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 // mkArchSymVec 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.
184 // Empty spaces between codeblocks will be padded with this value.
185 // For example an architecture might want to pad with a trap instruction to
186 // catch wayward programs. Architectures that do not define a padding value
187 // are padded with zeros.
194 Adddynrel func(*Target, *loader.Loader, *ArchSyms, loader.Sym, loader.Reloc, int) bool
196 // Archreloc is an arch-specific hook that assists in relocation processing
197 // (invoked by 'relocsym'); it handles target-specific relocation tasks.
198 // Here "rel" is the current relocation being examined, "sym" is the symbol
199 // containing the chunk of data to which the relocation applies, and "off"
200 // is the contents of the to-be-relocated data item (from sym.P). Return
201 // value is the appropriately relocated value (to be written back to the
202 // same spot in sym.P), number of external _host_ relocations needed (i.e.
203 // ELF/Mach-O/etc. relocations, not Go relocations, this must match Elfreloc1,
204 // etc.), and a boolean indicating success/failure (a failing value indicates
206 Archreloc func(*Target, *loader.Loader, *ArchSyms, loader.Reloc, loader.Sym,
207 int64) (relocatedOffset int64, nExtReloc int, ok bool)
208 // Archrelocvariant is a second arch-specific hook used for
209 // relocation processing; it handles relocations where r.Type is
210 // insufficient to describe the relocation (r.Variant !=
211 // sym.RV_NONE). Here "rel" is the relocation being applied, "sym"
212 // is the symbol containing the chunk of data to which the
213 // relocation applies, and "off" is the contents of the
214 // to-be-relocated data item (from sym.P). Return is an updated
216 Archrelocvariant func(target *Target, ldr *loader.Loader, rel loader.Reloc,
217 rv sym.RelocVariant, sym loader.Sym, offset int64, data []byte) (relocatedOffset int64)
219 // Generate a trampoline for a call from s to rs if necessary. ri is
220 // index of the relocation.
221 Trampoline func(ctxt *Link, ldr *loader.Loader, ri int, rs, s loader.Sym)
223 // Assembling the binary breaks into two phases, writing the code/data/
224 // dwarf information (which is rather generic), and some more architecture
225 // specific work like setting up the elf headers/dynamic relocations, etc.
226 // The phases are called "Asmb" and "Asmb2". Asmb2 needs to be defined for
227 // every architecture, but only if architecture has an Asmb function will
228 // it be used for assembly. Otherwise a generic assembly Asmb function is
230 Asmb func(*Link, *loader.Loader)
231 Asmb2 func(*Link, *loader.Loader)
233 // Extreloc is an arch-specific hook that converts a Go relocation to an
234 // external relocation. Return the external relocation and whether it is
236 Extreloc func(*Target, *loader.Loader, loader.Reloc, loader.Sym) (loader.ExtReloc, bool)
238 Gentext func(*Link, *loader.Loader) // Generate text before addressing has been performed.
239 Machoreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
240 MachorelocSize uint32 // size of an Mach-O relocation record, must match Machoreloc1.
241 PEreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
242 Xcoffreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
244 // Generate additional symbols for the native symbol table just prior to
246 GenSymsLate func(*Link, *loader.Loader)
248 // TLSIEtoLE converts a TLS Initial Executable relocation to
249 // a TLS Local Executable relocation.
251 // This is possible when a TLS IE relocation refers to a local
252 // symbol in an executable, which is typical when internally
253 // linking PIE binaries.
254 TLSIEtoLE func(P []byte, off, size int)
256 // optional override for assignAddress
257 AssignAddress func(ldr *loader.Loader, sect *sym.Section, n int, s loader.Sym, va uint64, isTramp bool) (*sym.Section, int, uint64)
259 // ELF specific information.
272 MINFUNC = 16 // minimum size for a function
275 // Symbol version of ABIInternal symbols. It is sym.SymVerABIInternal if ABI wrappers
276 // are used, 0 otherwise.
277 var abiInternalVer = sym.SymVerABIInternal
279 // DynlinkingGo reports whether we are producing Go code that can live
280 // in separate shared libraries linked together at runtime.
281 func (ctxt *Link) DynlinkingGo() bool {
283 panic("DynlinkingGo called before all symbols loaded")
285 return ctxt.BuildMode == BuildModeShared || ctxt.linkShared || ctxt.BuildMode == BuildModePlugin || ctxt.canUsePlugins
288 // CanUsePlugins reports whether a plugins can be used
289 func (ctxt *Link) CanUsePlugins() bool {
291 panic("CanUsePlugins called before all symbols loaded")
293 return ctxt.canUsePlugins
296 // NeedCodeSign reports whether we need to code-sign the output binary.
297 func (ctxt *Link) NeedCodeSign() bool {
298 return ctxt.IsDarwin() && ctxt.IsARM64()
310 debug_s bool // backup old value of debug['s']
314 liveness int64 // size of liveness data (funcdata), printed if -v
316 // See -strictdups command line flag.
317 checkStrictDups int // 0=off 1=warning 2=error
318 strictDupMsgCount int
323 Segrodata sym.Segment
324 Segrelrodata sym.Segment
328 Segments = []*sym.Segment{&Segtext, &Segrodata, &Segrelrodata, &Segdata, &Segdwarf}
331 const pkgdef = "__.PKGDEF"
334 // externalobj is set to true if we see an object compiled by
335 // the host compiler that is not from a package that is known
336 // to support internal linking mode.
339 // dynimportfail is a list of packages for which generating
340 // the dynimport file, _cgo_import.go, failed. If there are
341 // any of these objects, we must link externally. Issue 52863.
342 dynimportfail []string
344 // unknownObjFormat is set to true if we see an object whose
345 // format we don't recognize.
346 unknownObjFormat = false
351 func Lflag(ctxt *Link, arg string) {
352 ctxt.Libdir = append(ctxt.Libdir, arg)
356 * Unix doesn't like it when we write to a running (or, sometimes,
357 * recently run) binary, so remove the output file before writing it.
358 * On Windows 7, remove() can force a subsequent create() to fail.
359 * S_ISREG() does not exist on Plan 9.
361 func mayberemoveoutfile() {
362 if fi, err := os.Lstat(*flagOutfile); err == nil && !fi.Mode().IsRegular() {
365 os.Remove(*flagOutfile)
368 func libinit(ctxt *Link) {
369 Funcalign = thearch.Funcalign
371 // add goroot to the end of the libdir list.
375 if *flagInstallSuffix != "" {
377 suffix = *flagInstallSuffix
378 } else if *flagRace {
381 } else if *flagMsan {
384 } else if *flagAsan {
389 if buildcfg.GOROOT != "" {
390 Lflag(ctxt, filepath.Join(buildcfg.GOROOT, "pkg", fmt.Sprintf("%s_%s%s%s", buildcfg.GOOS, buildcfg.GOARCH, suffixsep, suffix)))
395 if err := ctxt.Out.Open(*flagOutfile); err != nil {
396 Exitf("cannot create %s: %v", *flagOutfile, err)
399 if *flagEntrySymbol == "" {
400 switch ctxt.BuildMode {
401 case BuildModeCShared, BuildModeCArchive:
402 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s_lib", buildcfg.GOARCH, buildcfg.GOOS)
403 case BuildModeExe, BuildModePIE:
404 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s", buildcfg.GOARCH, buildcfg.GOOS)
405 case BuildModeShared, BuildModePlugin:
406 // No *flagEntrySymbol for -buildmode=shared and plugin
408 Errorf(nil, "unknown *flagEntrySymbol for buildmode %v", ctxt.BuildMode)
413 func exitIfErrors() {
414 if nerrors != 0 || checkStrictDups > 1 && strictDupMsgCount > 0 {
426 func loadinternal(ctxt *Link, name string) *sym.Library {
427 zerofp := goobj.FingerprintType{}
428 if ctxt.linkShared && ctxt.PackageShlib != nil {
429 if shlib := ctxt.PackageShlib[name]; shlib != "" {
430 return addlibpath(ctxt, "internal", "internal", "", name, shlib, zerofp)
433 if ctxt.PackageFile != nil {
434 if pname := ctxt.PackageFile[name]; pname != "" {
435 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
437 ctxt.Logf("loadinternal: cannot find %s\n", name)
441 for _, libdir := range ctxt.Libdir {
443 shlibname := filepath.Join(libdir, name+".shlibname")
444 if ctxt.Debugvlog != 0 {
445 ctxt.Logf("searching for %s.a in %s\n", name, shlibname)
447 if _, err := os.Stat(shlibname); err == nil {
448 return addlibpath(ctxt, "internal", "internal", "", name, shlibname, zerofp)
451 pname := filepath.Join(libdir, name+".a")
452 if ctxt.Debugvlog != 0 {
453 ctxt.Logf("searching for %s.a in %s\n", name, pname)
455 if _, err := os.Stat(pname); err == nil {
456 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
460 if name == "runtime" {
461 Exitf("error: unable to find runtime.a")
463 ctxt.Logf("warning: unable to find %s.a\n", name)
467 // extld returns the current external linker.
468 func (ctxt *Link) extld() []string {
469 if len(flagExtld) == 0 {
470 // Return the default external linker for the platform.
471 // This only matters when link tool is called directly without explicit -extld,
472 // go tool already passes the correct linker in other cases.
473 switch buildcfg.GOOS {
474 case "darwin", "freebsd", "openbsd":
475 flagExtld = []string{"clang"}
477 flagExtld = []string{"gcc"}
483 // findLibPathCmd uses cmd command to find gcc library libname.
484 // It returns library full path if found, or "none" if not found.
485 func (ctxt *Link) findLibPathCmd(cmd, libname string) string {
486 extld := ctxt.extld()
487 name, args := extld[0], extld[1:]
488 args = append(args, hostlinkArchArgs(ctxt.Arch)...)
