mirror of
https://github.com/netbirdio/gvisor.git
synced 2026-05-22 17:12:49 -07:00
Etienne Perot
663e69bde4
This speeds up BPF evaluation by avoiding interface call overhead.
```
│ initial │ hey_look_no_interfaces │ even_fewer_interfaces │
│ sec/op │ sec/op vs base │ sec/op vs base │
Interpreter 26.31n ± 0% 21.87n ± 0% -16.88% (p=0.000 n=21+20) 14.26n ± 0% -45.80% (p=0.000 n=21+20)
```
PiperOrigin-RevId: 576591719
101 lines
3.0 KiB
Go
101 lines
3.0 KiB
Go
// Copyright 2018 The gVisor Authors.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
|
|
package bpf
|
|
|
|
import (
|
|
"encoding/binary"
|
|
)
|
|
|
|
// Input represents a source of input data for a BPF program. (BPF
|
|
// documentation sometimes refers to the input data as the "packet" due to its
|
|
// origins as a packet processing DSL.)
|
|
// Unaligned loads are supported.
|
|
type Input []byte
|
|
|
|
// These type definitions must have different GC shapes to ensure that
|
|
// the Go compiler generates distinct code paths for them.
|
|
// These do not have anything to do with the bit sizes of the loads
|
|
// later on; all that matters is that these types have distinct sizes
|
|
// from one another.
|
|
type (
|
|
// BigEndian uses big-endian byte ordering.
|
|
BigEndian uint8
|
|
|
|
// LittleEndian uses little-endian byte ordering.
|
|
LittleEndian uint16
|
|
|
|
// NativeEndian uses native byte ordering.
|
|
NativeEndian uint32
|
|
)
|
|
|
|
// Endianness represents a byte order.
|
|
type Endianness interface {
|
|
BigEndian | LittleEndian | NativeEndian
|
|
}
|
|
|
|
// load32 loads a 32-bit value.
|
|
//
|
|
//go:nosplit
|
|
func load32[endian Endianness](in Input, off uint32) (uint32, bool) {
|
|
if uint64(off)+4 > uint64(len(in)) {
|
|
return 0, false
|
|
}
|
|
// Casting to any is needed here to avoid a compilation error:
|
|
// https://go.googlesource.com/proposal/+/refs/heads/master/design/43651-type-parameters.md#why-not-permit-type-assertions-on-values-whose-type-is-a-type-parameter
|
|
var e endian
|
|
switch any(e).(type) {
|
|
case BigEndian:
|
|
return binary.BigEndian.Uint32(in[int(off):]), true
|
|
case LittleEndian:
|
|
return binary.LittleEndian.Uint32(in[int(off):]), true
|
|
case NativeEndian:
|
|
return binary.NativeEndian.Uint32(in[int(off):]), true
|
|
default:
|
|
panic("unreachable")
|
|
}
|
|
}
|
|
|
|
// load16 loads a 16-bit value.
|
|
//
|
|
//go:nosplit
|
|
func load16[endian Endianness](in Input, off uint32) (uint16, bool) {
|
|
if uint64(off)+2 > uint64(len(in)) {
|
|
return 0, false
|
|
}
|
|
// Casting to any is needed here to avoid a compilation error:
|
|
// https://go.googlesource.com/proposal/+/refs/heads/master/design/43651-type-parameters.md#why-not-permit-type-assertions-on-values-whose-type-is-a-type-parameter
|
|
var e endian
|
|
switch any(e).(type) {
|
|
case BigEndian:
|
|
return binary.BigEndian.Uint16(in[int(off):]), true
|
|
case LittleEndian:
|
|
return binary.LittleEndian.Uint16(in[int(off):]), true
|
|
case NativeEndian:
|
|
return binary.NativeEndian.Uint16(in[int(off):]), true
|
|
default:
|
|
panic("unreachable")
|
|
}
|
|
}
|
|
|
|
// load8 loads a single byte.
|
|
//
|
|
//go:nosplit
|
|
func load8(in Input, off uint32) (uint8, bool) {
|
|
if uint64(off)+1 > uint64(len(in)) {
|
|
return 0, false
|
|
}
|
|
return in[int(off)], true
|
|
}
|