[lttng-tools.git] / src / common / config / session-config.c

/*
 * Copyright (C) 2013 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License, version 2 only, as
 * published by the Free Software Foundation.
 *
 * 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
#include <assert.h>
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <inttypes.h>
#include <dirent.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdbool.h>

#include <common/defaults.h>
#include <common/error.h>
#include <common/macros.h>
#include <common/utils.h>
#include <common/compat/getenv.h>
#include <lttng/lttng-error.h>
#include <libxml/parser.h>
#include <libxml/valid.h>
#include <libxml/xmlschemas.h>
#include <libxml/tree.h>
#include <libxml/xpath.h>
#include <lttng/lttng.h>
#include <lttng/snapshot.h>

#include "session-config.h"
#include "config-internal.h"

struct handler_filter_args {
        const char* section;
        config_entry_handler_cb handler;
        void *user_data;
};

struct session_config_validation_ctx {
        xmlSchemaParserCtxtPtr parser_ctx;
        xmlSchemaPtr schema;
        xmlSchemaValidCtxtPtr schema_validation_ctx;
};

const char * const config_str_yes = "yes";
const char * const config_str_true = "true";
const char * const config_str_on = "on";
const char * const config_str_no = "no";
const char * const config_str_false = "false";
const char * const config_str_off = "off";
const char * const config_xml_encoding = "UTF-8";
const size_t config_xml_encoding_bytes_per_char = 2;    /* Size of the encoding's largest character */
const char * const config_xml_indent_string = "\t";
const char * const config_xml_true = "true";
const char * const config_xml_false = "false";

const char * const config_element_channel = "channel";
const char * const config_element_channels = "channels";
const char * const config_element_domain = "domain";
const char * const config_element_domains = "domains";
const char * const config_element_event = "event";
const char * const config_element_events = "events";
const char * const config_element_context = "context";
const char * const config_element_contexts = "contexts";
const char * const config_element_attributes = "attributes";
const char * const config_element_exclusion = "exclusion";
const char * const config_element_exclusions = "exclusions";
const char * const config_element_function_attributes = "function_attributes";
const char * const config_element_probe_attributes = "probe_attributes";
const char * const config_element_symbol_name = "symbol_name";
const char * const config_element_address = "address";
const char * const config_element_offset = "offset";
const char * const config_element_name = "name";
const char * const config_element_enabled = "enabled";
const char * const config_element_overwrite_mode = "overwrite_mode";
const char * const config_element_subbuf_size = "subbuffer_size";
const char * const config_element_num_subbuf = "subbuffer_count";
const char * const config_element_switch_timer_interval = "switch_timer_interval";
const char * const config_element_read_timer_interval = "read_timer_interval";
const char * const config_element_output = "output";
const char * const config_element_output_type = "output_type";
const char * const config_element_tracefile_size = "tracefile_size";
const char * const config_element_tracefile_count = "tracefile_count";
const char * const config_element_live_timer_interval = "live_timer_interval";
LTTNG_HIDDEN const char * const config_element_discarded_events = "discarded_events";
LTTNG_HIDDEN const char * const config_element_lost_packets = "lost_packets";
const char * const config_element_type = "type";
const char * const config_element_buffer_type = "buffer_type";
const char * const config_element_session = "session";
const char * const config_element_sessions = "sessions";
LTTNG_HIDDEN const char * const config_element_context_perf = "perf";
LTTNG_HIDDEN const char * const config_element_context_app = "app";
LTTNG_HIDDEN const char * const config_element_context_app_provider_name = "provider_name";
LTTNG_HIDDEN const char * const config_element_context_app_ctx_name = "ctx_name";
const char * const config_element_config = "config";
const char * const config_element_started = "started";
const char * const config_element_snapshot_mode = "snapshot_mode";
const char * const config_element_loglevel = "loglevel";
const char * const config_element_loglevel_type = "loglevel_type";
const char * const config_element_filter = "filter";
LTTNG_HIDDEN const char * const config_element_filter_expression = "filter_expression";
const char * const config_element_snapshot_outputs = "snapshot_outputs";
const char * const config_element_consumer_output = "consumer_output";
const char * const config_element_destination = "destination";
const char * const config_element_path = "path";
const char * const config_element_net_output = "net_output";
const char * const config_element_control_uri = "control_uri";
const char * const config_element_data_uri = "data_uri";
const char * const config_element_max_size = "max_size";
const char * const config_element_pid = "pid";
const char * const config_element_pids = "pids";
const char * const config_element_shared_memory_path = "shared_memory_path";
const char * const config_element_pid_tracker = "pid_tracker";
const char * const config_element_trackers = "trackers";
const char * const config_element_targets = "targets";
const char * const config_element_target_pid = "pid_target";
const char * const config_element_omit_name = "omit_name";
const char * const config_element_omit_output = "omit_output";

const char * const config_domain_type_kernel = "KERNEL";
const char * const config_domain_type_ust = "UST";
const char * const config_domain_type_jul = "JUL";
const char * const config_domain_type_log4j = "LOG4J";
const char * const config_domain_type_python = "PYTHON";

const char * const config_buffer_type_per_pid = "PER_PID";
const char * const config_buffer_type_per_uid = "PER_UID";
const char * const config_buffer_type_global = "GLOBAL";

const char * const config_overwrite_mode_discard = "DISCARD";
const char * const config_overwrite_mode_overwrite = "OVERWRITE";

const char * const config_output_type_splice = "SPLICE";
const char * const config_output_type_mmap = "MMAP";

const char * const config_loglevel_type_all = "ALL";
const char * const config_loglevel_type_range = "RANGE";
const char * const config_loglevel_type_single = "SINGLE";

const char * const config_event_type_all = "ALL";
const char * const config_event_type_tracepoint = "TRACEPOINT";
const char * const config_event_type_probe = "PROBE";
const char * const config_event_type_function = "FUNCTION";
const char * const config_event_type_function_entry = "FUNCTION_ENTRY";
const char * const config_event_type_noop = "NOOP";
const char * const config_event_type_syscall = "SYSCALL";
const char * const config_event_type_kprobe = "KPROBE";
const char * const config_event_type_kretprobe = "KRETPROBE";

const char * const config_event_context_pid = "PID";
const char * const config_event_context_procname = "PROCNAME";
const char * const config_event_context_prio = "PRIO";
const char * const config_event_context_nice = "NICE";
const char * const config_event_context_vpid = "VPID";
const char * const config_event_context_tid = "TID";
const char * const config_event_context_vtid = "VTID";
const char * const config_event_context_ppid = "PPID";
const char * const config_event_context_vppid = "VPPID";
const char * const config_event_context_pthread_id = "PTHREAD_ID";
const char * const config_event_context_hostname = "HOSTNAME";
const char * const config_event_context_ip = "IP";
const char * const config_event_context_perf_thread_counter = "PERF_THREAD_COUNTER";
LTTNG_HIDDEN const char * const config_event_context_app = "APP";
LTTNG_HIDDEN const char * const config_event_context_interruptible = "INTERRUPTIBLE";
LTTNG_HIDDEN const char * const config_event_context_preemptible = "PREEMPTIBLE";
LTTNG_HIDDEN const char * const config_event_context_need_reschedule = "NEED_RESCHEDULE";
LTTNG_HIDDEN const char * const config_event_context_migratable = "MIGRATABLE";

/* Deprecated symbols */
const char * const config_element_perf;

enum process_event_node_phase {
        CREATION = 0,
        ENABLE = 1,
};

struct consumer_output {
        int enabled;
        char *path;
        char *control_uri;
        char *data_uri;
};

static int config_entry_handler_filter(struct handler_filter_args *args,
                const char *section, const char *name, const char *value)
{
        int ret = 0;
        struct config_entry entry = { section, name, value };

        assert(args);

        if (!section || !name || !value) {
                ret = -EIO;
                goto end;
        }

        if (args->section) {
                if (strcmp(args->section, section)) {
                        goto end;
                }
        }

        ret = args->handler(&entry, args->user_data);
end:
        return ret;
}

LTTNG_HIDDEN
const char *config_get_domain_str(enum lttng_domain_type domain)
{
        const char *str_dom;

        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
                str_dom = config_domain_type_kernel;
                break;
        case LTTNG_DOMAIN_UST:
                str_dom = config_domain_type_ust;
                break;
        case LTTNG_DOMAIN_JUL:
                str_dom = config_domain_type_jul;
                break;
        case LTTNG_DOMAIN_LOG4J:
                str_dom = config_domain_type_log4j;
                break;
        case LTTNG_DOMAIN_PYTHON:
                str_dom = config_domain_type_python;
                break;
        default:
                assert(0);
        }

        return str_dom;
}

LTTNG_HIDDEN
const char *config_get_loglevel_type_string(
                enum lttng_loglevel_type loglevel_type)
{
        const char *loglevel_type_string;

        switch (loglevel_type) {
                case LTTNG_EVENT_LOGLEVEL_ALL:
                        loglevel_type_string = config_loglevel_type_all;
                        break;
                case LTTNG_EVENT_LOGLEVEL_RANGE:
                        loglevel_type_string = config_loglevel_type_range;
                        break;
                case LTTNG_EVENT_LOGLEVEL_SINGLE:
                        loglevel_type_string = config_loglevel_type_single;
                        break;
                default:
                        loglevel_type_string = NULL;
        }

        return loglevel_type_string;
}

LTTNG_HIDDEN
int config_get_section_entries(const char *override_path, const char *section,
                config_entry_handler_cb handler, void *user_data)
{
        int ret = 0;
        char *path;
        FILE *config_file = NULL;
        struct handler_filter_args filter = { section, handler, user_data };

        /* First, try system-wide conf. file. */
        path = DEFAULT_DAEMON_SYSTEM_CONFIGPATH;

        config_file = fopen(path, "r");
        if (config_file) {
                DBG("Loading daemon conf file at %s", path);
                /*
                 * Return value is not very important here since error or not, we
                 * continue and try the next possible conf. file.
                 */
                (void) ini_parse_file(config_file,
                                (ini_entry_handler) config_entry_handler_filter,
                                (void *) &filter);
                fclose(config_file);
        }

        /* Second is the user local configuration. */
        path = utils_get_home_dir();
        if (path) {
                char fullpath[PATH_MAX];

                ret = snprintf(fullpath, sizeof(fullpath),
                                DEFAULT_DAEMON_HOME_CONFIGPATH, path);
                if (ret < 0) {
                        PERROR("snprintf user conf. path");
                        goto error;
                }

                config_file = fopen(fullpath, "r");
                if (config_file) {
                        DBG("Loading daemon user conf file at %s", path);
                        /*
                         * Return value is not very important here since error or not, we
                         * continue and try the next possible conf. file.
                         */
                        (void) ini_parse_file(config_file,
                                        (ini_entry_handler) config_entry_handler_filter,
                                        (void *) &filter);
                        fclose(config_file);
                }
        }

        /* Final path is the one that the user might have provided. */
        if (override_path) {
                config_file = fopen(override_path, "r");
                if (config_file) {
                        DBG("Loading daemon command line conf file at %s", override_path);
                        (void) ini_parse_file(config_file,
                                        (ini_entry_handler) config_entry_handler_filter,
                                        (void *) &filter);
                        fclose(config_file);
                } else {
                        ERR("Failed to open daemon configuration file at %s",
                                override_path);
                        ret = -ENOENT;
                        goto error;
                }
        }

        /* Everything went well. */
        ret = 0;

error:
        return ret;
}

LTTNG_HIDDEN
int config_parse_value(const char *value)
{
        int i, ret = 0;
        char *endptr, *lower_str;
        size_t len;
        unsigned long v;

        len = strlen(value);
        if (!len) {
                ret = -1;
                goto end;
        }

        v = strtoul(value, &endptr, 10);
        if (endptr != value) {
                ret = v;
                goto end;
        }

        lower_str = zmalloc(len + 1);
        if (!lower_str) {
                PERROR("zmalloc");
                ret = -errno;
                goto end;
        }

        for (i = 0; i < len; i++) {
                lower_str[i] = tolower(value[i]);
        }

        if (!strcmp(lower_str, config_str_yes) ||
                !strcmp(lower_str, config_str_true) ||
                !strcmp(lower_str, config_str_on)) {
                ret = 1;
        } else if (!strcmp(lower_str, config_str_no) ||
                !strcmp(lower_str, config_str_false) ||
                !strcmp(lower_str, config_str_off)) {
                ret = 0;
        } else {
                ret = -1;
        }

        free(lower_str);
end:
        return ret;
}

/*
 * Returns a xmlChar string which must be released using xmlFree().
 */
static xmlChar *encode_string(const char *in_str)
{
        xmlChar *out_str = NULL;
        xmlCharEncodingHandlerPtr handler;
        int out_len, ret, in_len;

        assert(in_str);

        handler = xmlFindCharEncodingHandler(config_xml_encoding);
        if (!handler) {
                ERR("xmlFindCharEncodingHandler return NULL!. Configure issue!");
                goto end;
        }

        in_len = strlen(in_str);
        /*
         * Add 1 byte for the NULL terminted character. The factor 4 here is
         * used because UTF-8 characters can take up to 4 bytes.
         */
        out_len = (in_len * 4) + 1;
        out_str = xmlMalloc(out_len);
        if (!out_str) {
                goto end;
        }

        ret = handler->input(out_str, &out_len, (const xmlChar *) in_str, &in_len);
        if (ret < 0) {
                xmlFree(out_str);
                out_str = NULL;
                goto end;
        }

        /* out_len is now the size of out_str */
        out_str[out_len] = '\0';
end:
        return out_str;
}

