trigger: expose trigger owner uid
[lttng-tools.git] / src / lib / lttng-ctl / lttng-ctl.c
index 8ca8e46effc4e16c4dca3c54fb3697172f47b966..60dcdc7d33872cbf190e79b1dfe9e3385f72e545 100644 (file)
@@ -1,68 +1,64 @@
 /*
- * liblttngctl.c
+ * lttng-ctl.c
  *
  * Linux Trace Toolkit Control Library
  *
  * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
- * Copyright (C) 2016 Jérémie Galarneau <jeremie.galarneau@efficios.com>
+ * Copyright (C) 2016 Jérémie Galarneau <jeremie.galarneau@efficios.com>
  *
- * This library is free software; you can redistribute it and/or modify it
- * under the terms of the GNU Lesser General Public License, version 2.1 only,
- * as published by the Free Software Foundation.
+ * SPDX-License-Identifier: LGPL-2.1-only
  *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public License
- * along with this library; if not, write to the Free Software Foundation,
- * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #define _LGPL_SOURCE
 #include <assert.h>
 #include <grp.h>
-#include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 
 #include <common/common.h>
+#include <common/compat/errno.h>
+#include <common/compat/string.h>
 #include <common/defaults.h>
+#include <common/dynamic-buffer.h>
+#include <common/dynamic-array.h>
+#include <common/payload.h>
+#include <common/payload-view.h>
 #include <common/sessiond-comm/sessiond-comm.h>
+#include <common/tracker.h>
+#include <common/unix.h>
 #include <common/uri.h>
 #include <common/utils.h>
-#include <lttng/lttng.h>
+#include <lttng/channel-internal.h>
+#include <lttng/destruction-handle.h>
+#include <lttng/endpoint.h>
+#include <lttng/event-internal.h>
 #include <lttng/health-internal.h>
+#include <lttng/lttng.h>
+#include <lttng/session-descriptor-internal.h>
+#include <lttng/session-internal.h>
 #include <lttng/trigger/trigger-internal.h>
-#include <lttng/endpoint.h>
-#include <lttng/channel-internal.h>
+#include <lttng/userspace-probe-internal.h>
+#include <lttng/lttng-error.h>
 
-#include "filter/filter-ast.h"
-#include "filter/filter-parser.h"
-#include "filter/filter-bytecode.h"
-#include "filter/memstream.h"
+#include <common/filter/filter-ast.h>
+#include <common/filter/filter-parser.h>
+#include <common/filter/filter-bytecode.h>
+#include <common/filter/memstream.h>
 #include "lttng-ctl-helper.h"
 
-#ifdef DEBUG
-static const int print_xml = 1;
-#define dbg_printf(fmt, args...)       \
-       printf("[debug liblttng-ctl] " fmt, ## args)
-#else
-static const int print_xml = 0;
-#define dbg_printf(fmt, args...)                               \
+#define COPY_DOMAIN_PACKED(dst, src)                           \
 do {                                                           \
-       /* do nothing but check printf format */                \
-       if (0)                                                  \
-               printf("[debug liblttnctl] " fmt, ## args);     \
+       struct lttng_domain _tmp_domain;                        \
+                                                               \
+       lttng_ctl_copy_lttng_domain(&_tmp_domain, &src);        \
+       dst = _tmp_domain;                                      \
 } while (0)
-#endif
-
 
 /* Socket to session daemon for communication */
-static int sessiond_socket;
+static int sessiond_socket = -1;
 static char sessiond_sock_path[PATH_MAX];
 
 /* Variables */
@@ -176,11 +172,40 @@ end:
        return ret;
 }
 
+/*
+ * Send file descriptors to the session daemon.
+ *
+ * On success, returns the number of bytes sent (>=0)
+ * On error, returns -1
+ */
+static int send_session_fds(const int *fds, size_t nb_fd)
+{
+       int ret;
+
+       if (!connected) {
+               ret = -LTTNG_ERR_NO_SESSIOND;
+               goto end;
+       }
+
+       if (!fds || !nb_fd) {
+               ret = 0;
+               goto end;
+       }
+
+       ret = lttcomm_send_fds_unix_sock(sessiond_socket, fds, nb_fd);
+       if (ret < 0) {
+               ret = -LTTNG_ERR_FATAL;
+       }
+
+end:
+       return ret;
+}
+
 /*
  * Receive data from the sessiond socket.
  *
  * On success, returns the number of bytes received (>=0)
- * On error, returns -1 (recvmsg() error) or -ENOTCONN
+ * On error, returns a negative lttng_error_code.
  */
 static int recv_data_sessiond(void *buf, size_t len)
 {
@@ -200,6 +225,30 @@ end:
        return ret;
 }
 
+/*
+ * Receive a payload from the session daemon by appending to an existing
+ * payload.
+ * On success, returns the number of bytes received (>=0)
+ * On error, returns a negative lttng_error_code.
+ */
+static int recv_payload_sessiond(struct lttng_payload *payload, size_t len)
+{
+       int ret;
+       const size_t original_payload_size = payload->buffer.size;
+
+       ret = lttng_dynamic_buffer_set_size(
+                       &payload->buffer, payload->buffer.size + len);
+       if (ret) {
+               ret = -LTTNG_ERR_NOMEM;
+               goto end;
+       }
+
+       ret = recv_data_sessiond(
+                       payload->buffer.data + original_payload_size, len);
+end:
+       return ret;
+}
+
 /*
  * Check if we are in the specified group.
  *
@@ -208,15 +257,13 @@ end:
 LTTNG_HIDDEN
 int lttng_check_tracing_group(void)
 {
-       struct group *grp_tracing;      /* no free(). See getgrnam(3) */
-       gid_t *grp_list;
+       gid_t *grp_list, tracing_gid;
        int grp_list_size, grp_id, i;
        int ret = -1;
        const char *grp_name = tracing_group;
 
        /* Get GID of group 'tracing' */
-       grp_tracing = getgrnam(grp_name);
-       if (!grp_tracing) {
+       if (utils_get_group_id(grp_name, false, &tracing_gid)) {
                /* If grp_tracing is NULL, the group does not exist. */
                goto end;
        }
@@ -241,7 +288,7 @@ int lttng_check_tracing_group(void)
        }
 
        for (i = 0; i < grp_list_size; i++) {
-               if (grp_list[i] == grp_tracing->gr_gid) {
+               if (grp_list[i] == tracing_gid) {
                        ret = 1;
                        break;
                }
@@ -254,6 +301,50 @@ end:
        return ret;
 }
 
+static int check_enough_available_memory(size_t num_bytes_requested_per_cpu)
+{
+       int ret;
+       long num_cpu;
+       size_t best_mem_info;
+       size_t num_bytes_requested_total;
+
+       /*
+        * Get the number of CPU currently online to compute the amount of
+        * memory needed to create a buffer for every CPU.
+        */
+       num_cpu = sysconf(_SC_NPROCESSORS_ONLN);
+       if (num_cpu == -1) {
+               goto error;
+       }
+
+       num_bytes_requested_total = num_bytes_requested_per_cpu * num_cpu;
+
+       /*
+        * Try to get the `MemAvail` field of `/proc/meminfo`. This is the most
+        * reliable estimate we can get but it is only exposed by the kernel
+        * since 3.14. (See Linux kernel commit:
+        * 34e431b0ae398fc54ea69ff85ec700722c9da773)
+        */
+       ret = utils_get_memory_available(&best_mem_info);
+       if (ret >= 0) {
+               goto success;
+       }
+
+       /*
+        * As a backup plan, use `MemTotal` field of `/proc/meminfo`. This
+        * is a sanity check for obvious user error.
+        */
+       ret = utils_get_memory_total(&best_mem_info);
+       if (ret >= 0) {
+               goto success;
+       }
+
+error:
+       return -1;
+success:
+       return best_mem_info >= num_bytes_requested_total;
+}
+
 /*
  * Try connect to session daemon with sock_path.
  *
@@ -346,17 +437,12 @@ error:
 /*
  * Connect to the LTTng session daemon.
  *
- * On success, return 0. On error, return -1.
+ * On success, return the socket's file descriptor. On error, return -1.
  */
-static int connect_sessiond(void)
+LTTNG_HIDDEN int connect_sessiond(void)
 {
        int ret;
 
-       /* Don't try to connect if already connected. */
-       if (connected) {
-               return 0;
-       }
-
        ret = set_session_daemon_path();
        if (ret < 0) {
                goto error;
@@ -368,15 +454,18 @@ static int connect_sessiond(void)
                goto error;
        }
 
-       sessiond_socket = ret;
-       connected = 1;
-
-       return 0;
+       return ret;
 
 error:
        return -1;
 }
 
+static void reset_global_sessiond_connection_state(void)
+{
+       sessiond_socket = -1;
+       connected = 0;
+}
+
 /*
  *  Clean disconnect from the session daemon.
  *
@@ -388,8 +477,7 @@ static int disconnect_sessiond(void)
 
        if (connected) {
                ret = lttcomm_close_unix_sock(sessiond_socket);
-               sessiond_socket = 0;
-               connected = 0;
+               reset_global_sessiond_connection_state();
        }
 
        return ret;
@@ -445,15 +533,16 @@ end:
 
 /*
  * Ask the session daemon a specific command and put the data into buf.
- * Takes extra var. len. data as input to send to the session daemon.
+ * Takes extra var. len. data and file descriptors as input to send to the
+ * session daemon.
  *
  * Return size of data (only payload, not header) or a negative error code.
  */
 LTTNG_HIDDEN
-int lttng_ctl_ask_sessiond_varlen(struct lttcomm_session_msg *lsm,
-               const void *vardata, size_t vardata_len,
-               void **user_payload_buf, void **user_cmd_header_buf,
-               size_t *user_cmd_header_len)
+int lttng_ctl_ask_sessiond_fds_varlen(struct lttcomm_session_msg *lsm,
+               const int *fds, size_t nb_fd, const void *vardata,
+               size_t vardata_len, void **user_payload_buf,
+               void **user_cmd_header_buf, size_t *user_cmd_header_len)
 {
        int ret;
        size_t payload_len;
@@ -463,9 +552,11 @@ int lttng_ctl_ask_sessiond_varlen(struct lttcomm_session_msg *lsm,
        if (ret < 0) {
                ret = -LTTNG_ERR_NO_SESSIOND;
                goto end;
+       } else {
+               sessiond_socket = ret;
+               connected = 1;
        }
 