489 args = append(args, cmd)
490 if ctxt.Debugvlog != 0 {
491 ctxt.Logf("%s %v\n", extld, args)
493 out, err := exec.Command(name, args...).Output()
495 if ctxt.Debugvlog != 0 {
496 ctxt.Logf("not using a %s file because compiler failed\n%v\n%s\n", libname, err, out)
500 return strings.TrimSpace(string(out))
503 // findLibPath searches for library libname.
504 // It returns library full path if found, or "none" if not found.
505 func (ctxt *Link) findLibPath(libname string) string {
506 return ctxt.findLibPathCmd("--print-file-name="+libname, libname)
509 func (ctxt *Link) loadlib() {
511 switch *FlagStrictDups {
515 flags |= loader.FlagStrictDups
517 log.Fatalf("invalid -strictdups flag value %d", *FlagStrictDups)
519 elfsetstring1 := func(str string, off int) { elfsetstring(ctxt, 0, str, off) }
520 ctxt.loader = loader.NewLoader(flags, elfsetstring1, &ctxt.ErrorReporter.ErrorReporter)
521 ctxt.ErrorReporter.SymName = func(s loader.Sym) string {
522 return ctxt.loader.SymName(s)
525 // ctxt.Library grows during the loop, so not a range loop.
527 for ; i < len(ctxt.Library); i++ {
528 lib := ctxt.Library[i]
530 if ctxt.Debugvlog > 1 {
531 ctxt.Logf("autolib: %s (from %s)\n", lib.File, lib.Objref)
533 loadobjfile(ctxt, lib)
537 // load internal packages, if not already
539 loadinternal(ctxt, "runtime/race")
542 loadinternal(ctxt, "runtime/msan")
545 loadinternal(ctxt, "runtime/asan")
547 loadinternal(ctxt, "runtime")
548 for ; i < len(ctxt.Library); i++ {
549 lib := ctxt.Library[i]
551 loadobjfile(ctxt, lib)
554 // At this point, the Go objects are "preloaded". Not all the symbols are
555 // added to the symbol table (only defined package symbols are). Looking
556 // up symbol by name may not get expected result.
558 iscgo = ctxt.LibraryByPkg["runtime/cgo"] != nil
560 // Plugins a require cgo support to function. Similarly, plugins may require additional
561 // internal linker support on some platforms which may not be implemented.
562 ctxt.canUsePlugins = ctxt.LibraryByPkg["plugin"] != nil && iscgo
564 // We now have enough information to determine the link mode.
565 determineLinkMode(ctxt)
567 if ctxt.LinkMode == LinkExternal && !iscgo && !(buildcfg.GOOS == "darwin" && ctxt.BuildMode != BuildModePlugin && ctxt.Arch.Family == sys.AMD64) {
568 // This indicates a user requested -linkmode=external.
569 // The startup code uses an import of runtime/cgo to decide
570 // whether to initialize the TLS. So give it one. This could
571 // be handled differently but it's an unusual case.
572 if lib := loadinternal(ctxt, "runtime/cgo"); lib != nil && lib.Shlib == "" {
573 if ctxt.BuildMode == BuildModeShared || ctxt.linkShared {
574 Exitf("cannot implicitly include runtime/cgo in a shared library")
576 for ; i < len(ctxt.Library); i++ {
577 lib := ctxt.Library[i]
579 loadobjfile(ctxt, lib)
585 // Add non-package symbols and references of externally defined symbols.
586 ctxt.loader.LoadSyms(ctxt.Arch)
588 // Load symbols from shared libraries, after all Go object symbols are loaded.
589 for _, lib := range ctxt.Library {
591 if ctxt.Debugvlog > 1 {
592 ctxt.Logf("autolib: %s (from %s)\n", lib.Shlib, lib.Objref)
594 ldshlibsyms(ctxt, lib.Shlib)
598 // Process cgo directives (has to be done before host object loading).
599 ctxt.loadcgodirectives()
601 // Conditionally load host objects, or setup for external linking.
605 if ctxt.LinkMode == LinkInternal && len(hostobj) != 0 {
606 // If we have any undefined symbols in external
607 // objects, try to read them from the libgcc file.
609 undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
612 if ctxt.Debugvlog > 1 {
613 ctxt.Logf("loadlib: first unresolved is %s [%d] from %s [%d]\n",
614 ctxt.loader.SymName(undefs[0]), undefs[0],
615 ctxt.loader.SymName(froms[0]), froms[0])
619 if *flagLibGCC == "" {
620 *flagLibGCC = ctxt.findLibPathCmd("--print-libgcc-file-name", "libgcc")
622 if runtime.GOOS == "openbsd" && *flagLibGCC == "libgcc.a" {
623 // On OpenBSD `clang --print-libgcc-file-name` returns "libgcc.a".
624 // In this case we fail to load libgcc.a and can encounter link
625 // errors - see if we can find libcompiler_rt.a instead.
626 *flagLibGCC = ctxt.findLibPathCmd("--print-file-name=libcompiler_rt.a", "libcompiler_rt")
628 if ctxt.HeadType == objabi.Hwindows {
629 loadWindowsHostArchives(ctxt)
631 if *flagLibGCC != "none" {
632 hostArchive(ctxt, *flagLibGCC)
633 // For glibc systems, the linker setup used by GCC
636 // GROUP ( /lib/x86_64-linux-gnu/libc.so.6
637 // /usr/lib/x86_64-linux-gnu/libc_nonshared.a
638 // AS_NEEDED ( /lib64/ld-linux-x86-64.so.2 ) )
640 // where libc_nonshared.a contains a small set of
641 // symbols including "__stack_chk_fail_local" and a
642 // few others. Thus if we are doing internal linking
643 // and "__stack_chk_fail_local" is unresolved (most
644 // likely due to the use of -fstack-protector), try
645 // loading libc_nonshared.a to resolve it.
646 isunresolved := symbolsAreUnresolved(ctxt, []string{"__stack_chk_fail_local"})
648 if p := ctxt.findLibPath("libc_nonshared.a"); p != "none" {
656 // We've loaded all the code now.
659 strictDupMsgCount = ctxt.loader.NStrictDupMsgs()
662 // loadWindowsHostArchives loads in host archives and objects when
663 // doing internal linking on windows. Older toolchains seem to require
664 // just a single pass through the various archives, but some modern
665 // toolchains when linking a C program with mingw pass library paths
666 // multiple times to the linker, e.g. "... -lmingwex -lmingw32 ...
667 // -lmingwex -lmingw32 ...". To accommodate this behavior, we make two
668 // passes over the host archives below.
669 func loadWindowsHostArchives(ctxt *Link) {
671 for i := 0; any && i < 2; i++ {
672 // Link crt2.o (if present) to resolve "atexit" when
673 // using LLVM-based compilers.
674 isunresolved := symbolsAreUnresolved(ctxt, []string{"atexit"})
676 if p := ctxt.findLibPath("crt2.o"); p != "none" {
677 hostObject(ctxt, "crt2", p)
681 if p := ctxt.findLibPath("libsynchronization.a"); p != "none" {
685 if p := ctxt.findLibPath("libmingwex.a"); p != "none" {
688 if p := ctxt.findLibPath("libmingw32.a"); p != "none" {
691 // Link libmsvcrt.a to resolve '__acrt_iob_func' symbol
692 // (see https://golang.org/issue/23649 for details).
693 if p := ctxt.findLibPath("libmsvcrt.a"); p != "none" {
697 undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
700 if ctxt.Debugvlog > 1 {
701 ctxt.Logf("loadWindowsHostArchives: remaining unresolved is %s [%d] from %s [%d]\n",
702 ctxt.loader.SymName(undefs[0]), undefs[0],
703 ctxt.loader.SymName(froms[0]), froms[0])
707 // If needed, create the __CTOR_LIST__ and __DTOR_LIST__
708 // symbols (referenced by some of the mingw support library
709 // routines). Creation of these symbols is normally done by the
710 // linker if not already present.
711 want := []string{"__CTOR_LIST__", "__DTOR_LIST__"}
712 isunresolved := symbolsAreUnresolved(ctxt, want)
713 for k, w := range want {
715 sb := ctxt.loader.CreateSymForUpdate(w, 0)
716 sb.SetType(sym.SDATA)
717 sb.AddUint64(ctxt.Arch, 0)
718 sb.SetReachable(true)
719 ctxt.loader.SetAttrSpecial(sb.Sym(), true)
723 // Fix up references to DLL import symbols now that we're done
724 // pulling in new objects.
725 if err := loadpe.PostProcessImports(); err != nil {
726 Errorf(nil, "%v", err)
729 // TODO: maybe do something similar to peimporteddlls to collect
730 // all lib names and try link them all to final exe just like
731 // libmingwex.a and libmingw32.a:
734 #cgo windows LDFLAGS: -lmsvcrt -lm
740 // loadcgodirectives reads the previously discovered cgo directives, creating
741 // symbols in preparation for host object loading or use later in the link.
742 func (ctxt *Link) loadcgodirectives() {
744 hostObjSyms := make(map[loader.Sym]struct{})
745 for _, d := range ctxt.cgodata {
746 setCgoAttr(ctxt, d.file, d.pkg, d.directives, hostObjSyms)
750 if ctxt.LinkMode == LinkInternal {
751 // Drop all the cgo_import_static declarations.
752 // Turns out we won't be needing them.
753 for symIdx := range hostObjSyms {
754 if l.SymType(symIdx) == sym.SHOSTOBJ {
755 // If a symbol was marked both
756 // cgo_import_static and cgo_import_dynamic,
757 // then we want to make it cgo_import_dynamic
759 su := l.MakeSymbolUpdater(symIdx)
760 if l.SymExtname(symIdx) != "" && l.SymDynimplib(symIdx) != "" && !(l.AttrCgoExportStatic(symIdx) || l.AttrCgoExportDynamic(symIdx)) {
761 su.SetType(sym.SDYNIMPORT)
770 // Set up flags and special symbols depending on the platform build mode.
771 // This version works with loader.Loader.
