runtime/native/dalvik_system_ZygoteHooks.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.
  */

 #include "dalvik_system_ZygoteHooks.h"

 #include <stdlib.h>

 #include <android-base/logging.h>
 #include <android-base/stringprintf.h>

 #include "arch/instruction_set.h"
 #include "art_method-inl.h"
 #include "base/macros.h"
 #include "base/mutex.h"
 #include "base/runtime_debug.h"
 #include "debugger.h"
 #include "hidden_api.h"
 #include "jit/jit.h"
 #include "jni/java_vm_ext.h"
 #include "jni/jni_internal.h"
 #include "native_util.h"
 #include "nativehelper/jni_macros.h"
 #include "nativehelper/scoped_utf_chars.h"
 #include "non_debuggable_classes.h"
 #include "oat_file.h"
 #include "oat_file_manager.h"
 #include "scoped_thread_state_change-inl.h"
 #include "stack.h"
 #include "thread-current-inl.h"
 #include "thread_list.h"
 #include "trace.h"

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

 #include <sys/resource.h>

 namespace art {

 // Set to true to always determine the non-debuggable classes even if we would not allow a debugger
 // to actually attach.
 static bool kAlwaysCollectNonDebuggableClasses =
     RegisterRuntimeDebugFlag(&kAlwaysCollectNonDebuggableClasses);

 using android::base::StringPrintf;

 static void EnableDebugger() {
 #if defined(__linux__)
   // 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();
   }

   // Even if Yama is on a non-privileged native debugger should
   // be able to attach to the debuggable app.
   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) {
       PLOG(ERROR) << "prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY) failed for pid " << getpid();
     }
   }
 #endif
   // 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();
   }
 }

 class ClassSet {
  public:
   // The number of classes we reasonably expect to have to look at. Realistically the number is more
   // ~10 but there is little harm in having some extra.
   static constexpr int kClassSetCapacity = 100;

   explicit ClassSet(Thread* const self) : self_(self) {
     self_->GetJniEnv()->PushFrame(kClassSetCapacity);
   }

   ~ClassSet() {
     self_->GetJniEnv()->PopFrame();
   }

   void AddClass(ObjPtr<mirror::Class> klass) REQUIRES(Locks::mutator_lock_) {
     class_set_.insert(self_->GetJniEnv()->AddLocalReference<jclass>(klass));
   }

   const std::unordered_set<jclass>& GetClasses() const {
     return class_set_;
   }

  private:
   Thread* const self_;
   std::unordered_set<jclass> class_set_;
 };

 static void DoCollectNonDebuggableCallback(Thread* thread, void* data)
     REQUIRES(Locks::mutator_lock_) {
   class NonDebuggableStacksVisitor : public StackVisitor {
    public:
     NonDebuggableStacksVisitor(Thread* t, ClassSet* class_set)
         : StackVisitor(t, nullptr, StackVisitor::StackWalkKind::kIncludeInlinedFrames),
           class_set_(class_set) {}

     ~NonDebuggableStacksVisitor() override {}

     bool VisitFrame() override REQUIRES(Locks::mutator_lock_) {
       if (GetMethod()->IsRuntimeMethod()) {
         return true;
       }
       class_set_->AddClass(GetMethod()->GetDeclaringClass());
       if (kIsDebugBuild) {
         LOG(INFO) << GetMethod()->GetDeclaringClass()->PrettyClass()
                   << " might not be fully debuggable/deoptimizable due to "
                   << GetMethod()->PrettyMethod() << " appearing on the stack during zygote fork.";
       }
       return true;
     }

    private:
     ClassSet* class_set_;
   };
   NonDebuggableStacksVisitor visitor(thread, reinterpret_cast<ClassSet*>(data));
   visitor.WalkStack();
 }

 static void CollectNonDebuggableClasses() REQUIRES(!Locks::mutator_lock_) {
   Runtime* const runtime = Runtime::Current();
   Thread* const self = Thread::Current();
   // Get the mutator lock.
   ScopedObjectAccess soa(self);
   ClassSet classes(self);
   {
     // Drop the shared mutator lock.
     ScopedThreadSuspension sts(self, art::ThreadState::kNative);
     // Get exclusive mutator lock with suspend all.
     ScopedSuspendAll suspend("Checking stacks for non-obsoletable methods!",
                              /*long_suspend=*/false);
     MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
     runtime->GetThreadList()->ForEach(DoCollectNonDebuggableCallback, &classes);
   }
   for (jclass klass : classes.GetClasses()) {
     NonDebuggableClasses::AddNonDebuggableClass(klass);
   }
 }

