k3s/vendor/github.com/cilium/ebpf/collection.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

617 lines
15 KiB
Go

package ebpf
import (
"errors"
"fmt"
"io"
"math"
"reflect"
"strings"
"github.com/cilium/ebpf/asm"
"github.com/cilium/ebpf/internal"
"github.com/cilium/ebpf/internal/btf"
)
// CollectionOptions control loading a collection into the kernel.
//
// Maps and Programs are passed to NewMapWithOptions and NewProgramsWithOptions.
type CollectionOptions struct {
Maps MapOptions
Programs ProgramOptions
}
// CollectionSpec describes a collection.
type CollectionSpec struct {
Maps map[string]*MapSpec
Programs map[string]*ProgramSpec
}
// Copy returns a recursive copy of the spec.
func (cs *CollectionSpec) Copy() *CollectionSpec {
if cs == nil {
return nil
}
cpy := CollectionSpec{
Maps: make(map[string]*MapSpec, len(cs.Maps)),
Programs: make(map[string]*ProgramSpec, len(cs.Programs)),
}
for name, spec := range cs.Maps {
cpy.Maps[name] = spec.Copy()
}
for name, spec := range cs.Programs {
cpy.Programs[name] = spec.Copy()
}
return &cpy
}
// RewriteMaps replaces all references to specific maps.
//
// Use this function to use pre-existing maps instead of creating new ones
// when calling NewCollection. Any named maps are removed from CollectionSpec.Maps.
//
// Returns an error if a named map isn't used in at least one program.
func (cs *CollectionSpec) RewriteMaps(maps map[string]*Map) error {
for symbol, m := range maps {
// have we seen a program that uses this symbol / map
seen := false
fd := m.FD()
for progName, progSpec := range cs.Programs {
err := progSpec.Instructions.RewriteMapPtr(symbol, fd)
switch {
case err == nil:
seen = true
case asm.IsUnreferencedSymbol(err):
// Not all programs need to use the map
default:
return fmt.Errorf("program %s: %w", progName, err)
}
}
if !seen {
return fmt.Errorf("map %s not referenced by any programs", symbol)
}
// Prevent NewCollection from creating rewritten maps
delete(cs.Maps, symbol)
}
return nil
}
// RewriteConstants replaces the value of multiple constants.
//
// The constant must be defined like so in the C program:
//
// volatile const type foobar;
// volatile const type foobar = default;
//
// Replacement values must be of the same length as the C sizeof(type).
// If necessary, they are marshalled according to the same rules as
// map values.
//
// From Linux 5.5 the verifier will use constants to eliminate dead code.
//
// Returns an error if a constant doesn't exist.
func (cs *CollectionSpec) RewriteConstants(consts map[string]interface{}) error {
rodata := cs.Maps[".rodata"]
if rodata == nil {
return errors.New("missing .rodata section")
}
if rodata.BTF == nil {
return errors.New(".rodata section has no BTF")
}
if n := len(rodata.Contents); n != 1 {
return fmt.Errorf("expected one key in .rodata, found %d", n)
}
kv := rodata.Contents[0]
value, ok := kv.Value.([]byte)
if !ok {
return fmt.Errorf("first value in .rodata is %T not []byte", kv.Value)
}
buf := make([]byte, len(value))
copy(buf, value)
err := patchValue(buf, btf.MapValue(rodata.BTF), consts)
if err != nil {
return err
}
rodata.Contents[0] = MapKV{kv.Key, buf}
return nil
}
// Assign the contents of a CollectionSpec to a struct.
//
// This function is a short-cut to manually checking the presence
// of maps and programs in a collection spec. Consider using bpf2go if this
// sounds useful.
//
// The argument to must be a pointer to a struct. A field of the
// struct is updated with values from Programs or Maps if it
// has an `ebpf` tag and its type is *ProgramSpec or *MapSpec.
// The tag gives the name of the program or map as found in
// the CollectionSpec.
