1 // Inferno utils/8l/asm.c
2 // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/8l/asm.c
4 // Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
5 // Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
6 // Portions Copyright © 1997-1999 Vita Nuova Limited
7 // Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
8 // Portions Copyright © 2004,2006 Bruce Ellis
9 // Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
10 // Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
11 // Portions Copyright © 2009 The Go Authors. All rights reserved.
13 // Permission is hereby granted, free of charge, to any person obtaining a copy
14 // of this software and associated documentation files (the "Software"), to deal
15 // in the Software without restriction, including without limitation the rights
16 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
17 // copies of the Software, and to permit persons to whom the Software is
18 // furnished to do so, subject to the following conditions:
20 // The above copyright notice and this permission notice shall be included in
21 // all copies or substantial portions of the Software.
23 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
24 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
25 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
26 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
27 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
28 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
52 "cmd/internal/notsha256"
55 "cmd/link/internal/loadelf"
56 "cmd/link/internal/loader"
57 "cmd/link/internal/loadmacho"
58 "cmd/link/internal/loadpe"
59 "cmd/link/internal/loadxcoff"
60 "cmd/link/internal/sym"
63 // Data layout and relocation.
65 // Derived from Inferno utils/6l/l.h
66 // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6l/l.h
68 // Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
69 // Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
70 // Portions Copyright © 1997-1999 Vita Nuova Limited
71 // Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
72 // Portions Copyright © 2004,2006 Bruce Ellis
73 // Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
74 // Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
75 // Portions Copyright © 2009 The Go Authors. All rights reserved.
77 // Permission is hereby granted, free of charge, to any person obtaining a copy
78 // of this software and associated documentation files (the "Software"), to deal
79 // in the Software without restriction, including without limitation the rights
80 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
81 // copies of the Software, and to permit persons to whom the Software is
82 // furnished to do so, subject to the following conditions:
84 // The above copyright notice and this permission notice shall be included in
85 // all copies or substantial portions of the Software.
87 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
88 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
89 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
90 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
91 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
92 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
95 // ArchSyms holds a number of architecture specific symbols used during
96 // relocation. Rather than allowing them universal access to all symbols,
97 // we keep a subset for relocation application.
98 type ArchSyms struct {
104 LinkEditGOT loader.Sym
105 LinkEditPLT loader.Sym
108 DotTOC []loader.Sym // for each version
121 unreachableMethod loader.Sym
124 // mkArchSym is a helper for setArchSyms, to set up a special symbol.
125 func (ctxt *Link) mkArchSym(name string, ver int, ls *loader.Sym) {
126 *ls = ctxt.loader.LookupOrCreateSym(name, ver)
127 ctxt.loader.SetAttrReachable(*ls, true)
130 // mkArchVecSym is similar to setArchSyms, but operates on elements within
131 // a slice, where each element corresponds to some symbol version.
132 func (ctxt *Link) mkArchSymVec(name string, ver int, ls []loader.Sym) {
133 ls[ver] = ctxt.loader.LookupOrCreateSym(name, ver)
134 ctxt.loader.SetAttrReachable(ls[ver], true)
137 // setArchSyms sets up the ArchSyms structure, and must be called before
138 // relocations are applied.
139 func (ctxt *Link) setArchSyms() {
140 ctxt.mkArchSym(".got", 0, &ctxt.GOT)
141 ctxt.mkArchSym(".plt", 0, &ctxt.PLT)
142 ctxt.mkArchSym(".got.plt", 0, &ctxt.GOTPLT)
143 ctxt.mkArchSym(".dynamic", 0, &ctxt.Dynamic)
144 ctxt.mkArchSym(".dynsym", 0, &ctxt.DynSym)
145 ctxt.mkArchSym(".dynstr", 0, &ctxt.DynStr)
146 ctxt.mkArchSym("runtime.unreachableMethod", abiInternalVer, &ctxt.unreachableMethod)
149 ctxt.mkArchSym("TOC", 0, &ctxt.TOC)
151 ctxt.DotTOC = make([]loader.Sym, ctxt.MaxVersion()+1)
152 for i := 0; i <= ctxt.MaxVersion(); i++ {
153 if i >= sym.SymVerABICount && i < sym.SymVerStatic { // these versions are not used currently
156 ctxt.mkArchSymVec(".TOC.", i, ctxt.DotTOC)
160 ctxt.mkArchSym(".rel", 0, &ctxt.Rel)
161 ctxt.mkArchSym(".rela", 0, &ctxt.Rela)
162 ctxt.mkArchSym(".rel.plt", 0, &ctxt.RelPLT)
163 ctxt.mkArchSym(".rela.plt", 0, &ctxt.RelaPLT)
166 ctxt.mkArchSym(".linkedit.got", 0, &ctxt.LinkEditGOT)
167 ctxt.mkArchSym(".linkedit.plt", 0, &ctxt.LinkEditPLT)
178 // Threshold of total text size, used for trampoline insertion. If the total
179 // text size is smaller than TrampLimit, we won't need to insert trampolines.
180 // It is pretty close to the offset range of a direct CALL machine instruction.
181 // We leave some room for extra stuff like PLT stubs.
186 LinuxdynldMusl string
190 Dragonflydynld string
193 // Empty spaces between codeblocks will be padded with this value.
194 // For example an architecture might want to pad with a trap instruction to
195 // catch wayward programs. Architectures that do not define a padding value
196 // are padded with zeros.
203 Adddynrel func(*Target, *loader.Loader, *ArchSyms, loader.Sym, loader.Reloc, int) bool
205 // Archreloc is an arch-specific hook that assists in relocation processing
206 // (invoked by 'relocsym'); it handles target-specific relocation tasks.
207 // Here "rel" is the current relocation being examined, "sym" is the symbol
208 // containing the chunk of data to which the relocation applies, and "off"
209 // is the contents of the to-be-relocated data item (from sym.P). Return
210 // value is the appropriately relocated value (to be written back to the
211 // same spot in sym.P), number of external _host_ relocations needed (i.e.
212 // ELF/Mach-O/etc. relocations, not Go relocations, this must match Elfreloc1,
213 // etc.), and a boolean indicating success/failure (a failing value indicates
215 Archreloc func(*Target, *loader.Loader, *ArchSyms, loader.Reloc, loader.Sym,
216 int64) (relocatedOffset int64, nExtReloc int, ok bool)
217 // Archrelocvariant is a second arch-specific hook used for
218 // relocation processing; it handles relocations where r.Type is
219 // insufficient to describe the relocation (r.Variant !=
220 // sym.RV_NONE). Here "rel" is the relocation being applied, "sym"
221 // is the symbol containing the chunk of data to which the
222 // relocation applies, and "off" is the contents of the
223 // to-be-relocated data item (from sym.P). Return is an updated
225 Archrelocvariant func(target *Target, ldr *loader.Loader, rel loader.Reloc,
226 rv sym.RelocVariant, sym loader.Sym, offset int64, data []byte) (relocatedOffset int64)
228 // Generate a trampoline for a call from s to rs if necessary. ri is
229 // index of the relocation.
230 Trampoline func(ctxt *Link, ldr *loader.Loader, ri int, rs, s loader.Sym)
232 // Assembling the binary breaks into two phases, writing the code/data/
233 // dwarf information (which is rather generic), and some more architecture
234 // specific work like setting up the elf headers/dynamic relocations, etc.
235 // The phases are called "Asmb" and "Asmb2". Asmb2 needs to be defined for
236 // every architecture, but only if architecture has an Asmb function will
237 // it be used for assembly. Otherwise a generic assembly Asmb function is
239 Asmb func(*Link, *loader.Loader)
240 Asmb2 func(*Link, *loader.Loader)
242 // Extreloc is an arch-specific hook that converts a Go relocation to an
243 // external relocation. Return the external relocation and whether it is
245 Extreloc func(*Target, *loader.Loader, loader.Reloc, loader.Sym) (loader.ExtReloc, bool)
247 Elfreloc1 func(*Link, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int, int64) bool
248 ElfrelocSize uint32 // size of an ELF relocation record, must match Elfreloc1.
249 Elfsetupplt func(ctxt *Link, plt, gotplt *loader.SymbolBuilder, dynamic loader.Sym)
250 Gentext func(*Link, *loader.Loader) // Generate text before addressing has been performed.
251 Machoreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
252 MachorelocSize uint32 // size of an Mach-O relocation record, must match Machoreloc1.
253 PEreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
254 Xcoffreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
256 // Generate additional symbols for the native symbol table just prior to
258 GenSymsLate func(*Link, *loader.Loader)
260 // TLSIEtoLE converts a TLS Initial Executable relocation to
261 // a TLS Local Executable relocation.
263 // This is possible when a TLS IE relocation refers to a local
264 // symbol in an executable, which is typical when internally
265 // linking PIE binaries.
266 TLSIEtoLE func(P []byte, off, size int)
268 // optional override for assignAddress
269 AssignAddress func(ldr *loader.Loader, sect *sym.Section, n int, s loader.Sym, va uint64, isTramp bool) (*sym.Section, int, uint64)
281 MINFUNC = 16 // minimum size for a function
284 // Symbol version of ABIInternal symbols. It is sym.SymVerABIInternal if ABI wrappers
285 // are used, 0 otherwise.
286 var abiInternalVer = sym.SymVerABIInternal
288 // DynlinkingGo reports whether we are producing Go code that can live
289 // in separate shared libraries linked together at runtime.
290 func (ctxt *Link) DynlinkingGo() bool {
292 panic("DynlinkingGo called before all symbols loaded")
294 return ctxt.BuildMode == BuildModeShared || ctxt.linkShared || ctxt.BuildMode == BuildModePlugin || ctxt.canUsePlugins
297 // CanUsePlugins reports whether a plugins can be used
298 func (ctxt *Link) CanUsePlugins() bool {
300 panic("CanUsePlugins called before all symbols loaded")
302 return ctxt.canUsePlugins
305 // NeedCodeSign reports whether we need to code-sign the output binary.
306 func (ctxt *Link) NeedCodeSign() bool {
307 return ctxt.IsDarwin() && ctxt.IsARM64()
319 debug_s bool // backup old value of debug['s']
323 liveness int64 // size of liveness data (funcdata), printed if -v
325 // See -strictdups command line flag.
