update packages

vendor/golang.org/x/net/bpf/constants.go

@@ -70,57 +70,60 @@ type Extension int
 
 // Extension functions available in the Linux kernel.
 const (
+	// extOffset is the negative maximum number of instructions used
+	// to load instructions by overloading the K argument.
+	extOffset = -0x1000
 	// ExtLen returns the length of the packet.
 	ExtLen Extension = 1
 	// ExtProto returns the packet's L3 protocol type.
-	ExtProto = 0
+	ExtProto Extension = 0
 	// ExtType returns the packet's type (skb->pkt_type in the kernel)
 	//
 	// TODO: better documentation. How nice an API do we want to
 	// provide for these esoteric extensions?
-	ExtType = 4
+	ExtType Extension = 4
 	// ExtPayloadOffset returns the offset of the packet payload, or
 	// the first protocol header that the kernel does not know how to
 	// parse.
-	ExtPayloadOffset = 52
+	ExtPayloadOffset Extension = 52
 	// ExtInterfaceIndex returns the index of the interface on which
 	// the packet was received.
-	ExtInterfaceIndex = 8
+	ExtInterfaceIndex Extension = 8
 	// ExtNetlinkAttr returns the netlink attribute of type X at
 	// offset A.
-	ExtNetlinkAttr = 12
+	ExtNetlinkAttr Extension = 12
 	// ExtNetlinkAttrNested returns the nested netlink attribute of
 	// type X at offset A.
-	ExtNetlinkAttrNested = 16
+	ExtNetlinkAttrNested Extension = 16
 	// ExtMark returns the packet's mark value.
-	ExtMark = 20
+	ExtMark Extension = 20
 	// ExtQueue returns the packet's assigned hardware queue.
-	ExtQueue = 24
+	ExtQueue Extension = 24
 	// ExtLinkLayerType returns the packet's hardware address type
 	// (e.g. Ethernet, Infiniband).
-	ExtLinkLayerType = 28
+	ExtLinkLayerType Extension = 28
 	// ExtRXHash returns the packets receive hash.
 	//
 	// TODO: figure out what this rxhash actually is.
-	ExtRXHash = 32
+	ExtRXHash Extension = 32
 	// ExtCPUID returns the ID of the CPU processing the current
 	// packet.
-	ExtCPUID = 36
+	ExtCPUID Extension = 36
 	// ExtVLANTag returns the packet's VLAN tag.
-	ExtVLANTag = 44
+	ExtVLANTag Extension = 44
 	// ExtVLANTagPresent returns non-zero if the packet has a VLAN
 	// tag.
 	//
 	// TODO: I think this might be a lie: it reads bit 0x1000 of the
 	// VLAN header, which changed meaning in recent revisions of the
 	// spec - this extension may now return meaningless information.
-	ExtVLANTagPresent = 48
+	ExtVLANTagPresent Extension = 48
 	// ExtVLANProto returns 0x8100 if the frame has a VLAN header,
 	// 0x88a8 if the frame has a "Q-in-Q" double VLAN header, or some
 	// other value if no VLAN information is present.
-	ExtVLANProto = 60
+	ExtVLANProto Extension = 60
 	// ExtRand returns a uniformly random uint32.
-	ExtRand = 56
+	ExtRand Extension = 56
 )
 
 // The following gives names to various bit patterns used in opcode construction.

vendor/golang.org/x/net/bpf/doc.go

@@ -5,7 +5,8 @@
 /*
 
 Package bpf implements marshaling and unmarshaling of programs for the
-Berkeley Packet Filter virtual machine.
+Berkeley Packet Filter virtual machine, and provides a Go implementation
+of the virtual machine.
 
