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
|
/* Linux-dependent part of branch trace support for GDB, and GDBserver.
Copyright (C) 2013-2016 Free Software Foundation, Inc.
Contributed by Intel Corp. <markus.t.metzger@intel.com>
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "common-defs.h"
#include "linux-btrace.h"
#include "common-regcache.h"
#include "gdb_wait.h"
#include "x86-cpuid.h"
#include "filestuff.h"
#include <inttypes.h>
#ifdef HAVE_SYS_SYSCALL_H
#include <sys/syscall.h>
#endif
#if HAVE_LINUX_PERF_EVENT_H && defined(SYS_perf_event_open)
#include <unistd.h>
#include <sys/mman.h>
#include <sys/user.h>
#include "nat/gdb_ptrace.h"
#include <sys/types.h>
#include <signal.h>
/* A branch trace record in perf_event. */
struct perf_event_bts
{
/* The linear address of the branch source. */
uint64_t from;
/* The linear address of the branch destination. */
uint64_t to;
};
/* A perf_event branch trace sample. */
struct perf_event_sample
{
/* The perf_event sample header. */
struct perf_event_header header;
/* The perf_event branch tracing payload. */
struct perf_event_bts bts;
};
/* Identify the cpu we're running on. */
static struct btrace_cpu
btrace_this_cpu (void)
{
struct btrace_cpu cpu;
unsigned int eax, ebx, ecx, edx;
int ok;
memset (&cpu, 0, sizeof (cpu));
ok = x86_cpuid (0, &eax, &ebx, &ecx, &edx);
if (ok != 0)
{
if (ebx == signature_INTEL_ebx && ecx == signature_INTEL_ecx
&& edx == signature_INTEL_edx)
{
unsigned int cpuid, ignore;
ok = x86_cpuid (1, &cpuid, &ignore, &ignore, &ignore);
if (ok != 0)
{
cpu.vendor = CV_INTEL;
cpu.family = (cpuid >> 8) & 0xf;
cpu.model = (cpuid >> 4) & 0xf;
if (cpu.family == 0x6)
cpu.model += (cpuid >> 12) & 0xf0;
}
}
}
return cpu;
}
/* Return non-zero if there is new data in PEVENT; zero otherwise. */
static int
perf_event_new_data (const struct perf_event_buffer *pev)
{
return *pev->data_head != pev->last_head;
}
/* Try to determine the size of a pointer in bits for the OS.
This is the same as the size of a pointer for the inferior process
except when a 32-bit inferior is running on a 64-bit OS. */
/* Copy the last SIZE bytes from PEV ending at DATA_HEAD and return a pointer
to the memory holding the copy.
The caller is responsible for freeing the memory. */
static gdb_byte *
perf_event_read (const struct perf_event_buffer *pev, __u64 data_head,
size_t size)
{
const gdb_byte *begin, *end, *start, *stop;
gdb_byte *buffer;
size_t buffer_size;
__u64 data_tail;
if (size == 0)
return NULL;
gdb_assert (size <= data_head);
data_tail = data_head - size;
buffer_size = pev->size;
begin = pev->mem;
start = begin + data_tail % buffer_size;
stop = begin + data_head % buffer_size;
buffer = (gdb_byte *) xmalloc (size);
if (start < stop)
memcpy (buffer, start, stop - start);
else
{
end = begin + buffer_size;
memcpy (buffer, start, end - start);
memcpy (buffer + (end - start), begin, stop - begin);
}
return buffer;
}
/* Copy the perf event buffer data from PEV.
Store a pointer to the copy into DATA and its size in SIZE. */
static void
perf_event_read_all (struct perf_event_buffer *pev, gdb_byte **data,
size_t *psize)
{
size_t size;
__u64 data_head;
data_head = *pev->data_head;
size = pev->size;
if (data_head < size)
size = (size_t) data_head;
*data = perf_event_read (pev, data_head, size);
*psize = size;
pev->last_head = data_head;
}
/* Determine the event type.
