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
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
|
/* Thread-local storage handling in the ELF dynamic linker. Generic version.
Copyright (C) 2002-2018 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <assert.h>
#include <atomic.h>
#include <errno.h>
#include <libintl.h>
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/param.h>
#include <atomic.h>
#include <tls.h>
#include <dl-tls.h>
#include <ldsodefs.h>
static void _dl_print_dtv(const char *msg, dtv_t *dtv, int numentries);
/* Amount of excess space to allocate in the static TLS area
to allow dynamic loading of modules defining IE-model TLS data. */
#define TLS_STATIC_SURPLUS 64 + DL_NNS * 100
/* Out-of-memory handler. */
static void
__attribute__ ((__noreturn__))
oom (void)
{
_dl_fatal_printf ("cannot allocate memory for thread-local data: ABORT\n");
}
size_t
_dl_next_tls_modid (void)
{
size_t result;
if (__builtin_expect (GL(dl_tls_dtv_gaps), false))
{
size_t disp = 0;
struct dtv_slotinfo_list *runp = GL(dl_tls_dtv_slotinfo_list);
/* Note that this branch will never be executed during program
start since there are no gaps at that time. Therefore it
does not matter that the dl_tls_dtv_slotinfo is not allocated
yet when the function is called for the first times.
NB: the offset +1 is due to the fact that DTV[0] is used
for something else. */
result = GL(dl_tls_static_nelem) + 1;
if (result <= GL(dl_tls_max_dtv_idx))
do
{
while (result - disp < runp->len)
{
if (runp->slotinfo[result - disp].map == NULL)
break;
++result;
assert (result <= GL(dl_tls_max_dtv_idx) + 1);
}
if (result - disp < runp->len)
break;
disp += runp->len;
}
while ((runp = runp->next) != NULL);
if (result > GL(dl_tls_max_dtv_idx))
{
/* The new index must indeed be exactly one higher than the
previous high. */
assert (result == GL(dl_tls_max_dtv_idx) + 1);
/* There is no gap anymore. */
GL(dl_tls_dtv_gaps) = false;
goto nogaps;
}
}
else
{
/* No gaps, allocate a new entry. */
nogaps:
result = ++GL(dl_tls_max_dtv_idx);
}
return result;
}
size_t
_dl_count_modids (void)
{
/* It is rare that we have gaps; see elf/dl-open.c (_dl_open) where
we fail to load a module and unload it leaving a gap. If we don't
have gaps then the number of modids is the current maximum so
return that. */
if (__glibc_likely (!GL(dl_tls_dtv_gaps)))
return GL(dl_tls_max_dtv_idx);
/* We have gaps and are forced to count the non-NULL entries. */
size_t n = 0;
struct dtv_slotinfo_list *runp = GL(dl_tls_dtv_slotinfo_list);
while (runp != NULL)
{
for (size_t i = 0; i < runp->len; ++i)
if (runp->slotinfo[i].map != NULL)
++n;
runp = runp->next;
}
return n;
}
#ifdef SHARED
void
_dl_determine_tlsoffset (void)
{
size_t max_align = TLS_TCB_ALIGN;
size_t freetop = 0;
size_t freebottom = 0;
/* The first element of the dtv slot info list is allocated. */
assert (GL(dl_tls_dtv_slotinfo_list) != NULL);
/* There is at this point only one element in the
dl_tls_dtv_slotinfo_list list. */
assert (GL(dl_tls_dtv_slotinfo_list)->next == NULL);
struct dtv_slotinfo *slotinfo = GL(dl_tls_dtv_slotinfo_list)->slotinfo;
/* Determining the offset of the various parts of the static TLS
block has several dependencies. In addition we have to work
around bugs in some toolchains.
Each TLS block from the objects available at link time has a size
and an alignment requirement. The GNU ld computes the alignment
requirements for the data at the positions *in the file*, though.
I.e, it is not simply possible to allocate a block with the size
of the TLS program header entry. The data is layed out assuming
that the first byte of the TLS block fulfills
p_vaddr mod p_align == &TLS_BLOCK mod p_align
This means we have to add artificial padding at the beginning of
the TLS block. These bytes are never used for the TLS data in
this module but the first byte allocated must be aligned
according to mod p_align == 0 so that the first byte of the TLS
block is aligned according to p_vaddr mod p_align. This is ugly
and the linker can help by computing the offsets in the TLS block
assuming the first byte of the TLS block is aligned according to
p_align.
