Source file src/cmd/link/internal/ld/lib.go

     1  // Inferno utils/8l/asm.c
     2  // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/8l/asm.c
     3  //
     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.
    12  //
    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:
    19  //
    20  // The above copyright notice and this permission notice shall be included in
    21  // all copies or substantial portions of the Software.
    22  //
    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
    29  // THE SOFTWARE.
    30  
    31  package ld
    32  
    33  import (
    34  	"bytes"
    35  	"debug/elf"
    36  	"debug/macho"
    37  	"debug/pe"
    38  	"encoding/base64"
    39  	"encoding/binary"
    40  	"fmt"
    41  	"internal/buildcfg"
    42  	"internal/platform"
    43  	"io"
    44  	"log"
    45  	"os"
    46  	"os/exec"
    47  	"path/filepath"
    48  	"runtime"
    49  	"slices"
    50  	"sort"
    51  	"strings"
    52  	"sync"
    53  	"time"
    54  
    55  	"cmd/internal/bio"
    56  	"cmd/internal/goobj"
    57  	"cmd/internal/hash"
    58  	"cmd/internal/objabi"
    59  	"cmd/internal/sys"
    60  	"cmd/link/internal/loadelf"
    61  	"cmd/link/internal/loader"
    62  	"cmd/link/internal/loadmacho"
    63  	"cmd/link/internal/loadpe"
    64  	"cmd/link/internal/loadxcoff"
    65  	"cmd/link/internal/sym"
    66  )
    67  
    68  // Data layout and relocation.
    69  
    70  // Derived from Inferno utils/6l/l.h
    71  // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6l/l.h
    72  //
    73  //	Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
    74  //	Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
    75  //	Portions Copyright © 1997-1999 Vita Nuova Limited
    76  //	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
    77  //	Portions Copyright © 2004,2006 Bruce Ellis
    78  //	Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
    79  //	Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
    80  //	Portions Copyright © 2009 The Go Authors. All rights reserved.
    81  //
    82  // Permission is hereby granted, free of charge, to any person obtaining a copy
    83  // of this software and associated documentation files (the "Software"), to deal
    84  // in the Software without restriction, including without limitation the rights
    85  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    86  // copies of the Software, and to permit persons to whom the Software is
    87  // furnished to do so, subject to the following conditions:
    88  //
    89  // The above copyright notice and this permission notice shall be included in
    90  // all copies or substantial portions of the Software.
    91  //
    92  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    93  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    94  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
    95  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    96  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    97  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    98  // THE SOFTWARE.
    99  
   100  // ArchSyms holds a number of architecture specific symbols used during
   101  // relocation.  Rather than allowing them universal access to all symbols,
   102  // we keep a subset for relocation application.
   103  type ArchSyms struct {
   104  	Rel     loader.Sym
   105  	Rela    loader.Sym
   106  	RelPLT  loader.Sym
   107  	RelaPLT loader.Sym
   108  
   109  	LinkEditGOT loader.Sym
   110  	LinkEditPLT loader.Sym
   111  
   112  	TOC    loader.Sym
   113  	DotTOC []loader.Sym // for each version
   114  
   115  	GOT    loader.Sym
   116  	PLT    loader.Sym
   117  	GOTPLT loader.Sym
   118  
   119  	Tlsg      loader.Sym
   120  	Tlsoffset int
   121  
   122  	Dynamic loader.Sym
   123  	DynSym  loader.Sym
   124  	DynStr  loader.Sym
   125  
   126  	unreachableMethod loader.Sym
   127  
   128  	// Symbol containing a list of all the inittasks that need
   129  	// to be run at startup.
   130  	mainInittasks loader.Sym
   131  }
   132  
   133  // mkArchSym is a helper for setArchSyms, to set up a special symbol.
   134  func (ctxt *Link) mkArchSym(name string, ver int, ls *loader.Sym) {
   135  	*ls = ctxt.loader.LookupOrCreateSym(name, ver)
   136  	ctxt.loader.SetAttrReachable(*ls, true)
   137  }
   138  
   139  // mkArchSymVec is similar to  setArchSyms, but operates on elements within
   140  // a slice, where each element corresponds to some symbol version.
   141  func (ctxt *Link) mkArchSymVec(name string, ver int, ls []loader.Sym) {
   142  	ls[ver] = ctxt.loader.LookupOrCreateSym(name, ver)
   143  	ctxt.loader.SetAttrReachable(ls[ver], true)
   144  }
   145  
   146  // setArchSyms sets up the ArchSyms structure, and must be called before
   147  // relocations are applied.
   148  func (ctxt *Link) setArchSyms() {
   149  	ctxt.mkArchSym(".got", 0, &ctxt.GOT)
   150  	ctxt.mkArchSym(".plt", 0, &ctxt.PLT)
   151  	ctxt.mkArchSym(".got.plt", 0, &ctxt.GOTPLT)
   152  	ctxt.mkArchSym(".dynamic", 0, &ctxt.Dynamic)
   153  	ctxt.mkArchSym(".dynsym", 0, &ctxt.DynSym)
   154  	ctxt.mkArchSym(".dynstr", 0, &ctxt.DynStr)
   155  	ctxt.mkArchSym("runtime.unreachableMethod", abiInternalVer, &ctxt.unreachableMethod)
   156  
   157  	if ctxt.IsPPC64() {
   158  		ctxt.mkArchSym("TOC", 0, &ctxt.TOC)
   159  
   160  		ctxt.DotTOC = make([]loader.Sym, ctxt.MaxVersion()+1)
   161  		for i := 0; i <= ctxt.MaxVersion(); i++ {
   162  			if i >= sym.SymVerABICount && i < sym.SymVerStatic { // these versions are not used currently
   163  				continue
   164  			}
   165  			ctxt.mkArchSymVec(".TOC.", i, ctxt.DotTOC)
   166  		}
   167  	}
   168  	if ctxt.IsElf() {
   169  		ctxt.mkArchSym(".rel", 0, &ctxt.Rel)
   170  		ctxt.mkArchSym(".rela", 0, &ctxt.Rela)
   171  		ctxt.mkArchSym(".rel.plt", 0, &ctxt.RelPLT)
   172  		ctxt.mkArchSym(".rela.plt", 0, &ctxt.RelaPLT)
   173  	}
   174  	if ctxt.IsDarwin() {
   175  		ctxt.mkArchSym(".linkedit.got", 0, &ctxt.LinkEditGOT)
   176  		ctxt.mkArchSym(".linkedit.plt", 0, &ctxt.LinkEditPLT)
   177  	}
   178  }
   179  
   180  type Arch struct {
   181  	Funcalign  int
   182  	Maxalign   int
   183  	Minalign   int
   184  	Dwarfregsp int
   185  	Dwarfreglr int
   186  
   187  	// Threshold of total text size, used for trampoline insertion. If the total
   188  	// text size is smaller than TrampLimit, we won't need to insert trampolines.
   189  	// It is pretty close to the offset range of a direct CALL machine instruction.
   190  	// We leave some room for extra stuff like PLT stubs.
   191  	TrampLimit uint64
   192  
   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.
   197  	CodePad []byte
   198  
   199  	// Plan 9 variables.
   200  	Plan9Magic  uint32
   201  	Plan9_64Bit bool
   202  
   203  	Adddynrel func(*Target, *loader.Loader, *ArchSyms, loader.Sym, loader.Reloc, int) bool
   204  	Archinit  func(*Link)
   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 ELF.Reloc1,
   213  	// etc.), and a boolean indicating success/failure (a failing value indicates
   214  	// a fatal error).
   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
   224  	// offset value.
   225  	Archrelocvariant func(target *Target, ldr *loader.Loader, rel loader.Reloc,
   226  		rv sym.RelocVariant, sym loader.Sym, offset int64, data []byte) (relocatedOffset int64)
   227  
   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)
   231  
   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
   238  	// used.
   239  	Asmb  func(*Link, *loader.Loader)
   240  	Asmb2 func(*Link, *loader.Loader)
   241  
   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
   244  	// needed.
   245  	Extreloc func(*Target, *loader.Loader, loader.Reloc, loader.Sym) (loader.ExtReloc, bool)
   246  
   247  	Gentext        func(*Link, *loader.Loader) // Generate text before addressing has been performed.
   248  	Machoreloc1    func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
   249  	MachorelocSize uint32 // size of an Mach-O relocation record, must match Machoreloc1.
   250  	PEreloc1       func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
   251  	Xcoffreloc1    func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool
   252  
   253  	// Generate additional symbols for the native symbol table just prior to
   254  	// code generation.
   255  	GenSymsLate func(*Link, *loader.Loader)
   256  
   257  	// TLSIEtoLE converts a TLS Initial Executable relocation to
   258  	// a TLS Local Executable relocation.
   259  	//
   260  	// This is possible when a TLS IE relocation refers to a local
   261  	// symbol in an executable, which is typical when internally
   262  	// linking PIE binaries.
   263  	TLSIEtoLE func(P []byte, off, size int)
   264  
   265  	// optional override for assignAddress
   266  	AssignAddress func(ldr *loader.Loader, sect *sym.Section, n int, s loader.Sym, va uint64, isTramp bool) (*sym.Section, int, uint64)
   267  
   268  	// ELF specific information.
   269  	ELF ELFArch
   270  }
   271  
   272  var (
   273  	thearch Arch
   274  	lcSize  int32
   275  	rpath   Rpath
   276  	spSize  int32
   277  	symSize int32
   278  )
   279  
   280  // Symbol version of ABIInternal symbols. It is sym.SymVerABIInternal if ABI wrappers
   281  // are used, 0 otherwise.
   282  var abiInternalVer = sym.SymVerABIInternal
   283  
   284  // DynlinkingGo reports whether we are producing Go code that can live
   285  // in separate shared libraries linked together at runtime.
   286  func (ctxt *Link) DynlinkingGo() bool {
   287  	if !ctxt.Loaded {
   288  		panic("DynlinkingGo called before all symbols loaded")
   289  	}
   290  	return ctxt.BuildMode == BuildModeShared || ctxt.linkShared || ctxt.BuildMode == BuildModePlugin || ctxt.canUsePlugins
   291  }
   292  
   293  // CanUsePlugins reports whether a plugins can be used
   294  func (ctxt *Link) CanUsePlugins() bool {
   295  	if !ctxt.Loaded {
   296  		panic("CanUsePlugins called before all symbols loaded")
   297  	}
   298  	return ctxt.canUsePlugins
   299  }
   300  
   301  // NeedCodeSign reports whether we need to code-sign the output binary.
   302  func (ctxt *Link) NeedCodeSign() bool {
   303  	return ctxt.IsDarwin() && ctxt.IsARM64()
   304  }
   305  
   306  var (
   307  	dynlib          []string
   308  	ldflag          []string
   309  	havedynamic     int
   310  	Funcalign       int
   311  	iscgo           bool
   312  	elfglobalsymndx int
   313  	interpreter     string
   314  
   315  	debug_s bool // backup old value of debug['s']
   316  	HEADR   int32
   317  
   318  	nerrors  int
   319  	liveness int64 // size of liveness data (funcdata), printed if -v
   320  
   321  	// See -strictdups command line flag.
   322  	checkStrictDups   int // 0=off 1=warning 2=error
   323  	strictDupMsgCount int
   324  )
   325  
   326  var (
   327  	Segtext      sym.Segment
   328  	Segrodata    sym.Segment
   329  	Segrelrodata sym.Segment
   330  	Segdata      sym.Segment
   331  	Segdwarf     sym.Segment
   332  	Segpdata     sym.Segment // windows-only
   333  	Segxdata     sym.Segment // windows-only
   334  
   335  	Segments = []*sym.Segment{&Segtext, &Segrodata, &Segrelrodata, &Segdata, &Segdwarf, &Segpdata, &Segxdata}
   336  )
   337  
   338  const pkgdef = "__.PKGDEF"
   339  
   340  var (
   341  	// externalobj is set to true if we see an object compiled by
   342  	// the host compiler that is not from a package that is known
   343  	// to support internal linking mode.
   344  	externalobj = false
   345  
   346  	// dynimportfail is a list of packages for which generating
   347  	// the dynimport file, _cgo_import.go, failed. If there are
   348  	// any of these objects, we must link externally. Issue 52863.
   349  	dynimportfail []string
   350  
   351  	// preferlinkext is a list of packages for which the Go command
   352  	// noticed use of peculiar C flags. If we see any of these,
   353  	// default to linking externally unless overridden by the
   354  	// user. See issues #58619, #58620, and #58848.
   355  	preferlinkext []string
   356  
   357  	// unknownObjFormat is set to true if we see an object whose
   358  	// format we don't recognize.
   359  	unknownObjFormat = false
   360  
   361  	theline string
   362  )
   363  
   364  func Lflag(ctxt *Link, arg string) {
   365  	ctxt.Libdir = append(ctxt.Libdir, arg)
   366  }
   367  
   368  /*
   369   * Unix doesn't like it when we write to a running (or, sometimes,
   370   * recently run) binary, so remove the output file before writing it.
   371   * On Windows 7, remove() can force a subsequent create() to fail.
   372   * S_ISREG() does not exist on Plan 9.
   373   */
   374  func mayberemoveoutfile() {
   375  	if fi, err := os.Lstat(*flagOutfile); err == nil && !fi.Mode().IsRegular() {
   376  		return
   377  	}
   378  	os.Remove(*flagOutfile)
   379  }
   380  
   381  func libinit(ctxt *Link) {
   382  	if *FlagFuncAlign != 0 {
   383  		Funcalign = *FlagFuncAlign
   384  	} else {
   385  		Funcalign = thearch.Funcalign
   386  	}
   387  
   388  	// add goroot to the end of the libdir list.
   389  	suffix := ""
   390  
   391  	suffixsep := ""
   392  	if *flagInstallSuffix != "" {
   393  		suffixsep = "_"
   394  		suffix = *flagInstallSuffix
   395  	} else if *flagRace {
   396  		suffixsep = "_"
   397  		suffix = "race"
   398  	} else if *flagMsan {
   399  		suffixsep = "_"
   400  		suffix = "msan"
   401  	} else if *flagAsan {
   402  		suffixsep = "_"
   403  		suffix = "asan"
   404  	}
   405  
   406  	if buildcfg.GOROOT != "" {
   407  		Lflag(ctxt, filepath.Join(buildcfg.GOROOT, "pkg", fmt.Sprintf("%s_%s%s%s", buildcfg.GOOS, buildcfg.GOARCH, suffixsep, suffix)))
   408  	}
   409  
   410  	mayberemoveoutfile()
   411  
   412  	if err := ctxt.Out.Open(*flagOutfile); err != nil {
   413  		Exitf("cannot create %s: %v", *flagOutfile, err)
   414  	}
   415  
   416  	if *flagEntrySymbol == "" {
   417  		switch ctxt.BuildMode {
   418  		case BuildModeCShared, BuildModeCArchive:
   419  			*flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s_lib", buildcfg.GOARCH, buildcfg.GOOS)
   420  		case BuildModeExe, BuildModePIE:
   421  			*flagEntrySymbol = fmt.Sprintf("_rt0_%s_%s", buildcfg.GOARCH, buildcfg.GOOS)
   422  		case BuildModeShared, BuildModePlugin:
   423  			// No *flagEntrySymbol for -buildmode=shared and plugin
   424  		default:
   425  			Errorf("unknown *flagEntrySymbol for buildmode %v", ctxt.BuildMode)
   426  		}
   427  	}
   428  }
   429  
   430  func exitIfErrors() {
   431  	if nerrors != 0 || checkStrictDups > 1 && strictDupMsgCount > 0 {
   432  		mayberemoveoutfile()
   433  		Exit(2)
   434  	}
   435  
   436  }
   437  
   438  func errorexit() {
   439  	exitIfErrors()
   440  	Exit(0)
   441  }
   442  
   443  func loadinternal(ctxt *Link, name string) *sym.Library {
   444  	zerofp := goobj.FingerprintType{}
   445  	if ctxt.linkShared && ctxt.PackageShlib != nil {
   446  		if shlib := ctxt.PackageShlib[name]; shlib != "" {
   447  			return addlibpath(ctxt, "internal", "internal", "", name, shlib, zerofp)
   448  		}
   449  	}
   450  	if ctxt.PackageFile != nil {
   451  		if pname := ctxt.PackageFile[name]; pname != "" {
   452  			return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
   453  		}
   454  		ctxt.Logf("loadinternal: cannot find %s\n", name)
   455  		return nil
   456  	}
   457  
   458  	for _, libdir := range ctxt.Libdir {
   459  		if ctxt.linkShared {
   460  			shlibname := filepath.Join(libdir, name+".shlibname")
   461  			if ctxt.Debugvlog != 0 {
   462  				ctxt.Logf("searching for %s.a in %s\n", name, shlibname)
   463  			}
   464  			if _, err := os.Stat(shlibname); err == nil {
   465  				return addlibpath(ctxt, "internal", "internal", "", name, shlibname, zerofp)
   466  			}
   467  		}
   468  		pname := filepath.Join(libdir, name+".a")
   469  		if ctxt.Debugvlog != 0 {
   470  			ctxt.Logf("searching for %s.a in %s\n", name, pname)
   471  		}
   472  		if _, err := os.Stat(pname); err == nil {
   473  			return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
   474  		}
   475  	}
   476  
   477  	if name == "runtime" {
   478  		Exitf("error: unable to find runtime.a")
   479  	}
   480  	ctxt.Logf("warning: unable to find %s.a\n", name)
   481  	return nil
   482  }
   483  
   484  // extld returns the current external linker.
