1 // Inferno utils/8l/asm.c
2 // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/8l/asm.c
4 // Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
5 // Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
6 // Portions Copyright © 1997-1999 Vita Nuova Limited
7 // Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
8 // Portions Copyright © 2004,2006 Bruce Ellis
9 // Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
10 // Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
11 // Portions Copyright © 2009 The Go Authors. All rights reserved.
13 // Permission is hereby granted, free of charge, to any person obtaining a copy
14 // of this software and associated documentation files (the "Software"), to deal
15 // in the Software without restriction, including without limitation the rights
16 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
17 // copies of the Software, and to permit persons to whom the Software is
18 // furnished to do so, subject to the following conditions:
20 // The above copyright notice and this permission notice shall be included in
21 // all copies or substantial portions of the Software.
23 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
24 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
25 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
26 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
27 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
28 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
37 "cmd/internal/notsha256"
40 "cmd/link/internal/loadelf"
41 "cmd/link/internal/loader"
42 "cmd/link/internal/loadmacho"
43 "cmd/link/internal/loadpe"
44 "cmd/link/internal/loadxcoff"
45 "cmd/link/internal/sym"
63 // Data layout and relocation.
65 // Derived from Inferno utils/6l/l.h
66 // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6l/l.h
68 // Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
69 // Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
70 // Portions Copyright © 1997-1999 Vita Nuova Limited
71 // Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
72 // Portions Copyright © 2004,2006 Bruce Ellis
73 // Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
74 // Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
75 // Portions Copyright © 2009 The Go Authors. All rights reserved.
77 // Permission is hereby granted, free of charge, to any person obtaining a copy
78 // of this software and associated documentation files (the "Software"), to deal
79 // in the Software without restriction, including without limitation the rights
80 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
81 // copies of the Software, and to permit persons to whom the Software is
82 // furnished to do so, subject to the following conditions:
84 // The above copyright notice and this permission notice shall be included in
85 // all copies or substantial portions of the Software.
87 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
88 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
89 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
90 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
91 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
92 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
95 // ArchSyms holds a number of architecture specific symbols used during
96 // relocation. Rather than allowing them universal access to all symbols,
97 // we keep a subset for relocation application.
98 type ArchSyms struct {
104 LinkEditGOT loader.Sym
105 LinkEditPLT loader.Sym
108 DotTOC []loader.Sym // for each version
121 unreachableMethod loader.Sym
124 // mkArchSym is a helper for setArchSyms, to set up a special symbol.
125 func (ctxt *Link) mkArchSym(name string, ver int, ls *loader.Sym) {
126 *ls = ctxt.loader.LookupOrCreateSym(name, ver)
127 ctxt.loader.SetAttrReachable(*ls, true)
130 // mkArchVecSym is similar to setArchSyms, but operates on elements within
131 // a slice, where each element corresponds to some symbol version.
132 func (ctxt *Link) mkArchSymVec(name string, ver int, ls []loader.Sym) {
133 ls[ver] = ctxt.loader.LookupOrCreateSym(name, ver)
134 ctxt.loader.SetAttrReachable(ls[ver], true)
137 // setArchSyms sets up the ArchSyms structure, and must be called before
138 // relocations are applied.
139 func (ctxt *Link) setArchSyms() {
140 ctxt.mkArchSym(".got", 0, &ctxt.GOT)
141 ctxt.mkArchSym(".plt", 0, &ctxt.PLT)
142 ctxt.mkArchSym(".got.plt", 0, &ctxt.GOTPLT)
143 ctxt.mkArchSym(".dynamic", 0, &ctxt.Dynamic)
144 ctxt.mkArchSym(".dynsym", 0, &ctxt.DynSym)
145 ctxt.mkArchSym(".dynstr", 0, &ctxt.DynStr)
146 ctxt.mkArchSym("runtime.unreachableMethod", abiInternalVer, &ctxt.unreachableMethod)
149 ctxt.mkArchSym("TOC", 0, &ctxt.TOC)
151 ctxt.DotTOC = make([]loader.Sym, ctxt.MaxVersion()+1)
152 for i := 0; i <= ctxt.MaxVersion(); i++ {
153 if i >= sym.SymVerABICount && i < sym.SymVerStatic { // these versions are not used currently
156 ctxt.mkArchSymVec(".TOC.", i, ctxt.DotTOC)
160 ctxt.mkArchSym(".rel", 0, &ctxt.Rel)
161 ctxt.mkArchSym(".rela", 0, &ctxt.Rela)
162 ctxt.mkArchSym(".rel.plt", 0, &ctxt.RelPLT)
163 ctxt.mkArchSym(".rela.plt", 0, &ctxt.RelaPLT)
166 ctxt.mkArchSym(".linkedit.got", 0, &ctxt.LinkEditGOT)
167 ctxt.mkArchSym(".linkedit.plt", 0, &ctxt.LinkEditPLT)
178 // Threshold of total text size, used for trampoline insertion. If the total
179 // text size is smaller than TrampLimit, we won't need to insert trampolines.
180 // It is pretty close to the offset range of a direct CALL machine instruction.
181 // We leave some room for extra stuff like PLT stubs.
189 Dragonflydynld string
192 // Empty spaces between codeblocks will be padded with this value.
193 // For example an architecture might want to pad with a trap instruction to
194 // catch wayward programs. Architectures that do not define a padding value
195 // are padded with zeros.
202 Adddynrel func(*Target, *loader.Loader, *ArchSyms, loader.Sym, loader.Reloc, int) bool
204 // Archreloc is an arch-specific hook that assists in relocation processing
205 // (invoked by 'relocsym'); it handles target-specific relocation tasks.
206 // Here "rel" is the current relocation being examined, "sym" is the symbol
207 // containing the chunk of data to which the relocation applies, and "off"
208 // is the contents of the to-be-relocated data item (from sym.P). Return
209 // value is the appropriately relocated value (to be written back to the
210 // same spot in sym.P), number of external _host_ relocations needed (i.e.
211 // ELF/Mach-O/etc. relocations, not Go relocations, this must match Elfreloc1,
212 // etc.), and a boolean indicating success/failure (a failing value indicates
214 Archreloc func(*Target, *loader.Loader, *ArchSyms, loader.Reloc, loader.Sym,
215 int64) (relocatedOffset int64, nExtReloc int, ok bool)
216 // Archrelocvariant is a second arch-specific hook used for
217 // relocation processing; it handles relocations where r.Type is
218 // insufficient to describe the relocation (r.Variant !=
219 // sym.RV_NONE). Here "rel" is the relocation being applied, "sym"
220 // is the symbol containing the chunk of data to which the
221 // relocation applies, and "off" is the contents of the
222 // to-be-relocated data item (from sym.P). Return is an updated
224 Archrelocvariant func(target *Target, ldr *loader.Loader, rel loader.Reloc,
225 rv sym.RelocVariant, sym loader.Sym, offset int64, data []byte) (relocatedOffset int64)
227 // Generate a trampoline for a call from s to rs if necessary. ri is
228 // index of the relocation.
229 Trampoline func(ctxt *Link, ldr *loader.Loader, ri int, rs, s loader.Sym)
231 // Assembling the binary breaks into two phases, writing the code/data/
232 // dwarf information (which is rather generic), and some more architecture
233 // specific work like setting up the elf headers/dynamic relocations, etc.
234 // The phases are called "Asmb" and "Asmb2". Asmb2 needs to be defined for
235 // every architecture, but only if architecture has an Asmb function will
236 // it be used for assembly. Otherwise a generic assembly Asmb function is
238 Asmb func(*Link, *loader.Loader)
239 Asmb2 func(*Link, *loader.Loader)
241 // Extreloc is an arch-specific hook that converts a Go relocation to an
242 // external relocation. Return the external relocation and whether it is
244 Extreloc func(*Target, *loader.Loader, loader.Reloc, loader.Sym) (loader.ExtReloc, bool)
246 Elfreloc1 func(*Link, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int, int64) bool
247 ElfrelocSize uint32 // size of an ELF relocation record, must match Elfreloc1.
248 Elfsetupplt func(ctxt *Link, plt, gotplt *loader.SymbolBuilder, dynamic loader.Sym)
249 Gentext func(*Link, *loader.Loader) // Generate text before addressing has been performed.
250 Machoreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
251 MachorelocSize uint32 // size of an Mach-O relocation record, must match Machoreloc1.
252 PEreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
253 Xcoffreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
255 // Generate additional symbols for the native symbol table just prior to
257 GenSymsLate func(*Link, *loader.Loader)
259 // TLSIEtoLE converts a TLS Initial Executable relocation to
260 // a TLS Local Executable relocation.
262 // This is possible when a TLS IE relocation refers to a local
263 // symbol in an executable, which is typical when internally
264 // linking PIE binaries.
265 TLSIEtoLE func(P []byte, off, size int)
267 // optional override for assignAddress
268 AssignAddress func(ldr *loader.Loader, sect *sym.Section, n int, s loader.Sym, va uint64, isTramp bool) (*sym.Section, int, uint64)
280 MINFUNC = 16 // minimum size for a function
283 // Symbol version of ABIInternal symbols. It is sym.SymVerABIInternal if ABI wrappers
284 // are used, 0 otherwise.
285 var abiInternalVer = sym.SymVerABIInternal
287 // DynlinkingGo reports whether we are producing Go code that can live
288 // in separate shared libraries linked together at runtime.
289 func (ctxt *Link) DynlinkingGo() bool {
291 panic("DynlinkingGo called before all symbols loaded")
293 return ctxt.BuildMode == BuildModeShared || ctxt.linkShared || ctxt.BuildMode == BuildModePlugin || ctxt.canUsePlugins
296 // CanUsePlugins reports whether a plugins can be used
297 func (ctxt *Link) CanUsePlugins() bool {
299 panic("CanUsePlugins called before all symbols loaded")
301 return ctxt.canUsePlugins
304 // NeedCodeSign reports whether we need to code-sign the output binary.