Returns zero on success and fills in TYPE; returns -1 otherwise. */
static int
perf_event_pt_event_type (int *type)
{
FILE *file;
int found;
file = fopen ("/sys/bus/event_source/devices/intel_pt/type", "r");
if (file == NULL)
return -1;
found = fscanf (file, "%d", type);
fclose (file);
if (found == 1)
return 0;
return -1;
}
/* Try to determine the start address of the Linux kernel. */
static uint64_t
linux_determine_kernel_start (void)
{
static uint64_t kernel_start;
static int cached;
FILE *file;
if (cached != 0)
return kernel_start;
cached = 1;
file = gdb_fopen_cloexec ("/proc/kallsyms", "r");
if (file == NULL)
return kernel_start;
while (!feof (file))
{
char buffer[1024], symbol[8], *line;
uint64_t addr;
int match;
line = fgets (buffer, sizeof (buffer), file);
if (line == NULL)
break;
match = sscanf (line, "%" SCNx64 " %*[tT] %7s", &addr, symbol);
if (match != 2)
continue;
if (strcmp (symbol, "_text") == 0)
{
kernel_start = addr;
break;
}
}
fclose (file);
return kernel_start;
}
/* Check whether an address is in the kernel. */
static inline int
perf_event_is_kernel_addr (uint64_t addr)
{
uint64_t kernel_start;
kernel_start = linux_determine_kernel_start ();
if (kernel_start != 0ull)
return (addr >= kernel_start);
/* If we don't know the kernel's start address, let's check the most
significant bit. This will work at least for 64-bit kernels. */
return ((addr & (1ull << 63)) != 0);
}
/* Check whether a perf event record should be skipped. */
static inline int
perf_event_skip_bts_record (const struct perf_event_bts *bts)
{
/* The hardware may report branches from kernel into user space. Branches
from user into kernel space will be suppressed. We filter the former to
provide a consistent branch trace excluding kernel. */
return perf_event_is_kernel_addr (bts->from);
}
/* Perform a few consistency checks on a perf event sample record. This is
meant to catch cases when we get out of sync with the perf event stream. */
static inline int
perf_event_sample_ok (const struct perf_event_sample *sample)
{
if (sample->header.type != PERF_RECORD_SAMPLE)
return 0;
if (sample->header.size != sizeof (*sample))
return 0;
return 1;
}
/* Branch trace is collected in a circular buffer [begin; end) as pairs of from
and to addresses (plus a header).
Start points into that buffer at the next sample position.
We read the collected samples backwards from start.
While reading the samples, we convert the information into a list of blocks.
For two adjacent samples s1 and s2, we form a block b such that b.begin =
s1.to and b.end = s2.from.
In case the buffer overflows during sampling, one sample may have its lower
part at the end and its upper part at the beginning of the buffer. */
static VEC (btrace_block_s) *
perf_event_read_bts (struct btrace_target_info* tinfo, const uint8_t *begin,
const uint8_t *end, const uint8_t *start, size_t size)
{
VEC (btrace_block_s) *btrace = NULL;
struct perf_event_sample sample;
size_t read = 0;
struct btrace_block block = { 0, 0 };
struct regcache *regcache;
gdb_assert (begin <= start);
gdb_assert (start <= end);
/* The first block ends at the current pc. */
regcache = get_thread_regcache_for_ptid (tinfo->ptid);
block.end = regcache_read_pc (regcache);
/* The buffer may contain a partial record as its last entry (i.e. when the
buffer size is not a multiple of the sample size). */
read = sizeof (sample) - 1;
for (; read < size; read += sizeof (sample))
{
const struct perf_event_sample *psample;
/* Find the next perf_event sample in a backwards traversal. */
start -= sizeof (sample);
/* If we're still inside the buffer, we're done. */
if (begin <= start)
psample = (const struct perf_event_sample *) start;
else
{
int missing;
/* We're to the left of the ring buffer, we will wrap around and
reappear at the very right of the ring buffer. */
missing = (begin - start);
start = (end - missing);
/* If the entire sample is missing, we're done. */
if (missing == sizeof (sample))
psample = (const struct perf_event_sample *) start;
else
{
uint8_t *stack;
/* The sample wrapped around. The lower part is at the end and
the upper part is at the beginning of the buffer. */
stack = (uint8_t *) &sample;
/* Copy the two parts so we have a contiguous sample. */
memcpy (stack, start, missing);
memcpy (stack + missing, begin, sizeof (sample) - missing);
psample = &sample;
}
}
if (!perf_event_sample_ok (psample))
{
warning (_("Branch trace may be incomplete."));
break;
}
if (perf_event_skip_bts_record (&psample->bts))
continue;
/* We found a valid sample, so we can complete the current block. */
block.begin = psample->bts.to;
VEC_safe_push (btrace_block_s, btrace, &block);
/* Start the next block. */
block.end = psample->bts.from;
}
/* Push the last block (i.e. the first one of inferior execution), as well.
