Assert on unknown UST buffer type
[lttng-tools.git] / src / bin / lttng-sessiond / cmd.c
index 161680a6cdbda4ae27397efee2d6f4d694946083..aa030d3b1253f45a716cfa2386c8282c2173611a 100644 (file)
@@ -1,5 +1,6 @@
 /*
  * Copyright (C) 2012 - David Goulet <dgoulet@efficios.com>
+ * Copyright (C) 2016 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License, version 2 only, as
@@ -15,7 +16,7 @@
  * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#define _GNU_SOURCE
+#define _LGPL_SOURCE
 #include <assert.h>
 #include <inttypes.h>
 #include <urcu/list.h>
@@ -26,6 +27,8 @@
 #include <common/sessiond-comm/sessiond-comm.h>
 #include <common/relayd/relayd.h>
 #include <common/utils.h>
+#include <common/compat/string.h>
+#include <common/kernel-ctl/kernel-ctl.h>
 
 #include "channel.h"
 #include "consumer.h"
@@ -35,6 +38,9 @@
 #include "kernel-consumer.h"
 #include "lttng-sessiond.h"
 #include "utils.h"
+#include "syscall.h"
+#include "agent.h"
+#include "buffer-registry.h"
 
 #include "cmd.h"
 
 static pthread_mutex_t relayd_net_seq_idx_lock = PTHREAD_MUTEX_INITIALIZER;
 static uint64_t relayd_net_seq_idx;
 
+static int validate_event_name(const char *);
+static int validate_ust_event_name(const char *);
+static int cmd_enable_event_internal(struct ltt_session *session,
+               struct lttng_domain *domain,
+               char *channel_name, struct lttng_event *event,
+               char *filter_expression,
+               struct lttng_filter_bytecode *filter,
+               struct lttng_event_exclusion *exclusion,
+               int wpipe);
+
 /*
  * Create a session path used by list_lttng_sessions for the case that the
  * session consumer is on the network.
@@ -125,13 +141,98 @@ error:
        return ret;
 }
 
+/*
+ * Get run-time attributes if the session has been started (discarded events,
+ * lost packets).
+ */
+static int get_kernel_runtime_stats(struct ltt_session *session,
+               struct ltt_kernel_channel *kchan, uint64_t *discarded_events,
+               uint64_t *lost_packets)
+{
+       int ret;
+
+       if (!session->has_been_started) {
+               ret = 0;
+               *discarded_events = 0;
+               *lost_packets = 0;
+               goto end;
+       }
+
+       ret = consumer_get_discarded_events(session->id, kchan->fd,
+                       session->kernel_session->consumer,
+                       discarded_events);
+       if (ret < 0) {
+               goto end;
+       }
+
+       ret = consumer_get_lost_packets(session->id, kchan->fd,
+                       session->kernel_session->consumer,
+                       lost_packets);
+       if (ret < 0) {
+               goto end;
+       }
+
+end:
+       return ret;
+}
+
+/*
+ * Get run-time attributes if the session has been started (discarded events,
+ * lost packets).
+ */
+static int get_ust_runtime_stats(struct ltt_session *session,
+               struct ltt_ust_channel *uchan, uint64_t *discarded_events,
+               uint64_t *lost_packets)
+{
+       int ret;
+       struct ltt_ust_session *usess;
+
+       usess = session->ust_session;
+
+       if (!usess || !session->has_been_started) {
+               *discarded_events = 0;
+               *lost_packets = 0;
+               ret = 0;
+               goto end;
+       }
+
+       if (usess->buffer_type == LTTNG_BUFFER_PER_UID) {
+               ret = ust_app_uid_get_channel_runtime_stats(usess->id,
+                               &usess->buffer_reg_uid_list,
+                               usess->consumer, uchan->id,
+                               uchan->attr.overwrite,
+                               discarded_events,
+                               lost_packets);
+       } else if (usess->buffer_type == LTTNG_BUFFER_PER_PID) {
+               ret = ust_app_pid_get_channel_runtime_stats(usess,
+                               uchan, usess->consumer,
+                               uchan->attr.overwrite,
+                               discarded_events,
+                               lost_packets);
+               if (ret < 0) {
+                       goto end;
+               }
+               *discarded_events += uchan->per_pid_closed_app_discarded;
+               *lost_packets += uchan->per_pid_closed_app_lost;
+       } else {
+               ERR("Unsupported buffer type");
+               assert(0);
+               ret = -1;
+               goto end;
+       }
+
+end:
+       return ret;
+}
+
 /*
  * Fill lttng_channel array of all channels.
  */
-static void list_lttng_channels(int domain, struct ltt_session *session,
-               struct lttng_channel *channels)
+static void list_lttng_channels(enum lttng_domain_type domain,
+               struct ltt_session *session, struct lttng_channel *channels,
+               struct lttcomm_channel_extended *chan_exts)
 {
-       int i = 0;
+       int i = 0, ret;
        struct ltt_kernel_channel *kchan;
 
        DBG("Listing channels for session %s", session->name);
@@ -142,9 +243,19 @@ static void list_lttng_channels(int domain, struct ltt_session *session,
                if (session->kernel_session != NULL) {
                        cds_list_for_each_entry(kchan,
                                        &session->kernel_session->channel_list.head, list) {
+                               uint64_t discarded_events, lost_packets;
+
+                               ret = get_kernel_runtime_stats(session, kchan,
+                                               &discarded_events, &lost_packets);
+                               if (ret < 0) {
+                                       goto end;
+                               }
                                /* Copy lttng_channel struct to array */
                                memcpy(&channels[i], kchan->channel, sizeof(struct lttng_channel));
                                channels[i].enabled = kchan->enabled;
+                               chan_exts[i].discarded_events =
+                                               discarded_events;
+                               chan_exts[i].lost_packets = lost_packets;
                                i++;
                        }
                }
@@ -157,6 +268,8 @@ static void list_lttng_channels(int domain, struct ltt_session *session,
                rcu_read_lock();
                cds_lfht_for_each_entry(session->ust_session->domain_global.channels->ht,
                                &iter.iter, uchan, node.node) {
+                       uint64_t discarded_events, lost_packets;
+
                        strncpy(channels[i].name, uchan->name, LTTNG_SYMBOL_NAME_LEN);
                        channels[i].attr.overwrite = uchan->attr.overwrite;
                        channels[i].attr.subbuf_size = uchan->attr.subbuf_size;
@@ -166,12 +279,32 @@ static void list_lttng_channels(int domain, struct ltt_session *session,
                        channels[i].attr.read_timer_interval =
                                uchan->attr.read_timer_interval;
                        channels[i].enabled = uchan->enabled;
+                       channels[i].attr.tracefile_size = uchan->tracefile_size;
+                       channels[i].attr.tracefile_count = uchan->tracefile_count;
+
+                       /*
+                        * Map enum lttng_ust_output to enum lttng_event_output.
+                        */
                        switch (uchan->attr.output) {
                        case LTTNG_UST_MMAP:
-                       default:
                                channels[i].attr.output = LTTNG_EVENT_MMAP;
                                break;
+                       default:
+                               /*
+                                * LTTNG_UST_MMAP is the only supported UST
+                                * output mode.
+                                */
+                               assert(0);
+                               break;
+                       }
+
+                       ret = get_ust_runtime_stats(session, uchan,
+                                       &discarded_events, &lost_packets);
+                       if (ret < 0) {
+                               break;
                        }
+                       chan_exts[i].discarded_events = discarded_events;
+                       chan_exts[i].lost_packets = lost_packets;
                        i++;
                }
                rcu_read_unlock();
@@ -180,46 +313,130 @@ static void list_lttng_channels(int domain, struct ltt_session *session,
        default:
                break;
        }
+
+end:
+       return;
+}
+
+static void increment_extended_len(const char *filter_expression,
+               struct lttng_event_exclusion *exclusion, size_t *extended_len)
+{
+       *extended_len += sizeof(struct lttcomm_event_extended_header);
+
+       if (filter_expression) {
+               *extended_len += strlen(filter_expression) + 1;
+       }
+
+       if (exclusion) {
+               *extended_len += exclusion->count * LTTNG_SYMBOL_NAME_LEN;
+       }
+}
+
+static void append_extended_info(const char *filter_expression,
+               struct lttng_event_exclusion *exclusion, void **extended_at)
+{
+       struct lttcomm_event_extended_header extended_header;
+       size_t filter_len = 0;
+       size_t nb_exclusions = 0;
+
+       if (filter_expression) {
+               filter_len = strlen(filter_expression) + 1;
+       }
+
+       if (exclusion) {
+               nb_exclusions = exclusion->count;
+       }
+
+       /* Set header fields */
+       extended_header.filter_len = filter_len;
+       extended_header.nb_exclusions = nb_exclusions;
+
+       /* Copy header */
+       memcpy(*extended_at, &extended_header, sizeof(extended_header));
+       *extended_at += sizeof(extended_header);
+
+       /* Copy filter string */
+       if (filter_expression) {
+               memcpy(*extended_at, filter_expression, filter_len);
+               *extended_at += filter_len;
+       }
+
+       /* Copy exclusion names */
+       if (exclusion) {
+               size_t len = nb_exclusions * LTTNG_SYMBOL_NAME_LEN;
+
+               memcpy(*extended_at, &exclusion->names, len);
+               *extended_at += len;
+       }
 }
 
 /*
- * Create a list of JUL domain events.
+ * Create a list of agent domain events.
  *
  * Return number of events in list on success or else a negative value.
  */
-static int list_lttng_jul_events(struct jul_domain *dom,
-               struct lttng_event **events)
+static int list_lttng_agent_events(struct agent *agt,
+               struct lttng_event **events, size_t *total_size)
 {
        int i = 0, ret = 0;
        unsigned int nb_event = 0;
-       struct jul_event *event;
+       struct agent_event *event;
        struct lttng_event *tmp_events;
        struct lttng_ht_iter iter;
+       size_t extended_len = 0;
+       void *extended_at;
 
-       assert(dom);
+       assert(agt);
        assert(events);
 
-       DBG3("Listing JUL events");
+       DBG3("Listing agent events");
 
-       nb_event = lttng_ht_get_count(dom->events);
+       rcu_read_lock();
+       nb_event = lttng_ht_get_count(agt->events);
+       rcu_read_unlock();
        if (nb_event == 0) {
                ret = nb_event;
+               *total_size = 0;
                goto error;
        }
 
-       tmp_events = zmalloc(nb_event * sizeof(*tmp_events));
+       /* Compute required extended infos size */
+       extended_len = nb_event * sizeof(struct lttcomm_event_extended_header);
+
+       /*
+        * This is only valid because the commands which add events are
+        * processed in the same thread as the listing.
+        */
+       rcu_read_lock();
+       cds_lfht_for_each_entry(agt->events->ht, &iter.iter, event, node.node) {
+               increment_extended_len(event->filter_expression, NULL,
+                               &extended_len);
+       }
+       rcu_read_unlock();
+
+       *total_size = nb_event * sizeof(*tmp_events) + extended_len;
+       tmp_events = zmalloc(*total_size);
        if (!tmp_events) {
-               PERROR("zmalloc JUL events session");
+               PERROR("zmalloc agent events session");
                ret = -LTTNG_ERR_FATAL;
                goto error;
        }
 
+       extended_at = ((uint8_t *) tmp_events) +
+               nb_event * sizeof(struct lttng_event);
+
        rcu_read_lock();
-       cds_lfht_for_each_entry(dom->events->ht, &iter.iter, event, node.node) {
+       cds_lfht_for_each_entry(agt->events->ht, &iter.iter, event, node.node) {
                strncpy(tmp_events[i].name, event->name, sizeof(tmp_events[i].name));
                tmp_events[i].name[sizeof(tmp_events[i].name) - 1] = '\0';
                tmp_events[i].enabled = event->enabled;
+               tmp_events[i].loglevel = event->loglevel_value;
+               tmp_events[i].loglevel_type = event->loglevel_type;
                i++;
+
+               /* Append extended info */
+               append_extended_info(event->filter_expression, NULL,
+                               &extended_at);
        }
        rcu_read_unlock();
 
