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
123 // Symbol containing a list of all the inittasks that need
124 // to be run at startup.
125 mainInittasks loader.Sym
128 // mkArchSym is a helper for setArchSyms, to set up a special symbol.
129 func (ctxt *Link) mkArchSym(name string, ver int, ls *loader.Sym) {
130 *ls = ctxt.loader.LookupOrCreateSym(name, ver)
131 ctxt.loader.SetAttrReachable(*ls, true)
134 // mkArchSymVec is similar to setArchSyms, but operates on elements within
135 // a slice, where each element corresponds to some symbol version.
136 func (ctxt *Link) mkArchSymVec(name string, ver int, ls []loader.Sym) {
137 ls[ver] = ctxt.loader.LookupOrCreateSym(name, ver)
138 ctxt.loader.SetAttrReachable(ls[ver], true)
141 // setArchSyms sets up the ArchSyms structure, and must be called before
142 // relocations are applied.
143 func (ctxt *Link) setArchSyms() {
144 ctxt.mkArchSym(".got", 0, &ctxt.GOT)
145 ctxt.mkArchSym(".plt", 0, &ctxt.PLT)
146 ctxt.mkArchSym(".got.plt", 0, &ctxt.GOTPLT)
147 ctxt.mkArchSym(".dynamic", 0, &ctxt.Dynamic)
148 ctxt.mkArchSym(".dynsym", 0, &ctxt.DynSym)
149 ctxt.mkArchSym(".dynstr", 0, &ctxt.DynStr)
150 ctxt.mkArchSym("runtime.unreachableMethod", abiInternalVer, &ctxt.unreachableMethod)
153 ctxt.mkArchSym("TOC", 0, &ctxt.TOC)
155 ctxt.DotTOC = make([]loader.Sym, ctxt.MaxVersion()+1)
156 for i := 0; i <= ctxt.MaxVersion(); i++ {
157 if i >= sym.SymVerABICount && i < sym.SymVerStatic { // these versions are not used currently
160 ctxt.mkArchSymVec(".TOC.", i, ctxt.DotTOC)
164 ctxt.mkArchSym(".rel", 0, &ctxt.Rel)
165 ctxt.mkArchSym(".rela", 0, &ctxt.Rela)
166 ctxt.mkArchSym(".rel.plt", 0, &ctxt.RelPLT)
167 ctxt.mkArchSym(".rela.plt", 0, &ctxt.RelaPLT)
170 ctxt.mkArchSym(".linkedit.got", 0, &ctxt.LinkEditGOT)
171 ctxt.mkArchSym(".linkedit.plt", 0, &ctxt.LinkEditPLT)
182 // Threshold of total text size, used for trampoline insertion. If the total
183 // text size is smaller than TrampLimit, we won't need to insert trampolines.
184 // It is pretty close to the offset range of a direct CALL machine instruction.
185 // We leave some room for extra stuff like PLT stubs.
188 // Empty spaces between codeblocks will be padded with this value.
189 // For example an architecture might want to pad with a trap instruction to
190 // catch wayward programs. Architectures that do not define a padding value
191 // are padded with zeros.
198 Adddynrel func(*Target, *loader.Loader, *ArchSyms, loader.Sym, loader.Reloc, int) bool
200 // Archreloc is an arch-specific hook that assists in relocation processing
201 // (invoked by 'relocsym'); it handles target-specific relocation tasks.
202 // Here "rel" is the current relocation being examined, "sym" is the symbol
203 // containing the chunk of data to which the relocation applies, and "off"
204 // is the contents of the to-be-relocated data item (from sym.P). Return
205 // value is the appropriately relocated value (to be written back to the
206 // same spot in sym.P), number of external _host_ relocations needed (i.e.
207 // ELF/Mach-O/etc. relocations, not Go relocations, this must match ELF.Reloc1,
208 // etc.), and a boolean indicating success/failure (a failing value indicates
210 Archreloc func(*Target, *loader.Loader, *ArchSyms, loader.Reloc, loader.Sym,
211 int64) (relocatedOffset int64, nExtReloc int, ok bool)
212 // Archrelocvariant is a second arch-specific hook used for
213 // relocation processing; it handles relocations where r.Type is
214 // insufficient to describe the relocation (r.Variant !=
215 // sym.RV_NONE). Here "rel" is the relocation being applied, "sym"
216 // is the symbol containing the chunk of data to which the
217 // relocation applies, and "off" is the contents of the
218 // to-be-relocated data item (from sym.P). Return is an updated
220 Archrelocvariant func(target *Target, ldr *loader.Loader, rel loader.Reloc,
221 rv sym.RelocVariant, sym loader.Sym, offset int64, data []byte) (relocatedOffset int64)
223 // Generate a trampoline for a call from s to rs if necessary. ri is
224 // index of the relocation.
225 Trampoline func(ctxt *Link, ldr *loader.Loader, ri int, rs, s loader.Sym)
227 // Assembling the binary breaks into two phases, writing the code/data/
228 // dwarf information (which is rather generic), and some more architecture
229 // specific work like setting up the elf headers/dynamic relocations, etc.
230 // The phases are called "Asmb" and "Asmb2". Asmb2 needs to be defined for
231 // every architecture, but only if architecture has an Asmb function will
232 // it be used for assembly. Otherwise a generic assembly Asmb function is
234 Asmb func(*Link, *loader.Loader)
235 Asmb2 func(*Link, *loader.Loader)
237 // Extreloc is an arch-specific hook that converts a Go relocation to an
238 // external relocation. Return the external relocation and whether it is
240 Extreloc func(*Target, *loader.Loader, loader.Reloc, loader.Sym) (loader.ExtReloc, bool)
242 Gentext func(*Link, *loader.Loader) // Generate text before addressing has been performed.
243 Machoreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
244 MachorelocSize uint32 // size of an Mach-O relocation record, must match Machoreloc1.
245 PEreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
246 Xcoffreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
248 // Generate additional symbols for the native symbol table just prior to
250 GenSymsLate func(*Link, *loader.Loader)
252 // TLSIEtoLE converts a TLS Initial Executable relocation to
253 // a TLS Local Executable relocation.
255 // This is possible when a TLS IE relocation refers to a local
256 // symbol in an executable, which is typical when internally
257 // linking PIE binaries.
258 TLSIEtoLE func(P []byte, off, size int)
260 // optional override for assignAddress
261 AssignAddress func(ldr *loader.Loader, sect *sym.Section, n int, s loader.Sym, va uint64, isTramp bool) (*sym.Section, int, uint64)
263 // ELF specific information.
276 MINFUNC = 16 // minimum size for a function
279 // Symbol version of ABIInternal symbols. It is sym.SymVerABIInternal if ABI wrappers
280 // are used, 0 otherwise.
281 var abiInternalVer = sym.SymVerABIInternal
283 // DynlinkingGo reports whether we are producing Go code that can live
284 // in separate shared libraries linked together at runtime.
285 func (ctxt *Link) DynlinkingGo() bool {
287 panic("DynlinkingGo called before all symbols loaded")
289 return ctxt.BuildMode == BuildModeShared || ctxt.linkShared || ctxt.BuildMode == BuildModePlugin || ctxt.canUsePlugins
292 // CanUsePlugins reports whether a plugins can be used
293 func (ctxt *Link) CanUsePlugins() bool {
295 panic("CanUsePlugins called before all symbols loaded")
297 return ctxt.canUsePlugins
300 // NeedCodeSign reports whether we need to code-sign the output binary.
301 func (ctxt *Link) NeedCodeSign() bool {
302 return ctxt.IsDarwin() && ctxt.IsARM64()
314 debug_s bool // backup old value of debug['s']
318 liveness int64 // size of liveness data (funcdata), printed if -v
320 // See -strictdups command line flag.
321 checkStrictDups int // 0=off 1=warning 2=error
322 strictDupMsgCount int
327 Segrodata sym.Segment
328 Segrelrodata sym.Segment
331 Segpdata sym.Segment // windows-only
332 Segxdata sym.Segment // windows-only
334 Segments = []*sym.Segment{&Segtext, &Segrodata, &Segrelrodata, &Segdata, &Segdwarf, &Segpdata, &Segxdata}
337 const pkgdef = "__.PKGDEF"
340 // externalobj is set to true if we see an object compiled by
341 // the host compiler that is not from a package that is known
342 // to support internal linking mode.
345 // dynimportfail is a list of packages for which generating
346 // the dynimport file, _cgo_import.go, failed. If there are
347 // any of these objects, we must link externally. Issue 52863.
348 dynimportfail []string
350 // preferlinkext is a list of packages for which the Go command
351 // noticed use of peculiar C flags. If we see any of these,
352 // default to linking externally unless overridden by the
353 // user. See issues #58619, #58620, and #58848.
354 preferlinkext []string
356 // unknownObjFormat is set to true if we see an object whose
357 // format we don't recognize.
358 unknownObjFormat = false
363 func Lflag(ctxt *Link, arg string) {
364 ctxt.Libdir = append(ctxt.Libdir, arg)
368 * Unix doesn't like it when we write to a running (or, sometimes,
369 * recently run) binary, so remove the output file before writing it.
370 * On Windows 7, remove() can force a subsequent create() to fail.
371 * S_ISREG() does not exist on Plan 9.
373 func mayberemoveoutfile() {
374 if fi, err := os.Lstat(*flagOutfile); err == nil && !fi.Mode().IsRegular() {
377 os.Remove(*flagOutfile)
380 func libinit(ctxt *Link) {
381 Funcalign = thearch.Funcalign
383 // add goroot to the end of the libdir list.
