"unsafe"
)
-var realdwarf, linkseg *macho.Segment
-var dwarfstart, linkstart int64
-var dwarfaddr int64
-var linkoffset uint32
-
const (
pageAlign = 12 // 4096 = 1 << 12
)
order binary.ByteOrder
}
-func (r *loadCmdReader) Next() (cmd loadCmd, err error) {
+func (r *loadCmdReader) Next() (loadCmd, error) {
+ var cmd loadCmd
+
r.offset = r.next
- if _, err = r.f.Seek(r.offset, 0); err != nil {
- return
+ if _, err := r.f.Seek(r.offset, 0); err != nil {
+ return cmd, err
}
- if err = binary.Read(r.f, r.order, &cmd); err != nil {
- return
+ if err := binary.Read(r.f, r.order, &cmd); err != nil {
+ return cmd, err
}
r.next = r.offset + int64(cmd.Len)
- return
+ return cmd, nil
}
func (r loadCmdReader) ReadAt(offset int64, data interface{}) error {
return err
}
defer dwarff.Close()
- outf, err := os.Create(outexe)
+ outf, err := os.OpenFile(outexe, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0755)
if err != nil {
return err
}
- outf.Chmod(0755)
-
+ defer outf.Close()
dwarfm, err := macho.NewFile(dwarff)
if err != nil {
return err
}
+ defer dwarfm.Close()
// The string table needs to be the last thing in the file
// for code signing to work. So we'll need to move the
// linkedit section, but all the others can be copied directly.
- linkseg = exem.Segment("__LINKEDIT")
+ linkseg := exem.Segment("__LINKEDIT")
if linkseg == nil {
return fmt.Errorf("missing __LINKEDIT segment")
}
- if _, err = exef.Seek(0, 0); err != nil {
+ if _, err := exef.Seek(0, 0); err != nil {
return err
}
if _, err := io.CopyN(outf, exef, int64(linkseg.Offset)); err != nil {
return err
}
- realdwarf = dwarfm.Segment("__DWARF")
+ realdwarf := dwarfm.Segment("__DWARF")
if realdwarf == nil {
return fmt.Errorf("missing __DWARF segment")
}
// Now copy the dwarf data into the output.
// Kernel requires all loaded segments to be page-aligned in the file,
// even though we mark this one as being 0 bytes of virtual address space.
- dwarfstart = machoCalcStart(realdwarf.Offset, linkseg.Offset, pageAlign)
- if _, err = outf.Seek(dwarfstart, 0); err != nil {
+ dwarfstart := machoCalcStart(realdwarf.Offset, linkseg.Offset, pageAlign)
+ if _, err := outf.Seek(dwarfstart, 0); err != nil {
return err
}
- dwarfaddr = int64((linkseg.Addr + linkseg.Memsz + 1<<pageAlign - 1) &^ (1<<pageAlign - 1))
- if _, err = dwarff.Seek(int64(realdwarf.Offset), 0); err != nil {
+ if _, err := dwarff.Seek(int64(realdwarf.Offset), 0); err != nil {
return err
}
}
// And finally the linkedit section.
- if _, err = exef.Seek(int64(linkseg.Offset), 0); err != nil {
+ if _, err := exef.Seek(int64(linkseg.Offset), 0); err != nil {
return err
}
- linkstart = machoCalcStart(linkseg.Offset, uint64(dwarfstart)+dwarfsize, pageAlign)
- linkoffset = uint32(linkstart - int64(linkseg.Offset))
- if _, err = outf.Seek(linkstart, 0); err != nil {
+ linkstart := machoCalcStart(linkseg.Offset, uint64(dwarfstart)+dwarfsize, pageAlign)
+ if _, err := outf.Seek(linkstart, 0); err != nil {
return err
}
if _, err := io.Copy(outf, exef); err != nil {
// Now we need to update the headers.
textsect := exem.Section("__text")
- if linkseg == nil {
+ if textsect == nil {
return fmt.Errorf("missing __text section")
}
cmdOffset := unsafe.Sizeof(exem.FileHeader)
- is64bit := exem.Magic == macho.Magic64
- if is64bit {
+ if is64bit := exem.Magic == macho.Magic64; is64bit {
// mach_header_64 has one extra uint32.
