liblttng-ust/lttng-context-provider.c

   1 /*
   2  * lttng-context-provider.c
   3  *
   4  * LTTng UST application context provider.
   5  *
   6  * Copyright (C) 2016 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; only
  11  * version 2.1 of the License.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #define _LGPL_SOURCE
  24 #include <stddef.h>
  25 #include <stdint.h>
  26 #include <sys/types.h>
  27 #include <unistd.h>
  28
  29 #include <lttng/ust-context-provider.h>
  30
  31 #include "lttng-tracer-core.h"
  32 #include "jhash.h"
  33 #include "context-provider-internal.h"
  34 #include <helper.h>
  35
  36 #define CONTEXT_PROVIDER_HT_BITS        12
  37 #define CONTEXT_PROVIDER_HT_SIZE        (1U << CONTEXT_PROVIDER_HT_BITS)
  38 struct context_provider_ht {
  39         struct cds_hlist_head table[CONTEXT_PROVIDER_HT_SIZE];
  40 };
  41
  42 static struct context_provider_ht context_provider_ht;
  43
  44 static struct lttng_ust_context_provider *
  45                 lookup_provider_by_name(const char *name)
  46 {
  47         struct cds_hlist_head *head;
  48         struct cds_hlist_node *node;
  49         struct lttng_ust_context_provider *provider;
  50         uint32_t hash;
  51         const char *end;
  52         size_t len;
  53
  54         /* Lookup using everything before first ':' as key. */
  55         end = strchr(name, ':');
  56         if (end)
  57                 len = end - name;
  58         else
  59                 len = strlen(name);
  60         hash = jhash(name, len, 0);
  61         head = &context_provider_ht.table[hash & (CONTEXT_PROVIDER_HT_SIZE - 1)];
  62         cds_hlist_for_each_entry(provider, node, head, node) {
  63                 if (!strncmp(provider->name, name, len))
  64                         return provider;
  65         }
  66         return NULL;
  67 }
  68
  69 int lttng_ust_context_provider_register(struct lttng_ust_context_provider *provider)
  70 {
  71         struct cds_hlist_head *head;
  72         size_t name_len = strlen(provider->name);
  73         uint32_t hash;
  74         int ret = 0;
  75
  76         lttng_ust_fixup_tls();
  77
  78         /* Provider name starts with "$app.". */
  79         if (strncmp("$app.", provider->name, strlen("$app.")) != 0)
  80                 return -EINVAL;
  81         /* Provider name cannot contain a colon character. */
  82         if (strchr(provider->name, ':'))
  83                 return -EINVAL;
  84         if (ust_lock()) {
  85                 ret = -EBUSY;
  86                 goto end;
  87         }
  88         if (lookup_provider_by_name(provider->name)) {
  89                 ret = -EBUSY;
  90                 goto end;
  91         }
  92         hash = jhash(provider->name, name_len, 0);
  93         head = &context_provider_ht.table[hash & (CONTEXT_PROVIDER_HT_SIZE - 1)];
  94         cds_hlist_add_head(&provider->node, head);
  95
  96         lttng_ust_context_set_session_provider(provider->name,
  97                 provider->get_size, provider->record,
  98                 provider->get_value);
  99
 100         lttng_ust_context_set_event_notifier_group_provider(provider->name,
 101                 provider->get_size, provider->record,
 102                 provider->get_value);
 103 end:
 104         ust_unlock();
 105         return ret;
 106 }
 107
 108 void lttng_ust_context_provider_unregister(struct lttng_ust_context_provider *provider)
 109 {
 110         lttng_ust_fixup_tls();
 111
 112         if (ust_lock())
 113                 goto end;
 114         lttng_ust_context_set_session_provider(provider->name,
 115                 lttng_ust_dummy_get_size, lttng_ust_dummy_record,
 116                 lttng_ust_dummy_get_value);
 117
 118         lttng_ust_context_set_event_notifier_group_provider(provider->name,
 119                 lttng_ust_dummy_get_size, lttng_ust_dummy_record,
 120                 lttng_ust_dummy_get_value);
 121
 122         cds_hlist_del(&provider->node);
 123 end:
 124         ust_unlock();
 125 }
 126
 127 /*
 128  * Called with ust mutex held.
 129  * Add application context to array of context, even if the application
 130  * context is not currently loaded by application. It will then use the
 131  * dummy callbacks in that case.
 132  * Always performed before tracing is started, since it modifies
 133  * metadata describing the context.
 134  */
 135 int lttng_ust_add_app_context_to_ctx_rcu(const char *name,
 136                 struct lttng_ctx **ctx)
 137 {
 138         struct lttng_ust_context_provider *provider;
 139         struct lttng_ctx_field new_field;
 140         int ret;
 141
 142         if (*ctx && lttng_find_context(*ctx, name))
 143                 return -EEXIST;
 144         /*
 145          * For application context, add it by expanding
 146          * ctx array.
 147          */
 148         memset(&new_field, 0, sizeof(new_field));
 149         new_field.field_name = strdup(name);
 150         if (!new_field.field_name)
 151                 return -ENOMEM;
 152         new_field.event_field.name = new_field.field_name;
 153         new_field.event_field.type.atype = atype_dynamic;
 154         /*
 155          * If provider is not found, we add the context anyway, but
 156          * it will provide a dummy context.
 157          */
 158         provider = lookup_provider_by_name(name);
 159         if (provider) {
 160                 new_field.get_size = provider->get_size;
 161                 new_field.record = provider->record;
 162                 new_field.get_value = provider->get_value;
 163         } else {
 164                 new_field.get_size = lttng_ust_dummy_get_size;
 165                 new_field.record = lttng_ust_dummy_record;
 166                 new_field.get_value = lttng_ust_dummy_get_value;
 167         }
 168         ret = lttng_context_add_rcu(ctx, &new_field);
 169         if (ret) {
 170                 free(new_field.field_name);
 171                 return ret;
 172         }
 173         return 0;
 174 }