USAP entry to invalidate
   * @return True if an entry was invalidated; false otherwise
   */
  static bool RemoveUsapTableEntry(pid_t usap_pid) {
    for (UsapTableEntry& entry : gUsapTable) {
      if (entry.ClearForPID(usap_pid)) {
        --gUsapPoolCount;
        return true;
      }
    }
  
    return false;
  }
  
  /**
   * @return A vector of the read pipe FDs for each of the active USAPs.
   */
  std::vector<int> MakeUsapPipeReadFDVector() {
    std::vector<int> fd_vec;
    fd_vec.reserve(gUsapTable.size());
  
    for (UsapTableEntry& entry : gUsapTable) {
      auto entry_values = entry.GetValues();
  
      if (entry_values.has_value()) {
        fd_vec.push_back(entry_values.value().read_pipe_fd);
      }
    }
  
    return fd_vec;
  }
  
  static void UnmountStorageOnInit(JNIEnv* env) {
    // Zygote process unmount root storage space initially before every child processes are forked.
    // Every forked child processes (include SystemServer) only mount their own root storage space
    // and no need unmount storage operation in MountEmulatedStorage method.
    // Zygote process does not utilize root storage spaces and unshares its mount namespace below.
  
    // See storage config details at http://source.android.com/tech/storage/
    // Create private mount namespace shared by all children
    if (unshare(CLONE_NEWNS) == -1) {
      RuntimeAbort(env, __LINE__, "Failed to unshare()");
      return;
    }
  
    // Mark rootfs as being a slave so that changes from default
    // namespace only flow into our children.
    if (mount("rootfs", "/", nullptr, (MS_SLAVE | MS_REC), nullptr) == -1) {
      RuntimeAbort(env, __LINE__, "Failed to mount() rootfs as MS_SLAVE");
      return;
    }
  
    // Create a staging tmpfs that is shared by our children; they will
    // bind mount storage into their respective private namespaces, which
    // are isolated from each other.
    const char* target_base = getenv("EMULATED_STORAGE_TARGET");
    if (target_base != nullptr) {
  #define STRINGIFY_UID(x) __STRING(x)
      if (mount("tmpfs", target_base, "tmpfs", MS_NOSUID | MS_NODEV,
                "uid=0,gid=" STRINGIFY_UID(AID_SDCARD_R) ",mode=0751") == -1) {
        ALOGE("Failed to mount tmpfs to %s", target_base);
        RuntimeAbort(env, __LINE__, "Failed to mount tmpfs");
        return;
      }
  #undef STRINGIFY_UID
    }
  
    UnmountTree("/storage");
  }
  
  }  // anonymous namespace
  
  namespace android {
  
  static void com_android_internal_os_Zygote_nativePreApplicationInit(JNIEnv*, jclass) {
    PreApplicationInit();
  }
  
  static jint com_android_internal_os_Zygote_nativeForkAndSpecialize(
          JNIEnv* env, jclass, jint uid, jint gid, jintArray gids,
          jint runtime_flags, jobjectArray rlimits,
          jint mount_external, jstring se_info, jstring nice_name,
          jintArray managed_fds_to_close, jintArray managed_fds_to_ignore, jboolean is_child_zygote,
          jstring instruction_set, jstring app_data_dir) {
      jlong capabilities = CalculateCapabilities(env, uid, gid, gids, is_child_zygote);
  
      if (UNLIKELY(managed_fds_to_close == nullptr)) {
        ZygoteFailure(env, "zygote", nice_name, "Zygote received a null fds_to_close vector.");
      }
  
      std::vector<int> fds_to_close =
          ExtractJIntArray(env, "zygote", nice_name, managed_fds_to_close).value();
      std::vector<int> fds_to_ignore =
          ExtractJIntArray(env, "zygote", nice_name, managed_fds_to_ignore)
              .value_or(std::vector<int>());
  
      std::vector<int> usap_pipes = MakeUsapPipeReadFDVector();
  
      fds_to_close.insert(fds_to_close.end(), usap_pipes.begin(), usap_pipes.end());
      fds_to_ignore.insert(fds_to_ignore.end(), usap_pipes.begin(), usap_pipes.end());
  
      fds_to_close.push_back(gUsapPoolSocketFD);
  
      if (gUsapPoolEventFD != -1) {
        fds_to_close.push_back(gUsapPoolEventFD);
        fds_to_ignore.push_back(gUsapPoolEventFD);
      }
  