387 if *flagInstallSuffix != "" {
389 suffix = *flagInstallSuffix
390 } else if *flagRace {
393 } else if *flagMsan {
396 } else if *flagAsan {
401 if buildcfg.GOROOT != "" {
402 Lflag(ctxt, filepath.Join(buildcfg.GOROOT, "pkg", fmt.Sprintf("%s_%s%s%s", buildcfg.GOOS, buildcfg.GOARCH, suffixsep, suffix)))
407 if err := ctxt.Out.Open(*flagOutfile); err != nil {
408 Exitf("cannot create %s: %v", *flagOutfile, err)
411 if *flagEntrySymbol == "" {
412 switch ctxt.BuildMode {
413 case BuildModeCShared, BuildModeCArchive:
414 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s_lib", buildcfg.GOARCH, buildcfg.GOOS)
415 case BuildModeExe, BuildModePIE:
416 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s", buildcfg.GOARCH, buildcfg.GOOS)
417 case BuildModeShared, BuildModePlugin:
418 // No *flagEntrySymbol for -buildmode=shared and plugin
420 Errorf(nil, "unknown *flagEntrySymbol for buildmode %v", ctxt.BuildMode)
425 func exitIfErrors() {
426 if nerrors != 0 || checkStrictDups > 1 && strictDupMsgCount > 0 {
438 func loadinternal(ctxt *Link, name string) *sym.Library {
439 zerofp := goobj.FingerprintType{}
440 if ctxt.linkShared && ctxt.PackageShlib != nil {
441 if shlib := ctxt.PackageShlib[name]; shlib != "" {
442 return addlibpath(ctxt, "internal", "internal", "", name, shlib, zerofp)
445 if ctxt.PackageFile != nil {
446 if pname := ctxt.PackageFile[name]; pname != "" {
447 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
449 ctxt.Logf("loadinternal: cannot find %s\n", name)
453 for _, libdir := range ctxt.Libdir {
455 shlibname := filepath.Join(libdir, name+".shlibname")
456 if ctxt.Debugvlog != 0 {
457 ctxt.Logf("searching for %s.a in %s\n", name, shlibname)
459 if _, err := os.Stat(shlibname); err == nil {
460 return addlibpath(ctxt, "internal", "internal", "", name, shlibname, zerofp)
463 pname := filepath.Join(libdir, name+".a")
464 if ctxt.Debugvlog != 0 {
465 ctxt.Logf("searching for %s.a in %s\n", name, pname)
467 if _, err := os.Stat(pname); err == nil {
468 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
472 if name == "runtime" {
473 Exitf("error: unable to find runtime.a")
475 ctxt.Logf("warning: unable to find %s.a\n", name)
479 // extld returns the current external linker.
480 func (ctxt *Link) extld() []string {
481 if len(flagExtld) == 0 {
482 // Return the default external linker for the platform.
483 // This only matters when link tool is called directly without explicit -extld,
484 // go tool already passes the correct linker in other cases.
485 switch buildcfg.GOOS {
486 case "darwin", "freebsd", "openbsd":
487 flagExtld = []string{"clang"}
489 flagExtld = []string{"gcc"}
495 // findLibPathCmd uses cmd command to find gcc library libname.
496 // It returns library full path if found, or "none" if not found.
497 func (ctxt *Link) findLibPathCmd(cmd, libname string) string {
498 extld := ctxt.extld()
499 name, args := extld[0], extld[1:]
500 args = append(args, hostlinkArchArgs(ctxt.Arch)...)
501 args = append(args, cmd)
502 if ctxt.Debugvlog != 0 {
503 ctxt.Logf("%s %v\n", extld, args)
505 out, err := exec.Command(name, args...).Output()
507 if ctxt.Debugvlog != 0 {
508 ctxt.Logf("not using a %s file because compiler failed\n%v\n%s\n", libname, err, out)
512 return strings.TrimSpace(string(out))
515 // findLibPath searches for library libname.
516 // It returns library full path if found, or "none" if not found.
517 func (ctxt *Link) findLibPath(libname string) string {
518 return ctxt.findLibPathCmd("--print-file-name="+libname, libname)
521 func (ctxt *Link) loadlib() {
523 switch *FlagStrictDups {
527 flags |= loader.FlagStrictDups
529 log.Fatalf("invalid -strictdups flag value %d", *FlagStrictDups)
531 ctxt.loader = loader.NewLoader(flags, &ctxt.ErrorReporter.ErrorReporter)
532 ctxt.ErrorReporter.SymName = func(s loader.Sym) string {
533 return ctxt.loader.SymName(s)
536 // ctxt.Library grows during the loop, so not a range loop.
538 for ; i < len(ctxt.Library); i++ {
539 lib := ctxt.Library[i]
541 if ctxt.Debugvlog > 1 {
542 ctxt.Logf("autolib: %s (from %s)\n", lib.File, lib.Objref)
544 loadobjfile(ctxt, lib)
548 // load internal packages, if not already
550 loadinternal(ctxt, "runtime/race")
553 loadinternal(ctxt, "runtime/msan")
556 loadinternal(ctxt, "runtime/asan")
558 loadinternal(ctxt, "runtime")
559 for ; i < len(ctxt.Library); i++ {
560 lib := ctxt.Library[i]
562 loadobjfile(ctxt, lib)
565 // At this point, the Go objects are "preloaded". Not all the symbols are
566 // added to the symbol table (only defined package symbols are). Looking
567 // up symbol by name may not get expected result.
569 iscgo = ctxt.LibraryByPkg["runtime/cgo"] != nil
571 // Plugins a require cgo support to function. Similarly, plugins may require additional
572 // internal linker support on some platforms which may not be implemented.
573 ctxt.canUsePlugins = ctxt.LibraryByPkg["plugin"] != nil && iscgo
575 // We now have enough information to determine the link mode.
576 determineLinkMode(ctxt)
578 if ctxt.LinkMode == LinkExternal && !iscgo && !(buildcfg.GOOS == "darwin" && ctxt.BuildMode != BuildModePlugin && ctxt.Arch.Family == sys.AMD64) {
579 // This indicates a user requested -linkmode=external.
580 // The startup code uses an import of runtime/cgo to decide
581 // whether to initialize the TLS. So give it one. This could
582 // be handled differently but it's an unusual case.
583 if lib := loadinternal(ctxt, "runtime/cgo"); lib != nil && lib.Shlib == "" {
584 if ctxt.BuildMode == BuildModeShared || ctxt.linkShared {
585 Exitf("cannot implicitly include runtime/cgo in a shared library")
587 for ; i < len(ctxt.Library); i++ {
588 lib := ctxt.Library[i]
590 loadobjfile(ctxt, lib)
596 // Add non-package symbols and references of externally defined symbols.
597 ctxt.loader.LoadSyms(ctxt.Arch)
599 // Load symbols from shared libraries, after all Go object symbols are loaded.
600 for _, lib := range ctxt.Library {
602 if ctxt.Debugvlog > 1 {
603 ctxt.Logf("autolib: %s (from %s)\n", lib.Shlib, lib.Objref)
605 ldshlibsyms(ctxt, lib.Shlib)
609 // Process cgo directives (has to be done before host object loading).
610 ctxt.loadcgodirectives()
612 // Conditionally load host objects, or setup for external linking.
616 if ctxt.LinkMode == LinkInternal && len(hostobj) != 0 {
617 // If we have any undefined symbols in external
618 // objects, try to read them from the libgcc file.
620 undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
623 if ctxt.Debugvlog > 1 {
624 ctxt.Logf("loadlib: first unresolved is %s [%d] from %s [%d]\n",
625 ctxt.loader.SymName(undefs[0]), undefs[0],
626 ctxt.loader.SymName(froms[0]), froms[0])
630 if *flagLibGCC == "" {
631 *flagLibGCC = ctxt.findLibPathCmd("--print-libgcc-file-name", "libgcc")
633 if runtime.GOOS == "openbsd" && *flagLibGCC == "libgcc.a" {
634 // On OpenBSD `clang --print-libgcc-file-name` returns "libgcc.a".
635 // In this case we fail to load libgcc.a and can encounter link
636 // errors - see if we can find libcompiler_rt.a instead.
637 *flagLibGCC = ctxt.findLibPathCmd("--print-file-name=libcompiler_rt.a", "libcompiler_rt")
639 if ctxt.HeadType == objabi.Hwindows {
640 loadWindowsHostArchives(ctxt)
642 if *flagLibGCC != "none" {
643 hostArchive(ctxt, *flagLibGCC)
645 // For glibc systems, the linker setup used by GCC
648 // GROUP ( /lib/x86_64-linux-gnu/libc.so.6
649 // /usr/lib/x86_64-linux-gnu/libc_nonshared.a
650 // AS_NEEDED ( /lib64/ld-linux-x86-64.so.2 ) )
652 // where libc_nonshared.a contains a small set of
653 // symbols including "__stack_chk_fail_local" and a
654 // few others. Thus if we are doing internal linking
655 // and "__stack_chk_fail_local" is unresolved (most
656 // likely due to the use of -fstack-protector), try
657 // loading libc_nonshared.a to resolve it.
659 // On Alpine Linux (musl-based), the library providing
660 // this symbol is called libssp_nonshared.a.
661 isunresolved := symbolsAreUnresolved(ctxt, []string{"__stack_chk_fail_local"})
663 if p := ctxt.findLibPath("libc_nonshared.a"); p != "none" {
666 if p := ctxt.findLibPath("libssp_nonshared.a"); p != "none" {
673 // We've loaded all the code now.
676 strictDupMsgCount = ctxt.loader.NStrictDupMsgs()
679 // loadWindowsHostArchives loads in host archives and objects when
680 // doing internal linking on windows. Older toolchains seem to require
681 // just a single pass through the various archives, but some modern
682 // toolchains when linking a C program with mingw pass library paths
683 // multiple times to the linker, e.g. "... -lmingwex -lmingw32 ...
684 // -lmingwex -lmingw32 ...". To accommodate this behavior, we make two
685 // passes over the host archives below.
686 func loadWindowsHostArchives(ctxt *Link) {
688 for i := 0; any && i < 2; i++ {
689 // Link crt2.o (if present) to resolve "atexit" when
690 // using LLVM-based compilers.
691 isunresolved := symbolsAreUnresolved(ctxt, []string{"atexit"})
693 if p := ctxt.findLibPath("crt2.o"); p != "none" {
694 hostObject(ctxt, "crt2", p)
698 if p := ctxt.findLibPath("libsynchronization.a"); p != "none" {
702 if p := ctxt.findLibPath("libmingwex.a"); p != "none" {
705 if p := ctxt.findLibPath("libmingw32.a"); p != "none" {
708 // Link libmsvcrt.a to resolve '__acrt_iob_func' symbol
709 // (see https://golang.org/issue/23649 for details).
710 if p := ctxt.findLibPath("libmsvcrt.a"); p != "none" {
714 undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
717 if ctxt.Debugvlog > 1 {
718 ctxt.Logf("loadWindowsHostArchives: remaining unresolved is %s [%d] from %s [%d]\n",
719 ctxt.loader.SymName(undefs[0]), undefs[0],
720 ctxt.loader.SymName(froms[0]), froms[0])
724 // If needed, create the __CTOR_LIST__ and __DTOR_LIST__
725 // symbols (referenced by some of the mingw support library
726 // routines). Creation of these symbols is normally done by the
727 // linker if not already present.
