Add CPU hotplug support

[lttng-tools.git] / ltt-sessiond / main.c

/*
 * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * 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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

#define _GNU_SOURCE
#include <fcntl.h>
#include <getopt.h>
#include <grp.h>
#include <limits.h>
#include <poll.h>
#include <pthread.h>
#include <semaphore.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ipc.h>
#include <sys/mount.h>
#include <sys/shm.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <unistd.h>

#include <urcu/list.h>          /* URCU list library (-lurcu) */
#include <lttng/lttng.h>

#include "liblttsessiondcomm.h"
#include "ltt-sessiond.h"
#include "lttngerr.h"
#include "kernel-ctl.h"
#include "ust-ctl.h"
#include "session.h"
#include "traceable-app.h"
#include "lttng-kconsumerd.h"
#include "libustctl.h"
#include "utils.h"

/*
 * TODO:
 * teardown: signal SIGTERM handler -> write into pipe. Threads waits
 * with epoll on pipe and on other pipes/sockets for commands.  Main
 * simply waits on pthread join.
 */

/* Const values */
const char default_home_dir[] = DEFAULT_HOME_DIR;
const char default_tracing_group[] = LTTNG_DEFAULT_TRACING_GROUP;
const char default_ust_sock_dir[] = DEFAULT_UST_SOCK_DIR;
const char default_global_apps_pipe[] = DEFAULT_GLOBAL_APPS_PIPE;

/* Variables */
int opt_verbose;    /* Not static for lttngerr.h */
int opt_quiet;      /* Not static for lttngerr.h */
const char *progname;
const char *opt_tracing_group;
static int opt_sig_parent;
static int opt_daemon;
static int is_root;                     /* Set to 1 if the daemon is running as root */
static pid_t ppid;          /* Parent PID for --sig-parent option */
static pid_t kconsumerd_pid;
static struct pollfd *kernel_pollfd;

static char apps_unix_sock_path[PATH_MAX];                              /* Global application Unix socket path */
static char client_unix_sock_path[PATH_MAX];                    /* Global client Unix socket path */
static char kconsumerd_err_unix_sock_path[PATH_MAX];    /* kconsumerd error Unix socket path */
static char kconsumerd_cmd_unix_sock_path[PATH_MAX];    /* kconsumerd command Unix socket path */

/* Sockets and FDs */
static int client_sock;
static int apps_sock;
static int kconsumerd_err_sock;
static int kconsumerd_cmd_sock;
static int kernel_tracer_fd;
static int kernel_poll_pipe[2];

/* Pthread, Mutexes and Semaphores */
static pthread_t kconsumerd_thread;
static pthread_t apps_thread;
static pthread_t client_thread;
static pthread_t kernel_thread;
static sem_t kconsumerd_sem;

static pthread_mutex_t kconsumerd_pid_mutex;    /* Mutex to control kconsumerd pid assignation */

/*
 *  teardown_kernel_session
 *
 *  Complete teardown of a kernel session. This free all data structure
 *  related to a kernel session and update counter.
 */
static void teardown_kernel_session(struct ltt_session *session)
{
        if (session->kernel_session != NULL) {
                DBG("Tearing down kernel session");
                trace_destroy_kernel_session(session->kernel_session);
                /* Extra precaution */
                session->kernel_session = NULL;
        }
}

/*
 *  cleanup
 *
 *  Cleanup the daemon on exit
 */
static void cleanup()
{
        int ret;
        char *cmd;
        struct ltt_session *sess;

        DBG("Cleaning up");

        /* <fun> */
        MSG("\n%c[%d;%dm*** assert failed *** ==> %c[%dm", 27,1,31,27,0);
        MSG("%c[%d;%dmMatthew, BEET driven development works!%c[%dm",27,1,33,27,0);
        /* </fun> */

        /* Stopping all threads */
        DBG("Terminating all threads");
        pthread_cancel(client_thread);
        pthread_cancel(apps_thread);
        pthread_cancel(kernel_thread);
        if (kconsumerd_pid != 0) {
                pthread_cancel(kconsumerd_thread);
        }

        DBG("Unlinking all unix socket");
        unlink(client_unix_sock_path);
        unlink(apps_unix_sock_path);
        unlink(kconsumerd_err_unix_sock_path);

        DBG("Removing %s directory", LTTNG_RUNDIR);
        ret = asprintf(&cmd, "rm -rf " LTTNG_RUNDIR);
        if (ret < 0) {
                ERR("asprintf failed. Something is really wrong!");
        }

        /* Remove lttng run directory */
        ret = system(cmd);
        if (ret < 0) {
                ERR("Unable to clean " LTTNG_RUNDIR);
        }

        DBG("Cleaning up all session");
        /* Cleanup ALL session */
        cds_list_for_each_entry(sess, &ltt_session_list.head, list) {
                teardown_kernel_session(sess);
                // TODO complete session cleanup (including UST)
        }

        DBG("Closing kernel fd");
        close(kernel_tracer_fd);
        close(kernel_poll_pipe[0]);
        close(kernel_poll_pipe[1]);
}

/*
 *  send_unix_sock
 *
 *  Send data on a unix socket using the liblttsessiondcomm API.
 *
 *  Return lttcomm error code.
 */
static int send_unix_sock(int sock, void *buf, size_t len)
{
        /* Check valid length */
        if (len <= 0) {
                return -1;
        }

        return lttcomm_send_unix_sock(sock, buf, len);
}

/*
 *  clean_command_ctx
 *
 *  Free memory of a command context structure.
 */
static void clean_command_ctx(struct command_ctx *cmd_ctx)
{
        DBG("Clean command context structure %p", cmd_ctx);
        if (cmd_ctx) {
                if (cmd_ctx->llm) {
                        free(cmd_ctx->llm);
                }
                if (cmd_ctx->lsm) {
                        free(cmd_ctx->lsm);
                }
                free(cmd_ctx);
                cmd_ctx = NULL;
        }
}

/*
 *  send_kconsumerd_channel_fds
 *
 *  Send all stream fds of kernel channel to the consumer.
 */
static int send_kconsumerd_channel_fds(int sock, struct ltt_kernel_channel *channel)
{
        int ret;
        size_t nb_fd;
        struct ltt_kernel_stream *stream;
        struct lttcomm_kconsumerd_header lkh;
        struct lttcomm_kconsumerd_msg lkm;

        DBG("Sending fds of channel %s to kernel consumer", channel->channel->name);

        nb_fd = channel->stream_count;

        /* Setup header */
        lkh.payload_size = nb_fd * sizeof(struct lttcomm_kconsumerd_msg);
        lkh.cmd_type = ADD_STREAM;

        DBG("Sending kconsumerd header");

        ret = lttcomm_send_unix_sock(sock, &lkh, sizeof(struct lttcomm_kconsumerd_header));
        if (ret < 0) {
                perror("send kconsumerd header");
                goto error;
        }

        cds_list_for_each_entry(stream, &channel->stream_list.head, list) {
                if (stream->fd != 0) {
                        lkm.fd = stream->fd;
                        lkm.state = stream->state;
                        lkm.max_sb_size = channel->channel->attr.subbuf_size;
                        strncpy(lkm.path_name, stream->pathname, PATH_MAX);

                        DBG("Sending fd %d to kconsumerd", lkm.fd);

                        ret = lttcomm_send_fds_unix_sock(sock, &lkm, &lkm.fd, 1, sizeof(lkm));
                        if (ret < 0) {
                                perror("send kconsumerd fd");
                                goto error;
                        }
                }
        }

        DBG("Kconsumerd channel fds sent");

        return 0;

error:
        return ret;
}

/*
 *  send_kconsumerd_fds
 *
 *  Send all stream fds of the kernel session to the consumer.
 */
static int send_kconsumerd_fds(int sock, struct ltt_kernel_session *session)
{
        int ret;
        struct ltt_kernel_channel *chan;
        struct lttcomm_kconsumerd_header lkh;
        struct lttcomm_kconsumerd_msg lkm;

        /* Setup header */
        lkh.payload_size = sizeof(struct lttcomm_kconsumerd_msg);
        lkh.cmd_type = ADD_STREAM;

        DBG("Sending kconsumerd header for metadata");

        ret = lttcomm_send_unix_sock(sock, &lkh, sizeof(struct lttcomm_kconsumerd_header));
        if (ret < 0) {
                perror("send kconsumerd header");
                goto error;
        }

