OperWrt 启动过程

OpenWrt启动脚本分析

  1. 内核代码start_kernel函数执行的最后会调用kernel_init函数来启动用户空间的一号进程，标准linux默认是的/etc/init进程，但在OpenWRT里面会执行/etc/preinit，代码如下图992行：

  2. 下面分析/etc/preinit脚本

    /etc/preinit脚本内容如下：

    #!/bin/sh
# Copyright (C) 2006 OpenWrt.org
# Copyright (C) 2010 Vertical Communications

[ -z "$PREINIT" ] && exec /sbin/init

export PATH=/usr/sbin:/usr/bin:/sbin:/bin

pi_ifname=
pi_ip=192.168.1.1
pi_broadcast=192.168.1.255
pi_netmask=255.255.255.0

fs_failsafe_ifname=
fs_failsafe_ip=192.168.1.1
fs_failsafe_broadcast=192.168.1.255
fs_failsafe_netmask=255.255.255.0

fs_failsafe_wait_timeout=0

pi_suppress_stderr="y"
pi_init_suppress_stderr="y"
pi_init_path="/usr/sbin:/usr/bin:/sbin:/bin"
pi_init_cmd="/sbin/init"

. /lib/functions.sh
. /lib/functions/preinit.sh
. /lib/functions/system.sh

boot_hook_init preinit_essential
boot_hook_init preinit_main
boot_hook_init failsafe
boot_hook_init initramfs
boot_hook_init preinit_mount_root

for pi_source_file in /lib/preinit/*; do
        . $pi_source_file
done

boot_run_hook preinit_essential

pi_mount_skip_next=false
pi_jffs2_mount_success=false
pi_failsafe_net_message=false

boot_run_hook preinit_main

    拆解上面的脚本，逐步分析如下：

    1. 步骤1

      [ -z "$PREINIT" ] && exec /sbin/init

      分析： PREINIT变量当前没有值，所以执行exec /sbin/init，使用exec，表明/sbin/init替换进程上下文，pid保持不变，应该为1。

      下面分析/sbin/init干了什么，即分析函数init.c

      源码位于

      image-20220812140107019

      int  main(int argc, char **argv)  
{  
    pid_t pid;  
  
    sigaction(SIGTERM, &sa_shutdown, NULL);  
    sigaction(SIGUSR1, &sa_shutdown, NULL);  
    sigaction(SIGUSR2, &sa_shutdown, NULL);  
  
	/*  early
     *   |->early_mounts
     *   |      |-> mount
     *   |      |->early_dev 设置环境变量
     *   |->LOG("Console is alive")
     */
	early();
    
    /*  cmdline
     *      |-> get init_debug 获取init_debug等级
     */
	cmdline();
    
    /*  watchdog_init
     *      |->LOG("- watchdog -")
     */
	watchdog_init(1); 
  
    pid = fork();  
    if (!pid) {  
        /*  /sbin/kmodloader
         *      |-> /etc/modules-boot.d 加载驱动
         */
        char *kmod[] = { "/sbin/kmodloader", "/etc/modules-boot.d/", NULL };  
  
        if (debug < 3) {  
            int fd = open("/dev/null", O_RDWR);  
  
            if (fd > -1) {  
                dup2(fd, STDIN_FILENO);  
                dup2(fd, STDOUT_FILENO);  
                dup2(fd, STDERR_FILENO);  
                if (fd > STDERR_FILENO)  
                    close(fd);  
            }  
        }  
        execvp(kmod[0], kmod);  
        ERROR("Failed to start kmodloader\n");  
        exit(-1);  
    }  
    if (pid <= 0)  
        ERROR("Failed to start kmodloader instance\n");  
    uloop_init();  
    /*  preinit
     *      |-> LOG("- preinit -")
     *      |-> fork->procd
     *      |-> setenv("PREINIT"， "1"， 1)
     *      |-> fork->sh /etc/preinit
     */
    preinit();    //-------------->watchdog.c  
    uloop_run();  
  
    return 0;  
}

      • early()函數：主要四个功能：

        • early_mounts()： mount /proc， /sysfs， /dev， /tmp

        • early_env()： 使用/usr/sbin：/sbin：/usr/bin：/bin设置 PATH参数

        • 初始化/dev/console

        • 从init打印第一条消息："init: Console is alive"

      • cmdline()函数

        它从/proc/cmdline读取内核引导命令行并解析init_debug参数

      • watchdog_init(1)函数

        初始化监视程序 /dev/watchdog 并打印第二条消息 "init: - watchdog -"

