u-boot 1.3.4 cpu：s5pv210 架构体系armv7---BL2阶段内核引导细节do_bootm

内核启动：http://blog.chinaunix.net/uid-26202349-id-4829000.html
     可知道，最终会调用bootm命令。
   点击(此处)折叠或打开

bootcmd=nand read C0008000 600000 400000; nand read 30A00000 B00000 180000; bootm C0008000 30A00000

    从参数bootcmd可知道，启动过程，先从nand中读取内核（先跳过这部分)。然后启动内核，bootm.
   解析common/cmd_bootm.c代码
        ------------------------1.命令定义--------------------        

U_BOOT_CMD(
    bootm,    CFG_MAXARGS,    1,    do_bootm,
    "bootm   - boot application image from memory\n",
    "[addr [arg ...]]\n    - boot application image stored in memory\n"
    "\tpassing arguments 'arg ...'; when booting a Linux kernel,\n"
    "\t'arg' can be the address of an initrd image\n"
        ....
);

    ------------------------------2.内核结构体------------------------------------
    点击(此处)折叠或打开

static bootm_headers_t images;        /* pointers to os/initrd/fdt images */

    ------------------------------3.启动内核函数调用------------------------------------
点击(此处)折叠或打开

int do_bootm (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
{
    image_header_t    *hdr;
        //内核头部(含内核的加载地址和内核的入口地址)+真正内核=uImage
    ulong        addr;
    ulong        iflag;
    const char    *type_name;
    uint        unc_len = CFG_BOOTM_LEN;
    uint8_t        comp, type, os;

    void        *os_hdr;
    ulong        os_data, os_len;
    ulong        image_start, image_end;
    ulong        load_start, load_end;
    ulong        mem_start;
    phys_size_t    mem_size;

    struct lmb lmb;

    memset ((void *)&images, 0, sizeof (images));
        ..

    mem_start = getenv_bootm_low();
    mem_size = getenv_bootm_size();


    /* 内核处理：get kernel image header, start address and length */
    os_hdr = boot_get_kernel (cmdtp, flag, argc, argv,
            &images, &os_data, &os_len);
    if (os_len == 0) {
        puts ("ERROR: can't get kernel image!\n");
        return 1;
    }

    /* get image parameters */
    switch (genimg_get_format (os_hdr)) {
        ...
    }

    image_start = (ulong)os_hdr;
    load_end = 0;
    type_name = genimg_get_type_name (type);


       //判断压缩格式
    switch (comp) {
    case IH_COMP_NONE:
        if (load_start == (ulong)os_hdr) {
            printf ("   XIP %s ... ", type_name);
        } else {
            printf ("   Loading %s ... ", type_name);

            memmove_wd ((void *)load_start,
                 (void *)os_data, os_len, CHUNKSZ);
        }
        load_end = load_start + os_len;
        puts("OK\n");
        break;
    case IH_COMP_GZIP:
        printf ("   Uncompressing %s ... ", type_name);
        if (gunzip ((void *)load_start, unc_len,
                    (uchar *)os_data, &os_len) != 0) {
            puts ("GUNZIP: uncompress or overwrite error "
                "- must RESET board to recover\n");
            show_boot_progress (-6);
            do_reset (cmdtp, flag, argc, argv);
        }

        load_end = load_start + os_len;
        break;
#ifdef CONFIG_BZIP2
    case IH_COMP_BZIP2:
        printf ("   Uncompressing %s ... ", type_name);
        /*
         * If we've got less than 4 MB of malloc() space,
         * use slower decompression algorithm which requires
         * at most 2300 KB of memory.
         */
        int i = BZ2_bzBuffToBuffDecompress ((char*)load_start,
                    &unc_len, (char *)os_data, os_len,
                    CFG_MALLOC_LEN < (4096 * 1024), 0);
        if (i != BZ_OK) {
            printf ("BUNZIP2: uncompress or overwrite error %d "
                "- must RESET board to recover\n", i);
            show_boot_progress (-6);
            do_reset (cmdtp, flag, argc, argv);
        }

        load_end = load_start + unc_len;
        break;
#endif /* CONFIG_BZIP2 */
    default:
        if (iflag)
            enable_interrupts();
        printf ("Unimplemented compression type %d\n", comp);
        show_boot_progress (-7);
        return 1;
    }
    puts ("OK\n");
    debug ("   kernel loaded at 0x%08lx, end = 0x%08lx\n", load_start, load_end);
    show_boot_progress (7);

    if ((load_start < image_end) && (load_end > image_start)) {
        debug ("image_start = 0x%lX, image_end = 0x%lx\n", image_start, image_end);
        debug ("load_start = 0x%lx, load_end = 0x%lx\n", load_start, load_end);

        if (images.legacy_hdr_valid) {
            if (image_get_type (&images.legacy_hdr_os_copy) == IH_TYPE_MULTI)
                puts ("WARNING: legacy format multi component "
                    "image overwritten\n");
        } else {
            puts ("ERROR: new format image overwritten - "
                "must RESET the board to recover\n");
            show_boot_progress (-113);
            do_reset (cmdtp, flag, argc, argv);
        }
    }

    show_boot_progress (8);

    lmb_reserve(&lmb, load_start, (load_end - load_start));

#if defined(CONFIG_ZIMAGE_BOOT)
after_header_check:
    os = hdr->ih_os;
#endif

        //判断操作系统的类型

    switch (os) {
    default:            /* handled by (original) Linux case */
    case IH_OS_LINUX:
#ifdef CONFIG_SILENT_CONSOLE
        fixup_silent_linux();
#endif
        do_bootm_linux (cmdtp, flag, argc, argv, &images); //如果当前镜像为linux内核，则通过do_bootm_linux进行内核引导
        break;

            ...
}

        --------------4.do_bootm_linux启用------------------------------
击(此处)折叠或打开

void do_bootm_linux (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[],bootm_headers_t *images)
{
    ulong    initrd_start, initrd_end;
    ulong    ep = 0;
    bd_t    *bd = gd->bd; //获取bd信息
    char    *s;
    int    machid = bd->bi_arch_number; //获取机器码
    void    (*theKernel)(int zero, int arch, uint params); //定义theKernel启动程序指针，内核运行地址
    int    ret;

#ifdef CONFIG_CMDLINE_TAG
    char *commandline = getenv ("bootargs"); //获取bootargs参数
#endif

    /* find kernel entry point */

    if (images->legacy_hdr_valid) {
        ep = image_get_ep (&images->legacy_hdr_os_copy);

    } else {
        puts ("Could not find kernel entry point!\n");
        goto error;
    }
    theKernel = (void (*)(int, int, uint))ep; //将检索到的内核运行地址入口赋值给theKernel

    s = getenv ("machid"); //获取机器码
    if (s) {
        machid = simple_strtoul (s, NULL, 16);
        printf ("Using machid 0x%x from environment\n", machid);
    }


    cleanup_before_linux (); //为内核启动清空先关资源

    theKernel (0, machid, bd->bi_boot_params); //启动内核，一去不复返
                   r0   r1       r2

    /* does not return */
    return;

error:
    do_reset (cmdtp, flag, argc, argv);
    return;
}

------------------------------------------------------------------------------

## Booting kernel from Legacy Image at 40000000 ...
   Image Name:   Linux-2.6.35.7
   Created:      2013-09-15   7:42:33 UTC
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    4009840 Bytes =  3.8 MB
   Load Address: 20008000
   Entry Point:  20008000                 //ep值
   Verifying Checksum ... OK