Linux内核很吊之 module_init解析（下）

时间：2016-04-01 18:29:23 阅读：294 评论：0 收藏：0 [点我收藏+]

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<h1 style="margin:0px;padding:0px;color:#555555;font-family:‘microsoft yahei‘;line-height:35px;white-space:normal;background-color:#FFFFFF;"> <div style="text-align:center;"> Linux内核很吊之 module_init解析（下） </div> </h1> 个人笔记，欢迎转载，请注明出处，共同分享共同进步    <a target="_blank" href="http://blog.csdn.net/richard_liujh/article/details/46758073" style="text-decoration:none;color:#0C89CF;">http://blog.csdn.net/richard_liujh/article/details/46758073</a> -- 刘金辉 忙了一段时间，终于有时间把inux内核很吊之 module_init解析（下）整理完毕。 从上一篇博文<a target="_blank" href="http://blog.csdn.net/richard_liujh/article/details/45669207" style="text-decoration:none;color:#0C89CF;">http://blog.csdn.net/richard_liujh/article/details/45669207</a>介绍了module_init宏函数，简单来说上篇博文介绍module_init如何注册驱动的init函数，这篇博文将详细分析kernel启动过程又是如何执行我们注册的init函数。 如果了解过linux操作系统启动流程，那么当bootloader加载完kernel并解压并放置与内存中准备开始运行，首先被调用的函数是start_kernel。start_kernel函数顾名思义，内核从此准备开启了，但是start_kernel做的事情非常多，简单来说为内核启动做准备工作，复杂来说也是非常之多（包含了自旋锁检查、初始化栈、CPU中断、立即数、初始化页地址、内存管理等等等...）。所以这篇博文我们还是主要分析和module_init注册函数的执行过程。 start_kernel函数在 init/main.c文件中，由于start_kernel本身功能也比较多，所以为了简介分析过程我把函数从start_kernel到do_initcalls的调用过程按照如下方式展现出来 <div class="dp-highlighter bg_cpp" style="font-family:Consolas, ‘Courier New‘, Courier, mono, serif;font-size:12px;width:938.515625px;overflow:hidden;padding-top:1px;border-color:#CCCCCC;color:#555555;line-height:35px;white-space:normal;margin:18px 0px !important;background-color:#E7E5DC;"> <div class="bar" style="padding-left:45px;"> <div class="tools" style="padding:3px 8px 10px 10px;font-stretch:normal;font-size:9px;line-height:normal;font-family:Verdana, Geneva, Arial, Helvetica, sans-serif;color:silver;border-left-width:3px;border-left-style:solid;border-left-color:#999999;background-color:#F8F8F8;"> [cpp] <a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="ViewSource" title="view plain" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">view plain</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="CopyToClipboard" title="copy" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">copy</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="PrintSource" title="print" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">print</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="About" title="?" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">?</a> <div style="position:absolute;left:783px;top:692px;width:27px;height:15px;z-index:99;"> </div> </div> </div> <ol start="1" class="dp-cpp" style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> start_kernel -> reset_init -> kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">                                                     |   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">                                                     |->static int __ref kernel_init(void *unused)   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">                                                         |   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">                                                         |-> kernel_init_freeable( )   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">                                                                 |   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">                                                                 |-> do_basic_setup();   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">                                                                         |   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">                                                                         |——> do_initcalls();   </li> </ol> </div> 在上面的调用过程中，通过kernel_thread注册了一个任务kernel_init，kernel_thread的函数原型如下。 <div class="dp-highlighter bg_cpp" style="font-family:Consolas, ‘Courier New‘, Courier, mono, serif;font-size:12px;width:938.515625px;overflow:hidden;padding-top:1px;border-color:#CCCCCC;color:#555555;line-height:35px;white-space:normal;margin:18px 0px !important;background-color:#E7E5DC;"> <div class="bar" style="padding-left:45px;"> <div class="tools" style="padding:3px 8px 10px 10px;font-stretch:normal;font-size:9px;line-height:normal;font-family:Verdana, Geneva, Arial, Helvetica, sans-serif;color:silver;border-left-width:3px;border-left-style:solid;border-left-color:#999999;background-color:#F8F8F8;"> [cpp] <a 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style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> /*  </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">  * Create a kernel thread.  </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">  */   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;"> pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> {   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">         (unsigned long)arg, NULL, NULL);   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;"> }   </li> </ol> </div> kernel_thread创建了一个内核线程，也就是创建一个线程完成kernel_init的任务。