Merge changes Ib1c28c94,Id3485a2a,If5ad5acf,Idc9054bd,Ie4e7e25d

* changes:
  libbinder_ndk: eradicate global lock
  libbinder: add IBinder::withLock
  libbinder_ndk: remove global lock on proxy delete
  libbinder: attachObject APIs work with threads
  rename binderParcelTest binderUnitTest
diff --git a/cmds/lshal/Lshal.cpp b/cmds/lshal/Lshal.cpp
index bc99f4d..a5f98c2 100644
--- a/cmds/lshal/Lshal.cpp
+++ b/cmds/lshal/Lshal.cpp
@@ -142,12 +142,10 @@
         }
     }
 
-    PipeRelay relay(out, err, interfaceName, instanceName);
-
-    if (relay.initCheck() != OK) {
-        std::string msg = "PipeRelay::initCheck() FAILED w/ " + std::to_string(relay.initCheck());
-        err << msg << std::endl;
-        LOG(ERROR) << msg;
+    auto relay = PipeRelay::create(out, err, interfaceName + "/" + instanceName);
+    if (!relay.ok()) {
+        err << "Unable to create PipeRelay: " << relay.error() << std::endl;
+        LOG(ERROR) << "Unable to create PipeRelay: " << relay.error();
         return IO_ERROR;
     }
 
@@ -155,7 +153,7 @@
         native_handle_create(1 /* numFds */, 0 /* numInts */),
         native_handle_delete);
 
-    fdHandle->data[0] = relay.fd();
+    fdHandle->data[0] = relay.value()->fd().get();
 
     hardware::Return<void> ret = base->debug(fdHandle.get(), convert(options));
 
diff --git a/cmds/lshal/PipeRelay.cpp b/cmds/lshal/PipeRelay.cpp
index 4e97636..0c3fb96 100644
--- a/cmds/lshal/PipeRelay.cpp
+++ b/cmds/lshal/PipeRelay.cpp
@@ -16,143 +16,93 @@
 
 #include "PipeRelay.h"
 
-#include <sys/select.h>
-#include <sys/time.h>
+#include <sys/poll.h>
 #include <sys/types.h>
 #include <unistd.h>
 
-#include <atomic>
+#include <chrono>
+#include <optional>
 
-#include <utils/Thread.h>
+#include <android-base/unique_fd.h>
+
+using android::base::borrowed_fd;
+using android::base::Result;
+using android::base::unique_fd;
+using std::chrono_literals::operator""ms;
 
 namespace android {
 namespace lshal {
-
-static constexpr struct timeval READ_TIMEOUT { .tv_sec = 1, .tv_usec = 0 };
-
-static std::string getThreadName(std::string interfaceName, const std::string &instanceName) {
-    auto dot = interfaceName.rfind(".");
-    if (dot != std::string::npos) interfaceName = interfaceName.substr(dot + 1);
-    return "RelayThread_" + interfaceName + "_" + instanceName;
+Result<std::unique_ptr<PipeRelay>> PipeRelay::create(std::ostream& os,
+                                                     const NullableOStream<std::ostream>& err,
+                                                     const std::string& fqName) {
+    auto pipeRelay = std::unique_ptr<PipeRelay>(new PipeRelay());
+    unique_fd rfd;
+    if (!android::base::Pipe(&rfd, &pipeRelay->mWrite)) {
+        return android::base::ErrnoError() << "pipe()";
+    }
+    // Workaround for b/111997867: need a separate FD trigger because rfd can't receive POLLHUP
+    // when the write end is closed after the write end was sent through hwbinder.
+    unique_fd rfdTrigger;
+    if (!android::base::Pipe(&rfdTrigger, &pipeRelay->mWriteTrigger)) {
+        return android::base::ErrnoError() << "pipe() for trigger";
+    }
+    pipeRelay->mThread =
+            std::make_unique<std::thread>(&PipeRelay::thread, std::move(rfd), std::move(rfdTrigger),
+                                          &os, &err, fqName);
+    return pipeRelay;
 }
 
-struct PipeRelay::RelayThread : public Thread {
-    explicit RelayThread(int fd, std::ostream &os, const NullableOStream<std::ostream> &err,
-                         const std::string &fqName);
+void PipeRelay::thread(unique_fd rfd, unique_fd rfdTrigger, std::ostream* out,
+                       const NullableOStream<std::ostream>* err, std::string fqName) {
+    while (true) {
+        pollfd pfd[2];
+        pfd[0] = {.fd = rfd.get(), .events = POLLIN};
+        pfd[1] = {.fd = rfdTrigger.get(), .events = 0};
 
