1 // Inferno utils/8l/asm.c
2 // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/8l/asm.c
4 // Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
5 // Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
6 // Portions Copyright © 1997-1999 Vita Nuova Limited
7 // Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
8 // Portions Copyright © 2004,2006 Bruce Ellis
9 // Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
10 // Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
11 // Portions Copyright © 2009 The Go Authors. All rights reserved.
13 // Permission is hereby granted, free of charge, to any person obtaining a copy
14 // of this software and associated documentation files (the "Software"), to deal
15 // in the Software without restriction, including without limitation the rights
16 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
17 // copies of the Software, and to permit persons to whom the Software is
18 // furnished to do so, subject to the following conditions:
20 // The above copyright notice and this permission notice shall be included in
21 // all copies or substantial portions of the Software.
23 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
24 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
25 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
26 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
27 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
28 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
40 "cmd/link/internal/loadelf"
41 "cmd/link/internal/loader"
42 "cmd/link/internal/loadmacho"
43 "cmd/link/internal/loadpe"
44 "cmd/link/internal/loadxcoff"
45 "cmd/link/internal/sym"
53 exec "internal/execabs"
64 // Data layout and relocation.
66 // Derived from Inferno utils/6l/l.h
67 // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6l/l.h
69 // Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
70 // Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
71 // Portions Copyright © 1997-1999 Vita Nuova Limited
72 // Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
73 // Portions Copyright © 2004,2006 Bruce Ellis
74 // Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
75 // Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
76 // Portions Copyright © 2009 The Go Authors. All rights reserved.
78 // Permission is hereby granted, free of charge, to any person obtaining a copy
79 // of this software and associated documentation files (the "Software"), to deal
80 // in the Software without restriction, including without limitation the rights
81 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
82 // copies of the Software, and to permit persons to whom the Software is
83 // furnished to do so, subject to the following conditions:
85 // The above copyright notice and this permission notice shall be included in
86 // all copies or substantial portions of the Software.
88 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
89 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
90 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
91 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
92 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
93 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
96 // ArchSyms holds a number of architecture specific symbols used during
97 // relocation. Rather than allowing them universal access to all symbols,
98 // we keep a subset for relocation application.
99 type ArchSyms struct {
105 LinkEditGOT loader.Sym
106 LinkEditPLT loader.Sym
109 DotTOC []loader.Sym // for each version
122 unreachableMethod loader.Sym
125 // mkArchSym is a helper for setArchSyms, to set up a special symbol.
126 func (ctxt *Link) mkArchSym(name string, ver int, ls *loader.Sym) {
127 *ls = ctxt.loader.LookupOrCreateSym(name, ver)
128 ctxt.loader.SetAttrReachable(*ls, true)
131 // mkArchVecSym is similar to setArchSyms, but operates on elements within
132 // a slice, where each element corresponds to some symbol version.
133 func (ctxt *Link) mkArchSymVec(name string, ver int, ls []loader.Sym) {
134 ls[ver] = ctxt.loader.LookupOrCreateSym(name, ver)
135 ctxt.loader.SetAttrReachable(ls[ver], true)
138 // setArchSyms sets up the ArchSyms structure, and must be called before
139 // relocations are applied.
140 func (ctxt *Link) setArchSyms() {
141 ctxt.mkArchSym(".got", 0, &ctxt.GOT)
142 ctxt.mkArchSym(".plt", 0, &ctxt.PLT)
143 ctxt.mkArchSym(".got.plt", 0, &ctxt.GOTPLT)
144 ctxt.mkArchSym(".dynamic", 0, &ctxt.Dynamic)
145 ctxt.mkArchSym(".dynsym", 0, &ctxt.DynSym)
146 ctxt.mkArchSym(".dynstr", 0, &ctxt.DynStr)
147 ctxt.mkArchSym("runtime.unreachableMethod", abiInternalVer, &ctxt.unreachableMethod)
150 ctxt.mkArchSym("TOC", 0, &ctxt.TOC)
152 ctxt.DotTOC = make([]loader.Sym, ctxt.MaxVersion()+1)
153 for i := 0; i <= ctxt.MaxVersion(); i++ {
154 if i >= sym.SymVerABICount && i < sym.SymVerStatic { // these versions are not used currently
157 ctxt.mkArchSymVec(".TOC.", i, ctxt.DotTOC)
161 ctxt.mkArchSym(".rel", 0, &ctxt.Rel)
162 ctxt.mkArchSym(".rela", 0, &ctxt.Rela)
163 ctxt.mkArchSym(".rel.plt", 0, &ctxt.RelPLT)
164 ctxt.mkArchSym(".rela.plt", 0, &ctxt.RelaPLT)
167 ctxt.mkArchSym(".linkedit.got", 0, &ctxt.LinkEditGOT)
168 ctxt.mkArchSym(".linkedit.plt", 0, &ctxt.LinkEditPLT)
179 // Threshold of total text size, used for trampoline insertion. If the total
180 // text size is smaller than TrampLimit, we won't need to insert trampolines.
181 // It is pretty close to the offset range of a direct CALL machine instruction.
182 // We leave some room for extra stuff like PLT stubs.
190 Dragonflydynld string
193 // Empty spaces between codeblocks will be padded with this value.
194 // For example an architecture might want to pad with a trap instruction to
195 // catch wayward programs. Architectures that do not define a padding value
196 // are padded with zeros.
203 Adddynrel func(*Target, *loader.Loader, *ArchSyms, loader.Sym, loader.Reloc, int) bool
205 // Archreloc is an arch-specific hook that assists in relocation processing
206 // (invoked by 'relocsym'); it handles target-specific relocation tasks.
207 // Here "rel" is the current relocation being examined, "sym" is the symbol
208 // containing the chunk of data to which the relocation applies, and "off"
209 // is the contents of the to-be-relocated data item (from sym.P). Return
210 // value is the appropriately relocated value (to be written back to the
211 // same spot in sym.P), number of external _host_ relocations needed (i.e.
212 // ELF/Mach-O/etc. relocations, not Go relocations, this must match Elfreloc1,
213 // etc.), and a boolean indicating success/failure (a failing value indicates
215 Archreloc func(*Target, *loader.Loader, *ArchSyms, loader.Reloc, loader.Sym,
216 int64) (relocatedOffset int64, nExtReloc int, ok bool)
217 // Archrelocvariant is a second arch-specific hook used for
218 // relocation processing; it handles relocations where r.Type is
219 // insufficient to describe the relocation (r.Variant !=
220 // sym.RV_NONE). Here "rel" is the relocation being applied, "sym"
221 // is the symbol containing the chunk of data to which the
222 // relocation applies, and "off" is the contents of the
223 // to-be-relocated data item (from sym.P). Return is an updated
225 Archrelocvariant func(target *Target, ldr *loader.Loader, rel loader.Reloc,
226 rv sym.RelocVariant, sym loader.Sym, offset int64, data []byte) (relocatedOffset int64)
228 // Generate a trampoline for a call from s to rs if necessary. ri is
229 // index of the relocation.
230 Trampoline func(ctxt *Link, ldr *loader.Loader, ri int, rs, s loader.Sym)
232 // Assembling the binary breaks into two phases, writing the code/data/
233 // dwarf information (which is rather generic), and some more architecture
234 // specific work like setting up the elf headers/dynamic relocations, etc.
235 // The phases are called "Asmb" and "Asmb2". Asmb2 needs to be defined for
236 // every architecture, but only if architecture has an Asmb function will
237 // it be used for assembly. Otherwise a generic assembly Asmb function is
239 Asmb func(*Link, *loader.Loader)
240 Asmb2 func(*Link, *loader.Loader)
242 // Extreloc is an arch-specific hook that converts a Go relocation to an
243 // external relocation. Return the external relocation and whether it is
245 Extreloc func(*Target, *loader.Loader, loader.Reloc, loader.Sym) (loader.ExtReloc, bool)
247 Elfreloc1 func(*Link, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int, int64) bool
248 ElfrelocSize uint32 // size of an ELF relocation record, must match Elfreloc1.
249 Elfsetupplt func(ctxt *Link, plt, gotplt *loader.SymbolBuilder, dynamic loader.Sym)
250 Gentext func(*Link, *loader.Loader) // Generate text before addressing has been performed.
251 Machoreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
252 MachorelocSize uint32 // size of an Mach-O relocation record, must match Machoreloc1.
253 PEreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
254 Xcoffreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
256 // Generate additional symbols for the native symbol table just prior to
258 GenSymsLate func(*Link, *loader.Loader)
260 // TLSIEtoLE converts a TLS Initial Executable relocation to
261 // a TLS Local Executable relocation.
263 // This is possible when a TLS IE relocation refers to a local
264 // symbol in an executable, which is typical when internally
265 // linking PIE binaries.
266 TLSIEtoLE func(P []byte, off, size int)
268 // optional override for assignAddress
269 AssignAddress func(ldr *loader.Loader, sect *sym.Section, n int, s loader.Sym, va uint64, isTramp bool) (*sym.Section, int, uint64)
281 MINFUNC = 16 // minimum size for a function
284 // Symbol version of ABIInternal symbols. It is sym.SymVerABIInternal if ABI wrappers
285 // are used, 0 otherwise.
286 var abiInternalVer = sym.SymVerABIInternal
288 // DynlinkingGo reports whether we are producing Go code that can live
289 // in separate shared libraries linked together at runtime.
290 func (ctxt *Link) DynlinkingGo() bool {
292 panic("DynlinkingGo called before all symbols loaded")
294 return ctxt.BuildMode == BuildModeShared || ctxt.linkShared || ctxt.BuildMode == BuildModePlugin || ctxt.canUsePlugins
297 // CanUsePlugins reports whether a plugins can be used
298 func (ctxt *Link) CanUsePlugins() bool {
300 panic("CanUsePlugins called before all symbols loaded")
302 return ctxt.canUsePlugins
305 // NeedCodeSign reports whether we need to code-sign the output binary.