通过kernel_init的逐层调用，最后调用到我们目前最应该关心的函数do_initcalls； do_initcalls函数如下 <div class="dp-highlighter bg_cpp" style="font-family:Consolas, ‘Courier New‘, Courier, mono, serif;font-size:12px;width:938.515625px;overflow:hidden;padding-top:1px;border-color:#CCCCCC;color:#555555;line-height:35px;white-space:normal;margin:18px 0px !important;background-color:#E7E5DC;"> <div class="bar" style="padding-left:45px;"> <div class="tools" style="padding:3px 8px 10px 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0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">?</a> <div style="position:absolute;left:783px;top:1270px;width:27px;height:15px;z-index:99;"> </div> </div> </div> <ol start="1" class="dp-cpp" style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> static void __init do_initcalls(void)   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;"> {   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     int level;   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">    </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     for (level = 0; level < ARRAY_SIZE(initcall_levels) - 1; level++)   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">         do_initcall_level(level);   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> }   </li> </ol> </div> 这个函数看起来就非常简单了，里面有for循环，每循环一次就调用一次do_initcall_level(level)；其实可以发现在我们分析kernel源码时，大部分函数都能从函数名猜到函数的功能，这也是一名优秀程序猿的体现，大道至简，悟在天成。 接下来我们就开始具体分析do_initcalls函数啦~~ <div class="dp-highlighter bg_cpp" style="font-family:Consolas, ‘Courier New‘, Courier, mono, serif;font-size:12px;width:938.515625px;overflow:hidden;padding-top:1px;border-color:#CCCCCC;color:#555555;line-height:35px;white-space:normal;margin:18px 0px !important;background-color:#E7E5DC;"> 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0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">?</a> <div style="position:absolute;left:783px;top:1567px;width:27px;height:15px;z-index:99;"> </div> </div> </div> <ol start="1" class="dp-cpp" style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> for (level = 0; level < ARRAY_SIZE(initcall_levels) - 1; level++)   </li> </ol> </div> 这句for循环很简单，循环执行条件是level < ARRAY_SIZE(initcall_levels)。 ARRAY_SIZE是一个宏，用于求数组元素的个数，在文件include\linux\kernel.h文件中 <div class="dp-highlighter bg_cpp" 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!important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr))   </li> </ol> </div> 当然ARRAY_SIZE宏里面还多了一个__must_be_array()，这个主要是确保我们传过来的arr是一个数组，防止ARRAY_SIZE的误用。所以在我们写kernel驱动程序时，遇到需要求一个数组的大小请记得使用ARRAY_SIZE。有安全感又高大上...哈哈 那么，initcall_levels是不是数组呢？如果是，里面有什么内容？ 还是在文件main.c中有数组initcall_levels的定义 <div class="dp-highlighter bg_cpp" style="font-family:Consolas, ‘Courier New‘, Courier, mono, serif;font-size:12px;width:938.515625px;overflow:hidden;padding-top:1px;border-color:#CCCCCC;color:#555555;line-height:35px;white-space:normal;margin:18px 0px !important;background-color:#E7E5DC;"> <div class="bar" style="padding-left:45px;"> <div class="tools" style="padding:3px 8px 10px 10px;font-stretch:normal;font-size:9px;line-height:normal;font-family:Verdana, Geneva, Arial, Helvetica, sans-serif;color:silver;border-left-width:3px;border-left-style:solid;border-left-color:#999999;background-color:#F8F8F8;"> [cpp] <a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="ViewSource" title="view plain" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">view plain</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="CopyToClipboard" title="copy" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">copy</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="PrintSource" title="print" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">print</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="About" title="?" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">?</a> <div style="position:absolute;left:783px;top:1945px;width:27px;height:15px;z-index:99;"> </div> </div> </div> <ol start="1" class="dp-cpp" style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> static initcall_t *initcall_levels[] __initdata = {   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     __initcall0_start,   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     __initcall1_start,   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     __initcall2_start,   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     __initcall3_start,   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     __initcall4_start,   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     __initcall5_start,   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     __initcall6_start,   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     __initcall7_start,   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     __initcall_end,   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> };   </li> </ol> </div> 这个数组可不能小看他，如果看过<a target="_blank" href="http://blog.csdn.net/richard_liujh/article/details/45669207" style="text-decoration:none;color:#0C89CF;font-family:‘microsoft yahei‘;font-size:15px;line-height:35px;white-space:normal;background-color:#FFFFFF;">module_init解析(上)</a>的朋友，对数组里面的名字“__initcall0 __initcall1 ... __initcall7”有一点点印象吧。 