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", abiInternalVer, &ctxt.unreachableMethod)
150 ctxt.mkArchSym("TOC", 0, &ctxt.TOC)
152 ctxt.DotTOC = make([]loader.Sym, ctxt.MaxVersion()+1)
153 for i := 0; i <= ctxt.MaxVersion(); i++ {
154 if i >= sym.SymVerABICount && i < sym.SymVerStatic { // these versions are not used currently
157 ctxt.mkArchSymVec(".TOC.", i, ctxt.DotTOC)
161 ctxt.mkArchSym(".rel", 0, &ctxt.Rel)
162 ctxt.mkArchSym(".rela", 0, &ctxt.Rela)
163 ctxt.mkArchSym(".rel.plt", 0, &ctxt.RelPLT)
164 ctxt.mkArchSym(".rela.plt", 0, &ctxt.RelaPLT)
167 ctxt.mkArchSym(".linkedit.got", 0, &ctxt.LinkEditGOT)
168 ctxt.mkArchSym(".linkedit.plt", 0, &ctxt.LinkEditPLT)
179 // Threshold of total text size, used for trampoline insertion. If the total
180 // text size is smaller than TrampLimit, we won't need to insert trampolines.
181 // It is pretty close to the offset range of a direct CALL machine instruction.
182 // We leave some room for extra stuff like PLT stubs.
190 Dragonflydynld string
193 // Empty spaces between codeblocks will be padded with this value.
194 // For example an architecture might want to pad with a trap instruction to
195 // catch wayward programs. Architectures that do not define a padding value
196 // are padded with zeros.
203 Adddynrel func(*Target, *loader.Loader, *ArchSyms, loader.Sym, loader.Reloc, int) bool
205 // Archreloc is an arch-specific hook that assists in relocation processing
206 // (invoked by 'relocsym'); it handles target-specific relocation tasks.
207 // Here "rel" is the current relocation being examined, "sym" is the symbol
208 // containing the chunk of data to which the relocation applies, and "off"
209 // is the contents of the to-be-relocated data item (from sym.P). Return
210 // value is the appropriately relocated value (to be written back to the
211 // same spot in sym.P), number of external _host_ relocations needed (i.e.
212 // ELF/Mach-O/etc. relocations, not Go relocations, this must match Elfreloc1,
213 // etc.), and a boolean indicating success/failure (a failing value indicates
215 Archreloc func(*Target, *loader.Loader, *ArchSyms, loader.Reloc, loader.Sym,
216 int64) (relocatedOffset int64, nExtReloc int, ok bool)
217 // Archrelocvariant is a second arch-specific hook used for
218 // relocation processing; it handles relocations where r.Type is
219 // insufficient to describe the relocation (r.Variant !=
220 // sym.RV_NONE). Here "rel" is the relocation being applied, "sym"
221 // is the symbol containing the chunk of data to which the
222 // relocation applies, and "off" is the contents of the
223 // to-be-relocated data item (from sym.P). Return is an updated
225 Archrelocvariant func(target *Target, ldr *loader.Loader, rel loader.Reloc,
226 rv sym.RelocVariant, sym loader.Sym, offset int64, data []byte) (relocatedOffset int64)
228 // Generate a trampoline for a call from s to rs if necessary. ri is
229 // index of the relocation.
230 Trampoline func(ctxt *Link, ldr *loader.Loader, ri int, rs, s loader.Sym)
232 // Assembling the binary breaks into two phases, writing the code/data/
233 // dwarf information (which is rather generic), and some more architecture
234 // specific work like setting up the elf headers/dynamic relocations, etc.
235 // The phases are called "Asmb" and "Asmb2". Asmb2 needs to be defined for
236 // every architecture, but only if architecture has an Asmb function will
237 // it be used for assembly. Otherwise a generic assembly Asmb function is
239 Asmb func(*Link, *loader.Loader)
240 Asmb2 func(*Link, *loader.Loader)
242 // Extreloc is an arch-specific hook that converts a Go relocation to an
243 // external relocation. Return the external relocation and whether it is
245 Extreloc func(*Target, *loader.Loader, loader.Reloc, loader.Sym) (loader.ExtReloc, bool)
247 Elfreloc1 func(*Link, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int, int64) bool
248 ElfrelocSize uint32 // size of an ELF relocation record, must match Elfreloc1.
249 Elfsetupplt func(ctxt *Link, plt, gotplt *loader.SymbolBuilder, dynamic loader.Sym)
250 Gentext func(*Link, *loader.Loader) // Generate text before addressing has been performed.
251 Machoreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
252 MachorelocSize uint32 // size of an Mach-O relocation record, must match Machoreloc1.
253 PEreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
254 Xcoffreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
256 // Generate additional symbols for the native symbol table just prior to
258 GenSymsLate func(*Link, *loader.Loader)
260 // TLSIEtoLE converts a TLS Initial Executable relocation to
261 // a TLS Local Executable relocation.
263 // This is possible when a TLS IE relocation refers to a local
264 // symbol in an executable, which is typical when internally
265 // linking PIE binaries.
266 TLSIEtoLE func(P []byte, off, size int)
268 // optional override for assignAddress
269 AssignAddress func(ldr *loader.Loader, sect *sym.Section, n int, s loader.Sym, va uint64, isTramp bool) (*sym.Section, int, uint64)
281 MINFUNC = 16 // minimum size for a function
284 // Symbol version of ABIInternal symbols. It is sym.SymVerABIInternal if ABI wrappers
285 // are used, 0 otherwise.
286 var abiInternalVer = sym.SymVerABIInternal
288 // DynlinkingGo reports whether we are producing Go code that can live
289 // in separate shared libraries linked together at runtime.
290 func (ctxt *Link) DynlinkingGo() bool {
292 panic("DynlinkingGo called before all symbols loaded")
294 return ctxt.BuildMode == BuildModeShared || ctxt.linkShared || ctxt.BuildMode == BuildModePlugin || ctxt.canUsePlugins
297 // CanUsePlugins reports whether a plugins can be used
298 func (ctxt *Link) CanUsePlugins() bool {
300 panic("CanUsePlugins called before all symbols loaded")
302 return ctxt.canUsePlugins
305 // NeedCodeSign reports whether we need to code-sign the output binary.
306 func (ctxt *Link) NeedCodeSign() bool {
307 return ctxt.IsDarwin() && ctxt.IsARM64()
319 debug_s bool // backup old value of debug['s']
325 // See -strictdups command line flag.
326 checkStrictDups int // 0=off 1=warning 2=error
327 strictDupMsgCount int
332 Segrodata sym.Segment
333 Segrelrodata sym.Segment
337 Segments = []*sym.Segment{&Segtext, &Segrodata, &Segrelrodata, &Segdata, &Segdwarf}
340 const pkgdef = "__.PKGDEF"
343 // externalobj is set to true if we see an object compiled by
344 // the host compiler that is not from a package that is known
345 // to support internal linking mode.
348 // unknownObjFormat is set to true if we see an object whose
349 // format we don't recognize.
350 unknownObjFormat = false
355 func Lflag(ctxt *Link, arg string) {
356 ctxt.Libdir = append(ctxt.Libdir, arg)
360 * Unix doesn't like it when we write to a running (or, sometimes,
361 * recently run) binary, so remove the output file before writing it.
362 * On Windows 7, remove() can force a subsequent create() to fail.
363 * S_ISREG() does not exist on Plan 9.
365 func mayberemoveoutfile() {
366 if fi, err := os.Lstat(*flagOutfile); err == nil && !fi.Mode().IsRegular() {
369 os.Remove(*flagOutfile)
372 func libinit(ctxt *Link) {
373 Funcalign = thearch.Funcalign
375 // add goroot to the end of the libdir list.
