k3s/vendor/github.com/cilium/ebpf/internal/btf/btf.go
Brad Davidson e204d863a5 Update Kubernetes to v1.22.1
* Update Kubernetes to v1.22.1
* Update dependent modules to track with upstream

Signed-off-by: Brad Davidson <brad.davidson@rancher.com>
2021-08-20 18:47:16 -07:00

800 lines
19 KiB
Go

package btf
import (
"bytes"
"debug/elf"
"encoding/binary"
"errors"
"fmt"
"io"
"io/ioutil"
"math"
"os"
"reflect"
"sync"
"unsafe"
"github.com/cilium/ebpf/internal"
"github.com/cilium/ebpf/internal/unix"
)
const btfMagic = 0xeB9F
// Errors returned by BTF functions.
var (
ErrNotSupported = internal.ErrNotSupported
ErrNotFound = errors.New("not found")
ErrNoExtendedInfo = errors.New("no extended info")
)
// Spec represents decoded BTF.
type Spec struct {
rawTypes []rawType
strings stringTable
types []Type
namedTypes map[string][]namedType
funcInfos map[string]extInfo
lineInfos map[string]extInfo
coreRelos map[string]coreRelos
byteOrder binary.ByteOrder
}
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 ErrNotFound if the reader contains no BTF.
func LoadSpecFromReader(rd io.ReaderAt) (*Spec, error) {
file, err := internal.NewSafeELFFile(rd)
if err != nil {
return nil, err
}
defer file.Close()
btfSection, btfExtSection, sectionSizes, err := findBtfSections(file)
if err != nil {
return nil, err
}
if btfSection == nil {
return nil, fmt.Errorf("btf: %w", ErrNotFound)
}
symbols, err := file.Symbols()
if err != nil {
return nil, fmt.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
}
if int(symbol.Section) >= len(file.Sections) {
return nil, fmt.Errorf("symbol %s: invalid section %d", symbol.Name, symbol.Section)
}
secName := file.Sections[symbol.Section].Name
if _, ok := sectionSizes[secName]; !ok {
continue
}
if symbol.Value > math.MaxUint32 {
return nil, fmt.Errorf("section %s: symbol %s: size exceeds maximum", secName, symbol.Name)
}
variableOffsets[variable{secName, symbol.Name}] = uint32(symbol.Value)
}
spec, err := loadNakedSpec(btfSection.Open(), file.ByteOrder, sectionSizes, variableOffsets)
if err != nil {
return nil, err
}
if btfExtSection == nil {
return spec, nil
}
spec.funcInfos, spec.lineInfos, spec.coreRelos, err = parseExtInfos(btfExtSection.Open(), file.ByteOrder, spec.strings)
if err != nil {
return nil, fmt.Errorf("can't read ext info: %w", err)
}
return spec, nil
}
func findBtfSections(file *internal.SafeELFFile) (*elf.Section, *elf.Section, map[string]uint32, error) {
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, nil, nil, fmt.Errorf("section %s exceeds maximum size", sec.Name)
}
sectionSizes[sec.Name] = uint32(sec.Size)
}
}
return btfSection, btfExtSection, sectionSizes, nil
}
func loadSpecFromVmlinux(rd io.ReaderAt) (*Spec, error) {
file, err := internal.NewSafeELFFile(rd)
if err != nil {
return nil, err
}
defer file.Close()
btfSection, _, _, err := findBtfSections(file)
if err != nil {
return nil, fmt.Errorf(".BTF ELF section: %s", err)
}
if btfSection == nil {
return nil, fmt.Errorf("unable to find .BTF ELF section")
}
return loadNakedSpec(btfSection.Open(), file.ByteOrder, nil, nil)
}
func loadNakedSpec(btf io.ReadSeeker, bo binary.ByteOrder, sectionSizes map[string]uint32, variableOffsets map[variable]uint32) (*Spec, error) {
rawTypes, rawStrings, err := parseBTF(btf, bo)
if err != nil {
return nil, err
}
err = fixupDatasec(rawTypes, rawStrings, sectionSizes, variableOffsets)
if err != nil {
return nil, err
}
types, typesByName, err := inflateRawTypes(rawTypes, rawStrings)
if err != nil {
return nil, err
}
return &Spec{
rawTypes: rawTypes,
namedTypes: typesByName,
types: types,
strings: rawStrings,
byteOrder: bo,
}, nil
}
var kernelBTF struct {
sync.Mutex
*Spec
}
// LoadKernelSpec returns the current kernel's BTF information.
