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']
323 liveness int64 // size of liveness data (funcdata), printed if -v
325 // See -strictdups command line flag.
326 checkStrictDups int // 0=off 1=warning 2=error
327 strictDupMsgCount int
332 Segrodata sym.Segment
333 Segrelrodata sym.Segment
337 Segments = []*sym.Segment{&Segtext, &Segrodata, &Segrelrodata, &Segdata, &Segdwarf}
340 const pkgdef = "__.PKGDEF"
343 // externalobj is set to true if we see an object compiled by
344 // the host compiler that is not from a package that is known
345 // to support internal linking mode.
348 // 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 {
388 } else if *flagAsan {
393 if buildcfg.GOROOT != "" {
394 Lflag(ctxt, filepath.Join(buildcfg.GOROOT, "pkg", fmt.Sprintf("%s_%s%s%s", buildcfg.GOOS, buildcfg.GOARCH, suffixsep, suffix)))
399 if err := ctxt.Out.Open(*flagOutfile); err != nil {
400 Exitf("cannot create %s: %v", *flagOutfile, err)
403 if *flagEntrySymbol == "" {
404 switch ctxt.BuildMode {
405 case BuildModeCShared, BuildModeCArchive:
406 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s_lib", buildcfg.GOARCH, buildcfg.GOOS)
407 case BuildModeExe, BuildModePIE:
408 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s", buildcfg.GOARCH, buildcfg.GOOS)
409 case BuildModeShared, BuildModePlugin:
410 // No *flagEntrySymbol for -buildmode=shared and plugin
412 Errorf(nil, "unknown *flagEntrySymbol for buildmode %v", ctxt.BuildMode)
417 func exitIfErrors() {
418 if nerrors != 0 || checkStrictDups > 1 && strictDupMsgCount > 0 {
430 func loadinternal(ctxt *Link, name string) *sym.Library {
431 zerofp := goobj.FingerprintType{}
432 if ctxt.linkShared && ctxt.PackageShlib != nil {
433 if shlib := ctxt.PackageShlib[name]; shlib != "" {
434 return addlibpath(ctxt, "internal", "internal", "", name, shlib, zerofp)
437 if ctxt.PackageFile != nil {
438 if pname := ctxt.PackageFile[name]; pname != "" {
439 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
441 ctxt.Logf("loadinternal: cannot find %s\n", name)
445 for _, libdir := range ctxt.Libdir {
447 shlibname := filepath.Join(libdir, name+".shlibname")
448 if ctxt.Debugvlog != 0 {
449 ctxt.Logf("searching for %s.a in %s\n", name, shlibname)
451 if _, err := os.Stat(shlibname); err == nil {
452 return addlibpath(ctxt, "internal", "internal", "", name, shlibname, zerofp)
455 pname := filepath.Join(libdir, name+".a")
456 if ctxt.Debugvlog != 0 {
457 ctxt.Logf("searching for %s.a in %s\n", name, pname)
459 if _, err := os.Stat(pname); err == nil {
460 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
464 ctxt.Logf("warning: unable to find %s.a\n", name)
468 // extld returns the current external linker.
469 func (ctxt *Link) extld() []string {
470 if len(flagExtld) == 0 {
471 flagExtld = []string{"gcc"}
476 // findLibPathCmd uses cmd command to find gcc library libname.
477 // It returns library full path if found, or "none" if not found.
478 func (ctxt *Link) findLibPathCmd(cmd, libname string) string {
479 extld := ctxt.extld()
480 name, args := extld[0], extld[1:]
481 args = append(args, hostlinkArchArgs(ctxt.Arch)...)
482 args = append(args, cmd)
483 if ctxt.Debugvlog != 0 {
484 ctxt.Logf("%s %v\n", extld, args)
486 out, err := exec.Command(name, args...).Output()
488 if ctxt.Debugvlog != 0 {
489 ctxt.Logf("not using a %s file because compiler failed\n%v\n%s\n", libname, err, out)
493 return strings.TrimSpace(string(out))
496 // findLibPath searches for library libname.
497 // It returns library full path if found, or "none" if not found.
498 func (ctxt *Link) findLibPath(libname string) string {
499 return ctxt.findLibPathCmd("--print-file-name="+libname, libname)
502 func (ctxt *Link) loadlib() {
504 switch *FlagStrictDups {
508 flags |= loader.FlagStrictDups
510 log.Fatalf("invalid -strictdups flag value %d", *FlagStrictDups)
512 elfsetstring1 := func(str string, off int) { elfsetstring(ctxt, 0, str, off) }
513 ctxt.loader = loader.NewLoader(flags, elfsetstring1, &ctxt.ErrorReporter.ErrorReporter)
514 ctxt.ErrorReporter.SymName = func(s loader.Sym) string {
515 return ctxt.loader.SymName(s)
518 // ctxt.Library grows during the loop, so not a range loop.
520 for ; i < len(ctxt.Library); i++ {
521 lib := ctxt.Library[i]
523 if ctxt.Debugvlog > 1 {
524 ctxt.Logf("autolib: %s (from %s)\n", lib.File, lib.Objref)
526 loadobjfile(ctxt, lib)
530 // load internal packages, if not already
532 loadinternal(ctxt, "runtime/race")
535 loadinternal(ctxt, "runtime/msan")
538 loadinternal(ctxt, "runtime/asan")
540 loadinternal(ctxt, "runtime")
541 for ; i < len(ctxt.Library); i++ {
542 lib := ctxt.Library[i]
544 loadobjfile(ctxt, lib)
547 // At this point, the Go objects are "preloaded". Not all the symbols are
548 // added to the symbol table (only defined package symbols are). Looking
549 // up symbol by name may not get expected result.
551 iscgo = ctxt.LibraryByPkg["runtime/cgo"] != nil
553 // Plugins a require cgo support to function. Similarly, plugins may require additional
554 // internal linker support on some platforms which may not be implemented.
555 ctxt.canUsePlugins = ctxt.LibraryByPkg["plugin"] != nil && iscgo
557 // We now have enough information to determine the link mode.
558 determineLinkMode(ctxt)
560 if ctxt.LinkMode == LinkExternal && !iscgo && !(buildcfg.GOOS == "darwin" && ctxt.BuildMode != BuildModePlugin && ctxt.Arch.Family == sys.AMD64) {
561 // This indicates a user requested -linkmode=external.
562 // The startup code uses an import of runtime/cgo to decide
563 // whether to initialize the TLS. So give it one. This could
564 // be handled differently but it's an unusual case.
565 if lib := loadinternal(ctxt, "runtime/cgo"); lib != nil && lib.Shlib == "" {
566 if ctxt.BuildMode == BuildModeShared || ctxt.linkShared {
567 Exitf("cannot implicitly include runtime/cgo in a shared library")
569 for ; i < len(ctxt.Library); i++ {
570 lib := ctxt.Library[i]
572 loadobjfile(ctxt, lib)
578 // Add non-package symbols and references of externally defined symbols.
579 ctxt.loader.LoadSyms(ctxt.Arch)
581 // Load symbols from shared libraries, after all Go object symbols are loaded.
582 for _, lib := range ctxt.Library {
584 if ctxt.Debugvlog > 1 {
585 ctxt.Logf("autolib: %s (from %s)\n", lib.Shlib, lib.Objref)
587 ldshlibsyms(ctxt, lib.Shlib)
591 // Process cgo directives (has to be done before host object loading).
592 ctxt.loadcgodirectives()
594 // Conditionally load host objects, or setup for external linking.
598 if ctxt.LinkMode == LinkInternal && len(hostobj) != 0 {
599 // If we have any undefined symbols in external
600 // objects, try to read them from the libgcc file.
602 undefs := ctxt.loader.UndefinedRelocTargets(1)
607 if *flagLibGCC == "" {
608 *flagLibGCC = ctxt.findLibPathCmd("--print-libgcc-file-name", "libgcc")
610 if runtime.GOOS == "openbsd" && *flagLibGCC == "libgcc.a" {
611 // On OpenBSD `clang --print-libgcc-file-name` returns "libgcc.a".
612 // In this case we fail to load libgcc.a and can encounter link
613 // errors - see if we can find libcompiler_rt.a instead.