LTTNG_HIDDEN
struct config_writer *config_writer_create(int fd_output, int indent)
{
        int ret;
        struct config_writer *writer;
        xmlOutputBufferPtr buffer;

        writer = zmalloc(sizeof(struct config_writer));
        if (!writer) {
                PERROR("zmalloc config_writer_create");
                goto end;
        }

        buffer = xmlOutputBufferCreateFd(fd_output, NULL);
        if (!buffer) {
                goto error_destroy;
        }

        writer->writer = xmlNewTextWriter(buffer);
        ret = xmlTextWriterStartDocument(writer->writer, NULL,
                config_xml_encoding, NULL);
        if (ret < 0) {
                goto error_destroy;
        }

        ret = xmlTextWriterSetIndentString(writer->writer,
                BAD_CAST config_xml_indent_string);
        if (ret) {
                goto error_destroy;
        }

        ret = xmlTextWriterSetIndent(writer->writer, indent);
        if (ret) {
                goto error_destroy;
        }

end:
        return writer;
error_destroy:
        config_writer_destroy(writer);
        return NULL;
}

LTTNG_HIDDEN
int config_writer_destroy(struct config_writer *writer)
{
        int ret = 0;

        if (!writer) {
                ret = -EINVAL;
                goto end;
        }

        if (xmlTextWriterEndDocument(writer->writer) < 0) {
                WARN("Could not close XML document");
                ret = -EIO;
        }

        if (writer->writer) {
                xmlFreeTextWriter(writer->writer);
        }

        free(writer);
end:
        return ret;
}

LTTNG_HIDDEN
int config_writer_open_element(struct config_writer *writer,
        const char *element_name)
{
        int ret;
        xmlChar *encoded_element_name;

        if (!writer || !writer->writer || !element_name || !element_name[0]) {
                ret = -1;
                goto end;
        }

        encoded_element_name = encode_string(element_name);
        if (!encoded_element_name) {
                ret = -1;
                goto end;
        }

        ret = xmlTextWriterStartElement(writer->writer, encoded_element_name);
        xmlFree(encoded_element_name);
end:
        return ret >= 0 ? 0 : ret;
}

LTTNG_HIDDEN
int config_writer_write_attribute(struct config_writer *writer,
                const char *name, const char *value)
{
        int ret;
        xmlChar *encoded_name = NULL;
        xmlChar *encoded_value = NULL;

        if (!writer || !writer->writer || !name || !name[0]) {
                ret = -1;
                goto end;
        }

        encoded_name = encode_string(name);
        if (!encoded_name) {
                ret = -1;
                goto end;
        }

        encoded_value = encode_string(value);
        if (!encoded_value) {
                ret = -1;
                goto end;
        }

        ret = xmlTextWriterWriteAttribute(writer->writer, encoded_name,
                        encoded_value);
end:
        xmlFree(encoded_name);
        xmlFree(encoded_value);
        return ret >= 0 ? 0 : ret;
}

LTTNG_HIDDEN
int config_writer_close_element(struct config_writer *writer)
{
        int ret;

        if (!writer || !writer->writer) {
                ret = -1;
                goto end;
        }

        ret = xmlTextWriterEndElement(writer->writer);
end:
        return ret >= 0 ? 0 : ret;
}

LTTNG_HIDDEN
int config_writer_write_element_unsigned_int(struct config_writer *writer,
                const char *element_name, uint64_t value)
{
        int ret;
        xmlChar *encoded_element_name;

        if (!writer || !writer->writer || !element_name || !element_name[0]) {
                ret = -1;
                goto end;
        }

        encoded_element_name = encode_string(element_name);
        if (!encoded_element_name) {
                ret = -1;
                goto end;
        }

        ret = xmlTextWriterWriteFormatElement(writer->writer,
                encoded_element_name, "%" PRIu64, value);
        xmlFree(encoded_element_name);
end:
        return ret >= 0 ? 0 : ret;
}

LTTNG_HIDDEN
int config_writer_write_element_signed_int(struct config_writer *writer,
                const char *element_name, int64_t value)
{
        int ret;
        xmlChar *encoded_element_name;

        if (!writer || !writer->writer || !element_name || !element_name[0]) {
                ret = -1;
                goto end;
        }

        encoded_element_name = encode_string(element_name);
        if (!encoded_element_name) {
                ret = -1;
                goto end;
        }

        ret = xmlTextWriterWriteFormatElement(writer->writer,
                encoded_element_name, "%" PRIi64, value);
        xmlFree(encoded_element_name);
end:
        return ret >= 0 ? 0 : ret;
}

LTTNG_HIDDEN
int config_writer_write_element_bool(struct config_writer *writer,
                const char *element_name, int value)
{
        return config_writer_write_element_string(writer, element_name,
                value ? config_xml_true : config_xml_false);
}

LTTNG_HIDDEN
int config_writer_write_element_string(struct config_writer *writer,
                const char *element_name, const char *value)
{
        int ret;
        xmlChar *encoded_element_name = NULL;
        xmlChar *encoded_value = NULL;

        if (!writer || !writer->writer || !element_name || !element_name[0] ||
                !value) {
                ret = -1;
                goto end;
        }

        encoded_element_name = encode_string(element_name);
        if (!encoded_element_name) {
                ret = -1;
                goto end;
        }

        encoded_value = encode_string(value);
        if (!encoded_value) {
                ret = -1;
                goto end;
        }

        ret = xmlTextWriterWriteElement(writer->writer, encoded_element_name,
                        encoded_value);
end:
        xmlFree(encoded_element_name);
        xmlFree(encoded_value);
        return ret >= 0 ? 0 : ret;
}

LTTNG_HIDDEN
int config_writer_write_config_element(struct config_writer *writer,
                const struct config_element *element)
{
        int ret = 0;

        xmlNodePtr local_copy = NULL;
        xmlNodePtr place_holder = NULL;
        xmlDocPtr document = NULL;
        xmlBufferPtr buffer = NULL;

        assert(element);
        assert(element->element);
        assert(writer);

        /* Create a new doc and set root node as passed element */
        document = xmlNewDoc(BAD_CAST "1.0");
        document->parseFlags |= XML_PARSE_NOBLANKS;
        if (!document) {
                ERR("Unable to create xml document");
                ret = -1;
                goto end;
        }

        local_copy = xmlCopyNode(element->element, 1);
        if (!local_copy) {
                ERR("Unable to copy an xml node");
                ret = -1;
                goto end;
        }

        /* Hand off the local_copy to the xmlDoc */
        place_holder = xmlDocSetRootElement(document, local_copy);
        if (place_holder) {
                ERR("The document root was already set");
                xmlFreeNode(local_copy);
                ret = -1;
                goto end;
        }

        buffer = xmlBufferCreate();
        if (!buffer) {
                ret = -1;
                goto end;
        }

        ret = xmlNodeDump(buffer, document, local_copy, 0, 0);
        xmlTextWriterWriteRaw(writer->writer, xmlBufferContent(buffer));
end:
        xmlBufferFree(buffer);
        xmlFreeDoc(document);
        return ret;
}

static
void xml_error_handler(void *ctx, const char *format, ...)
{
        char *errMsg;
        va_list args;
        int ret;

        va_start(args, format);
        ret = vasprintf(&errMsg, format, args);
        va_end(args);
        if (ret == -1) {
                ERR("String allocation failed in xml error handler");
                return;
        }

        fprintf(stderr, "XML Error: %s", errMsg);
        free(errMsg);
}

static
void fini_session_config_validation_ctx(
        struct session_config_validation_ctx *ctx)
{
        if (ctx->parser_ctx) {
                xmlSchemaFreeParserCtxt(ctx->parser_ctx);
        }

        if (ctx->schema) {
                xmlSchemaFree(ctx->schema);
        }

        if (ctx->schema_validation_ctx) {
                xmlSchemaFreeValidCtxt(ctx->schema_validation_ctx);
        }

        memset(ctx, 0, sizeof(struct session_config_validation_ctx));
}

static
char *get_session_config_xsd_path()
{
        char *xsd_path;
        const char *base_path = lttng_secure_getenv(DEFAULT_SESSION_CONFIG_XSD_PATH_ENV);
        size_t base_path_len;
        size_t max_path_len;

        if (!base_path) {
                base_path = DEFAULT_SESSION_CONFIG_XSD_PATH;
        }

        base_path_len = strlen(base_path);
        max_path_len = base_path_len +
                sizeof(DEFAULT_SESSION_CONFIG_XSD_FILENAME) + 1;
        xsd_path = zmalloc(max_path_len);
        if (!xsd_path) {
                goto end;
        }

        strncpy(xsd_path, base_path, max_path_len);
        if (xsd_path[base_path_len - 1] != '/') {
                xsd_path[base_path_len++] = '/';
        }

        strncpy(xsd_path + base_path_len, DEFAULT_SESSION_CONFIG_XSD_FILENAME,
                max_path_len - base_path_len);
end:
        return xsd_path;
}

static
int init_session_config_validation_ctx(
        struct session_config_validation_ctx *ctx)
{
        int ret;
        char *xsd_path = get_session_config_xsd_path();

        if (!xsd_path) {
                ret = -LTTNG_ERR_NOMEM;
                goto end;
        }

        ctx->parser_ctx = xmlSchemaNewParserCtxt(xsd_path);
        if (!ctx->parser_ctx) {
                ERR("XSD parser context creation failed");
                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                goto end;
        }
        xmlSchemaSetParserErrors(ctx->parser_ctx, xml_error_handler,
                xml_error_handler, NULL);

        ctx->schema = xmlSchemaParse(ctx->parser_ctx);
        if (!ctx->schema) {
                ERR("XSD parsing failed");
                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                goto end;
        }

        ctx->schema_validation_ctx = xmlSchemaNewValidCtxt(ctx->schema);
        if (!ctx->schema_validation_ctx) {
                ERR("XSD validation context creation failed");
                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                goto end;
        }

        xmlSchemaSetValidErrors(ctx->schema_validation_ctx, xml_error_handler,
                        xml_error_handler, NULL);
        ret = 0;

end:
        if (ret) {
                fini_session_config_validation_ctx(ctx);
        }

        free(xsd_path);
        return ret;
}

static
int parse_uint(xmlChar *str, uint64_t *val)
{
        int ret;
        char *endptr;

        if (!str || !val) {
                ret = -1;
                goto end;
        }

        *val = strtoull((const char *) str, &endptr, 10);
        if (!endptr || *endptr) {
                ret = -1;
        } else {
                ret = 0;
        }

end:
        return ret;
}

static
int parse_int(xmlChar *str, int64_t *val)
{
        int ret;
        char *endptr;

        if (!str || !val) {
                ret = -1;
                goto end;
        }

        *val = strtoll((const char *) str, &endptr, 10);
        if (!endptr || *endptr) {
                ret = -1;
        } else {
                ret = 0;
        }

end:
        return ret;
}

static
int parse_bool(xmlChar *str, int *val)
{
        int ret = 0;

        if (!str || !val) {
                ret = -1;
                goto end;
        }

        if (!strcmp((const char *) str, config_xml_true)) {
                *val = 1;
        } else if (!strcmp((const char *) str, config_xml_false)) {
                *val = 0;
        } else {
                WARN("Invalid boolean value encoutered (%s).",
                        (const char *) str);
                ret = -1;
        }
end:
        return ret;
}

static
int get_domain_type(xmlChar *domain)
{
        int ret;

        if (!domain) {
                goto error;
        }

        if (!strcmp((char *) domain, config_domain_type_kernel)) {
                ret = LTTNG_DOMAIN_KERNEL;
        } else if (!strcmp((char *) domain, config_domain_type_ust)) {
                ret = LTTNG_DOMAIN_UST;
        } else if (!strcmp((char *) domain, config_domain_type_jul)) {
                ret = LTTNG_DOMAIN_JUL;
        } else if (!strcmp((char *) domain, config_domain_type_log4j)) {
                ret = LTTNG_DOMAIN_LOG4J;
        } else if (!strcmp((char *) domain, config_domain_type_python)) {
                ret = LTTNG_DOMAIN_PYTHON;
        } else {
                goto error;
        }

        return ret;
error:
        return -1;
}

static
int get_buffer_type(xmlChar *buffer_type)
{
        int ret;

        if (!buffer_type) {
                goto error;
        }

        if (!strcmp((char *) buffer_type, config_buffer_type_global)) {
                ret = LTTNG_BUFFER_GLOBAL;
        } else if (!strcmp((char *) buffer_type, config_buffer_type_per_uid)) {
                ret = LTTNG_BUFFER_PER_UID;
        } else if (!strcmp((char *) buffer_type, config_buffer_type_per_pid)) {
                ret = LTTNG_BUFFER_PER_PID;
        } else {
                goto error;
        }

        return ret;
error:
        return -1;
}

static
int get_overwrite_mode(xmlChar *overwrite_mode)
{
        int ret;

        if (!overwrite_mode) {
                goto error;
        }

        if (!strcmp((char *) overwrite_mode, config_overwrite_mode_overwrite)) {
                ret = 1;
        } else if (!strcmp((char *) overwrite_mode,
                config_overwrite_mode_discard)) {
                ret = 0;
        } else {
                goto error;
        }

        return ret;
error:
        return -1;
}

static
int get_output_type(xmlChar *output_type)
{
        int ret;

        if (!output_type) {
                goto error;
        }

        if (!strcmp((char *) output_type, config_output_type_mmap)) {
                ret = LTTNG_EVENT_MMAP;
        } else if (!strcmp((char *) output_type, config_output_type_splice)) {
                ret = LTTNG_EVENT_SPLICE;
        } else {
                goto error;
        }

        return ret;
error:
        return -1;
}

LTTNG_HIDDEN
int config_get_event_type(const char *event_type)
{
        int ret;

        if (!event_type) {
                goto error;
        }

        if (!strcmp(event_type, config_event_type_all)) {
                ret = LTTNG_EVENT_ALL;
        } else if (!strcmp(event_type, config_event_type_tracepoint)) {
                ret = LTTNG_EVENT_TRACEPOINT;
        } else if (!strcmp(event_type, config_event_type_probe)) {
                ret = LTTNG_EVENT_PROBE;
        } else if (!strcmp(event_type, config_event_type_function)) {
                ret = LTTNG_EVENT_FUNCTION;
        } else if (!strcmp(event_type,
                config_event_type_function_entry)) {
                ret = LTTNG_EVENT_FUNCTION_ENTRY;
        } else if (!strcmp(event_type, config_event_type_noop)) {
                ret = LTTNG_EVENT_NOOP;
        } else if (!strcmp(event_type, config_event_type_syscall)) {
                ret = LTTNG_EVENT_SYSCALL;
        } else {
                goto error;
        }

