[chore]: Bump github.com/KimMachineGun/automemlimit from 0.2.4 to 0.2.5 (#1666)

Bumps [github.com/KimMachineGun/automemlimit](https://github.com/KimMachineGun/automemlimit) from 0.2.4 to 0.2.5.
- [Release notes](https://github.com/KimMachineGun/automemlimit/releases)
- [Commits](https://github.com/KimMachineGun/automemlimit/compare/v0.2.4...v0.2.5)

---
updated-dependencies:
- dependency-name: github.com/KimMachineGun/automemlimit
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

1 files changed, 972 insertions, 0 deletions

diff --git a/vendor/github.com/cilium/ebpf/btf/core.go b/vendor/github.com/cilium/ebpf/btf/core.go
new file mode 100644
index 000000000..c48754809
--- /dev/null
+++ b/vendor/github.com/cilium/ebpf/btf/core.go
@@ -0,0 +1,972 @@
+package btf
+
+import (
+	"encoding/binary"
+	"errors"
+	"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 the difference in types between local and target.
+//
+// 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(local, target *Spec, relos []*CORERelocation) ([]COREFixup, error) {
+	if local.byteOrder != target.byteOrder {
+		return nil, fmt.Errorf("can't relocate %s against %s", local.byteOrder, 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)
+			}
+
+			id, err := local.TypeID(relo.typ)
+			if err != nil {
+				return nil, fmt.Errorf("%s: %w", relo.kind, err)
+			}
+
+			result[i] = COREFixup{
+				kind:   relo.kind,
+				local:  uint32(id),
+				target: uint32(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(local, target, localType, targets, group.relos)
+		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")
+
+// coreCalculateFixups calculates the fixups for the given relocations using
+// the "best" target.
+//
+// The best target is determined by scoring: the less poisoning we have to do
+// the better the target is.
+func coreCalculateFixups(localSpec, targetSpec *Spec, local Type, targets []Type, relos []*CORERelocation) ([]COREFixup, error) {
+	localID, err := localSpec.TypeID(local)
+	if err != nil {
+		return nil, fmt.Errorf("local type ID: %w", err)
+	}
+	local = Copy(local, UnderlyingType)
+
+	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(localSpec.byteOrder, local, localID, target, targetID, relo)
+			if err != nil {
+				return nil, fmt.Errorf("target %s: %w", target, 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(byteOrder binary.ByteOrder, local Type, localID TypeID, target Type, targetID TypeID, relo *CORERelocation) (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{}
+
+	switch relo.kind {
+	case reloTypeIDTarget, reloTypeSize, reloTypeExists:
+		if len(relo.accessor) > 1 || relo.accessor[0] != 0 {
+			return zero, fmt.Errorf("%s: unexpected accessor %v", relo.kind, relo.accessor)
+		}
+
+		err := coreAreTypesCompatible(local, target)
+		if errors.Is(err, errImpossibleRelocation) {
+			return poison()
+		}
+		if err != nil {
+			return zero, fmt.Errorf("relocation %s: %w", relo.kind, err)
+		}
+
+		switch relo.kind {
+		case reloTypeExists:
+			return fixup(1, 1)
+
+		case reloTypeIDTarget:
+			return fixup(uint32(localID), 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, fmt.Errorf("relocation %s: %w", relo.kind, 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),
+				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, fmt.Errorf("target %s: %w", target, 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 byteOrder == 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, fmt.Errorf("relocation %s: %w", relo.kind, 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 {
+	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}
+
+	// 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
+	}
+
+	if err := coreAreMembersCompatible(local.Type, target.Type); err != nil {
+		return coreField{}, coreField{}, fmt.Errorf("fields: %w", 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
+}
+
+/* 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 errImpossibleRelocation 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", errImpossibleRelocation)
+		}
+
+		switch lv := (localType).(type) {
+		case *Void, *Struct, *Union, *Enum, *Fwd, *Int:
+			// Nothing to do here
+
+		case *Pointer, *Array:
+			depth++
+			localType.walk(&localTs)
+			targetType.walk(&targetTs)
+
+		case *FuncProto:
+			tv := targetType.(*FuncProto)
+			if len(lv.Params) != len(tv.Params) {
+				return fmt.Errorf("function param mismatch: %w", errImpossibleRelocation)
+			}
+
+			depth++
+			localType.walk(&localTs)
+			targetType.walk(&targetTs)
+
+		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_compat 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)
+	}
+}