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

Documentation: cmd/link/internal/ld

     1  // Inferno utils/6l/obj.c
     2  // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6l/obj.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  	"bufio"
    35  	"cmd/internal/goobj"
    36  	"cmd/internal/objabi"
    37  	"cmd/internal/quoted"
    38  	"cmd/internal/sys"
    39  	"cmd/internal/telemetry/counter"
    40  	"cmd/link/internal/benchmark"
    41  	"flag"
    42  	"internal/buildcfg"
    43  	"log"
    44  	"os"
    45  	"runtime"
    46  	"runtime/pprof"
    47  	"strconv"
    48  	"strings"
    49  )
    50  
    51  var (
    52  	pkglistfornote []byte
    53  	windowsgui     bool // writes a "GUI binary" instead of a "console binary"
    54  	ownTmpDir      bool // set to true if tmp dir created by linker (e.g. no -tmpdir)
    55  )
    56  
    57  func init() {
    58  	flag.Var(&rpath, "r", "set the ELF dynamic linker search `path` to dir1:dir2:...")
    59  	flag.Var(&flagExtld, "extld", "use `linker` when linking in external mode")
    60  	flag.Var(&flagExtldflags, "extldflags", "pass `flags` to external linker")
    61  	flag.Var(&flagW, "w", "disable DWARF generation")
    62  }
    63  
    64  // Flags used by the linker. The exported flags are used by the architecture-specific packages.
    65  var (
    66  	flagBuildid = flag.String("buildid", "", "record `id` as Go toolchain build id")
    67  	flagBindNow = flag.Bool("bindnow", false, "mark a dynamically linked ELF object for immediate function binding")
    68  
    69  	flagOutfile    = flag.String("o", "", "write output to `file`")
    70  	flagPluginPath = flag.String("pluginpath", "", "full path name for plugin")
    71  
    72  	flagInstallSuffix = flag.String("installsuffix", "", "set package directory `suffix`")
    73  	flagDumpDep       = flag.Bool("dumpdep", false, "dump symbol dependency graph")
    74  	flagRace          = flag.Bool("race", false, "enable race detector")
    75  	flagMsan          = flag.Bool("msan", false, "enable MSan interface")
    76  	flagAsan          = flag.Bool("asan", false, "enable ASan interface")
    77  	flagAslr          = flag.Bool("aslr", true, "enable ASLR for buildmode=c-shared on windows")
    78  
    79  	flagFieldTrack = flag.String("k", "", "set field tracking `symbol`")
    80  	flagLibGCC     = flag.String("libgcc", "", "compiler support lib for internal linking; use \"none\" to disable")
    81  	flagTmpdir     = flag.String("tmpdir", "", "use `directory` for temporary files")
    82  
    83  	flagExtld      quoted.Flag
    84  	flagExtldflags quoted.Flag
    85  	flagExtar      = flag.String("extar", "", "archive program for buildmode=c-archive")
    86  
    87  	flagCaptureHostObjs = flag.String("capturehostobjs", "", "capture host object files loaded during internal linking to specified dir")
    88  
    89  	flagA             = flag.Bool("a", false, "no-op (deprecated)")
    90  	FlagC             = flag.Bool("c", false, "dump call graph")
    91  	FlagD             = flag.Bool("d", false, "disable dynamic executable")
    92  	flagF             = flag.Bool("f", false, "ignore version mismatch")
    93  	flagG             = flag.Bool("g", false, "disable go package data checks")
    94  	flagH             = flag.Bool("h", false, "halt on error")
    95  	flagN             = flag.Bool("n", false, "no-op (deprecated)")
    96  	FlagS             = flag.Bool("s", false, "disable symbol table")
    97  	flag8             bool // use 64-bit addresses in symbol table
    98  	flagHostBuildid   = flag.String("B", "", "set ELF NT_GNU_BUILD_ID `note` or Mach-O UUID; use \"gobuildid\" to generate it from the Go build ID")
    99  	flagInterpreter   = flag.String("I", "", "use `linker` as ELF dynamic linker")
   100  	flagCheckLinkname = flag.Bool("checklinkname", true, "check linkname symbol references")
   101  	FlagDebugTramp    = flag.Int("debugtramp", 0, "debug trampolines")
   102  	FlagDebugTextSize = flag.Int("debugtextsize", 0, "debug text section max size")
   103  	flagDebugNosplit  = flag.Bool("debugnosplit", false, "dump nosplit call graph")
   104  	FlagStrictDups    = flag.Int("strictdups", 0, "sanity check duplicate symbol contents during object file reading (1=warn 2=err).")
