驱动程序的调试
一. 打印: prink, 自制proc文件
UBOOT传入console=ttySAC0 console=tty1
1. 内核处理UBOOT传入的参数
console_setup
	add_preferred_console // 我想用名为"ttySAC0"的控制台，先记录下来

2. 硬件驱动的入口函数里:
	drivers/serial/s3c2410.c
		register_console(&s3c24xx_serial_console);		

3. printk
		vprintk
			/* Emit the output into the temporary buffer */
			// 先把输出信息放入临时BUFFER
			vscnprintf
			
			// Copy the output into log_buf.
			// 把临时BUFFER里的数据稍作处理，再写入log_buf
			// 比如printk("abc")会得到"<4>abc", 再写入log_buf
			// 可以用dmesg命令把log_buf里的数据打印出来重现内核的输出信息
			
			
			// 调用硬件的write函数输出
			release_console_sem();
				call_console_drivers(_con_start, _log_end);
					// 从log_buf得到数据，算出打印级别
					_call_console_drivers(start_print, cur_index, msg_level);			
						// 如果可以级别够格打印
						if ((msg_log_level < console_loglevel
							__call_console_drivers
								con->write(con, &LOG_BUF(start), end - start);




二. 根据内核打印的段错误信息分析
a. 作为模块：
1. 根据pc值确定该指令属于内核还是外加的模块
pc=0xbf000018 它属于什么的地址？是内核还是通过insmod加载的驱动程序？
先判断是否属于内核的地址: 看System.map确定内核的函数的地址范围:c0004000~c03265a4

如果不属于System.map里的范围，则它属于insmod加载的驱动程序

2. 假设它是加载的驱动程序引入的错误，怎么确定是哪一个驱动程序？
先看看加载的驱动程序的函数的地址范围
cat /proc/kallsyms  (内核函数、加载的函数的地址)
从这些信息里找到一个相近的地址, 这个地址<=0xbf000018
比如找到了：
bf000000 t first_drv_open	[first_drv]

3. 找到了first_drv.ko
在PC上反汇编它: arm-linux-objdump -D first_drv.ko > frist_drv.dis
在dis文件里找到first_drv_open

    first_drv.dis文件里              insmod后
00000000 <first_drv_open>:       bf000000 t first_drv_open	[first_drv]
00000018                         pc = bf000018
                                 



./firstdrvtest on
Unable to handle kernel paging request at virtual address 56000050
内核使用56000050来访问时发生了错误

pgd = c3eb0000
[56000050] *pgd=00000000
Internal error: Oops: 5 [#1]
Modules linked in: first_drv
CPU: 0    Not tainted  (2.6.22.6 #1)
PC is at first_drv_open+0x18(该指令的偏移)/0x3c(该函数的总大小) [first_drv]
PC就是发生错误的指令的地址
大多时候，PC值只会给出一个地址，不到指示说是在哪个函数里

LR is at chrdev_open+0x14c/0x164
LR寄存器的值

pc = 0xbf000018

pc : [<bf000018>]    lr : [<c008d888>]    psr: a0000013
sp : c3c7be88  ip : c3c7be98  fp : c3c7be94
r10: 00000000  r9 : c3c7a000  r8 : c049abc0
r7 : 00000000  r6 : 00000000  r5 : c3e740c0  r4 : c06d41e0
r3 : bf000000  r2 : 56000050  r1 : bf000964  r0 : 00000000
执行这条导致错误的指令时各个寄存器的值

Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  Segment user
Control: c000717f  Table: 33eb0000  DAC: 00000015
Process firstdrvtest (pid: 777, stack limit = 0xc3c7a258)
发生错误时当前进程的名称是firstdrvtest