-    bool threadLoop() override;
-    void setFinished();
-
-private:
-    int mFd;
-    std::ostream &mOutStream;
-    NullableOStream<std::ostream> mErrStream;
-
-    // If we were to use requestExit() and exitPending() instead, threadLoop()
-    // may not run at all by the time ~PipeRelay is called (i.e. debug() has
-    // returned from HAL). By using our own flag, we ensure that select() and
-    // read() are executed until data are drained.
-    std::atomic_bool mFinished;
-
-    std::string mFqName;
-
-    DISALLOW_COPY_AND_ASSIGN(RelayThread);
-};
-
-////////////////////////////////////////////////////////////////////////////////
-
-PipeRelay::RelayThread::RelayThread(int fd, std::ostream &os,
-                                    const NullableOStream<std::ostream> &err,
-                                    const std::string &fqName)
-      : mFd(fd), mOutStream(os), mErrStream(err), mFinished(false), mFqName(fqName) {}
-
-bool PipeRelay::RelayThread::threadLoop() {
-    char buffer[1024];
-
-    fd_set set;
-    FD_ZERO(&set);
-    FD_SET(mFd, &set);
-
-    struct timeval timeout = READ_TIMEOUT;
-
-    int res = TEMP_FAILURE_RETRY(select(mFd + 1, &set, nullptr, nullptr, &timeout));
-    if (res < 0) {
-        mErrStream << "debug " << mFqName << ": select() failed";
-        return false;
-    }
-
-    if (res == 0 || !FD_ISSET(mFd, &set)) {
-        if (mFinished) {
-            mErrStream << "debug " << mFqName
-                       << ": timeout reading from pipe, output may be truncated.";
-            return false;
+        int pollRes = poll(pfd, arraysize(pfd), -1 /* infinite timeout */);
+        if (pollRes < 0) {
+            int savedErrno = errno;
+            (*err) << "debug " << fqName << ": poll() failed: " << strerror(savedErrno)
+                   << std::endl;
+            break;
         }
-        // timeout, but debug() has not returned, so wait for HAL to finish.
-        return true;
-    }
 
-    // FD_ISSET(mFd, &set) == true. Data available, start reading
-    ssize_t n = TEMP_FAILURE_RETRY(read(mFd, buffer, sizeof(buffer)));
-
-    if (n < 0) {
-        mErrStream << "debug " << mFqName << ": read() failed";
-    }
-
-    if (n <= 0) {
-        return false;
-    }
-
-    mOutStream.write(buffer, n);
-
-    return true;
-}
-
-void PipeRelay::RelayThread::setFinished() {
-    mFinished = true;
-}
-
-////////////////////////////////////////////////////////////////////////////////
-
-PipeRelay::PipeRelay(std::ostream &os, const NullableOStream<std::ostream> &err,
-                     const std::string &interfaceName, const std::string &instanceName)
-      : mInitCheck(NO_INIT) {
-    int res = pipe(mFds);
-
-    if (res < 0) {
-        mInitCheck = -errno;
-        return;
-    }
-
-    mThread = new RelayThread(mFds[0], os, err, interfaceName + "/" + instanceName);
-    mInitCheck = mThread->run(getThreadName(interfaceName, instanceName).c_str());
-}
-
-void PipeRelay::CloseFd(int *fd) {
-    if (*fd >= 0) {
-        close(*fd);
-        *fd = -1;
+        if (pfd[0].revents & POLLIN) {
+            char buffer[1024];
+            ssize_t n = TEMP_FAILURE_RETRY(read(rfd.get(), buffer, sizeof(buffer)));
+            if (n < 0) {
+                int savedErrno = errno;
+                (*err) << "debug " << fqName << ": read() failed: " << strerror(savedErrno)
+                       << std::endl;
+                break;
+            }
+            if (n == 0) {
+                (*err) << "Warning: debug " << fqName << ": poll() indicates POLLIN but no data"
+                       << std::endl;
+                continue;
+            }
+            out->write(buffer, n);
+        }
+        if (pfd[0].revents & POLLHUP) {
+            break;
+        }
+        if (pfd[1].revents & POLLHUP) {
+            // ~PipeRelay is called on the main thread. |mWrite| has been flushed and closed.
+            // Ensure that our read end of the pipe doesn't have pending data, then exit.
+            if ((pfd[0].revents & POLLIN) == 0) {
+                break;
+            }
+        }
     }
 }
 