306 func (ctxt *Link) NeedCodeSign() bool {
307 return ctxt.IsDarwin() && ctxt.IsARM64()
319 debug_s bool // backup old value of debug['s']
323 liveness int64 // size of liveness data (funcdata), printed if -v
325 // See -strictdups command line flag.
326 checkStrictDups int // 0=off 1=warning 2=error
327 strictDupMsgCount int
332 Segrodata sym.Segment
333 Segrelrodata sym.Segment
337 Segments = []*sym.Segment{&Segtext, &Segrodata, &Segrelrodata, &Segdata, &Segdwarf}
340 const pkgdef = "__.PKGDEF"
343 // externalobj is set to true if we see an object compiled by
344 // the host compiler that is not from a package that is known
345 // to support internal linking mode.
348 // unknownObjFormat is set to true if we see an object whose
349 // format we don't recognize.
350 unknownObjFormat = false
355 func Lflag(ctxt *Link, arg string) {
356 ctxt.Libdir = append(ctxt.Libdir, arg)
360 * Unix doesn't like it when we write to a running (or, sometimes,
361 * recently run) binary, so remove the output file before writing it.
362 * On Windows 7, remove() can force a subsequent create() to fail.
363 * S_ISREG() does not exist on Plan 9.
365 func mayberemoveoutfile() {
366 if fi, err := os.Lstat(*flagOutfile); err == nil && !fi.Mode().IsRegular() {
369 os.Remove(*flagOutfile)
372 func libinit(ctxt *Link) {
373 Funcalign = thearch.Funcalign
375 // add goroot to the end of the libdir list.
379 if *flagInstallSuffix != "" {
381 suffix = *flagInstallSuffix
382 } else if *flagRace {
385 } else if *flagMsan {
388 } else if *flagAsan {
393 Lflag(ctxt, filepath.Join(buildcfg.GOROOT, "pkg", fmt.Sprintf("%s_%s%s%s", buildcfg.GOOS, buildcfg.GOARCH, suffixsep, suffix)))
397 if err := ctxt.Out.Open(*flagOutfile); err != nil {
398 Exitf("cannot create %s: %v", *flagOutfile, err)
401 if *flagEntrySymbol == "" {
402 switch ctxt.BuildMode {
403 case BuildModeCShared, BuildModeCArchive:
404 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s_lib", buildcfg.GOARCH, buildcfg.GOOS)
405 case BuildModeExe, BuildModePIE:
406 *flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s", buildcfg.GOARCH, buildcfg.GOOS)
407 case BuildModeShared, BuildModePlugin:
408 // No *flagEntrySymbol for -buildmode=shared and plugin
410 Errorf(nil, "unknown *flagEntrySymbol for buildmode %v", ctxt.BuildMode)
415 func exitIfErrors() {
416 if nerrors != 0 || checkStrictDups > 1 && strictDupMsgCount > 0 {
428 func loadinternal(ctxt *Link, name string) *sym.Library {
429 zerofp := goobj.FingerprintType{}
430 if ctxt.linkShared && ctxt.PackageShlib != nil {
431 if shlib := ctxt.PackageShlib[name]; shlib != "" {
432 return addlibpath(ctxt, "internal", "internal", "", name, shlib, zerofp)
435 if ctxt.PackageFile != nil {
436 if pname := ctxt.PackageFile[name]; pname != "" {
437 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
439 ctxt.Logf("loadinternal: cannot find %s\n", name)
443 for _, libdir := range ctxt.Libdir {
445 shlibname := filepath.Join(libdir, name+".shlibname")
446 if ctxt.Debugvlog != 0 {
447 ctxt.Logf("searching for %s.a in %s\n", name, shlibname)
449 if _, err := os.Stat(shlibname); err == nil {
450 return addlibpath(ctxt, "internal", "internal", "", name, shlibname, zerofp)
453 pname := filepath.Join(libdir, name+".a")
454 if ctxt.Debugvlog != 0 {
455 ctxt.Logf("searching for %s.a in %s\n", name, pname)
457 if _, err := os.Stat(pname); err == nil {
458 return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
462 ctxt.Logf("warning: unable to find %s.a\n", name)
466 // extld returns the current external linker.
467 func (ctxt *Link) extld() []string {
468 if len(flagExtld) == 0 {
469 flagExtld = []string{"gcc"}
474 // findLibPathCmd uses cmd command to find gcc library libname.
475 // It returns library full path if found, or "none" if not found.
476 func (ctxt *Link) findLibPathCmd(cmd, libname string) string {
477 extld := ctxt.extld()
478 name, args := extld[0], extld[1:]
479 args = append(args, hostlinkArchArgs(ctxt.Arch)...)
480 args = append(args, cmd)
481 if ctxt.Debugvlog != 0 {
482 ctxt.Logf("%s %v\n", extld, args)
484 out, err := exec.Command(name, args...).Output()
486 if ctxt.Debugvlog != 0 {
487 ctxt.Logf("not using a %s file because compiler failed\n%v\n%s\n", libname, err, out)
491 return strings.TrimSpace(string(out))
494 // findLibPath searches for library libname.
495 // It returns library full path if found, or "none" if not found.
496 func (ctxt *Link) findLibPath(libname string) string {
497 return ctxt.findLibPathCmd("--print-file-name="+libname, libname)
500 func (ctxt *Link) loadlib() {
502 switch *FlagStrictDups {
506 flags |= loader.FlagStrictDups
508 log.Fatalf("invalid -strictdups flag value %d", *FlagStrictDups)
510 elfsetstring1 := func(str string, off int) { elfsetstring(ctxt, 0, str, off) }
511 ctxt.loader = loader.NewLoader(flags, elfsetstring1, &ctxt.ErrorReporter.ErrorReporter)
512 ctxt.ErrorReporter.SymName = func(s loader.Sym) string {
513 return ctxt.loader.SymName(s)
516 // ctxt.Library grows during the loop, so not a range loop.
518 for ; i < len(ctxt.Library); i++ {
519 lib := ctxt.Library[i]
521 if ctxt.Debugvlog > 1 {
522 ctxt.Logf("autolib: %s (from %s)\n", lib.File, lib.Objref)
524 loadobjfile(ctxt, lib)
528 // load internal packages, if not already
530 loadinternal(ctxt, "runtime/race")
533 loadinternal(ctxt, "runtime/msan")
536 loadinternal(ctxt, "runtime/asan")
538 loadinternal(ctxt, "runtime")
539 for ; i < len(ctxt.Library); i++ {
540 lib := ctxt.Library[i]
542 loadobjfile(ctxt, lib)
545 // At this point, the Go objects are "preloaded". Not all the symbols are
546 // added to the symbol table (only defined package symbols are). Looking
547 // up symbol by name may not get expected result.
549 iscgo = ctxt.LibraryByPkg["runtime/cgo"] != nil
551 // Plugins a require cgo support to function. Similarly, plugins may require additional
552 // internal linker support on some platforms which may not be implemented.
553 ctxt.canUsePlugins = ctxt.LibraryByPkg["plugin"] != nil && iscgo
555 // We now have enough information to determine the link mode.
556 determineLinkMode(ctxt)
558 if ctxt.LinkMode == LinkExternal && !iscgo && !(buildcfg.GOOS == "darwin" && ctxt.BuildMode != BuildModePlugin && ctxt.Arch.Family == sys.AMD64) {
559 // This indicates a user requested -linkmode=external.
560 // The startup code uses an import of runtime/cgo to decide
561 // whether to initialize the TLS. So give it one. This could
562 // be handled differently but it's an unusual case.
563 if lib := loadinternal(ctxt, "runtime/cgo"); lib != nil && lib.Shlib == "" {
564 if ctxt.BuildMode == BuildModeShared || ctxt.linkShared {
565 Exitf("cannot implicitly include runtime/cgo in a shared library")
567 for ; i < len(ctxt.Library); i++ {
568 lib := ctxt.Library[i]
570 loadobjfile(ctxt, lib)
576 // Add non-package symbols and references of externally defined symbols.
577 ctxt.loader.LoadSyms(ctxt.Arch)
579 // Load symbols from shared libraries, after all Go object symbols are loaded.
580 for _, lib := range ctxt.Library {
582 if ctxt.Debugvlog > 1 {
583 ctxt.Logf("autolib: %s (from %s)\n", lib.Shlib, lib.Objref)
585 ldshlibsyms(ctxt, lib.Shlib)
589 // Process cgo directives (has to be done before host object loading).
590 ctxt.loadcgodirectives()
592 // Conditionally load host objects, or setup for external linking.
596 if ctxt.LinkMode == LinkInternal && len(hostobj) != 0 {
597 // If we have any undefined symbols in external
598 // objects, try to read them from the libgcc file.
600 undefs := ctxt.loader.UndefinedRelocTargets(1)
605 if *flagLibGCC == "" {
606 *flagLibGCC = ctxt.findLibPathCmd("--print-libgcc-file-name", "libgcc")
608 if runtime.GOOS == "openbsd" && *flagLibGCC == "libgcc.a" {
609 // On OpenBSD `clang --print-libgcc-file-name` returns "libgcc.a".
610 // In this case we fail to load libgcc.a and can encounter link
611 // errors - see if we can find libcompiler_rt.a instead.
612 *flagLibGCC = ctxt.findLibPathCmd("--print-file-name=libcompiler_rt.a", "libcompiler_rt")
614 if ctxt.HeadType == objabi.Hwindows {
615 if p := ctxt.findLibPath("libmingwex.a"); p != "none" {
618 if p := ctxt.findLibPath("libmingw32.a"); p != "none" {
621 // Link libmsvcrt.a to resolve '__acrt_iob_func' symbol
622 // (see https://golang.org/issue/23649 for details).