772 func (ctxt *Link) linksetup() {
773 switch ctxt.BuildMode {
774 case BuildModeCShared, BuildModePlugin:
775 symIdx := ctxt.loader.LookupOrCreateSym("runtime.islibrary", 0)
776 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
777 sb.SetType(sym.SNOPTRDATA)
779 case BuildModeCArchive:
780 symIdx := ctxt.loader.LookupOrCreateSym("runtime.isarchive", 0)
781 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
782 sb.SetType(sym.SNOPTRDATA)
786 // Recalculate pe parameters now that we have ctxt.LinkMode set.
787 if ctxt.HeadType == objabi.Hwindows {
791 if ctxt.LinkMode == LinkExternal {
792 // When external linking, we are creating an object file. The
793 // absolute address is irrelevant.
797 // If there are no dynamic libraries needed, gcc disables dynamic linking.
798 // Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13)
799 // assumes that a dynamic binary always refers to at least one dynamic library.
800 // Rather than be a source of test cases for glibc, disable dynamic linking
801 // the same way that gcc would.
803 // Exception: on OS X, programs such as Shark only work with dynamic
804 // binaries, so leave it enabled on OS X (Mach-O) binaries.
805 // Also leave it enabled on Solaris which doesn't support
806 // statically linked binaries.
807 if ctxt.BuildMode == BuildModeExe {
808 if havedynamic == 0 && ctxt.HeadType != objabi.Hdarwin && ctxt.HeadType != objabi.Hsolaris {
813 if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && buildcfg.GOOS != "aix" {
814 toc := ctxt.loader.LookupOrCreateSym(".TOC.", 0)
815 sb := ctxt.loader.MakeSymbolUpdater(toc)
816 sb.SetType(sym.SDYNIMPORT)
819 // The Android Q linker started to complain about underalignment of the our TLS
820 // section. We don't actually use the section on android, so don't
822 if buildcfg.GOOS != "android" {
823 tlsg := ctxt.loader.LookupOrCreateSym("runtime.tlsg", 0)
824 sb := ctxt.loader.MakeSymbolUpdater(tlsg)
826 // runtime.tlsg is used for external linking on platforms that do not define
827 // a variable to hold g in assembly (currently only intel).
829 sb.SetType(sym.STLSBSS)
830 sb.SetSize(int64(ctxt.Arch.PtrSize))
831 } else if sb.Type() != sym.SDYNIMPORT {
832 Errorf(nil, "runtime declared tlsg variable %v", sb.Type())
834 ctxt.loader.SetAttrReachable(tlsg, true)
838 var moduledata loader.Sym
839 var mdsb *loader.SymbolBuilder
840 if ctxt.BuildMode == BuildModePlugin {
841 moduledata = ctxt.loader.LookupOrCreateSym("local.pluginmoduledata", 0)
842 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
843 ctxt.loader.SetAttrLocal(moduledata, true)
845 moduledata = ctxt.loader.LookupOrCreateSym("runtime.firstmoduledata", 0)
846 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
848 if mdsb.Type() != 0 && mdsb.Type() != sym.SDYNIMPORT {
849 // If the module (toolchain-speak for "executable or shared
850 // library") we are linking contains the runtime package, it
851 // will define the runtime.firstmoduledata symbol and we
852 // truncate it back to 0 bytes so we can define its entire
853 // contents in symtab.go:symtab().
856 // In addition, on ARM, the runtime depends on the linker
857 // recording the value of GOARM.
858 if ctxt.Arch.Family == sys.ARM {
859 goarm := ctxt.loader.LookupOrCreateSym("runtime.goarm", 0)
860 sb := ctxt.loader.MakeSymbolUpdater(goarm)
861 sb.SetType(sym.SDATA)
863 sb.AddUint8(uint8(buildcfg.GOARM))
866 // Set runtime.disableMemoryProfiling bool if
867 // runtime.MemProfile is not retained in the binary after
868 // deadcode (and we're not dynamically linking).
869 memProfile := ctxt.loader.Lookup("runtime.MemProfile", abiInternalVer)
870 if memProfile != 0 && !ctxt.loader.AttrReachable(memProfile) && !ctxt.DynlinkingGo() {
871 memProfSym := ctxt.loader.LookupOrCreateSym("runtime.disableMemoryProfiling", 0)
872 sb := ctxt.loader.MakeSymbolUpdater(memProfSym)
873 sb.SetType(sym.SDATA)
875 sb.AddUint8(1) // true bool
878 // If OTOH the module does not contain the runtime package,
879 // create a local symbol for the moduledata.
880 moduledata = ctxt.loader.LookupOrCreateSym("local.moduledata", 0)
881 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
882 ctxt.loader.SetAttrLocal(moduledata, true)
884 // In all cases way we mark the moduledata as noptrdata to hide it from
886 mdsb.SetType(sym.SNOPTRDATA)
887 ctxt.loader.SetAttrReachable(moduledata, true)
888 ctxt.Moduledata = moduledata
890 if ctxt.Arch == sys.Arch386 && ctxt.HeadType != objabi.Hwindows {
891 if (ctxt.BuildMode == BuildModeCArchive && ctxt.IsELF) || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE || ctxt.DynlinkingGo() {
892 got := ctxt.loader.LookupOrCreateSym("_GLOBAL_OFFSET_TABLE_", 0)
893 sb := ctxt.loader.MakeSymbolUpdater(got)
894 sb.SetType(sym.SDYNIMPORT)
895 ctxt.loader.SetAttrReachable(got, true)
899 // DWARF-gen and other phases require that the unit Textp slices
900 // be populated, so that it can walk the functions in each unit.
901 // Call into the loader to do this (requires that we collect the
902 // set of internal libraries first). NB: might be simpler if we
903 // moved isRuntimeDepPkg to cmd/internal and then did the test in
904 // loader.AssignTextSymbolOrder.
905 ctxt.Library = postorder(ctxt.Library)
907 for _, lib := range ctxt.Library {
908 intlibs = append(intlibs, isRuntimeDepPkg(lib.Pkg))
910 ctxt.Textp = ctxt.loader.AssignTextSymbolOrder(ctxt.Library, intlibs, ctxt.Textp)
913 // mangleTypeSym shortens the names of symbols that represent Go types
914 // if they are visible in the symbol table.
916 // As the names of these symbols are derived from the string of
917 // the type, they can run to many kilobytes long. So we shorten
918 // them using a SHA-1 when the name appears in the final binary.
919 // This also removes characters that upset external linkers.
921 // These are the symbols that begin with the prefix 'type.' and
922 // contain run-time type information used by the runtime and reflect
923 // packages. All Go binaries contain these symbols, but only
924 // those programs loaded dynamically in multiple parts need these
925 // symbols to have entries in the symbol table.
926 func (ctxt *Link) mangleTypeSym() {
927 if ctxt.BuildMode != BuildModeShared && !ctxt.linkShared && ctxt.BuildMode != BuildModePlugin && !ctxt.CanUsePlugins() {
932 for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
933 if !ldr.AttrReachable(s) && !ctxt.linkShared {
934 // If -linkshared, the GCProg generation code may need to reach
935 // out to the shared library for the type descriptor's data, even
936 // the type descriptor itself is not actually needed at run time
937 // (therefore not reachable). We still need to mangle its name,
938 // so it is consistent with the one stored in the shared library.
941 name := ldr.SymName(s)
942 newName := typeSymbolMangle(name)
944 ldr.SetSymExtname(s, newName)
946 // When linking against a shared library, the Go object file may
947 // have reference to the original symbol name whereas the shared
948 // library provides a symbol with the mangled name. We need to
949 // copy the payload of mangled to original.
950 // XXX maybe there is a better way to do this.
951 dup := ldr.Lookup(newName, ldr.SymVersion(s))
954 dt := ldr.SymType(dup)
955 if st == sym.Sxxx && dt != sym.Sxxx {
963 // typeSymbolMangle mangles the given symbol name into something shorter.
965 // Keep the type:. prefix, which parts of the linker (like the
966 // DWARF generator) know means the symbol is not decodable.
967 // Leave type:runtime. symbols alone, because other parts of
968 // the linker manipulates them.
969 func typeSymbolMangle(name string) string {
970 if !strings.HasPrefix(name, "type:") {
973 if strings.HasPrefix(name, "type:runtime.") {
976 if len(name) <= 14 && !strings.Contains(name, "@") { // Issue 19529
979 hash := notsha256.Sum256([]byte(name))
984 return prefix + base64.StdEncoding.EncodeToString(hash[:6])
988 * look for the next file in an archive.
989 * adapted from libmach.
991 func nextar(bp *bio.Reader, off int64, a *ArHdr) int64 {
996 var buf [SAR_HDR]byte
997 if n, err := io.ReadFull(bp, buf[:]); err != nil {
998 if n == 0 && err != io.EOF {
1004 a.name = artrim(buf[0:16])
1005 a.date = artrim(buf[16:28])
1006 a.uid = artrim(buf[28:34])
1007 a.gid = artrim(buf[34:40])
1008 a.mode = artrim(buf[40:48])
1009 a.size = artrim(buf[48:58])
1010 a.fmag = artrim(buf[58:60])
1012 arsize := atolwhex(a.size)
1016 return arsize + SAR_HDR
1019 func loadobjfile(ctxt *Link, lib *sym.Library) {
1020 pkg := objabi.PathToPrefix(lib.Pkg)
1022 if ctxt.Debugvlog > 1 {
1023 ctxt.Logf("ldobj: %s (%s)\n", lib.File, pkg)
1025 f, err := bio.Open(lib.File)
1027 Exitf("cannot open file %s: %v", lib.File, err)
1031 if pkg == "main" && !lib.Main {
1032 Exitf("%s: not package main", lib.File)
1036 for i := 0; i < len(ARMAG); i++ {
1037 if c, err := f.ReadByte(); err == nil && c == ARMAG[i] {
1041 /* load it as a regular file */
1042 l := f.MustSeek(0, 2)
1044 ldobj(ctxt, f, lib, l, lib.File, lib.File)
1049 * load all the object files from the archive now.
