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📄 asm.go // 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 "fmt" // Assemble converts insts into raw instructions suitable for loading // into a BPF virtual machine. // // Currently, no optimization is attempted, the assembled program flow // is exactly as provided. func Assemble(insts []Instruction) ([]RawInstruction, error) { ret := make([]RawInstruction, len(insts)) var err error for i, inst := range insts { ret[i], err = inst.Assemble() if err != nil { return nil, fmt.Errorf("assembling instruction %d: %s", i+1, err) } } return ret, nil } // Disassemble attempts to parse raw back into // Instructions. Unrecognized RawInstructions are assumed to be an // extension not implemented by this package, and are passed through // unchanged to the output. The allDecoded value reports whether insts // contains no RawInstructions. func Disassemble(raw []RawInstruction) (insts []Instruction, allDecoded bool) { insts = make([]Instruction, len(raw)) allDecoded = true for i, r := range raw { insts[i] = r.Disassemble() if _, ok := insts[i].(RawInstruction); ok { allDecoded = false } } return insts, allDecoded }	1.24 KB	2025-05-25 12:27
📄 constants.go // 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 // A Register is a register of the BPF virtual machine. type Register uint16 const ( // RegA is the accumulator register. RegA is always the // destination register of ALU operations. RegA Register = iota // RegX is the indirection register, used by LoadIndirect // operations. RegX ) // An ALUOp is an arithmetic or logic operation. type ALUOp uint16 // ALU binary operation types. const ( ALUOpAdd ALUOp = iota << 4 ALUOpSub ALUOpMul ALUOpDiv ALUOpOr ALUOpAnd ALUOpShiftLeft ALUOpShiftRight aluOpNeg // Not exported because it's the only unary ALU operation, and gets its own instruction type. ALUOpMod ALUOpXor ) // A JumpTest is a comparison operator used in conditional jumps. type JumpTest uint16 // Supported operators for conditional jumps. // K can be RegX for JumpIfX const ( // K == A JumpEqual JumpTest = iota // K != A JumpNotEqual // K > A JumpGreaterThan // K < A JumpLessThan // K >= A JumpGreaterOrEqual // K <= A JumpLessOrEqual // K & A != 0 JumpBitsSet // K & A == 0 JumpBitsNotSet ) // An Extension is a function call provided by the kernel that // performs advanced operations that are expensive or impossible // within the BPF virtual machine. // // Extensions are only implemented by the Linux kernel. // // TODO: should we prune this list? Some of these extensions seem // either broken or near-impossible to use correctly, whereas other // (len, random, ifindex) are quite useful. 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 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 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 Extension = 52 // ExtInterfaceIndex returns the index of the interface on which // the packet was received. ExtInterfaceIndex Extension = 8 // ExtNetlinkAttr returns the netlink attribute of type X at // offset A. ExtNetlinkAttr Extension = 12 // ExtNetlinkAttrNested returns the nested netlink attribute of // type X at offset A. ExtNetlinkAttrNested Extension = 16 // ExtMark returns the packet's mark value. ExtMark Extension = 20 // ExtQueue returns the packet's assigned hardware queue. ExtQueue Extension = 24 // ExtLinkLayerType returns the packet's hardware address type // (e.g. Ethernet, Infiniband). ExtLinkLayerType Extension = 28 // ExtRXHash returns the packets receive hash. // // TODO: figure out what this rxhash actually is. ExtRXHash Extension = 32 // ExtCPUID returns the ID of the CPU processing the current // packet. ExtCPUID Extension = 36 // ExtVLANTag returns the packet's VLAN tag. 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 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 Extension = 60 // ExtRand returns a uniformly random uint32. ExtRand Extension = 56 ) // The following gives names to various bit patterns used in opcode construction. const ( opMaskCls uint16 = 0x7 // opClsLoad masks opMaskLoadDest = 0x01 opMaskLoadWidth = 0x18 opMaskLoadMode = 0xe0 // opClsALU & opClsJump opMaskOperand = 0x08 opMaskOperator = 0xf0 ) const ( // +---------------+-----------------+---+---+---+ // \| AddrMode (3b) \| LoadWidth (2b) \| 0 \| 0 \| 0 \| // +---------------+-----------------+---+---+---+ opClsLoadA uint16 = iota // +---------------+-----------------+---+---+---+ // \| AddrMode (3b) \| LoadWidth (2b) \| 0 \| 0 \| 1 \| // +---------------+-----------------+---+---+---+ opClsLoadX // +---+---+---+---+---+---+---+---+ // \| 0 \| 0 \| 0 \| 0 \| 0 \| 0 \| 1 \| 0 \| // +---+---+---+---+---+---+---+---+ opClsStoreA // +---+---+---+---+---+---+---+---+ // \| 0 \| 0 \| 0 \| 0 \| 0 \| 0 \| 1 \| 1 \| // +---+---+---+---+---+---+---+---+ opClsStoreX // +---------------+-----------------+---+---+---+ // \| Operator (4b) \| OperandSrc (1b) \| 1 \| 0 \| 0 \| // +---------------+-----------------+---+---+---+ opClsALU // +-----------------------------+---+---+---+---+ // \| TestOperator (4b) \| 0 \| 1 \| 0 \| 1 \| // +-----------------------------+---+---+---+---+ opClsJump // +---+-------------------------+---+---+---+---+ // \| 0 \| 0 \| 0 \| RetSrc (1b) \| 0 \| 1 \| 1 \| 0 \| // +---+-------------------------+---+---+---+---+ opClsReturn // +---+-------------------------+---+---+---+---+ // \| 0 \| 0 \| 0 \| TXAorTAX (1b) \| 0 \| 1 \| 1 \| 1 \| // +---+-------------------------+---+---+---+---+ opClsMisc ) const ( opAddrModeImmediate uint16 = iota << 5 opAddrModeAbsolute opAddrModeIndirect opAddrModeScratch opAddrModePacketLen // actually an extension, not an addressing mode. opAddrModeMemShift ) const ( opLoadWidth4 uint16 = iota << 3 opLoadWidth2 opLoadWidth1 ) // Operand for ALU and Jump instructions type opOperand uint16 // Supported operand sources. const ( opOperandConstant opOperand = iota << 3 opOperandX ) // An jumpOp is a conditional jump condition. type jumpOp uint16 // Supported jump conditions. const ( opJumpAlways jumpOp = iota << 4 opJumpEqual opJumpGT opJumpGE opJumpSet ) const ( opRetSrcConstant uint16 = iota << 4 opRetSrcA ) const ( opMiscTAX = 0x00 opMiscTXA = 0x80 )	6.04 KB	2025-05-25 12:27
📄 doc.go // 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 implements marshaling and unmarshaling of programs for the 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 userspace. However, it's been repurposed to other areas where running user code in-kernel is needed. For example, Linux's seccomp uses BPF to apply security policies to system calls. For simplicity, this documentation refers only to packets, but other uses of BPF have their own data payloads. BPF programs run in a restricted virtual machine. It has almost no access to kernel functions, and while conditional branches are allowed, they can only jump forwards, to guarantee that there are no infinite loops. # The virtual machine The BPF VM is an accumulator machine. Its main register, called register A, is an implicit source and destination in all arithmetic and logic operations. The machine also has 16 scratch registers for temporary storage, and an indirection register (register X) for indirect memory access. All registers are 32 bits wide. Each run of a BPF program is given one packet, which is placed in the VM's read-only "main memory". LoadAbsolute and LoadIndirect instructions can fetch up to 32 bits at a time into register A for examination. The goal of a BPF program is to produce and return a verdict (uint32), which tells the kernel what to do with the packet. In the context of packet filtering, the returned value is the number of bytes of the packet to forward to userspace, or 0 to ignore the packet. Other contexts like seccomp define their own return values. In order to simplify programs, attempts to read past the end of the packet terminate the program execution with a verdict of 0 (ignore packet). This means that the vast majority of BPF programs don't need to do any explicit bounds checking. In addition to the bytes of the packet, some BPF programs have access to extensions, which are essentially calls to kernel utility functions. Currently, the only extensions supported by this package are the Linux packet filter extensions. # Examples This packet filter selects all ARP packets. bpf.Assemble([]bpf.Instruction{ // Load "EtherType" field from the ethernet header. bpf.LoadAbsolute{Off: 12, Size: 2}, // Skip over the next instruction if EtherType is not ARP. bpf.JumpIf{Cond: bpf.JumpNotEqual, Val: 0x0806, SkipTrue: 1}, // Verdict is "send up to 4k of the packet to userspace." bpf.RetConstant{Val: 4096}, // Verdict is "ignore packet." bpf.RetConstant{Val: 0}, }) This packet filter captures a random 1% sample of traffic. bpf.Assemble([]bpf.Instruction{ // Get a 32-bit random number from the Linux kernel. bpf.LoadExtension{Num: bpf.ExtRand}, // 1% dice roll? bpf.JumpIf{Cond: bpf.JumpLessThan, Val: 2^32/100, SkipFalse: 1}, // Capture. bpf.RetConstant{Val: 4096}, // Ignore. bpf.RetConstant{Val: 0}, }) */ package bpf // import "golang.org/x/net/bpf"	3.14 KB	2025-05-25 12:27
