X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=src%2Fbin%2Flttng-sessiond%2Fust-registry.c;h=dea443d94fbb1e74fc9ecffd105cb3bf1fe7b42d;hp=31d33df4c72c294875dd26cd165ba692dcbb7b86;hb=7062f070b01e86c2e29490ea41e25f1f519ceadb;hpb=5d2e1e66a968d9e555f9b8b00d0589ebfaf3de32

diff --git a/src/bin/lttng-sessiond/ust-registry.c b/src/bin/lttng-sessiond/ust-registry.c
index 31d33df4c..dea443d94 100644
--- a/src/bin/lttng-sessiond/ust-registry.c
+++ b/src/bin/lttng-sessiond/ust-registry.c
@@ -14,11 +14,18 @@
  * this program; if not, write to the Free Software Foundation, Inc., 51
  * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
-#define _GNU_SOURCE
+
+#define _LGPL_SOURCE
 #include <assert.h>
+#include <inttypes.h>
 
 #include <common/common.h>
+#include <common/hashtable/utils.h>
+#include <lttng/lttng.h>
+
 #include "ust-registry.h"
+#include "ust-app.h"
+#include "utils.h"
 
 /*
  * Hash table match function for event in the registry.
@@ -36,13 +43,13 @@ static int ht_match_event(struct cds_lfht_node *node, const void *_key)
 	key = _key;
 
 	/* It has to be a perfect match. */
-	if (strncmp(event->name, key->name, sizeof(event->name)) != 0) {
+	if (strncmp(event->name, key->name, sizeof(event->name))) {
 		goto no_match;
 	}
 
 	/* It has to be a perfect match. */
 	if (strncmp(event->signature, key->signature,
-				strlen(event->signature) != 0)) {
+			strlen(event->signature))) {
 		goto no_match;
 	}
 
