summaryrefslogtreecommitdiffstats
path: root/arch/x86/kernel/ds.c
blob: 1c47390dd0e51ef7ccbd4698302a2b19bcf7ee20 (plain)
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
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
/*
 * Debug Store support
 *
 * This provides a low-level interface to the hardware's Debug Store
 * feature that is used for branch trace store (BTS) and
 * precise-event based sampling (PEBS).
 *
 * It manages:
 * - DS and BTS hardware configuration
 * - buffer overflow handling (to be done)
 * - buffer access
 *
 * It does not do:
 * - security checking (is the caller allowed to trace the task)
 * - buffer allocation (memory accounting)
 *
 *
 * Copyright (C) 2007-2009 Intel Corporation.
 * Markus Metzger <markus.t.metzger@intel.com>, 2007-2009
 */

#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/trace_clock.h>

#include <asm/ds.h>

#include "ds_selftest.h"

/*
 * The configuration for a particular DS hardware implementation:
 */
struct ds_configuration {
	/* The name of the configuration: */
	const char		*name;

	/* The size of pointer-typed fields in DS, BTS, and PEBS: */
	unsigned char		sizeof_ptr_field;

	/* The size of a BTS/PEBS record in bytes: */
	unsigned char		sizeof_rec[2];

	/* The number of pebs counter reset values in the DS structure. */
	unsigned char		nr_counter_reset;

	/* Control bit-masks indexed by enum ds_feature: */
	unsigned long		ctl[dsf_ctl_max];
};
static struct ds_configuration ds_cfg __read_mostly;


/* Maximal size of a DS configuration: */
#define MAX_SIZEOF_DS		0x80

/* Maximal size of a BTS record: */
#define MAX_SIZEOF_BTS		(3 * 8)

/* BTS and PEBS buffer alignment: */
#define DS_ALIGNMENT		(1 << 3)

/* Number of buffer pointers in DS: */
#define NUM_DS_PTR_FIELDS	8

/* Size of a pebs reset value in DS: */
#define PEBS_RESET_FIELD_SIZE	8

/* Mask of control bits in the DS MSR register: */
#define BTS_CONTROL				  \
	( ds_cfg.ctl[dsf_bts]			| \
	  ds_cfg.ctl[dsf_bts_kernel]		| \
	  ds_cfg.ctl[dsf_bts_user]		| \
	  ds_cfg.ctl[dsf_bts_overflow] )

/*
 * A BTS or PEBS tracer.
 *
 * This holds the configuration of the tracer and serves as a handle
 * to identify tracers.
 */
struct ds_tracer {
	/* The DS context (partially) owned by this tracer. */
	struct ds_context	*context;
	/* The buffer provided on ds_request() and its size in bytes. */
	void			*buffer;
	size_t			size;
};

struct bts_tracer {
	/* The common DS part: */
	struct ds_tracer	ds;

	/* The trace including the DS configuration: */
	struct bts_trace	trace;

	/* Buffer overflow notification function: */
	bts_ovfl_callback_t	ovfl;

	/* Active flags affecting trace collection. */
	unsigned int		flags;
};

struct pebs_tracer {
	/* The common DS part: */
	struct ds_tracer	ds;

	/* The trace including the DS configuration: */
	struct pebs_trace	trace;

	/* Buffer overflow notification function: */
	pebs_ovfl_callback_t	ovfl;
};

/*
 * Debug Store (DS) save area configuration (see Intel64 and IA32
 * Architectures Software Developer's Manual, section 18.5)
 *
 * The DS configuration consists of the following fields; different
 * architetures vary in the size of those fields.
 *
 * - double-word aligned base linear address of the BTS buffer
 * - write pointer into the BTS buffer
 * - end linear address of the BTS buffer (one byte beyond the end of
 *   the buffer)
 * - interrupt pointer into BTS buffer
 *   (interrupt occurs when write pointer passes interrupt pointer)
 * - double-word aligned base linear address of the PEBS buffer
 * - write pointer into the PEBS buffer
 * - end linear address of the PEBS buffer (one byte beyond the end of
 *   the buffer)
 * - interrupt pointer into PEBS buffer
 *   (interrupt occurs when write pointer passes interrupt pointer)
 * - value to which counter is reset following counter overflow
 *
 * Later architectures use 64bit pointers throughout, whereas earlier
 * architectures use 32bit pointers in 32bit mode.
 *
 *
 * We compute the base address for the first 8 fields based on:
 * - the field size stored in the DS configuration
 * - the relative field position
 * - an offset giving the start of the respective region
 *
 * This offset is further used to index various arrays holding
 * information for BTS and PEBS at the respective index.
 *
 * On later 32bit processors, we only access the lower 32bit of the
 * 64bit pointer fields. The upper halves will be zeroed out.
 */

enum ds_field {
	ds_buffer_base = 0,
	ds_index,
	ds_absolute_maximum,
	ds_interrupt_threshold,
};

enum ds_qualifier {
	ds_bts = 0,
	ds_pebs
};

static inline unsigned long
ds_get(const unsigned char *base, enum ds_qualifier qual, enum ds_field field)
{
	base += (ds_cfg.sizeof_ptr_field * (field + (4 * qual)));
	return *(unsigned long *)base;
}

static inline void
ds_set(unsigned char *base, enum ds_qualifier qual, enum ds_field field,
       unsigned long value)
{
	base += (ds_cfg.sizeof_ptr_field * (field + (4 * qual)));
	(*(unsigned long *)base) = value;
}


