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