Cannot enable kernel dynamic debugging on linux

问题

I have enabled the CONFIG_DYNAMIC_DEBUG flag in kernel config file, built & installed the kernel. Then, when I reboot, I can see /sys/kernel/debug/dynamic_debug/control.

However, when I tried to dynamically enable a module like so:

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

I got:

bash: /sys/kernel/debug/dynamic_debug/control: Permission denied

Notice that I'm using sudo.

回答1:

The redirection (with the > shell operator) is not performed as root. That's why you get a permission denied error. I suggest you run the whole command in a sub shell like:

sudo sh -c "echo 'module xhci_hcd +p' > /sys/kernel/debug/dynamic_debug/control"

回答2:

Just check if you have booted into the correct version of the kernel after enabling CONFIG_DYNAMIC_DEBUG ? Next check if debugfs is mounted.

Try with -n option (do not output the trailing newline)

echo -n 'module xhci_hcd +p' | sudo tee /sys/kernel/debug/dynamic_debug/control

Also try if you are able to debug a specific file for the ko:

echo -n 'file filename.c +p' | sudo tee /sys/kernel/debug/dynamic_debug/control

来源：https://stackoverflow.com/questions/26556246/cannot-enable-kernel-dynamic-debugging-on-linux