谈到数组，我们知道是元素的集合，那么initcall_levels数组中得元素是什么？？？（看下面的分析前，请先弄清楚数组指针 和指针数组的区别，不然容易走火入魔...<img alt="偷笑" src="http://static.blog.csdn.net/xheditor/xheditor_emot/default/titter.gif" style="border-style:none;border-width:initial;max-width:602px;height:auto;" />） <div class="dp-highlighter 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0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">print</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="About" title="?" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">?</a> <div style="position:absolute;left:783px;top:2315px;width:27px;height:15px;z-index:99;"> </div> </div> </div> <ol start="1" class="dp-cpp" style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> static initcall_t *initcall_levels[] __initdata = {   </li> </ol> </div> 很显然，这个数组定义非常高大上。不管如何高大上，总离不开最基本的知识吧。所以我先从两点去探索： 1. 数组的名字，根据数组标志性的‘[ ]’，我们应该很容易知道数组名字是initcall_levels 2.数组的元素类型，由于定义中出现了指针的符号‘ * ’，也很容知道initcall_levels原来是一个指针数组啦。 所以现在我们知道了initcall_levels数组里面保存的是指针啦，也就是指针的一个集合而已。掰掰脚趾数一下也能知道initcall_levels数组里面有9个元素，他们都是指针。哈哈 对于这个数组，我们先暂且到这儿，因为我们已经知道了数组的个数了，也就知道for循环的循环次数。（后面还会继续分析这个数组，所以要由印象） 我们再回来看看do_initcalls： <div class="dp-highlighter bg_cpp" style="font-family:Consolas, ‘Courier New‘, Courier, mono, serif;font-size:12px;width:938.515625px;overflow:hidden;padding-top:1px;border-color:#CCCCCC;color:#555555;line-height:35px;white-space:normal;margin:18px 0px !important;background-color:#E7E5DC;"> <div class="bar" style="padding-left:45px;"> <div class="tools" style="padding:3px 8px 10px 10px;font-stretch:normal;font-size:9px;line-height:normal;font-family:Verdana, Geneva, Arial, Helvetica, sans-serif;color:silver;border-left-width:3px;border-left-style:solid;border-left-color:#999999;background-color:#F8F8F8;"> [cpp] <a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="ViewSource" title="view plain" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">view plain</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="CopyToClipboard" title="copy" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 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0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">?</a> <div style="position:absolute;left:783px;top:2679px;width:27px;height:15px;z-index:99;"> </div> </div> </div> <ol start="1" class="dp-cpp" style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> static void __init do_initcalls(void)   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;"> {   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     int level;   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">    </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     for (level = 0; level < ARRAY_SIZE(initcall_levels) - 1; level++)   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">         do_initcall_level(level);   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> }   </li> </ol> </div> <div style="color:#555555;font-family:‘microsoft yahei‘;font-size:15px;line-height:35px;white-space:normal;background-color:#FFFFFF;"> ARRAY_SIZE求出了数组initcall_levels的元素个数为9，所以level变量从 0 ~ 7都是满足level < ARRAY_SIZE(initcall_levels) - 1既level < 9 - 1。一共循环了8次。 </div> 循环8此就调用了do_initcall_level(level) 8次。 do_initcall_level函数原型如下： <div class="dp-highlighter bg_cpp" style="font-family:Consolas, ‘Courier New‘, Courier, mono, serif;font-size:12px;width:938.515625px;overflow:hidden;padding-top:1px;border-color:#CCCCCC;color:#555555;line-height:35px;white-space:normal;margin:18px 0px !important;background-color:#E7E5DC;"> <div class="bar" style="padding-left:45px;"> <div class="tools" style="padding:3px 8px 10px 10px;font-stretch:normal;font-size:9px;line-height:normal;font-family:Verdana, Geneva, Arial, Helvetica, sans-serif;color:silver;border-left-width:3px;border-left-style:solid;border-left-color:#999999;background-color:#F8F8F8;"> [cpp] <a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="ViewSource" title="view plain" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">view plain</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="CopyToClipboard" title="copy" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">copy</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="PrintSource" title="print" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">print</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="About" title="?" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">?