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

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// 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, regA uint32) int {
	return jumpIfCommon(ins.Cond, ins.SkipTrue, ins.SkipFalse, regA, ins.Val)
}