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
37 "cmd/internal/notsha256"
40 "cmd/link/internal/loadelf"
41 "cmd/link/internal/loader"
42 "cmd/link/internal/loadmacho"
43 "cmd/link/internal/loadpe"
44 "cmd/link/internal/loadxcoff"
45 "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.
189 Dragonflydynld string
192 // Empty spaces between codeblocks will be padded with this value.
193 // For example an architecture might want to pad with a trap instruction to
194 // catch wayward programs. Architectures that do not define a padding value
195 // are padded with zeros.
202 Adddynrel func(*Target, *loader.Loader, *ArchSyms, loader.Sym, loader.Reloc, int) bool
204 // Archreloc is an arch-specific hook that assists in relocation processing
205 // (invoked by 'relocsym'); it handles target-specific relocation tasks.
206 // Here "rel" is the current relocation being examined, "sym" is the symbol
207 // containing the chunk of data to which the relocation applies, and "off"
208 // is the contents of the to-be-relocated data item (from sym.P). Return
209 // value is the appropriately relocated value (to be written back to the
210 // same spot in sym.P), number of external _host_ relocations needed (i.e.
211 // ELF/Mach-O/etc. relocations, not Go relocations, this must match Elfreloc1,
212 // etc.), and a boolean indicating success/failure (a failing value indicates
214 Archreloc func(*Target, *loader.Loader, *ArchSyms, loader.Reloc, loader.Sym,
215 int64) (relocatedOffset int64, nExtReloc int, ok bool)
216 // Archrelocvariant is a second arch-specific hook used for
217 // relocation processing; it handles relocations where r.Type is
218 // insufficient to describe the relocation (r.Variant !=
219 // sym.RV_NONE). Here "rel" is the relocation being applied, "sym"
220 // is the symbol containing the chunk of data to which the
221 // relocation applies, and "off" is the contents of the
222 // to-be-relocated data item (from sym.P). Return is an updated
224 Archrelocvariant func(target *Target, ldr *loader.Loader, rel loader.Reloc,
225 rv sym.RelocVariant, sym loader.Sym, offset int64, data []byte) (relocatedOffset int64)
227 // Generate a trampoline for a call from s to rs if necessary. ri is
228 // index of the relocation.
229 Trampoline func(ctxt *Link, ldr *loader.Loader, ri int, rs, s loader.Sym)
231 // Assembling the binary breaks into two phases, writing the code/data/
232 // dwarf information (which is rather generic), and some more architecture
233 // specific work like setting up the elf headers/dynamic relocations, etc.
234 // The phases are called "Asmb" and "Asmb2". Asmb2 needs to be defined for
235 // every architecture, but only if architecture has an Asmb function will
236 // it be used for assembly. Otherwise a generic assembly Asmb function is
238 Asmb func(*Link, *loader.Loader)
239 Asmb2 func(*Link, *loader.Loader)
241 // Extreloc is an arch-specific hook that converts a Go relocation to an
242 // external relocation. Return the external relocation and whether it is
244 Extreloc func(*Target, *loader.Loader, loader.Reloc, loader.Sym) (loader.ExtReloc, bool)
246 Elfreloc1 func(*Link, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int, int64) bool
247 ElfrelocSize uint32 // size of an ELF relocation record, must match Elfreloc1.
248 Elfsetupplt func(ctxt *Link, plt, gotplt *loader.SymbolBuilder, dynamic loader.Sym)
249 Gentext func(*Link, *loader.Loader) // Generate text before addressing has been performed.
250 Machoreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
251 MachorelocSize uint32 // size of an Mach-O relocation record, must match Machoreloc1.
252 PEreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
253 Xcoffreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
255 // Generate additional symbols for the native symbol table just prior to
257 GenSymsLate func(*Link, *loader.Loader)
259 // TLSIEtoLE converts a TLS Initial Executable relocation to
260 // a TLS Local Executable relocation.
262 // This is possible when a TLS IE relocation refers to a local
263 // symbol in an executable, which is typical when internally
264 // linking PIE binaries.
265 TLSIEtoLE func(P []byte, off, size int)
267 // optional override for assignAddress
268 AssignAddress func(ldr *loader.Loader, sect *sym.Section, n int, s loader.Sym, va uint64, isTramp bool) (*sym.Section, int, uint64)
280 MINFUNC = 16 // minimum size for a function
283 // Symbol version of ABIInternal symbols. It is sym.SymVerABIInternal if ABI wrappers
284 // are used, 0 otherwise.
285 var abiInternalVer = sym.SymVerABIInternal
287 // DynlinkingGo reports whether we are producing Go code that can live
288 // in separate shared libraries linked together at runtime.
289 func (ctxt *Link) DynlinkingGo() bool {
291 panic("DynlinkingGo called before all symbols loaded")
293 return ctxt.BuildMode == BuildModeShared || ctxt.linkShared || ctxt.BuildMode == BuildModePlugin || ctxt.canUsePlugins
296 // CanUsePlugins reports whether a plugins can be used
297 func (ctxt *Link) CanUsePlugins() bool {
299 panic("CanUsePlugins called before all symbols loaded")
301 return ctxt.canUsePlugins
304 // NeedCodeSign reports whether we need to code-sign the output binary.
305 func (ctxt *Link) NeedCodeSign() bool {
306 return ctxt.IsDarwin() && ctxt.IsARM64()
318 debug_s bool // backup old value of debug['s']
322 liveness int64 // size of liveness data (funcdata), printed if -v
324 // See -strictdups command line flag.
325 checkStrictDups int // 0=off 1=warning 2=error
326 strictDupMsgCount int
331 Segrodata sym.Segment
332 Segrelrodata sym.Segment
336 Segments = []*sym.Segment{&Segtext, &Segrodata, &Segrelrodata, &Segdata, &Segdwarf}
339 const pkgdef = "__.PKGDEF"
342 // externalobj is set to true if we see an object compiled by
343 // the host compiler that is not from a package that is known
344 // to support internal linking mode.
347 // dynimportfail is a list of packages for which generating
348 // the dynimport file, _cgo_import.go, failed. If there are
349 // any of these objects, we must link externally. Issue 52863.
350 dynimportfail []string
352 // unknownObjFormat is set to true if we see an object whose
353 // format we don't recognize.
354 unknownObjFormat = false
359 func Lflag(ctxt *Link, arg string) {
360 ctxt.Libdir = append(ctxt.Libdir, arg)
364 * Unix doesn't like it when we write to a running (or, sometimes,
365 * recently run) binary, so remove the output file before writing it.
366 * On Windows 7, remove() can force a subsequent create() to fail.
367 * S_ISREG() does not exist on Plan 9.
369 func mayberemoveoutfile() {
370 if fi, err := os.Lstat(*flagOutfile); err == nil && !fi.Mode().IsRegular() {
373 os.Remove(*flagOutfile)
376 func libinit(ctxt *Link) {
377 Funcalign = thearch.Funcalign
379 // add goroot to the end of the libdir list.
383 if *flagInstallSuffix != "" {
385 suffix = *flagInstallSuffix
386 } else if *flagRace {
389 } else if *flagMsan {
392 } else if *flagAsan {
397 if buildcfg.GOROOT != "" {
398 Lflag(ctxt, filepath.Join(buildcfg.GOROOT, "pkg", fmt.Sprintf("%s_%s%s%s", buildcfg.GOOS, buildcfg.GOARCH, suffixsep, suffix)))
403 if err := ctxt.Out.Open(*flagOutfile); err != nil {
404 Exitf("cannot create %s: %v", *flagOutfile, err)
407 if *flagEntrySymbol == "" {
408 switch ctxt.BuildMode {
409 case BuildModeCShared, BuildModeCArchive:
410 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s_lib", buildcfg.GOARCH, buildcfg.GOOS)
411 case BuildModeExe, BuildModePIE:
412 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s", buildcfg.GOARCH, buildcfg.GOOS)
413 case BuildModeShared, BuildModePlugin:
414 // No *flagEntrySymbol for -buildmode=shared and plugin
416 Errorf(nil, "unknown *flagEntrySymbol for buildmode %v", ctxt.BuildMode)
421 func exitIfErrors() {
422 if nerrors != 0 || checkStrictDups > 1 && strictDupMsgCount > 0 {
434 func loadinternal(ctxt *Link, name string) *sym.Library {
435 zerofp := goobj.FingerprintType{}
436 if ctxt.linkShared && ctxt.PackageShlib != nil {
437 if shlib := ctxt.PackageShlib[name]; shlib != "" {
438 return addlibpath(ctxt, "internal", "internal", "", name, shlib, zerofp)
441 if ctxt.PackageFile != nil {
442 if pname := ctxt.PackageFile[name]; pname != "" {
443 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
445 ctxt.Logf("loadinternal: cannot find %s\n", name)
449 for _, libdir := range ctxt.Libdir {
451 shlibname := filepath.Join(libdir, name+".shlibname")
452 if ctxt.Debugvlog != 0 {
453 ctxt.Logf("searching for %s.a in %s\n", name, shlibname)
455 if _, err := os.Stat(shlibname); err == nil {
456 return addlibpath(ctxt, "internal", "internal", "", name, shlibname, zerofp)
459 pname := filepath.Join(libdir, name+".a")
460 if ctxt.Debugvlog != 0 {
461 ctxt.Logf("searching for %s.a in %s\n", name, pname)
463 if _, err := os.Stat(pname); err == nil {
464 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
468 ctxt.Logf("warning: unable to find %s.a\n", name)
472 // extld returns the current external linker.