326 checkStrictDups int // 0=off 1=warning 2=error
327 strictDupMsgCount int
332 Segrodata sym.Segment
333 Segrelrodata sym.Segment
337 Segments = []*sym.Segment{&Segtext, &Segrodata, &Segrelrodata, &Segdata, &Segdwarf}
340 const pkgdef = "__.PKGDEF"
343 // externalobj is set to true if we see an object compiled by
344 // the host compiler that is not from a package that is known
345 // to support internal linking mode.
348 // dynimportfail is a list of packages for which generating
349 // the dynimport file, _cgo_import.go, failed. If there are
350 // any of these objects, we must link externally. Issue 52863.
351 dynimportfail []string
353 // unknownObjFormat is set to true if we see an object whose
354 // format we don't recognize.
355 unknownObjFormat = false
360 func Lflag(ctxt *Link, arg string) {
361 ctxt.Libdir = append(ctxt.Libdir, arg)
365 * Unix doesn't like it when we write to a running (or, sometimes,
366 * recently run) binary, so remove the output file before writing it.
367 * On Windows 7, remove() can force a subsequent create() to fail.
368 * S_ISREG() does not exist on Plan 9.
370 func mayberemoveoutfile() {
371 if fi, err := os.Lstat(*flagOutfile); err == nil && !fi.Mode().IsRegular() {
374 os.Remove(*flagOutfile)
377 func libinit(ctxt *Link) {
378 Funcalign = thearch.Funcalign
380 // add goroot to the end of the libdir list.
384 if *flagInstallSuffix != "" {
386 suffix = *flagInstallSuffix
387 } else if *flagRace {
390 } else if *flagMsan {
393 } else if *flagAsan {
398 if buildcfg.GOROOT != "" {
399 Lflag(ctxt, filepath.Join(buildcfg.GOROOT, "pkg", fmt.Sprintf("%s_%s%s%s", buildcfg.GOOS, buildcfg.GOARCH, suffixsep, suffix)))
404 if err := ctxt.Out.Open(*flagOutfile); err != nil {
405 Exitf("cannot create %s: %v", *flagOutfile, err)
408 if *flagEntrySymbol == "" {
409 switch ctxt.BuildMode {
410 case BuildModeCShared, BuildModeCArchive:
411 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s_lib", buildcfg.GOARCH, buildcfg.GOOS)
412 case BuildModeExe, BuildModePIE:
413 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s", buildcfg.GOARCH, buildcfg.GOOS)
414 case BuildModeShared, BuildModePlugin:
415 // No *flagEntrySymbol for -buildmode=shared and plugin
417 Errorf(nil, "unknown *flagEntrySymbol for buildmode %v", ctxt.BuildMode)
422 func exitIfErrors() {
423 if nerrors != 0 || checkStrictDups > 1 && strictDupMsgCount > 0 {
435 func loadinternal(ctxt *Link, name string) *sym.Library {
436 zerofp := goobj.FingerprintType{}
437 if ctxt.linkShared && ctxt.PackageShlib != nil {
438 if shlib := ctxt.PackageShlib[name]; shlib != "" {
439 return addlibpath(ctxt, "internal", "internal", "", name, shlib, zerofp)
442 if ctxt.PackageFile != nil {
443 if pname := ctxt.PackageFile[name]; pname != "" {
444 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
446 ctxt.Logf("loadinternal: cannot find %s\n", name)
450 for _, libdir := range ctxt.Libdir {
452 shlibname := filepath.Join(libdir, name+".shlibname")
453 if ctxt.Debugvlog != 0 {
454 ctxt.Logf("searching for %s.a in %s\n", name, shlibname)
456 if _, err := os.Stat(shlibname); err == nil {
457 return addlibpath(ctxt, "internal", "internal", "", name, shlibname, zerofp)
460 pname := filepath.Join(libdir, name+".a")
461 if ctxt.Debugvlog != 0 {
462 ctxt.Logf("searching for %s.a in %s\n", name, pname)
464 if _, err := os.Stat(pname); err == nil {
465 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
469 if name == "runtime" {
470 Exitf("error: unable to find runtime.a")
472 ctxt.Logf("warning: unable to find %s.a\n", name)
476 // extld returns the current external linker.
477 func (ctxt *Link) extld() []string {
478 if len(flagExtld) == 0 {
479 // Return the default external linker for the platform.
480 // This only matters when link tool is called directly without explicit -extld,
481 // go tool already passes the correct linker in other cases.
482 switch buildcfg.GOOS {
483 case "darwin", "freebsd", "openbsd":
484 flagExtld = []string{"clang"}
486 flagExtld = []string{"gcc"}
492 // findLibPathCmd uses cmd command to find gcc library libname.
493 // It returns library full path if found, or "none" if not found.
494 func (ctxt *Link) findLibPathCmd(cmd, libname string) string {
495 extld := ctxt.extld()
496 name, args := extld[0], extld[1:]
497 args = append(args, hostlinkArchArgs(ctxt.Arch)...)
498 args = append(args, cmd)
499 if ctxt.Debugvlog != 0 {
500 ctxt.Logf("%s %v\n", extld, args)
502 out, err := exec.Command(name, args...).Output()
504 if ctxt.Debugvlog != 0 {
505 ctxt.Logf("not using a %s file because compiler failed\n%v\n%s\n", libname, err, out)
509 return strings.TrimSpace(string(out))
512 // findLibPath searches for library libname.
513 // It returns library full path if found, or "none" if not found.
514 func (ctxt *Link) findLibPath(libname string) string {
515 return ctxt.findLibPathCmd("--print-file-name="+libname, libname)
518 func (ctxt *Link) loadlib() {
520 switch *FlagStrictDups {
524 flags |= loader.FlagStrictDups
526 log.Fatalf("invalid -strictdups flag value %d", *FlagStrictDups)
528 elfsetstring1 := func(str string, off int) { elfsetstring(ctxt, 0, str, off) }
529 ctxt.loader = loader.NewLoader(flags, elfsetstring1, &ctxt.ErrorReporter.ErrorReporter)
530 ctxt.ErrorReporter.SymName = func(s loader.Sym) string {
531 return ctxt.loader.SymName(s)
534 // ctxt.Library grows during the loop, so not a range loop.
536 for ; i < len(ctxt.Library); i++ {
537 lib := ctxt.Library[i]
539 if ctxt.Debugvlog > 1 {
540 ctxt.Logf("autolib: %s (from %s)\n", lib.File, lib.Objref)
542 loadobjfile(ctxt, lib)
546 // load internal packages, if not already
548 loadinternal(ctxt, "runtime/race")
551 loadinternal(ctxt, "runtime/msan")
554 loadinternal(ctxt, "runtime/asan")
556 loadinternal(ctxt, "runtime")
557 for ; i < len(ctxt.Library); i++ {
558 lib := ctxt.Library[i]
560 loadobjfile(ctxt, lib)
563 // At this point, the Go objects are "preloaded". Not all the symbols are
564 // added to the symbol table (only defined package symbols are). Looking
565 // up symbol by name may not get expected result.
567 iscgo = ctxt.LibraryByPkg["runtime/cgo"] != nil
569 // Plugins a require cgo support to function. Similarly, plugins may require additional
570 // internal linker support on some platforms which may not be implemented.
571 ctxt.canUsePlugins = ctxt.LibraryByPkg["plugin"] != nil && iscgo
573 // We now have enough information to determine the link mode.
574 determineLinkMode(ctxt)
576 if ctxt.LinkMode == LinkExternal && !iscgo && !(buildcfg.GOOS == "darwin" && ctxt.BuildMode != BuildModePlugin && ctxt.Arch.Family == sys.AMD64) {
577 // This indicates a user requested -linkmode=external.
578 // The startup code uses an import of runtime/cgo to decide
579 // whether to initialize the TLS. So give it one. This could
580 // be handled differently but it's an unusual case.
581 if lib := loadinternal(ctxt, "runtime/cgo"); lib != nil && lib.Shlib == "" {
582 if ctxt.BuildMode == BuildModeShared || ctxt.linkShared {
583 Exitf("cannot implicitly include runtime/cgo in a shared library")
585 for ; i < len(ctxt.Library); i++ {
586 lib := ctxt.Library[i]
588 loadobjfile(ctxt, lib)
594 // Add non-package symbols and references of externally defined symbols.
595 ctxt.loader.LoadSyms(ctxt.Arch)
597 // Load symbols from shared libraries, after all Go object symbols are loaded.
598 for _, lib := range ctxt.Library {
600 if ctxt.Debugvlog > 1 {
601 ctxt.Logf("autolib: %s (from %s)\n", lib.Shlib, lib.Objref)
603 ldshlibsyms(ctxt, lib.Shlib)
607 // Process cgo directives (has to be done before host object loading).
608 ctxt.loadcgodirectives()
610 // Conditionally load host objects, or setup for external linking.
614 if ctxt.LinkMode == LinkInternal && len(hostobj) != 0 {
615 // If we have any undefined symbols in external
616 // objects, try to read them from the libgcc file.
618 undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
621 if ctxt.Debugvlog > 1 {
622 ctxt.Logf("loadlib: first unresolved is %s [%d] from %s [%d]\n",
623 ctxt.loader.SymName(undefs[0]), undefs[0],
624 ctxt.loader.SymName(froms[0]), froms[0])
628 if *flagLibGCC == "" {
629 *flagLibGCC = ctxt.findLibPathCmd("--print-libgcc-file-name", "libgcc")
631 if runtime.GOOS == "openbsd" && *flagLibGCC == "libgcc.a" {
632 // On OpenBSD `clang --print-libgcc-file-name` returns "libgcc.a".
633 // In this case we fail to load libgcc.a and can encounter link
634 // errors - see if we can find libcompiler_rt.a instead.
635 *flagLibGCC = ctxt.findLibPathCmd("--print-file-name=libcompiler_rt.a", "libcompiler_rt")
637 if ctxt.HeadType == objabi.Hwindows {
638 loadWindowsHostArchives(ctxt)
640 if *flagLibGCC != "none" {
641 hostArchive(ctxt, *flagLibGCC)
646 // We've loaded all the code now.
