Improved documentation

src/build/elf/ELF.go

@@ -11,11 +11,12 @@ import (
 // ELF represents an ELF file.
 type ELF struct {
 	Header
-	CodeHeader ProgramHeader
-	PadCode    []byte
-	Code       []byte
-	PadData    []byte
-	Data       []byte
+	CodeHeader  ProgramHeader
+	DataHeader  ProgramHeader
+	CodePadding []byte
+	Code        []byte
+	DataPadding []byte
+	Data        []byte
 }
 
 // New creates a new ELF binary.
@@ -24,7 +25,7 @@ func New(code []byte, data []byte) *ELF {
 	dataPadding := Padding(dataOffset, config.Align)
 	dataOffset += dataPadding
 
-	elf := &ELF{
+	return &ELF{
 		Header: Header{
 			Magic:                       [4]byte{0x7F, 'E', 'L', 'F'},
 			Class:                       2,
@@ -41,7 +42,7 @@ func New(code []byte, data []byte) *ELF {
 			Flags:                       0,
 			Size:                        HeaderSize,
 			ProgramHeaderEntrySize:      ProgramHeaderSize,
-			ProgramHeaderEntryCount:     1,
+			ProgramHeaderEntryCount:     2,
 			SectionHeaderEntrySize:      SectionHeaderSize,
 			SectionHeaderEntryCount:     0,
 			SectionNameStringTableIndex: 0,
@@ -56,25 +57,30 @@ func New(code []byte, data []byte) *ELF {
 			SizeInMemory:    int64(len(code)),
 			Align:           config.Align,
 		},
-		PadCode: bytes.Repeat([]byte{0}, 8),
-		Code:    code,
-		PadData: bytes.Repeat([]byte{0}, int(dataPadding)),
-		Data:    data,
+		DataHeader: ProgramHeader{
+			Type:            ProgramTypeLOAD,
+			Flags:           ProgramFlagsReadable,
+			Offset:          dataOffset,
+			VirtualAddress:  config.BaseAddress + dataOffset,
+			PhysicalAddress: config.BaseAddress + dataOffset,
+			SizeInFile:      int64(len(data)),
+			SizeInMemory:    int64(len(data)),
+			Align:           config.Align,
+		},
+		CodePadding: nil,
+		Code:        code,
+		DataPadding: bytes.Repeat([]byte{0}, int(dataPadding)),
+		Data:        data,
 	}
-
-	return elf
-}
-
-func Padding(n int64, align int64) int64 {
-	return align - (n % align)
 }
 
 // Write writes the ELF64 format to the given writer.
 func (elf *ELF) Write(writer io.Writer) {
 	binary.Write(writer, binary.LittleEndian, &elf.Header)
 	binary.Write(writer, binary.LittleEndian, &elf.CodeHeader)
-	writer.Write(elf.PadCode)
+	binary.Write(writer, binary.LittleEndian, &elf.DataHeader)
+	writer.Write(elf.CodePadding)
 	writer.Write(elf.Code)
-	writer.Write(elf.PadData)
+	writer.Write(elf.DataPadding)
 	writer.Write(elf.Data)
 }