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  		isLLD = ctxt.isLLD()
  1520  		if isMSVC {
  1521  			// For various options, MSVC lld-link only accepts one dash.
  1522  			// TODO: It seems mingw clang supports one or two dashes,
  1523  			// maybe we can always use one dash,  but I'm not sure about
  1524  			// legacy compilers that currently work.
  1525  			wlPrefix = "-Wl,-"
  1526  		}
  1527  
  1528  		if windowsgui {
  1529  			argv = append(argv, "-mwindows")
  1530  		} else {
  1531  			argv = append(argv, "-mconsole")
  1532  		}
  1533  		// Mark as having awareness of terminal services, to avoid
  1534  		// ancient compatibility hacks.
  1535  
  1536  		argv = append(argv, wlPrefix+"tsaware")
  1537  
  1538  		// Enable DEP
  1539  		argv = append(argv, wlPrefix+"nxcompat")
  1540  
  1541  		if !isMSVC {
  1542  			peMajorVersion := PeMinimumTargetMajorVersion
  1543  			peMinorVersion := PeMinimumTargetMinorVersion
  1544  			if peMajorVersion >= 10 && !isLLD &&
  1545  				!peHasLoadConfigDirectorySupport(ctxt.Arch, argv[0]) {
  1546  				// The external linker doesn't support wiring up
  1547  				// _load_config_used to the PE Load Configuration
  1548  				// Directory. Windows 10+ validates this directory,
  1549  				// so fall back to an older version to avoid
  1550  				// load failures.
  1551  				peMajorVersion = 6
  1552  				peMinorVersion = 1
  1553  			}
  1554  			argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", peMajorVersion))
  1555  			argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", peMinorVersion))
  1556  			argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", peMajorVersion))
  1557  			argv = append(argv, fmt.Sprintf("-Wl,--minor-subsystem-version=%d", peMinorVersion))
  1558  		}
  1559  	case objabi.Haix:
  1560  		argv = append(argv, "-pthread")
  1561  		// prevent ld to reorder .text functions to keep the same
  1562  		// first/last functions for moduledata.
  1563  		argv = append(argv, "-Wl,-bnoobjreorder")
  1564  		// mcmodel=large is needed for every gcc generated files, but
  1565  		// ld still need -bbigtoc in order to allow larger TOC.
  1566  		argv = append(argv, "-mcmodel=large")
  1567  		argv = append(argv, "-Wl,-bbigtoc")
  1568  	}
  1569  
  1570  	// On PPC64, verify the external toolchain supports Power10. This is needed when
  1571  	// PC relative relocations might be generated by Go. Only targets compiling ELF
  1572  	// binaries might generate these relocations.
  1573  	if ctxt.IsPPC64() && ctxt.IsElf() && buildcfg.GOPPC64 >= 10 {
  1574  		if !linkerFlagSupported(ctxt.Arch, argv[0], "", "-mcpu=power10") {
  1575  			Exitf("The external toolchain does not support -mcpu=power10. " +
  1576  				" This is required to externally link GOPPC64 >= power10")
  1577  		}
  1578  	}
  1579  
  1580  	// Enable/disable ASLR on Windows.
  1581  	addASLRargs := func(argv []string, val bool) []string {
  1582  		// Old/ancient versions of GCC support "--dynamicbase" and
  1583  		// "--high-entropy-va" but don't enable it by default. In
  1584  		// addition, they don't accept "--disable-dynamicbase" or
  1585  		// "--no-dynamicbase", so the only way to disable ASLR is to
  1586  		// not pass any flags at all.
  1587  		//
  1588  		// More modern versions of GCC (and also clang) enable ASLR
  1589  		// by default. With these compilers, however you can turn it
  1590  		// off if you want using "--disable-dynamicbase" or
  1591  		// "--no-dynamicbase".
  1592  		//
  1593  		// The strategy below is to try using "--disable-dynamicbase";
  1594  		// if this succeeds, then assume we're working with more
  1595  		// modern compilers and act accordingly. If it fails, assume
  1596  		// an ancient compiler with ancient defaults.
  1597  		var dbopt string
  1598  		var heopt string
  1599  		dbon := wlPrefix + "dynamicbase"
  1600  		heon := wlPrefix + "high-entropy-va"
  1601  		dboff := wlPrefix + "disable-dynamicbase"
  1602  		heoff := wlPrefix + "disable-high-entropy-va"
  1603  		if isMSVC {
  1604  			heon = wlPrefix + "highentropyva"
  1605  			heoff = wlPrefix + "highentropyva:no"
  1606  			dboff = wlPrefix + "dynamicbase:no"
  1607  		}
  1608  		if val {
  1609  			dbopt = dbon
  1610  			heopt = heon
  1611  		} else {
  1612  			// Test to see whether "--disable-dynamicbase" works.
  1613  			newer := linkerFlagSupported(ctxt.Arch, argv[0], "", dboff)
  1614  			if newer {
  1615  				// Newer compiler, which supports both on/off options.
  1616  				dbopt = dboff
  1617  				heopt = heoff
  1618  			} else {
  1619  				// older toolchain: we have to say nothing in order to
  1620  				// get a no-ASLR binary.
  1621  				dbopt = ""
  1622  				heopt = ""
  1623  			}
  1624  		}
  1625  		if dbopt != "" {
  1626  			argv = append(argv, dbopt)
  1627  		}
  1628  		// enable high-entropy ASLR on 64-bit.
  1629  		if ctxt.Arch.PtrSize >= 8 && heopt != "" {
  1630  			argv = append(argv, heopt)
  1631  		}
  1632  		return argv
  1633  	}
  1634  
  1635  	switch ctxt.BuildMode {
  1636  	case BuildModeExe:
  1637  		if ctxt.HeadType == objabi.Hdarwin {
  1638  			if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() {
  1639  				argv = append(argv, "-Wl,-no_pie")
  1640  			}
  1641  		}
  1642  		if *flagRace && ctxt.HeadType == objabi.Hwindows {
  1643  			// Current windows/amd64 race detector tsan support
  1644  			// library can't handle PIE mode (see #53539 for more details).
  1645  			// For now, explicitly disable PIE (since some compilers
  1646  			// default to it) if -race is in effect.
  1647  			argv = addASLRargs(argv, false)
  1648  		}
  1649  	case BuildModePIE:
  1650  		switch ctxt.HeadType {
  1651  		case objabi.Hdarwin, objabi.Haix:
  1652  		case objabi.Hwindows:
  1653  			if *flagAslr && *flagRace {
  1654  				// Current windows/amd64 race detector tsan support
  1655  				// library can't handle PIE mode (see #53539 for more details).
  1656  				// Disable alsr if -race in effect.
  1657  				*flagAslr = false
  1658  			}
  1659  			argv = addASLRargs(argv, *flagAslr)
  1660  		default:
  1661  			// ELF.
  1662  			if ctxt.UseRelro() {
  1663  				argv = append(argv, "-Wl,-z,relro")
  1664  			}
  1665  			argv = append(argv, "-pie")
  1666  		}
  1667  	case BuildModeCShared:
  1668  		if ctxt.HeadType == objabi.Hdarwin {
  1669  			argv = append(argv, "-dynamiclib")
  1670  		} else {
  1671  			if ctxt.UseRelro() {
  1672  				argv = append(argv, "-Wl,-z,relro")
  1673  			}
  1674  			argv = append(argv, "-shared")
  1675  			if ctxt.HeadType == objabi.Hwindows {
  1676  				argv = addASLRargs(argv, *flagAslr)
  1677  			} else {
  1678  				// Pass -z nodelete to mark the shared library as
  1679  				// non-closeable: a dlclose will do nothing.
  1680  				argv = append(argv, "-Wl,-z,nodelete")
  1681  				// Only pass Bsymbolic on non-Windows.
  1682  				argv = append(argv, "-Wl,-Bsymbolic")
  1683  			}
  1684  		}
  1685  	case BuildModeShared:
  1686  		if ctxt.UseRelro() {
  1687  			argv = append(argv, "-Wl,-z,relro")
  1688  		}
  1689  		argv = append(argv, "-shared")
  1690  	case BuildModePlugin:
  1691  		if ctxt.HeadType == objabi.Hdarwin {
  1692  			argv = append(argv, "-dynamiclib")
  1693  		} else {
  1694  			if ctxt.UseRelro() {
  1695  				argv = append(argv, "-Wl,-z,relro")
  1696  			}
  1697  			argv = append(argv, "-shared")
  1698  		}
  1699  	}
  1700  
  1701  	var altLinker string
  1702  	if ctxt.IsELF && (ctxt.DynlinkingGo() || *flagBindNow) {
  1703  		// For ELF targets, when producing dynamically linked Go code
  1704  		// or when immediate binding is explicitly requested,
  1705  		// we force all symbol resolution to be done at program startup
  1706  		// because lazy PLT resolution can use large amounts of stack at
  1707  		// times we cannot allow it to do so.
  1708  		argv = append(argv, "-Wl,-z,now")
  1709  	}
  1710  
  1711  	if ctxt.IsELF && ctxt.DynlinkingGo() {
  1712  		// Do not let the host linker generate COPY relocations. These
  1713  		// can move symbols out of sections that rely on stable offsets
  1714  		// from the beginning of the section (like sym.STYPE).