-       /* Send command to session daemon */
        ret = send_session_msg(lsm);
        if (ret < 0) {
                /* Ret value is a valid lttng error code. */
@@ -478,6 +569,13 @@ int lttng_ctl_ask_sessiond_varlen(struct lttcomm_session_msg *lsm,
                goto end;
        }
 
+       /* Send fds */
+       ret = send_session_fds(fds, nb_fd);
+       if (ret < 0) {
+               /* Ret value is a valid lttng error code. */
+               goto end;
+       }
+
        /* Get header from data transmission */
        ret = recv_data_sessiond(&llm, sizeof(llm));
        if (ret < 0) {
@@ -512,6 +610,98 @@ end:
        return ret;
 }
 
+LTTNG_HIDDEN
+int lttng_ctl_ask_sessiond_payload(struct lttng_payload_view *message,
+       struct lttng_payload *reply)
+{
+       int ret;
+       struct lttcomm_lttng_msg llm;
+       const int fd_count = lttng_payload_view_get_fd_handle_count(message);
+
+       assert(reply->buffer.size == 0);
+       assert(lttng_dynamic_pointer_array_get_count(&reply->_fd_handles) == 0);
+
+       ret = connect_sessiond();
+       if (ret < 0) {
+               ret = -LTTNG_ERR_NO_SESSIOND;
+               goto end;
+       } else {
+               sessiond_socket = ret;
+               connected = 1;
+       }
+
+       /* Send command to session daemon */
+       ret = lttcomm_send_creds_unix_sock(sessiond_socket, message->buffer.data,
+                       message->buffer.size);
+       if (ret < 0) {
+               ret = -LTTNG_ERR_FATAL;
+               goto end;
+       }
+
+       if (fd_count > 0) {
+               ret = lttcomm_send_payload_view_fds_unix_sock(sessiond_socket,
+                               message);
+               if (ret < 0) {
+                       ret = -LTTNG_ERR_FATAL;
+                       goto end;
+               }
+       }
+
+       /* Get header from data transmission */
+       ret = recv_payload_sessiond(reply, sizeof(llm));
+       if (ret < 0) {
+               /* Ret value is a valid lttng error code. */
+               goto end;
+       }
+
+       llm = *((typeof(llm) *) reply->buffer.data);
+
+       /* Check error code if OK */
+       if (llm.ret_code != LTTNG_OK) {
+               ret = -llm.ret_code;
+               goto end;
+       }
+
+       if (llm.cmd_header_size > 0) {
+               ret = recv_payload_sessiond(reply, llm.cmd_header_size);
+               if (ret < 0) {
+                       goto end;
+               }
+       }
+
+       /* Get command header from data transmission */
+       if (llm.data_size > 0) {
+               ret = recv_payload_sessiond(reply, llm.data_size);
+               if (ret < 0) {
+                       goto end;
+               }
+       }
+
+       if (llm.fd_count > 0) {
+               ret = lttcomm_recv_payload_fds_unix_sock(
+                               sessiond_socket, llm.fd_count, reply);
+               if (ret < 0) {
+                       goto end;
+               }
+       }
+
+       /* Don't return the llm header to the caller. */
+       memmove(reply->buffer.data, reply->buffer.data + sizeof(llm),
+                       reply->buffer.size - sizeof(llm));
+       ret = lttng_dynamic_buffer_set_size(
+                       &reply->buffer, reply->buffer.size - sizeof(llm));
+       if (ret) {
+               /* Can't happen as size is reduced. */
+               abort();
+       }
+
+       ret = reply->buffer.size;
+
+end:
+       disconnect_sessiond();
+       return ret;
+}
+
 /*
  * Create lttng handle and return pointer.
  *
@@ -567,7 +757,7 @@ int lttng_register_consumer(struct lttng_handle *handle,
        lsm.cmd_type = LTTNG_REGISTER_CONSUMER;
        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));
-       lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
 
        lttng_ctl_copy_string(lsm.u.reg.path, socket_path,
                        sizeof(lsm.u.reg.path));
@@ -638,7 +828,7 @@ static int _lttng_stop_tracing(const char *session_name, int wait)
                 * call returned value indicates availability.
                 */
                if (data_ret) {
-                       usleep(DEFAULT_DATA_AVAILABILITY_WAIT_TIME);
+                       usleep(DEFAULT_DATA_AVAILABILITY_WAIT_TIME_US);
                }
        } while (data_ret != 0);
 
@@ -698,7 +888,7 @@ int lttng_add_context(struct lttng_handle *handle,
                                sizeof(lsm.u.context.channel_name));
        }
 
-       lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));
 
@@ -812,7 +1002,7 @@ static char *set_agent_filter(const char *filter, struct lttng_event *ev)
 
        /* Add loglevel filtering if any for the JUL domain. */
        if (ev->loglevel_type != LTTNG_EVENT_LOGLEVEL_ALL) {
-               char *op;
+               const char *op;
 
                if (ev->loglevel_type == LTTNG_EVENT_LOGLEVEL_RANGE) {
                        op = ">=";
@@ -846,133 +1036,6 @@ error:
        return NULL;
 }
 
-/*
- * Generate the filter bytecode from a given filter expression string. Put the
- * newly allocated parser context in ctxp and populate the lsm object with the
- * expression len.
- *
- * Return 0 on success else a LTTNG_ERR_* code and ctxp is untouched.
- */
-static int generate_filter(char *filter_expression,
-               struct lttcomm_session_msg *lsm, struct filter_parser_ctx **ctxp)
-{
-       int ret;
-       struct filter_parser_ctx *ctx = NULL;
-       FILE *fmem = NULL;
-
-       assert(filter_expression);
-       assert(lsm);
-       assert(ctxp);
-
-       /*
-        * Casting const to non-const, as the underlying function will use it in
-        * read-only mode.
-        */
-       fmem = lttng_fmemopen((void *) filter_expression,
-                       strlen(filter_expression), "r");
-       if (!fmem) {
-               fprintf(stderr, "Error opening memory as stream\n");
-               ret = -LTTNG_ERR_FILTER_NOMEM;
-               goto error;
-       }
-       ctx = filter_parser_ctx_alloc(fmem);
-       if (!ctx) {
-               fprintf(stderr, "Error allocating parser\n");
-               ret = -LTTNG_ERR_FILTER_NOMEM;
-               goto filter_alloc_error;
-       }
-       ret = filter_parser_ctx_append_ast(ctx);
-       if (ret) {
-               fprintf(stderr, "Parse error\n");
-               ret = -LTTNG_ERR_FILTER_INVAL;
-               goto parse_error;
-       }
-       if (print_xml) {
-               ret = filter_visitor_print_xml(ctx, stdout, 0);
-               if (ret) {
-                       fflush(stdout);
-                       fprintf(stderr, "XML print error\n");
-                       ret = -LTTNG_ERR_FILTER_INVAL;
-                       goto parse_error;
-               }
-       }
-
-       dbg_printf("Generating IR... ");
-       fflush(stdout);
-       ret = filter_visitor_ir_generate(ctx);
-       if (ret) {
-               fprintf(stderr, "Generate IR error\n");
-               ret = -LTTNG_ERR_FILTER_INVAL;
-               goto parse_error;
-       }
-       dbg_printf("done\n");
-
-       dbg_printf("Validating IR... ");
-       fflush(stdout);
-       ret = filter_visitor_ir_check_binary_op_nesting(ctx);
-       if (ret) {
-               ret = -LTTNG_ERR_FILTER_INVAL;
-               goto parse_error;
-       }
-
-       /* Normalize globbing patterns in the expression. */
-       ret = filter_visitor_ir_normalize_glob_patterns(ctx);
-       if (ret) {
-               ret = -LTTNG_ERR_FILTER_INVAL;
-               goto parse_error;
-       }
-
-       /* Validate strings used as literals in the expression. */
-       ret = filter_visitor_ir_validate_string(ctx);
-       if (ret) {
-               ret = -LTTNG_ERR_FILTER_INVAL;
-               goto parse_error;
-       }
-
-       /* Validate globbing patterns in the expression. */
-       ret = filter_visitor_ir_validate_globbing(ctx);
-       if (ret) {
-               ret = -LTTNG_ERR_FILTER_INVAL;
-               goto parse_error;
-       }
-
-       dbg_printf("done\n");
-
-       dbg_printf("Generating bytecode... ");
-       fflush(stdout);
-       ret = filter_visitor_bytecode_generate(ctx);
-       if (ret) {
-               fprintf(stderr, "Generate bytecode error\n");
-               ret = -LTTNG_ERR_FILTER_INVAL;
-               goto parse_error;
-       }
-       dbg_printf("done\n");
-       dbg_printf("Size of bytecode generated: %u bytes.\n",
-                       bytecode_get_len(&ctx->bytecode->b));
-
-       lsm->u.enable.bytecode_len = sizeof(ctx->bytecode->b)
-               + bytecode_get_len(&ctx->bytecode->b);
-       lsm->u.enable.expression_len = strlen(filter_expression) + 1;
-
-       /* No need to keep the memory stream. */
-       if (fclose(fmem) != 0) {
-               PERROR("fclose");
-       }
-
-       *ctxp = ctx;
-       return 0;
-
-parse_error:
-       filter_ir_free(ctx);
-       filter_parser_ctx_free(ctx);
-filter_alloc_error:
-       if (fclose(fmem) != 0) {
-               PERROR("fclose");
-       }
-error:
-       return ret;
-}
-
 /*
  * Enable event(s) for a channel, possibly with exclusions and a filter.
  * If no event name is specified, all events are enabled.
@@ -987,10 +1050,17 @@ int lttng_enable_event_with_exclusions(struct lttng_handle *handle,
                int exclusion_count, char **exclusion_list)
 {
        struct lttcomm_session_msg lsm;
-       char *varlen_data;
-       int ret = 0;
+       struct lttng_payload payload;
+       int ret = 0, i;
        unsigned int free_filter_expression = 0;
        struct filter_parser_ctx *ctx = NULL;
+
+       /*
+        * We have either a filter or some exclusions, so we need to set up
+        * a variable-length payload from where to send the data.
+        */
+       lttng_payload_init(&payload);
+
        /*
         * Cast as non-const since we may replace the filter expression
         * by a dynamically allocated string. Otherwise, the original
@@ -1030,8 +1100,7 @@ int lttng_enable_event_with_exclusions(struct lttng_handle *handle,
                lttng_ctl_copy_string(ev->name, "*", sizeof(ev->name));
        }
 