      pid_t pid = ForkCommon(env, false, fds_to_close, fds_to_ignore);
  
      if (pid == 0) {
        SpecializeCommon(env, uid, gid, gids, runtime_flags, rlimits,
                         capabilities, capabilities,
                         mount_external, se_info, nice_name, false,
                         is_child_zygote == JNI_TRUE, instruction_set, app_data_dir);
      }
      return pid;
  }
  
  static jint com_android_internal_os_Zygote_nativeForkSystemServer(
          JNIEnv* env, jclass, uid_t uid, gid_t gid, jintArray gids,
          jint runtime_flags, jobjectArray rlimits, jlong permitted_capabilities,
          jlong effective_capabilities) {
    std::vector<int> fds_to_close(MakeUsapPipeReadFDVector()),
                     fds_to_ignore(fds_to_close);
  
    fds_to_close.push_back(gUsapPoolSocketFD);
  
    if (gUsapPoolEventFD != -1) {
      fds_to_close.push_back(gUsapPoolEventFD);
      fds_to_ignore.push_back(gUsapPoolEventFD);
    }
  
    pid_t pid = ForkCommon(env, true,
                           fds_to_close,
                           fds_to_ignore);
    if (pid == 0) {
        SpecializeCommon(env, uid, gid, gids, runtime_flags, rlimits,
                         permitted_capabilities, effective_capabilities,
                         MOUNT_EXTERNAL_DEFAULT, nullptr, nullptr, true,
                         false, nullptr, nullptr);
    } else if (pid > 0) {
        // The zygote process checks whether the child process has died or not.
        ALOGI("System server process %d has been created", pid);
        gSystemServerPid = pid;
        // There is a slight window that the system server process has crashed
        // but it went unnoticed because we haven't published its pid yet. So
        // we recheck here just to make sure that all is well.
        int status;
        if (waitpid(pid, &status, WNOHANG) == pid) {
            ALOGE("System server process %d has died. Restarting Zygote!", pid);
            RuntimeAbort(env, __LINE__, "System server process has died. Restarting Zygote!");
        }
  
        if (UsePerAppMemcg()) {
            // Assign system_server to the correct memory cgroup.
            // Not all devices mount memcg so check if it is mounted first
            // to avoid unnecessarily printing errors and denials in the logs.
            if (!SetTaskProfiles(pid, std::vector<std::string>{"SystemMemoryProcess"})) {
                ALOGE("couldn't add process %d into system memcg group", pid);
            }
        }
    }
    return pid;
  }
  
  /**
   * A JNI function that forks an unspecialized app process from the Zygote while
   * ensuring proper file descriptor hygiene.
   *
   * @param env  Managed runtime environment
   * @param read_pipe_fd  The read FD for the USAP reporting pipe.  Manually closed by blastlas
   * in managed code.
   * @param write_pipe_fd  The write FD for the USAP reporting pipe.  Manually closed by the
   * zygote in managed code.
   * @param managed_session_socket_fds  A list of anonymous session sockets that must be ignored by
   * the FD hygiene code and automatically "closed" in the new USAP.
   * @return
   */
  static jint com_android_internal_os_Zygote_nativeForkUsap(JNIEnv* env,
                                                            jclass,
                                                            jint read_pipe_fd,
                                                            jint write_pipe_fd,
                                                            jintArray managed_session_socket_fds) {
    std::vector<int> fds_to_close(MakeUsapPipeReadFDVector()),
                     fds_to_ignore(fds_to_close);
  
    std::vector<int> session_socket_fds =
        ExtractJIntArray(env, "USAP", nullptr, managed_session_socket_fds)
            .value_or(std::vector<int>());
  
    // The USAP Pool Event FD is created during the initialization of the
    // USAP pool and should always be valid here.
  
