Repository navigation
Expand file tree
/
Copy pathcore.go
More file actions
990 lines (832 loc) · 28.1 KB
/
Copy pathcore.go
File metadata and controls
990 lines (832 loc) · 28.1 KB
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
package btf
import (
"encoding/binary"
"errors"
&quo
F438
t;fmt"
"math"
"reflect"
"strconv"
"strings"
"github.com/cilium/ebpf/asm"
)
// Code in this file is derived from libbpf, which is available under a BSD
// 2-Clause license.
// COREFixup is the result of computing a CO-RE relocation for a target.
type COREFixup struct {
kind coreKind
local uint32
target uint32
// True if there is no valid fixup. The instruction is replaced with an
// invalid dummy.
poison bool
// True if the validation of the local value should be skipped. Used by
// some kinds of bitfield relocations.
skipLocalValidation bool
}
func (f *COREFixup) equal(other COREFixup) bool {
return f.local == other.local && f.target == other.target
}
func (f *COREFixup) String() string {
if f.poison {
return fmt.Sprintf("%s=poison", f.kind)
}
return fmt.Sprintf("%s=%d->%d", f.kind, f.local, f.target)
}
func (f *COREFixup) Apply(ins *asm.Instruction) error {
if f.poison {
const badRelo = 0xbad2310
*ins = asm.BuiltinFunc(badRelo).Call()
return nil
}
switch class := ins.OpCode.Class(); class {
case asm.LdXClass, asm.StClass, asm.StXClass:
if want := int16(f.local); !f.skipLocalValidation && want != ins.Offset {
return fmt.Errorf("invalid offset %d, expected %d", ins.Offset, f.local)
}
if f.target > math.MaxInt16 {
return fmt.Errorf("offset %d exceeds MaxInt16", f.target)
}
ins.Offset = int16(f.target)
case asm.LdClass:
if !ins.IsConstantLoad(asm.DWord) {
return fmt.Errorf("not a dword-sized immediate load")
}
if want := int64(f.local); !f.skipLocalValidation && want != ins.Constant {
return fmt.Errorf("invalid immediate %d, expected %d (fixup: %v)", ins.Constant, want, f)
}
ins.Constant = int64(f.target)
case asm.ALUClass:
if ins.OpCode.ALUOp() == asm.Swap {
return fmt.Errorf("relocation against swap")
}
fallthrough
case asm.ALU64Class:
if src := ins.OpCode.Source(); src != asm.ImmSource {
return fmt.Errorf("invalid source %s", src)
}
if want := int64(f.local); !f.skipLocalValidation && want != ins.Constant {
return fmt.Errorf("invalid immediate %d, expected %d (fixup: %v, kind: %v, ins: %v)", ins.Constant, want, f, f.kind, ins)
}
if f.target > math.MaxInt32 {
return fmt.Errorf("immediate %d exceeds MaxInt32", f.target)
}
ins.Constant = int64(f.target)
default:
return fmt.Errorf("invalid class %s", class)
}
return nil
}
func (f COREFixup) isNonExistant() bool {
return f.kind.checksForExistence() && f.target == 0
}
// coreKind is the type of CO-RE relocation as specified in BPF source code.
type coreKind uint32
const (
reloFieldByteOffset coreKind = iota /* field byte offset */
reloFieldByteSize /* field size in bytes */
reloFieldExists /* field existence in target kernel */
reloFieldSigned /* field signedness (0 - unsigned, 1 - signed) */
reloFieldLShiftU64 /* bitfield-specific left bitshift */
reloFieldRShiftU64 /* bitfield-specific right bitshift */
reloTypeIDLocal /* type ID in local BPF object */
reloTypeIDTarget /* type ID in target kernel */
reloTypeExists /* type existence in target kernel */
reloTypeSize /* type size in bytes */
reloEnumvalExists /* enum value existence in target kernel */
reloEnumvalValue /* enum value integer value */
)
func (k coreKind) checksForExistence() bool {
return k == reloEnumvalExists || k == reloTypeExists || k == reloFieldExists
}
func (k coreKind) String() string {
switch k {
case reloFieldByteOffset:
return "byte_off"
case reloFieldByteSize:
return "byte_sz"
case reloFieldExists:
return "field_exists"
case reloFieldSigned:
return "signed"
case reloFieldLShiftU64:
return "lshift_u64"
case reloFieldRShiftU64:
return "rshift_u64"
case reloTypeIDLocal:
return "local_type_id"
case reloTypeIDTarget:
return "target_type_id"
case reloTypeExists:
return "type_exists"
case reloTypeSize:
return "type_size"
case reloEnumvalExists:
return "enumval_exists"
case reloEnumvalValue:
return "enumval_value"
default:
return "unknown"
}
}
// CORERelocate calculates changes needed to adjust eBPF instructions for differences
// in types.