473 func (ctxt *Link) extld() []string {
474 if len(flagExtld) == 0 {
475 flagExtld = []string{"gcc"}
480 // findLibPathCmd uses cmd command to find gcc library libname.
481 // It returns library full path if found, or "none" if not found.
482 func (ctxt *Link) findLibPathCmd(cmd, libname string) string {
483 extld := ctxt.extld()
484 name, args := extld[0], extld[1:]
485 args = append(args, hostlinkArchArgs(ctxt.Arch)...)
486 args = append(args, cmd)
487 if ctxt.Debugvlog != 0 {
488 ctxt.Logf("%s %v\n", extld, args)
490 out, err := exec.Command(name, args...).Output()
492 if ctxt.Debugvlog != 0 {
493 ctxt.Logf("not using a %s file because compiler failed\n%v\n%s\n", libname, err, out)
497 return strings.TrimSpace(string(out))
500 // findLibPath searches for library libname.
501 // It returns library full path if found, or "none" if not found.
502 func (ctxt *Link) findLibPath(libname string) string {
503 return ctxt.findLibPathCmd("--print-file-name="+libname, libname)
506 func (ctxt *Link) loadlib() {
508 switch *FlagStrictDups {
512 flags |= loader.FlagStrictDups
514 log.Fatalf("invalid -strictdups flag value %d", *FlagStrictDups)
516 elfsetstring1 := func(str string, off int) { elfsetstring(ctxt, 0, str, off) }
517 ctxt.loader = loader.NewLoader(flags, elfsetstring1, &ctxt.ErrorReporter.ErrorReporter)
518 ctxt.ErrorReporter.SymName = func(s loader.Sym) string {
519 return ctxt.loader.SymName(s)
522 // ctxt.Library grows during the loop, so not a range loop.
524 for ; i < len(ctxt.Library); i++ {
525 lib := ctxt.Library[i]
527 if ctxt.Debugvlog > 1 {
528 ctxt.Logf("autolib: %s (from %s)\n", lib.File, lib.Objref)
530 loadobjfile(ctxt, lib)
534 // load internal packages, if not already
536 loadinternal(ctxt, "runtime/race")
539 loadinternal(ctxt, "runtime/msan")
542 loadinternal(ctxt, "runtime/asan")
544 loadinternal(ctxt, "runtime")
545 for ; i < len(ctxt.Library); i++ {
546 lib := ctxt.Library[i]
548 loadobjfile(ctxt, lib)
551 // At this point, the Go objects are "preloaded". Not all the symbols are
552 // added to the symbol table (only defined package symbols are). Looking
553 // up symbol by name may not get expected result.
555 iscgo = ctxt.LibraryByPkg["runtime/cgo"] != nil
557 // Plugins a require cgo support to function. Similarly, plugins may require additional
558 // internal linker support on some platforms which may not be implemented.
559 ctxt.canUsePlugins = ctxt.LibraryByPkg["plugin"] != nil && iscgo
561 // We now have enough information to determine the link mode.
562 determineLinkMode(ctxt)
564 if ctxt.LinkMode == LinkExternal && !iscgo && !(buildcfg.GOOS == "darwin" && ctxt.BuildMode != BuildModePlugin && ctxt.Arch.Family == sys.AMD64) {
565 // This indicates a user requested -linkmode=external.
566 // The startup code uses an import of runtime/cgo to decide
567 // whether to initialize the TLS. So give it one. This could
568 // be handled differently but it's an unusual case.
569 if lib := loadinternal(ctxt, "runtime/cgo"); lib != nil && lib.Shlib == "" {
570 if ctxt.BuildMode == BuildModeShared || ctxt.linkShared {
571 Exitf("cannot implicitly include runtime/cgo in a shared library")
573 for ; i < len(ctxt.Library); i++ {
574 lib := ctxt.Library[i]
576 loadobjfile(ctxt, lib)
582 // Add non-package symbols and references of externally defined symbols.
583 ctxt.loader.LoadSyms(ctxt.Arch)
585 // Load symbols from shared libraries, after all Go object symbols are loaded.
586 for _, lib := range ctxt.Library {
588 if ctxt.Debugvlog > 1 {
589 ctxt.Logf("autolib: %s (from %s)\n", lib.Shlib, lib.Objref)
591 ldshlibsyms(ctxt, lib.Shlib)
595 // Process cgo directives (has to be done before host object loading).
596 ctxt.loadcgodirectives()
598 // Conditionally load host objects, or setup for external linking.
602 if ctxt.LinkMode == LinkInternal && len(hostobj) != 0 {
603 // If we have any undefined symbols in external
604 // objects, try to read them from the libgcc file.
606 undefs := ctxt.loader.UndefinedRelocTargets(1)
611 if *flagLibGCC == "" {
612 *flagLibGCC = ctxt.findLibPathCmd("--print-libgcc-file-name", "libgcc")
614 if runtime.GOOS == "openbsd" && *flagLibGCC == "libgcc.a" {
615 // On OpenBSD `clang --print-libgcc-file-name` returns "libgcc.a".
616 // In this case we fail to load libgcc.a and can encounter link
617 // errors - see if we can find libcompiler_rt.a instead.
618 *flagLibGCC = ctxt.findLibPathCmd("--print-file-name=libcompiler_rt.a", "libcompiler_rt")
620 if ctxt.HeadType == objabi.Hwindows {
621 loadWindowsHostArchives(ctxt)
623 if *flagLibGCC != "none" {
624 hostArchive(ctxt, *flagLibGCC)
629 // We've loaded all the code now.
634 strictDupMsgCount = ctxt.loader.NStrictDupMsgs()
637 // loadWindowsHostArchives loads in host archives and objects when
638 // doing internal linking on windows. Older toolchains seem to require
639 // just a single pass through the various archives, but some modern
640 // toolchains when linking a C program with mingw pass library paths
641 // multiple times to the linker, e.g. "... -lmingwex -lmingw32 ...
642 // -lmingwex -lmingw32 ...". To accommodate this behavior, we make two
643 // passes over the host archives below.
644 func loadWindowsHostArchives(ctxt *Link) {
646 for i := 0; any && i < 2; i++ {
647 // Link crt2.o (if present) to resolve "atexit" when
648 // using LLVM-based compilers.
649 isunresolved := symbolsAreUnresolved(ctxt, []string{"atexit"})
651 if p := ctxt.findLibPath("crt2.o"); p != "none" {
652 hostObject(ctxt, "crt2", p)
656 if p := ctxt.findLibPath("libsynchronization.a"); p != "none" {
660 if p := ctxt.findLibPath("libmingwex.a"); p != "none" {
663 if p := ctxt.findLibPath("libmingw32.a"); p != "none" {
666 // Link libmsvcrt.a to resolve '__acrt_iob_func' symbol
667 // (see https://golang.org/issue/23649 for details).
668 if p := ctxt.findLibPath("libmsvcrt.a"); p != "none" {
672 undefs := ctxt.loader.UndefinedRelocTargets(1)
677 // If needed, create the __CTOR_LIST__ and __DTOR_LIST__
678 // symbols (referenced by some of the mingw support library
679 // routines). Creation of these symbols is normally done by the
680 // linker if not already present.
681 want := []string{"__CTOR_LIST__", "__DTOR_LIST__"}
682 isunresolved := symbolsAreUnresolved(ctxt, want)
683 for k, w := range want {
685 sb := ctxt.loader.CreateSymForUpdate(w, 0)
686 sb.SetType(sym.SDATA)
687 sb.AddUint64(ctxt.Arch, 0)
688 sb.SetReachable(true)
689 ctxt.loader.SetAttrSpecial(sb.Sym(), true)
692 // TODO: maybe do something similar to peimporteddlls to collect
693 // all lib names and try link them all to final exe just like
694 // libmingwex.a and libmingw32.a:
697 #cgo windows LDFLAGS: -lmsvcrt -lm
703 // loadcgodirectives reads the previously discovered cgo directives, creating
704 // symbols in preparation for host object loading or use later in the link.
705 func (ctxt *Link) loadcgodirectives() {
707 hostObjSyms := make(map[loader.Sym]struct{})
708 for _, d := range ctxt.cgodata {
709 setCgoAttr(ctxt, d.file, d.pkg, d.directives, hostObjSyms)
713 if ctxt.LinkMode == LinkInternal {
714 // Drop all the cgo_import_static declarations.
715 // Turns out we won't be needing them.
