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         .next_uuid = 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         assert(ls);
  60
  61         cds_list_add(&ls->list, &ltt_session_list.head);
  62         return ltt_session_list.next_uuid++;
  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         assert(ls);
  73
  74         cds_list_del(&ls->list);
  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         assert(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         assert(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         assert(name);
 131
 132         DBG2("Trying to find session by name %s", name);
 133
 134         cds_list_for_each_entry(iter, &ltt_session_list.head, list) {
 135                 if (strncmp(iter->name, name, NAME_MAX) == 0) {
 136                         goto found;
 137                 }
 138         }
 139
 140         iter = NULL;
 141
 142 found:
 143         return iter;
 144 }
 145
 146 /*
 147  * Delete session from the session list and free the memory.
 148  *
 149  * Return -1 if no session is found.  On success, return 1;
 150  * Should *NOT* be called with RCU read-side lock held.
 151  */
 152 int session_destroy(struct ltt_session *session)
 153 {
 154         /* Safety check */
 155         assert(session);
 156
 157         DBG("Destroying session %s", session->name);
 158         del_session_list(session);
 159         pthread_mutex_destroy(&session->lock);
 160
 161         consumer_destroy_output(session->consumer);
 162         free(session);
 163
 164         return LTTNG_OK;
 165 }
 166
 167 /*
 168  * Create a brand new session and add it to the session list.
 169  */
 170 int session_create(char *name, uid_t uid, gid_t gid)
 171 {
 172         int ret;
 173         struct ltt_session *new_session;
 174
 175         /* Allocate session data structure */
 176         new_session = zmalloc(sizeof(struct ltt_session));
 177         if (new_session == NULL) {
 178                 PERROR("zmalloc");
 179                 ret = LTTNG_ERR_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 = LTTNG_ERR_FATAL;
 187                         goto error_asprintf;
 188                 }
 189         } else {
 190                 ERR("No session name given");
 191                 ret = LTTNG_ERR_FATAL;
 192                 goto error;
 193         }
 194
 195         /* Init kernel session */
 196         new_session->kernel_session = NULL;
 197         new_session->ust_session = NULL;
 198
 199         /* Init lock */
 200         pthread_mutex_init(&new_session->lock, NULL);
 201
 202         new_session->uid = uid;
 203         new_session->gid = gid;
 204
 205         /* Add new session to the session list */
 206         session_lock_list();
 207         new_session->id = add_session_list(new_session);
 208         session_unlock_list();
 209
 210         /*
 211          * Consumer is let to NULL since the create_session_uri command will set it
 212          * up and, if valid, assign it to the session.
 213          */
 214
 215         DBG("Tracing session %s created with ID %u by UID %d GID %d", name,
 216                         new_session->id, new_session->uid, new_session->gid);
 217
 218         return LTTNG_OK;
 219
 220 error:
 221 error_asprintf:
 222         free(new_session);
 223
 224 error_malloc:
 225         return ret;
 226 }
 227
 228 /*
 229  * Check if the UID or GID match the session. Root user has access to all
 230  * sessions.
 231  */
 232 int session_access_ok(struct ltt_session *session, uid_t uid, gid_t gid)
 233 {
 234         assert(session);
 235
 236         if (uid != session->uid && gid != session->gid && uid != 0) {
 237                 return 0;
 238         } else {
 239                 return 1;
 240         }
 241 }