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  		if ctxt.IsWindows() && ctxt.IsExternal() {
   873  			ctxt.loader.SetAttrNotInSymbolTable(tlsg, false)
   874  			tlsOffset := ctxt.loader.Lookup("runtime.tls_g", 0)
   875  			if tlsOffset == 0 {
   876  				Errorf("missing runtime.tls_g")
   877  			} else {
   878  				rel, _ := ctxt.loader.MakeSymbolUpdater(tlsOffset).AddRel(objabi.R_ADDROFF)
   879  				rel.SetOff(0)
   880  				rel.SetSiz(4)
   881  				rel.SetSym(tlsg)
   882  			}
   883  		}
   884  	}
   885  
   886  	var moduledata loader.Sym
   887  	var mdsb *loader.SymbolBuilder
   888  	if ctxt.BuildMode == BuildModePlugin {
   889  		moduledata = ctxt.loader.LookupOrCreateSym("local.pluginmoduledata", 0)
   890  		mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
   891  		ctxt.loader.SetAttrLocal(moduledata, true)
   892  	} else {
   893  		moduledata = ctxt.loader.LookupOrCreateSym("runtime.firstmoduledata", 0)
   894  		mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
   895  	}
   896  	if mdsb.Type() != 0 && mdsb.Type() != sym.SDYNIMPORT {
   897  		// If the module (toolchain-speak for "executable or shared
   898  		// library") we are linking contains the runtime package, it
   899  		// will define the runtime.firstmoduledata symbol and we
   900  		// truncate it back to 0 bytes so we can define its entire
   901  		// contents in symtab.go:symtab().
   902  		mdsb.SetSize(0)
   903  
   904  		// In addition, on ARM, the runtime depends on the linker
   905  		// recording the value of GOARM.
   906  		if ctxt.Arch.Family == sys.ARM {
   907  			goarm := ctxt.loader.LookupOrCreateSym("runtime.goarm", 0)
   908  			sb := ctxt.loader.MakeSymbolUpdater(goarm)
   909  			sb.SetType(sym.SNOPTRDATA)
   910  			sb.SetSize(0)
   911  			sb.AddUint8(uint8(buildcfg.GOARM.Version))
   912  
   913  			goarmsoftfp := ctxt.loader.LookupOrCreateSym("runtime.goarmsoftfp", 0)
   914  			sb2 := ctxt.loader.MakeSymbolUpdater(goarmsoftfp)
   915  			sb2.SetType(sym.SNOPTRDATA)
   916  			sb2.SetSize(0)
   917  			if buildcfg.GOARM.SoftFloat {
   918  				sb2.AddUint8(1)
   919  			} else {
   920  				sb2.AddUint8(0)
   921  			}
   922  		}
   923  
   924  		// Set runtime.disableMemoryProfiling bool if
   925  		// runtime.memProfileInternal is not retained in the binary after
   926  		// deadcode (and we're not dynamically linking).
   927  		memProfile := ctxt.loader.Lookup("runtime.memProfileInternal", abiInternalVer)
   928  		if memProfile != 0 && !ctxt.loader.AttrReachable(memProfile) && !ctxt.DynlinkingGo() {
   929  			memProfSym := ctxt.loader.LookupOrCreateSym("runtime.disableMemoryProfiling", 0)
   930  			sb := ctxt.loader.MakeSymbolUpdater(memProfSym)
   931  			sb.SetType(sym.SNOPTRDATA)
   932  			sb.SetSize(0)
   933  			sb.AddUint8(1) // true bool
   934  		}
   935  	} else {
   936  		// If OTOH the module does not contain the runtime package,
   937  		// create a local symbol for the moduledata.
   938  		moduledata = ctxt.loader.LookupOrCreateSym("local.moduledata", 0)
   939  		mdsb = ctxt.loader.MakeSymbolUpdater(moduledata)
   940  		ctxt.loader.SetAttrLocal(moduledata, true)
   941  	}
   942  	mdsb.SetType(sym.SMODULEDATA)
   943  	ctxt.loader.SetAttrReachable(moduledata, true)
   944  	ctxt.Moduledata = moduledata
   945  
   946  	if ctxt.Arch == sys.Arch386 && ctxt.HeadType != objabi.Hwindows {
   947  		if (ctxt.BuildMode == BuildModeCArchive && ctxt.IsELF) || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE || ctxt.DynlinkingGo() {
   948  			got := ctxt.loader.LookupOrCreateSym("_GLOBAL_OFFSET_TABLE_", 0)
   949  			sb := ctxt.loader.MakeSymbolUpdater(got)
   950  			sb.SetType(sym.SDYNIMPORT)
   951  			ctxt.loader.SetAttrReachable(got, true)
   952  		}
   953  	}
   954  
   955  	// DWARF-gen and other phases require that the unit Textp slices
   956  	// be populated, so that it can walk the functions in each unit.
   957  	// Call into the loader to do this (requires that we collect the
   958  	// set of internal libraries first). NB: might be simpler if we
   959  	// moved isRuntimeDepPkg to cmd/internal and then did the test in
   960  	// loader.AssignTextSymbolOrder.
   961  	ctxt.Library = postorder(ctxt.Library)
   962  	intlibs := []bool{}
   963  	for _, lib := range ctxt.Library {
   964  		intlibs = append(intlibs, isRuntimeDepPkg(lib.Pkg))
   965  	}
   966  	ctxt.Textp = ctxt.loader.AssignTextSymbolOrder(ctxt.Library, intlibs, ctxt.Textp)
   967  }
   968  
   969  // mangleTypeSym shortens the names of symbols that represent Go types
   970  // if they are visible in the symbol table.
   971  //
   972  // As the names of these symbols are derived from the string of
   973  // the type, they can run to many kilobytes long. So we shorten
   974  // them using a SHA-1 when the name appears in the final binary.
   975  // This also removes characters that upset external linkers.
   976  //
   977  // These are the symbols that begin with the prefix 'type.' and
   978  // contain run-time type information used by the runtime and reflect
   979  // packages. All Go binaries contain these symbols, but only
   980  // those programs loaded dynamically in multiple parts need these
   981  // symbols to have entries in the symbol table.
   982  func (ctxt *Link) mangleTypeSym() {
   983  	if ctxt.BuildMode != BuildModeShared && !ctxt.linkShared && ctxt.BuildMode != BuildModePlugin && !ctxt.CanUsePlugins() {
   984  		return
   985  	}
   986  
   987  	ldr := ctxt.loader
   988  	for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
   989  		if !ldr.AttrReachable(s) && !ctxt.linkShared {
   990  			// If -linkshared, the gc mask generation code may need to reach
   991  			// out to the shared library for the type descriptor's data, even
   992  			// the type descriptor itself is not actually needed at run time
   993  			// (therefore not reachable). We still need to mangle its name,
   994  			// so it is consistent with the one stored in the shared library.
   995  			continue
   996  		}
   997  		name := ldr.SymName(s)
   998  		newName := typeSymbolMangle(name)
   999  		if newName != name {
  1000  			ldr.SetSymExtname(s, newName)
  1001  
  1002  			// When linking against a shared library, the Go object file may
  1003  			// have reference to the original symbol name whereas the shared
  1004  			// library provides a symbol with the mangled name. We need to
  1005  			// copy the payload of mangled to original.
  1006  			// XXX maybe there is a better way to do this.
  1007  			dup := ldr.Lookup(newName, ldr.SymVersion(s))
  1008  			if dup != 0 {
  1009  				st := ldr.SymType(s)
  1010  				dt := ldr.SymType(dup)
  1011  				if st == sym.Sxxx && dt != sym.Sxxx {
  1012  					ldr.CopySym(dup, s)
  1013  				}
  1014  			}
  1015  		}
  1016  	}
  1017  }
  1018  
  1019  // typeSymbolMangle mangles the given symbol name into something shorter.
  1020  //
  1021  // Keep the type:. prefix, which parts of the linker (like the
  1022  // DWARF generator) know means the symbol is not decodable.
  1023  // Leave type:runtime. symbols alone, because other parts of
  1024  // the linker manipulates them.
  1025  func typeSymbolMangle(name string) string {
  1026  	isType := strings.HasPrefix(name, "type:")
  1027  	if !isType && !strings.Contains(name, "@") {
  1028  		// Issue 58800: instantiated symbols may include a type name, which may contain "@"
  1029  		return name
  1030  	}
  1031  	if strings.HasPrefix(name, "type:runtime.") {
  1032  		return name
  1033  	}
  1034  	if strings.HasPrefix(name, "go:string.") {
  1035  		// String symbols will be grouped to a single go:string.* symbol.
  1036  		// No need to mangle individual symbol names.
  1037  		return name
  1038  	}
  1039  	if len(name) <= 14 && !strings.Contains(name, "@") { // Issue 19529
  1040  		return name
  1041  	}
  1042  	if isType {
  1043  		hb := hash.Sum32([]byte(name[5:]))
  1044  		prefix := "type:"
  1045  		if name[5] == '.' {
  1046  			prefix = "type:."
  1047  		}
  1048  		return prefix + base64.StdEncoding.EncodeToString(hb[:6])
  1049  	}
  1050  	// instantiated symbol, replace type name in []
  1051  	i := strings.IndexByte(name, '[')
  1052  	j := strings.LastIndexByte(name, ']')
  1053  	if j == -1 || j <= i {
  1054  		j = len(name)
  1055  	}
  1056  	hb := hash.Sum32([]byte(name[i+1 : j]))
  1057  	return name[:i+1] + base64.StdEncoding.EncodeToString(hb[:6]) + name[j:]
  1058  }
  1059  
  1060  /*
  1061   * look for the next file in an archive.
  1062   * adapted from libmach.
  1063   */
  1064  func nextar(bp *bio.Reader, off int64, a *ArHdr) int64 {
  1065  	if off&1 != 0 {
  1066  		off++
  1067  	}
  1068  	bp.MustSeek(off, 0)
  1069  	var buf [SAR_HDR]byte
  1070  	if n, err := io.ReadFull(bp, buf[:]); err != nil {
  1071  		if n == 0 && err != io.EOF {
  1072  			return -1
  1073  		}
  1074  		return 0
  1075  	}
  1076  
  1077  	a.name = artrim(buf[0:16])
  1078  	a.date = artrim(buf[16:28])
  1079  	a.uid = artrim(buf[28:34])
  1080  	a.gid = artrim(buf[34:40])
  1081  	a.mode = artrim(buf[40:48])
  1082  	a.size = artrim(buf[48:58])
  1083  	a.fmag = artrim(buf[58:60])
  1084  
  1085  	arsize := atolwhex(a.size)
  1086  	if arsize&1 != 0 {
  1087  		arsize++
  1088  	}
  1089  	return arsize + SAR_HDR
  1090  }
  1091  
  1092  func loadobjfile(ctxt *Link, lib *sym.Library) {
  1093  	pkg := objabi.PathToPrefix(lib.Pkg)
  1094  
  1095  	if ctxt.Debugvlog > 1 {
  1096  		ctxt.Logf("ldobj: %s (%s)\n", lib.File, pkg)
  1097  	}
  1098  	f, err := bio.Open(lib.File)
  1099  	if err != nil {
  1100  		Exitf("cannot open file %s: %v", lib.File, err)
  1101  	}
  1102  	defer f.Close()
  1103  	defer func() {
  1104  		if pkg == "main" && !lib.Main {
  1105  			Exitf("%s: not package main", lib.File)
  1106  		}
  1107  	}()
  1108  
  1109  	for i := 0; i < len(ARMAG); i++ {
  1110  		if c, err := f.ReadByte(); err == nil && c == ARMAG[i] {
  1111  			continue
  1112  		}
  1113  
  1114  		/* load it as a regular file */
  1115  		l := f.MustSeek(0, 2)
  1116  		f.MustSeek(0, 0)
  1117  		ldobj(ctxt, f, lib, l, lib.File, lib.File)
  1118  		return
  1119  	}
  1120  
  1121  	/*
  1122  	 * load all the object files from the archive now.
  1123  	 * this gives us sequential file access and keeps us
  1124  	 * from needing to come back later to pick up more
  1125  	 * objects.  it breaks the usual C archive model, but
  1126  	 * this is Go, not C.  the common case in Go is that
  1127  	 * we need to load all the objects, and then we throw away
  1128  	 * the individual symbols that are unused.
  1129  	 *
  1130  	 * loading every object will also make it possible to
  1131  	 * load foreign objects not referenced by __.PKGDEF.
  1132  	 */
  1133  	var arhdr ArHdr
  1134  	off := f.Offset()
  1135  	for {
  1136  		l := nextar(f, off, &arhdr)
  1137  		if l == 0 {
  1138  			break
  1139  		}
  1140  		if l < 0 {
  1141  			Exitf("%s: malformed archive", lib.File)
  1142  		}
  1143  		off += l
  1144  
  1145  		// __.PKGDEF isn't a real Go object file, and it's
  1146  		// absent in -linkobj builds anyway. Skipping it
  1147  		// ensures consistency between -linkobj and normal
  1148  		// build modes.
