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
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"
53 exec "internal/execabs"
64 // Data layout and relocation.
66 // Derived from Inferno utils/6l/l.h
67 // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6l/l.h
69 // Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
70 // Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
71 // Portions Copyright © 1997-1999 Vita Nuova Limited
72 // Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
73 // Portions Copyright © 2004,2006 Bruce Ellis
74 // Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
75 // Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
76 // Portions Copyright © 2009 The Go Authors. All rights reserved.
78 // Permission is hereby granted, free of charge, to any person obtaining a copy
79 // of this software and associated documentation files (the "Software"), to deal
80 // in the Software without restriction, including without limitation the rights
81 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
82 // copies of the Software, and to permit persons to whom the Software is
83 // furnished to do so, subject to the following conditions:
85 // The above copyright notice and this permission notice shall be included in
86 // all copies or substantial portions of the Software.
88 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
89 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
90 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
91 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
92 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
93 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
96 // ArchSyms holds a number of architecture specific symbols used during
97 // relocation. Rather than allowing them universal access to all symbols,
98 // we keep a subset for relocation application.
99 type ArchSyms struct {
105 LinkEditGOT loader.Sym
106 LinkEditPLT loader.Sym
109 DotTOC []loader.Sym // for each version
122 unreachableMethod loader.Sym
125 // mkArchSym is a helper for setArchSyms, to set up a special symbol.
126 func (ctxt *Link) mkArchSym(name string, ver int, ls *loader.Sym) {
127 *ls = ctxt.loader.LookupOrCreateSym(name, ver)
128 ctxt.loader.SetAttrReachable(*ls, true)
131 // mkArchVecSym is similar to setArchSyms, but operates on elements within
132 // a slice, where each element corresponds to some symbol version.
133 func (ctxt *Link) mkArchSymVec(name string, ver int, ls []loader.Sym) {
134 ls[ver] = ctxt.loader.LookupOrCreateSym(name, ver)
135 ctxt.loader.SetAttrReachable(ls[ver], true)
138 // setArchSyms sets up the ArchSyms structure, and must be called before
139 // relocations are applied.
140 func (ctxt *Link) setArchSyms() {
141 ctxt.mkArchSym(".got", 0, &ctxt.GOT)
142 ctxt.mkArchSym(".plt", 0, &ctxt.PLT)
143 ctxt.mkArchSym(".got.plt", 0, &ctxt.GOTPLT)
144 ctxt.mkArchSym(".dynamic", 0, &ctxt.Dynamic)
145 ctxt.mkArchSym(".dynsym", 0, &ctxt.DynSym)
146 ctxt.mkArchSym(".dynstr", 0, &ctxt.DynStr)
147 ctxt.mkArchSym("runtime.unreachableMethod", sym.SymVerABIInternal, &ctxt.unreachableMethod)
150 ctxt.mkArchSym("TOC", 0, &ctxt.TOC)
152 // NB: note the +2 below for DotTOC2 compared to the +1 for
153 // DocTOC. This is because loadlibfull() creates an additional
154 // syms version during conversion of loader.Sym symbols to
155 // *sym.Symbol symbols. Symbols that are assigned this final
156 // version are not going to have TOC references, so it should
157 // be ok for them to inherit an invalid .TOC. symbol.
158 // TODO: revisit the +2, now that loadlibfull is gone.
159 ctxt.DotTOC = make([]loader.Sym, ctxt.MaxVersion()+2)
160 for i := 0; i <= ctxt.MaxVersion(); i++ {
161 if i >= 2 && i < sym.SymVerStatic { // these versions are not used currently
164 ctxt.mkArchSymVec(".TOC.", i, ctxt.DotTOC)
168 ctxt.mkArchSym(".rel", 0, &ctxt.Rel)
169 ctxt.mkArchSym(".rela", 0, &ctxt.Rela)
170 ctxt.mkArchSym(".rel.plt", 0, &ctxt.RelPLT)
171 ctxt.mkArchSym(".rela.plt", 0, &ctxt.RelaPLT)
174 ctxt.mkArchSym(".linkedit.got", 0, &ctxt.LinkEditGOT)
175 ctxt.mkArchSym(".linkedit.plt", 0, &ctxt.LinkEditPLT)
186 // Threshold of total text size, used for trampoline insertion. If the total
187 // text size is smaller than TrampLimit, we won't need to insert trampolines.
188 // It is pretty close to the offset range of a direct CALL machine instruction.
189 // We leave some room for extra stuff like PLT stubs.
197 Dragonflydynld string
200 // Empty spaces between codeblocks will be padded with this value.
201 // For example an architecture might want to pad with a trap instruction to
202 // catch wayward programs. Architectures that do not define a padding value
203 // are padded with zeros.
210 Adddynrel func(*Target, *loader.Loader, *ArchSyms, loader.Sym, loader.Reloc, int) bool
212 // Archreloc is an arch-specific hook that assists in relocation processing
213 // (invoked by 'relocsym'); it handles target-specific relocation tasks.
214 // Here "rel" is the current relocation being examined, "sym" is the symbol
215 // containing the chunk of data to which the relocation applies, and "off"
216 // is the contents of the to-be-relocated data item (from sym.P). Return
217 // value is the appropriately relocated value (to be written back to the
218 // same spot in sym.P), number of external _host_ relocations needed (i.e.
219 // ELF/Mach-O/etc. relocations, not Go relocations, this must match Elfreloc1,
220 // etc.), and a boolean indicating success/failure (a failing value indicates
222 Archreloc func(*Target, *loader.Loader, *ArchSyms, loader.Reloc, loader.Sym,
223 int64) (relocatedOffset int64, nExtReloc int, ok bool)
224 // Archrelocvariant is a second arch-specific hook used for
225 // relocation processing; it handles relocations where r.Type is
226 // insufficient to describe the relocation (r.Variant !=
227 // sym.RV_NONE). Here "rel" is the relocation being applied, "sym"
228 // is the symbol containing the chunk of data to which the
229 // relocation applies, and "off" is the contents of the
230 // to-be-relocated data item (from sym.P). Return is an updated
232 Archrelocvariant func(target *Target, ldr *loader.Loader, rel loader.Reloc,
233 rv sym.RelocVariant, sym loader.Sym, offset int64, data []byte) (relocatedOffset int64)
235 // Generate a trampoline for a call from s to rs if necessary. ri is
236 // index of the relocation.
237 Trampoline func(ctxt *Link, ldr *loader.Loader, ri int, rs, s loader.Sym)
239 // Assembling the binary breaks into two phases, writing the code/data/
240 // dwarf information (which is rather generic), and some more architecture
241 // specific work like setting up the elf headers/dynamic relocations, etc.
242 // The phases are called "Asmb" and "Asmb2". Asmb2 needs to be defined for
243 // every architecture, but only if architecture has an Asmb function will
244 // it be used for assembly. Otherwise a generic assembly Asmb function is
246 Asmb func(*Link, *loader.Loader)
247 Asmb2 func(*Link, *loader.Loader)
249 // Extreloc is an arch-specific hook that converts a Go relocation to an
250 // external relocation. Return the external relocation and whether it is
252 Extreloc func(*Target, *loader.Loader, loader.Reloc, loader.Sym) (loader.ExtReloc, bool)
254 Elfreloc1 func(*Link, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int, int64) bool
255 ElfrelocSize uint32 // size of an ELF relocation record, must match Elfreloc1.
256 Elfsetupplt func(ctxt *Link, plt, gotplt *loader.SymbolBuilder, dynamic loader.Sym)
257 Gentext func(*Link, *loader.Loader) // Generate text before addressing has been performed.
258 Machoreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
259 MachorelocSize uint32 // size of an Mach-O relocation record, must match Machoreloc1.
260 PEreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
261 Xcoffreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
263 // Generate additional symbols for the native symbol table just prior to
265 GenSymsLate func(*Link, *loader.Loader)
267 // TLSIEtoLE converts a TLS Initial Executable relocation to
268 // a TLS Local Executable relocation.
270 // This is possible when a TLS IE relocation refers to a local
271 // symbol in an executable, which is typical when internally
272 // linking PIE binaries.
273 TLSIEtoLE func(P []byte, off, size int)
275 // optional override for assignAddress
276 AssignAddress func(ldr *loader.Loader, sect *sym.Section, n int, s loader.Sym, va uint64, isTramp bool) (*sym.Section, int, uint64)
288 MINFUNC = 16 // minimum size for a function
291 // DynlinkingGo reports whether we are producing Go code that can live
292 // in separate shared libraries linked together at runtime.
293 func (ctxt *Link) DynlinkingGo() bool {
295 panic("DynlinkingGo called before all symbols loaded")
297 return ctxt.BuildMode == BuildModeShared || ctxt.linkShared || ctxt.BuildMode == BuildModePlugin || ctxt.canUsePlugins
300 // CanUsePlugins reports whether a plugins can be used
301 func (ctxt *Link) CanUsePlugins() bool {
303 panic("CanUsePlugins called before all symbols loaded")
305 return ctxt.canUsePlugins
308 // NeedCodeSign reports whether we need to code-sign the output binary.
309 func (ctxt *Link) NeedCodeSign() bool {
310 return ctxt.IsDarwin() && ctxt.IsARM64()
322 debug_s bool // backup old value of debug['s']
328 // See -strictdups command line flag.