/*
 * Locking is done only for allocating BTS or PEBS resources.
 */
static DEFINE_SPINLOCK(ds_lock);

/*
 * We either support (system-wide) per-cpu or per-thread allocation.
 * We distinguish the two based on the task_struct pointer, where a
 * NULL pointer indicates per-cpu allocation for the current cpu.
 *
 * Allocations are use-counted. As soon as resources are allocated,
 * further allocations must be of the same type (per-cpu or
 * per-thread). We model this by counting allocations (i.e. the number
 * of tracers of a certain type) for one type negatively:
 *   =0  no tracers
 *   >0  number of per-thread tracers
 *   <0  number of per-cpu tracers
 *
 * Tracers essentially gives the number of ds contexts for a certain
 * type of allocation.
 */
static atomic_t tracers = ATOMIC_INIT(0);

static inline int get_tracer(struct task_struct *task)
{
	int error;

	spin_lock_irq(&ds_lock);

	if (task) {
		error = -EPERM;
		if (atomic_read(&tracers) < 0)
			goto out;
		atomic_inc(&tracers);
	} else {
		error = -EPERM;
		if (atomic_read(&tracers) > 0)
			goto out;
		atomic_dec(&tracers);
	}

	error = 0;
out:
	spin_unlock_irq(&ds_lock);
	return error;
}

static inline void put_tracer(struct task_struct *task)
{
	if (task)
		atomic_dec(&tracers);
	else
		atomic_inc(&tracers);
}

/*
 * The DS context is either attached to a thread or to a cpu:
 * - in the former case, the thread_struct contains a pointer to the
 *   attached context.
 * - in the latter case, we use a static array of per-cpu context
 *   pointers.
 *
 * Contexts are use-counted. They are allocated on first access and
 * deallocated when the last user puts the context.
 */
struct ds_context {
	/* The DS configuration; goes into MSR_IA32_DS_AREA: */
	unsigned char		ds[MAX_SIZEOF_DS];

	/* The owner of the BTS and PEBS configuration, respectively: */
	struct bts_tracer	*bts_master;
	struct pebs_tracer	*pebs_master;

	/* Use count: */
	unsigned long		count;

	/* Pointer to the context pointer field: */
	struct ds_context	**this;

	/* The traced task; NULL for cpu tracing: */
	struct task_struct	*task;

	/* The traced cpu; only valid if task is NULL: */
	int			cpu;
};

static DEFINE_PER_CPU(struct ds_context *, cpu_ds_context);


static struct ds_context *ds_get_context(struct task_struct *task, int cpu)
{
	struct ds_context **p_context =
		(task ? &task->thread.ds_ctx : &per_cpu(cpu_ds_context, cpu));
	struct ds_context *context = NULL;
	struct ds_context *new_context = NULL;

	/* Chances are small that we already have a context. */
	new_context = kzalloc(sizeof(*new_context), GFP_KERNEL);
	if (!new_context)
		return NULL;

	spin_lock_irq(&ds_lock);

	context = *p_context;
	if (likely(!context)) {
		context = new_context;

		context->this = p_context;
		context->task = task;
		context->cpu = cpu;
		context->count = 0;

		*p_context = context;
	}

	context->count++;

	spin_unlock_irq(&ds_lock);

	if (context != new_context)
		kfree(new_context);

	return context;
}

static void ds_put_context(struct ds_context *context)
{
	struct task_struct *task;
	unsigned long irq;

	if (!context)
		return;

	spin_lock_irqsave(&ds_lock, irq);

	if (--context->count) {
		spin_unlock_irqrestore(&ds_lock, irq);
		return;
	}

	*(context->this) = NULL;

	task = context->task;

	if (task)
		clear_tsk_thread_flag(task, TIF_DS_AREA_MSR);

	/*
	 * We leave the (now dangling) pointer to the DS configuration in
	 * the DS_AREA msr. This is as good or as bad as replacing it with
	 * NULL - the hardware would crash if we enabled tracing.
	 *
	 * This saves us some problems with having to write an msr on a
	 * different cpu while preventing others from doing the same for the
	 * next context for that same cpu.
	 */

	spin_unlock_irqrestore(&ds_lock, irq);

	/* The context might still be in use for context switching. */
	if (task && (task != current))
		wait_task_context_switch(task);

	kfree(context);
}

static void ds_install_ds_area(struct ds_context *context)
{
	unsigned long ds;

	ds = (unsigned long)context->ds;

	/*
	 * There is a race between the bts master and the pebs master.
	 *
	 * The thread/cpu access is synchronized via get/put_cpu() for
	 * task tracing and via wrmsr_on_cpu for cpu tracing.
	 *
	 * If bts and pebs are collected for the same task or same cpu,
	 * the same confiuration is written twice.
	 */
	if (context->task) {
		get_cpu();
		if (context->task == current)
			wrmsrl(MSR_IA32_DS_AREA, ds);
		set_tsk_thread_flag(context->task, TIF_DS_AREA_MSR);
		put_cpu();
	} else
		wrmsr_on_cpu(context->cpu, MSR_IA32_DS_AREA,
			     (u32)((u64)ds), (u32)((u64)ds >> 32));
}