We don't know where it ends, but we know where it starts. If we're
reading delta trace, we can fill in the start address later on.
Otherwise we will prune it. */
block.begin = 0;
VEC_safe_push (btrace_block_s, btrace, &block);
return btrace;
}
/* Check whether the kernel supports BTS. */
static int
kernel_supports_bts (void)
{
struct perf_event_attr attr;
pid_t child, pid;
int status, file;
errno = 0;
child = fork ();
switch (child)
{
case -1:
warning (_("test bts: cannot fork: %s."), safe_strerror (errno));
return 0;
case 0:
status = ptrace (PTRACE_TRACEME, 0, NULL, NULL);
if (status != 0)
{
warning (_("test bts: cannot PTRACE_TRACEME: %s."),
safe_strerror (errno));
_exit (1);
}
status = raise (SIGTRAP);
if (status != 0)
{
warning (_("test bts: cannot raise SIGTRAP: %s."),
safe_strerror (errno));
_exit (1);
}
_exit (1);
default:
pid = waitpid (child, &status, 0);
if (pid != child)
{
warning (_("test bts: bad pid %ld, error: %s."),
(long) pid, safe_strerror (errno));
return 0;
}
if (!WIFSTOPPED (status))
{
warning (_("test bts: expected stop. status: %d."),
status);
return 0;
}
memset (&attr, 0, sizeof (attr));
attr.type = PERF_TYPE_HARDWARE;
attr.config = PERF_COUNT_HW_BRANCH_INSTRUCTIONS;
attr.sample_period = 1;
attr.sample_type = PERF_SAMPLE_IP | PERF_SAMPLE_ADDR;
attr.exclude_kernel = 1;
attr.exclude_hv = 1;
attr.exclude_idle = 1;
file = syscall (SYS_perf_event_open, &attr, child, -1, -1, 0);
if (file >= 0)
close (file);
kill (child, SIGKILL);
ptrace (PTRACE_KILL, child, NULL, NULL);
pid = waitpid (child, &status, 0);
if (pid != child)
{
warning (_("test bts: bad pid %ld, error: %s."),
(long) pid, safe_strerror (errno));
if (!WIFSIGNALED (status))
warning (_("test bts: expected killed. status: %d."),
status);
}
return (file >= 0);
}
}
/* Check whether the kernel supports Intel(R) Processor Trace. */
static int
kernel_supports_pt (void)
{
struct perf_event_attr attr;
pid_t child, pid;
int status, file, type;
errno = 0;
child = fork ();
switch (child)
{
case -1:
warning (_("test pt: cannot fork: %s."), safe_strerror (errno));
return 0;
case 0:
status = ptrace (PTRACE_TRACEME, 0, NULL, NULL);
if (status != 0)
{
warning (_("test pt: cannot PTRACE_TRACEME: %s."),
safe_strerror (errno));
_exit (1);
}
status = raise (SIGTRAP);
if (status != 0)
{
warning (_("test pt: cannot raise SIGTRAP: %s."),
safe_strerror (errno));
_exit (1);
}
_exit (1);
default:
pid = waitpid (child, &status, 0);
if (pid != child)
{
warning (_("test pt: bad pid %ld, error: %s."),
(long) pid, safe_strerror (errno));
return 0;
}
if (!WIFSTOPPED (status))
{
warning (_("test pt: expected stop. status: %d."),
status);
return 0;
}
status = perf_event_pt_event_type (&type);
if (status != 0)
file = -1;
else
{
memset (&attr, 0, sizeof (attr));
attr.size = sizeof (attr);
attr.type = type;
attr.exclude_kernel = 1;
attr.exclude_hv = 1;
attr.exclude_idle = 1;
file = syscall (SYS_perf_event_open, &attr, child, -1, -1, 0);
if (file >= 0)
close (file);
}
kill (child, SIGKILL);
ptrace (PTRACE_KILL, child, NULL, NULL);
pid = waitpid (child, &status, 0);
if (pid != child)
{
warning (_("test pt: bad pid %ld, error: %s."),
(long) pid, safe_strerror (errno));
