From e1e8d058a33f7566f9c565d04b0d8b56f9645c35 Mon Sep 17 00:00:00 2001 From: Dimitri Sokolyuk Date: Wed, 25 Apr 2018 09:28:54 +0200 Subject: add vendor --- vendor/golang.org/x/net/bpf/vm.go | 140 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 140 insertions(+) create mode 100644 vendor/golang.org/x/net/bpf/vm.go (limited to 'vendor/golang.org/x/net/bpf/vm.go') diff --git a/vendor/golang.org/x/net/bpf/vm.go b/vendor/golang.org/x/net/bpf/vm.go new file mode 100644 index 0000000..4c656f1 --- /dev/null +++ b/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 +} -- cgit v1.2.3