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cmd/link: rewrite some code without using reflection
In Mach-O DWARF combining, some code was written using reflection, so it could support both 32-bit and 64-bit Mach-O files without duplicating code. We no longer support 32-bit darwin platforms now. 32-bit support can go. Rewrite it with direct field access, for 64-bit only. Change-Id: If1338c3cd37cecf603f4df0c6eb0c890eaebfe5f Reviewed-on: https://go-review.googlesource.com/c/go/+/253557 Run-TryBot: Cherry Zhang <cherryyz@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Than McIntosh <thanm@google.com>
This commit is contained in:
Cherry Zhang
parent
e8f918535e
commit
ae3680b30b
@ -217,9 +217,9 @@ func machoCombineDwarf(ctxt *Link, exef *os.File, exem *macho.File, dsym, outexe
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linkoffset := uint64(linkstart) - linkseg.Offset
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switch cmd.Cmd {
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case macho.LoadCmdSegment64:
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err = machoUpdateSegment(reader, linkseg, linkoffset, &macho.Segment64{}, &macho.Section64{})
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err = machoUpdateSegment(reader, linkseg, linkoffset)
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case macho.LoadCmdSegment:
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err = machoUpdateSegment(reader, linkseg, linkoffset, &macho.Segment32{}, &macho.Section32{})
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panic("unexpected 32-bit segment")
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case LC_DYLD_INFO, LC_DYLD_INFO_ONLY:
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err = machoUpdateLoadCommand(reader, linkseg, linkoffset, &dyldInfoCmd{}, "RebaseOff", "BindOff", "WeakBindOff", "LazyBindOff", "ExportOff")
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case macho.LoadCmdSymtab:
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@ -313,70 +313,56 @@ func machoCompressSection(sectBytes []byte) (compressed bool, contents []byte, e
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// machoUpdateSegment updates the load command for a moved segment.
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// Only the linkedit segment should move, and it should have 0 sections.
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// seg should be a macho.Segment32 or macho.Segment64 as appropriate.
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// sect should be a macho.Section32 or macho.Section64 as appropriate.
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func machoUpdateSegment(r loadCmdReader, linkseg *macho.Segment, linkoffset uint64, seg, sect interface{}) error {
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if err := r.ReadAt(0, seg); err != nil {
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func machoUpdateSegment(r loadCmdReader, linkseg *macho.Segment, linkoffset uint64) error {
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var seg macho.Segment64
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if err := r.ReadAt(0, &seg); err != nil {
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return err
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}
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segValue := reflect.ValueOf(seg)
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offset := reflect.Indirect(segValue).FieldByName("Offset")
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// Only the linkedit segment moved, anything before that is fine.
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if offset.Uint() < linkseg.Offset {
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if seg.Offset < linkseg.Offset {
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return nil
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}
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offset.SetUint(offset.Uint() + linkoffset)
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if err := r.WriteAt(0, seg); err != nil {
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seg.Offset += linkoffset
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if err := r.WriteAt(0, &seg); err != nil {
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return err
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}
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// There shouldn't be any sections, but just to make sure...
