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
52 "cmd/internal/notsha256"
55 "cmd/link/internal/loadelf"
56 "cmd/link/internal/loader"
57 "cmd/link/internal/loadmacho"
58 "cmd/link/internal/loadpe"
59 "cmd/link/internal/loadxcoff"
60 "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.
186 LinuxdynldMusl string
190 Dragonflydynld string
193 // Empty spaces between codeblocks will be padded with this value.
194 // For example an architecture might want to pad with a trap instruction to
195 // catch wayward programs. Architectures that do not define a padding value
196 // are padded with zeros.
203 Adddynrel func(*Target, *loader.Loader, *ArchSyms, loader.Sym, loader.Reloc, int) bool
205 // Archreloc is an arch-specific hook that assists in relocation processing
206 // (invoked by 'relocsym'); it handles target-specific relocation tasks.
207 // Here "rel" is the current relocation being examined, "sym" is the symbol
208 // containing the chunk of data to which the relocation applies, and "off"
209 // is the contents of the to-be-relocated data item (from sym.P). Return
210 // value is the appropriately relocated value (to be written back to the
211 // same spot in sym.P), number of external _host_ relocations needed (i.e.
212 // ELF/Mach-O/etc. relocations, not Go relocations, this must match Elfreloc1,
213 // etc.), and a boolean indicating success/failure (a failing value indicates
215 Archreloc func(*Target, *loader.Loader, *ArchSyms, loader.Reloc, loader.Sym,
216 int64) (relocatedOffset int64, nExtReloc int, ok bool)
217 // Archrelocvariant is a second arch-specific hook used for
218 // relocation processing; it handles relocations where r.Type is
219 // insufficient to describe the relocation (r.Variant !=
220 // sym.RV_NONE). Here "rel" is the relocation being applied, "sym"
221 // is the symbol containing the chunk of data to which the
222 // relocation applies, and "off" is the contents of the
223 // to-be-relocated data item (from sym.P). Return is an updated
225 Archrelocvariant func(target *Target, ldr *loader.Loader, rel loader.Reloc,
226 rv sym.RelocVariant, sym loader.Sym, offset int64, data []byte) (relocatedOffset int64)
228 // Generate a trampoline for a call from s to rs if necessary. ri is
229 // index of the relocation.
230 Trampoline func(ctxt *Link, ldr *loader.Loader, ri int, rs, s loader.Sym)
232 // Assembling the binary breaks into two phases, writing the code/data/
233 // dwarf information (which is rather generic), and some more architecture
234 // specific work like setting up the elf headers/dynamic relocations, etc.
235 // The phases are called "Asmb" and "Asmb2". Asmb2 needs to be defined for
236 // every architecture, but only if architecture has an Asmb function will
237 // it be used for assembly. Otherwise a generic assembly Asmb function is
239 Asmb func(*Link, *loader.Loader)
240 Asmb2 func(*Link, *loader.Loader)
242 // Extreloc is an arch-specific hook that converts a Go relocation to an
243 // external relocation. Return the external relocation and whether it is
245 Extreloc func(*Target, *loader.Loader, loader.Reloc, loader.Sym) (loader.ExtReloc, bool)
247 Elfreloc1 func(*Link, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int, int64) bool
248 ElfrelocSize uint32 // size of an ELF relocation record, must match Elfreloc1.
249 Elfsetupplt func(ctxt *Link, plt, gotplt *loader.SymbolBuilder, dynamic loader.Sym)
250 Gentext func(*Link, *loader.Loader) // Generate text before addressing has been performed.
251 Machoreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
252 MachorelocSize uint32 // size of an Mach-O relocation record, must match Machoreloc1.
253 PEreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
254 Xcoffreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
256 // Generate additional symbols for the native symbol table just prior to
258 GenSymsLate func(*Link, *loader.Loader)
260 // TLSIEtoLE converts a TLS Initial Executable relocation to
261 // a TLS Local Executable relocation.
263 // This is possible when a TLS IE relocation refers to a local
264 // symbol in an executable, which is typical when internally
265 // linking PIE binaries.
266 TLSIEtoLE func(P []byte, off, size int)
268 // optional override for assignAddress
269 AssignAddress func(ldr *loader.Loader, sect *sym.Section, n int, s loader.Sym, va uint64, isTramp bool) (*sym.Section, int, uint64)
281 MINFUNC = 16 // minimum size for a function
284 // Symbol version of ABIInternal symbols. It is sym.SymVerABIInternal if ABI wrappers
285 // are used, 0 otherwise.
286 var abiInternalVer = sym.SymVerABIInternal
288 // DynlinkingGo reports whether we are producing Go code that can live
289 // in separate shared libraries linked together at runtime.
290 func (ctxt *Link) DynlinkingGo() bool {
292 panic("DynlinkingGo called before all symbols loaded")
294 return ctxt.BuildMode == BuildModeShared || ctxt.linkShared || ctxt.BuildMode == BuildModePlugin || ctxt.canUsePlugins
297 // CanUsePlugins reports whether a plugins can be used
298 func (ctxt *Link) CanUsePlugins() bool {
300 panic("CanUsePlugins called before all symbols loaded")
302 return ctxt.canUsePlugins
305 // NeedCodeSign reports whether we need to code-sign the output binary.
306 func (ctxt *Link) NeedCodeSign() bool {
307 return ctxt.IsDarwin() && ctxt.IsARM64()
319 debug_s bool // backup old value of debug['s']
323 liveness int64 // size of liveness data (funcdata), printed if -v
325 // See -strictdups command line flag.
326 checkStrictDups int // 0=off 1=warning 2=error
327 strictDupMsgCount int
332 Segrodata sym.Segment
333 Segrelrodata sym.Segment
337 Segments = []*sym.Segment{&Segtext, &Segrodata, &Segrelrodata, &Segdata, &Segdwarf}
340 const pkgdef = "__.PKGDEF"
343 // externalobj is set to true if we see an object compiled by
344 // the host compiler that is not from a package that is known
345 // to support internal linking mode.
348 // dynimportfail is a list of packages for which generating
349 // the dynimport file, _cgo_import.go, failed. If there are
350 // any of these objects, we must link externally. Issue 52863.
351 dynimportfail []string
353 // unknownObjFormat is set to true if we see an object whose
354 // format we don't recognize.
355 unknownObjFormat = false
360 func Lflag(ctxt *Link, arg string) {
361 ctxt.Libdir = append(ctxt.Libdir, arg)
365 * Unix doesn't like it when we write to a running (or, sometimes,
366 * recently run) binary, so remove the output file before writing it.
367 * On Windows 7, remove() can force a subsequent create() to fail.
368 * S_ISREG() does not exist on Plan 9.
370 func mayberemoveoutfile() {
371 if fi, err := os.Lstat(*flagOutfile); err == nil && !fi.Mode().IsRegular() {
374 os.Remove(*flagOutfile)
377 func libinit(ctxt *Link) {
378 Funcalign = thearch.Funcalign
380 // add goroot to the end of the libdir list.
384 if *flagInstallSuffix != "" {
386 suffix = *flagInstallSuffix
387 } else if *flagRace {
390 } else if *flagMsan {
393 } else if *flagAsan {
398 if buildcfg.GOROOT != "" {
399 Lflag(ctxt, filepath.Join(buildcfg.GOROOT, "pkg", fmt.Sprintf("%s_%s%s%s", buildcfg.GOOS, buildcfg.GOARCH, suffixsep, suffix)))
404 if err := ctxt.Out.Open(*flagOutfile); err != nil {
405 Exitf("cannot create %s: %v", *flagOutfile, err)
408 if *flagEntrySymbol == "" {
409 switch ctxt.BuildMode {
410 case BuildModeCShared, BuildModeCArchive:
411 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s_lib", buildcfg.GOARCH, buildcfg.GOOS)
412 case BuildModeExe, BuildModePIE:
413 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s", buildcfg.GOARCH, buildcfg.GOOS)
414 case BuildModeShared, BuildModePlugin:
415 // No *flagEntrySymbol for -buildmode=shared and plugin
417 Errorf(nil, "unknown *flagEntrySymbol for buildmode %v", ctxt.BuildMode)
422 func exitIfErrors() {
423 if nerrors != 0 || checkStrictDups > 1 && strictDupMsgCount > 0 {
435 func loadinternal(ctxt *Link, name string) *sym.Library {
436 zerofp := goobj.FingerprintType{}
437 if ctxt.linkShared && ctxt.PackageShlib != nil {
438 if shlib := ctxt.PackageShlib[name]; shlib != "" {
439 return addlibpath(ctxt, "internal", "internal", "", name, shlib, zerofp)
442 if ctxt.PackageFile != nil {
443 if pname := ctxt.PackageFile[name]; pname != "" {
444 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
446 ctxt.Logf("loadinternal: cannot find %s\n", name)
450 for _, libdir := range ctxt.Libdir {
452 shlibname := filepath.Join(libdir, name+".shlibname")
453 if ctxt.Debugvlog != 0 {
454 ctxt.Logf("searching for %s.a in %s\n", name, shlibname)
456 if _, err := os.Stat(shlibname); err == nil {
457 return addlibpath(ctxt, "internal", "internal", "", name, shlibname, zerofp)
460 pname := filepath.Join(libdir, name+".a")
461 if ctxt.Debugvlog != 0 {
462 ctxt.Logf("searching for %s.a in %s\n", name, pname)
464 if _, err := os.Stat(pname); err == nil {
465 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
469 ctxt.Logf("warning: unable to find %s.a\n", name)
473 // extld returns the current external linker.
