tracepoint probe refactoring: Move provider name to provider descriptor
authorMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fri, 26 Mar 2021 15:13:25 +0000 (11:13 -0400)
committerMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Mon, 29 Mar 2021 17:22:17 +0000 (13:22 -0400)
The provider name is currently repeated for each event name as:

  <provider name>:<event name>

This repetition requires that each event embeds the provider name within
its own name.

Use this ABI break to clean this up: instead, each event descriptor has
a pointer to its probe descriptor, and each probe descriptor has a
provider name.

Implement name size validation and event name formatting internal
helpers, and use them across the tracer.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ief8a4696a2030bf3b9c785b8422f382079c6bf06

include/lttng/ust-events.h
include/lttng/ust-tracepoint-event.h
liblttng-ust/lttng-events.c
liblttng-ust/lttng-probes.c
liblttng-ust/ust-events-internal.h

index 96504940ec3669941dff17ec0a7753d45f230ddd..1f55c00a3758dc4b4cbff8005e3abb17654ebffd 100644 (file)
@@ -258,7 +258,8 @@ struct lttng_ust_event_field {
 struct lttng_ust_event_desc {
        uint32_t struct_size;                   /* Size of this structure. */
 
-       const char *name;
+       const char *event_name;
+       struct lttng_ust_probe_desc *probe_desc;
        void (*probe_callback)(void);
        struct lttng_event_ctx *ctx;            /* context */
        struct lttng_ust_event_field **fields;  /* event payload */
@@ -282,7 +283,7 @@ struct lttng_ust_event_desc {
 struct lttng_ust_probe_desc {
        uint32_t struct_size;                   /* Size of this structure. */
 
-       const char *provider;
+       const char *provider_name;
        struct lttng_ust_event_desc **event_desc;
        unsigned int nr_events;
        struct cds_list_head head;              /* chain registered probes */
index 18f91c5f75b3e34d7a4d046bef809e0ac75d7c16..fcd5303170d29babaa4fb8f3972f9df8b9ad6b3e 100644 (file)
@@ -973,6 +973,19 @@ LTTNG_TP_EXTERN_C const char *_model_emf_uri___##__provider##___##__name   \
 
 #undef LTTNG_TP_EXTERN_C
 
+/*
+ * Stage 7.0 of tracepoint event generation.
+ *
+ * Declare toplevel descriptor for the whole probe.
+ * Unlike C, C++ does not allow tentative definitions. Therefore, we
+ * need to explicitly declare the variable with "extern", using hidden
+ * visibility to keep this symbol from being exported to the global
+ * symbol table.
+ */
+
+extern struct lttng_ust_probe_desc _TP_COMBINE_TOKENS(__probe_desc___, TRACEPOINT_PROVIDER)
+       __attribute__((visibility("hidden")));
+
 /*
  * Stage 7.1 of tracepoint event generation.
  *
@@ -994,7 +1007,8 @@ static const char *                                                               \
        __attribute__((weakref ("_model_emf_uri___" #_provider "___" #_name)));\
 static struct lttng_ust_event_desc __event_desc___##_provider##_##_name = {    \
        .struct_size = sizeof(struct lttng_ust_event_desc),                    \
-       .name = #_provider ":" #_name,                                         \
+       .event_name = #_name,                                                  \
+       .probe_desc = &__probe_desc___##_provider,                             \
        .probe_callback = (void (*)(void)) &__event_probe__##_provider##___##_template, \
        .ctx = NULL,                                                           \
        .fields = __event_fields___##_provider##___##_template,                \
@@ -1031,10 +1045,9 @@ static struct lttng_ust_event_desc *_TP_COMBINE_TOKENS(__event_desc___, TRACEPOI
  * Create a toplevel descriptor for the whole probe.
  */
 
-/* non-const because list head will be modified when registered. */
-static struct lttng_ust_probe_desc _TP_COMBINE_TOKENS(__probe_desc___, TRACEPOINT_PROVIDER) = {
+struct lttng_ust_probe_desc _TP_COMBINE_TOKENS(__probe_desc___, TRACEPOINT_PROVIDER) = {
        .struct_size = sizeof(struct lttng_ust_probe_desc),
-       .provider = __tp_stringify(TRACEPOINT_PROVIDER),
+       .provider_name = __tp_stringify(TRACEPOINT_PROVIDER),
        .event_desc = _TP_COMBINE_TOKENS(__event_desc___, TRACEPOINT_PROVIDER),
        .nr_events = _TP_ARRAY_SIZE(_TP_COMBINE_TOKENS(__event_desc___, TRACEPOINT_PROVIDER)) - 1,
        .head = { NULL, NULL },
index c81581b228e960ae2f1ae4ff2b44517cb842fca7..140e5caeea00cb27f5ddfc9df055ba5fc171ad50 100644 (file)
@@ -84,6 +84,22 @@ void lttng_event_notifier_group_sync_enablers(
 static
 void lttng_enabler_destroy(struct lttng_enabler *enabler);
 
