lttng-sessiond/session.c

   1 /*
   2  * Copyright (C)  2011 - David Goulet <david.goulet@polymtl.ca>
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; only version 2
   7  * of the License.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  17  */
  18
  19 #define _GNU_SOURCE
  20 #include <limits.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <sys/stat.h>
  25 #include <sys/types.h>
  26 #include <urcu.h>
  27
  28 #include <lttng-sessiond-comm.h>
  29 #include <lttngerr.h>
  30 #include <runas.h>
  31
  32 #include "hashtable.h"
  33 #include "session.h"
  34
  35 #include "../hashtable/hash.h"
  36
  37 /*
  38  * NOTES:
  39  *
  40  * No ltt_session.lock is taken here because those data structure are widely
  41  * spread across the lttng-tools code base so before caling functions below
  42  * that can read/write a session, the caller MUST acquire the session lock
  43  * using session_lock() and session_unlock().
  44  */
  45
  46 /*
  47  * Init tracing session list.
  48  *
  49  * Please see session.h for more explanation and correct usage of the list.
  50  */
  51 static struct ltt_session_list ltt_session_list = {
  52         .head = CDS_LIST_HEAD_INIT(ltt_session_list.head),
  53         .lock = PTHREAD_MUTEX_INITIALIZER,
  54         .count = 0,
  55 };
  56
  57 /*
  58  * Add a ltt_session structure to the global list.
  59  *
  60  * The caller MUST acquire the session list lock before.
  61  * Returns the unique identifier for the session.
  62  */
  63 static int add_session_list(struct ltt_session *ls)
  64 {
  65         cds_list_add(&ls->list, &ltt_session_list.head);
  66         return ++ltt_session_list.count;
  67 }
  68
  69 /*
  70  * Delete a ltt_session structure to the global list.
  71  *
  72  * The caller MUST acquire the session list lock before.
  73  */
  74 static void del_session_list(struct ltt_session *ls)
  75 {
  76         cds_list_del(&ls->list);
  77         /* Sanity check */
  78         if (ltt_session_list.count > 0) {
  79                 ltt_session_list.count--;
  80         }
  81 }
  82
  83 /*
  84  * Return a pointer to the session list.
  85  */
  86 struct ltt_session_list *session_get_list(void)
  87 {
  88         return &ltt_session_list;
  89 }
  90
  91 /*
  92  * Acquire session list lock
  93  */
  94 void session_lock_list(void)
  95 {
  96         pthread_mutex_lock(&ltt_session_list.lock);
  97 }
  98
  99 /*
 100  * Release session list lock
 101  */
 102 void session_unlock_list(void)
 103 {
 104         pthread_mutex_unlock(&ltt_session_list.lock);
 105 }
 106
 107 /*
 108  * Acquire session lock
 109  */
 110 void session_lock(struct ltt_session *session)
 111 {
 112         pthread_mutex_lock(&session->lock);
 113 }
 114
 115 /*
 116  * Release session lock
 117  */
 118 void session_unlock(struct ltt_session *session)
 119 {
 120         pthread_mutex_unlock(&session->lock);
 121 }
 122
 123 /*
 124  * Return a ltt_session structure ptr that matches name. If no session found,
 125  * NULL is returned. This must be called with the session lock held using
 126  * session_lock_list and session_unlock_list.
 127  */
 128 struct ltt_session *session_find_by_name(char *name)
 129 {
 130         struct ltt_session *iter;
 131
 132         DBG2("Trying to find session by name %s", name);
 133
 134         cds_list_for_each_entry(iter, &ltt_session_list.head, list) {
 135                 if (strncmp(iter->name, name, NAME_MAX) == 0) {
 136                         goto found;
 137                 }
 138         }
 139
 140         iter = NULL;
 141
 142 found:
 143         return iter;
 144 }
 145
 146 /*
 147  * Delete session from the session list and free the memory.
 148  *
 149  * Return -1 if no session is found.  On success, return 1;
 150  */
 151 int session_destroy(struct ltt_session *session)
 152 {
 153         /* Safety check */
 154         if (session == NULL) {
 155                 ERR("Session pointer was null on session destroy");
 156                 return LTTCOMM_OK;
 157         }
 158
 159         DBG("Destroying session %s", session->name);
 160         del_session_list(session);
 161         pthread_mutex_destroy(&session->lock);
 162         free(session);
 163
 164         return LTTCOMM_OK;
 165 }
 166
 167 /*
 168  * Create a brand new session and add it to the session list.
 169  */
 170 int session_create(char *name, char *path, uid_t uid, gid_t gid)
 171 {
 172         int ret;
 173         struct ltt_session *new_session;
 174
 175         new_session = session_find_by_name(name);
 176         if (new_session != NULL) {
 177                 ret = LTTCOMM_EXIST_SESS;
 178                 goto error_exist;
 179         }
 180
 181         /* Allocate session data structure */
 182         new_session = zmalloc(sizeof(struct ltt_session));
 183         if (new_session == NULL) {
 184                 perror("zmalloc");
 185                 ret = LTTCOMM_FATAL;
 186                 goto error_malloc;
 187         }
 188
 189         /* Define session name */
 190         if (name != NULL) {
 191                 if (snprintf(new_session->name, NAME_MAX, "%s", name) < 0) {
 192                         ret = LTTCOMM_FATAL;
 193                         goto error_asprintf;
 194                 }
 195         } else {
 196                 ERR("No session name given");
 197                 ret = LTTCOMM_FATAL;
 198                 goto error;
 199         }
 200
 201         /* Define session system path */
 202         if (path != NULL) {
 203                 if (snprintf(new_session->path, PATH_MAX, "%s", path) < 0) {
 204                         ret = LTTCOMM_FATAL;
 205                         goto error_asprintf;
 206                 }
 207         } else {
 208                 ERR("No session path given");
 209                 ret = LTTCOMM_FATAL;
 210                 goto error;
 211         }
 212
 213         /* Init kernel session */
 214         new_session->kernel_session = NULL;
 215         new_session->ust_session = NULL;
 216
 217         /* Init lock */
 218         pthread_mutex_init(&new_session->lock, NULL);
 219
 220         new_session->uid = uid;
 221         new_session->gid = gid;
 222
 223         ret = mkdir_recursive_run_as(new_session->path, S_IRWXU | S_IRWXG,
 224                         new_session->uid, new_session->gid);
 225         if (ret < 0) {
 226                 if (ret != -EEXIST) {
 227                         ERR("Trace directory creation error");
 228                         ret = LTTCOMM_CREATE_FAIL;
 229                         goto error;
 230                 }
 231         }
 232
 233         /* Add new session to the session list */
 234         session_lock_list();
 235         new_session->id = add_session_list(new_session);
 236         session_unlock_list();
 237
 238         DBG("Tracing session %s created in %s with ID %d by UID %d GID %d",
 239                 name, path, new_session->id,
 240                 new_session->uid, new_session->gid);
 241
 242         return LTTCOMM_OK;
 243
 244 error:
 245 error_asprintf:
 246         if (new_session != NULL) {
 247                 free(new_session);
 248         }
 249
 250 error_exist:
 251 error_malloc:
 252         return ret;
 253 }