1050 * this gives us sequential file access and keeps us
1051 * from needing to come back later to pick up more
1052 * objects. it breaks the usual C archive model, but
1053 * this is Go, not C. the common case in Go is that
1054 * we need to load all the objects, and then we throw away
1055 * the individual symbols that are unused.
1057 * loading every object will also make it possible to
1058 * load foreign objects not referenced by __.PKGDEF.
1063 l := nextar(f, off, &arhdr)
1068 Exitf("%s: malformed archive", lib.File)
1072 // __.PKGDEF isn't a real Go object file, and it's
1073 // absent in -linkobj builds anyway. Skipping it
1074 // ensures consistency between -linkobj and normal
1076 if arhdr.name == pkgdef {
1080 if arhdr.name == "dynimportfail" {
1081 dynimportfail = append(dynimportfail, lib.Pkg)
1084 // Skip other special (non-object-file) sections that
1085 // build tools may have added. Such sections must have
1086 // short names so that the suffix is not truncated.
1087 if len(arhdr.name) < 16 {
1088 if ext := filepath.Ext(arhdr.name); ext != ".o" && ext != ".syso" {
1093 pname := fmt.Sprintf("%s(%s)", lib.File, arhdr.name)
1094 l = atolwhex(arhdr.size)
1095 ldobj(ctxt, f, lib, l, pname, lib.File)
1099 type Hostobj struct {
1100 ld func(*Link, *bio.Reader, string, int64, string)
1108 var hostobj []Hostobj
1110 // These packages can use internal linking mode.
1111 // Others trigger external mode.
1112 var internalpkg = []string{
1113 "crypto/internal/boring",
1114 "crypto/internal/boring/syso",
1120 "runtime/race/internal/amd64v1",
1121 "runtime/race/internal/amd64v3",
1126 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 {
1128 for _, intpkg := range internalpkg {
1135 // DragonFly declares errno with __thread, which results in a symbol
1136 // type of R_386_TLS_GD or R_X86_64_TLSGD. The Go linker does not
1137 // currently know how to handle TLS relocations, hence we have to
1138 // force external linking for any libraries that link in code that
1139 // uses errno. This can be removed if the Go linker ever supports
1140 // these relocation types.
1141 if headType == objabi.Hdragonfly {
1142 if pkg == "net" || pkg == "os/user" {
1151 hostobj = append(hostobj, Hostobj{})
1152 h := &hostobj[len(hostobj)-1]
1162 func hostobjs(ctxt *Link) {
1163 if ctxt.LinkMode != LinkInternal {
1168 for i := 0; i < len(hostobj); i++ {
1170 f, err := bio.Open(h.file)
1172 Exitf("cannot reopen %s: %v", h.pn, err)
1174 f.MustSeek(h.off, 0)
1176 Errorf(nil, "%s: unrecognized object file format", h.pn)
1179 h.ld(ctxt, f, h.pkg, h.length, h.pn)
1180 if *flagCaptureHostObjs != "" {
1187 func hostlinksetup(ctxt *Link) {
1188 if ctxt.LinkMode != LinkExternal {
1192 // For external link, record that we need to tell the external linker -s,
1193 // and turn off -s internally: the external linker needs the symbol
1194 // information for its final link.
1198 // create temporary directory and arrange cleanup
1199 if *flagTmpdir == "" {
1200 dir, err := os.MkdirTemp("", "go-link-")
1207 os.RemoveAll(*flagTmpdir)
1211 // change our output to temporary object file
1212 if err := ctxt.Out.Close(); err != nil {
1213 Exitf("error closing output file")
1215 mayberemoveoutfile()
1217 p := filepath.Join(*flagTmpdir, "go.o")
1218 if err := ctxt.Out.Open(p); err != nil {
1219 Exitf("cannot create %s: %v", p, err)
1223 // hostobjCopy creates a copy of the object files in hostobj in a
1224 // temporary directory.
1225 func hostobjCopy() (paths []string) {
1226 var wg sync.WaitGroup
1227 sema := make(chan struct{}, runtime.NumCPU()) // limit open file descriptors
1228 for i, h := range hostobj {
1230 dst := filepath.Join(*flagTmpdir, fmt.Sprintf("%06d.o", i))
1231 paths = append(paths, dst)
1240 f, err := os.Open(h.file)
1242 Exitf("cannot reopen %s: %v", h.pn, err)
1245 if _, err := f.Seek(h.off, 0); err != nil {
1246 Exitf("cannot seek %s: %v", h.pn, err)
1249 w, err := os.Create(dst)
1251 Exitf("cannot create %s: %v", dst, err)
1253 if _, err := io.CopyN(w, f, h.length); err != nil {
1254 Exitf("cannot write %s: %v", dst, err)
1256 if err := w.Close(); err != nil {
1257 Exitf("cannot close %s: %v", dst, err)
1265 // writeGDBLinkerScript creates gcc linker script file in temp
1266 // directory. writeGDBLinkerScript returns created file path.
1267 // The script is used to work around gcc bug
1268 // (see https://golang.org/issue/20183 for details).
1269 func writeGDBLinkerScript() string {
1270 name := "fix_debug_gdb_scripts.ld"
1271 path := filepath.Join(*flagTmpdir, name)
1274 .debug_gdb_scripts BLOCK(__section_alignment__) (NOLOAD) :
1276 *(.debug_gdb_scripts)
1279 INSERT AFTER .debug_types;
1281 err := os.WriteFile(path, []byte(src), 0666)
1283 Errorf(nil, "WriteFile %s failed: %v", name, err)
1288 // archive builds a .a archive from the hostobj object files.
1289 func (ctxt *Link) archive() {
1290 if ctxt.BuildMode != BuildModeCArchive {
1296 if *flagExtar == "" {
1300 mayberemoveoutfile()
1302 // Force the buffer to flush here so that external
1303 // tools will see a complete file.
1304 if err := ctxt.Out.Close(); err != nil {
1305 Exitf("error closing %v", *flagOutfile)
1308 argv := []string{*flagExtar, "-q", "-c", "-s"}
1309 if ctxt.HeadType == objabi.Haix {
1310 argv = append(argv, "-X64")
1312 argv = append(argv, *flagOutfile)
1313 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1314 argv = append(argv, hostobjCopy()...)
1316 if ctxt.Debugvlog != 0 {
1317 ctxt.Logf("archive: %s\n", strings.Join(argv, " "))
1320 // If supported, use syscall.Exec() to invoke the archive command,
1321 // which should be the final remaining step needed for the link.
1322 // This will reduce peak RSS for the link (and speed up linking of
1323 // large applications), since when the archive command runs we
1324 // won't be holding onto all of the linker's live memory.
1325 if syscallExecSupported && !ownTmpDir {
1327 ctxt.execArchive(argv)
1328 panic("should not get here")
1331 // Otherwise invoke 'ar' in the usual way (fork + exec).
1332 if out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput(); err != nil {
1333 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1337 func (ctxt *Link) hostlink() {
1338 if ctxt.LinkMode != LinkExternal || nerrors > 0 {
1341 if ctxt.BuildMode == BuildModeCArchive {
1346 argv = append(argv, ctxt.extld()...)
1347 argv = append(argv, hostlinkArchArgs(ctxt.Arch)...)
1349 if *FlagS || debug_s {
1350 if ctxt.HeadType == objabi.Hdarwin {
1351 // Recent versions of macOS print
1352 // ld: warning: option -s is obsolete and being ignored
1353 // so do not pass any arguments.
1355 argv = append(argv, "-s")
1359 // On darwin, whether to combine DWARF into executable.
1360 // Only macOS supports unmapped segments such as our __DWARF segment.
1361 combineDwarf := ctxt.IsDarwin() && !*FlagS && !*FlagW && !debug_s && machoPlatform == PLATFORM_MACOS
1363 switch ctxt.HeadType {
1364 case objabi.Hdarwin:
1366 // Leave room for DWARF combining.
1367 // -headerpad is incompatible with -fembed-bitcode.
1368 argv = append(argv, "-Wl,-headerpad,1144")
1370 if ctxt.DynlinkingGo() && buildcfg.GOOS != "ios" {
1371 // -flat_namespace is deprecated on iOS.
1372 // It is useful for supporting plugins. We don't support plugins on iOS.
1373 // -flat_namespace may cause the dynamic linker to hang at forkExec when
1374 // resolving a lazy binding. See issue 38824.
1375 // Force eager resolution to work around.
1376 argv = append(argv, "-Wl,-flat_namespace", "-Wl,-bind_at_load")
1379 argv = append(argv, "-Wl,-S") // suppress STAB (symbolic debugging) symbols
1381 case objabi.Hopenbsd:
1382 argv = append(argv, "-Wl,-nopie")
1383 argv = append(argv, "-pthread")
1384 case objabi.Hwindows:
1386 argv = append(argv, "-mwindows")
1388 argv = append(argv, "-mconsole")
1390 // Mark as having awareness of terminal services, to avoid
1391 // ancient compatibility hacks.
1392 argv = append(argv, "-Wl,--tsaware")
1395 argv = append(argv, "-Wl,--nxcompat")
1397 argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", PeMinimumTargetMajorVersion))
1398 argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", PeMinimumTargetMinorVersion))
1399 argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", PeMinimumTargetMajorVersion))
1400 argv = append(argv, fmt.Sprintf("-Wl,--minor-subsystem-version=%d", PeMinimumTargetMinorVersion))
1402 argv = append(argv, "-pthread")
1403 // prevent ld to reorder .text functions to keep the same
1404 // first/last functions for moduledata.
1405 argv = append(argv, "-Wl,-bnoobjreorder")
1406 // mcmodel=large is needed for every gcc generated files, but
1407 // ld still need -bbigtoc in order to allow larger TOC.
