Merge pull request #1761 from erikwilson/release-1.16

Backport Release 1.16: Update runc to rc10

vendor/github.com/cilium/ebpf/collection.go

+package ebpf
+
+import (
+	"math"
+
+	"github.com/cilium/ebpf/asm"
+	"github.com/cilium/ebpf/internal"
+	"github.com/cilium/ebpf/internal/btf"
+	"golang.org/x/xerrors"
+)
+
+// CollectionOptions control loading a collection into the kernel.
+type CollectionOptions struct {
+	Programs ProgramOptions
+}
+
+// CollectionSpec describes a collection.
+type CollectionSpec struct {
+	Maps     map[string]*MapSpec
+	Programs map[string]*ProgramSpec
+}
+
+// Copy returns a recursive copy of the spec.
+func (cs *CollectionSpec) Copy() *CollectionSpec {
+	if cs == nil {
+		return nil
+	}
+
+	cpy := CollectionSpec{
+		Maps:     make(map[string]*MapSpec, len(cs.Maps)),
+		Programs: make(map[string]*ProgramSpec, len(cs.Programs)),
+	}
+
+	for name, spec := range cs.Maps {
+		cpy.Maps[name] = spec.Copy()
+	}
+
+	for name, spec := range cs.Programs {
+		cpy.Programs[name] = spec.Copy()
+	}
+
+	return &cpy
+}
+
+// RewriteMaps replaces all references to specific maps.
+//
+// Use this function to use pre-existing maps instead of creating new ones
+// when calling NewCollection. Any named maps are removed from CollectionSpec.Maps.
+//
+// Returns an error if a named map isn't used in at least one program.
+func (cs *CollectionSpec) RewriteMaps(maps map[string]*Map) error {
+	for symbol, m := range maps {
+		// have we seen a program that uses this symbol / map
+		seen := false
+		fd := m.FD()
+		for progName, progSpec := range cs.Programs {
+			err := progSpec.Instructions.RewriteMapPtr(symbol, fd)
+
+			switch {
+			case err == nil:
+				seen = true
+
+			case asm.IsUnreferencedSymbol(err):
+				// Not all programs need to use the map
+
+			default:
+				return xerrors.Errorf("program %s: %w", progName, err)
+			}
+		}
+
+		if !seen {
+			return xerrors.Errorf("map %s not referenced by any programs", symbol)
+		}
+
+		// Prevent NewCollection from creating rewritten maps
+		delete(cs.Maps, symbol)
+	}
+
+	return nil
+}
+
+// RewriteConstants replaces the value of multiple constants.
+//
+// The constant must be defined like so in the C program:
+//
+//    static volatile const type foobar;
+//    static volatile const type foobar = default;
+//
+// Replacement values must be of the same length as the C sizeof(type).
+// If necessary, they are marshalled according to the same rules as
+// map values.
+//
+// From Linux 5.5 the verifier will use constants to eliminate dead code.
+//
+// Returns an error if a constant doesn't exist.
+func (cs *CollectionSpec) RewriteConstants(consts map[string]interface{}) error {
+	rodata := cs.Maps[".rodata"]
+	if rodata == nil {
+		return xerrors.New("missing .rodata section")
+	}
+
+	if rodata.BTF == nil {
+		return xerrors.New(".rodata section has no BTF")
+	}
+
+	if n := len(rodata.Contents); n != 1 {
+		return xerrors.Errorf("expected one key in .rodata, found %d", n)
+	}
+
+	kv := rodata.Contents[0]
+	value, ok := kv.Value.([]byte)
+	if !ok {
+		return xerrors.Errorf("first value in .rodata is %T not []byte", kv.Value)
+	}
+
+	buf := make([]byte, len(value))
+	copy(buf, value)
+
+	err := patchValue(buf, btf.MapValue(rodata.BTF), consts)
+	if err != nil {
+		return err
+	}
+
+	rodata.Contents[0] = MapKV{kv.Key, buf}
+	return nil
+}
+
+// Collection is a collection of Programs and Maps associated
+// with their symbols
+type Collection struct {
+	Programs map[string]*Program
+	Maps     map[string]*Map
+}
+
+// NewCollection creates a Collection from a specification.
+//
+// Only maps referenced by at least one of the programs are initialized.
+func NewCollection(spec *CollectionSpec) (*Collection, error) {
+	return NewCollectionWithOptions(spec, CollectionOptions{})
+}
+
+// NewCollectionWithOptions creates a Collection from a specification.
+//
+// Only maps referenced by at least one of the programs are initialized.
+func NewCollectionWithOptions(spec *CollectionSpec, opts CollectionOptions) (coll *Collection, err error) {
+	var (
+		maps  = make(map[string]*Map)
+		progs = make(map[string]*Program)
+		btfs  = make(map[*btf.Spec]*btf.Handle)
+	)
+
+	defer func() {
+		for _, btf := range btfs {
+			btf.Close()
+		}
+
+		if err == nil {
+			return
+		}
+
+		for _, m := range maps {
+			m.Close()
+		}
+
+		for _, p := range progs {
+			p.Close()
+		}
+	}()
+
+	loadBTF := func(spec *btf.Spec) (*btf.Handle, error) {
+		if btfs[spec] != nil {
+			return btfs[spec], nil
+		}
+
+		handle, err := btf.NewHandle(spec)
+		if err != nil {
+			return nil, err
+		}
+
+		btfs[spec] = handle
+		return handle, nil
+	}
+
+	for mapName, mapSpec := range spec.Maps {
+		var handle *btf.Handle
+		if mapSpec.BTF != nil {
+			handle, err = loadBTF(btf.MapSpec(mapSpec.BTF))
+			if err != nil && !xerrors.Is(err, btf.ErrNotSupported) {
+				return nil, err
+			}
+		}
+
+		m, err := newMapWithBTF(mapSpec, handle)
+		if err != nil {
+			return nil, xerrors.Errorf("map %s: %w", mapName, err)
+		}
+		maps[mapName] = m
+	}
+
+	for progName, origProgSpec := range spec.Programs {
+		progSpec := origProgSpec.Copy()
+
+		// Rewrite any reference to a valid map.
+		for i := range progSpec.Instructions {
+			ins := &progSpec.Instructions[i]
+
+			if ins.OpCode != asm.LoadImmOp(asm.DWord) || ins.Reference == "" {
+				continue
+			}
+
+			if uint32(ins.Constant) != math.MaxUint32 {
+				// Don't overwrite maps already rewritten, users can
+				// rewrite programs in the spec themselves
+				continue
+			}
+
+			m := maps[ins.Reference]
+			if m == nil {
+				return nil, xerrors.Errorf("program %s: missing map %s", progName, ins.Reference)
+			}
+
+			fd := m.FD()
+			if fd < 0 {
+				return nil, xerrors.Errorf("map %s: %w", ins.Reference, internal.ErrClosedFd)
+			}
+			if err := ins.RewriteMapPtr(m.FD()); err != nil {
+				return nil, xerrors.Errorf("progam %s: map %s: %w", progName, ins.Reference, err)
+			}
+		}
+
+		var handle *btf.Handle
+		if progSpec.BTF != nil {
+			handle, err = loadBTF(btf.ProgramSpec(progSpec.BTF))
+			if err != nil && !xerrors.Is(err, btf.ErrNotSupported) {
+				return nil, err
+			}
+		}
+
+		prog, err := newProgramWithBTF(progSpec, handle, opts.Programs)
+		if err != nil {
+			return nil, xerrors.Errorf("program %s: %w", progName, err)
+		}
+		progs[progName] = prog
+	}
+
+	return &Collection{
+		progs,
+		maps,
+	}, nil
+}
+
+// LoadCollection parses an object file and converts it to a collection.
+func LoadCollection(file string) (*Collection, error) {
+	spec, err := LoadCollectionSpec(file)
+	if err != nil {
+		return nil, err
+	}
+	return NewCollection(spec)
+}
+
+// Close frees all maps and programs associated with the collection.
+//
+// The collection mustn't be used afterwards.
+func (coll *Collection) Close() {
+	for _, prog := range coll.Programs {
+		prog.Close()
+	}
+	for _, m := range coll.Maps {
+		m.Close()
+	}
+}
+
+// DetachMap removes the named map from the Collection.
+//
+// This means that a later call to Close() will not affect this map.
+//
+// Returns nil if no map of that name exists.
+func (coll *Collection) DetachMap(name string) *Map {
+	m := coll.Maps[name]
+	delete(coll.Maps, name)
+	return m
+}
+
+// DetachProgram removes the named program from the Collection.
+//
+// This means that a later call to Close() will not affect this program.
+//
+// Returns nil if no program of that name exists.
+func (coll *Collection) DetachProgram(name string) *Program {
+	p := coll.Programs[name]
+	delete(coll.Programs, name)
+	return p
+}