/*
 * Call the tracer's callback on a buffer overflow.
 *
 * context: the ds context
 * qual: the buffer type
 */
static void ds_overflow(struct ds_context *context, enum ds_qualifier qual)
{
	switch (qual) {
	case ds_bts:
		if (context->bts_master &&
		    context->bts_master->ovfl)
			context->bts_master->ovfl(context->bts_master);
		break;
	case ds_pebs:
		if (context->pebs_master &&
		    context->pebs_master->ovfl)
			context->pebs_master->ovfl(context->pebs_master);
		break;
	}
}


/*
 * Write raw data into the BTS or PEBS buffer.
 *
 * The remainder of any partially written record is zeroed out.
 *
 * context: the DS context
 * qual:    the buffer type
 * record:  the data to write
 * size:    the size of the data
 */
static int ds_write(struct ds_context *context, enum ds_qualifier qual,
		    const void *record, size_t size)
{
	int bytes_written = 0;

	if (!record)
		return -EINVAL;

	while (size) {
		unsigned long base, index, end, write_end, int_th;
		unsigned long write_size, adj_write_size;

		/*
		 * Write as much as possible without producing an
		 * overflow interrupt.
		 *
		 * Interrupt_threshold must either be
		 * - bigger than absolute_maximum or
		 * - point to a record between buffer_base and absolute_maximum
		 *
		 * Index points to a valid record.
		 */
		base   = ds_get(context->ds, qual, ds_buffer_base);
		index  = ds_get(context->ds, qual, ds_index);
		end    = ds_get(context->ds, qual, ds_absolute_maximum);
		int_th = ds_get(context->ds, qual, ds_interrupt_threshold);

		write_end = min(end, int_th);

		/*
		 * If we are already beyond the interrupt threshold,
		 * we fill the entire buffer.
		 */
		if (write_end <= index)
			write_end = end;

		if (write_end <= index)
			break;

		write_size = min((unsigned long) size, write_end - index);
		memcpy((void *)index, record, write_size);

		record = (const char *)record + write_size;
		size -= write_size;
		bytes_written += write_size;

		adj_write_size = write_size / ds_cfg.sizeof_rec[qual];
		adj_write_size *= ds_cfg.sizeof_rec[qual];

		/* Zero out trailing bytes. */
		memset((char *)index + write_size, 0,
		       adj_write_size - write_size);
		index += adj_write_size;

		if (index >= end)
			index = base;
		ds_set(context->ds, qual, ds_index, index);

		if (index >= int_th)
			ds_overflow(context, qual);
	}

	return bytes_written;
}


/*
 * Branch Trace Store (BTS) uses the following format. Different
 * architectures vary in the size of those fields.
 * - source linear address
 * - destination linear address
 * - flags
 *
 * Later architectures use 64bit pointers throughout, whereas earlier
 * architectures use 32bit pointers in 32bit mode.
 *
 * We compute the base address for the fields based on:
 * - the field size stored in the DS configuration
 * - the relative field position
 *
 * In order to store additional information in the BTS buffer, we use
 * a special source address to indicate that the record requires
 * special interpretation.
 *
 * Netburst indicated via a bit in the flags field whether the branch
 * was predicted; this is ignored.
 *
 * We use two levels of abstraction:
 * - the raw data level defined here
 * - an arch-independent level defined in ds.h
 */

enum bts_field {
	bts_from,
	bts_to,
	bts_flags,

	bts_qual		= bts_from,
	bts_clock		= bts_to,
	bts_pid			= bts_flags,

	bts_qual_mask		= (bts_qual_max - 1),
	bts_escape		= ((unsigned long)-1 & ~bts_qual_mask)
};

static inline unsigned long bts_get(const char *base, unsigned long field)
{
	base += (ds_cfg.sizeof_ptr_field * field);
	return *(unsigned long *)base;
}

static inline void bts_set(char *base, unsigned long field, unsigned long val)
{
	base += (ds_cfg.sizeof_ptr_field * field);
	(*(unsigned long *)base) = val;
}


/*
 * The raw BTS data is architecture dependent.
 *
 * For higher-level users, we give an arch-independent view.
 * - ds.h defines struct bts_struct
 * - bts_read translates one raw bts record into a bts_struct
 * - bts_write translates one bts_struct into the raw format and
 *   writes it into the top of the parameter tracer's buffer.
 *
 * return: bytes read/written on success; -Eerrno, otherwise
 */
static int
bts_read(struct bts_tracer *tracer, const void *at, struct bts_struct *out)
{
	if (!tracer)
		return -EINVAL;

	if (at < tracer->trace.ds.begin)
		return -EINVAL;

	if (tracer->trace.ds.end < (at + tracer->trace.ds.size))
		return -EINVAL;

