X-Git-Url: http://git.efficios.com/?p=lttng-tools.git;a=blobdiff_plain;f=src%2Fbin%2Flttng-sessiond%2Fkernel.c;h=d7c7984d201ba96c82d050eb71a48dca798c8e38;hp=53072f97187654dc37db1b6042f8100b375cbb70;hb=b8a1b0bd3964381c9ec6a8df26bd37cd7405a83f;hpb=3b9677124ab48bddc945ca67947c49b87b5853e0

diff --git a/src/bin/lttng-sessiond/kernel.c b/src/bin/lttng-sessiond/kernel.c
index 53072f971..d7c7984d2 100644
--- a/src/bin/lttng-sessiond/kernel.c
+++ b/src/bin/lttng-sessiond/kernel.c
@@ -1,18 +1,8 @@
 /*
- * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
+ * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
  *
- * 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 published by the Free Software Foundation.
+ * SPDX-License-Identifier: GPL-2.0-only
  *
- * This program 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 General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License along
- * with this program; if not, write to the Free Software Foundation, Inc.,
- * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
 #define _LGPL_SOURCE
@@ -22,19 +12,29 @@
 #include <string.h>
 #include <unistd.h>
 #include <inttypes.h>
+#include <sys/types.h>
 
 #include <common/common.h>
 #include <common/trace-chunk.h>
 #include <common/kernel-ctl/kernel-ctl.h>
 #include <common/kernel-ctl/kernel-ioctl.h>
 #include <common/sessiond-comm/sessiond-comm.h>
-
+#include <common/tracker.h>
+#include <common/utils.h>
+#include <lttng/event.h>
+#include <lttng/lttng-error.h>
+#include <lttng/tracker.h>
+
+#include "lttng-sessiond.h"
+#include "lttng-syscall.h"
 #include "consumer.h"
 #include "kernel.h"
 #include "kernel-consumer.h"
 #include "kern-modules.h"
 #include "utils.h"
 #include "rotate.h"
+#include "modprobe.h"
+#include "tracker.h"
 
 /*
  * Key used to reference a channel between the sessiond and the consumer. This
@@ -42,6 +42,10 @@
  */
 static uint64_t next_kernel_channel_key;
 
+static const char *module_proc_lttng = "/proc/lttng";
+
+static int kernel_tracer_fd = -1;
+
 #include <lttng/userspace-probe.h>
 #include <lttng/userspace-probe-internal.h>
 /*
@@ -92,7 +96,7 @@ error:
  * Create a new kernel session, register it to the kernel tracer and add it to
  * the session daemon session.
  */
-int kernel_create_session(struct ltt_session *session, int tracer_fd)
+int kernel_create_session(struct ltt_session *session)
 {
 	int ret;
 	struct ltt_kernel_session *lks;
@@ -107,7 +111,7 @@ int kernel_create_session(struct ltt_session *session, int tracer_fd)
 	}
 
 	/* Kernel tracer session creation */
-	ret = kernctl_create_session(tracer_fd);
+	ret = kernctl_create_session(kernel_tracer_fd);
 	if (ret < 0) {
 		PERROR("ioctl kernel create session");
 		goto error;
@@ -126,6 +130,26 @@ int kernel_create_session(struct ltt_session *session, int tracer_fd)
 
 	DBG("Kernel session created (fd: %d)", lks->fd);
 
+	/*
+	 * This is necessary since the creation time is present in the session
+	 * name when it is generated.
+	 */
+	if (session->has_auto_generated_name) {
+		ret = kernctl_session_set_name(lks->fd, DEFAULT_SESSION_NAME);
+	} else {
+		ret = kernctl_session_set_name(lks->fd, session->name);
+	}
+	if (ret) {
+		WARN("Could not set kernel session name for session %" PRIu64 " name: %s",
+			session->id, session->name);
+	}
+
+	ret = kernctl_session_set_creation_time(lks->fd, session->creation_time);
+	if (ret) {
+		WARN("Could not set kernel session creation time for session %" PRIu64 " name: %s",
+			session->id, session->name);
+	}
+
 	return 0;
 