        return ret;
error:
        return -1;
}

static
int get_loglevel_type(xmlChar *loglevel_type)
{
        int ret;

        if (!loglevel_type) {
                goto error;
        }

        if (!strcmp((char *) loglevel_type, config_loglevel_type_all)) {
                ret = LTTNG_EVENT_LOGLEVEL_ALL;
        } else if (!strcmp((char *) loglevel_type,
                config_loglevel_type_range)) {
                ret = LTTNG_EVENT_LOGLEVEL_RANGE;
        } else if (!strcmp((char *) loglevel_type,
                config_loglevel_type_single)) {
                ret = LTTNG_EVENT_LOGLEVEL_SINGLE;
        } else {
                goto error;
        }

        return ret;
error:
        return -1;
}

/*
 * Return the context type or -1 on error.
 */
static
int get_context_type(xmlChar *context_type)
{
        int ret;

        if (!context_type) {
                goto error;
        }

        if (!strcmp((char *) context_type, config_event_context_pid)) {
                ret = LTTNG_EVENT_CONTEXT_PID;
        } else if (!strcmp((char *) context_type,
                config_event_context_procname)) {
                ret = LTTNG_EVENT_CONTEXT_PROCNAME;
        } else if (!strcmp((char *) context_type,
                config_event_context_prio)) {
                ret = LTTNG_EVENT_CONTEXT_PRIO;
        } else if (!strcmp((char *) context_type,
                config_event_context_nice)) {
                ret = LTTNG_EVENT_CONTEXT_NICE;
        } else if (!strcmp((char *) context_type,
                config_event_context_vpid)) {
                ret = LTTNG_EVENT_CONTEXT_VPID;
        } else if (!strcmp((char *) context_type,
                config_event_context_tid)) {
                ret = LTTNG_EVENT_CONTEXT_TID;
        } else if (!strcmp((char *) context_type,
                config_event_context_vtid)) {
                ret = LTTNG_EVENT_CONTEXT_VTID;
        } else if (!strcmp((char *) context_type,
                config_event_context_ppid)) {
                ret = LTTNG_EVENT_CONTEXT_PPID;
        } else if (!strcmp((char *) context_type,
                config_event_context_vppid)) {
                ret = LTTNG_EVENT_CONTEXT_VPPID;
        } else if (!strcmp((char *) context_type,
                config_event_context_pthread_id)) {
                ret = LTTNG_EVENT_CONTEXT_PTHREAD_ID;
        } else if (!strcmp((char *) context_type,
                config_event_context_hostname)) {
                ret = LTTNG_EVENT_CONTEXT_HOSTNAME;
        } else if (!strcmp((char *) context_type,
                config_event_context_ip)) {
                ret = LTTNG_EVENT_CONTEXT_IP;
        } else if (!strcmp((char *) context_type,
                config_event_context_interruptible)) {
                ret = LTTNG_EVENT_CONTEXT_INTERRUPTIBLE;
        } else if (!strcmp((char *) context_type,
                config_event_context_preemptible)) {
                ret = LTTNG_EVENT_CONTEXT_PREEMPTIBLE;
        } else if (!strcmp((char *) context_type,
                config_event_context_need_reschedule)) {
                ret = LTTNG_EVENT_CONTEXT_NEED_RESCHEDULE;
        } else if (!strcmp((char *) context_type,
                config_event_context_migratable)) {
                ret = LTTNG_EVENT_CONTEXT_MIGRATABLE;
        } else {
                goto error;
        }

        return ret;
error:
        return -1;
}

static
int init_domain(xmlNodePtr domain_node, struct lttng_domain *domain)
{
        int ret;
        xmlNodePtr node;

        for (node = xmlFirstElementChild(domain_node); node;
                node = xmlNextElementSibling(node)) {
                if (!strcmp((const char *) node->name, config_element_type)) {
                        /* domain type */
                        xmlChar *node_content = xmlNodeGetContent(node);
                        if (!node_content) {
                                ret = -LTTNG_ERR_NOMEM;
                                goto end;
                        }

                        ret = get_domain_type(node_content);
                        free(node_content);
                        if (ret < 0) {
                                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                goto end;
                        }

                        domain->type = ret;
                } else if (!strcmp((const char *) node->name,
                        config_element_buffer_type)) {
                        /* buffer type */
                        xmlChar *node_content = xmlNodeGetContent(node);
                        if (!node_content) {
                                ret = -LTTNG_ERR_NOMEM;
                                goto end;
                        }

                        ret = get_buffer_type(node_content);
                        free(node_content);
                        if (ret < 0) {
                                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                goto end;
                        }

                        domain->buf_type = ret;
                }
        }
        ret = 0;
end:
        return ret;
}

static
int get_net_output_uris(xmlNodePtr net_output_node, char **control_uri,
        char **data_uri)
{
        xmlNodePtr node;

        for (node = xmlFirstElementChild(net_output_node); node;
                node = xmlNextElementSibling(node)) {
                if (!strcmp((const char *) node->name, config_element_control_uri)) {
                        /* control_uri */
                        *control_uri = (char *) xmlNodeGetContent(node);
                        if (!*control_uri) {
                                break;
                        }
                } else {
                        /* data_uri */
                        *data_uri = (char *) xmlNodeGetContent(node);
                        if (!*data_uri) {
                                break;
                        }
                }
        }

        return *control_uri || *data_uri ? 0 : -LTTNG_ERR_LOAD_INVALID_CONFIG;
}

static
int process_consumer_output(xmlNodePtr consumer_output_node,
        struct consumer_output *output)
{
        int ret;
        xmlNodePtr node;

        assert(output);

        for (node = xmlFirstElementChild(consumer_output_node); node;
                        node = xmlNextElementSibling(node)) {
                if (!strcmp((const char *) node->name, config_element_enabled)) {
                        xmlChar *enabled_str = xmlNodeGetContent(node);

                        /* enabled */
                        if (!enabled_str) {
                                ret = -LTTNG_ERR_NOMEM;
                                goto end;
                        }

                        ret = parse_bool(enabled_str, &output->enabled);
                        free(enabled_str);
                        if (ret) {
                                goto end;
                        }
                } else {
                        xmlNodePtr output_type_node;

                        /* destination */
                        output_type_node = xmlFirstElementChild(node);
                        if (!output_type_node) {
                                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                goto end;
                        }

                        if (!strcmp((const char *) output_type_node->name,
                                        config_element_path)) {
                                /* path */
                                output->path = (char *) xmlNodeGetContent(output_type_node);
                                if (!output->path) {
                                        ret = -LTTNG_ERR_NOMEM;
                                        goto end;
                                }
                        } else {
                                /* net_output */
                                ret = get_net_output_uris(output_type_node,
                                                &output->control_uri, &output->data_uri);
                                if (ret) {
                                        goto end;
                                }
                        }
                }
        }
        ret = 0;

end:
        if (ret) {
                free(output->path);
                free(output->control_uri);
                free(output->data_uri);
                memset(output, 0, sizeof(struct consumer_output));
        }
        return ret;
}

static
int create_session_net_output(const char *name, const char *control_uri,
                const char *data_uri)
{
        int ret;
        struct lttng_handle *handle;
        const char *uri = NULL;

        assert(name);

        handle = lttng_create_handle(name, NULL);
        if (!handle) {
                ret = -LTTNG_ERR_NOMEM;
                goto end;
        }

        if (!control_uri || !data_uri) {
                uri = control_uri ? control_uri : data_uri;
                control_uri = uri;
                data_uri = uri;
        }

        ret = lttng_set_consumer_url(handle, control_uri, data_uri);
        lttng_destroy_handle(handle);
end:
        return ret;
}

static
int create_snapshot_session(const char *session_name, xmlNodePtr output_node)
{
        int ret;
        xmlNodePtr node = NULL;
        xmlNodePtr snapshot_output_list_node;
        xmlNodePtr snapshot_output_node;

        assert(session_name);

        ret = lttng_create_session_snapshot(session_name, NULL);
        if (ret) {
                goto end;
        }

        if (!output_node) {
                goto end;
        }

        snapshot_output_list_node = xmlFirstElementChild(output_node);

        /* Parse and create snapshot outputs */

        for (snapshot_output_node =
                        xmlFirstElementChild(snapshot_output_list_node);
                        snapshot_output_node; snapshot_output_node =
                        xmlNextElementSibling(snapshot_output_node)) {
                char *name = NULL;
                uint64_t max_size = DEFAULT_SNAPSHOT_MAX_SIZE;
                struct consumer_output output = { 0 };
                struct lttng_snapshot_output *snapshot_output = NULL;

                for (node = xmlFirstElementChild(snapshot_output_node); node;
                                node = xmlNextElementSibling(node)) {
                        if (!strcmp((const char *) node->name,
                                config_element_name)) {
                                /* name */
                                name = (char *) xmlNodeGetContent(node);
                                if (!name) {
                                        ret = -LTTNG_ERR_NOMEM;
                                        goto error_snapshot_output;
                                }
                        } else if (!strcmp((const char *) node->name,
                                config_element_max_size)) {
                                xmlChar *content = xmlNodeGetContent(node);

                                /* max_size */
                                if (!content) {
                                        ret = -LTTNG_ERR_NOMEM;
                                        goto error_snapshot_output;
                                }
                                ret = parse_uint(content, &max_size);
                                free(content);
                                if (ret) {
                                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                        goto error_snapshot_output;
                                }
                        } else {
                                /* consumer_output */
                                ret = process_consumer_output(node, &output);
                                if (ret) {
                                        goto error_snapshot_output;
                                }
                        }
                }

                snapshot_output = lttng_snapshot_output_create();
                if (!snapshot_output) {
                        ret = -LTTNG_ERR_NOMEM;
                        goto error_snapshot_output;
                }

                if (!name) {
                        /* Generate a default name */
                        int pret;
                        pret = asprintf(&name, DEFAULT_SNAPSHOT_NAME "-%" PRIu32,
                                        lttng_snapshot_output_get_id(snapshot_output));
                        if (pret < 0) {
                                name = NULL;
                                PERROR("snprintf output name");
                                goto error_snapshot_output;
                        }
                }

                ret = lttng_snapshot_output_set_name(name, snapshot_output);
                if (ret) {
                        goto error_snapshot_output;
                }

                ret = lttng_snapshot_output_set_size(max_size, snapshot_output);
                if (ret) {
                        goto error_snapshot_output;
                }

                if (output.path) {
                        ret = lttng_snapshot_output_set_ctrl_url(output.path,
                                        snapshot_output);
                        if (ret) {
                                goto error_snapshot_output;
                        }
                } else {
                        if (output.control_uri) {
                                ret = lttng_snapshot_output_set_ctrl_url(output.control_uri,
                                                snapshot_output);
                                if (ret) {
                                        goto error_snapshot_output;
                                }
                        }

                        if (output.data_uri) {
                                ret = lttng_snapshot_output_set_data_url(output.data_uri,
                                                snapshot_output);
                                if (ret) {
                                        goto error_snapshot_output;
                                }
                        }
                }

                ret = lttng_snapshot_add_output(session_name, snapshot_output);
error_snapshot_output:
                free(name);
                free(output.path);
                free(output.control_uri);
                free(output.data_uri);
                lttng_snapshot_output_destroy(snapshot_output);
                if (ret) {
                        goto end;
                }
        }
end:
        return ret;
}

static
int create_session(const char *name,
        struct lttng_domain *kernel_domain,
        struct lttng_domain *ust_domain,
        struct lttng_domain *jul_domain,
        struct lttng_domain *log4j_domain,
        xmlNodePtr output_node,
        uint64_t live_timer_interval)
{
        int ret;
        struct consumer_output output = { 0 };
        xmlNodePtr consumer_output_node;

        assert(name);

        if (output_node) {
                consumer_output_node = xmlFirstElementChild(output_node);
                if (!consumer_output_node) {
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }

                if (strcmp((const char *) consumer_output_node->name,
                        config_element_consumer_output)) {
                        WARN("Invalid output type, expected %s node",
                                config_element_consumer_output);
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }

                ret = process_consumer_output(consumer_output_node, &output);
                if (ret) {
                        goto end;
                }
        }

        if (live_timer_interval != UINT64_MAX &&
                !output.control_uri && !output.data_uri) {
                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                goto end;
        }

        if (output.control_uri || output.data_uri) {
                /* network destination */
                if (live_timer_interval && live_timer_interval != UINT64_MAX) {
                        /*
                         * URLs are provided for sure since the test above make sure that
                         * with a live timer the data and control URIs are provided. So,
                         * NULL is passed here and will be set right after.
                         */
                        ret = lttng_create_session_live(name, NULL, live_timer_interval);
                } else {
                        ret = lttng_create_session(name, NULL);
                }
                if (ret) {
                        goto end;
                }

                ret = create_session_net_output(name, output.control_uri,
                                output.data_uri);
                if (ret) {
                        goto end;
                }

        } else {
                /* either local output or no output */
                ret = lttng_create_session(name, output.path);
                if (ret) {
                        goto end;
                }
        }
end:
        free(output.path);
        free(output.control_uri);
        free(output.data_uri);
        return ret;
}
static
int process_probe_attribute_node(xmlNodePtr probe_attribute_node,
        struct lttng_event_probe_attr *attr)
{
        int ret;

        assert(probe_attribute_node);
        assert(attr);

        if (!strcmp((const char *) probe_attribute_node->name,
                config_element_address)) {
                xmlChar *content;
                uint64_t addr = 0;

                /* addr */
                content = xmlNodeGetContent(probe_attribute_node);
                if (!content) {
                        ret = -LTTNG_ERR_NOMEM;
                        goto end;
                }

                ret = parse_uint(content, &addr);
                free(content);
                if (ret) {
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }

                attr->addr = addr;
        } else if (!strcmp((const char *) probe_attribute_node->name,
                config_element_offset)) {
                xmlChar *content;
                uint64_t offset = 0;