305 func (ctxt *Link) NeedCodeSign() bool {
306 return ctxt.IsDarwin() && ctxt.IsARM64()
318 debug_s bool // backup old value of debug['s']
322 liveness int64 // size of liveness data (funcdata), printed if -v
324 // See -strictdups command line flag.
325 checkStrictDups int // 0=off 1=warning 2=error
326 strictDupMsgCount int
331 Segrodata sym.Segment
332 Segrelrodata sym.Segment
336 Segments = []*sym.Segment{&Segtext, &Segrodata, &Segrelrodata, &Segdata, &Segdwarf}
339 const pkgdef = "__.PKGDEF"
342 // externalobj is set to true if we see an object compiled by
343 // the host compiler that is not from a package that is known
344 // to support internal linking mode.
347 // dynimportfail is a list of packages for which generating
348 // the dynimport file, _cgo_import.go, failed. If there are
349 // any of these objects, we must link externally. Issue 52863.
350 dynimportfail []string
352 // unknownObjFormat is set to true if we see an object whose
353 // format we don't recognize.
354 unknownObjFormat = false
359 func Lflag(ctxt *Link, arg string) {
360 ctxt.Libdir = append(ctxt.Libdir, arg)
364 * Unix doesn't like it when we write to a running (or, sometimes,
365 * recently run) binary, so remove the output file before writing it.
366 * On Windows 7, remove() can force a subsequent create() to fail.
367 * S_ISREG() does not exist on Plan 9.
369 func mayberemoveoutfile() {
370 if fi, err := os.Lstat(*flagOutfile); err == nil && !fi.Mode().IsRegular() {
373 os.Remove(*flagOutfile)
376 func libinit(ctxt *Link) {
377 Funcalign = thearch.Funcalign
379 // add goroot to the end of the libdir list.
383 if *flagInstallSuffix != "" {
385 suffix = *flagInstallSuffix
386 } else if *flagRace {
389 } else if *flagMsan {
392 } else if *flagAsan {
397 if buildcfg.GOROOT != "" {
398 Lflag(ctxt, filepath.Join(buildcfg.GOROOT, "pkg", fmt.Sprintf("%s_%s%s%s", buildcfg.GOOS, buildcfg.GOARCH, suffixsep, suffix)))
403 if err := ctxt.Out.Open(*flagOutfile); err != nil {
404 Exitf("cannot create %s: %v", *flagOutfile, err)
407 if *flagEntrySymbol == "" {
408 switch ctxt.BuildMode {
409 case BuildModeCShared, BuildModeCArchive:
410 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s_lib", buildcfg.GOARCH, buildcfg.GOOS)
411 case BuildModeExe, BuildModePIE:
412 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s", buildcfg.GOARCH, buildcfg.GOOS)
413 case BuildModeShared, BuildModePlugin:
414 // No *flagEntrySymbol for -buildmode=shared and plugin
416 Errorf(nil, "unknown *flagEntrySymbol for buildmode %v", ctxt.BuildMode)
421 func exitIfErrors() {
422 if nerrors != 0 || checkStrictDups > 1 && strictDupMsgCount > 0 {
434 func loadinternal(ctxt *Link, name string) *sym.Library {
435 zerofp := goobj.FingerprintType{}
436 if ctxt.linkShared && ctxt.PackageShlib != nil {
437 if shlib := ctxt.PackageShlib[name]; shlib != "" {
438 return addlibpath(ctxt, "internal", "internal", "", name, shlib, zerofp)
441 if ctxt.PackageFile != nil {
442 if pname := ctxt.PackageFile[name]; pname != "" {
443 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
445 ctxt.Logf("loadinternal: cannot find %s\n", name)
449 for _, libdir := range ctxt.Libdir {
451 shlibname := filepath.Join(libdir, name+".shlibname")
452 if ctxt.Debugvlog != 0 {
453 ctxt.Logf("searching for %s.a in %s\n", name, shlibname)
455 if _, err := os.Stat(shlibname); err == nil {
456 return addlibpath(ctxt, "internal", "internal", "", name, shlibname, zerofp)
459 pname := filepath.Join(libdir, name+".a")
460 if ctxt.Debugvlog != 0 {
461 ctxt.Logf("searching for %s.a in %s\n", name, pname)
463 if _, err := os.Stat(pname); err == nil {
464 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
468 ctxt.Logf("warning: unable to find %s.a\n", name)
472 // extld returns the current external linker.
473 func (ctxt *Link) extld() []string {
474 if len(flagExtld) == 0 {
475 flagExtld = []string{"gcc"}
480 // findLibPathCmd uses cmd command to find gcc library libname.
481 // It returns library full path if found, or "none" if not found.
482 func (ctxt *Link) findLibPathCmd(cmd, libname string) string {
483 extld := ctxt.extld()
484 name, args := extld[0], extld[1:]
485 args = append(args, hostlinkArchArgs(ctxt.Arch)...)
486 args = append(args, cmd)
487 if ctxt.Debugvlog != 0 {
488 ctxt.Logf("%s %v\n", extld, args)
490 out, err := exec.Command(name, args...).Output()
492 if ctxt.Debugvlog != 0 {
493 ctxt.Logf("not using a %s file because compiler failed\n%v\n%s\n", libname, err, out)
497 return strings.TrimSpace(string(out))
500 // findLibPath searches for library libname.
501 // It returns library full path if found, or "none" if not found.
502 func (ctxt *Link) findLibPath(libname string) string {
503 return ctxt.findLibPathCmd("--print-file-name="+libname, libname)
506 func (ctxt *Link) loadlib() {
508 switch *FlagStrictDups {
512 flags |= loader.FlagStrictDups
514 log.Fatalf("invalid -strictdups flag value %d", *FlagStrictDups)
516 elfsetstring1 := func(str string, off int) { elfsetstring(ctxt, 0, str, off) }
517 ctxt.loader = loader.NewLoader(flags, elfsetstring1, &ctxt.ErrorReporter.ErrorReporter)
518 ctxt.ErrorReporter.SymName = func(s loader.Sym) string {
519 return ctxt.loader.SymName(s)
522 // ctxt.Library grows during the loop, so not a range loop.
524 for ; i < len(ctxt.Library); i++ {
525 lib := ctxt.Library[i]
527 if ctxt.Debugvlog > 1 {
528 ctxt.Logf("autolib: %s (from %s)\n", lib.File, lib.Objref)
530 loadobjfile(ctxt, lib)
534 // load internal packages, if not already
536 loadinternal(ctxt, "runtime/race")
539 loadinternal(ctxt, "runtime/msan")
542 loadinternal(ctxt, "runtime/asan")
544 loadinternal(ctxt, "runtime")
545 for ; i < len(ctxt.Library); i++ {
546 lib := ctxt.Library[i]
548 loadobjfile(ctxt, lib)
551 // At this point, the Go objects are "preloaded". Not all the symbols are
552 // added to the symbol table (only defined package symbols are). Looking
553 // up symbol by name may not get expected result.
555 iscgo = ctxt.LibraryByPkg["runtime/cgo"] != nil
557 // Plugins a require cgo support to function. Similarly, plugins may require additional
558 // internal linker support on some platforms which may not be implemented.
559 ctxt.canUsePlugins = ctxt.LibraryByPkg["plugin"] != nil && iscgo
561 // We now have enough information to determine the link mode.
562 determineLinkMode(ctxt)
564 if ctxt.LinkMode == LinkExternal && !iscgo && !(buildcfg.GOOS == "darwin" && ctxt.BuildMode != BuildModePlugin && ctxt.Arch.Family == sys.AMD64) {
565 // This indicates a user requested -linkmode=external.
566 // The startup code uses an import of runtime/cgo to decide
567 // whether to initialize the TLS. So give it one. This could
568 // be handled differently but it's an unusual case.
569 if lib := loadinternal(ctxt, "runtime/cgo"); lib != nil && lib.Shlib == "" {
570 if ctxt.BuildMode == BuildModeShared || ctxt.linkShared {
571 Exitf("cannot implicitly include runtime/cgo in a shared library")
573 for ; i < len(ctxt.Library); i++ {
574 lib := ctxt.Library[i]
576 loadobjfile(ctxt, lib)
582 // Add non-package symbols and references of externally defined symbols.
583 ctxt.loader.LoadSyms(ctxt.Arch)
585 // Load symbols from shared libraries, after all Go object symbols are loaded.
586 for _, lib := range ctxt.Library {
588 if ctxt.Debugvlog > 1 {
589 ctxt.Logf("autolib: %s (from %s)\n", lib.Shlib, lib.Objref)
591 ldshlibsyms(ctxt, lib.Shlib)
595 // Process cgo directives (has to be done before host object loading).
596 ctxt.loadcgodirectives()
598 // Conditionally load host objects, or setup for external linking.
602 if ctxt.LinkMode == LinkInternal && len(hostobj) != 0 {
603 // If we have any undefined symbols in external
604 // objects, try to read them from the libgcc file.
606 undefs := ctxt.loader.UndefinedRelocTargets(1)
611 if *flagLibGCC == "" {
612 *flagLibGCC = ctxt.findLibPathCmd("--print-libgcc-file-name", "libgcc")
614 if runtime.GOOS == "openbsd" && *flagLibGCC == "libgcc.a" {
615 // On OpenBSD `clang --print-libgcc-file-name` returns "libgcc.a".