📄 instructions.go // 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 "fmt" // An Instruction is one instruction executed by the BPF virtual // machine. type Instruction interface { // Assemble assembles the Instruction into a RawInstruction. Assemble() (RawInstruction, error) } // A RawInstruction is a raw BPF virtual machine instruction. type RawInstruction struct { // Operation to execute. Op uint16 // For conditional jump instructions, the number of instructions // to skip if the condition is true/false. Jt uint8 Jf uint8 // Constant parameter. The meaning depends on the Op. K uint32 } // Assemble implements the Instruction Assemble method. func (ri RawInstruction) Assemble() (RawInstruction, error) { return ri, nil } // Disassemble parses ri into an Instruction and returns it. If ri is // not recognized by this package, ri itself is returned. func (ri RawInstruction) Disassemble() Instruction { switch ri.Op & opMaskCls { case opClsLoadA, opClsLoadX: reg := Register(ri.Op & opMaskLoadDest) sz := 0 switch ri.Op & opMaskLoadWidth { case opLoadWidth4: sz = 4 case opLoadWidth2: sz = 2 case opLoadWidth1: sz = 1 default: return ri } switch ri.Op & opMaskLoadMode { case opAddrModeImmediate: if sz != 4 { return ri } return LoadConstant{Dst: reg, Val: ri.K} case opAddrModeScratch: if sz != 4 \|\| ri.K > 15 { return ri } 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} case opAddrModePacketLen: if sz != 4 { return ri } return LoadExtension{Num: ExtLen} case opAddrModeMemShift: return LoadMemShift{Off: ri.K} default: return ri } case opClsStoreA: if ri.Op != opClsStoreA \|\| ri.K > 15 { return ri } return StoreScratch{Src: RegA, N: int(ri.K)} case opClsStoreX: if ri.Op != opClsStoreX \|\| ri.K > 15 { return ri } return StoreScratch{Src: RegX, N: int(ri.K)} case opClsALU: switch op := ALUOp(ri.Op & opMaskOperator); op { case ALUOpAdd, ALUOpSub, ALUOpMul, ALUOpDiv, ALUOpOr, ALUOpAnd, ALUOpShiftLeft, ALUOpShiftRight, ALUOpMod, ALUOpXor: switch operand := opOperand(ri.Op & opMaskOperand); operand { case opOperandX: return ALUOpX{Op: op} case opOperandConstant: return ALUOpConstant{Op: op, Val: ri.K} default: return ri } case aluOpNeg: return NegateA{} default: return ri } case opClsJump: switch op := jumpOp(ri.Op & opMaskOperator); op { case opJumpAlways: return Jump{Skip: ri.K} case opJumpEqual, opJumpGT, opJumpGE, opJumpSet: cond, skipTrue, skipFalse := jumpOpToTest(op, ri.Jt, ri.Jf) switch operand := opOperand(ri.Op & opMaskOperand); operand { case opOperandX: return JumpIfX{Cond: cond, SkipTrue: skipTrue, SkipFalse: skipFalse} case opOperandConstant: return JumpIf{Cond: cond, Val: ri.K, SkipTrue: skipTrue, SkipFalse: skipFalse} default: return ri } default: return ri } case opClsReturn: switch ri.Op { case opClsReturn \| opRetSrcA: return RetA{} case opClsReturn \| opRetSrcConstant: return RetConstant{Val: ri.K} default: return ri } case opClsMisc: switch ri.Op { case opClsMisc \| opMiscTAX: return TAX{} case opClsMisc \| opMiscTXA: return TXA{} default: return ri } default: panic("unreachable") // switch is exhaustive on the bit pattern } } func jumpOpToTest(op jumpOp, skipTrue uint8, skipFalse uint8) (JumpTest, uint8, uint8) { var test JumpTest // Decode "fake" jump conditions that don't appear in machine code // Ensures the Assemble -> Disassemble stage recreates the same instructions // See https://github.com/golang/go/issues/18470 if skipTrue == 0 { switch op { case opJumpEqual: test = JumpNotEqual case opJumpGT: test = JumpLessOrEqual case opJumpGE: test = JumpLessThan case opJumpSet: test = JumpBitsNotSet } return test, skipFalse, 0 } switch op { case opJumpEqual: test = JumpEqual case opJumpGT: test = JumpGreaterThan case opJumpGE: test = JumpGreaterOrEqual case opJumpSet: test = JumpBitsSet } return test, skipTrue, skipFalse } // LoadConstant loads Val into register Dst. type LoadConstant struct { Dst Register Val uint32 } // Assemble implements the Instruction Assemble method. func (a LoadConstant) Assemble() (RawInstruction, error) { return assembleLoad(a.Dst, 4, opAddrModeImmediate, a.Val) } // String returns 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 N int // 0-15 } // Assemble implements the Instruction Assemble method. func (a LoadScratch) Assemble() (RawInstruction, error) { if a.N < 0 \|\| a.N > 15 { return RawInstruction{}, fmt.Errorf("invalid scratch slot %d", a.N) } return assembleLoad(a.Dst, 4, opAddrModeScratch, uint32(a.N)) } // String returns 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 { Off uint32 Size int // 1, 2 or 4 } // Assemble implements the Instruction Assemble method. func (a LoadAbsolute) Assemble() (RawInstruction, error) { return assembleLoad(RegA, a.Size, opAddrModeAbsolute, a.Off) } // String returns 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 { Off uint32 Size int // 1, 2 or 4 } // Assemble implements the Instruction Assemble method. func (a LoadIndirect) Assemble() (RawInstruction, error) { return assembleLoad(RegA, a.Size, opAddrModeIndirect, a.Off) } // String returns 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. // // This instruction is mainly useful to load into X the length of an // IPv4 packet header in a single instruction, rather than have to do // the arithmetic on the header's first byte by hand. type LoadMemShift struct { Off uint32 } // Assemble implements the Instruction Assemble method. func (a LoadMemShift) Assemble() (RawInstruction, error) { return assembleLoad(RegX, 1, opAddrModeMemShift, a.Off) } // String returns 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 { Num Extension } // Assemble implements the Instruction Assemble method. func (a LoadExtension) Assemble() (RawInstruction, error) { if a.Num == ExtLen { return assembleLoad(RegA, 4, opAddrModePacketLen, 0) } return assembleLoad(RegA, 4, opAddrModeAbsolute, uint32(extOffset+a.Num)) } // String returns 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]. type StoreScratch struct { Src Register N int // 0-15 } // Assemble implements the Instruction Assemble method. func (a StoreScratch) Assemble() (RawInstruction, error) { if a.N < 0 \|\| a.N > 15 { return RawInstruction{}, fmt.Errorf("invalid scratch slot %d", a.N) } var op uint16 switch a.Src { case RegA: op = opClsStoreA case RegX: op = opClsStoreX default: return RawInstruction{}, fmt.Errorf("invalid source register %v", a.Src) } return RawInstruction{ Op: op, K: uint32(a.N), }, nil } // String returns 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 Val uint32 } // Assemble implements the Instruction Assemble method. func (a ALUOpConstant) Assemble() (RawInstruction, error) { return RawInstruction{ Op: opClsALU \| uint16(opOperandConstant) \| uint16(a.Op), K: a.Val, }, nil } // String returns 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 } // Assemble implements the Instruction Assemble method. func (a ALUOpX) Assemble() (RawInstruction, error) { return RawInstruction{ Op: opClsALU \| uint16(opOperandX) \| uint16(a.Op), }, nil } // String returns 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{} // Assemble implements the Instruction Assemble method. func (a NegateA) Assemble() (RawInstruction, error) { return RawInstruction{ Op: opClsALU \| uint16(aluOpNeg), }, nil } // String returns 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 } // Assemble implements the Instruction Assemble method. func (a Jump) Assemble() (RawInstruction, error) { return RawInstruction{ Op: opClsJump \| uint16(opJumpAlways), K: a.Skip, }, nil } // String returns 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 { Cond JumpTest Val uint32 SkipTrue uint8 SkipFalse uint8 } // Assemble implements the Instruction Assemble method. func (a JumpIf) Assemble() (RawInstruction, error) { return jumpToRaw(a.Cond, opOperandConstant, a.Val, a.SkipTrue, a.SkipFalse) } // String returns the instruction in assembler notation. func (a JumpIf) String() string { return jumpToString(a.Cond, fmt.Sprintf("#%d", a.Val), a.SkipTrue, a.SkipFalse) } // JumpIfX skips the following Skip instructions in the program if A // <Cond> X is true. type