runtime/native/dalvik_system_Zygote.cc - LeafOS-Project/android_art - Gitiles

 /*
  * 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.
  */

 // 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 <grp.h>
 #include <paths.h>
 #include <signal.h>
 #include <stdlib.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>

 #include "cutils/fs.h"
 #include "cutils/multiuser.h"
 #include "cutils/sched_policy.h"
 #include "debugger.h"
 #include "jni_internal.h"
 #include "JNIHelp.h"
 #include "ScopedLocalRef.h"
 #include "ScopedPrimitiveArray.h"
 #include "ScopedUtfChars.h"
 #include "thread-inl.h"
 #include "utils.h"

 #if defined(HAVE_PRCTL)
 #include <sys/prctl.h>
 #endif

 #include <selinux/android.h>

 #if defined(__linux__)
 #include <sys/personality.h>
 #include <sys/utsname.h>
 #include <sys/capability.h>
 #endif

 namespace art {

 static pid_t gSystemServerPid = 0;

 // Must match values in dalvik.system.Zygote.
 enum MountExternalKind {
   MOUNT_EXTERNAL_NONE = 0,
   MOUNT_EXTERNAL_SINGLEUSER = 1,
   MOUNT_EXTERNAL_MULTIUSER = 2,
   MOUNT_EXTERNAL_MULTIUSER_ALL = 3,
 };

 // 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;

   while ((pid = waitpid(-1, &status, WNOHANG)) > 0) {
      // Log process-death status that we care about.  In general it is
      // not safe to call LOG(...) from a signal handler because of
      // possible reentrancy.  However, we know a priori that the
      // current implementation of LOG() is safe to call from a SIGCHLD
      // handler in the zygote process.  If the LOG() implementation
      // changes its locking strategy or its use of syscalls within the
      // lazy-init critical section, its use here may become unsafe.
     if (WIFEXITED(status)) {
       if (WEXITSTATUS(status)) {
         LOG(INFO) << "Process " << pid << " exited cleanly (" << WEXITSTATUS(status) << ")";
       } else if (false) {
         LOG(INFO) << "Process " << pid << " exited cleanly (" << WEXITSTATUS(status) << ")";
       }
     } else if (WIFSIGNALED(status)) {
       if (WTERMSIG(status) != SIGKILL) {
         LOG(INFO) << "Process " << pid << " terminated by signal (" << WTERMSIG(status) << ")";
       } else if (false) {
         LOG(INFO) << "Process " << pid << " terminated by signal (" << WTERMSIG(status) << ")";
       }
 #ifdef WCOREDUMP
       if (WCOREDUMP(status)) {
         LOG(INFO) << "Process " << pid << " dumped core";
       }
 #endif /* ifdef WCOREDUMP */
     }

     // 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) {
       LOG(ERROR) << "Exit zygote because system server (" << pid << ") has terminated";
       kill(getpid(), SIGKILL);
     }
   }

   if (pid < 0) {
     PLOG(WARNING) << "Zygote SIGCHLD error in waitpid";
   }
 }

 // Configures the SIGCHLD handler 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.
 //
 // This ends up being called repeatedly before each fork(), but there's
 // no real harm in that.
 static void SetSigChldHandler() {
   struct sigaction sa;
   memset(&sa, 0, sizeof(sa));
   sa.sa_handler = SigChldHandler;

   int err = sigaction(SIGCHLD, &sa, NULL);
   if (err < 0) {
     PLOG(WARNING) << "Error setting SIGCHLD handler";
   }
 }

 // Sets the SIGCHLD handler back to default behavior in zygote children.
 static void UnsetSigChldHandler() {
   struct sigaction sa;
   memset(&sa, 0, sizeof(sa));
   sa.sa_handler = SIG_DFL;

   int err = sigaction(SIGCHLD, &sa, NULL);
   if (err < 0) {
     PLOG(WARNING) << "Error unsetting SIGCHLD handler";
   }
 }

 // Calls POSIX setgroups() using the int[] object as an argument.
 // A NULL argument is tolerated.
 static void SetGids(JNIEnv* env, jintArray javaGids) {
   if (javaGids == NULL) {
     return;
   }

   COMPILE_ASSERT(sizeof(gid_t) == sizeof(jint), sizeof_gid_and_jint_are_differerent);
   ScopedIntArrayRO gids(env, javaGids);
   CHECK(gids.get() != NULL);
   int rc = setgroups(gids.size(), reinterpret_cast<const gid_t*>(&gids[0]));
   if (rc == -1) {
     PLOG(FATAL) << "setgroups failed";
   }
 }