  1149  		if arhdr.name == pkgdef {
  1150  			continue
  1151  		}
  1152  
  1153  		if arhdr.name == "dynimportfail" {
  1154  			dynimportfail = append(dynimportfail, lib.Pkg)
  1155  		}
  1156  		if arhdr.name == "preferlinkext" {
  1157  			// Ignore this directive if -linkmode has been
  1158  			// set explicitly.
  1159  			if ctxt.LinkMode == LinkAuto {
  1160  				preferlinkext = append(preferlinkext, lib.Pkg)
  1161  			}
  1162  		}
  1163  
  1164  		// Skip other special (non-object-file) sections that
  1165  		// build tools may have added. Such sections must have
  1166  		// short names so that the suffix is not truncated.
  1167  		if len(arhdr.name) < 16 {
  1168  			if ext := filepath.Ext(arhdr.name); ext != ".o" && ext != ".syso" {
  1169  				continue
  1170  			}
  1171  		}
  1172  
  1173  		pname := fmt.Sprintf("%s(%s)", lib.File, arhdr.name)
  1174  		l = atolwhex(arhdr.size)
  1175  		ldobj(ctxt, f, lib, l, pname, lib.File)
  1176  	}
  1177  }
  1178  
  1179  type Hostobj struct {
  1180  	ld     func(*Link, *bio.Reader, string, int64, string)
  1181  	pkg    string
  1182  	pn     string
  1183  	file   string
  1184  	off    int64
  1185  	length int64
  1186  }
  1187  
  1188  var hostobj []Hostobj
  1189  
  1190  // These packages can use internal linking mode.
  1191  // Others trigger external mode.
  1192  var internalpkg = []string{
  1193  	"crypto/internal/boring",
  1194  	"crypto/internal/boring/syso",
  1195  	"crypto/x509",
  1196  	"net",
  1197  	"os/user",
  1198  	"runtime/cgo",
  1199  	"runtime/race",
  1200  	"runtime/race/internal/amd64v1",
  1201  	"runtime/race/internal/amd64v3",
  1202  	"runtime/msan",
  1203  	"runtime/asan",
  1204  }
  1205  
  1206  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 {
  1207  	isinternal := false
  1208  	for _, intpkg := range internalpkg {
  1209  		if pkg == intpkg {
  1210  			isinternal = true
  1211  			break
  1212  		}
  1213  	}
  1214  
  1215  	// DragonFly declares errno with __thread, which results in a symbol
  1216  	// type of R_386_TLS_GD or R_X86_64_TLSGD. The Go linker does not
  1217  	// currently know how to handle TLS relocations, hence we have to
  1218  	// force external linking for any libraries that link in code that
  1219  	// uses errno. This can be removed if the Go linker ever supports
  1220  	// these relocation types.
  1221  	if headType == objabi.Hdragonfly {
  1222  		if pkg == "net" || pkg == "os/user" {
  1223  			isinternal = false
  1224  		}
  1225  	}
  1226  
  1227  	if !isinternal {
  1228  		externalobj = true
  1229  	}
  1230  
  1231  	hostobj = append(hostobj, Hostobj{})
  1232  	h := &hostobj[len(hostobj)-1]
  1233  	h.ld = ld
  1234  	h.pkg = pkg
  1235  	h.pn = pn
  1236  	h.file = file
  1237  	h.off = f.Offset()
  1238  	h.length = length
  1239  	return h
  1240  }
  1241  
  1242  func hostobjs(ctxt *Link) {
  1243  	if ctxt.LinkMode != LinkInternal {
  1244  		return
  1245  	}
  1246  	var h *Hostobj
  1247  
  1248  	for i := 0; i < len(hostobj); i++ {
  1249  		h = &hostobj[i]
  1250  		f, err := bio.Open(h.file)
  1251  		if err != nil {
  1252  			Exitf("cannot reopen %s: %v", h.pn, err)
  1253  		}
  1254  		f.MustSeek(h.off, 0)
  1255  		if h.ld == nil {
  1256  			Errorf("%s: unrecognized object file format", h.pn)
  1257  			continue
  1258  		}
  1259  		h.ld(ctxt, f, h.pkg, h.length, h.pn)
  1260  		if *flagCaptureHostObjs != "" {
  1261  			captureHostObj(h)
  1262  		}
  1263  		f.Close()
  1264  	}
  1265  }
  1266  
  1267  func hostlinksetup(ctxt *Link) {
  1268  	if ctxt.LinkMode != LinkExternal {
  1269  		return
  1270  	}
  1271  
  1272  	// For external link, record that we need to tell the external linker -s,
  1273  	// and turn off -s internally: the external linker needs the symbol
  1274  	// information for its final link.
  1275  	debug_s = *FlagS
  1276  	*FlagS = false
  1277  
  1278  	// create temporary directory and arrange cleanup
  1279  	if *flagTmpdir == "" {
  1280  		dir, err := os.MkdirTemp("", "go-link-")
  1281  		if err != nil {
  1282  			log.Fatal(err)
  1283  		}
  1284  		*flagTmpdir = dir
  1285  		ownTmpDir = true
  1286  		AtExit(func() {
  1287  			os.RemoveAll(*flagTmpdir)
  1288  		})
  1289  	}
  1290  
  1291  	// change our output to temporary object file
  1292  	if err := ctxt.Out.Close(); err != nil {
  1293  		Exitf("error closing output file")
  1294  	}
  1295  	mayberemoveoutfile()
  1296  
  1297  	p := filepath.Join(*flagTmpdir, "go.o")
  1298  	if err := ctxt.Out.Open(p); err != nil {
  1299  		Exitf("cannot create %s: %v", p, err)
  1300  	}
  1301  }
  1302  
  1303  // cleanTimeStamps resets the timestamps for the specified list of
  1304  // existing files to the Unix epoch (1970-01-01 00:00:00 +0000 UTC).
  1305  // We take this step in order to help preserve reproducible builds;
  1306  // this seems to be primarily needed for external linking on Darwin
  1307  // with later versions of xcode, which (unfortunately) seem to want to
  1308  // incorporate object file times into the final output file's build
  1309  // ID. See issue 64947 for the unpleasant details.
  1310  func cleanTimeStamps(files []string) {
  1311  	epocht := time.Unix(0, 0)
  1312  	for _, f := range files {
  1313  		if err := os.Chtimes(f, epocht, epocht); err != nil {
  1314  			Exitf("cannot chtimes %s: %v", f, err)
  1315  		}
  1316  	}
  1317  }
  1318  
  1319  // hostobjCopy creates a copy of the object files in hostobj in a
  1320  // temporary directory.
  1321  func (ctxt *Link) hostobjCopy() (paths []string) {
  1322  	var wg sync.WaitGroup
  1323  	sema := make(chan struct{}, runtime.NumCPU()) // limit open file descriptors
  1324  	for i, h := range hostobj {
  1325  		h := h
  1326  		dst := filepath.Join(*flagTmpdir, fmt.Sprintf("%06d.o", i))
  1327  		paths = append(paths, dst)
  1328  		if ctxt.Debugvlog != 0 {
  1329  			ctxt.Logf("host obj copy: %s from pkg %s -> %s\n", h.pn, h.pkg, dst)
  1330  		}
  1331  
  1332  		wg.Add(1)
  1333  		go func() {
  1334  			sema <- struct{}{}
  1335  			defer func() {
  1336  				<-sema
  1337  				wg.Done()
  1338  			}()
  1339  			f, err := os.Open(h.file)
  1340  			if err != nil {
  1341  				Exitf("cannot reopen %s: %v", h.pn, err)
  1342  			}
  1343  			defer f.Close()
  1344  			if _, err := f.Seek(h.off, 0); err != nil {
  1345  				Exitf("cannot seek %s: %v", h.pn, err)
  1346  			}
  1347  
  1348  			w, err := os.Create(dst)
  1349  			if err != nil {
  1350  				Exitf("cannot create %s: %v", dst, err)
  1351  			}
  1352  			if _, err := io.CopyN(w, f, h.length); err != nil {
  1353  				Exitf("cannot write %s: %v", dst, err)
  1354  			}
  1355  			if err := w.Close(); err != nil {
  1356  				Exitf("cannot close %s: %v", dst, err)
  1357  			}
  1358  		}()
  1359  	}
  1360  	wg.Wait()
  1361  	return paths
  1362  }
  1363  
  1364  // writeGDBLinkerScript creates gcc linker script file in temp
  1365  // directory. writeGDBLinkerScript returns created file path.
  1366  // The script is used to work around gcc bug
  1367  // (see https://golang.org/issue/20183 for details).
  1368  func writeGDBLinkerScript() string {
  1369  	name := "fix_debug_gdb_scripts.ld"
  1370  	path := filepath.Join(*flagTmpdir, name)
  1371  	src := `SECTIONS
  1372  {
  1373    .debug_gdb_scripts BLOCK(__section_alignment__) (NOLOAD) :
  1374    {
  1375      *(.debug_gdb_scripts)
  1376    }
  1377  }
  1378  INSERT AFTER .debug_types;
  1379  `
  1380  	err := os.WriteFile(path, []byte(src), 0666)
  1381  	if err != nil {
  1382  		Errorf("WriteFile %s failed: %v", name, err)
  1383  	}
  1384  	return path
  1385  }
  1386  
  1387  type machoUpdateFunc func(ctxt *Link, exef *os.File, exem *macho.File, outexe string) error
  1388  
  1389  // archive builds a .a archive from the hostobj object files.
  1390  func (ctxt *Link) archive() {
  1391  	if ctxt.BuildMode != BuildModeCArchive {
  1392  		return
  1393  	}
  1394  
  1395  	exitIfErrors()
  1396  
  1397  	if *flagExtar == "" {
  1398  		const printProgName = "--print-prog-name=ar"
  1399  		cc := ctxt.extld()
  1400  		*flagExtar = "ar"
  1401  		if linkerFlagSupported(ctxt.Arch, cc[0], "", printProgName) {
  1402  			*flagExtar = ctxt.findExtLinkTool("ar")
  1403  		}
  1404  	}
  1405  
  1406  	mayberemoveoutfile()
  1407  
  1408  	// Force the buffer to flush here so that external
  1409  	// tools will see a complete file.
  1410  	if err := ctxt.Out.Close(); err != nil {
  1411  		Exitf("error closing %v", *flagOutfile)
  1412  	}
  1413  
  1414  	argv := []string{*flagExtar, "-q", "-c", "-s"}
  1415  	if ctxt.HeadType == objabi.Haix {
  1416  		argv = append(argv, "-X64")
  1417  	}
  1418  	godotopath := filepath.Join(*flagTmpdir, "go.o")
  1419  	cleanTimeStamps([]string{godotopath})
  1420  	hostObjCopyPaths := ctxt.hostobjCopy()
  1421  	cleanTimeStamps(hostObjCopyPaths)
  1422  
  1423  	argv = append(argv, *flagOutfile)
  1424  	argv = append(argv, godotopath)
  1425  	argv = append(argv, hostObjCopyPaths...)
  1426  
  1427  	if ctxt.Debugvlog != 0 {
  1428  		ctxt.Logf("archive: %s\n", strings.Join(argv, " "))
  1429  	}
  1430  
  1431  	// If supported, use syscall.Exec() to invoke the archive command,
  1432  	// which should be the final remaining step needed for the link.
  1433  	// This will reduce peak RSS for the link (and speed up linking of
  1434  	// large applications), since when the archive command runs we
  1435  	// won't be holding onto all of the linker's live memory.
  1436  	if syscallExecSupported && !ownTmpDir {
  1437  		runAtExitFuncs()
  1438  		ctxt.execArchive(argv)
  1439  		panic("should not get here")
  1440  	}
  1441  
  1442  	// Otherwise invoke 'ar' in the usual way (fork + exec).
  1443  	if out, err := exec.Command(argv[0], argv[1:]...).CombinedOutput(); err != nil {
  1444  		Exitf("running %s failed: %v\n%s", argv[0], err, out)
  1445  	}
  1446  }
  1447  
  1448  func (ctxt *Link) hostlink() {
  1449  	if ctxt.LinkMode != LinkExternal || nerrors > 0 {
  1450  		return
  1451  	}
  1452  	if ctxt.BuildMode == BuildModeCArchive {
  1453  		return
  1454  	}
  1455  
  1456  	var argv []string
  1457  	argv = append(argv, ctxt.extld()...)
  1458  	argv = append(argv, hostlinkArchArgs(ctxt.Arch)...)
  1459  
  1460  	if *FlagS || debug_s {
  1461  		if ctxt.HeadType == objabi.Hdarwin {
  1462  			// Recent versions of macOS print
  1463  			//	ld: warning: option -s is obsolete and being ignored
  1464  			// so do not pass any arguments (but we strip symbols below).
  1465  		} else {
  1466  			argv = append(argv, "-s")
  1467  		}
  1468  	} else if *FlagW {
  1469  		if !ctxt.IsAIX() && !ctxt.IsSolaris() { // The AIX and Solaris linkers' -S has different meaning
  1470  			argv = append(argv, "-Wl,-S") // suppress debugging symbols
  1471  		}
  1472  	}
  1473  
  1474  	// On darwin, whether to combine DWARF into executable.
