Added memory address patching

src/asm/Address.go

@@ -2,3 +2,6 @@ package asm
 
 // Address represents a memory address.
 type Address = uint32
+
+// Index references an instruction by its position.
+type Index = uint32

src/asm/Assembler.go

@@ -1,37 +1,78 @@
 package asm
 
 import (
+	"bytes"
+	"encoding/binary"
+
+	"git.akyoto.dev/cli/q/src/asm/x64"
+	"git.akyoto.dev/cli/q/src/config"
+	"git.akyoto.dev/cli/q/src/log"
 	"git.akyoto.dev/cli/q/src/register"
 )
 
 // Assembler contains a list of instructions.
 type Assembler struct {
 	instructions []Instruction
-	labels       map[string]int
+	labels       map[string]Index
+	verbose      bool
 }
 
 // New creates a new assembler.
 func New() *Assembler {
 	return &Assembler{
 		instructions: make([]Instruction, 0, 8),
-		labels:       map[string]int{},
+		labels:       map[string]Index{},
+		verbose:      true,
 	}
 }
 
 // Finalize generates the final machine code.
 func (a *Assembler) Finalize() *Result {
-	final := Result{}
+	result := &Result{}
+	pointers := map[Address]Address{}
+	code := bytes.NewBuffer(result.Code)
 
-	for _, instr := range a.instructions {
-		instr.Write(&final.Code)
+	for _, x := range a.instructions {
+		if a.verbose {
+			log.Info.Println(x.String())
+		}
+
+		switch x.Mnemonic {
+		case MOV:
+			x64.MoveRegNum32(code, uint8(x.Destination), uint32(x.Number))
+
+		case MOVDATA:
+			position := result.AddData(x.Data)
+			x64.MoveRegNum32(code, uint8(x.Destination), 0)
+			pointers[Address(code.Len()-4)] = position
+
+		case SYSCALL:
+			x64.Syscall(code)
+		}
 	}
 
-	return &final
+	result.Code = code.Bytes()
+	dataStart := config.BaseAddress + config.CodeOffset + Address(len(result.Code))
+
+	for codePos, dataPos := range pointers {
+		binary.LittleEndian.PutUint32(result.Code[codePos:codePos+4], dataStart+dataPos)
+	}
+
+	return result
 }
 
 // AddLabel creates a new label at the current position.
 func (a *Assembler) AddLabel(name string) {
-	a.labels[name] = len(a.instructions)
+	a.labels[name] = Index(len(a.instructions))
+}
+
+// MoveRegisterData moves a data section address into the given register.
+func (a *Assembler) MoveRegisterData(reg register.ID, data []byte) {
+	a.instructions = append(a.instructions, Instruction{
+		Mnemonic:    MOVDATA,
+		Destination: reg,
+		Data:        data,
+	})
 }
 
 // MoveRegisterNumber moves a number into the given register.

src/asm/Instruction.go

@@ -2,9 +2,7 @@ package asm
 
 import (
 	"fmt"
-	"io"
 
-	"git.akyoto.dev/cli/q/src/asm/x64"
 	"git.akyoto.dev/cli/q/src/register"
 )
 
@@ -14,16 +12,7 @@ type Instruction struct {
 	Source      register.ID
 	Destination register.ID
 	Number      uint64
-}
-
-// Write writes the machine code of the instruction.
-func (x *Instruction) Write(w io.ByteWriter) {
-	switch x.Mnemonic {
-	case MOV:
-		x64.MoveRegNum32(w, uint8(x.Destination), uint32(x.Number))
-	case SYSCALL:
-		x64.Syscall(w)
-	}
+	Data        []byte
 }
 
 // String returns the assembler representation of the instruction.
@@ -31,6 +20,8 @@ func (x *Instruction) String() string {
 	switch x.Mnemonic {
 	case MOV:
 		return fmt.Sprintf("%s %s, %x", x.Mnemonic, x.Destination, x.Number)
+	case MOVDATA:
+		return fmt.Sprintf("%s %s, %v", x.Mnemonic, x.Destination, x.Data)
 	case SYSCALL:
 		return x.Mnemonic.String()
 	default:

src/asm/Mnemonic.go

@@ -5,6 +5,7 @@ type Mnemonic uint8
 const (
 	NONE Mnemonic = iota
 	MOV
+	MOVDATA
 	SYSCALL
 )
 
@@ -13,6 +14,9 @@ func (m Mnemonic) String() string {
 	case MOV:
 		return "mov"
 
