vulkan-cereal/host-common/AndroidPipe.cpp

// Copyright 2020 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 "AndroidPipe.h"
#include "android_pipe_base.h"

#include "base/Optional.h"
#include "base/StringFormat.h"
#include "base/MemStream.h"
#include "base/Lock.h"
#include "android_pipe_device.h"
#include "android_pipe_host.h"
#include "DeviceContextRunner.h"
#include "VmLock.h"

#include <algorithm>
#include <memory>
#include <string>
#include <vector>
#include <unordered_set>

#include <assert.h>
#include <string.h>

#define DEBUG 0

#if DEBUG >= 1
#include <stdio.h>
#define D(...) fprintf(stderr, __VA_ARGS__), fprintf(stderr, "\n")
#else
#define D(...) (void)0
#endif

#if DEBUG >= 2
#define DD(...) fprintf(stderr, __VA_ARGS__), fprintf(stderr, "\n")
#else
#define DD(...) (void)0
#endif

#define E(...) fprintf(stderr, "ERROR:" __VA_ARGS__), fprintf(stderr, "\n")

static const AndroidPipeHwFuncs* getPipeHwFuncs(const void* hwPipe) {
    return *static_cast<const AndroidPipeHwFuncs* const *>(hwPipe);
}

using namespace android::base;

using AndroidPipe = android::AndroidPipe;
using BaseStream = android::base::Stream;
using CStream = ::Stream;
using OptionalString = android::base::Optional<std::string>;
using Service = android::AndroidPipe::Service;
using ServiceList = std::vector<std::unique_ptr<Service>>;
using VmLock = android::VmLock;
using android::base::MemStream;
using android::base::StringFormat;

static BaseStream* asBaseStream(CStream* stream) {
    return reinterpret_cast<BaseStream*>(stream);
}

#define CHECK_VM_STATE_LOCK() (void)0

namespace android {

namespace {

static bool isPipeOptional(const std::string& name) {
    return name == "OffworldPipe";
}

// Write an optional string |str| to |stream|. |str| can be null. Use
// readOptionalString() to read it back later.
static void writeOptionalString(BaseStream* stream, const char* str) {
    if (str) {
        stream->putByte(1);
        stream->putString(str);
    } else {
        stream->putByte(0);
    }
}

// Read an optional string from |stream|. If the result is not constructed
// (i.e. equals to false), this means the original |str| parameter was null.
static OptionalString readOptionalString(BaseStream* stream) {
    if (stream->getByte()) {
        return OptionalString(stream->getString());
    }
    return OptionalString();
}

// forward
Service* findServiceByName(const char* name);

// Implementation of a special AndroidPipe class used to model the state
// of a pipe connection before the service name has been written to the
// file descriptor by the guest. The most important method is onGuestSend()
// which will detect when this happens.
class ConnectorPipe : public AndroidPipe {
public:
    ConnectorPipe(void* hwPipe, Service* service)
        : AndroidPipe(hwPipe, service) {
        DD("%s: Creating new ConnectorPipe hwpipe=%p", __FUNCTION__, mHwPipe);
    }

    virtual void onGuestClose(PipeCloseReason reason) override {
        // nothing to do here
        DD("%s: closing ConnectorPipe hwpipe=%p prematurily (reason=%d)!",
           __func__, mHwPipe, (int)reason);
    }

    virtual unsigned onGuestPoll() const override {
        // A connector always want to receive data.
        DD("%s: polling hwpipe=%p", __FUNCTION__, mHwPipe);
        return PIPE_POLL_OUT;
    }

    virtual int onGuestRecv(AndroidPipeBuffer* buffers,
                            int numBuffers) override {
        // This pipe never wants to write to the guest, so getting there
        // is an error since PIPE_WAKE_IN is never signaled.
        DD("%s: trying to receive data from hwpipe=%p", __FUNCTION__, mHwPipe);
        return PIPE_ERROR_IO;
    }

