Dynamic Debug in Linux¶

How to enable targeted kernel debug messages without rebuilding the kernel.

This English edition keeps the original illustrations and reproducible command or configuration examples.

Reference diagram 1

Commands and configuration¶

CONFIG_DYNAMIC_DEBUG=y
CONFIG_DEBUG_FS=y

cat /sys/kernel/debug/dynamic_debug/control

echo 'file driver.c +p' > /sys/kernel/debug/dynamic_debug/control

echo 'file driver.c -p' > /sys/kernel/debug/dynamic_debug/control

echo 'func my_function +p' > /sys/kernel/debug/dynamic_debug/control

echo 'module my_module +p' > /sys/kernel/debug/dynamic_debug/control

pr_debug("Packet sent: %s\n", packet_data);

echo 'file net_driver.c +p' > /sys/kernel/debug/dynamic_debug/control

Practical notes¶

Test each change on a recoverable target, keep logs from the boot or failure path, and record the exact kernel and userspace versions used in the result.