栈
Stack: (0xc3c7be88 to 0xc3c7c000)
be80:                   c3c7bebc c3c7be98 c008d888 bf000010 00000000 c049abc0 
bea0: c3e740c0 c008d73c c0474e20 c3e766a8 c3c7bee4 c3c7bec0 c0089e48 c008d74c 
bec0: c049abc0 c3c7bf04 00000003 ffffff9c c002c044 c3d10000 c3c7befc c3c7bee8 
bee0: c0089f64 c0089d58 00000000 00000002 c3c7bf68 c3c7bf00 c0089fb8 c0089f40 
bf00: c3c7bf04 c3e766a8 c0474e20 00000000 00000000 c3eb1000 00000101 00000001 
bf20: 00000000 c3c7a000 c04a7468 c04a7460 ffffffe8 c3d10000 c3c7bf68 c3c7bf48 
bf40: c008a16c c009fc70 00000003 00000000 c049abc0 00000002 bec1fee0 c3c7bf94 
bf60: c3c7bf6c c008a2f4 c0089f88 00008520 bec1fed4 0000860c 00008670 00000005 
bf80: c002c044 4013365c c3c7bfa4 c3c7bf98 c008a3a8 c008a2b0 00000000 c3c7bfa8 
bfa0: c002bea0 c008a394 bec1fed4 0000860c 00008720 00000002 bec1fee0 00000001 
bfc0: bec1fed4 0000860c 00008670 00000002 00008520 00000000 4013365c bec1fea8 
bfe0: 00000000 bec1fe84 0000266c 400c98e0 60000010 00008720 00000000 00000000 

Backtrace: (回溯)
[<bf000000>] (first_drv_open+0x0/0x3c [first_drv]) from [<c008d888>] (chrdev_open+0x14c/0x164)
[<c008d73c>] (chrdev_open+0x0/0x164) from [<c0089e48>] (__dentry_open+0x100/0x1e8)
 r8:c3e766a8 r7:c0474e20 r6:c008d73c r5:c3e740c0 r4:c049abc0
[<c0089d48>] (__dentry_open+0x0/0x1e8) from [<c0089f64>] (nameidata_to_filp+0x34/0x48)
[<c0089f30>] (nameidata_to_filp+0x0/0x48) from [<c0089fb8>] (do_filp_open+0x40/0x48)
 r4:00000002
[<c0089f78>] (do_filp_open+0x0/0x48) from [<c008a2f4>] (do_sys_open+0x54/0xe4)
 r5:bec1fee0 r4:00000002
[<c008a2a0>] (do_sys_open+0x0/0xe4) from [<c008a3a8>] (sys_open+0x24/0x28)
[<c008a384>] (sys_open+0x0/0x28) from [<c002bea0>] (ret_fast_syscall+0x0/0x2c)
Code: e24cb004 e59f1024 e3a00000 e5912000 (e5923000) 
Segmentation fault
# 

b. 编入内核
Modules linked in:
CPU: 0    Not tainted  (2.6.22.6 #2)
PC is at first_drv_open+0x18/0x3c
LR is at chrdev_open+0x14c/0x164
pc : [<c014e6c0>]    lr : [<c008638c>]    psr: a0000013
sp : c3a03e88  ip : c3a03e98  fp : c3a03e94
r10: 00000000  r9 : c3a02000  r8 : c03f3c60
r7 : 00000000  r6 : 00000000  r5 : c38a0c50  r4 : c3c1e780
r3 : c014e6a8  r2 : 56000050  r1 : c031a47c  r0 : 00000000
Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  Segment user
Control: c000717f  Table: 339f0000  DAC: 00000015
Process firstdrvtest (pid: 750, stack limit = 0xc3a02258)

1. 根据pc值确定该指令属于内核还是外加的模块
pc=c014e6c0 属于内核(看System.map)

2. 反汇编内核: arm-linux-objdump -D vmlinux > vmlinux.dis
在dis文件里搜c014e6c0
c014e6a8 <first_drv_open>:
c014e6a8:       e1a0c00d        mov     ip, sp
c014e6ac:       e92dd800        stmdb   sp!, {fp, ip, lr, pc}
c014e6b0:       e24cb004        sub     fp, ip, #4      ; 0x4
c014e6b4:       e59f1024        ldr     r1, [pc, #36]   ; c014e6e0 <.text+0x1276e0>
c014e6b8:       e3a00000        mov     r0, #0  ; 0x0
c014e6bc:       e5912000        ldr     r2, [r1]
c014e6c0:       e5923000        ldr     r3, [r2] // 在此出错 r2=56000050



3. 根据栈信息分析函数调用过程
# ./firstdrvtest on
Unable to handle kernel paging request at virtual address 56000050
pgd = c3e78000
[56000050] *pgd=00000000
Internal error: Oops: 5 [#1]
Modules linked in: first_drv
CPU: 0    Not tainted  (2.6.22.6 #48)
PC is at first_drv_open+0x18/0x3c [first_drv]
LR is at chrdev_open+0x14c/0x164
pc : [<bf000018>]    lr : [<c008c888>]    psr: a0000013
3.1 根据PC确定出错位置
bf000018 属于 insmod的模块
bf000000 t first_drv_open       [first_drv]

