Commit 7fb20f9e authored by Alan Maguire's avatar Alan Maguire Committed by Daniel Borkmann
Browse files

bpf, doc: Remove references to warning message when using bpf_trace_printk() 



The BPF helper bpf_trace_printk() no longer uses trace_printk();
it is now triggers a dedicated trace event.  Hence the described
warning is no longer present, so remove the discussion of it as
it may confuse people.

Fixes: ac5a72ea ("bpf: Use dedicated bpf_trace_printk event instead of trace_printk()")
Signed-off-by: default avatarAlan Maguire <alan.maguire@oracle.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/1596801029-32395-1-git-send-email-alan.maguire@oracle.com
parent 929e54a9

Documentation/bpf/bpf_design_QA.rst

+0 −11
Original line number Diff line number Diff line
@@ -246,17 +246,6 @@ program is loaded the kernel will print warning message, so 
this helper is only useful for experiments and prototypes.

Tracing BPF programs are root only.



Q: bpf_trace_printk() helper warning

------------------------------------

Q: When bpf_trace_printk() helper is used the kernel prints nasty

warning message. Why is that?



A: This is done to nudge program authors into better interfaces when

programs need to pass data to user space. Like bpf_perf_event_output()

can be used to efficiently stream data via perf ring buffer.

BPF maps can be used for asynchronous data sharing between kernel

and user space. bpf_trace_printk() should only be used for debugging.



Q: New functionality via kernel modules?

----------------------------------------

Q: Can BPF functionality such as new program or map types, new