JumpIfX struct { Cond JumpTest SkipTrue uint8 SkipFalse uint8 } // Assemble implements the Instruction Assemble method. func (a JumpIfX) Assemble() (RawInstruction, error) { return jumpToRaw(a.Cond, opOperandX, 0, a.SkipTrue, a.SkipFalse) } // String returns the instruction in assembler notation. func (a JumpIfX) String() string { return jumpToString(a.Cond, "x", a.SkipTrue, a.SkipFalse) } // jumpToRaw assembles a jump instruction into a RawInstruction func jumpToRaw(test JumpTest, operand opOperand, k uint32, skipTrue, skipFalse uint8) (RawInstruction, error) { var ( cond jumpOp flip bool ) switch test { case JumpEqual: cond = opJumpEqual case JumpNotEqual: cond, flip = opJumpEqual, true case JumpGreaterThan: cond = opJumpGT case JumpLessThan: cond, flip = opJumpGE, true case JumpGreaterOrEqual: cond = opJumpGE case JumpLessOrEqual: cond, flip = opJumpGT, true case JumpBitsSet: cond = opJumpSet case JumpBitsNotSet: cond, flip = opJumpSet, true default: return RawInstruction{}, fmt.Errorf("unknown JumpTest %v", test) } jt, jf := skipTrue, skipFalse if flip { jt, jf = jf, jt } return RawInstruction{ Op: opClsJump \| uint16(cond) \| uint16(operand), Jt: jt, Jf: jf, K: k, }, nil } // jumpToString converts a jump instruction to assembler notation func jumpToString(cond JumpTest, operand string, skipTrue, skipFalse uint8) string { switch cond { // K == A case JumpEqual: return conditionalJump(operand, skipTrue, skipFalse, "jeq", "jneq") // K != A case JumpNotEqual: return fmt.Sprintf("jneq %s,%d", operand, skipTrue) // K > A case JumpGreaterThan: return conditionalJump(operand, skipTrue, skipFalse, "jgt", "jle") // K < A case JumpLessThan: return fmt.Sprintf("jlt %s,%d", operand, skipTrue) // K >= A case JumpGreaterOrEqual: return conditionalJump(operand, skipTrue, skipFalse, "jge", "jlt") // K <= A case JumpLessOrEqual: return fmt.Sprintf("jle %s,%d", operand, skipTrue) // K & A != 0 case JumpBitsSet: if skipFalse > 0 { return fmt.Sprintf("jset %s,%d,%d", operand, skipTrue, skipFalse) } return fmt.Sprintf("jset %s,%d", operand, skipTrue) // K & A == 0, there is no assembler instruction for JumpBitNotSet, use JumpBitSet and invert skips case JumpBitsNotSet: return jumpToString(JumpBitsSet, operand, skipFalse, skipTrue) default: return fmt.Sprintf("unknown JumpTest %#v", cond) } } func conditionalJump(operand string, skipTrue, skipFalse uint8, positiveJump, negativeJump string) string { if skipTrue > 0 { if skipFalse > 0 { return fmt.Sprintf("%s %s,%d,%d", positiveJump, operand, skipTrue, skipFalse) } return fmt.Sprintf("%s %s,%d", positiveJump, operand, skipTrue) } return fmt.Sprintf("%s %s,%d", negativeJump, operand, skipFalse) } // RetA exits the BPF program, returning the value of register A. type RetA struct{} // Assemble implements the Instruction Assemble method. func (a RetA) Assemble() (RawInstruction, error) { return RawInstruction{ Op: opClsReturn \| opRetSrcA, }, nil } // String returns 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 } // Assemble implements the Instruction Assemble method. func (a RetConstant) Assemble() (RawInstruction, error) { return RawInstruction{ Op: opClsReturn \| opRetSrcConstant, K: a.Val, }, nil } // String returns 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{} // Assemble implements the Instruction Assemble method. func (a TXA) Assemble() (RawInstruction, error) { return RawInstruction{ Op: opClsMisc \| opMiscTXA, }, nil } // String returns 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{} // Assemble implements the Instruction Assemble method. func (a TAX) Assemble() (RawInstruction, error) { return RawInstruction{ Op: opClsMisc \| opMiscTAX, }, nil } // String returns 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 sz uint16 ) switch dst { case RegA: cls = opClsLoadA case RegX: cls = opClsLoadX default: return RawInstruction{}, fmt.Errorf("invalid target register %v", dst) } switch loadSize { case 1: sz = opLoadWidth1 case 2: sz = opLoadWidth2 case 4: sz = opLoadWidth4 default: return RawInstruction{}, fmt.Errorf("invalid load byte length %d", sz) } return RawInstruction{ Op: cls \| sz \| mode, K: k, }, nil }	17.68 KB	2025-05-25 12:27
📄 instructions_test.go // 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 ( "fmt" "os" "reflect" "strconv" "strings" "testing" ) // This is a direct translation of the program in // testdata/all_instructions.txt. var allInstructions = []Instruction{ LoadConstant{Dst: RegA, Val: 42}, LoadConstant{Dst: RegX, Val: 42}, LoadScratch{Dst: RegA, N: 3}, LoadScratch{Dst: RegX, N: 3}, LoadAbsolute{Off: 42, Size: 1}, LoadAbsolute{Off: 42, Size: 2}, LoadAbsolute{Off: 42, Size: 4}, LoadIndirect{Off: 42, Size: 1}, LoadIndirect{Off: 42, Size: 2}, LoadIndirect{Off: 42, Size: 4}, LoadMemShift{Off: 42}, LoadExtension{Num: ExtLen}, LoadExtension{Num: ExtProto}, LoadExtension{Num: ExtType}, LoadExtension{Num: ExtRand}, StoreScratch{Src: RegA, N: 3}, StoreScratch{Src: RegX, N: 3}, ALUOpConstant{Op: ALUOpAdd, Val: 42}, ALUOpConstant{Op: ALUOpSub, Val: 42}, ALUOpConstant{Op: ALUOpMul, Val: 42}, ALUOpConstant{Op: ALUOpDiv, Val: 42}, ALUOpConstant{Op: ALUOpOr, Val: 42}, ALUOpConstant{Op: ALUOpAnd, Val: 42}, ALUOpConstant{Op: ALUOpShiftLeft, Val: 42}, ALUOpConstant{Op: ALUOpShiftRight, Val: 42}, ALUOpConstant{Op: ALUOpMod, Val: 42}, ALUOpConstant{Op: ALUOpXor, Val: 42}, ALUOpX{Op: ALUOpAdd}, ALUOpX{Op: ALUOpSub}, ALUOpX{Op: ALUOpMul}, ALUOpX{Op: ALUOpDiv}, ALUOpX{Op: ALUOpOr}, ALUOpX{Op: ALUOpAnd}, ALUOpX{Op: ALUOpShiftLeft}, ALUOpX{Op: ALUOpShiftRight}, ALUOpX{Op: ALUOpMod}, ALUOpX{Op: ALUOpXor}, NegateA{}, Jump{Skip: 17}, JumpIf{Cond: JumpEqual, Val: 42, SkipTrue: 15, SkipFalse: 16}, JumpIf{Cond: JumpNotEqual, Val: 42, SkipTrue: 15}, JumpIf{Cond: JumpLessThan, Val: 42, SkipTrue: 14}, JumpIf{Cond: JumpLessOrEqual, Val: 42, SkipTrue: 13}, JumpIf{Cond: JumpGreaterThan, Val: 42, SkipTrue: 11, SkipFalse: 12}, JumpIf{Cond: JumpGreaterOrEqual, Val: 42, SkipTrue: 10, SkipFalse: 11}, JumpIf{Cond: JumpBitsSet, Val: 42, SkipTrue: 9, SkipFalse: 10}, JumpIfX{Cond: JumpEqual, SkipTrue: 8, SkipFalse: 9}, JumpIfX{Cond: JumpNotEqual, SkipTrue: 8}, JumpIfX{Cond: JumpLessThan, SkipTrue: 7}, JumpIfX{Cond: JumpLessOrEqual, SkipTrue: 6}, JumpIfX{Cond: JumpGreaterThan, SkipTrue: 4, SkipFalse: 5}, JumpIfX{Cond: JumpGreaterOrEqual, SkipTrue: 3, SkipFalse: 4}, JumpIfX{Cond: JumpBitsSet, SkipTrue: 2, SkipFalse: 3}, TAX{}, TXA{}, RetA{}, RetConstant{Val: 42}, } var allInstructionsExpected = "testdata/all_instructions.bpf" // Check that we produce the same output as the canonical bpf_asm // linux kernel tool. func TestInterop(t testing.T) { out, err := Assemble(allInstructions) if err != nil { t.Fatalf("assembly of allInstructions program failed: %s", err) } t.Logf("Assembled program is %d instructions long", len(out)) bs, err := os.ReadFile(allInstructionsExpected) if err != nil { t.Fatalf("reading %s: %s", allInstructionsExpected, err) } // First statement is the number of statements, last statement is // empty. We just ignore both and rely on slice length. stmts := strings.Split(string(bs), ",") if len(stmts)-2 != len(out) { t.Fatalf("test program lengths don't match: %s has %d, Go implementation has %d", allInstructionsExpected, len(stmts)-2, len(allInstructions)) } for i, stmt := range stmts[1 : len(stmts)-2] { nums := strings.Split(stmt, " ") if len(nums) != 4 { t.Fatalf("malformed instruction %d in %s: %s", i+1, allInstructionsExpected, stmt) } actual := out[i] op, err := strconv.ParseUint(nums[0], 10, 16) if err != nil { t.Fatalf("malformed opcode %s in instruction %d of %s", nums[0], i+1, allInstructionsExpected) } if actual.Op != uint16(op) { t.Errorf("opcode mismatch on instruction %d (%#v): got 0x%02x, want 0x%02x", i+1, allInstructions[i], actual.Op, op) } jt, err := strconv.ParseUint(nums[1], 10, 8) if err != nil { t.Fatalf("malformed jt offset %s in instruction %d of %s", nums[1], i+1, allInstructionsExpected) } if actual.Jt != uint8(jt) { t.Errorf("jt mismatch on instruction %d (%#v): got %d, want %d", i+1, allInstructions[i], actual.Jt, jt) } jf, err := strconv.ParseUint(nums[2], 10, 8) if err != nil { t.Fatalf("malformed jf offset %s in instruction %d of %s", nums[2], i+1, allInstructionsExpected) } if actual.Jf != uint8(jf) { t.Errorf("jf mismatch on instruction %d (%#v): got %d, want %d", i+1, allInstructions[i], actual.Jf, jf) } k, err := strconv.ParseUint(nums[3], 10, 32) if err != nil { t.Fatalf("malformed constant %s in instruction %d of %s", nums[3], i+1, allInstructionsExpected) } if actual.K != uint32(k) { t.Errorf("constant mismatch on instruction %d (%#v): got %d, want %d", i+1, allInstructions[i], actual.K, k) } } } // Check that assembly and disassembly match each other. func TestAsmDisasm(t testing.T) { prog1, err := Assemble(allInstructions) if err != nil { t.Fatalf("assembly of allInstructions program failed: %s", err) } t.Logf("Assembled program is %d instructions long", len(prog1)) got, allDecoded := Disassemble(prog1) if !allDecoded { t.Errorf("Disassemble(Assemble(allInstructions)) produced unrecognized instructions:") for i, inst := range got { if r, ok := inst.