summaryrefslogtreecommitdiffstats
blob: a78319ff4c01be78d31480fa4719a295c1ae6e98 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
/*
 * Copyright (C) 2012-2014 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
// for manual checking of stale entries during LogBuffer::erase()
//#define DEBUG_CHECK_FOR_STALE_ENTRIES

#include <ctype.h>
#include <endian.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <sys/cdefs.h>
#include <sys/user.h>
#include <time.h>
#include <unistd.h>

#include <unordered_map>

#include <cutils/properties.h>
#include <private/android_logger.h>

#include "LogBuffer.h"
#include "LogKlog.h"
#include "LogReader.h"
#include "LogUtils.h"

#ifndef __predict_false
#define __predict_false(exp) __builtin_expect((exp) != 0, 0)
#endif

// Default
#define log_buffer_size(id) mMaxSize[id]

const log_time LogBuffer::pruneMargin(3, 0);

void LogBuffer::init() {
    log_id_for_each(i) {
        mLastSet[i] = false;
        mLast[i] = mLogElements.begin();

        if (setSize(i, __android_logger_get_buffer_size(i))) {
            setSize(i, LOG_BUFFER_MIN_SIZE);
        }
    }
    bool lastMonotonic = monotonic;
    monotonic = android_log_clockid() == CLOCK_MONOTONIC;
    if (lastMonotonic != monotonic) {
        //
        // Fixup all timestamps, may not be 100% accurate, but better than
        // throwing what we have away when we get 'surprised' by a change.
        // In-place element fixup so no need to check reader-lock. Entries
        // should already be in timestamp order, but we could end up with a
        // few out-of-order entries if new monotonics come in before we
        // are notified of the reinit change in status. A Typical example would
        // be:
        //  --------- beginning of system
        //      10.494082   184   201 D Cryptfs : Just triggered post_fs_data
        //  --------- beginning of kernel
        //       0.000000     0     0 I         : Initializing cgroup subsys
        // as the act of mounting /data would trigger persist.logd.timestamp to
        // be corrected. 1/30 corner case YMMV.
        //
        rdlock();
        LogBufferElementCollection::iterator it = mLogElements.begin();
        while ((it != mLogElements.end())) {
            LogBufferElement* e = *it;
            if (monotonic) {
                if (!android::isMonotonic(e->mRealTime)) {
                    LogKlog::convertRealToMonotonic(e->mRealTime);
                    if ((e->mRealTime.tv_nsec % 1000) == 0) {
                        e->mRealTime.tv_nsec++;
                    }
                }
            } else {
                if (android::isMonotonic(e->mRealTime)) {
                    LogKlog::convertMonotonicToReal(e->mRealTime);
                    if ((e->mRealTime.tv_nsec % 1000) == 0) {
                        e->mRealTime.tv_nsec++;
                    }
                }
            }
            ++it;
        }
        unlock();
    }

    // We may have been triggered by a SIGHUP. Release any sleeping reader
    // threads to dump their current content.
    //
    // NB: this is _not_ performed in the context of a SIGHUP, it is
    // performed during startup, and in context of reinit administrative thread
    LogTimeEntry::wrlock();

    LastLogTimes::iterator times = mTimes.begin();
    while (times != mTimes.end()) {
        LogTimeEntry* entry = (*times);
        if (entry->owned_Locked()) {
            entry->triggerReader_Locked();
        }
        times++;
    }

    LogTimeEntry::unlock();
}

LogBuffer::LogBuffer(LastLogTimes* times)
    : monotonic(android_log_clockid() == CLOCK_MONOTONIC), mTimes(*times) {
    pthread_rwlock_init(&mLogElementsLock, nullptr);

    log_id_for_each(i) {
        lastLoggedElements[i] = nullptr;
        droppedElements[i] = nullptr;
    }

    init();
}

LogBuffer::~LogBuffer() {
    log_id_for_each(i) {
        delete lastLoggedElements[i];
        delete droppedElements[i];
    }
}

enum match_type { DIFFERENT, SAME, SAME_LIBLOG };

static enum match_type identical(LogBufferElement* elem,
                                 LogBufferElement* last) {
    // is it mostly identical?
    //  if (!elem) return DIFFERENT;
    ssize_t lenl = elem->getMsgLen();
    if (lenl <= 0) return DIFFERENT;  // value if this represents a chatty elem
    //  if (!last) return DIFFERENT;
    ssize_t lenr = last->getMsgLen();
    if (lenr <= 0) return DIFFERENT;  // value if this represents a chatty elem
    //  if (elem->getLogId() != last->getLogId()) return DIFFERENT;
    if (elem->getUid() != last->getUid()) return DIFFERENT;
    if (elem->getPid() != last->getPid()) return DIFFERENT;
    if (elem->getTid() != last->getTid()) return DIFFERENT;

    // last is more than a minute old, stop squashing identical messages
    if (elem->getRealTime().nsec() >
        (last->getRealTime().nsec() + 60 * NS_PER_SEC))
        return DIFFERENT;