@@ -235,7 +452,8 @@ error:
  * Create a list of ust global domain events.
  */
 static int list_lttng_ust_global_events(char *channel_name,
-               struct ltt_ust_domain_global *ust_global, struct lttng_event **events)
+               struct ltt_ust_domain_global *ust_global,
+               struct lttng_event **events, size_t *total_size)
 {
        int i = 0, ret = 0;
        unsigned int nb_event = 0;
@@ -244,6 +462,8 @@ static int list_lttng_ust_global_events(char *channel_name,
        struct ltt_ust_channel *uchan;
        struct ltt_ust_event *uevent;
        struct lttng_event *tmp;
+       size_t extended_len = 0;
+       void *extended_at;
 
        DBG("Listing UST global events for channel %s", channel_name);
 
@@ -253,27 +473,51 @@ static int list_lttng_ust_global_events(char *channel_name,
        node = lttng_ht_iter_get_node_str(&iter);
        if (node == NULL) {
                ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
-               goto error;
+               goto end;
        }
 
        uchan = caa_container_of(&node->node, struct ltt_ust_channel, node.node);
 
-       nb_event += lttng_ht_get_count(uchan->events);
-
+       nb_event = lttng_ht_get_count(uchan->events);
        if (nb_event == 0) {
                ret = nb_event;
-               goto error;
+               *total_size = 0;
+               goto end;
        }
 
        DBG3("Listing UST global %d events", nb_event);
 
-       tmp = zmalloc(nb_event * sizeof(struct lttng_event));
+       /* Compute required extended infos size */
+       cds_lfht_for_each_entry(uchan->events->ht, &iter.iter, uevent, node.node) {
+               if (uevent->internal) {
+                       nb_event--;
+                       continue;
+               }
+
+               increment_extended_len(uevent->filter_expression,
+                       uevent->exclusion, &extended_len);
+       }
+       if (nb_event == 0) {
+               /* All events are internal, skip. */
+               ret = 0;
+               *total_size = 0;
+               goto end;
+       }
+
+       *total_size = nb_event * sizeof(struct lttng_event) + extended_len;
+       tmp = zmalloc(*total_size);
        if (tmp == NULL) {
-               ret = LTTNG_ERR_FATAL;
-               goto error;
+               ret = -LTTNG_ERR_FATAL;
+               goto end;
        }
 
+       extended_at = ((uint8_t *) tmp) + nb_event * sizeof(struct lttng_event);
+
        cds_lfht_for_each_entry(uchan->events->ht, &iter.iter, uevent, node.node) {
+               if (uevent->internal) {
+                       /* This event should remain hidden from clients */
+                       continue;
+               }
                strncpy(tmp[i].name, uevent->attr.name, LTTNG_SYMBOL_NAME_LEN);
                tmp[i].name[LTTNG_SYMBOL_NAME_LEN - 1] = '\0';
                tmp[i].enabled = uevent->enabled;
@@ -309,12 +553,15 @@ static int list_lttng_ust_global_events(char *channel_name,
                        tmp[i].exclusion = 1;
                }
                i++;
+
+               /* Append extended info */
+               append_extended_info(uevent->filter_expression,
+                       uevent->exclusion, &extended_at);
        }
 
        ret = nb_event;
        *events = tmp;
-
-error:
+end:
        rcu_read_unlock();
        return ret;
 }
@@ -323,12 +570,15 @@ error:
  * Fill lttng_event array of all kernel events in the channel.
  */
 static int list_lttng_kernel_events(char *channel_name,
-               struct ltt_kernel_session *kernel_session, struct lttng_event **events)
+               struct ltt_kernel_session *kernel_session,
+               struct lttng_event **events, size_t *total_size)
 {
        int i = 0, ret;
        unsigned int nb_event;
        struct ltt_kernel_event *event;
        struct ltt_kernel_channel *kchan;
+       size_t extended_len = 0;
+       void *extended_at;
 
        kchan = trace_kernel_get_channel_by_name(channel_name, kernel_session);
        if (kchan == NULL) {
@@ -341,20 +591,34 @@ static int list_lttng_kernel_events(char *channel_name,
        DBG("Listing events for channel %s", kchan->channel->name);
 
        if (nb_event == 0) {
+               *total_size = 0;
+               *events = NULL;
                goto end;
        }
 
-       *events = zmalloc(nb_event * sizeof(struct lttng_event));
+       /* Compute required extended infos size */
+       cds_list_for_each_entry(event, &kchan->events_list.head, list) {
+               increment_extended_len(event->filter_expression, NULL,
+                       &extended_len);
+       }
+
+       *total_size = nb_event * sizeof(struct lttng_event) + extended_len;
+       *events = zmalloc(*total_size);
        if (*events == NULL) {
                ret = LTTNG_ERR_FATAL;
                goto error;
        }
 
+       extended_at = ((void *) *events) +
+               nb_event * sizeof(struct lttng_event);
+
        /* Kernel channels */
        cds_list_for_each_entry(event, &kchan->events_list.head , list) {
                strncpy((*events)[i].name, event->event->name, LTTNG_SYMBOL_NAME_LEN);
                (*events)[i].name[LTTNG_SYMBOL_NAME_LEN - 1] = '\0';
                (*events)[i].enabled = event->enabled;
+               (*events)[i].filter =
+                               (unsigned char) !!event->filter_expression;
 
                switch (event->event->instrumentation) {
                case LTTNG_KERNEL_TRACEPOINT:
@@ -386,6 +650,10 @@ static int list_lttng_kernel_events(char *channel_name,
                        break;
                }
                i++;
+
+               /* Append extended info */
+               append_extended_info(event->filter_expression, NULL,
+                       &extended_at);
        }
 
 end:
@@ -401,7 +669,8 @@ error:
  * domain adding the default trace directory.
  */
 static int add_uri_to_consumer(struct consumer_output *consumer,
-               struct lttng_uri *uri, int domain, const char *session_name)
+               struct lttng_uri *uri, enum lttng_domain_type domain,
+               const char *session_name)
 {
        int ret = LTTNG_OK;
        const char *default_trace_dir;
@@ -537,7 +806,8 @@ error:
  * Else, it's stays untouched and a lttcomm error code is returned.
  */
 static int create_connect_relayd(struct lttng_uri *uri,
-               struct lttcomm_relayd_sock **relayd_sock)
+               struct lttcomm_relayd_sock **relayd_sock,
+               struct consumer_output *consumer)
 {
        int ret;
        struct lttcomm_relayd_sock *rsock;
@@ -573,6 +843,8 @@ static int create_connect_relayd(struct lttng_uri *uri,
                        ret = LTTNG_ERR_RELAYD_VERSION_FAIL;
                        goto close_sock;
                }
+               consumer->relay_major_version = rsock->major;
+               consumer->relay_minor_version = rsock->minor;
        } else if (uri->stype == LTTNG_STREAM_DATA) {
                DBG3("Creating relayd data socket from URI");
        } else {
@@ -598,8 +870,9 @@ error:
 /*
  * Connect to the relayd using URI and send the socket to the right consumer.
  */
-static int send_consumer_relayd_socket(int domain, unsigned int session_id,
-               struct lttng_uri *relayd_uri, struct consumer_output *consumer,
+static int send_consumer_relayd_socket(enum lttng_domain_type domain,
+               unsigned int session_id, struct lttng_uri *relayd_uri,
+               struct consumer_output *consumer,
                struct consumer_socket *consumer_sock,
                char *session_name, char *hostname, int session_live_timer)
 {
@@ -607,7 +880,7 @@ static int send_consumer_relayd_socket(int domain, unsigned int session_id,
        struct lttcomm_relayd_sock *rsock = NULL;
 
        /* Connect to relayd and make version check if uri is the control. */
-       ret = create_connect_relayd(relayd_uri, &rsock);
+       ret = create_connect_relayd(relayd_uri, &rsock, consumer);
        if (ret != LTTNG_OK) {
                goto error;
        }
@@ -669,9 +942,10 @@ error:
  * helper function to facilitate sending the information to the consumer for a
  * session.
  */
-static int send_consumer_relayd_sockets(int domain, unsigned int session_id,
-               struct consumer_output *consumer, struct consumer_socket *sock,
-               char *session_name, char *hostname, int session_live_timer)
+static int send_consumer_relayd_sockets(enum lttng_domain_type domain,
+               unsigned int session_id, struct consumer_output *consumer,
+               struct consumer_socket *sock, char *session_name,
+               char *hostname, int session_live_timer)
 {
        int ret = LTTNG_OK;
 
@@ -741,6 +1015,10 @@ int cmd_setup_relayd(struct ltt_session *session)
                        /* Session is now ready for network streaming. */
                        session->net_handle = 1;
                }
+               session->consumer->relay_major_version =
+                       usess->consumer->relay_major_version;
+               session->consumer->relay_minor_version =
+                       usess->consumer->relay_minor_version;
        }
 
        if (ksess && ksess->consumer && ksess->consumer->type == CONSUMER_DST_NET
@@ -759,6 +1037,10 @@ int cmd_setup_relayd(struct ltt_session *session)
                        /* Session is now ready for network streaming. */
                        session->net_handle = 1;
                }
+               session->consumer->relay_major_version =
+                       ksess->consumer->relay_major_version;
+               session->consumer->relay_minor_version =
+                       ksess->consumer->relay_minor_version;
        }
 
 error:
@@ -823,7 +1105,7 @@ static int start_kernel_session(struct ltt_kernel_session *ksess, int wpipe)
        /* Quiescent wait after starting trace */
        kernel_wait_quiescent(kernel_tracer_fd);
 
-       ksess->started = 1;
+       ksess->active = 1;
 
        ret = LTTNG_OK;
 
@@ -834,8 +1116,8 @@ error:
 /*
  * Command LTTNG_DISABLE_CHANNEL processed by the client thread.
  */
-int cmd_disable_channel(struct ltt_session *session, int domain,
-               char *channel_name)
+int cmd_disable_channel(struct ltt_session *session,
+               enum lttng_domain_type domain, char *channel_name)
 {
        int ret;
        struct ltt_ust_session *usess;
@@ -875,11 +1157,108 @@ int cmd_disable_channel(struct ltt_session *session, int domain,
                }
                break;
        }
-#if 0
-       case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
-       case LTTNG_DOMAIN_UST_EXEC_NAME:
-       case LTTNG_DOMAIN_UST_PID:
-#endif
+       default:
+               ret = LTTNG_ERR_UNKNOWN_DOMAIN;
+               goto error;
+       }
+
+       ret = LTTNG_OK;
+
+error:
+       rcu_read_unlock();
+       return ret;
+}
+
+/*
+ * Command LTTNG_TRACK_PID processed by the client thread.
+ *
+ * Called with session lock held.
+ */
+int cmd_track_pid(struct ltt_session *session, enum lttng_domain_type domain,
+               int pid)
+{
+       int ret;
+
+       rcu_read_lock();
+
+       switch (domain) {
+       case LTTNG_DOMAIN_KERNEL:
+       {
+               struct ltt_kernel_session *ksess;
+
+               ksess = session->kernel_session;
+
+               ret = kernel_track_pid(ksess, pid);
+               if (ret != LTTNG_OK) {
+                       goto error;
+               }
+
+               kernel_wait_quiescent(kernel_tracer_fd);
+               break;
+       }
+       case LTTNG_DOMAIN_UST:
+       {
+               struct ltt_ust_session *usess;
+
+               usess = session->ust_session;
+
+               ret = trace_ust_track_pid(usess, pid);
+               if (ret != LTTNG_OK) {
+                       goto error;
+               }
+               break;
+       }
+       default:
+               ret = LTTNG_ERR_UNKNOWN_DOMAIN;
+               goto error;
+       }
+
+       ret = LTTNG_OK;
+
+error:
+       rcu_read_unlock();
+       return ret;
+}
+
+/*
+ * Command LTTNG_UNTRACK_PID processed by the client thread.
+ *
+ * Called with session lock held.
+ */
+int cmd_untrack_pid(struct ltt_session *session, enum lttng_domain_type domain,
+               int pid)
+{
+       int ret;
+
+       rcu_read_lock();
+
+       switch (domain) {
+       case LTTNG_DOMAIN_KERNEL:
+       {
+               struct ltt_kernel_session *ksess;
+
+               ksess = session->kernel_session;
+
+               ret = kernel_untrack_pid(ksess, pid);
+               if (ret != LTTNG_OK) {
+                       goto error;
+               }
+
+               kernel_wait_quiescent(kernel_tracer_fd);
+               break;
+       }
+       case LTTNG_DOMAIN_UST:
+       {
+               struct ltt_ust_session *usess;
+
+               usess = session->ust_session;
+
+               ret = trace_ust_untrack_pid(usess, pid);
+               if (ret != LTTNG_OK) {
+                       goto error;
+               }
+               break;
+       }
        default:
                ret = LTTNG_ERR_UNKNOWN_DOMAIN;
                goto error;
@@ -903,11 +1282,21 @@ int cmd_enable_channel(struct ltt_session *session,
        int ret;
        struct ltt_ust_session *usess = session->ust_session;
        struct lttng_ht *chan_ht;
+       size_t len;
 
        assert(session);
        assert(attr);
        assert(domain);
 