(RawInstruction); ok { t.Logf(" insn %d, %#v --> %#v", i+1, allInstructions[i], r) } } } if len(allInstructions) != len(got) { t.Fatalf("disassembly changed program size: %d insns before, %d insns after", len(allInstructions), len(got)) } if !reflect.DeepEqual(allInstructions, got) { t.Errorf("program mutated by disassembly:") for i := range got { if !reflect.DeepEqual(allInstructions[i], got[i]) { t.Logf(" insn %d, s: %#v, p1: %#v, got: %#v", i+1, allInstructions[i], prog1[i], got[i]) } } } } type InvalidInstruction struct{} func (a InvalidInstruction) Assemble() (RawInstruction, error) { return RawInstruction{}, fmt.Errorf("Invalid Instruction") } func (a InvalidInstruction) String() string { return fmt.Sprintf("unknown instruction: %#v", a) } func TestString(t testing.T) { testCases := []struct { instruction Instruction assembler string }{ { instruction: LoadConstant{Dst: RegA, Val: 42}, assembler: "ld #42", }, { instruction: LoadConstant{Dst: RegX, Val: 42}, assembler: "ldx #42", }, { instruction: LoadConstant{Dst: 0xffff, Val: 42}, assembler: "unknown instruction: bpf.LoadConstant{Dst:0xffff, Val:0x2a}", }, { instruction: LoadScratch{Dst: RegA, N: 3}, assembler: "ld M[3]", }, { instruction: LoadScratch{Dst: RegX, N: 3}, assembler: "ldx M[3]", }, { instruction: LoadScratch{Dst: 0xffff, N: 3}, assembler: "unknown instruction: bpf.LoadScratch{Dst:0xffff, N:3}", }, { instruction: LoadAbsolute{Off: 42, Size: 1}, assembler: "ldb [42]", }, { instruction: LoadAbsolute{Off: 42, Size: 2}, assembler: "ldh [42]", }, { instruction: LoadAbsolute{Off: 42, Size: 4}, assembler: "ld [42]", }, { instruction: LoadAbsolute{Off: 42, Size: -1}, assembler: "unknown instruction: bpf.LoadAbsolute{Off:0x2a, Size:-1}", }, { instruction: LoadIndirect{Off: 42, Size: 1}, assembler: "ldb [x + 42]", }, { instruction: LoadIndirect{Off: 42, Size: 2}, assembler: "ldh [x + 42]", }, { instruction: LoadIndirect{Off: 42, Size: 4}, assembler: "ld [x + 42]", }, { instruction: LoadIndirect{Off: 42, Size: -1}, assembler: "unknown instruction: bpf.LoadIndirect{Off:0x2a, Size:-1}", }, { instruction: LoadMemShift{Off: 42}, assembler: "ldx 4([42]&0xf)", }, { instruction: LoadExtension{Num: ExtLen}, assembler: "ld #len", }, { instruction: LoadExtension{Num: ExtProto}, assembler: "ld #proto", }, { instruction: LoadExtension{Num: ExtType}, assembler: "ld #type", }, { instruction: LoadExtension{Num: ExtPayloadOffset}, assembler: "ld #poff", }, { instruction: LoadExtension{Num: ExtInterfaceIndex}, assembler: "ld #ifidx", }, { instruction: LoadExtension{Num: ExtNetlinkAttr}, assembler: "ld #nla", }, { instruction: LoadExtension{Num: ExtNetlinkAttrNested}, assembler: "ld #nlan", }, { instruction: LoadExtension{Num: ExtMark}, assembler: "ld #mark", }, { instruction: LoadExtension{Num: ExtQueue}, assembler: "ld #queue", }, { instruction: LoadExtension{Num: ExtLinkLayerType}, assembler: "ld #hatype", }, { instruction: LoadExtension{Num: ExtRXHash}, assembler: "ld #rxhash", }, { instruction: LoadExtension{Num: ExtCPUID}, assembler: "ld #cpu", }, { instruction: LoadExtension{Num: ExtVLANTag}, assembler: "ld #vlan_tci", }, { instruction: LoadExtension{Num: ExtVLANTagPresent}, assembler: "ld #vlan_avail", }, { instruction: LoadExtension{Num: ExtVLANProto}, assembler: "ld #vlan_tpid", }, { instruction: LoadExtension{Num: ExtRand}, assembler: "ld #rand", }, { instruction: LoadAbsolute{Off: 0xfffff038, Size: 4}, assembler: "ld #rand", }, { instruction: LoadExtension{Num: 0xfff}, assembler: "unknown instruction: bpf.LoadExtension{Num:4095}", }, { instruction: StoreScratch{Src: RegA, N: 3}, assembler: "st M[3]", }, { instruction: StoreScratch{Src: RegX, N: 3}, assembler: "stx M[3]", }, { instruction: StoreScratch{Src: 0xffff, N: 3}, assembler: "unknown instruction: bpf.StoreScratch{Src:0xffff, N:3}", }, { instruction: ALUOpConstant{Op: ALUOpAdd, Val: 42}, assembler: "add #42", }, { instruction: ALUOpConstant{Op: ALUOpSub, Val: 42}, assembler: "sub #42", }, { instruction: ALUOpConstant{Op: ALUOpMul, Val: 42}, assembler: "mul #42", }, { instruction: ALUOpConstant{Op: ALUOpDiv, Val: 42}, assembler: "div #42", }, { instruction: ALUOpConstant{Op: ALUOpOr, Val: 42}, assembler: "or #42", }, { instruction: ALUOpConstant{Op: ALUOpAnd, Val: 42}, assembler: "and #42", }, { instruction: ALUOpConstant{Op: ALUOpShiftLeft, Val: 42}, assembler: "lsh #42", }, { instruction: ALUOpConstant{Op: ALUOpShiftRight, Val: 42}, assembler: "rsh #42", }, { instruction: ALUOpConstant{Op: ALUOpMod, Val: 42}, assembler: "mod #42", }, { instruction: ALUOpConstant{Op: ALUOpXor, Val: 42}, assembler: "xor #42", }, { instruction: ALUOpConstant{Op: 0xffff, Val: 42}, assembler: "unknown instruction: bpf.ALUOpConstant{Op:0xffff, Val:0x2a}", }, { instruction: ALUOpX{Op: ALUOpAdd}, assembler: "add x", }, { instruction: ALUOpX{Op: ALUOpSub}, assembler: "sub x", }, { instruction: ALUOpX{Op: ALUOpMul}, assembler: "mul x", }, { instruction: ALUOpX{Op: ALUOpDiv}, assembler: "div x", }, { instruction: ALUOpX{Op: ALUOpOr}, assembler: "or x", }, { instruction: ALUOpX{Op: ALUOpAnd}, assembler: "and x", }, { instruction: ALUOpX{Op: ALUOpShiftLeft}, assembler: "lsh x", }, { instruction: ALUOpX{Op: ALUOpShiftRight}, assembler: "rsh x", }, { instruction: ALUOpX{Op: ALUOpMod}, assembler: "mod x", }, { instruction: ALUOpX{Op: ALUOpXor}, assembler: "xor x", }, { instruction: ALUOpX{Op: 0xffff}, assembler: "unknown instruction: bpf.ALUOpX{Op:0xffff}", }, { instruction: NegateA{}, assembler: "neg", }, { instruction: Jump{Skip: 10}, assembler: "ja 10", }, { instruction: JumpIf{Cond: JumpEqual, Val: 42, SkipTrue: 8, SkipFalse: 9}, assembler: "jeq #42,8,9", }, { instruction: JumpIf{Cond: JumpEqual, Val: 42, SkipTrue: 8}, assembler: "jeq #42,8", }, { instruction: JumpIf{Cond: JumpEqual, Val: 42, SkipFalse: 8}, assembler: "jneq #42,8", }, { instruction: JumpIf{Cond: JumpNotEqual, Val: 42, SkipTrue: 8}, assembler: "jneq #42,8", }, { instruction: JumpIf{Cond: JumpLessThan, Val: 42, SkipTrue: 7}, assembler: "jlt #42,7", }, { instruction: JumpIf{Cond: JumpLessOrEqual, Val: 42, SkipTrue: 6}, assembler: "jle #42,6", }, { instruction: JumpIf{Cond: JumpGreaterThan, Val: 42, SkipTrue: 4, SkipFalse: 5}, assembler: "jgt #42,4,5", }, { instruction: JumpIf{Cond: JumpGreaterThan, Val: 42, SkipTrue: 4}, assembler: "jgt #42,4", }, { instruction: JumpIf{Cond: JumpGreaterOrEqual, Val: 42, SkipTrue: 3, SkipFalse: 4}, assembler: "jge #42,3,4", }, { instruction: JumpIf{Cond: JumpGreaterOrEqual, Val: 42, SkipTrue: 3}, assembler: "jge #42,3", }, { instruction: JumpIf{Cond: JumpBitsSet, Val: 42, SkipTrue: 2, SkipFalse: 3}, assembler: "jset #42,2,3", }, { instruction: JumpIf{Cond: JumpBitsSet, Val: 42, SkipTrue: 2}, assembler: "jset #42,2", }, { instruction: JumpIf{Cond: JumpBitsNotSet, Val: 42, SkipTrue: 2, SkipFalse: 3}, assembler: "jset #42,3,2", }, { instruction: JumpIf{Cond: JumpBitsNotSet, Val: 42, SkipTrue: 2}, assembler: "jset #42,0,2", }, { instruction: JumpIf{Cond: 0xffff, Val: 42, SkipTrue: 1, SkipFalse: 2}, assembler: "unknown JumpTest 0xffff", }, { instruction: JumpIfX{Cond: JumpEqual, SkipTrue: 8, SkipFalse: 9}, assembler: "jeq x,8,9", }, { instruction: JumpIfX{Cond: JumpEqual, SkipTrue: 8}, assembler: "jeq x,8", }, { instruction: JumpIfX{Cond: JumpEqual, SkipFalse: 8}, assembler: "jneq x,8", }, { instruction: JumpIfX{Cond: JumpNotEqual, SkipTrue: 8}, assembler: "jneq x,8", }, { instruction: JumpIfX{Cond: JumpLessThan, SkipTrue: 7}, assembler: "jlt x,7", }, { instruction: JumpIfX{Cond: JumpLessOrEqual, SkipTrue: 6}, assembler: "jle x,6", }, { instruction: JumpIfX{Cond: JumpGreaterThan, SkipTrue: 4, SkipFalse: 5}, assembler: "jgt x,4,5", }, { instruction: JumpIfX{Cond: JumpGreaterThan, SkipTrue: 4}, assembler: "jgt x,4", }, { instruction: JumpIfX{Cond: JumpGreaterOrEqual, SkipTrue: 3, SkipFalse: 4}, assembler: "jge x,3,4", }, { instruction: JumpIfX{Cond: JumpGreaterOrEqual, SkipTrue: 3}, assembler: "jge x,3", }, { instruction: JumpIfX{Cond: JumpBitsSet, SkipTrue: 2, SkipFalse: 3}, assembler: "jset x,2,3", }, { instruction: JumpIfX{Cond: JumpBitsSet, SkipTrue: 2}, assembler: "jset x,2", }, { instruction: JumpIfX{Cond: JumpBitsNotSet, SkipTrue: 2, SkipFalse: 3}, assembler: "jset x,3,2", }, { instruction: JumpIfX{Cond: JumpBitsNotSet, SkipTrue: 2}, assembler: "jset x,0,2", }, { instruction: JumpIfX{Cond: 0xffff, SkipTrue: 1, SkipFalse: 2}, assembler: "unknown JumpTest 0xffff", }, { instruction: TAX{}, assembler: "tax", }, { instruction: TXA{}, assembler: "txa", }, { instruction: RetA{}, assembler: "ret a", }, { instruction: RetConstant{Val: 42}, assembler: "ret #42", }, // Invalid instruction { instruction: InvalidInstruction{}, assembler: "unknown instruction: bpf.InvalidInstruction{}", }, } for _, testCase := range testCases { if input, ok := testCase.instruction.(fmt.Stringer); ok { got := input.String() if got != testCase.assembler { t.Errorf("String did not return expected assembler notation, expected: %s, got: %s", testCase.assembler, got) } } else { t.Errorf("Instruction %#v is not a fmt.Stringer", testCase.instruction) } } }	15.17 KB	2025-05-25 12:27