   105  	FlagRound         = flag.Int64("R", -1, "set address rounding `quantum`")
   106  	FlagTextAddr      = flag.Int64("T", -1, "set the start address of text symbols")
   107  	flagEntrySymbol   = flag.String("E", "", "set `entry` symbol name")
   108  	flagPruneWeakMap  = flag.Bool("pruneweakmap", true, "prune weak mapinit refs")
   109  	flagRandLayout    = flag.Int64("randlayout", 0, "randomize function layout")
   110  	cpuprofile        = flag.String("cpuprofile", "", "write cpu profile to `file`")
   111  	memprofile        = flag.String("memprofile", "", "write memory profile to `file`")
   112  	memprofilerate    = flag.Int64("memprofilerate", 0, "set runtime.MemProfileRate to `rate`")
   113  	benchmarkFlag     = flag.String("benchmark", "", "set to 'mem' or 'cpu' to enable phase benchmarking")
   114  	benchmarkFileFlag = flag.String("benchmarkprofile", "", "emit phase profiles to `base`_phase.{cpu,mem}prof")
   115  
   116  	flagW ternaryFlag
   117  	FlagW = new(bool) // the -w flag, computed in main from flagW
   118  )
   119  
   120  // ternaryFlag is like a boolean flag, but has a default value that is
   121  // neither true nor false, allowing it to be set from context (e.g. from another
   122  // flag).
   123  // *ternaryFlag implements flag.Value.
   124  type ternaryFlag int
   125  
   126  const (
   127  	ternaryFlagUnset ternaryFlag = iota
   128  	ternaryFlagFalse
   129  	ternaryFlagTrue
   130  )
   131  
   132  func (t *ternaryFlag) Set(s string) error {
   133  	v, err := strconv.ParseBool(s)
   134  	if err != nil {
   135  		return err
   136  	}
   137  	if v {
   138  		*t = ternaryFlagTrue
   139  	} else {
   140  		*t = ternaryFlagFalse
   141  	}
   142  	return nil
   143  }
   144  
   145  func (t *ternaryFlag) String() string {
   146  	switch *t {
   147  	case ternaryFlagFalse:
   148  		return "false"
   149  	case ternaryFlagTrue:
   150  		return "true"
   151  	}
   152  	return "unset"
   153  }
   154  
   155  func (t *ternaryFlag) IsBoolFlag() bool { return true } // parse like a boolean flag
   156  
   157  // Main is the main entry point for the linker code.
   158  func Main(arch *sys.Arch, theArch Arch) {
   159  	log.SetPrefix("link: ")
   160  	log.SetFlags(0)
   161  	counter.Open()
   162  	counter.Inc("link/invocations")
   163  
   164  	thearch = theArch
   165  	ctxt := linknew(arch)
   166  	ctxt.Bso = bufio.NewWriter(os.Stdout)
   167  
   168  	// For testing behavior of go command when tools crash silently.
   169  	// Undocumented, not in standard flag parser to avoid
   170  	// exposing in usage message.
