mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-12-05 14:40:42 +01:00
898 lines
22 KiB
Go
898 lines
22 KiB
Go
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package btf
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import (
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"bufio"
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"bytes"
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"debug/elf"
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"encoding/binary"
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"errors"
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"fmt"
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"io"
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"math"
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"os"
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"reflect"
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"github.com/cilium/ebpf/internal"
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"github.com/cilium/ebpf/internal/sys"
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"github.com/cilium/ebpf/internal/unix"
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)
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const btfMagic = 0xeB9F
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// Errors returned by BTF functions.
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var (
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ErrNotSupported = internal.ErrNotSupported
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ErrNotFound = errors.New("not found")
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ErrNoExtendedInfo = errors.New("no extended info")
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)
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// ID represents the unique ID of a BTF object.
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type ID = sys.BTFID
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// Spec represents decoded BTF.
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type Spec struct {
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// Data from .BTF.
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rawTypes []rawType
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strings *stringTable
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// All types contained by the spec. For the base type, the position of
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// a type in the slice is its ID.
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types types
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// Type IDs indexed by type.
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typeIDs map[Type]TypeID
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// Types indexed by essential name.
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// Includes all struct flavors and types with the same name.
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namedTypes map[essentialName][]Type
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byteOrder binary.ByteOrder
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}
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type btfHeader struct {
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Magic uint16
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Version uint8
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Flags uint8
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HdrLen uint32
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TypeOff uint32
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TypeLen uint32
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StringOff uint32
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StringLen uint32
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}
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// typeStart returns the offset from the beginning of the .BTF section
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// to the start of its type entries.
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func (h *btfHeader) typeStart() int64 {
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return int64(h.HdrLen + h.TypeOff)
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}
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// stringStart returns the offset from the beginning of the .BTF section
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// to the start of its string table.
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func (h *btfHeader) stringStart() int64 {
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return int64(h.HdrLen + h.StringOff)
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}
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// LoadSpec opens file and calls LoadSpecFromReader on it.
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func LoadSpec(file string) (*Spec, error) {
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fh, err := os.Open(file)
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if err != nil {
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return nil, err
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}
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defer fh.Close()
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return LoadSpecFromReader(fh)
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}
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// LoadSpecFromReader reads from an ELF or a raw BTF blob.
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//
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// Returns ErrNotFound if reading from an ELF which contains no BTF. ExtInfos
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// may be nil.
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func LoadSpecFromReader(rd io.ReaderAt) (*Spec, error) {
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file, err := internal.NewSafeELFFile(rd)
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if err != nil {
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if bo := guessRawBTFByteOrder(rd); bo != nil {
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// Try to parse a naked BTF blob. This will return an error if
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// we encounter a Datasec, since we can't fix it up.
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spec, err := loadRawSpec(io.NewSectionReader(rd, 0, math.MaxInt64), bo, nil, nil)
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return spec, err
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}
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return nil, err
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}
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return loadSpecFromELF(file)
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}
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// LoadSpecAndExtInfosFromReader reads from an ELF.
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//
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// ExtInfos may be nil if the ELF doesn't contain section metadta.
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// Returns ErrNotFound if the ELF contains no BTF.
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func LoadSpecAndExtInfosFromReader(rd io.ReaderAt) (*Spec, *ExtInfos, error) {
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file, err := internal.NewSafeELFFile(rd)
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if err != nil {
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return nil, nil, err
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}
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spec, err := loadSpecFromELF(file)
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if err != nil {
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return nil, nil, err
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}
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extInfos, err := loadExtInfosFromELF(file, spec.types, spec.strings)
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if err != nil && !errors.Is(err, ErrNotFound) {
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return nil, nil, err
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}
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return spec, extInfos, nil
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}
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// variableOffsets extracts all symbols offsets from an ELF and indexes them by
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// section and variable name.
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//
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// References to variables in BTF data sections carry unsigned 32-bit offsets.
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// Some ELF symbols (e.g. in vmlinux) may point to virtual memory that is well
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// beyond this range. Since these symbols cannot be described by BTF info,
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// ignore them here.
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func variableOffsets(file *internal.SafeELFFile) (map[variable]uint32, error) {
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symbols, err := file.Symbols()
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if err != nil {
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return nil, fmt.Errorf("can't read symbols: %v", err)
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}
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variableOffsets := make(map[variable]uint32)
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for _, symbol := range symbols {
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if idx := symbol.Section; idx >= elf.SHN_LORESERVE && idx <= elf.SHN_HIRESERVE {
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// Ignore things like SHN_ABS
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continue
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}
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if symbol.Value > math.MaxUint32 {
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// VarSecinfo offset is u32, cannot reference symbols in higher regions.