614 *flagLibGCC = ctxt.findLibPathCmd("--print-file-name=libcompiler_rt.a", "libcompiler_rt")
616 if ctxt.HeadType == objabi.Hwindows {
617 if p := ctxt.findLibPath("libmingwex.a"); p != "none" {
620 if p := ctxt.findLibPath("libmingw32.a"); p != "none" {
623 // Link libmsvcrt.a to resolve '__acrt_iob_func' symbol
624 // (see https://golang.org/issue/23649 for details).
625 if p := ctxt.findLibPath("libmsvcrt.a"); p != "none" {
628 // TODO: maybe do something similar to peimporteddlls to collect all lib names
629 // and try link them all to final exe just like libmingwex.a and libmingw32.a:
632 #cgo windows LDFLAGS: -lmsvcrt -lm
637 if *flagLibGCC != "none" {
638 hostArchive(ctxt, *flagLibGCC)
643 // We've loaded all the code now.
648 strictDupMsgCount = ctxt.loader.NStrictDupMsgs()
651 // loadcgodirectives reads the previously discovered cgo directives, creating
652 // symbols in preparation for host object loading or use later in the link.
653 func (ctxt *Link) loadcgodirectives() {
655 hostObjSyms := make(map[loader.Sym]struct{})
656 for _, d := range ctxt.cgodata {
657 setCgoAttr(ctxt, d.file, d.pkg, d.directives, hostObjSyms)
661 if ctxt.LinkMode == LinkInternal {
662 // Drop all the cgo_import_static declarations.
663 // Turns out we won't be needing them.
664 for symIdx := range hostObjSyms {
665 if l.SymType(symIdx) == sym.SHOSTOBJ {
666 // If a symbol was marked both
667 // cgo_import_static and cgo_import_dynamic,
668 // then we want to make it cgo_import_dynamic
670 su := l.MakeSymbolUpdater(symIdx)
671 if l.SymExtname(symIdx) != "" && l.SymDynimplib(symIdx) != "" && !(l.AttrCgoExportStatic(symIdx) || l.AttrCgoExportDynamic(symIdx)) {
672 su.SetType(sym.SDYNIMPORT)
681 // Set up flags and special symbols depending on the platform build mode.
682 // This version works with loader.Loader.
683 func (ctxt *Link) linksetup() {
684 switch ctxt.BuildMode {
685 case BuildModeCShared, BuildModePlugin:
686 symIdx := ctxt.loader.LookupOrCreateSym("runtime.islibrary", 0)
687 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
688 sb.SetType(sym.SNOPTRDATA)
690 case BuildModeCArchive:
691 symIdx := ctxt.loader.LookupOrCreateSym("runtime.isarchive", 0)
692 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
693 sb.SetType(sym.SNOPTRDATA)
697 // Recalculate pe parameters now that we have ctxt.LinkMode set.
698 if ctxt.HeadType == objabi.Hwindows {
702 if ctxt.LinkMode == LinkExternal {
703 // When external linking, we are creating an object file. The
704 // absolute address is irrelevant.
708 // If there are no dynamic libraries needed, gcc disables dynamic linking.
709 // Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13)
710 // assumes that a dynamic binary always refers to at least one dynamic library.
711 // Rather than be a source of test cases for glibc, disable dynamic linking
712 // the same way that gcc would.
714 // Exception: on OS X, programs such as Shark only work with dynamic
715 // binaries, so leave it enabled on OS X (Mach-O) binaries.
716 // Also leave it enabled on Solaris which doesn't support
717 // statically linked binaries.
718 if ctxt.BuildMode == BuildModeExe {
719 if havedynamic == 0 && ctxt.HeadType != objabi.Hdarwin && ctxt.HeadType != objabi.Hsolaris {
724 if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && buildcfg.GOOS != "aix" {
725 toc := ctxt.loader.LookupOrCreateSym(".TOC.", 0)
726 sb := ctxt.loader.MakeSymbolUpdater(toc)
727 sb.SetType(sym.SDYNIMPORT)
730 // The Android Q linker started to complain about underalignment of the our TLS
731 // section. We don't actually use the section on android, so don't
733 if buildcfg.GOOS != "android" {
734 tlsg := ctxt.loader.LookupOrCreateSym("runtime.tlsg", 0)
735 sb := ctxt.loader.MakeSymbolUpdater(tlsg)
737 // runtime.tlsg is used for external linking on platforms that do not define
738 // a variable to hold g in assembly (currently only intel).
740 sb.SetType(sym.STLSBSS)
741 sb.SetSize(int64(ctxt.Arch.PtrSize))
742 } else if sb.Type() != sym.SDYNIMPORT {
743 Errorf(nil, "runtime declared tlsg variable %v", sb.Type())
745 ctxt.loader.SetAttrReachable(tlsg, true)
749 var moduledata loader.Sym
750 var mdsb *loader.SymbolBuilder
751 if ctxt.BuildMode == BuildModePlugin {
752 moduledata = ctxt.loader.LookupOrCreateSym("local.pluginmoduledata", 0)
753 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
754 ctxt.loader.SetAttrLocal(moduledata, true)
756 moduledata = ctxt.loader.LookupOrCreateSym("runtime.firstmoduledata", 0)
757 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
759 if mdsb.Type() != 0 && mdsb.Type() != sym.SDYNIMPORT {
760 // If the module (toolchain-speak for "executable or shared
761 // library") we are linking contains the runtime package, it
762 // will define the runtime.firstmoduledata symbol and we
763 // truncate it back to 0 bytes so we can define its entire
764 // contents in symtab.go:symtab().
767 // In addition, on ARM, the runtime depends on the linker
768 // recording the value of GOARM.
769 if ctxt.Arch.Family == sys.ARM {
770 goarm := ctxt.loader.LookupOrCreateSym("runtime.goarm", 0)
771 sb := ctxt.loader.MakeSymbolUpdater(goarm)
772 sb.SetType(sym.SDATA)
774 sb.AddUint8(uint8(buildcfg.GOARM))
777 // Set runtime.disableMemoryProfiling bool if
778 // runtime.MemProfile is not retained in the binary after
779 // deadcode (and we're not dynamically linking).
780 memProfile := ctxt.loader.Lookup("runtime.MemProfile", abiInternalVer)
781 if memProfile != 0 && !ctxt.loader.AttrReachable(memProfile) && !ctxt.DynlinkingGo() {
782 memProfSym := ctxt.loader.LookupOrCreateSym("runtime.disableMemoryProfiling", 0)
783 sb := ctxt.loader.MakeSymbolUpdater(memProfSym)
784 sb.SetType(sym.SDATA)
786 sb.AddUint8(1) // true bool
789 // If OTOH the module does not contain the runtime package,
790 // create a local symbol for the moduledata.
791 moduledata = ctxt.loader.LookupOrCreateSym("local.moduledata", 0)
792 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
793 ctxt.loader.SetAttrLocal(moduledata, true)
795 // In all cases way we mark the moduledata as noptrdata to hide it from
797 mdsb.SetType(sym.SNOPTRDATA)
798 ctxt.loader.SetAttrReachable(moduledata, true)
799 ctxt.Moduledata = moduledata
801 if ctxt.Arch == sys.Arch386 && ctxt.HeadType != objabi.Hwindows {
802 if (ctxt.BuildMode == BuildModeCArchive && ctxt.IsELF) || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE || ctxt.DynlinkingGo() {
803 got := ctxt.loader.LookupOrCreateSym("_GLOBAL_OFFSET_TABLE_", 0)
804 sb := ctxt.loader.MakeSymbolUpdater(got)
805 sb.SetType(sym.SDYNIMPORT)
806 ctxt.loader.SetAttrReachable(got, true)
810 // DWARF-gen and other phases require that the unit Textp slices
811 // be populated, so that it can walk the functions in each unit.
812 // Call into the loader to do this (requires that we collect the
813 // set of internal libraries first). NB: might be simpler if we
814 // moved isRuntimeDepPkg to cmd/internal and then did the test in
815 // loader.AssignTextSymbolOrder.
816 ctxt.Library = postorder(ctxt.Library)
818 for _, lib := range ctxt.Library {
819 intlibs = append(intlibs, isRuntimeDepPkg(lib.Pkg))
821 ctxt.Textp = ctxt.loader.AssignTextSymbolOrder(ctxt.Library, intlibs, ctxt.Textp)
824 // mangleTypeSym shortens the names of symbols that represent Go types
825 // if they are visible in the symbol table.
827 // As the names of these symbols are derived from the string of
828 // the type, they can run to many kilobytes long. So we shorten
829 // them using a SHA-1 when the name appears in the final binary.
