1 // Inferno utils/8l/asm.c
2 // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/8l/asm.c
4 // Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
5 // Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
6 // Portions Copyright © 1997-1999 Vita Nuova Limited
7 // Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
8 // Portions Copyright © 2004,2006 Bruce Ellis
9 // Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
10 // Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
11 // Portions Copyright © 2009 The Go Authors. All rights reserved.
13 // Permission is hereby granted, free of charge, to any person obtaining a copy
14 // of this software and associated documentation files (the "Software"), to deal
15 // in the Software without restriction, including without limitation the rights
16 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
17 // copies of the Software, and to permit persons to whom the Software is
18 // furnished to do so, subject to the following conditions:
20 // The above copyright notice and this permission notice shall be included in
21 // all copies or substantial portions of the Software.
23 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
24 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
25 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
26 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
27 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
28 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
52 "cmd/internal/notsha256"
55 "cmd/link/internal/loadelf"
56 "cmd/link/internal/loader"
57 "cmd/link/internal/loadmacho"
58 "cmd/link/internal/loadpe"
59 "cmd/link/internal/loadxcoff"
60 "cmd/link/internal/sym"
63 // Data layout and relocation.
65 // Derived from Inferno utils/6l/l.h
66 // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6l/l.h
68 // Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
69 // Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
70 // Portions Copyright © 1997-1999 Vita Nuova Limited
71 // Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
72 // Portions Copyright © 2004,2006 Bruce Ellis
73 // Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
74 // Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
75 // Portions Copyright © 2009 The Go Authors. All rights reserved.
77 // Permission is hereby granted, free of charge, to any person obtaining a copy
78 // of this software and associated documentation files (the "Software"), to deal
79 // in the Software without restriction, including without limitation the rights
80 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
81 // copies of the Software, and to permit persons to whom the Software is
82 // furnished to do so, subject to the following conditions:
84 // The above copyright notice and this permission notice shall be included in
85 // all copies or substantial portions of the Software.
87 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
88 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
89 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
90 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
91 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
92 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
95 // ArchSyms holds a number of architecture specific symbols used during
96 // relocation. Rather than allowing them universal access to all symbols,
97 // we keep a subset for relocation application.
98 type ArchSyms struct {
104 LinkEditGOT loader.Sym
105 LinkEditPLT loader.Sym
108 DotTOC []loader.Sym // for each version
121 unreachableMethod loader.Sym
124 // mkArchSym is a helper for setArchSyms, to set up a special symbol.
125 func (ctxt *Link) mkArchSym(name string, ver int, ls *loader.Sym) {
126 *ls = ctxt.loader.LookupOrCreateSym(name, ver)
127 ctxt.loader.SetAttrReachable(*ls, true)
130 // mkArchVecSym is similar to setArchSyms, but operates on elements within
131 // a slice, where each element corresponds to some symbol version.
132 func (ctxt *Link) mkArchSymVec(name string, ver int, ls []loader.Sym) {
133 ls[ver] = ctxt.loader.LookupOrCreateSym(name, ver)
134 ctxt.loader.SetAttrReachable(ls[ver], true)
137 // setArchSyms sets up the ArchSyms structure, and must be called before
138 // relocations are applied.
139 func (ctxt *Link) setArchSyms() {
140 ctxt.mkArchSym(".got", 0, &ctxt.GOT)
141 ctxt.mkArchSym(".plt", 0, &ctxt.PLT)
142 ctxt.mkArchSym(".got.plt", 0, &ctxt.GOTPLT)
143 ctxt.mkArchSym(".dynamic", 0, &ctxt.Dynamic)
144 ctxt.mkArchSym(".dynsym", 0, &ctxt.DynSym)
145 ctxt.mkArchSym(".dynstr", 0, &ctxt.DynStr)
146 ctxt.mkArchSym("runtime.unreachableMethod", abiInternalVer, &ctxt.unreachableMethod)
149 ctxt.mkArchSym("TOC", 0, &ctxt.TOC)
151 ctxt.DotTOC = make([]loader.Sym, ctxt.MaxVersion()+1)
152 for i := 0; i <= ctxt.MaxVersion(); i++ {
153 if i >= sym.SymVerABICount && i < sym.SymVerStatic { // these versions are not used currently
156 ctxt.mkArchSymVec(".TOC.", i, ctxt.DotTOC)
160 ctxt.mkArchSym(".rel", 0, &ctxt.Rel)
161 ctxt.mkArchSym(".rela", 0, &ctxt.Rela)
162 ctxt.mkArchSym(".rel.plt", 0, &ctxt.RelPLT)
163 ctxt.mkArchSym(".rela.plt", 0, &ctxt.RelaPLT)
166 ctxt.mkArchSym(".linkedit.got", 0, &ctxt.LinkEditGOT)
167 ctxt.mkArchSym(".linkedit.plt", 0, &ctxt.LinkEditPLT)
178 // Threshold of total text size, used for trampoline insertion. If the total
179 // text size is smaller than TrampLimit, we won't need to insert trampolines.
180 // It is pretty close to the offset range of a direct CALL machine instruction.
181 // We leave some room for extra stuff like PLT stubs.
186 LinuxdynldMusl string
190 Dragonflydynld string
193 // Empty spaces between codeblocks will be padded with this value.
194 // For example an architecture might want to pad with a trap instruction to
195 // catch wayward programs. Architectures that do not define a padding value
196 // are padded with zeros.
203 Adddynrel func(*Target, *loader.Loader, *ArchSyms, loader.Sym, loader.Reloc, int) bool
205 // Archreloc is an arch-specific hook that assists in relocation processing
206 // (invoked by 'relocsym'); it handles target-specific relocation tasks.
207 // Here "rel" is the current relocation being examined, "sym" is the symbol
208 // containing the chunk of data to which the relocation applies, and "off"
209 // is the contents of the to-be-relocated data item (from sym.P). Return
210 // value is the appropriately relocated value (to be written back to the
211 // same spot in sym.P), number of external _host_ relocations needed (i.e.
212 // ELF/Mach-O/etc. relocations, not Go relocations, this must match Elfreloc1,
213 // etc.), and a boolean indicating success/failure (a failing value indicates
215 Archreloc func(*Target, *loader.Loader, *ArchSyms, loader.Reloc, loader.Sym,
216 int64) (relocatedOffset int64, nExtReloc int, ok bool)
217 // Archrelocvariant is a second arch-specific hook used for
218 // relocation processing; it handles relocations where r.Type is
219 // insufficient to describe the relocation (r.Variant !=
220 // sym.RV_NONE). Here "rel" is the relocation being applied, "sym"
221 // is the symbol containing the chunk of data to which the
222 // relocation applies, and "off" is the contents of the
223 // to-be-relocated data item (from sym.P). Return is an updated
225 Archrelocvariant func(target *Target, ldr *loader.Loader, rel loader.Reloc,
226 rv sym.RelocVariant, sym loader.Sym, offset int64, data []byte) (relocatedOffset int64)
228 // Generate a trampoline for a call from s to rs if necessary. ri is
229 // index of the relocation.
230 Trampoline func(ctxt *Link, ldr *loader.Loader, ri int, rs, s loader.Sym)
232 // Assembling the binary breaks into two phases, writing the code/data/
233 // dwarf information (which is rather generic), and some more architecture
234 // specific work like setting up the elf headers/dynamic relocations, etc.
235 // The phases are called "Asmb" and "Asmb2". Asmb2 needs to be defined for
236 // every architecture, but only if architecture has an Asmb function will
237 // it be used for assembly. Otherwise a generic assembly Asmb function is
239 Asmb func(*Link, *loader.Loader)
240 Asmb2 func(*Link, *loader.Loader)
242 // Extreloc is an arch-specific hook that converts a Go relocation to an
243 // external relocation. Return the external relocation and whether it is
245 Extreloc func(*Target, *loader.Loader, loader.Reloc, loader.Sym) (loader.ExtReloc, bool)
247 Elfreloc1 func(*Link, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int, int64) bool
248 ElfrelocSize uint32 // size of an ELF relocation record, must match Elfreloc1.
249 Elfsetupplt func(ctxt *Link, plt, gotplt *loader.SymbolBuilder, dynamic loader.Sym)
250 Gentext func(*Link, *loader.Loader) // Generate text before addressing has been performed.
251 Machoreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
252 MachorelocSize uint32 // size of an Mach-O relocation record, must match Machoreloc1.
253 PEreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
254 Xcoffreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
256 // Generate additional symbols for the native symbol table just prior to
258 GenSymsLate func(*Link, *loader.Loader)
260 // TLSIEtoLE converts a TLS Initial Executable relocation to
261 // a TLS Local Executable relocation.
263 // This is possible when a TLS IE relocation refers to a local
264 // symbol in an executable, which is typical when internally
265 // linking PIE binaries.
266 TLSIEtoLE func(P []byte, off, size int)
268 // optional override for assignAddress
269 AssignAddress func(ldr *loader.Loader, sect *sym.Section, n int, s loader.Sym, va uint64, isTramp bool) (*sym.Section, int, uint64)
281 MINFUNC = 16 // minimum size for a function
284 // Symbol version of ABIInternal symbols. It is sym.SymVerABIInternal if ABI wrappers
285 // are used, 0 otherwise.
286 var abiInternalVer = sym.SymVerABIInternal
288 // DynlinkingGo reports whether we are producing Go code that can live
289 // in separate shared libraries linked together at runtime.
290 func (ctxt *Link) DynlinkingGo() bool {
292 panic("DynlinkingGo called before all symbols loaded")
294 return ctxt.BuildMode == BuildModeShared || ctxt.linkShared || ctxt.BuildMode == BuildModePlugin || ctxt.canUsePlugins
297 // CanUsePlugins reports whether a plugins can be used
298 func (ctxt *Link) CanUsePlugins() bool {
300 panic("CanUsePlugins called before all symbols loaded")
302 return ctxt.canUsePlugins
305 // NeedCodeSign reports whether we need to code-sign the output binary.
306 func (ctxt *Link) NeedCodeSign() bool {
307 return ctxt.IsDarwin() && ctxt.IsARM64()
319 debug_s bool // backup old value of debug['s']
323 liveness int64 // size of liveness data (funcdata), printed if -v
325 // See -strictdups command line flag.
