Source file src/cmd/link/internal/loader/loader.go

Documentation: cmd/link/internal/loader

     1  // Copyright 2019 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package loader
     6  
     7  import (
     8  	"bytes"
     9  	"cmd/internal/bio"
    10  	"cmd/internal/goobj"
    11  	"cmd/internal/obj"
    12  	"cmd/internal/objabi"
    13  	"cmd/internal/sys"
    14  	"cmd/link/internal/sym"
    15  	"debug/elf"
    16  	"fmt"
    17  	"internal/abi"
    18  	"io"
    19  	"log"
    20  	"math/bits"
    21  	"os"
    22  	"sort"
    23  	"strings"
    24  )
    25  
    26  var _ = fmt.Print
    27  
    28  // Sym encapsulates a global symbol index, used to identify a specific
    29  // Go symbol. The 0-valued Sym is corresponds to an invalid symbol.
    30  type Sym = sym.LoaderSym
    31  
    32  // Relocs encapsulates the set of relocations on a given symbol; an
    33  // instance of this type is returned by the Loader Relocs() method.
    34  type Relocs struct {
    35  	rs []goobj.Reloc
    36  
    37  	li uint32   // local index of symbol whose relocs we're examining
    38  	r  *oReader // object reader for containing package
    39  	l  *Loader  // loader
    40  }
    41  
    42  // ExtReloc contains the payload for an external relocation.
    43  type ExtReloc struct {
    44  	Xsym Sym
    45  	Xadd int64
    46  	Type objabi.RelocType
    47  	Size uint8
    48  }
    49  
    50  // Reloc holds a "handle" to access a relocation record from an
    51  // object file.
    52  type Reloc struct {
    53  	*goobj.Reloc
    54  	r *oReader
    55  	l *Loader
    56  }
    57  
    58  func (rel Reloc) Type() objabi.RelocType     { return objabi.RelocType(rel.Reloc.Type()) &^ objabi.R_WEAK }
    59  func (rel Reloc) Weak() bool                 { return objabi.RelocType(rel.Reloc.Type())&objabi.R_WEAK != 0 }
    60  func (rel Reloc) SetType(t objabi.RelocType) { rel.Reloc.SetType(uint16(t)) }
    61  func (rel Reloc) Sym() Sym                   { return rel.l.resolve(rel.r, rel.Reloc.Sym()) }
    62  func (rel Reloc) SetSym(s Sym)               { rel.Reloc.SetSym(goobj.SymRef{PkgIdx: 0, SymIdx: uint32(s)}) }
    63  func (rel Reloc) IsMarker() bool             { return rel.Siz() == 0 }
    64  
    65  // Aux holds a "handle" to access an aux symbol record from an
    66  // object file.
    67  type Aux struct {
    68  	*goobj.Aux
    69  	r *oReader
    70  	l *Loader
    71  }
    72  
    73  func (a Aux) Sym() Sym { return a.l.resolve(a.r, a.Aux.Sym()) }
    74  
    75  // oReader is a wrapper type of obj.Reader, along with some
    76  // extra information.
    77  type oReader struct {
    78  	*goobj.Reader
    79  	unit         *sym.CompilationUnit
    80  	version      int // version of static symbol
    81  	pkgprefix    string
    82  	syms         []Sym    // Sym's global index, indexed by local index
    83  	pkg          []uint32 // indices of referenced package by PkgIdx (index into loader.objs array)
    84  	ndef         int      // cache goobj.Reader.NSym()
    85  	nhashed64def int      // cache goobj.Reader.NHashed64Def()
    86  	nhasheddef   int      // cache goobj.Reader.NHashedDef()
    87  	objidx       uint32   // index of this reader in the objs slice
    88  }
    89  
    90  // Total number of defined symbols (package symbols, hashed symbols, and
    91  // non-package symbols).
    92  func (r *oReader) NAlldef() int { return r.ndef + r.nhashed64def + r.nhasheddef + r.NNonpkgdef() }
    93  
    94  type objIdx struct {
    95  	r *oReader
    96  	i Sym // start index
    97  }
    98  
    99  // objSym represents a symbol in an object file. It is a tuple of
   100  // the object and the symbol's local index.
   101  // For external symbols, objidx is the index of l.extReader (extObj),
   102  // s is its index into the payload array.
   103  // {0, 0} represents the nil symbol.
   104  type objSym struct {
   105  	objidx uint32 // index of the object (in l.objs array)
   106  	s      uint32 // local index
   107  }
   108  
   109  type nameVer struct {
   110  	name string
   111  	v    int
   112  }
   113  
   114  type Bitmap []uint32
   115  
   116  // set the i-th bit.
   117  func (bm Bitmap) Set(i Sym) {
   118  	n, r := uint(i)/32, uint(i)%32
   119  	bm[n] |= 1 << r
   120  }
   121  
   122  // unset the i-th bit.