   485  func (ctxt *Link) extld() []string {
   486  	if len(flagExtld) == 0 {
   487  		// Return the default external linker for the platform.
   488  		// This only matters when link tool is called directly without explicit -extld,
   489  		// go tool already passes the correct linker in other cases.
   490  		switch buildcfg.GOOS {
   491  		case "darwin", "freebsd", "openbsd":
   492  			flagExtld = []string{"clang"}
   493  		default:
   494  			flagExtld = []string{"gcc"}
   495  		}
   496  	}
   497  	return flagExtld
   498  }
   499  
   500  // findLibPathCmd uses cmd command to find gcc library libname.
   501  // It returns library full path if found, or "none" if not found.
   502  func (ctxt *Link) findLibPathCmd(cmd, libname string) string {
   503  	extld := ctxt.extld()
   504  	name, args := extld[0], extld[1:]
   505  	args = append(args, hostlinkArchArgs(ctxt.Arch)...)
   506  	args = append(args, cmd)
   507  	if ctxt.Debugvlog != 0 {
   508  		ctxt.Logf("%s %v\n", extld, args)
   509  	}
   510  	out, err := exec.Command(name, args...).Output()
   511  	if err != nil {
   512  		if ctxt.Debugvlog != 0 {
   513  			ctxt.Logf("not using a %s file because compiler failed\n%v\n%s\n", libname, err, out)
   514  		}
   515  		return "none"
   516  	}
   517  	return strings.TrimSpace(string(out))
   518  }
   519  
   520  // findLibPath searches for library libname.
   521  // It returns library full path if found, or "none" if not found.
   522  func (ctxt *Link) findLibPath(libname string) string {
   523  	return ctxt.findLibPathCmd("--print-file-name="+libname, libname)
   524  }
   525  
   526  func (ctxt *Link) loadlib() {
   527  	var flags uint32
   528  	if *flagCheckLinkname {
   529  		flags |= loader.FlagCheckLinkname
   530  	}
   531  	switch *FlagStrictDups {
   532  	case 0:
   533  		// nothing to do
   534  	case 1, 2:
   535  		flags |= loader.FlagStrictDups
   536  	default:
   537  		log.Fatalf("invalid -strictdups flag value %d", *FlagStrictDups)
   538  	}
   539  	ctxt.loader = loader.NewLoader(flags, &ctxt.ErrorReporter.ErrorReporter)
   540  	ctxt.ErrorReporter.SymName = func(s loader.Sym) string {
   541  		return ctxt.loader.SymName(s)
   542  	}
   543  
   544  	// ctxt.Library grows during the loop, so not a range loop.
   545  	i := 0
   546  	for ; i < len(ctxt.Library); i++ {
   547  		lib := ctxt.Library[i]
   548  		if lib.Shlib == "" {
   549  			if ctxt.Debugvlog > 1 {
   550  				ctxt.Logf("autolib: %s (from %s)\n", lib.File, lib.Objref)
   551  			}
   552  			loadobjfile(ctxt, lib)
   553  		}
   554  	}
   555  
   556  	// load internal packages, if not already
   557  	if *flagRace {
   558  		loadinternal(ctxt, "runtime/race")
   559  	}
   560  	if *flagMsan {
   561  		loadinternal(ctxt, "runtime/msan")
   562  	}
   563  	if *flagAsan {
   564  		loadinternal(ctxt, "runtime/asan")
   565  	}
   566  	loadinternal(ctxt, "runtime")
   567  	for ; i < len(ctxt.Library); i++ {
   568  		lib := ctxt.Library[i]
   569  		if lib.Shlib == "" {
   570  			loadobjfile(ctxt, lib)
   571  		}
   572  	}
   573  	// At this point, the Go objects are "preloaded". Not all the symbols are
   574  	// added to the symbol table (only defined package symbols are). Looking
   575  	// up symbol by name may not get expected result.
   576  
   577  	iscgo = ctxt.LibraryByPkg["runtime/cgo"] != nil
   578  
   579  	// Plugins a require cgo support to function. Similarly, plugins may require additional
   580  	// internal linker support on some platforms which may not be implemented.
   581  	ctxt.canUsePlugins = ctxt.LibraryByPkg["plugin"] != nil && iscgo &&
   582  		platform.BuildModeSupported("gc", "plugin", buildcfg.GOOS, buildcfg.GOARCH)
   583  
   584  	// We now have enough information to determine the link mode.
   585  	determineLinkMode(ctxt)
   586  
   587  	if ctxt.LinkMode == LinkExternal && !iscgo && !(buildcfg.GOOS == "darwin" && ctxt.BuildMode != BuildModePlugin && ctxt.Arch.Family == sys.AMD64) {
   588  		// This indicates a user requested -linkmode=external.
   589  		// The startup code uses an import of runtime/cgo to decide
   590  		// whether to initialize the TLS.  So give it one. This could
   591  		// be handled differently but it's an unusual case.
   592  		if lib := loadinternal(ctxt, "runtime/cgo"); lib != nil && lib.Shlib == "" {
   593  			if ctxt.BuildMode == BuildModeShared || ctxt.linkShared {
   594  				Exitf("cannot implicitly include runtime/cgo in a shared library")
   595  			}
   596  			for ; i < len(ctxt.Library); i++ {
   597  				lib := ctxt.Library[i]
   598  				if lib.Shlib == "" {
   599  					loadobjfile(ctxt, lib)
   600  				}
   601  			}
   602  		}
   603  	}
   604  
   605  	// Add non-package symbols and references of externally defined symbols.
   606  	ctxt.loader.LoadSyms(ctxt.Arch)
   607  
   608  	// Load symbols from shared libraries, after all Go object symbols are loaded.
   609  	for _, lib := range ctxt.Library {
   610  		if lib.Shlib != "" {
   611  			if ctxt.Debugvlog > 1 {
   612  				ctxt.Logf("autolib: %s (from %s)\n", lib.Shlib, lib.Objref)
   613  			}
   614  			ldshlibsyms(ctxt, lib.Shlib)
   615  		}
   616  	}
   617  
   618  	// Process cgo directives (has to be done before host object loading).
   619  	ctxt.loadcgodirectives()
   620  
   621  	// Conditionally load host objects, or setup for external linking.
   622  	hostobjs(ctxt)
   623  	hostlinksetup(ctxt)
   624  
   625  	if ctxt.LinkMode == LinkInternal && len(hostobj) != 0 {
   626  		// If we have any undefined symbols in external
   627  		// objects, try to read them from the libgcc file.
   628  		any := false
   629  		undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
   630  		if len(undefs) > 0 {
   631  			any = true
   632  			if ctxt.Debugvlog > 1 {
   633  				ctxt.Logf("loadlib: first unresolved is %s [%d] from %s [%d]\n",
   634  					ctxt.loader.SymName(undefs[0]), undefs[0],
   635  					ctxt.loader.SymName(froms[0]), froms[0])
   636  			}
   637  		}
   638  		if any {
   639  			if *flagLibGCC == "" {
   640  				*flagLibGCC = ctxt.findLibPathCmd("--print-libgcc-file-name", "libgcc")
   641  			}
   642  			if runtime.GOOS == "freebsd" && strings.HasPrefix(filepath.Base(*flagLibGCC), "libclang_rt.builtins") {
   643  				// On newer versions of FreeBSD, libgcc is returned as something like
   644  				// /usr/lib/clang/18/lib/freebsd/libclang_rt.builtins-x86_64.a.
   645  				// Unfortunately this ends up missing a bunch of symbols we need from
   646  				// libcompiler_rt.
   647  				*flagLibGCC = ctxt.findLibPathCmd("--print-file-name=libcompiler_rt.a", "libcompiler_rt")
   648  			}
   649  			if runtime.GOOS == "openbsd" && *flagLibGCC == "libgcc.a" {
   650  				// On OpenBSD `clang --print-libgcc-file-name` returns "libgcc.a".
   651  				// In this case we fail to load libgcc.a and can encounter link
   652  				// errors - see if we can find libcompiler_rt.a instead.
   653  				*flagLibGCC = ctxt.findLibPathCmd("--print-file-name=libcompiler_rt.a", "libcompiler_rt")
   654  			}
   655  			if ctxt.HeadType == objabi.Hwindows {
   656  				loadWindowsHostArchives(ctxt)
   657  			}
   658  			if *flagLibGCC != "none" {
   659  				hostArchive(ctxt, *flagLibGCC)
   660  			}
   661  			// For glibc systems, the linker setup used by GCC
   662  			// looks like
   663  			//
   664  			//  GROUP ( /lib/x86_64-linux-gnu/libc.so.6
   665  			//      /usr/lib/x86_64-linux-gnu/libc_nonshared.a
   666  			//      AS_NEEDED ( /lib64/ld-linux-x86-64.so.2 ) )
   667  			//
   668  			// where libc_nonshared.a contains a small set of
   669  			// symbols including "__stack_chk_fail_local" and a
   670  			// few others. Thus if we are doing internal linking
   671  			// and "__stack_chk_fail_local" is unresolved (most
   672  			// likely due to the use of -fstack-protector), try
   673  			// loading libc_nonshared.a to resolve it.
   674  			//
   675  			// On Alpine Linux (musl-based), the library providing
   676  			// this symbol is called libssp_nonshared.a.
   677  			isunresolved := symbolsAreUnresolved(ctxt, []string{"__stack_chk_fail_local"})
   678  			if isunresolved[0] {
   679  				if p := ctxt.findLibPath("libc_nonshared.a"); p != "none" {
   680  					hostArchive(ctxt, p)
   681  				}
   682  				if p := ctxt.findLibPath("libssp_nonshared.a"); p != "none" {
   683  					hostArchive(ctxt, p)
   684  				}
   685  			}
   686  		}
   687  	}
   688  
   689  	loadfips(ctxt)
   690  
   691  	// We've loaded all the code now.
   692  	ctxt.Loaded = true
   693  
   694  	strictDupMsgCount = ctxt.loader.NStrictDupMsgs()
   695  }
   696  
   697  // loadWindowsHostArchives loads in host archives and objects when
   698  // doing internal linking on windows. Older toolchains seem to require
   699  // just a single pass through the various archives, but some modern
   700  // toolchains when linking a C program with mingw pass library paths
   701  // multiple times to the linker, e.g. "... -lmingwex -lmingw32 ...
   702  // -lmingwex -lmingw32 ...". To accommodate this behavior, we make two
   703  // passes over the host archives below.
   704  func loadWindowsHostArchives(ctxt *Link) {
   705  	any := true
   706  	for i := 0; any && i < 2; i++ {
   707  		// Link crt2.o (if present) to resolve "atexit" when
   708  		// using LLVM-based compilers.
   709  		isunresolved := symbolsAreUnresolved(ctxt, []string{"atexit"})
   710  		if isunresolved[0] {
   711  			if p := ctxt.findLibPath("crt2.o"); p != "none" {
   712  				hostObject(ctxt, "crt2", p)
   713  			}
   714  		}
   715  		if *flagRace {
   716  			if p := ctxt.findLibPath("libsynchronization.a"); p != "none" {
   717  				hostArchive(ctxt, p)
   718  			}
   719  		}
   720  		if p := ctxt.findLibPath("libmingwex.a"); p != "none" {
   721  			hostArchive(ctxt, p)
   722  		}
   723  		if p := ctxt.findLibPath("libmingw32.a"); p != "none" {
   724  			hostArchive(ctxt, p)
   725  		}
   726  		// Link libmsvcrt.a to resolve '__acrt_iob_func' symbol
   727  		// (see https://golang.org/issue/23649 for details).
   728  		if p := ctxt.findLibPath("libmsvcrt.a"); p != "none" {
   729  			hostArchive(ctxt, p)
   730  		}
   731  		any = false
   732  		undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
   733  		if len(undefs) > 0 {
   734  			any = true
   735  			if ctxt.Debugvlog > 1 {
   736  				ctxt.Logf("loadWindowsHostArchives: remaining unresolved is %s [%d] from %s [%d]\n",
   737  					ctxt.loader.SymName(undefs[0]), undefs[0],
   738  					ctxt.loader.SymName(froms[0]), froms[0])
   739  			}
   740  		}
   741  	}
   742  	// If needed, create the __CTOR_LIST__ and __DTOR_LIST__
   743  	// symbols (referenced by some of the mingw support library
   744  	// routines). Creation of these symbols is normally done by the
   745  	// linker if not already present.
   746  	want := []string{"__CTOR_LIST__", "__DTOR_LIST__"}
   747  	isunresolved := symbolsAreUnresolved(ctxt, want)
   748  	for k, w := range want {
   749  		if isunresolved[k] {
   750  			sb := ctxt.loader.CreateSymForUpdate(w, 0)
   751  			sb.SetType(sym.SDATA)
   752  			sb.AddUint64(ctxt.Arch, 0)
   753  			sb.SetReachable(true)
   754  			ctxt.loader.SetAttrSpecial(sb.Sym(), true)
   755  		}
   756  	}
   757  
   758  	// Fix up references to DLL import symbols now that we're done
   759  	// pulling in new objects.
   760  	if err := loadpe.PostProcessImports(); err != nil {
   761  		Errorf("%v", err)
   762  	}
   763  
   764  	// TODO: maybe do something similar to peimporteddlls to collect
   765  	// all lib names and try link them all to final exe just like
   766  	// libmingwex.a and libmingw32.a:
   767  	/*
   768  		for:
   769  		#cgo windows LDFLAGS: -lmsvcrt -lm
   770  		import:
   771  		libmsvcrt.a libm.a
   772  	*/
   773  }
   774  
   775  // loadcgodirectives reads the previously discovered cgo directives, creating
   776  // symbols in preparation for host object loading or use later in the link.
   777  func (ctxt *Link) loadcgodirectives() {
   778  	l := ctxt.loader
   779  	hostObjSyms := make(map[loader.Sym]struct{})
   780  	for _, d := range ctxt.cgodata {
   781  		setCgoAttr(ctxt, d.file, d.pkg, d.directives, hostObjSyms)
   782  	}
   783  	ctxt.cgodata = nil
   784  
   785  	if ctxt.LinkMode == LinkInternal {
   786  		// Drop all the cgo_import_static declarations.
   787  		// Turns out we won't be needing them.
   788  		for symIdx := range hostObjSyms {
   789  			if l.SymType(symIdx) == sym.SHOSTOBJ {
   790  				// If a symbol was marked both
   791  				// cgo_import_static and cgo_import_dynamic,
   792  				// then we want to make it cgo_import_dynamic
   793  				// now.
   794  				su := l.MakeSymbolUpdater(symIdx)
   795  				if l.SymExtname(symIdx) != "" && l.SymDynimplib(symIdx) != "" && !(l.AttrCgoExportStatic(symIdx) || l.AttrCgoExportDynamic(symIdx)) {
   796  					su.SetType(sym.SDYNIMPORT)
   797  				} else {
   798  					su.SetType(0)
   799  				}
   800  			}
   801  		}
   802  	}
   803  }
   804  
   805  // Set up flags and special symbols depending on the platform build mode.
   806  // This version works with loader.Loader.
   807  func (ctxt *Link) linksetup() {
   808  	switch ctxt.BuildMode {
   809  	case BuildModeCShared, BuildModePlugin:
   810  		symIdx := ctxt.loader.LookupOrCreateSym("runtime.islibrary", 0)
   811  		sb := ctxt.loader.MakeSymbolUpdater(symIdx)
   812  		sb.SetType(sym.SNOPTRDATA)
   813  		sb.AddUint8(1)
   814  	case BuildModeCArchive:
   815  		symIdx := ctxt.loader.LookupOrCreateSym("runtime.isarchive", 0)
   816  		sb := ctxt.loader.MakeSymbolUpdater(symIdx)
   817  		sb.SetType(sym.SNOPTRDATA)
   818  		sb.AddUint8(1)
   819  	}
   820  
   821  	// Recalculate pe parameters now that we have ctxt.LinkMode set.
   822  	if ctxt.HeadType == objabi.Hwindows {
   823  		Peinit(ctxt)
   824  	}
   825  
   826  	if ctxt.LinkMode == LinkExternal {
   827  		// When external linking, we are creating an object file. The
   828  		// absolute address is irrelevant.
   829  		*FlagTextAddr = 0
   830  	}
   831  
   832  	// If there are no dynamic libraries needed, gcc disables dynamic linking.
   833  	// Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13)
   834  	// assumes that a dynamic binary always refers to at least one dynamic library.
   835  	// Rather than be a source of test cases for glibc, disable dynamic linking
   836  	// the same way that gcc would.
   837  	//
   838  	// Exception: on OS X, programs such as Shark only work with dynamic
   839  	// binaries, so leave it enabled on OS X (Mach-O) binaries.
   840  	// Also leave it enabled on Solaris which doesn't support
   841  	// statically linked binaries.