 // Must match values in com.android.internal.os.Zygote.
 enum {
   DEBUG_ENABLE_JDWP                  = 1,
   DEBUG_ENABLE_CHECKJNI              = 1 << 1,
   DEBUG_ENABLE_ASSERT                = 1 << 2,
   DEBUG_ENABLE_SAFEMODE              = 1 << 3,
   DEBUG_ENABLE_JNI_LOGGING           = 1 << 4,
   DEBUG_GENERATE_DEBUG_INFO          = 1 << 5,
   DEBUG_ALWAYS_JIT                   = 1 << 6,
   DEBUG_NATIVE_DEBUGGABLE            = 1 << 7,
   DEBUG_JAVA_DEBUGGABLE              = 1 << 8,
   DISABLE_VERIFIER                   = 1 << 9,
   ONLY_USE_SYSTEM_OAT_FILES          = 1 << 10,
   DEBUG_GENERATE_MINI_DEBUG_INFO     = 1 << 11,
   HIDDEN_API_ENFORCEMENT_POLICY_MASK = (1 << 12)
                                      | (1 << 13),
   PROFILE_SYSTEM_SERVER              = 1 << 14,

   // bits to shift (flags & HIDDEN_API_ENFORCEMENT_POLICY_MASK) by to get a value
   // corresponding to hiddenapi::EnforcementPolicy
   API_ENFORCEMENT_POLICY_SHIFT = CTZ(HIDDEN_API_ENFORCEMENT_POLICY_MASK),
 };

 static uint32_t EnableDebugFeatures(uint32_t runtime_flags) {
   Runtime* const runtime = Runtime::Current();
   if ((runtime_flags & DEBUG_ENABLE_CHECKJNI) != 0) {
     JavaVMExt* vm = runtime->GetJavaVM();
     if (!vm->IsCheckJniEnabled()) {
       LOG(INFO) << "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(INFO) << "Not late-enabling -Xcheck:jni (already on)";
     }
     runtime_flags &= ~DEBUG_ENABLE_CHECKJNI;
   }

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

   Dbg::SetJdwpAllowed((runtime_flags & DEBUG_ENABLE_JDWP) != 0);
   if ((runtime_flags & DEBUG_ENABLE_JDWP) != 0) {
     EnableDebugger();
   }
   runtime_flags &= ~DEBUG_ENABLE_JDWP;

   const bool safe_mode = (runtime_flags & DEBUG_ENABLE_SAFEMODE) != 0;
   if (safe_mode) {
     // Only quicken oat files.
     runtime->AddCompilerOption("--compiler-filter=quicken");
     runtime->SetSafeMode(true);
     runtime_flags &= ~DEBUG_ENABLE_SAFEMODE;
   }

   // This is for backwards compatibility with Dalvik.
   runtime_flags &= ~DEBUG_ENABLE_ASSERT;

   if ((runtime_flags & DEBUG_ALWAYS_JIT) != 0) {
     jit::JitOptions* jit_options = runtime->GetJITOptions();
     CHECK(jit_options != nullptr);
     Runtime::Current()->DoAndMaybeSwitchInterpreter([=]() {
         jit_options->SetJitAtFirstUse();
     });
     runtime_flags &= ~DEBUG_ALWAYS_JIT;
   }

   bool needs_non_debuggable_classes = false;
   if ((runtime_flags & DEBUG_JAVA_DEBUGGABLE) != 0) {
     runtime->AddCompilerOption("--debuggable");
     runtime_flags |= DEBUG_GENERATE_MINI_DEBUG_INFO;
     runtime->SetJavaDebuggable(true);
     // Deoptimize the boot image as it may be non-debuggable.
     runtime->DeoptimizeBootImage();
     runtime_flags &= ~DEBUG_JAVA_DEBUGGABLE;
     needs_non_debuggable_classes = true;
   }
   if (needs_non_debuggable_classes || kAlwaysCollectNonDebuggableClasses) {
     CollectNonDebuggableClasses();
   }

   if ((runtime_flags & DEBUG_NATIVE_DEBUGGABLE) != 0) {
     runtime->AddCompilerOption("--debuggable");
     runtime_flags |= DEBUG_GENERATE_DEBUG_INFO;
     runtime->SetNativeDebuggable(true);
     runtime_flags &= ~DEBUG_NATIVE_DEBUGGABLE;
   }

