[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, 897 insertions, 0 deletions

diff --git a/vendor/github.com/cilium/ebpf/btf/btf.go b/vendor/github.com/cilium/ebpf/btf/btf.go
new file mode 100644
index 000000000..a5969332a
--- /dev/null
+++ b/vendor/github.com/cilium/ebpf/btf/btf.go
@@ -0,0 +1,897 @@
+package btf
+
+import (
+	"bufio"
+	"bytes"
+	"debug/elf"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"math"
+	"os"
+	"reflect"
+
+	"github.com/cilium/ebpf/internal"
+	"github.com/cilium/ebpf/internal/sys"
+	"github.com/cilium/ebpf/internal/unix"
+)
+
+const btfMagic = 0xeB9F
+
+// Errors returned by BTF functions.
+var (
+	ErrNotSupported   = internal.ErrNotSupported
+	ErrNotFound       = errors.New("not found")
+	ErrNoExtendedInfo = errors.New("no extended info")
+)
+
+// ID represents the unique ID of a BTF object.
+type ID = sys.BTFID
+
+// Spec represents decoded BTF.
+type Spec struct {
+	// Data from .BTF.
+	rawTypes []rawType
+	strings  *stringTable
+
+	// All types contained by the spec. For the base type, the position of
+	// a type in the slice is its ID.
+	types types
+
+	// Type IDs indexed by type.
+	typeIDs map[Type]TypeID
+
+	// Types indexed by essential name.
+	// Includes all struct flavors and types with the same name.
+	namedTypes map[essentialName][]Type
+
+	byteOrder binary.ByteOrder
+}
+
+type btfHeader struct {
+	Magic   uint16
+	Version uint8
+	Flags   uint8
+	HdrLen  uint32
+
+	TypeOff   uint32
+	TypeLen   uint32
+	StringOff uint32
+	StringLen uint32
+}
+
+// typeStart returns the offset from the beginning of the .BTF section
+// to the start of its type entries.
+func (h *btfHeader) typeStart() int64 {
+	return int64(h.HdrLen + h.TypeOff)
+}
+
+// stringStart returns the offset from the beginning of the .BTF section
+// to the start of its string table.
+func (h *btfHeader) stringStart() int64 {
+	return int64(h.HdrLen + h.StringOff)
+}
+
+// LoadSpec opens file and calls LoadSpecFromReader on it.
+func LoadSpec(file string) (*Spec, error) {
+	fh, err := os.Open(file)
+	if err != nil {
+		return nil, err
+	}
+	defer fh.Close()
+
+	return LoadSpecFromReader(fh)
+}
+
+// LoadSpecFromReader reads from an ELF or a raw BTF blob.
+//
+// Returns ErrNotFound if reading from an ELF which contains no BTF. ExtInfos
+// may be nil.
+func LoadSpecFromReader(rd io.ReaderAt) (*Spec, error) {
+	file, err := internal.NewSafeELFFile(rd)
+	if err != nil {
+		if bo := guessRawBTFByteOrder(rd); bo != nil {
+			// Try to parse a naked BTF blob. This will return an error if
+			// we encounter a Datasec, since we can't fix it up.
+			spec, err := loadRawSpec(io.NewSectionReader(rd, 0, math.MaxInt64), bo, nil, nil)
+			return spec, err
+		}
+
+		return nil, err
+	}
+
+	return loadSpecFromELF(file)
+}
+
+// LoadSpecAndExtInfosFromReader reads from an ELF.
+//
+// ExtInfos may be nil if the ELF doesn't contain section metadta.
+// Returns ErrNotFound if the ELF contains no BTF.
+func LoadSpecAndExtInfosFromReader(rd io.ReaderAt) (*Spec, *ExtInfos, error) {
+	file, err := internal.NewSafeELFFile(rd)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	spec, err := loadSpecFromELF(file)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	extInfos, err := loadExtInfosFromELF(file, spec.types, spec.strings)
+	if err != nil && !errors.Is(err, ErrNotFound) {
+		return nil, nil, err
+	}
+
+	return spec, extInfos, nil
+}
+
+// variableOffsets extracts all symbols offsets from an ELF and indexes them by
+// section and variable name.
+//
+// References to variables in BTF data sections carry unsigned 32-bit offsets.