      • fork 一个新线程，让/sbin/kmodloader加载/etc/modules-boot.d下的设备驱动程序

        下面看下kmodloader.c内容：

            if (scan_loaded_modules())
        return -1;

    if (scan_module_folders())
        return -1;
        
    while (getline(&mod, &mod_len, fp) > 0) {
        char *nl = strchr(mod, '\n');
        struct module *m;
        char *opts;

        if (nl)
            *nl = '\0';

        opts = strchr(mod, ' ');
        if (opts)
            *opts++ = '\0';

        m = find_module(get_module_name(mod));
        if (!m || (m->state == LOADED))
            continue;

        if (opts)
            m->opts = strdup(opts);
        m->state = PROBE;
        if (basename(gl.gl_pathv[j])[0] - '0' <= 9)
            load_modprobe();

    }

        1. 从/proc/modules里面遍历所有已经安装的模块，包括模块名称和大小等信息，插入到avl树中，同时将节点状态设置为LOADED；

        2. 将/lib/modules/x.x.x路径保存到二维指针module_folders，遍历/lib/modules/x.x.x/*.ko，查看是否在avl树中，如果不在，添加到avl树中，同时将节点状态设置为SCANNED;

        3. 遍历/etc/modules-boot.d下所有文件并打开，判断当前模块是否在avl树中，如果存在且节点状态不为LOADED，则将此节点状态设置为PROBE，如果文件名第一个字符是0~9之间，则装载此模块，同时将此节点状态设置为LOADED;

      • uloop_init() 初始化uloop，这是一个事件循环。后来的sh /sbin/procd和sh /etc/preinit将由uloop管理

      • preinit()函数：有四个主要任务,preinit()函数如下:

        void
preinit(void)
{
    char *init[] = { "/bin/sh", "/etc/preinit", NULL };
    char *plug[] = {"/sbin/procd", "-h","/etc/hotplug-preinit.json",NULL };

    // 步骤1： 打印日志
    LOG("- preinit -\n");
    
    // 步骤2：fork一个新进程 执行/sbin/procd -h /etc/hotplug-preinit.json 
    // 进程结束后，回调 plugd_proc_cb 函数
    plugd_proc.cb = plugd_proc_cb;
    plugd_proc.pid = fork();
    if (!plugd_proc.pid) {
        execvp(plug[0], plug);
        ERROR("Failed to start plugd\n");
        exit(-1);
    }
    if (plugd_proc.pid <= 0) {
        ERROR("Failed to start new plugd instance\n");
        return;
    }
    uloop_process_add(&plugd_proc);
    // 步骤3：设置环境比变量
    setenv("PREINIT", "1", 1);

    // 步骤4：fork一个新进程 执行 /bin/sh /etc/preinit 脚本
    // 进程结束后，回调 spawn_procd 函数
    preinit_proc.cb = spawn_procd;
    preinit_proc.pid = fork();
    if (!preinit_proc.pid) {
        execvp(init[0], init);
        ERROR("Failed to start preinit\n");
        exit(-1);
    }
    if (preinit_proc.pid <= 0) {
        ERROR("Failed to start new preinit instance\n");
        return;
    }
    uloop_process_add(&preinit_proc);

    DEBUG(4, "Launched preinit instance, pid=%d\n", (int) preinit_proc.pid);
}

        分析过后可以发现preinit函数分别fork了两个进程procd和/etc/preinit下面分析这两个进程

        • /sbin/procd进程

          /sbin/procd -h /etc/hotplug-preinit.json

          /sbin/procd程序源码如下：可以看到由于-h作用，肯定会执行hotplug_run(optarg)

          int main(int argc, char **argv)
{
    int ch;
    char *dbglvl = getenv("DBGLVL");
    int ulog_channels = ULOG_KMSG;

    if (dbglvl) {
        debug = atoi(dbglvl);
        unsetenv("DBGLVL");
    }

    while ((ch = getopt(argc, argv, "d:s:h:S")) != -1) {
        switch (ch) {
        case 'h':
            /*  建立netlink通讯机制，完成内核的交互，监听uevent事件
             */
            return hotplug_run(optarg);
        case 's':
            ubus_socket = optarg;
            break;
        case 'd':
            debug = atoi(optarg);
            break;
        case 'S':
            ulog_channels = ULOG_STDIO;
            break;
        default:
            return usage(argv[0]);
        }
    }

    ulog_open(ulog_channels, LOG_DAEMON, "procd");

    setsid();
    uloop_init();
    procd_signal();
    if (getpid() != 1)
        procd_connect_ubus();
    else
        /* 状态机处理，实际效果如下
         * [ 6.596450] procd: - early -
         * [ 6.599817] procd: - watchdog -
         * [ 7.301153] procd: - ubus -
         * [ 7.362047] procd: - init -
         */
        procd_state_next();
    uloop_run();
    uloop_done();

    return 0;
}

          procd_state_next处理完状态之后设备设备会执行到rcS.c

          int rcS(char *pattern, char *param, void (*q_empty)(struct runqueue *))
{
    runqueue_init(&q);
    q.empty_cb = q_empty;
    q.max_running_tasks = 1;
    // 这里便是我们常见的自启动脚本的地方
	// 需要知道的是K开头的文件为stop，S开头的文件为start
	return _rc(&q, "/etc/rc.d", pattern, "*", param);
}