651 strictDupMsgCount = ctxt.loader.NStrictDupMsgs()
654 // loadWindowsHostArchives loads in host archives and objects when
655 // doing internal linking on windows. Older toolchains seem to require
656 // just a single pass through the various archives, but some modern
657 // toolchains when linking a C program with mingw pass library paths
658 // multiple times to the linker, e.g. "... -lmingwex -lmingw32 ...
659 // -lmingwex -lmingw32 ...". To accommodate this behavior, we make two
660 // passes over the host archives below.
661 func loadWindowsHostArchives(ctxt *Link) {
663 for i := 0; any && i < 2; i++ {
664 // Link crt2.o (if present) to resolve "atexit" when
665 // using LLVM-based compilers.
666 isunresolved := symbolsAreUnresolved(ctxt, []string{"atexit"})
668 if p := ctxt.findLibPath("crt2.o"); p != "none" {
669 hostObject(ctxt, "crt2", p)
673 if p := ctxt.findLibPath("libsynchronization.a"); p != "none" {
677 if p := ctxt.findLibPath("libmingwex.a"); p != "none" {
680 if p := ctxt.findLibPath("libmingw32.a"); p != "none" {
683 // Link libmsvcrt.a to resolve '__acrt_iob_func' symbol
684 // (see https://golang.org/issue/23649 for details).
685 if p := ctxt.findLibPath("libmsvcrt.a"); p != "none" {
689 undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
692 if ctxt.Debugvlog > 1 {
693 ctxt.Logf("loadWindowsHostArchives: remaining unresolved is %s [%d] from %s [%d]\n",
694 ctxt.loader.SymName(undefs[0]), undefs[0],
695 ctxt.loader.SymName(froms[0]), froms[0])
699 // If needed, create the __CTOR_LIST__ and __DTOR_LIST__
700 // symbols (referenced by some of the mingw support library
701 // routines). Creation of these symbols is normally done by the
702 // linker if not already present.
703 want := []string{"__CTOR_LIST__", "__DTOR_LIST__"}
704 isunresolved := symbolsAreUnresolved(ctxt, want)
705 for k, w := range want {
707 sb := ctxt.loader.CreateSymForUpdate(w, 0)
708 sb.SetType(sym.SDATA)
709 sb.AddUint64(ctxt.Arch, 0)
710 sb.SetReachable(true)
711 ctxt.loader.SetAttrSpecial(sb.Sym(), true)
715 // Fix up references to DLL import symbols now that we're done
716 // pulling in new objects.
717 if err := loadpe.PostProcessImports(); err != nil {
718 Errorf(nil, "%v", err)
721 // TODO: maybe do something similar to peimporteddlls to collect
722 // all lib names and try link them all to final exe just like
723 // libmingwex.a and libmingw32.a:
726 #cgo windows LDFLAGS: -lmsvcrt -lm
732 // loadcgodirectives reads the previously discovered cgo directives, creating
733 // symbols in preparation for host object loading or use later in the link.
734 func (ctxt *Link) loadcgodirectives() {
736 hostObjSyms := make(map[loader.Sym]struct{})
737 for _, d := range ctxt.cgodata {
738 setCgoAttr(ctxt, d.file, d.pkg, d.directives, hostObjSyms)
742 if ctxt.LinkMode == LinkInternal {
743 // Drop all the cgo_import_static declarations.
744 // Turns out we won't be needing them.
745 for symIdx := range hostObjSyms {
746 if l.SymType(symIdx) == sym.SHOSTOBJ {
747 // If a symbol was marked both
748 // cgo_import_static and cgo_import_dynamic,
749 // then we want to make it cgo_import_dynamic
751 su := l.MakeSymbolUpdater(symIdx)
752 if l.SymExtname(symIdx) != "" && l.SymDynimplib(symIdx) != "" && !(l.AttrCgoExportStatic(symIdx) || l.AttrCgoExportDynamic(symIdx)) {
753 su.SetType(sym.SDYNIMPORT)
762 // Set up flags and special symbols depending on the platform build mode.
763 // This version works with loader.Loader.
764 func (ctxt *Link) linksetup() {
765 switch ctxt.BuildMode {
766 case BuildModeCShared, BuildModePlugin:
767 symIdx := ctxt.loader.LookupOrCreateSym("runtime.islibrary", 0)
768 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
769 sb.SetType(sym.SNOPTRDATA)
771 case BuildModeCArchive:
772 symIdx := ctxt.loader.LookupOrCreateSym("runtime.isarchive", 0)
773 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
774 sb.SetType(sym.SNOPTRDATA)
778 // Recalculate pe parameters now that we have ctxt.LinkMode set.
779 if ctxt.HeadType == objabi.Hwindows {
783 if ctxt.LinkMode == LinkExternal {
784 // When external linking, we are creating an object file. The
785 // absolute address is irrelevant.
789 // If there are no dynamic libraries needed, gcc disables dynamic linking.
790 // Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13)
791 // assumes that a dynamic binary always refers to at least one dynamic library.
792 // Rather than be a source of test cases for glibc, disable dynamic linking
793 // the same way that gcc would.
795 // Exception: on OS X, programs such as Shark only work with dynamic
796 // binaries, so leave it enabled on OS X (Mach-O) binaries.
797 // Also leave it enabled on Solaris which doesn't support
798 // statically linked binaries.
799 if ctxt.BuildMode == BuildModeExe {
800 if havedynamic == 0 && ctxt.HeadType != objabi.Hdarwin && ctxt.HeadType != objabi.Hsolaris {
805 if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && buildcfg.GOOS != "aix" {
806 toc := ctxt.loader.LookupOrCreateSym(".TOC.", 0)
807 sb := ctxt.loader.MakeSymbolUpdater(toc)
808 sb.SetType(sym.SDYNIMPORT)
811 // The Android Q linker started to complain about underalignment of the our TLS
812 // section. We don't actually use the section on android, so don't
814 if buildcfg.GOOS != "android" {
815 tlsg := ctxt.loader.LookupOrCreateSym("runtime.tlsg", 0)
816 sb := ctxt.loader.MakeSymbolUpdater(tlsg)
818 // runtime.tlsg is used for external linking on platforms that do not define
819 // a variable to hold g in assembly (currently only intel).
821 sb.SetType(sym.STLSBSS)
822 sb.SetSize(int64(ctxt.Arch.PtrSize))
823 } else if sb.Type() != sym.SDYNIMPORT {
824 Errorf(nil, "runtime declared tlsg variable %v", sb.Type())
826 ctxt.loader.SetAttrReachable(tlsg, true)
830 var moduledata loader.Sym
831 var mdsb *loader.SymbolBuilder
832 if ctxt.BuildMode == BuildModePlugin {
833 moduledata = ctxt.loader.LookupOrCreateSym("local.pluginmoduledata", 0)
834 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
835 ctxt.loader.SetAttrLocal(moduledata, true)
837 moduledata = ctxt.loader.LookupOrCreateSym("runtime.firstmoduledata", 0)
838 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
840 if mdsb.Type() != 0 && mdsb.Type() != sym.SDYNIMPORT {
841 // If the module (toolchain-speak for "executable or shared
842 // library") we are linking contains the runtime package, it
843 // will define the runtime.firstmoduledata symbol and we
844 // truncate it back to 0 bytes so we can define its entire
845 // contents in symtab.go:symtab().
848 // In addition, on ARM, the runtime depends on the linker
849 // recording the value of GOARM.
850 if ctxt.Arch.Family == sys.ARM {
851 goarm := ctxt.loader.LookupOrCreateSym("runtime.goarm", 0)
852 sb := ctxt.loader.MakeSymbolUpdater(goarm)
853 sb.SetType(sym.SDATA)
855 sb.AddUint8(uint8(buildcfg.GOARM))
858 // Set runtime.disableMemoryProfiling bool if
859 // runtime.MemProfile is not retained in the binary after
860 // deadcode (and we're not dynamically linking).
861 memProfile := ctxt.loader.Lookup("runtime.MemProfile", abiInternalVer)
862 if memProfile != 0 && !ctxt.loader.AttrReachable(memProfile) && !ctxt.DynlinkingGo() {
863 memProfSym := ctxt.loader.LookupOrCreateSym("runtime.disableMemoryProfiling", 0)
864 sb := ctxt.loader.MakeSymbolUpdater(memProfSym)
865 sb.SetType(sym.SDATA)
867 sb.AddUint8(1) // true bool
870 // If OTOH the module does not contain the runtime package,
871 // create a local symbol for the moduledata.
872 moduledata = ctxt.loader.LookupOrCreateSym("local.moduledata", 0)
873 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
874 ctxt.loader.SetAttrLocal(moduledata, true)
876 // In all cases way we mark the moduledata as noptrdata to hide it from
878 mdsb.SetType(sym.SNOPTRDATA)
879 ctxt.loader.SetAttrReachable(moduledata, true)
880 ctxt.Moduledata = moduledata
882 if ctxt.Arch == sys.Arch386 && ctxt.HeadType != objabi.Hwindows {
883 if (ctxt.BuildMode == BuildModeCArchive && ctxt.IsELF) || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE || ctxt.DynlinkingGo() {
884 got := ctxt.loader.LookupOrCreateSym("_GLOBAL_OFFSET_TABLE_", 0)
885 sb := ctxt.loader.MakeSymbolUpdater(got)
886 sb.SetType(sym.SDYNIMPORT)
887 ctxt.loader.SetAttrReachable(got, true)
891 // DWARF-gen and other phases require that the unit Textp slices
892 // be populated, so that it can walk the functions in each unit.
893 // Call into the loader to do this (requires that we collect the
894 // set of internal libraries first). NB: might be simpler if we
895 // moved isRuntimeDepPkg to cmd/internal and then did the test in
896 // loader.AssignTextSymbolOrder.
897 ctxt.Library = postorder(ctxt.Library)
899 for _, lib := range ctxt.Library {
900 intlibs = append(intlibs, isRuntimeDepPkg(lib.Pkg))
902 ctxt.Textp = ctxt.loader.AssignTextSymbolOrder(ctxt.Library, intlibs, ctxt.Textp)
905 // mangleTypeSym shortens the names of symbols that represent Go types
906 // if they are visible in the symbol table.
908 // As the names of these symbols are derived from the string of
909 // the type, they can run to many kilobytes long. So we shorten
910 // them using a SHA-1 when the name appears in the final binary.
911 // This also removes characters that upset external linkers.