    // Identical message
    const char* msgl = elem->getMsg();
    const char* msgr = last->getMsg();
    if (lenl == lenr) {
        if (!fastcmp<memcmp>(msgl, msgr, lenl)) return SAME;
        // liblog tagged messages (content gets summed)
        if ((elem->getLogId() == LOG_ID_EVENTS) &&
            (lenl == sizeof(android_log_event_int_t)) &&
            !fastcmp<memcmp>(msgl, msgr, sizeof(android_log_event_int_t) -
                                             sizeof(int32_t)) &&
            (elem->getTag() == LIBLOG_LOG_TAG)) {
            return SAME_LIBLOG;
        }
    }

    // audit message (except sequence number) identical?
    if (last->isBinary() &&
        (lenl > static_cast<ssize_t>(sizeof(android_log_event_string_t))) &&
        (lenr > static_cast<ssize_t>(sizeof(android_log_event_string_t)))) {
        if (fastcmp<memcmp>(msgl, msgr, sizeof(android_log_event_string_t) -
                                            sizeof(int32_t))) {
            return DIFFERENT;
        }
        msgl += sizeof(android_log_event_string_t);
        lenl -= sizeof(android_log_event_string_t);
        msgr += sizeof(android_log_event_string_t);
        lenr -= sizeof(android_log_event_string_t);
    }
    static const char avc[] = "): avc: ";
    const char* avcl = android::strnstr(msgl, lenl, avc);
    if (!avcl) return DIFFERENT;
    lenl -= avcl - msgl;
    const char* avcr = android::strnstr(msgr, lenr, avc);
    if (!avcr) return DIFFERENT;
    lenr -= avcr - msgr;
    if (lenl != lenr) return DIFFERENT;
    if (fastcmp<memcmp>(avcl + strlen(avc), avcr + strlen(avc),
                        lenl - strlen(avc))) {
        return DIFFERENT;
    }
    return SAME;
}

int LogBuffer::log(log_id_t log_id, log_time realtime, uid_t uid, pid_t pid,
                   pid_t tid, const char* msg, unsigned short len) {
    if (log_id >= LOG_ID_MAX) {
        return -EINVAL;
    }

    // Slip the time by 1 nsec if the incoming lands on xxxxxx000 ns.
    // This prevents any chance that an outside source can request an
    // exact entry with time specified in ms or us precision.
    if ((realtime.tv_nsec % 1000) == 0) ++realtime.tv_nsec;

    LogBufferElement* elem =
        new LogBufferElement(log_id, realtime, uid, pid, tid, msg, len);
    if (log_id != LOG_ID_SECURITY) {
        int prio = ANDROID_LOG_INFO;
        const char* tag = nullptr;
        size_t tag_len = 0;
        if (log_id == LOG_ID_EVENTS || log_id == LOG_ID_STATS) {
            tag = tagToName(elem->getTag());
            if (tag) {
                tag_len = strlen(tag);
            }
        } else {
            prio = *msg;
            tag = msg + 1;
            tag_len = strnlen(tag, len - 1);
        }
        if (!__android_log_is_loggable_len(prio, tag, tag_len,
                                           ANDROID_LOG_VERBOSE)) {
            // Log traffic received to total
            wrlock();
            stats.addTotal(elem);
            unlock();
            delete elem;
            return -EACCES;
        }
    }