   842  	if ctxt.BuildMode == BuildModeExe {
   843  		if havedynamic == 0 && ctxt.HeadType != objabi.Hdarwin && ctxt.HeadType != objabi.Hsolaris {
   844  			*FlagD = true
   845  		}
   846  	}
   847  
   848  	if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && buildcfg.GOOS != "aix" {
   849  		toc := ctxt.loader.LookupOrCreateSym(".TOC.", 0)
   850  		sb := ctxt.loader.MakeSymbolUpdater(toc)
   851  		sb.SetType(sym.SDYNIMPORT)
   852  	}
   853  
   854  	// The Android Q linker started to complain about underalignment of the our TLS
   855  	// section. We don't actually use the section on android, so don't
   856  	// generate it.
   857  	if buildcfg.GOOS != "android" {
   858  		tlsg := ctxt.loader.LookupOrCreateSym("runtime.tlsg", 0)
   859  		sb := ctxt.loader.MakeSymbolUpdater(tlsg)
   860  
   861  		// runtime.tlsg is used for external linking on platforms that do not define
   862  		// a variable to hold g in assembly (currently only intel).
   863  		if sb.Type() == 0 {
   864  			sb.SetType(sym.STLSBSS)
   865  			sb.SetSize(int64(ctxt.Arch.PtrSize))
   866  		} else if sb.Type() != sym.SDYNIMPORT {
   867  			Errorf("runtime declared tlsg variable %v", sb.Type())
   868  		}
   869  		ctxt.loader.SetAttrReachable(tlsg, true)
   870  		ctxt.Tlsg = tlsg
   871  	}
   872  
   873  	var moduledata loader.Sym
   874  	var mdsb *loader.SymbolBuilder
   875  	if ctxt.BuildMode == BuildModePlugin {
   876  		moduledata = ctxt.loader.LookupOrCreateSym("local.pluginmoduledata", 0)
   877  		mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
   878  		ctxt.loader.SetAttrLocal(moduledata, true)
   879  	} else {
   880  		moduledata = ctxt.loader.LookupOrCreateSym("runtime.firstmoduledata", 0)
   881  		mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
   882  	}
   883  	if mdsb.Type() != 0 && mdsb.Type() != sym.SDYNIMPORT {
   884  		// If the module (toolchain-speak for "executable or shared
   885  		// library") we are linking contains the runtime package, it
   886  		// will define the runtime.firstmoduledata symbol and we
   887  		// truncate it back to 0 bytes so we can define its entire
   888  		// contents in symtab.go:symtab().
   889  		mdsb.SetSize(0)
   890  
   891  		// In addition, on ARM, the runtime depends on the linker
   892  		// recording the value of GOARM.
   893  		if ctxt.Arch.Family == sys.ARM {
   894  			goarm := ctxt.loader.LookupOrCreateSym("runtime.goarm", 0)
   895  			sb := ctxt.loader.MakeSymbolUpdater(goarm)
   896  			sb.SetType(sym.SNOPTRDATA)
   897  			sb.SetSize(0)
   898  			sb.AddUint8(uint8(buildcfg.GOARM.Version))
   899  
   900  			goarmsoftfp := ctxt.loader.LookupOrCreateSym("runtime.goarmsoftfp", 0)
   901  			sb2 := ctxt.loader.MakeSymbolUpdater(goarmsoftfp)
   902  			sb2.SetType(sym.SNOPTRDATA)
   903  			sb2.SetSize(0)
   904  			if buildcfg.GOARM.SoftFloat {
   905  				sb2.AddUint8(1)
   906  			} else {
   907  				sb2.AddUint8(0)
   908  			}
   909  		}
   910  
   911  		// Set runtime.disableMemoryProfiling bool if
   912  		// runtime.memProfileInternal is not retained in the binary after
   913  		// deadcode (and we're not dynamically linking).
   914  		memProfile := ctxt.loader.Lookup("runtime.memProfileInternal", abiInternalVer)
   915  		if memProfile != 0 && !ctxt.loader.AttrReachable(memProfile) && !ctxt.DynlinkingGo() {
   916  			memProfSym := ctxt.loader.LookupOrCreateSym("runtime.disableMemoryProfiling", 0)
   917  			sb := ctxt.loader.MakeSymbolUpdater(memProfSym)
   918  			sb.SetType(sym.SNOPTRDATA)
   919  			sb.SetSize(0)
   920  			sb.AddUint8(1) // true bool
   921  		}
   922  	} else {
   923  		// If OTOH the module does not contain the runtime package,
   924  		// create a local symbol for the moduledata.
   925  		moduledata = ctxt.loader.LookupOrCreateSym("local.moduledata", 0)
   926  		mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
   927  		ctxt.loader.SetAttrLocal(moduledata, true)
   928  	}
   929  	mdsb.SetType(sym.SMODULEDATA)
   930  	ctxt.loader.SetAttrReachable(moduledata, true)
   931  	ctxt.Moduledata = moduledata
   932  
   933  	if ctxt.Arch == sys.Arch386 && ctxt.HeadType != objabi.Hwindows {
   934  		if (ctxt.BuildMode == BuildModeCArchive && ctxt.IsELF) || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE || ctxt.DynlinkingGo() {
   935  			got := ctxt.loader.LookupOrCreateSym("_GLOBAL_OFFSET_TABLE_", 0)
   936  			sb := ctxt.loader.MakeSymbolUpdater(got)
   937  			sb.SetType(sym.SDYNIMPORT)
   938  			ctxt.loader.SetAttrReachable(got, true)
   939  		}
   940  	}
   941  
   942  	// DWARF-gen and other phases require that the unit Textp slices
   943  	// be populated, so that it can walk the functions in each unit.
   944  	// Call into the loader to do this (requires that we collect the
   945  	// set of internal libraries first). NB: might be simpler if we
   946  	// moved isRuntimeDepPkg to cmd/internal and then did the test in
   947  	// loader.AssignTextSymbolOrder.
   948  	ctxt.Library = postorder(ctxt.Library)
   949  	intlibs := []bool{}
   950  	for _, lib := range ctxt.Library {
   951  		intlibs = append(intlibs, isRuntimeDepPkg(lib.Pkg))
   952  	}
   953  	ctxt.Textp = ctxt.loader.AssignTextSymbolOrder(ctxt.Library, intlibs, ctxt.Textp)
   954  }
   955  
   956  // mangleTypeSym shortens the names of symbols that represent Go types
   957  // if they are visible in the symbol table.
   958  //
   959  // As the names of these symbols are derived from the string of
   960  // the type, they can run to many kilobytes long. So we shorten
   961  // them using a SHA-1 when the name appears in the final binary.
   962  // This also removes characters that upset external linkers.
   963  //
   964  // These are the symbols that begin with the prefix 'type.' and
   965  // contain run-time type information used by the runtime and reflect
   966  // packages. All Go binaries contain these symbols, but only
   967  // those programs loaded dynamically in multiple parts need these
   968  // symbols to have entries in the symbol table.
   969  func (ctxt *Link) mangleTypeSym() {
   970  	if ctxt.BuildMode != BuildModeShared && !ctxt.linkShared && ctxt.BuildMode != BuildModePlugin && !ctxt.CanUsePlugins() {
   971  		return
   972  	}
   973  
   974  	ldr := ctxt.loader
   975  	for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
   976  		if !ldr.AttrReachable(s) && !ctxt.linkShared {
   977  			// If -linkshared, the gc mask generation code may need to reach
   978  			// out to the shared library for the type descriptor's data, even
   979  			// the type descriptor itself is not actually needed at run time
   980  			// (therefore not reachable). We still need to mangle its name,
   981  			// so it is consistent with the one stored in the shared library.
   982  			continue
   983  		}
   984  		name := ldr.SymName(s)
   985  		newName := typeSymbolMangle(name)
   986  		if newName != name {
   987  			ldr.SetSymExtname(s, newName)
   988  
   989  			// When linking against a shared library, the Go object file may
   990  			// have reference to the original symbol name whereas the shared
   991  			// library provides a symbol with the mangled name. We need to
   992  			// copy the payload of mangled to original.
   993  			// XXX maybe there is a better way to do this.
   994  			dup := ldr.Lookup(newName, ldr.SymVersion(s))
   995  			if dup != 0 {
   996  				st := ldr.SymType(s)
   997  				dt := ldr.SymType(dup)
   998  				if st == sym.Sxxx && dt != sym.Sxxx {
   999  					ldr.CopySym(dup, s)
  1000  				}
  1001  			}
  1002  		}
  1003  	}
  1004  }
  1005  
  1006  // typeSymbolMangle mangles the given symbol name into something shorter.
  1007  //
  1008  // Keep the type:. prefix, which parts of the linker (like the
  1009  // DWARF generator) know means the symbol is not decodable.
  1010  // Leave type:runtime. symbols alone, because other parts of
  1011  // the linker manipulates them.
  1012  func typeSymbolMangle(name string) string {
  1013  	isType := strings.HasPrefix(name, "type:")
  1014  	if !isType && !strings.Contains(name, "@") {
  1015  		// Issue 58800: instantiated symbols may include a type name, which may contain "@"
  1016  		return name
  1017  	}
  1018  	if strings.HasPrefix(name, "type:runtime.") {
  1019  		return name
  1020  	}
  1021  	if strings.HasPrefix(name, "go:string.") {
  1022  		// String symbols will be grouped to a single go:string.* symbol.
  1023  		// No need to mangle individual symbol names.
  1024  		return name
  1025  	}
  1026  	if len(name) <= 14 && !strings.Contains(name, "@") { // Issue 19529
  1027  		return name
  1028  	}
  1029  	if isType {
  1030  		hb := hash.Sum32([]byte(name[5:]))
  1031  		prefix := "type:"
  1032  		if name[5] == '.' {
  1033  			prefix = "type:."
  1034  		}
  1035  		return prefix + base64.StdEncoding.EncodeToString(hb[:6])
  1036  	}
  1037  	// instantiated symbol, replace type name in []
  1038  	i := strings.IndexByte(name, '[')
  1039  	j := strings.LastIndexByte(name, ']')
  1040  	if j == -1 || j <= i {
  1041  		j = len(name)
  1042  	}
  1043  	hb := hash.Sum32([]byte(name[i+1 : j]))
  1044  	return name[:i+1] + base64.StdEncoding.EncodeToString(hb[:6]) + name[j:]
  1045  }
  1046  
  1047  /*
  1048   * look for the next file in an archive.
  1049   * adapted from libmach.
  1050   */
  1051  func nextar(bp *bio.Reader, off int64, a *ArHdr) int64 {
  1052  	if off&1 != 0 {
  1053  		off++
  1054  	}
  1055  	bp.MustSeek(off, 0)
  1056  	var buf [SAR_HDR]byte
  1057  	if n, err := io.ReadFull(bp, buf[:]); err != nil {
  1058  		if n == 0 && err != io.EOF {
  1059  			return -1
  1060  		}
  1061  		return 0
  1062  	}
  1063  
  1064  	a.name = artrim(buf[0:16])
  1065  	a.date = artrim(buf[16:28])
  1066  	a.uid = artrim(buf[28:34])
  1067  	a.gid = artrim(buf[34:40])
  1068  	a.mode = artrim(buf[40:48])
  1069  	a.size = artrim(buf[48:58])
  1070  	a.fmag = artrim(buf[58:60])
  1071  
  1072  	arsize := atolwhex(a.size)
  1073  	if arsize&1 != 0 {
  1074  		arsize++
  1075  	}
  1076  	return arsize + SAR_HDR
  1077  }
  1078  
  1079  func loadobjfile(ctxt *Link, lib *sym.Library) {
  1080  	pkg := objabi.PathToPrefix(lib.Pkg)
  1081  
  1082  	if ctxt.Debugvlog > 1 {
  1083  		ctxt.Logf("ldobj: %s (%s)\n", lib.File, pkg)
  1084  	}
  1085  	f, err := bio.Open(lib.File)
  1086  	if err != nil {
  1087  		Exitf("cannot open file %s: %v", lib.File, err)
  1088  	}
  1089  	defer f.Close()
  1090  	defer func() {
  1091  		if pkg == "main" && !lib.Main {
  1092  			Exitf("%s: not package main", lib.File)
  1093  		}
  1094  	}()
  1095  
  1096  	for i := 0; i < len(ARMAG); i++ {
  1097  		if c, err := f.ReadByte(); err == nil && c == ARMAG[i] {
  1098  			continue
  1099  		}
  1100  
  1101  		/* load it as a regular file */
  1102  		l := f.MustSeek(0, 2)
  1103  		f.MustSeek(0, 0)
  1104  		ldobj(ctxt, f, lib, l, lib.File, lib.File)
  1105  		return
  1106  	}
  1107  
  1108  	/*
  1109  	 * load all the object files from the archive now.
  1110  	 * this gives us sequential file access and keeps us
  1111  	 * from needing to come back later to pick up more
  1112  	 * objects.  it breaks the usual C archive model, but
  1113  	 * this is Go, not C.  the common case in Go is that
  1114  	 * we need to load all the objects, and then we throw away
  1115  	 * the individual symbols that are unused.
  1116  	 *
  1117  	 * loading every object will also make it possible to
  1118  	 * load foreign objects not referenced by __.PKGDEF.
  1119  	 */
  1120  	var arhdr ArHdr
  1121  	off := f.Offset()
  1122  	for {
  1123  		l := nextar(f, off, &arhdr)
  1124  		if l == 0 {
  1125  			break
  1126  		}
  1127  		if l < 0 {
  1128  			Exitf("%s: malformed archive", lib.File)
  1129  		}
  1130  		off += l
  1131  
  1132  		// __.PKGDEF isn't a real Go object file, and it's
  1133  		// absent in -linkobj builds anyway. Skipping it
  1134  		// ensures consistency between -linkobj and normal
  1135  		// build modes.
  1136  		if arhdr.name == pkgdef {
  1137  			continue
  1138  		}
  1139  
  1140  		if arhdr.name == "dynimportfail" {
  1141  			dynimportfail = append(dynimportfail, lib.Pkg)
  1142  		}
  1143  		if arhdr.name == "preferlinkext" {
  1144  			// Ignore this directive if -linkmode has been
  1145  			// set explicitly.
  1146  			if ctxt.LinkMode == LinkAuto {
  1147  				preferlinkext = append(preferlinkext, lib.Pkg)
  1148  			}
  1149  		}
  1150  
  1151  		// Skip other special (non-object-file) sections that
  1152  		// build tools may have added. Such sections must have
  1153  		// short names so that the suffix is not truncated.
  1154  		if len(arhdr.name) < 16 {
  1155  			if ext := filepath.Ext(arhdr.name); ext != ".o" && ext != ".syso" {
  1156  				continue
  1157  			}
  1158  		}
  1159  
  1160  		pname := fmt.Sprintf("%s(%s)", lib.File, arhdr.name)
  1161  		l = atolwhex(arhdr.size)
  1162  		ldobj(ctxt, f, lib, l, pname, lib.File)
  1163  	}
  1164  }
  1165  
  1166  type Hostobj struct {
  1167  	ld     func(*Link, *bio.Reader, string, int64, string)
  1168  	pkg    string
  1169  	pn     string
  1170  	file   string
  1171  	off    int64
  1172  	length int64
  1173  }
  1174  
  1175  var hostobj []Hostobj
  1176  
  1177  // These packages can use internal linking mode.
  1178  // Others trigger external mode.
  1179  var internalpkg = []string{
  1180  	"crypto/internal/boring",
  1181  	"crypto/internal/boring/syso",
  1182  	"crypto/x509",
  1183  	"net",
  1184  	"os/user",
  1185  	"runtime/cgo",
  1186  	"runtime/race",
  1187  	"runtime/race/internal/amd64v1",
  1188  	"runtime/race/internal/amd64v3",
  1189  	"runtime/msan",
  1190  	"runtime/asan",
  1191  }
  1192  
  1193  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 {
  1194  	isinternal := false
  1195  	for _, intpkg := range internalpkg {
  1196  		if pkg == intpkg {
  1197  			isinternal = true
  1198  			break
  1199  		}
  1200  	}
  1201  
  1202  	// DragonFly declares errno with __thread, which results in a symbol
  1203  	// type of R_386_TLS_GD or R_X86_64_TLSGD. The Go linker does not
  1204  	// currently know how to handle TLS relocations, hence we have to
  1205  	// force external linking for any libraries that link in code that
  1206  	// uses errno. This can be removed if the Go linker ever supports
  1207  	// these relocation types.
