四、uboot_引导内核

一、uboot引导内核

1、flash分区

1、flash分区（include/configs/mini2440.h）
#define MTDIDS_DEFAULT "nand0=nandflash0"
#define MTDPARTS_DEFAULT "mtdparts=nandflash0:256@0(bootloader)"\
							"128k(params)," \
							"2m(kernel)," \
                            "8m(jffs2)," \
                            "-(yaffs)"

2、uboot引导内核依赖两个变量

bootcmd= nand read 31000000 400000 500000 \; bootm 31000000

1、bootcmd（common/main.c : main_loop()）
s = getenv ("bootcmd");

2、执行bootm引导内核

3、读取头部
typedef struct image_header {
	uint32_t	ih_magic;	/* Image Header Magic Number	*/
	uint32_t	ih_hcrc;	/* Image Header CRC Checksum	*/
	uint32_t	ih_time;	/* Image Creation Timestamp	*/
	uint32_t	ih_size;	/* Image Data Size		*/
	uint32_t	ih_load;	/* Data	 Load  Address		*/
	uint32_t	ih_ep;		/* Entry Point Address		*/
	uint32_t	ih_dcrc;	/* Image Data CRC Checksum	*/
	uint8_t		ih_os;		/* Operating System		*/
	uint8_t		ih_arch;	/* CPU architecture		*/
	uint8_t		ih_type;	/* Image Type			*/
	uint8_t		ih_comp;	/* Compression Type		*/
	uint8_t		ih_name[IH_NMLEN];	/* Image Name		*/
} image_header_t;

4、启动内核
do_bootm_linux  (cmdtp, flag, argc, argv, addr, len_ptr, verify);

5、跳转至内核
<lib_arm/armlinuc.c>
void (*theKernel)(int zero, int arch, uint params);
theKernel = (void (*)(int, int, uint))ntohl(hdr->ih_ep);
theKernel (0, bd->bi_arch_number, bd->bi_boot_params);

6、内核参数
setup_start_tag (bd);
setup_memory_tags (bd);
setup_commandline_tag (bd, commandline);    //commandline来源于bootargs
setup_end_tag (bd)