linux-stable/kernel/trace/bpf_trace.h
Alan Maguire ac5a72ea5c bpf: Use dedicated bpf_trace_printk event instead of trace_printk()
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.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/r/20200628194334.6238b933@oasis.local.home
Link: https://lore.kernel.org/bpf/1594641154-18897-2-git-send-email-alan.maguire@oracle.com
2020-07-13 16:55:49 -07:00

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C

/* SPDX-License-Identifier: GPL-2.0 */
#undef TRACE_SYSTEM
#define TRACE_SYSTEM bpf_trace
#if !defined(_TRACE_BPF_TRACE_H) || defined(TRACE_HEADER_MULTI_READ)
#define _TRACE_BPF_TRACE_H
#include <linux/tracepoint.h>
TRACE_EVENT(bpf_trace_printk,
TP_PROTO(const char *bpf_string),
TP_ARGS(bpf_string),
TP_STRUCT__entry(
__string(bpf_string, bpf_string)
),
TP_fast_assign(
__assign_str(bpf_string, bpf_string);
),
TP_printk("%s", __get_str(bpf_string))
);
#endif /* _TRACE_BPF_TRACE_H */
#undef TRACE_INCLUDE_PATH
#define TRACE_INCLUDE_PATH .
#define TRACE_INCLUDE_FILE bpf_trace
#include <trace/define_trace.h>