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 ELF.Reloc1,
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 // preferlinkext is a list of packages for which the Go command
345 // noticed use of peculiar C flags. If we see any of these,
346 // default to linking externally unless overridden by the
347 // user. See issues #58619, #58620, and #58848.
348 preferlinkext []string
350 // unknownObjFormat is set to true if we see an object whose
351 // format we don't recognize.
352 unknownObjFormat = false
357 func Lflag(ctxt *Link, arg string) {
358 ctxt.Libdir = append(ctxt.Libdir, arg)
362 * Unix doesn't like it when we write to a running (or, sometimes,
363 * recently run) binary, so remove the output file before writing it.
364 * On Windows 7, remove() can force a subsequent create() to fail.
365 * S_ISREG() does not exist on Plan 9.
367 func mayberemoveoutfile() {
368 if fi, err := os.Lstat(*flagOutfile); err == nil && !fi.Mode().IsRegular() {
371 os.Remove(*flagOutfile)
374 func libinit(ctxt *Link) {
375 Funcalign = thearch.Funcalign
377 // add goroot to the end of the libdir list.
381 if *flagInstallSuffix != "" {
383 suffix = *flagInstallSuffix
384 } else if *flagRace {
387 } else if *flagMsan {
390 } else if *flagAsan {
395 if buildcfg.GOROOT != "" {
396 Lflag(ctxt, filepath.Join(buildcfg.GOROOT, "pkg", fmt.Sprintf("%s_%s%s%s", buildcfg.GOOS, buildcfg.GOARCH, suffixsep, suffix)))
401 if err := ctxt.Out.Open(*flagOutfile); err != nil {
402 Exitf("cannot create %s: %v", *flagOutfile, err)
405 if *flagEntrySymbol == "" {
406 switch ctxt.BuildMode {
407 case BuildModeCShared, BuildModeCArchive:
408 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s_lib", buildcfg.GOARCH, buildcfg.GOOS)
409 case BuildModeExe, BuildModePIE:
410 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s", buildcfg.GOARCH, buildcfg.GOOS)
411 case BuildModeShared, BuildModePlugin:
412 // No *flagEntrySymbol for -buildmode=shared and plugin
414 Errorf(nil, "unknown *flagEntrySymbol for buildmode %v", ctxt.BuildMode)
419 func exitIfErrors() {
420 if nerrors != 0 || checkStrictDups > 1 && strictDupMsgCount > 0 {
432 func loadinternal(ctxt *Link, name string) *sym.Library {
433 zerofp := goobj.FingerprintType{}
434 if ctxt.linkShared && ctxt.PackageShlib != nil {
435 if shlib := ctxt.PackageShlib[name]; shlib != "" {
436 return addlibpath(ctxt, "internal", "internal", "", name, shlib, zerofp)
439 if ctxt.PackageFile != nil {
440 if pname := ctxt.PackageFile[name]; pname != "" {
441 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
443 ctxt.Logf("loadinternal: cannot find %s\n", name)
447 for _, libdir := range ctxt.Libdir {
449 shlibname := filepath.Join(libdir, name+".shlibname")
450 if ctxt.Debugvlog != 0 {
451 ctxt.Logf("searching for %s.a in %s\n", name, shlibname)
453 if _, err := os.Stat(shlibname); err == nil {
454 return addlibpath(ctxt, "internal", "internal", "", name, shlibname, zerofp)
457 pname := filepath.Join(libdir, name+".a")
458 if ctxt.Debugvlog != 0 {
459 ctxt.Logf("searching for %s.a in %s\n", name, pname)
461 if _, err := os.Stat(pname); err == nil {
462 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
466 if name == "runtime" {
467 Exitf("error: unable to find runtime.a")
469 ctxt.Logf("warning: unable to find %s.a\n", name)
473 // extld returns the current external linker.
474 func (ctxt *Link) extld() []string {
475 if len(flagExtld) == 0 {
476 // Return the default external linker for the platform.
477 // This only matters when link tool is called directly without explicit -extld,
478 // go tool already passes the correct linker in other cases.
479 switch buildcfg.GOOS {
480 case "darwin", "freebsd", "openbsd":
481 flagExtld = []string{"clang"}
483 flagExtld = []string{"gcc"}
489 // findLibPathCmd uses cmd command to find gcc library libname.
490 // It returns library full path if found, or "none" if not found.
491 func (ctxt *Link) findLibPathCmd(cmd, libname string) string {
492 extld := ctxt.extld()
493 name, args := extld[0], extld[1:]
494 args = append(args, hostlinkArchArgs(ctxt.Arch)...)
495 args = append(args, cmd)
496 if ctxt.Debugvlog != 0 {
497 ctxt.Logf("%s %v\n", extld, args)
499 out, err := exec.Command(name, args...).Output()
501 if ctxt.Debugvlog != 0 {
502 ctxt.Logf("not using a %s file because compiler failed\n%v\n%s\n", libname, err, out)
506 return strings.TrimSpace(string(out))
509 // findLibPath searches for library libname.
510 // It returns library full path if found, or "none" if not found.
511 func (ctxt *Link) findLibPath(libname string) string {
512 return ctxt.findLibPathCmd("--print-file-name="+libname, libname)
515 func (ctxt *Link) loadlib() {
517 switch *FlagStrictDups {
521 flags |= loader.FlagStrictDups
523 log.Fatalf("invalid -strictdups flag value %d", *FlagStrictDups)
525 elfsetstring1 := func(str string, off int) { elfsetstring(ctxt, 0, str, off) }
526 ctxt.loader = loader.NewLoader(flags, elfsetstring1, &ctxt.ErrorReporter.ErrorReporter)
527 ctxt.ErrorReporter.SymName = func(s loader.Sym) string {
528 return ctxt.loader.SymName(s)
531 // ctxt.Library grows during the loop, so not a range loop.
533 for ; i < len(ctxt.Library); i++ {
534 lib := ctxt.Library[i]
536 if ctxt.Debugvlog > 1 {
537 ctxt.Logf("autolib: %s (from %s)\n", lib.File, lib.Objref)
539 loadobjfile(ctxt, lib)
543 // load internal packages, if not already
545 loadinternal(ctxt, "runtime/race")
548 loadinternal(ctxt, "runtime/msan")
551 loadinternal(ctxt, "runtime/asan")
553 loadinternal(ctxt, "runtime")
554 for ; i < len(ctxt.Library); i++ {
555 lib := ctxt.Library[i]
557 loadobjfile(ctxt, lib)
560 // At this point, the Go objects are "preloaded". Not all the symbols are
561 // added to the symbol table (only defined package symbols are). Looking
562 // up symbol by name may not get expected result.
564 iscgo = ctxt.LibraryByPkg["runtime/cgo"] != nil
566 // Plugins a require cgo support to function. Similarly, plugins may require additional
567 // internal linker support on some platforms which may not be implemented.
568 ctxt.canUsePlugins = ctxt.LibraryByPkg["plugin"] != nil && iscgo
570 // We now have enough information to determine the link mode.
571 determineLinkMode(ctxt)
573 if ctxt.LinkMode == LinkExternal && !iscgo && !(buildcfg.GOOS == "darwin" && ctxt.BuildMode != BuildModePlugin && ctxt.Arch.Family == sys.AMD64) {
574 // This indicates a user requested -linkmode=external.
575 // The startup code uses an import of runtime/cgo to decide
576 // whether to initialize the TLS. So give it one. This could
577 // be handled differently but it's an unusual case.
578 if lib := loadinternal(ctxt, "runtime/cgo"); lib != nil && lib.Shlib == "" {
579 if ctxt.BuildMode == BuildModeShared || ctxt.linkShared {
580 Exitf("cannot implicitly include runtime/cgo in a shared library")
582 for ; i < len(ctxt.Library); i++ {
583 lib := ctxt.Library[i]
585 loadobjfile(ctxt, lib)
591 // Add non-package symbols and references of externally defined symbols.
592 ctxt.loader.LoadSyms(ctxt.Arch)
594 // Load symbols from shared libraries, after all Go object symbols are loaded.
595 for _, lib := range ctxt.Library {
597 if ctxt.Debugvlog > 1 {
598 ctxt.Logf("autolib: %s (from %s)\n", lib.Shlib, lib.Objref)
600 ldshlibsyms(ctxt, lib.Shlib)
604 // Process cgo directives (has to be done before host object loading).
605 ctxt.loadcgodirectives()
607 // Conditionally load host objects, or setup for external linking.
611 if ctxt.LinkMode == LinkInternal && len(hostobj) != 0 {
612 // If we have any undefined symbols in external
613 // objects, try to read them from the libgcc file.
615 undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
618 if ctxt.Debugvlog > 1 {
619 ctxt.Logf("loadlib: first unresolved is %s [%d] from %s [%d]\n",
620 ctxt.loader.SymName(undefs[0]), undefs[0],
621 ctxt.loader.SymName(froms[0]), froms[0])
625 if *flagLibGCC == "" {
626 *flagLibGCC = ctxt.findLibPathCmd("--print-libgcc-file-name", "libgcc")
628 if runtime.GOOS == "openbsd" && *flagLibGCC == "libgcc.a" {
629 // On OpenBSD `clang --print-libgcc-file-name` returns "libgcc.a".
630 // In this case we fail to load libgcc.a and can encounter link
631 // errors - see if we can find libcompiler_rt.a instead.
