bootloader---17.引导内核

一、引导zImage

二、代码

 稍微整理一下代码，将头文件都放在include目录下。每一个模块一个头文件，这样结构比较清晰。

root@ubuntu:~/myboot_loader# tree

.

├── boot_zImage.c

├── include

│   ├── nand.h

│   ├── string.h

│   ├── uart.h

│   └── vsprintf.h

├── main.c

├── Makefile

├── nand.c

├── sdram.c

├── start.S

├── uart.c

├── u-boot.lds

└── vsprintf.c

1 directory, 13 files

2.1 main.c

点击(此处)折叠或打开

1. #include "uart.h"
   
2. #include "nand.h"
   
3. 
   
4. extern int boot_zImage(unsigned long from, unsigned long size);
   
5. void main(void)
   
6. {
   
7.     uart_init();        //初始化串口
   
8.     nand_init();    
   
9.     uart_printf("now boot the kernel\n");
   
10. 
    
11.     boot_zImage(0x200000, 0x200000);
    
12. }

程序跳到内存中的main函数之后，初始化串口和nand flash，然后引导内核。

2.2 boot_zImage.c 取自tq2440的u-boot

点击(此处)折叠或打开

1. #include "uart.h"
   
2. #include "nand.h"
   
3. #include "string.h"
   
4. 
   
5. #define LINUX_KERNEL_OFFSET         0x8000
   
6. #define LINUX_PARAM_OFFSET          0x100
   
7. #define LINUX_PAGE_SIZE             0x00001000
   
8. #define LINUX_PAGE_SHIFT            12
   
9. #define LINUX_ZIMAGE_MAGIC          0x016f2818
   
10. #define DRAM_SIZE                   0x04000000
    
11. #define CONFIG_BOOTARGS             "noinitrd root=/dev/mtdblock2 init=/linuxrc console=ttySAC0 mem=128M"
    
12. #define COMMAND_LINE_SIZE           256
    
13. #define MACH_TYPE_S3C2440           168
    
14. struct param_struct {
    
15.     union {
    
16.     struct {
    
17.      unsigned long page_size;        /* 0 */
    
18.      unsigned long nr_pages;        /* 4 */
    
19.      unsigned long ramdisk_size;        /* 8 */
    
20.      unsigned long flags;        /* 12 */
    
21. #define FLAG_READONLY    1
    
22. #define FLAG_RDLOAD    4
    
23. #define FLAG_RDPROMPT    8
    
24.      unsigned long rootdev;        /* 16 */
    
25.      unsigned long video_num_cols;    /* 20 */
    
26.      unsigned long video_num_rows;    /* 24 */
    
27.      unsigned long video_x;        /* 28 */
    
28.      unsigned long video_y;        /* 32 */
    
29.      unsigned long memc_control_reg;    /* 36 */
    
30.      unsigned char sounddefault;        /* 40 */
    
31.      unsigned char adfsdrives;        /* 41 */
    
32.      unsigned char bytes_per_char_h;    /* 42 */
    
33.      unsigned char bytes_per_char_v;    /* 43 */
    
34.      unsigned long pages_in_bank[4];    /* 44 */
    
35.      unsigned long pages_in_vram;    /* 60 */
    
36.      unsigned long initrd_start;        /* 64 */
    
37.      unsigned long initrd_size;        /* 68 */
    
38.      unsigned long rd_start;        /* 72 */
    
39.      unsigned long system_rev;        /* 76 */
    
40.      unsigned long system_serial_low;    /* 80 */
    
41.      unsigned long system_serial_high;    /* 84 */
    
42.      unsigned long mem_fclk_21285; /* 88 */
    
43.     } s;
    
44.     char unused[256];
    
45.     } u1;
    
46.     union {
    
47.     char paths[8][128];
    
48.     struct {
    
49.      unsigned long magic;
    
50.      char n[1024 - sizeof(unsigned long)];
    
51.     } s;
    
52.     } u2;
    
53.     char commandline[COMMAND_LINE_SIZE];
    
54. };
    
55. 
    