          注意：由于通过 uloop_process_add(&plugd_proc)函数将plugd_proc加入uloop中，当线程执行完后回调plugd_proc_cb函数

        • /etc/preinit进程

           /bin/sh /etc/preinit

          可以看到这里又回到了/etc/preinit脚本，不过此时PREINIT已经为1

          注意：通过 uloop_process_add(&preinit_proc)函数将preinit_proc加入uloop中，当线程执行完后回调spawn_procd函数，spawn_procd()将从/tmp/debuglevel读取系统调试级别，并将其设置为setenv DBGLVL。它还将看门狗fd设置为setenv WDTFD。

          最后，它将分叉真正的/sbin/procd作为deamon。

    2. 步骤2

      步骤1最终回到了/etc/preinit脚本，不过此时PREINIT已经为1，所以继续执行/etc/preinit下面的内容，如下代碼，沒什麽好分析的

      export PATH=/usr/sbin:/usr/bin:/sbin:/bin

pi_ifname=
pi_ip=192.168.1.1
pi_broadcast=192.168.1.255
pi_netmask=255.255.255.0

fs_failsafe_ifname=
fs_failsafe_ip=192.168.1.1
fs_failsafe_broadcast=192.168.1.255
fs_failsafe_netmask=255.255.255.0

fs_failsafe_wait_timeout=0

pi_suppress_stderr="y"
pi_init_suppress_stderr="y"
pi_init_path="/usr/sbin:/usr/bin:/sbin:/bin"
pi_init_cmd="/sbin/init"

    3. 步骤3

      注意.和/之间是有空格的，这里的点相当与souce命令，但souce是bash特有的，并不在POSIX标准中，.是通用的用法。使用.的意思是在当前shell环境下运行，并不会在子shell中运行。这几个shell脚本主要定义了shell函数，特别是preinit.sh中，定义了hook相关操作的函数

      . /lib/functions.sh
. /lib/functions/preinit.sh
. /lib/functions/system.sh

      我们需要重点看下/lib/functions/preinit.sh里面的三个函数

      boot_hook_init() {
        local hook="${1}_hook"
        export -n "PI_STACK_LIST=${PI_STACK_LIST:+$PI_STACK_LIST }$hook"
        export -n "$hook="
}

boot_hook_add() {
        local hook="${1}_hook${PI_HOOK_SPLICE:+_splice}"
        local func="${2}"

        [ -n "$func" ] && {
                local v; eval "v=\$$hook"
                export -n "$hook=${v:+$v }$func"
        }
}
boot_run_hook() {
        local hook="$1"
        local func

        while boot_hook_shift "$hook" func; do
                local ran; eval "ran=\$PI_RAN_$func"
                [ -n "$ran" ] || {
                        export -n "PI_RAN_$func=1"
                        $func "$1" "$2"
                }
        done
}

      函数功能如下：

      • boot_hook_init()：初始化一个函数队列

      • boot_hook_add()：往函数队列上增加函数

      • boot_run_hook()：遍历函数队列上的所有函数，找到对应的函数然后运行

    4. 步驟4

      boot_hook_init preinit_essential
boot_hook_init preinit_main
boot_hook_init failsafe
boot_hook_init initramfs
boot_hook_init preinit_mount_root

      可以看到，openwrt一共初始化了5类函数队列如下：

      • preinit_essential

      • preinit_main

      • failsafe

      • initramfs

      • preinit_mount_root

      那又哪些函数分别挂载到这五类队列上呢？继续往下分析

    5. 步骤5

      依次执行/lib/preinit/下面的所有脚本，其实仔细分析这些脚本，你会发现并没真的执行，只是将函数添加到步骤4上说的5类函数队列上

      for pi_source_file in /lib/preinit/*; do
    . $pi_source_file
done

      这些脚本如下：

      注意：80_mount_root 会对overlay目录进行挂载

      我们举例分析：lib/preinit/02_default_set_state

      可以看到

      把define_default_set_state()函数挂载到preinit_main函数列表中

      而define_default_set_state()函数的内容是

      define_default_set_state() {
        . /etc/diag.sh
}

      所以可以看到，這裏仅仅只是把函数挂载到5类函数队列中，并为真正执行，那么问题来了，到底什么时候执行？接着往下分析。

      先总结下这五类函数队列下都挂载了什么

      1. preinit_essential

      2. preinit_main

        • 【lib/preinit/02_default_set_state】脚本下的define_default_set_state()函数

          . /etc/diag.sh

        • 【lib/preinit/10_sysinfo】脚本下的do_sysinfo_generic()函数

          do_sysinfo_generic() {
        [ -d /proc/device-tree ] || return
        mkdir -p /tmp/sysinfo
        [ -e /tmp/sysinfo/board_name ] || \
                echo "$(strings /proc/device-tree/compatible | head -1)" > /tmp/sysinfo/board_name
        [ -e /tmp/sysinfo/model ] || \
                echo "$(cat /proc/device-tree/model)" > /tmp/sysinfo/model
}