379 if *flagInstallSuffix != "" {
381 suffix = *flagInstallSuffix
382 } else if *flagRace {
385 } else if *flagMsan {
390 Lflag(ctxt, filepath.Join(buildcfg.GOROOT, "pkg", fmt.Sprintf("%s_%s%s%s", buildcfg.GOOS, buildcfg.GOARCH, suffixsep, suffix)))
394 if err := ctxt.Out.Open(*flagOutfile); err != nil {
395 Exitf("cannot create %s: %v", *flagOutfile, err)
398 if *flagEntrySymbol == "" {
399 switch ctxt.BuildMode {
400 case BuildModeCShared, BuildModeCArchive:
401 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s_lib", buildcfg.GOARCH, buildcfg.GOOS)
402 case BuildModeExe, BuildModePIE:
403 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s", buildcfg.GOARCH, buildcfg.GOOS)
404 case BuildModeShared, BuildModePlugin:
405 // No *flagEntrySymbol for -buildmode=shared and plugin
407 Errorf(nil, "unknown *flagEntrySymbol for buildmode %v", ctxt.BuildMode)
412 func exitIfErrors() {
413 if nerrors != 0 || checkStrictDups > 1 && strictDupMsgCount > 0 {
425 func loadinternal(ctxt *Link, name string) *sym.Library {
426 zerofp := goobj.FingerprintType{}
427 if ctxt.linkShared && ctxt.PackageShlib != nil {
428 if shlib := ctxt.PackageShlib[name]; shlib != "" {
429 return addlibpath(ctxt, "internal", "internal", "", name, shlib, zerofp)
432 if ctxt.PackageFile != nil {
433 if pname := ctxt.PackageFile[name]; pname != "" {
434 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
436 ctxt.Logf("loadinternal: cannot find %s\n", name)
440 for _, libdir := range ctxt.Libdir {
442 shlibname := filepath.Join(libdir, name+".shlibname")
443 if ctxt.Debugvlog != 0 {
444 ctxt.Logf("searching for %s.a in %s\n", name, shlibname)
446 if _, err := os.Stat(shlibname); err == nil {
447 return addlibpath(ctxt, "internal", "internal", "", name, shlibname, zerofp)
450 pname := filepath.Join(libdir, name+".a")
451 if ctxt.Debugvlog != 0 {
452 ctxt.Logf("searching for %s.a in %s\n", name, pname)
454 if _, err := os.Stat(pname); err == nil {
455 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
459 ctxt.Logf("warning: unable to find %s.a\n", name)
463 // extld returns the current external linker.
464 func (ctxt *Link) extld() []string {
465 if len(flagExtld) == 0 {
466 flagExtld = []string{"gcc"}
471 // findLibPathCmd uses cmd command to find gcc library libname.
472 // It returns library full path if found, or "none" if not found.
473 func (ctxt *Link) findLibPathCmd(cmd, libname string) string {
474 extld := ctxt.extld()
475 name, args := extld[0], extld[1:]
476 args = append(args, hostlinkArchArgs(ctxt.Arch)...)
477 args = append(args, cmd)
478 if ctxt.Debugvlog != 0 {
479 ctxt.Logf("%s %v\n", extld, args)
481 out, err := exec.Command(name, args...).Output()
483 if ctxt.Debugvlog != 0 {
484 ctxt.Logf("not using a %s file because compiler failed\n%v\n%s\n", libname, err, out)
488 return strings.TrimSpace(string(out))
491 // findLibPath searches for library libname.
492 // It returns library full path if found, or "none" if not found.
493 func (ctxt *Link) findLibPath(libname string) string {
494 return ctxt.findLibPathCmd("--print-file-name="+libname, libname)
497 func (ctxt *Link) loadlib() {
499 switch *FlagStrictDups {
503 flags |= loader.FlagStrictDups
505 log.Fatalf("invalid -strictdups flag value %d", *FlagStrictDups)
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.LinkMode == LinkExternal {
695 // When external linking, we are creating an object file. The
696 // absolute address is irrelevant.
700 // If there are no dynamic libraries needed, gcc disables dynamic linking.
701 // Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13)
702 // assumes that a dynamic binary always refers to at least one dynamic library.
703 // Rather than be a source of test cases for glibc, disable dynamic linking
704 // the same way that gcc would.
706 // Exception: on OS X, programs such as Shark only work with dynamic
707 // binaries, so leave it enabled on OS X (Mach-O) binaries.
708 // Also leave it enabled on Solaris which doesn't support
709 // statically linked binaries.
710 if ctxt.BuildMode == BuildModeExe {
711 if havedynamic == 0 && ctxt.HeadType != objabi.Hdarwin && ctxt.HeadType != objabi.Hsolaris {
716 if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && buildcfg.GOOS != "aix" {
717 toc := ctxt.loader.LookupOrCreateSym(".TOC.", 0)
718 sb := ctxt.loader.MakeSymbolUpdater(toc)
719 sb.SetType(sym.SDYNIMPORT)
722 // The Android Q linker started to complain about underalignment of the our TLS
723 // section. We don't actually use the section on android, so don't
725 if buildcfg.GOOS != "android" {
726 tlsg := ctxt.loader.LookupOrCreateSym("runtime.tlsg", 0)
727 sb := ctxt.loader.MakeSymbolUpdater(tlsg)
729 // runtime.tlsg is used for external linking on platforms that do not define
730 // a variable to hold g in assembly (currently only intel).
732 sb.SetType(sym.STLSBSS)
733 sb.SetSize(int64(ctxt.Arch.PtrSize))
734 } else if sb.Type() != sym.SDYNIMPORT {
735 Errorf(nil, "runtime declared tlsg variable %v", sb.Type())
737 ctxt.loader.SetAttrReachable(tlsg, true)
741 var moduledata loader.Sym
742 var mdsb *loader.SymbolBuilder
743 if ctxt.BuildMode == BuildModePlugin {
744 moduledata = ctxt.loader.LookupOrCreateSym("local.pluginmoduledata", 0)
745 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
746 ctxt.loader.SetAttrLocal(moduledata, true)
748 moduledata = ctxt.loader.LookupOrCreateSym("runtime.firstmoduledata", 0)
749 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
751 if mdsb.Type() != 0 && mdsb.Type() != sym.SDYNIMPORT {
752 // If the module (toolchain-speak for "executable or shared
753 // library") we are linking contains the runtime package, it
754 // will define the runtime.firstmoduledata symbol and we
755 // truncate it back to 0 bytes so we can define its entire
756 // contents in symtab.go:symtab().
759 // In addition, on ARM, the runtime depends on the linker
760 // recording the value of GOARM.
761 if ctxt.Arch.Family == sys.ARM {
762 goarm := ctxt.loader.LookupOrCreateSym("runtime.goarm", 0)
763 sb := ctxt.loader.MakeSymbolUpdater(goarm)
764 sb.SetType(sym.SDATA)
766 sb.AddUint8(uint8(buildcfg.GOARM))
769 // Set runtime.disableMemoryProfiling bool if
770 // runtime.MemProfile is not retained in the binary after
771 // deadcode (and we're not dynamically linking).
772 memProfile := ctxt.loader.Lookup("runtime.MemProfile", abiInternalVer)
773 if memProfile != 0 && !ctxt.loader.AttrReachable(memProfile) && !ctxt.DynlinkingGo() {
774 memProfSym := ctxt.loader.LookupOrCreateSym("runtime.disableMemoryProfiling", 0)
775 sb := ctxt.loader.MakeSymbolUpdater(memProfSym)
776 sb.SetType(sym.SDATA)
778 sb.AddUint8(1) // true bool
781 // If OTOH the module does not contain the runtime package,
782 // create a local symbol for the moduledata.
783 moduledata = ctxt.loader.LookupOrCreateSym("local.moduledata", 0)
784 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
785 ctxt.loader.SetAttrLocal(moduledata, true)
787 // In all cases way we mark the moduledata as noptrdata to hide it from
789 mdsb.SetType(sym.SNOPTRDATA)
790 ctxt.loader.SetAttrReachable(moduledata, true)
791 ctxt.Moduledata = moduledata
793 if ctxt.Arch == sys.Arch386 && ctxt.HeadType != objabi.Hwindows {
794 if (ctxt.BuildMode == BuildModeCArchive && ctxt.IsELF) || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE || ctxt.DynlinkingGo() {
795 got := ctxt.loader.LookupOrCreateSym("_GLOBAL_OFFSET_TABLE_", 0)
796 sb := ctxt.loader.MakeSymbolUpdater(got)
797 sb.SetType(sym.SDYNIMPORT)
798 ctxt.loader.SetAttrReachable(got, true)
802 // DWARF-gen and other phases require that the unit Textp slices
803 // be populated, so that it can walk the functions in each unit.
804 // Call into the loader to do this (requires that we collect the
805 // set of internal libraries first). NB: might be simpler if we
806 // moved isRuntimeDepPkg to cmd/internal and then did the test in
807 // loader.AssignTextSymbolOrder.
