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 elfsetstring1 := func(str string, off int) { elfsetstring(ctxt, 0, str, off) }
532 ctxt.loader = loader.NewLoader(flags, elfsetstring1, &ctxt.ErrorReporter.ErrorReporter)
533 ctxt.ErrorReporter.SymName = func(s loader.Sym) string {
534 return ctxt.loader.SymName(s)
537 // ctxt.Library grows during the loop, so not a range loop.
539 for ; i < len(ctxt.Library); i++ {
540 lib := ctxt.Library[i]
542 if ctxt.Debugvlog > 1 {
543 ctxt.Logf("autolib: %s (from %s)\n", lib.File, lib.Objref)
545 loadobjfile(ctxt, lib)
549 // load internal packages, if not already
551 loadinternal(ctxt, "runtime/race")
554 loadinternal(ctxt, "runtime/msan")
557 loadinternal(ctxt, "runtime/asan")
559 loadinternal(ctxt, "runtime")
560 for ; i < len(ctxt.Library); i++ {
561 lib := ctxt.Library[i]
563 loadobjfile(ctxt, lib)
566 // At this point, the Go objects are "preloaded". Not all the symbols are
567 // added to the symbol table (only defined package symbols are). Looking
568 // up symbol by name may not get expected result.
570 iscgo = ctxt.LibraryByPkg["runtime/cgo"] != nil
572 // Plugins a require cgo support to function. Similarly, plugins may require additional
573 // internal linker support on some platforms which may not be implemented.
574 ctxt.canUsePlugins = ctxt.LibraryByPkg["plugin"] != nil && iscgo
576 // We now have enough information to determine the link mode.
577 determineLinkMode(ctxt)
579 if ctxt.LinkMode == LinkExternal && !iscgo && !(buildcfg.GOOS == "darwin" && ctxt.BuildMode != BuildModePlugin && ctxt.Arch.Family == sys.AMD64) {
580 // This indicates a user requested -linkmode=external.
581 // The startup code uses an import of runtime/cgo to decide
582 // whether to initialize the TLS. So give it one. This could
583 // be handled differently but it's an unusual case.
584 if lib := loadinternal(ctxt, "runtime/cgo"); lib != nil && lib.Shlib == "" {
585 if ctxt.BuildMode == BuildModeShared || ctxt.linkShared {
586 Exitf("cannot implicitly include runtime/cgo in a shared library")
588 for ; i < len(ctxt.Library); i++ {
589 lib := ctxt.Library[i]
591 loadobjfile(ctxt, lib)
597 // Add non-package symbols and references of externally defined symbols.
598 ctxt.loader.LoadSyms(ctxt.Arch)
600 // Load symbols from shared libraries, after all Go object symbols are loaded.
601 for _, lib := range ctxt.Library {
603 if ctxt.Debugvlog > 1 {
604 ctxt.Logf("autolib: %s (from %s)\n", lib.Shlib, lib.Objref)
606 ldshlibsyms(ctxt, lib.Shlib)
610 // Process cgo directives (has to be done before host object loading).
611 ctxt.loadcgodirectives()
613 // Conditionally load host objects, or setup for external linking.
617 if ctxt.LinkMode == LinkInternal && len(hostobj) != 0 {
618 // If we have any undefined symbols in external
619 // objects, try to read them from the libgcc file.
621 undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
624 if ctxt.Debugvlog > 1 {
625 ctxt.Logf("loadlib: first unresolved is %s [%d] from %s [%d]\n",
626 ctxt.loader.SymName(undefs[0]), undefs[0],
627 ctxt.loader.SymName(froms[0]), froms[0])
631 if *flagLibGCC == "" {
632 *flagLibGCC = ctxt.findLibPathCmd("--print-libgcc-file-name", "libgcc")
634 if runtime.GOOS == "openbsd" && *flagLibGCC == "libgcc.a" {
635 // On OpenBSD `clang --print-libgcc-file-name` returns "libgcc.a".
636 // In this case we fail to load libgcc.a and can encounter link
637 // errors - see if we can find libcompiler_rt.a instead.
638 *flagLibGCC = ctxt.findLibPathCmd("--print-file-name=libcompiler_rt.a", "libcompiler_rt")
640 if ctxt.HeadType == objabi.Hwindows {
641 loadWindowsHostArchives(ctxt)
643 if *flagLibGCC != "none" {
644 hostArchive(ctxt, *flagLibGCC)
646 // For glibc systems, the linker setup used by GCC
649 // GROUP ( /lib/x86_64-linux-gnu/libc.so.6
650 // /usr/lib/x86_64-linux-gnu/libc_nonshared.a
651 // AS_NEEDED ( /lib64/ld-linux-x86-64.so.2 ) )
653 // where libc_nonshared.a contains a small set of
654 // symbols including "__stack_chk_fail_local" and a
655 // few others. Thus if we are doing internal linking
656 // and "__stack_chk_fail_local" is unresolved (most
657 // likely due to the use of -fstack-protector), try
658 // loading libc_nonshared.a to resolve it.
660 // On Alpine Linux (musl-based), the library providing
661 // this symbol is called libssp_nonshared.a.
662 isunresolved := symbolsAreUnresolved(ctxt, []string{"__stack_chk_fail_local"})
664 if p := ctxt.findLibPath("libc_nonshared.a"); p != "none" {
667 if p := ctxt.findLibPath("libssp_nonshared.a"); p != "none" {
674 // We've loaded all the code now.
677 strictDupMsgCount = ctxt.loader.NStrictDupMsgs()
680 // loadWindowsHostArchives loads in host archives and objects when
681 // doing internal linking on windows. Older toolchains seem to require
682 // just a single pass through the various archives, but some modern
683 // toolchains when linking a C program with mingw pass library paths
684 // multiple times to the linker, e.g. "... -lmingwex -lmingw32 ...
685 // -lmingwex -lmingw32 ...". To accommodate this behavior, we make two
686 // passes over the host archives below.
687 func loadWindowsHostArchives(ctxt *Link) {
689 for i := 0; any && i < 2; i++ {
690 // Link crt2.o (if present) to resolve "atexit" when
691 // using LLVM-based compilers.
692 isunresolved := symbolsAreUnresolved(ctxt, []string{"atexit"})
694 if p := ctxt.findLibPath("crt2.o"); p != "none" {
695 hostObject(ctxt, "crt2", p)
699 if p := ctxt.findLibPath("libsynchronization.a"); p != "none" {
703 if p := ctxt.findLibPath("libmingwex.a"); p != "none" {
706 if p := ctxt.findLibPath("libmingw32.a"); p != "none" {
709 // Link libmsvcrt.a to resolve '__acrt_iob_func' symbol
710 // (see https://golang.org/issue/23649 for details).
711 if p := ctxt.findLibPath("libmsvcrt.a"); p != "none" {
715 undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
718 if ctxt.Debugvlog > 1 {
719 ctxt.Logf("loadWindowsHostArchives: remaining unresolved is %s [%d] from %s [%d]\n",
720 ctxt.loader.SymName(undefs[0]), undefs[0],
721 ctxt.loader.SymName(froms[0]), froms[0])
725 // If needed, create the __CTOR_LIST__ and __DTOR_LIST__
726 // symbols (referenced by some of the mingw support library
727 // routines). Creation of these symbols is normally done by the
728 // linker if not already present.
729 want := []string{"__CTOR_LIST__", "__DTOR_LIST__"}
730 isunresolved := symbolsAreUnresolved(ctxt, want)
731 for k, w := range want {
733 sb := ctxt.loader.CreateSymForUpdate(w, 0)
734 sb.SetType(sym.SDATA)
735 sb.AddUint64(ctxt.Arch, 0)
736 sb.SetReachable(true)
737 ctxt.loader.SetAttrSpecial(sb.Sym(), true)
741 // Fix up references to DLL import symbols now that we're done
742 // pulling in new objects.
743 if err := loadpe.PostProcessImports(); err != nil {
744 Errorf(nil, "%v", err)
747 // TODO: maybe do something similar to peimporteddlls to collect
748 // all lib names and try link them all to final exe just like
749 // libmingwex.a and libmingw32.a:
752 #cgo windows LDFLAGS: -lmsvcrt -lm
758 // loadcgodirectives reads the previously discovered cgo directives, creating
759 // symbols in preparation for host object loading or use later in the link.
760 func (ctxt *Link) loadcgodirectives() {
762 hostObjSyms := make(map[loader.Sym]struct{})
763 for _, d := range ctxt.cgodata {
764 setCgoAttr(ctxt, d.file, d.pkg, d.directives, hostObjSyms)
768 if ctxt.LinkMode == LinkInternal {
769 // Drop all the cgo_import_static declarations.
770 // Turns out we won't be needing them.