   if ((runtime_flags & DEBUG_GENERATE_MINI_DEBUG_INFO) != 0) {
     // Generate native minimal debug information to allow backtracing.
     runtime->AddCompilerOption("--generate-mini-debug-info");
     runtime_flags &= ~DEBUG_GENERATE_MINI_DEBUG_INFO;
   }

   if ((runtime_flags & DEBUG_GENERATE_DEBUG_INFO) != 0) {
     // Generate all native debug information we can (e.g. line-numbers).
     runtime->AddCompilerOption("--generate-debug-info");
     runtime_flags &= ~DEBUG_GENERATE_DEBUG_INFO;
   }

   return runtime_flags;
 }

 static jlong ZygoteHooks_nativePreFork(JNIEnv* env, jclass) {
   Runtime* runtime = Runtime::Current();
   CHECK(runtime->IsZygote()) << "runtime instance not started with -Xzygote";

   runtime->PreZygoteFork();

   if (Trace::GetMethodTracingMode() != TracingMode::kTracingInactive) {
     // Tracing active, pause it.
     Trace::Pause();
   }

   // Grab thread before fork potentially makes Thread::pthread_key_self_ unusable.
   return reinterpret_cast<jlong>(ThreadForEnv(env));
 }

 static void ZygoteHooks_nativePostForkSystemServer(JNIEnv* env ATTRIBUTE_UNUSED,
                                                    jclass klass ATTRIBUTE_UNUSED) {
   // This JIT code cache for system server is created whilst the runtime is still single threaded.
   // System server has a window where it can create executable pages for this purpose, but this is
   // turned off after this hook. Consequently, the only JIT mode supported is the dual-view JIT
   // where one mapping is R->RW and the other is RX. Single view requires RX->RWX->RX.
   Runtime::Current()->CreateJitCodeCache(/*rwx_memory_allowed=*/false);
 }

 static void ZygoteHooks_nativePostForkChild(JNIEnv* env,
                                             jclass,
                                             jlong token,
                                             jint runtime_flags,
                                             jboolean is_system_server,
                                             jboolean is_zygote,
                                             jstring instruction_set) {
   DCHECK(!(is_system_server && is_zygote));

   Thread* thread = reinterpret_cast<Thread*>(token);
   // Our system thread ID, etc, has changed so reset Thread state.
   thread->InitAfterFork();
   runtime_flags = EnableDebugFeatures(runtime_flags);
   hiddenapi::EnforcementPolicy api_enforcement_policy = hiddenapi::EnforcementPolicy::kNoChecks;
   bool dedupe_hidden_api_warnings = true;

   if ((runtime_flags & DISABLE_VERIFIER) != 0) {
     Runtime::Current()->DisableVerifier();
     runtime_flags &= ~DISABLE_VERIFIER;
   }

   if ((runtime_flags & ONLY_USE_SYSTEM_OAT_FILES) != 0) {
     Runtime::Current()->GetOatFileManager().SetOnlyUseSystemOatFiles();
     runtime_flags &= ~ONLY_USE_SYSTEM_OAT_FILES;
   }

   api_enforcement_policy = hiddenapi::EnforcementPolicyFromInt(
       (runtime_flags & HIDDEN_API_ENFORCEMENT_POLICY_MASK) >> API_ENFORCEMENT_POLICY_SHIFT);
   runtime_flags &= ~HIDDEN_API_ENFORCEMENT_POLICY_MASK;

   bool profile_system_server = (runtime_flags & PROFILE_SYSTEM_SERVER) == PROFILE_SYSTEM_SERVER;
   runtime_flags &= ~PROFILE_SYSTEM_SERVER;

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

   Runtime::Current()->GetHeap()->PostForkChildAction(thread);

   // Update tracing.
   if (Trace::GetMethodTracingMode() != TracingMode::kTracingInactive) {
     Trace::TraceOutputMode output_mode = Trace::GetOutputMode();
     Trace::TraceMode trace_mode = Trace::GetMode();
     size_t buffer_size = Trace::GetBufferSize();

     // Just drop it.
     Trace::Abort();

