Ensure UST channel output mode is LTTNG_UST_MMAP
[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 _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 #include "utils.h"
34
35 /*
36 * NOTES:
37 *
38 * No ltt_session.lock is taken here because those data structure are widely
39 * spread across the lttng-tools code base so before caling functions below
40 * that can read/write a session, the caller MUST acquire the session lock
41 * using session_lock() and session_unlock().
42 */
43
44 /*
45 * Init tracing session list.
46 *
47 * Please see session.h for more explanation and correct usage of the list.
48 */
49 static struct ltt_session_list ltt_session_list = {
50 .head = CDS_LIST_HEAD_INIT(ltt_session_list.head),
51 .lock = PTHREAD_MUTEX_INITIALIZER,
52 .next_uuid = 0,
53 };
54
55 /* These characters are forbidden in a session name. Used by validate_name. */
56 static const char *forbidden_name_chars = "/";
57
58 /* Global hash table to keep the sessions, indexed by id. */
59 static struct lttng_ht *ltt_sessions_ht_by_id = NULL;
60
61 /*
62 * Validate the session name for forbidden characters.
63 *
64 * Return 0 on success else -1 meaning a forbidden char. has been found.
65 */
66 static int validate_name(const char *name)
67 {
68 int ret;
69 char *tok, *tmp_name;
70
71 assert(name);
72
73 tmp_name = strdup(name);
74 if (!tmp_name) {
75 /* ENOMEM here. */
76 ret = -1;
77 goto error;
78 }
79
80 tok = strpbrk(tmp_name, forbidden_name_chars);
81 if (tok) {
82 DBG("Session name %s contains a forbidden character", name);
83 /* Forbidden character has been found. */
84 ret = -1;
85 goto error;
86 }
87 ret = 0;
88
89 error:
90 free(tmp_name);
91 return ret;
92 }
93
94 /*
95 * Add a ltt_session structure to the global list.
96 *
97 * The caller MUST acquire the session list lock before.
98 * Returns the unique identifier for the session.
99 */
100 static uint64_t add_session_list(struct ltt_session *ls)
101 {
102 assert(ls);
103
104 cds_list_add(&ls->list, &ltt_session_list.head);
105 return ltt_session_list.next_uuid++;
106 }
107
108 /*
109 * Delete a ltt_session structure to the global list.
110 *
111 * The caller MUST acquire the session list lock before.
112 */
113 static void del_session_list(struct ltt_session *ls)
114 {
115 assert(ls);
116
117 cds_list_del(&ls->list);
118 }
119
120 /*
121 * Return a pointer to the session list.
122 */
123 struct ltt_session_list *session_get_list(void)
124 {
125 return &ltt_session_list;
126 }
127
128 /*
129 * Acquire session list lock
130 */
131 void session_lock_list(void)
132 {
133 pthread_mutex_lock(&ltt_session_list.lock);
134 }
135
136 /*
137 * Release session list lock
138 */
139 void session_unlock_list(void)
140 {
141 pthread_mutex_unlock(&ltt_session_list.lock);
142 }
143
144 /*
145 * Allocate the ltt_sessions_ht_by_id HT.
146 */
147 int ltt_sessions_ht_alloc(void)
148 {
149 int ret = 0;
150
151 DBG("Allocating ltt_sessions_ht_by_id");
152 ltt_sessions_ht_by_id = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
153 if (!ltt_sessions_ht_by_id) {
154 ret = -1;
155 ERR("Failed to allocate ltt_sessions_ht_by_id");
156 goto end;
157 }
158 end:
159 return ret;
160 }
161
162 /*
163 * Destroy the ltt_sessions_ht_by_id HT.
164 */
165 void ltt_sessions_ht_destroy(void)
166 {
167 if (!ltt_sessions_ht_by_id) {
168 return;
169 }
170 ht_cleanup_push(ltt_sessions_ht_by_id);
171 ltt_sessions_ht_by_id = NULL;
172 }
173
174 /*
175 * Add a ltt_session to the ltt_sessions_ht_by_id.