The extra space which might be allocated before the first byte of
the TLS block need not go unused. The code below tries to use
that memory for the next TLS block. This can work if the total
memory requirement for the next TLS block is smaller than the
gap. */
#if TLS_TCB_AT_TP
/* We simply start with zero. */
size_t offset = 0;
for (size_t cnt = 0; slotinfo[cnt].map != NULL; ++cnt)
{
assert (cnt < GL(dl_tls_dtv_slotinfo_list)->len);
size_t firstbyte = (-slotinfo[cnt].map->l_tls_firstbyte_offset
& (slotinfo[cnt].map->l_tls_align - 1));
size_t off;
max_align = MAX (max_align, slotinfo[cnt].map->l_tls_align);
if (freebottom - freetop >= slotinfo[cnt].map->l_tls_blocksize)
{
off = roundup (freetop + slotinfo[cnt].map->l_tls_blocksize
- firstbyte, slotinfo[cnt].map->l_tls_align)
+ firstbyte;
if (off <= freebottom)
{
freetop = off;
/* XXX For some architectures we perhaps should store the
negative offset. */
slotinfo[cnt].map->l_tls_offset = off;
continue;
}
}
off = roundup (offset + slotinfo[cnt].map->l_tls_blocksize - firstbyte,
slotinfo[cnt].map->l_tls_align) + firstbyte;
if (off > offset + slotinfo[cnt].map->l_tls_blocksize
+ (freebottom - freetop))
{
freetop = offset;
freebottom = off - slotinfo[cnt].map->l_tls_blocksize;
}
offset = off;
/* XXX For some architectures we perhaps should store the
negative offset. */
slotinfo[cnt].map->l_tls_offset = off;
}
GL(dl_tls_static_used) = offset;
GL(dl_tls_static_size) = (roundup (offset + TLS_STATIC_SURPLUS, max_align)
+ TLS_TCB_SIZE);
#elif TLS_DTV_AT_TP
/* The TLS blocks start right after the TCB. */
size_t offset = TLS_TCB_SIZE;
for (size_t cnt = 0; slotinfo[cnt].map != NULL; ++cnt)
{
assert (cnt < GL(dl_tls_dtv_slotinfo_list)->len);
size_t firstbyte = (-slotinfo[cnt].map->l_tls_firstbyte_offset
& (slotinfo[cnt].map->l_tls_align - 1));
size_t off;
max_align = MAX (max_align, slotinfo[cnt].map->l_tls_align);
if (slotinfo[cnt].map->l_tls_blocksize <= freetop - freebottom)
{
off = roundup (freebottom, slotinfo[cnt].map->l_tls_align);
if (off - freebottom < firstbyte)
off += slotinfo[cnt].map->l_tls_align;
if (off + slotinfo[cnt].map->l_tls_blocksize - firstbyte <= freetop)
{
slotinfo[cnt].map->l_tls_offset = off - firstbyte;
freebottom = (off + slotinfo[cnt].map->l_tls_blocksize
- firstbyte);
continue;
}
}
off = roundup (offset, slotinfo[cnt].map->l_tls_align);
if (off - offset < firstbyte)
off += slotinfo[cnt].map->l_tls_align;
slotinfo[cnt].map->l_tls_offset = off - firstbyte;
if (off - firstbyte - offset > freetop - freebottom)
{
freebottom = offset;
freetop = off - firstbyte;
}
offset = off + slotinfo[cnt].map->l_tls_blocksize - firstbyte;
}
GL(dl_tls_static_used) = offset;
GL(dl_tls_static_size) = roundup (offset + TLS_STATIC_SURPLUS,
TLS_TCB_ALIGN);
#else
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
#endif
/* The alignment requirement for the static TLS block. */
GL(dl_tls_static_align) = max_align;
}
#endif /* SHARED */
static void *
allocate_dtv (void *result)
{
dtv_t *dtv;
size_t dtv_length;
/* We allocate a few more elements in the dtv than are needed for the
initial set of modules. This should avoid in most cases expansions
of the dtv. */
dtv_length = GL(dl_tls_max_dtv_idx) + DTV_SURPLUS;
dtv = __signal_safe_calloc (dtv_length + 2, sizeof (dtv_t));
if (dtv != NULL)
{
/* This is the initial length of the dtv. */
dtv[0].counter = dtv_length;
/* The rest of the dtv (including the generation counter) is
Initialize with zero to indicate nothing there. */
/* Add the dtv to the thread data structures. */
INSTALL_DTV (result, dtv);
}
else
result = NULL;
return result;
}
/* Get size and alignment requirements of the static TLS block. */
void
_dl_get_tls_static_info (size_t *sizep, size_t *alignp)
{
*sizep = GL(dl_tls_static_size);
*alignp = GL(dl_tls_static_align);
}
/* Derive the location of the pointer to the start of the original
allocation (before alignment) from the pointer to the TCB. */
static inline void **
tcb_to_pointer_to_free_location (void *tcb)
{
#if TLS_TCB_AT_TP
/* The TCB follows the TLS blocks, and the pointer to the front
follows the TCB. */
void **original_pointer_location = tcb + TLS_TCB_SIZE;
#elif TLS_DTV_AT_TP
/* The TCB comes first, preceded by the pre-TCB, and the pointer is
before that. */
void **original_pointer_location = tcb - TLS_PRE_TCB_SIZE - sizeof (void *);
#endif
return original_pointer_location;
}
void *
_dl_allocate_tls_storage (void)
{
void *result;
size_t size = GL(dl_tls_static_size);
#if TLS_DTV_AT_TP
/* Memory layout is:
[ TLS_PRE_TCB_SIZE ] [ TLS_TCB_SIZE ] [ TLS blocks ]
^ This should be returned. */
size += TLS_PRE_TCB_SIZE;
#endif
/* Perform the allocation. Reserve space for the required alignment
and the pointer to the original allocation. */
size_t alignment = GL(dl_tls_static_align);
void *allocated = malloc (size + alignment + sizeof (void *));
if (__glibc_unlikely (allocated == NULL))
return NULL;
/* Perform alignment and allocate the DTV. */
#if TLS_TCB_AT_TP
/* The TCB follows the TLS blocks, which determine the alignment.