//
// Returns a list of fixups which can be applied to instructions to make them
// match the target type(s).
//
// Fixups are returned in the order of relos, e.g. fixup[i] is the solution
// for relos[i].
func CORERelocate(relos []*CORERelocation, target *Spec, bo binary.ByteOrder) ([]COREFixup, error) {
if target == nil {
// Explicitly check for nil here since the argument used to be optional.
return nil, fmt.Errorf("target must be provided")
}
if bo != target.byteOrder {
return nil, fmt.Errorf("can't relocate %s against %s", bo, target.byteOrder)
}
type reloGroup struct {
relos []*CORERelocation
// Position of each relocation in relos.
indices []int
}
// Split relocations into per Type lists.
relosByType := make(map[Type]*reloGroup)
result := make([]COREFixup, len(relos))
for i, relo := range relos {
if relo.kind == reloTypeIDLocal {
// Filtering out reloTypeIDLocal here makes our lives a lot easier
// down the line, since it doesn't have a target at all.
if len(relo.accessor) > 1 || relo.accessor[0] != 0 {
return nil, fmt.Errorf("%s: unexpected accessor %v", relo.kind, relo.accessor)
}
result[i] = COREFixup{
kind: relo.kind,
local: uint32(relo.id),
// NB: Using relo.id as the target here is incorrect, since
// it doesn't match the BTF we generate on the fly. This isn't
// too bad for now since there are no uses of the local type ID
// in the kernel, yet.
target: uint32(relo.id),
}
continue
}
group, ok := relosByType[relo.typ]
if !ok {
group = &reloGroup{}
relosByType[relo.typ] = group
}
group.relos = append(group.relos, relo)
group.indices = append(group.indices, i)
}
for localType, group := range relosByType {
localTypeName := localType.TypeName()
if localTypeName == "" {
return nil, fmt.Errorf("relocate unnamed or anonymous type %s: %w", localType, ErrNotSupported)
}
targets := target.namedTypes[newEssentialName(localTypeName)]
fixups, err := coreCalculateFixups(group.relos, target, targets, bo)
if err != nil {
return nil, fmt.Errorf("relocate %s: %w", localType, err)
}
for j, index := range group.indices {
result[index] = fixups[j]
}
}
return result, nil
}
var errAmbiguousRelocation = errors.New("ambiguous relocation")
var errImpossibleRelocation = errors.New("impossible relocation")
var errIncompatibleTypes = errors.New("incompatible types")
// coreCalculateFixups finds the target type that best matches all relocations.
//
// All relos must target the same type.
//
// The best target is determined by scoring: the less poisoning we have to do
// the better the target is.
func coreCalculateFixups(relos []*CORERelocation, targetSpec *Spec, targets []Type, bo binary.ByteOrder) ([]COREFixup, error) {
bestScore := len(relos)
var bestFixups []COREFixup
for i := range targets {
targetID, err := targetSpec.TypeID(targets[i])
if err != nil {
return nil, fmt.Errorf("target type ID: %w", err)
}
target := Copy(targets[i], UnderlyingType)
score := 0 // lower is better
fixups := make([]COREFixup, 0, len(relos))
for _, relo := range relos {
fixup, err := coreCalculateFixup(relo, target, targetID, bo)
if err != nil {
return nil, fmt.Errorf("target %s: %s: %w", target, relo.kind, err)
}
if fixup.poison || fixup.isNonExistant() {
score++
}
fixups = append(fixups, fixup)
}
if score > bestScore {
// We have a better target already, ignore this one.
continue
}
if score < bestScore {
// This is the best target yet, use it.
bestScore = score
bestFixups = fixups
continue
}
// Some other target has the same score as the current one. Make sure
// the fixups agree with each other.
for i, fixup := range bestFixups {
if !fixup.equal(fixups[i]) {
return nil, fmt.Errorf("%s: multiple types match: %w", fixup.kind, errAmbiguousRelocation)
}
}
}
if bestFixups == nil {
// Nothing at all matched, probably because there are no suitable
// targets at all.