 PipeRelay::~PipeRelay() {
-    CloseFd(&mFds[1]);
-
-    if (mThread != nullptr) {
-        mThread->setFinished();
+    mWrite.reset();
+    mWriteTrigger.reset();
+    if (mThread != nullptr && mThread->joinable()) {
         mThread->join();
-        mThread.clear();
     }
-
-    CloseFd(&mFds[0]);
 }
 
-status_t PipeRelay::initCheck() const {
-    return mInitCheck;
-}
-
-int PipeRelay::fd() const {
-    return mFds[1];
-}
-
-}  // namespace lshal
-}  // namespace android
+} // namespace lshal
+} // namespace android
diff --git a/cmds/lshal/PipeRelay.h b/cmds/lshal/PipeRelay.h
index bd994b4..45ba982 100644
--- a/cmds/lshal/PipeRelay.h
+++ b/cmds/lshal/PipeRelay.h
@@ -16,42 +16,43 @@
 
 #pragma once
 
+#include <thread>
+
 #include <android-base/macros.h>
-#include <ostream>
+#include <android-base/result.h>
+#include <android-base/unique_fd.h>
 #include <utils/Errors.h>
 #include <utils/RefBase.h>
+#include <ostream>
 
 #include "NullableOStream.h"
 
 namespace android {
 namespace lshal {
 
-/* Creates an AF_UNIX socketpair and spawns a thread that relays any data
+/**
+ * Creates a pipe and spawns a thread that relays any data
  * written to the "write"-end of the pair to the specified output stream "os".
  */
 struct PipeRelay {
-    explicit PipeRelay(std::ostream& os,
-                       const NullableOStream<std::ostream>& err,
-                       const std::string& interfaceName,
-                       const std::string& instanceName);
+    static android::base::Result<std::unique_ptr<PipeRelay>> create(
+            std::ostream& os, const NullableOStream<std::ostream>& err, const std::string& fqName);
     ~PipeRelay();
 
-    status_t initCheck() const;
-
     // Returns the file descriptor corresponding to the "write"-end of the
     // connection.
-    int fd() const;
+    android::base::borrowed_fd fd() const { return mWrite; }
 
 private:
-    struct RelayThread;
-
-    status_t mInitCheck;
-    int mFds[2];
-    sp<RelayThread> mThread;
-
-    static void CloseFd(int *fd);
-
+    PipeRelay() = default;
     DISALLOW_COPY_AND_ASSIGN(PipeRelay);
+    static void thread(android::base::unique_fd rfd, android::base::unique_fd rfdTrigger,
+                       std::ostream* out, const NullableOStream<std::ostream>* err,
+                       std::string fqName);
+
+    android::base::unique_fd mWrite;
+    android::base::unique_fd mWriteTrigger;
+    std::unique_ptr<std::thread> mThread;
 };
 
 }  // namespace lshal
diff --git a/libs/binder/Android.bp b/libs/binder/Android.bp
index d8f8e55..da570f3 100644
--- a/libs/binder/Android.bp
+++ b/libs/binder/Android.bp
@@ -151,6 +151,7 @@
                 "libbase",
             ],
             srcs: [
+                "ServiceManagerHost.cpp",
                 "UtilsHost.cpp",
             ],
         },
diff --git a/libs/binder/IServiceManager.cpp b/libs/binder/IServiceManager.cpp
index d421060..2175fd4 100644
--- a/libs/binder/IServiceManager.cpp
+++ b/libs/binder/IServiceManager.cpp
@@ -35,6 +35,8 @@
 
 #ifdef __ANDROID__
 #include <cutils/properties.h>
+#else
+#include "ServiceManagerHost.h"
 #endif
 
 #include "Static.h"
@@ -84,8 +86,19 @@
     IBinder* onAsBinder() override {
         return IInterface::asBinder(mTheRealServiceManager).get();
     }
-private:
+
+protected:
     sp<AidlServiceManager> mTheRealServiceManager;
+
+    // Directly get the service in a way that, for lazy services, requests the service to be started
+    // if it is not currently started. This way, calls directly to ServiceManagerShim::getService
+    // will still have the 5s delay that is expected by a large amount of Android code.
+    //
+    // When implementing ServiceManagerShim, use realGetService instead of
+    // mTheRealServiceManager->getService so that it can be overridden in ServiceManagerHostShim.
+    virtual Status realGetService(const std::string& name, sp<IBinder>* _aidl_return) {
+        return mTheRealServiceManager->getService(name, _aidl_return);
+    }
 };
 
