Remove need for libbinderthreadstate.

Instead of having this library, libbinder/libhwbinder can keep track of
stack pointers so that when they recurse, we know which one was visited
most recently.

As with the original implementation of libbinderthreadstate, this is
somewhat of a hack. An explanation of why this is and what to do instead
is added in CallerUtils.h.

Bug: 148692216
Test: libbinderthreadstateutils_test
Change-Id: Ief28663728fb8786b06bf9e72238052b9af81d87
Merged-In: Ief28663728fb8786b06bf9e72238052b9af81d87
diff --git a/libs/binder/Android.bp b/libs/binder/Android.bp
index 1ee3853..5f9d400 100644
--- a/libs/binder/Android.bp
+++ b/libs/binder/Android.bp
@@ -138,7 +138,6 @@
         "liblog",
         "libcutils",
         "libutils",
-        "libbinderthreadstate",
     ],
 
     header_libs: [
diff --git a/libs/binder/IPCThreadState.cpp b/libs/binder/IPCThreadState.cpp
index 4981d7a..4dcd07a 100644
--- a/libs/binder/IPCThreadState.cpp
+++ b/libs/binder/IPCThreadState.cpp
@@ -17,7 +17,6 @@
 #define LOG_TAG "IPCThreadState"
 
 #include <binder/IPCThreadState.h>
-#include <binderthreadstate/IPCThreadStateBase.h>
 
 #include <binder/Binder.h>
 #include <binder/BpBinder.h>
@@ -803,6 +802,7 @@
 
 IPCThreadState::IPCThreadState()
     : mProcess(ProcessState::self()),
+      mServingStackPointer(nullptr),
       mWorkSource(kUnsetWorkSource),
       mPropagateWorkSource(false),
       mStrictModePolicy(0),
@@ -813,7 +813,6 @@
     clearCaller();
     mIn.setDataCapacity(256);
     mOut.setDataCapacity(256);
-    mIPCThreadStateBase = IPCThreadStateBase::self();
 }
 
 IPCThreadState::~IPCThreadState()
@@ -1163,9 +1162,6 @@
                 "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),
@@ -1173,6 +1169,9 @@
                 reinterpret_cast<const binder_size_t*>(tr.data.ptr.offsets),
                 tr.offsets_size/sizeof(binder_size_t), freeBuffer, this);
 
+            const void* origServingStackPointer = mServingStackPointer;
+            mServingStackPointer = &origServingStackPointer; // anything on the stack
+
             const pid_t origPid = mCallingPid;
             const char* origSid = mCallingSid;
             const uid_t origUid = mCallingUid;
@@ -1223,7 +1222,6 @@
                 error = the_context_object->transact(tr.code, buffer, &reply, tr.flags);
             }
 
-            mIPCThreadStateBase->popCurrentState();
             //ALOGI("<<<< TRANSACT from pid %d restore pid %d sid %s uid %d\n",
             //     mCallingPid, origPid, (origSid ? origSid : "<N/A>"), origUid);
 
@@ -1235,6 +1233,7 @@
                 LOG_ONEWAY("NOT sending reply to %d!", mCallingPid);
             }
 
+            mServingStackPointer = origServingStackPointer;
             mCallingPid = origPid;
             mCallingSid = origSid;
             mCallingUid = origUid;
@@ -1290,8 +1289,8 @@
     return result;
 }
 
-bool IPCThreadState::isServingCall() const {
-    return mIPCThreadStateBase->getCurrentBinderCallState() == IPCThreadStateBase::CallState::BINDER;
+const void* IPCThreadState::getServingStackPointer() const {
+     return mServingStackPointer;
 }
 
 void IPCThreadState::threadDestructor(void *st)
diff --git a/libs/binder/TEST_MAPPING b/libs/binder/TEST_MAPPING
index 7489afa..9aa7651 100644
--- a/libs/binder/TEST_MAPPING
+++ b/libs/binder/TEST_MAPPING
@@ -26,6 +26,9 @@
     },
     {
       "name": "aidl_lazy_test"
+    },
+    {
+      "name": "libbinderthreadstateutils_test"
     }
   ]
 }
diff --git a/libs/binder/include/binder/IPCThreadState.h b/libs/binder/include/binder/IPCThreadState.h
index ff9244e..4818889 100644
--- a/libs/binder/include/binder/IPCThreadState.h
+++ b/libs/binder/include/binder/IPCThreadState.h
@@ -29,8 +29,6 @@
 // ---------------------------------------------------------------------------
 namespace android {
 
-class IPCThreadStateBase;
-
 class IPCThreadState
 {
 public:
@@ -113,31 +111,12 @@
             // Service manager registration
             void                setTheContextObject(sp<BBinder> obj);
 
-            // 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.
+            // WARNING: DO NOT USE THIS API
             //
-            //  ----
-            // | 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;
+            // Returns a pointer to the stack from the last time a transaction
+            // was initiated by the kernel. Used to compare when making nested
+            // calls between multiple different transports.
+            const void*         getServingStackPointer() const;
 
             // The work source represents the UID of the process we should attribute the transaction
             // to. We use -1 to specify that the work source was not set using #setWorkSource.
@@ -181,6 +160,7 @@
             Parcel              mIn;
             Parcel              mOut;
             status_t            mLastError;
+            const void*         mServingStackPointer;
             pid_t               mCallingPid;
             const char*         mCallingSid;
             uid_t               mCallingUid;
@@ -191,7 +171,6 @@
             bool                mPropagateWorkSource;
             int32_t             mStrictModePolicy;
             int32_t             mLastTransactionBinderFlags;
-            IPCThreadStateBase  *mIPCThreadStateBase;
 
             ProcessState::CallRestriction mCallRestriction;
 };