728 want := []string{"__CTOR_LIST__", "__DTOR_LIST__"}
729 isunresolved := symbolsAreUnresolved(ctxt, want)
730 for k, w := range want {
732 sb := ctxt.loader.CreateSymForUpdate(w, 0)
733 sb.SetType(sym.SDATA)
734 sb.AddUint64(ctxt.Arch, 0)
735 sb.SetReachable(true)
736 ctxt.loader.SetAttrSpecial(sb.Sym(), true)
740 // Fix up references to DLL import symbols now that we're done
741 // pulling in new objects.
742 if err := loadpe.PostProcessImports(); err != nil {
743 Errorf(nil, "%v", err)
746 // TODO: maybe do something similar to peimporteddlls to collect
747 // all lib names and try link them all to final exe just like
748 // libmingwex.a and libmingw32.a:
751 #cgo windows LDFLAGS: -lmsvcrt -lm
757 // loadcgodirectives reads the previously discovered cgo directives, creating
758 // symbols in preparation for host object loading or use later in the link.
759 func (ctxt *Link) loadcgodirectives() {
761 hostObjSyms := make(map[loader.Sym]struct{})
762 for _, d := range ctxt.cgodata {
763 setCgoAttr(ctxt, d.file, d.pkg, d.directives, hostObjSyms)
767 if ctxt.LinkMode == LinkInternal {
768 // Drop all the cgo_import_static declarations.
769 // Turns out we won't be needing them.
770 for symIdx := range hostObjSyms {
771 if l.SymType(symIdx) == sym.SHOSTOBJ {
772 // If a symbol was marked both
773 // cgo_import_static and cgo_import_dynamic,
774 // then we want to make it cgo_import_dynamic
776 su := l.MakeSymbolUpdater(symIdx)
777 if l.SymExtname(symIdx) != "" && l.SymDynimplib(symIdx) != "" && !(l.AttrCgoExportStatic(symIdx) || l.AttrCgoExportDynamic(symIdx)) {
778 su.SetType(sym.SDYNIMPORT)
787 // Set up flags and special symbols depending on the platform build mode.
788 // This version works with loader.Loader.
789 func (ctxt *Link) linksetup() {
790 switch ctxt.BuildMode {
791 case BuildModeCShared, BuildModePlugin:
792 symIdx := ctxt.loader.LookupOrCreateSym("runtime.islibrary", 0)
793 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
794 sb.SetType(sym.SNOPTRDATA)
796 case BuildModeCArchive:
797 symIdx := ctxt.loader.LookupOrCreateSym("runtime.isarchive", 0)
798 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
799 sb.SetType(sym.SNOPTRDATA)
803 // Recalculate pe parameters now that we have ctxt.LinkMode set.
804 if ctxt.HeadType == objabi.Hwindows {
808 if ctxt.LinkMode == LinkExternal {
809 // When external linking, we are creating an object file. The
810 // absolute address is irrelevant.
814 // If there are no dynamic libraries needed, gcc disables dynamic linking.
815 // Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13)
816 // assumes that a dynamic binary always refers to at least one dynamic library.
817 // Rather than be a source of test cases for glibc, disable dynamic linking
818 // the same way that gcc would.
820 // Exception: on OS X, programs such as Shark only work with dynamic
821 // binaries, so leave it enabled on OS X (Mach-O) binaries.
822 // Also leave it enabled on Solaris which doesn't support
823 // statically linked binaries.
824 if ctxt.BuildMode == BuildModeExe {
825 if havedynamic == 0 && ctxt.HeadType != objabi.Hdarwin && ctxt.HeadType != objabi.Hsolaris {
830 if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && buildcfg.GOOS != "aix" {
831 toc := ctxt.loader.LookupOrCreateSym(".TOC.", 0)
832 sb := ctxt.loader.MakeSymbolUpdater(toc)
833 sb.SetType(sym.SDYNIMPORT)
836 // The Android Q linker started to complain about underalignment of the our TLS
837 // section. We don't actually use the section on android, so don't
839 if buildcfg.GOOS != "android" {
840 tlsg := ctxt.loader.LookupOrCreateSym("runtime.tlsg", 0)
841 sb := ctxt.loader.MakeSymbolUpdater(tlsg)
843 // runtime.tlsg is used for external linking on platforms that do not define
844 // a variable to hold g in assembly (currently only intel).
846 sb.SetType(sym.STLSBSS)
847 sb.SetSize(int64(ctxt.Arch.PtrSize))
848 } else if sb.Type() != sym.SDYNIMPORT {
849 Errorf(nil, "runtime declared tlsg variable %v", sb.Type())
851 ctxt.loader.SetAttrReachable(tlsg, true)
855 var moduledata loader.Sym
856 var mdsb *loader.SymbolBuilder
857 if ctxt.BuildMode == BuildModePlugin {
858 moduledata = ctxt.loader.LookupOrCreateSym("local.pluginmoduledata", 0)
859 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
860 ctxt.loader.SetAttrLocal(moduledata, true)
862 moduledata = ctxt.loader.LookupOrCreateSym("runtime.firstmoduledata", 0)
863 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
865 if mdsb.Type() != 0 && mdsb.Type() != sym.SDYNIMPORT {
866 // If the module (toolchain-speak for "executable or shared
867 // library") we are linking contains the runtime package, it
868 // will define the runtime.firstmoduledata symbol and we
869 // truncate it back to 0 bytes so we can define its entire
870 // contents in symtab.go:symtab().
873 // In addition, on ARM, the runtime depends on the linker
874 // recording the value of GOARM.
875 if ctxt.Arch.Family == sys.ARM {
876 goarm := ctxt.loader.LookupOrCreateSym("runtime.goarm", 0)
877 sb := ctxt.loader.MakeSymbolUpdater(goarm)
878 sb.SetType(sym.SDATA)
880 sb.AddUint8(uint8(buildcfg.GOARM))
883 // Set runtime.disableMemoryProfiling bool if
884 // runtime.MemProfile is not retained in the binary after
885 // deadcode (and we're not dynamically linking).
886 memProfile := ctxt.loader.Lookup("runtime.MemProfile", abiInternalVer)
887 if memProfile != 0 && !ctxt.loader.AttrReachable(memProfile) && !ctxt.DynlinkingGo() {
888 memProfSym := ctxt.loader.LookupOrCreateSym("runtime.disableMemoryProfiling", 0)
889 sb := ctxt.loader.MakeSymbolUpdater(memProfSym)
890 sb.SetType(sym.SDATA)
892 sb.AddUint8(1) // true bool
895 // If OTOH the module does not contain the runtime package,
896 // create a local symbol for the moduledata.
897 moduledata = ctxt.loader.LookupOrCreateSym("local.moduledata", 0)
898 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
899 ctxt.loader.SetAttrLocal(moduledata, true)
901 // In all cases way we mark the moduledata as noptrdata to hide it from
903 mdsb.SetType(sym.SNOPTRDATA)
904 ctxt.loader.SetAttrReachable(moduledata, true)
905 ctxt.Moduledata = moduledata
907 if ctxt.Arch == sys.Arch386 && ctxt.HeadType != objabi.Hwindows {
908 if (ctxt.BuildMode == BuildModeCArchive && ctxt.IsELF) || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE || ctxt.DynlinkingGo() {
909 got := ctxt.loader.LookupOrCreateSym("_GLOBAL_OFFSET_TABLE_", 0)
910 sb := ctxt.loader.MakeSymbolUpdater(got)
911 sb.SetType(sym.SDYNIMPORT)
912 ctxt.loader.SetAttrReachable(got, true)
916 // DWARF-gen and other phases require that the unit Textp slices
917 // be populated, so that it can walk the functions in each unit.
918 // Call into the loader to do this (requires that we collect the
919 // set of internal libraries first). NB: might be simpler if we
920 // moved isRuntimeDepPkg to cmd/internal and then did the test in
921 // loader.AssignTextSymbolOrder.
922 ctxt.Library = postorder(ctxt.Library)
924 for _, lib := range ctxt.Library {
925 intlibs = append(intlibs, isRuntimeDepPkg(lib.Pkg))
927 ctxt.Textp = ctxt.loader.AssignTextSymbolOrder(ctxt.Library, intlibs, ctxt.Textp)
930 // mangleTypeSym shortens the names of symbols that represent Go types
931 // if they are visible in the symbol table.
933 // As the names of these symbols are derived from the string of
934 // the type, they can run to many kilobytes long. So we shorten
935 // them using a SHA-1 when the name appears in the final binary.
936 // This also removes characters that upset external linkers.
938 // These are the symbols that begin with the prefix 'type.' and
939 // contain run-time type information used by the runtime and reflect
940 // packages. All Go binaries contain these symbols, but only
941 // those programs loaded dynamically in multiple parts need these
942 // symbols to have entries in the symbol table.
943 func (ctxt *Link) mangleTypeSym() {
944 if ctxt.BuildMode != BuildModeShared && !ctxt.linkShared && ctxt.BuildMode != BuildModePlugin && !ctxt.CanUsePlugins() {
949 for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
950 if !ldr.AttrReachable(s) && !ctxt.linkShared {
951 // If -linkshared, the GCProg generation code may need to reach
952 // out to the shared library for the type descriptor's data, even
953 // the type descriptor itself is not actually needed at run time
954 // (therefore not reachable). We still need to mangle its name,
955 // so it is consistent with the one stored in the shared library.
958 name := ldr.SymName(s)
959 newName := typeSymbolMangle(name)
961 ldr.SetSymExtname(s, newName)
963 // When linking against a shared library, the Go object file may
964 // have reference to the original symbol name whereas the shared
965 // library provides a symbol with the mangled name. We need to
966 // copy the payload of mangled to original.
967 // XXX maybe there is a better way to do this.
968 dup := ldr.Lookup(newName, ldr.SymVersion(s))
971 dt := ldr.SymType(dup)
972 if st == sym.Sxxx && dt != sym.Sxxx {
980 // typeSymbolMangle mangles the given symbol name into something shorter.
982 // Keep the type:. prefix, which parts of the linker (like the
983 // DWARF generator) know means the symbol is not decodable.
984 // Leave type:runtime. symbols alone, because other parts of
985 // the linker manipulates them.
986 func typeSymbolMangle(name string) string {
987 isType := strings.HasPrefix(name, "type:")
988 if !isType && !strings.Contains(name, "@") {
989 // Issue 58800: instantiated symbols may include a type name, which may contain "@"
992 if strings.HasPrefix(name, "type:runtime.") {
995 if len(name) <= 14 && !strings.Contains(name, "@") { // Issue 19529
999 hash := notsha256.Sum256([]byte(name[5:]))
1004 return prefix + base64.StdEncoding.EncodeToString(hash[:6])
1006 // instantiated symbol, replace type name in []
1007 i := strings.IndexByte(name, '[')
1008 j := strings.LastIndexByte(name, ']')
1012 hash := notsha256.Sum256([]byte(name[i+1 : j]))
1013 return name[:i+1] + base64.StdEncoding.EncodeToString(hash[:6]) + name[j:]
1017 * look for the next file in an archive.