913 // These are the symbols that begin with the prefix 'type.' and
914 // contain run-time type information used by the runtime and reflect
915 // packages. All Go binaries contain these symbols, but only
916 // those programs loaded dynamically in multiple parts need these
917 // symbols to have entries in the symbol table.
918 func (ctxt *Link) mangleTypeSym() {
919 if ctxt.BuildMode != BuildModeShared && !ctxt.linkShared && ctxt.BuildMode != BuildModePlugin && !ctxt.CanUsePlugins() {
924 for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
925 if !ldr.AttrReachable(s) && !ctxt.linkShared {
926 // If -linkshared, the GCProg generation code may need to reach
927 // out to the shared library for the type descriptor's data, even
928 // the type descriptor itself is not actually needed at run time
929 // (therefore not reachable). We still need to mangle its name,
930 // so it is consistent with the one stored in the shared library.
933 name := ldr.SymName(s)
934 newName := typeSymbolMangle(name)
936 ldr.SetSymExtname(s, newName)
938 // When linking against a shared library, the Go object file may
939 // have reference to the original symbol name whereas the shared
940 // library provides a symbol with the mangled name. We need to
941 // copy the payload of mangled to original.
942 // XXX maybe there is a better way to do this.
943 dup := ldr.Lookup(newName, ldr.SymVersion(s))
946 dt := ldr.SymType(dup)
947 if st == sym.Sxxx && dt != sym.Sxxx {
955 // typeSymbolMangle mangles the given symbol name into something shorter.
957 // Keep the type:. prefix, which parts of the linker (like the
958 // DWARF generator) know means the symbol is not decodable.
959 // Leave type:runtime. symbols alone, because other parts of
960 // the linker manipulates them.
961 func typeSymbolMangle(name string) string {
962 if !strings.HasPrefix(name, "type:") {
965 if strings.HasPrefix(name, "type:runtime.") {
968 if len(name) <= 14 && !strings.Contains(name, "@") { // Issue 19529
971 hash := notsha256.Sum256([]byte(name))
976 return prefix + base64.StdEncoding.EncodeToString(hash[:6])
980 * look for the next file in an archive.
981 * adapted from libmach.
983 func nextar(bp *bio.Reader, off int64, a *ArHdr) int64 {
988 var buf [SAR_HDR]byte
989 if n, err := io.ReadFull(bp, buf[:]); err != nil {
990 if n == 0 && err != io.EOF {
996 a.name = artrim(buf[0:16])
997 a.date = artrim(buf[16:28])
998 a.uid = artrim(buf[28:34])
999 a.gid = artrim(buf[34:40])
1000 a.mode = artrim(buf[40:48])
1001 a.size = artrim(buf[48:58])
1002 a.fmag = artrim(buf[58:60])
1004 arsize := atolwhex(a.size)
1008 return arsize + SAR_HDR
1011 func loadobjfile(ctxt *Link, lib *sym.Library) {
1012 pkg := objabi.PathToPrefix(lib.Pkg)
1014 if ctxt.Debugvlog > 1 {
1015 ctxt.Logf("ldobj: %s (%s)\n", lib.File, pkg)
1017 f, err := bio.Open(lib.File)
1019 Exitf("cannot open file %s: %v", lib.File, err)
1023 if pkg == "main" && !lib.Main {
1024 Exitf("%s: not package main", lib.File)
1028 for i := 0; i < len(ARMAG); i++ {
1029 if c, err := f.ReadByte(); err == nil && c == ARMAG[i] {
1033 /* load it as a regular file */
1034 l := f.MustSeek(0, 2)
1036 ldobj(ctxt, f, lib, l, lib.File, lib.File)
1041 * load all the object files from the archive now.
1042 * this gives us sequential file access and keeps us
1043 * from needing to come back later to pick up more
1044 * objects. it breaks the usual C archive model, but
1045 * this is Go, not C. the common case in Go is that
1046 * we need to load all the objects, and then we throw away
1047 * the individual symbols that are unused.
1049 * loading every object will also make it possible to
1050 * load foreign objects not referenced by __.PKGDEF.
1055 l := nextar(f, off, &arhdr)
1060 Exitf("%s: malformed archive", lib.File)
1064 // __.PKGDEF isn't a real Go object file, and it's
1065 // absent in -linkobj builds anyway. Skipping it
1066 // ensures consistency between -linkobj and normal
1068 if arhdr.name == pkgdef {
1072 if arhdr.name == "dynimportfail" {
1073 dynimportfail = append(dynimportfail, lib.Pkg)
1076 // Skip other special (non-object-file) sections that
1077 // build tools may have added. Such sections must have
1078 // short names so that the suffix is not truncated.
1079 if len(arhdr.name) < 16 {
1080 if ext := filepath.Ext(arhdr.name); ext != ".o" && ext != ".syso" {
1085 pname := fmt.Sprintf("%s(%s)", lib.File, arhdr.name)
1086 l = atolwhex(arhdr.size)
1087 ldobj(ctxt, f, lib, l, pname, lib.File)
1091 type Hostobj struct {
1092 ld func(*Link, *bio.Reader, string, int64, string)
1100 var hostobj []Hostobj
1102 // These packages can use internal linking mode.
1103 // Others trigger external mode.
1104 var internalpkg = []string{
1105 "crypto/internal/boring",
1106 "crypto/internal/boring/syso",
1112 "runtime/race/internal/amd64v1",
1113 "runtime/race/internal/amd64v3",
1118 func ldhostobj(ld func(*Link, *bio.Reader, string, int64, string), headType objabi.HeadType, f *bio.Reader, pkg string, length int64, pn string, file string) *Hostobj {
1120 for _, intpkg := range internalpkg {
1127 // DragonFly declares errno with __thread, which results in a symbol
1128 // type of R_386_TLS_GD or R_X86_64_TLSGD. The Go linker does not
1129 // currently know how to handle TLS relocations, hence we have to
1130 // force external linking for any libraries that link in code that
1131 // uses errno. This can be removed if the Go linker ever supports
1132 // these relocation types.
1133 if headType == objabi.Hdragonfly {
1134 if pkg == "net" || pkg == "os/user" {
1143 hostobj = append(hostobj, Hostobj{})
1144 h := &hostobj[len(hostobj)-1]
1154 func hostobjs(ctxt *Link) {
1155 if ctxt.LinkMode != LinkInternal {
1160 for i := 0; i < len(hostobj); i++ {
1162 f, err := bio.Open(h.file)
1164 Exitf("cannot reopen %s: %v", h.pn, err)
1166 f.MustSeek(h.off, 0)
1168 Errorf(nil, "%s: unrecognized object file format", h.pn)
1171 h.ld(ctxt, f, h.pkg, h.length, h.pn)
1172 if *flagCaptureHostObjs != "" {
1179 func hostlinksetup(ctxt *Link) {
1180 if ctxt.LinkMode != LinkExternal {
1184 // For external link, record that we need to tell the external linker -s,
1185 // and turn off -s internally: the external linker needs the symbol
1186 // information for its final link.
1190 // create temporary directory and arrange cleanup
1191 if *flagTmpdir == "" {
1192 dir, err := os.MkdirTemp("", "go-link-")
1199 os.RemoveAll(*flagTmpdir)
1203 // change our output to temporary object file
1204 if err := ctxt.Out.Close(); err != nil {
1205 Exitf("error closing output file")
1207 mayberemoveoutfile()
1209 p := filepath.Join(*flagTmpdir, "go.o")
1210 if err := ctxt.Out.Open(p); err != nil {
1211 Exitf("cannot create %s: %v", p, err)
1215 // hostobjCopy creates a copy of the object files in hostobj in a
1216 // temporary directory.
1217 func hostobjCopy() (paths []string) {
1218 var wg sync.WaitGroup
1219 sema := make(chan struct{}, runtime.NumCPU()) // limit open file descriptors
1220 for i, h := range hostobj {
1222 dst := filepath.Join(*flagTmpdir, fmt.Sprintf("%06d.o", i))
1223 paths = append(paths, dst)
1232 f, err := os.Open(h.file)
1234 Exitf("cannot reopen %s: %v", h.pn, err)
1237 if _, err := f.Seek(h.off, 0); err != nil {
1238 Exitf("cannot seek %s: %v", h.pn, err)
1241 w, err := os.Create(dst)
1243 Exitf("cannot create %s: %v", dst, err)
1245 if _, err := io.CopyN(w, f, h.length); err != nil {
1246 Exitf("cannot write %s: %v", dst, err)
1248 if err := w.Close(); err != nil {
1249 Exitf("cannot close %s: %v", dst, err)
1257 // writeGDBLinkerScript creates gcc linker script file in temp
1258 // directory. writeGDBLinkerScript returns created file path.
1259 // The script is used to work around gcc bug
1260 // (see https://golang.org/issue/20183 for details).
1261 func writeGDBLinkerScript() string {
1262 name := "fix_debug_gdb_scripts.ld"
1263 path := filepath.Join(*flagTmpdir, name)
1266 .debug_gdb_scripts BLOCK(__section_alignment__) (NOLOAD) :
1268 *(.debug_gdb_scripts)
1271 INSERT AFTER .debug_types;
1273 err := os.WriteFile(path, []byte(src), 0666)
1275 Errorf(nil, "WriteFile %s failed: %v", name, err)
1280 // archive builds a .a archive from the hostobj object files.
1281 func (ctxt *Link) archive() {
1282 if ctxt.BuildMode != BuildModeCArchive {
1288 if *flagExtar == "" {
1292 mayberemoveoutfile()
1294 // Force the buffer to flush here so that external
1295 // tools will see a complete file.
1296 if err := ctxt.Out.Close(); err != nil {
1297 Exitf("error closing %v", *flagOutfile)
1300 argv := []string{*flagExtar, "-q", "-c", "-s"}
1301 if ctxt.HeadType == objabi.Haix {
1302 argv = append(argv, "-X64")
1304 argv = append(argv, *flagOutfile)
1305 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1306 argv = append(argv, hostobjCopy()...)
1308 if ctxt.Debugvlog != 0 {
1309 ctxt.Logf("archive: %s\n", strings.Join(argv, " "))
1312 // If supported, use syscall.Exec() to invoke the archive command,
1313 // which should be the final remaining step needed for the link.