+bool lttng_ust_validate_event_name(const struct lttng_ust_event_desc *desc)
+{
+       if (strlen(desc->probe_desc->provider_name) + 1 +
+                       strlen(desc->event_name) >= LTTNG_UST_ABI_SYM_NAME_LEN)
+               return false;
+       return true;
+}
+
+void lttng_ust_format_event_name(const struct lttng_ust_event_desc *desc,
+               char *name)
+{
+       strcpy(name, desc->probe_desc->provider_name);
+       strcat(name, ":");
+       strcat(name, desc->event_name);
+}
+
 /*
  * Called with ust lock held.
  */
@@ -251,10 +267,12 @@ void register_event(struct lttng_ust_event_common *event)
 {
        int ret;
        struct lttng_ust_event_desc *desc;
+       char name[LTTNG_UST_ABI_SYM_NAME_LEN];
 
        assert(event->priv->registered == 0);
        desc = event->priv->desc;
-       ret = lttng_ust_tp_probe_register_queue_release(desc->name,
+       lttng_ust_format_event_name(desc, name);
+       ret = lttng_ust_tp_probe_register_queue_release(name,
                        desc->probe_callback,
                        event, desc->signature);
        WARN_ON_ONCE(ret);
@@ -267,10 +285,12 @@ void unregister_event(struct lttng_ust_event_common *event)
 {
        int ret;
        struct lttng_ust_event_desc *desc;
+       char name[LTTNG_UST_ABI_SYM_NAME_LEN];
 
        assert(event->priv->registered == 1);
        desc = event->priv->desc;
-       ret = lttng_ust_tp_probe_unregister_queue_release(desc->name,
+       lttng_ust_format_event_name(desc, name);
+       ret = lttng_ust_tp_probe_unregister_queue_release(name,
                        desc->probe_callback,
                        event);
        WARN_ON_ONCE(ret);
@@ -677,14 +697,14 @@ struct cds_hlist_head *borrow_hash_table_bucket(
                unsigned int hash_table_size,
                struct lttng_ust_event_desc *desc)
 {
-       const char *event_name;
+       char name[LTTNG_UST_ABI_SYM_NAME_LEN];
        size_t name_len;
        uint32_t hash;
 
-       event_name = desc->name;
-       name_len = strlen(event_name);
+       lttng_ust_format_event_name(desc, name);
+       name_len = strlen(name);
 
-       hash = jhash(event_name, name_len, 0);
+       hash = jhash(name, name_len, 0);
        return &hash_table[hash & (hash_table_size - 1)];
 }
 
@@ -695,6 +715,7 @@ static
 int lttng_event_recorder_create(struct lttng_ust_event_desc *desc,
                struct lttng_ust_channel_buffer *chan)
 {
+       char name[LTTNG_UST_ABI_SYM_NAME_LEN];
        struct lttng_ust_event_recorder *event_recorder;
        struct lttng_ust_event_recorder_private *event_recorder_priv;
        struct lttng_ust_session *session = chan->parent->session;
@@ -767,12 +788,14 @@ int lttng_event_recorder_create(struct lttng_ust_event_desc *desc,
        else
                uri = NULL;
 
+       lttng_ust_format_event_name(desc, name);
+
        /* Fetch event ID from sessiond */
        ret = ustcomm_register_event(notify_socket,
                session,
                session->priv->objd,
                chan->priv->parent.objd,
-               desc->name,
+               name,
                loglevel,
                desc->signature,
                desc->nr_fields,
@@ -877,12 +900,14 @@ static
 int lttng_desc_match_star_glob_enabler(struct lttng_ust_event_desc *desc,
                struct lttng_enabler *enabler)
 {
+       char name[LTTNG_UST_ABI_SYM_NAME_LEN];
        int loglevel = 0;
        unsigned int has_loglevel = 0;
 