632 *flagLibGCC = ctxt.findLibPathCmd("--print-file-name=libcompiler_rt.a", "libcompiler_rt")
634 if ctxt.HeadType == objabi.Hwindows {
635 loadWindowsHostArchives(ctxt)
637 if *flagLibGCC != "none" {
638 hostArchive(ctxt, *flagLibGCC)
640 // For glibc systems, the linker setup used by GCC
643 // GROUP ( /lib/x86_64-linux-gnu/libc.so.6
644 // /usr/lib/x86_64-linux-gnu/libc_nonshared.a
645 // AS_NEEDED ( /lib64/ld-linux-x86-64.so.2 ) )
647 // where libc_nonshared.a contains a small set of
648 // symbols including "__stack_chk_fail_local" and a
649 // few others. Thus if we are doing internal linking
650 // and "__stack_chk_fail_local" is unresolved (most
651 // likely due to the use of -fstack-protector), try
652 // loading libc_nonshared.a to resolve it.
654 // On Alpine Linux (musl-based), the library providing
655 // this symbol is called libssp_nonshared.a.
656 isunresolved := symbolsAreUnresolved(ctxt, []string{"__stack_chk_fail_local"})
658 if p := ctxt.findLibPath("libc_nonshared.a"); p != "none" {
661 if p := ctxt.findLibPath("libssp_nonshared.a"); p != "none" {
668 // We've loaded all the code now.
671 strictDupMsgCount = ctxt.loader.NStrictDupMsgs()
674 // loadWindowsHostArchives loads in host archives and objects when
675 // doing internal linking on windows. Older toolchains seem to require
676 // just a single pass through the various archives, but some modern
677 // toolchains when linking a C program with mingw pass library paths
678 // multiple times to the linker, e.g. "... -lmingwex -lmingw32 ...
679 // -lmingwex -lmingw32 ...". To accommodate this behavior, we make two
680 // passes over the host archives below.
681 func loadWindowsHostArchives(ctxt *Link) {
683 for i := 0; any && i < 2; i++ {
684 // Link crt2.o (if present) to resolve "atexit" when
685 // using LLVM-based compilers.
686 isunresolved := symbolsAreUnresolved(ctxt, []string{"atexit"})
688 if p := ctxt.findLibPath("crt2.o"); p != "none" {
689 hostObject(ctxt, "crt2", p)
693 if p := ctxt.findLibPath("libsynchronization.a"); p != "none" {
697 if p := ctxt.findLibPath("libmingwex.a"); p != "none" {
700 if p := ctxt.findLibPath("libmingw32.a"); p != "none" {
703 // Link libmsvcrt.a to resolve '__acrt_iob_func' symbol
704 // (see https://golang.org/issue/23649 for details).
705 if p := ctxt.findLibPath("libmsvcrt.a"); p != "none" {
709 undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
712 if ctxt.Debugvlog > 1 {
713 ctxt.Logf("loadWindowsHostArchives: remaining unresolved is %s [%d] from %s [%d]\n",
714 ctxt.loader.SymName(undefs[0]), undefs[0],
715 ctxt.loader.SymName(froms[0]), froms[0])
719 // If needed, create the __CTOR_LIST__ and __DTOR_LIST__
720 // symbols (referenced by some of the mingw support library
721 // routines). Creation of these symbols is normally done by the
722 // linker if not already present.
723 want := []string{"__CTOR_LIST__", "__DTOR_LIST__"}
724 isunresolved := symbolsAreUnresolved(ctxt, want)
725 for k, w := range want {
727 sb := ctxt.loader.CreateSymForUpdate(w, 0)
728 sb.SetType(sym.SDATA)
729 sb.AddUint64(ctxt.Arch, 0)
730 sb.SetReachable(true)
731 ctxt.loader.SetAttrSpecial(sb.Sym(), true)
735 // Fix up references to DLL import symbols now that we're done
736 // pulling in new objects.
737 if err := loadpe.PostProcessImports(); err != nil {
738 Errorf(nil, "%v", err)
741 // TODO: maybe do something similar to peimporteddlls to collect
742 // all lib names and try link them all to final exe just like
743 // libmingwex.a and libmingw32.a:
746 #cgo windows LDFLAGS: -lmsvcrt -lm
752 // loadcgodirectives reads the previously discovered cgo directives, creating
753 // symbols in preparation for host object loading or use later in the link.
754 func (ctxt *Link) loadcgodirectives() {
756 hostObjSyms := make(map[loader.Sym]struct{})
757 for _, d := range ctxt.cgodata {
758 setCgoAttr(ctxt, d.file, d.pkg, d.directives, hostObjSyms)
762 if ctxt.LinkMode == LinkInternal {
763 // Drop all the cgo_import_static declarations.
764 // Turns out we won't be needing them.
765 for symIdx := range hostObjSyms {
766 if l.SymType(symIdx) == sym.SHOSTOBJ {
767 // If a symbol was marked both
768 // cgo_import_static and cgo_import_dynamic,
769 // then we want to make it cgo_import_dynamic
771 su := l.MakeSymbolUpdater(symIdx)
772 if l.SymExtname(symIdx) != "" && l.SymDynimplib(symIdx) != "" && !(l.AttrCgoExportStatic(symIdx) || l.AttrCgoExportDynamic(symIdx)) {
773 su.SetType(sym.SDYNIMPORT)
782 // Set up flags and special symbols depending on the platform build mode.
783 // This version works with loader.Loader.
784 func (ctxt *Link) linksetup() {
785 switch ctxt.BuildMode {
786 case BuildModeCShared, BuildModePlugin:
787 symIdx := ctxt.loader.LookupOrCreateSym("runtime.islibrary", 0)
788 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
789 sb.SetType(sym.SNOPTRDATA)
791 case BuildModeCArchive:
792 symIdx := ctxt.loader.LookupOrCreateSym("runtime.isarchive", 0)
793 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
794 sb.SetType(sym.SNOPTRDATA)
798 // Recalculate pe parameters now that we have ctxt.LinkMode set.
799 if ctxt.HeadType == objabi.Hwindows {
803 if ctxt.LinkMode == LinkExternal {
804 // When external linking, we are creating an object file. The
805 // absolute address is irrelevant.
809 // If there are no dynamic libraries needed, gcc disables dynamic linking.
810 // Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13)
811 // assumes that a dynamic binary always refers to at least one dynamic library.
812 // Rather than be a source of test cases for glibc, disable dynamic linking
813 // the same way that gcc would.
815 // Exception: on OS X, programs such as Shark only work with dynamic
816 // binaries, so leave it enabled on OS X (Mach-O) binaries.
817 // Also leave it enabled on Solaris which doesn't support
818 // statically linked binaries.
819 if ctxt.BuildMode == BuildModeExe {
820 if havedynamic == 0 && ctxt.HeadType != objabi.Hdarwin && ctxt.HeadType != objabi.Hsolaris {
825 if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && buildcfg.GOOS != "aix" {
826 toc := ctxt.loader.LookupOrCreateSym(".TOC.", 0)
827 sb := ctxt.loader.MakeSymbolUpdater(toc)
828 sb.SetType(sym.SDYNIMPORT)
831 // The Android Q linker started to complain about underalignment of the our TLS
832 // section. We don't actually use the section on android, so don't
834 if buildcfg.GOOS != "android" {
835 tlsg := ctxt.loader.LookupOrCreateSym("runtime.tlsg", 0)
836 sb := ctxt.loader.MakeSymbolUpdater(tlsg)
838 // runtime.tlsg is used for external linking on platforms that do not define
839 // a variable to hold g in assembly (currently only intel).
841 sb.SetType(sym.STLSBSS)
842 sb.SetSize(int64(ctxt.Arch.PtrSize))
843 } else if sb.Type() != sym.SDYNIMPORT {
844 Errorf(nil, "runtime declared tlsg variable %v", sb.Type())
846 ctxt.loader.SetAttrReachable(tlsg, true)
850 var moduledata loader.Sym
851 var mdsb *loader.SymbolBuilder
852 if ctxt.BuildMode == BuildModePlugin {
853 moduledata = ctxt.loader.LookupOrCreateSym("local.pluginmoduledata", 0)
854 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
855 ctxt.loader.SetAttrLocal(moduledata, true)
857 moduledata = ctxt.loader.LookupOrCreateSym("runtime.firstmoduledata", 0)
858 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
860 if mdsb.Type() != 0 && mdsb.Type() != sym.SDYNIMPORT {
861 // If the module (toolchain-speak for "executable or shared
862 // library") we are linking contains the runtime package, it
863 // will define the runtime.firstmoduledata symbol and we
864 // truncate it back to 0 bytes so we can define its entire
865 // contents in symtab.go:symtab().
868 // In addition, on ARM, the runtime depends on the linker
869 // recording the value of GOARM.
870 if ctxt.Arch.Family == sys.ARM {
871 goarm := ctxt.loader.LookupOrCreateSym("runtime.goarm", 0)
872 sb := ctxt.loader.MakeSymbolUpdater(goarm)
873 sb.SetType(sym.SDATA)
875 sb.AddUint8(uint8(buildcfg.GOARM))
878 // Set runtime.disableMemoryProfiling bool if
879 // runtime.MemProfile is not retained in the binary after
880 // deadcode (and we're not dynamically linking).