1018 * adapted from libmach.
1020 func nextar(bp *bio.Reader, off int64, a *ArHdr) int64 {
1025 var buf [SAR_HDR]byte
1026 if n, err := io.ReadFull(bp, buf[:]); err != nil {
1027 if n == 0 && err != io.EOF {
1033 a.name = artrim(buf[0:16])
1034 a.date = artrim(buf[16:28])
1035 a.uid = artrim(buf[28:34])
1036 a.gid = artrim(buf[34:40])
1037 a.mode = artrim(buf[40:48])
1038 a.size = artrim(buf[48:58])
1039 a.fmag = artrim(buf[58:60])
1041 arsize := atolwhex(a.size)
1045 return arsize + SAR_HDR
1048 func loadobjfile(ctxt *Link, lib *sym.Library) {
1049 pkg := objabi.PathToPrefix(lib.Pkg)
1051 if ctxt.Debugvlog > 1 {
1052 ctxt.Logf("ldobj: %s (%s)\n", lib.File, pkg)
1054 f, err := bio.Open(lib.File)
1056 Exitf("cannot open file %s: %v", lib.File, err)
1060 if pkg == "main" && !lib.Main {
1061 Exitf("%s: not package main", lib.File)
1065 for i := 0; i < len(ARMAG); i++ {
1066 if c, err := f.ReadByte(); err == nil && c == ARMAG[i] {
1070 /* load it as a regular file */
1071 l := f.MustSeek(0, 2)
1073 ldobj(ctxt, f, lib, l, lib.File, lib.File)
1078 * load all the object files from the archive now.
1079 * this gives us sequential file access and keeps us
1080 * from needing to come back later to pick up more
1081 * objects. it breaks the usual C archive model, but
1082 * this is Go, not C. the common case in Go is that
1083 * we need to load all the objects, and then we throw away
1084 * the individual symbols that are unused.
1086 * loading every object will also make it possible to
1087 * load foreign objects not referenced by __.PKGDEF.
1092 l := nextar(f, off, &arhdr)
1097 Exitf("%s: malformed archive", lib.File)
1101 // __.PKGDEF isn't a real Go object file, and it's
1102 // absent in -linkobj builds anyway. Skipping it
1103 // ensures consistency between -linkobj and normal
1105 if arhdr.name == pkgdef {
1109 if arhdr.name == "dynimportfail" {
1110 dynimportfail = append(dynimportfail, lib.Pkg)
1112 if arhdr.name == "preferlinkext" {
1113 // Ignore this directive if -linkmode has been
1115 if ctxt.LinkMode == LinkAuto {
1116 preferlinkext = append(preferlinkext, lib.Pkg)
1120 // Skip other special (non-object-file) sections that
1121 // build tools may have added. Such sections must have
1122 // short names so that the suffix is not truncated.
1123 if len(arhdr.name) < 16 {
1124 if ext := filepath.Ext(arhdr.name); ext != ".o" && ext != ".syso" {
1129 pname := fmt.Sprintf("%s(%s)", lib.File, arhdr.name)
1130 l = atolwhex(arhdr.size)
1131 ldobj(ctxt, f, lib, l, pname, lib.File)
1135 type Hostobj struct {
1136 ld func(*Link, *bio.Reader, string, int64, string)
1144 var hostobj []Hostobj
1146 // These packages can use internal linking mode.
1147 // Others trigger external mode.
1148 var internalpkg = []string{
1149 "crypto/internal/boring",
1150 "crypto/internal/boring/syso",
1156 "runtime/race/internal/amd64v1",
1157 "runtime/race/internal/amd64v3",
1162 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 {
1164 for _, intpkg := range internalpkg {
1171 // DragonFly declares errno with __thread, which results in a symbol
1172 // type of R_386_TLS_GD or R_X86_64_TLSGD. The Go linker does not
1173 // currently know how to handle TLS relocations, hence we have to
1174 // force external linking for any libraries that link in code that
1175 // uses errno. This can be removed if the Go linker ever supports
1176 // these relocation types.
1177 if headType == objabi.Hdragonfly {
1178 if pkg == "net" || pkg == "os/user" {
1187 hostobj = append(hostobj, Hostobj{})
1188 h := &hostobj[len(hostobj)-1]
1198 func hostobjs(ctxt *Link) {
1199 if ctxt.LinkMode != LinkInternal {
1204 for i := 0; i < len(hostobj); i++ {
1206 f, err := bio.Open(h.file)
1208 Exitf("cannot reopen %s: %v", h.pn, err)
1210 f.MustSeek(h.off, 0)
1212 Errorf(nil, "%s: unrecognized object file format", h.pn)
1215 h.ld(ctxt, f, h.pkg, h.length, h.pn)
1216 if *flagCaptureHostObjs != "" {
1223 func hostlinksetup(ctxt *Link) {
1224 if ctxt.LinkMode != LinkExternal {
1228 // For external link, record that we need to tell the external linker -s,
1229 // and turn off -s internally: the external linker needs the symbol
1230 // information for its final link.
1234 // create temporary directory and arrange cleanup
1235 if *flagTmpdir == "" {
1236 dir, err := os.MkdirTemp("", "go-link-")
1243 os.RemoveAll(*flagTmpdir)
1247 // change our output to temporary object file
1248 if err := ctxt.Out.Close(); err != nil {
1249 Exitf("error closing output file")
1251 mayberemoveoutfile()
1253 p := filepath.Join(*flagTmpdir, "go.o")
1254 if err := ctxt.Out.Open(p); err != nil {
1255 Exitf("cannot create %s: %v", p, err)
1259 // hostobjCopy creates a copy of the object files in hostobj in a
1260 // temporary directory.
1261 func (ctxt *Link) hostobjCopy() (paths []string) {
1262 var wg sync.WaitGroup
1263 sema := make(chan struct{}, runtime.NumCPU()) // limit open file descriptors
1264 for i, h := range hostobj {
1266 dst := filepath.Join(*flagTmpdir, fmt.Sprintf("%06d.o", i))
1267 paths = append(paths, dst)
1268 if ctxt.Debugvlog != 0 {
1269 ctxt.Logf("host obj copy: %s from pkg %s -> %s\n", h.pn, h.pkg, dst)
1279 f, err := os.Open(h.file)
1281 Exitf("cannot reopen %s: %v", h.pn, err)
1284 if _, err := f.Seek(h.off, 0); err != nil {
1285 Exitf("cannot seek %s: %v", h.pn, err)
1288 w, err := os.Create(dst)
1290 Exitf("cannot create %s: %v", dst, err)
1292 if _, err := io.CopyN(w, f, h.length); err != nil {
1293 Exitf("cannot write %s: %v", dst, err)
1295 if err := w.Close(); err != nil {
1296 Exitf("cannot close %s: %v", dst, err)
1304 // writeGDBLinkerScript creates gcc linker script file in temp
1305 // directory. writeGDBLinkerScript returns created file path.
1306 // The script is used to work around gcc bug
1307 // (see https://golang.org/issue/20183 for details).
1308 func writeGDBLinkerScript() string {
1309 name := "fix_debug_gdb_scripts.ld"
1310 path := filepath.Join(*flagTmpdir, name)
1313 .debug_gdb_scripts BLOCK(__section_alignment__) (NOLOAD) :
1315 *(.debug_gdb_scripts)
1318 INSERT AFTER .debug_types;
1320 err := os.WriteFile(path, []byte(src), 0666)
1322 Errorf(nil, "WriteFile %s failed: %v", name, err)
1327 // archive builds a .a archive from the hostobj object files.
1328 func (ctxt *Link) archive() {
1329 if ctxt.BuildMode != BuildModeCArchive {
1335 if *flagExtar == "" {
1339 mayberemoveoutfile()
1341 // Force the buffer to flush here so that external
1342 // tools will see a complete file.
1343 if err := ctxt.Out.Close(); err != nil {
1344 Exitf("error closing %v", *flagOutfile)
1347 argv := []string{*flagExtar, "-q", "-c", "-s"}
1348 if ctxt.HeadType == objabi.Haix {
1349 argv = append(argv, "-X64")
1351 argv = append(argv, *flagOutfile)
1352 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1353 argv = append(argv, ctxt.hostobjCopy()...)
1355 if ctxt.Debugvlog != 0 {
1356 ctxt.Logf("archive: %s\n", strings.Join(argv, " "))
1359 // If supported, use syscall.Exec() to invoke the archive command,
1360 // which should be the final remaining step needed for the link.
1361 // This will reduce peak RSS for the link (and speed up linking of
1362 // large applications), since when the archive command runs we
1363 // won't be holding onto all of the linker's live memory.
1364 if syscallExecSupported && !ownTmpDir {
1366 ctxt.execArchive(argv)
1367 panic("should not get here")
1370 // Otherwise invoke 'ar' in the usual way (fork + exec).
1371 if out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput(); err != nil {
1372 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1376 func (ctxt *Link) hostlink() {
1377 if ctxt.LinkMode != LinkExternal || nerrors > 0 {
1380 if ctxt.BuildMode == BuildModeCArchive {
1385 argv = append(argv, ctxt.extld()...)
1386 argv = append(argv, hostlinkArchArgs(ctxt.Arch)...)
1388 if *FlagS || debug_s {
1389 if ctxt.HeadType == objabi.Hdarwin {
1390 // Recent versions of macOS print
1391 // ld: warning: option -s is obsolete and being ignored
1392 // so do not pass any arguments.
1394 argv = append(argv, "-s")
1398 // On darwin, whether to combine DWARF into executable.
1399 // Only macOS supports unmapped segments such as our __DWARF segment.
1400 combineDwarf := ctxt.IsDarwin() && !*FlagS && !*FlagW && !debug_s && machoPlatform == PLATFORM_MACOS
1402 switch ctxt.HeadType {
1403 case objabi.Hdarwin:
1405 // Leave room for DWARF combining.
1406 // -headerpad is incompatible with -fembed-bitcode.
1407 argv = append(argv, "-Wl,-headerpad,1144")
1409 if ctxt.DynlinkingGo() && buildcfg.GOOS != "ios" {
1410 // -flat_namespace is deprecated on iOS.
1411 // It is useful for supporting plugins. We don't support plugins on iOS.
