1 files changed, 173 insertions, 0 deletions
diff --git a/openjdkjvmti/transform.cc b/openjdkjvmti/transform.cc
index 753697dbe6..9c440ef367 100644
--- a/openjdkjvmti/transform.cc
+++ b/openjdkjvmti/transform.cc
@@ -70,13 +70,185 @@
 
 namespace openjdkjvmti {
 
+// A FaultHandler that will deal with initializing ClassDefinitions when they are actually needed.
+class TransformationFaultHandler final : public art::FaultHandler {
+ public:
+  explicit TransformationFaultHandler(art::FaultManager* manager)
+      : art::FaultHandler(manager),
+        uninitialized_class_definitions_lock_("JVMTI Initialized class definitions lock",
+                                              art::LockLevel::kSignalHandlingLock),
+        class_definition_initialized_cond_("JVMTI Initialized class definitions condition",
+                                           uninitialized_class_definitions_lock_) {
+    manager->AddHandler(this, /* generated_code= */ false);
+  }
+
+  ~TransformationFaultHandler() {
+    art::MutexLock mu(art::Thread::Current(), uninitialized_class_definitions_lock_);
+    uninitialized_class_definitions_.clear();
+  }
+
+  bool Action(int sig, siginfo_t* siginfo, void* context ATTRIBUTE_UNUSED) override {
+    DCHECK_EQ(sig, SIGSEGV);
+    art::Thread* self = art::Thread::Current();
+    uintptr_t ptr = reinterpret_cast<uintptr_t>(siginfo->si_addr);
+    if (UNLIKELY(uninitialized_class_definitions_lock_.IsExclusiveHeld(self))) {
+      // It's possible this is just some other unrelated segv that should be
+      // handled separately, continue to later handlers. This is likely due to
+      // running out of memory somewhere along the FixedUpDexFile pipeline and
+      // is likely unrecoverable. By returning false here though we will get a
+      // better, more accurate, stack-trace later that points to the actual
+      // issue.
+      LOG(WARNING) << "Recursive SEGV occurred during Transformation dequickening at 0x" << std::hex
+                   << ptr;
+      return false;
+    }
+    ArtClassDefinition* res = nullptr;
+
+    {
+      // NB Technically using a mutex and condition variables here is non-posix compliant but
+      // everything should be fine since both glibc and bionic implementations of mutexs and
+      // condition variables work fine so long as the thread was not interrupted during a
+      // lock/unlock (which it wasn't) on all architectures we care about.
+      art::MutexLock mu(self, uninitialized_class_definitions_lock_);
+      auto it = std::find_if(uninitialized_class_definitions_.begin(),
+                             uninitialized_class_definitions_.end(),
+                             [&](const auto op) { return op->ContainsAddress(ptr); });
+      if (it != uninitialized_class_definitions_.end()) {
+        res = *it;
+        // Remove the class definition.
+        uninitialized_class_definitions_.erase(it);
+        // Put it in the initializing list
+        initializing_class_definitions_.push_back(res);
+      } else {
+        // Wait for the ptr to be initialized (if it is currently initializing).
+        while (DefinitionIsInitializing(ptr)) {
+          WaitForClassInitializationToFinish();
+        }
+        // Return true (continue with user code) if we find that the definition has been
+        // initialized. Return false (continue on to next signal handler) if the definition is not
+        // initialized or found.
+        return std::find_if(initialized_class_definitions_.begin(),
+                            initialized_class_definitions_.end(),
+                            [&](const auto op) { return op->ContainsAddress(ptr); }) !=
+            initialized_class_definitions_.end();
+      }
+    }
+
+    if (LIKELY(self != nullptr)) {
+      CHECK_EQ(self->GetState(), art::ThreadState::kNative)
+          << "Transformation fault handler occurred outside of native mode";
+    }
+
+    VLOG(signals) << "Lazy initialization of dex file for transformation of " << res->GetName()
+                  << " during SEGV";
+    res->InitializeMemory();
+
+    {
+      art::MutexLock mu(self, uninitialized_class_definitions_lock_);
+      // Move to initialized state and notify waiters.
+      initializing_class_definitions_.erase(std::find(initializing_class_definitions_.begin(),
+                                                      initializing_class_definitions_.end(),
+                                                      res));
+      initialized_class_definitions_.push_back(res);
+      class_definition_initialized_cond_.Broadcast(self);
+    }
+
+    return true;
+  }
+
+  void RemoveDefinition(ArtClassDefinition* def) REQUIRES(!uninitialized_class_definitions_lock_) {
+    art::MutexLock mu(art::Thread::Current(), uninitialized_class_definitions_lock_);
+    auto it = std::find(uninitialized_class_definitions_.begin(),
+                        uninitialized_class_definitions_.end(),
+                        def);
+    if (it != uninitialized_class_definitions_.end()) {
+      uninitialized_class_definitions_.erase(it);
+      return;
+    }
+    while (std::find(initializing_class_definitions_.begin(),
+                     initializing_class_definitions_.end(),
+                     def) != initializing_class_definitions_.end()) {
+      WaitForClassInitializationToFinish();
+    }
+    it = std::find(initialized_class_definitions_.begin(),
+                   initialized_class_definitions_.end(),
+                   def);
+    CHECK(it != initialized_class_definitions_.end()) << "Could not find class definition for "
+                                                      << def->GetName();
+    initialized_class_definitions_.erase(it);
+  }
+
+  void AddArtDefinition(ArtClassDefinition* def) REQUIRES(!uninitialized_class_definitions_lock_) {
+    DCHECK(def->IsLazyDefinition());
+    art::MutexLock mu(art::Thread::Current(), uninitialized_class_definitions_lock_);
+    uninitialized_class_definitions_.push_back(def);
+  }
+
+ private:
+  bool DefinitionIsInitializing(uintptr_t ptr) REQUIRES(uninitialized_class_definitions_lock_) {
+    return std::find_if(initializing_class_definitions_.begin(),
+                        initializing_class_definitions_.end(),
+                        [&](const auto op) { return op->ContainsAddress(ptr); }) !=
+        initializing_class_definitions_.end();
+  }
+
+  void WaitForClassInitializationToFinish() REQUIRES(uninitialized_class_definitions_lock_) {
+    class_definition_initialized_cond_.Wait(art::Thread::Current());
+  }
+
+  art::Mutex uninitialized_class_definitions_lock_ ACQUIRED_BEFORE(art::Locks::abort_lock_);
+  art::ConditionVariable class_definition_initialized_cond_
+      GUARDED_BY(uninitialized_class_definitions_lock_);
+
+  // A list of the class definitions that have a non-readable map.
+  std::vector<ArtClassDefinition*> uninitialized_class_definitions_
+      GUARDED_BY(uninitialized_class_definitions_lock_);
+
+  // A list of class definitions that are currently undergoing unquickening. Threads should wait
+  // until the definition is no longer in this before returning.
+  std::vector<ArtClassDefinition*> initializing_class_definitions_
+      GUARDED_BY(uninitialized_class_definitions_lock_);
+
+  // A list of class definitions that are already unquickened. Threads should immediately return if
+  // it is here.
+  std::vector<ArtClassDefinition*> initialized_class_definitions_
+      GUARDED_BY(uninitialized_class_definitions_lock_);
+};
+
+static TransformationFaultHandler* gTransformFaultHandler = nullptr;
 static EventHandler* gEventHandler = nullptr;
 