(TCB alignment requirements have been taken into account when
calculating GL(dl_tls_static_align).) */
void *aligned = (void *) roundup ((uintptr_t) allocated, alignment);
result = aligned + size - TLS_TCB_SIZE;
/* Clear the TCB data structure. We can't ask the caller (i.e.
libpthread) to do it, because we will initialize the DTV et al. */
memset (result, '\0', TLS_TCB_SIZE);
#elif TLS_DTV_AT_TP
/* Pre-TCB and TCB come before the TLS blocks. The layout computed
in _dl_determine_tlsoffset assumes that the TCB is aligned to the
TLS block alignment, and not just the TLS blocks after it. This
can leave an unused alignment gap between the TCB and the TLS
blocks. */
result = (void *) roundup
(sizeof (void *) + TLS_PRE_TCB_SIZE + (uintptr_t) allocated,
alignment);
/* Clear the TCB data structure and TLS_PRE_TCB_SIZE bytes before
it. We can't ask the caller (i.e. libpthread) to do it, because
we will initialize the DTV et al. */
memset (result - TLS_PRE_TCB_SIZE, '\0', TLS_PRE_TCB_SIZE + TLS_TCB_SIZE);
#endif
/* Record the value of the original pointer for later
deallocation. */
*tcb_to_pointer_to_free_location (result) = allocated;
result = allocate_dtv (result);
if (result == NULL)
free (allocated);
return result;
}
#ifndef SHARED
extern dtv_t _dl_static_dtv[];
# define _dl_initial_dtv (&_dl_static_dtv[1])
#endif
static dtv_t *
_dl_resize_dtv (dtv_t *dtv)
{
/* Resize the dtv. */
dtv_t *newp;
/* Load GL(dl_tls_max_dtv_idx) atomically since it may be written to by
other threads concurrently. */
size_t newsize
= atomic_load_acquire (&GL(dl_tls_max_dtv_idx)) + DTV_SURPLUS;
size_t oldsize = dtv[-1].counter;
if (dtv == GL(dl_initial_dtv))
{
/* This is the initial dtv that was either statically allocated in
__libc_setup_tls or allocated during rtld startup using the
dl-minimal.c malloc instead of the real malloc. We can't free
it, we have to abandon the old storage. */
newp = __signal_safe_malloc ((2 + newsize) * sizeof (dtv_t));
if (newp == NULL)
oom ();
memcpy (newp, &dtv[-1], (2 + oldsize) * sizeof (dtv_t));
}
else
{
newp = __signal_safe_realloc (&dtv[-1],
(2 + newsize) * sizeof (dtv_t));
if (newp == NULL)
oom ();
}
newp[0].counter = newsize;
/* Clear the newly allocated part. */
memset (newp + 2 + oldsize, '\0',
(newsize - oldsize) * sizeof (dtv_t));
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("Resized dtv 0x%0*Zx, size %lu, to dtv 0x%0*Zx, size %lu\n",
(int) sizeof (void *) * 2, (unsigned long int) dtv,
oldsize,
(int) sizeof (void *) * 2, (unsigned long int) &newp[1],
newsize);
/* Return the generation counter. */
return &newp[1];
}
void *
_dl_allocate_tls_init (void *result)
{
if (result == NULL)
/* The memory allocation failed. */
return NULL;
dtv_t *dtv = GET_DTV (result);
struct dtv_slotinfo_list *listp;
size_t total = 0;
size_t maxgen = 0;
/* Check if the current dtv is big enough. */
if (dtv[-1].counter < GL(dl_tls_max_dtv_idx))
{
/* Resize the dtv. */
dtv = _dl_resize_dtv (dtv);
/* Install this new dtv in the thread data structures. */
INSTALL_DTV (result, &dtv[-1]);
}
/* We have to prepare the dtv for all currently loaded modules using
TLS. For those which are dynamically loaded we add the values
indicating deferred allocation. */
listp = GL(dl_tls_dtv_slotinfo_list);
while (1)
{
size_t cnt;
for (cnt = total == 0 ? 1 : 0; cnt < listp->len; ++cnt)
{
struct link_map *map;
void *dest;
/* Check for the total number of used slots. */
if (total + cnt > GL(dl_tls_max_dtv_idx))
break;
map = listp->slotinfo[cnt].map;
if (map == NULL)
/* Unused entry. */
continue;
/* Keep track of the maximum generation number. This might
not be the generation counter. */
assert (listp->slotinfo[cnt].gen <= GL(dl_tls_generation));
maxgen = MAX (maxgen, listp->slotinfo[cnt].gen);
dtv[map->l_tls_modid].pointer.val = TLS_DTV_UNALLOCATED;
dtv[map->l_tls_modid].pointer.to_free = NULL;
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("_dl_allocate_tls_init unallocates %sdtv 0x%0*Zx module %lu\n",
(dtv == THREAD_DTV () ? "own " : ""),
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
map->l_tls_modid);
if (map->l_tls_offset == NO_TLS_OFFSET
|| map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET)
continue;
assert (map->l_tls_modid == total + cnt);
assert (map->l_tls_blocksize >= map->l_tls_initimage_size);
#if TLS_TCB_AT_TP
assert ((size_t) map->l_tls_offset >= map->l_tls_blocksize);
dest = (char *) result - map->l_tls_offset;