  1715  		argv = append(argv, "-Wl,-z,nocopyreloc")
  1716  
  1717  		if buildcfg.GOOS == "android" {
  1718  			// Use lld to avoid errors from default linker (issue #38838)
  1719  			altLinker = "lld"
  1720  		}
  1721  
  1722  		if ctxt.Arch.InFamily(sys.ARM64) && buildcfg.GOOS == "linux" {
  1723  			// On ARM64, the GNU linker had issues with -znocopyreloc
  1724  			// and COPY relocations. This was fixed in GNU ld 2.36+.
  1725  			// https://sourceware.org/bugzilla/show_bug.cgi?id=19962
  1726  			// https://go.dev/issue/22040
  1727  			// And newer gold is deprecated, may lack new features/flags, or even missing
  1728  
  1729  			// If the default linker is GNU ld 2.35 or older, use gold
  1730  			useGold := false
  1731  			name, args := flagExtld[0], flagExtld[1:]
  1732  			args = append(args, "-Wl,--version")
  1733  			cmd := exec.Command(name, args...)
  1734  			if out, err := cmd.CombinedOutput(); err == nil {
  1735  				// Parse version from output like "GNU ld (GNU Binutils for Distro) 2.36.1"
  1736  				for line := range strings.Lines(string(out)) {
  1737  					if !strings.HasPrefix(line, "GNU ld ") {
  1738  						continue
  1739  					}
  1740  					fields := strings.Fields(line[len("GNU ld "):])
  1741  					var major, minor int
  1742  					if ret, err := fmt.Sscanf(fields[len(fields)-1], "%d.%d", &major, &minor); ret == 2 && err == nil {
  1743  						if major == 2 && minor <= 35 {
  1744  							useGold = true
  1745  						}
  1746  						break
  1747  					}
  1748  				}
  1749  			}
  1750  
  1751  			if useGold {
  1752  				// Use gold for older linkers
  1753  				altLinker = "gold"
  1754  
  1755  				// If gold is not installed, gcc will silently switch
  1756  				// back to ld.bfd. So we parse the version information
  1757  				// and provide a useful error if gold is missing.
  1758  				args = flagExtld[1:]
  1759  				args = append(args, "-fuse-ld=gold", "-Wl,--version")
  1760  				cmd = exec.Command(name, args...)
  1761  				if out, err := cmd.CombinedOutput(); err == nil {
  1762  					if !bytes.Contains(out, []byte("GNU gold")) {
  1763  						log.Fatalf("ARM64 external linker must be ld>=2.36 or gold (issue #15696, 22040), but is not: %s", out)
  1764  					}
  1765  				}
  1766  			}
  1767  		}
  1768  	}
  1769  	if ctxt.Arch.Family == sys.ARM64 && buildcfg.GOOS == "freebsd" {
  1770  		// Switch to ld.bfd on freebsd/arm64.
  1771  		altLinker = "bfd"
  1772  
  1773  		// Provide a useful error if ld.bfd is missing.
  1774  		name, args := flagExtld[0], flagExtld[1:]
  1775  		args = append(args, "-fuse-ld=bfd", "-Wl,--version")
  1776  		cmd := exec.Command(name, args...)
  1777  		if out, err := cmd.CombinedOutput(); err == nil {
  1778  			if !bytes.Contains(out, []byte("GNU ld")) {
  1779  				log.Fatalf("ARM64 external linker must be ld.bfd (issue #35197), please install devel/binutils")
  1780  			}
  1781  		}
  1782  	}
  1783  	if altLinker != "" {
  1784  		argv = append(argv, "-fuse-ld="+altLinker)
  1785  	}
  1786  
  1787  	if ctxt.IsELF && linkerFlagSupported(ctxt.Arch, argv[0], "", "-Wl,--build-id=0x1234567890abcdef") { // Solaris ld doesn't support --build-id.
  1788  		if len(buildinfo) > 0 {
  1789  			argv = append(argv, fmt.Sprintf("-Wl,--build-id=0x%x", buildinfo))
  1790  		} else if *flagHostBuildid == "none" {
  1791  			argv = append(argv, "-Wl,--build-id=none")
  1792  		}
  1793  	}
  1794  
  1795  	// On Windows, given -o foo, GCC will append ".exe" to produce
  1796  	// "foo.exe".  We have decided that we want to honor the -o
  1797  	// option. To make this work, we append a '.' so that GCC
  1798  	// will decide that the file already has an extension. We
  1799  	// only want to do this when producing a Windows output file
  1800  	// on a Windows host.
  1801  	outopt := *flagOutfile
  1802  	if buildcfg.GOOS == "windows" && runtime.GOOS == "windows" && filepath.Ext(outopt) == "" {
  1803  		outopt += "."
  1804  	}
  1805  	argv = append(argv, "-o")
  1806  	argv = append(argv, outopt)
  1807  
  1808  	if rpath.val != "" {
  1809  		argv = append(argv, fmt.Sprintf("-Wl,-rpath,%s", rpath.val))
  1810  	}
  1811  
  1812  	if *flagInterpreter != "" {
  1813  		// Many linkers support both -I and the --dynamic-linker flags
  1814  		// to set the ELF interpreter, but lld only supports
  1815  		// --dynamic-linker so prefer that (ld on very old Solaris only
  1816  		// supports -I but that seems less important).
  1817  		argv = append(argv, fmt.Sprintf("-Wl,--dynamic-linker,%s", *flagInterpreter))
  1818  	}
  1819  
  1820  	// Force global symbols to be exported for dlopen, etc.
  1821  	switch {
  1822  	case ctxt.IsELF:
  1823  		if ctxt.DynlinkingGo() || ctxt.BuildMode == BuildModeCShared || !linkerFlagSupported(ctxt.Arch, argv[0], altLinker, "-Wl,--export-dynamic-symbol=main") {
  1824  			argv = append(argv, "-rdynamic")
  1825  		} else {
  1826  			var exports []string
  1827  			ctxt.loader.ForAllCgoExportDynamic(func(s loader.Sym) {
  1828  				exports = append(exports, "-Wl,--export-dynamic-symbol="+ctxt.loader.SymExtname(s))
  1829  			})
  1830  			sort.Strings(exports)
  1831  			argv = append(argv, exports...)
  1832  		}
  1833  	case ctxt.IsAIX():
  1834  		fileName := xcoffCreateExportFile(ctxt)
  1835  		argv = append(argv, "-Wl,-bE:"+fileName)
  1836  	case ctxt.IsWindows() && !slices.Contains(flagExtldflags, wlPrefix+"export-all-symbols"):
  1837  		fileName := peCreateExportFile(ctxt, filepath.Base(outopt))
  1838  		prefix := ""
  1839  		if isMSVC {
  1840  			prefix = "-Wl,-def:"
  1841  		}
  1842  		argv = append(argv, prefix+fileName)
  1843  	}
  1844  
  1845  	const unusedArguments = "-Qunused-arguments"
  1846  	if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, unusedArguments) {
  1847  		argv = append(argv, unusedArguments)
  1848  	}
  1849  
  1850  	if ctxt.IsWindows() {
  1851  		// Suppress generation of the PE file header timestamp,
  1852  		// so as to avoid spurious build ID differences between
  1853  		// linked binaries that are otherwise identical other than
  1854  		// the date/time they were linked.
  1855  		const noTimeStamp = "-Wl,--no-insert-timestamp"
  1856  		if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, noTimeStamp) {
  1857  			argv = append(argv, noTimeStamp)
  1858  		}
  1859  	}
  1860  
  1861  	const compressDWARF = "-Wl,--compress-debug-sections=zlib"
  1862  	if ctxt.compressDWARF && linkerFlagSupported(ctxt.Arch, argv[0], altLinker, compressDWARF) {
  1863  		argv = append(argv, compressDWARF)
  1864  	}
  1865  
  1866  	hostObjCopyPaths := ctxt.hostobjCopy()
  1867  	cleanTimeStamps(hostObjCopyPaths)
  1868  	godotopath := filepath.Join(*flagTmpdir, "go.o")
  1869  	cleanTimeStamps([]string{godotopath})
  1870  
  1871  	argv = append(argv, godotopath)
  1872  	argv = append(argv, hostObjCopyPaths...)
  1873  	if ctxt.HeadType == objabi.Haix {
  1874  		// We want to have C files after Go files to remove
  1875  		// trampolines csects made by ld.
  1876  		argv = append(argv, "-nostartfiles")
  1877  		argv = append(argv, "/lib/crt0_64.o")
  1878  
  1879  		extld := ctxt.extld()
  1880  		name, args := extld[0], extld[1:]
  1881  		// Get starting files.
  1882  		getPathFile := func(file string) string {
  1883  			args := append(args, "-maix64", "--print-file-name="+file)
  1884  			out, err := exec.Command(name, args...).CombinedOutput()
  1885  			if err != nil {
  1886  				log.Fatalf("running %s failed: %v\n%s", extld, err, out)
  1887  			}
  1888  			return strings.Trim(string(out), "\n")
  1889  		}
  1890  		// Since GCC version 11, the 64-bit version of GCC starting files
  1891  		// are now suffixed by "_64". Even under "-maix64" multilib directory
  1892  		// "crtcxa.o" is 32-bit.