623 if p := ctxt.findLibPath("libmsvcrt.a"); p != "none" {
626 // TODO: maybe do something similar to peimporteddlls to collect all lib names
627 // and try link them all to final exe just like libmingwex.a and libmingw32.a:
630 #cgo windows LDFLAGS: -lmsvcrt -lm
635 if *flagLibGCC != "none" {
636 hostArchive(ctxt, *flagLibGCC)
641 // We've loaded all the code now.
646 strictDupMsgCount = ctxt.loader.NStrictDupMsgs()
649 // loadcgodirectives reads the previously discovered cgo directives, creating
650 // symbols in preparation for host object loading or use later in the link.
651 func (ctxt *Link) loadcgodirectives() {
653 hostObjSyms := make(map[loader.Sym]struct{})
654 for _, d := range ctxt.cgodata {
655 setCgoAttr(ctxt, d.file, d.pkg, d.directives, hostObjSyms)
659 if ctxt.LinkMode == LinkInternal {
660 // Drop all the cgo_import_static declarations.
661 // Turns out we won't be needing them.
662 for symIdx := range hostObjSyms {
663 if l.SymType(symIdx) == sym.SHOSTOBJ {
664 // If a symbol was marked both
665 // cgo_import_static and cgo_import_dynamic,
666 // then we want to make it cgo_import_dynamic
668 su := l.MakeSymbolUpdater(symIdx)
669 if l.SymExtname(symIdx) != "" && l.SymDynimplib(symIdx) != "" && !(l.AttrCgoExportStatic(symIdx) || l.AttrCgoExportDynamic(symIdx)) {
670 su.SetType(sym.SDYNIMPORT)
679 // Set up flags and special symbols depending on the platform build mode.
680 // This version works with loader.Loader.
681 func (ctxt *Link) linksetup() {
682 switch ctxt.BuildMode {
683 case BuildModeCShared, BuildModePlugin:
684 symIdx := ctxt.loader.LookupOrCreateSym("runtime.islibrary", 0)
685 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
686 sb.SetType(sym.SNOPTRDATA)
688 case BuildModeCArchive:
689 symIdx := ctxt.loader.LookupOrCreateSym("runtime.isarchive", 0)
690 sb := ctxt.loader.MakeSymbolUpdater(symIdx)
691 sb.SetType(sym.SNOPTRDATA)
695 // Recalculate pe parameters now that we have ctxt.LinkMode set.
696 if ctxt.HeadType == objabi.Hwindows {
700 if ctxt.LinkMode == LinkExternal {
701 // When external linking, we are creating an object file. The
702 // absolute address is irrelevant.
706 // If there are no dynamic libraries needed, gcc disables dynamic linking.
707 // Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13)
708 // assumes that a dynamic binary always refers to at least one dynamic library.
709 // Rather than be a source of test cases for glibc, disable dynamic linking
710 // the same way that gcc would.
712 // Exception: on OS X, programs such as Shark only work with dynamic
713 // binaries, so leave it enabled on OS X (Mach-O) binaries.
714 // Also leave it enabled on Solaris which doesn't support
715 // statically linked binaries.
716 if ctxt.BuildMode == BuildModeExe {
717 if havedynamic == 0 && ctxt.HeadType != objabi.Hdarwin && ctxt.HeadType != objabi.Hsolaris {
722 if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && buildcfg.GOOS != "aix" {
723 toc := ctxt.loader.LookupOrCreateSym(".TOC.", 0)
724 sb := ctxt.loader.MakeSymbolUpdater(toc)
725 sb.SetType(sym.SDYNIMPORT)
728 // The Android Q linker started to complain about underalignment of the our TLS
729 // section. We don't actually use the section on android, so don't
731 if buildcfg.GOOS != "android" {
732 tlsg := ctxt.loader.LookupOrCreateSym("runtime.tlsg", 0)
733 sb := ctxt.loader.MakeSymbolUpdater(tlsg)
735 // runtime.tlsg is used for external linking on platforms that do not define
736 // a variable to hold g in assembly (currently only intel).
738 sb.SetType(sym.STLSBSS)
739 sb.SetSize(int64(ctxt.Arch.PtrSize))
740 } else if sb.Type() != sym.SDYNIMPORT {
741 Errorf(nil, "runtime declared tlsg variable %v", sb.Type())
743 ctxt.loader.SetAttrReachable(tlsg, true)
747 var moduledata loader.Sym
748 var mdsb *loader.SymbolBuilder
749 if ctxt.BuildMode == BuildModePlugin {
750 moduledata = ctxt.loader.LookupOrCreateSym("local.pluginmoduledata", 0)
751 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
752 ctxt.loader.SetAttrLocal(moduledata, true)
754 moduledata = ctxt.loader.LookupOrCreateSym("runtime.firstmoduledata", 0)
755 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
757 if mdsb.Type() != 0 && mdsb.Type() != sym.SDYNIMPORT {
758 // If the module (toolchain-speak for "executable or shared
759 // library") we are linking contains the runtime package, it
760 // will define the runtime.firstmoduledata symbol and we
761 // truncate it back to 0 bytes so we can define its entire
762 // contents in symtab.go:symtab().
765 // In addition, on ARM, the runtime depends on the linker
766 // recording the value of GOARM.
767 if ctxt.Arch.Family == sys.ARM {
768 goarm := ctxt.loader.LookupOrCreateSym("runtime.goarm", 0)
769 sb := ctxt.loader.MakeSymbolUpdater(goarm)
770 sb.SetType(sym.SDATA)
772 sb.AddUint8(uint8(buildcfg.GOARM))
775 // Set runtime.disableMemoryProfiling bool if
776 // runtime.MemProfile is not retained in the binary after
777 // deadcode (and we're not dynamically linking).
778 memProfile := ctxt.loader.Lookup("runtime.MemProfile", abiInternalVer)
779 if memProfile != 0 && !ctxt.loader.AttrReachable(memProfile) && !ctxt.DynlinkingGo() {
780 memProfSym := ctxt.loader.LookupOrCreateSym("runtime.disableMemoryProfiling", 0)
781 sb := ctxt.loader.MakeSymbolUpdater(memProfSym)
782 sb.SetType(sym.SDATA)
784 sb.AddUint8(1) // true bool
787 // If OTOH the module does not contain the runtime package,
788 // create a local symbol for the moduledata.
789 moduledata = ctxt.loader.LookupOrCreateSym("local.moduledata", 0)
790 mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
791 ctxt.loader.SetAttrLocal(moduledata, true)
793 // In all cases way we mark the moduledata as noptrdata to hide it from
795 mdsb.SetType(sym.SNOPTRDATA)
796 ctxt.loader.SetAttrReachable(moduledata, true)
797 ctxt.Moduledata = moduledata
799 if ctxt.Arch == sys.Arch386 && ctxt.HeadType != objabi.Hwindows {
800 if (ctxt.BuildMode == BuildModeCArchive && ctxt.IsELF) || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE || ctxt.DynlinkingGo() {
801 got := ctxt.loader.LookupOrCreateSym("_GLOBAL_OFFSET_TABLE_", 0)
802 sb := ctxt.loader.MakeSymbolUpdater(got)
803 sb.SetType(sym.SDYNIMPORT)
804 ctxt.loader.SetAttrReachable(got, true)
808 // DWARF-gen and other phases require that the unit Textp slices
809 // be populated, so that it can walk the functions in each unit.
810 // Call into the loader to do this (requires that we collect the
811 // set of internal libraries first). NB: might be simpler if we
812 // moved isRuntimeDepPkg to cmd/internal and then did the test in
813 // loader.AssignTextSymbolOrder.
814 ctxt.Library = postorder(ctxt.Library)
816 for _, lib := range ctxt.Library {
817 intlibs = append(intlibs, isRuntimeDepPkg(lib.Pkg))
819 ctxt.Textp = ctxt.loader.AssignTextSymbolOrder(ctxt.Library, intlibs, ctxt.Textp)
822 // mangleTypeSym shortens the names of symbols that represent Go types
823 // if they are visible in the symbol table.
825 // As the names of these symbols are derived from the string of
826 // the type, they can run to many kilobytes long. So we shorten
827 // them using a SHA-1 when the name appears in the final binary.
828 // This also removes characters that upset external linkers.
830 // These are the symbols that begin with the prefix 'type.' and
831 // contain run-time type information used by the runtime and reflect
832 // packages. All Go binaries contain these symbols, but only
833 // those programs loaded dynamically in multiple parts need these
834 // symbols to have entries in the symbol table.
835 func (ctxt *Link) mangleTypeSym() {
836 if ctxt.BuildMode != BuildModeShared && !ctxt.linkShared && ctxt.BuildMode != BuildModePlugin && !ctxt.CanUsePlugins() {
841 for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
842 if !ldr.AttrReachable(s) && !ctxt.linkShared {
843 // If -linkshared, the GCProg generation code may need to reach
844 // out to the shared library for the type descriptor's data, even
845 // the type descriptor itself is not actually needed at run time
846 // (therefore not reachable). We still need to mangle its name,
847 // so it is consistent with the one stored in the shared library.
850 name := ldr.SymName(s)
851 newName := typeSymbolMangle(name)
853 ldr.SetSymExtname(s, newName)
855 // When linking against a shared library, the Go object file may
856 // have reference to the original symbol name whereas the shared
857 // library provides a symbol with the mangled name. We need to
858 // copy the payload of mangled to original.
859 // XXX maybe there is a better way to do this.