616 // In this case we fail to load libgcc.a and can encounter link
617 // errors - see if we can find libcompiler_rt.a instead.
618 *flagLibGCC = ctxt.findLibPathCmd("--print-file-name=libcompiler_rt.a", "libcompiler_rt")
620 if ctxt.HeadType == objabi.Hwindows {
621 loadWindowsHostArchives(ctxt)
623 if *flagLibGCC != "none" {
624 hostArchive(ctxt, *flagLibGCC)
629 // We've loaded all the code now.
634 strictDupMsgCount = ctxt.loader.NStrictDupMsgs()
637 // loadWindowsHostArchives loads in host archives and objects when
638 // doing internal linking on windows. Older toolchains seem to require
639 // just a single pass through the various archives, but some modern
640 // toolchains when linking a C program with mingw pass library paths
641 // multiple times to the linker, e.g. "... -lmingwex -lmingw32 ...
642 // -lmingwex -lmingw32 ...". To accommodate this behavior, we make two
643 // passes over the host archives below.
644 func loadWindowsHostArchives(ctxt *Link) {
646 for i := 0; any && i < 2; i++ {
647 // Link crt2.o (if present) to resolve "atexit" when
648 // using LLVM-based compilers.
649 isunresolved := symbolsAreUnresolved(ctxt, []string{"atexit"})
651 if p := ctxt.findLibPath("crt2.o"); p != "none" {
652 hostObject(ctxt, "crt2", p)
655 if p := ctxt.findLibPath("libmingwex.a"); p != "none" {
658 if p := ctxt.findLibPath("libmingw32.a"); p != "none" {
661 // Link libmsvcrt.a to resolve '__acrt_iob_func' symbol
662 // (see https://golang.org/issue/23649 for details).
663 if p := ctxt.findLibPath("libmsvcrt.a"); p != "none" {
667 undefs := ctxt.loader.UndefinedRelocTargets(1)
672 // If needed, create the __CTOR_LIST__ and __DTOR_LIST__
673 // symbols (referenced by some of the mingw support library
674 // routines). Creation of these symbols is normally done by the
675 // linker if not already present.
676 want := []string{"__CTOR_LIST__", "__DTOR_LIST__"}
677 isunresolved := symbolsAreUnresolved(ctxt, want)
678 for k, w := range want {
680 sb := ctxt.loader.CreateSymForUpdate(w, 0)
681 sb.SetType(sym.SDATA)
682 sb.AddUint64(ctxt.Arch, 0)
683 sb.SetReachable(true)
684 ctxt.loader.SetAttrSpecial(sb.Sym(), true)
687 // TODO: maybe do something similar to peimporteddlls to collect
688 // all lib names and try link them all to final exe just like
689 // libmingwex.a and libmingw32.a:
692 #cgo windows LDFLAGS: -lmsvcrt -lm
698 // loadcgodirectives reads the previously discovered cgo directives, creating
699 // symbols in preparation for host object loading or use later in the link.
700 func (ctxt *Link) loadcgodirectives() {
702 hostObjSyms := make(map[loader.Sym]struct{})
703 for _, d := range ctxt.cgodata {
704 setCgoAttr(ctxt, d.file, d.pkg, d.directives, hostObjSyms)
708 if ctxt.LinkMode == LinkInternal {
709 // Drop all the cgo_import_static declarations.
710 // Turns out we won't be needing them.
711 for symIdx := range hostObjSyms {
712 if l.SymType(symIdx) == sym.SHOSTOBJ {
713 // If a symbol was marked both
714 // cgo_import_static and cgo_import_dynamic,
715 // then we want to make it cgo_import_dynamic
717 su := l.MakeSymbolUpdater(symIdx)
718 if l.SymExtname(symIdx) != "" && l.SymDynimplib(symIdx) != "" && !(l.AttrCgoExportStatic(symIdx) || l.AttrCgoExportDynamic(symIdx)) {
719 su.SetType(sym.SDYNIMPORT)
728 // Set up flags and special symbols depending on the platform build mode.
729 // This version works with loader.Loader.
730 func (ctxt *Link) linksetup() {
731 switch ctxt.BuildMode {
732 case BuildModeCShared, BuildModePlugin:
733 symIdx := ctxt.loader.LookupOrCreateSym("runtime.islibrary", 0)
734 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
735 sb.SetType(sym.SNOPTRDATA)
737 case BuildModeCArchive:
738 symIdx := ctxt.loader.LookupOrCreateSym("runtime.isarchive", 0)
739 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
740 sb.SetType(sym.SNOPTRDATA)
744 // Recalculate pe parameters now that we have ctxt.LinkMode set.
745 if ctxt.HeadType == objabi.Hwindows {
749 if ctxt.LinkMode == LinkExternal {
750 // When external linking, we are creating an object file. The
751 // absolute address is irrelevant.
755 // If there are no dynamic libraries needed, gcc disables dynamic linking.
756 // Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13)
757 // assumes that a dynamic binary always refers to at least one dynamic library.
758 // Rather than be a source of test cases for glibc, disable dynamic linking
759 // the same way that gcc would.
761 // Exception: on OS X, programs such as Shark only work with dynamic
762 // binaries, so leave it enabled on OS X (Mach-O) binaries.
763 // Also leave it enabled on Solaris which doesn't support
764 // statically linked binaries.
765 if ctxt.BuildMode == BuildModeExe {
766 if havedynamic == 0 && ctxt.HeadType != objabi.Hdarwin && ctxt.HeadType != objabi.Hsolaris {
771 if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && buildcfg.GOOS != "aix" {
772 toc := ctxt.loader.LookupOrCreateSym(".TOC.", 0)
773 sb := ctxt.loader.MakeSymbolUpdater(toc)
774 sb.SetType(sym.SDYNIMPORT)
777 // The Android Q linker started to complain about underalignment of the our TLS
778 // section. We don't actually use the section on android, so don't
780 if buildcfg.GOOS != "android" {
781 tlsg := ctxt.loader.LookupOrCreateSym("runtime.tlsg", 0)
782 sb := ctxt.loader.MakeSymbolUpdater(tlsg)
784 // runtime.tlsg is used for external linking on platforms that do not define
785 // a variable to hold g in assembly (currently only intel).
787 sb.SetType(sym.STLSBSS)
788 sb.SetSize(int64(ctxt.Arch.PtrSize))
789 } else if sb.Type() != sym.SDYNIMPORT {
790 Errorf(nil, "runtime declared tlsg variable %v", sb.Type())
792 ctxt.loader.SetAttrReachable(tlsg, true)
796 var moduledata loader.Sym
797 var mdsb *loader.SymbolBuilder
798 if ctxt.BuildMode == BuildModePlugin {
799 moduledata = ctxt.loader.LookupOrCreateSym("local.pluginmoduledata", 0)
800 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
801 ctxt.loader.SetAttrLocal(moduledata, true)
803 moduledata = ctxt.loader.LookupOrCreateSym("runtime.firstmoduledata", 0)
804 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
806 if mdsb.Type() != 0 && mdsb.Type() != sym.SDYNIMPORT {
807 // If the module (toolchain-speak for "executable or shared
808 // library") we are linking contains the runtime package, it
809 // will define the runtime.firstmoduledata symbol and we
810 // truncate it back to 0 bytes so we can define its entire
811 // contents in symtab.go:symtab().
814 // In addition, on ARM, the runtime depends on the linker
815 // recording the value of GOARM.
816 if ctxt.Arch.Family == sys.ARM {
817 goarm := ctxt.loader.LookupOrCreateSym("runtime.goarm", 0)
818 sb := ctxt.loader.MakeSymbolUpdater(goarm)
819 sb.SetType(sym.SDATA)
821 sb.AddUint8(uint8(buildcfg.GOARM))
824 // Set runtime.disableMemoryProfiling bool if
825 // runtime.MemProfile is not retained in the binary after
826 // deadcode (and we're not dynamically linking).
827 memProfile := ctxt.loader.Lookup("runtime.MemProfile", abiInternalVer)
828 if memProfile != 0 && !ctxt.loader.AttrReachable(memProfile) && !ctxt.DynlinkingGo() {
829 memProfSym := ctxt.loader.LookupOrCreateSym("runtime.disableMemoryProfiling", 0)
830 sb := ctxt.loader.MakeSymbolUpdater(memProfSym)
831 sb.SetType(sym.SDATA)
833 sb.AddUint8(1) // true bool
836 // If OTOH the module does not contain the runtime package,
837 // create a local symbol for the moduledata.
838 moduledata = ctxt.loader.LookupOrCreateSym("local.moduledata", 0)
839 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
840 ctxt.loader.SetAttrLocal(moduledata, true)
842 // In all cases way we mark the moduledata as noptrdata to hide it from
844 mdsb.SetType(sym.SNOPTRDATA)
845 ctxt.loader.SetAttrReachable(moduledata, true)
846 ctxt.Moduledata = moduledata
848 if ctxt.Arch == sys.Arch386 && ctxt.HeadType != objabi.Hwindows {
849 if (ctxt.BuildMode == BuildModeCArchive && ctxt.IsELF) || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE || ctxt.DynlinkingGo() {
850 got := ctxt.loader.LookupOrCreateSym("_GLOBAL_OFFSET_TABLE_", 0)
851 sb := ctxt.loader.MakeSymbolUpdater(got)
852 sb.SetType(sym.SDYNIMPORT)
853 ctxt.loader.SetAttrReachable(got, true)
857 // DWARF-gen and other phases require that the unit Textp slices
858 // be populated, so that it can walk the functions in each unit.
859 // Call into the loader to do this (requires that we collect the
860 // set of internal libraries first). NB: might be simpler if we
861 // moved isRuntimeDepPkg to cmd/internal and then did the test in
862 // loader.AssignTextSymbolOrder.