  1893  		crtcxa := getPathFile("crtcxa_64.o")
  1894  		if !filepath.IsAbs(crtcxa) {
  1895  			crtcxa = getPathFile("crtcxa.o")
  1896  		}
  1897  		crtdbase := getPathFile("crtdbase_64.o")
  1898  		if !filepath.IsAbs(crtdbase) {
  1899  			crtdbase = getPathFile("crtdbase.o")
  1900  		}
  1901  		argv = append(argv, crtcxa)
  1902  		argv = append(argv, crtdbase)
  1903  	}
  1904  
  1905  	if ctxt.linkShared {
  1906  		seenDirs := make(map[string]bool)
  1907  		seenLibs := make(map[string]bool)
  1908  		addshlib := func(path string) {
  1909  			dir, base := filepath.Split(path)
  1910  			if !seenDirs[dir] {
  1911  				argv = append(argv, "-L"+dir)
  1912  				if !rpath.set {
  1913  					argv = append(argv, "-Wl,-rpath="+dir)
  1914  				}
  1915  				seenDirs[dir] = true
  1916  			}
  1917  			base = strings.TrimSuffix(base, ".so")
  1918  			base = strings.TrimPrefix(base, "lib")
  1919  			if !seenLibs[base] {
  1920  				argv = append(argv, "-l"+base)
  1921  				seenLibs[base] = true
  1922  			}
  1923  		}
  1924  		for _, shlib := range ctxt.Shlibs {
  1925  			addshlib(shlib.Path)
  1926  			for _, dep := range shlib.Deps {
  1927  				if dep == "" {
  1928  					continue
  1929  				}
  1930  				libpath := findshlib(ctxt, dep)
  1931  				if libpath != "" {
  1932  					addshlib(libpath)
  1933  				}
  1934  			}
  1935  		}
  1936  	}
  1937  
  1938  	// clang, unlike GCC, passes -rdynamic to the linker
  1939  	// even when linking with -static, causing a linker
  1940  	// error when using GNU ld. So take out -rdynamic if
  1941  	// we added it. We do it in this order, rather than
  1942  	// only adding -rdynamic later, so that -extldflags
  1943  	// can override -rdynamic without using -static.
  1944  	// Similarly for -Wl,--dynamic-linker.
  1945  	checkStatic := func(arg string) {
  1946  		if ctxt.IsELF && arg == "-static" {
  1947  			for i := range argv {
  1948  				if argv[i] == "-rdynamic" || strings.HasPrefix(argv[i], "-Wl,--dynamic-linker,") {
  1949  					argv[i] = "-static"
  1950  				}
  1951  			}
  1952  		}
  1953  	}
  1954  
  1955  	for _, p := range ldflag {
  1956  		argv = append(argv, p)
  1957  		checkStatic(p)
  1958  	}
  1959  
  1960  	// When building a program with the default -buildmode=exe the
  1961  	// gc compiler generates code requires DT_TEXTREL in a
  1962  	// position independent executable (PIE). On systems where the
  1963  	// toolchain creates PIEs by default, and where DT_TEXTREL
  1964  	// does not work, the resulting programs will not run. See
  1965  	// issue #17847. To avoid this problem pass -no-pie to the
  1966  	// toolchain if it is supported.
  1967  	if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared && !(ctxt.IsDarwin() && ctxt.IsARM64()) {
  1968  		// GCC uses -no-pie, clang uses -nopie.
  1969  		for _, nopie := range []string{"-no-pie", "-nopie"} {
  1970  			if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, nopie) {
  1971  				argv = append(argv, nopie)
  1972  				break
  1973  			}
  1974  		}
  1975  	}
  1976  
  1977  	for _, p := range flagExtldflags {
  1978  		argv = append(argv, p)
  1979  		checkStatic(p)
  1980  	}
  1981  	if ctxt.HeadType == objabi.Hwindows {
  1982  		// use gcc linker script to work around gcc bug
  1983  		// (see https://golang.org/issue/20183 for details).
  1984  		if !isLLD {
  1985  			p := writeGDBLinkerScript()
  1986  			argv = append(argv, "-Wl,-T,"+p)
  1987  		}
  1988  		if *flagRace {
  1989  			// Apparently --print-file-name doesn't work with -msvc clang.
  1990  			// (The library name is synchronization.lib, but even with that
  1991  			// name it still doesn't print the full path.) Assume it always
  1992  			// it.
  1993  			if isMSVC || ctxt.findLibPath("libsynchronization.a") != "libsynchronization.a" {
  1994  				argv = append(argv, "-lsynchronization")
  1995  			}
  1996  		}
  1997  		if !isMSVC {
  1998  			// libmingw32 and libmingwex have some inter-dependencies,
  1999  			// so must use linker groups.
  2000  			argv = append(argv, "-Wl,--start-group", "-lmingwex", "-lmingw32", "-Wl,--end-group")
  2001  		}
  2002  		argv = append(argv, peimporteddlls()...)
  2003  	}
  2004  
  2005  	argv = ctxt.passLongArgsInResponseFile(argv, altLinker)
  2006  
  2007  	if ctxt.Debugvlog != 0 {
  2008  		ctxt.Logf("host link:")
  2009  		for _, v := range argv {
  2010  			ctxt.Logf(" %q", v)
  2011  		}
  2012  		ctxt.Logf("\n")
  2013  	}
  2014  
  2015  	cmd := exec.Command(argv[0], argv[1:]...)
  2016  	out, err := cmd.CombinedOutput()
  2017  	if err != nil {
  2018  		Exitf("running %s failed: %v\n%s\n%s", argv[0], err, cmd, out)
  2019  	}
  2020  
  2021  	// Filter out useless linker warnings caused by bugs outside Go.
  2022  	// See also cmd/go/internal/work/exec.go's gccld method.
  2023  	var save [][]byte
  2024  	var skipLines int
  2025  	for _, line := range bytes.SplitAfter(out, []byte("\n")) {
  2026  		// golang.org/issue/26073 - Apple Xcode bug
  2027  		if bytes.Contains(line, []byte("ld: warning: text-based stub file")) {
  2028  			continue
  2029  		}
  2030  
  2031  		if skipLines > 0 {
  2032  			skipLines--
  2033  			continue
  2034  		}
  2035  
  2036  		// Remove TOC overflow warning on AIX.
  2037  		if bytes.Contains(line, []byte("ld: 0711-783")) {
  2038  			skipLines = 2
  2039  			continue
  2040  		}
  2041  
  2042  		save = append(save, line)
  2043  	}
  2044  	out = bytes.Join(save, nil)
  2045  
  2046  	if len(out) > 0 {
  2047  		// always print external output even if the command is successful, so that we don't
  2048  		// swallow linker warnings (see https://golang.org/issue/17935).
  2049  		if ctxt.IsDarwin() && ctxt.IsAMD64() {
  2050  			const noPieWarning = "ld: warning: -no_pie is deprecated when targeting new OS versions\n"
  2051  			if i := bytes.Index(out, []byte(noPieWarning)); i >= 0 {
  2052  				// swallow -no_pie deprecation warning, issue 54482
  2053  				out = append(out[:i], out[i+len(noPieWarning):]...)
  2054  			}
  2055  		}
  2056  		if ctxt.IsDarwin() {
  2057  			const bindAtLoadWarning = "ld: warning: -bind_at_load is deprecated on macOS\n"
  2058  			if i := bytes.Index(out, []byte(bindAtLoadWarning)); i >= 0 {
  2059  				// -bind_at_load is deprecated with ld-prime, but needed for
  2060  				// correctness with older versions of ld64. Swallow the warning.
  2061  				// TODO: maybe pass -bind_at_load conditionally based on C
  2062  				// linker version.
  2063  				out = append(out[:i], out[i+len(bindAtLoadWarning):]...)
  2064  			}
  2065  		}
  2066  		ctxt.Logf("%s", out)
  2067  	}
  2068  
  2069  	// Helper for updating a Macho binary in some way (shared between
  2070  	// dwarf combining and UUID update).
  2071  	updateMachoOutFile := func(op string, updateFunc machoUpdateFunc) {
  2072  		// For os.Rename to work reliably, must be in same directory as outfile.
  2073  		rewrittenOutput := *flagOutfile + "~"
  2074  		exef, err := os.Open(*flagOutfile)
  2075  		if err != nil {
  2076  			Exitf("%s: %s failed: %v", os.Args[0], op, err)
  2077  		}
  2078  		defer exef.Close()
  2079  		exem, err := macho.NewFile(exef)
  2080  		if err != nil {
  2081  			Exitf("%s: parsing Mach-O header failed: %v", os.Args[0], err)
  2082  		}
  2083  		if err := updateFunc(ctxt, exef, exem, rewrittenOutput); err != nil {
  2084  			Exitf("%s: %s failed: %v", os.Args[0], op, err)
  2085  		}
  2086  		os.Remove(*flagOutfile)
  2087  		if err := os.Rename(rewrittenOutput, *flagOutfile); err != nil {
  2088  			Exitf("%s: %v", os.Args[0], err)
  2089  		}
  2090  	}
  2091  
  2092  	uuidUpdated := false
  2093  	if combineDwarf {
  2094  		// Find "dsymutils" and "strip" tools using CC --print-prog-name.