  1208  	if headType == objabi.Hdragonfly {
  1209  		if pkg == "net" || pkg == "os/user" {
  1210  			isinternal = false
  1211  		}
  1212  	}
  1213  
  1214  	if !isinternal {
  1215  		externalobj = true
  1216  	}
  1217  
  1218  	hostobj = append(hostobj, Hostobj{})
  1219  	h := &hostobj[len(hostobj)-1]
  1220  	h.ld = ld
  1221  	h.pkg = pkg
  1222  	h.pn = pn
  1223  	h.file = file
  1224  	h.off = f.Offset()
  1225  	h.length = length
  1226  	return h
  1227  }
  1228  
  1229  func hostobjs(ctxt *Link) {
  1230  	if ctxt.LinkMode != LinkInternal {
  1231  		return
  1232  	}
  1233  	var h *Hostobj
  1234  
  1235  	for i := 0; i < len(hostobj); i++ {
  1236  		h = &hostobj[i]
  1237  		f, err := bio.Open(h.file)
  1238  		if err != nil {
  1239  			Exitf("cannot reopen %s: %v", h.pn, err)
  1240  		}
  1241  		f.MustSeek(h.off, 0)
  1242  		if h.ld == nil {
  1243  			Errorf("%s: unrecognized object file format", h.pn)
  1244  			continue
  1245  		}
  1246  		h.ld(ctxt, f, h.pkg, h.length, h.pn)
  1247  		if *flagCaptureHostObjs != "" {
  1248  			captureHostObj(h)
  1249  		}
  1250  		f.Close()
  1251  	}
  1252  }
  1253  
  1254  func hostlinksetup(ctxt *Link) {
  1255  	if ctxt.LinkMode != LinkExternal {
  1256  		return
  1257  	}
  1258  
  1259  	// For external link, record that we need to tell the external linker -s,
  1260  	// and turn off -s internally: the external linker needs the symbol
  1261  	// information for its final link.
  1262  	debug_s = *FlagS
  1263  	*FlagS = false
  1264  
  1265  	// create temporary directory and arrange cleanup
  1266  	if *flagTmpdir == "" {
  1267  		dir, err := os.MkdirTemp("", "go-link-")
  1268  		if err != nil {
  1269  			log.Fatal(err)
  1270  		}
  1271  		*flagTmpdir = dir
  1272  		ownTmpDir = true
  1273  		AtExit(func() {
  1274  			os.RemoveAll(*flagTmpdir)
  1275  		})
  1276  	}
  1277  
  1278  	// change our output to temporary object file
  1279  	if err := ctxt.Out.Close(); err != nil {
  1280  		Exitf("error closing output file")
  1281  	}
  1282  	mayberemoveoutfile()
  1283  
  1284  	p := filepath.Join(*flagTmpdir, "go.o")
  1285  	if err := ctxt.Out.Open(p); err != nil {
  1286  		Exitf("cannot create %s: %v", p, err)
  1287  	}
  1288  }
  1289  
  1290  // cleanTimeStamps resets the timestamps for the specified list of
  1291  // existing files to the Unix epoch (1970-01-01 00:00:00 +0000 UTC).
  1292  // We take this step in order to help preserve reproducible builds;
  1293  // this seems to be primarily needed for external linking on Darwin
  1294  // with later versions of xcode, which (unfortunately) seem to want to
  1295  // incorporate object file times into the final output file's build
  1296  // ID. See issue 64947 for the unpleasant details.
  1297  func cleanTimeStamps(files []string) {
  1298  	epocht := time.Unix(0, 0)
  1299  	for _, f := range files {
  1300  		if err := os.Chtimes(f, epocht, epocht); err != nil {
  1301  			Exitf("cannot chtimes %s: %v", f, err)
  1302  		}
  1303  	}
  1304  }
  1305  
  1306  // hostobjCopy creates a copy of the object files in hostobj in a
  1307  // temporary directory.
  1308  func (ctxt *Link) hostobjCopy() (paths []string) {
  1309  	var wg sync.WaitGroup
  1310  	sema := make(chan struct{}, runtime.NumCPU()) // limit open file descriptors
  1311  	for i, h := range hostobj {
  1312  		h := h
  1313  		dst := filepath.Join(*flagTmpdir, fmt.Sprintf("%06d.o", i))
  1314  		paths = append(paths, dst)
  1315  		if ctxt.Debugvlog != 0 {
  1316  			ctxt.Logf("host obj copy: %s from pkg %s -> %s\n", h.pn, h.pkg, dst)
  1317  		}
  1318  
  1319  		wg.Add(1)
  1320  		go func() {
  1321  			sema <- struct{}{}
  1322  			defer func() {
  1323  				<-sema
  1324  				wg.Done()
  1325  			}()
  1326  			f, err := os.Open(h.file)
  1327  			if err != nil {
  1328  				Exitf("cannot reopen %s: %v", h.pn, err)
  1329  			}
  1330  			defer f.Close()
  1331  			if _, err := f.Seek(h.off, 0); err != nil {
  1332  				Exitf("cannot seek %s: %v", h.pn, err)
  1333  			}
  1334  
  1335  			w, err := os.Create(dst)
  1336  			if err != nil {
  1337  				Exitf("cannot create %s: %v", dst, err)
  1338  			}
  1339  			if _, err := io.CopyN(w, f, h.length); err != nil {
  1340  				Exitf("cannot write %s: %v", dst, err)
  1341  			}
  1342  			if err := w.Close(); err != nil {
  1343  				Exitf("cannot close %s: %v", dst, err)
  1344  			}
  1345  		}()
  1346  	}
  1347  	wg.Wait()
  1348  	return paths
  1349  }
  1350  
  1351  // writeGDBLinkerScript creates gcc linker script file in temp
  1352  // directory. writeGDBLinkerScript returns created file path.
  1353  // The script is used to work around gcc bug
  1354  // (see https://golang.org/issue/20183 for details).
  1355  func writeGDBLinkerScript() string {
  1356  	name := "fix_debug_gdb_scripts.ld"
  1357  	path := filepath.Join(*flagTmpdir, name)
  1358  	src := `SECTIONS
  1359  {
  1360    .debug_gdb_scripts BLOCK(__section_alignment__) (NOLOAD) :
  1361    {
  1362      *(.debug_gdb_scripts)
  1363    }
  1364  }
  1365  INSERT AFTER .debug_types;
  1366  `
  1367  	err := os.WriteFile(path, []byte(src), 0666)
  1368  	if err != nil {
  1369  		Errorf("WriteFile %s failed: %v", name, err)
  1370  	}
  1371  	return path
  1372  }
  1373  
  1374  type machoUpdateFunc func(ctxt *Link, exef *os.File, exem *macho.File, outexe string) error
  1375  
  1376  // archive builds a .a archive from the hostobj object files.
  1377  func (ctxt *Link) archive() {
  1378  	if ctxt.BuildMode != BuildModeCArchive {
  1379  		return
  1380  	}
  1381  
  1382  	exitIfErrors()
  1383  
  1384  	if *flagExtar == "" {
  1385  		const printProgName = "--print-prog-name=ar"
  1386  		cc := ctxt.extld()
  1387  		*flagExtar = "ar"
  1388  		if linkerFlagSupported(ctxt.Arch, cc[0], "", printProgName) {
  1389  			*flagExtar = ctxt.findExtLinkTool("ar")
  1390  		}
  1391  	}
  1392  
  1393  	mayberemoveoutfile()
  1394  
  1395  	// Force the buffer to flush here so that external
  1396  	// tools will see a complete file.
  1397  	if err := ctxt.Out.Close(); err != nil {
  1398  		Exitf("error closing %v", *flagOutfile)
  1399  	}
  1400  
  1401  	argv := []string{*flagExtar, "-q", "-c", "-s"}
  1402  	if ctxt.HeadType == objabi.Haix {
  1403  		argv = append(argv, "-X64")
  1404  	}
  1405  	godotopath := filepath.Join(*flagTmpdir, "go.o")
  1406  	cleanTimeStamps([]string{godotopath})
  1407  	hostObjCopyPaths := ctxt.hostobjCopy()
  1408  	cleanTimeStamps(hostObjCopyPaths)
  1409  
  1410  	argv = append(argv, *flagOutfile)
  1411  	argv = append(argv, godotopath)
  1412  	argv = append(argv, hostObjCopyPaths...)
  1413  
  1414  	if ctxt.Debugvlog != 0 {
  1415  		ctxt.Logf("archive: %s\n", strings.Join(argv, " "))
  1416  	}
  1417  
  1418  	// If supported, use syscall.Exec() to invoke the archive command,
  1419  	// which should be the final remaining step needed for the link.
  1420  	// This will reduce peak RSS for the link (and speed up linking of
  1421  	// large applications), since when the archive command runs we
  1422  	// won't be holding onto all of the linker's live memory.
  1423  	if syscallExecSupported && !ownTmpDir {
  1424  		runAtExitFuncs()
  1425  		ctxt.execArchive(argv)
  1426  		panic("should not get here")
  1427  	}
  1428  
  1429  	// Otherwise invoke 'ar' in the usual way (fork + exec).
  1430  	if out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput(); err != nil {
  1431  		Exitf("running %s failed: %v\n%s", argv[0], err, out)
  1432  	}
  1433  }
  1434  
  1435  func (ctxt *Link) hostlink() {
  1436  	if ctxt.LinkMode != LinkExternal || nerrors > 0 {
  1437  		return
  1438  	}
  1439  	if ctxt.BuildMode == BuildModeCArchive {
  1440  		return
  1441  	}
  1442  
  1443  	var argv []string
  1444  	argv = append(argv, ctxt.extld()...)
  1445  	argv = append(argv, hostlinkArchArgs(ctxt.Arch)...)
  1446  
  1447  	if *FlagS || debug_s {
  1448  		if ctxt.HeadType == objabi.Hdarwin {
  1449  			// Recent versions of macOS print
  1450  			//	ld: warning: option -s is obsolete and being ignored
  1451  			// so do not pass any arguments (but we strip symbols below).
  1452  		} else {
  1453  			argv = append(argv, "-s")
  1454  		}
  1455  	} else if *FlagW {
  1456  		if !ctxt.IsAIX() && !ctxt.IsSolaris() { // The AIX and Solaris linkers' -S has different meaning
  1457  			argv = append(argv, "-Wl,-S") // suppress debugging symbols
  1458  		}
  1459  	}
  1460  
  1461  	// On darwin, whether to combine DWARF into executable.
  1462  	// Only macOS supports unmapped segments such as our __DWARF segment.
  1463  	combineDwarf := ctxt.IsDarwin() && !*FlagW && machoPlatform == PLATFORM_MACOS
  1464  
  1465  	var isMSVC, isLLD bool // used on Windows
  1466  	wlPrefix := "-Wl,--"
  1467  
  1468  	switch ctxt.HeadType {
  1469  	case objabi.Hdarwin:
  1470  		if combineDwarf {
  1471  			// Leave room for DWARF combining.
  1472  			// -headerpad is incompatible with -fembed-bitcode.
  1473  			argv = append(argv, "-Wl,-headerpad,1144")
  1474  		}
  1475  		if ctxt.DynlinkingGo() && buildcfg.GOOS != "ios" {
  1476  			// -flat_namespace is deprecated on iOS.
  1477  			// It is useful for supporting plugins. We don't support plugins on iOS.
  1478  			// -flat_namespace may cause the dynamic linker to hang at forkExec when
  1479  			// resolving a lazy binding. See issue 38824.
  1480  			// Force eager resolution to work around.
  1481  			argv = append(argv, "-Wl,-flat_namespace", "-Wl,-bind_at_load")
  1482  		}
  1483  		if !combineDwarf {
  1484  			argv = append(argv, "-Wl,-S") // suppress STAB (symbolic debugging) symbols
  1485  			if debug_s {
  1486  				// We are generating a binary with symbol table suppressed.
  1487  				// Suppress local symbols. We need to keep dynamically exported
  1488  				// and referenced symbols so the dynamic linker can resolve them.
  1489  				argv = append(argv, "-Wl,-x")
  1490  			}
  1491  		}
  1492  		if *flagRace {
  1493  			// With https://github.com/llvm/llvm-project/pull/182943, the race object
  1494  			// has a weak import of __dyld_get_dyld_header, which is only defined on
  1495  			// newer macOS (26.4+).
  1496  			argv = append(argv, "-Wl,-U,__dyld_get_dyld_header")
  1497  		}
  1498  		if *flagHostBuildid == "none" {
  1499  			argv = append(argv, "-Wl,-no_uuid")
  1500  		}
  1501  	case objabi.Hopenbsd:
  1502  		argv = append(argv, "-pthread")
  1503  		if ctxt.BuildMode != BuildModePIE {
  1504  			argv = append(argv, "-Wl,-nopie")
  1505  		}
  1506  		if linkerFlagSupported(ctxt.Arch, argv[0], "", "-Wl,-z,nobtcfi") {
  1507  			// -Wl,-z,nobtcfi is only supported on OpenBSD 7.4+, remove guard
  1508  			// when OpenBSD 7.5 is released and 7.3 is no longer supported.
  1509  			argv = append(argv, "-Wl,-z,nobtcfi")
  1510  		}
  1511  		if ctxt.Arch.InFamily(sys.ARM64) {
  1512  			// Disable execute-only on openbsd/arm64 - the Go arm64 assembler
  1513  			// currently stores constants in the text section rather than in rodata.
  1514  			// See issue #59615.
  1515  			argv = append(argv, "-Wl,--no-execute-only")
  1516  		}
  1517  	case objabi.Hwindows:
  1518  		isMSVC = ctxt.isMSVC()
  1519  		if !isMSVC {
  1520  			isLLD = ctxt.isLLD()
  1521  		}
  1522  		if isMSVC {
  1523  			// For various options, MSVC lld-link only accepts one dash.
  1524  			// TODO: It seems mingw clang supports one or two dashes,
  1525  			// maybe we can always use one dash,  but I'm not sure about
  1526  			// legacy compilers that currently work.
  1527  			wlPrefix = "-Wl,-"
  1528  		}
  1529  
  1530  		if windowsgui {
  1531  			argv = append(argv, "-mwindows")
  1532  		} else {
  1533  			argv = append(argv, "-mconsole")
  1534  		}
  1535  		// Mark as having awareness of terminal services, to avoid
  1536  		// ancient compatibility hacks.
  1537  
  1538  		argv = append(argv, wlPrefix+"tsaware")
  1539  
  1540  		// Enable DEP
  1541  		argv = append(argv, wlPrefix+"nxcompat")
  1542  
  1543  		if !isMSVC {
  1544  			peMajorVersion := PeMinimumTargetMajorVersion
  1545  			peMinorVersion := PeMinimumTargetMinorVersion
  1546  			if peMajorVersion >= 10 && !isLLD &&
  1547  				!peHasLoadConfigDirectorySupport(ctxt.Arch, argv[0]) {
  1548  				// The external linker doesn't support wiring up
  1549  				// _load_config_used to the PE Load Configuration
  1550  				// Directory. Windows 10+ validates this directory,
  1551  				// so fall back to an older version to avoid
  1552  				// load failures.
  1553  				peMajorVersion = 6
  1554  				peMinorVersion = 1
  1555  			}
  1556  			argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", peMajorVersion))
  1557  			argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", peMinorVersion))
  1558  			argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", peMajorVersion))
  1559  			argv = append(argv, fmt.Sprintf("-Wl,--minor-subsystem-version=%d", peMinorVersion))
  1560  		}
  1561  	case objabi.Haix:
  1562  		argv = append(argv, "-pthread")
  1563  		// prevent ld to reorder .text functions to keep the same
  1564  		// first/last functions for moduledata.
  1565  		argv = append(argv, "-Wl,-bnoobjreorder")
  1566  		// mcmodel=large is needed for every gcc generated files, but
  1567  		// ld still need -bbigtoc in order to allow larger TOC.
  1568  		argv = append(argv, "-mcmodel=large")
  1569  		argv = append(argv, "-Wl,-bbigtoc")
  1570  	}
  1571  
  1572  	// On PPC64, verify the external toolchain supports Power10. This is needed when
  1573  	// PC relative relocations might be generated by Go. Only targets compiling ELF
  1574  	// binaries might generate these relocations.
  1575  	if ctxt.IsPPC64() && ctxt.IsElf() && buildcfg.GOPPC64 >= 10 {
  1576  		if !linkerFlagSupported(ctxt.Arch, argv[0], "", "-mcpu=power10") {
  1577  			Exitf("The external toolchain does not support -mcpu=power10. " +
  1578  				" This is required to externally link GOPPC64 >= power10")
  1579  		}
  1580  	}
  1581  
  1582  	// Enable/disable ASLR on Windows.
  1583  	addASLRargs := func(argv []string, val bool) []string {
  1584  		// Old/ancient versions of GCC support "--dynamicbase" and
  1585  		// "--high-entropy-va" but don't enable it by default. In
  1586  		// addition, they don't accept "--disable-dynamicbase" or
  1587  		// "--no-dynamicbase", so the only way to disable ASLR is to
  1588  		// not pass any flags at all.
  1589  		//
  1590  		// More modern versions of GCC (and also clang) enable ASLR
  1591  		// by default. With these compilers, however you can turn it
  1592  		// off if you want using "--disable-dynamicbase" or
  1593  		// "--no-dynamicbase".
  1594  		//
  1595  		// The strategy below is to try using "--disable-dynamicbase";
  1596  		// if this succeeds, then assume we're working with more
  1597  		// modern compilers and act accordingly. If it fails, assume
  1598  		// an ancient compiler with ancient defaults.
