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 modify
   5  * it under the terms of the GNU General Public License, version 2 only,
   6  * as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  16  */
  17
  18 #define _GNU_SOURCE
  19 #include <limits.h>
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <sys/stat.h>
  24 #include <urcu.h>
  25
  26 #include <common/common.h>
  27 #include <common/sessiond-comm/sessiond-comm.h>
  28
  29 #include "session.h"
  30
  31 /*
  32  * NOTES:
  33  *
  34  * No ltt_session.lock is taken here because those data structure are widely
  35  * spread across the lttng-tools code base so before caling functions below
  36  * that can read/write a session, the caller MUST acquire the session lock
  37  * using session_lock() and session_unlock().
  38  */
  39
  40 /*
  41  * Init tracing session list.
  42  *
  43  * Please see session.h for more explanation and correct usage of the list.
  44  */
  45 static struct ltt_session_list ltt_session_list = {
  46         .head = CDS_LIST_HEAD_INIT(ltt_session_list.head),
  47         .lock = PTHREAD_MUTEX_INITIALIZER,
  48         .count = 0,
  49 };
  50
  51 /*
  52  * Add a ltt_session structure to the global list.
  53  *
  54  * The caller MUST acquire the session list lock before.
  55  * Returns the unique identifier for the session.
  56  */
  57 static unsigned int add_session_list(struct ltt_session *ls)
  58 {
  59         cds_list_add(&ls->list, &ltt_session_list.head);
  60         return ++ltt_session_list.count;
  61 }
  62
  63 /*
  64  * Delete a ltt_session structure to the global list.
  65  *
  66  * The caller MUST acquire the session list lock before.
  67  */
  68 static void del_session_list(struct ltt_session *ls)
  69 {
  70         cds_list_del(&ls->list);
  71         /* Sanity check */
  72         if (ltt_session_list.count > 0) {
  73                 ltt_session_list.count--;
  74         }
  75 }
  76
  77 /*
  78  * Return a pointer to the session list.
  79  */
  80 struct ltt_session_list *session_get_list(void)
  81 {
  82         return &ltt_session_list;
  83 }
  84
  85 /*
  86  * Acquire session list lock
  87  */
  88 void session_lock_list(void)
  89 {
  90         pthread_mutex_lock(&ltt_session_list.lock);
  91 }
  92
  93 /*
  94  * Release session list lock
  95  */
  96 void session_unlock_list(void)
  97 {
  98         pthread_mutex_unlock(&ltt_session_list.lock);
  99 }
 100
 101 /*
 102  * Acquire session lock
 103  */
 104 void session_lock(struct ltt_session *session)
 105 {
 106         pthread_mutex_lock(&session->lock);
 107 }
 108
 109 /*
 110  * Release session lock
 111  */
 112 void session_unlock(struct ltt_session *session)
 113 {
 114         pthread_mutex_unlock(&session->lock);
 115 }
 116
 117 /*
 118  * Return a ltt_session structure ptr that matches name. If no session found,
 119  * NULL is returned. This must be called with the session lock held using
 120  * session_lock_list and session_unlock_list.
 121  */
 122 struct ltt_session *session_find_by_name(char *name)
 123 {
 124         struct ltt_session *iter;
 125
 126         DBG2("Trying to find session by name %s", name);
 127
 128         cds_list_for_each_entry(iter, &ltt_session_list.head, list) {
 129                 if (strncmp(iter->name, name, NAME_MAX) == 0) {
 130                         goto found;
 131                 }
 132         }
 133
 134         iter = NULL;
 135
 136 found:
 137         return iter;
 138 }
 139
 140 /*
 141  * Delete session from the session list and free the memory.
 142  *
 143  * Return -1 if no session is found.  On success, return 1;
 144  */
 145 int session_destroy(struct ltt_session *session)
 146 {
 147         /* Safety check */
 148         if (session == NULL) {
 149                 ERR("Session pointer was null on session destroy");
 150                 return LTTCOMM_OK;
 151         }
 152
 153         DBG("Destroying session %s", session->name);
 154         del_session_list(session);
 155         pthread_mutex_destroy(&session->lock);
 156         free(session);
 157
 158         return LTTCOMM_OK;
 159 }
 160
 161 /*
 162  * Create a brand new session and add it to the session list.
 163  */
 164 int session_create(char *name, char *path, uid_t uid, gid_t gid)
 165 {
 166         int ret;
 167         struct ltt_session *new_session;
 168
 169         new_session = session_find_by_name(name);
 170         if (new_session != NULL) {
 171                 ret = LTTCOMM_EXIST_SESS;
 172                 goto error_exist;
 173         }
 174
 175         /* Allocate session data structure */
 176         new_session = zmalloc(sizeof(struct ltt_session));
 177         if (new_session == NULL) {
 178                 PERROR("zmalloc");
 179                 ret = LTTCOMM_FATAL;
 180                 goto error_malloc;
 181         }
 182
 183         /* Define session name */
 184         if (name != NULL) {
 185                 if (snprintf(new_session->name, NAME_MAX, "%s", name) < 0) {
 186                         ret = LTTCOMM_FATAL;
 187                         goto error_asprintf;
 188                 }
 189         } else {
 190                 ERR("No session name given");
 191                 ret = LTTCOMM_FATAL;
 192                 goto error;
 193         }
 194
 195         /* Define session system path */
 196         if (path != NULL) {
 197                 if (snprintf(new_session->path, PATH_MAX, "%s", path) < 0) {
 198                         ret = LTTCOMM_FATAL;
 199                         goto error_asprintf;
 200                 }
 201         } else {
 202                 ERR("No session path given");
 203                 ret = LTTCOMM_FATAL;
 204                 goto error;
 205         }
 206
 207         /* Init kernel session */
 208         new_session->kernel_session = NULL;
 209         new_session->ust_session = NULL;
 210
 211         /* Init lock */
 212         pthread_mutex_init(&new_session->lock, NULL);
 213
 214         new_session->uid = uid;
 215         new_session->gid = gid;
 216
 217         ret = run_as_mkdir_recursive(new_session->path, S_IRWXU | S_IRWXG,
 218                         new_session->uid, new_session->gid);
 219         if (ret < 0) {
 220                 if (ret != -EEXIST) {
 221                         ERR("Trace directory creation error");
 222                         ret = LTTCOMM_CREATE_DIR_FAIL;
 223                         goto error;
 224                 }
 225         }
 226
 227         /* Add new session to the session list */
 228         session_lock_list();
 229         new_session->id = add_session_list(new_session);
 230         session_unlock_list();
 231
 232         DBG("Tracing session %s created in %s with ID %u by UID %d GID %d",
 233                 name, path, new_session->id,
 234                 new_session->uid, new_session->gid);
 235
 236         return LTTCOMM_OK;
 237
 238 error:
 239 error_asprintf:
 240         if (new_session != NULL) {
 241                 free(new_session);
 242         }
 243
 244 error_exist:
 245 error_malloc:
 246         return ret;
 247 }