716 for symIdx := range hostObjSyms {
717 if l.SymType(symIdx) == sym.SHOSTOBJ {
718 // If a symbol was marked both
719 // cgo_import_static and cgo_import_dynamic,
720 // then we want to make it cgo_import_dynamic
722 su := l.MakeSymbolUpdater(symIdx)
723 if l.SymExtname(symIdx) != "" && l.SymDynimplib(symIdx) != "" && !(l.AttrCgoExportStatic(symIdx) || l.AttrCgoExportDynamic(symIdx)) {
724 su.SetType(sym.SDYNIMPORT)
733 // Set up flags and special symbols depending on the platform build mode.
734 // This version works with loader.Loader.
735 func (ctxt *Link) linksetup() {
736 switch ctxt.BuildMode {
737 case BuildModeCShared, BuildModePlugin:
738 symIdx := ctxt.loader.LookupOrCreateSym("runtime.islibrary", 0)
739 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
740 sb.SetType(sym.SNOPTRDATA)
742 case BuildModeCArchive:
743 symIdx := ctxt.loader.LookupOrCreateSym("runtime.isarchive", 0)
744 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
745 sb.SetType(sym.SNOPTRDATA)
749 // Recalculate pe parameters now that we have ctxt.LinkMode set.
750 if ctxt.HeadType == objabi.Hwindows {
754 if ctxt.LinkMode == LinkExternal {
755 // When external linking, we are creating an object file. The
756 // absolute address is irrelevant.
760 // If there are no dynamic libraries needed, gcc disables dynamic linking.
761 // Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13)
762 // assumes that a dynamic binary always refers to at least one dynamic library.
763 // Rather than be a source of test cases for glibc, disable dynamic linking
764 // the same way that gcc would.
766 // Exception: on OS X, programs such as Shark only work with dynamic
767 // binaries, so leave it enabled on OS X (Mach-O) binaries.
768 // Also leave it enabled on Solaris which doesn't support
769 // statically linked binaries.
770 if ctxt.BuildMode == BuildModeExe {
771 if havedynamic == 0 && ctxt.HeadType != objabi.Hdarwin && ctxt.HeadType != objabi.Hsolaris {
776 if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && buildcfg.GOOS != "aix" {
777 toc := ctxt.loader.LookupOrCreateSym(".TOC.", 0)
778 sb := ctxt.loader.MakeSymbolUpdater(toc)
779 sb.SetType(sym.SDYNIMPORT)
782 // The Android Q linker started to complain about underalignment of the our TLS
783 // section. We don't actually use the section on android, so don't
785 if buildcfg.GOOS != "android" {
786 tlsg := ctxt.loader.LookupOrCreateSym("runtime.tlsg", 0)
787 sb := ctxt.loader.MakeSymbolUpdater(tlsg)
789 // runtime.tlsg is used for external linking on platforms that do not define
790 // a variable to hold g in assembly (currently only intel).
792 sb.SetType(sym.STLSBSS)
793 sb.SetSize(int64(ctxt.Arch.PtrSize))
794 } else if sb.Type() != sym.SDYNIMPORT {
795 Errorf(nil, "runtime declared tlsg variable %v", sb.Type())
797 ctxt.loader.SetAttrReachable(tlsg, true)
801 var moduledata loader.Sym
802 var mdsb *loader.SymbolBuilder
803 if ctxt.BuildMode == BuildModePlugin {
804 moduledata = ctxt.loader.LookupOrCreateSym("local.pluginmoduledata", 0)
805 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
806 ctxt.loader.SetAttrLocal(moduledata, true)
808 moduledata = ctxt.loader.LookupOrCreateSym("runtime.firstmoduledata", 0)
809 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
811 if mdsb.Type() != 0 && mdsb.Type() != sym.SDYNIMPORT {
812 // If the module (toolchain-speak for "executable or shared
813 // library") we are linking contains the runtime package, it
814 // will define the runtime.firstmoduledata symbol and we
815 // truncate it back to 0 bytes so we can define its entire
816 // contents in symtab.go:symtab().
819 // In addition, on ARM, the runtime depends on the linker
820 // recording the value of GOARM.
821 if ctxt.Arch.Family == sys.ARM {
822 goarm := ctxt.loader.LookupOrCreateSym("runtime.goarm", 0)
823 sb := ctxt.loader.MakeSymbolUpdater(goarm)
824 sb.SetType(sym.SDATA)
826 sb.AddUint8(uint8(buildcfg.GOARM))
829 // Set runtime.disableMemoryProfiling bool if
830 // runtime.MemProfile is not retained in the binary after
831 // deadcode (and we're not dynamically linking).
832 memProfile := ctxt.loader.Lookup("runtime.MemProfile", abiInternalVer)
833 if memProfile != 0 && !ctxt.loader.AttrReachable(memProfile) && !ctxt.DynlinkingGo() {
834 memProfSym := ctxt.loader.LookupOrCreateSym("runtime.disableMemoryProfiling", 0)
835 sb := ctxt.loader.MakeSymbolUpdater(memProfSym)
836 sb.SetType(sym.SDATA)
838 sb.AddUint8(1) // true bool
841 // If OTOH the module does not contain the runtime package,
842 // create a local symbol for the moduledata.
843 moduledata = ctxt.loader.LookupOrCreateSym("local.moduledata", 0)
844 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
845 ctxt.loader.SetAttrLocal(moduledata, true)
847 // In all cases way we mark the moduledata as noptrdata to hide it from
849 mdsb.SetType(sym.SNOPTRDATA)
850 ctxt.loader.SetAttrReachable(moduledata, true)
851 ctxt.Moduledata = moduledata
853 if ctxt.Arch == sys.Arch386 && ctxt.HeadType != objabi.Hwindows {
854 if (ctxt.BuildMode == BuildModeCArchive && ctxt.IsELF) || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE || ctxt.DynlinkingGo() {
855 got := ctxt.loader.LookupOrCreateSym("_GLOBAL_OFFSET_TABLE_", 0)
856 sb := ctxt.loader.MakeSymbolUpdater(got)
857 sb.SetType(sym.SDYNIMPORT)
858 ctxt.loader.SetAttrReachable(got, true)
862 // DWARF-gen and other phases require that the unit Textp slices
863 // be populated, so that it can walk the functions in each unit.
864 // Call into the loader to do this (requires that we collect the
865 // set of internal libraries first). NB: might be simpler if we
866 // moved isRuntimeDepPkg to cmd/internal and then did the test in
867 // loader.AssignTextSymbolOrder.
868 ctxt.Library = postorder(ctxt.Library)
870 for _, lib := range ctxt.Library {
871 intlibs = append(intlibs, isRuntimeDepPkg(lib.Pkg))
873 ctxt.Textp = ctxt.loader.AssignTextSymbolOrder(ctxt.Library, intlibs, ctxt.Textp)
876 // mangleTypeSym shortens the names of symbols that represent Go types
877 // if they are visible in the symbol table.
879 // As the names of these symbols are derived from the string of
880 // the type, they can run to many kilobytes long. So we shorten
881 // them using a SHA-1 when the name appears in the final binary.
882 // This also removes characters that upset external linkers.
884 // These are the symbols that begin with the prefix 'type.' and
885 // contain run-time type information used by the runtime and reflect
886 // packages. All Go binaries contain these symbols, but only
887 // those programs loaded dynamically in multiple parts need these
888 // symbols to have entries in the symbol table.
889 func (ctxt *Link) mangleTypeSym() {
890 if ctxt.BuildMode != BuildModeShared && !ctxt.linkShared && ctxt.BuildMode != BuildModePlugin && !ctxt.CanUsePlugins() {
895 for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
896 if !ldr.AttrReachable(s) && !ctxt.linkShared {
897 // If -linkshared, the GCProg generation code may need to reach
898 // out to the shared library for the type descriptor's data, even
899 // the type descriptor itself is not actually needed at run time
900 // (therefore not reachable). We still need to mangle its name,
901 // so it is consistent with the one stored in the shared library.
904 name := ldr.SymName(s)
905 newName := typeSymbolMangle(name)
907 ldr.SetSymExtname(s, newName)
909 // When linking against a shared library, the Go object file may
910 // have reference to the original symbol name whereas the shared
911 // library provides a symbol with the mangled name. We need to
912 // copy the payload of mangled to original.
913 // XXX maybe there is a better way to do this.
914 dup := ldr.Lookup(newName, ldr.SymVersion(s))
917 dt := ldr.SymType(dup)
918 if st == sym.Sxxx && dt != sym.Sxxx {
926 // typeSymbolMangle mangles the given symbol name into something shorter.
928 // Keep the type.. prefix, which parts of the linker (like the
929 // DWARF generator) know means the symbol is not decodable.
930 // Leave type.runtime. symbols alone, because other parts of
931 // the linker manipulates them.
932 func typeSymbolMangle(name string) string {
933 if !strings.HasPrefix(name, "type.") {
936 if strings.HasPrefix(name, "type.runtime.") {
939 if len(name) <= 14 && !strings.Contains(name, "@") { // Issue 19529
942 hash := notsha256.Sum256([]byte(name))
947 return prefix + base64.StdEncoding.EncodeToString(hash[:6])
951 * look for the next file in an archive.
952 * adapted from libmach.
