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
39 "cmd/link/internal/loadelf"
40 "cmd/link/internal/loader"
41 "cmd/link/internal/loadmacho"
42 "cmd/link/internal/loadpe"
43 "cmd/link/internal/loadxcoff"
44 "cmd/link/internal/sym"
52 exec "internal/execabs"
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 // unknownObjFormat is set to true if we see an object whose
348 // format we don't recognize.
349 unknownObjFormat = false
354 func Lflag(ctxt *Link, arg string) {
355 ctxt.Libdir = append(ctxt.Libdir, arg)
359 * Unix doesn't like it when we write to a running (or, sometimes,
360 * recently run) binary, so remove the output file before writing it.
361 * On Windows 7, remove() can force a subsequent create() to fail.
362 * S_ISREG() does not exist on Plan 9.
364 func mayberemoveoutfile() {
365 if fi, err := os.Lstat(*flagOutfile); err == nil && !fi.Mode().IsRegular() {
368 os.Remove(*flagOutfile)
371 func libinit(ctxt *Link) {
372 Funcalign = thearch.Funcalign
374 // add goroot to the end of the libdir list.
378 if *flagInstallSuffix != "" {
380 suffix = *flagInstallSuffix
381 } else if *flagRace {
384 } else if *flagMsan {
387 } else if *flagAsan {
392 if buildcfg.GOROOT != "" {
393 Lflag(ctxt, filepath.Join(buildcfg.GOROOT, "pkg", fmt.Sprintf("%s_%s%s%s", buildcfg.GOOS, buildcfg.GOARCH, suffixsep, suffix)))
398 if err := ctxt.Out.Open(*flagOutfile); err != nil {
399 Exitf("cannot create %s: %v", *flagOutfile, err)
402 if *flagEntrySymbol == "" {
403 switch ctxt.BuildMode {
404 case BuildModeCShared, BuildModeCArchive:
405 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s_lib", buildcfg.GOARCH, buildcfg.GOOS)
406 case BuildModeExe, BuildModePIE:
407 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s", buildcfg.GOARCH, buildcfg.GOOS)
408 case BuildModeShared, BuildModePlugin:
409 // No *flagEntrySymbol for -buildmode=shared and plugin
411 Errorf(nil, "unknown *flagEntrySymbol for buildmode %v", ctxt.BuildMode)
416 func exitIfErrors() {
417 if nerrors != 0 || checkStrictDups > 1 && strictDupMsgCount > 0 {
429 func loadinternal(ctxt *Link, name string) *sym.Library {
430 zerofp := goobj.FingerprintType{}
431 if ctxt.linkShared && ctxt.PackageShlib != nil {
432 if shlib := ctxt.PackageShlib[name]; shlib != "" {
433 return addlibpath(ctxt, "internal", "internal", "", name, shlib, zerofp)
436 if ctxt.PackageFile != nil {
437 if pname := ctxt.PackageFile[name]; pname != "" {
438 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
440 ctxt.Logf("loadinternal: cannot find %s\n", name)
444 for _, libdir := range ctxt.Libdir {
446 shlibname := filepath.Join(libdir, name+".shlibname")
447 if ctxt.Debugvlog != 0 {
448 ctxt.Logf("searching for %s.a in %s\n", name, shlibname)
450 if _, err := os.Stat(shlibname); err == nil {
451 return addlibpath(ctxt, "internal", "internal", "", name, shlibname, zerofp)
454 pname := filepath.Join(libdir, name+".a")
455 if ctxt.Debugvlog != 0 {
456 ctxt.Logf("searching for %s.a in %s\n", name, pname)
458 if _, err := os.Stat(pname); err == nil {
459 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
463 ctxt.Logf("warning: unable to find %s.a\n", name)
467 // extld returns the current external linker.
468 func (ctxt *Link) extld() []string {
469 if len(flagExtld) == 0 {
470 flagExtld = []string{"gcc"}
475 // findLibPathCmd uses cmd command to find gcc library libname.
476 // It returns library full path if found, or "none" if not found.
477 func (ctxt *Link) findLibPathCmd(cmd, libname string) string {
478 extld := ctxt.extld()
479 name, args := extld[0], extld[1:]
480 args = append(args, hostlinkArchArgs(ctxt.Arch)...)
481 args = append(args, cmd)
482 if ctxt.Debugvlog != 0 {
483 ctxt.Logf("%s %v\n", extld, args)
485 out, err := exec.Command(name, args...).Output()
487 if ctxt.Debugvlog != 0 {
488 ctxt.Logf("not using a %s file because compiler failed\n%v\n%s\n", libname, err, out)
492 return strings.TrimSpace(string(out))
495 // findLibPath searches for library libname.
496 // It returns library full path if found, or "none" if not found.
497 func (ctxt *Link) findLibPath(libname string) string {
498 return ctxt.findLibPathCmd("--print-file-name="+libname, libname)
501 func (ctxt *Link) loadlib() {
503 switch *FlagStrictDups {
507 flags |= loader.FlagStrictDups
509 log.Fatalf("invalid -strictdups flag value %d", *FlagStrictDups)
511 elfsetstring1 := func(str string, off int) { elfsetstring(ctxt, 0, str, off) }
512 ctxt.loader = loader.NewLoader(flags, elfsetstring1, &ctxt.ErrorReporter.ErrorReporter)
513 ctxt.ErrorReporter.SymName = func(s loader.Sym) string {
514 return ctxt.loader.SymName(s)
517 // ctxt.Library grows during the loop, so not a range loop.
519 for ; i < len(ctxt.Library); i++ {
520 lib := ctxt.Library[i]
522 if ctxt.Debugvlog > 1 {
523 ctxt.Logf("autolib: %s (from %s)\n", lib.File, lib.Objref)
525 loadobjfile(ctxt, lib)
529 // load internal packages, if not already
531 loadinternal(ctxt, "runtime/race")
534 loadinternal(ctxt, "runtime/msan")
537 loadinternal(ctxt, "runtime/asan")
539 loadinternal(ctxt, "runtime")
540 for ; i < len(ctxt.Library); i++ {
541 lib := ctxt.Library[i]
543 loadobjfile(ctxt, lib)
546 // At this point, the Go objects are "preloaded". Not all the symbols are
547 // added to the symbol table (only defined package symbols are). Looking
548 // up symbol by name may not get expected result.
550 iscgo = ctxt.LibraryByPkg["runtime/cgo"] != nil
552 // Plugins a require cgo support to function. Similarly, plugins may require additional
553 // internal linker support on some platforms which may not be implemented.
554 ctxt.canUsePlugins = ctxt.LibraryByPkg["plugin"] != nil && iscgo
556 // We now have enough information to determine the link mode.
557 determineLinkMode(ctxt)
559 if ctxt.LinkMode == LinkExternal && !iscgo && !(buildcfg.GOOS == "darwin" && ctxt.BuildMode != BuildModePlugin && ctxt.Arch.Family == sys.AMD64) {
560 // This indicates a user requested -linkmode=external.
561 // The startup code uses an import of runtime/cgo to decide
562 // whether to initialize the TLS. So give it one. This could
563 // be handled differently but it's an unusual case.
564 if lib := loadinternal(ctxt, "runtime/cgo"); lib != nil && lib.Shlib == "" {
565 if ctxt.BuildMode == BuildModeShared || ctxt.linkShared {
566 Exitf("cannot implicitly include runtime/cgo in a shared library")
568 for ; i < len(ctxt.Library); i++ {
569 lib := ctxt.Library[i]
571 loadobjfile(ctxt, lib)
577 // Add non-package symbols and references of externally defined symbols.
578 ctxt.loader.LoadSyms(ctxt.Arch)
580 // Load symbols from shared libraries, after all Go object symbols are loaded.
581 for _, lib := range ctxt.Library {
583 if ctxt.Debugvlog > 1 {
584 ctxt.Logf("autolib: %s (from %s)\n", lib.Shlib, lib.Objref)
586 ldshlibsyms(ctxt, lib.Shlib)
590 // Process cgo directives (has to be done before host object loading).
591 ctxt.loadcgodirectives()
593 // Conditionally load host objects, or setup for external linking.
597 if ctxt.LinkMode == LinkInternal && len(hostobj) != 0 {
598 // If we have any undefined symbols in external
599 // objects, try to read them from the libgcc file.