474 func (ctxt *Link) extld() []string {
475 if len(flagExtld) == 0 {
476 flagExtld = []string{"gcc"}
481 // findLibPathCmd uses cmd command to find gcc library libname.
482 // It returns library full path if found, or "none" if not found.
483 func (ctxt *Link) findLibPathCmd(cmd, libname string) string {
484 extld := ctxt.extld()
485 name, args := extld[0], extld[1:]
486 args = append(args, hostlinkArchArgs(ctxt.Arch)...)
487 args = append(args, cmd)
488 if ctxt.Debugvlog != 0 {
489 ctxt.Logf("%s %v\n", extld, args)
491 out, err := exec.Command(name, args...).Output()
493 if ctxt.Debugvlog != 0 {
494 ctxt.Logf("not using a %s file because compiler failed\n%v\n%s\n", libname, err, out)
498 return strings.TrimSpace(string(out))
501 // findLibPath searches for library libname.
502 // It returns library full path if found, or "none" if not found.
503 func (ctxt *Link) findLibPath(libname string) string {
504 return ctxt.findLibPathCmd("--print-file-name="+libname, libname)
507 func (ctxt *Link) loadlib() {
509 switch *FlagStrictDups {
513 flags |= loader.FlagStrictDups
515 log.Fatalf("invalid -strictdups flag value %d", *FlagStrictDups)
517 elfsetstring1 := func(str string, off int) { elfsetstring(ctxt, 0, str, off) }
518 ctxt.loader = loader.NewLoader(flags, elfsetstring1, &ctxt.ErrorReporter.ErrorReporter)
519 ctxt.ErrorReporter.SymName = func(s loader.Sym) string {
520 return ctxt.loader.SymName(s)
523 // ctxt.Library grows during the loop, so not a range loop.
525 for ; i < len(ctxt.Library); i++ {
526 lib := ctxt.Library[i]
528 if ctxt.Debugvlog > 1 {
529 ctxt.Logf("autolib: %s (from %s)\n", lib.File, lib.Objref)
531 loadobjfile(ctxt, lib)
535 // load internal packages, if not already
537 loadinternal(ctxt, "runtime/race")
540 loadinternal(ctxt, "runtime/msan")
543 loadinternal(ctxt, "runtime/asan")
545 loadinternal(ctxt, "runtime")
546 for ; i < len(ctxt.Library); i++ {
547 lib := ctxt.Library[i]
549 loadobjfile(ctxt, lib)
552 // At this point, the Go objects are "preloaded". Not all the symbols are
553 // added to the symbol table (only defined package symbols are). Looking
554 // up symbol by name may not get expected result.
556 iscgo = ctxt.LibraryByPkg["runtime/cgo"] != nil
558 // Plugins a require cgo support to function. Similarly, plugins may require additional
559 // internal linker support on some platforms which may not be implemented.
560 ctxt.canUsePlugins = ctxt.LibraryByPkg["plugin"] != nil && iscgo
562 // We now have enough information to determine the link mode.
563 determineLinkMode(ctxt)
565 if ctxt.LinkMode == LinkExternal && !iscgo && !(buildcfg.GOOS == "darwin" && ctxt.BuildMode != BuildModePlugin && ctxt.Arch.Family == sys.AMD64) {
566 // This indicates a user requested -linkmode=external.
567 // The startup code uses an import of runtime/cgo to decide
568 // whether to initialize the TLS. So give it one. This could
569 // be handled differently but it's an unusual case.
570 if lib := loadinternal(ctxt, "runtime/cgo"); lib != nil && lib.Shlib == "" {
571 if ctxt.BuildMode == BuildModeShared || ctxt.linkShared {
572 Exitf("cannot implicitly include runtime/cgo in a shared library")
574 for ; i < len(ctxt.Library); i++ {
575 lib := ctxt.Library[i]
577 loadobjfile(ctxt, lib)
583 // Add non-package symbols and references of externally defined symbols.
584 ctxt.loader.LoadSyms(ctxt.Arch)
586 // Load symbols from shared libraries, after all Go object symbols are loaded.
587 for _, lib := range ctxt.Library {
589 if ctxt.Debugvlog > 1 {
590 ctxt.Logf("autolib: %s (from %s)\n", lib.Shlib, lib.Objref)
592 ldshlibsyms(ctxt, lib.Shlib)
596 // Process cgo directives (has to be done before host object loading).
597 ctxt.loadcgodirectives()
599 // Conditionally load host objects, or setup for external linking.
603 if ctxt.LinkMode == LinkInternal && len(hostobj) != 0 {
604 // If we have any undefined symbols in external
605 // objects, try to read them from the libgcc file.
607 undefs := ctxt.loader.UndefinedRelocTargets(1)
612 if *flagLibGCC == "" {
613 *flagLibGCC = ctxt.findLibPathCmd("--print-libgcc-file-name", "libgcc")
615 if runtime.GOOS == "openbsd" && *flagLibGCC == "libgcc.a" {
616 // On OpenBSD `clang --print-libgcc-file-name` returns "libgcc.a".
617 // In this case we fail to load libgcc.a and can encounter link
618 // errors - see if we can find libcompiler_rt.a instead.
619 *flagLibGCC = ctxt.findLibPathCmd("--print-file-name=libcompiler_rt.a", "libcompiler_rt")
621 if ctxt.HeadType == objabi.Hwindows {
622 loadWindowsHostArchives(ctxt)
624 if *flagLibGCC != "none" {
625 hostArchive(ctxt, *flagLibGCC)
630 // We've loaded all the code now.
635 strictDupMsgCount = ctxt.loader.NStrictDupMsgs()
638 // loadWindowsHostArchives loads in host archives and objects when
639 // doing internal linking on windows. Older toolchains seem to require
640 // just a single pass through the various archives, but some modern
641 // toolchains when linking a C program with mingw pass library paths
642 // multiple times to the linker, e.g. "... -lmingwex -lmingw32 ...
643 // -lmingwex -lmingw32 ...". To accommodate this behavior, we make two
644 // passes over the host archives below.
645 func loadWindowsHostArchives(ctxt *Link) {
647 for i := 0; any && i < 2; i++ {
648 // Link crt2.o (if present) to resolve "atexit" when
649 // using LLVM-based compilers.
650 isunresolved := symbolsAreUnresolved(ctxt, []string{"atexit"})
652 if p := ctxt.findLibPath("crt2.o"); p != "none" {
653 hostObject(ctxt, "crt2", p)
657 if p := ctxt.findLibPath("libsynchronization.a"); p != "none" {
661 if p := ctxt.findLibPath("libmingwex.a"); p != "none" {
664 if p := ctxt.findLibPath("libmingw32.a"); p != "none" {
667 // Link libmsvcrt.a to resolve '__acrt_iob_func' symbol
668 // (see https://golang.org/issue/23649 for details).
669 if p := ctxt.findLibPath("libmsvcrt.a"); p != "none" {
673 undefs := ctxt.loader.UndefinedRelocTargets(1)
678 // If needed, create the __CTOR_LIST__ and __DTOR_LIST__
679 // symbols (referenced by some of the mingw support library
680 // routines). Creation of these symbols is normally done by the
681 // linker if not already present.
682 want := []string{"__CTOR_LIST__", "__DTOR_LIST__"}
683 isunresolved := symbolsAreUnresolved(ctxt, want)
684 for k, w := range want {
686 sb := ctxt.loader.CreateSymForUpdate(w, 0)
687 sb.SetType(sym.SDATA)
688 sb.AddUint64(ctxt.Arch, 0)
689 sb.SetReachable(true)
690 ctxt.loader.SetAttrSpecial(sb.Sym(), true)
693 // TODO: maybe do something similar to peimporteddlls to collect
694 // all lib names and try link them all to final exe just like
695 // libmingwex.a and libmingw32.a:
698 #cgo windows LDFLAGS: -lmsvcrt -lm
704 // loadcgodirectives reads the previously discovered cgo directives, creating
705 // symbols in preparation for host object loading or use later in the link.
706 func (ctxt *Link) loadcgodirectives() {
708 hostObjSyms := make(map[loader.Sym]struct{})
709 for _, d := range ctxt.cgodata {
710 setCgoAttr(ctxt, d.file, d.pkg, d.directives, hostObjSyms)
714 if ctxt.LinkMode == LinkInternal {
715 // Drop all the cgo_import_static declarations.
716 // Turns out we won't be needing them.
717 for symIdx := range hostObjSyms {
718 if l.SymType(symIdx) == sym.SHOSTOBJ {
719 // If a symbol was marked both
720 // cgo_import_static and cgo_import_dynamic,
721 // then we want to make it cgo_import_dynamic
723 su := l.MakeSymbolUpdater(symIdx)
724 if l.SymExtname(symIdx) != "" && l.SymDynimplib(symIdx) != "" && !(l.AttrCgoExportStatic(symIdx) || l.AttrCgoExportDynamic(symIdx)) {
725 su.SetType(sym.SDYNIMPORT)
734 // Set up flags and special symbols depending on the platform build mode.