+       len = lttng_strnlen(attr->name, sizeof(attr->name));
+
+       /* Validate channel name */
+       if (attr->name[0] == '.' ||
+               memchr(attr->name, '/', len) != NULL) {
+               ret = LTTNG_ERR_INVALID_CHANNEL_NAME;
+               goto end;
+       }
+
        DBG("Enabling channel %s for session %s", attr->name, session->name);
 
        rcu_read_lock();
@@ -931,6 +1320,16 @@ int cmd_enable_channel(struct ltt_session *session,
                attr->attr.switch_timer_interval = 0;
        }
 
+       /*
+        * The ringbuffer (both in user space and kernel) behave badly in overwrite
+        * mode and with less than 2 subbuf so block it right away and send back an
+        * invalid attribute error.
+        */
+       if (attr->attr.overwrite && attr->attr.num_subbuf < 2) {
+               ret = LTTNG_ERR_INVALID;
+               goto error;
+       }
+
        switch (domain->type) {
        case LTTNG_DOMAIN_KERNEL:
        {
@@ -955,9 +1354,40 @@ int cmd_enable_channel(struct ltt_session *session,
                break;
        }
        case LTTNG_DOMAIN_UST:
+       case LTTNG_DOMAIN_JUL:
+       case LTTNG_DOMAIN_LOG4J:
+       case LTTNG_DOMAIN_PYTHON:
        {
                struct ltt_ust_channel *uchan;
 
+               /*
+                * FIXME
+                *
+                * Current agent implementation limitations force us to allow
+                * only one channel at once in "agent" subdomains. Each
+                * subdomain has a default channel name which must be strictly
+                * adhered to.
+                */
+               if (domain->type == LTTNG_DOMAIN_JUL) {
+                       if (strncmp(attr->name, DEFAULT_JUL_CHANNEL_NAME,
+                                       LTTNG_SYMBOL_NAME_LEN)) {
+                               ret = LTTNG_ERR_INVALID_CHANNEL_NAME;
+                               goto error;
+                       }
+               } else if (domain->type == LTTNG_DOMAIN_LOG4J) {
+                       if (strncmp(attr->name, DEFAULT_LOG4J_CHANNEL_NAME,
+                                       LTTNG_SYMBOL_NAME_LEN)) {
+                               ret = LTTNG_ERR_INVALID_CHANNEL_NAME;
+                               goto error;
+                       }
+               } else if (domain->type == LTTNG_DOMAIN_PYTHON) {
+                       if (strncmp(attr->name, DEFAULT_PYTHON_CHANNEL_NAME,
+                                       LTTNG_SYMBOL_NAME_LEN)) {
+                               ret = LTTNG_ERR_INVALID_CHANNEL_NAME;
+                               goto error;
+                       }
+               }
+
                chan_ht = usess->domain_global.channels;
 
                uchan = trace_ust_find_channel_by_name(chan_ht, attr->name);
@@ -978,17 +1408,34 @@ int cmd_enable_channel(struct ltt_session *session,
 
 error:
        rcu_read_unlock();
+end:
        return ret;
 }
 
-
 /*
  * Command LTTNG_DISABLE_EVENT processed by the client thread.
  */
-int cmd_disable_event(struct ltt_session *session, int domain,
-               char *channel_name, char *event_name)
+int cmd_disable_event(struct ltt_session *session,
+               enum lttng_domain_type domain, char *channel_name,
+               struct lttng_event *event)
 {
        int ret;
+       char *event_name;
+
+       DBG("Disable event command for event \'%s\'", event->name);
+
+       event_name = event->name;
+       if (validate_event_name(event_name)) {
+               ret = LTTNG_ERR_INVALID_EVENT_NAME;
+               goto error;
+       }
+
+       /* Error out on unhandled search criteria */
+       if (event->loglevel_type || event->loglevel != -1 || event->enabled
+                       || event->pid || event->filter || event->exclusion) {
+               ret = LTTNG_ERR_UNK;
+               goto error;
+       }
 
        rcu_read_lock();
 
@@ -1007,18 +1454,36 @@ int cmd_disable_event(struct ltt_session *session, int domain,
                 */
                if (ksess->has_non_default_channel && channel_name[0] == '\0') {
                        ret = LTTNG_ERR_NEED_CHANNEL_NAME;
-                       goto error;
+                       goto error_unlock;
                }
 
                kchan = trace_kernel_get_channel_by_name(channel_name, ksess);
                if (kchan == NULL) {
                        ret = LTTNG_ERR_KERN_CHAN_NOT_FOUND;
-                       goto error;
+                       goto error_unlock;
                }
 
-               ret = event_kernel_disable_tracepoint(kchan, event_name);
-               if (ret != LTTNG_OK) {
-                       goto error;
+               switch (event->type) {
+               case LTTNG_EVENT_ALL:
+               case LTTNG_EVENT_TRACEPOINT:
+               case LTTNG_EVENT_SYSCALL:
+               case LTTNG_EVENT_PROBE:
+               case LTTNG_EVENT_FUNCTION:
+               case LTTNG_EVENT_FUNCTION_ENTRY:/* fall-through */
+                       if (event_name[0] == '\0') {
+                               ret = event_kernel_disable_event(kchan,
+                                       NULL, event->type);
+                       } else {
+                               ret = event_kernel_disable_event(kchan,
+                                       event_name, event->type);
+                       }
+                       if (ret != LTTNG_OK) {
+                               goto error_unlock;
+                       }
+                       break;
+               default:
+                       ret = LTTNG_ERR_UNK;
+                       goto error_unlock;
                }
 
                kernel_wait_quiescent(kernel_tracer_fd);
@@ -1031,174 +1496,116 @@ int cmd_disable_event(struct ltt_session *session, int domain,
 
                usess = session->ust_session;
 
+               if (validate_ust_event_name(event_name)) {
+                       ret = LTTNG_ERR_INVALID_EVENT_NAME;
+                       goto error_unlock;
+               }
+
                /*
                 * If a non-default channel has been created in the
-                * session, explicitely require that -c chan_name needs
+                * session, explicitly require that -c chan_name needs
                 * to be provided.
                 */
                if (usess->has_non_default_channel && channel_name[0] == '\0') {
                        ret = LTTNG_ERR_NEED_CHANNEL_NAME;
-                       goto error;
+                       goto error_unlock;
                }
 
                uchan = trace_ust_find_channel_by_name(usess->domain_global.channels,
                                channel_name);
                if (uchan == NULL) {
                        ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
-                       goto error;
+                       goto error_unlock;
                }
 
-               ret = event_ust_disable_tracepoint(usess, uchan, event_name);
-               if (ret != LTTNG_OK) {
-                       goto error;
+               switch (event->type) {
+               case LTTNG_EVENT_ALL:
+                       /*
+                        * An empty event name means that everything
+                        * should be disabled.
+                        */
+                       if (event->name[0] == '\0') {
+                               ret = event_ust_disable_all_tracepoints(usess, uchan);
+                       } else {
+                               ret = event_ust_disable_tracepoint(usess, uchan,
+                                               event_name);
+                       }
+                       if (ret != LTTNG_OK) {
+                               goto error_unlock;
+                       }
+                       break;
+               default:
+                       ret = LTTNG_ERR_UNK;
+                       goto error_unlock;
                }
 
                DBG3("Disable UST event %s in channel %s completed", event_name,
                                channel_name);
                break;
        }
+       case LTTNG_DOMAIN_LOG4J:
        case LTTNG_DOMAIN_JUL:
+       case LTTNG_DOMAIN_PYTHON:
        {
+               struct agent *agt;
                struct ltt_ust_session *usess = session->ust_session;
 
                assert(usess);
 
-               ret = event_jul_disable(usess, event_name);
-               if (ret != LTTNG_OK) {
-                       goto error;
-               }
-
-               break;
-       }
-#if 0
-       case LTTNG_DOMAIN_UST_EXEC_NAME:
-       case LTTNG_DOMAIN_UST_PID:
-       case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
-#endif
-       default:
-               ret = LTTNG_ERR_UND;
-               goto error;
-       }
-
-       ret = LTTNG_OK;
-
-error:
-       rcu_read_unlock();
-       return ret;
-}
-
-/*
- * Command LTTNG_DISABLE_ALL_EVENT processed by the client thread.
- */
-int cmd_disable_event_all(struct ltt_session *session, int domain,
-               char *channel_name)
-{
-       int ret;
-
-       rcu_read_lock();
-
-       switch (domain) {
-       case LTTNG_DOMAIN_KERNEL:
-       {
-               struct ltt_kernel_session *ksess;
-               struct ltt_kernel_channel *kchan;
-
-               ksess = session->kernel_session;
-
-               /*
-                * If a non-default channel has been created in the
-                * session, explicitely require that -c chan_name needs
-                * to be provided.
-                */
-               if (ksess->has_non_default_channel && channel_name[0] == '\0') {
-                       ret = LTTNG_ERR_NEED_CHANNEL_NAME;
-                       goto error;
-               }
-
-               kchan = trace_kernel_get_channel_by_name(channel_name, ksess);
-               if (kchan == NULL) {
-                       ret = LTTNG_ERR_KERN_CHAN_NOT_FOUND;
-                       goto error;
+               switch (event->type) {
+               case LTTNG_EVENT_ALL:
+                       break;
+               default:
+                       ret = LTTNG_ERR_UNK;
+                       goto error_unlock;
                }
 
-               ret = event_kernel_disable_all(kchan);
-               if (ret != LTTNG_OK) {
-                       goto error;
+               agt = trace_ust_find_agent(usess, domain);
+               if (!agt) {
+                       ret = -LTTNG_ERR_UST_EVENT_NOT_FOUND;
+                       goto error_unlock;
                }
-
-               kernel_wait_quiescent(kernel_tracer_fd);
-               break;
-       }
-       case LTTNG_DOMAIN_UST:
-       {
-               struct ltt_ust_session *usess;
-               struct ltt_ust_channel *uchan;
-
-               usess = session->ust_session;
-
                /*
-                * If a non-default channel has been created in the
-                * session, explicitely require that -c chan_name needs
-                * to be provided.
+                * An empty event name means that everything
+                * should be disabled.
                 */
-               if (usess->has_non_default_channel && channel_name[0] == '\0') {
-                       ret = LTTNG_ERR_NEED_CHANNEL_NAME;
-                       goto error;
-               }
-
-               uchan = trace_ust_find_channel_by_name(usess->domain_global.channels,
-                               channel_name);
-               if (uchan == NULL) {
-                       ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
-                       goto error;
-               }
-
-               ret = event_ust_disable_all_tracepoints(usess, uchan);
-               if (ret != 0) {
-                       goto error;
+               if (event->name[0] == '\0') {
+                       ret = event_agent_disable_all(usess, agt);
+               } else {
+                       ret = event_agent_disable(usess, agt, event_name);
                }
-
-               DBG3("Disable all UST events in channel %s completed", channel_name);
-
-               break;
-       }
-       case LTTNG_DOMAIN_JUL:
-       {
-               struct ltt_ust_session *usess = session->ust_session;
-
-               assert(usess);
-
-               ret = event_jul_disable_all(usess);
                if (ret != LTTNG_OK) {
-                       goto error;
+                       goto error_unlock;
                }
 
                break;
        }
-#if 0
-       case LTTNG_DOMAIN_UST_EXEC_NAME:
-       case LTTNG_DOMAIN_UST_PID:
-       case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
-#endif
        default:
                ret = LTTNG_ERR_UND;
-               goto error;
+               goto error_unlock;
        }
 
        ret = LTTNG_OK;
 