 // 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). NULL is
 // treated as an empty array.
 static void SetRLimits(JNIEnv* env, jobjectArray javaRlimits) {
   if (javaRlimits == NULL) {
     return;
   }

   rlimit rlim;
   memset(&rlim, 0, sizeof(rlim));

   for (int i = 0; i < env->GetArrayLength(javaRlimits); ++i) {
     ScopedLocalRef<jobject> javaRlimitObject(env, env->GetObjectArrayElement(javaRlimits, i));
     ScopedIntArrayRO javaRlimit(env, reinterpret_cast<jintArray>(javaRlimitObject.get()));
     if (javaRlimit.size() != 3) {
       LOG(FATAL) << "rlimits array must have a second dimension of size 3";
     }

     rlim.rlim_cur = javaRlimit[1];
     rlim.rlim_max = javaRlimit[2];

     int rc = setrlimit(javaRlimit[0], &rlim);
     if (rc == -1) {
       PLOG(FATAL) << "setrlimit(" << javaRlimit[0] << ", "
                   << "{" << rlim.rlim_cur << ", " << rlim.rlim_max << "}) failed";
     }
   }
 }

 #if defined(HAVE_ANDROID_OS)

 // The debug malloc library needs to know whether it's the zygote or a child.
 extern "C" int gMallocLeakZygoteChild;

 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) {
     PLOG(ERROR) << "prctl(PR_SET_DUMPABLE) failed for pid " << getpid();
   }
   // We don't want core dumps, though, so set the core dump size to 0.
   rlimit rl;
   rl.rlim_cur = 0;
   rl.rlim_max = RLIM_INFINITY;
   if (setrlimit(RLIMIT_CORE, &rl) == -1) {
     PLOG(ERROR) << "setrlimit(RLIMIT_CORE) failed for pid " << getpid();
   }
 }

 static void EnableKeepCapabilities() {
   int rc = prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0);
   if (rc == -1) {
     PLOG(FATAL) << "prctl(PR_SET_KEEPCAPS) failed";
   }
 }

 static void DropCapabilitiesBoundingSet() {
   for (int i = 0; prctl(PR_CAPBSET_READ, i, 0, 0, 0) >= 0; i++) {
     if (i == CAP_NET_RAW) {
       // Don't break /system/bin/ping
       continue;
     }
     int rc = prctl(PR_CAPBSET_DROP, i, 0, 0, 0);
     if (rc == -1) {
       if (errno == EINVAL) {
         PLOG(ERROR) << "prctl(PR_CAPBSET_DROP) failed with EINVAL. Please verify "
                     << "your kernel is compiled with file capabilities support";
       } else {
         PLOG(FATAL) << "prctl(PR_CAPBSET_DROP) failed";
       }
     }
   }
 }

 static void SetCapabilities(int64_t permitted, int64_t effective) {
   __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;

   if (capset(&capheader, &capdata[0]) == -1) {
     PLOG(FATAL) << "capset(" << permitted << ", " << effective << ") failed";
   }
 }

 static void SetSchedulerPolicy() {
   errno = -set_sched_policy(0, SP_DEFAULT);
   if (errno != 0) {
     PLOG(FATAL) << "set_sched_policy(0, SP_DEFAULT) failed";
   }
 }

 #else

 static int gMallocLeakZygoteChild = 0;

 static void EnableDebugger() {}
 static void EnableKeepCapabilities() {}
 static void DropCapabilitiesBoundingSet() {}
 static void SetCapabilities(int64_t, int64_t) {}
 static void SetSchedulerPolicy() {}

 #endif

 static void EnableDebugFeatures(uint32_t debug_flags) {
   // Must match values in dalvik.system.Zygote.
   enum {
     DEBUG_ENABLE_DEBUGGER           = 1,
     DEBUG_ENABLE_CHECKJNI           = 1 << 1,
     DEBUG_ENABLE_ASSERT             = 1 << 2,
     DEBUG_ENABLE_SAFEMODE           = 1 << 3,
     DEBUG_ENABLE_JNI_LOGGING        = 1 << 4,
   };

   if ((debug_flags & DEBUG_ENABLE_CHECKJNI) != 0) {
     Runtime* runtime = Runtime::Current();
     JavaVMExt* vm = runtime->GetJavaVM();
     if (!vm->check_jni) {
       LOG(DEBUG) << "Late-enabling -Xcheck:jni";
       vm->SetCheckJniEnabled(true);
       // There's only one thread running at this point, so only one JNIEnv to fix up.
       Thread::Current()->GetJniEnv()->SetCheckJniEnabled(true);
     } else {
       LOG(DEBUG) << "Not late-enabling -Xcheck:jni (already on)";
     }
     debug_flags &= ~DEBUG_ENABLE_CHECKJNI;
   }

   if ((debug_flags & DEBUG_ENABLE_JNI_LOGGING) != 0) {
     gLogVerbosity.third_party_jni = true;
     debug_flags &= ~DEBUG_ENABLE_JNI_LOGGING;
   }

