On Wed, 14 Jul 2021 22:06:48 +0500 Ivan Koveshnikov <ikoveshnik@xxxxxxxxx> wrote: > Hi Ethy, Hi Ivan (and others behind the bushes) > > 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. Very useful info. I couldn't see my logs just because of this: unsupported format. Now it is OK. > > Here you can find some examples: > https://github.com/xdp-project/xdp-tutorial/tree/master/tracing03-xdp-debug-print Thanx Regards Ethy > > > 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 -- Ethy H. Brito /"\ InterNexo Ltda. \ / CAMPANHA DA FITA ASCII - CONTRA MAIL HTML +55 (12) 3797-6860 X ASCII RIBBON CAMPAIGN - AGAINST HTML MAIL S.J.Campos - Brasil / \ PGP key: http://www.inexo.com.br/~ethy/0xC3F222A0.asc
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