771 for symIdx := range hostObjSyms {
772 if l.SymType(symIdx) == sym.SHOSTOBJ {
773 // If a symbol was marked both
774 // cgo_import_static and cgo_import_dynamic,
775 // then we want to make it cgo_import_dynamic
777 su := l.MakeSymbolUpdater(symIdx)
778 if l.SymExtname(symIdx) != "" && l.SymDynimplib(symIdx) != "" && !(l.AttrCgoExportStatic(symIdx) || l.AttrCgoExportDynamic(symIdx)) {
779 su.SetType(sym.SDYNIMPORT)
788 // Set up flags and special symbols depending on the platform build mode.
789 // This version works with loader.Loader.
790 func (ctxt *Link) linksetup() {
791 switch ctxt.BuildMode {
792 case BuildModeCShared, BuildModePlugin:
793 symIdx := ctxt.loader.LookupOrCreateSym("runtime.islibrary", 0)
794 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
795 sb.SetType(sym.SNOPTRDATA)
797 case BuildModeCArchive:
798 symIdx := ctxt.loader.LookupOrCreateSym("runtime.isarchive", 0)
799 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
800 sb.SetType(sym.SNOPTRDATA)
804 // Recalculate pe parameters now that we have ctxt.LinkMode set.
805 if ctxt.HeadType == objabi.Hwindows {
809 if ctxt.LinkMode == LinkExternal {
810 // When external linking, we are creating an object file. The
811 // absolute address is irrelevant.
815 // If there are no dynamic libraries needed, gcc disables dynamic linking.
816 // Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13)
817 // assumes that a dynamic binary always refers to at least one dynamic library.
818 // Rather than be a source of test cases for glibc, disable dynamic linking
819 // the same way that gcc would.
821 // Exception: on OS X, programs such as Shark only work with dynamic
822 // binaries, so leave it enabled on OS X (Mach-O) binaries.
823 // Also leave it enabled on Solaris which doesn't support
824 // statically linked binaries.
825 if ctxt.BuildMode == BuildModeExe {
826 if havedynamic == 0 && ctxt.HeadType != objabi.Hdarwin && ctxt.HeadType != objabi.Hsolaris {
831 if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && buildcfg.GOOS != "aix" {
832 toc := ctxt.loader.LookupOrCreateSym(".TOC.", 0)
833 sb := ctxt.loader.MakeSymbolUpdater(toc)
834 sb.SetType(sym.SDYNIMPORT)
837 // The Android Q linker started to complain about underalignment of the our TLS
838 // section. We don't actually use the section on android, so don't
840 if buildcfg.GOOS != "android" {
841 tlsg := ctxt.loader.LookupOrCreateSym("runtime.tlsg", 0)
842 sb := ctxt.loader.MakeSymbolUpdater(tlsg)
844 // runtime.tlsg is used for external linking on platforms that do not define
845 // a variable to hold g in assembly (currently only intel).
847 sb.SetType(sym.STLSBSS)
848 sb.SetSize(int64(ctxt.Arch.PtrSize))
849 } else if sb.Type() != sym.SDYNIMPORT {
850 Errorf(nil, "runtime declared tlsg variable %v", sb.Type())
852 ctxt.loader.SetAttrReachable(tlsg, true)
856 var moduledata loader.Sym
857 var mdsb *loader.SymbolBuilder
858 if ctxt.BuildMode == BuildModePlugin {
859 moduledata = ctxt.loader.LookupOrCreateSym("local.pluginmoduledata", 0)
860 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
861 ctxt.loader.SetAttrLocal(moduledata, true)
863 moduledata = ctxt.loader.LookupOrCreateSym("runtime.firstmoduledata", 0)
864 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
866 if mdsb.Type() != 0 && mdsb.Type() != sym.SDYNIMPORT {
867 // If the module (toolchain-speak for "executable or shared
868 // library") we are linking contains the runtime package, it
869 // will define the runtime.firstmoduledata symbol and we
870 // truncate it back to 0 bytes so we can define its entire
871 // contents in symtab.go:symtab().
874 // In addition, on ARM, the runtime depends on the linker
875 // recording the value of GOARM.
876 if ctxt.Arch.Family == sys.ARM {
877 goarm := ctxt.loader.LookupOrCreateSym("runtime.goarm", 0)
878 sb := ctxt.loader.MakeSymbolUpdater(goarm)
879 sb.SetType(sym.SDATA)
881 sb.AddUint8(uint8(buildcfg.GOARM))
884 // Set runtime.disableMemoryProfiling bool if
885 // runtime.MemProfile is not retained in the binary after
886 // deadcode (and we're not dynamically linking).
887 memProfile := ctxt.loader.Lookup("runtime.MemProfile", abiInternalVer)
888 if memProfile != 0 && !ctxt.loader.AttrReachable(memProfile) && !ctxt.DynlinkingGo() {
889 memProfSym := ctxt.loader.LookupOrCreateSym("runtime.disableMemoryProfiling", 0)
890 sb := ctxt.loader.MakeSymbolUpdater(memProfSym)
891 sb.SetType(sym.SDATA)
893 sb.AddUint8(1) // true bool
896 // If OTOH the module does not contain the runtime package,
897 // create a local symbol for the moduledata.
898 moduledata = ctxt.loader.LookupOrCreateSym("local.moduledata", 0)
899 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
900 ctxt.loader.SetAttrLocal(moduledata, true)
902 // In all cases way we mark the moduledata as noptrdata to hide it from
904 mdsb.SetType(sym.SNOPTRDATA)
905 ctxt.loader.SetAttrReachable(moduledata, true)
906 ctxt.Moduledata = moduledata
908 if ctxt.Arch == sys.Arch386 && ctxt.HeadType != objabi.Hwindows {
909 if (ctxt.BuildMode == BuildModeCArchive && ctxt.IsELF) || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE || ctxt.DynlinkingGo() {
910 got := ctxt.loader.LookupOrCreateSym("_GLOBAL_OFFSET_TABLE_", 0)
911 sb := ctxt.loader.MakeSymbolUpdater(got)
912 sb.SetType(sym.SDYNIMPORT)
913 ctxt.loader.SetAttrReachable(got, true)
917 // DWARF-gen and other phases require that the unit Textp slices
918 // be populated, so that it can walk the functions in each unit.
919 // Call into the loader to do this (requires that we collect the
920 // set of internal libraries first). NB: might be simpler if we
921 // moved isRuntimeDepPkg to cmd/internal and then did the test in
922 // loader.AssignTextSymbolOrder.
923 ctxt.Library = postorder(ctxt.Library)
925 for _, lib := range ctxt.Library {
926 intlibs = append(intlibs, isRuntimeDepPkg(lib.Pkg))
928 ctxt.Textp = ctxt.loader.AssignTextSymbolOrder(ctxt.Library, intlibs, ctxt.Textp)
931 // mangleTypeSym shortens the names of symbols that represent Go types
932 // if they are visible in the symbol table.
934 // As the names of these symbols are derived from the string of
935 // the type, they can run to many kilobytes long. So we shorten
936 // them using a SHA-1 when the name appears in the final binary.
937 // This also removes characters that upset external linkers.
939 // These are the symbols that begin with the prefix 'type.' and
940 // contain run-time type information used by the runtime and reflect
941 // packages. All Go binaries contain these symbols, but only
942 // those programs loaded dynamically in multiple parts need these
943 // symbols to have entries in the symbol table.
944 func (ctxt *Link) mangleTypeSym() {
945 if ctxt.BuildMode != BuildModeShared && !ctxt.linkShared && ctxt.BuildMode != BuildModePlugin && !ctxt.CanUsePlugins() {
950 for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
951 if !ldr.AttrReachable(s) && !ctxt.linkShared {
952 // If -linkshared, the GCProg generation code may need to reach
953 // out to the shared library for the type descriptor's data, even
954 // the type descriptor itself is not actually needed at run time
955 // (therefore not reachable). We still need to mangle its name,
956 // so it is consistent with the one stored in the shared library.
959 name := ldr.SymName(s)
960 newName := typeSymbolMangle(name)
962 ldr.SetSymExtname(s, newName)
964 // When linking against a shared library, the Go object file may
965 // have reference to the original symbol name whereas the shared
966 // library provides a symbol with the mangled name. We need to
967 // copy the payload of mangled to original.
968 // XXX maybe there is a better way to do this.
969 dup := ldr.Lookup(newName, ldr.SymVersion(s))
972 dt := ldr.SymType(dup)
973 if st == sym.Sxxx && dt != sym.Sxxx {
981 // typeSymbolMangle mangles the given symbol name into something shorter.
983 // Keep the type:. prefix, which parts of the linker (like the
984 // DWARF generator) know means the symbol is not decodable.
985 // Leave type:runtime. symbols alone, because other parts of
986 // the linker manipulates them.