   171  	for _, arg := range os.Args {
   172  		if arg == "-crash_for_testing" {
   173  			os.Exit(2)
   174  		}
   175  	}
   176  
   177  	if buildcfg.GOROOT == "" {
   178  		// cmd/go clears the GOROOT variable when -trimpath is set,
   179  		// so omit it from the binary even if cmd/link itself has an
   180  		// embedded GOROOT value reported by runtime.GOROOT.
   181  	} else {
   182  		addstrdata1(ctxt, "runtime.defaultGOROOT="+buildcfg.GOROOT)
   183  	}
   184  
   185  	buildVersion := buildcfg.Version
   186  	if goexperiment := buildcfg.Experiment.String(); goexperiment != "" {
   187  		buildVersion += " X:" + goexperiment
   188  	}
   189  	addstrdata1(ctxt, "runtime.buildVersion="+buildVersion)
   190  
   191  	// TODO(matloob): define these above and then check flag values here
   192  	if ctxt.Arch.Family == sys.AMD64 && buildcfg.GOOS == "plan9" {
   193  		flag.BoolVar(&flag8, "8", false, "use 64-bit addresses in symbol table")
   194  	}
   195  	flagHeadType := flag.String("H", "", "set header `type`")
   196  	flag.BoolVar(&ctxt.linkShared, "linkshared", false, "link against installed Go shared libraries")
   197  	flag.Var(&ctxt.LinkMode, "linkmode", "set link `mode`")
   198  	flag.Var(&ctxt.BuildMode, "buildmode", "set build `mode`")
   199  	flag.BoolVar(&ctxt.compressDWARF, "compressdwarf", true, "compress DWARF if possible")
   200  	objabi.Flagfn1("L", "add specified `directory` to library path", func(a string) { Lflag(ctxt, a) })
   201  	objabi.AddVersionFlag() // -V
   202  	objabi.Flagfn1("X", "add string value `definition` of the form importpath.name=value", func(s string) { addstrdata1(ctxt, s) })
   203  	objabi.Flagcount("v", "print link trace", &ctxt.Debugvlog)
   204  	objabi.Flagfn1("importcfg", "read import configuration from `file`", ctxt.readImportCfg)
   205  
   206  	objabi.Flagparse(usage)
   207  	counter.CountFlags("link/flag:", *flag.CommandLine)
   208  
   209  	if ctxt.Debugvlog > 0 {
   210  		// dump symbol info on crash
   211  		defer func() { ctxt.loader.Dump() }()
   212  	}
   213  	if ctxt.Debugvlog > 1 {
   214  		// dump symbol info on error
   215  		AtExit(func() {
   216  			if nerrors > 0 {
   217  				ctxt.loader.Dump()
   218  			}
   219  		})
   220  	}
   221  
   222  	switch *flagHeadType {
   223  	case "":
   224  	case "windowsgui":
   225  		ctxt.HeadType = objabi.Hwindows
   226  		windowsgui = true
   227  	default:
   228  		if err := ctxt.HeadType.Set(*flagHeadType); err != nil {
   229  			Errorf(nil, "%v", err)
   230  			usage()
   231  		}
   232  	}
   233  	if ctxt.HeadType == objabi.Hunknown {
   234  		ctxt.HeadType.Set(buildcfg.GOOS)
   235  	}
   236  
   237  	if !*flagAslr && ctxt.BuildMode != BuildModeCShared {
   238  		Errorf(nil, "-aslr=false is only allowed for -buildmode=c-shared")
   239  		usage()
   240  	}
   241  
   242  	if *FlagD && ctxt.UsesLibc() {
   243  		Exitf("dynamic linking required on %s; -d flag cannot be used", buildcfg.GOOS)
   244  	}
   245  
   246  	isPowerOfTwo := func(n int64) bool {
   247  		return n > 0 && n&(n-1) == 0
   248  	}
   249  	if *FlagRound != -1 && (*FlagRound < 4096 || !isPowerOfTwo(*FlagRound)) {
   250  		Exitf("invalid -R value 0x%x", *FlagRound)