808 ctxt.Library = postorder(ctxt.Library)
810 for _, lib := range ctxt.Library {
811 intlibs = append(intlibs, isRuntimeDepPkg(lib.Pkg))
813 ctxt.Textp = ctxt.loader.AssignTextSymbolOrder(ctxt.Library, intlibs, ctxt.Textp)
816 // mangleTypeSym shortens the names of symbols that represent Go types
817 // if they are visible in the symbol table.
819 // As the names of these symbols are derived from the string of
820 // the type, they can run to many kilobytes long. So we shorten
821 // them using a SHA-1 when the name appears in the final binary.
822 // This also removes characters that upset external linkers.
824 // These are the symbols that begin with the prefix 'type.' and
825 // contain run-time type information used by the runtime and reflect
826 // packages. All Go binaries contain these symbols, but only
827 // those programs loaded dynamically in multiple parts need these
828 // symbols to have entries in the symbol table.
829 func (ctxt *Link) mangleTypeSym() {
830 if ctxt.BuildMode != BuildModeShared && !ctxt.linkShared && ctxt.BuildMode != BuildModePlugin && !ctxt.CanUsePlugins() {
835 for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
836 if !ldr.AttrReachable(s) && !ctxt.linkShared {
837 // If -linkshared, the GCProg generation code may need to reach
838 // out to the shared library for the type descriptor's data, even
839 // the type descriptor itself is not actually needed at run time
840 // (therefore not reachable). We still need to mangle its name,
841 // so it is consistent with the one stored in the shared library.
844 name := ldr.SymName(s)
845 newName := typeSymbolMangle(name)
847 ldr.SetSymExtname(s, newName)
849 // When linking against a shared library, the Go object file may
850 // have reference to the original symbol name whereas the shared
851 // library provides a symbol with the mangled name. We need to
852 // copy the payload of mangled to original.
853 // XXX maybe there is a better way to do this.
854 dup := ldr.Lookup(newName, ldr.SymVersion(s))
857 dt := ldr.SymType(dup)
858 if st == sym.Sxxx && dt != sym.Sxxx {
866 // typeSymbolMangle mangles the given symbol name into something shorter.
868 // Keep the type.. prefix, which parts of the linker (like the
869 // DWARF generator) know means the symbol is not decodable.
870 // Leave type.runtime. symbols alone, because other parts of
871 // the linker manipulates them.
872 func typeSymbolMangle(name string) string {
873 if !strings.HasPrefix(name, "type.") {
876 if strings.HasPrefix(name, "type.runtime.") {
879 if len(name) <= 14 && !strings.Contains(name, "@") { // Issue 19529
882 hash := sha1.Sum([]byte(name))
887 return prefix + base64.StdEncoding.EncodeToString(hash[:6])
891 * look for the next file in an archive.
892 * adapted from libmach.
894 func nextar(bp *bio.Reader, off int64, a *ArHdr) int64 {
899 var buf [SAR_HDR]byte
900 if n, err := io.ReadFull(bp, buf[:]); err != nil {
901 if n == 0 && err != io.EOF {
907 a.name = artrim(buf[0:16])
908 a.date = artrim(buf[16:28])
909 a.uid = artrim(buf[28:34])
910 a.gid = artrim(buf[34:40])
911 a.mode = artrim(buf[40:48])
912 a.size = artrim(buf[48:58])
913 a.fmag = artrim(buf[58:60])
915 arsize := atolwhex(a.size)
919 return arsize + SAR_HDR
922 func loadobjfile(ctxt *Link, lib *sym.Library) {
923 pkg := objabi.PathToPrefix(lib.Pkg)
925 if ctxt.Debugvlog > 1 {
926 ctxt.Logf("ldobj: %s (%s)\n", lib.File, pkg)
928 f, err := bio.Open(lib.File)
930 Exitf("cannot open file %s: %v", lib.File, err)
934 if pkg == "main" && !lib.Main {
935 Exitf("%s: not package main", lib.File)
939 for i := 0; i < len(ARMAG); i++ {
940 if c, err := f.ReadByte(); err == nil && c == ARMAG[i] {
944 /* load it as a regular file */
945 l := f.MustSeek(0, 2)
947 ldobj(ctxt, f, lib, l, lib.File, lib.File)
952 * load all the object files from the archive now.
953 * this gives us sequential file access and keeps us
954 * from needing to come back later to pick up more
955 * objects. it breaks the usual C archive model, but
956 * this is Go, not C. the common case in Go is that
957 * we need to load all the objects, and then we throw away
958 * the individual symbols that are unused.
960 * loading every object will also make it possible to
961 * load foreign objects not referenced by __.PKGDEF.
966 l := nextar(f, off, &arhdr)
971 Exitf("%s: malformed archive", lib.File)
975 // __.PKGDEF isn't a real Go object file, and it's
976 // absent in -linkobj builds anyway. Skipping it
977 // ensures consistency between -linkobj and normal
979 if arhdr.name == pkgdef {
983 // Skip other special (non-object-file) sections that
984 // build tools may have added. Such sections must have
985 // short names so that the suffix is not truncated.
986 if len(arhdr.name) < 16 {
987 if ext := filepath.Ext(arhdr.name); ext != ".o" && ext != ".syso" {
992 pname := fmt.Sprintf("%s(%s)", lib.File, arhdr.name)
993 l = atolwhex(arhdr.size)
994 ldobj(ctxt, f, lib, l, pname, lib.File)
998 type Hostobj struct {
999 ld func(*Link, *bio.Reader, string, int64, string)
1007 var hostobj []Hostobj
1009 // These packages can use internal linking mode.
1010 // Others trigger external mode.
1011 var internalpkg = []string{
1020 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 {
1022 for _, intpkg := range internalpkg {
1029 // DragonFly declares errno with __thread, which results in a symbol
1030 // type of R_386_TLS_GD or R_X86_64_TLSGD. The Go linker does not
1031 // currently know how to handle TLS relocations, hence we have to
1032 // force external linking for any libraries that link in code that
1033 // uses errno. This can be removed if the Go linker ever supports
1034 // these relocation types.
1035 if headType == objabi.Hdragonfly {
1036 if pkg == "net" || pkg == "os/user" {
1045 hostobj = append(hostobj, Hostobj{})
1046 h := &hostobj[len(hostobj)-1]
1056 func hostobjs(ctxt *Link) {
1057 if ctxt.LinkMode != LinkInternal {
1062 for i := 0; i < len(hostobj); i++ {
1064 f, err := bio.Open(h.file)
1066 Exitf("cannot reopen %s: %v", h.pn, err)
1069 f.MustSeek(h.off, 0)
1071 Errorf(nil, "%s: unrecognized object file format", h.pn)
1074 h.ld(ctxt, f, h.pkg, h.length, h.pn)
1079 func hostlinksetup(ctxt *Link) {
1080 if ctxt.LinkMode != LinkExternal {
1084 // For external link, record that we need to tell the external linker -s,
1085 // and turn off -s internally: the external linker needs the symbol
1086 // information for its final link.
1090 // create temporary directory and arrange cleanup
1091 if *flagTmpdir == "" {
1092 dir, err := ioutil.TempDir("", "go-link-")
1100 os.RemoveAll(*flagTmpdir)
1104 // change our output to temporary object file
1105 if err := ctxt.Out.Close(); err != nil {
1106 Exitf("error closing output file")
1108 mayberemoveoutfile()
1110 p := filepath.Join(*flagTmpdir, "go.o")
1111 if err := ctxt.Out.Open(p); err != nil {
1112 Exitf("cannot create %s: %v", p, err)
1116 // hostobjCopy creates a copy of the object files in hostobj in a
1117 // temporary directory.
1118 func hostobjCopy() (paths []string) {
1119 var wg sync.WaitGroup
1120 sema := make(chan struct{}, runtime.NumCPU()) // limit open file descriptors
1121 for i, h := range hostobj {
1123 dst := filepath.Join(*flagTmpdir, fmt.Sprintf("%06d.o", i))
1124 paths = append(paths, dst)
1133 f, err := os.Open(h.file)
1135 Exitf("cannot reopen %s: %v", h.pn, err)
1138 if _, err := f.Seek(h.off, 0); err != nil {
1139 Exitf("cannot seek %s: %v", h.pn, err)
1142 w, err := os.Create(dst)
1144 Exitf("cannot create %s: %v", dst, err)
1146 if _, err := io.CopyN(w, f, h.length); err != nil {
1147 Exitf("cannot write %s: %v", dst, err)
1149 if err := w.Close(); err != nil {
1150 Exitf("cannot close %s: %v", dst, err)
1158 // writeGDBLinkerScript creates gcc linker script file in temp
1159 // directory. writeGDBLinkerScript returns created file path.