                /* offset */
                content = xmlNodeGetContent(probe_attribute_node);
                if (!content) {
                        ret = -LTTNG_ERR_NOMEM;
                        goto end;
                }

                ret = parse_uint(content, &offset);
                free(content);
                if (ret) {
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }

                attr->offset = offset;
        } else if (!strcmp((const char *) probe_attribute_node->name,
                config_element_symbol_name)) {
                xmlChar *content;
                size_t name_len;

                /* symbol_name */
                content = xmlNodeGetContent(probe_attribute_node);
                if (!content) {
                        ret = -LTTNG_ERR_NOMEM;
                        goto end;
                }

                name_len = strlen((char *) content);
                if (name_len >= LTTNG_SYMBOL_NAME_LEN) {
                        WARN("symbol_name too long.");
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        free(content);
                        goto end;
                }

                strncpy(attr->symbol_name, (const char *) content, name_len);
                free(content);
        }
        ret = 0;
end:
        return ret;
}

static
int process_event_node(xmlNodePtr event_node, struct lttng_handle *handle,
        const char *channel_name, const enum process_event_node_phase phase)
{
        int ret = 0, i;
        xmlNodePtr node;
        struct lttng_event event;
        char **exclusions = NULL;
        unsigned long exclusion_count = 0;
        char *filter_expression = NULL;

        assert(event_node);
        assert(handle);
        assert(channel_name);

        memset(&event, 0, sizeof(event));

        /* Initialize default log level which varies by domain */
        switch (handle->domain.type)
        {
        case LTTNG_DOMAIN_JUL:
                event.loglevel = LTTNG_LOGLEVEL_JUL_ALL;
                break;
        case LTTNG_DOMAIN_LOG4J:
                event.loglevel = LTTNG_LOGLEVEL_LOG4J_ALL;
                break;
        case LTTNG_DOMAIN_PYTHON:
                event.loglevel = LTTNG_LOGLEVEL_PYTHON_DEBUG;
                break;
        case LTTNG_DOMAIN_UST:
        case LTTNG_DOMAIN_KERNEL:
                event.loglevel = LTTNG_LOGLEVEL_DEBUG;
                break;
        default:
                assert(0);
        }

        for (node = xmlFirstElementChild(event_node); node;
                node = xmlNextElementSibling(node)) {
                if (!strcmp((const char *) node->name, config_element_name)) {
                        xmlChar *content;
                        size_t name_len;

                        /* name */
                        content = xmlNodeGetContent(node);
                        if (!content) {
                                ret = -LTTNG_ERR_NOMEM;
                                goto end;
                        }

                        name_len = strlen((char *) content);
                        if (name_len >= LTTNG_SYMBOL_NAME_LEN) {
                                WARN("Channel name too long.");
                                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                free(content);
                                goto end;
                        }

                        strncpy(event.name, (const char *) content, name_len);
                        free(content);
                } else if (!strcmp((const char *) node->name,
                        config_element_enabled)) {
                        xmlChar *content = xmlNodeGetContent(node);

                        /* enabled */
                        if (!content) {
                                ret = -LTTNG_ERR_NOMEM;
                                goto end;
                        }

                        ret = parse_bool(content, &event.enabled);
                        free(content);
                        if (ret) {
                                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                goto end;
                        }
                } else if (!strcmp((const char *) node->name,
                        config_element_type)) {
                        xmlChar *content = xmlNodeGetContent(node);

                        /* type */
                        if (!content) {
                                ret = -LTTNG_ERR_NOMEM;
                                goto end;
                        }

                        ret = config_get_event_type((char *) content);
                        free(content);
                        if (ret < 0) {
                                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                goto end;
                        }

                        event.type = ret;
                } else if (!strcmp((const char *) node->name,
                        config_element_loglevel_type)) {
                        xmlChar *content = xmlNodeGetContent(node);

                        /* loglevel_type */
                        if (!content) {
                                ret = -LTTNG_ERR_NOMEM;
                                goto end;
                        }

                        ret = get_loglevel_type(content);
                        free(content);
                        if (ret < 0) {
                                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                goto end;
                        }

                        event.loglevel_type = ret;
                } else if (!strcmp((const char *) node->name,
                        config_element_loglevel)) {
                        xmlChar *content;
                        int64_t loglevel = 0;

                        /* loglevel */
                        content = xmlNodeGetContent(node);
                        if (!content) {
                                ret = -LTTNG_ERR_NOMEM;
                                goto end;
                        }

                        ret = parse_int(content, &loglevel);
                        free(content);
                        if (ret) {
                                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                goto end;
                        }

                        if (loglevel > INT_MAX || loglevel < INT_MIN) {
                                WARN("loglevel out of range.");
                                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                goto end;
                        }

                        event.loglevel = loglevel;
                } else if (!strcmp((const char *) node->name,
                        config_element_filter)) {
                        xmlChar *content =
                                xmlNodeGetContent(node);

                        /* filter */
                        if (!content) {
                                ret = -LTTNG_ERR_NOMEM;
                                goto end;
                        }

                        free(filter_expression);
                        filter_expression = strdup((char *) content);
                        free(content);
                        if (!filter_expression) {
                                ret = -LTTNG_ERR_NOMEM;
                                goto end;
                        }
                } else if (!strcmp((const char *) node->name,
                        config_element_exclusions)) {
                        xmlNodePtr exclusion_node;
                        int exclusion_index = 0;

                        /* exclusions */
                        if (exclusions) {
                                /*
                                 * Exclusions has already been initialized,
                                 * invalid file.
                                 */
                                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                goto end;
                        }

                        exclusion_count = xmlChildElementCount(node);
                        if (!exclusion_count) {
                                continue;
                        }

                        exclusions = zmalloc(exclusion_count * sizeof(char *));
                        if (!exclusions) {
                                exclusion_count = 0;
                                ret = -LTTNG_ERR_NOMEM;
                                goto end;
                        }

                        for (exclusion_node = xmlFirstElementChild(node); exclusion_node;
                                        exclusion_node = xmlNextElementSibling(exclusion_node)) {
                                xmlChar *content =
                                        xmlNodeGetContent(exclusion_node);

                                if (!content) {
                                        ret = -LTTNG_ERR_NOMEM;
                                        goto end;
                                }

                                exclusions[exclusion_index] = strdup((const char *) content);
                                free(content);
                                if (!exclusions[exclusion_index]) {
                                        ret = -LTTNG_ERR_NOMEM;
                                        goto end;
                                }
                                exclusion_index++;
                        }

                        event.exclusion = 1;
                } else if (!strcmp((const char *) node->name,
                        config_element_attributes)) {
                        xmlNodePtr attribute_node = xmlFirstElementChild(node);

                        /* attributes */
                        if (!attribute_node) {
                                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                goto end;
                        }

                        if (!strcmp((const char *) node->name,
                                                config_element_probe_attributes)) {
                                xmlNodePtr probe_attribute_node;

                                /* probe_attributes */
                                for (probe_attribute_node =
                                        xmlFirstElementChild(attribute_node); probe_attribute_node;
                                        probe_attribute_node = xmlNextElementSibling(
                                                        probe_attribute_node)) {

                                        ret = process_probe_attribute_node(probe_attribute_node,
                                                        &event.attr.probe);
                                        if (ret) {
                                                goto end;
                                        }
                                }
                        } else {
                                size_t sym_len;
                                xmlChar *content;
                                xmlNodePtr symbol_node = xmlFirstElementChild(attribute_node);

                                /* function_attributes */
                                content = xmlNodeGetContent(symbol_node);
                                if (!content) {
                                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                        goto end;
                                }

                                sym_len = strlen((char *) content);
                                if (sym_len >= LTTNG_SYMBOL_NAME_LEN) {
                                        WARN("Function name too long.");
                                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                        free(content);
                                        goto end;
                                }

                                strncpy(event.attr.ftrace.symbol_name, (char *) content,
                                                sym_len);
                                free(content);
                        }
                }
        }

        if ((event.enabled && phase == ENABLE) || phase == CREATION) {
                ret = lttng_enable_event_with_exclusions(handle, &event, channel_name,
                                filter_expression, exclusion_count, exclusions);
                if (ret < 0) {
                        WARN("Enabling event (name:%s) on load failed.", event.name);
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }
        }
end:
        for (i = 0; i < exclusion_count; i++) {
                free(exclusions[i]);
        }

        free(exclusions);
        free(filter_expression);
        return ret;
}

static
int process_events_node(xmlNodePtr events_node, struct lttng_handle *handle,
        const char *channel_name)
{
        int ret = 0;
        struct lttng_event event;
        xmlNodePtr node;

        assert(events_node);
        assert(handle);
        assert(channel_name);

        for (node = xmlFirstElementChild(events_node); node;
                node = xmlNextElementSibling(node)) {
                ret = process_event_node(node, handle, channel_name, CREATION);
                if (ret) {
                        goto end;
                }
        }

        /*
         * Disable all events to enable only the necessary events.
         * Limitations regarding lttng_disable_events and tuple descriptor
         * force this approach.
         */
        memset(&event, 0, sizeof(event));
        event.loglevel = -1;
        event.type = LTTNG_EVENT_ALL;
        ret = lttng_disable_event_ext(handle, &event, channel_name, NULL);
        if (ret) {
                goto end;
        }

        for (node = xmlFirstElementChild(events_node); node;
                        node = xmlNextElementSibling(node)) {
                ret = process_event_node(node, handle, channel_name, ENABLE);
                if (ret) {
                        goto end;
                }
        }

end:
        return ret;
}

static
int process_channel_attr_node(xmlNodePtr attr_node, bool snapshot_mode,
                enum lttng_domain_type domain, struct lttng_channel *channel,
                xmlNodePtr *contexts_node, xmlNodePtr *events_node)
{
        int ret;

        assert(attr_node);
        assert(channel);
        assert(contexts_node);
        assert(events_node);

        if (!strcmp((const char *) attr_node->name, config_element_name)) {
                xmlChar *content;
                size_t name_len;

                /* name */
                content = xmlNodeGetContent(attr_node);
                if (!content) {
                        ret = -LTTNG_ERR_NOMEM;
                        goto end;
                }

                name_len = strlen((char *) content);
                if (name_len >= LTTNG_SYMBOL_NAME_LEN) {
                        WARN("Channel name too long.");
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        free(content);
                        goto end;
                }

                strncpy(channel->name, (const char *) content, name_len);
                free(content);
        } else if (!strcmp((const char *) attr_node->name,
                        config_element_enabled)) {
                xmlChar *content;
                int enabled;

                /* enabled */
                content = xmlNodeGetContent(attr_node);
                if (!content) {
                        ret = -LTTNG_ERR_NOMEM;
                        goto end;
                }

                ret = parse_bool(content, &enabled);
                free(content);
                if (ret) {
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }

                channel->enabled = enabled;
        } else if (!strcmp((const char *) attr_node->name,
                        config_element_overwrite_mode)) {
                xmlChar *content;

                /* overwrite_mode */
                content = xmlNodeGetContent(attr_node);
                if (!content) {
                        ret = -LTTNG_ERR_NOMEM;
                        goto end;
                }

                ret = get_overwrite_mode(content);
                free(content);
                if (ret < 0) {
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }

                channel->attr.overwrite = ret;
        } else if (!strcmp((const char *) attr_node->name,
                        config_element_subbuf_size)) {
                xmlChar *content;

                /* subbuffer_size */
                content = xmlNodeGetContent(attr_node);
                if (!content) {
                        ret = -LTTNG_ERR_NOMEM;
                        goto end;
                }

                ret = parse_uint(content, &channel->attr.subbuf_size);
                free(content);
                if (ret) {
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }
        } else if (!strcmp((const char *) attr_node->name,
                        config_element_num_subbuf)) {
                xmlChar *content;

                /* subbuffer_count */
                content = xmlNodeGetContent(attr_node);
                if (!content) {
                        ret = -LTTNG_ERR_NOMEM;
                        goto end;
                }

                ret = parse_uint(content, &channel->attr.num_subbuf);
                free(content);
                if (ret) {
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }
        } else if (!strcmp((const char *) attr_node->name,
                        config_element_switch_timer_interval)) {
                xmlChar *content;
                uint64_t switch_timer_interval = 0;

                /* switch_timer_interval */
                content = xmlNodeGetContent(attr_node);
                if (!content) {
                        ret = -LTTNG_ERR_NOMEM;
                        goto end;
                }

                ret = parse_uint(content, &switch_timer_interval);
                free(content);
                if (ret) {
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }

                if (switch_timer_interval > UINT_MAX) {
                        WARN("switch_timer_interval out of range.");
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }

                channel->attr.switch_timer_interval =
                        switch_timer_interval;
        } else if (!strcmp((const char *) attr_node->name,
                        config_element_read_timer_interval)) {
                xmlChar *content;
                uint64_t read_timer_interval = 0;

                /* read_timer_interval */
                content = xmlNodeGetContent(attr_node);
                if (!content) {
                        ret = -LTTNG_ERR_NOMEM;
                        goto end;
                }

                ret = parse_uint(content, &read_timer_interval);
                free(content);
                if (ret) {
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }

                if (read_timer_interval > UINT_MAX) {
                        WARN("read_timer_interval out of range.");
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }

                channel->attr.read_timer_interval =
                        read_timer_interval;
        } else if (!strcmp((const char *) attr_node->name,
                        config_element_output_type)) {
                xmlChar *content;

                /* output_type */
                content = xmlNodeGetContent(attr_node);
                if (!content) {
                        ret = -LTTNG_ERR_NOMEM;
                        goto end;
                }

                ret = get_output_type(content);
                free(content);
                if (ret < 0) {
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }

                channel->attr.output = ret;
        } else if (!strcmp((const char *) attr_node->name,
                        config_element_tracefile_size)) {
                xmlChar *content;

                /* tracefile_size */
                content = xmlNodeGetContent(attr_node);
                if (!content) {
                        ret = -LTTNG_ERR_NOMEM;
                        goto end;
                }

                ret = parse_uint(content, &channel->attr.tracefile_size);
                free(content);
                if (ret) {
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }
        } else if (!strcmp((const char *) attr_node->name,
                        config_element_tracefile_count)) {
                xmlChar *content;

