InputDispatcher: Add InputTracerInterface for tracing input events

The interface documents how the tracer will interact with
InputDispatcher.

Bug: 210460522
Test: Build
Change-Id: Id97f9b0851f1248956b95e8b18b2302ecff1bff5

7 files changed, 260 insertions, 1 deletions

diff --git a/services/inputflinger/dispatcher/Entry.cpp b/services/inputflinger/dispatcher/Entry.cpp
index cc0d49c15e..2153d8a3f5 100644
--- a/services/inputflinger/dispatcher/Entry.cpp
+++ b/services/inputflinger/dispatcher/Entry.cpp
@@ -164,6 +164,11 @@ std::string KeyEntry::getDescription() const {
                         keyCode, scanCode, metaState, repeatCount, policyFlags);
 }
 
+std::ostream& operator<<(std::ostream& out, const KeyEntry& keyEntry) {
+    out << keyEntry.getDescription();
+    return out;
+}
+
 // --- TouchModeEntry ---
 
 TouchModeEntry::TouchModeEntry(int32_t id, nsecs_t eventTime, bool inTouchMode, int displayId)
diff --git a/services/inputflinger/dispatcher/Entry.h b/services/inputflinger/dispatcher/Entry.h
index e2e13c3fde..a915805182 100644
--- a/services/inputflinger/dispatcher/Entry.h
+++ b/services/inputflinger/dispatcher/Entry.h
@@ -18,6 +18,7 @@
 
 #include "InjectionState.h"
 #include "InputTarget.h"
+#include "trace/EventTrackerInterface.h"
 
 #include <gui/InputApplication.h>
 #include <input/Input.h>
@@ -125,6 +126,7 @@ struct KeyEntry : EventEntry {
     int32_t scanCode;
     int32_t metaState;
     nsecs_t downTime;
+    std::unique_ptr<trace::EventTrackerInterface> traceTracker;
 
     bool syntheticRepeat; // set to true for synthetic key repeats
 
@@ -147,6 +149,8 @@ struct KeyEntry : EventEntry {
     std::string getDescription() const override;
 };
 
+std::ostream& operator<<(std::ostream& out, const KeyEntry& motionEntry);
+
 struct MotionEntry : EventEntry {
     int32_t deviceId;
     uint32_t source;
@@ -165,6 +169,7 @@ struct MotionEntry : EventEntry {
     nsecs_t downTime;
     std::vector<PointerProperties> pointerProperties;
     std::vector<PointerCoords> pointerCoords;
+    std::unique_ptr<trace::EventTrackerInterface> traceTracker;
 
     size_t getPointerCount() const { return pointerProperties.size(); }
 
diff --git a/services/inputflinger/dispatcher/InputDispatcher.cpp b/services/inputflinger/dispatcher/InputDispatcher.cpp
index e998d917c0..0ddea7195a 100644
--- a/services/inputflinger/dispatcher/InputDispatcher.cpp
+++ b/services/inputflinger/dispatcher/InputDispatcher.cpp
@@ -78,6 +78,14 @@ static const bool REMOVE_APP_SWITCH_DROPS = true;
 namespace android::inputdispatcher {
 
 namespace {
+
+template <class Entry>
+void ensureEventTraced(const Entry& entry) {
+    if (!entry.traceTracker) {
+        LOG(FATAL) << "Expected event entry to be traced, but it wasn't: " << entry;
+    }
+}
+
 // Temporarily releases a held mutex for the lifetime of the instance.
 // Named to match std::scoped_lock
 class scoped_unlock {
@@ -783,6 +791,10 @@ Result<void> validateWindowInfosUpdate(const gui::WindowInfosUpdate& update) {
 // --- InputDispatcher ---
 
 InputDispatcher::InputDispatcher(InputDispatcherPolicyInterface& policy)
+      : InputDispatcher(policy, nullptr) {}
+
+InputDispatcher::InputDispatcher(InputDispatcherPolicyInterface& policy,
+                                 std::unique_ptr<trace::InputTracingBackendInterface> traceBackend)
       : mPolicy(policy),
         mPendingEvent(nullptr),
         mLastDropReason(DropReason::NOT_DROPPED),
@@ -807,6 +819,10 @@ InputDispatcher::InputDispatcher(InputDispatcherPolicyInterface& policy)
     SurfaceComposerClient::getDefault()->addWindowInfosListener(mWindowInfoListener);
 #endif
     mKeyRepeatState.lastKeyEntry = nullptr;
+
+    if (traceBackend) {
+        // TODO: Create input tracer instance.
+    }
 }
 