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continue
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}
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if int(symbol.Section) >= len(file.Sections) {
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return nil, fmt.Errorf("symbol %s: invalid section %d", symbol.Name, symbol.Section)
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}
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secName := file.Sections[symbol.Section].Name
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variableOffsets[variable{secName, symbol.Name}] = uint32(symbol.Value)
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}
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return variableOffsets, nil
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}
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func loadSpecFromELF(file *internal.SafeELFFile) (*Spec, error) {
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var (
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btfSection *elf.Section
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sectionSizes = make(map[string]uint32)
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)
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for _, sec := range file.Sections {
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switch sec.Name {
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case ".BTF":
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btfSection = sec
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default:
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if sec.Type != elf.SHT_PROGBITS && sec.Type != elf.SHT_NOBITS {
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break
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}
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if sec.Size > math.MaxUint32 {
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return nil, fmt.Errorf("section %s exceeds maximum size", sec.Name)
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}
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sectionSizes[sec.Name] = uint32(sec.Size)
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}
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}
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if btfSection == nil {
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return nil, fmt.Errorf("btf: %w", ErrNotFound)
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}
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vars, err := variableOffsets(file)
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if err != nil {
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return nil, err
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}
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if btfSection.ReaderAt == nil {
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return nil, fmt.Errorf("compressed BTF is not supported")
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}
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rawTypes, rawStrings, err := parseBTF(btfSection.ReaderAt, file.ByteOrder, nil)
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if err != nil {
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return nil, err
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}
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err = fixupDatasec(rawTypes, rawStrings, sectionSizes, vars)
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if err != nil {
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return nil, err
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}
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return inflateSpec(rawTypes, rawStrings, file.ByteOrder, nil)
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}
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func loadRawSpec(btf io.ReaderAt, bo binary.ByteOrder,
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baseTypes types, baseStrings *stringTable) (*Spec, error) {
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rawTypes, rawStrings, err := parseBTF(btf, bo, baseStrings)
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if err != nil {
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return nil, err
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}
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return inflateSpec(rawTypes, rawStrings, bo, baseTypes)
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}
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func inflateSpec(rawTypes []rawType, rawStrings *stringTable, bo binary.ByteOrder,
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baseTypes types) (*Spec, error) {
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types, err := inflateRawTypes(rawTypes, baseTypes, rawStrings)
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if err != nil {
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return nil, err
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}
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typeIDs, typesByName := indexTypes(types, TypeID(len(baseTypes)))
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return &Spec{
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rawTypes: rawTypes,
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namedTypes: typesByName,
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typeIDs: typeIDs,
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types: types,
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strings: rawStrings,
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byteOrder: bo,
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}, nil
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}
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func indexTypes(types []Type, typeIDOffset TypeID) (map[Type]TypeID, map[essentialName][]Type) {
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namedTypes := 0
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for _, typ := range types {
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if typ.TypeName() != "" {
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// Do a pre-pass to figure out how big types by name has to be.
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// Most types have unique names, so it's OK to ignore essentialName
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// here.
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namedTypes++
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}
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}
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typeIDs := make(map[Type]TypeID, len(types))
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typesByName := make(map[essentialName][]Type, namedTypes)
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for i, typ := range types {
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if name := newEssentialName(typ.TypeName()); name != "" {
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typesByName[name] = append(typesByName[name], typ)
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}
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typeIDs[typ] = TypeID(i) + typeIDOffset
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}
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return typeIDs, typesByName
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}
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// LoadKernelSpec returns the current kernel's BTF information.
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//
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// Defaults to /sys/kernel/btf/vmlinux and falls back to scanning the file system
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// for vmlinux ELFs. Returns an error wrapping ErrNotSupported if BTF is not enabled.
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func LoadKernelSpec() (*Spec, error) {
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fh, err := os.Open("/sys/kernel/btf/vmlinux")
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if err == nil {
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defer fh.Close()
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return loadRawSpec(fh, internal.NativeEndian, nil, nil)
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}
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file, err := findVMLinux()
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if err != nil {
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return nil, err
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}
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defer file.Close()
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return loadSpecFromELF(file)
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}
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// findVMLinux scans multiple well-known paths for vmlinux kernel images.
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func findVMLinux() (*internal.SafeELFFile, error) {
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release, err := internal.KernelRelease()
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if err != nil {
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return nil, err
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}
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// use same list of locations as libbpf
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// https://github.com/libbpf/libbpf/blob/9a3a42608dbe3731256a5682a125ac1e23bced8f/src/btf.c#L3114-L3122
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locations := []string{
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"/boot/vmlinux-%s",
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"/lib/modules/%s/vmlinux-%[1]s",
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"/lib/modules/%s/build/vmlinux",
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"/usr/lib/modules/%s/kernel/vmlinux",
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"/usr/lib/debug/boot/vmlinux-%s",
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"/usr/lib/debug/boot/vmlinux-%s.debug",
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"/usr/lib/debug/lib/modules/%s/vmlinux",
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}
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for _, loc := range locations {
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file, err := internal.OpenSafeELFFile(fmt.Sprintf(loc, release))
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if errors.Is(err, os.ErrNotExist) {
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continue
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}
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return file, err
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}
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return nil, fmt.Errorf("no BTF found for kernel version %s: %w", release, internal.ErrNotSupported)
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}
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// parseBTFHeader parses the header of the .BTF section.