  1475  	// Only macOS supports unmapped segments such as our __DWARF segment.
  1476  	combineDwarf := ctxt.IsDarwin() && !*FlagW && machoPlatform == PLATFORM_MACOS
  1477  
  1478  	var isMSVC, isLLD bool // used on Windows
  1479  	wlPrefix := "-Wl,--"
  1480  
  1481  	switch ctxt.HeadType {
  1482  	case objabi.Hdarwin:
  1483  		if combineDwarf {
  1484  			// Leave room for DWARF combining.
  1485  			// -headerpad is incompatible with -fembed-bitcode.
  1486  			argv = append(argv, "-Wl,-headerpad,1144")
  1487  		}
  1488  		if ctxt.DynlinkingGo() && buildcfg.GOOS != "ios" {
  1489  			// -flat_namespace is deprecated on iOS.
  1490  			// It is useful for supporting plugins. We don't support plugins on iOS.
  1491  			// -flat_namespace may cause the dynamic linker to hang at forkExec when
  1492  			// resolving a lazy binding. See issue 38824.
  1493  			// Force eager resolution to work around.
  1494  			argv = append(argv, "-Wl,-flat_namespace", "-Wl,-bind_at_load")
  1495  		}
  1496  		if !combineDwarf {
  1497  			argv = append(argv, "-Wl,-S") // suppress STAB (symbolic debugging) symbols
  1498  			if debug_s {
  1499  				// We are generating a binary with symbol table suppressed.
  1500  				// Suppress local symbols. We need to keep dynamically exported
  1501  				// and referenced symbols so the dynamic linker can resolve them.
  1502  				argv = append(argv, "-Wl,-x")
  1503  			}
  1504  		}
  1505  		if *flagRace {
  1506  			// With https://github.com/llvm/llvm-project/pull/182943, the race object
  1507  			// has a weak import of __dyld_get_dyld_header, which is only defined on
  1508  			// newer macOS (26.4+).
  1509  			argv = append(argv, "-Wl,-U,__dyld_get_dyld_header")
  1510  		}
  1511  		if *flagHostBuildid == "none" {
  1512  			argv = append(argv, "-Wl,-no_uuid")
  1513  		}
  1514  	case objabi.Hopenbsd:
  1515  		argv = append(argv, "-pthread")
  1516  		if ctxt.BuildMode != BuildModePIE {
  1517  			argv = append(argv, "-Wl,-nopie")
  1518  		}
  1519  		if linkerFlagSupported(ctxt.Arch, argv[0], "", "-Wl,-z,nobtcfi") {
  1520  			// -Wl,-z,nobtcfi is only supported on OpenBSD 7.4+, remove guard
  1521  			// when OpenBSD 7.5 is released and 7.3 is no longer supported.
  1522  			argv = append(argv, "-Wl,-z,nobtcfi")
  1523  		}
  1524  		if ctxt.Arch.InFamily(sys.ARM64) {
  1525  			// Disable execute-only on openbsd/arm64 - the Go arm64 assembler
  1526  			// currently stores constants in the text section rather than in rodata.
  1527  			// See issue #59615.
  1528  			argv = append(argv, "-Wl,--no-execute-only")
  1529  		}
  1530  	case objabi.Hwindows:
  1531  		isMSVC = ctxt.isMSVC()
  1532  		isLLD = ctxt.isLLD()
  1533  		if isMSVC {
  1534  			// For various options, MSVC lld-link only accepts one dash.
  1535  			// TODO: It seems mingw clang supports one or two dashes,
  1536  			// maybe we can always use one dash,  but I'm not sure about
  1537  			// legacy compilers that currently work.
  1538  			wlPrefix = "-Wl,-"
  1539  		}
  1540  
  1541  		if windowsgui {
  1542  			argv = append(argv, "-mwindows")
  1543  		} else {
  1544  			argv = append(argv, "-mconsole")
  1545  		}
  1546  		// Mark as having awareness of terminal services, to avoid
  1547  		// ancient compatibility hacks.
  1548  
  1549  		argv = append(argv, wlPrefix+"tsaware")
  1550  
  1551  		// Enable DEP
  1552  		argv = append(argv, wlPrefix+"nxcompat")
  1553  
  1554  		if !isMSVC {
  1555  			peMajorVersion := PeMinimumTargetMajorVersion
  1556  			peMinorVersion := PeMinimumTargetMinorVersion
  1557  			if peMajorVersion >= 10 && !isLLD &&
  1558  				!peHasLoadConfigDirectorySupport(ctxt.Arch, argv[0]) {
  1559  				// The external linker doesn't support wiring up
  1560  				// _load_config_used to the PE Load Configuration
  1561  				// Directory. Windows 10+ validates this directory,
  1562  				// so fall back to an older version to avoid
  1563  				// load failures.
  1564  				peMajorVersion = 6
  1565  				peMinorVersion = 1
  1566  			}
  1567  			argv = append(argv, fmt.Sprintf("-Wl,--major-os-version=%d", peMajorVersion))
  1568  			argv = append(argv, fmt.Sprintf("-Wl,--minor-os-version=%d", peMinorVersion))
  1569  			argv = append(argv, fmt.Sprintf("-Wl,--major-subsystem-version=%d", peMajorVersion))
  1570  			argv = append(argv, fmt.Sprintf("-Wl,--minor-subsystem-version=%d", peMinorVersion))
  1571  		}
  1572  	case objabi.Haix:
  1573  		argv = append(argv, "-pthread")
  1574  		// prevent ld to reorder .text functions to keep the same
  1575  		// first/last functions for moduledata.
  1576  		argv = append(argv, "-Wl,-bnoobjreorder")
  1577  		// mcmodel=large is needed for every gcc generated files, but
  1578  		// ld still need -bbigtoc in order to allow larger TOC.
  1579  		argv = append(argv, "-mcmodel=large")
  1580  		argv = append(argv, "-Wl,-bbigtoc")
  1581  	}
  1582  
  1583  	// On PPC64, verify the external toolchain supports Power10. This is needed when
  1584  	// PC relative relocations might be generated by Go. Only targets compiling ELF
  1585  	// binaries might generate these relocations.
  1586  	if ctxt.IsPPC64() && ctxt.IsElf() && buildcfg.GOPPC64 >= 10 {
  1587  		if !linkerFlagSupported(ctxt.Arch, argv[0], "", "-mcpu=power10") {
  1588  			Exitf("The external toolchain does not support -mcpu=power10. " +
  1589  				" This is required to externally link GOPPC64 >= power10")
  1590  		}
  1591  	}
  1592  
  1593  	// Enable/disable ASLR on Windows.
  1594  	addASLRargs := func(argv []string, val bool) []string {
  1595  		// Old/ancient versions of GCC support "--dynamicbase" and
  1596  		// "--high-entropy-va" but don't enable it by default. In
  1597  		// addition, they don't accept "--disable-dynamicbase" or
  1598  		// "--no-dynamicbase", so the only way to disable ASLR is to
  1599  		// not pass any flags at all.
  1600  		//
  1601  		// More modern versions of GCC (and also clang) enable ASLR
  1602  		// by default. With these compilers, however you can turn it
  1603  		// off if you want using "--disable-dynamicbase" or
  1604  		// "--no-dynamicbase".
  1605  		//
  1606  		// The strategy below is to try using "--disable-dynamicbase";
  1607  		// if this succeeds, then assume we're working with more
  1608  		// modern compilers and act accordingly. If it fails, assume
  1609  		// an ancient compiler with ancient defaults.
  1610  		var dbopt string
  1611  		var heopt string
  1612  		dbon := wlPrefix + "dynamicbase"
  1613  		heon := wlPrefix + "high-entropy-va"
  1614  		dboff := wlPrefix + "disable-dynamicbase"
  1615  		heoff := wlPrefix + "disable-high-entropy-va"
  1616  		if isMSVC {
  1617  			heon = wlPrefix + "highentropyva"
  1618  			heoff = wlPrefix + "highentropyva:no"
  1619  			dboff = wlPrefix + "dynamicbase:no"
  1620  		}
  1621  		if val {
  1622  			dbopt = dbon
  1623  			heopt = heon
  1624  		} else {
  1625  			// Test to see whether "--disable-dynamicbase" works.
  1626  			newer := linkerFlagSupported(ctxt.Arch, argv[0], "", dboff)
  1627  			if newer {
  1628  				// Newer compiler, which supports both on/off options.
  1629  				dbopt = dboff
  1630  				heopt = heoff
  1631  			} else {
  1632  				// older toolchain: we have to say nothing in order to
  1633  				// get a no-ASLR binary.
  1634  				dbopt = ""
  1635  				heopt = ""
  1636  			}
  1637  		}
  1638  		if dbopt != "" {
  1639  			argv = append(argv, dbopt)
  1640  		}
  1641  		// enable high-entropy ASLR on 64-bit.
  1642  		if ctxt.Arch.PtrSize >= 8 && heopt != "" {
  1643  			argv = append(argv, heopt)
  1644  		}
  1645  		return argv
  1646  	}
  1647  
  1648  	switch ctxt.BuildMode {
  1649  	case BuildModeExe:
  1650  		if ctxt.HeadType == objabi.Hdarwin {
  1651  			if machoPlatform == PLATFORM_MACOS && ctxt.IsAMD64() {
  1652  				argv = append(argv, "-Wl,-no_pie")
  1653  			}
  1654  		}
  1655  		if *flagRace && ctxt.HeadType == objabi.Hwindows {
  1656  			// Current windows/amd64 race detector tsan support
  1657  			// library can't handle PIE mode (see #53539 for more details).
  1658  			// For now, explicitly disable PIE (since some compilers
  1659  			// default to it) if -race is in effect.
  1660  			argv = addASLRargs(argv, false)
  1661  		}
  1662  	case BuildModePIE:
  1663  		switch ctxt.HeadType {
  1664  		case objabi.Hdarwin, objabi.Haix:
  1665  		case objabi.Hwindows:
  1666  			if *flagAslr && *flagRace {
  1667  				// Current windows/amd64 race detector tsan support
  1668  				// library can't handle PIE mode (see #53539 for more details).
  1669  				// Disable alsr if -race in effect.
  1670  				*flagAslr = false
  1671  			}
  1672  			argv = addASLRargs(argv, *flagAslr)
  1673  		default:
  1674  			// ELF.
  1675  			if ctxt.UseRelro() {
  1676  				argv = append(argv, "-Wl,-z,relro")
  1677  			}
  1678  			argv = append(argv, "-pie")
  1679  		}
  1680  	case BuildModeCShared:
  1681  		if ctxt.HeadType == objabi.Hdarwin {
  1682  			argv = append(argv, "-dynamiclib")
  1683  		} else {
  1684  			if ctxt.UseRelro() {
  1685  				argv = append(argv, "-Wl,-z,relro")
  1686  			}
  1687  			argv = append(argv, "-shared")
  1688  			if ctxt.HeadType == objabi.Hwindows {
  1689  				argv = addASLRargs(argv, *flagAslr)
  1690  			} else {
  1691  				// Pass -z nodelete to mark the shared library as
  1692  				// non-closeable: a dlclose will do nothing.
  1693  				argv = append(argv, "-Wl,-z,nodelete")
  1694  				// Only pass Bsymbolic on non-Windows.
  1695  				argv = append(argv, "-Wl,-Bsymbolic")
  1696  			}
  1697  		}
  1698  	case BuildModeShared:
  1699  		if ctxt.UseRelro() {
  1700  			argv = append(argv, "-Wl,-z,relro")
  1701  		}
  1702  		argv = append(argv, "-shared")
  1703  	case BuildModePlugin:
  1704  		if ctxt.HeadType == objabi.Hdarwin {
  1705  			argv = append(argv, "-dynamiclib")
  1706  		} else {
  1707  			if ctxt.UseRelro() {
  1708  				argv = append(argv, "-Wl,-z,relro")
  1709  			}
  1710  			argv = append(argv, "-shared")
  1711  		}
  1712  	}
  1713  
  1714  	var altLinker string
  1715  	if ctxt.IsELF && (ctxt.DynlinkingGo() || *flagBindNow) {
  1716  		// For ELF targets, when producing dynamically linked Go code
  1717  		// or when immediate binding is explicitly requested,
  1718  		// we force all symbol resolution to be done at program startup
  1719  		// because lazy PLT resolution can use large amounts of stack at
  1720  		// times we cannot allow it to do so.
  1721  		argv = append(argv, "-Wl,-z,now")
  1722  	}
  1723  
  1724  	if ctxt.IsELF && ctxt.DynlinkingGo() {
  1725  		// Do not let the host linker generate COPY relocations. These
  1726  		// can move symbols out of sections that rely on stable offsets
  1727  		// from the beginning of the section (like sym.STYPE).
