内核启动几乎都完成了， 出现这个错误，请问该如何运用backtrace查找原因啊？
VFS: Mounted root (nfs filesystem) on device 0:12.
Freeing init memory: 140K
Unable to handle kernel NULL pointer dereference at virtual address 00000000
pgd = c0004000
[00000000] *pgd=00000000
Internal error: Oops: 5 [#1]
Modules linked in:
CPU: 0    Not tainted  (2.6.30 #74)
PC is at tty_open+0x18c/0x400
LR is at tty_open+0xf4/0x400
pc : []    lr : []    psr: 60000013
sp : c3817e4c  ip : c3817e4c  fp : c3817e7c
r10: 00500001  r9 : c340ba2c  r8 : 00000001
r7 : 00000000  r6 : c387e7c0  r5 : 00000000  r4 : c3a96780
r3 : 00000000  r2 : 00000000  r1 : 0000002b  r0 : c03ac974
Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
Control: 0005317f  Table: 20004000  DAC: 00000017
Process swapper (pid: 1, stack limit = 0xc3816260)
Stack: (0xc3817e4c to 0xc3818000)
7e40:                            00000002 00000000 c0417724 c340ba2c fffffffa 
7e60: 00000000 c387e7c0 00000003 00000000 c3817ea4 c3817e80 c008f714 c018da3c 
7e80: 00000000 c387e7c0 c340ba2c c008f5d0 c380a2a0 c34056b4 c3817ecc c3817ea8 
7ea0: c008b824 c008f5e0 c387e7c0 c3814660 00000000 c383d000 ffffff9c c383d000 
7ec0: c3817eec c3817ed0 c008ba5c c008b6e0 00000000 c3814660 00000000 c3817f14 
7ee0: c3817f8c c3817ef0 c00960f0 c008ba20 c3817ee4 c3817f08 00000000 00000000 
7f00: 00000002 ffffffff 20000013 00000006 c0424340 c380a2a0 c34056b4 c3817f28 
7f20: c006ff9c c006f874 00000101 00000001 00000000 ffffffff c0424520 c0409970 
7f40: c3817f6c 00000000 00000000 c3815bc0 c3815bc8 00000000 00000003 00000000 
7f60: c387e7c0 00000000 00000002 00000000 00000000 ffffff9c 00000000 c383d000 
7f80: c3817fb8 c3817f90 c008bc28 c0095d3c 00000026 c040a1b8 c00241e0 00000000 
7fa0: 00000000 00000000 00000000 c3817fc8 c3817fbc c008bcdc c008bbd0 c3817fdc 
7fc0: c3817fcc c002b49c c008bcc8 c040a1b8 c3817ff4 c3817fe0 c0008a54 c002b47c 
7fe0: 00000000 00000000 00000000 c3817ff8 c00438c4 c00089a8 00200003 54000008 
Backtrace: 
[] (tty_open+0x0/0x400) from [] (chrdev_open+0x144/0x168)
[] (chrdev_open+0x0/0x168) from [] (__dentry_open+0x154/0x264)
 r8:c34056b4 r7:c380a2a0 r6:c008f5d0 r5:c340ba2c r4:c387e7c0
[] (__dentry_open+0x0/0x264) from [] (nameidata_to_filp+0x4c/0x64)
[] (nameidata_to_filp+0x0/0x64) from [] (do_filp_open+0x3c4/0x748)
 r5:c3817f14 r4:00000000
[] (do_filp_open+0x0/0x748) from [] (do_sys_open+0x68/0xf8)
[] (do_sys_open+0x0/0xf8) from [] (sys_open+0x24/0x28)
[] (sys_open+0x0/0x28) from [] (init_post+0x30/0x100)
[] (init_post+0x0/0x100) from [] (kernel_init+0xbc/0xe4)
 r4:c040a1b8
[] (kernel_init+0x0/0xe4) from [] (do_exit+0x0/0x588)
 r5:00000000 r4:00000000
Code: e3550000 1a000011 e59430b0 e51b202c (e5933000) 
---[ end trace d398db72783d970c ]---
Kernel panic - not syncing: Attempted to kill init!
Backtrace: 
[] (dump_backtrace+0x0/0x104) from [] (dump_stack+0x18/0x1c)
 r7:00000005 r6:c040a4fc r5:c3812c40 r4:c3816000
[] (dump_stack+0x0/0x1c) from [] (panic+0x40/0x10c)
[] (panic+0x0/0x10c) from [] (do_exit+0x218/0x588)
 r3:c03e9cbc r2:c3812c40 r1:c3812c40 r0:c0393818
[] (do_exit+0x0/0x588) from [] (die+0x134/0x154)
[] (die+0x0/0x154) from [] (__do_kernel_fault+0x6c/0x7c)
[] (__do_kernel_fault+0x0/0x7c) from [] (do_page_fault+0x200/0x220)
 r7:c3817e04 r6:00000005 r5:c3812c40 r4:ffffffff
[] (do_page_fault+0x0/0x220) from [] (do_translation_fault+0x20/0x80)
[] (do_translation_fault+0x0/0x80) from [] (do_DataAbort+0x3c/0xa0)
 r5:c03e60a8 r4:ffffffff
[] (do_DataAbort+0x0/0xa0) from [] (__dabt_svc+0x40/0x60)
Exception stack(0xc3817e04 to 0xc3817e4c)
7e00:          c03ac974 0000002b 00000000 00000000 c3a96780 00000000 c387e7c0 
7e20: 00000000 00000001 c340ba2c 00500001 c3817e7c c3817e4c c3817e4c c018db20 
7e40: c018dbb8 60000013 ffffffff                                              
 r8:00000001 r7:00000000 r6:c387e7c0 r5:c3817e38 r4:ffffffff
[] (tty_open+0x0/0x400) from [] (chrdev_open+0x144/0x168)
[] (chrdev_open+0x0/0x168) from [] (__dentry_open+0x154/0x264)
 r8:c34056b4 r7:c380a2a0 r6:c008f5d0 r5:c340ba2c r4:c387e7c0
[] (__dentry_open+0x0/0x264) from [] (nameidata_to_filp+0x4c/0x64)
[] (nameidata_to_filp+0x0/0x64) from [] (do_filp_open+0x3c4/0x748)
 r5:c3817f14 r4:00000000
[] (do_filp_open+0x0/0x748) from [] (do_sys_open+0x68/0xf8)
[] (do_sys_open+0x0/0xf8) from [] (sys_open+0x24/0x28)
[] (sys_open+0x0/0x28) from [] (init_post+0x30/0x100)
[] (init_post+0x0/0x100) from [] (kernel_init+0xbc/0xe4)
 r4:c040a1b8
[] (kernel_init+0x0/0xe4) from [] (do_exit+0x0/0x588)
 r5:00000000 r4:00000000

噢，也就是说，下载下来  2.6.30 #74 这个版本的代码，配置，编译，运行就出这个问题？

有没尝试为这个版本打上对应的patch，

如果没带patch的话，打上patch，再编译试试？ 如果是打了patch再编译而出问题的话，

那就看看代码吧

从提示来看还是你的内核有问题，似乎是tty驱动方面。

PC is at tty_open+0x18c/0x400

根据这个，看看是 在tty_open 函数源代码的哪一行出错了，再分析一下你相关的修改或者配置。