cmdOffset += unsafe.Sizeof(exem.Magic)
}
- dwarfCmdOffset := int64(cmdOffset) + int64(exem.FileHeader.Cmdsz)
- availablePadding := int64(textsect.Offset) - dwarfCmdOffset
- if availablePadding < int64(realdwarf.Len) {
- return fmt.Errorf("No room to add dwarf info. Need at least %d padding bytes, found %d", realdwarf.Len, availablePadding)
+ dwarfCmdOffset := uint32(cmdOffset) + exem.FileHeader.Cmdsz
+ availablePadding := textsect.Offset - dwarfCmdOffset
+ if availablePadding < realdwarf.Len {
+ return fmt.Errorf("no room to add dwarf info. Need at least %d padding bytes, found %d", realdwarf.Len, availablePadding)
}
// First, copy the dwarf load command into the header. It will be
// updated later with new offsets and lengths as necessary.
- if _, err = outf.Seek(dwarfCmdOffset, 0); err != nil {
+ if _, err := outf.Seek(int64(dwarfCmdOffset), 0); err != nil {
return err
}
if _, err := io.CopyN(outf, bytes.NewReader(realdwarf.Raw()), int64(realdwarf.Len)); err != nil {
return err
}
- if _, err = outf.Seek(int64(unsafe.Offsetof(exem.FileHeader.Ncmd)), 0); err != nil {
+ if _, err := outf.Seek(int64(unsafe.Offsetof(exem.FileHeader.Ncmd)), 0); err != nil {
return err
}
- if err = binary.Write(outf, exem.ByteOrder, exem.Ncmd+1); err != nil {
+ if err := binary.Write(outf, exem.ByteOrder, exem.Ncmd+1); err != nil {
return err
}
- if err = binary.Write(outf, exem.ByteOrder, exem.Cmdsz+realdwarf.Len); err != nil {
+ if err := binary.Write(outf, exem.ByteOrder, exem.Cmdsz+realdwarf.Len); err != nil {
return err
}
if err != nil {
return err
}
+ linkoffset := uint64(linkstart) - linkseg.Offset
switch cmd.Cmd {
case macho.LoadCmdSegment64:
- err = machoUpdateSegment(reader, &macho.Segment64{}, &macho.Section64{})
+ err = machoUpdateSegment(reader, linkseg, linkoffset, &macho.Segment64{}, &macho.Section64{})
case macho.LoadCmdSegment:
- err = machoUpdateSegment(reader, &macho.Segment32{}, &macho.Section32{})
+ err = machoUpdateSegment(reader, linkseg, linkoffset, &macho.Segment32{}, &macho.Section32{})
case LC_DYLD_INFO, LC_DYLD_INFO_ONLY:
- err = machoUpdateLoadCommand(reader, &dyldInfoCmd{}, "RebaseOff", "BindOff", "WeakBindOff", "LazyBindOff", "ExportOff")
+ err = machoUpdateLoadCommand(reader, linkseg, linkoffset, &dyldInfoCmd{}, "RebaseOff", "BindOff", "WeakBindOff", "LazyBindOff", "ExportOff")
case macho.LoadCmdSymtab:
- err = machoUpdateLoadCommand(reader, &macho.SymtabCmd{}, "Symoff", "Stroff")
+ err = machoUpdateLoadCommand(reader, linkseg, linkoffset, &macho.SymtabCmd{}, "Symoff", "Stroff")
case macho.LoadCmdDysymtab:
- err = machoUpdateLoadCommand(reader, &macho.DysymtabCmd{}, "Tocoffset", "Modtaboff", "Extrefsymoff", "Indirectsymoff", "Extreloff", "Locreloff")
+ err = machoUpdateLoadCommand(reader, linkseg, linkoffset, &macho.DysymtabCmd{}, "Tocoffset", "Modtaboff", "Extrefsymoff", "Indirectsymoff", "Extreloff", "Locreloff")
case LC_CODE_SIGNATURE, LC_SEGMENT_SPLIT_INFO, LC_FUNCTION_STARTS, LC_DATA_IN_CODE, LC_DYLIB_CODE_SIGN_DRS:
- err = machoUpdateLoadCommand(reader, &linkEditDataCmd{}, "DataOff")
+ err = machoUpdateLoadCommand(reader, linkseg, linkoffset, &linkEditDataCmd{}, "DataOff")
case LC_ENCRYPTION_INFO, LC_ENCRYPTION_INFO_64:
- err = machoUpdateLoadCommand(reader, &encryptionInfoCmd{}, "CryptOff")
+ err = machoUpdateLoadCommand(reader, linkseg, linkoffset, &encryptionInfoCmd{}, "CryptOff")
case macho.LoadCmdDylib, macho.LoadCmdThread, macho.LoadCmdUnixThread, LC_PREBOUND_DYLIB, LC_UUID, LC_VERSION_MIN_MACOSX, LC_VERSION_MIN_IPHONEOS, LC_SOURCE_VERSION, LC_MAIN, LC_LOAD_DYLINKER, LC_LOAD_WEAK_DYLIB, LC_REEXPORT_DYLIB, LC_RPATH, LC_ID_DYLIB, LC_SYMSEG, LC_LOADFVMLIB, LC_IDFVMLIB, LC_IDENT, LC_FVMFILE, LC_PREPAGE, LC_ID_DYLINKER, LC_ROUTINES, LC_SUB_FRAMEWORK, LC_SUB_UMBRELLA, LC_SUB_CLIENT, LC_SUB_LIBRARY, LC_TWOLEVEL_HINTS, LC_PREBIND_CKSUM, LC_ROUTINES_64, LC_LAZY_LOAD_DYLIB, LC_LOAD_UPWARD_DYLIB, LC_DYLD_ENVIRONMENT, LC_LINKER_OPTION, LC_LINKER_OPTIMIZATION_HINT, LC_VERSION_MIN_TVOS, LC_VERSION_MIN_WATCHOS, LC_VERSION_NOTE, LC_BUILD_VERSION:
// Nothing to update
default:
- err = fmt.Errorf("Unknown load command 0x%x (%s)\n", int(cmd.Cmd), cmd.Cmd)
+ err = fmt.Errorf("unknown load command 0x%x (%s)", int(cmd.Cmd), cmd.Cmd)
}
if err != nil {
return err
}
}
// Do the final update of the DWARF segment's load command.
- return machoUpdateDwarfHeader(&reader, compressedSects, dwarfsize)
+ return machoUpdateDwarfHeader(&reader, compressedSects, dwarfsize, dwarfstart, realdwarf)
}
// machoCompressSections tries to compress the DWARF segments in dwarfm,
dwarfseg := dwarfm.Segment("__DWARF")
var sects []*macho.Section
- var bytes []byte
+ var buf bytes.Buffer
for _, sect := range dwarfm.Sections {
if sect.Seg != "__DWARF" {
}
newSec := *sect
- newSec.Offset = uint32(dwarfseg.Offset) + uint32(len(bytes))
- newSec.Addr = dwarfseg.Addr + uint64(len(bytes))
+ newSec.Offset = uint32(dwarfseg.Offset) + uint32(buf.Len())
+ newSec.Addr = dwarfseg.Addr + uint64(buf.Len())
if compressed {
newSec.Name = "__z" + sect.Name[2:]
newSec.Size = uint64(len(contents))
}
sects = append(sects, &newSec)
- bytes = append(bytes, contents...)
+ buf.Write(contents)
}
- return sects, bytes, nil
+ return sects, buf.Bytes(), nil
}
// machoCompressSection compresses secBytes if it results in less data.
func machoCompressSection(sectBytes []byte) (compressed bool, contents []byte, err error) {
var buf bytes.Buffer
- buf.Write([]byte("ZLIB"))
+ buf.WriteString("ZLIB")
var sizeBytes [8]byte
binary.BigEndian.PutUint64(sizeBytes[:], uint64(len(sectBytes)))
buf.Write(sizeBytes[:])
if err := z.Close(); err != nil {
return false, nil, err
}
- if len(buf.Bytes()) >= len(sectBytes) {
+ if buf.Len() >= len(sectBytes) {
return false, sectBytes, nil
}
return true, buf.Bytes(), nil
// Only the linkedit segment should move, and it should have 0 sections.
// seg should be a macho.Segment32 or macho.Segment64 as appropriate.
// sect should be a macho.Section32 or macho.Section64 as appropriate.
-func machoUpdateSegment(r loadCmdReader, seg, sect interface{}) error {
+func machoUpdateSegment(r loadCmdReader, linkseg *macho.Segment, linkoffset uint64, seg, sect interface{}) error {
if err := r.ReadAt(0, seg); err != nil {
return err
}
segValue := reflect.ValueOf(seg)
offset := reflect.Indirect(segValue).FieldByName("Offset")
- // Only the linkedit segment moved, any thing before that is fine.