vendor/github.com/cilium/ebpf/doc.go

+// Package ebpf is a toolkit for working with eBPF programs.
+//
+// eBPF programs are small snippets of code which are executed directly
+// in a VM in the Linux kernel, which makes them very fast and flexible.
+// Many Linux subsystems now accept eBPF programs. This makes it possible
+// to implement highly application specific logic inside the kernel,
+// without having to modify the actual kernel itself.
+//
+// This package is designed for long-running processes which
+// want to use eBPF to implement part of their application logic. It has no
+// run-time dependencies outside of the library and the Linux kernel itself.
+// eBPF code should be compiled ahead of time using clang, and shipped with
+// your application as any other resource.
+//
+// This package doesn't include code required to attach eBPF to Linux
+// subsystems, since this varies per subsystem.
+package ebpf

vendor/github.com/cilium/ebpf/go.mod

+module github.com/cilium/ebpf
+
+go 1.12
+
+require (
+	golang.org/x/sys v0.0.0-20200124204421-9fbb57f87de9
+	golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543
+)

vendor/github.com/cilium/ebpf/go.sum

+golang.org/x/sys v0.0.0-20191022100944-742c48ecaeb7 h1:HmbHVPwrPEKPGLAcHSrMe6+hqSUlvZU0rab6x5EXfGU=
+golang.org/x/sys v0.0.0-20191022100944-742c48ecaeb7/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200124204421-9fbb57f87de9 h1:1/DFK4b7JH8DmkqhUk48onnSfrPzImPoVxuomtbT2nk=
+golang.org/x/sys v0.0.0-20200124204421-9fbb57f87de9/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

