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// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package bpf
// 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.
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
opMaskOperandSrc = 0x08
opMaskOperator = 0xf0
// opClsJump
opMaskJumpConst = 0x0f
opMaskJumpCond = 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
)
// Operator defined by ALUOp*
const (
opALUSrcConstant uint16 = iota << 3
opALUSrcX
)
const (
opJumpAlways = iota << 4
opJumpEqual
opJumpGT
opJumpGE
opJumpSet
)
const (
opRetSrcConstant uint16 = iota << 4
opRetSrcA
)
const (
opMiscTAX = 0x00
opMiscTXA = 0x80
)
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