1412 // -flat_namespace may cause the dynamic linker to hang at forkExec when
1413 // resolving a lazy binding. See issue 38824.
1414 // Force eager resolution to work around.
1415 argv = append(argv, "-Wl,-flat_namespace", "-Wl,-bind_at_load")
1418 argv = append(argv, "-Wl,-S") // suppress STAB (symbolic debugging) symbols
1420 case objabi.Hopenbsd:
1421 argv = append(argv, "-Wl,-nopie")
1422 argv = append(argv, "-pthread")
1423 if ctxt.Arch.InFamily(sys.ARM64) {
1424 // Disable execute-only on openbsd/arm64 - the Go arm64 assembler
1425 // currently stores constants in the text section rather than in rodata.
1426 // See issue #59615.
1427 argv = append(argv, "-Wl,--no-execute-only")
1429 case objabi.Hwindows:
1431 argv = append(argv, "-mwindows")
1433 argv = append(argv, "-mconsole")
1435 // Mark as having awareness of terminal services, to avoid
1436 // ancient compatibility hacks.
1437 argv = append(argv, "-Wl,--tsaware")
1440 argv = append(argv, "-Wl,--nxcompat")
1442 argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", PeMinimumTargetMajorVersion))
1443 argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", PeMinimumTargetMinorVersion))
1444 argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", PeMinimumTargetMajorVersion))
1445 argv = append(argv, fmt.Sprintf("-Wl,--minor-subsystem-version=%d", PeMinimumTargetMinorVersion))
1447 argv = append(argv, "-pthread")
1448 // prevent ld to reorder .text functions to keep the same
1449 // first/last functions for moduledata.
1450 argv = append(argv, "-Wl,-bnoobjreorder")
1451 // mcmodel=large is needed for every gcc generated files, but
1452 // ld still need -bbigtoc in order to allow larger TOC.
1453 argv = append(argv, "-mcmodel=large")
1454 argv = append(argv, "-Wl,-bbigtoc")
1457 // On PPC64, verify the external toolchain supports Power10. This is needed when
1458 // PC relative relocations might be generated by Go. Only targets compiling ELF
1459 // binaries might generate these relocations.
1460 if ctxt.IsPPC64() && ctxt.IsElf() && buildcfg.GOPPC64 >= 10 {
1461 if !linkerFlagSupported(ctxt.Arch, argv[0], "", "-mcpu=power10") {
1462 Exitf("The external toolchain does not support -mcpu=power10. " +
1463 " This is required to externally link GOPPC64 >= power10")
1467 // Enable/disable ASLR on Windows.
1468 addASLRargs := func(argv []string, val bool) []string {
1469 // Old/ancient versions of GCC support "--dynamicbase" and
1470 // "--high-entropy-va" but don't enable it by default. In
1471 // addition, they don't accept "--disable-dynamicbase" or
1472 // "--no-dynamicbase", so the only way to disable ASLR is to
1473 // not pass any flags at all.
1475 // More modern versions of GCC (and also clang) enable ASLR
1476 // by default. With these compilers, however you can turn it
1477 // off if you want using "--disable-dynamicbase" or
1478 // "--no-dynamicbase".
1480 // The strategy below is to try using "--disable-dynamicbase";
1481 // if this succeeds, then assume we're working with more
1482 // modern compilers and act accordingly. If it fails, assume
1483 // an ancient compiler with ancient defaults.
1486 dbon := "--dynamicbase"
1487 heon := "--high-entropy-va"
1488 dboff := "--disable-dynamicbase"
1489 heoff := "--disable-high-entropy-va"
1494 // Test to see whether "--disable-dynamicbase" works.
1495 newer := linkerFlagSupported(ctxt.Arch, argv[0], "", "-Wl,"+dboff)
1497 // Newer compiler, which supports both on/off options.
1501 // older toolchain: we have to say nothing in order to
1502 // get a no-ASLR binary.
1508 argv = append(argv, "-Wl,"+dbopt)
1510 // enable high-entropy ASLR on 64-bit.
1511 if ctxt.Arch.PtrSize >= 8 && heopt != "" {
1512 argv = append(argv, "-Wl,"+heopt)
1517 switch ctxt.BuildMode {
1519 if ctxt.HeadType == objabi.Hdarwin {
1520 if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() {
1521 argv = append(argv, "-Wl,-no_pie")
1524 if *flagRace && ctxt.HeadType == objabi.Hwindows {
1525 // Current windows/amd64 race detector tsan support
1526 // library can't handle PIE mode (see #53539 for more details).
1527 // For now, explicitly disable PIE (since some compilers
1528 // default to it) if -race is in effect.
1529 argv = addASLRargs(argv, false)
1532 switch ctxt.HeadType {
1533 case objabi.Hdarwin, objabi.Haix:
1534 case objabi.Hwindows:
1535 if *flagAslr && *flagRace {
1536 // Current windows/amd64 race detector tsan support
1537 // library can't handle PIE mode (see #53539 for more details).
1538 // Disable alsr if -race in effect.
1541 argv = addASLRargs(argv, *flagAslr)
1544 if ctxt.UseRelro() {
1545 argv = append(argv, "-Wl,-z,relro")
1547 argv = append(argv, "-pie")
1549 case BuildModeCShared:
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")
1557 if ctxt.HeadType == objabi.Hwindows {
1558 argv = addASLRargs(argv, *flagAslr)
1560 // Pass -z nodelete to mark the shared library as
1561 // non-closeable: a dlclose will do nothing.
1562 argv = append(argv, "-Wl,-z,nodelete")
1563 // Only pass Bsymbolic on non-Windows.
1564 argv = append(argv, "-Wl,-Bsymbolic")
1567 case BuildModeShared:
1568 if ctxt.UseRelro() {
1569 argv = append(argv, "-Wl,-z,relro")
1571 argv = append(argv, "-shared")
1572 case BuildModePlugin:
1573 if ctxt.HeadType == objabi.Hdarwin {
1574 argv = append(argv, "-dynamiclib")
1576 if ctxt.UseRelro() {
1577 argv = append(argv, "-Wl,-z,relro")
1579 argv = append(argv, "-shared")
1583 var altLinker string
1584 if ctxt.IsELF && ctxt.DynlinkingGo() {
1585 // We force all symbol resolution to be done at program startup
1586 // because lazy PLT resolution can use large amounts of stack at
1587 // times we cannot allow it to do so.
1588 argv = append(argv, "-Wl,-z,now")
1590 // Do not let the host linker generate COPY relocations. These
1591 // can move symbols out of sections that rely on stable offsets
1592 // from the beginning of the section (like sym.STYPE).
1593 argv = append(argv, "-Wl,-z,nocopyreloc")
1595 if buildcfg.GOOS == "android" {
1596 // Use lld to avoid errors from default linker (issue #38838)
1600 if ctxt.Arch.InFamily(sys.ARM64) && buildcfg.GOOS == "linux" {
1601 // On ARM64, the GNU linker will fail with
1602 // -znocopyreloc if it thinks a COPY relocation is
1603 // required. Switch to gold.
1604 // https://sourceware.org/bugzilla/show_bug.cgi?id=19962
1605 // https://go.dev/issue/22040
1608 // If gold is not installed, gcc will silently switch
1609 // back to ld.bfd. So we parse the version information
1610 // and provide a useful error if gold is missing.
1611 name, args := flagExtld[0], flagExtld[1:]
1612 args = append(args, "-fuse-ld=gold", "-Wl,--version")
1613 cmd := exec.Command(name, args...)
1614 if out, err := cmd.CombinedOutput(); err == nil {
1615 if !bytes.Contains(out, []byte("GNU gold")) {
1616 log.Fatalf("ARM64 external linker must be gold (issue #15696, 22040), but is not: %s", out)
1621 if ctxt.Arch.Family == sys.ARM64 && buildcfg.GOOS == "freebsd" {
1622 // Switch to ld.bfd on freebsd/arm64.
1625 // Provide a useful error if ld.bfd is missing.
1626 name, args := flagExtld[0], flagExtld[1:]
1627 args = append(args, "-fuse-ld=bfd", "-Wl,--version")
1628 cmd := exec.Command(name, args...)
1629 if out, err := cmd.CombinedOutput(); err == nil {
1630 if !bytes.Contains(out, []byte("GNU ld")) {
1631 log.Fatalf("ARM64 external linker must be ld.bfd (issue #35197), please install devel/binutils")
1635 if altLinker != "" {
1636 argv = append(argv, "-fuse-ld="+altLinker)
1639 if ctxt.IsELF && len(buildinfo) > 0 {
1640 argv = append(argv, fmt.Sprintf("-Wl,--build-id=0x%x", buildinfo))
1643 // On Windows, given -o foo, GCC will append ".exe" to produce
1644 // "foo.exe". We have decided that we want to honor the -o
1645 // option. To make this work, we append a '.' so that GCC
1646 // will decide that the file already has an extension. We
1647 // only want to do this when producing a Windows output file
1648 // on a Windows host.
1649 outopt := *flagOutfile
1650 if buildcfg.GOOS == "windows" && runtime.GOOS == "windows" && filepath.Ext(outopt) == "" {
1653 argv = append(argv, "-o")
1654 argv = append(argv, outopt)
1656 if rpath.val != "" {
1657 argv = append(argv, fmt.Sprintf("-Wl,-rpath,%s", rpath.val))
1660 if *flagInterpreter != "" {
1661 // Many linkers support both -I and the --dynamic-linker flags
1662 // to set the ELF interpreter, but lld only supports
1663 // --dynamic-linker so prefer that (ld on very old Solaris only
1664 // supports -I but that seems less important).
1665 argv = append(argv, fmt.Sprintf("-Wl,--dynamic-linker,%s", *flagInterpreter))
1668 // Force global symbols to be exported for dlopen, etc.
1670 if ctxt.DynlinkingGo() || ctxt.BuildMode == BuildModeCShared || !linkerFlagSupported(ctxt.Arch, argv[0], altLinker, "-Wl,--export-dynamic-symbol=main") {
1671 argv = append(argv, "-rdynamic")
1673 ctxt.loader.ForAllCgoExportDynamic(func(s loader.Sym) {
1674 argv = append(argv, "-Wl,--export-dynamic-symbol="+ctxt.loader.SymExtname(s))
1678 if ctxt.HeadType == objabi.Haix {
1679 fileName := xcoffCreateExportFile(ctxt)
1680 argv = append(argv, "-Wl,-bE:"+fileName)
1683 const unusedArguments = "-Qunused-arguments"
1684 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, unusedArguments) {
1685 argv = append(argv, unusedArguments)
1688 if ctxt.IsWindows() {
1689 // Suppress generation of the PE file header timestamp,
1690 // so as to avoid spurious build ID differences between
1691 // linked binaries that are otherwise identical other than
1692 // the date/time they were linked.