1408 argv = append(argv, "-mcmodel=large")
1409 argv = append(argv, "-Wl,-bbigtoc")
1412 // Enable/disable ASLR on Windows.
1413 addASLRargs := func(argv []string, val bool) []string {
1414 // Old/ancient versions of GCC support "--dynamicbase" and
1415 // "--high-entropy-va" but don't enable it by default. In
1416 // addition, they don't accept "--disable-dynamicbase" or
1417 // "--no-dynamicbase", so the only way to disable ASLR is to
1418 // not pass any flags at all.
1420 // More modern versions of GCC (and also clang) enable ASLR
1421 // by default. With these compilers, however you can turn it
1422 // off if you want using "--disable-dynamicbase" or
1423 // "--no-dynamicbase".
1425 // The strategy below is to try using "--disable-dynamicbase";
1426 // if this succeeds, then assume we're working with more
1427 // modern compilers and act accordingly. If it fails, assume
1428 // an ancient compiler with ancient defaults.
1431 dbon := "--dynamicbase"
1432 heon := "--high-entropy-va"
1433 dboff := "--disable-dynamicbase"
1434 heoff := "--disable-high-entropy-va"
1439 // Test to see whether "--disable-dynamicbase" works.
1440 newer := linkerFlagSupported(ctxt.Arch, argv[0], "", "-Wl,"+dboff)
1442 // Newer compiler, which supports both on/off options.
1446 // older toolchain: we have to say nothing in order to
1447 // get a no-ASLR binary.
1453 argv = append(argv, "-Wl,"+dbopt)
1455 // enable high-entropy ASLR on 64-bit.
1456 if ctxt.Arch.PtrSize >= 8 && heopt != "" {
1457 argv = append(argv, "-Wl,"+heopt)
1462 switch ctxt.BuildMode {
1464 if ctxt.HeadType == objabi.Hdarwin {
1465 if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() {
1466 argv = append(argv, "-Wl,-no_pie")
1469 if *flagRace && ctxt.HeadType == objabi.Hwindows {
1470 // Current windows/amd64 race detector tsan support
1471 // library can't handle PIE mode (see #53539 for more details).
1472 // For now, explicitly disable PIE (since some compilers
1473 // default to it) if -race is in effect.
1474 argv = addASLRargs(argv, false)
1477 switch ctxt.HeadType {
1478 case objabi.Hdarwin, objabi.Haix:
1479 case objabi.Hwindows:
1480 if *flagAslr && *flagRace {
1481 // Current windows/amd64 race detector tsan support
1482 // library can't handle PIE mode (see #53539 for more details).
1483 // Disable alsr if -race in effect.
1486 argv = addASLRargs(argv, *flagAslr)
1489 if ctxt.UseRelro() {
1490 argv = append(argv, "-Wl,-z,relro")
1492 argv = append(argv, "-pie")
1494 case BuildModeCShared:
1495 if ctxt.HeadType == objabi.Hdarwin {
1496 argv = append(argv, "-dynamiclib")
1498 if ctxt.UseRelro() {
1499 argv = append(argv, "-Wl,-z,relro")
1501 argv = append(argv, "-shared")
1502 if ctxt.HeadType == objabi.Hwindows {
1503 argv = addASLRargs(argv, *flagAslr)
1505 // Pass -z nodelete to mark the shared library as
1506 // non-closeable: a dlclose will do nothing.
1507 argv = append(argv, "-Wl,-z,nodelete")
1508 // Only pass Bsymbolic on non-Windows.
1509 argv = append(argv, "-Wl,-Bsymbolic")
1512 case BuildModeShared:
1513 if ctxt.UseRelro() {
1514 argv = append(argv, "-Wl,-z,relro")
1516 argv = append(argv, "-shared")
1517 case BuildModePlugin:
1518 if ctxt.HeadType == objabi.Hdarwin {
1519 argv = append(argv, "-dynamiclib")
1521 if ctxt.UseRelro() {
1522 argv = append(argv, "-Wl,-z,relro")
1524 argv = append(argv, "-shared")
1528 var altLinker string
1529 if ctxt.IsELF && ctxt.DynlinkingGo() {
1530 // We force all symbol resolution to be done at program startup
1531 // because lazy PLT resolution can use large amounts of stack at
1532 // times we cannot allow it to do so.
1533 argv = append(argv, "-Wl,-z,now")
1535 // Do not let the host linker generate COPY relocations. These
1536 // can move symbols out of sections that rely on stable offsets
1537 // from the beginning of the section (like sym.STYPE).
1538 argv = append(argv, "-Wl,-z,nocopyreloc")
1540 if buildcfg.GOOS == "android" {
1541 // Use lld to avoid errors from default linker (issue #38838)
1545 if ctxt.Arch.InFamily(sys.ARM, sys.ARM64) && buildcfg.GOOS == "linux" {
1546 // On ARM, the GNU linker will generate COPY relocations
1547 // even with -znocopyreloc set.
1548 // https://sourceware.org/bugzilla/show_bug.cgi?id=19962
1550 // On ARM64, the GNU linker will fail instead of
1551 // generating COPY relocations.
1553 // In both cases, switch to gold.
1556 // If gold is not installed, gcc will silently switch
1557 // back to ld.bfd. So we parse the version information
1558 // and provide a useful error if gold is missing.
1559 name, args := flagExtld[0], flagExtld[1:]
1560 args = append(args, "-fuse-ld=gold", "-Wl,--version")
1561 cmd := exec.Command(name, args...)
1562 if out, err := cmd.CombinedOutput(); err == nil {
1563 if !bytes.Contains(out, []byte("GNU gold")) {
1564 log.Fatalf("ARM external linker must be gold (issue #15696), but is not: %s", out)
1569 if ctxt.Arch.Family == sys.ARM64 && buildcfg.GOOS == "freebsd" {
1570 // Switch to ld.bfd on freebsd/arm64.
1573 // Provide a useful error if ld.bfd is missing.
1574 name, args := flagExtld[0], flagExtld[1:]
1575 args = append(args, "-fuse-ld=bfd", "-Wl,--version")
1576 cmd := exec.Command(name, args...)
1577 if out, err := cmd.CombinedOutput(); err == nil {
1578 if !bytes.Contains(out, []byte("GNU ld")) {
1579 log.Fatalf("ARM64 external linker must be ld.bfd (issue #35197), please install devel/binutils")
1583 if altLinker != "" {
1584 argv = append(argv, "-fuse-ld="+altLinker)
1587 if ctxt.IsELF && len(buildinfo) > 0 {
1588 argv = append(argv, fmt.Sprintf("-Wl,--build-id=0x%x", buildinfo))
1591 // On Windows, given -o foo, GCC will append ".exe" to produce
1592 // "foo.exe". We have decided that we want to honor the -o
1593 // option. To make this work, we append a '.' so that GCC
1594 // will decide that the file already has an extension. We
1595 // only want to do this when producing a Windows output file
1596 // on a Windows host.
1597 outopt := *flagOutfile
1598 if buildcfg.GOOS == "windows" && runtime.GOOS == "windows" && filepath.Ext(outopt) == "" {
1601 argv = append(argv, "-o")
1602 argv = append(argv, outopt)
1604 if rpath.val != "" {
1605 argv = append(argv, fmt.Sprintf("-Wl,-rpath,%s", rpath.val))
1608 if *flagInterpreter != "" {
1609 // Many linkers support both -I and the --dynamic-linker flags
1610 // to set the ELF interpreter, but lld only supports
1611 // --dynamic-linker so prefer that (ld on very old Solaris only
1612 // supports -I but that seems less important).
1613 argv = append(argv, fmt.Sprintf("-Wl,--dynamic-linker,%s", *flagInterpreter))
1616 // Force global symbols to be exported for dlopen, etc.
1618 if ctxt.DynlinkingGo() || ctxt.BuildMode == BuildModeCShared || !linkerFlagSupported(ctxt.Arch, argv[0], altLinker, "-Wl,--export-dynamic-symbol=main") {
1619 argv = append(argv, "-rdynamic")
1621 ctxt.loader.ForAllCgoExportDynamic(func(s loader.Sym) {
1622 argv = append(argv, "-Wl,--export-dynamic-symbol="+ctxt.loader.SymExtname(s))
1626 if ctxt.HeadType == objabi.Haix {
1627 fileName := xcoffCreateExportFile(ctxt)
1628 argv = append(argv, "-Wl,-bE:"+fileName)
1631 const unusedArguments = "-Qunused-arguments"
1632 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, unusedArguments) {
1633 argv = append(argv, unusedArguments)
1636 if ctxt.IsWindows() {
1637 // Suppress generation of the PE file header timestamp,
1638 // so as to avoid spurious build ID differences between
1639 // linked binaries that are otherwise identical other than
1640 // the date/time they were linked.
1641 const noTimeStamp = "-Wl,--no-insert-timestamp"
1642 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, noTimeStamp) {
1643 argv = append(argv, noTimeStamp)
1647 const compressDWARF = "-Wl,--compress-debug-sections=zlib"
1648 if ctxt.compressDWARF && linkerFlagSupported(ctxt.Arch, argv[0], altLinker, compressDWARF) {
1649 argv = append(argv, compressDWARF)
1652 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1653 argv = append(argv, hostobjCopy()...)
1654 if ctxt.HeadType == objabi.Haix {
1655 // We want to have C files after Go files to remove
1656 // trampolines csects made by ld.
1657 argv = append(argv, "-nostartfiles")
1658 argv = append(argv, "/lib/crt0_64.o")
1660 extld := ctxt.extld()
1661 name, args := extld[0], extld[1:]
1662 // Get starting files.
1663 getPathFile := func(file string) string {
1664 args := append(args, "-maix64", "--print-file-name="+file)
1665 out, err := exec.Command(name, args...).CombinedOutput()
1667 log.Fatalf("running %s failed: %v\n%s", extld, err, out)
1669 return strings.Trim(string(out), "\n")
1671 // Since GCC version 11, the 64-bit version of GCC starting files
1672 // are now suffixed by "_64". Even under "-maix64" multilib directory
1673 // "crtcxa.o" is 32-bit.