 error:
@@ -651,120 +675,370 @@ error:
 	return ret;
 }
 
+static
+struct process_attr_tracker *_kernel_get_process_attr_tracker(
+		struct ltt_kernel_session *session,
+		enum lttng_process_attr process_attr)
+{
+	switch (process_attr) {
+	case LTTNG_PROCESS_ATTR_PROCESS_ID:
+		return session->tracker_pid;
+	case LTTNG_PROCESS_ATTR_VIRTUAL_PROCESS_ID:
+		return session->tracker_vpid;
+	case LTTNG_PROCESS_ATTR_USER_ID:
+		return session->tracker_uid;
+	case LTTNG_PROCESS_ATTR_VIRTUAL_USER_ID:
+		return session->tracker_vuid;
+	case LTTNG_PROCESS_ATTR_GROUP_ID:
+		return session->tracker_gid;
+	case LTTNG_PROCESS_ATTR_VIRTUAL_GROUP_ID:
+		return session->tracker_vgid;
+	default:
+		return NULL;
+	}
+}
 
-int kernel_track_pid(struct ltt_kernel_session *session, int pid)
+const struct process_attr_tracker *kernel_get_process_attr_tracker(
+		struct ltt_kernel_session *session,
+		enum lttng_process_attr process_attr)
+{
+	return (const struct process_attr_tracker *)
+			_kernel_get_process_attr_tracker(session, process_attr);
+}
+
+enum lttng_error_code kernel_process_attr_tracker_set_tracking_policy(
+		struct ltt_kernel_session *session,
+		enum lttng_process_attr process_attr,
+		enum lttng_tracking_policy policy)
 {
 	int ret;
+	enum lttng_error_code ret_code = LTTNG_OK;
+	struct process_attr_tracker *tracker =
+			_kernel_get_process_attr_tracker(session, process_attr);
+	enum lttng_tracking_policy previous_policy;
+
+	if (!tracker) {
+		ret_code = LTTNG_ERR_INVALID;
+		goto end;
+	}
+
+	previous_policy = process_attr_tracker_get_tracking_policy(tracker);
+	ret = process_attr_tracker_set_tracking_policy(tracker, policy);
+	if (ret) {
+		ret_code = LTTNG_ERR_UNK;
+		goto end;
+	}
 
-	DBG("Kernel track PID %d for session id %" PRIu64 ".",
-			pid, session->id);
-	ret = kernctl_track_pid(session->fd, pid);
-	if (!ret) {
-		return LTTNG_OK;
+	if (previous_policy == policy) {
+		goto end;
+	}
+
+	switch (policy) {
+	case LTTNG_TRACKING_POLICY_INCLUDE_ALL:
+		if (process_attr == LTTNG_PROCESS_ATTR_PROCESS_ID) {
+			/*
+			 * Maintain a special case for the process ID process
+			 * attribute tracker as it was the only supported
+			 * attribute prior to 2.12.
+			 */
+			ret = kernctl_track_pid(session->fd, -1);
+		} else {
+			ret = kernctl_track_id(session->fd, process_attr, -1);
+		}
+		break;
+	case LTTNG_TRACKING_POLICY_EXCLUDE_ALL:
+	case LTTNG_TRACKING_POLICY_INCLUDE_SET:
+		/* fall-through. */
+		if (process_attr == LTTNG_PROCESS_ATTR_PROCESS_ID) {
+			/*
+			 * Maintain a special case for the process ID process
+			 * attribute tracker as it was the only supported
+			 * attribute prior to 2.12.
+			 */
+			ret = kernctl_untrack_pid(session->fd, -1);
+		} else {
+			ret = kernctl_untrack_id(session->fd, process_attr, -1);
+		}
+		break;
+	default:
+		abort();
 	}
+	/* kern-ctl error handling */
 	switch (-ret) {
+	case 0:
+		ret_code = LTTNG_OK;
+		break;
 	case EINVAL:
-		return LTTNG_ERR_INVALID;
+		ret_code = LTTNG_ERR_INVALID;
+		break;
 	case ENOMEM:
-		return LTTNG_ERR_NOMEM;
+		ret_code = LTTNG_ERR_NOMEM;
+		break;
 	case EEXIST:
-		return LTTNG_ERR_PID_TRACKED;
+		ret_code = LTTNG_ERR_PROCESS_ATTR_EXISTS;
+		break;
 	default:
-		return LTTNG_ERR_UNK;
+		ret_code = LTTNG_ERR_UNK;
+		break;
 	}
+end:
+	return ret_code;
 }
 