 InputDispatcher::~InputDispatcher() {
@@ -1108,6 +1124,10 @@ void InputDispatcher::dispatchOnceInnerLocked(nsecs_t& nextWakeupTime) {
                 dropReason = DropReason::BLOCKED;
             }
             done = dispatchKeyLocked(currentTime, keyEntry, &dropReason, nextWakeupTime);
+            if (done && mTracer) {
+                ensureEventTraced(*keyEntry);
+                mTracer->eventProcessingComplete(*keyEntry->traceTracker);
+            }
             break;
         }
 
@@ -1138,6 +1158,10 @@ void InputDispatcher::dispatchOnceInnerLocked(nsecs_t& nextWakeupTime) {
                 }
             }
             done = dispatchMotionLocked(currentTime, motionEntry, &dropReason, nextWakeupTime);
+            if (done && mTracer) {
+                ensureEventTraced(*motionEntry);
+                mTracer->eventProcessingComplete(*motionEntry->traceTracker);
+            }
             break;
         }
 
@@ -1249,6 +1273,9 @@ bool InputDispatcher::enqueueInboundEventLocked(std::unique_ptr<EventEntry> newE
             // If the application takes too long to catch up then we drop all events preceding
             // the app switch key.
             const KeyEntry& keyEntry = static_cast<const KeyEntry&>(entry);
+            if (mTracer) {
+                ensureEventTraced(keyEntry);
+            }
 
             if (!REMOVE_APP_SWITCH_DROPS) {
                 if (isAppSwitchKeyEvent(keyEntry)) {
@@ -1286,7 +1313,11 @@ bool InputDispatcher::enqueueInboundEventLocked(std::unique_ptr<EventEntry> newE
         case EventEntry::Type::MOTION: {
             LOG_ALWAYS_FATAL_IF((entry.policyFlags & POLICY_FLAG_TRUSTED) == 0,
                                 "Unexpected untrusted event.");
-            if (shouldPruneInboundQueueLocked(static_cast<const MotionEntry&>(entry))) {
+            const auto& motionEntry = static_cast<const MotionEntry&>(entry);
+            if (mTracer) {
+                ensureEventTraced(motionEntry);
+            }
+            if (shouldPruneInboundQueueLocked(motionEntry)) {
                 mNextUnblockedEvent = mInboundQueue.back();
                 needWake = true;
             }
@@ -1567,6 +1598,10 @@ std::shared_ptr<KeyEntry> InputDispatcher::synthesizeKeyRepeatLocked(nsecs_t cur
                                        entry->repeatCount + 1, entry->downTime);
 
     newEntry->syntheticRepeat = true;
+    if (mTracer) {
+        newEntry->traceTracker = mTracer->traceInboundEvent(*newEntry);
+    }
+
     mKeyRepeatState.lastKeyEntry = newEntry;
     mKeyRepeatState.nextRepeatTime = currentTime + mConfig.keyRepeatDelay;
     return newEntry;
@@ -1873,6 +1908,13 @@ bool InputDispatcher::dispatchKeyLocked(nsecs_t currentTime, std::shared_ptr<con
     // Add monitor channels from event's or focused display.
     addGlobalMonitoringTargetsLocked(inputTargets, getTargetDisplayId(*entry));
 
+    if (mTracer) {
+        ensureEventTraced(*entry);
+        for (const auto& target : inputTargets) {
+            mTracer->dispatchToTargetHint(*entry->traceTracker, target);
+        }
+    }
+
     // Dispatch the key.
     dispatchEventLocked(currentTime, entry, inputTargets);
     return true;
@@ -1998,6 +2040,13 @@ bool InputDispatcher::dispatchMotionLocked(nsecs_t currentTime,
     // Add monitor channels from event's or focused display.
     addGlobalMonitoringTargetsLocked(inputTargets, getTargetDisplayId(*entry));
 