+// Some ELF symbols (e.g. in vmlinux) may point to virtual memory that is well
+// beyond this range. Since these symbols cannot be described by BTF info,
+// ignore them here.
+func variableOffsets(file *internal.SafeELFFile) (map[variable]uint32, error) {
+	symbols, err := file.Symbols()
+	if err != nil {
+		return nil, fmt.Errorf("can't read symbols: %v", err)
+	}
+
+	variableOffsets := make(map[variable]uint32)
+	for _, symbol := range symbols {
+		if idx := symbol.Section; idx >= elf.SHN_LORESERVE && idx <= elf.SHN_HIRESERVE {
+			// Ignore things like SHN_ABS
+			continue
+		}
+
+		if symbol.Value > math.MaxUint32 {
+			// VarSecinfo offset is u32, cannot reference symbols in higher regions.
+			continue
+		}
+
+		if int(symbol.Section) >= len(file.Sections) {
+			return nil, fmt.Errorf("symbol %s: invalid section %d", symbol.Name, symbol.Section)
+		}
+
+		secName := file.Sections[symbol.Section].Name
+		variableOffsets[variable{secName, symbol.Name}] = uint32(symbol.Value)
+	}
+
+	return variableOffsets, nil
+}
+
+func loadSpecFromELF(file *internal.SafeELFFile) (*Spec, error) {
+	var (
+		btfSection   *elf.Section
+		sectionSizes = make(map[string]uint32)
+	)
+
+	for _, sec := range file.Sections {
+		switch sec.Name {
+		case ".BTF":
+			btfSection = sec
+		default:
+			if sec.Type != elf.SHT_PROGBITS && sec.Type != elf.SHT_NOBITS {
+				break
+			}
+
+			if sec.Size > math.MaxUint32 {
+				return nil, fmt.Errorf("section %s exceeds maximum size", sec.Name)
+			}
+
+			sectionSizes[sec.Name] = uint32(sec.Size)
+		}
+	}
+
+	if btfSection == nil {
+		return nil, fmt.Errorf("btf: %w", ErrNotFound)
+	}
+
+	vars, err := variableOffsets(file)
+	if err != nil {
+		return nil, err
+	}
+
+	if btfSection.ReaderAt == nil {
+		return nil, fmt.Errorf("compressed BTF is not supported")
+	}
+
+	rawTypes, rawStrings, err := parseBTF(btfSection.ReaderAt, file.ByteOrder, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	err = fixupDatasec(rawTypes, rawStrings, sectionSizes, vars)
+	if err != nil {
+		return nil, err
+	}
+
+	return inflateSpec(rawTypes, rawStrings, file.ByteOrder, nil)
+}
+
+func loadRawSpec(btf io.ReaderAt, bo binary.ByteOrder,
+	baseTypes types, baseStrings *stringTable) (*Spec, error) {
+
+	rawTypes, rawStrings, err := parseBTF(btf, bo, baseStrings)
+	if err != nil {
+		return nil, err
+	}
+
+	return inflateSpec(rawTypes, rawStrings, bo, baseTypes)
+}
+
+func inflateSpec(rawTypes []rawType, rawStrings *stringTable, bo binary.ByteOrder,
+	baseTypes types) (*Spec, error) {
+
+	types, err := inflateRawTypes(rawTypes, baseTypes, rawStrings)
+	if err != nil {
+		return nil, err
+	}
+
+	typeIDs, typesByName := indexTypes(types, TypeID(len(baseTypes)))
+
+	return &Spec{
+		rawTypes:   rawTypes,
+		namedTypes: typesByName,
+		typeIDs:    typeIDs,
+		types:      types,
+		strings:    rawStrings,
+		byteOrder:  bo,
+	}, nil
+}
+
+func indexTypes(types []Type, typeIDOffset TypeID) (map[Type]TypeID, map[essentialName][]Type) {
+	namedTypes := 0
+	for _, typ := range types {
+		if typ.TypeName() != "" {
+			// Do a pre-pass to figure out how big types by name has to be.
+			// Most types have unique names, so it's OK to ignore essentialName
+			// here.