1314 // This will reduce peak RSS for the link (and speed up linking of
1315 // large applications), since when the archive command runs we
1316 // won't be holding onto all of the linker's live memory.
1317 if syscallExecSupported && !ownTmpDir {
1319 ctxt.execArchive(argv)
1320 panic("should not get here")
1323 // Otherwise invoke 'ar' in the usual way (fork + exec).
1324 if out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput(); err != nil {
1325 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1329 func (ctxt *Link) hostlink() {
1330 if ctxt.LinkMode != LinkExternal || nerrors > 0 {
1333 if ctxt.BuildMode == BuildModeCArchive {
1338 argv = append(argv, ctxt.extld()...)
1339 argv = append(argv, hostlinkArchArgs(ctxt.Arch)...)
1341 if *FlagS || debug_s {
1342 if ctxt.HeadType == objabi.Hdarwin {
1343 // Recent versions of macOS print
1344 // ld: warning: option -s is obsolete and being ignored
1345 // so do not pass any arguments.
1347 argv = append(argv, "-s")
1351 // On darwin, whether to combine DWARF into executable.
1352 // Only macOS supports unmapped segments such as our __DWARF segment.
1353 combineDwarf := ctxt.IsDarwin() && !*FlagS && !*FlagW && !debug_s && machoPlatform == PLATFORM_MACOS
1355 switch ctxt.HeadType {
1356 case objabi.Hdarwin:
1358 // Leave room for DWARF combining.
1359 // -headerpad is incompatible with -fembed-bitcode.
1360 argv = append(argv, "-Wl,-headerpad,1144")
1362 if ctxt.DynlinkingGo() && buildcfg.GOOS != "ios" {
1363 // -flat_namespace is deprecated on iOS.
1364 // It is useful for supporting plugins. We don't support plugins on iOS.
1365 // -flat_namespace may cause the dynamic linker to hang at forkExec when
1366 // resolving a lazy binding. See issue 38824.
1367 // Force eager resolution to work around.
1368 argv = append(argv, "-Wl,-flat_namespace", "-Wl,-bind_at_load")
1371 argv = append(argv, "-Wl,-S") // suppress STAB (symbolic debugging) symbols
1373 case objabi.Hopenbsd:
1374 argv = append(argv, "-Wl,-nopie")
1375 argv = append(argv, "-pthread")
1376 case objabi.Hwindows:
1378 argv = append(argv, "-mwindows")
1380 argv = append(argv, "-mconsole")
1382 // Mark as having awareness of terminal services, to avoid
1383 // ancient compatibility hacks.
1384 argv = append(argv, "-Wl,--tsaware")
1387 argv = append(argv, "-Wl,--nxcompat")
1389 argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", PeMinimumTargetMajorVersion))
1390 argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", PeMinimumTargetMinorVersion))
1391 argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", PeMinimumTargetMajorVersion))
1392 argv = append(argv, fmt.Sprintf("-Wl,--minor-subsystem-version=%d", PeMinimumTargetMinorVersion))
1394 argv = append(argv, "-pthread")
1395 // prevent ld to reorder .text functions to keep the same
1396 // first/last functions for moduledata.
1397 argv = append(argv, "-Wl,-bnoobjreorder")
1398 // mcmodel=large is needed for every gcc generated files, but
1399 // ld still need -bbigtoc in order to allow larger TOC.
1400 argv = append(argv, "-mcmodel=large")
1401 argv = append(argv, "-Wl,-bbigtoc")
1404 // Enable/disable ASLR on Windows.
1405 addASLRargs := func(argv []string, val bool) []string {
1406 // Old/ancient versions of GCC support "--dynamicbase" and
1407 // "--high-entropy-va" but don't enable it by default. In
1408 // addition, they don't accept "--disable-dynamicbase" or
1409 // "--no-dynamicbase", so the only way to disable ASLR is to
1410 // not pass any flags at all.
1412 // More modern versions of GCC (and also clang) enable ASLR
1413 // by default. With these compilers, however you can turn it
1414 // off if you want using "--disable-dynamicbase" or
1415 // "--no-dynamicbase".
1417 // The strategy below is to try using "--disable-dynamicbase";
1418 // if this succeeds, then assume we're working with more
1419 // modern compilers and act accordingly. If it fails, assume
1420 // an ancient compiler with ancient defaults.
1423 dbon := "--dynamicbase"
1424 heon := "--high-entropy-va"
1425 dboff := "--disable-dynamicbase"
1426 heoff := "--disable-high-entropy-va"
1431 // Test to see whether "--disable-dynamicbase" works.
1432 newer := linkerFlagSupported(ctxt.Arch, argv[0], "", "-Wl,"+dboff)
1434 // Newer compiler, which supports both on/off options.
1438 // older toolchain: we have to say nothing in order to
1439 // get a no-ASLR binary.
1445 argv = append(argv, "-Wl,"+dbopt)
1447 // enable high-entropy ASLR on 64-bit.
1448 if ctxt.Arch.PtrSize >= 8 && heopt != "" {
1449 argv = append(argv, "-Wl,"+heopt)
1454 switch ctxt.BuildMode {
1456 if ctxt.HeadType == objabi.Hdarwin {
1457 if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() {
1458 argv = append(argv, "-Wl,-no_pie")
1461 if *flagRace && ctxt.HeadType == objabi.Hwindows {
1462 // Current windows/amd64 race detector tsan support
1463 // library can't handle PIE mode (see #53539 for more details).
1464 // For now, explicitly disable PIE (since some compilers
1465 // default to it) if -race is in effect.
1466 argv = addASLRargs(argv, false)
1469 switch ctxt.HeadType {
1470 case objabi.Hdarwin, objabi.Haix:
1471 case objabi.Hwindows:
1472 if *flagAslr && *flagRace {
1473 // Current windows/amd64 race detector tsan support
1474 // library can't handle PIE mode (see #53539 for more details).
1475 // Disable alsr if -race in effect.
1478 argv = addASLRargs(argv, *flagAslr)
1481 if ctxt.UseRelro() {
1482 argv = append(argv, "-Wl,-z,relro")
1484 argv = append(argv, "-pie")
1486 case BuildModeCShared:
1487 if ctxt.HeadType == objabi.Hdarwin {
1488 argv = append(argv, "-dynamiclib")
1490 if ctxt.UseRelro() {
1491 argv = append(argv, "-Wl,-z,relro")
1493 argv = append(argv, "-shared")
1494 if ctxt.HeadType == objabi.Hwindows {
1495 argv = addASLRargs(argv, *flagAslr)
1497 // Pass -z nodelete to mark the shared library as
1498 // non-closeable: a dlclose will do nothing.
1499 argv = append(argv, "-Wl,-z,nodelete")
1500 // Only pass Bsymbolic on non-Windows.
1501 argv = append(argv, "-Wl,-Bsymbolic")
1504 case BuildModeShared:
1505 if ctxt.UseRelro() {
1506 argv = append(argv, "-Wl,-z,relro")
1508 argv = append(argv, "-shared")
1509 case BuildModePlugin:
1510 if ctxt.HeadType == objabi.Hdarwin {
1511 argv = append(argv, "-dynamiclib")
1513 if ctxt.UseRelro() {
1514 argv = append(argv, "-Wl,-z,relro")
1516 argv = append(argv, "-shared")
1520 var altLinker string
1521 if ctxt.IsELF && ctxt.DynlinkingGo() {
1522 // We force all symbol resolution to be done at program startup
1523 // because lazy PLT resolution can use large amounts of stack at
1524 // times we cannot allow it to do so.
1525 argv = append(argv, "-Wl,-z,now")
1527 // Do not let the host linker generate COPY relocations. These
1528 // can move symbols out of sections that rely on stable offsets
1529 // from the beginning of the section (like sym.STYPE).
1530 argv = append(argv, "-Wl,-z,nocopyreloc")
1532 if buildcfg.GOOS == "android" {
1533 // Use lld to avoid errors from default linker (issue #38838)
1537 if ctxt.Arch.InFamily(sys.ARM, sys.ARM64) && buildcfg.GOOS == "linux" {
1538 // On ARM, the GNU linker will generate COPY relocations
1539 // even with -znocopyreloc set.
1540 // https://sourceware.org/bugzilla/show_bug.cgi?id=19962
1542 // On ARM64, the GNU linker will fail instead of
1543 // generating COPY relocations.
1545 // In both cases, switch to gold.
1548 // If gold is not installed, gcc will silently switch
1549 // back to ld.bfd. So we parse the version information
1550 // and provide a useful error if gold is missing.
1551 name, args := flagExtld[0], flagExtld[1:]
1552 args = append(args, "-fuse-ld=gold", "-Wl,--version")
1553 cmd := exec.Command(name, args...)
1554 if out, err := cmd.CombinedOutput(); err == nil {
1555 if !bytes.Contains(out, []byte("GNU gold")) {
1556 log.Fatalf("ARM external linker must be gold (issue #15696), but is not: %s", out)
1561 if ctxt.Arch.Family == sys.ARM64 && buildcfg.GOOS == "freebsd" {
1562 // Switch to ld.bfd on freebsd/arm64.
1565 // Provide a useful error if ld.bfd is missing.
1566 name, args := flagExtld[0], flagExtld[1:]
1567 args = append(args, "-fuse-ld=bfd", "-Wl,--version")
1568 cmd := exec.Command(name, args...)
1569 if out, err := cmd.CombinedOutput(); err == nil {
1570 if !bytes.Contains(out, []byte("GNU ld")) {
1571 log.Fatalf("ARM64 external linker must be ld.bfd (issue #35197), please install devel/binutils")
1575 if altLinker != "" {
1576 argv = append(argv, "-fuse-ld="+altLinker)
1579 if ctxt.IsELF && len(buildinfo) > 0 {
1580 argv = append(argv, fmt.Sprintf("-Wl,--build-id=0x%x", buildinfo))
1583 // On Windows, given -o foo, GCC will append ".exe" to produce
1584 // "foo.exe". We have decided that we want to honor the -o
1585 // option. To make this work, we append a '.' so that GCC
1586 // will decide that the file already has an extension. We
1587 // only want to do this when producing a Windows output file
1588 // on a Windows host.