987 func typeSymbolMangle(name string) string {
988 if !strings.HasPrefix(name, "type:") {
991 if strings.HasPrefix(name, "type:runtime.") {
994 if len(name) <= 14 && !strings.Contains(name, "@") { // Issue 19529
997 hash := notsha256.Sum256([]byte(name))
1002 return prefix + base64.StdEncoding.EncodeToString(hash[:6])
1006 * look for the next file in an archive.
1007 * adapted from libmach.
1009 func nextar(bp *bio.Reader, off int64, a *ArHdr) int64 {
1014 var buf [SAR_HDR]byte
1015 if n, err := io.ReadFull(bp, buf[:]); err != nil {
1016 if n == 0 && err != io.EOF {
1022 a.name = artrim(buf[0:16])
1023 a.date = artrim(buf[16:28])
1024 a.uid = artrim(buf[28:34])
1025 a.gid = artrim(buf[34:40])
1026 a.mode = artrim(buf[40:48])
1027 a.size = artrim(buf[48:58])
1028 a.fmag = artrim(buf[58:60])
1030 arsize := atolwhex(a.size)
1034 return arsize + SAR_HDR
1037 func loadobjfile(ctxt *Link, lib *sym.Library) {
1038 pkg := objabi.PathToPrefix(lib.Pkg)
1040 if ctxt.Debugvlog > 1 {
1041 ctxt.Logf("ldobj: %s (%s)\n", lib.File, pkg)
1043 f, err := bio.Open(lib.File)
1045 Exitf("cannot open file %s: %v", lib.File, err)
1049 if pkg == "main" && !lib.Main {
1050 Exitf("%s: not package main", lib.File)
1054 for i := 0; i < len(ARMAG); i++ {
1055 if c, err := f.ReadByte(); err == nil && c == ARMAG[i] {
1059 /* load it as a regular file */
1060 l := f.MustSeek(0, 2)
1062 ldobj(ctxt, f, lib, l, lib.File, lib.File)
1067 * load all the object files from the archive now.
1068 * this gives us sequential file access and keeps us
1069 * from needing to come back later to pick up more
1070 * objects. it breaks the usual C archive model, but
1071 * this is Go, not C. the common case in Go is that
1072 * we need to load all the objects, and then we throw away
1073 * the individual symbols that are unused.
1075 * loading every object will also make it possible to
1076 * load foreign objects not referenced by __.PKGDEF.
1081 l := nextar(f, off, &arhdr)
1086 Exitf("%s: malformed archive", lib.File)
1090 // __.PKGDEF isn't a real Go object file, and it's
1091 // absent in -linkobj builds anyway. Skipping it
1092 // ensures consistency between -linkobj and normal
1094 if arhdr.name == pkgdef {
1098 if arhdr.name == "dynimportfail" {
1099 dynimportfail = append(dynimportfail, lib.Pkg)
1101 if arhdr.name == "preferlinkext" {
1102 // Ignore this directive if -linkmode has been
1104 if ctxt.LinkMode == LinkAuto {
1105 preferlinkext = append(preferlinkext, lib.Pkg)
1109 // Skip other special (non-object-file) sections that
1110 // build tools may have added. Such sections must have
1111 // short names so that the suffix is not truncated.
1112 if len(arhdr.name) < 16 {
1113 if ext := filepath.Ext(arhdr.name); ext != ".o" && ext != ".syso" {
1118 pname := fmt.Sprintf("%s(%s)", lib.File, arhdr.name)
1119 l = atolwhex(arhdr.size)
1120 ldobj(ctxt, f, lib, l, pname, lib.File)
1124 type Hostobj struct {
1125 ld func(*Link, *bio.Reader, string, int64, string)
1133 var hostobj []Hostobj
1135 // These packages can use internal linking mode.
1136 // Others trigger external mode.
1137 var internalpkg = []string{
1138 "crypto/internal/boring",
1139 "crypto/internal/boring/syso",
1145 "runtime/race/internal/amd64v1",
1146 "runtime/race/internal/amd64v3",
1151 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 {
1153 for _, intpkg := range internalpkg {
1160 // DragonFly declares errno with __thread, which results in a symbol
1161 // type of R_386_TLS_GD or R_X86_64_TLSGD. The Go linker does not
1162 // currently know how to handle TLS relocations, hence we have to
1163 // force external linking for any libraries that link in code that
1164 // uses errno. This can be removed if the Go linker ever supports
1165 // these relocation types.
1166 if headType == objabi.Hdragonfly {
1167 if pkg == "net" || pkg == "os/user" {
1176 hostobj = append(hostobj, Hostobj{})
1177 h := &hostobj[len(hostobj)-1]
1187 func hostobjs(ctxt *Link) {
1188 if ctxt.LinkMode != LinkInternal {
1193 for i := 0; i < len(hostobj); i++ {
1195 f, err := bio.Open(h.file)
1197 Exitf("cannot reopen %s: %v", h.pn, err)
1199 f.MustSeek(h.off, 0)
1201 Errorf(nil, "%s: unrecognized object file format", h.pn)
1204 h.ld(ctxt, f, h.pkg, h.length, h.pn)
1205 if *flagCaptureHostObjs != "" {
1212 func hostlinksetup(ctxt *Link) {
1213 if ctxt.LinkMode != LinkExternal {
1217 // For external link, record that we need to tell the external linker -s,
1218 // and turn off -s internally: the external linker needs the symbol
1219 // information for its final link.
1223 // create temporary directory and arrange cleanup
1224 if *flagTmpdir == "" {
1225 dir, err := os.MkdirTemp("", "go-link-")
1232 os.RemoveAll(*flagTmpdir)
1236 // change our output to temporary object file
1237 if err := ctxt.Out.Close(); err != nil {
1238 Exitf("error closing output file")
1240 mayberemoveoutfile()
1242 p := filepath.Join(*flagTmpdir, "go.o")
1243 if err := ctxt.Out.Open(p); err != nil {
1244 Exitf("cannot create %s: %v", p, err)
1248 // hostobjCopy creates a copy of the object files in hostobj in a
1249 // temporary directory.
1250 func (ctxt *Link) hostobjCopy() (paths []string) {
1251 var wg sync.WaitGroup
1252 sema := make(chan struct{}, runtime.NumCPU()) // limit open file descriptors
1253 for i, h := range hostobj {
1255 dst := filepath.Join(*flagTmpdir, fmt.Sprintf("%06d.o", i))
1256 paths = append(paths, dst)
1257 if ctxt.Debugvlog != 0 {
1258 ctxt.Logf("host obj copy: %s from pkg %s -> %s\n", h.pn, h.pkg, dst)
1268 f, err := os.Open(h.file)
1270 Exitf("cannot reopen %s: %v", h.pn, err)
1273 if _, err := f.Seek(h.off, 0); err != nil {
1274 Exitf("cannot seek %s: %v", h.pn, err)
1277 w, err := os.Create(dst)
1279 Exitf("cannot create %s: %v", dst, err)
1281 if _, err := io.CopyN(w, f, h.length); err != nil {
1282 Exitf("cannot write %s: %v", dst, err)
1284 if err := w.Close(); err != nil {
1285 Exitf("cannot close %s: %v", dst, err)
1293 // writeGDBLinkerScript creates gcc linker script file in temp
1294 // directory. writeGDBLinkerScript returns created file path.
1295 // The script is used to work around gcc bug
1296 // (see https://golang.org/issue/20183 for details).
1297 func writeGDBLinkerScript() string {
1298 name := "fix_debug_gdb_scripts.ld"
1299 path := filepath.Join(*flagTmpdir, name)
1302 .debug_gdb_scripts BLOCK(__section_alignment__) (NOLOAD) :
1304 *(.debug_gdb_scripts)
1307 INSERT AFTER .debug_types;
1309 err := os.WriteFile(path, []byte(src), 0666)
1311 Errorf(nil, "WriteFile %s failed: %v", name, err)
1316 // archive builds a .a archive from the hostobj object files.
1317 func (ctxt *Link) archive() {
1318 if ctxt.BuildMode != BuildModeCArchive {
1324 if *flagExtar == "" {
1328 mayberemoveoutfile()
1330 // Force the buffer to flush here so that external
1331 // tools will see a complete file.
1332 if err := ctxt.Out.Close(); err != nil {
1333 Exitf("error closing %v", *flagOutfile)
1336 argv := []string{*flagExtar, "-q", "-c", "-s"}
1337 if ctxt.HeadType == objabi.Haix {
1338 argv = append(argv, "-X64")
1340 argv = append(argv, *flagOutfile)
1341 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1342 argv = append(argv, ctxt.hostobjCopy()...)
1344 if ctxt.Debugvlog != 0 {
1345 ctxt.Logf("archive: %s\n", strings.Join(argv, " "))
1348 // If supported, use syscall.Exec() to invoke the archive command,
1349 // which should be the final remaining step needed for the link.
1350 // This will reduce peak RSS for the link (and speed up linking of
1351 // large applications), since when the archive command runs we
1352 // won't be holding onto all of the linker's live memory.