    // TECHNICAL NOTE: This function reads data from the guest until it
    // finds a zero-terminated C-string. After that it parses it to find
    // a registered service corresponding to one of the allowed formats
    // (see below). In case of success, this creates a new AndroidPipe
    // instance and calls AndroidPipeHwFuncs::resetPipe() to associate it with
    // the current hardware-side |mHwPipe|, then *deletes* the current
    // instance! In case of error (e.g. invalid service name, or error during
    // initialization), PIPE_ERROR_INVAL will be returned, otherwise, the
    // number of bytes accepted from the guest is returned.
    virtual int onGuestSend(const AndroidPipeBuffer* buffers,
                            int numBuffers,
                            void** newPipePtr) override {
        int result = 0;
        size_t avail = kBufferSize - mPos;
        bool foundZero = false;
        for (; !foundZero && avail > 0 && numBuffers > 0;
             buffers++, numBuffers--) {
            const uint8_t* data = buffers[0].data;
            size_t count = std::min(avail, buffers[0].size);
            // Read up to |count| bytes, stopping after the first zero.
            size_t n = 0;
            while (n < count) {
                uint8_t byte = data[n++];
                mBuffer[mPos++] = (char) byte;
                if (!byte) {
                    foundZero = true;
                    break;
                }
            }
            result += static_cast<int>(n);
            avail -= n;
        }
        DD("%s: receiving %d connection bytes from hwpipe=%p", __FUNCTION__,
           result, mHwPipe);

        if (!foundZero) {
            if (avail == 0) {
                DD("%s: service name buffer full, force-closing connection",
                   __FUNCTION__);
                return PIPE_ERROR_IO;
            }
            // Still waiting for terminating zero.
            DD("%s: still waiting for terminating zero!", __FUNCTION__);
            return result;
        }

        // Acceptable formats for the connection string are:
        //
        //    pipe:<name>
        //    pipe:<name>:<arguments>
        //
        char* pipeName;
        char* pipeArgs;

        D("%s: connector: '%s'", __FUNCTION__, mBuffer);
        if (memcmp(mBuffer, "pipe:", 5) != 0) {
            // Nope, we don't handle these for now.
            D("%s: Unknown pipe connection: '%s'", __FUNCTION__, mBuffer);
            return PIPE_ERROR_INVAL;
        }

        pipeName = mBuffer + 5;
        pipeArgs = strchr(pipeName, ':');

        Service* svc = nullptr;

        // As a special case, if the service name is as:
        //    qemud:<name>
        //    qemud:<name>:args
        //
        // First look for a registered pipe service named "qemud:<name>"
        // and if not found, fallback to "qemud" only.
        //
        // This is useful to support qemud services that are now served
        // by a dedicated (and faster) pipe service, e.g. 'qemud:adb'
        // as currently implemented by QEMU2 (and soon by QEMU1).
        static const char kQemudPrefix[] = "qemud:";
        const size_t kQemudPrefixSize = sizeof(kQemudPrefix) - 1U;

        if (!::strncmp(pipeName, kQemudPrefix, kQemudPrefixSize)) {
            assert(pipeArgs == pipeName + kQemudPrefixSize - 1);
            char* pipeArgs2 = strchr(pipeArgs + 1, ':');
            if (pipeArgs2) {
                *pipeArgs2 = '\0';
            }
            svc = findServiceByName(pipeName);
            if (svc) {
                pipeArgs = pipeArgs2;
            } else if (pipeArgs2) {
                // Restore colon.
                *pipeArgs2 = ':';
            }
        }
        if (pipeArgs) {
            *pipeArgs++ = '\0';
            if (!pipeArgs) {
                pipeArgs = NULL;
            }
        }

        if (!svc) {
            svc = findServiceByName(pipeName);
        }

        if (!svc) {
            D("%s: Unknown server with name %s!", __FUNCTION__, pipeName);
            return PIPE_ERROR_INVAL;
        }

        AndroidPipe* newPipe = svc->create(mHwPipe, pipeArgs);
        if (!newPipe) {
            D("%s: Initialization failed for %s pipe!", __FUNCTION__, pipeName);
            return PIPE_ERROR_INVAL;
        }