        DBG("Sending metadata stream fd");

        if (session->metadata_stream_fd != 0) {
                /* Send metadata stream fd first */
                lkm.fd = session->metadata_stream_fd;
                lkm.state = ACTIVE_FD;
                lkm.max_sb_size = session->metadata->conf->attr.subbuf_size;
                strncpy(lkm.path_name, session->metadata->pathname, PATH_MAX);

                ret = lttcomm_send_fds_unix_sock(sock, &lkm, &lkm.fd, 1, sizeof(lkm));
                if (ret < 0) {
                        perror("send kconsumerd fd");
                        goto error;
                }
        }

        cds_list_for_each_entry(chan, &session->channel_list.head, list) {
                ret = send_kconsumerd_channel_fds(sock, chan);
                if (ret < 0) {
                        goto error;
                }
        }

        DBG("Kconsumerd fds (metadata and channel streams) sent");

        return 0;

error:
        return ret;
}

/*
 *      ust_connect_app
 *
 *      Return a socket connected to the libust communication socket
 *      of the application identified by the pid.
 *
 *      If the pid is not found in the traceable list,
 *      return -1 to indicate error.
 */
static int ust_connect_app(pid_t pid)
{
        int sock;
        struct ltt_traceable_app *lta;

        DBG("Connect to application pid %d", pid);

        lta = find_app_by_pid(pid);
        if (lta == NULL) {
                /* App not found */
                DBG("Application pid %d not found", pid);
                return -1;
        }

        sock = ustctl_connect_pid(lta->pid);
        if (sock < 0) {
                ERR("Fail connecting to the PID %d", pid);
        }

        return sock;
}

/*
 *      notify_apps
 *
 *  Notify apps by writing 42 to a named pipe using name.
 *      Every applications waiting for a ltt-sessiond will be notified
 *      and re-register automatically to the session daemon.
 *
 *      Return open or write error value.
 */
static int notify_apps(const char *name)
{
        int fd;
        int ret = -1;

        DBG("Notify the global application pipe");

        /* Try opening the global pipe */
        fd = open(name, O_WRONLY);
        if (fd < 0) {
                goto error;
        }

        /* Notify by writing on the pipe */
        ret = write(fd, "42", 2);
        if (ret < 0) {
                perror("write");
        }

error:
        return ret;
}

/*
 *  setup_lttng_msg
 *
 *  Setup the outgoing data buffer for the response (llm) by allocating the
 *  right amount of memory and copying the original information from the lsm
 *  structure.
 *
 *  Return total size of the buffer pointed by buf.
 */
static int setup_lttng_msg(struct command_ctx *cmd_ctx, size_t size)
{
        int ret, buf_size;

        buf_size = size;

        cmd_ctx->llm = malloc(sizeof(struct lttcomm_lttng_msg) + buf_size);
        if (cmd_ctx->llm == NULL) {
                perror("malloc");
                ret = -ENOMEM;
                goto error;
        }

        /* Copy common data */
        cmd_ctx->llm->cmd_type = cmd_ctx->lsm->cmd_type;
        cmd_ctx->llm->pid = cmd_ctx->lsm->pid;

        cmd_ctx->llm->data_size = size;
        cmd_ctx->lttng_msg_size = sizeof(struct lttcomm_lttng_msg) + buf_size;

        return buf_size;

error:
        return ret;
}

/*
 *  update_kernel_pollfd
 *
 *  Update the kernel pollfd set of all channel fd available over
 *  all tracing session. Add the wakeup pipe at the end of the set.
 */
static int update_kernel_pollfd(void)
{
        int i = 0;
        unsigned int nb_fd = 1;
        struct ltt_session *session;
        struct ltt_kernel_channel *channel;

        DBG("Updating kernel_pollfd");

        /* Get the number of channel of all kernel session */
        cds_list_for_each_entry(session, &ltt_session_list.head, list) {
                if (session->kernel_session == NULL) {
                        continue;
                }
                nb_fd += session->kernel_session->channel_count;
        }

        DBG("Resizing kernel_pollfd to size %d", nb_fd);

        kernel_pollfd = realloc(kernel_pollfd, nb_fd * sizeof(struct pollfd));
        if (kernel_pollfd == NULL) {
                perror("malloc kernel_pollfd");
                goto error;
        }

        cds_list_for_each_entry(session, &ltt_session_list.head, list) {
                if (session->kernel_session == NULL) {
                        continue;
                }
                if (i >= nb_fd) {
                        ERR("To much channel for kernel_pollfd size");
                        break;
                }
                cds_list_for_each_entry(channel, &session->kernel_session->channel_list.head, list) {
                        kernel_pollfd[i].fd = channel->fd;
                        kernel_pollfd[i].events = POLLIN | POLLRDNORM;
                        i++;
                }
        }

        /* Adding wake up pipe */
        kernel_pollfd[nb_fd - 1].fd = kernel_poll_pipe[0];
        kernel_pollfd[nb_fd - 1].events = POLLIN;

        return nb_fd;

error:
        return -1;
}

/*
 *  update_kernel_stream
 *
 *  Find the channel fd from 'fd' over all tracing session.  When found, check
 *  for new channel stream and send those stream fds to the kernel consumer.
 *
 *  Useful for CPU hotplug feature.
 */
static int update_kernel_stream(int fd)
{
        int ret = 0;
        struct ltt_session *session;
        struct ltt_kernel_channel *channel;

        DBG("Updating kernel streams for channel fd %d", fd);

        cds_list_for_each_entry(session, &ltt_session_list.head, list) {
                if (session->kernel_session == NULL) {
                        continue;
                }
                cds_list_for_each_entry(channel, &session->kernel_session->channel_list.head, list) {
                        if (channel->fd == fd) {
                                DBG("Channel found, updating kernel streams");
                                ret = kernel_open_channel_stream(channel);
                                if (ret < 0) {
                                        goto end;
                                }
                                /*
                                 * Have we already sent fds to the consumer? If yes, it means that
                                 * tracing is started so it is safe to send our updated stream fds.
                                 */
                                if (session->kernel_session->kconsumer_fds_sent == 1) {
                                        ret = send_kconsumerd_channel_fds(kconsumerd_cmd_sock, channel);
                                        if (ret < 0) {
                                                goto end;
                                        }
                                }
                                goto end;
                        }
                }
        }

end:
        return ret;
}

/*
 *  thread_manage_kernel
 *
 *  This thread manage event coming from the kernel.
 *
 *  Features supported in this thread:
 *   -) CPU Hotplug
 */
static void *thread_manage_kernel(void *data)
{
        int ret, i, nb_fd = 0;
        char tmp;
        int update_poll_flag = 1;

        DBG("Thread manage kernel started");

        while (1) {
                if (update_poll_flag == 1) {
                        nb_fd = update_kernel_pollfd();
                        if (nb_fd < 0) {
                                goto error;
                        }
                        update_poll_flag = 0;
                }

                DBG("Polling on %d fds", nb_fd);

                /* Poll infinite value of time */
                ret = poll(kernel_pollfd, nb_fd, -1);
                if (ret < 0) {
                        perror("poll kernel thread");
                        goto error;
                } else if (ret == 0) {
                        /* Should not happen since timeout is infinite */
                        continue;
                }

                DBG("Kernel poll event triggered");

                /*
                 * Check if the wake up pipe was triggered. If so, the kernel_pollfd
                 * must be updated.
                 */
                if (kernel_pollfd[nb_fd - 1].revents == POLLIN) {
                        ret = read(kernel_poll_pipe[0], &tmp, 1);
                        update_poll_flag = 1;
                        continue;
                }

                for (i = 0; i < nb_fd; i++) {
                        switch (kernel_pollfd[i].revents) {
                        /*
                         * New CPU detected by the kernel. Adding kernel stream to kernel
                         * session and updating the kernel consumer
                         */
                        case POLLIN | POLLRDNORM:
                                ret = update_kernel_stream(kernel_pollfd[i].fd);
                                if (ret < 0) {
                                        continue;
                                }
                                break;
                        }
                }
        }

error:
        DBG("Kernel thread dying");
        if (kernel_pollfd) {
                free(kernel_pollfd);
        }
        return NULL;
}

/*
 *  thread_manage_kconsumerd
 *
 *  This thread manage the kconsumerd error sent
 *  back to the session daemon.
 */
static void *thread_manage_kconsumerd(void *data)
{
        int sock, ret;
        enum lttcomm_return_code code;