+			namedTypes++
+		}
+	}
+
+	typeIDs := make(map[Type]TypeID, len(types))
+	typesByName := make(map[essentialName][]Type, namedTypes)
+
+	for i, typ := range types {
+		if name := newEssentialName(typ.TypeName()); name != "" {
+			typesByName[name] = append(typesByName[name], typ)
+		}
+		typeIDs[typ] = TypeID(i) + typeIDOffset
+	}
+
+	return typeIDs, typesByName
+}
+
+// LoadKernelSpec returns the current kernel's BTF information.
+//
+// Defaults to /sys/kernel/btf/vmlinux and falls back to scanning the file system
+// for vmlinux ELFs. Returns an error wrapping ErrNotSupported if BTF is not enabled.
+func LoadKernelSpec() (*Spec, error) {
+	fh, err := os.Open("/sys/kernel/btf/vmlinux")
+	if err == nil {
+		defer fh.Close()
+
+		return loadRawSpec(fh, internal.NativeEndian, nil, nil)
+	}
+
+	file, err := findVMLinux()
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	return loadSpecFromELF(file)
+}
+
+// findVMLinux scans multiple well-known paths for vmlinux kernel images.
+func findVMLinux() (*internal.SafeELFFile, error) {
+	release, err := internal.KernelRelease()
+	if err != nil {
+		return nil, err
+	}
+
+	// use same list of locations as libbpf
+	// https://github.com/libbpf/libbpf/blob/9a3a42608dbe3731256a5682a125ac1e23bced8f/src/btf.c#L3114-L3122
+	locations := []string{
+		"/boot/vmlinux-%s",
+		"/lib/modules/%s/vmlinux-%[1]s",
+		"/lib/modules/%s/build/vmlinux",
+		"/usr/lib/modules/%s/kernel/vmlinux",
+		"/usr/lib/debug/boot/vmlinux-%s",
+		"/usr/lib/debug/boot/vmlinux-%s.debug",
+		"/usr/lib/debug/lib/modules/%s/vmlinux",
+	}
+
+	for _, loc := range locations {
+		file, err := internal.OpenSafeELFFile(fmt.Sprintf(loc, release))
+		if errors.Is(err, os.ErrNotExist) {
+			continue
+		}
+		return file, err
+	}
+
+	return nil, fmt.Errorf("no BTF found for kernel version %s: %w", release, internal.ErrNotSupported)
+}
+
+// parseBTFHeader parses the header of the .BTF section.
+func parseBTFHeader(r io.Reader, bo binary.ByteOrder) (*btfHeader, error) {
+	var header btfHeader
+	if err := binary.Read(r, bo, &header); err != nil {
+		return nil, fmt.Errorf("can't read header: %v", err)
+	}
+
+	if header.Magic != btfMagic {
+		return nil, fmt.Errorf("incorrect magic value %v", header.Magic)
+	}
+
+	if header.Version != 1 {
+		return nil, fmt.Errorf("unexpected version %v", header.Version)
+	}
+
+	if header.Flags != 0 {
+		return nil, fmt.Errorf("unsupported flags %v", header.Flags)
+	}
+
+	remainder := int64(header.HdrLen) - int64(binary.Size(&header))
+	if remainder < 0 {
+		return nil, errors.New("header length shorter than btfHeader size")
+	}
+
+	if _, err := io.CopyN(internal.DiscardZeroes{}, r, remainder); err != nil {
+		return nil, fmt.Errorf("header padding: %v", err)
+	}
+
+	return &header, nil
+}
+
+func guessRawBTFByteOrder(r io.ReaderAt) binary.ByteOrder {
+	buf := new(bufio.Reader)
+	for _, bo := range []binary.ByteOrder{
+		binary.LittleEndian,
+		binary.BigEndian,
+	} {
+		buf.Reset(io.NewSectionReader(r, 0, math.MaxInt64))
+		if _, err := parseBTFHeader(buf, bo); err == nil {
+			return bo
+		}
+	}
+
+	return nil
+}
+
+// parseBTF reads a .BTF section into memory and parses it into a list of
+// raw types and a string table.