1160 // The script is used to work around gcc bug
1161 // (see https://golang.org/issue/20183 for details).
1162 func writeGDBLinkerScript() string {
1163 name := "fix_debug_gdb_scripts.ld"
1164 path := filepath.Join(*flagTmpdir, name)
1167 .debug_gdb_scripts BLOCK(__section_alignment__) (NOLOAD) :
1169 *(.debug_gdb_scripts)
1172 INSERT AFTER .debug_types;
1174 err := ioutil.WriteFile(path, []byte(src), 0666)
1176 Errorf(nil, "WriteFile %s failed: %v", name, err)
1181 // archive builds a .a archive from the hostobj object files.
1182 func (ctxt *Link) archive() {
1183 if ctxt.BuildMode != BuildModeCArchive {
1189 if *flagExtar == "" {
1193 mayberemoveoutfile()
1195 // Force the buffer to flush here so that external
1196 // tools will see a complete file.
1197 if err := ctxt.Out.Close(); err != nil {
1198 Exitf("error closing %v", *flagOutfile)
1201 argv := []string{*flagExtar, "-q", "-c", "-s"}
1202 if ctxt.HeadType == objabi.Haix {
1203 argv = append(argv, "-X64")
1205 argv = append(argv, *flagOutfile)
1206 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1207 argv = append(argv, hostobjCopy()...)
1209 if ctxt.Debugvlog != 0 {
1210 ctxt.Logf("archive: %s\n", strings.Join(argv, " "))
1213 // If supported, use syscall.Exec() to invoke the archive command,
1214 // which should be the final remaining step needed for the link.
1215 // This will reduce peak RSS for the link (and speed up linking of
1216 // large applications), since when the archive command runs we
1217 // won't be holding onto all of the linker's live memory.
1218 if syscallExecSupported && !ownTmpDir {
1220 ctxt.execArchive(argv)
1221 panic("should not get here")
1224 // Otherwise invoke 'ar' in the usual way (fork + exec).
1225 if out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput(); err != nil {
1226 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1230 func (ctxt *Link) hostlink() {
1231 if ctxt.LinkMode != LinkExternal || nerrors > 0 {
1234 if ctxt.BuildMode == BuildModeCArchive {
1239 argv = append(argv, ctxt.extld()...)
1240 argv = append(argv, hostlinkArchArgs(ctxt.Arch)...)
1242 if *FlagS || debug_s {
1243 if ctxt.HeadType == objabi.Hdarwin {
1244 // Recent versions of macOS print
1245 // ld: warning: option -s is obsolete and being ignored
1246 // so do not pass any arguments.
1248 argv = append(argv, "-s")
1252 // On darwin, whether to combine DWARF into executable.
1253 // Only macOS supports unmapped segments such as our __DWARF segment.
1254 combineDwarf := ctxt.IsDarwin() && !*FlagS && !*FlagW && !debug_s && machoPlatform == PLATFORM_MACOS
1256 switch ctxt.HeadType {
1257 case objabi.Hdarwin:
1259 // Leave room for DWARF combining.
1260 // -headerpad is incompatible with -fembed-bitcode.
1261 argv = append(argv, "-Wl,-headerpad,1144")
1263 if ctxt.DynlinkingGo() && buildcfg.GOOS != "ios" {
1264 // -flat_namespace is deprecated on iOS.
1265 // It is useful for supporting plugins. We don't support plugins on iOS.
1266 argv = append(argv, "-Wl,-flat_namespace")
1269 argv = append(argv, "-Wl,-S") // suppress STAB (symbolic debugging) symbols
1271 case objabi.Hopenbsd:
1272 argv = append(argv, "-Wl,-nopie")
1273 argv = append(argv, "-pthread")
1274 case objabi.Hwindows:
1276 argv = append(argv, "-mwindows")
1278 argv = append(argv, "-mconsole")
1280 // Mark as having awareness of terminal services, to avoid
1281 // ancient compatibility hacks.
1282 argv = append(argv, "-Wl,--tsaware")
1285 argv = append(argv, "-Wl,--nxcompat")
1287 argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", PeMinimumTargetMajorVersion))
1288 argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", PeMinimumTargetMinorVersion))
1289 argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", PeMinimumTargetMajorVersion))
1290 argv = append(argv, fmt.Sprintf("-Wl,--minor-subsystem-version=%d", PeMinimumTargetMinorVersion))
1292 argv = append(argv, "-pthread")
1293 // prevent ld to reorder .text functions to keep the same
1294 // first/last functions for moduledata.
1295 argv = append(argv, "-Wl,-bnoobjreorder")
1296 // mcmodel=large is needed for every gcc generated files, but
1297 // ld still need -bbigtoc in order to allow larger TOC.
1298 argv = append(argv, "-mcmodel=large")
1299 argv = append(argv, "-Wl,-bbigtoc")
1302 // Enable ASLR on Windows.
1303 addASLRargs := func(argv []string) []string {
1305 argv = append(argv, "-Wl,--dynamicbase")
1306 // enable high-entropy ASLR on 64-bit.
1307 if ctxt.Arch.PtrSize >= 8 {
1308 argv = append(argv, "-Wl,--high-entropy-va")
1313 switch ctxt.BuildMode {
1315 if ctxt.HeadType == objabi.Hdarwin {
1316 if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() {
1317 argv = append(argv, "-Wl,-no_pie")
1318 argv = append(argv, "-Wl,-pagezero_size,4000000")
1322 switch ctxt.HeadType {
1323 case objabi.Hdarwin, objabi.Haix:
1324 case objabi.Hwindows:
1325 argv = addASLRargs(argv)
1328 if ctxt.UseRelro() {
1329 argv = append(argv, "-Wl,-z,relro")
1331 argv = append(argv, "-pie")
1333 case BuildModeCShared:
1334 if ctxt.HeadType == objabi.Hdarwin {
1335 argv = append(argv, "-dynamiclib")
1337 if ctxt.UseRelro() {
1338 argv = append(argv, "-Wl,-z,relro")
1340 argv = append(argv, "-shared")
1341 if ctxt.HeadType == objabi.Hwindows {
1343 argv = addASLRargs(argv)
1346 // Pass -z nodelete to mark the shared library as
1347 // non-closeable: a dlclose will do nothing.
1348 argv = append(argv, "-Wl,-z,nodelete")
1349 // Only pass Bsymbolic on non-Windows.
1350 argv = append(argv, "-Wl,-Bsymbolic")
1353 case BuildModeShared:
1354 if ctxt.UseRelro() {
1355 argv = append(argv, "-Wl,-z,relro")
1357 argv = append(argv, "-shared")
1358 case BuildModePlugin:
1359 if ctxt.HeadType == objabi.Hdarwin {
1360 argv = append(argv, "-dynamiclib")
1362 if ctxt.UseRelro() {
1363 argv = append(argv, "-Wl,-z,relro")
1365 argv = append(argv, "-shared")
1369 var altLinker string
1370 if ctxt.IsELF && ctxt.DynlinkingGo() {
1371 // We force all symbol resolution to be done at program startup
1372 // because lazy PLT resolution can use large amounts of stack at
1373 // times we cannot allow it to do so.
1374 argv = append(argv, "-Wl,-znow")
1376 // Do not let the host linker generate COPY relocations. These
1377 // can move symbols out of sections that rely on stable offsets
1378 // from the beginning of the section (like sym.STYPE).
1379 argv = append(argv, "-Wl,-znocopyreloc")
1381 if buildcfg.GOOS == "android" {
1382 // Use lld to avoid errors from default linker (issue #38838)
1386 if ctxt.Arch.InFamily(sys.ARM, sys.ARM64) && buildcfg.GOOS == "linux" {
1387 // On ARM, the GNU linker will generate COPY relocations
1388 // even with -znocopyreloc set.
1389 // https://sourceware.org/bugzilla/show_bug.cgi?id=19962
1391 // On ARM64, the GNU linker will fail instead of
1392 // generating COPY relocations.
1394 // In both cases, switch to gold.
