1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: t -*-
3 * Copyright (c) 2012-2013 Samsung Electronics Co., Ltd.
19 #include <dynamic_config.h>
21 #include <logcommon.h>
22 #include "logconfig.h"
23 #include "loglimiter.h"
25 #define DEFAULT_CONFIG_LIMITER false
26 #define DEFAULT_CONFIG_PLOG true
27 #define DEFAULT_CONFIG_DEBUGMODE 0
28 #define DEFAULT_CONFIG_LIMITER_APPLY_TO_ALL_BUFFERS 0
31 * @brief Points to a function which writes a log message
32 * @details The function pointed to depends on the backend used
33 * @param[in] log_id ID of the buffer to log to. Belongs to (LOG_ID_INVALID, LOG_ID_MAX) non-inclusive
34 * @param[in] prio Priority of the message.
35 * @param[in] tag The message tag, identifies the sender.
36 * @param[in] msg The contents of the message.
37 * @return Returns the number of bytes written on success and a negative error value on error.
38 * @see __dlog_init_backend
40 int (*write_to_log)(log_id_t log_id, log_priority prio, const char *tag, const char *msg) = NULL;
41 void (*destroy_backend)();
43 pthread_rwlock_t log_limiter_lock = PTHREAD_RWLOCK_INITIALIZER;
44 static pthread_mutex_t log_construction_lock = PTHREAD_MUTEX_INITIALIZER;
45 static bool is_initialized = false;
47 extern void __dlog_init_pipe(const struct log_config *conf);
48 extern void __dlog_init_android(const struct log_config *conf);
51 static bool dynamic_config;
52 static bool plog[LOG_ID_MAX];
53 static bool plog_default_values[LOG_ID_MAX];
54 static bool enable_secure_logs = true;
57 static int fatal_assert;
58 static int limiter_apply_to_all_buffers;
60 static void __configure_limiter(struct log_config *config)
67 limiter = __log_limiter_create(config);
70 static int __configure_backend(struct log_config *config)
74 const char *const backend = log_config_get(config, "backend");
78 if (!strcmp(backend, "pipe"))
79 __dlog_init_pipe(config);
80 else if (!strcmp(backend, "logger"))
81 __dlog_init_android(config);
88 static void __set_plog_default_values()
90 for (size_t i = 0; i < NELEMS(plog); ++i)
91 plog_default_values[i] = plog[i];
94 static void __initialize_plog(const struct log_config *config)
98 const bool plog_default = log_config_get_boolean(config, "plog", DEFAULT_CONFIG_PLOG);
99 for (size_t i = 0; i < NELEMS(plog); ++i)
100 plog[i] = plog_default;
101 plog[LOG_ID_APPS] = true; // the default does not apply here for backward compatibility reasons.
102 __set_plog_default_values();
105 static void __configure_parameters(struct log_config *config)
109 __initialize_plog(config);
110 __update_plog(config);
111 __set_plog_default_values();
113 enable_secure_logs = log_config_get_boolean(config, "enable_secure_logs", enable_secure_logs);
114 debugmode = log_config_get_int(config, "debugmode", DEFAULT_CONFIG_DEBUGMODE);
115 fatal_assert = access(DEBUGMODE_FILE, F_OK) != -1;
116 limiter = log_config_get_boolean(config, "limiter", DEFAULT_CONFIG_LIMITER);
117 limiter_apply_to_all_buffers = log_config_get_int(config,
118 "limiter_apply_to_all_buffers",
119 DEFAULT_CONFIG_LIMITER_APPLY_TO_ALL_BUFFERS);
122 void __update_plog(const struct log_config *conf)
126 for (size_t i = 0; i < NELEMS(plog); ++i) {
127 char key[MAX_CONF_KEY_LEN];
128 const int r = snprintf(key, sizeof key, "enable_%s", log_name_by_id((log_id_t)i));
131 plog[i] = log_config_get_boolean(conf, key, plog_default_values[i]);
136 * @brief Configure the library
137 * @details Reads relevant config values
138 * @remarks This is more or less a constructor, but there are some obstacles
139 * to using it as such (i.e. with attribute constructor):
141 * - some important pieces of the system link to dlog, they start very early
142 * such that dlog can't properly initialize (which lasts for program lifetime)
143 * but don't actually log anything until later on and would be fine under lazy
144 * initialisation. The way to do it "properly" would be to expose this function
145 * into the API so that people can manually call it when they're ready, but
146 * one of the design goals of the current API is that it requires absolutely no
147 * other calls than `dlog_print`. Changing it would require somebody with a
148 * bird's eye view of the system to produce a design so I wouldn't count on it.
