看void __init setup_arch(char **cmdline_p)函数

void __init setup_arch(char **cmdline_p)
{定义变量

struct tag *tags = (struct tag *)&init_tags;
struct machine_desc *mdesc;
char *from = default_command_line;

unwind_init();
再次检测cpu
setup_processor();
再次检测Machine_ID 并返回board的结构体 struct machine_desc

mdesc = setup_machine(machine_arch_type);
machine_desc = mdesc;
machine_name = mdesc->name;

if (mdesc->soft_reboot)
reboot_setup("s");
if (__atags_pointer)     /*    __atags_pointer undefined    */
tags = phys_to_virt(__atags_pointer);
else if (mdesc->boot_params)    /*   执行    */
tags = phys_to_virt(mdesc->boot_params);


#if defined(CONFIG_DEPRECATED_PARAM_STRUCT)
if (tags->hdr.tag != ATAG_CORE)
convert_to_tag_list(tags);
#endif
if (tags->hdr.tag != ATAG_CORE)
tags = (struct tag *)&init_tags;
if (mdesc->fixup)
mdesc->fixup(mdesc, tags, &from, &meminfo);

解析uboot传递进来的tags 在setup.h中有
#define __tag  __used __attribute__((__section__(".taglist.init")))
#define __tagtable(tag, fn) \
static struct tagtable __tagtable_##fn  __tag = { tag, fn }
setup.c中 有

static int __init parse_tag_mem32(const struct tag *tag)
{
return arm_add_memory(tag->u.mem.start, tag->u.mem.size);
}
___tagtable(ATAG_MEM, parse_tag_mem32);

宏替换后得到：
 static struct tagtable __tagtable_parse_tag_cmdline
   __used __attribute__((__section__(".taglist.init"))) //强制到taglist属性段
={ATAG_MEM, parse_tag_mem32      }  
解析uboot传进来的tags       

if (tags->hdr.tag == ATAG_CORE) {
if (meminfo.nr_banks != 0)
squash_mem_tags(tags);
save_atags(tags);
parse_tags(tags);// go
}
    
				
					
						
							点击(此处)折叠或打开
						
					
					
						static void __init parse_tags(const struct tag *t)
{
    for (; t->hdr.size; t = tag_next(t))
        if (!parse_tag(t))
            printk(KERN_WARNING
                "Ignoring unrecognised tag 0x%08x\n",
                t->hdr.tag);
}
						
							            
							
								
									
										点击(此处)折叠或打开
									
								
								
									static int __init parse_tag(const struct tag *tag)
{
    extern struct tagtable __tagtable_begin, __tagtable_end;
    struct tagtable *t;

    for (t = &__tagtable_begin; t < &__tagtable_end; t++)
        if (tag->hdr.tag == t->tag) {
            t->parse(tag);
            break;
        }

    return t < &__tagtable_end;
}

init_mm.start_code = (unsigned long) _text;
init_mm.end_code   = (unsigned long) _etext;
init_mm.end_data   = (unsigned long) _edata;
init_mm.brk   = (unsigned long) _end;


/* parse_early_param needs a boot_command_line */
strlcpy(boot_command_line, from, COMMAND_LINE_SIZE);
/* populate cmd_line too for later use, preserving boot_command_line */
strlcpy(cmd_line, boot_command_line, COMMAND_LINE_SIZE);
*cmdline_p = cmd_line;
/* *****执行一些先期命令 *******/
parse_early_param();

struct obs_kernel_param {
    const char *str;
    int (*setup_func)(char *);
    int early;  //是否为早期处理函数
};

关于early和非early的函数

#define __setup_param(str, unique_id, fn, early)            \
    static const char __setup_str_##unique_id[] __initconst    \
        __aligned(1) = str; \
    static struct obs_kernel_param __setup_##unique_id    \
        __used __section(.init.setup)            \
        __attribute__((aligned((sizeof(long)))))    \
        = { __setup_str_##unique_id, fn, early }

#define __setup(str, fn)     \
__setup_param(str, fn, fn, 0)

#define early_param(str, fn)                    \
    __setup_param(str, fn, fn, 1)
对下面函数
static int __init init_setup(char *str)
{unsigned int i;
execute_command = str;
for (i = 1; i < MAX_INIT_ARGS; i++)
argv_init[i] = NULL;return 1;}
__setup("init=", init_setup);
宏替换得：
static const char __setup_str_init_setup[] __initconst __aligned(1) = "init=";
static struct obs_kernel_param  __setup_init_setup
  __used __section(.init.setup)     __attribute__((aligned((sizeof(long)))))
       = { __setup_str_init_setup, init_setup, 0 }

对下面函数：
static int __init nosmp(char *str)
{
setup_max_cpus = 0;
arch_disable_smp_support();
return 0;
}
early_param("nosmp", nosmp);
宏替换得：
static const char __setup_str_nosmp[] __initconst  __aligned(1) = nosmp;
  static struct obs_kernel_param   __setup_nosmp
    __used __section(.init.setup)        __attribute__((aligned((sizeof(long)))))
    = { __setup_str_nosmp, nosmp, 1 }

arm_memblock_init(&meminfo, mdesc);
/******最终调用了medesc->map_io()*****/
paging_init(mdesc);
/****paging_init(mdesc)-->  devicemaps_init(mdesc)-->mdesc->map_io()
如果平台为smdk2440的board则相当于调用了smdk2440_map_io在mach-smdk2440.c中定义****/
request_standard_resources(mdesc);
#ifdef CONFIG_SMP
if (is_smp())
smp_init_cpus();
#endif
reserve_crashkernel();
cpu_init();
tcm_init();
#ifdef CONFIG_MULTI_IRQ_HANDLER
handle_arch_irq = mdesc->handle_irq;
#endif
#ifdef CONFIG_VT
#if defined(CONFIG_VGA_CONSOLE)
conswitchp = &vga_con;
#elif defined(CONFIG_DUMMY_CONSOLE)
conswitchp = &dummy_con;
#endif
#endif
early_trap_init();

/*如果设备描述结构体定义了init_early函数（应该是早期初始化之意），则在这里调用。*/
if (mdesc->init_early)
mdesc->init_early();
}