-error:
+error_unlock:
        rcu_read_unlock();
+error:
        return ret;
 }
 
 /*
  * Command LTTNG_ADD_CONTEXT processed by the client thread.
  */
-int cmd_add_context(struct ltt_session *session, int domain,
+int cmd_add_context(struct ltt_session *session, enum lttng_domain_type domain,
                char *channel_name, struct lttng_event_context *ctx, int kwpipe)
 {
        int ret, chan_kern_created = 0, chan_ust_created = 0;
+       char *app_ctx_provider_name = NULL, *app_ctx_name = NULL;
+
+       if (ctx->ctx == LTTNG_EVENT_CONTEXT_APP_CONTEXT) {
+               app_ctx_provider_name = ctx->u.app_ctx.provider_name;
+               app_ctx_name = ctx->u.app_ctx.ctx_name;
+       }
 
        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
@@ -1218,6 +1625,29 @@ int cmd_add_context(struct ltt_session *session, int domain,
                        goto error;
                }
                break;
+       case LTTNG_DOMAIN_JUL:
+       case LTTNG_DOMAIN_LOG4J:
+       {
+               /*
+                * Validate channel name.
+                * If no channel name is given and the domain is JUL or LOG4J,
+                * set it to the appropriate domain-specific channel name. If
+                * a name is provided but does not match the expexted channel
+                * name, return an error.
+                */
+               if (domain == LTTNG_DOMAIN_JUL && *channel_name &&
+                               strcmp(channel_name,
+                               DEFAULT_JUL_CHANNEL_NAME)) {
+                       ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
+                       goto error;
+               } else if (domain == LTTNG_DOMAIN_LOG4J && *channel_name &&
+                               strcmp(channel_name,
+                               DEFAULT_LOG4J_CHANNEL_NAME)) {
+                       ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
+                       goto error;
+               }
+               /* break is _not_ missing here. */
+       }
        case LTTNG_DOMAIN_UST:
        {
                struct ltt_ust_session *usess = session->ust_session;
@@ -1245,22 +1675,22 @@ int cmd_add_context(struct ltt_session *session, int domain,
                }
 
                ret = context_ust_add(usess, domain, ctx, channel_name);
+               free(app_ctx_provider_name);
+               free(app_ctx_name);
+               app_ctx_name = NULL;
+               app_ctx_provider_name = NULL;
                if (ret != LTTNG_OK) {
                        goto error;
                }
                break;
        }
-#if 0
-       case LTTNG_DOMAIN_UST_EXEC_NAME:
-       case LTTNG_DOMAIN_UST_PID:
-       case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
-#endif
        default:
                ret = LTTNG_ERR_UND;
                goto error;
        }
 
-       return LTTNG_OK;
+       ret = LTTNG_OK;
+       goto end;
 
 error:
        if (chan_kern_created) {
@@ -1284,18 +1714,93 @@ error:
                                uchan);
                trace_ust_destroy_channel(uchan);
        }
+end:
+       free(app_ctx_provider_name);
+       free(app_ctx_name);
+       return ret;
+}
+
+static int validate_event_name(const char *name)
+{
+       int ret = 0;
+       const char *c = name;
+       const char *event_name_end = c + LTTNG_SYMBOL_NAME_LEN;
+       bool null_terminated = false;
+
+       /*
+        * Make sure that unescaped wildcards are only used as the last
+        * character of the event name.
+        */
+       while (c < event_name_end) {
+               switch (*c) {
+               case '\0':
+                       null_terminated = true;
+                       goto end;
+               case '\\':
+                       c++;
+                       break;
+               case '*':
+                       if ((c + 1) < event_name_end && *(c + 1)) {
+                               /* Wildcard is not the last character */
+                               ret = LTTNG_ERR_INVALID_EVENT_NAME;
+                               goto end;
+                       }
+               default:
+                       break;
+               }
+               c++;
+       }
+end:
+       if (!ret && !null_terminated) {
+               ret = LTTNG_ERR_INVALID_EVENT_NAME;
+       }
+       return ret;
+}
+
+static inline bool name_starts_with(const char *name, const char *prefix)
+{
+       const size_t max_cmp_len = min(strlen(prefix), LTTNG_SYMBOL_NAME_LEN);
+
+       return !strncmp(name, prefix, max_cmp_len);
+}
+
+/* Perform userspace-specific event name validation */
+static int validate_ust_event_name(const char *name)
+{
+       int ret = 0;
+
+       if (!name) {
+               ret = -1;
+               goto end;
+       }
+
+       /*
+        * Check name against all internal UST event component namespaces used
+        * by the agents.
+        */
+       if (name_starts_with(name, DEFAULT_JUL_EVENT_COMPONENT) ||
+               name_starts_with(name, DEFAULT_LOG4J_EVENT_COMPONENT) ||
+               name_starts_with(name, DEFAULT_PYTHON_EVENT_COMPONENT)) {
+               ret = -1;
+       }
+
+end:
        return ret;
 }
 
 /*
- * Command LTTNG_ENABLE_EVENT processed by the client thread.
+ * Internal version of cmd_enable_event() with a supplemental
+ * "internal_event" flag which is used to enable internal events which should
+ * be hidden from clients. Such events are used in the agent implementation to
+ * enable the events through which all "agent" events are funeled.
  */
-int cmd_enable_event(struct ltt_session *session, struct lttng_domain *domain,
+static int _cmd_enable_event(struct ltt_session *session,
+               struct lttng_domain *domain,
                char *channel_name, struct lttng_event *event,
                char *filter_expression,
                struct lttng_filter_bytecode *filter,
                struct lttng_event_exclusion *exclusion,
-               int wpipe)
+               int wpipe, bool internal_event)
 {
        int ret, channel_created = 0;
        struct lttng_channel *attr;
@@ -1304,8 +1809,18 @@ int cmd_enable_event(struct ltt_session *session, struct lttng_domain *domain,
        assert(event);
        assert(channel_name);
 
+       /* If we have a filter, we must have its filter expression */
+       assert(!(!!filter_expression ^ !!filter));
+
+       DBG("Enable event command for event \'%s\'", event->name);
+
        rcu_read_lock();
 
+       ret = validate_event_name(event->name);
+       if (ret) {
+               goto error;
+       }
+
        switch (domain->type) {
        case LTTNG_DOMAIN_KERNEL:
        {
@@ -1352,12 +1867,88 @@ int cmd_enable_event(struct ltt_session *session, struct lttng_domain *domain,
                        goto error;
                }
 
-               ret = event_kernel_enable_tracepoint(kchan, event);
-               if (ret != LTTNG_OK) {
-                       if (channel_created) {
-                               /* Let's not leak a useless channel. */
-                               kernel_destroy_channel(kchan);
+               switch (event->type) {
+               case LTTNG_EVENT_ALL:
+               {
+                       char *filter_expression_a = NULL;
+                       struct lttng_filter_bytecode *filter_a = NULL;
+
+                       /*
+                        * We need to duplicate filter_expression and filter,
+                        * because ownership is passed to first enable
+                        * event.
+                        */
+                       if (filter_expression) {
+                               filter_expression_a = strdup(filter_expression);
+                               if (!filter_expression_a) {
+                                       ret = LTTNG_ERR_FATAL;
+                                       goto error;
+                               }
+                       }
+                       if (filter) {
+                               filter_a = zmalloc(sizeof(*filter_a) + filter->len);
+                               if (!filter_a) {
+                                       free(filter_expression_a);
+                                       ret = LTTNG_ERR_FATAL;
+                                       goto error;
+                               }
+                               memcpy(filter_a, filter, sizeof(*filter_a) + filter->len);
                        }
+                       event->type = LTTNG_EVENT_TRACEPOINT;   /* Hack */
+                       ret = event_kernel_enable_event(kchan, event,
+                               filter_expression, filter);
+                       /* We have passed ownership */
+                       filter_expression = NULL;
+                       filter = NULL;
+                       if (ret != LTTNG_OK) {
+                               if (channel_created) {
+                                       /* Let's not leak a useless channel. */
+                                       kernel_destroy_channel(kchan);
+                               }
+                               free(filter_expression_a);
+                               free(filter_a);
+                               goto error;
+                       }
+                       event->type = LTTNG_EVENT_SYSCALL;      /* Hack */
+                       ret = event_kernel_enable_event(kchan, event,
+                               filter_expression_a, filter_a);
+                       /* We have passed ownership */
+                       filter_expression_a = NULL;
+                       filter_a = NULL;
+                       if (ret != LTTNG_OK) {
+                               goto error;
+                       }
+                       break;
+               }
+               case LTTNG_EVENT_PROBE:
+               case LTTNG_EVENT_FUNCTION:
+               case LTTNG_EVENT_FUNCTION_ENTRY:
+               case LTTNG_EVENT_TRACEPOINT:
+                       ret = event_kernel_enable_event(kchan, event,
+                               filter_expression, filter);
+                       /* We have passed ownership */
+                       filter_expression = NULL;
+                       filter = NULL;
+                       if (ret != LTTNG_OK) {
+                               if (channel_created) {
+                                       /* Let's not leak a useless channel. */
+                                       kernel_destroy_channel(kchan);
+                               }
+                               goto error;
+                       }
+                       break;
+               case LTTNG_EVENT_SYSCALL:
+                       ret = event_kernel_enable_event(kchan, event,
+                               filter_expression, filter);
+                       /* We have passed ownership */
+                       filter_expression = NULL;
+                       filter = NULL;
+                       if (ret != LTTNG_OK) {
+                               goto error;
+                       }
+                       break;
+               default:
+                       ret = LTTNG_ERR_UNK;
                        goto error;
                }
 
@@ -1407,33 +1998,79 @@ int cmd_enable_event(struct ltt_session *session, struct lttng_domain *domain,
                        assert(uchan);
                }
 
+               if (uchan->domain != LTTNG_DOMAIN_UST && !internal_event) {
+                       /*
+                        * Don't allow users to add UST events to channels which
+                        * are assigned to a userspace subdomain (JUL, Log4J,
+                        * Python, etc.).
+                        */
+                       ret = LTTNG_ERR_INVALID_CHANNEL_DOMAIN;
+                       goto error;
+               }
+
+               if (!internal_event) {
+                       /*
+                        * Ensure the event name is not reserved for internal
+                        * use.
+                        */
+                       ret = validate_ust_event_name(event->name);
+                       if (ret) {
+                               WARN("Userspace event name %s failed validation.",
+                                               event->name ?
+                                               event->name : "NULL");
+                               ret = LTTNG_ERR_INVALID_EVENT_NAME;
+                               goto error;
+                       }
+               }
+
                /* At this point, the session and channel exist on the tracer */
                ret = event_ust_enable_tracepoint(usess, uchan, event,
-                               filter_expression, filter, exclusion);
-               if (ret != LTTNG_OK) {
+                               filter_expression, filter, exclusion,
+                               internal_event);
+               /* We have passed ownership */
+               filter_expression = NULL;
+               filter = NULL;
+               exclusion = NULL;
+               if (ret == LTTNG_ERR_UST_EVENT_ENABLED) {
+                       goto already_enabled;
+               } else if (ret != LTTNG_OK) {
                        goto error;
                }
                break;
        }
+       case LTTNG_DOMAIN_LOG4J:
        case LTTNG_DOMAIN_JUL:
+       case LTTNG_DOMAIN_PYTHON:
        {
+               const char *default_event_name, *default_chan_name;
+               struct agent *agt;
                struct lttng_event uevent;
                struct lttng_domain tmp_dom;
                struct ltt_ust_session *usess = session->ust_session;
 
                assert(usess);
 
-               /* Create the default JUL tracepoint. */
+               agt = trace_ust_find_agent(usess, domain->type);
+               if (!agt) {
+                       agt = agent_create(domain->type);
+                       if (!agt) {
+                               ret = LTTNG_ERR_NOMEM;
+                               goto error;
+                       }
+                       agent_add(agt, usess->agents);
+               }
+
+               /* Create the default tracepoint. */
                memset(&uevent, 0, sizeof(uevent));
                uevent.type = LTTNG_EVENT_TRACEPOINT;
                uevent.loglevel_type = LTTNG_EVENT_LOGLEVEL_ALL;
-               if (is_root) {
-                       strncpy(uevent.name, DEFAULT_SYS_JUL_EVENT_NAME,
-                                       sizeof(uevent.name));
-               } else {
-                       strncpy(uevent.name, DEFAULT_USER_JUL_EVENT_NAME,
-                                       sizeof(uevent.name));
+               default_event_name = event_get_default_agent_ust_name(
+                               domain->type);
+               if (!default_event_name) {
+                       ret = LTTNG_ERR_FATAL;
+                       goto error;
                }
+               strncpy(uevent.name, default_event_name, sizeof(uevent.name));
                uevent.name[sizeof(uevent.name) - 1] = '\0';
 