735 // This version works with loader.Loader.
736 func (ctxt *Link) linksetup() {
737 switch ctxt.BuildMode {
738 case BuildModeCShared, BuildModePlugin:
739 symIdx := ctxt.loader.LookupOrCreateSym("runtime.islibrary", 0)
740 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
741 sb.SetType(sym.SNOPTRDATA)
743 case BuildModeCArchive:
744 symIdx := ctxt.loader.LookupOrCreateSym("runtime.isarchive", 0)
745 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
746 sb.SetType(sym.SNOPTRDATA)
750 // Recalculate pe parameters now that we have ctxt.LinkMode set.
751 if ctxt.HeadType == objabi.Hwindows {
755 if ctxt.LinkMode == LinkExternal {
756 // When external linking, we are creating an object file. The
757 // absolute address is irrelevant.
761 // If there are no dynamic libraries needed, gcc disables dynamic linking.
762 // Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13)
763 // assumes that a dynamic binary always refers to at least one dynamic library.
764 // Rather than be a source of test cases for glibc, disable dynamic linking
765 // the same way that gcc would.
767 // Exception: on OS X, programs such as Shark only work with dynamic
768 // binaries, so leave it enabled on OS X (Mach-O) binaries.
769 // Also leave it enabled on Solaris which doesn't support
770 // statically linked binaries.
771 if ctxt.BuildMode == BuildModeExe {
772 if havedynamic == 0 && ctxt.HeadType != objabi.Hdarwin && ctxt.HeadType != objabi.Hsolaris {
777 if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && buildcfg.GOOS != "aix" {
778 toc := ctxt.loader.LookupOrCreateSym(".TOC.", 0)
779 sb := ctxt.loader.MakeSymbolUpdater(toc)
780 sb.SetType(sym.SDYNIMPORT)
783 // The Android Q linker started to complain about underalignment of the our TLS
784 // section. We don't actually use the section on android, so don't
786 if buildcfg.GOOS != "android" {
787 tlsg := ctxt.loader.LookupOrCreateSym("runtime.tlsg", 0)
788 sb := ctxt.loader.MakeSymbolUpdater(tlsg)
790 // runtime.tlsg is used for external linking on platforms that do not define
791 // a variable to hold g in assembly (currently only intel).
793 sb.SetType(sym.STLSBSS)
794 sb.SetSize(int64(ctxt.Arch.PtrSize))
795 } else if sb.Type() != sym.SDYNIMPORT {
796 Errorf(nil, "runtime declared tlsg variable %v", sb.Type())
798 ctxt.loader.SetAttrReachable(tlsg, true)
802 var moduledata loader.Sym
803 var mdsb *loader.SymbolBuilder
804 if ctxt.BuildMode == BuildModePlugin {
805 moduledata = ctxt.loader.LookupOrCreateSym("local.pluginmoduledata", 0)
806 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
807 ctxt.loader.SetAttrLocal(moduledata, true)
809 moduledata = ctxt.loader.LookupOrCreateSym("runtime.firstmoduledata", 0)
810 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
812 if mdsb.Type() != 0 && mdsb.Type() != sym.SDYNIMPORT {
813 // If the module (toolchain-speak for "executable or shared
814 // library") we are linking contains the runtime package, it
815 // will define the runtime.firstmoduledata symbol and we
816 // truncate it back to 0 bytes so we can define its entire
817 // contents in symtab.go:symtab().
820 // In addition, on ARM, the runtime depends on the linker
821 // recording the value of GOARM.
822 if ctxt.Arch.Family == sys.ARM {
823 goarm := ctxt.loader.LookupOrCreateSym("runtime.goarm", 0)
824 sb := ctxt.loader.MakeSymbolUpdater(goarm)
825 sb.SetType(sym.SDATA)
827 sb.AddUint8(uint8(buildcfg.GOARM))
830 // Set runtime.disableMemoryProfiling bool if
831 // runtime.MemProfile is not retained in the binary after
832 // deadcode (and we're not dynamically linking).
833 memProfile := ctxt.loader.Lookup("runtime.MemProfile", abiInternalVer)
834 if memProfile != 0 && !ctxt.loader.AttrReachable(memProfile) && !ctxt.DynlinkingGo() {
835 memProfSym := ctxt.loader.LookupOrCreateSym("runtime.disableMemoryProfiling", 0)
836 sb := ctxt.loader.MakeSymbolUpdater(memProfSym)
837 sb.SetType(sym.SDATA)
839 sb.AddUint8(1) // true bool
842 // If OTOH the module does not contain the runtime package,
843 // create a local symbol for the moduledata.
844 moduledata = ctxt.loader.LookupOrCreateSym("local.moduledata", 0)
845 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
846 ctxt.loader.SetAttrLocal(moduledata, true)
848 // In all cases way we mark the moduledata as noptrdata to hide it from
850 mdsb.SetType(sym.SNOPTRDATA)
851 ctxt.loader.SetAttrReachable(moduledata, true)
852 ctxt.Moduledata = moduledata
854 if ctxt.Arch == sys.Arch386 && ctxt.HeadType != objabi.Hwindows {
855 if (ctxt.BuildMode == BuildModeCArchive && ctxt.IsELF) || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE || ctxt.DynlinkingGo() {
856 got := ctxt.loader.LookupOrCreateSym("_GLOBAL_OFFSET_TABLE_", 0)
857 sb := ctxt.loader.MakeSymbolUpdater(got)
858 sb.SetType(sym.SDYNIMPORT)
859 ctxt.loader.SetAttrReachable(got, true)
863 // DWARF-gen and other phases require that the unit Textp slices
864 // be populated, so that it can walk the functions in each unit.
865 // Call into the loader to do this (requires that we collect the
866 // set of internal libraries first). NB: might be simpler if we
867 // moved isRuntimeDepPkg to cmd/internal and then did the test in
868 // loader.AssignTextSymbolOrder.
869 ctxt.Library = postorder(ctxt.Library)
871 for _, lib := range ctxt.Library {
872 intlibs = append(intlibs, isRuntimeDepPkg(lib.Pkg))
874 ctxt.Textp = ctxt.loader.AssignTextSymbolOrder(ctxt.Library, intlibs, ctxt.Textp)
877 // mangleTypeSym shortens the names of symbols that represent Go types
878 // if they are visible in the symbol table.
880 // As the names of these symbols are derived from the string of
881 // the type, they can run to many kilobytes long. So we shorten
882 // them using a SHA-1 when the name appears in the final binary.
883 // This also removes characters that upset external linkers.
885 // These are the symbols that begin with the prefix 'type.' and
886 // contain run-time type information used by the runtime and reflect
887 // packages. All Go binaries contain these symbols, but only
888 // those programs loaded dynamically in multiple parts need these
889 // symbols to have entries in the symbol table.
890 func (ctxt *Link) mangleTypeSym() {
891 if ctxt.BuildMode != BuildModeShared && !ctxt.linkShared && ctxt.BuildMode != BuildModePlugin && !ctxt.CanUsePlugins() {
896 for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
897 if !ldr.AttrReachable(s) && !ctxt.linkShared {
898 // If -linkshared, the GCProg generation code may need to reach
899 // out to the shared library for the type descriptor's data, even
900 // the type descriptor itself is not actually needed at run time
901 // (therefore not reachable). We still need to mangle its name,
902 // so it is consistent with the one stored in the shared library.
905 name := ldr.SymName(s)
906 newName := typeSymbolMangle(name)
908 ldr.SetSymExtname(s, newName)
910 // When linking against a shared library, the Go object file may
911 // have reference to the original symbol name whereas the shared
912 // library provides a symbol with the mangled name. We need to
913 // copy the payload of mangled to original.
914 // XXX maybe there is a better way to do this.
915 dup := ldr.Lookup(newName, ldr.SymVersion(s))
918 dt := ldr.SymType(dup)
919 if st == sym.Sxxx && dt != sym.Sxxx {
927 // typeSymbolMangle mangles the given symbol name into something shorter.
929 // Keep the type:. prefix, which parts of the linker (like the
930 // DWARF generator) know means the symbol is not decodable.
931 // Leave type:runtime. symbols alone, because other parts of
932 // the linker manipulates them.
933 func typeSymbolMangle(name string) string {
934 if !strings.HasPrefix(name, "type:") {
937 if strings.HasPrefix(name, "type:runtime.") {
940 if len(name) <= 14 && !strings.Contains(name, "@") { // Issue 19529
943 hash := notsha256.Sum256([]byte(name))
948 return prefix + base64.StdEncoding.EncodeToString(hash[:6])
952 * look for the next file in an archive.
953 * adapted from libmach.