-       lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);
-       /* FIXME: copying non-packed struct to packed struct. */
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
        memcpy(&lsm.u.enable.event, ev, sizeof(lsm.u.enable.event));
 
        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
@@ -1039,23 +1108,6 @@ int lttng_enable_event_with_exclusions(struct lttng_handle *handle,
        lsm.u.enable.exclusion_count = exclusion_count;
        lsm.u.enable.bytecode_len = 0;
 
-       /*
-        * For the JUL domain, a filter is enforced except for the enable all
-        * event. This is done to avoid having the event in all sessions thus
-        * filtering by logger name.
-        */
-       if (exclusion_count == 0 && filter_expression == NULL &&
-                       (handle->domain.type != LTTNG_DOMAIN_JUL &&
-                               handle->domain.type != LTTNG_DOMAIN_LOG4J &&
-                               handle->domain.type != LTTNG_DOMAIN_PYTHON)) {
-               goto ask_sessiond;
-       }
-
-       /*
-        * We have either a filter or some exclusions, so we need to set up
-        * a variable-length memory block from where to send the data.
-        */
-
        /* Parse filter expression. */
        if (filter_expression != NULL || handle->domain.type == LTTNG_DOMAIN_JUL
                        || handle->domain.type == LTTNG_DOMAIN_LOG4J
@@ -1086,47 +1138,113 @@ int lttng_enable_event_with_exclusions(struct lttng_handle *handle,
                        }
                }
 
-               ret = generate_filter(filter_expression, &lsm, &ctx);
+               ret = filter_parser_ctx_create_from_filter_expression(filter_expression, &ctx);
                if (ret) {
                        goto filter_error;
                }
+
+               lsm.u.enable.bytecode_len = sizeof(ctx->bytecode->b)
+                       + bytecode_get_len(&ctx->bytecode->b);
+               lsm.u.enable.expression_len = strlen(filter_expression) + 1;
        }
 
-       varlen_data = zmalloc(lsm.u.enable.bytecode_len
-                       + lsm.u.enable.expression_len
-                       + LTTNG_SYMBOL_NAME_LEN * exclusion_count);
-       if (!varlen_data) {
+       ret = lttng_dynamic_buffer_set_capacity(&payload.buffer,
+                       lsm.u.enable.bytecode_len +
+                                       lsm.u.enable.expression_len +
+                                       LTTNG_SYMBOL_NAME_LEN *
+                                                       exclusion_count);
+       if (ret) {
                ret = -LTTNG_ERR_EXCLUSION_NOMEM;
                goto mem_error;
        }
 
        /* Put exclusion names first in the data. */
-       while (exclusion_count--) {
-               strncpy(varlen_data + LTTNG_SYMBOL_NAME_LEN * exclusion_count,
-                       *(exclusion_list + exclusion_count),
-                       LTTNG_SYMBOL_NAME_LEN - 1);
+       for (i = 0; i < exclusion_count; i++) {
+               size_t exclusion_len;
+
+               exclusion_len = lttng_strnlen(*(exclusion_list + i),
+                               LTTNG_SYMBOL_NAME_LEN);
+               if (exclusion_len == LTTNG_SYMBOL_NAME_LEN) {
+                       /* Exclusion is not NULL-terminated. */
+                       ret = -LTTNG_ERR_INVALID;
+                       goto mem_error;
+               }
+
+               ret = lttng_dynamic_buffer_append(&payload.buffer,
+                               *(exclusion_list + i), LTTNG_SYMBOL_NAME_LEN);
+               if (ret) {
+                       goto mem_error;
+               }
        }
+
        /* Add filter expression next. */
-       if (lsm.u.enable.expression_len != 0) {
-               memcpy(varlen_data
-                       + LTTNG_SYMBOL_NAME_LEN * lsm.u.enable.exclusion_count,
-                       filter_expression,
-                       lsm.u.enable.expression_len);
+       if (filter_expression) {
+               ret = lttng_dynamic_buffer_append(&payload.buffer,
+                               filter_expression, lsm.u.enable.expression_len);
+               if (ret) {
+                       goto mem_error;
+               }
        }
        /* Add filter bytecode next. */
        if (ctx && lsm.u.enable.bytecode_len != 0) {
-               memcpy(varlen_data
-                       + LTTNG_SYMBOL_NAME_LEN * lsm.u.enable.exclusion_count
-                       + lsm.u.enable.expression_len,
-                       &ctx->bytecode->b,
-                       lsm.u.enable.bytecode_len);
+               ret = lttng_dynamic_buffer_append(&payload.buffer,
+                               &ctx->bytecode->b, lsm.u.enable.bytecode_len);
+               if (ret) {
+                       goto mem_error;
+               }
        }
+       if (ev->extended.ptr) {
+               struct lttng_event_extended *ev_ext =
+                       (struct lttng_event_extended *) ev->extended.ptr;
+
+               if (ev_ext->probe_location) {
+                       /*
+                        * lttng_userspace_probe_location_serialize returns the
+                        * number of bytes that was appended to the buffer.
+                        */
+                       ret = lttng_userspace_probe_location_serialize(
+                                       ev_ext->probe_location, &payload);
+                       if (ret < 0) {
+                               goto mem_error;
+                       }
 
-       ret = lttng_ctl_ask_sessiond_varlen_no_cmd_header(&lsm, varlen_data,
-                       (LTTNG_SYMBOL_NAME_LEN * lsm.u.enable.exclusion_count) +
-                       lsm.u.enable.bytecode_len + lsm.u.enable.expression_len,
-                       NULL);
-       free(varlen_data);
+                       /*
+                        * Set the size of the userspace probe location element
+                        * of the buffer so that the receiving side knows where
+                        * to split it.
+                        */
+                       lsm.u.enable.userspace_probe_location_len = ret;
+               }
+       }
+
+       {
+               struct lttng_payload_view view = lttng_payload_view_from_payload(
+                       &payload, 0, -1);
+               int fd_count = lttng_payload_view_get_fd_handle_count(&view);
+               int fd_to_send;
+
+               if (fd_count < 0) {
+                       goto mem_error;
+               }
+
+               assert(fd_count == 0 || fd_count == 1);
+               if (fd_count == 1) {
+                       struct fd_handle *handle =
+                                       lttng_payload_view_pop_fd_handle(&view);
+
+                       if (!handle) {
+                               goto mem_error;
+                       }
+
+                       fd_to_send = fd_handle_get_fd(handle);
+                       fd_handle_put(handle);
+               }
+
+               ret = lttng_ctl_ask_sessiond_fds_varlen(&lsm,
+                               fd_count ? &fd_to_send : NULL, fd_count,
+                               view.buffer.size ? view.buffer.data : NULL,
+                               view.buffer.size, NULL, NULL, 0);
+       }
 
 mem_error:
        if (filter_expression && ctx) {
@@ -1148,6 +1266,7 @@ error:
         * Return directly to the caller and don't ask the sessiond since
         * something went wrong in the parsing of data above.
         */
+       lttng_payload_reset(&payload);
        return ret;
 
 ask_sessiond:
@@ -1199,8 +1318,7 @@ int lttng_disable_event_ext(struct lttng_handle *handle,
 
        lsm.cmd_type = LTTNG_DISABLE_EVENT;
 
-       lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);
-       /* FIXME: copying non-packed struct to packed struct. */
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
        memcpy(&lsm.u.disable.event, ev, sizeof(lsm.u.disable.event));
 
        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
@@ -1254,10 +1372,14 @@ int lttng_disable_event_ext(struct lttng_handle *handle,
                        }
                }
 
-               ret = generate_filter(filter_expression, &lsm, &ctx);
+               ret = filter_parser_ctx_create_from_filter_expression(filter_expression, &ctx);
                if (ret) {
                        goto filter_error;
                }
+
+               lsm.u.enable.bytecode_len = sizeof(ctx->bytecode->b)
+                       + bytecode_get_len(&ctx->bytecode->b);
+               lsm.u.enable.expression_len = strlen(filter_expression) + 1;
        }
 
        varlen_data = zmalloc(lsm.u.disable.bytecode_len
@@ -1399,6 +1521,7 @@ int lttng_enable_channel(struct lttng_handle *handle,
                struct lttng_channel *in_chan)
 {
        struct lttcomm_session_msg lsm;
+       size_t total_buffer_size_needed_per_cpu = 0;
 
        /* NULL arguments are forbidden. No default values. */
        if (handle == NULL || in_chan == NULL) {
@@ -1434,8 +1557,18 @@ int lttng_enable_channel(struct lttng_handle *handle,
                memcpy(&lsm.u.channel.extended, extended, sizeof(*extended));
        }
 
+       /*
+        * Verify that the amount of memory required to create the requested
+        * buffer is available on the system at the moment.
+        */
+       total_buffer_size_needed_per_cpu = lsm.u.channel.chan.attr.num_subbuf *
+               lsm.u.channel.chan.attr.subbuf_size;
+       if (!check_enough_available_memory(total_buffer_size_needed_per_cpu)) {
+               return -LTTNG_ERR_NOMEM;
+       }
+
        lsm.cmd_type = LTTNG_ENABLE_CHANNEL;
-       lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
 