1397 // If gold is not installed, gcc will silently switch
1398 // back to ld.bfd. So we parse the version information
1399 // and provide a useful error if gold is missing.
1400 name, args := flagExtld[0], flagExtld[1:]
1401 args = append(args, "-fuse-ld=gold", "-Wl,--version")
1402 cmd := exec.Command(name, args...)
1403 if out, err := cmd.CombinedOutput(); err == nil {
1404 if !bytes.Contains(out, []byte("GNU gold")) {
1405 log.Fatalf("ARM external linker must be gold (issue #15696), but is not: %s", out)
1410 if ctxt.Arch.Family == sys.ARM64 && buildcfg.GOOS == "freebsd" {
1411 // Switch to ld.bfd on freebsd/arm64.
1414 // Provide a useful error if ld.bfd is missing.
1415 name, args := flagExtld[0], flagExtld[1:]
1416 args = append(args, "-fuse-ld=bfd", "-Wl,--version")
1417 cmd := exec.Command(name, args...)
1418 if out, err := cmd.CombinedOutput(); err == nil {
1419 if !bytes.Contains(out, []byte("GNU ld")) {
1420 log.Fatalf("ARM64 external linker must be ld.bfd (issue #35197), please install devel/binutils")
1424 if altLinker != "" {
1425 argv = append(argv, "-fuse-ld="+altLinker)
1428 if ctxt.IsELF && len(buildinfo) > 0 {
1429 argv = append(argv, fmt.Sprintf("-Wl,--build-id=0x%x", buildinfo))
1432 // On Windows, given -o foo, GCC will append ".exe" to produce
1433 // "foo.exe". We have decided that we want to honor the -o
1434 // option. To make this work, we append a '.' so that GCC
1435 // will decide that the file already has an extension. We
1436 // only want to do this when producing a Windows output file
1437 // on a Windows host.
1438 outopt := *flagOutfile
1439 if buildcfg.GOOS == "windows" && runtime.GOOS == "windows" && filepath.Ext(outopt) == "" {
1442 argv = append(argv, "-o")
1443 argv = append(argv, outopt)
1445 if rpath.val != "" {
1446 argv = append(argv, fmt.Sprintf("-Wl,-rpath,%s", rpath.val))
1449 if *flagInterpreter != "" {
1450 // Many linkers support both -I and the --dynamic-linker flags
1451 // to set the ELF interpreter, but lld only supports
1452 // --dynamic-linker so prefer that (ld on very old Solaris only
1453 // supports -I but that seems less important).
1454 argv = append(argv, fmt.Sprintf("-Wl,--dynamic-linker,%s", *flagInterpreter))
1457 // Force global symbols to be exported for dlopen, etc.
1459 argv = append(argv, "-rdynamic")
1461 if ctxt.HeadType == objabi.Haix {
1462 fileName := xcoffCreateExportFile(ctxt)
1463 argv = append(argv, "-Wl,-bE:"+fileName)
1466 const unusedArguments = "-Qunused-arguments"
1467 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, unusedArguments) {
1468 argv = append(argv, unusedArguments)
1471 const compressDWARF = "-Wl,--compress-debug-sections=zlib-gnu"
1472 if ctxt.compressDWARF && linkerFlagSupported(ctxt.Arch, argv[0], altLinker, compressDWARF) {
1473 argv = append(argv, compressDWARF)
1476 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1477 argv = append(argv, hostobjCopy()...)
1478 if ctxt.HeadType == objabi.Haix {
1479 // We want to have C files after Go files to remove
1480 // trampolines csects made by ld.
1481 argv = append(argv, "-nostartfiles")
1482 argv = append(argv, "/lib/crt0_64.o")
1484 extld := ctxt.extld()
1485 name, args := extld[0], extld[1:]
1486 // Get starting files.
1487 getPathFile := func(file string) string {
1488 args := append(args, "-maix64", "--print-file-name="+file)
1489 out, err := exec.Command(name, args...).CombinedOutput()
1491 log.Fatalf("running %s failed: %v\n%s", extld, err, out)
1493 return strings.Trim(string(out), "\n")
1495 argv = append(argv, getPathFile("crtcxa.o"))
1496 argv = append(argv, getPathFile("crtdbase.o"))
1499 if ctxt.linkShared {
1500 seenDirs := make(map[string]bool)
1501 seenLibs := make(map[string]bool)
1502 addshlib := func(path string) {
1503 dir, base := filepath.Split(path)
1505 argv = append(argv, "-L"+dir)
1507 argv = append(argv, "-Wl,-rpath="+dir)
1509 seenDirs[dir] = true
1511 base = strings.TrimSuffix(base, ".so")
1512 base = strings.TrimPrefix(base, "lib")
1513 if !seenLibs[base] {
1514 argv = append(argv, "-l"+base)
1515 seenLibs[base] = true
1518 for _, shlib := range ctxt.Shlibs {
1519 addshlib(shlib.Path)
1520 for _, dep := range shlib.Deps {
1524 libpath := findshlib(ctxt, dep)
1532 // clang, unlike GCC, passes -rdynamic to the linker
1533 // even when linking with -static, causing a linker
1534 // error when using GNU ld. So take out -rdynamic if
1535 // we added it. We do it in this order, rather than
1536 // only adding -rdynamic later, so that -extldflags
1537 // can override -rdynamic without using -static.
1538 // Similarly for -Wl,--dynamic-linker.
1539 checkStatic := func(arg string) {
1540 if ctxt.IsELF && arg == "-static" {
1541 for i := range argv {
1542 if argv[i] == "-rdynamic" || strings.HasPrefix(argv[i], "-Wl,--dynamic-linker,") {
1549 for _, p := range ldflag {
1550 argv = append(argv, p)
1554 // When building a program with the default -buildmode=exe the
1555 // gc compiler generates code requires DT_TEXTREL in a
1556 // position independent executable (PIE). On systems where the
1557 // toolchain creates PIEs by default, and where DT_TEXTREL
1558 // does not work, the resulting programs will not run. See
1559 // issue #17847. To avoid this problem pass -no-pie to the
1560 // toolchain if it is supported.
1561 if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared && !(ctxt.IsDarwin() && ctxt.IsARM64()) {
1562 // GCC uses -no-pie, clang uses -nopie.
1563 for _, nopie := range []string{"-no-pie", "-nopie"} {
1564 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, nopie) {
1565 argv = append(argv, nopie)
1571 for _, p := range flagExtldflags {
1572 argv = append(argv, p)
1575 if ctxt.HeadType == objabi.Hwindows {
1576 // Determine which linker we're using. Add in the extldflags in
1577 // case used has specified "-fuse-ld=...".
1578 extld := ctxt.extld()
1579 name, args := extld[0], extld[1:]
1580 args = append(args, flagExtldflags...)
1581 args = append(args, "-Wl,--version")
1582 cmd := exec.Command(name, args...)
1584 if out, err := cmd.CombinedOutput(); err == nil {
1585 if bytes.Contains(out, []byte("LLD ")) {
1590 // use gcc linker script to work around gcc bug
1591 // (see https://golang.org/issue/20183 for details).
1593 p := writeGDBLinkerScript()
1594 argv = append(argv, "-Wl,-T,"+p)
1596 // libmingw32 and libmingwex have some inter-dependencies,
1597 // so must use linker groups.
1598 argv = append(argv, "-Wl,--start-group", "-lmingwex", "-lmingw32", "-Wl,--end-group")
1599 argv = append(argv, peimporteddlls()...)
1602 if ctxt.Debugvlog != 0 {
1603 ctxt.Logf("host link:")
1604 for _, v := range argv {
1610 out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput()
1612 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1615 // Filter out useless linker warnings caused by bugs outside Go.
1616 // See also cmd/go/internal/work/exec.go's gccld method.
1619 for _, line := range bytes.SplitAfter(out, []byte("\n")) {
1620 // golang.org/issue/26073 - Apple Xcode bug
1621 if bytes.Contains(line, []byte("ld: warning: text-based stub file")) {
1630 // Remove TOC overflow warning on AIX.
1631 if bytes.Contains(line, []byte("ld: 0711-783")) {
1636 save = append(save, line)
1638 out = bytes.Join(save, nil)
1641 // always print external output even if the command is successful, so that we don't
1642 // swallow linker warnings (see https://golang.org/issue/17935).
1643 ctxt.Logf("%s", out)
1647 // Find "dsymutils" and "strip" tools using CC --print-prog-name.