-int kernel_untrack_pid(struct ltt_kernel_session *session, int pid)
+enum lttng_error_code kernel_process_attr_tracker_inclusion_set_add_value(
+		struct ltt_kernel_session *session,
+		enum lttng_process_attr process_attr,
+		const struct process_attr_value *value)
 {
-	int ret;
+	int ret, integral_value;
+	enum lttng_error_code ret_code;
+	struct process_attr_tracker *tracker;
+	enum process_attr_tracker_status status;
+
+	/*
+	 * Convert process attribute tracker value to the integral
+	 * representation required by the kern-ctl API.
+	 */
+	switch (process_attr) {
+	case LTTNG_PROCESS_ATTR_PROCESS_ID:
+	case LTTNG_PROCESS_ATTR_VIRTUAL_PROCESS_ID:
+		integral_value = (int) value->value.pid;
+		break;
+	case LTTNG_PROCESS_ATTR_USER_ID:
+	case LTTNG_PROCESS_ATTR_VIRTUAL_USER_ID:
+		if (value->type == LTTNG_PROCESS_ATTR_VALUE_TYPE_USER_NAME) {
+			uid_t uid;
+
+			ret_code = utils_user_id_from_name(
+					value->value.user_name, &uid);
+			if (ret_code != LTTNG_OK) {
+				goto end;
+			}
+			integral_value = (int) uid;
+		} else {
+			integral_value = (int) value->value.uid;
+		}
+		break;
+	case LTTNG_PROCESS_ATTR_GROUP_ID:
+	case LTTNG_PROCESS_ATTR_VIRTUAL_GROUP_ID:
+		if (value->type == LTTNG_PROCESS_ATTR_VALUE_TYPE_GROUP_NAME) {
+			gid_t gid;
+
+			ret_code = utils_group_id_from_name(
+					value->value.group_name, &gid);
+			if (ret_code != LTTNG_OK) {
+				goto end;
+			}
+			integral_value = (int) gid;
+		} else {
+			integral_value = (int) value->value.gid;
+		}
+		break;
+	default:
+		ret_code = LTTNG_ERR_INVALID;
+		goto end;
+	}
+
+	tracker = _kernel_get_process_attr_tracker(session, process_attr);
+	if (!tracker) {
+		ret_code = LTTNG_ERR_INVALID;
+		goto end;
+	}
+
+	status = process_attr_tracker_inclusion_set_add_value(tracker, value);
+	if (status != PROCESS_ATTR_TRACKER_STATUS_OK) {
+		switch (status) {
+		case PROCESS_ATTR_TRACKER_STATUS_EXISTS:
+			ret_code = LTTNG_ERR_PROCESS_ATTR_EXISTS;
+			break;
+		case PROCESS_ATTR_TRACKER_STATUS_INVALID_TRACKING_POLICY:
+			ret_code = LTTNG_ERR_PROCESS_ATTR_TRACKER_INVALID_TRACKING_POLICY;
+			break;
+		case PROCESS_ATTR_TRACKER_STATUS_ERROR:
+		default:
+			ret_code = LTTNG_ERR_UNK;
+			break;
+		}
+		goto end;
+	}
 