        • 【lib/preinit/40_run_failsafe_hook】脚本下的run_failsafe_hook()函数

          run_failsafe_hook() {
    if [ "$FAILSAFE" = "true" ]; then
        boot_run_hook failsafe
        lock -w /tmp/.failsafe
    fi
}

        • 【lib/preinit/70_initramfs_test】脚本下的initramfs_test()函数

          initramfs_test() {
        if [ -n "$INITRAMFS" ]; then
                boot_run_hook initramfs
                preinit_ip_deconfig
                break
        fi
}

        • 【lib/preinit/81_load_wifi_board_bin】脚本下的do_load_ipq4019_board_bin()函数

          
#!/bin/sh
#
# Copyright (c) 2015 The Linux Foundation. All rights reserved.
# Copyright (C) 2011 OpenWrt.org

. /lib/read_caldata_to_fs.sh

boot_hook_add preinit_main do_load_ipq4019_board_bin

          注意：这里会先执行. /lib/read_caldata_to_fs.sh脚本,do_load_ipq4019_board_bin()函数暂时不知在哪？

          /lib/read_caldata_to_fs.sh脚本内容如下：

          #!/bin/sh
#
# Copyright (c) 2015 The Linux Foundation. All rights reserved.
# Copyright (C) 2011 OpenWrt.org

. /lib/ipq806x.sh

do_load_ipq4019_board_bin()
{
    local board=$(ipq806x_board_name)
    local mtdblock=$(find_mtd_part 0:ART)

    local apdk="/tmp"

    if [ -z "$mtdblock" ]; then
        # read from mmc
        mtdblock=$(find_mmc_part 0:ART)
    fi

    [ -n "$mtdblock" ] || return

    # load board.bin
    case "$board" in
            ap-dk0*)
                    mkdir -p ${apdk}
                    dd if=${mtdblock} of=${apdk}/wifi0.caldata bs=32 count=377 skip=128
                    dd if=${mtdblock} of=${apdk}/wifi1.caldata bs=32 count=377 skip=640
            ;;
            ap16* | ap148*)
                    mkdir -p ${apdk}
                    dd if=${mtdblock} of=${apdk}/wifi0.caldata bs=32 count=377 skip=128
                    dd if=${mtdblock} of=${apdk}/wifi1.caldata bs=32 count=377 skip=640
                    dd if=${mtdblock} of=${apdk}/wifi2.caldata bs=32 count=377 skip=1152
            ;;
            ap-hk14 | ap-hk01-c6)
                    FILESIZE=131072
                    mkdir -p ${apdk}/IPQ8074
                    dd if=${mtdblock} of=${apdk}/IPQ8074/caldata.bin bs=1 count=$FILESIZE skip=4096
                    ln -s ${apdk}/IPQ8074/caldata.bin /lib/firmware/IPQ8074/caldata.bin

                    mkdir -p ${apdk}/qcn9000
                    dd if=${mtdblock} of=${apdk}/qcn9000/caldata_1.bin bs=1 count=$FILESIZE skip=157696
                    ln -s ${apdk}/qcn9000/caldata_1.bin /lib/firmware/qcn9000/caldata_1.bin
            ;;
            ap-hk01-*)
                    HK_BD_FILENAME=/lib/firmware/IPQ8074/bdwlan.bin
                    mkdir -p ${apdk}/IPQ8074
                    if [ -f "$HK_BD_FILENAME" ]; then
                        FILESIZE=$(stat -Lc%s "$HK_BD_FILENAME")
                    else
                        FILESIZE=131072
                    fi
                    dd if=${mtdblock} of=${apdk}/IPQ8074/caldata.bin bs=1 count=$FILESIZE skip=4096
                    [ -L /lib/firmware/IPQ8074/caldata.bin ] || \
                    ln -s ${apdk}/IPQ8074/caldata.bin /lib/firmware/IPQ8074/caldata.bin
            ;;
            ap-hk10-*)
                    FILESIZE=131072
                    mkdir -p ${apdk}/IPQ8074
                    dd if=${mtdblock} of=${apdk}/IPQ8074/caldata.bin bs=1 count=$FILESIZE skip=4096
                    ln -s ${apdk}/IPQ8074/caldata.bin /lib/firmware/IPQ8074/caldata.bin

