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