	memset(out, 0, sizeof(*out));
	if ((bts_get(at, bts_qual) & ~bts_qual_mask) == bts_escape) {
		out->qualifier = (bts_get(at, bts_qual) & bts_qual_mask);
		out->variant.event.clock = bts_get(at, bts_clock);
		out->variant.event.pid = bts_get(at, bts_pid);
	} else {
		out->qualifier = bts_branch;
		out->variant.lbr.from = bts_get(at, bts_from);
		out->variant.lbr.to   = bts_get(at, bts_to);

		if (!out->variant.lbr.from && !out->variant.lbr.to)
			out->qualifier = bts_invalid;
	}

	return ds_cfg.sizeof_rec[ds_bts];
}

static int bts_write(struct bts_tracer *tracer, const struct bts_struct *in)
{
	unsigned char raw[MAX_SIZEOF_BTS];

	if (!tracer)
		return -EINVAL;

	if (MAX_SIZEOF_BTS < ds_cfg.sizeof_rec[ds_bts])
		return -EOVERFLOW;

	switch (in->qualifier) {
	case bts_invalid:
		bts_set(raw, bts_from, 0);
		bts_set(raw, bts_to, 0);
		bts_set(raw, bts_flags, 0);
		break;
	case bts_branch:
		bts_set(raw, bts_from, in->variant.lbr.from);
		bts_set(raw, bts_to,   in->variant.lbr.to);
		bts_set(raw, bts_flags, 0);
		break;
	case bts_task_arrives:
	case bts_task_departs:
		bts_set(raw, bts_qual, (bts_escape | in->qualifier));
		bts_set(raw, bts_clock, in->variant.event.clock);
		bts_set(raw, bts_pid, in->variant.event.pid);
		break;
	default:
		return -EINVAL;
	}

	return ds_write(tracer->ds.context, ds_bts, raw,
			ds_cfg.sizeof_rec[ds_bts]);
}


static void ds_write_config(struct ds_context *context,
			    struct ds_trace *cfg, enum ds_qualifier qual)
{
	unsigned char *ds = context->ds;

	ds_set(ds, qual, ds_buffer_base, (unsigned long)cfg->begin);
	ds_set(ds, qual, ds_index, (unsigned long)cfg->top);
	ds_set(ds, qual, ds_absolute_maximum, (unsigned long)cfg->end);
	ds_set(ds, qual, ds_interrupt_threshold, (unsigned long)cfg->ith);
}

static void ds_read_config(struct ds_context *context,
			   struct ds_trace *cfg, enum ds_qualifier qual)
{
	unsigned char *ds = context->ds;

	cfg->begin = (void *)ds_get(ds, qual, ds_buffer_base);
	cfg->top = (void *)ds_get(ds, qual, ds_index);
	cfg->end = (void *)ds_get(ds, qual, ds_absolute_maximum);
	cfg->ith = (void *)ds_get(ds, qual, ds_interrupt_threshold);
}

static void ds_init_ds_trace(struct ds_trace *trace, enum ds_qualifier qual,
			     void *base, size_t size, size_t ith,
			     unsigned int flags) {
	unsigned long buffer, adj;

	/*
	 * Adjust the buffer address and size to meet alignment
	 * constraints:
	 * - buffer is double-word aligned
	 * - size is multiple of record size
	 *
	 * We checked the size at the very beginning; we have enough
	 * space to do the adjustment.
	 */
	buffer = (unsigned long)base;

	adj = ALIGN(buffer, DS_ALIGNMENT) - buffer;
	buffer += adj;
	size   -= adj;

	trace->n = size / ds_cfg.sizeof_rec[qual];
	trace->size = ds_cfg.sizeof_rec[qual];

	size = (trace->n * trace->size);

	trace->begin = (void *)buffer;
	trace->top = trace->begin;
	trace->end = (void *)(buffer + size);
	/*
	 * The value for 'no threshold' is -1, which will set the
	 * threshold outside of the buffer, just like we want it.
	 */
	ith *= ds_cfg.sizeof_rec[qual];
	trace->ith = (void *)(buffer + size - ith);

	trace->flags = flags;
}


static int ds_request(struct ds_tracer *tracer, struct ds_trace *trace,
		      enum ds_qualifier qual, struct task_struct *task,
		      int cpu, void *base, size_t size, size_t th)
{
	struct ds_context *context;
	int error;
	size_t req_size;

	error = -EOPNOTSUPP;
	if (!ds_cfg.sizeof_rec[qual])
		goto out;

	error = -EINVAL;
	if (!base)
		goto out;

	req_size = ds_cfg.sizeof_rec[qual];
	/* We might need space for alignment adjustments. */
	if (!IS_ALIGNED((unsigned long)base, DS_ALIGNMENT))
		req_size += DS_ALIGNMENT;

	error = -EINVAL;
	if (size < req_size)
		goto out;

	if (th != (size_t)-1) {
		th *= ds_cfg.sizeof_rec[qual];

		error = -EINVAL;
		if (size <= th)
			goto out;
	}

	tracer->buffer = base;
	tracer->size = size;

	error = -ENOMEM;
	context = ds_get_context(task, cpu);
	if (!context)
		goto out;
	tracer->context = context;