@@ -53,16 +60,207 @@ no_match:
 	return 0;
 }
 
+static unsigned long ht_hash_event(void *_key, unsigned long seed)
+{
+	uint64_t xored_key;
+	struct ust_registry_event *key = _key;
+
+	assert(key);
+
+	xored_key = (uint64_t) (hash_key_str(key->name, seed) ^
+			hash_key_str(key->signature, seed));
+
+	return hash_key_u64(&xored_key, seed);
+}
+
+static int compare_enums(const struct ust_registry_enum *reg_enum_a,
+		const struct ust_registry_enum *reg_enum_b)
+{
+	int ret = 0;
+	size_t i;
+
+	assert(strcmp(reg_enum_a->name, reg_enum_b->name) == 0);
+	if (reg_enum_a->nr_entries != reg_enum_b->nr_entries) {
+		ret = -1;
+		goto end;
+	}
+	for (i = 0; i < reg_enum_a->nr_entries; i++) {
+		const struct ustctl_enum_entry *entries_a, *entries_b;
+
+		entries_a = &reg_enum_a->entries[i];
+		entries_b = &reg_enum_b->entries[i];
+		if (entries_a->start != entries_b->start) {
+			ret = -1;
+			goto end;
+		}
+		if (entries_a->end != entries_b->end) {
+			ret = -1;
+			goto end;
+		}
+		if (strcmp(entries_a->string, entries_b->string)) {
+			ret = -1;
+			goto end;
+		}
+	}
+end:
+	return ret;
+}
+
+/*
+ * Hash table match function for enumerations in the session. Match is
+ * performed on enumeration name, and confirmed by comparing the enum
+ * entries.
+ */
+static int ht_match_enum(struct cds_lfht_node *node, const void *_key)
+{
+	struct ust_registry_enum *_enum;
+	const struct ust_registry_enum *key;
+
+	assert(node);
+	assert(_key);
+
+	_enum = caa_container_of(node, struct ust_registry_enum,
+			node.node);
+	assert(_enum);
+	key = _key;
+
+	if (strncmp(_enum->name, key->name, LTTNG_UST_SYM_NAME_LEN)) {
+		goto no_match;
+	}
+	if (compare_enums(_enum, key)) {
+		goto no_match;
+	}
+
+	/* Match. */
+	return 1;
+
+no_match:
+	return 0;
+}
+
+/*
+ * Hash table match function for enumerations in the session. Match is
+ * performed by enumeration ID.
+ */
+static int ht_match_enum_id(struct cds_lfht_node *node, const void *_key)
+{
+	struct ust_registry_enum *_enum;
+	const struct ust_registry_enum *key = _key;
+
+	assert(node);
+	assert(_key);
+
+	_enum = caa_container_of(node, struct ust_registry_enum, node.node);
+	assert(_enum);
+
+	if (_enum->id != key->id) {
+		goto no_match;
+	}
+
+	/* Match. */
+	return 1;
+
+no_match:
+	return 0;
+}
+
+/*
+ * Hash table hash function for enumerations in the session. The
+ * enumeration name is used for hashing.
+ */
+static unsigned long ht_hash_enum(void *_key, unsigned long seed)
+{
+	struct ust_registry_enum *key = _key;
+
+	assert(key);
+	return hash_key_str(key->name, seed);
+}
+
+/*
+ * Return negative value on error, 0 if OK.
+ *
