Implemented data labels

src/build/elf/ELF.go

@@ -1,6 +1,7 @@
 package elf
 
 import (
+	"bytes"
 	"encoding/binary"
 	"io"
 
@@ -10,13 +11,19 @@ import (
 // ELF represents an ELF file.
 type ELF struct {
 	Header
-	ProgramHeader
-	Code []byte
-	Data []byte
+	CodeHeader ProgramHeader
+	PadCode    []byte
+	Code       []byte
+	PadData    []byte
+	Data       []byte
 }
 
 // New creates a new ELF binary.
 func New(code []byte, data []byte) *ELF {
+	dataOffset := config.CodeOffset + int64(len(code))
+	dataPadding := Padding(dataOffset, config.Align)
+	dataOffset += dataPadding
+
 	elf := &ELF{
 		Header: Header{
 			Magic:                       [4]byte{0x7F, 'E', 'L', 'F'},
@@ -39,9 +46,9 @@ func New(code []byte, data []byte) *ELF {
 			SectionHeaderEntryCount:     0,
 			SectionNameStringTableIndex: 0,
 		},
-		ProgramHeader: ProgramHeader{
+		CodeHeader: ProgramHeader{
 			Type:            ProgramTypeLOAD,
-			Flags:           ProgramFlagsExecutable,
+			Flags:           ProgramFlagsExecutable | ProgramFlagsReadable,
 			Offset:          config.CodeOffset,
 			VirtualAddress:  config.BaseAddress + config.CodeOffset,
 			PhysicalAddress: config.BaseAddress + config.CodeOffset,
@@ -49,18 +56,25 @@ func New(code []byte, data []byte) *ELF {
 			SizeInMemory:    int64(len(code)),
 			Align:           config.Align,
 		},
-		Code: code,
-		Data: data,
+		PadCode: bytes.Repeat([]byte{0}, 8),
+		Code:    code,
+		PadData: 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.ProgramHeader)
-	writer.Write([]byte{0, 0, 0, 0, 0, 0, 0, 0})
+	binary.Write(writer, binary.LittleEndian, &elf.CodeHeader)
+	writer.Write(elf.PadCode)
 	writer.Write(elf.Code)
+	writer.Write(elf.PadData)
 	writer.Write(elf.Data)
 }