  2095  		dsymutilCmd := ctxt.findExtLinkTool("dsymutil")
  2096  		stripCmd := ctxt.findExtLinkTool("strip")
  2097  
  2098  		dsym := filepath.Join(*flagTmpdir, "go.dwarf")
  2099  		cmd := exec.Command(dsymutilCmd, "-f", *flagOutfile, "-o", dsym)
  2100  		// dsymutil may not clean up its temp directory at exit.
  2101  		// Set DSYMUTIL_REPRODUCER_PATH to work around. see issue 59026.
  2102  		// dsymutil (Apple LLVM version 16.0.0) deletes the directory
  2103  		// even if it is not empty. We still need our tmpdir, so give a
  2104  		// subdirectory to dsymutil.
  2105  		dsymDir := filepath.Join(*flagTmpdir, "dsymutil")
  2106  		err := os.MkdirAll(dsymDir, 0777)
  2107  		if err != nil {
  2108  			Exitf("fail to create temp dir: %v", err)
  2109  		}
  2110  		cmd.Env = append(os.Environ(), "DSYMUTIL_REPRODUCER_PATH="+dsymDir)
  2111  		if ctxt.Debugvlog != 0 {
  2112  			ctxt.Logf("host link dsymutil:")
  2113  			for _, v := range cmd.Args {
  2114  				ctxt.Logf(" %q", v)
  2115  			}
  2116  			ctxt.Logf("\n")
  2117  		}
  2118  		if out, err := cmd.CombinedOutput(); err != nil {
  2119  			Exitf("%s: running dsymutil failed: %v\n%s\n%s", os.Args[0], err, cmd, out)
  2120  		}
  2121  		// Remove STAB (symbolic debugging) symbols after we are done with them (by dsymutil).
  2122  		// They contain temporary file paths and make the build not reproducible.
  2123  		var stripArgs = []string{"-S"}
  2124  		if debug_s {
  2125  			// We are generating a binary with symbol table suppressed.
  2126  			// Suppress local symbols. We need to keep dynamically exported
  2127  			// and referenced symbols so the dynamic linker can resolve them.
  2128  			stripArgs = append(stripArgs, "-x")
  2129  		}
  2130  		stripArgs = append(stripArgs, *flagOutfile)
  2131  		if ctxt.Debugvlog != 0 {
  2132  			ctxt.Logf("host link strip: %q", stripCmd)
  2133  			for _, v := range stripArgs {
  2134  				ctxt.Logf(" %q", v)
  2135  			}
  2136  			ctxt.Logf("\n")
  2137  		}
  2138  		cmd = exec.Command(stripCmd, stripArgs...)
  2139  		if out, err := cmd.CombinedOutput(); err != nil {
  2140  			Exitf("%s: running strip failed: %v\n%s\n%s", os.Args[0], err, cmd, out)
  2141  		}
  2142  		// Skip combining if `dsymutil` didn't generate a file. See #11994.
  2143  		if _, err := os.Stat(dsym); err == nil {
  2144  			updateMachoOutFile("combining dwarf",
  2145  				func(ctxt *Link, exef *os.File, exem *macho.File, outexe string) error {
  2146  					return machoCombineDwarf(ctxt, exef, exem, dsym, outexe)
  2147  				})
  2148  			uuidUpdated = true
  2149  		}
  2150  	}
  2151  	if ctxt.IsDarwin() && !uuidUpdated && len(buildinfo) > 0 {
  2152  		updateMachoOutFile("rewriting uuid",
  2153  			func(ctxt *Link, exef *os.File, exem *macho.File, outexe string) error {
  2154  				return machoRewriteUuid(ctxt, exef, exem, outexe)
  2155  			})
  2156  	}
  2157  	hostlinkfips(ctxt, *flagOutfile, *flagFipso)
  2158  	if ctxt.NeedCodeSign() {
  2159  		err := machoCodeSign(ctxt, *flagOutfile)
  2160  		if err != nil {
  2161  			Exitf("%s: code signing failed: %v", os.Args[0], err)
  2162  		}
  2163  	}
  2164  }
  2165  
  2166  // passLongArgsInResponseFile writes the arguments into a file if they
  2167  // are very long.
  2168  func (ctxt *Link) passLongArgsInResponseFile(argv []string, altLinker string) []string {
  2169  	c := 0
  2170  	for _, arg := range argv {
  2171  		c += len(arg)
  2172  	}
  2173  
  2174  	if c < sys.ExecArgLengthLimit {
  2175  		return argv
  2176  	}
  2177  
  2178  	// Only use response files if they are supported.
  2179  	response := filepath.Join(*flagTmpdir, "response")
  2180  	if err := os.WriteFile(response, nil, 0644); err != nil {
  2181  		log.Fatalf("failed while testing response file: %v", err)
  2182  	}
  2183  	if !linkerFlagSupported(ctxt.Arch, argv[0], altLinker, "@"+response) {
  2184  		if ctxt.Debugvlog != 0 {
  2185  			ctxt.Logf("not using response file because linker does not support one")
  2186  		}
  2187  		return argv
  2188  	}
  2189  
  2190  	var buf bytes.Buffer
  2191  	for _, arg := range argv[1:] {
  2192  		// The external linker response file supports quoted strings.
  2193  		fmt.Fprintf(&buf, "%q\n", arg)
  2194  	}
  2195  	if err := os.WriteFile(response, buf.Bytes(), 0644); err != nil {
  2196  		log.Fatalf("failed while writing response file: %v", err)
  2197  	}
  2198  	if ctxt.Debugvlog != 0 {
  2199  		ctxt.Logf("response file %s contents:\n%s", response, buf.Bytes())
  2200  	}
  2201  	return []string{
  2202  		argv[0],
  2203  		"@" + response,
  2204  	}
  2205  }
  2206  
  2207  var createTrivialCOnce sync.Once
  2208  
  2209  func linkerFlagSupported(arch *sys.Arch, linker, altLinker, flag string) bool {
  2210  	createTrivialCOnce.Do(func() {
  2211  		src := filepath.Join(*flagTmpdir, "trivial.c")
  2212  		if err := os.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
  2213  			Errorf("WriteFile trivial.c failed: %v", err)
  2214  		}
  2215  	})
  2216  
  2217  	flags := hostlinkArchArgs(arch)
  2218  
  2219  	moreFlags := trimLinkerArgv(append(ldflag, flagExtldflags...))
  2220  	flags = append(flags, moreFlags...)
  2221  
  2222  	if altLinker != "" {
  2223  		flags = append(flags, "-fuse-ld="+altLinker)
  2224  	}
  2225  	trivialPath := filepath.Join(*flagTmpdir, "trivial.c")
  2226  	outPath := filepath.Join(*flagTmpdir, "a.out")
  2227  	flags = append(flags, "-o", outPath, flag, trivialPath)
  2228  
  2229  	cmd := exec.Command(linker, flags...)
  2230  	cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
  2231  	out, err := cmd.CombinedOutput()
  2232  	// GCC says "unrecognized command line option ‘-no-pie’"
  2233  	// clang says "unknown argument: '-no-pie'"
  2234  	return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
  2235  }
  2236  
  2237  // peHasLoadConfigDirectorySupport checks whether the external linker
  2238  // populates the PE Load Configuration Directory data directory entry
  2239  // when it encounters a _load_config_used symbol.
  2240  //
  2241  // GNU ld gained this support in binutils 2.45. MSVC link.exe and
  2242  // LLVM lld-link have always supported it.
  2243  func peHasLoadConfigDirectorySupport(arch *sys.Arch, linker string) bool {
  2244  	src := filepath.Join(*flagTmpdir, "loadcfg_test.c")
  2245  	if err := os.WriteFile(src, []byte(`
  2246  #ifdef _WIN64
  2247  typedef unsigned long long uintptr;
  2248  #else
  2249  typedef unsigned long uintptr;
  2250  #endif
  2251  const uintptr _load_config_used[2] = { sizeof(_load_config_used), 0 };
  2252  int main() { return 0; }
  2253  `), 0666); err != nil {
  2254  		return false
  2255  	}
  2256  
  2257  	outPath := filepath.Join(*flagTmpdir, "loadcfg_test.exe")
  2258  	flags := hostlinkArchArgs(arch)
  2259  	flags = append(flags, "-o", outPath, src)
  2260  	cmd := exec.Command(linker, flags...)
  2261  	cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
  2262  	if err := cmd.Run(); err != nil {
  2263  		return false
  2264  	}
  2265  
  2266  	f, err := pe.Open(outPath)
  2267  	if err != nil {
  2268  		return false
  2269  	}
  2270  	defer f.Close()
  2271  
  2272  	switch oh := f.OptionalHeader.(type) {
  2273  	case *pe.OptionalHeader64:
  2274  		if int(pe.IMAGE_DIRECTORY_ENTRY_LOAD_CONFIG) < len(oh.DataDirectory) {
  2275  			return oh.DataDirectory[pe.IMAGE_DIRECTORY_ENTRY_LOAD_CONFIG].VirtualAddress != 0
  2276  		}
  2277  	case *pe.OptionalHeader32:
  2278  		if int(pe.IMAGE_DIRECTORY_ENTRY_LOAD_CONFIG) < len(oh.DataDirectory) {
  2279  			return oh.DataDirectory[pe.IMAGE_DIRECTORY_ENTRY_LOAD_CONFIG].VirtualAddress != 0
  2280  		}
  2281  	}
  2282  	return false
  2283  }
  2284  
  2285  // trimLinkerArgv returns a new copy of argv that does not include flags
  2286  // that are not relevant for testing whether some linker option works.