881 memProfile := ctxt.loader.Lookup("runtime.MemProfile", abiInternalVer)
882 if memProfile != 0 && !ctxt.loader.AttrReachable(memProfile) && !ctxt.DynlinkingGo() {
883 memProfSym := ctxt.loader.LookupOrCreateSym("runtime.disableMemoryProfiling", 0)
884 sb := ctxt.loader.MakeSymbolUpdater(memProfSym)
885 sb.SetType(sym.SDATA)
887 sb.AddUint8(1) // true bool
890 // If OTOH the module does not contain the runtime package,
891 // create a local symbol for the moduledata.
892 moduledata = ctxt.loader.LookupOrCreateSym("local.moduledata", 0)
893 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
894 ctxt.loader.SetAttrLocal(moduledata, true)
896 // In all cases way we mark the moduledata as noptrdata to hide it from
898 mdsb.SetType(sym.SNOPTRDATA)
899 ctxt.loader.SetAttrReachable(moduledata, true)
900 ctxt.Moduledata = moduledata
902 if ctxt.Arch == sys.Arch386 && ctxt.HeadType != objabi.Hwindows {
903 if (ctxt.BuildMode == BuildModeCArchive && ctxt.IsELF) || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE || ctxt.DynlinkingGo() {
904 got := ctxt.loader.LookupOrCreateSym("_GLOBAL_OFFSET_TABLE_", 0)
905 sb := ctxt.loader.MakeSymbolUpdater(got)
906 sb.SetType(sym.SDYNIMPORT)
907 ctxt.loader.SetAttrReachable(got, true)
911 // DWARF-gen and other phases require that the unit Textp slices
912 // be populated, so that it can walk the functions in each unit.
913 // Call into the loader to do this (requires that we collect the
914 // set of internal libraries first). NB: might be simpler if we
915 // moved isRuntimeDepPkg to cmd/internal and then did the test in
916 // loader.AssignTextSymbolOrder.
917 ctxt.Library = postorder(ctxt.Library)
919 for _, lib := range ctxt.Library {
920 intlibs = append(intlibs, isRuntimeDepPkg(lib.Pkg))
922 ctxt.Textp = ctxt.loader.AssignTextSymbolOrder(ctxt.Library, intlibs, ctxt.Textp)
925 // mangleTypeSym shortens the names of symbols that represent Go types
926 // if they are visible in the symbol table.
928 // As the names of these symbols are derived from the string of
929 // the type, they can run to many kilobytes long. So we shorten
930 // them using a SHA-1 when the name appears in the final binary.
931 // This also removes characters that upset external linkers.
933 // These are the symbols that begin with the prefix 'type.' and
934 // contain run-time type information used by the runtime and reflect
935 // packages. All Go binaries contain these symbols, but only
936 // those programs loaded dynamically in multiple parts need these
937 // symbols to have entries in the symbol table.
938 func (ctxt *Link) mangleTypeSym() {
939 if ctxt.BuildMode != BuildModeShared && !ctxt.linkShared && ctxt.BuildMode != BuildModePlugin && !ctxt.CanUsePlugins() {
944 for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
945 if !ldr.AttrReachable(s) && !ctxt.linkShared {
946 // If -linkshared, the GCProg generation code may need to reach
947 // out to the shared library for the type descriptor's data, even
948 // the type descriptor itself is not actually needed at run time
949 // (therefore not reachable). We still need to mangle its name,
950 // so it is consistent with the one stored in the shared library.
953 name := ldr.SymName(s)
954 newName := typeSymbolMangle(name)
956 ldr.SetSymExtname(s, newName)
958 // When linking against a shared library, the Go object file may
959 // have reference to the original symbol name whereas the shared
960 // library provides a symbol with the mangled name. We need to
961 // copy the payload of mangled to original.
962 // XXX maybe there is a better way to do this.
963 dup := ldr.Lookup(newName, ldr.SymVersion(s))
966 dt := ldr.SymType(dup)
967 if st == sym.Sxxx && dt != sym.Sxxx {
975 // typeSymbolMangle mangles the given symbol name into something shorter.
977 // Keep the type:. prefix, which parts of the linker (like the
978 // DWARF generator) know means the symbol is not decodable.
979 // Leave type:runtime. symbols alone, because other parts of
980 // the linker manipulates them.
981 func typeSymbolMangle(name string) string {
982 if !strings.HasPrefix(name, "type:") {
985 if strings.HasPrefix(name, "type:runtime.") {
988 if len(name) <= 14 && !strings.Contains(name, "@") { // Issue 19529
991 hash := notsha256.Sum256([]byte(name))
996 return prefix + base64.StdEncoding.EncodeToString(hash[:6])
1000 * look for the next file in an archive.
1001 * adapted from libmach.
1003 func nextar(bp *bio.Reader, off int64, a *ArHdr) int64 {
1008 var buf [SAR_HDR]byte
1009 if n, err := io.ReadFull(bp, buf[:]); err != nil {
1010 if n == 0 && err != io.EOF {
1016 a.name = artrim(buf[0:16])
1017 a.date = artrim(buf[16:28])
1018 a.uid = artrim(buf[28:34])
1019 a.gid = artrim(buf[34:40])
1020 a.mode = artrim(buf[40:48])
1021 a.size = artrim(buf[48:58])
1022 a.fmag = artrim(buf[58:60])
1024 arsize := atolwhex(a.size)
1028 return arsize + SAR_HDR
1031 func loadobjfile(ctxt *Link, lib *sym.Library) {
1032 pkg := objabi.PathToPrefix(lib.Pkg)
1034 if ctxt.Debugvlog > 1 {
1035 ctxt.Logf("ldobj: %s (%s)\n", lib.File, pkg)
1037 f, err := bio.Open(lib.File)
1039 Exitf("cannot open file %s: %v", lib.File, err)
1043 if pkg == "main" && !lib.Main {
1044 Exitf("%s: not package main", lib.File)
1048 for i := 0; i < len(ARMAG); i++ {
1049 if c, err := f.ReadByte(); err == nil && c == ARMAG[i] {
1053 /* load it as a regular file */
1054 l := f.MustSeek(0, 2)
1056 ldobj(ctxt, f, lib, l, lib.File, lib.File)
1061 * load all the object files from the archive now.
1062 * this gives us sequential file access and keeps us
1063 * from needing to come back later to pick up more
1064 * objects. it breaks the usual C archive model, but
1065 * this is Go, not C. the common case in Go is that
1066 * we need to load all the objects, and then we throw away
1067 * the individual symbols that are unused.
1069 * loading every object will also make it possible to
1070 * load foreign objects not referenced by __.PKGDEF.
1075 l := nextar(f, off, &arhdr)
1080 Exitf("%s: malformed archive", lib.File)
1084 // __.PKGDEF isn't a real Go object file, and it's
1085 // absent in -linkobj builds anyway. Skipping it
1086 // ensures consistency between -linkobj and normal
1088 if arhdr.name == pkgdef {
1092 if arhdr.name == "dynimportfail" {
1093 dynimportfail = append(dynimportfail, lib.Pkg)
1095 if arhdr.name == "preferlinkext" {
1096 // Ignore this directive if -linkmode has been
1098 if ctxt.LinkMode == LinkAuto {
1099 preferlinkext = append(preferlinkext, lib.Pkg)
1103 // Skip other special (non-object-file) sections that
1104 // build tools may have added. Such sections must have
1105 // short names so that the suffix is not truncated.
1106 if len(arhdr.name) < 16 {
1107 if ext := filepath.Ext(arhdr.name); ext != ".o" && ext != ".syso" {
1112 pname := fmt.Sprintf("%s(%s)", lib.File, arhdr.name)
1113 l = atolwhex(arhdr.size)
1114 ldobj(ctxt, f, lib, l, pname, lib.File)
1118 type Hostobj struct {
1119 ld func(*Link, *bio.Reader, string, int64, string)
1127 var hostobj []Hostobj
1129 // These packages can use internal linking mode.
1130 // Others trigger external mode.
1131 var internalpkg = []string{
1132 "crypto/internal/boring",
1133 "crypto/internal/boring/syso",
1139 "runtime/race/internal/amd64v1",
1140 "runtime/race/internal/amd64v3",
1145 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 {
1147 for _, intpkg := range internalpkg {
1154 // DragonFly declares errno with __thread, which results in a symbol
1155 // type of R_386_TLS_GD or R_X86_64_TLSGD. The Go linker does not
1156 // currently know how to handle TLS relocations, hence we have to
1157 // force external linking for any libraries that link in code that
1158 // uses errno. This can be removed if the Go linker ever supports
1159 // these relocation types.
1160 if headType == objabi.Hdragonfly {
1161 if pkg == "net" || pkg == "os/user" {
1170 hostobj = append(hostobj, Hostobj{})
1171 h := &hostobj[len(hostobj)-1]
1181 func hostobjs(ctxt *Link) {
1182 if ctxt.LinkMode != LinkInternal {
1187 for i := 0; i < len(hostobj); i++ {
1189 f, err := bio.Open(h.file)
1191 Exitf("cannot reopen %s: %v", h.pn, err)
1193 f.MustSeek(h.off, 0)
1195 Errorf(nil, "%s: unrecognized object file format", h.pn)
1198 h.ld(ctxt, f, h.pkg, h.length, h.pn)
1199 if *flagCaptureHostObjs != "" {
1206 func hostlinksetup(ctxt *Link) {
1207 if ctxt.LinkMode != LinkExternal {
1211 // For external link, record that we need to tell the external linker -s,
1212 // and turn off -s internally: the external linker needs the symbol
1213 // information for its final link.