329 checkStrictDups int // 0=off 1=warning 2=error
330 strictDupMsgCount int
335 Segrodata sym.Segment
336 Segrelrodata sym.Segment
340 Segments = []*sym.Segment{&Segtext, &Segrodata, &Segrelrodata, &Segdata, &Segdwarf}
343 const pkgdef = "__.PKGDEF"
346 // Set if we see an object compiled by the host compiler that is not
347 // from a package that is known to support internal linking mode.
352 func Lflag(ctxt *Link, arg string) {
353 ctxt.Libdir = append(ctxt.Libdir, arg)
357 * Unix doesn't like it when we write to a running (or, sometimes,
358 * recently run) binary, so remove the output file before writing it.
359 * On Windows 7, remove() can force a subsequent create() to fail.
360 * S_ISREG() does not exist on Plan 9.
362 func mayberemoveoutfile() {
363 if fi, err := os.Lstat(*flagOutfile); err == nil && !fi.Mode().IsRegular() {
366 os.Remove(*flagOutfile)
369 func libinit(ctxt *Link) {
370 Funcalign = thearch.Funcalign
372 // add goroot to the end of the libdir list.
376 if *flagInstallSuffix != "" {
378 suffix = *flagInstallSuffix
379 } else if *flagRace {
382 } else if *flagMsan {
387 Lflag(ctxt, filepath.Join(buildcfg.GOROOT, "pkg", fmt.Sprintf("%s_%s%s%s", buildcfg.GOOS, buildcfg.GOARCH, suffixsep, suffix)))
391 if err := ctxt.Out.Open(*flagOutfile); err != nil {
392 Exitf("cannot create %s: %v", *flagOutfile, err)
395 if *flagEntrySymbol == "" {
396 switch ctxt.BuildMode {
397 case BuildModeCShared, BuildModeCArchive:
398 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s_lib", buildcfg.GOARCH, buildcfg.GOOS)
399 case BuildModeExe, BuildModePIE:
400 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s", buildcfg.GOARCH, buildcfg.GOOS)
401 case BuildModeShared, BuildModePlugin:
402 // No *flagEntrySymbol for -buildmode=shared and plugin
404 Errorf(nil, "unknown *flagEntrySymbol for buildmode %v", ctxt.BuildMode)
409 func exitIfErrors() {
410 if nerrors != 0 || checkStrictDups > 1 && strictDupMsgCount > 0 {
422 func loadinternal(ctxt *Link, name string) *sym.Library {
423 zerofp := goobj.FingerprintType{}
424 if ctxt.linkShared && ctxt.PackageShlib != nil {
425 if shlib := ctxt.PackageShlib[name]; shlib != "" {
426 return addlibpath(ctxt, "internal", "internal", "", name, shlib, zerofp)
429 if ctxt.PackageFile != nil {
430 if pname := ctxt.PackageFile[name]; pname != "" {
431 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
433 ctxt.Logf("loadinternal: cannot find %s\n", name)
437 for _, libdir := range ctxt.Libdir {
439 shlibname := filepath.Join(libdir, name+".shlibname")
440 if ctxt.Debugvlog != 0 {
441 ctxt.Logf("searching for %s.a in %s\n", name, shlibname)
443 if _, err := os.Stat(shlibname); err == nil {
444 return addlibpath(ctxt, "internal", "internal", "", name, shlibname, zerofp)
447 pname := filepath.Join(libdir, name+".a")
448 if ctxt.Debugvlog != 0 {
449 ctxt.Logf("searching for %s.a in %s\n", name, pname)
451 if _, err := os.Stat(pname); err == nil {
452 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
456 ctxt.Logf("warning: unable to find %s.a\n", name)
460 // extld returns the current external linker.
461 func (ctxt *Link) extld() string {
462 if *flagExtld == "" {
468 // findLibPathCmd uses cmd command to find gcc library libname.
469 // It returns library full path if found, or "none" if not found.
470 func (ctxt *Link) findLibPathCmd(cmd, libname string) string {
471 extld := ctxt.extld()
472 args := hostlinkArchArgs(ctxt.Arch)
473 args = append(args, cmd)
474 if ctxt.Debugvlog != 0 {
475 ctxt.Logf("%s %v\n", extld, args)
477 out, err := exec.Command(extld, args...).Output()
479 if ctxt.Debugvlog != 0 {
480 ctxt.Logf("not using a %s file because compiler failed\n%v\n%s\n", libname, err, out)
484 return strings.TrimSpace(string(out))
487 // findLibPath searches for library libname.
488 // It returns library full path if found, or "none" if not found.
489 func (ctxt *Link) findLibPath(libname string) string {
490 return ctxt.findLibPathCmd("--print-file-name="+libname, libname)
493 func (ctxt *Link) loadlib() {
495 switch *FlagStrictDups {
499 flags |= loader.FlagStrictDups
501 log.Fatalf("invalid -strictdups flag value %d", *FlagStrictDups)
503 if !buildcfg.Experiment.RegabiWrappers {
504 // Use ABI aliases if ABI wrappers are not used.
505 flags |= loader.FlagUseABIAlias
507 elfsetstring1 := func(str string, off int) { elfsetstring(ctxt, 0, str, off) }
508 ctxt.loader = loader.NewLoader(flags, elfsetstring1, &ctxt.ErrorReporter.ErrorReporter)
509 ctxt.ErrorReporter.SymName = func(s loader.Sym) string {
510 return ctxt.loader.SymName(s)
513 // ctxt.Library grows during the loop, so not a range loop.
515 for ; i < len(ctxt.Library); i++ {
516 lib := ctxt.Library[i]
518 if ctxt.Debugvlog > 1 {
519 ctxt.Logf("autolib: %s (from %s)\n", lib.File, lib.Objref)
521 loadobjfile(ctxt, lib)
525 // load internal packages, if not already
527 loadinternal(ctxt, "runtime/race")
530 loadinternal(ctxt, "runtime/msan")
532 loadinternal(ctxt, "runtime")
533 for ; i < len(ctxt.Library); i++ {
534 lib := ctxt.Library[i]
536 loadobjfile(ctxt, lib)
539 // At this point, the Go objects are "preloaded". Not all the symbols are
540 // added to the symbol table (only defined package symbols are). Looking
541 // up symbol by name may not get expected result.
543 iscgo = ctxt.LibraryByPkg["runtime/cgo"] != nil
545 // Plugins a require cgo support to function. Similarly, plugins may require additional
546 // internal linker support on some platforms which may not be implemented.
547 ctxt.canUsePlugins = ctxt.LibraryByPkg["plugin"] != nil && iscgo
549 // We now have enough information to determine the link mode.
550 determineLinkMode(ctxt)
552 if ctxt.LinkMode == LinkExternal && !iscgo && !(buildcfg.GOOS == "darwin" && ctxt.BuildMode != BuildModePlugin && ctxt.Arch.Family == sys.AMD64) {
553 // This indicates a user requested -linkmode=external.
554 // The startup code uses an import of runtime/cgo to decide
555 // whether to initialize the TLS. So give it one. This could
556 // be handled differently but it's an unusual case.
557 if lib := loadinternal(ctxt, "runtime/cgo"); lib != nil && lib.Shlib == "" {
558 if ctxt.BuildMode == BuildModeShared || ctxt.linkShared {
559 Exitf("cannot implicitly include runtime/cgo in a shared library")
561 for ; i < len(ctxt.Library); i++ {
562 lib := ctxt.Library[i]
564 loadobjfile(ctxt, lib)
570 // Add non-package symbols and references of externally defined symbols.
571 ctxt.loader.LoadSyms(ctxt.Arch)
573 // Load symbols from shared libraries, after all Go object symbols are loaded.
574 for _, lib := range ctxt.Library {
576 if ctxt.Debugvlog > 1 {
577 ctxt.Logf("autolib: %s (from %s)\n", lib.Shlib, lib.Objref)
579 ldshlibsyms(ctxt, lib.Shlib)
583 // Process cgo directives (has to be done before host object loading).
584 ctxt.loadcgodirectives()
586 // Conditionally load host objects, or setup for external linking.
590 if ctxt.LinkMode == LinkInternal && len(hostobj) != 0 {
591 // If we have any undefined symbols in external
592 // objects, try to read them from the libgcc file.
594 undefs := ctxt.loader.UndefinedRelocTargets(1)
599 if *flagLibGCC == "" {
600 *flagLibGCC = ctxt.findLibPathCmd("--print-libgcc-file-name", "libgcc")
602 if runtime.GOOS == "openbsd" && *flagLibGCC == "libgcc.a" {
603 // On OpenBSD `clang --print-libgcc-file-name` returns "libgcc.a".
604 // In this case we fail to load libgcc.a and can encounter link
605 // errors - see if we can find libcompiler_rt.a instead.
606 *flagLibGCC = ctxt.findLibPathCmd("--print-file-name=libcompiler_rt.a", "libcompiler_rt")
608 if ctxt.HeadType == objabi.Hwindows {
609 if p := ctxt.findLibPath("libmingwex.a"); p != "none" {
612 if p := ctxt.findLibPath("libmingw32.a"); p != "none" {
615 // Link libmsvcrt.a to resolve '__acrt_iob_func' symbol
616 // (see https://golang.org/issue/23649 for details).
617 if p := ctxt.findLibPath("libmsvcrt.a"); p != "none" {
620 // TODO: maybe do something similar to peimporteddlls to collect all lib names
621 // and try link them all to final exe just like libmingwex.a and libmingw32.a:
624 #cgo windows LDFLAGS: -lmsvcrt -lm
629 if *flagLibGCC != "none" {
630 hostArchive(ctxt, *flagLibGCC)
635 // We've loaded all the code now.