                /* tracefile_count */
                content = xmlNodeGetContent(attr_node);
                if (!content) {
                        ret = -LTTNG_ERR_NOMEM;
                        goto end;
                }

                ret = parse_uint(content, &channel->attr.tracefile_count);
                free(content);
                if (ret) {
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }
        } else if (!strcmp((const char *) attr_node->name,
                        config_element_live_timer_interval)) {
                xmlChar *content;
                uint64_t live_timer_interval = 0;

                /* live_timer_interval */
                content = xmlNodeGetContent(attr_node);
                if (!content) {
                        ret = -LTTNG_ERR_NOMEM;
                        goto end;
                }

                ret = parse_uint(content, &live_timer_interval);
                free(content);
                if (ret) {
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }

                if (live_timer_interval > UINT_MAX) {
                        WARN("live_timer_interval out of range.");
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }

                channel->attr.live_timer_interval =
                        live_timer_interval;
        } else if (!strcmp((const char *) attr_node->name,
                        config_element_events)) {
                /* events */
                *events_node = attr_node;
        } else {
                /* contexts */
                *contexts_node = attr_node;
        }

        ret = 0;
end:
        return ret;
}

static
int process_context_node(xmlNodePtr context_node,
        struct lttng_handle *handle, const char *channel_name)
{
        int ret;
        struct lttng_event_context context;
        xmlNodePtr context_child_node = xmlFirstElementChild(context_node);

        assert(handle);
        assert(channel_name);

        if (!context_child_node) {
                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                goto end;
        }

        memset(&context, 0, sizeof(context));

        if (!strcmp((const char *) context_child_node->name,
                config_element_type)) {
                /* type */
                xmlChar *content = xmlNodeGetContent(context_child_node);

                if (!content) {
                        ret = -LTTNG_ERR_NOMEM;
                        goto end;
                }

                ret = get_context_type(content);
                free(content);
                if (ret < 0) {
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }

                context.ctx = ret;
        } else if (!strcmp((const char *) context_child_node->name,
                config_element_context_perf)) {
                /* perf */
                xmlNodePtr perf_attr_node;

                context.ctx = handle->domain.type == LTTNG_DOMAIN_KERNEL ?
                        LTTNG_EVENT_CONTEXT_PERF_CPU_COUNTER :
                        LTTNG_EVENT_CONTEXT_PERF_THREAD_COUNTER;
                for (perf_attr_node = xmlFirstElementChild(context_child_node);
                        perf_attr_node; perf_attr_node =
                                xmlNextElementSibling(perf_attr_node)) {
                        if (!strcmp((const char *) perf_attr_node->name,
                                config_element_type)) {
                                xmlChar *content;
                                uint64_t type = 0;

                                /* type */
                                content = xmlNodeGetContent(perf_attr_node);
                                if (!content) {
                                        ret = -LTTNG_ERR_NOMEM;
                                        goto end;
                                }

                                ret = parse_uint(content, &type);
                                free(content);
                                if (ret) {
                                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                        goto end;
                                }

                                if (type > UINT32_MAX) {
                                        WARN("perf context type out of range.");
                                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                        goto end;
                                }

                                context.u.perf_counter.type = type;
                        } else if (!strcmp((const char *) perf_attr_node->name,
                                config_element_config)) {
                                xmlChar *content;
                                uint64_t config = 0;

                                /* config */
                                content = xmlNodeGetContent(perf_attr_node);
                                if (!content) {
                                        ret = -LTTNG_ERR_NOMEM;
                                        goto end;
                                }

                                ret = parse_uint(content, &config);
                                free(content);
                                if (ret) {
                                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                        goto end;
                                }

                                context.u.perf_counter.config = config;
                        } else if (!strcmp((const char *) perf_attr_node->name,
                                config_element_name)) {
                                xmlChar *content;
                                size_t name_len;

                                /* name */
                                content = xmlNodeGetContent(perf_attr_node);
                                if (!content) {
                                        ret = -LTTNG_ERR_NOMEM;
                                        goto end;
                                }

                                name_len = strlen((char *) content);
                                if (name_len >= LTTNG_SYMBOL_NAME_LEN) {
                                        WARN("perf context name too long.");
                                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                        free(content);
                                        goto end;
                                }

                                strncpy(context.u.perf_counter.name, (const char *) content,
                                                name_len);
                                free(content);
                        }
                }
        } else if (!strcmp((const char *) context_child_node->name,
                config_element_context_app)) {
                /* application context */
                xmlNodePtr app_ctx_node;

                context.ctx = LTTNG_EVENT_CONTEXT_APP_CONTEXT;
                for (app_ctx_node = xmlFirstElementChild(context_child_node);
                                app_ctx_node; app_ctx_node =
                                xmlNextElementSibling(app_ctx_node)) {
                        xmlChar *content;
                        char **target = strcmp(
                                (const char *) app_ctx_node->name,
                                config_element_context_app_provider_name) == 0 ?
                                        &context.u.app_ctx.provider_name :
                                        &context.u.app_ctx.ctx_name;

                        content = xmlNodeGetContent(app_ctx_node);
                        if (!content) {
                                ret = -LTTNG_ERR_NOMEM;
                                goto end;
                        }

                        *target = (char *) content;
                }
        } else {
                /* Unrecognized context type */
                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                goto end;
        }

        ret = lttng_add_context(handle, &context, NULL, channel_name);
        if (context.ctx == LTTNG_EVENT_CONTEXT_APP_CONTEXT) {
                free(context.u.app_ctx.provider_name);
                free(context.u.app_ctx.ctx_name);
        }
end:
        return ret;
}

static
int process_contexts_node(xmlNodePtr contexts_node,
        struct lttng_handle *handle, const char *channel_name)
{
        int ret = 0;
        xmlNodePtr context_node;

        for (context_node = xmlFirstElementChild(contexts_node); context_node;
                        context_node = xmlNextElementSibling(context_node)) {
                ret = process_context_node(context_node, handle, channel_name);
                if (ret) {
                        goto end;
                }
        }
end:
        return ret;
}

static
int process_pid_tracker_node(xmlNodePtr pid_tracker_node,
        struct lttng_handle *handle)
{
        int ret = 0, child;
        xmlNodePtr targets_node = NULL;
        xmlNodePtr node;

        assert(handle);
        assert(pid_tracker_node);
        /* get the targets node */
        for (node = xmlFirstElementChild(pid_tracker_node); node;
                node = xmlNextElementSibling(node)) {
                if (!strcmp((const char *) node->name,
                                config_element_targets)) {
                        targets_node = node;
                        break;
                }
        }

        if (!targets_node) {
                ret = LTTNG_ERR_INVALID;
                goto end;
        }

        /* Go through all pid_target node */
        child = xmlChildElementCount(targets_node);
        if (child == 0) {
                /* The session is explicitly set to target nothing. */
                ret = lttng_untrack_pid(handle, -1);
                if (ret) {
                        goto end;
                }
        }
        for (node = xmlFirstElementChild(targets_node); node;
                        node = xmlNextElementSibling(node)) {
                xmlNodePtr pid_target_node = node;

                /* get pid node and track it */
                for (node = xmlFirstElementChild(pid_target_node); node;
                        node = xmlNextElementSibling(node)) {
                        if (!strcmp((const char *) node->name,
                                        config_element_pid)) {
                                int64_t pid;
                                xmlChar *content = NULL;

                                content = xmlNodeGetContent(node);
                                if (!content) {
                                        ret = LTTNG_ERR_LOAD_INVALID_CONFIG;
                                        goto end;
                                }

                                ret = parse_int(content, &pid);
                                free(content);
                                if (ret) {
                                        ret = LTTNG_ERR_LOAD_INVALID_CONFIG;
                                        goto end;
                                }

                                ret = lttng_track_pid(handle, (int) pid);
                                if (ret) {
                                        goto end;
                                }
                        }
                }
                node = pid_target_node;
        }

end:
        return ret;
}


static
int process_domain_node(xmlNodePtr domain_node, const char *session_name,
                bool snapshot_mode)
{
        int ret;
        struct lttng_domain domain = { 0 };
        struct lttng_handle *handle = NULL;
        xmlNodePtr channels_node = NULL;
        xmlNodePtr trackers_node = NULL;
        xmlNodePtr pid_tracker_node = NULL;
        xmlNodePtr node;

        assert(session_name);

        ret = init_domain(domain_node, &domain);
        if (ret) {
                goto end;
        }

        handle = lttng_create_handle(session_name, &domain);
        if (!handle) {
                ret = -LTTNG_ERR_NOMEM;
                goto end;
        }

        /* get the channels node */
        for (node = xmlFirstElementChild(domain_node); node;
                node = xmlNextElementSibling(node)) {
                if (!strcmp((const char *) node->name,
                        config_element_channels)) {
                        channels_node = node;
                        break;
                }
        }

        if (!channels_node) {
                goto end;
        }

        /* create all channels */
        for (node = xmlFirstElementChild(channels_node); node;
                node = xmlNextElementSibling(node)) {
                struct lttng_channel channel;
                xmlNodePtr contexts_node = NULL;
                xmlNodePtr events_node = NULL;
                xmlNodePtr channel_attr_node;

                memset(&channel, 0, sizeof(channel));
                lttng_channel_set_default_attr(&domain, &channel.attr);

                for (channel_attr_node = xmlFirstElementChild(node);
                        channel_attr_node; channel_attr_node =
                        xmlNextElementSibling(channel_attr_node)) {
                        ret = process_channel_attr_node(channel_attr_node,
                                snapshot_mode, domain.type, &channel,
                                &contexts_node, &events_node);
                        if (ret) {
                                goto end;
                        }
                }

                if (!channel.name) {
                        ERR("Encountered a channel with no name attribute.");
                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                        goto end;
                }

                ret = lttng_enable_channel(handle, &channel);
                if (ret < 0) {
                        goto end;
                }

                ret = process_events_node(events_node, handle, channel.name);
                if (ret) {
                        goto end;
                }

                ret = process_contexts_node(contexts_node, handle,
                        channel.name);
                if (ret) {
                        goto end;
                }
        }

        /* get the trackers node */
        for (node = xmlFirstElementChild(domain_node); node;
                        node = xmlNextElementSibling(node)) {
                if (!strcmp((const char *) node->name,
                                        config_element_trackers)) {
                        trackers_node = node;
                        break;
                }
        }

        if (!trackers_node) {
                goto end;
        }

        for (node = xmlFirstElementChild(trackers_node); node;
                        node = xmlNextElementSibling(node)) {
                if (!strcmp((const char *)node->name,config_element_pid_tracker)) {
                        pid_tracker_node = node;
                        ret = process_pid_tracker_node(pid_tracker_node, handle);
                        if (ret) {
                                goto end;
                        }
                }
        }

        if (!pid_tracker_node) {
                lttng_track_pid(handle, -1);
        }

end:
        lttng_destroy_handle(handle);
        return ret;
}

static
int process_session_node(xmlNodePtr session_node, const char *session_name,
                int override)
{
        int ret, started = -1, snapshot_mode = -1;
        uint64_t live_timer_interval = UINT64_MAX;
        xmlChar *name = NULL;
        xmlChar *shm_path = NULL;
        xmlNodePtr domains_node = NULL;
        xmlNodePtr output_node = NULL;
        xmlNodePtr node;
        struct lttng_domain *kernel_domain = NULL;
        struct lttng_domain *ust_domain = NULL;
        struct lttng_domain *jul_domain = NULL;
        struct lttng_domain *log4j_domain = NULL;
        struct lttng_domain *python_domain = NULL;

        for (node = xmlFirstElementChild(session_node); node;
                node = xmlNextElementSibling(node)) {
                if (!name && !strcmp((const char *) node->name,
                        config_element_name)) {
                        /* name */
                        xmlChar *node_content = xmlNodeGetContent(node);
                        if (!node_content) {
                                ret = -LTTNG_ERR_NOMEM;
                                goto error;
                        }

                        name = node_content;
                } else if (!domains_node && !strcmp((const char *) node->name,
                        config_element_domains)) {
                        /* domains */
                        domains_node = node;
                } else if (started == -1 && !strcmp((const char *) node->name,
                        config_element_started)) {
                        /* started */
                        xmlChar *node_content = xmlNodeGetContent(node);
                        if (!node_content) {
                                ret = -LTTNG_ERR_NOMEM;
                                goto error;
                        }

                        ret = parse_bool(node_content, &started);
                        free(node_content);
                        if (ret) {
                                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                goto error;
                        }
                } else if (!output_node && !strcmp((const char *) node->name,
                        config_element_output)) {
                        /* output */
                        output_node = node;
                } else if (!shm_path && !strcmp((const char *) node->name,
                        config_element_shared_memory_path)) {
                        /* shared memory path */
                        xmlChar *node_content = xmlNodeGetContent(node);
                        if (!node_content) {
                                ret = -LTTNG_ERR_NOMEM;
                                goto error;
                        }

                        shm_path = node_content;
                } else {
                        /* attributes, snapshot_mode or live_timer_interval */
                        xmlNodePtr attributes_child =
                                xmlFirstElementChild(node);

                        if (!strcmp((const char *) attributes_child->name,
                                config_element_snapshot_mode)) {
                                /* snapshot_mode */
                                xmlChar *snapshot_mode_content =
                                        xmlNodeGetContent(attributes_child);
                                if (!snapshot_mode_content) {
                                        ret = -LTTNG_ERR_NOMEM;
                                        goto error;
                                }

                                ret = parse_bool(snapshot_mode_content, &snapshot_mode);
                                free(snapshot_mode_content);
                                if (ret) {
                                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                        goto error;
                                }
                        } else {
                                /* live_timer_interval */
                                xmlChar *timer_interval_content =
                                        xmlNodeGetContent(attributes_child);
                                if (!timer_interval_content) {
                                        ret = -LTTNG_ERR_NOMEM;
                                        goto error;
                                }