601 undefs := ctxt.loader.UndefinedRelocTargets(1)
606 if *flagLibGCC == "" {
607 *flagLibGCC = ctxt.findLibPathCmd("--print-libgcc-file-name", "libgcc")
609 if runtime.GOOS == "openbsd" && *flagLibGCC == "libgcc.a" {
610 // On OpenBSD `clang --print-libgcc-file-name` returns "libgcc.a".
611 // In this case we fail to load libgcc.a and can encounter link
612 // errors - see if we can find libcompiler_rt.a instead.
613 *flagLibGCC = ctxt.findLibPathCmd("--print-file-name=libcompiler_rt.a", "libcompiler_rt")
615 if ctxt.HeadType == objabi.Hwindows {
616 loadWindowsHostArchives(ctxt)
618 if *flagLibGCC != "none" {
619 hostArchive(ctxt, *flagLibGCC)
624 // We've loaded all the code now.
629 strictDupMsgCount = ctxt.loader.NStrictDupMsgs()
632 // loadWindowsHostArchives loads in host archives and objects when
633 // doing internal linking on windows. Older toolchains seem to require
634 // just a single pass through the various archives, but some modern
635 // toolchains when linking a C program with mingw pass library paths
636 // multiple times to the linker, e.g. "... -lmingwex -lmingw32 ...
637 // -lmingwex -lmingw32 ...". To accommodate this behavior, we make two
638 // passes over the host archives below.
639 func loadWindowsHostArchives(ctxt *Link) {
641 for i := 0; any && i < 2; i++ {
642 // Link crt2.o (if present) to resolve "atexit" when
643 // using LLVM-based compilers.
644 isunresolved := symbolsAreUnresolved(ctxt, []string{"atexit"})
646 if p := ctxt.findLibPath("crt2.o"); p != "none" {
647 hostObject(ctxt, "crt2", p)
650 if p := ctxt.findLibPath("libmingwex.a"); p != "none" {
653 if p := ctxt.findLibPath("libmingw32.a"); p != "none" {
656 // Link libmsvcrt.a to resolve '__acrt_iob_func' symbol
657 // (see https://golang.org/issue/23649 for details).
658 if p := ctxt.findLibPath("libmsvcrt.a"); p != "none" {
662 undefs := ctxt.loader.UndefinedRelocTargets(1)
667 // If needed, create the __CTOR_LIST__ and __DTOR_LIST__
668 // symbols (referenced by some of the mingw support library
669 // routines). Creation of these symbols is normally done by the
670 // linker if not already present.
671 want := []string{"__CTOR_LIST__", "__DTOR_LIST__"}
672 isunresolved := symbolsAreUnresolved(ctxt, want)
673 for k, w := range want {
675 sb := ctxt.loader.CreateSymForUpdate(w, 0)
676 sb.SetType(sym.SDATA)
677 sb.AddUint64(ctxt.Arch, 0)
678 sb.SetReachable(true)
679 ctxt.loader.SetAttrSpecial(sb.Sym(), true)
682 // TODO: maybe do something similar to peimporteddlls to collect
683 // all lib names and try link them all to final exe just like
684 // libmingwex.a and libmingw32.a:
687 #cgo windows LDFLAGS: -lmsvcrt -lm
693 // loadcgodirectives reads the previously discovered cgo directives, creating
694 // symbols in preparation for host object loading or use later in the link.
695 func (ctxt *Link) loadcgodirectives() {
697 hostObjSyms := make(map[loader.Sym]struct{})
698 for _, d := range ctxt.cgodata {
699 setCgoAttr(ctxt, d.file, d.pkg, d.directives, hostObjSyms)
703 if ctxt.LinkMode == LinkInternal {
704 // Drop all the cgo_import_static declarations.
705 // Turns out we won't be needing them.
706 for symIdx := range hostObjSyms {
707 if l.SymType(symIdx) == sym.SHOSTOBJ {
708 // If a symbol was marked both
709 // cgo_import_static and cgo_import_dynamic,
710 // then we want to make it cgo_import_dynamic
712 su := l.MakeSymbolUpdater(symIdx)
713 if l.SymExtname(symIdx) != "" && l.SymDynimplib(symIdx) != "" && !(l.AttrCgoExportStatic(symIdx) || l.AttrCgoExportDynamic(symIdx)) {
714 su.SetType(sym.SDYNIMPORT)
723 // Set up flags and special symbols depending on the platform build mode.
724 // This version works with loader.Loader.
725 func (ctxt *Link) linksetup() {
726 switch ctxt.BuildMode {
727 case BuildModeCShared, BuildModePlugin:
728 symIdx := ctxt.loader.LookupOrCreateSym("runtime.islibrary", 0)
729 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
730 sb.SetType(sym.SNOPTRDATA)
732 case BuildModeCArchive:
733 symIdx := ctxt.loader.LookupOrCreateSym("runtime.isarchive", 0)
734 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
735 sb.SetType(sym.SNOPTRDATA)
739 // Recalculate pe parameters now that we have ctxt.LinkMode set.
740 if ctxt.HeadType == objabi.Hwindows {
744 if ctxt.LinkMode == LinkExternal {
745 // When external linking, we are creating an object file. The
746 // absolute address is irrelevant.
750 // If there are no dynamic libraries needed, gcc disables dynamic linking.
751 // Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13)
752 // assumes that a dynamic binary always refers to at least one dynamic library.
753 // Rather than be a source of test cases for glibc, disable dynamic linking
754 // the same way that gcc would.
756 // Exception: on OS X, programs such as Shark only work with dynamic
757 // binaries, so leave it enabled on OS X (Mach-O) binaries.
758 // Also leave it enabled on Solaris which doesn't support
759 // statically linked binaries.
760 if ctxt.BuildMode == BuildModeExe {
761 if havedynamic == 0 && ctxt.HeadType != objabi.Hdarwin && ctxt.HeadType != objabi.Hsolaris {
766 if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && buildcfg.GOOS != "aix" {
767 toc := ctxt.loader.LookupOrCreateSym(".TOC.", 0)
768 sb := ctxt.loader.MakeSymbolUpdater(toc)
769 sb.SetType(sym.SDYNIMPORT)
772 // The Android Q linker started to complain about underalignment of the our TLS
773 // section. We don't actually use the section on android, so don't
775 if buildcfg.GOOS != "android" {
776 tlsg := ctxt.loader.LookupOrCreateSym("runtime.tlsg", 0)
777 sb := ctxt.loader.MakeSymbolUpdater(tlsg)
779 // runtime.tlsg is used for external linking on platforms that do not define
780 // a variable to hold g in assembly (currently only intel).
782 sb.SetType(sym.STLSBSS)
783 sb.SetSize(int64(ctxt.Arch.PtrSize))
784 } else if sb.Type() != sym.SDYNIMPORT {
785 Errorf(nil, "runtime declared tlsg variable %v", sb.Type())
787 ctxt.loader.SetAttrReachable(tlsg, true)
791 var moduledata loader.Sym
792 var mdsb *loader.SymbolBuilder
793 if ctxt.BuildMode == BuildModePlugin {
794 moduledata = ctxt.loader.LookupOrCreateSym("local.pluginmoduledata", 0)
795 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
796 ctxt.loader.SetAttrLocal(moduledata, true)
798 moduledata = ctxt.loader.LookupOrCreateSym("runtime.firstmoduledata", 0)
799 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
801 if mdsb.Type() != 0 && mdsb.Type() != sym.SDYNIMPORT {
802 // If the module (toolchain-speak for "executable or shared
803 // library") we are linking contains the runtime package, it
804 // will define the runtime.firstmoduledata symbol and we
805 // truncate it back to 0 bytes so we can define its entire
806 // contents in symtab.go:symtab().
809 // In addition, on ARM, the runtime depends on the linker
810 // recording the value of GOARM.
811 if ctxt.Arch.Family == sys.ARM {
812 goarm := ctxt.loader.LookupOrCreateSym("runtime.goarm", 0)
813 sb := ctxt.loader.MakeSymbolUpdater(goarm)
814 sb.SetType(sym.SDATA)
816 sb.AddUint8(uint8(buildcfg.GOARM))
819 // Set runtime.disableMemoryProfiling bool if
820 // runtime.MemProfile is not retained in the binary after
821 // deadcode (and we're not dynamically linking).