//
// Poison everything except checksForExistence.
bestFixups = make([]COREFixup, len(relos))
for i, relo := range relos {
if relo.kind.checksForExistence() {
bestFixups[i] = COREFixup{kind: relo.kind, local: 1, target: 0}
} else {
bestFixups[i] = COREFixup{kind: relo.kind, poison: true}
}
}
}
return bestFixups, nil
}
// coreCalculateFixup calculates the fixup for a single local type, target type
// and relocation.
func coreCalculateFixup(relo *CORERelocation, target Type, targetID TypeID, bo binary.ByteOrder) (COREFixup, error) {
fixup := func(local, target uint32) (COREFixup, error) {
return COREFixup{kind: relo.kind, local: local, target: target}, nil
}
fixupWithoutValidation := func(local, target uint32) (COREFixup, error) {
return COREFixup{kind: relo.kind, local: local, target: target, skipLocalValidation: true}, nil
}
poison := func() (COREFixup, error) {
if relo.kind.checksForExistence() {
return fixup(1, 0)
}
return COREFixup{kind: relo.kind, poison: true}, nil
}
zero := COREFixup{}
local := Copy(relo.typ, UnderlyingType)
switch relo.kind {
case reloTypeIDTarget, reloTypeSize, reloTypeExists:
if len(relo.accessor) > 1 || relo.accessor[0] != 0 {
return zero, fmt.Errorf("unexpected accessor %v", relo.accessor)
}
err := coreAreTypesCompatible(local, target)
if errors.Is(err, errIncompatibleTypes) {
return poison()
}
if err != nil {
return zero, err
}
switch relo.kind {
case reloTypeExists:
return fixup(1, 1)
case reloTypeIDTarget:
return fixup(uint32(relo.id), uint32(targetID))
case reloTypeSize:
localSize, err := Sizeof(local)
if err != nil {
return zero, err
}
targetSize, err := Sizeof(target)
if err != nil {
return zero, err
}
return fixup(uint32(localSize), uint32(targetSize))
}
case reloEnumvalValue, reloEnumvalExists:
localValue, targetValue, err := coreFindEnumValue(local, relo.accessor, target)
if errors.Is(err, errImpossibleRelocation) {
return poison()
}
if err != nil {
return zero, err
}
switch relo.kind {
case reloEnumvalExists:
return fixup(1, 1)
case reloEnumvalValue:
return fixup(uint32(localValue.Value), uint32(targetValue.Value))
}
case reloFieldSigned:
switch local.(type) {
case *Enum:
return fixup(1, 1)
case *Int:
return fixup(
uint32(local.(*Int).Encoding&Signed),
8BD0
uint32(target.(*Int).Encoding&Signed),
)
default:
return fixupWithoutValidation(0, 0)
}
case reloFieldByteOffset, reloFieldByteSize, reloFieldExists, reloFieldLShiftU64, reloFieldRShiftU64:
if _, ok := target.(*Fwd); ok {
// We can't relocate fields using a forward declaration, so
// skip it. If a non-forward declaration is present in the BTF
// we'll find it in one of the other iterations.
