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  * The session list count CANNOT be decremented, as it is used as unique
  68  * identifier for the session in UST app hash table lookups.
  69  */
  70 static void del_session_list(struct ltt_session *ls)
  71 {
  72         cds_list_del(&ls->list);
  73 }
  74
  75 /*
  76  * Return a pointer to the session list.
  77  */
  78 struct ltt_session_list *session_get_list(void)
  79 {
  80         return &ltt_session_list;
  81 }
  82
  83 /*
  84  * Acquire session list lock
  85  */
  86 void session_lock_list(void)
  87 {
  88         pthread_mutex_lock(&ltt_session_list.lock);
  89 }
  90
  91 /*
  92  * Release session list lock
  93  */
  94 void session_unlock_list(void)
  95 {
  96         pthread_mutex_unlock(&ltt_session_list.lock);
  97 }
  98
  99 /*
 100  * Acquire session lock
 101  */
 102 void session_lock(struct ltt_session *session)
 103 {
 104         pthread_mutex_lock(&session->lock);
 105 }
 106
 107 /*
 108  * Release session lock
 109  */
 110 void session_unlock(struct ltt_session *session)
 111 {
 112         pthread_mutex_unlock(&session->lock);
 113 }
 114
 115 /*
 116  * Return a ltt_session structure ptr that matches name. If no session found,
 117  * NULL is returned. This must be called with the session lock held using
 118  * session_lock_list and session_unlock_list.
 119  */
 120 struct ltt_session *session_find_by_name(char *name)
 121 {
 122         struct ltt_session *iter;
 123
 124         DBG2("Trying to find session by name %s", name);
 125
 126         cds_list_for_each_entry(iter, &ltt_session_list.head, list) {
 127                 if (strncmp(iter->name, name, NAME_MAX) == 0) {
 128                         goto found;
 129                 }
 130         }
 131
 132         iter = NULL;
 133
 134 found:
 135         return iter;
 136 }
 137
 138 /*
 139  * Delete session from the session list and free the memory.
 140  *
 141  * Return -1 if no session is found.  On success, return 1;
 142  */
 143 int session_destroy(struct ltt_session *session)
 144 {
 145         /* Safety check */
 146         if (session == NULL) {
 147                 ERR("Session pointer was null on session destroy");
 148                 return LTTCOMM_OK;
 149         }
 150
 151         DBG("Destroying session %s", session->name);
 152         del_session_list(session);
 153         pthread_mutex_destroy(&session->lock);
 154         free(session);
 155
 156         return LTTCOMM_OK;
 157 }
 158
 159 /*
 160  * Create a brand new session and add it to the session list.
 161  */
 162 int session_create(char *name, char *path, uid_t uid, gid_t gid)
 163 {
 164         int ret;
 165         struct ltt_session *new_session;
 166
 167         new_session = session_find_by_name(name);
 168         if (new_session != NULL) {
 169                 ret = LTTCOMM_EXIST_SESS;
 170                 goto error_exist;
 171         }
 172
 173         /* Allocate session data structure */
 174         new_session = zmalloc(sizeof(struct ltt_session));
 175         if (new_session == NULL) {
 176                 PERROR("zmalloc");
 177                 ret = LTTCOMM_FATAL;
 178                 goto error_malloc;
 179         }
 180
 181         /* Define session name */
 182         if (name != NULL) {
 183                 if (snprintf(new_session->name, NAME_MAX, "%s", name) < 0) {
 184                         ret = LTTCOMM_FATAL;
 185                         goto error_asprintf;
 186                 }
 187         } else {
 188                 ERR("No session name given");
 189                 ret = LTTCOMM_FATAL;
 190                 goto error;
 191         }
 192
 193         /* Define session system path */
 194         if (path != NULL) {
 195                 if (snprintf(new_session->path, PATH_MAX, "%s", path) < 0) {
 196                         ret = LTTCOMM_FATAL;
 197                         goto error_asprintf;
 198                 }
 199         } else {
 200                 ERR("No session path given");
 201                 ret = LTTCOMM_FATAL;
 202                 goto error;
 203         }
 204
 205         /* Init kernel session */
 206         new_session->kernel_session = NULL;
 207         new_session->ust_session = NULL;
 208
 209         /* Init lock */
 210         pthread_mutex_init(&new_session->lock, NULL);
 211
 212         new_session->uid = uid;
 213         new_session->gid = gid;
 214
 215         ret = run_as_mkdir_recursive(new_session->path, S_IRWXU | S_IRWXG,
 216                         new_session->uid, new_session->gid);
 217         if (ret < 0) {
 218                 if (ret != -EEXIST) {
 219                         ERR("Trace directory creation error");
 220                         ret = LTTCOMM_CREATE_DIR_FAIL;
 221                         goto error;
 222                 }
 223         }
 224
 225         /* Add new session to the session list */
 226         session_lock_list();
 227         new_session->id = add_session_list(new_session);
 228         session_unlock_list();
 229
 230         DBG("Tracing session %s created in %s with ID %u by UID %d GID %d",
 231                 name, path, new_session->id,
 232                 new_session->uid, new_session->gid);
 233
 234         return LTTCOMM_OK;
 235
 236 error:
 237 error_asprintf:
 238         if (new_session != NULL) {
 239                 free(new_session);
 240         }
 241
 242 error_exist:
 243 error_malloc:
 244         return ret;
 245 }