150 * - the constructor would need to have as high of a priority as possible (so as
151 * to minimize the risk of another library's constructor using uninitialized data)
152 * but at the same time others might want some room to wrap functions before
153 * dlog uses them (think mprobe/mcheck). This would also require a design pass.
158 bool __configure(void)
160 __attribute__((cleanup(log_config_free))) struct log_config config;
162 if (log_config_read(&config) < 0)
165 dynamic_config = __dynamic_config_create(&config);
167 __configure_parameters(&config);
169 if (!__configure_backend(&config)) {
170 __dynamic_config_destroy();
171 dynamic_config = false;
175 __configure_limiter(&config);
179 static void __attribute__((constructor(101))) __install_pipe_handler(void)
181 /* We mask SIGPIPE signal because most applications do not install their
182 * own SIGPIPE handler. Default behaviour in SIGPIPE case is to abort the
183 * process. SIGPIPE occurs when e.g. dlog daemon closes read pipe endpoint.
185 * We do this in the library constructor (at maximum priority) and not
186 * during regular (lazy) initialisation so as to prevent overwriting the
187 * program's actual signal handler, if it has one.
189 * In theory this is not required for the Android logger backend; however,
190 * this early we don't yet know the backend and also it is good to behave
191 * consistently in this regard anyway.
193 * We don't revert this in a destructor because Unix signals are bonkers
194 * and we have no way to do this cleanly. Most libdlog users don't use
195 * runtime linking so this would mostly done at program exit either way. */
196 signal(SIGPIPE, SIG_IGN);
199 static bool first = true;
200 static bool initialize()
205 /* The mutex acts as a barrier, but otherwise the C language's
206 * machine abstraction is single-threaded. This means that the
207 * compiler is free to rearrange calls inside the mutex according
208 * to the as-if rule because it doesn't care if another thread can
209 * access it in parallel. In particular, `is_initialized = true`
210 * directly after `__configure()` could be rearranged to go in
211 * front of it because it is not touched inside that function
212 * if the compiler thinks it helps somehow (not unlikely: since
213 * it is checked before the mutex, it is very probable for it to
214 * still be in the CPU register or something like that). On top
215 * of that, some architectures (in particular, armv7l) don't have
216 * strict memory guarantees and can reorder actual memory stores
217 * on their own, even if the compiler didn't do anything fancy
218 * when creating machine code. For more info about the issue,
219 * see https://www.aristeia.com/Papers/DDJ_Jul_Aug_2004_revised.pdf
221 * Ultimately this means that there needs to be some sort of
222 * barrier between `__configure` and `is_initialized = true`,
223 * and the simplest way to achieve that is to just wait until
224 * the second entry into the mutex. */
227 pthread_mutex_lock(&log_construction_lock);
229 first = !__configure();
231 is_initialized = true;
233 pthread_mutex_unlock(&log_construction_lock);
238 * @brief Fatal assertion
239 * @details Conditionally crash the sucka who sent the log
240 * @param[in] prio Priority of the log
242 static void __dlog_fatal_assert(int prio)
244 assert(!fatal_assert || (prio != DLOG_FATAL));
248 * @brief Check log validity
249 * @details Checks whether the log is valid and eligible for printing
250 * @param[in] log_id The target buffer ID
251 * @param[in] prio The log's priority
252 * @param[in] tag The log's tag
253 * @return DLOG_ERROR_NONE on success, else an error code.