+    if (mTracer) {
+        ensureEventTraced(*entry);
+        for (const auto& target : inputTargets) {
+            mTracer->dispatchToTargetHint(*entry->traceTracker, target);
+        }
+    }
+
     // Dispatch the motion.
     dispatchEventLocked(currentTime, entry, inputTargets);
     return true;
@@ -3635,6 +3684,7 @@ status_t InputDispatcher::publishMotionEvent(Connection& connection,
     PointerCoords scaledCoords[MAX_POINTERS];
     const PointerCoords* usingCoords = motionEntry.pointerCoords.data();
 
+    // TODO(b/316355518): Do not modify coords before dispatch.
     // Set the X and Y offset and X and Y scale depending on the input source.
     if ((motionEntry.source & AINPUT_SOURCE_CLASS_POINTER) &&
         !(dispatchEntry.targetFlags.test(InputTarget::Flags::ZERO_COORDS))) {
@@ -3710,6 +3760,9 @@ void InputDispatcher::startDispatchCycleLocked(nsecs_t currentTime,
                                                   keyEntry.keyCode, keyEntry.scanCode,
                                                   keyEntry.metaState, keyEntry.repeatCount,
                                                   keyEntry.downTime, keyEntry.eventTime);
+                if (mTracer) {
+                    mTracer->traceEventDispatch(*dispatchEntry, keyEntry.traceTracker.get());
+                }
                 break;
             }
 
@@ -3718,7 +3771,11 @@ void InputDispatcher::startDispatchCycleLocked(nsecs_t currentTime,
                     LOG(INFO) << "Publishing " << *dispatchEntry << " to "
                               << connection->getInputChannelName();
                 }
+                const MotionEntry& motionEntry = static_cast<const MotionEntry&>(eventEntry);
                 status = publishMotionEvent(*connection, *dispatchEntry);
+                if (mTracer) {
+                    mTracer->traceEventDispatch(*dispatchEntry, motionEntry.traceTracker.get());
+                }
                 break;
             }
 
@@ -4400,6 +4457,9 @@ void InputDispatcher::notifyKey(const NotifyKeyArgs& args) {
                                            args.deviceId, args.source, args.displayId, policyFlags,
                                            args.action, flags, keyCode, args.scanCode, metaState,
                                            repeatCount, args.downTime);
+        if (mTracer) {
+            newEntry->traceTracker = mTracer->traceInboundEvent(*newEntry);
+        }
 
         needWake = enqueueInboundEventLocked(std::move(newEntry));
         mLock.unlock();
@@ -4526,6 +4586,9 @@ void InputDispatcher::notifyMotion(const NotifyMotionArgs& args) {
                                               args.yPrecision, args.xCursorPosition,
                                               args.yCursorPosition, args.downTime,
                                               args.pointerProperties, args.pointerCoords);
+        if (mTracer) {
+            newEntry->traceTracker = mTracer->traceInboundEvent(*newEntry);
+        }
 
         if (args.id != android::os::IInputConstants::INVALID_INPUT_EVENT_ID &&
             IdGenerator::getSource(args.id) == IdGenerator::Source::INPUT_READER &&
@@ -4713,6 +4776,9 @@ InputEventInjectionResult InputDispatcher::injectInputEvent(const InputEvent* ev
                                                incomingKey.getScanCode(), metaState,
                                                incomingKey.getRepeatCount(),
                                                incomingKey.getDownTime());
+            if (mTracer) {
+                injectedEntry->traceTracker = mTracer->traceInboundEvent(*injectedEntry);
+            }
             injectedEntries.push(std::move(injectedEntry));
             break;
         }
@@ -4770,6 +4836,9 @@ InputEventInjectionResult InputDispatcher::injectInputEvent(const InputEvent* ev
                                                                              samplePointerCoords +
                                                                                      pointerCount));
             transformMotionEntryForInjectionLocked(*injectedEntry, motionEvent.getTransform());
+            if (mTracer) {
+                injectedEntry->traceTracker = mTracer->traceInboundEvent(*injectedEntry);
+            }
             injectedEntries.push(std::move(injectedEntry));
             for (size_t i = motionEvent.getHistorySize(); i > 0; i--) {
                 sampleEventTimes += 1;
@@ -5869,6 +5938,8 @@ void InputDispatcher::dumpDispatchStateLocked(std::string& dump) const {
                          ns2ms(mConfig.keyRepeatTimeout));
     dump += mLatencyTracker.dump(INDENT2);
     dump += mLatencyAggregator.dump(INDENT2);
+    dump += INDENT "InputTracer: ";
+    dump += mTracer == nullptr ? "Disabled" : "Enabled";
 }
 