326 checkStrictDups int // 0=off 1=warning 2=error
327 strictDupMsgCount int
332 Segrodata sym.Segment
333 Segrelrodata sym.Segment
337 Segments = []*sym.Segment{&Segtext, &Segrodata, &Segrelrodata, &Segdata, &Segdwarf}
340 const pkgdef = "__.PKGDEF"
343 // externalobj is set to true if we see an object compiled by
344 // the host compiler that is not from a package that is known
345 // to support internal linking mode.
348 // dynimportfail is a list of packages for which generating
349 // the dynimport file, _cgo_import.go, failed. If there are
350 // any of these objects, we must link externally. Issue 52863.
351 dynimportfail []string
353 // unknownObjFormat is set to true if we see an object whose
354 // format we don't recognize.
355 unknownObjFormat = false
360 func Lflag(ctxt *Link, arg string) {
361 ctxt.Libdir = append(ctxt.Libdir, arg)
365 * Unix doesn't like it when we write to a running (or, sometimes,
366 * recently run) binary, so remove the output file before writing it.
367 * On Windows 7, remove() can force a subsequent create() to fail.
368 * S_ISREG() does not exist on Plan 9.
370 func mayberemoveoutfile() {
371 if fi, err := os.Lstat(*flagOutfile); err == nil && !fi.Mode().IsRegular() {
374 os.Remove(*flagOutfile)
377 func libinit(ctxt *Link) {
378 Funcalign = thearch.Funcalign
380 // add goroot to the end of the libdir list.
384 if *flagInstallSuffix != "" {
386 suffix = *flagInstallSuffix
387 } else if *flagRace {
390 } else if *flagMsan {
393 } else if *flagAsan {
398 if buildcfg.GOROOT != "" {
399 Lflag(ctxt, filepath.Join(buildcfg.GOROOT, "pkg", fmt.Sprintf("%s_%s%s%s", buildcfg.GOOS, buildcfg.GOARCH, suffixsep, suffix)))
404 if err := ctxt.Out.Open(*flagOutfile); err != nil {
405 Exitf("cannot create %s: %v", *flagOutfile, err)
408 if *flagEntrySymbol == "" {
409 switch ctxt.BuildMode {
410 case BuildModeCShared, BuildModeCArchive:
411 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s_lib", buildcfg.GOARCH, buildcfg.GOOS)
412 case BuildModeExe, BuildModePIE:
413 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s", buildcfg.GOARCH, buildcfg.GOOS)
414 case BuildModeShared, BuildModePlugin:
415 // No *flagEntrySymbol for -buildmode=shared and plugin
417 Errorf(nil, "unknown *flagEntrySymbol for buildmode %v", ctxt.BuildMode)
422 func exitIfErrors() {
423 if nerrors != 0 || checkStrictDups > 1 && strictDupMsgCount > 0 {
435 func loadinternal(ctxt *Link, name string) *sym.Library {
436 zerofp := goobj.FingerprintType{}
437 if ctxt.linkShared && ctxt.PackageShlib != nil {
438 if shlib := ctxt.PackageShlib[name]; shlib != "" {
439 return addlibpath(ctxt, "internal", "internal", "", name, shlib, zerofp)
442 if ctxt.PackageFile != nil {
443 if pname := ctxt.PackageFile[name]; pname != "" {
444 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
446 ctxt.Logf("loadinternal: cannot find %s\n", name)
450 for _, libdir := range ctxt.Libdir {
452 shlibname := filepath.Join(libdir, name+".shlibname")
453 if ctxt.Debugvlog != 0 {
454 ctxt.Logf("searching for %s.a in %s\n", name, shlibname)
456 if _, err := os.Stat(shlibname); err == nil {
457 return addlibpath(ctxt, "internal", "internal", "", name, shlibname, zerofp)
460 pname := filepath.Join(libdir, name+".a")
461 if ctxt.Debugvlog != 0 {
462 ctxt.Logf("searching for %s.a in %s\n", name, pname)
464 if _, err := os.Stat(pname); err == nil {
465 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
469 if name == "runtime" {
470 Exitf("error: unable to find runtime.a")
472 ctxt.Logf("warning: unable to find %s.a\n", name)
476 // extld returns the current external linker.
477 func (ctxt *Link) extld() []string {
478 if len(flagExtld) == 0 {
479 // Return the default external linker for the platform.
480 // This only matters when link tool is called directly without explicit -extld,
481 // go tool already passes the correct linker in other cases.
482 switch buildcfg.GOOS {
483 case "darwin", "freebsd", "openbsd":
484 flagExtld = []string{"clang"}
486 flagExtld = []string{"gcc"}
492 // findLibPathCmd uses cmd command to find gcc library libname.
493 // It returns library full path if found, or "none" if not found.
494 func (ctxt *Link) findLibPathCmd(cmd, libname string) string {
495 extld := ctxt.extld()
496 name, args := extld[0], extld[1:]
497 args = append(args, hostlinkArchArgs(ctxt.Arch)...)
498 args = append(args, cmd)
499 if ctxt.Debugvlog != 0 {
500 ctxt.Logf("%s %v\n", extld, args)
502 out, err := exec.Command(name, args...).Output()
504 if ctxt.Debugvlog != 0 {
505 ctxt.Logf("not using a %s file because compiler failed\n%v\n%s\n", libname, err, out)
509 return strings.TrimSpace(string(out))
512 // findLibPath searches for library libname.
513 // It returns library full path if found, or "none" if not found.
514 func (ctxt *Link) findLibPath(libname string) string {
515 return ctxt.findLibPathCmd("--print-file-name="+libname, libname)
518 func (ctxt *Link) loadlib() {
520 switch *FlagStrictDups {
524 flags |= loader.FlagStrictDups
526 log.Fatalf("invalid -strictdups flag value %d", *FlagStrictDups)
528 elfsetstring1 := func(str string, off int) { elfsetstring(ctxt, 0, str, off) }
529 ctxt.loader = loader.NewLoader(flags, elfsetstring1, &ctxt.ErrorReporter.ErrorReporter)
530 ctxt.ErrorReporter.SymName = func(s loader.Sym) string {
531 return ctxt.loader.SymName(s)
534 // ctxt.Library grows during the loop, so not a range loop.
536 for ; i < len(ctxt.Library); i++ {
537 lib := ctxt.Library[i]
539 if ctxt.Debugvlog > 1 {
540 ctxt.Logf("autolib: %s (from %s)\n", lib.File, lib.Objref)
542 loadobjfile(ctxt, lib)
546 // load internal packages, if not already
548 loadinternal(ctxt, "runtime/race")
551 loadinternal(ctxt, "runtime/msan")
554 loadinternal(ctxt, "runtime/asan")
556 loadinternal(ctxt, "runtime")
557 for ; i < len(ctxt.Library); i++ {
558 lib := ctxt.Library[i]
560 loadobjfile(ctxt, lib)
563 // At this point, the Go objects are "preloaded". Not all the symbols are
564 // added to the symbol table (only defined package symbols are). Looking
565 // up symbol by name may not get expected result.
567 iscgo = ctxt.LibraryByPkg["runtime/cgo"] != nil
569 // Plugins a require cgo support to function. Similarly, plugins may require additional
570 // internal linker support on some platforms which may not be implemented.
571 ctxt.canUsePlugins = ctxt.LibraryByPkg["plugin"] != nil && iscgo
573 // We now have enough information to determine the link mode.
574 determineLinkMode(ctxt)
576 if ctxt.LinkMode == LinkExternal && !iscgo && !(buildcfg.GOOS == "darwin" && ctxt.BuildMode != BuildModePlugin && ctxt.Arch.Family == sys.AMD64) {
577 // This indicates a user requested -linkmode=external.
578 // The startup code uses an import of runtime/cgo to decide
579 // whether to initialize the TLS. So give it one. This could
580 // be handled differently but it's an unusual case.
581 if lib := loadinternal(ctxt, "runtime/cgo"); lib != nil && lib.Shlib == "" {
582 if ctxt.BuildMode == BuildModeShared || ctxt.linkShared {
583 Exitf("cannot implicitly include runtime/cgo in a shared library")
585 for ; i < len(ctxt.Library); i++ {
586 lib := ctxt.Library[i]
588 loadobjfile(ctxt, lib)
594 // Add non-package symbols and references of externally defined symbols.
595 ctxt.loader.LoadSyms(ctxt.Arch)
597 // Load symbols from shared libraries, after all Go object symbols are loaded.
598 for _, lib := range ctxt.Library {
600 if ctxt.Debugvlog > 1 {
601 ctxt.Logf("autolib: %s (from %s)\n", lib.Shlib, lib.Objref)
603 ldshlibsyms(ctxt, lib.Shlib)
607 // Process cgo directives (has to be done before host object loading).
608 ctxt.loadcgodirectives()
610 // Conditionally load host objects, or setup for external linking.
614 if ctxt.LinkMode == LinkInternal && len(hostobj) != 0 {
615 // If we have any undefined symbols in external
616 // objects, try to read them from the libgcc file.
618 undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
621 if ctxt.Debugvlog > 1 {
622 ctxt.Logf("loadlib: first unresolved is %s [%d] from %s [%d]\n",
623 ctxt.loader.SymName(undefs[0]), undefs[0],
624 ctxt.loader.SymName(froms[0]), froms[0])
628 if *flagLibGCC == "" {
629 *flagLibGCC = ctxt.findLibPathCmd("--print-libgcc-file-name", "libgcc")
631 if runtime.GOOS == "openbsd" && *flagLibGCC == "libgcc.a" {
632 // On OpenBSD `clang --print-libgcc-file-name` returns "libgcc.a".
633 // In this case we fail to load libgcc.a and can encounter link
634 // errors - see if we can find libcompiler_rt.a instead.
635 *flagLibGCC = ctxt.findLibPathCmd("--print-file-name=libcompiler_rt.a", "libcompiler_rt")
637 if ctxt.HeadType == objabi.Hwindows {
638 loadWindowsHostArchives(ctxt)
640 if *flagLibGCC != "none" {
641 hostArchive(ctxt, *flagLibGCC)
646 // We've loaded all the code now.