                                ret = parse_uint(timer_interval_content, &live_timer_interval);
                                free(timer_interval_content);
                                if (ret) {
                                        ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                                        goto error;
                                }
                        }
                }
        }

        if (!name) {
                /* Mandatory attribute, as defined in the session XSD */
                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                goto error;
        }

        if (session_name && strcmp((char *) name, session_name)) {
                /* This is not the session we are looking for */
                ret = -LTTNG_ERR_NO_SESSION;
                goto error;
        }

        /* Init domains to create the session handles */
        for (node = xmlFirstElementChild(domains_node); node;
                node = xmlNextElementSibling(node)) {
                struct lttng_domain *domain;

                domain = zmalloc(sizeof(*domain));
                if (!domain) {
                        ret = -LTTNG_ERR_NOMEM;
                        goto error;
                }

                ret = init_domain(node, domain);
                if (ret) {
                        goto domain_init_error;
                }

                switch (domain->type) {
                case LTTNG_DOMAIN_KERNEL:
                        if (kernel_domain) {
                                /* Same domain seen twice, invalid! */
                                goto domain_init_error;
                        }
                        kernel_domain = domain;
                        break;
                case LTTNG_DOMAIN_UST:
                        if (ust_domain) {
                                /* Same domain seen twice, invalid! */
                                goto domain_init_error;
                        }
                        ust_domain = domain;
                        break;
                case LTTNG_DOMAIN_JUL:
                        if (jul_domain) {
                                /* Same domain seen twice, invalid! */
                                goto domain_init_error;
                        }
                        jul_domain = domain;
                        break;
                case LTTNG_DOMAIN_LOG4J:
                        if (log4j_domain) {
                                /* Same domain seen twice, invalid! */
                                goto domain_init_error;
                        }
                        log4j_domain = domain;
                        break;
                case LTTNG_DOMAIN_PYTHON:
                        if (python_domain) {
                                /* Same domain seen twice, invalid! */
                                goto domain_init_error;
                        }
                        python_domain = domain;
                        break;
                default:
                        WARN("Invalid domain type");
                        goto domain_init_error;
                }
                continue;
domain_init_error:
                free(domain);
                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                goto error;
        }

        if (override) {
                /* Destroy session if it exists */
                ret = lttng_destroy_session((const char *) name);
                if (ret && ret != -LTTNG_ERR_SESS_NOT_FOUND) {
                        ERR("Failed to destroy existing session.");
                        goto error;
                }
        }

        /* Create session type depending on output type */
        if (snapshot_mode && snapshot_mode != -1) {
                ret = create_snapshot_session((const char *) name, output_node);
        } else if (live_timer_interval &&
                live_timer_interval != UINT64_MAX) {
                ret = create_session((const char *) name, kernel_domain,
                                ust_domain, jul_domain, log4j_domain,
                                output_node, live_timer_interval);
        } else {
                /* regular session */
                ret = create_session((const char *) name, kernel_domain,
                                ust_domain, jul_domain, log4j_domain,
                                output_node, UINT64_MAX);
        }
        if (ret) {
                goto error;
        }

        if (shm_path) {
                ret = lttng_set_session_shm_path((const char *) name,
                                (const char *) shm_path);
                if (ret) {
                        goto error;
                }
        }

        for (node = xmlFirstElementChild(domains_node); node;
                node = xmlNextElementSibling(node)) {
                ret = process_domain_node(node, (const char *) name,
                                snapshot_mode == 1);
                if (ret) {
                        goto end;
                }
        }

        if (started) {
                ret = lttng_start_tracing((const char *) name);
                if (ret) {
                        goto end;
                }
        }

end:
        if (ret < 0) {
                ERR("Failed to load session %s: %s", (const char *) name,
                        lttng_strerror(ret));
                lttng_destroy_session((const char *) name);
        }

error:
        free(kernel_domain);
        free(ust_domain);
        free(jul_domain);
        free(log4j_domain);
        free(python_domain);
        xmlFree(name);
        xmlFree(shm_path);
        return ret;
}

/*
 * Return 1 if the given path is readable by the current UID or 0 if not.
 * Return -1 if the path is EPERM.
 */
static int validate_file_read_creds(const char *path)
{
        int ret;

        assert(path);

        /* Can we read the file. */
        ret = access(path, R_OK);
        if (!ret) {
                goto valid;
        }
        if (errno == EACCES) {
                return -1;
        } else {
                /* Invalid. */
                return 0;
        }
valid:
        return 1;
}

static
int load_session_from_file(const char *path, const char *session_name,
        struct session_config_validation_ctx *validation_ctx, int override)
{
        int ret, session_found = !session_name;
        xmlDocPtr doc = NULL;
        xmlNodePtr sessions_node;
        xmlNodePtr session_node;

        assert(path);
        assert(validation_ctx);

        ret = validate_file_read_creds(path);
        if (ret != 1) {
                if (ret == -1) {
                        ret = -LTTNG_ERR_EPERM;
                } else {
                        ret = -LTTNG_ERR_LOAD_SESSION_NOENT;
                }
                goto end;
        }

        doc = xmlParseFile(path);
        if (!doc) {
                ret = -LTTNG_ERR_LOAD_IO_FAIL;
                goto end;
        }

        ret = xmlSchemaValidateDoc(validation_ctx->schema_validation_ctx, doc);
        if (ret) {
                ERR("Session configuration file validation failed");
                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                goto end;
        }

        sessions_node = xmlDocGetRootElement(doc);
        if (!sessions_node) {
                goto end;
        }

        for (session_node = xmlFirstElementChild(sessions_node);
                session_node; session_node =
                        xmlNextElementSibling(session_node)) {
                ret = process_session_node(session_node,
                        session_name, override);
                if (session_name && ret == 0) {
                        /* Target session found and loaded */
                        session_found = 1;
                        break;
                }
        }
end:
        xmlFreeDoc(doc);
        if (!ret) {
                ret = session_found ? 0 : -LTTNG_ERR_LOAD_SESSION_NOENT;
        }
        return ret;
}

static
int load_session_from_document(struct config_document *document, const char *session_name,
                struct session_config_validation_ctx *validation_ctx, int override)
{
        int ret, session_found = !session_name;
        xmlNodePtr sessions_node;
        xmlNodePtr session_node;

        assert(validation_ctx);

        ret = xmlSchemaValidateDoc(validation_ctx->schema_validation_ctx, document->document);
        if (ret) {
                ERR("Session configuration file validation failed");
                ret = -LTTNG_ERR_LOAD_INVALID_CONFIG;
                goto end;
        }

        sessions_node = xmlDocGetRootElement(document->document);
        if (!sessions_node) {
                goto end;
        }

        for (session_node = xmlFirstElementChild(sessions_node);
                session_node; session_node =
                        xmlNextElementSibling(session_node)) {
                ret = process_session_node(session_node,
                        session_name, override);
                if (session_name && ret == 0) {
                        /* Target session found and loaded */
                        session_found = 1;
                        break;
                }
        }
end:
        if (!ret) {
                ret = session_found ? 0 : -LTTNG_ERR_LOAD_SESSION_NOENT;
        }
        return ret;
}

/* Allocate dirent as recommended by READDIR(3), NOTES on readdir_r */
static
struct dirent *alloc_dirent(const char *path)
{
        size_t len;
        long name_max;
        struct dirent *entry;

        name_max = pathconf(path, _PC_NAME_MAX);
        if (name_max == -1) {
                name_max = PATH_MAX;
        }
        len = offsetof(struct dirent, d_name) + name_max + 1;
        entry = zmalloc(len);
        return entry;
}

static
int load_session_from_path(const char *path, const char *session_name,
        struct session_config_validation_ctx *validation_ctx, int override)
{
        int ret, session_found = !session_name;
        DIR *directory = NULL;

        assert(path);
        assert(validation_ctx);

        directory = opendir(path);
        if (!directory) {
                switch (errno) {
                case ENOTDIR:
                        /* Try the file loading. */
                        break;
                case ENOENT:
                        ret = -LTTNG_ERR_LOAD_SESSION_NOENT;
                        goto end;
                default:
                        ret = -LTTNG_ERR_LOAD_IO_FAIL;
                        goto end;
                }
        }
        if (directory) {
                struct dirent *entry;
                struct dirent *result;
                char *file_path = NULL;
                size_t path_len = strlen(path);

                if (path_len >= PATH_MAX) {
                        ret = -LTTNG_ERR_INVALID;
                        goto end;
                }

                entry = alloc_dirent(path);
                if (!entry) {
                        ret = -LTTNG_ERR_NOMEM;
                        goto end;
                }

                file_path = zmalloc(PATH_MAX);
                if (!file_path) {
                        ret = -LTTNG_ERR_NOMEM;
                        free(entry);
                        goto end;
                }

                strncpy(file_path, path, path_len);
                if (file_path[path_len - 1] != '/') {
                        file_path[path_len++] = '/';
                }

                ret = 0;
                /* Search for *.lttng files */
                while (!readdir_r(directory, entry, &result) && result) {
                        size_t file_name_len = strlen(result->d_name);

                        if (file_name_len <=
                                sizeof(DEFAULT_SESSION_CONFIG_FILE_EXTENSION)) {
                                continue;
                        }

                        if (path_len + file_name_len >= PATH_MAX) {
                                continue;
                        }

                        if (strcmp(DEFAULT_SESSION_CONFIG_FILE_EXTENSION,
                                result->d_name + file_name_len - sizeof(
                                DEFAULT_SESSION_CONFIG_FILE_EXTENSION) + 1)) {
                                continue;
                        }

                        strncpy(file_path + path_len, result->d_name, file_name_len);
                        file_path[path_len + file_name_len] = '\0';

                        ret = load_session_from_file(file_path, session_name,
                                validation_ctx, override);
                        if (session_name && !ret) {
                                session_found = 1;
                                break;
                        }
                }

                free(entry);
                free(file_path);
        } else {
                ret = load_session_from_file(path, session_name,
                        validation_ctx, override);
                if (ret) {
                        goto end;
                } else {
                        session_found = 1;
                }
        }

end:
        if (directory) {
                if (closedir(directory)) {
                        PERROR("closedir");
                }
        }

        if (session_found) {
                ret = 0;
        }

        return ret;
}

/*
 * Validate that the given path's credentials and the current process have the
 * same UID. If so, return 1 else return 0 if it does NOT match.
 */
static int validate_path_creds(const char *path)
{
        int ret, uid = getuid();
        struct stat buf;

        assert(path);

        if (uid == 0) {
                goto valid;
        }

        ret = stat(path, &buf);
        if (ret < 0) {
                if (errno != ENOENT) {
                        PERROR("stat");
                }
                ret = -LTTNG_ERR_INVALID;
                goto valid;
        }

        if (buf.st_uid != uid) {
                goto invalid;
        }

valid:
        return 1;
invalid:
        return 0;
}

LTTNG_HIDDEN
int config_load_session(const char *path, const char *session_name,
                int override, unsigned int autoload)
{
        int ret;
        bool session_loaded = false;
        const char *path_ptr = NULL;
        struct session_config_validation_ctx validation_ctx = { 0 };

        ret = init_session_config_validation_ctx(&validation_ctx);
        if (ret) {
                goto end;
        }

        if (!path) {
                char *home_path;
                const char *sys_path;

                /* Try home path */
                home_path = utils_get_home_dir();
                if (home_path) {
                        char path[PATH_MAX];

                        /*
                         * Try user session configuration path. Ignore error here so we can
                         * continue loading the system wide sessions.
                         */
                        if (autoload) {
                                ret = snprintf(path, sizeof(path),
                                                DEFAULT_SESSION_HOME_CONFIGPATH "/"
                                                DEFAULT_SESSION_CONFIG_AUTOLOAD, home_path);
                                if (ret < 0) {
                                        PERROR("snprintf session autoload home config path");
                                        goto end;
                                }

                                /*
                                 * Credentials are only validated for the autoload in order to
                                 * avoid any user session daemon to try to load kernel sessions
                                 * automatically and failing all the times.
                                 */
                                ret = validate_path_creds(path);
                                if (ret) {
                                        path_ptr = path;
                                }
                        } else {
                                ret = snprintf(path, sizeof(path),
                                                DEFAULT_SESSION_HOME_CONFIGPATH, home_path);
                                if (ret < 0) {
                                        PERROR("snprintf session home config path");
                                        goto end;
                                }
                                path_ptr = path;
                        }
                        if (path_ptr) {
                                ret = load_session_from_path(path_ptr, session_name,
                                                &validation_ctx, override);
                                if (ret && ret != -LTTNG_ERR_LOAD_SESSION_NOENT) {
                                        goto end;
                                }
                                /*
                                 * Continue even if the session was found since we have to try
                                 * the system wide sessions.
                                 */
                                session_loaded = true;
                        }
                }

                /* Reset path pointer for the system wide dir. */
                path_ptr = NULL;

                /* Try system wide configuration directory. */
                if (autoload) {
                        sys_path = DEFAULT_SESSION_SYSTEM_CONFIGPATH "/"
                                DEFAULT_SESSION_CONFIG_AUTOLOAD;
                        ret = validate_path_creds(sys_path);
                        if (ret) {
                                path_ptr = sys_path;
                        }
                } else {
                        sys_path = DEFAULT_SESSION_SYSTEM_CONFIGPATH;
                        path_ptr = sys_path;
                }

                if (path_ptr) {
                        ret = load_session_from_path(path_ptr, session_name,
                                        &validation_ctx, override);
                        if (!ret) {
                                session_loaded = true;
                        }
                }
        } else {
                ret = access(path, F_OK);
                if (ret < 0) {
                        PERROR("access");
                        switch (errno) {
                        case ENOENT:
                                ret = -LTTNG_ERR_INVALID;
                                WARN("Session configuration path does not exist.");
                                break;
                        case EACCES:
                                ret = -LTTNG_ERR_EPERM;
                                break;
                        default:
                                ret = -LTTNG_ERR_UNK;
                                break;
                        }
                        goto end;
                }

                ret = load_session_from_path(path, session_name,
                        &validation_ctx, override);
        }
end:
        fini_session_config_validation_ctx(&validation_ctx);
        if (ret == -LTTNG_ERR_LOAD_SESSION_NOENT && !session_name && !path) {
                /*
                 * Don't report an error if no sessions are found when called
                 * without a session_name or a search path.
                 */
                ret = 0;
        }

        if (session_loaded && ret == -LTTNG_ERR_LOAD_SESSION_NOENT) {
                /* A matching session was found in one of the search paths. */
                ret = 0;
        }
        return ret;
}

static
void __attribute__((destructor)) session_config_exit(void)
{
        xmlCleanupParser();
}