860 dup := ldr.Lookup(newName, ldr.SymVersion(s))
863 dt := ldr.SymType(dup)
864 if st == sym.Sxxx && dt != sym.Sxxx {
872 // typeSymbolMangle mangles the given symbol name into something shorter.
874 // Keep the type.. prefix, which parts of the linker (like the
875 // DWARF generator) know means the symbol is not decodable.
876 // Leave type.runtime. symbols alone, because other parts of
877 // the linker manipulates them.
878 func typeSymbolMangle(name string) string {
879 if !strings.HasPrefix(name, "type.") {
882 if strings.HasPrefix(name, "type.runtime.") {
885 if len(name) <= 14 && !strings.Contains(name, "@") { // Issue 19529
888 hash := sha1.Sum([]byte(name))
893 return prefix + base64.StdEncoding.EncodeToString(hash[:6])
897 * look for the next file in an archive.
898 * adapted from libmach.
900 func nextar(bp *bio.Reader, off int64, a *ArHdr) int64 {
905 var buf [SAR_HDR]byte
906 if n, err := io.ReadFull(bp, buf[:]); err != nil {
907 if n == 0 && err != io.EOF {
913 a.name = artrim(buf[0:16])
914 a.date = artrim(buf[16:28])
915 a.uid = artrim(buf[28:34])
916 a.gid = artrim(buf[34:40])
917 a.mode = artrim(buf[40:48])
918 a.size = artrim(buf[48:58])
919 a.fmag = artrim(buf[58:60])
921 arsize := atolwhex(a.size)
925 return arsize + SAR_HDR
928 func loadobjfile(ctxt *Link, lib *sym.Library) {
929 pkg := objabi.PathToPrefix(lib.Pkg)
931 if ctxt.Debugvlog > 1 {
932 ctxt.Logf("ldobj: %s (%s)\n", lib.File, pkg)
934 f, err := bio.Open(lib.File)
936 Exitf("cannot open file %s: %v", lib.File, err)
940 if pkg == "main" && !lib.Main {
941 Exitf("%s: not package main", lib.File)
945 for i := 0; i < len(ARMAG); i++ {
946 if c, err := f.ReadByte(); err == nil && c == ARMAG[i] {
950 /* load it as a regular file */
951 l := f.MustSeek(0, 2)
953 ldobj(ctxt, f, lib, l, lib.File, lib.File)
958 * load all the object files from the archive now.
959 * this gives us sequential file access and keeps us
960 * from needing to come back later to pick up more
961 * objects. it breaks the usual C archive model, but
962 * this is Go, not C. the common case in Go is that
963 * we need to load all the objects, and then we throw away
964 * the individual symbols that are unused.
966 * loading every object will also make it possible to
967 * load foreign objects not referenced by __.PKGDEF.
972 l := nextar(f, off, &arhdr)
977 Exitf("%s: malformed archive", lib.File)
981 // __.PKGDEF isn't a real Go object file, and it's
982 // absent in -linkobj builds anyway. Skipping it
983 // ensures consistency between -linkobj and normal
985 if arhdr.name == pkgdef {
989 // Skip other special (non-object-file) sections that
990 // build tools may have added. Such sections must have
991 // short names so that the suffix is not truncated.
992 if len(arhdr.name) < 16 {
993 if ext := filepath.Ext(arhdr.name); ext != ".o" && ext != ".syso" {
998 pname := fmt.Sprintf("%s(%s)", lib.File, arhdr.name)
999 l = atolwhex(arhdr.size)
1000 ldobj(ctxt, f, lib, l, pname, lib.File)
1004 type Hostobj struct {
1005 ld func(*Link, *bio.Reader, string, int64, string)
1013 var hostobj []Hostobj
1015 // These packages can use internal linking mode.
1016 // Others trigger external mode.
1017 var internalpkg = []string{
1018 "crypto/internal/boring",
1028 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 {
1030 for _, intpkg := range internalpkg {
1037 // DragonFly declares errno with __thread, which results in a symbol
1038 // type of R_386_TLS_GD or R_X86_64_TLSGD. The Go linker does not
1039 // currently know how to handle TLS relocations, hence we have to
1040 // force external linking for any libraries that link in code that
1041 // uses errno. This can be removed if the Go linker ever supports
1042 // these relocation types.
1043 if headType == objabi.Hdragonfly {
1044 if pkg == "net" || pkg == "os/user" {
1053 hostobj = append(hostobj, Hostobj{})
1054 h := &hostobj[len(hostobj)-1]
1064 func hostobjs(ctxt *Link) {
1065 if ctxt.LinkMode != LinkInternal {
1070 for i := 0; i < len(hostobj); i++ {
1072 f, err := bio.Open(h.file)
1074 Exitf("cannot reopen %s: %v", h.pn, err)
1077 f.MustSeek(h.off, 0)
1079 Errorf(nil, "%s: unrecognized object file format", h.pn)
1082 h.ld(ctxt, f, h.pkg, h.length, h.pn)
1087 func hostlinksetup(ctxt *Link) {
1088 if ctxt.LinkMode != LinkExternal {
1092 // For external link, record that we need to tell the external linker -s,
1093 // and turn off -s internally: the external linker needs the symbol
1094 // information for its final link.
1098 // create temporary directory and arrange cleanup
1099 if *flagTmpdir == "" {
1100 dir, err := ioutil.TempDir("", "go-link-")
1108 os.RemoveAll(*flagTmpdir)
1112 // change our output to temporary object file
1113 if err := ctxt.Out.Close(); err != nil {
1114 Exitf("error closing output file")
1116 mayberemoveoutfile()
1118 p := filepath.Join(*flagTmpdir, "go.o")
1119 if err := ctxt.Out.Open(p); err != nil {
1120 Exitf("cannot create %s: %v", p, err)
1124 // hostobjCopy creates a copy of the object files in hostobj in a
1125 // temporary directory.
1126 func hostobjCopy() (paths []string) {
1127 var wg sync.WaitGroup
1128 sema := make(chan struct{}, runtime.NumCPU()) // limit open file descriptors
1129 for i, h := range hostobj {
1131 dst := filepath.Join(*flagTmpdir, fmt.Sprintf("%06d.o", i))
1132 paths = append(paths, dst)
1141 f, err := os.Open(h.file)
1143 Exitf("cannot reopen %s: %v", h.pn, err)
1146 if _, err := f.Seek(h.off, 0); err != nil {
1147 Exitf("cannot seek %s: %v", h.pn, err)
1150 w, err := os.Create(dst)
1152 Exitf("cannot create %s: %v", dst, err)
1154 if _, err := io.CopyN(w, f, h.length); err != nil {
1155 Exitf("cannot write %s: %v", dst, err)
1157 if err := w.Close(); err != nil {
1158 Exitf("cannot close %s: %v", dst, err)
1166 // writeGDBLinkerScript creates gcc linker script file in temp
1167 // directory. writeGDBLinkerScript returns created file path.
1168 // The script is used to work around gcc bug
1169 // (see https://golang.org/issue/20183 for details).
1170 func writeGDBLinkerScript() string {
1171 name := "fix_debug_gdb_scripts.ld"
1172 path := filepath.Join(*flagTmpdir, name)
1175 .debug_gdb_scripts BLOCK(__section_alignment__) (NOLOAD) :
1177 *(.debug_gdb_scripts)
1180 INSERT AFTER .debug_types;
1182 err := ioutil.WriteFile(path, []byte(src), 0666)
1184 Errorf(nil, "WriteFile %s failed: %v", name, err)
1189 // archive builds a .a archive from the hostobj object files.
1190 func (ctxt *Link) archive() {
1191 if ctxt.BuildMode != BuildModeCArchive {
1197 if *flagExtar == "" {
1201 mayberemoveoutfile()
1203 // Force the buffer to flush here so that external
1204 // tools will see a complete file.
1205 if err := ctxt.Out.Close(); err != nil {
1206 Exitf("error closing %v", *flagOutfile)
1209 argv := []string{*flagExtar, "-q", "-c", "-s"}
1210 if ctxt.HeadType == objabi.Haix {
1211 argv = append(argv, "-X64")
1213 argv = append(argv, *flagOutfile)
1214 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1215 argv = append(argv, hostobjCopy()...)
1217 if ctxt.Debugvlog != 0 {
1218 ctxt.Logf("archive: %s\n", strings.Join(argv, " "))
1221 // If supported, use syscall.Exec() to invoke the archive command,
1222 // which should be the final remaining step needed for the link.
1223 // This will reduce peak RSS for the link (and speed up linking of
1224 // large applications), since when the archive command runs we
1225 // won't be holding onto all of the linker's live memory.
1226 if syscallExecSupported && !ownTmpDir {
1228 ctxt.execArchive(argv)
1229 panic("should not get here")
1232 // Otherwise invoke 'ar' in the usual way (fork + exec).
1233 if out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput(); err != nil {
1234 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1238 func (ctxt *Link) hostlink() {
1239 if ctxt.LinkMode != LinkExternal || nerrors > 0 {
1242 if ctxt.BuildMode == BuildModeCArchive {
1247 argv = append(argv, ctxt.extld()...)
1248 argv = append(argv, hostlinkArchArgs(ctxt.Arch)...)
1250 if *FlagS || debug_s {
1251 if ctxt.HeadType == objabi.Hdarwin {
1252 // Recent versions of macOS print
1253 // ld: warning: option -s is obsolete and being ignored
1254 // so do not pass any arguments.
1256 argv = append(argv, "-s")
1260 // On darwin, whether to combine DWARF into executable.
1261 // Only macOS supports unmapped segments such as our __DWARF segment.