+ * TODO: we could add stricter verification of more types to catch
+ * errors in liblttng-ust implementation earlier than consumption by the
+ * trace reader.
+ */
+static
+int validate_event_field(struct ustctl_field *field,
+		const char *event_name,
+		struct ust_app *app)
+{
+	int ret = 0;
+
+	switch(field->type.atype) {
+	case ustctl_atype_integer:
+	case ustctl_atype_enum:
+	case ustctl_atype_array:
+	case ustctl_atype_sequence:
+	case ustctl_atype_string:
+	case ustctl_atype_variant:
+		break;
+	case ustctl_atype_struct:
+		if (field->type.u._struct.nr_fields != 0) {
+			WARN("Unsupported non-empty struct field.");
+			ret = -EINVAL;
+			goto end;
+		}
+		break;
+
+	case ustctl_atype_float:
+		switch (field->type.u.basic._float.mant_dig) {
+		case 0:
+			WARN("UST application '%s' (pid: %d) has unknown float mantissa '%u' "
+				"in field '%s', rejecting event '%s'",
+				app->name, app->pid,
+				field->type.u.basic._float.mant_dig,
+				field->name,
+				event_name);
+			ret = -EINVAL;
+			goto end;
+		default:
+			break;
+		}
+		break;
+
+	default:
+		ret = -ENOENT;
+		goto end;
+	}
+end:
+	return ret;
+}
+
+static
+int validate_event_fields(size_t nr_fields, struct ustctl_field *fields,
+		const char *event_name, struct ust_app *app)
+{
+	unsigned int i;
+
+	for (i = 0; i < nr_fields; i++) {
+		if (validate_event_field(&fields[i], event_name, app) < 0)
+			return -EINVAL;
+	}
+	return 0;
+}
+
 /*
  * Allocate event and initialize it. This does NOT set a valid event id from a
  * registry.
  */
 static struct ust_registry_event *alloc_event(int session_objd,
 		int channel_objd, char *name, char *sig, size_t nr_fields,
-		struct ustctl_field *fields, int loglevel, char *model_emf_uri)
+		struct ustctl_field *fields, int loglevel_value,
+		char *model_emf_uri, struct ust_app *app)
 {
 	struct ust_registry_event *event = NULL;
 
+	/*
+	 * Ensure that the field content is valid.
+	 */
+	if (validate_event_fields(nr_fields, fields, name, app) < 0) {
+		return NULL;
+	}
+
 	event = zmalloc(sizeof(*event));
 	if (!event) {
 		PERROR("zmalloc ust registry event");
@@ -75,14 +273,14 @@ static struct ust_registry_event *alloc_event(int session_objd,
 	event->signature = sig;
 	event->nr_fields = nr_fields;
 	event->fields = fields;
-	event->loglevel = loglevel;
+	event->loglevel_value = loglevel_value;
 	event->model_emf_uri = model_emf_uri;
 	if (name) {
 		/* Copy event name and force NULL byte. */
 		strncpy(event->name, name, sizeof(event->name));
 		event->name[sizeof(event->name) - 1] = '\0';
 	}
-	lttng_ht_node_init_str(&event->node, event->name);
+	cds_lfht_node_init(&event->node.node);
 
