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.
30 #include <dynamic_config.h>
32 #include <logcommon.h>
33 #include "logconfig.h"
34 #include "loglimiter.h"
36 #define DEFAULT_CONFIG_LIMITER false
37 #define DEFAULT_CONFIG_PLOG true
38 #define DEFAULT_CONFIG_DEBUGMODE 0
39 #define DEFAULT_CONFIG_LIMITER_APPLY_TO_ALL_BUFFERS 0
42 * @brief Points to a function which writes a log message
43 * @details The function pointed to depends on the backend used
44 * @param[in] log_id ID of the buffer to log to. Belongs to (LOG_ID_INVALID, LOG_ID_MAX) non-inclusive
45 * @param[in] prio Priority of the message.
46 * @param[in] tag The message tag, identifies the sender.
47 * @param[in] msg The contents of the message.
48 * @return Returns the number of bytes written on success and a negative error value on error.
49 * @see __dlog_init_backend
51 int (*write_to_log)(log_id_t log_id, log_priority prio, const char *tag, const char *msg) = NULL;
52 void (*destroy_backend)();
54 pthread_rwlock_t log_limiter_lock = PTHREAD_RWLOCK_INITIALIZER;
55 static pthread_rwlock_t log_destruction_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);
64 bool plog[LOG_ID_MAX];
65 bool plog_default_values[LOG_ID_MAX];
68 static int fatal_assert;
69 static int limiter_apply_to_all_buffers;
71 static void __configure_limiter(struct log_config *config)
78 limiter = __log_limiter_create(config);
81 static int __configure_backend(struct log_config *config)
85 const char *const backend = log_config_get(config, "backend");
89 if (!strcmp(backend, "pipe"))
90 __dlog_init_pipe(config);
91 else if (!strcmp(backend, "logger"))
92 __dlog_init_android(config);
99 static void __set_plog_default_values()
101 for (int i = 0; i < NELEMS(plog); ++i)
102 plog_default_values[i] = plog[i];
105 static void __initialize_plog(const struct log_config *config)
109 const bool plog_default = log_config_get_boolean(config, "plog", DEFAULT_CONFIG_PLOG);
110 for (int i = 0; i < NELEMS(plog); ++i)
111 plog[i] = plog_default;
112 plog[LOG_ID_APPS] = true; // the default does not apply here for backward compatibility reasons.
113 __set_plog_default_values();
116 static void __configure_parameters(struct log_config *config)
120 __initialize_plog(config);
121 __update_plog(config);
122 __set_plog_default_values();
124 debugmode = log_config_get_int(config, "debugmode", DEFAULT_CONFIG_DEBUGMODE);
125 fatal_assert = access(DEBUGMODE_FILE, F_OK) != -1;
126 limiter = log_config_get_boolean(config, "limiter", DEFAULT_CONFIG_LIMITER);
127 limiter_apply_to_all_buffers = log_config_get_int(config,
128 "limiter_apply_to_all_buffers",
129 DEFAULT_CONFIG_LIMITER_APPLY_TO_ALL_BUFFERS);
132 void __update_plog(const struct log_config *conf)
136 for (int i = 0; i < NELEMS(plog); ++i) {
137 char key[MAX_CONF_KEY_LEN];
138 const int r = snprintf(key, sizeof key, "enable_%s", log_name_by_id((log_id_t)i));
141 plog[i] = log_config_get_boolean(conf, key, plog_default_values[i]);
146 * @brief Configure the library
147 * @details Reads relevant config values
148 * @remarks This is more or less a constructor, but there are some obstacles
149 * to using it as such (i.e. with attribute constructor):
151 * - some important pieces of the system link to dlog, they start very early
152 * such that dlog can't properly initialize (which lasts for program lifetime)
153 * but don't actually log anything until later on and would be fine under lazy
154 * initialisation. The way to do it "properly" would be to expose this function
155 * into the API so that people can manually call it when they're ready, but
156 * one of the design goals of the current API is that it requires absolutely no
157 * other calls than `dlog_print`. Changing it would require somebody with a
158 * bird's eye view of the system to produce a design so I wouldn't count on it.