return poison()
}
localField, targetField, err := coreFindField(local, relo.accessor, target)
if errors.Is(err, errImpossibleRelocation) {
return poison()
}
if err != nil {
return zero, err
}
maybeSkipValidation := func(f COREFixup, err error) (COREFixup, error) {
f.skipLocalValidation = localField.bitfieldSize > 0
return f, err
}
switch relo.kind {
case reloFieldExists:
return fixup(1, 1)
case reloFieldByteOffset:
return maybeSkipValidation(fixup(localField.offset, targetField.offset))
case reloFieldByteSize:
localSize, err := Sizeof(localField.Type)
if err != nil {
return zero, err
}
targetSize, err := Sizeof(targetField.Type)
if err != nil {
return zero, err
}
return maybeSkipValidation(fixup(uint32(localSize), uint32(targetSize)))
case reloFieldLShiftU64:
var target uint32
if bo == binary.LittleEndian {
targetSize, err := targetField.sizeBits()
if err != nil {
return zero, err
}
target = uint32(64 - targetField.bitfieldOffset - targetSize)
} else {
loadWidth, err := Sizeof(targetField.Type)
if err != nil {
return zero, err
}
target = uint32(64 - Bits(loadWidth*8) + targetField.bitfieldOffset)
}
return fixupWithoutValidation(0, target)
case reloFieldRShiftU64:
targetSize, err := targetField.sizeBits()
if err != nil {
return zero, err
}
return fixupWithoutValidation(0, uint32(64-targetSize))
}
}
return zero, ErrNotSupported
}
/* coreAccessor contains a path through a struct. It contains at least one index.
*
* The interpretation depends on the kind of the relocation. The following is
* taken from struct bpf_core_relo in libbpf_internal.h:
*
* - for field-based relocations, string encodes an accessed field using
* a sequence of field and array indices, separated by colon (:). It's
* conceptually very close to LLVM's getelementptr ([0]) instruction's
* arguments for identifying offset to a field.
* - for type-based relocations, strings is expected to be just "0";
* - for enum value-based relocations, string contains an index of enum
* value within its enum type;
*
* Example to provide a better feel.
*
* struct sample {
* int a;
* struct {
* int b[10];
* };
* };
*
* struct sample s = ...;
* int x = &s->a; // encoded as "0:0" (a is field #0)
* int y = &s->b[5]; // encoded as "0:1:0:5" (anon struct is field #1,
* // b is field #0 inside anon struct, accessing elem #5)
* int z = &s[10]->b; // encoded as "10:1" (ptr is used as an array)
*/
type coreAccessor []int
func parseCOREAccessor(accessor string) (coreAccessor, error) {
if accessor == "" {
return nil, fmt.Errorf("empty accessor")
}
parts := strings.Split(accessor, ":")
result := make(coreAccessor, 0, len(parts))
for _, part := range parts {
// 31 bits to avoid overflowing int on 32 bit platforms.
index, err := strconv.ParseUint(part, 10, 31)
if err != nil {
return nil, fmt.Errorf("accessor index %q: %s", part, err)
}
result = append(result, int(index))
}
return result, nil
}
func (ca coreAccessor) String() string {
strs := make([]string, 0, len(ca))
for _, i := range ca {
strs = append(strs, strconv.Itoa(i))
}
return strings.Join(strs, ":")
}
func (ca coreAccessor) enumValue(t Type) (*EnumValue, error) {
e, ok := t.(*Enum)
if !ok {
return nil, fmt.Errorf("not an enum: %s", t)
}
if len(ca) > 1 {
return nil, fmt.Errorf("invalid accessor %s for enum", ca)
}
i := ca[0]
if i >= len(e.Values) {
return nil, fmt.Errorf("invalid index %d for %s", i, e)
}
return &e.Values[i], nil
}
// coreField represents the position of a "child" of a composite type from the
// start of that type.
//
// /- start of composite
// | offset * 8 | bitfieldOffset | bitfieldSize | ... |
// \- start of field end of field -/
type coreField struct {
Type Type
// The position of the field from the start of the composite type in bytes.
offset uint32
// The offset of the bitfield in bits from the start of the field.
bitfieldOffset Bits
// The size of the bitfield in bits.
//
// Zero if the field is not a bitfield.
bitfieldSize Bits
}
func (cf *coreField) adjustOffsetToNthElement(n int) error {
if n == 0 {
return nil
}
size, err := Sizeof(cf.Type)
if err != nil {
return err
}
cf.offset += uint32(n) * uint32(size)
return nil
}
func (cf *coreField) adjustOffsetBits(offset Bits) error {
align, err := alignof(cf.Type)
if err != nil {
return err
}
// We can compute the load offset by:
// 1) converting the bit offset to bytes with a flooring division.
