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

Makefile.am

@@ -1,7 +1,7 @@
 ACLOCAL_AMFLAGS = -I m4
 
 AM_CPPFLAGS = $(all_includes) -I$(top_srcdir)/include
-SUBDIRS = include src src/vty src/codec src/gsm src/coding src/gb src/ctrl src/sim src/pseudotalloc src/usb utils tests
+SUBDIRS = include src src/vty src/codec src/gsm src/coding src/gb src/ctrl src/sim src/pseudotalloc src/usb utils tapset tests
 
 pkgconfigdir = $(libdir)/pkgconfig
 pkgconfig_DATA = libosmocore.pc libosmocodec.pc libosmovty.pc libosmogsm.pc \

configure.ac

@@ -433,6 +433,38 @@ AC_MSG_CHECKING([whether to enable ARM NEON instructions support])
 AC_MSG_RESULT([$neon])
 AM_CONDITIONAL(HAVE_NEON, [test "x$neon" != "xno"])
 
+#
+# SystemTap support
+#
+AC_MSG_CHECKING([whether to include systemtap tracing support])
+AC_ARG_ENABLE([systemtap],
+	      [AS_HELP_STRING([--enable-systemtap],
+			      [Enable inclusion of systemtap trace support])],
+	      [ENABLE_SYSTEMTAP="${enableval}"], [ENABLE_SYSTEMTAP='no'])
+AM_CONDITIONAL([ENABLE_SYSTEMTAP], [test x$ENABLE_SYSTEMTAP = xyes])
+AC_MSG_RESULT(${ENABLE_SYSTEMTAP})
+
+if test "x${ENABLE_SYSTEMTAP}" = xyes; then
+  # Additional configuration for --enable-systemtap is HERE
+  AC_CHECK_PROGS(DTRACE, dtrace)
+  if test -z "$DTRACE"; then
+    AC_MSG_ERROR([dtrace not found])
+  fi
+  AC_CHECK_HEADER([sys/sdt.h], [SDT_H_FOUND='yes'],
+                [SDT_H_FOUND='no';
+                   AC_MSG_ERROR([systemtap support needs sys/sdt.h header])])
+  AC_DEFINE([HAVE_SYSTEMTAP], [1], [Define to 1 if using SystemTap probes.])
+  AC_ARG_WITH([tapset-install-dir],
+	      [AS_HELP_STRING([--with-tapset-install-dir],
+	         [The absolute path where the tapset dir will be installed])],
+	      [if test "x${withval}" = x; then
+		 ABS_TAPSET_DIR="\$(datadir)/systemtap/tapset"
+	       else
+		 ABS_TAPSET_DIR="${withval}"
+	       fi], [ABS_TAPSET_DIR="\$(datadir)/systemtap/tapset"])
+  AC_SUBST(ABS_TAPSET_DIR)
+fi
+
 
 OSMO_AC_CODE_COVERAGE
 
@@ -487,6 +519,7 @@ AC_OUTPUT(
 	src/gb/Makefile
 	src/ctrl/Makefile
 	src/pseudotalloc/Makefile
+	tapset/Makefile
 	tests/Makefile
 	tests/atlocal
 	utils/Makefile

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' $< > $@

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

src/probes.d

@@ -0,0 +1,4 @@
+provider libosmocore {
+	probe log_start();
+	probe log_done();
+};

tapset/Makefile.am

@@ -0,0 +1,22 @@
+.PHONY: clean-local install-data-hook uninstall-local
+
+EXTRA_DIST = libosmocore.stp
+TAPSET_FILES = $(EXTRA_DIST)
+TAPSET_INSTALL_DIR = $(DESTDIR)@ABS_TAPSET_DIR@
+
+if ENABLE_SYSTEMTAP
+all-local: $(TAPSET_FILES)
+
+clean-local:
+
+install-data-hook:
+	$(MKDIR_P) $(TAPSET_INSTALL_DIR)
+	$(INSTALL_DATA) $(TAPSET_FILES) $(TAPSET_INSTALL_DIR)
+
+uninstall-local:
+	@list='$(TAPSET_FILES)'; for p in $$list; do \
+	  echo " rm -f '$(TAPSET_INSTALL_DIR)/$$p'"; \
+	  rm -f "$(TAPSET_INSTALL_DIR)/$$p"; \
+	done
+
+endif

tapset/libosmocore.stp

@@ -0,0 +1,18 @@
+/* libosmocore tapset
+ *
+ * This file is part of libosmocore.
+ *
+ * Each probe defines the probe name and a full probestr which consist of the probe name and between
+ * brackets all argument names and values.
+ */
+
+probe libosmocore_log_start = process("libosmocore").mark("log_start")
+{
+ count = $arg1;
+ probestr = sprintf("%s(count=%d), $$name, count);
+}
+
+probe libosmocore_log_done = process("libosmocore").mark("log_done")
+{
+ probestr = sprintf("%s", $$name);
+}