Re: [PATCH v2 bpf-next 1/2] bpf: use dedicated bpf_trace_printk event instead of trace_printk()

From: Andrii Nakryiko
Date: Fri Jul 10 2020 - 16:56:01 EST


On Fri, Jul 10, 2020 at 7:25 AM Alan Maguire <alan.maguire@xxxxxxxxxx> wrote:
>
> The bpf helper bpf_trace_printk() uses trace_printk() under the hood.
> This leads to an alarming warning message originating from trace
> buffer allocation which occurs the first time a program using
> bpf_trace_printk() is loaded.
>
> We can instead create a trace event for bpf_trace_printk() and enable
> it in-kernel when/if we encounter a program using the
> bpf_trace_printk() helper. With this approach, trace_printk()
> is not used directly and no warning message appears.
>
> This work was started by Steven (see Link) and finished by Alan; added
> Steven's Signed-off-by with his permission.
>
> Link: https://lore.kernel.org/r/20200628194334.6238b933@xxxxxxxxxxxxxxxx
> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
> Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
> ---

LGTM.

Acked-by: Andrii Nakryiko <andriin@xxxxxx>

> kernel/trace/Makefile | 2 ++
> kernel/trace/bpf_trace.c | 41 ++++++++++++++++++++++++++++++++++++-----
> kernel/trace/bpf_trace.h | 34 ++++++++++++++++++++++++++++++++++
> 3 files changed, 72 insertions(+), 5 deletions(-)
> create mode 100644 kernel/trace/bpf_trace.h
>

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