</a> <div style="position:absolute;left:783px;top:3011px;width:27px;height:15px;z-index:99;"> </div> </div> </div> <ol start="1" class="dp-cpp" style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> static void __init do_initcall_level(int level)   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;"> {   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     extern const struct kernel_param __start___param[], __stop___param[];   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     initcall_t *fn;   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">    </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     strcpy(static_command_line, saved_command_line);   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     parse_args(initcall_level_names[level],   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">            static_command_line, __start___param,   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">            __stop___param - __start___param,   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">            level, level,   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">            &repair_env_string);   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">    </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     for (fn = initcall_levels[level]; fn < initcall_levels[level+1]; fn++)   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">         do_one_initcall(*fn);   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> }   </li> </ol> </div> 在do_initcall_level函数中，有如下部分是和内核初始化过程调用parse_args对选项进行解析并调用相关函数去处理的。其中的__start___param和__stop___param也是可以在内核链接脚本vmlinux.lds中找到的。 <div class="dp-highlighter bg_cpp" style="font-family:Consolas, ‘Courier New‘, Courier, mono, serif;font-size:12px;width:938.515625px;overflow:hidden;padding-top:1px;border-color:#CCCCCC;color:#555555;line-height:35px;white-space:normal;margin:18px 0px !important;background-color:#E7E5DC;"> <div class="bar" style="padding-left:45px;"> <div class="tools" style="padding:3px 8px 10px 10px;font-stretch:normal;font-size:9px;line-height:normal;font-family:Verdana, Geneva, Arial, Helvetica, sans-serif;color:silver;border-left-width:3px;border-left-style:solid;border-left-color:#999999;background-color:#F8F8F8;"> [cpp] <a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="ViewSource" title="view plain" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">view plain</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="CopyToClipboard" title="copy" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">copy</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="PrintSource" title="print" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">print</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="About" title="?" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">?</a> <div style="position:absolute;left:783px;top:3417px;width:27px;height:15px;z-index:99;"> </div> </div> </div> <ol start="1" class="dp-cpp" style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> extern const struct kernel_param __start___param[], __stop___param[];   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">    </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> strcpy(static_command_line, saved_command_line);   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;"> parse_args(initcall_level_names[level],   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">        static_command_line, __start___param,   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">        __stop___param - __start___param,   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">        level, level,   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">        &repair_env_string);   </li> </ol> </div> <div style="color:#555555;font-family:‘microsoft yahei‘;font-size:15px;line-height:35px;white-space:normal;background-color:#FFFFFF;"> 如果将上面初始化过程中命令行参数解析过程忽略，那么就剩下的内容也就是我们最想看到的内容了 </div> <div style="color:#555555;font-family:‘microsoft yahei‘;font-size:15px;line-height:35px;white-space:normal;background-color:#FFFFFF;"> </div> <div class="dp-highlighter bg_cpp" style="font-family:Consolas, ‘Courier New‘, Courier, mono, 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style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">?</a> <div style="position:absolute;left:783px;top:3662px;width:27px;height:15px;z-index:99;"> </div> </div> </div> <ol start="1" class="dp-cpp" style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> for (fn = initcall_levels[level]; fn < initcall_levels[level+1]; fn++)   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     do_one_initcall(*fn);   </li> </ol> </div> 这个也很简单，不就是一个for循环嘛，so easy~！！<img alt="骂人" src="http://static.blog.csdn.net/xheditor/xheditor_emot/default/curse.gif" style="border-style:none;border-width:initial;max-width:602px;height:auto;" /> 那么接下来我们就开始分析这个for循环： 1. for循环开始，fn = initcall_levels[level]，initcall_levels是上面分析过的数组，数组里面存放着指针，所以fn也应该是指针咯。