#elif TLS_DTV_AT_TP
dest = (char *) result + map->l_tls_offset;
#else
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
#endif
/* Set up the DTV entry. The simplified __tls_get_addr that
some platforms use in static programs requires it. */
dtv[map->l_tls_modid].pointer.val = dest;
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("_dl_allocate_tls_init sets %sdtv 0x%0*Zx module %lu to 0x%0*Zx\n",
(dtv == THREAD_DTV () ? "own " : ""),
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
map->l_tls_modid,
(int) sizeof (void *) * 2,
(unsigned long int) dest);
/* Copy the initialization image and clear the BSS part. */
memset (__mempcpy (dest, map->l_tls_initimage,
map->l_tls_initimage_size), '\0',
map->l_tls_blocksize - map->l_tls_initimage_size);
}
total += cnt;
if (total >= GL(dl_tls_max_dtv_idx))
break;
listp = listp->next;
assert (listp != NULL);
}
/* The DTV version is up-to-date now. */
dtv[0].counter = maxgen;
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_print_dtv ("_dl_allocate_tls_init return ", dtv, 10);
return result;
}
rtld_hidden_def (_dl_allocate_tls_init)
void *
_dl_allocate_tls (void *mem)
{
return _dl_allocate_tls_init (mem == NULL
? _dl_allocate_tls_storage ()
: allocate_dtv (mem));
}
rtld_hidden_def (_dl_allocate_tls)
/* Clear the given dtv. (We have this here because __signal_safe_free is
not visible to nptl/allocatestack.c.) */
void
_dl_clear_dtv (dtv_t *dtv)
{
for (size_t cnt = 0; cnt < dtv[-1].counter; ++cnt)
__signal_safe_free (dtv[1 + cnt].pointer.to_free);
memset (dtv, '\0', (dtv[-1].counter + 1) * sizeof (dtv_t));
}
rtld_hidden_def (_dl_clear_dtv)
void
_dl_deallocate_tls (void *tcb, bool dealloc_tcb)
{
dtv_t *dtv = GET_DTV (tcb);
/* We need to free the memory allocated for non-static TLS. */
for (size_t cnt = 0; cnt < dtv[-1].counter; ++cnt)
__signal_safe_free (dtv[1 + cnt].pointer.to_free);
/* The array starts with dtv[-1]. */
if (dtv != GL(dl_initial_dtv))
__signal_safe_free (dtv - 1);
if (dealloc_tcb)
free (*tcb_to_pointer_to_free_location (tcb));
}
rtld_hidden_def (_dl_deallocate_tls)
#ifdef SHARED
/* The __tls_get_addr function has two basic forms which differ in the
arguments. The IA-64 form takes two parameters, the module ID and
offset. The form used, among others, on IA-32 takes a reference to
a special structure which contain the same information. The second
form seems to be more often used (in the moment) so we default to
it. Users of the IA-64 form have to provide adequate definitions
of the following macros. */
# ifndef GET_ADDR_ARGS
# define GET_ADDR_ARGS tls_index *ti
# define GET_ADDR_PARAM ti
# endif
# ifndef GET_ADDR_MODULE
# define GET_ADDR_MODULE ti->ti_module
# endif
# ifndef GET_ADDR_OFFSET
# define GET_ADDR_OFFSET ti->ti_offset
# endif
/* Allocate one DTV entry. */
static struct dtv_pointer
allocate_dtv_entry (size_t alignment, size_t size)
{
if (powerof2 (alignment) && alignment <= _Alignof (max_align_t))
{
/* The alignment is supported by malloc. */
void *ptr = malloc (size);
return (struct dtv_pointer) { ptr, ptr };
}
/* Emulate memalign to by manually aligning a pointer returned by
malloc. First compute the size with an overflow check. */
size_t alloc_size = size + alignment;
if (alloc_size < size)
return (struct dtv_pointer) {};
/* Perform the allocation. This is the pointer we need to free
later. */
void *start = malloc (alloc_size);
if (start == NULL)
return (struct dtv_pointer) {};
/* Find the aligned position within the larger allocation. */
void *aligned = (void *) roundup ((uintptr_t) start, alignment);
return (struct dtv_pointer) { .val = aligned, .to_free = start };
}
static struct dtv_pointer
allocate_and_init (struct link_map *map)
{
struct dtv_pointer result = allocate_dtv_entry
(map->l_tls_align, map->l_tls_blocksize);
if (result.val == NULL)
oom ();
/* Initialize the memory. */
memset (__mempcpy (result.val, map->l_tls_initimage,
map->l_tls_initimage_size),
'\0', map->l_tls_blocksize - map->l_tls_initimage_size);
return result;
}
static void
signal_safe_allocate_and_init (dtv_t *dtv, struct link_map *map)
{
void *newp;
newp = __signal_safe_memalign (map->l_tls_align, map->l_tls_blocksize);
if (newp == NULL)
oom ();
/* Initialize the memory. Since this is our thread's space, we are
under a signal mask, and no one has touched this section before,
we can safely just overwrite whatever's there. */