56. /*
    
57.  * Disable IRQs
    
58.  */
    
59. #define local_irq_disable()                    \
    
60.     ({                            \
    
61.         unsigned long temp;                \
    
62.     __asm__ __volatile__(                    \
    
63.     "mrs    %0, cpsr        @ local_irq_disable\n"    \
    
64. "    orr    %0, %0, #128\n"                    \
    
65. "    msr    cpsr_c, %0"                    \
    
66.     : "=r" (temp)                        \
    
67.     :                            \
    
68.     : "memory", "cc");                    \
    
69.     })
    
70. 
    
71. static inline void cpu_arm920_cache_clean_invalidate_all(void)
    
72. {
    
73. __asm__(
    
74.     "    mov    r1, #0\n"
    
75.     "    mov    r1, #7 << 5\n"         /* 8 segments */
    
76.     "1:    orr    r3, r1, #63 << 26\n"     /* 64 entries */
    
77.     "2:    mcr    p15, 0, r3, c7, c14, 2\n" /* clean & invalidate D index */
    
78.     "    subs    r3, r3, #1 << 26\n"
    
79.     "    bcs    2b\n"             /* entries 64 to 0 */
    
80.     "    subs    r1, r1, #1 << 5\n"
    
81.     "    bcs    1b\n"             /* segments 7 to 0 */
    
82.     "    mcr    p15, 0, r1, c7, c5, 0\n" /* invalidate I cache */
    
83.     "    mcr    p15, 0, r1, c7, c10, 4\n" /* drain WB */
    
84.     );
    
85. }
    
86. 
    
87. void cache_clean_invalidate(void)
    
88. {
    
89.     cpu_arm920_cache_clean_invalidate_all();
    
90. }
    
91. 
    
92. static inline void cpu_arm920_tlb_invalidate_all(void)
    
93. {
    
94.     __asm__(
    
95.         "mov    r0, #0\n"
    
96.         "mcr    p15, 0, r0, c7, c10, 4\n"    /* drain WB */
    
97.         "mcr    p15, 0, r0, c8, c7, 0\n"    /* invalidate I & D TLBs */
    
98.         );
    
99. }
    
100. 
     
101. void tlb_invalidate(void)
     
102. {
     
103.     cpu_arm920_tlb_invalidate_all();
     
104. }
     
105. 
     
106. 
     
107. void call_linux(long a0, long a1, long a2)
     
108. {
     
109.      local_irq_disable();
     
110.     cache_clean_invalidate();
     
111.     tlb_invalidate();
     
112. 
     
113. __asm__(
     
114.     "mov    r0, %0\n"
     
115.     "mov    r1, %1\n"
     
116.     "mov    r2, %2\n"
     
117.     "mov    ip, #0\n"
     
118.     "mcr    p15, 0, ip, c13, c0, 0\n"    /* zero PID */
     
119.     "mcr    p15, 0, ip, c7, c7, 0\n"    /* invalidate I,D caches */
     
120.     "mcr    p15, 0, ip, c7, c10, 4\n"    /* drain write buffer */
     
121.     "mcr    p15, 0, ip, c8, c7, 0\n"    /* invalidate I,D TLBs */
     
122.     "mrc    p15, 0, ip, c1, c0, 0\n"    /* get control register */
     
123.     "bic    ip, ip, #0x0001\n"        /* disable MMU */
     
124.     "mcr    p15, 0, ip, c1, c0, 0\n"    /* write control register */
     
125.     "mov    pc, r2\n"
     
126.     "nop\n"
     
127.     "nop\n"
     
128.     : /* no outpus */
     
129.     : "r" (a0), "r" (a1), "r" (a2)
     
130.     : "r0","r1","r2","ip"
     
131.     );
     
132. }
     
133. 
     
