linux pstore驱动分析和调试
1.简介
pstore（persistent storage）
主要用于存储内核异常时的log信息。实现方式是，管理一块“非易失性的存储空间”，如不断电的RAM或外部存储，当系统异常时，将log信息写到Pstore管理的存储空间，直到下一次系统正常时，在将log读出来，以文件形式提供给用户使用。
ramoops指的是采用ram保存oops信息的一个功能，在内核开关中用3个开关控制：PSTORE_CONSOLE控制是否保存控制台输出，PSTORE_FTRACE控制是否保存函数调用序列，PSTORE_RAM控制是否保存panic/oops信息。
pstore简单来说就是一个小文件系统。主要是读取Android设备内核日志时会用到该模块。
2.整体框架
3. 配置
3.1. dts
32位操作系统如下配置
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reserved-memory { #address-cells = <2>; #size-cells = <2>; ranges; reg = <0x50008000 0x100000>; reg-names = "reserved-memory "; };
ramoops { compatible = "ramoops "; record-size = <0x0 0x20000>; console-size = <0x0 0x20000>; ftrace-size = <0x0 0x20000>; pmsg-size = <0x0 0x20000>; memory-region = <&reserved-memory>; status = "okay"; }; |
由于dts指定的是物理地址，如果内核地址为0x40008000那么可以把pstore地址配置为0x50008000，留出256M空间给内核使用。reg这么配置是32位。每个日志是128KB，总大小是1M，最多可有8个。
3.2. Kconfig
文件路径：linux/fs/pstore/Kconfig
部分内容如下
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config PSTORE tristate "Persistent store support" select CRYPTO if PSTORE_COMPRESS default n help This option enables generic access to platform level persistent storage via "pstore" filesystem that can be mounted as /dev/pstore. Only useful if you have a platform level driver that registers with pstore to provide the data, so you probably should just go say "Y" (or "M") to a platform specific persistent store driver (e.g. ACPI_APEI on X86) which will select this for you. If you don't have a platform persistent store driver, say N.
config PSTORE_CONSOLE bool "Log kernel console messages" depends on PSTORE help When the option is enabled, pstore will log all kernel messages, even if no oops or panic happened.
config PSTORE_PMSG bool "Log user space messages" depends on PSTORE help When the option is enabled, pstore will export a character interface /dev/pmsg0 to log user space messages. On reboot data can be retrieved from /sys/fs/pstore/pmsg-ramoops-[ID].
If unsure, say N.
config PSTORE_FTRACE bool "Persistent function tracer" depends on PSTORE depends on FUNCTION_TRACER depends on DEBUG_FS help With this option kernel traces function calls into a persistent ram buffer that can be decoded and dumped after reboot through pstore filesystem. It can be used to determine what function was last called before a reset or panic.
If unsure, say N.
config PSTORE_RAM tristate "Log panic/oops to a RAM buffer" depends on PSTORE depends on HAS_IOMEM depends on HAVE_MEMBLOCK select REED_SOLOMON select REED_SOLOMON_ENC8 select REED_SOLOMON_DEC8 help This enables panic and oops messages to be logged to a circular buffer in RAM where it can be read back at some later point.
Note that for historical reasons, the module will be named "ramoops.ko".
For more information, see Documentation/admin-guide/ramoops.rst.
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根据Kconfig文件，对应的配置选项为
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选项 |
Kconfig选项 |
含义 |
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PSTORE_CONSOLE |
Log kernel console messages |
内核日志信息 |
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PSTORE_PMSG |
Log user space messages |
用户日志信息 |
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PSTORE_FTRACE |
Persistent function tracer |
函数调用关系 |
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PSTORE_RAM |
Log panic/oops to a RAM buffer" |
内核崩溃或错误日志 |
3.3. makefile
文件路径：fs/pstore/makefile
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# SPDX-License-Identifier: GPL-2.0 # # Makefile for the linux pstorefs routines. #
obj-$(CONFIG_PSTORE) += pstore.o
pstore-objs += inode.o platform.o pstore-$(CONFIG_PSTORE_FTRACE) += ftrace.o
pstore-$(CONFIG_PSTORE_PMSG) += pmsg.o
ramoops-objs += ram.o ram_core.o obj-$(CONFIG_PSTORE_RAM) += ramoops.o |
默认就已经配好了。
3.4. menuconfig配置
如下面三张图配置对应的选项
3.5. 编译
make kernel -j8
4. 测试
查看模pstore模块开起来没有
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dmesg | grep -i pstore dmesg | grep -i ramoops |
日志生成目录
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cd /sys/fs/pstore |
生成一个内核日志和用户日志
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reboot |
产生一个崩溃日志
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echo c > /proc/sysrq-trigger |
产生函数调用日志
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echo 1 > /proc/sys/kernel/sysrq |
5. 测试参考资料
Documentation/ramoops.txt
https://blog.csdn.net/zgp2917/article/details/107711813
https://blog.csdn.net/qq_27125121/article/details/78666907
https://www.cnblogs.com/ZanyRain/p/10076645.html
http://huaqianlee.github.io/2020/11/13/Android/pstore/