vendor/github.com/cilium/ebpf/internal/btf/btf.go

+package btf
+
+import (
+	"bytes"
+	"debug/elf"
+	"encoding/binary"
+	"io"
+	"io/ioutil"
+	"math"
+	"reflect"
+	"unsafe"
+
+	"github.com/cilium/ebpf/internal"
+	"github.com/cilium/ebpf/internal/unix"
+
+	"golang.org/x/xerrors"
+)
+
+const btfMagic = 0xeB9F
+
+// Errors returned by BTF functions.
+var (
+	ErrNotSupported = internal.ErrNotSupported
+)
+
+// Spec represents decoded BTF.
+type Spec struct {
+	rawTypes  []rawType
+	strings   stringTable
+	types     map[string][]Type
+	funcInfos map[string]extInfo
+	lineInfos map[string]extInfo
+}
+
+type btfHeader struct {
+	Magic   uint16
+	Version uint8
+	Flags   uint8
+	HdrLen  uint32
+
+	TypeOff   uint32
+	TypeLen   uint32
+	StringOff uint32
+	StringLen uint32
+}
+
+// LoadSpecFromReader reads BTF sections from an ELF.
+//
+// Returns a nil Spec and no error if no BTF was present.
+func LoadSpecFromReader(rd io.ReaderAt) (*Spec, error) {
+	file, err := elf.NewFile(rd)
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	var (
+		btfSection    *elf.Section
+		btfExtSection *elf.Section
+		sectionSizes  = make(map[string]uint32)
+	)
+
+	for _, sec := range file.Sections {
+		switch sec.Name {
+		case ".BTF":
+			btfSection = sec
+		case ".BTF.ext":
+			btfExtSection = sec
+		default:
+			if sec.Type != elf.SHT_PROGBITS && sec.Type != elf.SHT_NOBITS {
+				break
+			}
+
+			if sec.Size > math.MaxUint32 {
+				return nil, xerrors.Errorf("section %s exceeds maximum size", sec.Name)
+			}
+
+			sectionSizes[sec.Name] = uint32(sec.Size)
+		}
+	}
+
+	if btfSection == nil {
+		return nil, nil
+	}
+
+	symbols, err := file.Symbols()
+	if err != nil {
+		return nil, xerrors.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
+		}
+
+		secName := file.Sections[symbol.Section].Name
+		if _, ok := sectionSizes[secName]; !ok {
+			continue
+		}
+
+		if symbol.Value > math.MaxUint32 {
+			return nil, xerrors.Errorf("section %s: symbol %s: size exceeds maximum", secName, symbol.Name)
+		}
+
+		variableOffsets[variable{secName, symbol.Name}] = uint32(symbol.Value)
+	}
+
+	rawTypes, rawStrings, err := parseBTF(btfSection.Open(), file.ByteOrder)
+	if err != nil {
+		return nil, err
+	}
+
+	err = fixupDatasec(rawTypes, rawStrings, sectionSizes, variableOffsets)
+	if err != nil {
+		return nil, err
+	}
+
+	types, err := inflateRawTypes(rawTypes, rawStrings)
+	if err != nil {
+		return nil, err
+	}
+
+	var (
+		funcInfos = make(map[string]extInfo)
+		lineInfos = make(map[string]extInfo)
+	)
+	if btfExtSection != nil {
+		funcInfos, lineInfos, err = parseExtInfos(btfExtSection.Open(), file.ByteOrder, rawStrings)
+		if err != nil {
+			return nil, xerrors.Errorf("can't read ext info: %w", err)
+		}
+	}
+
+	return &Spec{
+		rawTypes:  rawTypes,
+		types:     types,
+		strings:   rawStrings,
+		funcInfos: funcInfos,
+		lineInfos: lineInfos,
+	}, nil
+}
+
+func parseBTF(btf io.ReadSeeker, bo binary.ByteOrder) ([]rawType, stringTable, error) {
+	rawBTF, err := ioutil.ReadAll(btf)
+	if err != nil {
+		return nil, nil, xerrors.Errorf("can't read BTF: %v", err)
+	}
+
+	rd := bytes.NewReader(rawBTF)
+
+	var header btfHeader
+	if err := binary.Read(rd, bo, &header); err != nil {
+		return nil, nil, xerrors.Errorf("can't read header: %v", err)
+	}
+
+	if header.Magic != btfMagic {
+		return nil, nil, xerrors.Errorf("incorrect magic value %v", header.Magic)
+	}
+
+	if header.Version != 1 {
+		return nil, nil, xerrors.Errorf("unexpected version %v", header.Version)
+	}
+
+	if header.Flags != 0 {
+		return nil, nil, xerrors.Errorf("unsupported flags %v", header.Flags)
+	}
+
+	remainder := int64(header.HdrLen) - int64(binary.Size(&header))
+	if remainder < 0 {
+		return nil, nil, xerrors.New("header is too short")
+	}
+
+	if _, err := io.CopyN(internal.DiscardZeroes{}, rd, remainder); err != nil {
+		return nil, nil, xerrors.Errorf("header padding: %v", err)
+	}
+
+	if _, err := rd.Seek(int64(header.HdrLen+header.StringOff), io.SeekStart); err != nil {
+		return nil, nil, xerrors.Errorf("can't seek to start of string section: %v", err)
+	}
+
+	rawStrings, err := readStringTable(io.LimitReader(rd, int64(header.StringLen)))
+	if err != nil {
+		return nil, nil, xerrors.Errorf("can't read type names: %w", err)
+	}
+
+	if _, err := rd.Seek(int64(header.HdrLen+header.TypeOff), io.SeekStart); err != nil {
+		return nil, nil, xerrors.Errorf("can't seek to start of type section: %v", err)
+	}
+
+	rawTypes, err := readTypes(io.LimitReader(rd, int64(header.TypeLen)), bo)
+	if err != nil {
+		return nil, nil, xerrors.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
+		}
+
+		size, ok := sectionSizes[name]
+		if !ok {
+			return xerrors.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 xerrors.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 xerrors.Errorf("data section %s: can't get name for type %d: %w", name, id, err)
+			}
+
+			offset, ok := variableOffsets[variable{name, varName}]
+			if !ok {
+				return xerrors.Errorf("data section %s: missing offset for variable %s", name, varName)
+			}
+
+			secinfos[j].Offset = offset
+		}
+	}
+
+	return nil
+}
+
+func (s *Spec) marshal(bo binary.ByteOrder) ([]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 _, typ := range s.rawTypes {
+		if err := typ.Marshal(&buf, bo); err != nil {
+			return nil, xerrors.Errorf("can't marshal BTF: %w", err)
+		}
+	}
+
+	typeLen := uint32(buf.Len() - headerLen)
+
+	// Write string section after type section.
+	_, _ = buf.Write(s.strings)
+
+	// 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(len(s.strings)),
+	}
+
+	raw := buf.Bytes()
+	err := binary.Write(sliceWriter(raw[:headerLen]), bo, header)
+	if err != nil {
+		return nil, xerrors.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, xerrors.New("size doesn't match")
+	}
+
+	return copy(sw, p), nil
+}
+
+// Program finds the BTF for a specific section.
+//
+// Length is the number of bytes in the raw BPF instruction stream.
+//
+// Returns an error if there is no BTF.
+func (s *Spec) Program(name string, length uint64) (*Program, error) {
+	if length == 0 {
+		return nil, xerrors.New("length musn't be zero")
+	}
+
+	funcInfos, funcOK := s.funcInfos[name]
+	lineInfos, lineOK := s.lineInfos[name]
+
+	if !funcOK && !lineOK {
+		return nil, xerrors.Errorf("no BTF for program %s", name)
+	}
+
+	return &Program{s, length, funcInfos, lineInfos}, nil
+}
+
+// Map finds the BTF for a map.
+//
+// Returns an error if there is no BTF for the given name.
+func (s *Spec) Map(name string) (*Map, []Member, error) {
+	var mapVar Var
+	if err := s.FindType(name, &mapVar); err != nil {
