Improved alignment function
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7092cb6626
commit
bec409dbd0
@ -1,3 +1,7 @@
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write(_ Int, _ Pointer, _ Int) -> Int {
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return 0
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}
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exit(_ Int) {
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return
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}
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@ -337,12 +337,11 @@ restart:
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}
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data, dataLabels = a.Data.Finalize()
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dataStart := Address(config.BaseAddress) + config.CodeOffset + Address(len(code))
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dataStart += exe.Padding(dataStart, config.Align)
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dataStart := config.BaseAddress + config.CodeOffset + len(code)
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dataStart, _ = exe.Align(dataStart, config.Align)
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for _, pointer := range dataPointers {
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address := dataStart + pointer.Resolve()
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address := Address(dataStart) + pointer.Resolve()
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slice := code[pointer.Position : pointer.Position+4]
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binary.LittleEndian.PutUint32(slice, uint32(address))
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}
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7
src/exe/Align.go
Normal file
7
src/exe/Align.go
Normal file
@ -0,0 +1,7 @@
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package exe
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// Align calculates the next aligned address and the padding needed.
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func Align[T int | uint | int64 | uint64 | int32 | uint32](n T, alignment T) (T, T) {
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aligned := (n + (alignment - 1)) & ^(alignment - 1)
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return aligned, aligned - n
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}
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@ -1,6 +0,0 @@
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package exe
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// Padding calculates the padding needed to align `n` bytes with the specified alignment.
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func Padding[T int | uint | int64 | uint64 | int32 | uint32](n T, align T) T {
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return align - (n % align)
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}
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@ -21,10 +21,8 @@ func Write(writer io.Writer, code []byte, data []byte) {
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const HeaderEnd = HeaderSize + ProgramHeaderSize*2
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var (
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codePadding = exe.Padding(HeaderEnd, config.Align)
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codeEnd = config.CodeOffset + len(code)
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dataPadding = exe.Padding(codeEnd, config.Align)
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dataStart = codeEnd + dataPadding
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codeStart, codePadding = exe.Align(HeaderEnd, config.Align)
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dataStart, dataPadding = exe.Align(codeStart+len(code), config.Align)
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)
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elf := &ELF{
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@ -74,11 +72,11 @@ func Write(writer io.Writer, code []byte, data []byte) {
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binary.Write(writer, binary.LittleEndian, &elf.Header)
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binary.Write(writer, binary.LittleEndian, &elf.CodeHeader)
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binary.Write(writer, binary.LittleEndian, &elf.DataHeader)
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writer.Write(bytes.Repeat([]byte{0}, codePadding))
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writer.Write(bytes.Repeat([]byte{0x00}, codePadding))
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writer.Write(code)
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if len(data) > 0 {
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writer.Write(bytes.Repeat([]byte{0}, dataPadding))
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writer.Write(bytes.Repeat([]byte{0x00}, dataPadding))
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writer.Write(data)
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}
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}
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@ -26,10 +26,8 @@ func Write(writer io.Writer, code []byte, data []byte) {
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)
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var (
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codePadding = exe.Padding(HeaderEnd, config.Align)
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codeEnd = config.CodeOffset + len(code)
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dataPadding = exe.Padding(codeEnd, config.Align)
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dataStart = codeEnd + dataPadding
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codeStart, codePadding = exe.Align(HeaderEnd, config.Align)
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dataStart, dataPadding = exe.Align(codeStart+len(code), config.Align)
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)
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m := &MachO{
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@ -61,9 +59,9 @@ func Write(writer io.Writer, code []byte, data []byte) {
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Length: Segment64Size,
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Name: [16]byte{'_', '_', 'T', 'E', 'X', 'T'},
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Address: config.BaseAddress,
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SizeInMemory: uint64(codeEnd),
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SizeInMemory: uint64(codeStart + len(code)),
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Offset: 0,
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SizeInFile: uint64(codeEnd),
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SizeInFile: uint64(codeStart + len(code)),
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NumSections: 0,
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Flag: 0,
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MaxProt: ProtReadable | ProtExecutable,
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@ -119,8 +117,8 @@ func Write(writer io.Writer, code []byte, data []byte) {
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binary.Write(writer, binary.LittleEndian, &m.DataHeader)
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binary.Write(writer, binary.LittleEndian, &m.UnixThread)
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writer.Write(bytes.Repeat([]byte{0}, int(codePadding)))
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writer.Write(bytes.Repeat([]byte{0x00}, int(codePadding)))
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writer.Write(code)
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writer.Write(bytes.Repeat([]byte{0}, int(dataPadding)))
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writer.Write(bytes.Repeat([]byte{0x00}, int(dataPadding)))
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writer.Write(data)
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}
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@ -9,31 +9,36 @@ import (
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"git.akyoto.dev/cli/q/src/exe"
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)
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const NumSections = 2
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// EXE is the portable executable format used on Windows.