1217 // create temporary directory and arrange cleanup
1218 if *flagTmpdir == "" {
1219 dir, err := os.MkdirTemp("", "go-link-")
1226 os.RemoveAll(*flagTmpdir)
1230 // change our output to temporary object file
1231 if err := ctxt.Out.Close(); err != nil {
1232 Exitf("error closing output file")
1234 mayberemoveoutfile()
1236 p := filepath.Join(*flagTmpdir, "go.o")
1237 if err := ctxt.Out.Open(p); err != nil {
1238 Exitf("cannot create %s: %v", p, err)
1242 // hostobjCopy creates a copy of the object files in hostobj in a
1243 // temporary directory.
1244 func (ctxt *Link) hostobjCopy() (paths []string) {
1245 var wg sync.WaitGroup
1246 sema := make(chan struct{}, runtime.NumCPU()) // limit open file descriptors
1247 for i, h := range hostobj {
1249 dst := filepath.Join(*flagTmpdir, fmt.Sprintf("%06d.o", i))
1250 paths = append(paths, dst)
1251 if ctxt.Debugvlog != 0 {
1252 ctxt.Logf("host obj copy: %s from pkg %s -> %s\n", h.pn, h.pkg, dst)
1262 f, err := os.Open(h.file)
1264 Exitf("cannot reopen %s: %v", h.pn, err)
1267 if _, err := f.Seek(h.off, 0); err != nil {
1268 Exitf("cannot seek %s: %v", h.pn, err)
1271 w, err := os.Create(dst)
1273 Exitf("cannot create %s: %v", dst, err)
1275 if _, err := io.CopyN(w, f, h.length); err != nil {
1276 Exitf("cannot write %s: %v", dst, err)
1278 if err := w.Close(); err != nil {
1279 Exitf("cannot close %s: %v", dst, err)
1287 // writeGDBLinkerScript creates gcc linker script file in temp
1288 // directory. writeGDBLinkerScript returns created file path.
1289 // The script is used to work around gcc bug
1290 // (see https://golang.org/issue/20183 for details).
1291 func writeGDBLinkerScript() string {
1292 name := "fix_debug_gdb_scripts.ld"
1293 path := filepath.Join(*flagTmpdir, name)
1296 .debug_gdb_scripts BLOCK(__section_alignment__) (NOLOAD) :
1298 *(.debug_gdb_scripts)
1301 INSERT AFTER .debug_types;
1303 err := os.WriteFile(path, []byte(src), 0666)
1305 Errorf(nil, "WriteFile %s failed: %v", name, err)
1310 // archive builds a .a archive from the hostobj object files.
1311 func (ctxt *Link) archive() {
1312 if ctxt.BuildMode != BuildModeCArchive {
1318 if *flagExtar == "" {
1322 mayberemoveoutfile()
1324 // Force the buffer to flush here so that external
1325 // tools will see a complete file.
1326 if err := ctxt.Out.Close(); err != nil {
1327 Exitf("error closing %v", *flagOutfile)
1330 argv := []string{*flagExtar, "-q", "-c", "-s"}
1331 if ctxt.HeadType == objabi.Haix {
1332 argv = append(argv, "-X64")
1334 argv = append(argv, *flagOutfile)
1335 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1336 argv = append(argv, ctxt.hostobjCopy()...)
1338 if ctxt.Debugvlog != 0 {
1339 ctxt.Logf("archive: %s\n", strings.Join(argv, " "))
1342 // If supported, use syscall.Exec() to invoke the archive command,
1343 // which should be the final remaining step needed for the link.
1344 // This will reduce peak RSS for the link (and speed up linking of
1345 // large applications), since when the archive command runs we
1346 // won't be holding onto all of the linker's live memory.
1347 if syscallExecSupported && !ownTmpDir {
1349 ctxt.execArchive(argv)
1350 panic("should not get here")
1353 // Otherwise invoke 'ar' in the usual way (fork + exec).
1354 if out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput(); err != nil {
1355 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1359 func (ctxt *Link) hostlink() {
1360 if ctxt.LinkMode != LinkExternal || nerrors > 0 {
1363 if ctxt.BuildMode == BuildModeCArchive {
1368 argv = append(argv, ctxt.extld()...)
1369 argv = append(argv, hostlinkArchArgs(ctxt.Arch)...)
1371 if *FlagS || debug_s {
1372 if ctxt.HeadType == objabi.Hdarwin {
1373 // Recent versions of macOS print
1374 // ld: warning: option -s is obsolete and being ignored
1375 // so do not pass any arguments.
1377 argv = append(argv, "-s")
1381 // On darwin, whether to combine DWARF into executable.
1382 // Only macOS supports unmapped segments such as our __DWARF segment.
1383 combineDwarf := ctxt.IsDarwin() && !*FlagS && !*FlagW && !debug_s && machoPlatform == PLATFORM_MACOS
1385 switch ctxt.HeadType {
1386 case objabi.Hdarwin:
1388 // Leave room for DWARF combining.
1389 // -headerpad is incompatible with -fembed-bitcode.
1390 argv = append(argv, "-Wl,-headerpad,1144")
1392 if ctxt.DynlinkingGo() && buildcfg.GOOS != "ios" {
1393 // -flat_namespace is deprecated on iOS.
1394 // It is useful for supporting plugins. We don't support plugins on iOS.
1395 // -flat_namespace may cause the dynamic linker to hang at forkExec when
1396 // resolving a lazy binding. See issue 38824.
1397 // Force eager resolution to work around.
1398 argv = append(argv, "-Wl,-flat_namespace", "-Wl,-bind_at_load")
1401 argv = append(argv, "-Wl,-S") // suppress STAB (symbolic debugging) symbols
1403 case objabi.Hopenbsd:
1404 argv = append(argv, "-Wl,-nopie")
1405 argv = append(argv, "-pthread")
1406 case objabi.Hwindows:
1408 argv = append(argv, "-mwindows")
1410 argv = append(argv, "-mconsole")
1412 // Mark as having awareness of terminal services, to avoid
1413 // ancient compatibility hacks.
1414 argv = append(argv, "-Wl,--tsaware")
1417 argv = append(argv, "-Wl,--nxcompat")
1419 argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", PeMinimumTargetMajorVersion))
1420 argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", PeMinimumTargetMinorVersion))
1421 argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", PeMinimumTargetMajorVersion))
1422 argv = append(argv, fmt.Sprintf("-Wl,--minor-subsystem-version=%d", PeMinimumTargetMinorVersion))
1424 argv = append(argv, "-pthread")
1425 // prevent ld to reorder .text functions to keep the same
1426 // first/last functions for moduledata.
1427 argv = append(argv, "-Wl,-bnoobjreorder")
1428 // mcmodel=large is needed for every gcc generated files, but
1429 // ld still need -bbigtoc in order to allow larger TOC.
1430 argv = append(argv, "-mcmodel=large")
1431 argv = append(argv, "-Wl,-bbigtoc")
1434 // On PPC64, verify the external toolchain supports Power10. This is needed when
1435 // PC relative relocations might be generated by Go. Only targets compiling ELF
1436 // binaries might generate these relocations.
1437 if ctxt.IsPPC64() && ctxt.IsElf() && buildcfg.GOPPC64 >= 10 {
1438 if !linkerFlagSupported(ctxt.Arch, argv[0], "", "-mcpu=power10") {
1439 Exitf("The external toolchain does not support -mcpu=power10. " +
1440 " This is required to externally link GOPPC64 >= power10")
1444 // Enable/disable ASLR on Windows.
1445 addASLRargs := func(argv []string, val bool) []string {
1446 // Old/ancient versions of GCC support "--dynamicbase" and
1447 // "--high-entropy-va" but don't enable it by default. In
1448 // addition, they don't accept "--disable-dynamicbase" or
1449 // "--no-dynamicbase", so the only way to disable ASLR is to
1450 // not pass any flags at all.
1452 // More modern versions of GCC (and also clang) enable ASLR
1453 // by default. With these compilers, however you can turn it
1454 // off if you want using "--disable-dynamicbase" or
1455 // "--no-dynamicbase".
1457 // The strategy below is to try using "--disable-dynamicbase";
1458 // if this succeeds, then assume we're working with more
1459 // modern compilers and act accordingly. If it fails, assume
1460 // an ancient compiler with ancient defaults.
1463 dbon := "--dynamicbase"
1464 heon := "--high-entropy-va"
1465 dboff := "--disable-dynamicbase"
1466 heoff := "--disable-high-entropy-va"
1471 // Test to see whether "--disable-dynamicbase" works.
1472 newer := linkerFlagSupported(ctxt.Arch, argv[0], "", "-Wl,"+dboff)
1474 // Newer compiler, which supports both on/off options.
1478 // older toolchain: we have to say nothing in order to
1479 // get a no-ASLR binary.
1485 argv = append(argv, "-Wl,"+dbopt)
1487 // enable high-entropy ASLR on 64-bit.
1488 if ctxt.Arch.PtrSize >= 8 && heopt != "" {
1489 argv = append(argv, "-Wl,"+heopt)
1494 switch ctxt.BuildMode {
1496 if ctxt.HeadType == objabi.Hdarwin {
1497 if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() {
1498 argv = append(argv, "-Wl,-no_pie")
1501 if *flagRace && ctxt.HeadType == objabi.Hwindows {
1502 // Current windows/amd64 race detector tsan support
1503 // library can't handle PIE mode (see #53539 for more details).
