src/bin/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 <common/common.h>
  29 #include <common/sessiond-comm/sessiond-comm.h>
  30
  31 #include "session.h"
  32
  33 /*
  34  * NOTES:
  35  *
  36  * No ltt_session.lock is taken here because those data structure are widely
  37  * spread across the lttng-tools code base so before caling functions below
  38  * that can read/write a session, the caller MUST acquire the session lock
  39  * using session_lock() and session_unlock().
  40  */
  41
  42 /*
  43  * Init tracing session list.
  44  *
  45  * Please see session.h for more explanation and correct usage of the list.
  46  */
  47 static struct ltt_session_list ltt_session_list = {
  48         .head = CDS_LIST_HEAD_INIT(ltt_session_list.head),
  49         .lock = PTHREAD_MUTEX_INITIALIZER,
  50         .count = 0,
  51 };
  52
  53 /*
  54  * Add a ltt_session structure to the global list.
  55  *
  56  * The caller MUST acquire the session list lock before.
  57  * Returns the unique identifier for the session.
  58  */
  59 static int add_session_list(struct ltt_session *ls)
  60 {
  61         cds_list_add(&ls->list, &ltt_session_list.head);
  62         return ++ltt_session_list.count;
  63 }
  64
  65 /*
  66  * Delete a ltt_session structure to the global list.
  67  *
  68  * The caller MUST acquire the session list lock before.
  69  */
  70 static void del_session_list(struct ltt_session *ls)
  71 {
  72         cds_list_del(&ls->list);
  73         /* Sanity check */
  74         if (ltt_session_list.count > 0) {
  75                 ltt_session_list.count--;
  76         }
  77 }
  78
  79 /*
  80  * Return a pointer to the session list.
  81  */
  82 struct ltt_session_list *session_get_list(void)
  83 {
  84         return &ltt_session_list;
  85 }
  86
  87 /*
  88  * Acquire session list lock
  89  */
  90 void session_lock_list(void)
  91 {
  92         pthread_mutex_lock(&ltt_session_list.lock);
  93 }
  94
  95 /*
  96  * Release session list lock
  97  */
  98 void session_unlock_list(void)
  99 {
 100         pthread_mutex_unlock(&ltt_session_list.lock);
 101 }
 102
 103 /*
 104  * Acquire session lock
 105  */
 106 void session_lock(struct ltt_session *session)
 107 {
 108         pthread_mutex_lock(&session->lock);
 109 }
 110
 111 /*
 112  * Release session lock
 113  */
 114 void session_unlock(struct ltt_session *session)
 115 {
 116         pthread_mutex_unlock(&session->lock);
 117 }
 118
 119 /*
 120  * Return a ltt_session structure ptr that matches name. If no session found,
 121  * NULL is returned. This must be called with the session lock held using
 122  * session_lock_list and session_unlock_list.
 123  */
 124 struct ltt_session *session_find_by_name(char *name)
 125 {
 126         struct ltt_session *iter;
 127
 128         DBG2("Trying to find session by name %s", name);
 129
 130         cds_list_for_each_entry(iter, &ltt_session_list.head, list) {
 131                 if (strncmp(iter->name, name, NAME_MAX) == 0) {
 132                         goto found;
 133                 }
 134         }
 135
 136         iter = NULL;
 137
 138 found:
 139         return iter;
 140 }
 141
 142 /*
 143  * Delete session from the session list and free the memory.
 144  *
 145  * Return -1 if no session is found.  On success, return 1;
 146  */
 147 int session_destroy(struct ltt_session *session)
 148 {
 149         /* Safety check */
 150         if (session == NULL) {
 151                 ERR("Session pointer was null on session destroy");
 152                 return LTTCOMM_OK;
 153         }
 154
 155         DBG("Destroying session %s", session->name);
 156         del_session_list(session);
 157         pthread_mutex_destroy(&session->lock);
 158         free(session);
 159
 160         return LTTCOMM_OK;
 161 }
 162
 163 /*
 164  * Create a brand new session and add it to the session list.
 165  */
 166 int session_create(char *name, char *path, uid_t uid, gid_t gid)
 167 {
 168         int ret;
 169         struct ltt_session *new_session;
 170
 171         new_session = session_find_by_name(name);
 172         if (new_session != NULL) {
 173                 ret = LTTCOMM_EXIST_SESS;
 174                 goto error_exist;
 175         }
 176
 177         /* Allocate session data structure */
 178         new_session = zmalloc(sizeof(struct ltt_session));
 179         if (new_session == NULL) {
 180                 PERROR("zmalloc");
 181                 ret = LTTCOMM_FATAL;
 182                 goto error_malloc;
 183         }
 184
 185         /* Define session name */
 186         if (name != NULL) {
 187                 if (snprintf(new_session->name, NAME_MAX, "%s", name) < 0) {
 188                         ret = LTTCOMM_FATAL;
 189                         goto error_asprintf;
 190                 }
 191         } else {
 192                 ERR("No session name given");
 193                 ret = LTTCOMM_FATAL;
 194                 goto error;
 195         }
 196
 197         /* Define session system path */
 198         if (path != NULL) {
 199                 if (snprintf(new_session->path, PATH_MAX, "%s", path) < 0) {
 200                         ret = LTTCOMM_FATAL;
 201                         goto error_asprintf;
 202                 }
 203         } else {
 204                 ERR("No session path given");
 205                 ret = LTTCOMM_FATAL;
 206                 goto error;
 207         }
 208
 209         /* Init kernel session */
 210         new_session->kernel_session = NULL;
 211         new_session->ust_session = NULL;
 212
 213         /* Init lock */
 214         pthread_mutex_init(&new_session->lock, NULL);
 215
 216         new_session->uid = uid;
 217         new_session->gid = gid;
 218
 219         ret = run_as_mkdir_recursive(new_session->path, S_IRWXU | S_IRWXG,
 220                         new_session->uid, new_session->gid);
 221         if (ret < 0) {
 222                 if (ret != -EEXIST) {
 223                         ERR("Trace directory creation error");
 224                         ret = LTTCOMM_CREATE_DIR_FAIL;
 225                         goto error;
 226                 }
 227         }
 228
 229         /* Add new session to the session list */
 230         session_lock_list();
 231         new_session->id = add_session_list(new_session);
 232         session_unlock_list();
 233
 234         DBG("Tracing session %s created in %s with ID %d by UID %d GID %d",
 235                 name, path, new_session->id,
 236                 new_session->uid, new_session->gid);
 237
 238         return LTTCOMM_OK;
 239
 240 error:
 241 error_asprintf:
 242         if (new_session != NULL) {
 243                 free(new_session);
 244         }
 245
 246 error_exist:
 247 error_malloc:
 248         return ret;
 249 }