Fix: don't start session if no channel
[lttng-tools.git] / src / bin / lttng-sessiond / session.c
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1/*
2 * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
3 *
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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.
91d76f53 7 *
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8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
d14d33bf 10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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11 * GNU General Public License for more details.
12 *
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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.
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16 */
17
18#define _GNU_SOURCE
6c9cc2ab 19#include <limits.h>
d022620a 20#include <inttypes.h>
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21#include <stdio.h>
22#include <stdlib.h>
23#include <string.h>
a304c14c 24#include <sys/stat.h>
f6a9efaa 25#include <urcu.h>
5b74c7b1 26
990570ed 27#include <common/common.h>
db758600 28#include <common/sessiond-comm/sessiond-comm.h>
1e307fab 29
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30#include "session.h"
31
8c0faa1d 32/*
b5541356 33 * NOTES:
8c0faa1d 34 *
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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
54d01ffb 38 * using session_lock() and session_unlock().
8c0faa1d 39 */
8c0faa1d 40
5b74c7b1 41/*
b5541356 42 * Init tracing session list.
5b74c7b1 43 *
b5541356 44 * Please see session.h for more explanation and correct usage of the list.
5b74c7b1 45 */
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46static struct ltt_session_list ltt_session_list = {
47 .head = CDS_LIST_HEAD_INIT(ltt_session_list.head),
48 .lock = PTHREAD_MUTEX_INITIALIZER,
a24f7994 49 .next_uuid = 0,
b5541356 50};
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51
52/*
050349bb 53 * Add a ltt_session structure to the global list.
5b74c7b1 54 *
050349bb 55 * The caller MUST acquire the session list lock before.
44e96653 56 * Returns the unique identifier for the session.
5b74c7b1 57 */
d022620a 58static uint64_t add_session_list(struct ltt_session *ls)
5b74c7b1 59{
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60 assert(ls);
61
5b74c7b1 62 cds_list_add(&ls->list, &ltt_session_list.head);
a24f7994 63 return ltt_session_list.next_uuid++;
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64}
65
66/*
050349bb 67 * Delete a ltt_session structure to the global list.
b5541356 68 *
050349bb 69 * The caller MUST acquire the session list lock before.
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70 */
71static void del_session_list(struct ltt_session *ls)
72{
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73 assert(ls);
74
5b74c7b1 75 cds_list_del(&ls->list);
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76}
77
b5541356 78/*
050349bb 79 * Return a pointer to the session list.
b5541356 80 */
54d01ffb 81struct ltt_session_list *session_get_list(void)
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82{
83 return &ltt_session_list;
84}
85
86/*
6c9cc2ab 87 * Acquire session list lock
b5541356 88 */
54d01ffb 89void session_lock_list(void)
b5541356 90{
6c9cc2ab 91 pthread_mutex_lock(&ltt_session_list.lock);
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92}
93
94/*
6c9cc2ab 95 * Release session list lock
b5541356 96 */
54d01ffb 97void session_unlock_list(void)
b5541356 98{
6c9cc2ab 99 pthread_mutex_unlock(&ltt_session_list.lock);
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100}
101
102/*
6c9cc2ab 103 * Acquire session lock
b5541356 104 */
54d01ffb 105void session_lock(struct ltt_session *session)
b5541356 106{
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107 assert(session);
108
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109 pthread_mutex_lock(&session->lock);
110}
b5541356 111
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112/*
113 * Release session lock
114 */
54d01ffb 115void session_unlock(struct ltt_session *session)
6c9cc2ab 116{
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117 assert(session);
118
6c9cc2ab 119 pthread_mutex_unlock(&session->lock);
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120}
121
5b74c7b1 122/*
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123 * Return a ltt_session structure ptr that matches name. If no session found,
124 * NULL is returned. This must be called with the session lock held using
125 * session_lock_list and session_unlock_list.
5b74c7b1 126 */
54d01ffb 127struct ltt_session *session_find_by_name(char *name)
5b74c7b1 128{
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129 struct ltt_session *iter;
130
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131 assert(name);
132
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133 DBG2("Trying to find session by name %s", name);
134
5b74c7b1 135 cds_list_for_each_entry(iter, &ltt_session_list.head, list) {
1b110e1b 136 if (strncmp(iter->name, name, NAME_MAX) == 0) {
74babd95 137 goto found;
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138 }
139 }
140
74babd95 141 iter = NULL;
5b74c7b1 142
74babd95 143found:
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144 return iter;
145}
146
147/*
050349bb 148 * Delete session from the session list and free the memory.