   123  func (bm Bitmap) Unset(i Sym) {
   124  	n, r := uint(i)/32, uint(i)%32
   125  	bm[n] &^= (1 << r)
   126  }
   127  
   128  // whether the i-th bit is set.
   129  func (bm Bitmap) Has(i Sym) bool {
   130  	n, r := uint(i)/32, uint(i)%32
   131  	return bm[n]&(1<<r) != 0
   132  }
   133  
   134  // return current length of bitmap in bits.
   135  func (bm Bitmap) Len() int {
   136  	return len(bm) * 32
   137  }
   138  
   139  // return the number of bits set.
   140  func (bm Bitmap) Count() int {
   141  	s := 0
   142  	for _, x := range bm {
   143  		s += bits.OnesCount32(x)
   144  	}
   145  	return s
   146  }
   147  
   148  func MakeBitmap(n int) Bitmap {
   149  	return make(Bitmap, (n+31)/32)
   150  }
   151  
   152  // growBitmap insures that the specified bitmap has enough capacity,
   153  // reallocating (doubling the size) if needed.
   154  func growBitmap(reqLen int, b Bitmap) Bitmap {
   155  	curLen := b.Len()
   156  	if reqLen > curLen {
   157  		b = append(b, MakeBitmap(reqLen+1-curLen)...)
   158  	}
   159  	return b
   160  }
   161  
   162  type symAndSize struct {
   163  	sym  Sym
   164  	size uint32
   165  }
   166  
   167  // A Loader loads new object files and resolves indexed symbol references.
   168  //
   169  // Notes on the layout of global symbol index space:
   170  //
   171  //   - Go object files are read before host object files; each Go object
   172  //     read adds its defined package symbols to the global index space.
   173  //     Nonpackage symbols are not yet added.
   174  //
   175  //   - In loader.LoadNonpkgSyms, add non-package defined symbols and
   176  //     references in all object files to the global index space.
   177  //
   178  //   - Host object file loading happens; the host object loader does a
   179  //     name/version lookup for each symbol it finds; this can wind up
   180  //     extending the external symbol index space range. The host object
   181  //     loader stores symbol payloads in loader.payloads using SymbolBuilder.
   182  //
   183  //   - Each symbol gets a unique global index. For duplicated and
   184  //     overwriting/overwritten symbols, the second (or later) appearance
   185  //     of the symbol gets the same global index as the first appearance.
   186  type Loader struct {
   187  	start       map[*oReader]Sym // map from object file to its start index
   188  	objs        []objIdx         // sorted by start index (i.e. objIdx.i)
   189  	extStart    Sym              // from this index on, the symbols are externally defined
   190  	builtinSyms []Sym            // global index of builtin symbols
   191  
   192  	objSyms []objSym // global index mapping to local index
   193  
   194  	symsByName    [2]map[string]Sym // map symbol name to index, two maps are for ABI0 and ABIInternal
   195  	extStaticSyms map[nameVer]Sym   // externally defined static symbols, keyed by name
   196  
   197  	extReader    *oReader // a dummy oReader, for external symbols
   198  	payloadBatch []extSymPayload
   199  	payloads     []*extSymPayload // contents of linker-materialized external syms
   200  	values       []int64          // symbol values, indexed by global sym index
   201  
   202  	sects    []*sym.Section // sections
   203  	symSects []uint16       // symbol's section, index to sects array
   204  
   205  	align []uint8 // symbol 2^N alignment, indexed by global index
   206  
   207  	deferReturnTramp map[Sym]bool // whether the symbol is a trampoline of a deferreturn call
   208  
   209  	objByPkg map[string]uint32 // map package path to the index of its Go object reader
   210  
   211  	anonVersion int // most recently assigned ext static sym pseudo-version
   212  
   213  	// Bitmaps and other side structures used to store data used to store
   214  	// symbol flags/attributes; these are to be accessed via the
   215  	// corresponding loader "AttrXXX" and "SetAttrXXX" methods. Please
   216  	// visit the comments on these methods for more details on the
   217  	// semantics / interpretation of the specific flags or attribute.
   218  	attrReachable        Bitmap // reachable symbols, indexed by global index
   219  	attrOnList           Bitmap // "on list" symbols, indexed by global index
   220  	attrLocal            Bitmap // "local" symbols, indexed by global index
   221  	attrNotInSymbolTable Bitmap // "not in symtab" symbols, indexed by global idx
   222  	attrUsedInIface      Bitmap // "used in interface" symbols, indexed by global idx
   223  	attrSpecial          Bitmap // "special" frame symbols, indexed by global idx
   224  	attrVisibilityHidden Bitmap // hidden symbols, indexed by ext sym index
   225  	attrDuplicateOK      Bitmap // dupOK symbols, indexed by ext sym index
   226  	attrShared           Bitmap // shared symbols, indexed by ext sym index
   227  	attrExternal         Bitmap // external symbols, indexed by ext sym index
   228  	generatedSyms        Bitmap // symbols that generate their content, indexed by ext sym idx
   229  
   230  	attrReadOnly         map[Sym]bool     // readonly data for this sym
   231  	attrCgoExportDynamic map[Sym]struct{} // "cgo_export_dynamic" symbols
   232  	attrCgoExportStatic  map[Sym]struct{} // "cgo_export_static" symbols
   233  
   234  	// Outer and Sub relations for symbols.
