1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: t -*-
3 * Copyright (c) 2005-2008, The Android Open Source Project
4 * Copyright (c) 2012-2013 Samsung Electronics Co., Ltd.
6 * Licensed under the Apache License, Version 2.0 (the License);
7 * you may not use this file except in compliance with the License.
8 * You may obtain a copy of the License at
10 * http://www.apache.org/licenses/LICENSE-2.0
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
31 #include <dynamic_config.h>
33 #include <logcommon.h>
34 #include "logconfig.h"
35 #include "loglimiter.h"
37 #define DEFAULT_CONFIG_LIMITER false
38 #define DEFAULT_CONFIG_PLOG true
39 #define DEFAULT_CONFIG_DEBUGMODE 0
40 #define DEFAULT_CONFIG_LIMITER_APPLY_TO_ALL_BUFFERS 0
43 * @brief Points to a function which writes a log message
44 * @details The function pointed to depends on the backend used
45 * @param[in] log_id ID of the buffer to log to. Belongs to (LOG_ID_INVALID, LOG_ID_MAX) non-inclusive
46 * @param[in] prio Priority of the message.
47 * @param[in] tag The message tag, identifies the sender.
48 * @param[in] msg The contents of the message.
49 * @return Returns the number of bytes written on success and a negative error value on error.
50 * @see __dlog_init_backend
52 int (*write_to_log)(log_id_t log_id, log_priority prio, const char *tag, const char *msg) = NULL;
53 void (*destroy_backend)();
55 pthread_rwlock_t log_limiter_lock = PTHREAD_RWLOCK_INITIALIZER;
56 static pthread_mutex_t log_construction_lock = PTHREAD_MUTEX_INITIALIZER;
57 static bool is_initialized = false;
59 extern void __dlog_init_pipe(const struct log_config *conf);
60 extern void __dlog_init_android(const struct log_config *conf);
63 static bool dynamic_config;
64 static bool plog[LOG_ID_MAX];
65 static bool plog_default_values[LOG_ID_MAX];
66 static bool enable_secure_logs = true;
69 static int fatal_assert;
70 static int limiter_apply_to_all_buffers;
72 static void __configure_limiter(struct log_config *config)
79 limiter = __log_limiter_create(config);
82 static int __configure_backend(struct log_config *config)
86 const char *const backend = log_config_get(config, "backend");
90 if (!strcmp(backend, "pipe"))
91 __dlog_init_pipe(config);
92 else if (!strcmp(backend, "logger"))
93 __dlog_init_android(config);
100 static void __set_plog_default_values()
102 for (size_t i = 0; i < NELEMS(plog); ++i)
103 plog_default_values[i] = plog[i];
106 static void __initialize_plog(const struct log_config *config)
110 const bool plog_default = log_config_get_boolean(config, "plog", DEFAULT_CONFIG_PLOG);
111 for (size_t i = 0; i < NELEMS(plog); ++i)
112 plog[i] = plog_default;
113 plog[LOG_ID_APPS] = true; // the default does not apply here for backward compatibility reasons.
114 __set_plog_default_values();
117 static void __configure_parameters(struct log_config *config)
121 __initialize_plog(config);
122 __update_plog(config);
123 __set_plog_default_values();
125 enable_secure_logs = log_config_get_boolean(config, "enable_secure_logs", enable_secure_logs);
126 debugmode = log_config_get_int(config, "debugmode", DEFAULT_CONFIG_DEBUGMODE);
127 fatal_assert = access(DEBUGMODE_FILE, F_OK) != -1;
128 limiter = log_config_get_boolean(config, "limiter", DEFAULT_CONFIG_LIMITER);
129 limiter_apply_to_all_buffers = log_config_get_int(config,
130 "limiter_apply_to_all_buffers",
131 DEFAULT_CONFIG_LIMITER_APPLY_TO_ALL_BUFFERS);
134 void __update_plog(const struct log_config *conf)
138 for (size_t i = 0; i < NELEMS(plog); ++i) {
139 char key[MAX_CONF_KEY_LEN];
140 const int r = snprintf(key, sizeof key, "enable_%s", log_name_by_id((log_id_t)i));
143 plog[i] = log_config_get_boolean(conf, key, plog_default_values[i]);
148 * @brief Configure the library
149 * @details Reads relevant config values
150 * @remarks This is more or less a constructor, but there are some obstacles
151 * to using it as such (i.e. with attribute constructor):
153 * - some important pieces of the system link to dlog, they start very early
154 * such that dlog can't properly initialize (which lasts for program lifetime)
155 * but don't actually log anything until later on and would be fine under lazy
156 * initialisation. The way to do it "properly" would be to expose this function
157 * into the API so that people can manually call it when they're ready, but
158 * one of the design goals of the current API is that it requires absolutely no
159 * other calls than `dlog_print`. Changing it would require somebody with a
160 * bird's eye view of the system to produce a design so I wouldn't count on it.
