--- /dev/null
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !js,!nacl,!plan9,!solaris,!windows
+
+/*
+
+Splitdwarf uncompresses and copies the DWARF segment of a Mach-O
+executable into the "dSYM" file expected by lldb and ports of gdb
+on OSX.
+
+Usage: splitdwarf osxMachoFile [ osxDsymFile ]
+
+Unless a dSYM file name is provided on the command line,
+splitdwarf will place it where the OSX tools expect it, in
+"<osxMachoFile>.dSYM/Contents/Resources/DWARF/<osxMachoFile>",
+creating directories as necessary.
+
+*/
+package main // import "golang.org/x/tools/cmd/splitdwarf"
+
+import (
+ "crypto/sha256"
+ "fmt"
+ "io"
+ "os"
+ "path/filepath"
+ "strings"
+ "syscall"
+
+ "golang.org/x/tools/cmd/splitdwarf/internal/macho"
+)
+
+const (
+ pageAlign = 12 // 4096 = 1 << 12
+)
+
+func note(format string, why ...interface{}) {
+ fmt.Fprintf(os.Stderr, format+"\n", why...)
+}
+
+func fail(format string, why ...interface{}) {
+ note(format, why...)
+ os.Exit(1)
+}
+
+// splitdwarf inputexe [ outputdwarf ]
+func main() {
+ if len(os.Args) < 2 || len(os.Args) > 3 {
+ fmt.Printf(`
+Usage: %s input_exe [ output_dsym ]
+Reads the executable input_exe, uncompresses and copies debugging
+information into output_dsym. If output_dsym is not specified,
+the path
+ input_exe.dSYM/Contents/Resources/DWARF/input_exe
+is used instead. That is the path that gdb and lldb expect
+on OSX. Input_exe needs a UUID segment; if that is missing,
+then one is created and added. In that case, the permissions
+for input_exe need to allow writing.
+`, os.Args[0])
+ return
+ }
+
+ // Read input, find DWARF, be sure it looks right
+ inputExe := os.Args[1]
+ exeFile, err := os.Open(inputExe)
+ if err != nil {
+ fail("%v", err)
+ }
+ exeMacho, err := macho.NewFile(exeFile)
+ if err != nil {
+ fail("(internal) Couldn't create macho, %v", err)
+ }
+ // Postpone dealing with output till input is known-good
+
+ // describe(&exeMacho.FileTOC)
+
+ // Offsets into __LINKEDIT:
+ //
+ // Command LC_SYMTAB =
+ // (1) number of symbols at file offset (within link edit section) of 16-byte symbol table entries
+ // struct {
+ // StringTableIndex uint32
+ // Type, SectionIndex uint8
+ // Description uint16
+ // Value uint64
+ // }
+ //
+ // (2) string table offset and size. Strings are zero-byte terminated. First must be " ".
+ //
+ // Command LC_DYSYMTAB = indices within symtab (above), except for IndSym
+ // IndSym Offset = file offset (within link edit section) of 4-byte indices within symtab.
+ //
+ // Section __TEXT.__symbol_stub1.
+ // Offset and size (Reserved2) locate and describe a table for thios section.
+ // Symbols beginning at IndirectSymIndex (Reserved1) (see LC_DYSYMTAB.IndSymOffset) refer to this table.
+ // (These table entries are apparently PLTs [Procedure Linkage Table/Trampoline])
+ //
+ // Section __DATA.__nl_symbol_ptr.
+ // Reserved1 seems to be an index within the Indirect symbols (see LC_DYSYMTAB.IndSymOffset)
+ // Some of these symbols appear to be duplicates of other indirect symbols appearing early
+ //
+ // Section __DATA.__la_symbol_ptr.
+ // Reserved1 seems to be an index within the Indirect symbols (see LC_DYSYMTAB.IndSymOffset)
+ // Some of these symbols appear to be duplicates of other indirect symbols appearing early
+ //
+
+ // Create a File for the output dwarf.
+ // Copy header, file type is MH_DSYM
+ // Copy the relevant load commands
+
+ // LoadCmdUuid
+ // Symtab -- very abbreviated (Use DYSYMTAB Iextdefsym, Nextdefsym to identify these).