955 func nextar(bp *bio.Reader, off int64, a *ArHdr) int64 {
960 var buf [SAR_HDR]byte
961 if n, err := io.ReadFull(bp, buf[:]); err != nil {
962 if n == 0 && err != io.EOF {
968 a.name = artrim(buf[0:16])
969 a.date = artrim(buf[16:28])
970 a.uid = artrim(buf[28:34])
971 a.gid = artrim(buf[34:40])
972 a.mode = artrim(buf[40:48])
973 a.size = artrim(buf[48:58])
974 a.fmag = artrim(buf[58:60])
976 arsize := atolwhex(a.size)
980 return arsize + SAR_HDR
983 func loadobjfile(ctxt *Link, lib *sym.Library) {
984 pkg := objabi.PathToPrefix(lib.Pkg)
986 if ctxt.Debugvlog > 1 {
987 ctxt.Logf("ldobj: %s (%s)\n", lib.File, pkg)
989 f, err := bio.Open(lib.File)
991 Exitf("cannot open file %s: %v", lib.File, err)
995 if pkg == "main" && !lib.Main {
996 Exitf("%s: not package main", lib.File)
1000 for i := 0; i < len(ARMAG); i++ {
1001 if c, err := f.ReadByte(); err == nil && c == ARMAG[i] {
1005 /* load it as a regular file */
1006 l := f.MustSeek(0, 2)
1008 ldobj(ctxt, f, lib, l, lib.File, lib.File)
1013 * load all the object files from the archive now.
1014 * this gives us sequential file access and keeps us
1015 * from needing to come back later to pick up more
1016 * objects. it breaks the usual C archive model, but
1017 * this is Go, not C. the common case in Go is that
1018 * we need to load all the objects, and then we throw away
1019 * the individual symbols that are unused.
1021 * loading every object will also make it possible to
1022 * load foreign objects not referenced by __.PKGDEF.
1027 l := nextar(f, off, &arhdr)
1032 Exitf("%s: malformed archive", lib.File)
1036 // __.PKGDEF isn't a real Go object file, and it's
1037 // absent in -linkobj builds anyway. Skipping it
1038 // ensures consistency between -linkobj and normal
1040 if arhdr.name == pkgdef {
1044 if arhdr.name == "dynimportfail" {
1045 dynimportfail = append(dynimportfail, lib.Pkg)
1048 // Skip other special (non-object-file) sections that
1049 // build tools may have added. Such sections must have
1050 // short names so that the suffix is not truncated.
1051 if len(arhdr.name) < 16 {
1052 if ext := filepath.Ext(arhdr.name); ext != ".o" && ext != ".syso" {
1057 pname := fmt.Sprintf("%s(%s)", lib.File, arhdr.name)
1058 l = atolwhex(arhdr.size)
1059 ldobj(ctxt, f, lib, l, pname, lib.File)
1063 type Hostobj struct {
1064 ld func(*Link, *bio.Reader, string, int64, string)
1072 var hostobj []Hostobj
1074 // These packages can use internal linking mode.
1075 // Others trigger external mode.
1076 var internalpkg = []string{
1077 "crypto/internal/boring",
1078 "crypto/internal/boring/syso",
1088 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 {
1090 for _, intpkg := range internalpkg {
1097 // DragonFly declares errno with __thread, which results in a symbol
1098 // type of R_386_TLS_GD or R_X86_64_TLSGD. The Go linker does not
1099 // currently know how to handle TLS relocations, hence we have to
1100 // force external linking for any libraries that link in code that
1101 // uses errno. This can be removed if the Go linker ever supports
1102 // these relocation types.
1103 if headType == objabi.Hdragonfly {
1104 if pkg == "net" || pkg == "os/user" {
1113 hostobj = append(hostobj, Hostobj{})
1114 h := &hostobj[len(hostobj)-1]
1124 func hostobjs(ctxt *Link) {
1125 if ctxt.LinkMode != LinkInternal {
1130 for i := 0; i < len(hostobj); i++ {
1132 f, err := bio.Open(h.file)
1134 Exitf("cannot reopen %s: %v", h.pn, err)
1137 f.MustSeek(h.off, 0)
1139 Errorf(nil, "%s: unrecognized object file format", h.pn)
1142 h.ld(ctxt, f, h.pkg, h.length, h.pn)
1147 func hostlinksetup(ctxt *Link) {
1148 if ctxt.LinkMode != LinkExternal {
1152 // For external link, record that we need to tell the external linker -s,
1153 // and turn off -s internally: the external linker needs the symbol
1154 // information for its final link.
1158 // create temporary directory and arrange cleanup
1159 if *flagTmpdir == "" {
1160 dir, err := os.MkdirTemp("", "go-link-")
1167 os.RemoveAll(*flagTmpdir)
1171 // change our output to temporary object file
1172 if err := ctxt.Out.Close(); err != nil {
1173 Exitf("error closing output file")
1175 mayberemoveoutfile()
1177 p := filepath.Join(*flagTmpdir, "go.o")
1178 if err := ctxt.Out.Open(p); err != nil {
1179 Exitf("cannot create %s: %v", p, err)
1183 // hostobjCopy creates a copy of the object files in hostobj in a
1184 // temporary directory.
1185 func hostobjCopy() (paths []string) {
1186 var wg sync.WaitGroup
1187 sema := make(chan struct{}, runtime.NumCPU()) // limit open file descriptors
1188 for i, h := range hostobj {
1190 dst := filepath.Join(*flagTmpdir, fmt.Sprintf("%06d.o", i))
1191 paths = append(paths, dst)
1200 f, err := os.Open(h.file)
1202 Exitf("cannot reopen %s: %v", h.pn, err)
1205 if _, err := f.Seek(h.off, 0); err != nil {
1206 Exitf("cannot seek %s: %v", h.pn, err)
1209 w, err := os.Create(dst)
1211 Exitf("cannot create %s: %v", dst, err)
1213 if _, err := io.CopyN(w, f, h.length); err != nil {
1214 Exitf("cannot write %s: %v", dst, err)
1216 if err := w.Close(); err != nil {
1217 Exitf("cannot close %s: %v", dst, err)
1225 // writeGDBLinkerScript creates gcc linker script file in temp
1226 // directory. writeGDBLinkerScript returns created file path.
1227 // The script is used to work around gcc bug
1228 // (see https://golang.org/issue/20183 for details).
1229 func writeGDBLinkerScript() string {
1230 name := "fix_debug_gdb_scripts.ld"
1231 path := filepath.Join(*flagTmpdir, name)
1234 .debug_gdb_scripts BLOCK(__section_alignment__) (NOLOAD) :
1236 *(.debug_gdb_scripts)
1239 INSERT AFTER .debug_types;
1241 err := os.WriteFile(path, []byte(src), 0666)
1243 Errorf(nil, "WriteFile %s failed: %v", name, err)
1248 // archive builds a .a archive from the hostobj object files.
1249 func (ctxt *Link) archive() {
1250 if ctxt.BuildMode != BuildModeCArchive {
1256 if *flagExtar == "" {
1260 mayberemoveoutfile()
1262 // Force the buffer to flush here so that external
1263 // tools will see a complete file.
1264 if err := ctxt.Out.Close(); err != nil {
1265 Exitf("error closing %v", *flagOutfile)
1268 argv := []string{*flagExtar, "-q", "-c", "-s"}
1269 if ctxt.HeadType == objabi.Haix {
1270 argv = append(argv, "-X64")
1272 argv = append(argv, *flagOutfile)
1273 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1274 argv = append(argv, hostobjCopy()...)
1276 if ctxt.Debugvlog != 0 {
1277 ctxt.Logf("archive: %s\n", strings.Join(argv, " "))
1280 // If supported, use syscall.Exec() to invoke the archive command,
1281 // which should be the final remaining step needed for the link.
1282 // This will reduce peak RSS for the link (and speed up linking of
1283 // large applications), since when the archive command runs we
1284 // won't be holding onto all of the linker's live memory.
1285 if syscallExecSupported && !ownTmpDir {
1287 ctxt.execArchive(argv)
1288 panic("should not get here")
1291 // Otherwise invoke 'ar' in the usual way (fork + exec).
1292 if out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput(); err != nil {
1293 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1297 func (ctxt *Link) hostlink() {
1298 if ctxt.LinkMode != LinkExternal || nerrors > 0 {
1301 if ctxt.BuildMode == BuildModeCArchive {
1306 argv = append(argv, ctxt.extld()...)
1307 argv = append(argv, hostlinkArchArgs(ctxt.Arch)...)
1309 if *FlagS || debug_s {
1310 if ctxt.HeadType == objabi.Hdarwin {
1311 // Recent versions of macOS print
1312 // ld: warning: option -s is obsolete and being ignored
1313 // so do not pass any arguments.
1315 argv = append(argv, "-s")
1319 // On darwin, whether to combine DWARF into executable.
1320 // Only macOS supports unmapped segments such as our __DWARF segment.
1321 combineDwarf := ctxt.IsDarwin() && !*FlagS && !*FlagW && !debug_s && machoPlatform == PLATFORM_MACOS
1323 switch ctxt.HeadType {
1324 case objabi.Hdarwin:
1326 // Leave room for DWARF combining.
1327 // -headerpad is incompatible with -fembed-bitcode.
1328 argv = append(argv, "-Wl,-headerpad,1144")
1330 if ctxt.DynlinkingGo() && buildcfg.GOOS != "ios" {
1331 // -flat_namespace is deprecated on iOS.
1332 // It is useful for supporting plugins. We don't support plugins on iOS.
1333 // -flat_namespace may cause the dynamic linker to hang at forkExec when
1334 // resolving a lazy binding. See issue 38824.