     // Only restart if it was streaming mode.
     // TODO: Expose buffer size, so we can also do file mode.
     if (output_mode == Trace::TraceOutputMode::kStreaming) {
       static constexpr size_t kMaxProcessNameLength = 100;
       char name_buf[kMaxProcessNameLength] = {};
       int rc = pthread_getname_np(pthread_self(), name_buf, kMaxProcessNameLength);
       std::string proc_name;

       if (rc == 0) {
           // On success use the pthread name.
           proc_name = name_buf;
       }

       if (proc_name.empty() || proc_name == "zygote" || proc_name == "zygote64") {
         // Either no process name, or the name hasn't been changed, yet. Just use pid.
         pid_t pid = getpid();
         proc_name = StringPrintf("%u", static_cast<uint32_t>(pid));
       }

       std::string trace_file = StringPrintf("/data/misc/trace/%s.trace.bin", proc_name.c_str());
       Trace::Start(trace_file.c_str(),
                    buffer_size,
                    0,   // TODO: Expose flags.
                    output_mode,
                    trace_mode,
                    0);  // TODO: Expose interval.
       if (thread->IsExceptionPending()) {
         ScopedObjectAccess soa(env);
         thread->ClearException();
       }
     }
   }

   bool do_hidden_api_checks = api_enforcement_policy != hiddenapi::EnforcementPolicy::kNoChecks;
   DCHECK(!(is_system_server && do_hidden_api_checks))
       << "SystemServer should be forked with EnforcementPolicy::kDisable";
   DCHECK(!(is_zygote && do_hidden_api_checks))
       << "Child zygote processes should be forked with EnforcementPolicy::kDisable";
   Runtime::Current()->SetHiddenApiEnforcementPolicy(api_enforcement_policy);
   Runtime::Current()->SetDedupeHiddenApiWarnings(dedupe_hidden_api_warnings);
   if (api_enforcement_policy != hiddenapi::EnforcementPolicy::kNoChecks &&
       Runtime::Current()->GetHiddenApiEventLogSampleRate() != 0) {
     // Hidden API checks are enabled, and we are sampling access for the event log. Initialize the
     // random seed, to ensure the sampling is actually random. We do this post-fork, as doing it
     // pre-fork would result in the same sequence for every forked process.
     std::srand(static_cast<uint32_t>(NanoTime()));
   }

   // Clear the hidden API warning flag, in case it was set.
   Runtime::Current()->SetPendingHiddenApiWarning(false);

   if (is_zygote) {
     // If creating a child-zygote, do not call into the runtime's post-fork logic.
     // Doing so would spin up threads for Binder and JDWP. Instead, the Java side
     // of the child process will call a static main in a class specified by the parent.
     return;
   }

   if (instruction_set != nullptr && !is_system_server) {
     ScopedUtfChars isa_string(env, instruction_set);
     InstructionSet isa = GetInstructionSetFromString(isa_string.c_str());
     Runtime::NativeBridgeAction action = Runtime::NativeBridgeAction::kUnload;
     if (isa != InstructionSet::kNone && isa != kRuntimeISA) {
       action = Runtime::NativeBridgeAction::kInitialize;
     }
     Runtime::Current()->InitNonZygoteOrPostFork(
         env, is_system_server, action, isa_string.c_str());
   } else {
     Runtime::Current()->InitNonZygoteOrPostFork(
         env,
         is_system_server,
         Runtime::NativeBridgeAction::kUnload,
         /*isa=*/ nullptr,
         profile_system_server);
   }
 }

 static void ZygoteHooks_startZygoteNoThreadCreation(JNIEnv* env ATTRIBUTE_UNUSED,
                                                     jclass klass ATTRIBUTE_UNUSED) {
   Runtime::Current()->SetZygoteNoThreadSection(true);
 }

 static void ZygoteHooks_stopZygoteNoThreadCreation(JNIEnv* env ATTRIBUTE_UNUSED,
                                                    jclass klass ATTRIBUTE_UNUSED) {
   Runtime::Current()->SetZygoteNoThreadSection(false);
 }

 static JNINativeMethod gMethods[] = {
   NATIVE_METHOD(ZygoteHooks, nativePreFork, "()J"),
   NATIVE_METHOD(ZygoteHooks, nativePostForkSystemServer, "()V"),
   NATIVE_METHOD(ZygoteHooks, nativePostForkChild, "(JIZZLjava/lang/String;)V"),
   NATIVE_METHOD(ZygoteHooks, startZygoteNoThreadCreation, "()V"),
   NATIVE_METHOD(ZygoteHooks, stopZygoteNoThreadCreation, "()V"),
 };

 void register_dalvik_system_ZygoteHooks(JNIEnv* env) {
   REGISTER_NATIVE_METHODS("dalvik/system/ZygoteHooks");
 }