memset (__mempcpy (newp, map->l_tls_initimage,
map->l_tls_initimage_size),
'\0', map->l_tls_blocksize - map->l_tls_initimage_size);
dtv->pointer.val = newp;
dtv->pointer.to_free = newp;
}
struct link_map *
_dl_update_slotinfo (unsigned long int req_modid)
{
struct link_map *the_map = NULL;
dtv_t *dtv = THREAD_DTV ();
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
// (should mention module name?)
_dl_debug_printf ("Updating slot info for own dtv 0x%0*Zx module %lu\n",
(int) sizeof (void *) * 2, (unsigned long int) dtv,
req_modid);
/* The global dl_tls_dtv_slotinfo array contains for each module
index the generation counter current when the entry was created.
This array never shrinks so that all module indices which were
valid at some time can be used to access it. Before the first
use of a new module index in this function the array was extended
appropriately. Access also does not have to be guarded against
modifications of the array. It is assumed that pointer-size
values can be read atomically even in SMP environments. It is
possible that other threads at the same time dynamically load
code and therefore add to the slotinfo list. This is a problem
since we must not pick up any information about incomplete work.
The solution to this is to ignore all dtv slots which were
created after the one we are currently interested. We know that
dynamic loading for this module is completed and this is the last
load operation we know finished. */
unsigned long int idx = req_modid;
struct dtv_slotinfo_list *listp = GL(dl_tls_dtv_slotinfo_list);
while (idx >= listp->len)
{
idx -= listp->len;
listp = listp->next;
}
if (dtv[0].counter < listp->slotinfo[idx].gen)
{
/* The generation counter for the slot is higher than what the
current dtv implements. We have to update the whole dtv but
only those entries with a generation counter <= the one for
the entry we need. */
size_t new_gen = listp->slotinfo[idx].gen;
size_t total = 0;
sigset_t old;
if (GLRO(dl_async_signal_safe)) {
_dl_mask_all_signals (&old);
/* We use the signal mask as a lock against reentrancy here.
Check that a signal taken before the lock didn't already
update us. */
dtv = THREAD_DTV ();
if (dtv[0].counter >= listp->slotinfo[idx].gen)
{
_dl_unmask_signals (&old);
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("Slot info update for own dtv 0x%0*Zx module %lu done, exiting early\n",
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
req_modid);
return the_map;
}
}
/* We have to look through the entire dtv slotinfo list. */
listp = GL(dl_tls_dtv_slotinfo_list);
do
{
for (size_t cnt = total == 0 ? 1 : 0; cnt < listp->len; ++cnt)
{
size_t gen = listp->slotinfo[cnt].gen;
if (gen > new_gen)
/* This is a slot for a generation younger than the
one we are handling now. It might be incompletely
set up so ignore it. */
continue;
/* If the entry is older than the current dtv layout we
know we don't have to handle it. */
if (gen <= dtv[0].counter)
continue;
/* If there is no map this means the entry is empty. */
struct link_map *map = listp->slotinfo[cnt].map;
if (map == NULL)
{
if (dtv[-1].counter >= total + cnt)
{
/* If this modid was used at some point the memory
might still be allocated. */
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("Slot info update for own dtv 0x%0*Zx module %lu unallocating 0x%0*Zx\n",
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
total + cnt,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[total + cnt].pointer.val);
__signal_safe_free (dtv[total + cnt].pointer.to_free);
dtv[total + cnt].pointer.val = TLS_DTV_UNALLOCATED;
dtv[total + cnt].pointer.to_free = NULL;
}
continue;
}
/* Check whether the current dtv array is large enough. */
size_t modid = map->l_tls_modid;
assert (total + cnt == modid);
if (dtv[-1].counter < modid)
{
/* Resize the dtv. */
dtv = _dl_resize_dtv (dtv);
assert (modid <= dtv[-1].counter);
/* Install this new dtv in the thread data
structures. */
INSTALL_NEW_DTV (dtv);
}
/* If there is currently memory allocate for this
dtv entry free it. */
/* XXX Ideally we will at some point create a memory
pool. */
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("Slot info update for own dtv 0x%0*Zx module %lu unallocating 0x%0*Zx\n",
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
modid,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[modid].pointer.val);
__signal_safe_free (dtv[modid].pointer.to_free);
dtv[modid].pointer.val = TLS_DTV_UNALLOCATED;