1335 // Force eager resolution to work around.
1336 argv = append(argv, "-Wl,-flat_namespace", "-Wl,-bind_at_load")
1339 argv = append(argv, "-Wl,-S") // suppress STAB (symbolic debugging) symbols
1341 case objabi.Hopenbsd:
1342 argv = append(argv, "-Wl,-nopie")
1343 argv = append(argv, "-pthread")
1344 case objabi.Hwindows:
1346 argv = append(argv, "-mwindows")
1348 argv = append(argv, "-mconsole")
1350 // Mark as having awareness of terminal services, to avoid
1351 // ancient compatibility hacks.
1352 argv = append(argv, "-Wl,--tsaware")
1355 argv = append(argv, "-Wl,--nxcompat")
1357 argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", PeMinimumTargetMajorVersion))
1358 argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", PeMinimumTargetMinorVersion))
1359 argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", PeMinimumTargetMajorVersion))
1360 argv = append(argv, fmt.Sprintf("-Wl,--minor-subsystem-version=%d", PeMinimumTargetMinorVersion))
1362 argv = append(argv, "-pthread")
1363 // prevent ld to reorder .text functions to keep the same
1364 // first/last functions for moduledata.
1365 argv = append(argv, "-Wl,-bnoobjreorder")
1366 // mcmodel=large is needed for every gcc generated files, but
1367 // ld still need -bbigtoc in order to allow larger TOC.
1368 argv = append(argv, "-mcmodel=large")
1369 argv = append(argv, "-Wl,-bbigtoc")
1372 // Enable/disable ASLR on Windows.
1373 addASLRargs := func(argv []string, val bool) []string {
1374 // Old/ancient versions of GCC support "--dynamicbase" and
1375 // "--high-entropy-va" but don't enable it by default. In
1376 // addition, they don't accept "--disable-dynamicbase" or
1377 // "--no-dynamicbase", so the only way to disable ASLR is to
1378 // not pass any flags at all.
1380 // More modern versions of GCC (and also clang) enable ASLR
1381 // by default. With these compilers, however you can turn it
1382 // off if you want using "--disable-dynamicbase" or
1383 // "--no-dynamicbase".
1385 // The strategy below is to try using "--disable-dynamicbase";
1386 // if this succeeds, then assume we're working with more
1387 // modern compilers and act accordingly. If it fails, assume
1388 // an ancient compiler with ancient defaults.
1391 dbon := "--dynamicbase"
1392 heon := "--high-entropy-va"
1393 dboff := "--disable-dynamicbase"
1394 heoff := "--disable-high-entropy-va"
1399 // Test to see whether "--disable-dynamicbase" works.
1400 newer := linkerFlagSupported(ctxt.Arch, argv[0], "", "-Wl,"+dboff)
1402 // Newer compiler, which supports both on/off options.
1406 // older toolchain: we have to say nothing in order to
1407 // get a no-ASLR binary.
1413 argv = append(argv, "-Wl,"+dbopt)
1415 // enable high-entropy ASLR on 64-bit.
1416 if ctxt.Arch.PtrSize >= 8 && heopt != "" {
1417 argv = append(argv, "-Wl,"+heopt)
1422 switch ctxt.BuildMode {
1424 if ctxt.HeadType == objabi.Hdarwin {
1425 if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() {
1426 argv = append(argv, "-Wl,-no_pie")
1429 if *flagRace && ctxt.HeadType == objabi.Hwindows {
1430 // Current windows/amd64 race detector tsan support
1431 // library can't handle PIE mode (see #53539 for more details).
1432 // For now, explicitly disable PIE (since some compilers
1433 // default to it) if -race is in effect.
1434 argv = addASLRargs(argv, false)
1437 switch ctxt.HeadType {
1438 case objabi.Hdarwin, objabi.Haix:
1439 case objabi.Hwindows:
1440 if *flagAslr && *flagRace {
1441 // Current windows/amd64 race detector tsan support
1442 // library can't handle PIE mode (see #53539 for more details).
1443 // Disable alsr if -race in effect.
1446 argv = addASLRargs(argv, *flagAslr)
1449 if ctxt.UseRelro() {
1450 argv = append(argv, "-Wl,-z,relro")
1452 argv = append(argv, "-pie")
1454 case BuildModeCShared:
1455 if ctxt.HeadType == objabi.Hdarwin {
1456 argv = append(argv, "-dynamiclib")
1458 if ctxt.UseRelro() {
1459 argv = append(argv, "-Wl,-z,relro")
1461 argv = append(argv, "-shared")
1462 if ctxt.HeadType == objabi.Hwindows {
1463 argv = addASLRargs(argv, *flagAslr)
1465 // Pass -z nodelete to mark the shared library as
1466 // non-closeable: a dlclose will do nothing.
1467 argv = append(argv, "-Wl,-z,nodelete")
1468 // Only pass Bsymbolic on non-Windows.
1469 argv = append(argv, "-Wl,-Bsymbolic")
1472 case BuildModeShared:
1473 if ctxt.UseRelro() {
1474 argv = append(argv, "-Wl,-z,relro")
1476 argv = append(argv, "-shared")
1477 case BuildModePlugin:
1478 if ctxt.HeadType == objabi.Hdarwin {
1479 argv = append(argv, "-dynamiclib")
1481 if ctxt.UseRelro() {
1482 argv = append(argv, "-Wl,-z,relro")
1484 argv = append(argv, "-shared")
1488 var altLinker string
1489 if ctxt.IsELF && ctxt.DynlinkingGo() {
1490 // We force all symbol resolution to be done at program startup
1491 // because lazy PLT resolution can use large amounts of stack at
1492 // times we cannot allow it to do so.
1493 argv = append(argv, "-Wl,-z,now")
1495 // Do not let the host linker generate COPY relocations. These
1496 // can move symbols out of sections that rely on stable offsets
1497 // from the beginning of the section (like sym.STYPE).
1498 argv = append(argv, "-Wl,-z,nocopyreloc")
1500 if buildcfg.GOOS == "android" {
1501 // Use lld to avoid errors from default linker (issue #38838)
1505 if ctxt.Arch.InFamily(sys.ARM, sys.ARM64) && buildcfg.GOOS == "linux" {
1506 // On ARM, the GNU linker will generate COPY relocations
1507 // even with -znocopyreloc set.
1508 // https://sourceware.org/bugzilla/show_bug.cgi?id=19962
1510 // On ARM64, the GNU linker will fail instead of
1511 // generating COPY relocations.
1513 // In both cases, switch to gold.
1516 // If gold is not installed, gcc will silently switch
1517 // back to ld.bfd. So we parse the version information
1518 // and provide a useful error if gold is missing.
1519 name, args := flagExtld[0], flagExtld[1:]
1520 args = append(args, "-fuse-ld=gold", "-Wl,--version")
1521 cmd := exec.Command(name, args...)
1522 if out, err := cmd.CombinedOutput(); err == nil {
1523 if !bytes.Contains(out, []byte("GNU gold")) {
1524 log.Fatalf("ARM external linker must be gold (issue #15696), but is not: %s", out)
1529 if ctxt.Arch.Family == sys.ARM64 && buildcfg.GOOS == "freebsd" {
1530 // Switch to ld.bfd on freebsd/arm64.
1533 // Provide a useful error if ld.bfd is missing.
1534 name, args := flagExtld[0], flagExtld[1:]
1535 args = append(args, "-fuse-ld=bfd", "-Wl,--version")
1536 cmd := exec.Command(name, args...)
1537 if out, err := cmd.CombinedOutput(); err == nil {
1538 if !bytes.Contains(out, []byte("GNU ld")) {
1539 log.Fatalf("ARM64 external linker must be ld.bfd (issue #35197), please install devel/binutils")
1543 if altLinker != "" {
1544 argv = append(argv, "-fuse-ld="+altLinker)
1547 if ctxt.IsELF && len(buildinfo) > 0 {
1548 argv = append(argv, fmt.Sprintf("-Wl,--build-id=0x%x", buildinfo))
1551 // On Windows, given -o foo, GCC will append ".exe" to produce
1552 // "foo.exe". We have decided that we want to honor the -o
1553 // option. To make this work, we append a '.' so that GCC
1554 // will decide that the file already has an extension. We
1555 // only want to do this when producing a Windows output file
1556 // on a Windows host.
1557 outopt := *flagOutfile
1558 if buildcfg.GOOS == "windows" && runtime.GOOS == "windows" && filepath.Ext(outopt) == "" {
1561 argv = append(argv, "-o")
1562 argv = append(argv, outopt)
1564 if rpath.val != "" {
1565 argv = append(argv, fmt.Sprintf("-Wl,-rpath,%s", rpath.val))
1568 if *flagInterpreter != "" {
1569 // Many linkers support both -I and the --dynamic-linker flags
1570 // to set the ELF interpreter, but lld only supports
1571 // --dynamic-linker so prefer that (ld on very old Solaris only
1572 // supports -I but that seems less important).
1573 argv = append(argv, fmt.Sprintf("-Wl,--dynamic-linker,%s", *flagInterpreter))
1576 // Force global symbols to be exported for dlopen, etc.