 }  // 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.
	*/

	#include "dalvik_system_ZygoteHooks.h"

	#include <stdlib.h>

	#include <android-base/logging.h>
	#include <android-base/stringprintf.h>

	#include "arch/instruction_set.h"
	#include "art_method-inl.h"
	#include "base/macros.h"
	#include "base/mutex.h"
	#include "base/runtime_debug.h"
	#include "debugger.h"
	#include "hidden_api.h"
	#include "jit/jit.h"
	#include "jni/java_vm_ext.h"
	#include "jni/jni_internal.h"
	#include "native_util.h"
	#include "nativehelper/jni_macros.h"
	#include "nativehelper/scoped_utf_chars.h"
	#include "non_debuggable_classes.h"
	#include "oat_file.h"
	#include "oat_file_manager.h"
	#include "scoped_thread_state_change-inl.h"
	#include "stack.h"
	#include "thread-current-inl.h"
	#include "thread_list.h"
	#include "trace.h"

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

	#include <sys/resource.h>

	namespace art {

	// Set to true to always determine the non-debuggable classes even if we would not allow a debugger
	// to actually attach.
	static bool kAlwaysCollectNonDebuggableClasses =
	RegisterRuntimeDebugFlag(&kAlwaysCollectNonDebuggableClasses);

	using android::base::StringPrintf;

	static void EnableDebugger() {
	#if defined(__linux__)
	// 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();
	}

	// Even if Yama is on a non-privileged native debugger should
	// be able to attach to the debuggable app.
	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) {
	PLOG(ERROR) << "prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY) failed for pid " << getpid();
	}
	}
	#endif
	// 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();
	}
	}

	class ClassSet {
	public:
	// The number of classes we reasonably expect to have to look at. Realistically the number is more
	// ~10 but there is little harm in having some extra.
	static constexpr int kClassSetCapacity = 100;

	explicit ClassSet(Thread* const self) : self_(self) {
	self_->GetJniEnv()->PushFrame(kClassSetCapacity);
	}

	~ClassSet() {
	self_->GetJniEnv()->PopFrame();
	}

	void AddClass(ObjPtr<mirror::Class> klass) REQUIRES(Locks::mutator_lock_) {
	class_set_.insert(self_->GetJniEnv()->AddLocalReference<jclass>(klass));
	}

	const std::unordered_set<jclass>& GetClasses() const {
	return class_set_;
	}

	private:
	Thread* const self_;
	std::unordered_set<jclass> class_set_;
	};

	static void DoCollectNonDebuggableCallback(Thread* thread, void* data)
	REQUIRES(Locks::mutator_lock_) {
	class NonDebuggableStacksVisitor : public StackVisitor {
	public:
	NonDebuggableStacksVisitor(Thread* t, ClassSet* class_set)
	: StackVisitor(t, nullptr, StackVisitor::StackWalkKind::kIncludeInlinedFrames),
	class_set_(class_set) {}

	~NonDebuggableStacksVisitor() override {}

	bool VisitFrame() override REQUIRES(Locks::mutator_lock_) {
	if (GetMethod()->IsRuntimeMethod()) {
	return true;
	}
	class_set_->AddClass(GetMethod()->GetDeclaringClass());
	if (kIsDebugBuild) {
	LOG(INFO) << GetMethod()->GetDeclaringClass()->PrettyClass()
	<< " might not be fully debuggable/deoptimizable due to "
	<< GetMethod()->PrettyMethod() << " appearing on the stack during zygote fork.";
	}
	return true;
	}

	private:
	ClassSet* class_set_;
	};
	NonDebuggableStacksVisitor visitor(thread, reinterpret_cast<ClassSet*>(data));
	visitor.WalkStack();
	}

	static void CollectNonDebuggableClasses() REQUIRES(!Locks::mutator_lock_) {
	Runtime* const runtime = Runtime::Current();
	Thread* const self = Thread::Current();
	// Get the mutator lock.
	ScopedObjectAccess soa(self);
	ClassSet classes(self);
	{
	// Drop the shared mutator lock.
	ScopedThreadSuspension sts(self, art::ThreadState::kNative);
	// Get exclusive mutator lock with suspend all.
	ScopedSuspendAll suspend("Checking stacks for non-obsoletable methods!",
	/long_suspend=/false);
	MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
	runtime->GetThreadList()->ForEach(DoCollectNonDebuggableCallback, &classes);
	}
	for (jclass klass : classes.GetClasses()) {
	NonDebuggableClasses::AddNonDebuggableClass(klass);
	}
	}