954 func nextar(bp *bio.Reader, off int64, a *ArHdr) int64 {
959 var buf [SAR_HDR]byte
960 if n, err := io.ReadFull(bp, buf[:]); err != nil {
961 if n == 0 && err != io.EOF {
967 a.name = artrim(buf[0:16])
968 a.date = artrim(buf[16:28])
969 a.uid = artrim(buf[28:34])
970 a.gid = artrim(buf[34:40])
971 a.mode = artrim(buf[40:48])
972 a.size = artrim(buf[48:58])
973 a.fmag = artrim(buf[58:60])
975 arsize := atolwhex(a.size)
979 return arsize + SAR_HDR
982 func loadobjfile(ctxt *Link, lib *sym.Library) {
983 pkg := objabi.PathToPrefix(lib.Pkg)
985 if ctxt.Debugvlog > 1 {
986 ctxt.Logf("ldobj: %s (%s)\n", lib.File, pkg)
988 f, err := bio.Open(lib.File)
990 Exitf("cannot open file %s: %v", lib.File, err)
994 if pkg == "main" && !lib.Main {
995 Exitf("%s: not package main", lib.File)
999 for i := 0; i < len(ARMAG); i++ {
1000 if c, err := f.ReadByte(); err == nil && c == ARMAG[i] {
1004 /* load it as a regular file */
1005 l := f.MustSeek(0, 2)
1007 ldobj(ctxt, f, lib, l, lib.File, lib.File)
1012 * load all the object files from the archive now.
1013 * this gives us sequential file access and keeps us
1014 * from needing to come back later to pick up more
1015 * objects. it breaks the usual C archive model, but
1016 * this is Go, not C. the common case in Go is that
1017 * we need to load all the objects, and then we throw away
1018 * the individual symbols that are unused.
1020 * loading every object will also make it possible to
1021 * load foreign objects not referenced by __.PKGDEF.
1026 l := nextar(f, off, &arhdr)
1031 Exitf("%s: malformed archive", lib.File)
1035 // __.PKGDEF isn't a real Go object file, and it's
1036 // absent in -linkobj builds anyway. Skipping it
1037 // ensures consistency between -linkobj and normal
1039 if arhdr.name == pkgdef {
1043 if arhdr.name == "dynimportfail" {
1044 dynimportfail = append(dynimportfail, lib.Pkg)
1047 // Skip other special (non-object-file) sections that
1048 // build tools may have added. Such sections must have
1049 // short names so that the suffix is not truncated.
1050 if len(arhdr.name) < 16 {
1051 if ext := filepath.Ext(arhdr.name); ext != ".o" && ext != ".syso" {
1056 pname := fmt.Sprintf("%s(%s)", lib.File, arhdr.name)
1057 l = atolwhex(arhdr.size)
1058 ldobj(ctxt, f, lib, l, pname, lib.File)
1062 type Hostobj struct {
1063 ld func(*Link, *bio.Reader, string, int64, string)
1071 var hostobj []Hostobj
1073 // These packages can use internal linking mode.
1074 // Others trigger external mode.
1075 var internalpkg = []string{
1076 "crypto/internal/boring",
1077 "crypto/internal/boring/syso",
1087 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 {
1089 for _, intpkg := range internalpkg {
1096 // DragonFly declares errno with __thread, which results in a symbol
1097 // type of R_386_TLS_GD or R_X86_64_TLSGD. The Go linker does not
1098 // currently know how to handle TLS relocations, hence we have to
1099 // force external linking for any libraries that link in code that
1100 // uses errno. This can be removed if the Go linker ever supports
1101 // these relocation types.
1102 if headType == objabi.Hdragonfly {
1103 if pkg == "net" || pkg == "os/user" {
1112 hostobj = append(hostobj, Hostobj{})
1113 h := &hostobj[len(hostobj)-1]
1123 func hostobjs(ctxt *Link) {
1124 if ctxt.LinkMode != LinkInternal {
1129 for i := 0; i < len(hostobj); i++ {
1131 f, err := bio.Open(h.file)
1133 Exitf("cannot reopen %s: %v", h.pn, err)
1136 f.MustSeek(h.off, 0)
1138 Errorf(nil, "%s: unrecognized object file format", h.pn)
1141 h.ld(ctxt, f, h.pkg, h.length, h.pn)
1146 func hostlinksetup(ctxt *Link) {
1147 if ctxt.LinkMode != LinkExternal {
1151 // For external link, record that we need to tell the external linker -s,
1152 // and turn off -s internally: the external linker needs the symbol
1153 // information for its final link.
1157 // create temporary directory and arrange cleanup
1158 if *flagTmpdir == "" {
1159 dir, err := ioutil.TempDir("", "go-link-")
1166 os.RemoveAll(*flagTmpdir)
1170 // change our output to temporary object file
1171 if err := ctxt.Out.Close(); err != nil {
1172 Exitf("error closing output file")
1174 mayberemoveoutfile()
1176 p := filepath.Join(*flagTmpdir, "go.o")
1177 if err := ctxt.Out.Open(p); err != nil {
1178 Exitf("cannot create %s: %v", p, err)
1182 // hostobjCopy creates a copy of the object files in hostobj in a
1183 // temporary directory.
1184 func hostobjCopy() (paths []string) {
1185 var wg sync.WaitGroup
1186 sema := make(chan struct{}, runtime.NumCPU()) // limit open file descriptors
1187 for i, h := range hostobj {
1189 dst := filepath.Join(*flagTmpdir, fmt.Sprintf("%06d.o", i))
1190 paths = append(paths, dst)
1199 f, err := os.Open(h.file)
1201 Exitf("cannot reopen %s: %v", h.pn, err)
1204 if _, err := f.Seek(h.off, 0); err != nil {
1205 Exitf("cannot seek %s: %v", h.pn, err)
1208 w, err := os.Create(dst)
1210 Exitf("cannot create %s: %v", dst, err)
1212 if _, err := io.CopyN(w, f, h.length); err != nil {
1213 Exitf("cannot write %s: %v", dst, err)
1215 if err := w.Close(); err != nil {
1216 Exitf("cannot close %s: %v", dst, err)
1224 // writeGDBLinkerScript creates gcc linker script file in temp
1225 // directory. writeGDBLinkerScript returns created file path.
1226 // The script is used to work around gcc bug
1227 // (see https://golang.org/issue/20183 for details).
1228 func writeGDBLinkerScript() string {
1229 name := "fix_debug_gdb_scripts.ld"
1230 path := filepath.Join(*flagTmpdir, name)
1233 .debug_gdb_scripts BLOCK(__section_alignment__) (NOLOAD) :
1235 *(.debug_gdb_scripts)
1238 INSERT AFTER .debug_types;
1240 err := ioutil.WriteFile(path, []byte(src), 0666)
1242 Errorf(nil, "WriteFile %s failed: %v", name, err)
1247 // archive builds a .a archive from the hostobj object files.
1248 func (ctxt *Link) archive() {
1249 if ctxt.BuildMode != BuildModeCArchive {
1255 if *flagExtar == "" {
1259 mayberemoveoutfile()
1261 // Force the buffer to flush here so that external
1262 // tools will see a complete file.
1263 if err := ctxt.Out.Close(); err != nil {
1264 Exitf("error closing %v", *flagOutfile)
1267 argv := []string{*flagExtar, "-q", "-c", "-s"}
1268 if ctxt.HeadType == objabi.Haix {
1269 argv = append(argv, "-X64")
1271 argv = append(argv, *flagOutfile)
1272 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1273 argv = append(argv, hostobjCopy()...)
1275 if ctxt.Debugvlog != 0 {
1276 ctxt.Logf("archive: %s\n", strings.Join(argv, " "))
1279 // If supported, use syscall.Exec() to invoke the archive command,
1280 // which should be the final remaining step needed for the link.
1281 // This will reduce peak RSS for the link (and speed up linking of
1282 // large applications), since when the archive command runs we
1283 // won't be holding onto all of the linker's live memory.
1284 if syscallExecSupported && !ownTmpDir {
1286 ctxt.execArchive(argv)
1287 panic("should not get here")
1290 // Otherwise invoke 'ar' in the usual way (fork + exec).
1291 if out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput(); err != nil {
1292 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1296 func (ctxt *Link) hostlink() {
1297 if ctxt.LinkMode != LinkExternal || nerrors > 0 {
1300 if ctxt.BuildMode == BuildModeCArchive {
1305 argv = append(argv, ctxt.extld()...)
1306 argv = append(argv, hostlinkArchArgs(ctxt.Arch)...)
1308 if *FlagS || debug_s {
1309 if ctxt.HeadType == objabi.Hdarwin {
1310 // Recent versions of macOS print
1311 // ld: warning: option -s is obsolete and being ignored
1312 // so do not pass any arguments.
1314 argv = append(argv, "-s")
1318 // On darwin, whether to combine DWARF into executable.
1319 // Only macOS supports unmapped segments such as our __DWARF segment.
1320 combineDwarf := ctxt.IsDarwin() && !*FlagS && !*FlagW && !debug_s && machoPlatform == PLATFORM_MACOS
1322 switch ctxt.HeadType {
1323 case objabi.Hdarwin:
1325 // Leave room for DWARF combining.