 BPF's main use is to specify a packet filter for network taps, so that
 the kernel doesn't have to expensively copy every packet it sees to

vendor/golang.org/x/net/bpf/instructions.go

@@ -57,6 +57,9 @@ func (ri RawInstruction) Disassemble() Instruction {
 			}
 			return LoadScratch{Dst: reg, N: int(ri.K)}
 		case opAddrModeAbsolute:
+			if ri.K > extOffset+0xffffffff {
+				return LoadExtension{Num: Extension(-extOffset + ri.K)}
+			}
 			return LoadAbsolute{Size: sz, Off: ri.K}
 		case opAddrModeIndirect:
 			return LoadIndirect{Size: sz, Off: ri.K}
@@ -104,6 +107,14 @@ func (ri RawInstruction) Disassemble() Instruction {
 		case opJumpAlways:
 			return Jump{Skip: ri.K}
 		case opJumpEqual:
+			if ri.Jt == 0 {
+				return JumpIf{
+					Cond:      JumpNotEqual,
+					Val:       ri.K,
+					SkipTrue:  ri.Jf,
+					SkipFalse: 0,
+				}
+			}
 			return JumpIf{
 				Cond:      JumpEqual,
 				Val:       ri.K,
@@ -111,6 +122,14 @@ func (ri RawInstruction) Disassemble() Instruction {
 				SkipFalse: ri.Jf,
 			}
 		case opJumpGT:
+			if ri.Jt == 0 {
+				return JumpIf{
+					Cond:      JumpLessOrEqual,
+					Val:       ri.K,
+					SkipTrue:  ri.Jf,
+					SkipFalse: 0,
+				}
+			}
 			return JumpIf{
 				Cond:      JumpGreaterThan,
 				Val:       ri.K,
@@ -118,6 +137,14 @@ func (ri RawInstruction) Disassemble() Instruction {
 				SkipFalse: ri.Jf,
 			}
 		case opJumpGE:
+			if ri.Jt == 0 {
+				return JumpIf{
+					Cond:      JumpLessThan,
+					Val:       ri.K,
+					SkipTrue:  ri.Jf,
+					SkipFalse: 0,
+				}
+			}
 			return JumpIf{
 				Cond:      JumpGreaterOrEqual,
 				Val:       ri.K,
@@ -171,6 +198,18 @@ func (a LoadConstant) Assemble() (RawInstruction, error) {
 	return assembleLoad(a.Dst, 4, opAddrModeImmediate, a.Val)
 }
 
+// String returns the the instruction in assembler notation.
+func (a LoadConstant) String() string {
+	switch a.Dst {
+	case RegA:
+		return fmt.Sprintf("ld #%d", a.Val)
+	case RegX:
+		return fmt.Sprintf("ldx #%d", a.Val)
+	default:
+		return fmt.Sprintf("unknown instruction: %#v", a)
+	}
+}
+
 // LoadScratch loads scratch[N] into register Dst.
 type LoadScratch struct {
 	Dst Register
@@ -185,6 +224,18 @@ func (a LoadScratch) Assemble() (RawInstruction, error) {
 	return assembleLoad(a.Dst, 4, opAddrModeScratch, uint32(a.N))
 }
 
+// String returns the the instruction in assembler notation.
+func (a LoadScratch) String() string {
+	switch a.Dst {
+	case RegA:
+		return fmt.Sprintf("ld M[%d]", a.N)
+	case RegX:
+		return fmt.Sprintf("ldx M[%d]", a.N)
+	default:
+		return fmt.Sprintf("unknown instruction: %#v", a)
+	}
+}
+
 // LoadAbsolute loads packet[Off:Off+Size] as an integer value into
 // register A.
 type LoadAbsolute struct {
@@ -197,6 +248,23 @@ func (a LoadAbsolute) Assemble() (RawInstruction, error) {
 	return assembleLoad(RegA, a.Size, opAddrModeAbsolute, a.Off)
 }
 
+// String returns the the instruction in assembler notation.
+func (a LoadAbsolute) String() string {
+	switch a.Size {
+	case 1: // byte
+		return fmt.Sprintf("ldb [%d]", a.Off)
+	case 2: // half word
+		return fmt.Sprintf("ldh [%d]", a.Off)
+	case 4: // word
+		if a.Off > extOffset+0xffffffff {
+			return LoadExtension{Num: Extension(a.Off + 0x1000)}.String()
+		}
+		return fmt.Sprintf("ld [%d]", a.Off)
+	default:
+		return fmt.Sprintf("unknown instruction: %#v", a)
+	}
+}
+
 // LoadIndirect loads packet[X+Off:X+Off+Size] as an integer value
 // into register A.
 type LoadIndirect struct {
@@ -209,6 +277,20 @@ func (a LoadIndirect) Assemble() (RawInstruction, error) {
 	return assembleLoad(RegA, a.Size, opAddrModeIndirect, a.Off)
 }
 
