U-Boot直接引导zImage内核

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[])
{
	ulong	iflag;
	ulong	addr;
	ulong	data, len, checksum;
	ulong  *len_ptr;
	uint	unc_len = CFG_BOOTM_LEN;
	int	i, 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;
12. #ifdef CONFIG_CMDLINE_TAG
13. char *commandline = getenv ("bootargs");
14. #endif
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_TAG
	char *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.