        // Swap your host-side pipe instance with this one weird trick!
        D("%s: starting new pipe %p (swapping %p) for service %s",
          __FUNCTION__,
          newPipe,
          mHwPipe,
          pipeName);

        newPipe->setFlags(mFlags);
        *newPipePtr = newPipe;
        delete this;

        return result;
    }

    virtual void onGuestWantWakeOn(int wakeFlags) override {
        // nothing to do here
        DD("%s: signaling wakeFlags=%d for hwpipe=%p", __FUNCTION__, wakeFlags,
           mHwPipe);
    }

    virtual void onSave(BaseStream* stream) override {
        DD("%s: saving connector state for hwpipe=%p", __FUNCTION__, mHwPipe);
        stream->putBe32(mPos);
        stream->write(mBuffer, mPos);
    }

    bool onLoad(BaseStream* stream) {
        DD("%s: loading connector state for hwpipe=%p", __FUNCTION__, mHwPipe);
        int32_t len = stream->getBe32();
        if (len < 0 || len > kBufferSize) {
            D("%s: invalid length %d (expected 0 <= len <= %d)", __FUNCTION__,
              static_cast<int>(len), kBufferSize);
            return false;
        }
        mPos = (int)len;
        int ret = (int)stream->read(mBuffer, mPos);
        DD("%s: read %d bytes (%d expected)", __FUNCTION__, ret, mPos);
        return (ret == mPos);
    }

private:
    static constexpr int kBufferSize = 128;
    char mBuffer[kBufferSize];
    int mPos = 0;
};

// Associated AndroidPipe::Service class for ConnectorPipe instances.
class ConnectorService : public Service {
public:
    ConnectorService() : Service("<connector>") {}

    virtual AndroidPipe* create(void* hwPipe, const char* args) override {
        return new ConnectorPipe(hwPipe, this);
    }

    virtual bool canLoad() const override { return true; }

    virtual AndroidPipe* load(void* hwPipe,
                              const char* args,
                              BaseStream* stream) override {
        ConnectorPipe* pipe = new ConnectorPipe(hwPipe, this);
        if (!pipe->onLoad(stream)) {
            delete pipe;
            return nullptr;
        }
        return pipe;
    }
};

// A helper class used to send signalWake() and closeFromHost() commands to
// the device thread, depending on the threading mode setup by the emulation
// engine.
struct PipeWakeCommand {
    void* hwPipe;
    int wakeFlags;
};

class PipeWaker final : public DeviceContextRunner<PipeWakeCommand> {
public:
    void signalWake(void* hwPipe, int wakeFlags) {
        queueDeviceOperation({ hwPipe, wakeFlags });
    }
    void closeFromHost(void* hwPipe) {
        signalWake(hwPipe, PIPE_WAKE_CLOSED);
    }
    void abortPending(void* hwPipe) {
        removeAllPendingOperations([hwPipe](const PipeWakeCommand& cmd) {
            return cmd.hwPipe == hwPipe;
        });
    }
    void abortAllPending() {
        removeAllPendingOperations([](const PipeWakeCommand& cmd) {
            return true;
        });
    }

    int getPendingFlags(void* hwPipe) const {
        int flags = 0;
        forEachPendingOperation([hwPipe, &flags](const PipeWakeCommand& cmd) {
            if (cmd.hwPipe == hwPipe) {
                flags |= cmd.wakeFlags;
            }
        });
        return flags;
    }

private:
    virtual void performDeviceOperation(const PipeWakeCommand& wake_cmd) {
        void* hwPipe = wake_cmd.hwPipe;
        int flags = wake_cmd.wakeFlags;

        // Not used when in virtio mode.
        if (flags & PIPE_WAKE_CLOSED) {
            getPipeHwFuncs(hwPipe)->closeFromHost(hwPipe);
        } else {
            getPipeHwFuncs(hwPipe)->signalWake(hwPipe, flags);
        }
    }
};

struct Globals {
    ServiceList services;
    ConnectorService connectorService;
    PipeWaker pipeWaker;