1504 // For now, explicitly disable PIE (since some compilers
1505 // default to it) if -race is in effect.
1506 argv = addASLRargs(argv, false)
1509 switch ctxt.HeadType {
1510 case objabi.Hdarwin, objabi.Haix:
1511 case objabi.Hwindows:
1512 if *flagAslr && *flagRace {
1513 // Current windows/amd64 race detector tsan support
1514 // library can't handle PIE mode (see #53539 for more details).
1515 // Disable alsr if -race in effect.
1518 argv = addASLRargs(argv, *flagAslr)
1521 if ctxt.UseRelro() {
1522 argv = append(argv, "-Wl,-z,relro")
1524 argv = append(argv, "-pie")
1526 case BuildModeCShared:
1527 if ctxt.HeadType == objabi.Hdarwin {
1528 argv = append(argv, "-dynamiclib")
1530 if ctxt.UseRelro() {
1531 argv = append(argv, "-Wl,-z,relro")
1533 argv = append(argv, "-shared")
1534 if ctxt.HeadType == objabi.Hwindows {
1535 argv = addASLRargs(argv, *flagAslr)
1537 // Pass -z nodelete to mark the shared library as
1538 // non-closeable: a dlclose will do nothing.
1539 argv = append(argv, "-Wl,-z,nodelete")
1540 // Only pass Bsymbolic on non-Windows.
1541 argv = append(argv, "-Wl,-Bsymbolic")
1544 case BuildModeShared:
1545 if ctxt.UseRelro() {
1546 argv = append(argv, "-Wl,-z,relro")
1548 argv = append(argv, "-shared")
1549 case BuildModePlugin:
1550 if ctxt.HeadType == objabi.Hdarwin {
1551 argv = append(argv, "-dynamiclib")
1553 if ctxt.UseRelro() {
1554 argv = append(argv, "-Wl,-z,relro")
1556 argv = append(argv, "-shared")
1560 var altLinker string
1561 if ctxt.IsELF && ctxt.DynlinkingGo() {
1562 // We force all symbol resolution to be done at program startup
1563 // because lazy PLT resolution can use large amounts of stack at
1564 // times we cannot allow it to do so.
1565 argv = append(argv, "-Wl,-z,now")
1567 // Do not let the host linker generate COPY relocations. These
1568 // can move symbols out of sections that rely on stable offsets
1569 // from the beginning of the section (like sym.STYPE).
1570 argv = append(argv, "-Wl,-z,nocopyreloc")
1572 if buildcfg.GOOS == "android" {
1573 // Use lld to avoid errors from default linker (issue #38838)
1577 if ctxt.Arch.InFamily(sys.ARM64) && buildcfg.GOOS == "linux" {
1578 // On ARM64, the GNU linker will fail with
1579 // -znocopyreloc if it thinks a COPY relocation is
1580 // required. Switch to gold.
1581 // https://sourceware.org/bugzilla/show_bug.cgi?id=19962
1582 // https://go.dev/issue/22040
1585 // If gold is not installed, gcc will silently switch
1586 // back to ld.bfd. So we parse the version information
1587 // and provide a useful error if gold is missing.
1588 name, args := flagExtld[0], flagExtld[1:]
1589 args = append(args, "-fuse-ld=gold", "-Wl,--version")
1590 cmd := exec.Command(name, args...)
1591 if out, err := cmd.CombinedOutput(); err == nil {
1592 if !bytes.Contains(out, []byte("GNU gold")) {
1593 log.Fatalf("ARM64 external linker must be gold (issue #15696, 22040), but is not: %s", out)
1598 if ctxt.Arch.Family == sys.ARM64 && buildcfg.GOOS == "freebsd" {
1599 // Switch to ld.bfd on freebsd/arm64.
1602 // Provide a useful error if ld.bfd is missing.
1603 name, args := flagExtld[0], flagExtld[1:]
1604 args = append(args, "-fuse-ld=bfd", "-Wl,--version")
1605 cmd := exec.Command(name, args...)
1606 if out, err := cmd.CombinedOutput(); err == nil {
1607 if !bytes.Contains(out, []byte("GNU ld")) {
1608 log.Fatalf("ARM64 external linker must be ld.bfd (issue #35197), please install devel/binutils")
1612 if altLinker != "" {
1613 argv = append(argv, "-fuse-ld="+altLinker)
1616 if ctxt.IsELF && len(buildinfo) > 0 {
1617 argv = append(argv, fmt.Sprintf("-Wl,--build-id=0x%x", buildinfo))
1620 // On Windows, given -o foo, GCC will append ".exe" to produce
1621 // "foo.exe". We have decided that we want to honor the -o
1622 // option. To make this work, we append a '.' so that GCC
1623 // will decide that the file already has an extension. We
1624 // only want to do this when producing a Windows output file
1625 // on a Windows host.
1626 outopt := *flagOutfile
1627 if buildcfg.GOOS == "windows" && runtime.GOOS == "windows" && filepath.Ext(outopt) == "" {
1630 argv = append(argv, "-o")
1631 argv = append(argv, outopt)
1633 if rpath.val != "" {
1634 argv = append(argv, fmt.Sprintf("-Wl,-rpath,%s", rpath.val))
1637 if *flagInterpreter != "" {
1638 // Many linkers support both -I and the --dynamic-linker flags
1639 // to set the ELF interpreter, but lld only supports
1640 // --dynamic-linker so prefer that (ld on very old Solaris only
1641 // supports -I but that seems less important).
1642 argv = append(argv, fmt.Sprintf("-Wl,--dynamic-linker,%s", *flagInterpreter))
1645 // Force global symbols to be exported for dlopen, etc.
1647 if ctxt.DynlinkingGo() || ctxt.BuildMode == BuildModeCShared || !linkerFlagSupported(ctxt.Arch, argv[0], altLinker, "-Wl,--export-dynamic-symbol=main") {
1648 argv = append(argv, "-rdynamic")
1650 ctxt.loader.ForAllCgoExportDynamic(func(s loader.Sym) {
1651 argv = append(argv, "-Wl,--export-dynamic-symbol="+ctxt.loader.SymExtname(s))
1655 if ctxt.HeadType == objabi.Haix {
1656 fileName := xcoffCreateExportFile(ctxt)
1657 argv = append(argv, "-Wl,-bE:"+fileName)
1660 const unusedArguments = "-Qunused-arguments"
1661 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, unusedArguments) {
1662 argv = append(argv, unusedArguments)
1665 if ctxt.IsWindows() {
1666 // Suppress generation of the PE file header timestamp,
1667 // so as to avoid spurious build ID differences between
1668 // linked binaries that are otherwise identical other than
1669 // the date/time they were linked.
1670 const noTimeStamp = "-Wl,--no-insert-timestamp"
1671 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, noTimeStamp) {
1672 argv = append(argv, noTimeStamp)
1676 const compressDWARF = "-Wl,--compress-debug-sections=zlib"
1677 if ctxt.compressDWARF && linkerFlagSupported(ctxt.Arch, argv[0], altLinker, compressDWARF) {
1678 argv = append(argv, compressDWARF)
1681 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1682 argv = append(argv, ctxt.hostobjCopy()...)
1683 if ctxt.HeadType == objabi.Haix {
1684 // We want to have C files after Go files to remove
1685 // trampolines csects made by ld.
1686 argv = append(argv, "-nostartfiles")
1687 argv = append(argv, "/lib/crt0_64.o")
1689 extld := ctxt.extld()
1690 name, args := extld[0], extld[1:]
1691 // Get starting files.
1692 getPathFile := func(file string) string {
1693 args := append(args, "-maix64", "--print-file-name="+file)
1694 out, err := exec.Command(name, args...).CombinedOutput()
1696 log.Fatalf("running %s failed: %v\n%s", extld, err, out)
1698 return strings.Trim(string(out), "\n")
1700 // Since GCC version 11, the 64-bit version of GCC starting files
1701 // are now suffixed by "_64". Even under "-maix64" multilib directory
1702 // "crtcxa.o" is 32-bit.
1703 crtcxa := getPathFile("crtcxa_64.o")
1704 if !filepath.IsAbs(crtcxa) {
1705 crtcxa = getPathFile("crtcxa.o")
1707 crtdbase := getPathFile("crtdbase_64.o")
1708 if !filepath.IsAbs(crtdbase) {
1709 crtdbase = getPathFile("crtdbase.o")
1711 argv = append(argv, crtcxa)
1712 argv = append(argv, crtdbase)
1715 if ctxt.linkShared {
1716 seenDirs := make(map[string]bool)
1717 seenLibs := make(map[string]bool)
1718 addshlib := func(path string) {
1719 dir, base := filepath.Split(path)
1721 argv = append(argv, "-L"+dir)
1723 argv = append(argv, "-Wl,-rpath="+dir)
1725 seenDirs[dir] = true
1727 base = strings.TrimSuffix(base, ".so")
1728 base = strings.TrimPrefix(base, "lib")
1729 if !seenLibs[base] {
1730 argv = append(argv, "-l"+base)
1731 seenLibs[base] = true
1734 for _, shlib := range ctxt.Shlibs {
1735 addshlib(shlib.Path)
1736 for _, dep := range shlib.Deps {
1740 libpath := findshlib(ctxt, dep)
1748 // clang, unlike GCC, passes -rdynamic to the linker
1749 // even when linking with -static, causing a linker
1750 // error when using GNU ld. So take out -rdynamic if
1751 // we added it. We do it in this order, rather than
1752 // only adding -rdynamic later, so that -extldflags
1753 // can override -rdynamic without using -static.
