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