gotosocial/vendor/github.com/cilium/ebpf/btf/ext_info.go
dependabot[bot] 57dc742c76
[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>
2023-04-03 11:16:17 +02:00

722 lines
20 KiB
Go

package btf
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"io"
"math"
"sort"
"github.com/cilium/ebpf/asm"
"github.com/cilium/ebpf/internal"
)
// ExtInfos contains ELF section metadata.
type ExtInfos struct {
// The slices are sorted by offset in ascending order.
funcInfos map[string][]funcInfo
lineInfos map[string][]lineInfo
relocationInfos map[string][]coreRelocationInfo
}
// loadExtInfosFromELF parses ext infos from the .BTF.ext section in an ELF.
//
// Returns an error wrapping ErrNotFound if no ext infos are present.
func loadExtInfosFromELF(file *internal.SafeELFFile, ts types, strings *stringTable) (*ExtInfos, error) {
section := file.Section(".BTF.ext")
if section == nil {
return nil, fmt.Errorf("btf ext infos: %w", ErrNotFound)
}
if section.ReaderAt == nil {
return nil, fmt.Errorf("compressed ext_info is not supported")
}
return loadExtInfos(section.ReaderAt, file.ByteOrder, ts, strings)
}
// loadExtInfos parses bare ext infos.
func loadExtInfos(r io.ReaderAt, bo binary.ByteOrder, ts types, strings *stringTable) (*ExtInfos, error) {
// Open unbuffered section reader. binary.Read() calls io.ReadFull on
// the header structs, resulting in one syscall per header.
headerRd := io.NewSectionReader(r, 0, math.MaxInt64)
extHeader, err := parseBTFExtHeader(headerRd, bo)
if err != nil {
return nil, fmt.Errorf("parsing BTF extension header: %w", err)
}
coreHeader, err := parseBTFExtCOREHeader(headerRd, bo, extHeader)
if err != nil {
return nil, fmt.Errorf("parsing BTF CO-RE header: %w", err)
}
buf := internal.NewBufferedSectionReader(r, extHeader.funcInfoStart(), int64(extHeader.FuncInfoLen))
btfFuncInfos, err := parseFuncInfos(buf, bo, strings)
if err != nil {
return nil, fmt.Errorf("parsing BTF function info: %w", err)
}
funcInfos := make(map[string][]funcInfo, len(btfFuncInfos))
for section, bfis := range btfFuncInfos {
funcInfos[section], err = newFuncInfos(bfis, ts)
if err != nil {
return nil, fmt.Errorf("section %s: func infos: %w", section, err)
}
}
buf = internal.NewBufferedSectionReader(r, extHeader.lineInfoStart(), int64(extHeader.LineInfoLen))
btfLineInfos, err := parseLineInfos(buf, bo, strings)
if err != nil {
return nil, fmt.Errorf("parsing BTF line info: %w", err)
}
lineInfos := make(map[string][]lineInfo, len(btfLineInfos))
for section, blis := range btfLineInfos {
lineInfos[section], err = newLineInfos(blis, strings)
if err != nil {
return nil, fmt.Errorf("section %s: line infos: %w", section, err)
}
}
if coreHeader == nil || coreHeader.COREReloLen == 0 {
return &ExtInfos{funcInfos, lineInfos, nil}, nil
}
var btfCORERelos map[string][]bpfCORERelo
buf = internal.NewBufferedSectionReader(r, extHeader.coreReloStart(coreHeader), int64(coreHeader.COREReloLen))
btfCORERelos, err = parseCORERelos(buf, bo, strings)
if err != nil {
return nil, fmt.Errorf("parsing CO-RE relocation info: %w", err)
}
coreRelos := make(map[string][]coreRelocationInfo, len(btfCORERelos))
for section, brs := range btfCORERelos {
coreRelos[section], err = newRelocationInfos(brs, ts, strings)
if err != nil {
return nil, fmt.Errorf("section %s: CO-RE relocations: %w", section, err)
}
}
return &ExtInfos{funcInfos, lineInfos, coreRelos}, nil
}
type funcInfoMeta struct{}
type coreRelocationMeta struct{}
// Assign per-section metadata from BTF to a section's instructions.