1353 if syscallExecSupported && !ownTmpDir {
1355 ctxt.execArchive(argv)
1356 panic("should not get here")
1359 // Otherwise invoke 'ar' in the usual way (fork + exec).
1360 if out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput(); err != nil {
1361 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1365 func (ctxt *Link) hostlink() {
1366 if ctxt.LinkMode != LinkExternal || nerrors > 0 {
1369 if ctxt.BuildMode == BuildModeCArchive {
1374 argv = append(argv, ctxt.extld()...)
1375 argv = append(argv, hostlinkArchArgs(ctxt.Arch)...)
1377 if *FlagS || debug_s {
1378 if ctxt.HeadType == objabi.Hdarwin {
1379 // Recent versions of macOS print
1380 // ld: warning: option -s is obsolete and being ignored
1381 // so do not pass any arguments.
1383 argv = append(argv, "-s")
1387 // On darwin, whether to combine DWARF into executable.
1388 // Only macOS supports unmapped segments such as our __DWARF segment.
1389 combineDwarf := ctxt.IsDarwin() && !*FlagS && !*FlagW && !debug_s && machoPlatform == PLATFORM_MACOS
1391 switch ctxt.HeadType {
1392 case objabi.Hdarwin:
1394 // Leave room for DWARF combining.
1395 // -headerpad is incompatible with -fembed-bitcode.
1396 argv = append(argv, "-Wl,-headerpad,1144")
1398 if ctxt.DynlinkingGo() && buildcfg.GOOS != "ios" {
1399 // -flat_namespace is deprecated on iOS.
1400 // It is useful for supporting plugins. We don't support plugins on iOS.
1401 // -flat_namespace may cause the dynamic linker to hang at forkExec when
1402 // resolving a lazy binding. See issue 38824.
1403 // Force eager resolution to work around.
1404 argv = append(argv, "-Wl,-flat_namespace", "-Wl,-bind_at_load")
1407 argv = append(argv, "-Wl,-S") // suppress STAB (symbolic debugging) symbols
1409 case objabi.Hopenbsd:
1410 argv = append(argv, "-Wl,-nopie")
1411 argv = append(argv, "-pthread")
1412 if ctxt.Arch.InFamily(sys.ARM64) {
1413 // Disable execute-only on openbsd/arm64 - the Go arm64 assembler
1414 // currently stores constants in the text section rather than in rodata.
1415 // See issue #59615.
1416 argv = append(argv, "-Wl,--no-execute-only")
1418 case objabi.Hwindows:
1420 argv = append(argv, "-mwindows")
1422 argv = append(argv, "-mconsole")
1424 // Mark as having awareness of terminal services, to avoid
1425 // ancient compatibility hacks.
1426 argv = append(argv, "-Wl,--tsaware")
1429 argv = append(argv, "-Wl,--nxcompat")
1431 argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", PeMinimumTargetMajorVersion))
1432 argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", PeMinimumTargetMinorVersion))
1433 argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", PeMinimumTargetMajorVersion))
1434 argv = append(argv, fmt.Sprintf("-Wl,--minor-subsystem-version=%d", PeMinimumTargetMinorVersion))
1436 argv = append(argv, "-pthread")
1437 // prevent ld to reorder .text functions to keep the same
1438 // first/last functions for moduledata.
1439 argv = append(argv, "-Wl,-bnoobjreorder")
1440 // mcmodel=large is needed for every gcc generated files, but
1441 // ld still need -bbigtoc in order to allow larger TOC.
1442 argv = append(argv, "-mcmodel=large")
1443 argv = append(argv, "-Wl,-bbigtoc")
1446 // On PPC64, verify the external toolchain supports Power10. This is needed when
1447 // PC relative relocations might be generated by Go. Only targets compiling ELF
1448 // binaries might generate these relocations.
1449 if ctxt.IsPPC64() && ctxt.IsElf() && buildcfg.GOPPC64 >= 10 {
1450 if !linkerFlagSupported(ctxt.Arch, argv[0], "", "-mcpu=power10") {
1451 Exitf("The external toolchain does not support -mcpu=power10. " +
1452 " This is required to externally link GOPPC64 >= power10")
1456 // Enable/disable ASLR on Windows.
1457 addASLRargs := func(argv []string, val bool) []string {
1458 // Old/ancient versions of GCC support "--dynamicbase" and
1459 // "--high-entropy-va" but don't enable it by default. In
1460 // addition, they don't accept "--disable-dynamicbase" or
1461 // "--no-dynamicbase", so the only way to disable ASLR is to
1462 // not pass any flags at all.
1464 // More modern versions of GCC (and also clang) enable ASLR
1465 // by default. With these compilers, however you can turn it
1466 // off if you want using "--disable-dynamicbase" or
1467 // "--no-dynamicbase".
1469 // The strategy below is to try using "--disable-dynamicbase";
1470 // if this succeeds, then assume we're working with more
1471 // modern compilers and act accordingly. If it fails, assume
1472 // an ancient compiler with ancient defaults.
1475 dbon := "--dynamicbase"
1476 heon := "--high-entropy-va"
1477 dboff := "--disable-dynamicbase"
1478 heoff := "--disable-high-entropy-va"
1483 // Test to see whether "--disable-dynamicbase" works.
1484 newer := linkerFlagSupported(ctxt.Arch, argv[0], "", "-Wl,"+dboff)
1486 // Newer compiler, which supports both on/off options.
1490 // older toolchain: we have to say nothing in order to
1491 // get a no-ASLR binary.
1497 argv = append(argv, "-Wl,"+dbopt)
1499 // enable high-entropy ASLR on 64-bit.
1500 if ctxt.Arch.PtrSize >= 8 && heopt != "" {
1501 argv = append(argv, "-Wl,"+heopt)
1506 switch ctxt.BuildMode {
1508 if ctxt.HeadType == objabi.Hdarwin {
1509 if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() {
1510 argv = append(argv, "-Wl,-no_pie")
1513 if *flagRace && ctxt.HeadType == objabi.Hwindows {
1514 // Current windows/amd64 race detector tsan support
1515 // library can't handle PIE mode (see #53539 for more details).
1516 // For now, explicitly disable PIE (since some compilers
1517 // default to it) if -race is in effect.
1518 argv = addASLRargs(argv, false)
1521 switch ctxt.HeadType {
1522 case objabi.Hdarwin, objabi.Haix:
1523 case objabi.Hwindows:
1524 if *flagAslr && *flagRace {
1525 // Current windows/amd64 race detector tsan support
1526 // library can't handle PIE mode (see #53539 for more details).
1527 // Disable alsr if -race in effect.
1530 argv = addASLRargs(argv, *flagAslr)
1533 if ctxt.UseRelro() {
1534 argv = append(argv, "-Wl,-z,relro")
1536 argv = append(argv, "-pie")
1538 case BuildModeCShared:
1539 if ctxt.HeadType == objabi.Hdarwin {
1540 argv = append(argv, "-dynamiclib")
1542 if ctxt.UseRelro() {
1543 argv = append(argv, "-Wl,-z,relro")
1545 argv = append(argv, "-shared")
1546 if ctxt.HeadType == objabi.Hwindows {
1547 argv = addASLRargs(argv, *flagAslr)
1549 // Pass -z nodelete to mark the shared library as
1550 // non-closeable: a dlclose will do nothing.
1551 argv = append(argv, "-Wl,-z,nodelete")
1552 // Only pass Bsymbolic on non-Windows.
1553 argv = append(argv, "-Wl,-Bsymbolic")
1556 case BuildModeShared:
1557 if ctxt.UseRelro() {
1558 argv = append(argv, "-Wl,-z,relro")
1560 argv = append(argv, "-shared")
1561 case BuildModePlugin:
1562 if ctxt.HeadType == objabi.Hdarwin {
1563 argv = append(argv, "-dynamiclib")
1565 if ctxt.UseRelro() {
1566 argv = append(argv, "-Wl,-z,relro")
1568 argv = append(argv, "-shared")
1572 var altLinker string
1573 if ctxt.IsELF && ctxt.DynlinkingGo() {
1574 // We force all symbol resolution to be done at program startup
1575 // because lazy PLT resolution can use large amounts of stack at
1576 // times we cannot allow it to do so.
1577 argv = append(argv, "-Wl,-z,now")
1579 // Do not let the host linker generate COPY relocations. These
1580 // can move symbols out of sections that rely on stable offsets
1581 // from the beginning of the section (like sym.STYPE).
1582 argv = append(argv, "-Wl,-z,nocopyreloc")
1584 if buildcfg.GOOS == "android" {
1585 // Use lld to avoid errors from default linker (issue #38838)
1589 if ctxt.Arch.InFamily(sys.ARM64) && buildcfg.GOOS == "linux" {
1590 // On ARM64, the GNU linker will fail with
1591 // -znocopyreloc if it thinks a COPY relocation is
1592 // required. Switch to gold.