254 * @retval DLOG_ERROR_INVALID_PARAMETER Invalid parameter
256 static int dlog_check_validity(log_id_t log_id, int prio, const char *tag)
260 return DLOG_ERROR_INVALID_PARAMETER;
262 if (log_id <= LOG_ID_INVALID || LOG_ID_MAX <= log_id)
263 return DLOG_ERROR_INVALID_PARAMETER;
265 return DLOG_ERROR_NONE;
269 * @brief Check log against limiter rules
270 * @details Checks whether the log passes current limiter rules
271 * @param[in] log_id The target buffer ID
272 * @param[in] prio The log's priority
273 * @param[in] tag The log's tag
274 * @return DLOG_ERROR_NONE on success, else an error code.
275 * @retval DLOG_ERROR_NOT_PERMITTED Not permitted
277 static int dlog_check_limiter(log_id_t log_id, int prio, const char *tag)
279 if (!debugmode && prio <= DLOG_DEBUG)
280 return DLOG_ERROR_NOT_PERMITTED;
283 __dynamic_config_update();
287 if (!pthread_rwlock_rdlock(&log_limiter_lock)) {
288 should_log = __log_limiter_pass_log(tag, prio);
289 pthread_rwlock_unlock(&log_limiter_lock);
293 return DLOG_ERROR_NOT_PERMITTED;
294 } else if (should_log < 0) {
295 write_to_log(log_id, prio, tag,
296 "Your log has been blocked due to limit of log lines per minute.");
297 return DLOG_ERROR_NOT_PERMITTED;
301 /* This can change due to __dynamic_config_update(), but is atomic and its
302 * value implies nothing else so does not need to be under a lock. */
304 return DLOG_ERROR_NOT_PERMITTED;
306 return DLOG_ERROR_NONE;
309 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)
311 if ((check_should_log || limiter_apply_to_all_buffers) && (dlog_check_limiter(log_id, prio, tag) < 0))
312 return DLOG_ERROR_NONE;
314 char buf[LOG_MAX_PAYLOAD_SIZE];
315 vsnprintf(buf, sizeof buf, fmt, ap);
316 return write_to_log(log_id, prio, tag, buf);
319 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, bool secure_log)
321 int ret = dlog_check_validity(log_id, prio, tag);
325 /* Threads can be cancelled before they give up a lock.
326 * Therefore cancellation is temporarily disabled.
327 * This solution is comparatively simple and cheap.
328 * The other solutions (cleanup handlers, robust mutexes)
329 * would be much more complicated and also inflict larger
330 * runtime costs. The downside of disabling cancellation
331 * is not a problem in our case because it is temporary
332 * and very brief so we don't keep an obsolete thread
333 * for much longer than we otherwise would. */
334 int old_cancel_state;
335 pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &old_cancel_state);
337 /* The only thing that needs to be protected here is `write_to_log` since
338 * all other resources already have their own specific locks (and even the
339 * pointer could be made to point at a null handler instead of a true NULL)
340 * but giving this guarantee makes everything a lot simpler as it removes
341 * the risk of something suddenly becoming NULL during processing. */
342 if (!initialize() || !write_to_log)
343 ret = DLOG_ERROR_NOT_PERMITTED;
344 else if (secure_log && !enable_secure_logs)
347 ret = __write_to_log_critical_section(log_id, prio, tag, fmt, ap, check_should_log);
349 pthread_setcancelstate(old_cancel_state, NULL);
354 int __critical_log_append_timestamp(char *buf, size_t buflen)
356 /* NB: the timestamp may slightly differ from the one that gets
357 * added onto the copy that goes into the regular buffer, and
358 * timestamp acquisition is duplicated. This would ideally be
359 * solved, but timestamps are currently added fairly deep in
360 * backend-specific functions so for now this will have to do.