    // Searches for a service position in the |services| list and returns the
    // index. |startPosHint| is a _hint_ and suggests where to start from.
    // Returns the index of the service or -1 if there's no |name| service.
    int findServicePositionByName(const char* name,
                                  const int startPosHint = 0) const {
        const auto searchByNameFunc =
                [name](const std::unique_ptr<Service>& service) {
                    return service->name() == name;
                };

        // First, try to search starting from the hint position.
        auto end = services.end();
        auto it = std::find_if(services.begin() + startPosHint, end,
                               searchByNameFunc);

        // If there was a hint that didn't help, continue searching from the
        // beginning of the contatiner to check the rest of it.
        if (it == end && startPosHint > 0) {
            end = services.begin() + startPosHint;
            it = std::find_if(services.begin(), end, searchByNameFunc);
        }

        return it == end ? -1 : it - services.begin();
    }

    Service* loadServiceByName(BaseStream* stream) {
        OptionalString serviceName = readOptionalString(stream);
        if (!serviceName) {
            DD("%s: no name (assuming connector state)", __FUNCTION__);
            return &connectorService;
        }
        DD("%s: found [%s]", __FUNCTION__, serviceName->c_str());
        return findServiceByName(serviceName->c_str());
    }
};

static Globals* sGlobals() { static Globals* g = new Globals; return g; }

Service* findServiceByName(const char* name) {
    const int pos = sGlobals()->findServicePositionByName(name);
    return pos < 0 ? nullptr : sGlobals()->services[pos].get();
}

AndroidPipe* loadPipeFromStreamCommon(BaseStream* stream,
                                      void* hwPipe,
                                      Service* service,
                                      char* pForceClose) {
    *pForceClose = 0;

    OptionalString args = readOptionalString(stream);
    AndroidPipe* pipe = nullptr;
    if (service->canLoad()) {
        DD("%s: loading state for [%s] hwpipe=%p", __FUNCTION__,
           service->name().c_str(), hwPipe);
        pipe = service->load(hwPipe, args ? args->c_str() : nullptr, stream);
        if (!pipe) {
            *pForceClose = 1;
        }
    } else {
        DD("%s: force-closing hwpipe=%p", __FUNCTION__, hwPipe);
        *pForceClose = 1;
    }

    const int pendingFlags = stream->getBe32();
    if (pendingFlags && pipe && !*pForceClose) {
        if (!hwPipe) {
            fprintf(stderr, "fatal: AndroidPipe::%s [%s]: hwPipe is NULL (flags = 0x%x)\n",
                    __func__, pipe->name(), unsigned(pendingFlags));
            abort();
        }
        sGlobals()->pipeWaker.signalWake(hwPipe, pendingFlags);
        DD("%s: singalled wake flags %d for pipe hwpipe=%p", __func__,
           pendingFlags, hwPipe);
    }

    return pipe;
}

}  // namespace

// static
void AndroidPipe::initThreading(VmLock* vmLock) {
    // TODO: Make this work in qemu with the actual goldfish pipe device.
    // In virtio land, this won't be needed, so include trivial timer interface.
    sGlobals()->pipeWaker.init(vmLock, {
        // installFunc
        [](DeviceContextRunner<PipeWakeCommand>* dcr, std::function<void()> installedFunc) {
            (void)dcr;
            (void)installedFunc;
        },
        // uninstallFunc
        [](DeviceContextRunner<PipeWakeCommand>* dcr) {
            (void)dcr;
        },
        // startWithTimeoutFunc
        [](DeviceContextRunner<PipeWakeCommand>* dcr, uint64_t timeout) {
            (void)dcr;
            (void)timeout;
        }
    });
}

AndroidPipe::~AndroidPipe() {
    DD("%s: for hwpipe=%p (host %p '%s')", __FUNCTION__, mHwPipe, this,
       mService->name().c_str());
}

// static
void AndroidPipe::Service::add(std::unique_ptr<Service> service) {
    DD("Adding new pipe service '%s' this=%p", service->name().c_str(),
       service.get());
    sGlobals()->services.push_back(std::move(service));
}