1578 argv = append(argv, "-rdynamic")
1580 if ctxt.HeadType == objabi.Haix {
1581 fileName := xcoffCreateExportFile(ctxt)
1582 argv = append(argv, "-Wl,-bE:"+fileName)
1585 const unusedArguments = "-Qunused-arguments"
1586 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, unusedArguments) {
1587 argv = append(argv, unusedArguments)
1590 const compressDWARF = "-Wl,--compress-debug-sections=zlib"
1591 if ctxt.compressDWARF && linkerFlagSupported(ctxt.Arch, argv[0], altLinker, compressDWARF) {
1592 argv = append(argv, compressDWARF)
1595 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1596 argv = append(argv, hostobjCopy()...)
1597 if ctxt.HeadType == objabi.Haix {
1598 // We want to have C files after Go files to remove
1599 // trampolines csects made by ld.
1600 argv = append(argv, "-nostartfiles")
1601 argv = append(argv, "/lib/crt0_64.o")
1603 extld := ctxt.extld()
1604 name, args := extld[0], extld[1:]
1605 // Get starting files.
1606 getPathFile := func(file string) string {
1607 args := append(args, "-maix64", "--print-file-name="+file)
1608 out, err := exec.Command(name, args...).CombinedOutput()
1610 log.Fatalf("running %s failed: %v\n%s", extld, err, out)
1612 return strings.Trim(string(out), "\n")
1614 // Since GCC version 11, the 64-bit version of GCC starting files
1615 // are now suffixed by "_64". Even under "-maix64" multilib directory
1616 // "crtcxa.o" is 32-bit.
1617 crtcxa := getPathFile("crtcxa_64.o")
1618 if !filepath.IsAbs(crtcxa) {
1619 crtcxa = getPathFile("crtcxa.o")
1621 crtdbase := getPathFile("crtdbase_64.o")
1622 if !filepath.IsAbs(crtdbase) {
1623 crtdbase = getPathFile("crtdbase.o")
1625 argv = append(argv, crtcxa)
1626 argv = append(argv, crtdbase)
1629 if ctxt.linkShared {
1630 seenDirs := make(map[string]bool)
1631 seenLibs := make(map[string]bool)
1632 addshlib := func(path string) {
1633 dir, base := filepath.Split(path)
1635 argv = append(argv, "-L"+dir)
1637 argv = append(argv, "-Wl,-rpath="+dir)
1639 seenDirs[dir] = true
1641 base = strings.TrimSuffix(base, ".so")
1642 base = strings.TrimPrefix(base, "lib")
1643 if !seenLibs[base] {
1644 argv = append(argv, "-l"+base)
1645 seenLibs[base] = true
1648 for _, shlib := range ctxt.Shlibs {
1649 addshlib(shlib.Path)
1650 for _, dep := range shlib.Deps {
1654 libpath := findshlib(ctxt, dep)
1662 // clang, unlike GCC, passes -rdynamic to the linker
1663 // even when linking with -static, causing a linker
1664 // error when using GNU ld. So take out -rdynamic if
1665 // we added it. We do it in this order, rather than
1666 // only adding -rdynamic later, so that -extldflags
1667 // can override -rdynamic without using -static.
1668 // Similarly for -Wl,--dynamic-linker.
1669 checkStatic := func(arg string) {
1670 if ctxt.IsELF && arg == "-static" {
1671 for i := range argv {
1672 if argv[i] == "-rdynamic" || strings.HasPrefix(argv[i], "-Wl,--dynamic-linker,") {
1679 for _, p := range ldflag {
1680 argv = append(argv, p)
1684 // When building a program with the default -buildmode=exe the
1685 // gc compiler generates code requires DT_TEXTREL in a
1686 // position independent executable (PIE). On systems where the
1687 // toolchain creates PIEs by default, and where DT_TEXTREL
1688 // does not work, the resulting programs will not run. See
1689 // issue #17847. To avoid this problem pass -no-pie to the
1690 // toolchain if it is supported.
1691 if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared && !(ctxt.IsDarwin() && ctxt.IsARM64()) {
1692 // GCC uses -no-pie, clang uses -nopie.
1693 for _, nopie := range []string{"-no-pie", "-nopie"} {
1694 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, nopie) {
1695 argv = append(argv, nopie)
1701 for _, p := range flagExtldflags {
1702 argv = append(argv, p)
1705 if ctxt.HeadType == objabi.Hwindows {
1706 // Determine which linker we're using. Add in the extldflags in
1707 // case used has specified "-fuse-ld=...".
1708 extld := ctxt.extld()
1709 name, args := extld[0], extld[1:]
1710 args = append(args, flagExtldflags...)
1711 args = append(args, "-Wl,--version")
1712 cmd := exec.Command(name, args...)
1714 if out, err := cmd.CombinedOutput(); err == nil {
1715 if bytes.Contains(out, []byte("LLD ")) {
1720 // use gcc linker script to work around gcc bug
1721 // (see https://golang.org/issue/20183 for details).
1723 p := writeGDBLinkerScript()
1724 argv = append(argv, "-Wl,-T,"+p)
1727 if p := ctxt.findLibPath("libsynchronization.a"); p != "libsynchronization.a" {
1728 argv = append(argv, "-lsynchronization")
1731 // libmingw32 and libmingwex have some inter-dependencies,
1732 // so must use linker groups.
1733 argv = append(argv, "-Wl,--start-group", "-lmingwex", "-lmingw32", "-Wl,--end-group")
1734 argv = append(argv, peimporteddlls()...)
1737 if ctxt.Debugvlog != 0 {
1738 ctxt.Logf("host link:")
1739 for _, v := range argv {
1745 out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput()
1747 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1750 // Filter out useless linker warnings caused by bugs outside Go.
1751 // See also cmd/go/internal/work/exec.go's gccld method.
1754 for _, line := range bytes.SplitAfter(out, []byte("\n")) {
1755 // golang.org/issue/26073 - Apple Xcode bug
1756 if bytes.Contains(line, []byte("ld: warning: text-based stub file")) {
1765 // Remove TOC overflow warning on AIX.
1766 if bytes.Contains(line, []byte("ld: 0711-783")) {
1771 save = append(save, line)
1773 out = bytes.Join(save, nil)
1776 // always print external output even if the command is successful, so that we don't
1777 // swallow linker warnings (see https://golang.org/issue/17935).
1778 if ctxt.IsDarwin() && ctxt.IsAMD64() {
1779 const noPieWarning = "ld: warning: -no_pie is deprecated when targeting new OS versions\n"
1780 if i := bytes.Index(out, []byte(noPieWarning)); i >= 0 {
1781 // swallow -no_pie deprecation warning, issue 54482
1782 out = append(out[:i], out[i+len(noPieWarning):]...)
1785 ctxt.Logf("%s", out)
1789 // Find "dsymutils" and "strip" tools using CC --print-prog-name.
1791 cc = append(cc, ctxt.extld()...)
1792 cc = append(cc, hostlinkArchArgs(ctxt.Arch)...)
1793 cc = append(cc, "--print-prog-name", "dsymutil")
1794 out, err := exec.Command(cc[0], cc[1:]...).CombinedOutput()
1796 Exitf("%s: finding dsymutil failed: %v\n%s", os.Args[0], err, out)
1798 dsymutilCmd := strings.TrimSuffix(string(out), "\n")
1800 cc[len(cc)-1] = "strip"
1801 out, err = exec.Command(cc[0], cc[1:]...).CombinedOutput()
1803 Exitf("%s: finding strip failed: %v\n%s", os.Args[0], err, out)
1805 stripCmd := strings.TrimSuffix(string(out), "\n")
1807 dsym := filepath.Join(*flagTmpdir, "go.dwarf")
1808 if out, err := exec.Command(dsymutilCmd, "-f", *flagOutfile, "-o", dsym).CombinedOutput(); err != nil {
1809 Exitf("%s: running dsymutil failed: %v\n%s", os.Args[0], err, out)
1811 // Remove STAB (symbolic debugging) symbols after we are done with them (by dsymutil).
1812 // They contain temporary file paths and make the build not reproducible.
1813 if out, err := exec.Command(stripCmd, "-S", *flagOutfile).CombinedOutput(); err != nil {
1814 Exitf("%s: running strip failed: %v\n%s", os.Args[0], err, out)
1816 // Skip combining if `dsymutil` didn't generate a file. See #11994.
1817 if _, err := os.Stat(dsym); os.IsNotExist(err) {
1820 // For os.Rename to work reliably, must be in same directory as outfile.