1589 outopt := *flagOutfile
1590 if buildcfg.GOOS == "windows" && runtime.GOOS == "windows" && filepath.Ext(outopt) == "" {
1593 argv = append(argv, "-o")
1594 argv = append(argv, outopt)
1596 if rpath.val != "" {
1597 argv = append(argv, fmt.Sprintf("-Wl,-rpath,%s", rpath.val))
1600 if *flagInterpreter != "" {
1601 // Many linkers support both -I and the --dynamic-linker flags
1602 // to set the ELF interpreter, but lld only supports
1603 // --dynamic-linker so prefer that (ld on very old Solaris only
1604 // supports -I but that seems less important).
1605 argv = append(argv, fmt.Sprintf("-Wl,--dynamic-linker,%s", *flagInterpreter))
1608 // Force global symbols to be exported for dlopen, etc.
1610 argv = append(argv, "-rdynamic")
1612 if ctxt.HeadType == objabi.Haix {
1613 fileName := xcoffCreateExportFile(ctxt)
1614 argv = append(argv, "-Wl,-bE:"+fileName)
1617 const unusedArguments = "-Qunused-arguments"
1618 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, unusedArguments) {
1619 argv = append(argv, unusedArguments)
1622 if ctxt.IsWindows() {
1623 // Suppress generation of the PE file header timestamp,
1624 // so as to avoid spurious build ID differences between
1625 // linked binaries that are otherwise identical other than
1626 // the date/time they were linked.
1627 const noTimeStamp = "-Wl,--no-insert-timestamp"
1628 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, noTimeStamp) {
1629 argv = append(argv, noTimeStamp)
1633 const compressDWARF = "-Wl,--compress-debug-sections=zlib"
1634 if ctxt.compressDWARF && linkerFlagSupported(ctxt.Arch, argv[0], altLinker, compressDWARF) {
1635 argv = append(argv, compressDWARF)
1638 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1639 argv = append(argv, hostobjCopy()...)
1640 if ctxt.HeadType == objabi.Haix {
1641 // We want to have C files after Go files to remove
1642 // trampolines csects made by ld.
1643 argv = append(argv, "-nostartfiles")
1644 argv = append(argv, "/lib/crt0_64.o")
1646 extld := ctxt.extld()
1647 name, args := extld[0], extld[1:]
1648 // Get starting files.
1649 getPathFile := func(file string) string {
1650 args := append(args, "-maix64", "--print-file-name="+file)
1651 out, err := exec.Command(name, args...).CombinedOutput()
1653 log.Fatalf("running %s failed: %v\n%s", extld, err, out)
1655 return strings.Trim(string(out), "\n")
1657 // Since GCC version 11, the 64-bit version of GCC starting files
1658 // are now suffixed by "_64". Even under "-maix64" multilib directory
1659 // "crtcxa.o" is 32-bit.
1660 crtcxa := getPathFile("crtcxa_64.o")
1661 if !filepath.IsAbs(crtcxa) {
1662 crtcxa = getPathFile("crtcxa.o")
1664 crtdbase := getPathFile("crtdbase_64.o")
1665 if !filepath.IsAbs(crtdbase) {
1666 crtdbase = getPathFile("crtdbase.o")
1668 argv = append(argv, crtcxa)
1669 argv = append(argv, crtdbase)
1672 if ctxt.linkShared {
1673 seenDirs := make(map[string]bool)
1674 seenLibs := make(map[string]bool)
1675 addshlib := func(path string) {
1676 dir, base := filepath.Split(path)
1678 argv = append(argv, "-L"+dir)
1680 argv = append(argv, "-Wl,-rpath="+dir)
1682 seenDirs[dir] = true
1684 base = strings.TrimSuffix(base, ".so")
1685 base = strings.TrimPrefix(base, "lib")
1686 if !seenLibs[base] {
1687 argv = append(argv, "-l"+base)
1688 seenLibs[base] = true
1691 for _, shlib := range ctxt.Shlibs {
1692 addshlib(shlib.Path)
1693 for _, dep := range shlib.Deps {
1697 libpath := findshlib(ctxt, dep)
1705 // clang, unlike GCC, passes -rdynamic to the linker
1706 // even when linking with -static, causing a linker
1707 // error when using GNU ld. So take out -rdynamic if
1708 // we added it. We do it in this order, rather than
1709 // only adding -rdynamic later, so that -extldflags
1710 // can override -rdynamic without using -static.
1711 // Similarly for -Wl,--dynamic-linker.
1712 checkStatic := func(arg string) {
1713 if ctxt.IsELF && arg == "-static" {
1714 for i := range argv {
1715 if argv[i] == "-rdynamic" || strings.HasPrefix(argv[i], "-Wl,--dynamic-linker,") {
1722 for _, p := range ldflag {
1723 argv = append(argv, p)
1727 // When building a program with the default -buildmode=exe the
1728 // gc compiler generates code requires DT_TEXTREL in a
1729 // position independent executable (PIE). On systems where the
1730 // toolchain creates PIEs by default, and where DT_TEXTREL
1731 // does not work, the resulting programs will not run. See
1732 // issue #17847. To avoid this problem pass -no-pie to the
1733 // toolchain if it is supported.
1734 if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared && !(ctxt.IsDarwin() && ctxt.IsARM64()) {
1735 // GCC uses -no-pie, clang uses -nopie.
1736 for _, nopie := range []string{"-no-pie", "-nopie"} {
1737 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, nopie) {
1738 argv = append(argv, nopie)
1744 for _, p := range flagExtldflags {
1745 argv = append(argv, p)
1748 if ctxt.HeadType == objabi.Hwindows {
1749 // Determine which linker we're using. Add in the extldflags in
1750 // case used has specified "-fuse-ld=...".
1751 extld := ctxt.extld()
1752 name, args := extld[0], extld[1:]
1753 args = append(args, flagExtldflags...)
1754 args = append(args, "-Wl,--version")
1755 cmd := exec.Command(name, args...)
1757 if out, err := cmd.CombinedOutput(); err == nil {
1758 if bytes.Contains(out, []byte("LLD ")) {
1763 // use gcc linker script to work around gcc bug
1764 // (see https://golang.org/issue/20183 for details).
1766 p := writeGDBLinkerScript()
1767 argv = append(argv, "-Wl,-T,"+p)
1770 if p := ctxt.findLibPath("libsynchronization.a"); p != "libsynchronization.a" {
1771 argv = append(argv, "-lsynchronization")
1774 // libmingw32 and libmingwex have some inter-dependencies,
1775 // so must use linker groups.
1776 argv = append(argv, "-Wl,--start-group", "-lmingwex", "-lmingw32", "-Wl,--end-group")
1777 argv = append(argv, peimporteddlls()...)
1780 if ctxt.Debugvlog != 0 {
1781 ctxt.Logf("host link:")
1782 for _, v := range argv {
1788 out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput()
1790 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1793 // Filter out useless linker warnings caused by bugs outside Go.
1794 // See also cmd/go/internal/work/exec.go's gccld method.
1797 for _, line := range bytes.SplitAfter(out, []byte("\n")) {
1798 // golang.org/issue/26073 - Apple Xcode bug
1799 if bytes.Contains(line, []byte("ld: warning: text-based stub file")) {
1808 // Remove TOC overflow warning on AIX.
1809 if bytes.Contains(line, []byte("ld: 0711-783")) {
1814 save = append(save, line)
1816 out = bytes.Join(save, nil)
1819 // always print external output even if the command is successful, so that we don't
1820 // swallow linker warnings (see https://golang.org/issue/17935).
1821 if ctxt.IsDarwin() && ctxt.IsAMD64() {
1822 const noPieWarning = "ld: warning: -no_pie is deprecated when targeting new OS versions\n"
1823 if i := bytes.Index(out, []byte(noPieWarning)); i >= 0 {
1824 // swallow -no_pie deprecation warning, issue 54482
1825 out = append(out[:i], out[i+len(noPieWarning):]...)
1828 ctxt.Logf("%s", out)
1832 // Find "dsymutils" and "strip" tools using CC --print-prog-name.
1834 cc = append(cc, ctxt.extld()...)
1835 cc = append(cc, hostlinkArchArgs(ctxt.Arch)...)
1836 cc = append(cc, "--print-prog-name", "dsymutil")
1837 out, err := exec.Command(cc[0], cc[1:]...).CombinedOutput()
1839 Exitf("%s: finding dsymutil failed: %v\n%s", os.Args[0], err, out)
1841 dsymutilCmd := strings.TrimSuffix(string(out), "\n")
1843 cc[len(cc)-1] = "strip"
1844 out, err = exec.Command(cc[0], cc[1:]...).CombinedOutput()
1846 Exitf("%s: finding strip failed: %v\n%s", os.Args[0], err, out)
1848 stripCmd := strings.TrimSuffix(string(out), "\n")
1850 dsym := filepath.Join(*flagTmpdir, "go.dwarf")
1851 if out, err := exec.Command(dsymutilCmd, "-f", *flagOutfile, "-o", dsym).CombinedOutput(); err != nil {
1852 Exitf("%s: running dsymutil failed: %v\n%s", os.Args[0], err, out)
1854 // Remove STAB (symbolic debugging) symbols after we are done with them (by dsymutil).
1855 // They contain temporary file paths and make the build not reproducible.
1856 if out, err := exec.Command(stripCmd, "-S", *flagOutfile).CombinedOutput(); err != nil {
1857 Exitf("%s: running strip failed: %v\n%s", os.Args[0], err, out)
1859 // Skip combining if `dsymutil` didn't generate a file. See #11994.
1860 if _, err := os.Stat(dsym); os.IsNotExist(err) {
1863 // For os.Rename to work reliably, must be in same directory as outfile.