        DBG("[thread] Manage kconsumerd started");

        ret = lttcomm_listen_unix_sock(kconsumerd_err_sock);
        if (ret < 0) {
                goto error;
        }

        sock = lttcomm_accept_unix_sock(kconsumerd_err_sock);
        if (sock < 0) {
                goto error;
        }

        /* Getting status code from kconsumerd */
        ret = lttcomm_recv_unix_sock(sock, &code, sizeof(enum lttcomm_return_code));
        if (ret <= 0) {
                goto error;
        }

        if (code == KCONSUMERD_COMMAND_SOCK_READY) {
                kconsumerd_cmd_sock = lttcomm_connect_unix_sock(kconsumerd_cmd_unix_sock_path);
                if (kconsumerd_cmd_sock < 0) {
                        sem_post(&kconsumerd_sem);
                        perror("kconsumerd connect");
                        goto error;
                }
                /* Signal condition to tell that the kconsumerd is ready */
                sem_post(&kconsumerd_sem);
                DBG("Kconsumerd command socket ready");
        } else {
                DBG("Kconsumerd error when waiting for SOCK_READY : %s",
                                lttcomm_get_readable_code(-code));
                goto error;
        }

        /* Wait for any kconsumerd error */
        ret = lttcomm_recv_unix_sock(sock, &code, sizeof(enum lttcomm_return_code));
        if (ret <= 0) {
                ERR("Kconsumerd closed the command socket");
                goto error;
        }

        ERR("Kconsumerd return code : %s", lttcomm_get_readable_code(-code));

error:
        kconsumerd_pid = 0;
        DBG("Kconsumerd thread dying");
        return NULL;
}

/*
 *      thread_manage_apps
 *
 *      This thread manage the application socket communication
 */
static void *thread_manage_apps(void *data)
{
        int sock, ret;

        /* TODO: Something more elegant is needed but fine for now */
        /* FIXME: change all types to either uint8_t, uint32_t, uint64_t
         * for 32-bit vs 64-bit compat processes. */
        /* replicate in ust with version number */
        struct {
                int reg;        /* 1:register, 0:unregister */
                pid_t pid;
                uid_t uid;
        } reg_msg;

        DBG("[thread] Manage apps started");

        ret = lttcomm_listen_unix_sock(apps_sock);
        if (ret < 0) {
                goto error;
        }

        /* Notify all applications to register */
        notify_apps(default_global_apps_pipe);

        while (1) {
                DBG("Accepting application registration");
                /* Blocking call, waiting for transmission */
                sock = lttcomm_accept_unix_sock(apps_sock);
                if (sock < 0) {
                        goto error;
                }

                /* Basic recv here to handle the very simple data
                 * that the libust send to register (reg_msg).
                 */
                ret = recv(sock, &reg_msg, sizeof(reg_msg), 0);
                if (ret < 0) {
                        perror("recv");
                        continue;
                }

                /* Add application to the global traceable list */
                if (reg_msg.reg == 1) {
                        /* Registering */
                        ret = register_traceable_app(reg_msg.pid, reg_msg.uid);
                        if (ret < 0) {
                                /* register_traceable_app only return an error with
                                 * ENOMEM. At this point, we better stop everything.
                                 */
                                goto error;
                        }
                } else {
                        /* Unregistering */
                        unregister_traceable_app(reg_msg.pid);
                }
        }

error:

        return NULL;
}

/*
 *  spawn_kconsumerd_thread
 *
 *  Start the thread_manage_kconsumerd. This must be done after a kconsumerd
 *  exec or it will fails.
 */
static int spawn_kconsumerd_thread(void)
{
        int ret;

        /* Setup semaphore */
        sem_init(&kconsumerd_sem, 0, 0);

        ret = pthread_create(&kconsumerd_thread, NULL, thread_manage_kconsumerd, (void *) NULL);
        if (ret != 0) {
                perror("pthread_create kconsumerd");
                goto error;
        }

        /* Wait for the kconsumerd thread to be ready */
        sem_wait(&kconsumerd_sem);

        if (kconsumerd_pid == 0) {
                ERR("Kconsumerd did not start");
                goto error;
        }

        return 0;

error:
        ret = LTTCOMM_KERN_CONSUMER_FAIL;
        return ret;
}

/*
 *  spawn_kconsumerd
 *
 *  Fork and exec a kernel consumer daemon (kconsumerd).
 *
 *  NOTE: It is very important to fork a kconsumerd BEFORE opening any kernel
 *  file descriptor using the libkernelctl or kernel-ctl functions. So, a
 *  kernel consumer MUST only be spawned before creating a kernel session.
 *
 *  Return pid if successful else -1.
 */
static pid_t spawn_kconsumerd(void)
{
        int ret;
        pid_t pid;

        DBG("Spawning kconsumerd");

        pid = fork();
        if (pid == 0) {
                /*
                 * Exec kconsumerd.
                 */
                execlp("ltt-kconsumerd", "ltt-kconsumerd", "--verbose", NULL);
                if (errno != 0) {
                        perror("kernel start consumer exec");
                }
                exit(EXIT_FAILURE);
        } else if (pid > 0) {
                ret = pid;
                goto error;
        } else {
                perror("kernel start consumer fork");
                ret = -errno;
                goto error;
        }

error:
        return ret;
}

/*
 *  start_kconsumerd
 *
 *  Spawn the kconsumerd daemon and session daemon thread.
 */
static int start_kconsumerd(void)
{
        int ret;

        pthread_mutex_lock(&kconsumerd_pid_mutex);
        if (kconsumerd_pid != 0) {
                goto end;
        }

        ret = spawn_kconsumerd();
        if (ret < 0) {
                ERR("Spawning kconsumerd failed");
                ret = LTTCOMM_KERN_CONSUMER_FAIL;
                pthread_mutex_unlock(&kconsumerd_pid_mutex);
                goto error;
        }

        /* Setting up the global kconsumerd_pid */
        kconsumerd_pid = ret;
        pthread_mutex_unlock(&kconsumerd_pid_mutex);

        DBG("Kconsumerd pid %d", ret);

        DBG("Spawning kconsumerd thread");
        ret = spawn_kconsumerd_thread();
        if (ret < 0) {
                ERR("Fatal error spawning kconsumerd thread");
                goto error;
        }

end:
        pthread_mutex_unlock(&kconsumerd_pid_mutex);
        return 0;

error:
        return ret;
}

/*
 *  modprobe_kernel_modules
 */
static int modprobe_kernel_modules(void)
{
        int ret = 0, i = 0;
        char modprobe[256];

        while (kernel_modules_list[i] != NULL) {
                ret = snprintf(modprobe, sizeof(modprobe), "/sbin/modprobe %s",
                                kernel_modules_list[i]);
                if (ret < 0) {
                        perror("snprintf modprobe");
                        goto error;
                }
                ret = system(modprobe);
                if (ret < 0) {
                        ERR("Unable to load module %s", kernel_modules_list[i]);
                }
                DBG("Modprobe successfully %s", kernel_modules_list[i]);
                i++;
        }

error:
        return ret;
}

/*
 *  mount_debugfs
 */
static int mount_debugfs(char *path)
{
        int ret;
        char *type = "debugfs";

        ret = mkdir_recursive(path, S_IRWXU | S_IRWXG);
        if (ret < 0) {
                goto error;
        }

        ret = mount(type, path, type, 0, NULL);
        if (ret < 0) {
                perror("mount debugfs");
                goto error;
        }

        DBG("Mounted debugfs successfully at %s", path);

error:
        return ret;
}

/*
 *  init_kernel_tracer
 *
 *  Setup necessary data for kernel tracer action.
 */
static void init_kernel_tracer(void)
{
        int ret;
        char *proc_mounts = "/proc/mounts";
        char line[256];
        char *debugfs_path = NULL, *lttng_path;
        FILE *fp;

        /* Detect debugfs */
        fp = fopen(proc_mounts, "r");
        if (fp == NULL) {
                ERR("Unable to probe %s", proc_mounts);
                goto error;
        }

        while (fgets(line, sizeof(line), fp) != NULL) {
                if (strstr(line, "debugfs") != NULL) {
                        /* Remove first string */
                        strtok(line, " ");
                        /* Dup string here so we can reuse line later on */
                        debugfs_path = strdup(strtok(NULL, " "));
                        DBG("Got debugfs path : %s", debugfs_path);
                        break;
                }
        }

        fclose(fp);

        /* Mount debugfs if needded */
        if (debugfs_path == NULL) {
                ret = asprintf(&debugfs_path, "/mnt/debugfs");
                if (ret < 0) {
                        perror("asprintf debugfs path");
                        goto error;
                }
                ret = mount_debugfs(debugfs_path);
                if (ret < 0) {
                        goto error;
                }
        }