1754 // Similarly for -Wl,--dynamic-linker.
1755 checkStatic := func(arg string) {
1756 if ctxt.IsELF && arg == "-static" {
1757 for i := range argv {
1758 if argv[i] == "-rdynamic" || strings.HasPrefix(argv[i], "-Wl,--dynamic-linker,") {
1765 for _, p := range ldflag {
1766 argv = append(argv, p)
1770 // When building a program with the default -buildmode=exe the
1771 // gc compiler generates code requires DT_TEXTREL in a
1772 // position independent executable (PIE). On systems where the
1773 // toolchain creates PIEs by default, and where DT_TEXTREL
1774 // does not work, the resulting programs will not run. See
1775 // issue #17847. To avoid this problem pass -no-pie to the
1776 // toolchain if it is supported.
1777 if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared && !(ctxt.IsDarwin() && ctxt.IsARM64()) {
1778 // GCC uses -no-pie, clang uses -nopie.
1779 for _, nopie := range []string{"-no-pie", "-nopie"} {
1780 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, nopie) {
1781 argv = append(argv, nopie)
1787 for _, p := range flagExtldflags {
1788 argv = append(argv, p)
1791 if ctxt.HeadType == objabi.Hwindows {
1792 // Determine which linker we're using. Add in the extldflags in
1793 // case used has specified "-fuse-ld=...".
1794 extld := ctxt.extld()
1795 name, args := extld[0], extld[1:]
1796 args = append(args, trimLinkerArgv(flagExtldflags)...)
1797 args = append(args, "-Wl,--version")
1798 cmd := exec.Command(name, args...)
1800 if out, err := cmd.CombinedOutput(); err == nil {
1801 if bytes.Contains(out, []byte("LLD ")) {
1806 // use gcc linker script to work around gcc bug
1807 // (see https://golang.org/issue/20183 for details).
1809 p := writeGDBLinkerScript()
1810 argv = append(argv, "-Wl,-T,"+p)
1813 if p := ctxt.findLibPath("libsynchronization.a"); p != "libsynchronization.a" {
1814 argv = append(argv, "-lsynchronization")
1817 // libmingw32 and libmingwex have some inter-dependencies,
1818 // so must use linker groups.
1819 argv = append(argv, "-Wl,--start-group", "-lmingwex", "-lmingw32", "-Wl,--end-group")
1820 argv = append(argv, peimporteddlls()...)
1823 argv = ctxt.passLongArgsInResponseFile(argv, altLinker)
1825 if ctxt.Debugvlog != 0 {
1826 ctxt.Logf("host link:")
1827 for _, v := range argv {
1833 out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput()
1835 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1838 // Filter out useless linker warnings caused by bugs outside Go.
1839 // See also cmd/go/internal/work/exec.go's gccld method.
1842 for _, line := range bytes.SplitAfter(out, []byte("\n")) {
1843 // golang.org/issue/26073 - Apple Xcode bug
1844 if bytes.Contains(line, []byte("ld: warning: text-based stub file")) {
1853 // Remove TOC overflow warning on AIX.
1854 if bytes.Contains(line, []byte("ld: 0711-783")) {
1859 save = append(save, line)
1861 out = bytes.Join(save, nil)
1864 // always print external output even if the command is successful, so that we don't
1865 // swallow linker warnings (see https://golang.org/issue/17935).
1866 if ctxt.IsDarwin() && ctxt.IsAMD64() {
1867 const noPieWarning = "ld: warning: -no_pie is deprecated when targeting new OS versions\n"
1868 if i := bytes.Index(out, []byte(noPieWarning)); i >= 0 {
1869 // swallow -no_pie deprecation warning, issue 54482
1870 out = append(out[:i], out[i+len(noPieWarning):]...)
1873 ctxt.Logf("%s", out)
1877 // Find "dsymutils" and "strip" tools using CC --print-prog-name.
1879 cc = append(cc, ctxt.extld()...)
1880 cc = append(cc, hostlinkArchArgs(ctxt.Arch)...)
1881 cc = append(cc, "--print-prog-name", "dsymutil")
1882 out, err := exec.Command(cc[0], cc[1:]...).CombinedOutput()
1884 Exitf("%s: finding dsymutil failed: %v\n%s", os.Args[0], err, out)
1886 dsymutilCmd := strings.TrimSuffix(string(out), "\n")
1888 cc[len(cc)-1] = "strip"
1889 out, err = exec.Command(cc[0], cc[1:]...).CombinedOutput()
1891 Exitf("%s: finding strip failed: %v\n%s", os.Args[0], err, out)
1893 stripCmd := strings.TrimSuffix(string(out), "\n")
1895 dsym := filepath.Join(*flagTmpdir, "go.dwarf")
1896 if out, err := exec.Command(dsymutilCmd, "-f", *flagOutfile, "-o", dsym).CombinedOutput(); err != nil {
1897 Exitf("%s: running dsymutil failed: %v\n%s", os.Args[0], err, out)
1899 // Remove STAB (symbolic debugging) symbols after we are done with them (by dsymutil).
1900 // They contain temporary file paths and make the build not reproducible.
1901 if out, err := exec.Command(stripCmd, "-S", *flagOutfile).CombinedOutput(); err != nil {
1902 Exitf("%s: running strip failed: %v\n%s", os.Args[0], err, out)
1904 // Skip combining if `dsymutil` didn't generate a file. See #11994.
1905 if _, err := os.Stat(dsym); os.IsNotExist(err) {
1908 // For os.Rename to work reliably, must be in same directory as outfile.
1909 combinedOutput := *flagOutfile + "~"
1910 exef, err := os.Open(*flagOutfile)
1912 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1915 exem, err := macho.NewFile(exef)
1917 Exitf("%s: parsing Mach-O header failed: %v", os.Args[0], err)
1919 if err := machoCombineDwarf(ctxt, exef, exem, dsym, combinedOutput); err != nil {
1920 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1922 os.Remove(*flagOutfile)
1923 if err := os.Rename(combinedOutput, *flagOutfile); err != nil {
1924 Exitf("%s: %v", os.Args[0], err)
1927 if ctxt.NeedCodeSign() {
1928 err := machoCodeSign(ctxt, *flagOutfile)
1930 Exitf("%s: code signing failed: %v", os.Args[0], err)
1935 // passLongArgsInResponseFile writes the arguments into a file if they
1937 func (ctxt *Link) passLongArgsInResponseFile(argv []string, altLinker string) []string {
1939 for _, arg := range argv {
1943 if c < sys.ExecArgLengthLimit {
1947 // Only use response files if they are supported.
1948 response := filepath.Join(*flagTmpdir, "response")
1949 if err := os.WriteFile(response, nil, 0644); err != nil {
1950 log.Fatalf("failed while testing response file: %v", err)
1952 if !linkerFlagSupported(ctxt.Arch, argv[0], altLinker, "@"+response) {
1953 if ctxt.Debugvlog != 0 {
1954 ctxt.Logf("not using response file because linker does not support one")
1959 var buf bytes.Buffer
1960 for _, arg := range argv[1:] {
1961 // The external linker response file supports quoted strings.
1962 fmt.Fprintf(&buf, "%q\n", arg)
1964 if err := os.WriteFile(response, buf.Bytes(), 0644); err != nil {
1965 log.Fatalf("failed while writing response file: %v", err)
1967 if ctxt.Debugvlog != 0 {
1968 ctxt.Logf("response file %s contents:\n%s", response, buf.Bytes())
1976 var createTrivialCOnce sync.Once
1978 func linkerFlagSupported(arch *sys.Arch, linker, altLinker, flag string) bool {
1979 createTrivialCOnce.Do(func() {
1980 src := filepath.Join(*flagTmpdir, "trivial.c")
1981 if err := os.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
1982 Errorf(nil, "WriteFile trivial.c failed: %v", err)
1986 flags := hostlinkArchArgs(arch)
1988 moreFlags := trimLinkerArgv(append(flagExtldflags, ldflag...))
1989 flags = append(flags, moreFlags...)
1991 if altLinker != "" {
1992 flags = append(flags, "-fuse-ld="+altLinker)
1994 flags = append(flags, flag, "trivial.c")
1996 cmd := exec.Command(linker, flags...)
1997 cmd.Dir = *flagTmpdir
1998 cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
1999 out, err := cmd.CombinedOutput()
2000 // GCC says "unrecognized command line option ‘-no-pie’"
2001 // clang says "unknown argument: '-no-pie'"
2002 return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
2005 // trimLinkerArgv returns a new copy of argv that does not include flags
2006 // that are not relevant for testing whether some linker option works.
2007 func trimLinkerArgv(argv []string) []string {
2008 flagsWithNextArgSkip := []string{
2017 flagsWithNextArgKeep := []string{
2023 prefixesToKeep := []string{
2037 for _, f := range argv {
2039 flags = append(flags, f)
2043 } else if f == "" || f[0] != '-' {
2044 } else if contains(flagsWithNextArgSkip, f) {
2046 } else if contains(flagsWithNextArgKeep, f) {
2047 flags = append(flags, f)
2050 for _, p := range prefixesToKeep {
2051 if strings.HasPrefix(f, p) {
2052 flags = append(flags, f)
2061 // hostlinkArchArgs returns arguments to pass to the external linker
2062 // based on the architecture.