   235  	outer []Sym // indexed by global index
   236  	sub   map[Sym]Sym
   237  
   238  	dynimplib   map[Sym]string      // stores Dynimplib symbol attribute
   239  	dynimpvers  map[Sym]string      // stores Dynimpvers symbol attribute
   240  	localentry  map[Sym]uint8       // stores Localentry symbol attribute
   241  	extname     map[Sym]string      // stores Extname symbol attribute
   242  	elfType     map[Sym]elf.SymType // stores elf type symbol property
   243  	elfSym      map[Sym]int32       // stores elf sym symbol property
   244  	localElfSym map[Sym]int32       // stores "local" elf sym symbol property
   245  	symPkg      map[Sym]string      // stores package for symbol, or library for shlib-derived syms
   246  	plt         map[Sym]int32       // stores dynimport for pe objects
   247  	got         map[Sym]int32       // stores got for pe objects
   248  	dynid       map[Sym]int32       // stores Dynid for symbol
   249  
   250  	relocVariant map[relocId]sym.RelocVariant // stores variant relocs
   251  
   252  	// Used to implement field tracking; created during deadcode if
   253  	// field tracking is enabled. Reachparent[K] contains the index of
   254  	// the symbol that triggered the marking of symbol K as live.
   255  	Reachparent []Sym
   256  
   257  	// CgoExports records cgo-exported symbols by SymName.
   258  	CgoExports map[string]Sym
   259  
   260  	flags uint32
   261  
   262  	strictDupMsgs int // number of strict-dup warning/errors, when FlagStrictDups is enabled
   263  
   264  	errorReporter *ErrorReporter
   265  
   266  	npkgsyms    int // number of package symbols, for accounting
   267  	nhashedsyms int // number of hashed symbols, for accounting
   268  }
   269  
   270  const (
   271  	pkgDef = iota
   272  	hashed64Def
   273  	hashedDef
   274  	nonPkgDef
   275  	nonPkgRef
   276  )
   277  
   278  // objidx
   279  const (
   280  	nilObj = iota
   281  	extObj
   282  	goObjStart
   283  )
   284  
   285  // extSymPayload holds the payload (data + relocations) for linker-synthesized
   286  // external symbols (note that symbol value is stored in a separate slice).
   287  type extSymPayload struct {
   288  	name   string // TODO: would this be better as offset into str table?
   289  	size   int64
   290  	ver    int
   291  	kind   sym.SymKind
   292  	objidx uint32 // index of original object if sym made by cloneToExternal
   293  	relocs []goobj.Reloc
   294  	data   []byte
   295  	auxs   []goobj.Aux
   296  }
   297  
   298  const (
   299  	// Loader.flags
   300  	FlagStrictDups = 1 << iota
   301  )
   302  
   303  func NewLoader(flags uint32, reporter *ErrorReporter) *Loader {
   304  	nbuiltin := goobj.NBuiltin()
   305  	extReader := &oReader{objidx: extObj}
   306  	ldr := &Loader{
   307  		start:                make(map[*oReader]Sym),
   308  		objs:                 []objIdx{{}, {extReader, 0}}, // reserve index 0 for nil symbol, 1 for external symbols
   309  		objSyms:              make([]objSym, 1, 1),         // This will get overwritten later.
   310  		extReader:            extReader,
   311  		symsByName:           [2]map[string]Sym{make(map[string]Sym, 80000), make(map[string]Sym, 50000)}, // preallocate ~2MB for ABI0 and ~1MB for ABI1 symbols
   312  		objByPkg:             make(map[string]uint32),
   313  		sub:                  make(map[Sym]Sym),
   314  		dynimplib:            make(map[Sym]string),
   315  		dynimpvers:           make(map[Sym]string),
   316  		localentry:           make(map[Sym]uint8),
   317  		extname:              make(map[Sym]string),
   318  		attrReadOnly:         make(map[Sym]bool),
   319  		elfType:              make(map[Sym]elf.SymType),
   320  		elfSym:               make(map[Sym]int32),
   321  		localElfSym:          make(map[Sym]int32),
   322  		symPkg:               make(map[Sym]string),
   323  		plt:                  make(map[Sym]int32),
   324  		got:                  make(map[Sym]int32),
   325  		dynid:                make(map[Sym]int32),
   326  		attrCgoExportDynamic: make(map[Sym]struct{}),
   327  		attrCgoExportStatic:  make(map[Sym]struct{}),
   328  		deferReturnTramp:     make(map[Sym]bool),
   329  		extStaticSyms:        make(map[nameVer]Sym),
   330  		builtinSyms:          make([]Sym, nbuiltin),
   331  		flags:                flags,
   332  		errorReporter:        reporter,
   333  		sects:                []*sym.Section{nil}, // reserve index 0 for nil section
   334  	}
   335  	reporter.ldr = ldr
   336  	return ldr
   337  }
   338  
   339  // Add object file r, return the start index.