// static
void AndroidPipe::Service::resetAll() {
    DD("Resetting all pipe services");
    sGlobals()->services.clear();
}

void AndroidPipe::signalWake(int wakeFlags) {
    // i.e., pipe not using normal pipe device
    if (mFlags) return;
    if (!mHwPipe) {
        fprintf(stderr, "AndroidPipe::%s [%s]: hwPipe is NULL (flags = 0x%x)\n",
                __func__, name(), (unsigned)wakeFlags);
        abort();
    }
    sGlobals()->pipeWaker.signalWake(mHwPipe, wakeFlags);
}

void AndroidPipe::closeFromHost() {
    // i.e., pipe not using normal pipe device
    if (mFlags) return;
    if (!mHwPipe) {
        fprintf(stderr, "AndroidPipe::%s [%s]: hwPipe is NULL\n", __func__, name());
        abort();
    }
    sGlobals()->pipeWaker.closeFromHost(mHwPipe);
}

void AndroidPipe::abortPendingOperation() {
    // i.e., pipe not using normal pipe device
    if (mFlags) return;

    if (!mHwPipe) {
        fprintf(stderr, "AndroidPipe::%s [%s]: hwPipe is NULL\n", __func__, name());
        abort();
    }
    sGlobals()->pipeWaker.abortPending(mHwPipe);
}

void AndroidPipe::saveToStream(BaseStream* stream) {
    // First, write service name.
    if (mService == &sGlobals()->connectorService) {
        // A connector pipe
        stream->putByte(0);
    } else {
        // A regular service pipe.
        stream->putByte(1);
        stream->putString(mService->name());
    }

    MemStream pipeStream;
    writeOptionalString(&pipeStream, mArgs.c_str());

    // Save pipe-specific state now.
    if (mService->canLoad()) {
        mService->savePipe(this, &pipeStream);
    }

    // Save the pending wake or close operations as well.
    const int pendingFlags = sGlobals()->pipeWaker.getPendingFlags(mHwPipe);
    pipeStream.putBe32(pendingFlags);

    pipeStream.save(stream);
}

// static
AndroidPipe* AndroidPipe::loadFromStream(BaseStream* stream,
                                         void* hwPipe,
                                         char* pForceClose) {
    Service* service = sGlobals()->loadServiceByName(stream);
    // Always load the pipeStream, it allows us to safely skip loading streams.
    MemStream pipeStream;
    pipeStream.load(stream);

    if (!service) {
        return nullptr;
    }
    return loadPipeFromStreamCommon(&pipeStream, hwPipe, service, pForceClose);
}

// static
AndroidPipe* AndroidPipe::loadFromStreamLegacy(BaseStream* stream,
                                               void* hwPipe,
                                               uint64_t* pChannel,
                                               unsigned char* pWakes,
                                               unsigned char* pClosed,
                                               char* pForceClose) {
    Service* service = sGlobals()->loadServiceByName(stream);
    // Always load the pipeStream, it allows us to safely skip loading streams.
    MemStream pipeStream;
    pipeStream.load(stream);

    if (!service) {
        return nullptr;
    }
    *pChannel = pipeStream.getBe64();
    *pWakes = pipeStream.getByte();
    *pClosed = pipeStream.getByte();

    return loadPipeFromStreamCommon(&pipeStream, hwPipe, service, pForceClose);
}

}  // namespace android

// API for the virtual device.

void android_pipe_reset_services() {
    AndroidPipe::Service::resetAll();
}

void* android_pipe_guest_open(void* hwpipe) {
    CHECK_VM_STATE_LOCK();
    DD("%s: Creating new connector pipe for hwpipe=%p", __FUNCTION__, hwpipe);
    return android::sGlobals()->connectorService.create(hwpipe, nullptr);
}

void* android_pipe_guest_open_with_flags(void* hwpipe, uint32_t flags) {
    CHECK_VM_STATE_LOCK();
    DD("%s: Creating new connector pipe for hwpipe=%p", __FUNCTION__, hwpipe);
    auto pipe = android::sGlobals()->connectorService.create(hwpipe, nullptr);
    pipe->setFlags((AndroidPipeFlags)flags);
    return pipe;
}

