Debugging using bpf_printk / bpf_trace_printk?

[XieGuochao]

Hello, I want to do some simple observations first before developing tools.

However, it seems that the bpf_printk or bpf_trace_printk does not work and nothing is printed on the terminal. Is it common? Is there any simple alternative to print something in the BPF program? Is there any guide for debugging/observation?

[lmb]

bpf_printk doesn't write to the console, it writes to the kernel's trace pipe. Take a look at https://man7.org/linux/man-pages/man7/bpf-helpers.7.html for entry bpf_trace_printk.