863 ctxt.Library = postorder(ctxt.Library)
865 for _, lib := range ctxt.Library {
866 intlibs = append(intlibs, isRuntimeDepPkg(lib.Pkg))
868 ctxt.Textp = ctxt.loader.AssignTextSymbolOrder(ctxt.Library, intlibs, ctxt.Textp)
871 // mangleTypeSym shortens the names of symbols that represent Go types
872 // if they are visible in the symbol table.
874 // As the names of these symbols are derived from the string of
875 // the type, they can run to many kilobytes long. So we shorten
876 // them using a SHA-1 when the name appears in the final binary.
877 // This also removes characters that upset external linkers.
879 // These are the symbols that begin with the prefix 'type.' and
880 // contain run-time type information used by the runtime and reflect
881 // packages. All Go binaries contain these symbols, but only
882 // those programs loaded dynamically in multiple parts need these
883 // symbols to have entries in the symbol table.
884 func (ctxt *Link) mangleTypeSym() {
885 if ctxt.BuildMode != BuildModeShared && !ctxt.linkShared && ctxt.BuildMode != BuildModePlugin && !ctxt.CanUsePlugins() {
890 for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
891 if !ldr.AttrReachable(s) && !ctxt.linkShared {
892 // If -linkshared, the GCProg generation code may need to reach
893 // out to the shared library for the type descriptor's data, even
894 // the type descriptor itself is not actually needed at run time
895 // (therefore not reachable). We still need to mangle its name,
896 // so it is consistent with the one stored in the shared library.
899 name := ldr.SymName(s)
900 newName := typeSymbolMangle(name)
902 ldr.SetSymExtname(s, newName)
904 // When linking against a shared library, the Go object file may
905 // have reference to the original symbol name whereas the shared
906 // library provides a symbol with the mangled name. We need to
907 // copy the payload of mangled to original.
908 // XXX maybe there is a better way to do this.
909 dup := ldr.Lookup(newName, ldr.SymVersion(s))
912 dt := ldr.SymType(dup)
913 if st == sym.Sxxx && dt != sym.Sxxx {
921 // typeSymbolMangle mangles the given symbol name into something shorter.
923 // Keep the type.. prefix, which parts of the linker (like the
924 // DWARF generator) know means the symbol is not decodable.
925 // Leave type.runtime. symbols alone, because other parts of
926 // the linker manipulates them.
927 func typeSymbolMangle(name string) string {
928 if !strings.HasPrefix(name, "type.") {
931 if strings.HasPrefix(name, "type.runtime.") {
934 if len(name) <= 14 && !strings.Contains(name, "@") { // Issue 19529
937 hash := notsha256.Sum256([]byte(name))
942 return prefix + base64.StdEncoding.EncodeToString(hash[:6])
946 * look for the next file in an archive.
947 * adapted from libmach.
949 func nextar(bp *bio.Reader, off int64, a *ArHdr) int64 {
954 var buf [SAR_HDR]byte
955 if n, err := io.ReadFull(bp, buf[:]); err != nil {
956 if n == 0 && err != io.EOF {
962 a.name = artrim(buf[0:16])
963 a.date = artrim(buf[16:28])
964 a.uid = artrim(buf[28:34])
965 a.gid = artrim(buf[34:40])
966 a.mode = artrim(buf[40:48])
967 a.size = artrim(buf[48:58])
968 a.fmag = artrim(buf[58:60])
970 arsize := atolwhex(a.size)
974 return arsize + SAR_HDR
977 func loadobjfile(ctxt *Link, lib *sym.Library) {
978 pkg := objabi.PathToPrefix(lib.Pkg)
980 if ctxt.Debugvlog > 1 {
981 ctxt.Logf("ldobj: %s (%s)\n", lib.File, pkg)
983 f, err := bio.Open(lib.File)
985 Exitf("cannot open file %s: %v", lib.File, err)
989 if pkg == "main" && !lib.Main {
990 Exitf("%s: not package main", lib.File)
994 for i := 0; i < len(ARMAG); i++ {
995 if c, err := f.ReadByte(); err == nil && c == ARMAG[i] {
999 /* load it as a regular file */
1000 l := f.MustSeek(0, 2)
1002 ldobj(ctxt, f, lib, l, lib.File, lib.File)
1007 * load all the object files from the archive now.
1008 * this gives us sequential file access and keeps us
1009 * from needing to come back later to pick up more
1010 * objects. it breaks the usual C archive model, but
1011 * this is Go, not C. the common case in Go is that
1012 * we need to load all the objects, and then we throw away
1013 * the individual symbols that are unused.
1015 * loading every object will also make it possible to
1016 * load foreign objects not referenced by __.PKGDEF.
1021 l := nextar(f, off, &arhdr)
1026 Exitf("%s: malformed archive", lib.File)
1030 // __.PKGDEF isn't a real Go object file, and it's
1031 // absent in -linkobj builds anyway. Skipping it
1032 // ensures consistency between -linkobj and normal
1034 if arhdr.name == pkgdef {
1038 if arhdr.name == "dynimportfail" {
1039 dynimportfail = append(dynimportfail, lib.Pkg)
1042 // Skip other special (non-object-file) sections that
1043 // build tools may have added. Such sections must have
1044 // short names so that the suffix is not truncated.
1045 if len(arhdr.name) < 16 {
1046 if ext := filepath.Ext(arhdr.name); ext != ".o" && ext != ".syso" {
1051 pname := fmt.Sprintf("%s(%s)", lib.File, arhdr.name)
1052 l = atolwhex(arhdr.size)
1053 ldobj(ctxt, f, lib, l, pname, lib.File)
1057 type Hostobj struct {
1058 ld func(*Link, *bio.Reader, string, int64, string)
1066 var hostobj []Hostobj
1068 // These packages can use internal linking mode.
1069 // Others trigger external mode.
1070 var internalpkg = []string{
1071 "crypto/internal/boring",
1072 "crypto/internal/boring/syso",
1082 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 {
1084 for _, intpkg := range internalpkg {
1091 // DragonFly declares errno with __thread, which results in a symbol
1092 // type of R_386_TLS_GD or R_X86_64_TLSGD. The Go linker does not
1093 // currently know how to handle TLS relocations, hence we have to
1094 // force external linking for any libraries that link in code that
1095 // uses errno. This can be removed if the Go linker ever supports
1096 // these relocation types.
1097 if headType == objabi.Hdragonfly {
1098 if pkg == "net" || pkg == "os/user" {
1107 hostobj = append(hostobj, Hostobj{})
1108 h := &hostobj[len(hostobj)-1]
1118 func hostobjs(ctxt *Link) {
1119 if ctxt.LinkMode != LinkInternal {
1124 for i := 0; i < len(hostobj); i++ {
1126 f, err := bio.Open(h.file)
1128 Exitf("cannot reopen %s: %v", h.pn, err)
1131 f.MustSeek(h.off, 0)
1133 Errorf(nil, "%s: unrecognized object file format", h.pn)
1136 h.ld(ctxt, f, h.pkg, h.length, h.pn)
1141 func hostlinksetup(ctxt *Link) {
1142 if ctxt.LinkMode != LinkExternal {
1146 // For external link, record that we need to tell the external linker -s,
1147 // and turn off -s internally: the external linker needs the symbol
1148 // information for its final link.
1152 // create temporary directory and arrange cleanup
1153 if *flagTmpdir == "" {
1154 dir, err := ioutil.TempDir("", "go-link-")
1161 os.RemoveAll(*flagTmpdir)
1165 // change our output to temporary object file
1166 if err := ctxt.Out.Close(); err != nil {
1167 Exitf("error closing output file")
1169 mayberemoveoutfile()
1171 p := filepath.Join(*flagTmpdir, "go.o")
1172 if err := ctxt.Out.Open(p); err != nil {
1173 Exitf("cannot create %s: %v", p, err)
1177 // hostobjCopy creates a copy of the object files in hostobj in a
1178 // temporary directory.
1179 func hostobjCopy() (paths []string) {
1180 var wg sync.WaitGroup
1181 sema := make(chan struct{}, runtime.NumCPU()) // limit open file descriptors
1182 for i, h := range hostobj {
1184 dst := filepath.Join(*flagTmpdir, fmt.Sprintf("%06d.o", i))
1185 paths = append(paths, dst)
1194 f, err := os.Open(h.file)
1196 Exitf("cannot reopen %s: %v", h.pn, err)
1199 if _, err := f.Seek(h.off, 0); err != nil {
1200 Exitf("cannot seek %s: %v", h.pn, err)
1203 w, err := os.Create(dst)
1205 Exitf("cannot create %s: %v", dst, err)
1207 if _, err := io.CopyN(w, f, h.length); err != nil {
1208 Exitf("cannot write %s: %v", dst, err)
1210 if err := w.Close(); err != nil {
1211 Exitf("cannot close %s: %v", dst, err)
1219 // writeGDBLinkerScript creates gcc linker script file in temp
1220 // directory. writeGDBLinkerScript returns created file path.
1221 // The script is used to work around gcc bug
1222 // (see https://golang.org/issue/20183 for details).
1223 func writeGDBLinkerScript() string {
1224 name := "fix_debug_gdb_scripts.ld"
1225 path := filepath.Join(*flagTmpdir, name)
1228 .debug_gdb_scripts BLOCK(__section_alignment__) (NOLOAD) :
1230 *(.debug_gdb_scripts)
1233 INSERT AFTER .debug_types;
1235 err := ioutil.WriteFile(path, []byte(src), 0666)
1237 Errorf(nil, "WriteFile %s failed: %v", name, err)
1242 // archive builds a .a archive from the hostobj object files.