1593 // https://sourceware.org/bugzilla/show_bug.cgi?id=19962
1594 // https://go.dev/issue/22040
1597 // If gold is not installed, gcc will silently switch
1598 // back to ld.bfd. So we parse the version information
1599 // and provide a useful error if gold is missing.
1600 name, args := flagExtld[0], flagExtld[1:]
1601 args = append(args, "-fuse-ld=gold", "-Wl,--version")
1602 cmd := exec.Command(name, args...)
1603 if out, err := cmd.CombinedOutput(); err == nil {
1604 if !bytes.Contains(out, []byte("GNU gold")) {
1605 log.Fatalf("ARM64 external linker must be gold (issue #15696, 22040), but is not: %s", out)
1610 if ctxt.Arch.Family == sys.ARM64 && buildcfg.GOOS == "freebsd" {
1611 // Switch to ld.bfd on freebsd/arm64.
1614 // Provide a useful error if ld.bfd is missing.
1615 name, args := flagExtld[0], flagExtld[1:]
1616 args = append(args, "-fuse-ld=bfd", "-Wl,--version")
1617 cmd := exec.Command(name, args...)
1618 if out, err := cmd.CombinedOutput(); err == nil {
1619 if !bytes.Contains(out, []byte("GNU ld")) {
1620 log.Fatalf("ARM64 external linker must be ld.bfd (issue #35197), please install devel/binutils")
1624 if altLinker != "" {
1625 argv = append(argv, "-fuse-ld="+altLinker)
1628 if ctxt.IsELF && len(buildinfo) > 0 {
1629 argv = append(argv, fmt.Sprintf("-Wl,--build-id=0x%x", buildinfo))
1632 // On Windows, given -o foo, GCC will append ".exe" to produce
1633 // "foo.exe". We have decided that we want to honor the -o
1634 // option. To make this work, we append a '.' so that GCC
1635 // will decide that the file already has an extension. We
1636 // only want to do this when producing a Windows output file
1637 // on a Windows host.
1638 outopt := *flagOutfile
1639 if buildcfg.GOOS == "windows" && runtime.GOOS == "windows" && filepath.Ext(outopt) == "" {
1642 argv = append(argv, "-o")
1643 argv = append(argv, outopt)
1645 if rpath.val != "" {
1646 argv = append(argv, fmt.Sprintf("-Wl,-rpath,%s", rpath.val))
1649 if *flagInterpreter != "" {
1650 // Many linkers support both -I and the --dynamic-linker flags
1651 // to set the ELF interpreter, but lld only supports
1652 // --dynamic-linker so prefer that (ld on very old Solaris only
1653 // supports -I but that seems less important).
1654 argv = append(argv, fmt.Sprintf("-Wl,--dynamic-linker,%s", *flagInterpreter))
1657 // Force global symbols to be exported for dlopen, etc.
1659 if ctxt.DynlinkingGo() || ctxt.BuildMode == BuildModeCShared || !linkerFlagSupported(ctxt.Arch, argv[0], altLinker, "-Wl,--export-dynamic-symbol=main") {
1660 argv = append(argv, "-rdynamic")
1662 ctxt.loader.ForAllCgoExportDynamic(func(s loader.Sym) {
1663 argv = append(argv, "-Wl,--export-dynamic-symbol="+ctxt.loader.SymExtname(s))
1667 if ctxt.HeadType == objabi.Haix {
1668 fileName := xcoffCreateExportFile(ctxt)
1669 argv = append(argv, "-Wl,-bE:"+fileName)
1672 const unusedArguments = "-Qunused-arguments"
1673 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, unusedArguments) {
1674 argv = append(argv, unusedArguments)
1677 if ctxt.IsWindows() {
1678 // Suppress generation of the PE file header timestamp,
1679 // so as to avoid spurious build ID differences between
1680 // linked binaries that are otherwise identical other than
1681 // the date/time they were linked.
1682 const noTimeStamp = "-Wl,--no-insert-timestamp"
1683 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, noTimeStamp) {
1684 argv = append(argv, noTimeStamp)
1688 const compressDWARF = "-Wl,--compress-debug-sections=zlib"
1689 if ctxt.compressDWARF && linkerFlagSupported(ctxt.Arch, argv[0], altLinker, compressDWARF) {
1690 argv = append(argv, compressDWARF)
1693 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1694 argv = append(argv, ctxt.hostobjCopy()...)
1695 if ctxt.HeadType == objabi.Haix {
1696 // We want to have C files after Go files to remove
1697 // trampolines csects made by ld.
1698 argv = append(argv, "-nostartfiles")
1699 argv = append(argv, "/lib/crt0_64.o")
1701 extld := ctxt.extld()
1702 name, args := extld[0], extld[1:]
1703 // Get starting files.
1704 getPathFile := func(file string) string {
1705 args := append(args, "-maix64", "--print-file-name="+file)
1706 out, err := exec.Command(name, args...).CombinedOutput()
1708 log.Fatalf("running %s failed: %v\n%s", extld, err, out)
1710 return strings.Trim(string(out), "\n")
1712 // Since GCC version 11, the 64-bit version of GCC starting files
1713 // are now suffixed by "_64". Even under "-maix64" multilib directory
1714 // "crtcxa.o" is 32-bit.
1715 crtcxa := getPathFile("crtcxa_64.o")
1716 if !filepath.IsAbs(crtcxa) {
1717 crtcxa = getPathFile("crtcxa.o")
1719 crtdbase := getPathFile("crtdbase_64.o")
1720 if !filepath.IsAbs(crtdbase) {
1721 crtdbase = getPathFile("crtdbase.o")
1723 argv = append(argv, crtcxa)
1724 argv = append(argv, crtdbase)
1727 if ctxt.linkShared {
1728 seenDirs := make(map[string]bool)
1729 seenLibs := make(map[string]bool)
1730 addshlib := func(path string) {
1731 dir, base := filepath.Split(path)
1733 argv = append(argv, "-L"+dir)
1735 argv = append(argv, "-Wl,-rpath="+dir)
1737 seenDirs[dir] = true
1739 base = strings.TrimSuffix(base, ".so")
1740 base = strings.TrimPrefix(base, "lib")
1741 if !seenLibs[base] {
1742 argv = append(argv, "-l"+base)
1743 seenLibs[base] = true
1746 for _, shlib := range ctxt.Shlibs {
1747 addshlib(shlib.Path)
1748 for _, dep := range shlib.Deps {
1752 libpath := findshlib(ctxt, dep)
1760 // clang, unlike GCC, passes -rdynamic to the linker
1761 // even when linking with -static, causing a linker
1762 // error when using GNU ld. So take out -rdynamic if
1763 // we added it. We do it in this order, rather than
1764 // only adding -rdynamic later, so that -extldflags
1765 // can override -rdynamic without using -static.
1766 // Similarly for -Wl,--dynamic-linker.
1767 checkStatic := func(arg string) {
1768 if ctxt.IsELF && arg == "-static" {
1769 for i := range argv {
1770 if argv[i] == "-rdynamic" || strings.HasPrefix(argv[i], "-Wl,--dynamic-linker,") {
1777 for _, p := range ldflag {
1778 argv = append(argv, p)
1782 // When building a program with the default -buildmode=exe the
1783 // gc compiler generates code requires DT_TEXTREL in a
1784 // position independent executable (PIE). On systems where the
1785 // toolchain creates PIEs by default, and where DT_TEXTREL
1786 // does not work, the resulting programs will not run. See
1787 // issue #17847. To avoid this problem pass -no-pie to the
1788 // toolchain if it is supported.
1789 if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared && !(ctxt.IsDarwin() && ctxt.IsARM64()) {
1790 // GCC uses -no-pie, clang uses -nopie.
1791 for _, nopie := range []string{"-no-pie", "-nopie"} {
1792 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, nopie) {
1793 argv = append(argv, nopie)
1799 for _, p := range flagExtldflags {
1800 argv = append(argv, p)
1803 if ctxt.HeadType == objabi.Hwindows {
1804 // Determine which linker we're using. Add in the extldflags in
1805 // case used has specified "-fuse-ld=...".
1806 extld := ctxt.extld()
1807 name, args := extld[0], extld[1:]
1808 args = append(args, trimLinkerArgv(flagExtldflags)...)
1809 args = append(args, "-Wl,--version")
1810 cmd := exec.Command(name, args...)
1812 if out, err := cmd.CombinedOutput(); err == nil {
1813 if bytes.Contains(out, []byte("LLD ")) {
1818 // use gcc linker script to work around gcc bug
1819 // (see https://golang.org/issue/20183 for details).
