// cpos == unitstart + 4 + 2 + 4
	lsu.AddUint8(1)                // minimum_instruction_length
	lsu.AddUint8(is_stmt)          // default_is_stmt
	lsu.AddUint8(LINE_BASE & 0xFF) // line_base
	lsu.AddUint8(LINE_RANGE)       // line_range
	lsu.AddUint8(OPCODE_BASE)      // opcode_base
	lsu.AddUint8(0)                // standard_opcode_lengths[1]
	lsu.AddUint8(1)                // standard_opcode_lengths[2]

	updateRequested bool
}

func (m *keyUpdateMsg) marshal() ([]byte, error) {
	var b cryptobyte.Builder
	b.AddUint8(typeKeyUpdate)
	b.AddUint24LengthPrefixed(func(b *cryptobyte.Builder) {
		if m.updateRequested {
			b.AddUint8(1)
		} else {
			b.AddUint8(0)
		}
	})

	return b.Bytes()
}

func (m *keyUpdateMsg) unmarshal(data []byte) bool {

		gnuattributes.AddUint8('A')               // version 'A'
		gnuattributes.AddUint32(ctxt.Arch, 15)    // length 15 including itself
		gnuattributes.AddBytes([]byte("gnu\x00")) // "gnu\0"
		gnuattributes.AddUint8(1)                 // 1:file, 2: section, 3: symbol, 1 here
		gnuattributes.AddUint32(ctxt.Arch, 7)     // tag length, including tag, 7 here
		gnuattributes.AddUint8(4)                 // 4 for FP, 8 for MSA

			sb.SetType(sym.SDATA)
			sb.SetSize(0)
			sb.AddUint8(uint8(buildcfg.GOARM.Version))

			goarmsoftfp := ctxt.loader.LookupOrCreateSym("runtime.goarmsoftfp", 0)
			sb2 := ctxt.loader.MakeSymbolUpdater(goarmsoftfp)
			sb2.SetType(sym.SDATA)
			sb2.SetSize(0)
			if buildcfg.GOARM.SoftFloat {
				sb2.AddUint8(1)
			} else {
				sb2.AddUint8(0)
			}
		}