   340  func (l *Loader) addObj(pkg string, r *oReader) Sym {
   341  	if _, ok := l.start[r]; ok {
   342  		panic("already added")
   343  	}
   344  	pkg = objabi.PathToPrefix(pkg) // the object file contains escaped package path
   345  	if _, ok := l.objByPkg[pkg]; !ok {
   346  		l.objByPkg[pkg] = r.objidx
   347  	}
   348  	i := Sym(len(l.objSyms))
   349  	l.start[r] = i
   350  	l.objs = append(l.objs, objIdx{r, i})
   351  	return i
   352  }
   353  
   354  // Add a symbol from an object file, return the global index.
   355  // If the symbol already exist, it returns the index of that symbol.
   356  func (st *loadState) addSym(name string, ver int, r *oReader, li uint32, kind int, osym *goobj.Sym) Sym {
   357  	l := st.l
   358  	if l.extStart != 0 {
   359  		panic("addSym called after external symbol is created")
   360  	}
   361  	i := Sym(len(l.objSyms))
   362  	if int(i) != len(l.objSyms) { // overflow
   363  		panic("too many symbols")
   364  	}
   365  	addToGlobal := func() {
   366  		l.objSyms = append(l.objSyms, objSym{r.objidx, li})
   367  	}
   368  	if name == "" && kind != hashed64Def && kind != hashedDef {
   369  		addToGlobal()
   370  		return i // unnamed aux symbol
   371  	}
   372  	if ver == r.version {
   373  		// Static symbol. Add its global index but don't
   374  		// add to name lookup table, as it cannot be
   375  		// referenced by name.
   376  		addToGlobal()
   377  		return i
   378  	}
   379  	switch kind {
   380  	case pkgDef:
   381  		// Defined package symbols cannot be dup to each other.
   382  		// We load all the package symbols first, so we don't need
   383  		// to check dup here.
   384  		// We still add it to the lookup table, as it may still be
   385  		// referenced by name (e.g. through linkname).
   386  		l.symsByName[ver][name] = i
   387  		addToGlobal()
   388  		return i
   389  	case hashed64Def, hashedDef:
   390  		// Hashed (content-addressable) symbol. Check the hash
   391  		// but don't add to name lookup table, as they are not
   392  		// referenced by name. Also no need to do overwriting
   393  		// check, as same hash indicates same content.
   394  		var checkHash func() (symAndSize, bool)
   395  		var addToHashMap func(symAndSize)
   396  		var h64 uint64        // only used for hashed64Def
   397  		var h *goobj.HashType // only used for hashedDef
   398  		if kind == hashed64Def {
   399  			checkHash = func() (symAndSize, bool) {
   400  				h64 = r.Hash64(li - uint32(r.ndef))
   401  				s, existed := st.hashed64Syms[h64]
   402  				return s, existed
   403  			}
   404  			addToHashMap = func(ss symAndSize) { st.hashed64Syms[h64] = ss }
   405  		} else {
   406  			checkHash = func() (symAndSize, bool) {
   407  				h = r.Hash(li - uint32(r.ndef+r.nhashed64def))
   408  				s, existed := st.hashedSyms[*h]
   409  				return s, existed
   410  			}
   411  			addToHashMap = func(ss symAndSize) { st.hashedSyms[*h] = ss }
   412  		}
   413  		siz := osym.Siz()
   414  		if s, existed := checkHash(); existed {
   415  			// The content hash is built from symbol data and relocations. In the
   416  			// object file, the symbol data may not always contain trailing zeros,
   417  			// e.g. for [5]int{1,2,3} and [100]int{1,2,3}, the data is same
   418  			// (although the size is different).
   419  			// Also, for short symbols, the content hash is the identity function of
   420  			// the 8 bytes, and trailing zeros doesn't change the hash value, e.g.
   421  			// hash("A") == hash("A\0\0\0").
   422  			// So when two symbols have the same hash, we need to use the one with
   423  			// larger size.
   424  			if siz > s.size {
   425  				// New symbol has larger size, use the new one. Rewrite the index mapping.