640 strictDupMsgCount = ctxt.loader.NStrictDupMsgs()
643 // loadcgodirectives reads the previously discovered cgo directives, creating
644 // symbols in preparation for host object loading or use later in the link.
645 func (ctxt *Link) loadcgodirectives() {
647 hostObjSyms := make(map[loader.Sym]struct{})
648 for _, d := range ctxt.cgodata {
649 setCgoAttr(ctxt, d.file, d.pkg, d.directives, hostObjSyms)
653 if ctxt.LinkMode == LinkInternal {
654 // Drop all the cgo_import_static declarations.
655 // Turns out we won't be needing them.
656 for symIdx := range hostObjSyms {
657 if l.SymType(symIdx) == sym.SHOSTOBJ {
658 // If a symbol was marked both
659 // cgo_import_static and cgo_import_dynamic,
660 // then we want to make it cgo_import_dynamic
662 su := l.MakeSymbolUpdater(symIdx)
663 if l.SymExtname(symIdx) != "" && l.SymDynimplib(symIdx) != "" && !(l.AttrCgoExportStatic(symIdx) || l.AttrCgoExportDynamic(symIdx)) {
664 su.SetType(sym.SDYNIMPORT)
673 // Set up flags and special symbols depending on the platform build mode.
674 // This version works with loader.Loader.
675 func (ctxt *Link) linksetup() {
676 switch ctxt.BuildMode {
677 case BuildModeCShared, BuildModePlugin:
678 symIdx := ctxt.loader.LookupOrCreateSym("runtime.islibrary", 0)
679 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
680 sb.SetType(sym.SNOPTRDATA)
682 case BuildModeCArchive:
683 symIdx := ctxt.loader.LookupOrCreateSym("runtime.isarchive", 0)
684 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
685 sb.SetType(sym.SNOPTRDATA)
689 // Recalculate pe parameters now that we have ctxt.LinkMode set.
690 if ctxt.HeadType == objabi.Hwindows {
694 if ctxt.HeadType == objabi.Hdarwin && ctxt.LinkMode == LinkExternal {
698 // If there are no dynamic libraries needed, gcc disables dynamic linking.
699 // Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13)
700 // assumes that a dynamic binary always refers to at least one dynamic library.
701 // Rather than be a source of test cases for glibc, disable dynamic linking
702 // the same way that gcc would.
704 // Exception: on OS X, programs such as Shark only work with dynamic
705 // binaries, so leave it enabled on OS X (Mach-O) binaries.
706 // Also leave it enabled on Solaris which doesn't support
707 // statically linked binaries.
708 if ctxt.BuildMode == BuildModeExe {
709 if havedynamic == 0 && ctxt.HeadType != objabi.Hdarwin && ctxt.HeadType != objabi.Hsolaris {
714 if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && buildcfg.GOOS != "aix" {
715 toc := ctxt.loader.LookupOrCreateSym(".TOC.", 0)
716 sb := ctxt.loader.MakeSymbolUpdater(toc)
717 sb.SetType(sym.SDYNIMPORT)
720 // The Android Q linker started to complain about underalignment of the our TLS
721 // section. We don't actually use the section on android, so don't
723 if buildcfg.GOOS != "android" {
724 tlsg := ctxt.loader.LookupOrCreateSym("runtime.tlsg", 0)
725 sb := ctxt.loader.MakeSymbolUpdater(tlsg)
727 // runtime.tlsg is used for external linking on platforms that do not define
728 // a variable to hold g in assembly (currently only intel).
730 sb.SetType(sym.STLSBSS)
731 sb.SetSize(int64(ctxt.Arch.PtrSize))
732 } else if sb.Type() != sym.SDYNIMPORT {
733 Errorf(nil, "runtime declared tlsg variable %v", sb.Type())
735 ctxt.loader.SetAttrReachable(tlsg, true)
739 var moduledata loader.Sym
740 var mdsb *loader.SymbolBuilder
741 if ctxt.BuildMode == BuildModePlugin {
742 moduledata = ctxt.loader.LookupOrCreateSym("local.pluginmoduledata", 0)
743 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
744 ctxt.loader.SetAttrLocal(moduledata, true)
746 moduledata = ctxt.loader.LookupOrCreateSym("runtime.firstmoduledata", 0)
747 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
749 if mdsb.Type() != 0 && mdsb.Type() != sym.SDYNIMPORT {
750 // If the module (toolchain-speak for "executable or shared
751 // library") we are linking contains the runtime package, it
752 // will define the runtime.firstmoduledata symbol and we
753 // truncate it back to 0 bytes so we can define its entire
754 // contents in symtab.go:symtab().
757 // In addition, on ARM, the runtime depends on the linker
758 // recording the value of GOARM.
759 if ctxt.Arch.Family == sys.ARM {
760 goarm := ctxt.loader.LookupOrCreateSym("runtime.goarm", 0)
761 sb := ctxt.loader.MakeSymbolUpdater(goarm)
762 sb.SetType(sym.SDATA)
764 sb.AddUint8(uint8(buildcfg.GOARM))
767 // Set runtime.disableMemoryProfiling bool if
768 // runtime.MemProfile is not retained in the binary after
769 // deadcode (and we're not dynamically linking).
770 memProfile := ctxt.loader.Lookup("runtime.MemProfile", sym.SymVerABIInternal)
771 if memProfile != 0 && !ctxt.loader.AttrReachable(memProfile) && !ctxt.DynlinkingGo() {
772 memProfSym := ctxt.loader.LookupOrCreateSym("runtime.disableMemoryProfiling", 0)
773 sb := ctxt.loader.MakeSymbolUpdater(memProfSym)
774 sb.SetType(sym.SDATA)
776 sb.AddUint8(1) // true bool
779 // If OTOH the module does not contain the runtime package,
780 // create a local symbol for the moduledata.
781 moduledata = ctxt.loader.LookupOrCreateSym("local.moduledata", 0)
782 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
783 ctxt.loader.SetAttrLocal(moduledata, true)
785 // In all cases way we mark the moduledata as noptrdata to hide it from
787 mdsb.SetType(sym.SNOPTRDATA)
788 ctxt.loader.SetAttrReachable(moduledata, true)
789 ctxt.Moduledata = moduledata
791 if ctxt.Arch == sys.Arch386 && ctxt.HeadType != objabi.Hwindows {
792 if (ctxt.BuildMode == BuildModeCArchive && ctxt.IsELF) || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE || ctxt.DynlinkingGo() {
793 got := ctxt.loader.LookupOrCreateSym("_GLOBAL_OFFSET_TABLE_", 0)
794 sb := ctxt.loader.MakeSymbolUpdater(got)
795 sb.SetType(sym.SDYNIMPORT)
796 ctxt.loader.SetAttrReachable(got, true)
800 // DWARF-gen and other phases require that the unit Textp slices
801 // be populated, so that it can walk the functions in each unit.
802 // Call into the loader to do this (requires that we collect the
803 // set of internal libraries first). NB: might be simpler if we
804 // moved isRuntimeDepPkg to cmd/internal and then did the test in
805 // loader.AssignTextSymbolOrder.
806 ctxt.Library = postorder(ctxt.Library)
808 for _, lib := range ctxt.Library {
809 intlibs = append(intlibs, isRuntimeDepPkg(lib.Pkg))
811 ctxt.Textp = ctxt.loader.AssignTextSymbolOrder(ctxt.Library, intlibs, ctxt.Textp)
814 // mangleTypeSym shortens the names of symbols that represent Go types
815 // if they are visible in the symbol table.
817 // As the names of these symbols are derived from the string of
818 // the type, they can run to many kilobytes long. So we shorten
819 // them using a SHA-1 when the name appears in the final binary.
820 // This also removes characters that upset external linkers.
822 // These are the symbols that begin with the prefix 'type.' and
823 // contain run-time type information used by the runtime and reflect
824 // packages. All Go binaries contain these symbols, but only
825 // those programs loaded dynamically in multiple parts need these
826 // symbols to have entries in the symbol table.
827 func (ctxt *Link) mangleTypeSym() {
828 if ctxt.BuildMode != BuildModeShared && !ctxt.linkShared && ctxt.BuildMode != BuildModePlugin && !ctxt.CanUsePlugins() {
833 for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
834 if !ldr.AttrReachable(s) && !ctxt.linkShared {
835 // If -linkshared, the GCProg generation code may need to reach
836 // out to the shared library for the type descriptor's data, even
837 // the type descriptor itself is not actually needed at run time
838 // (therefore not reachable). We still need to mangle its name,
839 // so it is consistent with the one stored in the shared library.
842 name := ldr.SymName(s)
843 newName := typeSymbolMangle(name)
845 ldr.SetSymExtname(s, newName)
847 // When linking against a shared library, the Go object file may
848 // have reference to the original symbol name whereas the shared
849 // library provides a symbol with the mangled name. We need to
850 // copy the payload of mangled to original.
851 // XXX maybe there is a better way to do this.
852 dup := ldr.Lookup(newName, ldr.SymVersion(s))
855 dt := ldr.SymType(dup)
856 if st == sym.Sxxx && dt != sym.Sxxx {
864 // typeSymbolMangle mangles the given symbol name into something shorter.
866 // Keep the type.. prefix, which parts of the linker (like the
867 // DWARF generator) know means the symbol is not decodable.