                    mkdir -p ${apdk}/qcn9000
                    dd if=${mtdblock} of=${apdk}/qcn9000/caldata_1.bin bs=1 count=$FILESIZE skip=157696
                    dd if=${mtdblock} of=${apdk}/qcn9000/caldata_2.bin bs=1 count=$FILESIZE skip=311296
                    ln -s ${apdk}/qcn9000/caldata_1.bin /lib/firmware/qcn9000/caldata_1.bin
                    ln -s ${apdk}/qcn9000/caldata_2.bin /lib/firmware/qcn9000/caldata_2.bin
            ;;
            ap-hk* | ap-ac* | ap-oa*)
                    HK_BD_FILENAME=/lib/firmware/IPQ8074/bdwlan.bin
                    mkdir -p ${apdk}/IPQ8074
                    dd if=${mtdblock} of=${apdk}/wifi1.caldata bs=1 count=12064 skip=208896
                    if [ -f "$HK_BD_FILENAME" ]; then
                        FILESIZE=$(stat -Lc%s "$HK_BD_FILENAME")
                    else
                        FILESIZE=131072
                    fi
                    dd if=${mtdblock} of=${apdk}/IPQ8074/caldata.bin bs=1 count=$FILESIZE skip=4096
                    [ -L /lib/firmware/IPQ8074/caldata.bin ] || \
                    ln -s ${apdk}/IPQ8074/caldata.bin /lib/firmware/IPQ8074/caldata.bin
            ;;
            ap-cp01-c3*)
                    CP_BD_FILENAME=/lib/firmware/IPQ6018/bdwlan.bin
                    mkdir -p ${apdk}/IPQ6018
                    if [ -f "$CP_BD_FILENAME" ]; then
                        FILESIZE=$(stat -Lc%s "$CP_BD_FILENAME")
                    else
                        FILESIZE=65536
                    fi
                    dd if=${mtdblock} of=${apdk}/IPQ6018/caldata.bin bs=1 count=$FILESIZE skip=4096
                    [ -L /lib/firmware/IPQ6018/caldata.bin ] || \
                    ln -s ${apdk}/IPQ6018/caldata.bin /lib/firmware/IPQ6018/caldata.bin

                    mkdir -p ${apdk}/qcn9000
                    FILESIZE=131072
                    dd if=${mtdblock} of=${apdk}/qcn9000/caldata_1.bin bs=1 count=$FILESIZE skip=157696
                    ln -s ${apdk}/qcn9000/caldata_1.bin /lib/firmware/qcn9000/caldata_1.bin
            ;;
            ap-mp02.1* | db-mp02.1*)
                    mkdir -p ${apdk}/IPQ5018
                    FILESIZE=131072

                    #FTM Daemon compresses the caldata and writes the lzma file in ART Partition
                    dd if=${mtdblock} of=${apdk}/virtual_art.bin.lzma
                    lzma -fdv --single-stream ${apdk}/virtual_art.bin.lzma || {
                    # Create dummy virtual_art.bin file of size 512K
                    dd if=/dev/zero of=${apdk}/virtual_art.bin bs=1024 count=512
                    }

                    dd if=${apdk}/virtual_art.bin of=${apdk}/IPQ5018/caldata.bin bs=1 count=$FILESIZE skip=4096

                    mkdir -p ${apdk}/qcn6122
                    # Read after 154KB
                    dd if=${apdk}/virtual_art.bin of=${apdk}/qcn6122/caldata_1.bin bs=1 count=$FILESIZE skip=157696
                    # Read after 304KB
                    dd if=${apdk}/virtual_art.bin of=${apdk}/qcn6122/caldata_2.bin bs=1 count=$FILESIZE skip=311296

                    ln -s ${apdk}/IPQ5018/caldata.bin /lib/firmware/IPQ5018/caldata.bin
                    # To Remove later
                    ln -s ${apdk}/qcn6122/caldata_1.bin /lib/firmware/qcn9100/caldata_1.bin
                    ln -s ${apdk}/qcn6122/caldata_2.bin /lib/firmware/qcn9100/caldata_2.bin

                    ln -s ${apdk}/qcn6122/caldata_1.bin /lib/firmware/qcn6122/caldata_1.bin
                    ln -s ${apdk}/qcn6122/caldata_2.bin /lib/firmware/qcn6122/caldata_2.bin
            ;;
            ap-mp03.1)
                    mkdir -p ${apdk}/IPQ5018
                    FILESIZE=131072

                    if [ -e /sys/firmware/devicetree/base/compressed_art ]
                    then
                        #FTM Daemon compresses the caldata and writes the lzma file in ART Partition
                        dd if=${mtdblock} of=${apdk}/virtual_art.bin.lzma
                        lzma -fdv --single-stream ${apdk}/virtual_art.bin.lzma || {
                        # Create dummy virtual_art.bin file of size 512K
                        dd if=/dev/zero of=${apdk}/virtual_art.bin bs=1024 count=512
                        }