1821 combinedOutput := *flagOutfile + "~"
1822 exef, err := os.Open(*flagOutfile)
1824 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1827 exem, err := macho.NewFile(exef)
1829 Exitf("%s: parsing Mach-O header failed: %v", os.Args[0], err)
1831 if err := machoCombineDwarf(ctxt, exef, exem, dsym, combinedOutput); err != nil {
1832 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1834 os.Remove(*flagOutfile)
1835 if err := os.Rename(combinedOutput, *flagOutfile); err != nil {
1836 Exitf("%s: %v", os.Args[0], err)
1839 if ctxt.NeedCodeSign() {
1840 err := machoCodeSign(ctxt, *flagOutfile)
1842 Exitf("%s: code signing failed: %v", os.Args[0], err)
1847 var createTrivialCOnce sync.Once
1849 func linkerFlagSupported(arch *sys.Arch, linker, altLinker, flag string) bool {
1850 createTrivialCOnce.Do(func() {
1851 src := filepath.Join(*flagTmpdir, "trivial.c")
1852 if err := os.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
1853 Errorf(nil, "WriteFile trivial.c failed: %v", err)
1857 flagsWithNextArgSkip := []string{
1866 flagsWithNextArgKeep := []string{
1872 prefixesToKeep := []string{
1883 flags := hostlinkArchArgs(arch)
1886 for _, f := range append(flagExtldflags, ldflag...) {
1888 flags = append(flags, f)
1892 } else if f == "" || f[0] != '-' {
1893 } else if contains(flagsWithNextArgSkip, f) {
1895 } else if contains(flagsWithNextArgKeep, f) {
1896 flags = append(flags, f)
1899 for _, p := range prefixesToKeep {
1900 if strings.HasPrefix(f, p) {
1901 flags = append(flags, f)
1908 if altLinker != "" {
1909 flags = append(flags, "-fuse-ld="+altLinker)
1911 flags = append(flags, flag, "trivial.c")
1913 cmd := exec.Command(linker, flags...)
1914 cmd.Dir = *flagTmpdir
1915 cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
1916 out, err := cmd.CombinedOutput()
1917 // GCC says "unrecognized command line option ‘-no-pie’"
1918 // clang says "unknown argument: '-no-pie'"
1919 return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
1922 // hostlinkArchArgs returns arguments to pass to the external linker
1923 // based on the architecture.
1924 func hostlinkArchArgs(arch *sys.Arch) []string {
1925 switch arch.Family {
1927 return []string{"-m32"}
1929 if buildcfg.GOOS == "darwin" {
1930 return []string{"-arch", "x86_64", "-m64"}
1932 return []string{"-m64"}
1934 return []string{"-m64"}
1936 return []string{"-marm"}
1938 if buildcfg.GOOS == "darwin" {
1939 return []string{"-arch", "arm64"}
1942 return []string{"-mabi=lp64d"}
1944 return []string{"-mabi=64"}
1946 return []string{"-mabi=32"}
1948 if buildcfg.GOOS == "aix" {
1949 return []string{"-maix64"}
1951 return []string{"-m64"}
1958 var wantHdr = objabi.HeaderString()
1960 // ldobj loads an input object. If it is a host object (an object
1961 // compiled by a non-Go compiler) it returns the Hostobj pointer. If
1962 // it is a Go object, it returns nil.
1963 func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string, file string) *Hostobj {
1964 pkg := objabi.PathToPrefix(lib.Pkg)
1966 eof := f.Offset() + length
1972 f.MustSeek(start, 0)
1974 unit := &sym.CompilationUnit{Lib: lib}
1975 lib.Units = append(lib.Units, unit)
1977 magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
1978 if magic == 0x7f454c46 { // \x7F E L F
1979 ldelf := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1980 textp, flags, err := loadelf.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn, ehdr.Flags)
1982 Errorf(nil, "%v", err)
1986 ctxt.Textp = append(ctxt.Textp, textp...)
1988 return ldhostobj(ldelf, ctxt.HeadType, f, pkg, length, pn, file)
1991 if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
1992 ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1993 textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1995 Errorf(nil, "%v", err)
1998 ctxt.Textp = append(ctxt.Textp, textp...)
2000 return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
2008 ldpe := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2009 textp, rsrc, err := loadpe.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2011 Errorf(nil, "%v", err)
2015 setpersrc(ctxt, rsrc)
2017 ctxt.Textp = append(ctxt.Textp, textp...)
2019 return ldhostobj(ldpe, ctxt.HeadType, f, pkg, length, pn, file)
2022 if c1 == 0x01 && (c2 == 0xD7 || c2 == 0xF7) {
2023 ldxcoff := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
2024 textp, err := loadxcoff.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
2026 Errorf(nil, "%v", err)
2029 ctxt.Textp = append(ctxt.Textp, textp...)
2031 return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
2034 if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
2035 // An unrecognized object is just passed to the external linker.
2036 // If we try to read symbols from this object, we will
2037 // report an error at that time.
2038 unknownObjFormat = true
2039 return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
2042 /* check the header */
2043 line, err := f.ReadString('\n')
2045 Errorf(nil, "truncated object file: %s: %v", pn, err)
2049 if !strings.HasPrefix(line, "go object ") {
2050 if strings.HasSuffix(pn, ".go") {
2051 Exitf("%s: uncompiled .go source file", pn)
2055 if line == ctxt.Arch.Name {
2056 // old header format: just $GOOS
2057 Errorf(nil, "%s: stale object file", pn)
2061 Errorf(nil, "%s: not an object file: @%d %q", pn, start, line)
2065 // First, check that the basic GOOS, GOARCH, and Version match.
2066 if line != wantHdr {
2067 Errorf(nil, "%s: linked object header mismatch:\nhave %q\nwant %q\n", pn, line, wantHdr)
2070 // Skip over exports and other info -- ends with \n!\n.
2072 // Note: It's possible for "\n!\n" to appear within the binary
2073 // package export data format. To avoid truncating the package
2074 // definition prematurely (issue 21703), we keep track of
2075 // how many "$$" delimiters we've seen.
2077 import0 := f.Offset()
2079 c1 = '\n' // the last line ended in \n
2085 if markers%2 == 0 && c2 == '!' && c3 == '\n' {
2088 if c2 == '$' && c3 == '$' {
2097 Errorf(nil, "truncated object file: %s", pn)
2102 import1 := f.Offset()
2104 f.MustSeek(import0, 0)
2105 ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
2106 f.MustSeek(import1, 0)
2108 fingerprint := ctxt.loader.Preload(ctxt.IncVersion(), f, lib, unit, eof-f.Offset())
2109 if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
2110 // Check fingerprint, to ensure the importing and imported packages
2111 // have consistent view of symbol indices.
2112 // Normally the go command should ensure this. But in case something
2113 // goes wrong, it could lead to obscure bugs like run-time crash.
2114 // Check it here to be sure.
2115 if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
2116 lib.Fingerprint = fingerprint
2118 checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
2121 addImports(ctxt, lib, pn)
2125 // symbolsAreUnresolved scans through the loader's list of unresolved
2126 // symbols and checks to see whether any of them match the names of the
2127 // symbols in 'want'. Return value is a list of bools, with list[K] set
2128 // to true if there is an unresolved reference to the symbol in want[K].
2129 func symbolsAreUnresolved(ctxt *Link, want []string) []bool {
2130 returnAllUndefs := -1
2131 undefs := ctxt.loader.UndefinedRelocTargets(returnAllUndefs)
2132 seen := make(map[loader.Sym]struct{})
2133 rval := make([]bool, len(want))
2134 wantm := make(map[string]int)
2135 for k, w := range want {
2139 for _, s := range undefs {
2140 if _, ok := seen[s]; ok {
2143 seen[s] = struct{}{}
2144 if k, ok := wantm[ctxt.loader.SymName(s)]; ok {
2147 if count == len(want) {
2155 // hostObject reads a single host object file (compare to "hostArchive").
2156 // This is used as part of internal linking when we need to pull in
2157 // files such as "crt?.o".
2158 func hostObject(ctxt *Link, objname string, path string) {
2159 if ctxt.Debugvlog > 1 {
2160 ctxt.Logf("hostObject(%s)\n", path)
2162 objlib := sym.Library{
2165 f, err := bio.Open(path)
2167 Exitf("cannot open host object %q file %s: %v", objname, path, err)
2170 h := ldobj(ctxt, f, &objlib, 0, path, path)
2172 Exitf("unrecognized object file format in %s", path)
2174 f.MustSeek(h.off, 0)
2175 h.ld(ctxt, f, h.pkg, h.length, h.pn)
2178 func checkFingerprint(lib *sym.Library, libfp goobj.FingerprintType, src string, srcfp goobj.FingerprintType) {
2180 Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
2184 func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
2185 data := make([]byte, sym.Size)
2186 sect := f.Sections[sym.Section]
2187 if sect.Type != elf.SHT_PROGBITS && sect.Type != elf.SHT_NOTE {
2188 Errorf(nil, "reading %s from non-data section", sym.Name)
2190 n, err := sect.ReadAt(data, int64(sym.Value-sect.Addr))
2191 if uint64(n) != sym.Size {
2192 Errorf(nil, "reading contents of %s: %v", sym.Name, err)
2197 func readwithpad(r io.Reader, sz int32) ([]byte, error) {
2198 data := make([]byte, Rnd(int64(sz), 4))
2199 _, err := io.ReadFull(r, data)
2207 func readnote(f *elf.File, name []byte, typ int32) ([]byte, error) {
2208 for _, sect := range f.Sections {
2209 if sect.Type != elf.SHT_NOTE {
2214 var namesize, descsize, noteType int32
2215 err := binary.Read(r, f.ByteOrder, &namesize)
2220 return nil, fmt.Errorf("read namesize failed: %v", err)
2222 err = binary.Read(r, f.ByteOrder, &descsize)
2224 return nil, fmt.Errorf("read descsize failed: %v", err)
2226 err = binary.Read(r, f.ByteOrder, ¬eType)
2228 return nil, fmt.Errorf("read type failed: %v", err)
2230 noteName, err := readwithpad(r, namesize)
2232 return nil, fmt.Errorf("read name failed: %v", err)
2234 desc, err := readwithpad(r, descsize)
2236 return nil, fmt.Errorf("read desc failed: %v", err)
2238 if string(name) == string(noteName) && typ == noteType {
2246 func findshlib(ctxt *Link, shlib string) string {
2247 if filepath.IsAbs(shlib) {
2250 for _, libdir := range ctxt.Libdir {
2251 libpath := filepath.Join(libdir, shlib)
2252 if _, err := os.Stat(libpath); err == nil {
2256 Errorf(nil, "cannot find shared library: %s", shlib)
2260 func ldshlibsyms(ctxt *Link, shlib string) {
2262 if filepath.IsAbs(shlib) {
2264 shlib = filepath.Base(shlib)
2266 libpath = findshlib(ctxt, shlib)
2271 for _, processedlib := range ctxt.Shlibs {
2272 if processedlib.Path == libpath {
2276 if ctxt.Debugvlog > 1 {
2277 ctxt.Logf("ldshlibsyms: found library with name %s at %s\n", shlib, libpath)
2280 f, err := elf.Open(libpath)
2282 Errorf(nil, "cannot open shared library: %s", libpath)
2285 // Keep the file open as decodetypeGcprog needs to read from it.