	/*
	 * Defer any tracer-specific initialization work for the context until
	 * context ownership has been clarified.
	 */

	error = 0;
 out:
	return error;
}

static struct bts_tracer *ds_request_bts(struct task_struct *task, int cpu,
					 void *base, size_t size,
					 bts_ovfl_callback_t ovfl, size_t th,
					 unsigned int flags)
{
	struct bts_tracer *tracer;
	int error;

	/* Buffer overflow notification is not yet implemented. */
	error = -EOPNOTSUPP;
	if (ovfl)
		goto out;

	error = get_tracer(task);
	if (error < 0)
		goto out;

	error = -ENOMEM;
	tracer = kzalloc(sizeof(*tracer), GFP_KERNEL);
	if (!tracer)
		goto out_put_tracer;
	tracer->ovfl = ovfl;

	/* Do some more error checking and acquire a tracing context. */
	error = ds_request(&tracer->ds, &tracer->trace.ds,
			   ds_bts, task, cpu, base, size, th);
	if (error < 0)
		goto out_tracer;

	/* Claim the bts part of the tracing context we acquired above. */
	spin_lock_irq(&ds_lock);

	error = -EPERM;
	if (tracer->ds.context->bts_master)
		goto out_unlock;
	tracer->ds.context->bts_master = tracer;

	spin_unlock_irq(&ds_lock);

	/*
	 * Now that we own the bts part of the context, let's complete the
	 * initialization for that part.
	 */
	ds_init_ds_trace(&tracer->trace.ds, ds_bts, base, size, th, flags);
	ds_write_config(tracer->ds.context, &tracer->trace.ds, ds_bts);
	ds_install_ds_area(tracer->ds.context);

	tracer->trace.read  = bts_read;
	tracer->trace.write = bts_write;

	/* Start tracing. */
	ds_resume_bts(tracer);

	return tracer;

 out_unlock:
	spin_unlock_irq(&ds_lock);
	ds_put_context(tracer->ds.context);
 out_tracer:
	kfree(tracer);
 out_put_tracer:
	put_tracer(task);
 out:
	return ERR_PTR(error);
}

struct bts_tracer *ds_request_bts_task(struct task_struct *task,
				       void *base, size_t size,
				       bts_ovfl_callback_t ovfl,
				       size_t th, unsigned int flags)
{
	return ds_request_bts(task, 0, base, size, ovfl, th, flags);
}

struct bts_tracer *ds_request_bts_cpu(int cpu, void *base, size_t size,
				      bts_ovfl_callback_t ovfl,
				      size_t th, unsigned int flags)
{
	return ds_request_bts(NULL, cpu, base, size, ovfl, th, flags);
}

static struct pebs_tracer *ds_request_pebs(struct task_struct *task, int cpu,
					   void *base, size_t size,
					   pebs_ovfl_callback_t ovfl, size_t th,
					   unsigned int flags)
{
	struct pebs_tracer *tracer;
	int error;

	/* Buffer overflow notification is not yet implemented. */
	error = -EOPNOTSUPP;
	if (ovfl)
		goto out;

	error = get_tracer(task);
	if (error < 0)
		goto out;

	error = -ENOMEM;
	tracer = kzalloc(sizeof(*tracer), GFP_KERNEL);
	if (!tracer)
		goto out_put_tracer;
	tracer->ovfl = ovfl;

	/* Do some more error checking and acquire a tracing context. */
	error = ds_request(&tracer->ds, &tracer->trace.ds,
			   ds_pebs, task, cpu, base, size, th);
	if (error < 0)
		goto out_tracer;

	/* Claim the pebs part of the tracing context we acquired above. */
	spin_lock_irq(&ds_lock);

	error = -EPERM;
	if (tracer->ds.context->pebs_master)
		goto out_unlock;
	tracer->ds.context->pebs_master = tracer;

	spin_unlock_irq(&ds_lock);

	/*
	 * Now that we own the pebs part of the context, let's complete the
	 * initialization for that part.
	 */
	ds_init_ds_trace(&tracer->trace.ds, ds_pebs, base, size, th, flags);
	ds_write_config(tracer->ds.context, &tracer->trace.ds, ds_pebs);
	ds_install_ds_area(tracer->ds.context);

	/* Start tracing. */
	ds_resume_pebs(tracer);

	return tracer;

 out_unlock:
	spin_unlock_irq(&ds_lock);
	ds_put_context(tracer->ds.context);
 out_tracer:
	kfree(tracer);
 out_put_tracer:
	put_tracer(task);
 out:
	return ERR_PTR(error);
}

struct pebs_tracer *ds_request_pebs_task(struct task_struct *task,
					 void *base, size_t size,
					 pebs_ovfl_callback_t ovfl,
					 size_t th, unsigned int flags)
{
	return ds_request_pebs(task, 0, base, size, ovfl, th, flags);
}

struct pebs_tracer *ds_request_pebs_cpu(int cpu, void *base, size_t size,
					pebs_ovfl_callback_t ovfl,
					size_t th, unsigned int flags)
{
	return ds_request_pebs(NULL, cpu, base, size, ovfl, th, flags);
}

static void ds_free_bts(struct bts_tracer *tracer)
{
	struct task_struct *task;

	task = tracer->ds.context->task;