+       lttng_ust_format_event_name(desc, name);
        assert(enabler->format_type == LTTNG_ENABLER_FORMAT_STAR_GLOB);
        if (!strutils_star_glob_match(enabler->event_param.name, SIZE_MAX,
-                       desc->name, SIZE_MAX))
+                       name, SIZE_MAX))
                return 0;
        if (desc->loglevel) {
                loglevel = *(*desc->loglevel);
@@ -900,11 +925,13 @@ static
 int lttng_desc_match_event_enabler(struct lttng_ust_event_desc *desc,
                struct lttng_enabler *enabler)
 {
+       char name[LTTNG_UST_ABI_SYM_NAME_LEN];
        int loglevel = 0;
        unsigned int has_loglevel = 0;
 
+       lttng_ust_format_event_name(desc, name);
        assert(enabler->format_type == LTTNG_ENABLER_FORMAT_EVENT);
-       if (strcmp(desc->name, enabler->event_param.name))
+       if (strcmp(name, enabler->event_param.name))
                return 0;
        if (desc->loglevel) {
                loglevel = *(*desc->loglevel);
@@ -945,8 +972,14 @@ int lttng_desc_match_enabler(struct lttng_ust_event_desc *desc,
                                excluder_name = (char *) (excluder->excluder.names)
                                                + count * LTTNG_UST_ABI_SYM_NAME_LEN;
                                len = strnlen(excluder_name, LTTNG_UST_ABI_SYM_NAME_LEN);
-                               if (len > 0 && strutils_star_glob_match(excluder_name, len, desc->name, SIZE_MAX))
-                                       return 0;
+                               if (len > 0) {
+                                       char name[LTTNG_UST_ABI_SYM_NAME_LEN];
+
+                                       lttng_ust_format_event_name(desc, name);
+                                       if (strutils_star_glob_match(excluder_name, len, name, SIZE_MAX)) {
+                                               return 0;
+                                       }
+                               }
                        }
                }
                return 1;
@@ -1052,8 +1085,9 @@ void lttng_create_event_recorder_if_missing(struct lttng_event_enabler *event_en
                        ret = lttng_event_recorder_create(probe_desc->event_desc[i],
                                        event_enabler->chan);
                        if (ret) {
-                               DBG("Unable to create event %s, error %d\n",
-                                       probe_desc->event_desc[i]->name, ret);
+                               DBG("Unable to create event \"%s:%s\", error %d\n",
+                                       probe_desc->provider_name,
+                                       probe_desc->event_desc[i]->event_name, ret);
                        }
                }
        }
@@ -1772,12 +1806,12 @@ void lttng_create_event_notifier_if_missing(
 
                        /* Check that the probe supports event notifiers, else report the error. */
                        if (!lttng_ust_probe_supports_event_notifier(probe_desc)) {
-                               ERR("Probe \"%s\" contains event \"%s\" which matches an enabled event notifier, "
+                               ERR("Probe \"%s\" contains event \"%s:%s\" which matches an enabled event notifier, "
                                        "but its version (%u.%u) is too old and does not implement event notifiers. "
                                        "It needs to be recompiled against a newer version of LTTng-UST, otherwise "
                                        "this event will not generate any notification.",
-                                       probe_desc->provider,
-                                       desc->name,
+                                       probe_desc->provider_name,
+                                       probe_desc->provider_name, desc->event_name,
                                        probe_desc->major,
                                        probe_desc->minor);
                                continue;
@@ -1790,8 +1824,9 @@ void lttng_create_event_notifier_if_missing(
                                event_notifier_enabler->error_counter_index,
                                event_notifier_group);
                        if (ret) {
-                               DBG("Unable to create event_notifier %s, error %d\n",
-                                       probe_desc->event_desc[i]->name, ret);
+                               DBG("Unable to create event_notifier \"%s:%s\", error %d\n",
+                                       probe_desc->provider_name,
+                                       probe_desc->event_desc[i]->event_name, ret);
                        }
                }
        }
index 00ce54cb36a9117338cecf4cc1bc3496f0b94227..95a1c12bbe2ff2d5cf331f08c7d3d6c2e05d002f 100644 (file)
@@ -41,23 +41,29 @@ static CDS_LIST_HEAD(lazy_probe_init);
 static int lazy_nesting;
 
