log_read.c revision 6c1b07fbbd0ccce0e4fdf79abd38494cc622d67e 
1/*
2** Copyright 2013, The Android Open Source Project
3**
4** Licensed under the Apache License, Version 2.0 (the "License");
5** you may not use this file except in compliance with the License.
6** You may obtain a copy of the License at
7**
8**     http://www.apache.org/licenses/LICENSE-2.0
9**
10** Unless required by applicable law or agreed to in writing, software
11** distributed under the License is distributed on an "AS IS" BASIS,
12** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13** See the License for the specific language governing permissions and
14** limitations under the License.
15*/
16
17#define _GNU_SOURCE /* asprintf for x86 host */
18#include <errno.h>
19#include <fcntl.h>
20#include <poll.h>
21#include <string.h>
22#include <stdio.h>
23#include <stdlib.h>
24#include <cutils/list.h>
25#include <log/log.h>
26#include <log/logger.h>
27
28typedef char bool;
29#define false (const bool)0
30#define true (const bool)1
31
32#define LOG_FILE_DIR "/dev/log/"
33
34#define LOG_TIMEOUT_MS 5
35
36#define logger_for_each(logger, logger_list) \
37    for (logger = node_to_item((logger_list)->node.next, struct logger, node); \
38         logger != node_to_item(&(logger_list)->node, struct logger, node); \
39         logger = node_to_item((logger)->node.next, struct logger, node))
40
41/* In the future, we would like to make this list extensible */
42static const char *LOG_NAME[LOG_ID_MAX] = {
43    [LOG_ID_MAIN] = "main",
44    [LOG_ID_RADIO] = "radio",
45    [LOG_ID_EVENTS] = "events",
46    [LOG_ID_SYSTEM] = "system"
47};
48
49const char *android_log_id_to_name(log_id_t log_id) {
50    if (log_id >= LOG_ID_MAX) {
51        log_id = LOG_ID_MAIN;
52    }
53    return LOG_NAME[log_id];
54}
55
56static int accessmode(int mode)
57{
58    if ((mode & O_ACCMODE) == O_WRONLY) {
59        return W_OK;
60    }
61    if ((mode & O_ACCMODE) == O_RDWR) {
62        return R_OK | W_OK;
63    }
64    return R_OK;
65}
66
67/* repeated fragment */
68static int check_allocate_accessible(char **n, const char *b, int mode)
69{
70    *n = NULL;
71
72    if (!b) {
73        return -EINVAL;
74    }
75
76    asprintf(n, LOG_FILE_DIR "%s", b);
77    if (!*n) {
78        return -1;
79    }
80
81    return access(*n, accessmode(mode));
82}
83
84log_id_t android_name_to_log_id(const char *logName) {
85    const char *b;
86    char *n;
87    int ret;
88
89    if (!logName) {
90        return -1; /* NB: log_id_t is unsigned */
91    }
92    b = strrchr(logName, '/');
93    if (!b) {
94        b = logName;
95    } else {
96        ++b;
97    }
98
99    ret = check_allocate_accessible(&n, b, O_RDONLY);
100    free(n);
101    if (ret) {
102        return ret;
103    }
104
105    for(ret = LOG_ID_MIN; ret < LOG_ID_MAX; ++ret) {
106        const char *l = LOG_NAME[ret];
107        if (l && !strcmp(b, l)) {
108            return ret;
109        }
110    }
111    return -1;   /* should never happen */
112}
113
114struct logger_list {
115    struct listnode node;
116    int mode;
117    unsigned int tail;
118    pid_t pid;
119    unsigned int queued_lines;
120    int timeout_ms;
121    int error;
122    bool flush;
123    bool valid_entry; /* valiant(?) effort to deal with memory starvation */
124    struct log_msg entry;
125};
126
127struct log_list {
128    struct listnode node;
129    struct log_msg entry; /* Truncated to event->len() + 1 to save space */
130};
131
132struct logger {
133    struct listnode node;
134    struct logger_list *top;
135    int fd;
136    log_id_t id;
137    short *revents;
138    struct listnode log_list;
139};
140
141/* android_logger_alloc unimplemented, no use case */
142/* android_logger_free not exported */
143static void android_logger_free(struct logger *logger)
144{
145    if (!logger) {
146        return;
147    }
148
149    while (!list_empty(&logger->log_list)) {
150        struct log_list *entry = node_to_item(
151            list_head(&logger->log_list), struct log_list, node);
152        list_remove(&entry->node);
153        free(entry);
154        if (logger->top->queued_lines) {
155            logger->top->queued_lines--;
156        }
157    }
158
159    if (logger->fd >= 0) {
160        close(logger->fd);
161    }
162
163    list_remove(&logger->node);
164
165    free(logger);
166}
167
168log_id_t android_logger_get_id(struct logger *logger)
169{
170    return logger->id;
171}
172
173/* worker for sending the command to the logger */
174static int logger_ioctl(struct logger *logger, int cmd, int mode)
175{
176    char *n;
177    int  f, ret;
178
179    if (!logger || !logger->top) {
180        return -EFAULT;
181    }
182
183    if (((mode & O_ACCMODE) == O_RDWR)
184     || (((mode ^ logger->top->mode) & O_ACCMODE) == 0)) {
