src/common/testpoint/testpoint.c

   1 /*
   2  * Copyright (C) 2012 - Christian Babeux <christian.babeux@efficios.com>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License, version 2 only,
   6  * as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  11  * more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  16  */
  17
  18 #ifndef NTESTPOINT
  19
  20 #define _GNU_SOURCE /* for RTLD_DEFAULT GNU extension */
  21 #define _LGPL_SOURCE
  22 #include <dlfcn.h>  /* for dlsym   */
  23 #include <stdlib.h> /* for getenv  */
  24 #include <string.h> /* for strncmp */
  25
  26 #include "testpoint.h"
  27
  28 /* Environment variable used to enable the testpoints facilities. */
  29 static const char *lttng_testpoint_env_var = "LTTNG_TESTPOINT_ENABLE";
  30
  31 /* Testpoint toggle flag */
  32 int lttng_testpoint_activated;
  33
  34 /*
  35  * Toggle the support for testpoints on the application startup.
  36  */
  37 static void __attribute__((constructor)) lttng_testpoint_check(void)
  38 {
  39         char *testpoint_env_val = NULL;
  40
  41         testpoint_env_val = getenv(lttng_testpoint_env_var);
  42         if (testpoint_env_val != NULL
  43                         && (strncmp(testpoint_env_val, "1", 1) == 0)) {
  44                 lttng_testpoint_activated = 1;
  45         }
  46 }
  47
  48 /*
  49  * Lookup a symbol by name.
  50  *
  51  * Return the address where the symbol is loaded or NULL if the symbol was not
  52  * found.
  53  */
  54 void *lttng_testpoint_lookup(const char *name)
  55 {
  56         if (!name) {
  57                 return NULL;
  58         }
  59
  60         return dlsym(RTLD_DEFAULT, name);
  61 }
  62
  63 #endif /* NTESTPOINT */