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