1864 combinedOutput := *flagOutfile + "~"
1865 exef, err := os.Open(*flagOutfile)
1867 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1870 exem, err := macho.NewFile(exef)
1872 Exitf("%s: parsing Mach-O header failed: %v", os.Args[0], err)
1874 if err := machoCombineDwarf(ctxt, exef, exem, dsym, combinedOutput); err != nil {
1875 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1877 os.Remove(*flagOutfile)
1878 if err := os.Rename(combinedOutput, *flagOutfile); err != nil {
1879 Exitf("%s: %v", os.Args[0], err)
1882 if ctxt.NeedCodeSign() {
1883 err := machoCodeSign(ctxt, *flagOutfile)
1885 Exitf("%s: code signing failed: %v", os.Args[0], err)
1890 var createTrivialCOnce sync.Once
1892 func linkerFlagSupported(arch *sys.Arch, linker, altLinker, flag string) bool {
1893 createTrivialCOnce.Do(func() {
1894 src := filepath.Join(*flagTmpdir, "trivial.c")
1895 if err := os.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
1896 Errorf(nil, "WriteFile trivial.c failed: %v", err)
1900 flagsWithNextArgSkip := []string{
1909 flagsWithNextArgKeep := []string{
1915 prefixesToKeep := []string{
1926 flags := hostlinkArchArgs(arch)
1929 for _, f := range append(flagExtldflags, ldflag...) {
1931 flags = append(flags, f)
1935 } else if f == "" || f[0] != '-' {
1936 } else if contains(flagsWithNextArgSkip, f) {
1938 } else if contains(flagsWithNextArgKeep, f) {
1939 flags = append(flags, f)
1942 for _, p := range prefixesToKeep {
1943 if strings.HasPrefix(f, p) {
1944 flags = append(flags, f)
1951 if altLinker != "" {
1952 flags = append(flags, "-fuse-ld="+altLinker)
1954 flags = append(flags, flag, "trivial.c")
1956 cmd := exec.Command(linker, flags...)
1957 cmd.Dir = *flagTmpdir
1958 cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
1959 out, err := cmd.CombinedOutput()
1960 // GCC says "unrecognized command line option ‘-no-pie’"
1961 // clang says "unknown argument: '-no-pie'"
1962 return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
1965 // hostlinkArchArgs returns arguments to pass to the external linker
1966 // based on the architecture.
1967 func hostlinkArchArgs(arch *sys.Arch) []string {
1968 switch arch.Family {
1970 return []string{"-m32"}
1972 if buildcfg.GOOS == "darwin" {
1973 return []string{"-arch", "x86_64", "-m64"}
1975 return []string{"-m64"}
1977 return []string{"-m64"}
1979 return []string{"-marm"}
1981 if buildcfg.GOOS == "darwin" {
1982 return []string{"-arch", "arm64"}
1985 return []string{"-mabi=lp64d"}
1987 return []string{"-mabi=64"}
1989 return []string{"-mabi=32"}
1991 if buildcfg.GOOS == "aix" {
1992 return []string{"-maix64"}
1994 return []string{"-m64"}
2001 var wantHdr = objabi.HeaderString()
2003 // ldobj loads an input object. If it is a host object (an object
2004 // compiled by a non-Go compiler) it returns the Hostobj pointer. If
2005 // it is a Go object, it returns nil.
2006 func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string, file string) *Hostobj {
2007 pkg := objabi.PathToPrefix(lib.Pkg)
2009 eof := f.Offset() + length
2015 f.MustSeek(start, 0)
2017 unit := &sym.CompilationUnit{Lib: lib}
2018 lib.Units = append(lib.Units, unit)
2020 magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
2021 if magic == 0x7f454c46 { // \x7F E L F
2022 ldelf := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2023 textp, flags, err := loadelf.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn, ehdr.Flags)
2025 Errorf(nil, "%v", err)
2029 ctxt.Textp = append(ctxt.Textp, textp...)
2031 return ldhostobj(ldelf, ctxt.HeadType, f, pkg, length, pn, file)
2034 if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
2035 ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2036 textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2038 Errorf(nil, "%v", err)
2041 ctxt.Textp = append(ctxt.Textp, textp...)
2043 return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
2051 ldpe := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2052 textp, rsrc, err := loadpe.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2054 Errorf(nil, "%v", err)
2058 setpersrc(ctxt, rsrc)
2060 ctxt.Textp = append(ctxt.Textp, textp...)
2062 return ldhostobj(ldpe, ctxt.HeadType, f, pkg, length, pn, file)
2065 if c1 == 0x01 && (c2 == 0xD7 || c2 == 0xF7) {
2066 ldxcoff := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2067 textp, err := loadxcoff.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2069 Errorf(nil, "%v", err)
2072 ctxt.Textp = append(ctxt.Textp, textp...)
2074 return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
2077 if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
2078 // An unrecognized object is just passed to the external linker.
2079 // If we try to read symbols from this object, we will
2080 // report an error at that time.
2081 unknownObjFormat = true
2082 return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
2085 /* check the header */
2086 line, err := f.ReadString('\n')
2088 Errorf(nil, "truncated object file: %s: %v", pn, err)
2092 if !strings.HasPrefix(line, "go object ") {
2093 if strings.HasSuffix(pn, ".go") {
2094 Exitf("%s: uncompiled .go source file", pn)
2098 if line == ctxt.Arch.Name {
2099 // old header format: just $GOOS
2100 Errorf(nil, "%s: stale object file", pn)
2104 Errorf(nil, "%s: not an object file: @%d %q", pn, start, line)
2108 // First, check that the basic GOOS, GOARCH, and Version match.
2109 if line != wantHdr {
2110 Errorf(nil, "%s: linked object header mismatch:\nhave %q\nwant %q\n", pn, line, wantHdr)
2113 // Skip over exports and other info -- ends with \n!\n.
2115 // Note: It's possible for "\n!\n" to appear within the binary
2116 // package export data format. To avoid truncating the package
2117 // definition prematurely (issue 21703), we keep track of
2118 // how many "$$" delimiters we've seen.
2120 import0 := f.Offset()
2122 c1 = '\n' // the last line ended in \n
2128 if markers%2 == 0 && c2 == '!' && c3 == '\n' {
2131 if c2 == '$' && c3 == '$' {
2140 Errorf(nil, "truncated object file: %s", pn)
2145 import1 := f.Offset()
2147 f.MustSeek(import0, 0)
2148 ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
2149 f.MustSeek(import1, 0)
2151 fingerprint := ctxt.loader.Preload(ctxt.IncVersion(), f, lib, unit, eof-f.Offset())
2152 if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
2153 // Check fingerprint, to ensure the importing and imported packages
2154 // have consistent view of symbol indices.
2155 // Normally the go command should ensure this. But in case something
2156 // goes wrong, it could lead to obscure bugs like run-time crash.
2157 // Check it here to be sure.
2158 if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
2159 lib.Fingerprint = fingerprint
2161 checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
2164 addImports(ctxt, lib, pn)
2168 // symbolsAreUnresolved scans through the loader's list of unresolved
2169 // symbols and checks to see whether any of them match the names of the
2170 // symbols in 'want'. Return value is a list of bools, with list[K] set
2171 // to true if there is an unresolved reference to the symbol in want[K].
2172 func symbolsAreUnresolved(ctxt *Link, want []string) []bool {
2173 returnAllUndefs := -1
2174 undefs, _ := ctxt.loader.UndefinedRelocTargets(returnAllUndefs)
2175 seen := make(map[loader.Sym]struct{})
2176 rval := make([]bool, len(want))
2177 wantm := make(map[string]int)
2178 for k, w := range want {
2182 for _, s := range undefs {
2183 if _, ok := seen[s]; ok {
2186 seen[s] = struct{}{}
2187 if k, ok := wantm[ctxt.loader.SymName(s)]; ok {
2190 if count == len(want) {
2198 // hostObject reads a single host object file (compare to "hostArchive").
2199 // This is used as part of internal linking when we need to pull in
2200 // files such as "crt?.o".
2201 func hostObject(ctxt *Link, objname string, path string) {
2202 if ctxt.Debugvlog > 1 {
2203 ctxt.Logf("hostObject(%s)\n", path)
2205 objlib := sym.Library{
2208 f, err := bio.Open(path)
2210 Exitf("cannot open host object %q file %s: %v", objname, path, err)
2213 h := ldobj(ctxt, f, &objlib, 0, path, path)
2215 Exitf("unrecognized object file format in %s", path)
2218 h.length = f.MustSeek(0, 2)
2219 f.MustSeek(h.off, 0)
2220 h.ld(ctxt, f, h.pkg, h.length, h.pn)
2221 if *flagCaptureHostObjs != "" {
2226 func checkFingerprint(lib *sym.Library, libfp goobj.FingerprintType, src string, srcfp goobj.FingerprintType) {
2228 Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
2232 func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
2233 data := make([]byte, sym.Size)
2234 sect := f.Sections[sym.Section]
2235 if sect.Type != elf.SHT_PROGBITS && sect.Type != elf.SHT_NOTE {
2236 Errorf(nil, "reading %s from non-data section", sym.Name)
2238 n, err := sect.ReadAt(data, int64(sym.Value-sect.Addr))
2239 if uint64(n) != sym.Size {
2240 Errorf(nil, "reading contents of %s: %v", sym.Name, err)
2245 func readwithpad(r io.Reader, sz int32) ([]byte, error) {
2246 data := make([]byte, Rnd(int64(sz), 4))
2247 _, err := io.ReadFull(r, data)
2255 func readnote(f *elf.File, name []byte, typ int32) ([]byte, error) {
2256 for _, sect := range f.Sections {
2257 if sect.Type != elf.SHT_NOTE {
2262 var namesize, descsize, noteType int32
2263 err := binary.Read(r, f.ByteOrder, &namesize)
2268 return nil, fmt.Errorf("read namesize failed: %v", err)
2270 err = binary.Read(r, f.ByteOrder, &descsize)
2272 return nil, fmt.Errorf("read descsize failed: %v", err)
2274 err = binary.Read(r, f.ByteOrder, ¬eType)
2276 return nil, fmt.Errorf("read type failed: %v", err)
2278 noteName, err := readwithpad(r, namesize)
2280 return nil, fmt.Errorf("read name failed: %v", err)
2282 desc, err := readwithpad(r, descsize)
2284 return nil, fmt.Errorf("read desc failed: %v", err)
2286 if string(name) == string(noteName) && typ == noteType {
2294 func findshlib(ctxt *Link, shlib string) string {
2295 if filepath.IsAbs(shlib) {
2298 for _, libdir := range ctxt.Libdir {
2299 libpath := filepath.Join(libdir, shlib)
2300 if _, err := os.Stat(libpath); err == nil {
2304 Errorf(nil, "cannot find shared library: %s", shlib)
2308 func ldshlibsyms(ctxt *Link, shlib string) {
2310 if filepath.IsAbs(shlib) {
2312 shlib = filepath.Base(shlib)
2314 libpath = findshlib(ctxt, shlib)
2319 for _, processedlib := range ctxt.Shlibs {
2320 if processedlib.Path == libpath {
2324 if ctxt.Debugvlog > 1 {
2325 ctxt.Logf("ldshlibsyms: found library with name %s at %s\n", shlib, libpath)
2328 f, err := elf.Open(libpath)
2330 Errorf(nil, "cannot open shared library: %s", libpath)
2333 // Keep the file open as decodetypeGcprog needs to read from it.
