package ebpf import ( "bytes" "encoding" "encoding/binary" "errors" "fmt" "reflect" "runtime" "unsafe" "github.com/cilium/ebpf/internal" ) // marshalPtr converts an arbitrary value into a pointer suitable // to be passed to the kernel. // // As an optimization, it returns the original value if it is an // unsafe.Pointer. func marshalPtr(data interface{}, length int) (internal.Pointer, error) { if ptr, ok := data.(unsafe.Pointer); ok { return internal.NewPointer(ptr), nil } buf, err := marshalBytes(data, length) if err != nil { return internal.Pointer{}, err } return internal.NewSlicePointer(buf), nil } // marshalBytes converts an arbitrary value into a byte buffer. // // Prefer using Map.marshalKey and Map.marshalValue if possible, since // those have special cases that allow more types to be encoded. // // Returns an error if the given value isn't representable in exactly // length bytes. func marshalBytes(data interface{}, length int) (buf []byte, err error) { switch value := data.(type) { case encoding.BinaryMarshaler: buf, err = value.MarshalBinary() case string: buf = []byte(value) case []byte: buf = value case unsafe.Pointer: err = errors.New("can't marshal from unsafe.Pointer") case Map, *Map, Program, *Program: err = fmt.Errorf("can't marshal %T", value) default: var wr bytes.Buffer err = binary.Write(&wr, internal.NativeEndian, value) if err != nil { err = fmt.Errorf("encoding %T: %v", value, err) } buf = wr.Bytes() } if err != nil { return nil, err } if len(buf) != length { return nil, fmt.Errorf("%T doesn't marshal to %d bytes", data, length) } return buf, nil } func makeBuffer(dst interface{}, length int) (internal.Pointer, []byte) { if ptr, ok := dst.(unsafe.Pointer); ok { return internal.NewPointer(ptr), nil } buf := make([]byte, length) return internal.NewSlicePointer(buf), buf } // unmarshalBytes converts a byte buffer into an arbitrary value. // // Prefer using Map.unmarshalKey and Map.unmarshalValue if possible, since // those have special cases that allow more types to be encoded. func unmarshalBytes(data interface{}, buf []byte) error { switch value := data.(type) { case unsafe.Pointer: // This could be solved in Go 1.17 by unsafe.Slice instead. (https://github.com/golang/go/issues/19367) // We could opt for removing unsafe.Pointer support in the lib as well. sh := &reflect.SliceHeader{ //nolint:govet Data: uintptr(value), Len: len(buf), Cap: len(buf), } dst := *(*[]byte)(unsafe.Pointer(sh)) copy(dst, buf) runtime.KeepAlive(value) return nil case Map, *Map, Program, *Program: return fmt.Errorf("can't unmarshal into %T", value) case encoding.BinaryUnmarshaler: return value.UnmarshalBinary(buf) case *string: *value = string(buf) return nil case *[]byte: *value = buf return nil case string: return errors.New("require pointer to string") case []byte: return errors.New("require pointer to []byte") default: rd := bytes.NewReader(buf) if err := binary.Read(rd, internal.NativeEndian, value); err != nil { return fmt.Errorf("decoding %T: %v", value, err) } return nil } } // marshalPerCPUValue encodes a slice containing one value per // possible CPU into a buffer of bytes. // // Values are initialized to zero if the slice has less elements than CPUs. // // slice must have a type like []elementType. func marshalPerCPUValue(slice interface{}, elemLength int) (internal.Pointer, error) { sliceType := reflect.TypeOf(slice) if sliceType.Kind() != reflect.Slice { return internal.Pointer{}, errors.New("per-CPU value requires slice") } possibleCPUs, err := internal.PossibleCPUs() if err != nil { return internal.Pointer{}, err } sliceValue := reflect.ValueOf(slice) sliceLen := sliceValue.Len() if sliceLen > possibleCPUs { return internal.Pointer{}, fmt.Errorf("per-CPU value exceeds number of CPUs") } alignedElemLength := align(elemLength, 8) buf := make([]byte, alignedElemLength*possibleCPUs) for i := 0; i < sliceLen; i++ { elem := sliceValue.Index(i).Interface() elemBytes, err := marshalBytes(elem, elemLength) if err != nil { return internal.Pointer{}, err } offset := i * alignedElemLength copy(buf[offset:offset+elemLength], elemBytes) } return internal.NewSlicePointer(buf), nil } // unmarshalPerCPUValue decodes a buffer into a slice containing one value per // possible CPU. // // valueOut must have a type like *[]elementType func unmarshalPerCPUValue(slicePtr interface{}, elemLength int, buf []byte) error { slicePtrType := reflect.TypeOf(slicePtr) if slicePtrType.Kind() != reflect.Ptr || slicePtrType.Elem().Kind() != reflect.Slice { return fmt.Errorf("per-cpu value requires pointer to slice") } possibleCPUs, err := internal.PossibleCPUs() if err != nil { return err } sliceType := slicePtrType.Elem() slice := reflect.MakeSlice(sliceType, possibleCPUs, possibleCPUs) sliceElemType := sliceType.Elem() sliceElemIsPointer := sliceElemType.Kind() == reflect.Ptr if sliceElemIsPointer { sliceElemType = sliceElemType.Elem() } step := len(buf) / possibleCPUs if step < elemLength { return fmt.Errorf("per-cpu element length is larger than available data") } for i := 0; i < possibleCPUs; i++ { var elem interface{} if sliceElemIsPointer { newElem := reflect.New(sliceElemType) slice.Index(i).Set(newElem) elem = newElem.Interface() } else { elem = slice.Index(i).Addr().Interface() } // Make a copy, since unmarshal can hold on to itemBytes elemBytes := make([]byte, elemLength) copy(elemBytes, buf[:elemLength]) err := unmarshalBytes(elem, elemBytes) if err != nil { return fmt.Errorf("cpu %d: %w", i, err) } buf = buf[step:] } reflect.ValueOf(slicePtr).Elem().Set(slice) return nil } func align(n, alignment int) int { return (int(n) + alignment - 1) / alignment * alignment }