	WARN_ON_ONCE(tracer->ds.context->bts_master != tracer);
	tracer->ds.context->bts_master = NULL;

	/* Make sure tracing stopped and the tracer is not in use. */
	if (task && (task != current))
		wait_task_context_switch(task);

	ds_put_context(tracer->ds.context);
	put_tracer(task);

	kfree(tracer);
}

void ds_release_bts(struct bts_tracer *tracer)
{
	might_sleep();

	if (!tracer)
		return;

	ds_suspend_bts(tracer);
	ds_free_bts(tracer);
}

int ds_release_bts_noirq(struct bts_tracer *tracer)
{
	struct task_struct *task;
	unsigned long irq;
	int error;

	if (!tracer)
		return 0;

	task = tracer->ds.context->task;

	local_irq_save(irq);

	error = -EPERM;
	if (!task &&
	    (tracer->ds.context->cpu != smp_processor_id()))
		goto out;

	error = -EPERM;
	if (task && (task != current))
		goto out;

	ds_suspend_bts_noirq(tracer);
	ds_free_bts(tracer);

	error = 0;
 out:
	local_irq_restore(irq);
	return error;
}

static void update_task_debugctlmsr(struct task_struct *task,
				    unsigned long debugctlmsr)
{
	task->thread.debugctlmsr = debugctlmsr;

	get_cpu();
	if (task == current)
		update_debugctlmsr(debugctlmsr);
	put_cpu();
}

void ds_suspend_bts(struct bts_tracer *tracer)
{
	struct task_struct *task;
	unsigned long debugctlmsr;
	int cpu;

	if (!tracer)
		return;

	tracer->flags = 0;

	task = tracer->ds.context->task;
	cpu  = tracer->ds.context->cpu;

	WARN_ON(!task && irqs_disabled());

	debugctlmsr = (task ?
		       task->thread.debugctlmsr :
		       get_debugctlmsr_on_cpu(cpu));
	debugctlmsr &= ~BTS_CONTROL;

	if (task)
		update_task_debugctlmsr(task, debugctlmsr);
	else
		update_debugctlmsr_on_cpu(cpu, debugctlmsr);
}

int ds_suspend_bts_noirq(struct bts_tracer *tracer)
{
	struct task_struct *task;
	unsigned long debugctlmsr, irq;
	int cpu, error = 0;

	if (!tracer)
		return 0;

	tracer->flags = 0;

	task = tracer->ds.context->task;
	cpu  = tracer->ds.context->cpu;

	local_irq_save(irq);

	error = -EPERM;
	if (!task && (cpu != smp_processor_id()))
		goto out;

	debugctlmsr = (task ?
		       task->thread.debugctlmsr :
		       get_debugctlmsr());
	debugctlmsr &= ~BTS_CONTROL;

	if (task)
		update_task_debugctlmsr(task, debugctlmsr);
	else
		update_debugctlmsr(debugctlmsr);

	error = 0;
 out:
	local_irq_restore(irq);
	return error;
}

static unsigned long ds_bts_control(struct bts_tracer *tracer)
{
	unsigned long control;

	control = ds_cfg.ctl[dsf_bts];
	if (!(tracer->trace.ds.flags & BTS_KERNEL))
		control |= ds_cfg.ctl[dsf_bts_kernel];
	if (!(tracer->trace.ds.flags & BTS_USER))
		control |= ds_cfg.ctl[dsf_bts_user];

	return control;
}

void ds_resume_bts(struct bts_tracer *tracer)
{
	struct task_struct *task;
	unsigned long debugctlmsr;
	int cpu;

	if (!tracer)
		return;

	tracer->flags = tracer->trace.ds.flags;

	task = tracer->ds.context->task;
	cpu  = tracer->ds.context->cpu;

	WARN_ON(!task && irqs_disabled());

	debugctlmsr = (task ?
		       task->thread.debugctlmsr :
		       get_debugctlmsr_on_cpu(cpu));
	debugctlmsr |= ds_bts_control(tracer);

	if (task)
		update_task_debugctlmsr(task, debugctlmsr);
	else
		update_debugctlmsr_on_cpu(cpu, debugctlmsr);
}

int ds_resume_bts_noirq(struct bts_tracer *tracer)
{
	struct task_struct *task;
	unsigned long debugctlmsr, irq;
	int cpu, error = 0;

	if (!tracer)
		return 0;

	tracer->flags = tracer->trace.ds.flags;

	task = tracer->ds.context->task;
	cpu  = tracer->ds.context->cpu;

	local_irq_save(irq);

	error = -EPERM;
	if (!task && (cpu != smp_processor_id()))
		goto out;

	debugctlmsr = (task ?
		       task->thread.debugctlmsr :
		       get_debugctlmsr());
	debugctlmsr |= ds_bts_control(tracer);

	if (task)
		update_task_debugctlmsr(task, debugctlmsr);
	else
		update_debugctlmsr(debugctlmsr);

	error = 0;
 out:
	local_irq_restore(irq);
	return error;
}

static void ds_free_pebs(struct pebs_tracer *tracer)
{
	struct task_struct *task;

	task = tracer->ds.context->task;