822 memProfile := ctxt.loader.Lookup("runtime.MemProfile", abiInternalVer)
823 if memProfile != 0 && !ctxt.loader.AttrReachable(memProfile) && !ctxt.DynlinkingGo() {
824 memProfSym := ctxt.loader.LookupOrCreateSym("runtime.disableMemoryProfiling", 0)
825 sb := ctxt.loader.MakeSymbolUpdater(memProfSym)
826 sb.SetType(sym.SDATA)
828 sb.AddUint8(1) // true bool
831 // If OTOH the module does not contain the runtime package,
832 // create a local symbol for the moduledata.
833 moduledata = ctxt.loader.LookupOrCreateSym("local.moduledata", 0)
834 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
835 ctxt.loader.SetAttrLocal(moduledata, true)
837 // In all cases way we mark the moduledata as noptrdata to hide it from
839 mdsb.SetType(sym.SNOPTRDATA)
840 ctxt.loader.SetAttrReachable(moduledata, true)
841 ctxt.Moduledata = moduledata
843 if ctxt.Arch == sys.Arch386 && ctxt.HeadType != objabi.Hwindows {
844 if (ctxt.BuildMode == BuildModeCArchive && ctxt.IsELF) || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE || ctxt.DynlinkingGo() {
845 got := ctxt.loader.LookupOrCreateSym("_GLOBAL_OFFSET_TABLE_", 0)
846 sb := ctxt.loader.MakeSymbolUpdater(got)
847 sb.SetType(sym.SDYNIMPORT)
848 ctxt.loader.SetAttrReachable(got, true)
852 // DWARF-gen and other phases require that the unit Textp slices
853 // be populated, so that it can walk the functions in each unit.
854 // Call into the loader to do this (requires that we collect the
855 // set of internal libraries first). NB: might be simpler if we
856 // moved isRuntimeDepPkg to cmd/internal and then did the test in
857 // loader.AssignTextSymbolOrder.
858 ctxt.Library = postorder(ctxt.Library)
860 for _, lib := range ctxt.Library {
861 intlibs = append(intlibs, isRuntimeDepPkg(lib.Pkg))
863 ctxt.Textp = ctxt.loader.AssignTextSymbolOrder(ctxt.Library, intlibs, ctxt.Textp)
866 // mangleTypeSym shortens the names of symbols that represent Go types
867 // if they are visible in the symbol table.
869 // As the names of these symbols are derived from the string of
870 // the type, they can run to many kilobytes long. So we shorten
871 // them using a SHA-1 when the name appears in the final binary.
872 // This also removes characters that upset external linkers.
874 // These are the symbols that begin with the prefix 'type.' and
875 // contain run-time type information used by the runtime and reflect
876 // packages. All Go binaries contain these symbols, but only
877 // those programs loaded dynamically in multiple parts need these
878 // symbols to have entries in the symbol table.
879 func (ctxt *Link) mangleTypeSym() {
880 if ctxt.BuildMode != BuildModeShared && !ctxt.linkShared && ctxt.BuildMode != BuildModePlugin && !ctxt.CanUsePlugins() {
885 for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
886 if !ldr.AttrReachable(s) && !ctxt.linkShared {
887 // If -linkshared, the GCProg generation code may need to reach
888 // out to the shared library for the type descriptor's data, even
889 // the type descriptor itself is not actually needed at run time
890 // (therefore not reachable). We still need to mangle its name,
891 // so it is consistent with the one stored in the shared library.
894 name := ldr.SymName(s)
895 newName := typeSymbolMangle(name)
897 ldr.SetSymExtname(s, newName)
899 // When linking against a shared library, the Go object file may
900 // have reference to the original symbol name whereas the shared
901 // library provides a symbol with the mangled name. We need to
902 // copy the payload of mangled to original.
903 // XXX maybe there is a better way to do this.
904 dup := ldr.Lookup(newName, ldr.SymVersion(s))
907 dt := ldr.SymType(dup)
908 if st == sym.Sxxx && dt != sym.Sxxx {
916 // typeSymbolMangle mangles the given symbol name into something shorter.
918 // Keep the type.. prefix, which parts of the linker (like the
919 // DWARF generator) know means the symbol is not decodable.
920 // Leave type.runtime. symbols alone, because other parts of
921 // the linker manipulates them.
922 func typeSymbolMangle(name string) string {
923 if !strings.HasPrefix(name, "type.") {
926 if strings.HasPrefix(name, "type.runtime.") {
929 if len(name) <= 14 && !strings.Contains(name, "@") { // Issue 19529
932 hash := sha1.Sum([]byte(name))
937 return prefix + base64.StdEncoding.EncodeToString(hash[:6])
941 * look for the next file in an archive.
942 * adapted from libmach.
944 func nextar(bp *bio.Reader, off int64, a *ArHdr) int64 {
949 var buf [SAR_HDR]byte
950 if n, err := io.ReadFull(bp, buf[:]); err != nil {
951 if n == 0 && err != io.EOF {
957 a.name = artrim(buf[0:16])
958 a.date = artrim(buf[16:28])
959 a.uid = artrim(buf[28:34])
960 a.gid = artrim(buf[34:40])
961 a.mode = artrim(buf[40:48])
962 a.size = artrim(buf[48:58])
963 a.fmag = artrim(buf[58:60])
965 arsize := atolwhex(a.size)
969 return arsize + SAR_HDR
972 func loadobjfile(ctxt *Link, lib *sym.Library) {
973 pkg := objabi.PathToPrefix(lib.Pkg)
975 if ctxt.Debugvlog > 1 {
976 ctxt.Logf("ldobj: %s (%s)\n", lib.File, pkg)
978 f, err := bio.Open(lib.File)
980 Exitf("cannot open file %s: %v", lib.File, err)
984 if pkg == "main" && !lib.Main {
985 Exitf("%s: not package main", lib.File)
989 for i := 0; i < len(ARMAG); i++ {
990 if c, err := f.ReadByte(); err == nil && c == ARMAG[i] {
994 /* load it as a regular file */
995 l := f.MustSeek(0, 2)
997 ldobj(ctxt, f, lib, l, lib.File, lib.File)
1002 * load all the object files from the archive now.
1003 * this gives us sequential file access and keeps us
1004 * from needing to come back later to pick up more
1005 * objects. it breaks the usual C archive model, but
1006 * this is Go, not C. the common case in Go is that
1007 * we need to load all the objects, and then we throw away
1008 * the individual symbols that are unused.
1010 * loading every object will also make it possible to
1011 * load foreign objects not referenced by __.PKGDEF.
1016 l := nextar(f, off, &arhdr)
1021 Exitf("%s: malformed archive", lib.File)
1025 // __.PKGDEF isn't a real Go object file, and it's
1026 // absent in -linkobj builds anyway. Skipping it
1027 // ensures consistency between -linkobj and normal
1029 if arhdr.name == pkgdef {
1033 // Skip other special (non-object-file) sections that
1034 // build tools may have added. Such sections must have
1035 // short names so that the suffix is not truncated.
1036 if len(arhdr.name) < 16 {
1037 if ext := filepath.Ext(arhdr.name); ext != ".o" && ext != ".syso" {
1042 pname := fmt.Sprintf("%s(%s)", lib.File, arhdr.name)
1043 l = atolwhex(arhdr.size)
1044 ldobj(ctxt, f, lib, l, pname, lib.File)
1048 type Hostobj struct {
1049 ld func(*Link, *bio.Reader, string, int64, string)
1057 var hostobj []Hostobj
1059 // These packages can use internal linking mode.
1060 // Others trigger external mode.
1061 var internalpkg = []string{
1062 "crypto/internal/boring",
1072 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 {
1074 for _, intpkg := range internalpkg {
1081 // DragonFly declares errno with __thread, which results in a symbol
1082 // type of R_386_TLS_GD or R_X86_64_TLSGD. The Go linker does not
1083 // currently know how to handle TLS relocations, hence we have to
1084 // force external linking for any libraries that link in code that
1085 // uses errno. This can be removed if the Go linker ever supports
1086 // these relocation types.