   251  	}
   252  
   253  	checkStrictDups = *FlagStrictDups
   254  
   255  	switch flagW {
   256  	case ternaryFlagFalse:
   257  		*FlagW = false
   258  	case ternaryFlagTrue:
   259  		*FlagW = true
   260  	case ternaryFlagUnset:
   261  		*FlagW = *FlagS // -s implies -w if not explicitly set
   262  		if ctxt.IsDarwin() && ctxt.BuildMode == BuildModeCShared {
   263  			*FlagW = true // default to -w in c-shared mode on darwin, see #61229
   264  		}
   265  	}
   266  
   267  	if !buildcfg.Experiment.RegabiWrappers {
   268  		abiInternalVer = 0
   269  	}
   270  
   271  	startProfile()
   272  	if ctxt.BuildMode == BuildModeUnset {
   273  		ctxt.BuildMode.Set("exe")
   274  	}
   275  
   276  	if ctxt.BuildMode != BuildModeShared && flag.NArg() != 1 {
   277  		usage()
   278  	}
   279  
   280  	if *flagOutfile == "" {
   281  		*flagOutfile = "a.out"
   282  		if ctxt.HeadType == objabi.Hwindows {
   283  			*flagOutfile += ".exe"
   284  		}
   285  	}
   286  
   287  	interpreter = *flagInterpreter
   288  
   289  	if *flagBuildid == "" && ctxt.Target.IsOpenbsd() {
   290  		// TODO(jsing): Remove once direct syscalls are no longer in use.
   291  		// OpenBSD 6.7 onwards will not permit direct syscalls from a
   292  		// dynamically linked binary unless it identifies the binary
   293  		// contains a .note.go.buildid ELF note. See issue #36435.
   294  		*flagBuildid = "go-openbsd"
   295  	}
   296  
   297  	if *flagHostBuildid != "" {
   298  		addbuildinfo(ctxt)
   299  	}
   300  
   301  	// enable benchmarking
   302  	var bench *benchmark.Metrics
   303  	if len(*benchmarkFlag) != 0 {
   304  		if *benchmarkFlag == "mem" {
   305  			bench = benchmark.New(benchmark.GC, *benchmarkFileFlag)
   306  		} else if *benchmarkFlag == "cpu" {
   307  			bench = benchmark.New(benchmark.NoGC, *benchmarkFileFlag)
   308  		} else {
   309  			Errorf(nil, "unknown benchmark flag: %q", *benchmarkFlag)
   310  			usage()
   311  		}
   312  	}
   313  
   314  	bench.Start("libinit")
   315  	libinit(ctxt) // creates outfile
   316  	bench.Start("computeTLSOffset")
   317  	ctxt.computeTLSOffset()
   318  	bench.Start("Archinit")
   319  	thearch.Archinit(ctxt)
   320  
   321  	if ctxt.linkShared && !ctxt.IsELF {
   322  		Exitf("-linkshared can only be used on elf systems")
   323  	}
   324  
   325  	if ctxt.Debugvlog != 0 {
   326  		onOff := func(b bool) string {
   327  			if b {
   328  				return "on"
   329  			}
   330  			return "off"
   331  		}
   332  		ctxt.Logf("build mode: %s, symbol table: %s, DWARF: %s\n", ctxt.BuildMode, onOff(!*FlagS), onOff(dwarfEnabled(ctxt)))
   333  		ctxt.Logf("HEADER = -H%d -T0x%x -R0x%x\n", ctxt.HeadType, uint64(*FlagTextAddr), uint32(*FlagRound))
   334  	}
   335  
   336  	zerofp := goobj.FingerprintType{}
   337  	switch ctxt.BuildMode {
   338  	case BuildModeShared:
   339  		for i := 0; i < flag.NArg(); i++ {
   340  			arg := flag.Arg(i)
   341  			parts := strings.SplitN(arg, "=", 2)
   342  			var pkgpath, file string
   343  			if len(parts) == 1 {
   344  				pkgpath, file = "main", arg
   345  			} else {
   346  				pkgpath, file = parts[0], parts[1]
   347  			}
   348  			pkglistfornote = append(pkglistfornote, pkgpath...)