  1599  		var dbopt string
  1600  		var heopt string
  1601  		dbon := wlPrefix + "dynamicbase"
  1602  		heon := wlPrefix + "high-entropy-va"
  1603  		dboff := wlPrefix + "disable-dynamicbase"
  1604  		heoff := wlPrefix + "disable-high-entropy-va"
  1605  		if isMSVC {
  1606  			heon = wlPrefix + "highentropyva"
  1607  			heoff = wlPrefix + "highentropyva:no"
  1608  			dboff = wlPrefix + "dynamicbase:no"
  1609  		}
  1610  		if val {
  1611  			dbopt = dbon
  1612  			heopt = heon
  1613  		} else {
  1614  			// Test to see whether "--disable-dynamicbase" works.
  1615  			newer := linkerFlagSupported(ctxt.Arch, argv[0], "", dboff)
  1616  			if newer {
  1617  				// Newer compiler, which supports both on/off options.
  1618  				dbopt = dboff
  1619  				heopt = heoff
  1620  			} else {
  1621  				// older toolchain: we have to say nothing in order to
  1622  				// get a no-ASLR binary.
  1623  				dbopt = ""
  1624  				heopt = ""
  1625  			}
  1626  		}
  1627  		if dbopt != "" {
  1628  			argv = append(argv, dbopt)
  1629  		}
  1630  		// enable high-entropy ASLR on 64-bit.
  1631  		if ctxt.Arch.PtrSize >= 8 && heopt != "" {
  1632  			argv = append(argv, heopt)
  1633  		}
  1634  		return argv
  1635  	}
  1636  
  1637  	switch ctxt.BuildMode {
  1638  	case BuildModeExe:
  1639  		if ctxt.HeadType == objabi.Hdarwin {
  1640  			if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() {
  1641  				argv = append(argv, "-Wl,-no_pie")
  1642  			}
  1643  		}
  1644  		if *flagRace && ctxt.HeadType == objabi.Hwindows {
  1645  			// Current windows/amd64 race detector tsan support
  1646  			// library can't handle PIE mode (see #53539 for more details).
  1647  			// For now, explicitly disable PIE (since some compilers
  1648  			// default to it) if -race is in effect.
  1649  			argv = addASLRargs(argv, false)
  1650  		}
  1651  	case BuildModePIE:
  1652  		switch ctxt.HeadType {
  1653  		case objabi.Hdarwin, objabi.Haix:
  1654  		case objabi.Hwindows:
  1655  			if *flagAslr && *flagRace {
  1656  				// Current windows/amd64 race detector tsan support
  1657  				// library can't handle PIE mode (see #53539 for more details).
  1658  				// Disable alsr if -race in effect.
  1659  				*flagAslr = false
  1660  			}
  1661  			argv = addASLRargs(argv, *flagAslr)
  1662  		default:
  1663  			// ELF.
  1664  			if ctxt.UseRelro() {
  1665  				argv = append(argv, "-Wl,-z,relro")
  1666  			}
  1667  			argv = append(argv, "-pie")
  1668  		}
  1669  	case BuildModeCShared:
  1670  		if ctxt.HeadType == objabi.Hdarwin {
  1671  			argv = append(argv, "-dynamiclib")
  1672  		} else {
  1673  			if ctxt.UseRelro() {
  1674  				argv = append(argv, "-Wl,-z,relro")
  1675  			}
  1676  			argv = append(argv, "-shared")
  1677  			if ctxt.HeadType == objabi.Hwindows {
  1678  				argv = addASLRargs(argv, *flagAslr)
  1679  			} else {
  1680  				// Pass -z nodelete to mark the shared library as
  1681  				// non-closeable: a dlclose will do nothing.
  1682  				argv = append(argv, "-Wl,-z,nodelete")
  1683  				// Only pass Bsymbolic on non-Windows.
  1684  				argv = append(argv, "-Wl,-Bsymbolic")
  1685  			}
  1686  		}
  1687  	case BuildModeShared:
  1688  		if ctxt.UseRelro() {
  1689  			argv = append(argv, "-Wl,-z,relro")
  1690  		}
  1691  		argv = append(argv, "-shared")
  1692  	case BuildModePlugin:
  1693  		if ctxt.HeadType == objabi.Hdarwin {
  1694  			argv = append(argv, "-dynamiclib")
  1695  		} else {
  1696  			if ctxt.UseRelro() {
  1697  				argv = append(argv, "-Wl,-z,relro")
  1698  			}
  1699  			argv = append(argv, "-shared")
  1700  		}
  1701  	}
  1702  
  1703  	var altLinker string
  1704  	if ctxt.IsELF && (ctxt.DynlinkingGo() || *flagBindNow) {
  1705  		// For ELF targets, when producing dynamically linked Go code
  1706  		// or when immediate binding is explicitly requested,
  1707  		// we force all symbol resolution to be done at program startup
  1708  		// because lazy PLT resolution can use large amounts of stack at
  1709  		// times we cannot allow it to do so.
  1710  		argv = append(argv, "-Wl,-z,now")
  1711  	}
  1712  
  1713  	if ctxt.IsELF && ctxt.DynlinkingGo() {
  1714  		// Do not let the host linker generate COPY relocations. These
  1715  		// can move symbols out of sections that rely on stable offsets
  1716  		// from the beginning of the section (like sym.STYPE).
  1717  		argv = append(argv, "-Wl,-z,nocopyreloc")
  1718  
  1719  		if buildcfg.GOOS == "android" {
  1720  			// Use lld to avoid errors from default linker (issue #38838)
  1721  			altLinker = "lld"
  1722  		}
  1723  
  1724  		if ctxt.Arch.InFamily(sys.ARM64) && buildcfg.GOOS == "linux" {
  1725  			// On ARM64, the GNU linker had issues with -znocopyreloc
  1726  			// and COPY relocations. This was fixed in GNU ld 2.36+.
  1727  			// https://sourceware.org/bugzilla/show_bug.cgi?id=19962
  1728  			// https://go.dev/issue/22040
  1729  			// And newer gold is deprecated, may lack new features/flags, or even missing
  1730  
  1731  			// If the default linker is GNU ld 2.35 or older, use gold
  1732  			useGold := false
  1733  			name, args := flagExtld[0], flagExtld[1:]
  1734  			args = append(args, "-Wl,--version")
  1735  			cmd := exec.Command(name, args...)
  1736  			if out, err := cmd.CombinedOutput(); err == nil {
  1737  				// Parse version from output like "GNU ld (GNU Binutils for Distro) 2.36.1"
  1738  				for line := range strings.Lines(string(out)) {
  1739  					if !strings.HasPrefix(line, "GNU ld ") {
  1740  						continue
  1741  					}
  1742  					fields := strings.Fields(line[len("GNU ld "):])
  1743  					var major, minor int
  1744  					if ret, err := fmt.Sscanf(fields[len(fields)-1], "%d.%d", &major, &minor); ret == 2 && err == nil {
  1745  						if major == 2 && minor <= 35 {
  1746  							useGold = true
  1747  						}
  1748  						break
  1749  					}
  1750  				}
  1751  			}
  1752  
  1753  			if useGold {
  1754  				// Use gold for older linkers
  1755  				altLinker = "gold"
  1756  
  1757  				// If gold is not installed, gcc will silently switch
  1758  				// back to ld.bfd. So we parse the version information
  1759  				// and provide a useful error if gold is missing.
  1760  				args = flagExtld[1:]
  1761  				args = append(args, "-fuse-ld=gold", "-Wl,--version")
  1762  				cmd = exec.Command(name, args...)
  1763  				if out, err := cmd.CombinedOutput(); err == nil {
  1764  					if !bytes.Contains(out, []byte("GNU gold")) {
  1765  						log.Fatalf("ARM64 external linker must be ld>=2.36 or gold (issue #15696, 22040), but is not: %s", out)
  1766  					}
  1767  				}
  1768  			}
  1769  		}
  1770  	}
  1771  	if ctxt.Arch.Family == sys.ARM64 && buildcfg.GOOS == "freebsd" {
  1772  		// Switch to ld.bfd on freebsd/arm64.
  1773  		altLinker = "bfd"
  1774  
  1775  		// Provide a useful error if ld.bfd is missing.
  1776  		name, args := flagExtld[0], flagExtld[1:]
  1777  		args = append(args, "-fuse-ld=bfd", "-Wl,--version")
  1778  		cmd := exec.Command(name, args...)
  1779  		if out, err := cmd.CombinedOutput(); err == nil {
  1780  			if !bytes.Contains(out, []byte("GNU ld")) {
  1781  				log.Fatalf("ARM64 external linker must be ld.bfd (issue #35197), please install devel/binutils")
  1782  			}
  1783  		}
  1784  	}
  1785  	if altLinker != "" {
  1786  		argv = append(argv, "-fuse-ld="+altLinker)
  1787  	}
  1788  
  1789  	if ctxt.IsELF && linkerFlagSupported(ctxt.Arch, argv[0], "", "-Wl,--build-id=0x1234567890abcdef") { // Solaris ld doesn't support --build-id.
  1790  		if len(buildinfo) > 0 {
  1791  			argv = append(argv, fmt.Sprintf("-Wl,--build-id=0x%x", buildinfo))
  1792  		} else if *flagHostBuildid == "none" {
  1793  			argv = append(argv, "-Wl,--build-id=none")
  1794  		}
  1795  	}
  1796  
  1797  	// On Windows, given -o foo, GCC will append ".exe" to produce
  1798  	// "foo.exe".  We have decided that we want to honor the -o
  1799  	// option. To make this work, we append a '.' so that GCC
  1800  	// will decide that the file already has an extension. We
  1801  	// only want to do this when producing a Windows output file
  1802  	// on a Windows host.
  1803  	outopt := *flagOutfile
  1804  	if buildcfg.GOOS == "windows" && runtime.GOOS == "windows" && filepath.Ext(outopt) == "" {
  1805  		outopt += "."
  1806  	}
  1807  	argv = append(argv, "-o")
  1808  	argv = append(argv, outopt)
  1809  
  1810  	if rpath.val != "" {
  1811  		argv = append(argv, fmt.Sprintf("-Wl,-rpath,%s", rpath.val))
  1812  	}
  1813  
  1814  	if *flagInterpreter != "" {
  1815  		// Many linkers support both -I and the --dynamic-linker flags
  1816  		// to set the ELF interpreter, but lld only supports
  1817  		// --dynamic-linker so prefer that (ld on very old Solaris only
  1818  		// supports -I but that seems less important).
  1819  		argv = append(argv, fmt.Sprintf("-Wl,--dynamic-linker,%s", *flagInterpreter))
  1820  	}
  1821  
  1822  	// Force global symbols to be exported for dlopen, etc.
  1823  	switch {
  1824  	case ctxt.IsELF:
  1825  		if ctxt.DynlinkingGo() || ctxt.BuildMode == BuildModeCShared || !linkerFlagSupported(ctxt.Arch, argv[0], altLinker, "-Wl,--export-dynamic-symbol=main") {
  1826  			argv = append(argv, "-rdynamic")
  1827  		} else {
  1828  			var exports []string
  1829  			ctxt.loader.ForAllCgoExportDynamic(func(s loader.Sym) {
  1830  				exports = append(exports, "-Wl,--export-dynamic-symbol="+ctxt.loader.SymExtname(s))
  1831  			})
  1832  			sort.Strings(exports)
  1833  			argv = append(argv, exports...)
  1834  		}
  1835  	case ctxt.IsAIX():
  1836  		fileName := xcoffCreateExportFile(ctxt)
  1837  		argv = append(argv, "-Wl,-bE:"+fileName)
  1838  	case ctxt.IsWindows() && !slices.Contains(flagExtldflags, wlPrefix+"export-all-symbols"):
  1839  		fileName := peCreateExportFile(ctxt, filepath.Base(outopt))
  1840  		prefix := ""
  1841  		if isMSVC {
  1842  			prefix = "-Wl,-def:"
  1843  		}
  1844  		argv = append(argv, prefix+fileName)
  1845  	}
  1846  
  1847  	const unusedArguments = "-Qunused-arguments"
  1848  	if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, unusedArguments) {
  1849  		argv = append(argv, unusedArguments)
  1850  	}
  1851  
  1852  	if ctxt.IsWindows() {
  1853  		// Suppress generation of the PE file header timestamp,
  1854  		// so as to avoid spurious build ID differences between
  1855  		// linked binaries that are otherwise identical other than
  1856  		// the date/time they were linked.
  1857  		const noTimeStamp = "-Wl,--no-insert-timestamp"
  1858  		if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, noTimeStamp) {
  1859  			argv = append(argv, noTimeStamp)
  1860  		}
  1861  	}
  1862  
  1863  	const compressDWARF = "-Wl,--compress-debug-sections=zlib"
  1864  	if ctxt.compressDWARF && linkerFlagSupported(ctxt.Arch, argv[0], altLinker, compressDWARF) {
  1865  		argv = append(argv, compressDWARF)
  1866  	}
  1867  
  1868  	hostObjCopyPaths := ctxt.hostobjCopy()
  1869  	cleanTimeStamps(hostObjCopyPaths)
  1870  	godotopath := filepath.Join(*flagTmpdir, "go.o")
  1871  	cleanTimeStamps([]string{godotopath})
  1872  
  1873  	argv = append(argv, godotopath)
  1874  	argv = append(argv, hostObjCopyPaths...)
  1875  	if ctxt.HeadType == objabi.Haix {
  1876  		// We want to have C files after Go files to remove
  1877  		// trampolines csects made by ld.
  1878  		argv = append(argv, "-nostartfiles")
  1879  		argv = append(argv, "/lib/crt0_64.o")
  1880  
  1881  		extld := ctxt.extld()
  1882  		name, args := extld[0], extld[1:]
  1883  		// Get starting files.
  1884  		getPathFile := func(file string) string {
  1885  			args := append(args, "-maix64", "--print-file-name="+file)
  1886  			out, err := exec.Command(name, args...).CombinedOutput()
  1887  			if err != nil {
  1888  				log.Fatalf("running %s failed: %v\n%s", extld, err, out)
  1889  			}
  1890  			return strings.Trim(string(out), "\n")
  1891  		}
  1892  		// Since GCC version 11, the 64-bit version of GCC starting files
  1893  		// are now suffixed by "_64". Even under "-maix64" multilib directory
  1894  		// "crtcxa.o" is 32-bit.
  1895  		crtcxa := getPathFile("crtcxa_64.o")
  1896  		if !filepath.IsAbs(crtcxa) {
  1897  			crtcxa = getPathFile("crtcxa.o")
  1898  		}
  1899  		crtdbase := getPathFile("crtdbase_64.o")
  1900  		if !filepath.IsAbs(crtdbase) {
  1901  			crtdbase = getPathFile("crtdbase.o")
  1902  		}
  1903  		argv = append(argv, crtcxa)
  1904  		argv = append(argv, crtdbase)
  1905  	}
  1906  
  1907  	if ctxt.linkShared {
  1908  		seenDirs := make(map[string]bool)
  1909  		seenLibs := make(map[string]bool)
  1910  		addshlib := func(path string) {
  1911  			dir, base := filepath.Split(path)
  1912  			if !seenDirs[dir] {
  1913  				argv = append(argv, "-L"+dir)
  1914  				if !rpath.set {
  1915  					argv = append(argv, "-Wl,-rpath="+dir)
  1916  				}
  1917  				seenDirs[dir] = true
  1918  			}
  1919  			base = strings.TrimSuffix(base, ".so")
  1920  			base = strings.TrimPrefix(base, "lib")
  1921  			if !seenLibs[base] {
  1922  				argv = append(argv, "-l"+base)
  1923  				seenLibs[base] = true
  1924  			}
  1925  		}
  1926  		for _, shlib := range ctxt.Shlibs {
  1927  			addshlib(shlib.Path)
  1928  			for _, dep := range shlib.Deps {
  1929  				if dep == "" {
  1930  					continue
  1931  				}
  1932  				libpath := findshlib(ctxt, dep)
  1933  				if libpath != "" {
  1934  					addshlib(libpath)
  1935  				}
  1936  			}
  1937  		}
  1938  	}
  1939  
  1940  	// clang, unlike GCC, passes -rdynamic to the linker
  1941  	// even when linking with -static, causing a linker
  1942  	// error when using GNU ld. So take out -rdynamic if
  1943  	// we added it. We do it in this order, rather than
  1944  	// only adding -rdynamic later, so that -extldflags
  1945  	// can override -rdynamic without using -static.
  1946  	// Similarly for -Wl,--dynamic-linker.
  1947  	checkStatic := func(arg string) {
  1948  		if ctxt.IsELF && arg == "-static" {
  1949  			for i := range argv {
  1950  				if argv[i] == "-rdynamic" || strings.HasPrefix(argv[i], "-Wl,--dynamic-linker,") {
  1951  					argv[i] = "-static"
  1952  				}
  1953  			}
  1954  		}
  1955  	}
  1956  
  1957  	for _, p := range ldflag {
  1958  		argv = append(argv, p)
  1959  		checkStatic(p)
  1960  	}
  1961  
  1962  	// When building a program with the default -buildmode=exe the
  1963  	// gc compiler generates code requires DT_TEXTREL in a
  1964  	// position independent executable (PIE). On systems where the
  1965  	// toolchain creates PIEs by default, and where DT_TEXTREL
  1966  	// does not work, the resulting programs will not run. See
  1967  	// issue #17847. To avoid this problem pass -no-pie to the
  1968  	// toolchain if it is supported.