  2287  func trimLinkerArgv(argv []string) []string {
  2288  	flagsWithNextArgSkip := []string{
  2289  		"-F",
  2290  		"-l",
  2291  		"-framework",
  2292  		"-Wl,-framework",
  2293  		"-Wl,-rpath",
  2294  		"-Wl,-undefined",
  2295  	}
  2296  	flagsWithNextArgKeep := []string{
  2297  		"-B",
  2298  		"-L",
  2299  		"-arch",
  2300  		"-isysroot",
  2301  		"--sysroot",
  2302  		"-target",
  2303  		"--target",
  2304  		"-resource-dir",
  2305  		"-rtlib",
  2306  		"--rtlib",
  2307  		"-stdlib",
  2308  		"--stdlib",
  2309  		"-unwindlib",
  2310  		"--unwindlib",
  2311  	}
  2312  	prefixesToKeep := []string{
  2313  		"-B",
  2314  		"-L",
  2315  		"-f",
  2316  		"-m",
  2317  		"-p",
  2318  		"-Wl,",
  2319  		"-arch",
  2320  		"-isysroot",
  2321  		"--sysroot",
  2322  		"-target",
  2323  		"--target",
  2324  		"-resource-dir",
  2325  		"-rtlib",
  2326  		"--rtlib",
  2327  		"-stdlib",
  2328  		"--stdlib",
  2329  		"-unwindlib",
  2330  		"--unwindlib",
  2331  		"-nostdlib++",
  2332  		"-nostdlib",
  2333  		"-nodefaultlibs",
  2334  		"-nostartfiles",
  2335  		"-nostdinc++",
  2336  		"-nostdinc",
  2337  		"-nobuiltininc",
  2338  	}
  2339  
  2340  	var flags []string
  2341  	keep := false
  2342  	skip := false
  2343  	for _, f := range argv {
  2344  		if keep {
  2345  			flags = append(flags, f)
  2346  			keep = false
  2347  		} else if skip {
  2348  			skip = false
  2349  		} else if f == "" || f[0] != '-' {
  2350  		} else if slices.Contains(flagsWithNextArgSkip, f) {
  2351  			skip = true
  2352  		} else if slices.Contains(flagsWithNextArgKeep, f) {
  2353  			flags = append(flags, f)
  2354  			keep = true
  2355  		} else {
  2356  			for _, p := range prefixesToKeep {
  2357  				if strings.HasPrefix(f, p) {
  2358  					flags = append(flags, f)
  2359  					break
  2360  				}
  2361  			}
  2362  		}
  2363  	}
  2364  	return flags
  2365  }
  2366  
  2367  // hostlinkArchArgs returns arguments to pass to the external linker
  2368  // based on the architecture.
  2369  func hostlinkArchArgs(arch *sys.Arch) []string {
  2370  	switch arch.Family {
  2371  	case sys.I386:
  2372  		return []string{"-m32"}
  2373  	case sys.AMD64:
  2374  		if buildcfg.GOOS == "darwin" {
  2375  			return []string{"-arch", "x86_64", "-m64"}
  2376  		}
  2377  		return []string{"-m64"}
  2378  	case sys.S390X:
  2379  		return []string{"-m64"}
  2380  	case sys.ARM:
  2381  		return []string{"-marm"}
  2382  	case sys.ARM64:
  2383  		if buildcfg.GOOS == "darwin" {
  2384  			return []string{"-arch", "arm64"}
  2385  		}
  2386  	case sys.Loong64:
  2387  		return []string{"-mabi=lp64d"}
  2388  	case sys.MIPS64:
  2389  		return []string{"-mabi=64"}
  2390  	case sys.MIPS:
  2391  		return []string{"-mabi=32"}
  2392  	case sys.PPC64:
  2393  		if buildcfg.GOOS == "aix" {
  2394  			return []string{"-maix64"}
  2395  		} else {
  2396  			return []string{"-m64"}
  2397  		}
  2398  
  2399  	}
  2400  	return nil
  2401  }
  2402  
  2403  var wantHdr = objabi.HeaderString()
  2404  
  2405  // ldobj loads an input object. If it is a host object (an object
  2406  // compiled by a non-Go compiler) it returns the Hostobj pointer. If
  2407  // it is a Go object, it returns nil.
  2408  func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string, file string) *Hostobj {
  2409  	pkg := objabi.PathToPrefix(lib.Pkg)
  2410  
  2411  	eof := f.Offset() + length
  2412  	start := f.Offset()
  2413  	c1 := bgetc(f)
  2414  	c2 := bgetc(f)
  2415  	c3 := bgetc(f)
  2416  	c4 := bgetc(f)
  2417  	f.MustSeek(start, 0)
  2418  
  2419  	unit := &sym.CompilationUnit{Lib: lib}
  2420  	lib.Units = append(lib.Units, unit)
  2421  
  2422  	magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
  2423  	if magic == 0x7f454c46 { // \x7F E L F
  2424  		ldelf := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
  2425  			textp, flags, err := loadelf.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn, ehdr.Flags)
  2426  			if err != nil {
  2427  				Errorf("%v", err)
  2428  				return
  2429  			}
  2430  			ehdr.Flags = flags
  2431  			ctxt.Textp = append(ctxt.Textp, textp...)
  2432  		}
  2433  		return ldhostobj(ldelf, ctxt.HeadType, f, pkg, length, pn, file)
  2434  	}
  2435  
  2436  	if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
  2437  		ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
  2438  			textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
  2439  			if err != nil {
  2440  				Errorf("%v", err)
  2441  				return
  2442  			}
  2443  			ctxt.Textp = append(ctxt.Textp, textp...)
  2444  		}
  2445  		return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
  2446  	}
  2447  
  2448  	switch c1<<8 | c2 {
  2449  	case 0x4c01, // 386
  2450  		0x6486, // amd64
  2451  		0xc401, // arm
  2452  		0x64aa: // arm64
  2453  		ldpe := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
  2454  			ls, err := loadpe.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
  2455  			if err != nil {
  2456  				Errorf("%v", err)
  2457  				return
  2458  			}
  2459  			if len(ls.Resources) != 0 {
  2460  				setpersrc(ctxt, ls.Resources)
  2461  			}
  2462  			sehp.pdata = append(sehp.pdata, ls.PData...)
  2463  			if ls.XData != 0 {
  2464  				sehp.xdata = append(sehp.xdata, ls.XData)
  2465  			}
  2466  			ctxt.Textp = append(ctxt.Textp, ls.Textp...)
  2467  		}
  2468  		return ldhostobj(ldpe, ctxt.HeadType, f, pkg, length, pn, file)
  2469  	}
  2470  
  2471  	if c1 == 0x01 && (c2 == 0xD7 || c2 == 0xF7) {
  2472  		ldxcoff := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
  2473  			textp, err := loadxcoff.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
  2474  			if err != nil {
  2475  				Errorf("%v", err)
  2476  				return
  2477  			}
  2478  			ctxt.Textp = append(ctxt.Textp, textp...)
  2479  		}
  2480  		return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
  2481  	}
  2482  
  2483  	if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
  2484  		// An unrecognized object is just passed to the external linker.
  2485  		// If we try to read symbols from this object, we will
  2486  		// report an error at that time.
  2487  		unknownObjFormat = true
  2488  		return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
  2489  	}
  2490  
  2491  	/* check the header */
  2492  	line, err := f.ReadString('\n')
  2493  	if err != nil {
  2494  		Errorf("truncated object file: %s: %v", pn, err)
  2495  		return nil
  2496  	}
  2497  
  2498  	if !strings.HasPrefix(line, "go object ") {
  2499  		if strings.HasSuffix(pn, ".go") {
  2500  			Exitf("%s: uncompiled .go source file", pn)
  2501  			return nil
  2502  		}
  2503  
  2504  		if line == ctxt.Arch.Name {
  2505  			// old header format: just $GOOS
  2506  			Errorf("%s: stale object file", pn)
  2507  			return nil
  2508  		}
  2509  
  2510  		Errorf("%s: not an object file: @%d %q", pn, start, line)
  2511  		return nil
  2512  	}
  2513  
  2514  	// First, check that the basic GOOS, GOARCH, and Version match.
  2515  	if line != wantHdr {
  2516  		Errorf("%s: linked object header mismatch:\nhave %q\nwant %q\n", pn, line, wantHdr)
  2517  	}
  2518  
  2519  	// Skip over exports and other info -- ends with \n!\n.
  2520  	//
  2521  	// Note: It's possible for "\n!\n" to appear within the binary
  2522  	// package export data format. To avoid truncating the package
  2523  	// definition prematurely (issue 21703), we keep track of
  2524  	// how many "$$" delimiters we've seen.