1243 func (ctxt *Link) archive() {
1244 if ctxt.BuildMode != BuildModeCArchive {
1250 if *flagExtar == "" {
1254 mayberemoveoutfile()
1256 // Force the buffer to flush here so that external
1257 // tools will see a complete file.
1258 if err := ctxt.Out.Close(); err != nil {
1259 Exitf("error closing %v", *flagOutfile)
1262 argv := []string{*flagExtar, "-q", "-c", "-s"}
1263 if ctxt.HeadType == objabi.Haix {
1264 argv = append(argv, "-X64")
1266 argv = append(argv, *flagOutfile)
1267 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1268 argv = append(argv, hostobjCopy()...)
1270 if ctxt.Debugvlog != 0 {
1271 ctxt.Logf("archive: %s\n", strings.Join(argv, " "))
1274 // If supported, use syscall.Exec() to invoke the archive command,
1275 // which should be the final remaining step needed for the link.
1276 // This will reduce peak RSS for the link (and speed up linking of
1277 // large applications), since when the archive command runs we
1278 // won't be holding onto all of the linker's live memory.
1279 if syscallExecSupported && !ownTmpDir {
1281 ctxt.execArchive(argv)
1282 panic("should not get here")
1285 // Otherwise invoke 'ar' in the usual way (fork + exec).
1286 if out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput(); err != nil {
1287 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1291 func (ctxt *Link) hostlink() {
1292 if ctxt.LinkMode != LinkExternal || nerrors > 0 {
1295 if ctxt.BuildMode == BuildModeCArchive {
1300 argv = append(argv, ctxt.extld()...)
1301 argv = append(argv, hostlinkArchArgs(ctxt.Arch)...)
1303 if *FlagS || debug_s {
1304 if ctxt.HeadType == objabi.Hdarwin {
1305 // Recent versions of macOS print
1306 // ld: warning: option -s is obsolete and being ignored
1307 // so do not pass any arguments.
1309 argv = append(argv, "-s")
1313 // On darwin, whether to combine DWARF into executable.
1314 // Only macOS supports unmapped segments such as our __DWARF segment.
1315 combineDwarf := ctxt.IsDarwin() && !*FlagS && !*FlagW && !debug_s && machoPlatform == PLATFORM_MACOS
1317 switch ctxt.HeadType {
1318 case objabi.Hdarwin:
1320 // Leave room for DWARF combining.
1321 // -headerpad is incompatible with -fembed-bitcode.
1322 argv = append(argv, "-Wl,-headerpad,1144")
1324 if ctxt.DynlinkingGo() && buildcfg.GOOS != "ios" {
1325 // -flat_namespace is deprecated on iOS.
1326 // It is useful for supporting plugins. We don't support plugins on iOS.
1327 // -flat_namespace may cause the dynamic linker to hang at forkExec when
1328 // resolving a lazy binding. See issue 38824.
1329 // Force eager resolution to work around.
1330 argv = append(argv, "-Wl,-flat_namespace", "-Wl,-bind_at_load")
1333 argv = append(argv, "-Wl,-S") // suppress STAB (symbolic debugging) symbols
1335 case objabi.Hopenbsd:
1336 argv = append(argv, "-Wl,-nopie")
1337 argv = append(argv, "-pthread")
1338 case objabi.Hwindows:
1340 argv = append(argv, "-mwindows")
1342 argv = append(argv, "-mconsole")
1344 // Mark as having awareness of terminal services, to avoid
1345 // ancient compatibility hacks.
1346 argv = append(argv, "-Wl,--tsaware")
1349 argv = append(argv, "-Wl,--nxcompat")
1351 argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", PeMinimumTargetMajorVersion))
1352 argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", PeMinimumTargetMinorVersion))
1353 argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", PeMinimumTargetMajorVersion))
1354 argv = append(argv, fmt.Sprintf("-Wl,--minor-subsystem-version=%d", PeMinimumTargetMinorVersion))
1356 argv = append(argv, "-pthread")
1357 // prevent ld to reorder .text functions to keep the same
1358 // first/last functions for moduledata.
1359 argv = append(argv, "-Wl,-bnoobjreorder")
1360 // mcmodel=large is needed for every gcc generated files, but
1361 // ld still need -bbigtoc in order to allow larger TOC.
1362 argv = append(argv, "-mcmodel=large")
1363 argv = append(argv, "-Wl,-bbigtoc")
1366 // Enable/disable ASLR on Windows.
1367 addASLRargs := func(argv []string, val bool) []string {
1368 // Old/ancient versions of GCC support "--dynamicbase" and
1369 // "--high-entropy-va" but don't enable it by default. In
1370 // addition, they don't accept "--disable-dynamicbase" or
1371 // "--no-dynamicbase", so the only way to disable ASLR is to
1372 // not pass any flags at all.
1374 // More modern versions of GCC (and also clang) enable ASLR
1375 // by default. With these compilers, however you can turn it
1376 // off if you want using "--disable-dynamicbase" or
1377 // "--no-dynamicbase".
1379 // The strategy below is to try using "--disable-dynamicbase";
1380 // if this succeeds, then assume we're working with more
1381 // modern compilers and act accordingly. If it fails, assume
1382 // an ancient compiler with ancient defaults.
1385 dbon := "--dynamicbase"
1386 heon := "--high-entropy-va"
1387 dboff := "--disable-dynamicbase"
1388 heoff := "--disable-high-entropy-va"
1393 // Test to see whether "--disable-dynamicbase" works.
1394 newer := linkerFlagSupported(ctxt.Arch, argv[0], "", "-Wl,"+dboff)
1396 // Newer compiler, which supports both on/off options.
1400 // older toolchain: we have to say nothing in order to
1401 // get a no-ASLR binary.
1407 argv = append(argv, "-Wl,"+dbopt)
1409 // enable high-entropy ASLR on 64-bit.
1410 if ctxt.Arch.PtrSize >= 8 && heopt != "" {
1411 argv = append(argv, "-Wl,"+heopt)
1416 switch ctxt.BuildMode {
1418 if ctxt.HeadType == objabi.Hdarwin {
1419 if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() {
1420 argv = append(argv, "-Wl,-no_pie")
1421 argv = append(argv, "-Wl,-pagezero_size,4000000")
1425 switch ctxt.HeadType {
1426 case objabi.Hdarwin, objabi.Haix:
1427 case objabi.Hwindows:
1428 argv = addASLRargs(argv, *flagAslr)
1431 if ctxt.UseRelro() {
1432 argv = append(argv, "-Wl,-z,relro")
1434 argv = append(argv, "-pie")
1436 case BuildModeCShared:
1437 if ctxt.HeadType == objabi.Hdarwin {
1438 argv = append(argv, "-dynamiclib")
1440 if ctxt.UseRelro() {
1441 argv = append(argv, "-Wl,-z,relro")
1443 argv = append(argv, "-shared")
1444 if ctxt.HeadType == objabi.Hwindows {
1445 argv = addASLRargs(argv, *flagAslr)
1447 // Pass -z nodelete to mark the shared library as
1448 // non-closeable: a dlclose will do nothing.
1449 argv = append(argv, "-Wl,-z,nodelete")
1450 // Only pass Bsymbolic on non-Windows.
1451 argv = append(argv, "-Wl,-Bsymbolic")
1454 case BuildModeShared:
1455 if ctxt.UseRelro() {
1456 argv = append(argv, "-Wl,-z,relro")
1458 argv = append(argv, "-shared")
1459 case BuildModePlugin:
1460 if ctxt.HeadType == objabi.Hdarwin {
1461 argv = append(argv, "-dynamiclib")
1463 if ctxt.UseRelro() {
1464 argv = append(argv, "-Wl,-z,relro")
1466 argv = append(argv, "-shared")
1470 var altLinker string
1471 if ctxt.IsELF && ctxt.DynlinkingGo() {
1472 // We force all symbol resolution to be done at program startup
1473 // because lazy PLT resolution can use large amounts of stack at
1474 // times we cannot allow it to do so.
1475 argv = append(argv, "-Wl,-z,now")
1477 // Do not let the host linker generate COPY relocations. These
1478 // can move symbols out of sections that rely on stable offsets
1479 // from the beginning of the section (like sym.STYPE).
1480 argv = append(argv, "-Wl,-z,nocopyreloc")
1482 if buildcfg.GOOS == "android" {
1483 // Use lld to avoid errors from default linker (issue #38838)
1487 if ctxt.Arch.InFamily(sys.ARM, sys.ARM64) && buildcfg.GOOS == "linux" {
1488 // On ARM, the GNU linker will generate COPY relocations
1489 // even with -znocopyreloc set.
1490 // https://sourceware.org/bugzilla/show_bug.cgi?id=19962
1492 // On ARM64, the GNU linker will fail instead of
1493 // generating COPY relocations.
1495 // In both cases, switch to gold.
1498 // If gold is not installed, gcc will silently switch
1499 // back to ld.bfd. So we parse the version information
1500 // and provide a useful error if gold is missing.
1501 name, args := flagExtld[0], flagExtld[1:]
1502 args = append(args, "-fuse-ld=gold", "-Wl,--version")
1503 cmd := exec.Command(name, args...)
1504 if out, err := cmd.CombinedOutput(); err == nil {
1505 if !bytes.Contains(out, []byte("GNU gold")) {
1506 log.Fatalf("ARM external linker must be gold (issue #15696), but is not: %s", out)
1511 if ctxt.Arch.Family == sys.ARM64 && buildcfg.GOOS == "freebsd" {
1512 // Switch to ld.bfd on freebsd/arm64.
1515 // Provide a useful error if ld.bfd is missing.
