U-Boot与内核的关系(2)

2.bootm命令的实现

/* common/cmd_bootm.c */int do_bootm(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[]){ulong iflag;ulong addr;ulong data, len, checksum;ulong *len_ptr;uint unc_len = 0x400000;int i, verify;char *name, *s;int (*aool)(int, char *[]);image_header_t *hdr = &header;s = getenv("verify");verify = (s && (*s == 'n')) ? 0 : 1);if (argc < 2){addr = load_addr;} else {addr = simple_strtoul(argv[1], NULL, 16);}SHOW_BOOT_PROGRESS(1);printf("## Bootingn image at %08lx .../n", addr);/* Copy header so we can blank CRC field for re-calculation */memmove(&header, (char *)addr, sizeof(image_header_t));if (ntohl(hdr->ih_magic) != IH_MAGIC){puts("Bad Magic Number/n");SHOW_BOOT_PROGRESS(-1);return 1;}SHOW_BOOT_PROGRESS(2);data = (ulong)&header;len = sizeof(image_header_t);checksum = ntohl(hdr->ih_hcrc);hdr->ih_hcrc = 0;if (crc32(0, (char *)data, len) != checksum) {puts("Bad Header Checksum/n");SHOW_BOOT_PROGRESS(-2);return 1;}SHOW_BOOT_PROGRESS(3);/* for multi-file images we need the data part, too */print_image_hdr((image_header_t *)addr);data = addr + sizeof(image_header_t);len = ntohl(hdr->ih_size);if (verify) {puts(" Verifying Checksum ... ");if (crc32(0, (char *)data, len) != ntohl(hdr->ih_dcrc)) {printf("Bad Data CRC/n");SHOW_BOOT_PROGRESS(-3);return 1;}printf("OK/n");}SHOW_BOOT_PROGRESS(4);len_ptr = (ulong *)data;...switch (hdr->ih_os) {default:/* handled by (original) Linux case */case IH_OS_LINUX:do_bootm_linux(cmdtp, flag, argc, argv, addr, len_ptr, verify);break;...}} 

bootm命令调用do_bootm函数。这个函数专门用来引导各种操作系统映像，可以支持引导Linux，vxWorks，QNX等操作系统。

引导Linux的时候，调用do_bottom_linux()函数。