    wrlock();
    LogBufferElement* currentLast = lastLoggedElements[log_id];
    if (currentLast) {
        LogBufferElement* dropped = droppedElements[log_id];
        unsigned short count = dropped ? dropped->getDropped() : 0;
        //
        // State Init
        //     incoming:
        //         dropped = nullptr
        //         currentLast = nullptr;
        //         elem = incoming message
        //     outgoing:
        //         dropped = nullptr -> State 0
        //         currentLast = copy of elem
        //         log elem
        // State 0
        //     incoming:
        //         count = 0
        //         dropped = nullptr
        //         currentLast = copy of last message
        //         elem = incoming message
        //     outgoing: if match != DIFFERENT
        //         dropped = copy of first identical message -> State 1
        //         currentLast = reference to elem
        //     break: if match == DIFFERENT
        //         dropped = nullptr -> State 0
        //         delete copy of last message (incoming currentLast)
        //         currentLast = copy of elem
        //         log elem
        // State 1
        //     incoming:
        //         count = 0
        //         dropped = copy of first identical message
        //         currentLast = reference to last held-back incoming
        //                       message
        //         elem = incoming message
        //     outgoing: if match == SAME
        //         delete copy of first identical message (dropped)
        //         dropped = reference to last held-back incoming
        //                   message set to chatty count of 1 -> State 2
        //         currentLast = reference to elem
        //     outgoing: if match == SAME_LIBLOG
        //         dropped = copy of first identical message -> State 1
        //         take sum of currentLast and elem
        //         if sum overflows:
        //             log currentLast
        //             currentLast = reference to elem
        //         else
        //             delete currentLast
        //             currentLast = reference to elem, sum liblog.
        //     break: if match == DIFFERENT
        //         delete dropped
        //         dropped = nullptr -> State 0
        //         log reference to last held-back (currentLast)
        //         currentLast = copy of elem
        //         log elem
        // State 2
        //     incoming:
        //         count = chatty count
        //         dropped = chatty message holding count
        //         currentLast = reference to last held-back incoming
        //                       message.
        //         dropped = chatty message holding count
        //         elem = incoming message
        //     outgoing: if match != DIFFERENT
        //         delete chatty message holding count
        //         dropped = reference to last held-back incoming
        //                   message, set to chatty count + 1
        //         currentLast = reference to elem
        //     break: if match == DIFFERENT
        //         log dropped (chatty message)
        //         dropped = nullptr -> State 0
        //         log reference to last held-back (currentLast)
        //         currentLast = copy of elem
        //         log elem
        //
        enum match_type match = identical(elem, currentLast);
        if (match != DIFFERENT) {
            if (dropped) {
                // Sum up liblog tag messages?
                if ((count == 0) /* at Pass 1 */ && (match == SAME_LIBLOG)) {
                    android_log_event_int_t* event =
                        reinterpret_cast<android_log_event_int_t*>(
                            const_cast<char*>(currentLast->getMsg()));
                    //
                    // To unit test, differentiate with something like:
                    //    event->header.tag = htole32(CHATTY_LOG_TAG);
                    // here, then instead of delete currentLast below,
                    // log(currentLast) to see the incremental sums form.
                    //
                    uint32_t swab = event->payload.data;
                    unsigned long long total = htole32(swab);
                    event = reinterpret_cast<android_log_event_int_t*>(
                        const_cast<char*>(elem->getMsg()));
                    swab = event->payload.data;

                    lastLoggedElements[LOG_ID_EVENTS] = elem;
                    total += htole32(swab);
                    // check for overflow
                    if (total >= UINT32_MAX) {
                        log(currentLast);
                        unlock();
                        return len;
                    }
                    stats.addTotal(currentLast);
                    delete currentLast;
                    swab = total;
                    event->payload.data = htole32(swab);
                    unlock();
                    return len;
                }
                if (count == USHRT_MAX) {
                    log(dropped);
                    count = 1;
                } else {
                    delete dropped;
                    ++count;
                }
            }
            if (count) {
                stats.addTotal(currentLast);
                currentLast->setDropped(count);
            }
            droppedElements[log_id] = currentLast;
            lastLoggedElements[log_id] = elem;
            unlock();
            return len;
        }
        if (dropped) {         // State 1 or 2
            if (count) {       // State 2
                log(dropped);  // report chatty
            } else {           // State 1
                delete dropped;
            }
            droppedElements[log_id] = nullptr;
            log(currentLast);  // report last message in the series
        } else {               // State 0
            delete currentLast;
        }
    }
    lastLoggedElements[log_id] = new LogBufferElement(*elem);

    log(elem);
    unlock();

    return len;
}

// assumes LogBuffer::wrlock() held, owns elem, look after garbage collection
void LogBuffer::log(LogBufferElement* elem) {
    // cap on how far back we will sort in-place, otherwise append
    static uint32_t too_far_back = 5;  // five seconds
    // Insert elements in time sorted order if possible
    //  NB: if end is region locked, place element at end of list
    LogBufferElementCollection::iterator it = mLogElements.end();
    LogBufferElementCollection::iterator last = it;
    if (__predict_true(it != mLogElements.begin())) --it;
    if (__predict_false(it == mLogElements.begin()) ||
        __predict_true((*it)->getRealTime() <= elem->getRealTime()) ||
        __predict_false((((*it)->getRealTime().tv_sec - too_far_back) >
                         elem->getRealTime().tv_sec) &&
                        (elem->getLogId() != LOG_ID_KERNEL) &&
                        ((*it)->getLogId() != LOG_ID_KERNEL))) {
        mLogElements.push_back(elem);
    } else {
        log_time end = log_time::EPOCH;
        bool end_set = false;
        bool end_always = false;

        LogTimeEntry::rdlock();

        LastLogTimes::iterator times = mTimes.begin();
        while (times != mTimes.end()) {
            LogTimeEntry* entry = (*times);
            if (entry->owned_Locked()) {
                if (!entry->mNonBlock) {
                    end_always = true;
                    break;
                }
                // it passing mEnd is blocked by the following checks.
                if (!end_set || (end <= entry->mEnd)) {
                    end = entry->mEnd;
                    end_set = true;
                }
            }
            times++;
        }

        if (end_always || (end_set && (end > (*it)->getRealTime()))) {
            mLogElements.push_back(elem);
        } else {
            // should be short as timestamps are localized near end()
            do {
                last = it;
                if (__predict_false(it == mLogElements.begin())) {
                    break;
                }
                --it;
            } while (((*it)->getRealTime() > elem->getRealTime()) &&
                     (!end_set || (end <= (*it)->getRealTime())));
            mLogElements.insert(last, elem);
        }
        LogTimeEntry::unlock();
    }

