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|
package main
import (
"bufio"
"encoding/binary"
"os"
"regexp"
"strconv"
"strings"
)
type PosPair struct {
pos uint
section uint8
}
// Map for labels and their addresses
var labels map[string]PosPair = make(map[string]PosPair)
var SectionPos [4]uint
var SectionStart [4]uint
const (
TEXT = 0
DATA = 1
RODATA = 2
BSS = 3
)
func LabelFind(path string, dTemp, rTemp *os.File) {
// This will track the current section, default is .text
var Section uint8 = TEXT
file, err := os.Open(path)
if err != nil {
panic(err)
}
defer file.Close()
input := bufio.NewScanner(file)
for input.Scan() {
i := &SectionPos[Section]
switch input.Text() {
case "":
continue
case ".text":
Section = TEXT
continue
case ".data":
Section = DATA
continue
case ".rodata":
Section = RODATA
continue
case ".bss":
Section = BSS
continue
}
s, err := Parse(input.Text())
if err != nil {
panic(err)
}
if len(s) == 1 && s[0] == "" {
continue
}
hasLabel, err := regexp.MatchString("^.*:", s[0])
if err != nil {
panic(err)
}
if hasLabel {
labels[strings.ReplaceAll(s[0], ":", "")] = PosPair{*i, Section}
if len(s) == 1 {
continue
} else {
s = s[1:]
}
}
offset, err := CalcOffset(s, Section, dTemp, rTemp)
if err != nil {
panic(err)
}
if Section == TEXT && s[0] == "la" {
offset += 4
}
*i += offset
}
SectionStart[0] = 0
SectionStart[1] = SectionPos[0]
SectionStart[2] = SectionPos[1] + SectionPos[1]
SectionStart[3] = SectionPos[2] + SectionPos[2]
}
func CalcOffset(s []string, Section uint8, dTemp, rTemp *os.File) (uint, error) {
var offset uint
if Section != TEXT {
b, err := EncodeData(s)
if err != nil {
return 0, err
}
if Section == DATA {
_, err := dTemp.Write(b)
if err != nil {
return 0, err
}
} else if Section == RODATA {
_, err := rTemp.Write(b)
if err != nil {
return 0, err
}
}
offset = uint(len(b))
} else {
offset = 4
}
return offset, nil
}
func EncodeData(line []string) ([]byte, error) {
var size int
var err error = nil
var data int64
isString := false
isData := false
nullTerm := false
line[1] = strings.ReplaceAll(line[1], "\"", "")
switch line[0] {
case ".space":
size, err = strconv.Atoi(line[1])
case ".word":
size = 4
isData = true
case ".byte":
size = 1
isData = true
case ".half":
size = 2
isData = true
case ".asciiz":
size = len(line[1]) + 1
isString = true
nullTerm = true
case ".ascii":
size = len(line[1])
isString = true
}
if err != nil {
return nil, err
}
bytes := make([]byte, size)
if isData {
if strings.Contains(line[1], "0x") {
line[1] = strings.ReplaceAll(line[1], "0x", "")
var t uint64
t, err = strconv.ParseUint(line[1], 16, size*8)
data = int64(t)
} else {
data, err = strconv.ParseInt(line[1], 10, size*8)
}
if err != nil {
return nil, err
}
switch size {
case 1:
bytes[0] = uint8(data)
case 2:
binary.NativeEndian.PutUint16(bytes, uint16(data))
case 4:
binary.NativeEndian.PutUint32(bytes, uint32(data))
}
} else if isString {
if nullTerm {
for i, b := range []byte(line[1]) {
bytes[i] = b
}
bytes[size-1] = 0
} else {
bytes = []byte(line[1])
}
}
return bytes, nil
}
|
