liblttng-ust/lttng-getcpu.c

   1 /*
   2  * Copyright (C) 2014  Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; version 2.1 of
   7  * the License.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public
  15  * License along with this library; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
  17  */
  18
  19 #define _GNU_SOURCE
  20 #include <error.h>
  21 #include <dlfcn.h>
  22 #include <stdlib.h>
  23 #include <usterr-signal-safe.h>
  24 #include <lttng/ust-getcpu.h>
  25 #include <urcu/system.h>
  26 #include <urcu/arch.h>
  27
  28 #include "getenv.h"
  29 #include "../libringbuffer/getcpu.h"
  30
  31 int (*lttng_get_cpu)(void);
  32
  33 static
  34 void *getcpu_handle;
  35
  36 int lttng_ust_getcpu_override(int (*getcpu)(void))
  37 {
  38         CMM_STORE_SHARED(lttng_get_cpu, getcpu);
  39         return 0;
  40 }
  41
  42 void lttng_ust_getcpu_init(void)
  43 {
  44         const char *libname;
  45         void (*libinit)(void);
  46
  47         if (getcpu_handle)
  48                 return;
  49         libname = lttng_secure_getenv("LTTNG_UST_GETCPU_PLUGIN");
  50         if (!libname)
  51                 return;
  52         getcpu_handle = dlopen(libname, RTLD_NOW);
  53         if (!getcpu_handle) {
  54                 PERROR("Cannot load LTTng UST getcpu override library %s",
  55                         libname);
  56                 return;
  57         }
  58         dlerror();
  59         libinit = (void (*)(void)) dlsym(getcpu_handle,
  60                 "lttng_ust_getcpu_plugin_init");
  61         if (!libinit) {
  62                 PERROR("Cannot find LTTng UST getcpu override library %s initialization function lttng_ust_getcpu_plugin_init()",
  63                         libname);
  64                 return;
  65         }
  66         libinit();
  67 }