   426  				l.objSyms[s.sym] = objSym{r.objidx, li}
   427  				addToHashMap(symAndSize{s.sym, siz})
   428  			}
   429  			return s.sym
   430  		}
   431  		addToHashMap(symAndSize{i, siz})
   432  		addToGlobal()
   433  		return i
   434  	}
   435  
   436  	// Non-package (named) symbol. Check if it already exists.
   437  	oldi, existed := l.symsByName[ver][name]
   438  	if !existed {
   439  		l.symsByName[ver][name] = i
   440  		addToGlobal()
   441  		return i
   442  	}
   443  	// symbol already exists
   444  	if osym.Dupok() {
   445  		if l.flags&FlagStrictDups != 0 {
   446  			l.checkdup(name, r, li, oldi)
   447  		}
   448  		// Fix for issue #47185 -- given two dupok symbols with
   449  		// different sizes, favor symbol with larger size. See
   450  		// also issue #46653.
   451  		szdup := l.SymSize(oldi)
   452  		sz := int64(r.Sym(li).Siz())
   453  		if szdup < sz {
   454  			// new symbol overwrites old symbol.
   455  			l.objSyms[oldi] = objSym{r.objidx, li}
   456  		}
   457  		return oldi
   458  	}
   459  	oldr, oldli := l.toLocal(oldi)
   460  	oldsym := oldr.Sym(oldli)
   461  	if oldsym.Dupok() {
   462  		return oldi
   463  	}
   464  	overwrite := r.DataSize(li) != 0
   465  	if overwrite {
   466  		// new symbol overwrites old symbol.
   467  		oldtyp := sym.AbiSymKindToSymKind[objabi.SymKind(oldsym.Type())]
   468  		if !(oldtyp.IsData() && oldr.DataSize(oldli) == 0) {
   469  			log.Fatalf("duplicated definition of symbol %s, from %s and %s", name, r.unit.Lib.Pkg, oldr.unit.Lib.Pkg)
   470  		}
   471  		l.objSyms[oldi] = objSym{r.objidx, li}
   472  	} else {
   473  		// old symbol overwrites new symbol.
   474  		typ := sym.AbiSymKindToSymKind[objabi.SymKind(oldsym.Type())]
   475  		if !typ.IsData() { // only allow overwriting data symbol
   476  			log.Fatalf("duplicated definition of symbol %s, from %s and %s", name, r.unit.Lib.Pkg, oldr.unit.Lib.Pkg)
   477  		}
   478  	}
   479  	return oldi
   480  }
   481  
   482  // newExtSym creates a new external sym with the specified
   483  // name/version.
   484  func (l *Loader) newExtSym(name string, ver int) Sym {
   485  	i := Sym(len(l.objSyms))
   486  	if int(i) != len(l.objSyms) { // overflow
   487  		panic("too many symbols")
   488  	}
   489  	if l.extStart == 0 {
   490  		l.extStart = i
   491  	}
   492  	l.growValues(int(i) + 1)
   493  	l.growOuter(int(i) + 1)
   494  	l.growAttrBitmaps(int(i) + 1)
   495  	pi := l.newPayload(name, ver)
   496  	l.objSyms = append(l.objSyms, objSym{l.extReader.objidx, uint32(pi)})
   497  	l.extReader.syms = append(l.extReader.syms, i)
   498  	return i
   499  }
   500  
   501  // LookupOrCreateSym looks up the symbol with the specified name/version,
   502  // returning its Sym index if found. If the lookup fails, a new external
   503  // Sym will be created, entered into the lookup tables, and returned.
   504  func (l *Loader) LookupOrCreateSym(name string, ver int) Sym {
   505  	i := l.Lookup(name, ver)
   506  	if i != 0 {
   507  		return i
   508  	}
   509  	i = l.newExtSym(name, ver)
   510  	static := ver >= sym.SymVerStatic || ver < 0
   511  	if static {
   512  		l.extStaticSyms[nameVer{name, ver}] = i
   513  	} else {
   514  		l.symsByName[ver][name] = i
   515  	}
   516  	return i
   517  }
   518  
   519  // AddCgoExport records a cgo-exported symbol in l.CgoExports.
   520  // This table is used to identify the correct Go symbol ABI to use
   521  // to resolve references from host objects (which don't have ABIs).
   522  func (l *Loader) AddCgoExport(s Sym) {
   523  	if l.CgoExports == nil {
   524  		l.CgoExports = make(map[string]Sym)
   525  	}
   526  	l.CgoExports[l.SymName(s)] = s
   527  }
   528  
   529  // LookupOrCreateCgoExport is like LookupOrCreateSym, but if ver
   530  // indicates a global symbol, it uses the CgoExport table to determine
   531  // the appropriate symbol version (ABI) to use. ver must be either 0
   532  // or a static symbol version.
