Use dlsym to load libstatssocket API

Also fixes a bug in the tests where the platform version was being
checked by querying version.release instead of version.codename
(currently, version.release == 10, while version.codename == R).

Test: bit libstatspush_compat_test:* (on Q and R)
Test: libsstatssocket.so is not placed in resolv apex (on R)

1|bonito:/ $ ls apex/com.android.resolv/lib64
libclang_rt.ubsan_standalone-aarch64-android.so
libcrypto.so
libnetd_resolv.so
libssl.so

Test: NETWORK_DNS_EVENT_REPORTED atom is logged to statsd (on R)
    - adb shell cmd stats print-stats (atom 116 count > 0)

Bug: 148743333
Change-Id: Ib3eaa32835905bcf6e3b003054bf0f3c4e7ec0a4
Merged-In: Ib3eaa32835905bcf6e3b003054bf0f3c4e7ec0a4
(cherry picked from commit 9848eb4f1c6780c0cfb253417d7542663421fb7e)
diff --git a/libstats/push_compat/StatsEventCompat.cpp b/libstats/push_compat/StatsEventCompat.cpp
index b065af2..e1a86ae 100644
--- a/libstats/push_compat/StatsEventCompat.cpp
+++ b/libstats/push_compat/StatsEventCompat.cpp
@@ -40,10 +40,10 @@
         GetProperty("ro.build.version.codename", "") == "R" ||
         android_get_device_api_level() > __ANDROID_API_Q__;
 
-// definitions of static class variables
+// initializations of static class variables
 bool StatsEventCompat::mAttemptedLoad = false;
-void* StatsEventCompat::mStatsEventApi = nullptr;
 std::mutex StatsEventCompat::mLoadLock;
+AStatsEventApi StatsEventCompat::mAStatsEventApi;
 
 static int64_t elapsedRealtimeNano() {
     return std::chrono::time_point_cast<std::chrono::nanoseconds>(boot_clock::now())
@@ -56,11 +56,10 @@
     // environment
     {
         std::lock_guard<std::mutex> lg(mLoadLock);
-        if (!mAttemptedLoad) {
+        if (!mAttemptedLoad && mPlatformAtLeastR) {
             void* handle = dlopen("libstatssocket.so", RTLD_NOW);
             if (handle) {
-                //                mStatsEventApi = (struct AStatsEvent_apiTable*)dlsym(handle,
-                //                "table");
+                initializeApiTableLocked(handle);
             } else {
                 ALOGE("dlopen failed: %s\n", dlerror());
             }
@@ -68,61 +67,93 @@
         mAttemptedLoad = true;
     }
 
-    if (mStatsEventApi) {
-        //        mEventR = mStatsEventApi->obtain();
-    } else if (!mPlatformAtLeastR) {
+    if (useRSchema()) {
+        mEventR = mAStatsEventApi.obtain();
+    } else if (useQSchema()) {
         mEventQ << elapsedRealtimeNano();
     }
 }
 