  1728  		argv = append(argv, "-Wl,-z,nocopyreloc")
  1729  
  1730  		if buildcfg.GOOS == "android" {
  1731  			// Use lld to avoid errors from default linker (issue #38838)
  1732  			altLinker = "lld"
  1733  		}
  1734  
  1735  		if ctxt.Arch.InFamily(sys.ARM64) && buildcfg.GOOS == "linux" {
  1736  			// On ARM64, the GNU linker had issues with -znocopyreloc
  1737  			// and COPY relocations. This was fixed in GNU ld 2.36+.
  1738  			// https://sourceware.org/bugzilla/show_bug.cgi?id=19962
  1739  			// https://go.dev/issue/22040
  1740  			// And newer gold is deprecated, may lack new features/flags, or even missing
  1741  
  1742  			// If the default linker is GNU ld 2.35 or older, use gold
  1743  			useGold := false
  1744  			name, args := flagExtld[0], flagExtld[1:]
  1745  			args = append(args, "-Wl,--version")
  1746  			cmd := exec.Command(name, args...)
  1747  			if out, err := cmd.CombinedOutput(); err == nil {
  1748  				// Parse version from output like "GNU ld (GNU Binutils for Distro) 2.36.1"
  1749  				for line := range strings.Lines(string(out)) {
  1750  					if !strings.HasPrefix(line, "GNU ld ") {
  1751  						continue
  1752  					}
  1753  					fields := strings.Fields(line[len("GNU ld "):])
  1754  					var major, minor int
  1755  					if ret, err := fmt.Sscanf(fields[len(fields)-1], "%d.%d", &major, &minor); ret == 2 && err == nil {
  1756  						if major == 2 && minor <= 35 {
  1757  							useGold = true
  1758  						}
  1759  						break
  1760  					}
  1761  				}
  1762  			}
  1763  
  1764  			if useGold {
  1765  				// Use gold for older linkers
  1766  				altLinker = "gold"
  1767  
  1768  				// If gold is not installed, gcc will silently switch
  1769  				// back to ld.bfd. So we parse the version information
  1770  				// and provide a useful error if gold is missing.
  1771  				args = flagExtld[1:]
  1772  				args = append(args, "-fuse-ld=gold", "-Wl,--version")
  1773  				cmd = exec.Command(name, args...)
  1774  				if out, err := cmd.CombinedOutput(); err == nil {
  1775  					if !bytes.Contains(out, []byte("GNU gold")) {
  1776  						log.Fatalf("ARM64 external linker must be ld>=2.36 or gold (issue #15696, 22040), but is not: %s", out)
  1777  					}
  1778  				}
  1779  			}
  1780  		}
  1781  	}
  1782  	if ctxt.Arch.Family == sys.ARM64 && buildcfg.GOOS == "freebsd" {
  1783  		// Switch to ld.bfd on freebsd/arm64.
  1784  		altLinker = "bfd"
  1785  
  1786  		// Provide a useful error if ld.bfd is missing.
  1787  		name, args := flagExtld[0], flagExtld[1:]
  1788  		args = append(args, "-fuse-ld=bfd", "-Wl,--version")
  1789  		cmd := exec.Command(name, args...)
  1790  		if out, err := cmd.CombinedOutput(); err == nil {
  1791  			if !bytes.Contains(out, []byte("GNU ld")) {
  1792  				log.Fatalf("ARM64 external linker must be ld.bfd (issue #35197), please install devel/binutils")
  1793  			}
  1794  		}
  1795  	}
  1796  	if altLinker != "" {
  1797  		argv = append(argv, "-fuse-ld="+altLinker)
  1798  	}
  1799  
  1800  	if ctxt.IsELF && linkerFlagSupported(ctxt.Arch, argv[0], "", "-Wl,--build-id=0x1234567890abcdef") { // Solaris ld doesn't support --build-id.
  1801  		if len(buildinfo) > 0 {
  1802  			argv = append(argv, fmt.Sprintf("-Wl,--build-id=0x%x", buildinfo))
  1803  		} else if *flagHostBuildid == "none" {
  1804  			argv = append(argv, "-Wl,--build-id=none")
  1805  		}
  1806  	}
  1807  
  1808  	// On Windows, given -o foo, GCC will append ".exe" to produce
  1809  	// "foo.exe".  We have decided that we want to honor the -o
  1810  	// option. To make this work, we append a '.' so that GCC
  1811  	// will decide that the file already has an extension. We
  1812  	// only want to do this when producing a Windows output file
  1813  	// on a Windows host.
  1814  	outopt := *flagOutfile
  1815  	if buildcfg.GOOS == "windows" && runtime.GOOS == "windows" && filepath.Ext(outopt) == "" {
  1816  		outopt += "."
  1817  	}
  1818  	argv = append(argv, "-o")
  1819  	argv = append(argv, outopt)
  1820  
  1821  	if rpath.val != "" {
  1822  		argv = append(argv, fmt.Sprintf("-Wl,-rpath,%s", rpath.val))
  1823  	}
  1824  
  1825  	if *flagInterpreter != "" {
  1826  		// Many linkers support both -I and the --dynamic-linker flags
  1827  		// to set the ELF interpreter, but lld only supports
  1828  		// --dynamic-linker so prefer that (ld on very old Solaris only
  1829  		// supports -I but that seems less important).
  1830  		argv = append(argv, fmt.Sprintf("-Wl,--dynamic-linker,%s", *flagInterpreter))
  1831  	}
  1832  
  1833  	// Force global symbols to be exported for dlopen, etc.
  1834  	switch {
  1835  	case ctxt.IsELF:
  1836  		if ctxt.DynlinkingGo() || ctxt.BuildMode == BuildModeCShared || !linkerFlagSupported(ctxt.Arch, argv[0], altLinker, "-Wl,--export-dynamic-symbol=main") {
  1837  			argv = append(argv, "-rdynamic")
  1838  		} else {
  1839  			var exports []string
  1840  			ctxt.loader.ForAllCgoExportDynamic(func(s loader.Sym) {
  1841  				exports = append(exports, "-Wl,--export-dynamic-symbol="+ctxt.loader.SymExtname(s))
  1842  			})
  1843  			sort.Strings(exports)
  1844  			argv = append(argv, exports...)
  1845  		}
  1846  	case ctxt.IsAIX():
  1847  		fileName := xcoffCreateExportFile(ctxt)
  1848  		argv = append(argv, "-Wl,-bE:"+fileName)
  1849  	case ctxt.IsWindows() && !slices.Contains(flagExtldflags, wlPrefix+"export-all-symbols"):
  1850  		fileName := peCreateExportFile(ctxt, filepath.Base(outopt))
  1851  		prefix := ""
  1852  		if isMSVC {
  1853  			prefix = "-Wl,-def:"
  1854  		}
  1855  		argv = append(argv, prefix+fileName)
  1856  	}
  1857  
  1858  	const unusedArguments = "-Qunused-arguments"
  1859  	if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, unusedArguments) {
  1860  		argv = append(argv, unusedArguments)
  1861  	}
  1862  
  1863  	if ctxt.IsWindows() {
  1864  		// Suppress generation of the PE file header timestamp,
  1865  		// so as to avoid spurious build ID differences between
  1866  		// linked binaries that are otherwise identical other than
  1867  		// the date/time they were linked.
  1868  		const noTimeStamp = "-Wl,--no-insert-timestamp"
  1869  		if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, noTimeStamp) {
  1870  			argv = append(argv, noTimeStamp)
  1871  		}
  1872  	}
  1873  
  1874  	const compressDWARF = "-Wl,--compress-debug-sections=zlib"
  1875  	if ctxt.compressDWARF && linkerFlagSupported(ctxt.Arch, argv[0], altLinker, compressDWARF) {
  1876  		argv = append(argv, compressDWARF)
  1877  	}
  1878  
  1879  	hostObjCopyPaths := ctxt.hostobjCopy()
  1880  	cleanTimeStamps(hostObjCopyPaths)
  1881  	godotopath := filepath.Join(*flagTmpdir, "go.o")
  1882  	cleanTimeStamps([]string{godotopath})
  1883  
  1884  	argv = append(argv, godotopath)
  1885  	argv = append(argv, hostObjCopyPaths...)
  1886  	if ctxt.HeadType == objabi.Haix {
  1887  		// We want to have C files after Go files to remove
  1888  		// trampolines csects made by ld.
  1889  		argv = append(argv, "-nostartfiles")
  1890  
  1891  		extld := ctxt.extld()
  1892  		name, args := extld[0], extld[1:]
  1893  		// Get starting files.
  1894  		getPathFile := func(file string) string {
  1895  			args := append(args, "-maix64", "--print-file-name="+file)
  1896  			out, err := exec.Command(name, args...).CombinedOutput()
  1897  			if err != nil {
  1898  				log.Fatalf("running %s failed: %v\n%s", extld, err, out)
  1899  			}
  1900  			return strings.Trim(string(out), "\n")
  1901  		}
  1902  		argv = append(argv, getPathFile("crt0_64.o"))
  1903  		// Since GCC version 11, the 64-bit version of GCC starting files
  1904  		// are now suffixed by "_64". Even under "-maix64" multilib directory
  1905  		// "crtcxa.o" is 32-bit.
  1906  		crtcxa := getPathFile("crtcxa_64.o")
  1907  		if !filepath.IsAbs(crtcxa) {
  1908  			crtcxa = getPathFile("crtcxa.o")
  1909  		}
  1910  		crtdbase := getPathFile("crtdbase_64.o")
  1911  		if !filepath.IsAbs(crtdbase) {
  1912  			crtdbase = getPathFile("crtdbase.o")
  1913  		}
  1914  		argv = append(argv, crtcxa)
  1915  		argv = append(argv, crtdbase)
  1916  	}
  1917  
  1918  	if ctxt.linkShared {
  1919  		seenDirs := make(map[string]bool)
  1920  		seenLibs := make(map[string]bool)
  1921  		addshlib := func(path string) {
  1922  			dir, base := filepath.Split(path)
  1923  			if !seenDirs[dir] {
  1924  				argv = append(argv, "-L"+dir)
  1925  				if !rpath.set {
  1926  					argv = append(argv, "-Wl,-rpath="+dir)
  1927  				}
  1928  				seenDirs[dir] = true
  1929  			}
  1930  			base = strings.TrimSuffix(base, ".so")
  1931  			base = strings.TrimPrefix(base, "lib")
  1932  			if !seenLibs[base] {
  1933  				argv = append(argv, "-l"+base)
  1934  				seenLibs[base] = true
  1935  			}
  1936  		}
  1937  		for _, shlib := range ctxt.Shlibs {
  1938  			addshlib(shlib.Path)
  1939  			for _, dep := range shlib.Deps {
  1940  				if dep == "" {
  1941  					continue
  1942  				}
  1943  				libpath := findshlib(ctxt, dep)
  1944  				if libpath != "" {
  1945  					addshlib(libpath)
  1946  				}
  1947  			}
  1948  		}
  1949  	}
  1950  
  1951  	// clang, unlike GCC, passes -rdynamic to the linker
  1952  	// even when linking with -static, causing a linker
  1953  	// error when using GNU ld. So take out -rdynamic if
  1954  	// we added it. We do it in this order, rather than
  1955  	// only adding -rdynamic later, so that -extldflags
  1956  	// can override -rdynamic without using -static.
  1957  	// Similarly for -Wl,--dynamic-linker.
  1958  	checkStatic := func(arg string) {
  1959  		if ctxt.IsELF && arg == "-static" {
  1960  			for i := range argv {
  1961  				if argv[i] == "-rdynamic" || strings.HasPrefix(argv[i], "-Wl,--dynamic-linker,") {
  1962  					argv[i] = "-static"
  1963  				}
  1964  			}
  1965  		}
  1966  	}
  1967  
  1968  	for _, p := range ldflag {
  1969  		argv = append(argv, p)
  1970  		checkStatic(p)
  1971  	}
  1972  
  1973  	// When building a program with the default -buildmode=exe the
  1974  	// gc compiler generates code requires DT_TEXTREL in a
  1975  	// position independent executable (PIE). On systems where the
  1976  	// toolchain creates PIEs by default, and where DT_TEXTREL
  1977  	// does not work, the resulting programs will not run. See
  1978  	// issue #17847. To avoid this problem pass -no-pie to the
  1979  	// toolchain if it is supported.
  1980  	if ctxt.BuildMode == BuildModeExe && !ctxt.linkShared && !(ctxt.IsDarwin() && ctxt.IsARM64()) {
  1981  		// GCC uses -no-pie, clang uses -nopie.
  1982  		for _, nopie := range []string{"-no-pie", "-nopie"} {
  1983  			if linkerFlagSupported(ctxt.Arch, argv[0], altLinker, nopie) {
  1984  				argv = append(argv, nopie)
  1985  				break
  1986  			}
  1987  		}
  1988  	}
  1989  
  1990  	for _, p := range flagExtldflags {
  1991  		argv = append(argv, p)
  1992  		checkStatic(p)
  1993  	}
  1994  	if ctxt.HeadType == objabi.Hwindows {
  1995  		// use gcc linker script to work around gcc bug
  1996  		// (see https://golang.org/issue/20183 for details).