   349  			pkglistfornote = append(pkglistfornote, '\n')
   350  			addlibpath(ctxt, "command line", "command line", file, pkgpath, "", zerofp)
   351  		}
   352  	case BuildModePlugin:
   353  		addlibpath(ctxt, "command line", "command line", flag.Arg(0), *flagPluginPath, "", zerofp)
   354  	default:
   355  		addlibpath(ctxt, "command line", "command line", flag.Arg(0), "main", "", zerofp)
   356  	}
   357  	bench.Start("loadlib")
   358  	ctxt.loadlib()
   359  
   360  	bench.Start("inittasks")
   361  	ctxt.inittasks()
   362  
   363  	bench.Start("deadcode")
   364  	deadcode(ctxt)
   365  
   366  	bench.Start("linksetup")
   367  	ctxt.linksetup()
   368  
   369  	bench.Start("dostrdata")
   370  	ctxt.dostrdata()
   371  	if buildcfg.Experiment.FieldTrack {
   372  		bench.Start("fieldtrack")
   373  		fieldtrack(ctxt.Arch, ctxt.loader)
   374  	}
   375  
   376  	bench.Start("dwarfGenerateDebugInfo")
   377  	dwarfGenerateDebugInfo(ctxt)
   378  
   379  	bench.Start("callgraph")
   380  	ctxt.callgraph()
   381  
   382  	bench.Start("doStackCheck")
   383  	ctxt.doStackCheck()
   384  
   385  	bench.Start("mangleTypeSym")
   386  	ctxt.mangleTypeSym()
   387  
   388  	if ctxt.IsELF {
   389  		bench.Start("doelf")
   390  		ctxt.doelf()
   391  	}
   392  	if ctxt.IsDarwin() {
   393  		bench.Start("domacho")
   394  		ctxt.domacho()
   395  	}
   396  	if ctxt.IsWindows() {
   397  		bench.Start("dope")
   398  		ctxt.dope()
   399  		bench.Start("windynrelocsyms")
   400  		ctxt.windynrelocsyms()
   401  	}
   402  	if ctxt.IsAIX() {
   403  		bench.Start("doxcoff")
   404  		ctxt.doxcoff()
   405  	}
   406  
   407  	bench.Start("textbuildid")
   408  	ctxt.textbuildid()
   409  	bench.Start("addexport")
   410  	ctxt.setArchSyms()
   411  	ctxt.addexport()
   412  	bench.Start("Gentext")
   413  	thearch.Gentext(ctxt, ctxt.loader) // trampolines, call stubs, etc.
   414  
   415  	bench.Start("textaddress")
   416  	ctxt.textaddress()
   417  	bench.Start("typelink")
   418  	ctxt.typelink()
   419  	bench.Start("buildinfo")
   420  	ctxt.buildinfo()
   421  	bench.Start("pclntab")
   422  	containers := ctxt.findContainerSyms()
   423  	pclnState := ctxt.pclntab(containers)
   424  	bench.Start("findfunctab")
   425  	ctxt.findfunctab(pclnState, containers)
   426  	bench.Start("dwarfGenerateDebugSyms")
   427  	dwarfGenerateDebugSyms(ctxt)
   428  	bench.Start("symtab")
   429  	symGroupType := ctxt.symtab(pclnState)
   430  	bench.Start("dodata")
   431  	ctxt.dodata(symGroupType)
   432  	bench.Start("address")
   433  	order := ctxt.address()
   434  	bench.Start("dwarfcompress")
   435  	dwarfcompress(ctxt)
   436  	bench.Start("layout")
   437  	filesize := ctxt.layout(order)
   438  
   439  	// Write out the output file.