1262 combineDwarf := ctxt.IsDarwin() && !*FlagS && !*FlagW && !debug_s && machoPlatform == PLATFORM_MACOS
1264 switch ctxt.HeadType {
1265 case objabi.Hdarwin:
1267 // Leave room for DWARF combining.
1268 // -headerpad is incompatible with -fembed-bitcode.
1269 argv = append(argv, "-Wl,-headerpad,1144")
1271 if ctxt.DynlinkingGo() && buildcfg.GOOS != "ios" {
1272 // -flat_namespace is deprecated on iOS.
1273 // It is useful for supporting plugins. We don't support plugins on iOS.
1274 argv = append(argv, "-Wl,-flat_namespace")
1277 argv = append(argv, "-Wl,-S") // suppress STAB (symbolic debugging) symbols
1279 case objabi.Hopenbsd:
1280 argv = append(argv, "-Wl,-nopie")
1281 argv = append(argv, "-pthread")
1282 case objabi.Hwindows:
1284 argv = append(argv, "-mwindows")
1286 argv = append(argv, "-mconsole")
1288 // Mark as having awareness of terminal services, to avoid
1289 // ancient compatibility hacks.
1290 argv = append(argv, "-Wl,--tsaware")
1293 argv = append(argv, "-Wl,--nxcompat")
1295 argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", PeMinimumTargetMajorVersion))
1296 argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", PeMinimumTargetMinorVersion))
1297 argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", PeMinimumTargetMajorVersion))
1298 argv = append(argv, fmt.Sprintf("-Wl,--minor-subsystem-version=%d", PeMinimumTargetMinorVersion))
1300 argv = append(argv, "-pthread")
1301 // prevent ld to reorder .text functions to keep the same
1302 // first/last functions for moduledata.
1303 argv = append(argv, "-Wl,-bnoobjreorder")
1304 // mcmodel=large is needed for every gcc generated files, but
1305 // ld still need -bbigtoc in order to allow larger TOC.
1306 argv = append(argv, "-mcmodel=large")
1307 argv = append(argv, "-Wl,-bbigtoc")
1310 // Enable ASLR on Windows.
1311 addASLRargs := func(argv []string) []string {
1313 argv = append(argv, "-Wl,--dynamicbase")
1314 // enable high-entropy ASLR on 64-bit.
1315 if ctxt.Arch.PtrSize >= 8 {
1316 argv = append(argv, "-Wl,--high-entropy-va")
1321 switch ctxt.BuildMode {
1323 if ctxt.HeadType == objabi.Hdarwin {
1324 if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() {
1325 argv = append(argv, "-Wl,-no_pie")
1326 argv = append(argv, "-Wl,-pagezero_size,4000000")
1330 switch ctxt.HeadType {
1331 case objabi.Hdarwin, objabi.Haix:
1332 case objabi.Hwindows:
1333 argv = addASLRargs(argv)
1336 if ctxt.UseRelro() {
1337 argv = append(argv, "-Wl,-z,relro")
1339 argv = append(argv, "-pie")
1341 case BuildModeCShared:
1342 if ctxt.HeadType == objabi.Hdarwin {
1343 argv = append(argv, "-dynamiclib")
1345 if ctxt.UseRelro() {
1346 argv = append(argv, "-Wl,-z,relro")
1348 argv = append(argv, "-shared")
1349 if ctxt.HeadType == objabi.Hwindows {
1351 argv = addASLRargs(argv)
1354 // Pass -z nodelete to mark the shared library as
1355 // non-closeable: a dlclose will do nothing.
1356 argv = append(argv, "-Wl,-z,nodelete")
1357 // Only pass Bsymbolic on non-Windows.
1358 argv = append(argv, "-Wl,-Bsymbolic")
1361 case BuildModeShared:
1362 if ctxt.UseRelro() {
1363 argv = append(argv, "-Wl,-z,relro")
1365 argv = append(argv, "-shared")
1366 case BuildModePlugin:
1367 if ctxt.HeadType == objabi.Hdarwin {
1368 argv = append(argv, "-dynamiclib")
1370 if ctxt.UseRelro() {
1371 argv = append(argv, "-Wl,-z,relro")
1373 argv = append(argv, "-shared")
1377 var altLinker string
1378 if ctxt.IsELF && ctxt.DynlinkingGo() {
1379 // We force all symbol resolution to be done at program startup
1380 // because lazy PLT resolution can use large amounts of stack at
1381 // times we cannot allow it to do so.
1382 argv = append(argv, "-Wl,-znow")
1384 // Do not let the host linker generate COPY relocations. These
1385 // can move symbols out of sections that rely on stable offsets
1386 // from the beginning of the section (like sym.STYPE).
1387 argv = append(argv, "-Wl,-znocopyreloc")
1389 if buildcfg.GOOS == "android" {
1390 // Use lld to avoid errors from default linker (issue #38838)
1394 if ctxt.Arch.InFamily(sys.ARM, sys.ARM64) && buildcfg.GOOS == "linux" {
1395 // On ARM, the GNU linker will generate COPY relocations
1396 // even with -znocopyreloc set.
1397 // https://sourceware.org/bugzilla/show_bug.cgi?id=19962
1399 // On ARM64, the GNU linker will fail instead of
1400 // generating COPY relocations.
1402 // In both cases, switch to gold.
1405 // If gold is not installed, gcc will silently switch
1406 // back to ld.bfd. So we parse the version information
1407 // and provide a useful error if gold is missing.
1408 name, args := flagExtld[0], flagExtld[1:]
1409 args = append(args, "-fuse-ld=gold", "-Wl,--version")
1410 cmd := exec.Command(name, args...)
1411 if out, err := cmd.CombinedOutput(); err == nil {
1412 if !bytes.Contains(out, []byte("GNU gold")) {
1413 log.Fatalf("ARM external linker must be gold (issue #15696), but is not: %s", out)
1418 if ctxt.Arch.Family == sys.ARM64 && buildcfg.GOOS == "freebsd" {
1419 // Switch to ld.bfd on freebsd/arm64.
1422 // Provide a useful error if ld.bfd is missing.
1423 name, args := flagExtld[0], flagExtld[1:]
1424 args = append(args, "-fuse-ld=bfd", "-Wl,--version")
1425 cmd := exec.Command(name, args...)
1426 if out, err := cmd.CombinedOutput(); err == nil {
1427 if !bytes.Contains(out, []byte("GNU ld")) {
1428 log.Fatalf("ARM64 external linker must be ld.bfd (issue #35197), please install devel/binutils")
1432 if altLinker != "" {
1433 argv = append(argv, "-fuse-ld="+altLinker)
1436 if ctxt.IsELF && len(buildinfo) > 0 {
1437 argv = append(argv, fmt.Sprintf("-Wl,--build-id=0x%x", buildinfo))
1440 // On Windows, given -o foo, GCC will append ".exe" to produce
1441 // "foo.exe". We have decided that we want to honor the -o
1442 // option. To make this work, we append a '.' so that GCC
1443 // will decide that the file already has an extension. We
1444 // only want to do this when producing a Windows output file
1445 // on a Windows host.
1446 outopt := *flagOutfile
1447 if buildcfg.GOOS == "windows" && runtime.GOOS == "windows" && filepath.Ext(outopt) == "" {
1450 argv = append(argv, "-o")
1451 argv = append(argv, outopt)
1453 if rpath.val != "" {
1454 argv = append(argv, fmt.Sprintf("-Wl,-rpath,%s", rpath.val))
1457 if *flagInterpreter != "" {
1458 // Many linkers support both -I and the --dynamic-linker flags
1459 // to set the ELF interpreter, but lld only supports
1460 // --dynamic-linker so prefer that (ld on very old Solaris only
1461 // supports -I but that seems less important).
1462 argv = append(argv, fmt.Sprintf("-Wl,--dynamic-linker,%s", *flagInterpreter))
1465 // Force global symbols to be exported for dlopen, etc.
1467 argv = append(argv, "-rdynamic")
1469 if ctxt.HeadType == objabi.Haix {
1470 fileName := xcoffCreateExportFile(ctxt)
1471 argv = append(argv, "-Wl,-bE:"+fileName)
1474 const unusedArguments = "-Qunused-arguments"
1475 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, unusedArguments) {
1476 argv = append(argv, unusedArguments)
1479 const compressDWARF = "-Wl,--compress-debug-sections=zlib-gnu"
1480 if ctxt.compressDWARF && linkerFlagSupported(ctxt.Arch, argv[0], altLinker, compressDWARF) {
1481 argv = append(argv, compressDWARF)
1484 argv = append(argv, filepath.Join(*flagTmpdir, "go.o"))
1485 argv = append(argv, hostobjCopy()...)
1486 if ctxt.HeadType == objabi.Haix {
1487 // We want to have C files after Go files to remove
1488 // trampolines csects made by ld.
1489 argv = append(argv, "-nostartfiles")
1490 argv = append(argv, "/lib/crt0_64.o")
1492 extld := ctxt.extld()
1493 name, args := extld[0], extld[1:]
1494 // Get starting files.