134. /*
     
135.  * pram_base: base address of linux paramter
     
136.  */
     
137. static void setup_linux_param(unsigned long param_base)
     
138. {
     
139.     struct param_struct *params = (struct param_struct *)param_base; 
     
140.     char *linux_cmd = CONFIG_BOOTARGS    ;
     
141. 
     
142.     memset((unsigned char*)params, 0, sizeof(struct param_struct));
     
143. 
     
144.     params->u1.s.page_size = LINUX_PAGE_SIZE;
     
145.     params->u1.s.nr_pages = (DRAM_SIZE >> LINUX_PAGE_SHIFT);
     
146. 
     
147.     /* set linux command line */
     
148.     memcpy(params->commandline, linux_cmd, strlen(linux_cmd) + 1);
     
149. }
     
150. 
     
151. int boot_zImage(unsigned long from, unsigned long size)
     
152. {
     
153.     int ret;
     
154.     unsigned long boot_mem_base;    /* base address of bootable memory */
     
155.     unsigned long to;
     
156.     unsigned long mach_type;
     
157. 
     
158.     boot_mem_base = 0x30000000;
     
159. 
     
160.     /* copy kerne image */
     
161.     to = boot_mem_base + LINUX_KERNEL_OFFSET;
     
162.     uart_printf("Copy kernel from 0x%08lx to 0x%08lx, size = 0x%08lx ...\n ", from, to, size);
     
163. 
     
164.     nand_read_page((unsigned char *)to, (unsigned long)from, (int)size);
     
165. 
     
166.     uart_printf("read over! next check \n");
     
167. 
     
168.     //uart_printf("read ok!\n");
     
169. 
     
170.     if (*(unsigned long *)(to + 9*4) != LINUX_ZIMAGE_MAGIC) {
     
171.         uart_printf("Warning: this binary is not compressed linux kernel image\n");
     
172.         uart_printf("zImage magic = 0x%08lx\n", *(unsigned long *)(to + 9*4));
     
173.         return -1;
     
174.     }
     
175. 
     
176.     /* Setup linux parameters and linux command line */
     
177.     setup_linux_param(boot_mem_base + LINUX_PARAM_OFFSET);
     
178. 
     
179.     /* Get machine type */
     
180.     mach_type = MACH_TYPE_S3C2440;
     
181.     //    printk("MACH_TYPE = %d\n", mach_type);
     
182. 
     
183.     /* Go Go Go */
     
184.     uart_printf("NOW, Booting Linux......\n");    
     
185.     call_linux(0, mach_type, to);
     
186. 
     
187.     return 0;    
     
188. }

boot_zImage函数，

   a. 首先将内核从nand flash的0x00200000复制到0x30008000，复制大小为0x00200000

   b. 检查文件头是否正确

   c. 在u-boot与内核约定的参数起始地址0x30000100处，设置linux的启动参数

   d. 最后启动内核 

不过这个程序还存在问题：启动时会卡在nand_read_page处大约20秒左右，下一步看问题出在什么地方？

三、

   3.1 这样一个最最最最基本的bootloader就完成了，

  root@ubuntu:~/myboot_loader# ll  u-boot.bin 

  -rwxr-xr-x 1 root root  6796 2012-05-31 00:44 u-boot.bin*

   大小是6796，大约是6.7K.

   3.2 这个bootloader可以进一步精简，把vsprintf去掉之后

root@ubuntu:~/myboot_loader_noprint# ll u-boot.bin 

-rwxr-xr-x 1 root root 2868 2012-05-31 00:48 u-boot.bin*

   大小只有2868个字节。当然如果是小于4K，程序就可以直接在sram中进行，那么先把bootloader复制到内存这一步也可以省略，相信代码可以更小。

 myboot_loader.rar  (将后缀名改为tar.gz, 卡在nand_read_page中大约20秒)

   myboot_loader_noprint.rar   (将后缀名改为tar.gz，卡在nand_read_page中大约20秒，并且有时会直接卡死)