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 #define _LGPL_SOURCE
  20 #include <limits.h>
  21 #include <inttypes.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <sys/stat.h>
  26 #include <urcu.h>
  27 #include <dirent.h>
  28 #include <sys/types.h>
  29
  30 #include <common/common.h>
  31 #include <common/sessiond-comm/sessiond-comm.h>
  32
  33 #include "session.h"
  34
  35 /*
  36  * NOTES:
  37  *
  38  * No ltt_session.lock is taken here because those data structure are widely
  39  * spread across the lttng-tools code base so before caling functions below
  40  * that can read/write a session, the caller MUST acquire the session lock
  41  * using session_lock() and session_unlock().
  42  */
  43
  44 /*
  45  * Init tracing session list.
  46  *
  47  * Please see session.h for more explanation and correct usage of the list.
  48  */
  49 static struct ltt_session_list ltt_session_list = {
  50         .head = CDS_LIST_HEAD_INIT(ltt_session_list.head),
  51         .lock = PTHREAD_MUTEX_INITIALIZER,
  52         .next_uuid = 0,
  53 };
  54
  55 /* These characters are forbidden in a session name. Used by validate_name. */
  56 static const char *forbidden_name_chars = "/";
  57
  58 /*
  59  * Validate the session name for forbidden characters.
  60  *
  61  * Return 0 on success else -1 meaning a forbidden char. has been found.
  62  */
  63 static int validate_name(const char *name)
  64 {
  65         int ret;
  66         char *tok, *tmp_name;
  67
  68         assert(name);
  69
  70         tmp_name = strdup(name);
  71         if (!tmp_name) {
  72                 /* ENOMEM here. */
  73                 ret = -1;
  74                 goto error;
  75         }
  76
  77         tok = strpbrk(tmp_name, forbidden_name_chars);
  78         if (tok) {
  79                 DBG("Session name %s contains a forbidden character", name);
  80                 /* Forbidden character has been found. */
  81                 ret = -1;
  82                 goto error;
  83         }
  84         ret = 0;
  85
  86 error:
  87         free(tmp_name);
  88         return ret;
  89 }
  90
  91 /*
  92  * Add a ltt_session structure to the global list.
  93  *
  94  * The caller MUST acquire the session list lock before.
  95  * Returns the unique identifier for the session.
  96  */
  97 static uint64_t add_session_list(struct ltt_session *ls)
  98 {
  99         assert(ls);
 100
 101         cds_list_add(&ls->list, &ltt_session_list.head);
 102         return ltt_session_list.next_uuid++;
 103 }
 104
 105 /*
 106  * Delete a ltt_session structure to the global list.
 107  *
 108  * The caller MUST acquire the session list lock before.
 109  */
 110 static void del_session_list(struct ltt_session *ls)
 111 {
 112         assert(ls);
 113
 114         cds_list_del(&ls->list);
 115 }
 116
 117 /*
 118  * Return a pointer to the session list.
 119  */
 120 struct ltt_session_list *session_get_list(void)
 121 {
 122         return &ltt_session_list;
 123 }
 124
 125 /*
 126  * Acquire session list lock
 127  */
 128 void session_lock_list(void)
 129 {
 130         pthread_mutex_lock(&ltt_session_list.lock);
 131 }
 132
 133 /*
 134  * Release session list lock
 135  */
 136 void session_unlock_list(void)
 137 {
 138         pthread_mutex_unlock(&ltt_session_list.lock);
 139 }
 140
 141 /*
 142  * Acquire session lock
 143  */
 144 void session_lock(struct ltt_session *session)
 145 {
 146         assert(session);
 147
 148         pthread_mutex_lock(&session->lock);
 149 }
 150
 151 /*
 152  * Release session lock
 153  */
 154 void session_unlock(struct ltt_session *session)
 155 {
 156         assert(session);
 157
 158         pthread_mutex_unlock(&session->lock);
 159 }
 160
 161 /*
 162  * Return a ltt_session structure ptr that matches name. If no session found,
 163  * NULL is returned. This must be called with the session lock held using
 164  * session_lock_list and session_unlock_list.