   Dbg::SetJdwpAllowed((debug_flags & DEBUG_ENABLE_DEBUGGER) != 0);
   if ((debug_flags & DEBUG_ENABLE_DEBUGGER) != 0) {
     EnableDebugger();
   }
   debug_flags &= ~DEBUG_ENABLE_DEBUGGER;

   // These two are for backwards compatibility with Dalvik.
   debug_flags &= ~DEBUG_ENABLE_ASSERT;
   debug_flags &= ~DEBUG_ENABLE_SAFEMODE;

   if (debug_flags != 0) {
     LOG(ERROR) << StringPrintf("Unknown bits set in debug_flags: %#x", debug_flags);
   }
 }

 // Create a private mount namespace and bind mount appropriate emulated
 // storage for the given user.
 static bool MountEmulatedStorage(uid_t uid, jint mount_mode) {
   if (mount_mode == MOUNT_EXTERNAL_NONE) {
     return true;
   }

   // See storage config details at http://source.android.com/tech/storage/
   userid_t user_id = multiuser_get_user_id(uid);

   // Create a second private mount namespace for our process
   if (unshare(CLONE_NEWNS) == -1) {
       PLOG(WARNING) << "Failed to unshare()";
       return false;
   }

   // Create bind mounts to expose external storage
   if (mount_mode == MOUNT_EXTERNAL_MULTIUSER || mount_mode == MOUNT_EXTERNAL_MULTIUSER_ALL) {
     // These paths must already be created by init.rc
     const char* source = getenv("EMULATED_STORAGE_SOURCE");
     const char* target = getenv("EMULATED_STORAGE_TARGET");
     const char* legacy = getenv("EXTERNAL_STORAGE");
     if (source == NULL || target == NULL || legacy == NULL) {
       LOG(WARNING) << "Storage environment undefined; unable to provide external storage";
       return false;
     }

     // Prepare source paths

     // /mnt/shell/emulated/0
     std::string source_user(StringPrintf("%s/%d", source, user_id));
     // /storage/emulated/0
     std::string target_user(StringPrintf("%s/%d", target, user_id));

     if (fs_prepare_dir(source_user.c_str(), 0000, 0, 0) == -1
         || fs_prepare_dir(target_user.c_str(), 0000, 0, 0) == -1) {
       return false;
     }

     if (mount_mode == MOUNT_EXTERNAL_MULTIUSER_ALL) {
       // Mount entire external storage tree for all users
       if (TEMP_FAILURE_RETRY(mount(source, target, NULL, MS_BIND, NULL)) == -1) {
         PLOG(WARNING) << "Failed to mount " << source << " to " << target;
         return false;
       }
     } else {
       // Only mount user-specific external storage
       if (TEMP_FAILURE_RETRY(
               mount(source_user.c_str(), target_user.c_str(), NULL, MS_BIND, NULL)) == -1) {
         PLOG(WARNING) << "Failed to mount " << source_user << " to " << target_user;
         return false;
       }
     }

     if (fs_prepare_dir(legacy, 0000, 0, 0) == -1) {
         return false;
     }

     // Finally, mount user-specific path into place for legacy users
     if (TEMP_FAILURE_RETRY(
             mount(target_user.c_str(), legacy, NULL, MS_BIND | MS_REC, NULL)) == -1) {
       PLOG(WARNING) << "Failed to mount " << target_user << " to " << legacy;
       return false;
     }
   } else {
     LOG(WARNING) << "Mount mode " << mount_mode << " unsupported";
     return false;
   }

   return true;
 }

 #if defined(__linux__)
 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
 }
 #endif

 // Utility routine to fork zygote and specialize the child process.
 static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArray javaGids,
                                      jint debug_flags, jobjectArray javaRlimits,
                                      jlong permittedCapabilities, jlong effectiveCapabilities,
                                      jint mount_external,
                                      jstring java_se_info, jstring java_se_name,
                                      bool is_system_server) {
   Runtime* runtime = Runtime::Current();
   CHECK(runtime->IsZygote()) << "runtime instance not started with -Xzygote";
   if (!runtime->PreZygoteFork()) {
     LOG(FATAL) << "pre-fork heap failed";
   }

   SetSigChldHandler();

   // Grab thread before fork potentially makes Thread::pthread_key_self_ unusable.
   Thread* self = Thread::Current();

   // dvmDumpLoaderStats("zygote");  // TODO: ?
   pid_t pid = fork();

   if (pid == 0) {
     // The child process.
     gMallocLeakZygoteChild = 1;

     // Keep capabilities across UID change, unless we're staying root.
     if (uid != 0) {
       EnableKeepCapabilities();
     }