   533  func (l *Loader) LookupOrCreateCgoExport(name string, ver int) Sym {
   534  	if ver >= sym.SymVerStatic {
   535  		return l.LookupOrCreateSym(name, ver)
   536  	}
   537  	if ver != 0 {
   538  		panic("ver must be 0 or a static version")
   539  	}
   540  	// Look for a cgo-exported symbol from Go.
   541  	if s, ok := l.CgoExports[name]; ok {
   542  		return s
   543  	}
   544  	// Otherwise, this must just be a symbol in the host object.
   545  	// Create a version 0 symbol for it.
   546  	return l.LookupOrCreateSym(name, 0)
   547  }
   548  
   549  func (l *Loader) IsExternal(i Sym) bool {
   550  	r, _ := l.toLocal(i)
   551  	return l.isExtReader(r)
   552  }
   553  
   554  func (l *Loader) isExtReader(r *oReader) bool {
   555  	return r == l.extReader
   556  }
   557  
   558  // For external symbol, return its index in the payloads array.
   559  // XXX result is actually not a global index. We (ab)use the Sym type
   560  // so we don't need conversion for accessing bitmaps.
   561  func (l *Loader) extIndex(i Sym) Sym {
   562  	_, li := l.toLocal(i)
   563  	return Sym(li)
   564  }
   565  
   566  // Get a new payload for external symbol, return its index in
   567  // the payloads array.
   568  func (l *Loader) newPayload(name string, ver int) int {
   569  	pi := len(l.payloads)
   570  	pp := l.allocPayload()
   571  	pp.name = name
   572  	pp.ver = ver
   573  	l.payloads = append(l.payloads, pp)
   574  	l.growExtAttrBitmaps()
   575  	return pi
   576  }
   577  
   578  // getPayload returns a pointer to the extSymPayload struct for an
   579  // external symbol if the symbol has a payload. Will panic if the
   580  // symbol in question is bogus (zero or not an external sym).
   581  func (l *Loader) getPayload(i Sym) *extSymPayload {
   582  	if !l.IsExternal(i) {
   583  		panic(fmt.Sprintf("bogus symbol index %d in getPayload", i))
   584  	}
   585  	pi := l.extIndex(i)
   586  	return l.payloads[pi]
   587  }
   588  
   589  // allocPayload allocates a new payload.
   590  func (l *Loader) allocPayload() *extSymPayload {
   591  	batch := l.payloadBatch
   592  	if len(batch) == 0 {
   593  		batch = make([]extSymPayload, 1000)
   594  	}
   595  	p := &batch[0]
   596  	l.payloadBatch = batch[1:]
   597  	return p
   598  }
   599  
   600  func (ms *extSymPayload) Grow(siz int64) {
   601  	if int64(int(siz)) != siz {
   602  		log.Fatalf("symgrow size %d too long", siz)
   603  	}
   604  	if int64(len(ms.data)) >= siz {
   605  		return
   606  	}
   607  	if cap(ms.data) < int(siz) {
   608  		cl := len(ms.data)
   609  		ms.data = append(ms.data, make([]byte, int(siz)+1-cl)...)
   610  		ms.data = ms.data[0:cl]
   611  	}
   612  	ms.data = ms.data[:siz]
   613  }
   614  
   615  // Convert a local index to a global index.
   616  func (l *Loader) toGlobal(r *oReader, i uint32) Sym {
   617  	return r.syms[i]
   618  }
   619  
   620  // Convert a global index to a local index.
   621  func (l *Loader) toLocal(i Sym) (*oReader, uint32) {
   622  	return l.objs[l.objSyms[i].objidx].r, l.objSyms[i].s
   623  }
   624  
   625  // Resolve a local symbol reference. Return global index.
   626  func (l *Loader) resolve(r *oReader, s goobj.SymRef) Sym {
   627  	var rr *oReader
   628  	switch p := s.PkgIdx; p {
   629  	case goobj.PkgIdxInvalid:
   630  		// {0, X} with non-zero X is never a valid sym reference from a Go object.
   631  		// We steal this space for symbol references from external objects.
   632  		// In this case, X is just the global index.