+	case MOVDATA:
+		return "mov"
+
 	case SYSCALL:
 		return "syscall"
 	}

src/asm/Result.go

@@ -4,6 +4,19 @@ import "bytes"
 
 // Result is the compilation result and contains the machine code as well as the data.
 type Result struct {
-	Code bytes.Buffer
-	Data bytes.Buffer
+	Code []byte
+	Data []byte
+}
+
+// AddData adds the given bytes to the data block and returns the address relative to the start of the data section.
+func (result *Result) AddData(block []byte) Address {
+	position := bytes.Index(result.Data, block)
+
+	if position != -1 {
+		return Address(position)
+	}
+
+	address := Address(len(result.Data))
+	result.Data = append(result.Data, block...)
+	return address
 }

src/build/Build.go

@@ -43,8 +43,16 @@ func (build *Build) Run() error {
 
 	a.MoveRegisterNumber(register.Syscall0, syscall.Write)
 	a.MoveRegisterNumber(register.Syscall1, 1)
-	a.MoveRegisterNumber(register.Syscall2, 0x4000a2)
-	a.MoveRegisterNumber(register.Syscall3, 6)
+	hello := []byte("Hello\n")
+	a.MoveRegisterData(register.Syscall2, hello)
+	a.MoveRegisterNumber(register.Syscall3, uint64(len(hello)))
+	a.Syscall()
+
+	a.MoveRegisterNumber(register.Syscall0, syscall.Write)
+	a.MoveRegisterNumber(register.Syscall1, 1)
+	world := []byte("World\n")
+	a.MoveRegisterData(register.Syscall2, world)
+	a.MoveRegisterNumber(register.Syscall3, uint64(len(world)))
 	a.Syscall()
 
 	a.MoveRegisterNumber(register.Syscall0, syscall.Exit)
@@ -52,13 +60,12 @@ func (build *Build) Run() error {
 	a.Syscall()
 
 	result := a.Finalize()
-	result.Data.WriteString("Hello\n")
 
 	if !build.WriteExecutable {
 		return nil
 	}
 
-	return writeToDisk(build.Executable(), result.Code.Bytes(), result.Data.Bytes())
+	return writeToDisk(build.Executable(), result.Code, result.Data)
 }
 
 // Compile compiles all the functions.

src/config/config.go

@@ -0,0 +1,8 @@
+package config
+
+const (
+	MinAddress  = 0x10000
+	BaseAddress = 0x40 * MinAddress
+	CodeOffset  = 0x80
+	Align       = 0x10
+)

src/elf/ELF.go

@@ -3,11 +3,8 @@ package elf
 import (
 	"encoding/binary"
 	"io"
-)
 
-const (
-	minAddress  = 0x10000
-	baseAddress = 0x40 * minAddress
+	"git.akyoto.dev/cli/q/src/config"
 )
 
 // ELF represents an ELF file.
@@ -31,7 +28,7 @@ func New(code []byte, data []byte) *ELF {
 			Type:                        TypeExecutable,
 			Architecture:                ArchitectureAMD64,
 			FileVersion:                 1,
-			EntryPointInMemory:          baseAddress + 0x80,
+			EntryPointInMemory:          config.BaseAddress + config.CodeOffset,
 			ProgramHeaderOffset:         HeaderSize,
 			SectionHeaderOffset:         0,
 			Flags:                       0,
@@ -45,12 +42,12 @@ func New(code []byte, data []byte) *ELF {
 		ProgramHeader: ProgramHeader{
 			Type:            ProgramTypeLOAD,
 			Flags:           ProgramFlagsExecutable,
-			Offset:          0x80,
-			VirtualAddress:  baseAddress + 0x80,
-			PhysicalAddress: baseAddress + 0x80,
+			Offset:          config.CodeOffset,
+			VirtualAddress:  config.BaseAddress + config.CodeOffset,
+			PhysicalAddress: config.BaseAddress + config.CodeOffset,
 			SizeInFile:      int64(len(code)),
 			SizeInMemory:    int64(len(code)),
-			Align:           Align,
+			Align:           config.Align,
 		},
 		Code: code,
 		Data: data,

src/elf/Header.go

@@ -5,7 +5,6 @@ const (
 	TypeExecutable    = 2
 	ArchitectureAMD64 = 0x3E
 	HeaderSize        = 64
-	Align             = 16
 )
 
 // Header contains general information.