+func parseBTF(btf io.ReaderAt, bo binary.ByteOrder, baseStrings *stringTable) ([]rawType, *stringTable, error) {
+	buf := internal.NewBufferedSectionReader(btf, 0, math.MaxInt64)
+	header, err := parseBTFHeader(buf, bo)
+	if err != nil {
+		return nil, nil, fmt.Errorf("parsing .BTF header: %v", err)
+	}
+
+	rawStrings, err := readStringTable(io.NewSectionReader(btf, header.stringStart(), int64(header.StringLen)),
+		baseStrings)
+	if err != nil {
+		return nil, nil, fmt.Errorf("can't read type names: %w", err)
+	}
+
+	buf.Reset(io.NewSectionReader(btf, header.typeStart(), int64(header.TypeLen)))
+	rawTypes, err := readTypes(buf, bo, header.TypeLen)
+	if err != nil {
+		return nil, nil, fmt.Errorf("can't read types: %w", err)
+	}
+
+	return rawTypes, rawStrings, nil
+}
+
+type variable struct {
+	section string
+	name    string
+}
+
+func fixupDatasec(rawTypes []rawType, rawStrings *stringTable, sectionSizes map[string]uint32, variableOffsets map[variable]uint32) error {
+	for i, rawType := range rawTypes {
+		if rawType.Kind() != kindDatasec {
+			continue
+		}
+
+		name, err := rawStrings.Lookup(rawType.NameOff)
+		if err != nil {
+			return err
+		}
+
+		if name == ".kconfig" || name == ".ksyms" {
+			return fmt.Errorf("reference to %s: %w", name, ErrNotSupported)
+		}
+
+		if rawTypes[i].SizeType != 0 {
+			continue
+		}
+
+		size, ok := sectionSizes[name]
+		if !ok {
+			return fmt.Errorf("data section %s: missing size", name)
+		}
+
+		rawTypes[i].SizeType = size
+
+		secinfos := rawType.data.([]btfVarSecinfo)
+		for j, secInfo := range secinfos {
+			id := int(secInfo.Type - 1)
+			if id >= len(rawTypes) {
+				return fmt.Errorf("data section %s: invalid type id %d for variable %d", name, id, j)
+			}
+
+			varName, err := rawStrings.Lookup(rawTypes[id].NameOff)
+			if err != nil {
+				return fmt.Errorf("data section %s: can't get name for type %d: %w", name, id, err)
+			}
+
+			offset, ok := variableOffsets[variable{name, varName}]
+			if !ok {
+				return fmt.Errorf("data section %s: missing offset for variable %s", name, varName)
+			}
+
+			secinfos[j].Offset = offset
+		}
+	}
+
+	return nil
+}
+
+// Copy creates a copy of Spec.
+func (s *Spec) Copy() *Spec {
+	types := copyTypes(s.types, nil)
+
+	typeIDOffset := TypeID(0)
+	if len(s.types) != 0 {
+		typeIDOffset = s.typeIDs[s.types[0]]
+	}
+	typeIDs, typesByName := indexTypes(types, typeIDOffset)
+
+	// NB: Other parts of spec are not copied since they are immutable.
+	return &Spec{
+		s.rawTypes,
+		s.strings,
+		types,
+		typeIDs,
+		typesByName,
+		s.byteOrder,
+	}
+}
+
+type marshalOpts struct {
+	ByteOrder        binary.ByteOrder
+	StripFuncLinkage bool
+}
+
+func (s *Spec) marshal(opts marshalOpts) ([]byte, error) {
+	var (
+		buf       bytes.Buffer
+		header    = new(btfHeader)
+		headerLen = binary.Size(header)
+	)
+
+	// Reserve space for the header. We have to write it last since
+	// we don't know the size of the type section yet.
+	_, _ = buf.Write(make([]byte, headerLen))
+
+	// Write type section, just after the header.
+	for _, raw := range s.rawTypes {
+		switch {
+		case opts.StripFuncLinkage && raw.Kind() == kindFunc:
+			raw.SetLinkage(StaticFunc)
+		}
+
+		if err := raw.Marshal(&buf, opts.ByteOrder); err != nil {
+			return nil, fmt.Errorf("can't marshal BTF: %w", err)
+		}
+	}
+
+	typeLen := uint32(buf.Len() - headerLen)
+
+	// Write string section after type section.
+	stringsLen := s.strings.Length()
+	buf.Grow(stringsLen)
+	if err := s.strings.Marshal(&buf); err != nil {
+		return nil, err
+	}
+
+	// Fill out the header, and write it out.