        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));
@@ -1463,59 +1596,7 @@ int lttng_disable_channel(struct lttng_handle *handle, const char *name)
        lttng_ctl_copy_string(lsm.u.disable.channel_name, name,
                        sizeof(lsm.u.disable.channel_name));
 
-       lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);
-
-       lttng_ctl_copy_string(lsm.session.name, handle->session_name,
-                       sizeof(lsm.session.name));
-
-       return lttng_ctl_ask_sessiond(&lsm, NULL);
-}
-
-/*
- * Add PID to session tracker.
- * Return 0 on success else a negative LTTng error code.
- */
-int lttng_track_pid(struct lttng_handle *handle, int pid)
-{
-       struct lttcomm_session_msg lsm;
-
-       /* NULL arguments are forbidden. No default values. */
-       if (handle == NULL) {
-               return -LTTNG_ERR_INVALID;
-       }
-
-       memset(&lsm, 0, sizeof(lsm));
-
-       lsm.cmd_type = LTTNG_TRACK_PID;
-       lsm.u.pid_tracker.pid = pid;
-
-       lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);
-
-       lttng_ctl_copy_string(lsm.session.name, handle->session_name,
-                       sizeof(lsm.session.name));
-
-       return lttng_ctl_ask_sessiond(&lsm, NULL);
-}
-
-/*
- * Remove PID from session tracker.
- * Return 0 on success else a negative LTTng error code.
- */
-int lttng_untrack_pid(struct lttng_handle *handle, int pid)
-{
-       struct lttcomm_session_msg lsm;
-
-       /* NULL arguments are forbidden. No default values. */
-       if (handle == NULL) {
-               return -LTTNG_ERR_INVALID;
-       }
-
-       memset(&lsm, 0, sizeof(lsm));
-
-       lsm.cmd_type = LTTNG_UNTRACK_PID;
-       lsm.u.pid_tracker.pid = pid;
-
-       lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
 
        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));
@@ -1541,7 +1622,7 @@ int lttng_list_tracepoints(struct lttng_handle *handle,
 
        memset(&lsm, 0, sizeof(lsm));
        lsm.cmd_type = LTTNG_LIST_TRACEPOINTS;
-       lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
 
        ret = lttng_ctl_ask_sessiond(&lsm, (void **) events);
        if (ret < 0) {
@@ -1569,7 +1650,7 @@ int lttng_list_tracepoint_fields(struct lttng_handle *handle,
 
        memset(&lsm, 0, sizeof(lsm));
        lsm.cmd_type = LTTNG_LIST_TRACEPOINT_FIELDS;
-       lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
 
        ret = lttng_ctl_ask_sessiond(&lsm, (void **) fields);
        if (ret < 0) {
@@ -1617,81 +1698,296 @@ const char *lttng_strerror(int code)
        return error_get_str(code);
 }
 
+enum lttng_error_code lttng_create_session_ext(
+               struct lttng_session_descriptor *session_descriptor)
+{
+       enum lttng_error_code ret_code;
+       struct lttcomm_session_msg lsm = {
+               .cmd_type = LTTNG_CREATE_SESSION_EXT,
+       };
+       void *reply = NULL;
+       struct lttng_buffer_view reply_view;
+       int reply_ret;
+       bool sessiond_must_generate_ouput;
+       struct lttng_dynamic_buffer payload;
+       int ret;
+       size_t descriptor_size;
+       struct lttng_session_descriptor *descriptor_reply = NULL;
+
+       lttng_dynamic_buffer_init(&payload);
+       if (!session_descriptor) {
+               ret_code = LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       sessiond_must_generate_ouput =
+                       !lttng_session_descriptor_is_output_destination_initialized(
+                               session_descriptor);
+       if (sessiond_must_generate_ouput) {
+               const char *home_dir = utils_get_home_dir();
+               size_t home_dir_len = home_dir ? strlen(home_dir) + 1 : 0;
+
+               if (!home_dir || home_dir_len > LTTNG_PATH_MAX) {
+                       ret_code = LTTNG_ERR_FATAL;
+                       goto end;
+               }
+
+               lsm.u.create_session.home_dir_size = (uint16_t) home_dir_len;
+               ret = lttng_dynamic_buffer_append(&payload, home_dir,
+                               home_dir_len);
+               if (ret) {
+                       ret_code = LTTNG_ERR_NOMEM;
+                       goto end;
+               }
+       }
+
+       descriptor_size = payload.size;
+       ret = lttng_session_descriptor_serialize(session_descriptor,
+                       &payload);
+       if (ret) {
+               ret_code = LTTNG_ERR_INVALID;
+               goto end;
+       }
+       descriptor_size = payload.size - descriptor_size;
+       lsm.u.create_session.session_descriptor_size = descriptor_size;
+
+       /* Command returns a session descriptor on success. */
+       reply_ret = lttng_ctl_ask_sessiond_varlen_no_cmd_header(&lsm, payload.data,
+                       payload.size, &reply);
+       if (reply_ret < 0) {
+               ret_code = -reply_ret;
+               goto end;
+       } else if (reply_ret == 0) {
+               /* Socket unexpectedly closed by the session daemon. */
+               ret_code = LTTNG_ERR_FATAL;
+               goto end;
+       }
+
+       reply_view = lttng_buffer_view_init(reply, 0, reply_ret);
+       ret = lttng_session_descriptor_create_from_buffer(&reply_view,
+                       &descriptor_reply);
+       if (ret < 0) {
+               ret_code = LTTNG_ERR_FATAL;
+               goto end;
+       }
+       ret_code = LTTNG_OK;
+       lttng_session_descriptor_assign(session_descriptor, descriptor_reply);
+end:
+       free(reply);
+       lttng_dynamic_buffer_reset(&payload);
+       lttng_session_descriptor_destroy(descriptor_reply);
+       return ret_code;
+}
+
 /*
- * Create a brand new session using name and url for destination.
+ * Create a new session using name and url for destination.
  *
- * Returns LTTNG_OK on success or a negative error code.
+ * Return 0 on success else a negative LTTng error code.
  */
 int lttng_create_session(const char *name, const char *url)
 {
        int ret;
        ssize_t size;
-       struct lttcomm_session_msg lsm;
        struct lttng_uri *uris = NULL;
+       struct lttng_session_descriptor *descriptor = NULL;
+       enum lttng_error_code ret_code;
 
-       if (name == NULL) {
-               return -LTTNG_ERR_INVALID;
+       if (!name) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
        }
 
-       memset(&lsm, 0, sizeof(lsm));
-
-       lsm.cmd_type = LTTNG_CREATE_SESSION;
-       lttng_ctl_copy_string(lsm.session.name, name, sizeof(lsm.session.name));
-
-       /* There should never be a data URL */
        size = uri_parse_str_urls(url, NULL, &uris);
        if (size < 0) {
-               return -LTTNG_ERR_INVALID;
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
        }
+       switch (size) {
+       case 0:
+               descriptor = lttng_session_descriptor_create(name);
+               break;
+       case 1:
+               if (uris[0].dtype != LTTNG_DST_PATH) {
+                       ret = -LTTNG_ERR_INVALID;
+                       goto end;
+               }
+               descriptor = lttng_session_descriptor_local_create(name,
+                               uris[0].dst.path);
+               break;
+       case 2:
+               descriptor = lttng_session_descriptor_network_create(name, url,
+                               NULL);
+               break;
+       default:
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+       if (!descriptor) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+       ret_code = lttng_create_session_ext(descriptor);
+       ret = ret_code == LTTNG_OK ? 0 : -ret_code;
+end:
+       lttng_session_descriptor_destroy(descriptor);
+       free(uris);
+       return ret;
+}
 
-       lsm.u.uri.size = size;
+/*
+ * Create a session exclusively used for snapshot.
+ *
+ * Return 0 on success else a negative LTTng error code.
+ */
+int lttng_create_session_snapshot(const char *name, const char *snapshot_url)
+{
+       int ret;
+       enum lttng_error_code ret_code;
+       ssize_t size;
+       struct lttng_uri *uris = NULL;
+       struct lttng_session_descriptor *descriptor = NULL;
 
-       ret = lttng_ctl_ask_sessiond_varlen_no_cmd_header(&lsm, uris,
-                       sizeof(struct lttng_uri) * size, NULL);
+       if (!name) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       size = uri_parse_str_urls(snapshot_url, NULL, &uris);
+       if (size < 0) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+       /*
+        * If the user does not specify a custom subdir, use the session name.
+        */
+       if (size > 0 && uris[0].dtype != LTTNG_DST_PATH &&
+                       strlen(uris[0].subdir) == 0) {
+               ret = snprintf(uris[0].subdir, sizeof(uris[0].subdir), "%s",
+                               name);
+               if (ret < 0) {
+                       PERROR("Failed to set session name as network destination sub-directory");
+                       ret = -LTTNG_ERR_FATAL;
+                       goto end;
+               } else if (ret >= sizeof(uris[0].subdir)) {
+                       /* Truncated output. */
+                       ret = -LTTNG_ERR_INVALID;
+                       goto end;
+               }
+       }
 
+       switch (size) {
+       case 0:
+               descriptor = lttng_session_descriptor_snapshot_create(name);
+               break;
+       case 1:
+               if (uris[0].dtype != LTTNG_DST_PATH) {
+                       ret = -LTTNG_ERR_INVALID;
+                       goto end;
+               }
+               descriptor = lttng_session_descriptor_snapshot_local_create(
+                               name,
+                               uris[0].dst.path);
+               break;
+       case 2:
+               descriptor = lttng_session_descriptor_snapshot_network_create(
+                               name,
+                               snapshot_url,
+                               NULL);
+               break;
+       default:
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+       if (!descriptor) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+       ret_code = lttng_create_session_ext(descriptor);
+       ret = ret_code == LTTNG_OK ? 0 : -ret_code;
+end:
+       lttng_session_descriptor_destroy(descriptor);
        free(uris);
        return ret;
 }
 