 void InputDispatcher::dumpMonitors(std::string& dump, const std::vector<Monitor>& monitors) const {
diff --git a/services/inputflinger/dispatcher/InputDispatcher.h b/services/inputflinger/dispatcher/InputDispatcher.h
index 3567288f1d..5b455313e8 100644
--- a/services/inputflinger/dispatcher/InputDispatcher.h
+++ b/services/inputflinger/dispatcher/InputDispatcher.h
@@ -32,6 +32,8 @@
 #include "Monitor.h"
 #include "TouchState.h"
 #include "TouchedWindow.h"
+#include "trace/InputTracerInterface.h"
+#include "trace/InputTracingBackendInterface.h"
 
 #include <attestation/HmacKeyManager.h>
 #include <gui/InputApplication.h>
@@ -82,6 +84,9 @@ public:
     static constexpr bool kDefaultInTouchMode = true;
 
     explicit InputDispatcher(InputDispatcherPolicyInterface& policy);
+    // Constructor used for testing.
+    explicit InputDispatcher(InputDispatcherPolicyInterface&,
+                             std::unique_ptr<trace::InputTracingBackendInterface>);
     ~InputDispatcher() override;
 
     void dump(std::string& dump) const override;
@@ -172,6 +177,9 @@ private:
     std::condition_variable mDispatcherIsAlive;
     mutable std::condition_variable mDispatcherEnteredIdle;
 
+    // Input event tracer. The tracer will only exist on builds where input tracing is allowed.
+    std::unique_ptr<trace::InputTracerInterface> mTracer GUARDED_BY(mLock);
+
     sp<Looper> mLooper;
 