func (ei *ExtInfos) Assign(insns asm.Instructions, section string) {
funcInfos := ei.funcInfos[section]
lineInfos := ei.lineInfos[section]
reloInfos := ei.relocationInfos[section]
iter := insns.Iterate()
for iter.Next() {
if len(funcInfos) > 0 && funcInfos[0].offset == iter.Offset {
iter.Ins.Metadata.Set(funcInfoMeta{}, funcInfos[0].fn)
funcInfos = funcInfos[1:]
}
if len(lineInfos) > 0 && lineInfos[0].offset == iter.Offset {
*iter.Ins = iter.Ins.WithSource(lineInfos[0].line)
lineInfos = lineInfos[1:]
}
if len(reloInfos) > 0 && reloInfos[0].offset == iter.Offset {
iter.Ins.Metadata.Set(coreRelocationMeta{}, reloInfos[0].relo)
reloInfos = reloInfos[1:]
}
}
}
// MarshalExtInfos encodes function and line info embedded in insns into kernel
// wire format.
func MarshalExtInfos(insns asm.Instructions, typeID func(Type) (TypeID, error)) (funcInfos, lineInfos []byte, _ error) {
iter := insns.Iterate()
var fiBuf, liBuf bytes.Buffer
for iter.Next() {
if fn := FuncMetadata(iter.Ins); fn != nil {
fi := &funcInfo{
fn: fn,
offset: iter.Offset,
}
if err := fi.marshal(&fiBuf, typeID); err != nil {
return nil, nil, fmt.Errorf("write func info: %w", err)
}
}
if line, ok := iter.Ins.Source().(*Line); ok {
li := &lineInfo{
line: line,
offset: iter.Offset,
}
if err := li.marshal(&liBuf); err != nil {
return nil, nil, fmt.Errorf("write line info: %w", err)
}
}
}
return fiBuf.Bytes(), liBuf.Bytes(), nil
}
// btfExtHeader is found at the start of the .BTF.ext section.
type btfExtHeader struct {
Magic uint16
Version uint8
Flags uint8
// HdrLen is larger than the size of struct btfExtHeader when it is
// immediately followed by a btfExtCOREHeader.
HdrLen uint32
FuncInfoOff uint32
FuncInfoLen uint32
LineInfoOff uint32
LineInfoLen uint32
}
// parseBTFExtHeader parses the header of the .BTF.ext section.
func parseBTFExtHeader(r io.Reader, bo binary.ByteOrder) (*btfExtHeader, error) {
var header btfExtHeader
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)
}
if int64(header.HdrLen) < int64(binary.Size(&header)) {
return nil, fmt.Errorf("header length shorter than btfExtHeader size")
}
return &header, nil
}
// funcInfoStart returns the offset from the beginning of the .BTF.ext section
// to the start of its func_info entries.
func (h *btfExtHeader) funcInfoStart() int64 {
return int64(h.HdrLen + h.FuncInfoOff)
}
// lineInfoStart returns the offset from the beginning of the .BTF.ext section
// to the start of its line_info entries.
func (h *btfExtHeader) lineInfoStart() int64 {
return int64(h.HdrLen + h.LineInfoOff)
}
// coreReloStart returns the offset from the beginning of the .BTF.ext section
// to the start of its CO-RE relocation entries.
func (h *btfExtHeader) coreReloStart(ch *btfExtCOREHeader) int64 {
return int64(h.HdrLen + ch.COREReloOff)
}
// btfExtCOREHeader is found right after the btfExtHeader when its HdrLen
// field is larger than its size.
type btfExtCOREHeader struct {
COREReloOff uint32
COREReloLen uint32
}
// parseBTFExtCOREHeader parses the tail of the .BTF.ext header. If additional
// header bytes are present, extHeader.HdrLen will be larger than the struct,
// indicating the presence of a CO-RE extension header.
func parseBTFExtCOREHeader(r io.Reader, bo binary.ByteOrder, extHeader *btfExtHeader) (*btfExtCOREHeader, error) {
extHdrSize := int64(binary.Size(&extHeader))
remainder := int64(extHeader.HdrLen) - extHdrSize
if remainder == 0 {
return nil, nil
}
var coreHeader btfExtCOREHeader
if err := binary.Read(r, bo, &coreHeader); err != nil {
return nil, fmt.Errorf("can't read header: %v", err)
}
return &coreHeader, nil
}
type btfExtInfoSec struct {
SecNameOff uint32
NumInfo uint32
}
// parseExtInfoSec parses a btf_ext_info_sec header within .BTF.ext,
// appearing within func_info and line_info sub-sections.