1326 // -headerpad is incompatible with -fembed-bitcode.
1327 argv = append(argv, "-Wl,-headerpad,1144")
1329 if ctxt.DynlinkingGo() && buildcfg.GOOS != "ios" {
1330 // -flat_namespace is deprecated on iOS.
1331 // It is useful for supporting plugins. We don't support plugins on iOS.
1332 // -flat_namespace may cause the dynamic linker to hang at forkExec when
1333 // resolving a lazy binding. See issue 38824.
1334 // Force eager resolution to work around.
1335 argv = append(argv, "-Wl,-flat_namespace", "-Wl,-bind_at_load")
1338 argv = append(argv, "-Wl,-S") // suppress STAB (symbolic debugging) symbols
1340 case objabi.Hopenbsd:
1341 argv = append(argv, "-Wl,-nopie")
1342 argv = append(argv, "-pthread")
1343 case objabi.Hwindows:
1345 argv = append(argv, "-mwindows")
1347 argv = append(argv, "-mconsole")
1349 // Mark as having awareness of terminal services, to avoid
1350 // ancient compatibility hacks.
1351 argv = append(argv, "-Wl,--tsaware")
1354 argv = append(argv, "-Wl,--nxcompat")
1356 argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", PeMinimumTargetMajorVersion))
1357 argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", PeMinimumTargetMinorVersion))
1358 argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", PeMinimumTargetMajorVersion))
1359 argv = append(argv, fmt.Sprintf("-Wl,--minor-subsystem-version=%d", PeMinimumTargetMinorVersion))
1361 argv = append(argv, "-pthread")
1362 // prevent ld to reorder .text functions to keep the same
1363 // first/last functions for moduledata.
1364 argv = append(argv, "-Wl,-bnoobjreorder")
1365 // mcmodel=large is needed for every gcc generated files, but
1366 // ld still need -bbigtoc in order to allow larger TOC.
1367 argv = append(argv, "-mcmodel=large")
1368 argv = append(argv, "-Wl,-bbigtoc")
1371 // Enable/disable ASLR on Windows.
1372 addASLRargs := func(argv []string, val bool) []string {
1373 // Old/ancient versions of GCC support "--dynamicbase" and
1374 // "--high-entropy-va" but don't enable it by default. In
1375 // addition, they don't accept "--disable-dynamicbase" or
1376 // "--no-dynamicbase", so the only way to disable ASLR is to
1377 // not pass any flags at all.
1379 // More modern versions of GCC (and also clang) enable ASLR
1380 // by default. With these compilers, however you can turn it
1381 // off if you want using "--disable-dynamicbase" or
1382 // "--no-dynamicbase".
1384 // The strategy below is to try using "--disable-dynamicbase";
1385 // if this succeeds, then assume we're working with more
1386 // modern compilers and act accordingly. If it fails, assume
1387 // an ancient compiler with ancient defaults.
1390 dbon := "--dynamicbase"
1391 heon := "--high-entropy-va"
1392 dboff := "--disable-dynamicbase"
1393 heoff := "--disable-high-entropy-va"
1398 // Test to see whether "--disable-dynamicbase" works.
1399 newer := linkerFlagSupported(ctxt.Arch, argv[0], "", "-Wl,"+dboff)
1401 // Newer compiler, which supports both on/off options.
1405 // older toolchain: we have to say nothing in order to
1406 // get a no-ASLR binary.
1412 argv = append(argv, "-Wl,"+dbopt)
1414 // enable high-entropy ASLR on 64-bit.
1415 if ctxt.Arch.PtrSize >= 8 && heopt != "" {
1416 argv = append(argv, "-Wl,"+heopt)
1421 switch ctxt.BuildMode {
1423 if ctxt.HeadType == objabi.Hdarwin {
1424 if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() {
1425 argv = append(argv, "-Wl,-no_pie")
1426 argv = append(argv, "-Wl,-pagezero_size,4000000")
1430 switch ctxt.HeadType {
1431 case objabi.Hdarwin, objabi.Haix:
1432 case objabi.Hwindows:
1433 argv = addASLRargs(argv, *flagAslr)
1436 if ctxt.UseRelro() {
1437 argv = append(argv, "-Wl,-z,relro")
1439 argv = append(argv, "-pie")
1441 case BuildModeCShared:
1442 if ctxt.HeadType == objabi.Hdarwin {
1443 argv = append(argv, "-dynamiclib")
1445 if ctxt.UseRelro() {
1446 argv = append(argv, "-Wl,-z,relro")
1448 argv = append(argv, "-shared")
1449 if ctxt.HeadType == objabi.Hwindows {
1450 argv = addASLRargs(argv, *flagAslr)
1452 // Pass -z nodelete to mark the shared library as
1453 // non-closeable: a dlclose will do nothing.
1454 argv = append(argv, "-Wl,-z,nodelete")
1455 // Only pass Bsymbolic on non-Windows.
1456 argv = append(argv, "-Wl,-Bsymbolic")
1459 case BuildModeShared:
1460 if ctxt.UseRelro() {
1461 argv = append(argv, "-Wl,-z,relro")
1463 argv = append(argv, "-shared")
1464 case BuildModePlugin:
1465 if ctxt.HeadType == objabi.Hdarwin {
1466 argv = append(argv, "-dynamiclib")
1468 if ctxt.UseRelro() {
1469 argv = append(argv, "-Wl,-z,relro")
1471 argv = append(argv, "-shared")
1475 var altLinker string
1476 if ctxt.IsELF && ctxt.DynlinkingGo() {
1477 // We force all symbol resolution to be done at program startup
1478 // because lazy PLT resolution can use large amounts of stack at
1479 // times we cannot allow it to do so.
1480 argv = append(argv, "-Wl,-z,now")
1482 // Do not let the host linker generate COPY relocations. These
1483 // can move symbols out of sections that rely on stable offsets
1484 // from the beginning of the section (like sym.STYPE).
1485 argv = append(argv, "-Wl,-z,nocopyreloc")
1487 if buildcfg.GOOS == "android" {
1488 // Use lld to avoid errors from default linker (issue #38838)
1492 if ctxt.Arch.InFamily(sys.ARM, sys.ARM64) && buildcfg.GOOS == "linux" {
1493 // On ARM, the GNU linker will generate COPY relocations
1494 // even with -znocopyreloc set.
1495 // https://sourceware.org/bugzilla/show_bug.cgi?id=19962
1497 // On ARM64, the GNU linker will fail instead of
1498 // generating COPY relocations.
1500 // In both cases, switch to gold.
1503 // If gold is not installed, gcc will silently switch
1504 // back to ld.bfd. So we parse the version information
1505 // and provide a useful error if gold is missing.
1506 name, args := flagExtld[0], flagExtld[1:]
1507 args = append(args, "-fuse-ld=gold", "-Wl,--version")
1508 cmd := exec.Command(name, args...)
1509 if out, err := cmd.CombinedOutput(); err == nil {
1510 if !bytes.Contains(out, []byte("GNU gold")) {
1511 log.Fatalf("ARM external linker must be gold (issue #15696), but is not: %s", out)
1516 if ctxt.Arch.Family == sys.ARM64 && buildcfg.GOOS == "freebsd" {
1517 // Switch to ld.bfd on freebsd/arm64.
1520 // Provide a useful error if ld.bfd is missing.
1521 name, args := flagExtld[0], flagExtld[1:]
1522 args = append(args, "-fuse-ld=bfd", "-Wl,--version")
1523 cmd := exec.Command(name, args...)
1524 if out, err := cmd.CombinedOutput(); err == nil {
1525 if !bytes.Contains(out, []byte("GNU ld")) {
1526 log.Fatalf("ARM64 external linker must be ld.bfd (issue #35197), please install devel/binutils")
1530 if altLinker != "" {
1531 argv = append(argv, "-fuse-ld="+altLinker)
1534 if ctxt.IsELF && len(buildinfo) > 0 {
1535 argv = append(argv, fmt.Sprintf("-Wl,--build-id=0x%x", buildinfo))
1538 // On Windows, given -o foo, GCC will append ".exe" to produce
1539 // "foo.exe". We have decided that we want to honor the -o
1540 // option. To make this work, we append a '.' so that GCC
1541 // will decide that the file already has an extension. We
1542 // only want to do this when producing a Windows output file
1543 // on a Windows host.
1544 outopt := *flagOutfile
1545 if buildcfg.GOOS == "windows" && runtime.GOOS == "windows" && filepath.Ext(outopt) == "" {
1548 argv = append(argv, "-o")
1549 argv = append(argv, outopt)
1551 if rpath.val != "" {
1552 argv = append(argv, fmt.Sprintf("-Wl,-rpath,%s", rpath.val))
1555 if *flagInterpreter != "" {
1556 // Many linkers support both -I and the --dynamic-linker flags
1557 // to set the ELF interpreter, but lld only supports
1558 // --dynamic-linker so prefer that (ld on very old Solaris only
1559 // supports -I but that seems less important).
1560 argv = append(argv, fmt.Sprintf("-Wl,--dynamic-linker,%s", *flagInterpreter))
1563 // Force global symbols to be exported for dlopen, etc.