-	DBG("Kernel untrack PID %d for session id %" PRIu64 ".",
-			pid, session->id);
-	ret = kernctl_untrack_pid(session->fd, pid);
-	if (!ret) {
-		return LTTNG_OK;
+	DBG("Kernel track %s %d for session id %" PRIu64,
+			lttng_process_attr_to_string(process_attr),
+			integral_value, session->id);
+	if (process_attr == LTTNG_PROCESS_ATTR_PROCESS_ID) {
+		/*
+		 * Maintain a special case for the process ID process attribute
+		 * tracker as it was the only supported attribute prior to 2.12.
+		 */
+		ret = kernctl_track_pid(session->fd, integral_value);
+	} else {
+		ret = kernctl_track_id(
+				session->fd, process_attr, integral_value);
 	}
+	if (ret == 0) {
+		ret_code = LTTNG_OK;
+		goto end;
+	}
+
+	kernel_wait_quiescent();
+
+	/* kern-ctl error handling */
 	switch (-ret) {
+	case 0:
+		ret_code = LTTNG_OK;
+		break;
 	case EINVAL:
-		return LTTNG_ERR_INVALID;
+		ret_code = LTTNG_ERR_INVALID;
+		break;
 	case ENOMEM:
-		return LTTNG_ERR_NOMEM;
-	case ENOENT:
-		return LTTNG_ERR_PID_NOT_TRACKED;
+		ret_code = LTTNG_ERR_NOMEM;
+		break;
+	case EEXIST:
+		ret_code = LTTNG_ERR_PROCESS_ATTR_EXISTS;
+		break;
 	default:
-		return LTTNG_ERR_UNK;
+		ret_code = LTTNG_ERR_UNK;
+		break;
 	}
+
+	/* Attempt to remove the value from the tracker. */
+	status = process_attr_tracker_inclusion_set_remove_value(
+			tracker, value);
+	if (status != PROCESS_ATTR_TRACKER_STATUS_OK) {
+		ERR("Failed to roll-back the tracking of kernel %s process attribute %d while handling a kern-ctl error",
+				lttng_process_attr_to_string(process_attr),
+				integral_value);
+	}
+end:
+	return ret_code;
 }
 
-ssize_t kernel_list_tracker_pids(struct ltt_kernel_session *session,
-		int **_pids)
+enum lttng_error_code kernel_process_attr_tracker_inclusion_set_remove_value(
+		struct ltt_kernel_session *session,
+		enum lttng_process_attr process_attr,
+		const struct process_attr_value *value)
 {
-	int fd, ret;
-	int pid;
-	ssize_t nbmem, count = 0;
-	FILE *fp;
-	int *pids;
+	int ret, integral_value;
+	enum lttng_error_code ret_code;
+	struct process_attr_tracker *tracker;
+	enum process_attr_tracker_status status;
 
-	fd = kernctl_list_tracker_pids(session->fd);
-	if (fd < 0) {
-		PERROR("kernel tracker pids list");
-		goto error;
+	/*
+	 * Convert process attribute tracker value to the integral
+	 * representation required by the kern-ctl API.
+	 */
+	switch (process_attr) {
+	case LTTNG_PROCESS_ATTR_PROCESS_ID:
+	case LTTNG_PROCESS_ATTR_VIRTUAL_PROCESS_ID:
+		integral_value = (int) value->value.pid;
+		break;
+	case LTTNG_PROCESS_ATTR_USER_ID:
+	case LTTNG_PROCESS_ATTR_VIRTUAL_USER_ID:
+		if (value->type == LTTNG_PROCESS_ATTR_VALUE_TYPE_USER_NAME) {
+			uid_t uid;
+
+			ret_code = utils_user_id_from_name(
+					value->value.user_name, &uid);
+			if (ret_code != LTTNG_OK) {
+				goto end;
+			}
+			integral_value = (int) uid;
+		} else {
+			integral_value = (int) value->value.uid;
+		}
+		break;
+	case LTTNG_PROCESS_ATTR_GROUP_ID:
+	case LTTNG_PROCESS_ATTR_VIRTUAL_GROUP_ID:
+		if (value->type == LTTNG_PROCESS_ATTR_VALUE_TYPE_GROUP_NAME) {
+			gid_t gid;
+
+			ret_code = utils_group_id_from_name(
+					value->value.group_name, &gid);
+			if (ret_code != LTTNG_OK) {
+				goto end;
+			}
+			integral_value = (int) gid;
+		} else {
+			integral_value = (int) value->value.gid;
+		}
+		break;
+	default:
+		ret_code = LTTNG_ERR_INVALID;
+		goto end;
 	}
 
-	fp = fdopen(fd, "r");
-	if (fp == NULL) {
-		PERROR("kernel tracker pids list fdopen");
-		goto error_fp;
+	tracker = _kernel_get_process_attr_tracker(session, process_attr);
+	if (!tracker) {
+		ret_code = LTTNG_ERR_INVALID;
+		goto end;
 	}
 