+	header = &btfHeader{
+		Magic:     btfMagic,
+		Version:   1,
+		Flags:     0,
+		HdrLen:    uint32(headerLen),
+		TypeOff:   0,
+		TypeLen:   typeLen,
+		StringOff: typeLen,
+		StringLen: uint32(stringsLen),
+	}
+
+	raw := buf.Bytes()
+	err := binary.Write(sliceWriter(raw[:headerLen]), opts.ByteOrder, header)
+	if err != nil {
+		return nil, fmt.Errorf("can't write header: %v", err)
+	}
+
+	return raw, nil
+}
+
+type sliceWriter []byte
+
+func (sw sliceWriter) Write(p []byte) (int, error) {
+	if len(p) != len(sw) {
+		return 0, errors.New("size doesn't match")
+	}
+
+	return copy(sw, p), nil
+}
+
+// TypeByID returns the BTF Type with the given type ID.
+//
+// Returns an error wrapping ErrNotFound if a Type with the given ID
+// does not exist in the Spec.
+func (s *Spec) TypeByID(id TypeID) (Type, error) {
+	return s.types.ByID(id)
+}
+
+// TypeID returns the ID for a given Type.
+//
+// Returns an error wrapping ErrNoFound if the type isn't part of the Spec.
+func (s *Spec) TypeID(typ Type) (TypeID, error) {
+	if _, ok := typ.(*Void); ok {
+		// Equality is weird for void, since it is a zero sized type.
+		return 0, nil
+	}
+
+	id, ok := s.typeIDs[typ]
+	if !ok {
+		return 0, fmt.Errorf("no ID for type %s: %w", typ, ErrNotFound)
+	}
+
+	return id, nil
+}
+
+// AnyTypesByName returns a list of BTF Types with the given name.
+//
+// If the BTF blob describes multiple compilation units like vmlinux, multiple
+// Types with the same name and kind can exist, but might not describe the same
+// data structure.
+//
+// Returns an error wrapping ErrNotFound if no matching Type exists in the Spec.
+func (s *Spec) AnyTypesByName(name string) ([]Type, error) {
+	types := s.namedTypes[newEssentialName(name)]
+	if len(types) == 0 {
+		return nil, fmt.Errorf("type name %s: %w", name, ErrNotFound)
+	}
+
+	// Return a copy to prevent changes to namedTypes.
+	result := make([]Type, 0, len(types))
+	for _, t := range types {
+		// Match against the full name, not just the essential one
+		// in case the type being looked up is a struct flavor.
+		if t.TypeName() == name {
+			result = append(result, t)
+		}
+	}
+	return result, nil
+}
+
+// AnyTypeByName returns a Type with the given name.
+//
+// Returns an error if multiple types of that name exist.
+func (s *Spec) AnyTypeByName(name string) (Type, error) {
+	types, err := s.AnyTypesByName(name)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(types) > 1 {
+		return nil, fmt.Errorf("found multiple types: %v", types)
+	}
+
+	return types[0], nil
+}
+
+// TypeByName searches for a Type with a specific name. Since multiple
+// Types with the same name can exist, the parameter typ is taken to
+// narrow down the search in case of a clash.
+//
+// typ must be a non-nil pointer to an implementation of a Type.
+// On success, the address of the found Type will be copied to typ.
+//
+// Returns an error wrapping ErrNotFound if no matching
+// Type exists in the Spec. If multiple candidates are found,
+// an error is returned.
+func (s *Spec) TypeByName(name string, typ interface{}) error {
+	typValue := reflect.ValueOf(typ)
+	if typValue.Kind() != reflect.Ptr {
+		return fmt.Errorf("%T is not a pointer", typ)
+	}
+
+	typPtr := typValue.Elem()
+	if !typPtr.CanSet() {
+		return fmt.Errorf("%T cannot be set", typ)
+	}
+
+	wanted := typPtr.Type()
+	if !wanted.AssignableTo(reflect.TypeOf((*Type)(nil)).Elem()) {
+		return fmt.Errorf("%T does not satisfy Type interface", typ)
+	}
+
+	types, err := s.AnyTypesByName(name)
+	if err != nil {
+		return err
+	}
+
+	var candidate Type
+	for _, typ := range types {
+		if reflect.TypeOf(typ) != wanted {
+			continue
+		}
+
+		if candidate != nil {
+			return fmt.Errorf("type %s: multiple candidates for %T", name, typ)
+		}
+
+		candidate = typ
+	}
+
+	if candidate == nil {
+		return fmt.Errorf("type %s: %w", name, ErrNotFound)
+	}
+
+	typPtr.Set(reflect.ValueOf(candidate))
+
+	return nil
+}
+
+// LoadSplitSpecFromReader loads split BTF from a reader.