 [[clang::no_destroy]] static std::once_flag gSmOnce;
@@ -319,7 +332,7 @@
     const std::string name = String8(name16).c_str();
 
     sp<IBinder> out;
-    if (Status status = mTheRealServiceManager->getService(name, &out); !status.isOk()) {
+    if (Status status = realGetService(name, &out); !status.isOk()) {
         ALOGW("Failed to getService in waitForService for %s: %s", name.c_str(),
               status.toString8().c_str());
         return nullptr;
@@ -363,7 +376,7 @@
         // - init gets death signal, but doesn't know it needs to restart
         //   the service
         // - we need to request service again to get it to start
-        if (Status status = mTheRealServiceManager->getService(name, &out); !status.isOk()) {
+        if (Status status = realGetService(name, &out); !status.isOk()) {
             ALOGW("Failed to getService in waitForService on later try for %s: %s", name.c_str(),
                   status.toString8().c_str());
             return nullptr;
@@ -412,4 +425,38 @@
     return declared ? std::optional<String16>(String16(declared.value().c_str())) : std::nullopt;
 }
 
+#ifndef __ANDROID__
+// ServiceManagerShim for host. Implements the old libbinder android::IServiceManager API.
+// The internal implementation of the AIDL interface android::os::IServiceManager calls into
+// on-device service manager.
+class ServiceManagerHostShim : public ServiceManagerShim {
+public:
+    using ServiceManagerShim::ServiceManagerShim;
+    // ServiceManagerShim::getService is based on checkService, so no need to override it.
+    sp<IBinder> checkService(const String16& name) const override {
+        return getDeviceService({String8(name).c_str()});
+    }
+
+protected:
+    // Override realGetService for ServiceManagerShim::waitForService.
+    Status realGetService(const std::string& name, sp<IBinder>* _aidl_return) {
+        *_aidl_return = getDeviceService({"-g", name});
+        return Status::ok();
+    }
+};
+sp<IServiceManager> createRpcDelegateServiceManager() {
+    auto binder = getDeviceService({"manager"});
+    if (binder == nullptr) {
+        ALOGE("getDeviceService(\"manager\") returns null");
+        return nullptr;
+    }
+    auto interface = AidlServiceManager::asInterface(binder);
+    if (interface == nullptr) {
+        ALOGE("getDeviceService(\"manager\") returns non service manager");
+        return nullptr;
+    }
+    return sp<ServiceManagerHostShim>::make(interface);
+}
+#endif
+
 } // namespace android
diff --git a/libs/binder/LazyServiceRegistrar.cpp b/libs/binder/LazyServiceRegistrar.cpp
index 6165911..f66993f 100644
--- a/libs/binder/LazyServiceRegistrar.cpp
+++ b/libs/binder/LazyServiceRegistrar.cpp
@@ -40,9 +40,9 @@
 
     void setActiveServicesCallback(const std::function<bool(bool)>& activeServicesCallback);
 
-    bool tryUnregister();
+    bool tryUnregisterLocked();
 
-    void reRegister();
+    void reRegisterLocked();
 
 protected:
     Status onClients(const sp<IBinder>& service, bool clients) override;
@@ -59,6 +59,9 @@
         bool registered = true;
     };
 
+    bool registerServiceLocked(const sp<IBinder>& service, const std::string& name,
+                               bool allowIsolated, int dumpFlags);
+
     /**
      * Looks up a service guaranteed to be registered (service from onClients).
      */
@@ -68,7 +71,7 @@
      * Unregisters all services that we can. If we can't unregister all, re-register other
      * services.
      */
-    void tryShutdown();
+    void tryShutdownLocked();
 
     /**
      * Try to shutdown the process, unless:
@@ -76,7 +79,10 @@
      * - The active services count callback returns 'true', or
      * - Some services have clients.
      */
-    void maybeTryShutdown();
+    void maybeTryShutdownLocked();
+
+    // for below
+    std::mutex mMutex;
 
     // count of services with clients
     size_t mNumConnectedServices;
@@ -117,6 +123,13 @@
 
 bool ClientCounterCallbackImpl::registerService(const sp<IBinder>& service, const std::string& name,
                                             bool allowIsolated, int dumpFlags) {
+    std::lock_guard<std::mutex> lock(mMutex);
+    return registerServiceLocked(service, name, allowIsolated, dumpFlags);
+}
+
+bool ClientCounterCallbackImpl::registerServiceLocked(const sp<IBinder>& service,
+                                                      const std::string& name, bool allowIsolated,
+                                                      int dumpFlags) {
     auto manager = interface_cast<AidlServiceManager>(asBinder(defaultServiceManager()));
 
     bool reRegister = mRegisteredServices.count(name) > 0;
@@ -164,14 +177,15 @@
 }
 
 void ClientCounterCallbackImpl::forcePersist(bool persist) {
+    std::lock_guard<std::mutex> lock(mMutex);
     mForcePersist = persist;
     if (!mForcePersist) {
         // Attempt a shutdown in case the number of clients hit 0 while the flag was on
-        maybeTryShutdown();
+        maybeTryShutdownLocked();
     }
 }
 