void android_pipe_guest_close(void* internalPipe, PipeCloseReason reason) {
    CHECK_VM_STATE_LOCK();
    auto pipe = static_cast<android::AndroidPipe*>(internalPipe);
    if (pipe) {
        D("%s: host=%p [%s] reason=%d", __FUNCTION__, pipe, pipe->name(),
            (int)reason);
        pipe->abortPendingOperation();
        pipe->onGuestClose(reason);
    }
}

template <class Func>
static void forEachServiceToStream(CStream* stream, Func&& func) {
    BaseStream* const bs = asBaseStream(stream);
    bs->putBe16(android::sGlobals()->services.size());
    for (const auto& service : android::sGlobals()->services) {
        bs->putString(service->name());

        // Write to the pipeStream first so that we know the length and can
        // enable skipping loading specific pipes on load, see isPipeOptional.
        MemStream pipeStream;
        func(service.get(), &pipeStream);
        pipeStream.save(bs);
    }
}

template <class Func>
static void forEachServiceFromStream(CStream* stream, Func&& func) {
    const auto& services = android::sGlobals()->services;
    BaseStream* const bs = asBaseStream(stream);
    const int count = bs->getBe16();
    int servicePos = -1;
    std::unordered_set<Service*> missingServices;
    for (const auto& service : services) {
        missingServices.insert(service.get());
    }
    for (int i = 0; i < count; ++i) {
        const auto name = bs->getString();
        servicePos = android::sGlobals()->findServicePositionByName(
                                 name.c_str(), servicePos + 1);

        // Always load the pipeStream, so that if the pipe is missing it does
        // not corrupt the next pipe.
        MemStream pipeStream;
        pipeStream.load(bs);

        if (servicePos >= 0) {
            const auto& service = services[servicePos];
            func(service.get(), &pipeStream);
            missingServices.erase(service.get());
        } else if (android::isPipeOptional(name)) {
            D("%s: Skipping optional pipe %s\n", __FUNCTION__, name.c_str());
        } else {
            assert(false && "Service for snapshot pipe does not exist");
            E("%s: Could not load pipe %s, service does not exist\n",
              __FUNCTION__, name.c_str());
        }
    }

    // Now call the same function for all services that weren't in the snapshot.
    // Pass |nullptr| instead of the stream pointer to make sure they know
    // that while we're loading from a snapshot these services aren't part
    // of it.
    for (const auto service : missingServices) {
        func(service, nullptr);
    }
}

void android_pipe_guest_pre_load(CStream* stream) {
    CHECK_VM_STATE_LOCK();
    // We may not call qemu_set_irq() until the snapshot is loaded.
    android::sGlobals()->pipeWaker.abortAllPending();
    android::sGlobals()->pipeWaker.setContextRunMode(
                android::ContextRunMode::DeferAlways);
    forEachServiceFromStream(stream, [](Service* service, BaseStream* bs) {
        if (service->canLoad()) {
            service->preLoad(bs);
        }
    });
}

void android_pipe_guest_post_load(CStream* stream) {
    CHECK_VM_STATE_LOCK();
    forEachServiceFromStream(stream, [](Service* service, BaseStream* bs) {
        if (service->canLoad()) {
            service->postLoad(bs);
        }
    });
    // Restore the regular handling of pipe interrupt requests.
    android::sGlobals()->pipeWaker.setContextRunMode(
                android::ContextRunMode::DeferIfNotLocked);
}

void android_pipe_guest_pre_save(CStream* stream) {
    CHECK_VM_STATE_LOCK();
    forEachServiceToStream(stream, [](Service* service, BaseStream* bs) {
        if (service->canLoad()) {
            service->preSave(bs);
        }
    });
}

void android_pipe_guest_post_save(CStream* stream) {
    CHECK_VM_STATE_LOCK();
    forEachServiceToStream(stream, [](Service* service, BaseStream* bs) {
        if (service->canLoad()) {
            service->postSave(bs);
        }
    });
}