162 * - the constructor would need to have as high of a priority as possible (so as
163 * to minimize the risk of another library's constructor using uninitialized data)
164 * but at the same time others might want some room to wrap functions before
165 * dlog uses them (think mprobe/mcheck). This would also require a design pass.
170 bool __configure(void)
172 __attribute__((cleanup(log_config_free))) struct log_config config;
174 if (log_config_read(&config) < 0)
177 dynamic_config = __dynamic_config_create(&config);
179 __configure_parameters(&config);
181 if (!__configure_backend(&config)) {
182 __dynamic_config_destroy();
183 dynamic_config = false;
187 __configure_limiter(&config);
191 static void __attribute__((constructor(101))) __install_pipe_handler(void)
193 /* We mask SIGPIPE signal because most applications do not install their
194 * own SIGPIPE handler. Default behaviour in SIGPIPE case is to abort the
195 * process. SIGPIPE occurs when e.g. dlog daemon closes read pipe endpoint.
197 * We do this in the library constructor (at maximum priority) and not
198 * during regular (lazy) initialisation so as to prevent overwriting the
199 * program's actual signal handler, if it has one.
201 * In theory this is not required for the Android logger backend; however,
202 * this early we don't yet know the backend and also it is good to behave
203 * consistently in this regard anyway.
205 * We don't revert this in a destructor because Unix signals are bonkers
206 * and we have no way to do this cleanly. Most libdlog users don't use
207 * runtime linking so this would mostly done at program exit either way. */
208 signal(SIGPIPE, SIG_IGN);
211 static bool first = true;
212 static bool initialize()
217 /* The mutex acts as a barrier, but otherwise the C language's
218 * machine abstraction is single-threaded. This means that the
219 * compiler is free to rearrange calls inside the mutex according
220 * to the as-if rule because it doesn't care if another thread can
221 * access it in parallel. In particular, `is_initialized = true`
222 * directly after `__configure()` could be rearranged to go in
223 * front of it because it is not touched inside that function
224 * if the compiler thinks it helps somehow (not unlikely: since
225 * it is checked before the mutex, it is very probable for it to
226 * still be in the CPU register or something like that). On top
227 * of that, some architectures (in particular, armv7l) don't have
228 * strict memory guarantees and can reorder actual memory stores
229 * on their own, even if the compiler didn't do anything fancy
230 * when creating machine code. For more info about the issue,
231 * see https://www.aristeia.com/Papers/DDJ_Jul_Aug_2004_revised.pdf
233 * Ultimately this means that there needs to be some sort of
234 * barrier between `__configure` and `is_initialized = true`,
235 * and the simplest way to achieve that is to just wait until
236 * the second entry into the mutex. */
239 pthread_mutex_lock(&log_construction_lock);
241 first = !__configure();
243 is_initialized = true;
245 pthread_mutex_unlock(&log_construction_lock);
250 * @brief Fatal assertion
251 * @details Conditionally crash the sucka who sent the log
252 * @param[in] prio Priority of the log
254 static void __dlog_fatal_assert(int prio)
256 assert(!fatal_assert || (prio != DLOG_FATAL));
260 * @brief Check log validity
261 * @details Checks whether the log is valid and eligible for printing
262 * @param[in] log_id The target buffer ID
263 * @param[in] prio The log's priority
264 * @param[in] tag The log's tag
265 * @return DLOG_ERROR_NONE on success, else an error code.