        /* Modprobe lttng kernel modules */
        ret = modprobe_kernel_modules();
        if (ret < 0) {
                goto error;
        }

        /* Setup lttng kernel path */
        ret = asprintf(&lttng_path, "%s/lttng", debugfs_path);
        if (ret < 0) {
                perror("asprintf lttng path");
                goto error;
        }

        /* Open debugfs lttng */
        kernel_tracer_fd = open(lttng_path, O_RDWR);
        if (kernel_tracer_fd < 0) {
                DBG("Failed to open %s", lttng_path);
                goto error;
        }

        free(lttng_path);
        free(debugfs_path);
        DBG("Kernel tracer fd %d", kernel_tracer_fd);
        return;

error:
        if (lttng_path) {
                free(lttng_path);
        }
        if (debugfs_path) {
                free(debugfs_path);
        }
        WARN("No kernel tracer available");
        kernel_tracer_fd = 0;
        return;
}

/*
 *  start_kernel_trace
 *
 *  Start tracing by creating trace directory and sending FDs to the kernel
 *  consumer.
 */
static int start_kernel_trace(struct ltt_kernel_session *session)
{
        int ret;

        if (session->kconsumer_fds_sent == 0) {
                ret = send_kconsumerd_fds(kconsumerd_cmd_sock, session);
                if (ret < 0) {
                        ERR("Send kconsumerd fds failed");
                        ret = LTTCOMM_KERN_CONSUMER_FAIL;
                        goto error;
                }

                session->kconsumer_fds_sent = 1;
        }

error:
        return ret;
}

/*
 * Notify kernel thread to update it's pollfd.
 */
static int notify_kernel_pollfd(void)
{
        int ret;

        /* Inform kernel thread of the new kernel channel */
        ret = write(kernel_poll_pipe[1], "!", 1);
        if (ret < 0) {
                perror("write kernel poll pipe");
        }

        return ret;
}

/*
 *  init_default_channel
 *
 *  Allocate a channel structure and fill it.
 */
static struct lttng_channel *init_default_channel(void)
{
        struct lttng_channel *chan;

        chan = malloc(sizeof(struct lttng_channel));
        if (chan == NULL) {
                perror("init channel malloc");
                goto error;
        }

        if (snprintf(chan->name, NAME_MAX, DEFAULT_CHANNEL_NAME) < 0) {
                perror("snprintf defautl channel name");
                return NULL;
        }

        chan->attr.overwrite = DEFAULT_CHANNEL_OVERWRITE;
        chan->attr.subbuf_size = DEFAULT_CHANNEL_SUBBUF_SIZE;
        chan->attr.num_subbuf = DEFAULT_CHANNEL_SUBBUF_NUM;
        chan->attr.switch_timer_interval = DEFAULT_CHANNEL_SWITCH_TIMER;
        chan->attr.read_timer_interval = DEFAULT_CHANNEL_READ_TIMER;
        chan->attr.output = DEFAULT_KERNEL_CHANNEL_OUTPUT;

error:
        return chan;
}

/*
 *  create_kernel_session
 *
 *  Create a kernel tracer session then create the default channel.
 */
static int create_kernel_session(struct ltt_session *session)
{
        int ret;
        struct lttng_channel *chan;

        DBG("Creating kernel session");

        ret = kernel_create_session(session, kernel_tracer_fd);
        if (ret < 0) {
                ret = LTTCOMM_KERN_SESS_FAIL;
                goto error;
        }

        chan = init_default_channel();
        if (chan == NULL) {
                ret = LTTCOMM_FATAL;
                goto error;
        }

        ret = mkdir_recursive(session->path, S_IRWXU | S_IRWXG );
        if (ret < 0) {
                if (ret != EEXIST) {
                        ERR("Trace directory creation error");
                        goto error;
                }
        }

        DBG("Creating default kernel channel %s", DEFAULT_CHANNEL_NAME);

        ret = kernel_create_channel(session->kernel_session, chan, session->path);
        if (ret < 0) {
                ret = LTTCOMM_KERN_CHAN_FAIL;
                goto error;
        }

        ret = notify_kernel_pollfd();

error:
        return ret;
}

/*
 *      process_client_msg
 *
 *  Process the command requested by the lttng client within the command
 *  context structure.  This function make sure that the return structure (llm)
 *  is set and ready for transmission before returning.
 *
 *      Return any error encountered or 0 for success.
 */
static int process_client_msg(struct command_ctx *cmd_ctx)
{
        int ret;

        DBG("Processing client command %d", cmd_ctx->lsm->cmd_type);

        /* Listing commands don't need a session */
        switch (cmd_ctx->lsm->cmd_type) {
        case LTTNG_CREATE_SESSION:
        case LTTNG_LIST_SESSIONS:
        case LTTNG_LIST_EVENTS:
        case LTTNG_KERNEL_LIST_EVENTS:
        case LTTNG_LIST_TRACEABLE_APPS:
                break;
        default:
                DBG("Getting session %s by name", cmd_ctx->lsm->session_name);
                cmd_ctx->session = find_session_by_name(cmd_ctx->lsm->session_name);
                if (cmd_ctx->session == NULL) {
                        /* If session name not found */
                        if (cmd_ctx->lsm->session_name != NULL) {
                                ret = LTTCOMM_SESS_NOT_FOUND;
                        } else {        /* If no session name specified */
                                ret = LTTCOMM_SELECT_SESS;
                        }
                        goto error;
                }
                break;
        }

        /*
         * Check kernel command for kernel session.
         */
        switch (cmd_ctx->lsm->cmd_type) {
        case LTTNG_KERNEL_ADD_CONTEXT:
        case LTTNG_KERNEL_CREATE_CHANNEL:
        case LTTNG_KERNEL_DISABLE_ALL_EVENT:
        case LTTNG_KERNEL_DISABLE_CHANNEL:
        case LTTNG_KERNEL_DISABLE_EVENT:
        case LTTNG_KERNEL_ENABLE_ALL_EVENT:
        case LTTNG_KERNEL_ENABLE_CHANNEL:
        case LTTNG_KERNEL_ENABLE_EVENT:
        case LTTNG_KERNEL_LIST_EVENTS:
                /* Kernel tracer check */
                if (kernel_tracer_fd == 0) {
                        init_kernel_tracer();
                        if (kernel_tracer_fd == 0) {
                                ret = LTTCOMM_KERN_NA;
                                goto error;
                        }
                }

                /* Need a session for kernel command */
                if (cmd_ctx->lsm->cmd_type != LTTNG_KERNEL_LIST_EVENTS &&
                                cmd_ctx->session->kernel_session == NULL) {

                        ret = create_kernel_session(cmd_ctx->session);
                        if (ret < 0) {
                                ret = LTTCOMM_KERN_SESS_FAIL;
                                goto error;
                        }

                        /* Start the kernel consumer daemon */
                        if (kconsumerd_pid == 0) {
                                ret = start_kconsumerd();
                                if (ret < 0) {
                                        goto error;
                                }
                        }
                }
        }

        /* Connect to ust apps if available pid */
        if (cmd_ctx->lsm->pid > 0) {
                /* Connect to app using ustctl API */
                cmd_ctx->ust_sock = ust_connect_app(cmd_ctx->lsm->pid);
                if (cmd_ctx->ust_sock < 0) {
                        ret = LTTCOMM_NO_TRACEABLE;
                        goto error;
                }
        }

        /* Process by command type */
        switch (cmd_ctx->lsm->cmd_type) {
        case LTTNG_KERNEL_ADD_CONTEXT:
        {
                int found = 0, no_event = 0;
                struct ltt_kernel_channel *chan;
                struct ltt_kernel_event *event;