1565 argv = append(argv, "-rdynamic")
1567 if ctxt.HeadType == objabi.Haix {
1568 fileName := xcoffCreateExportFile(ctxt)
1569 argv = append(argv, "-Wl,-bE:"+fileName)
1572 const unusedArguments = "-Qunused-arguments"
1573 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, unusedArguments) {
1574 argv = append(argv, unusedArguments)
1577 const compressDWARF = "-Wl,--compress-debug-sections=zlib"
1578 if ctxt.compressDWARF && linkerFlagSupported(ctxt.Arch, argv[0], altLinker, compressDWARF) {
1579 argv = append(argv, compressDWARF)
1582 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1583 argv = append(argv, hostobjCopy()...)
1584 if ctxt.HeadType == objabi.Haix {
1585 // We want to have C files after Go files to remove
1586 // trampolines csects made by ld.
1587 argv = append(argv, "-nostartfiles")
1588 argv = append(argv, "/lib/crt0_64.o")
1590 extld := ctxt.extld()
1591 name, args := extld[0], extld[1:]
1592 // Get starting files.
1593 getPathFile := func(file string) string {
1594 args := append(args, "-maix64", "--print-file-name="+file)
1595 out, err := exec.Command(name, args...).CombinedOutput()
1597 log.Fatalf("running %s failed: %v\n%s", extld, err, out)
1599 return strings.Trim(string(out), "\n")
1601 // Since GCC version 11, the 64-bit version of GCC starting files
1602 // are now suffixed by "_64". Even under "-maix64" multilib directory
1603 // "crtcxa.o" is 32-bit.
1604 crtcxa := getPathFile("crtcxa_64.o")
1605 if !filepath.IsAbs(crtcxa) {
1606 crtcxa = getPathFile("crtcxa.o")
1608 crtdbase := getPathFile("crtdbase_64.o")
1609 if !filepath.IsAbs(crtdbase) {
1610 crtdbase = getPathFile("crtdbase.o")
1612 argv = append(argv, crtcxa)
1613 argv = append(argv, crtdbase)
1616 if ctxt.linkShared {
1617 seenDirs := make(map[string]bool)
1618 seenLibs := make(map[string]bool)
1619 addshlib := func(path string) {
1620 dir, base := filepath.Split(path)
1622 argv = append(argv, "-L"+dir)
1624 argv = append(argv, "-Wl,-rpath="+dir)
1626 seenDirs[dir] = true
1628 base = strings.TrimSuffix(base, ".so")
1629 base = strings.TrimPrefix(base, "lib")
1630 if !seenLibs[base] {
1631 argv = append(argv, "-l"+base)
1632 seenLibs[base] = true
1635 for _, shlib := range ctxt.Shlibs {
1636 addshlib(shlib.Path)
1637 for _, dep := range shlib.Deps {
1641 libpath := findshlib(ctxt, dep)
1649 // clang, unlike GCC, passes -rdynamic to the linker
1650 // even when linking with -static, causing a linker
1651 // error when using GNU ld. So take out -rdynamic if
1652 // we added it. We do it in this order, rather than
1653 // only adding -rdynamic later, so that -extldflags
1654 // can override -rdynamic without using -static.
1655 // Similarly for -Wl,--dynamic-linker.
1656 checkStatic := func(arg string) {
1657 if ctxt.IsELF && arg == "-static" {
1658 for i := range argv {
1659 if argv[i] == "-rdynamic" || strings.HasPrefix(argv[i], "-Wl,--dynamic-linker,") {
1666 for _, p := range ldflag {
1667 argv = append(argv, p)
1671 // When building a program with the default -buildmode=exe the
1672 // gc compiler generates code requires DT_TEXTREL in a
1673 // position independent executable (PIE). On systems where the
1674 // toolchain creates PIEs by default, and where DT_TEXTREL
1675 // does not work, the resulting programs will not run. See
1676 // issue #17847. To avoid this problem pass -no-pie to the
1677 // toolchain if it is supported.
1678 if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared && !(ctxt.IsDarwin() && ctxt.IsARM64()) {
1679 // GCC uses -no-pie, clang uses -nopie.
1680 for _, nopie := range []string{"-no-pie", "-nopie"} {
1681 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, nopie) {
1682 argv = append(argv, nopie)
1688 for _, p := range flagExtldflags {
1689 argv = append(argv, p)
1692 if ctxt.HeadType == objabi.Hwindows {
1693 // Determine which linker we're using. Add in the extldflags in
1694 // case used has specified "-fuse-ld=...".
1695 extld := ctxt.extld()
1696 name, args := extld[0], extld[1:]
1697 args = append(args, flagExtldflags...)
1698 args = append(args, "-Wl,--version")
1699 cmd := exec.Command(name, args...)
1701 if out, err := cmd.CombinedOutput(); err == nil {
1702 if bytes.Contains(out, []byte("LLD ")) {
1707 // use gcc linker script to work around gcc bug
1708 // (see https://golang.org/issue/20183 for details).
1710 p := writeGDBLinkerScript()
1711 argv = append(argv, "-Wl,-T,"+p)
1714 if p := ctxt.findLibPath("libsynchronization.a"); p != "libsynchronization.a" {
1715 argv = append(argv, "-lsynchronization")
1718 // libmingw32 and libmingwex have some inter-dependencies,
1719 // so must use linker groups.
1720 argv = append(argv, "-Wl,--start-group", "-lmingwex", "-lmingw32", "-Wl,--end-group")
1721 argv = append(argv, peimporteddlls()...)
1724 if ctxt.Debugvlog != 0 {
1725 ctxt.Logf("host link:")
1726 for _, v := range argv {
1732 out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput()
1734 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1737 // Filter out useless linker warnings caused by bugs outside Go.
1738 // See also cmd/go/internal/work/exec.go's gccld method.
1741 for _, line := range bytes.SplitAfter(out, []byte("\n")) {
1742 // golang.org/issue/26073 - Apple Xcode bug
1743 if bytes.Contains(line, []byte("ld: warning: text-based stub file")) {
1752 // Remove TOC overflow warning on AIX.
1753 if bytes.Contains(line, []byte("ld: 0711-783")) {
1758 save = append(save, line)
1760 out = bytes.Join(save, nil)
1763 // always print external output even if the command is successful, so that we don't
1764 // swallow linker warnings (see https://golang.org/issue/17935).
1765 ctxt.Logf("%s", out)
1769 // Find "dsymutils" and "strip" tools using CC --print-prog-name.
1771 cc = append(cc, ctxt.extld()...)
1772 cc = append(cc, hostlinkArchArgs(ctxt.Arch)...)
1773 cc = append(cc, "--print-prog-name", "dsymutil")
1774 out, err := exec.Command(cc[0], cc[1:]...).CombinedOutput()
1776 Exitf("%s: finding dsymutil failed: %v\n%s", os.Args[0], err, out)
1778 dsymutilCmd := strings.TrimSuffix(string(out), "\n")
1780 cc[len(cc)-1] = "strip"
1781 out, err = exec.Command(cc[0], cc[1:]...).CombinedOutput()
1783 Exitf("%s: finding strip failed: %v\n%s", os.Args[0], err, out)
1785 stripCmd := strings.TrimSuffix(string(out), "\n")
1787 dsym := filepath.Join(*flagTmpdir, "go.dwarf")
1788 if out, err := exec.Command(dsymutilCmd, "-f", *flagOutfile, "-o", dsym).CombinedOutput(); err != nil {
1789 Exitf("%s: running dsymutil failed: %v\n%s", os.Args[0], err, out)
1791 // Remove STAB (symbolic debugging) symbols after we are done with them (by dsymutil).
1792 // They contain temporary file paths and make the build not reproducible.
1793 if out, err := exec.Command(stripCmd, "-S", *flagOutfile).CombinedOutput(); err != nil {
1794 Exitf("%s: running strip failed: %v\n%s", os.Args[0], err, out)
1796 // Skip combining if `dsymutil` didn't generate a file. See #11994.
1797 if _, err := os.Stat(dsym); os.IsNotExist(err) {
1800 // For os.Rename to work reliably, must be in same directory as outfile.
