內核調試 arm-none-linux-gnueabi-addr2line 工具使用

通過OOPS信息中PC寄存器的值可以知道出錯指令的地址，通過棧回朔信息可以知道出錯時的函數調用的關系，根據這兩點可以很快定位錯誤。

修改drivers/net/ethernet/davicom/dm9000.c，在dm9000_probe函數中u32 id_val;下增加下面語句：

int *ptr  =NULL;
*ptr=0xff;

編譯內核下載到開發板上，內核啟動會出現如類似下信息：

Unable to handle kernel NULL pointer dereference at virtual address 00000000
pgd = c0004000
[00000000] *pgd=00000000
Internal error: Oops: 805 [#1] PREEMPT SMP ARM
Modules linked in:
CPU: 1 PID: 1 Comm: swapper/0 Not tainted 3.14.0 #11
task: ee8a0000 ti: ee8a4000 task.ti: ee8a4000
PC is at dm9000_probe+0x1c/0x8f0
LR is at platform_drv_probe+0x18/0x48
pc : [<c0277cc8>]    lr : [<c0247f7c>]    psr: 60000153
sp : ee8a5e48  ip : 00000000  fp : 00000000
r10: c052a4fc  r9 : 00000000  r8 : c0591e98
r7 : 00000000  r6 : ee97c810  r5 : ee97c800  r4 : 00000000
r3 : 000000ff  r2 : 00000000  r1 : ee8a5de8  r0 : ee97c800
Flags: nZCv  IRQs on  FIQs off  Mode SVC_32  ISA ARM  Segment kernel
Control: 10c5387d  Table: 4000404a  DAC: 00000015
Process swapper/0 (pid: 1, stack limit = 0xee8a4240)
Stack: (0xee8a5e48 to 0xee8a6000)
5e40: 				ee975cf0 00000000 ee1503a8 00000001 c0561afc ee150438
5e60: 00000000 ee97c810 c0591e98 ee97c810 00000000 c0591e98 c0561afc c052a4fc
5e80: 00000000 c0247f7c c0247f64 c05d931c c0591e98 c0246668 ee97c810 c0591e98
5ea0: ee97c844 00000000 c054332c c0246804 c0591e98 c0246778 00000000 c0244fbc
5ec0: ee805478 ee9771c0 c0591e98 eeb73a00 c0590028 c0245e28 c04c3128 c0591e98
5ee0: 00000000 c0591e98 00000000 c054e2ac c059f280 c0246e1c 00000000 ee8a4000
5f00: 00000000 c00087b4 ee903b00 c05c3d50 60000153 c0571c00 60000100 c0571c00
5f20: 00000000 00000000 c0571bfc 00000000 c0505bc8 ef7fc918 00000089 c0034c6c
5f40: c04ca680 c0505338 00000006 00000006 00000000 c054e2c8 c054e2cc 00000006
5f60: c054e2ac c059f280 00000089 c052a4fc 00000000 c052ac4c 00000006 00000006
5f80: c052a4fc c003e0dc 00000000 c03b46ec 00000000 00000000 00000000 00000000
5fa0: 00000000 c03b46f4 00000000 c000e4b8 00000000 00000000 00000000 00000000
5fc0: 0000000000000000 00000000 00000000 00000000 00000000 00000000 00000000
5fe0: 00000000 00000000 00000000 00000000 00000013 00000000 ffffffff ffffffff
[<c0277cc8>] (dm9000_probe) from [<c0247f7c>] (platform_drv_probe+0x18/0x48)
[<c0247f7c>] (platform_drv_probe) from [<c0246668>] (driver_probe_device+0x100/0x210)
[<c0246668>] (driver_probe_device) from [<c0246804>] (__driver_attach+0x8c/0x90)
[<c0246804>] (__driver_attach) from [<c0244fbc>] (bus_for_each_dev+0x58/0x88) 
[<c0244fbc>] (bus_for_each_dev) from [<c0245e28>] (bus_add_driver+0xd8/0x1cc) 
[<c0245e28>] (bus_add_driver) from [<c0246e1c>] (driver_register+0x78/0xf4)
[<c0246e1c>] (driver_register) from [<c00087b4>] (do_one_initcall+0x30/0x144)
[<c00087b4>] (do_one_initcall) from [<c052ac4c>] (kernel_init_freeable+0xfc/0x1c8)
[<c052ac4c>] (kernel_init_freeable) from [<c03b46f4>] (kernel_init+0x8/0xe4)

錯誤分析：

1、第一行，說明是空指針造成的錯誤

Unable to handle kernel NULL pointer dereference at virtual address 00000000

2、寄存器信息主要是PC的值

PC is at dm9000_probe+0x1c/0x8f0
pc : [<c0277cc8>]

方法一、錯誤定位

arm-none-linux-gnueabi-objdump -D vmlinux > vmlinux.dis

文件vmlinux.dis非常大打開需要一定時間

對於大多數情況，從反匯編代碼定位到C代碼並不會如此容易，需要有較強的閱讀匯編代碼的能力。

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方法二、錯誤定位　

通過addr2line去定位

 arm-none-linux-gnueabi-addr2line 0xc0277cc8-e vmlinux  -f