-	nbmem = KERNEL_TRACKER_PIDS_INIT_LIST_SIZE;
-	pids = zmalloc(sizeof(*pids) * nbmem);
-	if (pids == NULL) {
-		PERROR("alloc list pids");
-		count = -ENOMEM;
+	status = process_attr_tracker_inclusion_set_remove_value(
+			tracker, value);
+	if (status != PROCESS_ATTR_TRACKER_STATUS_OK) {
+		switch (status) {
+		case PROCESS_ATTR_TRACKER_STATUS_MISSING:
+			ret_code = LTTNG_ERR_PROCESS_ATTR_MISSING;
+			break;
+		case PROCESS_ATTR_TRACKER_STATUS_INVALID_TRACKING_POLICY:
+			ret_code = LTTNG_ERR_PROCESS_ATTR_TRACKER_INVALID_TRACKING_POLICY;
+			break;
+		case PROCESS_ATTR_TRACKER_STATUS_ERROR:
+		default:
+			ret_code = LTTNG_ERR_UNK;
+			break;
+		}
 		goto end;
 	}
 
-	while (fscanf(fp, "process { pid = %u; };\n", &pid) == 1) {
-		if (count >= nbmem) {
-			int *new_pids;
-			size_t new_nbmem;
-
-			new_nbmem = nbmem << 1;
-			DBG("Reallocating pids list from %zu to %zu entries",
-					nbmem, new_nbmem);
-			new_pids = realloc(pids, new_nbmem * sizeof(*new_pids));
-			if (new_pids == NULL) {
-				PERROR("realloc list events");
-				free(pids);
-				count = -ENOMEM;
-				goto end;
-			}
-			/* Zero the new memory */
-			memset(new_pids + nbmem, 0,
-				(new_nbmem - nbmem) * sizeof(*new_pids));
-			nbmem = new_nbmem;
-			pids = new_pids;
-		}
-		pids[count++] = pid;
+	DBG("Kernel track %s %d for session id %" PRIu64,
+			lttng_process_attr_to_string(process_attr),
+			integral_value, session->id);
+	if (process_attr == LTTNG_PROCESS_ATTR_PROCESS_ID) {
+		/*
+		 * Maintain a special case for the process ID process attribute
+		 * tracker as it was the only supported attribute prior to 2.12.
+		 */
+		ret = kernctl_untrack_pid(session->fd, integral_value);
+	} else {
+		ret = kernctl_untrack_id(
+				session->fd, process_attr, integral_value);
 	}
+	if (ret == 0) {
+		ret_code = LTTNG_OK;
+		goto end;
+	}
+	kernel_wait_quiescent();
 
-	*_pids = pids;
-	DBG("Kernel list tracker pids done (%zd pids)", count);
-end:
-	ret = fclose(fp);	/* closes both fp and fd */
-	if (ret) {
-		PERROR("fclose");
+	/* kern-ctl error handling */
+	switch (-ret) {
+	case 0:
+		ret_code = LTTNG_OK;
+		break;
+	case EINVAL:
+		ret_code = LTTNG_ERR_INVALID;
+		break;
+	case ENOMEM:
+		ret_code = LTTNG_ERR_NOMEM;
+		break;
+	case ENOENT:
+		ret_code = LTTNG_ERR_PROCESS_ATTR_MISSING;
+		break;
+	default:
+		ret_code = LTTNG_ERR_UNK;
+		break;
 	}
-	return count;
 
-error_fp:
-	ret = close(fd);
-	if (ret) {
-		PERROR("close");
+	/* Attempt to add the value to the tracker. */
+	status = process_attr_tracker_inclusion_set_add_value(
+			tracker, value);
+	if (status != PROCESS_ATTR_TRACKER_STATUS_OK) {
+		ERR("Failed to roll-back the tracking of kernel %s process attribute %d while handling a kern-ctl error",
+				lttng_process_attr_to_string(process_attr),
+				integral_value);
 	}
-error:
-	return -1;
+end:
+	return ret_code;
 }
 
 /*
@@ -836,9 +1110,10 @@ error:
 /*
  * Make a kernel wait to make sure in-flight probe have completed.
  */
-void kernel_wait_quiescent(int fd)
+void kernel_wait_quiescent(void)
 {
 	int ret;
+	int fd = kernel_tracer_fd;
 