                        dd if=${apdk}/virtual_art.bin of=${apdk}/IPQ5018/caldata.bin bs=1 count=$FILESIZE skip=4096

                        mkdir -p ${apdk}/qcn9000
                        # Read after 154KB
                        dd if=${apdk}/virtual_art.bin of=${apdk}/qcn9000/caldata_1.bin bs=1 count=$FILESIZE skip=157696
                    else
                        dd if=${mtdblock} of=${apdk}/IPQ5018/caldata.bin bs=1 count=$FILESIZE skip=4096

                        mkdir -p ${apdk}/qcn9000
                        dd if=${mtdblock} of=${apdk}/qcn9000/caldata_1.bin bs=1 count=$FILESIZE skip=157696
                    fi

                    ln -s ${apdk}/IPQ5018/caldata.bin /lib/firmware/IPQ5018/caldata.bin
                    ln -s ${apdk}/qcn9000/caldata_1.bin /lib/firmware/qcn9000/caldata_1.bin
            ;;
            ap-mp03.1-* | db-mp03.1-* | ap-mp03.6*)
                    MP_BD_FILENAME=/lib/firmware/IPQ5018/bdwlan.bin
                    mkdir -p ${apdk}/IPQ5018
                    if [ -f "$MP_BD_FILENAME" ]; then
                        FILESIZE=$(stat -Lc%s "$MP_BD_FILENAME")
                    else
                        FILESIZE=131072
                    fi
                    dd if=${mtdblock} of=${apdk}/IPQ5018/caldata.bin bs=1 count=$FILESIZE skip=4096
                    ln -s ${apdk}/IPQ5018/caldata.bin /lib/firmware/IPQ5018/caldata.bin

                    mkdir -p ${apdk}/qcn9000
                    dd if=${mtdblock} of=${apdk}/qcn9000/caldata_1.bin bs=1 count=$FILESIZE skip=157696
                    ln -s ${apdk}/qcn9000/caldata_1.bin /lib/firmware/qcn9000/caldata_1.bin
            ;;
            ap-mp03.5*)
                    MP_BD_FILENAME=/lib/firmware/IPQ5018/bdwlan.bin
                    mkdir -p ${apdk}/IPQ5018
                    if [ -f "$MP_BD_FILENAME" ]; then
                        FILESIZE=$(stat -Lc%s "$MP_BD_FILENAME")
                    else
                        FILESIZE=131072
                    fi
                    dd if=${mtdblock} of=${apdk}/IPQ5018/caldata.bin bs=1 count=$FILESIZE skip=4096
                    ln -s ${apdk}/IPQ5018/caldata.bin /lib/firmware/IPQ5018/caldata.bin

                    mkdir -p ${apdk}/qcn6122
                    dd if=${mtdblock} of=${apdk}/qcn6122/caldata_1.bin bs=1 count=$FILESIZE skip=157696
                    # To remove later
                    ln -s ${apdk}/qcn6122/caldata_1.bin /lib/firmware/qcn9100/caldata_1.bin

                    ln -s ${apdk}/qcn6122/caldata_1.bin /lib/firmware/qcn6122/caldata_1.bin

                    dd if=${mtdblock} of=${apdk}/qcn6122/caldata_2.bin bs=1 count=$FILESIZE skip=311296
                    # To remove later
                    ln -s ${apdk}/qcn6122/caldata_2.bin /lib/firmware/qcn9100/caldata_2.bin
                    ln -s ${apdk}/qcn6122/caldata_2.bin /lib/firmware/qcn6122/caldata_2.bin
            ;;
            ap-mp03.3* | db-mp03.3* | tb-mp04*)
                    MP_BD_FILENAME=/lib/firmware/IPQ5018/bdwlan.bin
                    mkdir -p ${apdk}/IPQ5018
                    if [ -f "$MP_BD_FILENAME" ]; then
                        FILESIZE=$(stat -Lc%s "$MP_BD_FILENAME")
                    else
                        FILESIZE=131072
                    fi
                    dd if=${mtdblock} of=${apdk}/IPQ5018/caldata.bin bs=1 count=$FILESIZE skip=4096
                    ln -s ${apdk}/IPQ5018/caldata.bin /lib/firmware/IPQ5018/caldata.bin

                    mkdir -p ${apdk}/qcn6122
                    dd if=${mtdblock} of=${apdk}/qcn6122/caldata_1.bin bs=1 count=$FILESIZE skip=157696
                    # To remove later
                    ln -s ${apdk}/qcn6122/caldata_1.bin /lib/firmware/qcn9100/caldata_1.bin