830 // This also removes characters that upset external linkers.
832 // These are the symbols that begin with the prefix 'type.' and
833 // contain run-time type information used by the runtime and reflect
834 // packages. All Go binaries contain these symbols, but only
835 // those programs loaded dynamically in multiple parts need these
836 // symbols to have entries in the symbol table.
837 func (ctxt *Link) mangleTypeSym() {
838 if ctxt.BuildMode != BuildModeShared && !ctxt.linkShared && ctxt.BuildMode != BuildModePlugin && !ctxt.CanUsePlugins() {
843 for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
844 if !ldr.AttrReachable(s) && !ctxt.linkShared {
845 // If -linkshared, the GCProg generation code may need to reach
846 // out to the shared library for the type descriptor's data, even
847 // the type descriptor itself is not actually needed at run time
848 // (therefore not reachable). We still need to mangle its name,
849 // so it is consistent with the one stored in the shared library.
852 name := ldr.SymName(s)
853 newName := typeSymbolMangle(name)
855 ldr.SetSymExtname(s, newName)
857 // When linking against a shared library, the Go object file may
858 // have reference to the original symbol name whereas the shared
859 // library provides a symbol with the mangled name. We need to
860 // copy the payload of mangled to original.
861 // XXX maybe there is a better way to do this.
862 dup := ldr.Lookup(newName, ldr.SymVersion(s))
865 dt := ldr.SymType(dup)
866 if st == sym.Sxxx && dt != sym.Sxxx {
874 // typeSymbolMangle mangles the given symbol name into something shorter.
876 // Keep the type.. prefix, which parts of the linker (like the
877 // DWARF generator) know means the symbol is not decodable.
878 // Leave type.runtime. symbols alone, because other parts of
879 // the linker manipulates them.
880 func typeSymbolMangle(name string) string {
881 if !strings.HasPrefix(name, "type.") {
884 if strings.HasPrefix(name, "type.runtime.") {
887 if len(name) <= 14 && !strings.Contains(name, "@") { // Issue 19529
890 hash := sha1.Sum([]byte(name))
895 return prefix + base64.StdEncoding.EncodeToString(hash[:6])
899 * look for the next file in an archive.
900 * adapted from libmach.
902 func nextar(bp *bio.Reader, off int64, a *ArHdr) int64 {
907 var buf [SAR_HDR]byte
908 if n, err := io.ReadFull(bp, buf[:]); err != nil {
909 if n == 0 && err != io.EOF {
915 a.name = artrim(buf[0:16])
916 a.date = artrim(buf[16:28])
917 a.uid = artrim(buf[28:34])
918 a.gid = artrim(buf[34:40])
919 a.mode = artrim(buf[40:48])
920 a.size = artrim(buf[48:58])
921 a.fmag = artrim(buf[58:60])
923 arsize := atolwhex(a.size)
927 return arsize + SAR_HDR
930 func loadobjfile(ctxt *Link, lib *sym.Library) {
931 pkg := objabi.PathToPrefix(lib.Pkg)
933 if ctxt.Debugvlog > 1 {
934 ctxt.Logf("ldobj: %s (%s)\n", lib.File, pkg)
936 f, err := bio.Open(lib.File)
938 Exitf("cannot open file %s: %v", lib.File, err)
942 if pkg == "main" && !lib.Main {
943 Exitf("%s: not package main", lib.File)
947 for i := 0; i < len(ARMAG); i++ {
948 if c, err := f.ReadByte(); err == nil && c == ARMAG[i] {
952 /* load it as a regular file */
953 l := f.MustSeek(0, 2)
955 ldobj(ctxt, f, lib, l, lib.File, lib.File)
960 * load all the object files from the archive now.
961 * this gives us sequential file access and keeps us
962 * from needing to come back later to pick up more
963 * objects. it breaks the usual C archive model, but
964 * this is Go, not C. the common case in Go is that
965 * we need to load all the objects, and then we throw away
966 * the individual symbols that are unused.
968 * loading every object will also make it possible to
969 * load foreign objects not referenced by __.PKGDEF.
974 l := nextar(f, off, &arhdr)
979 Exitf("%s: malformed archive", lib.File)
983 // __.PKGDEF isn't a real Go object file, and it's
984 // absent in -linkobj builds anyway. Skipping it
985 // ensures consistency between -linkobj and normal
987 if arhdr.name == pkgdef {
991 // Skip other special (non-object-file) sections that
992 // build tools may have added. Such sections must have
993 // short names so that the suffix is not truncated.
994 if len(arhdr.name) < 16 {
995 if ext := filepath.Ext(arhdr.name); ext != ".o" && ext != ".syso" {
1000 pname := fmt.Sprintf("%s(%s)", lib.File, arhdr.name)
1001 l = atolwhex(arhdr.size)
1002 ldobj(ctxt, f, lib, l, pname, lib.File)
1006 type Hostobj struct {
1007 ld func(*Link, *bio.Reader, string, int64, string)
1015 var hostobj []Hostobj
1017 // These packages can use internal linking mode.
1018 // Others trigger external mode.
1019 var internalpkg = []string{
1029 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 {
1031 for _, intpkg := range internalpkg {
1038 // DragonFly declares errno with __thread, which results in a symbol
1039 // type of R_386_TLS_GD or R_X86_64_TLSGD. The Go linker does not
1040 // currently know how to handle TLS relocations, hence we have to
1041 // force external linking for any libraries that link in code that
1042 // uses errno. This can be removed if the Go linker ever supports
1043 // these relocation types.
1044 if headType == objabi.Hdragonfly {
1045 if pkg == "net" || pkg == "os/user" {
1054 hostobj = append(hostobj, Hostobj{})
1055 h := &hostobj[len(hostobj)-1]
1065 func hostobjs(ctxt *Link) {
1066 if ctxt.LinkMode != LinkInternal {
1071 for i := 0; i < len(hostobj); i++ {
1073 f, err := bio.Open(h.file)
1075 Exitf("cannot reopen %s: %v", h.pn, err)
1078 f.MustSeek(h.off, 0)
1080 Errorf(nil, "%s: unrecognized object file format", h.pn)
1083 h.ld(ctxt, f, h.pkg, h.length, h.pn)
1088 func hostlinksetup(ctxt *Link) {
1089 if ctxt.LinkMode != LinkExternal {
1093 // For external link, record that we need to tell the external linker -s,
1094 // and turn off -s internally: the external linker needs the symbol
1095 // information for its final link.
1099 // create temporary directory and arrange cleanup
1100 if *flagTmpdir == "" {
1101 dir, err := ioutil.TempDir("", "go-link-")
1108 os.RemoveAll(*flagTmpdir)
1112 // change our output to temporary object file
1113 if err := ctxt.Out.Close(); err != nil {
1114 Exitf("error closing output file")
1116 mayberemoveoutfile()
1118 p := filepath.Join(*flagTmpdir, "go.o")
1119 if err := ctxt.Out.Open(p); err != nil {
1120 Exitf("cannot create %s: %v", p, err)
1124 // hostobjCopy creates a copy of the object files in hostobj in a
1125 // temporary directory.
1126 func hostobjCopy() (paths []string) {
1127 var wg sync.WaitGroup
1128 sema := make(chan struct{}, runtime.NumCPU()) // limit open file descriptors
1129 for i, h := range hostobj {
1131 dst := filepath.Join(*flagTmpdir, fmt.Sprintf("%06d.o", i))
1132 paths = append(paths, dst)
1141 f, err := os.Open(h.file)
1143 Exitf("cannot reopen %s: %v", h.pn, err)
1146 if _, err := f.Seek(h.off, 0); err != nil {
1147 Exitf("cannot seek %s: %v", h.pn, err)
1150 w, err := os.Create(dst)
1152 Exitf("cannot create %s: %v", dst, err)
1154 if _, err := io.CopyN(w, f, h.length); err != nil {
1155 Exitf("cannot write %s: %v", dst, err)
1157 if err := w.Close(); err != nil {
1158 Exitf("cannot close %s: %v", dst, err)
1166 // writeGDBLinkerScript creates gcc linker script file in temp
1167 // directory. writeGDBLinkerScript returns created file path.
1168 // The script is used to work around gcc bug
1169 // (see https://golang.org/issue/20183 for details).