649 strictDupMsgCount = ctxt.loader.NStrictDupMsgs()
652 // loadWindowsHostArchives loads in host archives and objects when
653 // doing internal linking on windows. Older toolchains seem to require
654 // just a single pass through the various archives, but some modern
655 // toolchains when linking a C program with mingw pass library paths
656 // multiple times to the linker, e.g. "... -lmingwex -lmingw32 ...
657 // -lmingwex -lmingw32 ...". To accommodate this behavior, we make two
658 // passes over the host archives below.
659 func loadWindowsHostArchives(ctxt *Link) {
661 for i := 0; any && i < 2; i++ {
662 // Link crt2.o (if present) to resolve "atexit" when
663 // using LLVM-based compilers.
664 isunresolved := symbolsAreUnresolved(ctxt, []string{"atexit"})
666 if p := ctxt.findLibPath("crt2.o"); p != "none" {
667 hostObject(ctxt, "crt2", p)
671 if p := ctxt.findLibPath("libsynchronization.a"); p != "none" {
675 if p := ctxt.findLibPath("libmingwex.a"); p != "none" {
678 if p := ctxt.findLibPath("libmingw32.a"); p != "none" {
681 // Link libmsvcrt.a to resolve '__acrt_iob_func' symbol
682 // (see https://golang.org/issue/23649 for details).
683 if p := ctxt.findLibPath("libmsvcrt.a"); p != "none" {
687 undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
690 if ctxt.Debugvlog > 1 {
691 ctxt.Logf("loadWindowsHostArchives: remaining unresolved is %s [%d] from %s [%d]\n",
692 ctxt.loader.SymName(undefs[0]), undefs[0],
693 ctxt.loader.SymName(froms[0]), froms[0])
697 // If needed, create the __CTOR_LIST__ and __DTOR_LIST__
698 // symbols (referenced by some of the mingw support library
699 // routines). Creation of these symbols is normally done by the
700 // linker if not already present.
701 want := []string{"__CTOR_LIST__", "__DTOR_LIST__"}
702 isunresolved := symbolsAreUnresolved(ctxt, want)
703 for k, w := range want {
705 sb := ctxt.loader.CreateSymForUpdate(w, 0)
706 sb.SetType(sym.SDATA)
707 sb.AddUint64(ctxt.Arch, 0)
708 sb.SetReachable(true)
709 ctxt.loader.SetAttrSpecial(sb.Sym(), true)
713 // Fix up references to DLL import symbols now that we're done
714 // pulling in new objects.
715 if err := loadpe.PostProcessImports(); err != nil {
716 Errorf(nil, "%v", err)
719 // TODO: maybe do something similar to peimporteddlls to collect
720 // all lib names and try link them all to final exe just like
721 // libmingwex.a and libmingw32.a:
724 #cgo windows LDFLAGS: -lmsvcrt -lm
730 // loadcgodirectives reads the previously discovered cgo directives, creating
731 // symbols in preparation for host object loading or use later in the link.
732 func (ctxt *Link) loadcgodirectives() {
734 hostObjSyms := make(map[loader.Sym]struct{})
735 for _, d := range ctxt.cgodata {
736 setCgoAttr(ctxt, d.file, d.pkg, d.directives, hostObjSyms)
740 if ctxt.LinkMode == LinkInternal {
741 // Drop all the cgo_import_static declarations.
742 // Turns out we won't be needing them.
743 for symIdx := range hostObjSyms {
744 if l.SymType(symIdx) == sym.SHOSTOBJ {
745 // If a symbol was marked both
746 // cgo_import_static and cgo_import_dynamic,
747 // then we want to make it cgo_import_dynamic
749 su := l.MakeSymbolUpdater(symIdx)
750 if l.SymExtname(symIdx) != "" && l.SymDynimplib(symIdx) != "" && !(l.AttrCgoExportStatic(symIdx) || l.AttrCgoExportDynamic(symIdx)) {
751 su.SetType(sym.SDYNIMPORT)
760 // Set up flags and special symbols depending on the platform build mode.
761 // This version works with loader.Loader.
762 func (ctxt *Link) linksetup() {
763 switch ctxt.BuildMode {
764 case BuildModeCShared, BuildModePlugin:
765 symIdx := ctxt.loader.LookupOrCreateSym("runtime.islibrary", 0)
766 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
767 sb.SetType(sym.SNOPTRDATA)
769 case BuildModeCArchive:
770 symIdx := ctxt.loader.LookupOrCreateSym("runtime.isarchive", 0)
771 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
772 sb.SetType(sym.SNOPTRDATA)
776 // Recalculate pe parameters now that we have ctxt.LinkMode set.
777 if ctxt.HeadType == objabi.Hwindows {
781 if ctxt.LinkMode == LinkExternal {
782 // When external linking, we are creating an object file. The
783 // absolute address is irrelevant.
787 // If there are no dynamic libraries needed, gcc disables dynamic linking.
788 // Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13)
789 // assumes that a dynamic binary always refers to at least one dynamic library.
790 // Rather than be a source of test cases for glibc, disable dynamic linking
791 // the same way that gcc would.
793 // Exception: on OS X, programs such as Shark only work with dynamic
794 // binaries, so leave it enabled on OS X (Mach-O) binaries.
795 // Also leave it enabled on Solaris which doesn't support
796 // statically linked binaries.
797 if ctxt.BuildMode == BuildModeExe {
798 if havedynamic == 0 && ctxt.HeadType != objabi.Hdarwin && ctxt.HeadType != objabi.Hsolaris {
803 if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && buildcfg.GOOS != "aix" {
804 toc := ctxt.loader.LookupOrCreateSym(".TOC.", 0)
805 sb := ctxt.loader.MakeSymbolUpdater(toc)
806 sb.SetType(sym.SDYNIMPORT)
809 // The Android Q linker started to complain about underalignment of the our TLS
810 // section. We don't actually use the section on android, so don't
812 if buildcfg.GOOS != "android" {
813 tlsg := ctxt.loader.LookupOrCreateSym("runtime.tlsg", 0)
814 sb := ctxt.loader.MakeSymbolUpdater(tlsg)
816 // runtime.tlsg is used for external linking on platforms that do not define
817 // a variable to hold g in assembly (currently only intel).
819 sb.SetType(sym.STLSBSS)
820 sb.SetSize(int64(ctxt.Arch.PtrSize))
821 } else if sb.Type() != sym.SDYNIMPORT {
822 Errorf(nil, "runtime declared tlsg variable %v", sb.Type())
824 ctxt.loader.SetAttrReachable(tlsg, true)
828 var moduledata loader.Sym
829 var mdsb *loader.SymbolBuilder
830 if ctxt.BuildMode == BuildModePlugin {
831 moduledata = ctxt.loader.LookupOrCreateSym("local.pluginmoduledata", 0)
832 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
833 ctxt.loader.SetAttrLocal(moduledata, true)
835 moduledata = ctxt.loader.LookupOrCreateSym("runtime.firstmoduledata", 0)
836 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
838 if mdsb.Type() != 0 && mdsb.Type() != sym.SDYNIMPORT {
839 // If the module (toolchain-speak for "executable or shared
840 // library") we are linking contains the runtime package, it
841 // will define the runtime.firstmoduledata symbol and we
842 // truncate it back to 0 bytes so we can define its entire
843 // contents in symtab.go:symtab().
846 // In addition, on ARM, the runtime depends on the linker
847 // recording the value of GOARM.
848 if ctxt.Arch.Family == sys.ARM {
849 goarm := ctxt.loader.LookupOrCreateSym("runtime.goarm", 0)
850 sb := ctxt.loader.MakeSymbolUpdater(goarm)
851 sb.SetType(sym.SDATA)
853 sb.AddUint8(uint8(buildcfg.GOARM))
856 // Set runtime.disableMemoryProfiling bool if
857 // runtime.MemProfile is not retained in the binary after
858 // deadcode (and we're not dynamically linking).
859 memProfile := ctxt.loader.Lookup("runtime.MemProfile", abiInternalVer)
860 if memProfile != 0 && !ctxt.loader.AttrReachable(memProfile) && !ctxt.DynlinkingGo() {
861 memProfSym := ctxt.loader.LookupOrCreateSym("runtime.disableMemoryProfiling", 0)
862 sb := ctxt.loader.MakeSymbolUpdater(memProfSym)
863 sb.SetType(sym.SDATA)
865 sb.AddUint8(1) // true bool
868 // If OTOH the module does not contain the runtime package,
869 // create a local symbol for the moduledata.
870 moduledata = ctxt.loader.LookupOrCreateSym("local.moduledata", 0)
871 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
872 ctxt.loader.SetAttrLocal(moduledata, true)
874 // In all cases way we mark the moduledata as noptrdata to hide it from
876 mdsb.SetType(sym.SNOPTRDATA)
877 ctxt.loader.SetAttrReachable(moduledata, true)
878 ctxt.Moduledata = moduledata
880 if ctxt.Arch == sys.Arch386 && ctxt.HeadType != objabi.Hwindows {
881 if (ctxt.BuildMode == BuildModeCArchive && ctxt.IsELF) || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE || ctxt.DynlinkingGo() {
882 got := ctxt.loader.LookupOrCreateSym("_GLOBAL_OFFSET_TABLE_", 0)
883 sb := ctxt.loader.MakeSymbolUpdater(got)
884 sb.SetType(sym.SDYNIMPORT)
885 ctxt.loader.SetAttrReachable(got, true)
889 // DWARF-gen and other phases require that the unit Textp slices
890 // be populated, so that it can walk the functions in each unit.
891 // Call into the loader to do this (requires that we collect the
892 // set of internal libraries first). NB: might be simpler if we
893 // moved isRuntimeDepPkg to cmd/internal and then did the test in
894 // loader.AssignTextSymbolOrder.
895 ctxt.Library = postorder(ctxt.Library)
897 for _, lib := range ctxt.Library {
898 intlibs = append(intlibs, isRuntimeDepPkg(lib.Pkg))
900 ctxt.Textp = ctxt.loader.AssignTextSymbolOrder(ctxt.Library, intlibs, ctxt.Textp)
903 // mangleTypeSym shortens the names of symbols that represent Go types
904 // if they are visible in the symbol table.
906 // As the names of these symbols are derived from the string of
907 // the type, they can run to many kilobytes long. So we shorten
908 // them using a SHA-1 when the name appears in the final binary.