 StatsEventCompat::~StatsEventCompat() {
-    //    if (mStatsEventApi) mStatsEventApi->release(mEventR);
+    if (useRSchema()) mAStatsEventApi.release(mEventR);
+}
+
+// Populates the AStatsEventApi struct by calling dlsym to find the address of
+// each API function.
+void StatsEventCompat::initializeApiTableLocked(void* handle) {
+    mAStatsEventApi.obtain = (AStatsEvent* (*)())dlsym(handle, "AStatsEvent_obtain");
+    mAStatsEventApi.build = (void (*)(AStatsEvent*))dlsym(handle, "AStatsEvent_build");
+    mAStatsEventApi.write = (int (*)(AStatsEvent*))dlsym(handle, "AStatsEvent_write");
+    mAStatsEventApi.release = (void (*)(AStatsEvent*))dlsym(handle, "AStatsEvent_release");
+    mAStatsEventApi.setAtomId =
+            (void (*)(AStatsEvent*, uint32_t))dlsym(handle, "AStatsEvent_setAtomId");
+    mAStatsEventApi.writeInt32 =
+            (void (*)(AStatsEvent*, int32_t))dlsym(handle, "AStatsEvent_writeInt32");
+    mAStatsEventApi.writeInt64 =
+            (void (*)(AStatsEvent*, int64_t))dlsym(handle, "AStatsEvent_writeInt64");
+    mAStatsEventApi.writeFloat =
+            (void (*)(AStatsEvent*, float))dlsym(handle, "AStatsEvent_writeFloat");
+    mAStatsEventApi.writeBool =
+            (void (*)(AStatsEvent*, bool))dlsym(handle, "AStatsEvent_writeBool");
+    mAStatsEventApi.writeByteArray = (void (*)(AStatsEvent*, const uint8_t*, size_t))dlsym(
+            handle, "AStatsEvent_writeByteArray");
+    mAStatsEventApi.writeString =
+            (void (*)(AStatsEvent*, const char*))dlsym(handle, "AStatsEvent_writeString");
+    mAStatsEventApi.writeAttributionChain =
+            (void (*)(AStatsEvent*, const uint32_t*, const char* const*, uint8_t))dlsym(
+                    handle, "AStatsEvent_writeAttributionChain");
+    mAStatsEventApi.addBoolAnnotation =
+            (void (*)(AStatsEvent*, uint8_t, bool))dlsym(handle, "AStatsEvent_addBoolAnnotation");
+    mAStatsEventApi.addInt32Annotation = (void (*)(AStatsEvent*, uint8_t, int32_t))dlsym(
+            handle, "AStatsEvent_addInt32Annotation");
+
+    mAStatsEventApi.initialized = true;
 }
 
 void StatsEventCompat::setAtomId(int32_t atomId) {
-    if (mStatsEventApi) {
-        //        mStatsEventApi->setAtomId(mEventR, (uint32_t)atomId);
-    } else if (!mPlatformAtLeastR) {
+    if (useRSchema()) {
+        mAStatsEventApi.setAtomId(mEventR, (uint32_t)atomId);
+    } else if (useQSchema()) {
         mEventQ << atomId;
     }
 }
 
 void StatsEventCompat::writeInt32(int32_t value) {
-    if (mStatsEventApi) {
-        //        mStatsEventApi->writeInt32(mEventR, value);
-    } else if (!mPlatformAtLeastR) {
+    if (useRSchema()) {
+        mAStatsEventApi.writeInt32(mEventR, value);
+    } else if (useQSchema()) {
         mEventQ << value;
     }
 }
 
 void StatsEventCompat::writeInt64(int64_t value) {
-    if (mStatsEventApi) {
-        //        mStatsEventApi->writeInt64(mEventR, value);
-    } else if (!mPlatformAtLeastR) {
+    if (useRSchema()) {
+        mAStatsEventApi.writeInt64(mEventR, value);
+    } else if (useQSchema()) {
         mEventQ << value;
     }
 }
 
 void StatsEventCompat::writeFloat(float value) {
-    if (mStatsEventApi) {
-        //        mStatsEventApi->writeFloat(mEventR, value);
-    } else if (!mPlatformAtLeastR) {
+    if (useRSchema()) {
+        mAStatsEventApi.writeFloat(mEventR, value);
+    } else if (useQSchema()) {
         mEventQ << value;
     }
 }
 
 void StatsEventCompat::writeBool(bool value) {
-    if (mStatsEventApi) {
-        //        mStatsEventApi->writeBool(mEventR, value);
-    } else if (!mPlatformAtLeastR) {
+    if (useRSchema()) {
+        mAStatsEventApi.writeBool(mEventR, value);
+    } else if (useQSchema()) {
         mEventQ << value;
     }
 }
 