+// String returns the the instruction in assembler notation.
+func (a LoadIndirect) String() string {
+	switch a.Size {
+	case 1: // byte
+		return fmt.Sprintf("ldb [x + %d]", a.Off)
+	case 2: // half word
+		return fmt.Sprintf("ldh [x + %d]", a.Off)
+	case 4: // word
+		return fmt.Sprintf("ld [x + %d]", a.Off)
+	default:
+		return fmt.Sprintf("unknown instruction: %#v", a)
+	}
+}
+
 // LoadMemShift multiplies the first 4 bits of the byte at packet[Off]
 // by 4 and stores the result in register X.
 //
@@ -224,6 +306,11 @@ func (a LoadMemShift) Assemble() (RawInstruction, error) {
 	return assembleLoad(RegX, 1, opAddrModeMemShift, a.Off)
 }
 
+// String returns the the instruction in assembler notation.
+func (a LoadMemShift) String() string {
+	return fmt.Sprintf("ldx 4*([%d]&0xf)", a.Off)
+}
+
 // LoadExtension invokes a linux-specific extension and stores the
 // result in register A.
 type LoadExtension struct {
@@ -235,7 +322,47 @@ func (a LoadExtension) Assemble() (RawInstruction, error) {
 	if a.Num == ExtLen {
 		return assembleLoad(RegA, 4, opAddrModePacketLen, 0)
 	}
-	return assembleLoad(RegA, 4, opAddrModeAbsolute, uint32(-0x1000+a.Num))
+	return assembleLoad(RegA, 4, opAddrModeAbsolute, uint32(extOffset+a.Num))
+}
+
+// String returns the the instruction in assembler notation.
+func (a LoadExtension) String() string {
+	switch a.Num {
+	case ExtLen:
+		return "ld #len"
+	case ExtProto:
+		return "ld #proto"
+	case ExtType:
+		return "ld #type"
+	case ExtPayloadOffset:
+		return "ld #poff"
+	case ExtInterfaceIndex:
+		return "ld #ifidx"
+	case ExtNetlinkAttr:
+		return "ld #nla"
+	case ExtNetlinkAttrNested:
+		return "ld #nlan"
+	case ExtMark:
+		return "ld #mark"
+	case ExtQueue:
+		return "ld #queue"
+	case ExtLinkLayerType:
+		return "ld #hatype"
+	case ExtRXHash:
+		return "ld #rxhash"
+	case ExtCPUID:
+		return "ld #cpu"
+	case ExtVLANTag:
+		return "ld #vlan_tci"
+	case ExtVLANTagPresent:
+		return "ld #vlan_avail"
+	case ExtVLANProto:
+		return "ld #vlan_tpid"
+	case ExtRand:
+		return "ld #rand"
+	default:
+		return fmt.Sprintf("unknown instruction: %#v", a)
+	}
 }
 
 // StoreScratch stores register Src into scratch[N].
@@ -265,6 +392,18 @@ func (a StoreScratch) Assemble() (RawInstruction, error) {
 	}, nil
 }
 
+// String returns the the instruction in assembler notation.
+func (a StoreScratch) String() string {
+	switch a.Src {
+	case RegA:
+		return fmt.Sprintf("st M[%d]", a.N)
+	case RegX:
+		return fmt.Sprintf("stx M[%d]", a.N)
+	default:
+		return fmt.Sprintf("unknown instruction: %#v", a)
+	}
+}
+
 // ALUOpConstant executes A = A <Op> Val.
 type ALUOpConstant struct {
 	Op  ALUOp
@@ -279,6 +418,34 @@ func (a ALUOpConstant) Assemble() (RawInstruction, error) {
 	}, nil
 }
 
