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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: ac5a72ea5c ("bpf: Use dedicated bpf_trace_printk event instead of trace_printk()")
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/1596801029-32395-1-git-send-email-alan.maguire@oracle.com
This commit is contained in:
Alan Maguire 2020-08-07 12:50:29 +01:00 committed by Daniel Borkmann
parent 929e54a989
commit 7fb20f9e90
1 changed files with 0 additions and 11 deletions
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Documentation/bpf/bpf_design_QA.rst
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@ -246,17 +246,6 @@ program is loaded the kernel will print warning message, so
this helper is only useful for experiments and prototypes. this helper is only useful for experiments and prototypes.
Tracing BPF programs are root only. 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: New functionality via kernel modules?
---------------------------------------- ----------------------------------------
Q: Can BPF functionality such as new program or map types, new Q: Can BPF functionality such as new program or map types, new