5b74c7b1 149 *
050349bb 150 * Return -1 if no session is found. On success, return 1;
36b588ed 151 * Should *NOT* be called with RCU read-side lock held.
5b74c7b1 152 */
271933a4 153int session_destroy(struct ltt_session *session)
5b74c7b1 154{
271933a4 155 /* Safety check */
0525e9ae 156 assert(session);
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157
158 DBG("Destroying session %s", session->name);
159 del_session_list(session);
271933a4 160 pthread_mutex_destroy(&session->lock);
07424f16 161
07424f16 162 consumer_destroy_output(session->consumer);
6dc3064a 163 snapshot_destroy(&session->snapshot);
271933a4 164 free(session);
5b74c7b1 165
f73fabfd 166 return LTTNG_OK;
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167}
168
169/*
050349bb 170 * Create a brand new session and add it to the session list.
5b74c7b1 171 */
dec56f6c 172int session_create(char *name, uid_t uid, gid_t gid)
5b74c7b1 173{
f3ed775e 174 int ret;
5b74c7b1 175 struct ltt_session *new_session;
e07ae692 176
5b74c7b1 177 /* Allocate session data structure */
ba7f0ae5 178 new_session = zmalloc(sizeof(struct ltt_session));
5b74c7b1 179 if (new_session == NULL) {
df0f840b 180 PERROR("zmalloc");
f73fabfd 181 ret = LTTNG_ERR_FATAL;
f3ed775e 182 goto error_malloc;
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183 }
184
f3ed775e 185 /* Define session name */
5b74c7b1 186 if (name != NULL) {
74babd95 187 if (snprintf(new_session->name, NAME_MAX, "%s", name) < 0) {
f73fabfd 188 ret = LTTNG_ERR_FATAL;
f3ed775e 189 goto error_asprintf;
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190 }
191 } else {
f3ed775e 192 ERR("No session name given");
f73fabfd 193 ret = LTTNG_ERR_FATAL;
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194 goto error;
195 }
196
d3e2ba59 197 ret = gethostname(new_session->hostname, sizeof(new_session->hostname));
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198 if (ret < 0) {
199 if (errno == ENAMETOOLONG) {
200 new_session->hostname[sizeof(new_session->hostname) - 1] = '\0';
201 } else {
202 ret = LTTNG_ERR_FATAL;
203 goto error;
204 }
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205 }
206
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207 /* Init kernel session */
208 new_session->kernel_session = NULL;
f6a9efaa 209 new_session->ust_session = NULL;
1657e9bb 210
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211 /* Init lock */
212 pthread_mutex_init(&new_session->lock, NULL);
5b74c7b1 213
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214 new_session->uid = uid;
215 new_session->gid = gid;
216
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217 ret = snapshot_init(&new_session->snapshot);
218 if (ret < 0) {
219 ret = LTTNG_ERR_NOMEM;
220 goto error;
221 }
222
b5541356 223 /* Add new session to the session list */
54d01ffb 224 session_lock_list();
a991f516 225 new_session->id = add_session_list(new_session);
54d01ffb 226 session_unlock_list();
b5541356 227
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228 /*
229 * Consumer is let to NULL since the create_session_uri command will set it
230 * up and, if valid, assign it to the session.
231 */
232
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233 DBG("Tracing session %s created with ID %" PRIu64 " by UID %d GID %d",
234 name, new_session->id, new_session->uid, new_session->gid);
b082db07 235
f73fabfd 236 return LTTNG_OK;
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237
238error:
f3ed775e 239error_asprintf:
0e428499 240 free(new_session);
5b74c7b1 241
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242error_malloc:
243 return ret;
5b74c7b1 244}
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245
246/*
247 * Check if the UID or GID match the session. Root user has access to all
248 * sessions.
249 */
250int session_access_ok(struct ltt_session *session, uid_t uid, gid_t gid)
251{
252 assert(session);
253
254 if (uid != session->uid && gid != session->gid && uid != 0) {
255 return 0;
256 } else {
257 return 1;
258 }
259}
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