2286 // TODO: fix. Maybe mmap the file.
2289 hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
2291 Errorf(nil, "cannot read ABI hash from shared library %s: %v", libpath, err)
2295 depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
2297 Errorf(nil, "cannot read dep list from shared library %s: %v", libpath, err)
2301 for _, dep := range strings.Split(string(depsbytes), "\n") {
2305 if !filepath.IsAbs(dep) {
2306 // If the dep can be interpreted as a path relative to the shlib
2307 // in which it was found, do that. Otherwise, we will leave it
2308 // to be resolved by libdir lookup.
2309 abs := filepath.Join(filepath.Dir(libpath), dep)
2310 if _, err := os.Stat(abs); err == nil {
2314 deps = append(deps, dep)
2317 syms, err := f.DynamicSymbols()
2319 Errorf(nil, "cannot read symbols from shared library: %s", libpath)
2323 for _, elfsym := range syms {
2324 if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
2328 // Symbols whose names start with "type:" are compiler generated,
2329 // so make functions with that prefix internal.
2331 symname := elfsym.Name // (unmangled) symbol name
2332 if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type:") {
2333 ver = abiInternalVer
2334 } else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC {
2335 // Demangle the ABI name. Keep in sync with symtab.go:mangleABIName.
2336 if strings.HasSuffix(elfsym.Name, ".abiinternal") {
2337 ver = sym.SymVerABIInternal
2338 symname = strings.TrimSuffix(elfsym.Name, ".abiinternal")
2339 } else if strings.HasSuffix(elfsym.Name, ".abi0") {
2341 symname = strings.TrimSuffix(elfsym.Name, ".abi0")
2346 s := l.LookupOrCreateSym(symname, ver)
2348 // Because loadlib above loads all .a files before loading
2349 // any shared libraries, any non-dynimport symbols we find
2350 // that duplicate symbols already loaded should be ignored
2351 // (the symbols from the .a files "win").
2352 if l.SymType(s) != 0 && l.SymType(s) != sym.SDYNIMPORT {
2355 su := l.MakeSymbolUpdater(s)
2356 su.SetType(sym.SDYNIMPORT)
2357 l.SetSymElfType(s, elf.ST_TYPE(elfsym.Info))
2358 su.SetSize(int64(elfsym.Size))
2359 if elfsym.Section != elf.SHN_UNDEF {
2360 // Set .File for the library that actually defines the symbol.
2361 l.SetSymPkg(s, libpath)
2363 // The decodetype_* functions in decodetype.go need access to
2365 sname := l.SymName(s)
2366 if strings.HasPrefix(sname, "type:") && !strings.HasPrefix(sname, "type:.") {
2367 su.SetData(readelfsymboldata(ctxt, f, &elfsym))
2371 if symname != elfsym.Name {
2372 l.SetSymExtname(s, elfsym.Name)
2375 ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f})
2378 func addsection(ldr *loader.Loader, arch *sys.Arch, seg *sym.Segment, name string, rwx int) *sym.Section {
2379 sect := ldr.NewSection()
2380 sect.Rwx = uint8(rwx)
2383 sect.Align = int32(arch.PtrSize) // everything is at least pointer-aligned
2384 seg.Sections = append(seg.Sections, sect)
2389 fmt.Fprintf(os.Stderr, "usage: link [options] main.o\n")
2390 objabi.Flagprint(os.Stderr)
2394 type SymbolType int8 // TODO: after genasmsym is gone, maybe rename to plan9typeChar or something
2397 // see also https://9p.io/magic/man2html/1/nm
2398 TextSym SymbolType = 'T'
2399 DataSym SymbolType = 'D'
2400 BSSSym SymbolType = 'B'
2401 UndefinedSym SymbolType = 'U'
2402 TLSSym SymbolType = 't'
2403 FrameSym SymbolType = 'm'
2404 ParamSym SymbolType = 'p'
2405 AutoSym SymbolType = 'a'
2407 // Deleted auto (not a real sym, just placeholder for type)
2408 DeletedAutoSym = 'x'
2411 // defineInternal defines a symbol used internally by the go runtime.
2412 func (ctxt *Link) defineInternal(p string, t sym.SymKind) loader.Sym {
2413 s := ctxt.loader.CreateSymForUpdate(p, 0)
2420 func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) loader.Sym {
2421 s := ctxt.defineInternal(p, t)
2422 ctxt.loader.SetSymValue(s, v)
2426 func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
2427 if uint64(addr) >= Segdata.Vaddr {
2428 return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
2430 if uint64(addr) >= Segtext.Vaddr {
2431 return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
2433 ldr.Errorf(s, "invalid datoff %#x", addr)
2437 func Entryvalue(ctxt *Link) int64 {
2438 a := *flagEntrySymbol
2439 if a[0] >= '0' && a[0] <= '9' {
2443 s := ldr.Lookup(a, 0)
2445 Errorf(nil, "missing entry symbol %q", a)
2448 st := ldr.SymType(s)
2450 return *FlagTextAddr
2452 if !ctxt.IsAIX() && st != sym.STEXT {
2453 ldr.Errorf(s, "entry not text")
2455 return ldr.SymValue(s)
2458 func (ctxt *Link) callgraph() {
2464 for _, s := range ctxt.Textp {
2465 relocs := ldr.Relocs(s)
2466 for i := 0; i < relocs.Count(); i++ {
2472 if r.Type().IsDirectCall() && ldr.SymType(rs) == sym.STEXT {
2473 ctxt.Logf("%s calls %s\n", ldr.SymName(s), ldr.SymName(rs))
2479 func Rnd(v int64, r int64) int64 {
2492 func bgetc(r *bio.Reader) int {
2493 c, err := r.ReadByte()
2496 log.Fatalf("reading input: %v", err)
2503 type markKind uint8 // for postorder traversal
2510 func postorder(libs []*sym.Library) []*sym.Library {
2511 order := make([]*sym.Library, 0, len(libs)) // hold the result
2512 mark := make(map[*sym.Library]markKind, len(libs))
2513 for _, lib := range libs {
2514 dfs(lib, mark, &order)
2519 func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library) {
2520 if mark[lib] == visited {
2523 if mark[lib] == visiting {
2524 panic("found import cycle while visiting " + lib.Pkg)
2526 mark[lib] = visiting
2527 for _, i := range lib.Imports {
2531 *order = append(*order, lib)
2534 func ElfSymForReloc(ctxt *Link, s loader.Sym) int32 {
2535 // If putelfsym created a local version of this symbol, use that in all
2537 les := ctxt.loader.SymLocalElfSym(s)
2541 return ctxt.loader.SymElfSym(s)
2545 func AddGotSym(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, elfRelocTyp uint32) {
2546 if ldr.SymGot(s) >= 0 {
2550 Adddynsym(ldr, target, syms, s)
2551 got := ldr.MakeSymbolUpdater(syms.GOT)
2552 ldr.SetGot(s, int32(got.Size()))
2553 got.AddUint(target.Arch, 0)
2556 if target.Arch.PtrSize == 8 {
2557 rela := ldr.MakeSymbolUpdater(syms.Rela)
2558 rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2559 rela.AddUint64(target.Arch, elf.R_INFO(uint32(ldr.SymDynid(s)), elfRelocTyp))
2560 rela.AddUint64(target.Arch, 0)
2562 rel := ldr.MakeSymbolUpdater(syms.Rel)
2563 rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2564 rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), elfRelocTyp))
2566 } else if target.IsDarwin() {
2567 leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT)
2568 leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
2569 if target.IsPIE() && target.IsInternal() {
2570 // Mach-O relocations are a royal pain to lay out.
2571 // They use a compact stateful bytecode representation.
2572 // Here we record what are needed and encode them later.
2573 MachoAddBind(int64(ldr.SymGot(s)), s)
2576 ldr.Errorf(s, "addgotsym: unsupported binary format")