 	DBG("Kernel quiescent wait on %d", fd);
 
@@ -997,7 +1272,7 @@ error:
 /*
  * Get the event list from the kernel tracer and return the number of elements.
  */
-ssize_t kernel_list_events(int tracer_fd, struct lttng_event **events)
+ssize_t kernel_list_events(struct lttng_event **events)
 {
 	int fd, ret;
 	char *event;
@@ -1007,7 +1282,7 @@ ssize_t kernel_list_events(int tracer_fd, struct lttng_event **events)
 
 	assert(events);
 
-	fd = kernctl_tracepoint_list(tracer_fd);
+	fd = kernctl_tracepoint_list(kernel_tracer_fd);
 	if (fd < 0) {
 		PERROR("kernel tracepoint list");
 		goto error;
@@ -1081,13 +1356,12 @@ error:
 /*
  * Get kernel version and validate it.
  */
-int kernel_validate_version(int tracer_fd,
-		struct lttng_kernel_tracer_version *version,
+int kernel_validate_version(struct lttng_kernel_tracer_version *version,
 		struct lttng_kernel_tracer_abi_version *abi_version)
 {
 	int ret;
 
-	ret = kernctl_tracer_version(tracer_fd, version);
+	ret = kernctl_tracer_version(kernel_tracer_fd, version);
 	if (ret < 0) {
 		ERR("Failed to retrieve the lttng-modules version");
 		goto error;
@@ -1099,7 +1373,7 @@ int kernel_validate_version(int tracer_fd,
 			version->major, VERSION_MAJOR);
 		goto error_version;
 	}
-	ret = kernctl_tracer_abi_version(tracer_fd, abi_version);
+	ret = kernctl_tracer_abi_version(kernel_tracer_fd, abi_version);
 	if (ret < 0) {
 		ERR("Failed to retrieve lttng-modules ABI version");
 		goto error;
@@ -1261,6 +1535,7 @@ enum lttng_error_code kernel_snapshot_record(
 	struct lttng_ht_iter iter;
 	struct ltt_kernel_metadata *saved_metadata;
 	char *trace_path = NULL;
+	size_t consumer_path_offset = 0;
 
 	assert(ksess);
 	assert(ksess->consumer);
@@ -1287,7 +1562,7 @@ enum lttng_error_code kernel_snapshot_record(
 	}
 
 	trace_path = setup_channel_trace_path(ksess->consumer,
-			DEFAULT_KERNEL_TRACE_DIR);
+			DEFAULT_KERNEL_TRACE_DIR, &consumer_path_offset);
 	if (!trace_path) {
 		status = LTTNG_ERR_INVALID;
 		goto error;
@@ -1310,7 +1585,7 @@ enum lttng_error_code kernel_snapshot_record(
 		cds_list_for_each_entry(chan, &ksess->channel_list.head, list) {
 			status = consumer_snapshot_channel(socket, chan->key, output, 0,
 					ksess->uid, ksess->gid,
-					trace_path, wait,
+					&trace_path[consumer_path_offset], wait,
 					nb_packets_per_stream);
 			if (status != LTTNG_OK) {
 				(void) kernel_consumer_destroy_metadata(socket,
@@ -1321,7 +1596,8 @@ enum lttng_error_code kernel_snapshot_record(
 
 		/* Snapshot metadata, */
 		status = consumer_snapshot_channel(socket, ksess->metadata->key, output,
-				1, ksess->uid, ksess->gid, trace_path, wait, 0);
+				1, ksess->uid, ksess->gid, &trace_path[consumer_path_offset],
+				wait, 0);
 		if (status != LTTNG_OK) {
 			goto error_consumer;
 		}
@@ -1372,12 +1648,12 @@ int kernel_syscall_mask(int chan_fd, char **syscall_mask, uint32_t *nr_bits)
  * Return 1 on success, 0 when feature is not supported, negative value in case
  * of errors.
  */
-int kernel_supports_ring_buffer_snapshot_sample_positions(int tracer_fd)
+int kernel_supports_ring_buffer_snapshot_sample_positions(void)
 {
 	int ret = 0; // Not supported by default
 	struct lttng_kernel_tracer_abi_version abi;
 
