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出现拔出USB线缆时kernel会有oops错误,以下是对kernel oops错误调试的简单记录,该方法也适用于panic错误。 - Unable to handle kernel NULL pointer dereference at virtual address 00000020
- pgd = 80004000
- [00000020] *pgd=00000000
- Internal error: Oops: 17 [#1] PREEMPT
- last sysfs file: /sys/devices/platform/mxsdhci.2/mmc_host/mmc0/mmc0:0001/boot_bus_config
- CPU: 0 Not tainted (2.6.35.3 #10)
- PC is at fsg_main_thread+0x144/0x730
- LR is at schedule+0x2ac/0x328
- pc : [<8025b0b4>] lr : [<802ac778>] psr: 60000013
- sp : cfcd3f88 ip : cfcd3f38 fp : cfcd3fc4
- r10: cfcd2000 r9 : cf081640 r8 : 00000200
- r7 : 80356ac8 r6 : cfcd2000 r5 : cf081678 r4 : cf081600
- r3 : 00000000 r2 : 00000000 r1 : 00000000 r0 : 00000000
- Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment kernel
- Control: 10c5387d Table: bd2a0019 DAC: 00000017
- Process file-storage-ga (pid: 871, stack limit = 0xcfcd22e8)
- Stack: (0xcfcd3f88 to 0xcfcd4000)
- 3f80: cf08167c cfcd3f98 802ac648 cf0816b0 00000000 cf029ed8
- 3fa0: cfcd3fcc 8025af70 cf081600 00000000 00000000 00000000 cfcd3ff4 cfcd3fc8
- 3fc0: 8006565c 8025af7c 00000000 00000000 cfcd3fd0 cfcd3fd0 cf029ed8 800655d8
- 3fe0: 80051d14 00000013 00000000 cfcd3ff8 80051d14 800655e4 eda8ff35 f7efad76
- Backtrace:
- [<8025af70>] (fsg_main_thread+0x0/0x730) from [<8006565c>] (kthread+0x84/0x8c)
- [<800655d8>] (kthread+0x0/0x8c) from [<80051d14>] (do_exit+0x0/0x65c)
- r7:00000013 r6:80051d14 r5:800655d8 r4:cf029ed8
- Code: e5953004 e3530001 1afffff8 e5953018 (e5932020)
- ---[ end trace 38aa9563884a33ec ]---
遇 到了空指针错误,PC指针指向fsg_main_thread+0x144 处,fsg_main_thread()函数位于driver/usb/gadgate/file_storage.c这个文件内,但是0x144的 offset是哪一行呢?由于发生这个oops的kernel缺省没有包含debug信息,所以需要重新生成一个带debug info的vmlinux,步骤如下: - kernel hacking->Kernel debugging->Compile the kernel with debug info
打开编译好的kernel vmlinux所在目录的符号表文件System.map,搜索fsg_main_thread,找到所在的行,最左边的就是fsg_main_thread的地址了,即8025af70,偏移0x144,最终出错的地址是: - 0x8025af70+0x144=0x8025b0b4
此时用编译kernel的toolchain中的gdb工具打开带调式符号的vmlinux, - toolchain/arm-eabi-4.4.3/bin/arm-eabi-gdb kernel/vmlinux
- Breakpoint 1 at 0x8025b0b4 : file drivers/usb/gadget/file_storage.c, line 2750.
拿到了行号就可以继续深入debug了,在该行前后加一些BUG_ON()宏对变量进行测试,最终找到出错的语句。 转载地址:http://medmi.baihongyu.com/