                /*
@@ -1444,249 +2081,78 @@ int cmd_enable_event(struct ltt_session *session, struct lttng_domain *domain,
                memcpy(&tmp_dom, domain, sizeof(tmp_dom));
                tmp_dom.type = LTTNG_DOMAIN_UST;
 
-               ret = cmd_enable_event(session, &tmp_dom, DEFAULT_JUL_CHANNEL_NAME,
-                       &uevent, NULL, NULL, NULL, wpipe);
-               if (ret != LTTNG_OK && ret != LTTNG_ERR_UST_EVENT_ENABLED) {
-                       goto error;
-               }
-
-               /* The wild card * means that everything should be enabled. */
-               if (strncmp(event->name, "*", 1) == 0 && strlen(event->name) == 1) {
-                       ret = event_jul_enable_all(usess, event);
-               } else {
-                       ret = event_jul_enable(usess, event);
-               }
-               if (ret != LTTNG_OK) {
-                       goto error;
-               }
-
-               break;
-       }
-#if 0
-       case LTTNG_DOMAIN_UST_EXEC_NAME:
-       case LTTNG_DOMAIN_UST_PID:
-       case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
-#endif
-       default:
-               ret = LTTNG_ERR_UND;
-               goto error;
-       }
-
-       ret = LTTNG_OK;
-
-error:
-       rcu_read_unlock();
-       return ret;
-}
-
-/*
- * Command LTTNG_ENABLE_ALL_EVENT processed by the client thread.
- */
-int cmd_enable_event_all(struct ltt_session *session,
-               struct lttng_domain *domain, char *channel_name, int event_type,
-               char *filter_expression,
-               struct lttng_filter_bytecode *filter, int wpipe)
-{
-       int ret;
-       struct lttng_channel *attr;
-
-       assert(session);
-       assert(channel_name);
-
-       rcu_read_lock();
-
-       switch (domain->type) {
-       case LTTNG_DOMAIN_KERNEL:
-       {
-               struct ltt_kernel_channel *kchan;
-
-               assert(session->kernel_session);
-
-               /*
-                * If a non-default channel has been created in the
-                * session, explicitely require that -c chan_name needs
-                * to be provided.
-                */
-               if (session->kernel_session->has_non_default_channel
-                               && channel_name[0] == '\0') {
-                       ret = LTTNG_ERR_NEED_CHANNEL_NAME;
-                       goto error;
-               }
-
-               kchan = trace_kernel_get_channel_by_name(channel_name,
-                               session->kernel_session);
-               if (kchan == NULL) {
-                       /* Create default channel */
-                       attr = channel_new_default_attr(LTTNG_DOMAIN_KERNEL,
-                                       LTTNG_BUFFER_GLOBAL);
-                       if (attr == NULL) {
-                               ret = LTTNG_ERR_FATAL;
-                               goto error;
-                       }
-                       strncpy(attr->name, channel_name, sizeof(attr->name));
-
-                       ret = cmd_enable_channel(session, domain, attr, wpipe);
-                       if (ret != LTTNG_OK) {
-                               free(attr);
-                               goto error;
-                       }
-                       free(attr);
-
-                       /* Get the newly created kernel channel pointer */
-                       kchan = trace_kernel_get_channel_by_name(channel_name,
-                                       session->kernel_session);
-                       assert(kchan);
-               }
-
-               switch (event_type) {
-               case LTTNG_EVENT_SYSCALL:
-                       ret = event_kernel_enable_all_syscalls(kchan, kernel_tracer_fd);
+               switch (domain->type) {
+               case LTTNG_DOMAIN_LOG4J:
+                       default_chan_name = DEFAULT_LOG4J_CHANNEL_NAME;
                        break;
-               case LTTNG_EVENT_TRACEPOINT:
-                       /*
-                        * This call enables all LTTNG_KERNEL_TRACEPOINTS and
-                        * events already registered to the channel.
-                        */
-                       ret = event_kernel_enable_all_tracepoints(kchan, kernel_tracer_fd);
+               case LTTNG_DOMAIN_JUL:
+                       default_chan_name = DEFAULT_JUL_CHANNEL_NAME;
                        break;
-               case LTTNG_EVENT_ALL:
-                       /* Enable syscalls and tracepoints */
-                       ret = event_kernel_enable_all(kchan, kernel_tracer_fd);
+               case LTTNG_DOMAIN_PYTHON:
+                       default_chan_name = DEFAULT_PYTHON_CHANNEL_NAME;
                        break;
                default:
-                       ret = LTTNG_ERR_KERN_ENABLE_FAIL;
-                       goto error;
-               }
-
-               /* Manage return value */
-               if (ret != LTTNG_OK) {
-                       /*
-                        * On error, cmd_enable_channel call will take care of destroying
-                        * the created channel if it was needed.
-                        */
-                       goto error;
+                       /* The switch/case we are in makes this impossible */
+                       assert(0);
                }
 
-               kernel_wait_quiescent(kernel_tracer_fd);
-               break;
-       }
-       case LTTNG_DOMAIN_UST:
-       {
-               struct ltt_ust_channel *uchan;
-               struct ltt_ust_session *usess = session->ust_session;
+               {
+                       char *filter_expression_copy = NULL;
+                       struct lttng_filter_bytecode *filter_copy = NULL;
 
-               assert(usess);
+                       if (filter) {
+                               const size_t filter_size = sizeof(
+                                               struct lttng_filter_bytecode)
+                                               + filter->len;
 
-               /*
-                * If a non-default channel has been created in the
-                * session, explicitely require that -c chan_name needs
-                * to be provided.
-                */
-               if (usess->has_non_default_channel && channel_name[0] == '\0') {
-                       ret = LTTNG_ERR_NEED_CHANNEL_NAME;
-                       goto error;
-               }
+                               filter_copy = zmalloc(filter_size);
+                               if (!filter_copy) {
+                                       ret = LTTNG_ERR_NOMEM;
+                                       goto error;
+                               }
+                               memcpy(filter_copy, filter, filter_size);
 
-               /* Get channel from global UST domain */
-               uchan = trace_ust_find_channel_by_name(usess->domain_global.channels,
-                               channel_name);
-               if (uchan == NULL) {
-                       /* Create default channel */
-                       attr = channel_new_default_attr(LTTNG_DOMAIN_UST,
-                                       usess->buffer_type);
-                       if (attr == NULL) {
-                               ret = LTTNG_ERR_FATAL;
-                               goto error;
-                       }
-                       strncpy(attr->name, channel_name, sizeof(attr->name));
+                               filter_expression_copy =
+                                               strdup(filter_expression);
+                               if (!filter_expression) {
+                                       ret = LTTNG_ERR_NOMEM;
+                               }
 
-                       ret = cmd_enable_channel(session, domain, attr, wpipe);
-                       if (ret != LTTNG_OK) {
-                               free(attr);
-                               goto error;
+                               if (!filter_expression_copy || !filter_copy) {
+                                       free(filter_expression_copy);
+                                       free(filter_copy);
+                                       goto error;
+                               }
                        }
-                       free(attr);
 
-                       /* Get the newly created channel reference back */
-                       uchan = trace_ust_find_channel_by_name(
-                                       usess->domain_global.channels, channel_name);
-                       assert(uchan);
+                       ret = cmd_enable_event_internal(session, &tmp_dom,
+                                       (char *) default_chan_name,
+                                       &uevent, filter_expression_copy,
+                                       filter_copy, NULL, wpipe);
                }
 
-               /* At this point, the session and channel exist on the tracer */
-
-               switch (event_type) {
-               case LTTNG_EVENT_ALL:
-               case LTTNG_EVENT_TRACEPOINT:
-                       ret = event_ust_enable_all_tracepoints(usess, uchan,
-                               filter_expression, filter);
-                       if (ret != LTTNG_OK) {
-                               goto error;
-                       }
-                       break;
-               default:
-                       ret = LTTNG_ERR_UST_ENABLE_FAIL;
-                       goto error;
-               }
-
-               /* Manage return value */
-               if (ret != LTTNG_OK) {
+               if (ret == LTTNG_ERR_UST_EVENT_ENABLED) {
+                       goto already_enabled;
+               } else if (ret != LTTNG_OK) {
                        goto error;
                }
 
-               break;
-       }
-       case LTTNG_DOMAIN_JUL:
-       {
-               struct lttng_event uevent, event;
-               struct lttng_domain tmp_dom;
-               struct ltt_ust_session *usess = session->ust_session;
-
-               assert(usess);
-
-               /* Create the default JUL tracepoint. */
-               uevent.type = LTTNG_EVENT_TRACEPOINT;
-               uevent.loglevel_type = LTTNG_EVENT_LOGLEVEL_ALL;
-               if (is_root) {
-                       strncpy(uevent.name, DEFAULT_SYS_JUL_EVENT_NAME,
-                                       sizeof(uevent.name));
+               /* The wild card * means that everything should be enabled. */
+               if (strncmp(event->name, "*", 1) == 0 && strlen(event->name) == 1) {
+                       ret = event_agent_enable_all(usess, agt, event, filter,
+                                       filter_expression);
                } else {
-                       strncpy(uevent.name, DEFAULT_USER_JUL_EVENT_NAME,
-                                       sizeof(uevent.name));
-               }
-               uevent.name[sizeof(uevent.name) - 1] = '\0';
-
-               /*
-                * The domain type is changed because we are about to enable the
-                * default channel and event for the JUL domain that are hardcoded.
-                * This happens in the UST domain.
-                */
-               memcpy(&tmp_dom, domain, sizeof(tmp_dom));
-               tmp_dom.type = LTTNG_DOMAIN_UST;
-
-               ret = cmd_enable_event(session, &tmp_dom, DEFAULT_JUL_CHANNEL_NAME,
-                       &uevent, NULL, NULL, NULL, wpipe);
-               if (ret != LTTNG_OK && ret != LTTNG_ERR_UST_EVENT_ENABLED) {
-                       goto error;
+                       ret = event_agent_enable(usess, agt, event, filter,
+                                       filter_expression);
                }
-
-               event.loglevel = LTTNG_LOGLEVEL_JUL_ALL;
-               event.loglevel_type = LTTNG_EVENT_LOGLEVEL_ALL;
-               strncpy(event.name, "*", sizeof(event.name));
-               event.name[sizeof(event.name) - 1] = '\0';
-
-               ret = event_jul_enable_all(usess, &event);
+               filter = NULL;
+               filter_expression = NULL;
                if (ret != LTTNG_OK) {
                        goto error;
                }
 
                break;
        }
-#if 0
-       case LTTNG_DOMAIN_UST_EXEC_NAME:
-       case LTTNG_DOMAIN_UST_PID:
-       case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
-#endif
        default:
                ret = LTTNG_ERR_UND;
                goto error;
@@ -1694,16 +2160,52 @@ int cmd_enable_event_all(struct ltt_session *session,
 
        ret = LTTNG_OK;
 
+already_enabled:
 error:
+       free(filter_expression);
+       free(filter);
+       free(exclusion);
        rcu_read_unlock();
        return ret;
 }
 
+/*
+ * Command LTTNG_ENABLE_EVENT processed by the client thread.
+ * We own filter, exclusion, and filter_expression.
+ */
+int cmd_enable_event(struct ltt_session *session, struct lttng_domain *domain,
+               char *channel_name, struct lttng_event *event,
+               char *filter_expression,
+               struct lttng_filter_bytecode *filter,
+               struct lttng_event_exclusion *exclusion,
+               int wpipe)
+{
+       return _cmd_enable_event(session, domain, channel_name, event,
+                       filter_expression, filter, exclusion, wpipe, false);
+}
+
+/*
+ * Enable an event which is internal to LTTng. An internal should
+ * never be made visible to clients and are immune to checks such as
+ * reserved names.
+ */
+static int cmd_enable_event_internal(struct ltt_session *session,
+               struct lttng_domain *domain,
+               char *channel_name, struct lttng_event *event,
+               char *filter_expression,
+               struct lttng_filter_bytecode *filter,
+               struct lttng_event_exclusion *exclusion,
+               int wpipe)
+{
+       return _cmd_enable_event(session, domain, channel_name, event,
+                       filter_expression, filter, exclusion, wpipe, true);
+}
 