-	ret = kernctl_tracer_abi_version(tracer_fd, &abi);
+	ret = kernctl_tracer_abi_version(kernel_tracer_fd, &abi);
 	if (ret < 0) {
 		ERR("Failed to retrieve lttng-modules ABI version");
 		goto error;
@@ -1397,6 +1673,38 @@ error:
 	return ret;
 }
 
+/*
+ * Check for the support of the packet sequence number via abi version number.
+ *
+ * Return 1 on success, 0 when feature is not supported, negative value in case
+ * of errors.
+ */
+int kernel_supports_ring_buffer_packet_sequence_number(void)
+{
+	int ret = 0; // Not supported by default
+	struct lttng_kernel_tracer_abi_version abi;
+
+	ret = kernctl_tracer_abi_version(kernel_tracer_fd, &abi);
+	if (ret < 0) {
+		ERR("Failed to retrieve lttng-modules ABI version");
+		goto error;
+	}
+
+	/*
+	 * Packet sequence number was introduced in LTTng 2.8,
+	 * lttng-modules ABI 2.1.
+	 */
+	if (abi.major >= 2 && abi.minor >= 1) {
+		/* Supported */
+		ret = 1;
+	} else {
+		/* Not supported */
+		ret = 0;
+	}
+error:
+	return ret;
+}
+
 /*
  * Rotate a kernel session.
  *
@@ -1426,7 +1734,7 @@ enum lttng_error_code kernel_rotate_session(struct ltt_session *session)
 			socket, node.node) {
 		struct ltt_kernel_channel *chan;
 
