trace: Helper macro to disambiguate identifiers

In order to disambiguate the subsystem and event_name identifiers in the
tor_trace() macro, add TR_SUBSYS() and TR_EV() which help to identify the
parameters of tor_trace() explicitly.

Signed-off-by: David Goulet <dgoulet@torproject.org>

src/core/or/circuitbuild.c

@@ -500,7 +500,7 @@ circuit_establish_circuit(uint8_t purpose, extend_info_t *exit_ei, int flags)
     return NULL;
   }
 
-  tor_trace(circuit, establish, circ);
+  tor_trace(TR_SUBSYS(circuit), TR_EV(establish), circ);
   return circ;
 }
 
@@ -983,7 +983,7 @@ circuit_send_first_onion_skin(origin_circuit_t *circ)
 
   if (circuit_deliver_create_cell(TO_CIRCUIT(circ), &cc, 0) < 0)
     return - END_CIRC_REASON_RESOURCELIMIT;
-  tor_trace(circuit, first_onion_skin, circ, circ->cpath);
+  tor_trace(TR_SUBSYS(circuit), TR_EV(first_onion_skin), circ, circ->cpath);
 
   circ->cpath->state = CPATH_STATE_AWAITING_KEYS;
   circuit_set_state(TO_CIRCUIT(circ), CIRCUIT_STATE_BUILDING);
@@ -1147,7 +1147,7 @@ circuit_send_intermediate_onion_skin(origin_circuit_t *circ,
       return 0; /* circuit is closed */
   }
   hop->state = CPATH_STATE_AWAITING_KEYS;
-  tor_trace(circuit, intermediate_onion_skin, circ, hop);
+  tor_trace(TR_SUBSYS(circuit), TR_EV(intermediate_onion_skin), circ, hop);
   return 0;
 }
 

src/core/or/circuitlist.c

@@ -100,7 +100,6 @@
 #include "lib/compress/compress_zlib.h"
 #include "lib/compress/compress_zstd.h"
 #include "lib/buf/buffers.h"
-#include "lib/trace/events.h"
 
 #include "core/or/ocirc_event.h"
 
@@ -568,7 +567,7 @@ circuit_set_state(circuit_t *circ, uint8_t state)
   if (state == CIRCUIT_STATE_GUARD_WAIT || state == CIRCUIT_STATE_OPEN)
     tor_assert(!circ->n_chan_create_cell);
 
-  tor_trace(circuit, change_state, circ, circ->state, state);
+  tor_trace(TR_SUBSYS(circuit), TR_EV(change_state), circ, circ->state, state);
   circ->state = state;
   if (CIRCUIT_IS_ORIGIN(circ))
     circuit_state_publish(circ);
@@ -1083,7 +1082,7 @@ origin_circuit_new(void)
               prediction_time_remaining);
   }
 
-  tor_trace(circuit, new_origin, circ);
+  tor_trace(TR_SUBSYS(circuit), TR_EV(new_origin), circ);
   return circ;
 }
 
@@ -1106,7 +1105,7 @@ or_circuit_new(circid_t p_circ_id, channel_t *p_chan)
 
   init_circuit_base(TO_CIRCUIT(circ));
 
-  tor_trace(circuit, new_or, circ);
+  tor_trace(TR_SUBSYS(circuit), TR_EV(new_or), circ);
   return circ;
 }
 
@@ -1261,7 +1260,7 @@ circuit_free_(circuit_t *circ)
 
   /* Tracepoint. Data within the circuit object is recorded so do this before
    * the actual memory free. */
-  tor_trace(circuit, free, circ);
+  tor_trace(TR_SUBSYS(circuit), TR_EV(free), circ);
 
   if (should_free) {
     memwipe(mem, 0xAA, memlen); /* poison memory */
@@ -2285,7 +2284,7 @@ circuit_mark_for_close_, (circuit_t *circ, int reason, int line,
            CIRCUIT_IS_ORIGIN(circ) ?
               TO_ORIGIN_CIRCUIT(circ)->global_identifier : 0,
            file, line, orig_reason, reason);
-  tor_trace(circuit, mark_for_close, circ);
+  tor_trace(TR_SUBSYS(circuit), TR_EV(mark_for_close), circ);
 }
 