     std::shared_ptr<const EventEntry> mPendingEvent GUARDED_BY(mLock);
diff --git a/services/inputflinger/dispatcher/trace/EventTrackerInterface.h b/services/inputflinger/dispatcher/trace/EventTrackerInterface.h
new file mode 100644
index 0000000000..929820e0a6
--- /dev/null
+++ b/services/inputflinger/dispatcher/trace/EventTrackerInterface.h
@@ -0,0 +1,32 @@
+/*
+ * Copyright 2024 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.
+ */
+
+#pragma once
+
+namespace android::inputdispatcher::trace {
+
+/**
+ * A tracker used to track the lifecycle of a traced input event.
+ * The tracker should be stored inside the traced event. When the event goes out of scope after
+ * the dispatcher has finished processing it, the tracker will call back into the tracer to
+ * initiate cleanup.
+ */
+class EventTrackerInterface {
+public:
+    virtual ~EventTrackerInterface() = default;
+};
+
+} // namespace android::inputdispatcher::trace
diff --git a/services/inputflinger/dispatcher/trace/InputTracerInterface.h b/services/inputflinger/dispatcher/trace/InputTracerInterface.h
new file mode 100644
index 0000000000..c6cd7de4b6
--- /dev/null
+++ b/services/inputflinger/dispatcher/trace/InputTracerInterface.h
@@ -0,0 +1,87 @@
+/*
+ * Copyright 2024 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.
+ */
+
+#pragma once
+
+#include "../Entry.h"
+#include "../InputTarget.h"
+#include "EventTrackerInterface.h"
+
+namespace android::inputdispatcher::trace {
+
+/**
+ * InputTracerInterface is the tracing interface for InputDispatcher.
+ *
+ * The tracer is responsible for tracing information about input events and where they are
+ * dispatched. The trace is logged to the backend using the InputTracingBackendInterface.
+ *
+ * A normal traced event should have the following lifecycle:
+ *  - The EventTracker is obtained from traceInboundEvent(), after which point the event
+ *    should not change.
+ *  - While the event is being processed, dispatchToTargetHint() is called for each target that
+ *    the event will be eventually sent to.
+ *  - Once all targets have been determined, eventProcessingComplete() is called, at which point
+ *    the tracer will have enough information to commit the event to the trace.
+ *  - For each event that is dispatched to the client, traceEventDispatch() is called, and the
+ *    tracer will record that the event was sent to the client.
+ */
+class InputTracerInterface {
+public:
+    InputTracerInterface() = default;
+    virtual ~InputTracerInterface() = default;
+    InputTracerInterface(const InputTracerInterface&) = delete;
+    InputTracerInterface& operator=(const InputTracerInterface&) = delete;
+
+    /**
+     * Trace an input event that is being processed by InputDispatcher. The event must not be
+     * modified after it is traced to keep the traced event consistent with the event that is
+     * eventually dispatched. An EventTracker is returned for each traced event that should be used
+     * to track the event's lifecycle inside InputDispatcher.
+     */
+    virtual std::unique_ptr<EventTrackerInterface> traceInboundEvent(const EventEntry&) = 0;
+
+    /**
+     * Notify the tracer that the traced event will be sent to the given InputTarget.
+     * The tracer may change how the event is logged depending on the target. For example,
+     * events targeting certain UIDs may be logged as sensitive events.
+     * This may be called 0 or more times for each tracked event before event processing is
+     * completed.
+     */
+    virtual void dispatchToTargetHint(const EventTrackerInterface&, const InputTarget&) = 0;
+
+    /**
+     * Notify the tracer that the event processing is complete. This may be called at most once
+     * for each traced event. If a tracked event is dropped before it can be processed, it is
+     * possible that this is never called before the EventTracker is destroyed.
+     *
+     * This is used to commit the event to the trace in a timely manner, rather than always
+     * waiting for the event to go out of scope (and thus for the EventTracker to be destroyed)
+     * before committing. The point at which the event is destroyed can depend on several factors
+     * outside of our control, such as how long apps take to respond, so we don't want to depend on
+     * that.
+     */
+    virtual void eventProcessingComplete(const EventTrackerInterface&) = 0;
+
+    /**
+     * Trace an input event being successfully dispatched to a window. The dispatched event may
+     * be a previously traced inbound event, or it may be a synthesized event that has not been
+     * previously traced. For inbound events that were previously traced, the EventTracker cookie
+     * must be provided. For events that were not previously traced, the cookie must be null.
+     */
+    virtual void traceEventDispatch(const DispatchEntry&, const EventTrackerInterface*) = 0;
+};
+
+} // namespace android::inputdispatcher::trace
diff --git a/services/inputflinger/dispatcher/trace/InputTracingBackendInterface.h b/services/inputflinger/dispatcher/trace/InputTracingBackendInterface.h
new file mode 100644
index 0000000000..b430a5bb28
--- /dev/null
+++ b/services/inputflinger/dispatcher/trace/InputTracingBackendInterface.h
@@ -0,0 +1,51 @@
+/*
+ * Copyright 2024 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.
+ */
+
+#pragma once
+
+#include "../Entry.h"
+
+namespace android::inputdispatcher::trace {
+
+/**
+ * An interface for the tracing backend, used for setting a custom backend for testing.
+ */
+class InputTracingBackendInterface {
+public:
+    virtual ~InputTracingBackendInterface() = default;
+
+    /** Trace a KeyEvent. */
+    virtual void traceKeyEvent(const KeyEntry&) const = 0;
+
+    /** Trace a MotionEvent. */
+    virtual void traceMotionEvent(const MotionEntry&) const = 0;
+
+    /** Trace an event being sent to a window. */
+    struct WindowDispatchArgs {
+        std::variant<MotionEntry, KeyEntry> eventEntry;
+        nsecs_t deliveryTime;
+        int32_t resolvedFlags;
+        gui::Uid targetUid;
+        int64_t vsyncId;
+        int32_t windowId;
+        ui::Transform transform;
+        ui::Transform rawTransform;
+        std::array<uint8_t, 32> hmac;
+    };
+    virtual void traceWindowDispatch(const WindowDispatchArgs&) const = 0;
+};
+
+} // namespace android::inputdispatcher::trace