lttng-probes.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-probes.c
   4  *
   5  * Holds LTTng probes registry.
   6  *
   7  * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/list.h>
  12 #include <linux/mutex.h>
  13 #include <linux/seq_file.h>
  14
  15 #include <lttng/events.h>
  16
  17 /*
  18  * probe list is protected by sessions lock.
  19  */
  20 static LIST_HEAD(_probe_list);
  21
  22 /*
  23  * List of probes registered by not yet processed.
  24  */
  25 static LIST_HEAD(lazy_probe_init);
  26
  27 /*
  28  * lazy_nesting counter ensures we don't trigger lazy probe registration
  29  * fixup while we are performing the fixup. It is protected by the
  30  * sessions lock.
  31  */
  32 static int lazy_nesting;
  33
  34 DEFINE_PER_CPU(struct lttng_dynamic_len_stack, lttng_dynamic_len_stack);
  35
  36 EXPORT_PER_CPU_SYMBOL_GPL(lttng_dynamic_len_stack);
  37
  38 /*
  39  * Called under sessions lock.
  40  */
  41 static
  42 int check_event_provider(struct lttng_probe_desc *desc)
  43 {
  44         int i;
  45         size_t provider_name_len;
  46
  47         provider_name_len = strnlen(desc->provider,
  48                                 LTTNG_KERNEL_SYM_NAME_LEN - 1);
  49         for (i = 0; i < desc->nr_events; i++) {
  50                 if (strncmp(desc->event_desc[i]->name,
  51                                 desc->provider,
  52                                 provider_name_len))
  53                         return 0;       /* provider mismatch */
  54                 /*
  55                  * The event needs to contain at least provider name + _ +
  56                  * one or more letter.
  57                  */
  58                 if (strlen(desc->event_desc[i]->name) <= provider_name_len + 1)
  59                         return 0;       /* provider mismatch */
  60                 if (desc->event_desc[i]->name[provider_name_len] != '_')
  61                         return 0;       /* provider mismatch */
  62         }
  63         return 1;
  64 }
  65
  66 /*
  67  * Called under sessions lock.
  68  */
  69 static
  70 void lttng_lazy_probe_register(struct lttng_probe_desc *desc)
  71 {
  72         struct lttng_probe_desc *iter;
  73         struct list_head *probe_list;
  74
  75         /*
  76          * Each provider enforce that every event name begins with the
  77          * provider name. Check this in an assertion for extra
  78          * carefulness. This ensures we cannot have duplicate event
  79          * names across providers.
  80          */
  81         WARN_ON_ONCE(!check_event_provider(desc));
  82
  83         /*
  84          * The provider ensures there are no duplicate event names.
  85          * Duplicated TRACEPOINT_EVENT event names would generate a
  86          * compile-time error due to duplicated symbol names.
  87          */
  88
  89         /*
  90          * We sort the providers by struct lttng_probe_desc pointer
  91          * address.
  92          */
  93         probe_list = &_probe_list;
  94         list_for_each_entry_reverse(iter, probe_list, head) {
  95                 BUG_ON(iter == desc); /* Should never be in the list twice */
  96                 if (iter < desc) {
  97                         /* We belong to the location right after iter. */
  98                         list_add(&desc->head, &iter->head);
  99                         goto desc_added;
 100                 }
 101         }
 102         /* We should be added at the head of the list */
 103         list_add(&desc->head, probe_list);
 104 desc_added:
 105         pr_debug("LTTng: just registered probe %s containing %u events\n",
 106                 desc->provider, desc->nr_events);
 107 }
 108
 109 /*
 110  * Called under sessions lock.
 111  */
 112 static
 113 void fixup_lazy_probes(void)
 114 {
 115         struct lttng_probe_desc *iter, *tmp;
 116         int ret;
 117
 118         lazy_nesting++;
 119         list_for_each_entry_safe(iter, tmp,
 120                         &lazy_probe_init, lazy_init_head) {
 121                 lttng_lazy_probe_register(iter);
 122                 iter->lazy = 0;
 123                 list_del(&iter->lazy_init_head);
 124         }
 125         ret = lttng_fix_pending_events();
 126         WARN_ON_ONCE(ret);
 127         lazy_nesting--;
 128 }
 129
 130 /*
 131  * Called under sessions lock.
 132  */
 133 struct list_head *lttng_get_probe_list_head(void)
 134 {
 135         if (!lazy_nesting && !list_empty(&lazy_probe_init))
 136                 fixup_lazy_probes();
 137         return &_probe_list;
 138 }
 139
 140 static
 141 const struct lttng_probe_desc *find_provider(const char *provider)
 142 {
 143         struct lttng_probe_desc *iter;
 144         struct list_head *probe_list;
 145
 146         probe_list = lttng_get_probe_list_head();
 147         list_for_each_entry(iter, probe_list, head) {
 148                 if (!strcmp(iter->provider, provider))
 149                         return iter;
 150         }
 151         return NULL;
 152 }
 153
 154 int lttng_probe_register(struct lttng_probe_desc *desc)
 155 {
 156         int ret = 0;
 157
 158         lttng_lock_sessions();
 159
 160         /*
 161          * Check if the provider has already been registered.