1821 p := writeGDBLinkerScript()
1822 argv = append(argv, "-Wl,-T,"+p)
1825 if p := ctxt.findLibPath("libsynchronization.a"); p != "libsynchronization.a" {
1826 argv = append(argv, "-lsynchronization")
1829 // libmingw32 and libmingwex have some inter-dependencies,
1830 // so must use linker groups.
1831 argv = append(argv, "-Wl,--start-group", "-lmingwex", "-lmingw32", "-Wl,--end-group")
1832 argv = append(argv, peimporteddlls()...)
1835 argv = ctxt.passLongArgsInResponseFile(argv, altLinker)
1837 if ctxt.Debugvlog != 0 {
1838 ctxt.Logf("host link:")
1839 for _, v := range argv {
1845 out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput()
1847 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1850 // Filter out useless linker warnings caused by bugs outside Go.
1851 // See also cmd/go/internal/work/exec.go's gccld method.
1854 for _, line := range bytes.SplitAfter(out, []byte("\n")) {
1855 // golang.org/issue/26073 - Apple Xcode bug
1856 if bytes.Contains(line, []byte("ld: warning: text-based stub file")) {
1865 // Remove TOC overflow warning on AIX.
1866 if bytes.Contains(line, []byte("ld: 0711-783")) {
1871 save = append(save, line)
1873 out = bytes.Join(save, nil)
1876 // always print external output even if the command is successful, so that we don't
1877 // swallow linker warnings (see https://golang.org/issue/17935).
1878 if ctxt.IsDarwin() && ctxt.IsAMD64() {
1879 const noPieWarning = "ld: warning: -no_pie is deprecated when targeting new OS versions\n"
1880 if i := bytes.Index(out, []byte(noPieWarning)); i >= 0 {
1881 // swallow -no_pie deprecation warning, issue 54482
1882 out = append(out[:i], out[i+len(noPieWarning):]...)
1885 ctxt.Logf("%s", out)
1889 // Find "dsymutils" and "strip" tools using CC --print-prog-name.
1891 cc = append(cc, ctxt.extld()...)
1892 cc = append(cc, hostlinkArchArgs(ctxt.Arch)...)
1893 cc = append(cc, "--print-prog-name", "dsymutil")
1894 out, err := exec.Command(cc[0], cc[1:]...).CombinedOutput()
1896 Exitf("%s: finding dsymutil failed: %v\n%s", os.Args[0], err, out)
1898 dsymutilCmd := strings.TrimSuffix(string(out), "\n")
1900 cc[len(cc)-1] = "strip"
1901 out, err = exec.Command(cc[0], cc[1:]...).CombinedOutput()
1903 Exitf("%s: finding strip failed: %v\n%s", os.Args[0], err, out)
1905 stripCmd := strings.TrimSuffix(string(out), "\n")
1907 dsym := filepath.Join(*flagTmpdir, "go.dwarf")
1908 cmd := exec.Command(dsymutilCmd, "-f", *flagOutfile, "-o", dsym)
1909 // dsymutil may not clean up its temp directory at exit.
1910 // Set DSYMUTIL_REPRODUCER_PATH to work around. see issue 59026.
1911 cmd.Env = append(os.Environ(), "DSYMUTIL_REPRODUCER_PATH="+*flagTmpdir)
1912 if out, err := cmd.CombinedOutput(); err != nil {
1913 Exitf("%s: running dsymutil failed: %v\n%s", os.Args[0], err, out)
1915 // Remove STAB (symbolic debugging) symbols after we are done with them (by dsymutil).
1916 // They contain temporary file paths and make the build not reproducible.
1917 if out, err := exec.Command(stripCmd, "-S", *flagOutfile).CombinedOutput(); err != nil {
1918 Exitf("%s: running strip failed: %v\n%s", os.Args[0], err, out)
1920 // Skip combining if `dsymutil` didn't generate a file. See #11994.
1921 if _, err := os.Stat(dsym); os.IsNotExist(err) {
1924 // For os.Rename to work reliably, must be in same directory as outfile.
1925 combinedOutput := *flagOutfile + "~"
1926 exef, err := os.Open(*flagOutfile)
1928 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1931 exem, err := macho.NewFile(exef)
1933 Exitf("%s: parsing Mach-O header failed: %v", os.Args[0], err)
1935 if err := machoCombineDwarf(ctxt, exef, exem, dsym, combinedOutput); err != nil {
1936 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1938 os.Remove(*flagOutfile)
1939 if err := os.Rename(combinedOutput, *flagOutfile); err != nil {
1940 Exitf("%s: %v", os.Args[0], err)
1943 if ctxt.NeedCodeSign() {
1944 err := machoCodeSign(ctxt, *flagOutfile)
1946 Exitf("%s: code signing failed: %v", os.Args[0], err)
1951 // passLongArgsInResponseFile writes the arguments into a file if they
1953 func (ctxt *Link) passLongArgsInResponseFile(argv []string, altLinker string) []string {
1955 for _, arg := range argv {
1959 if c < sys.ExecArgLengthLimit {
1963 // Only use response files if they are supported.
1964 response := filepath.Join(*flagTmpdir, "response")
1965 if err := os.WriteFile(response, nil, 0644); err != nil {
1966 log.Fatalf("failed while testing response file: %v", err)
1968 if !linkerFlagSupported(ctxt.Arch, argv[0], altLinker, "@"+response) {
1969 if ctxt.Debugvlog != 0 {
1970 ctxt.Logf("not using response file because linker does not support one")
1975 var buf bytes.Buffer
1976 for _, arg := range argv[1:] {
1977 // The external linker response file supports quoted strings.
1978 fmt.Fprintf(&buf, "%q\n", arg)
1980 if err := os.WriteFile(response, buf.Bytes(), 0644); err != nil {
1981 log.Fatalf("failed while writing response file: %v", err)
1983 if ctxt.Debugvlog != 0 {
1984 ctxt.Logf("response file %s contents:\n%s", response, buf.Bytes())
1992 var createTrivialCOnce sync.Once
1994 func linkerFlagSupported(arch *sys.Arch, linker, altLinker, flag string) bool {
1995 createTrivialCOnce.Do(func() {
1996 src := filepath.Join(*flagTmpdir, "trivial.c")
1997 if err := os.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
1998 Errorf(nil, "WriteFile trivial.c failed: %v", err)
2002 flags := hostlinkArchArgs(arch)
2004 moreFlags := trimLinkerArgv(append(flagExtldflags, ldflag...))
2005 flags = append(flags, moreFlags...)
2007 if altLinker != "" {
2008 flags = append(flags, "-fuse-ld="+altLinker)
2010 flags = append(flags, flag, "trivial.c")
2012 cmd := exec.Command(linker, flags...)
2013 cmd.Dir = *flagTmpdir
2014 cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
2015 out, err := cmd.CombinedOutput()
2016 // GCC says "unrecognized command line option ‘-no-pie’"
2017 // clang says "unknown argument: '-no-pie'"
2018 return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
2021 // trimLinkerArgv returns a new copy of argv that does not include flags
2022 // that are not relevant for testing whether some linker option works.
2023 func trimLinkerArgv(argv []string) []string {
2024 flagsWithNextArgSkip := []string{
2033 flagsWithNextArgKeep := []string{
2039 prefixesToKeep := []string{
2053 for _, f := range argv {
2055 flags = append(flags, f)
2059 } else if f == "" || f[0] != '-' {
2060 } else if contains(flagsWithNextArgSkip, f) {
2062 } else if contains(flagsWithNextArgKeep, f) {
2063 flags = append(flags, f)
2066 for _, p := range prefixesToKeep {
2067 if strings.HasPrefix(f, p) {
2068 flags = append(flags, f)
2077 // hostlinkArchArgs returns arguments to pass to the external linker
2078 // based on the architecture.
2079 func hostlinkArchArgs(arch *sys.Arch) []string {
2080 switch arch.Family {
2082 return []string{"-m32"}
2084 if buildcfg.GOOS == "darwin" {
2085 return []string{"-arch", "x86_64", "-m64"}
2087 return []string{"-m64"}
2089 return []string{"-m64"}
2091 return []string{"-marm"}
2093 if buildcfg.GOOS == "darwin" {
2094 return []string{"-arch", "arm64"}
2097 return []string{"-mabi=lp64d"}
2099 return []string{"-mabi=64"}
2101 return []string{"-mabi=32"}
2103 if buildcfg.GOOS == "aix" {
2104 return []string{"-maix64"}
2106 return []string{"-m64"}
2113 var wantHdr = objabi.HeaderString()
2115 // ldobj loads an input object. If it is a host object (an object
2116 // compiled by a non-Go compiler) it returns the Hostobj pointer. If
2117 // it is a Go object, it returns nil.