 
 void Transformer::Register(EventHandler* eh) {
+  // Although we create this the fault handler is actually owned by the 'art::fault_manager' which
+  // will take care of destroying it.
+  if (art::MemMap::kCanReplaceMapping && ArtClassDefinition::kEnableOnDemandDexDequicken) {
+    gTransformFaultHandler = new TransformationFaultHandler(&art::fault_manager);
+  }
   gEventHandler = eh;
 }
 
+// Simple helper to add and remove the class definition from the fault handler.
+class ScopedDefinitionHandler {
+ public:
+  explicit ScopedDefinitionHandler(ArtClassDefinition* def)
+      : def_(def), is_lazy_(def_->IsLazyDefinition()) {
+    if (is_lazy_) {
+      gTransformFaultHandler->AddArtDefinition(def_);
+    }
+  }
+
+  ~ScopedDefinitionHandler() {
+    if (is_lazy_) {
+      gTransformFaultHandler->RemoveDefinition(def_);
+    }
+  }
+
+ private:
+  ArtClassDefinition* def_;
+  bool is_lazy_;
+};
+
 // Initialize templates.
 template
 void Transformer::TransformSingleClassDirect<ArtJvmtiEvent::kClassFileLoadHookNonRetransformable>(
@@ -100,6 +272,7 @@ void Transformer::TransformSingleClassDirect(EventHandler* event_handler,
   // native state early. This also avoids any problems that the FaultHandler might have in
   // determining if an access to the dex_data is from generated code or not.
   art::ScopedThreadStateChange stsc(self, art::ThreadState::kNative);
+  ScopedDefinitionHandler handler(def);
   jint new_len = -1;
   unsigned char* new_data = nullptr;
   art::ArrayRef<const unsigned char> dex_data = def->GetDexData();