1649 cc = append(cc, ctxt.extld()...)
1650 cc = append(cc, hostlinkArchArgs(ctxt.Arch)...)
1651 cc = append(cc, "--print-prog-name", "dsymutil")
1652 out, err := exec.Command(cc[0], cc[1:]...).CombinedOutput()
1654 Exitf("%s: finding dsymutil failed: %v\n%s", os.Args[0], err, out)
1656 dsymutilCmd := strings.TrimSuffix(string(out), "\n")
1658 cc[len(cc)-1] = "strip"
1659 out, err = exec.Command(cc[0], cc[1:]...).CombinedOutput()
1661 Exitf("%s: finding strip failed: %v\n%s", os.Args[0], err, out)
1663 stripCmd := strings.TrimSuffix(string(out), "\n")
1665 dsym := filepath.Join(*flagTmpdir, "go.dwarf")
1666 if out, err := exec.Command(dsymutilCmd, "-f", *flagOutfile, "-o", dsym).CombinedOutput(); err != nil {
1667 Exitf("%s: running dsymutil failed: %v\n%s", os.Args[0], err, out)
1669 // Remove STAB (symbolic debugging) symbols after we are done with them (by dsymutil).
1670 // They contain temporary file paths and make the build not reproducible.
1671 if out, err := exec.Command(stripCmd, "-S", *flagOutfile).CombinedOutput(); err != nil {
1672 Exitf("%s: running strip failed: %v\n%s", os.Args[0], err, out)
1674 // Skip combining if `dsymutil` didn't generate a file. See #11994.
1675 if _, err := os.Stat(dsym); os.IsNotExist(err) {
1678 // For os.Rename to work reliably, must be in same directory as outfile.
1679 combinedOutput := *flagOutfile + "~"
1680 exef, err := os.Open(*flagOutfile)
1682 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1685 exem, err := macho.NewFile(exef)
1687 Exitf("%s: parsing Mach-O header failed: %v", os.Args[0], err)
1689 if err := machoCombineDwarf(ctxt, exef, exem, dsym, combinedOutput); err != nil {
1690 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1692 os.Remove(*flagOutfile)
1693 if err := os.Rename(combinedOutput, *flagOutfile); err != nil {
1694 Exitf("%s: %v", os.Args[0], err)
1697 if ctxt.NeedCodeSign() {
1698 err := machoCodeSign(ctxt, *flagOutfile)
1700 Exitf("%s: code signing failed: %v", os.Args[0], err)
1705 var createTrivialCOnce sync.Once
1707 func linkerFlagSupported(arch *sys.Arch, linker, altLinker, flag string) bool {
1708 createTrivialCOnce.Do(func() {
1709 src := filepath.Join(*flagTmpdir, "trivial.c")
1710 if err := ioutil.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
1711 Errorf(nil, "WriteFile trivial.c failed: %v", err)
1715 flagsWithNextArgSkip := []string{
1724 flagsWithNextArgKeep := []string{
1730 prefixesToKeep := []string{
1741 flags := hostlinkArchArgs(arch)
1744 for _, f := range append(flagExtldflags, ldflag...) {
1746 flags = append(flags, f)
1750 } else if f == "" || f[0] != '-' {
1751 } else if contains(flagsWithNextArgSkip, f) {
1753 } else if contains(flagsWithNextArgKeep, f) {
1754 flags = append(flags, f)
1757 for _, p := range prefixesToKeep {
1758 if strings.HasPrefix(f, p) {
1759 flags = append(flags, f)
1766 if altLinker != "" {
1767 flags = append(flags, "-fuse-ld="+altLinker)
1769 flags = append(flags, flag, "trivial.c")
1771 cmd := exec.Command(linker, flags...)
1772 cmd.Dir = *flagTmpdir
1773 cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
1774 out, err := cmd.CombinedOutput()
1775 // GCC says "unrecognized command line option ‘-no-pie’"
1776 // clang says "unknown argument: '-no-pie'"
1777 return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
1780 // hostlinkArchArgs returns arguments to pass to the external linker
1781 // based on the architecture.
1782 func hostlinkArchArgs(arch *sys.Arch) []string {
1783 switch arch.Family {
1785 return []string{"-m32"}
1787 if buildcfg.GOOS == "darwin" {
1788 return []string{"-arch", "x86_64", "-m64"}
1790 return []string{"-m64"}
1792 return []string{"-m64"}
1794 return []string{"-marm"}
1796 if buildcfg.GOOS == "darwin" {
1797 return []string{"-arch", "arm64"}
1800 return []string{"-mabi=64"}
1802 return []string{"-mabi=32"}
1804 if buildcfg.GOOS == "aix" {
1805 return []string{"-maix64"}
1807 return []string{"-m64"}
1814 var wantHdr = objabi.HeaderString()
1816 // ldobj loads an input object. If it is a host object (an object
1817 // compiled by a non-Go compiler) it returns the Hostobj pointer. If
1818 // it is a Go object, it returns nil.
1819 func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string, file string) *Hostobj {
1820 pkg := objabi.PathToPrefix(lib.Pkg)
1822 eof := f.Offset() + length
1828 f.MustSeek(start, 0)
1830 unit := &sym.CompilationUnit{Lib: lib}
1831 lib.Units = append(lib.Units, unit)
1833 magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
1834 if magic == 0x7f454c46 { // \x7F E L F
1835 ldelf := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1836 textp, flags, err := loadelf.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn, ehdr.Flags)
1838 Errorf(nil, "%v", err)
1842 ctxt.Textp = append(ctxt.Textp, textp...)
1844 return ldhostobj(ldelf, ctxt.HeadType, f, pkg, length, pn, file)
1847 if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
1848 ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1849 textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1851 Errorf(nil, "%v", err)
1854 ctxt.Textp = append(ctxt.Textp, textp...)
1856 return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
1864 ldpe := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1865 textp, rsrc, err := loadpe.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1867 Errorf(nil, "%v", err)
1871 setpersrc(ctxt, rsrc)
1873 ctxt.Textp = append(ctxt.Textp, textp...)
1875 return ldhostobj(ldpe, ctxt.HeadType, f, pkg, length, pn, file)
1878 if c1 == 0x01 && (c2 == 0xD7 || c2 == 0xF7) {
1879 ldxcoff := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1880 textp, err := loadxcoff.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1882 Errorf(nil, "%v", err)
1885 ctxt.Textp = append(ctxt.Textp, textp...)
1887 return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
1890 if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
1891 // An unrecognized object is just passed to the external linker.
1892 // If we try to read symbols from this object, we will
1893 // report an error at that time.
1894 unknownObjFormat = true
1895 return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
1898 /* check the header */
1899 line, err := f.ReadString('\n')
1901 Errorf(nil, "truncated object file: %s: %v", pn, err)
1905 if !strings.HasPrefix(line, "go object ") {
1906 if strings.HasSuffix(pn, ".go") {
1907 Exitf("%s: uncompiled .go source file", pn)
1911 if line == ctxt.Arch.Name {
1912 // old header format: just $GOOS
1913 Errorf(nil, "%s: stale object file", pn)
1917 Errorf(nil, "%s: not an object file: @%d %q", pn, start, line)
1921 // First, check that the basic GOOS, GOARCH, and Version match.
1922 if line != wantHdr {
1923 Errorf(nil, "%s: linked object header mismatch:\nhave %q\nwant %q\n", pn, line, wantHdr)
1926 // Skip over exports and other info -- ends with \n!\n.
1928 // Note: It's possible for "\n!\n" to appear within the binary
1929 // package export data format. To avoid truncating the package
1930 // definition prematurely (issue 21703), we keep track of
1931 // how many "$$" delimiters we've seen.
1933 import0 := f.Offset()
1935 c1 = '\n' // the last line ended in \n
1941 if markers%2 == 0 && c2 == '!' && c3 == '\n' {
1944 if c2 == '$' && c3 == '$' {
1953 Errorf(nil, "truncated object file: %s", pn)
1958 import1 := f.Offset()
1960 f.MustSeek(import0, 0)
1961 ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
1962 f.MustSeek(import1, 0)
1964 fingerprint := ctxt.loader.Preload(ctxt.IncVersion(), f, lib, unit, eof-f.Offset())
1965 if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
1966 // Check fingerprint, to ensure the importing and imported packages
1967 // have consistent view of symbol indices.