1087 if headType == objabi.Hdragonfly {
1088 if pkg == "net" || pkg == "os/user" {
1097 hostobj = append(hostobj, Hostobj{})
1098 h := &hostobj[len(hostobj)-1]
1108 func hostobjs(ctxt *Link) {
1109 if ctxt.LinkMode != LinkInternal {
1114 for i := 0; i < len(hostobj); i++ {
1116 f, err := bio.Open(h.file)
1118 Exitf("cannot reopen %s: %v", h.pn, err)
1121 f.MustSeek(h.off, 0)
1123 Errorf(nil, "%s: unrecognized object file format", h.pn)
1126 h.ld(ctxt, f, h.pkg, h.length, h.pn)
1131 func hostlinksetup(ctxt *Link) {
1132 if ctxt.LinkMode != LinkExternal {
1136 // For external link, record that we need to tell the external linker -s,
1137 // and turn off -s internally: the external linker needs the symbol
1138 // information for its final link.
1142 // create temporary directory and arrange cleanup
1143 if *flagTmpdir == "" {
1144 dir, err := ioutil.TempDir("", "go-link-")
1151 os.RemoveAll(*flagTmpdir)
1155 // change our output to temporary object file
1156 if err := ctxt.Out.Close(); err != nil {
1157 Exitf("error closing output file")
1159 mayberemoveoutfile()
1161 p := filepath.Join(*flagTmpdir, "go.o")
1162 if err := ctxt.Out.Open(p); err != nil {
1163 Exitf("cannot create %s: %v", p, err)
1167 // hostobjCopy creates a copy of the object files in hostobj in a
1168 // temporary directory.
1169 func hostobjCopy() (paths []string) {
1170 var wg sync.WaitGroup
1171 sema := make(chan struct{}, runtime.NumCPU()) // limit open file descriptors
1172 for i, h := range hostobj {
1174 dst := filepath.Join(*flagTmpdir, fmt.Sprintf("%06d.o", i))
1175 paths = append(paths, dst)
1184 f, err := os.Open(h.file)
1186 Exitf("cannot reopen %s: %v", h.pn, err)
1189 if _, err := f.Seek(h.off, 0); err != nil {
1190 Exitf("cannot seek %s: %v", h.pn, err)
1193 w, err := os.Create(dst)
1195 Exitf("cannot create %s: %v", dst, err)
1197 if _, err := io.CopyN(w, f, h.length); err != nil {
1198 Exitf("cannot write %s: %v", dst, err)
1200 if err := w.Close(); err != nil {
1201 Exitf("cannot close %s: %v", dst, err)
1209 // writeGDBLinkerScript creates gcc linker script file in temp
1210 // directory. writeGDBLinkerScript returns created file path.
1211 // The script is used to work around gcc bug
1212 // (see https://golang.org/issue/20183 for details).
1213 func writeGDBLinkerScript() string {
1214 name := "fix_debug_gdb_scripts.ld"
1215 path := filepath.Join(*flagTmpdir, name)
1218 .debug_gdb_scripts BLOCK(__section_alignment__) (NOLOAD) :
1220 *(.debug_gdb_scripts)
1223 INSERT AFTER .debug_types;
1225 err := ioutil.WriteFile(path, []byte(src), 0666)
1227 Errorf(nil, "WriteFile %s failed: %v", name, err)
1232 // archive builds a .a archive from the hostobj object files.
1233 func (ctxt *Link) archive() {
1234 if ctxt.BuildMode != BuildModeCArchive {
1240 if *flagExtar == "" {
1244 mayberemoveoutfile()
1246 // Force the buffer to flush here so that external
1247 // tools will see a complete file.
1248 if err := ctxt.Out.Close(); err != nil {
1249 Exitf("error closing %v", *flagOutfile)
1252 argv := []string{*flagExtar, "-q", "-c", "-s"}
1253 if ctxt.HeadType == objabi.Haix {
1254 argv = append(argv, "-X64")
1256 argv = append(argv, *flagOutfile)
1257 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1258 argv = append(argv, hostobjCopy()...)
1260 if ctxt.Debugvlog != 0 {
1261 ctxt.Logf("archive: %s\n", strings.Join(argv, " "))
1264 // If supported, use syscall.Exec() to invoke the archive command,
1265 // which should be the final remaining step needed for the link.
1266 // This will reduce peak RSS for the link (and speed up linking of
1267 // large applications), since when the archive command runs we
1268 // won't be holding onto all of the linker's live memory.
1269 if syscallExecSupported && !ownTmpDir {
1271 ctxt.execArchive(argv)
1272 panic("should not get here")
1275 // Otherwise invoke 'ar' in the usual way (fork + exec).
1276 if out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput(); err != nil {
1277 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1281 func (ctxt *Link) hostlink() {
1282 if ctxt.LinkMode != LinkExternal || nerrors > 0 {
1285 if ctxt.BuildMode == BuildModeCArchive {
1290 argv = append(argv, ctxt.extld()...)
1291 argv = append(argv, hostlinkArchArgs(ctxt.Arch)...)
1293 if *FlagS || debug_s {
1294 if ctxt.HeadType == objabi.Hdarwin {
1295 // Recent versions of macOS print
1296 // ld: warning: option -s is obsolete and being ignored
1297 // so do not pass any arguments.
1299 argv = append(argv, "-s")
1303 // On darwin, whether to combine DWARF into executable.
1304 // Only macOS supports unmapped segments such as our __DWARF segment.
1305 combineDwarf := ctxt.IsDarwin() && !*FlagS && !*FlagW && !debug_s && machoPlatform == PLATFORM_MACOS
1307 switch ctxt.HeadType {
1308 case objabi.Hdarwin:
1310 // Leave room for DWARF combining.
1311 // -headerpad is incompatible with -fembed-bitcode.
1312 argv = append(argv, "-Wl,-headerpad,1144")
1314 if ctxt.DynlinkingGo() && buildcfg.GOOS != "ios" {
1315 // -flat_namespace is deprecated on iOS.
1316 // It is useful for supporting plugins. We don't support plugins on iOS.
1317 // -flat_namespace may cause the dynamic linker to hang at forkExec when
1318 // resolving a lazy binding. See issue 38824.
1319 // Force eager resolution to work around.
1320 argv = append(argv, "-Wl,-flat_namespace", "-Wl,-bind_at_load")
1323 argv = append(argv, "-Wl,-S") // suppress STAB (symbolic debugging) symbols
1325 case objabi.Hopenbsd:
1326 argv = append(argv, "-Wl,-nopie")
1327 argv = append(argv, "-pthread")
1328 case objabi.Hwindows:
1330 argv = append(argv, "-mwindows")
1332 argv = append(argv, "-mconsole")
1334 // Mark as having awareness of terminal services, to avoid
1335 // ancient compatibility hacks.
1336 argv = append(argv, "-Wl,--tsaware")
1339 argv = append(argv, "-Wl,--nxcompat")
1341 argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", PeMinimumTargetMajorVersion))
1342 argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", PeMinimumTargetMinorVersion))
1343 argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", PeMinimumTargetMajorVersion))
1344 argv = append(argv, fmt.Sprintf("-Wl,--minor-subsystem-version=%d", PeMinimumTargetMinorVersion))
1346 argv = append(argv, "-pthread")
1347 // prevent ld to reorder .text functions to keep the same
1348 // first/last functions for moduledata.
1349 argv = append(argv, "-Wl,-bnoobjreorder")
1350 // mcmodel=large is needed for every gcc generated files, but
1351 // ld still need -bbigtoc in order to allow larger TOC.
1352 argv = append(argv, "-mcmodel=large")
1353 argv = append(argv, "-Wl,-bbigtoc")
1356 // Enable/disable ASLR on Windows.
1357 addASLRargs := func(argv []string, val bool) []string {
1358 // Old/ancient versions of GCC support "--dynamicbase" and
1359 // "--high-entropy-va" but don't enable it by default. In
1360 // addition, they don't accept "--disable-dynamicbase" or
1361 // "--no-dynamicbase", so the only way to disable ASLR is to
1362 // not pass any flags at all.
1364 // More modern versions of GCC (and also clang) enable ASLR
1365 // by default. With these compilers, however you can turn it
1366 // off if you want using "--disable-dynamicbase" or
1367 // "--no-dynamicbase".
1369 // The strategy below is to try using "--disable-dynamicbase";
1370 // if this succeeds, then assume we're working with more
1371 // modern compilers and act accordingly. If it fails, assume
1372 // an ancient compiler with ancient defaults.