  1997  		if !isLLD {
  1998  			p := writeGDBLinkerScript()
  1999  			argv = append(argv, "-Wl,-T,"+p)
  2000  		}
  2001  		if *flagRace {
  2002  			// Apparently --print-file-name doesn't work with -msvc clang.
  2003  			// (The library name is synchronization.lib, but even with that
  2004  			// name it still doesn't print the full path.) Assume it always
  2005  			// it.
  2006  			if isMSVC || ctxt.findLibPath("libsynchronization.a") != "libsynchronization.a" {
  2007  				argv = append(argv, "-lsynchronization")
  2008  			}
  2009  		}
  2010  		if !isMSVC {
  2011  			// libmingw32 and libmingwex have some inter-dependencies,
  2012  			// so must use linker groups.
  2013  			argv = append(argv, "-Wl,--start-group", "-lmingwex", "-lmingw32", "-Wl,--end-group")
  2014  		}
  2015  		argv = append(argv, peimporteddlls()...)
  2016  	}
  2017  
  2018  	argv = ctxt.passLongArgsInResponseFile(argv, altLinker)
  2019  
  2020  	if ctxt.Debugvlog != 0 {
  2021  		ctxt.Logf("host link:")
  2022  		for _, v := range argv {
  2023  			ctxt.Logf(" %q", v)
  2024  		}
  2025  		ctxt.Logf("\n")
  2026  	}
  2027  
  2028  	cmd := exec.Command(argv[0], argv[1:]...)
  2029  	out, err := cmd.CombinedOutput()
  2030  	if err != nil {
  2031  		Exitf("running %s failed: %v\n%s\n%s", argv[0], err, cmd, out)
  2032  	}
  2033  
  2034  	// Filter out useless linker warnings caused by bugs outside Go.
  2035  	// See also cmd/go/internal/work/exec.go's gccld method.
  2036  	var save [][]byte
  2037  	var skipLines int
  2038  	for _, line := range bytes.SplitAfter(out, []byte("\n")) {
  2039  		// golang.org/issue/26073 - Apple Xcode bug
  2040  		if bytes.Contains(line, []byte("ld: warning: text-based stub file")) {
  2041  			continue
  2042  		}
  2043  
  2044  		if skipLines > 0 {
  2045  			skipLines--
  2046  			continue
  2047  		}
  2048  
  2049  		// Remove TOC overflow warning on AIX.
  2050  		if bytes.Contains(line, []byte("ld: 0711-783")) {
  2051  			skipLines = 2
  2052  			continue
  2053  		}
  2054  
  2055  		save = append(save, line)
  2056  	}
  2057  	out = bytes.Join(save, nil)
  2058  
  2059  	if len(out) > 0 {
  2060  		// always print external output even if the command is successful, so that we don't
  2061  		// swallow linker warnings (see https://golang.org/issue/17935).
  2062  		if ctxt.IsDarwin() && ctxt.IsAMD64() {
  2063  			const noPieWarning = "ld: warning: -no_pie is deprecated when targeting new OS versions\n"
  2064  			if i := bytes.Index(out, []byte(noPieWarning)); i >= 0 {
  2065  				// swallow -no_pie deprecation warning, issue 54482
  2066  				out = append(out[:i], out[i+len(noPieWarning):]...)
  2067  			}
  2068  		}
  2069  		if ctxt.IsDarwin() {
  2070  			const bindAtLoadWarning = "ld: warning: -bind_at_load is deprecated on macOS\n"
  2071  			if i := bytes.Index(out, []byte(bindAtLoadWarning)); i >= 0 {
  2072  				// -bind_at_load is deprecated with ld-prime, but needed for
  2073  				// correctness with older versions of ld64. Swallow the warning.
  2074  				// TODO: maybe pass -bind_at_load conditionally based on C
  2075  				// linker version.
  2076  				out = append(out[:i], out[i+len(bindAtLoadWarning):]...)
  2077  			}
  2078  		}
  2079  		ctxt.Logf("%s", out)
  2080  	}
  2081  
  2082  	// Helper for updating a Macho binary in some way (shared between
  2083  	// dwarf combining and UUID update).
  2084  	updateMachoOutFile := func(op string, updateFunc machoUpdateFunc) {
  2085  		// For os.Rename to work reliably, must be in same directory as outfile.
  2086  		rewrittenOutput := *flagOutfile + "~"
  2087  		exef, err := os.Open(*flagOutfile)
  2088  		if err != nil {
  2089  			Exitf("%s: %s failed: %v", os.Args[0], op, err)
  2090  		}
  2091  		defer exef.Close()
  2092  		exem, err := macho.NewFile(exef)
  2093  		if err != nil {
  2094  			Exitf("%s: parsing Mach-O header failed: %v", os.Args[0], err)
  2095  		}
  2096  		if err := updateFunc(ctxt, exef, exem, rewrittenOutput); err != nil {
  2097  			Exitf("%s: %s failed: %v", os.Args[0], op, err)
  2098  		}
  2099  		os.Remove(*flagOutfile)
  2100  		if err := os.Rename(rewrittenOutput, *flagOutfile); err != nil {
  2101  			Exitf("%s: %v", os.Args[0], err)
  2102  		}
  2103  	}
  2104  
  2105  	uuidUpdated := false
  2106  	if combineDwarf {
  2107  		// Find "dsymutils" and "strip" tools using CC --print-prog-name.
  2108  		dsymutilCmd := ctxt.findExtLinkTool("dsymutil")
  2109  		stripCmd := ctxt.findExtLinkTool("strip")
  2110  
  2111  		dsym := filepath.Join(*flagTmpdir, "go.dwarf")
  2112  		cmd := exec.Command(dsymutilCmd, "-f", *flagOutfile, "-o", dsym)
  2113  		// dsymutil may not clean up its temp directory at exit.
  2114  		// Set DSYMUTIL_REPRODUCER_PATH to work around. see issue 59026.
  2115  		// dsymutil (Apple LLVM version 16.0.0) deletes the directory
  2116  		// even if it is not empty. We still need our tmpdir, so give a
  2117  		// subdirectory to dsymutil.
  2118  		dsymDir := filepath.Join(*flagTmpdir, "dsymutil")
  2119  		err := os.MkdirAll(dsymDir, 0777)
  2120  		if err != nil {
  2121  			Exitf("fail to create temp dir: %v", err)
  2122  		}
  2123  		cmd.Env = append(os.Environ(), "DSYMUTIL_REPRODUCER_PATH="+dsymDir)
  2124  		if ctxt.Debugvlog != 0 {
  2125  			ctxt.Logf("host link dsymutil:")
  2126  			for _, v := range cmd.Args {
  2127  				ctxt.Logf(" %q", v)
  2128  			}
  2129  			ctxt.Logf("\n")
  2130  		}
  2131  		if out, err := cmd.CombinedOutput(); err != nil {
  2132  			Exitf("%s: running dsymutil failed: %v\n%s\n%s", os.Args[0], err, cmd, out)
  2133  		}
  2134  		// Remove STAB (symbolic debugging) symbols after we are done with them (by dsymutil).
  2135  		// They contain temporary file paths and make the build not reproducible.
  2136  		var stripArgs = []string{"-S"}
  2137  		if debug_s {
  2138  			// We are generating a binary with symbol table suppressed.
  2139  			// Suppress local symbols. We need to keep dynamically exported
  2140  			// and referenced symbols so the dynamic linker can resolve them.
  2141  			stripArgs = append(stripArgs, "-x")
  2142  		}
  2143  		stripArgs = append(stripArgs, *flagOutfile)
  2144  		if ctxt.Debugvlog != 0 {
  2145  			ctxt.Logf("host link strip: %q", stripCmd)
  2146  			for _, v := range stripArgs {
  2147  				ctxt.Logf(" %q", v)
  2148  			}
  2149  			ctxt.Logf("\n")
  2150  		}
  2151  		cmd = exec.Command(stripCmd, stripArgs...)
  2152  		if out, err := cmd.CombinedOutput(); err != nil {
  2153  			Exitf("%s: running strip failed: %v\n%s\n%s", os.Args[0], err, cmd, out)
  2154  		}
  2155  		// Skip combining if `dsymutil` didn't generate a file. See #11994.
  2156  		if _, err := os.Stat(dsym); err == nil {
  2157  			updateMachoOutFile("combining dwarf",
  2158  				func(ctxt *Link, exef *os.File, exem *macho.File, outexe string) error {
  2159  					return machoCombineDwarf(ctxt, exef, exem, dsym, outexe)
  2160  				})
  2161  			uuidUpdated = true
  2162  		}
  2163  	}
  2164  	if ctxt.IsDarwin() && !uuidUpdated && len(buildinfo) > 0 {
  2165  		updateMachoOutFile("rewriting uuid",
  2166  			func(ctxt *Link, exef *os.File, exem *macho.File, outexe string) error {
  2167  				return machoRewriteUuid(ctxt, exef, exem, outexe)
  2168  			})
  2169  	}
  2170  	hostlinkfips(ctxt, *flagOutfile, *flagFipso)
  2171  	if ctxt.NeedCodeSign() {
  2172  		err := machoCodeSign(ctxt, *flagOutfile)
  2173  		if err != nil {
  2174  			Exitf("%s: code signing failed: %v", os.Args[0], err)
  2175  		}
  2176  	}
  2177  }
  2178  
  2179  // passLongArgsInResponseFile writes the arguments into a file if they
  2180  // are very long.
  2181  func (ctxt *Link) passLongArgsInResponseFile(argv []string, altLinker string) []string {
  2182  	c := 0
  2183  	for _, arg := range argv {
  2184  		c += len(arg)
  2185  	}
  2186  
  2187  	if c < sys.ExecArgLengthLimit {
  2188  		return argv
  2189  	}
  2190  
  2191  	// Only use response files if they are supported.
  2192  	response := filepath.Join(*flagTmpdir, "response")
  2193  	if err := os.WriteFile(response, nil, 0644); err != nil {
  2194  		log.Fatalf("failed while testing response file: %v", err)
  2195  	}
  2196  	if !linkerFlagSupported(ctxt.Arch, argv[0], altLinker, "@"+response) {
  2197  		if ctxt.Debugvlog != 0 {
  2198  			ctxt.Logf("not using response file because linker does not support one")
  2199  		}
  2200  		return argv
  2201  	}
  2202  
  2203  	var buf bytes.Buffer
  2204  	for _, arg := range argv[1:] {
  2205  		// The external linker response file supports quoted strings.
  2206  		fmt.Fprintf(&buf, "%q\n", arg)
  2207  	}
  2208  	if err := os.WriteFile(response, buf.Bytes(), 0644); err != nil {
  2209  		log.Fatalf("failed while writing response file: %v", err)
  2210  	}
  2211  	if ctxt.Debugvlog != 0 {
  2212  		ctxt.Logf("response file %s contents:\n%s", response, buf.Bytes())
  2213  	}
  2214  	return []string{
  2215  		argv[0],
  2216  		"@" + response,
  2217  	}
  2218  }
  2219  
  2220  var createTrivialCOnce sync.Once
  2221  
  2222  func linkerFlagSupported(arch *sys.Arch, linker, altLinker, flag string) bool {
  2223  	createTrivialCOnce.Do(func() {
  2224  		src := filepath.Join(*flagTmpdir, "trivial.c")
  2225  		if err := os.WriteFile(src, []byte("int main() { return 0; }"), 0666); err != nil {
  2226  			Errorf("WriteFile trivial.c failed: %v", err)
  2227  		}
  2228  	})
  2229  
  2230  	flags := hostlinkArchArgs(arch)
  2231  
  2232  	moreFlags := trimLinkerArgv(append(ldflag, flagExtldflags...))
  2233  	flags = append(flags, moreFlags...)
  2234  
  2235  	if altLinker != "" {
  2236  		flags = append(flags, "-fuse-ld="+altLinker)
  2237  	}
  2238  	trivialPath := filepath.Join(*flagTmpdir, "trivial.c")
  2239  	outPath := filepath.Join(*flagTmpdir, "a.out")
  2240  	flags = append(flags, "-o", outPath, flag, trivialPath)
  2241  
  2242  	cmd := exec.Command(linker, flags...)
  2243  	cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
  2244  	out, err := cmd.CombinedOutput()
  2245  	// GCC says "unrecognized command line option ‘-no-pie’"
  2246  	// clang says "unknown argument: '-no-pie'"
  2247  	return err == nil && !bytes.Contains(out, []byte("unrecognized")) && !bytes.Contains(out, []byte("unknown"))
  2248  }
  2249  
  2250  // peHasLoadConfigDirectorySupport checks whether the external linker
  2251  // populates the PE Load Configuration Directory data directory entry
  2252  // when it encounters a _load_config_used symbol.
  2253  //
  2254  // GNU ld gained this support in binutils 2.45. MSVC link.exe and
  2255  // LLVM lld-link have always supported it.