+ // Only the linkedit segment moved, anything before that is fine.
if offset.Uint() < linkseg.Offset {
return nil
}
- offset.SetUint(offset.Uint() + uint64(linkoffset))
+ offset.SetUint(offset.Uint() + linkoffset)
if err := r.WriteAt(0, seg); err != nil {
return err
}
// There shouldn't be any sections, but just to make sure...
- return machoUpdateSections(r, segValue, reflect.ValueOf(sect), uint64(linkoffset), 0, nil)
+ return machoUpdateSections(r, segValue, reflect.ValueOf(sect), linkoffset, nil)
}
-func machoUpdateSections(r loadCmdReader, seg, sect reflect.Value, deltaOffset, deltaAddr uint64, compressedSects []*macho.Section) error {
+func machoUpdateSections(r loadCmdReader, seg, sect reflect.Value, deltaOffset uint64, compressedSects []*macho.Section) error {
iseg := reflect.Indirect(seg)
nsect := iseg.FieldByName("Nsect").Uint()
if nsect == 0 {
offsetField.SetUint(uint64(cSect.Offset) + deltaOffset)
}
if cSect.Addr != 0 {
- addrField.SetUint(cSect.Addr + deltaAddr)
+ addrField.SetUint(cSect.Addr)
}
} else {
if offsetField.Uint() != 0 {
reloffField.SetUint(reloffField.Uint() + deltaOffset)
}
if addrField.Uint() != 0 {
- addrField.SetUint(addrField.Uint() + deltaAddr)
+ addrField.SetUint(addrField.Uint())
}
}
if err := r.WriteAt(sectOffset, sect.Interface()); err != nil {
}
// machoUpdateDwarfHeader updates the DWARF segment load command.
-func machoUpdateDwarfHeader(r *loadCmdReader, compressedSects []*macho.Section, dwarfsize uint64) error {
+func machoUpdateDwarfHeader(r *loadCmdReader, compressedSects []*macho.Section, dwarfsize uint64, dwarfstart int64, realdwarf *macho.Segment) error {
var seg, sect interface{}
cmd, err := r.Next()
if err != nil {
segv.FieldByName("Filesz").SetUint(dwarfsize)
}
- deltaOffset := uint64(dwarfstart) - realdwarf.Offset
- deltaAddr := uint64(dwarfaddr) - realdwarf.Addr
-
// We want the DWARF segment to be considered non-loadable, so
// force vmaddr and vmsize to zero. In addition, set the initial
// protection to zero so as to make the dynamic loader happy,
segv.FieldByName("Addr").SetUint(0)
segv.FieldByName("Memsz").SetUint(0)
segv.FieldByName("Prot").SetUint(0)
- deltaAddr = 0
if err := r.WriteAt(0, seg); err != nil {
return err
}
- return machoUpdateSections(*r, segv, reflect.ValueOf(sect), deltaOffset, deltaAddr, compressedSects)
+ return machoUpdateSections(*r, segv, reflect.ValueOf(sect), uint64(dwarfstart)-realdwarf.Offset, compressedSects)
}
-func machoUpdateLoadCommand(r loadCmdReader, cmd interface{}, fields ...string) error {
+func machoUpdateLoadCommand(r loadCmdReader, linkseg *macho.Segment, linkoffset uint64, cmd interface{}, fields ...string) error {
if err := r.ReadAt(0, cmd); err != nil {
return err
}
for _, name := range fields {
field := value.FieldByName(name)
- fieldval := field.Uint()
- if fieldval >= linkseg.Offset {
- field.SetUint(fieldval + uint64(linkoffset))
+ if fieldval := field.Uint(); fieldval >= linkseg.Offset {
+ field.SetUint(fieldval + linkoffset)
}
}
if err := r.WriteAt(0, cmd); err != nil {
func machoCalcStart(origAddr, newAddr uint64, alignExp uint32) int64 {
align := uint64(1 << alignExp)
- if (origAddr % align) == (newAddr % align) {
+ origMod, newMod := origAddr%align, newAddr%align
+ if origMod == newMod {
return int64(newAddr)
}
- padding := (align - (newAddr % align))
- padding += origAddr % align
- return int64(padding + newAddr)
+ return int64(newAddr + align + origMod - newMod)
}