//
// struct {
// Foo *ebpf.ProgramSpec `ebpf:"xdp_foo"`
// Bar *ebpf.MapSpec `ebpf:"bar_map"`
// Ignored int
// }
//
// Returns an error if any of the fields can't be found, or
// if the same map or program is assigned multiple times.
func (cs *CollectionSpec) Assign(to interface{}) error {
valueOf := func(typ reflect.Type, name string) (reflect.Value, error) {
switch typ {
case reflect.TypeOf((*ProgramSpec)(nil)):
p := cs.Programs[name]
if p == nil {
return reflect.Value{}, fmt.Errorf("missing program %q", name)
}
return reflect.ValueOf(p), nil
case reflect.TypeOf((*MapSpec)(nil)):
m := cs.Maps[name]
if m == nil {
return reflect.Value{}, fmt.Errorf("missing map %q", name)
}
return reflect.ValueOf(m), nil
default:
return reflect.Value{}, fmt.Errorf("unsupported type %s", typ)
}
}
return assignValues(to, valueOf)
}
// LoadAndAssign maps and programs into the kernel and assign them to a struct.
//
// This function is a short-cut to manually checking the presence
// of maps and programs in a collection spec. Consider using bpf2go if this
// sounds useful.
//
// The argument to must be a pointer to a struct. A field of the
// struct is updated with values from Programs or Maps if it
// has an `ebpf` tag and its type is *Program or *Map.
// The tag gives the name of the program or map as found in
// the CollectionSpec.
//
// struct {
// Foo *ebpf.Program `ebpf:"xdp_foo"`
// Bar *ebpf.Map `ebpf:"bar_map"`
// Ignored int
// }
//
// opts may be nil.
//
// Returns an error if any of the fields can't be found, or
// if the same map or program is assigned multiple times.
func (cs *CollectionSpec) LoadAndAssign(to interface{}, opts *CollectionOptions) error {
if opts == nil {
opts = &CollectionOptions{}
}
loadMap, loadProgram, done, cleanup := lazyLoadCollection(cs, opts)
defer cleanup()
valueOf := func(typ reflect.Type, name string) (reflect.Value, error) {
switch typ {
case reflect.TypeOf((*Program)(nil)):
p, err := loadProgram(name)
if err != nil {
return reflect.Value{}, err
}
return reflect.ValueOf(p), nil
case reflect.TypeOf((*Map)(nil)):
m, err := loadMap(name)
if err != nil {
return reflect.Value{}, err
}
return reflect.ValueOf(m), nil
default:
return reflect.Value{}, fmt.Errorf("unsupported type %s", typ)
}
}
if err := assignValues(to, valueOf); err != nil {
return err
}
done()
return nil
}
// Collection is a collection of Programs and Maps associated
// with their symbols
type Collection struct {
Programs map[string]*Program
Maps map[string]*Map
}
// NewCollection creates a Collection from a specification.
func NewCollection(spec *CollectionSpec) (*Collection, error) {
return NewCollectionWithOptions(spec, CollectionOptions{})
}
// NewCollectionWithOptions creates a Collection from a specification.