    fds_to_close.push_back(gZygoteSocketFD);
    fds_to_close.push_back(gUsapPoolEventFD);
    fds_to_close.insert(fds_to_close.end(), session_socket_fds.begin(), session_socket_fds.end());
  
    fds_to_ignore.push_back(gZygoteSocketFD);
    fds_to_ignore.push_back(gUsapPoolSocketFD);
    fds_to_ignore.push_back(gUsapPoolEventFD);
    fds_to_ignore.push_back(read_pipe_fd);
    fds_to_ignore.push_back(write_pipe_fd);
    fds_to_ignore.insert(fds_to_ignore.end(), session_socket_fds.begin(), session_socket_fds.end());
  
    pid_t usap_pid = ForkCommon(env, /* is_system_server= */ false, fds_to_close, fds_to_ignore);
  
    if (usap_pid != 0) {
      ++gUsapPoolCount;
      AddUsapTableEntry(usap_pid, read_pipe_fd);
    }
  
    return usap_pid;
  }
  
  static void com_android_internal_os_Zygote_nativeAllowFileAcrossFork(
          JNIEnv* env, jclass, jstring path) {
      ScopedUtfChars path_native(env, path);
      const char* path_cstr = path_native.c_str();
      if (!path_cstr) {
          RuntimeAbort(env, __LINE__, "path_cstr == nullptr");
      }
      FileDescriptorWhitelist::Get()->Allow(path_cstr);
  }
  
  static void com_android_internal_os_Zygote_nativeInstallSeccompUidGidFilter(
          JNIEnv* env, jclass, jint uidGidMin, jint uidGidMax) {
    if (!gIsSecurityEnforced) {
      ALOGI("seccomp disabled by setenforce 0");
      return;
    }
  
    bool installed = install_setuidgid_seccomp_filter(uidGidMin, uidGidMax);
    if (!installed) {
        RuntimeAbort(env, __LINE__, "Could not install setuid/setgid seccomp filter.");
    }
  }
  
  /**
   * Called from an unspecialized app process to specialize the process for a
   * given application.
   *
   * @param env  Managed runtime environment
   * @param uid  User ID of the new application
   * @param gid  Group ID of the new application
   * @param gids  Extra groups that the process belongs to
   * @param runtime_flags  Flags for changing the behavior of the managed runtime
   * @param rlimits  Resource limits
   * @param mount_external  The mode (read/write/normal) that external storage will be mounted with
   * @param se_info  SELinux policy information
   * @param nice_name  New name for this process
   * @param is_child_zygote  If the process is to become a WebViewZygote
   * @param instruction_set  The instruction set expected/requested by the new application
   * @param app_data_dir  Path to the application's data directory
   */
  static void com_android_internal_os_Zygote_nativeSpecializeAppProcess(
      JNIEnv* env, jclass, jint uid, jint gid, jintArray gids,
      jint runtime_flags, jobjectArray rlimits,
      jint mount_external, jstring se_info, jstring nice_name,
      jboolean is_child_zygote, jstring instruction_set, jstring app_data_dir) {
    jlong capabilities = CalculateCapabilities(env, uid, gid, gids, is_child_zygote);
  
    SpecializeCommon(env, uid, gid, gids, runtime_flags, rlimits,
                     capabilities, capabilities,
                     mount_external, se_info, nice_name, false,
                     is_child_zygote == JNI_TRUE, instruction_set, app_data_dir);
  }
  
  /**
   * A helper method for fetching socket file descriptors that were opened by init from the
   * environment.
   *
   * @param env  Managed runtime environment
   * @param is_primary  If this process is the primary or secondary Zygote; used to compute the name
   * of the environment variable storing the file descriptors.
   */
  static void com_android_internal_os_Zygote_nativeInitNativeState(JNIEnv* env, jclass,
                                                                   jboolean is_primary) {
    /*
     * Obtain file descriptors created by init from the environment.
     */
  
    std::string android_socket_prefix(ANDROID_SOCKET_PREFIX);
    std::string env_var_name = android_socket_prefix + (is_primary ? "zygote" : "zygote_secondary");
    char* env_var_val = getenv(env_var_name.c_str());
  
    if (env_var_val != nullptr) {
      gZygoteSocketFD = atoi(env_var_val);
      ALOGV("Zygote:zygoteSocketFD = %d", gZygoteSocketFD);
    } else {
      ALOGE("Unable to fetch Zygote socket file descriptor");
    }
  
    env_var_name = android_socket_prefix + (is_primary ? "usap_pool_primary" : "usap_pool_secondary");
    env_var_val = getenv(env_var_name.c_str());
  
    if (env_var_val != nullptr) {
      gUsapPoolSocketFD = atoi(env_var_val);
      ALOGV("Zygote:usapPoolSocketFD = %d", gUsapPoolSocketFD);
    } else {
      ALOGE("Unable to fetch USAP pool socket file descriptor");
    }
  