 /*
  * Command LTTNG_LIST_TRACEPOINTS processed by the client thread.
  */
-ssize_t cmd_list_tracepoints(int domain, struct lttng_event **events)
+ssize_t cmd_list_tracepoints(enum lttng_domain_type domain,
+               struct lttng_event **events)
 {
        int ret;
        ssize_t nb_events = 0;
@@ -1723,8 +2225,10 @@ ssize_t cmd_list_tracepoints(int domain, struct lttng_event **events)
                        goto error;
                }
                break;
+       case LTTNG_DOMAIN_LOG4J:
        case LTTNG_DOMAIN_JUL:
-               nb_events = jul_list_events(events);
+       case LTTNG_DOMAIN_PYTHON:
+               nb_events = agent_list_events(events, domain);
                if (nb_events < 0) {
                        ret = LTTNG_ERR_UST_LIST_FAIL;
                        goto error;
@@ -1735,37 +2239,93 @@ ssize_t cmd_list_tracepoints(int domain, struct lttng_event **events)
                goto error;
        }
 
-       return nb_events;
+       return nb_events;
+
+error:
+       /* Return negative value to differentiate return code */
+       return -ret;
+}
+
+/*
+ * Command LTTNG_LIST_TRACEPOINT_FIELDS processed by the client thread.
+ */
+ssize_t cmd_list_tracepoint_fields(enum lttng_domain_type domain,
+               struct lttng_event_field **fields)
+{
+       int ret;
+       ssize_t nb_fields = 0;
+
+       switch (domain) {
+       case LTTNG_DOMAIN_UST:
+               nb_fields = ust_app_list_event_fields(fields);
+               if (nb_fields < 0) {
+                       ret = LTTNG_ERR_UST_LIST_FAIL;
+                       goto error;
+               }
+               break;
+       case LTTNG_DOMAIN_KERNEL:
+       default:        /* fall-through */
+               ret = LTTNG_ERR_UND;
+               goto error;
+       }
+
+       return nb_fields;
 
 error:
        /* Return negative value to differentiate return code */
        return -ret;
 }
 
+ssize_t cmd_list_syscalls(struct lttng_event **events)
+{
+       return syscall_table_list(events);
+}
+
 /*
- * Command LTTNG_LIST_TRACEPOINT_FIELDS processed by the client thread.
+ * Command LTTNG_LIST_TRACKER_PIDS processed by the client thread.
+ *
+ * Called with session lock held.
  */
-ssize_t cmd_list_tracepoint_fields(int domain,
-               struct lttng_event_field **fields)
+ssize_t cmd_list_tracker_pids(struct ltt_session *session,
+               enum lttng_domain_type domain, int32_t **pids)
 {
        int ret;
-       ssize_t nb_fields = 0;
+       ssize_t nr_pids = 0;
 
        switch (domain) {
+       case LTTNG_DOMAIN_KERNEL:
+       {
+               struct ltt_kernel_session *ksess;
+
+               ksess = session->kernel_session;
+               nr_pids = kernel_list_tracker_pids(ksess, pids);
+               if (nr_pids < 0) {
+                       ret = LTTNG_ERR_KERN_LIST_FAIL;
+                       goto error;
+               }
+               break;
+       }
        case LTTNG_DOMAIN_UST:
-               nb_fields = ust_app_list_event_fields(fields);
-               if (nb_fields < 0) {
+       {
+               struct ltt_ust_session *usess;
+
+               usess = session->ust_session;
+               nr_pids = trace_ust_list_tracker_pids(usess, pids);
+               if (nr_pids < 0) {
                        ret = LTTNG_ERR_UST_LIST_FAIL;
                        goto error;
                }
                break;
-       case LTTNG_DOMAIN_KERNEL:
-       default:        /* fall-through */
+       }
+       case LTTNG_DOMAIN_LOG4J:
+       case LTTNG_DOMAIN_JUL:
+       case LTTNG_DOMAIN_PYTHON:
+       default:
                ret = LTTNG_ERR_UND;
                goto error;
        }
 
-       return nb_fields;
+       return nr_pids;
 
 error:
        /* Return negative value to differentiate return code */
@@ -1774,6 +2334,8 @@ error:
 
 /*
  * Command LTTNG_START_TRACE processed by the client thread.
+ *
+ * Called with session mutex held.
  */
 int cmd_start_trace(struct ltt_session *session)
 {
@@ -1819,7 +2381,11 @@ int cmd_start_trace(struct ltt_session *session)
 
        /* Flag session that trace should start automatically */
        if (usess) {
-               usess->start_trace = 1;
+               /*
+                * Even though the start trace might fail, flag this session active so
+                * other application coming in are started by default.
+                */
+               usess->active = 1;
 
                ret = ust_app_start_trace_all(usess);
                if (ret < 0) {
@@ -1861,7 +2427,7 @@ int cmd_stop_trace(struct ltt_session *session)
        }
 
        /* Kernel tracer */
-       if (ksession && ksession->started) {
+       if (ksession && ksession->active) {
                DBG("Stop kernel tracing");
 
                /* Flush metadata if exist */
@@ -1888,11 +2454,15 @@ int cmd_stop_trace(struct ltt_session *session)
 
                kernel_wait_quiescent(kernel_tracer_fd);
 
-               ksession->started = 0;
+               ksession->active = 0;
        }
 
-       if (usess && usess->start_trace) {
-               usess->start_trace = 0;
+       if (usess && usess->active) {
+               /*
+                * Even though the stop trace might fail, flag this session inactive so
+                * other application coming in are not started by default.
+                */
+               usess->active = 0;
 
                ret = ust_app_stop_trace_all(usess);
                if (ret < 0) {
@@ -1912,13 +2482,12 @@ error:
 /*
  * Command LTTNG_SET_CONSUMER_URI processed by the client thread.
  */
-int cmd_set_consumer_uri(int domain, struct ltt_session *session,
-               size_t nb_uri, struct lttng_uri *uris)
+int cmd_set_consumer_uri(struct ltt_session *session, size_t nb_uri,
+               struct lttng_uri *uris)
 {
        int ret, i;
        struct ltt_kernel_session *ksess = session->kernel_session;
        struct ltt_ust_session *usess = session->ust_session;
-       struct consumer_output *consumer = NULL;
 
        assert(session);
        assert(uris);
@@ -1930,41 +2499,54 @@ int cmd_set_consumer_uri(int domain, struct ltt_session *session,
                goto error;
        }
 
-       /*
-        * This case switch makes sure the domain session has a temporary consumer
-        * so the URL can be set.
-        */
-       switch (domain) {
-       case 0:
-               /* Code flow error. A session MUST always have a consumer object */
-               assert(session->consumer);
-               /*
-                * The URL will be added to the tracing session consumer instead of a
-                * specific domain consumer.
-                */
-               consumer = session->consumer;
-               break;
-       case LTTNG_DOMAIN_KERNEL:
-               /* Code flow error if we don't have a kernel session here. */
-               assert(ksess);
-               assert(ksess->consumer);
-               consumer = ksess->consumer;
-               break;
-       case LTTNG_DOMAIN_UST:
-               /* Code flow error if we don't have a kernel session here. */
-               assert(usess);
-               assert(usess->consumer);
-               consumer = usess->consumer;
-               break;
-       }
-
+       /* Set the "global" consumer URIs */
        for (i = 0; i < nb_uri; i++) {
-               ret = add_uri_to_consumer(consumer, &uris[i], domain, session->name);
+               ret = add_uri_to_consumer(session->consumer,
+                               &uris[i], 0, session->name);
                if (ret != LTTNG_OK) {
                        goto error;
                }
        }
 
+       /* Set UST session URIs */
+       if (session->ust_session) {
+               for (i = 0; i < nb_uri; i++) {
+                       ret = add_uri_to_consumer(
+                                       session->ust_session->consumer,
+                                       &uris[i], LTTNG_DOMAIN_UST,
+                                       session->name);
+                       if (ret != LTTNG_OK) {
+                               goto error;
+                       }
+               }
+       }
+
+       /* Set kernel session URIs */
+       if (session->kernel_session) {
+               for (i = 0; i < nb_uri; i++) {
+                       ret = add_uri_to_consumer(
+                                       session->kernel_session->consumer,
+                                       &uris[i], LTTNG_DOMAIN_KERNEL,
+                                       session->name);
+                       if (ret != LTTNG_OK) {
+                               goto error;
+                       }
+               }
+       }
+
+       /*
+        * Make sure to set the session in output mode after we set URI since a
+        * session can be created without URL (thus flagged in no output mode).
+        */
+       session->output_traces = 1;
+       if (ksess) {
+               ksess->output_traces = 1;
+       }
+
+       if (usess) {
+               usess->output_traces = 1;
+       }
+
        /* All good! */
        ret = LTTNG_OK;
 
@@ -2023,7 +2605,7 @@ int cmd_create_session_uri(char *name, struct lttng_uri *uris,
        }
 
        if (uris) {
-               ret = cmd_set_consumer_uri(0, session, nb_uri, uris);
+               ret = cmd_set_consumer_uri(session, nb_uri, uris);
                if (ret != LTTNG_OK) {
                        goto consumer_error;
                }
@@ -2061,7 +2643,7 @@ int cmd_create_session_snapshot(char *name, struct lttng_uri *uris,
         * Create session in no output mode with URIs set to NULL. The uris we've
         * received are for a default snapshot output if one.
         */
-       ret = cmd_create_session_uri(name, NULL, 0, creds, -1);
+       ret = cmd_create_session_uri(name, NULL, 0, creds, 0);
        if (ret != LTTNG_OK) {
                goto error;
        }
@@ -2112,6 +2694,8 @@ error:
 
 /*
  * Command LTTNG_DESTROY_SESSION processed by the client thread.
+ *
+ * Called with session lock held.
  */
 int cmd_destroy_session(struct ltt_session *session, int wpipe)
 {
@@ -2160,7 +2744,8 @@ int cmd_destroy_session(struct ltt_session *session, int wpipe)
 /*
  * Command LTTNG_CALIBRATE processed by the client thread.
  */
-int cmd_calibrate(int domain, struct lttng_calibrate *calibrate)
+int cmd_calibrate(enum lttng_domain_type domain,
+               struct lttng_calibrate *calibrate)
 {
        int ret;
 
@@ -2217,8 +2802,9 @@ error:
 /*
  * Command LTTNG_REGISTER_CONSUMER processed by the client thread.
  */
-int cmd_register_consumer(struct ltt_session *session, int domain,
-               const char *sock_path, struct consumer_data *cdata)
+int cmd_register_consumer(struct ltt_session *session,
+               enum lttng_domain_type domain, const char *sock_path,
+               struct consumer_data *cdata)
 {
        int ret, sock;
        struct consumer_socket *socket = NULL;
@@ -2300,6 +2886,8 @@ ssize_t cmd_list_domains(struct ltt_session *session,
 {
        int ret, index = 0;
        ssize_t nb_dom = 0;
+       struct agent *agt;
+       struct lttng_ht_iter iter;
 
        if (session->kernel_session != NULL) {
                DBG3("Listing domains found kernel domain");
@@ -2310,9 +2898,18 @@ ssize_t cmd_list_domains(struct ltt_session *session,
                DBG3("Listing domains found UST global domain");
                nb_dom++;
 
-               if (session->ust_session->domain_jul.being_used) {
-                       nb_dom++;
+               rcu_read_lock();
+               cds_lfht_for_each_entry(session->ust_session->agents->ht, &iter.iter,
+                               agt, node.node) {
+                       if (agt->being_used) {
+                               nb_dom++;
+                       }
                }
+               rcu_read_unlock();
+       }
+
+       if (!nb_dom) {
+               goto end;
        }
 