+		return nil, nil, err
+	}
+
+	mapStruct, ok := mapVar.Type.(*Struct)
+	if !ok {
+		return nil, nil, xerrors.Errorf("expected struct, have %s", mapVar.Type)
+	}
+
+	var key, value Type
+	for _, member := range mapStruct.Members {
+		switch member.Name {
+		case "key":
+			key = member.Type
+
+		case "value":
+			value = member.Type
+		}
+	}
+
+	if key == nil {
+		return nil, nil, xerrors.Errorf("map %s: missing 'key' in type", name)
+	}
+
+	if value == nil {
+		return nil, nil, xerrors.Errorf("map %s: missing 'value' in type", name)
+	}
+
+	return &Map{s, key, value}, mapStruct.Members, nil
+}
+
+// Datasec returns the BTF required to create maps which represent data sections.
+func (s *Spec) Datasec(name string) (*Map, error) {
+	var datasec Datasec
+	if err := s.FindType(name, &datasec); err != nil {
+		return nil, xerrors.Errorf("data section %s: can't get BTF: %w", name, err)
+	}
+
+	return &Map{s, &Void{}, &datasec}, nil
+}
+
+var errNotFound = xerrors.New("not found")
+
+// FindType searches for a type with a specific name.
+//
+// hint determines the type of the returned Type.
+//
+// Returns an error if there is no or multiple matches.
+func (s *Spec) FindType(name string, typ Type) error {
+	var (
+		wanted    = reflect.TypeOf(typ)
+		candidate Type
+	)
+
+	for _, typ := range s.types[name] {
+		if reflect.TypeOf(typ) != wanted {
+			continue
+		}
+
+		if candidate != nil {
+			return xerrors.Errorf("type %s: multiple candidates for %T", name, typ)
+		}
+
+		candidate = typ
+	}
+
+	if candidate == nil {
+		return xerrors.Errorf("type %s: %w", name, errNotFound)
+	}
+
+	value := reflect.Indirect(reflect.ValueOf(copyType(candidate)))
+	reflect.Indirect(reflect.ValueOf(typ)).Set(value)
+	return nil
+}
+
+// Handle is a reference to BTF loaded into the kernel.
+type Handle struct {
+	fd *internal.FD
+}
+
+// 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
+	}
+
+	btf, err := spec.marshal(internal.NativeEndian)
+	if err != nil {
+		return nil, xerrors.Errorf("can't marshal BTF: %w", err)
+	}
+
+	if uint64(len(btf)) > math.MaxUint32 {
+		return nil, xerrors.New("BTF exceeds the maximum size")
+	}
+
+	attr := &bpfLoadBTFAttr{
+		btf:     internal.NewSlicePointer(btf),
+		btfSize: uint32(len(btf)),
+	}
+
+	fd, err := bpfLoadBTF(attr)
+	if err != nil {
+		logBuf := make([]byte, 64*1024)
+		attr.logBuf = internal.NewSlicePointer(logBuf)
+		attr.btfLogSize = uint32(len(logBuf))
+		attr.btfLogLevel = 1
+		_, logErr := bpfLoadBTF(attr)
+		return nil, internal.ErrorWithLog(err, logBuf, logErr)
+	}
+
+	return &Handle{fd}, nil
+}
+
+// Close destroys the handle.
+//
+// Subsequent calls to FD will return an invalid value.
+func (h *Handle) Close() error {
+	return h.fd.Close()
+}
+
+// FD returns the file descriptor for the handle.
+func (h *Handle) FD() int {
+	value, err := h.fd.Value()
+	if err != nil {
+		return -1
+	}
+
+	return int(value)
+}
+
+// Map is the BTF for a map.
+type Map struct {
+	spec       *Spec
+	key, value Type
+}
+
+// MapSpec should be a method on Map, but is a free function
+// to hide it from users of the ebpf package.
+func MapSpec(m *Map) *Spec {
+	return m.spec
+}
+
+// MapKey should be a method on Map, but is a free function
+// to hide it from users of the ebpf package.
+func MapKey(m *Map) Type {
+	return m.key
+}
+
+// MapValue should be a method on Map, but is a free function
+// to hide it from users of the ebpf package.
+func MapValue(m *Map) Type {
+	return m.value
+}
+
+// Program is the BTF information for a stream of instructions.
+type Program struct {
+	spec                 *Spec
+	length               uint64
+	funcInfos, lineInfos extInfo
+}
+
+// ProgramSpec returns the Spec needed for loading function and line infos into the kernel.
+//
+// This is a free function instead of a method to hide it from users
+// of package ebpf.
+func ProgramSpec(s *Program) *Spec {
+	return s.spec
+}
+
+// ProgramAppend the information from other to the Program.
+//
+// This is a free function instead of a method to hide it from users
+// of package ebpf.
+func ProgramAppend(s, other *Program) error {
+	funcInfos, err := s.funcInfos.append(other.funcInfos, s.length)
+	if err != nil {
+		return xerrors.Errorf("func infos: %w", err)
+	}
+
+	lineInfos, err := s.lineInfos.append(other.lineInfos, s.length)
+	if err != nil {
+		return xerrors.Errorf("line infos: %w", err)
+	}
+
+	s.length += other.length
+	s.funcInfos = funcInfos
+	s.lineInfos = lineInfos
+	return nil
+}
+
+// ProgramFuncInfos returns the binary form of BTF function infos.
+//
+// This is a free function instead of a method to hide it from users
+// of package ebpf.
+func ProgramFuncInfos(s *Program) (recordSize uint32, bytes []byte, err error) {
+	bytes, err = s.funcInfos.MarshalBinary()
+	if err != nil {
+		return 0, nil, err
+	}
+
+	return s.funcInfos.recordSize, bytes, nil
+}
+
+// ProgramLineInfos returns the binary form of BTF line infos.
+//
+// This is a free function instead of a method to hide it from users
+// of package ebpf.
+func ProgramLineInfos(s *Program) (recordSize uint32, bytes []byte, err error) {
+	bytes, err = s.lineInfos.MarshalBinary()
+	if err != nil {
+		return 0, nil, err
+	}
+
+	return s.lineInfos.recordSize, bytes, nil
+}
+
+type bpfLoadBTFAttr struct {
+	btf         internal.Pointer
+	logBuf      internal.Pointer
+	btfSize     uint32
+	btfLogSize  uint32
+	btfLogLevel uint32
+}
+
+func bpfLoadBTF(attr *bpfLoadBTFAttr) (*internal.FD, error) {
+	const _BTFLoad = 18
+
+	fd, err := internal.BPF(_BTFLoad, unsafe.Pointer(attr), unsafe.Sizeof(*attr))
+	if err != nil {
+		return nil, err
+	}
+
+	return internal.NewFD(uint32(fd)), nil
+}
+
+func minimalBTF(bo binary.ByteOrder) []byte {
+	const minHeaderLength = 24
+
+	var (
+		types struct {
+			Integer btfType
+			Var     btfType
+			btfVar  struct{ Linkage uint32 }
+		}
+		typLen  = uint32(binary.Size(&types))
+		strings = []byte{0, 'a', 0}
+		header  = btfHeader{
+			Magic:     btfMagic,
+			Version:   1,
+			HdrLen:    minHeaderLength,
+			TypeOff:   0,
+			TypeLen:   typLen,
+			StringOff: typLen,
+			StringLen: uint32(len(strings)),
+		}
+	)
+
+	// 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
+
+	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() bool {
+	btf := minimalBTF(internal.NativeEndian)
+	fd, err := bpfLoadBTF(&bpfLoadBTFAttr{
+		btf:     internal.NewSlicePointer(btf),
+		btfSize: uint32(len(btf)),
+	})
+	if err == nil {
+		fd.Close()
+	}
+	// Check for EINVAL specifically, rather than err != nil since we
+	// otherwise misdetect due to insufficient permissions.
+	return !xerrors.Is(err, unix.EINVAL)
+})

