init/firmware_handler.cpp

/*
 * Copyright (C) 2017 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 "firmware_handler.h"

#include <fcntl.h>
#include <sys/sendfile.h>
#include <sys/wait.h>
#include <unistd.h>

#include <string>
#include <thread>

#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/unique_fd.h>

#include "util.h"

static void LoadFirmware(const Uevent& uevent, const std::string& root, int fw_fd, size_t fw_size,
                         int loading_fd, int data_fd) {
    // Start transfer.
    android::base::WriteFully(loading_fd, "1", 1);

    // Copy the firmware.
    int rc = sendfile(data_fd, fw_fd, nullptr, fw_size);
    if (rc == -1) {
        PLOG(ERROR) << "firmware: sendfile failed { '" << root << "', '" << uevent.firmware
                    << "' }";
    }

    // Tell the firmware whether to abort or commit.
    const char* response = (rc != -1) ? "0" : "-1";
    android::base::WriteFully(loading_fd, response, strlen(response));
}

static bool IsBooting() {
    return access("/dev/.booting", F_OK) == 0;
}

static void ProcessFirmwareEvent(const Uevent& uevent) {
    int booting = IsBooting();

    LOG(INFO) << "firmware: loading '" << uevent.firmware << "' for '" << uevent.path << "'";

    std::string root = "/sys" + uevent.path;
    std::string loading = root + "/loading";
    std::string data = root + "/data";

    android::base::unique_fd loading_fd(open(loading.c_str(), O_WRONLY | O_CLOEXEC));
    if (loading_fd == -1) {
        PLOG(ERROR) << "couldn't open firmware loading fd for " << uevent.firmware;
        return;
    }

    android::base::unique_fd data_fd(open(data.c_str(), O_WRONLY | O_CLOEXEC));
    if (data_fd == -1) {
        PLOG(ERROR) << "couldn't open firmware data fd for " << uevent.firmware;
        return;
    }

    static const char* firmware_dirs[] = {"/etc/firmware/", "/vendor/firmware/",
                                          "/firmware/image/"};

try_loading_again:
    for (size_t i = 0; i < arraysize(firmware_dirs); i++) {
        std::string file = firmware_dirs[i] + uevent.firmware;
        android::base::unique_fd fw_fd(open(file.c_str(), O_RDONLY | O_CLOEXEC));
        struct stat sb;
        if (fw_fd != -1 && fstat(fw_fd, &sb) != -1) {
            LoadFirmware(uevent, root, fw_fd, sb.st_size, loading_fd, data_fd);
            return;
        }
    }

    if (booting) {
        // If we're not fully booted, we may be missing
        // filesystems needed for firmware, wait and retry.
        std::this_thread::sleep_for(100ms);
        booting = IsBooting();
        goto try_loading_again;
    }

    LOG(ERROR) << "firmware: could not find firmware for " << uevent.firmware;

    // Write "-1" as our response to the kernel's firmware request, since we have nothing for it.
    write(loading_fd, "-1", 2);
}

void HandleFirmwareEvent(const Uevent& uevent) {
    if (uevent.subsystem != "firmware" || uevent.action != "add") return;

    // Loading the firmware in a child means we can do that in parallel...
    // We double fork instead of waiting for these processes.
    pid_t pid = fork();
    if (pid == -1) {
        PLOG(ERROR) << "could not fork to process firmware event for " << uevent.firmware;
        return;
    }

    if (pid == 0) {
        pid = fork();
        if (pid == -1) {
            PLOG(ERROR) << "could not fork a sceond time to process firmware event for "
                        << uevent.firmware;
            _exit(EXIT_FAILURE);
        }
        if (pid == 0) {
            Timer t;
            ProcessFirmwareEvent(uevent);
            LOG(INFO) << "loading " << uevent.path << " took " << t;
            _exit(EXIT_SUCCESS);
        }

        _exit(EXIT_SUCCESS);
    }

    waitpid(pid, nullptr, 0);
}