185        return ioctl(logger->fd, cmd);
186    }
187
188    /* We go here if android_logger_list_open got mode wrong for this ioctl */
189    ret = check_allocate_accessible(&n, android_log_id_to_name(logger->id), mode);
190    if (ret) {
191        free(n);
192        return ret;
193    }
194
195    f = open(n, mode);
196    free(n);
197    if (f < 0) {
198        return f;
199    }
200
201    ret = ioctl(f, cmd);
202    close (f);
203
204    return ret;
205}
206
207int android_logger_clear(struct logger *logger)
208{
209    return logger_ioctl(logger, LOGGER_FLUSH_LOG, O_WRONLY);
210}
211
212/* returns the total size of the log's ring buffer */
213int android_logger_get_log_size(struct logger *logger)
214{
215    return logger_ioctl(logger, LOGGER_GET_LOG_BUF_SIZE, O_RDWR);
216}
217
218/*
219 * returns the readable size of the log's ring buffer (that is, amount of the
220 * log consumed)
221 */
222int android_logger_get_log_readable_size(struct logger *logger)
223{
224    return logger_ioctl(logger, LOGGER_GET_LOG_LEN, O_RDONLY);
225}
226
227/*
228 * returns the logger version
229 */
230int android_logger_get_log_version(struct logger *logger)
231{
232    int ret = logger_ioctl(logger, LOGGER_GET_VERSION, O_RDWR);
233    return (ret < 0) ? 1 : ret;
234}
235
236struct logger_list *android_logger_list_alloc(int mode,
237                                              unsigned int tail,
238                                              pid_t pid)
239{
240    struct logger_list *logger_list;
241
242    logger_list = calloc(1, sizeof(*logger_list));
243    if (!logger_list) {
244        return NULL;
245    }
246    list_init(&logger_list->node);
247    logger_list->mode = mode;
248    logger_list->tail = tail;
249    logger_list->pid = pid;
250    return logger_list;
251}
252
253/* android_logger_list_register unimplemented, no use case */
254/* android_logger_list_unregister unimplemented, no use case */
255
256/* Open the named log and add it to the logger list */
257struct logger *android_logger_open(struct logger_list *logger_list,
258                                   log_id_t id)
259{
260    struct listnode *node;
261    struct logger *logger;
262    char *n;
263
264    if (!logger_list || (id >= LOG_ID_MAX)) {
265        goto err;
266    }
267
268    logger_for_each(logger, logger_list) {
269        if (logger->id == id) {
270            goto ok;
271        }
272    }
273
274    logger = calloc(1, sizeof(*logger));
275    if (!logger) {
276        goto err;
277    }
278
279    if (check_allocate_accessible(&n, android_log_id_to_name(id),
280                                  logger_list->mode)) {
281        goto err_name;
282    }
283
284    logger->fd = open(n, logger_list->mode);
285    if (logger->fd < 0) {
286        goto err_name;
287    }
288
289    free(n);
290    logger->id = id;
291    list_init(&logger->log_list);
292    list_add_tail(&logger_list->node, &logger->node);
293    logger->top = logger_list;
294    logger_list->timeout_ms = LOG_TIMEOUT_MS;
295    goto ok;
296
297err_name:
298    free(n);
299err_logger:
300    free(logger);
301err:
302    logger = NULL;
303ok:
304    return logger;
305}
306
307/* Open the single named log and make it part of a new logger list */
308struct logger_list *android_logger_list_open(log_id_t id,
309                                             int mode,
310                                             unsigned int tail,
311                                             pid_t pid)
312{
313    struct logger_list *logger_list = android_logger_list_alloc(mode, tail, pid);
314    if (!logger_list) {
315        return NULL;
316    }
317
318    if (!android_logger_open(logger_list, id)) {
319        android_logger_list_free(logger_list);
320        return NULL;
321    }
322
323    return logger_list;
324}
325
326/* prevent memory starvation when backfilling */
327static unsigned int queue_threshold(struct logger_list *logger_list)
328{
329    return (logger_list->tail < 64) ? 64 : logger_list->tail;
330}
331
332static bool low_queue(struct listnode *node)
333{
334    /* low is considered less than 2 */
335    return list_head(node) == list_tail(node);
336}
337
338/* Flush queues in sequential order, one at a time */
339static int android_logger_list_flush(struct logger_list *logger_list,
340                                     struct log_msg *log_msg)
341{
342    int ret = 0;
343    struct log_list *firstentry = NULL;
344
345    while ((ret == 0)
346     && (logger_list->flush
347      || (logger_list->queued_lines > logger_list->tail))) {
348        struct logger *logger;
349
350        /* Merge sort */
351        bool at_least_one_is_low = false;
352        struct logger *firstlogger = NULL;
353        firstentry = NULL;
354
355        logger_for_each(logger, logger_list) {