+ // Segment __PAGEZERO
+ // Segment __TEXT (zero the size, zero the offset of each section)
+ // Segment __DATA (zero the size, zero the offset of each section)
+ // Segment __LINKEDIT (contains the symbols and strings from Symtab)
+ // Segment __DWARF (uncompressed)
+
+ var uuid *macho.Uuid
+ for _, l := range exeMacho.Loads {
+ switch l.Command() {
+ case macho.LcUuid:
+ uuid = l.(*macho.Uuid)
+ }
+ }
+
+ // Ensure a given load is not nil
+ nonnilC := func(l macho.Load, s string) {
+ if l == nil {
+ fail("input file %s lacks load command %s", inputExe, s)
+ }
+ }
+
+ // Find a segment by name and ensure it is not nil
+ nonnilS := func(s string) *macho.Segment {
+ l := exeMacho.Segment(s)
+ if l == nil {
+ fail("input file %s lacks segment %s", inputExe, s)
+ }
+ return l
+ }
+
+ newtoc := exeMacho.FileTOC.DerivedCopy(macho.MhDsym, 0)
+
+ symtab := exeMacho.Symtab
+ dysymtab := exeMacho.Dysymtab // Not appearing in output, but necessary to construct output
+ nonnilC(symtab, "symtab")
+ nonnilC(dysymtab, "dysymtab")
+ text := nonnilS("__TEXT")
+ data := nonnilS("__DATA")
+ linkedit := nonnilS("__LINKEDIT")
+ pagezero := nonnilS("__PAGEZERO")
+
+ newtext := text.CopyZeroed()
+ newdata := data.CopyZeroed()
+ newsymtab := symtab.Copy()
+
+ // Linkedit segment contain symbols and strings;
+ // Symtab refers to offsets into linkedit.
+ // This next bit initializes newsymtab and sets up data structures for the linkedit segment
+ linkeditsyms := []macho.Nlist64{}
+ linkeditstrings := []string{}
+
+ // Linkedit will begin at the second page, i.e., offset is one page from beginning
+ // Symbols come first
+ linkeditsymbase := uint32(1) << pageAlign
+
+ // Strings come second, offset by the number of symbols times their size.
+ // Only those symbols from dysymtab.defsym are written into the debugging information.
+ linkeditstringbase := linkeditsymbase + exeMacho.FileTOC.SymbolSize()*dysymtab.Nextdefsym
+
+ // The first two bytes of the strings are reserved for space, null (' ', \000)
+ linkeditstringcur := uint32(2)
+
+ newsymtab.Syms = newsymtab.Syms[:0]
+ newsymtab.Symoff = linkeditsymbase
+ newsymtab.Stroff = linkeditstringbase
+ newsymtab.Nsyms = dysymtab.Nextdefsym
+ for i := uint32(0); i < dysymtab.Nextdefsym; i++ {
+ ii := i + dysymtab.Iextdefsym
+ oldsym := symtab.Syms[ii]
+ newsymtab.Syms = append(newsymtab.Syms, oldsym)
+
+ linkeditsyms = append(linkeditsyms, macho.Nlist64{Name: uint32(linkeditstringcur),
+ Type: oldsym.Type, Sect: oldsym.Sect, Desc: oldsym.Desc, Value: oldsym.Value})
+ linkeditstringcur += uint32(len(oldsym.Name)) + 1
+ linkeditstrings = append(linkeditstrings, oldsym.Name)
+ }
+ newsymtab.Strsize = linkeditstringcur
+
+ exeNeedsUuid := uuid == nil
+ if exeNeedsUuid {
+ uuid = &macho.Uuid{macho.UuidCmd{LoadCmd: macho.LcUuid}}
+ uuid.Len = uuid.LoadSize(newtoc)
+ copy(uuid.Id[0:], contentuuid(&exeMacho.FileTOC)[0:16])
+ uuid.Id[6] = uuid.Id[6]&^0xf0 | 0x40 // version 4 (pseudo-random); see section 4.1.3
+ uuid.Id[8] = uuid.Id[8]&^0xc0 | 0x80 // variant bits; see section 4.1.1
+ }
+ newtoc.AddLoad(uuid)
+
+ // For the specified segment (assumed to be in exeMacho) make a copy of its
+ // sections with appropriate fields zeroed out, and append them to the
+ // currently-last segment in newtoc.
+ copyZOdSections := func(g *macho.Segment) {
+ for i := g.Firstsect; i < g.Firstsect+g.Nsect; i++ {
+ s := exeMacho.Sections[i].Copy()
+ s.Offset = 0
+ s.Reloff = 0
+ s.Nreloc = 0
+ newtoc.AddSection(s)
+ }
+ }
+
+ newtoc.AddLoad(newsymtab)
+ newtoc.AddSegment(pagezero)
+ newtoc.AddSegment(newtext)
+ copyZOdSections(text)
+ newtoc.AddSegment(newdata)
+ copyZOdSections(data)
+
+ newlinkedit := linkedit.Copy()
+ newlinkedit.Offset = uint64(linkeditsymbase)
+ newlinkedit.Filesz = uint64(linkeditstringcur)
+ newlinkedit.Addr = macho.RoundUp(newdata.Addr+newdata.Memsz, 1<<pageAlign) // Follows data sections in file
+ newlinkedit.Memsz = macho.RoundUp(newlinkedit.Filesz, 1<<pageAlign)
+ // The rest should copy over fine.
