Hi Ethy, Correct. The output is available via file `/sys/kernel/debug/tracing/trace_pipe`. There are other helper programs that can also read it, like `bpftool prog tracelog` or `tc exec bpf dbg`. But you need to pay attention, what you're trying to print, since `bpf_printk()` supports much fewer formats than usual `printk()`. I.e. only `%d %i %u %x %ld %li %lu %lx %lld %lli %llu %llx %p %s` conversion specifiers are allowed. If an unsupported specifier is spotted, the string is silently dropped and never appears in trace log. Here you can find some examples: https://github.com/xdp-project/xdp-tutorial/tree/master/tracing03-xdp-debug-print Best regards, Ivan Koveshnikov On Wed, 14 Jul 2021 at 08:08, Ethy H. Brito <ethy.brito@xxxxxxxxxxxx> wrote: > > > Hi! > > I am working on some minor modifications in xdp-cpumap-tc to accommodate NAT at WAN side. > But the things are not working as expected. > > How can bpf_debug be used to help debugging? > > I read that its output ends-up in /sys/kernel/debug/tracing/trace_pipe. > But how can it be read? > I tried "cat trace_pipe" but this produced no output whatsoever. > > Any hints will be appreciated. > > Thanx > > Regards > > Ethy
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