356            struct listnode *node;
357            struct log_list *oldest = NULL;
358
359            /* kernel logger channels not necessarily time-sort order */
360            list_for_each(node, &logger->log_list) {
361                struct log_list *entry = node_to_item(node,
362                                                      struct log_list, node);
363                if (!oldest
364                 || (entry->entry.entry.sec < oldest->entry.entry.sec)
365                 || ((entry->entry.entry.sec == oldest->entry.entry.sec)
366                  && (entry->entry.entry.nsec < oldest->entry.entry.nsec))) {
367                     oldest = entry;
368                }
369            }
370
371            if (!oldest) {
372                at_least_one_is_low = true;
373                continue;
374            } else if (low_queue(&logger->log_list)) {
375                at_least_one_is_low = true;
376            }
377
378            if (!firstentry
379             || (oldest->entry.entry.sec < firstentry->entry.entry.sec)
380             || ((oldest->entry.entry.sec == firstentry->entry.entry.sec)
381              && (oldest->entry.entry.nsec < firstentry->entry.entry.nsec))) {
382                firstentry = oldest;
383                firstlogger = logger;
384            }
385        }
386
387        if (!firstentry) {
388            break;
389        }
390
391        /* when trimming list, tries to keep one entry behind in each bucket */
392        if (!logger_list->flush
393         && at_least_one_is_low
394         && (logger_list->queued_lines < queue_threshold(logger_list))) {
395            break;
396        }
397
398        /* within tail?, send! */
399        if ((logger_list->tail == 0)
400         || (logger_list->queued_lines <= logger_list->tail)) {
401            ret = firstentry->entry.entry.hdr_size;
402            if (!ret) {
403                ret = sizeof(firstentry->entry.entry_v1);
404            }
405            ret += firstentry->entry.entry.len;
406
407            memcpy(log_msg->buf, firstentry->entry.buf, ret + 1);
408            log_msg->extra.id = firstlogger->id;
409        }
410
411        /* next entry */
412        list_remove(&firstentry->node);
413        free(firstentry);
414        if (logger_list->queued_lines) {
415            logger_list->queued_lines--;
416        }
417    }
418
419    /* Flushed the list, no longer in tail mode for continuing content */
420    if (logger_list->flush && !firstentry) {
421        logger_list->tail = 0;
422    }
423    return ret;
424}
425
426/* Read from the selected logs */
427int android_logger_list_read(struct logger_list *logger_list,
428                             struct log_msg *log_msg)
429{
430    struct logger *logger;
431    nfds_t nfds;
432    struct pollfd *p, *pollfds = NULL;
433    int error = 0, ret = 0;
434
435    memset(log_msg, 0, sizeof(struct log_msg));
436
437    if (!logger_list) {
438        return -ENODEV;
439    }
440
441    if (!(accessmode(logger_list->mode) & R_OK)) {
442        logger_list->error = EPERM;
443        goto done;
444    }
445
446    nfds = 0;
447    logger_for_each(logger, logger_list) {
448        ++nfds;
449    }
450    if (nfds <= 0) {
451        error = ENODEV;
452        goto done;
453    }
454
455    /* Do we have anything to offer from the buffer or state? */
456    if (logger_list->valid_entry) { /* implies we are also in a flush state */
457        goto flush;
458    }
459
460    ret = android_logger_list_flush(logger_list, log_msg);
461    if (ret) {
462        goto done;
463    }
464
465    if (logger_list->error) { /* implies we are also in a flush state */
466        goto done;
467    }
468
469    /* Lets start grinding on metal */
470    pollfds = calloc(nfds, sizeof(struct pollfd));
471    if (!pollfds) {
472        error = ENOMEM;
473        goto flush;
474    }
475
476    p = pollfds;
477    logger_for_each(logger, logger_list) {
478        p->fd = logger->fd;
479        p->events = POLLIN;
480        logger->revents = &p->revents;
481        ++p;
482    }
483
484    while (!ret && !error) {
485        int result;
486
487        /* If we oversleep it's ok, i.e. ignore EINTR. */
488        result = TEMP_FAILURE_RETRY(
489            poll(pollfds, nfds, logger_list->timeout_ms));
490
491        if (result <= 0) {
492            if (result) {
493                error = errno;
494            } else if (logger_list->mode & O_NDELAY) {
495                error = EAGAIN;
496            } else {
497                logger_list->timeout_ms = 0;
498            }
499
500            logger_list->flush = true;
501            goto try_flush;
502        }
503
504        logger_list->timeout_ms = LOG_TIMEOUT_MS;
505
506        /* Anti starvation */