 void StatsEventCompat::writeByteArray(const char* buffer, size_t length) {
-    if (mStatsEventApi) {
-        //        mStatsEventApi->writeByteArray(mEventR, (const uint8_t*)buffer, length);
-    } else if (!mPlatformAtLeastR) {
+    if (useRSchema()) {
+        mAStatsEventApi.writeByteArray(mEventR, reinterpret_cast<const uint8_t*>(buffer), length);
+    } else if (useQSchema()) {
         mEventQ.AppendCharArray(buffer, length);
     }
 }
@@ -130,19 +161,19 @@
 void StatsEventCompat::writeString(const char* value) {
     if (value == nullptr) value = "";
 
-    if (mStatsEventApi) {
-        //        mStatsEventApi->writeString(mEventR, value);
-    } else if (!mPlatformAtLeastR) {
+    if (useRSchema()) {
+        mAStatsEventApi.writeString(mEventR, value);
+    } else if (useQSchema()) {
         mEventQ << value;
     }
 }
 
 void StatsEventCompat::writeAttributionChain(const int32_t* uids, size_t numUids,
                                              const vector<const char*>& tags) {
-    if (mStatsEventApi) {
-        //        mStatsEventApi->writeAttributionChain(mEventR, (const uint32_t*)uids, tags.data(),
-        //                                                (uint8_t)numUids);
-    } else if (!mPlatformAtLeastR) {
+    if (useRSchema()) {
+        mAStatsEventApi.writeAttributionChain(mEventR, (const uint32_t*)uids, tags.data(),
+                                              (uint8_t)numUids);
+    } else if (useQSchema()) {
         mEventQ.begin();
         for (size_t i = 0; i < numUids; i++) {
             mEventQ.begin();
@@ -159,8 +190,8 @@
                                           const map<int, int64_t>& int64Map,
                                           const map<int, const char*>& stringMap,
                                           const map<int, float>& floatMap) {
-    // Key value pairs are not supported with AStatsEvent.
-    if (!mPlatformAtLeastR) {
+    // AStatsEvent does not support key value pairs.
+    if (useQSchema()) {
         mEventQ.begin();
         writeKeyValuePairMap(int32Map);
         writeKeyValuePairMap(int64Map);
@@ -187,34 +218,36 @@
 template void StatsEventCompat::writeKeyValuePairMap<const char*>(const map<int, const char*>&);
 
 void StatsEventCompat::addBoolAnnotation(uint8_t annotationId, bool value) {
-    // Workaround for unused params.
-    (void)annotationId;
-    (void)value;
-    //    if (mStatsEventApi) mStatsEventApi->addBoolAnnotation(mEventR, annotationId, value);
+    if (useRSchema()) {
+        mAStatsEventApi.addBoolAnnotation(mEventR, annotationId, value);
+    }
     // Don't do anything if on Q.
 }
 
 void StatsEventCompat::addInt32Annotation(uint8_t annotationId, int32_t value) {
-    // Workaround for unused params.
-    (void)annotationId;
-    (void)value;
-    //    if (mStatsEventApi) mStatsEventApi->addInt32Annotation(mEventR, annotationId, value);
+    if (useRSchema()) {
+        mAStatsEventApi.addInt32Annotation(mEventR, annotationId, value);
+    }
     // Don't do anything if on Q.
 }
 
 int StatsEventCompat::writeToSocket() {
-    if (mStatsEventApi) {
-        //        mStatsEventApi->build(mEventR);
-        //        return mStatsEventApi->write(mEventR);
+    if (useRSchema()) {
+        mAStatsEventApi.build(mEventR);
+        return mAStatsEventApi.write(mEventR);
     }
 
-    if (!mPlatformAtLeastR) return mEventQ.write(LOG_ID_STATS);
+    if (useQSchema()) return mEventQ.write(LOG_ID_STATS);
 