+//
+// Types from base are used to resolve references in the split BTF.
+// The returned Spec only contains types from the split BTF, not from the base.
+func LoadSplitSpecFromReader(r io.ReaderAt, base *Spec) (*Spec, error) {
+	return loadRawSpec(r, internal.NativeEndian, base.types, base.strings)
+}
+
+// TypesIterator iterates over types of a given spec.
+type TypesIterator struct {
+	spec  *Spec
+	index int
+	// The last visited type in the spec.
+	Type Type
+}
+
+// Iterate returns the types iterator.
+func (s *Spec) Iterate() *TypesIterator {
+	return &TypesIterator{spec: s, index: 0}
+}
+
+// Next returns true as long as there are any remaining types.
+func (iter *TypesIterator) Next() bool {
+	if len(iter.spec.types) <= iter.index {
+		return false
+	}
+
+	iter.Type = iter.spec.types[iter.index]
+	iter.index++
+	return true
+}
+
+// Handle is a reference to BTF loaded into the kernel.
+type Handle struct {
+	fd *sys.FD
+
+	// Size of the raw BTF in bytes.
+	size uint32
+}
+
+// NewHandle loads BTF into the kernel.
+//
+// Returns ErrNotSupported if BTF is not supported.
+func NewHandle(spec *Spec) (*Handle, error) {
+	if err := haveBTF(); err != nil {
+		return nil, err
+	}
+
+	if spec.byteOrder != internal.NativeEndian {
+		return nil, fmt.Errorf("can't load %s BTF on %s", spec.byteOrder, internal.NativeEndian)
+	}
+
+	btf, err := spec.marshal(marshalOpts{
+		ByteOrder:        internal.NativeEndian,
+		StripFuncLinkage: haveFuncLinkage() != nil,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("can't marshal BTF: %w", err)
+	}
+
+	if uint64(len(btf)) > math.MaxUint32 {
+		return nil, errors.New("BTF exceeds the maximum size")
+	}
+
+	attr := &sys.BtfLoadAttr{
+		Btf:     sys.NewSlicePointer(btf),
+		BtfSize: uint32(len(btf)),
+	}
+
+	fd, err := sys.BtfLoad(attr)
+	if err != nil {
+		logBuf := make([]byte, 64*1024)
+		attr.BtfLogBuf = sys.NewSlicePointer(logBuf)
+		attr.BtfLogSize = uint32(len(logBuf))
+		attr.BtfLogLevel = 1
+		// NB: The syscall will never return ENOSPC as of 5.18-rc4.
+		_, _ = sys.BtfLoad(attr)
+		return nil, internal.ErrorWithLog(err, logBuf)
+	}
+
+	return &Handle{fd, attr.BtfSize}, nil
+}
+
+// NewHandleFromID returns the BTF handle for a given id.
+//
+// Prefer calling [ebpf.Program.Handle] or [ebpf.Map.Handle] if possible.
+//
+// Returns ErrNotExist, if there is no BTF with the given id.
+//
+// Requires CAP_SYS_ADMIN.
+func NewHandleFromID(id ID) (*Handle, error) {
+	fd, err := sys.BtfGetFdById(&sys.BtfGetFdByIdAttr{
+		Id: uint32(id),
+	})
+	if err != nil {
+		return nil, fmt.Errorf("get FD for ID %d: %w", id, err)
+	}
+
+	info, err := newHandleInfoFromFD(fd)
+	if err != nil {
+		_ = fd.Close()
+		return nil, err
+	}
+
+	return &Handle{fd, info.size}, nil
+}
+
+// Spec parses the kernel BTF into Go types.
+//
+// base is used to decode split BTF and may be nil.