  1969  	if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared && !(ctxt.IsDarwin() && ctxt.IsARM64()) {
  1970  		// GCC uses -no-pie, clang uses -nopie.
  1971  		for _, nopie := range []string{"-no-pie", "-nopie"} {
  1972  			if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, nopie) {
  1973  				argv = append(argv, nopie)
  1974  				break
  1975  			}
  1976  		}
  1977  	}
  1978  
  1979  	for _, p := range flagExtldflags {
  1980  		argv = append(argv, p)
  1981  		checkStatic(p)
  1982  	}
  1983  	if ctxt.HeadType == objabi.Hwindows {
  1984  		// use gcc linker script to work around gcc bug
  1985  		// (see https://golang.org/issue/20183 for details).
  1986  		if !isLLD {
  1987  			p := writeGDBLinkerScript()
  1988  			argv = append(argv, "-Wl,-T,"+p)
  1989  		}
  1990  		if *flagRace {
  1991  			// Apparently --print-file-name doesn't work with -msvc clang.
  1992  			// (The library name is synchronization.lib, but even with that
  1993  			// name it still doesn't print the full path.) Assume it always
  1994  			// it.
  1995  			if isMSVC || ctxt.findLibPath("libsynchronization.a") != "libsynchronization.a" {
  1996  				argv = append(argv, "-lsynchronization")
  1997  			}
  1998  		}
  1999  		if !isMSVC {
  2000  			// libmingw32 and libmingwex have some inter-dependencies,
  2001  			// so must use linker groups.
  2002  			argv = append(argv, "-Wl,--start-group", "-lmingwex", "-lmingw32", "-Wl,--end-group")
  2003  		}
  2004  		argv = append(argv, peimporteddlls()...)
  2005  	}
  2006  
  2007  	argv = ctxt.passLongArgsInResponseFile(argv, altLinker)
  2008  
  2009  	if ctxt.Debugvlog != 0 {
  2010  		ctxt.Logf("host link:")
  2011  		for _, v := range argv {
  2012  			ctxt.Logf(" %q", v)
  2013  		}
  2014  		ctxt.Logf("\n")
  2015  	}
  2016  
  2017  	cmd := exec.Command(argv[0], argv[1:]...)
  2018  	out, err := cmd.CombinedOutput()
  2019  	if err != nil {
  2020  		Exitf("running %s failed: %v\n%s\n%s", argv[0], err, cmd, out)
  2021  	}
  2022  
  2023  	// Filter out useless linker warnings caused by bugs outside Go.
  2024  	// See also cmd/go/internal/work/exec.go's gccld method.
  2025  	var save [][]byte
  2026  	var skipLines int
  2027  	for _, line := range bytes.SplitAfter(out, []byte("\n")) {
  2028  		// golang.org/issue/26073 - Apple Xcode bug
  2029  		if bytes.Contains(line, []byte("ld: warning: text-based stub file")) {
  2030  			continue
  2031  		}
  2032  
  2033  		if skipLines > 0 {
  2034  			skipLines--
  2035  			continue
  2036  		}
  2037  
  2038  		// Remove TOC overflow warning on AIX.
  2039  		if bytes.Contains(line, []byte("ld: 0711-783")) {
  2040  			skipLines = 2
  2041  			continue
  2042  		}
  2043  
  2044  		save = append(save, line)
  2045  	}
  2046  	out = bytes.Join(save, nil)
  2047  
  2048  	if len(out) > 0 {
  2049  		// always print external output even if the command is successful, so that we don't
  2050  		// swallow linker warnings (see https://golang.org/issue/17935).
  2051  		if ctxt.IsDarwin() && ctxt.IsAMD64() {
  2052  			const noPieWarning = "ld: warning: -no_pie is deprecated when targeting new OS versions\n"
  2053  			if i := bytes.Index(out, []byte(noPieWarning)); i >= 0 {
  2054  				// swallow -no_pie deprecation warning, issue 54482
  2055  				out = append(out[:i], out[i+len(noPieWarning):]...)
  2056  			}
  2057  		}
  2058  		if ctxt.IsDarwin() {
  2059  			const bindAtLoadWarning = "ld: warning: -bind_at_load is deprecated on macOS\n"
  2060  			if i := bytes.Index(out, []byte(bindAtLoadWarning)); i >= 0 {
  2061  				// -bind_at_load is deprecated with ld-prime, but needed for
  2062  				// correctness with older versions of ld64. Swallow the warning.
  2063  				// TODO: maybe pass -bind_at_load conditionally based on C
  2064  				// linker version.
  2065  				out = append(out[:i], out[i+len(bindAtLoadWarning):]...)
  2066  			}
  2067  		}
  2068  		ctxt.Logf("%s", out)
  2069  	}
  2070  
  2071  	// Helper for updating a Macho binary in some way (shared between
  2072  	// dwarf combining and UUID update).
  2073  	updateMachoOutFile := func(op string, updateFunc machoUpdateFunc) {
  2074  		// For os.Rename to work reliably, must be in same directory as outfile.
  2075  		rewrittenOutput := *flagOutfile + "~"
  2076  		exef, err := os.Open(*flagOutfile)
  2077  		if err != nil {
  2078  			Exitf("%s: %s failed: %v", os.Args[0], op, err)
  2079  		}
  2080  		defer exef.Close()
  2081  		exem, err := macho.NewFile(exef)
  2082  		if err != nil {
  2083  			Exitf("%s: parsing Mach-O header failed: %v", os.Args[0], err)
  2084  		}
  2085  		if err := updateFunc(ctxt, exef, exem, rewrittenOutput); err != nil {
  2086  			Exitf("%s: %s failed: %v", os.Args[0], op, err)
  2087  		}
  2088  		os.Remove(*flagOutfile)
  2089  		if err := os.Rename(rewrittenOutput, *flagOutfile); err != nil {
  2090  			Exitf("%s: %v", os.Args[0], err)
  2091  		}
  2092  	}
  2093  
  2094  	uuidUpdated := false
  2095  	if combineDwarf {
  2096  		// Find "dsymutils" and "strip" tools using CC --print-prog-name.
  2097  		dsymutilCmd := ctxt.findExtLinkTool("dsymutil")
  2098  		stripCmd := ctxt.findExtLinkTool("strip")
  2099  
  2100  		dsym := filepath.Join(*flagTmpdir, "go.dwarf")
  2101  		cmd := exec.Command(dsymutilCmd, "-f", *flagOutfile, "-o", dsym)
  2102  		// dsymutil may not clean up its temp directory at exit.
  2103  		// Set DSYMUTIL_REPRODUCER_PATH to work around. see issue 59026.
  2104  		// dsymutil (Apple LLVM version 16.0.0) deletes the directory
  2105  		// even if it is not empty. We still need our tmpdir, so give a
  2106  		// subdirectory to dsymutil.
  2107  		dsymDir := filepath.Join(*flagTmpdir, "dsymutil")
  2108  		err := os.MkdirAll(dsymDir, 0777)
  2109  		if err != nil {
  2110  			Exitf("fail to create temp dir: %v", err)
  2111  		}
  2112  		cmd.Env = append(os.Environ(), "DSYMUTIL_REPRODUCER_PATH="+dsymDir)
  2113  		if ctxt.Debugvlog != 0 {
  2114  			ctxt.Logf("host link dsymutil:")
  2115  			for _, v := range cmd.Args {
  2116  				ctxt.Logf(" %q", v)
  2117  			}
  2118  			ctxt.Logf("\n")
  2119  		}
  2120  		if out, err := cmd.CombinedOutput(); err != nil {
  2121  			Exitf("%s: running dsymutil failed: %v\n%s\n%s", os.Args[0], err, cmd, out)
  2122  		}
  2123  		// Remove STAB (symbolic debugging) symbols after we are done with them (by dsymutil).
  2124  		// They contain temporary file paths and make the build not reproducible.
  2125  		var stripArgs = []string{"-S"}
  2126  		if debug_s {
  2127  			// We are generating a binary with symbol table suppressed.
  2128  			// Suppress local symbols. We need to keep dynamically exported
  2129  			// and referenced symbols so the dynamic linker can resolve them.
  2130  			stripArgs = append(stripArgs, "-x")
  2131  		}
  2132  		stripArgs = append(stripArgs, *flagOutfile)
  2133  		if ctxt.Debugvlog != 0 {
  2134  			ctxt.Logf("host link strip: %q", stripCmd)
  2135  			for _, v := range stripArgs {
  2136  				ctxt.Logf(" %q", v)
  2137  			}
  2138  			ctxt.Logf("\n")
  2139  		}
  2140  		cmd = exec.Command(stripCmd, stripArgs...)
  2141  		if out, err := cmd.CombinedOutput(); err != nil {
  2142  			Exitf("%s: running strip failed: %v\n%s\n%s", os.Args[0], err, cmd, out)
  2143  		}
  2144  		// Skip combining if `dsymutil` didn't generate a file. See #11994.
  2145  		if _, err := os.Stat(dsym); err == nil {
  2146  			updateMachoOutFile("combining dwarf",
  2147  				func(ctxt *Link, exef *os.File, exem *macho.File, outexe string) error {
  2148  					return machoCombineDwarf(ctxt, exef, exem, dsym, outexe)
  2149  				})
  2150  			uuidUpdated = true
  2151  		}
  2152  	}
  2153  	if ctxt.IsDarwin() && !uuidUpdated && len(buildinfo) > 0 {
  2154  		updateMachoOutFile("rewriting uuid",
  2155  			func(ctxt *Link, exef *os.File, exem *macho.File, outexe string) error {
  2156  				return machoRewriteUuid(ctxt, exef, exem, outexe)
  2157  			})
  2158  	}
  2159  	hostlinkfips(ctxt, *flagOutfile, *flagFipso)
  2160  	if ctxt.NeedCodeSign() {
  2161  		err := machoCodeSign(ctxt, *flagOutfile)
  2162  		if err != nil {
  2163  			Exitf("%s: code signing failed: %v", os.Args[0], err)
  2164  		}
  2165  	}
  2166  }
  2167  
  2168  // passLongArgsInResponseFile writes the arguments into a file if they
  2169  // are very long.
  2170  func (ctxt *Link) passLongArgsInResponseFile(argv []string, altLinker string) []string {
  2171  	c := 0
  2172  	for _, arg := range argv {
  2173  		c += len(arg)
  2174  	}
  2175  
  2176  	if c < sys.ExecArgLengthLimit {
  2177  		return argv
  2178  	}
  2179  
  2180  	// Only use response files if they are supported.
  2181  	response := filepath.Join(*flagTmpdir, "response")
  2182  	if err := os.WriteFile(response, nil, 0644); err != nil {
  2183  		log.Fatalf("failed while testing response file: %v", err)
  2184  	}
  2185  	if !linkerFlagSupported(ctxt.Arch, argv[0], altLinker, "@"+response) {
  2186  		if ctxt.Debugvlog != 0 {
  2187  			ctxt.Logf("not using response file because linker does not support one")
  2188  		}
  2189  		return argv
  2190  	}
  2191  
  2192  	var buf bytes.Buffer
  2193  	for _, arg := range argv[1:] {
  2194  		// The external linker response file supports quoted strings.
  2195  		fmt.Fprintf(&buf, "%q\n", arg)
  2196  	}
  2197  	if err := os.WriteFile(response, buf.Bytes(), 0644); err != nil {
  2198  		log.Fatalf("failed while writing response file: %v", err)
  2199  	}
  2200  	if ctxt.Debugvlog != 0 {
  2201  		ctxt.Logf("response file %s contents:\n%s", response, buf.Bytes())
  2202  	}
  2203  	return []string{
  2204  		argv[0],
  2205  		"@" + response,
  2206  	}
  2207  }
  2208  
  2209  var createTrivialCOnce sync.Once
  2210  
  2211  func linkerFlagSupported(arch *sys.Arch, linker, altLinker, flag string) bool {
  2212  	createTrivialCOnce.Do(func() {
  2213  		src := filepath.Join(*flagTmpdir, "trivial.c")
  2214  		if err := os.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
  2215  			Errorf("WriteFile trivial.c failed: %v", err)
  2216  		}
  2217  	})
  2218  
  2219  	flags := hostlinkArchArgs(arch)
  2220  
  2221  	moreFlags := trimLinkerArgv(append(ldflag, flagExtldflags...))
  2222  	flags = append(flags, moreFlags...)
  2223  
  2224  	if altLinker != "" {
  2225  		flags = append(flags, "-fuse-ld="+altLinker)
  2226  	}
  2227  	trivialPath := filepath.Join(*flagTmpdir, "trivial.c")
  2228  	outPath := filepath.Join(*flagTmpdir, "a.out")
  2229  	flags = append(flags, "-o", outPath, flag, trivialPath)
  2230  
  2231  	cmd := exec.Command(linker, flags...)
  2232  	cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
  2233  	out, err := cmd.CombinedOutput()
  2234  	// GCC says "unrecognized command line option ‘-no-pie’"
  2235  	// clang says "unknown argument: '-no-pie'"
  2236  	return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
  2237  }
  2238  
  2239  // peHasLoadConfigDirectorySupport checks whether the external linker
  2240  // populates the PE Load Configuration Directory data directory entry
  2241  // when it encounters a _load_config_used symbol.
  2242  //
  2243  // GNU ld gained this support in binutils 2.45. MSVC link.exe and
  2244  // LLVM lld-link have always supported it.
  2245  func peHasLoadConfigDirectorySupport(arch *sys.Arch, linker string) bool {
  2246  	src := filepath.Join(*flagTmpdir, "loadcfg_test.c")
  2247  	if err := os.WriteFile(src, []byte(`
  2248  #ifdef _WIN64
  2249  typedef unsigned long long uintptr;
  2250  #else
  2251  typedef unsigned long uintptr;
  2252  #endif
  2253  const uintptr _load_config_used[2] = { sizeof(_load_config_used), 0 };
  2254  int main() { return 0; }
  2255  `), 0666); err != nil {
  2256  		return false
  2257  	}
  2258  
  2259  	outPath := filepath.Join(*flagTmpdir, "loadcfg_test.exe")
  2260  	flags := hostlinkArchArgs(arch)
  2261  	flags = append(flags, "-o", outPath, src)
  2262  	cmd := exec.Command(linker, flags...)
  2263  	cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
  2264  	if err := cmd.Run(); err != nil {
  2265  		return false
  2266  	}
  2267  
  2268  	f, err := pe.Open(outPath)
  2269  	if err != nil {
  2270  		return false
  2271  	}
  2272  	defer f.Close()
  2273  
  2274  	switch oh := f.OptionalHeader.(type) {
  2275  	case *pe.OptionalHeader64:
  2276  		if int(pe.IMAGE_DIRECTORY_ENTRY_LOAD_CONFIG) < len(oh.DataDirectory) {
  2277  			return oh.DataDirectory[pe.IMAGE_DIRECTORY_ENTRY_LOAD_CONFIG].VirtualAddress != 0
  2278  		}
  2279  	case *pe.OptionalHeader32:
  2280  		if int(pe.IMAGE_DIRECTORY_ENTRY_LOAD_CONFIG) < len(oh.DataDirectory) {
  2281  			return oh.DataDirectory[pe.IMAGE_DIRECTORY_ENTRY_LOAD_CONFIG].VirtualAddress != 0
  2282  		}
  2283  	}
  2284  	return false
  2285  }
  2286  
  2287  // trimLinkerArgv returns a new copy of argv that does not include flags
  2288  // that are not relevant for testing whether some linker option works.
  2289  func trimLinkerArgv(argv []string) []string {
  2290  	flagsWithNextArgSkip := []string{
  2291  		"-F",
  2292  		"-l",
  2293  		"-framework",
  2294  		"-Wl,-framework",
  2295  		"-Wl,-rpath",
  2296  		"-Wl,-undefined",
  2297  	}
  2298  	flagsWithNextArgKeep := []string{
  2299  		"-B",
  2300  		"-L",
  2301  		"-arch",
  2302  		"-isysroot",
  2303  		"--sysroot",
  2304  		"-target",
  2305  		"--target",
  2306  		"-resource-dir",
  2307  		"-rtlib",
  2308  		"--rtlib",
  2309  		"-stdlib",
  2310  		"--stdlib",
  2311  		"-unwindlib",
  2312  		"--unwindlib",
  2313  	}
  2314  	prefixesToKeep := []string{
  2315  		"-B",
  2316  		"-L",
  2317  		"-f",
  2318  		"-m",
  2319  		"-p",
  2320  		"-Wl,",
  2321  		"-arch",
  2322  		"-isysroot",
  2323  		"--sysroot",
  2324  		"-target",
  2325  		"--target",
  2326  		"-resource-dir",
  2327  		"-rtlib",
  2328  		"--rtlib",
  2329  		"-stdlib",
  2330  		"--stdlib",
  2331  		"-unwindlib",
  2332  		"--unwindlib",
  2333  		"-nostdlib++",
  2334  		"-nostdlib",
  2335  		"-nodefaultlibs",
  2336  		"-nostartfiles",
  2337  		"-nostdinc++",
  2338  		"-nostdinc",
  2339  		"-nobuiltininc",
  2340  	}
  2341  
  2342  	var flags []string
  2343  	keep := false
  2344  	skip := false
  2345  	for _, f := range argv {
  2346  		if keep {
  2347  			flags = append(flags, f)
  2348  			keep = false
  2349  		} else if skip {
  2350  			skip = false
  2351  		} else if f == "" || f[0] != '-' {
  2352  		} else if slices.Contains(flagsWithNextArgSkip, f) {
  2353  			skip = true
  2354  		} else if slices.Contains(flagsWithNextArgKeep, f) {
  2355  			flags = append(flags, f)
  2356  			keep = true
  2357  		} else {
  2358  			for _, p := range prefixesToKeep {
  2359  				if strings.HasPrefix(f, p) {
  2360  					flags = append(flags, f)
  2361  					break
  2362  				}
  2363  			}
  2364  		}
  2365  	}
  2366  	return flags
  2367  }
  2368  
  2369  // hostlinkArchArgs returns arguments to pass to the external linker
  2370  // based on the architecture.