📄 setter.go // Copyright 2017 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 // A Setter is a type which can attach a compiled BPF filter to itself. type Setter interface { SetBPF(filter []RawInstruction) error }	310 B	2025-05-25 12:27
📁 testdata	-	2025-05-25 12:27
📄 vm.go // 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) } case JumpIfX: 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 JumpIfX: jump := jumpIfX(ins, regA, regX) 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 }	4.03 KB	2025-05-25 12:27
📄 vm_aluop_test.go // 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_test import ( "testing" "golang.org/x/net/bpf" ) func TestVMALUOpAdd(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 1, }, bpf.ALUOpConstant{ Op: bpf.ALUOpAdd, Val: 3, }, bpf.RetA{}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 8, 2, 3, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 3, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMALUOpSub(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 1, }, bpf.TAX{}, bpf.ALUOpX{ Op: bpf.ALUOpSub, }, bpf.RetA{}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 1, 2, 3, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 0, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMALUOpMul(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 1, }, bpf.ALUOpConstant{ Op: bpf.ALUOpMul, Val: 2, }, bpf.RetA{}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 6, 2, 3, 4, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 4, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMALUOpDiv(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 1, }, bpf.ALUOpConstant{ Op: bpf.ALUOpDiv, Val: 2, }, bpf.RetA{}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 20, 2, 3, 4, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 2, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMALUOpDivByZeroALUOpConstant(t testing.T) { _, _, err := testVM(t, []bpf.Instruction{ bpf.ALUOpConstant{ Op: bpf.ALUOpDiv, Val: 0, }, bpf.RetA{}, }) if errStr(err) != "cannot divide by zero using ALUOpConstant" { t.Fatalf("unexpected error: %v", err) } } func TestVMALUOpDivByZeroALUOpX(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ // Load byte 0 into X bpf.LoadAbsolute{ Off: 8, Size: 1, }, bpf.TAX{}, // Load byte 1 into A bpf.LoadAbsolute{ Off: 9, Size: 1, }, // Attempt to perform 1/0 bpf.ALUOpX{ Op: bpf.ALUOpDiv, }, // Return 4 bytes if program does not terminate bpf.LoadConstant{ Val: 12, }, bpf.RetA{}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, 1, 3, 4, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 0, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMALUOpOr(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 2, }, bpf.ALUOpConstant{ Op: bpf.ALUOpOr, Val: 0x01, }, bpf.RetA{}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00, 0x10, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0xff, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 9, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMALUOpAnd(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 2, }, bpf.ALUOpConstant{ Op: bpf.ALUOpAnd, Val: 0x0019, }, bpf.RetA{}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xaa, 0x09, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 1, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMALUOpShiftLeft(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 1, }, bpf.ALUOpConstant{ Op: bpf.ALUOpShiftLeft, Val: 0x01, }, bpf.JumpIf{ Cond: bpf.JumpEqual, Val: 0x02, SkipTrue: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 9, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x01, 0xaa, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 1, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMALUOpShiftRight(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 1, }, bpf.ALUOpConstant{ Op: bpf.ALUOpShiftRight, Val: 0x01, }, bpf.JumpIf{ Cond: bpf.JumpEqual, Val: 0x04, SkipTrue: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 9, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x08, 0xff, 0xff, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 1, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMALUOpMod(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 1, }, bpf.ALUOpConstant{ Op: bpf.ALUOpMod, Val: 20, }, bpf.RetA{}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 30, 0, 0, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 2, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMALUOpModByZeroALUOpConstant(t testing.T) { _, _, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 1, }, bpf.ALUOpConstant{ Op: bpf.ALUOpMod, Val: 0, }, bpf.RetA{}, }) if errStr(err) != "cannot divide by zero using ALUOpConstant" { t.Fatalf("unexpected error: %v", err) } } func TestVMALUOpModByZeroALUOpX(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ // Load byte 0 into X bpf.LoadAbsolute{ Off: 8, Size: 1, }, bpf.TAX{}, // Load byte 1 into A bpf.LoadAbsolute{ Off: 9, Size: 1, }, // Attempt to perform 1%0 bpf.ALUOpX{ Op: bpf.ALUOpMod, }, // Return 4 bytes if program does not terminate bpf.LoadConstant{ Val: 12, }, bpf.RetA{}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, 1, 3, 4, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 0, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMALUOpXor(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 1, }, bpf.ALUOpConstant{ Op: bpf.ALUOpXor, Val: 0x0a, }, bpf.JumpIf{ Cond: bpf.JumpEqual, Val: 0x01, SkipTrue: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 9, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x0b, 0x00, 0x00, 0x00, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 1, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMALUOpUnknown(t *testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 1, }, bpf.ALUOpConstant{ Op: bpf.ALUOpAdd, Val: 1, }, // Verify that an unknown operation is a no-op bpf.ALUOpConstant{ Op: 100, }, bpf.JumpIf{ Cond: bpf.JumpEqual, Val: 0x02, SkipTrue: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 9, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 1, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 1, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } }	9.66 KB	2025-05-25 12:27
📄 vm_bpf_test.go // 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_test import ( "net" "runtime" "testing" "time" "golang.org/x/net/bpf" "golang.org/x/net/ipv4" "golang.org/x/net/ipv6" "golang.org/x/net/nettest" "golang.org/x/sys/cpu" ) // A virtualMachine is a BPF virtual machine which can process an // input packet against a BPF program and render a verdict. type virtualMachine interface { Run(in []byte) (int, error) } // All BPF tests against both the Go VM and OS VM are assumed to // be used with a UDP socket. As a result, the entire contents // of a UDP datagram is sent through the BPF program, but only // the body after the UDP header will ever be returned in output. // testVM sets up a Go BPF VM, and if available, a native OS BPF VM // for integration testing. func testVM(t testing.T, filter []bpf.Instruction) (virtualMachine, func(), error) { goVM, err := bpf.NewVM(filter) if err != nil { // Some tests expect an error, so this error must be returned // instead of fatally exiting the test return nil, nil, err } mvm := &multiVirtualMachine{ goVM: goVM, t: t, } // For linux with a little endian CPU, the Go VM and OS VM have exactly the // same output for the same input program and packet. Compare both. done := func() {} if runtime.GOOS == "linux" && !cpu.IsBigEndian { osVM, osVMDone := testOSVM(t, filter) done = func() { osVMDone() } mvm.osVM = osVM } return mvm, done, nil } // udpHeaderLen