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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/link/internal/benchmark"
    40  	"flag"
    41  	"internal/buildcfg"
    42  	"log"
    43  	"os"
    44  	"runtime"
    45  	"runtime/pprof"
    46  	"strconv"
    47  	"strings"
    48  )
    49  
    50  var (
    51  	pkglistfornote []byte
    52  	windowsgui     bool // writes a "GUI binary" instead of a "console binary"
    53  	ownTmpDir      bool // set to true if tmp dir created by linker (e.g. no -tmpdir)
    54  )
    55  
    56  func init() {
    57  	flag.Var(&rpath, "r", "set the ELF dynamic linker search `path` to dir1:dir2:...")
    58  	flag.Var(&flagExtld, "extld", "use `linker` when linking in external mode")
    59  	flag.Var(&flagExtldflags, "extldflags", "pass `flags` to external linker")
    60  	flag.Var(&flagW, "w", "disable DWARF generation")
    61  }
    62  
    63  // Flags used by the linker. The exported flags are used by the architecture-specific packages.
    64  var (
    65  	flagBuildid = flag.String("buildid", "", "record `id` as Go toolchain build id")
    66  
    67  	flagOutfile    = flag.String("o", "", "write output to `file`")
    68  	flagPluginPath = flag.String("pluginpath", "", "full path name for plugin")
    69  
    70  	flagInstallSuffix = flag.String("installsuffix", "", "set package directory `suffix`")
    71  	flagDumpDep       = flag.Bool("dumpdep", false, "dump symbol dependency graph")
    72  	flagRace          = flag.Bool("race", false, "enable race detector")
    73  	flagMsan          = flag.Bool("msan", false, "enable MSan interface")
    74  	flagAsan          = flag.Bool("asan", false, "enable ASan interface")
    75  	flagAslr          = flag.Bool("aslr", true, "enable ASLR for buildmode=c-shared on windows")
    76  
    77  	flagFieldTrack = flag.String("k", "", "set field tracking `symbol`")
    78  	flagLibGCC     = flag.String("libgcc", "", "compiler support lib for internal linking; use \"none\" to disable")
    79  	flagTmpdir     = flag.String("tmpdir", "", "use `directory` for temporary files")
    80  
    81  	flagExtld      quoted.Flag
    82  	flagExtldflags quoted.Flag
    83  	flagExtar      = flag.String("extar", "", "archive program for buildmode=c-archive")
    84  
    85  	flagCaptureHostObjs = flag.String("capturehostobjs", "", "capture host object files loaded during internal linking to specified dir")
    86  
    87  	flagA             = flag.Bool("a", false, "no-op (deprecated)")
    88  	FlagC             = flag.Bool("c", false, "dump call graph")
    89  	FlagD             = flag.Bool("d", false, "disable dynamic executable")
    90  	flagF             = flag.Bool("f", false, "ignore version mismatch")
    91  	flagG             = flag.Bool("g", false, "disable go package data checks")
    92  	flagH             = flag.Bool("h", false, "halt on error")
    93  	flagN             = flag.Bool("n", false, "no-op (deprecated)")
    94  	FlagS             = flag.Bool("s", false, "disable symbol table")
    95  	flag8             bool // use 64-bit addresses in symbol table
    96  	flagInterpreter   = flag.String("I", "", "use `linker` as ELF dynamic linker")
    97  	FlagDebugTramp    = flag.Int("debugtramp", 0, "debug trampolines")
    98  	FlagDebugTextSize = flag.Int("debugtextsize", 0, "debug text section max size")
    99  	flagDebugNosplit  = flag.Bool("debugnosplit", false, "dump nosplit call graph")
   100  	FlagStrictDups    = flag.Int("strictdups", 0, "sanity check duplicate symbol contents during object file reading (1=warn 2=err).")