// These headers appear once for each program section in the ELF and are
// followed by one or more func/line_info records for the section.
func parseExtInfoSec(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 secName == "" {
return "", nil, fmt.Errorf("extinfo header refers to empty section name")
}
if infoHeader.NumInfo == 0 {
return "", nil, fmt.Errorf("section %s has zero records", secName)
}
return secName, &infoHeader, nil
}
// parseExtInfoRecordSize parses the uint32 at the beginning of a func_infos
// or line_infos segment that describes the length of all extInfoRecords in
// that segment.
func parseExtInfoRecordSize(r io.Reader, bo binary.ByteOrder) (uint32, error) {
const maxRecordSize = 256
var recordSize uint32
if err := binary.Read(r, bo, &recordSize); err != nil {
return 0, fmt.Errorf("can't read record size: %v", err)
}
if recordSize < 4 {
// Need at least InsnOff worth of bytes per record.
return 0, errors.New("record size too short")
}
if recordSize > maxRecordSize {
return 0, fmt.Errorf("record size %v exceeds %v", recordSize, maxRecordSize)
}
return recordSize, nil
}
// The size of a FuncInfo in BTF wire format.
var FuncInfoSize = uint32(binary.Size(bpfFuncInfo{}))
type funcInfo struct {
fn *Func
offset asm.RawInstructionOffset
}
type bpfFuncInfo struct {
// Instruction offset of the function within an ELF section.
InsnOff uint32
TypeID TypeID
}
func newFuncInfo(fi bpfFuncInfo, ts types) (*funcInfo, error) {
typ, err := ts.ByID(fi.TypeID)
if err != nil {
return nil, err
}
fn, ok := typ.(*Func)
if !ok {
return nil, fmt.Errorf("type ID %d is a %T, but expected a Func", fi.TypeID, typ)
}
// C doesn't have anonymous functions, but check just in case.
if fn.Name == "" {
return nil, fmt.Errorf("func with type ID %d doesn't have a name", fi.TypeID)
}
return &funcInfo{
fn,
asm.RawInstructionOffset(fi.InsnOff),
}, nil
}
func newFuncInfos(bfis []bpfFuncInfo, ts types) ([]funcInfo, error) {
fis := make([]funcInfo, 0, len(bfis))
for _, bfi := range bfis {
fi, err := newFuncInfo(bfi, ts)
if err != nil {
return nil, fmt.Errorf("offset %d: %w", bfi.InsnOff, err)
}
fis = append(fis, *fi)
}
sort.Slice(fis, func(i, j int) bool {
return fis[i].offset <= fis[j].offset
})
return fis, nil
}
// marshal into the BTF wire format.
func (fi *funcInfo) marshal(w io.Writer, typeID func(Type) (TypeID, error)) error {
id, err := typeID(fi.fn)
if err != nil {
return err
}
bfi := bpfFuncInfo{
InsnOff: uint32(fi.offset),
TypeID: id,
}
return binary.Write(w, internal.NativeEndian, &bfi)
}
// parseLineInfos parses a func_info sub-section within .BTF.ext ito a map of
// func infos indexed by section name.
func parseFuncInfos(r io.Reader, bo binary.ByteOrder, strings *stringTable) (map[string][]bpfFuncInfo, error) {
recordSize, err := parseExtInfoRecordSize(r, bo)
if err != nil {
return nil, err
}
result := make(map[string][]bpfFuncInfo)
for {
secName, infoHeader, err := parseExtInfoSec(r, bo, strings)
if errors.Is(err, io.EOF) {
return result, nil
}
if err != nil {
return nil, err
}
records, err := parseFuncInfoRecords(r, bo, recordSize, infoHeader.NumInfo)
if err != nil {
return nil, fmt.Errorf("section %v: %w", secName, err)
}
result[secName] = records
}
}
// parseFuncInfoRecords parses a stream of func_infos into a funcInfos.
// These records appear after a btf_ext_info_sec header in the func_info
// sub-section of .BTF.ext.
func parseFuncInfoRecords(r io.Reader, bo binary.ByteOrder, recordSize uint32, recordNum uint32) ([]bpfFuncInfo, error) {
var out []bpfFuncInfo
var fi bpfFuncInfo
if exp, got := FuncInfoSize, recordSize; exp != got {
// BTF blob's record size is longer than we know how to parse.
return nil, fmt.Errorf("expected FuncInfo record size %d, but BTF blob contains %d", exp, got)
}
for i := uint32(0); i < recordNum; i++ {
if err := binary.Read(r, bo, &fi); err != nil {
return nil, fmt.Errorf("can't read function info: %v", err)
}
if fi.InsnOff%asm.InstructionSize != 0 {
return nil, fmt.Errorf("offset %v is not aligned with instruction size", fi.InsnOff)
}
// ELF tracks offset in bytes, the kernel expects raw BPF instructions.