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func parseBTFHeader(r io.Reader, bo binary.ByteOrder) (*btfHeader, error) {
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var header btfHeader
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if err := binary.Read(r, bo, &header); err != nil {
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return nil, fmt.Errorf("can't read header: %v", err)
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}
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if header.Magic != btfMagic {
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return nil, fmt.Errorf("incorrect magic value %v", header.Magic)
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}
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if header.Version != 1 {
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return nil, fmt.Errorf("unexpected version %v", header.Version)
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}
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if header.Flags != 0 {
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return nil, fmt.Errorf("unsupported flags %v", header.Flags)
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}
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remainder := int64(header.HdrLen) - int64(binary.Size(&header))
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if remainder < 0 {
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return nil, errors.New("header length shorter than btfHeader size")
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}
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if _, err := io.CopyN(internal.DiscardZeroes{}, r, remainder); err != nil {
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return nil, fmt.Errorf("header padding: %v", err)
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}
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return &header, nil
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}
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func guessRawBTFByteOrder(r io.ReaderAt) binary.ByteOrder {
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buf := new(bufio.Reader)
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for _, bo := range []binary.ByteOrder{
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binary.LittleEndian,
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binary.BigEndian,
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} {
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buf.Reset(io.NewSectionReader(r, 0, math.MaxInt64))
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if _, err := parseBTFHeader(buf, bo); err == nil {
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return bo
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}
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}
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return nil
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}
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// parseBTF reads a .BTF section into memory and parses it into a list of
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// raw types and a string table.
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func parseBTF(btf io.ReaderAt, bo binary.ByteOrder, baseStrings *stringTable) ([]rawType, *stringTable, error) {
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buf := internal.NewBufferedSectionReader(btf, 0, math.MaxInt64)
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header, err := parseBTFHeader(buf, bo)
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if err != nil {
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return nil, nil, fmt.Errorf("parsing .BTF header: %v", err)
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}
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rawStrings, err := readStringTable(io.NewSectionReader(btf, header.stringStart(), int64(header.StringLen)),
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baseStrings)
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if err != nil {
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return nil, nil, fmt.Errorf("can't read type names: %w", err)
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}
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buf.Reset(io.NewSectionReader(btf, header.typeStart(), int64(header.TypeLen)))
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rawTypes, err := readTypes(buf, bo, header.TypeLen)
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if err != nil {
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return nil, nil, fmt.Errorf("can't read types: %w", err)
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}
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return rawTypes, rawStrings, nil
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}
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type variable struct {
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section string
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name string
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}
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func fixupDatasec(rawTypes []rawType, rawStrings *stringTable, sectionSizes map[string]uint32, variableOffsets map[variable]uint32) error {
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for i, rawType := range rawTypes {
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if rawType.Kind() != kindDatasec {
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continue
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}
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name, err := rawStrings.Lookup(rawType.NameOff)
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if err != nil {
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return err
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}
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if name == ".kconfig" || name == ".ksyms" {
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return fmt.Errorf("reference to %s: %w", name, ErrNotSupported)
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}
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if rawTypes[i].SizeType != 0 {
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continue
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}
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size, ok := sectionSizes[name]
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if !ok {
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return fmt.Errorf("data section %s: missing size", name)
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}
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rawTypes[i].SizeType = size
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secinfos := rawType.data.([]btfVarSecinfo)
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for j, secInfo := range secinfos {
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id := int(secInfo.Type - 1)
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if id >= len(rawTypes) {
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return fmt.Errorf("data section %s: invalid type id %d for variable %d", name, id, j)
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}
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varName, err := rawStrings.Lookup(rawTypes[id].NameOff)
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if err != nil {
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return fmt.Errorf("data section %s: can't get name for type %d: %w", name, id, err)
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}
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offset, ok := variableOffsets[variable{name, varName}]
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if !ok {
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return fmt.Errorf("data section %s: missing offset for variable %s", name, varName)
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}
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secinfos[j].Offset = offset
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}
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}
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return nil
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}
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// Copy creates a copy of Spec.
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func (s *Spec) Copy() *Spec {
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types := copyTypes(s.types, nil)
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typeIDOffset := TypeID(0)
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if len(s.types) != 0 {
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||
|
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
|
||
|
})
|