vendor/github.com/cilium/ebpf/internal/btf/btf_types.go

+package btf
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+
+	"golang.org/x/xerrors"
+)
+
+// btfKind describes a Type.
+type btfKind uint8
+
+// Equivalents of the BTF_KIND_* constants.
+const (
+	kindUnknown btfKind = iota
+	kindInt
+	kindPointer
+	kindArray
+	kindStruct
+	kindUnion
+	kindEnum
+	kindForward
+	kindTypedef
+	kindVolatile
+	kindConst
+	kindRestrict
+	// Added ~4.20
+	kindFunc
+	kindFuncProto
+	// Added ~5.1
+	kindVar
+	kindDatasec
+)
+
+const (
+	btfTypeKindShift = 24
+	btfTypeKindLen   = 4
+	btfTypeVlenShift = 0
+	btfTypeVlenMask  = 16
+)
+
+// btfType is equivalent to struct btf_type in Documentation/bpf/btf.rst.
+type btfType struct {
+	NameOff uint32
+	/* "info" bits arrangement
+	 * bits  0-15: vlen (e.g. # of struct's members)
+	 * bits 16-23: unused
+	 * bits 24-27: kind (e.g. int, ptr, array...etc)
+	 * bits 28-30: unused
+	 * bit     31: kind_flag, currently used by
+	 *             struct, union and fwd
+	 */
+	Info uint32
+	/* "size" is used by INT, ENUM, STRUCT and UNION.
+	 * "size" tells the size of the type it is describing.
+	 *
+	 * "type" is used by PTR, TYPEDEF, VOLATILE, CONST, RESTRICT,
+	 * FUNC and FUNC_PROTO.
+	 * "type" is a type_id referring to another type.
+	 */
+	SizeType uint32
+}
+
+func (k btfKind) String() string {
+	switch k {
+	case kindUnknown:
+		return "Unknown"
+	case kindInt:
+		return "Integer"
+	case kindPointer:
+		return "Pointer"
+	case kindArray:
+		return "Array"
+	case kindStruct:
+		return "Struct"
+	case kindUnion:
+		return "Union"
+	case kindEnum:
+		return "Enumeration"
+	case kindForward:
+		return "Forward"
+	case kindTypedef:
+		return "Typedef"
+	case kindVolatile:
+		return "Volatile"
+	case kindConst:
+		return "Const"
+	case kindRestrict:
+		return "Restrict"
+	case kindFunc:
+		return "Function"
+	case kindFuncProto:
+		return "Function Proto"
+	case kindVar:
+		return "Variable"
+	case kindDatasec:
+		return "Section"
+	default:
+		return fmt.Sprintf("Unknown (%d)", k)
+	}
+}
+
+func mask(len uint32) uint32 {
+	return (1 << len) - 1
+}
+
+func (bt *btfType) info(len, shift uint32) uint32 {
+	return (bt.Info >> shift) & mask(len)
+}
+
+func (bt *btfType) setInfo(value, len, shift uint32) {
+	bt.Info &^= mask(len) << shift
+	bt.Info |= (value & mask(len)) << shift
+}
+
+func (bt *btfType) Kind() btfKind {
+	return btfKind(bt.info(btfTypeKindLen, btfTypeKindShift))
+}
+
+func (bt *btfType) SetKind(kind btfKind) {
+	bt.setInfo(uint32(kind), btfTypeKindLen, btfTypeKindShift)
+}
+
+func (bt *btfType) Vlen() int {
+	return int(bt.info(btfTypeVlenMask, btfTypeVlenShift))
+}
+
+func (bt *btfType) SetVlen(vlen int) {
+	bt.setInfo(uint32(vlen), btfTypeVlenMask, btfTypeVlenShift)
+}
+
+func (bt *btfType) Type() TypeID {
+	// TODO: Panic here if wrong kind?
+	return TypeID(bt.SizeType)
+}
+
+func (bt *btfType) Size() uint32 {
+	// TODO: Panic here if wrong kind?
+	return bt.SizeType
+}
+
+type rawType struct {
+	btfType
+	data interface{}
+}
+
+func (rt *rawType) Marshal(w io.Writer, bo binary.ByteOrder) error {
+	if err := binary.Write(w, bo, &rt.btfType); err != nil {
+		return err
+	}
+
+	if rt.data == nil {
+		return nil
+	}
+
+	return binary.Write(w, bo, rt.data)
+}
+
+type btfArray struct {
+	Type      TypeID
+	IndexType TypeID
+	Nelems    uint32
+}
+
+type btfMember struct {
+	NameOff uint32
+	Type    TypeID
+	Offset  uint32
+}
+
+type btfVarSecinfo struct {
+	Type   TypeID
+	Offset uint32
+	Size   uint32
+}
+
+type btfVariable struct {
+	Linkage uint32
+}
+
+func readTypes(r io.Reader, bo binary.ByteOrder) ([]rawType, error) {
+	var (
+		header btfType
+		types  []rawType
+	)
+
+	for id := TypeID(1); ; id++ {
+		if err := binary.Read(r, bo, &header); err == io.EOF {
+			return types, nil
+		} else if err != nil {
+			return nil, xerrors.Errorf("can't read type info for id %v: %v", id, err)
+		}
+
+		var data interface{}
+		switch header.Kind() {
+		case kindInt:
+			// sizeof(uint32)
+			data = make([]byte, 4)
+		case kindPointer:
+		case kindArray:
+			data = new(btfArray)
+		case kindStruct:
+			fallthrough
+		case kindUnion:
+			data = make([]btfMember, header.Vlen())
+		case kindEnum:
+			// sizeof(struct btf_enum)
+			data = make([]byte, header.Vlen()*4*2)
+		case kindForward:
+		case kindTypedef:
+		case kindVolatile:
+		case kindConst:
+		case kindRestrict:
+		case kindFunc:
+		case kindFuncProto:
+			// sizeof(struct btf_param)
+			data = make([]byte, header.Vlen()*4*2)
+		case kindVar:
+			data = new(btfVariable)
+		case kindDatasec:
+			data = make([]btfVarSecinfo, header.Vlen())
+		default:
+			return nil, xerrors.Errorf("type id %v: unknown kind: %v", id, header.Kind())
+		}
+
+		if data == nil {
+			types = append(types, rawType{header, nil})
+			continue
+		}
+
+		if err := binary.Read(r, bo, data); err != nil {
+			return nil, xerrors.Errorf("type id %d: kind %v: can't read %T: %v", id, header.Kind(), data, err)
+		}
+
+		types = append(types, rawType{header, data})
+	}
+}

vendor/github.com/cilium/ebpf/internal/btf/doc.go

+// Package btf handles data encoded according to the BPF Type Format.
+//
+// The canonical documentation lives in the Linux kernel repository and is
+// available at https://www.kernel.org/doc/html/latest/bpf/btf.html
+//
+// The API is very much unstable. You should only use this via the main
+// ebpf library.
+package btf

