Added Mach-O file format

src/macho/MachO.go

@@ -0,0 +1,107 @@
+package macho
+
+import (
+	"bytes"
+	"encoding/binary"
+	"io"
+
+	"git.akyoto.dev/cli/q/src/config"
+)
+
+// MachO is the executable format used on MacOS.
+type MachO struct {
+	Header
+	Code []byte
+	Data []byte
+}
+
+// New creates a new Mach-O binary.
+func New(code []byte, data []byte) *MachO {
+	return &MachO{
+		Header: Header{
+			Magic:             0xFEEDFACF,
+			Architecture:      CPU_X86_64,
+			MicroArchitecture: 0x80000003,
+			Type:              TypeExecute,
+			NumCommands:       3,
+			SizeCommands:      0x48*2 + 184,
+			Flags:             FlagNoUndefs,
+			Reserved:          0,
+		},
+		Code: code,
+		Data: data,
+	}
+}
+
+// Write writes the Mach-O format to the given writer.
+func (m *MachO) Write(writer io.Writer) {
+	binary.Write(writer, binary.LittleEndian, &m.Header)
+
+	binary.Write(writer, binary.LittleEndian, &Segment64{
+		LoadCommand:  LcSegment64,
+		Length:       0x48,
+		Name:         [16]byte{'_', '_', 'P', 'A', 'G', 'E', 'Z', 'E', 'R', 'O'},
+		Address:      0,
+		SizeInMemory: config.BaseAddress,
+		Offset:       0,
+		SizeInFile:   0,
+		NumSections:  0,
+		Flag:         0,
+		MaxProt:      0,
+		InitProt:     0,
+	})
+
+	codeStart := 32 + m.Header.SizeCommands
+	totalSize := uint64(codeStart) + uint64(len(m.Code))
+
+	binary.Write(writer, binary.LittleEndian, &Segment64{
+		LoadCommand:  LcSegment64,
+		Length:       0x48,
+		Name:         [16]byte{'_', '_', 'T', 'E', 'X', 'T'},
+		Address:      config.BaseAddress,
+		SizeInMemory: totalSize,
+		Offset:       0,
+		SizeInFile:   totalSize,
+		NumSections:  0,
+		Flag:         0,
+		MaxProt:      ProtReadable | ProtWritable | ProtExecutable,
+		InitProt:     ProtReadable | ProtExecutable,
+	})
+
+	binary.Write(writer, binary.LittleEndian, &Thread{
+		LoadCommand: LcUnixthread,
+		Len:         184,
+		Type:        0x4,
+	})
+
+	binary.Write(writer, binary.LittleEndian, []uint32{
+		42,
+		0, 0,
+		0, 0,
+		0, 0,
+		0, 0,
+		0, 0,
+		0, 0,
+		0, 0,
+		0, 0,
+		0, 0,
+		0, 0,
+		0, 0,
+		0, 0,
+		0, 0,
+		0, 0,
+		0, 0,
+		0, 0,
+		config.BaseAddress + uint32(codeStart), 0,
+		0, 0,
+		0, 0,
+		0, 0,
+		0, 0,
+	})
+
+	writer.Write(m.Code)
+
+	if totalSize < 4096 {
+		writer.Write(bytes.Repeat([]byte{0}, 4096-int(totalSize)))
+	}
+}