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 <inttypes.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <sys/stat.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         .next_uuid = 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 uint64_t add_session_list(struct ltt_session *ls)
  59 {
  60         assert(ls);
  61
  62         cds_list_add(&ls->list, &ltt_session_list.head);
  63         return ltt_session_list.next_uuid++;
  64 }
  65
  66 /*
  67  * Delete a ltt_session structure to the global list.
  68  *
  69  * The caller MUST acquire the session list lock before.
  70  */
  71 static void del_session_list(struct ltt_session *ls)
  72 {
  73         assert(ls);
  74
  75         cds_list_del(&ls->list);
  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         assert(session);
 108
 109         pthread_mutex_lock(&session->lock);
 110 }
 111
 112 /*
 113  * Release session lock
 114  */
 115 void session_unlock(struct ltt_session *session)
 116 {
 117         assert(session);
 118
 119         pthread_mutex_unlock(&session->lock);
 120 }
 121
 122 /*
 123  * Return a ltt_session structure ptr that matches name. If no session found,
 124  * NULL is returned. This must be called with the session lock held using
 125  * session_lock_list and session_unlock_list.
 126  */
 127 struct ltt_session *session_find_by_name(char *name)
 128 {
 129         struct ltt_session *iter;
 130
 131         assert(name);
 132
 133         DBG2("Trying to find session by name %s", name);
 134
 135         cds_list_for_each_entry(iter, &ltt_session_list.head, list) {
 136                 if (strncmp(iter->name, name, NAME_MAX) == 0) {
 137                         goto found;
 138                 }
 139         }
 140
 141         iter = NULL;
 142
 143 found:
 144         return iter;
 145 }
 146
 147 /*
 148  * Delete session from the session list and free the memory.
 149  *
 150  * Return -1 if no session is found.  On success, return 1;
 151  * Should *NOT* be called with RCU read-side lock held.
 152  */
 153 int session_destroy(struct ltt_session *session)
 154 {
 155         /* Safety check */
 156         assert(session);
 157
 158         DBG("Destroying session %s", session->name);
 159         del_session_list(session);
 160         pthread_mutex_destroy(&session->lock);
 161
 162         consumer_destroy_output(session->consumer);
 163         snapshot_destroy(&session->snapshot);
 164         free(session);
 165
 166         return LTTNG_OK;
 167 }
 168
 169 /*
 170  * Create a brand new session and add it to the session list.
 171  */
 172 int session_create(char *name, uid_t uid, gid_t gid)
 173 {
 174         int ret;
 175         struct ltt_session *new_session;
 176
 177         /* Allocate session data structure */
 178         new_session = zmalloc(sizeof(struct ltt_session));
 179         if (new_session == NULL) {
 180                 PERROR("zmalloc");
 181                 ret = LTTNG_ERR_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 = LTTNG_ERR_FATAL;
 189                         goto error_asprintf;
 190                 }
 191         } else {
 192                 ERR("No session name given");
 193                 ret = LTTNG_ERR_FATAL;
 194                 goto error;
 195         }
 196
 197         ret = gethostname(new_session->hostname, sizeof(new_session->hostname));
 198         if (ret < 0) {
 199                 if (errno == ENAMETOOLONG) {
 200                         new_session->hostname[sizeof(new_session->hostname) - 1] = '\0';
 201                 } else {
 202                         ret = LTTNG_ERR_FATAL;
 203                         goto error;
 204                 }
 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 = snapshot_init(&new_session->snapshot);
 218         if (ret < 0) {
 219                 ret = LTTNG_ERR_NOMEM;
 220                 goto error;
 221         }
 222
 223         /* Add new session to the session list */
 224         session_lock_list();
 225         new_session->id = add_session_list(new_session);
 226         session_unlock_list();
 227
 228         /*
 229          * Consumer is let to NULL since the create_session_uri command will set it
 230          * up and, if valid, assign it to the session.
 231          */
 232
 233         DBG("Tracing session %s created with ID %" PRIu64 " by UID %d GID %d",
 234                         name, new_session->id, new_session->uid, new_session->gid);
 235
 236         return LTTNG_OK;
 237
 238 error:
 239 error_asprintf:
 240         free(new_session);
 241
 242 error_malloc:
 243         return ret;
 244 }
 245
 246 /*
 247  * Check if the UID or GID match the session. Root user has access to all
 248  * sessions.
 249  */
 250 int session_access_ok(struct ltt_session *session, uid_t uid, gid_t gid)
 251 {
 252         assert(session);
 253
 254         if (uid != session->uid && gid != session->gid && uid != 0) {
 255                 return 0;
 256         } else {
 257                 return 1;
 258         }
 259 }