        *domains = zmalloc(nb_dom * sizeof(struct lttng_domain));
@@ -2323,6 +2920,10 @@ ssize_t cmd_list_domains(struct ltt_session *session,
 
        if (session->kernel_session != NULL) {
                (*domains)[index].type = LTTNG_DOMAIN_KERNEL;
+
+               /* Kernel session buffer type is always GLOBAL */
+               (*domains)[index].buf_type = LTTNG_BUFFER_GLOBAL;
+
                index++;
        }
 
@@ -2331,13 +2932,18 @@ ssize_t cmd_list_domains(struct ltt_session *session,
                (*domains)[index].buf_type = session->ust_session->buffer_type;
                index++;
 
-               if (session->ust_session->domain_jul.being_used) {
-                       (*domains)[index].type = LTTNG_DOMAIN_JUL;
-                       (*domains)[index].buf_type = session->ust_session->buffer_type;
-                       index++;
+               rcu_read_lock();
+               cds_lfht_for_each_entry(session->ust_session->agents->ht, &iter.iter,
+                               agt, node.node) {
+                       if (agt->being_used) {
+                               (*domains)[index].type = agt->domain;
+                               (*domains)[index].buf_type = session->ust_session->buffer_type;
+                               index++;
+                       }
                }
+               rcu_read_unlock();
        }
-
+end:
        return nb_dom;
 
 error:
@@ -2349,11 +2955,10 @@ error:
 /*
  * Command LTTNG_LIST_CHANNELS processed by the client thread.
  */
-ssize_t cmd_list_channels(int domain, struct ltt_session *session,
-               struct lttng_channel **channels)
+ssize_t cmd_list_channels(enum lttng_domain_type domain,
+               struct ltt_session *session, struct lttng_channel **channels)
 {
-       int ret;
-       ssize_t nb_chan = 0;
+       ssize_t nb_chan = 0, payload_size = 0, ret;
 
        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
@@ -2362,51 +2967,58 @@ ssize_t cmd_list_channels(int domain, struct ltt_session *session,
                }
                DBG3("Number of kernel channels %zd", nb_chan);
                if (nb_chan <= 0) {
-                       ret = LTTNG_ERR_KERN_CHAN_NOT_FOUND;
+                       ret = -LTTNG_ERR_KERN_CHAN_NOT_FOUND;
+                       goto end;
                }
                break;
        case LTTNG_DOMAIN_UST:
                if (session->ust_session != NULL) {
+                       rcu_read_lock();
                        nb_chan = lttng_ht_get_count(
-                                       session->ust_session->domain_global.channels);
+                               session->ust_session->domain_global.channels);
+                       rcu_read_unlock();
                }
                DBG3("Number of UST global channels %zd", nb_chan);
-               if (nb_chan <= 0) {
-                       ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
+               if (nb_chan < 0) {
+                       ret = -LTTNG_ERR_UST_CHAN_NOT_FOUND;
+                       goto end;
                }
                break;
        default:
-               *channels = NULL;
-               ret = LTTNG_ERR_UND;
-               goto error;
+               ret = -LTTNG_ERR_UND;
+               goto end;
        }
 
        if (nb_chan > 0) {
-               *channels = zmalloc(nb_chan * sizeof(struct lttng_channel));
+               const size_t channel_size = sizeof(struct lttng_channel) +
+                       sizeof(struct lttcomm_channel_extended);
+               struct lttcomm_channel_extended *channel_exts;
+
+               payload_size = nb_chan * channel_size;
+               *channels = zmalloc(payload_size);
                if (*channels == NULL) {
-                       ret = LTTNG_ERR_FATAL;
-                       goto error;
+                       ret = -LTTNG_ERR_FATAL;
+                       goto end;
                }
 
-               list_lttng_channels(domain, session, *channels);
+               channel_exts = ((void *) *channels) +
+                               (nb_chan * sizeof(struct lttng_channel));
+               list_lttng_channels(domain, session, *channels, channel_exts);
        } else {
                *channels = NULL;
-               /* Ret value was set in the domain switch case */
-               goto error;
        }
 
-       return nb_chan;
-
-error:
-       /* Return negative value to differentiate return code */
-       return -ret;
+       ret = payload_size;
+end:
+       return ret;
 }
 
 /*
  * Command LTTNG_LIST_EVENTS processed by the client thread.
  */
-ssize_t cmd_list_events(int domain, struct ltt_session *session,
-               char *channel_name, struct lttng_event **events)
+ssize_t cmd_list_events(enum lttng_domain_type domain,
+               struct ltt_session *session, char *channel_name,
+               struct lttng_event **events, size_t *total_size)
 {
        int ret = 0;
        ssize_t nb_event = 0;
@@ -2415,21 +3027,37 @@ ssize_t cmd_list_events(int domain, struct ltt_session *session,
        case LTTNG_DOMAIN_KERNEL:
                if (session->kernel_session != NULL) {
                        nb_event = list_lttng_kernel_events(channel_name,
-                                       session->kernel_session, events);
+                                       session->kernel_session, events,
+                                       total_size);
                }
                break;
        case LTTNG_DOMAIN_UST:
        {
                if (session->ust_session != NULL) {
                        nb_event = list_lttng_ust_global_events(channel_name,
-                                       &session->ust_session->domain_global, events);
+                                       &session->ust_session->domain_global, events,
+                                       total_size);
                }
                break;
        }
+       case LTTNG_DOMAIN_LOG4J:
        case LTTNG_DOMAIN_JUL:
+       case LTTNG_DOMAIN_PYTHON:
                if (session->ust_session) {
-                       nb_event = list_lttng_jul_events(
-                                       &session->ust_session->domain_jul, events);
+                       struct lttng_ht_iter iter;
+                       struct agent *agt;
+
+                       rcu_read_lock();
+                       cds_lfht_for_each_entry(session->ust_session->agents->ht,
+                                       &iter.iter, agt, node.node) {
+                               if (agt->domain == domain) {
+                                       nb_event = list_lttng_agent_events(
+                                                       agt, events,
+                                                       total_size);
+                                       break;
+                               }
+                       }
+                       rcu_read_unlock();
                }
                break;
        default:
@@ -2678,7 +3306,7 @@ ssize_t cmd_snapshot_list_outputs(struct ltt_session *session,
                struct lttng_snapshot_output **outputs)
 {
        int ret, idx = 0;
-       struct lttng_snapshot_output *list;
+       struct lttng_snapshot_output *list = NULL;
        struct lttng_ht_iter iter;
        struct snapshot_output *output;
 
@@ -2692,7 +3320,7 @@ ssize_t cmd_snapshot_list_outputs(struct ltt_session *session,
         * set in no output mode.
         */
        if (session->output_traces) {
-               ret = LTTNG_ERR_EPERM;
+               ret = -LTTNG_ERR_EPERM;
                goto error;
        }
 
@@ -2703,11 +3331,12 @@ ssize_t cmd_snapshot_list_outputs(struct ltt_session *session,
 
        list = zmalloc(session->snapshot.nb_output * sizeof(*list));
        if (!list) {
-               ret = LTTNG_ERR_NOMEM;
+               ret = -LTTNG_ERR_NOMEM;
                goto error;
        }
 
        /* Copy list from session to the new list object. */
+       rcu_read_lock();
        cds_lfht_for_each_entry(session->snapshot.output_ht->ht, &iter.iter,
                        output, node.node) {
                assert(output->consumer);
@@ -2722,30 +3351,180 @@ ssize_t cmd_snapshot_list_outputs(struct ltt_session *session,
                        ret = uri_to_str_url(&output->consumer->dst.net.control,
                                        list[idx].ctrl_url, sizeof(list[idx].ctrl_url));
                        if (ret < 0) {
-                               ret = LTTNG_ERR_NOMEM;
-                               goto free_error;
+                               ret = -LTTNG_ERR_NOMEM;
+                               goto error;
                        }
 
                        /* Data URI. */
                        ret = uri_to_str_url(&output->consumer->dst.net.data,
                                        list[idx].data_url, sizeof(list[idx].data_url));
                        if (ret < 0) {
-                               ret = LTTNG_ERR_NOMEM;
-                               goto free_error;
+                               ret = -LTTNG_ERR_NOMEM;
+                               goto error;
                        }
                }
                idx++;
        }
 
        *outputs = list;
-       return session->snapshot.nb_output;
-
-free_error:
-       free(list);
+       list = NULL;
+       ret = session->snapshot.nb_output;
 error:
-       return -ret;
+       free(list);
+       rcu_read_unlock();
+       return ret;
+}
+
+/*
+ * Check if we can regenerate the metadata for this session.
+ * Only kernel, UST per-uid and non-live sessions are supported.
+ *
+ * Return 0 if the metadata can be generated, a LTTNG_ERR code otherwise.
+ */
+static
+int check_metadata_regenerate_support(struct ltt_session *session)
+{
+       int ret;
+
+       assert(session);
+
+       if (session->live_timer != 0) {
+               ret = LTTNG_ERR_LIVE_SESSION;
+               goto end;
+       }
+       if (!session->active) {
+               ret = LTTNG_ERR_SESSION_NOT_STARTED;
+               goto end;
+       }
+       if (session->ust_session) {
+               switch (session->ust_session->buffer_type) {
+               case LTTNG_BUFFER_PER_UID:
+                       break;
+               case LTTNG_BUFFER_PER_PID:
+                       ret = LTTNG_ERR_PER_PID_SESSION;
+                       goto end;
+               default:
+                       assert(0);
+                       ret = LTTNG_ERR_UNK;
+                       goto end;
+               }
+       }
+       if (session->consumer->type == CONSUMER_DST_NET &&
+                       session->consumer->relay_minor_version < 8) {
+               ret = LTTNG_ERR_RELAYD_VERSION_FAIL;
+               goto end;
+       }
+       ret = 0;
+
+end:
+       return ret;
+}
+
+static
+int ust_metadata_regenerate(struct ltt_ust_session *usess)
+{
+       int ret = 0;
+       struct buffer_reg_uid *uid_reg = NULL;
+       struct buffer_reg_session *session_reg = NULL;
+
+       rcu_read_lock();
+       cds_list_for_each_entry(uid_reg, &usess->buffer_reg_uid_list, lnode) {
+               struct ust_registry_session *registry;
+               struct ust_registry_channel *chan;
+               struct lttng_ht_iter iter_chan;
+
+               session_reg = uid_reg->registry;
+               registry = session_reg->reg.ust;
+
+               pthread_mutex_lock(&registry->lock);
+               registry->metadata_len_sent = 0;
+               memset(registry->metadata, 0, registry->metadata_alloc_len);
+               registry->metadata_len = 0;
+               registry->metadata_version++;
+               ret = ust_metadata_session_statedump(registry, NULL,
+                               registry->major, registry->minor);
+               if (ret) {
+                       pthread_mutex_unlock(&registry->lock);
+                       ERR("Failed to generate session metadata (err = %d)",
+                                       ret);
+                       goto end;
+               }
+               cds_lfht_for_each_entry(registry->channels->ht, &iter_chan.iter,
+                               chan, node.node) {
+                       struct ust_registry_event *event;
+                       struct lttng_ht_iter iter_event;
+
+                       ret = ust_metadata_channel_statedump(registry, chan);
+                       if (ret) {
+                               pthread_mutex_unlock(&registry->lock);
+                               ERR("Failed to generate channel metadata "
+                                               "(err = %d)", ret);
+                               goto end;
+                       }
+                       cds_lfht_for_each_entry(chan->ht->ht, &iter_event.iter,
+                                       event, node.node) {
+                               ret = ust_metadata_event_statedump(registry,
+                                               chan, event);
+                               if (ret) {
+                                       pthread_mutex_unlock(&registry->lock);
+                                       ERR("Failed to generate event metadata "
+                                                       "(err = %d)", ret);
+                                       goto end;
+                               }
+                       }
+               }
+               pthread_mutex_unlock(&registry->lock);
+       }
+
+end:
+       rcu_read_unlock();
+       return ret;
+}
+
+/*
+ * Command LTTNG_METADATA_REGENERATE from the lttng-ctl library.
+ *
+ * Ask the consumer to truncate the existing metadata file(s) and
+ * then regenerate the metadata. Live and per-pid sessions are not
+ * supported and return an error.
+ *
+ * Return 0 on success or else a LTTNG_ERR code.
+ */
+int cmd_metadata_regenerate(struct ltt_session *session)
+{
+       int ret;
+
+       assert(session);
+
+       ret = check_metadata_regenerate_support(session);
+       if (ret) {
+               goto end;
+       }
+
+       if (session->kernel_session) {
+               ret = kernctl_session_metadata_regenerate(
+                               session->kernel_session->fd);
+               if (ret < 0) {
+                       ERR("Failed to regenerate the kernel metadata");
+                       goto end;
+               }
+       }
+
+       if (session->ust_session) {
+               ret = ust_metadata_regenerate(session->ust_session);
+               if (ret < 0) {
+                       ERR("Failed to regenerate the UST metadata");
+                       goto end;
+               }
+       }
+       DBG("Cmd metadata regenerate for session %s", session->name);
+       ret = LTTNG_OK;
+
+end:
+       return ret;
 }
 