1801 combinedOutput := *flagOutfile + "~"
1802 exef, err := os.Open(*flagOutfile)
1804 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1807 exem, err := macho.NewFile(exef)
1809 Exitf("%s: parsing Mach-O header failed: %v", os.Args[0], err)
1811 if err := machoCombineDwarf(ctxt, exef, exem, dsym, combinedOutput); err != nil {
1812 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1814 os.Remove(*flagOutfile)
1815 if err := os.Rename(combinedOutput, *flagOutfile); err != nil {
1816 Exitf("%s: %v", os.Args[0], err)
1819 if ctxt.NeedCodeSign() {
1820 err := machoCodeSign(ctxt, *flagOutfile)
1822 Exitf("%s: code signing failed: %v", os.Args[0], err)
1827 var createTrivialCOnce sync.Once
1829 func linkerFlagSupported(arch *sys.Arch, linker, altLinker, flag string) bool {
1830 createTrivialCOnce.Do(func() {
1831 src := filepath.Join(*flagTmpdir, "trivial.c")
1832 if err := ioutil.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
1833 Errorf(nil, "WriteFile trivial.c failed: %v", err)
1837 flagsWithNextArgSkip := []string{
1846 flagsWithNextArgKeep := []string{
1852 prefixesToKeep := []string{
1863 flags := hostlinkArchArgs(arch)
1866 for _, f := range append(flagExtldflags, ldflag...) {
1868 flags = append(flags, f)
1872 } else if f == "" || f[0] != '-' {
1873 } else if contains(flagsWithNextArgSkip, f) {
1875 } else if contains(flagsWithNextArgKeep, f) {
1876 flags = append(flags, f)
1879 for _, p := range prefixesToKeep {
1880 if strings.HasPrefix(f, p) {
1881 flags = append(flags, f)
1888 if altLinker != "" {
1889 flags = append(flags, "-fuse-ld="+altLinker)
1891 flags = append(flags, flag, "trivial.c")
1893 cmd := exec.Command(linker, flags...)
1894 cmd.Dir = *flagTmpdir
1895 cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
1896 out, err := cmd.CombinedOutput()
1897 // GCC says "unrecognized command line option ‘-no-pie’"
1898 // clang says "unknown argument: '-no-pie'"
1899 return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
1902 // hostlinkArchArgs returns arguments to pass to the external linker
1903 // based on the architecture.
1904 func hostlinkArchArgs(arch *sys.Arch) []string {
1905 switch arch.Family {
1907 return []string{"-m32"}
1909 if buildcfg.GOOS == "darwin" {
1910 return []string{"-arch", "x86_64", "-m64"}
1912 return []string{"-m64"}
1914 return []string{"-m64"}
1916 return []string{"-marm"}
1918 if buildcfg.GOOS == "darwin" {
1919 return []string{"-arch", "arm64"}
1922 return []string{"-mabi=lp64d"}
1924 return []string{"-mabi=64"}
1926 return []string{"-mabi=32"}
1928 if buildcfg.GOOS == "aix" {
1929 return []string{"-maix64"}
1931 return []string{"-m64"}
1938 var wantHdr = objabi.HeaderString()
1940 // ldobj loads an input object. If it is a host object (an object
1941 // compiled by a non-Go compiler) it returns the Hostobj pointer. If
1942 // it is a Go object, it returns nil.
1943 func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string, file string) *Hostobj {
1944 pkg := objabi.PathToPrefix(lib.Pkg)
1946 eof := f.Offset() + length
1952 f.MustSeek(start, 0)
1954 unit := &sym.CompilationUnit{Lib: lib}
1955 lib.Units = append(lib.Units, unit)
1957 magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
1958 if magic == 0x7f454c46 { // \x7F E L F
1959 ldelf := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1960 textp, flags, err := loadelf.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn, ehdr.Flags)
1962 Errorf(nil, "%v", err)
1966 ctxt.Textp = append(ctxt.Textp, textp...)
1968 return ldhostobj(ldelf, ctxt.HeadType, f, pkg, length, pn, file)
1971 if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
1972 ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1973 textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1975 Errorf(nil, "%v", err)
1978 ctxt.Textp = append(ctxt.Textp, textp...)
1980 return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
1988 ldpe := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1989 textp, rsrc, err := loadpe.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1991 Errorf(nil, "%v", err)
1995 setpersrc(ctxt, rsrc)
1997 ctxt.Textp = append(ctxt.Textp, textp...)
1999 return ldhostobj(ldpe, ctxt.HeadType, f, pkg, length, pn, file)
2002 if c1 == 0x01 && (c2 == 0xD7 || c2 == 0xF7) {
2003 ldxcoff := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2004 textp, err := loadxcoff.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2006 Errorf(nil, "%v", err)
2009 ctxt.Textp = append(ctxt.Textp, textp...)
2011 return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
2014 if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
2015 // An unrecognized object is just passed to the external linker.
2016 // If we try to read symbols from this object, we will
2017 // report an error at that time.
2018 unknownObjFormat = true
2019 return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
2022 /* check the header */
2023 line, err := f.ReadString('\n')
2025 Errorf(nil, "truncated object file: %s: %v", pn, err)
2029 if !strings.HasPrefix(line, "go object ") {
2030 if strings.HasSuffix(pn, ".go") {
2031 Exitf("%s: uncompiled .go source file", pn)
2035 if line == ctxt.Arch.Name {
2036 // old header format: just $GOOS
2037 Errorf(nil, "%s: stale object file", pn)
2041 Errorf(nil, "%s: not an object file: @%d %q", pn, start, line)
2045 // First, check that the basic GOOS, GOARCH, and Version match.
2046 if line != wantHdr {
2047 Errorf(nil, "%s: linked object header mismatch:\nhave %q\nwant %q\n", pn, line, wantHdr)
2050 // Skip over exports and other info -- ends with \n!\n.
2052 // Note: It's possible for "\n!\n" to appear within the binary
2053 // package export data format. To avoid truncating the package
2054 // definition prematurely (issue 21703), we keep track of
2055 // how many "$$" delimiters we've seen.
2057 import0 := f.Offset()
2059 c1 = '\n' // the last line ended in \n
2065 if markers%2 == 0 && c2 == '!' && c3 == '\n' {
2068 if c2 == '$' && c3 == '$' {
2077 Errorf(nil, "truncated object file: %s", pn)
2082 import1 := f.Offset()
2084 f.MustSeek(import0, 0)
2085 ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
2086 f.MustSeek(import1, 0)
2088 fingerprint := ctxt.loader.Preload(ctxt.IncVersion(), f, lib, unit, eof-f.Offset())
2089 if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
2090 // Check fingerprint, to ensure the importing and imported packages
2091 // have consistent view of symbol indices.
2092 // Normally the go command should ensure this. But in case something
2093 // goes wrong, it could lead to obscure bugs like run-time crash.
2094 // Check it here to be sure.
2095 if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
2096 lib.Fingerprint = fingerprint
2098 checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
2101 addImports(ctxt, lib, pn)
2105 // symbolsAreUnresolved scans through the loader's list of unresolved
2106 // symbols and checks to see whether any of them match the names of the
2107 // symbols in 'want'. Return value is a list of bools, with list[K] set
2108 // to true if there is an unresolved reference to the symbol in want[K].
2109 func symbolsAreUnresolved(ctxt *Link, want []string) []bool {
2110 returnAllUndefs := -1
2111 undefs := ctxt.loader.UndefinedRelocTargets(returnAllUndefs)
2112 seen := make(map[loader.Sym]struct{})
2113 rval := make([]bool, len(want))
2114 wantm := make(map[string]int)
2115 for k, w := range want {
2119 for _, s := range undefs {
2120 if _, ok := seen[s]; ok {
2123 seen[s] = struct{}{}
2124 if k, ok := wantm[ctxt.loader.SymName(s)]; ok {
2127 if count == len(want) {
2135 // hostObject reads a single host object file (compare to "hostArchive").
2136 // This is used as part of internal linking when we need to pull in
2137 // files such as "crt?.o".
2138 func hostObject(ctxt *Link, objname string, path string) {
2139 if ctxt.Debugvlog > 1 {
2140 ctxt.Logf("hostObject(%s)\n", path)
2142 objlib := sym.Library{
2145 f, err := bio.Open(path)
2147 Exitf("cannot open host object %q file %s: %v", objname, path, err)
2150 h := ldobj(ctxt, f, &objlib, 0, path, path)
2152 Exitf("unrecognized object file format in %s", path)
2154 f.MustSeek(h.off, 0)
2155 h.ld(ctxt, f, h.pkg, h.length, h.pn)
2158 func checkFingerprint(lib *sym.Library, libfp goobj.FingerprintType, src string, srcfp goobj.FingerprintType) {
2160 Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
2164 func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
2165 data := make([]byte, sym.Size)
2166 sect := f.Sections[sym.Section]
2167 if sect.Type != elf.SHT_PROGBITS && sect.Type != elf.SHT_NOTE {
2168 Errorf(nil, "reading %s from non-data section", sym.Name)
2170 n, err := sect.ReadAt(data, int64(sym.Value-sect.Addr))
2171 if uint64(n) != sym.Size {
2172 Errorf(nil, "reading contents of %s: %v", sym.Name, err)
2177 func readwithpad(r io.Reader, sz int32) ([]byte, error) {
2178 data := make([]byte, Rnd(int64(sz), 4))
2179 _, err := io.ReadFull(r, data)
2187 func readnote(f *elf.File, name []byte, typ int32) ([]byte, error) {
2188 for _, sect := range f.Sections {
2189 if sect.Type != elf.SHT_NOTE {
2194 var namesize, descsize, noteType int32
2195 err := binary.Read(r, f.ByteOrder, &namesize)
2200 return nil, fmt.Errorf("read namesize failed: %v", err)
2202 err = binary.Read(r, f.ByteOrder, &descsize)
2204 return nil, fmt.Errorf("read descsize failed: %v", err)
2206 err = binary.Read(r, f.ByteOrder, ¬eType)
2208 return nil, fmt.Errorf("read type failed: %v", err)
2210 noteName, err := readwithpad(r, namesize)
2212 return nil, fmt.Errorf("read name failed: %v", err)
2214 desc, err := readwithpad(r, descsize)
2216 return nil, fmt.Errorf("read desc failed: %v", err)
2218 if string(name) == string(noteName) && typ == noteType {
2226 func findshlib(ctxt *Link, shlib string) string {
2227 if filepath.IsAbs(shlib) {
2230 for _, libdir := range ctxt.Libdir {
2231 libpath := filepath.Join(libdir, shlib)
2232 if _, err := os.Stat(libpath); err == nil {
2236 Errorf(nil, "cannot find shared library: %s", shlib)
2240 func ldshlibsyms(ctxt *Link, shlib string) {
2242 if filepath.IsAbs(shlib) {
2244 shlib = filepath.Base(shlib)
2246 libpath = findshlib(ctxt, shlib)
2251 for _, processedlib := range ctxt.Shlibs {
2252 if processedlib.Path == libpath {
2256 if ctxt.Debugvlog > 1 {
2257 ctxt.Logf("ldshlibsyms: found library with name %s at %s\n", shlib, libpath)
2260 f, err := elf.Open(libpath)
2262 Errorf(nil, "cannot open shared library: %s", libpath)
2265 // Keep the file open as decodetypeGcprog needs to read from it.