1170 func writeGDBLinkerScript() string {
1171 name := "fix_debug_gdb_scripts.ld"
1172 path := filepath.Join(*flagTmpdir, name)
1175 .debug_gdb_scripts BLOCK(__section_alignment__) (NOLOAD) :
1177 *(.debug_gdb_scripts)
1180 INSERT AFTER .debug_types;
1182 err := ioutil.WriteFile(path, []byte(src), 0666)
1184 Errorf(nil, "WriteFile %s failed: %v", name, err)
1189 // archive builds a .a archive from the hostobj object files.
1190 func (ctxt *Link) archive() {
1191 if ctxt.BuildMode != BuildModeCArchive {
1197 if *flagExtar == "" {
1201 mayberemoveoutfile()
1203 // Force the buffer to flush here so that external
1204 // tools will see a complete file.
1205 if err := ctxt.Out.Close(); err != nil {
1206 Exitf("error closing %v", *flagOutfile)
1209 argv := []string{*flagExtar, "-q", "-c", "-s"}
1210 if ctxt.HeadType == objabi.Haix {
1211 argv = append(argv, "-X64")
1213 argv = append(argv, *flagOutfile)
1214 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1215 argv = append(argv, hostobjCopy()...)
1217 if ctxt.Debugvlog != 0 {
1218 ctxt.Logf("archive: %s\n", strings.Join(argv, " "))
1221 // If supported, use syscall.Exec() to invoke the archive command,
1222 // which should be the final remaining step needed for the link.
1223 // This will reduce peak RSS for the link (and speed up linking of
1224 // large applications), since when the archive command runs we
1225 // won't be holding onto all of the linker's live memory.
1226 if syscallExecSupported && !ownTmpDir {
1228 ctxt.execArchive(argv)
1229 panic("should not get here")
1232 // Otherwise invoke 'ar' in the usual way (fork + exec).
1233 if out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput(); err != nil {
1234 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1238 func (ctxt *Link) hostlink() {
1239 if ctxt.LinkMode != LinkExternal || nerrors > 0 {
1242 if ctxt.BuildMode == BuildModeCArchive {
1247 argv = append(argv, ctxt.extld()...)
1248 argv = append(argv, hostlinkArchArgs(ctxt.Arch)...)
1250 if *FlagS || debug_s {
1251 if ctxt.HeadType == objabi.Hdarwin {
1252 // Recent versions of macOS print
1253 // ld: warning: option -s is obsolete and being ignored
1254 // so do not pass any arguments.
1256 argv = append(argv, "-s")
1260 // On darwin, whether to combine DWARF into executable.
1261 // Only macOS supports unmapped segments such as our __DWARF segment.
1262 combineDwarf := ctxt.IsDarwin() && !*FlagS && !*FlagW && !debug_s && machoPlatform == PLATFORM_MACOS
1264 switch ctxt.HeadType {
1265 case objabi.Hdarwin:
1267 // Leave room for DWARF combining.
1268 // -headerpad is incompatible with -fembed-bitcode.
1269 argv = append(argv, "-Wl,-headerpad,1144")
1271 if ctxt.DynlinkingGo() && buildcfg.GOOS != "ios" {
1272 // -flat_namespace is deprecated on iOS.
1273 // It is useful for supporting plugins. We don't support plugins on iOS.
1274 // -flat_namespace may cause the dynamic linker to hang at forkExec when
1275 // resolving a lazy binding. See issue 38824.
1276 // Force eager resolution to work around.
1277 argv = append(argv, "-Wl,-flat_namespace", "-Wl,-bind_at_load")
1280 argv = append(argv, "-Wl,-S") // suppress STAB (symbolic debugging) symbols
1282 case objabi.Hopenbsd:
1283 argv = append(argv, "-Wl,-nopie")
1284 argv = append(argv, "-pthread")
1285 case objabi.Hwindows:
1287 argv = append(argv, "-mwindows")
1289 argv = append(argv, "-mconsole")
1291 // Mark as having awareness of terminal services, to avoid
1292 // ancient compatibility hacks.
1293 argv = append(argv, "-Wl,--tsaware")
1296 argv = append(argv, "-Wl,--nxcompat")
1298 argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", PeMinimumTargetMajorVersion))
1299 argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", PeMinimumTargetMinorVersion))
1300 argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", PeMinimumTargetMajorVersion))
1301 argv = append(argv, fmt.Sprintf("-Wl,--minor-subsystem-version=%d", PeMinimumTargetMinorVersion))
1303 argv = append(argv, "-pthread")
1304 // prevent ld to reorder .text functions to keep the same
1305 // first/last functions for moduledata.
1306 argv = append(argv, "-Wl,-bnoobjreorder")
1307 // mcmodel=large is needed for every gcc generated files, but
1308 // ld still need -bbigtoc in order to allow larger TOC.
1309 argv = append(argv, "-mcmodel=large")
1310 argv = append(argv, "-Wl,-bbigtoc")
1313 // Enable ASLR on Windows.
1314 addASLRargs := func(argv []string) []string {
1316 argv = append(argv, "-Wl,--dynamicbase")
1317 // enable high-entropy ASLR on 64-bit.
1318 if ctxt.Arch.PtrSize >= 8 {
1319 argv = append(argv, "-Wl,--high-entropy-va")
1324 switch ctxt.BuildMode {
1326 if ctxt.HeadType == objabi.Hdarwin {
1327 if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() {
1328 argv = append(argv, "-Wl,-no_pie")
1329 argv = append(argv, "-Wl,-pagezero_size,4000000")
1333 switch ctxt.HeadType {
1334 case objabi.Hdarwin, objabi.Haix:
1335 case objabi.Hwindows:
1336 argv = addASLRargs(argv)
1339 if ctxt.UseRelro() {
1340 argv = append(argv, "-Wl,-z,relro")
1342 argv = append(argv, "-pie")
1344 case BuildModeCShared:
1345 if ctxt.HeadType == objabi.Hdarwin {
1346 argv = append(argv, "-dynamiclib")
1348 if ctxt.UseRelro() {
1349 argv = append(argv, "-Wl,-z,relro")
1351 argv = append(argv, "-shared")
1352 if ctxt.HeadType == objabi.Hwindows {
1354 argv = addASLRargs(argv)
1357 // Pass -z nodelete to mark the shared library as
1358 // non-closeable: a dlclose will do nothing.
1359 argv = append(argv, "-Wl,-z,nodelete")
1360 // Only pass Bsymbolic on non-Windows.
1361 argv = append(argv, "-Wl,-Bsymbolic")
1364 case BuildModeShared:
1365 if ctxt.UseRelro() {
1366 argv = append(argv, "-Wl,-z,relro")
1368 argv = append(argv, "-shared")
1369 case BuildModePlugin:
1370 if ctxt.HeadType == objabi.Hdarwin {
1371 argv = append(argv, "-dynamiclib")
1373 if ctxt.UseRelro() {
1374 argv = append(argv, "-Wl,-z,relro")
1376 argv = append(argv, "-shared")
1380 var altLinker string
1381 if ctxt.IsELF && ctxt.DynlinkingGo() {
1382 // We force all symbol resolution to be done at program startup
1383 // because lazy PLT resolution can use large amounts of stack at
1384 // times we cannot allow it to do so.
1385 argv = append(argv, "-Wl,-znow")
1387 // Do not let the host linker generate COPY relocations. These
1388 // can move symbols out of sections that rely on stable offsets
1389 // from the beginning of the section (like sym.STYPE).
1390 argv = append(argv, "-Wl,-znocopyreloc")
1392 if buildcfg.GOOS == "android" {
1393 // Use lld to avoid errors from default linker (issue #38838)
1397 if ctxt.Arch.InFamily(sys.ARM, sys.ARM64) && buildcfg.GOOS == "linux" {
1398 // On ARM, the GNU linker will generate COPY relocations
1399 // even with -znocopyreloc set.
1400 // https://sourceware.org/bugzilla/show_bug.cgi?id=19962
1402 // On ARM64, the GNU linker will fail instead of
1403 // generating COPY relocations.
1405 // In both cases, switch to gold.
1408 // If gold is not installed, gcc will silently switch
1409 // back to ld.bfd. So we parse the version information
1410 // and provide a useful error if gold is missing.
1411 name, args := flagExtld[0], flagExtld[1:]
1412 args = append(args, "-fuse-ld=gold", "-Wl,--version")
1413 cmd := exec.Command(name, args...)