                    ln -s ${apdk}/qcn6122/caldata_1.bin /lib/firmware/qcn6122/caldata_1.bin

                    mkdir -p ${apdk}/qcn9000
                    dd if=${mtdblock} of=${apdk}/qcn9000/caldata_2.bin bs=1 count=$FILESIZE skip=311296
                    ln -s ${apdk}/qcn9000/caldata_2.bin /lib/firmware/qcn9000/caldata_2.bin
            ;;
            ap-mp03.4*)
                    MP_BD_FILENAME=/lib/firmware/IPQ5018/bdwlan.bin
                    mkdir -p ${apdk}/IPQ5018
                    if [ -f "$MP_BD_FILENAME" ]; then
                        FILESIZE=$(stat -Lc%s "$MP_BD_FILENAME")
                    else
                        FILESIZE=131072
                    fi
                    dd if=${mtdblock} of=${apdk}/IPQ5018/caldata.bin bs=1 count=$FILESIZE skip=4096
                    ln -s ${apdk}/IPQ5018/caldata.bin /lib/firmware/IPQ5018/caldata.bin

                    mkdir -p ${apdk}/qcn9000
                    dd if=${mtdblock} of=${apdk}/qcn9000/caldata_1.bin bs=1 count=$FILESIZE skip=157696
                    ln -s ${apdk}/qcn9000/caldata_1.bin /lib/firmware/qcn9000/caldata_1.bin

                    mkdir -p ${apdk}/qcn9000
                    dd if=${mtdblock} of=${apdk}/qcn9000/caldata_2.bin bs=1 count=$FILESIZE skip=311296
                    ln -s ${apdk}/qcn9000/caldata_2.bin /lib/firmware/qcn9000/caldata_2.bin
            ;;
            ap-mp*)
                    MP_BD_FILENAME=/lib/firmware/IPQ5018/bdwlan.bin
                    mkdir -p ${apdk}/IPQ5018
                    if [ -f "$MP_BD_FILENAME" ]; then
                        FILESIZE=$(stat -Lc%s "$MP_BD_FILENAME")
                    else
                        FILESIZE=131072
                    fi
                    dd if=${mtdblock} of=${apdk}/IPQ5018/caldata.bin bs=1 count=$FILESIZE skip=4096
                    [ -L /lib/firmware/IPQ5018/caldata.bin ] || \
                    ln -s ${apdk}/IPQ5018/caldata.bin /lib/firmware/IPQ5018/caldata.bin
            ;;
            ap-cp*)
                    CP_BD_FILENAME=/lib/firmware/IPQ6018/bdwlan.bin
                    mkdir -p ${apdk}/IPQ6018
                    if [ -f "$CP_BD_FILENAME" ]; then
                        FILESIZE=$(stat -Lc%s "$CP_BD_FILENAME")
                    else
                        FILESIZE=65536
                    fi
                    dd if=${mtdblock} of=${apdk}/IPQ6018/caldata.bin bs=1 count=$FILESIZE skip=4096
                    [ -L /lib/firmware/IPQ6018/caldata.bin ] || \
                    ln -s ${apdk}/IPQ6018/caldata.bin /lib/firmware/IPQ6018/caldata.bin
            ;;
   esac
}

        • 【lib/preinit/99_10_run_init】脚本下的run_init()函数

          run_init() {
        preinit_ip_deconfig
}

        • 【lib/preinit/03_preinit_do_ipq806x.sh】脚本下的do_ipq806x()函数

          do_ipq806x() {
        . /lib/ipq806x.sh

        ipq806x_board_detect
}

        • 【lib/preinit/30_failsafe_wait】脚本下的failsafe_wait() 函數和

          failsafe_wait() {
        FAILSAFE=
        grep -q 'failsafe=' /proc/cmdline && FAILSAFE=true && export FAILSAFE
        if [ "$FAILSAFE" != "true" ]; then
                pi_failsafe_net_message=true
                preinit_net_echo "Please press button now to enter failsafe"
                pi_failsafe_net_message=false
                fs_wait_for_key f 'to enter failsafe mode' $fs_failsafe_wait_timeout && FAILSAFE=true
                [ -f "/tmp/failsafe_button" ] && FAILSAFE=true && echo "- failsafe button "`cat /tmp/failsafe_button`" was pressed -"
                [ "$FAILSAFE" = "true" ] && export FAILSAFE && touch /tmp/failsafe
        fi
}

        • 【lib/preinit/50_indicate_regular_preinit】脚本下的indicate_regular_preinit() 函数

          indicate_regular_preinit() {
        preinit_net_echo "Continuing with Regular Preinit\n"
        set_state preinit_regular
}