     DropCapabilitiesBoundingSet();

     if (!MountEmulatedStorage(uid, mount_external)) {
       PLOG(WARNING) << "Failed to mount emulated storage";
       if (errno == ENOTCONN || errno == EROFS) {
         // When device is actively encrypting, we get ENOTCONN here
         // since FUSE was mounted before the framework restarted.
         // When encrypted device is booting, we get EROFS since
         // FUSE hasn't been created yet by init.
         // In either case, continue without external storage.
       } else {
         LOG(FATAL) << "Cannot continue without emulated storage";
       }
     }

     SetGids(env, javaGids);

     SetRLimits(env, javaRlimits);

     int rc = setresgid(gid, gid, gid);
     if (rc == -1) {
       PLOG(FATAL) << "setresgid(" << gid << ") failed";
     }

     rc = setresuid(uid, uid, uid);
     if (rc == -1) {
       PLOG(FATAL) << "setresuid(" << uid << ") failed";
     }

 #if defined(__linux__)
     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) {
             PLOG(WARNING) << "personality(" << new_personality << ") failed";
         }
     }
 #endif

     SetCapabilities(permittedCapabilities, effectiveCapabilities);

     SetSchedulerPolicy();

 #if defined(HAVE_ANDROID_OS)
     {  // NOLINT(whitespace/braces)
       const char* se_info_c_str = NULL;
       UniquePtr<ScopedUtfChars> se_info;
       if (java_se_info != NULL) {
           se_info.reset(new ScopedUtfChars(env, java_se_info));
           se_info_c_str = se_info->c_str();
           CHECK(se_info_c_str != NULL);
       }
       const char* se_name_c_str = NULL;
       UniquePtr<ScopedUtfChars> se_name;
       if (java_se_name != NULL) {
           se_name.reset(new ScopedUtfChars(env, java_se_name));
           se_name_c_str = se_name->c_str();
           CHECK(se_name_c_str != NULL);
       }
       rc = selinux_android_setcontext(uid, is_system_server, se_info_c_str, se_name_c_str);
       if (rc == -1) {
         PLOG(FATAL) << "selinux_android_setcontext(" << uid << ", "
                     << (is_system_server ? "true" : "false") << ", "
                     << "\"" << se_info_c_str << "\", \"" << se_name_c_str << "\") failed";
       }

       // Make it easier to debug audit logs by setting the main thread's name to the
       // nice name rather than "app_process".
       if (se_info_c_str == NULL && is_system_server) {
         se_name_c_str = "system_server";
       }
       if (se_info_c_str != NULL) {
         SetThreadName(se_name_c_str);
       }
     }
 #else
     UNUSED(is_system_server);
     UNUSED(java_se_info);
     UNUSED(java_se_name);
 #endif

     // Our system thread ID, etc, has changed so reset Thread state.
     self->InitAfterFork();

     EnableDebugFeatures(debug_flags);

     UnsetSigChldHandler();
     runtime->DidForkFromZygote();
   } else if (pid > 0) {
     // the parent process
   }
   return pid;
 }

 static jint Zygote_nativeForkAndSpecialize(JNIEnv* env, jclass, jint uid, jint gid, jintArray gids,
                                            jint debug_flags, jobjectArray rlimits,
                                            jint mount_external, jstring se_info, jstring se_name) {
   return ForkAndSpecializeCommon(env, uid, gid, gids, debug_flags, rlimits, 0, 0, mount_external,
                                  se_info, se_name, false);
 }

 static jint Zygote_nativeForkSystemServer(JNIEnv* env, jclass, uid_t uid, gid_t gid, jintArray gids,
                                           jint debug_flags, jobjectArray rlimits,
                                           jlong permittedCapabilities,
                                           jlong effectiveCapabilities) {
   pid_t pid = ForkAndSpecializeCommon(env, uid, gid, gids,
                                       debug_flags, rlimits,
                                       permittedCapabilities, effectiveCapabilities,
                                       MOUNT_EXTERNAL_NONE, NULL, NULL, true);
   if (pid > 0) {
       // The zygote process checks whether the child process has died or not.
       LOG(INFO) << "System server process " << pid << " has been created";
       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) {
           LOG(FATAL) << "System server process " << pid << " has died. Restarting Zygote!";
       }
   }
   return pid;
 }

 static JNINativeMethod gMethods[] = {
   NATIVE_METHOD(Zygote, nativeForkAndSpecialize, "(II[II[[IILjava/lang/String;Ljava/lang/String;)I"),
   NATIVE_METHOD(Zygote, nativeForkSystemServer, "(II[II[[IJJ)I"),
 };

 void register_dalvik_system_Zygote(JNIEnv* env) {
   REGISTER_NATIVE_METHODS("dalvik/system/Zygote");
 }