1375 dbon := "--dynamicbase"
1376 heon := "--high-entropy-va"
1377 dboff := "--disable-dynamicbase"
1378 heoff := "--disable-high-entropy-va"
1383 // Test to see whether "--disable-dynamicbase" works.
1384 newer := linkerFlagSupported(ctxt.Arch, argv[0], "", "-Wl,"+dboff)
1386 // Newer compiler, which supports both on/off options.
1390 // older toolchain: we have to say nothing in order to
1391 // get a no-ASLR binary.
1397 argv = append(argv, "-Wl,"+dbopt)
1399 // enable high-entropy ASLR on 64-bit.
1400 if ctxt.Arch.PtrSize >= 8 && heopt != "" {
1401 argv = append(argv, "-Wl,"+heopt)
1406 switch ctxt.BuildMode {
1408 if ctxt.HeadType == objabi.Hdarwin {
1409 if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() {
1410 argv = append(argv, "-Wl,-no_pie")
1411 argv = append(argv, "-Wl,-pagezero_size,4000000")
1415 switch ctxt.HeadType {
1416 case objabi.Hdarwin, objabi.Haix:
1417 case objabi.Hwindows:
1418 argv = addASLRargs(argv, *flagAslr)
1421 if ctxt.UseRelro() {
1422 argv = append(argv, "-Wl,-z,relro")
1424 argv = append(argv, "-pie")
1426 case BuildModeCShared:
1427 if ctxt.HeadType == objabi.Hdarwin {
1428 argv = append(argv, "-dynamiclib")
1430 if ctxt.UseRelro() {
1431 argv = append(argv, "-Wl,-z,relro")
1433 argv = append(argv, "-shared")
1434 if ctxt.HeadType == objabi.Hwindows {
1435 argv = addASLRargs(argv, *flagAslr)
1437 // Pass -z nodelete to mark the shared library as
1438 // non-closeable: a dlclose will do nothing.
1439 argv = append(argv, "-Wl,-z,nodelete")
1440 // Only pass Bsymbolic on non-Windows.
1441 argv = append(argv, "-Wl,-Bsymbolic")
1444 case BuildModeShared:
1445 if ctxt.UseRelro() {
1446 argv = append(argv, "-Wl,-z,relro")
1448 argv = append(argv, "-shared")
1449 case BuildModePlugin:
1450 if ctxt.HeadType == objabi.Hdarwin {
1451 argv = append(argv, "-dynamiclib")
1453 if ctxt.UseRelro() {
1454 argv = append(argv, "-Wl,-z,relro")
1456 argv = append(argv, "-shared")
1460 var altLinker string
1461 if ctxt.IsELF && ctxt.DynlinkingGo() {
1462 // We force all symbol resolution to be done at program startup
1463 // because lazy PLT resolution can use large amounts of stack at
1464 // times we cannot allow it to do so.
1465 argv = append(argv, "-Wl,-znow")
1467 // Do not let the host linker generate COPY relocations. These
1468 // can move symbols out of sections that rely on stable offsets
1469 // from the beginning of the section (like sym.STYPE).
1470 argv = append(argv, "-Wl,-znocopyreloc")
1472 if buildcfg.GOOS == "android" {
1473 // Use lld to avoid errors from default linker (issue #38838)
1477 if ctxt.Arch.InFamily(sys.ARM, sys.ARM64) && buildcfg.GOOS == "linux" {
1478 // On ARM, the GNU linker will generate COPY relocations
1479 // even with -znocopyreloc set.
1480 // https://sourceware.org/bugzilla/show_bug.cgi?id=19962
1482 // On ARM64, the GNU linker will fail instead of
1483 // generating COPY relocations.
1485 // In both cases, switch to gold.
1488 // If gold is not installed, gcc will silently switch
1489 // back to ld.bfd. So we parse the version information
1490 // and provide a useful error if gold is missing.
1491 name, args := flagExtld[0], flagExtld[1:]
1492 args = append(args, "-fuse-ld=gold", "-Wl,--version")
1493 cmd := exec.Command(name, args...)
1494 if out, err := cmd.CombinedOutput(); err == nil {
1495 if !bytes.Contains(out, []byte("GNU gold")) {
1496 log.Fatalf("ARM external linker must be gold (issue #15696), but is not: %s", out)
1501 if ctxt.Arch.Family == sys.ARM64 && buildcfg.GOOS == "freebsd" {
1502 // Switch to ld.bfd on freebsd/arm64.
1505 // Provide a useful error if ld.bfd is missing.
1506 name, args := flagExtld[0], flagExtld[1:]
1507 args = append(args, "-fuse-ld=bfd", "-Wl,--version")
1508 cmd := exec.Command(name, args...)
1509 if out, err := cmd.CombinedOutput(); err == nil {
1510 if !bytes.Contains(out, []byte("GNU ld")) {
1511 log.Fatalf("ARM64 external linker must be ld.bfd (issue #35197), please install devel/binutils")
1515 if altLinker != "" {
1516 argv = append(argv, "-fuse-ld="+altLinker)
1519 if ctxt.IsELF && len(buildinfo) > 0 {
1520 argv = append(argv, fmt.Sprintf("-Wl,--build-id=0x%x", buildinfo))
1523 // On Windows, given -o foo, GCC will append ".exe" to produce
1524 // "foo.exe". We have decided that we want to honor the -o
1525 // option. To make this work, we append a '.' so that GCC
1526 // will decide that the file already has an extension. We
1527 // only want to do this when producing a Windows output file
1528 // on a Windows host.
1529 outopt := *flagOutfile
1530 if buildcfg.GOOS == "windows" && runtime.GOOS == "windows" && filepath.Ext(outopt) == "" {
1533 argv = append(argv, "-o")
1534 argv = append(argv, outopt)
1536 if rpath.val != "" {
1537 argv = append(argv, fmt.Sprintf("-Wl,-rpath,%s", rpath.val))
1540 if *flagInterpreter != "" {
1541 // Many linkers support both -I and the --dynamic-linker flags
1542 // to set the ELF interpreter, but lld only supports
1543 // --dynamic-linker so prefer that (ld on very old Solaris only
1544 // supports -I but that seems less important).
1545 argv = append(argv, fmt.Sprintf("-Wl,--dynamic-linker,%s", *flagInterpreter))
1548 // Force global symbols to be exported for dlopen, etc.
1550 argv = append(argv, "-rdynamic")
1552 if ctxt.HeadType == objabi.Haix {
1553 fileName := xcoffCreateExportFile(ctxt)
1554 argv = append(argv, "-Wl,-bE:"+fileName)
1557 const unusedArguments = "-Qunused-arguments"
1558 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, unusedArguments) {
1559 argv = append(argv, unusedArguments)
1562 const compressDWARF = "-Wl,--compress-debug-sections=zlib"
1563 if ctxt.compressDWARF && linkerFlagSupported(ctxt.Arch, argv[0], altLinker, compressDWARF) {
1564 argv = append(argv, compressDWARF)
1567 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1568 argv = append(argv, hostobjCopy()...)
1569 if ctxt.HeadType == objabi.Haix {
1570 // We want to have C files after Go files to remove
1571 // trampolines csects made by ld.
1572 argv = append(argv, "-nostartfiles")
1573 argv = append(argv, "/lib/crt0_64.o")
1575 extld := ctxt.extld()
1576 name, args := extld[0], extld[1:]
1577 // Get starting files.
1578 getPathFile := func(file string) string {
1579 args := append(args, "-maix64", "--print-file-name="+file)
1580 out, err := exec.Command(name, args...).CombinedOutput()
1582 log.Fatalf("running %s failed: %v\n%s", extld, err, out)
1584 return strings.Trim(string(out), "\n")
1586 // Since GCC version 11, the 64-bit version of GCC starting files
1587 // are now suffixed by "_64". Even under "-maix64" multilib directory
1588 // "crtcxa.o" is 32-bit.