  2256  func peHasLoadConfigDirectorySupport(arch *sys.Arch, linker string) bool {
  2257  	src := filepath.Join(*flagTmpdir, "loadcfg_test.c")
  2258  	if err := os.WriteFile(src, []byte(`
  2259  #ifdef _WIN64
  2260  typedef unsigned long long uintptr;
  2261  #else
  2262  typedef unsigned long uintptr;
  2263  #endif
  2264  const uintptr _load_config_used[2] = { sizeof(_load_config_used), 0 };
  2265  int main() { return 0; }
  2266  `), 0666); err != nil {
  2267  		return false
  2268  	}
  2269  
  2270  	outPath := filepath.Join(*flagTmpdir, "loadcfg_test.exe")
  2271  	flags := hostlinkArchArgs(arch)
  2272  	flags = append(flags, "-o", outPath, src)
  2273  	cmd := exec.Command(linker, flags...)
  2274  	cmd.Env = append([]string{"LC_ALL=C"}, os.Environ()...)
  2275  	if err := cmd.Run(); err != nil {
  2276  		return false
  2277  	}
  2278  
  2279  	f, err := pe.Open(outPath)
  2280  	if err != nil {
  2281  		return false
  2282  	}
  2283  	defer f.Close()
  2284  
  2285  	switch oh := f.OptionalHeader.(type) {
  2286  	case *pe.OptionalHeader64:
  2287  		if int(pe.IMAGE_DIRECTORY_ENTRY_LOAD_CONFIG) < len(oh.DataDirectory) {
  2288  			return oh.DataDirectory[pe.IMAGE_DIRECTORY_ENTRY_LOAD_CONFIG].VirtualAddress != 0
  2289  		}
  2290  	case *pe.OptionalHeader32:
  2291  		if int(pe.IMAGE_DIRECTORY_ENTRY_LOAD_CONFIG) < len(oh.DataDirectory) {
  2292  			return oh.DataDirectory[pe.IMAGE_DIRECTORY_ENTRY_LOAD_CONFIG].VirtualAddress != 0
  2293  		}
  2294  	}
  2295  	return false
  2296  }
  2297  
  2298  // trimLinkerArgv returns a new copy of argv that does not include flags
  2299  // that are not relevant for testing whether some linker option works.
  2300  func trimLinkerArgv(argv []string) []string {
  2301  	flagsWithNextArgSkip := []string{
  2302  		"-F",
  2303  		"-l",
  2304  		"-framework",
  2305  		"-Wl,-framework",
  2306  		"-Wl,-rpath",
  2307  		"-Wl,-undefined",
  2308  	}
  2309  	flagsWithNextArgKeep := []string{
  2310  		"-B",
  2311  		"-L",
  2312  		"-arch",
  2313  		"-isysroot",
  2314  		"--sysroot",
  2315  		"-target",
  2316  		"--target",
  2317  		"-resource-dir",
  2318  		"-rtlib",
  2319  		"--rtlib",
  2320  		"-stdlib",
  2321  		"--stdlib",
  2322  		"-unwindlib",
  2323  		"--unwindlib",
  2324  	}
  2325  	prefixesToKeep := []string{
  2326  		"-B",
  2327  		"-L",
  2328  		"-f",
  2329  		"-m",
  2330  		"-p",
  2331  		"-Wl,",
  2332  		"-arch",
  2333  		"-isysroot",
  2334  		"--sysroot",
  2335  		"-target",
  2336  		"--target",
  2337  		"-resource-dir",
  2338  		"-rtlib",
  2339  		"--rtlib",
  2340  		"-stdlib",
  2341  		"--stdlib",
  2342  		"-unwindlib",
  2343  		"--unwindlib",
  2344  		"-nostdlib++",
  2345  		"-nostdlib",
  2346  		"-nodefaultlibs",
  2347  		"-nostartfiles",
  2348  		"-nostdinc++",
  2349  		"-nostdinc",
  2350  		"-nobuiltininc",
  2351  	}
  2352  
  2353  	var flags []string
  2354  	keep := false
  2355  	skip := false
  2356  	for _, f := range argv {
  2357  		if keep {
  2358  			flags = append(flags, f)
  2359  			keep = false
  2360  		} else if skip {
  2361  			skip = false
  2362  		} else if f == "" || f[0] != '-' {
  2363  		} else if slices.Contains(flagsWithNextArgSkip, f) {
  2364  			skip = true
  2365  		} else if slices.Contains(flagsWithNextArgKeep, f) {
  2366  			flags = append(flags, f)
  2367  			keep = true
  2368  		} else {
  2369  			for _, p := range prefixesToKeep {
  2370  				if strings.HasPrefix(f, p) {
  2371  					flags = append(flags, f)
  2372  					break
  2373  				}
  2374  			}
  2375  		}
  2376  	}
  2377  	return flags
  2378  }
  2379  
  2380  // hostlinkArchArgs returns arguments to pass to the external linker
  2381  // based on the architecture.
  2382  func hostlinkArchArgs(arch *sys.Arch) []string {
  2383  	switch arch.Family {
  2384  	case sys.I386:
  2385  		return []string{"-m32"}
  2386  	case sys.AMD64:
  2387  		if buildcfg.GOOS == "darwin" {
  2388  			return []string{"-arch", "x86_64", "-m64"}
  2389  		}
  2390  		return []string{"-m64"}
  2391  	case sys.S390X:
  2392  		return []string{"-m64"}
  2393  	case sys.ARM:
  2394  		return []string{"-marm"}
  2395  	case sys.ARM64:
  2396  		if buildcfg.GOOS == "darwin" {
  2397  			return []string{"-arch", "arm64"}
  2398  		}
  2399  	case sys.Loong64:
  2400  		return []string{"-mabi=lp64d"}
  2401  	case sys.MIPS64:
  2402  		return []string{"-mabi=64"}
  2403  	case sys.MIPS:
  2404  		return []string{"-mabi=32"}
  2405  	case sys.PPC64:
  2406  		if buildcfg.GOOS == "aix" {
  2407  			return []string{"-maix64"}
  2408  		} else {
  2409  			return []string{"-m64"}
  2410  		}
  2411  
  2412  	}
  2413  	return nil
  2414  }
  2415  
  2416  var wantHdr = objabi.HeaderString()
  2417  
  2418  // ldobj loads an input object. If it is a host object (an object
  2419  // compiled by a non-Go compiler) it returns the Hostobj pointer. If
  2420  // it is a Go object, it returns nil.
  2421  func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string, file string) *Hostobj {
  2422  	pkg := objabi.PathToPrefix(lib.Pkg)
  2423  
  2424  	eof := f.Offset() + length
  2425  	start := f.Offset()
  2426  	c1 := bgetc(f)
  2427  	c2 := bgetc(f)
  2428  	c3 := bgetc(f)
  2429  	c4 := bgetc(f)
  2430  	f.MustSeek(start, 0)
  2431  
  2432  	unit := &sym.CompilationUnit{Lib: lib}
  2433  	lib.Units = append(lib.Units, unit)
  2434  
  2435  	magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
  2436  	if magic == 0x7f454c46 { // \x7F E L F
  2437  		ldelf := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
  2438  			textp, flags, err := loadelf.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn, ehdr.Flags)
  2439  			if err != nil {
  2440  				Errorf("%v", err)
  2441  				return
  2442  			}
  2443  			ehdr.Flags = flags
  2444  			ctxt.Textp = append(ctxt.Textp, textp...)
  2445  		}
  2446  		return ldhostobj(ldelf, ctxt.HeadType, f, pkg, length, pn, file)
  2447  	}
  2448  
  2449  	if magic&^1 == 0xfeedface || magic&^0x01000000 == 0xcefaedfe {
  2450  		ldmacho := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
  2451  			textp, err := loadmacho.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
  2452  			if err != nil {
  2453  				Errorf("%v", err)
  2454  				return
  2455  			}
  2456  			ctxt.Textp = append(ctxt.Textp, textp...)
  2457  		}
  2458  		return ldhostobj(ldmacho, ctxt.HeadType, f, pkg, length, pn, file)
  2459  	}
  2460  
  2461  	switch c1<<8 | c2 {
  2462  	case 0x4c01, // 386
  2463  		0x6486, // amd64
  2464  		0xc401, // arm
  2465  		0x64aa: // arm64
  2466  		ldpe := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
  2467  			ls, err := loadpe.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
  2468  			if err != nil {
  2469  				Errorf("%v", err)
  2470  				return
  2471  			}
  2472  			if len(ls.Resources) != 0 {
  2473  				setpersrc(ctxt, ls.Resources)
  2474  			}
  2475  			sehp.pdata = append(sehp.pdata, ls.PData...)
  2476  			if ls.XData != 0 {
  2477  				sehp.xdata = append(sehp.xdata, ls.XData)
  2478  			}
  2479  			ctxt.Textp = append(ctxt.Textp, ls.Textp...)
  2480  		}
  2481  		return ldhostobj(ldpe, ctxt.HeadType, f, pkg, length, pn, file)
  2482  	}
  2483  
  2484  	if c1 == 0x01 && (c2 == 0xD7 || c2 == 0xF7) {
  2485  		ldxcoff := func(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
  2486  			textp, err := loadxcoff.Load(ctxt.loader, ctxt.Arch, ctxt.IncVersion(), f, pkg, length, pn)
  2487  			if err != nil {
  2488  				Errorf("%v", err)
  2489  				return
  2490  			}
  2491  			ctxt.Textp = append(ctxt.Textp, textp...)
  2492  		}
  2493  		return ldhostobj(ldxcoff, ctxt.HeadType, f, pkg, length, pn, file)
  2494  	}
  2495  
  2496  	if c1 != 'g' || c2 != 'o' || c3 != ' ' || c4 != 'o' {
  2497  		// An unrecognized object is just passed to the external linker.
  2498  		// If we try to read symbols from this object, we will
  2499  		// report an error at that time.
  2500  		unknownObjFormat = true
  2501  		return ldhostobj(nil, ctxt.HeadType, f, pkg, length, pn, file)
  2502  	}
  2503  
  2504  	/* check the header */
  2505  	line, err := f.ReadString('\n')
  2506  	if err != nil {
  2507  		Errorf("truncated object file: %s: %v", pn, err)
  2508  		return nil
  2509  	}
  2510  
  2511  	if !strings.HasPrefix(line, "go object ") {
  2512  		if strings.HasSuffix(pn, ".go") {
  2513  			Exitf("%s: uncompiled .go source file", pn)
  2514  			return nil
  2515  		}
  2516  
  2517  		if line == ctxt.Arch.Name {
  2518  			// old header format: just $GOOS
  2519  			Errorf("%s: stale object file", pn)
  2520  			return nil
  2521  		}
  2522  
  2523  		Errorf("%s: not an object file: @%d %q", pn, start, line)
  2524  		return nil
  2525  	}
  2526  
  2527  	// First, check that the basic GOOS, GOARCH, and Version match.
  2528  	if line != wantHdr && !*flagF {
  2529  		Errorf("%s: linked object header mismatch:\nhave %q\nwant %q\n", pn, line, wantHdr)
  2530  	}
  2531  
  2532  	// Skip over exports and other info -- ends with \n!\n.
  2533  	//
  2534  	// Note: It's possible for "\n!\n" to appear within the binary
  2535  	// package export data format. To avoid truncating the package
  2536  	// definition prematurely (issue 21703), we keep track of
  2537  	// how many "$$" delimiters we've seen.
  2538  
  2539  	import0 := f.Offset()
  2540  
  2541  	c1 = '\n' // the last line ended in \n
  2542  	c2 = bgetc(f)
  2543  	c3 = bgetc(f)
  2544  	markers := 0
  2545  	for {
  2546  		if c1 == '\n' {
  2547  			if markers%2 == 0 && c2 == '!' && c3 == '\n' {
  2548  				break
  2549  			}
  2550  			if c2 == '$' && c3 == '$' {
  2551  				markers++
  2552  			}
  2553  		}
  2554  
  2555  		c1 = c2
  2556  		c2 = c3
  2557  		c3 = bgetc(f)
  2558  		if c3 == -1 {
  2559  			Errorf("truncated object file: %s", pn)
  2560  			return nil
  2561  		}
  2562  	}
  2563  
  2564  	import1 := f.Offset()
  2565  
  2566  	f.MustSeek(import0, 0)
  2567  	ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
  2568  	f.MustSeek(import1, 0)
  2569  
  2570  	fingerprint := ctxt.loader.Preload(ctxt.IncVersion(), f, lib, unit, eof-f.Offset())
  2571  	if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
  2572  		// Check fingerprint, to ensure the importing and imported packages
  2573  		// have consistent view of symbol indices.
  2574  		// Normally the go command should ensure this. But in case something
  2575  		// goes wrong, it could lead to obscure bugs like run-time crash.
  2576  		// Check it here to be sure.
  2577  		if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
  2578  			lib.Fingerprint = fingerprint
  2579  		}
  2580  		checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
  2581  	}
  2582  
  2583  	addImports(ctxt, lib, pn)
  2584  	return nil
  2585  }
  2586  
  2587  // symbolsAreUnresolved scans through the loader's list of unresolved
  2588  // symbols and checks to see whether any of them match the names of the
  2589  // symbols in 'want'. Return value is a list of bools, with list[K] set
  2590  // to true if there is an unresolved reference to the symbol in want[K].