   101  	FlagRound         = flag.Int64("R", -1, "set address rounding `quantum`")
   102  	FlagTextAddr      = flag.Int64("T", -1, "set the start address of text symbols")
   103  	flagEntrySymbol   = flag.String("E", "", "set `entry` symbol name")
   104  	flagPruneWeakMap  = flag.Bool("pruneweakmap", true, "prune weak mapinit refs")
   105  	cpuprofile        = flag.String("cpuprofile", "", "write cpu profile to `file`")
   106  	memprofile        = flag.String("memprofile", "", "write memory profile to `file`")
   107  	memprofilerate    = flag.Int64("memprofilerate", 0, "set runtime.MemProfileRate to `rate`")
   108  	benchmarkFlag     = flag.String("benchmark", "", "set to 'mem' or 'cpu' to enable phase benchmarking")
   109  	benchmarkFileFlag = flag.String("benchmarkprofile", "", "emit phase profiles to `base`_phase.{cpu,mem}prof")
   110  
   111  	flagW ternaryFlag
   112  	FlagW = new(bool) // the -w flag, computed in main from flagW
   113  )
   114  
   115  // ternaryFlag is like a boolean flag, but has a default value that is
   116  // neither true nor false, allowing it to be set from context (e.g. from another
   117  // flag).
   118  // *ternaryFlag implements flag.Value.
   119  type ternaryFlag int
   120  
   121  const (
   122  	ternaryFlagUnset ternaryFlag = iota
   123  	ternaryFlagFalse
   124  	ternaryFlagTrue
   125  )
   126  
   127  func (t *ternaryFlag) Set(s string) error {
   128  	v, err := strconv.ParseBool(s)
   129  	if err != nil {
   130  		return err
   131  	}
   132  	if v {
   133  		*t = ternaryFlagTrue
   134  	} else {
   135  		*t = ternaryFlagFalse
   136  	}
   137  	return nil
   138  }
   139  
   140  func (t *ternaryFlag) String() string {
   141  	switch *t {
   142  	case ternaryFlagFalse:
   143  		return "false"
   144  	case ternaryFlagTrue:
   145  		return "true"
   146  	}
   147  	return "unset"
   148  }
   149  
   150  func (t *ternaryFlag) IsBoolFlag() bool { return true } // parse like a boolean flag
   151  
   152  // Main is the main entry point for the linker code.
   153  func Main(arch *sys.Arch, theArch Arch) {
   154  	log.SetPrefix("link: ")
   155  	log.SetFlags(0)
   156  
   157  	thearch = theArch
   158  	ctxt := linknew(arch)
   159  	ctxt.Bso = bufio.NewWriter(os.Stdout)
   160  
   161  	// For testing behavior of go command when tools crash silently.
   162  	// Undocumented, not in standard flag parser to avoid
   163  	// exposing in usage message.
   164  	for _, arg := range os.Args {
   165  		if arg == "-crash_for_testing" {
   166  			os.Exit(2)
   167  		}
   168  	}
   169  
   170  	if final := gorootFinal(); final == "$GOROOT" {
   171  		// cmd/go sets GOROOT_FINAL to the dummy value "$GOROOT" when -trimpath is set,
   172  		// but runtime.GOROOT() should return the empty string, not a bogus value.
   173  		// (See https://go.dev/issue/51461.)
   174  	} else {
   175  		addstrdata1(ctxt, "runtime.defaultGOROOT="+final)
   176  	}
   177  
   178  	buildVersion := buildcfg.Version
   179  	if goexperiment := buildcfg.Experiment.String(); goexperiment != "" {
   180  		buildVersion += " X:" + goexperiment
   181  	}
   182  	addstrdata1(ctxt, "runtime.buildVersion="+buildVersion)
   183  
   184  	// TODO(matloob): define these above and then check flag values here
   185  	if ctxt.Arch.Family == sys.AMD64 && buildcfg.GOOS == "plan9" {
   186  		flag.BoolVar(&flag8, "8", false, "use 64-bit addresses in symbol table")
   187  	}
   188  	flagHeadType := flag.String("H", "", "set header `type`")
   189  	flag.BoolVar(&ctxt.linkShared, "linkshared", false, "link against installed Go shared libraries")