266 * @retval DLOG_ERROR_INVALID_PARAMETER Invalid parameter
268 static int dlog_check_validity(log_id_t log_id, int prio, const char *tag)
272 return DLOG_ERROR_INVALID_PARAMETER;
274 if (log_id <= LOG_ID_INVALID || LOG_ID_MAX <= log_id)
275 return DLOG_ERROR_INVALID_PARAMETER;
277 return DLOG_ERROR_NONE;
281 * @brief Check log against limiter rules
282 * @details Checks whether the log passes current limiter rules
283 * @param[in] log_id The target buffer ID
284 * @param[in] prio The log's priority
285 * @param[in] tag The log's tag
286 * @return DLOG_ERROR_NONE on success, else an error code.
287 * @retval DLOG_ERROR_NOT_PERMITTED Not permitted
289 static int dlog_check_limiter(log_id_t log_id, int prio, const char *tag)
291 if (!debugmode && prio <= DLOG_DEBUG)
292 return DLOG_ERROR_NOT_PERMITTED;
295 __dynamic_config_update();
299 if (!pthread_rwlock_rdlock(&log_limiter_lock)) {
300 should_log = __log_limiter_pass_log(tag, prio);
301 pthread_rwlock_unlock(&log_limiter_lock);
305 return DLOG_ERROR_NOT_PERMITTED;
306 } else if (should_log < 0) {
307 write_to_log(log_id, prio, tag,
308 "Your log has been blocked due to limit of log lines per minute.");
309 return DLOG_ERROR_NOT_PERMITTED;
313 /* This can change due to __dynamic_config_update(), but is atomic and its
314 * value implies nothing else so does not need to be under a lock. */
316 return DLOG_ERROR_NOT_PERMITTED;
318 return DLOG_ERROR_NONE;
321 static int __write_to_log_critical_section(log_id_t log_id, int prio, const char *tag, const char *fmt, va_list ap, bool check_should_log)
323 if ((check_should_log || limiter_apply_to_all_buffers) && (dlog_check_limiter(log_id, prio, tag) < 0))
324 return DLOG_ERROR_NONE;
326 char buf[LOG_MAX_PAYLOAD_SIZE];
327 vsnprintf(buf, sizeof buf, fmt, ap);
328 return write_to_log(log_id, prio, tag, buf);
331 static int __write_to_log(log_id_t log_id, int prio, const char *tag, const char *fmt, va_list ap, bool check_should_log)
333 int ret = dlog_check_validity(log_id, prio, tag);
337 /* Threads can be cancelled before they give up a lock.
338 * Therefore cancellation is temporarily disabled.
339 * This solution is comparatively simple and cheap.
340 * The other solutions (cleanup handlers, robust mutexes)
341 * would be much more complicated and also inflict larger
342 * runtime costs. The downside of disabling cancellation
343 * is not a problem in our case because it is temporary
344 * and very brief so we don't keep an obsolete thread
345 * for much longer than we otherwise would. */
346 int old_cancel_state;
347 pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &old_cancel_state);
349 /* The only thing that needs to be protected here is `write_to_log` since
350 * all other resources already have their own specific locks (and even the
351 * pointer could be made to point at a null handler instead of a true NULL)
352 * but giving this guarantee makes everything a lot simpler as it removes
353 * the risk of something suddenly becoming NULL during processing. */
354 ret = !initialize() || !write_to_log
355 ? DLOG_ERROR_NOT_PERMITTED
356 : __write_to_log_critical_section(log_id, prio, tag, fmt, ap, check_should_log)
359 pthread_setcancelstate(old_cancel_state, NULL);
364 int __critical_log_append_timestamp(char *buf, size_t buflen)
366 /* NB: the timestamp may slightly differ from the one that gets
367 * added onto the copy that goes into the regular buffer, and
368 * timestamp acquisition is duplicated. This would ideally be
369 * solved, but timestamps are currently added fairly deep in
370 * backend-specific functions so for now this will have to do.
