liblttng-ust/lttng-clock.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-clock.h>
  25 #include <urcu/system.h>
  26 #include <urcu/arch.h>
  27
  28 #include "clock.h"
  29 #include "getenv.h"
  30
  31 struct lttng_trace_clock *lttng_trace_clock;
  32
  33 static
  34 struct lttng_trace_clock user_tc;
  35
  36 static
  37 void *clock_handle;
  38
  39 int lttng_ust_trace_clock_set_read64_cb(uint64_t (*read64)(void))
  40 {
  41         if (CMM_LOAD_SHARED(lttng_trace_clock))
  42                 return -EBUSY;
  43         user_tc.read64 = read64;
  44         return 0;
  45 }
  46
  47 int lttng_ust_trace_clock_set_freq_cb(uint64_t (*freq)(void))
  48 {
  49         if (CMM_LOAD_SHARED(lttng_trace_clock))
  50                 return -EBUSY;
  51         user_tc.freq = freq;
  52         return 0;
  53 }
  54
  55 int lttng_ust_trace_clock_set_uuid_cb(int (*uuid)(char *uuid))
  56 {
  57         if (CMM_LOAD_SHARED(lttng_trace_clock))
  58                 return -EBUSY;
  59         user_tc.uuid = uuid;
  60         return 0;
  61 }
  62
  63 int lttng_ust_trace_clock_set_name_cb(const char *(*name)(void))
  64 {
  65         if (CMM_LOAD_SHARED(lttng_trace_clock))
  66                 return -EBUSY;
  67         user_tc.name = name;
  68         return 0;
  69 }
  70
  71 int lttng_ust_trace_clock_set_description_cb(const char *(*description)(void))
  72 {
  73         if (CMM_LOAD_SHARED(lttng_trace_clock))
  74                 return -EBUSY;
  75         user_tc.description = description;
  76         return 0;
  77 }
  78
  79 int lttng_ust_enable_trace_clock_override(void)
  80 {
  81         if (CMM_LOAD_SHARED(lttng_trace_clock))
  82                 return -EBUSY;
  83         if (!user_tc.read64)
  84                 return -EINVAL;
  85         if (!user_tc.freq)
  86                 return -EINVAL;
  87         if (!user_tc.name)
  88                 return -EINVAL;
  89         if (!user_tc.description)
  90                 return -EINVAL;
  91         /* Use default uuid cb when NULL */
  92         cmm_smp_mb();   /* Store callbacks before trace clock */
  93         CMM_STORE_SHARED(lttng_trace_clock, &user_tc);
  94         return 0;
  95 }
  96
  97 void lttng_ust_clock_init(void)
  98 {
  99         const char *libname;
 100         void (*libinit)(void);
 101
 102         if (clock_handle)
 103                 return;
 104         libname = lttng_secure_getenv("LTTNG_UST_CLOCK_PLUGIN");
 105         if (!libname)
 106                 return;
 107         clock_handle = dlopen(libname, RTLD_NOW);
 108         if (!clock_handle) {
 109                 PERROR("Cannot load LTTng UST clock override library %s",
 110                         libname);
 111                 return;
 112         }
 113         dlerror();
 114         libinit = (void (*)(void)) dlsym(clock_handle,
 115                 "lttng_ust_clock_plugin_init");
 116         if (!libinit) {
 117                 PERROR("Cannot find LTTng UST clock override library %s initialization function lttng_ust_clock_plugin_init()",
 118                         libname);
 119                 return;
 120         }
 121         libinit();
 122 }