                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                /* Check if event name is given */
                if (strlen(cmd_ctx->lsm->u.context.event_name) == 0) {
                        no_event = 1;
                }

                if (strlen(cmd_ctx->lsm->u.context.channel_name) == 0) {
                        /* Go over all channels */
                        DBG("Adding context to all channels");
                        cds_list_for_each_entry(chan,
                                        &cmd_ctx->session->kernel_session->channel_list.head, list) {
                                if (no_event) {
                                        ret = kernel_add_channel_context(chan,
                                                        &cmd_ctx->lsm->u.context.ctx);
                                        if (ret < 0) {
                                                continue;
                                        }
                                } else {
                                        event = get_kernel_event_by_name(cmd_ctx->lsm->u.context.event_name, chan);
                                        if (event != NULL) {
                                                ret = kernel_add_event_context(event,
                                                                &cmd_ctx->lsm->u.context.ctx);
                                                if (ret < 0) {
                                                        ret = LTTCOMM_KERN_CONTEXT_FAIL;
                                                        goto error;
                                                }
                                                found = 1;
                                                break;
                                        }
                                }
                        }
                } else {
                        chan = get_kernel_channel_by_name(cmd_ctx->lsm->u.context.channel_name,
                                        cmd_ctx->session->kernel_session);
                        if (chan == NULL) {
                                ret = LTTCOMM_KERN_CHAN_NOT_FOUND;
                                goto error;
                        }

                        if (no_event) {
                                ret = kernel_add_channel_context(chan,
                                                &cmd_ctx->lsm->u.context.ctx);
                                if (ret < 0) {
                                        ret = LTTCOMM_KERN_CONTEXT_FAIL;
                                        goto error;
                                }
                        } else {
                                event = get_kernel_event_by_name(cmd_ctx->lsm->u.context.event_name, chan);
                                if (event != NULL) {
                                        ret = kernel_add_event_context(event,
                                                        &cmd_ctx->lsm->u.context.ctx);
                                        if (ret < 0) {
                                                ret = LTTCOMM_KERN_CONTEXT_FAIL;
                                                goto error;
                                        }
                                }
                        }
                }

                if (!found && !no_event) {
                        ret = LTTCOMM_NO_EVENT;
                        goto error;
                }

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_KERNEL_CREATE_CHANNEL:
        {
                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                /* Kernel tracer */
                DBG("Creating kernel channel");

                ret = kernel_create_channel(cmd_ctx->session->kernel_session,
                                &cmd_ctx->lsm->u.channel.chan, cmd_ctx->session->path);
                if (ret < 0) {
                        ret = LTTCOMM_KERN_CHAN_FAIL;
                        goto error;
                }

                ret = notify_kernel_pollfd();
                if (ret < 0) {
                        ret = LTTCOMM_FATAL;
                        goto error;
                }

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_KERNEL_DISABLE_CHANNEL:
        {
                struct ltt_kernel_channel *chan;

                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                chan = get_kernel_channel_by_name(cmd_ctx->lsm->u.disable.channel_name,
                                cmd_ctx->session->kernel_session);
                if (chan == NULL) {
                        ret = LTTCOMM_KERN_CHAN_NOT_FOUND;
                        goto error;
                } else if (chan->enabled == 1) {
                        ret = kernel_disable_channel(chan);
                        if (ret < 0) {
                                if (ret != EEXIST) {
                                        ret = LTTCOMM_KERN_CHAN_DISABLE_FAIL;
                                }
                                goto error;
                        }
                }

                kernel_wait_quiescent(kernel_tracer_fd);
                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_KERNEL_DISABLE_EVENT:
        {
                struct ltt_kernel_channel *chan;
                struct ltt_kernel_event *ev;

                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                chan = get_kernel_channel_by_name(cmd_ctx->lsm->u.disable.channel_name,
                                cmd_ctx->session->kernel_session);
                if (chan == NULL) {
                        ret = LTTCOMM_KERN_CHAN_NOT_FOUND;
                        goto error;
                }

                ev = get_kernel_event_by_name(cmd_ctx->lsm->u.disable.name, chan);
                if (ev != NULL) {
                        DBG("Disabling kernel event %s for channel %s.",
                                        cmd_ctx->lsm->u.disable.name, cmd_ctx->lsm->u.disable.channel_name);
                        ret = kernel_disable_event(ev);
                        if (ret < 0) {
                                ret = LTTCOMM_KERN_ENABLE_FAIL;
                                goto error;
                        }
                }

                kernel_wait_quiescent(kernel_tracer_fd);
                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_KERNEL_DISABLE_ALL_EVENT:
        {
                struct ltt_kernel_channel *chan;
                struct ltt_kernel_event *ev;

                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                DBG("Disabling all enabled kernel events");

                chan = get_kernel_channel_by_name(cmd_ctx->lsm->u.disable.channel_name,
                                cmd_ctx->session->kernel_session);
                if (chan == NULL) {
                        ret = LTTCOMM_KERN_CHAN_NOT_FOUND;
                        goto error;
                }

                /* For each event in the kernel session */
                cds_list_for_each_entry(ev, &chan->events_list.head, list) {
                        DBG("Disabling kernel event %s for channel %s.",
                                        ev->event->name, cmd_ctx->lsm->u.disable.channel_name);
                        ret = kernel_disable_event(ev);
                        if (ret < 0) {
                                continue;
                        }
                }

                /* Quiescent wait after event disable */
                kernel_wait_quiescent(kernel_tracer_fd);
                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_KERNEL_ENABLE_CHANNEL:
        {
                struct ltt_kernel_channel *chan;

                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                chan = get_kernel_channel_by_name(cmd_ctx->lsm->u.enable.channel_name,
                                cmd_ctx->session->kernel_session);
                if (chan == NULL) {
                        ret = LTTCOMM_KERN_CHAN_NOT_FOUND;
                        goto error;
                } else if (chan->enabled == 0) {
                        ret = kernel_enable_channel(chan);
                        if (ret < 0) {
                                if (ret != EEXIST) {
                                        ret = LTTCOMM_KERN_CHAN_ENABLE_FAIL;
                                }
                                goto error;
                        }
                }

                kernel_wait_quiescent(kernel_tracer_fd);
                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_KERNEL_ENABLE_EVENT:
        {
                struct ltt_kernel_channel *chan;
                struct ltt_kernel_event *ev;

                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                chan = get_kernel_channel_by_name(cmd_ctx->lsm->u.enable.channel_name,
                                cmd_ctx->session->kernel_session);
                if (chan == NULL) {
                        ret = LTTCOMM_KERN_CHAN_NOT_FOUND;
                        goto error;
                }

                ev = get_kernel_event_by_name(cmd_ctx->lsm->u.enable.event.name, chan);
                if (ev == NULL) {
                        DBG("Creating kernel event %s for channel %s.",
                                        cmd_ctx->lsm->u.enable.event.name, chan->channel->name);
                        ret = kernel_create_event(&cmd_ctx->lsm->u.enable.event, chan);
                } else {
                        DBG("Enabling kernel event %s for channel %s.",
                                        cmd_ctx->lsm->u.enable.event.name, chan->channel->name);
                        ret = kernel_enable_event(ev);
                }

                if (ret < 0) {
                        ret = LTTCOMM_KERN_ENABLE_FAIL;
                        goto error;
                }

                kernel_wait_quiescent(kernel_tracer_fd);
                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_KERNEL_ENABLE_ALL_EVENT:
        {
                int pos, size;
                char *event_list, *event, *ptr;
                struct ltt_kernel_channel *chan;
                struct ltt_kernel_event *ev;
                struct lttng_event ev_attr;

                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                DBG("Enabling all kernel event");

                chan = get_kernel_channel_by_name(cmd_ctx->lsm->u.enable.channel_name,
                                cmd_ctx->session->kernel_session);
                if (chan == NULL) {
                        ret = LTTCOMM_KERN_CHAN_NOT_FOUND;
                        goto error;
                }

                /* For each event in the kernel session */
                cds_list_for_each_entry(ev, &chan->events_list.head, list) {
                        DBG("Enabling kernel event %s for channel %s.",
                                        ev->event->name, chan->channel->name);
                        ret = kernel_enable_event(ev);
                        if (ret < 0) {
                                continue;
                        }
                }

                size = kernel_list_events(kernel_tracer_fd, &event_list);
                if (size < 0) {
                        ret = LTTCOMM_KERN_LIST_FAIL;
                        goto error;
                }

                ptr = event_list;
                while ((size = sscanf(ptr, "event { name = %m[^;]; };%n\n", &event, &pos)) == 1) {
                        ev = get_kernel_event_by_name(event, chan);
                        if (ev == NULL) {
                                strncpy(ev_attr.name, event, LTTNG_SYM_NAME_LEN);
                                /* Default event type for enable all */
                                ev_attr.type = LTTNG_EVENT_TRACEPOINTS;
                                /* Enable each single tracepoint event */
                                ret = kernel_create_event(&ev_attr, chan);
                                if (ret < 0) {
                                        /* Ignore error here and continue */
                                }
                        }