160 * - the constructor would need to have as high of a priority as possible (so as
161 * to minimize the risk of another library's constructor using uninitialized data)
162 * but at the same time others might want some room to wrap functions before
163 * dlog uses them (think mprobe/mcheck). This would also require a design pass.
168 void __configure(void)
170 struct log_config config;
172 if (log_config_read(&config) < 0)
175 dynamic_config = __dynamic_config_create(&config);
177 __configure_parameters(&config);
179 if (!__configure_backend(&config))
182 __configure_limiter(&config);
185 log_config_free(&config);
189 static bool first = true;
190 static void initialize()
195 /* The mutex acts as a barrier, but otherwise the C language's
196 * machine abstraction is single-threaded. This means that the
197 * compiler is free to rearrange calls inside the mutex according
198 * to the as-if rule because it doesn't care if another thread can
199 * access it in parallel. In particular, `is_initialized = true`
200 * directly after `__configure()` could be rearranged to go in
201 * front of it because it is not touched inside that function
202 * if the compiler thinks it helps somehow (not unlikely: since
203 * it is checked before the mutex, it is very probable for it to
204 * still be in the CPU register or something like that). On top
205 * of that, some architectures (in particular, armv7l) don't have
206 * strict memory guarantees and can reorder actual memory stores
207 * on their own, even if the compiler didn't do anything fancy
208 * when creating machine code. For more info about the issue,
209 * see https://www.aristeia.com/Papers/DDJ_Jul_Aug_2004_revised.pdf
211 * Ultimately this means that there needs to be some sort of
212 * barrier between `__configure` and `is_initialized = true`,
213 * and the simplest way to achieve that is to just wait until
214 * the second entry into the mutex. */
216 pthread_mutex_lock(&log_construction_lock);
219 first = false; // pop this cherry
221 is_initialized = true;
223 pthread_mutex_unlock(&log_construction_lock);
227 * @brief Fatal assertion
228 * @details Conditionally crash the sucka who sent the log
229 * @param[in] prio Priority of the log
231 static void __dlog_fatal_assert(int prio)
233 assert(!fatal_assert || (prio != DLOG_FATAL));
237 * @brief Check log validity
238 * @details Checks whether the log is valid and eligible for printing
239 * @param[in] log_id The target buffer ID
240 * @param[in] prio The log's priority
241 * @param[in] tag The log's tag
242 * @return DLOG_ERROR_NONE on success, else an error code.
243 * @retval DLOG_ERROR_INVALID_PARAMETER Invalid parameter
245 static int dlog_check_validity(log_id_t log_id, int prio, const char *tag)
248 return DLOG_ERROR_INVALID_PARAMETER;
250 if (log_id <= LOG_ID_INVALID || LOG_ID_MAX <= log_id)
251 return DLOG_ERROR_INVALID_PARAMETER;
253 return DLOG_ERROR_NONE;
257 * @brief Check log against limiter rules
258 * @details Checks whether the log passes current limiter rules
259 * @param[in] log_id The target buffer ID
260 * @param[in] prio The log's priority
261 * @param[in] tag The log's tag
262 * @return DLOG_ERROR_NONE on success, else an error code.
