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 "../common/hashtable.h"
  33 #include "session.h"
  34
  35 /*
  36  * NOTES:
  37  *
  38  * No ltt_session.lock is taken here because those data structure are widely
  39  * spread across the lttng-tools code base so before caling functions below
  40  * that can read/write a session, the caller MUST acquire the session lock
  41  * using session_lock() and session_unlock().
  42  */
  43
  44 /*
  45  * Init tracing session list.
  46  *
  47  * Please see session.h for more explanation and correct usage of the list.
  48  */
  49 static struct ltt_session_list ltt_session_list = {
  50         .head = CDS_LIST_HEAD_INIT(ltt_session_list.head),
  51         .lock = PTHREAD_MUTEX_INITIALIZER,
  52         .count = 0,
  53 };
  54
  55 /*
  56  * Add a ltt_session structure to the global list.
  57  *
  58  * The caller MUST acquire the session list lock before.
  59  * Returns the unique identifier for the session.
  60  */
  61 static int add_session_list(struct ltt_session *ls)
  62 {
  63         cds_list_add(&ls->list, &ltt_session_list.head);
  64         return ++ltt_session_list.count;
  65 }
  66
  67 /*
  68  * Delete a ltt_session structure to the global list.
  69  *
  70  * The caller MUST acquire the session list lock before.
  71  */
  72 static void del_session_list(struct ltt_session *ls)
  73 {
  74         cds_list_del(&ls->list);
  75         /* Sanity check */
  76         if (ltt_session_list.count > 0) {
  77                 ltt_session_list.count--;
  78         }
  79 }
  80
  81 /*
  82  * Return a pointer to the session list.
  83  */
  84 struct ltt_session_list *session_get_list(void)
  85 {
  86         return &ltt_session_list;
  87 }
  88
  89 /*
  90  * Acquire session list lock
  91  */
  92 void session_lock_list(void)
  93 {
  94         pthread_mutex_lock(&ltt_session_list.lock);
  95 }
  96
  97 /*
  98  * Release session list lock
  99  */
 100 void session_unlock_list(void)
 101 {
 102         pthread_mutex_unlock(&ltt_session_list.lock);
 103 }
 104
 105 /*
 106  * Acquire session lock
 107  */
 108 void session_lock(struct ltt_session *session)
 109 {
 110         pthread_mutex_lock(&session->lock);
 111 }
 112
 113 /*
 114  * Release session lock
 115  */
 116 void session_unlock(struct ltt_session *session)
 117 {
 118         pthread_mutex_unlock(&session->lock);
 119 }
 120
 121 /*
 122  * Return a ltt_session structure ptr that matches name. If no session found,
 123  * NULL is returned. This must be called with the session lock held using
 124  * session_lock_list and session_unlock_list.
 125  */
 126 struct ltt_session *session_find_by_name(char *name)
 127 {
 128         struct ltt_session *iter;
 129
 130         DBG2("Trying to find session by name %s", name);
 131
 132         cds_list_for_each_entry(iter, &ltt_session_list.head, list) {
 133                 if (strncmp(iter->name, name, NAME_MAX) == 0) {
 134                         goto found;
 135                 }
 136         }
 137
 138         iter = NULL;
 139
 140 found:
 141         return iter;
 142 }
 143
 144 /*
 145  * Delete session from the session list and free the memory.
 146  *
 147  * Return -1 if no session is found.  On success, return 1;
 148  */
 149 int session_destroy(struct ltt_session *session)
 150 {
 151         /* Safety check */
 152         if (session == NULL) {
 153                 ERR("Session pointer was null on session destroy");
 154                 return LTTCOMM_OK;
 155         }
 156
 157         DBG("Destroying session %s", session->name);
 158         del_session_list(session);
 159         pthread_mutex_destroy(&session->lock);
 160         free(session);
 161
 162         return LTTCOMM_OK;
 163 }
 164
 165 /*
 166  * Create a brand new session and add it to the session list.
 167  */
 168 int session_create(char *name, char *path, uid_t uid, gid_t gid)
 169 {
 170         int ret;
 171         struct ltt_session *new_session;
 172
 173         new_session = session_find_by_name(name);
 174         if (new_session != NULL) {
 175                 ret = LTTCOMM_EXIST_SESS;
 176                 goto error_exist;
 177         }
 178
 179         /* Allocate session data structure */
 180         new_session = zmalloc(sizeof(struct ltt_session));
 181         if (new_session == NULL) {
 182                 perror("zmalloc");
 183                 ret = LTTCOMM_FATAL;
 184                 goto error_malloc;
 185         }
 186
 187         /* Define session name */
 188         if (name != NULL) {
 189                 if (snprintf(new_session->name, NAME_MAX, "%s", name) < 0) {
 190                         ret = LTTCOMM_FATAL;
 191                         goto error_asprintf;
 192                 }
 193         } else {
 194                 ERR("No session name given");
 195                 ret = LTTCOMM_FATAL;
 196                 goto error;
 197         }
 198
 199         /* Define session system path */
 200         if (path != NULL) {
 201                 if (snprintf(new_session->path, PATH_MAX, "%s", path) < 0) {
 202                         ret = LTTCOMM_FATAL;
 203                         goto error_asprintf;
 204                 }
 205         } else {
 206                 ERR("No session path given");
 207                 ret = LTTCOMM_FATAL;
 208                 goto error;
 209         }
 210
 211         /* Init kernel session */
 212         new_session->kernel_session = NULL;
 213         new_session->ust_session = NULL;
 214
 215         /* Init lock */
 216         pthread_mutex_init(&new_session->lock, NULL);
 217
 218         new_session->uid = uid;
 219         new_session->gid = gid;
 220
 221         ret = mkdir_recursive_run_as(new_session->path, S_IRWXU | S_IRWXG,
 222                         new_session->uid, new_session->gid);
 223         if (ret < 0) {
 224                 if (ret != -EEXIST) {
 225                         ERR("Trace directory creation error");
 226                         ret = LTTCOMM_CREATE_FAIL;
 227                         goto error;
 228                 }
 229         }
 230
 231         /* Add new session to the session list */
 232         session_lock_list();
 233         new_session->id = add_session_list(new_session);
 234         session_unlock_list();
 235
 236         DBG("Tracing session %s created in %s with ID %d by UID %d GID %d",
 237                 name, path, new_session->id,
 238                 new_session->uid, new_session->gid);
 239
 240         return LTTCOMM_OK;
 241
 242 error:
 243 error_asprintf:
 244         if (new_session != NULL) {
 245                 free(new_session);
 246         }
 247
 248 error_exist:
 249 error_malloc:
 250         return ret;
 251 }