1414 if out, err := cmd.CombinedOutput(); err == nil {
1415 if !bytes.Contains(out, []byte("GNU gold")) {
1416 log.Fatalf("ARM external linker must be gold (issue #15696), but is not: %s", out)
1421 if ctxt.Arch.Family == sys.ARM64 && buildcfg.GOOS == "freebsd" {
1422 // Switch to ld.bfd on freebsd/arm64.
1425 // Provide a useful error if ld.bfd is missing.
1426 name, args := flagExtld[0], flagExtld[1:]
1427 args = append(args, "-fuse-ld=bfd", "-Wl,--version")
1428 cmd := exec.Command(name, args...)
1429 if out, err := cmd.CombinedOutput(); err == nil {
1430 if !bytes.Contains(out, []byte("GNU ld")) {
1431 log.Fatalf("ARM64 external linker must be ld.bfd (issue #35197), please install devel/binutils")
1435 if altLinker != "" {
1436 argv = append(argv, "-fuse-ld="+altLinker)
1439 if ctxt.IsELF && len(buildinfo) > 0 {
1440 argv = append(argv, fmt.Sprintf("-Wl,--build-id=0x%x", buildinfo))
1443 // On Windows, given -o foo, GCC will append ".exe" to produce
1444 // "foo.exe". We have decided that we want to honor the -o
1445 // option. To make this work, we append a '.' so that GCC
1446 // will decide that the file already has an extension. We
1447 // only want to do this when producing a Windows output file
1448 // on a Windows host.
1449 outopt := *flagOutfile
1450 if buildcfg.GOOS == "windows" && runtime.GOOS == "windows" && filepath.Ext(outopt) == "" {
1453 argv = append(argv, "-o")
1454 argv = append(argv, outopt)
1456 if rpath.val != "" {
1457 argv = append(argv, fmt.Sprintf("-Wl,-rpath,%s", rpath.val))
1460 if *flagInterpreter != "" {
1461 // Many linkers support both -I and the --dynamic-linker flags
1462 // to set the ELF interpreter, but lld only supports
1463 // --dynamic-linker so prefer that (ld on very old Solaris only
1464 // supports -I but that seems less important).
1465 argv = append(argv, fmt.Sprintf("-Wl,--dynamic-linker,%s", *flagInterpreter))
1468 // Force global symbols to be exported for dlopen, etc.
1470 argv = append(argv, "-rdynamic")
1472 if ctxt.HeadType == objabi.Haix {
1473 fileName := xcoffCreateExportFile(ctxt)
1474 argv = append(argv, "-Wl,-bE:"+fileName)
1477 const unusedArguments = "-Qunused-arguments"
1478 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, unusedArguments) {
1479 argv = append(argv, unusedArguments)
1482 const compressDWARF = "-Wl,--compress-debug-sections=zlib"
1483 if ctxt.compressDWARF && linkerFlagSupported(ctxt.Arch, argv[0], altLinker, compressDWARF) {
1484 argv = append(argv, compressDWARF)
1487 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1488 argv = append(argv, hostobjCopy()...)
1489 if ctxt.HeadType == objabi.Haix {
1490 // We want to have C files after Go files to remove
1491 // trampolines csects made by ld.
1492 argv = append(argv, "-nostartfiles")
1493 argv = append(argv, "/lib/crt0_64.o")
1495 extld := ctxt.extld()
1496 name, args := extld[0], extld[1:]
1497 // Get starting files.
1498 getPathFile := func(file string) string {
1499 args := append(args, "-maix64", "--print-file-name="+file)
1500 out, err := exec.Command(name, args...).CombinedOutput()
1502 log.Fatalf("running %s failed: %v\n%s", extld, err, out)
1504 return strings.Trim(string(out), "\n")
1506 // Since GCC version 11, the 64-bit version of GCC starting files
1507 // are now suffixed by "_64". Even under "-maix64" multilib directory
1508 // "crtcxa.o" is 32-bit.
1509 crtcxa := getPathFile("crtcxa_64.o")
1510 if !filepath.IsAbs(crtcxa) {
1511 crtcxa = getPathFile("crtcxa.o")
1513 crtdbase := getPathFile("crtdbase_64.o")
1514 if !filepath.IsAbs(crtdbase) {
1515 crtdbase = getPathFile("crtdbase.o")
1517 argv = append(argv, crtcxa)
1518 argv = append(argv, crtdbase)
1521 if ctxt.linkShared {
1522 seenDirs := make(map[string]bool)
1523 seenLibs := make(map[string]bool)
1524 addshlib := func(path string) {
1525 dir, base := filepath.Split(path)
1527 argv = append(argv, "-L"+dir)
1529 argv = append(argv, "-Wl,-rpath="+dir)
1531 seenDirs[dir] = true
1533 base = strings.TrimSuffix(base, ".so")
1534 base = strings.TrimPrefix(base, "lib")
1535 if !seenLibs[base] {
1536 argv = append(argv, "-l"+base)
1537 seenLibs[base] = true
1540 for _, shlib := range ctxt.Shlibs {
1541 addshlib(shlib.Path)
1542 for _, dep := range shlib.Deps {
1546 libpath := findshlib(ctxt, dep)
1554 // clang, unlike GCC, passes -rdynamic to the linker
1555 // even when linking with -static, causing a linker
1556 // error when using GNU ld. So take out -rdynamic if
1557 // we added it. We do it in this order, rather than
1558 // only adding -rdynamic later, so that -extldflags
1559 // can override -rdynamic without using -static.
1560 // Similarly for -Wl,--dynamic-linker.
1561 checkStatic := func(arg string) {
1562 if ctxt.IsELF && arg == "-static" {
1563 for i := range argv {
1564 if argv[i] == "-rdynamic" || strings.HasPrefix(argv[i], "-Wl,--dynamic-linker,") {
1571 for _, p := range ldflag {
1572 argv = append(argv, p)
1576 // When building a program with the default -buildmode=exe the
1577 // gc compiler generates code requires DT_TEXTREL in a
1578 // position independent executable (PIE). On systems where the
1579 // toolchain creates PIEs by default, and where DT_TEXTREL
1580 // does not work, the resulting programs will not run. See
1581 // issue #17847. To avoid this problem pass -no-pie to the
1582 // toolchain if it is supported.
1583 if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared && !(ctxt.IsDarwin() && ctxt.IsARM64()) {
1584 // GCC uses -no-pie, clang uses -nopie.
1585 for _, nopie := range []string{"-no-pie", "-nopie"} {
1586 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, nopie) {
1587 argv = append(argv, nopie)
1593 for _, p := range flagExtldflags {
1594 argv = append(argv, p)
1597 if ctxt.HeadType == objabi.Hwindows {
1598 // Determine which linker we're using. Add in the extldflags in
1599 // case used has specified "-fuse-ld=...".
1600 extld := ctxt.extld()
1601 name, args := extld[0], extld[1:]
1602 args = append(args, flagExtldflags...)
1603 args = append(args, "-Wl,--version")
1604 cmd := exec.Command(name, args...)
1606 if out, err := cmd.CombinedOutput(); err == nil {
1607 if bytes.Contains(out, []byte("LLD ")) {
1612 // use gcc linker script to work around gcc bug
1613 // (see https://golang.org/issue/20183 for details).
1615 p := writeGDBLinkerScript()
1616 argv = append(argv, "-Wl,-T,"+p)
1618 // libmingw32 and libmingwex have some inter-dependencies,
1619 // so must use linker groups.
1620 argv = append(argv, "-Wl,--start-group", "-lmingwex", "-lmingw32", "-Wl,--end-group")
1621 argv = append(argv, peimporteddlls()...)
1624 if ctxt.Debugvlog != 0 {
1625 ctxt.Logf("host link:")
1626 for _, v := range argv {
1632 out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput()
1634 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1637 // Filter out useless linker warnings caused by bugs outside Go.
1638 // See also cmd/go/internal/work/exec.go's gccld method.
1641 for _, line := range bytes.SplitAfter(out, []byte("\n")) {
1642 // golang.org/issue/26073 - Apple Xcode bug
1643 if bytes.Contains(line, []byte("ld: warning: text-based stub file")) {
1652 // Remove TOC overflow warning on AIX.
1653 if bytes.Contains(line, []byte("ld: 0711-783")) {
1658 save = append(save, line)
1660 out = bytes.Join(save, nil)
1663 // always print external output even if the command is successful, so that we don't
1664 // swallow linker warnings (see https://golang.org/issue/17935).