 165  */
 166 struct ltt_session *session_find_by_name(const char *name)
 167 {
 168         struct ltt_session *iter;
 169
 170         assert(name);
 171
 172         DBG2("Trying to find session by name %s", name);
 173
 174         cds_list_for_each_entry(iter, &ltt_session_list.head, list) {
 175                 if (strncmp(iter->name, name, NAME_MAX) == 0) {
 176                         goto found;
 177                 }
 178         }
 179
 180         iter = NULL;
 181
 182 found:
 183         return iter;
 184 }
 185
 186 /*
 187  * Delete session from the session list and free the memory.
 188  *
 189  * Return -1 if no session is found.  On success, return 1;
 190  * Should *NOT* be called with RCU read-side lock held.
 191  */
 192 int session_destroy(struct ltt_session *session)
 193 {
 194         /* Safety check */
 195         assert(session);
 196
 197         DBG("Destroying session %s", session->name);
 198         del_session_list(session);
 199         pthread_mutex_destroy(&session->lock);
 200
 201         consumer_destroy_output(session->consumer);
 202         snapshot_destroy(&session->snapshot);
 203         free(session);
 204
 205         return LTTNG_OK;
 206 }
 207
 208 /*
 209  * Create a brand new session and add it to the session list.
 210  */
 211 int session_create(char *name, uid_t uid, gid_t gid)
 212 {
 213         int ret;
 214         struct ltt_session *new_session;
 215
 216         /* Allocate session data structure */
 217         new_session = zmalloc(sizeof(struct ltt_session));
 218         if (new_session == NULL) {
 219                 PERROR("zmalloc");
 220                 ret = LTTNG_ERR_FATAL;
 221                 goto error_malloc;
 222         }
 223
 224         /* Define session name */
 225         if (name != NULL) {
 226                 if (snprintf(new_session->name, NAME_MAX, "%s", name) < 0) {
 227                         ret = LTTNG_ERR_FATAL;
 228                         goto error_asprintf;
 229                 }
 230         } else {
 231                 ERR("No session name given");
 232                 ret = LTTNG_ERR_FATAL;
 233                 goto error;
 234         }
 235
 236         ret = validate_name(name);
 237         if (ret < 0) {
 238                 ret = LTTNG_ERR_SESSION_INVALID_CHAR;
 239                 goto error;
 240         }
 241
 242         ret = gethostname(new_session->hostname, sizeof(new_session->hostname));
 243         if (ret < 0) {
 244                 if (errno == ENAMETOOLONG) {
 245                         new_session->hostname[sizeof(new_session->hostname) - 1] = '\0';
 246                 } else {
 247                         ret = LTTNG_ERR_FATAL;
 248                         goto error;
 249                 }
 250         }
 251
 252         /* Init kernel session */
 253         new_session->kernel_session = NULL;
 254         new_session->ust_session = NULL;
 255
 256         /* Init lock */
 257         pthread_mutex_init(&new_session->lock, NULL);
 258
 259         new_session->uid = uid;
 260         new_session->gid = gid;
 261
 262         ret = snapshot_init(&new_session->snapshot);
 263         if (ret < 0) {
 264                 ret = LTTNG_ERR_NOMEM;
 265                 goto error;
 266         }
 267
 268         /* Add new session to the session list */
 269         session_lock_list();
 270         new_session->id = add_session_list(new_session);
 271         session_unlock_list();
 272
 273         /*
 274          * Consumer is let to NULL since the create_session_uri command will set it
 275          * up and, if valid, assign it to the session.
 276          */
 277
 278         DBG("Tracing session %s created with ID %" PRIu64 " by UID %d GID %d",
 279                         name, new_session->id, new_session->uid, new_session->gid);
 280
 281         return LTTNG_OK;
 282
 283 error:
 284 error_asprintf:
 285         free(new_session);
 286
 287 error_malloc:
 288         return ret;
 289 }
 290
 291 /*
 292  * Check if the UID or GID match the session. Root user has access to all
 293  * sessions.
 294  */
 295 int session_access_ok(struct ltt_session *session, uid_t uid, gid_t gid)
 296 {
 297         assert(session);
 298
 299         if (uid != session->uid && gid != session->gid && uid != 0) {
 300                 return 0;
 301         } else {
 302                 return 1;
 303         }
 304 }