mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-12-12 01:50:41 +01:00
238 lines
5.3 KiB
Go
238 lines
5.3 KiB
Go
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package asm
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import (
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"fmt"
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"strings"
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)
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//go:generate stringer -output opcode_string.go -type=Class
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type encoding int
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const (
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unknownEncoding encoding = iota
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loadOrStore
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jumpOrALU
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)
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// Class of operations
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//
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// msb lsb
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// +---+--+---+
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// | ?? |CLS|
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// +---+--+---+
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type Class uint8
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const classMask OpCode = 0x07
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const (
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// LdClass load memory
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LdClass Class = 0x00
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// LdXClass load memory from constant
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LdXClass Class = 0x01
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// StClass load register from memory
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StClass Class = 0x02
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// StXClass load register from constant
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StXClass Class = 0x03
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// ALUClass arithmetic operators
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ALUClass Class = 0x04
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// JumpClass jump operators
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JumpClass Class = 0x05
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// ALU64Class arithmetic in 64 bit mode
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ALU64Class Class = 0x07
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)
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func (cls Class) encoding() encoding {
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switch cls {
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case LdClass, LdXClass, StClass, StXClass:
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return loadOrStore
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case ALU64Class, ALUClass, JumpClass:
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return jumpOrALU
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default:
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return unknownEncoding
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}
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}
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// OpCode is a packed eBPF opcode.
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//
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// Its encoding is defined by a Class value:
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//
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// msb lsb
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// +----+-+---+
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// | ???? |CLS|
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// +----+-+---+
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type OpCode uint8
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// InvalidOpCode is returned by setters on OpCode
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const InvalidOpCode OpCode = 0xff
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// rawInstructions returns the number of BPF instructions required
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// to encode this opcode.
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func (op OpCode) rawInstructions() int {
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if op.isDWordLoad() {
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return 2
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}
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return 1
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}
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func (op OpCode) isDWordLoad() bool {
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return op == LoadImmOp(DWord)
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}
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// Class returns the class of operation.
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func (op OpCode) Class() Class {
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return Class(op & classMask)
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}
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// Mode returns the mode for load and store operations.
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func (op OpCode) Mode() Mode {
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if op.Class().encoding() != loadOrStore {
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return InvalidMode
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}
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return Mode(op & modeMask)
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}
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// Size returns the size for load and store operations.
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func (op OpCode) Size() Size {
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if op.Class().encoding() != loadOrStore {
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return InvalidSize
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}
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return Size(op & sizeMask)
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}
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// Source returns the source for branch and ALU operations.
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func (op OpCode) Source() Source {
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if op.Class().encoding() != jumpOrALU || op.ALUOp() == Swap {
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return InvalidSource
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}
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return Source(op & sourceMask)
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}
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// ALUOp returns the ALUOp.
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func (op OpCode) ALUOp() ALUOp {
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if op.Class().encoding() != jumpOrALU {
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return InvalidALUOp
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}
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return ALUOp(op & aluMask)
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}
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// Endianness returns the Endianness for a byte swap instruction.
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func (op OpCode) Endianness() Endianness {
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if op.ALUOp() != Swap {
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return InvalidEndian
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}
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return Endianness(op & endianMask)
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}
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// JumpOp returns the JumpOp.
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func (op OpCode) JumpOp() JumpOp {
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if op.Class().encoding() != jumpOrALU {
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return InvalidJumpOp
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}
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return JumpOp(op & jumpMask)
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}
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// SetMode sets the mode on load and store operations.
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//
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// Returns InvalidOpCode if op is of the wrong class.
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func (op OpCode) SetMode(mode Mode) OpCode {
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if op.Class().encoding() != loadOrStore || !valid(OpCode(mode), modeMask) {
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return InvalidOpCode
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}
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return (op & ^modeMask) | OpCode(mode)
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}
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// SetSize sets the size on load and store operations.
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//
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// Returns InvalidOpCode if op is of the wrong class.
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func (op OpCode) SetSize(size Size) OpCode {
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if op.Class().encoding() != loadOrStore || !valid(OpCode(size), sizeMask) {
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return InvalidOpCode
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}
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return (op & ^sizeMask) | OpCode(size)
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}
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// SetSource sets the source on jump and ALU operations.
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//
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// Returns InvalidOpCode if op is of the wrong class.
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func (op OpCode) SetSource(source Source) OpCode {
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if op.Class().encoding() != jumpOrALU || !valid(OpCode(source), sourceMask) {
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return InvalidOpCode
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}
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return (op & ^sourceMask) | OpCode(source)
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}
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// SetALUOp sets the ALUOp on ALU operations.
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//
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// Returns InvalidOpCode if op is of the wrong class.
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func (op OpCode) SetALUOp(alu ALUOp) OpCode {
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class := op.Class()
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if (class != ALUClass && class != ALU64Class) || !valid(OpCode(alu), aluMask) {
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return InvalidOpCode
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}
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return (op & ^aluMask) | OpCode(alu)
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}
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// SetJumpOp sets the JumpOp on jump operations.
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//
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// Returns InvalidOpCode if op is of the wrong class.
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func (op OpCode) SetJumpOp(jump JumpOp) OpCode {
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if op.Class() != JumpClass || !valid(OpCode(jump), jumpMask) {
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return InvalidOpCode
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}
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return (op & ^jumpMask) | OpCode(jump)
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}
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func (op OpCode) String() string {
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var f strings.Builder
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switch class := op.Class(); class {
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case LdClass, LdXClass, StClass, StXClass:
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f.WriteString(strings.TrimSuffix(class.String(), "Class"))
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mode := op.Mode()
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f.WriteString(strings.TrimSuffix(mode.String(), "Mode"))
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switch op.Size() {
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case DWord:
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f.WriteString("DW")
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case Word:
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f.WriteString("W")
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case Half:
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f.WriteString("H")
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case Byte:
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f.WriteString("B")
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}
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case ALU64Class, ALUClass:
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f.WriteString(op.ALUOp().String())
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if op.ALUOp() == Swap {
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// Width for Endian is controlled by Constant
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f.WriteString(op.Endianness().String())
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} else {
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if class == ALUClass {
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f.WriteString("32")
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}
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f.WriteString(strings.TrimSuffix(op.Source().String(), "Source"))
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}
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case JumpClass:
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f.WriteString(op.JumpOp().String())
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if jop := op.JumpOp(); jop != Exit && jop != Call {
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f.WriteString(strings.TrimSuffix(op.Source().String(), "Source"))
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}
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default:
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fmt.Fprintf(&f, "OpCode(%#x)", uint8(op))
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}
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return f.String()
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}
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// valid returns true if all bits in value are covered by mask.
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func valid(value, mask OpCode) bool {
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return value & ^mask == 0
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}
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