 /*
- * Destroy session using name.
- * Returns size of returned session payload data or a negative error code.
+ * Create a session exclusively used for live.
+ *
+ * Return 0 on success else a negative LTTng error code.
  */
-static
-int _lttng_destroy_session(const char *session_name)
+int lttng_create_session_live(const char *name, const char *url,
+               unsigned int timer_interval)
 {
-       struct lttcomm_session_msg lsm;
+       int ret;
+       enum lttng_error_code ret_code;
+       struct lttng_session_descriptor *descriptor = NULL;
 
-       if (session_name == NULL) {
-               return -LTTNG_ERR_INVALID;
+       if (!name) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
        }
 
-       memset(&lsm, 0, sizeof(lsm));
-       lsm.cmd_type = LTTNG_DESTROY_SESSION;
-
-       lttng_ctl_copy_string(lsm.session.name, session_name,
-                       sizeof(lsm.session.name));
-
-       return lttng_ctl_ask_sessiond(&lsm, NULL);
+       if (url) {
+               descriptor = lttng_session_descriptor_live_network_create(
+                               name, url, NULL, timer_interval);
+       } else {
+               descriptor = lttng_session_descriptor_live_create(
+                               name, timer_interval);
+       }
+       if (!descriptor) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+       ret_code = lttng_create_session_ext(descriptor);
+       ret = ret_code == LTTNG_OK ? 0 : -ret_code;
+end:
+       lttng_session_descriptor_destroy(descriptor);
+       return ret;
 }
 
 /*
  * Stop the session and wait for the data before destroying it
+ *
+ * Return 0 on success else a negative LTTng error code.
  */
 int lttng_destroy_session(const char *session_name)
 {
        int ret;
+       enum lttng_error_code ret_code;
+       enum lttng_destruction_handle_status status;
+       struct lttng_destruction_handle *handle = NULL;
 
        /*
-        * Stop the tracing and wait for the data.
+        * Stop the tracing and wait for the data to be
+        * consumed.
         */
        ret = _lttng_stop_tracing(session_name, 1);
        if (ret && ret != -LTTNG_ERR_TRACE_ALREADY_STOPPED) {
                goto end;
        }
 
-       ret = _lttng_destroy_session(session_name);
+       ret_code = lttng_destroy_session_ext(session_name, &handle);
+       if (ret_code != LTTNG_OK) {
+               ret = (int) -ret_code;
+               goto end;
+       }
+       assert(handle);
+
+       /* Block until the completion of the destruction of the session. */
+       status = lttng_destruction_handle_wait_for_completion(handle, -1);
+       if (status != LTTNG_DESTRUCTION_HANDLE_STATUS_COMPLETED) {
+               ret = -LTTNG_ERR_UNK;
+               goto end;
+       }
+
+       status = lttng_destruction_handle_get_result(handle, &ret_code);
+       if (status != LTTNG_DESTRUCTION_HANDLE_STATUS_OK) {
+               ret = -LTTNG_ERR_UNK;
+               goto end;
+       }
+       ret = ret_code == LTTNG_OK ? 0 : -ret_code;
 end:
+       lttng_destruction_handle_destroy(handle);
        return ret;
 }
 
@@ -1700,21 +1996,10 @@ end:
  */
 int lttng_destroy_session_no_wait(const char *session_name)
 {
-       int ret;
-
-       /*
-        * Stop the tracing without waiting for the data.
-        * The session might already have been stopped, so just
-        * skip this error.
-        */
-       ret = _lttng_stop_tracing(session_name, 0);
-       if (ret && ret != -LTTNG_ERR_TRACE_ALREADY_STOPPED) {
-               goto end;
-       }
+       enum lttng_error_code ret_code;
 
-       ret = _lttng_destroy_session(session_name);
-end:
-       return ret;
+       ret_code = lttng_destroy_session_ext(session_name, NULL);
+       return ret_code == LTTNG_OK ? ret_code : -ret_code;
 }
 
 /*
@@ -1723,19 +2008,72 @@ end:
  * Returns the number of lttng_session entries in sessions;
  * on error, returns a negative value.
  */
-int lttng_list_sessions(struct lttng_session **sessions)
+int lttng_list_sessions(struct lttng_session **out_sessions)
 {
        int ret;
        struct lttcomm_session_msg lsm;
+       const size_t session_size = sizeof(struct lttng_session) +
+                       sizeof(struct lttng_session_extended);
+       size_t session_count, i;
+       struct lttng_session_extended *sessions_extended_begin;
+       struct lttng_session *sessions = NULL;
 
        memset(&lsm, 0, sizeof(lsm));
        lsm.cmd_type = LTTNG_LIST_SESSIONS;
-       ret = lttng_ctl_ask_sessiond(&lsm, (void**) sessions);
-       if (ret < 0) {
-               return ret;
+       ret = lttng_ctl_ask_sessiond(&lsm, (void**) &sessions);
+       if (ret <= 0) {
+               goto end;
+       }
+       if (!sessions) {
+               ret = -LTTNG_ERR_FATAL;
+               goto end;
        }
 
-       return ret / sizeof(struct lttng_session);
+       if (ret % session_size) {
+               ret = -LTTNG_ERR_UNK;
+               free(sessions);
+               *out_sessions = NULL;
+               goto end;
+       }
+       session_count = (size_t) ret / session_size;
+       sessions_extended_begin = (struct lttng_session_extended *)
+                       (&sessions[session_count]);
+
+       /* Set extended session info pointers. */
+       for (i = 0; i < session_count; i++) {
+               struct lttng_session *session = &sessions[i];
+               struct lttng_session_extended *extended =
+                               &(sessions_extended_begin[i]);
+
+               session->extended.ptr = extended;
+       }
+
+       ret = (int) session_count;
+       *out_sessions = sessions;
+end:
+       return ret;
+}
+
+enum lttng_error_code lttng_session_get_creation_time(
+               const struct lttng_session *session, uint64_t *creation_time)
+{
+       enum lttng_error_code ret = LTTNG_OK;
+       struct lttng_session_extended *extended;
+
+       if (!session || !creation_time || !session->extended.ptr) {
+               ret = LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       extended = session->extended.ptr;
+       if (!extended->creation_time.is_set) {
+               /* Not created on the session daemon yet. */
+               ret = LTTNG_ERR_SESSION_NOT_EXIST;
+               goto end;
+       }
+       *creation_time = extended->creation_time.value;
+end:
+       return ret;
 }
 
 int lttng_set_session_shm_path(const char *session_name,
@@ -1814,7 +2152,7 @@ int lttng_list_channels(struct lttng_handle *handle,
        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));
 
-       lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
 
        ret = lttng_ctl_ask_sessiond(&lsm, (void**) channels);
        if (ret < 0) {
@@ -1854,156 +2192,297 @@ int lttng_list_events(struct lttng_handle *handle,
                const char *channel_name, struct lttng_event **events)
 {
        int ret;
-       struct lttcomm_session_msg lsm;
-       struct lttcomm_event_command_header *cmd_header = NULL;
-       size_t cmd_header_len;
+       struct lttcomm_session_msg lsm = {};
+       const struct lttcomm_event_command_header *cmd_header = NULL;
        uint32_t nb_events, i;
-       void *extended_at;
+       const void *comm_ext_at;
+       struct lttng_dynamic_buffer listing;
+       size_t storage_req;
+       struct lttng_payload payload;
+       struct lttng_payload payload_copy;
+       struct lttng_payload_view lsm_view =
+                       lttng_payload_view_init_from_buffer(
+                               (const char *) &lsm, 0, sizeof(lsm));
+       struct lttng_buffer_view cmd_header_view;
+       struct lttng_buffer_view cmd_payload_view;
+       struct lttng_buffer_view flat_events_view;
+       struct lttng_buffer_view ext_view;
 
        /* Safety check. An handle and channel name are mandatory */
        if (handle == NULL || channel_name == NULL) {
-               return -LTTNG_ERR_INVALID;
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
        }
 
-       memset(&lsm, 0, sizeof(lsm));
+       lttng_payload_init(&payload);
+       lttng_payload_init(&payload_copy);
+
        lsm.cmd_type = LTTNG_LIST_EVENTS;
        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));
        lttng_ctl_copy_string(lsm.u.list.channel_name, channel_name,
                        sizeof(lsm.u.list.channel_name));
-       lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
 
-       ret = lttng_ctl_ask_sessiond_varlen(&lsm, NULL, 0, (void **) events,
-               (void **) &cmd_header, &cmd_header_len);
+       ret = lttng_ctl_ask_sessiond_payload(&lsm_view, &payload);
        if (ret < 0) {
-               goto error;
-       }
-
-       /* Set number of events and free command header */
-       nb_events = cmd_header->nb_events;
-       if (nb_events > INT_MAX) {
-               ret = -EOVERFLOW;
-               goto error;
+               goto end;
        }
-       ret = (int) nb_events;
-       free(cmd_header);
-       cmd_header = NULL;
 
-       /* Set extended info pointers */
-       extended_at = ((void*) (*events)) +
-                       nb_events * sizeof(struct lttng_event);
-
-       for (i = 0; i < nb_events; i++) {
-               struct lttcomm_event_extended_header *ext_header;
-               struct lttng_event *event = &(*events)[i];
-
-               event->extended.ptr = extended_at;
-               ext_header =
-                       (struct lttcomm_event_extended_header *) extended_at;
-               extended_at += sizeof(*ext_header);
-               extended_at += ext_header->filter_len;
-               extended_at +=
-                       ext_header->nb_exclusions * LTTNG_SYMBOL_NAME_LEN;
+       /*
+        * A copy of the payload is performed since it will be
+        * consumed twice. Consuming the same payload twice is invalid since
+        * it will cause any received file descriptor to become "shared"
+        * between different instances of the resulting objects.
+        */
+       ret = lttng_payload_copy(&payload, &payload_copy);
+       if (ret) {
+               ret = -LTTNG_ERR_NOMEM;
+               goto end;
        }
 