  2371  func hostlinkArchArgs(arch *sys.Arch) []string {
  2372  	switch arch.Family {
  2373  	case sys.I386:
  2374  		return []string{"-m32"}
  2375  	case sys.AMD64:
  2376  		if buildcfg.GOOS == "darwin" {
  2377  			return []string{"-arch", "x86_64", "-m64"}
  2378  		}
  2379  		return []string{"-m64"}
  2380  	case sys.S390X:
  2381  		return []string{"-m64"}
  2382  	case sys.ARM:
  2383  		return []string{"-marm"}
  2384  	case sys.ARM64:
  2385  		if buildcfg.GOOS == "darwin" {
  2386  			return []string{"-arch", "arm64"}
  2387  		}
  2388  	case sys.Loong64:
  2389  		return []string{"-mabi=lp64d"}
  2390  	case sys.MIPS64:
  2391  		return []string{"-mabi=64"}
  2392  	case sys.MIPS:
  2393  		return []string{"-mabi=32"}
  2394  	case sys.PPC64:
  2395  		if buildcfg.GOOS == "aix" {
  2396  			return []string{"-maix64"}
  2397  		} else {
  2398  			return []string{"-m64"}
  2399  		}
  2400  
  2401  	}
  2402  	return nil
  2403  }
  2404  
  2405  var wantHdr = objabi.HeaderString()
  2406  
  2407  // ldobj loads an input object. If it is a host object (an object
  2408  // compiled by a non-Go compiler) it returns the Hostobj pointer. If
  2409  // it is a Go object, it returns nil.
  2410  func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string, file string) *Hostobj {
  2411  	pkg := objabi.PathToPrefix(lib.Pkg)
  2412  
  2413  	eof := f.Offset() + length
  2414  	start := f.Offset()
  2415  	c1 := bgetc(f)
  2416  	c2 := bgetc(f)
  2417  	c3 := bgetc(f)
  2418  	c4 := bgetc(f)
  2419  	f.MustSeek(start, 0)
  2420  
  2421  	unit := &sym.CompilationUnit{Lib: lib}
  2422  	lib.Units = append(lib.Units, unit)
  2423  
  2424  	magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
  2425  	if magic == 0x7f454c46 { // \x7F E L F
  2426  		ldelf := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
  2427  			textp, flags, err := loadelf.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn, ehdr.Flags)
  2428  			if err != nil {
  2429  				Errorf("%v", err)
  2430  				return
  2431  			}
  2432  			ehdr.Flags = flags
  2433  			ctxt.Textp = append(ctxt.Textp, textp...)
  2434  		}
  2435  		return ldhostobj(ldelf, ctxt.HeadType, f, pkg, length, pn, file)
  2436  	}
  2437  
  2438  	if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
  2439  		ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
  2440  			textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
  2441  			if err != nil {
  2442  				Errorf("%v", err)
  2443  				return
  2444  			}
  2445  			ctxt.Textp = append(ctxt.Textp, textp...)
  2446  		}
  2447  		return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
  2448  	}
  2449  
  2450  	switch c1<<8 | c2 {
  2451  	case 0x4c01, // 386
  2452  		0x6486, // amd64
  2453  		0xc401, // arm
  2454  		0x64aa: // arm64
  2455  		ldpe := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
  2456  			ls, err := loadpe.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
  2457  			if err != nil {
  2458  				Errorf("%v", err)
  2459  				return
  2460  			}
  2461  			if len(ls.Resources) != 0 {
  2462  				setpersrc(ctxt, ls.Resources)
  2463  			}
  2464  			sehp.pdata = append(sehp.pdata, ls.PData...)
  2465  			if ls.XData != 0 {
  2466  				sehp.xdata = append(sehp.xdata, ls.XData)
  2467  			}
  2468  			ctxt.Textp = append(ctxt.Textp, ls.Textp...)
  2469  		}
  2470  		return ldhostobj(ldpe, ctxt.HeadType, f, pkg, length, pn, file)
  2471  	}
  2472  
  2473  	if c1 == 0x01 && (c2 == 0xD7 || c2 == 0xF7) {
  2474  		ldxcoff := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
  2475  			textp, err := loadxcoff.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
  2476  			if err != nil {
  2477  				Errorf("%v", err)
  2478  				return
  2479  			}
  2480  			ctxt.Textp = append(ctxt.Textp, textp...)
  2481  		}
  2482  		return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
  2483  	}
  2484  
  2485  	if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
  2486  		// An unrecognized object is just passed to the external linker.
  2487  		// If we try to read symbols from this object, we will
  2488  		// report an error at that time.
  2489  		unknownObjFormat = true
  2490  		return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
  2491  	}
  2492  
  2493  	/* check the header */
  2494  	line, err := f.ReadString('\n')
  2495  	if err != nil {
  2496  		Errorf("truncated object file: %s: %v", pn, err)
  2497  		return nil
  2498  	}
  2499  
  2500  	if !strings.HasPrefix(line, "go object ") {
  2501  		if strings.HasSuffix(pn, ".go") {
  2502  			Exitf("%s: uncompiled .go source file", pn)
  2503  			return nil
  2504  		}
  2505  
  2506  		if line == ctxt.Arch.Name {
  2507  			// old header format: just $GOOS
  2508  			Errorf("%s: stale object file", pn)
  2509  			return nil
  2510  		}
  2511  
  2512  		Errorf("%s: not an object file: @%d %q", pn, start, line)
  2513  		return nil
  2514  	}
  2515  
  2516  	// First, check that the basic GOOS, GOARCH, and Version match.
  2517  	if line != wantHdr {
  2518  		Errorf("%s: linked object header mismatch:\nhave %q\nwant %q\n", pn, line, wantHdr)
  2519  	}
  2520  
  2521  	// Skip over exports and other info -- ends with \n!\n.
  2522  	//
  2523  	// Note: It's possible for "\n!\n" to appear within the binary
  2524  	// package export data format. To avoid truncating the package
  2525  	// definition prematurely (issue 21703), we keep track of
  2526  	// how many "$$" delimiters we've seen.
  2527  
  2528  	import0 := f.Offset()
  2529  
  2530  	c1 = '\n' // the last line ended in \n
  2531  	c2 = bgetc(f)
  2532  	c3 = bgetc(f)
  2533  	markers := 0
  2534  	for {
  2535  		if c1 == '\n' {
  2536  			if markers%2 == 0 && c2 == '!' && c3 == '\n' {
  2537  				break
  2538  			}
  2539  			if c2 == '$' && c3 == '$' {
  2540  				markers++
  2541  			}
  2542  		}
  2543  
  2544  		c1 = c2
  2545  		c2 = c3
  2546  		c3 = bgetc(f)
  2547  		if c3 == -1 {
  2548  			Errorf("truncated object file: %s", pn)
  2549  			return nil
  2550  		}
  2551  	}
  2552  
  2553  	import1 := f.Offset()
  2554  
  2555  	f.MustSeek(import0, 0)
  2556  	ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
  2557  	f.MustSeek(import1, 0)
  2558  
  2559  	fingerprint := ctxt.loader.Preload(ctxt.IncVersion(), f, lib, unit, eof-f.Offset())
  2560  	if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
  2561  		// Check fingerprint, to ensure the importing and imported packages
  2562  		// have consistent view of symbol indices.
  2563  		// Normally the go command should ensure this. But in case something
  2564  		// goes wrong, it could lead to obscure bugs like run-time crash.
  2565  		// Check it here to be sure.
  2566  		if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
  2567  			lib.Fingerprint = fingerprint
  2568  		}
  2569  		checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
  2570  	}
  2571  
  2572  	addImports(ctxt, lib, pn)
  2573  	return nil
  2574  }
  2575  
  2576  // symbolsAreUnresolved scans through the loader's list of unresolved
  2577  // symbols and checks to see whether any of them match the names of the
  2578  // symbols in 'want'. Return value is a list of bools, with list[K] set
  2579  // to true if there is an unresolved reference to the symbol in want[K].
  2580  func symbolsAreUnresolved(ctxt *Link, want []string) []bool {
  2581  	returnAllUndefs := -1
  2582  	undefs, _ := ctxt.loader.UndefinedRelocTargets(returnAllUndefs)
  2583  	seen := make(map[loader.Sym]struct{})
  2584  	rval := make([]bool, len(want))
  2585  	wantm := make(map[string]int)
  2586  	for k, w := range want {
  2587  		wantm[w] = k
  2588  	}
  2589  	count := 0
  2590  	for _, s := range undefs {
  2591  		if _, ok := seen[s]; ok {
  2592  			continue
  2593  		}
  2594  		seen[s] = struct{}{}
  2595  		if k, ok := wantm[ctxt.loader.SymName(s)]; ok {
  2596  			rval[k] = true
  2597  			count++
  2598  			if count == len(want) {
  2599  				return rval
  2600  			}
  2601  		}
  2602  	}
  2603  	return rval
  2604  }
  2605  
  2606  // hostObject reads a single host object file (compare to "hostArchive").
  2607  // This is used as part of internal linking when we need to pull in
  2608  // files such as "crt?.o".
  2609  func hostObject(ctxt *Link, objname string, path string) {
  2610  	if ctxt.Debugvlog > 1 {
  2611  		ctxt.Logf("hostObject(%s)\n", path)
  2612  	}
  2613  	objlib := sym.Library{
  2614  		Pkg: objname,
  2615  	}
  2616  	f, err := bio.Open(path)
  2617  	if err != nil {
  2618  		Exitf("cannot open host object %q file %s: %v", objname, path, err)
  2619  	}
  2620  	defer f.Close()
  2621  	h := ldobj(ctxt, f, &objlib, 0, path, path)
  2622  	if h.ld == nil {
  2623  		Exitf("unrecognized object file format in %s", path)
  2624  	}
  2625  	h.file = path
  2626  	h.length = f.MustSeek(0, 2)
  2627  	f.MustSeek(h.off, 0)
  2628  	h.ld(ctxt, f, h.pkg, h.length, h.pn)
  2629  	if *flagCaptureHostObjs != "" {
  2630  		captureHostObj(h)
  2631  	}
  2632  }
  2633  
  2634  func checkFingerprint(lib *sym.Library, libfp goobj.FingerprintType, src string, srcfp goobj.FingerprintType) {
  2635  	if libfp != srcfp {
  2636  		Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
  2637  	}
  2638  }
  2639  
  2640  func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
  2641  	data := make([]byte, sym.Size)
  2642  	sect := f.Sections[sym.Section]
  2643  	if sect.Type != elf.SHT_PROGBITS && sect.Type != elf.SHT_NOTE {
  2644  		Errorf("reading %s from non-data section", sym.Name)
  2645  	}
  2646  	n, err := sect.ReadAt(data, int64(sym.Value-sect.Addr))
  2647  	if uint64(n) != sym.Size {
  2648  		Errorf("reading contents of %s: %v", sym.Name, err)
  2649  	}
  2650  	return data
  2651  }
  2652  
  2653  func readwithpad(r io.Reader, sz int32) ([]byte, error) {
  2654  	data := make([]byte, Rnd(int64(sz), 4))
  2655  	_, err := io.ReadFull(r, data)
  2656  	if err != nil {
  2657  		return nil, err
  2658  	}
  2659  	data = data[:sz]
  2660  	return data, nil
  2661  }
  2662  
  2663  func readnote(f *elf.File, name []byte, typ int32) ([]byte, error) {
  2664  	for _, sect := range f.Sections {
  2665  		if sect.Type != elf.SHT_NOTE {
  2666  			continue
  2667  		}
  2668  		r := sect.Open()
  2669  		for {
  2670  			var namesize, descsize, noteType int32
  2671  			err := binary.Read(r, f.ByteOrder, &namesize)
  2672  			if err != nil {
  2673  				if err == io.EOF {
  2674  					break
  2675  				}
  2676  				return nil, fmt.Errorf("read namesize failed: %v", err)
  2677  			}
  2678  			err = binary.Read(r, f.ByteOrder, &descsize)
  2679  			if err != nil {
  2680  				return nil, fmt.Errorf("read descsize failed: %v", err)
  2681  			}
  2682  			err = binary.Read(r, f.ByteOrder, &noteType)
  2683  			if err != nil {
  2684  				return nil, fmt.Errorf("read type failed: %v", err)
  2685  			}
  2686  			noteName, err := readwithpad(r, namesize)
  2687  			if err != nil {
  2688  				return nil, fmt.Errorf("read name failed: %v", err)
  2689  			}
  2690  			desc, err := readwithpad(r, descsize)
  2691  			if err != nil {
  2692  				return nil, fmt.Errorf("read desc failed: %v", err)
  2693  			}
  2694  			if string(name) == string(noteName) && typ == noteType {
  2695  				return desc, nil
  2696  			}
  2697  		}
  2698  	}
  2699  	return nil, nil
  2700  }
  2701  
  2702  func findshlib(ctxt *Link, shlib string) string {
  2703  	if filepath.IsAbs(shlib) {
  2704  		return shlib
  2705  	}
  2706  	for _, libdir := range ctxt.Libdir {
  2707  		libpath := filepath.Join(libdir, shlib)
  2708  		if _, err := os.Stat(libpath); err == nil {
  2709  			return libpath
  2710  		}
  2711  	}
  2712  	Errorf("cannot find shared library: %s", shlib)
  2713  	return ""
  2714  }
  2715  
  2716  func ldshlibsyms(ctxt *Link, shlib string) {
  2717  	var libpath string
  2718  	if filepath.IsAbs(shlib) {
  2719  		libpath = shlib
  2720  		shlib = filepath.Base(shlib)
  2721  	} else {
  2722  		libpath = findshlib(ctxt, shlib)
  2723  		if libpath == "" {
  2724  			return
  2725  		}
  2726  	}
  2727  	for _, processedlib := range ctxt.Shlibs {
  2728  		if processedlib.Path == libpath {
  2729  			return
  2730  		}
  2731  	}
  2732  	if ctxt.Debugvlog > 1 {
  2733  		ctxt.Logf("ldshlibsyms: found library with name %s at %s\n", shlib, libpath)
  2734  	}
  2735  
  2736  	f, err := elf.Open(libpath)
  2737  	if err != nil {
  2738  		Errorf("cannot open shared library: %s", libpath)
  2739  		return
  2740  	}
  2741  	// Keep the file open as decodetypeGcprog needs to read from it.
  2742  	// TODO: fix. Maybe mmap the file.
  2743  	//defer f.Close()
  2744  
  2745  	hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
  2746  	if err != nil {
  2747  		Errorf("cannot read ABI hash from shared library %s: %v", libpath, err)
  2748  		return
  2749  	}
  2750  
  2751  	depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
  2752  	if err != nil {
  2753  		Errorf("cannot read dep list from shared library %s: %v", libpath, err)
  2754  		return
  2755  	}
  2756  	var deps []string
  2757  	for _, dep := range strings.Split(string(depsbytes), "\n") {
  2758  		if dep == "" {
  2759  			continue
  2760  		}
  2761  		if !filepath.IsAbs(dep) {
  2762  			// If the dep can be interpreted as a path relative to the shlib
  2763  			// in which it was found, do that. Otherwise, we will leave it
  2764  			// to be resolved by libdir lookup.
  2765  			abs := filepath.Join(filepath.Dir(libpath), dep)
  2766  			if _, err := os.Stat(abs); err == nil {
  2767  				dep = abs
  2768  			}
  2769  		}
  2770  		deps = append(deps, dep)
  2771  	}
  2772  
  2773  	syms, err := f.DynamicSymbols()
  2774  	if err != nil {
  2775  		Errorf("cannot read symbols from shared library: %s", libpath)
  2776  		return
  2777  	}
  2778  
  2779  	symAddr := map[string]uint64{}
  2780  	for _, elfsym := range syms {
  2781  		if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
  2782  			continue
  2783  		}
  2784  
  2785  		// Symbols whose names start with "type:" are compiler generated,
  2786  		// so make functions with that prefix internal.
  2787  		ver := 0
  2788  		symname := elfsym.Name // (unmangled) symbol name
  2789  		if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type:") {
  2790  			ver = abiInternalVer
  2791  		} else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC {
  2792  			// Demangle the ABI name. Keep in sync with symtab.go:mangleABIName.