1665 ctxt.Logf("%s", out)
1669 // Find "dsymutils" and "strip" tools using CC --print-prog-name.
1671 cc = append(cc, ctxt.extld()...)
1672 cc = append(cc, hostlinkArchArgs(ctxt.Arch)...)
1673 cc = append(cc, "--print-prog-name", "dsymutil")
1674 out, err := exec.Command(cc[0], cc[1:]...).CombinedOutput()
1676 Exitf("%s: finding dsymutil failed: %v\n%s", os.Args[0], err, out)
1678 dsymutilCmd := strings.TrimSuffix(string(out), "\n")
1680 cc[len(cc)-1] = "strip"
1681 out, err = exec.Command(cc[0], cc[1:]...).CombinedOutput()
1683 Exitf("%s: finding strip failed: %v\n%s", os.Args[0], err, out)
1685 stripCmd := strings.TrimSuffix(string(out), "\n")
1687 dsym := filepath.Join(*flagTmpdir, "go.dwarf")
1688 if out, err := exec.Command(dsymutilCmd, "-f", *flagOutfile, "-o", dsym).CombinedOutput(); err != nil {
1689 Exitf("%s: running dsymutil failed: %v\n%s", os.Args[0], err, out)
1691 // Remove STAB (symbolic debugging) symbols after we are done with them (by dsymutil).
1692 // They contain temporary file paths and make the build not reproducible.
1693 if out, err := exec.Command(stripCmd, "-S", *flagOutfile).CombinedOutput(); err != nil {
1694 Exitf("%s: running strip failed: %v\n%s", os.Args[0], err, out)
1696 // Skip combining if `dsymutil` didn't generate a file. See #11994.
1697 if _, err := os.Stat(dsym); os.IsNotExist(err) {
1700 // For os.Rename to work reliably, must be in same directory as outfile.
1701 combinedOutput := *flagOutfile + "~"
1702 exef, err := os.Open(*flagOutfile)
1704 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1707 exem, err := macho.NewFile(exef)
1709 Exitf("%s: parsing Mach-O header failed: %v", os.Args[0], err)
1711 if err := machoCombineDwarf(ctxt, exef, exem, dsym, combinedOutput); err != nil {
1712 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1714 os.Remove(*flagOutfile)
1715 if err := os.Rename(combinedOutput, *flagOutfile); err != nil {
1716 Exitf("%s: %v", os.Args[0], err)
1719 if ctxt.NeedCodeSign() {
1720 err := machoCodeSign(ctxt, *flagOutfile)
1722 Exitf("%s: code signing failed: %v", os.Args[0], err)
1727 var createTrivialCOnce sync.Once
1729 func linkerFlagSupported(arch *sys.Arch, linker, altLinker, flag string) bool {
1730 createTrivialCOnce.Do(func() {
1731 src := filepath.Join(*flagTmpdir, "trivial.c")
1732 if err := ioutil.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
1733 Errorf(nil, "WriteFile trivial.c failed: %v", err)
1737 flagsWithNextArgSkip := []string{
1746 flagsWithNextArgKeep := []string{
1752 prefixesToKeep := []string{
1763 flags := hostlinkArchArgs(arch)
1766 for _, f := range append(flagExtldflags, ldflag...) {
1768 flags = append(flags, f)
1772 } else if f == "" || f[0] != '-' {
1773 } else if contains(flagsWithNextArgSkip, f) {
1775 } else if contains(flagsWithNextArgKeep, f) {
1776 flags = append(flags, f)
1779 for _, p := range prefixesToKeep {
1780 if strings.HasPrefix(f, p) {
1781 flags = append(flags, f)
1788 if altLinker != "" {
1789 flags = append(flags, "-fuse-ld="+altLinker)
1791 flags = append(flags, flag, "trivial.c")
1793 cmd := exec.Command(linker, flags...)
1794 cmd.Dir = *flagTmpdir
1795 cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
1796 out, err := cmd.CombinedOutput()
1797 // GCC says "unrecognized command line option ‘-no-pie’"
1798 // clang says "unknown argument: '-no-pie'"
1799 return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
1802 // hostlinkArchArgs returns arguments to pass to the external linker
1803 // based on the architecture.
1804 func hostlinkArchArgs(arch *sys.Arch) []string {
1805 switch arch.Family {
1807 return []string{"-m32"}
1809 if buildcfg.GOOS == "darwin" {
1810 return []string{"-arch", "x86_64", "-m64"}
1812 return []string{"-m64"}
1814 return []string{"-m64"}
1816 return []string{"-marm"}
1818 if buildcfg.GOOS == "darwin" {
1819 return []string{"-arch", "arm64"}
1822 return []string{"-mabi=64"}
1824 return []string{"-mabi=32"}
1826 if buildcfg.GOOS == "aix" {
1827 return []string{"-maix64"}
1829 return []string{"-m64"}
1836 var wantHdr = objabi.HeaderString()
1838 // ldobj loads an input object. If it is a host object (an object
1839 // compiled by a non-Go compiler) it returns the Hostobj pointer. If
1840 // it is a Go object, it returns nil.
1841 func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string, file string) *Hostobj {
1842 pkg := objabi.PathToPrefix(lib.Pkg)
1844 eof := f.Offset() + length
1850 f.MustSeek(start, 0)
1852 unit := &sym.CompilationUnit{Lib: lib}
1853 lib.Units = append(lib.Units, unit)
1855 magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
1856 if magic == 0x7f454c46 { // \x7F E L F
1857 ldelf := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1858 textp, flags, err := loadelf.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn, ehdr.Flags)
1860 Errorf(nil, "%v", err)
1864 ctxt.Textp = append(ctxt.Textp, textp...)
1866 return ldhostobj(ldelf, ctxt.HeadType, f, pkg, length, pn, file)
1869 if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
1870 ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1871 textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1873 Errorf(nil, "%v", err)
1876 ctxt.Textp = append(ctxt.Textp, textp...)
1878 return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
1886 ldpe := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1887 textp, rsrc, err := loadpe.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1889 Errorf(nil, "%v", err)
1893 setpersrc(ctxt, rsrc)
1895 ctxt.Textp = append(ctxt.Textp, textp...)
1897 return ldhostobj(ldpe, ctxt.HeadType, f, pkg, length, pn, file)
1900 if c1 == 0x01 && (c2 == 0xD7 || c2 == 0xF7) {
1901 ldxcoff := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1902 textp, err := loadxcoff.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1904 Errorf(nil, "%v", err)
1907 ctxt.Textp = append(ctxt.Textp, textp...)
1909 return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
1912 if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
1913 // An unrecognized object is just passed to the external linker.
1914 // If we try to read symbols from this object, we will
1915 // report an error at that time.
1916 unknownObjFormat = true
1917 return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
1920 /* check the header */
1921 line, err := f.ReadString('\n')
1923 Errorf(nil, "truncated object file: %s: %v", pn, err)
1927 if !strings.HasPrefix(line, "go object ") {
1928 if strings.HasSuffix(pn, ".go") {
1929 Exitf("%s: uncompiled .go source file", pn)
1933 if line == ctxt.Arch.Name {
1934 // old header format: just $GOOS
1935 Errorf(nil, "%s: stale object file", pn)
1939 Errorf(nil, "%s: not an object file: @%d %q", pn, start, line)
1943 // First, check that the basic GOOS, GOARCH, and Version match.
1944 if line != wantHdr {
1945 Errorf(nil, "%s: linked object header mismatch:\nhave %q\nwant %q\n", pn, line, wantHdr)
1948 // Skip over exports and other info -- ends with \n!\n.
1950 // Note: It's possible for "\n!\n" to appear within the binary
1951 // package export data format. To avoid truncating the package
1952 // definition prematurely (issue 21703), we keep track of
1953 // how many "$$" delimiters we've seen.
1955 import0 := f.Offset()
1957 c1 = '\n' // the last line ended in \n
1963 if markers%2 == 0 && c2 == '!' && c3 == '\n' {
1966 if c2 == '$' && c3 == '$' {
1975 Errorf(nil, "truncated object file: %s", pn)
1980 import1 := f.Offset()
1982 f.MustSeek(import0, 0)
1983 ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
1984 f.MustSeek(import1, 0)
1986 fingerprint := ctxt.loader.Preload(ctxt.IncVersion(), f, lib, unit, eof-f.Offset())
1987 if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
1988 // Check fingerprint, to ensure the importing and imported packages
1989 // have consistent view of symbol indices.
