U-Boot直接引导zImage内核

 

         U-boot1.1.6只能只能就能过mkimage工具加工后的内核镜像文件。mkimage工具给zImage增加了一个64B大小的头。U-Boot是通过bootm命令来引导Linux内核的，bootm命令调用do_bootm函数来mkimage工具增加的头，最后调用do_bootm_linux函数引导去掉了mkimage工具增加的头的Linux内核，也就是zImage，启动的流程可以参考图解U-Boot：引导内核分析这篇博客。

     要让U-Boot直接引导zImage内核，只需在do_bootm函数中去掉对mkimage工具增加的头的分析，直接调用do_bootm_linux函数引导zImage内核即可。下面是经过修改的do_bootm函数，修改的部分用///////////包围起来了，省略号后面的就不需要改动了。这个函数common/cmd_bootm.c文件中。

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1. int do_bootm (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[]) 
2. { 
3.     ulong   iflag; 
4.     ulong   addr; 
5.     ulong   data, len, checksum; 
6.     ulong  *len_ptr; 
7.     uint    unc_len = CFG_BOOTM_LEN; 
8.     int i, verify; 
9.     char    *name, *s; 
10.     int (*appl)(int, char *[]); 
11.     image_header_t *hdr = &header; 
12.     s = getenv ("verify"); 
13.     verify = (s && (*s == 'n')) ? 0 : 1; 
14.     if (argc < 2) { 
15.         addr = load_addr; 
16.     } else { 
17.         addr = simple_strtoul(argv[1], NULL, 16); 
18.     } 
19.     SHOW_BOOT_PROGRESS (1); 
20. ////////////////////////////////////////////////////////////////////////////////// 
21.     //printf ("## Booting image at %08lx ...\n", addr); 
22.     printf ("## Booting from zImage at %08lx ---by ce123\n", addr); 
23. #ifdef CONFIG_SILENT_CONSOLE 
24.         fixup_silent_linux(); 
25. #endif 
26.         do_bootm_linux  (cmdtp, flag, argc, argv, 
27.                  addr, len_ptr, verify); 
28. ////////////////////////////////////////////////////////////////////////////////// 
29. ...... 

int do_bootm (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[]){ulongiflag;ulongaddr;ulongdata, len, checksum;ulong  *len_ptr;uintunc_len = CFG_BOOTM_LEN;inti, verify;char*name, *s;int(*appl)(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 ("## Booting image at %08lx ...\n", addr);printf ("## Booting from zImage at %08lx ---by ce123\n", addr);#ifdef CONFIG_SILENT_CONSOLE    fixup_silent_linux();#endif    do_bootm_linux  (cmdtp, flag, argc, argv,     addr, len_ptr, verify);//////////////////////////////////////////////////////////////////////////////////......

接下来还要修改一下lib_arm/armlinux.c中的do_bootm_linux函数。这里主要是修改kernal的加载地址（theKernel = (void (*)(int, int, uint))addr）。这就要求我们将zImage内核下载内存的addr处。并且用bootm addr进行引导，默认的地址是0x30008000，如果直接使用bootm进行引导，则需要将内核下载到0x30008000，否则无法引导内核。

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1. void do_bootm_linux (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[], 
2.              ulong addr, ulong *len_ptr, int verify) 
3. { 
4.     ulong len = 0, checksum; 
5.     ulong initrd_start, initrd_end; 
6.     ulong data; 
7.     void (*theKernel)(int zero, int arch, uint params); 
8.     image_header_t *hdr = &header; 
9.     bd_t *bd = gd->bd; 
10.  
11.  
12. #ifdef CONFIG_CMDLINE_TAG 
13.     char *commandline = getenv ("bootargs"); 
14. #endif 
15.  
16.  
17.     //theKernel = (void (*)(int, int, uint))ntohl(hdr->ih_ep); 
18.     theKernel = (void (*)(int, int, uint))addr; 

void do_bootm_linux (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[],     ulong addr, ulong *len_ptr, int verify){ulong len = 0, checksum;ulong initrd_start, initrd_end;ulong data;void (*theKernel)(int zero, int arch, uint params);image_header_t *hdr = &header;bd_t *bd = gd->bd;#ifdef CONFIG_CMDLINE_TAGchar *commandline = getenv ("bootargs");#endif//theKernel = (void (*)(int, int, uint))ntohl(hdr->ih_ep);theKernel = (void (*)(int, int, uint))addr;

下面是引导信息：

U-Boot 1.1.6 (Mar 11 2012 - 14:06:15)


DRAM:  64 MB
Flash:  2 MB
NAND:  256 MiB
In:    serial
Out:   serial
Err:   serial
Hit any key to stop autoboot:  0

NAND read: device 0 offset 0x240000, size 0x200000
2097152 bytes read: OK
## Booting from zImage at 30008000 ---by ce123

Starting kernel ...

Uncompressing Linux.............................................................
............................................................. done, booting the
kernel.