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 <stdio.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <sys/stat.h>
  24 #include <urcu.h>
  25
  26 #include <common/common.h>
  27 #include <common/sessiond-comm/sessiond-comm.h>
  28
  29 #include "session.h"
  30
  31 /*
  32  * NOTES:
  33  *
  34  * No ltt_session.lock is taken here because those data structure are widely
  35  * spread across the lttng-tools code base so before caling functions below
  36  * that can read/write a session, the caller MUST acquire the session lock
  37  * using session_lock() and session_unlock().
  38  */
  39
  40 /*
  41  * Init tracing session list.
  42  *
  43  * Please see session.h for more explanation and correct usage of the list.
  44  */
  45 static struct ltt_session_list ltt_session_list = {
  46         .head = CDS_LIST_HEAD_INIT(ltt_session_list.head),
  47         .lock = PTHREAD_MUTEX_INITIALIZER,
  48         .next_uuid = 0,
  49 };
  50
  51 /*
  52  * Add a ltt_session structure to the global list.
  53  *
  54  * The caller MUST acquire the session list lock before.
  55  * Returns the unique identifier for the session.
  56  */
  57 static unsigned int add_session_list(struct ltt_session *ls)
  58 {
  59         cds_list_add(&ls->list, &ltt_session_list.head);
  60         return ltt_session_list.next_uuid++;
  61 }
  62
  63 /*
  64  * Delete a ltt_session structure to the global list.
  65  *
  66  * The caller MUST acquire the session list lock before.
  67  */
  68 static void del_session_list(struct ltt_session *ls)
  69 {
  70         cds_list_del(&ls->list);
  71 }
  72
  73 /*
  74  * Return a pointer to the session list.
  75  */
  76 struct ltt_session_list *session_get_list(void)
  77 {
  78         return &ltt_session_list;
  79 }
  80
  81 /*
  82  * Acquire session list lock
  83  */
  84 void session_lock_list(void)
  85 {
  86         pthread_mutex_lock(&ltt_session_list.lock);
  87 }
  88
  89 /*
  90  * Release session list lock
  91  */
  92 void session_unlock_list(void)
  93 {
  94         pthread_mutex_unlock(&ltt_session_list.lock);
  95 }
  96
  97 /*
  98  * Acquire session lock
  99  */
 100 void session_lock(struct ltt_session *session)
 101 {
 102         pthread_mutex_lock(&session->lock);
 103 }
 104
 105 /*
 106  * Release session lock
 107  */
 108 void session_unlock(struct ltt_session *session)
 109 {
 110         pthread_mutex_unlock(&session->lock);
 111 }
 112
 113 /*
 114  * Return a ltt_session structure ptr that matches name. If no session found,
 115  * NULL is returned. This must be called with the session lock held using
 116  * session_lock_list and session_unlock_list.
 117  */
 118 struct ltt_session *session_find_by_name(char *name)
 119 {
 120         struct ltt_session *iter;
 121
 122         DBG2("Trying to find session by name %s", name);
 123
 124         cds_list_for_each_entry(iter, &ltt_session_list.head, list) {
 125                 if (strncmp(iter->name, name, NAME_MAX) == 0) {
 126                         goto found;
 127                 }
 128         }
 129
 130         iter = NULL;
 131
 132 found:
 133         return iter;
 134 }
 135
 136 /*
 137  * Delete session from the session list and free the memory.
 138  *
 139  * Return -1 if no session is found.  On success, return 1;
 140  */
 141 int session_destroy(struct ltt_session *session)
 142 {
 143         /* Safety check */
 144         if (session == NULL) {
 145                 ERR("Session pointer was null on session destroy");
 146                 return LTTNG_OK;
 147         }
 148
 149         DBG("Destroying session %s", session->name);
 150         del_session_list(session);
 151         pthread_mutex_destroy(&session->lock);
 152
 153         rcu_read_lock();
 154         consumer_destroy_output(session->consumer);
 155         rcu_read_unlock();
 156         free(session);
 157
 158         return LTTNG_OK;
 159 }
 160
 161 /*
 162  * Create a brand new session and add it to the session list.
 163  */
 164 int session_create(char *name, char *path, uid_t uid, gid_t gid)
 165 {
 166         int ret;
 167         struct ltt_session *new_session;
 168
 169         /* Allocate session data structure */
 170         new_session = zmalloc(sizeof(struct ltt_session));
 171         if (new_session == NULL) {
 172                 PERROR("zmalloc");
 173                 ret = LTTNG_ERR_FATAL;
 174                 goto error_malloc;
 175         }
 176
 177         /* Define session name */
 178         if (name != NULL) {
 179                 if (snprintf(new_session->name, NAME_MAX, "%s", name) < 0) {
 180                         ret = LTTNG_ERR_FATAL;
 181                         goto error_asprintf;
 182                 }
 183         } else {
 184                 ERR("No session name given");
 185                 ret = LTTNG_ERR_FATAL;
 186                 goto error;
 187         }
 188
 189         /* Define session system path */
 190         if (path != NULL) {
 191                 if (snprintf(new_session->path, PATH_MAX, "%s", path) < 0) {
 192                         ret = LTTNG_ERR_FATAL;
 193                         goto error_asprintf;
 194                 }
 195                 new_session->start_consumer = 1;
 196         } else {
 197                 /* No path indicates that there is no use for a consumer. */
 198                 new_session->start_consumer = 0;
 199                 new_session->path[0] = '\0';
 200         }
 201
 202         /* Init kernel session */
 203         new_session->kernel_session = NULL;
 204         new_session->ust_session = NULL;
 205
 206         /* Init lock */
 207         pthread_mutex_init(&new_session->lock, NULL);
 208
 209         new_session->uid = uid;
 210         new_session->gid = gid;
 211
 212         /* Mkdir if we have a valid path and length */
 213         if (strlen(new_session->path) > 0) {
 214                 ret = run_as_mkdir_recursive(new_session->path, S_IRWXU | S_IRWXG,
 215                                 new_session->uid, new_session->gid);
 216                 if (ret < 0) {
 217                         if (ret != -EEXIST) {
 218                                 ERR("Trace directory creation error");
 219                                 ret = LTTNG_ERR_CREATE_DIR_FAIL;
 220                                 goto error;
 221                         }
 222                 }
 223         }
 224
 225         /* Add new session to the session list */
 226         session_lock_list();
 227         new_session->id = add_session_list(new_session);
 228         session_unlock_list();
 229
 230         /*
 231          * Consumer is let to NULL since the create_session_uri command will set it
 232          * up and, if valid, assign it to the session.
 233          */
 234
 235         DBG("Tracing session %s created in %s with ID %u by UID %d GID %d", name,
 236                         path, new_session->id, new_session->uid, new_session->gid);
 237
 238         return LTTNG_OK;
 239
 240 error:
 241 error_asprintf:
 242         if (new_session != NULL) {
 243                 free(new_session);
 244         }
 245
 246 error_malloc:
 247         return ret;
 248 }
 249
 250 /*
 251  * Check if the UID or GID match the session. Root user has access to all
 252  * sessions.
 253  */
 254 int session_access_ok(struct ltt_session *session, uid_t uid, gid_t gid)
 255 {
 256         assert(session);
 257
 258         if (uid != session->uid && gid != session->gid && uid != 0) {
 259                 return 0;
 260         } else {
 261                 return 1;
 262         }
 263 }