-                /* For each channel, ask the consumer to rotate it. */
+		/* For each channel, ask the consumer to rotate it. */
 		cds_list_for_each_entry(chan, &ksess->channel_list.head, list) {
 			DBG("Rotate kernel channel %" PRIu64 ", session %s",
 					chan->key, session->name);
@@ -1434,7 +1742,7 @@ enum lttng_error_code kernel_rotate_session(struct ltt_session *session)
 					ksess->uid, ksess->gid, ksess->consumer,
 					/* is_metadata_channel */ false);
 			if (ret < 0) {
-				status = LTTNG_ERR_KERN_CONSUMER_FAIL;
+				status = LTTNG_ERR_ROTATION_FAIL_CONSUMER;
 				goto error;
 			}
 		}
@@ -1446,7 +1754,7 @@ enum lttng_error_code kernel_rotate_session(struct ltt_session *session)
 				ksess->uid, ksess->gid, ksess->consumer,
 				/* is_metadata_channel */ true);
 		if (ret < 0) {
-			status = LTTNG_ERR_KERN_CONSUMER_FAIL;
+			status = LTTNG_ERR_ROTATION_FAIL_CONSUMER;
 			goto error;
 		}
 	}
@@ -1480,3 +1788,189 @@ error:
 	rcu_read_unlock();
 	return ret;
 }
+
+/*
+ * Setup necessary data for kernel tracer action.
+ */
+LTTNG_HIDDEN
+int init_kernel_tracer(void)
+{
+	int ret;
+	bool is_root = !getuid();
+
+	/* Modprobe lttng kernel modules */
+	ret = modprobe_lttng_control();
+	if (ret < 0) {
+		goto error;
+	}
+
+	/* Open debugfs lttng */
+	kernel_tracer_fd = open(module_proc_lttng, O_RDWR);
+	if (kernel_tracer_fd < 0) {
+		DBG("Failed to open %s", module_proc_lttng);
+		goto error_open;
+	}
+
+	/* Validate kernel version */
+	ret = kernel_validate_version(&kernel_tracer_version,
+			&kernel_tracer_abi_version);
+	if (ret < 0) {
+		goto error_version;
+	}
+
+	ret = modprobe_lttng_data();
+	if (ret < 0) {
+		goto error_modules;
+	}
+
+	ret = kernel_supports_ring_buffer_snapshot_sample_positions();
+	if (ret < 0) {
+		goto error_modules;
+	}
+
+	if (ret < 1) {
+		WARN("Kernel tracer does not support buffer monitoring. "
+			"The monitoring timer of channels in the kernel domain "
+			"will be set to 0 (disabled).");
+	}
+
+	DBG("Kernel tracer fd %d", kernel_tracer_fd);
+
+	ret = syscall_init_table(kernel_tracer_fd);
+	if (ret < 0) {
+		ERR("Unable to populate syscall table. Syscall tracing won't "
+			"work for this session daemon.");
+	}
+	return 0;
+
+error_version:
+	modprobe_remove_lttng_control();
+	ret = close(kernel_tracer_fd);
+	if (ret) {
+		PERROR("close");
+	}
+	kernel_tracer_fd = -1;
+	return LTTNG_ERR_KERN_VERSION;
+
+error_modules:
+	ret = close(kernel_tracer_fd);
+	if (ret) {
+		PERROR("close");
+	}
+
+error_open:
+	modprobe_remove_lttng_control();
+
+error:
+	WARN("No kernel tracer available");
+	kernel_tracer_fd = -1;
+	if (!is_root) {
+		return LTTNG_ERR_NEED_ROOT_SESSIOND;
+	} else {
+		return LTTNG_ERR_KERN_NA;
+	}
+}
+
+LTTNG_HIDDEN
+void cleanup_kernel_tracer(void)
+{
+	int ret;
+
+	DBG2("Closing kernel fd");
+	if (kernel_tracer_fd >= 0) {
+		ret = close(kernel_tracer_fd);
+		if (ret) {
+			PERROR("close");
+		}
+		kernel_tracer_fd = -1;
+	}
+	DBG("Unloading kernel modules");
+	modprobe_remove_lttng_all();
+	free(syscall_table);
+}
+
+LTTNG_HIDDEN
+bool kernel_tracer_is_initialized(void)
+{
+	return kernel_tracer_fd >= 0;
+}
+
+/*
+ *  Clear a kernel session.
+ *
+ * Return LTTNG_OK on success or else an LTTng error code.
+ */
+enum lttng_error_code kernel_clear_session(struct ltt_session *session)
+{
+	int ret;
+	enum lttng_error_code status = LTTNG_OK;
+	struct consumer_socket *socket;
+	struct lttng_ht_iter iter;
+	struct ltt_kernel_session *ksess = session->kernel_session;
+
+	assert(ksess);
+	assert(ksess->consumer);
+
+	DBG("Clear kernel session %s (session %" PRIu64 ")",
+			session->name, session->id);
+
+	rcu_read_lock();
+
+	if (ksess->active) {
+		ERR("Expecting inactive session %s (%" PRIu64 ")", session->name, session->id);
+		status = LTTNG_ERR_FATAL;
+		goto end;
+	}
+
+	/*
+	 * Note that this loop will end after one iteration given that there is
+	 * only one kernel consumer.
+	 */
+	cds_lfht_for_each_entry(ksess->consumer->socks->ht, &iter.iter,
+			socket, node.node) {
+		struct ltt_kernel_channel *chan;
+
+		/* For each channel, ask the consumer to clear it. */
+		cds_list_for_each_entry(chan, &ksess->channel_list.head, list) {
+			DBG("Clear kernel channel %" PRIu64 ", session %s",
+					chan->key, session->name);
+			ret = consumer_clear_channel(socket, chan->key);
+			if (ret < 0) {
+				goto error;
+			}
+		}
+
+		if (!ksess->metadata) {
+			/*
+			 * Nothing to do for the metadata.
+			 * This is a snapshot session.
+			 * The metadata is genererated on the fly.
+			 */
+			continue;
+		}
+
+		/*
+		 * Clear the metadata channel.
+		 * Metadata channel is not cleared per se but we still need to
+		 * perform a rotation operation on it behind the scene.
+		 */
+		ret = consumer_clear_channel(socket, ksess->metadata->key);
+		if (ret < 0) {
+			goto error;
+		}
+	}
+
+	goto end;
+error:
+	switch (-ret) {
+	case LTTCOMM_CONSUMERD_RELAYD_CLEAR_DISALLOWED:
+	      status = LTTNG_ERR_CLEAR_RELAY_DISALLOWED;
+	      break;
+	default:
+	      status = LTTNG_ERR_CLEAR_FAIL_CONSUMER;
+	      break;
+	}
+end:
+	rcu_read_unlock();
+	return status;
+}