   633  		if l.isExtReader(r) {
   634  			return Sym(s.SymIdx)
   635  		}
   636  		if s.SymIdx != 0 {
   637  			panic("bad sym ref")
   638  		}
   639  		return 0
   640  	case goobj.PkgIdxHashed64:
   641  		i := int(s.SymIdx) + r.ndef
   642  		return r.syms[i]
   643  	case goobj.PkgIdxHashed:
   644  		i := int(s.SymIdx) + r.ndef + r.nhashed64def
   645  		return r.syms[i]
   646  	case goobj.PkgIdxNone:
   647  		i := int(s.SymIdx) + r.ndef + r.nhashed64def + r.nhasheddef
   648  		return r.syms[i]
   649  	case goobj.PkgIdxBuiltin:
   650  		if bi := l.builtinSyms[s.SymIdx]; bi != 0 {
   651  			return bi
   652  		}
   653  		l.reportMissingBuiltin(int(s.SymIdx), r.unit.Lib.Pkg)
   654  		return 0
   655  	case goobj.PkgIdxSelf:
   656  		rr = r
   657  	default:
   658  		rr = l.objs[r.pkg[p]].r
   659  	}
   660  	return l.toGlobal(rr, s.SymIdx)
   661  }
   662  
   663  // reportMissingBuiltin issues an error in the case where we have a
   664  // relocation against a runtime builtin whose definition is not found
   665  // when the runtime package is built. The canonical example is
   666  // "runtime.racefuncenter" -- currently if you do something like
   667  //
   668  //	go build -gcflags=-race myprogram.go
   669  //
   670  // the compiler will insert calls to the builtin runtime.racefuncenter,
   671  // but the version of the runtime used for linkage won't actually contain
   672  // definitions of that symbol. See issue #42396 for details.
   673  //
   674  // As currently implemented, this is a fatal error. This has drawbacks
   675  // in that if there are multiple missing builtins, the error will only
   676  // cite the first one. On the plus side, terminating the link here has
   677  // advantages in that we won't run the risk of panics or crashes later
   678  // on in the linker due to R_CALL relocations with 0-valued target
   679  // symbols.
   680  func (l *Loader) reportMissingBuiltin(bsym int, reflib string) {
   681  	bname, _ := goobj.BuiltinName(bsym)
   682  	log.Fatalf("reference to undefined builtin %q from package %q",
   683  		bname, reflib)
   684  }
   685  
   686  // Look up a symbol by name, return global index, or 0 if not found.
   687  // This is more like Syms.ROLookup than Lookup -- it doesn't create
   688  // new symbol.
   689  func (l *Loader) Lookup(name string, ver int) Sym {
   690  	if ver >= sym.SymVerStatic || ver < 0 {
   691  		return l.extStaticSyms[nameVer{name, ver}]
   692  	}
   693  	return l.symsByName[ver][name]
   694  }
   695  
   696  // Check that duplicate symbols have same contents.
   697  func (l *Loader) checkdup(name string, r *oReader, li uint32, dup Sym) {
   698  	p := r.Data(li)
   699  	rdup, ldup := l.toLocal(dup)
   700  	pdup := rdup.Data(ldup)
   701  	reason := "same length but different contents"
   702  	if len(p) != len(pdup) {
   703  		reason = fmt.Sprintf("new length %d != old length %d", len(p), len(pdup))
   704  	} else if bytes.Equal(p, pdup) {
   705  		// For BSS symbols, we need to check size as well, see issue 46653.
   706  		szdup := l.SymSize(dup)
   707  		sz := int64(r.Sym(li).Siz())
   708  		if szdup == sz {
   709  			return
   710  		}
   711  		reason = fmt.Sprintf("different sizes: new size %d != old size %d",
   712  			sz, szdup)
   713  	}
   714  	fmt.Fprintf(os.Stderr, "cmd/link: while reading object for '%v': duplicate symbol '%s', previous def at '%v', with mismatched payload: %s\n", r.unit.Lib, name, rdup.unit.Lib, reason)
   715  
   716  	// For the moment, allow DWARF subprogram DIEs for
   717  	// auto-generated wrapper functions. What seems to happen
   718  	// here is that we get different line numbers on formal
   719  	// params; I am guessing that the pos is being inherited
   720  	// from the spot where the wrapper is needed.
   721  	allowed := strings.HasPrefix(name, "go:info.go.interface") ||
   722  		strings.HasPrefix(name, "go:info.go.builtin") ||
   723  		strings.HasPrefix(name, "go:debuglines")
   724  	if !allowed {
   725  		l.strictDupMsgs++
   726  	}
   727  }
   728  
   729  func (l *Loader) NStrictDupMsgs() int { return l.strictDupMsgs }
   730  
   731  // Number of total symbols.
   732  func (l *Loader) NSym() int {
   733  	return len(l.objSyms)
   734  }
   735  
   736  // Number of defined Go symbols.
   737  func (l *Loader) NDef() int {
   738  	return int(l.extStart)
   739  }
   740  
   741  // Number of reachable symbols.
   742  func (l *Loader) NReachableSym() int {
   743  	return l.attrReachable.Count()
   744  }
   745  
   746  // Returns the name of the i-th symbol.
   747  func (l *Loader) SymName(i Sym) string {
   748  	if l.IsExternal(i) {
   749  		pp := l.getPayload(i)
   750  		return pp.name
   751  	}
   752  	r, li := l.toLocal(i)
   753  	if r == nil {
   754  		return "?"
   755  	}
   756  	return r.Sym(li).Name(r.Reader)
   757  }
   758  
   759  // Returns the version of the i-th symbol.