+ newtoc.AddSegment(newlinkedit)
+
+ dwarf := nonnilS("__DWARF")
+ newdwarf := dwarf.CopyZeroed()
+ newdwarf.Offset = macho.RoundUp(newlinkedit.Offset+newlinkedit.Filesz, 1<<pageAlign)
+ newdwarf.Filesz = dwarf.UncompressedSize(&exeMacho.FileTOC, 1)
+ newdwarf.Addr = newlinkedit.Addr + newlinkedit.Memsz // Follows linkedit sections in file.
+ newdwarf.Memsz = macho.RoundUp(newdwarf.Filesz, 1<<pageAlign)
+ newtoc.AddSegment(newdwarf)
+
+ // Map out Dwarf sections (that is, this is section descriptors, not their contents).
+ offset := uint32(newdwarf.Offset)
+ for i := dwarf.Firstsect; i < dwarf.Firstsect+dwarf.Nsect; i++ {
+ o := exeMacho.Sections[i]
+ s := o.Copy()
+ s.Offset = offset
+ us := o.UncompressedSize()
+ if s.Size < us {
+ s.Size = uint64(us)
+ s.Align = 0 // This is apparently true for debugging sections; not sure if it generalizes.
+ }
+ offset += uint32(us)
+ if strings.HasPrefix(s.Name, "__z") {
+ s.Name = "__" + s.Name[3:] // remove "z"
+ }
+ s.Reloff = 0
+ s.Nreloc = 0
+ newtoc.AddSection(s)
+ }
+
+ // Write segments/sections.
+ // Only dwarf and linkedit contain anything interesting.
+
+ // Memory map the output file to get the buffer directly.
+ outDwarf := inputExe + ".dSYM/Contents/Resources/DWARF"
+ if len(os.Args) > 2 {
+ outDwarf = os.Args[2]
+ } else {
+ err := os.MkdirAll(outDwarf, 0755)
+ if err != nil {
+ fail("%v", err)
+ }
+ outDwarf = filepath.Join(outDwarf, filepath.Base(inputExe))
+ }
+ dwarfFile, buffer := CreateMmapFile(outDwarf, int64(newtoc.FileSize()))
+
+ // (1) Linkedit segment
+ // Symbol table
+ offset = uint32(newlinkedit.Offset)
+ for i := range linkeditsyms {
+ if exeMacho.Magic == macho.Magic64 {
+ offset += linkeditsyms[i].Put64(buffer[offset:], newtoc.ByteOrder)
+ } else {
+ offset += linkeditsyms[i].Put32(buffer[offset:], newtoc.ByteOrder)
+ }
+ }
+
+ // Initial two bytes of string table, followed by actual zero-terminated strings.
+ buffer[linkeditstringbase] = ' '
+ buffer[linkeditstringbase+1] = 0
+ offset = linkeditstringbase + 2
+ for _, str := range linkeditstrings {
+ for i := 0; i < len(str); i++ {
+ buffer[offset] = str[i]
+ offset++
+ }
+ buffer[offset] = 0
+ offset++
+ }
+
+ // (2) DWARF segment
+ ioff := newdwarf.Firstsect - dwarf.Firstsect
+ for i := dwarf.Firstsect; i < dwarf.Firstsect+dwarf.Nsect; i++ {
+ s := exeMacho.Sections[i]
+ j := i + ioff
+ s.PutUncompressedData(buffer[newtoc.Sections[j].Offset:])
+ }
+
+ // Because "text" overlaps the header and the loads, write them afterwards, just in case.
+ // Write header.