    stats.add(elem);
    maybePrune(elem->getLogId());
}

// Prune at most 10% of the log entries or maxPrune, whichever is less.
//
// LogBuffer::wrlock() must be held when this function is called.
void LogBuffer::maybePrune(log_id_t id) {
    size_t sizes = stats.sizes(id);
    unsigned long maxSize = log_buffer_size(id);
    if (sizes > maxSize) {
        size_t sizeOver = sizes - ((maxSize * 9) / 10);
        size_t elements = stats.realElements(id);
        size_t minElements = elements / 100;
        if (minElements < minPrune) {
            minElements = minPrune;
        }
        unsigned long pruneRows = elements * sizeOver / sizes;
        if (pruneRows < minElements) {
            pruneRows = minElements;
        }
        if (pruneRows > maxPrune) {
            pruneRows = maxPrune;
        }
        prune(id, pruneRows);
    }
}

LogBufferElementCollection::iterator LogBuffer::erase(
    LogBufferElementCollection::iterator it, bool coalesce) {
    LogBufferElement* element = *it;
    log_id_t id = element->getLogId();

    // Remove iterator references in the various lists that will become stale
    // after the element is erased from the main logging list.

    {  // start of scope for found iterator
        int key = ((id == LOG_ID_EVENTS) || (id == LOG_ID_SECURITY))
                      ? element->getTag()
                      : element->getUid();
        LogBufferIteratorMap::iterator found = mLastWorst[id].find(key);
        if ((found != mLastWorst[id].end()) && (it == found->second)) {
            mLastWorst[id].erase(found);
        }
    }

    {  // start of scope for pid found iterator
        // element->getUid() may not be AID_SYSTEM for next-best-watermark.
        // will not assume id != LOG_ID_EVENTS or LOG_ID_SECURITY for KISS and
        // long term code stability, find() check should be fast for those ids.
        LogBufferPidIteratorMap::iterator found =
            mLastWorstPidOfSystem[id].find(element->getPid());
        if ((found != mLastWorstPidOfSystem[id].end()) &&
            (it == found->second)) {
            mLastWorstPidOfSystem[id].erase(found);
        }
    }

    bool setLast[LOG_ID_MAX];
    bool doSetLast = false;
    log_id_for_each(i) {
        doSetLast |= setLast[i] = mLastSet[i] && (it == mLast[i]);
    }
#ifdef DEBUG_CHECK_FOR_STALE_ENTRIES
    LogBufferElementCollection::iterator bad = it;
    int key = ((id == LOG_ID_EVENTS) || (id == LOG_ID_SECURITY))
                  ? element->getTag()
                  : element->getUid();
#endif
    it = mLogElements.erase(it);
    if (doSetLast) {
        log_id_for_each(i) {
            if (setLast[i]) {
                if (__predict_false(it == mLogElements.end())) {  // impossible
                    mLastSet[i] = false;
                    mLast[i] = mLogElements.begin();
                } else {
                    mLast[i] = it;  // push down the road as next-best-watermark
                }
            }
        }
    }
#ifdef DEBUG_CHECK_FOR_STALE_ENTRIES
    log_id_for_each(i) {
        for (auto b : mLastWorst[i]) {
            if (bad == b.second) {
                android::prdebug("stale mLastWorst[%d] key=%d mykey=%d\n", i,
                                 b.first, key);
            }
        }
        for (auto b : mLastWorstPidOfSystem[i]) {
            if (bad == b.second) {
                android::prdebug("stale mLastWorstPidOfSystem[%d] pid=%d\n", i,
                                 b.first);
            }
        }
        if (mLastSet[i] && (bad == mLast[i])) {
            android::prdebug("stale mLast[%d]\n", i);
            mLastSet[i] = false;
            mLast[i] = mLogElements.begin();
        }
    }
#endif
    if (coalesce) {
        stats.erase(element);
    } else {
        stats.subtract(element);
    }
    delete element;

    return it;
}

// Define a temporary mechanism to report the last LogBufferElement pointer
// for the specified uid, pid and tid. Used below to help merge-sort when
// pruning for worst UID.
class LogBufferElementKey {
    const union {
        struct {
            uint32_t uid;
            uint16_t pid;
            uint16_t tid;
        } __packed;
        uint64_t value;
    } __packed;

   public:
    LogBufferElementKey(uid_t uid, pid_t pid, pid_t tid)
        : uid(uid), pid(pid), tid(tid) {
    }
    explicit LogBufferElementKey(uint64_t key) : value(key) {
    }

    uint64_t getKey() {
        return value;
    }
};

class LogBufferElementLast {
    typedef std::unordered_map<uint64_t, LogBufferElement*> LogBufferElementMap;
    LogBufferElementMap map;