1990 // Normally the go command should ensure this. But in case something
1991 // goes wrong, it could lead to obscure bugs like run-time crash.
1992 // Check it here to be sure.
1993 if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
1994 lib.Fingerprint = fingerprint
1996 checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
1999 addImports(ctxt, lib, pn)
2003 func checkFingerprint(lib *sym.Library, libfp goobj.FingerprintType, src string, srcfp goobj.FingerprintType) {
2005 Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
2009 func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
2010 data := make([]byte, sym.Size)
2011 sect := f.Sections[sym.Section]
2012 if sect.Type != elf.SHT_PROGBITS && sect.Type != elf.SHT_NOTE {
2013 Errorf(nil, "reading %s from non-data section", sym.Name)
2015 n, err := sect.ReadAt(data, int64(sym.Value-sect.Addr))
2016 if uint64(n) != sym.Size {
2017 Errorf(nil, "reading contents of %s: %v", sym.Name, err)
2022 func readwithpad(r io.Reader, sz int32) ([]byte, error) {
2023 data := make([]byte, Rnd(int64(sz), 4))
2024 _, err := io.ReadFull(r, data)
2032 func readnote(f *elf.File, name []byte, typ int32) ([]byte, error) {
2033 for _, sect := range f.Sections {
2034 if sect.Type != elf.SHT_NOTE {
2039 var namesize, descsize, noteType int32
2040 err := binary.Read(r, f.ByteOrder, &namesize)
2045 return nil, fmt.Errorf("read namesize failed: %v", err)
2047 err = binary.Read(r, f.ByteOrder, &descsize)
2049 return nil, fmt.Errorf("read descsize failed: %v", err)
2051 err = binary.Read(r, f.ByteOrder, ¬eType)
2053 return nil, fmt.Errorf("read type failed: %v", err)
2055 noteName, err := readwithpad(r, namesize)
2057 return nil, fmt.Errorf("read name failed: %v", err)
2059 desc, err := readwithpad(r, descsize)
2061 return nil, fmt.Errorf("read desc failed: %v", err)
2063 if string(name) == string(noteName) && typ == noteType {
2071 func findshlib(ctxt *Link, shlib string) string {
2072 if filepath.IsAbs(shlib) {
2075 for _, libdir := range ctxt.Libdir {
2076 libpath := filepath.Join(libdir, shlib)
2077 if _, err := os.Stat(libpath); err == nil {
2081 Errorf(nil, "cannot find shared library: %s", shlib)
2085 func ldshlibsyms(ctxt *Link, shlib string) {
2087 if filepath.IsAbs(shlib) {
2089 shlib = filepath.Base(shlib)
2091 libpath = findshlib(ctxt, shlib)
2096 for _, processedlib := range ctxt.Shlibs {
2097 if processedlib.Path == libpath {
2101 if ctxt.Debugvlog > 1 {
2102 ctxt.Logf("ldshlibsyms: found library with name %s at %s\n", shlib, libpath)
2105 f, err := elf.Open(libpath)
2107 Errorf(nil, "cannot open shared library: %s", libpath)
2110 // Keep the file open as decodetypeGcprog needs to read from it.
2111 // TODO: fix. Maybe mmap the file.
2114 hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
2116 Errorf(nil, "cannot read ABI hash from shared library %s: %v", libpath, err)
2120 depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
2122 Errorf(nil, "cannot read dep list from shared library %s: %v", libpath, err)
2126 for _, dep := range strings.Split(string(depsbytes), "\n") {
2130 if !filepath.IsAbs(dep) {
2131 // If the dep can be interpreted as a path relative to the shlib
2132 // in which it was found, do that. Otherwise, we will leave it
2133 // to be resolved by libdir lookup.
2134 abs := filepath.Join(filepath.Dir(libpath), dep)
2135 if _, err := os.Stat(abs); err == nil {
2139 deps = append(deps, dep)
2142 syms, err := f.DynamicSymbols()
2144 Errorf(nil, "cannot read symbols from shared library: %s", libpath)
2148 for _, elfsym := range syms {
2149 if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
2153 // Symbols whose names start with "type." are compiler
2154 // generated, so make functions with that prefix internal.
2156 symname := elfsym.Name // (unmangled) symbol name
2157 if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type.") {
2158 ver = abiInternalVer
2159 } else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC {
2160 // Demangle the ABI name. Keep in sync with symtab.go:mangleABIName.
2161 if strings.HasSuffix(elfsym.Name, ".abiinternal") {
2162 ver = sym.SymVerABIInternal
2163 symname = strings.TrimSuffix(elfsym.Name, ".abiinternal")
2164 } else if strings.HasSuffix(elfsym.Name, ".abi0") {
2166 symname = strings.TrimSuffix(elfsym.Name, ".abi0")
2171 s := l.LookupOrCreateSym(symname, ver)
2173 // Because loadlib above loads all .a files before loading
2174 // any shared libraries, any non-dynimport symbols we find
2175 // that duplicate symbols already loaded should be ignored
2176 // (the symbols from the .a files "win").
2177 if l.SymType(s) != 0 && l.SymType(s) != sym.SDYNIMPORT {
2180 su := l.MakeSymbolUpdater(s)
2181 su.SetType(sym.SDYNIMPORT)
2182 l.SetSymElfType(s, elf.ST_TYPE(elfsym.Info))
2183 su.SetSize(int64(elfsym.Size))
2184 if elfsym.Section != elf.SHN_UNDEF {
2185 // Set .File for the library that actually defines the symbol.
2186 l.SetSymPkg(s, libpath)
2188 // The decodetype_* functions in decodetype.go need access to
2190 sname := l.SymName(s)
2191 if strings.HasPrefix(sname, "type.") && !strings.HasPrefix(sname, "type..") {
2192 su.SetData(readelfsymboldata(ctxt, f, &elfsym))
2196 if symname != elfsym.Name {
2197 l.SetSymExtname(s, elfsym.Name)
2200 ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f})
2203 func addsection(ldr *loader.Loader, arch *sys.Arch, seg *sym.Segment, name string, rwx int) *sym.Section {
2204 sect := ldr.NewSection()
2205 sect.Rwx = uint8(rwx)
2208 sect.Align = int32(arch.PtrSize) // everything is at least pointer-aligned
2209 seg.Sections = append(seg.Sections, sect)
2216 limit int // limit on entry to sym
2219 func haslinkregister(ctxt *Link) bool {
2220 return ctxt.FixedFrameSize() != 0
2223 func callsize(ctxt *Link) int {
2224 if haslinkregister(ctxt) {
2227 return ctxt.Arch.RegSize
2230 type stkChk struct {
2233 morestack loader.Sym
2237 // Walk the call tree and check that there is always enough stack space
2238 // for the call frames, especially for a chain of nosplit functions.
2239 func (ctxt *Link) dostkcheck() {
2244 morestack: ldr.Lookup("runtime.morestack", 0),
2245 done: loader.MakeBitmap(ldr.NSym()),
2248 // Every splitting function ensures that there are at least StackLimit
2249 // bytes available below SP when the splitting prologue finishes.
2250 // If the splitting function calls F, then F begins execution with
2251 // at least StackLimit - callsize() bytes available.
2252 // Check that every function behaves correctly with this amount
2253 // of stack, following direct calls in order to piece together chains
2254 // of non-splitting functions.
2256 ch.limit = objabi.StackLimit - callsize(ctxt)
2257 if buildcfg.GOARCH == "arm64" {
2258 // need extra 8 bytes below SP to save FP
2262 // Check every function, but do the nosplit functions in a first pass,
2263 // to make the printed failure chains as short as possible.
2264 for _, s := range ctxt.Textp {
2265 if ldr.IsNoSplit(s) {
2271 for _, s := range ctxt.Textp {
2272 if !ldr.IsNoSplit(s) {
2279 func (sc *stkChk) check(up *chain, depth int) int {
2285 // Don't duplicate work: only need to consider each
2286 // function at top of safe zone once.
2287 top := limit == objabi.StackLimit-callsize(ctxt)
2296 sc.ctxt.Errorf(s, "nosplit stack check too deep")
2301 if ldr.AttrExternal(s) {
2302 // external function.
2303 // should never be called directly.
2304 // onlyctxt.Diagnose the direct caller.
2305 // TODO(mwhudson): actually think about this.