2063 func hostlinkArchArgs(arch *sys.Arch) []string {
2064 switch arch.Family {
2066 return []string{"-m32"}
2068 if buildcfg.GOOS == "darwin" {
2069 return []string{"-arch", "x86_64", "-m64"}
2071 return []string{"-m64"}
2073 return []string{"-m64"}
2075 return []string{"-marm"}
2077 if buildcfg.GOOS == "darwin" {
2078 return []string{"-arch", "arm64"}
2081 return []string{"-mabi=lp64d"}
2083 return []string{"-mabi=64"}
2085 return []string{"-mabi=32"}
2087 if buildcfg.GOOS == "aix" {
2088 return []string{"-maix64"}
2090 return []string{"-m64"}
2097 var wantHdr = objabi.HeaderString()
2099 // ldobj loads an input object. If it is a host object (an object
2100 // compiled by a non-Go compiler) it returns the Hostobj pointer. If
2101 // it is a Go object, it returns nil.
2102 func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string, file string) *Hostobj {
2103 pkg := objabi.PathToPrefix(lib.Pkg)
2105 eof := f.Offset() + length
2111 f.MustSeek(start, 0)
2113 unit := &sym.CompilationUnit{Lib: lib}
2114 lib.Units = append(lib.Units, unit)
2116 magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
2117 if magic == 0x7f454c46 { // \x7F E L F
2118 ldelf := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2119 textp, flags, err := loadelf.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn, ehdr.Flags)
2121 Errorf(nil, "%v", err)
2125 ctxt.Textp = append(ctxt.Textp, textp...)
2127 return ldhostobj(ldelf, ctxt.HeadType, f, pkg, length, pn, file)
2130 if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
2131 ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2132 textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2134 Errorf(nil, "%v", err)
2137 ctxt.Textp = append(ctxt.Textp, textp...)
2139 return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
2147 ldpe := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2148 textp, rsrc, err := loadpe.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2150 Errorf(nil, "%v", err)
2154 setpersrc(ctxt, rsrc)
2156 ctxt.Textp = append(ctxt.Textp, textp...)
2158 return ldhostobj(ldpe, ctxt.HeadType, f, pkg, length, pn, file)
2161 if c1 == 0x01 && (c2 == 0xD7 || c2 == 0xF7) {
2162 ldxcoff := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2163 textp, err := loadxcoff.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2165 Errorf(nil, "%v", err)
2168 ctxt.Textp = append(ctxt.Textp, textp...)
2170 return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
2173 if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
2174 // An unrecognized object is just passed to the external linker.
2175 // If we try to read symbols from this object, we will
2176 // report an error at that time.
2177 unknownObjFormat = true
2178 return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
2181 /* check the header */
2182 line, err := f.ReadString('\n')
2184 Errorf(nil, "truncated object file: %s: %v", pn, err)
2188 if !strings.HasPrefix(line, "go object ") {
2189 if strings.HasSuffix(pn, ".go") {
2190 Exitf("%s: uncompiled .go source file", pn)
2194 if line == ctxt.Arch.Name {
2195 // old header format: just $GOOS
2196 Errorf(nil, "%s: stale object file", pn)
2200 Errorf(nil, "%s: not an object file: @%d %q", pn, start, line)
2204 // First, check that the basic GOOS, GOARCH, and Version match.
2205 if line != wantHdr {
2206 Errorf(nil, "%s: linked object header mismatch:\nhave %q\nwant %q\n", pn, line, wantHdr)
2209 // Skip over exports and other info -- ends with \n!\n.
2211 // Note: It's possible for "\n!\n" to appear within the binary
2212 // package export data format. To avoid truncating the package
2213 // definition prematurely (issue 21703), we keep track of
2214 // how many "$$" delimiters we've seen.
2216 import0 := f.Offset()
2218 c1 = '\n' // the last line ended in \n
2224 if markers%2 == 0 && c2 == '!' && c3 == '\n' {
2227 if c2 == '$' && c3 == '$' {
2236 Errorf(nil, "truncated object file: %s", pn)
2241 import1 := f.Offset()
2243 f.MustSeek(import0, 0)
2244 ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
2245 f.MustSeek(import1, 0)
2247 fingerprint := ctxt.loader.Preload(ctxt.IncVersion(), f, lib, unit, eof-f.Offset())
2248 if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
2249 // Check fingerprint, to ensure the importing and imported packages
2250 // have consistent view of symbol indices.
2251 // Normally the go command should ensure this. But in case something
2252 // goes wrong, it could lead to obscure bugs like run-time crash.
2253 // Check it here to be sure.
2254 if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
2255 lib.Fingerprint = fingerprint
2257 checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
2260 addImports(ctxt, lib, pn)
2264 // symbolsAreUnresolved scans through the loader's list of unresolved
2265 // symbols and checks to see whether any of them match the names of the
2266 // symbols in 'want'. Return value is a list of bools, with list[K] set
2267 // to true if there is an unresolved reference to the symbol in want[K].
2268 func symbolsAreUnresolved(ctxt *Link, want []string) []bool {
2269 returnAllUndefs := -1
2270 undefs, _ := ctxt.loader.UndefinedRelocTargets(returnAllUndefs)
2271 seen := make(map[loader.Sym]struct{})
2272 rval := make([]bool, len(want))
2273 wantm := make(map[string]int)
2274 for k, w := range want {
2278 for _, s := range undefs {
2279 if _, ok := seen[s]; ok {
2282 seen[s] = struct{}{}
2283 if k, ok := wantm[ctxt.loader.SymName(s)]; ok {
2286 if count == len(want) {
2294 // hostObject reads a single host object file (compare to "hostArchive").
2295 // This is used as part of internal linking when we need to pull in
2296 // files such as "crt?.o".
2297 func hostObject(ctxt *Link, objname string, path string) {
2298 if ctxt.Debugvlog > 1 {
2299 ctxt.Logf("hostObject(%s)\n", path)
2301 objlib := sym.Library{
2304 f, err := bio.Open(path)
2306 Exitf("cannot open host object %q file %s: %v", objname, path, err)
2309 h := ldobj(ctxt, f, &objlib, 0, path, path)
2311 Exitf("unrecognized object file format in %s", path)
2314 h.length = f.MustSeek(0, 2)
2315 f.MustSeek(h.off, 0)
2316 h.ld(ctxt, f, h.pkg, h.length, h.pn)
2317 if *flagCaptureHostObjs != "" {
2322 func checkFingerprint(lib *sym.Library, libfp goobj.FingerprintType, src string, srcfp goobj.FingerprintType) {
2324 Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
2328 func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
2329 data := make([]byte, sym.Size)
2330 sect := f.Sections[sym.Section]
2331 if sect.Type != elf.SHT_PROGBITS && sect.Type != elf.SHT_NOTE {
2332 Errorf(nil, "reading %s from non-data section", sym.Name)
2334 n, err := sect.ReadAt(data, int64(sym.Value-sect.Addr))
2335 if uint64(n) != sym.Size {
2336 Errorf(nil, "reading contents of %s: %v", sym.Name, err)
2341 func readwithpad(r io.Reader, sz int32) ([]byte, error) {
2342 data := make([]byte, Rnd(int64(sz), 4))
2343 _, err := io.ReadFull(r, data)
2351 func readnote(f *elf.File, name []byte, typ int32) ([]byte, error) {
2352 for _, sect := range f.Sections {
2353 if sect.Type != elf.SHT_NOTE {
2358 var namesize, descsize, noteType int32
2359 err := binary.Read(r, f.ByteOrder, &namesize)
2364 return nil, fmt.Errorf("read namesize failed: %v", err)
2366 err = binary.Read(r, f.ByteOrder, &descsize)
2368 return nil, fmt.Errorf("read descsize failed: %v", err)
2370 err = binary.Read(r, f.ByteOrder, ¬eType)
2372 return nil, fmt.Errorf("read type failed: %v", err)
2374 noteName, err := readwithpad(r, namesize)
2376 return nil, fmt.Errorf("read name failed: %v", err)
2378 desc, err := readwithpad(r, descsize)
2380 return nil, fmt.Errorf("read desc failed: %v", err)
2382 if string(name) == string(noteName) && typ == noteType {
2390 func findshlib(ctxt *Link, shlib string) string {
2391 if filepath.IsAbs(shlib) {
2394 for _, libdir := range ctxt.Libdir {
2395 libpath := filepath.Join(libdir, shlib)
2396 if _, err := os.Stat(libpath); err == nil {
2400 Errorf(nil, "cannot find shared library: %s", shlib)
2404 func ldshlibsyms(ctxt *Link, shlib string) {
2406 if filepath.IsAbs(shlib) {
2408 shlib = filepath.Base(shlib)
2410 libpath = findshlib(ctxt, shlib)
2415 for _, processedlib := range ctxt.Shlibs {
2416 if processedlib.Path == libpath {
2420 if ctxt.Debugvlog > 1 {
2421 ctxt.Logf("ldshlibsyms: found library with name %s at %s\n", shlib, libpath)
2424 f, err := elf.Open(libpath)
2426 Errorf(nil, "cannot open shared library: %s", libpath)
2429 // Keep the file open as decodetypeGcprog needs to read from it.
2430 // TODO: fix. Maybe mmap the file.