+func (h *Handle) Spec(base *Spec) (*Spec, error) {
+	var btfInfo sys.BtfInfo
+	btfBuffer := make([]byte, h.size)
+	btfInfo.Btf, btfInfo.BtfSize = sys.NewSlicePointerLen(btfBuffer)
+
+	if err := sys.ObjInfo(h.fd, &btfInfo); err != nil {
+		return nil, err
+	}
+
+	var baseTypes types
+	var baseStrings *stringTable
+	if base != nil {
+		baseTypes = base.types
+		baseStrings = base.strings
+	}
+
+	return loadRawSpec(bytes.NewReader(btfBuffer), internal.NativeEndian, baseTypes, baseStrings)
+}
+
+// Close destroys the handle.
+//
+// Subsequent calls to FD will return an invalid value.
+func (h *Handle) Close() error {
+	if h == nil {
+		return nil
+	}
+
+	return h.fd.Close()
+}
+
+// FD returns the file descriptor for the handle.
+func (h *Handle) FD() int {
+	return h.fd.Int()
+}
+
+// Info returns metadata about the handle.
+func (h *Handle) Info() (*HandleInfo, error) {
+	return newHandleInfoFromFD(h.fd)
+}
+
+func marshalBTF(types interface{}, strings []byte, bo binary.ByteOrder) []byte {
+	const minHeaderLength = 24
+
+	typesLen := uint32(binary.Size(types))
+	header := btfHeader{
+		Magic:     btfMagic,
+		Version:   1,
+		HdrLen:    minHeaderLength,
+		TypeOff:   0,
+		TypeLen:   typesLen,
+		StringOff: typesLen,
+		StringLen: uint32(len(strings)),
+	}
+
+	buf := new(bytes.Buffer)
+	_ = binary.Write(buf, bo, &header)
+	_ = binary.Write(buf, bo, types)
+	buf.Write(strings)
+
+	return buf.Bytes()
+}
+
+var haveBTF = internal.FeatureTest("BTF", "5.1", func() error {
+	var (
+		types struct {
+			Integer btfType
+			Var     btfType
+			btfVar  struct{ Linkage uint32 }
+		}
+		strings = []byte{0, 'a', 0}
+	)
+
+	// We use a BTF_KIND_VAR here, to make sure that
+	// the kernel understands BTF at least as well as we
+	// do. BTF_KIND_VAR was introduced ~5.1.
+	types.Integer.SetKind(kindPointer)
+	types.Var.NameOff = 1
+	types.Var.SetKind(kindVar)
+	types.Var.SizeType = 1
+
+	btf := marshalBTF(&types, strings, internal.NativeEndian)
+
+	fd, err := sys.BtfLoad(&sys.BtfLoadAttr{
+		Btf:     sys.NewSlicePointer(btf),
+		BtfSize: uint32(len(btf)),
+	})
+	if errors.Is(err, unix.EINVAL) || errors.Is(err, unix.EPERM) {
+		// Treat both EINVAL and EPERM as not supported: loading the program
+		// might still succeed without BTF.
+		return internal.ErrNotSupported
+	}
+	if err != nil {
+		return err
+	}
+
+	fd.Close()
+	return nil
+})
+
+var haveFuncLinkage = internal.FeatureTest("BTF func linkage", "5.6", func() error {
+	if err := haveBTF(); err != nil {
+		return err
+	}
+
+	var (
+		types struct {
+			FuncProto btfType
+			Func      btfType
+		}
+		strings = []byte{0, 'a', 0}
+	)
+
+	types.FuncProto.SetKind(kindFuncProto)
+	types.Func.SetKind(kindFunc)
+	types.Func.SizeType = 1 // aka FuncProto
+	types.Func.NameOff = 1
+	types.Func.SetLinkage(GlobalFunc)
+
+	btf := marshalBTF(&types, strings, internal.NativeEndian)
+
+	fd, err := sys.BtfLoad(&sys.BtfLoadAttr{
+		Btf:     sys.NewSlicePointer(btf),
+		BtfSize: uint32(len(btf)),
+	})
+	if errors.Is(err, unix.EINVAL) {
+		return internal.ErrNotSupported
+	}
+	if err != nil {
+		return err
+	}
+
+	fd.Close()
+	return nil
+})