dtv[modid].pointer.to_free = NULL;
if (modid == req_modid)
the_map = map;
}
total += listp->len;
}
while ((listp = listp->next) != NULL);
/* This will be the new maximum generation counter. */
dtv[0].counter = new_gen;
if (GLRO(dl_async_signal_safe))
_dl_unmask_signals (&old);
}
return the_map;
}
static void *
__attribute_noinline__
tls_get_addr_tail (GET_ADDR_ARGS, dtv_t *dtv, struct link_map *the_map)
{
/* The allocation was deferred. Do it now. */
if (the_map == NULL)
{
/* Find the link map for this module. */
size_t idx = GET_ADDR_MODULE;
struct dtv_slotinfo_list *listp = GL(dl_tls_dtv_slotinfo_list);
while (idx >= listp->len)
{
idx -= listp->len;
listp = listp->next;
}
the_map = listp->slotinfo[idx].map;
}
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
{
char *map_name = (the_map->l_name ? the_map->l_name : "no name");
_dl_debug_printf ("tls_get_addr_tail entry, own dtv 0x%0*Zx module %lu (%s) pointer.val = 0x%0*Zx\n",
(int) sizeof (void *) * 2, (unsigned long int) dtv,
GET_ADDR_MODULE, map_name,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[GET_ADDR_MODULE].pointer.val);
}
if (!GLRO(dl_async_signal_safe)) {
/* Make sure that, if a dlopen running in parallel forces the
variable into static storage, we'll wait until the address in the
static TLS block is set up, and use that. If we're undecided
yet, make sure we make the decision holding the lock as well. */
if (__glibc_unlikely (the_map->l_tls_offset
!= FORCED_DYNAMIC_TLS_OFFSET))
{
__rtld_lock_lock_recursive (GL(dl_load_lock));
if (__glibc_likely (the_map->l_tls_offset == NO_TLS_OFFSET))
{
the_map->l_tls_offset = FORCED_DYNAMIC_TLS_OFFSET;
__rtld_lock_unlock_recursive (GL(dl_load_lock));
}
else if (__glibc_likely (the_map->l_tls_offset
!= FORCED_DYNAMIC_TLS_OFFSET))
{
#if TLS_TCB_AT_TP
void *p = (char *) THREAD_SELF - the_map->l_tls_offset;
#elif TLS_DTV_AT_TP
void *p = (char *) THREAD_SELF + the_map->l_tls_offset + TLS_PRE_TCB_SIZE;
#else
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
#endif
__rtld_lock_unlock_recursive (GL(dl_load_lock));
dtv[GET_ADDR_MODULE].pointer.to_free = NULL;
dtv[GET_ADDR_MODULE].pointer.val = p;
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("tls_get_addr_tail sets own dtv 0x%0*Zx module %lu pointer.val to 0x%0*Zx, returns\n",
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
GET_ADDR_MODULE,
(int) sizeof (void *) * 2,
(unsigned long int) p);
return (char *) p + GET_ADDR_OFFSET;
}
else
__rtld_lock_unlock_recursive (GL(dl_load_lock));
}
struct dtv_pointer result = allocate_and_init (the_map);
dtv[GET_ADDR_MODULE].pointer = result;
assert (result.to_free != NULL);
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("tls_get_addr_tail sets own dtv 0x%0*Zx module %lu pointer.val to 0x%0*Zx, returns\n",
(int) sizeof (void *) * 2, (unsigned long int) dtv,
GET_ADDR_MODULE,
(int) sizeof (void *) * 2, (unsigned long int) result.val);
return (char *) result.val + GET_ADDR_OFFSET;
} else {
sigset_t old;
_dl_mask_all_signals (&old);
/* As with update_slotinfo, we use the sigmask as a check against
reentrancy. */
if (dtv[GET_ADDR_MODULE].pointer.val != TLS_DTV_UNALLOCATED)
{
_dl_unmask_signals (&old);
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("tls_get_addr_tail keeps own dtv pointer.val, returns\n");
return (char *) dtv[GET_ADDR_MODULE].pointer.val + GET_ADDR_OFFSET;
}
/* Synchronize against a parallel dlopen() forcing this variable
into static storage. If that happens, we have to be more careful
about initializing the area, as that dlopen() will be iterating
the threads to do so itself. */
ptrdiff_t offset = the_map->l_tls_offset;
if (offset == NO_TLS_OFFSET)
{
/* l_tls_offset starts out at NO_TLS_OFFSET, and all attempts to
change it go from NO_TLS_OFFSET to some other value. We use
compare_and_exchange to ensure only one attempt succeeds. We
don't actually need any memory ordering here, but _acq is the
weakest available. */
(void) atomic_compare_and_exchange_bool_acq (&the_map->l_tls_offset,
FORCED_DYNAMIC_TLS_OFFSET,
NO_TLS_OFFSET);
offset = the_map->l_tls_offset;
assert (offset != NO_TLS_OFFSET);
}
if (offset == FORCED_DYNAMIC_TLS_OFFSET)
{
signal_safe_allocate_and_init (&dtv[GET_ADDR_MODULE], the_map);
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("tls_get_addr_tail allocates own dtv 0x%0*Zx module %lu pointer.val = 0x%0*Zx\n",