is the length of a UDP header. const udpHeaderLen = 8 // A multiVirtualMachine is a virtualMachine which can call out to both the Go VM // and the native OS VM, if the OS VM is available. type multiVirtualMachine struct { goVM virtualMachine osVM virtualMachine t testing.T } func (mvm multiVirtualMachine) Run(in []byte) (int, error) { if len(in) < udpHeaderLen { mvm.t.Fatalf("input must be at least length of UDP header (%d), got: %d", udpHeaderLen, len(in)) } // All tests have a UDP header as part of input, because the OS VM // packets always will. For the Go VM, this output is trimmed before // being sent back to tests. goOut, goErr := mvm.goVM.Run(in) if goOut >= udpHeaderLen { goOut -= udpHeaderLen } // If Go output is larger than the size of the packet, packet filtering // interop tests must trim the output bytes to the length of the packet. // The BPF VM should not do this on its own, as other uses of it do // not trim the output byte count. trim := len(in) - udpHeaderLen if goOut > trim { goOut = trim } // When the OS VM is not available, process using the Go VM alone if mvm.osVM == nil { return goOut, goErr } // The OS VM will apply its own UDP header, so remove the pseudo header // that the Go VM needs. osOut, err := mvm.osVM.Run(in[udpHeaderLen:]) if err != nil { mvm.t.Fatalf("error while running OS VM: %v", err) } // Verify both VMs return same number of bytes var mismatch bool if goOut != osOut { mismatch = true mvm.t.Logf("output byte count does not match:\n- go: %v\n- os: %v", goOut, osOut) } if mismatch { mvm.t.Fatal("Go BPF and OS BPF packet outputs do not match") } return goOut, goErr } // An osVirtualMachine is a virtualMachine which uses the OS's BPF VM for // processing BPF programs. type osVirtualMachine struct { l net.PacketConn s net.Conn } // testOSVM creates a virtualMachine which uses the OS's BPF VM by injecting // packets into a UDP listener with a BPF program attached to it. func testOSVM(t testing.T, filter []bpf.Instruction) (virtualMachine, func()) { l, err := nettest.NewLocalPacketListener("udp") if err != nil { t.Fatalf("failed to open OS VM UDP listener: %v", err) } prog, err := bpf.Assemble(filter) if err != nil { t.Fatalf("failed to compile BPF program: %v", err) } ip := l.LocalAddr().(net.UDPAddr).IP if ip.To4() != nil && ip.To16() == nil { err = ipv4.NewPacketConn(l).SetBPF(prog) } else { err = ipv6.NewPacketConn(l).SetBPF(prog) } if err != nil { t.Fatalf("failed to attach BPF program to listener: %v", err) } s, err := net.Dial(l.LocalAddr().Network(), l.LocalAddr().String()) if err != nil { t.Fatalf("failed to dial connection to listener: %v", err) } done := func() { _ = s.Close() _ = l.Close() } return &osVirtualMachine{ l: l, s: s, }, done } // Run sends the input bytes into the OS's BPF VM and returns its verdict. func (vm osVirtualMachine) Run(in []byte) (int, error) { go func() { _, _ = vm.s.Write(in) }() vm.l.SetDeadline(time.Now().Add(50 * time.Millisecond)) var b [512]byte n, _, err := vm.l.ReadFrom(b[:]) if err != nil { // A timeout indicates that BPF filtered out the packet, and thus, // no input should be returned. if nerr, ok := err.(net.Error); ok && nerr.Timeout() { return n, nil } return n, err } return n, nil }	4.82 KB	2025-05-25 12:27
📄 vm_extension_test.go // 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_test import ( "testing" "golang.org/x/net/bpf" ) func TestVMLoadExtensionNotImplemented(t testing.T) { _, _, err := testVM(t, []bpf.Instruction{ bpf.LoadExtension{ Num: 100, }, bpf.RetA{}, }) if errStr(err) != "extension 100 not implemented" { t.Fatalf("unexpected error: %v", err) } } func TestVMLoadExtensionExtLen(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadExtension{ Num: bpf.ExtLen, }, bpf.RetA{}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, 1, 2, 3, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 4, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } }	1.01 KB	2025-05-25 12:27
📄 vm_instructions.go // 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) } func jumpIfX(ins JumpIfX, regA uint32, regX uint32) int { return jumpIfCommon(ins.Cond, ins.SkipTrue, ins.SkipFalse, regA, regX) } func jumpIfCommon(cond JumpTest, skipTrue, skipFalse uint8, regA uint32, value uint32) int { var ok bool switch cond { case JumpEqual: ok = regA == value case JumpNotEqual: ok = regA != value case JumpGreaterThan: ok = regA > value case JumpLessThan: ok = regA < value case JumpGreaterOrEqual: ok = regA >= value case JumpLessOrEqual: ok = regA <= value case JumpBitsSet: ok = (regA & value) != 0 case JumpBitsNotSet: ok = (regA & value) == 0 } if ok { return int(skipTrue) } return int(skipFalse) } func loadAbsolute(ins LoadAbsolute, in []byte) (uint32, bool) { offset := int(ins.Off) size := 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 := ins.Size return loadCommon(in, offset, size) } func loadMemShift(ins LoadMemShift, in []byte) (uint32, bool) { offset := int(ins.Off) // Size of LoadMemShift is always 1 byte if !inBounds(len(in), offset, 1) { 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 }	3.87 KB	2025-05-25 12:27
📄 vm_jump_test.go // 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_test import ( "testing" "golang.org/x/net/bpf" ) func TestVMJumpOne(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 1, }, bpf.Jump{ Skip: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 9, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 1, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 1, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMJumpOutOfProgram(t testing.T) { _, _, err := testVM(t, []bpf.Instruction{ bpf.Jump{ Skip: 1, }, bpf.RetA{}, }) if errStr(err) != "cannot jump 1 instructions; jumping past program bounds" { t.Fatalf("unexpected error: %v", err) } } func TestVMJumpIfTrueOutOfProgram(t testing.T) { _, _, err := testVM(t, []bpf.Instruction{ bpf.JumpIf{ Cond: bpf.JumpEqual, SkipTrue: 2, }, bpf.RetA{}, }) if errStr(err) != "cannot jump 2 instructions in true case; jumping past program bounds" { t.Fatalf("unexpected error: %v", err) } } func TestVMJumpIfFalseOutOfProgram(t testing.T) { _, _, err := testVM(t, []bpf.Instruction{ bpf.JumpIf{ Cond: bpf.JumpEqual, SkipFalse: 3, }, bpf.RetA{}, }) if errStr(err) != "cannot jump 3 instructions in false case; jumping past program bounds" { t.Fatalf("unexpected error: %v", err) } } func TestVMJumpIfXTrueOutOfProgram(t testing.T) { _, _, err := testVM(t, []bpf.Instruction{ bpf.JumpIfX{ Cond: bpf.JumpEqual, SkipTrue: 2, }, bpf.RetA{}, }) if errStr(err) != "cannot jump 2 instructions in true case; jumping past program bounds" { t.Fatalf("unexpected error: %v", err) } } func TestVMJumpIfXFalseOutOfProgram(t testing.T) { _, _, err := testVM(t, []bpf.Instruction{ bpf.JumpIfX{ Cond: bpf.JumpEqual, SkipFalse: 3, }, bpf.RetA{}, }) if errStr(err) != "cannot jump 3 instructions in false case; jumping past program bounds" { t.Fatalf("unexpected error: %v", err) } } func TestVMJumpIfEqual(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 1, }, bpf.JumpIf{ Cond: bpf.JumpEqual, Val: 1, SkipTrue: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 9, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 1, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 1, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMJumpIfNotEqual(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 1, }, bpf.JumpIf{ Cond: bpf.JumpNotEqual, Val: 1, SkipFalse: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 9, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 1, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 1, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMJumpIfGreaterThan(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 4, }, bpf.JumpIf{ Cond: bpf.JumpGreaterThan, Val: 0x00010202, SkipTrue: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 12, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, 1, 2, 3, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 4, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMJumpIfLessThan(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 4, }, bpf.JumpIf{ Cond: bpf.JumpLessThan, Val: 0xff010203, SkipTrue: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 12, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, 1, 2, 3, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 4, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMJumpIfGreaterOrEqual(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 4, }, bpf.JumpIf{ Cond: bpf.JumpGreaterOrEqual, Val: 0x00010203, SkipTrue: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 12, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, 1, 2, 3, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 4, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMJumpIfLessOrEqual(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 4, }, bpf.JumpIf{ Cond: bpf.JumpLessOrEqual, Val: 0xff010203, SkipTrue: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 12, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, 1, 2, 3, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 4, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMJumpIfBitsSet(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 2, }, bpf.JumpIf{ Cond: bpf.JumpBitsSet, Val: 0x1122, SkipTrue: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 10, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x01, 0x02, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 2, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMJumpIfBitsNotSet(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 2, }, bpf.JumpIf{ Cond: bpf.JumpBitsNotSet, Val: 0x1221, SkipTrue: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 10, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x01, 0x02, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 2, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMJumpIfXEqual(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 1, }, bpf.LoadConstant{ Dst: bpf.RegX, Val: 1, }, bpf.JumpIfX{ Cond: bpf.JumpEqual, SkipTrue: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 9, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 1, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 1, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMJumpIfXNotEqual(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 1, }, bpf.LoadConstant{ Dst: bpf.RegX, Val: 1, }, bpf.JumpIfX{ Cond: bpf.JumpNotEqual, SkipFalse: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 9, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 1, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 1, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMJumpIfXGreaterThan(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 4, }, bpf.LoadConstant{ Dst: bpf.RegX, Val: 0x00010202, }, bpf.JumpIfX{ Cond: bpf.JumpGreaterThan, SkipTrue: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 12, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, 1, 2, 3, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 4, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMJumpIfXLessThan(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 4, }, bpf.LoadConstant{ Dst: bpf.RegX, Val: 0xff010203, }, bpf.JumpIfX{ Cond: bpf.JumpLessThan, SkipTrue: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 12, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, 1, 2, 3, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 4, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMJumpIfXGreaterOrEqual(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 4, }, bpf.LoadConstant{ Dst: bpf.RegX, Val: 0x00010203, }, bpf.JumpIfX{ Cond: bpf.JumpGreaterOrEqual, SkipTrue: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 12, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, 1, 2, 3, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 4, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMJumpIfXLessOrEqual(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 4, }, bpf.LoadConstant{ Dst: bpf.RegX, Val: 0xff010203, }, bpf.JumpIfX{ Cond: bpf.JumpLessOrEqual, SkipTrue: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 12, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, 1, 2, 3, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 4, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMJumpIfXBitsSet(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 2, }, bpf.LoadConstant{ Dst: bpf.RegX, Val: 0x1122, }, bpf.JumpIfX{ Cond: bpf.JumpBitsSet, SkipTrue: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 10, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x01, 0x02, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 2, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMJumpIfXBitsNotSet(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 2, }, bpf.LoadConstant{ Dst: bpf.RegX, Val: 0x1221, }, bpf.JumpIfX{ Cond: bpf.JumpBitsNotSet, SkipTrue: 1, }, bpf.RetConstant{ Val: 0, }, bpf.RetConstant{ Val: 10, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x01, 0x02, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 2, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } }	13.53 KB	2025-05-25 12:27
📄 vm_load_test.go // 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_test import ( "net" "testing" "golang.org/x/net/bpf" "golang.org/x/net/ipv4" ) func TestVMLoadAbsoluteOffsetOutOfBounds(t testing.T) { pkt := []byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, 1, 2, 3, } vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: uint32(len(pkt)), Size: 1, }, // Out of bounds should return 0, return 1 to tell if execution continued bpf.RetConstant{Val: 1}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run(pkt) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 0, out; want != got { t.Fatalf("unexpected result:\n- want: %d\n- got: %d", want, got) } } func TestVMLoadAbsoluteOffsetPlusSizeOutOfBounds(t testing.T) { pkt := []byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, } vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: uint32(len(pkt) - 1), Size: 2, }, // Out of bounds should return 0, return 1 to tell if execution continued bpf.RetConstant{Val: 1}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run(pkt) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 0, out; want != got { t.Fatalf("unexpected result:\n- want: %d\n- got: %d", want, got) } } func TestVMLoadAbsoluteBadInstructionSize(t testing.T) { _, _, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Size: 5, }, bpf.RetA{}, }) if errStr(err) != "assembling instruction 1: invalid load byte length 0" { t.Fatalf("unexpected error: %v", err) } } func TestVMLoadConstantOK(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadConstant{ Dst: bpf.RegX, Val: 9, }, bpf.TXA{}, bpf.RetA{}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 1, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMLoadIndirectOutOfBounds(t testing.T) { pkt := []byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, } vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadIndirect{ Off: uint32(len(pkt)), Size: 1, }, // Out of bounds should return 0, return 1 to tell if execution continued bpf.RetConstant{Val: 1}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run(pkt) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 0, out; want != got { t.Fatalf("unexpected result:\n- want: %d\n- got: %d", want, got) } } func TestVMLoadMemShiftOutOfBounds(t testing.T) { pkt := []byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, } vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadMemShift{ Off: uint32(len(pkt)), }, // Out of bounds should return 0, return 1 to tell if execution continued bpf.RetConstant{Val: 1}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run(pkt) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 0, out; want != got { t.Fatalf("unexpected result:\n- want: %d\n- got: %d", want, got) } } const ( dhcp4Port = 53 ) func TestVMLoadMemShiftLoadIndirectNoResult(t testing.T) { vm, in, done := testDHCPv4(t) defer done() // Append mostly empty UDP header with incorrect DHCPv4 port in = append(in, []byte{ 0, 0, 0, dhcp4Port + 1, 0, 0, 0, 0, }...) out, err := vm.Run(in) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 0, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMLoadMemShiftLoadIndirectOK(t testing.T) { vm, in, done := testDHCPv4(t) defer done() // Append mostly empty UDP header with correct DHCPv4 port in = append(in, []byte{ 0, 0, 0, dhcp4Port, 0, 0, 0, 0, }...) out, err := vm.Run(in) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := len(in)-8, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func testDHCPv4(t *testing.T) (virtualMachine, []byte, func()) { // DHCPv4 test data courtesy of David Anderson: // https://github.com/google/netboot/blob/master/dhcp4/conn_linux.go#L59-L70 vm, done, err := testVM(t, []bpf.Instruction{ // Load IPv4 packet length bpf.LoadMemShift{Off: 8}, // Get UDP dport bpf.LoadIndirect{Off: 8 + 2, Size: 2}, // Correct dport? bpf.JumpIf{Cond: bpf.JumpEqual, Val: dhcp4Port, SkipFalse: 1}, // Accept bpf.RetConstant{Val: 1500}, // Ignore bpf.RetConstant{Val: 0}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } // Minimal requirements to make a valid IPv4 header h := &ipv4.Header{ Len: ipv4.HeaderLen, Src: net.IPv4(192, 168, 1, 1), Dst: net.IPv4(192, 168, 1, 2), } hb, err := h.Marshal() if err != nil { t.Fatalf("failed to marshal IPv4 header: %v", err) } hb = append([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, }, hb...) return vm, hb, done }	5.56 KB	2025-05-25 12:27