909 // This also removes characters that upset external linkers.
911 // These are the symbols that begin with the prefix 'type.' and
912 // contain run-time type information used by the runtime and reflect
913 // packages. All Go binaries contain these symbols, but only
914 // those programs loaded dynamically in multiple parts need these
915 // symbols to have entries in the symbol table.
916 func (ctxt *Link) mangleTypeSym() {
917 if ctxt.BuildMode != BuildModeShared && !ctxt.linkShared && ctxt.BuildMode != BuildModePlugin && !ctxt.CanUsePlugins() {
922 for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
923 if !ldr.AttrReachable(s) && !ctxt.linkShared {
924 // If -linkshared, the GCProg generation code may need to reach
925 // out to the shared library for the type descriptor's data, even
926 // the type descriptor itself is not actually needed at run time
927 // (therefore not reachable). We still need to mangle its name,
928 // so it is consistent with the one stored in the shared library.
931 name := ldr.SymName(s)
932 newName := typeSymbolMangle(name)
934 ldr.SetSymExtname(s, newName)
936 // When linking against a shared library, the Go object file may
937 // have reference to the original symbol name whereas the shared
938 // library provides a symbol with the mangled name. We need to
939 // copy the payload of mangled to original.
940 // XXX maybe there is a better way to do this.
941 dup := ldr.Lookup(newName, ldr.SymVersion(s))
944 dt := ldr.SymType(dup)
945 if st == sym.Sxxx && dt != sym.Sxxx {
953 // typeSymbolMangle mangles the given symbol name into something shorter.
955 // Keep the type:. prefix, which parts of the linker (like the
956 // DWARF generator) know means the symbol is not decodable.
957 // Leave type:runtime. symbols alone, because other parts of
958 // the linker manipulates them.
959 func typeSymbolMangle(name string) string {
960 if !strings.HasPrefix(name, "type:") {
963 if strings.HasPrefix(name, "type:runtime.") {
966 if len(name) <= 14 && !strings.Contains(name, "@") { // Issue 19529
969 hash := notsha256.Sum256([]byte(name))
974 return prefix + base64.StdEncoding.EncodeToString(hash[:6])
978 * look for the next file in an archive.
979 * adapted from libmach.
981 func nextar(bp *bio.Reader, off int64, a *ArHdr) int64 {
986 var buf [SAR_HDR]byte
987 if n, err := io.ReadFull(bp, buf[:]); err != nil {
988 if n == 0 && err != io.EOF {
994 a.name = artrim(buf[0:16])
995 a.date = artrim(buf[16:28])
996 a.uid = artrim(buf[28:34])
997 a.gid = artrim(buf[34:40])
998 a.mode = artrim(buf[40:48])
999 a.size = artrim(buf[48:58])
1000 a.fmag = artrim(buf[58:60])
1002 arsize := atolwhex(a.size)
1006 return arsize + SAR_HDR
1009 func loadobjfile(ctxt *Link, lib *sym.Library) {
1010 pkg := objabi.PathToPrefix(lib.Pkg)
1012 if ctxt.Debugvlog > 1 {
1013 ctxt.Logf("ldobj: %s (%s)\n", lib.File, pkg)
1015 f, err := bio.Open(lib.File)
1017 Exitf("cannot open file %s: %v", lib.File, err)
1021 if pkg == "main" && !lib.Main {
1022 Exitf("%s: not package main", lib.File)
1026 for i := 0; i < len(ARMAG); i++ {
1027 if c, err := f.ReadByte(); err == nil && c == ARMAG[i] {
1031 /* load it as a regular file */
1032 l := f.MustSeek(0, 2)
1034 ldobj(ctxt, f, lib, l, lib.File, lib.File)
1039 * load all the object files from the archive now.
1040 * this gives us sequential file access and keeps us
1041 * from needing to come back later to pick up more
1042 * objects. it breaks the usual C archive model, but
1043 * this is Go, not C. the common case in Go is that
1044 * we need to load all the objects, and then we throw away
1045 * the individual symbols that are unused.
1047 * loading every object will also make it possible to
1048 * load foreign objects not referenced by __.PKGDEF.
1053 l := nextar(f, off, &arhdr)
1058 Exitf("%s: malformed archive", lib.File)
1062 // __.PKGDEF isn't a real Go object file, and it's
1063 // absent in -linkobj builds anyway. Skipping it
1064 // ensures consistency between -linkobj and normal
1066 if arhdr.name == pkgdef {
1070 if arhdr.name == "dynimportfail" {
1071 dynimportfail = append(dynimportfail, lib.Pkg)
1074 // Skip other special (non-object-file) sections that
1075 // build tools may have added. Such sections must have
1076 // short names so that the suffix is not truncated.
1077 if len(arhdr.name) < 16 {
1078 if ext := filepath.Ext(arhdr.name); ext != ".o" && ext != ".syso" {
1083 pname := fmt.Sprintf("%s(%s)", lib.File, arhdr.name)
1084 l = atolwhex(arhdr.size)
1085 ldobj(ctxt, f, lib, l, pname, lib.File)
1089 type Hostobj struct {
1090 ld func(*Link, *bio.Reader, string, int64, string)
1098 var hostobj []Hostobj
1100 // These packages can use internal linking mode.
1101 // Others trigger external mode.
1102 var internalpkg = []string{
1103 "crypto/internal/boring",
1104 "crypto/internal/boring/syso",
1110 "runtime/race/internal/amd64v1",
1111 "runtime/race/internal/amd64v3",
1116 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 {
1118 for _, intpkg := range internalpkg {
1125 // DragonFly declares errno with __thread, which results in a symbol
1126 // type of R_386_TLS_GD or R_X86_64_TLSGD. The Go linker does not
1127 // currently know how to handle TLS relocations, hence we have to
1128 // force external linking for any libraries that link in code that
1129 // uses errno. This can be removed if the Go linker ever supports
1130 // these relocation types.
1131 if headType == objabi.Hdragonfly {
1132 if pkg == "net" || pkg == "os/user" {
1141 hostobj = append(hostobj, Hostobj{})
1142 h := &hostobj[len(hostobj)-1]
1152 func hostobjs(ctxt *Link) {
1153 if ctxt.LinkMode != LinkInternal {
1158 for i := 0; i < len(hostobj); i++ {
1160 f, err := bio.Open(h.file)
1162 Exitf("cannot reopen %s: %v", h.pn, err)
1164 f.MustSeek(h.off, 0)
1166 Errorf(nil, "%s: unrecognized object file format", h.pn)
1169 h.ld(ctxt, f, h.pkg, h.length, h.pn)
1170 if *flagCaptureHostObjs != "" {
1177 func hostlinksetup(ctxt *Link) {
1178 if ctxt.LinkMode != LinkExternal {
1182 // For external link, record that we need to tell the external linker -s,
1183 // and turn off -s internally: the external linker needs the symbol
1184 // information for its final link.
1188 // create temporary directory and arrange cleanup
1189 if *flagTmpdir == "" {
1190 dir, err := os.MkdirTemp("", "go-link-")
1197 os.RemoveAll(*flagTmpdir)
1201 // change our output to temporary object file
1202 if err := ctxt.Out.Close(); err != nil {
1203 Exitf("error closing output file")
1205 mayberemoveoutfile()
1207 p := filepath.Join(*flagTmpdir, "go.o")
1208 if err := ctxt.Out.Open(p); err != nil {
1209 Exitf("cannot create %s: %v", p, err)
1213 // hostobjCopy creates a copy of the object files in hostobj in a
1214 // temporary directory.
1215 func hostobjCopy() (paths []string) {
1216 var wg sync.WaitGroup
1217 sema := make(chan struct{}, runtime.NumCPU()) // limit open file descriptors
1218 for i, h := range hostobj {
1220 dst := filepath.Join(*flagTmpdir, fmt.Sprintf("%06d.o", i))
1221 paths = append(paths, dst)
1230 f, err := os.Open(h.file)
1232 Exitf("cannot reopen %s: %v", h.pn, err)
1235 if _, err := f.Seek(h.off, 0); err != nil {
1236 Exitf("cannot seek %s: %v", h.pn, err)
1239 w, err := os.Create(dst)
1241 Exitf("cannot create %s: %v", dst, err)
1243 if _, err := io.CopyN(w, f, h.length); err != nil {
1244 Exitf("cannot write %s: %v", dst, err)
1246 if err := w.Close(); err != nil {
1247 Exitf("cannot close %s: %v", dst, err)
1255 // writeGDBLinkerScript creates gcc linker script file in temp
1256 // directory. writeGDBLinkerScript returns created file path.
1257 // The script is used to work around gcc bug
1258 // (see https://golang.org/issue/20183 for details).
1259 func writeGDBLinkerScript() string {
1260 name := "fix_debug_gdb_scripts.ld"
1261 path := filepath.Join(*flagTmpdir, name)
1264 .debug_gdb_scripts BLOCK(__section_alignment__) (NOLOAD) :
1266 *(.debug_gdb_scripts)
1269 INSERT AFTER .debug_types;
1271 err := os.WriteFile(path, []byte(src), 0666)
1273 Errorf(nil, "WriteFile %s failed: %v", name, err)
1278 // archive builds a .a archive from the hostobj object files.
1279 func (ctxt *Link) archive() {
1280 if ctxt.BuildMode != BuildModeCArchive {
1286 if *flagExtar == "" {
1290 mayberemoveoutfile()
1292 // Force the buffer to flush here so that external
1293 // tools will see a complete file.
1294 if err := ctxt.Out.Close(); err != nil {
1295 Exitf("error closing %v", *flagOutfile)
1298 argv := []string{*flagExtar, "-q", "-c", "-s"}
1299 if ctxt.HeadType == objabi.Haix {
1300 argv = append(argv, "-X64")
1302 argv = append(argv, *flagOutfile)
1303 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1304 argv = append(argv, hostobjCopy()...)
1306 if ctxt.Debugvlog != 0 {
1307 ctxt.Logf("archive: %s\n", strings.Join(argv, " "))
1310 // If supported, use syscall.Exec() to invoke the archive command,
1311 // which should be the final remaining step needed for the link.
1312 // This will reduce peak RSS for the link (and speed up linking of
1313 // large applications), since when the archive command runs we
1314 // won't be holding onto all of the linker's live memory.