1674 crtcxa := getPathFile("crtcxa_64.o")
1675 if !filepath.IsAbs(crtcxa) {
1676 crtcxa = getPathFile("crtcxa.o")
1678 crtdbase := getPathFile("crtdbase_64.o")
1679 if !filepath.IsAbs(crtdbase) {
1680 crtdbase = getPathFile("crtdbase.o")
1682 argv = append(argv, crtcxa)
1683 argv = append(argv, crtdbase)
1686 if ctxt.linkShared {
1687 seenDirs := make(map[string]bool)
1688 seenLibs := make(map[string]bool)
1689 addshlib := func(path string) {
1690 dir, base := filepath.Split(path)
1692 argv = append(argv, "-L"+dir)
1694 argv = append(argv, "-Wl,-rpath="+dir)
1696 seenDirs[dir] = true
1698 base = strings.TrimSuffix(base, ".so")
1699 base = strings.TrimPrefix(base, "lib")
1700 if !seenLibs[base] {
1701 argv = append(argv, "-l"+base)
1702 seenLibs[base] = true
1705 for _, shlib := range ctxt.Shlibs {
1706 addshlib(shlib.Path)
1707 for _, dep := range shlib.Deps {
1711 libpath := findshlib(ctxt, dep)
1719 // clang, unlike GCC, passes -rdynamic to the linker
1720 // even when linking with -static, causing a linker
1721 // error when using GNU ld. So take out -rdynamic if
1722 // we added it. We do it in this order, rather than
1723 // only adding -rdynamic later, so that -extldflags
1724 // can override -rdynamic without using -static.
1725 // Similarly for -Wl,--dynamic-linker.
1726 checkStatic := func(arg string) {
1727 if ctxt.IsELF && arg == "-static" {
1728 for i := range argv {
1729 if argv[i] == "-rdynamic" || strings.HasPrefix(argv[i], "-Wl,--dynamic-linker,") {
1736 for _, p := range ldflag {
1737 argv = append(argv, p)
1741 // When building a program with the default -buildmode=exe the
1742 // gc compiler generates code requires DT_TEXTREL in a
1743 // position independent executable (PIE). On systems where the
1744 // toolchain creates PIEs by default, and where DT_TEXTREL
1745 // does not work, the resulting programs will not run. See
1746 // issue #17847. To avoid this problem pass -no-pie to the
1747 // toolchain if it is supported.
1748 if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared && !(ctxt.IsDarwin() && ctxt.IsARM64()) {
1749 // GCC uses -no-pie, clang uses -nopie.
1750 for _, nopie := range []string{"-no-pie", "-nopie"} {
1751 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, nopie) {
1752 argv = append(argv, nopie)
1758 for _, p := range flagExtldflags {
1759 argv = append(argv, p)
1762 if ctxt.HeadType == objabi.Hwindows {
1763 // Determine which linker we're using. Add in the extldflags in
1764 // case used has specified "-fuse-ld=...".
1765 extld := ctxt.extld()
1766 name, args := extld[0], extld[1:]
1767 args = append(args, trimLinkerArgv(flagExtldflags)...)
1768 args = append(args, "-Wl,--version")
1769 cmd := exec.Command(name, args...)
1771 if out, err := cmd.CombinedOutput(); err == nil {
1772 if bytes.Contains(out, []byte("LLD ")) {
1777 // use gcc linker script to work around gcc bug
1778 // (see https://golang.org/issue/20183 for details).
1780 p := writeGDBLinkerScript()
1781 argv = append(argv, "-Wl,-T,"+p)
1784 if p := ctxt.findLibPath("libsynchronization.a"); p != "libsynchronization.a" {
1785 argv = append(argv, "-lsynchronization")
1788 // libmingw32 and libmingwex have some inter-dependencies,
1789 // so must use linker groups.
1790 argv = append(argv, "-Wl,--start-group", "-lmingwex", "-lmingw32", "-Wl,--end-group")
1791 argv = append(argv, peimporteddlls()...)
1794 argv = ctxt.passLongArgsInResponseFile(argv, altLinker)
1796 if ctxt.Debugvlog != 0 {
1797 ctxt.Logf("host link:")
1798 for _, v := range argv {
1804 out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput()
1806 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1809 // Filter out useless linker warnings caused by bugs outside Go.
1810 // See also cmd/go/internal/work/exec.go's gccld method.
1813 for _, line := range bytes.SplitAfter(out, []byte("\n")) {
1814 // golang.org/issue/26073 - Apple Xcode bug
1815 if bytes.Contains(line, []byte("ld: warning: text-based stub file")) {
1824 // Remove TOC overflow warning on AIX.
1825 if bytes.Contains(line, []byte("ld: 0711-783")) {
1830 save = append(save, line)
1832 out = bytes.Join(save, nil)
1835 // always print external output even if the command is successful, so that we don't
1836 // swallow linker warnings (see https://golang.org/issue/17935).
1837 if ctxt.IsDarwin() && ctxt.IsAMD64() {
1838 const noPieWarning = "ld: warning: -no_pie is deprecated when targeting new OS versions\n"
1839 if i := bytes.Index(out, []byte(noPieWarning)); i >= 0 {
1840 // swallow -no_pie deprecation warning, issue 54482
1841 out = append(out[:i], out[i+len(noPieWarning):]...)
1844 ctxt.Logf("%s", out)
1848 // Find "dsymutils" and "strip" tools using CC --print-prog-name.
1850 cc = append(cc, ctxt.extld()...)
1851 cc = append(cc, hostlinkArchArgs(ctxt.Arch)...)
1852 cc = append(cc, "--print-prog-name", "dsymutil")
1853 out, err := exec.Command(cc[0], cc[1:]...).CombinedOutput()
1855 Exitf("%s: finding dsymutil failed: %v\n%s", os.Args[0], err, out)
1857 dsymutilCmd := strings.TrimSuffix(string(out), "\n")
1859 cc[len(cc)-1] = "strip"
1860 out, err = exec.Command(cc[0], cc[1:]...).CombinedOutput()
1862 Exitf("%s: finding strip failed: %v\n%s", os.Args[0], err, out)
1864 stripCmd := strings.TrimSuffix(string(out), "\n")
1866 dsym := filepath.Join(*flagTmpdir, "go.dwarf")
1867 if out, err := exec.Command(dsymutilCmd, "-f", *flagOutfile, "-o", dsym).CombinedOutput(); err != nil {
1868 Exitf("%s: running dsymutil failed: %v\n%s", os.Args[0], err, out)
1870 // Remove STAB (symbolic debugging) symbols after we are done with them (by dsymutil).
1871 // They contain temporary file paths and make the build not reproducible.
1872 if out, err := exec.Command(stripCmd, "-S", *flagOutfile).CombinedOutput(); err != nil {
1873 Exitf("%s: running strip failed: %v\n%s", os.Args[0], err, out)
1875 // Skip combining if `dsymutil` didn't generate a file. See #11994.
1876 if _, err := os.Stat(dsym); os.IsNotExist(err) {
1879 // For os.Rename to work reliably, must be in same directory as outfile.
1880 combinedOutput := *flagOutfile + "~"
1881 exef, err := os.Open(*flagOutfile)
1883 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1886 exem, err := macho.NewFile(exef)
1888 Exitf("%s: parsing Mach-O header failed: %v", os.Args[0], err)
1890 if err := machoCombineDwarf(ctxt, exef, exem, dsym, combinedOutput); err != nil {
1891 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1893 os.Remove(*flagOutfile)
1894 if err := os.Rename(combinedOutput, *flagOutfile); err != nil {
1895 Exitf("%s: %v", os.Args[0], err)
1898 if ctxt.NeedCodeSign() {
1899 err := machoCodeSign(ctxt, *flagOutfile)
1901 Exitf("%s: code signing failed: %v", os.Args[0], err)
1906 // passLongArgsInResponseFile writes the arguments into a file if they
1908 func (ctxt *Link) passLongArgsInResponseFile(argv []string, altLinker string) []string {
1910 for _, arg := range argv {
1914 if c < sys.ExecArgLengthLimit {
1918 // Only use response files if they are supported.
1919 response := filepath.Join(*flagTmpdir, "response")
1920 if err := os.WriteFile(response, nil, 0644); err != nil {
1921 log.Fatalf("failed while testing response file: %v", err)
1923 if !linkerFlagSupported(ctxt.Arch, argv[0], altLinker, "@"+response) {
1924 if ctxt.Debugvlog != 0 {
1925 ctxt.Logf("not using response file because linker does not support one")
1930 var buf bytes.Buffer
1931 for _, arg := range argv[1:] {
1932 // The external linker response file supports quoted strings.
1933 fmt.Fprintf(&buf, "%q\n", arg)
1935 if err := os.WriteFile(response, buf.Bytes(), 0644); err != nil {
1936 log.Fatalf("failed while writing response file: %v", err)
1938 if ctxt.Debugvlog != 0 {
1939 ctxt.Logf("response file %s contents:\n%s", response, buf.Bytes())
1947 var createTrivialCOnce sync.Once
1949 func linkerFlagSupported(arch *sys.Arch, linker, altLinker, flag string) bool {
1950 createTrivialCOnce.Do(func() {
1951 src := filepath.Join(*flagTmpdir, "trivial.c")
1952 if err := os.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
1953 Errorf(nil, "WriteFile trivial.c failed: %v", err)
1957 flags := hostlinkArchArgs(arch)
1959 moreFlags := trimLinkerArgv(append(flagExtldflags, ldflag...))
1960 flags = append(flags, moreFlags...)
1962 if altLinker != "" {
1963 flags = append(flags, "-fuse-ld="+altLinker)
1965 flags = append(flags, flag, "trivial.c")
1967 cmd := exec.Command(linker, flags...)
