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 <sys/types.h>
  25 #include <urcu.h>
  26
  27 #include <common/common.h>
  28 #include <common/sessiond-comm/sessiond-comm.h>
  29
  30 #include "session.h"
  31
  32 /*
  33  * NOTES:
  34  *
  35  * No ltt_session.lock is taken here because those data structure are widely
  36  * spread across the lttng-tools code base so before caling functions below
  37  * that can read/write a session, the caller MUST acquire the session lock
  38  * using session_lock() and session_unlock().
  39  */
  40
  41 /*
  42  * Init tracing session list.
  43  *
  44  * Please see session.h for more explanation and correct usage of the list.
  45  */
  46 static struct ltt_session_list ltt_session_list = {
  47         .head = CDS_LIST_HEAD_INIT(ltt_session_list.head),
  48         .lock = PTHREAD_MUTEX_INITIALIZER,
  49         .count = 0,
  50 };
  51
  52 /*
  53  * Add a ltt_session structure to the global list.
  54  *
  55  * The caller MUST acquire the session list lock before.
  56  * Returns the unique identifier for the session.
  57  */
  58 static int add_session_list(struct ltt_session *ls)
  59 {
  60         cds_list_add(&ls->list, &ltt_session_list.head);
  61         return ++ltt_session_list.count;
  62 }
  63
  64 /*
  65  * Delete a ltt_session structure to the global list.
  66  *
  67  * The caller MUST acquire the session list lock before.
  68  */
  69 static void del_session_list(struct ltt_session *ls)
  70 {
  71         cds_list_del(&ls->list);
  72         /* Sanity check */
  73         if (ltt_session_list.count > 0) {
  74                 ltt_session_list.count--;
  75         }
  76 }
  77
  78 /*
  79  * Return a pointer to the session list.
  80  */
  81 struct ltt_session_list *session_get_list(void)
  82 {
  83         return &ltt_session_list;
  84 }
  85
  86 /*
  87  * Acquire session list lock
  88  */
  89 void session_lock_list(void)
  90 {
  91         pthread_mutex_lock(&ltt_session_list.lock);
  92 }
  93
  94 /*
  95  * Release session list lock
  96  */
  97 void session_unlock_list(void)
  98 {
  99         pthread_mutex_unlock(&ltt_session_list.lock);
 100 }
 101
 102 /*
 103  * Acquire session lock
 104  */
 105 void session_lock(struct ltt_session *session)
 106 {
 107         pthread_mutex_lock(&session->lock);
 108 }
 109
 110 /*
 111  * Release session lock
 112  */
 113 void session_unlock(struct ltt_session *session)
 114 {
 115         pthread_mutex_unlock(&session->lock);
 116 }
 117
 118 /*
 119  * Return a ltt_session structure ptr that matches name. If no session found,
 120  * NULL is returned. This must be called with the session lock held using
 121  * session_lock_list and session_unlock_list.
 122  */
 123 struct ltt_session *session_find_by_name(char *name)
 124 {
 125         struct ltt_session *iter;
 126
 127         DBG2("Trying to find session by name %s", name);
 128
 129         cds_list_for_each_entry(iter, &ltt_session_list.head, list) {
 130                 if (strncmp(iter->name, name, NAME_MAX) == 0) {
 131                         goto found;
 132                 }
 133         }
 134
 135         iter = NULL;
 136
 137 found:
 138         return iter;
 139 }
 140
 141 /*
 142  * Delete session from the session list and free the memory.
 143  *
 144  * Return -1 if no session is found.  On success, return 1;
 145  */
 146 int session_destroy(struct ltt_session *session)
 147 {
 148         /* Safety check */
 149         if (session == NULL) {
 150                 ERR("Session pointer was null on session destroy");
 151                 return LTTCOMM_OK;
 152         }
 153
 154         DBG("Destroying session %s", session->name);
 155         del_session_list(session);
 156         pthread_mutex_destroy(&session->lock);
 157         free(session);
 158
 159         return LTTCOMM_OK;
 160 }
 161
 162 /*
 163  * Create a brand new session and add it to the session list.
 164  */
 165 int session_create(char *name, char *path, uid_t uid, gid_t gid)
 166 {
 167         int ret;
 168         struct ltt_session *new_session;
 169
 170         new_session = session_find_by_name(name);
 171         if (new_session != NULL) {
 172                 ret = LTTCOMM_EXIST_SESS;
 173                 goto error_exist;
 174         }
 175
 176         /* Allocate session data structure */
 177         new_session = zmalloc(sizeof(struct ltt_session));
 178         if (new_session == NULL) {
 179                 PERROR("zmalloc");
 180                 ret = LTTCOMM_FATAL;
 181                 goto error_malloc;
 182         }
 183
 184         /* Define session name */
 185         if (name != NULL) {
 186                 if (snprintf(new_session->name, NAME_MAX, "%s", name) < 0) {
 187                         ret = LTTCOMM_FATAL;
 188                         goto error_asprintf;
 189                 }
 190         } else {
 191                 ERR("No session name given");
 192                 ret = LTTCOMM_FATAL;
 193                 goto error;
 194         }
 195
 196         /* Define session system path */
 197         if (path != NULL) {
 198                 if (snprintf(new_session->path, PATH_MAX, "%s", path) < 0) {
 199                         ret = LTTCOMM_FATAL;
 200                         goto error_asprintf;
 201                 }
 202         } else {
 203                 ERR("No session path given");
 204                 ret = LTTCOMM_FATAL;
 205                 goto error;
 206         }
 207
 208         /* Init kernel session */
 209         new_session->kernel_session = NULL;
 210         new_session->ust_session = NULL;
 211
 212         /* Init lock */
 213         pthread_mutex_init(&new_session->lock, NULL);
 214
 215         new_session->uid = uid;
 216         new_session->gid = gid;
 217
 218         ret = run_as_mkdir_recursive(new_session->path, S_IRWXU | S_IRWXG,
 219                         new_session->uid, new_session->gid);
 220         if (ret < 0) {
 221                 if (ret != -EEXIST) {
 222                         ERR("Trace directory creation error");
 223                         ret = LTTCOMM_CREATE_DIR_FAIL;
 224                         goto error;
 225                 }
 226         }
 227
 228         /* Add new session to the session list */
 229         session_lock_list();
 230         new_session->id = add_session_list(new_session);
 231         session_unlock_list();
 232
 233         DBG("Tracing session %s created in %s with ID %d by UID %d GID %d",
 234                 name, path, new_session->id,
 235                 new_session->uid, new_session->gid);
 236
 237         return LTTCOMM_OK;
 238
 239 error:
 240 error_asprintf:
 241         if (new_session != NULL) {
 242                 free(new_session);
 243         }
 244
 245 error_exist:
 246 error_malloc:
 247         return ret;
 248 }