From 433005c87c88912358bfd02d4b0d997b52b04013 Mon Sep 17 00:00:00 2001
From: Harald Welte <laforge@osmocom.org>
Date: Sat, 26 Sep 2020 11:51:32 +0200
Subject: initial support for static userspace probes via systemtap

This adds a --enable-systemtap configure option, which will then
add static tracepoints to the generated libosmocore binary.

At this point, only two tracepoints are supported: log_start
and log_done.  They can be used to trace the amount of time
a libosmocore-using application spends in potentiall blocking calls to
log to stderr or to files.

Related: OS#4311
Change-Id: I7e1ab664241deb524c9582cbd1bec31af46c747e
---
 src/Makefile.am | 12 ++++++++++++
 src/logging.c   | 13 +++++++++++++
 src/probes.d    |  4 ++++
 3 files changed, 29 insertions(+)
 create mode 100644 src/probes.d

(limited to 'src')

diff --git a/src/Makefile.am b/src/Makefile.am
index dd31db88..a2566a33 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -29,6 +29,7 @@ libosmocore_la_SOURCES = context.c timer.c timer_gettimeofday.c timer_clockgetti
 			 use_count.c \
 			 exec.c \
 			 it_q.c \
+			 probes.d \
 			 $(NULL)
 
 if HAVE_SSSE3
@@ -82,5 +83,16 @@ libosmocore_la_SOURCES += mnl.c
 libosmocore_la_LIBADD += $(LIBMNL_LIBS)
 endif
 
+if ENABLE_SYSTEMTAP
+probes.h: probes.d
+	$(DTRACE) -C -h -s $< -o $@
+
+probes.lo: probes.d
+	$(LIBTOOL) --mode=compile $(AM_V_lt) --tag=CC env CFLAGS="$(CFLAGS)" $(DTRACE) -C -G -s $< -o $@
+
+BUILT_SOURCES += probes.h probes.lo
+libosmocore_la_LIBADD += probes.lo
+endif
+
 crc%gen.c: crcXXgen.c.tpl
 	$(AM_V_GEN)sed -e's/XX/$*/g' $< > $@
diff --git a/src/logging.c b/src/logging.c
index 60dba64c..a40008e9 100644
--- a/src/logging.c
+++ b/src/logging.c
@@ -44,6 +44,17 @@
 #include <syslog.h>
 #endif
 
+#ifdef HAVE_SYSTEMTAP
+/* include the generated probes header and put markers in code */
+#include "probes.h"
+#define TRACE(probe) probe
+#define TRACE_ENABLED(probe) probe ## _ENABLED()
+#else
+/* Wrap the probe to allow it to be removed when no systemtap available */
+#define TRACE(probe)
+#define TRACE_ENABLED(probe) (0)
+#endif /* HAVE_SYSTEMTAP */
+
 #include <time.h>
 #include <sys/time.h>
 #include <errno.h>
@@ -670,9 +681,11 @@ void logp2(int subsys, unsigned int level, const char *file, int line, int cont,
 {
 	va_list ap;
 
+	TRACE(LIBOSMOCORE_LOG_START());
 	va_start(ap, format);
 	osmo_vlogp(subsys, level, file, line, cont, format, ap);
 	va_end(ap);
+	TRACE(LIBOSMOCORE_LOG_DONE());
 }
 
 /*! Register a new log target with the logging core
diff --git a/src/probes.d b/src/probes.d
new file mode 100644
index 00000000..c16eb1ee
--- /dev/null
+++ b/src/probes.d
@@ -0,0 +1,4 @@
+provider libosmocore {
+	probe log_start();
+	probe log_done();
+};
-- 
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