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

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package btf
import (
"bufio"
"bytes"
"encoding/binary"
"errors"
"fmt"
"io"
"io/ioutil"
"github.com/cilium/ebpf/asm"
"github.com/cilium/ebpf/internal"
)
type btfExtHeader struct {
Magic uint16
Version uint8
Flags uint8
HdrLen uint32
FuncInfoOff uint32
FuncInfoLen uint32
LineInfoOff uint32
LineInfoLen uint32
}
type btfExtCoreHeader struct {
CoreReloOff uint32
CoreReloLen uint32
}
func parseExtInfos(r io.ReadSeeker, bo binary.ByteOrder, strings stringTable) (funcInfo, lineInfo map[string]extInfo, coreRelos map[string]bpfCoreRelos, err error) {
var header btfExtHeader
var coreHeader btfExtCoreHeader
if err := binary.Read(r, bo, &header); err != nil {
return nil, nil, nil, fmt.Errorf("can't read header: %v", err)
}
if header.Magic != btfMagic {
return nil, nil, nil, fmt.Errorf("incorrect magic value %v", header.Magic)
}
if header.Version != 1 {
return nil, nil, nil, fmt.Errorf("unexpected version %v", header.Version)
}
if header.Flags != 0 {
return nil, nil, nil, fmt.Errorf("unsupported flags %v", header.Flags)
}
remainder := int64(header.HdrLen) - int64(binary.Size(&header))
if remainder < 0 {
return nil, nil, nil, errors.New("header is too short")
}
coreHdrSize := int64(binary.Size(&coreHeader))
if remainder >= coreHdrSize {
if err := binary.Read(r, bo, &coreHeader); err != nil {
return nil, nil, nil, fmt.Errorf("can't read CO-RE relocation header: %v", err)
}
remainder -= coreHdrSize
}
// 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, nil, fmt.Errorf("header padding: %v", err)
}
if _, err := r.Seek(int64(header.HdrLen+header.FuncInfoOff), io.SeekStart); err != nil {
return nil, nil, nil, fmt.Errorf("can't seek to function info section: %v", err)
}
buf := bufio.NewReader(io.LimitReader(r, int64(header.FuncInfoLen)))
funcInfo, err = parseExtInfo(buf, bo, strings)
if err != nil {
return nil, nil, nil, fmt.Errorf("function info: %w", err)
}
if _, err := r.Seek(int64(header.HdrLen+header.LineInfoOff), io.SeekStart); err != nil {
return nil, nil, nil, fmt.Errorf("can't seek to line info section: %v", err)
}
buf = bufio.NewReader(io.LimitReader(r, int64(header.LineInfoLen)))
lineInfo, err = parseExtInfo(buf, bo, strings)
if err != nil {
return nil, nil, nil, fmt.Errorf("line info: %w", err)
}
if coreHeader.CoreReloOff > 0 && coreHeader.CoreReloLen > 0 {
if _, err := r.Seek(int64(header.HdrLen+coreHeader.CoreReloOff), io.SeekStart); err != nil {
return nil, nil, nil, fmt.Errorf("can't seek to CO-RE relocation section: %v", err)
}
coreRelos, err = parseExtInfoRelos(io.LimitReader(r, int64(coreHeader.CoreReloLen)), bo, strings)
if err != nil {
return nil, nil, nil, fmt.Errorf("CO-RE relocation info: %w", err)
}
}
return funcInfo, lineInfo, coreRelos, 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{}, fmt.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, fmt.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) {
const maxRecordSize = 256
var recordSize uint32
if err := binary.Read(r, bo, &recordSize); err != nil {
return nil, fmt.Errorf("can't read record size: %v", err)
}
if recordSize < 4 {
// Need at least insnOff
return nil, errors.New("record size too short")
}
if recordSize > maxRecordSize {
return nil, fmt.Errorf("record size %v exceeds %v", recordSize, maxRecordSize)
}
result := make(map[string]extInfo)
for {
secName, infoHeader, err := parseExtInfoHeader(r, bo, strings)
if errors.Is(err, io.EOF) {
return result, nil
}
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, fmt.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, fmt.Errorf("section %v: can't read record: %v", secName, err)
}
if byteOff%asm.InstructionSize != 0 {
return nil, fmt.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,
}
}
}
// bpfCoreRelo matches `struct bpf_core_relo` from the kernel
type bpfCoreRelo struct {
InsnOff uint32
TypeID TypeID
AccessStrOff uint32
ReloKind coreReloKind
}
type bpfCoreRelos []bpfCoreRelo
// append two slices of extInfoRelo to each other. The InsnOff of b are adjusted
// by offset.
func (r bpfCoreRelos) append(other bpfCoreRelos, offset uint64) bpfCoreRelos {
result := make([]bpfCoreRelo, 0, len(r)+len(other))
result = append(result, r...)
for _, relo := range other {
relo.InsnOff += uint32(offset)
result = append(result, relo)
}
return result
}
var extInfoReloSize = binary.Size(bpfCoreRelo{})
func parseExtInfoRelos(r io.Reader, bo binary.ByteOrder, strings stringTable) (map[string]bpfCoreRelos, error) {
var recordSize uint32
if err := binary.Read(r, bo, &recordSize); err != nil {
return nil, fmt.Errorf("read record size: %v", err)
}
if recordSize != uint32(extInfoReloSize) {
return nil, fmt.Errorf("expected record size %d, got %d", extInfoReloSize, recordSize)
}
result := make(map[string]bpfCoreRelos)
for {
secName, infoHeader, err := parseExtInfoHeader(r, bo, strings)
if errors.Is(err, io.EOF) {
return result, nil
}
var relos []bpfCoreRelo
for i := uint32(0); i < infoHeader.NumInfo; i++ {
var relo bpfCoreRelo
if err := binary.Read(r, bo, &relo); err != nil {
return nil, fmt.Errorf("section %v: read record: %v", secName, err)
}
if relo.InsnOff%asm.InstructionSize != 0 {
return nil, fmt.Errorf("section %v: offset %v is not aligned with instruction size", secName, relo.InsnOff)
}
relos = append(relos, relo)
}
result[secName] = relos
}
}
func parseExtInfoHeader(r io.Reader, bo binary.ByteOrder, strings stringTable) (string, *btfExtInfoSec, error) {
var infoHeader btfExtInfoSec
if err := binary.Read(r, bo, &infoHeader); err != nil {
return "", nil, fmt.Errorf("read ext info header: %w", err)
}
secName, err := strings.Lookup(infoHeader.SecNameOff)
if err != nil {
return "", nil, fmt.Errorf("get section name: %w", err)
}
if infoHeader.NumInfo == 0 {
return "", nil, fmt.Errorf("section %s has zero records", secName)
}
return secName, &infoHeader, nil
}