1693 const noTimeStamp = "-Wl,--no-insert-timestamp"
1694 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, noTimeStamp) {
1695 argv = append(argv, noTimeStamp)
1699 const compressDWARF = "-Wl,--compress-debug-sections=zlib"
1700 if ctxt.compressDWARF && linkerFlagSupported(ctxt.Arch, argv[0], altLinker, compressDWARF) {
1701 argv = append(argv, compressDWARF)
1704 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1705 argv = append(argv, ctxt.hostobjCopy()...)
1706 if ctxt.HeadType == objabi.Haix {
1707 // We want to have C files after Go files to remove
1708 // trampolines csects made by ld.
1709 argv = append(argv, "-nostartfiles")
1710 argv = append(argv, "/lib/crt0_64.o")
1712 extld := ctxt.extld()
1713 name, args := extld[0], extld[1:]
1714 // Get starting files.
1715 getPathFile := func(file string) string {
1716 args := append(args, "-maix64", "--print-file-name="+file)
1717 out, err := exec.Command(name, args...).CombinedOutput()
1719 log.Fatalf("running %s failed: %v\n%s", extld, err, out)
1721 return strings.Trim(string(out), "\n")
1723 // Since GCC version 11, the 64-bit version of GCC starting files
1724 // are now suffixed by "_64". Even under "-maix64" multilib directory
1725 // "crtcxa.o" is 32-bit.
1726 crtcxa := getPathFile("crtcxa_64.o")
1727 if !filepath.IsAbs(crtcxa) {
1728 crtcxa = getPathFile("crtcxa.o")
1730 crtdbase := getPathFile("crtdbase_64.o")
1731 if !filepath.IsAbs(crtdbase) {
1732 crtdbase = getPathFile("crtdbase.o")
1734 argv = append(argv, crtcxa)
1735 argv = append(argv, crtdbase)
1738 if ctxt.linkShared {
1739 seenDirs := make(map[string]bool)
1740 seenLibs := make(map[string]bool)
1741 addshlib := func(path string) {
1742 dir, base := filepath.Split(path)
1744 argv = append(argv, "-L"+dir)
1746 argv = append(argv, "-Wl,-rpath="+dir)
1748 seenDirs[dir] = true
1750 base = strings.TrimSuffix(base, ".so")
1751 base = strings.TrimPrefix(base, "lib")
1752 if !seenLibs[base] {
1753 argv = append(argv, "-l"+base)
1754 seenLibs[base] = true
1757 for _, shlib := range ctxt.Shlibs {
1758 addshlib(shlib.Path)
1759 for _, dep := range shlib.Deps {
1763 libpath := findshlib(ctxt, dep)
1771 // clang, unlike GCC, passes -rdynamic to the linker
1772 // even when linking with -static, causing a linker
1773 // error when using GNU ld. So take out -rdynamic if
1774 // we added it. We do it in this order, rather than
1775 // only adding -rdynamic later, so that -extldflags
1776 // can override -rdynamic without using -static.
1777 // Similarly for -Wl,--dynamic-linker.
1778 checkStatic := func(arg string) {
1779 if ctxt.IsELF && arg == "-static" {
1780 for i := range argv {
1781 if argv[i] == "-rdynamic" || strings.HasPrefix(argv[i], "-Wl,--dynamic-linker,") {
1788 for _, p := range ldflag {
1789 argv = append(argv, p)
1793 // When building a program with the default -buildmode=exe the
1794 // gc compiler generates code requires DT_TEXTREL in a
1795 // position independent executable (PIE). On systems where the
1796 // toolchain creates PIEs by default, and where DT_TEXTREL
1797 // does not work, the resulting programs will not run. See
1798 // issue #17847. To avoid this problem pass -no-pie to the
1799 // toolchain if it is supported.
1800 if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared && !(ctxt.IsDarwin() && ctxt.IsARM64()) {
1801 // GCC uses -no-pie, clang uses -nopie.
1802 for _, nopie := range []string{"-no-pie", "-nopie"} {
1803 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, nopie) {
1804 argv = append(argv, nopie)
1810 for _, p := range flagExtldflags {
1811 argv = append(argv, p)
1814 if ctxt.HeadType == objabi.Hwindows {
1815 // Determine which linker we're using. Add in the extldflags in
1816 // case used has specified "-fuse-ld=...".
1817 extld := ctxt.extld()
1818 name, args := extld[0], extld[1:]
1819 args = append(args, trimLinkerArgv(flagExtldflags)...)
1820 args = append(args, "-Wl,--version")
1821 cmd := exec.Command(name, args...)
1823 if out, err := cmd.CombinedOutput(); err == nil {
1824 if bytes.Contains(out, []byte("LLD ")) {
1829 // use gcc linker script to work around gcc bug
1830 // (see https://golang.org/issue/20183 for details).
1832 p := writeGDBLinkerScript()
1833 argv = append(argv, "-Wl,-T,"+p)
1836 if p := ctxt.findLibPath("libsynchronization.a"); p != "libsynchronization.a" {
1837 argv = append(argv, "-lsynchronization")
1840 // libmingw32 and libmingwex have some inter-dependencies,
1841 // so must use linker groups.
1842 argv = append(argv, "-Wl,--start-group", "-lmingwex", "-lmingw32", "-Wl,--end-group")
1843 argv = append(argv, peimporteddlls()...)
1846 argv = ctxt.passLongArgsInResponseFile(argv, altLinker)
1848 if ctxt.Debugvlog != 0 {
1849 ctxt.Logf("host link:")
1850 for _, v := range argv {
1856 out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput()
1858 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1861 // Filter out useless linker warnings caused by bugs outside Go.
1862 // See also cmd/go/internal/work/exec.go's gccld method.
1865 for _, line := range bytes.SplitAfter(out, []byte("\n")) {
1866 // golang.org/issue/26073 - Apple Xcode bug
1867 if bytes.Contains(line, []byte("ld: warning: text-based stub file")) {
1876 // Remove TOC overflow warning on AIX.
1877 if bytes.Contains(line, []byte("ld: 0711-783")) {
1882 save = append(save, line)
1884 out = bytes.Join(save, nil)
1887 // always print external output even if the command is successful, so that we don't
1888 // swallow linker warnings (see https://golang.org/issue/17935).
1889 if ctxt.IsDarwin() && ctxt.IsAMD64() {
1890 const noPieWarning = "ld: warning: -no_pie is deprecated when targeting new OS versions\n"
1891 if i := bytes.Index(out, []byte(noPieWarning)); i >= 0 {
1892 // swallow -no_pie deprecation warning, issue 54482
1893 out = append(out[:i], out[i+len(noPieWarning):]...)
1896 ctxt.Logf("%s", out)
1900 // Find "dsymutils" and "strip" tools using CC --print-prog-name.
1902 cc = append(cc, ctxt.extld()...)
1903 cc = append(cc, hostlinkArchArgs(ctxt.Arch)...)
1904 cc = append(cc, "--print-prog-name", "dsymutil")
1905 out, err := exec.Command(cc[0], cc[1:]...).CombinedOutput()
1907 Exitf("%s: finding dsymutil failed: %v\n%s", os.Args[0], err, out)
1909 dsymutilCmd := strings.TrimSuffix(string(out), "\n")
1911 cc[len(cc)-1] = "strip"
1912 out, err = exec.Command(cc[0], cc[1:]...).CombinedOutput()
1914 Exitf("%s: finding strip failed: %v\n%s", os.Args[0], err, out)
1916 stripCmd := strings.TrimSuffix(string(out), "\n")
1918 dsym := filepath.Join(*flagTmpdir, "go.dwarf")
1919 cmd := exec.Command(dsymutilCmd, "-f", *flagOutfile, "-o", dsym)
1920 // dsymutil may not clean up its temp directory at exit.
1921 // Set DSYMUTIL_REPRODUCER_PATH to work around. see issue 59026.
1922 cmd.Env = append(os.Environ(), "DSYMUTIL_REPRODUCER_PATH="+*flagTmpdir)
1923 if out, err := cmd.CombinedOutput(); err != nil {
1924 Exitf("%s: running dsymutil failed: %v\n%s", os.Args[0], err, out)
1926 // Remove STAB (symbolic debugging) symbols after we are done with them (by dsymutil).
1927 // They contain temporary file paths and make the build not reproducible.
1928 if out, err := exec.Command(stripCmd, "-S", *flagOutfile).CombinedOutput(); err != nil {
1929 Exitf("%s: running strip failed: %v\n%s", os.Args[0], err, out)
1931 // Skip combining if `dsymutil` didn't generate a file. See #11994.
1932 if _, err := os.Stat(dsym); os.IsNotExist(err) {
1935 // For os.Rename to work reliably, must be in same directory as outfile.
1936 combinedOutput := *flagOutfile + "~"
1937 exef, err := os.Open(*flagOutfile)
1939 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1942 exem, err := macho.NewFile(exef)
1944 Exitf("%s: parsing Mach-O header failed: %v", os.Args[0], err)
1946 if err := machoCombineDwarf(ctxt, exef, exem, dsym, combinedOutput); err != nil {
1947 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1949 os.Remove(*flagOutfile)
1950 if err := os.Rename(combinedOutput, *flagOutfile); err != nil {
1951 Exitf("%s: %v", os.Args[0], err)
1954 if ctxt.NeedCodeSign() {
1955 err := machoCodeSign(ctxt, *flagOutfile)
1957 Exitf("%s: code signing failed: %v", os.Args[0], err)
1962 // passLongArgsInResponseFile writes the arguments into a file if they
1964 func (ctxt *Link) passLongArgsInResponseFile(argv []string, altLinker string) []string {
1966 for _, arg := range argv {
1970 if c < sys.ExecArgLengthLimit {
1974 // Only use response files if they are supported.
1975 response := filepath.Join(*flagTmpdir, "response")
1976 if err := os.WriteFile(response, nil, 0644); err != nil {
1977 log.Fatalf("failed while testing response file: %v", err)
1979 if !linkerFlagSupported(ctxt.Arch, argv[0], altLinker, "@"+response) {
1980 if ctxt.Debugvlog != 0 {
1981 ctxt.Logf("not using response file because linker does not support one")
1986 var buf bytes.Buffer
1987 for _, arg := range argv[1:] {
1988 // The external linker response file supports quoted strings.