// Convert as early as possible.
fi.InsnOff /= asm.InstructionSize
out = append(out, fi)
}
return out, nil
}
var LineInfoSize = uint32(binary.Size(bpfLineInfo{}))
// Line represents the location and contents of a single line of source
// code a BPF ELF was compiled from.
type Line struct {
fileName string
line string
lineNumber uint32
lineColumn uint32
// TODO: We should get rid of the fields below, but for that we need to be
// able to write BTF.
fileNameOff uint32
lineOff uint32
}
func (li *Line) FileName() string {
return li.fileName
}
func (li *Line) Line() string {
return li.line
}
func (li *Line) LineNumber() uint32 {
return li.lineNumber
}
func (li *Line) LineColumn() uint32 {
return li.lineColumn
}
func (li *Line) String() string {
return li.line
}
type lineInfo struct {
line *Line
offset asm.RawInstructionOffset
}
// Constants for the format of bpfLineInfo.LineCol.
const (
bpfLineShift = 10
bpfLineMax = (1 << (32 - bpfLineShift)) - 1
bpfColumnMax = (1 << bpfLineShift) - 1
)
type bpfLineInfo struct {
// Instruction offset of the line within the whole instruction stream, in instructions.
InsnOff uint32
FileNameOff uint32
LineOff uint32
LineCol uint32
}
func newLineInfo(li bpfLineInfo, strings *stringTable) (*lineInfo, error) {
line, err := strings.Lookup(li.LineOff)
if err != nil {
return nil, fmt.Errorf("lookup of line: %w", err)
}
fileName, err := strings.Lookup(li.FileNameOff)
if err != nil {
return nil, fmt.Errorf("lookup of filename: %w", err)
}
lineNumber := li.LineCol >> bpfLineShift
lineColumn := li.LineCol & bpfColumnMax
return &lineInfo{
&Line{
fileName,
line,
lineNumber,
lineColumn,
li.FileNameOff,
li.LineOff,
},
asm.RawInstructionOffset(li.InsnOff),
}, nil
}
func newLineInfos(blis []bpfLineInfo, strings *stringTable) ([]lineInfo, error) {
lis := make([]lineInfo, 0, len(blis))
for _, bli := range blis {
li, err := newLineInfo(bli, strings)
if err != nil {
return nil, fmt.Errorf("offset %d: %w", bli.InsnOff, err)
}
lis = append(lis, *li)
}
sort.Slice(lis, func(i, j int) bool {
return lis[i].offset <= lis[j].offset
})
return lis, nil
}
// marshal writes the binary representation of the LineInfo to w.
func (li *lineInfo) marshal(w io.Writer) error {
line := li.line
if line.lineNumber > bpfLineMax {
return fmt.Errorf("line %d exceeds %d", line.lineNumber, bpfLineMax)
}
if line.lineColumn > bpfColumnMax {
return fmt.Errorf("column %d exceeds %d", line.lineColumn, bpfColumnMax)
}
bli := bpfLineInfo{
uint32(li.offset),
line.fileNameOff,
line.lineOff,
(line.lineNumber << bpfLineShift) | line.lineColumn,
}
return binary.Write(w, internal.NativeEndian, &bli)
}
// parseLineInfos parses a line_info sub-section within .BTF.ext ito a map of
// line infos indexed by section name.
func parseLineInfos(r io.Reader, bo binary.ByteOrder, strings *stringTable) (map[string][]bpfLineInfo, error) {
recordSize, err := parseExtInfoRecordSize(r, bo)
if err != nil {
return nil, err
}
result := make(map[string][]bpfLineInfo)
for {
secName, infoHeader, err := parseExtInfoSec(r, bo, strings)
if errors.Is(err, io.EOF) {
return result, nil
}
if err != nil {
return nil, err
}
records, err := parseLineInfoRecords(r, bo, recordSize, infoHeader.NumInfo)
if err != nil {
return nil, fmt.Errorf("section %v: %w", secName, err)
}
result[secName] = records
}
}
// parseLineInfoRecords parses a stream of line_infos into a lineInfos.