-bool ClientCounterCallbackImpl::tryUnregister() {
+bool ClientCounterCallbackImpl::tryUnregisterLocked() {
     auto manager = interface_cast<AidlServiceManager>(asBinder(defaultServiceManager()));
 
     for (auto& [name, entry] : mRegisteredServices) {
@@ -187,15 +201,14 @@
     return true;
 }
 
-void ClientCounterCallbackImpl::reRegister() {
+void ClientCounterCallbackImpl::reRegisterLocked() {
     for (auto& [name, entry] : mRegisteredServices) {
         // re-register entry if not already registered
         if (entry.registered) {
             continue;
         }
 
-        if (!registerService(entry.service, name, entry.allowIsolated,
-                             entry.dumpFlags)) {
+        if (!registerServiceLocked(entry.service, name, entry.allowIsolated, entry.dumpFlags)) {
             // Must restart. Otherwise, clients will never be able to get a hold of this service.
             LOG_ALWAYS_FATAL("Bad state: could not re-register services");
         }
@@ -204,7 +217,7 @@
     }
 }
 
-void ClientCounterCallbackImpl::maybeTryShutdown() {
+void ClientCounterCallbackImpl::maybeTryShutdownLocked() {
     if (mForcePersist) {
         ALOGI("Shutdown prevented by forcePersist override flag.");
         return;
@@ -223,15 +236,12 @@
     // client count change event, try to shutdown the process if its services
     // have no clients.
     if (!handledInCallback && mNumConnectedServices == 0) {
-        tryShutdown();
+        tryShutdownLocked();
     }
 }
 
-/**
- * onClients is oneway, so no need to worry about multi-threading. Note that this means multiple
- * invocations could occur on different threads however.
- */
 Status ClientCounterCallbackImpl::onClients(const sp<IBinder>& service, bool clients) {
+    std::lock_guard<std::mutex> lock(mMutex);
     auto & [name, registered] = *assertRegisteredService(service);
     if (registered.clients == clients) {
         LOG_ALWAYS_FATAL("Process already thought %s had clients: %d but servicemanager has "
@@ -252,23 +262,24 @@
     ALOGI("Process has %zu (of %zu available) client(s) in use after notification %s has clients: %d",
           mNumConnectedServices, mRegisteredServices.size(), name.c_str(), clients);
 
-    maybeTryShutdown();
+    maybeTryShutdownLocked();
     return Status::ok();
 }
 
- void ClientCounterCallbackImpl::tryShutdown() {
-     ALOGI("Trying to shut down the service. No clients in use for any service in process.");
+void ClientCounterCallbackImpl::tryShutdownLocked() {
+    ALOGI("Trying to shut down the service. No clients in use for any service in process.");
 
-    if (tryUnregister()) {
-         ALOGI("Unregistered all clients and exiting");
-         exit(EXIT_SUCCESS);
-     }
+    if (tryUnregisterLocked()) {
+        ALOGI("Unregistered all clients and exiting");
+        exit(EXIT_SUCCESS);
+    }
 
-    reRegister();
+    reRegisterLocked();
 }
 
 void ClientCounterCallbackImpl::setActiveServicesCallback(const std::function<bool(bool)>&
                                                           activeServicesCallback) {
+    std::lock_guard<std::mutex> lock(mMutex);
     mActiveServicesCallback = activeServicesCallback;
 }
 
@@ -291,11 +302,15 @@
 }
 
 bool ClientCounterCallback::tryUnregister() {
-    return mImpl->tryUnregister();
+    // see comments in header, this should only be called from the active
+    // services callback, see also b/191781736
+    return mImpl->tryUnregisterLocked();
 }
 
 void ClientCounterCallback::reRegister() {
-    mImpl->reRegister();
+    // see comments in header, this should only be called from the active
+    // services callback, see also b/191781736
+    mImpl->reRegisterLocked();
 }
 
 }  // namespace internal
diff --git a/libs/binder/RpcServer.cpp b/libs/binder/RpcServer.cpp
index a8f3fa8..2a87ae4 100644
--- a/libs/binder/RpcServer.cpp
+++ b/libs/binder/RpcServer.cpp
@@ -278,7 +278,7 @@
                 return;
             }
 