2306 // TODO(khr): disabled for now. Calls to external functions can only happen on the g0 stack.
2307 // See the trampolines in src/runtime/sys_darwin_$ARCH.go.
2308 //if depth == 1 && ldr.SymType(s) != sym.SXREF && !ctxt.DynlinkingGo() &&
2309 // ctxt.BuildMode != BuildModeCArchive && ctxt.BuildMode != BuildModePIE && ctxt.BuildMode != BuildModeCShared && ctxt.BuildMode != BuildModePlugin {
2310 // Errorf(s, "call to external function")
2314 info := ldr.FuncInfo(s)
2315 if !info.Valid() { // external function. see above.
2324 // morestack looks like it calls functions,
2325 // but it switches the stack pointer first.
2326 if s == sc.morestack {
2333 if !ldr.IsNoSplit(s) {
2334 // Ensure we have enough stack to call morestack.
2335 ch.limit = limit - callsize(ctxt)
2336 ch.sym = sc.morestack
2337 if sc.check(&ch, depth+1) < 0 {
2343 // Raise limit to allow frame.
2344 locals := info.Locals()
2345 limit = objabi.StackLimit + int(locals) + int(ctxt.FixedFrameSize())
2348 // Walk through sp adjustments in function, consuming relocs.
2349 relocs := ldr.Relocs(s)
2351 pcsp := obj.NewPCIter(uint32(ctxt.Arch.MinLC))
2353 for pcsp.Init(ldr.Data(ldr.Pcsp(s))); !pcsp.Done; pcsp.Next() {
2354 // pcsp.value is in effect for [pcsp.pc, pcsp.nextpc).
2356 // Check stack size in effect for this span.
2357 if int32(limit)-pcsp.Value < 0 {
2358 sc.broke(up, int(int32(limit)-pcsp.Value))
2362 // Process calls in this span.
2363 for ; ri < relocs.Count(); ri++ {
2365 if uint32(r.Off()) >= pcsp.NextPC {
2370 case t.IsDirectCall():
2371 ch.limit = int(int32(limit) - pcsp.Value - int32(callsize(ctxt)))
2373 if sc.check(&ch, depth+1) < 0 {
2377 // Indirect call. Assume it is a call to a splitting function,
2378 // so we have to make sure it can call morestack.
2379 // Arrange the data structures to report both calls, so that
2380 // if there is an error, stkprint shows all the steps involved.
2381 case t == objabi.R_CALLIND:
2382 ch.limit = int(int32(limit) - pcsp.Value - int32(callsize(ctxt)))
2384 ch1.limit = ch.limit - callsize(ctxt) // for morestack in called prologue
2386 ch1.sym = sc.morestack
2387 if sc.check(&ch1, depth+2) < 0 {
2397 func (sc *stkChk) broke(ch *chain, limit int) {
2398 sc.ctxt.Errorf(ch.sym, "nosplit stack overflow")
2402 func (sc *stkChk) print(ch *chain, limit int) {
2407 name = fmt.Sprintf("%s<%d>", ldr.SymName(ch.sym), ldr.SymVersion(ch.sym))
2408 if ldr.IsNoSplit(ch.sym) {
2409 name += " (nosplit)"
2412 name = "function pointer"
2416 // top of chain. ch.sym != 0.
2417 if ldr.IsNoSplit(ch.sym) {
2418 fmt.Printf("\t%d\tassumed on entry to %s\n", ch.limit, name)
2420 fmt.Printf("\t%d\tguaranteed after split check in %s\n", ch.limit, name)
2423 sc.print(ch.up, ch.limit+callsize(ctxt))
2424 if !haslinkregister(ctxt) {
2425 fmt.Printf("\t%d\ton entry to %s\n", ch.limit, name)
2429 if ch.limit != limit {
2430 fmt.Printf("\t%d\tafter %s uses %d\n", limit, name, ch.limit-limit)
2435 fmt.Fprintf(os.Stderr, "usage: link [options] main.o\n")
2436 objabi.Flagprint(os.Stderr)
2440 type SymbolType int8 // TODO: after genasmsym is gone, maybe rename to plan9typeChar or something
2443 // see also https://9p.io/magic/man2html/1/nm
2444 TextSym SymbolType = 'T'
2445 DataSym SymbolType = 'D'
2446 BSSSym SymbolType = 'B'
2447 UndefinedSym SymbolType = 'U'
2448 TLSSym SymbolType = 't'
2449 FrameSym SymbolType = 'm'
2450 ParamSym SymbolType = 'p'
2451 AutoSym SymbolType = 'a'
2453 // Deleted auto (not a real sym, just placeholder for type)
2454 DeletedAutoSym = 'x'
2457 // defineInternal defines a symbol used internally by the go runtime.
2458 func (ctxt *Link) defineInternal(p string, t sym.SymKind) loader.Sym {
2459 s := ctxt.loader.CreateSymForUpdate(p, 0)
2466 func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) loader.Sym {
2467 s := ctxt.defineInternal(p, t)
2468 ctxt.loader.SetSymValue(s, v)
2472 func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
2473 if uint64(addr) >= Segdata.Vaddr {
2474 return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
2476 if uint64(addr) >= Segtext.Vaddr {
2477 return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
2479 ldr.Errorf(s, "invalid datoff %#x", addr)
2483 func Entryvalue(ctxt *Link) int64 {
2484 a := *flagEntrySymbol
2485 if a[0] >= '0' && a[0] <= '9' {
2489 s := ldr.Lookup(a, 0)
2490 st := ldr.SymType(s)
2492 return *FlagTextAddr
2494 if !ctxt.IsAIX() && st != sym.STEXT {
2495 ldr.Errorf(s, "entry not text")
2497 return ldr.SymValue(s)
2500 func (ctxt *Link) callgraph() {
2506 for _, s := range ctxt.Textp {
2507 relocs := ldr.Relocs(s)
2508 for i := 0; i < relocs.Count(); i++ {
2514 if r.Type().IsDirectCall() && ldr.SymType(rs) == sym.STEXT {
2515 ctxt.Logf("%s calls %s\n", ldr.SymName(s), ldr.SymName(rs))
2521 func Rnd(v int64, r int64) int64 {
2534 func bgetc(r *bio.Reader) int {
2535 c, err := r.ReadByte()
2538 log.Fatalf("reading input: %v", err)
2545 type markKind uint8 // for postorder traversal
2552 func postorder(libs []*sym.Library) []*sym.Library {
2553 order := make([]*sym.Library, 0, len(libs)) // hold the result
2554 mark := make(map[*sym.Library]markKind, len(libs))
2555 for _, lib := range libs {
2556 dfs(lib, mark, &order)
2561 func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library) {
2562 if mark[lib] == visited {
2565 if mark[lib] == visiting {
2566 panic("found import cycle while visiting " + lib.Pkg)
2568 mark[lib] = visiting
2569 for _, i := range lib.Imports {
2573 *order = append(*order, lib)
2576 func ElfSymForReloc(ctxt *Link, s loader.Sym) int32 {
2577 // If putelfsym created a local version of this symbol, use that in all
2579 les := ctxt.loader.SymLocalElfSym(s)
2583 return ctxt.loader.SymElfSym(s)
2587 func AddGotSym(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, elfRelocTyp uint32) {
2588 if ldr.SymGot(s) >= 0 {
2592 Adddynsym(ldr, target, syms, s)
2593 got := ldr.MakeSymbolUpdater(syms.GOT)
2594 ldr.SetGot(s, int32(got.Size()))
2595 got.AddUint(target.Arch, 0)
2598 if target.Arch.PtrSize == 8 {
2599 rela := ldr.MakeSymbolUpdater(syms.Rela)
2600 rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2601 rela.AddUint64(target.Arch, elf.R_INFO(uint32(ldr.SymDynid(s)), elfRelocTyp))
2602 rela.AddUint64(target.Arch, 0)
2604 rel := ldr.MakeSymbolUpdater(syms.Rel)
2605 rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2606 rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), elfRelocTyp))
2608 } else if target.IsDarwin() {
2609 leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT)
2610 leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
2611 if target.IsPIE() && target.IsInternal() {
2612 // Mach-O relocations are a royal pain to lay out.
2613 // They use a compact stateful bytecode representation.
2614 // Here we record what are needed and encode them later.
2615 MachoAddBind(int64(ldr.SymGot(s)), s)
2618 ldr.Errorf(s, "addgotsym: unsupported binary format")