 error:
 	return event;
@@ -110,8 +308,8 @@ static void destroy_event(struct ust_registry_event *event)
  */
 static void destroy_event_rcu(struct rcu_head *head)
 {
-	struct lttng_ht_node_str *node =
-		caa_container_of(head, struct lttng_ht_node_str, head);
+	struct lttng_ht_node_u64 *node =
+		caa_container_of(head, struct lttng_ht_node_u64, head);
 	struct ust_registry_event *event =
 		caa_container_of(node, struct ust_registry_event, node);
 
@@ -128,7 +326,7 @@ static void destroy_event_rcu(struct rcu_head *head)
 struct ust_registry_event *ust_registry_find_event(
 		struct ust_registry_channel *chan, char *name, char *sig)
 {
-	struct lttng_ht_node_str *node;
+	struct lttng_ht_node_u64 *node;
 	struct lttng_ht_iter iter;
 	struct ust_registry_event *event = NULL;
 	struct ust_registry_event key;
@@ -142,9 +340,9 @@ struct ust_registry_event *ust_registry_find_event(
 	key.name[sizeof(key.name) - 1] = '\0';
 	key.signature = sig;
 
-	cds_lfht_lookup(chan->ht->ht, chan->ht->hash_fct(name, lttng_ht_seed),
+	cds_lfht_lookup(chan->ht->ht, chan->ht->hash_fct(&key, lttng_ht_seed),
 			chan->ht->match_fct, &key, &iter.iter);
-	node = lttng_ht_iter_get_node_str(&iter);
+	node = lttng_ht_iter_get_node_u64(&iter);
 	if (!node) {
 		goto end;
 	}
@@ -165,19 +363,23 @@ end:
  * Should be called with session registry mutex held.
  */
 int ust_registry_create_event(struct ust_registry_session *session,
-		struct ust_registry_channel *chan,
-		int session_objd, int channel_objd, char *name, char *sig,
-		size_t nr_fields, struct ustctl_field *fields, int loglevel,
-		char *model_emf_uri, uint32_t *event_id)
+		uint64_t chan_key, int session_objd, int channel_objd, char *name,
+		char *sig, size_t nr_fields, struct ustctl_field *fields,
+		int loglevel_value, char *model_emf_uri, int buffer_type,
+		uint32_t *event_id_p, struct ust_app *app)
 {
 	int ret;
+	uint32_t event_id;
 	struct cds_lfht_node *nptr;
 	struct ust_registry_event *event = NULL;
+	struct ust_registry_channel *chan;
 
 	assert(session);
-	assert(chan);
 	assert(name);
 	assert(sig);
+	assert(event_id_p);
+
+	rcu_read_lock();
 
 	/*
 	 * This should not happen but since it comes from the UST tracer, an
@@ -185,62 +387,85 @@ int ust_registry_create_event(struct ust_registry_session *session,
 	 */
 	if (session_objd < 0 || channel_objd < 0) {
 		ret = -EINVAL;
-		goto error;
+		goto error_free;
+	}
+
+	chan = ust_registry_channel_find(session, chan_key);
+	if (!chan) {
+		ret = -EINVAL;
+		goto error_free;
 	}
 
 	/* Check if we've reached the maximum possible id. */
 	if (ust_registry_is_max_id(chan->used_event_id)) {
 		ret = -ENOENT;
-		goto error;
+		goto error_free;
 	}
 
 	event = alloc_event(session_objd, channel_objd, name, sig, nr_fields,
-			fields, loglevel, model_emf_uri);
+			fields, loglevel_value, model_emf_uri, app);
 	if (!event) {
 		ret = -ENOMEM;
-		goto error;
+		goto error_free;
 	}
 