   public:
    bool coalesce(LogBufferElement* element, unsigned short dropped) {
        LogBufferElementKey key(element->getUid(), element->getPid(),
                                element->getTid());
        LogBufferElementMap::iterator it = map.find(key.getKey());
        if (it != map.end()) {
            LogBufferElement* found = it->second;
            unsigned short moreDropped = found->getDropped();
            if ((dropped + moreDropped) > USHRT_MAX) {
                map.erase(it);
            } else {
                found->setDropped(dropped + moreDropped);
                return true;
            }
        }
        return false;
    }

    void add(LogBufferElement* element) {
        LogBufferElementKey key(element->getUid(), element->getPid(),
                                element->getTid());
        map[key.getKey()] = element;
    }

    inline void clear() {
        map.clear();
    }

    void clear(LogBufferElement* element) {
        log_time current =
            element->getRealTime() - log_time(EXPIRE_RATELIMIT, 0);
        for (LogBufferElementMap::iterator it = map.begin(); it != map.end();) {
            LogBufferElement* mapElement = it->second;
            if ((mapElement->getDropped() >= EXPIRE_THRESHOLD) &&
                (current > mapElement->getRealTime())) {
                it = map.erase(it);
            } else {
                ++it;
            }
        }
    }
};

// Determine if watermark is within pruneMargin + 1s from the end of the list,
// the caller will use this result to set an internal busy flag indicating
// the prune operation could not be completed because a reader is blocking
// the request.
bool LogBuffer::isBusy(log_time watermark) {
    LogBufferElementCollection::iterator ei = mLogElements.end();
    --ei;
    return watermark < ((*ei)->getRealTime() - pruneMargin - log_time(1, 0));
}

// If the selected reader is blocking our pruning progress, decide on
// what kind of mitigation is necessary to unblock the situation.
void LogBuffer::kickMe(LogTimeEntry* me, log_id_t id, unsigned long pruneRows) {
    if (stats.sizes(id) > (2 * log_buffer_size(id))) {  // +100%
        // A misbehaving or slow reader has its connection
        // dropped if we hit too much memory pressure.
        me->release_Locked();
    } else if (me->mTimeout.tv_sec || me->mTimeout.tv_nsec) {
        // Allow a blocked WRAP timeout reader to
        // trigger and start reporting the log data.
        me->triggerReader_Locked();
    } else {
        // tell slow reader to skip entries to catch up
        me->triggerSkip_Locked(id, pruneRows);
    }
}

// prune "pruneRows" of type "id" from the buffer.
//
// This garbage collection task is used to expire log entries. It is called to
// remove all logs (clear), all UID logs (unprivileged clear), or every
// 256 or 10% of the total logs (whichever is less) to prune the logs.
//
// First there is a prep phase where we discover the reader region lock that
// acts as a backstop to any pruning activity to stop there and go no further.
//
// There are three major pruning loops that follow. All expire from the oldest
// entries. Since there are multiple log buffers, the Android logging facility
// will appear to drop entries 'in the middle' when looking at multiple log
// sources and buffers. This effect is slightly more prominent when we prune
// the worst offender by logging source. Thus the logs slowly loose content
// and value as you move back in time. This is preferred since chatty sources
// invariably move the logs value down faster as less chatty sources would be
// expired in the noise.
//
// The first loop performs blacklisting and worst offender pruning. Falling
// through when there are no notable worst offenders and have not hit the
// region lock preventing further worst offender pruning. This loop also looks
// after managing the chatty log entries and merging to help provide
// statistical basis for blame. The chatty entries are not a notification of
// how much logs you may have, but instead represent how much logs you would
// have had in a virtual log buffer that is extended to cover all the in-memory
// logs without loss. They last much longer than the represented pruned logs
// since they get multiplied by the gains in the non-chatty log sources.
//
// The second loop get complicated because an algorithm of watermarks and
// history is maintained to reduce the order and keep processing time
// down to a minimum at scale. These algorithms can be costly in the face
// of larger log buffers, or severly limited processing time granted to a
// background task at lowest priority.
//
// This second loop does straight-up expiration from the end of the logs
// (again, remember for the specified log buffer id) but does some whitelist
// preservation. Thus whitelist is a Hail Mary low priority, blacklists and
// spam filtration all take priority. This second loop also checks if a region
// lock is causing us to buffer too much in the logs to help the reader(s),
// and will tell the slowest reader thread to skip log entries, and if
// persistent and hits a further threshold, kill the reader thread.
//
// The third thread is optional, and only gets hit if there was a whitelist
// and more needs to be pruned against the backstop of the region lock.
//
// LogBuffer::wrlock() must be held when this function is called.
//
bool LogBuffer::prune(log_id_t id, unsigned long pruneRows, uid_t caller_uid) {
    LogTimeEntry* oldest = nullptr;
    bool busy = false;
    bool clearAll = pruneRows == ULONG_MAX;

    LogTimeEntry::rdlock();

    // Region locked?
    LastLogTimes::iterator times = mTimes.begin();
    while (times != mTimes.end()) {
        LogTimeEntry* entry = (*times);
        if (entry->owned_Locked() && entry->isWatching(id) &&
            (!oldest || (oldest->mStart > entry->mStart) ||
             ((oldest->mStart == entry->mStart) &&
              (entry->mTimeout.tv_sec || entry->mTimeout.tv_nsec)))) {
            oldest = entry;
        }
        times++;
    }
    log_time watermark(log_time::tv_sec_max, log_time::tv_nsec_max);
    if (oldest) watermark = oldest->mStart - pruneMargin;