2118 func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string, file string) *Hostobj {
2119 pkg := objabi.PathToPrefix(lib.Pkg)
2121 eof := f.Offset() + length
2127 f.MustSeek(start, 0)
2129 unit := &sym.CompilationUnit{Lib: lib}
2130 lib.Units = append(lib.Units, unit)
2132 magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
2133 if magic == 0x7f454c46 { // \x7F E L F
2134 ldelf := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2135 textp, flags, err := loadelf.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn, ehdr.Flags)
2137 Errorf(nil, "%v", err)
2141 ctxt.Textp = append(ctxt.Textp, textp...)
2143 return ldhostobj(ldelf, ctxt.HeadType, f, pkg, length, pn, file)
2146 if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
2147 ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2148 textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2150 Errorf(nil, "%v", err)
2153 ctxt.Textp = append(ctxt.Textp, textp...)
2155 return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
2163 ldpe := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2164 textp, rsrc, err := loadpe.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2166 Errorf(nil, "%v", err)
2170 setpersrc(ctxt, rsrc)
2172 ctxt.Textp = append(ctxt.Textp, textp...)
2174 return ldhostobj(ldpe, ctxt.HeadType, f, pkg, length, pn, file)
2177 if c1 == 0x01 && (c2 == 0xD7 || c2 == 0xF7) {
2178 ldxcoff := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2179 textp, err := loadxcoff.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2181 Errorf(nil, "%v", err)
2184 ctxt.Textp = append(ctxt.Textp, textp...)
2186 return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
2189 if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
2190 // An unrecognized object is just passed to the external linker.
2191 // If we try to read symbols from this object, we will
2192 // report an error at that time.
2193 unknownObjFormat = true
2194 return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
2197 /* check the header */
2198 line, err := f.ReadString('\n')
2200 Errorf(nil, "truncated object file: %s: %v", pn, err)
2204 if !strings.HasPrefix(line, "go object ") {
2205 if strings.HasSuffix(pn, ".go") {
2206 Exitf("%s: uncompiled .go source file", pn)
2210 if line == ctxt.Arch.Name {
2211 // old header format: just $GOOS
2212 Errorf(nil, "%s: stale object file", pn)
2216 Errorf(nil, "%s: not an object file: @%d %q", pn, start, line)
2220 // First, check that the basic GOOS, GOARCH, and Version match.
2221 if line != wantHdr {
2222 Errorf(nil, "%s: linked object header mismatch:\nhave %q\nwant %q\n", pn, line, wantHdr)
2225 // Skip over exports and other info -- ends with \n!\n.
2227 // Note: It's possible for "\n!\n" to appear within the binary
2228 // package export data format. To avoid truncating the package
2229 // definition prematurely (issue 21703), we keep track of
2230 // how many "$$" delimiters we've seen.
2232 import0 := f.Offset()
2234 c1 = '\n' // the last line ended in \n
2240 if markers%2 == 0 && c2 == '!' && c3 == '\n' {
2243 if c2 == '$' && c3 == '$' {
2252 Errorf(nil, "truncated object file: %s", pn)
2257 import1 := f.Offset()
2259 f.MustSeek(import0, 0)
2260 ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
2261 f.MustSeek(import1, 0)
2263 fingerprint := ctxt.loader.Preload(ctxt.IncVersion(), f, lib, unit, eof-f.Offset())
2264 if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
2265 // Check fingerprint, to ensure the importing and imported packages
2266 // have consistent view of symbol indices.
2267 // Normally the go command should ensure this. But in case something
2268 // goes wrong, it could lead to obscure bugs like run-time crash.
2269 // Check it here to be sure.
2270 if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
2271 lib.Fingerprint = fingerprint
2273 checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
2276 addImports(ctxt, lib, pn)
2280 // symbolsAreUnresolved scans through the loader's list of unresolved
2281 // symbols and checks to see whether any of them match the names of the
2282 // symbols in 'want'. Return value is a list of bools, with list[K] set
2283 // to true if there is an unresolved reference to the symbol in want[K].
2284 func symbolsAreUnresolved(ctxt *Link, want []string) []bool {
2285 returnAllUndefs := -1
2286 undefs, _ := ctxt.loader.UndefinedRelocTargets(returnAllUndefs)
2287 seen := make(map[loader.Sym]struct{})
2288 rval := make([]bool, len(want))
2289 wantm := make(map[string]int)
2290 for k, w := range want {
2294 for _, s := range undefs {
2295 if _, ok := seen[s]; ok {
2298 seen[s] = struct{}{}
2299 if k, ok := wantm[ctxt.loader.SymName(s)]; ok {
2302 if count == len(want) {
2310 // hostObject reads a single host object file (compare to "hostArchive").
2311 // This is used as part of internal linking when we need to pull in
2312 // files such as "crt?.o".
2313 func hostObject(ctxt *Link, objname string, path string) {
2314 if ctxt.Debugvlog > 1 {
2315 ctxt.Logf("hostObject(%s)\n", path)
2317 objlib := sym.Library{
2320 f, err := bio.Open(path)
2322 Exitf("cannot open host object %q file %s: %v", objname, path, err)
2325 h := ldobj(ctxt, f, &objlib, 0, path, path)
2327 Exitf("unrecognized object file format in %s", path)
2330 h.length = f.MustSeek(0, 2)
2331 f.MustSeek(h.off, 0)
2332 h.ld(ctxt, f, h.pkg, h.length, h.pn)
2333 if *flagCaptureHostObjs != "" {
2338 func checkFingerprint(lib *sym.Library, libfp goobj.FingerprintType, src string, srcfp goobj.FingerprintType) {
2340 Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
2344 func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
2345 data := make([]byte, sym.Size)
2346 sect := f.Sections[sym.Section]
2347 if sect.Type != elf.SHT_PROGBITS && sect.Type != elf.SHT_NOTE {
2348 Errorf(nil, "reading %s from non-data section", sym.Name)
2350 n, err := sect.ReadAt(data, int64(sym.Value-sect.Addr))
2351 if uint64(n) != sym.Size {
2352 Errorf(nil, "reading contents of %s: %v", sym.Name, err)
2357 func readwithpad(r io.Reader, sz int32) ([]byte, error) {
2358 data := make([]byte, Rnd(int64(sz), 4))
2359 _, err := io.ReadFull(r, data)
2367 func readnote(f *elf.File, name []byte, typ int32) ([]byte, error) {
2368 for _, sect := range f.Sections {
2369 if sect.Type != elf.SHT_NOTE {
2374 var namesize, descsize, noteType int32
2375 err := binary.Read(r, f.ByteOrder, &namesize)
2380 return nil, fmt.Errorf("read namesize failed: %v", err)
2382 err = binary.Read(r, f.ByteOrder, &descsize)
2384 return nil, fmt.Errorf("read descsize failed: %v", err)
2386 err = binary.Read(r, f.ByteOrder, ¬eType)
2388 return nil, fmt.Errorf("read type failed: %v", err)
2390 noteName, err := readwithpad(r, namesize)
2392 return nil, fmt.Errorf("read name failed: %v", err)
2394 desc, err := readwithpad(r, descsize)
2396 return nil, fmt.Errorf("read desc failed: %v", err)
2398 if string(name) == string(noteName) && typ == noteType {
2406 func findshlib(ctxt *Link, shlib string) string {
2407 if filepath.IsAbs(shlib) {
2410 for _, libdir := range ctxt.Libdir {
2411 libpath := filepath.Join(libdir, shlib)
2412 if _, err := os.Stat(libpath); err == nil {
2416 Errorf(nil, "cannot find shared library: %s", shlib)
2420 func ldshlibsyms(ctxt *Link, shlib string) {
2422 if filepath.IsAbs(shlib) {
2424 shlib = filepath.Base(shlib)
2426 libpath = findshlib(ctxt, shlib)
2431 for _, processedlib := range ctxt.Shlibs {
2432 if processedlib.Path == libpath {
2436 if ctxt.Debugvlog > 1 {
2437 ctxt.Logf("ldshlibsyms: found library with name %s at %s\n", shlib, libpath)
2440 f, err := elf.Open(libpath)
2442 Errorf(nil, "cannot open shared library: %s", libpath)
2445 // Keep the file open as decodetypeGcprog needs to read from it.
2446 // TODO: fix. Maybe mmap the file.
2449 hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
2451 Errorf(nil, "cannot read ABI hash from shared library %s: %v", libpath, err)
2455 depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
2457 Errorf(nil, "cannot read dep list from shared library %s: %v", libpath, err)
2461 for _, dep := range strings.Split(string(depsbytes), "\n") {
2465 if !filepath.IsAbs(dep) {
2466 // If the dep can be interpreted as a path relative to the shlib
2467 // in which it was found, do that. Otherwise, we will leave it
2468 // to be resolved by libdir lookup.
2469 abs := filepath.Join(filepath.Dir(libpath), dep)
2470 if _, err := os.Stat(abs); err == nil {
2474 deps = append(deps, dep)
2477 syms, err := f.DynamicSymbols()
2479 Errorf(nil, "cannot read symbols from shared library: %s", libpath)
2483 for _, elfsym := range syms {
2484 if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
2488 // Symbols whose names start with "type:" are compiler generated,
2489 // so make functions with that prefix internal.
