vendor: add d2g/dhcp4server
This commit is contained in:
Dan Williams
434
vendor/golang.org/x/net/bpf/instructions.go
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vendored
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434
vendor/golang.org/x/net/bpf/instructions.go
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// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package bpf
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import "fmt"
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// An Instruction is one instruction executed by the BPF virtual
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// machine.
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type Instruction interface {
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// Assemble assembles the Instruction into a RawInstruction.
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Assemble() (RawInstruction, error)
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}
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// A RawInstruction is a raw BPF virtual machine instruction.
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type RawInstruction struct {
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// Operation to execute.
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Op uint16
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// For conditional jump instructions, the number of instructions
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// to skip if the condition is true/false.
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Jt uint8
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Jf uint8
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// Constant parameter. The meaning depends on the Op.
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K uint32
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}
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// Assemble implements the Instruction Assemble method.
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func (ri RawInstruction) Assemble() (RawInstruction, error) { return ri, nil }
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// Disassemble parses ri into an Instruction and returns it. If ri is
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// not recognized by this package, ri itself is returned.
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func (ri RawInstruction) Disassemble() Instruction {
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switch ri.Op & opMaskCls {
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case opClsLoadA, opClsLoadX:
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reg := Register(ri.Op & opMaskLoadDest)
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sz := 0
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switch ri.Op & opMaskLoadWidth {
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case opLoadWidth4:
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sz = 4
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case opLoadWidth2:
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sz = 2
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case opLoadWidth1:
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sz = 1
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default:
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return ri
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}
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switch ri.Op & opMaskLoadMode {
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case opAddrModeImmediate:
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if sz != 4 {
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return ri
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}
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return LoadConstant{Dst: reg, Val: ri.K}
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case opAddrModeScratch:
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if sz != 4 || ri.K > 15 {
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return ri
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}
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return LoadScratch{Dst: reg, N: int(ri.K)}
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case opAddrModeAbsolute:
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return LoadAbsolute{Size: sz, Off: ri.K}
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case opAddrModeIndirect:
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return LoadIndirect{Size: sz, Off: ri.K}
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case opAddrModePacketLen:
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if sz != 4 {
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return ri
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}
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return LoadExtension{Num: ExtLen}
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case opAddrModeMemShift:
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return LoadMemShift{Off: ri.K}
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default:
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return ri
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}
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case opClsStoreA:
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if ri.Op != opClsStoreA || ri.K > 15 {
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return ri
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}
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return StoreScratch{Src: RegA, N: int(ri.K)}
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case opClsStoreX:
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if ri.Op != opClsStoreX || ri.K > 15 {
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return ri
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}
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return StoreScratch{Src: RegX, N: int(ri.K)}
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case opClsALU:
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switch op := ALUOp(ri.Op & opMaskOperator); op {
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case ALUOpAdd, ALUOpSub, ALUOpMul, ALUOpDiv, ALUOpOr, ALUOpAnd, ALUOpShiftLeft, ALUOpShiftRight, ALUOpMod, ALUOpXor:
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if ri.Op&opMaskOperandSrc != 0 {
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return ALUOpX{Op: op}
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}
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return ALUOpConstant{Op: op, Val: ri.K}
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case aluOpNeg:
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return NegateA{}
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default:
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return ri
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}
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case opClsJump:
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if ri.Op&opMaskJumpConst != opClsJump {
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return ri
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}
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switch ri.Op & opMaskJumpCond {
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case opJumpAlways:
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return Jump{Skip: ri.K}
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case opJumpEqual:
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return JumpIf{
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Cond: JumpEqual,
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Val: ri.K,
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SkipTrue: ri.Jt,
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SkipFalse: ri.Jf,
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}
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case opJumpGT:
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return JumpIf{
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Cond: JumpGreaterThan,
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Val: ri.K,
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SkipTrue: ri.Jt,
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SkipFalse: ri.Jf,
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}
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case opJumpGE:
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return JumpIf{
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Cond: JumpGreaterOrEqual,
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Val: ri.K,
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SkipTrue: ri.Jt,
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SkipFalse: ri.Jf,
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}
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case opJumpSet:
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return JumpIf{
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Cond: JumpBitsSet,
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Val: ri.K,
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SkipTrue: ri.Jt,
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SkipFalse: ri.Jf,
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}
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default:
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return ri
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}
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case opClsReturn:
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switch ri.Op {
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case opClsReturn | opRetSrcA:
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return RetA{}
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case opClsReturn | opRetSrcConstant:
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return RetConstant{Val: ri.K}
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default:
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return ri
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}
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case opClsMisc:
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switch ri.Op {
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case opClsMisc | opMiscTAX:
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return TAX{}
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case opClsMisc | opMiscTXA:
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return TXA{}
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default:
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return ri
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}
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default:
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panic("unreachable") // switch is exhaustive on the bit pattern
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}
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}
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// LoadConstant loads Val into register Dst.