-    // We reach here only if we're on R, but libstatspush_compat was unable to
+    // We reach here only if we're on R, but libstatssocket was unable to
     // be loaded using dlopen.
     return -ENOLINK;
 }
 
-bool StatsEventCompat::usesNewSchema() {
-    return mStatsEventApi != nullptr;
+bool StatsEventCompat::useRSchema() {
+    return mPlatformAtLeastR && mAStatsEventApi.initialized;
+}
+
+bool StatsEventCompat::useQSchema() {
+    return !mPlatformAtLeastR;
 }
diff --git a/libstats/push_compat/include/StatsEventCompat.h b/libstats/push_compat/include/StatsEventCompat.h
index ad423a1..00bf48b 100644
--- a/libstats/push_compat/include/StatsEventCompat.h
+++ b/libstats/push_compat/include/StatsEventCompat.h
@@ -26,6 +26,26 @@
 using std::map;
 using std::vector;
 
+struct AStatsEventApi {
+    // Indicates whether the below function pointers have been set using dlsym.
+    bool initialized = false;
+
+    AStatsEvent* (*obtain)(void);
+    void (*build)(AStatsEvent*);
+    int (*write)(AStatsEvent*);
+    void (*release)(AStatsEvent*);
+    void (*setAtomId)(AStatsEvent*, uint32_t);
+    void (*writeInt32)(AStatsEvent*, int32_t);
+    void (*writeInt64)(AStatsEvent*, int64_t);
+    void (*writeFloat)(AStatsEvent*, float);
+    void (*writeBool)(AStatsEvent*, bool);
+    void (*writeByteArray)(AStatsEvent*, const uint8_t*, size_t);
+    void (*writeString)(AStatsEvent*, const char*);
+    void (*writeAttributionChain)(AStatsEvent*, const uint32_t*, const char* const*, uint8_t);
+    void (*addBoolAnnotation)(AStatsEvent*, uint8_t, bool);
+    void (*addInt32Annotation)(AStatsEvent*, uint8_t, int32_t);
+};
+
 class StatsEventCompat {
   public:
     StatsEventCompat();
@@ -57,8 +77,7 @@
     const static bool mPlatformAtLeastR;
     static bool mAttemptedLoad;
     static std::mutex mLoadLock;
-    //    static struct AStatsEvent_apiTable* mStatsEventApi;
-    static void* mStatsEventApi;
+    static AStatsEventApi mAStatsEventApi;
 
     // non-static member variables
     AStatsEvent* mEventR = nullptr;
@@ -67,6 +86,9 @@
     template <class T>
     void writeKeyValuePairMap(const map<int, T>& keyValuePairMap);
 
-    bool usesNewSchema();
+    void initializeApiTableLocked(void* handle);
+    bool useRSchema();
+    bool useQSchema();
+
     FRIEND_TEST(StatsEventCompatTest, TestDynamicLoading);
 };
diff --git a/libstats/push_compat/tests/StatsEventCompat_test.cpp b/libstats/push_compat/tests/StatsEventCompat_test.cpp
index 2be24ec..dcb3797 100644
--- a/libstats/push_compat/tests/StatsEventCompat_test.cpp
+++ b/libstats/push_compat/tests/StatsEventCompat_test.cpp
@@ -29,10 +29,10 @@
  *
  * TODO(b/146019024): migrate to android_get_device_api_level()
  */
-const static bool mPlatformAtLeastR = GetProperty("ro.build.version.release", "") == "R" ||
+const static bool mPlatformAtLeastR = GetProperty("ro.build.version.codename", "") == "R" ||
                                       android_get_device_api_level() > __ANDROID_API_Q__;
 
 TEST(StatsEventCompatTest, TestDynamicLoading) {
     StatsEventCompat event;
-    EXPECT_EQ(mPlatformAtLeastR, event.usesNewSchema());
+    EXPECT_EQ(mPlatformAtLeastR, event.useRSchema());
 }