1968 // Normally the go command should ensure this. But in case something
1969 // goes wrong, it could lead to obscure bugs like run-time crash.
1970 // Check it here to be sure.
1971 if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
1972 lib.Fingerprint = fingerprint
1974 checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
1977 addImports(ctxt, lib, pn)
1981 func checkFingerprint(lib *sym.Library, libfp goobj.FingerprintType, src string, srcfp goobj.FingerprintType) {
1983 Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
1987 func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
1988 data := make([]byte, sym.Size)
1989 sect := f.Sections[sym.Section]
1990 if sect.Type != elf.SHT_PROGBITS && sect.Type != elf.SHT_NOTE {
1991 Errorf(nil, "reading %s from non-data section", sym.Name)
1993 n, err := sect.ReadAt(data, int64(sym.Value-sect.Addr))
1994 if uint64(n) != sym.Size {
1995 Errorf(nil, "reading contents of %s: %v", sym.Name, err)
2000 func readwithpad(r io.Reader, sz int32) ([]byte, error) {
2001 data := make([]byte, Rnd(int64(sz), 4))
2002 _, err := io.ReadFull(r, data)
2010 func readnote(f *elf.File, name []byte, typ int32) ([]byte, error) {
2011 for _, sect := range f.Sections {
2012 if sect.Type != elf.SHT_NOTE {
2017 var namesize, descsize, noteType int32
2018 err := binary.Read(r, f.ByteOrder, &namesize)
2023 return nil, fmt.Errorf("read namesize failed: %v", err)
2025 err = binary.Read(r, f.ByteOrder, &descsize)
2027 return nil, fmt.Errorf("read descsize failed: %v", err)
2029 err = binary.Read(r, f.ByteOrder, ¬eType)
2031 return nil, fmt.Errorf("read type failed: %v", err)
2033 noteName, err := readwithpad(r, namesize)
2035 return nil, fmt.Errorf("read name failed: %v", err)
2037 desc, err := readwithpad(r, descsize)
2039 return nil, fmt.Errorf("read desc failed: %v", err)
2041 if string(name) == string(noteName) && typ == noteType {
2049 func findshlib(ctxt *Link, shlib string) string {
2050 if filepath.IsAbs(shlib) {
2053 for _, libdir := range ctxt.Libdir {
2054 libpath := filepath.Join(libdir, shlib)
2055 if _, err := os.Stat(libpath); err == nil {
2059 Errorf(nil, "cannot find shared library: %s", shlib)
2063 func ldshlibsyms(ctxt *Link, shlib string) {
2065 if filepath.IsAbs(shlib) {
2067 shlib = filepath.Base(shlib)
2069 libpath = findshlib(ctxt, shlib)
2074 for _, processedlib := range ctxt.Shlibs {
2075 if processedlib.Path == libpath {
2079 if ctxt.Debugvlog > 1 {
2080 ctxt.Logf("ldshlibsyms: found library with name %s at %s\n", shlib, libpath)
2083 f, err := elf.Open(libpath)
2085 Errorf(nil, "cannot open shared library: %s", libpath)
2088 // Keep the file open as decodetypeGcprog needs to read from it.
2089 // TODO: fix. Maybe mmap the file.
2092 hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
2094 Errorf(nil, "cannot read ABI hash from shared library %s: %v", libpath, err)
2098 depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
2100 Errorf(nil, "cannot read dep list from shared library %s: %v", libpath, err)
2104 for _, dep := range strings.Split(string(depsbytes), "\n") {
2108 if !filepath.IsAbs(dep) {
2109 // If the dep can be interpreted as a path relative to the shlib
2110 // in which it was found, do that. Otherwise, we will leave it
2111 // to be resolved by libdir lookup.
2112 abs := filepath.Join(filepath.Dir(libpath), dep)
2113 if _, err := os.Stat(abs); err == nil {
2117 deps = append(deps, dep)
2120 syms, err := f.DynamicSymbols()
2122 Errorf(nil, "cannot read symbols from shared library: %s", libpath)
2126 for _, elfsym := range syms {
2127 if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
2131 // Symbols whose names start with "type." are compiler
2132 // generated, so make functions with that prefix internal.
2134 symname := elfsym.Name // (unmangled) symbol name
2135 if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type.") {
2136 ver = abiInternalVer
2137 } else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC {
2138 // Demangle the ABI name. Keep in sync with symtab.go:mangleABIName.
2139 if strings.HasSuffix(elfsym.Name, ".abiinternal") {
2140 ver = sym.SymVerABIInternal
2141 symname = strings.TrimSuffix(elfsym.Name, ".abiinternal")
2142 } else if strings.HasSuffix(elfsym.Name, ".abi0") {
2144 symname = strings.TrimSuffix(elfsym.Name, ".abi0")
2149 s := l.LookupOrCreateSym(symname, ver)
2151 // Because loadlib above loads all .a files before loading
2152 // any shared libraries, any non-dynimport symbols we find
2153 // that duplicate symbols already loaded should be ignored
2154 // (the symbols from the .a files "win").
2155 if l.SymType(s) != 0 && l.SymType(s) != sym.SDYNIMPORT {
2158 su := l.MakeSymbolUpdater(s)
2159 su.SetType(sym.SDYNIMPORT)
2160 l.SetSymElfType(s, elf.ST_TYPE(elfsym.Info))
2161 su.SetSize(int64(elfsym.Size))
2162 if elfsym.Section != elf.SHN_UNDEF {
2163 // Set .File for the library that actually defines the symbol.
2164 l.SetSymPkg(s, libpath)
2166 // The decodetype_* functions in decodetype.go need access to
2168 sname := l.SymName(s)
2169 if strings.HasPrefix(sname, "type.") && !strings.HasPrefix(sname, "type..") {
2170 su.SetData(readelfsymboldata(ctxt, f, &elfsym))
2174 if symname != elfsym.Name {
2175 l.SetSymExtname(s, elfsym.Name)
2178 ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f})
2181 func addsection(ldr *loader.Loader, arch *sys.Arch, seg *sym.Segment, name string, rwx int) *sym.Section {
2182 sect := ldr.NewSection()
2183 sect.Rwx = uint8(rwx)
2186 sect.Align = int32(arch.PtrSize) // everything is at least pointer-aligned
2187 seg.Sections = append(seg.Sections, sect)
2194 limit int // limit on entry to sym
2197 func haslinkregister(ctxt *Link) bool {
2198 return ctxt.FixedFrameSize() != 0
2201 func callsize(ctxt *Link) int {
2202 if haslinkregister(ctxt) {
2205 return ctxt.Arch.RegSize
2208 type stkChk struct {
2211 morestack loader.Sym
2215 // Walk the call tree and check that there is always enough stack space
2216 // for the call frames, especially for a chain of nosplit functions.
2217 func (ctxt *Link) dostkcheck() {
2222 morestack: ldr.Lookup("runtime.morestack", 0),
2223 done: loader.MakeBitmap(ldr.NSym()),
2226 // Every splitting function ensures that there are at least StackLimit
2227 // bytes available below SP when the splitting prologue finishes.
2228 // If the splitting function calls F, then F begins execution with
2229 // at least StackLimit - callsize() bytes available.
2230 // Check that every function behaves correctly with this amount
2231 // of stack, following direct calls in order to piece together chains
2232 // of non-splitting functions.
2234 ch.limit = objabi.StackLimit - callsize(ctxt)
2235 if buildcfg.GOARCH == "arm64" {
2236 // need extra 8 bytes below SP to save FP
2240 // Check every function, but do the nosplit functions in a first pass,
2241 // to make the printed failure chains as short as possible.
2242 for _, s := range ctxt.Textp {
2243 if ldr.IsNoSplit(s) {
2249 for _, s := range ctxt.Textp {
2250 if !ldr.IsNoSplit(s) {
2257 func (sc *stkChk) check(up *chain, depth int) int {
2263 // Don't duplicate work: only need to consider each
2264 // function at top of safe zone once.
2265 top := limit == objabi.StackLimit-callsize(ctxt)
2274 sc.ctxt.Errorf(s, "nosplit stack check too deep")
2279 if ldr.AttrExternal(s) {
2280 // external function.
2281 // should never be called directly.
2282 // onlyctxt.Diagnose the direct caller.
2283 // TODO(mwhudson): actually think about this.
2284 // TODO(khr): disabled for now. Calls to external functions can only happen on the g0 stack.