 162          */
 163         if (find_provider(desc->provider)) {
 164                 ret = -EEXIST;
 165                 goto end;
 166         }
 167         list_add(&desc->lazy_init_head, &lazy_probe_init);
 168         desc->lazy = 1;
 169         pr_debug("LTTng: adding probe %s containing %u events to lazy registration list\n",
 170                 desc->provider, desc->nr_events);
 171         /*
 172          * If there is at least one active session, we need to register
 173          * the probe immediately, since we cannot delay event
 174          * registration because they are needed ASAP.
 175          */
 176         if (lttng_session_active())
 177                 fixup_lazy_probes();
 178 end:
 179         lttng_unlock_sessions();
 180         return ret;
 181 }
 182 EXPORT_SYMBOL_GPL(lttng_probe_register);
 183
 184 void lttng_probe_unregister(struct lttng_probe_desc *desc)
 185 {
 186         lttng_lock_sessions();
 187         if (!desc->lazy)
 188                 list_del(&desc->head);
 189         else
 190                 list_del(&desc->lazy_init_head);
 191         pr_debug("LTTng: just unregistered probe %s\n", desc->provider);
 192         lttng_unlock_sessions();
 193 }
 194 EXPORT_SYMBOL_GPL(lttng_probe_unregister);
 195
 196 /*
 197  * TODO: this is O(nr_probes * nb_events), could be faster.
 198  * Called with sessions lock held.
 199  */
 200 static
 201 const struct lttng_event_desc *find_event(const char *name)
 202 {
 203         struct lttng_probe_desc *probe_desc;
 204         int i;
 205
 206         list_for_each_entry(probe_desc, &_probe_list, head) {
 207                 for (i = 0; i < probe_desc->nr_events; i++) {
 208                         if (!strcmp(probe_desc->event_desc[i]->name, name))
 209                                 return probe_desc->event_desc[i];
 210                         }
 211         }
 212         return NULL;
 213 }
 214
 215 /*
 216  * Called with sessions lock held.
 217  */
 218 const struct lttng_event_desc *lttng_event_get(const char *name)
 219 {
 220         const struct lttng_event_desc *event;
 221         int ret;
 222
 223         event = find_event(name);
 224         if (!event)
 225                 return NULL;
 226         ret = try_module_get(event->owner);
 227         WARN_ON_ONCE(!ret);
 228         return event;
 229 }
 230 EXPORT_SYMBOL_GPL(lttng_event_get);
 231
 232 /*
 233  * Called with sessions lock held.
 234  */
 235 void lttng_event_put(const struct lttng_event_desc *event)
 236 {
 237         module_put(event->owner);
 238 }
 239 EXPORT_SYMBOL_GPL(lttng_event_put);
 240
 241 static
 242 void *tp_list_start(struct seq_file *m, loff_t *pos)
 243 {
 244         struct lttng_probe_desc *probe_desc;
 245         struct list_head *probe_list;
 246         int iter = 0, i;
 247
 248         lttng_lock_sessions();
 249         probe_list = lttng_get_probe_list_head();
 250         list_for_each_entry(probe_desc, probe_list, head) {
 251                 for (i = 0; i < probe_desc->nr_events; i++) {
 252                         if (iter++ >= *pos)
 253                                 return (void *) probe_desc->event_desc[i];
 254                 }
 255         }
 256         /* End of list */
 257         return NULL;
 258 }
 259
 260 static
 261 void *tp_list_next(struct seq_file *m, void *p, loff_t *ppos)
 262 {
 263         struct lttng_probe_desc *probe_desc;
 264         struct list_head *probe_list;
 265         int iter = 0, i;
 266
 267         (*ppos)++;
 268         probe_list = lttng_get_probe_list_head();
 269         list_for_each_entry(probe_desc, probe_list, head) {
 270                 for (i = 0; i < probe_desc->nr_events; i++) {
 271                         if (iter++ >= *ppos)
 272                                 return (void *) probe_desc->event_desc[i];
 273                 }
 274         }
 275         /* End of list */
 276         return NULL;
 277 }
 278
 279 static
 280 void tp_list_stop(struct seq_file *m, void *p)
 281 {
 282         lttng_unlock_sessions();
 283 }
 284
 285 static
 286 int tp_list_show(struct seq_file *m, void *p)
 287 {
 288         const struct lttng_event_desc *probe_desc = p;
 289
 290         seq_printf(m,   "event { name = %s; };\n",
 291                    probe_desc->name);
 292         return 0;
 293 }
 294
 295 static
 296 const struct seq_operations lttng_tracepoint_list_seq_ops = {
 297         .start = tp_list_start,
 298         .next = tp_list_next,
 299         .stop = tp_list_stop,
 300         .show = tp_list_show,
 301 };
 302
 303 static
 304 int lttng_tracepoint_list_open(struct inode *inode, struct file *file)
 305 {
 306         return seq_open(file, &lttng_tracepoint_list_seq_ops);
 307 }
 308
 309 const struct file_operations lttng_tracepoint_list_fops = {
 310         .owner = THIS_MODULE,
 311         .open = lttng_tracepoint_list_open,
 312         .read = seq_read,
 313         .llseek = seq_lseek,
 314         .release = seq_release,
 315 };
 316
 317 int lttng_probes_init(void)
 318 {
 319         int cpu;
 320
 321         for_each_possible_cpu(cpu)
 322                 per_cpu_ptr(&lttng_dynamic_len_stack, cpu)->offset = 0;
 323         return 0;
 324 }