868 // Leave type.runtime. symbols alone, because other parts of
869 // the linker manipulates them.
870 func typeSymbolMangle(name string) string {
871 if !strings.HasPrefix(name, "type.") {
874 if strings.HasPrefix(name, "type.runtime.") {
877 if len(name) <= 14 && !strings.Contains(name, "@") { // Issue 19529
880 hash := sha1.Sum([]byte(name))
885 return prefix + base64.StdEncoding.EncodeToString(hash[:6])
889 * look for the next file in an archive.
890 * adapted from libmach.
892 func nextar(bp *bio.Reader, off int64, a *ArHdr) int64 {
897 var buf [SAR_HDR]byte
898 if n, err := io.ReadFull(bp, buf[:]); err != nil {
899 if n == 0 && err != io.EOF {
905 a.name = artrim(buf[0:16])
906 a.date = artrim(buf[16:28])
907 a.uid = artrim(buf[28:34])
908 a.gid = artrim(buf[34:40])
909 a.mode = artrim(buf[40:48])
910 a.size = artrim(buf[48:58])
911 a.fmag = artrim(buf[58:60])
913 arsize := atolwhex(a.size)
917 return arsize + SAR_HDR
920 func loadobjfile(ctxt *Link, lib *sym.Library) {
921 pkg := objabi.PathToPrefix(lib.Pkg)
923 if ctxt.Debugvlog > 1 {
924 ctxt.Logf("ldobj: %s (%s)\n", lib.File, pkg)
926 f, err := bio.Open(lib.File)
928 Exitf("cannot open file %s: %v", lib.File, err)
932 if pkg == "main" && !lib.Main {
933 Exitf("%s: not package main", lib.File)
937 for i := 0; i < len(ARMAG); i++ {
938 if c, err := f.ReadByte(); err == nil && c == ARMAG[i] {
942 /* load it as a regular file */
943 l := f.MustSeek(0, 2)
945 ldobj(ctxt, f, lib, l, lib.File, lib.File)
950 * load all the object files from the archive now.
951 * this gives us sequential file access and keeps us
952 * from needing to come back later to pick up more
953 * objects. it breaks the usual C archive model, but
954 * this is Go, not C. the common case in Go is that
955 * we need to load all the objects, and then we throw away
956 * the individual symbols that are unused.
958 * loading every object will also make it possible to
959 * load foreign objects not referenced by __.PKGDEF.
964 l := nextar(f, off, &arhdr)
969 Exitf("%s: malformed archive", lib.File)
973 // __.PKGDEF isn't a real Go object file, and it's
974 // absent in -linkobj builds anyway. Skipping it
975 // ensures consistency between -linkobj and normal
977 if arhdr.name == pkgdef {
981 // Skip other special (non-object-file) sections that
982 // build tools may have added. Such sections must have
983 // short names so that the suffix is not truncated.
984 if len(arhdr.name) < 16 {
985 if ext := filepath.Ext(arhdr.name); ext != ".o" && ext != ".syso" {
990 pname := fmt.Sprintf("%s(%s)", lib.File, arhdr.name)
991 l = atolwhex(arhdr.size)
992 ldobj(ctxt, f, lib, l, pname, lib.File)
996 type Hostobj struct {
997 ld func(*Link, *bio.Reader, string, int64, string)
1005 var hostobj []Hostobj
1007 // These packages can use internal linking mode.
1008 // Others trigger external mode.
1009 var internalpkg = []string{
1018 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 {
1020 for _, intpkg := range internalpkg {
1027 // DragonFly declares errno with __thread, which results in a symbol
1028 // type of R_386_TLS_GD or R_X86_64_TLSGD. The Go linker does not
1029 // currently know how to handle TLS relocations, hence we have to
1030 // force external linking for any libraries that link in code that
1031 // uses errno. This can be removed if the Go linker ever supports
1032 // these relocation types.
1033 if headType == objabi.Hdragonfly {
1034 if pkg == "net" || pkg == "os/user" {
1043 hostobj = append(hostobj, Hostobj{})
1044 h := &hostobj[len(hostobj)-1]
1054 func hostobjs(ctxt *Link) {
1055 if ctxt.LinkMode != LinkInternal {
1060 for i := 0; i < len(hostobj); i++ {
1062 f, err := bio.Open(h.file)
1064 Exitf("cannot reopen %s: %v", h.pn, err)
1067 f.MustSeek(h.off, 0)
1068 h.ld(ctxt, f, h.pkg, h.length, h.pn)
1073 func hostlinksetup(ctxt *Link) {
1074 if ctxt.LinkMode != LinkExternal {
1078 // For external link, record that we need to tell the external linker -s,
1079 // and turn off -s internally: the external linker needs the symbol
1080 // information for its final link.
1084 // create temporary directory and arrange cleanup
1085 if *flagTmpdir == "" {
1086 dir, err := ioutil.TempDir("", "go-link-")
1094 os.RemoveAll(*flagTmpdir)
1098 // change our output to temporary object file
1099 if err := ctxt.Out.Close(); err != nil {
1100 Exitf("error closing output file")
1102 mayberemoveoutfile()
1104 p := filepath.Join(*flagTmpdir, "go.o")
1105 if err := ctxt.Out.Open(p); err != nil {
1106 Exitf("cannot create %s: %v", p, err)
1110 // hostobjCopy creates a copy of the object files in hostobj in a
1111 // temporary directory.
1112 func hostobjCopy() (paths []string) {
1113 var wg sync.WaitGroup
1114 sema := make(chan struct{}, runtime.NumCPU()) // limit open file descriptors
1115 for i, h := range hostobj {
1117 dst := filepath.Join(*flagTmpdir, fmt.Sprintf("%06d.o", i))
1118 paths = append(paths, dst)
1127 f, err := os.Open(h.file)
1129 Exitf("cannot reopen %s: %v", h.pn, err)
1132 if _, err := f.Seek(h.off, 0); err != nil {
1133 Exitf("cannot seek %s: %v", h.pn, err)
1136 w, err := os.Create(dst)
1138 Exitf("cannot create %s: %v", dst, err)
1140 if _, err := io.CopyN(w, f, h.length); err != nil {
1141 Exitf("cannot write %s: %v", dst, err)
1143 if err := w.Close(); err != nil {
1144 Exitf("cannot close %s: %v", dst, err)
1152 // writeGDBLinkerScript creates gcc linker script file in temp
1153 // directory. writeGDBLinkerScript returns created file path.
1154 // The script is used to work around gcc bug
1155 // (see https://golang.org/issue/20183 for details).
1156 func writeGDBLinkerScript() string {
1157 name := "fix_debug_gdb_scripts.ld"
1158 path := filepath.Join(*flagTmpdir, name)
1161 .debug_gdb_scripts BLOCK(__section_alignment__) (NOLOAD) :
1163 *(.debug_gdb_scripts)
1166 INSERT AFTER .debug_types;
1168 err := ioutil.WriteFile(path, []byte(src), 0666)
1170 Errorf(nil, "WriteFile %s failed: %v", name, err)
1175 // archive builds a .a archive from the hostobj object files.
1176 func (ctxt *Link) archive() {
1177 if ctxt.BuildMode != BuildModeCArchive {
1183 if *flagExtar == "" {
1187 mayberemoveoutfile()
1189 // Force the buffer to flush here so that external
1190 // tools will see a complete file.
1191 if err := ctxt.Out.Close(); err != nil {
1192 Exitf("error closing %v", *flagOutfile)
1195 argv := []string{*flagExtar, "-q", "-c", "-s"}
1196 if ctxt.HeadType == objabi.Haix {
1197 argv = append(argv, "-X64")
1199 argv = append(argv, *flagOutfile)
1200 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1201 argv = append(argv, hostobjCopy()...)
1203 if ctxt.Debugvlog != 0 {
1204 ctxt.Logf("archive: %s\n", strings.Join(argv, " "))
1207 // If supported, use syscall.Exec() to invoke the archive command,
1208 // which should be the final remaining step needed for the link.
1209 // This will reduce peak RSS for the link (and speed up linking of
1210 // large applications), since when the archive command runs we
1211 // won't be holding onto all of the linker's live memory.
1212 if syscallExecSupported && !ownTmpDir {
1214 ctxt.execArchive(argv)
1215 panic("should not get here")
1218 // Otherwise invoke 'ar' in the usual way (fork + exec).
1219 if out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput(); err != nil {
1220 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1224 func (ctxt *Link) hostlink() {
1225 if ctxt.LinkMode != LinkExternal || nerrors > 0 {
1228 if ctxt.BuildMode == BuildModeCArchive {
1233 argv = append(argv, ctxt.extld())
1234 argv = append(argv, hostlinkArchArgs(ctxt.Arch)...)
1236 if *FlagS || debug_s {
1237 if ctxt.HeadType == objabi.Hdarwin {
1238 // Recent versions of macOS print
1239 // ld: warning: option -s is obsolete and being ignored
1240 // so do not pass any arguments.
1242 argv = append(argv, "-s")
1246 // On darwin, whether to combine DWARF into executable.
1247 // Only macOS supports unmapped segments such as our __DWARF segment.
1248 combineDwarf := ctxt.IsDarwin() && !*FlagS && !*FlagW && !debug_s && machoPlatform == PLATFORM_MACOS
1250 switch ctxt.HeadType {
1251 case objabi.Hdarwin:
1253 // Leave room for DWARF combining.