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return machoUpdateSections(r, segValue, reflect.ValueOf(sect), linkoffset, nil)
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return machoUpdateSections(r, &seg, linkoffset, nil)
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}
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func machoUpdateSections(r loadCmdReader, seg, sect reflect.Value, deltaOffset uint64, compressedSects []*macho.Section) error {
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iseg := reflect.Indirect(seg)
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nsect := iseg.FieldByName("Nsect").Uint()
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func machoUpdateSections(r loadCmdReader, seg *macho.Segment64, deltaOffset uint64, compressedSects []*macho.Section) error {
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nsect := seg.Nsect
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if nsect == 0 {
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return nil
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}
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sectOffset := int64(iseg.Type().Size())
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sectOffset := int64(unsafe.Sizeof(*seg))
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isect := reflect.Indirect(sect)
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offsetField := isect.FieldByName("Offset")
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reloffField := isect.FieldByName("Reloff")
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addrField := isect.FieldByName("Addr")
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nameField := isect.FieldByName("Name")
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sizeField := isect.FieldByName("Size")
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sectSize := int64(isect.Type().Size())
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for i := uint64(0); i < nsect; i++ {
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if err := r.ReadAt(sectOffset, sect.Interface()); err != nil {
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var sect macho.Section64
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sectSize := int64(unsafe.Sizeof(sect))
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for i := uint32(0); i < nsect; i++ {
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if err := r.ReadAt(sectOffset, §); err != nil {
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return err
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}
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if compressedSects != nil {
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cSect := compressedSects[i]
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var name [16]byte
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copy(name[:], []byte(cSect.Name))
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nameField.Set(reflect.ValueOf(name))
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sizeField.SetUint(cSect.Size)
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copy(sect.Name[:], cSect.Name)
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sect.Size = cSect.Size
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if cSect.Offset != 0 {
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offsetField.SetUint(uint64(cSect.Offset) + deltaOffset)
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sect.Offset = cSect.Offset + uint32(deltaOffset)
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}
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if cSect.Addr != 0 {
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addrField.SetUint(cSect.Addr)
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sect.Addr = cSect.Addr
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}
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} else {
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if offsetField.Uint() != 0 {
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offsetField.SetUint(offsetField.Uint() + deltaOffset)
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if sect.Offset != 0 {
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sect.Offset += uint32(deltaOffset)
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}
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if reloffField.Uint() != 0 {
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reloffField.SetUint(reloffField.Uint() + deltaOffset)
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}
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if addrField.Uint() != 0 {
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addrField.SetUint(addrField.Uint())
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if sect.Reloff != 0 {
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sect.Reloff += uint32(deltaOffset)
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}
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}
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if err := r.WriteAt(sectOffset, sect.Interface()); err != nil {
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if err := r.WriteAt(sectOffset, §); err != nil {
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return err
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}
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sectOffset += sectSize
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@ -386,32 +372,27 @@ func machoUpdateSections(r loadCmdReader, seg, sect reflect.Value, deltaOffset u
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// machoUpdateDwarfHeader updates the DWARF segment load command.
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func machoUpdateDwarfHeader(r *loadCmdReader, compressedSects []*macho.Section, dwarfsize uint64, dwarfstart int64, realdwarf *macho.Segment) error {
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var seg, sect interface{}
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cmd, err := r.Next()
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if err != nil {
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return err
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}
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if cmd.Cmd == macho.LoadCmdSegment64 {
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seg = new(macho.Segment64)
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sect = new(macho.Section64)
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} else {
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seg = new(macho.Segment32)
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sect = new(macho.Section32)
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if cmd.Cmd != macho.LoadCmdSegment64 {
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panic("not a Segment64")
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}
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if err := r.ReadAt(0, seg); err != nil {
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var seg macho.Segment64
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if err := r.ReadAt(0, &seg); err != nil {
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return err
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}
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segv := reflect.ValueOf(seg).Elem()
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segv.FieldByName("Offset").SetUint(uint64(dwarfstart))
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seg.Offset = uint64(dwarfstart)
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if compressedSects != nil {
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var segSize uint64
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for _, newSect := range compressedSects {
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segSize += newSect.Size
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}
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segv.FieldByName("Filesz").SetUint(segSize)
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seg.Filesz = segSize
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} else {
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segv.FieldByName("Filesz").SetUint(dwarfsize)
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seg.Filesz = dwarfsize
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}
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// We want the DWARF segment to be considered non-loadable, so
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@ -424,14 +405,14 @@ func machoUpdateDwarfHeader(r *loadCmdReader, compressedSects []*macho.Section,
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// in ImageLoaderMachO.cpp (various versions can be found online, see
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// https://opensource.apple.com/source/dyld/dyld-519.2.2/src/ImageLoaderMachO.cpp.auto.html
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// as one example).
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segv.FieldByName("Addr").SetUint(0)
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segv.FieldByName("Memsz").SetUint(0)
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segv.FieldByName("Prot").SetUint(0)
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seg.Addr = 0
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seg.Memsz = 0
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seg.Prot = 0
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if err := r.WriteAt(0, seg); err != nil {
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if err := r.WriteAt(0, &seg); err != nil {
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return err
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}
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return machoUpdateSections(*r, segv, reflect.ValueOf(sect), uint64(dwarfstart)-realdwarf.Offset, compressedSects)
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return machoUpdateSections(*r, &seg, uint64(dwarfstart)-realdwarf.Offset, compressedSects)
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}
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func machoUpdateLoadCommand(r loadCmdReader, linkseg *macho.Segment, linkoffset uint64, cmd interface{}, fields ...string) error {
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