2433 hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
2435 Errorf(nil, "cannot read ABI hash from shared library %s: %v", libpath, err)
2439 depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
2441 Errorf(nil, "cannot read dep list from shared library %s: %v", libpath, err)
2445 for _, dep := range strings.Split(string(depsbytes), "\n") {
2449 if !filepath.IsAbs(dep) {
2450 // If the dep can be interpreted as a path relative to the shlib
2451 // in which it was found, do that. Otherwise, we will leave it
2452 // to be resolved by libdir lookup.
2453 abs := filepath.Join(filepath.Dir(libpath), dep)
2454 if _, err := os.Stat(abs); err == nil {
2458 deps = append(deps, dep)
2461 syms, err := f.DynamicSymbols()
2463 Errorf(nil, "cannot read symbols from shared library: %s", libpath)
2467 for _, elfsym := range syms {
2468 if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
2472 // Symbols whose names start with "type:" are compiler generated,
2473 // so make functions with that prefix internal.
2475 symname := elfsym.Name // (unmangled) symbol name
2476 if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type:") {
2477 ver = abiInternalVer
2478 } else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC {
2479 // Demangle the ABI name. Keep in sync with symtab.go:mangleABIName.
2480 if strings.HasSuffix(elfsym.Name, ".abiinternal") {
2481 ver = sym.SymVerABIInternal
2482 symname = strings.TrimSuffix(elfsym.Name, ".abiinternal")
2483 } else if strings.HasSuffix(elfsym.Name, ".abi0") {
2485 symname = strings.TrimSuffix(elfsym.Name, ".abi0")
2490 s := l.LookupOrCreateSym(symname, ver)
2492 // Because loadlib above loads all .a files before loading
2493 // any shared libraries, any non-dynimport symbols we find
2494 // that duplicate symbols already loaded should be ignored
2495 // (the symbols from the .a files "win").
2496 if l.SymType(s) != 0 && l.SymType(s) != sym.SDYNIMPORT {
2499 su := l.MakeSymbolUpdater(s)
2500 su.SetType(sym.SDYNIMPORT)
2501 l.SetSymElfType(s, elf.ST_TYPE(elfsym.Info))
2502 su.SetSize(int64(elfsym.Size))
2503 if elfsym.Section != elf.SHN_UNDEF {
2504 // Set .File for the library that actually defines the symbol.
2505 l.SetSymPkg(s, libpath)
2507 // The decodetype_* functions in decodetype.go need access to
2509 sname := l.SymName(s)
2510 if strings.HasPrefix(sname, "type:") && !strings.HasPrefix(sname, "type:.") {
2511 su.SetData(readelfsymboldata(ctxt, f, &elfsym))
2515 if symname != elfsym.Name {
2516 l.SetSymExtname(s, elfsym.Name)
2519 ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f})
2522 func addsection(ldr *loader.Loader, arch *sys.Arch, seg *sym.Segment, name string, rwx int) *sym.Section {
2523 sect := ldr.NewSection()
2524 sect.Rwx = uint8(rwx)
2527 sect.Align = int32(arch.PtrSize) // everything is at least pointer-aligned
2528 seg.Sections = append(seg.Sections, sect)
2533 fmt.Fprintf(os.Stderr, "usage: link [options] main.o\n")
2534 objabi.Flagprint(os.Stderr)
2538 type SymbolType int8 // TODO: after genasmsym is gone, maybe rename to plan9typeChar or something
2541 // see also https://9p.io/magic/man2html/1/nm
2542 TextSym SymbolType = 'T'
2543 DataSym SymbolType = 'D'
2544 BSSSym SymbolType = 'B'
2545 UndefinedSym SymbolType = 'U'
2546 TLSSym SymbolType = 't'
2547 FrameSym SymbolType = 'm'
2548 ParamSym SymbolType = 'p'
2549 AutoSym SymbolType = 'a'
2551 // Deleted auto (not a real sym, just placeholder for type)
2552 DeletedAutoSym = 'x'
2555 // defineInternal defines a symbol used internally by the go runtime.
2556 func (ctxt *Link) defineInternal(p string, t sym.SymKind) loader.Sym {
2557 s := ctxt.loader.CreateSymForUpdate(p, 0)
2564 func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) loader.Sym {
2565 s := ctxt.defineInternal(p, t)
2566 ctxt.loader.SetSymValue(s, v)
2570 func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
2571 if uint64(addr) >= Segdata.Vaddr {
2572 return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
2574 if uint64(addr) >= Segtext.Vaddr {
2575 return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
2577 ldr.Errorf(s, "invalid datoff %#x", addr)
2581 func Entryvalue(ctxt *Link) int64 {
2582 a := *flagEntrySymbol
2583 if a[0] >= '0' && a[0] <= '9' {
2587 s := ldr.Lookup(a, 0)
2589 Errorf(nil, "missing entry symbol %q", a)
2592 st := ldr.SymType(s)
2594 return *FlagTextAddr
2596 if !ctxt.IsAIX() && st != sym.STEXT {
2597 ldr.Errorf(s, "entry not text")
2599 return ldr.SymValue(s)
2602 func (ctxt *Link) callgraph() {
2608 for _, s := range ctxt.Textp {
2609 relocs := ldr.Relocs(s)
2610 for i := 0; i < relocs.Count(); i++ {
2616 if r.Type().IsDirectCall() && ldr.SymType(rs) == sym.STEXT {
2617 ctxt.Logf("%s calls %s\n", ldr.SymName(s), ldr.SymName(rs))
2623 func Rnd(v int64, r int64) int64 {
2636 func bgetc(r *bio.Reader) int {
2637 c, err := r.ReadByte()
2640 log.Fatalf("reading input: %v", err)
2647 type markKind uint8 // for postorder traversal
2654 func postorder(libs []*sym.Library) []*sym.Library {
2655 order := make([]*sym.Library, 0, len(libs)) // hold the result
2656 mark := make(map[*sym.Library]markKind, len(libs))
2657 for _, lib := range libs {
2658 dfs(lib, mark, &order)
2663 func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library) {
2664 if mark[lib] == visited {
2667 if mark[lib] == visiting {
2668 panic("found import cycle while visiting " + lib.Pkg)
2670 mark[lib] = visiting
2671 for _, i := range lib.Imports {
2675 *order = append(*order, lib)
2678 func ElfSymForReloc(ctxt *Link, s loader.Sym) int32 {
2679 // If putelfsym created a local version of this symbol, use that in all
2681 les := ctxt.loader.SymLocalElfSym(s)
2685 return ctxt.loader.SymElfSym(s)
2689 func AddGotSym(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, elfRelocTyp uint32) {
2690 if ldr.SymGot(s) >= 0 {
2694 Adddynsym(ldr, target, syms, s)
2695 got := ldr.MakeSymbolUpdater(syms.GOT)
2696 ldr.SetGot(s, int32(got.Size()))
2697 got.AddUint(target.Arch, 0)
2700 if target.Arch.PtrSize == 8 {
2701 rela := ldr.MakeSymbolUpdater(syms.Rela)
2702 rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2703 rela.AddUint64(target.Arch, elf.R_INFO(uint32(ldr.SymDynid(s)), elfRelocTyp))
2704 rela.AddUint64(target.Arch, 0)
2706 rel := ldr.MakeSymbolUpdater(syms.Rel)
2707 rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2708 rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), elfRelocTyp))
2710 } else if target.IsDarwin() {
2711 leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT)
2712 leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
2713 if target.IsPIE() && target.IsInternal() {
2714 // Mach-O relocations are a royal pain to lay out.
2715 // They use a compact stateful bytecode representation.
2716 // Here we record what are needed and encode them later.
2717 MachoAddBind(int64(ldr.SymGot(s)), s)
2720 ldr.Errorf(s, "addgotsym: unsupported binary format")
2724 var hostobjcounter int
2726 // captureHostObj writes out the content of a host object (pulled from
2727 // an archive or loaded from a *.o file directly) to a directory
2728 // specified via the linker's "-capturehostobjs" debugging flag. This
2729 // is intended to make it easier for a developer to inspect the actual
2730 // object feeding into "CGO internal" link step.
2731 func captureHostObj(h *Hostobj) {
2732 // Form paths for info file and obj file.
2733 ofile := fmt.Sprintf("captured-obj-%d.o", hostobjcounter)
2734 ifile := fmt.Sprintf("captured-obj-%d.txt", hostobjcounter)
2736 opath := filepath.Join(*flagCaptureHostObjs, ofile)
2737 ipath := filepath.Join(*flagCaptureHostObjs, ifile)
2739 // Write the info file.
2740 info := fmt.Sprintf("pkg: %s\npn: %s\nfile: %s\noff: %d\nlen: %d\n",
2741 h.pkg, h.pn, h.file, h.off, h.length)
2742 if err := os.WriteFile(ipath, []byte(info), 0666); err != nil {
2743 log.Fatalf("error writing captured host obj info %s: %v", ipath, err)
2746 readObjData := func() []byte {
2747 inf, err := os.Open(h.file)
2749 log.Fatalf("capturing host obj: open failed on %s: %v", h.pn, err)
2751 res := make([]byte, h.length)
2752 if n, err := inf.ReadAt(res, h.off); err != nil || n != int(h.length) {
2753 log.Fatalf("capturing host obj: readat failed on %s: %v", h.pn, err)
2758 // Write the object file.
2759 if err := os.WriteFile(opath, readObjData(), 0666); err != nil {
2760 log.Fatalf("error writing captured host object %s: %v", opath, err)
2763 fmt.Fprintf(os.Stderr, "link: info: captured host object %s to %s\n",