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 /* These characters are forbidden in a session name. Used by validate_name. */
  53 static const char *forbidden_name_chars = "/";
  54
  55 /*
  56  * Validate the session name for forbidden characters.
  57  *
  58  * Return 0 on success else -1 meaning a forbidden char. has been found.
  59  */
  60 static int validate_name(const char *name)
  61 {
  62         int ret;
  63         char *tok, *tmp_name;
  64
  65         assert(name);
  66
  67         tmp_name = strdup(name);
  68         if (!tmp_name) {
  69                 /* ENOMEM here. */
  70                 ret = -1;
  71                 goto error;
  72         }
  73
  74         tok = strpbrk(tmp_name, forbidden_name_chars);
  75         if (tok) {
  76                 DBG("Session name %s contains a forbidden character", name);
  77                 /* Forbidden character has been found. */
  78                 ret = -1;
  79                 goto error;
  80         }
  81         ret = 0;
  82
  83 error:
  84         free(tmp_name);
  85         return ret;
  86 }
  87
  88 /*
  89  * Add a ltt_session structure to the global list.
  90  *
  91  * The caller MUST acquire the session list lock before.
  92  * Returns the unique identifier for the session.
  93  */
  94 static uint64_t add_session_list(struct ltt_session *ls)
  95 {
  96         assert(ls);
  97
  98         cds_list_add(&ls->list, &ltt_session_list.head);
  99         return ltt_session_list.next_uuid++;
 100 }
 101
 102 /*
 103  * Delete a ltt_session structure to the global list.
 104  *
 105  * The caller MUST acquire the session list lock before.
 106  */
 107 static void del_session_list(struct ltt_session *ls)
 108 {
 109         assert(ls);
 110
 111         cds_list_del(&ls->list);
 112 }
 113
 114 /*
 115  * Return a pointer to the session list.
 116  */
 117 struct ltt_session_list *session_get_list(void)
 118 {
 119         return &ltt_session_list;
 120 }
 121
 122 /*
 123  * Acquire session list lock
 124  */
 125 void session_lock_list(void)
 126 {
 127         pthread_mutex_lock(&ltt_session_list.lock);
 128 }
 129
 130 /*
 131  * Release session list lock
 132  */
 133 void session_unlock_list(void)
 134 {
 135         pthread_mutex_unlock(&ltt_session_list.lock);
 136 }
 137
 138 /*
 139  * Acquire session lock
 140  */
 141 void session_lock(struct ltt_session *session)
 142 {
 143         assert(session);
 144
 145         pthread_mutex_lock(&session->lock);
 146 }
 147
 148 /*
 149  * Release session lock
 150  */
 151 void session_unlock(struct ltt_session *session)
 152 {
 153         assert(session);
 154
 155         pthread_mutex_unlock(&session->lock);
 156 }
 157
 158 /*
 159  * Return a ltt_session structure ptr that matches name. If no session found,
 160  * NULL is returned. This must be called with the session lock held using
 161  * session_lock_list and session_unlock_list.
 162  */
 163 struct ltt_session *session_find_by_name(char *name)
 164 {
 165         struct ltt_session *iter;
 166
 167         assert(name);
 168
 169         DBG2("Trying to find session by name %s", name);
 170
 171         cds_list_for_each_entry(iter, &ltt_session_list.head, list) {
 172                 if (strncmp(iter->name, name, NAME_MAX) == 0) {
 173                         goto found;
 174                 }
 175         }
 176
 177         iter = NULL;
 178
 179 found:
 180         return iter;
 181 }
 182
 183 /*
 184  * Delete session from the session list and free the memory.
 185  *
 186  * Return -1 if no session is found.  On success, return 1;
 187  * Should *NOT* be called with RCU read-side lock held.
 188  */
 189 int session_destroy(struct ltt_session *session)
 190 {
 191         /* Safety check */
 192         assert(session);
 193
 194         DBG("Destroying session %s", session->name);
 195         del_session_list(session);
 196         pthread_mutex_destroy(&session->lock);
 197
 198         consumer_destroy_output(session->consumer);
 199         snapshot_destroy(&session->snapshot);
 200         free(session);
 201
 202         return LTTNG_OK;
 203 }
 204
 205 /*
 206  * Create a brand new session and add it to the session list.
 207  */
 208 int session_create(char *name, uid_t uid, gid_t gid)
 209 {
 210         int ret;
 211         struct ltt_session *new_session;
 212
 213         /* Allocate session data structure */
 214         new_session = zmalloc(sizeof(struct ltt_session));
 215         if (new_session == NULL) {
 216                 PERROR("zmalloc");
 217                 ret = LTTNG_ERR_FATAL;
 218                 goto error_malloc;
 219         }
 220
 221         /* Define session name */
 222         if (name != NULL) {
 223                 if (snprintf(new_session->name, NAME_MAX, "%s", name) < 0) {
 224                         ret = LTTNG_ERR_FATAL;
 225                         goto error_asprintf;
 226                 }
 227         } else {
 228                 ERR("No session name given");
 229                 ret = LTTNG_ERR_FATAL;
 230                 goto error;
 231         }
 232
 233         ret = validate_name(name);
 234         if (ret < 0) {
 235                 ret = LTTNG_ERR_SESSION_INVALID_CHAR;
 236                 goto error;
 237         }
 238
 239         ret = gethostname(new_session->hostname, sizeof(new_session->hostname));
 240         if (ret < 0) {
 241                 if (errno == ENAMETOOLONG) {
 242                         new_session->hostname[sizeof(new_session->hostname) - 1] = '\0';
 243                 } else {
 244                         ret = LTTNG_ERR_FATAL;
 245                         goto error;
 246                 }
 247         }
 248
 249         /* Init kernel session */
 250         new_session->kernel_session = NULL;
 251         new_session->ust_session = NULL;
 252
 253         /* Init lock */
 254         pthread_mutex_init(&new_session->lock, NULL);
 255
 256         new_session->uid = uid;
 257         new_session->gid = gid;
 258
 259         ret = snapshot_init(&new_session->snapshot);
 260         if (ret < 0) {
 261                 ret = LTTNG_ERR_NOMEM;
 262                 goto error;
 263         }
 264
 265         /* Add new session to the session list */
 266         session_lock_list();
 267         new_session->id = add_session_list(new_session);
 268         session_unlock_list();
 269
 270         /*
 271          * Consumer is let to NULL since the create_session_uri command will set it
 272          * up and, if valid, assign it to the session.
 273          */
 274
 275         DBG("Tracing session %s created with ID %" PRIu64 " by UID %d GID %d",
 276                         name, new_session->id, new_session->uid, new_session->gid);
 277
 278         return LTTNG_OK;
 279
 280 error:
 281 error_asprintf:
 282         free(new_session);
 283
 284 error_malloc:
 285         return ret;
 286 }
 287
 288 /*
 289  * Check if the UID or GID match the session. Root user has access to all
 290  * sessions.
 291  */
 292 int session_access_ok(struct ltt_session *session, uid_t uid, gid_t gid)
 293 {
 294         assert(session);
 295
 296         if (uid != session->uid && gid != session->gid && uid != 0) {
 297                 return 0;
 298         } else {
 299                 return 1;
 300         }
 301 }