    /*
     * Security Initialization
     */
  
    // security_getenforce is not allowed on app process. Initialize and cache
    // the value before zygote forks.
    gIsSecurityEnforced = security_getenforce();
  
    selinux_android_seapp_context_init();
  
    /*
     * Storage Initialization
     */
  
    UnmountStorageOnInit(env);
  
    /*
     * Performance Initialization
     */
  
    if (!SetTaskProfiles(0, {})) {
      ZygoteFailure(env, "zygote", nullptr, "Zygote SetTaskProfiles failed");
    }
  
    /*
     * ashmem initialization to avoid dlopen overhead
     */
    ashmem_init();
  }
  
  /**
   * @param env  Managed runtime environment
   * @return  A managed array of raw file descriptors for the read ends of the USAP reporting
   * pipes.
   */
  static jintArray com_android_internal_os_Zygote_nativeGetUsapPipeFDs(JNIEnv* env, jclass) {
    std::vector<int> usap_fds = MakeUsapPipeReadFDVector();
  
    jintArray managed_usap_fds = env->NewIntArray(usap_fds.size());
    env->SetIntArrayRegion(managed_usap_fds, 0, usap_fds.size(), usap_fds.data());
  
    return managed_usap_fds;
  }
  
  /**
   * A JNI wrapper around RemoveUsapTableEntry.
   *
   * @param env  Managed runtime environment
   * @param usap_pid  Process ID of the USAP entry to invalidate
   * @return  True if an entry was invalidated; false otherwise.
   */
  static jboolean com_android_internal_os_Zygote_nativeRemoveUsapTableEntry(JNIEnv* env, jclass,
                                                                            jint usap_pid) {
    return RemoveUsapTableEntry(usap_pid);
  }
  
  /**
   * Creates the USAP pool event FD if it doesn't exist and returns it.  This is used by the
   * ZygoteServer poll loop to know when to re-fill the USAP pool.
   *
   * @param env  Managed runtime environment
   * @return A raw event file descriptor used to communicate (from the signal handler) when the
   * Zygote receives a SIGCHLD for a USAP
   */
  static jint com_android_internal_os_Zygote_nativeGetUsapPoolEventFD(JNIEnv* env, jclass) {
    if (gUsapPoolEventFD == -1) {
      if ((gUsapPoolEventFD = eventfd(0, 0)) == -1) {
        ZygoteFailure(env, "zygote", nullptr, StringPrintf("Unable to create eventfd: %s", strerror(errno)));
      }
    }
  
    return gUsapPoolEventFD;
  }
  
  /**
   * @param env  Managed runtime environment
   * @return The number of USAPs currently in the USAP pool
   */
  static jint com_android_internal_os_Zygote_nativeGetUsapPoolCount(JNIEnv* env, jclass) {
    return gUsapPoolCount;
  }
  
  /**
   * Kills all processes currently in the USAP pool and closes their read pipe
   * FDs.
   *
   * @param env  Managed runtime environment
   */
  static void com_android_internal_os_Zygote_nativeEmptyUsapPool(JNIEnv* env, jclass) {
    for (auto& entry : gUsapTable) {
      auto entry_storage = entry.GetValues();
  
      if (entry_storage.has_value()) {
        kill(entry_storage.value().pid, SIGTERM);
  
        // Clean up the USAP table entry here.  This avoids a potential race
        // where a newly created USAP might not be able to find a valid table
        // entry if signal handler (which would normally do the cleanup) doesn't
        // run between now and when the new process is created.
  
        close(entry_storage.value().read_pipe_fd);
  
        // Avoid a second atomic load by invalidating instead of clearing.
        entry.Invalidate();
        --gUsapPoolCount;
      }
    }
  }
  
  static int disable_execute_only(struct dl_phdr_info *info, size_t size, void *data) {
    // Search for any execute-only segments and mark them read+execute.
    for (int i = 0; i < info->dlpi_phnum; i++) {
      if ((info->dlpi_phdr[i].p_type == PT_LOAD) && (info->dlpi_phdr[i].p_flags == PF_X)) {
        mprotect(reinterpret_cast<void*>(info->dlpi_addr + info->dlpi_phdr[i].p_vaddr),
                info->dlpi_phdr[i].p_memsz, PROT_READ | PROT_EXEC);
      }
    }
    // Return non-zero to exit dl_iterate_phdr.
    return 0;
  }
  