    LogBufferElementCollection::iterator it;

    if (__predict_false(caller_uid != AID_ROOT)) {  // unlikely
        // Only here if clear all request from non system source, so chatty
        // filter logistics is not required.
        it = mLastSet[id] ? mLast[id] : mLogElements.begin();
        while (it != mLogElements.end()) {
            LogBufferElement* element = *it;

            if ((element->getLogId() != id) ||
                (element->getUid() != caller_uid)) {
                ++it;
                continue;
            }

            if (!mLastSet[id] || ((*mLast[id])->getLogId() != id)) {
                mLast[id] = it;
                mLastSet[id] = true;
            }

            if (oldest && (watermark <= element->getRealTime())) {
                busy = isBusy(watermark);
                if (busy) kickMe(oldest, id, pruneRows);
                break;
            }

            it = erase(it);
            if (--pruneRows == 0) {
                break;
            }
        }
        LogTimeEntry::unlock();
        return busy;
    }

    // prune by worst offenders; by blacklist, UID, and by PID of system UID
    bool hasBlacklist = (id != LOG_ID_SECURITY) && mPrune.naughty();
    while (!clearAll && (pruneRows > 0)) {
        // recalculate the worst offender on every batched pass
        int worst = -1;  // not valid for getUid() or getKey()
        size_t worst_sizes = 0;
        size_t second_worst_sizes = 0;
        pid_t worstPid = 0;  // POSIX guarantees PID != 0

        if (worstUidEnabledForLogid(id) && mPrune.worstUidEnabled()) {
            // Calculate threshold as 12.5% of available storage
            size_t threshold = log_buffer_size(id) / 8;

            if ((id == LOG_ID_EVENTS) || (id == LOG_ID_SECURITY)) {
                stats.sortTags(AID_ROOT, (pid_t)0, 2, id)
                    .findWorst(worst, worst_sizes, second_worst_sizes,
                               threshold);
                // per-pid filter for AID_SYSTEM sources is too complex
            } else {
                stats.sort(AID_ROOT, (pid_t)0, 2, id)
                    .findWorst(worst, worst_sizes, second_worst_sizes,
                               threshold);

                if ((worst == AID_SYSTEM) && mPrune.worstPidOfSystemEnabled()) {
                    stats.sortPids(worst, (pid_t)0, 2, id)
                        .findWorst(worstPid, worst_sizes, second_worst_sizes);
                }
            }
        }

        // skip if we have neither worst nor naughty filters
        if ((worst == -1) && !hasBlacklist) {
            break;
        }

        bool kick = false;
        bool leading = true;
        it = mLastSet[id] ? mLast[id] : mLogElements.begin();
        // Perform at least one mandatory garbage collection cycle in following
        // - clear leading chatty tags
        // - coalesce chatty tags
        // - check age-out of preserved logs
        bool gc = pruneRows <= 1;
        if (!gc && (worst != -1)) {
            {  // begin scope for worst found iterator
                LogBufferIteratorMap::iterator found =
                    mLastWorst[id].find(worst);
                if ((found != mLastWorst[id].end()) &&
                    (found->second != mLogElements.end())) {
                    leading = false;
                    it = found->second;
                }
            }
            if (worstPid) {  // begin scope for pid worst found iterator
                // FYI: worstPid only set if !LOG_ID_EVENTS and
                //      !LOG_ID_SECURITY, not going to make that assumption ...
                LogBufferPidIteratorMap::iterator found =
                    mLastWorstPidOfSystem[id].find(worstPid);
                if ((found != mLastWorstPidOfSystem[id].end()) &&
                    (found->second != mLogElements.end())) {
                    leading = false;
                    it = found->second;
                }
            }
        }
        static const timespec too_old = { EXPIRE_HOUR_THRESHOLD * 60 * 60, 0 };
        LogBufferElementCollection::iterator lastt;
        lastt = mLogElements.end();
        --lastt;
        LogBufferElementLast last;
        while (it != mLogElements.end()) {
            LogBufferElement* element = *it;

            if (oldest && (watermark <= element->getRealTime())) {
                busy = isBusy(watermark);
                // Do not let chatty eliding trigger any reader mitigation
                break;
            }

            if (element->getLogId() != id) {
                ++it;
                continue;
            }
            // below this point element->getLogId() == id

            if (leading && (!mLastSet[id] || ((*mLast[id])->getLogId() != id))) {
                mLast[id] = it;
                mLastSet[id] = true;
            }

            unsigned short dropped = element->getDropped();

