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 <sys/types.h>
  26 #include <unistd.h>
  27 #include <lttng/ust-context-provider.h>
  28 #include "lttng-tracer-core.h"
  29 #include "jhash.h"
  30 #include <helper.h>
  31
  32 #define CONTEXT_PROVIDER_HT_BITS        12
  33 #define CONTEXT_PROVIDER_HT_SIZE        (1U << CONTEXT_PROVIDER_HT_BITS)
  34 struct context_provider_ht {
  35         struct cds_hlist_head table[CONTEXT_PROVIDER_HT_SIZE];
  36 };
  37
  38 static struct context_provider_ht context_provider_ht;
  39
  40 static struct lttng_ust_context_provider *
  41                 lookup_provider_by_name(const char *name)
  42 {
  43         struct cds_hlist_head *head;
  44         struct cds_hlist_node *node;
  45         struct lttng_ust_context_provider *provider;
  46         uint32_t hash;
  47         const char *end;
  48         size_t len;
  49
  50         /* Lookup using everything before first ':' as key. */
  51         end = strchr(name, ':');
  52         if (end)
  53                 len = end - name;
  54         else
  55                 len = strlen(name);
  56         hash = jhash(name, len, 0);
  57         head = &context_provider_ht.table[hash & (CONTEXT_PROVIDER_HT_SIZE - 1)];
  58         cds_hlist_for_each_entry(provider, node, head, node) {
  59                 if (!strncmp(provider->name, name, len))
  60                         return provider;
  61         }
  62         return NULL;
  63 }
  64
  65 int lttng_ust_context_provider_register(struct lttng_ust_context_provider *provider)
  66 {
  67         struct cds_hlist_head *head;
  68         size_t name_len = strlen(provider->name);
  69         uint32_t hash;
  70         int ret = 0;
  71
  72         lttng_ust_fixup_tls();
  73
  74         /* Provider name starts with "$app.". */
  75         if (strncmp("$app.", provider->name, strlen("$app.")) != 0)
  76                 return -EINVAL;
  77         /* Provider name cannot contain a colon character. */
  78         if (strchr(provider->name, ':'))
  79                 return -EINVAL;
  80         if (ust_lock()) {
  81                 ret = -EBUSY;
  82                 goto end;
  83         }
  84         if (lookup_provider_by_name(provider->name)) {
  85                 ret = -EBUSY;
  86                 goto end;
  87         }
  88         hash = jhash(provider->name, name_len, 0);
  89         head = &context_provider_ht.table[hash & (CONTEXT_PROVIDER_HT_SIZE - 1)];
  90         cds_hlist_add_head(&provider->node, head);
  91         lttng_ust_context_set_session_provider(provider->name,
  92                 provider->get_size, provider->record,
  93                 provider->get_value);
  94 end:
  95         ust_unlock();
  96         return ret;
  97 }
  98
  99 void lttng_ust_context_provider_unregister(struct lttng_ust_context_provider *provider)
 100 {
 101         lttng_ust_fixup_tls();
 102
 103         if (ust_lock())
 104                 goto end;
 105         lttng_ust_context_set_session_provider(provider->name,
 106                 lttng_ust_dummy_get_size, lttng_ust_dummy_record,
 107                 lttng_ust_dummy_get_value);
 108         cds_hlist_del(&provider->node);
 109 end:
 110         ust_unlock();
 111 }
 112
 113 /*
 114  * Called with ust mutex held.
 115  * Add application context to array of context, even if the application
 116  * context is not currently loaded by application. It will then use the
 117  * dummy callbacks in that case.
 118  * Always performed before tracing is started, since it modifies
 119  * metadata describing the context.
 120  */
 121 int lttng_ust_add_app_context_to_ctx_rcu(const char *name,
 122                 struct lttng_ctx **ctx)
 123 {
 124         struct lttng_ust_context_provider *provider;
 125         struct lttng_ctx_field new_field;
 126         int ret;
 127
 128         if (*ctx && lttng_find_context(*ctx, name))
 129                 return -EEXIST;
 130         /*
 131          * For application context, add it by expanding
 132          * ctx array.
 133          */
 134         memset(&new_field, 0, sizeof(new_field));
 135         new_field.field_name = strdup(name);
 136         if (!new_field.field_name)
 137                 return -ENOMEM;
 138         new_field.event_field.name = new_field.field_name;
 139         new_field.event_field.type.atype = atype_dynamic;
 140         /*
 141          * If provider is not found, we add the context anyway, but
 142          * it will provide a dummy context.
 143          */
 144         provider = lookup_provider_by_name(name);
 145         if (provider) {
 146                 new_field.get_size = provider->get_size;
 147                 new_field.record = provider->record;
 148                 new_field.get_value = provider->get_value;
 149         } else {
 150                 new_field.get_size = lttng_ust_dummy_get_size;
 151                 new_field.record = lttng_ust_dummy_record;
 152                 new_field.get_value = lttng_ust_dummy_get_value;
 153         }
 154         ret = lttng_context_add_rcu(ctx, &new_field);
 155         if (ret) {
 156                 free(new_field.field_name);
 157                 return ret;
 158         }
 159         return 0;
 160 }