LTTNG_HIDDEN
struct config_document *config_document_get(const char *path, int xsd_validation)
{
        int ret;
        struct config_document *document = NULL;
        struct session_config_validation_ctx validation_ctx = { 0 };

        assert(path);

        ret = access(path, F_OK);
        if (ret < 0) {
                PERROR("access");
                switch (errno) {
                case ENOENT:
                        ERR("Configuration document path does not exist.");
                        break;
                case EACCES:
                        ERR("Configuration document permission denied.");
                        break;
                default:
                        ERR("Configuration document unknown error.");
                        break;
                }
                goto end;
        }

        ret = init_session_config_validation_ctx(&validation_ctx);
        if (ret) {
                goto end;
        }

        ret = validate_file_read_creds(path);
        if (ret != 1) {
                if (ret == -1) {
                        ERR("Configuration document permission denied.");
                } else {
                        ERR("Configuration document does not exist.");
                }
                goto end;
        }

        document = zmalloc(sizeof(struct config_document));
        if (!document) {
                PERROR("zmalloc");
                goto end;
        }

        /*
         * Do not care of blanks and also make sure that direct dump have no
         * indentations in them
         */
        xmlKeepBlanksDefault(0);
        document->document = xmlParseFile(path);
        if (!document->document) {
                ERR("Configuration document parsing failed.");
                goto error;
        }

        /* TODO: REMOVE */
        ret = 0;
        if (xsd_validation) {
                ret = xmlSchemaValidateDoc(validation_ctx.schema_validation_ctx,
                                document->document);
        }
        if (ret) {
                ERR("Session configuration file validation failed");
                goto error;
        }

end:
        fini_session_config_validation_ctx(&validation_ctx);
        return document;
error:
        xmlFreeDoc(document->document);
        free(document);
        return NULL;
}

LTTNG_HIDDEN
void config_document_free(struct config_document *document)
{
        if (document) {
                xmlFreeDoc(document->document);
                document->document = NULL;
        }

        free(document);
}

LTTNG_HIDDEN
int config_document_replace_element_value(struct config_document *document,
                const char *xpath, const char *value)
{
        int ret = 0;
        int xpath_result_size;

        xmlXPathContextPtr xpath_context = NULL;
        xmlXPathObjectPtr xpath_object = NULL;
        xmlNodeSetPtr xpath_result_set = NULL;
        xmlChar *internal_xpath = NULL;
        xmlChar *internal_value = NULL;

        assert(document);
        assert(xpath);
        assert(value);

        internal_xpath = encode_string(xpath);
        if (!internal_xpath) {
                ret = -LTTNG_ERR_NOMEM;
                ERR("Unable to encode xpath string");
                goto end;
        }

        internal_value = encode_string(value);
        if (!internal_value) {
                ret = -LTTNG_ERR_NOMEM;
                ERR("Unable to encode xpath replace value string");
                goto end;
        }

        /* Initialize xpath context */
        xpath_context = xmlXPathNewContext(document->document);
        if (!xpath_context) {
                ret = -LTTNG_ERR_NOMEM;
                ERR("Unable to create xpath context");
                goto end;
        }

        /* Evaluate de xpath expression */
        xpath_object = xmlXPathEvalExpression(internal_xpath, xpath_context);
        if (!xpath_object) {
                ret = -LTTNG_ERR_CONFIG_INVALID_QUERY;
                goto end;
        }

        /* TODO: from here could be extracted and previopus could be a step in
         * subsequent operation, modify/substitute/delete node.
         */
        xpath_result_set = xpath_object->nodesetval;
        if (!xpath_result_set) {
                ret = -LTTNG_ERR_CONFIG_EMPTY_SET;
                goto end;
        }

        xpath_result_size = xpath_result_set->nodeNr;

        /*
         * Reverse traversal since last element could be nested under parent
         * element present in the result set.
         */
        for (int i = xpath_result_size - 1; i >=0; i--) {
                assert(xpath_result_set->nodeTab[i]);
                xmlNodeSetContent(xpath_result_set->nodeTab[i], internal_value);

                /*
                 * Libxml2 quirk regarding the freing and namesplace node see
                 * libxml2 example and documentation for more details.
                 */
                if (xpath_result_set->nodeTab[i]->type != XML_NAMESPACE_DECL) {
                        xpath_result_set->nodeTab[i] = NULL;
                }
        }

end:
        xmlXPathFreeContext(xpath_context);
        xmlXPathFreeObject(xpath_object);
        xmlFree(internal_xpath);
        xmlFree(internal_value);
        return ret;
}

LTTNG_HIDDEN
int config_load_configuration_sessions(struct config_document *document,
                const char *session_name, int override)
{
        int ret;
        struct session_config_validation_ctx validation_ctx = { 0 };

        ret = init_session_config_validation_ctx(&validation_ctx);
        if (ret) {
                goto end;
        }
        ret = load_session_from_document(document, session_name,
                        &validation_ctx, override);
end:
        fini_session_config_validation_ctx(&validation_ctx);
        return ret;
}

LTTNG_HIDDEN
int config_document_replace_element(struct config_document *document,
                const char *xpath, const struct config_element *element)
{
        int ret = 0;
        int xpath_result_size;

        xmlXPathContextPtr xpath_context = NULL;
        xmlXPathObjectPtr xpath_object = NULL;
        xmlNodeSetPtr xpath_result_set = NULL;
        xmlChar *internal_xpath = NULL;
        xmlNodePtr old_node = NULL;
        xmlNodePtr copy = NULL;

        assert(document);
        assert(xpath);
        assert(element);
        assert(element->element);

        internal_xpath = encode_string(xpath);
        if (!internal_xpath) {
                ret = -LTTNG_ERR_NOMEM;
                ERR("Unable to encode xpath string");
                goto end;
        }

        /* Initialize xpath context */
        xpath_context = xmlXPathNewContext(document->document);
        if (!xpath_context) {
                ret = -LTTNG_ERR_NOMEM;
                ERR("Unable to create xpath context");
                goto end;
        }

        /* Evaluate the xpath expression */
        xpath_object = xmlXPathEvalExpression(internal_xpath, xpath_context);
        if (!xpath_object) {
                ret = -LTTNG_ERR_CONFIG_INVALID_QUERY;
                goto end;
        }

        xpath_result_set = xpath_object->nodesetval;
        if (!xpath_result_set) {
                ret = -LTTNG_ERR_CONFIG_EMPTY_SET;
                goto end;
        }

        xpath_result_size = xpath_result_set->nodeNr;

        if (xpath_result_size > 1) {
                ret = -LTTNG_ERR_CONFIG_INVALID_COUNT;
                goto end;
        }

        if (xpath_result_size == 0) {
                ret = -LTTNG_ERR_CONFIG_INVALID_COUNT;
                goto end;
        }

        assert(xpath_result_set->nodeTab[0]);

        /* Do a copy of the element to ease caller memory management */
        copy = xmlCopyNode(element->element, 1);
        if (!copy) {
                ret = -LTTNG_ERR_NOMEM;
                goto end;
        }

        old_node = xmlReplaceNode(xpath_result_set->nodeTab[0], copy);
        if (xpath_result_set->nodeTab[0]->type != XML_NAMESPACE_DECL)
                   xpath_result_set->nodeTab[0] = NULL;
        if (!old_node) {
                ret = -LTTNG_ERR_CONFIG_REPLACEMENT;
                xmlFreeNode(copy);
                goto end;
        }
        xmlUnlinkNode(old_node);
        xmlFreeNode(old_node);
end:
        xmlXPathFreeContext(xpath_context);
        xmlXPathFreeObject(xpath_object);
        xmlFree(internal_xpath);
        return ret;
}

LTTNG_HIDDEN
char *config_document_get_element_value(struct config_document *document,
                const char *xpath)
{
        char *value = NULL;
        int xpath_result_size;
        int value_result_size;

        xmlXPathContextPtr xpath_context = NULL;
        xmlXPathObjectPtr xpath_object = NULL;
        xmlNodeSetPtr xpath_result_set = NULL;
        xmlChar *internal_xpath = NULL;
        xmlChar *internal_value = NULL;

        assert(document);
        assert(xpath);

        internal_xpath = encode_string(xpath);
        if (!internal_xpath) {
                value = NULL;
                ERR("Unable to encode xpath string");
                goto end;
        }

        /* Initialize xpath context */
        xpath_context = xmlXPathNewContext(document->document);
        if (!xpath_context) {
                value = NULL;
                ERR("Unable to create xpath context");
                goto end;
        }

        /* Evaluate the xpath expression */
        xpath_object = xmlXPathEvalExpression(internal_xpath, xpath_context);
        if (!xpath_object) {
                value = NULL;
                ERR("Unable to evaluate xpath query (invalid query format)");
                goto end;
        }

        xpath_result_set = xpath_object->nodesetval;
        if (!xpath_result_set) {
                value = NULL;
                goto end;
        }

        xpath_result_size = xpath_result_set->nodeNr;

        if (xpath_result_size > 1) {
                ERR("To many result while fetching config element value");
                value = NULL;
                goto end;
        }

        if (xpath_result_size == 0) {
                value = NULL;
                goto end;
        }

        /*
         * Reverse traversal since last element could be nested under parent
         * element present in the result set.
         */
        assert(xpath_result_set->nodeTab[0]);
        internal_value = xmlNodeGetContent(xpath_result_set->nodeTab[0]);
        if (!internal_value) {
                value = NULL;
                goto end;
        }

        value_result_size  = xmlStrlen(internal_value);
        value = calloc(value_result_size + 1, sizeof(char));
        strncpy(value, (char *) internal_value, value_result_size);

end:
        xmlXPathFreeContext(xpath_context);
        xmlXPathFreeObject(xpath_object);
        xmlFree(internal_xpath);
        xmlFree(internal_value);
        return value;
}

LTTNG_HIDDEN
int config_document_element_exist(struct config_document *document,
                const char *xpath)
{
        int exist = 0;
        int xpath_result_size;

        xmlXPathContextPtr xpath_context = NULL;
        xmlXPathObjectPtr xpath_object = NULL;
        xmlNodeSetPtr xpath_result_set = NULL;
        xmlChar *internal_xpath = NULL;

        assert(document);
        assert(document->document);
        assert(xpath);

        internal_xpath = encode_string(xpath);
        if (!internal_xpath) {
                ERR("Unable to encode xpath string");
                goto end;
        }

        /* Initialize xpath context */
        xpath_context = xmlXPathNewContext(document->document);
        if (!xpath_context) {
                ERR("Unable to create xpath context");
                goto end;
        }

        /* Evaluate the xpath expression */
        xpath_object = xmlXPathEvalExpression(internal_xpath, xpath_context);
        if (!xpath_object) {
                ERR("Unable to evaluate xpath query (invalid query format)");
                goto end;
        }

        xpath_result_set = xpath_object->nodesetval;
        if (!xpath_result_set) {
                goto end;
        }

        xpath_result_size = xpath_result_set->nodeNr;

        if (xpath_result_size > 0) {
                exist = 1;
        }
end:
        xmlXPathFreeContext(xpath_context);
        xmlXPathFreeObject(xpath_object);
        xmlFree(internal_xpath);
        return exist;

}

LTTNG_HIDDEN
struct config_element *config_element_create(const char *name,
                const char* value)
{
        struct config_element *element;

        assert(name);

        xmlChar *internal_name = NULL;
        xmlChar *internal_value = NULL;

        internal_name = encode_string(name);
        if (!internal_name) {
                ERR("Unable to encode config element name string");
                element = NULL;
                goto end;
        }


        if (value) {
                internal_value = encode_string(value);
                if (!internal_value) {
                        ERR("Unable to encode config_element value string");
                        element = NULL;
                        goto end;
                }
        }

        element = zmalloc(sizeof(struct config_element));
        if (!element) {
                goto end;
        }

        element->element = xmlNewNode(NULL, internal_name);
        if (!element->element) {
                free(element);
                element = NULL;
                goto end;
        }

        if (internal_value) {
                xmlNodeAddContent(element->element, internal_value);
        }
end:
        xmlFree(internal_name);
        xmlFree(internal_value);
        return element;
}

LTTNG_HIDDEN
int config_element_add_child(struct config_element *parent,
                const struct config_element *child)
{
        assert(parent);
        assert(child);
        assert(parent->element);
        assert(child->element);

        int ret = 0;
        xmlNodePtr node = NULL;
        xmlNodePtr copy = NULL;

        /* Do a copy to ease the memory management for caller */
        copy = xmlCopyNode(child->element, 1);
        if (!copy) {
                ret = -LTTNG_ERR_NOMEM;
                goto error;
        }
        node = xmlAddChild(parent->element, copy);
        if (!node) {
                xmlFreeNode(copy);
                ret = -LTTNG_ERR_CONFIG_ADD_CHILD;
                goto error;
        }
error:
        return ret;
}


LTTNG_HIDDEN
int config_document_insert_element(struct config_document *document,
                const char *xpath, const struct config_element *element)
{
        int ret = 0;
        int xpath_result_size;

        xmlXPathContextPtr xpath_context = NULL;
        xmlXPathObjectPtr xpath_object = NULL;
        xmlNodeSetPtr xpath_result_set = NULL;
        xmlChar *internal_xpath = NULL;
        xmlNodePtr child_node = NULL;
        xmlNodePtr local_copy = NULL;

        assert(document);
        assert(xpath);
        assert(element);
        assert(element->element);

        internal_xpath = encode_string(xpath);
        if (!internal_xpath) {
                ret = -LTTNG_ERR_NOMEM;
                goto end;
        }