2334 // TODO: fix. Maybe mmap the file.
2337 hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
2339 Errorf(nil, "cannot read ABI hash from shared library %s: %v", libpath, err)
2343 depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
2345 Errorf(nil, "cannot read dep list from shared library %s: %v", libpath, err)
2349 for _, dep := range strings.Split(string(depsbytes), "\n") {
2353 if !filepath.IsAbs(dep) {
2354 // If the dep can be interpreted as a path relative to the shlib
2355 // in which it was found, do that. Otherwise, we will leave it
2356 // to be resolved by libdir lookup.
2357 abs := filepath.Join(filepath.Dir(libpath), dep)
2358 if _, err := os.Stat(abs); err == nil {
2362 deps = append(deps, dep)
2365 syms, err := f.DynamicSymbols()
2367 Errorf(nil, "cannot read symbols from shared library: %s", libpath)
2371 for _, elfsym := range syms {
2372 if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
2376 // Symbols whose names start with "type:" are compiler generated,
2377 // so make functions with that prefix internal.
2379 symname := elfsym.Name // (unmangled) symbol name
2380 if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type:") {
2381 ver = abiInternalVer
2382 } else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC {
2383 // Demangle the ABI name. Keep in sync with symtab.go:mangleABIName.
2384 if strings.HasSuffix(elfsym.Name, ".abiinternal") {
2385 ver = sym.SymVerABIInternal
2386 symname = strings.TrimSuffix(elfsym.Name, ".abiinternal")
2387 } else if strings.HasSuffix(elfsym.Name, ".abi0") {
2389 symname = strings.TrimSuffix(elfsym.Name, ".abi0")
2394 s := l.LookupOrCreateSym(symname, ver)
2396 // Because loadlib above loads all .a files before loading
2397 // any shared libraries, any non-dynimport symbols we find
2398 // that duplicate symbols already loaded should be ignored
2399 // (the symbols from the .a files "win").
2400 if l.SymType(s) != 0 && l.SymType(s) != sym.SDYNIMPORT {
2403 su := l.MakeSymbolUpdater(s)
2404 su.SetType(sym.SDYNIMPORT)
2405 l.SetSymElfType(s, elf.ST_TYPE(elfsym.Info))
2406 su.SetSize(int64(elfsym.Size))
2407 if elfsym.Section != elf.SHN_UNDEF {
2408 // Set .File for the library that actually defines the symbol.
2409 l.SetSymPkg(s, libpath)
2411 // The decodetype_* functions in decodetype.go need access to
2413 sname := l.SymName(s)
2414 if strings.HasPrefix(sname, "type:") && !strings.HasPrefix(sname, "type:.") {
2415 su.SetData(readelfsymboldata(ctxt, f, &elfsym))
2419 if symname != elfsym.Name {
2420 l.SetSymExtname(s, elfsym.Name)
2423 ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f})
2426 func addsection(ldr *loader.Loader, arch *sys.Arch, seg *sym.Segment, name string, rwx int) *sym.Section {
2427 sect := ldr.NewSection()
2428 sect.Rwx = uint8(rwx)
2431 sect.Align = int32(arch.PtrSize) // everything is at least pointer-aligned
2432 seg.Sections = append(seg.Sections, sect)
2437 fmt.Fprintf(os.Stderr, "usage: link [options] main.o\n")
2438 objabi.Flagprint(os.Stderr)
2442 type SymbolType int8 // TODO: after genasmsym is gone, maybe rename to plan9typeChar or something
2445 // see also https://9p.io/magic/man2html/1/nm
2446 TextSym SymbolType = 'T'
2447 DataSym SymbolType = 'D'
2448 BSSSym SymbolType = 'B'
2449 UndefinedSym SymbolType = 'U'
2450 TLSSym SymbolType = 't'
2451 FrameSym SymbolType = 'm'
2452 ParamSym SymbolType = 'p'
2453 AutoSym SymbolType = 'a'
2455 // Deleted auto (not a real sym, just placeholder for type)
2456 DeletedAutoSym = 'x'
2459 // defineInternal defines a symbol used internally by the go runtime.
2460 func (ctxt *Link) defineInternal(p string, t sym.SymKind) loader.Sym {
2461 s := ctxt.loader.CreateSymForUpdate(p, 0)
2468 func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) loader.Sym {
2469 s := ctxt.defineInternal(p, t)
2470 ctxt.loader.SetSymValue(s, v)
2474 func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
2475 if uint64(addr) >= Segdata.Vaddr {
2476 return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
2478 if uint64(addr) >= Segtext.Vaddr {
2479 return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
2481 ldr.Errorf(s, "invalid datoff %#x", addr)
2485 func Entryvalue(ctxt *Link) int64 {
2486 a := *flagEntrySymbol
2487 if a[0] >= '0' && a[0] <= '9' {
2491 s := ldr.Lookup(a, 0)
2493 Errorf(nil, "missing entry symbol %q", a)
2496 st := ldr.SymType(s)
2498 return *FlagTextAddr
2500 if !ctxt.IsAIX() && st != sym.STEXT {
2501 ldr.Errorf(s, "entry not text")
2503 return ldr.SymValue(s)
2506 func (ctxt *Link) callgraph() {
2512 for _, s := range ctxt.Textp {
2513 relocs := ldr.Relocs(s)
2514 for i := 0; i < relocs.Count(); i++ {
2520 if r.Type().IsDirectCall() && ldr.SymType(rs) == sym.STEXT {
2521 ctxt.Logf("%s calls %s\n", ldr.SymName(s), ldr.SymName(rs))
2527 func Rnd(v int64, r int64) int64 {
2540 func bgetc(r *bio.Reader) int {
2541 c, err := r.ReadByte()
2544 log.Fatalf("reading input: %v", err)
2551 type markKind uint8 // for postorder traversal
2558 func postorder(libs []*sym.Library) []*sym.Library {
2559 order := make([]*sym.Library, 0, len(libs)) // hold the result
2560 mark := make(map[*sym.Library]markKind, len(libs))
2561 for _, lib := range libs {
2562 dfs(lib, mark, &order)
2567 func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library) {
2568 if mark[lib] == visited {
2571 if mark[lib] == visiting {
2572 panic("found import cycle while visiting " + lib.Pkg)
2574 mark[lib] = visiting
2575 for _, i := range lib.Imports {
2579 *order = append(*order, lib)
2582 func ElfSymForReloc(ctxt *Link, s loader.Sym) int32 {
2583 // If putelfsym created a local version of this symbol, use that in all
2585 les := ctxt.loader.SymLocalElfSym(s)
2589 return ctxt.loader.SymElfSym(s)
2593 func AddGotSym(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, elfRelocTyp uint32) {
2594 if ldr.SymGot(s) >= 0 {
2598 Adddynsym(ldr, target, syms, s)
2599 got := ldr.MakeSymbolUpdater(syms.GOT)
2600 ldr.SetGot(s, int32(got.Size()))
2601 got.AddUint(target.Arch, 0)
2604 if target.Arch.PtrSize == 8 {
2605 rela := ldr.MakeSymbolUpdater(syms.Rela)
2606 rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2607 rela.AddUint64(target.Arch, elf.R_INFO(uint32(ldr.SymDynid(s)), elfRelocTyp))
2608 rela.AddUint64(target.Arch, 0)
2610 rel := ldr.MakeSymbolUpdater(syms.Rel)
2611 rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2612 rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), elfRelocTyp))
2614 } else if target.IsDarwin() {
2615 leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT)
2616 leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
2617 if target.IsPIE() && target.IsInternal() {
2618 // Mach-O relocations are a royal pain to lay out.
2619 // They use a compact stateful bytecode representation.
2620 // Here we record what are needed and encode them later.
2621 MachoAddBind(int64(ldr.SymGot(s)), s)
2624 ldr.Errorf(s, "addgotsym: unsupported binary format")
2628 var hostobjcounter int
2630 // captureHostObj writes out the content of a host object (pulled from
2631 // an archive or loaded from a *.o file directly) to a directory
2632 // specified via the linker's "-capturehostobjs" debugging flag. This
2633 // is intended to make it easier for a developer to inspect the actual
2634 // object feeding into "CGO internal" link step.
2635 func captureHostObj(h *Hostobj) {
2636 // Form paths for info file and obj file.
2637 ofile := fmt.Sprintf("captured-obj-%d.o", hostobjcounter)
2638 ifile := fmt.Sprintf("captured-obj-%d.txt", hostobjcounter)
2640 opath := filepath.Join(*flagCaptureHostObjs, ofile)
2641 ipath := filepath.Join(*flagCaptureHostObjs, ifile)
2643 // Write the info file.
2644 info := fmt.Sprintf("pkg: %s\npn: %s\nfile: %s\noff: %d\nlen: %d\n",
2645 h.pkg, h.pn, h.file, h.off, h.length)
2646 if err := os.WriteFile(ipath, []byte(info), 0666); err != nil {
2647 log.Fatalf("error writing captured host obj info %s: %v", ipath, err)
2650 readObjData := func() []byte {
2651 inf, err := os.Open(h.file)
2653 log.Fatalf("capturing host obj: open failed on %s: %v", h.pn, err)
2655 res := make([]byte, h.length)
2656 if n, err := inf.ReadAt(res, h.off); err != nil || n != int(h.length) {
2657 log.Fatalf("capturing host obj: readat failed on %s: %v", h.pn, err)
2662 // Write the object file.
2663 if err := os.WriteFile(opath, readObjData(), 0666); err != nil {
2664 log.Fatalf("error writing captured host object %s: %v", opath, err)
2667 fmt.Fprintf(os.Stderr, "link: info: captured host object %s to %s\n",