1315 if syscallExecSupported && !ownTmpDir {
1317 ctxt.execArchive(argv)
1318 panic("should not get here")
1321 // Otherwise invoke 'ar' in the usual way (fork + exec).
1322 if out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput(); err != nil {
1323 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1327 func (ctxt *Link) hostlink() {
1328 if ctxt.LinkMode != LinkExternal || nerrors > 0 {
1331 if ctxt.BuildMode == BuildModeCArchive {
1336 argv = append(argv, ctxt.extld()...)
1337 argv = append(argv, hostlinkArchArgs(ctxt.Arch)...)
1339 if *FlagS || debug_s {
1340 if ctxt.HeadType == objabi.Hdarwin {
1341 // Recent versions of macOS print
1342 // ld: warning: option -s is obsolete and being ignored
1343 // so do not pass any arguments.
1345 argv = append(argv, "-s")
1349 // On darwin, whether to combine DWARF into executable.
1350 // Only macOS supports unmapped segments such as our __DWARF segment.
1351 combineDwarf := ctxt.IsDarwin() && !*FlagS && !*FlagW && !debug_s && machoPlatform == PLATFORM_MACOS
1353 switch ctxt.HeadType {
1354 case objabi.Hdarwin:
1356 // Leave room for DWARF combining.
1357 // -headerpad is incompatible with -fembed-bitcode.
1358 argv = append(argv, "-Wl,-headerpad,1144")
1360 if ctxt.DynlinkingGo() && buildcfg.GOOS != "ios" {
1361 // -flat_namespace is deprecated on iOS.
1362 // It is useful for supporting plugins. We don't support plugins on iOS.
1363 // -flat_namespace may cause the dynamic linker to hang at forkExec when
1364 // resolving a lazy binding. See issue 38824.
1365 // Force eager resolution to work around.
1366 argv = append(argv, "-Wl,-flat_namespace", "-Wl,-bind_at_load")
1369 argv = append(argv, "-Wl,-S") // suppress STAB (symbolic debugging) symbols
1371 case objabi.Hopenbsd:
1372 argv = append(argv, "-Wl,-nopie")
1373 argv = append(argv, "-pthread")
1374 case objabi.Hwindows:
1376 argv = append(argv, "-mwindows")
1378 argv = append(argv, "-mconsole")
1380 // Mark as having awareness of terminal services, to avoid
1381 // ancient compatibility hacks.
1382 argv = append(argv, "-Wl,--tsaware")
1385 argv = append(argv, "-Wl,--nxcompat")
1387 argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", PeMinimumTargetMajorVersion))
1388 argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", PeMinimumTargetMinorVersion))
1389 argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", PeMinimumTargetMajorVersion))
1390 argv = append(argv, fmt.Sprintf("-Wl,--minor-subsystem-version=%d", PeMinimumTargetMinorVersion))
1392 argv = append(argv, "-pthread")
1393 // prevent ld to reorder .text functions to keep the same
1394 // first/last functions for moduledata.
1395 argv = append(argv, "-Wl,-bnoobjreorder")
1396 // mcmodel=large is needed for every gcc generated files, but
1397 // ld still need -bbigtoc in order to allow larger TOC.
1398 argv = append(argv, "-mcmodel=large")
1399 argv = append(argv, "-Wl,-bbigtoc")
1402 // Enable/disable ASLR on Windows.
1403 addASLRargs := func(argv []string, val bool) []string {
1404 // Old/ancient versions of GCC support "--dynamicbase" and
1405 // "--high-entropy-va" but don't enable it by default. In
1406 // addition, they don't accept "--disable-dynamicbase" or
1407 // "--no-dynamicbase", so the only way to disable ASLR is to
1408 // not pass any flags at all.
1410 // More modern versions of GCC (and also clang) enable ASLR
1411 // by default. With these compilers, however you can turn it
1412 // off if you want using "--disable-dynamicbase" or
1413 // "--no-dynamicbase".
1415 // The strategy below is to try using "--disable-dynamicbase";
1416 // if this succeeds, then assume we're working with more
1417 // modern compilers and act accordingly. If it fails, assume
1418 // an ancient compiler with ancient defaults.
1421 dbon := "--dynamicbase"
1422 heon := "--high-entropy-va"
1423 dboff := "--disable-dynamicbase"
1424 heoff := "--disable-high-entropy-va"
1429 // Test to see whether "--disable-dynamicbase" works.
1430 newer := linkerFlagSupported(ctxt.Arch, argv[0], "", "-Wl,"+dboff)
1432 // Newer compiler, which supports both on/off options.
1436 // older toolchain: we have to say nothing in order to
1437 // get a no-ASLR binary.
1443 argv = append(argv, "-Wl,"+dbopt)
1445 // enable high-entropy ASLR on 64-bit.
1446 if ctxt.Arch.PtrSize >= 8 && heopt != "" {
1447 argv = append(argv, "-Wl,"+heopt)
1452 switch ctxt.BuildMode {
1454 if ctxt.HeadType == objabi.Hdarwin {
1455 if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() {
1456 argv = append(argv, "-Wl,-no_pie")
1459 if *flagRace && ctxt.HeadType == objabi.Hwindows {
1460 // Current windows/amd64 race detector tsan support
1461 // library can't handle PIE mode (see #53539 for more details).
1462 // For now, explicitly disable PIE (since some compilers
1463 // default to it) if -race is in effect.
1464 argv = addASLRargs(argv, false)
1467 switch ctxt.HeadType {
1468 case objabi.Hdarwin, objabi.Haix:
1469 case objabi.Hwindows:
1470 if *flagAslr && *flagRace {
1471 // Current windows/amd64 race detector tsan support
1472 // library can't handle PIE mode (see #53539 for more details).
1473 // Disable alsr if -race in effect.
1476 argv = addASLRargs(argv, *flagAslr)
1479 if ctxt.UseRelro() {
1480 argv = append(argv, "-Wl,-z,relro")
1482 argv = append(argv, "-pie")
1484 case BuildModeCShared:
1485 if ctxt.HeadType == objabi.Hdarwin {
1486 argv = append(argv, "-dynamiclib")
1488 if ctxt.UseRelro() {
1489 argv = append(argv, "-Wl,-z,relro")
1491 argv = append(argv, "-shared")
1492 if ctxt.HeadType == objabi.Hwindows {
1493 argv = addASLRargs(argv, *flagAslr)
1495 // Pass -z nodelete to mark the shared library as
1496 // non-closeable: a dlclose will do nothing.
1497 argv = append(argv, "-Wl,-z,nodelete")
1498 // Only pass Bsymbolic on non-Windows.
1499 argv = append(argv, "-Wl,-Bsymbolic")
1502 case BuildModeShared:
1503 if ctxt.UseRelro() {
1504 argv = append(argv, "-Wl,-z,relro")
1506 argv = append(argv, "-shared")
1507 case BuildModePlugin:
1508 if ctxt.HeadType == objabi.Hdarwin {
1509 argv = append(argv, "-dynamiclib")
1511 if ctxt.UseRelro() {
1512 argv = append(argv, "-Wl,-z,relro")
1514 argv = append(argv, "-shared")
1518 var altLinker string
1519 if ctxt.IsELF && ctxt.DynlinkingGo() {
1520 // We force all symbol resolution to be done at program startup
1521 // because lazy PLT resolution can use large amounts of stack at
1522 // times we cannot allow it to do so.
1523 argv = append(argv, "-Wl,-z,now")
1525 // Do not let the host linker generate COPY relocations. These
1526 // can move symbols out of sections that rely on stable offsets
1527 // from the beginning of the section (like sym.STYPE).
1528 argv = append(argv, "-Wl,-z,nocopyreloc")
1530 if buildcfg.GOOS == "android" {
1531 // Use lld to avoid errors from default linker (issue #38838)
1535 if ctxt.Arch.InFamily(sys.ARM, sys.ARM64) && buildcfg.GOOS == "linux" {
1536 // On ARM, the GNU linker will generate COPY relocations
1537 // even with -znocopyreloc set.
1538 // https://sourceware.org/bugzilla/show_bug.cgi?id=19962
1540 // On ARM64, the GNU linker will fail instead of
1541 // generating COPY relocations.
1543 // In both cases, switch to gold.
1546 // If gold is not installed, gcc will silently switch
1547 // back to ld.bfd. So we parse the version information
1548 // and provide a useful error if gold is missing.
1549 name, args := flagExtld[0], flagExtld[1:]
1550 args = append(args, "-fuse-ld=gold", "-Wl,--version")
1551 cmd := exec.Command(name, args...)
1552 if out, err := cmd.CombinedOutput(); err == nil {
1553 if !bytes.Contains(out, []byte("GNU gold")) {
1554 log.Fatalf("ARM external linker must be gold (issue #15696), but is not: %s", out)
1559 if ctxt.Arch.Family == sys.ARM64 && buildcfg.GOOS == "freebsd" {
1560 // Switch to ld.bfd on freebsd/arm64.
1563 // Provide a useful error if ld.bfd is missing.
1564 name, args := flagExtld[0], flagExtld[1:]
1565 args = append(args, "-fuse-ld=bfd", "-Wl,--version")
1566 cmd := exec.Command(name, args...)
1567 if out, err := cmd.CombinedOutput(); err == nil {
1568 if !bytes.Contains(out, []byte("GNU ld")) {
1569 log.Fatalf("ARM64 external linker must be ld.bfd (issue #35197), please install devel/binutils")
1573 if altLinker != "" {
1574 argv = append(argv, "-fuse-ld="+altLinker)
1577 if ctxt.IsELF && len(buildinfo) > 0 {
1578 argv = append(argv, fmt.Sprintf("-Wl,--build-id=0x%x", buildinfo))
1581 // On Windows, given -o foo, GCC will append ".exe" to produce
1582 // "foo.exe". We have decided that we want to honor the -o
1583 // option. To make this work, we append a '.' so that GCC
1584 // will decide that the file already has an extension. We
1585 // only want to do this when producing a Windows output file
1586 // on a Windows host.