void android_pipe_guest_save(void* internalPipe, CStream* stream) {
    CHECK_VM_STATE_LOCK();
    auto pipe = static_cast<android::AndroidPipe*>(internalPipe);
    DD("%s: host=%p [%s]", __FUNCTION__, pipe, pipe->name());
    pipe->saveToStream(asBaseStream(stream));
}

void* android_pipe_guest_load(CStream* stream,
                              void* hwPipe,
                              char* pForceClose) {
    CHECK_VM_STATE_LOCK();
    DD("%s: hwpipe=%p", __FUNCTION__, hwPipe);
    return AndroidPipe::loadFromStream(asBaseStream(stream), hwPipe,
                                       pForceClose);
}

void* android_pipe_guest_load_legacy(CStream* stream,
                                     void* hwPipe,
                                     uint64_t* pChannel,
                                     unsigned char* pWakes,
                                     unsigned char* pClosed,
                                     char* pForceClose) {
    CHECK_VM_STATE_LOCK();
    DD("%s: hwpipe=%p", __FUNCTION__, hwPipe);
    return android::AndroidPipe::loadFromStreamLegacy(asBaseStream(stream),
                                                      hwPipe, pChannel, pWakes,
                                                      pClosed, pForceClose);
}

unsigned android_pipe_guest_poll(void* internalPipe) {
    CHECK_VM_STATE_LOCK();
    auto pipe = static_cast<AndroidPipe*>(internalPipe);
    DD("%s: host=%p [%s]", __FUNCTION__, pipe, pipe->name());
    return pipe->onGuestPoll();
}

int android_pipe_guest_recv(void* internalPipe,
                            AndroidPipeBuffer* buffers,
                            int numBuffers) {
    CHECK_VM_STATE_LOCK();
    auto pipe = static_cast<AndroidPipe*>(internalPipe);
    // Note that pipe may be deleted during this call, so it's not safe to
    // access pipe after this point.
    return pipe->onGuestRecv(buffers, numBuffers);
}

int android_pipe_guest_send(void** internalPipe,
                            const AndroidPipeBuffer* buffers,
                            int numBuffers) {
    CHECK_VM_STATE_LOCK();
    auto pipe = static_cast<AndroidPipe*>(*internalPipe);
    // Note that pipe may be deleted during this call, so it's not safe to
    // access pipe after this point.
    return pipe->onGuestSend(buffers, numBuffers, internalPipe);
}

void android_pipe_guest_wake_on(void* internalPipe, unsigned wakes) {
    CHECK_VM_STATE_LOCK();
    auto pipe = static_cast<AndroidPipe*>(internalPipe);
    pipe->onGuestWantWakeOn(wakes);
}

// API implemented by the virtual device.
void android_pipe_host_close(void* hwpipe) {
    auto pipe = static_cast<android::AndroidPipe*>(hwpipe);
    D("%s: host=%p [%s]", __FUNCTION__, pipe, pipe->name());
    android::sGlobals()->pipeWaker.closeFromHost(pipe);
}

void android_pipe_host_signal_wake(void* hwpipe, unsigned flags) {
    android::sGlobals()->pipeWaker.signalWake(hwpipe, flags);
}

// Not used when in virtio mode.
int android_pipe_get_id(void* hwpipe) {
    return getPipeHwFuncs(hwpipe)->getPipeId(hwpipe);
}

static std::vector<std::pair<void*(*)(int), const char*>> lookup_by_id_callbacks;

void android_pipe_append_lookup_by_id_callback(void*(*cb)(int), const char* tag) {
    lookup_by_id_callbacks.push_back({cb, tag});
}

void* android_pipe_lookup_by_id(const int id) {
    void* hwPipeFound = nullptr;
    const char* tagFound = "(null)";

    for (const auto &cb : lookup_by_id_callbacks) {
        void* hwPipe = (*cb.first)(id);
        if (hwPipe) {
            if (hwPipeFound) {
                fprintf(stderr, "%s: Pipe id (%d) is not unique, at least two "
                        "pipes are found: `%s` and `%s`\n",
                        __func__, id, tagFound, cb.second);
                abort();
            } else {
                hwPipeFound = hwPipe;
                tagFound = cb.second;
            }
        }
    }

    return hwPipeFound;
}