1989 fmt.Fprintf(&buf, "%q\n", arg)
1991 if err := os.WriteFile(response, buf.Bytes(), 0644); err != nil {
1992 log.Fatalf("failed while writing response file: %v", err)
1994 if ctxt.Debugvlog != 0 {
1995 ctxt.Logf("response file %s contents:\n%s", response, buf.Bytes())
2003 var createTrivialCOnce sync.Once
2005 func linkerFlagSupported(arch *sys.Arch, linker, altLinker, flag string) bool {
2006 createTrivialCOnce.Do(func() {
2007 src := filepath.Join(*flagTmpdir, "trivial.c")
2008 if err := os.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
2009 Errorf(nil, "WriteFile trivial.c failed: %v", err)
2013 flags := hostlinkArchArgs(arch)
2015 moreFlags := trimLinkerArgv(append(flagExtldflags, ldflag...))
2016 flags = append(flags, moreFlags...)
2018 if altLinker != "" {
2019 flags = append(flags, "-fuse-ld="+altLinker)
2021 trivialPath := filepath.Join(*flagTmpdir, "trivial.c")
2022 outPath := filepath.Join(*flagTmpdir, "a.out")
2023 flags = append(flags, "-o", outPath, flag, trivialPath)
2025 cmd := exec.Command(linker, flags...)
2026 cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
2027 out, err := cmd.CombinedOutput()
2028 // GCC says "unrecognized command line option ‘-no-pie’"
2029 // clang says "unknown argument: '-no-pie'"
2030 return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
2033 // trimLinkerArgv returns a new copy of argv that does not include flags
2034 // that are not relevant for testing whether some linker option works.
2035 func trimLinkerArgv(argv []string) []string {
2036 flagsWithNextArgSkip := []string{
2045 flagsWithNextArgKeep := []string{
2051 prefixesToKeep := []string{
2065 for _, f := range argv {
2067 flags = append(flags, f)
2071 } else if f == "" || f[0] != '-' {
2072 } else if contains(flagsWithNextArgSkip, f) {
2074 } else if contains(flagsWithNextArgKeep, f) {
2075 flags = append(flags, f)
2078 for _, p := range prefixesToKeep {
2079 if strings.HasPrefix(f, p) {
2080 flags = append(flags, f)
2089 // hostlinkArchArgs returns arguments to pass to the external linker
2090 // based on the architecture.
2091 func hostlinkArchArgs(arch *sys.Arch) []string {
2092 switch arch.Family {
2094 return []string{"-m32"}
2096 if buildcfg.GOOS == "darwin" {
2097 return []string{"-arch", "x86_64", "-m64"}
2099 return []string{"-m64"}
2101 return []string{"-m64"}
2103 return []string{"-marm"}
2105 if buildcfg.GOOS == "darwin" {
2106 return []string{"-arch", "arm64"}
2109 return []string{"-mabi=lp64d"}
2111 return []string{"-mabi=64"}
2113 return []string{"-mabi=32"}
2115 if buildcfg.GOOS == "aix" {
2116 return []string{"-maix64"}
2118 return []string{"-m64"}
2125 var wantHdr = objabi.HeaderString()
2127 // ldobj loads an input object. If it is a host object (an object
2128 // compiled by a non-Go compiler) it returns the Hostobj pointer. If
2129 // it is a Go object, it returns nil.
2130 func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string, file string) *Hostobj {
2131 pkg := objabi.PathToPrefix(lib.Pkg)
2133 eof := f.Offset() + length
2139 f.MustSeek(start, 0)
2141 unit := &sym.CompilationUnit{Lib: lib}
2142 lib.Units = append(lib.Units, unit)
2144 magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
2145 if magic == 0x7f454c46 { // \x7F E L F
2146 ldelf := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2147 textp, flags, err := loadelf.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn, ehdr.Flags)
2149 Errorf(nil, "%v", err)
2153 ctxt.Textp = append(ctxt.Textp, textp...)
2155 return ldhostobj(ldelf, ctxt.HeadType, f, pkg, length, pn, file)
2158 if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
2159 ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2160 textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2162 Errorf(nil, "%v", err)
2165 ctxt.Textp = append(ctxt.Textp, textp...)
2167 return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
2175 ldpe := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2176 textp, rsrc, err := loadpe.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2178 Errorf(nil, "%v", err)
2182 setpersrc(ctxt, rsrc)
2184 ctxt.Textp = append(ctxt.Textp, textp...)
2186 return ldhostobj(ldpe, ctxt.HeadType, f, pkg, length, pn, file)
2189 if c1 == 0x01 && (c2 == 0xD7 || c2 == 0xF7) {
2190 ldxcoff := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2191 textp, err := loadxcoff.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2193 Errorf(nil, "%v", err)
2196 ctxt.Textp = append(ctxt.Textp, textp...)
2198 return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
2201 if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
2202 // An unrecognized object is just passed to the external linker.
2203 // If we try to read symbols from this object, we will
2204 // report an error at that time.
2205 unknownObjFormat = true
2206 return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
2209 /* check the header */
2210 line, err := f.ReadString('\n')
2212 Errorf(nil, "truncated object file: %s: %v", pn, err)
2216 if !strings.HasPrefix(line, "go object ") {
2217 if strings.HasSuffix(pn, ".go") {
2218 Exitf("%s: uncompiled .go source file", pn)
2222 if line == ctxt.Arch.Name {
2223 // old header format: just $GOOS
2224 Errorf(nil, "%s: stale object file", pn)
2228 Errorf(nil, "%s: not an object file: @%d %q", pn, start, line)
2232 // First, check that the basic GOOS, GOARCH, and Version match.
2233 if line != wantHdr {
2234 Errorf(nil, "%s: linked object header mismatch:\nhave %q\nwant %q\n", pn, line, wantHdr)
2237 // Skip over exports and other info -- ends with \n!\n.
2239 // Note: It's possible for "\n!\n" to appear within the binary
2240 // package export data format. To avoid truncating the package
2241 // definition prematurely (issue 21703), we keep track of
2242 // how many "$$" delimiters we've seen.
2244 import0 := f.Offset()
2246 c1 = '\n' // the last line ended in \n
2252 if markers%2 == 0 && c2 == '!' && c3 == '\n' {
2255 if c2 == '$' && c3 == '$' {
2264 Errorf(nil, "truncated object file: %s", pn)
2269 import1 := f.Offset()
2271 f.MustSeek(import0, 0)
2272 ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
2273 f.MustSeek(import1, 0)
2275 fingerprint := ctxt.loader.Preload(ctxt.IncVersion(), f, lib, unit, eof-f.Offset())
2276 if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
2277 // Check fingerprint, to ensure the importing and imported packages
2278 // have consistent view of symbol indices.
2279 // Normally the go command should ensure this. But in case something
2280 // goes wrong, it could lead to obscure bugs like run-time crash.
2281 // Check it here to be sure.
2282 if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
2283 lib.Fingerprint = fingerprint
2285 checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
2288 addImports(ctxt, lib, pn)
2292 // symbolsAreUnresolved scans through the loader's list of unresolved
2293 // symbols and checks to see whether any of them match the names of the
2294 // symbols in 'want'. Return value is a list of bools, with list[K] set
2295 // to true if there is an unresolved reference to the symbol in want[K].
2296 func symbolsAreUnresolved(ctxt *Link, want []string) []bool {
2297 returnAllUndefs := -1
2298 undefs, _ := ctxt.loader.UndefinedRelocTargets(returnAllUndefs)
2299 seen := make(map[loader.Sym]struct{})
2300 rval := make([]bool, len(want))
2301 wantm := make(map[string]int)
2302 for k, w := range want {
2306 for _, s := range undefs {
2307 if _, ok := seen[s]; ok {
2310 seen[s] = struct{}{}
2311 if k, ok := wantm[ctxt.loader.SymName(s)]; ok {
2314 if count == len(want) {
2322 // hostObject reads a single host object file (compare to "hostArchive").
2323 // This is used as part of internal linking when we need to pull in
2324 // files such as "crt?.o".
2325 func hostObject(ctxt *Link, objname string, path string) {
2326 if ctxt.Debugvlog > 1 {
2327 ctxt.Logf("hostObject(%s)\n", path)
2329 objlib := sym.Library{
2332 f, err := bio.Open(path)
2334 Exitf("cannot open host object %q file %s: %v", objname, path, err)
2337 h := ldobj(ctxt, f, &objlib, 0, path, path)
2339 Exitf("unrecognized object file format in %s", path)
2342 h.length = f.MustSeek(0, 2)
2343 f.MustSeek(h.off, 0)
2344 h.ld(ctxt, f, h.pkg, h.length, h.pn)
2345 if *flagCaptureHostObjs != "" {
2350 func checkFingerprint(lib *sym.Library, libfp goobj.FingerprintType, src string, srcfp goobj.FingerprintType) {
2352 Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
2356 func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
2357 data := make([]byte, sym.Size)
2358 sect := f.Sections[sym.Section]
2359 if sect.Type != elf.SHT_PROGBITS && sect.Type != elf.SHT_NOTE {
2360 Errorf(nil, "reading %s from non-data section", sym.Name)
2362 n, err := sect.ReadAt(data, int64(sym.Value-sect.Addr))
2363 if uint64(n) != sym.Size {
2364 Errorf(nil, "reading contents of %s: %v", sym.Name, err)
2369 func readwithpad(r io.Reader, sz int32) ([]byte, error) {
2370 data := make([]byte, Rnd(int64(sz), 4))
2371 _, err := io.ReadFull(r, data)
2379 func readnote(f *elf.File, name []byte, typ int32) ([]byte, error) {
2380 for _, sect := range f.Sections {
2381 if sect.Type != elf.SHT_NOTE {
2386 var namesize, descsize, noteType int32
2387 err := binary.Read(r, f.ByteOrder, &namesize)
2392 return nil, fmt.Errorf("read namesize failed: %v", err)
2394 err = binary.Read(r, f.ByteOrder, &descsize)
2396 return nil, fmt.Errorf("read descsize failed: %v", err)
2398 err = binary.Read(r, f.ByteOrder, ¬eType)
2400 return nil, fmt.Errorf("read type failed: %v", err)
2402 noteName, err := readwithpad(r, namesize)
2404 return nil, fmt.Errorf("read name failed: %v", err)
2406 desc, err := readwithpad(r, descsize)
2408 return nil, fmt.Errorf("read desc failed: %v", err)
2410 if string(name) == string(noteName) && typ == noteType {
2418 func findshlib(ctxt *Link, shlib string) string {
2419 if filepath.IsAbs(shlib) {
2422 for _, libdir := range ctxt.Libdir {
2423 libpath := filepath.Join(libdir, shlib)
2424 if _, err := os.Stat(libpath); err == nil {
2428 Errorf(nil, "cannot find shared library: %s", shlib)
2432 func ldshlibsyms(ctxt *Link, shlib string) {
2434 if filepath.IsAbs(shlib) {
2436 shlib = filepath.Base(shlib)
2438 libpath = findshlib(ctxt, shlib)
2443 for _, processedlib := range ctxt.Shlibs {
2444 if processedlib.Path == libpath {
2448 if ctxt.Debugvlog > 1 {
2449 ctxt.Logf("ldshlibsyms: found library with name %s at %s\n", shlib, libpath)
2452 f, err := elf.Open(libpath)
2454 Errorf(nil, "cannot open shared library: %s", libpath)
2457 // Keep the file open as decodetypeGcprog needs to read from it.