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type EXE struct {
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DOSHeader
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NTHeader
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OptionalHeader64
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Sections [NumSections]SectionHeader
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Sections []SectionHeader
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}
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// Write writes the EXE file to the given writer.
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func Write(writer io.Writer, code []byte, data []byte) {
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const (
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HeaderEnd = DOSHeaderSize + NTHeaderSize + OptionalHeader64Size + SectionHeaderSize*NumSections
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)
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NumSections := 1
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if len(data) != 0 {
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NumSections += 1
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}
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HeaderEnd := DOSHeaderSize + NTHeaderSize + OptionalHeader64Size + SectionHeaderSize*NumSections
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var (
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codePadding = exe.Padding(HeaderEnd, config.Align)
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codeEnd = config.CodeOffset + len(code)
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dataPadding = exe.Padding(codeEnd, config.Align)
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dataStart = codeEnd + dataPadding
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codeStart, codePadding = exe.Align(HeaderEnd, config.Align)
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dataStart, dataPadding = exe.Align(codeStart+len(code), config.Align)
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)
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imageSize := dataStart + len(data)
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imageSize += exe.Padding(imageSize, config.Align)
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imageSize := codeStart + len(code)
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if len(data) != 0 {
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imageSize = dataStart + len(data)
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}
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imageSize, _ = exe.Align(imageSize, config.Align)
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pe := &EXE{
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DOSHeader: DOSHeader{
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@ -43,7 +48,7 @@ func Write(writer io.Writer, code []byte, data []byte) {
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NTHeader: NTHeader{
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Signature: [4]byte{'P', 'E', 0, 0},
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Machine: IMAGE_FILE_MACHINE_AMD64,
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NumberOfSections: NumSections,
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NumberOfSections: uint16(NumSections),
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SizeOfOptionalHeader: OptionalHeader64Size,
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Characteristics: IMAGE_FILE_EXECUTABLE_IMAGE | IMAGE_FILE_LARGE_ADDRESS_AWARE,
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},
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@ -61,7 +66,7 @@ func Write(writer io.Writer, code []byte, data []byte) {
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MajorSubsystemVersion: 0x06,
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SizeOfImage: uint32(imageSize),
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SizeOfHeaders: config.CodeOffset, // section bodies begin here
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Subsystem: IMAGE_SUBSYSTEM_WINDOWS_GUI,
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Subsystem: IMAGE_SUBSYSTEM_WINDOWS_CUI,
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DllCharacteristics: IMAGE_DLLCHARACTERISTICS_HIGH_ENTROPY_VA | IMAGE_DLLCHARACTERISTICS_DYNAMIC_BASE | IMAGE_DLLCHARACTERISTICS_NX_COMPAT | IMAGE_DLLCHARACTERISTICS_TERMINAL_SERVER_AWARE,
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SizeOfStackReserve: 0x100000,
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SizeOfStackCommit: 0x1000,
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@ -87,7 +92,7 @@ func Write(writer io.Writer, code []byte, data []byte) {
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{VirtualAddress: 0, Size: 0},
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},
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},
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Sections: [NumSections]SectionHeader{
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Sections: []SectionHeader{
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{
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Name: [8]byte{'.', 't', 'e', 'x', 't'},
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VirtualSize: uint32(len(code)),
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@ -110,10 +115,13 @@ func Write(writer io.Writer, code []byte, data []byte) {
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binary.Write(writer, binary.LittleEndian, &pe.DOSHeader)
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binary.Write(writer, binary.LittleEndian, &pe.NTHeader)
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binary.Write(writer, binary.LittleEndian, &pe.OptionalHeader64)
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binary.Write(writer, binary.LittleEndian, &pe.Sections)
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binary.Write(writer, binary.LittleEndian, pe.Sections[:NumSections])
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writer.Write(bytes.Repeat([]byte{0}, int(codePadding)))
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writer.Write(bytes.Repeat([]byte{0x00}, int(codePadding)))
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writer.Write(code)
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writer.Write(bytes.Repeat([]byte{0}, int(dataPadding)))
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writer.Write(data)
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if len(data) != 0 {
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writer.Write(bytes.Repeat([]byte{0x00}, int(dataPadding)))
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writer.Write(data)
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}
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}
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@ -1,5 +1,10 @@
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## Portable Executable
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## Notes
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Unlike Linux, Windows does not ignore zero-length sections and will fail loading them because they don't exist within the file.
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Adding a single byte to the section can fix this problem, but it's easier to just remove the section header entirely.
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## Links
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- https://learn.microsoft.com/en-us/previous-versions/ms809762(v=msdn.10)
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