1254 // -headerpad is incompatible with -fembed-bitcode.
1255 argv = append(argv, "-Wl,-headerpad,1144")
1257 if ctxt.DynlinkingGo() && buildcfg.GOOS != "ios" {
1258 // -flat_namespace is deprecated on iOS.
1259 // It is useful for supporting plugins. We don't support plugins on iOS.
1260 argv = append(argv, "-Wl,-flat_namespace")
1263 argv = append(argv, "-Wl,-S") // suppress STAB (symbolic debugging) symbols
1265 case objabi.Hopenbsd:
1266 argv = append(argv, "-Wl,-nopie")
1267 argv = append(argv, "-pthread")
1268 case objabi.Hwindows:
1270 argv = append(argv, "-mwindows")
1272 argv = append(argv, "-mconsole")
1274 // Mark as having awareness of terminal services, to avoid
1275 // ancient compatibility hacks.
1276 argv = append(argv, "-Wl,--tsaware")
1279 argv = append(argv, "-Wl,--nxcompat")
1281 argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", PeMinimumTargetMajorVersion))
1282 argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", PeMinimumTargetMinorVersion))
1283 argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", PeMinimumTargetMajorVersion))
1284 argv = append(argv, fmt.Sprintf("-Wl,--minor-subsystem-version=%d", PeMinimumTargetMinorVersion))
1286 argv = append(argv, "-pthread")
1287 // prevent ld to reorder .text functions to keep the same
1288 // first/last functions for moduledata.
1289 argv = append(argv, "-Wl,-bnoobjreorder")
1290 // mcmodel=large is needed for every gcc generated files, but
1291 // ld still need -bbigtoc in order to allow larger TOC.
1292 argv = append(argv, "-mcmodel=large")
1293 argv = append(argv, "-Wl,-bbigtoc")
1296 // Enable ASLR on Windows.
1297 addASLRargs := func(argv []string) []string {
1299 argv = append(argv, "-Wl,--dynamicbase")
1300 // enable high-entropy ASLR on 64-bit.
1301 if ctxt.Arch.PtrSize >= 8 {
1302 argv = append(argv, "-Wl,--high-entropy-va")
1307 switch ctxt.BuildMode {
1309 if ctxt.HeadType == objabi.Hdarwin {
1310 if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() {
1311 argv = append(argv, "-Wl,-no_pie")
1312 argv = append(argv, "-Wl,-pagezero_size,4000000")
1316 switch ctxt.HeadType {
1317 case objabi.Hdarwin, objabi.Haix:
1318 case objabi.Hwindows:
1319 argv = addASLRargs(argv)
1322 if ctxt.UseRelro() {
1323 argv = append(argv, "-Wl,-z,relro")
1325 argv = append(argv, "-pie")
1327 case BuildModeCShared:
1328 if ctxt.HeadType == objabi.Hdarwin {
1329 argv = append(argv, "-dynamiclib")
1331 if ctxt.UseRelro() {
1332 argv = append(argv, "-Wl,-z,relro")
1334 argv = append(argv, "-shared")
1335 if ctxt.HeadType == objabi.Hwindows {
1337 argv = addASLRargs(argv)
1340 // Pass -z nodelete to mark the shared library as
1341 // non-closeable: a dlclose will do nothing.
1342 argv = append(argv, "-Wl,-z,nodelete")
1343 // Only pass Bsymbolic on non-Windows.
1344 argv = append(argv, "-Wl,-Bsymbolic")
1347 case BuildModeShared:
1348 if ctxt.UseRelro() {
1349 argv = append(argv, "-Wl,-z,relro")
1351 argv = append(argv, "-shared")
1352 case BuildModePlugin:
1353 if ctxt.HeadType == objabi.Hdarwin {
1354 argv = append(argv, "-dynamiclib")
1356 if ctxt.UseRelro() {
1357 argv = append(argv, "-Wl,-z,relro")
1359 argv = append(argv, "-shared")
1363 var altLinker string
1364 if ctxt.IsELF && ctxt.DynlinkingGo() {
1365 // We force all symbol resolution to be done at program startup
1366 // because lazy PLT resolution can use large amounts of stack at
1367 // times we cannot allow it to do so.
1368 argv = append(argv, "-Wl,-znow")
1370 // Do not let the host linker generate COPY relocations. These
1371 // can move symbols out of sections that rely on stable offsets
1372 // from the beginning of the section (like sym.STYPE).
1373 argv = append(argv, "-Wl,-znocopyreloc")
1375 if buildcfg.GOOS == "android" {
1376 // Use lld to avoid errors from default linker (issue #38838)
1380 if ctxt.Arch.InFamily(sys.ARM, sys.ARM64) && buildcfg.GOOS == "linux" {
1381 // On ARM, the GNU linker will generate COPY relocations
1382 // even with -znocopyreloc set.
1383 // https://sourceware.org/bugzilla/show_bug.cgi?id=19962
1385 // On ARM64, the GNU linker will fail instead of
1386 // generating COPY relocations.
1388 // In both cases, switch to gold.
1391 // If gold is not installed, gcc will silently switch
1392 // back to ld.bfd. So we parse the version information
1393 // and provide a useful error if gold is missing.
1394 cmd := exec.Command(*flagExtld, "-fuse-ld=gold", "-Wl,--version")
1395 if out, err := cmd.CombinedOutput(); err == nil {
1396 if !bytes.Contains(out, []byte("GNU gold")) {
1397 log.Fatalf("ARM external linker must be gold (issue #15696), but is not: %s", out)
1402 if ctxt.Arch.Family == sys.ARM64 && buildcfg.GOOS == "freebsd" {
1403 // Switch to ld.bfd on freebsd/arm64.
1406 // Provide a useful error if ld.bfd is missing.
1407 cmd := exec.Command(*flagExtld, "-fuse-ld=bfd", "-Wl,--version")
1408 if out, err := cmd.CombinedOutput(); err == nil {
1409 if !bytes.Contains(out, []byte("GNU ld")) {
1410 log.Fatalf("ARM64 external linker must be ld.bfd (issue #35197), please install devel/binutils")
1414 if altLinker != "" {
1415 argv = append(argv, "-fuse-ld="+altLinker)
1418 if ctxt.IsELF && len(buildinfo) > 0 {
1419 argv = append(argv, fmt.Sprintf("-Wl,--build-id=0x%x", buildinfo))
1422 // On Windows, given -o foo, GCC will append ".exe" to produce
1423 // "foo.exe". We have decided that we want to honor the -o
1424 // option. To make this work, we append a '.' so that GCC
1425 // will decide that the file already has an extension. We
1426 // only want to do this when producing a Windows output file
1427 // on a Windows host.
1428 outopt := *flagOutfile
1429 if buildcfg.GOOS == "windows" && runtime.GOOS == "windows" && filepath.Ext(outopt) == "" {
1432 argv = append(argv, "-o")
1433 argv = append(argv, outopt)
1435 if rpath.val != "" {
1436 argv = append(argv, fmt.Sprintf("-Wl,-rpath,%s", rpath.val))
1439 if *flagInterpreter != "" {
1440 // Many linkers support both -I and the --dynamic-linker flags
1441 // to set the ELF interpreter, but lld only supports
1442 // --dynamic-linker so prefer that (ld on very old Solaris only
1443 // supports -I but that seems less important).
1444 argv = append(argv, fmt.Sprintf("-Wl,--dynamic-linker,%s", *flagInterpreter))
1447 // Force global symbols to be exported for dlopen, etc.
1449 argv = append(argv, "-rdynamic")
1451 if ctxt.HeadType == objabi.Haix {
1452 fileName := xcoffCreateExportFile(ctxt)
1453 argv = append(argv, "-Wl,-bE:"+fileName)
1456 const unusedArguments = "-Qunused-arguments"
1457 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, unusedArguments) {
1458 argv = append(argv, unusedArguments)
1461 const compressDWARF = "-Wl,--compress-debug-sections=zlib-gnu"
1462 if ctxt.compressDWARF && linkerFlagSupported(ctxt.Arch, argv[0], altLinker, compressDWARF) {
1463 argv = append(argv, compressDWARF)
1466 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1467 argv = append(argv, hostobjCopy()...)
1468 if ctxt.HeadType == objabi.Haix {
1469 // We want to have C files after Go files to remove
1470 // trampolines csects made by ld.
1471 argv = append(argv, "-nostartfiles")
1472 argv = append(argv, "/lib/crt0_64.o")
1474 extld := ctxt.extld()
1475 // Get starting files.
1476 getPathFile := func(file string) string {
1477 args := []string{"-maix64", "--print-file-name=" + file}
1478 out, err := exec.Command(extld, args...).CombinedOutput()
1480 log.Fatalf("running %s failed: %v\n%s", extld, err, out)
1482 return strings.Trim(string(out), "\n")
1484 argv = append(argv, getPathFile("crtcxa.o"))
1485 argv = append(argv, getPathFile("crtdbase.o"))
1488 if ctxt.linkShared {
1489 seenDirs := make(map[string]bool)
1490 seenLibs := make(map[string]bool)
1491 addshlib := func(path string) {
1492 dir, base := filepath.Split(path)
1494 argv = append(argv, "-L"+dir)
1496 argv = append(argv, "-Wl,-rpath="+dir)
1498 seenDirs[dir] = true
1500 base = strings.TrimSuffix(base, ".so")
1501 base = strings.TrimPrefix(base, "lib")
1502 if !seenLibs[base] {
1503 argv = append(argv, "-l"+base)
1504 seenLibs[base] = true
1507 for _, shlib := range ctxt.Shlibs {
1508 addshlib(shlib.Path)
1509 for _, dep := range shlib.Deps {
1513 libpath := findshlib(ctxt, dep)
1521 // clang, unlike GCC, passes -rdynamic to the linker
1522 // even when linking with -static, causing a linker
1523 // error when using GNU ld. So take out -rdynamic if
1524 // we added it. We do it in this order, rather than
1525 // only adding -rdynamic later, so that -extldflags
1526 // can override -rdynamic without using -static.