+
 /*
  * Send relayd sockets from snapshot output to consumer. Ignore request if the
  * snapshot output is *not* set with a remote destination.
@@ -2799,7 +3578,7 @@ error:
  */
 static int record_kernel_snapshot(struct ltt_kernel_session *ksess,
                struct snapshot_output *output, struct ltt_session *session,
-               int wait, int nb_streams)
+               int wait, uint64_t nb_packets_per_stream)
 {
        int ret;
 
@@ -2830,17 +3609,19 @@ static int record_kernel_snapshot(struct ltt_kernel_session *ksess,
                goto error_snapshot;
        }
 
-       ret = kernel_snapshot_record(ksess, output, wait, nb_streams);
+       ret = kernel_snapshot_record(ksess, output, wait, nb_packets_per_stream);
        if (ret != LTTNG_OK) {
                goto error_snapshot;
        }
 
        ret = LTTNG_OK;
+       goto end;
 
 error_snapshot:
        /* Clean up copied sockets so this output can use some other later on. */
        consumer_destroy_output_sockets(output->consumer);
 error:
+end:
        return ret;
 }
 
@@ -2851,7 +3632,7 @@ error:
  */
 static int record_ust_snapshot(struct ltt_ust_session *usess,
                struct snapshot_output *output, struct ltt_session *session,
-               int wait, int nb_streams)
+               int wait, uint64_t nb_packets_per_stream)
 {
        int ret;
 
@@ -2882,7 +3663,7 @@ static int record_ust_snapshot(struct ltt_ust_session *usess,
                goto error_snapshot;
        }
 
-       ret = ust_app_snapshot_record(usess, output, wait, nb_streams);
+       ret = ust_app_snapshot_record(usess, output, wait, nb_packets_per_stream);
        if (ret < 0) {
                switch (-ret) {
                case EINVAL:
@@ -2907,27 +3688,90 @@ error:
        return ret;
 }
 
-/*
- * Returns the total number of streams for a session or a negative value
- * on error.
- */
-static unsigned int get_total_nb_stream(struct ltt_session *session)
+static
+uint64_t get_session_size_one_more_packet_per_stream(struct ltt_session *session,
+       uint64_t cur_nr_packets)
 {
-       unsigned int total_streams = 0;
+       uint64_t tot_size = 0;
 
        if (session->kernel_session) {
+               struct ltt_kernel_channel *chan;
                struct ltt_kernel_session *ksess = session->kernel_session;
 
-               total_streams += ksess->stream_count_global;
+               cds_list_for_each_entry(chan, &ksess->channel_list.head, list) {
+                       if (cur_nr_packets >= chan->channel->attr.num_subbuf) {
+                               /*
+                                * Don't take channel into account if we
+                                * already grab all its packets.
+                                */
+                               continue;
+                       }
+                       tot_size += chan->channel->attr.subbuf_size
+                               * chan->stream_count;
+               }
        }
 
        if (session->ust_session) {
                struct ltt_ust_session *usess = session->ust_session;
 
-               total_streams += ust_app_get_nb_stream(usess);
+               tot_size += ust_app_get_size_one_more_packet_per_stream(usess,
+                               cur_nr_packets);
+       }
+
+       return tot_size;
+}
+
+/*
+ * Calculate the number of packets we can grab from each stream that
+ * fits within the overall snapshot max size.
+ *
+ * Returns -1 on error, 0 means infinite number of packets, else > 0 is
+ * the number of packets per stream.
+ *
+ * TODO: this approach is not perfect: we consider the worse case
+ * (packet filling the sub-buffers) as an upper bound, but we could do
+ * better if we do this calculation while we actually grab the packet
+ * content: we would know how much padding we don't actually store into
+ * the file.
+ *
+ * This algorithm is currently bounded by the number of packets per
+ * stream.
+ *
+ * Since we call this algorithm before actually grabbing the data, it's
+ * an approximation: for instance, applications could appear/disappear
+ * in between this call and actually grabbing data.
+ */
+static
+int64_t get_session_nb_packets_per_stream(struct ltt_session *session, uint64_t max_size)
+{
+       int64_t size_left;
+       uint64_t cur_nb_packets = 0;
+
+       if (!max_size) {
+               return 0;       /* Infinite */
        }
 
-       return total_streams;
+       size_left = max_size;
+       for (;;) {
+               uint64_t one_more_packet_tot_size;
+
+               one_more_packet_tot_size = get_session_size_one_more_packet_per_stream(session,
+                                       cur_nb_packets);
+               if (!one_more_packet_tot_size) {
+                       /* We are already grabbing all packets. */
+                       break;
+               }
+               size_left -= one_more_packet_tot_size;
+               if (size_left < 0) {
+                       break;
+               }
+               cur_nb_packets++;
+       }
+       if (!cur_nb_packets) {
+               /* Not enough room to grab one packet of each stream, error. */
+               return -1;
+       }
+       return cur_nb_packets;
 }
 
 /*
@@ -2944,9 +3788,10 @@ int cmd_snapshot_record(struct ltt_session *session,
        int ret = LTTNG_OK;
        unsigned int use_tmp_output = 0;
        struct snapshot_output tmp_output;
-       unsigned int nb_streams, snapshot_success = 0;
+       unsigned int snapshot_success = 0;
 
        assert(session);
+       assert(output);
 
        DBG("Cmd snapshot record for session %s", session->name);
 
@@ -2966,7 +3811,7 @@ int cmd_snapshot_record(struct ltt_session *session,
        }
 
        /* Use temporary output for the session. */
-       if (output && *output->ctrl_url != '\0') {
+       if (*output->ctrl_url != '\0') {
                ret = snapshot_output_init(output->max_size, output->name,
                                output->ctrl_url, output->data_url, session->consumer,
                                &tmp_output, NULL);
@@ -2983,18 +3828,20 @@ int cmd_snapshot_record(struct ltt_session *session,
                use_tmp_output = 1;
        }
 
-       /*
-        * Get the total number of stream of that session which is used by the
-        * maximum size of the snapshot feature.
-        */
-       nb_streams = get_total_nb_stream(session);
-
        if (session->kernel_session) {
                struct ltt_kernel_session *ksess = session->kernel_session;
 
                if (use_tmp_output) {
+                       int64_t nb_packets_per_stream;
+
+                       nb_packets_per_stream = get_session_nb_packets_per_stream(session,
+                                       tmp_output.max_size);
+                       if (nb_packets_per_stream < 0) {
+                               ret = LTTNG_ERR_MAX_SIZE_INVALID;
+                               goto error;
+                       }
                        ret = record_kernel_snapshot(ksess, &tmp_output, session,
-                                       wait, nb_streams);
+                                       wait, nb_packets_per_stream);
                        if (ret != LTTNG_OK) {
                                goto error;
                        }
@@ -3006,6 +3853,8 @@ int cmd_snapshot_record(struct ltt_session *session,
                        rcu_read_lock();
                        cds_lfht_for_each_entry(session->snapshot.output_ht->ht,
                                        &iter.iter, sout, node.node) {
+                               int64_t nb_packets_per_stream;
+
                                /*
                                 * Make a local copy of the output and assign the possible
                                 * temporary value given by the caller.
@@ -3013,11 +3862,17 @@ int cmd_snapshot_record(struct ltt_session *session,
                                memset(&tmp_output, 0, sizeof(tmp_output));
                                memcpy(&tmp_output, sout, sizeof(tmp_output));
 
-                               /* Use temporary max size. */
                                if (output->max_size != (uint64_t) -1ULL) {
                                        tmp_output.max_size = output->max_size;
                                }
 
+                               nb_packets_per_stream = get_session_nb_packets_per_stream(session,
+                                               tmp_output.max_size);
+                               if (nb_packets_per_stream < 0) {
+                                       ret = LTTNG_ERR_MAX_SIZE_INVALID;
+                                       goto error;
+                               }
+
                                /* Use temporary name. */
                                if (*output->name != '\0') {
                                        strncpy(tmp_output.name, output->name,
@@ -3027,7 +3882,7 @@ int cmd_snapshot_record(struct ltt_session *session,
                                tmp_output.nb_snapshot = session->snapshot.nb_snapshot;
 
                                ret = record_kernel_snapshot(ksess, &tmp_output,
-                                               session, wait, nb_streams);
+                                               session, wait, nb_packets_per_stream);
                                if (ret != LTTNG_OK) {
                                        rcu_read_unlock();
                                        goto error;
@@ -3042,8 +3897,16 @@ int cmd_snapshot_record(struct ltt_session *session,
                struct ltt_ust_session *usess = session->ust_session;
 
                if (use_tmp_output) {
+                       int64_t nb_packets_per_stream;
+
+                       nb_packets_per_stream = get_session_nb_packets_per_stream(session,
+                                       tmp_output.max_size);
+                       if (nb_packets_per_stream < 0) {
+                               ret = LTTNG_ERR_MAX_SIZE_INVALID;
+                               goto error;
+                       }
                        ret = record_ust_snapshot(usess, &tmp_output, session,
-                                       wait, nb_streams);
+                                       wait, nb_packets_per_stream);
                        if (ret != LTTNG_OK) {
                                goto error;
                        }
@@ -3055,6 +3918,8 @@ int cmd_snapshot_record(struct ltt_session *session,
                        rcu_read_lock();
                        cds_lfht_for_each_entry(session->snapshot.output_ht->ht,
                                        &iter.iter, sout, node.node) {
+                               int64_t nb_packets_per_stream;
+
                                /*
                                 * Make a local copy of the output and assign the possible
                                 * temporary value given by the caller.
@@ -3062,11 +3927,18 @@ int cmd_snapshot_record(struct ltt_session *session,
                                memset(&tmp_output, 0, sizeof(tmp_output));
                                memcpy(&tmp_output, sout, sizeof(tmp_output));
 
-                               /* Use temporary max size. */
                                if (output->max_size != (uint64_t) -1ULL) {
                                        tmp_output.max_size = output->max_size;
                                }
 
+                               nb_packets_per_stream = get_session_nb_packets_per_stream(session,
+                                               tmp_output.max_size);
+                               if (nb_packets_per_stream < 0) {
+                                       ret = LTTNG_ERR_MAX_SIZE_INVALID;
+                                       rcu_read_unlock();
+                                       goto error;
+                               }
+
                                /* Use temporary name. */
                                if (*output->name != '\0') {
                                        strncpy(tmp_output.name, output->name,
@@ -3076,7 +3948,7 @@ int cmd_snapshot_record(struct ltt_session *session,
                                tmp_output.nb_snapshot = session->snapshot.nb_snapshot;
 
                                ret = record_ust_snapshot(usess, &tmp_output, session,
-                                               wait, nb_streams);
+                                               wait, nb_packets_per_stream);
                                if (ret != LTTNG_OK) {
                                        rcu_read_unlock();
                                        goto error;
@@ -3097,6 +3969,29 @@ error:
        return ret;
 }
 
+/*
+ * Command LTTNG_SET_SESSION_SHM_PATH processed by the client thread.
+ */
+int cmd_set_session_shm_path(struct ltt_session *session,
+               const char *shm_path)
+{
+       /* Safety net */
+       assert(session);
+
+       /*
+        * Can only set shm path before session is started.
+        */
+       if (session->has_been_started) {
+               return LTTNG_ERR_SESSION_STARTED;
+       }
+
+       strncpy(session->shm_path, shm_path,
+               sizeof(session->shm_path));
+       session->shm_path[sizeof(session->shm_path) - 1] = '\0';
+
+       return 0;
+}
+
 /*
  * Init command subsystem.
  */
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