-	event->id = ust_registry_get_next_event_id(chan);
-
 	DBG3("UST registry creating event with event: %s, sig: %s, id: %u, "
-			"chan_objd: %u, sess_objd: %u", event->name, event->signature,
-			event->id, event->channel_objd, event->session_objd);
+			"chan_objd: %u, sess_objd: %u, chan_id: %u", event->name,
+			event->signature, event->id, event->channel_objd,
+			event->session_objd, chan->chan_id);
 
-	rcu_read_lock();
 	/*
 	 * This is an add unique with a custom match function for event. The node
 	 * are matched using the event name and signature.
 	 */
-	nptr = cds_lfht_add_unique(chan->ht->ht, chan->ht->hash_fct(event->node.key,
+	nptr = cds_lfht_add_unique(chan->ht->ht, chan->ht->hash_fct(event,
 				lttng_ht_seed), chan->ht->match_fct, event, &event->node.node);
 	if (nptr != &event->node.node) {
-		ERR("UST registry create event add unique failed for event: %s, "
-				"sig: %s, id: %u, chan_objd: %u, sess_objd: %u", event->name,
-				event->signature, event->id, event->channel_objd,
-				event->session_objd);
-		ret = -EINVAL;
-		goto error_unlock;
+		if (buffer_type == LTTNG_BUFFER_PER_UID) {
+			/*
+			 * This is normal, we just have to send the event id of the
+			 * returned node and make sure we destroy the previously allocated
+			 * event object.
+			 */
+			destroy_event(event);
+			event = caa_container_of(nptr, struct ust_registry_event,
+					node.node);
+			assert(event);
+			event_id = event->id;
+		} else {
+			ERR("UST registry create event add unique failed for event: %s, "
+					"sig: %s, id: %u, chan_objd: %u, sess_objd: %u",
+					event->name, event->signature, event->id,
+					event->channel_objd, event->session_objd);
+			ret = -EINVAL;
+			goto error_unlock;
+		}
+	} else {
+		/* Request next event id if the node was successfully added. */
+		event_id = event->id = ust_registry_get_next_event_id(chan);
 	}
 
-	/* Set event id if user wants it. */
-	if (event_id) {
-		*event_id = event->id;
-	}
-	rcu_read_unlock();
+	*event_id_p = event_id;
 
-	/* Append to metadata */
-	ret = ust_metadata_event_statedump(session, chan, event);
-	if (ret) {
-		ERR("Error appending event metadata (errno = %d)", ret);
-		return ret;
+	if (!event->metadata_dumped) {
+		/* Append to metadata */
+		ret = ust_metadata_event_statedump(session, chan, event);
+		if (ret) {
+			ERR("Error appending event metadata (errno = %d)", ret);
+			rcu_read_unlock();
+			return ret;
+		}
 	}
 
+	rcu_read_unlock();
 	return 0;
 
+error_free:
+	free(sig);
+	free(fields);
+	free(model_emf_uri);
 error_unlock:
 	rcu_read_unlock();
-error:
 	destroy_event(event);
 	return ret;
 }
@@ -268,50 +493,335 @@ void ust_registry_destroy_event(struct ust_registry_channel *chan,
 	return;
 }
 
+static void destroy_enum(struct ust_registry_enum *reg_enum)
+{
+	if (!reg_enum) {
+		return;
+	}
+	free(reg_enum->entries);
+	free(reg_enum);
+}
+
+static void destroy_enum_rcu(struct rcu_head *head)
+{
+	struct ust_registry_enum *reg_enum =
+		caa_container_of(head, struct ust_registry_enum, rcu_head);
+
+	destroy_enum(reg_enum);
+}
+
 /*
- * Initialize registry with default values.
+ * Lookup enumeration by name and comparing enumeration entries.
+ * Needs to be called from RCU read-side critical section.
  */
-void ust_registry_channel_init(struct ust_registry_session *session,
-		struct ust_registry_channel *chan)
+struct ust_registry_enum *
+	ust_registry_lookup_enum(struct ust_registry_session *session,
+		const struct ust_registry_enum *reg_enum_lookup)
 {
-	assert(chan);
+	struct ust_registry_enum *reg_enum = NULL;
+	struct lttng_ht_node_str *node;
+	struct lttng_ht_iter iter;
 
