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 #include "lttng-tracer-core.h"
  31 #include "jhash.h"
  32 #include <helper.h>
  33
  34 #define CONTEXT_PROVIDER_HT_BITS        12
  35 #define CONTEXT_PROVIDER_HT_SIZE        (1U << CONTEXT_PROVIDER_HT_BITS)
  36 struct context_provider_ht {
  37         struct cds_hlist_head table[CONTEXT_PROVIDER_HT_SIZE];
  38 };
  39
  40 static struct context_provider_ht context_provider_ht;
  41
  42 static struct lttng_ust_context_provider *
  43                 lookup_provider_by_name(const char *name)
  44 {
  45         struct cds_hlist_head *head;
  46         struct cds_hlist_node *node;
  47         struct lttng_ust_context_provider *provider;
  48         uint32_t hash;
  49         const char *end;
  50         size_t len;
  51
  52         /* Lookup using everything before first ':' as key. */
  53         end = strchr(name, ':');
  54         if (end)
  55                 len = end - name;
  56         else
  57                 len = strlen(name);
  58         hash = jhash(name, len, 0);
  59         head = &context_provider_ht.table[hash & (CONTEXT_PROVIDER_HT_SIZE - 1)];
  60         cds_hlist_for_each_entry(provider, node, head, node) {
  61                 if (!strncmp(provider->name, name, len))
  62                         return provider;
  63         }
  64         return NULL;
  65 }
  66
  67 int lttng_ust_context_provider_register(struct lttng_ust_context_provider *provider)
  68 {
  69         struct cds_hlist_head *head;
  70         size_t name_len = strlen(provider->name);
  71         uint32_t hash;
  72         int ret = 0;
  73
  74         lttng_ust_fixup_tls();
  75
  76         /* Provider name starts with "$app.". */
  77         if (strncmp("$app.", provider->name, strlen("$app.")) != 0)
  78                 return -EINVAL;
  79         /* Provider name cannot contain a colon character. */
  80         if (strchr(provider->name, ':'))
  81                 return -EINVAL;
  82         if (ust_lock()) {
  83                 ret = -EBUSY;
  84                 goto end;
  85         }
  86         if (lookup_provider_by_name(provider->name)) {
  87                 ret = -EBUSY;
  88                 goto end;
  89         }
  90         hash = jhash(provider->name, name_len, 0);
  91         head = &context_provider_ht.table[hash & (CONTEXT_PROVIDER_HT_SIZE - 1)];
  92         cds_hlist_add_head(&provider->node, head);
  93         lttng_ust_context_set_session_provider(provider->name,
  94                 provider->get_size, provider->record,
  95                 provider->get_value);
  96 end:
  97         ust_unlock();
  98         return ret;
  99 }
 100
 101 void lttng_ust_context_provider_unregister(struct lttng_ust_context_provider *provider)
 102 {
 103         lttng_ust_fixup_tls();
 104
 105         if (ust_lock())
 106                 goto end;
 107         lttng_ust_context_set_session_provider(provider->name,
 108                 lttng_ust_dummy_get_size, lttng_ust_dummy_record,
 109                 lttng_ust_dummy_get_value);
 110         cds_hlist_del(&provider->node);
 111 end:
 112         ust_unlock();
 113 }
 114
 115 /*
 116  * Called with ust mutex held.
 117  * Add application context to array of context, even if the application
 118  * context is not currently loaded by application. It will then use the
 119  * dummy callbacks in that case.
 120  * Always performed before tracing is started, since it modifies
 121  * metadata describing the context.
 122  */
 123 int lttng_ust_add_app_context_to_ctx_rcu(const char *name,
 124                 struct lttng_ctx **ctx)
 125 {
 126         struct lttng_ust_context_provider *provider;
 127         struct lttng_ctx_field new_field;
 128         int ret;
 129
 130         if (*ctx && lttng_find_context(*ctx, name))
 131                 return -EEXIST;
 132         /*
 133          * For application context, add it by expanding
 134          * ctx array.
 135          */
 136         memset(&new_field, 0, sizeof(new_field));
 137         new_field.field_name = strdup(name);
 138         if (!new_field.field_name)
 139                 return -ENOMEM;
 140         new_field.event_field.name = new_field.field_name;
 141         new_field.event_field.type.atype = atype_dynamic;
 142         /*
 143          * If provider is not found, we add the context anyway, but
 144          * it will provide a dummy context.
 145          */
 146         provider = lookup_provider_by_name(name);
 147         if (provider) {
 148                 new_field.get_size = provider->get_size;
 149                 new_field.record = provider->record;
 150                 new_field.get_value = provider->get_value;
 151         } else {
 152                 new_field.get_size = lttng_ust_dummy_get_size;
 153                 new_field.record = lttng_ust_dummy_record;
 154                 new_field.get_value = lttng_ust_dummy_get_value;
 155         }
 156         ret = lttng_context_add_rcu(ctx, &new_field);
 157         if (ret) {
 158                 free(new_field.field_name);
 159                 return ret;
 160         }
 161         return 0;
 162 }