1968 cmd.Dir = *flagTmpdir
1969 cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
1970 out, err := cmd.CombinedOutput()
1971 // GCC says "unrecognized command line option ‘-no-pie’"
1972 // clang says "unknown argument: '-no-pie'"
1973 return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
1976 // trimLinkerArgv returns a new copy of argv that does not include flags
1977 // that are not relevant for testing whether some linker option works.
1978 func trimLinkerArgv(argv []string) []string {
1979 flagsWithNextArgSkip := []string{
1988 flagsWithNextArgKeep := []string{
1994 prefixesToKeep := []string{
2008 for _, f := range argv {
2010 flags = append(flags, f)
2014 } else if f == "" || f[0] != '-' {
2015 } else if contains(flagsWithNextArgSkip, f) {
2017 } else if contains(flagsWithNextArgKeep, f) {
2018 flags = append(flags, f)
2021 for _, p := range prefixesToKeep {
2022 if strings.HasPrefix(f, p) {
2023 flags = append(flags, f)
2032 // hostlinkArchArgs returns arguments to pass to the external linker
2033 // based on the architecture.
2034 func hostlinkArchArgs(arch *sys.Arch) []string {
2035 switch arch.Family {
2037 return []string{"-m32"}
2039 if buildcfg.GOOS == "darwin" {
2040 return []string{"-arch", "x86_64", "-m64"}
2042 return []string{"-m64"}
2044 return []string{"-m64"}
2046 return []string{"-marm"}
2048 if buildcfg.GOOS == "darwin" {
2049 return []string{"-arch", "arm64"}
2052 return []string{"-mabi=lp64d"}
2054 return []string{"-mabi=64"}
2056 return []string{"-mabi=32"}
2058 if buildcfg.GOOS == "aix" {
2059 return []string{"-maix64"}
2061 return []string{"-m64"}
2068 var wantHdr = objabi.HeaderString()
2070 // ldobj loads an input object. If it is a host object (an object
2071 // compiled by a non-Go compiler) it returns the Hostobj pointer. If
2072 // it is a Go object, it returns nil.
2073 func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string, file string) *Hostobj {
2074 pkg := objabi.PathToPrefix(lib.Pkg)
2076 eof := f.Offset() + length
2082 f.MustSeek(start, 0)
2084 unit := &sym.CompilationUnit{Lib: lib}
2085 lib.Units = append(lib.Units, unit)
2087 magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
2088 if magic == 0x7f454c46 { // \x7F E L F
2089 ldelf := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2090 textp, flags, err := loadelf.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn, ehdr.Flags)
2092 Errorf(nil, "%v", err)
2096 ctxt.Textp = append(ctxt.Textp, textp...)
2098 return ldhostobj(ldelf, ctxt.HeadType, f, pkg, length, pn, file)
2101 if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
2102 ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2103 textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2105 Errorf(nil, "%v", err)
2108 ctxt.Textp = append(ctxt.Textp, textp...)
2110 return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
2118 ldpe := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2119 textp, rsrc, err := loadpe.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2121 Errorf(nil, "%v", err)
2125 setpersrc(ctxt, rsrc)
2127 ctxt.Textp = append(ctxt.Textp, textp...)
2129 return ldhostobj(ldpe, ctxt.HeadType, f, pkg, length, pn, file)
2132 if c1 == 0x01 && (c2 == 0xD7 || c2 == 0xF7) {
2133 ldxcoff := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2134 textp, err := loadxcoff.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2136 Errorf(nil, "%v", err)
2139 ctxt.Textp = append(ctxt.Textp, textp...)
2141 return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
2144 if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
2145 // An unrecognized object is just passed to the external linker.
2146 // If we try to read symbols from this object, we will
2147 // report an error at that time.
2148 unknownObjFormat = true
2149 return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
2152 /* check the header */
2153 line, err := f.ReadString('\n')
2155 Errorf(nil, "truncated object file: %s: %v", pn, err)
2159 if !strings.HasPrefix(line, "go object ") {
2160 if strings.HasSuffix(pn, ".go") {
2161 Exitf("%s: uncompiled .go source file", pn)
2165 if line == ctxt.Arch.Name {
2166 // old header format: just $GOOS
2167 Errorf(nil, "%s: stale object file", pn)
2171 Errorf(nil, "%s: not an object file: @%d %q", pn, start, line)
2175 // First, check that the basic GOOS, GOARCH, and Version match.
2176 if line != wantHdr {
2177 Errorf(nil, "%s: linked object header mismatch:\nhave %q\nwant %q\n", pn, line, wantHdr)
2180 // Skip over exports and other info -- ends with \n!\n.
2182 // Note: It's possible for "\n!\n" to appear within the binary
2183 // package export data format. To avoid truncating the package
2184 // definition prematurely (issue 21703), we keep track of
2185 // how many "$$" delimiters we've seen.
2187 import0 := f.Offset()
2189 c1 = '\n' // the last line ended in \n
2195 if markers%2 == 0 && c2 == '!' && c3 == '\n' {
2198 if c2 == '$' && c3 == '$' {
2207 Errorf(nil, "truncated object file: %s", pn)
2212 import1 := f.Offset()
2214 f.MustSeek(import0, 0)
2215 ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
2216 f.MustSeek(import1, 0)
2218 fingerprint := ctxt.loader.Preload(ctxt.IncVersion(), f, lib, unit, eof-f.Offset())
2219 if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
2220 // Check fingerprint, to ensure the importing and imported packages
2221 // have consistent view of symbol indices.
2222 // Normally the go command should ensure this. But in case something
2223 // goes wrong, it could lead to obscure bugs like run-time crash.
2224 // Check it here to be sure.
2225 if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
2226 lib.Fingerprint = fingerprint
2228 checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
2231 addImports(ctxt, lib, pn)
2235 // symbolsAreUnresolved scans through the loader's list of unresolved
2236 // symbols and checks to see whether any of them match the names of the
2237 // symbols in 'want'. Return value is a list of bools, with list[K] set
2238 // to true if there is an unresolved reference to the symbol in want[K].
2239 func symbolsAreUnresolved(ctxt *Link, want []string) []bool {
2240 returnAllUndefs := -1
2241 undefs, _ := ctxt.loader.UndefinedRelocTargets(returnAllUndefs)
2242 seen := make(map[loader.Sym]struct{})
2243 rval := make([]bool, len(want))
2244 wantm := make(map[string]int)
2245 for k, w := range want {
2249 for _, s := range undefs {
2250 if _, ok := seen[s]; ok {
2253 seen[s] = struct{}{}
2254 if k, ok := wantm[ctxt.loader.SymName(s)]; ok {
2257 if count == len(want) {
2265 // hostObject reads a single host object file (compare to "hostArchive").
2266 // This is used as part of internal linking when we need to pull in
2267 // files such as "crt?.o".
2268 func hostObject(ctxt *Link, objname string, path string) {
2269 if ctxt.Debugvlog > 1 {
2270 ctxt.Logf("hostObject(%s)\n", path)
2272 objlib := sym.Library{
2275 f, err := bio.Open(path)
2277 Exitf("cannot open host object %q file %s: %v", objname, path, err)
2280 h := ldobj(ctxt, f, &objlib, 0, path, path)
2282 Exitf("unrecognized object file format in %s", path)
2285 h.length = f.MustSeek(0, 2)
2286 f.MustSeek(h.off, 0)
2287 h.ld(ctxt, f, h.pkg, h.length, h.pn)
2288 if *flagCaptureHostObjs != "" {
2293 func checkFingerprint(lib *sym.Library, libfp goobj.FingerprintType, src string, srcfp goobj.FingerprintType) {
2295 Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
2299 func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
2300 data := make([]byte, sym.Size)
2301 sect := f.Sections[sym.Section]
2302 if sect.Type != elf.SHT_PROGBITS && sect.Type != elf.SHT_NOTE {
2303 Errorf(nil, "reading %s from non-data section", sym.Name)
2305 n, err := sect.ReadAt(data, int64(sym.Value-sect.Addr))
2306 if uint64(n) != sym.Size {
2307 Errorf(nil, "reading contents of %s: %v", sym.Name, err)
2312 func readwithpad(r io.Reader, sz int32) ([]byte, error) {
2313 data := make([]byte, Rnd(int64(sz), 4))
2314 _, err := io.ReadFull(r, data)
2322 func readnote(f *elf.File, name []byte, typ int32) ([]byte, error) {
2323 for _, sect := range f.Sections {
2324 if sect.Type != elf.SHT_NOTE {
2329 var namesize, descsize, noteType int32
2330 err := binary.Read(r, f.ByteOrder, &namesize)
2335 return nil, fmt.Errorf("read namesize failed: %v", err)
2337 err = binary.Read(r, f.ByteOrder, &descsize)
2339 return nil, fmt.Errorf("read descsize failed: %v", err)
2341 err = binary.Read(r, f.ByteOrder, ¬eType)
2343 return nil, fmt.Errorf("read type failed: %v", err)
2345 noteName, err := readwithpad(r, namesize)
2347 return nil, fmt.Errorf("read name failed: %v", err)
2349 desc, err := readwithpad(r, descsize)
2351 return nil, fmt.Errorf("read desc failed: %v", err)
2353 if string(name) == string(noteName) && typ == noteType {
2361 func findshlib(ctxt *Link, shlib string) string {
2362 if filepath.IsAbs(shlib) {
2365 for _, libdir := range ctxt.Libdir {
2366 libpath := filepath.Join(libdir, shlib)
2367 if _, err := os.Stat(libpath); err == nil {
2371 Errorf(nil, "cannot find shared library: %s", shlib)
2375 func ldshlibsyms(ctxt *Link, shlib string) {
2377 if filepath.IsAbs(shlib) {
2379 shlib = filepath.Base(shlib)
2381 libpath = findshlib(ctxt, shlib)
2386 for _, processedlib := range ctxt.Shlibs {
2387 if processedlib.Path == libpath {
2391 if ctxt.Debugvlog > 1 {
2392 ctxt.Logf("ldshlibsyms: found library with name %s at %s\n", shlib, libpath)
2395 f, err := elf.Open(libpath)
2397 Errorf(nil, "cannot open shared library: %s", libpath)
2400 // Keep the file open as decodetypeGcprog needs to read from it.