// 2) dividing and multiplying that offset by the alignment, yielding the
// load size aligned offset.
offsetBytes := uint32(offset/8) / uint32(align) * uint32(align)
// The number of bits remaining is the bit offset less the number of bits
// we can "skip" with the aligned offset.
cf.bitfieldOffset = offset - Bits(offsetBytes*8)
// We know that cf.offset is aligned at to at least align since we get it
// from the compiler via BTF. Adding an aligned offsetBytes preserves the
// alignment.
cf.offset += offsetBytes
return nil
}
func (cf *coreField) sizeBits() (Bits, error) {
if cf.bitfieldSize > 0 {
return cf.bitfieldSize, nil
}
// Someone is trying to access a non-bitfield via a bit shift relocation.
// This happens when a field changes from a bitfield to a regular field
// between kernel versions. Synthesise the size to make the shifts work.
size, err := Sizeof(cf.Type)
if err != nil {
return 0, nil
}
return Bits(size * 8), nil
}
// coreFindField descends into the local type using the accessor and tries to
// find an equivalent field in target at each step.
//
// Returns the field and the offset of the field from the start of
// target in bits.
func coreFindField(localT Type, localAcc coreAccessor, targetT Type) (coreField, coreField, error) {
local := coreField{Type: localT}
target := coreField{Type: targetT}
if err := coreAreMembersCompatible(local.Type, target.Type); err != nil {
return coreField{}, coreField{}, fmt.Errorf("fields: %w", err)
}
// The first index is used to offset a pointer of the base type like
// when accessing an array.
if err := local.adjustOffsetToNthElement(localAcc[0]); err != nil {
return coreField{}, coreField{}, err
}
if err := target.adjustOffsetToNthElement(localAcc[0]); err != nil {
return coreField{}, coreField{}, err
}
var localMaybeFlex, targetMaybeFlex bool
for i, acc := range localAcc[1:] {
switch localType := local.Type.(type) {
case composite:
// For composite types acc is used to find the field in the local type,
// and then we try to find a field in target with the same name.
localMembers := localType.members()
if acc >= len(localMembers) {
return coreField{}, coreField{}, fmt.Errorf("invalid accessor %d for %s", acc, localType)
}
localMember := localMembers[acc]
if localMember.Name == "" {
_, ok := localMember.Type.(composite)
if !ok {
return coreField{}, coreField{}, fmt.Errorf("unnamed field with type %s: %s", localMember.Type, ErrNotSupported)
}
// This is an anonymous struct or union, ignore it.
local = coreField{
Type: localMember.Type,
offset: local.offset + localMember.Offset.Bytes(),
}
localMaybeFlex = false
continue
}
targetType, ok := target.Type.(composite)
if !ok {
return coreField{}, coreField{}, fmt.Errorf("target not composite: %w", errImpossibleRelocation)
}
targetMember, last, err := coreFindMember(targetType, localMember.Name)
if err != nil {
return coreField{}, coreField{}, err
}
local = coreField{
Type: localMember.Type,
offset: local.offset,
bitfieldSize: localMember.BitfieldSize,
}
localMaybeFlex = acc == len(localMembers)-1
target = coreField{
Type: targetMember.Type,
offset: target.offset,
bitfieldSize: targetMember.BitfieldSize,
}
targetMaybeFlex = last
if local.bitfieldSize == 0 && target.bitfieldSize == 0 {
local.offset += localMember.Offset.Bytes()
target.offset += targetMember.Offset.Bytes()
break
}
// Either of the members is a bitfield. Make sure we're at the
// end of the accessor.
if next := i + 1; next < len(localAcc[1:]) {
return coreField{}, coreField{}, fmt.Errorf("can't descend into bitfield")
}
if err := local.adjustOffsetBits(localMember.Offset); err != nil {
return coreField{}, coreField{}, err
}
if err := target.adjustOffsetBits(targetMember.Offset); err != nil {
return coreField{}, coreField{}, err
}
case *Array:
// For arrays, acc is the index in the target.