//
// Requires a >= 5.5 kernel with CONFIG_DEBUG_INFO_BTF enabled. Returns
// ErrNotSupported if BTF is not enabled.
func LoadKernelSpec() (*Spec, error) {
kernelBTF.Lock()
defer kernelBTF.Unlock()
if kernelBTF.Spec != nil {
return kernelBTF.Spec, nil
}
var err error
kernelBTF.Spec, err = loadKernelSpec()
return kernelBTF.Spec, err
}
func loadKernelSpec() (*Spec, error) {
release, err := unix.KernelRelease()
if err != nil {
return nil, fmt.Errorf("can't read kernel release number: %w", err)
}
fh, err := os.Open("/sys/kernel/btf/vmlinux")
if err == nil {
defer fh.Close()
return loadNakedSpec(fh, internal.NativeEndian, nil, nil)
}
// use same list of locations as libbpf
// https://github.com/libbpf/libbpf/blob/9a3a42608dbe3731256a5682a125ac1e23bced8f/src/btf.c#L3114-L3122
locations := []string{
"/boot/vmlinux-%s",
"/lib/modules/%s/vmlinux-%[1]s",
"/lib/modules/%s/build/vmlinux",
"/usr/lib/modules/%s/kernel/vmlinux",
"/usr/lib/debug/boot/vmlinux-%s",
"/usr/lib/debug/boot/vmlinux-%s.debug",
"/usr/lib/debug/lib/modules/%s/vmlinux",
}
for _, loc := range locations {
path := fmt.Sprintf(loc, release)
fh, err := os.Open(path)
if err != nil {
continue
}
defer fh.Close()
return loadSpecFromVmlinux(fh)
}
return nil, fmt.Errorf("no BTF for kernel version %s: %w", release, internal.ErrNotSupported)
}
func parseBTF(btf io.ReadSeeker, bo binary.ByteOrder) ([]rawType, stringTable, error) {
rawBTF, err := ioutil.ReadAll(btf)
if err != nil {
return nil, nil, fmt.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, fmt.Errorf("can't read header: %v", err)
}
if header.Magic != btfMagic {
return nil, nil, fmt.Errorf("incorrect magic value %v", header.Magic)
}
if header.Version != 1 {
return nil, nil, fmt.Errorf("unexpected version %v", header.Version)
}
if header.Flags != 0 {
return nil, nil, fmt.Errorf("unsupported flags %v", header.Flags)
}
remainder := int64(header.HdrLen) - int64(binary.Size(&header))
if remainder < 0 {
return nil, nil, errors.New("header is too short")
}
if _, err := io.CopyN(internal.DiscardZeroes{}, rd, remainder); err != nil {
return nil, nil, fmt.Errorf("header padding: %v", err)
}
if _, err := rd.Seek(int64(header.HdrLen+header.StringOff), io.SeekStart); err != nil {
return nil, nil, fmt.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, fmt.Errorf("can't read type names: %w", err)
}
if _, err := rd.Seek(int64(header.HdrLen+header.TypeOff), io.SeekStart); err != nil {
return nil, nil, fmt.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, fmt.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
}
if name == ".kconfig" || name == ".ksyms" {
return fmt.Errorf("reference to %s: %w", name, ErrNotSupported)
}
if rawTypes[i].SizeType != 0 {
continue
}
size, ok := sectionSizes[name]
if !ok {
return fmt.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 fmt.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 fmt.Errorf("data section %s: can't get name for type %d: %w", name, id, err)
}
offset, ok := variableOffsets[variable{name, varName}]
if !ok {
return fmt.Errorf("data section %s: missing offset for variable %s", name, varName)
}
secinfos[j].Offset = offset
}
}
return nil
}
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.