func NewCollectionWithOptions(spec *CollectionSpec, opts CollectionOptions) (*Collection, error) {
loadMap, loadProgram, done, cleanup := lazyLoadCollection(spec, &opts)
defer cleanup()
for mapName := range spec.Maps {
_, err := loadMap(mapName)
if err != nil {
return nil, err
}
}
for progName := range spec.Programs {
_, err := loadProgram(progName)
if err != nil {
return nil, err
}
}
maps, progs := done()
return &Collection{
progs,
maps,
}, nil
}
type handleCache struct {
btfHandles map[*btf.Spec]*btf.Handle
btfSpecs map[io.ReaderAt]*btf.Spec
}
func newHandleCache() *handleCache {
return &handleCache{
btfHandles: make(map[*btf.Spec]*btf.Handle),
btfSpecs: make(map[io.ReaderAt]*btf.Spec),
}
}
func (hc handleCache) btfHandle(spec *btf.Spec) (*btf.Handle, error) {
if hc.btfHandles[spec] != nil {
return hc.btfHandles[spec], nil
}
handle, err := btf.NewHandle(spec)
if err != nil {
return nil, err
}
hc.btfHandles[spec] = handle
return handle, nil
}
func (hc handleCache) btfSpec(rd io.ReaderAt) (*btf.Spec, error) {
if hc.btfSpecs[rd] != nil {
return hc.btfSpecs[rd], nil
}
spec, err := btf.LoadSpecFromReader(rd)
if err != nil {
return nil, err
}
hc.btfSpecs[rd] = spec
return spec, nil
}
func (hc handleCache) close() {
for _, handle := range hc.btfHandles {
handle.Close()
}
hc.btfHandles = nil
hc.btfSpecs = nil
}
func lazyLoadCollection(coll *CollectionSpec, opts *CollectionOptions) (
loadMap func(string) (*Map, error),
loadProgram func(string) (*Program, error),
done func() (map[string]*Map, map[string]*Program),
cleanup func(),
) {
var (
maps = make(map[string]*Map)
progs = make(map[string]*Program)
handles = newHandleCache()
skipMapsAndProgs = false
)
cleanup = func() {
handles.close()
if skipMapsAndProgs {
return
}
for _, m := range maps {
m.Close()
}
for _, p := range progs {
p.Close()
}
}
done = func() (map[string]*Map, map[string]*Program) {
skipMapsAndProgs = true
return maps, progs
}
loadMap = func(mapName string) (*Map, error) {
if m := maps[mapName]; m != nil {
return m, nil
}
mapSpec := coll.Maps[mapName]
if mapSpec == nil {
return nil, fmt.Errorf("missing map %s", mapName)
}
m, err := newMapWithOptions(mapSpec, opts.Maps, handles)
if err != nil {
return nil, fmt.Errorf("map %s: %w", mapName, err)
}
maps[mapName] = m
return m, nil
}
loadProgram = func(progName string) (*Program, error) {
if prog := progs[progName]; prog != nil {
return prog, nil
}
progSpec := coll.Programs[progName]
if progSpec == nil {
return nil, fmt.Errorf("unknown program %s", progName)
}
progSpec = progSpec.Copy()
// Rewrite any reference to a valid map.
for i := range progSpec.Instructions {
ins := &progSpec.Instructions[i]
if !ins.IsLoadFromMap() || ins.Reference == "" {
continue
}
if uint32(ins.Constant) != math.MaxUint32 {
// Don't overwrite maps already rewritten, users can
// rewrite programs in the spec themselves
continue
}
m, err := loadMap(ins.Reference)
if err != nil {
return nil, fmt.Errorf("program %s: %w", progName, err)
}
fd := m.FD()
if fd < 0 {
return nil, fmt.Errorf("map %s: %w", ins.Reference, internal.ErrClosedFd)
}
if err := ins.RewriteMapPtr(m.FD()); err != nil {
return nil, fmt.Errorf("progam %s: map %s: %w", progName, ins.Reference, err)
}
}
prog, err := newProgramWithOptions(progSpec, opts.Programs, handles)
if err != nil {
return nil, fmt.Errorf("program %s: %w", progName, err)
}
progs[progName] = prog
return prog, nil
}
return
}
// LoadCollection parses an object file and converts it to a collection.
func LoadCollection(file string) (*Collection, error) {
spec, err := LoadCollectionSpec(file)
if err != nil {
return nil, err
}
return NewCollection(spec)
}
// Close frees all maps and programs associated with the collection.
//
// The collection mustn't be used afterwards.
func (coll *Collection) Close() {
for _, prog := range coll.Programs {
prog.Close()
}
for _, m := range coll.Maps {
m.Close()
}
}
// DetachMap removes the named map from the Collection.
//
// This means that a later call to Close() will not affect this map.
//
// Returns nil if no map of that name exists.
func (coll *Collection) DetachMap(name string) *Map {
m := coll.Maps[name]
delete(coll.Maps, name)
return m
}
// DetachProgram removes the named program from the Collection.