-       return ret;
-error:
-       free(cmd_header);
-       free(*events);
-       return ret;
-}
-
-int lttng_event_get_filter_expression(struct lttng_event *event,
-       const char **filter_expression)
-{
-       int ret = 0;
-       struct lttcomm_event_extended_header *ext_header;
-
-       if (!event || !filter_expression) {
-               ret = -LTTNG_ERR_INVALID;
+       cmd_header_view = lttng_buffer_view_from_dynamic_buffer(
+               &payload.buffer, 0, sizeof(*cmd_header));
+       if (!cmd_header_view.data) {
+               ret = -LTTNG_ERR_INVALID_PROTOCOL;
                goto end;
        }
 
-       ext_header = event->extended.ptr;
+       cmd_header = (typeof(cmd_header)) cmd_header_view.data;
 
-       if (!ext_header) {
-               /*
-                * This can happen since the lttng_event structure is
-                * used for other tasks where this pointer is never set.
-                */
-               *filter_expression = NULL;
+       /* Set number of events and free command header */
+       nb_events = cmd_header->nb_events;
+       if (nb_events > INT_MAX) {
+               ret = -LTTNG_ERR_OVERFLOW;
                goto end;
        }
 
-       if (ext_header->filter_len) {
-               *filter_expression = ((const char *) (ext_header)) +
-                               sizeof(*ext_header);
-       } else {
-               *filter_expression = NULL;
-       }
+       cmd_payload_view = lttng_buffer_view_from_dynamic_buffer(
+                       &payload.buffer, sizeof(*cmd_header), -1);
 
-end:
-       return ret;
-}
+       /*
+        * The buffer that is returned must contain a "flat" version of
+        * the events that are returned. In other words, all pointers
+        * within an lttng_event must point to a location within the returned
+        * buffer so that the user may free everything by simply calling free()
+        * on the returned buffer. This is needed in order to maintain API
+        * compatibility.
+        *
+        * A first pass is performed to compute the size of the buffer that
+        * must be allocated. A second pass is then performed to setup
+        * the returned events so that their members always point within the
+        * buffer.
+        *
+        * The layout of the returned buffer is as follows:
+        *   - struct lttng_event[nb_events],
+        *   - nb_events times the following:
+        *     - struct lttng_event_extended,
+        *     - flattened version of userspace_probe_location
+        *     - filter_expression
+        *     - exclusions
+        *     - padding to align to 64-bits
+        */
+       ext_view = lttng_buffer_view_from_view(&cmd_payload_view,
+                       nb_events * sizeof(struct lttng_event), -1);
+       comm_ext_at = ext_view.data;
+       storage_req = nb_events * sizeof(struct lttng_event);
+       {
+               struct lttng_payload_view payload_view =
+                               lttng_payload_view_from_payload(&payload, 0, -1);
+
+               for (i = 0; i < nb_events; i++) {
+                       const struct lttcomm_event_extended_header *ext_comm =
+                                       (struct lttcomm_event_extended_header *)
+                                                       comm_ext_at;
+                       int probe_storage_req = 0;
+
+                       comm_ext_at += sizeof(*ext_comm);
+                       comm_ext_at += ext_comm->filter_len;
+                       comm_ext_at += ext_comm->nb_exclusions *
+                                       LTTNG_SYMBOL_NAME_LEN;
+
+                       if (ext_comm->userspace_probe_location_len) {
+                               struct lttng_userspace_probe_location
+                                               *probe_location = NULL;
+                               struct lttng_payload_view probe_location_view = lttng_payload_view_from_view(
+                                               &payload_view,
+                                               (const char *) comm_ext_at -
+                                                               payload_view.buffer.data,
+                                               ext_comm->userspace_probe_location_len);
 
-int lttng_event_get_exclusion_name_count(struct lttng_event *event)
-{
-       int ret;
-       struct lttcomm_event_extended_header *ext_header;
+                               /*
+                                * Create a temporary userspace probe location
+                                * to determine the size needed by a "flattened"
+                                * version of that same probe location.
+                                */
+                               ret = lttng_userspace_probe_location_create_from_payload(
+                                               &probe_location_view,
+                                               &probe_location);
+                               if (ret < 0) {
+                                       ret = -LTTNG_ERR_PROBE_LOCATION_INVAL;
+                                       goto end;
+                               }
 
-       if (!event) {
-               ret = -LTTNG_ERR_INVALID;
-               goto end;
-       }
+                               ret = lttng_userspace_probe_location_flatten(
+                                               probe_location, NULL);
+                               lttng_userspace_probe_location_destroy(
+                                               probe_location);
+                               if (ret < 0) {
+                                       ret = -LTTNG_ERR_PROBE_LOCATION_INVAL;
+                                       goto end;
+                               }
+
+                               probe_storage_req = ret;
+                               comm_ext_at += ext_comm->userspace_probe_location_len;
+                       }
 
-       ext_header = event->extended.ptr;
-       if (!ext_header) {
-               /*
-                * This can happen since the lttng_event structure is
-                * used for other tasks where this pointer is never set.
-                */
-               ret = 0;
-               goto end;
+                       storage_req += sizeof(struct lttng_event_extended);
+                       storage_req += ext_comm->filter_len;
+                       storage_req += ext_comm->nb_exclusions *
+                                       LTTNG_SYMBOL_NAME_LEN;
+                       /* Padding to ensure the flat probe is aligned. */
+                       storage_req = ALIGN_TO(storage_req, sizeof(uint64_t));
+                       storage_req += probe_storage_req;
+               }
        }
 
-       if (ext_header->nb_exclusions > INT_MAX) {
-               ret = -LTTNG_ERR_OVERFLOW;
+       lttng_dynamic_buffer_init(&listing);
+       /*
+        * We must ensure that "listing" is never resized so as to preserve
+        * the validity of the flattened objects.
+        */
+       ret = lttng_dynamic_buffer_set_capacity(&listing, storage_req);
+       if (ret) {
+               ret = -LTTNG_ERR_NOMEM;
                goto end;
        }
-       ret = (int) ext_header->nb_exclusions;
-end:
-       return ret;
-}
 
-int lttng_event_get_exclusion_name(struct lttng_event *event,
-               size_t index, const char **exclusion_name)
-{
-       int ret = 0;
-       struct lttcomm_event_extended_header *ext_header;
-       void *at;
+       cmd_payload_view = lttng_buffer_view_from_dynamic_buffer(
+               &payload_copy.buffer, sizeof(*cmd_header), -1);
+       flat_events_view = lttng_buffer_view_from_view(&cmd_payload_view, 0,
+                       nb_events * sizeof(struct lttng_event));
+       ret = lttng_dynamic_buffer_append_view(&listing, &flat_events_view);
+       if (ret) {
+               ret = -LTTNG_ERR_NOMEM;
+               goto free_dynamic_buffer;
+       }
+
+       ext_view = lttng_buffer_view_from_view(&cmd_payload_view,
+                       nb_events * sizeof(struct lttng_event), -1);
+       comm_ext_at = ext_view.data;
+
+       {
+               struct lttng_payload_view payload_copy_view =
+                               lttng_payload_view_from_payload(
+                                               &payload_copy, 0, -1);
+
+               for (i = 0; i < nb_events; i++) {
+                       struct lttng_event *event = (typeof(event))(
+                                       listing.data +
+                                       (sizeof(struct lttng_event) * i));
+                       const struct lttcomm_event_extended_header *ext_comm =
+                                       (typeof(ext_comm)) comm_ext_at;
+                       struct lttng_event_extended *event_extended =
+                                       (typeof(event_extended))(listing.data +
+                                                       listing.size);
+
+                       /* Insert struct lttng_event_extended. */
+                       ret = lttng_dynamic_buffer_set_size(&listing,
+                                       listing.size + sizeof(*event_extended));
+                       if (ret) {
+                               ret = -LTTNG_ERR_NOMEM;
+                               goto free_dynamic_buffer;
+                       }
+                       event->extended.ptr = event_extended;
+
+                       comm_ext_at += sizeof(*ext_comm);
+
+                       /* Insert filter expression. */
+                       if (ext_comm->filter_len) {
+                               event_extended->filter_expression =
+                                               listing.data + listing.size;
+                               ret = lttng_dynamic_buffer_append(&listing,
+                                               comm_ext_at,
+                                               ext_comm->filter_len);
+                               if (ret) {
+                                       ret = -LTTNG_ERR_NOMEM;
+                                       goto free_dynamic_buffer;
+                               }
+                               comm_ext_at += ext_comm->filter_len;
+                       }
 
-       if (!event || !exclusion_name) {
-               ret = -LTTNG_ERR_INVALID;
-               goto end;
-       }
+                       /* Insert exclusions. */
+                       if (ext_comm->nb_exclusions) {
+                               event_extended->exclusions.count =
+                                               ext_comm->nb_exclusions;
+                               event_extended->exclusions.strings =
+                                               listing.data + listing.size;
+
+                               ret = lttng_dynamic_buffer_append(&listing,
+                                               comm_ext_at,
+                                               ext_comm->nb_exclusions *
+                                                               LTTNG_SYMBOL_NAME_LEN);
+                               if (ret) {
+                                       ret = -LTTNG_ERR_NOMEM;
+                                       goto free_dynamic_buffer;
+                               }
+                               comm_ext_at += ext_comm->nb_exclusions *
+                                               LTTNG_SYMBOL_NAME_LEN;
+                       }
 
-       ext_header = event->extended.ptr;
-       if (!ext_header) {
-               ret = -LTTNG_ERR_INVALID;
-               goto end;
-       }
+                       /* Insert padding to align to 64-bits. */
+                       ret = lttng_dynamic_buffer_set_size(&listing,
+                                       ALIGN_TO(listing.size,
+                                                       sizeof(uint64_t)));
+                       if (ret) {
+                               ret = -LTTNG_ERR_NOMEM;
+                               goto free_dynamic_buffer;
+                       }
 
