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 <ust-context-provider.h>
  16
  17 #include "context-internal.h"
  18 #include "lttng-tracer-core.h"
  19 #include "jhash.h"
  20 #include "context-provider-internal.h"
  21 #include <ust-helper.h>
  22
  23 #define CONTEXT_PROVIDER_HT_BITS        12
  24 #define CONTEXT_PROVIDER_HT_SIZE        (1U << CONTEXT_PROVIDER_HT_BITS)
  25 struct context_provider_ht {
  26         struct cds_hlist_head table[CONTEXT_PROVIDER_HT_SIZE];
  27 };
  28
  29 static struct context_provider_ht context_provider_ht;
  30
  31 static struct lttng_ust_context_provider *
  32                 lookup_provider_by_name(const char *name)
  33 {
  34         struct cds_hlist_head *head;
  35         struct cds_hlist_node *node;
  36         struct lttng_ust_context_provider *provider;
  37         uint32_t hash;
  38         const char *end;
  39         size_t len;
  40
  41         /* Lookup using everything before first ':' as key. */
  42         end = strchr(name, ':');
  43         if (end)
  44                 len = end - name;
  45         else
  46                 len = strlen(name);
  47         hash = jhash(name, len, 0);
  48         head = &context_provider_ht.table[hash & (CONTEXT_PROVIDER_HT_SIZE - 1)];
  49         cds_hlist_for_each_entry(provider, node, head, node) {
  50                 if (!strncmp(provider->name, name, len))
  51                         return provider;
  52         }
  53         return NULL;
  54 }
  55
  56 int lttng_ust_context_provider_register(struct lttng_ust_context_provider *provider)
  57 {
  58         struct cds_hlist_head *head;
  59         size_t name_len = strlen(provider->name);
  60         uint32_t hash;
  61         int ret = 0;
  62
  63         lttng_ust_fixup_tls();
  64
  65         /* Provider name starts with "$app.". */
  66         if (strncmp("$app.", provider->name, strlen("$app.")) != 0)
  67                 return -EINVAL;
  68         /* Provider name cannot contain a colon character. */
  69         if (strchr(provider->name, ':'))
  70                 return -EINVAL;
  71         if (ust_lock()) {
  72                 ret = -EBUSY;
  73                 goto end;
  74         }
  75         if (lookup_provider_by_name(provider->name)) {
  76                 ret = -EBUSY;
  77                 goto end;
  78         }
  79         hash = jhash(provider->name, name_len, 0);
  80         head = &context_provider_ht.table[hash & (CONTEXT_PROVIDER_HT_SIZE - 1)];
  81         cds_hlist_add_head(&provider->node, head);
  82
  83         lttng_ust_context_set_session_provider(provider->name,
  84                 provider->get_size, provider->record,
  85                 provider->get_value);
  86
  87         lttng_ust_context_set_event_notifier_group_provider(provider->name,
  88                 provider->get_size, provider->record,
  89                 provider->get_value);
  90 end:
  91         ust_unlock();
  92         return ret;
  93 }
  94
  95 void lttng_ust_context_provider_unregister(struct lttng_ust_context_provider *provider)
  96 {
  97         lttng_ust_fixup_tls();
  98
  99         if (ust_lock())
 100                 goto end;
 101         lttng_ust_context_set_session_provider(provider->name,
 102                 lttng_ust_dummy_get_size, lttng_ust_dummy_record,
 103                 lttng_ust_dummy_get_value);
 104
 105         lttng_ust_context_set_event_notifier_group_provider(provider->name,
 106                 lttng_ust_dummy_get_size, lttng_ust_dummy_record,
 107                 lttng_ust_dummy_get_value);
 108
 109         cds_hlist_del(&provider->node);
 110 end:
 111         ust_unlock();
 112 }
 113
 114 /*
 115  * Called with ust mutex held.
 116  * Add application context to array of context, even if the application
 117  * context is not currently loaded by application. It will then use the
 118  * dummy callbacks in that case.
 119  * Always performed before tracing is started, since it modifies
 120  * metadata describing the context.
 121  */
 122 int lttng_ust_add_app_context_to_ctx_rcu(const char *name,
 123                 struct lttng_ust_ctx **ctx)
 124 {
 125         struct lttng_ust_context_provider *provider;
 126         struct lttng_ust_ctx_field *new_field = NULL;
 127         int ret;
 128
 129         if (*ctx && lttng_find_context(*ctx, name))
 130                 return -EEXIST;
 131         new_field = zmalloc(sizeof(struct lttng_ust_ctx_field));
 132         if (!new_field) {
 133                 ret = -ENOMEM;
 134                 goto error_field_alloc;
 135         }
 136         new_field->struct_size = sizeof(struct lttng_ust_ctx_field);
 137         new_field->event_field = zmalloc(sizeof(struct lttng_ust_event_field));
 138         if (!new_field->event_field) {
 139                 ret = -ENOMEM;
 140                 goto error_event_field_alloc;
 141         }
 142         new_field->event_field->name = strdup(name);
 143         if (!new_field->event_field->name) {
 144                 ret = -ENOMEM;
 145                 goto error_field_name_alloc;
 146         }
 147         new_field->event_field->type = zmalloc(sizeof(struct lttng_ust_type_common));
 148         if (!new_field->event_field->type) {
 149                 ret = -ENOMEM;
 150                 goto error_field_type_alloc;
 151         }
 152         new_field->event_field->type->type = lttng_ust_type_dynamic;
 153         /*
 154          * If provider is not found, we add the context anyway, but
 155          * it will provide a dummy context.
 156          */
 157         provider = lookup_provider_by_name(name);
 158         if (provider) {
 159                 new_field->get_size = provider->get_size;
 160                 new_field->record = provider->record;
 161                 new_field->get_value = provider->get_value;
 162         } else {
 163                 new_field->get_size = lttng_ust_dummy_get_size;
 164                 new_field->record = lttng_ust_dummy_record;
 165                 new_field->get_value = lttng_ust_dummy_get_value;
 166         }
 167         /*
 168          * For application context, add it by expanding
 169          * ctx array. Ownership of new_field is passed to the callee on
 170          * success.
 171          */
 172         ret = lttng_context_add_rcu(ctx, new_field);
 173         if (ret) {
 174                 free(new_field->event_field->type);
 175                 free((char *) new_field->event_field->name);
 176                 free(new_field->event_field);
 177                 free(new_field);
 178                 return ret;
 179         }
 180         return 0;
 181
 182 error_field_type_alloc:
 183         free((char *) new_field->event_field->name);
 184 error_field_name_alloc:
 185         free(new_field->event_field);
 186 error_event_field_alloc:
 187         free(new_field);
 188 error_field_alloc:
 189         return ret;
 190 }