那么看看fn的定义 <div class="dp-highlighter bg_cpp" style="font-family:Consolas, ‘Courier New‘, Courier, mono, serif;font-size:12px;width:938.515625px;overflow:hidden;padding-top:1px;border-color:#CCCCCC;color:#555555;line-height:35px;white-space:normal;margin:18px 0px !important;background-color:#E7E5DC;"> <div class="bar" style="padding-left:45px;"> <div class="tools" style="padding:3px 8px 10px 10px;font-stretch:normal;font-size:9px;line-height:normal;font-family:Verdana, Geneva, 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0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">?</a> <div style="position:absolute;left:783px;top:3905px;width:27px;height:15px;z-index:99;"> </div> </div> </div> <ol start="1" class="dp-cpp" style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> initcall_t *fn;   </li> </ol> </div> fn确实是一个initcall_t类型的指针，那initcall_t是什么？ 在文件include\linux\init.h文件中找到其定义 <div class="dp-highlighter bg_cpp" style="font-family:Consolas, ‘Courier New‘, Courier, mono, 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style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">?</a> <div style="position:absolute;left:783px;top:4059px;width:27px;height:15px;z-index:99;"> </div> </div> </div> <ol start="1" class="dp-cpp" style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> /*  </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">  * Used for initialization calls..  </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">  */   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;"> typedef int (*initcall_t)(void);   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> typedef void (*exitcall_t)(void);   </li> </ol> </div> 从上面的定义可以知道，initcall_t原来是一个函数指针的类型定义。函数的返回值是int类型，参数是空 void。从注释也可以看出，initcall_t是初始化调用的。 简单来说，fn是一个函数指针。 2. 每循环一次，fn++。循环执行的条件是fn < initcall_levels[level+1]; 这里fn++就不是很容易理解了，毕竟不是一个普通的变量而是一个函数指针，那么fn++有何作用呢？？ 首先，fn = initcall_levels[level]，所以我们还是有必要去再看看initcall_levels数组了（之前暂时没有分析的，现在开始分析了） <div class="dp-highlighter bg_cpp" style="font-family:Consolas, ‘Courier New‘, Courier, mono, serif;font-size:12px;width:938.515625px;overflow:hidden;padding-top:1px;border-color:#CCCCCC;color:#555555;line-height:35px;white-space:normal;margin:18px 0px !important;background-color:#E7E5DC;"> <div class="bar" style="padding-left:45px;"> <div class="tools" style="padding:3px 8px 10px 10px;font-stretch:normal;font-size:9px;line-height:normal;font-family:Verdana, Geneva, Arial, Helvetica, 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style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> static initcall_t *initcall_levels[] __initdata = {   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     __initcall0_start,   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     __initcall1_start,   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     __initcall2_start,   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     __initcall3_start,   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     __initcall4_start,   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     __initcall5_start,   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     __initcall6_start,   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     __initcall7_start,   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     __initcall_end,   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> };   </li> </ol> </div> 已经知道了initcall_levels是一个指针数组，也就是说数组的元素都是指针，指针是指向什么类型的数据呢？是initcall_t类型的，上面刚刚分析过initcall_t是函数指针的类型定义。 这样一来，initcall_levels数组里面保存的元素都是数组指针啦。 很显然这是通过枚举的方式定义了数组initcall_levels，那么元素值是多少？？（数组中元素是分别是 __initcall0_start __initcall1_start __initcall2_start ... __initcall7_start __initcall_end） 通过寻找会发现在main.c文件中有如下的声明 <div class="dp-highlighter bg_cpp" style="font-family:Consolas, ‘Courier New‘, Courier, mono, serif;font-size:12px;width:938.515625px;overflow:hidden;padding-top:1px;border-color:#CCCCCC;color:#555555;line-height:35px;white-space:normal;margin:18px 0px !important;background-color:#E7E5DC;"> <div class="bar" style="padding-left:45px;"> <div class="tools" style="padding:3px 8px 10px 10px;font-stretch:normal;font-size:9px;line-height:normal;font-family:Verdana, Geneva, Arial, Helvetica, sans-serif;color:silver;border-left-width:3px;border-left-style:solid;border-left-color:#999999;background-color:#F8F8F8;"> [cpp] <a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="ViewSource" title="view plain" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">view plain</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="CopyToClipboard" title="copy" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 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0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">?