1587 outopt := *flagOutfile
1588 if buildcfg.GOOS == "windows" && runtime.GOOS == "windows" && filepath.Ext(outopt) == "" {
1591 argv = append(argv, "-o")
1592 argv = append(argv, outopt)
1594 if rpath.val != "" {
1595 argv = append(argv, fmt.Sprintf("-Wl,-rpath,%s", rpath.val))
1598 if *flagInterpreter != "" {
1599 // Many linkers support both -I and the --dynamic-linker flags
1600 // to set the ELF interpreter, but lld only supports
1601 // --dynamic-linker so prefer that (ld on very old Solaris only
1602 // supports -I but that seems less important).
1603 argv = append(argv, fmt.Sprintf("-Wl,--dynamic-linker,%s", *flagInterpreter))
1606 // Force global symbols to be exported for dlopen, etc.
1608 argv = append(argv, "-rdynamic")
1610 if ctxt.HeadType == objabi.Haix {
1611 fileName := xcoffCreateExportFile(ctxt)
1612 argv = append(argv, "-Wl,-bE:"+fileName)
1615 const unusedArguments = "-Qunused-arguments"
1616 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, unusedArguments) {
1617 argv = append(argv, unusedArguments)
1620 if ctxt.IsWindows() {
1621 // Suppress generation of the PE file header timestamp,
1622 // so as to avoid spurious build ID differences between
1623 // linked binaries that are otherwise identical other than
1624 // the date/time they were linked.
1625 const noTimeStamp = "-Wl,--no-insert-timestamp"
1626 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, noTimeStamp) {
1627 argv = append(argv, noTimeStamp)
1631 const compressDWARF = "-Wl,--compress-debug-sections=zlib"
1632 if ctxt.compressDWARF && linkerFlagSupported(ctxt.Arch, argv[0], altLinker, compressDWARF) {
1633 argv = append(argv, compressDWARF)
1636 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1637 argv = append(argv, hostobjCopy()...)
1638 if ctxt.HeadType == objabi.Haix {
1639 // We want to have C files after Go files to remove
1640 // trampolines csects made by ld.
1641 argv = append(argv, "-nostartfiles")
1642 argv = append(argv, "/lib/crt0_64.o")
1644 extld := ctxt.extld()
1645 name, args := extld[0], extld[1:]
1646 // Get starting files.
1647 getPathFile := func(file string) string {
1648 args := append(args, "-maix64", "--print-file-name="+file)
1649 out, err := exec.Command(name, args...).CombinedOutput()
1651 log.Fatalf("running %s failed: %v\n%s", extld, err, out)
1653 return strings.Trim(string(out), "\n")
1655 // Since GCC version 11, the 64-bit version of GCC starting files
1656 // are now suffixed by "_64". Even under "-maix64" multilib directory
1657 // "crtcxa.o" is 32-bit.
1658 crtcxa := getPathFile("crtcxa_64.o")
1659 if !filepath.IsAbs(crtcxa) {
1660 crtcxa = getPathFile("crtcxa.o")
1662 crtdbase := getPathFile("crtdbase_64.o")
1663 if !filepath.IsAbs(crtdbase) {
1664 crtdbase = getPathFile("crtdbase.o")
1666 argv = append(argv, crtcxa)
1667 argv = append(argv, crtdbase)
1670 if ctxt.linkShared {
1671 seenDirs := make(map[string]bool)
1672 seenLibs := make(map[string]bool)
1673 addshlib := func(path string) {
1674 dir, base := filepath.Split(path)
1676 argv = append(argv, "-L"+dir)
1678 argv = append(argv, "-Wl,-rpath="+dir)
1680 seenDirs[dir] = true
1682 base = strings.TrimSuffix(base, ".so")
1683 base = strings.TrimPrefix(base, "lib")
1684 if !seenLibs[base] {
1685 argv = append(argv, "-l"+base)
1686 seenLibs[base] = true
1689 for _, shlib := range ctxt.Shlibs {
1690 addshlib(shlib.Path)
1691 for _, dep := range shlib.Deps {
1695 libpath := findshlib(ctxt, dep)
1703 // clang, unlike GCC, passes -rdynamic to the linker
1704 // even when linking with -static, causing a linker
1705 // error when using GNU ld. So take out -rdynamic if
1706 // we added it. We do it in this order, rather than
1707 // only adding -rdynamic later, so that -extldflags
1708 // can override -rdynamic without using -static.
1709 // Similarly for -Wl,--dynamic-linker.
1710 checkStatic := func(arg string) {
1711 if ctxt.IsELF && arg == "-static" {
1712 for i := range argv {
1713 if argv[i] == "-rdynamic" || strings.HasPrefix(argv[i], "-Wl,--dynamic-linker,") {
1720 for _, p := range ldflag {
1721 argv = append(argv, p)
1725 // When building a program with the default -buildmode=exe the
1726 // gc compiler generates code requires DT_TEXTREL in a
1727 // position independent executable (PIE). On systems where the
1728 // toolchain creates PIEs by default, and where DT_TEXTREL
1729 // does not work, the resulting programs will not run. See
1730 // issue #17847. To avoid this problem pass -no-pie to the
1731 // toolchain if it is supported.
1732 if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared && !(ctxt.IsDarwin() && ctxt.IsARM64()) {
1733 // GCC uses -no-pie, clang uses -nopie.
1734 for _, nopie := range []string{"-no-pie", "-nopie"} {
1735 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, nopie) {
1736 argv = append(argv, nopie)
1742 for _, p := range flagExtldflags {
1743 argv = append(argv, p)
1746 if ctxt.HeadType == objabi.Hwindows {
1747 // Determine which linker we're using. Add in the extldflags in
1748 // case used has specified "-fuse-ld=...".
1749 extld := ctxt.extld()
1750 name, args := extld[0], extld[1:]
1751 args = append(args, flagExtldflags...)
1752 args = append(args, "-Wl,--version")
1753 cmd := exec.Command(name, args...)
1755 if out, err := cmd.CombinedOutput(); err == nil {
1756 if bytes.Contains(out, []byte("LLD ")) {
1761 // use gcc linker script to work around gcc bug
1762 // (see https://golang.org/issue/20183 for details).
1764 p := writeGDBLinkerScript()
1765 argv = append(argv, "-Wl,-T,"+p)
1768 if p := ctxt.findLibPath("libsynchronization.a"); p != "libsynchronization.a" {
1769 argv = append(argv, "-lsynchronization")
1772 // libmingw32 and libmingwex have some inter-dependencies,
1773 // so must use linker groups.
1774 argv = append(argv, "-Wl,--start-group", "-lmingwex", "-lmingw32", "-Wl,--end-group")
1775 argv = append(argv, peimporteddlls()...)
1778 if ctxt.Debugvlog != 0 {
1779 ctxt.Logf("host link:")
1780 for _, v := range argv {
1786 out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput()
1788 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1791 // Filter out useless linker warnings caused by bugs outside Go.
1792 // See also cmd/go/internal/work/exec.go's gccld method.
1795 for _, line := range bytes.SplitAfter(out, []byte("\n")) {
1796 // golang.org/issue/26073 - Apple Xcode bug
1797 if bytes.Contains(line, []byte("ld: warning: text-based stub file")) {
1806 // Remove TOC overflow warning on AIX.
1807 if bytes.Contains(line, []byte("ld: 0711-783")) {
1812 save = append(save, line)
1814 out = bytes.Join(save, nil)
1817 // always print external output even if the command is successful, so that we don't
1818 // swallow linker warnings (see https://golang.org/issue/17935).
1819 if ctxt.IsDarwin() && ctxt.IsAMD64() {
1820 const noPieWarning = "ld: warning: -no_pie is deprecated when targeting new OS versions\n"
1821 if i := bytes.Index(out, []byte(noPieWarning)); i >= 0 {
1822 // swallow -no_pie deprecation warning, issue 54482
1823 out = append(out[:i], out[i+len(noPieWarning):]...)
1826 ctxt.Logf("%s", out)
1830 // Find "dsymutils" and "strip" tools using CC --print-prog-name.
1832 cc = append(cc, ctxt.extld()...)
1833 cc = append(cc, hostlinkArchArgs(ctxt.Arch)...)
1834 cc = append(cc, "--print-prog-name", "dsymutil")
1835 out, err := exec.Command(cc[0], cc[1:]...).CombinedOutput()
1837 Exitf("%s: finding dsymutil failed: %v\n%s", os.Args[0], err, out)
1839 dsymutilCmd := strings.TrimSuffix(string(out), "\n")
1841 cc[len(cc)-1] = "strip"
1842 out, err = exec.Command(cc[0], cc[1:]...).CombinedOutput()
1844 Exitf("%s: finding strip failed: %v\n%s", os.Args[0], err, out)
1846 stripCmd := strings.TrimSuffix(string(out), "\n")
1848 dsym := filepath.Join(*flagTmpdir, "go.dwarf")
1849 if out, err := exec.Command(dsymutilCmd, "-f", *flagOutfile, "-o", dsym).CombinedOutput(); err != nil {
1850 Exitf("%s: running dsymutil failed: %v\n%s", os.Args[0], err, out)
1852 // Remove STAB (symbolic debugging) symbols after we are done with them (by dsymutil).
1853 // They contain temporary file paths and make the build not reproducible.
1854 if out, err := exec.Command(stripCmd, "-S", *flagOutfile).CombinedOutput(); err != nil {
1855 Exitf("%s: running strip failed: %v\n%s", os.Args[0], err, out)
1857 // Skip combining if `dsymutil` didn't generate a file. See #11994.
1858 if _, err := os.Stat(dsym); os.IsNotExist(err) {
1861 // For os.Rename to work reliably, must be in same directory as outfile.