  2591  func symbolsAreUnresolved(ctxt *Link, want []string) []bool {
  2592  	returnAllUndefs := -1
  2593  	undefs, _ := ctxt.loader.UndefinedRelocTargets(returnAllUndefs)
  2594  	seen := make(map[loader.Sym]struct{})
  2595  	rval := make([]bool, len(want))
  2596  	wantm := make(map[string]int)
  2597  	for k, w := range want {
  2598  		wantm[w] = k
  2599  	}
  2600  	count := 0
  2601  	for _, s := range undefs {
  2602  		if _, ok := seen[s]; ok {
  2603  			continue
  2604  		}
  2605  		seen[s] = struct{}{}
  2606  		if k, ok := wantm[ctxt.loader.SymName(s)]; ok {
  2607  			rval[k] = true
  2608  			count++
  2609  			if count == len(want) {
  2610  				return rval
  2611  			}
  2612  		}
  2613  	}
  2614  	return rval
  2615  }
  2616  
  2617  // hostObject reads a single host object file (compare to "hostArchive").
  2618  // This is used as part of internal linking when we need to pull in
  2619  // files such as "crt?.o".
  2620  func hostObject(ctxt *Link, objname string, path string) {
  2621  	if ctxt.Debugvlog > 1 {
  2622  		ctxt.Logf("hostObject(%s)\n", path)
  2623  	}
  2624  	objlib := sym.Library{
  2625  		Pkg: objname,
  2626  	}
  2627  	f, err := bio.Open(path)
  2628  	if err != nil {
  2629  		Exitf("cannot open host object %q file %s: %v", objname, path, err)
  2630  	}
  2631  	defer f.Close()
  2632  	h := ldobj(ctxt, f, &objlib, 0, path, path)
  2633  	if h.ld == nil {
  2634  		Exitf("unrecognized object file format in %s", path)
  2635  	}
  2636  	h.file = path
  2637  	h.length = f.MustSeek(0, 2)
  2638  	f.MustSeek(h.off, 0)
  2639  	h.ld(ctxt, f, h.pkg, h.length, h.pn)
  2640  	if *flagCaptureHostObjs != "" {
  2641  		captureHostObj(h)
  2642  	}
  2643  }
  2644  
  2645  func checkFingerprint(lib *sym.Library, libfp goobj.FingerprintType, src string, srcfp goobj.FingerprintType) {
  2646  	if libfp != srcfp {
  2647  		Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
  2648  	}
  2649  }
  2650  
  2651  func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
  2652  	data := make([]byte, sym.Size)
  2653  	sect := f.Sections[sym.Section]
  2654  	if sect.Type != elf.SHT_PROGBITS && sect.Type != elf.SHT_NOTE {
  2655  		Errorf("reading %s from non-data section", sym.Name)
  2656  	}
  2657  	n, err := sect.ReadAt(data, int64(sym.Value-sect.Addr))
  2658  	if uint64(n) != sym.Size {
  2659  		Errorf("reading contents of %s: %v", sym.Name, err)
  2660  	}
  2661  	return data
  2662  }
  2663  
  2664  func readwithpad(r io.Reader, sz int32) ([]byte, error) {
  2665  	data := make([]byte, Rnd(int64(sz), 4))
  2666  	_, err := io.ReadFull(r, data)
  2667  	if err != nil {
  2668  		return nil, err
  2669  	}
  2670  	data = data[:sz]
  2671  	return data, nil
  2672  }
  2673  
  2674  func readnote(f *elf.File, name []byte, typ int32) ([]byte, error) {
  2675  	for _, sect := range f.Sections {
  2676  		if sect.Type != elf.SHT_NOTE {
  2677  			continue
  2678  		}
  2679  		r := sect.Open()
  2680  		for {
  2681  			var namesize, descsize, noteType int32
  2682  			err := binary.Read(r, f.ByteOrder, &namesize)
  2683  			if err != nil {
  2684  				if err == io.EOF {
  2685  					break
  2686  				}
  2687  				return nil, fmt.Errorf("read namesize failed: %v", err)
  2688  			}
  2689  			err = binary.Read(r, f.ByteOrder, &descsize)
  2690  			if err != nil {
  2691  				return nil, fmt.Errorf("read descsize failed: %v", err)
  2692  			}
  2693  			err = binary.Read(r, f.ByteOrder, &noteType)
  2694  			if err != nil {
  2695  				return nil, fmt.Errorf("read type failed: %v", err)
  2696  			}
  2697  			noteName, err := readwithpad(r, namesize)
  2698  			if err != nil {
  2699  				return nil, fmt.Errorf("read name failed: %v", err)
  2700  			}
  2701  			desc, err := readwithpad(r, descsize)
  2702  			if err != nil {
  2703  				return nil, fmt.Errorf("read desc failed: %v", err)
  2704  			}
  2705  			if string(name) == string(noteName) && typ == noteType {
  2706  				return desc, nil
  2707  			}
  2708  		}
  2709  	}
  2710  	return nil, nil
  2711  }
  2712  
  2713  func findshlib(ctxt *Link, shlib string) string {
  2714  	if filepath.IsAbs(shlib) {
  2715  		return shlib
  2716  	}
  2717  	for _, libdir := range ctxt.Libdir {
  2718  		libpath := filepath.Join(libdir, shlib)
  2719  		if _, err := os.Stat(libpath); err == nil {
  2720  			return libpath
  2721  		}
  2722  	}
  2723  	Errorf("cannot find shared library: %s", shlib)
  2724  	return ""
  2725  }
  2726  
  2727  func ldshlibsyms(ctxt *Link, shlib string) {
  2728  	var libpath string
  2729  	if filepath.IsAbs(shlib) {
  2730  		libpath = shlib
  2731  		shlib = filepath.Base(shlib)
  2732  	} else {
  2733  		libpath = findshlib(ctxt, shlib)
  2734  		if libpath == "" {
  2735  			return
  2736  		}
  2737  	}
  2738  	for _, processedlib := range ctxt.Shlibs {
  2739  		if processedlib.Path == libpath {
  2740  			return
  2741  		}
  2742  	}
  2743  	if ctxt.Debugvlog > 1 {
  2744  		ctxt.Logf("ldshlibsyms: found library with name %s at %s\n", shlib, libpath)
  2745  	}
  2746  
  2747  	f, err := elf.Open(libpath)
  2748  	if err != nil {
  2749  		Errorf("cannot open shared library: %s", libpath)
  2750  		return
  2751  	}
  2752  	// Keep the file open as decodetypeGcprog needs to read from it.
  2753  	// TODO: fix. Maybe mmap the file.
  2754  	//defer f.Close()
  2755  
  2756  	hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
  2757  	if err != nil {
  2758  		Errorf("cannot read ABI hash from shared library %s: %v", libpath, err)
  2759  		return
  2760  	}
  2761  
  2762  	depsbytes, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GODEPS_TAG)
  2763  	if err != nil {
  2764  		Errorf("cannot read dep list from shared library %s: %v", libpath, err)
  2765  		return
  2766  	}
  2767  	var deps []string
  2768  	for _, dep := range strings.Split(string(depsbytes), "\n") {
  2769  		if dep == "" {
  2770  			continue
  2771  		}
  2772  		if !filepath.IsAbs(dep) {
  2773  			// If the dep can be interpreted as a path relative to the shlib
  2774  			// in which it was found, do that. Otherwise, we will leave it
  2775  			// to be resolved by libdir lookup.
  2776  			abs := filepath.Join(filepath.Dir(libpath), dep)
  2777  			if _, err := os.Stat(abs); err == nil {
  2778  				dep = abs
  2779  			}
  2780  		}
  2781  		deps = append(deps, dep)
  2782  	}
  2783  
  2784  	syms, err := f.DynamicSymbols()
  2785  	if err != nil {
  2786  		Errorf("cannot read symbols from shared library: %s", libpath)
  2787  		return
  2788  	}
  2789  
  2790  	symAddr := map[string]uint64{}
  2791  	for _, elfsym := range syms {
  2792  		if elf.ST_TYPE(elfsym.Info) == elf.STT_NOTYPE || elf.ST_TYPE(elfsym.Info) == elf.STT_SECTION {
  2793  			continue
  2794  		}
  2795  
  2796  		// Symbols whose names start with "type:" are compiler generated,
  2797  		// so make functions with that prefix internal.
  2798  		ver := 0
  2799  		symname := elfsym.Name // (unmangled) symbol name
  2800  		if elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC && strings.HasPrefix(elfsym.Name, "type:") {
  2801  			ver = abiInternalVer
  2802  		} else if buildcfg.Experiment.RegabiWrappers && elf.ST_TYPE(elfsym.Info) == elf.STT_FUNC {
  2803  			// Demangle the ABI name. Keep in sync with symtab.go:mangleABIName.
  2804  			if strings.HasSuffix(elfsym.Name, ".abiinternal") {
  2805  				ver = sym.SymVerABIInternal
  2806  				symname = strings.TrimSuffix(elfsym.Name, ".abiinternal")
  2807  			} else if strings.HasSuffix(elfsym.Name, ".abi0") {
  2808  				ver = 0
  2809  				symname = strings.TrimSuffix(elfsym.Name, ".abi0")
  2810  			}
  2811  		}
  2812  
  2813  		l := ctxt.loader
  2814  		s := l.LookupOrCreateSym(symname, ver)
  2815  
  2816  		// Because loadlib above loads all .a files before loading
  2817  		// any shared libraries, any non-dynimport symbols we find
  2818  		// that duplicate symbols already loaded should be ignored
  2819  		// (the symbols from the .a files "win").
  2820  		if l.SymType(s) != 0 && l.SymType(s) != sym.SDYNIMPORT {
  2821  			continue
  2822  		}
  2823  		su := l.MakeSymbolUpdater(s)
  2824  		su.SetType(sym.SDYNIMPORT)
  2825  		l.SetSymElfType(s, elf.ST_TYPE(elfsym.Info))
  2826  		su.SetSize(int64(elfsym.Size))
  2827  		if elfsym.Section != elf.SHN_UNDEF {
  2828  			// Set .File for the library that actually defines the symbol.
  2829  			l.SetSymPkg(s, libpath)
  2830  
  2831  			// The decodetype_* functions in decodetype.go need access to
  2832  			// the type data.
  2833  			sname := l.SymName(s)
  2834  			if strings.HasPrefix(sname, "type:") && !strings.HasPrefix(sname, "type:.") {
  2835  				su.SetData(readelfsymboldata(ctxt, f, &elfsym))
  2836  			}
  2837  		}
  2838  
  2839  		if symname != elfsym.Name {
  2840  			l.SetSymExtname(s, elfsym.Name)
  2841  		}
  2842  		symAddr[elfsym.Name] = elfsym.Value
  2843  	}
  2844  
  2845  	// Load relocations.
  2846  	// We only really need these for grokking the links between type descriptors
  2847  	// when dynamic linking.
  2848  	relocTarget := map[uint64]string{}
  2849  	addends := false
  2850  	sect := f.SectionByType(elf.SHT_REL)
  2851  	if sect == nil {
  2852  		sect = f.SectionByType(elf.SHT_RELA)
  2853  		if sect == nil {
  2854  			log.Fatalf("can't find SHT_REL or SHT_RELA section of %s", shlib)
  2855  		}
  2856  		addends = true
  2857  	}
  2858  	// TODO: Multiple SHT_RELA/SHT_REL sections?
  2859  	data, err := sect.Data()
  2860  	if err != nil {
  2861  		log.Fatalf("can't read relocation section of %s: %v", shlib, err)
  2862  	}
  2863  	bo := f.ByteOrder
  2864  	for len(data) > 0 {
  2865  		var off, idx uint64
  2866  		var addend int64
  2867  		switch f.Class {
  2868  		case elf.ELFCLASS64:
  2869  			off = bo.Uint64(data)
  2870  			info := bo.Uint64(data[8:])
  2871  			data = data[16:]
  2872  			if addends {
  2873  				addend = int64(bo.Uint64(data))
  2874  				data = data[8:]
  2875  			}
  2876  
  2877  			idx = info >> 32
  2878  			typ := info & 0xffff
  2879  			// buildmode=shared is only supported for amd64,arm64,loong64,s390x,ppc64le.
  2880  			// (List found by looking at the translation of R_ADDR by ../$ARCH/asm.go:elfreloc1)
  2881  			switch typ {
  2882  			case uint64(elf.R_X86_64_64):
  2883  			case uint64(elf.R_AARCH64_ABS64):
  2884  			case uint64(elf.R_LARCH_64):
  2885  			case uint64(elf.R_390_64):
  2886  			case uint64(elf.R_PPC64_ADDR64):
  2887  			default:
  2888  				continue
  2889  			}
  2890  		case elf.ELFCLASS32:
  2891  			off = uint64(bo.Uint32(data))
  2892  			info := bo.Uint32(data[4:])
  2893  			data = data[8:]
  2894  			if addends {
  2895  				addend = int64(int32(bo.Uint32(data)))
  2896  				data = data[4:]
  2897  			}
  2898  
  2899  			idx = uint64(info >> 8)
  2900  			typ := info & 0xff
  2901  			// buildmode=shared is only supported for 386,arm.