            // remove any leading drops
            if (leading && dropped) {
                it = erase(it);
                continue;
            }

            if (dropped && last.coalesce(element, dropped)) {
                it = erase(it, true);
                continue;
            }

            int key = ((id == LOG_ID_EVENTS) || (id == LOG_ID_SECURITY))
                          ? element->getTag()
                          : element->getUid();

            if (hasBlacklist && mPrune.naughty(element)) {
                last.clear(element);
                it = erase(it);
                if (dropped) {
                    continue;
                }

                pruneRows--;
                if (pruneRows == 0) {
                    break;
                }

                if (key == worst) {
                    kick = true;
                    if (worst_sizes < second_worst_sizes) {
                        break;
                    }
                    worst_sizes -= element->getMsgLen();
                }
                continue;
            }

            if ((element->getRealTime() < ((*lastt)->getRealTime() - too_old)) ||
                (element->getRealTime() > (*lastt)->getRealTime())) {
                break;
            }

            if (dropped) {
                last.add(element);
                if (worstPid &&
                    ((!gc && (element->getPid() == worstPid)) ||
                     (mLastWorstPidOfSystem[id].find(element->getPid()) ==
                      mLastWorstPidOfSystem[id].end()))) {
                    // element->getUid() may not be AID_SYSTEM, next best
                    // watermark if current one empty. id is not LOG_ID_EVENTS
                    // or LOG_ID_SECURITY because of worstPid check.
                    mLastWorstPidOfSystem[id][element->getPid()] = it;
                }
                if ((!gc && !worstPid && (key == worst)) ||
                    (mLastWorst[id].find(key) == mLastWorst[id].end())) {
                    mLastWorst[id][key] = it;
                }
                ++it;
                continue;
            }

            if ((key != worst) ||
                (worstPid && (element->getPid() != worstPid))) {
                leading = false;
                last.clear(element);
                ++it;
                continue;
            }
            // key == worst below here
            // If worstPid set, then element->getPid() == worstPid below here

            pruneRows--;
            if (pruneRows == 0) {
                break;
            }

            kick = true;

            unsigned short len = element->getMsgLen();

            // do not create any leading drops
            if (leading) {
                it = erase(it);
            } else {
                stats.drop(element);
                element->setDropped(1);
                if (last.coalesce(element, 1)) {
                    it = erase(it, true);
                } else {
                    last.add(element);
                    if (worstPid &&
                        (!gc || (mLastWorstPidOfSystem[id].find(worstPid) ==
                                 mLastWorstPidOfSystem[id].end()))) {
                        // element->getUid() may not be AID_SYSTEM, next best
                        // watermark if current one empty. id is not
                        // LOG_ID_EVENTS or LOG_ID_SECURITY because of worstPid.
                        mLastWorstPidOfSystem[id][worstPid] = it;
                    }
                    if ((!gc && !worstPid) ||
                        (mLastWorst[id].find(worst) == mLastWorst[id].end())) {
                        mLastWorst[id][worst] = it;
                    }
                    ++it;
                }
            }
            if (worst_sizes < second_worst_sizes) {
                break;
            }
            worst_sizes -= len;
        }
        last.clear();

        if (!kick || !mPrune.worstUidEnabled()) {
            break;  // the following loop will ask bad clients to skip/drop
        }
    }

    bool whitelist = false;
    bool hasWhitelist = (id != LOG_ID_SECURITY) && mPrune.nice() && !clearAll;
    it = mLastSet[id] ? mLast[id] : mLogElements.begin();
    while ((pruneRows > 0) && (it != mLogElements.end())) {
        LogBufferElement* element = *it;

        if (element->getLogId() != id) {
            it++;
            continue;
        }

        if (!mLastSet[id] || ((*mLast[id])->getLogId() != id)) {
            mLast[id] = it;
            mLastSet[id] = true;
        }

        if (oldest && (watermark <= element->getRealTime())) {
            busy = isBusy(watermark);
            if (!whitelist && busy) kickMe(oldest, id, pruneRows);
            break;
        }

        if (hasWhitelist && !element->getDropped() && mPrune.nice(element)) {
            // WhiteListed
            whitelist = true;
            it++;
            continue;
        }

        it = erase(it);
        pruneRows--;
    }

    // Do not save the whitelist if we are reader range limited
    if (whitelist && (pruneRows > 0)) {
        it = mLastSet[id] ? mLast[id] : mLogElements.begin();
        while ((it != mLogElements.end()) && (pruneRows > 0)) {
            LogBufferElement* element = *it;

            if (element->getLogId() != id) {
                ++it;
                continue;
            }

            if (!mLastSet[id] || ((*mLast[id])->getLogId() != id)) {
                mLast[id] = it;
                mLastSet[id] = true;
            }

            if (oldest && (watermark <= element->getRealTime())) {
                busy = isBusy(watermark);
                if (busy) kickMe(oldest, id, pruneRows);
                break;
            }

            it = erase(it);
            pruneRows--;
        }
    }

    LogTimeEntry::unlock();

