GoToSocial/vendor/github.com/cilium/ebpf/marshalers.go

217 lines
5.6 KiB
Go

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:
sh := &reflect.SliceHeader{
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
}