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
GET_ADDR_MODULE,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[GET_ADDR_MODULE].pointer.val);
}
/* It can happen that slot info updates will un-allocate a pointer (possibly
due to a bug elsewhere), which leaves us waiting indefinitely for the
dlopen that will never happen. Emulate the async-signal-unsafe case above
and use a static TLS address. */
else if (dtv[GET_ADDR_MODULE].pointer.val == TLS_DTV_UNALLOCATED)
{
#if TLS_TCB_AT_TP
void *p = (char *) THREAD_SELF - the_map->l_tls_offset;
#elif TLS_DTV_AT_TP
void *p = (char *) THREAD_SELF + the_map->l_tls_offset + TLS_PRE_TCB_SIZE;
#else
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
#endif
dtv[GET_ADDR_MODULE].pointer.to_free = NULL;
dtv[GET_ADDR_MODULE].pointer.val = p;
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("tls_get_addr_tail sets unallocated own dtv 0x%0*Zx module %lu pointer.val = 0x%0*Zx\n",
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
GET_ADDR_MODULE,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[GET_ADDR_MODULE].pointer.val);
}
else
{
void ** volatile pp = &dtv[GET_ADDR_MODULE].pointer.val;
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("tls_get_addr_tail waiting for own dtv 0x%0*Zx module %lu to be allocated\n",
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
GET_ADDR_MODULE);
while (atomic_forced_read (*pp) == TLS_DTV_UNALLOCATED)
{
/* for lack of a better (safe) thing to do, just spin.
Someone else (not us; it's done under a signal mask) set
this map to a static TLS offset, and they'll iterate all
threads to initialize it. They'll eventually write
to pointer.val, at which point we know they've fully
completed initialization. */
atomic_spin_nop ();
}
/* Make sure we've picked up their initialization of the actual
block; this pairs against the write barrier in
init_one_static_tls, guaranteeing that we see their write of
the tls_initimage into the static region. */
atomic_read_barrier ();
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
_dl_debug_printf ("tls_get_addr_tail sees own dtv 0x%0*Zx module %lu has pointer.val = 0x%0*Zx\n",
(int) sizeof (void *) * 2,
(unsigned long int) dtv,
GET_ADDR_MODULE,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[GET_ADDR_MODULE].pointer.val);
}
assert (dtv[GET_ADDR_MODULE].pointer.val != TLS_DTV_UNALLOCATED);
_dl_unmask_signals (&old);
return (char *) dtv[GET_ADDR_MODULE].pointer.val + GET_ADDR_OFFSET;
}
}
static struct link_map *
__attribute_noinline__
update_get_addr (GET_ADDR_ARGS)
{
struct link_map *the_map = _dl_update_slotinfo (GET_ADDR_MODULE);
dtv_t *dtv = THREAD_DTV ();
void *p = dtv[GET_ADDR_MODULE].pointer.val;
if (__glibc_unlikely (p == TLS_DTV_UNALLOCATED))
return tls_get_addr_tail (GET_ADDR_PARAM, dtv, the_map);
return (void *) p + GET_ADDR_OFFSET;
}
/* For all machines that have a non-macro version of __tls_get_addr, we
want to use rtld_hidden_proto/rtld_hidden_def in order to call the
internal alias for __tls_get_addr from ld.so. This avoids a PLT entry
in ld.so for __tls_get_addr. */
#ifndef __tls_get_addr
extern void * __tls_get_addr (GET_ADDR_ARGS);
rtld_hidden_proto (__tls_get_addr)
rtld_hidden_def (__tls_get_addr)
#endif
/* The generic dynamic and local dynamic model cannot be used in
statically linked applications. */
void *
__tls_get_addr (GET_ADDR_ARGS)
{
dtv_t *dtv = THREAD_DTV ();
if (__glibc_unlikely (dtv[0].counter != GL(dl_tls_generation)))
return update_get_addr (GET_ADDR_PARAM);
void *p = dtv[GET_ADDR_MODULE].pointer.val;
if (__glibc_unlikely (p == TLS_DTV_UNALLOCATED))
return tls_get_addr_tail (GET_ADDR_PARAM, dtv, NULL);
return (char *) p + GET_ADDR_OFFSET;
}
#endif
/* Look up the module's TLS block as for __tls_get_addr,
but never touch anything. Return null if it's not allocated yet. */
void *
_dl_tls_get_addr_soft (struct link_map *l)
{
if (__glibc_unlikely (l->l_tls_modid == 0))
/* This module has no TLS segment. */
return NULL;
dtv_t *dtv = THREAD_DTV ();
if (__glibc_unlikely (dtv[0].counter != GL(dl_tls_generation)))
{
/* This thread's DTV is not completely current,
but it might already cover this module. */
if (l->l_tls_modid >= dtv[-1].counter)
/* Nope. */
return NULL;
size_t idx = l->l_tls_modid;
struct dtv_slotinfo_list *listp = GL(dl_tls_dtv_slotinfo_list);
while (idx >= listp->len)
{
idx -= listp->len;
listp = listp->next;
}
/* We've reached the slot for this module.