1527 // Similarly for -Wl,--dynamic-linker.
1528 checkStatic := func(arg string) {
1529 if ctxt.IsELF && arg == "-static" {
1530 for i := range argv {
1531 if argv[i] == "-rdynamic" || strings.HasPrefix(argv[i], "-Wl,--dynamic-linker,") {
1538 for _, p := range ldflag {
1539 argv = append(argv, p)
1543 // When building a program with the default -buildmode=exe the
1544 // gc compiler generates code requires DT_TEXTREL in a
1545 // position independent executable (PIE). On systems where the
1546 // toolchain creates PIEs by default, and where DT_TEXTREL
1547 // does not work, the resulting programs will not run. See
1548 // issue #17847. To avoid this problem pass -no-pie to the
1549 // toolchain if it is supported.
1550 if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared && !(ctxt.IsDarwin() && ctxt.IsARM64()) {
1551 // GCC uses -no-pie, clang uses -nopie.
1552 for _, nopie := range []string{"-no-pie", "-nopie"} {
1553 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, nopie) {
1554 argv = append(argv, nopie)
1560 for _, p := range strings.Fields(*flagExtldflags) {
1561 argv = append(argv, p)
1564 if ctxt.HeadType == objabi.Hwindows {
1565 // Determine which linker we're using. Add in the extldflags in
1566 // case used has specified "-fuse-ld=...".
1567 cmd := exec.Command(*flagExtld, *flagExtldflags, "-Wl,--version")
1569 if out, err := cmd.CombinedOutput(); err == nil {
1570 if bytes.Contains(out, []byte("LLD ")) {
1575 // use gcc linker script to work around gcc bug
1576 // (see https://golang.org/issue/20183 for details).
1578 p := writeGDBLinkerScript()
1579 argv = append(argv, "-Wl,-T,"+p)
1581 // libmingw32 and libmingwex have some inter-dependencies,
1582 // so must use linker groups.
1583 argv = append(argv, "-Wl,--start-group", "-lmingwex", "-lmingw32", "-Wl,--end-group")
1584 argv = append(argv, peimporteddlls()...)
1587 if ctxt.Debugvlog != 0 {
1588 ctxt.Logf("host link:")
1589 for _, v := range argv {
1595 out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput()
1597 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1600 // Filter out useless linker warnings caused by bugs outside Go.
1601 // See also cmd/go/internal/work/exec.go's gccld method.
1604 for _, line := range bytes.SplitAfter(out, []byte("\n")) {
1605 // golang.org/issue/26073 - Apple Xcode bug
1606 if bytes.Contains(line, []byte("ld: warning: text-based stub file")) {
1615 // Remove TOC overflow warning on AIX.
1616 if bytes.Contains(line, []byte("ld: 0711-783")) {
1621 save = append(save, line)
1623 out = bytes.Join(save, nil)
1626 // always print external output even if the command is successful, so that we don't
1627 // swallow linker warnings (see https://golang.org/issue/17935).
1628 ctxt.Logf("%s", out)
1632 dsym := filepath.Join(*flagTmpdir, "go.dwarf")
1633 if out, err := exec.Command("xcrun", "dsymutil", "-f", *flagOutfile, "-o", dsym).CombinedOutput(); err != nil {
1634 Exitf("%s: running dsymutil failed: %v\n%s", os.Args[0], err, out)
1636 // Remove STAB (symbolic debugging) symbols after we are done with them (by dsymutil).
1637 // They contain temporary file paths and make the build not reproducible.
1638 if out, err := exec.Command("xcrun", "strip", "-S", *flagOutfile).CombinedOutput(); err != nil {
1639 Exitf("%s: running strip failed: %v\n%s", os.Args[0], err, out)
1641 // Skip combining if `dsymutil` didn't generate a file. See #11994.
1642 if _, err := os.Stat(dsym); os.IsNotExist(err) {
1645 // For os.Rename to work reliably, must be in same directory as outfile.
1646 combinedOutput := *flagOutfile + "~"
1647 exef, err := os.Open(*flagOutfile)
1649 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1652 exem, err := macho.NewFile(exef)
1654 Exitf("%s: parsing Mach-O header failed: %v", os.Args[0], err)
1656 if err := machoCombineDwarf(ctxt, exef, exem, dsym, combinedOutput); err != nil {
1657 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1659 os.Remove(*flagOutfile)
1660 if err := os.Rename(combinedOutput, *flagOutfile); err != nil {
1661 Exitf("%s: %v", os.Args[0], err)
1664 if ctxt.NeedCodeSign() {
1665 err := machoCodeSign(ctxt, *flagOutfile)
1667 Exitf("%s: code signing failed: %v", os.Args[0], err)
1672 var createTrivialCOnce sync.Once
1674 func linkerFlagSupported(arch *sys.Arch, linker, altLinker, flag string) bool {
1675 createTrivialCOnce.Do(func() {
1676 src := filepath.Join(*flagTmpdir, "trivial.c")
1677 if err := ioutil.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
1678 Errorf(nil, "WriteFile trivial.c failed: %v", err)
1682 flagsWithNextArgSkip := []string{
1691 flagsWithNextArgKeep := []string{
1697 prefixesToKeep := []string{
1708 flags := hostlinkArchArgs(arch)
1711 extldflags := strings.Fields(*flagExtldflags)
1712 for _, f := range append(extldflags, ldflag...) {
1714 flags = append(flags, f)
1718 } else if f == "" || f[0] != '-' {
1719 } else if contains(flagsWithNextArgSkip, f) {
1721 } else if contains(flagsWithNextArgKeep, f) {
1722 flags = append(flags, f)
1725 for _, p := range prefixesToKeep {
1726 if strings.HasPrefix(f, p) {
1727 flags = append(flags, f)
1734 if altLinker != "" {
1735 flags = append(flags, "-fuse-ld="+altLinker)
1737 flags = append(flags, flag, "trivial.c")
1739 cmd := exec.Command(linker, flags...)
1740 cmd.Dir = *flagTmpdir
1741 cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
1742 out, err := cmd.CombinedOutput()
1743 // GCC says "unrecognized command line option ‘-no-pie’"
1744 // clang says "unknown argument: '-no-pie'"
1745 return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
1748 // hostlinkArchArgs returns arguments to pass to the external linker
1749 // based on the architecture.
1750 func hostlinkArchArgs(arch *sys.Arch) []string {
1751 switch arch.Family {
1753 return []string{"-m32"}
1755 if buildcfg.GOOS == "darwin" {
1756 return []string{"-arch", "x86_64", "-m64"}
1758 return []string{"-m64"}
1760 return []string{"-m64"}
1762 return []string{"-marm"}
1764 if buildcfg.GOOS == "darwin" {
1765 return []string{"-arch", "arm64"}
1768 return []string{"-mabi=64"}
1770 return []string{"-mabi=32"}
1772 if buildcfg.GOOS == "aix" {
1773 return []string{"-maix64"}
1775 return []string{"-m64"}
1782 var wantHdr = objabi.HeaderString()
1784 // ldobj loads an input object. If it is a host object (an object
1785 // compiled by a non-Go compiler) it returns the Hostobj pointer. If
1786 // it is a Go object, it returns nil.
1787 func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string, file string) *Hostobj {
1788 pkg := objabi.PathToPrefix(lib.Pkg)
1790 eof := f.Offset() + length
1796 f.MustSeek(start, 0)
1798 unit := &sym.CompilationUnit{Lib: lib}
1799 lib.Units = append(lib.Units, unit)
1801 magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
1802 if magic == 0x7f454c46 { // \x7F E L F
1803 ldelf := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1804 textp, flags, err := loadelf.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn, ehdr.Flags)
1806 Errorf(nil, "%v", err)
1810 ctxt.Textp = append(ctxt.Textp, textp...)
1812 return ldhostobj(ldelf, ctxt.HeadType, f, pkg, length, pn, file)
1815 if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
1816 ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1817 textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1819 Errorf(nil, "%v", err)
1822 ctxt.Textp = append(ctxt.Textp, textp...)
1824 return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
1832 ldpe := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1833 textp, rsrc, err := loadpe.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1835 Errorf(nil, "%v", err)
1839 setpersrc(ctxt, rsrc)
1841 ctxt.Textp = append(ctxt.Textp, textp...)
1843 return ldhostobj(ldpe, ctxt.HeadType, f, pkg, length, pn, file)
1846 if c1 == 0x01 && (c2 == 0xD7 || c2 == 0xF7) {
1847 ldxcoff := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1848 textp, err := loadxcoff.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1850 Errorf(nil, "%v", err)
1853 ctxt.Textp = append(ctxt.Textp, textp...)