📄 vm_ret_test.go // 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_test import ( "testing" "golang.org/x/net/bpf" ) func TestVMRetA(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 1, }, bpf.RetA{}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 9, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 1, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMRetALargerThanInput(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadAbsolute{ Off: 8, Size: 2, }, bpf.RetA{}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, 255, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 2, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMRetConstant(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.RetConstant{ Val: 9, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, 1, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 1, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMRetConstantLargerThanInput(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.RetConstant{ Val: 16, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, 1, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 2, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } }	2.31 KB	2025-05-25 12:27
📄 vm_scratch_test.go // 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_test import ( "testing" "golang.org/x/net/bpf" ) func TestVMStoreScratchInvalidScratchRegisterTooSmall(t testing.T) { _, _, err := testVM(t, []bpf.Instruction{ bpf.StoreScratch{ Src: bpf.RegA, N: -1, }, bpf.RetA{}, }) if errStr(err) != "assembling instruction 1: invalid scratch slot -1" { t.Fatalf("unexpected error: %v", err) } } func TestVMStoreScratchInvalidScratchRegisterTooLarge(t testing.T) { _, _, err := testVM(t, []bpf.Instruction{ bpf.StoreScratch{ Src: bpf.RegA, N: 16, }, bpf.RetA{}, }) if errStr(err) != "assembling instruction 1: invalid scratch slot 16" { t.Fatalf("unexpected error: %v", err) } } func TestVMStoreScratchUnknownSourceRegister(t testing.T) { _, _, err := testVM(t, []bpf.Instruction{ bpf.StoreScratch{ Src: 100, N: 0, }, bpf.RetA{}, }) if errStr(err) != "assembling instruction 1: invalid source register 100" { t.Fatalf("unexpected error: %v", err) } } func TestVMLoadScratchInvalidScratchRegisterTooSmall(t testing.T) { _, _, err := testVM(t, []bpf.Instruction{ bpf.LoadScratch{ Dst: bpf.RegX, N: -1, }, bpf.RetA{}, }) if errStr(err) != "assembling instruction 1: invalid scratch slot -1" { t.Fatalf("unexpected error: %v", err) } } func TestVMLoadScratchInvalidScratchRegisterTooLarge(t testing.T) { _, _, err := testVM(t, []bpf.Instruction{ bpf.LoadScratch{ Dst: bpf.RegX, N: 16, }, bpf.RetA{}, }) if errStr(err) != "assembling instruction 1: invalid scratch slot 16" { t.Fatalf("unexpected error: %v", err) } } func TestVMLoadScratchUnknownDestinationRegister(t testing.T) { _, _, err := testVM(t, []bpf.Instruction{ bpf.LoadScratch{ Dst: 100, N: 0, }, bpf.RetA{}, }) if errStr(err) != "assembling instruction 1: invalid target register 100" { t.Fatalf("unexpected error: %v", err) } } func TestVMStoreScratchLoadScratchOneValue(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ // Load byte 255 bpf.LoadAbsolute{ Off: 8, Size: 1, }, // Copy to X and store in scratch[0] bpf.TAX{}, bpf.StoreScratch{ Src: bpf.RegX, N: 0, }, // Load byte 1 bpf.LoadAbsolute{ Off: 9, Size: 1, }, // Overwrite 1 with 255 from scratch[0] bpf.LoadScratch{ Dst: bpf.RegA, N: 0, }, // Return 255 bpf.RetA{}, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 255, 1, 2, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 3, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } } func TestVMStoreScratchLoadScratchMultipleValues(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ // Load byte 10 bpf.LoadAbsolute{ Off: 8, Size: 1, }, // Store in scratch[0] bpf.StoreScratch{ Src: bpf.RegA, N: 0, }, // Load byte 20 bpf.LoadAbsolute{ Off: 9, Size: 1, }, // Store in scratch[1] bpf.StoreScratch{ Src: bpf.RegA, N: 1, }, // Load byte 30 bpf.LoadAbsolute{ Off: 10, Size: 1, }, // Store in scratch[2] bpf.StoreScratch{ Src: bpf.RegA, N: 2, }, // Load byte 1 bpf.LoadAbsolute{ Off: 11, Size: 1, }, // Store in scratch[3] bpf.StoreScratch{ Src: bpf.RegA, N: 3, }, // Load in byte 10 to X bpf.LoadScratch{ Dst: bpf.RegX, N: 0, }, // Copy X -> A bpf.TXA{}, // Verify value is 10 bpf.JumpIf{ Cond: bpf.JumpEqual, Val: 10, SkipTrue: 1, }, // Fail test if incorrect bpf.RetConstant{ Val: 0, }, // Load in byte 20 to A bpf.LoadScratch{ Dst: bpf.RegA, N: 1, }, // Verify value is 20 bpf.JumpIf{ Cond: bpf.JumpEqual, Val: 20, SkipTrue: 1, }, // Fail test if incorrect bpf.RetConstant{ Val: 0, }, // Load in byte 30 to A bpf.LoadScratch{ Dst: bpf.RegA, N: 2, }, // Verify value is 30 bpf.JumpIf{ Cond: bpf.JumpEqual, Val: 30, SkipTrue: 1, }, // Fail test if incorrect bpf.RetConstant{ Val: 0, }, // Return first two bytes on success bpf.RetConstant{ Val: 10, }, }) if err != nil { t.Fatalf("failed to load BPF program: %v", err) } defer done() out, err := vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 10, 20, 30, 1, }) if err != nil { t.Fatalf("unexpected error while running program: %v", err) } if want, got := 2, out; want != got { t.Fatalf("unexpected number of output bytes:\n- want: %d\n- got: %d", want, got) } }	4.73 KB	2025-05-25 12:27
📄 vm_test.go // 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_test import ( "fmt" "testing" "golang.org/x/net/bpf" ) var _ bpf.Instruction = unknown{} type unknown struct{} func (unknown) Assemble() (bpf.RawInstruction, error) { return bpf.RawInstruction{}, nil } func TestVMUnknownInstruction(t testing.T) { vm, done, err := testVM(t, []bpf.Instruction{ bpf.LoadConstant{ Dst: bpf.RegA, Val: 100, }, // Should terminate the program with an error immediately unknown{}, bpf.RetA{}, }) if err != nil { t.Fatalf("unexpected error: %v", err) } defer done() _, err = vm.Run([]byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00, 0x00, }) if errStr(err) != "unknown Instruction at index 1: bpf_test.unknown" { t.Fatalf("unexpected error while running program: %v", err) } } func TestVMNoReturnInstruction(t testing.T) { _, _, err := testVM(t, []bpf.Instruction{ bpf.LoadConstant{ Dst: bpf.RegA, Val: 1, }, }) if errStr(err) != "BPF program must end with RetA or RetConstant" { t.Fatalf("unexpected error: %v", err) } } func TestVMNoInputInstructions(t *testing.T) { _, _, err := testVM(t, []bpf.Instruction{}) if errStr(err) != "one or more Instructions must be specified" { t.Fatalf("unexpected error: %v", err) } } // ExampleNewVM demonstrates usage of a VM, using an Ethernet frame // as input and checking its EtherType to determine if it should be accepted. func ExampleNewVM() { // Offset \| Length \| Comment // ------------------------- // 00 \| 06 \| Ethernet destination MAC address // 06 \| 06 \| Ethernet source MAC address // 12 \| 02 \| Ethernet EtherType const ( etOff = 12 etLen = 2 etARP = 0x0806 ) // Set up a VM to filter traffic based on if its EtherType // matches the ARP EtherType. vm, err := bpf.NewVM([]bpf.Instruction{ // Load EtherType value from Ethernet header bpf.LoadAbsolute{ Off: etOff, Size: etLen, }, // If EtherType is equal to the ARP EtherType, jump to allow // packet to be accepted bpf.JumpIf{ Cond: bpf.JumpEqual, Val: etARP, SkipTrue: 1, }, // EtherType does not match the ARP EtherType bpf.RetConstant{ Val: 0, }, // EtherType matches the ARP EtherType, accept up to 1500 // bytes of packet bpf.RetConstant{ Val: 1500, }, }) if err != nil { panic(fmt.Sprintf("failed to load BPF program: %v", err)) } // Create an Ethernet frame with the ARP EtherType for testing frame := []byte{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x08, 0x06, // Payload omitted for brevity } // Run our VM's BPF program using the Ethernet frame as input out, err := vm.Run(frame) if err != nil { panic(fmt.Sprintf("failed to accept Ethernet frame: %v", err)) } // BPF VM can return a byte count greater than the number of input // bytes, so trim the output to match the input byte length if out > len(frame) { out = len(frame) } fmt.Printf("out: %d bytes", out) // Output: // out: 14 bytes } // errStr returns the string representation of an error, or // "<nil>" if it is nil. func errStr(err error) string { if err == nil { return "<nil>" } return err.Error() }	3.25 KB	2025-05-25 12:27

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