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type LoadConstant struct {
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Dst Register
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Val uint32
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}
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// Assemble implements the Instruction Assemble method.
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func (a LoadConstant) Assemble() (RawInstruction, error) {
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return assembleLoad(a.Dst, 4, opAddrModeImmediate, a.Val)
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}
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// LoadScratch loads scratch[N] into register Dst.
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type LoadScratch struct {
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Dst Register
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N int // 0-15
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}
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// Assemble implements the Instruction Assemble method.
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func (a LoadScratch) Assemble() (RawInstruction, error) {
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if a.N < 0 || a.N > 15 {
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return RawInstruction{}, fmt.Errorf("invalid scratch slot %d", a.N)
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}
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return assembleLoad(a.Dst, 4, opAddrModeScratch, uint32(a.N))
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}
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// LoadAbsolute loads packet[Off:Off+Size] as an integer value into
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// register A.
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type LoadAbsolute struct {
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Off uint32
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Size int // 1, 2 or 4
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}
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// Assemble implements the Instruction Assemble method.
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func (a LoadAbsolute) Assemble() (RawInstruction, error) {
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return assembleLoad(RegA, a.Size, opAddrModeAbsolute, a.Off)
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}
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// LoadIndirect loads packet[X+Off:X+Off+Size] as an integer value
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// into register A.
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type LoadIndirect struct {
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Off uint32
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Size int // 1, 2 or 4
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}
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// Assemble implements the Instruction Assemble method.
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func (a LoadIndirect) Assemble() (RawInstruction, error) {
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return assembleLoad(RegA, a.Size, opAddrModeIndirect, a.Off)
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}
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// LoadMemShift multiplies the first 4 bits of the byte at packet[Off]
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// by 4 and stores the result in register X.
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//
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// This instruction is mainly useful to load into X the length of an
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// IPv4 packet header in a single instruction, rather than have to do
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// the arithmetic on the header's first byte by hand.
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type LoadMemShift struct {
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Off uint32
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}
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// Assemble implements the Instruction Assemble method.
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func (a LoadMemShift) Assemble() (RawInstruction, error) {
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return assembleLoad(RegX, 1, opAddrModeMemShift, a.Off)
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}
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// LoadExtension invokes a linux-specific extension and stores the
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// result in register A.
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type LoadExtension struct {
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Num Extension
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}
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// Assemble implements the Instruction Assemble method.
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func (a LoadExtension) Assemble() (RawInstruction, error) {
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if a.Num == ExtLen {
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return assembleLoad(RegA, 4, opAddrModePacketLen, 0)
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}
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return assembleLoad(RegA, 4, opAddrModeAbsolute, uint32(-0x1000+a.Num))
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}
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// StoreScratch stores register Src into scratch[N].
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type StoreScratch struct {
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Src Register
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N int // 0-15
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}
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// Assemble implements the Instruction Assemble method.
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func (a StoreScratch) Assemble() (RawInstruction, error) {
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if a.N < 0 || a.N > 15 {
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return RawInstruction{}, fmt.Errorf("invalid scratch slot %d", a.N)
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}
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var op uint16
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switch a.Src {
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case RegA:
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op = opClsStoreA
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case RegX:
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op = opClsStoreX
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default:
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return RawInstruction{}, fmt.Errorf("invalid source register %v", a.Src)
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}
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return RawInstruction{
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Op: op,
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K: uint32(a.N),
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}, nil
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}
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// ALUOpConstant executes A = A <Op> Val.
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type ALUOpConstant struct {
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Op ALUOp
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Val uint32
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}
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// Assemble implements the Instruction Assemble method.
