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

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