1516 name, args := flagExtld[0], flagExtld[1:]
1517 args = append(args, "-fuse-ld=bfd", "-Wl,--version")
1518 cmd := exec.Command(name, args...)
1519 if out, err := cmd.CombinedOutput(); err == nil {
1520 if !bytes.Contains(out, []byte("GNU ld")) {
1521 log.Fatalf("ARM64 external linker must be ld.bfd (issue #35197), please install devel/binutils")
1525 if altLinker != "" {
1526 argv = append(argv, "-fuse-ld="+altLinker)
1529 if ctxt.IsELF && len(buildinfo) > 0 {
1530 argv = append(argv, fmt.Sprintf("-Wl,--build-id=0x%x", buildinfo))
1533 // On Windows, given -o foo, GCC will append ".exe" to produce
1534 // "foo.exe". We have decided that we want to honor the -o
1535 // option. To make this work, we append a '.' so that GCC
1536 // will decide that the file already has an extension. We
1537 // only want to do this when producing a Windows output file
1538 // on a Windows host.
1539 outopt := *flagOutfile
1540 if buildcfg.GOOS == "windows" && runtime.GOOS == "windows" && filepath.Ext(outopt) == "" {
1543 argv = append(argv, "-o")
1544 argv = append(argv, outopt)
1546 if rpath.val != "" {
1547 argv = append(argv, fmt.Sprintf("-Wl,-rpath,%s", rpath.val))
1550 if *flagInterpreter != "" {
1551 // Many linkers support both -I and the --dynamic-linker flags
1552 // to set the ELF interpreter, but lld only supports
1553 // --dynamic-linker so prefer that (ld on very old Solaris only
1554 // supports -I but that seems less important).
1555 argv = append(argv, fmt.Sprintf("-Wl,--dynamic-linker,%s", *flagInterpreter))
1558 // Force global symbols to be exported for dlopen, etc.
1560 argv = append(argv, "-rdynamic")
1562 if ctxt.HeadType == objabi.Haix {
1563 fileName := xcoffCreateExportFile(ctxt)
1564 argv = append(argv, "-Wl,-bE:"+fileName)
1567 const unusedArguments = "-Qunused-arguments"
1568 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, unusedArguments) {
1569 argv = append(argv, unusedArguments)
1572 const compressDWARF = "-Wl,--compress-debug-sections=zlib"
1573 if ctxt.compressDWARF && linkerFlagSupported(ctxt.Arch, argv[0], altLinker, compressDWARF) {
1574 argv = append(argv, compressDWARF)
1577 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1578 argv = append(argv, hostobjCopy()...)
1579 if ctxt.HeadType == objabi.Haix {
1580 // We want to have C files after Go files to remove
1581 // trampolines csects made by ld.
1582 argv = append(argv, "-nostartfiles")
1583 argv = append(argv, "/lib/crt0_64.o")
1585 extld := ctxt.extld()
1586 name, args := extld[0], extld[1:]
1587 // Get starting files.
1588 getPathFile := func(file string) string {
1589 args := append(args, "-maix64", "--print-file-name="+file)
1590 out, err := exec.Command(name, args...).CombinedOutput()
1592 log.Fatalf("running %s failed: %v\n%s", extld, err, out)
1594 return strings.Trim(string(out), "\n")
1596 // Since GCC version 11, the 64-bit version of GCC starting files
1597 // are now suffixed by "_64". Even under "-maix64" multilib directory
1598 // "crtcxa.o" is 32-bit.
1599 crtcxa := getPathFile("crtcxa_64.o")
1600 if !filepath.IsAbs(crtcxa) {
1601 crtcxa = getPathFile("crtcxa.o")
1603 crtdbase := getPathFile("crtdbase_64.o")
1604 if !filepath.IsAbs(crtdbase) {
1605 crtdbase = getPathFile("crtdbase.o")
1607 argv = append(argv, crtcxa)
1608 argv = append(argv, crtdbase)
1611 if ctxt.linkShared {
1612 seenDirs := make(map[string]bool)
1613 seenLibs := make(map[string]bool)
1614 addshlib := func(path string) {
1615 dir, base := filepath.Split(path)
1617 argv = append(argv, "-L"+dir)
1619 argv = append(argv, "-Wl,-rpath="+dir)
1621 seenDirs[dir] = true
1623 base = strings.TrimSuffix(base, ".so")
1624 base = strings.TrimPrefix(base, "lib")
1625 if !seenLibs[base] {
1626 argv = append(argv, "-l"+base)
1627 seenLibs[base] = true
1630 for _, shlib := range ctxt.Shlibs {
1631 addshlib(shlib.Path)
1632 for _, dep := range shlib.Deps {
1636 libpath := findshlib(ctxt, dep)
1644 // clang, unlike GCC, passes -rdynamic to the linker
1645 // even when linking with -static, causing a linker
1646 // error when using GNU ld. So take out -rdynamic if
1647 // we added it. We do it in this order, rather than
1648 // only adding -rdynamic later, so that -extldflags
1649 // can override -rdynamic without using -static.
1650 // Similarly for -Wl,--dynamic-linker.
1651 checkStatic := func(arg string) {
1652 if ctxt.IsELF && arg == "-static" {
1653 for i := range argv {
1654 if argv[i] == "-rdynamic" || strings.HasPrefix(argv[i], "-Wl,--dynamic-linker,") {
1661 for _, p := range ldflag {
1662 argv = append(argv, p)
1666 // When building a program with the default -buildmode=exe the
1667 // gc compiler generates code requires DT_TEXTREL in a
1668 // position independent executable (PIE). On systems where the
1669 // toolchain creates PIEs by default, and where DT_TEXTREL
1670 // does not work, the resulting programs will not run. See
1671 // issue #17847. To avoid this problem pass -no-pie to the
1672 // toolchain if it is supported.
1673 if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared && !(ctxt.IsDarwin() && ctxt.IsARM64()) {
1674 // GCC uses -no-pie, clang uses -nopie.
1675 for _, nopie := range []string{"-no-pie", "-nopie"} {
1676 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, nopie) {
1677 argv = append(argv, nopie)
1683 for _, p := range flagExtldflags {
1684 argv = append(argv, p)
1687 if ctxt.HeadType == objabi.Hwindows {
1688 // Determine which linker we're using. Add in the extldflags in
1689 // case used has specified "-fuse-ld=...".
1690 extld := ctxt.extld()
1691 name, args := extld[0], extld[1:]
1692 args = append(args, flagExtldflags...)
1693 args = append(args, "-Wl,--version")
1694 cmd := exec.Command(name, args...)
1696 if out, err := cmd.CombinedOutput(); err == nil {
1697 if bytes.Contains(out, []byte("LLD ")) {
1702 // use gcc linker script to work around gcc bug
1703 // (see https://golang.org/issue/20183 for details).
1705 p := writeGDBLinkerScript()
1706 argv = append(argv, "-Wl,-T,"+p)
1708 // libmingw32 and libmingwex have some inter-dependencies,
1709 // so must use linker groups.
1710 argv = append(argv, "-Wl,--start-group", "-lmingwex", "-lmingw32", "-Wl,--end-group")
1711 argv = append(argv, peimporteddlls()...)
1714 if ctxt.Debugvlog != 0 {
1715 ctxt.Logf("host link:")
1716 for _, v := range argv {
1722 out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput()
1724 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1727 // Filter out useless linker warnings caused by bugs outside Go.
1728 // See also cmd/go/internal/work/exec.go's gccld method.
1731 for _, line := range bytes.SplitAfter(out, []byte("\n")) {
1732 // golang.org/issue/26073 - Apple Xcode bug
1733 if bytes.Contains(line, []byte("ld: warning: text-based stub file")) {
1742 // Remove TOC overflow warning on AIX.
1743 if bytes.Contains(line, []byte("ld: 0711-783")) {
1748 save = append(save, line)
1750 out = bytes.Join(save, nil)
1753 // always print external output even if the command is successful, so that we don't
1754 // swallow linker warnings (see https://golang.org/issue/17935).
1755 ctxt.Logf("%s", out)
1759 // Find "dsymutils" and "strip" tools using CC --print-prog-name.
1761 cc = append(cc, ctxt.extld()...)
1762 cc = append(cc, hostlinkArchArgs(ctxt.Arch)...)
1763 cc = append(cc, "--print-prog-name", "dsymutil")
1764 out, err := exec.Command(cc[0], cc[1:]...).CombinedOutput()
1766 Exitf("%s: finding dsymutil failed: %v\n%s", os.Args[0], err, out)
1768 dsymutilCmd := strings.TrimSuffix(string(out), "\n")
1770 cc[len(cc)-1] = "strip"
1771 out, err = exec.Command(cc[0], cc[1:]...).CombinedOutput()
1773 Exitf("%s: finding strip failed: %v\n%s", os.Args[0], err, out)
1775 stripCmd := strings.TrimSuffix(string(out), "\n")
1777 dsym := filepath.Join(*flagTmpdir, "go.dwarf")
1778 if out, err := exec.Command(dsymutilCmd, "-f", *flagOutfile, "-o", dsym).CombinedOutput(); err != nil {
1779 Exitf("%s: running dsymutil failed: %v\n%s", os.Args[0], err, out)
1781 // Remove STAB (symbolic debugging) symbols after we are done with them (by dsymutil).
1782 // They contain temporary file paths and make the build not reproducible.
1783 if out, err := exec.Command(stripCmd, "-S", *flagOutfile).CombinedOutput(); err != nil {
1784 Exitf("%s: running strip failed: %v\n%s", os.Args[0], err, out)
1786 // Skip combining if `dsymutil` didn't generate a file. See #11994.
