【34】通过sys文件系统修改modules 参数

朱雀 2024-04-18 17:19 13阅读 0赞

参考文献  
https://devarea.com/linux-kernel-development-kernel-module-parameters/  
https://stackoverflow.com/questions/11031554/kernel-module-parameters-changes-using-sys-module/33655017  
https://www.kernel.org/doc/Documentation/ABI/stable/sysfs-module  
https://devarea.com/linux-kernel-development-kernel-module-parameters/

/sys/module有系统中所有模块的信息，不论这些模块是以内联(inlined)方式编译到内核映像文件(vmlinuz)中还是编译为外部模块(ko文件)，都可能会出现在 /sys/module 中：  
编译为外部模块(ko文件)在加载后会出现对应的 /sys/module/<module\_name>/, 并且在这个目录下会出现一些属性文件和属性目录来表示此外部模块的一些信息，如版本号、加载状态、所提供的驱动程序等；  
编译为内联方式的模块则只在当它有非0属性的模块参数时会出现对应的 /sys/module/<module\_name>, 这些模块的可用参数会出现在 /sys/modules//parameters/<param\_name> 中，  
如 /sys/module/printk/parameters/time 这个可读写参数控制着内联模块 printk 在打印内核消息时是否加上时间前缀；  
所有内联模块的参数也可以由 “<module\_name>.<param\_name>=” 的形式写在内核启动参数上，如启动内核时加上参数 “printk.time=1” 与 向 “/sys/module/printk/parameters/time” 写入1的效果相同；  
没有非0属性参数的内联模块不会出现于此。

What: /sys/module  
Description:  
The /sys/module tree consists of the following structure:

/sys/module/MODULENAME
    	The name of the module that is in the kernel.  This
    	module name will always show up if the module is loaded as a
    	dynamic module.  If it is built directly into the kernel, it
    	will only show up if it has a version or at least one
    	parameter.
    
    	Note: The conditions of creation in the built-in case are not
    	by design and may be removed in the future.
    	
    /sys/module/MODULENAME/parameters
    	This directory contains individual files that are each
    	individual parameters of the module that are able to be
    	changed at runtime.  See the individual module
    	documentation as to the contents of these parameters and
    	what they accomplish.
    
    	Note: The individual parameter names and values are not
    	considered stable, only the fact that they will be
    	placed in this location within sysfs.  See the
    	individual driver documentation for details as to the
    	stability of the different parameters.
    
    
    /sys/module/MODULENAME/refcnt
    	If the module is able to be unloaded from the kernel, this file
    	will contain the current reference count of the module.
    
    	Note: If the module is built into the kernel, or if the
    	CONFIG_MODULE_UNLOAD kernel configuration value is not enabled,
    	this file will not be present.

下面我们找个pciehp的模块看看下面三个模块参数，pciehp\_debug,pciehp\_poll\_mode和pciehp\_poll\_time  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmppYXNlbg_size_16_color_FFFFFF_t_70]

\[root@localhost parameters\]\# pwd  
**/sys/module/pciehp/parameters**  
\[root@localhost parameters\]\# ll  
total 0  
\-rw-r–r--. 1 root root 4096 Sep 9 21:31 pciehp\_debug  
\-rw-r–r--. 1 root root 4096 Sep 9 21:31 pciehp\_force  
\-rw-r–r--. 1 root root 4096 Sep 9 21:31 pciehp\_poll\_mode  
\-rw-r–r--. 1 root root 4096 Sep 9 21:31 pciehp\_poll\_time  
\[root@localhost parameters\]\# cat pciehp\_debug  
N  
\[root@localhost parameters\]\# cat pciehp\_force  
N  
\[root@localhost parameters\]\# cat pciehp\_poll\_mode  
N  
\[root@localhost parameters\]\# cat pciehp\_poll\_time  
0  
\-------------我们看到三个参数都是0