+// String returns the the instruction in assembler notation.
+func (a ALUOpConstant) String() string {
+	switch a.Op {
+	case ALUOpAdd:
+		return fmt.Sprintf("add #%d", a.Val)
+	case ALUOpSub:
+		return fmt.Sprintf("sub #%d", a.Val)
+	case ALUOpMul:
+		return fmt.Sprintf("mul #%d", a.Val)
+	case ALUOpDiv:
+		return fmt.Sprintf("div #%d", a.Val)
+	case ALUOpMod:
+		return fmt.Sprintf("mod #%d", a.Val)
+	case ALUOpAnd:
+		return fmt.Sprintf("and #%d", a.Val)
+	case ALUOpOr:
+		return fmt.Sprintf("or #%d", a.Val)
+	case ALUOpXor:
+		return fmt.Sprintf("xor #%d", a.Val)
+	case ALUOpShiftLeft:
+		return fmt.Sprintf("lsh #%d", a.Val)
+	case ALUOpShiftRight:
+		return fmt.Sprintf("rsh #%d", a.Val)
+	default:
+		return fmt.Sprintf("unknown instruction: %#v", a)
+	}
+}
+
 // ALUOpX executes A = A <Op> X
 type ALUOpX struct {
 	Op ALUOp
@@ -291,6 +458,34 @@ func (a ALUOpX) Assemble() (RawInstruction, error) {
 	}, nil
 }
 
+// String returns the the instruction in assembler notation.
+func (a ALUOpX) String() string {
+	switch a.Op {
+	case ALUOpAdd:
+		return "add x"
+	case ALUOpSub:
+		return "sub x"
+	case ALUOpMul:
+		return "mul x"
+	case ALUOpDiv:
+		return "div x"
+	case ALUOpMod:
+		return "mod x"
+	case ALUOpAnd:
+		return "and x"
+	case ALUOpOr:
+		return "or x"
+	case ALUOpXor:
+		return "xor x"
+	case ALUOpShiftLeft:
+		return "lsh x"
+	case ALUOpShiftRight:
+		return "rsh x"
+	default:
+		return fmt.Sprintf("unknown instruction: %#v", a)
+	}
+}
+
 // NegateA executes A = -A.
 type NegateA struct{}
 
@@ -301,6 +496,11 @@ func (a NegateA) Assemble() (RawInstruction, error) {
 	}, nil
 }
 
+// String returns the the instruction in assembler notation.
+func (a NegateA) String() string {
+	return fmt.Sprintf("neg")
+}
+
 // Jump skips the following Skip instructions in the program.
 type Jump struct {
 	Skip uint32
@@ -314,6 +514,11 @@ func (a Jump) Assemble() (RawInstruction, error) {
 	}, nil
 }
 
+// String returns the the instruction in assembler notation.
+func (a Jump) String() string {
+	return fmt.Sprintf("ja %d", a.Skip)
+}
+
 // JumpIf skips the following Skip instructions in the program if A
 // <Cond> Val is true.
 type JumpIf struct {
@@ -361,6 +566,51 @@ func (a JumpIf) Assemble() (RawInstruction, error) {
 	}, nil
 }
 