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func (a ALUOpConstant) Assemble() (RawInstruction, error) {
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return RawInstruction{
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Op: opClsALU | opALUSrcConstant | uint16(a.Op),
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K: a.Val,
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}, nil
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}
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// ALUOpX executes A = A <Op> X
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type ALUOpX struct {
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Op ALUOp
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}
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// Assemble implements the Instruction Assemble method.
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func (a ALUOpX) Assemble() (RawInstruction, error) {
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return RawInstruction{
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Op: opClsALU | opALUSrcX | uint16(a.Op),
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}, nil
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}
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// NegateA executes A = -A.
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type NegateA struct{}
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// Assemble implements the Instruction Assemble method.
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func (a NegateA) Assemble() (RawInstruction, error) {
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return RawInstruction{
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Op: opClsALU | uint16(aluOpNeg),
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}, nil
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}
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// Jump skips the following Skip instructions in the program.
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type Jump struct {
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Skip uint32
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}
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// Assemble implements the Instruction Assemble method.
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func (a Jump) Assemble() (RawInstruction, error) {
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return RawInstruction{
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Op: opClsJump | opJumpAlways,
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K: a.Skip,
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}, nil
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}
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// JumpIf skips the following Skip instructions in the program if A
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// <Cond> Val is true.
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type JumpIf struct {
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Cond JumpTest
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Val uint32
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SkipTrue uint8
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SkipFalse uint8
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}
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// Assemble implements the Instruction Assemble method.
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func (a JumpIf) Assemble() (RawInstruction, error) {
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var (
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cond uint16
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flip bool
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)
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switch a.Cond {
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case JumpEqual:
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cond = opJumpEqual
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case JumpNotEqual:
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cond, flip = opJumpEqual, true
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case JumpGreaterThan:
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cond = opJumpGT
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case JumpLessThan:
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cond, flip = opJumpGE, true
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case JumpGreaterOrEqual:
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cond = opJumpGE
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case JumpLessOrEqual:
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cond, flip = opJumpGT, true
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case JumpBitsSet:
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cond = opJumpSet
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case JumpBitsNotSet:
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cond, flip = opJumpSet, true
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default:
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return RawInstruction{}, fmt.Errorf("unknown JumpTest %v", a.Cond)
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}
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jt, jf := a.SkipTrue, a.SkipFalse
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if flip {
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jt, jf = jf, jt
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}
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return RawInstruction{
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Op: opClsJump | cond,
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Jt: jt,
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Jf: jf,
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K: a.Val,
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}, nil
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}
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// RetA exits the BPF program, returning the value of register A.
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type RetA struct{}
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// Assemble implements the Instruction Assemble method.
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func (a RetA) Assemble() (RawInstruction, error) {
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return RawInstruction{
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Op: opClsReturn | opRetSrcA,
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}, nil
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}
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// RetConstant exits the BPF program, returning a constant value.
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type RetConstant struct {
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Val uint32
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}
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// Assemble implements the Instruction Assemble method.
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func (a RetConstant) Assemble() (RawInstruction, error) {
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return RawInstruction{
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Op: opClsReturn | opRetSrcConstant,
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K: a.Val,
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}, nil
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}
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// TXA copies the value of register X to register A.
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type TXA struct{}
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// Assemble implements the Instruction Assemble method.
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func (a TXA) Assemble() (RawInstruction, error) {
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return RawInstruction{
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Op: opClsMisc | opMiscTXA,
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}, nil
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}
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// TAX copies the value of register A to register X.
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type TAX struct{}
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// Assemble implements the Instruction Assemble method.
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func (a TAX) Assemble() (RawInstruction, error) {
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return RawInstruction{
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Op: opClsMisc | opMiscTAX,
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}, nil
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}
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func assembleLoad(dst Register, loadSize int, mode uint16, k uint32) (RawInstruction, error) {
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var (
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cls uint16
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sz uint16
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)
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switch dst {
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case RegA:
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cls = opClsLoadA
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case RegX:
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cls = opClsLoadX
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default:
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return RawInstruction{}, fmt.Errorf("invalid target register %v", dst)
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}
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switch loadSize {
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case 1:
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sz = opLoadWidth1
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case 2:
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sz = opLoadWidth2
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case 4:
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sz = opLoadWidth4
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default:
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return RawInstruction{}, fmt.Errorf("invalid load byte length %d", sz)
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}
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return RawInstruction{
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Op: cls | sz | mode,
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K: k,
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}, nil
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}
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