vendor/github.com/cilium/ebpf/internal/btf/ext_info.go

+package btf
+
+import (
+	"bytes"
+	"encoding/binary"
+	"io"
+	"io/ioutil"
+
+	"github.com/cilium/ebpf/asm"
+	"github.com/cilium/ebpf/internal"
+
+	"golang.org/x/xerrors"
+)
+
+type btfExtHeader struct {
+	Magic   uint16
+	Version uint8
+	Flags   uint8
+	HdrLen  uint32
+
+	FuncInfoOff uint32
+	FuncInfoLen uint32
+	LineInfoOff uint32
+	LineInfoLen uint32
+}
+
+func parseExtInfos(r io.ReadSeeker, bo binary.ByteOrder, strings stringTable) (funcInfo, lineInfo map[string]extInfo, err error) {
+	var header btfExtHeader
+	if err := binary.Read(r, bo, &header); err != nil {
+		return nil, nil, xerrors.Errorf("can't read header: %v", err)
+	}
+
+	if header.Magic != btfMagic {
+		return nil, nil, xerrors.Errorf("incorrect magic value %v", header.Magic)
+	}
+
+	if header.Version != 1 {
+		return nil, nil, xerrors.Errorf("unexpected version %v", header.Version)
+	}
+
+	if header.Flags != 0 {
+		return nil, nil, xerrors.Errorf("unsupported flags %v", header.Flags)
+	}
+
+	remainder := int64(header.HdrLen) - int64(binary.Size(&header))
+	if remainder < 0 {
+		return nil, nil, xerrors.New("header is too short")
+	}
+
+	// Of course, the .BTF.ext header has different semantics than the
+	// .BTF ext header. We need to ignore non-null values.
+	_, err = io.CopyN(ioutil.Discard, r, remainder)
+	if err != nil {
+		return nil, nil, xerrors.Errorf("header padding: %v", err)
+	}
+
+	if _, err := r.Seek(int64(header.HdrLen+header.FuncInfoOff), io.SeekStart); err != nil {
+		return nil, nil, xerrors.Errorf("can't seek to function info section: %v", err)
+	}
+
+	funcInfo, err = parseExtInfo(io.LimitReader(r, int64(header.FuncInfoLen)), bo, strings)
+	if err != nil {
+		return nil, nil, xerrors.Errorf("function info: %w", err)
+	}
+
+	if _, err := r.Seek(int64(header.HdrLen+header.LineInfoOff), io.SeekStart); err != nil {
+		return nil, nil, xerrors.Errorf("can't seek to line info section: %v", err)
+	}
+
+	lineInfo, err = parseExtInfo(io.LimitReader(r, int64(header.LineInfoLen)), bo, strings)
+	if err != nil {
+		return nil, nil, xerrors.Errorf("line info: %w", err)
+	}
+
+	return funcInfo, lineInfo, nil
+}
+
+type btfExtInfoSec struct {
+	SecNameOff uint32
+	NumInfo    uint32
+}
+
+type extInfoRecord struct {
+	InsnOff uint64
+	Opaque  []byte
+}
+
+type extInfo struct {
+	recordSize uint32
+	records    []extInfoRecord
+}
+
+func (ei extInfo) append(other extInfo, offset uint64) (extInfo, error) {
+	if other.recordSize != ei.recordSize {
+		return extInfo{}, xerrors.Errorf("ext_info record size mismatch, want %d (got %d)", ei.recordSize, other.recordSize)
+	}
+
+	records := make([]extInfoRecord, 0, len(ei.records)+len(other.records))
+	records = append(records, ei.records...)
+	for _, info := range other.records {
+		records = append(records, extInfoRecord{
+			InsnOff: info.InsnOff + offset,
+			Opaque:  info.Opaque,
+		})
+	}
+	return extInfo{ei.recordSize, records}, nil
+}
+
+func (ei extInfo) MarshalBinary() ([]byte, error) {
+	if len(ei.records) == 0 {
+		return nil, nil
+	}
+
+	buf := bytes.NewBuffer(make([]byte, 0, int(ei.recordSize)*len(ei.records)))
+	for _, info := range ei.records {
+		// The kernel expects offsets in number of raw bpf instructions,
+		// while the ELF tracks it in bytes.
+		insnOff := uint32(info.InsnOff / asm.InstructionSize)
+		if err := binary.Write(buf, internal.NativeEndian, insnOff); err != nil {
+			return nil, xerrors.Errorf("can't write instruction offset: %v", err)
+		}
+
+		buf.Write(info.Opaque)
+	}
+
+	return buf.Bytes(), nil
+}
+
+func parseExtInfo(r io.Reader, bo binary.ByteOrder, strings stringTable) (map[string]extInfo, error) {
+	var recordSize uint32
+	if err := binary.Read(r, bo, &recordSize); err != nil {
+		return nil, xerrors.Errorf("can't read record size: %v", err)
+	}
+
+	if recordSize < 4 {
+		// Need at least insnOff
+		return nil, xerrors.New("record size too short")
+	}
+
+	result := make(map[string]extInfo)
+	for {
+		var infoHeader btfExtInfoSec
+		if err := binary.Read(r, bo, &infoHeader); err == io.EOF {
+			return result, nil
+		} else if err != nil {
+			return nil, xerrors.Errorf("can't read ext info header: %v", err)
+		}
+
+		secName, err := strings.Lookup(infoHeader.SecNameOff)
+		if err != nil {
+			return nil, xerrors.Errorf("can't get section name: %w", err)
+		}
+
+		if infoHeader.NumInfo == 0 {
+			return nil, xerrors.Errorf("section %s has invalid number of records", secName)
+		}
+
+		var records []extInfoRecord
+		for i := uint32(0); i < infoHeader.NumInfo; i++ {
+			var byteOff uint32
+			if err := binary.Read(r, bo, &byteOff); err != nil {
+				return nil, xerrors.Errorf("section %v: can't read extended info offset: %v", secName, err)
+			}
+
+			buf := make([]byte, int(recordSize-4))
+			if _, err := io.ReadFull(r, buf); err != nil {
+				return nil, xerrors.Errorf("section %v: can't read record: %v", secName, err)
+			}
+
+			if byteOff%asm.InstructionSize != 0 {
+				return nil, xerrors.Errorf("section %v: offset %v is not aligned with instruction size", secName, byteOff)
+			}
+
+			records = append(records, extInfoRecord{uint64(byteOff), buf})
+		}
+
+		result[secName] = extInfo{
+			recordSize,
+			records,
+		}
+	}
+}

vendor/github.com/cilium/ebpf/internal/btf/strings.go

+package btf
+
+import (
+	"bytes"
+	"io"
+	"io/ioutil"
+
+	"golang.org/x/xerrors"
+)
+
+type stringTable []byte
+
+func readStringTable(r io.Reader) (stringTable, error) {
+	contents, err := ioutil.ReadAll(r)
+	if err != nil {
+		return nil, xerrors.Errorf("can't read string table: %v", err)
+	}
+
+	if len(contents) < 1 {
+		return nil, xerrors.New("string table is empty")
+	}
+
+	if contents[0] != '\x00' {
+		return nil, xerrors.New("first item in string table is non-empty")
+	}
+
+	if contents[len(contents)-1] != '\x00' {
+		return nil, xerrors.New("string table isn't null terminated")
+	}
+
+	return stringTable(contents), nil
+}
+
+func (st stringTable) Lookup(offset uint32) (string, error) {
+	if int64(offset) > int64(^uint(0)>>1) {
+		return "", xerrors.Errorf("offset %d overflows int", offset)
+	}
+
+	pos := int(offset)
+	if pos >= len(st) {
+		return "", xerrors.Errorf("offset %d is out of bounds", offset)
+	}
+
+	if pos > 0 && st[pos-1] != '\x00' {
+		return "", xerrors.Errorf("offset %d isn't start of a string", offset)
+	}
+
+	str := st[pos:]
+	end := bytes.IndexByte(str, '\x00')
+	if end == -1 {
+		return "", xerrors.Errorf("offset %d isn't null terminated", offset)
+	}
+
+	return string(str[:end]), nil
+}
+
+func (st stringTable) LookupName(offset uint32) (Name, error) {
+	str, err := st.Lookup(offset)
+	return Name(str), err
+}

