linux kernel 의 config 설정과 관련된 부분
2. Linux Print 관련 Debug
관련내용
https://elinux.org/Debugging_by_printing
- Kernel Config 설정확인
$ cd linux $ vi .config
# # printk and dmesg options # CONFIG_PRINTK_TIME=y // printk의 time 정보 CONFIG_MESSAGE_LOGLEVEL_DEFAULT=4 // Log Level 설정 # CONFIG_BOOT_PRINTK_DELAY is not set # CONFIG_DYNAMIC_DEBUG is not set
| Name | String | Meaning | alias function |
|---|---|---|---|
| KERN_EMERG | "0" | Emergency messages, system is about to crash or is unstable | pr_emerg |
| KERN_ALERT | "1" | Something bad happened and action must be taken immediately | pr_alert |
| KERN_CRIT | "2" | A critical condition occurred like a serious hardware/software failure | pr_emerg |
| KERN_ERR | "3" | An error condition, often used by drivers to indicate difficulties with the hardware | pr_crit |
| KERN_WARNING | "4" | A warning, meaning nothing serious by itself but might indicate problems | pr_err |
| KERN_NOTICE | "5" | Nothing serious, but notably nevertheless. Often used to report security events. | pr_notice |
| KERN_INFO | "6" | Informational message e.g. startup information at driver initialization | pr_info |
| KERN_DEBUG | "7" | Debug messages | pr_debug |
| KERN_DEFAULT | "d" | The default kernel loglevel | |
| KERN_CONT | "" | "continued" line of log printout | pr_cont |
아래와 같이 printk로 각각 debug 가능
printk(KERN_NOTICE "Kernel command line: %s\n", boot_command_line);
- 초기의 디버깅
추후 필요 없다면 삭제
CONFIG_EARLY_PRINTK=y CONFIG_DEBUG_KERNEL=y Kernel Hacking-> Kernel low-level debugging functions
http://forum.falinux.com/zbxe/index.php?mid=lecture_tip&page=82&document_srl=519453
- 별도의 각각의 Device의 Debug가 필요하다면 설정
CONFIG_SND_VERBOSE_PRINTK CONFIG_SND_DEBUG
https://cateee.net/lkddb/web-lkddb/SND_DEBUG.html
2.1 User에서 Kernel Message 설정 및 확인
일반적인 Kernel Debug방법이며, printk를 이용하여 쉽게 debug가 가능하며, dmesg를 이용하여 boot time 역시 쉽게 알수 있다.
- User에서 Kernel printk 설정
$ cat /proc/sys/kernel/printk 7 4 1 3 current default minimum boot-time-default $ sudo -s $ echo 3 > /proc/sys/kernel/printk $ cat /proc/sys/kernel/printk // current 만 변경 3 4 1 3 $ echo "7 4 1 7" > /proc/sys/kernel/printk $ cat /proc/sys/kernel/printk // reboot 되면 원래 설정으로 돌아감 7 4 1 7 $ dmesg // kernel message 확인
https://www.kernel.org/doc/Documentation/
https://www.kernel.org/doc/Documentation/kernel-parameters.txt