2491 symname := elfsym.Name // (unmangled) symbol name
2492 if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type:") {
2493 ver = abiInternalVer
2494 } else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC {
2495 // Demangle the ABI name. Keep in sync with symtab.go:mangleABIName.
2496 if strings.HasSuffix(elfsym.Name, ".abiinternal") {
2497 ver = sym.SymVerABIInternal
2498 symname = strings.TrimSuffix(elfsym.Name, ".abiinternal")
2499 } else if strings.HasSuffix(elfsym.Name, ".abi0") {
2501 symname = strings.TrimSuffix(elfsym.Name, ".abi0")
2506 s := l.LookupOrCreateSym(symname, ver)
2508 // Because loadlib above loads all .a files before loading
2509 // any shared libraries, any non-dynimport symbols we find
2510 // that duplicate symbols already loaded should be ignored
2511 // (the symbols from the .a files "win").
2512 if l.SymType(s) != 0 && l.SymType(s) != sym.SDYNIMPORT {
2515 su := l.MakeSymbolUpdater(s)
2516 su.SetType(sym.SDYNIMPORT)
2517 l.SetSymElfType(s, elf.ST_TYPE(elfsym.Info))
2518 su.SetSize(int64(elfsym.Size))
2519 if elfsym.Section != elf.SHN_UNDEF {
2520 // Set .File for the library that actually defines the symbol.
2521 l.SetSymPkg(s, libpath)
2523 // The decodetype_* functions in decodetype.go need access to
2525 sname := l.SymName(s)
2526 if strings.HasPrefix(sname, "type:") && !strings.HasPrefix(sname, "type:.") {
2527 su.SetData(readelfsymboldata(ctxt, f, &elfsym))
2531 if symname != elfsym.Name {
2532 l.SetSymExtname(s, elfsym.Name)
2535 ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f})
2538 func addsection(ldr *loader.Loader, arch *sys.Arch, seg *sym.Segment, name string, rwx int) *sym.Section {
2539 sect := ldr.NewSection()
2540 sect.Rwx = uint8(rwx)
2543 sect.Align = int32(arch.PtrSize) // everything is at least pointer-aligned
2544 seg.Sections = append(seg.Sections, sect)
2549 fmt.Fprintf(os.Stderr, "usage: link [options] main.o\n")
2550 objabi.Flagprint(os.Stderr)
2554 type SymbolType int8 // TODO: after genasmsym is gone, maybe rename to plan9typeChar or something
2557 // see also https://9p.io/magic/man2html/1/nm
2558 TextSym SymbolType = 'T'
2559 DataSym SymbolType = 'D'
2560 BSSSym SymbolType = 'B'
2561 UndefinedSym SymbolType = 'U'
2562 TLSSym SymbolType = 't'
2563 FrameSym SymbolType = 'm'
2564 ParamSym SymbolType = 'p'
2565 AutoSym SymbolType = 'a'
2567 // Deleted auto (not a real sym, just placeholder for type)
2568 DeletedAutoSym = 'x'
2571 // defineInternal defines a symbol used internally by the go runtime.
2572 func (ctxt *Link) defineInternal(p string, t sym.SymKind) loader.Sym {
2573 s := ctxt.loader.CreateSymForUpdate(p, 0)
2580 func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) loader.Sym {
2581 s := ctxt.defineInternal(p, t)
2582 ctxt.loader.SetSymValue(s, v)
2586 func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
2587 if uint64(addr) >= Segdata.Vaddr {
2588 return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
2590 if uint64(addr) >= Segtext.Vaddr {
2591 return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
2593 ldr.Errorf(s, "invalid datoff %#x", addr)
2597 func Entryvalue(ctxt *Link) int64 {
2598 a := *flagEntrySymbol
2599 if a[0] >= '0' && a[0] <= '9' {
2603 s := ldr.Lookup(a, 0)
2605 Errorf(nil, "missing entry symbol %q", a)
2608 st := ldr.SymType(s)
2610 return *FlagTextAddr
2612 if !ctxt.IsAIX() && st != sym.STEXT {
2613 ldr.Errorf(s, "entry not text")
2615 return ldr.SymValue(s)
2618 func (ctxt *Link) callgraph() {
2624 for _, s := range ctxt.Textp {
2625 relocs := ldr.Relocs(s)
2626 for i := 0; i < relocs.Count(); i++ {
2632 if r.Type().IsDirectCall() && ldr.SymType(rs) == sym.STEXT {
2633 ctxt.Logf("%s calls %s\n", ldr.SymName(s), ldr.SymName(rs))
2639 func Rnd(v int64, r int64) int64 {
2652 func bgetc(r *bio.Reader) int {
2653 c, err := r.ReadByte()
2656 log.Fatalf("reading input: %v", err)
2663 type markKind uint8 // for postorder traversal
2670 func postorder(libs []*sym.Library) []*sym.Library {
2671 order := make([]*sym.Library, 0, len(libs)) // hold the result
2672 mark := make(map[*sym.Library]markKind, len(libs))
2673 for _, lib := range libs {
2674 dfs(lib, mark, &order)
2679 func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library) {
2680 if mark[lib] == visited {
2683 if mark[lib] == visiting {
2684 panic("found import cycle while visiting " + lib.Pkg)
2686 mark[lib] = visiting
2687 for _, i := range lib.Imports {
2691 *order = append(*order, lib)
2694 func ElfSymForReloc(ctxt *Link, s loader.Sym) int32 {
2695 // If putelfsym created a local version of this symbol, use that in all
2697 les := ctxt.loader.SymLocalElfSym(s)
2701 return ctxt.loader.SymElfSym(s)
2705 func AddGotSym(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, elfRelocTyp uint32) {
2706 if ldr.SymGot(s) >= 0 {
2710 Adddynsym(ldr, target, syms, s)
2711 got := ldr.MakeSymbolUpdater(syms.GOT)
2712 ldr.SetGot(s, int32(got.Size()))
2713 got.AddUint(target.Arch, 0)
2716 if target.Arch.PtrSize == 8 {
2717 rela := ldr.MakeSymbolUpdater(syms.Rela)
2718 rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2719 rela.AddUint64(target.Arch, elf.R_INFO(uint32(ldr.SymDynid(s)), elfRelocTyp))
2720 rela.AddUint64(target.Arch, 0)
2722 rel := ldr.MakeSymbolUpdater(syms.Rel)
2723 rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2724 rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), elfRelocTyp))
2726 } else if target.IsDarwin() {
2727 leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT)
2728 leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
2729 if target.IsPIE() && target.IsInternal() {
2730 // Mach-O relocations are a royal pain to lay out.
2731 // They use a compact stateful bytecode representation.
2732 // Here we record what are needed and encode them later.
2733 MachoAddBind(int64(ldr.SymGot(s)), s)
2736 ldr.Errorf(s, "addgotsym: unsupported binary format")
2740 var hostobjcounter int
2742 // captureHostObj writes out the content of a host object (pulled from
2743 // an archive or loaded from a *.o file directly) to a directory
2744 // specified via the linker's "-capturehostobjs" debugging flag. This
2745 // is intended to make it easier for a developer to inspect the actual
2746 // object feeding into "CGO internal" link step.
2747 func captureHostObj(h *Hostobj) {
2748 // Form paths for info file and obj file.
2749 ofile := fmt.Sprintf("captured-obj-%d.o", hostobjcounter)
2750 ifile := fmt.Sprintf("captured-obj-%d.txt", hostobjcounter)
2752 opath := filepath.Join(*flagCaptureHostObjs, ofile)
2753 ipath := filepath.Join(*flagCaptureHostObjs, ifile)
2755 // Write the info file.
2756 info := fmt.Sprintf("pkg: %s\npn: %s\nfile: %s\noff: %d\nlen: %d\n",
2757 h.pkg, h.pn, h.file, h.off, h.length)
2758 if err := os.WriteFile(ipath, []byte(info), 0666); err != nil {
2759 log.Fatalf("error writing captured host obj info %s: %v", ipath, err)
2762 readObjData := func() []byte {
2763 inf, err := os.Open(h.file)
2765 log.Fatalf("capturing host obj: open failed on %s: %v", h.pn, err)
2767 res := make([]byte, h.length)
2768 if n, err := inf.ReadAt(res, h.off); err != nil || n != int(h.length) {
2769 log.Fatalf("capturing host obj: readat failed on %s: %v", h.pn, err)
2774 // Write the object file.
2775 if err := os.WriteFile(opath, readObjData(), 0666); err != nil {
2776 log.Fatalf("error writing captured host object %s: %v", opath, err)
2779 fmt.Fprintf(os.Stderr, "link: info: captured host object %s to %s\n",