361 * Also, since we're the sender, there is just this one set of
362 * timestamps, i.e. the send timestamp! The usual alternative
363 * set of receive timestamps will never have the opportunity
364 * to get added to the entry since this log is supposed to end
365 * up straight in the file (there's potentially the trusted
366 * writer binary but we're trying to keep the set of actions
367 * it needs to do to the minimum and those timestamps would
368 * in practice be the same anyway). */
371 clock_gettime(CLOCK_REALTIME, &ts);
372 const time_t tt = ts.tv_sec;
373 const long int real_millisec = ts.tv_nsec / 1000000;
374 clock_gettime(CLOCK_MONOTONIC, &ts);
375 #ifdef HAVE_LOCALTIME_R
377 struct tm *const ptm = localtime_r(&tt, &tmBuf);
379 struct tm *const ptm = localtime(&tt);
381 assert(ptm); // we're in a short lived fork so asserts are fine and make things simple
383 int len = strftime(buf, buflen, "%m-%d %H:%M:%S", ptm);
386 int tmp_len = snprintf(buf + len, buflen - len, ".%03ld", real_millisec);
388 assert(tmp_len < buflen - len);
391 tmp_len = strftime(buf + len, buflen - len, "%z ", ptm);
392 assert(tmp_len != 0);
395 tmp_len = snprintf(buf + len, buflen - len, "%5lu.%03ld", ts.tv_sec, ts.tv_nsec / 1000000);
397 assert(tmp_len < buflen - len);
403 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)
405 int len = __critical_log_append_timestamp(buf, buflen);
406 const int metadata_len = snprintf(buf + len, buflen - len, " P%5d T%5d B%-6s %c/%-8s: ",
409 log_name_by_id(log_id),
410 filter_pri_to_char(prio),
411 tag ?: "CRITICAL_NO_TAG");
412 assert(metadata_len > 0);
413 if (metadata_len >= buflen - len)
414 return buflen - 1; // can genuinely happen with an exceedingly large tag
417 const int content_len = vsnprintf(buf + len, buflen - len, fmt, ap);
418 assert(content_len >= 0); // 0 is legit with format == ""
419 if (content_len >= buflen - len)
427 __attribute__ ((noreturn))
429 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)
431 char buf[LOG_MAX_PAYLOAD_SIZE + 128]; // extra space for some metadata
432 const int len = __critical_log_build_msg(buf, sizeof buf - 1, main_pid, main_tid, log_id, prio, tag, fmt, ap);
436 static const char *const path = "/usr/libexec/dlog-log-critical";
437 execl(path, path /* argv[0] convention */, buf, (char *) NULL);
440 /* Compilers are sometimes smart enough to recognize _exit's
441 * noreturn attribute, even if we wrap it with something that
442 * returns. This causes it to behave in unexpected ways, for
443 * example it can blow up the program regardless or it can
444 * optimize some conditionals out (and incorrectly enter them
445 * after the exit call fails to actually exit). This makes it
446 * unsuitable for tests. */
448 _exit(1); // not the regular `exit` so as not to trigger any `atexit` handlers prematurely
452 #ifndef UNIT_TEST // contains forks and exits, these don't work well with wrapping (see above)
453 void __critical_log(log_id_t log_id, int prio, const char *tag, const char *fmt, va_list ap)
455 /* Critical log functionality is mostly done in a separate binary
456 * to handle security correctly (else every process would have to
457 * possess the necessary privilege to write onto that file, which
458 * would be opening a fairly nasty can of worms from the security
459 * point of view). Our use of exec() is why a simple thread would
460 * not suffice and we're resorting to a fork.