-	memset(chan, 0, sizeof(struct ust_registry_channel));
+	cds_lfht_lookup(session->enums->ht,
+			ht_hash_enum((void *) &reg_enum_lookup, lttng_ht_seed),
+			ht_match_enum, &reg_enum_lookup, &iter.iter);
+	node = lttng_ht_iter_get_node_str(&iter);
+	if (!node) {
+	        goto end;
+	}
+	reg_enum = caa_container_of(node, struct ust_registry_enum, node);
+end:
+	return reg_enum;
+}
 
-	chan->ht = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
-	assert(chan->ht);
+/*
+ * Lookup enumeration by enum ID.
+ * Needs to be called from RCU read-side critical section.
+ */
+struct ust_registry_enum *
+	ust_registry_lookup_enum_by_id(struct ust_registry_session *session,
+		const char *enum_name, uint64_t enum_id)
+{
+	struct ust_registry_enum *reg_enum = NULL;
+	struct lttng_ht_node_str *node;
+	struct lttng_ht_iter iter;
+	struct ust_registry_enum reg_enum_lookup;
+
+	memset(&reg_enum_lookup, 0, sizeof(reg_enum_lookup));
+	strncpy(reg_enum_lookup.name, enum_name, LTTNG_UST_SYM_NAME_LEN);
+	reg_enum_lookup.name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
+	reg_enum_lookup.id = enum_id;
+	cds_lfht_lookup(session->enums->ht,
+			ht_hash_enum((void *) &reg_enum_lookup, lttng_ht_seed),
+			ht_match_enum_id, &reg_enum_lookup, &iter.iter);
+	node = lttng_ht_iter_get_node_str(&iter);
+	if (!node) {
+	        goto end;
+	}
+	reg_enum = caa_container_of(node, struct ust_registry_enum, node);
+end:
+	return reg_enum;
+}
 
-	/* Set custom match function. */
-	chan->ht->match_fct = ht_match_event;
+/*
+ * Create a ust_registry_enum from the given parameters and add it to the
+ * registry hash table, or find it if already there.
+ *
+ * On success, return 0 else a negative value.
+ *
+ * Should be called with session registry mutex held.
+ *
+ * We receive ownership of entries.
+ */
+int ust_registry_create_or_find_enum(struct ust_registry_session *session,
+		int session_objd, char *enum_name,
+		struct ustctl_enum_entry *entries, size_t nr_entries,
+		uint64_t *enum_id)
+{
+	int ret = 0;
+	struct cds_lfht_node *nodep;
+	struct ust_registry_enum *reg_enum = NULL, *old_reg_enum;
+
+	assert(session);
+	assert(enum_name);
+
+	rcu_read_lock();
+
+	/*
+	 * This should not happen but since it comes from the UST tracer, an
+	 * external party, don't assert and simply validate values.
+	 */
+	if (session_objd < 0) {
+		ret = -EINVAL;
+		goto end;
+	}
+
+	/* Check if the enumeration was already dumped */
+	reg_enum = zmalloc(sizeof(*reg_enum));
+	if (!reg_enum) {
+		PERROR("zmalloc ust registry enumeration");
+		ret = -ENOMEM;
+		goto end;
+	}
+	strncpy(reg_enum->name, enum_name, LTTNG_UST_SYM_NAME_LEN);
+	reg_enum->name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
+	/* entries will be owned by reg_enum. */
+	reg_enum->entries = entries;
+	reg_enum->nr_entries = nr_entries;
+	entries = NULL;
+
+	old_reg_enum = ust_registry_lookup_enum(session, reg_enum);
+	if (old_reg_enum) {
+		DBG("enum %s already in sess_objd: %u", enum_name, session_objd);
+		/* Fall through. Use prior enum. */
+		destroy_enum(reg_enum);
+		reg_enum = old_reg_enum;
+	} else {
+		DBG("UST registry creating enum: %s, sess_objd: %u",
+				enum_name, session_objd);
+		if (session->next_enum_id == -1ULL) {
+			ret = -EOVERFLOW;
+			destroy_enum(reg_enum);
+			goto end;
+		}
+		reg_enum->id = session->next_enum_id++;
+		cds_lfht_node_init(&reg_enum->node.node);
+		nodep = cds_lfht_add_unique(session->enums->ht,
+				ht_hash_enum(reg_enum, lttng_ht_seed),
+				ht_match_enum_id, reg_enum,
+				&reg_enum->node.node);
+		assert(nodep == &reg_enum->node.node);
+	}
+	DBG("UST registry reply with enum %s with id %" PRIu64 " in sess_objd: %u",
+			enum_name, reg_enum->id, session_objd);
+	*enum_id = reg_enum->id;
+end:
+	free(entries);
+	rcu_read_unlock();
+	return ret;
+}
+
+/*
+ * For a given enumeration in a registry, delete the entry and destroy
+ * the enumeration.
+ * This MUST be called within a RCU read side lock section.
+ */
+void ust_registry_destroy_enum(struct ust_registry_session *reg_session,
+		struct ust_registry_enum *reg_enum)
+{
+	int ret;
+	struct lttng_ht_iter iter;
+
+	assert(reg_session);
+	assert(reg_enum);
+
+	/* Delete the node first. */
+	iter.iter.node = &reg_enum->node.node;
+	ret = lttng_ht_del(reg_session->enums, &iter);
+	assert(!ret);
+	call_rcu(&reg_enum->rcu_head, destroy_enum_rcu);
+}
+
+/*
+ * We need to execute ht_destroy outside of RCU read-side critical
+ * section and outside of call_rcu thread, so we postpone its execution
+ * using ht_cleanup_push. It is simpler than to change the semantic of
+ * the many callers of delete_ust_app_session().
+ */
+static
+void destroy_channel_rcu(struct rcu_head *head)
+{
+	struct ust_registry_channel *chan =
+		caa_container_of(head, struct ust_registry_channel, rcu_head);
+
+	if (chan->ht) {
+		ht_cleanup_push(chan->ht);
+	}
+	free(chan->ctx_fields);
+	free(chan);
 }
 