-            RpcAddress sessionId = RpcAddress::zero();
+            sessionId = RpcAddress::zero();
             size_t tries = 0;
             do {
                 // don't block if there is some entropy issue
diff --git a/libs/binder/RpcSession.cpp b/libs/binder/RpcSession.cpp
index 4f55eef..ee5e8bb 100644
--- a/libs/binder/RpcSession.cpp
+++ b/libs/binder/RpcSession.cpp
@@ -198,6 +198,8 @@
     uint8_t* buffer = reinterpret_cast<uint8_t*>(data);
     uint8_t* end = buffer + size;
 
+    MAYBE_WAIT_IN_FLAKE_MODE;
+
     status_t status;
     while ((status = triggerablePollRead(fd)) == OK) {
         ssize_t readSize = TEMP_FAILURE_RETRY(recv(fd.get(), buffer, end - buffer, MSG_NOSIGNAL));
diff --git a/libs/binder/RpcState.cpp b/libs/binder/RpcState.cpp
index fd2eff6..b5eaaa3 100644
--- a/libs/binder/RpcState.cpp
+++ b/libs/binder/RpcState.cpp
@@ -26,12 +26,28 @@
 #include "Debug.h"
 #include "RpcWireFormat.h"
 
+#include <random>
+
 #include <inttypes.h>
 
 namespace android {
 
 using base::ScopeGuard;
 
+#ifdef RPC_FLAKE_PRONE
+void rpcMaybeWaitToFlake() {
+    static std::random_device r;
+    static std::mutex m;
+
+    unsigned num;
+    {
+        std::lock_guard<std::mutex> lock(m);
+        num = r();
+    }
+    if (num % 10 == 0) usleep(num % 1000);
+}
+#endif
+
 RpcState::RpcState() {}
 RpcState::~RpcState() {}
 
@@ -260,6 +276,8 @@
     LOG_RPC_DETAIL("Sending %s on fd %d: %s", what, connection->fd.get(),
                    hexString(data, size).c_str());
 
+    MAYBE_WAIT_IN_FLAKE_MODE;
+
     if (size > std::numeric_limits<ssize_t>::max()) {
         ALOGE("Cannot send %s at size %zu (too big)", what, size);
         (void)session->shutdownAndWait(false);
@@ -483,7 +501,7 @@
     delete[] const_cast<uint8_t*>(data - offsetof(RpcWireReply, data));
     (void)dataSize;
     LOG_ALWAYS_FATAL_IF(objects != nullptr);
-    LOG_ALWAYS_FATAL_IF(objectsCount, 0);
+    LOG_ALWAYS_FATAL_IF(objectsCount != 0, "%zu objects remaining", objectsCount);
 }
 
 status_t RpcState::waitForReply(const sp<RpcSession::RpcConnection>& connection,
diff --git a/libs/binder/RpcState.h b/libs/binder/RpcState.h
index 529dee5..8201eba 100644
--- a/libs/binder/RpcState.h
+++ b/libs/binder/RpcState.h
@@ -42,6 +42,15 @@
 #define LOG_RPC_DETAIL(...) ALOGV(__VA_ARGS__) // for type checking
 #endif
 