1589 crtcxa := getPathFile("crtcxa_64.o")
1590 if !filepath.IsAbs(crtcxa) {
1591 crtcxa = getPathFile("crtcxa.o")
1593 crtdbase := getPathFile("crtdbase_64.o")
1594 if !filepath.IsAbs(crtdbase) {
1595 crtdbase = getPathFile("crtdbase.o")
1597 argv = append(argv, crtcxa)
1598 argv = append(argv, crtdbase)
1601 if ctxt.linkShared {
1602 seenDirs := make(map[string]bool)
1603 seenLibs := make(map[string]bool)
1604 addshlib := func(path string) {
1605 dir, base := filepath.Split(path)
1607 argv = append(argv, "-L"+dir)
1609 argv = append(argv, "-Wl,-rpath="+dir)
1611 seenDirs[dir] = true
1613 base = strings.TrimSuffix(base, ".so")
1614 base = strings.TrimPrefix(base, "lib")
1615 if !seenLibs[base] {
1616 argv = append(argv, "-l"+base)
1617 seenLibs[base] = true
1620 for _, shlib := range ctxt.Shlibs {
1621 addshlib(shlib.Path)
1622 for _, dep := range shlib.Deps {
1626 libpath := findshlib(ctxt, dep)
1634 // clang, unlike GCC, passes -rdynamic to the linker
1635 // even when linking with -static, causing a linker
1636 // error when using GNU ld. So take out -rdynamic if
1637 // we added it. We do it in this order, rather than
1638 // only adding -rdynamic later, so that -extldflags
1639 // can override -rdynamic without using -static.
1640 // Similarly for -Wl,--dynamic-linker.
1641 checkStatic := func(arg string) {
1642 if ctxt.IsELF && arg == "-static" {
1643 for i := range argv {
1644 if argv[i] == "-rdynamic" || strings.HasPrefix(argv[i], "-Wl,--dynamic-linker,") {
1651 for _, p := range ldflag {
1652 argv = append(argv, p)
1656 // When building a program with the default -buildmode=exe the
1657 // gc compiler generates code requires DT_TEXTREL in a
1658 // position independent executable (PIE). On systems where the
1659 // toolchain creates PIEs by default, and where DT_TEXTREL
1660 // does not work, the resulting programs will not run. See
1661 // issue #17847. To avoid this problem pass -no-pie to the
1662 // toolchain if it is supported.
1663 if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared && !(ctxt.IsDarwin() && ctxt.IsARM64()) {
1664 // GCC uses -no-pie, clang uses -nopie.
1665 for _, nopie := range []string{"-no-pie", "-nopie"} {
1666 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, nopie) {
1667 argv = append(argv, nopie)
1673 for _, p := range flagExtldflags {
1674 argv = append(argv, p)
1677 if ctxt.HeadType == objabi.Hwindows {
1678 // Determine which linker we're using. Add in the extldflags in
1679 // case used has specified "-fuse-ld=...".
1680 extld := ctxt.extld()
1681 name, args := extld[0], extld[1:]
1682 args = append(args, flagExtldflags...)
1683 args = append(args, "-Wl,--version")
1684 cmd := exec.Command(name, args...)
1686 if out, err := cmd.CombinedOutput(); err == nil {
1687 if bytes.Contains(out, []byte("LLD ")) {
1692 // use gcc linker script to work around gcc bug
1693 // (see https://golang.org/issue/20183 for details).
1695 p := writeGDBLinkerScript()
1696 argv = append(argv, "-Wl,-T,"+p)
1698 // libmingw32 and libmingwex have some inter-dependencies,
1699 // so must use linker groups.
1700 argv = append(argv, "-Wl,--start-group", "-lmingwex", "-lmingw32", "-Wl,--end-group")
1701 argv = append(argv, peimporteddlls()...)
1704 if ctxt.Debugvlog != 0 {
1705 ctxt.Logf("host link:")
1706 for _, v := range argv {
1712 out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput()
1714 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1717 // Filter out useless linker warnings caused by bugs outside Go.
1718 // See also cmd/go/internal/work/exec.go's gccld method.
1721 for _, line := range bytes.SplitAfter(out, []byte("\n")) {
1722 // golang.org/issue/26073 - Apple Xcode bug
1723 if bytes.Contains(line, []byte("ld: warning: text-based stub file")) {
1732 // Remove TOC overflow warning on AIX.
1733 if bytes.Contains(line, []byte("ld: 0711-783")) {
1738 save = append(save, line)
1740 out = bytes.Join(save, nil)
1743 // always print external output even if the command is successful, so that we don't
1744 // swallow linker warnings (see https://golang.org/issue/17935).
1745 ctxt.Logf("%s", out)
1749 // Find "dsymutils" and "strip" tools using CC --print-prog-name.
1751 cc = append(cc, ctxt.extld()...)
1752 cc = append(cc, hostlinkArchArgs(ctxt.Arch)...)
1753 cc = append(cc, "--print-prog-name", "dsymutil")
1754 out, err := exec.Command(cc[0], cc[1:]...).CombinedOutput()
1756 Exitf("%s: finding dsymutil failed: %v\n%s", os.Args[0], err, out)
1758 dsymutilCmd := strings.TrimSuffix(string(out), "\n")
1760 cc[len(cc)-1] = "strip"
1761 out, err = exec.Command(cc[0], cc[1:]...).CombinedOutput()
1763 Exitf("%s: finding strip failed: %v\n%s", os.Args[0], err, out)
1765 stripCmd := strings.TrimSuffix(string(out), "\n")
1767 dsym := filepath.Join(*flagTmpdir, "go.dwarf")
1768 if out, err := exec.Command(dsymutilCmd, "-f", *flagOutfile, "-o", dsym).CombinedOutput(); err != nil {
1769 Exitf("%s: running dsymutil failed: %v\n%s", os.Args[0], err, out)
1771 // Remove STAB (symbolic debugging) symbols after we are done with them (by dsymutil).
1772 // They contain temporary file paths and make the build not reproducible.
1773 if out, err := exec.Command(stripCmd, "-S", *flagOutfile).CombinedOutput(); err != nil {
1774 Exitf("%s: running strip failed: %v\n%s", os.Args[0], err, out)
1776 // Skip combining if `dsymutil` didn't generate a file. See #11994.
1777 if _, err := os.Stat(dsym); os.IsNotExist(err) {
1780 // For os.Rename to work reliably, must be in same directory as outfile.
1781 combinedOutput := *flagOutfile + "~"
1782 exef, err := os.Open(*flagOutfile)
1784 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1787 exem, err := macho.NewFile(exef)
1789 Exitf("%s: parsing Mach-O header failed: %v", os.Args[0], err)
1791 if err := machoCombineDwarf(ctxt, exef, exem, dsym, combinedOutput); err != nil {
1792 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1794 os.Remove(*flagOutfile)
1795 if err := os.Rename(combinedOutput, *flagOutfile); err != nil {
1796 Exitf("%s: %v", os.Args[0], err)
1799 if ctxt.NeedCodeSign() {
1800 err := machoCodeSign(ctxt, *flagOutfile)
1802 Exitf("%s: code signing failed: %v", os.Args[0], err)
1807 var createTrivialCOnce sync.Once
1809 func linkerFlagSupported(arch *sys.Arch, linker, altLinker, flag string) bool {
1810 createTrivialCOnce.Do(func() {
1811 src := filepath.Join(*flagTmpdir, "trivial.c")
1812 if err := ioutil.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
1813 Errorf(nil, "WriteFile trivial.c failed: %v", err)
1817 flagsWithNextArgSkip := []string{
1826 flagsWithNextArgKeep := []string{
1832 prefixesToKeep := []string{
1843 flags := hostlinkArchArgs(arch)
1846 for _, f := range append(flagExtldflags, ldflag...) {
1848 flags = append(flags, f)
1852 } else if f == "" || f[0] != '-' {
1853 } else if contains(flagsWithNextArgSkip, f) {
1855 } else if contains(flagsWithNextArgKeep, f) {
1856 flags = append(flags, f)
1859 for _, p := range prefixesToKeep {
1860 if strings.HasPrefix(f, p) {
1861 flags = append(flags, f)
1868 if altLinker != "" {
1869 flags = append(flags, "-fuse-ld="+altLinker)
1871 flags = append(flags, flag, "trivial.c")
1873 cmd := exec.Command(linker, flags...)
1874 cmd.Dir = *flagTmpdir
1875 cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
1876 out, err := cmd.CombinedOutput()
1877 // GCC says "unrecognized command line option ‘-no-pie’"
1878 // clang says "unknown argument: '-no-pie'"
1879 return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
1882 // hostlinkArchArgs returns arguments to pass to the external linker
1883 // based on the architecture.