	// Must match values in com.android.internal.os.Zygote.
	enum {
	DEBUG_ENABLE_JDWP = 1,
	DEBUG_ENABLE_CHECKJNI = 1 << 1,
	DEBUG_ENABLE_ASSERT = 1 << 2,
	DEBUG_ENABLE_SAFEMODE = 1 << 3,
	DEBUG_ENABLE_JNI_LOGGING = 1 << 4,
	DEBUG_GENERATE_DEBUG_INFO = 1 << 5,
	DEBUG_ALWAYS_JIT = 1 << 6,
	DEBUG_NATIVE_DEBUGGABLE = 1 << 7,
	DEBUG_JAVA_DEBUGGABLE = 1 << 8,
	DISABLE_VERIFIER = 1 << 9,
	ONLY_USE_SYSTEM_OAT_FILES = 1 << 10,
	DEBUG_GENERATE_MINI_DEBUG_INFO = 1 << 11,
	HIDDEN_API_ENFORCEMENT_POLICY_MASK = (1 << 12)
	\| (1 << 13),
	PROFILE_SYSTEM_SERVER = 1 << 14,

	// bits to shift (flags & HIDDEN_API_ENFORCEMENT_POLICY_MASK) by to get a value
	// corresponding to hiddenapi::EnforcementPolicy
	API_ENFORCEMENT_POLICY_SHIFT = CTZ(HIDDEN_API_ENFORCEMENT_POLICY_MASK),
	};

	static uint32_t EnableDebugFeatures(uint32_t runtime_flags) {
	Runtime* const runtime = Runtime::Current();
	if ((runtime_flags & DEBUG_ENABLE_CHECKJNI) != 0) {
	JavaVMExt* vm = runtime->GetJavaVM();
	if (!vm->IsCheckJniEnabled()) {
	LOG(INFO) << "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(INFO) << "Not late-enabling -Xcheck:jni (already on)";
	}
	runtime_flags &= ~DEBUG_ENABLE_CHECKJNI;
	}

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

	Dbg::SetJdwpAllowed((runtime_flags & DEBUG_ENABLE_JDWP) != 0);
	if ((runtime_flags & DEBUG_ENABLE_JDWP) != 0) {
	EnableDebugger();
	}
	runtime_flags &= ~DEBUG_ENABLE_JDWP;

	const bool safe_mode = (runtime_flags & DEBUG_ENABLE_SAFEMODE) != 0;
	if (safe_mode) {
	// Only quicken oat files.
	runtime->AddCompilerOption("--compiler-filter=quicken");
	runtime->SetSafeMode(true);
	runtime_flags &= ~DEBUG_ENABLE_SAFEMODE;
	}

	// This is for backwards compatibility with Dalvik.
	runtime_flags &= ~DEBUG_ENABLE_ASSERT;

	if ((runtime_flags & DEBUG_ALWAYS_JIT) != 0) {
	jit::JitOptions* jit_options = runtime->GetJITOptions();
	CHECK(jit_options != nullptr);
	Runtime::Current()->DoAndMaybeSwitchInterpreter([=]() {
	jit_options->SetJitAtFirstUse();
	});
	runtime_flags &= ~DEBUG_ALWAYS_JIT;
	}

	bool needs_non_debuggable_classes = false;
	if ((runtime_flags & DEBUG_JAVA_DEBUGGABLE) != 0) {
	runtime->AddCompilerOption("--debuggable");
	runtime_flags \|= DEBUG_GENERATE_MINI_DEBUG_INFO;
	runtime->SetJavaDebuggable(true);
	// Deoptimize the boot image as it may be non-debuggable.
	runtime->DeoptimizeBootImage();
	runtime_flags &= ~DEBUG_JAVA_DEBUGGABLE;
	needs_non_debuggable_classes = true;
	}
	if (needs_non_debuggable_classes \|\| kAlwaysCollectNonDebuggableClasses) {
	CollectNonDebuggableClasses();
	}

	if ((runtime_flags & DEBUG_NATIVE_DEBUGGABLE) != 0) {
	runtime->AddCompilerOption("--debuggable");
	runtime_flags \|= DEBUG_GENERATE_DEBUG_INFO;
	runtime->SetNativeDebuggable(true);
	runtime_flags &= ~DEBUG_NATIVE_DEBUGGABLE;
	}