-       if (index >= ext_header->nb_exclusions) {
-               ret = -LTTNG_ERR_INVALID;
-               goto end;
-       }
+                       /* Insert flattened userspace probe location. */
+                       if (ext_comm->userspace_probe_location_len) {
+                               struct lttng_userspace_probe_location
+                                               *probe_location = NULL;
+                               struct lttng_payload_view probe_location_view = lttng_payload_view_from_view(
+                                               &payload_copy_view,
+                                               (const char *) comm_ext_at -
+                                                               payload_copy_view.buffer.data,
+                                               ext_comm->userspace_probe_location_len);
+
+                               ret = lttng_userspace_probe_location_create_from_payload(
+                                               &probe_location_view,
+                                               &probe_location);
+                               if (ret < 0) {
+                                       ret = -LTTNG_ERR_PROBE_LOCATION_INVAL;
+                                       goto free_dynamic_buffer;
+                               }
+
+                               event_extended->probe_location = (struct lttng_userspace_probe_location
+                                                               *) (listing.data +
+                                               listing.size);
+                               ret = lttng_userspace_probe_location_flatten(
+                                               probe_location, &listing);
+                               lttng_userspace_probe_location_destroy(
+                                               probe_location);
+                               if (ret < 0) {
+                                       ret = -LTTNG_ERR_PROBE_LOCATION_INVAL;
+                                       goto free_dynamic_buffer;
+                               }
 
-       at = (void *) ext_header + sizeof(*ext_header);
-       at += ext_header->filter_len;
-       at += index * LTTNG_SYMBOL_NAME_LEN;
-       *exclusion_name = at;
+                               comm_ext_at += ext_comm->userspace_probe_location_len;
+                       }
+               }
+       }
 
+       /* Don't reset listing buffer as we return its content. */
+       *events = (struct lttng_event *) listing.data;
+       lttng_dynamic_buffer_init(&listing);
+       ret = (int) nb_events;
+free_dynamic_buffer:
+       lttng_dynamic_buffer_reset(&listing);
 end:
+       lttng_payload_reset(&payload);
+       lttng_payload_reset(&payload_copy);
        return ret;
 }
 
@@ -2315,7 +2794,7 @@ int lttng_set_consumer_url(struct lttng_handle *handle,
 
        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));
-       lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
 
        size = uri_parse_str_urls(control_url, data_url, &uris);
        if (size < 0) {
@@ -2334,6 +2813,7 @@ int lttng_set_consumer_url(struct lttng_handle *handle,
 /*
  * [OBSOLETE]
  */
+int lttng_enable_consumer(struct lttng_handle *handle);
 int lttng_enable_consumer(struct lttng_handle *handle)
 {
        return -ENOSYS;
@@ -2342,77 +2822,21 @@ int lttng_enable_consumer(struct lttng_handle *handle)
 /*
  * [OBSOLETE]
  */
+int lttng_disable_consumer(struct lttng_handle *handle);
 int lttng_disable_consumer(struct lttng_handle *handle)
 {
        return -ENOSYS;
 }
 
 /*
- * This is an extension of create session that is ONLY and SHOULD only be used
- * by the lttng command line program. It exists to avoid using URI parsing in
- * the lttng client.
- *
- * We need the date and time for the trace path subdirectory for the case where
- * the user does NOT define one using either -o or -U. Using the normal
- * lttng_create_session API call, we have no clue on the session daemon side if
- * the URL was generated automatically by the client or define by the user.
- *
- * So this function "wrapper" is hidden from the public API, takes the datetime
- * string and appends it if necessary to the URI subdirectory before sending it
- * to the session daemon.
- *
- * With this extra function, the lttng_create_session call behavior is not
- * changed and the timestamp is appended to the URI on the session daemon side
- * if necessary.
+ * [OBSOLETE]
  */
+int _lttng_create_session_ext(const char *name, const char *url,
+               const char *datetime);
 int _lttng_create_session_ext(const char *name, const char *url,
                const char *datetime)
 {
-       int ret;
-       ssize_t size;
-       struct lttcomm_session_msg lsm;
-       struct lttng_uri *uris = NULL;
-
-       if (name == NULL || datetime == NULL) {
-               return -LTTNG_ERR_INVALID;
-       }
-
-       memset(&lsm, 0, sizeof(lsm));
-
-       lsm.cmd_type = LTTNG_CREATE_SESSION;
-       lttng_ctl_copy_string(lsm.session.name, name, sizeof(lsm.session.name));
-
-       /* There should never be a data URL. */
-       size = uri_parse_str_urls(url, NULL, &uris);
-       if (size < 0) {
-               ret = -LTTNG_ERR_INVALID;
-               goto error;
-       }
-
-       lsm.u.uri.size = size;
-
-       if (size > 0 && uris[0].dtype != LTTNG_DST_PATH && strlen(uris[0].subdir) == 0) {
-               /* Don't append datetime if the name was automatically created. */
-               if (strncmp(name, DEFAULT_SESSION_NAME "-",
-                                       strlen(DEFAULT_SESSION_NAME) + 1)) {
-                       ret = snprintf(uris[0].subdir, sizeof(uris[0].subdir), "%s-%s",
-                                       name, datetime);
-               } else {
-                       ret = snprintf(uris[0].subdir, sizeof(uris[0].subdir), "%s", name);
-               }
-               if (ret < 0) {
-                       PERROR("snprintf uri subdir");
-                       ret = -LTTNG_ERR_FATAL;
-                       goto error;
-               }
-       }
-
-       ret = lttng_ctl_ask_sessiond_varlen_no_cmd_header(&lsm, uris,
-                       sizeof(struct lttng_uri) * size, NULL);
-
-error:
-       free(uris);
-       return ret;
+       return -ENOSYS;
 }
 
 /*
@@ -2443,6 +2867,10 @@ int lttng_data_pending(const char *session_name)
                /* Unexpected payload size */
                ret = -LTTNG_ERR_INVALID;
                goto end;
+       } else if (!pending) {
+               /* Internal error. */
+               ret = -LTTNG_ERR_UNK;
+               goto end;
        }
 
        ret = (int) *pending;
@@ -2451,149 +2879,6 @@ end:
        return ret;
 }
 
-/*
- * Create a session exclusively used for snapshot.
- *
- * Returns LTTNG_OK on success or a negative error code.
- */
-int lttng_create_session_snapshot(const char *name, const char *snapshot_url)
-{
-       int ret;
-       ssize_t size;
-       struct lttcomm_session_msg lsm;
-       struct lttng_uri *uris = NULL;
-
-       if (name == NULL) {
-               return -LTTNG_ERR_INVALID;
-       }
-
-       memset(&lsm, 0, sizeof(lsm));
-
-       lsm.cmd_type = LTTNG_CREATE_SESSION_SNAPSHOT;
-       lttng_ctl_copy_string(lsm.session.name, name, sizeof(lsm.session.name));
-
-       size = uri_parse_str_urls(snapshot_url, NULL, &uris);
-       if (size < 0) {
-               return -LTTNG_ERR_INVALID;
-       }
-
-       lsm.u.uri.size = size;
-
-       /*
-        * If the user does not specify a custom subdir, use the session name.
-        */
-       if (size > 0 && uris[0].dtype != LTTNG_DST_PATH && strlen(uris[0].subdir) == 0) {
-               ret = snprintf(uris[0].subdir, sizeof(uris[0].subdir), "%s", name);
-               if (ret < 0) {
-                       PERROR("snprintf uri subdir");
-                       ret = -LTTNG_ERR_FATAL;
-                       goto error;
-               }
-       }
-
-       ret = lttng_ctl_ask_sessiond_varlen_no_cmd_header(&lsm, uris,
-                       sizeof(struct lttng_uri) * size, NULL);
-
-error:
-       free(uris);
-       return ret;
-}
-
-/*
- * Create a session exclusively used for live.
- *
- * Returns LTTNG_OK on success or a negative error code.
- */
-int lttng_create_session_live(const char *name, const char *url,
-               unsigned int timer_interval)
-{
-       int ret;
-       ssize_t size;
-       struct lttcomm_session_msg lsm;
-       struct lttng_uri *uris = NULL;
-
-       if (name == NULL || timer_interval == 0) {
-               return -LTTNG_ERR_INVALID;
-       }
-
-       memset(&lsm, 0, sizeof(lsm));
-
-       lsm.cmd_type = LTTNG_CREATE_SESSION_LIVE;
-       lttng_ctl_copy_string(lsm.session.name, name, sizeof(lsm.session.name));
-
-       if (url) {
-               size = uri_parse_str_urls(url, NULL, &uris);
-               if (size <= 0) {
-                       ret = -LTTNG_ERR_INVALID;
-                       goto end;
-               }
-
-               /* file:// is not accepted for live session. */
-               if (uris[0].dtype == LTTNG_DST_PATH) {
-                       ret = -LTTNG_ERR_INVALID;
-                       goto end;
-               }
-       } else {
-               size = 0;
-       }
-
-       lsm.u.session_live.nb_uri = size;
-       lsm.u.session_live.timer_interval = timer_interval;
-
-       ret = lttng_ctl_ask_sessiond_varlen_no_cmd_header(&lsm, uris,
-                       sizeof(struct lttng_uri) * size, NULL);
-
-end:
-       free(uris);
-       return ret;
-}
-
-/*
- * List PIDs in the tracker.
- *
- * enabled is set to whether the PID tracker is enabled.
- * pids is set to an allocated array of PIDs currently tracked. On
- * success, pids must be freed by the caller.
- * nr_pids is set to the number of entries contained by the pids array.
- *
- * Returns 0 on success, else a negative LTTng error code.
- */
-int lttng_list_tracker_pids(struct lttng_handle *handle,
-               int *_enabled, int32_t **_pids, size_t *_nr_pids)
-{
-       int ret;
-       int enabled = 1;
-       struct lttcomm_session_msg lsm;
-       size_t nr_pids;
-       int32_t *pids;
-
-       if (handle == NULL) {
-               return -LTTNG_ERR_INVALID;
-       }
-
-       memset(&lsm, 0, sizeof(lsm));
-       lsm.cmd_type = LTTNG_LIST_TRACKER_PIDS;
-       lttng_ctl_copy_string(lsm.session.name, handle->session_name,
-                       sizeof(lsm.session.name));
-       lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);
-
-       ret = lttng_ctl_ask_sessiond(&lsm, (void **) &pids);
-       if (ret < 0) {
-               return ret;
-       }
-       nr_pids = ret / sizeof(int32_t);
-       if (nr_pids == 1 && pids[0] == -1) {
-               free(pids);
-               pids = NULL;
-               enabled = 0;
-               nr_pids = 0;
-       }
-       *_enabled = enabled;
-       *_pids = pids;
-       *_nr_pids = nr_pids;
-       return 0;
-}
-
 /*
  * Regenerate the metadata for a session.
  * Return 0 on success, a negative error code on error.
@@ -2665,44 +2950,92 @@ end:
 int lttng_register_trigger(struct lttng_trigger *trigger)
 {
        int ret;
-       struct lttcomm_session_msg lsm;
-       char *trigger_buf = NULL;
-       ssize_t trigger_size;
+       struct lttcomm_session_msg lsm = {
+               .cmd_type = LTTNG_REGISTER_TRIGGER,
+       };
+       struct lttcomm_session_msg *message_lsm;
+       struct lttng_payload message;
+       struct lttng_payload reply;
+       const struct lttng_credentials user_creds = {
+               .uid = LTTNG_OPTIONAL_INIT_VALUE(geteuid()),
+               .gid = LTTNG_OPTIONAL_INIT_UNSET,
+       };
+
+       lttng_payload_init(&message);
+       lttng_payload_init(&reply);
 
