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219 lines
5.9 KiB
Go
219 lines
5.9 KiB
Go
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// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package bpf
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// A Register is a register of the BPF virtual machine.
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type Register uint16
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const (
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// RegA is the accumulator register. RegA is always the
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// destination register of ALU operations.
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RegA Register = iota
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// RegX is the indirection register, used by LoadIndirect
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// operations.
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RegX
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)
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// An ALUOp is an arithmetic or logic operation.
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type ALUOp uint16
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// ALU binary operation types.
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const (
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ALUOpAdd ALUOp = iota << 4
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ALUOpSub
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ALUOpMul
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ALUOpDiv
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ALUOpOr
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ALUOpAnd
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ALUOpShiftLeft
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ALUOpShiftRight
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aluOpNeg // Not exported because it's the only unary ALU operation, and gets its own instruction type.
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ALUOpMod
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ALUOpXor
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)
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// A JumpTest is a comparison operator used in conditional jumps.
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type JumpTest uint16
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// Supported operators for conditional jumps.
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const (
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// K == A
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JumpEqual JumpTest = iota
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// K != A
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JumpNotEqual
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// K > A
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JumpGreaterThan
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// K < A
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JumpLessThan
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// K >= A
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JumpGreaterOrEqual
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// K <= A
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JumpLessOrEqual
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// K & A != 0
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JumpBitsSet
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// K & A == 0
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JumpBitsNotSet
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)
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// An Extension is a function call provided by the kernel that
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// performs advanced operations that are expensive or impossible
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// within the BPF virtual machine.
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//
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// Extensions are only implemented by the Linux kernel.
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//
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// TODO: should we prune this list? Some of these extensions seem
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// either broken or near-impossible to use correctly, whereas other
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// (len, random, ifindex) are quite useful.
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type Extension int
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// Extension functions available in the Linux kernel.
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const (
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// extOffset is the negative maximum number of instructions used
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// to load instructions by overloading the K argument.
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extOffset = -0x1000
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// ExtLen returns the length of the packet.
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ExtLen Extension = 1
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// ExtProto returns the packet's L3 protocol type.
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ExtProto Extension = 0
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// ExtType returns the packet's type (skb->pkt_type in the kernel)
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//
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// TODO: better documentation. How nice an API do we want to
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// provide for these esoteric extensions?
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ExtType Extension = 4
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// ExtPayloadOffset returns the offset of the packet payload, or
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// the first protocol header that the kernel does not know how to
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// parse.
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ExtPayloadOffset Extension = 52
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// ExtInterfaceIndex returns the index of the interface on which
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// the packet was received.
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ExtInterfaceIndex Extension = 8
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// ExtNetlinkAttr returns the netlink attribute of type X at
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// offset A.
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ExtNetlinkAttr Extension = 12
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// ExtNetlinkAttrNested returns the nested netlink attribute of
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// type X at offset A.
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ExtNetlinkAttrNested Extension = 16
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// ExtMark returns the packet's mark value.
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ExtMark Extension = 20
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// ExtQueue returns the packet's assigned hardware queue.
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ExtQueue Extension = 24
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// ExtLinkLayerType returns the packet's hardware address type
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// (e.g. Ethernet, Infiniband).
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ExtLinkLayerType Extension = 28
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// ExtRXHash returns the packets receive hash.
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//
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// TODO: figure out what this rxhash actually is.
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ExtRXHash Extension = 32
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// ExtCPUID returns the ID of the CPU processing the current
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// packet.
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ExtCPUID Extension = 36
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// ExtVLANTag returns the packet's VLAN tag.
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ExtVLANTag Extension = 44
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// ExtVLANTagPresent returns non-zero if the packet has a VLAN
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// tag.
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//
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// TODO: I think this might be a lie: it reads bit 0x1000 of the
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// VLAN header, which changed meaning in recent revisions of the
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// spec - this extension may now return meaningless information.
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ExtVLANTagPresent Extension = 48
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// ExtVLANProto returns 0x8100 if the frame has a VLAN header,
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// 0x88a8 if the frame has a "Q-in-Q" double VLAN header, or some
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// other value if no VLAN information is present.
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ExtVLANProto Extension = 60
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// ExtRand returns a uniformly random uint32.
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ExtRand Extension = 56
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)
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// The following gives names to various bit patterns used in opcode construction.
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const (
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opMaskCls uint16 = 0x7
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// opClsLoad masks
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opMaskLoadDest = 0x01
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opMaskLoadWidth = 0x18
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opMaskLoadMode = 0xe0
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// opClsALU
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opMaskOperandSrc = 0x08
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opMaskOperator = 0xf0
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// opClsJump
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opMaskJumpConst = 0x0f
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opMaskJumpCond = 0xf0
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)
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const (
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// +---------------+-----------------+---+---+---+
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// | AddrMode (3b) | LoadWidth (2b) | 0 | 0 | 0 |
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// +---------------+-----------------+---+---+---+
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opClsLoadA uint16 = iota
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// +---------------+-----------------+---+---+---+
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// | AddrMode (3b) | LoadWidth (2b) | 0 | 0 | 1 |
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// +---------------+-----------------+---+---+---+
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opClsLoadX
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// +---+---+---+---+---+---+---+---+
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// | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 |
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// +---+---+---+---+---+---+---+---+
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opClsStoreA
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// +---+---+---+---+---+---+---+---+
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// | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 |
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// +---+---+---+---+---+---+---+---+
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opClsStoreX
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// +---------------+-----------------+---+---+---+
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// | Operator (4b) | OperandSrc (1b) | 1 | 0 | 0 |
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// +---------------+-----------------+---+---+---+
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opClsALU
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// +-----------------------------+---+---+---+---+
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// | TestOperator (4b) | 0 | 1 | 0 | 1 |
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// +-----------------------------+---+---+---+---+
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opClsJump
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// +---+-------------------------+---+---+---+---+
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// | 0 | 0 | 0 | RetSrc (1b) | 0 | 1 | 1 | 0 |
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// +---+-------------------------+---+---+---+---+
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opClsReturn
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// +---+-------------------------+---+---+---+---+
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// | 0 | 0 | 0 | TXAorTAX (1b) | 0 | 1 | 1 | 1 |
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// +---+-------------------------+---+---+---+---+
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opClsMisc
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)
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const (
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opAddrModeImmediate uint16 = iota << 5
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opAddrModeAbsolute
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opAddrModeIndirect
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opAddrModeScratch
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opAddrModePacketLen // actually an extension, not an addressing mode.
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opAddrModeMemShift
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)
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const (
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opLoadWidth4 uint16 = iota << 3
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opLoadWidth2
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opLoadWidth1
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)
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// Operator defined by ALUOp*
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const (
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opALUSrcConstant uint16 = iota << 3
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opALUSrcX
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)
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const (
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opJumpAlways = iota << 4
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opJumpEqual
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opJumpGT
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opJumpGE
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opJumpSet
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)
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const (
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opRetSrcConstant uint16 = iota << 4
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opRetSrcA
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)
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const (
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opMiscTAX = 0x00
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opMiscTXA = 0x80
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)
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