1855 return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
1858 /* check the header */
1859 line, err := f.ReadString('\n')
1861 Errorf(nil, "truncated object file: %s: %v", pn, err)
1865 if !strings.HasPrefix(line, "go object ") {
1866 if strings.HasSuffix(pn, ".go") {
1867 Exitf("%s: uncompiled .go source file", pn)
1871 if line == ctxt.Arch.Name {
1872 // old header format: just $GOOS
1873 Errorf(nil, "%s: stale object file", pn)
1877 Errorf(nil, "%s: not an object file: @%d %02x%02x%02x%02x", pn, start, c1, c2, c3, c4)
1881 // First, check that the basic GOOS, GOARCH, and Version match.
1882 if line != wantHdr {
1883 Errorf(nil, "%s: linked object header mismatch:\nhave %q\nwant %q\n", pn, line, wantHdr)
1886 // Skip over exports and other info -- ends with \n!\n.
1888 // Note: It's possible for "\n!\n" to appear within the binary
1889 // package export data format. To avoid truncating the package
1890 // definition prematurely (issue 21703), we keep track of
1891 // how many "$$" delimiters we've seen.
1893 import0 := f.Offset()
1895 c1 = '\n' // the last line ended in \n
1901 if markers%2 == 0 && c2 == '!' && c3 == '\n' {
1904 if c2 == '$' && c3 == '$' {
1913 Errorf(nil, "truncated object file: %s", pn)
1918 import1 := f.Offset()
1920 f.MustSeek(import0, 0)
1921 ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
1922 f.MustSeek(import1, 0)
1924 fingerprint := ctxt.loader.Preload(ctxt.IncVersion(), f, lib, unit, eof-f.Offset())
1925 if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
1926 // Check fingerprint, to ensure the importing and imported packages
1927 // have consistent view of symbol indices.
1928 // Normally the go command should ensure this. But in case something
1929 // goes wrong, it could lead to obscure bugs like run-time crash.
1930 // Check it here to be sure.
1931 if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
1932 lib.Fingerprint = fingerprint
1934 checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
1937 addImports(ctxt, lib, pn)
1941 func checkFingerprint(lib *sym.Library, libfp goobj.FingerprintType, src string, srcfp goobj.FingerprintType) {
1943 Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
1947 func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
1948 data := make([]byte, sym.Size)
1949 sect := f.Sections[sym.Section]
1950 if sect.Type != elf.SHT_PROGBITS && sect.Type != elf.SHT_NOTE {
1951 Errorf(nil, "reading %s from non-data section", sym.Name)
1953 n, err := sect.ReadAt(data, int64(sym.Value-sect.Addr))
1954 if uint64(n) != sym.Size {
1955 Errorf(nil, "reading contents of %s: %v", sym.Name, err)
1960 func readwithpad(r io.Reader, sz int32) ([]byte, error) {
1961 data := make([]byte, Rnd(int64(sz), 4))
1962 _, err := io.ReadFull(r, data)
1970 func readnote(f *elf.File, name []byte, typ int32) ([]byte, error) {
1971 for _, sect := range f.Sections {
1972 if sect.Type != elf.SHT_NOTE {
1977 var namesize, descsize, noteType int32
1978 err := binary.Read(r, f.ByteOrder, &namesize)
1983 return nil, fmt.Errorf("read namesize failed: %v", err)
1985 err = binary.Read(r, f.ByteOrder, &descsize)
1987 return nil, fmt.Errorf("read descsize failed: %v", err)
1989 err = binary.Read(r, f.ByteOrder, ¬eType)
1991 return nil, fmt.Errorf("read type failed: %v", err)
1993 noteName, err := readwithpad(r, namesize)
1995 return nil, fmt.Errorf("read name failed: %v", err)
1997 desc, err := readwithpad(r, descsize)
1999 return nil, fmt.Errorf("read desc failed: %v", err)
2001 if string(name) == string(noteName) && typ == noteType {
2009 func findshlib(ctxt *Link, shlib string) string {
2010 if filepath.IsAbs(shlib) {
2013 for _, libdir := range ctxt.Libdir {
2014 libpath := filepath.Join(libdir, shlib)
2015 if _, err := os.Stat(libpath); err == nil {
2019 Errorf(nil, "cannot find shared library: %s", shlib)
2023 func ldshlibsyms(ctxt *Link, shlib string) {
2025 if filepath.IsAbs(shlib) {
2027 shlib = filepath.Base(shlib)
2029 libpath = findshlib(ctxt, shlib)
2034 for _, processedlib := range ctxt.Shlibs {
2035 if processedlib.Path == libpath {
2039 if ctxt.Debugvlog > 1 {
2040 ctxt.Logf("ldshlibsyms: found library with name %s at %s\n", shlib, libpath)
2043 f, err := elf.Open(libpath)
2045 Errorf(nil, "cannot open shared library: %s", libpath)
2048 // Keep the file open as decodetypeGcprog needs to read from it.
2049 // TODO: fix. Maybe mmap the file.
2052 hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
2054 Errorf(nil, "cannot read ABI hash from shared library %s: %v", libpath, err)
2058 depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
2060 Errorf(nil, "cannot read dep list from shared library %s: %v", libpath, err)
2064 for _, dep := range strings.Split(string(depsbytes), "\n") {
2068 if !filepath.IsAbs(dep) {
2069 // If the dep can be interpreted as a path relative to the shlib
2070 // in which it was found, do that. Otherwise, we will leave it
2071 // to be resolved by libdir lookup.
2072 abs := filepath.Join(filepath.Dir(libpath), dep)
2073 if _, err := os.Stat(abs); err == nil {
2077 deps = append(deps, dep)
2080 syms, err := f.DynamicSymbols()
2082 Errorf(nil, "cannot read symbols from shared library: %s", libpath)
2086 for _, elfsym := range syms {
2087 if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
2091 // Symbols whose names start with "type." are compiler
2092 // generated, so make functions with that prefix internal.
2094 symname := elfsym.Name // (unmangled) symbol name
2095 if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type.") {
2096 ver = sym.SymVerABIInternal
2097 } else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC {
2098 // Demangle the ABI name. Keep in sync with symtab.go:mangleABIName.
2099 if strings.HasSuffix(elfsym.Name, ".abiinternal") {
2100 ver = sym.SymVerABIInternal
2101 symname = strings.TrimSuffix(elfsym.Name, ".abiinternal")
2102 } else if strings.HasSuffix(elfsym.Name, ".abi0") {
2104 symname = strings.TrimSuffix(elfsym.Name, ".abi0")
2109 s := l.LookupOrCreateSym(symname, ver)
2111 // Because loadlib above loads all .a files before loading
2112 // any shared libraries, any non-dynimport symbols we find
2113 // that duplicate symbols already loaded should be ignored
2114 // (the symbols from the .a files "win").
2115 if l.SymType(s) != 0 && l.SymType(s) != sym.SDYNIMPORT {
2118 su := l.MakeSymbolUpdater(s)
2119 su.SetType(sym.SDYNIMPORT)
2120 l.SetSymElfType(s, elf.ST_TYPE(elfsym.Info))
2121 su.SetSize(int64(elfsym.Size))
2122 if elfsym.Section != elf.SHN_UNDEF {
2123 // Set .File for the library that actually defines the symbol.
2124 l.SetSymPkg(s, libpath)
2126 // The decodetype_* functions in decodetype.go need access to
2128 sname := l.SymName(s)
2129 if strings.HasPrefix(sname, "type.") && !strings.HasPrefix(sname, "type..") {
2130 su.SetData(readelfsymboldata(ctxt, f, &elfsym))
2134 if symname != elfsym.Name {
2135 l.SetSymExtname(s, elfsym.Name)
2138 // For function symbols, if ABI wrappers are not used, we don't
2139 // know what ABI is available, so alias it under both ABIs.
2140 if !buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && ver == 0 {
2141 alias := ctxt.loader.LookupOrCreateSym(symname, sym.SymVerABIInternal)
2142 if l.SymType(alias) != 0 {
2145 su := l.MakeSymbolUpdater(alias)
2146 su.SetType(sym.SABIALIAS)
2147 r, _ := su.AddRel(0) // type doesn't matter
2151 ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f})
2154 func addsection(ldr *loader.Loader, arch *sys.Arch, seg *sym.Segment, name string, rwx int) *sym.Section {
2155 sect := ldr.NewSection()
2156 sect.Rwx = uint8(rwx)
2159 sect.Align = int32(arch.PtrSize) // everything is at least pointer-aligned
2160 seg.Sections = append(seg.Sections, sect)
2167 limit int // limit on entry to sym
2170 func haslinkregister(ctxt *Link) bool {
2171 return ctxt.FixedFrameSize() != 0
2174 func callsize(ctxt *Link) int {
2175 if haslinkregister(ctxt) {
2178 return ctxt.Arch.RegSize
2181 type stkChk struct {
2184 morestack loader.Sym
2188 // Walk the call tree and check that there is always enough stack space
2189 // for the call frames, especially for a chain of nosplit functions.
2190 func (ctxt *Link) dostkcheck() {
2195 morestack: ldr.Lookup("runtime.morestack", 0),
2196 done: loader.MakeBitmap(ldr.NSym()),
2199 // Every splitting function ensures that there are at least StackLimit
2200 // bytes available below SP when the splitting prologue finishes.
2201 // If the splitting function calls F, then F begins execution with
2202 // at least StackLimit - callsize() bytes available.
2203 // Check that every function behaves correctly with this amount
2204 // of stack, following direct calls in order to piece together chains
2205 // of non-splitting functions.