+// String returns the the instruction in assembler notation.
+func (a JumpIf) String() string {
+	switch a.Cond {
+	// K == A
+	case JumpEqual:
+		return conditionalJump(a, "jeq", "jneq")
+	// K != A
+	case JumpNotEqual:
+		return fmt.Sprintf("jneq #%d,%d", a.Val, a.SkipTrue)
+	// K > A
+	case JumpGreaterThan:
+		return conditionalJump(a, "jgt", "jle")
+	// K < A
+	case JumpLessThan:
+		return fmt.Sprintf("jlt #%d,%d", a.Val, a.SkipTrue)
+	// K >= A
+	case JumpGreaterOrEqual:
+		return conditionalJump(a, "jge", "jlt")
+	// K <= A
+	case JumpLessOrEqual:
+		return fmt.Sprintf("jle #%d,%d", a.Val, a.SkipTrue)
+	// K & A != 0
+	case JumpBitsSet:
+		if a.SkipFalse > 0 {
+			return fmt.Sprintf("jset #%d,%d,%d", a.Val, a.SkipTrue, a.SkipFalse)
+		}
+		return fmt.Sprintf("jset #%d,%d", a.Val, a.SkipTrue)
+	// K & A == 0, there is no assembler instruction for JumpBitNotSet, use JumpBitSet and invert skips
+	case JumpBitsNotSet:
+		return JumpIf{Cond: JumpBitsSet, SkipTrue: a.SkipFalse, SkipFalse: a.SkipTrue, Val: a.Val}.String()
+	default:
+		return fmt.Sprintf("unknown instruction: %#v", a)
+	}
+}
+
+func conditionalJump(inst JumpIf, positiveJump, negativeJump string) string {
+	if inst.SkipTrue > 0 {
+		if inst.SkipFalse > 0 {
+			return fmt.Sprintf("%s #%d,%d,%d", positiveJump, inst.Val, inst.SkipTrue, inst.SkipFalse)
+		}
+		return fmt.Sprintf("%s #%d,%d", positiveJump, inst.Val, inst.SkipTrue)
+	}
+	return fmt.Sprintf("%s #%d,%d", negativeJump, inst.Val, inst.SkipFalse)
+}
+
 // RetA exits the BPF program, returning the value of register A.
 type RetA struct{}
 
@@ -371,6 +621,11 @@ func (a RetA) Assemble() (RawInstruction, error) {
 	}, nil
 }
 
+// String returns the the instruction in assembler notation.
+func (a RetA) String() string {
+	return fmt.Sprintf("ret a")
+}
+
 // RetConstant exits the BPF program, returning a constant value.
 type RetConstant struct {
 	Val uint32
@@ -384,6 +639,11 @@ func (a RetConstant) Assemble() (RawInstruction, error) {
 	}, nil
 }
 
+// String returns the the instruction in assembler notation.
+func (a RetConstant) String() string {
+	return fmt.Sprintf("ret #%d", a.Val)
+}
+
 // TXA copies the value of register X to register A.
 type TXA struct{}
 
@@ -394,6 +654,11 @@ func (a TXA) Assemble() (RawInstruction, error) {
 	}, nil
 }
 
+// String returns the the instruction in assembler notation.
+func (a TXA) String() string {
+	return fmt.Sprintf("txa")
+}
+
 // TAX copies the value of register A to register X.
 type TAX struct{}
 
@@ -404,6 +669,11 @@ func (a TAX) Assemble() (RawInstruction, error) {
 	}, nil
 }
 
+// String returns the the instruction in assembler notation.
+func (a TAX) String() string {
+	return fmt.Sprintf("tax")
+}
+
 func assembleLoad(dst Register, loadSize int, mode uint16, k uint32) (RawInstruction, error) {
 	var (
 		cls uint16

