base/HidlSupport.cpp

/*
 * Copyright (C) 2016 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 "HidlSupport"

#include <hidl/HidlSupport.h>

#include <android-base/logging.h>

#ifdef LIBHIDL_TARGET_DEBUGGABLE
#include <cutils/properties.h>
#include <dlfcn.h>
#include <regex>
#include <utility>
#endif

namespace android {
namespace hardware {

static const char *const kEmptyString = "";

hidl_string::hidl_string()
    : mBuffer(kEmptyString),
      mSize(0),
      mOwnsBuffer(false) {
}

hidl_string::~hidl_string() {
    clear();
}

hidl_string::hidl_string(const char *s) : hidl_string() {
    copyFrom(s, strlen(s));
}

hidl_string::hidl_string(const char *s, size_t length) : hidl_string() {
    copyFrom(s, length);
}

hidl_string::hidl_string(const hidl_string &other): hidl_string() {
    copyFrom(other.c_str(), other.size());
}

hidl_string::hidl_string(const std::string &s) : hidl_string() {
    copyFrom(s.c_str(), s.size());
}

hidl_string::hidl_string(hidl_string &&other): hidl_string() {
    moveFrom(std::forward<hidl_string>(other));
}

hidl_string &hidl_string::operator=(hidl_string &&other) {
    if (this != &other) {
        clear();
        moveFrom(std::forward<hidl_string>(other));
    }
    return *this;
}

hidl_string &hidl_string::operator=(const hidl_string &other) {
    if (this != &other) {
        clear();
        copyFrom(other.c_str(), other.size());
    }

    return *this;
}

hidl_string &hidl_string::operator=(const char *s) {
    clear();
    copyFrom(s, strlen(s));
    return *this;
}

hidl_string &hidl_string::operator=(const std::string &s) {
    clear();
    copyFrom(s.c_str(), s.size());
    return *this;
}

hidl_string::operator std::string() const {
    return std::string(mBuffer, mSize);
}

hidl_string::operator const char *() const {
    return mBuffer;
}

void hidl_string::copyFrom(const char *data, size_t size) {
    // assume my resources are freed.

    if (size > UINT32_MAX) {
        LOG(FATAL) << "string size can't exceed 2^32 bytes.";
    }
    char *buf = (char *)malloc(size + 1);
    memcpy(buf, data, size);
    buf[size] = '\0';
    mBuffer = buf;

    mSize = static_cast<uint32_t>(size);
    mOwnsBuffer = true;
}

void hidl_string::moveFrom(hidl_string &&other) {
    // assume my resources are freed.

    mBuffer = other.mBuffer;
    mSize = other.mSize;
    mOwnsBuffer = other.mOwnsBuffer;

    other.mOwnsBuffer = false;
}

void hidl_string::clear() {
    if (mOwnsBuffer && (mBuffer != kEmptyString)) {
        free(const_cast<char *>(static_cast<const char *>(mBuffer)));
    }

    mBuffer = kEmptyString;
    mSize = 0;
    mOwnsBuffer = false;
}

void hidl_string::setToExternal(const char *data, size_t size) {
    if (size > UINT32_MAX) {
        LOG(FATAL) << "string size can't exceed 2^32 bytes.";
    }
    clear();

    mBuffer = data;
    mSize = static_cast<uint32_t>(size);
    mOwnsBuffer = false;
}

const char *hidl_string::c_str() const {
    return mBuffer;
}

size_t hidl_string::size() const {
    return mSize;
}

bool hidl_string::empty() const {
    return mSize == 0;
}

// ----------------------------------------------------------------------
// HidlInstrumentor implementation.
HidlInstrumentor::HidlInstrumentor(const std::string &prefix)
        : mInstrumentationLibPrefix(prefix) {
    configureInstrumentation(false);
}

HidlInstrumentor:: ~HidlInstrumentor() {}

void HidlInstrumentor::configureInstrumentation(bool log) {
    bool enable_instrumentation = property_get_bool(
            "hal.instrumentation.enable",
            false);
    if (enable_instrumentation != mEnableInstrumentation) {
        mEnableInstrumentation = enable_instrumentation;
        if (mEnableInstrumentation) {
            if (log) {
                LOG(INFO) << "Enable instrumentation.";
            }
            registerInstrumentationCallbacks (&mInstrumentationCallbacks);
        } else {
            if (log) {
                LOG(INFO) << "Disable instrumentation.";
            }
            mInstrumentationCallbacks.clear();
        }
    }
}

void HidlInstrumentor::registerInstrumentationCallbacks(
        std::vector<InstrumentationCallback> *instrumentationCallbacks) {
#ifdef LIBHIDL_TARGET_DEBUGGABLE
    std::vector<std::string> instrumentationLibPaths;
    char instrumentation_lib_path[PROPERTY_VALUE_MAX];
    if (property_get("hal.instrumentation.lib.path",
                     instrumentation_lib_path,
                     "") > 0) {
        instrumentationLibPaths.push_back(instrumentation_lib_path);
    } else {
        instrumentationLibPaths.push_back(HAL_LIBRARY_PATH_SYSTEM);
        instrumentationLibPaths.push_back(HAL_LIBRARY_PATH_VENDOR);
        instrumentationLibPaths.push_back(HAL_LIBRARY_PATH_ODM);
    }

    for (auto path : instrumentationLibPaths) {
        DIR *dir = opendir(path.c_str());
        if (dir == 0) {
            LOG(WARNING) << path << " does not exist. ";
            return;
        }

        struct dirent *file;
        while ((file = readdir(dir)) != NULL) {
            if (!isInstrumentationLib(file))
                continue;

            void *handle = dlopen((path + file->d_name).c_str(), RTLD_NOW);
            if (handle == nullptr) {
                LOG(WARNING) << "couldn't load file: " << file->d_name
                    << " error: " << dlerror();
                continue;
            }
            using cb_fun = void (*)(
                    const InstrumentationEvent,
                    const char *,
                    const char *,
                    const char *,
                    const char *,
                    std::vector<void *> *);
            auto cb = (cb_fun)dlsym(handle, "HIDL_INSTRUMENTATION_FUNCTION");
            if (cb == nullptr) {
                LOG(WARNING)
                    << "couldn't find symbol: HIDL_INSTRUMENTATION_FUNCTION, "
                       "error: "
                    << dlerror();
                continue;
            }
            instrumentationCallbacks->push_back(cb);
            LOG(INFO) << "Register instrumentation callback from "
                << file->d_name;
        }
        closedir(dir);
    }
#else
    // No-op for user builds.
    return;
#endif
}

bool HidlInstrumentor::isInstrumentationLib(const dirent *file) {
#ifdef LIBHIDL_TARGET_DEBUGGABLE
    if (file->d_type != DT_REG) return false;
    std::cmatch cm;
    std::regex e("^" + mInstrumentationLibPrefix + "(.*).profiler.so$");
    if (std::regex_match(file->d_name, cm, e)) return true;
#endif
    return false;
}

}  // namespace hardware
}  // namespace android