   190  	flag.Var(&ctxt.LinkMode, "linkmode", "set link `mode`")
   191  	flag.Var(&ctxt.BuildMode, "buildmode", "set build `mode`")
   192  	flag.BoolVar(&ctxt.compressDWARF, "compressdwarf", true, "compress DWARF if possible")
   193  	objabi.Flagfn1("B", "add an ELF NT_GNU_BUILD_ID `note` when using ELF; use \"gobuildid\" to generate it from the Go build ID", addbuildinfo)
   194  	objabi.Flagfn1("L", "add specified `directory` to library path", func(a string) { Lflag(ctxt, a) })
   195  	objabi.AddVersionFlag() // -V
   196  	objabi.Flagfn1("X", "add string value `definition` of the form importpath.name=value", func(s string) { addstrdata1(ctxt, s) })
   197  	objabi.Flagcount("v", "print link trace", &ctxt.Debugvlog)
   198  	objabi.Flagfn1("importcfg", "read import configuration from `file`", ctxt.readImportCfg)
   199  
   200  	objabi.Flagparse(usage)
   201  
   202  	if ctxt.Debugvlog > 0 {
   203  		// dump symbol info on crash
   204  		defer func() { ctxt.loader.Dump() }()
   205  	}
   206  	if ctxt.Debugvlog > 1 {
   207  		// dump symbol info on error
   208  		AtExit(func() {
   209  			if nerrors > 0 {
   210  				ctxt.loader.Dump()
   211  			}
   212  		})
   213  	}
   214  
   215  	switch *flagHeadType {
   216  	case "":
   217  	case "windowsgui":
   218  		ctxt.HeadType = objabi.Hwindows
   219  		windowsgui = true
   220  	default:
   221  		if err := ctxt.HeadType.Set(*flagHeadType); err != nil {
   222  			Errorf(nil, "%v", err)
   223  			usage()
   224  		}
   225  	}
   226  	if ctxt.HeadType == objabi.Hunknown {
   227  		ctxt.HeadType.Set(buildcfg.GOOS)
   228  	}
   229  
   230  	if !*flagAslr && ctxt.BuildMode != BuildModeCShared {
   231  		Errorf(nil, "-aslr=false is only allowed for -buildmode=c-shared")
   232  		usage()
   233  	}
   234  
   235  	if *FlagD && ctxt.UsesLibc() {
   236  		Exitf("dynamic linking required on %s; -d flag cannot be used", buildcfg.GOOS)
   237  	}
   238  
   239  	isPowerOfTwo := func(n int64) bool {
   240  		return n > 0 && n&(n-1) == 0
   241  	}
   242  	if *FlagRound != -1 && (*FlagRound < 4096 || !isPowerOfTwo(*FlagRound)) {
   243  		Exitf("invalid -R value 0x%x", *FlagRound)
   244  	}
   245  
   246  	checkStrictDups = *FlagStrictDups
   247  
   248  	switch flagW {
   249  	case ternaryFlagFalse:
   250  		*FlagW = false
   251  	case ternaryFlagTrue:
   252  		*FlagW = true
   253  	case ternaryFlagUnset:
   254  		*FlagW = *FlagS // -s implies -w if not explicitly set
   255  		if ctxt.IsDarwin() && ctxt.BuildMode == BuildModeCShared {
   256  			*FlagW = true // default to -w in c-shared mode on darwin, see #61229
   257  		}
   258  	}
   259  
   260  	if !buildcfg.Experiment.RegabiWrappers {
   261  		abiInternalVer = 0
   262  	}
   263  
   264  	startProfile()
   265  	if ctxt.BuildMode == BuildModeUnset {
   266  		ctxt.BuildMode.Set("exe")
   267  	}
   268  
   269  	if ctxt.BuildMode != BuildModeShared && flag.NArg() != 1 {
   270  		usage()
   271  	}
   272  
   273  	if *flagOutfile == "" {
   274  		*flagOutfile = "a.out"
   275  		if ctxt.HeadType == objabi.Hwindows {
   276  			*flagOutfile += ".exe"
   277  		}
   278  	}
   279  
   280  	interpreter = *flagInterpreter
   281  
   282  	if *flagBuildid == "" && ctxt.Target.IsOpenbsd() {
   283  		// TODO(jsing): Remove once direct syscalls are no longer in use.
   284  		// OpenBSD 6.7 onwards will not permit direct syscalls from a
   285  		// dynamically linked binary unless it identifies the binary
   286  		// contains a .note.go.buildid ELF note. See issue #36435.