	if ((runtime_flags & DEBUG_GENERATE_MINI_DEBUG_INFO) != 0) {
	// Generate native minimal debug information to allow backtracing.
	runtime->AddCompilerOption("--generate-mini-debug-info");
	runtime_flags &= ~DEBUG_GENERATE_MINI_DEBUG_INFO;
	}

	if ((runtime_flags & DEBUG_GENERATE_DEBUG_INFO) != 0) {
	// Generate all native debug information we can (e.g. line-numbers).
	runtime->AddCompilerOption("--generate-debug-info");
	runtime_flags &= ~DEBUG_GENERATE_DEBUG_INFO;
	}

	return runtime_flags;
	}

	static jlong ZygoteHooks_nativePreFork(JNIEnv* env, jclass) {
	Runtime* runtime = Runtime::Current();
	CHECK(runtime->IsZygote()) << "runtime instance not started with -Xzygote";

	runtime->PreZygoteFork();

	if (Trace::GetMethodTracingMode() != TracingMode::kTracingInactive) {
	// Tracing active, pause it.
	Trace::Pause();
	}

	// Grab thread before fork potentially makes Thread::pthread_key_self_ unusable.
	return reinterpret_cast<jlong>(ThreadForEnv(env));
	}

	static void ZygoteHooks_nativePostForkSystemServer(JNIEnv* env ATTRIBUTE_UNUSED,
	jclass klass ATTRIBUTE_UNUSED) {
	// This JIT code cache for system server is created whilst the runtime is still single threaded.
	// System server has a window where it can create executable pages for this purpose, but this is
	// turned off after this hook. Consequently, the only JIT mode supported is the dual-view JIT
	// where one mapping is R->RW and the other is RX. Single view requires RX->RWX->RX.
	Runtime::Current()->CreateJitCodeCache(/rwx_memory_allowed=/false);
	}

	static void ZygoteHooks_nativePostForkChild(JNIEnv* env,
	jclass,
	jlong token,
	jint runtime_flags,
	jboolean is_system_server,
	jboolean is_zygote,
	jstring instruction_set) {
	DCHECK(!(is_system_server && is_zygote));

	Thread* thread = reinterpret_cast<Thread*>(token);
	// Our system thread ID, etc, has changed so reset Thread state.
	thread->InitAfterFork();
	runtime_flags = EnableDebugFeatures(runtime_flags);
	hiddenapi::EnforcementPolicy api_enforcement_policy = hiddenapi::EnforcementPolicy::kNoChecks;
	bool dedupe_hidden_api_warnings = true;

	if ((runtime_flags & DISABLE_VERIFIER) != 0) {
	Runtime::Current()->DisableVerifier();
	runtime_flags &= ~DISABLE_VERIFIER;
	}

	if ((runtime_flags & ONLY_USE_SYSTEM_OAT_FILES) != 0) {
	Runtime::Current()->GetOatFileManager().SetOnlyUseSystemOatFiles();
	runtime_flags &= ~ONLY_USE_SYSTEM_OAT_FILES;
	}

	api_enforcement_policy = hiddenapi::EnforcementPolicyFromInt(
	(runtime_flags & HIDDEN_API_ENFORCEMENT_POLICY_MASK) >> API_ENFORCEMENT_POLICY_SHIFT);
	runtime_flags &= ~HIDDEN_API_ENFORCEMENT_POLICY_MASK;

	bool profile_system_server = (runtime_flags & PROFILE_SYSTEM_SERVER) == PROFILE_SYSTEM_SERVER;
	runtime_flags &= ~PROFILE_SYSTEM_SERVER;

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

	Runtime::Current()->GetHeap()->PostForkChildAction(thread);

	// Update tracing.
	if (Trace::GetMethodTracingMode() != TracingMode::kTracingInactive) {
	Trace::TraceOutputMode output_mode = Trace::GetOutputMode();
	Trace::TraceMode trace_mode = Trace::GetMode();
	size_t buffer_size = Trace::GetBufferSize();

	// Just drop it.
	Trace::Abort();