 }  // namespace art
	/*
	* 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.
	*/

	// 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 <grp.h>
	#include <paths.h>
	#include <signal.h>
	#include <stdlib.h>
	#include <sys/types.h>
	#include <sys/wait.h>
	#include <unistd.h>

	#include "cutils/fs.h"
	#include "cutils/multiuser.h"
	#include "cutils/sched_policy.h"
	#include "debugger.h"
	#include "jni_internal.h"
	#include "JNIHelp.h"
	#include "ScopedLocalRef.h"
	#include "ScopedPrimitiveArray.h"
	#include "ScopedUtfChars.h"
	#include "thread-inl.h"
	#include "utils.h"

	#if defined(HAVE_PRCTL)
	#include <sys/prctl.h>
	#endif

	#include <selinux/android.h>

	#if defined(__linux__)
	#include <sys/personality.h>
	#include <sys/utsname.h>
	#include <sys/capability.h>
	#endif

	namespace art {

	static pid_t gSystemServerPid = 0;

	// Must match values in dalvik.system.Zygote.
	enum MountExternalKind {
	MOUNT_EXTERNAL_NONE = 0,
	MOUNT_EXTERNAL_SINGLEUSER = 1,
	MOUNT_EXTERNAL_MULTIUSER = 2,
	MOUNT_EXTERNAL_MULTIUSER_ALL = 3,
	};

	// 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;

	while ((pid = waitpid(-1, &status, WNOHANG)) > 0) {
	// Log process-death status that we care about. In general it is
	// not safe to call LOG(...) from a signal handler because of
	// possible reentrancy. However, we know a priori that the
	// current implementation of LOG() is safe to call from a SIGCHLD
	// handler in the zygote process. If the LOG() implementation
	// changes its locking strategy or its use of syscalls within the
	// lazy-init critical section, its use here may become unsafe.
	if (WIFEXITED(status)) {
	if (WEXITSTATUS(status)) {
	LOG(INFO) << "Process " << pid << " exited cleanly (" << WEXITSTATUS(status) << ")";
	} else if (false) {
	LOG(INFO) << "Process " << pid << " exited cleanly (" << WEXITSTATUS(status) << ")";
	}
	} else if (WIFSIGNALED(status)) {
	if (WTERMSIG(status) != SIGKILL) {
	LOG(INFO) << "Process " << pid << " terminated by signal (" << WTERMSIG(status) << ")";
	} else if (false) {
	LOG(INFO) << "Process " << pid << " terminated by signal (" << WTERMSIG(status) << ")";
	}
	#ifdef WCOREDUMP
	if (WCOREDUMP(status)) {
	LOG(INFO) << "Process " << pid << " dumped core";
	}
	#endif /* ifdef WCOREDUMP */
	}

	// 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) {
	LOG(ERROR) << "Exit zygote because system server (" << pid << ") has terminated";
	kill(getpid(), SIGKILL);
	}
	}

	if (pid < 0) {
	PLOG(WARNING) << "Zygote SIGCHLD error in waitpid";
	}
	}

	// Configures the SIGCHLD handler 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.
	//
	// This ends up being called repeatedly before each fork(), but there's
	// no real harm in that.
	static void SetSigChldHandler() {
	struct sigaction sa;
	memset(&sa, 0, sizeof(sa));
	sa.sa_handler = SigChldHandler;

	int err = sigaction(SIGCHLD, &sa, NULL);
	if (err < 0) {
	PLOG(WARNING) << "Error setting SIGCHLD handler";
	}
	}

	// Sets the SIGCHLD handler back to default behavior in zygote children.
	static void UnsetSigChldHandler() {
	struct sigaction sa;
	memset(&sa, 0, sizeof(sa));
	sa.sa_handler = SIG_DFL;

	int err = sigaction(SIGCHLD, &sa, NULL);
	if (err < 0) {
	PLOG(WARNING) << "Error unsetting SIGCHLD handler";
	}
	}

	// Calls POSIX setgroups() using the int[] object as an argument.
	// A NULL argument is tolerated.
	static void SetGids(JNIEnv* env, jintArray javaGids) {
	if (javaGids == NULL) {
	return;
	}

	COMPILE_ASSERT(sizeof(gid_t) == sizeof(jint), sizeof_gid_and_jint_are_differerent);
	ScopedIntArrayRO gids(env, javaGids);
	CHECK(gids.get() != NULL);
	int rc = setgroups(gids.size(), reinterpret_cast<const gid_t*>(&gids[0]));
	if (rc == -1) {
	PLOG(FATAL) << "setgroups failed";
	}
	}

