liblttng-ust/lttng-context-provider.c

   1 /*
   2  * SPDX-License-Identifier: LGPL-2.1-only
   3  *
   4  * Copyright (C) 2016 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * LTTng UST application context provider.
   7  */
   8
   9 #define _LGPL_SOURCE
  10 #include <stddef.h>
  11 #include <stdint.h>
  12 #include <sys/types.h>
  13 #include <unistd.h>
  14
  15 #include <lttng/ust-context-provider.h>
  16
  17 #include "lttng-tracer-core.h"
  18 #include "jhash.h"
  19 #include "context-provider-internal.h"
  20 #include <helper.h>
  21
  22 #define CONTEXT_PROVIDER_HT_BITS        12
  23 #define CONTEXT_PROVIDER_HT_SIZE        (1U << CONTEXT_PROVIDER_HT_BITS)
  24 struct context_provider_ht {
  25         struct cds_hlist_head table[CONTEXT_PROVIDER_HT_SIZE];
  26 };
  27
  28 static struct context_provider_ht context_provider_ht;
  29
  30 static struct lttng_ust_context_provider *
  31                 lookup_provider_by_name(const char *name)
  32 {
  33         struct cds_hlist_head *head;
  34         struct cds_hlist_node *node;
  35         struct lttng_ust_context_provider *provider;
  36         uint32_t hash;
  37         const char *end;
  38         size_t len;
  39
  40         /* Lookup using everything before first ':' as key. */
  41         end = strchr(name, ':');
  42         if (end)
  43                 len = end - name;
  44         else
  45                 len = strlen(name);
  46         hash = jhash(name, len, 0);
  47         head = &context_provider_ht.table[hash & (CONTEXT_PROVIDER_HT_SIZE - 1)];
  48         cds_hlist_for_each_entry(provider, node, head, node) {
  49                 if (!strncmp(provider->name, name, len))
  50                         return provider;
  51         }
  52         return NULL;
  53 }
  54
  55 int lttng_ust_context_provider_register(struct lttng_ust_context_provider *provider)
  56 {
  57         struct cds_hlist_head *head;
  58         size_t name_len = strlen(provider->name);
  59         uint32_t hash;
  60         int ret = 0;
  61
  62         lttng_ust_fixup_tls();
  63
  64         /* Provider name starts with "$app.". */
  65         if (strncmp("$app.", provider->name, strlen("$app.")) != 0)
  66                 return -EINVAL;
  67         /* Provider name cannot contain a colon character. */
  68         if (strchr(provider->name, ':'))
  69                 return -EINVAL;
  70         if (ust_lock()) {
  71                 ret = -EBUSY;
  72                 goto end;
  73         }
  74         if (lookup_provider_by_name(provider->name)) {
  75                 ret = -EBUSY;
  76                 goto end;
  77         }
  78         hash = jhash(provider->name, name_len, 0);
  79         head = &context_provider_ht.table[hash & (CONTEXT_PROVIDER_HT_SIZE - 1)];
  80         cds_hlist_add_head(&provider->node, head);
  81
  82         lttng_ust_context_set_session_provider(provider->name,
  83                 provider->get_size, provider->record,
  84                 provider->get_value);
  85
  86         lttng_ust_context_set_event_notifier_group_provider(provider->name,
  87                 provider->get_size, provider->record,
  88                 provider->get_value);
  89 end:
  90         ust_unlock();
  91         return ret;
  92 }
  93
  94 void lttng_ust_context_provider_unregister(struct lttng_ust_context_provider *provider)
  95 {
  96         lttng_ust_fixup_tls();
  97
  98         if (ust_lock())
  99                 goto end;
 100         lttng_ust_context_set_session_provider(provider->name,
 101                 lttng_ust_dummy_get_size, lttng_ust_dummy_record,
 102                 lttng_ust_dummy_get_value);
 103
 104         lttng_ust_context_set_event_notifier_group_provider(provider->name,
 105                 lttng_ust_dummy_get_size, lttng_ust_dummy_record,
 106                 lttng_ust_dummy_get_value);
 107
 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 }