debugfs-webgui

Simpler, more flexible and convenient Linux kernel dynamic debug (dyndbg)

Features

• multiple configs for each file
• display only files of interest
• update, save and restore configs

Target system requirements

• web server (e.g. Apache2) + PHP

Install

• copy files to the target system
• make them accessible through the web server

Manual

• Open http://target-ip/webserver-path-to-degufs.html/debugfs.html
• f, l, m, t flags are applied on page load/refresh, also use checkboxes
• click Edit list to display all files and select the files of interest
• click Apply to debugfs to apply restored config to debugfs - restored config is not applied on page load/refresh - it's just read from the stored config file.
• click on a filename to expand available debug options
• use checkboxes to control (command is sent on change)
• click read lines from debugfs if the source has changed (line numbers got shifted) to update config - checkboxes will keep their states.
• use the green dropdown menu in the file's table to create and select individual configs.
• click Save to persistent storage - copies current config from tmpfs to the target system's persistent storage (mounted rootfs, the same dir as debugfs.php)
• click Switch off debug to turn off debug in all of the files of interest.

Notes

• debugfs.json stored the same dir as debugfs.php is the global file in json format. It stores all individual configs.
• jquery.ajax.queue.js plugin is used to send ajax requests sequentially to resolve racing condition in accessing the global config file.
• On page load/refresh debugfs.php tries to restore the global config in the following order:
• from tmpfs (/tmp/debugfs.json) - is a working copy, don't not forget to save it before reboot.
• from the target system's persistent storage (debugfs.json - mounted rootfs, the same dir as debugfs.php). Copied to /tmp/debugfs.json.
• from debugfs (/sys/kernel/debug/dynamic_debug/control). Copied into /tmp/debugfs.json. Save to persistent storage - to create persistent config.
• Depending on the number of selected files ajax requests can take some time:
  • single debug message - quick
  • f,l,m,t, apply to debugfs - 100+ ms - depends on the number of files.

Behind the scenes

• PHP - converts json config to queries and back, applies queries to dyndbg, stores configs, responds to ajax requests.
• JavaScript + libraries:
• jQuery
• jquery.ajax.queue.js
• Bootstrap