507        if (!logger_list->flush
508         && (logger_list->queued_lines > (queue_threshold(logger_list) / 2))) {
509            /* Any queues with input pending that is low? */
510            bool starving = false;
511            logger_for_each(logger, logger_list) {
512                if ((*(logger->revents) & POLLIN)
513                 && low_queue(&logger->log_list)) {
514                    starving = true;
515                    break;
516                }
517            }
518
519            /* pushback on any queues that are not low */
520            if (starving) {
521                logger_for_each(logger, logger_list) {
522                    if ((*(logger->revents) & POLLIN)
523                     && !low_queue(&logger->log_list)) {
524                        *(logger->revents) &= ~POLLIN;
525                    }
526                }
527            }
528        }
529
530        logger_for_each(logger, logger_list) {
531            unsigned int hdr_size;
532            struct log_list *entry;
533
534            if (!(*(logger->revents) & POLLIN)) {
535                continue;
536            }
537
538            memset(logger_list->entry.buf, 0, sizeof(struct log_msg));
539            /* NOTE: driver guarantees we read exactly one full entry */
540            result = read(logger->fd, logger_list->entry.buf,
541                          LOGGER_ENTRY_MAX_LEN);
542            if (result <= 0) {
543                if (!result) {
544                    error = EIO;
545                } else if (errno != EINTR) {
546                    error = errno;
547                }
548                continue;
549            }
550
551            if (logger_list->pid
552             && (logger_list->pid != logger_list->entry.entry.pid)) {
553                continue;
554            }
555
556            hdr_size = logger_list->entry.entry.hdr_size;
557            if (!hdr_size) {
558                hdr_size = sizeof(logger_list->entry.entry_v1);
559            }
560
561            if ((hdr_size > sizeof(struct log_msg))
562             || (logger_list->entry.entry.len
563               > sizeof(logger_list->entry.buf) - hdr_size)
564             || (logger_list->entry.entry.len != result - hdr_size)) {
565                error = EINVAL;
566                continue;
567            }
568
569            logger_list->entry.extra.id = logger->id;
570
571            /* speedup: If not tail, and only one list, send directly */
572            if (!logger_list->tail
573             && (list_head(&logger_list->node)
574              == list_tail(&logger_list->node))) {
575                ret = result;
576                memcpy(log_msg->buf, logger_list->entry.buf, result + 1);
577                log_msg->extra.id = logger->id;
578                break;
579            }
580
581            entry = malloc(sizeof(*entry) - sizeof(entry->entry) + result + 1);
582
583            if (!entry) {
584                logger_list->valid_entry = true;
585                error = ENOMEM;
586                break;
587            }
588
589            logger_list->queued_lines++;
590
591            memcpy(entry->entry.buf, logger_list->entry.buf, result);
592            entry->entry.buf[result] = '\0';
593            list_add_tail(&logger->log_list, &entry->node);
594        }
595
596        if (ret <= 0) {
597try_flush:
598            ret = android_logger_list_flush(logger_list, log_msg);
599        }
600    }
601
602    free(pollfds);
603
604flush:
605    if (error) {
606        logger_list->flush = true;
607    }
608
609    if (ret <= 0) {
610        ret = android_logger_list_flush(logger_list, log_msg);
611
612        if (!ret && logger_list->valid_entry) {
613            ret = logger_list->entry.entry.hdr_size;
614            if (!ret) {
615                ret = sizeof(logger_list->entry.entry_v1);
616            }
617            ret += logger_list->entry.entry.len;
618
619            memcpy(log_msg->buf, logger_list->entry.buf,
620                   sizeof(struct log_msg));
621            logger_list->valid_entry = false;
622        }
623    }
624
625done:
626    if (logger_list->error) {
627        error = logger_list->error;
628    }
629    if (error) {
630        logger_list->error = error;
631        if (!ret) {
632            ret = -error;
633        }
634    }
635    return ret;
636}
637
638/* Close all the logs */
639void android_logger_list_free(struct logger_list *logger_list)
640{
641    if (logger_list == NULL) {
642        return;
643    }
644
645    while (!list_empty(&logger_list->node)) {
646        struct listnode *node = list_head(&logger_list->node);
647        struct logger *logger = node_to_item(node, struct logger, node);
648        android_logger_free(logger);
649    }
650
651    free(logger_list);
652}
653