ENTRY(stext):         ... ...                           //启动内核b start_kernel                    //跳转start_kernel()

asmlinkage void __init start_kernel(void)
{...setup_arch(&command_line);           //解析uboot传入的启动参数setup_command_line(command_line);    //解析uboot传入的启动参数..../*查找内核参数*/parse_early_param(){do_early_param()；              //从__setup_start到__setup_end查找early非0的函数,后面会分析} /*查找内核参数*/unknown_bootoption()                 {obsolete_checksetup();      //从__setup_start到__setup_end查找early为0的函数,后面会分析}...rest_init();                                //进入rest_init()
}

static void noinline __init_refok rest_init(void)
{kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);  //启动init进程，然后进入kernel_init中启动应用程序... ...}

static int __init kernel_init(void * unused)
{... ...prepare_namespace()              //进入prepare_namespace函数,挂载系统{... ...      / /通过解析出来的命令行参数” root=/dev/mtdblock3”来挂接根文件系统 mount_root();   //开始挂载} init_post()                               //进入init_post() 函数,运行应用程序{
      /*   打开dev/console,并提供输入、输出、错误提示    */
      if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)   printk(KERN_WARNING "Warning: unable to open an initial console.\n");(void) sys_dup(0);(void) sys_dup(0);         ... ...     run_init_process("/sbin/init");        //执行应用程序run_init_process("/etc/init");         //执行应用程序run_init_process("/bin/init");        //执行应用程序run_init_process("/bin/sh");         //执行应用程序
}

 void __init prepare_namespace(void){... ...
if (saved_root_name[0]) //判断saved_root_name[0]数组是否为空
{
root_device_name = saved_root_name;
if (!strncmp(root_device_name, "mtd", 3)) {     //比较root_device_name数组是否已mtd开头？mount_block_root(root_device_name, root_mountflags);
  goto out; }                              //是mtd，则跳转到out,直接挂载ROOT_DEV = name_to_dev_t(root_device_name);
if (strncmp(root_device_name, "/dev/", 5) == 0) //比较是不是已/dev/开头
root_device_name += 5;                 //是的话，+5找到mtd开头
}is_floppy = MAJOR(ROOT_DEV) == FLOPPY_MAJOR;
if (initrd_load())
goto out;
if (is_floppy && rd_doload && rd_load_disk(0))
ROOT_DEV = Root_RAM0;
mount_root();       //将实际文件系统挂载到rootfs的/root目录out:sys_mount(".", "/", NULL, MS_MOVE, NULL);sys_chroot(".");security_sb_post_mountroot();
}

static int __init root_dev_setup(char *line)
{strlcpy(saved_root_name, line, sizeof(saved_root_name));        //复制saved_root_name数组return 1;
}
__setup("root=", root_dev_setup);

#define __setup_param(str, unique_id, fn, early)          \    //定义__setup_param(str, unique_id, fn, early)
/*定义字符串数组__setup_str_##unique_id[]=str; \表示还在define中     */
static char __setup_str_##unique_id[] __initdata = str;    \      //相当于: __setup_str_ root_dev_setup[]="root="
/*定义结构体obs_kernel_param型__setup_##unique_id*/
static struct  obs_kernel_param  __setup_##unique_id\             __attribute_used__                                   \__attribute__((__section__(".init.setup")))        \    //设置.init.setup段__attribute__((aligned((sizeof(long)))))    \= { __setup_str_##unique_id, fn, early }   //将"root=",root_dev_setup,0 放在 .init.setup段中#define __setup(str, fn)                   \        //定义__setup(str, fn)使用__setup_param(str, fn, fn, 0)__setup_param(str, fn, fn, 0)

311   . = ALIGN(16);
312   __setup_start = .;
313    *(.init.setup)                 //存放.init.setup段
314   __setup_end = .;

static int __init do_early_param(char *param, char *val)
{
struct obs_kernel_param  *p;                //定义obs_kernel_param结构体指针*p
for (p = __setup_start; p < __setup_end; p++)   //查找.init.setup段的内容
{if (p->early && strcmp(param, p->str) == 0) {  if (p->setup_func(val) != 0)                //处理early非0的函数printk(KERN_WARNING"Malformed early option '%s'\n", param);
}}
}

struct obs_kernel_param {const char *str;                //__setup_str_ root_dev_setup[]=”root=”int (*setup_func)(char *);        // root_dev_setup(char *line)int early;                     // early=0
};

static int __init obsolete_checksetup(char *line)
{
struct obs_kernel_param *p;         //定义obs_kernel_param型结构体指针
int had_early_param = 0;p = __setup_start;
do {int n = strlen(p->str);if (!strncmp(line, p->str, n))            //确定是否有内容{if (p->early) {                          //early非0,则不执行函数         if (line[n] == '\0' || line[n] == '=')had_early_param = 1;}
          else if (!p->setup_func) {                //  处理early为0的函数，printk(KERN_WARNING "Parameter %s is obsolete,"" ignored\n", p->str);return 1; }           else if (p->setup_func(line + n))             //处理early为0的函数return 1;}p++;} while (p < __setup_end);        //从__setup_start到__setup_end查找return had_early_param;
}

static struct mtd_partition smdk_default_nand_part[] = {[0] = {                                      // mtdblock0.name   = "bootloader",.size   = 0x00040000,.offset         = 0,},[1] = {                                      // mtdblock1.name   = "params",.offset = MTDPART_OFS_APPEND,  //表示紧跟着前面的地址后面,为偏移地址,= 0x00040000.size   = 0x00020000,},[2] = {                                     // mtdblock2.name   = "kernel",.offset = MTDPART_OFS_APPEND, //表示紧跟着前面的地址后面,为偏移地址,= 0x00060000.size   = 0x00200000,},[3] = {                                     // mtdblock3.name   = "root",.offset = MTDPART_OFS_APPEND, //表示紧跟着前面的地址后面,为偏移地址,= 0x00260000.size   = MTDPART_SIZ_FULL,}};