                        /* Move pointer to the next line */
                        ptr += pos + 1;
                        free(event);
                }

                free(event_list);

                /* Quiescent wait after event enable */
                kernel_wait_quiescent(kernel_tracer_fd);
                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_KERNEL_LIST_EVENTS:
        {
                char *event_list;
                ssize_t size = 0;

                DBG("Listing kernel events");

                size = kernel_list_events(kernel_tracer_fd, &event_list);
                if (size < 0) {
                        ret = LTTCOMM_KERN_LIST_FAIL;
                        goto error;
                }

                /*
                 * Setup lttng message with payload size set to the event list size in
                 * bytes and then copy list into the llm payload.
                 */
                ret = setup_lttng_msg(cmd_ctx, size);
                if (ret < 0) {
                        goto setup_error;
                }

                /* Copy event list into message payload */
                memcpy(cmd_ctx->llm->payload, event_list, size);

                free(event_list);

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_START_TRACE:
        {
                struct ltt_kernel_channel *chan;

                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                /* Kernel tracing */
                if (cmd_ctx->session->kernel_session != NULL) {
                        if (cmd_ctx->session->kernel_session->metadata == NULL) {
                                DBG("Open kernel metadata");
                                ret = kernel_open_metadata(cmd_ctx->session->kernel_session,
                                                cmd_ctx->session->path);
                                if (ret < 0) {
                                        ret = LTTCOMM_KERN_META_FAIL;
                                        goto error;
                                }
                        }

                        if (cmd_ctx->session->kernel_session->metadata_stream_fd == 0) {
                                DBG("Opening kernel metadata stream");
                                if (cmd_ctx->session->kernel_session->metadata_stream_fd == 0) {
                                        ret = kernel_open_metadata_stream(cmd_ctx->session->kernel_session);
                                        if (ret < 0) {
                                                ERR("Kernel create metadata stream failed");
                                                ret = LTTCOMM_KERN_STREAM_FAIL;
                                                goto error;
                                        }
                                }
                        }

                        /* For each channel */
                        cds_list_for_each_entry(chan, &cmd_ctx->session->kernel_session->channel_list.head, list) {
                                if (chan->stream_count == 0) {
                                        ret = kernel_open_channel_stream(chan);
                                        if (ret < 0) {
                                                ERR("Kernel create channel stream failed");
                                                ret = LTTCOMM_KERN_STREAM_FAIL;
                                                goto error;
                                        }
                                        /* Update the stream global counter */
                                        cmd_ctx->session->kernel_session->stream_count_global += ret;
                                }
                        }

                        DBG("Start kernel tracing");
                        ret = kernel_start_session(cmd_ctx->session->kernel_session);
                        if (ret < 0) {
                                ERR("Kernel start session failed");
                                ret = LTTCOMM_KERN_START_FAIL;
                                goto error;
                        }

                        ret = start_kernel_trace(cmd_ctx->session->kernel_session);
                        if (ret < 0) {
                                ret = LTTCOMM_KERN_START_FAIL;
                                goto error;
                        }

                        /* Quiescent wait after starting trace */
                        kernel_wait_quiescent(kernel_tracer_fd);
                }

                /* TODO: Start all UST traces */

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_STOP_TRACE:
        {
                struct ltt_kernel_channel *chan;
                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                /* Kernel tracer */
                if (cmd_ctx->session->kernel_session != NULL) {
                        DBG("Stop kernel tracing");

                        ret = kernel_metadata_flush_buffer(cmd_ctx->session->kernel_session->metadata_stream_fd);
                        if (ret < 0) {
                                ERR("Kernel metadata flush failed");
                        }

                        cds_list_for_each_entry(chan, &cmd_ctx->session->kernel_session->channel_list.head, list) {
                                ret = kernel_flush_buffer(chan);
                                if (ret < 0) {
                                        ERR("Kernel flush buffer error");
                                }
                        }

                        ret = kernel_stop_session(cmd_ctx->session->kernel_session);
                        if (ret < 0) {
                                ERR("Kernel stop session failed");
                                ret = LTTCOMM_KERN_STOP_FAIL;
                                goto error;
                        }

                        /* Quiescent wait after stopping trace */
                        kernel_wait_quiescent(kernel_tracer_fd);
                }

                /* TODO : User-space tracer */

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_CREATE_SESSION:
        {
                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                ret = create_session(cmd_ctx->lsm->session_name, cmd_ctx->lsm->path);
                if (ret < 0) {
                        if (ret == -EEXIST) {
                                ret = LTTCOMM_EXIST_SESS;
                        } else {
                                ret = LTTCOMM_FATAL;
                        }
                        goto error;
                }

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_DESTROY_SESSION:
        {
                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                /* Clean kernel session teardown */
                teardown_kernel_session(cmd_ctx->session);

                ret = destroy_session(cmd_ctx->lsm->session_name);
                if (ret < 0) {
                        ret = LTTCOMM_FATAL;
                        goto error;
                }

                /*
                 * Must notify the kernel thread here to update it's pollfd in order to
                 * remove the channel(s)' fd just destroyed.
                 */
                ret = notify_kernel_pollfd();
                if (ret < 0) {
                        ret = LTTCOMM_FATAL;
                        goto error;
                }

                ret = LTTCOMM_OK;
                break;
        }
        /*
        case LTTNG_LIST_TRACES:
        {
                unsigned int trace_count;

                trace_count = get_trace_count_per_session(cmd_ctx->session);
                if (trace_count == 0) {
                        ret = LTTCOMM_NO_TRACE;
                        goto error;
                }

                ret = setup_lttng_msg(cmd_ctx, sizeof(struct lttng_trace) * trace_count);
                if (ret < 0) {
                        goto setup_error;
                }

                get_traces_per_session(cmd_ctx->session,
                                (struct lttng_trace *)(cmd_ctx->llm->payload));

                ret = LTTCOMM_OK;
                break;
        }
        */
        /*
        case UST_CREATE_TRACE:
        {
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                ret = ust_create_trace(cmd_ctx);
                if (ret < 0) {
                        goto error;
                }
                break;
        }
        */
        case LTTNG_LIST_TRACEABLE_APPS:
        {
                unsigned int app_count;

                app_count = get_app_count();
                DBG("Traceable application count : %d", app_count);
                if (app_count == 0) {
                        ret = LTTCOMM_NO_APPS;
                        goto error;
                }

                ret = setup_lttng_msg(cmd_ctx, sizeof(pid_t) * app_count);
                if (ret < 0) {
                        goto setup_error;
                }

                get_app_list_pids((pid_t *)(cmd_ctx->llm->payload));

                ret = LTTCOMM_OK;
                break;
        }
        /*
        case UST_START_TRACE:
        {
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                ret = ust_start_trace(cmd_ctx);
                if (ret < 0) {
                        goto setup_error;
                }
                break;
        }
        case UST_STOP_TRACE:
        {
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                ret = ust_stop_trace(cmd_ctx);
                if (ret < 0) {
                        goto setup_error;
                }
                break;
        }
        */
        case LTTNG_LIST_SESSIONS:
        {
                unsigned int session_count;

                session_count = get_session_count();
                if (session_count == 0) {
                        ret = LTTCOMM_NO_SESSION;
                        goto error;
                }

                ret = setup_lttng_msg(cmd_ctx, sizeof(struct lttng_session) * session_count);
                if (ret < 0) {
                        goto setup_error;
                }

                get_lttng_session((struct lttng_session *)(cmd_ctx->llm->payload));

                ret = LTTCOMM_OK;
                break;
        }
        default:
                /* Undefined command */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                ret = LTTCOMM_UND;
                break;
        }

        /* Set return code */
        cmd_ctx->llm->ret_code = ret;

        return ret;

error:
        if (cmd_ctx->llm == NULL) {
                DBG("Missing llm structure. Allocating one.");
                if (setup_lttng_msg(cmd_ctx, 0) < 0) {
                        goto setup_error;
                }
        }
        /* Notify client of error */
        cmd_ctx->llm->ret_code = ret;

setup_error:
        return ret;
}

/*
 *      thread_manage_clients
 *
 *      This thread manage all clients request using the unix
 *      client socket for communication.
 */
static void *thread_manage_clients(void *data)
{
        int sock, ret;
        struct command_ctx *cmd_ctx;

        DBG("[thread] Manage client started");

        ret = lttcomm_listen_unix_sock(client_sock);
        if (ret < 0) {
                goto error;
        }

        /* Notify parent pid that we are ready
         * to accept command for client side.
         */
        if (opt_sig_parent) {
                kill(ppid, SIGCHLD);
        }

        while (1) {
                /* Blocking call, waiting for transmission */
                DBG("Accepting client command ...");
                sock = lttcomm_accept_unix_sock(client_sock);
                if (sock < 0) {
                        goto error;
                }

                /* Allocate context command to process the client request */
                cmd_ctx = malloc(sizeof(struct command_ctx));

                /* Allocate data buffer for reception */
                cmd_ctx->lsm = malloc(sizeof(struct lttcomm_session_msg));
                cmd_ctx->llm = NULL;
                cmd_ctx->session = NULL;

                /*
                 * Data is received from the lttng client. The struct
                 * lttcomm_session_msg (lsm) contains the command and data request of
                 * the client.
                 */
                DBG("Receiving data from client ...");
                ret = lttcomm_recv_unix_sock(sock, cmd_ctx->lsm, sizeof(struct lttcomm_session_msg));
                if (ret <= 0) {
                        continue;
                }

                // TODO: Validate cmd_ctx including sanity check for security purpose.