1884 func hostlinkArchArgs(arch *sys.Arch) []string {
1885 switch arch.Family {
1887 return []string{"-m32"}
1889 if buildcfg.GOOS == "darwin" {
1890 return []string{"-arch", "x86_64", "-m64"}
1892 return []string{"-m64"}
1894 return []string{"-m64"}
1896 return []string{"-marm"}
1898 if buildcfg.GOOS == "darwin" {
1899 return []string{"-arch", "arm64"}
1902 return []string{"-mabi=64"}
1904 return []string{"-mabi=32"}
1906 if buildcfg.GOOS == "aix" {
1907 return []string{"-maix64"}
1909 return []string{"-m64"}
1916 var wantHdr = objabi.HeaderString()
1918 // ldobj loads an input object. If it is a host object (an object
1919 // compiled by a non-Go compiler) it returns the Hostobj pointer. If
1920 // it is a Go object, it returns nil.
1921 func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string, file string) *Hostobj {
1922 pkg := objabi.PathToPrefix(lib.Pkg)
1924 eof := f.Offset() + length
1930 f.MustSeek(start, 0)
1932 unit := &sym.CompilationUnit{Lib: lib}
1933 lib.Units = append(lib.Units, unit)
1935 magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
1936 if magic == 0x7f454c46 { // \x7F E L F
1937 ldelf := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1938 textp, flags, err := loadelf.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn, ehdr.Flags)
1940 Errorf(nil, "%v", err)
1944 ctxt.Textp = append(ctxt.Textp, textp...)
1946 return ldhostobj(ldelf, ctxt.HeadType, f, pkg, length, pn, file)
1949 if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
1950 ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1951 textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1953 Errorf(nil, "%v", err)
1956 ctxt.Textp = append(ctxt.Textp, textp...)
1958 return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
1966 ldpe := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1967 textp, rsrc, err := loadpe.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1969 Errorf(nil, "%v", err)
1973 setpersrc(ctxt, rsrc)
1975 ctxt.Textp = append(ctxt.Textp, textp...)
1977 return ldhostobj(ldpe, ctxt.HeadType, f, pkg, length, pn, file)
1980 if c1 == 0x01 && (c2 == 0xD7 || c2 == 0xF7) {
1981 ldxcoff := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1982 textp, err := loadxcoff.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1984 Errorf(nil, "%v", err)
1987 ctxt.Textp = append(ctxt.Textp, textp...)
1989 return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
1992 if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
1993 // An unrecognized object is just passed to the external linker.
1994 // If we try to read symbols from this object, we will
1995 // report an error at that time.
1996 unknownObjFormat = true
1997 return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
2000 /* check the header */
2001 line, err := f.ReadString('\n')
2003 Errorf(nil, "truncated object file: %s: %v", pn, err)
2007 if !strings.HasPrefix(line, "go object ") {
2008 if strings.HasSuffix(pn, ".go") {
2009 Exitf("%s: uncompiled .go source file", pn)
2013 if line == ctxt.Arch.Name {
2014 // old header format: just $GOOS
2015 Errorf(nil, "%s: stale object file", pn)
2019 Errorf(nil, "%s: not an object file: @%d %q", pn, start, line)
2023 // First, check that the basic GOOS, GOARCH, and Version match.
2024 if line != wantHdr {
2025 Errorf(nil, "%s: linked object header mismatch:\nhave %q\nwant %q\n", pn, line, wantHdr)
2028 // Skip over exports and other info -- ends with \n!\n.
2030 // Note: It's possible for "\n!\n" to appear within the binary
2031 // package export data format. To avoid truncating the package
2032 // definition prematurely (issue 21703), we keep track of
2033 // how many "$$" delimiters we've seen.
2035 import0 := f.Offset()
2037 c1 = '\n' // the last line ended in \n
2043 if markers%2 == 0 && c2 == '!' && c3 == '\n' {
2046 if c2 == '$' && c3 == '$' {
2055 Errorf(nil, "truncated object file: %s", pn)
2060 import1 := f.Offset()
2062 f.MustSeek(import0, 0)
2063 ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
2064 f.MustSeek(import1, 0)
2066 fingerprint := ctxt.loader.Preload(ctxt.IncVersion(), f, lib, unit, eof-f.Offset())
2067 if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
2068 // Check fingerprint, to ensure the importing and imported packages
2069 // have consistent view of symbol indices.
2070 // Normally the go command should ensure this. But in case something
2071 // goes wrong, it could lead to obscure bugs like run-time crash.
2072 // Check it here to be sure.
2073 if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
2074 lib.Fingerprint = fingerprint
2076 checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
2079 addImports(ctxt, lib, pn)
2083 // symbolsAreUnresolved scans through the loader's list of unresolved
2084 // symbols and checks to see whether any of them match the names of the
2085 // symbols in 'want'. Return value is a list of bools, with list[K] set
2086 // to true if there is an unresolved reference to the symbol in want[K].
2087 func symbolsAreUnresolved(ctxt *Link, want []string) []bool {
2088 returnAllUndefs := -1
2089 undefs := ctxt.loader.UndefinedRelocTargets(returnAllUndefs)
2090 seen := make(map[loader.Sym]struct{})
2091 rval := make([]bool, len(want))
2092 wantm := make(map[string]int)
2093 for k, w := range want {
2097 for _, s := range undefs {
2098 if _, ok := seen[s]; ok {
2101 seen[s] = struct{}{}
2102 if k, ok := wantm[ctxt.loader.SymName(s)]; ok {
2105 if count == len(want) {
2113 // hostObject reads a single host object file (compare to "hostArchive").
2114 // This is used as part of internal linking when we need to pull in
2115 // files such as "crt?.o".
2116 func hostObject(ctxt *Link, objname string, path string) {
2117 if ctxt.Debugvlog > 1 {
2118 ctxt.Logf("hostObject(%s)\n", path)
2120 objlib := sym.Library{
2123 f, err := bio.Open(path)
2125 Exitf("cannot open host object %q file %s: %v", objname, path, err)
2128 h := ldobj(ctxt, f, &objlib, 0, path, path)
2130 Exitf("unrecognized object file format in %s", path)
2132 f.MustSeek(h.off, 0)
2133 h.ld(ctxt, f, h.pkg, h.length, h.pn)
2136 func checkFingerprint(lib *sym.Library, libfp goobj.FingerprintType, src string, srcfp goobj.FingerprintType) {
2138 Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
2142 func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
2143 data := make([]byte, sym.Size)
2144 sect := f.Sections[sym.Section]
2145 if sect.Type != elf.SHT_PROGBITS && sect.Type != elf.SHT_NOTE {
2146 Errorf(nil, "reading %s from non-data section", sym.Name)
2148 n, err := sect.ReadAt(data, int64(sym.Value-sect.Addr))
2149 if uint64(n) != sym.Size {
2150 Errorf(nil, "reading contents of %s: %v", sym.Name, err)
2155 func readwithpad(r io.Reader, sz int32) ([]byte, error) {
2156 data := make([]byte, Rnd(int64(sz), 4))
2157 _, err := io.ReadFull(r, data)
2165 func readnote(f *elf.File, name []byte, typ int32) ([]byte, error) {
2166 for _, sect := range f.Sections {
2167 if sect.Type != elf.SHT_NOTE {
2172 var namesize, descsize, noteType int32
2173 err := binary.Read(r, f.ByteOrder, &namesize)
2178 return nil, fmt.Errorf("read namesize failed: %v", err)
2180 err = binary.Read(r, f.ByteOrder, &descsize)
2182 return nil, fmt.Errorf("read descsize failed: %v", err)
2184 err = binary.Read(r, f.ByteOrder, ¬eType)
2186 return nil, fmt.Errorf("read type failed: %v", err)
2188 noteName, err := readwithpad(r, namesize)
2190 return nil, fmt.Errorf("read name failed: %v", err)
2192 desc, err := readwithpad(r, descsize)
2194 return nil, fmt.Errorf("read desc failed: %v", err)
2196 if string(name) == string(noteName) && typ == noteType {
2204 func findshlib(ctxt *Link, shlib string) string {
2205 if filepath.IsAbs(shlib) {
2208 for _, libdir := range ctxt.Libdir {
2209 libpath := filepath.Join(libdir, shlib)
2210 if _, err := os.Stat(libpath); err == nil {
2214 Errorf(nil, "cannot find shared library: %s", shlib)
2218 func ldshlibsyms(ctxt *Link, shlib string) {
2220 if filepath.IsAbs(shlib) {
2222 shlib = filepath.Base(shlib)
2224 libpath = findshlib(ctxt, shlib)
2229 for _, processedlib := range ctxt.Shlibs {
2230 if processedlib.Path == libpath {
2234 if ctxt.Debugvlog > 1 {
2235 ctxt.Logf("ldshlibsyms: found library with name %s at %s\n", shlib, libpath)
2238 f, err := elf.Open(libpath)
2240 Errorf(nil, "cannot open shared library: %s", libpath)
2243 // Keep the file open as decodetypeGcprog needs to read from it.