  2902  			switch typ {
  2903  			case uint32(elf.R_386_32):
  2904  			case uint32(elf.R_ARM_ABS32):
  2905  			default:
  2906  				continue
  2907  			}
  2908  		default:
  2909  			log.Fatalf("unknown bit size %s", f.Class)
  2910  		}
  2911  		if addend != 0 {
  2912  			continue
  2913  		}
  2914  		relocTarget[off] = syms[idx-1].Name
  2915  	}
  2916  
  2917  	ctxt.Shlibs = append(ctxt.Shlibs, Shlib{Path: libpath, Hash: hash, Deps: deps, File: f, symAddr: symAddr, relocTarget: relocTarget})
  2918  }
  2919  
  2920  func addsection(ldr *loader.Loader, arch *sys.Arch, seg *sym.Segment, name string, rwx int) *sym.Section {
  2921  	sect := ldr.NewSection()
  2922  	sect.Rwx = uint8(rwx)
  2923  	sect.Name = name
  2924  	sect.Seg = seg
  2925  	sect.Align = int32(arch.PtrSize) // everything is at least pointer-aligned
  2926  	seg.Sections = append(seg.Sections, sect)
  2927  	return sect
  2928  }
  2929  
  2930  func usage() {
  2931  	fmt.Fprintf(os.Stderr, "usage: link [options] main.o\n")
  2932  	objabi.Flagprint(os.Stderr)
  2933  	Exit(2)
  2934  }
  2935  
  2936  type SymbolType int8 // TODO: after genasmsym is gone, maybe rename to plan9typeChar or something
  2937  
  2938  const (
  2939  	// see also https://9p.io/magic/man2html/1/nm
  2940  	TextSym      SymbolType = 'T'
  2941  	DataSym      SymbolType = 'D'
  2942  	BSSSym       SymbolType = 'B'
  2943  	UndefinedSym SymbolType = 'U'
  2944  	TLSSym       SymbolType = 't'
  2945  	FrameSym     SymbolType = 'm'
  2946  	ParamSym     SymbolType = 'p'
  2947  	AutoSym      SymbolType = 'a'
  2948  
  2949  	// Deleted auto (not a real sym, just placeholder for type)
  2950  	DeletedAutoSym = 'x'
  2951  )
  2952  
  2953  // defineInternal defines a symbol used internally by the go runtime.
  2954  func (ctxt *Link) defineInternal(p string, t sym.SymKind) loader.Sym {
  2955  	s := ctxt.loader.CreateSymForUpdate(p, 0)
  2956  	s.SetType(t)
  2957  	s.SetSpecial(true)
  2958  	s.SetLocal(true)
  2959  	return s.Sym()
  2960  }
  2961  
  2962  func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) loader.Sym {
  2963  	s := ctxt.defineInternal(p, t)
  2964  	ctxt.loader.SetSymValue(s, v)
  2965  	return s
  2966  }
  2967  
  2968  func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
  2969  	if uint64(addr) >= Segdata.Vaddr {
  2970  		return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
  2971  	}
  2972  	if uint64(addr) >= Segtext.Vaddr {
  2973  		return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
  2974  	}
  2975  	ldr.Errorf(s, "invalid datoff %#x", addr)
  2976  	return 0
  2977  }
  2978  
  2979  func Entryvalue(ctxt *Link) int64 {
  2980  	a := *flagEntrySymbol
  2981  	if a[0] >= '0' && a[0] <= '9' {
  2982  		return atolwhex(a)
  2983  	}
  2984  	ldr := ctxt.loader
  2985  	s := ldr.Lookup(a, 0)
  2986  	if s == 0 {
  2987  		Errorf("missing entry symbol %q", a)
  2988  		return 0
  2989  	}
  2990  	st := ldr.SymType(s)
  2991  	if st == 0 {
  2992  		return *FlagTextAddr
  2993  	}
  2994  	if !ctxt.IsAIX() && !st.IsText() {
  2995  		ldr.Errorf(s, "entry not text")
  2996  	}
  2997  	return ldr.SymValue(s)
  2998  }
  2999  
  3000  func (ctxt *Link) callgraph() {
  3001  	if !*FlagC {
  3002  		return
  3003  	}
  3004  
  3005  	ldr := ctxt.loader
  3006  	for _, s := range ctxt.Textp {
  3007  		relocs := ldr.Relocs(s)
  3008  		for i := 0; i < relocs.Count(); i++ {
  3009  			r := relocs.At(i)
  3010  			rs := r.Sym()
  3011  			if rs == 0 {
  3012  				continue
  3013  			}
  3014  			if r.Type().IsDirectCall() && ldr.SymType(rs).IsText() {
  3015  				ctxt.Logf("%s calls %s\n", ldr.SymName(s), ldr.SymName(rs))
  3016  			}
  3017  		}
  3018  	}
  3019  }
  3020  
  3021  func Rnd(v int64, r int64) int64 {
  3022  	if r <= 0 {
  3023  		return v
  3024  	}
  3025  	v += r - 1
  3026  	c := v % r
  3027  	if c < 0 {
  3028  		c += r
  3029  	}
  3030  	v -= c
  3031  	return v
  3032  }
  3033  
  3034  func bgetc(r *bio.Reader) int {
  3035  	c, err := r.ReadByte()
  3036  	if err != nil {
  3037  		if err != io.EOF {
  3038  			log.Fatalf("reading input: %v", err)
  3039  		}
  3040  		return -1
  3041  	}
  3042  	return int(c)
  3043  }
  3044  
  3045  type markKind uint8 // for postorder traversal
  3046  const (
  3047  	_ markKind = iota
  3048  	visiting
  3049  	visited
  3050  )
  3051  
  3052  func postorder(libs []*sym.Library) []*sym.Library {
  3053  	order := make([]*sym.Library, 0, len(libs)) // hold the result
  3054  	mark := make(map[*sym.Library]markKind, len(libs))
  3055  	for _, lib := range libs {
  3056  		dfs(lib, mark, &order)
  3057  	}
  3058  	return order
  3059  }
  3060  
  3061  func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library) {
  3062  	if mark[lib] == visited {
  3063  		return
  3064  	}
  3065  	if mark[lib] == visiting {
  3066  		panic("found import cycle while visiting " + lib.Pkg)
  3067  	}
  3068  	mark[lib] = visiting
  3069  	for _, i := range lib.Imports {
  3070  		dfs(i, mark, order)
  3071  	}
  3072  	mark[lib] = visited
  3073  	*order = append(*order, lib)
  3074  }
  3075  
  3076  func ElfSymForReloc(ctxt *Link, s loader.Sym) int32 {
  3077  	// If putelfsym created a local version of this symbol, use that in all
  3078  	// relocations.
  3079  	les := ctxt.loader.SymLocalElfSym(s)
  3080  	if les != 0 {
  3081  		return les
  3082  	} else {
  3083  		return ctxt.loader.SymElfSym(s)
  3084  	}
  3085  }
  3086  
  3087  func AddGotSym(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, elfRelocTyp uint32) {
  3088  	if ldr.SymGot(s) >= 0 {
  3089  		return
  3090  	}
  3091  
  3092  	Adddynsym(ldr, target, syms, s)
  3093  	got := ldr.MakeSymbolUpdater(syms.GOT)
  3094  	ldr.SetGot(s, int32(got.Size()))
  3095  	got.AddUint(target.Arch, 0)
  3096  
  3097  	if target.IsElf() {
  3098  		if target.Arch.PtrSize == 8 {
  3099  			rela := ldr.MakeSymbolUpdater(syms.Rela)
  3100  			rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
  3101  			rela.AddUint64(target.Arch, elf.R_INFO(uint32(ldr.SymDynid(s)), elfRelocTyp))
  3102  			rela.AddUint64(target.Arch, 0)
  3103  		} else {
  3104  			rel := ldr.MakeSymbolUpdater(syms.Rel)
  3105  			rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
  3106  			rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), elfRelocTyp))
  3107  		}
  3108  	} else if target.IsDarwin() {
  3109  		leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT)
  3110  		leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
  3111  		if target.IsPIE() && target.IsInternal() {
  3112  			// Mach-O relocations are a royal pain to lay out.
  3113  			// They use a compact stateful bytecode representation.
  3114  			// Here we record what are needed and encode them later.
  3115  			MachoAddBind(syms.GOT, int64(ldr.SymGot(s)), s)
  3116  		}
  3117  	} else {
  3118  		ldr.Errorf(s, "addgotsym: unsupported binary format")
  3119  	}
  3120  }
  3121  
  3122  var hostobjcounter int
  3123  
  3124  // captureHostObj writes out the content of a host object (pulled from
  3125  // an archive or loaded from a *.o file directly) to a directory
  3126  // specified via the linker's "-capturehostobjs" debugging flag. This
  3127  // is intended to make it easier for a developer to inspect the actual
  3128  // object feeding into "CGO internal" link step.
  3129  func captureHostObj(h *Hostobj) {
  3130  	// Form paths for info file and obj file.
  3131  	ofile := fmt.Sprintf("captured-obj-%d.o", hostobjcounter)
  3132  	ifile := fmt.Sprintf("captured-obj-%d.txt", hostobjcounter)
  3133  	hostobjcounter++
  3134  	opath := filepath.Join(*flagCaptureHostObjs, ofile)
  3135  	ipath := filepath.Join(*flagCaptureHostObjs, ifile)
  3136  
  3137  	// Write the info file.
  3138  	info := fmt.Sprintf("pkg: %s\npn: %s\nfile: %s\noff: %d\nlen: %d\n",
  3139  		h.pkg, h.pn, h.file, h.off, h.length)
  3140  	if err := os.WriteFile(ipath, []byte(info), 0666); err != nil {
  3141  		log.Fatalf("error writing captured host obj info %s: %v", ipath, err)
  3142  	}
  3143  
  3144  	readObjData := func() []byte {
  3145  		inf, err := os.Open(h.file)
  3146  		if err != nil {
  3147  			log.Fatalf("capturing host obj: open failed on %s: %v", h.pn, err)
  3148  		}
  3149  		defer inf.Close()
  3150  		res := make([]byte, h.length)
  3151  		if n, err := inf.ReadAt(res, h.off); err != nil || n != int(h.length) {
  3152  			log.Fatalf("capturing host obj: readat failed on %s: %v", h.pn, err)
  3153  		}
  3154  		return res
  3155  	}
  3156  
  3157  	// Write the object file.
  3158  	if err := os.WriteFile(opath, readObjData(), 0666); err != nil {
  3159  		log.Fatalf("error writing captured host object %s: %v", opath, err)
  3160  	}
  3161  
  3162  	fmt.Fprintf(os.Stderr, "link: info: captured host object %s to %s\n",
  3163  		h.file, opath)
  3164  }
  3165  
  3166  // findExtLinkTool invokes the external linker CC with --print-prog-name
  3167  // passing the name of the tool we're interested in, such as "strip",
  3168  // "ar", or "dsymutil", and returns the path passed back from the command.
  3169  func (ctxt *Link) findExtLinkTool(toolname string) string {
  3170  	var cc []string
  3171  	cc = append(cc, ctxt.extld()...)
  3172  	cc = append(cc, hostlinkArchArgs(ctxt.Arch)...)
  3173  	cc = append(cc, "--print-prog-name", toolname)
  3174  	out, err := exec.Command(cc[0], cc[1:]...).CombinedOutput()
  3175  	if err != nil {
  3176  		Exitf("%s: finding %s failed: %v\n%s", os.Args[0], toolname, err, out)
  3177  	}
  3178  	cmdpath := strings.TrimRight(string(out), "\r\n")
  3179  	return cmdpath
  3180  }
  3181  
  3182  // isMSVC reports whether the C toolchain is clang with a -msvc target,
  3183  // e.g. the clang bundled in MSVC.
  3184  func (ctxt *Link) isMSVC() bool {
  3185  	extld := ctxt.extld()
  3186  	name, args := extld[0], extld[1:]
  3187  	args = append(args, trimLinkerArgv(flagExtldflags)...)
  3188  	args = append(args, "--version")
  3189  	cmd := exec.Command(name, args...)
  3190  	if out, err := cmd.CombinedOutput(); err == nil {
  3191  		if bytes.Contains(out, []byte("-msvc\n")) || bytes.Contains(out, []byte("-msvc\r")) {
  3192  			return true
  3193  		}
  3194  	}
  3195  	return false
  3196  }
  3197  
  3198  // isLLD reports whether the C toolchain is using LLD as the linker.
  3199  func (ctxt *Link) isLLD() bool {
  3200  	extld := ctxt.extld()
  3201  	name, args := extld[0], extld[1:]
  3202  	args = append(args, trimLinkerArgv(flagExtldflags)...)
  3203  	args = append(args, "-Wl,--version")
  3204  	cmd := exec.Command(name, args...)
  3205  	if out, err := cmd.CombinedOutput(); err == nil {
  3206  		if bytes.Contains(out, []byte("LLD ")) {
  3207  			return true
  3208  		}
  3209  	}
  3210  	return false
  3211  }
  3212  

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