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