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btf_types.go
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/
btf_types.go
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package btf
import (
"encoding/binary"
"errors"
"fmt"
"io"
"unsafe"
"github.com/cilium/ebpf/internal"
)
//go:generate go run golang.org/x/tools/cmd/stringer@latest -linecomment -output=btf_types_string.go -type=FuncLinkage,VarLinkage,btfKind
// btfKind describes a Type.
type btfKind uint8
// Equivalents of the BTF_KIND_* constants.
const (
kindUnknown btfKind = iota // Unknown
kindInt // Int
kindPointer // Pointer
kindArray // Array
kindStruct // Struct
kindUnion // Union
kindEnum // Enum
kindForward // Forward
kindTypedef // Typedef
kindVolatile // Volatile
kindConst // Const
kindRestrict // Restrict
// Added ~4.20
kindFunc // Func
kindFuncProto // FuncProto
// Added ~5.1
kindVar // Var
kindDatasec // Datasec
// Added ~5.13
kindFloat // Float
// Added 5.16
kindDeclTag // DeclTag
kindTypeTag // TypeTag
// Added 6.0
kindEnum64 // Enum64
)
// FuncLinkage describes BTF function linkage metadata.
type FuncLinkage int
// Equivalent of enum btf_func_linkage.
const (
StaticFunc FuncLinkage = iota // static
GlobalFunc // global
ExternFunc // extern
)
// VarLinkage describes BTF variable linkage metadata.
type VarLinkage int
const (
StaticVar VarLinkage = iota // static
GlobalVar // global
ExternVar // extern
)
const (
btfTypeKindShift = 24
btfTypeKindLen = 5
btfTypeVlenShift = 0
btfTypeVlenMask = 16
btfTypeKindFlagShift = 31
btfTypeKindFlagMask = 1
)
var btfHeaderLen = binary.Size(&btfHeader{})
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)
}
// 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
}
var btfTypeLen = binary.Size(btfType{})
// 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), linkage
* bits 16-23: unused
* bits 24-28: kind (e.g. int, ptr, array...etc)
* bits 29-30: 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
}
var btfTypeSize = int(unsafe.Sizeof(btfType{}))
func unmarshalBtfType(bt *btfType, b []byte, bo binary.ByteOrder) (int, error) {
if len(b) < btfTypeSize {
return 0, fmt.Errorf("not enough bytes to unmarshal btfType")
}
bt.NameOff = bo.Uint32(b[0:])
bt.Info = bo.Uint32(b[4:])
bt.SizeType = bo.Uint32(b[8:])
return btfTypeSize, nil
}
func mask(len uint32) uint32 {
return (1 << len) - 1
}
func readBits(value, len, shift uint32) uint32 {
return (value >> shift) & mask(len)
}
func writeBits(value, len, shift, new uint32) uint32 {
value &^= mask(len) << shift
value |= (new & mask(len)) << shift
return value
}
func (bt *btfType) info(len, shift uint32) uint32 {
return readBits(bt.Info, len, shift)
}
func (bt *btfType) setInfo(value, len, shift uint32) {
bt.Info = writeBits(bt.Info, len, shift, value)
}
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) kindFlagBool() bool {
return bt.info(btfTypeKindFlagMask, btfTypeKindFlagShift) == 1
}
func (bt *btfType) setKindFlagBool(set bool) {
var value uint32
if set {
value = 1
}
bt.setInfo(value, btfTypeKindFlagMask, btfTypeKindFlagShift)
}
// Bitfield returns true if the struct or union contain a bitfield.
func (bt *btfType) Bitfield() bool {
return bt.kindFlagBool()
}
func (bt *btfType) SetBitfield(isBitfield bool) {
bt.setKindFlagBool(isBitfield)
}
func (bt *btfType) FwdKind() FwdKind {
return FwdKind(bt.info(btfTypeKindFlagMask, btfTypeKindFlagShift))
}
func (bt *btfType) SetFwdKind(kind FwdKind) {
bt.setInfo(uint32(kind), btfTypeKindFlagMask, btfTypeKindFlagShift)
}
func (bt *btfType) Signed() bool {
return bt.kindFlagBool()
}
func (bt *btfType) SetSigned(signed bool) {
bt.setKindFlagBool(signed)
}
func (bt *btfType) Linkage() FuncLinkage {
return FuncLinkage(bt.info(btfTypeVlenMask, btfTypeVlenShift))
}
func (bt *btfType) SetLinkage(linkage FuncLinkage) {
bt.setInfo(uint32(linkage), btfTypeVlenMask, btfTypeVlenShift)
}
func (bt *btfType) Type() TypeID {
// TODO: Panic here if wrong kind?
