关于天嵌提供的U-BOOT-1.1.6

最近在学习UBOOT，自已也已成功移植了UBOOT1.1.6版本，但跟天嵌提供的UBOOT1.1.6版本相比，不能引导未加头信息的内核(zImage)，于是看了天嵌的UBOOT，详细如下：
1、定义了“boot_zImage”这个命令，命令的函数在lib_arm/boot_zImage.c中实现；
2、执行“boot_zImage”命令时调用do_boot_zImage()， do_boot_zImage()调用boot_zImage(0x200000,0x300000)（传入的参数意义是：0x200000是内核映像文件在NAND的偏移地址，0x300000是内核映像文件的SIZE）；
3、在boot_zImage()函数中实现了从NAND拷贝到SDRAM、设置机器ID、设置启动参数等并最终调用call_linux(0, mach_type, to)，跳转到内核入口处执行了。

代码如下：

1. 
   
2. int boot_zImage(ulong from, size_t size)
   
3. {
   
4. int ret;
   
5. ulong boot_mem_base; /* base address of bootable memory */
   
6. ulong to;
   
7. ulong mach_type;
   
8. boot_mem_base = 0x30000000;
   
9. /* copy kerne image */
   
10. to = boot_mem_base + LINUX_KERNEL_OFFSET;//内核入口地址 = 0x30008000
    
11. printf("Copy linux kernel from 0x%08lx to 0x%08lx, size = 0x%08lx ... ",
    
12.   from, to, size);
    
13. ret = copy_kernel_img(to, (char *)from, size);//从NAND的0x200000处读0x300000大小的内核到0x30008000处
    
14. if (ret) {
    
15.   printf("failed\n");
    
16.   return -1;
    
17. } else {
    
18.   printf("Copy Kernel to SDRAM done,");
    
19. }
    
20. if (*(ulong *)(to + 9*4) != LINUX_ZIMAGE_MAGIC) {
    
21.   printf("Warning: this binary is not compressed linux kernel image\n");
    
22.   printf("zImage magic = 0x%08lx\n", *(ulong *)(to + 9*4));
    
23. } else {
    
24. //  printf("zImage magic = 0x%08lx\n", *(ulong *)(to + 9*4));
    
25.   ;
    
26. }
    
27. /* Setup linux parameters and linux command line */
    
28. setup_linux_param(boot_mem_base + LINUX_PARAM_OFFSET);//0x30000100,设置内存、命令行参数等
    
29. /* Get machine type */
    
30. mach_type = MACH_TYPE_S3C2440;//机器ID
    
31. // printf("MACH_TYPE = %d\n", mach_type);
    
32. /* Go Go Go */
    
33. printf("NOW, Booting Linux......\n");
    
34. call_linux(0, mach_type, to);//启动内核
    
35. return 0;
    
36. }
    
37. 
    
38. 
    
39. //启动内核 r0 = 0,r1 = ID,r2 = 0x30008000
    
40. void  call_linux(long a0, long a1, long a2)
    
41. {
    
42.   local_irq_disable();
    
43. cache_clean_invalidate();
    
44. tlb_invalidate();
    
45. __asm__(
    
46. "mov r0, %0\n"
    
47. "mov r1, %1\n"
    
48. "mov r2, %2\n"
    
49. "mov ip, #0\n"
    
50. "mcr p15, 0, ip, c13, c0, 0\n" /* zero PID */
    
51. "mcr p15, 0, ip, c7, c7, 0\n" /* invalidate I,D caches */
    
52. "mcr p15, 0, ip, c7, c10, 4\n" /* drain write buffer */
    
53. "mcr p15, 0, ip, c8, c7, 0\n" /* invalidate I,D TLBs */
    
54. "mrc p15, 0, ip, c1, c0, 0\n" /* get control register */
    
55. "bic ip, ip, #0x0001\n"  /* disable MMU */
    
56. "mcr p15, 0, ip, c1, c0, 0\n" /* write control register */
    
57. "mov pc, r2\n"//pc = 0x30008000，跳到内核处执行
    
58. "nop\n"
    
59. "nop\n"
    
60. : /* no outpus */
    
61. : "r" (a0), "r" (a1), "r" (a2)
    
62. : "r0","r1","r2","ip"
    
63. );
    

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疑问：以上“r2”为什么是内核的入口地址而不是参数的地址，因为还未学习内核，所以不懂。难道这就是zImage和uImage的区别？{:2_30:}