diff --git a/libs/binder/Android.bp b/libs/binder/Android.bp
index 61b8818..da10687 100644
--- a/libs/binder/Android.bp
+++ b/libs/binder/Android.bp
@@ -119,6 +119,7 @@
         "liblog",
         "libcutils",
         "libutils",
+        "libbinderthreadstate",
     ],
 
     header_libs: [
diff --git a/libs/binder/IPCThreadState.cpp b/libs/binder/IPCThreadState.cpp
index b2217b5..f052bcb 100644
--- a/libs/binder/IPCThreadState.cpp
+++ b/libs/binder/IPCThreadState.cpp
@@ -17,6 +17,7 @@
 #define LOG_TAG "IPCThreadState"
 
 #include <binder/IPCThreadState.h>
+#include <binderthreadstate/IPCThreadStateBase.h>
 
 #include <binder/Binder.h>
 #include <binder/BpBinder.h>
@@ -742,6 +743,7 @@
     clearCaller();
     mIn.setDataCapacity(256);
     mOut.setDataCapacity(256);
+    mIPCThreadStateBase = IPCThreadStateBase::self();
 }
 
 IPCThreadState::~IPCThreadState()
@@ -1082,6 +1084,9 @@
                 "Not enough command data for brTRANSACTION");
             if (result != NO_ERROR) break;
 
+            //Record the fact that we're in a binder call.
+            mIPCThreadStateBase->pushCurrentState(
+                IPCThreadStateBase::CallState::BINDER);
             Parcel buffer;
             buffer.ipcSetDataReference(
                 reinterpret_cast<const uint8_t*>(tr.data.ptr.buffer),
@@ -1129,6 +1134,7 @@
                 error = the_context_object->transact(tr.code, buffer, &reply, tr.flags);
             }
 
+            mIPCThreadStateBase->popCurrentState();
             //ALOGI("<<<< TRANSACT from pid %d restore pid %d uid %d\n",
             //     mCallingPid, origPid, origUid);
 
@@ -1192,6 +1198,10 @@
     return result;
 }
 
+bool IPCThreadState::isServingCall() const {
+    return mIPCThreadStateBase->getCurrentBinderCallState() == IPCThreadStateBase::CallState::BINDER;
+}
+
 void IPCThreadState::threadDestructor(void *st)
 {
         IPCThreadState* const self = static_cast<IPCThreadState*>(st);
diff --git a/libs/binder/include/binder/IPCThreadState.h b/libs/binder/include/binder/IPCThreadState.h
index dce3f38..40b51ad 100644
--- a/libs/binder/include/binder/IPCThreadState.h
+++ b/libs/binder/include/binder/IPCThreadState.h
@@ -29,6 +29,8 @@
 // ---------------------------------------------------------------------------
 namespace android {
 
+class IPCThreadStateBase;
+
 class IPCThreadState
 {
 public:
@@ -89,6 +91,33 @@
             // the maximum number of binder threads threads allowed for this process.
             void                blockUntilThreadAvailable();
 
+
+            // Is this thread currently serving a binder call. This method
+            // returns true if while traversing backwards from the function call
+            // stack for this thread, we encounter a function serving a binder
+            // call before encountering a hwbinder call / hitting the end of the
+            // call stack.
+            // Eg: If thread T1 went through the following call pattern
+            //     1) T1 receives and executes hwbinder call H1.
+            //     2) While handling H1, T1 makes binder call B1.
+            //     3) The handler of B1, calls into T1 with a callback B2.
+            // If isServingCall() is called during H1 before 3), this method
+            // will return false, else true.
+            //
+            //  ----
+            // | B2 | ---> While callback B2 is being handled, during 3).
+            //  ----
+            // | H1 | ---> While H1 is being handled.
+            //  ----
+            // Fig: Thread Call stack while handling B2
+            //
+            // This is since after 3), while traversing the thread call stack,
+            // we hit a binder call before a hwbinder call / end of stack. This
+            // method may be typically used to determine whether to use
+            // hardware::IPCThreadState methods or IPCThreadState methods to
+            // infer information about thread state.
+            bool                isServingCall() const;
+
 private:
                                 IPCThreadState();
                                 ~IPCThreadState();
@@ -128,6 +157,7 @@
             uid_t               mCallingUid;
             int32_t             mStrictModePolicy;
             int32_t             mLastTransactionBinderFlags;
+            IPCThreadStateBase  *mIPCThreadStateBase;
 };
 