+ newtoc.Put(buffer)
+
+ err = syscall.Munmap(buffer)
+ if err != nil {
+ fail("Munmap %s for dwarf output failed, %v", outDwarf, err)
+ }
+ err = dwarfFile.Close()
+ if err != nil {
+ fail("Close %s for dwarf output after mmap/munmap failed, %v", outDwarf, err)
+ }
+
+ if exeNeedsUuid { // Map the original exe, modify the header, and write the UUID command
+ hdr := exeMacho.FileTOC.FileHeader
+ oldCommandEnd := hdr.SizeCommands + newtoc.HdrSize()
+ hdr.NCommands += 1
+ hdr.SizeCommands += uuid.LoadSize(newtoc)
+
+ mapf, err := os.OpenFile(inputExe, os.O_RDWR, 0)
+ if err != nil {
+ fail("Updating UUID in binary failed, %v", err)
+ }
+ exebuf, err := syscall.Mmap(int(mapf.Fd()), 0, int(macho.RoundUp(uint64(hdr.SizeCommands), 1<<pageAlign)),
+ syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_FILE|syscall.MAP_SHARED)
+ if err != nil {
+ fail("Mmap of %s for UUID update failed, %v", inputExe, err)
+ }
+ _ = hdr.Put(exebuf, newtoc.ByteOrder)
+ _ = uuid.Put(exebuf[oldCommandEnd:], newtoc.ByteOrder)
+ err = syscall.Munmap(exebuf)
+ if err != nil {
+ fail("Munmap of %s for UUID update failed, %v", inputExe, err)
+ }
+ }
+}
+
+// CreateMmapFile creates the file 'outDwarf' of the specified size, mmaps that file,
+// and returns the file descriptor and mapped buffer.
+func CreateMmapFile(outDwarf string, size int64) (*os.File, []byte) {
+ dwarfFile, err := os.OpenFile(outDwarf, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0666)
+ if err != nil {
+ fail("Open for mmap failed, %v", err)
+ }
+ err = os.Truncate(outDwarf, size)
+ if err != nil {
+ fail("Truncate/extend of %s to %d bytes failed, %v", dwarfFile, size, err)
+ }
+ buffer, err := syscall.Mmap(int(dwarfFile.Fd()), 0, int(size), syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_FILE|syscall.MAP_SHARED)
+ if err != nil {
+ fail("Mmap %s for dwarf output update failed, %v", outDwarf, err)
+ }
+ return dwarfFile, buffer
+}
+
+func describe(exem *macho.FileTOC) {
+ note("Type = %s, Flags=0x%x", exem.Type, uint32(exem.Flags))
+ for i, l := range exem.Loads {
+ if s, ok := l.(*macho.Segment); ok {
+ fmt.Printf("Load %d is Segment %s, offset=0x%x, filesz=%d, addr=0x%x, memsz=%d, nsect=%d\n", i, s.Name,
+ s.Offset, s.Filesz, s.Addr, s.Memsz, s.Nsect)
+ for j := uint32(0); j < s.Nsect; j++ {
+ c := exem.Sections[j+s.Firstsect]
+ fmt.Printf(" Section %s, offset=0x%x, size=%d, addr=0x%x, flags=0x%x, nreloc=%d, res1=%d, res2=%d, res3=%d\n", c.Name, c.Offset, c.Size, c.Addr, c.Flags, c.Nreloc, c.Reserved1, c.Reserved2, c.Reserved3)
+ }
+ } else {
+ fmt.Printf("Load %d is %v\n", i, l)
+ }
+ }
+ if exem.SizeCommands != exem.LoadSize() {
+ fail("recorded command size %d does not equal computed command size %d", exem.SizeCommands, exem.LoadSize())
+ } else {
+ note("recorded command size %d, computed command size %d", exem.SizeCommands, exem.LoadSize())
+ }
+ note("File size is %d", exem.FileSize())
+}
+
+// contentuuid returns a UUID derived from (some of) the content of an executable.
+// specifically included are the non-DWARF sections, specifically excluded are things
+// that surely depend on the presence or absence of DWARF sections (e.g., section
+// numbers, positions with file, number of load commands).
+// (It was considered desirable if this was insensitive to the presence of the
+// __DWARF segment, however because it is not last, it moves other segments,
+// whose contents appear to contain file offset references.)
+func contentuuid(exem *macho.FileTOC) []byte {
+ h := sha256.New()
+ for _, l := range exem.Loads {
+ if l.Command() == macho.LcUuid {
+ continue
+ }
+ if s, ok := l.(*macho.Segment); ok {
+ if s.Name == "__DWARF" || s.Name == "__PAGEZERO" {
+ continue
+ }
+ for j := uint32(0); j < s.Nsect; j++ {
+ c := exem.Sections[j+s.Firstsect]
+ io.Copy(h, c.Open())
+ }
+ } // Getting dependence on other load commands right is fiddly.
+ }
+ return h.Sum(nil)
+}
projects / dotfiles / .git / blobdiff