 /*
- * Called under ust lock.
+ * Validate that each event within the probe provider refers to the
+ * right probe, and that the resulting name is not too long.
  */
 static
-int check_event_provider(struct lttng_ust_probe_desc *desc)
+bool check_event_provider(struct lttng_ust_probe_desc *probe_desc)
 {
        int i;
-       size_t provider_name_len;
-
-       provider_name_len = strnlen(desc->provider,
-                               LTTNG_UST_ABI_SYM_NAME_LEN - 1);
-       for (i = 0; i < desc->nr_events; i++) {
-               if (strncmp(desc->event_desc[i]->name,
-                               desc->provider,
-                               provider_name_len))
-                       return 0;       /* provider mismatch */
+
+       for (i = 0; i < probe_desc->nr_events; i++) {
+               const struct lttng_ust_event_desc *event_desc = probe_desc->event_desc[i];
+
+               if (event_desc->probe_desc != probe_desc) {
+                       ERR("Error registering probe provider '%s'. Event '%s:%s' refers to the wrong provider descriptor.",
+                               probe_desc->provider_name, probe_desc->provider_name, event_desc->event_name);
+                       return false;   /* provider mismatch */
+               }
+               if (!lttng_ust_validate_event_name(event_desc)) {
+                       ERR("Error registering probe provider '%s'. Event '%s:%s' name is too long.",
+                               probe_desc->provider_name, probe_desc->provider_name, event_desc->event_name);
+                       return false;   /* provider mismatch */
+               }
        }
-       return 1;
+       return true;
 }
 
 /*
@@ -69,14 +75,6 @@ void lttng_lazy_probe_register(struct lttng_ust_probe_desc *desc)
        struct lttng_ust_probe_desc *iter;
        struct cds_list_head *probe_list;
 
-       /*
-        * Each provider enforce that every event name begins with the
-        * provider name. Check this in an assertion for extra
-        * carefulness. This ensures we cannot have duplicate event
-        * names across providers.
-        */
-       assert(check_event_provider(desc));
-
        /*
         * The provider ensures there are no duplicate event names.
         * Duplicated TRACEPOINT_EVENT event names would generate a
@@ -100,7 +98,7 @@ void lttng_lazy_probe_register(struct lttng_ust_probe_desc *desc)
        cds_list_add(&desc->head, probe_list);
 desc_added:
        DBG("just registered probe %s containing %u events",
-               desc->provider, desc->nr_events);
+               desc->provider_name, desc->nr_events);
 }
 
 /*
@@ -143,7 +141,7 @@ int check_provider_version(struct lttng_ust_probe_desc *desc)
        if (desc->major <= LTTNG_UST_PROVIDER_MAJOR) {
                DBG("Provider \"%s\" accepted, version %u.%u is compatible "
                        "with LTTng UST provider version %u.%u.",
-                       desc->provider, desc->major, desc->minor,
+                       desc->provider_name, desc->major, desc->minor,
                        LTTNG_UST_PROVIDER_MAJOR,
                        LTTNG_UST_PROVIDER_MINOR);
                if (desc->major < LTTNG_UST_PROVIDER_MAJOR) {
@@ -156,7 +154,7 @@ int check_provider_version(struct lttng_ust_probe_desc *desc)
                ERR("Provider \"%s\" rejected, version %u.%u is incompatible "
                        "with LTTng UST provider version %u.%u. Please upgrade "
                        "LTTng UST.",
-                       desc->provider, desc->major, desc->minor,
+                       desc->provider_name, desc->major, desc->minor,
                        LTTNG_UST_PROVIDER_MAJOR,
                        LTTNG_UST_PROVIDER_MINOR);
                return 0;               /* reject */
@@ -176,13 +174,15 @@ int lttng_ust_probe_register(struct lttng_ust_probe_desc *desc)
         */
        if (!check_provider_version(desc))
                return 0;
+       if (!check_event_provider(desc))
+               return 0;
 
        ust_lock_nocheck();
 
        cds_list_add(&desc->lazy_init_head, &lazy_probe_init);
        desc->lazy = 1;
        DBG("adding probe %s containing %u events to lazy registration list",
-               desc->provider, desc->nr_events);
+               desc->provider_name, desc->nr_events);
        /*
         * If there is at least one active session, we need to register
         * the probe immediately, since we cannot delay event
@@ -211,7 +211,7 @@ void lttng_ust_probe_unregister(struct lttng_ust_probe_desc *desc)
                cds_list_del(&desc->lazy_init_head);
 
        lttng_probe_provider_unregister_events(desc);
-       DBG("just unregistered probes of provider %s", desc->provider);
+       DBG("just unregistered probes of provider %s", desc->provider_name);
 
        ust_unlock();
 }
@@ -239,20 +239,22 @@ int lttng_probes_get_event_list(struct lttng_ust_tracepoint_list *list)
        CDS_INIT_LIST_HEAD(&list->head);
        cds_list_for_each_entry(probe_desc, probe_list, head) {
                for (i = 0; i < probe_desc->nr_events; i++) {
+                       const struct lttng_ust_event_desc *event_desc =
+                               probe_desc->event_desc[i];
                        struct tp_list_entry *list_entry;
 