 }; // namespace android
diff --git a/libs/binderthreadstate/Android.bp b/libs/binderthreadstate/Android.bp
new file mode 100644
index 0000000..7106cbb
--- /dev/null
+++ b/libs/binderthreadstate/Android.bp
@@ -0,0 +1,44 @@
+// Copyright (C) 2018 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.
+
+cc_library {
+    name: "libbinderthreadstate",
+    recovery_available: true,
+    vendor_available: false,
+    vndk: {
+        enabled: true,
+        support_system_process: true,
+    },
+    srcs: [
+        "IPCThreadStateBase.cpp",
+    ],
+
+    shared_libs: [
+        "libbase",
+        "liblog",
+        "libcutils",
+        "libutils",
+    ],
+
+    export_include_dirs: ["include"],
+
+    sanitize: {
+        misc_undefined: ["integer"],
+    },
+
+    cflags: [
+        "-Wall",
+        "-Werror",
+    ],
+}
diff --git a/libs/binderthreadstate/IPCThreadStateBase.cpp b/libs/binderthreadstate/IPCThreadStateBase.cpp
new file mode 100644
index 0000000..fede151
--- /dev/null
+++ b/libs/binderthreadstate/IPCThreadStateBase.cpp
@@ -0,0 +1,89 @@
+/*
+ * Copyright (C) 2018 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.
+ */
+
+#define LOG_TAG "IPCThreadStateBase"
+
+#include <binderthreadstate/IPCThreadStateBase.h>
+#include <android-base/macros.h>
+
+#include <utils/Log.h>
+
+#include <errno.h>
+#include <inttypes.h>
+#include <pthread.h>
+
+namespace android {
+
+static pthread_mutex_t gTLSMutex = PTHREAD_MUTEX_INITIALIZER;
+static bool gHaveTLS = false;
+static pthread_key_t gTLS = 0;
+
+IPCThreadStateBase::IPCThreadStateBase() {
+    pthread_setspecific(gTLS, this);
+}
+
+IPCThreadStateBase* IPCThreadStateBase::self()
+{
+    if (gHaveTLS) {
+restart:
+        const pthread_key_t k = gTLS;
+        IPCThreadStateBase* st = (IPCThreadStateBase*)pthread_getspecific(k);
+        if (st) return st;
+        return new IPCThreadStateBase;
+    }
+
+    pthread_mutex_lock(&gTLSMutex);
+    if (!gHaveTLS) {
+        int key_create_value = pthread_key_create(&gTLS, threadDestructor);
+        if (key_create_value != 0) {
+            pthread_mutex_unlock(&gTLSMutex);
+            ALOGW("IPCThreadStateBase::self() unable to create TLS key, expect a crash: %s\n",
+                    strerror(key_create_value));
+            return nullptr;
+        }
+        gHaveTLS = true;
+    }
+    pthread_mutex_unlock(&gTLSMutex);
+    goto restart;
+}
+
+void IPCThreadStateBase::pushCurrentState(CallState callState) {
+    mCallStateStack.emplace(callState);
+}
+
+IPCThreadStateBase::CallState IPCThreadStateBase::popCurrentState() {
+    ALOG_ASSERT(mCallStateStack.size > 0);
+    CallState val = mCallStateStack.top();
+    mCallStateStack.pop();
+    return val;
+}
+
+IPCThreadStateBase::CallState IPCThreadStateBase::getCurrentBinderCallState() {
+    if (mCallStateStack.size() > 0) {
+        return mCallStateStack.top();
+    }
+    return CallState::NONE;
+}
+
+void IPCThreadStateBase::threadDestructor(void *st)
+{
+    IPCThreadStateBase* const self = static_cast<IPCThreadStateBase*>(st);
+    if (self) {
+        delete self;
+    }
+}
+
+}; // namespace android
diff --git a/libs/binderthreadstate/include/binderthreadstate/IPCThreadStateBase.h b/libs/binderthreadstate/include/binderthreadstate/IPCThreadStateBase.h
new file mode 100644
index 0000000..6fdcc84
--- /dev/null
+++ b/libs/binderthreadstate/include/binderthreadstate/IPCThreadStateBase.h
@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2018 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.
+ */
+
+#ifndef BINDER_THREADSTATE_IPC_THREADSTATE_BASE_H
+#define BINDER_THREADSTATE_IPC_THREADSTATE_BASE_H
+
+#include <stack>
+namespace android {
+
+class IPCThreadStateBase {
+public:
+    enum CallState {
+        HWBINDER,
+        BINDER,
+        NONE,
+    };
+    static IPCThreadStateBase* self();
+    void pushCurrentState(CallState callState);
+    CallState popCurrentState();
+    CallState getCurrentBinderCallState();
+
+private:
+    IPCThreadStateBase();
+    static void threadDestructor(void *st);
+
+    std::stack<CallState> mCallStateStack;
+};
+
+}; // namespace android
+
+#endif // BINDER_THREADSTATE_IPC_THREADSTATE_BASE_H