_, _ = 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]), 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
}
// Program finds the BTF for a specific section.
//
// Length is the number of bytes in the raw BPF instruction stream.
//
// Returns an error which may wrap ErrNoExtendedInfo if the Spec doesn't
// contain extended BTF info.
func (s *Spec) Program(name string, length uint64) (*Program, error) {
if length == 0 {
return nil, errors.New("length musn't be zero")
}
if s.funcInfos == nil && s.lineInfos == nil && s.coreRelos == nil {
return nil, fmt.Errorf("BTF for section %s: %w", name, ErrNoExtendedInfo)
}
funcInfos, funcOK := s.funcInfos[name]
lineInfos, lineOK := s.lineInfos[name]
relos, coreOK := s.coreRelos[name]
if !funcOK && !lineOK && !coreOK {
return nil, fmt.Errorf("no extended BTF info for section %s", name)
}
return &Program{s, length, funcInfos, lineInfos, relos}, 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, fmt.Errorf("data section %s: can't get BTF: %w", name, err)
}
m := NewMap(s, &Void{}, &datasec)
return &m, nil
}
// FindType searches for a type with a specific name.
//
// hint determines the type of the returned Type.
//
// Returns an error wrapping ErrNotFound if no matching
// type exists in spec.
func (s *Spec) FindType(name string, typ Type) error {
var (
wanted = reflect.TypeOf(typ)
candidate Type
)
for _, typ := range s.namedTypes[essentialName(name)] {
if reflect.TypeOf(typ) != wanted {
continue
}
// Match against the full name, not just the essential one.
if typ.name() != name {
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)
}
cpy, _ := copyType(candidate, nil)
value := reflect.Indirect(reflect.ValueOf(cpy))
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
}
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 := &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
}
// NewMap returns a new Map containing the given values.
// The key and value arguments are initialized to Void if nil values are given.
func NewMap(spec *Spec, key Type, value Type) Map {
if key == nil {
key = &Void{}
}
if value == nil {
value = &Void{}
}
return Map{
spec: spec,
key: key,
value: value,
}
}
// 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
coreRelos coreRelos
}
// 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 fmt.Errorf("func infos: %w", err)
}
lineInfos, err := s.lineInfos.append(other.lineInfos, s.length)
if err != nil {
return fmt.Errorf("line infos: %w", err)
}
s.funcInfos = funcInfos
s.lineInfos = lineInfos
s.coreRelos = s.coreRelos.append(other.coreRelos, s.length)
s.length += other.length
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
}
// ProgramFixups returns the changes required to adjust the program to the target.
//
// This is a free function instead of a method to hide it from users
// of package ebpf.
func ProgramFixups(s *Program, target *Spec) (COREFixups, error) {
if len(s.coreRelos) == 0 {
return nil, nil
}
if target == nil {
var err error
target, err = LoadKernelSpec()
if err != nil {
return nil, err
}
}
return coreRelocate(s.spec, target, s.coreRelos)
}
type bpfLoadBTFAttr struct {
btf internal.Pointer
logBuf internal.Pointer
btfSize uint32
btfLogSize uint32
btfLogLevel uint32
}
func bpfLoadBTF(attr *bpfLoadBTFAttr) (*internal.FD, error) {
fd, err := internal.BPF(internal.BPF_BTF_LOAD, unsafe.Pointer(attr), unsafe.Sizeof(*attr))
if err != nil {
return nil, err
}
return internal.NewFD(uint32(fd)), nil
}
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 := bpfLoadBTF(&bpfLoadBTFAttr{
btf: internal.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 := bpfLoadBTF(&bpfLoadBTFAttr{
btf: internal.NewSlicePointer(btf),
btfSize: uint32(len(btf)),
})
if errors.Is(err, unix.EINVAL) {
return internal.ErrNotSupported
}
if err != nil {
return err
}
fd.Close()
return nil
})