1787 if _, err := os.Stat(dsym); os.IsNotExist(err) {
1790 // For os.Rename to work reliably, must be in same directory as outfile.
1791 combinedOutput := *flagOutfile + "~"
1792 exef, err := os.Open(*flagOutfile)
1794 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1797 exem, err := macho.NewFile(exef)
1799 Exitf("%s: parsing Mach-O header failed: %v", os.Args[0], err)
1801 if err := machoCombineDwarf(ctxt, exef, exem, dsym, combinedOutput); err != nil {
1802 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1804 os.Remove(*flagOutfile)
1805 if err := os.Rename(combinedOutput, *flagOutfile); err != nil {
1806 Exitf("%s: %v", os.Args[0], err)
1809 if ctxt.NeedCodeSign() {
1810 err := machoCodeSign(ctxt, *flagOutfile)
1812 Exitf("%s: code signing failed: %v", os.Args[0], err)
1817 var createTrivialCOnce sync.Once
1819 func linkerFlagSupported(arch *sys.Arch, linker, altLinker, flag string) bool {
1820 createTrivialCOnce.Do(func() {
1821 src := filepath.Join(*flagTmpdir, "trivial.c")
1822 if err := ioutil.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
1823 Errorf(nil, "WriteFile trivial.c failed: %v", err)
1827 flagsWithNextArgSkip := []string{
1836 flagsWithNextArgKeep := []string{
1842 prefixesToKeep := []string{
1853 flags := hostlinkArchArgs(arch)
1856 for _, f := range append(flagExtldflags, ldflag...) {
1858 flags = append(flags, f)
1862 } else if f == "" || f[0] != '-' {
1863 } else if contains(flagsWithNextArgSkip, f) {
1865 } else if contains(flagsWithNextArgKeep, f) {
1866 flags = append(flags, f)
1869 for _, p := range prefixesToKeep {
1870 if strings.HasPrefix(f, p) {
1871 flags = append(flags, f)
1878 if altLinker != "" {
1879 flags = append(flags, "-fuse-ld="+altLinker)
1881 flags = append(flags, flag, "trivial.c")
1883 cmd := exec.Command(linker, flags...)
1884 cmd.Dir = *flagTmpdir
1885 cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
1886 out, err := cmd.CombinedOutput()
1887 // GCC says "unrecognized command line option ‘-no-pie’"
1888 // clang says "unknown argument: '-no-pie'"
1889 return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
1892 // hostlinkArchArgs returns arguments to pass to the external linker
1893 // based on the architecture.
1894 func hostlinkArchArgs(arch *sys.Arch) []string {
1895 switch arch.Family {
1897 return []string{"-m32"}
1899 if buildcfg.GOOS == "darwin" {
1900 return []string{"-arch", "x86_64", "-m64"}
1902 return []string{"-m64"}
1904 return []string{"-m64"}
1906 return []string{"-marm"}
1908 if buildcfg.GOOS == "darwin" {
1909 return []string{"-arch", "arm64"}
1912 return []string{"-mabi=lp64d"}
1914 return []string{"-mabi=64"}
1916 return []string{"-mabi=32"}
1918 if buildcfg.GOOS == "aix" {
1919 return []string{"-maix64"}
1921 return []string{"-m64"}
1928 var wantHdr = objabi.HeaderString()
1930 // ldobj loads an input object. If it is a host object (an object
1931 // compiled by a non-Go compiler) it returns the Hostobj pointer. If
1932 // it is a Go object, it returns nil.
1933 func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string, file string) *Hostobj {
1934 pkg := objabi.PathToPrefix(lib.Pkg)
1936 eof := f.Offset() + length
1942 f.MustSeek(start, 0)
1944 unit := &sym.CompilationUnit{Lib: lib}
1945 lib.Units = append(lib.Units, unit)
1947 magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
1948 if magic == 0x7f454c46 { // \x7F E L F
1949 ldelf := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1950 textp, flags, err := loadelf.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn, ehdr.Flags)
1952 Errorf(nil, "%v", err)
1956 ctxt.Textp = append(ctxt.Textp, textp...)
1958 return ldhostobj(ldelf, ctxt.HeadType, f, pkg, length, pn, file)
1961 if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
1962 ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1963 textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1965 Errorf(nil, "%v", err)
1968 ctxt.Textp = append(ctxt.Textp, textp...)
1970 return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
1978 ldpe := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1979 textp, rsrc, err := loadpe.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1981 Errorf(nil, "%v", err)
1985 setpersrc(ctxt, rsrc)
1987 ctxt.Textp = append(ctxt.Textp, textp...)
1989 return ldhostobj(ldpe, ctxt.HeadType, f, pkg, length, pn, file)
1992 if c1 == 0x01 && (c2 == 0xD7 || c2 == 0xF7) {
1993 ldxcoff := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1994 textp, err := loadxcoff.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1996 Errorf(nil, "%v", err)
1999 ctxt.Textp = append(ctxt.Textp, textp...)
2001 return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
2004 if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
2005 // An unrecognized object is just passed to the external linker.
2006 // If we try to read symbols from this object, we will
2007 // report an error at that time.
2008 unknownObjFormat = true
2009 return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
2012 /* check the header */
2013 line, err := f.ReadString('\n')
2015 Errorf(nil, "truncated object file: %s: %v", pn, err)
2019 if !strings.HasPrefix(line, "go object ") {
2020 if strings.HasSuffix(pn, ".go") {
2021 Exitf("%s: uncompiled .go source file", pn)
2025 if line == ctxt.Arch.Name {
2026 // old header format: just $GOOS
2027 Errorf(nil, "%s: stale object file", pn)
2031 Errorf(nil, "%s: not an object file: @%d %q", pn, start, line)
2035 // First, check that the basic GOOS, GOARCH, and Version match.
2036 if line != wantHdr {
2037 Errorf(nil, "%s: linked object header mismatch:\nhave %q\nwant %q\n", pn, line, wantHdr)
2040 // Skip over exports and other info -- ends with \n!\n.
2042 // Note: It's possible for "\n!\n" to appear within the binary
2043 // package export data format. To avoid truncating the package
2044 // definition prematurely (issue 21703), we keep track of
2045 // how many "$$" delimiters we've seen.
2047 import0 := f.Offset()
2049 c1 = '\n' // the last line ended in \n
2055 if markers%2 == 0 && c2 == '!' && c3 == '\n' {
2058 if c2 == '$' && c3 == '$' {
2067 Errorf(nil, "truncated object file: %s", pn)
2072 import1 := f.Offset()
2074 f.MustSeek(import0, 0)
2075 ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
2076 f.MustSeek(import1, 0)
2078 fingerprint := ctxt.loader.Preload(ctxt.IncVersion(), f, lib, unit, eof-f.Offset())
2079 if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
2080 // Check fingerprint, to ensure the importing and imported packages
2081 // have consistent view of symbol indices.
2082 // Normally the go command should ensure this. But in case something
2083 // goes wrong, it could lead to obscure bugs like run-time crash.
2084 // Check it here to be sure.
2085 if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
2086 lib.Fingerprint = fingerprint
2088 checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
2091 addImports(ctxt, lib, pn)
2095 // symbolsAreUnresolved scans through the loader's list of unresolved
2096 // symbols and checks to see whether any of them match the names of the
2097 // symbols in 'want'. Return value is a list of bools, with list[K] set
2098 // to true if there is an unresolved reference to the symbol in want[K].
2099 func symbolsAreUnresolved(ctxt *Link, want []string) []bool {
2100 returnAllUndefs := -1
2101 undefs := ctxt.loader.UndefinedRelocTargets(returnAllUndefs)
2102 seen := make(map[loader.Sym]struct{})
2103 rval := make([]bool, len(want))
2104 wantm := make(map[string]int)
2105 for k, w := range want {
2109 for _, s := range undefs {
2110 if _, ok := seen[s]; ok {
2113 seen[s] = struct{}{}
2114 if k, ok := wantm[ctxt.loader.SymName(s)]; ok {
2117 if count == len(want) {
2125 // hostObject reads a single host object file (compare to "hostArchive").
2126 // This is used as part of internal linking when we need to pull in
2127 // files such as "crt?.o".