263 * @retval DLOG_ERROR_NOT_PERMITTED Not permitted
265 static int dlog_check_limiter(log_id_t log_id, int prio, const char *tag)
267 if (!debugmode && prio <= DLOG_DEBUG)
268 return DLOG_ERROR_NOT_PERMITTED;
271 __dynamic_config_update();
274 pthread_rwlock_rdlock(&log_limiter_lock);
275 int should_log = __log_limiter_pass_log(tag, prio);
276 pthread_rwlock_unlock(&log_limiter_lock);
279 return DLOG_ERROR_NOT_PERMITTED;
280 } else if (should_log < 0) {
281 write_to_log(log_id, prio, tag,
282 "Your log has been blocked due to limit of log lines per minute.");
283 return DLOG_ERROR_NOT_PERMITTED;
287 /* This can change due to __dynamic_config_update(), but is atomic and its
288 * value implies nothing else so does not need to be under a lock. */
290 return DLOG_ERROR_NOT_PERMITTED;
292 return DLOG_ERROR_NONE;
295 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)
297 if ((check_should_log || limiter_apply_to_all_buffers) && (dlog_check_limiter(log_id, prio, tag) < 0))
298 return DLOG_ERROR_NONE;
300 char buf[LOG_MAX_PAYLOAD_SIZE];
301 vsnprintf(buf, sizeof buf, fmt, ap);
302 return write_to_log(log_id, prio, tag, buf);
305 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)
307 int ret = dlog_check_validity(log_id, prio, tag);
311 /* The only thing that needs to be protected here is `write_to_log` since
312 * all other resources already have their own specific locks (and even the
313 * pointer could be made to point at a null handler instead of a true NULL)
314 * but giving this guarantee makes everything a lot simpler as it removes
315 * the risk of something suddenly becoming NULL during processing. */
316 pthread_rwlock_rdlock(&log_destruction_lock);
318 ret = write_to_log ? __write_to_log_critical_section(log_id, prio, tag, fmt, ap, check_should_log) : DLOG_ERROR_NOT_PERMITTED;
319 pthread_rwlock_unlock(&log_destruction_lock);
326 * @details Print a log line
327 * @param[in] log_id The target buffer ID
328 * @param[in] prio Priority
330 * @param[in] fmt Format (same as printf)
331 * @param[in] ap Argument list
332 * @return Bytes written, or negative error
334 int __dlog_vprint(log_id_t log_id, int prio, const char *tag, const char *fmt, va_list ap)
336 int ret = __write_to_log(log_id, prio, tag, fmt, ap, true);
337 __dlog_fatal_assert(prio);
344 * @details Print a log line
345 * @param[in] log_id The target buffer ID
346 * @param[in] prio Priority
348 * @param[in] fmt Format (same as printf)
349 * @return Bytes written, or negative error
351 int __dlog_print(log_id_t log_id, int prio, const char *tag, const char *fmt, ...)
356 int ret = __dlog_vprint(log_id, prio, tag, fmt, ap);
362 int dlog_vprint(log_priority prio, const char *tag, const char *fmt, va_list ap)
364 return __write_to_log(LOG_ID_APPS, prio, tag, fmt, ap, false);
367 int dlog_print(log_priority prio, const char *tag, const char *fmt, ...)
372 int ret = dlog_vprint(prio, tag, fmt, ap);
379 * @brief Finalize DLog
380 * @details Finalizes and deallocates the library
381 * @notes Used directly in tests; brings back the pre-init state
386 void __dlog_fini(void)
388 if (destroy_backend) {
390 destroy_backend = NULL;
393 is_initialized = false;
396 __log_limiter_destroy();
397 __dynamic_config_destroy();
403 static void __attribute__((destructor))
407 pthread_rwlock_wrlock(&log_destruction_lock);
410 /* IMPORTANT! The lock is NEVER RELEASED. This is done ON PURPOSE.
411 * The critical section can still be reached in some ways, NONE LEGAL.
413 * The first is that the program links the library dynamically and keeps
414 * pointers to API functions past dlclose(). This is UNDEFINED BEHAVIOUR
415 * and the implementation is NOT REQUIRED to keep the functions in memory
416 * AT ALL and doing this COULD HAVE ALREADY CRASHED the program under a
417 * different implementation.
419 * The second is when linking statically and FAILING TO JOIN threads before
420 * exit(). These threads then typically keep running and can access the
421 * library interface. However, they WILL DIE ANY MOMENT NOW ANYWAY so
422 * getting deadlocked is of no consequence.
424 * In theory it would be possible to detect that destruction has already
425 * taken place and reinitialize the library to salvage a logging attempt.
426 * This is a HORRIBLE IDEA since without a destructor to rely on, either
427 * those RESOURCES WOULD LEAK or we would have to MASSIVELY CONVOLUTE our
428 * logic for manual destruction in such cases. */