1495 getPathFile := func(file string) string {
1496 args := append(args, "-maix64", "--print-file-name="+file)
1497 out, err := exec.Command(name, args...).CombinedOutput()
1499 log.Fatalf("running %s failed: %v\n%s", extld, err, out)
1501 return strings.Trim(string(out), "\n")
1503 argv = append(argv, getPathFile("crtcxa.o"))
1504 argv = append(argv, getPathFile("crtdbase.o"))
1507 if ctxt.linkShared {
1508 seenDirs := make(map[string]bool)
1509 seenLibs := make(map[string]bool)
1510 addshlib := func(path string) {
1511 dir, base := filepath.Split(path)
1513 argv = append(argv, "-L"+dir)
1515 argv = append(argv, "-Wl,-rpath="+dir)
1517 seenDirs[dir] = true
1519 base = strings.TrimSuffix(base, ".so")
1520 base = strings.TrimPrefix(base, "lib")
1521 if !seenLibs[base] {
1522 argv = append(argv, "-l"+base)
1523 seenLibs[base] = true
1526 for _, shlib := range ctxt.Shlibs {
1527 addshlib(shlib.Path)
1528 for _, dep := range shlib.Deps {
1532 libpath := findshlib(ctxt, dep)
1540 // clang, unlike GCC, passes -rdynamic to the linker
1541 // even when linking with -static, causing a linker
1542 // error when using GNU ld. So take out -rdynamic if
1543 // we added it. We do it in this order, rather than
1544 // only adding -rdynamic later, so that -extldflags
1545 // can override -rdynamic without using -static.
1546 // Similarly for -Wl,--dynamic-linker.
1547 checkStatic := func(arg string) {
1548 if ctxt.IsELF && arg == "-static" {
1549 for i := range argv {
1550 if argv[i] == "-rdynamic" || strings.HasPrefix(argv[i], "-Wl,--dynamic-linker,") {
1557 for _, p := range ldflag {
1558 argv = append(argv, p)
1562 // When building a program with the default -buildmode=exe the
1563 // gc compiler generates code requires DT_TEXTREL in a
1564 // position independent executable (PIE). On systems where the
1565 // toolchain creates PIEs by default, and where DT_TEXTREL
1566 // does not work, the resulting programs will not run. See
1567 // issue #17847. To avoid this problem pass -no-pie to the
1568 // toolchain if it is supported.
1569 if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared && !(ctxt.IsDarwin() && ctxt.IsARM64()) {
1570 // GCC uses -no-pie, clang uses -nopie.
1571 for _, nopie := range []string{"-no-pie", "-nopie"} {
1572 if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, nopie) {
1573 argv = append(argv, nopie)
1579 for _, p := range flagExtldflags {
1580 argv = append(argv, p)
1583 if ctxt.HeadType == objabi.Hwindows {
1584 // Determine which linker we're using. Add in the extldflags in
1585 // case used has specified "-fuse-ld=...".
1586 extld := ctxt.extld()
1587 name, args := extld[0], extld[1:]
1588 args = append(args, flagExtldflags...)
1589 args = append(args, "-Wl,--version")
1590 cmd := exec.Command(name, args...)
1592 if out, err := cmd.CombinedOutput(); err == nil {
1593 if bytes.Contains(out, []byte("LLD ")) {
1598 // use gcc linker script to work around gcc bug
1599 // (see https://golang.org/issue/20183 for details).
1601 p := writeGDBLinkerScript()
1602 argv = append(argv, "-Wl,-T,"+p)
1604 // libmingw32 and libmingwex have some inter-dependencies,
1605 // so must use linker groups.
1606 argv = append(argv, "-Wl,--start-group", "-lmingwex", "-lmingw32", "-Wl,--end-group")
1607 argv = append(argv, peimporteddlls()...)
1610 if ctxt.Debugvlog != 0 {
1611 ctxt.Logf("host link:")
1612 for _, v := range argv {
1618 out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput()
1620 Exitf("running %s failed: %v\n%s", argv[0], err, out)
1623 // Filter out useless linker warnings caused by bugs outside Go.
1624 // See also cmd/go/internal/work/exec.go's gccld method.
1627 for _, line := range bytes.SplitAfter(out, []byte("\n")) {
1628 // golang.org/issue/26073 - Apple Xcode bug
1629 if bytes.Contains(line, []byte("ld: warning: text-based stub file")) {
1638 // Remove TOC overflow warning on AIX.
1639 if bytes.Contains(line, []byte("ld: 0711-783")) {
1644 save = append(save, line)
1646 out = bytes.Join(save, nil)
1649 // always print external output even if the command is successful, so that we don't
1650 // swallow linker warnings (see https://golang.org/issue/17935).
1651 ctxt.Logf("%s", out)
1655 // Find "dsymutils" and "strip" tools using CC --print-prog-name.
1657 cc = append(cc, ctxt.extld()...)
1658 cc = append(cc, hostlinkArchArgs(ctxt.Arch)...)
1659 cc = append(cc, "--print-prog-name", "dsymutil")
1660 out, err := exec.Command(cc[0], cc[1:]...).CombinedOutput()
1662 Exitf("%s: finding dsymutil failed: %v\n%s", os.Args[0], err, out)
1664 dsymutilCmd := strings.TrimSuffix(string(out), "\n")
1666 cc[len(cc)-1] = "strip"
1667 out, err = exec.Command(cc[0], cc[1:]...).CombinedOutput()
1669 Exitf("%s: finding strip failed: %v\n%s", os.Args[0], err, out)
1671 stripCmd := strings.TrimSuffix(string(out), "\n")
1673 dsym := filepath.Join(*flagTmpdir, "go.dwarf")
1674 if out, err := exec.Command(dsymutilCmd, "-f", *flagOutfile, "-o", dsym).CombinedOutput(); err != nil {
1675 Exitf("%s: running dsymutil failed: %v\n%s", os.Args[0], err, out)
1677 // Remove STAB (symbolic debugging) symbols after we are done with them (by dsymutil).
1678 // They contain temporary file paths and make the build not reproducible.
1679 if out, err := exec.Command(stripCmd, "-S", *flagOutfile).CombinedOutput(); err != nil {
1680 Exitf("%s: running strip failed: %v\n%s", os.Args[0], err, out)
1682 // Skip combining if `dsymutil` didn't generate a file. See #11994.
1683 if _, err := os.Stat(dsym); os.IsNotExist(err) {
1686 // For os.Rename to work reliably, must be in same directory as outfile.
1687 combinedOutput := *flagOutfile + "~"
1688 exef, err := os.Open(*flagOutfile)
1690 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1693 exem, err := macho.NewFile(exef)
1695 Exitf("%s: parsing Mach-O header failed: %v", os.Args[0], err)
1697 if err := machoCombineDwarf(ctxt, exef, exem, dsym, combinedOutput); err != nil {
1698 Exitf("%s: combining dwarf failed: %v", os.Args[0], err)
1700 os.Remove(*flagOutfile)
1701 if err := os.Rename(combinedOutput, *flagOutfile); err != nil {
1702 Exitf("%s: %v", os.Args[0], err)
1705 if ctxt.NeedCodeSign() {
1706 err := machoCodeSign(ctxt, *flagOutfile)
1708 Exitf("%s: code signing failed: %v", os.Args[0], err)
1713 var createTrivialCOnce sync.Once
1715 func linkerFlagSupported(arch *sys.Arch, linker, altLinker, flag string) bool {
1716 createTrivialCOnce.Do(func() {
1717 src := filepath.Join(*flagTmpdir, "trivial.c")
1718 if err := ioutil.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
1719 Errorf(nil, "WriteFile trivial.c failed: %v", err)
1723 flagsWithNextArgSkip := []string{
1732 flagsWithNextArgKeep := []string{
1738 prefixesToKeep := []string{
1749 flags := hostlinkArchArgs(arch)
1752 for _, f := range append(flagExtldflags, ldflag...) {
1754 flags = append(flags, f)
1758 } else if f == "" || f[0] != '-' {
1759 } else if contains(flagsWithNextArgSkip, f) {
1761 } else if contains(flagsWithNextArgKeep, f) {
1762 flags = append(flags, f)
1765 for _, p := range prefixesToKeep {
1766 if strings.HasPrefix(f, p) {
1767 flags = append(flags, f)
1774 if altLinker != "" {
1775 flags = append(flags, "-fuse-ld="+altLinker)
1777 flags = append(flags, flag, "trivial.c")
1779 cmd := exec.Command(linker, flags...)
1780 cmd.Dir = *flagTmpdir
1781 cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
1782 out, err := cmd.CombinedOutput()
1783 // GCC says "unrecognized command line option ‘-no-pie’"
1784 // clang says "unknown argument: '-no-pie'"
1785 return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
1788 // hostlinkArchArgs returns arguments to pass to the external linker
1789 // based on the architecture.
1790 func hostlinkArchArgs(arch *sys.Arch) []string {
1791 switch arch.Family {
1793 return []string{"-m32"}
1795 if buildcfg.GOOS == "darwin" {
1796 return []string{"-arch", "x86_64", "-m64"}
1798 return []string{"-m64"}
1800 return []string{"-m64"}
1802 return []string{"-marm"}
1804 if buildcfg.GOOS == "darwin" {
1805 return []string{"-arch", "arm64"}
1808 return []string{"-mabi=64"}
1810 return []string{"-mabi=32"}
1812 if buildcfg.GOOS == "aix" {
1813 return []string{"-maix64"}
1815 return []string{"-m64"}
1822 var wantHdr = objabi.HeaderString()
1824 // ldobj loads an input object. If it is a host object (an object
1825 // compiled by a non-Go compiler) it returns the Hostobj pointer. If
1826 // it is a Go object, it returns nil.
1827 func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string, file string) *Hostobj {
1828 pkg := objabi.PathToPrefix(lib.Pkg)
1830 eof := f.Offset() + length
1836 f.MustSeek(start, 0)
1838 unit := &sym.CompilationUnit{Lib: lib}
1839 lib.Units = append(lib.Units, unit)
1841 magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
1842 if magic == 0x7f454c46 { // \x7F E L F
1843 ldelf := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1844 textp, flags, err := loadelf.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn, ehdr.Flags)
1846 Errorf(nil, "%v", err)
1850 ctxt.Textp = append(ctxt.Textp, textp...)