   287  		*flagBuildid = "go-openbsd"
   288  	}
   289  
   290  	// enable benchmarking
   291  	var bench *benchmark.Metrics
   292  	if len(*benchmarkFlag) != 0 {
   293  		if *benchmarkFlag == "mem" {
   294  			bench = benchmark.New(benchmark.GC, *benchmarkFileFlag)
   295  		} else if *benchmarkFlag == "cpu" {
   296  			bench = benchmark.New(benchmark.NoGC, *benchmarkFileFlag)
   297  		} else {
   298  			Errorf(nil, "unknown benchmark flag: %q", *benchmarkFlag)
   299  			usage()
   300  		}
   301  	}
   302  
   303  	bench.Start("libinit")
   304  	libinit(ctxt) // creates outfile
   305  	bench.Start("computeTLSOffset")
   306  	ctxt.computeTLSOffset()
   307  	bench.Start("Archinit")
   308  	thearch.Archinit(ctxt)
   309  
   310  	if ctxt.linkShared && !ctxt.IsELF {
   311  		Exitf("-linkshared can only be used on elf systems")
   312  	}
   313  
   314  	if ctxt.Debugvlog != 0 {
   315  		onOff := func(b bool) string {
   316  			if b {
   317  				return "on"
   318  			}
   319  			return "off"
   320  		}
   321  		ctxt.Logf("build mode: %s, symbol table: %s, DWARF: %s\n", ctxt.BuildMode, onOff(!*FlagS), onOff(dwarfEnabled(ctxt)))
   322  		ctxt.Logf("HEADER = -H%d -T0x%x -R0x%x\n", ctxt.HeadType, uint64(*FlagTextAddr), uint32(*FlagRound))
   323  	}
   324  
   325  	zerofp := goobj.FingerprintType{}
   326  	switch ctxt.BuildMode {
   327  	case BuildModeShared:
   328  		for i := 0; i < flag.NArg(); i++ {
   329  			arg := flag.Arg(i)
   330  			parts := strings.SplitN(arg, "=", 2)
   331  			var pkgpath, file string
   332  			if len(parts) == 1 {
   333  				pkgpath, file = "main", arg
   334  			} else {
   335  				pkgpath, file = parts[0], parts[1]
   336  			}
   337  			pkglistfornote = append(pkglistfornote, pkgpath...)
   338  			pkglistfornote = append(pkglistfornote, '\n')
   339  			addlibpath(ctxt, "command line", "command line", file, pkgpath, "", zerofp)
   340  		}
   341  	case BuildModePlugin:
   342  		addlibpath(ctxt, "command line", "command line", flag.Arg(0), *flagPluginPath, "", zerofp)
   343  	default:
   344  		addlibpath(ctxt, "command line", "command line", flag.Arg(0), "main", "", zerofp)
   345  	}
   346  	bench.Start("loadlib")
   347  	ctxt.loadlib()
   348  
   349  	bench.Start("inittasks")
   350  	ctxt.inittasks()
   351  
   352  	bench.Start("deadcode")
   353  	deadcode(ctxt)
   354  
   355  	bench.Start("linksetup")
   356  	ctxt.linksetup()
   357  
   358  	bench.Start("dostrdata")
   359  	ctxt.dostrdata()
   360  	if buildcfg.Experiment.FieldTrack {
   361  		bench.Start("fieldtrack")
   362  		fieldtrack(ctxt.Arch, ctxt.loader)
   363  	}
   364  
   365  	bench.Start("dwarfGenerateDebugInfo")
   366  	dwarfGenerateDebugInfo(ctxt)
   367  
   368  	bench.Start("callgraph")
   369  	ctxt.callgraph()
   370  
   371  	bench.Start("doStackCheck")
   372  	ctxt.doStackCheck()
   373  
   374  	bench.Start("mangleTypeSym")
   375  	ctxt.mangleTypeSym()
   376  
   377  	if ctxt.IsELF {
   378  		bench.Start("doelf")
   379  		ctxt.doelf()
   380  	}
   381  	if ctxt.IsDarwin() {
   382  		bench.Start("domacho")
   383  		ctxt.domacho()
   384  	}
   385  	if ctxt.IsWindows() {
   386  		bench.Start("dope")
   387  		ctxt.dope()
   388  		bench.Start("windynrelocsyms")
   389  		ctxt.windynrelocsyms()
   390  	}
   391  	if ctxt.IsAIX() {
   392  		bench.Start("doxcoff")
   393  		ctxt.doxcoff()
   394  	}
   395  
   396  	bench.Start("textbuildid")
   397  	ctxt.textbuildid()
   398  	bench.Start("addexport")
   399  	ctxt.setArchSyms()
   400  	ctxt.addexport()
   401  	bench.Start("Gentext")
   402  	thearch.Gentext(ctxt, ctxt.loader) // trampolines, call stubs, etc.