targetType, ok := target.Type.(*Array)
if !ok {
return coreField{}, coreField{}, fmt.Errorf("target not array: %w", errImpossibleRelocation)
}
if localType.Nelems == 0 && !localMaybeFlex {
return coreField{}, coreField{}, fmt.Errorf("local type has invalid flexible array")
}
if targetType.Nelems == 0 && !targetMaybeFlex {
return coreField{}, coreField{}, fmt.Errorf("target type has invalid flexible array")
}
if localType.Nelems > 0 && acc >= int(localType.Nelems) {
return coreField{}, coreField{}, fmt.Errorf("invalid access of %s at index %d", localType, acc)
}
if targetType.Nelems > 0 && acc >= int(targetType.Nelems) {
return coreField{}, coreField{}, fmt.Errorf("out of bounds access of target: %w", errImpossibleRelocation)
}
local = coreField{
Type: localType.Type,
offset: local.offset,
}
localMaybeFlex = false
if err := local.adjustOffsetToNthElement(acc); err != nil {
return coreField{}, coreField{}, err
}
target = coreField{
Type: targetType.Type,
offset: target.offset,
}
targetMaybeFlex = false
if err := target.adjustOffsetToNthElement(acc); err != nil {
return coreField{}, coreField{}, err
}
default:
return coreField{}, coreField{}, fmt.Errorf("relocate field of %T: %w", localType, ErrNotSupported)
}
if err := coreAreMembersCompatible(local.Type, target.Type); err != nil {
return coreField{}, coreField{}, err
}
}
return local, target, nil
}
// coreFindMember finds a member in a composite type while handling anonymous
// structs and unions.
func coreFindMember(typ composite, name string) (Member, bool, error) {
if name == "" {
return Member{}, false, errors.New("can't search for anonymous member")
}
type offsetTarget struct {
composite
offset Bits
}
targets := []offsetTarget{{typ, 0}}
visited := make(map[composite]bool)
for i := 0; i < len(targets); i++ {
target := targets[i]
// Only visit targets once to prevent infinite recursion.
if visited[target] {
continue
}
if len(visited) >= maxTypeDepth {
// This check is different than libbpf, which restricts the entire
// path to BPF_CORE_SPEC_MAX_LEN items.
return Member{}, false, fmt.Errorf("type is nested too deep")
}
visited[target] = true
members := target.members()
for j, member := range members {
if member.Name == name {
// NB: This is safe because member is a copy.
member.Offset += target.offset
return member, j == len(members)-1, nil
}
// The names don't match, but this member could be an anonymous struct
// or union.
if member.Name != "" {
continue
}
comp, ok := member.Type.(composite)
if !ok {
return Member{}, false, fmt.Errorf("anonymous non-composite type %T not allowed", member.Type)
}
targets = append(targets, offsetTarget{comp, target.offset + member.Offset})
}
}
return Member{}, false, fmt.Errorf("no matching member: %w", errImpossibleRelocation)
}
// coreFindEnumValue follows localAcc to find the equivalent enum value in target.
func coreFindEnumValue(local Type, localAcc coreAccessor, target Type) (localValue, targetValue *EnumValue, _ error) {
localValue, err := localAcc.enumValue(local)
if err != nil {
return nil, nil, err
}
targetEnum, ok := target.(*Enum)
if !ok {
return nil, nil, errImpossibleRelocation
}
localName := newEssentialName(localValue.Name)
for i, targetValue := range targetEnum.Values {
if newEssentialName(targetValue.Name) != localName {
continue
}
return localValue, &targetEnum.Values[i], nil
}
return nil, nil, errImpossibleRelocation
}
// CheckTypeCompatibility checks local and target types for Compatibility according to CO-RE rules.
//
// Only layout compatibility is checked, ignoring names of the root type.
func CheckTypeCompatibility(localType Type, targetType Type) error {
l := Copy(localType, UnderlyingType)
t := Copy(targetType, UnderlyingType)
return coreAreTypesCompatible(l, t)
}
/* The comment below is from bpf_core_types_are_compat in libbpf.c:
*
* Check local and target types for compatibility. This check is used for
* type-based CO-RE relocations and follow slightly different rules than
* field-based relocations. This function assumes that root types were already
* checked for name match. Beyond that initial root-level name check, names
* are completely ignored. Compatibility rules are as follows:
* - any two STRUCTs/UNIONs/FWDs/ENUMs/INTs are considered compatible, but
* kind should match for local and target types (i.e., STRUCT is not
* compatible with UNION);
* - for ENUMs, the size is ignored;
* - for INT, size and signedness are ignored;
* - for ARRAY, dimensionality is ignored, element types are checked for
* compatibility recursively;
* - CONST/VOLATILE/RESTRICT modifiers are ignored;
* - TYPEDEFs/PTRs are compatible if types they pointing to are compatible;
* - FUNC_PROTOs are compatible if they have compatible signature: same
* number of input args and compatible return and argument types.