371 * Also, since we're the sender, there is just this one set of
372 * timestamps, i.e. the send timestamp! The usual alternative
373 * set of receive timestamps will never have the opportunity
374 * to get added to the entry since this log is supposed to end
375 * up straight in the file (there's potentially the trusted
376 * writer binary but we're trying to keep the set of actions
377 * it needs to do to the minimum and those timestamps would
378 * in practice be the same anyway). */
381 clock_gettime(CLOCK_REALTIME, &ts);
382 const time_t tt = ts.tv_sec;
383 const long int real_millisec = ts.tv_nsec / 1000000;
384 clock_gettime(CLOCK_MONOTONIC, &ts);
385 #ifdef HAVE_LOCALTIME_R
387 struct tm *const ptm = localtime_r(&tt, &tmBuf);
389 struct tm *const ptm = localtime(&tt);
391 assert(ptm); // we're in a short lived fork so asserts are fine and make things simple
393 int len = strftime(buf, buflen, "%m-%d %H:%M:%S", ptm);
396 int tmp_len = snprintf(buf + len, buflen - len, ".%03ld", real_millisec);
398 assert(tmp_len < buflen - len);
401 tmp_len = strftime(buf + len, buflen - len, "%z ", ptm);
402 assert(tmp_len != 0);
405 tmp_len = snprintf(buf + len, buflen - len, "%5lu.%03ld", ts.tv_sec, ts.tv_nsec / 1000000);
407 assert(tmp_len < buflen - len);
413 int __critical_log_build_msg(char *buf, size_t buflen, pid_t main_pid, pid_t main_tid, log_id_t log_id, int prio, const char *tag, const char *fmt, va_list ap)
415 int len = __critical_log_append_timestamp(buf, buflen);
416 const int metadata_len = snprintf(buf + len, buflen - len, " P%5d T%5d B%-6s %c/%-8s: ",
419 log_name_by_id(log_id),
420 filter_pri_to_char(prio),
421 tag ?: "CRITICAL_NO_TAG");
422 assert(metadata_len > 0);
423 if (metadata_len >= buflen - len)
424 return buflen - 1; // can genuinely happen with an exceedingly large tag
427 const int content_len = vsnprintf(buf + len, buflen - len, fmt, ap);
428 assert(content_len >= 0); // 0 is legit with format == ""
429 if (content_len >= buflen - len)
437 __attribute__ ((noreturn))
439 void __critical_log_child(pid_t main_pid, pid_t main_tid, log_id_t log_id, int prio, const char *tag, const char *fmt, va_list ap)
441 char buf[LOG_MAX_PAYLOAD_SIZE + 128]; // extra space for some metadata
442 const int len = __critical_log_build_msg(buf, sizeof buf - 1, main_pid, main_tid, log_id, prio, tag, fmt, ap);
446 static const char *const path = "/usr/libexec/dlog-log-critical";
447 execl(path, path /* argv[0] convention */, buf, (char *) NULL);
450 /* Compilers are sometimes smart enough to recognize _exit's
451 * noreturn attribute, even if we wrap it with something that
452 * returns. This causes it to behave in unexpected ways, for
453 * example it can blow up the program regardless or it can
454 * optimize some conditionals out (and incorrectly enter them
455 * after the exit call fails to actually exit). This makes it
456 * unsuitable for tests. */
458 _exit(1); // not the regular `exit` so as not to trigger any `atexit` handlers prematurely
462 #ifndef UNIT_TEST // contains forks and exits, these don't work well with wrapping (see above)
463 void __critical_log(log_id_t log_id, int prio, const char *tag, const char *fmt, va_list ap)
465 /* Critical log functionality is mostly done in a separate binary
466 * to handle security correctly (else every process would have to
467 * possess the necessary privilege to write onto that file, which
468 * would be opening a fairly nasty can of worms from the security
469 * point of view). Our use of exec() is why a simple thread would
470 * not suffice and we're resorting to a fork.