vendor/github.com/cilium/ebpf/internal/btf/types.go

+package btf
+
+import (
+	"math"
+
+	"golang.org/x/xerrors"
+)
+
+const maxTypeDepth = 32
+
+// TypeID identifies a type in a BTF section.
+type TypeID uint32
+
+// ID implements part of the Type interface.
+func (tid TypeID) ID() TypeID {
+	return tid
+}
+
+// Type represents a type described by BTF.
+type Type interface {
+	ID() TypeID
+
+	// Make a copy of the type, without copying Type members.
+	copy() Type
+
+	walk(*copyStack)
+}
+
+// Name identifies a type.
+//
+// Anonymous types have an empty name.
+type Name string
+
+func (n Name) name() string {
+	return string(n)
+}
+
+// Void is the unit type of BTF.
+type Void struct{}
+
+func (v Void) ID() TypeID      { return 0 }
+func (v Void) copy() Type      { return Void{} }
+func (v Void) walk(*copyStack) {}
+
+// Int is an integer of a given length.
+type Int struct {
+	TypeID
+	Name
+
+	// The size of the integer in bytes.
+	Size uint32
+}
+
+func (i *Int) size() uint32    { return i.Size }
+func (i *Int) walk(*copyStack) {}
+func (i *Int) copy() Type {
+	cpy := *i
+	return &cpy
+}
+
+// Pointer is a pointer to another type.
+type Pointer struct {
+	TypeID
+	Target Type
+}
+
+func (p *Pointer) size() uint32       { return 8 }
+func (p *Pointer) walk(cs *copyStack) { cs.push(&p.Target) }
+func (p *Pointer) copy() Type {
+	cpy := *p
+	return &cpy
+}
+
+// Array is an array with a fixed number of elements.
+type Array struct {
+	TypeID
+	Type   Type
+	Nelems uint32
+}
+
+func (arr *Array) walk(cs *copyStack) { cs.push(&arr.Type) }
+func (arr *Array) copy() Type {
+	cpy := *arr
+	return &cpy
+}
+
+// Struct is a compound type of consecutive members.
+type Struct struct {
+	TypeID
+	Name
+	// The size of the struct including padding, in bytes
+	Size    uint32
+	Members []Member
+}
+
+func (s *Struct) size() uint32 { return s.Size }
+
+func (s *Struct) walk(cs *copyStack) {
+	for i := range s.Members {
+		cs.push(&s.Members[i].Type)
+	}
+}
+
+func (s *Struct) copy() Type {
+	cpy := *s
+	cpy.Members = make([]Member, len(s.Members))
+	copy(cpy.Members, s.Members)
+	return &cpy
+}
+
+// Union is a compound type where members occupy the same memory.
+type Union struct {
+	TypeID
+	Name
+	// The size of the union including padding, in bytes.
+	Size    uint32
+	Members []Member
+}
+
+func (u *Union) size() uint32 { return u.Size }
+
+func (u *Union) walk(cs *copyStack) {
+	for i := range u.Members {
+		cs.push(&u.Members[i].Type)
+	}
+}
+
+func (u *Union) copy() Type {
+	cpy := *u
+	cpy.Members = make([]Member, len(u.Members))
+	copy(cpy.Members, u.Members)
+	return &cpy
+}
+
+// Member is part of a Struct or Union.
+//
+// It is not a valid Type.
+type Member struct {
+	Name
+	Type   Type
+	Offset uint32
+}
+
+// Enum lists possible values.
+type Enum struct {
+	TypeID
+	Name
+}
+
+func (e *Enum) size() uint32    { return 4 }
+func (e *Enum) walk(*copyStack) {}
+func (e *Enum) copy() Type {
+	cpy := *e
+	return &cpy
+}
+
+// Fwd is a forward declaration of a Type.
+type Fwd struct {
+	TypeID
+	Name
+}
+
+func (f *Fwd) walk(*copyStack) {}
+func (f *Fwd) copy() Type {
+	cpy := *f
+	return &cpy
+}
+
+// Typedef is an alias of a Type.
+type Typedef struct {
+	TypeID
+	Name
+	Type Type
+}
+
+func (td *Typedef) walk(cs *copyStack) { cs.push(&td.Type) }
+func (td *Typedef) copy() Type {
+	cpy := *td
+	return &cpy
+}
+
+// Volatile is a modifier.
+type Volatile struct {
+	TypeID
+	Type Type
+}
+
+func (v *Volatile) walk(cs *copyStack) { cs.push(&v.Type) }
+func (v *Volatile) copy() Type {
+	cpy := *v
+	return &cpy
+}
+
+// Const is a modifier.
+type Const struct {
+	TypeID
+	Type Type
+}
+
+func (c *Const) walk(cs *copyStack) { cs.push(&c.Type) }
+func (c *Const) copy() Type {
+	cpy := *c
+	return &cpy
+}
+
+// Restrict is a modifier.
+type Restrict struct {
+	TypeID
+	Type Type
+}
+
+func (r *Restrict) walk(cs *copyStack) { cs.push(&r.Type) }
+func (r *Restrict) copy() Type {
+	cpy := *r
+	return &cpy
+}
+
+// Func is a function definition.
+type Func struct {
+	TypeID
+	Name
+	Type Type
+}
+
+func (f *Func) walk(cs *copyStack) { cs.push(&f.Type) }
+func (f *Func) copy() Type {
+	cpy := *f
+	return &cpy
+}
+
+// FuncProto is a function declaration.
+type FuncProto struct {
+	TypeID
+	Return Type
+	// Parameters not supported yet
+}
+
+func (fp *FuncProto) walk(cs *copyStack) { cs.push(&fp.Return) }
+func (fp *FuncProto) copy() Type {
+	cpy := *fp
+	return &cpy
+}
+
+// Var is a global variable.
+type Var struct {
+	TypeID
+	Name
+	Type Type
+}
+
+func (v *Var) walk(cs *copyStack) { cs.push(&v.Type) }
+func (v *Var) copy() Type {
+	cpy := *v
+	return &cpy
+}
+
+// Datasec is a global program section containing data.
+type Datasec struct {
+	TypeID
+	Name
+	Size uint32
+	Vars []VarSecinfo
+}
+
+func (ds *Datasec) size() uint32 { return ds.Size }
+
+func (ds *Datasec) walk(cs *copyStack) {
+	for i := range ds.Vars {
+		cs.push(&ds.Vars[i].Type)
+	}
+}
+
+func (ds *Datasec) copy() Type {
+	cpy := *ds
+	cpy.Vars = make([]VarSecinfo, len(ds.Vars))
+	copy(cpy.Vars, ds.Vars)
+	return &cpy
+}
+
+// VarSecinfo describes variable in a Datasec
+type VarSecinfo struct {
+	Type   Type
+	Offset uint32
+	Size   uint32
+}
+
+type sizer interface {
+	size() uint32
+}
+
+var (
+	_ sizer = (*Int)(nil)
+	_ sizer = (*Pointer)(nil)
+	_ sizer = (*Struct)(nil)
+	_ sizer = (*Union)(nil)
+	_ sizer = (*Enum)(nil)
+	_ sizer = (*Datasec)(nil)
+)
+
+// Sizeof returns the size of a type in bytes.
+//
+// Returns an error if the size can't be computed.
+func Sizeof(typ Type) (int, error) {
+	var (
+		n    = int64(1)
+		elem int64
+	)
+
+	for i := 0; i < maxTypeDepth; i++ {
+		switch v := typ.(type) {
+		case *Array:
+			if n > 0 && int64(v.Nelems) > math.MaxInt64/n {
+				return 0, xerrors.New("overflow")
+			}
+
+			// Arrays may be of zero length, which allows
+			// n to be zero as well.
+			n *= int64(v.Nelems)
+			typ = v.Type
+			continue
+
+		case sizer:
+			elem = int64(v.size())
+
+		case *Typedef:
+			typ = v.Type
+			continue
+		case *Volatile:
+			typ = v.Type
+			continue
+		case *Const:
+			typ = v.Type
+			continue
+		case *Restrict:
+			typ = v.Type
+			continue
+
+		default:
+			return 0, xerrors.Errorf("unrecognized type %T", typ)
+		}
+
+		if n > 0 && elem > math.MaxInt64/n {
+			return 0, xerrors.New("overflow")
+		}
+
+		size := n * elem
+		if int64(int(size)) != size {
+			return 0, xerrors.New("overflow")
+		}
+
+		return int(size), nil
+	}
+
+	return 0, xerrors.New("exceeded type depth")
+}
+
+// copy a Type recursively.
+//
+// typ may form a cycle.
+func copyType(typ Type) Type {
+	var (
+		copies = make(map[Type]Type)
+		work   copyStack
+	)
+
+	for t := &typ; t != nil; t = work.pop() {
+		// *t is the identity of the type.
+		if cpy := copies[*t]; cpy != nil {
+			*t = cpy
+			continue
+		}
+
+		cpy := (*t).copy()
+		copies[*t] = cpy
+		*t = cpy
+
+		// Mark any nested types for copying.
+		cpy.walk(&work)
+	}
+
+	return typ
+}
+
+// copyStack keeps track of pointers to types which still
+// need to be copied.
+type copyStack []*Type
+
+// push adds a type to the stack.
+func (cs *copyStack) push(t *Type) {
+	*cs = append(*cs, t)
+}
+
+// pop returns the topmost Type, or nil.
+func (cs *copyStack) pop() *Type {
+	n := len(*cs)
+	if n == 0 {
+		return nil
+	}
+
+	t := (*cs)[n-1]
+	*cs = (*cs)[:n-1]
+	return t
+}
+
+type namer interface {
+	name() string
+}
+
+var _ namer = Name("")
+
+// inflateRawTypes takes a list of raw btf types linked via type IDs, and turns
+// it into a graph of Types connected via pointers.
+//
+// Returns a map of named types (so, where NameOff is non-zero). Since BTF ignores
+// compilation units, multiple types may share the same name. A Type may form a
+// cyclic graph by pointing at itself.
+func inflateRawTypes(rawTypes []rawType, rawStrings stringTable) (namedTypes map[string][]Type, err error) {
+	type fixupDef struct {
+		id           TypeID
+		expectedKind btfKind
+		typ          *Type
+	}
+
+	var fixups []fixupDef
+	fixup := func(id TypeID, expectedKind btfKind, typ *Type) {
+		fixups = append(fixups, fixupDef{id, expectedKind, typ})
+	}
+
+	convertMembers := func(raw []btfMember) ([]Member, error) {
+		// NB: The fixup below relies on pre-allocating this array to
+		// work, since otherwise append might re-allocate members.
+		members := make([]Member, 0, len(raw))
+		for i, btfMember := range raw {
+			name, err := rawStrings.LookupName(btfMember.NameOff)
+			if err != nil {
+				return nil, xerrors.Errorf("can't get name for member %d: %w", i, err)
+			}
+			members = append(members, Member{
+				Name:   name,
+				Offset: btfMember.Offset,
+			})
+		}
+		for i := range members {
+			fixup(raw[i].Type, kindUnknown, &members[i].Type)
+		}
+		return members, nil
+	}
+
+	types := make([]Type, 0, len(rawTypes))
+	types = append(types, Void{})
+	namedTypes = make(map[string][]Type)
+
+	for i, raw := range rawTypes {
+		var (
+			// Void is defined to always be type ID 0, and is thus
+			// omitted from BTF.
+			id  = TypeID(i + 1)
+			typ Type
+		)
+
+		name, err := rawStrings.LookupName(raw.NameOff)
+		if err != nil {
+			return nil, xerrors.Errorf("can't get name for type id %d: %w", id, err)
+		}
+
+		switch raw.Kind() {
+		case kindInt:
+			typ = &Int{id, name, raw.Size()}
+
+		case kindPointer:
+			ptr := &Pointer{id, nil}
+			fixup(raw.Type(), kindUnknown, &ptr.Target)
+			typ = ptr
+
+		case kindArray:
+			btfArr := raw.data.(*btfArray)
+
+			// IndexType is unused according to btf.rst.
+			// Don't make it available right now.
+			arr := &Array{id, nil, btfArr.Nelems}
+			fixup(btfArr.Type, kindUnknown, &arr.Type)
+			typ = arr
+
+		case kindStruct:
+			members, err := convertMembers(raw.data.([]btfMember))
+			if err != nil {
+				return nil, xerrors.Errorf("struct %s (id %d): %w", name, id, err)
+			}
+			typ = &Struct{id, name, raw.Size(), members}
+
+		case kindUnion:
+			members, err := convertMembers(raw.data.([]btfMember))
+			if err != nil {
+				return nil, xerrors.Errorf("union %s (id %d): %w", name, id, err)
+			}
+			typ = &Union{id, name, raw.Size(), members}
+
+		case kindEnum:
+			typ = &Enum{id, name}
+
+		case kindForward:
+			typ = &Fwd{id, name}
+
+		case kindTypedef:
+			typedef := &Typedef{id, name, nil}
+			fixup(raw.Type(), kindUnknown, &typedef.Type)
+			typ = typedef
+
+		case kindVolatile:
+			volatile := &Volatile{id, nil}
+			fixup(raw.Type(), kindUnknown, &volatile.Type)
+			typ = volatile
+
+		case kindConst:
+			cnst := &Const{id, nil}
+			fixup(raw.Type(), kindUnknown, &cnst.Type)
+			typ = cnst
+
+		case kindRestrict:
+			restrict := &Restrict{id, nil}
+			fixup(raw.Type(), kindUnknown, &restrict.Type)
+			typ = restrict
+
+		case kindFunc:
+			fn := &Func{id, name, nil}
+			fixup(raw.Type(), kindFuncProto, &fn.Type)
+			typ = fn
+
+		case kindFuncProto:
+			fp := &FuncProto{id, nil}
+			fixup(raw.Type(), kindUnknown, &fp.Return)
+			typ = fp
+
+		case kindVar:
+			v := &Var{id, name, nil}
+			fixup(raw.Type(), kindUnknown, &v.Type)
+			typ = v
+
+		case kindDatasec:
+			btfVars := raw.data.([]btfVarSecinfo)
+			vars := make([]VarSecinfo, 0, len(btfVars))
+			for _, btfVar := range btfVars {
+				vars = append(vars, VarSecinfo{
+					Offset: btfVar.Offset,
+					Size:   btfVar.Size,
+				})
+			}
+			for i := range vars {
+				fixup(btfVars[i].Type, kindVar, &vars[i].Type)
+			}
+			typ = &Datasec{id, name, raw.SizeType, vars}
+
+		default:
+			return nil, xerrors.Errorf("type id %d: unknown kind: %v", id, raw.Kind())
+		}
+
+		types = append(types, typ)
+
+		if namer, ok := typ.(namer); ok {
+			if name := namer.name(); name != "" {
+				namedTypes[name] = append(namedTypes[name], typ)
+			}
+		}
+	}
+
+	for _, fixup := range fixups {
+		i := int(fixup.id)
+		if i >= len(types) {
+			return nil, xerrors.Errorf("reference to invalid type id: %d", fixup.id)
+		}
+
+		// Default void (id 0) to unknown
+		rawKind := kindUnknown
+		if i > 0 {
+			rawKind = rawTypes[i-1].Kind()
+		}
+
+		if expected := fixup.expectedKind; expected != kindUnknown && rawKind != expected {
+			return nil, xerrors.Errorf("expected type id %d to have kind %s, found %s", fixup.id, expected, rawKind)
+		}
+
+		*fixup.typ = types[i]
+	}
+
+	return namedTypes, nil
+}