+#define RPC_FLAKE_PRONE false
+
+#ifdef RPC_FLAKE_PRONE
+void rpcMaybeWaitToFlake();
+#define MAYBE_WAIT_IN_FLAKE_MODE rpcMaybeWaitToFlake()
+#else
+#define MAYBE_WAIT_IN_FLAKE_MODE do {} while (false)
+#endif
+
 /**
  * Abstracts away management of ref counts and the wire format from
  * RpcSession
diff --git a/libs/binder/ServiceManagerHost.cpp b/libs/binder/ServiceManagerHost.cpp
new file mode 100644
index 0000000..07f5778
--- /dev/null
+++ b/libs/binder/ServiceManagerHost.cpp
@@ -0,0 +1,176 @@
+/*
+ * Copyright (C) 2021 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 "ServiceManagerHost.h"
+
+#include <android-base/parseint.h>
+#include <android-base/strings.h>
+#include <binder/IServiceManager.h>
+#include <binder/RpcSession.h>
+
+#include "UtilsHost.h"
+
+namespace android {
+
+namespace {
+
+const void* kDeviceServiceExtraId = "DeviceServiceExtra";
+
+// Parse stdout of program execution to string. If any error, return 0.
+unsigned int parsePortNumber(const std::string& out, const std::string& what) {
+    auto trimmed = android::base::Trim(out);
+    unsigned int port = 0;
+    if (!android::base::ParseUint(trimmed, &port)) {
+        int savedErrno = errno;
+        ALOGE("%s is not a valid %s: %s", trimmed.c_str(), what.c_str(), strerror(savedErrno));
+        return 0;
+    }
+    if (port == 0) {
+        ALOGE("0 is not a valid %s", what.c_str());
+        return 0; // explicitly
+    }
+    return port;
+}
+
+// RAII object for adb forwarding
+class AdbForwarder {
+public:
+    AdbForwarder() = default;
+    static std::optional<AdbForwarder> forward(unsigned int devicePort);
+    AdbForwarder(AdbForwarder&& other) noexcept { (*this) = std::move(other); }
+    AdbForwarder& operator=(AdbForwarder&&) noexcept;
+    ~AdbForwarder();
+    [[nodiscard]] const std::optional<unsigned int>& hostPort() const { return mPort; }
+
+private:
+    DISALLOW_COPY_AND_ASSIGN(AdbForwarder);
+    explicit AdbForwarder(unsigned int port) : mPort(port) {}
+    std::optional<unsigned int> mPort;
+};
+std::optional<AdbForwarder> AdbForwarder::forward(unsigned int devicePort) {
+    auto result =
+            execute({"adb", "forward", "tcp:0", "tcp:" + std::to_string(devicePort)}, nullptr);
+    if (!result.ok()) {
+        ALOGE("Unable to run `adb forward tcp:0 tcp:%d`: %s", devicePort,
+              result.error().message().c_str());
+        return std::nullopt;
+    }
+    // Must end with exit code 0 (`has_value() && value() == 0`)
+    if (result->exitCode.value_or(1) != 0) {
+        ALOGE("Unable to run `adb forward tcp:0 tcp:%d`, command exits with %s", devicePort,
+              result->toString().c_str());
+        return std::nullopt;
+    }
+    if (!result->stderr.empty()) {
+        LOG_HOST("`adb forward tcp:0 tcp:%d` writes to stderr: %s", devicePort,
+                 result->stderr.c_str());
+    }
+
+    unsigned int hostPort = parsePortNumber(result->stdout, "host port");
+    if (hostPort == 0) return std::nullopt;
+
+    return AdbForwarder(hostPort);
+}
+
+AdbForwarder& AdbForwarder::operator=(AdbForwarder&& other) noexcept {
+    std::swap(mPort, other.mPort);
+    return *this;
+}
+
+AdbForwarder::~AdbForwarder() {
+    if (!mPort.has_value()) return;
+
+    auto result = execute({"adb", "forward", "--remove", "tcp:" + std::to_string(*mPort)}, nullptr);
+    if (!result.ok()) {
+        ALOGE("Unable to run `adb forward --remove tcp:%d`: %s", *mPort,
+              result.error().message().c_str());
+        return;
+    }
+    // Must end with exit code 0 (`has_value() && value() == 0`)
+    if (result->exitCode.value_or(1) != 0) {
+        ALOGE("Unable to run `adb forward --remove tcp:%d`, command exits with %s", *mPort,
+              result->toString().c_str());
+        return;
+    }
+    if (!result->stderr.empty()) {
+        LOG_HOST("`adb forward --remove tcp:%d` writes to stderr: %s", *mPort,
+                 result->stderr.c_str());
+    }
+
+    LOG_HOST("Successfully run `adb forward --remove tcp:%d`", *mPort);
+}
+
+void cleanupCommandResult(const void* id, void* obj, void* /* cookie */) {
+    LOG_ALWAYS_FATAL_IF(id != kDeviceServiceExtraId,
+                        "cleanupCommandResult invoked with mismatched ID %p, "
+                        "expected %p",
+                        id, kDeviceServiceExtraId);
+    auto ptr = static_cast<CommandResult*>(obj);
+    delete ptr;
+}
+
+} // namespace
+
+sp<IBinder> getDeviceService(std::vector<std::string>&& serviceDispatcherArgs) {
+    std::vector<std::string> prefix{"adb", "shell", "servicedispatcher"};