2244 // TODO: fix. Maybe mmap the file.
2247 hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
2249 Errorf(nil, "cannot read ABI hash from shared library %s: %v", libpath, err)
2253 depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
2255 Errorf(nil, "cannot read dep list from shared library %s: %v", libpath, err)
2259 for _, dep := range strings.Split(string(depsbytes), "\n") {
2263 if !filepath.IsAbs(dep) {
2264 // If the dep can be interpreted as a path relative to the shlib
2265 // in which it was found, do that. Otherwise, we will leave it
2266 // to be resolved by libdir lookup.
2267 abs := filepath.Join(filepath.Dir(libpath), dep)
2268 if _, err := os.Stat(abs); err == nil {
2272 deps = append(deps, dep)
2275 syms, err := f.DynamicSymbols()
2277 Errorf(nil, "cannot read symbols from shared library: %s", libpath)
2281 for _, elfsym := range syms {
2282 if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
2286 // Symbols whose names start with "type." are compiler
2287 // generated, so make functions with that prefix internal.
2289 symname := elfsym.Name // (unmangled) symbol name
2290 if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type.") {
2291 ver = abiInternalVer
2292 } else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC {
2293 // Demangle the ABI name. Keep in sync with symtab.go:mangleABIName.
2294 if strings.HasSuffix(elfsym.Name, ".abiinternal") {
2295 ver = sym.SymVerABIInternal
2296 symname = strings.TrimSuffix(elfsym.Name, ".abiinternal")
2297 } else if strings.HasSuffix(elfsym.Name, ".abi0") {
2299 symname = strings.TrimSuffix(elfsym.Name, ".abi0")
2304 s := l.LookupOrCreateSym(symname, ver)
2306 // Because loadlib above loads all .a files before loading
2307 // any shared libraries, any non-dynimport symbols we find
2308 // that duplicate symbols already loaded should be ignored
2309 // (the symbols from the .a files "win").
2310 if l.SymType(s) != 0 && l.SymType(s) != sym.SDYNIMPORT {
2313 su := l.MakeSymbolUpdater(s)
2314 su.SetType(sym.SDYNIMPORT)
2315 l.SetSymElfType(s, elf.ST_TYPE(elfsym.Info))
2316 su.SetSize(int64(elfsym.Size))
2317 if elfsym.Section != elf.SHN_UNDEF {
2318 // Set .File for the library that actually defines the symbol.
2319 l.SetSymPkg(s, libpath)
2321 // The decodetype_* functions in decodetype.go need access to
2323 sname := l.SymName(s)
2324 if strings.HasPrefix(sname, "type.") && !strings.HasPrefix(sname, "type..") {
2325 su.SetData(readelfsymboldata(ctxt, f, &elfsym))
2329 if symname != elfsym.Name {
2330 l.SetSymExtname(s, elfsym.Name)
2333 ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f})
2336 func addsection(ldr *loader.Loader, arch *sys.Arch, seg *sym.Segment, name string, rwx int) *sym.Section {
2337 sect := ldr.NewSection()
2338 sect.Rwx = uint8(rwx)
2341 sect.Align = int32(arch.PtrSize) // everything is at least pointer-aligned
2342 seg.Sections = append(seg.Sections, sect)
2347 fmt.Fprintf(os.Stderr, "usage: link [options] main.o\n")
2348 objabi.Flagprint(os.Stderr)
2352 type SymbolType int8 // TODO: after genasmsym is gone, maybe rename to plan9typeChar or something
2355 // see also https://9p.io/magic/man2html/1/nm
2356 TextSym SymbolType = 'T'
2357 DataSym SymbolType = 'D'
2358 BSSSym SymbolType = 'B'
2359 UndefinedSym SymbolType = 'U'
2360 TLSSym SymbolType = 't'
2361 FrameSym SymbolType = 'm'
2362 ParamSym SymbolType = 'p'
2363 AutoSym SymbolType = 'a'
2365 // Deleted auto (not a real sym, just placeholder for type)
2366 DeletedAutoSym = 'x'
2369 // defineInternal defines a symbol used internally by the go runtime.
2370 func (ctxt *Link) defineInternal(p string, t sym.SymKind) loader.Sym {
2371 s := ctxt.loader.CreateSymForUpdate(p, 0)
2378 func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) loader.Sym {
2379 s := ctxt.defineInternal(p, t)
2380 ctxt.loader.SetSymValue(s, v)
2384 func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
2385 if uint64(addr) >= Segdata.Vaddr {
2386 return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
2388 if uint64(addr) >= Segtext.Vaddr {
2389 return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
2391 ldr.Errorf(s, "invalid datoff %#x", addr)
2395 func Entryvalue(ctxt *Link) int64 {
2396 a := *flagEntrySymbol
2397 if a[0] >= '0' && a[0] <= '9' {
2401 s := ldr.Lookup(a, 0)
2402 st := ldr.SymType(s)
2404 return *FlagTextAddr
2406 if !ctxt.IsAIX() && st != sym.STEXT {
2407 ldr.Errorf(s, "entry not text")
2409 return ldr.SymValue(s)
2412 func (ctxt *Link) callgraph() {
2418 for _, s := range ctxt.Textp {
2419 relocs := ldr.Relocs(s)
2420 for i := 0; i < relocs.Count(); i++ {
2426 if r.Type().IsDirectCall() && ldr.SymType(rs) == sym.STEXT {
2427 ctxt.Logf("%s calls %s\n", ldr.SymName(s), ldr.SymName(rs))
2433 func Rnd(v int64, r int64) int64 {
2446 func bgetc(r *bio.Reader) int {
2447 c, err := r.ReadByte()
2450 log.Fatalf("reading input: %v", err)
2457 type markKind uint8 // for postorder traversal
2464 func postorder(libs []*sym.Library) []*sym.Library {
2465 order := make([]*sym.Library, 0, len(libs)) // hold the result
2466 mark := make(map[*sym.Library]markKind, len(libs))
2467 for _, lib := range libs {
2468 dfs(lib, mark, &order)
2473 func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library) {
2474 if mark[lib] == visited {
2477 if mark[lib] == visiting {
2478 panic("found import cycle while visiting " + lib.Pkg)
2480 mark[lib] = visiting
2481 for _, i := range lib.Imports {
2485 *order = append(*order, lib)
2488 func ElfSymForReloc(ctxt *Link, s loader.Sym) int32 {
2489 // If putelfsym created a local version of this symbol, use that in all
2491 les := ctxt.loader.SymLocalElfSym(s)
2495 return ctxt.loader.SymElfSym(s)
2499 func AddGotSym(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, elfRelocTyp uint32) {
2500 if ldr.SymGot(s) >= 0 {
2504 Adddynsym(ldr, target, syms, s)
2505 got := ldr.MakeSymbolUpdater(syms.GOT)
2506 ldr.SetGot(s, int32(got.Size()))
2507 got.AddUint(target.Arch, 0)
2510 if target.Arch.PtrSize == 8 {
2511 rela := ldr.MakeSymbolUpdater(syms.Rela)
2512 rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2513 rela.AddUint64(target.Arch, elf.R_INFO(uint32(ldr.SymDynid(s)), elfRelocTyp))
2514 rela.AddUint64(target.Arch, 0)
2516 rel := ldr.MakeSymbolUpdater(syms.Rel)
2517 rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2518 rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), elfRelocTyp))
2520 } else if target.IsDarwin() {
2521 leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT)
2522 leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
2523 if target.IsPIE() && target.IsInternal() {
2524 // Mach-O relocations are a royal pain to lay out.
2525 // They use a compact stateful bytecode representation.
2526 // Here we record what are needed and encode them later.
2527 MachoAddBind(int64(ldr.SymGot(s)), s)
2530 ldr.Errorf(s, "addgotsym: unsupported binary format")