2207 ch.limit = objabi.StackLimit - callsize(ctxt)
2208 if buildcfg.GOARCH == "arm64" {
2209 // need extra 8 bytes below SP to save FP
2213 // Check every function, but do the nosplit functions in a first pass,
2214 // to make the printed failure chains as short as possible.
2215 for _, s := range ctxt.Textp {
2216 if ldr.IsNoSplit(s) {
2222 for _, s := range ctxt.Textp {
2223 if !ldr.IsNoSplit(s) {
2230 func (sc *stkChk) check(up *chain, depth int) int {
2236 // Don't duplicate work: only need to consider each
2237 // function at top of safe zone once.
2238 top := limit == objabi.StackLimit-callsize(ctxt)
2247 sc.ctxt.Errorf(s, "nosplit stack check too deep")
2252 if ldr.AttrExternal(s) {
2253 // external function.
2254 // should never be called directly.
2255 // onlyctxt.Diagnose the direct caller.
2256 // TODO(mwhudson): actually think about this.
2257 // TODO(khr): disabled for now. Calls to external functions can only happen on the g0 stack.
2258 // See the trampolines in src/runtime/sys_darwin_$ARCH.go.
2259 //if depth == 1 && ldr.SymType(s) != sym.SXREF && !ctxt.DynlinkingGo() &&
2260 // ctxt.BuildMode != BuildModeCArchive && ctxt.BuildMode != BuildModePIE && ctxt.BuildMode != BuildModeCShared && ctxt.BuildMode != BuildModePlugin {
2261 // Errorf(s, "call to external function")
2265 info := ldr.FuncInfo(s)
2266 if !info.Valid() { // external function. see above.
2275 // morestack looks like it calls functions,
2276 // but it switches the stack pointer first.
2277 if s == sc.morestack {
2284 if !ldr.IsNoSplit(s) {
2285 // Ensure we have enough stack to call morestack.
2286 ch.limit = limit - callsize(ctxt)
2287 ch.sym = sc.morestack
2288 if sc.check(&ch, depth+1) < 0 {
2294 // Raise limit to allow frame.
2295 locals := info.Locals()
2296 limit = objabi.StackLimit + int(locals) + int(ctxt.FixedFrameSize())
2299 // Walk through sp adjustments in function, consuming relocs.
2300 relocs := ldr.Relocs(s)
2302 pcsp := obj.NewPCIter(uint32(ctxt.Arch.MinLC))
2304 for pcsp.Init(ldr.Data(info.Pcsp())); !pcsp.Done; pcsp.Next() {
2305 // pcsp.value is in effect for [pcsp.pc, pcsp.nextpc).
2307 // Check stack size in effect for this span.
2308 if int32(limit)-pcsp.Value < 0 {
2309 sc.broke(up, int(int32(limit)-pcsp.Value))
2313 // Process calls in this span.
2314 for ; ri < relocs.Count(); ri++ {
2316 if uint32(r.Off()) >= pcsp.NextPC {
2321 case t.IsDirectCall():
2322 ch.limit = int(int32(limit) - pcsp.Value - int32(callsize(ctxt)))
2324 if sc.check(&ch, depth+1) < 0 {
2328 // Indirect call. Assume it is a call to a splitting function,
2329 // so we have to make sure it can call morestack.
2330 // Arrange the data structures to report both calls, so that
2331 // if there is an error, stkprint shows all the steps involved.
2332 case t == objabi.R_CALLIND:
2333 ch.limit = int(int32(limit) - pcsp.Value - int32(callsize(ctxt)))
2335 ch1.limit = ch.limit - callsize(ctxt) // for morestack in called prologue
2337 ch1.sym = sc.morestack
2338 if sc.check(&ch1, depth+2) < 0 {
2348 func (sc *stkChk) broke(ch *chain, limit int) {
2349 sc.ctxt.Errorf(ch.sym, "nosplit stack overflow")
2353 func (sc *stkChk) print(ch *chain, limit int) {
2358 name = fmt.Sprintf("%s<%d>", ldr.SymName(ch.sym), ldr.SymVersion(ch.sym))
2359 if ldr.IsNoSplit(ch.sym) {
2360 name += " (nosplit)"
2363 name = "function pointer"
2367 // top of chain. ch.sym != 0.
2368 if ldr.IsNoSplit(ch.sym) {
2369 fmt.Printf("\t%d\tassumed on entry to %s\n", ch.limit, name)
2371 fmt.Printf("\t%d\tguaranteed after split check in %s\n", ch.limit, name)
2374 sc.print(ch.up, ch.limit+callsize(ctxt))
2375 if !haslinkregister(ctxt) {
2376 fmt.Printf("\t%d\ton entry to %s\n", ch.limit, name)
2380 if ch.limit != limit {
2381 fmt.Printf("\t%d\tafter %s uses %d\n", limit, name, ch.limit-limit)
2386 fmt.Fprintf(os.Stderr, "usage: link [options] main.o\n")
2387 objabi.Flagprint(os.Stderr)
2391 type SymbolType int8 // TODO: after genasmsym is gone, maybe rename to plan9typeChar or something
2394 // see also https://9p.io/magic/man2html/1/nm
2395 TextSym SymbolType = 'T'
2396 DataSym SymbolType = 'D'
2397 BSSSym SymbolType = 'B'
2398 UndefinedSym SymbolType = 'U'
2399 TLSSym SymbolType = 't'
2400 FrameSym SymbolType = 'm'
2401 ParamSym SymbolType = 'p'
2402 AutoSym SymbolType = 'a'
2404 // Deleted auto (not a real sym, just placeholder for type)
2405 DeletedAutoSym = 'x'
2408 // defineInternal defines a symbol used internally by the go runtime.
2409 func (ctxt *Link) defineInternal(p string, t sym.SymKind) loader.Sym {
2410 s := ctxt.loader.CreateSymForUpdate(p, 0)
2417 func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) loader.Sym {
2418 s := ctxt.defineInternal(p, t)
2419 ctxt.loader.SetSymValue(s, v)
2423 func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
2424 if uint64(addr) >= Segdata.Vaddr {
2425 return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
2427 if uint64(addr) >= Segtext.Vaddr {
2428 return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
2430 ldr.Errorf(s, "invalid datoff %#x", addr)
2434 func Entryvalue(ctxt *Link) int64 {
2435 a := *flagEntrySymbol
2436 if a[0] >= '0' && a[0] <= '9' {
2440 s := ldr.Lookup(a, 0)
2441 st := ldr.SymType(s)
2443 return *FlagTextAddr
2445 if !ctxt.IsAIX() && st != sym.STEXT {
2446 ldr.Errorf(s, "entry not text")
2448 return ldr.SymValue(s)
2451 func (ctxt *Link) callgraph() {
2457 for _, s := range ctxt.Textp {
2458 relocs := ldr.Relocs(s)
2459 for i := 0; i < relocs.Count(); i++ {
2465 if r.Type().IsDirectCall() && (ldr.SymType(rs) == sym.STEXT || ldr.SymType(rs) == sym.SABIALIAS) {
2466 ctxt.Logf("%s calls %s\n", ldr.SymName(s), ldr.SymName(rs))
2472 func Rnd(v int64, r int64) int64 {
2485 func bgetc(r *bio.Reader) int {
2486 c, err := r.ReadByte()
2489 log.Fatalf("reading input: %v", err)
2496 type markKind uint8 // for postorder traversal
2503 func postorder(libs []*sym.Library) []*sym.Library {
2504 order := make([]*sym.Library, 0, len(libs)) // hold the result
2505 mark := make(map[*sym.Library]markKind, len(libs))
2506 for _, lib := range libs {
2507 dfs(lib, mark, &order)
2512 func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library) {
2513 if mark[lib] == visited {
2516 if mark[lib] == visiting {
2517 panic("found import cycle while visiting " + lib.Pkg)
2519 mark[lib] = visiting
2520 for _, i := range lib.Imports {
2524 *order = append(*order, lib)
2527 func ElfSymForReloc(ctxt *Link, s loader.Sym) int32 {
2528 // If putelfsym created a local version of this symbol, use that in all
2530 les := ctxt.loader.SymLocalElfSym(s)
2534 return ctxt.loader.SymElfSym(s)
2538 func AddGotSym(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, elfRelocTyp uint32) {
2539 if ldr.SymGot(s) >= 0 {
2543 Adddynsym(ldr, target, syms, s)
2544 got := ldr.MakeSymbolUpdater(syms.GOT)
2545 ldr.SetGot(s, int32(got.Size()))
2546 got.AddUint(target.Arch, 0)
2549 if target.Arch.PtrSize == 8 {
2550 rela := ldr.MakeSymbolUpdater(syms.Rela)
2551 rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2552 rela.AddUint64(target.Arch, elf.R_INFO(uint32(ldr.SymDynid(s)), elfRelocTyp))
2553 rela.AddUint64(target.Arch, 0)
2555 rel := ldr.MakeSymbolUpdater(syms.Rel)
2556 rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2557 rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), elfRelocTyp))
2559 } else if target.IsDarwin() {
2560 leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT)
2561 leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
2562 if target.IsPIE() && target.IsInternal() {
2563 // Mach-O relocations are a royal pain to lay out.
2564 // They use a compact stateful bytecode representation.
2565 // Here we record what are needed and encode them later.
2566 MachoAddBind(int64(ldr.SymGot(s)), s)
2569 ldr.Errorf(s, "addgotsym: unsupported binary format")