 /*
  * Destroy every element of the registry and free the memory. This does NOT
  * free the registry pointer since it might not have been allocated before so
  * it's the caller responsability.
- *
- * This MUST be called within a RCU read side lock section.
  */
-void ust_registry_channel_destroy(struct ust_registry_session *session,
-		struct ust_registry_channel *chan)
+static void destroy_channel(struct ust_registry_channel *chan)
 {
 	struct lttng_ht_iter iter;
 	struct ust_registry_event *event;
 
 	assert(chan);
 
+	rcu_read_lock();
 	/* Destroy all event associated with this registry. */
 	cds_lfht_for_each_entry(chan->ht->ht, &iter.iter, event, node.node) {
 		/* Delete the node from the ht and free it. */
 		ust_registry_destroy_event(chan, event);
 	}
-	lttng_ht_destroy(chan->ht);
+	rcu_read_unlock();
+	call_rcu(&chan->rcu_head, destroy_channel_rcu);
 }
 
 /*
  * Initialize registry with default values.
  */
-int ust_registry_session_init(struct ust_registry_session *session,
+int ust_registry_channel_add(struct ust_registry_session *session,
+		uint64_t key)
+{
+	int ret = 0;
+	struct ust_registry_channel *chan;
+
+	assert(session);
+
+	chan = zmalloc(sizeof(*chan));
+	if (!chan) {
+		PERROR("zmalloc ust registry channel");
+		ret = -ENOMEM;
+		goto error_alloc;
+	}
+
+	chan->ht = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
+	if (!chan->ht) {
+		ret = -ENOMEM;
+		goto error;
+	}
+
+	/* Set custom match function. */
+	chan->ht->match_fct = ht_match_event;
+	chan->ht->hash_fct = ht_hash_event;
+
+	/*
+	 * Assign a channel ID right now since the event notification comes
+	 * *before* the channel notify so the ID needs to be set at this point so
+	 * the metadata can be dumped for that event.
+	 */
+	if (ust_registry_is_max_id(session->used_channel_id)) {
+		ret = -1;
+		goto error;
+	}
+	chan->chan_id = ust_registry_get_next_chan_id(session);
+
+	rcu_read_lock();
+	lttng_ht_node_init_u64(&chan->node, key);
+	lttng_ht_add_unique_u64(session->channels, &chan->node);
+	rcu_read_unlock();
+
+	return 0;
+
+error:
+	destroy_channel(chan);
+error_alloc:
+	return ret;
+}
+
+/*
+ * Find a channel in the given registry. RCU read side lock MUST be acquired
+ * before calling this function and as long as the event reference is kept by
+ * the caller.
+ *
+ * On success, the pointer is returned else NULL.
+ */
+struct ust_registry_channel *ust_registry_channel_find(
+		struct ust_registry_session *session, uint64_t key)
+{
+	struct lttng_ht_node_u64 *node;
+	struct lttng_ht_iter iter;
+	struct ust_registry_channel *chan = NULL;
+
+	assert(session);
+	assert(session->channels);
+
+	DBG3("UST registry channel finding key %" PRIu64, key);
+
+	lttng_ht_lookup(session->channels, &key, &iter);
+	node = lttng_ht_iter_get_node_u64(&iter);
+	if (!node) {
+		goto end;
+	}
+	chan = caa_container_of(node, struct ust_registry_channel, node);
+
+end:
+	return chan;
+}
+
+/*
+ * Remove channel using key from registry and free memory.
+ */
+void ust_registry_channel_del_free(struct ust_registry_session *session,
+		uint64_t key)
+{
+	struct lttng_ht_iter iter;
+	struct ust_registry_channel *chan;
+	int ret;
+
+	assert(session);
+
+	rcu_read_lock();
+	chan = ust_registry_channel_find(session, key);
+	if (!chan) {
+		rcu_read_unlock();
+		goto end;
+	}
+
+	iter.iter.node = &chan->node.node;
+	ret = lttng_ht_del(session->channels, &iter);
+	assert(!ret);
+	rcu_read_unlock();
+	destroy_channel(chan);
+
+end:
+	return;
+}
+
+/*
+ * Initialize registry with default values and set the newly allocated session
+ * pointer to sessionp.
+ *
+ * Return 0 on success and sessionp is set or else return -1 and sessionp is
+ * kept untouched.
+ */
+int ust_registry_session_init(struct ust_registry_session **sessionp,
 		struct ust_app *app,
 		uint32_t bits_per_long,
 		uint32_t uint8_t_alignment,
@@ -319,13 +829,24 @@ int ust_registry_session_init(struct ust_registry_session *session,
 		uint32_t uint32_t_alignment,
 		uint32_t uint64_t_alignment,
 		uint32_t long_alignment,
-		int byte_order)
+		int byte_order,
+		uint32_t major,
+		uint32_t minor,
+		const char *root_shm_path,
+		const char *shm_path,
+		uid_t euid,
+		gid_t egid)
 {
 	int ret;
+	struct ust_registry_session *session;
 
-	assert(session);
+	assert(sessionp);
 
-	memset(session, 0, sizeof(struct ust_registry_session));
+	session = zmalloc(sizeof(*session));
+	if (!session) {
+		PERROR("zmalloc ust registry session");
+		goto error_alloc;
+	}
 