1852 return ldhostobj(ldelf, ctxt.HeadType, f, pkg, length, pn, file)
1855 if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
1856 ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1857 textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1859 Errorf(nil, "%v", err)
1862 ctxt.Textp = append(ctxt.Textp, textp...)
1864 return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
1872 ldpe := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1873 textp, rsrc, err := loadpe.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1875 Errorf(nil, "%v", err)
1879 setpersrc(ctxt, rsrc)
1881 ctxt.Textp = append(ctxt.Textp, textp...)
1883 return ldhostobj(ldpe, ctxt.HeadType, f, pkg, length, pn, file)
1886 if c1 == 0x01 && (c2 == 0xD7 || c2 == 0xF7) {
1887 ldxcoff := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
1888 textp, err := loadxcoff.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
1890 Errorf(nil, "%v", err)
1893 ctxt.Textp = append(ctxt.Textp, textp...)
1895 return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
1898 if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
1899 // An unrecognized object is just passed to the external linker.
1900 // If we try to read symbols from this object, we will
1901 // report an error at that time.
1902 unknownObjFormat = true
1903 return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
1906 /* check the header */
1907 line, err := f.ReadString('\n')
1909 Errorf(nil, "truncated object file: %s: %v", pn, err)
1913 if !strings.HasPrefix(line, "go object ") {
1914 if strings.HasSuffix(pn, ".go") {
1915 Exitf("%s: uncompiled .go source file", pn)
1919 if line == ctxt.Arch.Name {
1920 // old header format: just $GOOS
1921 Errorf(nil, "%s: stale object file", pn)
1925 Errorf(nil, "%s: not an object file: @%d %q", pn, start, line)
1929 // First, check that the basic GOOS, GOARCH, and Version match.
1930 if line != wantHdr {
1931 Errorf(nil, "%s: linked object header mismatch:\nhave %q\nwant %q\n", pn, line, wantHdr)
1934 // Skip over exports and other info -- ends with \n!\n.
1936 // Note: It's possible for "\n!\n" to appear within the binary
1937 // package export data format. To avoid truncating the package
1938 // definition prematurely (issue 21703), we keep track of
1939 // how many "$$" delimiters we've seen.
1941 import0 := f.Offset()
1943 c1 = '\n' // the last line ended in \n
1949 if markers%2 == 0 && c2 == '!' && c3 == '\n' {
1952 if c2 == '$' && c3 == '$' {
1961 Errorf(nil, "truncated object file: %s", pn)
1966 import1 := f.Offset()
1968 f.MustSeek(import0, 0)
1969 ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
1970 f.MustSeek(import1, 0)
1972 fingerprint := ctxt.loader.Preload(ctxt.IncVersion(), f, lib, unit, eof-f.Offset())
1973 if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
1974 // Check fingerprint, to ensure the importing and imported packages
1975 // have consistent view of symbol indices.
1976 // Normally the go command should ensure this. But in case something
1977 // goes wrong, it could lead to obscure bugs like run-time crash.
1978 // Check it here to be sure.
1979 if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
1980 lib.Fingerprint = fingerprint
1982 checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
1985 addImports(ctxt, lib, pn)
1989 func checkFingerprint(lib *sym.Library, libfp goobj.FingerprintType, src string, srcfp goobj.FingerprintType) {
1991 Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
1995 func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
1996 data := make([]byte, sym.Size)
1997 sect := f.Sections[sym.Section]
1998 if sect.Type != elf.SHT_PROGBITS && sect.Type != elf.SHT_NOTE {
1999 Errorf(nil, "reading %s from non-data section", sym.Name)
2001 n, err := sect.ReadAt(data, int64(sym.Value-sect.Addr))
2002 if uint64(n) != sym.Size {
2003 Errorf(nil, "reading contents of %s: %v", sym.Name, err)
2008 func readwithpad(r io.Reader, sz int32) ([]byte, error) {
2009 data := make([]byte, Rnd(int64(sz), 4))
2010 _, err := io.ReadFull(r, data)
2018 func readnote(f *elf.File, name []byte, typ int32) ([]byte, error) {
2019 for _, sect := range f.Sections {
2020 if sect.Type != elf.SHT_NOTE {
2025 var namesize, descsize, noteType int32
2026 err := binary.Read(r, f.ByteOrder, &namesize)
2031 return nil, fmt.Errorf("read namesize failed: %v", err)
2033 err = binary.Read(r, f.ByteOrder, &descsize)
2035 return nil, fmt.Errorf("read descsize failed: %v", err)
2037 err = binary.Read(r, f.ByteOrder, ¬eType)
2039 return nil, fmt.Errorf("read type failed: %v", err)
2041 noteName, err := readwithpad(r, namesize)
2043 return nil, fmt.Errorf("read name failed: %v", err)
2045 desc, err := readwithpad(r, descsize)
2047 return nil, fmt.Errorf("read desc failed: %v", err)
2049 if string(name) == string(noteName) && typ == noteType {
2057 func findshlib(ctxt *Link, shlib string) string {
2058 if filepath.IsAbs(shlib) {
2061 for _, libdir := range ctxt.Libdir {
2062 libpath := filepath.Join(libdir, shlib)
2063 if _, err := os.Stat(libpath); err == nil {
2067 Errorf(nil, "cannot find shared library: %s", shlib)
2071 func ldshlibsyms(ctxt *Link, shlib string) {
2073 if filepath.IsAbs(shlib) {
2075 shlib = filepath.Base(shlib)
2077 libpath = findshlib(ctxt, shlib)
2082 for _, processedlib := range ctxt.Shlibs {
2083 if processedlib.Path == libpath {
2087 if ctxt.Debugvlog > 1 {
2088 ctxt.Logf("ldshlibsyms: found library with name %s at %s\n", shlib, libpath)
2091 f, err := elf.Open(libpath)
2093 Errorf(nil, "cannot open shared library: %s", libpath)
2096 // Keep the file open as decodetypeGcprog needs to read from it.
2097 // TODO: fix. Maybe mmap the file.
2100 hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
2102 Errorf(nil, "cannot read ABI hash from shared library %s: %v", libpath, err)
2106 depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
2108 Errorf(nil, "cannot read dep list from shared library %s: %v", libpath, err)
2112 for _, dep := range strings.Split(string(depsbytes), "\n") {
2116 if !filepath.IsAbs(dep) {
2117 // If the dep can be interpreted as a path relative to the shlib
2118 // in which it was found, do that. Otherwise, we will leave it
2119 // to be resolved by libdir lookup.
2120 abs := filepath.Join(filepath.Dir(libpath), dep)
2121 if _, err := os.Stat(abs); err == nil {
2125 deps = append(deps, dep)
2128 syms, err := f.DynamicSymbols()
2130 Errorf(nil, "cannot read symbols from shared library: %s", libpath)
2134 for _, elfsym := range syms {
2135 if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
2139 // Symbols whose names start with "type." are compiler
2140 // generated, so make functions with that prefix internal.
2142 symname := elfsym.Name // (unmangled) symbol name
2143 if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type.") {
2144 ver = abiInternalVer
2145 } else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC {
2146 // Demangle the ABI name. Keep in sync with symtab.go:mangleABIName.
2147 if strings.HasSuffix(elfsym.Name, ".abiinternal") {
2148 ver = sym.SymVerABIInternal
2149 symname = strings.TrimSuffix(elfsym.Name, ".abiinternal")
2150 } else if strings.HasSuffix(elfsym.Name, ".abi0") {
2152 symname = strings.TrimSuffix(elfsym.Name, ".abi0")
2157 s := l.LookupOrCreateSym(symname, ver)
2159 // Because loadlib above loads all .a files before loading
2160 // any shared libraries, any non-dynimport symbols we find
2161 // that duplicate symbols already loaded should be ignored
2162 // (the symbols from the .a files "win").
2163 if l.SymType(s) != 0 && l.SymType(s) != sym.SDYNIMPORT {
2166 su := l.MakeSymbolUpdater(s)
2167 su.SetType(sym.SDYNIMPORT)
2168 l.SetSymElfType(s, elf.ST_TYPE(elfsym.Info))
2169 su.SetSize(int64(elfsym.Size))
2170 if elfsym.Section != elf.SHN_UNDEF {
2171 // Set .File for the library that actually defines the symbol.
2172 l.SetSymPkg(s, libpath)
2174 // The decodetype_* functions in decodetype.go need access to
2176 sname := l.SymName(s)
2177 if strings.HasPrefix(sname, "type.") && !strings.HasPrefix(sname, "type..") {
2178 su.SetData(readelfsymboldata(ctxt, f, &elfsym))
2182 if symname != elfsym.Name {
2183 l.SetSymExtname(s, elfsym.Name)
2186 ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f})
2189 func addsection(ldr *loader.Loader, arch *sys.Arch, seg *sym.Segment, name string, rwx int) *sym.Section {
2190 sect := ldr.NewSection()
2191 sect.Rwx = uint8(rwx)
2194 sect.Align = int32(arch.PtrSize) // everything is at least pointer-aligned
2195 seg.Sections = append(seg.Sections, sect)
2202 limit int // limit on entry to sym
2205 func haslinkregister(ctxt *Link) bool {
2206 return ctxt.FixedFrameSize() != 0
2209 func callsize(ctxt *Link) int {
2210 if haslinkregister(ctxt) {
2213 return ctxt.Arch.RegSize
2216 type stkChk struct {
2219 morestack loader.Sym
2223 // Walk the call tree and check that there is always enough stack space
2224 // for the call frames, especially for a chain of nosplit functions.
2225 func (ctxt *Link) dostkcheck() {
2230 morestack: ldr.Lookup("runtime.morestack", 0),
2231 done: loader.MakeBitmap(ldr.NSym()),
2234 // Every splitting function ensures that there are at least StackLimit
2235 // bytes available below SP when the splitting prologue finishes.