  2793  			if strings.HasSuffix(elfsym.Name, ".abiinternal") {
  2794  				ver = sym.SymVerABIInternal
  2795  				symname = strings.TrimSuffix(elfsym.Name, ".abiinternal")
  2796  			} else if strings.HasSuffix(elfsym.Name, ".abi0") {
  2797  				ver = 0
  2798  				symname = strings.TrimSuffix(elfsym.Name, ".abi0")
  2799  			}
  2800  		}
  2801  
  2802  		l := ctxt.loader
  2803  		s := l.LookupOrCreateSym(symname, ver)
  2804  
  2805  		// Because loadlib above loads all .a files before loading
  2806  		// any shared libraries, any non-dynimport symbols we find
  2807  		// that duplicate symbols already loaded should be ignored
  2808  		// (the symbols from the .a files "win").
  2809  		if l.SymType(s) != 0 && l.SymType(s) != sym.SDYNIMPORT {
  2810  			continue
  2811  		}
  2812  		su := l.MakeSymbolUpdater(s)
  2813  		su.SetType(sym.SDYNIMPORT)
  2814  		l.SetSymElfType(s, elf.ST_TYPE(elfsym.Info))
  2815  		su.SetSize(int64(elfsym.Size))
  2816  		if elfsym.Section != elf.SHN_UNDEF {
  2817  			// Set .File for the library that actually defines the symbol.
  2818  			l.SetSymPkg(s, libpath)
  2819  
  2820  			// The decodetype_* functions in decodetype.go need access to
  2821  			// the type data.
  2822  			sname := l.SymName(s)
  2823  			if strings.HasPrefix(sname, "type:") && !strings.HasPrefix(sname, "type:.") {
  2824  				su.SetData(readelfsymboldata(ctxt, f, &elfsym))
  2825  			}
  2826  		}
  2827  
  2828  		if symname != elfsym.Name {
  2829  			l.SetSymExtname(s, elfsym.Name)
  2830  		}
  2831  		symAddr[elfsym.Name] = elfsym.Value
  2832  	}
  2833  
  2834  	// Load relocations.
  2835  	// We only really need these for grokking the links between type descriptors
  2836  	// when dynamic linking.
  2837  	relocTarget := map[uint64]string{}
  2838  	addends := false
  2839  	sect := f.SectionByType(elf.SHT_REL)
  2840  	if sect == nil {
  2841  		sect = f.SectionByType(elf.SHT_RELA)
  2842  		if sect == nil {
  2843  			log.Fatalf("can't find SHT_REL or SHT_RELA section of %s", shlib)
  2844  		}
  2845  		addends = true
  2846  	}
  2847  	// TODO: Multiple SHT_RELA/SHT_REL sections?
  2848  	data, err := sect.Data()
  2849  	if err != nil {
  2850  		log.Fatalf("can't read relocation section of %s: %v", shlib, err)
  2851  	}
  2852  	bo := f.ByteOrder
  2853  	for len(data) > 0 {
  2854  		var off, idx uint64
  2855  		var addend int64
  2856  		switch f.Class {
  2857  		case elf.ELFCLASS64:
  2858  			off = bo.Uint64(data)
  2859  			info := bo.Uint64(data[8:])
  2860  			data = data[16:]
  2861  			if addends {
  2862  				addend = int64(bo.Uint64(data))
  2863  				data = data[8:]
  2864  			}
  2865  
  2866  			idx = info >> 32
  2867  			typ := info & 0xffff
  2868  			// buildmode=shared is only supported for amd64,arm64,loong64,s390x,ppc64le.
  2869  			// (List found by looking at the translation of R_ADDR by ../$ARCH/asm.go:elfreloc1)
  2870  			switch typ {
  2871  			case uint64(elf.R_X86_64_64):
  2872  			case uint64(elf.R_AARCH64_ABS64):
  2873  			case uint64(elf.R_LARCH_64):
  2874  			case uint64(elf.R_390_64):
  2875  			case uint64(elf.R_PPC64_ADDR64):
  2876  			default:
  2877  				continue
  2878  			}
  2879  		case elf.ELFCLASS32:
  2880  			off = uint64(bo.Uint32(data))
  2881  			info := bo.Uint32(data[4:])
  2882  			data = data[8:]
  2883  			if addends {
  2884  				addend = int64(int32(bo.Uint32(data)))
  2885  				data = data[4:]
  2886  			}
  2887  
  2888  			idx = uint64(info >> 8)
  2889  			typ := info & 0xff
  2890  			// buildmode=shared is only supported for 386,arm.
  2891  			switch typ {
  2892  			case uint32(elf.R_386_32):
  2893  			case uint32(elf.R_ARM_ABS32):
  2894  			default:
  2895  				continue
  2896  			}
  2897  		default:
  2898  			log.Fatalf("unknown bit size %s", f.Class)
  2899  		}
  2900  		if addend != 0 {
  2901  			continue
  2902  		}
  2903  		relocTarget[off] = syms[idx-1].Name
  2904  	}
  2905  
  2906  	ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f, symAddr: symAddr, relocTarget: relocTarget})
  2907  }
  2908  
  2909  func addsection(ldr *loader.Loader, arch *sys.Arch, seg *sym.Segment, name string, rwx int) *sym.Section {
  2910  	sect := ldr.NewSection()
  2911  	sect.Rwx = uint8(rwx)
  2912  	sect.Name = name
  2913  	sect.Seg = seg
  2914  	sect.Align = int32(arch.PtrSize) // everything is at least pointer-aligned
  2915  	seg.Sections = append(seg.Sections, sect)
  2916  	return sect
  2917  }
  2918  
  2919  func usage() {
  2920  	fmt.Fprintf(os.Stderr, "usage: link [options] main.o\n")
  2921  	objabi.Flagprint(os.Stderr)
  2922  	Exit(2)
  2923  }
  2924  
  2925  type SymbolType int8 // TODO: after genasmsym is gone, maybe rename to plan9typeChar or something
  2926  
  2927  const (
  2928  	// see also https://9p.io/magic/man2html/1/nm
  2929  	TextSym      SymbolType = 'T'
  2930  	DataSym      SymbolType = 'D'
  2931  	BSSSym       SymbolType = 'B'
  2932  	UndefinedSym SymbolType = 'U'
  2933  	TLSSym       SymbolType = 't'
  2934  	FrameSym     SymbolType = 'm'
  2935  	ParamSym     SymbolType = 'p'
  2936  	AutoSym      SymbolType = 'a'
  2937  
  2938  	// Deleted auto (not a real sym, just placeholder for type)
  2939  	DeletedAutoSym = 'x'
  2940  )
  2941  
  2942  // defineInternal defines a symbol used internally by the go runtime.
  2943  func (ctxt *Link) defineInternal(p string, t sym.SymKind) loader.Sym {
  2944  	s := ctxt.loader.CreateSymForUpdate(p, 0)
  2945  	s.SetType(t)
  2946  	s.SetSpecial(true)
  2947  	s.SetLocal(true)
  2948  	return s.Sym()
  2949  }
  2950  
  2951  func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) loader.Sym {
  2952  	s := ctxt.defineInternal(p, t)
  2953  	ctxt.loader.SetSymValue(s, v)
  2954  	return s
  2955  }
  2956  
  2957  func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
  2958  	if uint64(addr) >= Segdata.Vaddr {
  2959  		return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
  2960  	}
  2961  	if uint64(addr) >= Segtext.Vaddr {
  2962  		return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
  2963  	}
  2964  	ldr.Errorf(s, "invalid datoff %#x", addr)
  2965  	return 0
  2966  }
  2967  
  2968  func Entryvalue(ctxt *Link) int64 {
  2969  	a := *flagEntrySymbol
  2970  	if a[0] >= '0' && a[0] <= '9' {
  2971  		return atolwhex(a)
  2972  	}
  2973  	ldr := ctxt.loader
  2974  	s := ldr.Lookup(a, 0)
  2975  	if s == 0 {
  2976  		Errorf("missing entry symbol %q", a)
  2977  		return 0
  2978  	}
  2979  	st := ldr.SymType(s)
  2980  	if st == 0 {
  2981  		return *FlagTextAddr
  2982  	}
  2983  	if !ctxt.IsAIX() && !st.IsText() {
  2984  		ldr.Errorf(s, "entry not text")
  2985  	}
  2986  	return ldr.SymValue(s)
  2987  }
  2988  
  2989  func (ctxt *Link) callgraph() {
  2990  	if !*FlagC {
  2991  		return
  2992  	}
  2993  
  2994  	ldr := ctxt.loader
  2995  	for _, s := range ctxt.Textp {
  2996  		relocs := ldr.Relocs(s)
  2997  		for i := 0; i < relocs.Count(); i++ {
  2998  			r := relocs.At(i)
  2999  			rs := r.Sym()
  3000  			if rs == 0 {
  3001  				continue
  3002  			}
  3003  			if r.Type().IsDirectCall() && ldr.SymType(rs).IsText() {
  3004  				ctxt.Logf("%s calls %s\n", ldr.SymName(s), ldr.SymName(rs))
  3005  			}
  3006  		}
  3007  	}
  3008  }
  3009  
  3010  func Rnd(v int64, r int64) int64 {
  3011  	if r <= 0 {
  3012  		return v
  3013  	}
  3014  	v += r - 1
  3015  	c := v % r
  3016  	if c < 0 {
  3017  		c += r
  3018  	}
  3019  	v -= c
  3020  	return v
  3021  }
  3022  
  3023  func bgetc(r *bio.Reader) int {
  3024  	c, err := r.ReadByte()
  3025  	if err != nil {
  3026  		if err != io.EOF {
  3027  			log.Fatalf("reading input: %v", err)
  3028  		}
  3029  		return -1
  3030  	}
  3031  	return int(c)
  3032  }
  3033  
  3034  type markKind uint8 // for postorder traversal
  3035  const (
  3036  	_ markKind = iota
  3037  	visiting
  3038  	visited
  3039  )
  3040  
  3041  func postorder(libs []*sym.Library) []*sym.Library {
  3042  	order := make([]*sym.Library, 0, len(libs)) // hold the result
  3043  	mark := make(map[*sym.Library]markKind, len(libs))
  3044  	for _, lib := range libs {
  3045  		dfs(lib, mark, &order)
  3046  	}
  3047  	return order
  3048  }
  3049  
  3050  func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library) {
  3051  	if mark[lib] == visited {
  3052  		return
  3053  	}
  3054  	if mark[lib] == visiting {
  3055  		panic("found import cycle while visiting " + lib.Pkg)
  3056  	}
  3057  	mark[lib] = visiting
  3058  	for _, i := range lib.Imports {
  3059  		dfs(i, mark, order)
  3060  	}
  3061  	mark[lib] = visited
  3062  	*order = append(*order, lib)
  3063  }
  3064  
  3065  func ElfSymForReloc(ctxt *Link, s loader.Sym) int32 {
  3066  	// If putelfsym created a local version of this symbol, use that in all
  3067  	// relocations.
  3068  	les := ctxt.loader.SymLocalElfSym(s)
  3069  	if les != 0 {
  3070  		return les
  3071  	} else {
  3072  		return ctxt.loader.SymElfSym(s)
  3073  	}
  3074  }
  3075  
  3076  func AddGotSym(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, elfRelocTyp uint32) {
  3077  	if ldr.SymGot(s) >= 0 {
  3078  		return
  3079  	}
  3080  
  3081  	Adddynsym(ldr, target, syms, s)
  3082  	got := ldr.MakeSymbolUpdater(syms.GOT)
  3083  	ldr.SetGot(s, int32(got.Size()))
  3084  	got.AddUint(target.Arch, 0)
  3085  
  3086  	if target.IsElf() {
  3087  		if target.Arch.PtrSize == 8 {
  3088  			rela := ldr.MakeSymbolUpdater(syms.Rela)
  3089  			rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
  3090  			rela.AddUint64(target.Arch, elf.R_INFO(uint32(ldr.SymDynid(s)), elfRelocTyp))
  3091  			rela.AddUint64(target.Arch, 0)
  3092  		} else {
  3093  			rel := ldr.MakeSymbolUpdater(syms.Rel)
  3094  			rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
  3095  			rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), elfRelocTyp))
  3096  		}
  3097  	} else if target.IsDarwin() {
  3098  		leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT)
  3099  		leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
  3100  		if target.IsPIE() && target.IsInternal() {
  3101  			// Mach-O relocations are a royal pain to lay out.
  3102  			// They use a compact stateful bytecode representation.
  3103  			// Here we record what are needed and encode them later.
  3104  			MachoAddBind(syms.GOT, int64(ldr.SymGot(s)), s)
  3105  		}
  3106  	} else {
  3107  		ldr.Errorf(s, "addgotsym: unsupported binary format")
  3108  	}
  3109  }
  3110  
  3111  var hostobjcounter int
  3112  
  3113  // captureHostObj writes out the content of a host object (pulled from
  3114  // an archive or loaded from a *.o file directly) to a directory
  3115  // specified via the linker's "-capturehostobjs" debugging flag. This
  3116  // is intended to make it easier for a developer to inspect the actual
  3117  // object feeding into "CGO internal" link step.
  3118  func captureHostObj(h *Hostobj) {
  3119  	// Form paths for info file and obj file.
  3120  	ofile := fmt.Sprintf("captured-obj-%d.o", hostobjcounter)
  3121  	ifile := fmt.Sprintf("captured-obj-%d.txt", hostobjcounter)
  3122  	hostobjcounter++
  3123  	opath := filepath.Join(*flagCaptureHostObjs, ofile)
  3124  	ipath := filepath.Join(*flagCaptureHostObjs, ifile)
  3125  
  3126  	// Write the info file.
  3127  	info := fmt.Sprintf("pkg: %s\npn: %s\nfile: %s\noff: %d\nlen: %d\n",
  3128  		h.pkg, h.pn, h.file, h.off, h.length)
  3129  	if err := os.WriteFile(ipath, []byte(info), 0666); err != nil {
  3130  		log.Fatalf("error writing captured host obj info %s: %v", ipath, err)
  3131  	}
  3132  
  3133  	readObjData := func() []byte {
  3134  		inf, err := os.Open(h.file)
  3135  		if err != nil {
  3136  			log.Fatalf("capturing host obj: open failed on %s: %v", h.pn, err)
  3137  		}
  3138  		defer inf.Close()
  3139  		res := make([]byte, h.length)
  3140  		if n, err := inf.ReadAt(res, h.off); err != nil || n != int(h.length) {
  3141  			log.Fatalf("capturing host obj: readat failed on %s: %v", h.pn, err)
  3142  		}
  3143  		return res
  3144  	}
  3145  
  3146  	// Write the object file.
  3147  	if err := os.WriteFile(opath, readObjData(), 0666); err != nil {
  3148  		log.Fatalf("error writing captured host object %s: %v", opath, err)
  3149  	}
  3150  
  3151  	fmt.Fprintf(os.Stderr, "link: info: captured host object %s to %s\n",
  3152  		h.file, opath)
  3153  }
  3154  
  3155  // findExtLinkTool invokes the external linker CC with --print-prog-name
  3156  // passing the name of the tool we're interested in, such as "strip",
  3157  // "ar", or "dsymutil", and returns the path passed back from the command.
  3158  func (ctxt *Link) findExtLinkTool(toolname string) string {
  3159  	var cc []string
  3160  	cc = append(cc, ctxt.extld()...)
  3161  	cc = append(cc, hostlinkArchArgs(ctxt.Arch)...)
  3162  	cc = append(cc, "--print-prog-name", toolname)
  3163  	out, err := exec.Command(cc[0], cc[1:]...).CombinedOutput()
  3164  	if err != nil {
  3165  		Exitf("%s: finding %s failed: %v\n%s", os.Args[0], toolname, err, out)
  3166  	}
  3167  	cmdpath := strings.TrimRight(string(out), "\r\n")
  3168  	return cmdpath
  3169  }
  3170  
  3171  // isMSVC reports whether the C toolchain is clang with a -msvc target,
  3172  // e.g. the clang bundled in MSVC.
  3173  func (ctxt *Link) isMSVC() bool {
  3174  	extld := ctxt.extld()
  3175  	name, args := extld[0], extld[1:]
  3176  	args = append(args, trimLinkerArgv(flagExtldflags)...)
  3177  	args = append(args, "--version")
  3178  	cmd := exec.Command(name, args...)
  3179  	if out, err := cmd.CombinedOutput(); err == nil {
  3180  		if bytes.Contains(out, []byte("-msvc\n")) || bytes.Contains(out, []byte("-msvc\r")) {
  3181  			return true
  3182  		}
  3183  	}
  3184  	return false
  3185  }
  3186  
  3187  // isLLD reports whether the C toolchain is using LLD as the linker.
  3188  func (ctxt *Link) isLLD() bool {
  3189  	extld := ctxt.extld()
  3190  	name, args := extld[0], extld[1:]
  3191  	args = append(args, trimLinkerArgv(flagExtldflags)...)
  3192  	args = append(args, "-Wl,--version")
  3193  	cmd := exec.Command(name, args...)
  3194  	if out, err := cmd.CombinedOutput(); err == nil {
  3195  		if bytes.Contains(out, []byte("LLD ")) {
  3196  			return true
  3197  		}
  3198  	}
  3199  	return false
  3200  }
  3201  

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