+                       /* Skip event if name is too long. */
+                       if (!lttng_ust_validate_event_name(event_desc))
+                               continue;
                        list_entry = zmalloc(sizeof(*list_entry));
                        if (!list_entry)
                                goto err_nomem;
                        cds_list_add(&list_entry->head, &list->head);
-                       strncpy(list_entry->tp.name,
-                               probe_desc->event_desc[i]->name,
-                               LTTNG_UST_ABI_SYM_NAME_LEN);
-                       list_entry->tp.name[LTTNG_UST_ABI_SYM_NAME_LEN - 1] = '\0';
-                       if (!probe_desc->event_desc[i]->loglevel) {
+                       lttng_ust_format_event_name(event_desc, list_entry->tp.name);
+                       if (!event_desc->loglevel) {
                                list_entry->tp.loglevel = TRACE_DEFAULT;
                        } else {
-                               list_entry->tp.loglevel = *(*probe_desc->event_desc[i]->loglevel);
+                               list_entry->tp.loglevel = *(*event_desc->loglevel);
                        }
                }
        }
@@ -319,14 +321,14 @@ int lttng_probes_get_field_list(struct lttng_ust_field_list *list)
                                /* Events without fields. */
                                struct tp_field_list_entry *list_entry;
 
+                               /* Skip event if name is too long. */
+                               if (!lttng_ust_validate_event_name(event_desc))
+                                       continue;
                                list_entry = zmalloc(sizeof(*list_entry));
                                if (!list_entry)
                                        goto err_nomem;
                                cds_list_add(&list_entry->head, &list->head);
-                               strncpy(list_entry->field.event_name,
-                                       event_desc->name,
-                                       LTTNG_UST_ABI_SYM_NAME_LEN);
-                               list_entry->field.event_name[LTTNG_UST_ABI_SYM_NAME_LEN - 1] = '\0';
+                               lttng_ust_format_event_name(event_desc, list_entry->field.event_name);
                                list_entry->field.field_name[0] = '\0';
                                list_entry->field.type = LTTNG_UST_ABI_FIELD_OTHER;
                                if (!event_desc->loglevel) {
@@ -342,14 +344,14 @@ int lttng_probes_get_field_list(struct lttng_ust_field_list *list)
                                        event_desc->fields[j];
                                struct tp_field_list_entry *list_entry;
 
+                               /* Skip event if name is too long. */
+                               if (!lttng_ust_validate_event_name(event_desc))
+                                       continue;
                                list_entry = zmalloc(sizeof(*list_entry));
                                if (!list_entry)
                                        goto err_nomem;
                                cds_list_add(&list_entry->head, &list->head);
-                               strncpy(list_entry->field.event_name,
-                                       event_desc->name,
-                                       LTTNG_UST_ABI_SYM_NAME_LEN);
-                               list_entry->field.event_name[LTTNG_UST_ABI_SYM_NAME_LEN - 1] = '\0';
+                               lttng_ust_format_event_name(event_desc, list_entry->field.event_name);
                                strncpy(list_entry->field.field_name,
                                        event_field->name,
                                        LTTNG_UST_ABI_SYM_NAME_LEN);
index 0a5d213ce9e2ed5b481a415692a61a431d730b61..e632050434c83a2fa06ab790c7570f90a0b5db6d 100644 (file)
@@ -899,4 +899,11 @@ __attribute__((visibility("hidden")))
 int lttng_ust_session_uuid_validate(struct lttng_ust_session *session,
                unsigned char *uuid);
 
+__attribute__((visibility("hidden")))
+bool lttng_ust_validate_event_name(const struct lttng_ust_event_desc *desc);
+
+__attribute__((visibility("hidden")))
+void lttng_ust_format_event_name(const struct lttng_ust_event_desc *desc,
+               char *name);
+
 #endif /* _LTTNG_UST_EVENTS_INTERNAL_H */
This page took 0.034507 seconds and 4 git commands to generate.