2236 // If the splitting function calls F, then F begins execution with
2237 // at least StackLimit - callsize() bytes available.
2238 // Check that every function behaves correctly with this amount
2239 // of stack, following direct calls in order to piece together chains
2240 // of non-splitting functions.
2242 ch.limit = objabi.StackLimit - callsize(ctxt)
2243 if buildcfg.GOARCH == "arm64" {
2244 // need extra 8 bytes below SP to save FP
2248 // Check every function, but do the nosplit functions in a first pass,
2249 // to make the printed failure chains as short as possible.
2250 for _, s := range ctxt.Textp {
2251 if ldr.IsNoSplit(s) {
2257 for _, s := range ctxt.Textp {
2258 if !ldr.IsNoSplit(s) {
2265 func (sc *stkChk) check(up *chain, depth int) int {
2271 // Don't duplicate work: only need to consider each
2272 // function at top of safe zone once.
2273 top := limit == objabi.StackLimit-callsize(ctxt)
2282 sc.ctxt.Errorf(s, "nosplit stack check too deep")
2287 if ldr.AttrExternal(s) {
2288 // external function.
2289 // should never be called directly.
2290 // onlyctxt.Diagnose the direct caller.
2291 // TODO(mwhudson): actually think about this.
2292 // TODO(khr): disabled for now. Calls to external functions can only happen on the g0 stack.
2293 // See the trampolines in src/runtime/sys_darwin_$ARCH.go.
2294 //if depth == 1 && ldr.SymType(s) != sym.SXREF && !ctxt.DynlinkingGo() &&
2295 // ctxt.BuildMode != BuildModeCArchive && ctxt.BuildMode != BuildModePIE && ctxt.BuildMode != BuildModeCShared && ctxt.BuildMode != BuildModePlugin {
2296 // Errorf(s, "call to external function")
2300 info := ldr.FuncInfo(s)
2301 if !info.Valid() { // external function. see above.
2310 // morestack looks like it calls functions,
2311 // but it switches the stack pointer first.
2312 if s == sc.morestack {
2319 if !ldr.IsNoSplit(s) {
2320 // Ensure we have enough stack to call morestack.
2321 ch.limit = limit - callsize(ctxt)
2322 ch.sym = sc.morestack
2323 if sc.check(&ch, depth+1) < 0 {
2329 // Raise limit to allow frame.
2330 locals := info.Locals()
2331 limit = objabi.StackLimit + int(locals) + int(ctxt.FixedFrameSize())
2334 // Walk through sp adjustments in function, consuming relocs.
2335 relocs := ldr.Relocs(s)
2337 pcsp := obj.NewPCIter(uint32(ctxt.Arch.MinLC))
2339 for pcsp.Init(ldr.Data(ldr.Pcsp(s))); !pcsp.Done; pcsp.Next() {
2340 // pcsp.value is in effect for [pcsp.pc, pcsp.nextpc).
2342 // Check stack size in effect for this span.
2343 if int32(limit)-pcsp.Value < 0 {
2344 sc.broke(up, int(int32(limit)-pcsp.Value))
2348 // Process calls in this span.
2349 for ; ri < relocs.Count(); ri++ {
2351 if uint32(r.Off()) >= pcsp.NextPC {
2356 case t.IsDirectCall():
2357 ch.limit = int(int32(limit) - pcsp.Value - int32(callsize(ctxt)))
2359 if sc.check(&ch, depth+1) < 0 {
2363 // Indirect call. Assume it is a call to a splitting function,
2364 // so we have to make sure it can call morestack.
2365 // Arrange the data structures to report both calls, so that
2366 // if there is an error, stkprint shows all the steps involved.
2367 case t == objabi.R_CALLIND:
2368 ch.limit = int(int32(limit) - pcsp.Value - int32(callsize(ctxt)))
2370 ch1.limit = ch.limit - callsize(ctxt) // for morestack in called prologue
2372 ch1.sym = sc.morestack
2373 if sc.check(&ch1, depth+2) < 0 {
2383 func (sc *stkChk) broke(ch *chain, limit int) {
2384 sc.ctxt.Errorf(ch.sym, "nosplit stack overflow")
2388 func (sc *stkChk) print(ch *chain, limit int) {
2393 name = fmt.Sprintf("%s<%d>", ldr.SymName(ch.sym), ldr.SymVersion(ch.sym))
2394 if ldr.IsNoSplit(ch.sym) {
2395 name += " (nosplit)"
2398 name = "function pointer"
2402 // top of chain. ch.sym != 0.
2403 if ldr.IsNoSplit(ch.sym) {
2404 fmt.Printf("\t%d\tassumed on entry to %s\n", ch.limit, name)
2406 fmt.Printf("\t%d\tguaranteed after split check in %s\n", ch.limit, name)
2409 sc.print(ch.up, ch.limit+callsize(ctxt))
2410 if !haslinkregister(ctxt) {
2411 fmt.Printf("\t%d\ton entry to %s\n", ch.limit, name)
2415 if ch.limit != limit {
2416 fmt.Printf("\t%d\tafter %s uses %d\n", limit, name, ch.limit-limit)
2421 fmt.Fprintf(os.Stderr, "usage: link [options] main.o\n")
2422 objabi.Flagprint(os.Stderr)
2426 type SymbolType int8 // TODO: after genasmsym is gone, maybe rename to plan9typeChar or something
2429 // see also https://9p.io/magic/man2html/1/nm
2430 TextSym SymbolType = 'T'
2431 DataSym SymbolType = 'D'
2432 BSSSym SymbolType = 'B'
2433 UndefinedSym SymbolType = 'U'
2434 TLSSym SymbolType = 't'
2435 FrameSym SymbolType = 'm'
2436 ParamSym SymbolType = 'p'
2437 AutoSym SymbolType = 'a'
2439 // Deleted auto (not a real sym, just placeholder for type)
2440 DeletedAutoSym = 'x'
2443 // defineInternal defines a symbol used internally by the go runtime.
2444 func (ctxt *Link) defineInternal(p string, t sym.SymKind) loader.Sym {
2445 s := ctxt.loader.CreateSymForUpdate(p, 0)
2452 func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) loader.Sym {
2453 s := ctxt.defineInternal(p, t)
2454 ctxt.loader.SetSymValue(s, v)
2458 func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
2459 if uint64(addr) >= Segdata.Vaddr {
2460 return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
2462 if uint64(addr) >= Segtext.Vaddr {
2463 return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
2465 ldr.Errorf(s, "invalid datoff %#x", addr)
2469 func Entryvalue(ctxt *Link) int64 {
2470 a := *flagEntrySymbol
2471 if a[0] >= '0' && a[0] <= '9' {
2475 s := ldr.Lookup(a, 0)
2476 st := ldr.SymType(s)
2478 return *FlagTextAddr
2480 if !ctxt.IsAIX() && st != sym.STEXT {
2481 ldr.Errorf(s, "entry not text")
2483 return ldr.SymValue(s)
2486 func (ctxt *Link) callgraph() {
2492 for _, s := range ctxt.Textp {
2493 relocs := ldr.Relocs(s)
2494 for i := 0; i < relocs.Count(); i++ {
2500 if r.Type().IsDirectCall() && ldr.SymType(rs) == sym.STEXT {
2501 ctxt.Logf("%s calls %s\n", ldr.SymName(s), ldr.SymName(rs))
2507 func Rnd(v int64, r int64) int64 {
2520 func bgetc(r *bio.Reader) int {
2521 c, err := r.ReadByte()
2524 log.Fatalf("reading input: %v", err)
2531 type markKind uint8 // for postorder traversal
2538 func postorder(libs []*sym.Library) []*sym.Library {
2539 order := make([]*sym.Library, 0, len(libs)) // hold the result
2540 mark := make(map[*sym.Library]markKind, len(libs))
2541 for _, lib := range libs {
2542 dfs(lib, mark, &order)
2547 func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library) {
2548 if mark[lib] == visited {
2551 if mark[lib] == visiting {
2552 panic("found import cycle while visiting " + lib.Pkg)
2554 mark[lib] = visiting
2555 for _, i := range lib.Imports {
2559 *order = append(*order, lib)
2562 func ElfSymForReloc(ctxt *Link, s loader.Sym) int32 {
2563 // If putelfsym created a local version of this symbol, use that in all
2565 les := ctxt.loader.SymLocalElfSym(s)
2569 return ctxt.loader.SymElfSym(s)
2573 func AddGotSym(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, elfRelocTyp uint32) {
2574 if ldr.SymGot(s) >= 0 {
2578 Adddynsym(ldr, target, syms, s)
2579 got := ldr.MakeSymbolUpdater(syms.GOT)
2580 ldr.SetGot(s, int32(got.Size()))
2581 got.AddUint(target.Arch, 0)
2584 if target.Arch.PtrSize == 8 {
2585 rela := ldr.MakeSymbolUpdater(syms.Rela)
2586 rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2587 rela.AddUint64(target.Arch, elf.R_INFO(uint32(ldr.SymDynid(s)), elfRelocTyp))
2588 rela.AddUint64(target.Arch, 0)
2590 rel := ldr.MakeSymbolUpdater(syms.Rel)
2591 rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
2592 rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), elfRelocTyp))
2594 } else if target.IsDarwin() {
2595 leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT)
2596 leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
2597 if target.IsPIE() && target.IsInternal() {
2598 // Mach-O relocations are a royal pain to lay out.
2599 // They use a compact stateful bytecode representation.
2600 // Here we record what are needed and encode them later.
2601 MachoAddBind(int64(ldr.SymGot(s)), s)
2604 ldr.Errorf(s, "addgotsym: unsupported binary format")