vendor/golang.org/x/net/bpf/vm.go

@@ -0,0 +1,140 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package bpf
+
+import (
+	"errors"
+	"fmt"
+)
+
+// A VM is an emulated BPF virtual machine.
+type VM struct {
+	filter []Instruction
+}
+
+// NewVM returns a new VM using the input BPF program.
+func NewVM(filter []Instruction) (*VM, error) {
+	if len(filter) == 0 {
+		return nil, errors.New("one or more Instructions must be specified")
+	}
+
+	for i, ins := range filter {
+		check := len(filter) - (i + 1)
+		switch ins := ins.(type) {
+		// Check for out-of-bounds jumps in instructions
+		case Jump:
+			if check <= int(ins.Skip) {
+				return nil, fmt.Errorf("cannot jump %d instructions; jumping past program bounds", ins.Skip)
+			}
+		case JumpIf:
+			if check <= int(ins.SkipTrue) {
+				return nil, fmt.Errorf("cannot jump %d instructions in true case; jumping past program bounds", ins.SkipTrue)
+			}
+			if check <= int(ins.SkipFalse) {
+				return nil, fmt.Errorf("cannot jump %d instructions in false case; jumping past program bounds", ins.SkipFalse)
+			}
+		// Check for division or modulus by zero
+		case ALUOpConstant:
+			if ins.Val != 0 {
+				break
+			}
+
+			switch ins.Op {
+			case ALUOpDiv, ALUOpMod:
+				return nil, errors.New("cannot divide by zero using ALUOpConstant")
+			}
+		// Check for unknown extensions
+		case LoadExtension:
+			switch ins.Num {
+			case ExtLen:
+			default:
+				return nil, fmt.Errorf("extension %d not implemented", ins.Num)
+			}
+		}
+	}
+
+	// Make sure last instruction is a return instruction
+	switch filter[len(filter)-1].(type) {
+	case RetA, RetConstant:
+	default:
+		return nil, errors.New("BPF program must end with RetA or RetConstant")
+	}
+
+	// Though our VM works using disassembled instructions, we
+	// attempt to assemble the input filter anyway to ensure it is compatible
+	// with an operating system VM.
+	_, err := Assemble(filter)
+
+	return &VM{
+		filter: filter,
+	}, err
+}
+
+// Run runs the VM's BPF program against the input bytes.
+// Run returns the number of bytes accepted by the BPF program, and any errors
+// which occurred while processing the program.
+func (v *VM) Run(in []byte) (int, error) {
+	var (
+		// Registers of the virtual machine
+		regA       uint32
+		regX       uint32
+		regScratch [16]uint32
+
+		// OK is true if the program should continue processing the next
+		// instruction, or false if not, causing the loop to break
+		ok = true
+	)
+
+	// TODO(mdlayher): implement:
+	// - NegateA:
+	//   - would require a change from uint32 registers to int32
+	//     registers
+
+	// TODO(mdlayher): add interop tests that check signedness of ALU
+	// operations against kernel implementation, and make sure Go
+	// implementation matches behavior
+
+	for i := 0; i < len(v.filter) && ok; i++ {
+		ins := v.filter[i]
+
+		switch ins := ins.(type) {
+		case ALUOpConstant:
+			regA = aluOpConstant(ins, regA)
+		case ALUOpX:
+			regA, ok = aluOpX(ins, regA, regX)
+		case Jump:
+			i += int(ins.Skip)
+		case JumpIf:
+			jump := jumpIf(ins, regA)
+			i += jump
+		case LoadAbsolute:
+			regA, ok = loadAbsolute(ins, in)
+		case LoadConstant:
+			regA, regX = loadConstant(ins, regA, regX)
+		case LoadExtension:
+			regA = loadExtension(ins, in)
+		case LoadIndirect:
+			regA, ok = loadIndirect(ins, in, regX)
+		case LoadMemShift:
+			regX, ok = loadMemShift(ins, in)
+		case LoadScratch:
+			regA, regX = loadScratch(ins, regScratch, regA, regX)
+		case RetA:
+			return int(regA), nil
+		case RetConstant:
+			return int(ins.Val), nil
+		case StoreScratch:
+			regScratch = storeScratch(ins, regScratch, regA, regX)
+		case TAX:
+			regX = regA
+		case TXA:
+			regA = regX
+		default:
+			return 0, fmt.Errorf("unknown Instruction at index %d: %T", i, ins)
+		}
+	}
+
+	return 0, nil
+}