472 * The double fork, much like a double barreled 12 gauge shotgun,
473 * is an elegant solution designed to stop a zombie army. We'd be
474 * creating zombie processes if we didn't wait() for the children
475 * we spawn, but we don't really want to do that since it results
476 * in a needless delay. Instead, the writer process is actually a
477 * grandchild, with our direct child exiting immediately just for
478 * us to have something to wait on that is guaranteed not to take
479 * too long. The orphaned grandchild is adopted by init, who will
480 * take care to reap it when it dies. In addition to avoiding the
481 * delay, the client will not have any unexpected children (which
482 * could ruin logic in its own waits).
485 * ┌───────┐ ┌─────────┐ ┌─────────────┐ ┌────────┐
486 * │ pid 1 ├──>│ libdlog ├──>│ immediately ├──>│ execs │
487 * │ init │ │ client │ │ exits │ │ writer │
488 * └───────┘ └─────────┘ └─────────────┘ └────────┘
490 * Afterwards, libdlog has no children:
491 * ┌───────┐ ┌─────────┐ ┌────────┐
492 * │ pid 1 ├──>│ libdlog │ ┌─────────>│ writer │
493 * │ init ├─┐ │ client │ │ │ binary │
494 * └───────┘ │ └─────────┘ │ └────────┘
495 * └──────────────────────┘
498 const pid_t main_pid = getpid();
499 const pid_t main_tid = gettid();
501 const int temporary_exiter_pid = fork();
502 if (temporary_exiter_pid < 0)
504 if (temporary_exiter_pid != 0) {
505 waitpid(temporary_exiter_pid, NULL, 0);
509 const int child_pid = fork();
515 __critical_log_child(main_pid, main_tid, log_id, prio, tag, fmt, ap);
518 int __dlog_critical_print(log_id_t log_id, int prio, const char *tag, const char *fmt, ...)
523 __critical_log(log_id, prio, tag, fmt, ap);
527 int ret = __dlog_vprint(log_id, prio, tag, fmt, ap);
536 * @details Print a log line
537 * @param[in] log_id The target buffer ID
538 * @param[in] prio Priority
540 * @param[in] fmt Format (same as printf)
541 * @param[in] ap Argument list
542 * @return Bytes written, or negative error
544 int __dlog_vprint(log_id_t log_id, int prio, const char *tag, const char *fmt, va_list ap)
546 int ret = __write_to_log(log_id, prio, tag, fmt, ap, true);
547 __dlog_fatal_assert(prio);
554 * @details Print a log line
555 * @param[in] log_id The target buffer ID
556 * @param[in] prio Priority
558 * @param[in] fmt Format (same as printf)
559 * @return Bytes written, or negative error
561 int __dlog_print(log_id_t log_id, int prio, const char *tag, const char *fmt, ...)
566 int ret = __dlog_vprint(log_id, prio, tag, fmt, ap);
574 * @details Print a log line
575 * @param[in] log_id The target buffer ID
576 * @param[in] prio Priority
578 * @param[in] fmt Format (same as printf)
579 * @return Bytes written, or negative error
581 int __dlog_sec_print(log_id_t log_id, int prio, const char *tag, const char *fmt, ...)
583 if (!enable_secure_logs)
589 int ret = __dlog_vprint(log_id, prio, tag, fmt, ap);
595 int dlog_vprint(log_priority prio, const char *tag, const char *fmt, va_list ap)
597 return __write_to_log(LOG_ID_APPS, prio, tag, fmt, ap, false);
600 int dlog_print(log_priority prio, const char *tag, const char *fmt, ...)
605 int ret = dlog_vprint(prio, tag, fmt, ap);
612 * @brief Finalize DLog
613 * @details Finalizes and deallocates the library
614 * @notes Used directly in tests; brings back the pre-init state
616 void __dlog_fini(void)
618 if (destroy_backend) {
620 destroy_backend = NULL;
623 is_initialized = false;
626 __log_limiter_destroy();
627 __dynamic_config_destroy();