runtime/native/dalvik_system_ZygoteHooks.cc

/*
 * 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/stringprintf.h"

#include "arch/instruction_set.h"
#include "art_method-inl.h"
#include "debugger.h"
#include "java_vm_ext.h"
#include "jit/jit.h"
#include "jni_internal.h"
#include "JNIHelp.h"
#include "non_debuggable_classes.h"
#include "scoped_thread_state_change-inl.h"
#include "ScopedUtfChars.h"
#include "thread-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 constexpr bool kAlwaysCollectNonDebuggableClasses = kIsDebugBuild;

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.Ptr()));
  }

  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);
  }
}

static void EnableDebugFeatures(uint32_t debug_flags) {
  // 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,
  };

  Runtime* const runtime = Runtime::Current();
  if ((debug_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)";
    }
    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_JDWP) != 0);
  if ((debug_flags & DEBUG_ENABLE_JDWP) != 0) {
    EnableDebugger();
  }
  debug_flags &= ~DEBUG_ENABLE_JDWP;

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

  const bool generate_debug_info = (debug_flags & DEBUG_GENERATE_DEBUG_INFO) != 0;
  if (generate_debug_info) {
    runtime->AddCompilerOption("--generate-debug-info");
    debug_flags &= ~DEBUG_GENERATE_DEBUG_INFO;
  }

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

  if ((debug_flags & DEBUG_ALWAYS_JIT) != 0) {
    jit::JitOptions* jit_options = runtime->GetJITOptions();
    CHECK(jit_options != nullptr);
    jit_options->SetJitAtFirstUse();
    debug_flags &= ~DEBUG_ALWAYS_JIT;
  }

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

  if ((debug_flags & DEBUG_NATIVE_DEBUGGABLE) != 0) {
    runtime->AddCompilerOption("--debuggable");
    runtime->AddCompilerOption("--generate-debug-info");
    runtime->SetNativeDebuggable(true);
    debug_flags &= ~DEBUG_NATIVE_DEBUGGABLE;
  }

  if (debug_flags != 0) {
    LOG(ERROR) << StringPrintf("Unknown bits set in debug_flags: %#x", debug_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_nativePostForkChild(JNIEnv* env,
                                            jclass,
                                            jlong token,
                                            jint debug_flags,
                                            jboolean is_system_server,
                                            jstring instruction_set) {
  Thread* thread = reinterpret_cast<Thread*>(token);
  // Our system thread ID, etc, has changed so reset Thread state.
  thread->InitAfterFork();
  EnableDebugFeatures(debug_flags);

  // 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(),
                   -1,
                   buffer_size,
                   0,   // TODO: Expose flags.
                   output_mode,
                   trace_mode,
                   0);  // TODO: Expose interval.
      if (thread->IsExceptionPending()) {
        ScopedObjectAccess soa(env);
        thread->ClearException();
      }
    }
  }

  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 != 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, nullptr);
  }
}

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, nativePostForkChild, "(JIZLjava/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