2128 func hostObject(ctxt *Link, objname string, path string) {
2129 if ctxt.Debugvlog > 1 {
2130 ctxt.Logf("hostObject(%s)\n", path)
2132 objlib := sym.Library{
2135 f, err := bio.Open(path)
2137 Exitf("cannot open host object %q file %s: %v", objname, path, err)
2140 h := ldobj(ctxt, f, &objlib, 0, path, path)
2142 Exitf("unrecognized object file format in %s", path)
2144 f.MustSeek(h.off, 0)
2145 h.ld(ctxt, f, h.pkg, h.length, h.pn)
2148 func checkFingerprint(lib *sym.Library, libfp goobj.FingerprintType, src string, srcfp goobj.FingerprintType) {
2150 Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
2154 func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
2155 data := make([]byte, sym.Size)
2156 sect := f.Sections[sym.Section]
2157 if sect.Type != elf.SHT_PROGBITS && sect.Type != elf.SHT_NOTE {
2158 Errorf(nil, "reading %s from non-data section", sym.Name)
2160 n, err := sect.ReadAt(data, int64(sym.Value-sect.Addr))
2161 if uint64(n) != sym.Size {
2162 Errorf(nil, "reading contents of %s: %v", sym.Name, err)
2167 func readwithpad(r io.Reader, sz int32) ([]byte, error) {
2168 data := make([]byte, Rnd(int64(sz), 4))
2169 _, err := io.ReadFull(r, data)
2177 func readnote(f *elf.File, name []byte, typ int32) ([]byte, error) {
2178 for _, sect := range f.Sections {
2179 if sect.Type != elf.SHT_NOTE {
2184 var namesize, descsize, noteType int32
2185 err := binary.Read(r, f.ByteOrder, &namesize)
2190 return nil, fmt.Errorf("read namesize failed: %v", err)
2192 err = binary.Read(r, f.ByteOrder, &descsize)
2194 return nil, fmt.Errorf("read descsize failed: %v", err)
2196 err = binary.Read(r, f.ByteOrder, ¬eType)
2198 return nil, fmt.Errorf("read type failed: %v", err)
2200 noteName, err := readwithpad(r, namesize)
2202 return nil, fmt.Errorf("read name failed: %v", err)
2204 desc, err := readwithpad(r, descsize)
2206 return nil, fmt.Errorf("read desc failed: %v", err)
2208 if string(name) == string(noteName) && typ == noteType {
2216 func findshlib(ctxt *Link, shlib string) string {
2217 if filepath.IsAbs(shlib) {
2220 for _, libdir := range ctxt.Libdir {
2221 libpath := filepath.Join(libdir, shlib)
2222 if _, err := os.Stat(libpath); err == nil {
2226 Errorf(nil, "cannot find shared library: %s", shlib)
2230 func ldshlibsyms(ctxt *Link, shlib string) {
2232 if filepath.IsAbs(shlib) {
2234 shlib = filepath.Base(shlib)
2236 libpath = findshlib(ctxt, shlib)
2241 for _, processedlib := range ctxt.Shlibs {
2242 if processedlib.Path == libpath {
2246 if ctxt.Debugvlog > 1 {
2247 ctxt.Logf("ldshlibsyms: found library with name %s at %s\n", shlib, libpath)
2250 f, err := elf.Open(libpath)
2252 Errorf(nil, "cannot open shared library: %s", libpath)
2255 // Keep the file open as decodetypeGcprog needs to read from it.
2256 // TODO: fix. Maybe mmap the file.
2259 hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
2261 Errorf(nil, "cannot read ABI hash from shared library %s: %v", libpath, err)
2265 depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
2267 Errorf(nil, "cannot read dep list from shared library %s: %v", libpath, err)
2271 for _, dep := range strings.Split(string(depsbytes), "\n") {
2275 if !filepath.IsAbs(dep) {
2276 // If the dep can be interpreted as a path relative to the shlib
2277 // in which it was found, do that. Otherwise, we will leave it
2278 // to be resolved by libdir lookup.
2279 abs := filepath.Join(filepath.Dir(libpath), dep)
2280 if _, err := os.Stat(abs); err == nil {
2284 deps = append(deps, dep)
2287 syms, err := f.DynamicSymbols()
2289 Errorf(nil, "cannot read symbols from shared library: %s", libpath)
2293 for _, elfsym := range syms {
2294 if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
2298 // Symbols whose names start with "type." are compiler
2299 // generated, so make functions with that prefix internal.
2301 symname := elfsym.Name // (unmangled) symbol name
2302 if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type.") {
2303 ver = abiInternalVer
2304 } else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC {
2305 // Demangle the ABI name. Keep in sync with symtab.go:mangleABIName.
2306 if strings.HasSuffix(elfsym.Name, ".abiinternal") {
2307 ver = sym.SymVerABIInternal
2308 symname = strings.TrimSuffix(elfsym.Name, ".abiinternal")
2309 } else if strings.HasSuffix(elfsym.Name, ".abi0") {
2311 symname = strings.TrimSuffix(elfsym.Name, ".abi0")
2316 s := l.LookupOrCreateSym(symname, ver)
2318 // Because loadlib above loads all .a files before loading
2319 // any shared libraries, any non-dynimport symbols we find
2320 // that duplicate symbols already loaded should be ignored
2321 // (the symbols from the .a files "win").
2322 if l.SymType(s) != 0 && l.SymType(s) != sym.SDYNIMPORT {
2325 su := l.MakeSymbolUpdater(s)
2326 su.SetType(sym.SDYNIMPORT)
2327 l.SetSymElfType(s, elf.ST_TYPE(elfsym.Info))
2328 su.SetSize(int64(elfsym.Size))
2329 if elfsym.Section != elf.SHN_UNDEF {
2330 // Set .File for the library that actually defines the symbol.
2331 l.SetSymPkg(s, libpath)
2333 // The decodetype_* functions in decodetype.go need access to
2335 sname := l.SymName(s)
2336 if strings.HasPrefix(sname, "type.") && !strings.HasPrefix(sname, "type..") {
2337 su.SetData(readelfsymboldata(ctxt, f, &elfsym))
2341 if symname != elfsym.Name {
2342 l.SetSymExtname(s, elfsym.Name)
2345 ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f})
2348 func addsection(ldr *loader.Loader, arch *sys.Arch, seg *sym.Segment, name string, rwx int) *sym.Section {
2349 sect := ldr.NewSection()
2350 sect.Rwx = uint8(rwx)
2353 sect.Align = int32(arch.PtrSize) // everything is at least pointer-aligned
2354 seg.Sections = append(seg.Sections, sect)
2359 fmt.Fprintf(os.Stderr, "usage: link [options] main.o\n")
2360 objabi.Flagprint(os.Stderr)
2364 type SymbolType int8 // TODO: after genasmsym is gone, maybe rename to plan9typeChar or something
2367 // see also https://9p.io/magic/man2html/1/nm
2368 TextSym SymbolType = 'T'
2369 DataSym SymbolType = 'D'
2370 BSSSym SymbolType = 'B'
2371 UndefinedSym SymbolType = 'U'
2372 TLSSym SymbolType = 't'
2373 FrameSym SymbolType = 'm'
2374 ParamSym SymbolType = 'p'
2375 AutoSym SymbolType = 'a'
2377 // Deleted auto (not a real sym, just placeholder for type)
2378 DeletedAutoSym = 'x'
2381 // defineInternal defines a symbol used internally by the go runtime.
2382 func (ctxt *Link) defineInternal(p string, t sym.SymKind) loader.Sym {
2383 s := ctxt.loader.CreateSymForUpdate(p, 0)
2390 func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) loader.Sym {
2391 s := ctxt.defineInternal(p, t)
2392 ctxt.loader.SetSymValue(s, v)
2396 func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
2397 if uint64(addr) >= Segdata.Vaddr {
2398 return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
2400 if uint64(addr) >= Segtext.Vaddr {
2401 return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
2403 ldr.Errorf(s, "invalid datoff %#x", addr)
2407 func Entryvalue(ctxt *Link) int64 {
2408 a := *flagEntrySymbol
2409 if a[0] >= '0' && a[0] <= '9' {
2413 s := ldr.Lookup(a, 0)
2414 st := ldr.SymType(s)
2416 return *FlagTextAddr
2418 if !ctxt.IsAIX() && st != sym.STEXT {
2419 ldr.Errorf(s, "entry not text")
2421 return ldr.SymValue(s)
2424 func (ctxt *Link) callgraph() {
2430 for _, s := range ctxt.Textp {
2431 relocs := ldr.Relocs(s)
2432 for i := 0; i < relocs.Count(); i++ {
2438 if r.Type().IsDirectCall() && ldr.SymType(rs) == sym.STEXT {
2439 ctxt.Logf("%s calls %s\n", ldr.SymName(s), ldr.SymName(rs))
2445 func Rnd(v int64, r int64) int64 {
2458 func bgetc(r *bio.Reader) int {
2459 c, err := r.ReadByte()
2462 log.Fatalf("reading input: %v", err)
2469 type markKind uint8 // for postorder traversal
2476 func postorder(libs []*sym.Library) []*sym.Library {
2477 order := make([]*sym.Library, 0, len(libs)) // hold the result
2478 mark := make(map[*sym.Library]markKind, len(libs))
2479 for _, lib := range libs {
2480 dfs(lib, mark, &order)
2485 func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library) {
2486 if mark[lib] == visited {
2489 if mark[lib] == visiting {
2490 panic("found import cycle while visiting " + lib.Pkg)
2492 mark[lib] = visiting
2493 for _, i := range lib.Imports {
2497 *order = append(*order, lib)
2500 func ElfSymForReloc(ctxt *Link, s loader.Sym) int32 {
2501 // If putelfsym created a local version of this symbol, use that in all
2503 les := ctxt.loader.SymLocalElfSym(s)
2507 return ctxt.loader.SymElfSym(s)
2511 func AddGotSym(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, elfRelocTyp uint32) {
2512 if ldr.SymGot(s) >= 0 {
2516 Adddynsym(ldr, target, syms, s)
2517 got := ldr.MakeSymbolUpdater(syms.GOT)
2518 ldr.SetGot(s, int32(got.Size()))
2519 got.AddUint(target.Arch, 0)
2522 if target.Arch.PtrSize == 8 {
2523 rela := ldr.MakeSymbolUpdater(syms.Rela)
2524 rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2525 rela.AddUint64(target.Arch, elf.R_INFO(uint32(ldr.SymDynid(s)), elfRelocTyp))
2526 rela.AddUint64(target.Arch, 0)
2528 rel := ldr.MakeSymbolUpdater(syms.Rel)
2529 rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2530 rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), elfRelocTyp))
2532 } else if target.IsDarwin() {
2533 leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT)
2534 leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
2535 if target.IsPIE() && target.IsInternal() {
2536 // Mach-O relocations are a royal pain to lay out.
2537 // They use a compact stateful bytecode representation.
2538 // Here we record what are needed and encode them later.
2539 MachoAddBind(int64(ldr.SymGot(s)), s)
2542 ldr.Errorf(s, "addgotsym: unsupported binary format")