diff --git a/libs/binder/Stability.cpp b/libs/binder/Stability.cpp
new file mode 100644
index 0000000..d6d312a
--- /dev/null
+++ b/libs/binder/Stability.cpp
@@ -0,0 +1,117 @@
+/*
+ * Copyright (C) 2019 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 <binder/Stability.h>
+
+namespace android {
+namespace internal {
+
+void Stability::markCompilationUnit(IBinder* binder) {
+#ifdef __ANDROID_VNDK__
+constexpr Stability::Level kLocalStability = Stability::Level::VENDOR;
+#else
+constexpr Stability::Level kLocalStability = Stability::Level::SYSTEM;
+#endif
+
+    status_t result = set(binder, kLocalStability);
+    LOG_ALWAYS_FATAL_IF(result != OK, "Should only mark known object.");
+}
+
+void Stability::markVintf(IBinder* binder) {
+    status_t result = set(binder, Level::VINTF);
+    LOG_ALWAYS_FATAL_IF(result != OK, "Should only mark known object.");
+}
+
+status_t Stability::set(IBinder* binder, int32_t stability) {
+    Level currentStability = get(binder);
+
+    // null binder is always written w/ 'UNDECLARED' stability
+    if (binder == nullptr) {
+        if (stability == UNDECLARED) {
+            return OK;
+        } else {
+            ALOGE("Null binder written with stability %s.", stabilityString(stability).c_str());
+            return BAD_TYPE;
+        }
+    }
+
+    if (!isDeclaredStability(stability)) {
+        // There are UNDECLARED sets because some binder interfaces don't set their stability, and
+        // then UNDECLARED stability is sent on the other side.
+        if (stability != UNDECLARED) {
+            ALOGE("Can only set known stability, not %d.", stability);
+            return BAD_TYPE;
+        }
+    }
+
+    if (currentStability != Level::UNDECLARED && currentStability != stability) {
+        ALOGE("Interface being set with %s but it is already marked as %s.",
+            stabilityString(stability).c_str(), stabilityString(stability).c_str());
+        return BAD_TYPE;
+    }
+
+    if (currentStability == stability) return OK;
+
+    binder->attachObject(
+        reinterpret_cast<void*>(&Stability::get),
+        reinterpret_cast<void*>(stability),
+        nullptr /*cleanupCookie*/,
+        nullptr /*cleanup function*/);
+
+    return OK;
+}
+
+Stability::Level Stability::get(IBinder* binder) {
+    if (binder == nullptr) return UNDECLARED;
+
+    return static_cast<Level>(reinterpret_cast<intptr_t>(
+        binder->findObject(reinterpret_cast<void*>(&Stability::get))));
+}
+
+bool Stability::check(int32_t provided, Level required) {
+    bool stable = (provided & required) == required;
+
+    if (!isDeclaredStability(provided) && provided != UNDECLARED) {
+        ALOGE("Unknown stability when checking interface stability %d.", provided);
+
+        stable = false;
+    }
+
+    if (!stable) {
+        ALOGE("Interface with %s cannot accept interface with %s.",
+            stabilityString(required).c_str(),
+            stabilityString(provided).c_str());
+    }
+
+    return stable;
+}
+
+bool Stability::isDeclaredStability(int32_t stability) {
+    return stability == VENDOR || stability == SYSTEM || stability == VINTF;
+}
+
+std::string Stability::stabilityString(int32_t stability) {
+    switch (stability) {
+        case Level::UNDECLARED: return "undeclared stability";
+        case Level::VENDOR: return "vendor stability";
+        case Level::SYSTEM: return "system stability";
+        case Level::VINTF: return "vintf stability";
+    }
+    return "unknown stability " + std::to_string(stability);
+}
+
+}  // namespace internal
+}  // namespace stability
\ No newline at end of file