 	pthread_mutex_init(&session->lock, NULL);
 	session->bits_per_long = bits_per_long;
@@ -335,6 +856,60 @@ int ust_registry_session_init(struct ust_registry_session *session,
 	session->uint64_t_alignment = uint64_t_alignment;
 	session->long_alignment = long_alignment;
 	session->byte_order = byte_order;
+	session->metadata_fd = -1;
+	session->uid = euid;
+	session->gid = egid;
+	session->next_enum_id = 0;
+	session->major = major;
+	session->minor = minor;
+	strncpy(session->root_shm_path, root_shm_path,
+		sizeof(session->root_shm_path));
+	session->root_shm_path[sizeof(session->root_shm_path) - 1] = '\0';
+	if (shm_path[0]) {
+		strncpy(session->shm_path, shm_path,
+			sizeof(session->shm_path));
+		session->shm_path[sizeof(session->shm_path) - 1] = '\0';
+		strncpy(session->metadata_path, shm_path,
+			sizeof(session->metadata_path));
+		session->metadata_path[sizeof(session->metadata_path) - 1] = '\0';
+		strncat(session->metadata_path, "/metadata",
+			sizeof(session->metadata_path)
+				- strlen(session->metadata_path) - 1);
+	}
+	if (session->shm_path[0]) {
+		ret = run_as_mkdir_recursive(session->shm_path,
+			S_IRWXU | S_IRWXG,
+			euid, egid);
+		if (ret) {
+			PERROR("run_as_mkdir_recursive");
+			goto error;
+		}
+	}
+	if (session->metadata_path[0]) {
+		/* Create metadata file */
+		ret = run_as_open(session->metadata_path,
+			O_WRONLY | O_CREAT | O_EXCL,
+			S_IRUSR | S_IWUSR, euid, egid);
+		if (ret < 0) {
+			PERROR("Opening metadata file");
+			goto error;
+		}
+		session->metadata_fd = ret;
+	}
+
+	session->enums = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
+	if (!session->enums) {
+		ret = -ENOMEM;
+		goto error;
+	}
+	/* hash/match functions are specified at call site. */
+	session->enums->match_fct = NULL;
+	session->enums->hash_fct = NULL;
+
+	session->channels = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
+	if (!session->channels) {
+		goto error;
+	}
 
 	ret = lttng_uuid_generate(session->uuid);
 	if (ret) {
@@ -343,16 +918,21 @@ int ust_registry_session_init(struct ust_registry_session *session,
 	}
 
 	pthread_mutex_lock(&session->lock);
-	ret = ust_metadata_session_statedump(session, app);
+	ret = ust_metadata_session_statedump(session, app, major, minor);
 	pthread_mutex_unlock(&session->lock);
 	if (ret) {
 		ERR("Failed to generate session metadata (errno = %d)", ret);
 		goto error;
 	}
 
+	*sessionp = session;
+
 	return 0;
 
 error:
+	ust_registry_session_destroy(session);
+	free(session);
+error_alloc:
 	return -1;
 }
 
@@ -363,10 +943,60 @@ error:
 void ust_registry_session_destroy(struct ust_registry_session *reg)
 {
 	int ret;
+	struct lttng_ht_iter iter;
+	struct ust_registry_channel *chan;
+	struct ust_registry_enum *reg_enum;
+
+	if (!reg) {
+		return;
+	}
 
 	/* On error, EBUSY can be returned if lock. Code flow error. */
 	ret = pthread_mutex_destroy(&reg->lock);
 	assert(!ret);
 
+	if (reg->channels) {
+		rcu_read_lock();
+		/* Destroy all event associated with this registry. */
+		cds_lfht_for_each_entry(reg->channels->ht, &iter.iter, chan,
+				node.node) {
+			/* Delete the node from the ht and free it. */
+			ret = lttng_ht_del(reg->channels, &iter);
+			assert(!ret);
+			destroy_channel(chan);
+		}
+		rcu_read_unlock();
+		ht_cleanup_push(reg->channels);
+	}
+
 	free(reg->metadata);
+	if (reg->metadata_fd >= 0) {
+		ret = close(reg->metadata_fd);
+		if (ret) {
+			PERROR("close");
+		}
+		ret = run_as_unlink(reg->metadata_path,
+				reg->uid, reg->gid);
+		if (ret) {
+			PERROR("unlink");
+		}
+	}
+	if (reg->root_shm_path[0]) {
+		/*
+		 * Try deleting the directory hierarchy.
+		 */
+		(void) run_as_recursive_rmdir(reg->root_shm_path,
+				reg->uid, reg->gid);
+	}
+	/* Destroy the enum hash table */
+	if (reg->enums) {
+		rcu_read_lock();
+		/* Destroy all enum entries associated with this registry. */
+		cds_lfht_for_each_entry(reg->enums->ht, &iter.iter, reg_enum,
+				node.node) {
+			ust_registry_destroy_enum(reg, reg_enum);
+		}
+		rcu_read_unlock();
+		ht_cleanup_push(reg->enums);
+	}
 }