// These records appear after a btf_ext_info_sec header in the line_info
// sub-section of .BTF.ext.
func parseLineInfoRecords(r io.Reader, bo binary.ByteOrder, recordSize uint32, recordNum uint32) ([]bpfLineInfo, error) {
var out []bpfLineInfo
var li bpfLineInfo
if exp, got := uint32(binary.Size(li)), recordSize; exp != got {
// BTF blob's record size is longer than we know how to parse.
return nil, fmt.Errorf("expected LineInfo record size %d, but BTF blob contains %d", exp, got)
}
for i := uint32(0); i < recordNum; i++ {
if err := binary.Read(r, bo, &li); err != nil {
return nil, fmt.Errorf("can't read line info: %v", err)
}
if li.InsnOff%asm.InstructionSize != 0 {
return nil, fmt.Errorf("offset %v is not aligned with instruction size", li.InsnOff)
}
// ELF tracks offset in bytes, the kernel expects raw BPF instructions.
// Convert as early as possible.
li.InsnOff /= asm.InstructionSize
out = append(out, li)
}
return out, nil
}
// bpfCORERelo matches the kernel's struct bpf_core_relo.
type bpfCORERelo struct {
InsnOff uint32
TypeID TypeID
AccessStrOff uint32
Kind coreKind
}
type CORERelocation struct {
typ Type
accessor coreAccessor
kind coreKind
}
func CORERelocationMetadata(ins *asm.Instruction) *CORERelocation {
relo, _ := ins.Metadata.Get(coreRelocationMeta{}).(*CORERelocation)
return relo
}
type coreRelocationInfo struct {
relo *CORERelocation
offset asm.RawInstructionOffset
}
func newRelocationInfo(relo bpfCORERelo, ts types, strings *stringTable) (*coreRelocationInfo, error) {
typ, err := ts.ByID(relo.TypeID)
if err != nil {
return nil, err
}
accessorStr, err := strings.Lookup(relo.AccessStrOff)
if err != nil {
return nil, err
}
accessor, err := parseCOREAccessor(accessorStr)
if err != nil {
return nil, fmt.Errorf("accessor %q: %s", accessorStr, err)
}
return &coreRelocationInfo{
&CORERelocation{
typ,
accessor,
relo.Kind,
},
asm.RawInstructionOffset(relo.InsnOff),
}, nil
}
func newRelocationInfos(brs []bpfCORERelo, ts types, strings *stringTable) ([]coreRelocationInfo, error) {
rs := make([]coreRelocationInfo, 0, len(brs))
for _, br := range brs {
relo, err := newRelocationInfo(br, ts, strings)
if err != nil {
return nil, fmt.Errorf("offset %d: %w", br.InsnOff, err)
}
rs = append(rs, *relo)
}
sort.Slice(rs, func(i, j int) bool {
return rs[i].offset < rs[j].offset
})
return rs, nil
}
var extInfoReloSize = binary.Size(bpfCORERelo{})
// parseCORERelos parses a core_relos sub-section within .BTF.ext ito a map of
// CO-RE relocations indexed by section name.
func parseCORERelos(r io.Reader, bo binary.ByteOrder, strings *stringTable) (map[string][]bpfCORERelo, error) {
recordSize, err := parseExtInfoRecordSize(r, bo)
if err != nil {
return nil, err
}
if recordSize != uint32(extInfoReloSize) {
return nil, fmt.Errorf("expected record size %d, got %d", extInfoReloSize, recordSize)
}
result := make(map[string][]bpfCORERelo)
for {
secName, infoHeader, err := parseExtInfoSec(r, bo, strings)
if errors.Is(err, io.EOF) {
return result, nil
}
if err != nil {
return nil, err
}
records, err := parseCOREReloRecords(r, bo, recordSize, infoHeader.NumInfo)
if err != nil {
return nil, fmt.Errorf("section %v: %w", secName, err)
}
result[secName] = records
}
}
// parseCOREReloRecords parses a stream of CO-RE relocation entries into a
// coreRelos. These records appear after a btf_ext_info_sec header in the
// core_relos sub-section of .BTF.ext.
func parseCOREReloRecords(r io.Reader, bo binary.ByteOrder, recordSize uint32, recordNum uint32) ([]bpfCORERelo, error) {
var out []bpfCORERelo
var relo bpfCORERelo
for i := uint32(0); i < recordNum; i++ {
if err := binary.Read(r, bo, &relo); err != nil {
return nil, fmt.Errorf("can't read CO-RE relocation: %v", err)
}
if relo.InsnOff%asm.InstructionSize != 0 {
return nil, fmt.Errorf("offset %v is not aligned with instruction size", relo.InsnOff)
}
// ELF tracks offset in bytes, the kernel expects raw BPF instructions.
// Convert as early as possible.
relo.InsnOff /= asm.InstructionSize
out = append(out, relo)
}
return out, nil
}