3.2 确定它属于哪个函数
反汇编first_drv.ko






sp : c3e69e88  ip : c3e69e98  fp : c3e69e94
r10: 00000000  r9 : c3e68000  r8 : c0490620
r7 : 00000000  r6 : 00000000  r5 : c3e320a0  r4 : c06a8300
r3 : bf000000  r2 : 56000050  r1 : bf000964  r0 : 00000000
Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  Segment user
Control: c000717f  Table: 33e78000  DAC: 00000015
Process firstdrvtest (pid: 752, stack limit = 0xc3e68258)
Stack: (0xc3e69e88 to 0xc3e6a000)
9e80:                   c3e69ebc c3e69e98 c008c888 bf000010 00000000 c0490620 
                        first_drv_open'sp    lr             chrdev_open'sp

9ea0: c3e320a0 c008c73c c0465e20 c3e36cb4 c3e69ee4 c3e69ec0 c0088e48 c008c74c 
                                                            lr    
                                                                                 
9ec0: c0490620 c3e69f04 00000003 ffffff9c c002b044 c06e0000 c3e69efc c3e69ee8 
      __dentry_open'sp

9ee0: c0088f64 c0088d58 00000000 00000002 c3e69f68 c3e69f00 c0088fb8 c0088f40 
      lr                nameidata_to_filp'sp                lr
      
9f00: c3e69f04 c3e36cb4 c0465e20 00000000 00000000 c3e79000 00000101 00000001 
      do_filp_open'sp

9f20: 00000000 c3e68000 c04c1468 c04c1460 ffffffe8 c06e0000 c3e69f68 c3e69f48 
9f40: c008916c c009ec70 00000003 00000000 c0490620 00000002 be94eee0 c3e69f94 
9f60: c3e69f6c c00892f4 c0088f88 00008520 be94eed4 0000860c 00008670 00000005 
               lr                do_sys_open'sp

9f80: c002b044 4013365c c3e69fa4 c3e69f98 c00893a8 c00892b0 00000000 c3e69fa8 
                                          lr                sys_open'sp

9fa0: c002aea0 c0089394 be94eed4 0000860c 00008720 00000002 be94eee0 00000001 
      lr                ret_fast_syscall'sp
                        
9fc0: be94eed4 0000860c 00008670 00000002 00008520 00000000 4013365c be94eea8 
9fe0: 00000000 be94ee84 0000266c 400c98e0 60000010 00008720 00000000 00000000 


三. 自制工具
寄存器编辑器


四. 修改内核来定位系统僵死问题
./firstdrvtest on 
asm_do_IRQ => s3c2410_timer_interrupt : pid = 752, task name = firstdrvtest
pc = bf000084
asm_do_IRQ => s3c2410_timer_interrupt : pid = 752, task name = firstdrvtest
pc = bf000084   // 对于中断, pc-4才是发生中断瞬间的地址

看/proc/kallsyms                                
first_drv.dis
00000000 <first_drv_open>:                     bf000000 t first_drv_open	[first_drv]         
0000003c <first_drv_write>:
  3c:	e1a0c00d 	mov	ip, sp
  40:	e92dd800 	stmdb	sp!, {fp, ip, lr, pc}
  44:	e24cb004 	sub	fp, ip, #4	; 0x4
  48:	e24dd004 	sub	sp, sp, #4	; 0x4
  4c:	e3cd3d7f 	bic	r3, sp, #8128	; 0x1fc0
  50:	e3c3303f 	bic	r3, r3, #63	; 0x3f
  54:	e5933008 	ldr	r3, [r3, #8]
  58:	e0910002 	adds	r0, r1, r2
  5c:	30d00003 	sbcccs	r0, r0, r3
  60:	33a03000 	movcc	r3, #0	; 0x0
  64:	e3530000 	cmp	r3, #0	; 0x0
  68:	e24b0010 	sub	r0, fp, #16	; 0x10
  6c:	1a00001c 	bne	e4 <init_module+0x5c>
  70:	ebfffffe 	bl	70 <first_drv_write+0x34>
  74:	ea00001f 	b	f8 <init_module+0x70>
  78:	e3520000 	cmp	r2, #0	; 0x0
  7c:	11a01002 	movne	r1, r2
  80:	1bfffffe 	blne	80 <first_drv_write+0x44>       // 卡死的地方
  84:	ea00001f 	b	108 <init_module+0x80>