2401 // TODO: fix. Maybe mmap the file.
2404 hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
2406 Errorf(nil, "cannot read ABI hash from shared library %s: %v", libpath, err)
2410 depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
2412 Errorf(nil, "cannot read dep list from shared library %s: %v", libpath, err)
2416 for _, dep := range strings.Split(string(depsbytes), "\n") {
2420 if !filepath.IsAbs(dep) {
2421 // If the dep can be interpreted as a path relative to the shlib
2422 // in which it was found, do that. Otherwise, we will leave it
2423 // to be resolved by libdir lookup.
2424 abs := filepath.Join(filepath.Dir(libpath), dep)
2425 if _, err := os.Stat(abs); err == nil {
2429 deps = append(deps, dep)
2432 syms, err := f.DynamicSymbols()
2434 Errorf(nil, "cannot read symbols from shared library: %s", libpath)
2438 for _, elfsym := range syms {
2439 if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
2443 // Symbols whose names start with "type:" are compiler generated,
2444 // so make functions with that prefix internal.
2446 symname := elfsym.Name // (unmangled) symbol name
2447 if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type:") {
2448 ver = abiInternalVer
2449 } else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC {
2450 // Demangle the ABI name. Keep in sync with symtab.go:mangleABIName.
2451 if strings.HasSuffix(elfsym.Name, ".abiinternal") {
2452 ver = sym.SymVerABIInternal
2453 symname = strings.TrimSuffix(elfsym.Name, ".abiinternal")
2454 } else if strings.HasSuffix(elfsym.Name, ".abi0") {
2456 symname = strings.TrimSuffix(elfsym.Name, ".abi0")
2461 s := l.LookupOrCreateSym(symname, ver)
2463 // Because loadlib above loads all .a files before loading
2464 // any shared libraries, any non-dynimport symbols we find
2465 // that duplicate symbols already loaded should be ignored
2466 // (the symbols from the .a files "win").
2467 if l.SymType(s) != 0 && l.SymType(s) != sym.SDYNIMPORT {
2470 su := l.MakeSymbolUpdater(s)
2471 su.SetType(sym.SDYNIMPORT)
2472 l.SetSymElfType(s, elf.ST_TYPE(elfsym.Info))
2473 su.SetSize(int64(elfsym.Size))
2474 if elfsym.Section != elf.SHN_UNDEF {
2475 // Set .File for the library that actually defines the symbol.
2476 l.SetSymPkg(s, libpath)
2478 // The decodetype_* functions in decodetype.go need access to
2480 sname := l.SymName(s)
2481 if strings.HasPrefix(sname, "type:") && !strings.HasPrefix(sname, "type:.") {
2482 su.SetData(readelfsymboldata(ctxt, f, &elfsym))
2486 if symname != elfsym.Name {
2487 l.SetSymExtname(s, elfsym.Name)
2490 ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f})
2493 func addsection(ldr *loader.Loader, arch *sys.Arch, seg *sym.Segment, name string, rwx int) *sym.Section {
2494 sect := ldr.NewSection()
2495 sect.Rwx = uint8(rwx)
2498 sect.Align = int32(arch.PtrSize) // everything is at least pointer-aligned
2499 seg.Sections = append(seg.Sections, sect)
2504 fmt.Fprintf(os.Stderr, "usage: link [options] main.o\n")
2505 objabi.Flagprint(os.Stderr)
2509 type SymbolType int8 // TODO: after genasmsym is gone, maybe rename to plan9typeChar or something
2512 // see also https://9p.io/magic/man2html/1/nm
2513 TextSym SymbolType = 'T'
2514 DataSym SymbolType = 'D'
2515 BSSSym SymbolType = 'B'
2516 UndefinedSym SymbolType = 'U'
2517 TLSSym SymbolType = 't'
2518 FrameSym SymbolType = 'm'
2519 ParamSym SymbolType = 'p'
2520 AutoSym SymbolType = 'a'
2522 // Deleted auto (not a real sym, just placeholder for type)
2523 DeletedAutoSym = 'x'
2526 // defineInternal defines a symbol used internally by the go runtime.
2527 func (ctxt *Link) defineInternal(p string, t sym.SymKind) loader.Sym {
2528 s := ctxt.loader.CreateSymForUpdate(p, 0)
2535 func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) loader.Sym {
2536 s := ctxt.defineInternal(p, t)
2537 ctxt.loader.SetSymValue(s, v)
2541 func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
2542 if uint64(addr) >= Segdata.Vaddr {
2543 return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
2545 if uint64(addr) >= Segtext.Vaddr {
2546 return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
2548 ldr.Errorf(s, "invalid datoff %#x", addr)
2552 func Entryvalue(ctxt *Link) int64 {
2553 a := *flagEntrySymbol
2554 if a[0] >= '0' && a[0] <= '9' {
2558 s := ldr.Lookup(a, 0)
2560 Errorf(nil, "missing entry symbol %q", a)
2563 st := ldr.SymType(s)
2565 return *FlagTextAddr
2567 if !ctxt.IsAIX() && st != sym.STEXT {
2568 ldr.Errorf(s, "entry not text")
2570 return ldr.SymValue(s)
2573 func (ctxt *Link) callgraph() {
2579 for _, s := range ctxt.Textp {
2580 relocs := ldr.Relocs(s)
2581 for i := 0; i < relocs.Count(); i++ {
2587 if r.Type().IsDirectCall() && ldr.SymType(rs) == sym.STEXT {
2588 ctxt.Logf("%s calls %s\n", ldr.SymName(s), ldr.SymName(rs))
2594 func Rnd(v int64, r int64) int64 {
2607 func bgetc(r *bio.Reader) int {
2608 c, err := r.ReadByte()
2611 log.Fatalf("reading input: %v", err)
2618 type markKind uint8 // for postorder traversal
2625 func postorder(libs []*sym.Library) []*sym.Library {
2626 order := make([]*sym.Library, 0, len(libs)) // hold the result
2627 mark := make(map[*sym.Library]markKind, len(libs))
2628 for _, lib := range libs {
2629 dfs(lib, mark, &order)
2634 func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library) {
2635 if mark[lib] == visited {
2638 if mark[lib] == visiting {
2639 panic("found import cycle while visiting " + lib.Pkg)
2641 mark[lib] = visiting
2642 for _, i := range lib.Imports {
2646 *order = append(*order, lib)
2649 func ElfSymForReloc(ctxt *Link, s loader.Sym) int32 {
2650 // If putelfsym created a local version of this symbol, use that in all
2652 les := ctxt.loader.SymLocalElfSym(s)
2656 return ctxt.loader.SymElfSym(s)
2660 func AddGotSym(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, elfRelocTyp uint32) {
2661 if ldr.SymGot(s) >= 0 {
2665 Adddynsym(ldr, target, syms, s)
2666 got := ldr.MakeSymbolUpdater(syms.GOT)
2667 ldr.SetGot(s, int32(got.Size()))
2668 got.AddUint(target.Arch, 0)
2671 if target.Arch.PtrSize == 8 {
2672 rela := ldr.MakeSymbolUpdater(syms.Rela)
2673 rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2674 rela.AddUint64(target.Arch, elf.R_INFO(uint32(ldr.SymDynid(s)), elfRelocTyp))
2675 rela.AddUint64(target.Arch, 0)
2677 rel := ldr.MakeSymbolUpdater(syms.Rel)
2678 rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2679 rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), elfRelocTyp))
2681 } else if target.IsDarwin() {
2682 leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT)
2683 leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
2684 if target.IsPIE() && target.IsInternal() {
2685 // Mach-O relocations are a royal pain to lay out.
2686 // They use a compact stateful bytecode representation.
2687 // Here we record what are needed and encode them later.
2688 MachoAddBind(int64(ldr.SymGot(s)), s)
2691 ldr.Errorf(s, "addgotsym: unsupported binary format")
2695 var hostobjcounter int
2697 // captureHostObj writes out the content of a host object (pulled from
2698 // an archive or loaded from a *.o file directly) to a directory
2699 // specified via the linker's "-capturehostobjs" debugging flag. This
2700 // is intended to make it easier for a developer to inspect the actual
2701 // object feeding into "CGO internal" link step.
2702 func captureHostObj(h *Hostobj) {
2703 // Form paths for info file and obj file.
2704 ofile := fmt.Sprintf("captured-obj-%d.o", hostobjcounter)
2705 ifile := fmt.Sprintf("captured-obj-%d.txt", hostobjcounter)
2707 opath := filepath.Join(*flagCaptureHostObjs, ofile)
2708 ipath := filepath.Join(*flagCaptureHostObjs, ifile)
2710 // Write the info file.
2711 info := fmt.Sprintf("pkg: %s\npn: %s\nfile: %s\noff: %d\nlen: %d\n",
2712 h.pkg, h.pn, h.file, h.off, h.length)
2713 if err := os.WriteFile(ipath, []byte(info), 0666); err != nil {
2714 log.Fatalf("error writing captured host obj info %s: %v", ipath, err)
2717 readObjData := func() []byte {
2718 inf, err := os.Open(h.file)
2720 log.Fatalf("capturing host obj: open failed on %s: %v", h.pn, err)
2722 res := make([]byte, h.length)
2723 if n, err := inf.ReadAt(res, h.off); err != nil || n != int(h.length) {
2724 log.Fatalf("capturing host obj: readat failed on %s: %v", h.pn, err)
2729 // Write the object file.
2730 if err := os.WriteFile(opath, readObjData(), 0666); err != nil {
2731 log.Fatalf("error writing captured host object %s: %v", opath, err)
2734 fmt.Fprintf(os.Stderr, "link: info: captured host object %s to %s\n",