    return (pruneRows > 0) && busy;
}

// clear all rows of type "id" from the buffer.
bool LogBuffer::clear(log_id_t id, uid_t uid) {
    bool busy = true;
    // If it takes more than 4 tries (seconds) to clear, then kill reader(s)
    for (int retry = 4;;) {
        if (retry == 1) {  // last pass
            // Check if it is still busy after the sleep, we say prune
            // one entry, not another clear run, so we are looking for
            // the quick side effect of the return value to tell us if
            // we have a _blocked_ reader.
            wrlock();
            busy = prune(id, 1, uid);
            unlock();
            // It is still busy, blocked reader(s), lets kill them all!
            // otherwise, lets be a good citizen and preserve the slow
            // readers and let the clear run (below) deal with determining
            // if we are still blocked and return an error code to caller.
            if (busy) {
                LogTimeEntry::wrlock();
                LastLogTimes::iterator times = mTimes.begin();
                while (times != mTimes.end()) {
                    LogTimeEntry* entry = (*times);
                    // Killer punch
                    if (entry->owned_Locked() && entry->isWatching(id)) {
                        entry->release_Locked();
                    }
                    times++;
                }
                LogTimeEntry::unlock();
            }
        }
        wrlock();
        busy = prune(id, ULONG_MAX, uid);
        unlock();
        if (!busy || !--retry) {
            break;
        }
        sleep(1);  // Let reader(s) catch up after notification
    }
    return busy;
}

// get the used space associated with "id".
unsigned long LogBuffer::getSizeUsed(log_id_t id) {
    rdlock();
    size_t retval = stats.sizes(id);
    unlock();
    return retval;
}

// set the total space allocated to "id"
int LogBuffer::setSize(log_id_t id, unsigned long size) {
    // Reasonable limits ...
    if (!__android_logger_valid_buffer_size(size)) {
        return -1;
    }
    wrlock();
    log_buffer_size(id) = size;
    unlock();
    return 0;
}

// get the total space allocated to "id"
unsigned long LogBuffer::getSize(log_id_t id) {
    rdlock();
    size_t retval = log_buffer_size(id);
    unlock();
    return retval;
}

log_time LogBuffer::flushTo(SocketClient* reader, const log_time& start,
                            pid_t* lastTid, bool privileged, bool security,
                            int (*filter)(const LogBufferElement* element,
                                          void* arg),
                            void* arg) {
    LogBufferElementCollection::iterator it;
    uid_t uid = reader->getUid();

    rdlock();

    if (start == log_time::EPOCH) {
        // client wants to start from the beginning
        it = mLogElements.begin();
    } else {
        // 3 second limit to continue search for out-of-order entries.
        log_time min = start - pruneMargin;

        // Cap to 300 iterations we look back for out-of-order entries.
        size_t count = 300;

        // Client wants to start from some specified time. Chances are
        // we are better off starting from the end of the time sorted list.
        LogBufferElementCollection::iterator last;
        for (last = it = mLogElements.end(); it != mLogElements.begin();
             /* do nothing */) {
            --it;
            LogBufferElement* element = *it;
            if (element->getRealTime() > start) {
                last = it;
            } else if (element->getRealTime() == start) {
                last = ++it;
                break;
            } else if (!--count || (element->getRealTime() < min)) {
                break;
            }
        }
        it = last;
    }

    log_time curr = start;

    LogBufferElement* lastElement = nullptr;  // iterator corruption paranoia
    static const size_t maxSkip = 4194304;    // maximum entries to skip
    size_t skip = maxSkip;
    for (; it != mLogElements.end(); ++it) {
        LogBufferElement* element = *it;

        if (!--skip) {
            android::prdebug("reader.per: too many elements skipped");
            break;
        }
        if (element == lastElement) {
            android::prdebug("reader.per: identical elements");
            break;
        }
        lastElement = element;

        if (!privileged && (element->getUid() != uid)) {
            continue;
        }

        if (!security && (element->getLogId() == LOG_ID_SECURITY)) {
            continue;
        }

        // NB: calling out to another object with wrlock() held (safe)
        if (filter) {
            int ret = (*filter)(element, arg);
            if (ret == false) {
                continue;
            }
            if (ret != true) {
                break;
            }
        }

        bool sameTid = false;
        if (lastTid) {
            sameTid = lastTid[element->getLogId()] == element->getTid();
            // Dropped (chatty) immediately following a valid log from the
            // same source in the same log buffer indicates we have a
            // multiple identical squash.  chatty that differs source
            // is due to spam filter.  chatty to chatty of different
            // source is also due to spam filter.
            lastTid[element->getLogId()] =
                (element->getDropped() && !sameTid) ? 0 : element->getTid();
        }

        unlock();

        // range locking in LastLogTimes looks after us
        curr = element->flushTo(reader, this, privileged, sameTid);

        if (curr == element->FLUSH_ERROR) {
            return curr;
        }

        skip = maxSkip;
        rdlock();
    }
    unlock();

    return curr;
}

std::string LogBuffer::formatStatistics(uid_t uid, pid_t pid,
                                        unsigned int logMask) {
    wrlock();

    std::string ret = stats.format(uid, pid, logMask);

    unlock();

    return ret;
}