vendor/golang.org/x/net/bpf/vm_instructions.go

@@ -0,0 +1,174 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package bpf
+
+import (
+	"encoding/binary"
+	"fmt"
+)
+
+func aluOpConstant(ins ALUOpConstant, regA uint32) uint32 {
+	return aluOpCommon(ins.Op, regA, ins.Val)
+}
+
+func aluOpX(ins ALUOpX, regA uint32, regX uint32) (uint32, bool) {
+	// Guard against division or modulus by zero by terminating
+	// the program, as the OS BPF VM does
+	if regX == 0 {
+		switch ins.Op {
+		case ALUOpDiv, ALUOpMod:
+			return 0, false
+		}
+	}
+
+	return aluOpCommon(ins.Op, regA, regX), true
+}
+
+func aluOpCommon(op ALUOp, regA uint32, value uint32) uint32 {
+	switch op {
+	case ALUOpAdd:
+		return regA + value
+	case ALUOpSub:
+		return regA - value
+	case ALUOpMul:
+		return regA * value
+	case ALUOpDiv:
+		// Division by zero not permitted by NewVM and aluOpX checks
+		return regA / value
+	case ALUOpOr:
+		return regA | value
+	case ALUOpAnd:
+		return regA & value
+	case ALUOpShiftLeft:
+		return regA << value
+	case ALUOpShiftRight:
+		return regA >> value
+	case ALUOpMod:
+		// Modulus by zero not permitted by NewVM and aluOpX checks
+		return regA % value
+	case ALUOpXor:
+		return regA ^ value
+	default:
+		return regA
+	}
+}
+
+func jumpIf(ins JumpIf, value uint32) int {
+	var ok bool
+	inV := uint32(ins.Val)
+
+	switch ins.Cond {
+	case JumpEqual:
+		ok = value == inV
+	case JumpNotEqual:
+		ok = value != inV
+	case JumpGreaterThan:
+		ok = value > inV
+	case JumpLessThan:
+		ok = value < inV
+	case JumpGreaterOrEqual:
+		ok = value >= inV
+	case JumpLessOrEqual:
+		ok = value <= inV
+	case JumpBitsSet:
+		ok = (value & inV) != 0
+	case JumpBitsNotSet:
+		ok = (value & inV) == 0
+	}
+
+	if ok {
+		return int(ins.SkipTrue)
+	}
+
+	return int(ins.SkipFalse)
+}
+
+func loadAbsolute(ins LoadAbsolute, in []byte) (uint32, bool) {
+	offset := int(ins.Off)
+	size := int(ins.Size)
+
+	return loadCommon(in, offset, size)
+}
+
+func loadConstant(ins LoadConstant, regA uint32, regX uint32) (uint32, uint32) {
+	switch ins.Dst {
+	case RegA:
+		regA = ins.Val
+	case RegX:
+		regX = ins.Val
+	}
+
+	return regA, regX
+}
+
+func loadExtension(ins LoadExtension, in []byte) uint32 {
+	switch ins.Num {
+	case ExtLen:
+		return uint32(len(in))
+	default:
+		panic(fmt.Sprintf("unimplemented extension: %d", ins.Num))
+	}
+}
+
+func loadIndirect(ins LoadIndirect, in []byte, regX uint32) (uint32, bool) {
+	offset := int(ins.Off) + int(regX)
+	size := int(ins.Size)
+
+	return loadCommon(in, offset, size)
+}
+
+func loadMemShift(ins LoadMemShift, in []byte) (uint32, bool) {
+	offset := int(ins.Off)
+
+	if !inBounds(len(in), offset, 0) {
+		return 0, false
+	}
+
+	// Mask off high 4 bits and multiply low 4 bits by 4
+	return uint32(in[offset]&0x0f) * 4, true
+}
+
+func inBounds(inLen int, offset int, size int) bool {
+	return offset+size <= inLen
+}
+
+func loadCommon(in []byte, offset int, size int) (uint32, bool) {
+	if !inBounds(len(in), offset, size) {
+		return 0, false
+	}
+
+	switch size {
+	case 1:
+		return uint32(in[offset]), true
+	case 2:
+		return uint32(binary.BigEndian.Uint16(in[offset : offset+size])), true
+	case 4:
+		return uint32(binary.BigEndian.Uint32(in[offset : offset+size])), true
+	default:
+		panic(fmt.Sprintf("invalid load size: %d", size))
+	}
+}
+
+func loadScratch(ins LoadScratch, regScratch [16]uint32, regA uint32, regX uint32) (uint32, uint32) {
+	switch ins.Dst {
+	case RegA:
+		regA = regScratch[ins.N]
+	case RegX:
+		regX = regScratch[ins.N]
+	}
+
+	return regA, regX
+}
+
+func storeScratch(ins StoreScratch, regScratch [16]uint32, regA uint32, regX uint32) [16]uint32 {
+	switch ins.Src {
+	case RegA:
+		regScratch[ins.N] = regA
+	case RegX:
+		regScratch[ins.N] = regX
+	}
+
+	return regScratch
+}