if (!WIFSIGNALED (status))
warning (_("test pt: expected killed. status: %d."),
status);
}
return (file >= 0);
}
}
/* Check whether an Intel cpu supports BTS. */
static int
intel_supports_bts (const struct btrace_cpu *cpu)
{
switch (cpu->family)
{
case 0x6:
switch (cpu->model)
{
case 0x1a: /* Nehalem */
case 0x1f:
case 0x1e:
case 0x2e:
case 0x25: /* Westmere */
case 0x2c:
case 0x2f:
case 0x2a: /* Sandy Bridge */
case 0x2d:
case 0x3a: /* Ivy Bridge */
/* AAJ122: LBR, BTM, or BTS records may have incorrect branch
"from" information afer an EIST transition, T-states, C1E, or
Adaptive Thermal Throttling. */
return 0;
}
}
return 1;
}
/* Check whether the cpu supports BTS. */
static int
cpu_supports_bts (void)
{
struct btrace_cpu cpu;
cpu = btrace_this_cpu ();
switch (cpu.vendor)
{
default:
/* Don't know about others. Let's assume they do. */
return 1;
case CV_INTEL:
return intel_supports_bts (&cpu);
}
}
/* Check whether the linux target supports BTS. */
static int
linux_supports_bts (void)
{
static int cached;
if (cached == 0)
{
if (!kernel_supports_bts ())
cached = -1;
else if (!cpu_supports_bts ())
cached = -1;
else
cached = 1;
}
return cached > 0;
}
/* Check whether the linux target supports Intel(R) Processor Trace. */
static int
linux_supports_pt (void)
{
static int cached;
if (cached == 0)
{
if (!kernel_supports_pt ())
cached = -1;
else
cached = 1;
}
return cached > 0;
}
/* See linux-btrace.h. */
int
linux_supports_btrace (struct target_ops *ops, enum btrace_format format)
{
switch (format)
{
case BTRACE_FORMAT_NONE:
return 0;
case BTRACE_FORMAT_BTS:
return linux_supports_bts ();
case BTRACE_FORMAT_PT:
return linux_supports_pt ();
}
internal_error (__FILE__, __LINE__, _("Unknown branch trace format"));
}
/* Enable branch tracing in BTS format. */
static struct btrace_target_info *
linux_enable_bts (ptid_t ptid, const struct btrace_config_bts *conf)
{
struct perf_event_mmap_page *header;
struct btrace_target_info *tinfo;
struct btrace_tinfo_bts *bts;
size_t size, pages;
__u64 data_offset;
int pid, pg;
tinfo = XCNEW (struct btrace_target_info);
tinfo->ptid = ptid;
tinfo->conf.format = BTRACE_FORMAT_BTS;
bts = &tinfo->variant.bts;
bts->attr.size = sizeof (bts->attr);
bts->attr.type = PERF_TYPE_HARDWARE;
bts->attr.config = PERF_COUNT_HW_BRANCH_INSTRUCTIONS;
bts->attr.sample_period = 1;
/* We sample from and to address. */
bts->attr.sample_type = PERF_SAMPLE_IP | PERF_SAMPLE_ADDR;
bts->attr.exclude_kernel = 1;
bts->attr.exclude_hv = 1;
bts->attr.exclude_idle = 1;
pid = ptid_get_lwp (ptid);
if (pid == 0)
pid = ptid_get_pid (ptid);
errno = 0;
bts->file = syscall (SYS_perf_event_open, &bts->attr, pid, -1, -1, 0);
if (bts->file < 0)
goto err_out;
/* Convert the requested size in bytes to pages (rounding up). */
pages = ((size_t) conf->size / PAGE_SIZE
+ ((conf->size % PAGE_SIZE) == 0 ? 0 : 1));
/* We need at least one page. */
if (pages == 0)
pages = 1;
/* The buffer size can be requested in powers of two pages. Adjust PAGES
to the next power of two. */
for (pg = 0; pages != ((size_t) 1 << pg); ++pg)
if ((pages & ((size_t) 1 << pg)) != 0)
pages += ((size_t) 1 << pg);
/* We try to allocate the requested size.