2285 // See the trampolines in src/runtime/sys_darwin_$ARCH.go.
2286 //if depth == 1 && ldr.SymType(s) != sym.SXREF && !ctxt.DynlinkingGo() &&
2287 // ctxt.BuildMode != BuildModeCArchive && ctxt.BuildMode != BuildModePIE && ctxt.BuildMode != BuildModeCShared && ctxt.BuildMode != BuildModePlugin {
2288 // Errorf(s, "call to external function")
2292 info := ldr.FuncInfo(s)
2293 if !info.Valid() { // external function. see above.
2302 // morestack looks like it calls functions,
2303 // but it switches the stack pointer first.
2304 if s == sc.morestack {
2311 if !ldr.IsNoSplit(s) {
2312 // Ensure we have enough stack to call morestack.
2313 ch.limit = limit - callsize(ctxt)
2314 ch.sym = sc.morestack
2315 if sc.check(&ch, depth+1) < 0 {
2321 // Raise limit to allow frame.
2322 locals := info.Locals()
2323 limit = objabi.StackLimit + int(locals) + int(ctxt.FixedFrameSize())
2326 // Walk through sp adjustments in function, consuming relocs.
2327 relocs := ldr.Relocs(s)
2329 pcsp := obj.NewPCIter(uint32(ctxt.Arch.MinLC))
2331 for pcsp.Init(ldr.Data(ldr.Pcsp(s))); !pcsp.Done; pcsp.Next() {
2332 // pcsp.value is in effect for [pcsp.pc, pcsp.nextpc).
2334 // Check stack size in effect for this span.
2335 if int32(limit)-pcsp.Value < 0 {
2336 sc.broke(up, int(int32(limit)-pcsp.Value))
2340 // Process calls in this span.
2341 for ; ri < relocs.Count(); ri++ {
2343 if uint32(r.Off()) >= pcsp.NextPC {
2348 case t.IsDirectCall():
2349 ch.limit = int(int32(limit) - pcsp.Value - int32(callsize(ctxt)))
2351 if sc.check(&ch, depth+1) < 0 {
2355 // Indirect call. Assume it is a call to a splitting function,
2356 // so we have to make sure it can call morestack.
2357 // Arrange the data structures to report both calls, so that
2358 // if there is an error, stkprint shows all the steps involved.
2359 case t == objabi.R_CALLIND:
2360 ch.limit = int(int32(limit) - pcsp.Value - int32(callsize(ctxt)))
2362 ch1.limit = ch.limit - callsize(ctxt) // for morestack in called prologue
2364 ch1.sym = sc.morestack
2365 if sc.check(&ch1, depth+2) < 0 {
2375 func (sc *stkChk) broke(ch *chain, limit int) {
2376 sc.ctxt.Errorf(ch.sym, "nosplit stack overflow")
2380 func (sc *stkChk) print(ch *chain, limit int) {
2385 name = fmt.Sprintf("%s<%d>", ldr.SymName(ch.sym), ldr.SymVersion(ch.sym))
2386 if ldr.IsNoSplit(ch.sym) {
2387 name += " (nosplit)"
2390 name = "function pointer"
2394 // top of chain. ch.sym != 0.
2395 if ldr.IsNoSplit(ch.sym) {
2396 fmt.Printf("\t%d\tassumed on entry to %s\n", ch.limit, name)
2398 fmt.Printf("\t%d\tguaranteed after split check in %s\n", ch.limit, name)
2401 sc.print(ch.up, ch.limit+callsize(ctxt))
2402 if !haslinkregister(ctxt) {
2403 fmt.Printf("\t%d\ton entry to %s\n", ch.limit, name)
2407 if ch.limit != limit {
2408 fmt.Printf("\t%d\tafter %s uses %d\n", limit, name, ch.limit-limit)
2413 fmt.Fprintf(os.Stderr, "usage: link [options] main.o\n")
2414 objabi.Flagprint(os.Stderr)
2418 type SymbolType int8 // TODO: after genasmsym is gone, maybe rename to plan9typeChar or something
2421 // see also https://9p.io/magic/man2html/1/nm
2422 TextSym SymbolType = 'T'
2423 DataSym SymbolType = 'D'
2424 BSSSym SymbolType = 'B'
2425 UndefinedSym SymbolType = 'U'
2426 TLSSym SymbolType = 't'
2427 FrameSym SymbolType = 'm'
2428 ParamSym SymbolType = 'p'
2429 AutoSym SymbolType = 'a'
2431 // Deleted auto (not a real sym, just placeholder for type)
2432 DeletedAutoSym = 'x'
2435 // defineInternal defines a symbol used internally by the go runtime.
2436 func (ctxt *Link) defineInternal(p string, t sym.SymKind) loader.Sym {
2437 s := ctxt.loader.CreateSymForUpdate(p, 0)
2444 func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) loader.Sym {
2445 s := ctxt.defineInternal(p, t)
2446 ctxt.loader.SetSymValue(s, v)
2450 func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
2451 if uint64(addr) >= Segdata.Vaddr {
2452 return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
2454 if uint64(addr) >= Segtext.Vaddr {
2455 return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
2457 ldr.Errorf(s, "invalid datoff %#x", addr)
2461 func Entryvalue(ctxt *Link) int64 {
2462 a := *flagEntrySymbol
2463 if a[0] >= '0' && a[0] <= '9' {
2467 s := ldr.Lookup(a, 0)
2468 st := ldr.SymType(s)
2470 return *FlagTextAddr
2472 if !ctxt.IsAIX() && st != sym.STEXT {
2473 ldr.Errorf(s, "entry not text")
2475 return ldr.SymValue(s)
2478 func (ctxt *Link) callgraph() {
2484 for _, s := range ctxt.Textp {
2485 relocs := ldr.Relocs(s)
2486 for i := 0; i < relocs.Count(); i++ {
2492 if r.Type().IsDirectCall() && ldr.SymType(rs) == sym.STEXT {
2493 ctxt.Logf("%s calls %s\n", ldr.SymName(s), ldr.SymName(rs))
2499 func Rnd(v int64, r int64) int64 {
2512 func bgetc(r *bio.Reader) int {
2513 c, err := r.ReadByte()
2516 log.Fatalf("reading input: %v", err)
2523 type markKind uint8 // for postorder traversal
2530 func postorder(libs []*sym.Library) []*sym.Library {
2531 order := make([]*sym.Library, 0, len(libs)) // hold the result
2532 mark := make(map[*sym.Library]markKind, len(libs))
2533 for _, lib := range libs {
2534 dfs(lib, mark, &order)
2539 func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library) {
2540 if mark[lib] == visited {
2543 if mark[lib] == visiting {
2544 panic("found import cycle while visiting " + lib.Pkg)
2546 mark[lib] = visiting
2547 for _, i := range lib.Imports {
2551 *order = append(*order, lib)
2554 func ElfSymForReloc(ctxt *Link, s loader.Sym) int32 {
2555 // If putelfsym created a local version of this symbol, use that in all
2557 les := ctxt.loader.SymLocalElfSym(s)
2561 return ctxt.loader.SymElfSym(s)
2565 func AddGotSym(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, elfRelocTyp uint32) {
2566 if ldr.SymGot(s) >= 0 {
2570 Adddynsym(ldr, target, syms, s)
2571 got := ldr.MakeSymbolUpdater(syms.GOT)
2572 ldr.SetGot(s, int32(got.Size()))
2573 got.AddUint(target.Arch, 0)
2576 if target.Arch.PtrSize == 8 {
2577 rela := ldr.MakeSymbolUpdater(syms.Rela)
2578 rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2579 rela.AddUint64(target.Arch, elf.R_INFO(uint32(ldr.SymDynid(s)), elfRelocTyp))
2580 rela.AddUint64(target.Arch, 0)
2582 rel := ldr.MakeSymbolUpdater(syms.Rel)
2583 rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2584 rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), elfRelocTyp))
2586 } else if target.IsDarwin() {
2587 leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT)
2588 leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
2589 if target.IsPIE() && target.IsInternal() {
2590 // Mach-O relocations are a royal pain to lay out.
2591 // They use a compact stateful bytecode representation.
2592 // Here we record what are needed and encode them later.
2593 MachoAddBind(int64(ldr.SymGot(s)), s)
2596 ldr.Errorf(s, "addgotsym: unsupported binary format")