  2525  
  2526  	import0 := f.Offset()
  2527  
  2528  	c1 = '\n' // the last line ended in \n
  2529  	c2 = bgetc(f)
  2530  	c3 = bgetc(f)
  2531  	markers := 0
  2532  	for {
  2533  		if c1 == '\n' {
  2534  			if markers%2 == 0 && c2 == '!' && c3 == '\n' {
  2535  				break
  2536  			}
  2537  			if c2 == '$' && c3 == '$' {
  2538  				markers++
  2539  			}
  2540  		}
  2541  
  2542  		c1 = c2
  2543  		c2 = c3
  2544  		c3 = bgetc(f)
  2545  		if c3 == -1 {
  2546  			Errorf("truncated object file: %s", pn)
  2547  			return nil
  2548  		}
  2549  	}
  2550  
  2551  	import1 := f.Offset()
  2552  
  2553  	f.MustSeek(import0, 0)
  2554  	ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
  2555  	f.MustSeek(import1, 0)
  2556  
  2557  	fingerprint := ctxt.loader.Preload(ctxt.IncVersion(), f, lib, unit, eof-f.Offset())
  2558  	if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
  2559  		// Check fingerprint, to ensure the importing and imported packages
  2560  		// have consistent view of symbol indices.
  2561  		// Normally the go command should ensure this. But in case something
  2562  		// goes wrong, it could lead to obscure bugs like run-time crash.
  2563  		// Check it here to be sure.
  2564  		if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
  2565  			lib.Fingerprint = fingerprint
  2566  		}
  2567  		checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
  2568  	}
  2569  
  2570  	addImports(ctxt, lib, pn)
  2571  	return nil
  2572  }
  2573  
  2574  // symbolsAreUnresolved scans through the loader's list of unresolved
  2575  // symbols and checks to see whether any of them match the names of the
  2576  // symbols in 'want'. Return value is a list of bools, with list[K] set
  2577  // to true if there is an unresolved reference to the symbol in want[K].
  2578  func symbolsAreUnresolved(ctxt *Link, want []string) []bool {
  2579  	returnAllUndefs := -1
  2580  	undefs, _ := ctxt.loader.UndefinedRelocTargets(returnAllUndefs)
  2581  	seen := make(map[loader.Sym]struct{})
  2582  	rval := make([]bool, len(want))
  2583  	wantm := make(map[string]int)
  2584  	for k, w := range want {
  2585  		wantm[w] = k
  2586  	}
  2587  	count := 0
  2588  	for _, s := range undefs {
  2589  		if _, ok := seen[s]; ok {
  2590  			continue
  2591  		}
  2592  		seen[s] = struct{}{}
  2593  		if k, ok := wantm[ctxt.loader.SymName(s)]; ok {
  2594  			rval[k] = true
  2595  			count++
  2596  			if count == len(want) {
  2597  				return rval
  2598  			}
  2599  		}
  2600  	}
  2601  	return rval
  2602  }
  2603  
  2604  // hostObject reads a single host object file (compare to "hostArchive").
  2605  // This is used as part of internal linking when we need to pull in
  2606  // files such as "crt?.o".
  2607  func hostObject(ctxt *Link, objname string, path string) {
  2608  	if ctxt.Debugvlog > 1 {
  2609  		ctxt.Logf("hostObject(%s)\n", path)
  2610  	}
  2611  	objlib := sym.Library{
  2612  		Pkg: objname,
  2613  	}
  2614  	f, err := bio.Open(path)
  2615  	if err != nil {
  2616  		Exitf("cannot open host object %q file %s: %v", objname, path, err)
  2617  	}
  2618  	defer f.Close()
  2619  	h := ldobj(ctxt, f, &objlib, 0, path, path)
  2620  	if h.ld == nil {
  2621  		Exitf("unrecognized object file format in %s", path)
  2622  	}
  2623  	h.file = path
  2624  	h.length = f.MustSeek(0, 2)
  2625  	f.MustSeek(h.off, 0)
  2626  	h.ld(ctxt, f, h.pkg, h.length, h.pn)
  2627  	if *flagCaptureHostObjs != "" {
  2628  		captureHostObj(h)
  2629  	}
  2630  }
  2631  
  2632  func checkFingerprint(lib *sym.Library, libfp goobj.FingerprintType, src string, srcfp goobj.FingerprintType) {
  2633  	if libfp != srcfp {
  2634  		Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
  2635  	}
  2636  }
  2637  
  2638  func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
  2639  	data := make([]byte, sym.Size)
  2640  	sect := f.Sections[sym.Section]
  2641  	if sect.Type != elf.SHT_PROGBITS && sect.Type != elf.SHT_NOTE {
  2642  		Errorf("reading %s from non-data section", sym.Name)
  2643  	}
  2644  	n, err := sect.ReadAt(data, int64(sym.Value-sect.Addr))
  2645  	if uint64(n) != sym.Size {
  2646  		Errorf("reading contents of %s: %v", sym.Name, err)
  2647  	}
  2648  	return data
  2649  }
  2650  
  2651  func readwithpad(r io.Reader, sz int32) ([]byte, error) {
  2652  	data := make([]byte, Rnd(int64(sz), 4))
  2653  	_, err := io.ReadFull(r, data)
  2654  	if err != nil {
  2655  		return nil, err
  2656  	}
  2657  	data = data[:sz]
  2658  	return data, nil
  2659  }
  2660  
  2661  func readnote(f *elf.File, name []byte, typ int32) ([]byte, error) {
  2662  	for _, sect := range f.Sections {
  2663  		if sect.Type != elf.SHT_NOTE {
  2664  			continue
  2665  		}
  2666  		r := sect.Open()
  2667  		for {
  2668  			var namesize, descsize, noteType int32
  2669  			err := binary.Read(r, f.ByteOrder, &namesize)
  2670  			if err != nil {
  2671  				if err == io.EOF {
  2672  					break
  2673  				}
  2674  				return nil, fmt.Errorf("read namesize failed: %v", err)
  2675  			}
  2676  			err = binary.Read(r, f.ByteOrder, &descsize)
  2677  			if err != nil {
  2678  				return nil, fmt.Errorf("read descsize failed: %v", err)
  2679  			}
  2680  			err = binary.Read(r, f.ByteOrder, &noteType)
  2681  			if err != nil {
  2682  				return nil, fmt.Errorf("read type failed: %v", err)
  2683  			}
  2684  			noteName, err := readwithpad(r, namesize)
  2685  			if err != nil {
  2686  				return nil, fmt.Errorf("read name failed: %v", err)
  2687  			}
  2688  			desc, err := readwithpad(r, descsize)
  2689  			if err != nil {
  2690  				return nil, fmt.Errorf("read desc failed: %v", err)
  2691  			}
  2692  			if string(name) == string(noteName) && typ == noteType {
  2693  				return desc, nil
  2694  			}
  2695  		}
  2696  	}
  2697  	return nil, nil
  2698  }
  2699  
  2700  func findshlib(ctxt *Link, shlib string) string {
  2701  	if filepath.IsAbs(shlib) {
  2702  		return shlib
  2703  	}
  2704  	for _, libdir := range ctxt.Libdir {
  2705  		libpath := filepath.Join(libdir, shlib)
  2706  		if _, err := os.Stat(libpath); err == nil {
  2707  			return libpath
  2708  		}
  2709  	}
  2710  	Errorf("cannot find shared library: %s", shlib)
  2711  	return ""
  2712  }
  2713  
  2714  func ldshlibsyms(ctxt *Link, shlib string) {
  2715  	var libpath string
  2716  	if filepath.IsAbs(shlib) {
  2717  		libpath = shlib
  2718  		shlib = filepath.Base(shlib)
  2719  	} else {
  2720  		libpath = findshlib(ctxt, shlib)
  2721  		if libpath == "" {
  2722  			return
  2723  		}
  2724  	}
  2725  	for _, processedlib := range ctxt.Shlibs {
  2726  		if processedlib.Path == libpath {
  2727  			return
  2728  		}
  2729  	}
  2730  	if ctxt.Debugvlog > 1 {
  2731  		ctxt.Logf("ldshlibsyms: found library with name %s at %s\n", shlib, libpath)
  2732  	}
  2733  
  2734  	f, err := elf.Open(libpath)
  2735  	if err != nil {
  2736  		Errorf("cannot open shared library: %s", libpath)
  2737  		return
  2738  	}
  2739  	// Keep the file open as decodetypeGcprog needs to read from it.
  2740  	// TODO: fix. Maybe mmap the file.
  2741  	//defer f.Close()
  2742  
  2743  	hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
  2744  	if err != nil {
  2745  		Errorf("cannot read ABI hash from shared library %s: %v", libpath, err)
  2746  		return
  2747  	}
  2748  
  2749  	depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
  2750  	if err != nil {
  2751  		Errorf("cannot read dep list from shared library %s: %v", libpath, err)
  2752  		return
  2753  	}
  2754  	var deps []string
  2755  	for _, dep := range strings.Split(string(depsbytes), "\n") {
  2756  		if dep == "" {
  2757  			continue
  2758  		}
  2759  		if !filepath.IsAbs(dep) {
  2760  			// If the dep can be interpreted as a path relative to the shlib
  2761  			// in which it was found, do that. Otherwise, we will leave it
  2762  			// to be resolved by libdir lookup.
