Tor  0.4.6.0-alpha-dev
events.h
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1 /* Copyright (c) 2017-2020, The Tor Project, Inc. */
2 /* See LICENSE for licensing information */
3 
4 /**
5  * \file events.h
6  * \brief Header file for Tor tracing instrumentation definition.
7  **/
8 
9 #ifndef TOR_LIB_TRACE_EVENTS_H
10 #define TOR_LIB_TRACE_EVENTS_H
11 
12 #include "orconfig.h"
13 
14 /*
15  * A tracepoint signature is defined as follow:
16  *
17  * tor_trace(<subsystem>, <event_name>, <args>...)
18  *
19  * If tracing is enabled, the tor_trace() macro is mapped to all possible
20  * instrumentations (defined below). Each instrumentation type MUST define a
21  * top level macro (TOR_TRACE_<type>) so it can be inserted into each
22  * tracepoint.
23  *
24  * In case no tracing is enabled (HAVE_TRACING), tracepoints are NOP and thus
25  * have no execution cost.
26  *
27  * Currently, three types of instrumentation are supported:
28  *
29  * log-debug: Every tracepoints is mapped to a log_debug() statement.
30  *
31  * User Statically-Defined Tracing (USDT): Probes that can be used with perf,
32  * dtrace, SystemTap, DTrace and BPF Compiler Collection (BCC).
33  *
34  * LTTng-UST: Probes for the LTTng Userspace Tracer. If USDT interface
35  * (sdt.h) is available, the USDT probes are also generated by LTTng thus
36  * enabling this instrumentation provides both probes.
37  */
38 
39 /** Helper to disambiguate these identifiers in the code base. They should
40  * only be used with tor_trace() like so:
41  *
42  * tor_trace(TR_SUBSYS(circuit), TR_EV(opened), ...);
43  */
44 
45 #define TR_SUBSYS(name) tor_ ## name
46 #define TR_EV(name) name
47 
48 #ifdef HAVE_TRACING
49 
50 #define tor_trace(subsystem, event_name, ...) \
51  do { \
52  TOR_TRACE_LOG_DEBUG(subsystem, event_name); \
53  TOR_TRACE_USDT(subsystem, event_name, ## __VA_ARGS__); \
54  TOR_TRACE_LTTNG(subsystem, event_name, ## __VA_ARGS__); \
55  } while (0)
56 
57 /* This corresponds to the --enable-tracing-instrumentation-log-debug
58  * configure option which maps all tracepoints to a log_debug() statement. */
59 #include "lib/trace/debug.h"
60 
61 /* This corresponds to the --enable-tracing-instrumentation-usdt configure
62  * option which will generate USDT probes for each tracepoints. */
63 #include "lib/trace/usdt/usdt.h"
64 
65 /* This corresponds to the --enable-tracing-instrumentation-lttng configure
66  * option which will generate LTTng probes for each tracepoints. */
67 #include "lib/trace/lttng/lttng.h"
68 
69 #else /* !defined(HAVE_TRACING) */
70 
71 /* Reaching this point, tracing is disabled thus we NOP every tracepoints
72  * declaration so we have no execution cost at runtime. */
73 #define tor_trace(subsystem, name, ...)
74 
75 #endif /* defined(HAVE_TRACING) */
76 
77 #endif /* !defined(TOR_LIB_TRACE_EVENTS_H) */
lttng.h
Header file for lttng.c.
debug.h
Macros for debugging our event-trace support.