	// 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). NULL is
	// treated as an empty array.
	static void SetRLimits(JNIEnv* env, jobjectArray javaRlimits) {
	if (javaRlimits == NULL) {
	return;
	}

	rlimit rlim;
	memset(&rlim, 0, sizeof(rlim));

	for (int i = 0; i < env->GetArrayLength(javaRlimits); ++i) {
	ScopedLocalRef<jobject> javaRlimitObject(env, env->GetObjectArrayElement(javaRlimits, i));
	ScopedIntArrayRO javaRlimit(env, reinterpret_cast<jintArray>(javaRlimitObject.get()));
	if (javaRlimit.size() != 3) {
	LOG(FATAL) << "rlimits array must have a second dimension of size 3";
	}

	rlim.rlim_cur = javaRlimit[1];
	rlim.rlim_max = javaRlimit[2];

	int rc = setrlimit(javaRlimit[0], &rlim);
	if (rc == -1) {
	PLOG(FATAL) << "setrlimit(" << javaRlimit[0] << ", "
	<< "{" << rlim.rlim_cur << ", " << rlim.rlim_max << "}) failed";
	}
	}
	}

	#if defined(HAVE_ANDROID_OS)

	// The debug malloc library needs to know whether it's the zygote or a child.
	extern "C" int gMallocLeakZygoteChild;

	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) {
	PLOG(ERROR) << "prctl(PR_SET_DUMPABLE) failed for pid " << getpid();
	}
	// We don't want core dumps, though, so set the core dump size to 0.
	rlimit rl;
	rl.rlim_cur = 0;
	rl.rlim_max = RLIM_INFINITY;
	if (setrlimit(RLIMIT_CORE, &rl) == -1) {
	PLOG(ERROR) << "setrlimit(RLIMIT_CORE) failed for pid " << getpid();
	}
	}

	static void EnableKeepCapabilities() {
	int rc = prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0);
	if (rc == -1) {
	PLOG(FATAL) << "prctl(PR_SET_KEEPCAPS) failed";
	}
	}

	static void DropCapabilitiesBoundingSet() {
	for (int i = 0; prctl(PR_CAPBSET_READ, i, 0, 0, 0) >= 0; i++) {
	if (i == CAP_NET_RAW) {
	// Don't break /system/bin/ping
	continue;
	}
	int rc = prctl(PR_CAPBSET_DROP, i, 0, 0, 0);
	if (rc == -1) {
	if (errno == EINVAL) {
	PLOG(ERROR) << "prctl(PR_CAPBSET_DROP) failed with EINVAL. Please verify "
	<< "your kernel is compiled with file capabilities support";
	} else {
	PLOG(FATAL) << "prctl(PR_CAPBSET_DROP) failed";
	}
	}
	}
	}

	static void SetCapabilities(int64_t permitted, int64_t effective) {
	__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;

	if (capset(&capheader, &capdata[0]) == -1) {
	PLOG(FATAL) << "capset(" << permitted << ", " << effective << ") failed";
	}
	}

	static void SetSchedulerPolicy() {
	errno = -set_sched_policy(0, SP_DEFAULT);
	if (errno != 0) {
	PLOG(FATAL) << "set_sched_policy(0, SP_DEFAULT) failed";
	}
	}

	#else

	static int gMallocLeakZygoteChild = 0;

	static void EnableDebugger() {}
	static void EnableKeepCapabilities() {}
	static void DropCapabilitiesBoundingSet() {}
	static void SetCapabilities(int64_t, int64_t) {}
	static void SetSchedulerPolicy() {}

	#endif

	static void EnableDebugFeatures(uint32_t debug_flags) {
	// Must match values in dalvik.system.Zygote.
	enum {
	DEBUG_ENABLE_DEBUGGER = 1,
	DEBUG_ENABLE_CHECKJNI = 1 << 1,
	DEBUG_ENABLE_ASSERT = 1 << 2,
	DEBUG_ENABLE_SAFEMODE = 1 << 3,
	DEBUG_ENABLE_JNI_LOGGING = 1 << 4,
	};

	if ((debug_flags & DEBUG_ENABLE_CHECKJNI) != 0) {
	Runtime* runtime = Runtime::Current();
	JavaVMExt* vm = runtime->GetJavaVM();
	if (!vm->check_jni) {
	LOG(DEBUG) << "Late-enabling -Xcheck:jni";
	vm->SetCheckJniEnabled(true);
	// There's only one thread running at this point, so only one JNIEnv to fix up.
	Thread::Current()->GetJniEnv()->SetCheckJniEnabled(true);
	} else {
	LOG(DEBUG) << "Not late-enabling -Xcheck:jni (already on)";
	}
	debug_flags &= ~DEBUG_ENABLE_CHECKJNI;
	}

	if ((debug_flags & DEBUG_ENABLE_JNI_LOGGING) != 0) {
	gLogVerbosity.third_party_jni = true;
	debug_flags &= ~DEBUG_ENABLE_JNI_LOGGING;
	}