  2763  			abs := filepath.Join(filepath.Dir(libpath), dep)
  2764  			if _, err := os.Stat(abs); err == nil {
  2765  				dep = abs
  2766  			}
  2767  		}
  2768  		deps = append(deps, dep)
  2769  	}
  2770  
  2771  	syms, err := f.DynamicSymbols()
  2772  	if err != nil {
  2773  		Errorf("cannot read symbols from shared library: %s", libpath)
  2774  		return
  2775  	}
  2776  
  2777  	symAddr := map[string]uint64{}
  2778  	for _, elfsym := range syms {
  2779  		if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
  2780  			continue
  2781  		}
  2782  
  2783  		// Symbols whose names start with "type:" are compiler generated,
  2784  		// so make functions with that prefix internal.
  2785  		ver := 0
  2786  		symname := elfsym.Name // (unmangled) symbol name
  2787  		if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type:") {
  2788  			ver = abiInternalVer
  2789  		} else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC {
  2790  			// Demangle the ABI name. Keep in sync with symtab.go:mangleABIName.
  2791  			if strings.HasSuffix(elfsym.Name, ".abiinternal") {
  2792  				ver = sym.SymVerABIInternal
  2793  				symname = strings.TrimSuffix(elfsym.Name, ".abiinternal")
  2794  			} else if strings.HasSuffix(elfsym.Name, ".abi0") {
  2795  				ver = 0
  2796  				symname = strings.TrimSuffix(elfsym.Name, ".abi0")
  2797  			}
  2798  		}
  2799  
  2800  		l := ctxt.loader
  2801  		s := l.LookupOrCreateSym(symname, ver)
  2802  
  2803  		// Because loadlib above loads all .a files before loading
  2804  		// any shared libraries, any non-dynimport symbols we find
  2805  		// that duplicate symbols already loaded should be ignored
  2806  		// (the symbols from the .a files "win").
  2807  		if l.SymType(s) != 0 && l.SymType(s) != sym.SDYNIMPORT {
  2808  			continue
  2809  		}
  2810  		su := l.MakeSymbolUpdater(s)
  2811  		su.SetType(sym.SDYNIMPORT)
  2812  		l.SetSymElfType(s, elf.ST_TYPE(elfsym.Info))
  2813  		su.SetSize(int64(elfsym.Size))
  2814  		if elfsym.Section != elf.SHN_UNDEF {
  2815  			// Set .File for the library that actually defines the symbol.
  2816  			l.SetSymPkg(s, libpath)
  2817  
  2818  			// The decodetype_* functions in decodetype.go need access to
  2819  			// the type data.
  2820  			sname := l.SymName(s)
  2821  			if strings.HasPrefix(sname, "type:") && !strings.HasPrefix(sname, "type:.") {
  2822  				su.SetData(readelfsymboldata(ctxt, f, &elfsym))
  2823  			}
  2824  		}
  2825  
  2826  		if symname != elfsym.Name {
  2827  			l.SetSymExtname(s, elfsym.Name)
  2828  		}
  2829  		symAddr[elfsym.Name] = elfsym.Value
  2830  	}
  2831  
  2832  	// Load relocations.
  2833  	// We only really need these for grokking the links between type descriptors
  2834  	// when dynamic linking.
  2835  	relocTarget := map[uint64]string{}
  2836  	addends := false
  2837  	sect := f.SectionByType(elf.SHT_REL)
  2838  	if sect == nil {
  2839  		sect = f.SectionByType(elf.SHT_RELA)
  2840  		if sect == nil {
  2841  			log.Fatalf("can't find SHT_REL or SHT_RELA section of %s", shlib)
  2842  		}
  2843  		addends = true
  2844  	}
  2845  	// TODO: Multiple SHT_RELA/SHT_REL sections?
  2846  	data, err := sect.Data()
  2847  	if err != nil {
  2848  		log.Fatalf("can't read relocation section of %s: %v", shlib, err)
  2849  	}
  2850  	bo := f.ByteOrder
  2851  	for len(data) > 0 {
  2852  		var off, idx uint64
  2853  		var addend int64
  2854  		switch f.Class {
  2855  		case elf.ELFCLASS64:
  2856  			off = bo.Uint64(data)
  2857  			info := bo.Uint64(data[8:])
  2858  			data = data[16:]
  2859  			if addends {
  2860  				addend = int64(bo.Uint64(data))
  2861  				data = data[8:]
  2862  			}
  2863  
  2864  			idx = info >> 32
  2865  			typ := info & 0xffff
  2866  			// buildmode=shared is only supported for amd64,arm64,loong64,s390x,ppc64le.
  2867  			// (List found by looking at the translation of R_ADDR by ../$ARCH/asm.go:elfreloc1)
  2868  			switch typ {
  2869  			case uint64(elf.R_X86_64_64):
  2870  			case uint64(elf.R_AARCH64_ABS64):
  2871  			case uint64(elf.R_LARCH_64):
  2872  			case uint64(elf.R_390_64):
  2873  			case uint64(elf.R_PPC64_ADDR64):
  2874  			default:
  2875  				continue
  2876  			}
  2877  		case elf.ELFCLASS32:
  2878  			off = uint64(bo.Uint32(data))
  2879  			info := bo.Uint32(data[4:])
  2880  			data = data[8:]
  2881  			if addends {
  2882  				addend = int64(int32(bo.Uint32(data)))
  2883  				data = data[4:]
  2884  			}
  2885  
  2886  			idx = uint64(info >> 8)
  2887  			typ := info & 0xff
  2888  			// buildmode=shared is only supported for 386,arm.
  2889  			switch typ {
  2890  			case uint32(elf.R_386_32):
  2891  			case uint32(elf.R_ARM_ABS32):
  2892  			default:
  2893  				continue
  2894  			}
  2895  		default:
  2896  			log.Fatalf("unknown bit size %s", f.Class)
  2897  		}
  2898  		if addend != 0 {
  2899  			continue
  2900  		}
  2901  		relocTarget[off] = syms[idx-1].Name
  2902  	}
  2903  
  2904  	ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f, symAddr: symAddr, relocTarget: relocTarget})
  2905  }
  2906  
  2907  func addsection(ldr *loader.Loader, arch *sys.Arch, seg *sym.Segment, name string, rwx int) *sym.Section {
  2908  	sect := ldr.NewSection()
  2909  	sect.Rwx = uint8(rwx)
  2910  	sect.Name = name
  2911  	sect.Seg = seg
  2912  	sect.Align = int32(arch.PtrSize) // everything is at least pointer-aligned
  2913  	seg.Sections = append(seg.Sections, sect)
  2914  	return sect
  2915  }
  2916  
  2917  func usage() {
  2918  	fmt.Fprintf(os.Stderr, "usage: link [options] main.o\n")
  2919  	objabi.Flagprint(os.Stderr)
  2920  	Exit(2)
  2921  }
  2922  
  2923  type SymbolType int8 // TODO: after genasmsym is gone, maybe rename to plan9typeChar or something
  2924  
  2925  const (
  2926  	// see also https://9p.io/magic/man2html/1/nm
  2927  	TextSym      SymbolType = 'T'
  2928  	DataSym      SymbolType = 'D'
  2929  	BSSSym       SymbolType = 'B'
  2930  	UndefinedSym SymbolType = 'U'
  2931  	TLSSym       SymbolType = 't'
  2932  	FrameSym     SymbolType = 'm'
  2933  	ParamSym     SymbolType = 'p'
  2934  	AutoSym      SymbolType = 'a'
  2935  
  2936  	// Deleted auto (not a real sym, just placeholder for type)
  2937  	DeletedAutoSym = 'x'
  2938  )
  2939  
  2940  // defineInternal defines a symbol used internally by the go runtime.