        if (!trigger) {
                ret = -LTTNG_ERR_INVALID;
                goto end;
        }
 
-       if (!lttng_trigger_validate(trigger)) {
-               ret = -LTTNG_ERR_INVALID_TRIGGER;
-               goto end;
+       if (!trigger->creds.uid.is_set) {
+               /* Use the client's credentials as the trigger credentials. */
+               lttng_trigger_set_credentials(trigger, &user_creds);
+       } else {
+               /*
+                * Validate that either the current trigger credentials and the
+                * client credentials are identical or that the current user is
+                * root. The root user can register, unregister triggers for
+                * himself and other users.
+                *
+                * This check is also present on the sessiond side, using the
+                * credentials passed on the socket. These check are all
+                * "safety" checks.
+                */
+               const struct lttng_credentials *trigger_creds =
+                               lttng_trigger_get_credentials(trigger);
+
+               if (!lttng_credentials_is_equal_uid(trigger_creds, &user_creds)) {
+                       if (lttng_credentials_get_uid(&user_creds) != 0) {
+                               ret = -LTTNG_ERR_EPERM;
+                               goto end;
+                       }
+               }
        }
 
-       trigger_size = lttng_trigger_serialize(trigger, NULL);
-       if (trigger_size < 0) {
-               ret = -LTTNG_ERR_UNK;
+       if (!lttng_trigger_validate(trigger)) {
+               ret = -LTTNG_ERR_INVALID_TRIGGER;
                goto end;
        }
 
-       trigger_buf = zmalloc(trigger_size);
-       if (!trigger_buf) {
+       ret = lttng_dynamic_buffer_append(&message.buffer, &lsm, sizeof(lsm));
+       if (ret) {
                ret = -LTTNG_ERR_NOMEM;
                goto end;
        }
 
-       memset(&lsm, 0, sizeof(lsm));
-       lsm.cmd_type = LTTNG_REGISTER_TRIGGER;
-       if (lttng_trigger_serialize(trigger, trigger_buf) < 0) {
+       /*
+        * This is needed to populate the trigger object size for the command
+        * header.
+       */
+       message_lsm = (struct lttcomm_session_msg *) message.buffer.data;
+
+       ret = lttng_trigger_serialize(trigger, &message);
+       if (ret < 0) {
                ret = -LTTNG_ERR_UNK;
                goto end;
        }
 
-       lsm.u.trigger.length = (uint32_t) trigger_size;
-       ret = lttng_ctl_ask_sessiond_varlen_no_cmd_header(&lsm, trigger_buf,
-                       trigger_size, NULL);
+       message_lsm->u.trigger.length = (uint32_t) message.buffer.size - sizeof(lsm);
+
+       {
+               struct lttng_payload_view message_view =
+                               lttng_payload_view_from_payload(
+                                               &message, 0, -1);
+
+               message_lsm->fd_count = lttng_payload_view_get_fd_handle_count(
+                               &message_view);
+               ret = lttng_ctl_ask_sessiond_payload(&message_view, &reply);
+               if (ret < 0) {
+                       goto end;
+               }
+       }
+
+       ret = 0;
 end:
-       free(trigger_buf);
+       lttng_payload_reset(&message);
+       lttng_payload_reset(&reply);
        return ret;
 }
 
@@ -2710,87 +3043,97 @@ int lttng_unregister_trigger(struct lttng_trigger *trigger)
 {
        int ret;
        struct lttcomm_session_msg lsm;
-       char *trigger_buf = NULL;
-       ssize_t trigger_size;
+       struct lttcomm_session_msg *message_lsm;
+       struct lttng_payload message;
+       struct lttng_payload reply;
+       const struct lttng_credentials user_creds = {
+               .uid = LTTNG_OPTIONAL_INIT_VALUE(geteuid()),
+               .gid = LTTNG_OPTIONAL_INIT_UNSET,
+       };
+
+       lttng_payload_init(&message);
+       lttng_payload_init(&reply);
 
        if (!trigger) {
                ret = -LTTNG_ERR_INVALID;
                goto end;
        }
 
-       if (!lttng_trigger_validate(trigger)) {
-               ret = -LTTNG_ERR_INVALID;
-               goto end;
-       }
+       if (!trigger->creds.uid.is_set) {
+               /* Use the client's credentials as the trigger credentials. */
+               lttng_trigger_set_credentials(trigger, &user_creds);
+       } else {
+               /*
+                * Validate that either the current trigger credentials and the
+                * client credentials are identical or that the current user is
+                * root. The root user can register, unregister triggers for
+                * himself and other users.
+                *
+                * This check is also present on the sessiond side, using the
+                * credentials passed on the socket. These check are all
+                * "safety" checks.
+                */
+               const struct lttng_credentials *trigger_creds =
+                               lttng_trigger_get_credentials(trigger);
 
-       trigger_size = lttng_trigger_serialize(trigger, NULL);
-       if (trigger_size < 0) {
-               ret = -LTTNG_ERR_UNK;
-               goto end;
+               if (!lttng_credentials_is_equal_uid(trigger_creds, &user_creds)) {
+                       if (lttng_credentials_get_uid(&user_creds) != 0) {
+                               ret = -LTTNG_ERR_EPERM;
+                               goto end;
+                       }
+               }
        }
 
-       trigger_buf = zmalloc(trigger_size);
-       if (!trigger_buf) {
-               ret = -LTTNG_ERR_NOMEM;
+       if (!lttng_trigger_validate(trigger)) {
+               ret = -LTTNG_ERR_INVALID_TRIGGER;
                goto end;
        }
 
        memset(&lsm, 0, sizeof(lsm));
        lsm.cmd_type = LTTNG_UNREGISTER_TRIGGER;
-       if (lttng_trigger_serialize(trigger, trigger_buf) < 0) {
-               ret = -LTTNG_ERR_UNK;
-               goto end;
-       }
-
-       lsm.u.trigger.length = (uint32_t) trigger_size;
-       ret = lttng_ctl_ask_sessiond_varlen_no_cmd_header(&lsm, trigger_buf,
-                       trigger_size, NULL);
-end:
-       free(trigger_buf);
-       return ret;
-}
-
-int lttng_session_get_current_archive_location(const char *session_name,
-               char **chunk_path)
-{
-       struct lttcomm_session_msg lsm;
-       struct lttng_session_get_current_output_return *output_return = NULL;
-       int ret;
-       size_t path_len;
 
-       memset(&lsm, 0, sizeof(lsm));
-       lsm.cmd_type = LTTNG_SESSION_GET_CURRENT_OUTPUT;
-       ret = lttng_strncpy(lsm.session.name, session_name,
-                       sizeof(lsm.session.name));
+       ret = lttng_dynamic_buffer_append(&message.buffer, &lsm, sizeof(lsm));
        if (ret) {
-               ret = -LTTNG_ERR_INVALID;
+               ret = -LTTNG_ERR_NOMEM;
                goto end;
        }
 
-       ret = lttng_ctl_ask_sessiond(&lsm, (void **) &output_return);
+       /*
+        * This is needed to populate the trigger object size for the command
+        * header and number of fds sent.
+       */
+       message_lsm = (struct lttcomm_session_msg *) message.buffer.data;
+
+       ret = lttng_trigger_serialize(trigger, &message);
        if (ret < 0) {
-               ret = -1;
+               ret = -LTTNG_ERR_UNK;
                goto end;
        }
 
-       path_len = lttng_strnlen(output_return->path,
-                       sizeof(output_return->path));
-       if (path_len == 0 || path_len == sizeof(output_return->path)) {
-               ret = -LTTNG_ERR_NO_SESSION_OUTPUT;
-               goto end;
-       }
+       message_lsm->u.trigger.length = (uint32_t) message.buffer.size - sizeof(lsm);
 
-       *chunk_path = zmalloc(path_len + 1);
-       if (!*chunk_path) {
-               ret = -1;
-               goto end;
+       {
+               struct lttng_payload_view message_view =
+                               lttng_payload_view_from_payload(
+                                               &message, 0, -1);
+
+               /*
+                * Update the message header with the number of fd that will be
+                * sent.
+                */
+               message_lsm->fd_count = lttng_payload_view_get_fd_handle_count(
+                               &message_view);
+
+               ret = lttng_ctl_ask_sessiond_payload(&message_view, &reply);
+               if (ret < 0) {
+                       goto end;
+               }
        }
-       memcpy(*chunk_path, output_return->path, path_len);
 
        ret = 0;
-
 end:
-       free(output_return);
+       lttng_payload_reset(&message);
+       lttng_payload_reset(&reply);
        return ret;
 }
 
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