	Dbg::SetJdwpAllowed((debug_flags & DEBUG_ENABLE_DEBUGGER) != 0);
	if ((debug_flags & DEBUG_ENABLE_DEBUGGER) != 0) {
	EnableDebugger();
	}
	debug_flags &= ~DEBUG_ENABLE_DEBUGGER;

	// These two are for backwards compatibility with Dalvik.
	debug_flags &= ~DEBUG_ENABLE_ASSERT;
	debug_flags &= ~DEBUG_ENABLE_SAFEMODE;

	if (debug_flags != 0) {
	LOG(ERROR) << StringPrintf("Unknown bits set in debug_flags: %#x", debug_flags);
	}
	}

	// Create a private mount namespace and bind mount appropriate emulated
	// storage for the given user.
	static bool MountEmulatedStorage(uid_t uid, jint mount_mode) {
	if (mount_mode == MOUNT_EXTERNAL_NONE) {
	return true;
	}

	// See storage config details at http://source.android.com/tech/storage/
	userid_t user_id = multiuser_get_user_id(uid);

	// Create a second private mount namespace for our process
	if (unshare(CLONE_NEWNS) == -1) {
	PLOG(WARNING) << "Failed to unshare()";
	return false;
	}

	// Create bind mounts to expose external storage
	if (mount_mode == MOUNT_EXTERNAL_MULTIUSER \|\| mount_mode == MOUNT_EXTERNAL_MULTIUSER_ALL) {
	// These paths must already be created by init.rc
	const char* source = getenv("EMULATED_STORAGE_SOURCE");
	const char* target = getenv("EMULATED_STORAGE_TARGET");
	const char* legacy = getenv("EXTERNAL_STORAGE");
	if (source == NULL \|\| target == NULL \|\| legacy == NULL) {
	LOG(WARNING) << "Storage environment undefined; unable to provide external storage";
	return false;
	}

	// Prepare source paths

	// /mnt/shell/emulated/0
	std::string source_user(StringPrintf("%s/%d", source, user_id));
	// /storage/emulated/0
	std::string target_user(StringPrintf("%s/%d", target, user_id));

	if (fs_prepare_dir(source_user.c_str(), 0000, 0, 0) == -1
	\|\| fs_prepare_dir(target_user.c_str(), 0000, 0, 0) == -1) {
	return false;
	}

	if (mount_mode == MOUNT_EXTERNAL_MULTIUSER_ALL) {
	// Mount entire external storage tree for all users
	if (TEMP_FAILURE_RETRY(mount(source, target, NULL, MS_BIND, NULL)) == -1) {
	PLOG(WARNING) << "Failed to mount " << source << " to " << target;
	return false;
	}
	} else {
	// Only mount user-specific external storage
	if (TEMP_FAILURE_RETRY(
	mount(source_user.c_str(), target_user.c_str(), NULL, MS_BIND, NULL)) == -1) {
	PLOG(WARNING) << "Failed to mount " << source_user << " to " << target_user;
	return false;
	}
	}

	if (fs_prepare_dir(legacy, 0000, 0, 0) == -1) {
	return false;
	}

	// Finally, mount user-specific path into place for legacy users
	if (TEMP_FAILURE_RETRY(
	mount(target_user.c_str(), legacy, NULL, MS_BIND \| MS_REC, NULL)) == -1) {
	PLOG(WARNING) << "Failed to mount " << target_user << " to " << legacy;
	return false;
	}
	} else {
	LOG(WARNING) << "Mount mode " << mount_mode << " unsupported";
	return false;
	}

	return true;
	}

	#if defined(__linux__)
	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
	}
	#endif

	// Utility routine to fork zygote and specialize the child process.
	static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArray javaGids,
	jint debug_flags, jobjectArray javaRlimits,
	jlong permittedCapabilities, jlong effectiveCapabilities,
	jint mount_external,
	jstring java_se_info, jstring java_se_name,
	bool is_system_server) {
	Runtime* runtime = Runtime::Current();
	CHECK(runtime->IsZygote()) << "runtime instance not started with -Xzygote";
	if (!runtime->PreZygoteFork()) {
	LOG(FATAL) << "pre-fork heap failed";
	}

	SetSigChldHandler();

	// Grab thread before fork potentially makes Thread::pthread_key_self_ unusable.
	Thread* self = Thread::Current();

	// dvmDumpLoaderStats("zygote"); // TODO: ?
	pid_t pid = fork();

	if (pid == 0) {
	// The child process.
	gMallocLeakZygoteChild = 1;

	// Keep capabilities across UID change, unless we're staying root.
	if (uid != 0) {
	EnableKeepCapabilities();
	}