176 * If unallocated, the ltt_sessions_ht_by_id HT is allocated.
177 * The session list lock must be held.
178 */
179 static void add_session_ht(struct ltt_session *ls)
180 {
181 int ret;
182
183 assert(ls);
184
185 if (!ltt_sessions_ht_by_id) {
186 ret = ltt_sessions_ht_alloc();
187 if (ret) {
188 ERR("Error allocating the sessions HT");
189 goto end;
190 }
191 }
192 lttng_ht_node_init_u64(&ls->node, ls->id);
193 lttng_ht_add_unique_u64(ltt_sessions_ht_by_id, &ls->node);
194
195 end:
196 return;
197 }
198
199 /*
200 * Test if ltt_sessions_ht_by_id is empty.
201 * Return 1 if empty, 0 if not empty.
202 * The session list lock must be held.
203 */
204 static int ltt_sessions_ht_empty()
205 {
206 int ret;
207
208 if (!ltt_sessions_ht_by_id) {
209 ret = 1;
210 goto end;
211 }
212
213 ret = lttng_ht_get_count(ltt_sessions_ht_by_id) ? 0 : 1;
214 end:
215 return ret;
216 }
217
218 /*
219 * Remove a ltt_session from the ltt_sessions_ht_by_id.
220 * If empty, the ltt_sessions_ht_by_id HT is freed.
221 * The session list lock must be held.
222 */
223 static void del_session_ht(struct ltt_session *ls)
224 {
225 struct lttng_ht_iter iter;
226 int ret;
227
228 assert(ls);
229 assert(ltt_sessions_ht_by_id);
230
231 iter.iter.node = &ls->node.node;
232 ret = lttng_ht_del(ltt_sessions_ht_by_id, &iter);
233 assert(!ret);
234
235 if (ltt_sessions_ht_empty()) {
236 DBG("Empty ltt_sessions_ht_by_id, destroying it");
237 ltt_sessions_ht_destroy();
238 }
239 }
240
241 /*
242 * Acquire session lock
243 */
244 void session_lock(struct ltt_session *session)
245 {
246 assert(session);
247
248 pthread_mutex_lock(&session->lock);
249 }
250
251 /*
252 * Release session lock
253 */
254 void session_unlock(struct ltt_session *session)
255 {
256 assert(session);
257
258 pthread_mutex_unlock(&session->lock);
259 }
260
261 /*
262 * Return a ltt_session structure ptr that matches name. If no session found,
263 * NULL is returned. This must be called with the session list lock held using
264 * session_lock_list and session_unlock_list.
265 */
266 struct ltt_session *session_find_by_name(const char *name)
267 {
268 struct ltt_session *iter;
269
270 assert(name);
271
272 DBG2("Trying to find session by name %s", name);
273
274 cds_list_for_each_entry(iter, &ltt_session_list.head, list) {
275 if (strncmp(iter->name, name, NAME_MAX) == 0) {
276 goto found;
277 }
278 }
279
280 iter = NULL;
281
282 found:
283 return iter;
284 }
285
286 /*
287 * Return an ltt_session that matches the id. If no session is found,
288 * NULL is returned. This must be called with rcu_read_lock and
289 * session list lock held (to guarantee the lifetime of the session).
290 */
291 struct ltt_session *session_find_by_id(uint64_t id)
292 {
293 struct lttng_ht_node_u64 *node;
294 struct lttng_ht_iter iter;
295 struct ltt_session *ls;
296
297 lttng_ht_lookup(ltt_sessions_ht_by_id, &id, &iter);
298 node = lttng_ht_iter_get_node_u64(&iter);
299 if (node == NULL) {
300 goto error;
301 }
302 ls = caa_container_of(node, struct ltt_session, node);
303
304 DBG3("Session %" PRIu64 " found by id.", id);
305 return ls;
306
307 error:
308 DBG3("Session %" PRIu64 " NOT found by id", id);
309 return NULL;
310 }
311
312 /*
313 * Delete session from the session list and free the memory.
