Added a section for machine code instructions in Mach-O

src/macho/Constants.go

@@ -3,6 +3,6 @@ package macho
 const (
 	BaseAddress  = 0x1000000
 	NumCommands  = 7
-	SizeCommands = Segment64Size*3 + DyldInfoCommandSize + MainSize + DylinkerCommandSize + len(LinkerString) + DylibCommandSize + len(LibSystemString)
+	SizeCommands = Segment64Size*3 + Section64Size + DyldInfoCommandSize + MainSize + DylinkerCommandSize + len(LinkerString) + DylibCommandSize + len(LibSystemString)
 	HeaderEnd    = HeaderSize + SizeCommands
 )

src/macho/Header.go

@@ -11,5 +11,5 @@ type Header struct {
 	NumCommands       uint32
 	SizeCommands      uint32
 	Flags             HeaderFlags
-	Reserved          uint32
+	_                 uint32
 }

src/macho/MachO.go

@@ -12,8 +12,9 @@ import (
 type MachO struct {
 	Header
 	PageZero        Segment64
-	CodeHeader      Segment64
-	DataHeader      Segment64
+	CodeSegment     Segment64
+	CodeSection     Section64
+	DataSegment     Segment64
 	MainHeader      Main
 	InfoHeader      DyldInfoCommand
 	LinkerHeader    DylinkerCommand
@@ -36,7 +37,6 @@ func Write(writer io.WriteSeeker, b *build.Build, codeBytes []byte, dataBytes []
 			NumCommands:       NumCommands,
 			SizeCommands:      uint32(SizeCommands),
 			Flags:             FlagNoUndefs | FlagDyldLink | FlagTwoLevel | FlagPIE | FlagNoHeapExecution,
-			Reserved:          0,
 		},
 		PageZero: Segment64{
 			LoadCommand:  LcSegment64,
@@ -51,20 +51,29 @@ func Write(writer io.WriteSeeker, b *build.Build, codeBytes []byte, dataBytes []
 			MaxProt:      0,
 			InitProt:     0,
 		},
-		CodeHeader: Segment64{
+		CodeSegment: Segment64{
 			LoadCommand:  LcSegment64,
-			Length:       Segment64Size,
+			Length:       Segment64Size + Section64Size,
 			Name:         [16]byte{'_', '_', 'T', 'E', 'X', 'T'},
 			Address:      uint64(BaseAddress),
 			SizeInMemory: uint64(code.MemoryOffset + len(code.Bytes)),
 			Offset:       0,
 			SizeInFile:   uint64(code.FileOffset + len(code.Bytes)),
-			NumSections:  0,
+			NumSections:  1,
 			Flag:         0,
 			MaxProt:      ProtReadable | ProtExecutable,
 			InitProt:     ProtReadable | ProtExecutable,
 		},
-		DataHeader: Segment64{
+		CodeSection: Section64{
+			SectionName: [16]byte{'_', '_', 't', 'e', 'x', 't'},
+			SegmentName: [16]byte{'_', '_', 'T', 'E', 'X', 'T'},
+			Address:     uint64(BaseAddress + code.MemoryOffset),
+			Size:        uint64(len(code.Bytes)),
+			Offset:      uint32(code.FileOffset),
+			Align:       6,
+			Flags:       FlagPureInstructions,
+		},
+		DataSegment: Segment64{
 			LoadCommand:  LcSegment64,
 			Length:       Segment64Size,
 			Name:         [16]byte{'_', '_', 'D', 'A', 'T', 'A', '_', 'C', 'O', 'N', 'S', 'T'},
@@ -101,8 +110,9 @@ func Write(writer io.WriteSeeker, b *build.Build, codeBytes []byte, dataBytes []
 
 	binary.Write(writer, binary.LittleEndian, &m.Header)
 	binary.Write(writer, binary.LittleEndian, &m.PageZero)
-	binary.Write(writer, binary.LittleEndian, &m.CodeHeader)
-	binary.Write(writer, binary.LittleEndian, &m.DataHeader)
+	binary.Write(writer, binary.LittleEndian, &m.CodeSegment)
+	binary.Write(writer, binary.LittleEndian, &m.CodeSection)
+	binary.Write(writer, binary.LittleEndian, &m.DataSegment)
 	binary.Write(writer, binary.LittleEndian, &m.MainHeader)
 	binary.Write(writer, binary.LittleEndian, &m.InfoHeader)
 	binary.Write(writer, binary.LittleEndian, &m.LinkerHeader)

src/macho/Section64.go

@@ -0,0 +1,19 @@
+package macho
+
+const Section64Size = 80
+
+// Section64 is one of multiple sections in a segment.
+type Section64 struct {
+	SectionName      [16]byte
+	SegmentName      [16]byte
+	Address          uint64
+	Size             uint64
+	Offset           uint32
+	Align            uint32
+	RelocationOffset uint32
+	NumRelocations   uint32
+	Flags            SectionFlags
+	_                uint32
+	_                uint32
+	_                uint32
+}

src/macho/SectionFlags.go

@@ -0,0 +1,7 @@
+package macho
+
+type SectionFlags uint32
+
+const (
+	FlagPureInstructions SectionFlags = 0x80000000
+)