  /**
   * @param env  Managed runtime environment
   * @return  True if disable was successful.
   */
  static jboolean com_android_internal_os_Zygote_nativeDisableExecuteOnly(JNIEnv* env, jclass) {
    return dl_iterate_phdr(disable_execute_only, nullptr) == 0;
  }
  
  static void com_android_internal_os_Zygote_nativeBlockSigTerm(JNIEnv* env, jclass) {
    auto fail_fn = std::bind(ZygoteFailure, env, "usap", nullptr, _1);
    BlockSignal(SIGTERM, fail_fn);
  }
  
  static void com_android_internal_os_Zygote_nativeUnblockSigTerm(JNIEnv* env, jclass) {
    auto fail_fn = std::bind(ZygoteFailure, env, "usap", nullptr, _1);
    UnblockSignal(SIGTERM, fail_fn);
  }
  
  static const JNINativeMethod gMethods[] = {
      { "nativeForkAndSpecialize",
        "(II[II[[IILjava/lang/String;Ljava/lang/String;[I[IZLjava/lang/String;Ljava/lang/String;)I",
        (void *) com_android_internal_os_Zygote_nativeForkAndSpecialize },
      { "nativeForkSystemServer", "(II[II[[IJJ)I",
        (void *) com_android_internal_os_Zygote_nativeForkSystemServer },
      { "nativeAllowFileAcrossFork", "(Ljava/lang/String;)V",
        (void *) com_android_internal_os_Zygote_nativeAllowFileAcrossFork },
      { "nativePreApplicationInit", "()V",
        (void *) com_android_internal_os_Zygote_nativePreApplicationInit },
      { "nativeInstallSeccompUidGidFilter", "(II)V",
        (void *) com_android_internal_os_Zygote_nativeInstallSeccompUidGidFilter },
      { "nativeForkUsap", "(II[I)I",
        (void *) com_android_internal_os_Zygote_nativeForkUsap },
      { "nativeSpecializeAppProcess",
        "(II[II[[IILjava/lang/String;Ljava/lang/String;ZLjava/lang/String;Ljava/lang/String;)V",
        (void *) com_android_internal_os_Zygote_nativeSpecializeAppProcess },
      { "nativeInitNativeState", "(Z)V",
        (void *) com_android_internal_os_Zygote_nativeInitNativeState },
      { "nativeGetUsapPipeFDs", "()[I",
        (void *) com_android_internal_os_Zygote_nativeGetUsapPipeFDs },
      { "nativeRemoveUsapTableEntry", "(I)Z",
        (void *) com_android_internal_os_Zygote_nativeRemoveUsapTableEntry },
      { "nativeGetUsapPoolEventFD", "()I",
        (void *) com_android_internal_os_Zygote_nativeGetUsapPoolEventFD },
      { "nativeGetUsapPoolCount", "()I",
        (void *) com_android_internal_os_Zygote_nativeGetUsapPoolCount },
      { "nativeEmptyUsapPool", "()V",
        (void *) com_android_internal_os_Zygote_nativeEmptyUsapPool },
      { "nativeDisableExecuteOnly", "()Z",
        (void *) com_android_internal_os_Zygote_nativeDisableExecuteOnly },
      { "nativeBlockSigTerm", "()V",
        (void* ) com_android_internal_os_Zygote_nativeBlockSigTerm },
      { "nativeUnblockSigTerm", "()V",
        (void* ) com_android_internal_os_Zygote_nativeUnblockSigTerm }
  };
  
  int register_com_android_internal_os_Zygote(JNIEnv* env) {
    gZygoteClass = MakeGlobalRefOrDie(env, FindClassOrDie(env, kZygoteClassName));
    gCallPostForkSystemServerHooks = GetStaticMethodIDOrDie(env, gZygoteClass,
                                                            "callPostForkSystemServerHooks",
                                                            "()V");
    gCallPostForkChildHooks = GetStaticMethodIDOrDie(env, gZygoteClass, "callPostForkChildHooks",
                                                     "(IZZLjava/lang/String;)V");
  
    gZygoteInitClass = MakeGlobalRefOrDie(env, FindClassOrDie(env, kZygoteInitClassName));
    gCreateSystemServerClassLoader = GetStaticMethodIDOrDie(env, gZygoteInitClass,
                                                            "createSystemServerClassLoader",
                                                            "()V");
  
    RegisterMethodsOrDie(env, "com/android/internal/os/Zygote", gMethods, NELEM(gMethods));
  
    return JNI_OK;
  }
  }  // namespace android
  