   440  	// It is split into two parts (Asmb and Asmb2). The first
   441  	// part writes most of the content (sections and segments),
   442  	// for which we have computed the size and offset, in a
   443  	// mmap'd region. The second part writes more content, for
   444  	// which we don't know the size.
   445  	if ctxt.Arch.Family != sys.Wasm {
   446  		// Don't mmap if we're building for Wasm. Wasm file
   447  		// layout is very different so filesize is meaningless.
   448  		if err := ctxt.Out.Mmap(filesize); err != nil {
   449  			Exitf("mapping output file failed: %v", err)
   450  		}
   451  	}
   452  	// asmb will redirect symbols to the output file mmap, and relocations
   453  	// will be applied directly there.
   454  	bench.Start("Asmb")
   455  	asmb(ctxt)
   456  
   457  	exitIfErrors()
   458  
   459  	// Generate additional symbols for the native symbol table just prior
   460  	// to code generation.
   461  	bench.Start("GenSymsLate")
   462  	if thearch.GenSymsLate != nil {
   463  		thearch.GenSymsLate(ctxt, ctxt.loader)
   464  	}
   465  
   466  	bench.Start("Asmb2")
   467  	asmb2(ctxt)
   468  
   469  	bench.Start("Munmap")
   470  	ctxt.Out.Close() // Close handles Munmapping if necessary.
   471  
   472  	bench.Start("hostlink")
   473  	ctxt.hostlink()
   474  	if ctxt.Debugvlog != 0 {
   475  		ctxt.Logf("%s", ctxt.loader.Stat())
   476  		ctxt.Logf("%d liveness data\n", liveness)
   477  	}
   478  	bench.Start("Flush")
   479  	ctxt.Bso.Flush()
   480  	bench.Start("archive")
   481  	ctxt.archive()
   482  	bench.Report(os.Stdout)
   483  
   484  	errorexit()
   485  }
   486  
   487  type Rpath struct {
   488  	set bool
   489  	val string
   490  }
   491  
   492  func (r *Rpath) Set(val string) error {
   493  	r.set = true
   494  	r.val = val
   495  	return nil
   496  }
   497  
   498  func (r *Rpath) String() string {
   499  	return r.val
   500  }
   501  
   502  func startProfile() {
   503  	if *cpuprofile != "" {
   504  		f, err := os.Create(*cpuprofile)
   505  		if err != nil {
   506  			log.Fatalf("%v", err)
   507  		}
   508  		if err := pprof.StartCPUProfile(f); err != nil {
   509  			log.Fatalf("%v", err)
   510  		}
   511  		AtExit(func() {
   512  			pprof.StopCPUProfile()
   513  			if err = f.Close(); err != nil {
   514  				log.Fatalf("error closing cpu profile: %v", err)
   515  			}
   516  		})
   517  	}
   518  	if *memprofile != "" {
   519  		if *memprofilerate != 0 {
   520  			runtime.MemProfileRate = int(*memprofilerate)
   521  		}
   522  		f, err := os.Create(*memprofile)
   523  		if err != nil {
   524  			log.Fatalf("%v", err)
   525  		}
   526  		AtExit(func() {
   527  			// Profile all outstanding allocations.
   528  			runtime.GC()
   529  			// compilebench parses the memory profile to extract memstats,
   530  			// which are only written in the legacy pprof format.
   531  			// See golang.org/issue/18641 and runtime/pprof/pprof.go:writeHeap.
   532  			const writeLegacyFormat = 1
   533  			if err := pprof.Lookup("heap").WriteTo(f, writeLegacyFormat); err != nil {
   534  				log.Fatalf("%v", err)
   535  			}
   536  			// Close the file after writing the profile.
   537  			if err := f.Close(); err != nil {
   538  				log.Fatalf("could not close %v: %v", *memprofile, err)
   539  			}
   540  		})
   541  	}
   542  }
   543  

View as plain text