return TypeID(bt.SizeType)
}
func (bt *btfType) SetType(id TypeID) {
bt.SizeType = uint32(id)
}
func (bt *btfType) Size() uint32 {
// TODO: Panic here if wrong kind?
return bt.SizeType
}
func (bt *btfType) SetSize(size uint32) {
bt.SizeType = size
}
func (bt *btfType) Marshal(w io.Writer, bo binary.ByteOrder) error {
buf := make([]byte, unsafe.Sizeof(*bt))
bo.PutUint32(buf[0:], bt.NameOff)
bo.PutUint32(buf[4:], bt.Info)
bo.PutUint32(buf[8:], bt.SizeType)
_, err := w.Write(buf)
return err
}
type rawType struct {
btfType
data interface{}
}
func (rt *rawType) Marshal(w io.Writer, bo binary.ByteOrder) error {
if err := rt.btfType.Marshal(w, bo); err != nil {
return err
}
if rt.data == nil {
return nil
}
return binary.Write(w, bo, rt.data)
}
// btfInt encodes additional data for integers.
//
// ? ? ? ? e e e e o o o o o o o o ? ? ? ? ? ? ? ? b b b b b b b b
// ? = undefined
// e = encoding
// o = offset (bitfields?)
// b = bits (bitfields)
type btfInt struct {
Raw uint32
}
const (
btfIntEncodingLen = 4
btfIntEncodingShift = 24
btfIntOffsetLen = 8
btfIntOffsetShift = 16
btfIntBitsLen = 8
btfIntBitsShift = 0
)
var btfIntLen = int(unsafe.Sizeof(btfInt{}))
func unmarshalBtfInt(bi *btfInt, b []byte, bo binary.ByteOrder) (int, error) {
if len(b) < btfIntLen {
return 0, fmt.Errorf("not enough bytes to unmarshal btfInt")
}
bi.Raw = bo.Uint32(b[0:])
return btfIntLen, nil
}
func (bi btfInt) Encoding() IntEncoding {
return IntEncoding(readBits(bi.Raw, btfIntEncodingLen, btfIntEncodingShift))
}
func (bi *btfInt) SetEncoding(e IntEncoding) {
bi.Raw = writeBits(uint32(bi.Raw), btfIntEncodingLen, btfIntEncodingShift, uint32(e))
}
func (bi btfInt) Offset() Bits {
return Bits(readBits(bi.Raw, btfIntOffsetLen, btfIntOffsetShift))
}
func (bi *btfInt) SetOffset(offset uint32) {
bi.Raw = writeBits(bi.Raw, btfIntOffsetLen, btfIntOffsetShift, offset)
}
func (bi btfInt) Bits() Bits {
return Bits(readBits(bi.Raw, btfIntBitsLen, btfIntBitsShift))
}
func (bi *btfInt) SetBits(bits byte) {
bi.Raw = writeBits(bi.Raw, btfIntBitsLen, btfIntBitsShift, uint32(bits))
}
type btfArray struct {
Type TypeID
IndexType TypeID
Nelems uint32
}
var btfArrayLen = int(unsafe.Sizeof(btfArray{}))
func unmarshalBtfArray(ba *btfArray, b []byte, bo binary.ByteOrder) (int, error) {
if len(b) < btfArrayLen {
return 0, fmt.Errorf("not enough bytes to unmarshal btfArray")
}
ba.Type = TypeID(bo.Uint32(b[0:]))
ba.IndexType = TypeID(bo.Uint32(b[4:]))
ba.Nelems = bo.Uint32(b[8:])
return btfArrayLen, nil
}
type btfMember struct {
NameOff uint32
Type TypeID
Offset uint32
}
var btfMemberLen = int(unsafe.Sizeof(btfMember{}))
func unmarshalBtfMembers(members []btfMember, b []byte, bo binary.ByteOrder) (int, error) {
off := 0
for i := range members {
if off+btfMemberLen > len(b) {
return 0, fmt.Errorf("not enough bytes to unmarshal btfMember %d", i)