462 * The double fork, much like a double barreled 12 gauge shotgun,
463 * is an elegant solution designed to stop a zombie army. We'd be
464 * creating zombie processes if we didn't wait() for the children
465 * we spawn, but we don't really want to do that since it results
466 * in a needless delay. Instead, the writer process is actually a
467 * grandchild, with our direct child exiting immediately just for
468 * us to have something to wait on that is guaranteed not to take
469 * too long. The orphaned grandchild is adopted by init, who will
470 * take care to reap it when it dies. In addition to avoiding the
471 * delay, the client will not have any unexpected children (which
472 * could ruin logic in its own waits).
475 * ┌───────┐ ┌─────────┐ ┌─────────────┐ ┌────────┐
476 * │ pid 1 ├──>│ libdlog ├──>│ immediately ├──>│ execs │
477 * │ init │ │ client │ │ exits │ │ writer │
478 * └───────┘ └─────────┘ └─────────────┘ └────────┘
480 * Afterwards, libdlog has no children:
481 * ┌───────┐ ┌─────────┐ ┌────────┐
482 * │ pid 1 ├──>│ libdlog │ ┌─────────>│ writer │
483 * │ init ├─┐ │ client │ │ │ binary │
484 * └───────┘ │ └─────────┘ │ └────────┘
485 * └──────────────────────┘
488 const pid_t main_pid = getpid();
489 const pid_t main_tid = gettid();
491 const int temporary_exiter_pid = fork();
492 if (temporary_exiter_pid < 0)
494 if (temporary_exiter_pid != 0) {
495 waitpid(temporary_exiter_pid, NULL, 0);
499 const int child_pid = fork();
505 __critical_log_child(main_pid, main_tid, log_id, prio, tag, fmt, ap);
508 int __dlog_critical_print(log_id_t log_id, int prio, const char *tag, const char *fmt, ...)
513 __critical_log(log_id, prio, tag, fmt, ap);
517 int ret = __dlog_vprint(log_id, prio, tag, fmt, ap);
526 * @details Print a log line
527 * @param[in] log_id The target buffer ID
528 * @param[in] prio Priority
530 * @param[in] fmt Format (same as printf)
531 * @param[in] ap Argument list
532 * @return Bytes written, or negative error
534 int __dlog_vprint(log_id_t log_id, int prio, const char *tag, const char *fmt, va_list ap)
536 int ret = __write_to_log(log_id, prio, tag, fmt, ap, true, false);
537 __dlog_fatal_assert(prio);
544 * @details Print a log line
545 * @param[in] log_id The target buffer ID
546 * @param[in] prio Priority
548 * @param[in] fmt Format (same as printf)
549 * @return Bytes written, or negative error
551 int __dlog_print(log_id_t log_id, int prio, const char *tag, const char *fmt, ...)
556 int ret = __dlog_vprint(log_id, prio, tag, fmt, ap);
564 * @details Print a log line
565 * @param[in] log_id The target buffer ID
566 * @param[in] prio Priority
568 * @param[in] fmt Format (same as printf)
569 * @return Bytes written, or negative error
571 int __dlog_sec_print(log_id_t log_id, int prio, const char *tag, const char *fmt, ...)
573 if (!enable_secure_logs)
579 int ret = __write_to_log(log_id, prio, tag, fmt, ap, true, true);
580 __dlog_fatal_assert(prio);
586 int dlog_vprint(log_priority prio, const char *tag, const char *fmt, va_list ap)
588 return __write_to_log(LOG_ID_APPS, prio, tag, fmt, ap, false, false);
591 int dlog_print(log_priority prio, const char *tag, const char *fmt, ...)
596 int ret = dlog_vprint(prio, tag, fmt, ap);
603 * @brief Finalize DLog
604 * @details Finalizes and deallocates the library
605 * @notes Used directly in tests; brings back the pre-init state
607 void __dlog_fini(void)
609 if (destroy_backend) {
611 destroy_backend = NULL;
614 is_initialized = false;
617 __log_limiter_destroy();
618 __dynamic_config_destroy();