        • 【lib/preinit/80_mount_root】脚本下的do_mount_root() 函數

          do_mount_root() {
        echo "Before mount_root"
        mount_root
        boot_run_hook preinit_mount_root
        [ -f /sysupgrade.tgz ] && {
                echo "- config restore -"
                cd /
                tar xzf /sysupgrade.tgz
        }
        echo "After mount_root"
}

        • 【lib/preinit/10_indicate_preinit】脚本下的preinit_ip() 函數和pi_indicate_preinit()函數

          preinit_ip() {
        # if the preinit interface isn't specified and ifname is set in
        # preinit.arch use that interface
        if [ -z "$pi_ifname" ]; then
                pi_ifname=$ifname
        fi

        [ -n "$pi_ifname" ] && grep -q "$pi_ifname" /proc/net/dev && {
                ifconfig $pi_ifname $pi_ip netmask $pi_netmask broadcast $pi_broadcast up
        }
}



pi_indicate_preinit() {
        preinit_net_echo "Doing OpenWrt Preinit\n"
        set_state preinit
}

      3. failsafe

        • 【lib/preinit/10_indicate_failsafe】脚本下的indicate_failsafe() 函數

          indicate_failsafe() {
        echo "- failsafe -"
        preinit_net_echo "Entering Failsafe!\n"
        indicate_failsafe_led
}

        • 【lib/preinit/99_10_failsafe_login】脚本下的failsafe_netlogin() 函數和failsafe_shell()函數

          failsafe_netlogin () {
        dropbearkey -t rsa -s 1024 -f /tmp/dropbear_failsafe_host_key
        dropbear -r /tmp/dropbear_failsafe_host_key <> /dev/null 2>&1
}

failsafe_shell() {
        lock /tmp/.failsafe
        ash --login
        echo "Please reboot system when done with failsafe network logins"
}

      4. initramfs

      5. preinit_mount_root

      总结：可以看出目前只用了preinit_main和failsafe两个函数队列

      1. preinit_main

        • 【lib/preinit/02_default_set_state】

        • 【lib/preinit/40_run_failsafe_hook 】

        • 【lib/preinit/10_sysinfo 】

        • 【lib/preinit/70_initramfs_test】

        • 【 lib/preinit/81_load_wifi_board_bin】

        • 【lib/preinit/99_10_run_init】

        • 【lib/preinit/03_preinit_do_ipq806x.sh  】

        • 【lib/preinit/10_indicate_preinit 】

        • 【lib/preinit/30_failsafe_wait】

        • 【 lib/preinit/50_indicate_regular_preinit】

        • 【 lib/preinit/80_mount_root】

      2. failsafe

        • 【lib/preinit/99_10_failsafe_login】

        • 【 lib/preinit/10_indicate_failsafe】

    6. 步骤6

      继续分析/etc/perinit 脚本

      boot_run_hook preinit_essential # 执行preinit_essential队列下的所有函数，这里应该是空
boot_run_hook preinit_main      # 执行preinit_main队列下的所有函数 如步骤5中所述，所有的中注册的函数

    7. 步骤7

      /etc/perinit 脚本执行完毕结束。

  3. 按照/etc/inittab文件执行其他的启动项

    Linux原生系统/etc/inittab是有是有busybox下的/sbin/init在下面这个地方调用

    来来解释的，但是openwrt是有/sbin/procd来解释的，目的是为了初始化文件系统。

    新看下/etc/inittab内容

    从图中内容可以看出：/etc/inittab会执行/etc/init.d/rcS脚本，但是吧，openwrt把这个脚本去掉，了，所以我们在etc目录下根本找不到这个脚本。取而代之的如下：

    1. ::sysinit:/etc/init.d/rcS S boot

      功能：开机的时候按照etc/rc.d目录下S开头的数值顺序，执行脚本

    2. ::shutdown:/etc/init.d/rcS K shutdown

      功能：关机的时候按照etc/rc.d目录下K开头的数值顺序，执行脚本

  4. 所以下面肯定要分析etc/rc.d/S*开头的启动脚本

    重点分析：

    1. S10boot

      调用uci_apply_defaults 执行第一次开机时候的UCI配置初始化，该函数执行/etc/uci-defaults下的所有脚本，执行成功后就删除掉了，因此该目录下的脚本只有在第一次开机的时候才会执行。

    2. S10system

      根据UCI配置文件/etc/confing/system 配置系统

    3. S11sysctl

      根据/etc/sysctl.cofig 设置系统配置（[-f /etc/sysctl.conf] && sysctl -p -e >&-)）

    4. S19firewall

      启动防火墙fw3 该工具在Openwrt工具包 packgae/network/config/firewall

    5. S20network

      根据UCI配置文件/etc/config/network ,使用守护进程/sbin/netifd 来配置网络