	DropCapabilitiesBoundingSet();

	if (!MountEmulatedStorage(uid, mount_external)) {
	PLOG(WARNING) << "Failed to mount emulated storage";
	if (errno == ENOTCONN \|\| errno == EROFS) {
	// When device is actively encrypting, we get ENOTCONN here
	// since FUSE was mounted before the framework restarted.
	// When encrypted device is booting, we get EROFS since
	// FUSE hasn't been created yet by init.
	// In either case, continue without external storage.
	} else {
	LOG(FATAL) << "Cannot continue without emulated storage";
	}
	}

	SetGids(env, javaGids);

	SetRLimits(env, javaRlimits);

	int rc = setresgid(gid, gid, gid);
	if (rc == -1) {
	PLOG(FATAL) << "setresgid(" << gid << ") failed";
	}

	rc = setresuid(uid, uid, uid);
	if (rc == -1) {
	PLOG(FATAL) << "setresuid(" << uid << ") failed";
	}

	#if defined(__linux__)
	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) {
	PLOG(WARNING) << "personality(" << new_personality << ") failed";
	}
	}
	#endif

	SetCapabilities(permittedCapabilities, effectiveCapabilities);

	SetSchedulerPolicy();

	#if defined(HAVE_ANDROID_OS)
	{ // NOLINT(whitespace/braces)
	const char* se_info_c_str = NULL;
	UniquePtr<ScopedUtfChars> se_info;
	if (java_se_info != NULL) {
	se_info.reset(new ScopedUtfChars(env, java_se_info));
	se_info_c_str = se_info->c_str();
	CHECK(se_info_c_str != NULL);
	}
	const char* se_name_c_str = NULL;
	UniquePtr<ScopedUtfChars> se_name;
	if (java_se_name != NULL) {
	se_name.reset(new ScopedUtfChars(env, java_se_name));
	se_name_c_str = se_name->c_str();
	CHECK(se_name_c_str != NULL);
	}
	rc = selinux_android_setcontext(uid, is_system_server, se_info_c_str, se_name_c_str);
	if (rc == -1) {
	PLOG(FATAL) << "selinux_android_setcontext(" << uid << ", "
	<< (is_system_server ? "true" : "false") << ", "
	<< "\"" << se_info_c_str << "\", \"" << se_name_c_str << "\") failed";
	}

	// Make it easier to debug audit logs by setting the main thread's name to the
	// nice name rather than "app_process".
	if (se_info_c_str == NULL && is_system_server) {
	se_name_c_str = "system_server";
	}
	if (se_info_c_str != NULL) {
	SetThreadName(se_name_c_str);
	}
	}
	#else
	UNUSED(is_system_server);
	UNUSED(java_se_info);
	UNUSED(java_se_name);
	#endif

	// Our system thread ID, etc, has changed so reset Thread state.
	self->InitAfterFork();

	EnableDebugFeatures(debug_flags);

	UnsetSigChldHandler();
	runtime->DidForkFromZygote();
	} else if (pid > 0) {
	// the parent process
	}
	return pid;
	}

	static jint Zygote_nativeForkAndSpecialize(JNIEnv* env, jclass, jint uid, jint gid, jintArray gids,
	jint debug_flags, jobjectArray rlimits,
	jint mount_external, jstring se_info, jstring se_name) {
	return ForkAndSpecializeCommon(env, uid, gid, gids, debug_flags, rlimits, 0, 0, mount_external,
	se_info, se_name, false);
	}

	static jint Zygote_nativeForkSystemServer(JNIEnv* env, jclass, uid_t uid, gid_t gid, jintArray gids,
	jint debug_flags, jobjectArray rlimits,
	jlong permittedCapabilities,
	jlong effectiveCapabilities) {
	pid_t pid = ForkAndSpecializeCommon(env, uid, gid, gids,
	debug_flags, rlimits,
	permittedCapabilities, effectiveCapabilities,
	MOUNT_EXTERNAL_NONE, NULL, NULL, true);
	if (pid > 0) {
	// The zygote process checks whether the child process has died or not.
	LOG(INFO) << "System server process " << pid << " has been created";
	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) {
	LOG(FATAL) << "System server process " << pid << " has died. Restarting Zygote!";
	}
	}
	return pid;
	}

	static JNINativeMethod gMethods[] = {
	NATIVE_METHOD(Zygote, nativeForkAndSpecialize, "(II[II[[IILjava/lang/String;Ljava/lang/String;)I"),
	NATIVE_METHOD(Zygote, nativeForkSystemServer, "(II[II[[IJJ)I"),
	};

	void register_dalvik_system_Zygote(JNIEnv* env) {
	REGISTER_NATIVE_METHODS("dalvik/system/Zygote");
	}

	} // namespace art