1862 combinedOutput := *flagOutfile + "~"
1863 exef, err := os.Open(*flagOutfile)
1865 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1868 exem, err := macho.NewFile(exef)
1870 Exitf("%s: parsing Mach-O header failed: %v", os.Args[0], err)
1872 if err := machoCombineDwarf(ctxt, exef, exem, dsym, combinedOutput); err != nil {
1873 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1875 os.Remove(*flagOutfile)
1876 if err := os.Rename(combinedOutput, *flagOutfile); err != nil {
1877 Exitf("%s: %v", os.Args[0], err)
1880 if ctxt.NeedCodeSign() {
1881 err := machoCodeSign(ctxt, *flagOutfile)
1883 Exitf("%s: code signing failed: %v", os.Args[0], err)
1888 var createTrivialCOnce sync.Once
1890 func linkerFlagSupported(arch *sys.Arch, linker, altLinker, flag string) bool {
1891 createTrivialCOnce.Do(func() {
1892 src := filepath.Join(*flagTmpdir, "trivial.c")
1893 if err := os.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
1894 Errorf(nil, "WriteFile trivial.c failed: %v", err)
1898 flagsWithNextArgSkip := []string{
1907 flagsWithNextArgKeep := []string{
1913 prefixesToKeep := []string{
1924 flags := hostlinkArchArgs(arch)
1927 for _, f := range append(flagExtldflags, ldflag...) {
1929 flags = append(flags, f)
1933 } else if f == "" || f[0] != '-' {
1934 } else if contains(flagsWithNextArgSkip, f) {
1936 } else if contains(flagsWithNextArgKeep, f) {
1937 flags = append(flags, f)
1940 for _, p := range prefixesToKeep {
1941 if strings.HasPrefix(f, p) {
1942 flags = append(flags, f)
1949 if altLinker != "" {
1950 flags = append(flags, "-fuse-ld="+altLinker)
1952 flags = append(flags, flag, "trivial.c")
1954 cmd := exec.Command(linker, flags...)
1955 cmd.Dir = *flagTmpdir
1956 cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
1957 out, err := cmd.CombinedOutput()
1958 // GCC says "unrecognized command line option ‘-no-pie’"
1959 // clang says "unknown argument: '-no-pie'"
1960 return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
1963 // hostlinkArchArgs returns arguments to pass to the external linker
1964 // based on the architecture.
1965 func hostlinkArchArgs(arch *sys.Arch) []string {
1966 switch arch.Family {
1968 return []string{"-m32"}
1970 if buildcfg.GOOS == "darwin" {
1971 return []string{"-arch", "x86_64", "-m64"}
1973 return []string{"-m64"}
1975 return []string{"-m64"}
1977 return []string{"-marm"}
1979 if buildcfg.GOOS == "darwin" {
1980 return []string{"-arch", "arm64"}
1983 return []string{"-mabi=lp64d"}
1985 return []string{"-mabi=64"}
1987 return []string{"-mabi=32"}
1989 if buildcfg.GOOS == "aix" {
1990 return []string{"-maix64"}
1992 return []string{"-m64"}
1999 var wantHdr = objabi.HeaderString()
2001 // ldobj loads an input object. If it is a host object (an object
2002 // compiled by a non-Go compiler) it returns the Hostobj pointer. If
2003 // it is a Go object, it returns nil.
2004 func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string, file string) *Hostobj {
2005 pkg := objabi.PathToPrefix(lib.Pkg)
2007 eof := f.Offset() + length
2013 f.MustSeek(start, 0)
2015 unit := &sym.CompilationUnit{Lib: lib}
2016 lib.Units = append(lib.Units, unit)
2018 magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
2019 if magic == 0x7f454c46 { // \x7F E L F
2020 ldelf := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2021 textp, flags, err := loadelf.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn, ehdr.Flags)
2023 Errorf(nil, "%v", err)
2027 ctxt.Textp = append(ctxt.Textp, textp...)
2029 return ldhostobj(ldelf, ctxt.HeadType, f, pkg, length, pn, file)
2032 if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
2033 ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2034 textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2036 Errorf(nil, "%v", err)
2039 ctxt.Textp = append(ctxt.Textp, textp...)
2041 return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
2049 ldpe := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2050 textp, rsrc, err := loadpe.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2052 Errorf(nil, "%v", err)
2056 setpersrc(ctxt, rsrc)
2058 ctxt.Textp = append(ctxt.Textp, textp...)
2060 return ldhostobj(ldpe, ctxt.HeadType, f, pkg, length, pn, file)
2063 if c1 == 0x01 && (c2 == 0xD7 || c2 == 0xF7) {
2064 ldxcoff := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2065 textp, err := loadxcoff.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2067 Errorf(nil, "%v", err)
2070 ctxt.Textp = append(ctxt.Textp, textp...)
2072 return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
2075 if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
2076 // An unrecognized object is just passed to the external linker.
2077 // If we try to read symbols from this object, we will
2078 // report an error at that time.
2079 unknownObjFormat = true
2080 return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
2083 /* check the header */
2084 line, err := f.ReadString('\n')
2086 Errorf(nil, "truncated object file: %s: %v", pn, err)
2090 if !strings.HasPrefix(line, "go object ") {
2091 if strings.HasSuffix(pn, ".go") {
2092 Exitf("%s: uncompiled .go source file", pn)
2096 if line == ctxt.Arch.Name {
2097 // old header format: just $GOOS
2098 Errorf(nil, "%s: stale object file", pn)
2102 Errorf(nil, "%s: not an object file: @%d %q", pn, start, line)
2106 // First, check that the basic GOOS, GOARCH, and Version match.
2107 if line != wantHdr {
2108 Errorf(nil, "%s: linked object header mismatch:\nhave %q\nwant %q\n", pn, line, wantHdr)
2111 // Skip over exports and other info -- ends with \n!\n.
2113 // Note: It's possible for "\n!\n" to appear within the binary
2114 // package export data format. To avoid truncating the package
2115 // definition prematurely (issue 21703), we keep track of
2116 // how many "$$" delimiters we've seen.
2118 import0 := f.Offset()
2120 c1 = '\n' // the last line ended in \n
2126 if markers%2 == 0 && c2 == '!' && c3 == '\n' {
2129 if c2 == '$' && c3 == '$' {
2138 Errorf(nil, "truncated object file: %s", pn)
2143 import1 := f.Offset()
2145 f.MustSeek(import0, 0)
2146 ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
2147 f.MustSeek(import1, 0)
2149 fingerprint := ctxt.loader.Preload(ctxt.IncVersion(), f, lib, unit, eof-f.Offset())
2150 if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
2151 // Check fingerprint, to ensure the importing and imported packages
2152 // have consistent view of symbol indices.
2153 // Normally the go command should ensure this. But in case something
2154 // goes wrong, it could lead to obscure bugs like run-time crash.
2155 // Check it here to be sure.
2156 if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
2157 lib.Fingerprint = fingerprint
2159 checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
2162 addImports(ctxt, lib, pn)
2166 // symbolsAreUnresolved scans through the loader's list of unresolved
2167 // symbols and checks to see whether any of them match the names of the
2168 // symbols in 'want'. Return value is a list of bools, with list[K] set
2169 // to true if there is an unresolved reference to the symbol in want[K].
2170 func symbolsAreUnresolved(ctxt *Link, want []string) []bool {
2171 returnAllUndefs := -1
2172 undefs, _ := ctxt.loader.UndefinedRelocTargets(returnAllUndefs)
2173 seen := make(map[loader.Sym]struct{})
2174 rval := make([]bool, len(want))
2175 wantm := make(map[string]int)
2176 for k, w := range want {
2180 for _, s := range undefs {
2181 if _, ok := seen[s]; ok {
2184 seen[s] = struct{}{}
2185 if k, ok := wantm[ctxt.loader.SymName(s)]; ok {
2188 if count == len(want) {
2196 // hostObject reads a single host object file (compare to "hostArchive").
2197 // This is used as part of internal linking when we need to pull in
2198 // files such as "crt?.o".
2199 func hostObject(ctxt *Link, objname string, path string) {
2200 if ctxt.Debugvlog > 1 {
2201 ctxt.Logf("hostObject(%s)\n", path)
2203 objlib := sym.Library{
2206 f, err := bio.Open(path)
2208 Exitf("cannot open host object %q file %s: %v", objname, path, err)
2211 h := ldobj(ctxt, f, &objlib, 0, path, path)
2213 Exitf("unrecognized object file format in %s", path)
2216 h.length = f.MustSeek(0, 2)
2217 f.MustSeek(h.off, 0)
2218 h.ld(ctxt, f, h.pkg, h.length, h.pn)
2219 if *flagCaptureHostObjs != "" {
2224 func checkFingerprint(lib *sym.Library, libfp goobj.FingerprintType, src string, srcfp goobj.FingerprintType) {
2226 Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
2230 func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
2231 data := make([]byte, sym.Size)
2232 sect := f.Sections[sym.Section]
2233 if sect.Type != elf.SHT_PROGBITS && sect.Type != elf.SHT_NOTE {
2234 Errorf(nil, "reading %s from non-data section", sym.Name)
2236 n, err := sect.ReadAt(data, int64(sym.Value-sect.Addr))
2237 if uint64(n) != sym.Size {
2238 Errorf(nil, "reading contents of %s: %v", sym.Name, err)
2243 func readwithpad(r io.Reader, sz int32) ([]byte, error) {
2244 data := make([]byte, Rnd(int64(sz), 4))
2245 _, err := io.ReadFull(r, data)
2253 func readnote(f *elf.File, name []byte, typ int32) ([]byte, error) {
2254 for _, sect := range f.Sections {
2255 if sect.Type != elf.SHT_NOTE {
2260 var namesize, descsize, noteType int32
2261 err := binary.Read(r, f.ByteOrder, &namesize)
2266 return nil, fmt.Errorf("read namesize failed: %v", err)
2268 err = binary.Read(r, f.ByteOrder, &descsize)
2270 return nil, fmt.Errorf("read descsize failed: %v", err)
2272 err = binary.Read(r, f.ByteOrder, ¬eType)
2274 return nil, fmt.Errorf("read type failed: %v", err)
2276 noteName, err := readwithpad(r, namesize)
2278 return nil, fmt.Errorf("read name failed: %v", err)
2280 desc, err := readwithpad(r, descsize)
2282 return nil, fmt.Errorf("read desc failed: %v", err)
2284 if string(name) == string(noteName) && typ == noteType {
2292 func findshlib(ctxt *Link, shlib string) string {
2293 if filepath.IsAbs(shlib) {
2296 for _, libdir := range ctxt.Libdir {
2297 libpath := filepath.Join(libdir, shlib)
2298 if _, err := os.Stat(libpath); err == nil {
2302 Errorf(nil, "cannot find shared library: %s", shlib)
2306 func ldshlibsyms(ctxt *Link, shlib string) {
2308 if filepath.IsAbs(shlib) {
2310 shlib = filepath.Base(shlib)
2312 libpath = findshlib(ctxt, shlib)
2317 for _, processedlib := range ctxt.Shlibs {
2318 if processedlib.Path == libpath {
2322 if ctxt.Debugvlog > 1 {
2323 ctxt.Logf("ldshlibsyms: found library with name %s at %s\n", shlib, libpath)
2326 f, err := elf.Open(libpath)
2328 Errorf(nil, "cannot open shared library: %s", libpath)
2331 // Keep the file open as decodetypeGcprog needs to read from it.