If its generation counter is higher than the DTV's,
this thread does not know about this module yet. */
if (dtv[0].counter < listp->slotinfo[idx].gen)
return NULL;
}
void *data = dtv[l->l_tls_modid].pointer.val;
if (__glibc_unlikely (data == TLS_DTV_UNALLOCATED))
/* The DTV is current, but this thread has not yet needed
to allocate this module's segment. */
data = NULL;
return data;
}
void
_dl_add_to_slotinfo (struct link_map *l)
{
/* Now that we know the object is loaded successfully add
modules containing TLS data to the dtv info table. We
might have to increase its size. */
struct dtv_slotinfo_list *listp;
struct dtv_slotinfo_list *prevp;
size_t idx = l->l_tls_modid;
/* Find the place in the dtv slotinfo list. */
listp = GL(dl_tls_dtv_slotinfo_list);
prevp = NULL; /* Needed to shut up gcc. */
do
{
/* Does it fit in the array of this list element? */
if (idx < listp->len)
break;
idx -= listp->len;
prevp = listp;
listp = listp->next;
}
while (listp != NULL);
if (listp == NULL)
{
/* When we come here it means we have to add a new element
to the slotinfo list. And the new module must be in
the first slot. */
assert (idx == 0);
listp = prevp->next = (struct dtv_slotinfo_list *)
malloc (sizeof (struct dtv_slotinfo_list)
+ TLS_SLOTINFO_SURPLUS * sizeof (struct dtv_slotinfo));
if (listp == NULL)
{
/* We ran out of memory. We will simply fail this
call but don't undo anything we did so far. The
application will crash or be terminated anyway very
soon. */
/* We have to do this since some entries in the dtv
slotinfo array might already point to this
generation. */
++GL(dl_tls_generation);
_dl_signal_error (ENOMEM, "dlopen", NULL, N_("\
cannot create TLS data structures"));
}
listp->len = TLS_SLOTINFO_SURPLUS;
listp->next = NULL;
memset (listp->slotinfo, '\0',
TLS_SLOTINFO_SURPLUS * sizeof (struct dtv_slotinfo));
}
/* Add the information into the slotinfo data structure. */
listp->slotinfo[idx].map = l;
listp->slotinfo[idx].gen = GL(dl_tls_generation) + 1;
}
/* Return a thread id of the current thread if we are debugging tls and the
value is meaningful. */
pid_t
_dl_tls_tid (void)
{
if (!__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_TLS))
return 0;
#ifdef SHARED
if (GL(dl_initial_dtv) == NULL)
return 0;
#endif
struct pthread *thr = THREAD_SELF;
return thr->tid;
}
/* Print all or part of a dtv. Note that the output may be large; for instance
nptl/tst-stack4 has dtv's with hundreds of entries. */
static void
_dl_print_dtv (const char *msg, dtv_t *dtv, int numentries)
{
size_t cnt, last_used, num_to_print, i;
cnt = dtv[-1].counter;
last_used = 0;
for (i = 1; i <= cnt; ++i)
{
if (dtv[i].pointer.val || dtv[i].pointer.to_free)
last_used = i;
}
num_to_print = last_used;
if (numentries >= 0 && numentries < num_to_print)
num_to_print = numentries;
_dl_debug_printf ("%sdtv 0x%0*Zx has %lu used of %lu entries, generation %lu\n",
msg,
(int) sizeof (void *) * 2, (unsigned long int) dtv,
last_used, cnt, dtv[0].counter);
for (i = 1; i <= num_to_print; ++i)
{
if (dtv[i].pointer.to_free == dtv[i].pointer.val)
_dl_debug_printf ("%*lu: pointer.val = 0x%0*Zx to_free = same\n",
4, i,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[i].pointer.val);
else if (dtv[i].pointer.to_free)
_dl_debug_printf ("%*lu: pointer.val = 0x%0*Zx to_free = 0x%0*Zx\n",
4, i,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[i].pointer.val,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[i].pointer.to_free);
else
_dl_debug_printf ("%*lu: pointer.val = 0x%0*Zx\n",
4, i,
(int) sizeof (void *) * 2,
(unsigned long int) dtv[i].pointer.val);
}
if (num_to_print < last_used)
_dl_debug_printf (" [...]\n");
}
|