* These rules are not set in stone and probably will be adjusted as we get
* more experience with using BPF CO-RE relocations.
*
* Returns errIncompatibleTypes if types are not compatible.
*/
func coreAreTypesCompatible(localType Type, targetType Type) error {
var (
localTs, targetTs typeDeque
l, t = &localType, &targetType
depth = 0
)
for ; l != nil && t != nil; l, t = localTs.Shift(), targetTs.Shift() {
if depth >= maxTypeDepth {
return errors.New("types are nested too deep")
}
localType = *l
targetType = *t
if reflect.TypeOf(localType) != reflect.TypeOf(targetType) {
return fmt.Errorf("type mismatch: %w", errIncompatibleTypes)
}
switch lv := (localType).(type) {
case *Void, *Struct, *Union, *Enum, *Fwd, *Int:
// Nothing to do here
case *Pointer, *Array:
depth++
walkType(localType, localTs.Push)
walkType(targetType, targetTs.Push)
case *FuncProto:
tv := targetType.(*FuncProto)
if len(lv.Params) != len(tv.Params) {
return fmt.Errorf("function param mismatch: %w", errIncompatibleTypes)
}
depth++
walkType(localType, localTs.Push)
walkType(targetType, targetTs.Push)
default:
return fmt.Errorf("unsupported type %T", localType)
}
}
if l != nil {
return fmt.Errorf("dangling local type %T", *l)
}
if t != nil {
return fmt.Errorf("dangling target type %T", *t)
}
return nil
}
/* coreAreMembersCompatible checks two types for field-based relocation compatibility.
*
* The comment below is from bpf_core_fields_are_comp
6BF6
at in libbpf.c:
*
* Check two types for compatibility for the purpose of field access
* relocation. const/volatile/restrict and typedefs are skipped to ensure we
* are relocating semantically compatible entities:
* - any two STRUCTs/UNIONs are compatible and can be mixed;
* - any two FWDs are compatible, if their names match (modulo flavor suffix);
* - any two PTRs are always compatible;
* - for ENUMs, names should be the same (ignoring flavor suffix) or at
* least one of enums should be anonymous;
* - for ENUMs, check sizes, names are ignored;
* - for INT, size and signedness are ignored;
* - any two FLOATs are always compatible;
* - for ARRAY, dimensionality is ignored, element types are checked for
* compatibility recursively;
* [ NB: coreAreMembersCompatible doesn't recurse, this check is done
* by coreFindField. ]
* - everything else shouldn't be ever a target of relocation.
* These rules are not set in stone and probably will be adjusted as we get
* more experience with using BPF CO-RE relocations.
*
* Returns errImpossibleRelocation if the members are not compatible.
*/
func coreAreMembersCompatible(localType Type, targetType Type) error {
doNamesMatch := func(a, b string) error {
if a == "" || b == "" {
// allow anonymous and named type to match
return nil
}
if newEssentialName(a) == newEssentialName(b) {
return nil
}
return fmt.Errorf("names don't match: %w", errImpossibleRelocation)
}
_, lok := localType.(composite)
_, tok := targetType.(composite)
if lok && tok {
return nil
}
if reflect.TypeOf(localType) != reflect.TypeOf(targetType) {
return fmt.Errorf("type mismatch: %w", errImpossibleRelocation)
}
switch lv := localType.(type) {
case *Array, *Pointer, *Float, *Int:
return nil
case *Enum:
tv := targetType.(*Enum)
return doNamesMatch(lv.Name, tv.Name)
case *Fwd:
tv := targetType.(*Fwd)
return doNamesMatch(lv.Name, tv.Name)
default:
return fmt.Errorf("type %s: %w", localType, ErrNotSupported)
}
}