+    serviceDispatcherArgs.insert(serviceDispatcherArgs.begin(), prefix.begin(), prefix.end());
+
+    auto result = execute(std::move(serviceDispatcherArgs), &CommandResult::stdoutEndsWithNewLine);
+    if (!result.ok()) {
+        ALOGE("%s", result.error().message().c_str());
+        return nullptr;
+    }
+
+    // `servicedispatcher` process must be alive to keep the port open.
+    if (result->exitCode.has_value()) {
+        ALOGE("Command exits with: %s", result->toString().c_str());
+        return nullptr;
+    }
+    if (!result->stderr.empty()) {
+        LOG_HOST("servicedispatcher writes to stderr: %s", result->stderr.c_str());
+    }
+
+    if (!result->stdoutEndsWithNewLine()) {
+        ALOGE("Unexpected command result: %s", result->toString().c_str());
+        return nullptr;
+    }
+
+    unsigned int devicePort = parsePortNumber(result->stdout, "device port");
+    if (devicePort == 0) return nullptr;
+
+    auto forwardResult = AdbForwarder::forward(devicePort);
+    if (!forwardResult.has_value()) {
+        return nullptr;
+    }
+    LOG_ALWAYS_FATAL_IF(!forwardResult->hostPort().has_value());
+
+    auto rpcSession = RpcSession::make();
+    if (!rpcSession->setupInetClient("127.0.0.1", *forwardResult->hostPort())) {
+        ALOGE("Unable to set up inet client on host port %u", *forwardResult->hostPort());
+        return nullptr;
+    }
+    auto binder = rpcSession->getRootObject();
+    if (binder == nullptr) {
+        ALOGE("RpcSession::getRootObject returns nullptr");
+        return nullptr;
+    }
+    binder->attachObject(kDeviceServiceExtraId,
+                         static_cast<void*>(new CommandResult(std::move(*result))), nullptr,
+                         &cleanupCommandResult);
+    return binder;
+}
+
+} // namespace android
diff --git a/libs/binder/ServiceManagerHost.h b/libs/binder/ServiceManagerHost.h
new file mode 100644
index 0000000..e59724c
--- /dev/null
+++ b/libs/binder/ServiceManagerHost.h
@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2021 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 <android-base/macros.h>
+#include <android/os/IServiceManager.h>
+
+namespace android {
+
+// Get a service on device by running servicedispatcher with the given args, e.g.
+//     getDeviceService({"foo"});
+// Return nullptr on any error.
+// When the returned binder object is destroyed, remove adb forwarding and kills
+// the long-running servicedispatcher process.
+sp<IBinder> getDeviceService(std::vector<std::string>&& serviceDispatcherArgs);
+
+} // namespace android
diff --git a/libs/binder/TEST_MAPPING b/libs/binder/TEST_MAPPING
index fbbfcdc..748fa72 100644
--- a/libs/binder/TEST_MAPPING
+++ b/libs/binder/TEST_MAPPING
@@ -31,7 +31,7 @@
       "name": "binderStabilityTest"
     },
     {
-      "name": "binderUtilsTest"
+      "name": "binderUtilsHostTest"
     },
     {
       "name": "libbinder_ndk_unit_test"
diff --git a/libs/binder/include/binder/IServiceManager.h b/libs/binder/include/binder/IServiceManager.h
index 3dbe2c4..8e46147 100644
--- a/libs/binder/include/binder/IServiceManager.h
+++ b/libs/binder/include/binder/IServiceManager.h
@@ -169,4 +169,17 @@
                             int32_t* outPid, int32_t* outUid);
 bool checkPermission(const String16& permission, pid_t pid, uid_t uid);
 
+#ifndef __ANDROID__
+// Create an IServiceManager that delegates the service manager on the device via adb.
+// This is can be set as the default service manager at program start, so that
+// defaultServiceManager() returns it:
+//    int main() {
+//        setDefaultServiceManager(createRpcDelegateServiceManager());
+//        auto sm = defaultServiceManager();
+//        // ...
+//    }
+// Resources are cleaned up when the object is destroyed.
+sp<IServiceManager> createRpcDelegateServiceManager();
+#endif
+
 } // namespace android
diff --git a/libs/binder/include/binder/LazyServiceRegistrar.h b/libs/binder/include/binder/LazyServiceRegistrar.h
index f3ba830..2e22b84 100644
--- a/libs/binder/include/binder/LazyServiceRegistrar.h
+++ b/libs/binder/include/binder/LazyServiceRegistrar.h
@@ -79,9 +79,10 @@
       */
      void setActiveServicesCallback(const std::function<bool(bool)>& activeServicesCallback);
 
-    /**
+     /**
       * Try to unregister all services previously registered with 'registerService'.
-      * Returns 'true' if successful.
+      * Returns 'true' if successful. This should only be called within the callback registered by
+      * setActiveServicesCallback.
       */
      bool tryUnregister();