        /* Initialize xpath context */
        xpath_context = xmlXPathNewContext(document->document);
        if (!xpath_context) {
                ret = -LTTNG_ERR_NOMEM;
                goto end;
        }

        /* Evaluate the xpath expression */
        xpath_object = xmlXPathEvalExpression(internal_xpath, xpath_context);
        if (!xpath_object) {
                ret = -LTTNG_ERR_CONFIG_INVALID_QUERY;
                goto end;
        }

        xpath_result_set = xpath_object->nodesetval;
        if (!xpath_result_set) {
                ret = -LTTNG_ERR_CONFIG_EMPTY_SET;
                goto end;
        }

        xpath_result_size = xpath_result_set->nodeNr;

        if (xpath_result_size > 1) {
                ret = -LTTNG_ERR_CONFIG_INVALID_COUNT;
                goto end;
        }

        if (xpath_result_size == 0) {
                ret = -LTTNG_ERR_CONFIG_INVALID_COUNT;
                goto end;
        }

        assert(xpath_result_set->nodeTab[0]);
        /* Do a copy to simply memory management */
        local_copy = xmlCopyNode(element->element, 1);
        if (!local_copy) {
                ret = -LTTNG_ERR_NOMEM;
                goto end;
        }

        child_node = xmlAddChild(xpath_result_set->nodeTab[0], local_copy);
        if (!child_node) {
                ret = -LTTNG_ERR_CONFIG_ADD_CHILD;
                xmlFreeNode(local_copy);
                goto end;
        }
end:
        xmlXPathFreeContext(xpath_context);
        xmlXPathFreeObject(xpath_object);
        xmlFree(internal_xpath);
        return ret;
}

LTTNG_HIDDEN
void config_element_free(struct config_element *element) {
        if (element && element->element) {
                xmlFreeNode(element->element);
        }

        free(element);
}

LTTNG_HIDDEN
void config_element_free_array(struct config_element **array, int size) {

        if (array) {
                for (int i = 0; i < size; i++) {
                        if (!array[i]) {
                                continue;
                        }
                        if (array[i]->element) {
                                xmlFreeNode(array[i]->element);
                        }
                        free(array[i]);
                }
        }
        free(array);
}

LTTNG_HIDDEN
void config_document_get_element_array(const struct config_document *document, const char *xpath, struct config_element ***element_array, int *array_size)
{
        int xpath_result_size;

        xmlXPathContextPtr xpath_context = NULL;
        xmlXPathObjectPtr xpath_object = NULL;
        xmlNodeSetPtr xpath_result_set = NULL;
        xmlChar *internal_xpath = NULL;
        xmlChar *internal_value = NULL;

        assert(document);
        assert(xpath);

        *element_array=NULL;
        *array_size=0;


        internal_xpath = encode_string(xpath);
        if (!internal_xpath) {
                ERR("Unable to encode xpath string");
                goto end;
        }

        /* Initialize xpath context */
        xpath_context = xmlXPathNewContext(document->document);
        if (!xpath_context) {
                ERR("Unable to create xpath context");
                goto end;
        }

        /* Evaluate the xpath expression */
        xpath_object = xmlXPathEvalExpression(internal_xpath, xpath_context);
        if (!xpath_object) {
                ERR("Unable to evaluate xpath query (invalid query format)");
                goto end;
        }

        xpath_result_set = xpath_object->nodesetval;
        if (!xpath_result_set) {
                goto end;
        }

        xpath_result_size = xpath_result_set->nodeNr;

        if (xpath_result_size == 0) {
                goto end;
        }

        /* alloc the array */
        *element_array = calloc(xpath_result_size, sizeof(struct config_element *));
        *array_size = xpath_result_size;
        if (!element_array) {
                ERR("Calloc config element array");
                goto end;
        }

        for (int i = 0; i < xpath_result_size; i++) {
                xmlNodePtr node_copy = NULL;
                node_copy = xmlCopyNode(xpath_result_set->nodeTab[i], 1);
                if (!node_copy) {
                        ERR("Xml copy of event node");
                        goto error;
                }
                /* Hand off ownership */
                (*element_array)[i] = malloc(sizeof(struct config_element));
                if (!((*element_array)[i])){
                        ERR("Malloc config_element array");
                        xmlFreeNode(node_copy);
                        goto error;
                };
                (*element_array)[i]->element = node_copy;
        }
end:
        xmlXPathFreeContext(xpath_context);
        xmlXPathFreeObject(xpath_object);
        xmlFree(internal_xpath);
        xmlFree(internal_value);
        return;
error:

        if (element_array) {
                config_element_free_array(*element_array, *array_size);
        }

        *array_size = 0;

        xmlXPathFreeContext(xpath_context);
        xmlXPathFreeObject(xpath_object);
        xmlFree(internal_xpath);
        xmlFree(internal_value);
        return;
}

LTTNG_HIDDEN
void config_element_get_element_array(const struct config_element *element, const char *xpath, struct config_element ***element_array, int *array_size)
{
        int xpath_result_size;

        xmlXPathContextPtr xpath_context = NULL;
        xmlXPathObjectPtr xpath_object = NULL;
        xmlNodeSetPtr xpath_result_set = NULL;
        xmlChar *internal_xpath = NULL;
        xmlChar *internal_value = NULL;
        xmlNodePtr local_copy = NULL;
        xmlNodePtr place_holder = NULL;
        xmlDocPtr document = NULL;

        assert(element);
        assert(element->element);
        assert(xpath);

        *element_array=NULL;
        *array_size=0;

        /* Create a new doc and set root node as passed element */
        document = xmlNewDoc(BAD_CAST "1.0");
        if (!document) {
                ERR("Unable to create xml document");
                goto end;
        }

        local_copy = xmlCopyNode(element->element, 1);
        if (!local_copy) {
                ERR("Unable to copy an xml node");
                goto end;
        }

        /* Hand off the local_copy to the xmlDoc */
        place_holder = xmlDocSetRootElement(document, local_copy);
        if (place_holder) {
                ERR("The document root was already set");
                xmlFreeNode(local_copy);
                goto end;
        }

        internal_xpath = encode_string(xpath);
        if (!internal_xpath) {
                ERR("Unable to encode xpath string");
                goto end;
        }

        /* Initialize xpath context */
        xpath_context = xmlXPathNewContext(document);
        if (!xpath_context) {
                ERR("Unable to create xpath context");
                goto end;
        }

        /* Evaluate the xpath expression */
        xpath_object = xmlXPathEvalExpression(internal_xpath, xpath_context);
        if (!xpath_object) {
                ERR("Unable to evaluate xpath query (invalid query format)");
                goto end;
        }

        xpath_result_set = xpath_object->nodesetval;
        if (!xpath_result_set) {
                goto end;
        }

        xpath_result_size = xpath_result_set->nodeNr;

        if (xpath_result_size == 0) {
                goto end;
        }

        /* alloc the array */
        *element_array = calloc(xpath_result_size, sizeof(struct config_element *));
        *array_size = xpath_result_size;
        if (!element_array) {
                ERR("Calloc config element array");
                goto end;
        }

        for (int i = 0; i < xpath_result_size; i++) {
                xmlNodePtr node_copy = NULL;
                node_copy = xmlCopyNode(xpath_result_set->nodeTab[i], 1);
                if (!node_copy) {
                        ERR("Xml copy of event node");
                        goto error;
                }
                /* Hand off ownership */
                (*element_array)[i] = malloc(sizeof(struct config_element));
                if (!((*element_array)[i])){
                        ERR("Malloc config_element array");
                        xmlFreeNode(node_copy);
                        goto error;
                };
                (*element_array)[i]->element = node_copy;
        }
end:
        xmlXPathFreeContext(xpath_context);
        xmlXPathFreeObject(xpath_object);
        xmlFree(internal_xpath);
        xmlFree(internal_value);
        xmlFreeDoc(document);
        return;
error:

        if (element_array) {
                config_element_free_array(*element_array, *array_size);
        }

        *array_size = 0;

        xmlXPathFreeContext(xpath_context);
        xmlXPathFreeObject(xpath_object);
        xmlFree(internal_xpath);
        xmlFree(internal_value);
        return;
}
/* Create an internal copy of the config_element.
 * The users is responsible for the freeing of the passed child.
 */
LTTNG_HIDDEN
int config_element_add_or_replace_child(struct config_element *parent, struct config_element *child)
{
        assert(parent);
        assert(child);
        assert(parent->element);
        assert(child->element);

        int ret = 0;
        xmlNodePtr local_copy;
        xmlNodePtr x_ret = NULL;
        xmlNodePtr iterator = NULL;

        xmlNodePtr x_parent = parent->element;
        xmlNodePtr x_child = child->element;

        /* Find and delete the node with the same name if present */
        iterator = x_parent->children;
        while (iterator != NULL) {
                if ((!xmlStrcmp(iterator->name, x_child->name))){
                        xmlNodePtr del = iterator;
                        iterator = iterator->next;
                        xmlUnlinkNode(del);
                        xmlFreeNode(del);
                } else {
                        iterator = iterator->next;
                }
        }

        /* Add the child */
        local_copy = xmlCopyNode(x_child, 1);
        if (!local_copy) {
                ERR("Duplication of node to be insert failed");
                ret = -LTTNG_ERR_CONFIG_ADD_CHILD;
                goto end;
        }
        x_ret = xmlAddChild(x_parent, local_copy);
        if (!x_ret) {
                xmlFreeNode(local_copy);
                ret = -LTTNG_ERR_CONFIG_ADD_CHILD;
        }
end:
        return ret;
}

LTTNG_HIDDEN
char *config_element_get_element_value(const struct config_element *element, const char *xpath)
{
        char *value = NULL;
        int xpath_result_size;
        int value_result_size;

        xmlXPathContextPtr xpath_context = NULL;
        xmlXPathObjectPtr xpath_object = NULL;
        xmlNodeSetPtr xpath_result_set = NULL;
        xmlChar *internal_xpath = NULL;
        xmlChar *internal_value = NULL;
        xmlDocPtr document = NULL;
        xmlNodePtr local_copy = NULL;
        xmlNodePtr place_holder = NULL;

        assert(element);
        assert(element->element);
        assert(xpath);

        /* Create a new doc and set root node as passed element */
        document = xmlNewDoc(BAD_CAST "1.0");
        if (!document) {
                value = NULL;
                ERR("Unable to create xml document");
                goto end;
        }

        local_copy = xmlCopyNode(element->element, 1);
        if (!local_copy) {
                value = NULL;
                ERR("Unable to copy an xml node");
                goto end;
        }

        /* Hand off the local_copy to the xmlDoc */
        place_holder = xmlDocSetRootElement(document, local_copy);
        if (place_holder) {
                value = NULL;
                ERR("The document root was already set");
                xmlFreeNode(local_copy);
                goto end;
        }

        internal_xpath = encode_string(xpath);
        if (!internal_xpath) {
                /*TODO set valid error */
                value = NULL;
                ERR("Unable to encode xpath string");
                goto end;
        }

        /* Initialize xpath context */
        xpath_context = xmlXPathNewContext(document);
        if (!xpath_context) {
                /*TODO set valid error */
                value = NULL;
                ERR("Unable to create xpath context");
                goto end;
        }

        /* Evaluate the xpath expression */
        xpath_object = xmlXPathEvalExpression(internal_xpath, xpath_context);
        if (!xpath_object) {
                /*TODO set valid error */
                value = NULL;
                ERR("Unable to evaluate xpath query (invalid query format)");
                goto end;
        }

        xpath_result_set = xpath_object->nodesetval;
        if (!xpath_result_set) {
                /*TODO set valid error */
                value = NULL;
                goto end;
        }

        xpath_result_size = xpath_result_set->nodeNr;

        if (xpath_result_size > 1) {
                /*TODO set valid error */
                ERR("To many result while fetching config element value");
                value = NULL;
                goto end;
        }

        if (xpath_result_size == 0) {
                value = NULL;
                goto end;
        }

        assert(xpath_result_set->nodeTab[0]);
        internal_value = xmlNodeGetContent(xpath_result_set->nodeTab[0]);
        if (!internal_value) {
                value = NULL;
                goto end;
        }

        value_result_size  = xmlStrlen(internal_value);
        value = calloc(value_result_size + 1, sizeof(char));
        strncpy(value, (char *) internal_value, value_result_size);

end:
        xmlXPathFreeContext(xpath_context);
        xmlXPathFreeObject(xpath_object);
        xmlFree(internal_xpath);
        xmlFree(internal_value);
        xmlFreeDoc(document);
        return value;

}

LTTNG_HIDDEN
int config_process_event_element(const struct config_element *element, const char *session_name, int domain_type, const char *channel_name) {

        int ret = 0;
        xmlNodePtr node;
        struct lttng_domain domain;
        struct lttng_handle *handle;

        assert(element);
        assert(element->element);

        memset(&domain, 0, sizeof(struct lttng_domain));

        /* Create handle */
        domain.type = domain_type;
        switch (domain.type) {
        case LTTNG_DOMAIN_KERNEL:
                domain.buf_type = LTTNG_BUFFER_GLOBAL;
                break;
        case LTTNG_DOMAIN_UST:
        case LTTNG_DOMAIN_JUL:
        case LTTNG_DOMAIN_LOG4J:
        case LTTNG_DOMAIN_PYTHON:
                domain.buf_type = LTTNG_BUFFER_PER_UID;
                break;
        case LTTNG_DOMAIN_NONE:
        default:
                assert(0);
        }

        handle = lttng_create_handle(session_name, &domain);
        if (!handle) {
                ret = -LTTNG_ERR_HANDLE_CREATION;
                goto error;
        }


        node = element->element;
        /* Check if element is really and event */
        if (xmlStrcmp(BAD_CAST config_element_event, node->name)) {
                ret = -LTTNG_ERR_CONFIG_INVALID_ELEMENT;
                goto error;
        }

        ret = process_event_node(node, handle, channel_name, ENABLE);
        if (ret) {
                goto error;
        }
error:
        free(handle);
        return ret;
}