	WARN_ON_ONCE(tracer->ds.context->pebs_master != tracer);
	tracer->ds.context->pebs_master = NULL;

	ds_put_context(tracer->ds.context);
	put_tracer(task);

	kfree(tracer);
}

void ds_release_pebs(struct pebs_tracer *tracer)
{
	might_sleep();

	if (!tracer)
		return;

	ds_suspend_pebs(tracer);
	ds_free_pebs(tracer);
}

int ds_release_pebs_noirq(struct pebs_tracer *tracer)
{
	struct task_struct *task;
	unsigned long irq;
	int error;

	if (!tracer)
		return 0;

	task = tracer->ds.context->task;

	local_irq_save(irq);

	error = -EPERM;
	if (!task &&
	    (tracer->ds.context->cpu != smp_processor_id()))
		goto out;

	error = -EPERM;
	if (task && (task != current))
		goto out;

	ds_suspend_pebs_noirq(tracer);
	ds_free_pebs(tracer);

	error = 0;
 out:
	local_irq_restore(irq);
	return error;
}

void ds_suspend_pebs(struct pebs_tracer *tracer)
{

}

int ds_suspend_pebs_noirq(struct pebs_tracer *tracer)
{
	return 0;
}

void ds_resume_pebs(struct pebs_tracer *tracer)
{

}

int ds_resume_pebs_noirq(struct pebs_tracer *tracer)
{
	return 0;
}

const struct bts_trace *ds_read_bts(struct bts_tracer *tracer)
{
	if (!tracer)
		return NULL;

	ds_read_config(tracer->ds.context, &tracer->trace.ds, ds_bts);
	return &tracer->trace;
}

const struct pebs_trace *ds_read_pebs(struct pebs_tracer *tracer)
{
	if (!tracer)
		return NULL;

	ds_read_config(tracer->ds.context, &tracer->trace.ds, ds_pebs);

	tracer->trace.counters = ds_cfg.nr_counter_reset;
	memcpy(tracer->trace.counter_reset,
	       tracer->ds.context->ds +
	       (NUM_DS_PTR_FIELDS * ds_cfg.sizeof_ptr_field),
	       ds_cfg.nr_counter_reset * PEBS_RESET_FIELD_SIZE);

	return &tracer->trace;
}

int ds_reset_bts(struct bts_tracer *tracer)
{
	if (!tracer)
		return -EINVAL;

	tracer->trace.ds.top = tracer->trace.ds.begin;

	ds_set(tracer->ds.context->ds, ds_bts, ds_index,
	       (unsigned long)tracer->trace.ds.top);

	return 0;
}

int ds_reset_pebs(struct pebs_tracer *tracer)
{
	if (!tracer)
		return -EINVAL;

	tracer->trace.ds.top = tracer->trace.ds.begin;

	ds_set(tracer->ds.context->ds, ds_pebs, ds_index,
	       (unsigned long)tracer->trace.ds.top);

	return 0;
}

int ds_set_pebs_reset(struct pebs_tracer *tracer,
		      unsigned int counter, u64 value)
{
	if (!tracer)
		return -EINVAL;

	if (ds_cfg.nr_counter_reset < counter)
		return -EINVAL;

	*(u64 *)(tracer->ds.context->ds +
		 (NUM_DS_PTR_FIELDS * ds_cfg.sizeof_ptr_field) +
		 (counter * PEBS_RESET_FIELD_SIZE)) = value;

	return 0;
}

static const struct ds_configuration ds_cfg_netburst = {
	.name = "Netburst",
	.ctl[dsf_bts]		= (1 << 2) | (1 << 3),
	.ctl[dsf_bts_kernel]	= (1 << 5),
	.ctl[dsf_bts_user]	= (1 << 6),
	.nr_counter_reset	= 1,
};
static const struct ds_configuration ds_cfg_pentium_m = {
	.name = "Pentium M",
	.ctl[dsf_bts]		= (1 << 6) | (1 << 7),
	.nr_counter_reset	= 1,
};
static const struct ds_configuration ds_cfg_core2_atom = {
	.name = "Core 2/Atom",
	.ctl[dsf_bts]		= (1 << 6) | (1 << 7),
	.ctl[dsf_bts_kernel]	= (1 << 9),
	.ctl[dsf_bts_user]	= (1 << 10),
	.nr_counter_reset	= 1,
};
static const struct ds_configuration ds_cfg_core_i7 = {
	.name = "Core i7",
	.ctl[dsf_bts]		= (1 << 6) | (1 << 7),
	.ctl[dsf_bts_kernel]	= (1 << 9),
	.ctl[dsf_bts_user]	= (1 << 10),
	.nr_counter_reset	= 4,
};

static void
ds_configure(const struct ds_configuration *cfg,
	     struct cpuinfo_x86 *cpu)
{
	unsigned long nr_pebs_fields = 0;

	printk(KERN_INFO "[ds] using %s configuration\n", cfg->name);