//
// This means that a later call to Close() will not affect this program.
//
// Returns nil if no program of that name exists.
func (coll *Collection) DetachProgram(name string) *Program {
p := coll.Programs[name]
delete(coll.Programs, name)
return p
}
// Assign the contents of a collection to a struct.
//
// Deprecated: use CollectionSpec.Assign instead. It provides the same
// functionality but creates only the maps and programs requested.
func (coll *Collection) Assign(to interface{}) error {
assignedMaps := make(map[string]struct{})
assignedPrograms := make(map[string]struct{})
valueOf := func(typ reflect.Type, name string) (reflect.Value, error) {
switch typ {
case reflect.TypeOf((*Program)(nil)):
p := coll.Programs[name]
if p == nil {
return reflect.Value{}, fmt.Errorf("missing program %q", name)
}
assignedPrograms[name] = struct{}{}
return reflect.ValueOf(p), nil
case reflect.TypeOf((*Map)(nil)):
m := coll.Maps[name]
if m == nil {
return reflect.Value{}, fmt.Errorf("missing map %q", name)
}
assignedMaps[name] = struct{}{}
return reflect.ValueOf(m), nil
default:
return reflect.Value{}, fmt.Errorf("unsupported type %s", typ)
}
}
if err := assignValues(to, valueOf); err != nil {
return err
}
for name := range assignedPrograms {
coll.DetachProgram(name)
}
for name := range assignedMaps {
coll.DetachMap(name)
}
return nil
}
func assignValues(to interface{}, valueOf func(reflect.Type, string) (reflect.Value, error)) error {
type structField struct {
reflect.StructField
value reflect.Value
}
var (
fields []structField
visitedTypes = make(map[reflect.Type]bool)
flattenStruct func(reflect.Value) error
)
flattenStruct = func(structVal reflect.Value) error {
structType := structVal.Type()
if structType.Kind() != reflect.Struct {
return fmt.Errorf("%s is not a struct", structType)
}
if visitedTypes[structType] {
return fmt.Errorf("recursion on type %s", structType)
}
for i := 0; i < structType.NumField(); i++ {
field := structField{structType.Field(i), structVal.Field(i)}
name := field.Tag.Get("ebpf")
if name != "" {
fields = append(fields, field)
continue
}
var err error
switch field.Type.Kind() {
case reflect.Ptr:
if field.Type.Elem().Kind() != reflect.Struct {
continue
}
if field.value.IsNil() {
return fmt.Errorf("nil pointer to %s", structType)
}
err = flattenStruct(field.value.Elem())
case reflect.Struct:
err = flattenStruct(field.value)
default:
continue
}
if err != nil {
return fmt.Errorf("field %s: %w", field.Name, err)
}
}
return nil
}
toValue := reflect.ValueOf(to)
if toValue.Type().Kind() != reflect.Ptr {
return fmt.Errorf("%T is not a pointer to struct", to)
}
if toValue.IsNil() {
return fmt.Errorf("nil pointer to %T", to)
}
if err := flattenStruct(toValue.Elem()); err != nil {
return err
}
type elem struct {
// Either *Map or *Program
typ reflect.Type
name string
}
assignedTo := make(map[elem]string)
for _, field := range fields {
name := field.Tag.Get("ebpf")
if strings.Contains(name, ",") {
return fmt.Errorf("field %s: ebpf tag contains a comma", field.Name)
}
e := elem{field.Type, name}
if assignedField := assignedTo[e]; assignedField != "" {
return fmt.Errorf("field %s: %q was already assigned to %s", field.Name, name, assignedField)
}
value, err := valueOf(field.Type, name)
if err != nil {
return fmt.Errorf("field %s: %w", field.Name, err)
}
if !field.value.CanSet() {
return fmt.Errorf("field %s: can't set value", field.Name)
}
field.value.Set(value)
assignedTo[e] = field.Name
}
return nil
}