}
members[i].NameOff = bo.Uint32(b[off+0:])
members[i].Type = TypeID(bo.Uint32(b[off+4:]))
members[i].Offset = bo.Uint32(b[off+8:])
off += btfMemberLen
}
return off, nil
}
type btfVarSecinfo struct {
Type TypeID
Offset uint32
Size uint32
}
var btfVarSecinfoLen = int(unsafe.Sizeof(btfVarSecinfo{}))
func unmarshalBtfVarSecInfos(secinfos []btfVarSecinfo, b []byte, bo binary.ByteOrder) (int, error) {
off := 0
for i := range secinfos {
if off+btfVarSecinfoLen > len(b) {
return 0, fmt.Errorf("not enough bytes to unmarshal btfVarSecinfo %d", i)
}
secinfos[i].Type = TypeID(bo.Uint32(b[off+0:]))
secinfos[i].Offset = bo.Uint32(b[off+4:])
secinfos[i].Size = bo.Uint32(b[off+8:])
off += btfVarSecinfoLen
}
return off, nil
}
type btfVariable struct {
Linkage uint32
}
var btfVariableLen = int(unsafe.Sizeof(btfVariable{}))
func unmarshalBtfVariable(bv *btfVariable, b []byte, bo binary.ByteOrder) (int, error) {
if len(b) < btfVariableLen {
return 0, fmt.Errorf("not enough bytes to unmarshal btfVariable")
}
bv.Linkage = bo.Uint32(b[0:])
return btfVariableLen, nil
}
type btfEnum struct {
NameOff uint32
Val uint32
}
var btfEnumLen = int(unsafe.Sizeof(btfEnum{}))
func unmarshalBtfEnums(enums []btfEnum, b []byte, bo binary.ByteOrder) (int, error) {
off := 0
for i := range enums {
if off+btfEnumLen > len(b) {
return 0, fmt.Errorf("not enough bytes to unmarshal btfEnum %d", i)
}
enums[i].NameOff = bo.Uint32(b[off+0:])
enums[i].Val = bo.Uint32(b[off+4:])
off += btfEnumLen
}
return off, nil
}
type btfEnum64 struct {
NameOff uint32
ValLo32 uint32
ValHi32 uint32
}
var btfEnum64Len = int(unsafe.Sizeof(btfEnum64{}))
func unmarshalBtfEnums64(enums []btfEnum64, b []byte, bo binary.ByteOrder) (int, error) {
off := 0
for i := range enums {
if off+btfEnum64Len > len(b) {
return 0, fmt.Errorf("not enough bytes to unmarshal btfEnum64 %d", i)
}
enums[i].NameOff = bo.Uint32(b[off+0:])
enums[i].ValLo32 = bo.Uint32(b[off+4:])
enums[i].ValHi32 = bo.Uint32(b[off+8:])
off += btfEnum64Len
}
return off, nil
}
type btfParam struct {
NameOff uint32
Type TypeID
}
var btfParamLen = int(unsafe.Sizeof(btfParam{}))
func unmarshalBtfParams(params []btfParam, b []byte, bo binary.ByteOrder) (int, error) {
off := 0
for i := range params {
if off+btfParamLen > len(b) {
return 0, fmt.Errorf("not enough bytes to unmarshal btfParam %d", i)
}
params[i].NameOff = bo.Uint32(b[off+0:])
params[i].Type = TypeID(bo.Uint32(b[off+4:]))
off += btfParamLen
}
return off, nil
}
type btfDeclTag struct {
ComponentIdx uint32
}
var btfDeclTagLen = int(unsafe.Sizeof(btfDeclTag{}))
func unmarshalBtfDeclTag(bdt *btfDeclTag, b []byte, bo binary.ByteOrder) (int, error) {
if len(b) < btfDeclTagLen {
return 0, fmt.Errorf("not enough bytes to unmarshal btfDeclTag")
}
bdt.ComponentIdx = bo.Uint32(b[0:])
return btfDeclTagLen, nil
}