GoToSocial/vendor/github.com/cilium/ebpf/asm/opcode.go

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package asm
import (
"fmt"
"strings"
)
//go:generate stringer -output opcode_string.go -type=Class
type encoding int
const (
unknownEncoding encoding = iota
loadOrStore
jumpOrALU
)
// Class of operations
//
// msb lsb
// +---+--+---+
// | ?? |CLS|
// +---+--+---+
type Class uint8
const classMask OpCode = 0x07
const (
// LdClass load memory
LdClass Class = 0x00
// LdXClass load memory from constant
LdXClass Class = 0x01
// StClass load register from memory
StClass Class = 0x02
// StXClass load register from constant
StXClass Class = 0x03
// ALUClass arithmetic operators
ALUClass Class = 0x04
// JumpClass jump operators
JumpClass Class = 0x05
// ALU64Class arithmetic in 64 bit mode
ALU64Class Class = 0x07
)
func (cls Class) encoding() encoding {
switch cls {
case LdClass, LdXClass, StClass, StXClass:
return loadOrStore
case ALU64Class, ALUClass, JumpClass:
return jumpOrALU
default:
return unknownEncoding
}
}
// OpCode is a packed eBPF opcode.
//
// Its encoding is defined by a Class value:
//
// msb lsb
// +----+-+---+
// | ???? |CLS|
// +----+-+---+
type OpCode uint8
// InvalidOpCode is returned by setters on OpCode
const InvalidOpCode OpCode = 0xff
// rawInstructions returns the number of BPF instructions required
// to encode this opcode.
func (op OpCode) rawInstructions() int {
if op.isDWordLoad() {
return 2
}
return 1
}
func (op OpCode) isDWordLoad() bool {
return op == LoadImmOp(DWord)
}
// Class returns the class of operation.
func (op OpCode) Class() Class {
return Class(op & classMask)
}
// Mode returns the mode for load and store operations.
func (op OpCode) Mode() Mode {
if op.Class().encoding() != loadOrStore {
return InvalidMode
}
return Mode(op & modeMask)
}
// Size returns the size for load and store operations.
func (op OpCode) Size() Size {
if op.Class().encoding() != loadOrStore {
return InvalidSize
}
return Size(op & sizeMask)
}
// Source returns the source for branch and ALU operations.
func (op OpCode) Source() Source {
if op.Class().encoding() != jumpOrALU || op.ALUOp() == Swap {
return InvalidSource
}
return Source(op & sourceMask)
}
// ALUOp returns the ALUOp.
func (op OpCode) ALUOp() ALUOp {
if op.Class().encoding() != jumpOrALU {
return InvalidALUOp
}
return ALUOp(op & aluMask)
}
// Endianness returns the Endianness for a byte swap instruction.
func (op OpCode) Endianness() Endianness {
if op.ALUOp() != Swap {
return InvalidEndian
}
return Endianness(op & endianMask)
}
// JumpOp returns the JumpOp.
func (op OpCode) JumpOp() JumpOp {
if op.Class().encoding() != jumpOrALU {
return InvalidJumpOp
}
return JumpOp(op & jumpMask)
}
// SetMode sets the mode on load and store operations.
//
// Returns InvalidOpCode if op is of the wrong class.
func (op OpCode) SetMode(mode Mode) OpCode {
if op.Class().encoding() != loadOrStore || !valid(OpCode(mode), modeMask) {
return InvalidOpCode
}
return (op & ^modeMask) | OpCode(mode)
}
// SetSize sets the size on load and store operations.
//
// Returns InvalidOpCode if op is of the wrong class.
func (op OpCode) SetSize(size Size) OpCode {
if op.Class().encoding() != loadOrStore || !valid(OpCode(size), sizeMask) {
return InvalidOpCode
}
return (op & ^sizeMask) | OpCode(size)
}
// SetSource sets the source on jump and ALU operations.
//
// Returns InvalidOpCode if op is of the wrong class.
func (op OpCode) SetSource(source Source) OpCode {
if op.Class().encoding() != jumpOrALU || !valid(OpCode(source), sourceMask) {
return InvalidOpCode
}
return (op & ^sourceMask) | OpCode(source)
}
// SetALUOp sets the ALUOp on ALU operations.
//
// Returns InvalidOpCode if op is of the wrong class.
func (op OpCode) SetALUOp(alu ALUOp) OpCode {
class := op.Class()
if (class != ALUClass && class != ALU64Class) || !valid(OpCode(alu), aluMask) {
return InvalidOpCode
}
return (op & ^aluMask) | OpCode(alu)
}
// SetJumpOp sets the JumpOp on jump operations.
//
// Returns InvalidOpCode if op is of the wrong class.
func (op OpCode) SetJumpOp(jump JumpOp) OpCode {
if op.Class() != JumpClass || !valid(OpCode(jump), jumpMask) {
return InvalidOpCode
}
return (op & ^jumpMask) | OpCode(jump)
}
func (op OpCode) String() string {
var f strings.Builder
switch class := op.Class(); class {
case LdClass, LdXClass, StClass, StXClass:
f.WriteString(strings.TrimSuffix(class.String(), "Class"))
mode := op.Mode()
f.WriteString(strings.TrimSuffix(mode.String(), "Mode"))
switch op.Size() {
case DWord:
f.WriteString("DW")
case Word:
f.WriteString("W")
case Half:
f.WriteString("H")
case Byte:
f.WriteString("B")
}
case ALU64Class, ALUClass:
f.WriteString(op.ALUOp().String())
if op.ALUOp() == Swap {
// Width for Endian is controlled by Constant
f.WriteString(op.Endianness().String())
} else {
if class == ALUClass {
f.WriteString("32")
}
f.WriteString(strings.TrimSuffix(op.Source().String(), "Source"))
}
case JumpClass:
f.WriteString(op.JumpOp().String())
if jop := op.JumpOp(); jop != Exit && jop != Call {
f.WriteString(strings.TrimSuffix(op.Source().String(), "Source"))
}
default:
fmt.Fprintf(&f, "OpCode(%#x)", uint8(op))
}
return f.String()
}
// valid returns true if all bits in value are covered by mask.
func valid(value, mask OpCode) bool {
return value & ^mask == 0
}