\[root@localhost parameters\]\# echo 1 > pciehp\_debug  
\[root@localhost parameters\]\# cat pciehp\_debug  
Y  
\-------------往pciehp\_debug 写1后，pciehp\_debug 变成Y

\[root@localhost parameters\]\# cat /sys/bus/pci/slots/  
18/ 19/ 50/ 51/

\[root@localhost parameters\]\# cat /sys/bus/pci/slots/50/module/parameters/pciehp\_debug  
Y  
\[root@localhost parameters\]\# cat /sys/bus/pci/slots/18/module/parameters/pciehp\_debug  
Y  
\-------------sys/bus/pci/slots/slot\_number//module/parameters/pciehp\_debug 和/sys/module/pciehp/parameters/pciehp\_debug是一样的

\[root@localhost parameters\]\# echo 0 >/sys/bus/pci/slots/50/module/parameters/pciehp\_debug  
\[root@localhost parameters\]\# cat /sys/bus/pci/slots/50/module/parameters/pciehp\_debug  
N  
\[root@localhost parameters\]\# cat /sys/bus/pci/slots/18/module/parameters/pciehp\_debug  
N  
\[root@localhost parameters\]\# pwd  
/sys/module/pciehp/parameters  
\[root@localhost parameters\]\# cat pciehp\_debug  
N

\-------------往/sys/bus/pci/slots/50/module/parameters/pciehp\_debug 写0后，可以看到所有的pciehp\_debug 都变成了0

**我们看一下/sys/bus/pci/slots/slot\_number下的module其实是link到/sys/modulles/pciehp的**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmppYXNlbg_size_16_color_FFFFFF_t_70 1]  
![在这里插入图片描述][20190910102440218.png]

接下来，我们来做个试验，我们把pciehp\_debug改成1，然后查看电源状态  
root@localhost parameters\]\# pwd  
/sys/bus/pci/slots/18/module/parameters  
\[root@localhost parameters\]\#  
\[root@localhost parameters\]\# echo 1 > pciehp\_debug  
\[root@localhost parameters\]\# cat pciehp\_debug  
Y  
\[root@localhost parameters\]\# cat /sys/module/pciehp/parameters/pciehp\_debug  
Y  
\[root@localhost parameters\]\# cat /sys/bus/pci/slots/18/power  
0  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmppYXNlbg_size_16_color_FFFFFF_t_70 2]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmppYXNlbg_size_16_color_FFFFFF_t_70 3]  
![在这里插入图片描述][20190910095830817.png]  
我们发现pciehp\_debug为1时，pciehp\_get\_power\_status函数可以打印出debug信息

我们把pciehp\_debug改成0  
\[root@localhost parameters\]\# pwd  
/sys/bus/pci/slots/18/module/parameters  
\[root@localhost parameters\]\# echo 0 > pciehp\_debug  
\[root@localhost parameters\]\# cat pciehp\_debug  
N  
\[root@localhost parameters\]\# cat /sys/module/pciehp/parameters/pciehp\_debug  
N  
\[root@localhost parameters\]\# cat /sys/bus/pci/slots/18/power  
0  
\[root@localhost parameters\]\#  
发现，仍然可以获取电源状态，但是没有任何打印。

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmppYXNlbg_size_16_color_FFFFFF_t_70]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/f4c0a6d0cef0450180ed1a856c4d6e27.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmppYXNlbg_size_16_color_FFFFFF_t_70 1]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/be18bc242cdc498c9f4a89a24ff030bf.png
[20190910102440218.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/aecb6def76804993afc941ea68870f97.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmppYXNlbg_size_16_color_FFFFFF_t_70 2]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/623610ae8aa841cfa43d122711f134ed.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbmppYXNlbg_size_16_color_FFFFFF_t_70 3]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/12d950b715784feb83b2d133afded877.png
[20190910095830817.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/e1c61305bd3e4184b5719ff38c71f57a.png