314 *
315 * Return -1 if no session is found. On success, return 1;
316 * Should *NOT* be called with RCU read-side lock held.
317 */
318 int session_destroy(struct ltt_session *session)
319 {
320 /* Safety check */
321 assert(session);
322
323 DBG("Destroying session %s", session->name);
324 del_session_list(session);
325 pthread_mutex_destroy(&session->lock);
326 del_session_ht(session);
327
328 consumer_output_put(session->consumer);
329 snapshot_destroy(&session->snapshot);
330 free(session);
331
332 return LTTNG_OK;
333 }
334
335 /*
336 * Create a brand new session and add it to the session list.
337 */
338 int session_create(char *name, uid_t uid, gid_t gid)
339 {
340 int ret;
341 struct ltt_session *new_session;
342
343 /* Allocate session data structure */
344 new_session = zmalloc(sizeof(struct ltt_session));
345 if (new_session == NULL) {
346 PERROR("zmalloc");
347 ret = LTTNG_ERR_FATAL;
348 goto error_malloc;
349 }
350
351 /* Define session name */
352 if (name != NULL) {
353 if (snprintf(new_session->name, NAME_MAX, "%s", name) < 0) {
354 ret = LTTNG_ERR_FATAL;
355 goto error_asprintf;
356 }
357 } else {
358 ERR("No session name given");
359 ret = LTTNG_ERR_FATAL;
360 goto error;
361 }
362
363 ret = validate_name(name);
364 if (ret < 0) {
365 ret = LTTNG_ERR_SESSION_INVALID_CHAR;
366 goto error;
367 }
368
369 ret = gethostname(new_session->hostname, sizeof(new_session->hostname));
370 if (ret < 0) {
371 if (errno == ENAMETOOLONG) {
372 new_session->hostname[sizeof(new_session->hostname) - 1] = '\0';
373 } else {
374 ret = LTTNG_ERR_FATAL;
375 goto error;
376 }
377 }
378
379 /* Init kernel session */
380 new_session->kernel_session = NULL;
381 new_session->ust_session = NULL;
382
383 /* Init lock */
384 pthread_mutex_init(&new_session->lock, NULL);
385
386 new_session->uid = uid;
387 new_session->gid = gid;
388
389 ret = snapshot_init(&new_session->snapshot);
390 if (ret < 0) {
391 ret = LTTNG_ERR_NOMEM;
392 goto error;
393 }
394
395 /* Add new session to the session list */
396 session_lock_list();
397 new_session->id = add_session_list(new_session);
398 /*
399 * Add the new session to the ltt_sessions_ht_by_id.
400 * No ownership is taken by the hash table; it is merely
401 * a wrapper around the session list used for faster access
402 * by session id.
403 */
404 add_session_ht(new_session);
405 session_unlock_list();
406
407 /*
408 * Consumer is let to NULL since the create_session_uri command will set it
409 * up and, if valid, assign it to the session.
410 */
411 DBG("Tracing session %s created with ID %" PRIu64 " by UID %d GID %d",
412 name, new_session->id, new_session->uid, new_session->gid);
413
414 return LTTNG_OK;
415
416 error:
417 error_asprintf:
418 free(new_session);
419
420 error_malloc:
421 return ret;
422 }
423
424 /*
425 * Check if the UID or GID match the session. Root user has access to all
426 * sessions.
427 */
428 int session_access_ok(struct ltt_session *session, uid_t uid, gid_t gid)
429 {
430 assert(session);
431
432 if (uid != session->uid && gid != session->gid && uid != 0) {
433 return 0;
434 } else {
435 return 1;
436 }
437 }
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