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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.
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