                /*
                 * This function dispatch the work to the kernel or userspace tracer
                 * libs and fill the lttcomm_lttng_msg data structure of all the needed
                 * informations for the client. The command context struct contains
                 * everything this function may needs.
                 */
                ret = process_client_msg(cmd_ctx);
                if (ret < 0) {
                        /* TODO: Inform client somehow of the fatal error. At this point,
                         * ret < 0 means that a malloc failed (ENOMEM). */
                        /* Error detected but still accept command */
                        clean_command_ctx(cmd_ctx);
                        continue;
                }

                DBG("Sending response (size: %d, retcode: %d)",
                                cmd_ctx->lttng_msg_size, cmd_ctx->llm->ret_code);
                ret = send_unix_sock(sock, cmd_ctx->llm, cmd_ctx->lttng_msg_size);
                if (ret < 0) {
                        ERR("Failed to send data back to client");
                }

                clean_command_ctx(cmd_ctx);

                /* End of transmission */
                close(sock);
        }

error:
        return NULL;
}


/*
 * usage function on stderr
 */
static void usage(void)
{
        fprintf(stderr, "Usage: %s OPTIONS\n\nOptions:\n", progname);
        fprintf(stderr, "  -h, --help                         Display this usage.\n");
        fprintf(stderr, "  -c, --client-sock PATH             Specify path for the client unix socket\n");
        fprintf(stderr, "  -a, --apps-sock PATH               Specify path for apps unix socket\n");
        fprintf(stderr, "      --kconsumerd-err-sock PATH     Specify path for the kernel consumer error socket\n");
        fprintf(stderr, "      --kconsumerd-cmd-sock PATH     Specify path for the kernel consumer command socket\n");
        fprintf(stderr, "  -d, --daemonize                    Start as a daemon.\n");
        fprintf(stderr, "  -g, --group NAME                   Specify the tracing group name. (default: tracing)\n");
        fprintf(stderr, "  -V, --version                      Show version number.\n");
        fprintf(stderr, "  -S, --sig-parent                   Send SIGCHLD to parent pid to notify readiness.\n");
        fprintf(stderr, "  -q, --quiet                        No output at all.\n");
        fprintf(stderr, "  -v, --verbose                      Verbose mode. Activate DBG() macro.\n");
}

/*
 * daemon argument parsing
 */
static int parse_args(int argc, char **argv)
{
        int c;

        static struct option long_options[] = {
                { "client-sock", 1, 0, 'c' },
                { "apps-sock", 1, 0, 'a' },
                { "kconsumerd-cmd-sock", 1, 0, 0 },
                { "kconsumerd-err-sock", 1, 0, 0 },
                { "daemonize", 0, 0, 'd' },
                { "sig-parent", 0, 0, 'S' },
                { "help", 0, 0, 'h' },
                { "group", 1, 0, 'g' },
                { "version", 0, 0, 'V' },
                { "quiet", 0, 0, 'q' },
                { "verbose", 0, 0, 'v' },
                { NULL, 0, 0, 0 }
        };

        while (1) {
                int option_index = 0;
                c = getopt_long(argc, argv, "dhqvVS" "a:c:g:s:E:C:", long_options, &option_index);
                if (c == -1) {
                        break;
                }

                switch (c) {
                case 0:
                        fprintf(stderr, "option %s", long_options[option_index].name);
                        if (optarg) {
                                fprintf(stderr, " with arg %s\n", optarg);
                        }
                        break;
                case 'c':
                        snprintf(client_unix_sock_path, PATH_MAX, "%s", optarg);
                        break;
                case 'a':
                        snprintf(apps_unix_sock_path, PATH_MAX, "%s", optarg);
                        break;
                case 'd':
                        opt_daemon = 1;
                        break;
                case 'g':
                        opt_tracing_group = strdup(optarg);
                        break;
                case 'h':
                        usage();
                        exit(EXIT_FAILURE);
                case 'V':
                        fprintf(stdout, "%s\n", VERSION);
                        exit(EXIT_SUCCESS);
                case 'S':
                        opt_sig_parent = 1;
                        break;
                case 'E':
                        snprintf(kconsumerd_err_unix_sock_path, PATH_MAX, "%s", optarg);
                        break;
                case 'C':
                        snprintf(kconsumerd_cmd_unix_sock_path, PATH_MAX, "%s", optarg);
                        break;
                case 'q':
                        opt_quiet = 1;
                        break;
                case 'v':
                        opt_verbose = 1;
                        break;
                default:
                        /* Unknown option or other error.
                         * Error is printed by getopt, just return */
                        return -1;
                }
        }

        return 0;
}

/*
 *      init_daemon_socket
 *
 *      Creates the two needed socket by the daemon.
 *          apps_sock - The communication socket for all UST apps.
 *          client_sock - The communication of the cli tool (lttng).
 */
static int init_daemon_socket()
{
        int ret = 0;
        mode_t old_umask;

        old_umask = umask(0);

        /* Create client tool unix socket */
        client_sock = lttcomm_create_unix_sock(client_unix_sock_path);
        if (client_sock < 0) {
                ERR("Create unix sock failed: %s", client_unix_sock_path);
                ret = -1;
                goto end;
        }

        /* File permission MUST be 660 */
        ret = chmod(client_unix_sock_path, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
        if (ret < 0) {
                ERR("Set file permissions failed: %s", client_unix_sock_path);
                perror("chmod");
                goto end;
        }

        /* Create the application unix socket */
        apps_sock = lttcomm_create_unix_sock(apps_unix_sock_path);
        if (apps_sock < 0) {
                ERR("Create unix sock failed: %s", apps_unix_sock_path);
                ret = -1;
                goto end;
        }

        /* File permission MUST be 666 */
        ret = chmod(apps_unix_sock_path, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
        if (ret < 0) {
                ERR("Set file permissions failed: %s", apps_unix_sock_path);
                perror("chmod");
                goto end;
        }

end:
        umask(old_umask);
        return ret;
}

/*
 *      check_existing_daemon
 *
 *      Check if the global socket is available.
 *  If yes, error is returned.
 */
static int check_existing_daemon()
{
        int ret;

        ret = access(client_unix_sock_path, F_OK);
        if (ret == 0) {
                ret = access(apps_unix_sock_path, F_OK);
        }

        return ret;
}

/*
 *  set_permissions
 *
 *  Set the tracing group gid onto the client socket.
 *
 *  Race window between mkdir and chown is OK because we are going from
 *  more permissive (root.root) to les permissive (root.tracing).
 */
static int set_permissions(void)
{
        int ret;
        struct group *grp;

        /* Decide which group name to use */
        (opt_tracing_group != NULL) ?
                (grp = getgrnam(opt_tracing_group)) :
                (grp = getgrnam(default_tracing_group));

        if (grp == NULL) {
                if (is_root) {
                        WARN("No tracing group detected");
                        ret = 0;
                } else {
                        ERR("Missing tracing group. Aborting execution.");
                        ret = -1;
                }
                goto end;
        }

        /* Set lttng run dir */
        ret = chown(LTTNG_RUNDIR, 0, grp->gr_gid);
        if (ret < 0) {
                ERR("Unable to set group on " LTTNG_RUNDIR);
                perror("chown");
        }

        /* lttng client socket path */
        ret = chown(client_unix_sock_path, 0, grp->gr_gid);
        if (ret < 0) {
                ERR("Unable to set group on %s", client_unix_sock_path);
                perror("chown");
        }