	// Only restart if it was streaming mode.
	// TODO: Expose buffer size, so we can also do file mode.
	if (output_mode == Trace::TraceOutputMode::kStreaming) {
	static constexpr size_t kMaxProcessNameLength = 100;
	char name_buf[kMaxProcessNameLength] = {};
	int rc = pthread_getname_np(pthread_self(), name_buf, kMaxProcessNameLength);
	std::string proc_name;

	if (rc == 0) {
	// On success use the pthread name.
	proc_name = name_buf;
	}

	if (proc_name.empty() \|\| proc_name == "zygote" \|\| proc_name == "zygote64") {
	// Either no process name, or the name hasn't been changed, yet. Just use pid.
	pid_t pid = getpid();
	proc_name = StringPrintf("%u", static_cast<uint32_t>(pid));
	}

	std::string trace_file = StringPrintf("/data/misc/trace/%s.trace.bin", proc_name.c_str());
	Trace::Start(trace_file.c_str(),
	buffer_size,
	0, // TODO: Expose flags.
	output_mode,
	trace_mode,
	0); // TODO: Expose interval.
	if (thread->IsExceptionPending()) {
	ScopedObjectAccess soa(env);
	thread->ClearException();
	}
	}
	}

	bool do_hidden_api_checks = api_enforcement_policy != hiddenapi::EnforcementPolicy::kNoChecks;
	DCHECK(!(is_system_server && do_hidden_api_checks))
	<< "SystemServer should be forked with EnforcementPolicy::kDisable";
	DCHECK(!(is_zygote && do_hidden_api_checks))
	<< "Child zygote processes should be forked with EnforcementPolicy::kDisable";
	Runtime::Current()->SetHiddenApiEnforcementPolicy(api_enforcement_policy);
	Runtime::Current()->SetDedupeHiddenApiWarnings(dedupe_hidden_api_warnings);
	if (api_enforcement_policy != hiddenapi::EnforcementPolicy::kNoChecks &&
	Runtime::Current()->GetHiddenApiEventLogSampleRate() != 0) {
	// Hidden API checks are enabled, and we are sampling access for the event log. Initialize the
	// random seed, to ensure the sampling is actually random. We do this post-fork, as doing it
	// pre-fork would result in the same sequence for every forked process.
	std::srand(static_cast<uint32_t>(NanoTime()));
	}

	// Clear the hidden API warning flag, in case it was set.
	Runtime::Current()->SetPendingHiddenApiWarning(false);

	if (is_zygote) {
	// If creating a child-zygote, do not call into the runtime's post-fork logic.
	// Doing so would spin up threads for Binder and JDWP. Instead, the Java side
	// of the child process will call a static main in a class specified by the parent.
	return;
	}

	if (instruction_set != nullptr && !is_system_server) {
	ScopedUtfChars isa_string(env, instruction_set);
	InstructionSet isa = GetInstructionSetFromString(isa_string.c_str());
	Runtime::NativeBridgeAction action = Runtime::NativeBridgeAction::kUnload;
	if (isa != InstructionSet::kNone && isa != kRuntimeISA) {
	action = Runtime::NativeBridgeAction::kInitialize;
	}
	Runtime::Current()->InitNonZygoteOrPostFork(
	env, is_system_server, action, isa_string.c_str());
	} else {
	Runtime::Current()->InitNonZygoteOrPostFork(
	env,
	is_system_server,
	Runtime::NativeBridgeAction::kUnload,
	/isa=/ nullptr,
	profile_system_server);
	}
	}

	static void ZygoteHooks_startZygoteNoThreadCreation(JNIEnv* env ATTRIBUTE_UNUSED,
	jclass klass ATTRIBUTE_UNUSED) {
	Runtime::Current()->SetZygoteNoThreadSection(true);
	}

	static void ZygoteHooks_stopZygoteNoThreadCreation(JNIEnv* env ATTRIBUTE_UNUSED,
	jclass klass ATTRIBUTE_UNUSED) {
	Runtime::Current()->SetZygoteNoThreadSection(false);
	}

	static JNINativeMethod gMethods[] = {
	NATIVE_METHOD(ZygoteHooks, nativePreFork, "()J"),
	NATIVE_METHOD(ZygoteHooks, nativePostForkSystemServer, "()V"),
	NATIVE_METHOD(ZygoteHooks, nativePostForkChild, "(JIZZLjava/lang/String;)V"),
	NATIVE_METHOD(ZygoteHooks, startZygoteNoThreadCreation, "()V"),
	NATIVE_METHOD(ZygoteHooks, stopZygoteNoThreadCreation, "()V"),
	};

	void register_dalvik_system_ZygoteHooks(JNIEnv* env) {
	REGISTER_NATIVE_METHODS("dalvik/system/ZygoteHooks");
	}

	} // namespace art