New testpoint mechanism to instrument binaries for testing

[lttng-tools.git] / src / common / testpoint / testpoint.c

diff --git a/src/common/testpoint/testpoint.c b/src/common/testpoint/testpoint.c
new file mode 100644 (file)
index 0000000..6893a41
--- /dev/null
+++ b/src/common/testpoint/testpoint.c
@@ -0,0 +1,62 @@
+/*
+ * Copyright (C) 2012 - Christian Babeux <christian.babeux@efficios.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2 only,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef NTESTPOINT
+
+#define _GNU_SOURCE /* for RTLD_DEFAULT GNU extension */
+#include <dlfcn.h>  /* for dlsym   */
+#include <stdlib.h> /* for getenv  */
+#include <string.h> /* for strncmp */
+
+#include "testpoint.h"
+
+/* Environment variable used to enable the testpoints facilities. */
+static const char *lttng_testpoint_env_var = "LTTNG_TESTPOINT_ENABLE";
+
+/* Testpoint toggle flag */
+int lttng_testpoint_activated;
+
+/*
+ * Toggle the support for testpoints on the application startup.
+ */
+static void __attribute__((constructor)) lttng_testpoint_check(void)
+{
+       char *testpoint_env_val = NULL;
+
+       testpoint_env_val = getenv(lttng_testpoint_env_var);
+       if (testpoint_env_val != NULL
+                       && (strncmp(testpoint_env_val, "1", 1) == 0)) {
+               lttng_testpoint_activated = 1;
+       }
+}
+
+/*
+ * Lookup a symbol by name.
+ *
+ * Return the address where the symbol is loaded or NULL if the symbol was not
+ * found.
+ */
+void *lttng_testpoint_lookup(const char *name)
+{
+       if (!name) {
+               return NULL;
+       }
+
+       return dlsym(RTLD_DEFAULT, name);
+}
+
+#endif /* NTESTPOINT */