</a> <div style="position:absolute;left:783px;top:4899px;width:27px;height:15px;z-index:99;"> </div> </div> </div> <ol start="1" class="dp-cpp" style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> extern initcall_t __initcall_start[];   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;"> extern initcall_t __initcall0_start[];   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> extern initcall_t __initcall1_start[];   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;"> extern initcall_t __initcall2_start[];   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> extern initcall_t __initcall3_start[];   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;"> extern initcall_t __initcall4_start[];   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> extern initcall_t __initcall5_start[];   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;"> extern initcall_t __initcall6_start[];   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> extern initcall_t __initcall7_start[];   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;"> extern initcall_t __initcall_end[];   </li> </ol> </div> 所以__initcall0_start __initcall1_start __initcall2_start ... __initcall7_start __initcall_end都是initcall_t类型的数组名，数组名也就是指针。只是这些都是extern声明的，所以在本文件里面找不到他们的定义出。那么他们在哪一个文件？？答案还是链接脚本 vmlinux.lds，而且我们已经看过这些名字很多次了... 下面再次把链接脚本中相关的内容拿出来：（相关的解释请参考<a target="_blank" href="http://blog.csdn.net/richard_liujh/article/details/45669207" style="text-decoration:none;color:#0C89CF;"> module_init 解析--上</a>） <div class="dp-highlighter bg_cpp" style="font-family:Consolas, ‘Courier New‘, Courier, mono, serif;font-size:12px;width:938.515625px;overflow:hidden;padding-top:1px;border-color:#CCCCCC;color:#555555;line-height:35px;white-space:normal;margin:18px 0px !important;background-color:#E7E5DC;"> <div class="bar" style="padding-left:45px;"> <div class="tools" style="padding:3px 8px 10px 10px;font-stretch:normal;font-size:9px;line-height:normal;font-family:Verdana, Geneva, Arial, Helvetica, sans-serif;color:silver;border-left-width:3px;border-left-style:solid;border-left-color:#999999;background-color:#F8F8F8;"> [cpp] <a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="ViewSource" title="view plain" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">view plain</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="CopyToClipboard" title="copy" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">copy</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="PrintSource" title="print" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">print</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="About" title="?" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">?</a> <div style="position:absolute;left:783px;top:5285px;width:27px;height:15px;z-index:99;"> </div> </div> </div> <ol start="1" class="dp-cpp" style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> __init_begin = .;   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">  . = ALIGN(4096); .init.text : AT(ADDR(.init.text) - 0) { _sinittext = .; *(.init.text) *(.cpuinit.text) *(.meminit.text) _einittext = .; }   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">  .init.data : AT(ADDR(.init.data) - 0) { *(.init.data) *(.cpuinit.data) *(.meminit.data) *(.init.rodata) *(.cpuinit.rodata) *(.meminit.rodata) . = ALIGN(32); __dtb_start = .; *(.dtb.init.rodata) __dtb_end = .; . = ALIGN(16); __setup_start = .; *(.init.setup) __setup_end = .; __initcall_start = .; *(.initcallearly.init) __initcall0_start = .; *(.initcall0.init) *(.initcall0s.init) __initcall1_start = .; *(.initcall1.init) *(.initcall1s.init) __initcall2_start = .; *(.initcall2.init) *(.initcall2s.init) __initcall3_start = .; *(.initcall3.init) *(.initcall3s.init) __initcall4_start = .; *(.initcall4.init) *(.initcall4s.init) __initcall5_start = .; *(.initcall5.init) *(.initcall5s.init) __initcallrootfs_start = .; *(.initcallrootfs.init) *(.initcallrootfss.init) __initcall6_start = .; *(.initcall6.init) *(.initcall6s.init) __initcall7_start = .; *(.initcall7.init) *(.initcall7s.init) __initcall_end = .; __con_initcall_start = .; *(.con_initcall.init) __con_initcall_end = .; __security_initcall_start = .; *(.security_initcall.init) __security_initcall_end = .; . = ALIGN(4); __initramfs_start = .; *(.init.ramfs) . = ALIGN(8); *(.init.ramfs.info) }   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">  . = ALIGN(4);   </li> </ol> </div> 所以在main.c文件中extern声明的那些数组__initcall0_start  ... __initcall7_start __initcall_end其实就是上面链接脚本vmlinux.lds中定义的标号（也可以暂且简单粗暴认为是地址）。 为了好理解，把其中的__initcall0_start单独拿出来 <div class="dp-highlighter bg_cpp" style="font-family:Consolas, ‘Courier New‘, Courier, mono, serif;font-size:12px;width:938.515625px;overflow:hidden;padding-top:1px;border-color:#CCCCCC;color:#555555;line-height:35px;white-space:normal;margin:18px 0px !important;background-color:#E7E5DC;"> <div class="bar" style="padding-left:45px;"> <div class="tools" style="padding:3px 8px 10px 10px;font-stretch:normal;font-size:9px;line-height:normal;font-family:Verdana, Geneva, Arial, Helvetica, sans-serif;color:silver;border-left-width:3px;border-left-style:solid;border-left-color:#999999;background-color:#F8F8F8;"> [cpp] <a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="ViewSource" title="view plain" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">view plain</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="CopyToClipboard" title="copy" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">copy</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="PrintSource" title="print" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">print</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="About" title="?" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">?</a> <div style="position:absolute;left:783px;top:5726px;width:27px;height:15px;z-index:99;"> </div> </div> </div> <ol start="1" class="dp-cpp" style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> __initcall0_start = .; *(.initcall0.init) *(.initcall0s.init)   </li> </ol> </div> 这里的意思是，__initcall0_start 是一段地址的开始，从这个地址开始链接所有.initcall0.init和.initcall0s.init段的内容。那.initcall0.init和.initcall0s.init段有什么东东？？这就是<a target="_blank" href="http://blog.csdn.net/richard_liujh/article/details/45669207" style="text-decoration:none;color:#0C89CF;font-family:‘microsoft yahei‘;font-size:15px;line-height:35px;white-space:normal;background-color:#FFFFFF;">上篇博文</a>中解释的。简单来说，就是我们通过module_init(xxx)添加的内容，只是module_init对应的level值默认为6而已。 总而言之，__initcallN_start(其中N = 0,1,2...7)地址开始存放了一系列优先级为N的函数。我们通过module_init注册的函数优先级为6 现在我们回过头再去看看上面的for循环 <div 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0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">print</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="About" title="?" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">?</a> <div style="position:absolute;left:783px;top:5985px;width:27px;height:15px;z-index:99;"> </div> </div> </div> <ol start="1" class="dp-cpp" style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> for (fn = initcall_levels[level]; fn < initcall_levels[level+1]; fn++)   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;"> <span style="white-space: pre;">      do_one_initcall(*fn);   </li> </ol> </div> 一开始fn = initcall_levels[level]，假设level = 0。也就是fn = initcall_levels[0] = __initcall0_start。所以fn指向了链接脚本中的__initcall0_start地址，每当fn++也就是fn逐次指向注册到.initcall0.init和.initcall0s.init段中的函数地址了。for循环的条件是fn <initcall_levels[level + 1] = initcall_levels[0 + 1] = initcall_level[1] = __initcall1_start。 为了能直观看出fn增加的范围，用如下的简易方式表达一下。 __initcall0_start  __initcall1_start  __initcall2_start  __initcall3_start ... ... __initcall7_start  __initcall_end | <----- fn++ ---->|| <----- fn++ --->| | <----- fn++ --->| | <----- fn++ --->|... ... | <----- fn++ --->| END 了解这一点，我们已经接近胜利的彼岸~~ <div class="dp-highlighter bg_cpp" style="font-family:Consolas, ‘Courier New‘, Courier, mono, serif;font-size:12px;width:938.515625px;overflow:hidden;padding-top:1px;border-color:#CCCCCC;color:#555555;line-height:35px;white-space:normal;margin:18px 0px !important;background-color:#E7E5DC;"> <div class="bar" style="padding-left:45px;"> <div class="tools" style="padding:3px 8px 10px 10px;font-stretch:normal;font-size:9px;line-height:normal;font-family:Verdana, Geneva, Arial, Helvetica, sans-serif;color:silver;border-left-width:3px;border-left-style:solid;border-left-color:#999999;background-color:#F8F8F8;"> [cpp] <a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="ViewSource" title="view plain" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">view plain</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="CopyToClipboard" title="copy" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">copy</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="PrintSource" title="print" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">print</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="About" title="?" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">?</a> <div style="position:absolute;left:783px;top:6332px;width:27px;height:15px;z-index:99;"> </div> </div> </div> <ol start="1" class="dp-cpp" style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> for (fn = initcall_levels[level]; fn < initcall_levels[level+1]; fn++)   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     do_one_initcall(*fn);   </li> </ol> </div> 最后我们要了解的就是for循环每次执行的内容do_one_initcall(*fn)，其函数原型如下 <div class="dp-highlighter bg_cpp" style="font-family:Consolas, ‘Courier New‘, Courier, mono, serif;font-size:12px;width:938.515625px;overflow:hidden;padding-top:1px;border-color:#CCCCCC;color:#555555;line-height:35px;white-space:normal;margin:18px 0px !important;background-color:#E7E5DC;"> <div class="bar" style="padding-left:45px;"> <div class="tools" style="padding:3px 8px 10px 10px;font-stretch:normal;font-size:9px;line-height:normal;font-family:Verdana, Geneva, Arial, Helvetica, sans-serif;color:silver;border-left-width:3px;border-left-style:solid;border-left-color:#999999;background-color:#F8F8F8;"> [cpp] <a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="ViewSource" title="view plain" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">view plain</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="CopyToClipboard" title="copy" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">copy</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="PrintSource" title="print" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">print</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="About" title="?" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">?</a> <div style="position:absolute;left:783px;top:6469px;width:27px;height:15px;z-index:99;"> </div> </div> </div> <ol start="1" class="dp-cpp" style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> int __init_or_module do_one_initcall(initcall_t fn)   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;"> {   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     int count = preempt_count();   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     int ret;   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">    </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     if (initcall_debug)   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">         ret = do_one_initcall_debug(fn);   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     else   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">         ret = fn();   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">    </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     msgbuf[0] = 0;   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">    </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     if (preempt_count() != count) {   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">         sprintf(msgbuf, "preemption imbalance ");   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">         preempt_count() = count;   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     }   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     if (irqs_disabled()) {   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">         strlcat(msgbuf, "disabled interrupts ", sizeof(msgbuf));   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">         local_irq_enable();   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     }   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     WARN(msgbuf[0], "initcall %pF returned with %s\n", fn, msgbuf);   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">    </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;">     return ret;   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;"> }   </li> </ol> </div> do_one_initcall函数就非常简单了，让我们看看最重要的内容如下 <div class="dp-highlighter bg_cpp" style="font-family:Consolas, ‘Courier New‘, Courier, mono, serif;font-size:12px;width:938.515625px;overflow:hidden;padding-top:1px;border-color:#CCCCCC;color:#555555;line-height:35px;white-space:normal;margin:18px 0px !important;background-color:#E7E5DC;"> <div class="bar" style="padding-left:45px;"> <div class="tools" style="padding:3px 8px 10px 10px;font-stretch:normal;font-size:9px;line-height:normal;font-family:Verdana, Geneva, Arial, Helvetica, sans-serif;color:silver;border-left-width:3px;border-left-style:solid;border-left-color:#999999;background-color:#F8F8F8;"> [cpp] <a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="ViewSource" title="view plain" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">view plain</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="CopyToClipboard" title="copy" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">copy</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="PrintSource" title="print" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">print</a><a href="http://blog.csdn.net/richard_liujh/article/details/46758073#" class="About" title="?" style="text-decoration:none;border:none;padding:0px;margin:0px 10px 0px 0px;font-size:9px;color:#0C89CF;background-image:none;background-attachment:initial;background-color:inherit;background-size:initial;background-origin:initial;background-clip:initial;background-position:initial;background-repeat:initial;">?</a> <div style="position:absolute;left:783px;top:7002px;width:27px;height:15px;z-index:99;"> </div> </div> </div> <ol start="1" class="dp-cpp" style="padding:0px;border:none;color:#5C5C5C;margin:0px 0px 1px 45px !important;background-color:#FFFFFF;"> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> if (initcall_debug)   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     ret = do_one_initcall_debug(fn);   </li> <li class="alt" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:inherit;line-height:18px;background-color:#F5FAE2;"> else   </li> <li class="" style="margin:0px !important;padding:0px 3px 0px 10px !important;border-style:none none none solid;border-left-width:3px;border-left-color:#999999;list-style:decimal-leading-zero outside;color:#555555;line-height:18px;background-color:#F5FAE2;">     ret = fn();   </li> </ol> </div> 这里就是判断是不是debug模式，无非debug会多一些调试的操作。但是不管是哪一种，他们都执行 ret = fn( ); 因为fn就是函数指针，fn指向的是我们注册到__initcall0_start  ... __initcall7_start的一系列函数。所以 fn( ); 就是调用这些函数。当然也包括了驱动中module_init注册的函数啦，只是通过module_init注册的level等级是6，for循环是从level = 0开始的，这也能看出0是优先级最高，7是优先级最低的。 到现在，module_init的作用已经全部分析完毕~

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Linux内核很吊之 module_init解析 （下）

Linux内核很吊之 module_init解析（下）