        /* kconsumerd error socket path */
        ret = chown(kconsumerd_err_unix_sock_path, 0, grp->gr_gid);
        if (ret < 0) {
                ERR("Unable to set group on %s", kconsumerd_err_unix_sock_path);
                perror("chown");
        }

        DBG("All permissions are set");

end:
        return ret;
}

/*
 *  create_kernel_poll_pipe
 *
 *  Create the pipe used to wake up the kernel thread.
 */
static int create_kernel_poll_pipe(void)
{
        return pipe2(kernel_poll_pipe, O_CLOEXEC);
}

/*
 *  create_lttng_rundir
 *
 *  Create the lttng run directory needed for all
 *  global sockets and pipe.
 */
static int create_lttng_rundir(void)
{
        int ret;

        ret = mkdir(LTTNG_RUNDIR, S_IRWXU | S_IRWXG );
        if (ret < 0) {
                if (errno != EEXIST) {
                        ERR("Unable to create " LTTNG_RUNDIR);
                        goto error;
                } else {
                        ret = 0;
                }
        }

error:
        return ret;
}

/*
 *  set_kconsumerd_sockets
 *
 *  Setup sockets and directory needed by the kconsumerd
 *  communication with the session daemon.
 */
static int set_kconsumerd_sockets(void)
{
        int ret;

        if (strlen(kconsumerd_err_unix_sock_path) == 0) {
                snprintf(kconsumerd_err_unix_sock_path, PATH_MAX, KCONSUMERD_ERR_SOCK_PATH);
        }

        if (strlen(kconsumerd_cmd_unix_sock_path) == 0) {
                snprintf(kconsumerd_cmd_unix_sock_path, PATH_MAX, KCONSUMERD_CMD_SOCK_PATH);
        }

        ret = mkdir(KCONSUMERD_PATH, S_IRWXU | S_IRWXG);
        if (ret < 0) {
                if (errno != EEXIST) {
                        ERR("Failed to create " KCONSUMERD_PATH);
                        goto error;
                }
                ret = 0;
        }

        /* Create the kconsumerd error unix socket */
        kconsumerd_err_sock = lttcomm_create_unix_sock(kconsumerd_err_unix_sock_path);
        if (kconsumerd_err_sock < 0) {
                ERR("Create unix sock failed: %s", kconsumerd_err_unix_sock_path);
                ret = -1;
                goto error;
        }

        /* File permission MUST be 660 */
        ret = chmod(kconsumerd_err_unix_sock_path, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
        if (ret < 0) {
                ERR("Set file permissions failed: %s", kconsumerd_err_unix_sock_path);
                perror("chmod");
                goto error;
        }

error:
        return ret;
}

/*
 *  sighandler
 *
 *  Signal handler for the daemon
 */
static void sighandler(int sig)
{
        switch (sig) {
                case SIGPIPE:
                        DBG("SIGPIPE catched");
                        return;
                case SIGINT:
                        DBG("SIGINT catched");
                        cleanup();
                        break;
                case SIGTERM:
                        DBG("SIGTERM catched");
                        cleanup();
                        break;
                default:
                        break;
        }

        exit(EXIT_SUCCESS);
}

/*
 *  set_signal_handler
 *
 *  Setup signal handler for :
 *              SIGINT, SIGTERM, SIGPIPE
 */
static int set_signal_handler(void)
{
        int ret = 0;
        struct sigaction sa;
        sigset_t sigset;

        if ((ret = sigemptyset(&sigset)) < 0) {
                perror("sigemptyset");
                return ret;
        }

        sa.sa_handler = sighandler;
        sa.sa_mask = sigset;
        sa.sa_flags = 0;
        if ((ret = sigaction(SIGTERM, &sa, NULL)) < 0) {
                perror("sigaction");
                return ret;
        }

        if ((ret = sigaction(SIGINT, &sa, NULL)) < 0) {
                perror("sigaction");
                return ret;
        }

        if ((ret = sigaction(SIGPIPE, &sa, NULL)) < 0) {
                perror("sigaction");
                return ret;
        }

        DBG("Signal handler set for SIGTERM, SIGPIPE and SIGINT");

        return ret;
}

/*
 *  set_ulimit
 *
 *  Set open files limit to unlimited. This daemon can open a large number of
 *  file descriptors in order to consumer multiple kernel traces.
 */
static void set_ulimit(void)
{
        int ret;
        struct rlimit lim;

        lim.rlim_cur = 65535;
        lim.rlim_max = 65535;

        ret = setrlimit(RLIMIT_NOFILE, &lim);
        if (ret < 0) {
                perror("failed to set open files limit");
        }
}

/*
 * main
 */
int main(int argc, char **argv)
{
        int ret = 0;
        void *status;
        const char *home_path;

        /* Parse arguments */
        progname = argv[0];
        if ((ret = parse_args(argc, argv) < 0)) {
                goto error;
        }

        /* Daemonize */
        if (opt_daemon) {
                ret = daemon(0, 0);
                if (ret < 0) {
                        perror("daemon");
                        goto error;
                }
        }

        /* Check if daemon is UID = 0 */
        is_root = !getuid();

        if (is_root) {
                ret = create_lttng_rundir();
                if (ret < 0) {
                        goto error;
                }

                if (strlen(apps_unix_sock_path) == 0) {
                        snprintf(apps_unix_sock_path, PATH_MAX,
                                        DEFAULT_GLOBAL_APPS_UNIX_SOCK);
                }

                if (strlen(client_unix_sock_path) == 0) {
                        snprintf(client_unix_sock_path, PATH_MAX,
                                        DEFAULT_GLOBAL_CLIENT_UNIX_SOCK);
                }

                ret = set_kconsumerd_sockets();
                if (ret < 0) {
                        goto error;
                }

                /* Setup kernel tracer */
                init_kernel_tracer();

                /* Set ulimit for open files */
                set_ulimit();
        } else {
                home_path = get_home_dir();
                if (home_path == NULL) {
                        ERR("Can't get HOME directory for sockets creation.\n \
                                 Please specify --socket PATH.");
                        goto error;
                }

                if (strlen(apps_unix_sock_path) == 0) {
                        snprintf(apps_unix_sock_path, PATH_MAX,
                                        DEFAULT_HOME_APPS_UNIX_SOCK, home_path);
                }

                /* Set the cli tool unix socket path */
                if (strlen(client_unix_sock_path) == 0) {
                        snprintf(client_unix_sock_path, PATH_MAX,
                                        DEFAULT_HOME_CLIENT_UNIX_SOCK, home_path);
                }
        }

        DBG("Client socket path %s", client_unix_sock_path);
        DBG("Application socket path %s", apps_unix_sock_path);

        /* See if daemon already exist. If any of the two
         * socket needed by the daemon are present, this test fails
         */
        if ((ret = check_existing_daemon()) == 0) {
                ERR("Already running daemon.\n");
                /* We do not goto error because we must not
                 * cleanup() because a daemon is already running.
                 */
                exit(EXIT_FAILURE);
        }

        if (set_signal_handler() < 0) {
                goto error;
        }

        /* Setup the needed unix socket */
        if (init_daemon_socket() < 0) {
                goto error;
        }

        /* Set credentials to socket */
        if (is_root && (set_permissions() < 0)) {
                goto error;
        }

        /* Get parent pid if -S, --sig-parent is specified. */
        if (opt_sig_parent) {
                ppid = getppid();
        }

        /* Setup the kernel pipe for waking up the kernel thread */
        if (create_kernel_poll_pipe() < 0) {
                goto error;
        }

        while (1) {
                /* Create thread to manage the client socket */
                ret = pthread_create(&client_thread, NULL, thread_manage_clients, (void *) NULL);
                if (ret != 0) {
                        perror("pthread_create");
                        goto error;
                }

                /* Create thread to manage application socket */
                ret = pthread_create(&apps_thread, NULL, thread_manage_apps, (void *) NULL);
                if (ret != 0) {
                        perror("pthread_create");
                        goto error;
                }

                /* Create kernel thread to manage kernel event */
                ret = pthread_create(&kernel_thread, NULL, thread_manage_kernel, (void *) NULL);
                if (ret != 0) {
                        perror("pthread_create");
                        goto error;
                }

                ret = pthread_join(client_thread, &status);
                if (ret != 0) {
                        perror("pthread_join");
                        goto error;
                }
        }

        cleanup();
        exit(EXIT_SUCCESS);

error:
        cleanup();
        exit(EXIT_FAILURE);
}