#ifdef __i386__
	nr_pebs_fields = 10;
#else
	nr_pebs_fields = 18;
#endif

	/*
	 * Starting with version 2, architectural performance
	 * monitoring supports a format specifier.
	 */
	if ((cpuid_eax(0xa) & 0xff) > 1) {
		unsigned long perf_capabilities, format;

		rdmsrl(MSR_IA32_PERF_CAPABILITIES, perf_capabilities);

		format = (perf_capabilities >> 8) & 0xf;

		switch (format) {
		case 0:
			nr_pebs_fields = 18;
			break;
		case 1:
			nr_pebs_fields = 22;
			break;
		default:
			printk(KERN_INFO
			       "[ds] unknown PEBS format: %lu\n", format);
			nr_pebs_fields = 0;
			break;
		}
	}

	memset(&ds_cfg, 0, sizeof(ds_cfg));
	ds_cfg = *cfg;

	ds_cfg.sizeof_ptr_field =
		(cpu_has(cpu, X86_FEATURE_DTES64) ? 8 : 4);

	ds_cfg.sizeof_rec[ds_bts]  = ds_cfg.sizeof_ptr_field * 3;
	ds_cfg.sizeof_rec[ds_pebs] = ds_cfg.sizeof_ptr_field * nr_pebs_fields;

	if (!cpu_has(cpu, X86_FEATURE_BTS)) {
		ds_cfg.sizeof_rec[ds_bts] = 0;
		printk(KERN_INFO "[ds] bts not available\n");
	}
	if (!cpu_has(cpu, X86_FEATURE_PEBS)) {
		ds_cfg.sizeof_rec[ds_pebs] = 0;
		printk(KERN_INFO "[ds] pebs not available\n");
	}

	printk(KERN_INFO "[ds] sizes: address: %u bit, ",
	       8 * ds_cfg.sizeof_ptr_field);
	printk("bts/pebs record: %u/%u bytes\n",
	       ds_cfg.sizeof_rec[ds_bts], ds_cfg.sizeof_rec[ds_pebs]);

	WARN_ON_ONCE(MAX_PEBS_COUNTERS < ds_cfg.nr_counter_reset);
}

void __cpuinit ds_init_intel(struct cpuinfo_x86 *c)
{
	/* Only configure the first cpu. Others are identical. */
	if (ds_cfg.name)
		return;

	switch (c->x86) {
	case 0x6:
		switch (c->x86_model) {
		case 0x9:
		case 0xd: /* Pentium M */
			ds_configure(&ds_cfg_pentium_m, c);
			break;
		case 0xf:
		case 0x17: /* Core2 */
		case 0x1c: /* Atom */
			ds_configure(&ds_cfg_core2_atom, c);
			break;
		case 0x1a: /* Core i7 */
			ds_configure(&ds_cfg_core_i7, c);
			break;
		default:
			/* Sorry, don't know about them. */
			break;
		}
		break;
	case 0xf:
		switch (c->x86_model) {
		case 0x0:
		case 0x1:
		case 0x2: /* Netburst */
			ds_configure(&ds_cfg_netburst, c);
			break;
		default:
			/* Sorry, don't know about them. */
			break;
		}
		break;
	default:
		/* Sorry, don't know about them. */
		break;
	}
}

static inline void ds_take_timestamp(struct ds_context *context,
				     enum bts_qualifier qualifier,
				     struct task_struct *task)
{
	struct bts_tracer *tracer = context->bts_master;
	struct bts_struct ts;

	/* Prevent compilers from reading the tracer pointer twice. */
	barrier();

	if (!tracer || !(tracer->flags & BTS_TIMESTAMPS))
		return;

	memset(&ts, 0, sizeof(ts));
	ts.qualifier		= qualifier;
	ts.variant.event.clock	= trace_clock_global();
	ts.variant.event.pid	= task->pid;

	bts_write(tracer, &ts);
}

/*
 * Change the DS configuration from tracing prev to tracing next.
 */
void ds_switch_to(struct task_struct *prev, struct task_struct *next)
{
	struct ds_context *prev_ctx	= prev->thread.ds_ctx;
	struct ds_context *next_ctx	= next->thread.ds_ctx;
	unsigned long debugctlmsr	= next->thread.debugctlmsr;

	/* Make sure all data is read before we start. */
	barrier();

	if (prev_ctx) {
		update_debugctlmsr(0);

		ds_take_timestamp(prev_ctx, bts_task_departs, prev);
	}

	if (next_ctx) {
		ds_take_timestamp(next_ctx, bts_task_arrives, next);

		wrmsrl(MSR_IA32_DS_AREA, (unsigned long)next_ctx->ds);
	}

	update_debugctlmsr(debugctlmsr);
}

static __init int ds_selftest(void)
{
	if (ds_cfg.sizeof_rec[ds_bts]) {
		int error;

		error = ds_selftest_bts();
		if (error) {
			WARN(1, "[ds] selftest failed. disabling bts.\n");
			ds_cfg.sizeof_rec[ds_bts] = 0;
		}
	}

	if (ds_cfg.sizeof_rec[ds_pebs]) {
		int error;

		error = ds_selftest_pebs();
		if (error) {
			WARN(1, "[ds] selftest failed. disabling pebs.\n");
			ds_cfg.sizeof_rec[ds_pebs] = 0;
		}
	}

	return 0;
}
device_initcall(ds_selftest);
OpenPOWER on IntegriCloud