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/* Copyright (c) 2017-2021, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* \file events.h
* \brief Header file for Tor tracing instrumentation definition.
**/
#ifndef TOR_LIB_TRACE_EVENTS_H
#define TOR_LIB_TRACE_EVENTS_H
#include "orconfig.h"
/*
* A tracepoint signature is defined as follow:
*
* tor_trace(<subsystem>, <event_name>, <args>...)
*
* If tracing is enabled, the tor_trace() macro is mapped to all possible
* instrumentations (defined below). Each instrumentation type MUST define a
* top level macro (TOR_TRACE_<type>) so it can be inserted into each
* tracepoint.
*
* In case no tracing is enabled (HAVE_TRACING), tracepoints are NOP and thus
* have no execution cost.
*
* Currently, three types of instrumentation are supported:
*
* log-debug: Every tracepoints is mapped to a log_debug() statement.
*
* User Statically-Defined Tracing (USDT): Probes that can be used with perf,
* dtrace, SystemTap, DTrace and BPF Compiler Collection (BCC).
*
* LTTng-UST: Probes for the LTTng Userspace Tracer. If USDT interface
* (sdt.h) is available, the USDT probes are also generated by LTTng thus
* enabling this instrumentation provides both probes.
*/
/** Helper to disambiguate these identifiers in the code base. They should
* only be used with tor_trace() like so:
*
* tor_trace(TR_SUBSYS(circuit), TR_EV(opened), ...);
*/
#define TR_SUBSYS(name) tor_ ## name
#define TR_EV(name) name
#ifdef HAVE_TRACING
#define tor_trace(subsystem, event_name, ...) \
do { \
TOR_TRACE_LOG_DEBUG(subsystem, event_name); \
TOR_TRACE_USDT(subsystem, event_name, ## __VA_ARGS__); \
TOR_TRACE_LTTNG(subsystem, event_name, ## __VA_ARGS__); \
} while (0)
/* This corresponds to the --enable-tracing-instrumentation-log-debug
* configure option which maps all tracepoints to a log_debug() statement. */
#include "lib/trace/debug.h"
/* This corresponds to the --enable-tracing-instrumentation-usdt configure
* option which will generate USDT probes for each tracepoints. */
#include "lib/trace/usdt/usdt.h"
/* This corresponds to the --enable-tracing-instrumentation-lttng configure
* option which will generate LTTng probes for each tracepoints. */
#include "lib/trace/lttng/lttng.h"
#else /* !defined(HAVE_TRACING) */
/* Reaching this point, tracing is disabled thus we NOP every tracepoints
* declaration so we have no execution cost at runtime. */
#define tor_trace(subsystem, name, ...)
#endif /* defined(HAVE_TRACING) */
#endif /* !defined(TOR_LIB_TRACE_EVENTS_H) */
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