   403  
   404  	bench.Start("textaddress")
   405  	ctxt.textaddress()
   406  	bench.Start("typelink")
   407  	ctxt.typelink()
   408  	bench.Start("buildinfo")
   409  	ctxt.buildinfo()
   410  	bench.Start("pclntab")
   411  	containers := ctxt.findContainerSyms()
   412  	pclnState := ctxt.pclntab(containers)
   413  	bench.Start("findfunctab")
   414  	ctxt.findfunctab(pclnState, containers)
   415  	bench.Start("dwarfGenerateDebugSyms")
   416  	dwarfGenerateDebugSyms(ctxt)
   417  	bench.Start("symtab")
   418  	symGroupType := ctxt.symtab(pclnState)
   419  	bench.Start("dodata")
   420  	ctxt.dodata(symGroupType)
   421  	bench.Start("address")
   422  	order := ctxt.address()
   423  	bench.Start("dwarfcompress")
   424  	dwarfcompress(ctxt)
   425  	bench.Start("layout")
   426  	filesize := ctxt.layout(order)
   427  
   428  	// Write out the output file.
   429  	// It is split into two parts (Asmb and Asmb2). The first
   430  	// part writes most of the content (sections and segments),
   431  	// for which we have computed the size and offset, in a
   432  	// mmap'd region. The second part writes more content, for
   433  	// which we don't know the size.
   434  	if ctxt.Arch.Family != sys.Wasm {
   435  		// Don't mmap if we're building for Wasm. Wasm file
   436  		// layout is very different so filesize is meaningless.
   437  		if err := ctxt.Out.Mmap(filesize); err != nil {
   438  			Exitf("mapping output file failed: %v", err)
   439  		}
   440  	}
   441  	// asmb will redirect symbols to the output file mmap, and relocations
   442  	// will be applied directly there.
   443  	bench.Start("Asmb")
   444  	asmb(ctxt)
   445  
   446  	exitIfErrors()
   447  
   448  	// Generate additional symbols for the native symbol table just prior
   449  	// to code generation.
   450  	bench.Start("GenSymsLate")
   451  	if thearch.GenSymsLate != nil {
   452  		thearch.GenSymsLate(ctxt, ctxt.loader)
   453  	}
   454  
   455  	bench.Start("Asmb2")
   456  	asmb2(ctxt)
   457  
   458  	bench.Start("Munmap")
   459  	ctxt.Out.Close() // Close handles Munmapping if necessary.
   460  
   461  	bench.Start("hostlink")
   462  	ctxt.hostlink()
   463  	if ctxt.Debugvlog != 0 {
   464  		ctxt.Logf("%s", ctxt.loader.Stat())
   465  		ctxt.Logf("%d liveness data\n", liveness)
   466  	}
   467  	bench.Start("Flush")
   468  	ctxt.Bso.Flush()
   469  	bench.Start("archive")
   470  	ctxt.archive()
   471  	bench.Report(os.Stdout)
   472  
   473  	errorexit()
   474  }
   475  
   476  type Rpath struct {
   477  	set bool
   478  	val string
   479  }
   480  
   481  func (r *Rpath) Set(val string) error {
   482  	r.set = true
   483  	r.val = val
   484  	return nil
   485  }
   486  
   487  func (r *Rpath) String() string {
   488  	return r.val
   489  }
   490  
   491  func startProfile() {
   492  	if *cpuprofile != "" {
   493  		f, err := os.Create(*cpuprofile)
   494  		if err != nil {
   495  			log.Fatalf("%v", err)
   496  		}
   497  		if err := pprof.StartCPUProfile(f); err != nil {
   498  			log.Fatalf("%v", err)
   499  		}
   500  		AtExit(pprof.StopCPUProfile)
   501  	}
   502  	if *memprofile != "" {
   503  		if *memprofilerate != 0 {
   504  			runtime.MemProfileRate = int(*memprofilerate)
   505  		}
   506  		f, err := os.Create(*memprofile)
   507  		if err != nil {
   508  			log.Fatalf("%v", err)
   509  		}
   510  		AtExit(func() {
   511  			// Profile all outstanding allocations.
   512  			runtime.GC()
   513  			// compilebench parses the memory profile to extract memstats,
   514  			// which are only written in the legacy pprof format.
   515  			// See golang.org/issue/18641 and runtime/pprof/pprof.go:writeHeap.
   516  			const writeLegacyFormat = 1
   517  			if err := pprof.Lookup("heap").WriteTo(f, writeLegacyFormat); err != nil {
   518  				log.Fatalf("%v", err)
   519  			}
   520  		})
   521  	}
   522  }
   523  

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