If that fails, try to get as much as we can. */
for (; pages > 0; pages >>= 1)
{
size_t length;
__u64 data_size;
data_size = (__u64) pages * PAGE_SIZE;
/* Don't ask for more than we can represent in the configuration. */
if ((__u64) UINT_MAX < data_size)
continue;
size = (size_t) data_size;
length = size + PAGE_SIZE;
/* Check for overflows. */
if ((__u64) length != data_size + PAGE_SIZE)
continue;
/* The number of pages we request needs to be a power of two. */
header = ((struct perf_event_mmap_page *)
mmap (NULL, length, PROT_READ, MAP_SHARED, bts->file, 0));
if (header != MAP_FAILED)
break;
}
if (pages == 0)
goto err_file;
data_offset = PAGE_SIZE;
#if defined (PERF_ATTR_SIZE_VER5)
if (offsetof (struct perf_event_mmap_page, data_size) <= header->size)
{
__u64 data_size;
data_offset = header->data_offset;
data_size = header->data_size;
size = (unsigned int) data_size;
/* Check for overflows. */
if ((__u64) size != data_size)
{
munmap ((void *) header, size + PAGE_SIZE);
goto err_file;
}
}
#endif /* defined (PERF_ATTR_SIZE_VER5) */
bts->header = header;
bts->bts.mem = ((const uint8_t *) header) + data_offset;
bts->bts.size = size;
bts->bts.data_head = &header->data_head;
bts->bts.last_head = 0ull;
tinfo->conf.bts.size = (unsigned int) size;
return tinfo;
err_file:
/* We were not able to allocate any buffer. */
close (bts->file);
err_out:
xfree (tinfo);
return NULL;
}
#if defined (PERF_ATTR_SIZE_VER5)
/* Enable branch tracing in Intel(R) Processor Trace format. */
static struct btrace_target_info *
linux_enable_pt (ptid_t ptid, const struct btrace_config_pt *conf)
{
struct perf_event_mmap_page *header;
struct btrace_target_info *tinfo;
struct btrace_tinfo_pt *pt;
size_t pages, size;
int pid, pg, errcode, type;
if (conf->size == 0)
return NULL;
errcode = perf_event_pt_event_type (&type);
if (errcode != 0)
return NULL;
pid = ptid_get_lwp (ptid);
if (pid == 0)
pid = ptid_get_pid (ptid);
tinfo = XCNEW (struct btrace_target_info);
tinfo->ptid = ptid;
tinfo->conf.format = BTRACE_FORMAT_PT;
pt = &tinfo->variant.pt;
pt->attr.size = sizeof (pt->attr);
pt->attr.type = type;
pt->attr.exclude_kernel = 1;
pt->attr.exclude_hv = 1;
pt->attr.exclude_idle = 1;
errno = 0;
pt->file = syscall (SYS_perf_event_open, &pt->attr, pid, -1, -1, 0);
if (pt->file < 0)
goto err;
/* Allocate the configuration page. */
header = ((struct perf_event_mmap_page *)
mmap (NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED,
pt->file, 0));
if (header == MAP_FAILED)
goto err_file;
header->aux_offset = header->data_offset + header->data_size;
/* Convert the requested size in bytes to pages (rounding up). */
pages = ((size_t) conf->size / PAGE_SIZE
+ ((conf->size % PAGE_SIZE) == 0 ? 0 : 1));
/* We need at least one page. */
if (pages == 0)
pages = 1;
/* The buffer size can be requested in powers of two pages. Adjust PAGES
to the next power of two. */
for (pg = 0; pages != ((size_t) 1 << pg); ++pg)
if ((pages & ((size_t) 1 << pg)) != 0)
pages += ((size_t) 1 << pg);
/* We try to allocate the requested size.