 /** Called immediately before freeing a marked circuit <b>circ</b> from

src/core/or/circuituse.c

@@ -840,7 +840,7 @@ circuit_expire_building(void)
                  -1);
 
     circuit_log_path(LOG_INFO,LD_CIRC,TO_ORIGIN_CIRCUIT(victim));
-    tor_trace(circuit, timeout, TO_ORIGIN_CIRCUIT(victim));
+    tor_trace(TR_SUBSYS(circuit), TR_EV(timeout), TO_ORIGIN_CIRCUIT(victim));
     if (victim->purpose == CIRCUIT_PURPOSE_C_MEASURE_TIMEOUT)
       circuit_mark_for_close(victim, END_CIRC_REASON_MEASUREMENT_EXPIRED);
     else
@@ -1505,7 +1505,8 @@ circuit_expire_old_circuits_clientside(void)
       /* Don't do this magic for testing circuits. Their death is governed
        * by circuit_expire_building */
       if (circ->purpose != CIRCUIT_PURPOSE_PATH_BIAS_TESTING) {
-        tor_trace(circuit, idle_timeout, TO_ORIGIN_CIRCUIT(circ));
+        tor_trace(TR_SUBSYS(circuit), TR_EV(idle_timeout),
+                  TO_ORIGIN_CIRCUIT(circ));
         circuit_mark_for_close(circ, END_CIRC_REASON_FINISHED);
       }
     } else if (!circ->timestamp_dirty && circ->state == CIRCUIT_STATE_OPEN) {
@@ -1526,7 +1527,8 @@ circuit_expire_old_circuits_clientside(void)
                     " that has been unused for %ld msec.",
                    TO_ORIGIN_CIRCUIT(circ)->global_identifier,
                    tv_mdiff(&circ->timestamp_began, &now));
-          tor_trace(circuit, idle_timeout, TO_ORIGIN_CIRCUIT(circ));
+          tor_trace(TR_SUBSYS(circuit), TR_EV(idle_timeout),
+                    TO_ORIGIN_CIRCUIT(circ));
           circuit_mark_for_close(circ, END_CIRC_REASON_FINISHED);
         } else if (!TO_ORIGIN_CIRCUIT(circ)->is_ancient) {
           /* Server-side rend joined circuits can end up really old, because
@@ -1689,7 +1691,7 @@ circuit_testing_failed(origin_circuit_t *circ, int at_last_hop)
 void
 circuit_has_opened(origin_circuit_t *circ)
 {
-  tor_trace(circuit, opened, circ);
+  tor_trace(TR_SUBSYS(circuit), TR_EV(opened), circ);
   circuit_event_status(circ, CIRC_EVENT_BUILT, 0);
 
   /* Remember that this circuit has finished building. Now if we start
@@ -2212,7 +2214,7 @@ circuit_launch_by_extend_info(uint8_t purpose,
           return NULL;
       }
 
-      tor_trace(circuit, cannibalized, circ);
+      tor_trace(TR_SUBSYS(circuit), TR_EV(cannibalized), circ);
       return circ;
     }
   }
@@ -3144,7 +3146,8 @@ circuit_change_purpose(circuit_t *circ, uint8_t new_purpose)
 
   old_purpose = circ->purpose;
   circ->purpose = new_purpose;
-  tor_trace(circuit, change_purpose, circ, old_purpose, new_purpose);
+  tor_trace(TR_SUBSYS(circuit), TR_EV(change_purpose), circ, old_purpose,
+            new_purpose);
 
   if (CIRCUIT_IS_ORIGIN(circ)) {
     control_event_circuit_purpose_changed(TO_ORIGIN_CIRCUIT(circ),

src/core/or/trace_probes_circuit.h

@@ -10,7 +10,7 @@
 #ifndef TOR_TRACE_PROBES_CIRCUIT_H
 #define TOR_TRACE_PROBES_CIRCUIT_H
 
-#include "orconfig.h"
+#include "lib/trace/events.h"
 
 /* We only build the following if LTTng instrumentation has been enabled. */
 #ifdef USE_TRACING_INSTRUMENTATION_LTTNG

src/lib/trace/events.h

@@ -9,6 +9,8 @@
 #ifndef TOR_LIB_TRACE_EVENTS_H
 #define TOR_LIB_TRACE_EVENTS_H
 
+#include "orconfig.h"
+
 /*
  * A tracepoint signature is defined as follow:
  *
@@ -34,13 +36,22 @@
  *  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(tor_ ## subsystem, event_name);             \
+    TOR_TRACE_LOG_DEBUG(subsystem, event_name);             \
-    TOR_TRACE_USDT(tor_ ## subsystem, event_name, ## __VA_ARGS__);  \
+    TOR_TRACE_USDT(subsystem, event_name, ## __VA_ARGS__);  \
-    TOR_TRACE_LTTNG(tor_ ## subsystem, event_name, ## __VA_ARGS__); \
+    TOR_TRACE_LTTNG(subsystem, event_name, ## __VA_ARGS__); \
   } while (0)
 
 /* This corresponds to the --enable-tracing-instrumentation-log-debug