2332 // TODO: fix. Maybe mmap the file.
2335 hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
2337 Errorf(nil, "cannot read ABI hash from shared library %s: %v", libpath, err)
2341 depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
2343 Errorf(nil, "cannot read dep list from shared library %s: %v", libpath, err)
2347 for _, dep := range strings.Split(string(depsbytes), "\n") {
2351 if !filepath.IsAbs(dep) {
2352 // If the dep can be interpreted as a path relative to the shlib
2353 // in which it was found, do that. Otherwise, we will leave it
2354 // to be resolved by libdir lookup.
2355 abs := filepath.Join(filepath.Dir(libpath), dep)
2356 if _, err := os.Stat(abs); err == nil {
2360 deps = append(deps, dep)
2363 syms, err := f.DynamicSymbols()
2365 Errorf(nil, "cannot read symbols from shared library: %s", libpath)
2369 for _, elfsym := range syms {
2370 if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
2374 // Symbols whose names start with "type:" are compiler generated,
2375 // so make functions with that prefix internal.
2377 symname := elfsym.Name // (unmangled) symbol name
2378 if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type:") {
2379 ver = abiInternalVer
2380 } else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC {
2381 // Demangle the ABI name. Keep in sync with symtab.go:mangleABIName.
2382 if strings.HasSuffix(elfsym.Name, ".abiinternal") {
2383 ver = sym.SymVerABIInternal
2384 symname = strings.TrimSuffix(elfsym.Name, ".abiinternal")
2385 } else if strings.HasSuffix(elfsym.Name, ".abi0") {
2387 symname = strings.TrimSuffix(elfsym.Name, ".abi0")
2392 s := l.LookupOrCreateSym(symname, ver)
2394 // Because loadlib above loads all .a files before loading
2395 // any shared libraries, any non-dynimport symbols we find
2396 // that duplicate symbols already loaded should be ignored
2397 // (the symbols from the .a files "win").
2398 if l.SymType(s) != 0 && l.SymType(s) != sym.SDYNIMPORT {
2401 su := l.MakeSymbolUpdater(s)
2402 su.SetType(sym.SDYNIMPORT)
2403 l.SetSymElfType(s, elf.ST_TYPE(elfsym.Info))
2404 su.SetSize(int64(elfsym.Size))
2405 if elfsym.Section != elf.SHN_UNDEF {
2406 // Set .File for the library that actually defines the symbol.
2407 l.SetSymPkg(s, libpath)
2409 // The decodetype_* functions in decodetype.go need access to
2411 sname := l.SymName(s)
2412 if strings.HasPrefix(sname, "type:") && !strings.HasPrefix(sname, "type:.") {
2413 su.SetData(readelfsymboldata(ctxt, f, &elfsym))
2417 if symname != elfsym.Name {
2418 l.SetSymExtname(s, elfsym.Name)
2421 ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f})
2424 func addsection(ldr *loader.Loader, arch *sys.Arch, seg *sym.Segment, name string, rwx int) *sym.Section {
2425 sect := ldr.NewSection()
2426 sect.Rwx = uint8(rwx)
2429 sect.Align = int32(arch.PtrSize) // everything is at least pointer-aligned
2430 seg.Sections = append(seg.Sections, sect)
2435 fmt.Fprintf(os.Stderr, "usage: link [options] main.o\n")
2436 objabi.Flagprint(os.Stderr)
2440 type SymbolType int8 // TODO: after genasmsym is gone, maybe rename to plan9typeChar or something
2443 // see also https://9p.io/magic/man2html/1/nm
2444 TextSym SymbolType = 'T'
2445 DataSym SymbolType = 'D'
2446 BSSSym SymbolType = 'B'
2447 UndefinedSym SymbolType = 'U'
2448 TLSSym SymbolType = 't'
2449 FrameSym SymbolType = 'm'
2450 ParamSym SymbolType = 'p'
2451 AutoSym SymbolType = 'a'
2453 // Deleted auto (not a real sym, just placeholder for type)
2454 DeletedAutoSym = 'x'
2457 // defineInternal defines a symbol used internally by the go runtime.
2458 func (ctxt *Link) defineInternal(p string, t sym.SymKind) loader.Sym {
2459 s := ctxt.loader.CreateSymForUpdate(p, 0)
2466 func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) loader.Sym {
2467 s := ctxt.defineInternal(p, t)
2468 ctxt.loader.SetSymValue(s, v)
2472 func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
2473 if uint64(addr) >= Segdata.Vaddr {
2474 return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
2476 if uint64(addr) >= Segtext.Vaddr {
2477 return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
2479 ldr.Errorf(s, "invalid datoff %#x", addr)
2483 func Entryvalue(ctxt *Link) int64 {
2484 a := *flagEntrySymbol
2485 if a[0] >= '0' && a[0] <= '9' {
2489 s := ldr.Lookup(a, 0)
2491 Errorf(nil, "missing entry symbol %q", a)
2494 st := ldr.SymType(s)
2496 return *FlagTextAddr
2498 if !ctxt.IsAIX() && st != sym.STEXT {
2499 ldr.Errorf(s, "entry not text")
2501 return ldr.SymValue(s)
2504 func (ctxt *Link) callgraph() {
2510 for _, s := range ctxt.Textp {
2511 relocs := ldr.Relocs(s)
2512 for i := 0; i < relocs.Count(); i++ {
2518 if r.Type().IsDirectCall() && ldr.SymType(rs) == sym.STEXT {
2519 ctxt.Logf("%s calls %s\n", ldr.SymName(s), ldr.SymName(rs))
2525 func Rnd(v int64, r int64) int64 {
2538 func bgetc(r *bio.Reader) int {
2539 c, err := r.ReadByte()
2542 log.Fatalf("reading input: %v", err)
2549 type markKind uint8 // for postorder traversal
2556 func postorder(libs []*sym.Library) []*sym.Library {
2557 order := make([]*sym.Library, 0, len(libs)) // hold the result
2558 mark := make(map[*sym.Library]markKind, len(libs))
2559 for _, lib := range libs {
2560 dfs(lib, mark, &order)
2565 func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library) {
2566 if mark[lib] == visited {
2569 if mark[lib] == visiting {
2570 panic("found import cycle while visiting " + lib.Pkg)
2572 mark[lib] = visiting
2573 for _, i := range lib.Imports {
2577 *order = append(*order, lib)
2580 func ElfSymForReloc(ctxt *Link, s loader.Sym) int32 {
2581 // If putelfsym created a local version of this symbol, use that in all
2583 les := ctxt.loader.SymLocalElfSym(s)
2587 return ctxt.loader.SymElfSym(s)
2591 func AddGotSym(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, elfRelocTyp uint32) {
2592 if ldr.SymGot(s) >= 0 {
2596 Adddynsym(ldr, target, syms, s)
2597 got := ldr.MakeSymbolUpdater(syms.GOT)
2598 ldr.SetGot(s, int32(got.Size()))
2599 got.AddUint(target.Arch, 0)
2602 if target.Arch.PtrSize == 8 {
2603 rela := ldr.MakeSymbolUpdater(syms.Rela)
2604 rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2605 rela.AddUint64(target.Arch, elf.R_INFO(uint32(ldr.SymDynid(s)), elfRelocTyp))
2606 rela.AddUint64(target.Arch, 0)
2608 rel := ldr.MakeSymbolUpdater(syms.Rel)
2609 rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2610 rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), elfRelocTyp))
2612 } else if target.IsDarwin() {
2613 leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT)
2614 leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
2615 if target.IsPIE() && target.IsInternal() {
2616 // Mach-O relocations are a royal pain to lay out.
2617 // They use a compact stateful bytecode representation.
2618 // Here we record what are needed and encode them later.
2619 MachoAddBind(int64(ldr.SymGot(s)), s)
2622 ldr.Errorf(s, "addgotsym: unsupported binary format")
2626 var hostobjcounter int
2628 // captureHostObj writes out the content of a host object (pulled from
2629 // an archive or loaded from a *.o file directly) to a directory
2630 // specified via the linker's "-capturehostobjs" debugging flag. This
2631 // is intended to make it easier for a developer to inspect the actual
2632 // object feeding into "CGO internal" link step.
2633 func captureHostObj(h *Hostobj) {
2634 // Form paths for info file and obj file.
2635 ofile := fmt.Sprintf("captured-obj-%d.o", hostobjcounter)
2636 ifile := fmt.Sprintf("captured-obj-%d.txt", hostobjcounter)
2638 opath := filepath.Join(*flagCaptureHostObjs, ofile)
2639 ipath := filepath.Join(*flagCaptureHostObjs, ifile)
2641 // Write the info file.
2642 info := fmt.Sprintf("pkg: %s\npn: %s\nfile: %s\noff: %d\nlen: %d\n",
2643 h.pkg, h.pn, h.file, h.off, h.length)
2644 if err := os.WriteFile(ipath, []byte(info), 0666); err != nil {
2645 log.Fatalf("error writing captured host obj info %s: %v", ipath, err)
2648 readObjData := func() []byte {
2649 inf, err := os.Open(h.file)
2651 log.Fatalf("capturing host obj: open failed on %s: %v", h.pn, err)
2653 res := make([]byte, h.length)
2654 if n, err := inf.ReadAt(res, h.off); err != nil || n != int(h.length) {
2655 log.Fatalf("capturing host obj: readat failed on %s: %v", h.pn, err)
2660 // Write the object file.
2661 if err := os.WriteFile(opath, readObjData(), 0666); err != nil {
2662 log.Fatalf("error writing captured host object %s: %v", opath, err)
2665 fmt.Fprintf(os.Stderr, "link: info: captured host object %s to %s\n",