If that fails, try to get as much as we can. */
for (; pages > 0; pages >>= 1)
{
size_t length;
__u64 data_size;
data_size = (__u64) pages * PAGE_SIZE;
/* Don't ask for more than we can represent in the configuration. */
if ((__u64) UINT_MAX < data_size)
continue;
size = (size_t) data_size;
/* Check for overflows. */
if ((__u64) size != data_size)
continue;
header->aux_size = data_size;
length = size;
pt->pt.mem = ((const uint8_t *)
mmap (NULL, length, PROT_READ, MAP_SHARED, pt->file,
header->aux_offset));
if (pt->pt.mem != MAP_FAILED)
break;
}
if (pages == 0)
goto err_conf;
pt->header = header;
pt->pt.size = size;
pt->pt.data_head = &header->aux_head;
tinfo->conf.pt.size = (unsigned int) size;
return tinfo;
err_conf:
munmap((void *) header, PAGE_SIZE);
err_file:
close (pt->file);
err:
xfree (tinfo);
return NULL;
}
#else /* !defined (PERF_ATTR_SIZE_VER5) */
static struct btrace_target_info *
linux_enable_pt (ptid_t ptid, const struct btrace_config_pt *conf)
{
errno = EOPNOTSUPP;
return NULL;
}
#endif /* !defined (PERF_ATTR_SIZE_VER5) */
/* See linux-btrace.h. */
struct btrace_target_info *
linux_enable_btrace (ptid_t ptid, const struct btrace_config *conf)
{
struct btrace_target_info *tinfo;
tinfo = NULL;
switch (conf->format)
{
case BTRACE_FORMAT_NONE:
break;
case BTRACE_FORMAT_BTS:
tinfo = linux_enable_bts (ptid, &conf->bts);
break;
case BTRACE_FORMAT_PT:
tinfo = linux_enable_pt (ptid, &conf->pt);
break;
}
return tinfo;
}
/* Disable BTS tracing. */
static enum btrace_error
linux_disable_bts (struct btrace_tinfo_bts *tinfo)
{
munmap((void *) tinfo->header, tinfo->bts.size + PAGE_SIZE);
close (tinfo->file);
return BTRACE_ERR_NONE;
}
/* Disable Intel(R) Processor Trace tracing. */
static enum btrace_error
linux_disable_pt (struct btrace_tinfo_pt *tinfo)
{
munmap((void *) tinfo->pt.mem, tinfo->pt.size);
munmap((void *) tinfo->header, PAGE_SIZE);
close (tinfo->file);
return BTRACE_ERR_NONE;
}
/* See linux-btrace.h. */
enum btrace_error
linux_disable_btrace (struct btrace_target_info *tinfo)
{
enum btrace_error errcode;
errcode = BTRACE_ERR_NOT_SUPPORTED;
switch (tinfo->conf.format)
{
case BTRACE_FORMAT_NONE:
break;
case BTRACE_FORMAT_BTS:
errcode = linux_disable_bts (&tinfo->variant.bts);
break;
case BTRACE_FORMAT_PT:
errcode = linux_disable_pt (&tinfo->variant.pt);
break;
}
if (errcode == BTRACE_ERR_NONE)
xfree (tinfo);
return errcode;
}
/* Read branch trace data in BTS format for the thread given by TINFO into
BTRACE using the TYPE reading method. */
static enum btrace_error
linux_read_bts (struct btrace_data_bts *btrace,
struct btrace_target_info *tinfo,
enum btrace_read_type type)
{
struct perf_event_buffer *pevent;
const uint8_t *begin, *end, *start;
size_t buffer_size, size;
__u64 data_head, data_tail;
unsigned int retries = 5;
pevent = &tinfo->variant.bts.bts;
/* For delta reads, we return at least the partial last block containing
the current PC. */
if (type == BTRACE_READ_NEW && !perf_event_new_data (pevent))
return BTRACE_ERR_NONE;
buffer_size = pevent->size;
data_tail = pevent->last_head;
/* We may need to retry reading the trace. See below. */
while (retries--)
{
data_head = *pevent->data_head;
/* Delete any leftover trace from the previous iteration. */
VEC_free (btrace_block_s, btrace->blocks);
if (type == BTRACE_READ_DELTA)
{
__u64 data_size;
/* Determine the number of bytes to read and check for buffer
overflows. */
/* Check for data head overflows. We might be able to recover from
those but they are very unlikely and it's not really worth the
effort, I think. */
if (data_head < data_tail)
return BTRACE_ERR_OVERFLOW;
/* If the buffer is smaller than the trace delta, we overflowed. */
data_size = data_head - data_tail;
if (buffer_size < data_size)
return BTRACE_ERR_OVERFLOW;
/* DATA_SIZE <= BUFFER_SIZE and therefore fits into a size_t. */
size = (size_t) data_size;
}
else
{
/* Read the entire buffer. */
size = buffer_size;
/* Adjust the size if the buffer has not overflowed, yet. */
if (data_head < size)
size = (size_t) data_head;
}
/* Data_head keeps growing; the buffer itself is circular. */
begin = pevent->mem;
start = begin + data_head % buffer_size;
if (data_head <= buffer_size)
end = start;
else
end = begin + pevent->size;
btrace->blocks = perf_event_read_bts (tinfo, begin, end, start, size);
/* The stopping thread notifies its ptracer before it is scheduled out.