  2941  func (ctxt *Link) defineInternal(p string, t sym.SymKind) loader.Sym {
  2942  	s := ctxt.loader.CreateSymForUpdate(p, 0)
  2943  	s.SetType(t)
  2944  	s.SetSpecial(true)
  2945  	s.SetLocal(true)
  2946  	return s.Sym()
  2947  }
  2948  
  2949  func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) loader.Sym {
  2950  	s := ctxt.defineInternal(p, t)
  2951  	ctxt.loader.SetSymValue(s, v)
  2952  	return s
  2953  }
  2954  
  2955  func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
  2956  	if uint64(addr) >= Segdata.Vaddr {
  2957  		return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
  2958  	}
  2959  	if uint64(addr) >= Segtext.Vaddr {
  2960  		return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
  2961  	}
  2962  	ldr.Errorf(s, "invalid datoff %#x", addr)
  2963  	return 0
  2964  }
  2965  
  2966  func Entryvalue(ctxt *Link) int64 {
  2967  	a := *flagEntrySymbol
  2968  	if a[0] >= '0' && a[0] <= '9' {
  2969  		return atolwhex(a)
  2970  	}
  2971  	ldr := ctxt.loader
  2972  	s := ldr.Lookup(a, 0)
  2973  	if s == 0 {
  2974  		Errorf("missing entry symbol %q", a)
  2975  		return 0
  2976  	}
  2977  	st := ldr.SymType(s)
  2978  	if st == 0 {
  2979  		return *FlagTextAddr
  2980  	}
  2981  	if !ctxt.IsAIX() && !st.IsText() {
  2982  		ldr.Errorf(s, "entry not text")
  2983  	}
  2984  	return ldr.SymValue(s)
  2985  }
  2986  
  2987  func (ctxt *Link) callgraph() {
  2988  	if !*FlagC {
  2989  		return
  2990  	}
  2991  
  2992  	ldr := ctxt.loader
  2993  	for _, s := range ctxt.Textp {
  2994  		relocs := ldr.Relocs(s)
  2995  		for i := 0; i < relocs.Count(); i++ {
  2996  			r := relocs.At(i)
  2997  			rs := r.Sym()
  2998  			if rs == 0 {
  2999  				continue
  3000  			}
  3001  			if r.Type().IsDirectCall() && ldr.SymType(rs).IsText() {
  3002  				ctxt.Logf("%s calls %s\n", ldr.SymName(s), ldr.SymName(rs))
  3003  			}
  3004  		}
  3005  	}
  3006  }
  3007  
  3008  func Rnd(v int64, r int64) int64 {
  3009  	if r <= 0 {
  3010  		return v
  3011  	}
  3012  	v += r - 1
  3013  	c := v % r
  3014  	if c < 0 {
  3015  		c += r
  3016  	}
  3017  	v -= c
  3018  	return v
  3019  }
  3020  
  3021  func bgetc(r *bio.Reader) int {
  3022  	c, err := r.ReadByte()
  3023  	if err != nil {
  3024  		if err != io.EOF {
  3025  			log.Fatalf("reading input: %v", err)
  3026  		}
  3027  		return -1
  3028  	}
  3029  	return int(c)
  3030  }
  3031  
  3032  type markKind uint8 // for postorder traversal
  3033  const (
  3034  	_ markKind = iota
  3035  	visiting
  3036  	visited
  3037  )
  3038  
  3039  func postorder(libs []*sym.Library) []*sym.Library {
  3040  	order := make([]*sym.Library, 0, len(libs)) // hold the result
  3041  	mark := make(map[*sym.Library]markKind, len(libs))
  3042  	for _, lib := range libs {
  3043  		dfs(lib, mark, &order)
  3044  	}
  3045  	return order
  3046  }
  3047  
  3048  func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library) {
  3049  	if mark[lib] == visited {
  3050  		return
  3051  	}
  3052  	if mark[lib] == visiting {
  3053  		panic("found import cycle while visiting " + lib.Pkg)
  3054  	}
  3055  	mark[lib] = visiting
  3056  	for _, i := range lib.Imports {
  3057  		dfs(i, mark, order)
  3058  	}
  3059  	mark[lib] = visited
  3060  	*order = append(*order, lib)
  3061  }
  3062  
  3063  func ElfSymForReloc(ctxt *Link, s loader.Sym) int32 {
  3064  	// If putelfsym created a local version of this symbol, use that in all
  3065  	// relocations.
  3066  	les := ctxt.loader.SymLocalElfSym(s)
  3067  	if les != 0 {
  3068  		return les
  3069  	} else {
  3070  		return ctxt.loader.SymElfSym(s)
  3071  	}
  3072  }
  3073  
  3074  func AddGotSym(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, elfRelocTyp uint32) {
  3075  	if ldr.SymGot(s) >= 0 {
  3076  		return
  3077  	}
  3078  
  3079  	Adddynsym(ldr, target, syms, s)
  3080  	got := ldr.MakeSymbolUpdater(syms.GOT)
  3081  	ldr.SetGot(s, int32(got.Size()))
  3082  	got.AddUint(target.Arch, 0)
  3083  
  3084  	if target.IsElf() {
  3085  		if target.Arch.PtrSize == 8 {
  3086  			rela := ldr.MakeSymbolUpdater(syms.Rela)
  3087  			rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
  3088  			rela.AddUint64(target.Arch, elf.R_INFO(uint32(ldr.SymDynid(s)), elfRelocTyp))
  3089  			rela.AddUint64(target.Arch, 0)
  3090  		} else {
  3091  			rel := ldr.MakeSymbolUpdater(syms.Rel)
  3092  			rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
  3093  			rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), elfRelocTyp))
  3094  		}
  3095  	} else if target.IsDarwin() {
  3096  		leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT)
  3097  		leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
  3098  		if target.IsPIE() && target.IsInternal() {
  3099  			// Mach-O relocations are a royal pain to lay out.
  3100  			// They use a compact stateful bytecode representation.
  3101  			// Here we record what are needed and encode them later.
  3102  			MachoAddBind(syms.GOT, int64(ldr.SymGot(s)), s)
  3103  		}
  3104  	} else {
  3105  		ldr.Errorf(s, "addgotsym: unsupported binary format")
  3106  	}
  3107  }
  3108  
  3109  var hostobjcounter int
  3110  
  3111  // captureHostObj writes out the content of a host object (pulled from
  3112  // an archive or loaded from a *.o file directly) to a directory
  3113  // specified via the linker's "-capturehostobjs" debugging flag. This
  3114  // is intended to make it easier for a developer to inspect the actual
  3115  // object feeding into "CGO internal" link step.
  3116  func captureHostObj(h *Hostobj) {
  3117  	// Form paths for info file and obj file.
  3118  	ofile := fmt.Sprintf("captured-obj-%d.o", hostobjcounter)
  3119  	ifile := fmt.Sprintf("captured-obj-%d.txt", hostobjcounter)
  3120  	hostobjcounter++
  3121  	opath := filepath.Join(*flagCaptureHostObjs, ofile)
  3122  	ipath := filepath.Join(*flagCaptureHostObjs, ifile)
  3123  
  3124  	// Write the info file.
  3125  	info := fmt.Sprintf("pkg: %s\npn: %s\nfile: %s\noff: %d\nlen: %d\n",
  3126  		h.pkg, h.pn, h.file, h.off, h.length)
  3127  	if err := os.WriteFile(ipath, []byte(info), 0666); err != nil {
  3128  		log.Fatalf("error writing captured host obj info %s: %v", ipath, err)
  3129  	}
  3130  
  3131  	readObjData := func() []byte {
  3132  		inf, err := os.Open(h.file)
  3133  		if err != nil {
  3134  			log.Fatalf("capturing host obj: open failed on %s: %v", h.pn, err)
  3135  		}
  3136  		defer inf.Close()
  3137  		res := make([]byte, h.length)
  3138  		if n, err := inf.ReadAt(res, h.off); err != nil || n != int(h.length) {
  3139  			log.Fatalf("capturing host obj: readat failed on %s: %v", h.pn, err)
  3140  		}
  3141  		return res
  3142  	}
  3143  
  3144  	// Write the object file.
  3145  	if err := os.WriteFile(opath, readObjData(), 0666); err != nil {
  3146  		log.Fatalf("error writing captured host object %s: %v", opath, err)
  3147  	}
  3148  
  3149  	fmt.Fprintf(os.Stderr, "link: info: captured host object %s to %s\n",
  3150  		h.file, opath)
  3151  }
  3152  
  3153  // findExtLinkTool invokes the external linker CC with --print-prog-name
  3154  // passing the name of the tool we're interested in, such as "strip",
  3155  // "ar", or "dsymutil", and returns the path passed back from the command.
  3156  func (ctxt *Link) findExtLinkTool(toolname string) string {
  3157  	var cc []string
  3158  	cc = append(cc, ctxt.extld()...)
  3159  	cc = append(cc, hostlinkArchArgs(ctxt.Arch)...)
  3160  	cc = append(cc, "--print-prog-name", toolname)
  3161  	out, err := exec.Command(cc[0], cc[1:]...).CombinedOutput()
  3162  	if err != nil {
  3163  		Exitf("%s: finding %s failed: %v\n%s", os.Args[0], toolname, err, out)
  3164  	}
  3165  	cmdpath := strings.TrimRight(string(out), "\r\n")
  3166  	return cmdpath
  3167  }
  3168  
  3169  // isMSVC reports whether the C toolchain is clang with a -msvc target,
  3170  // e.g. the clang bundled in MSVC.
  3171  func (ctxt *Link) isMSVC() bool {
  3172  	extld := ctxt.extld()
  3173  	name, args := extld[0], extld[1:]
  3174  	args = append(args, trimLinkerArgv(flagExtldflags)...)
  3175  	args = append(args, "--version")
  3176  	cmd := exec.Command(name, args...)
  3177  	if out, err := cmd.CombinedOutput(); err == nil {
  3178  		if bytes.Contains(out, []byte("-msvc\n")) || bytes.Contains(out, []byte("-msvc\r")) {
  3179  			return true
  3180  		}
  3181  	}
  3182  	return false
  3183  }
  3184  
  3185  // isLLD reports whether the C toolchain is using LLD as the linker.
  3186  func (ctxt *Link) isLLD() bool {
  3187  	extld := ctxt.extld()
  3188  	name, args := extld[0], extld[1:]
  3189  	args = append(args, trimLinkerArgv(flagExtldflags)...)
  3190  	args = append(args, "-Wl,--version")
  3191  	cmd := exec.Command(name, args...)
  3192  	if out, err := cmd.CombinedOutput(); err == nil {
  3193  		if bytes.Contains(out, []byte("LLD ")) {
  3194  			return true
  3195  		}
  3196  	}
  3197  	return false
  3198  }
  3199  

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