2266 // TODO: fix. Maybe mmap the file.
2269 hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
2271 Errorf(nil, "cannot read ABI hash from shared library %s: %v", libpath, err)
2275 depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
2277 Errorf(nil, "cannot read dep list from shared library %s: %v", libpath, err)
2281 for _, dep := range strings.Split(string(depsbytes), "\n") {
2285 if !filepath.IsAbs(dep) {
2286 // If the dep can be interpreted as a path relative to the shlib
2287 // in which it was found, do that. Otherwise, we will leave it
2288 // to be resolved by libdir lookup.
2289 abs := filepath.Join(filepath.Dir(libpath), dep)
2290 if _, err := os.Stat(abs); err == nil {
2294 deps = append(deps, dep)
2297 syms, err := f.DynamicSymbols()
2299 Errorf(nil, "cannot read symbols from shared library: %s", libpath)
2303 for _, elfsym := range syms {
2304 if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
2308 // Symbols whose names start with "type." are compiler
2309 // generated, so make functions with that prefix internal.
2311 symname := elfsym.Name // (unmangled) symbol name
2312 if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type.") {
2313 ver = abiInternalVer
2314 } else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC {
2315 // Demangle the ABI name. Keep in sync with symtab.go:mangleABIName.
2316 if strings.HasSuffix(elfsym.Name, ".abiinternal") {
2317 ver = sym.SymVerABIInternal
2318 symname = strings.TrimSuffix(elfsym.Name, ".abiinternal")
2319 } else if strings.HasSuffix(elfsym.Name, ".abi0") {
2321 symname = strings.TrimSuffix(elfsym.Name, ".abi0")
2326 s := l.LookupOrCreateSym(symname, ver)
2328 // Because loadlib above loads all .a files before loading
2329 // any shared libraries, any non-dynimport symbols we find
2330 // that duplicate symbols already loaded should be ignored
2331 // (the symbols from the .a files "win").
2332 if l.SymType(s) != 0 && l.SymType(s) != sym.SDYNIMPORT {
2335 su := l.MakeSymbolUpdater(s)
2336 su.SetType(sym.SDYNIMPORT)
2337 l.SetSymElfType(s, elf.ST_TYPE(elfsym.Info))
2338 su.SetSize(int64(elfsym.Size))
2339 if elfsym.Section != elf.SHN_UNDEF {
2340 // Set .File for the library that actually defines the symbol.
2341 l.SetSymPkg(s, libpath)
2343 // The decodetype_* functions in decodetype.go need access to
2345 sname := l.SymName(s)
2346 if strings.HasPrefix(sname, "type.") && !strings.HasPrefix(sname, "type..") {
2347 su.SetData(readelfsymboldata(ctxt, f, &elfsym))
2351 if symname != elfsym.Name {
2352 l.SetSymExtname(s, elfsym.Name)
2355 ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f})
2358 func addsection(ldr *loader.Loader, arch *sys.Arch, seg *sym.Segment, name string, rwx int) *sym.Section {
2359 sect := ldr.NewSection()
2360 sect.Rwx = uint8(rwx)
2363 sect.Align = int32(arch.PtrSize) // everything is at least pointer-aligned
2364 seg.Sections = append(seg.Sections, sect)
2369 fmt.Fprintf(os.Stderr, "usage: link [options] main.o\n")
2370 objabi.Flagprint(os.Stderr)
2374 type SymbolType int8 // TODO: after genasmsym is gone, maybe rename to plan9typeChar or something
2377 // see also https://9p.io/magic/man2html/1/nm
2378 TextSym SymbolType = 'T'
2379 DataSym SymbolType = 'D'
2380 BSSSym SymbolType = 'B'
2381 UndefinedSym SymbolType = 'U'
2382 TLSSym SymbolType = 't'
2383 FrameSym SymbolType = 'm'
2384 ParamSym SymbolType = 'p'
2385 AutoSym SymbolType = 'a'
2387 // Deleted auto (not a real sym, just placeholder for type)
2388 DeletedAutoSym = 'x'
2391 // defineInternal defines a symbol used internally by the go runtime.
2392 func (ctxt *Link) defineInternal(p string, t sym.SymKind) loader.Sym {
2393 s := ctxt.loader.CreateSymForUpdate(p, 0)
2400 func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) loader.Sym {
2401 s := ctxt.defineInternal(p, t)
2402 ctxt.loader.SetSymValue(s, v)
2406 func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
2407 if uint64(addr) >= Segdata.Vaddr {
2408 return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
2410 if uint64(addr) >= Segtext.Vaddr {
2411 return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
2413 ldr.Errorf(s, "invalid datoff %#x", addr)
2417 func Entryvalue(ctxt *Link) int64 {
2418 a := *flagEntrySymbol
2419 if a[0] >= '0' && a[0] <= '9' {
2423 s := ldr.Lookup(a, 0)
2424 st := ldr.SymType(s)
2426 return *FlagTextAddr
2428 if !ctxt.IsAIX() && st != sym.STEXT {
2429 ldr.Errorf(s, "entry not text")
2431 return ldr.SymValue(s)
2434 func (ctxt *Link) callgraph() {
2440 for _, s := range ctxt.Textp {
2441 relocs := ldr.Relocs(s)
2442 for i := 0; i < relocs.Count(); i++ {
2448 if r.Type().IsDirectCall() && ldr.SymType(rs) == sym.STEXT {
2449 ctxt.Logf("%s calls %s\n", ldr.SymName(s), ldr.SymName(rs))
2455 func Rnd(v int64, r int64) int64 {
2468 func bgetc(r *bio.Reader) int {
2469 c, err := r.ReadByte()
2472 log.Fatalf("reading input: %v", err)
2479 type markKind uint8 // for postorder traversal
2486 func postorder(libs []*sym.Library) []*sym.Library {
2487 order := make([]*sym.Library, 0, len(libs)) // hold the result
2488 mark := make(map[*sym.Library]markKind, len(libs))
2489 for _, lib := range libs {
2490 dfs(lib, mark, &order)
2495 func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library) {
2496 if mark[lib] == visited {
2499 if mark[lib] == visiting {
2500 panic("found import cycle while visiting " + lib.Pkg)
2502 mark[lib] = visiting
2503 for _, i := range lib.Imports {
2507 *order = append(*order, lib)
2510 func ElfSymForReloc(ctxt *Link, s loader.Sym) int32 {
2511 // If putelfsym created a local version of this symbol, use that in all
2513 les := ctxt.loader.SymLocalElfSym(s)
2517 return ctxt.loader.SymElfSym(s)
2521 func AddGotSym(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, elfRelocTyp uint32) {
2522 if ldr.SymGot(s) >= 0 {
2526 Adddynsym(ldr, target, syms, s)
2527 got := ldr.MakeSymbolUpdater(syms.GOT)
2528 ldr.SetGot(s, int32(got.Size()))
2529 got.AddUint(target.Arch, 0)
2532 if target.Arch.PtrSize == 8 {
2533 rela := ldr.MakeSymbolUpdater(syms.Rela)
2534 rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2535 rela.AddUint64(target.Arch, elf.R_INFO(uint32(ldr.SymDynid(s)), elfRelocTyp))
2536 rela.AddUint64(target.Arch, 0)
2538 rel := ldr.MakeSymbolUpdater(syms.Rel)
2539 rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2540 rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), elfRelocTyp))
2542 } else if target.IsDarwin() {
2543 leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT)
2544 leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
2545 if target.IsPIE() && target.IsInternal() {
2546 // Mach-O relocations are a royal pain to lay out.
2547 // They use a compact stateful bytecode representation.
2548 // Here we record what are needed and encode them later.
2549 MachoAddBind(int64(ldr.SymGot(s)), s)
2552 ldr.Errorf(s, "addgotsym: unsupported binary format")