On multi-core systems, the debugger might therefore run while the
kernel might be writing the last branch trace records.
Let's check whether the data head moved while we read the trace. */
if (data_head == *pevent->data_head)
break;
}
pevent->last_head = data_head;
/* Prune the incomplete last block (i.e. the first one of inferior execution)
if we're not doing a delta read. There is no way of filling in its zeroed
BEGIN element. */
if (!VEC_empty (btrace_block_s, btrace->blocks)
&& type != BTRACE_READ_DELTA)
VEC_pop (btrace_block_s, btrace->blocks);
return BTRACE_ERR_NONE;
}
/* Fill in the Intel(R) Processor Trace configuration information. */
static void
linux_fill_btrace_pt_config (struct btrace_data_pt_config *conf)
{
conf->cpu = btrace_this_cpu ();
}
/* Read branch trace data in Intel(R) Processor Trace format for the thread
given by TINFO into BTRACE using the TYPE reading method. */
static enum btrace_error
linux_read_pt (struct btrace_data_pt *btrace,
struct btrace_target_info *tinfo,
enum btrace_read_type type)
{
struct perf_event_buffer *pt;
pt = &tinfo->variant.pt.pt;
linux_fill_btrace_pt_config (&btrace->config);
switch (type)
{
case BTRACE_READ_DELTA:
/* We don't support delta reads. The data head (i.e. aux_head) wraps
around to stay inside the aux buffer. */
return BTRACE_ERR_NOT_SUPPORTED;
case BTRACE_READ_NEW:
if (!perf_event_new_data (pt))
return BTRACE_ERR_NONE;
/* Fall through. */
case BTRACE_READ_ALL:
perf_event_read_all (pt, &btrace->data, &btrace->size);
return BTRACE_ERR_NONE;
}
internal_error (__FILE__, __LINE__, _("Unkown btrace read type."));
}
/* See linux-btrace.h. */
enum btrace_error
linux_read_btrace (struct btrace_data *btrace,
struct btrace_target_info *tinfo,
enum btrace_read_type type)
{
switch (tinfo->conf.format)
{
case BTRACE_FORMAT_NONE:
return BTRACE_ERR_NOT_SUPPORTED;
case BTRACE_FORMAT_BTS:
/* We read btrace in BTS format. */
btrace->format = BTRACE_FORMAT_BTS;
btrace->variant.bts.blocks = NULL;
return linux_read_bts (&btrace->variant.bts, tinfo, type);
case BTRACE_FORMAT_PT:
/* We read btrace in Intel(R) Processor Trace format. */
btrace->format = BTRACE_FORMAT_PT;
btrace->variant.pt.data = NULL;
btrace->variant.pt.size = 0;
return linux_read_pt (&btrace->variant.pt, tinfo, type);
}
internal_error (__FILE__, __LINE__, _("Unkown branch trace format."));
}
/* See linux-btrace.h. */
const struct btrace_config *
linux_btrace_conf (const struct btrace_target_info *tinfo)
{
return &tinfo->conf;
}
#else /* !HAVE_LINUX_PERF_EVENT_H */
/* See linux-btrace.h. */
int
linux_supports_btrace (struct target_ops *ops, enum btrace_format format)
{
return 0;
}
/* See linux-btrace.h. */
struct btrace_target_info *
linux_enable_btrace (ptid_t ptid, const struct btrace_config *conf)
{
return NULL;
}
/* See linux-btrace.h. */
enum btrace_error
linux_disable_btrace (struct btrace_target_info *tinfo)
{
return BTRACE_ERR_NOT_SUPPORTED;
}
/* See linux-btrace.h. */
enum btrace_error
linux_read_btrace (struct btrace_data *btrace,
struct btrace_target_info *tinfo,
enum btrace_read_type type)
{
return BTRACE_ERR_NOT_SUPPORTED;
}
/* See linux-btrace.h. */
const struct btrace_config *
linux_btrace_conf (const struct btrace_target_info *tinfo)
{
return NULL;
}
#endif /* !HAVE_LINUX_PERF_EVENT_H */
|