2458 // TODO: fix. Maybe mmap the file.
2461 hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
2463 Errorf(nil, "cannot read ABI hash from shared library %s: %v", libpath, err)
2467 depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
2469 Errorf(nil, "cannot read dep list from shared library %s: %v", libpath, err)
2473 for _, dep := range strings.Split(string(depsbytes), "\n") {
2477 if !filepath.IsAbs(dep) {
2478 // If the dep can be interpreted as a path relative to the shlib
2479 // in which it was found, do that. Otherwise, we will leave it
2480 // to be resolved by libdir lookup.
2481 abs := filepath.Join(filepath.Dir(libpath), dep)
2482 if _, err := os.Stat(abs); err == nil {
2486 deps = append(deps, dep)
2489 syms, err := f.DynamicSymbols()
2491 Errorf(nil, "cannot read symbols from shared library: %s", libpath)
2495 for _, elfsym := range syms {
2496 if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
2500 // Symbols whose names start with "type:" are compiler generated,
2501 // so make functions with that prefix internal.
2503 symname := elfsym.Name // (unmangled) symbol name
2504 if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type:") {
2505 ver = abiInternalVer
2506 } else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC {
2507 // Demangle the ABI name. Keep in sync with symtab.go:mangleABIName.
2508 if strings.HasSuffix(elfsym.Name, ".abiinternal") {
2509 ver = sym.SymVerABIInternal
2510 symname = strings.TrimSuffix(elfsym.Name, ".abiinternal")
2511 } else if strings.HasSuffix(elfsym.Name, ".abi0") {
2513 symname = strings.TrimSuffix(elfsym.Name, ".abi0")
2518 s := l.LookupOrCreateSym(symname, ver)
2520 // Because loadlib above loads all .a files before loading
2521 // any shared libraries, any non-dynimport symbols we find
2522 // that duplicate symbols already loaded should be ignored
2523 // (the symbols from the .a files "win").
2524 if l.SymType(s) != 0 && l.SymType(s) != sym.SDYNIMPORT {
2527 su := l.MakeSymbolUpdater(s)
2528 su.SetType(sym.SDYNIMPORT)
2529 l.SetSymElfType(s, elf.ST_TYPE(elfsym.Info))
2530 su.SetSize(int64(elfsym.Size))
2531 if elfsym.Section != elf.SHN_UNDEF {
2532 // Set .File for the library that actually defines the symbol.
2533 l.SetSymPkg(s, libpath)
2535 // The decodetype_* functions in decodetype.go need access to
2537 sname := l.SymName(s)
2538 if strings.HasPrefix(sname, "type:") && !strings.HasPrefix(sname, "type:.") {
2539 su.SetData(readelfsymboldata(ctxt, f, &elfsym))
2543 if symname != elfsym.Name {
2544 l.SetSymExtname(s, elfsym.Name)
2547 ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f})
2550 func addsection(ldr *loader.Loader, arch *sys.Arch, seg *sym.Segment, name string, rwx int) *sym.Section {
2551 sect := ldr.NewSection()
2552 sect.Rwx = uint8(rwx)
2555 sect.Align = int32(arch.PtrSize) // everything is at least pointer-aligned
2556 seg.Sections = append(seg.Sections, sect)
2561 fmt.Fprintf(os.Stderr, "usage: link [options] main.o\n")
2562 objabi.Flagprint(os.Stderr)
2566 type SymbolType int8 // TODO: after genasmsym is gone, maybe rename to plan9typeChar or something
2569 // see also https://9p.io/magic/man2html/1/nm
2570 TextSym SymbolType = 'T'
2571 DataSym SymbolType = 'D'
2572 BSSSym SymbolType = 'B'
2573 UndefinedSym SymbolType = 'U'
2574 TLSSym SymbolType = 't'
2575 FrameSym SymbolType = 'm'
2576 ParamSym SymbolType = 'p'
2577 AutoSym SymbolType = 'a'
2579 // Deleted auto (not a real sym, just placeholder for type)
2580 DeletedAutoSym = 'x'
2583 // defineInternal defines a symbol used internally by the go runtime.
2584 func (ctxt *Link) defineInternal(p string, t sym.SymKind) loader.Sym {
2585 s := ctxt.loader.CreateSymForUpdate(p, 0)
2592 func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) loader.Sym {
2593 s := ctxt.defineInternal(p, t)
2594 ctxt.loader.SetSymValue(s, v)
2598 func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
2599 if uint64(addr) >= Segdata.Vaddr {
2600 return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
2602 if uint64(addr) >= Segtext.Vaddr {
2603 return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
2605 ldr.Errorf(s, "invalid datoff %#x", addr)
2609 func Entryvalue(ctxt *Link) int64 {
2610 a := *flagEntrySymbol
2611 if a[0] >= '0' && a[0] <= '9' {
2615 s := ldr.Lookup(a, 0)
2617 Errorf(nil, "missing entry symbol %q", a)
2620 st := ldr.SymType(s)
2622 return *FlagTextAddr
2624 if !ctxt.IsAIX() && st != sym.STEXT {
2625 ldr.Errorf(s, "entry not text")
2627 return ldr.SymValue(s)
2630 func (ctxt *Link) callgraph() {
2636 for _, s := range ctxt.Textp {
2637 relocs := ldr.Relocs(s)
2638 for i := 0; i < relocs.Count(); i++ {
2644 if r.Type().IsDirectCall() && ldr.SymType(rs) == sym.STEXT {
2645 ctxt.Logf("%s calls %s\n", ldr.SymName(s), ldr.SymName(rs))
2651 func Rnd(v int64, r int64) int64 {
2664 func bgetc(r *bio.Reader) int {
2665 c, err := r.ReadByte()
2668 log.Fatalf("reading input: %v", err)
2675 type markKind uint8 // for postorder traversal
2682 func postorder(libs []*sym.Library) []*sym.Library {
2683 order := make([]*sym.Library, 0, len(libs)) // hold the result
2684 mark := make(map[*sym.Library]markKind, len(libs))
2685 for _, lib := range libs {
2686 dfs(lib, mark, &order)
2691 func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library) {
2692 if mark[lib] == visited {
2695 if mark[lib] == visiting {
2696 panic("found import cycle while visiting " + lib.Pkg)
2698 mark[lib] = visiting
2699 for _, i := range lib.Imports {
2703 *order = append(*order, lib)
2706 func ElfSymForReloc(ctxt *Link, s loader.Sym) int32 {
2707 // If putelfsym created a local version of this symbol, use that in all
2709 les := ctxt.loader.SymLocalElfSym(s)
2713 return ctxt.loader.SymElfSym(s)
2717 func AddGotSym(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, elfRelocTyp uint32) {
2718 if ldr.SymGot(s) >= 0 {
2722 Adddynsym(ldr, target, syms, s)
2723 got := ldr.MakeSymbolUpdater(syms.GOT)
2724 ldr.SetGot(s, int32(got.Size()))
2725 got.AddUint(target.Arch, 0)
2728 if target.Arch.PtrSize == 8 {
2729 rela := ldr.MakeSymbolUpdater(syms.Rela)
2730 rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2731 rela.AddUint64(target.Arch, elf.R_INFO(uint32(ldr.SymDynid(s)), elfRelocTyp))
2732 rela.AddUint64(target.Arch, 0)
2734 rel := ldr.MakeSymbolUpdater(syms.Rel)
2735 rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2736 rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), elfRelocTyp))
2738 } else if target.IsDarwin() {
2739 leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT)
2740 leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
2741 if target.IsPIE() && target.IsInternal() {
2742 // Mach-O relocations are a royal pain to lay out.
2743 // They use a compact stateful bytecode representation.
2744 // Here we record what are needed and encode them later.
2745 MachoAddBind(int64(ldr.SymGot(s)), s)
2748 ldr.Errorf(s, "addgotsym: unsupported binary format")
2752 var hostobjcounter int
2754 // captureHostObj writes out the content of a host object (pulled from
2755 // an archive or loaded from a *.o file directly) to a directory
2756 // specified via the linker's "-capturehostobjs" debugging flag. This
2757 // is intended to make it easier for a developer to inspect the actual
2758 // object feeding into "CGO internal" link step.
2759 func captureHostObj(h *Hostobj) {
2760 // Form paths for info file and obj file.
2761 ofile := fmt.Sprintf("captured-obj-%d.o", hostobjcounter)
2762 ifile := fmt.Sprintf("captured-obj-%d.txt", hostobjcounter)
2764 opath := filepath.Join(*flagCaptureHostObjs, ofile)
2765 ipath := filepath.Join(*flagCaptureHostObjs, ifile)
2767 // Write the info file.
2768 info := fmt.Sprintf("pkg: %s\npn: %s\nfile: %s\noff: %d\nlen: %d\n",
2769 h.pkg, h.pn, h.file, h.off, h.length)
2770 if err := os.WriteFile(ipath, []byte(info), 0666); err != nil {
2771 log.Fatalf("error writing captured host obj info %s: %v", ipath, err)
2774 readObjData := func() []byte {
2775 inf, err := os.Open(h.file)
2777 log.Fatalf("capturing host obj: open failed on %s: %v", h.pn, err)
2779 res := make([]byte, h.length)
2780 if n, err := inf.ReadAt(res, h.off); err != nil || n != int(h.length) {
2781 log.Fatalf("capturing host obj: readat failed on %s: %v", h.pn, err)
2786 // Write the object file.
2787 if err := os.WriteFile(opath, readObjData(), 0666); err != nil {
2788 log.Fatalf("error writing captured host object %s: %v", opath, err)
2791 fmt.Fprintf(os.Stderr, "link: info: captured host object %s to %s\n",