   760  func (l *Loader) SymVersion(i Sym) int {
   761  	if l.IsExternal(i) {
   762  		pp := l.getPayload(i)
   763  		return pp.ver
   764  	}
   765  	r, li := l.toLocal(i)
   766  	return int(abiToVer(r.Sym(li).ABI(), r.version))
   767  }
   768  
   769  func (l *Loader) IsFileLocal(i Sym) bool {
   770  	return l.SymVersion(i) >= sym.SymVerStatic
   771  }
   772  
   773  // IsFromAssembly returns true if this symbol is derived from an
   774  // object file generated by the Go assembler.
   775  func (l *Loader) IsFromAssembly(i Sym) bool {
   776  	if l.IsExternal(i) {
   777  		return false
   778  	}
   779  	r, _ := l.toLocal(i)
   780  	return r.FromAssembly()
   781  }
   782  
   783  // Returns the type of the i-th symbol.
   784  func (l *Loader) SymType(i Sym) sym.SymKind {
   785  	if l.IsExternal(i) {
   786  		pp := l.getPayload(i)
   787  		if pp != nil {
   788  			return pp.kind
   789  		}
   790  		return 0
   791  	}
   792  	r, li := l.toLocal(i)
   793  	return sym.AbiSymKindToSymKind[objabi.SymKind(r.Sym(li).Type())]
   794  }
   795  
   796  // Returns the attributes of the i-th symbol.
   797  func (l *Loader) SymAttr(i Sym) uint8 {
   798  	if l.IsExternal(i) {
   799  		// TODO: do something? External symbols have different representation of attributes.
   800  		// For now, ReflectMethod, NoSplit, GoType, and Typelink are used and they cannot be
   801  		// set by external symbol.
   802  		return 0
   803  	}
   804  	r, li := l.toLocal(i)
   805  	return r.Sym(li).Flag()
   806  }
   807  
   808  // Returns the size of the i-th symbol.
   809  func (l *Loader) SymSize(i Sym) int64 {
   810  	if l.IsExternal(i) {
   811  		pp := l.getPayload(i)
   812  		return pp.size
   813  	}
   814  	r, li := l.toLocal(i)
   815  	return int64(r.Sym(li).Siz())
   816  }
   817  
   818  // AttrReachable returns true for symbols that are transitively
   819  // referenced from the entry points. Unreachable symbols are not
   820  // written to the output.
   821  func (l *Loader) AttrReachable(i Sym) bool {
   822  	return l.attrReachable.Has(i)
   823  }
   824  
   825  // SetAttrReachable sets the reachability property for a symbol (see
   826  // AttrReachable).
   827  func (l *Loader) SetAttrReachable(i Sym, v bool) {
   828  	if v {
   829  		l.attrReachable.Set(i)
   830  	} else {
   831  		l.attrReachable.Unset(i)
   832  	}
   833  }
   834  
   835  // AttrOnList returns true for symbols that are on some list (such as
   836  // the list of all text symbols, or one of the lists of data symbols)
   837  // and is consulted to avoid bugs where a symbol is put on a list
   838  // twice.
   839  func (l *Loader) AttrOnList(i Sym) bool {
   840  	return l.attrOnList.Has(i)
   841  }
   842  
   843  // SetAttrOnList sets the "on list" property for a symbol (see
   844  // AttrOnList).
   845  func (l *Loader) SetAttrOnList(i Sym, v bool) {
   846  	if v {
   847  		l.attrOnList.Set(i)
   848  	} else {
   849  		l.attrOnList.Unset(i)
   850  	}
   851  }
   852  
   853  // AttrLocal returns true for symbols that are only visible within the
   854  // module (executable or shared library) being linked. This attribute
   855  // is applied to thunks and certain other linker-generated symbols.
   856  func (l *Loader) AttrLocal(i Sym) bool {
   857  	return l.attrLocal.Has(i)
   858  }
   859  
   860  // SetAttrLocal the "local" property for a symbol (see AttrLocal above).
   861  func (l *Loader) SetAttrLocal(i Sym, v bool) {
   862  	if v {
   863  		l.attrLocal.Set(i)
   864  	} else {
   865  		l.attrLocal.Unset(i)
   866  	}
   867  }
   868  
   869  // AttrUsedInIface returns true for a type symbol that is used in
   870  // an interface.
   871  func (l *Loader) AttrUsedInIface(i Sym) bool {
   872  	return l.attrUsedInIface.Has(i)
   873  }
   874  
   875  func (l *Loader) SetAttrUsedInIface(i Sym, v bool) {
   876  	if v {
   877  		l.attrUsedInIface.Set(i)
   878  	} else {
   879  		l.attrUsedInIface.Unset(i)
   880  	}
   881  }
   882  
   883  // SymAddr checks that a symbol is reachable, and returns its value.
   884  func (l *Loader) SymAddr(i Sym) int64 {
   885  	if !l.AttrReachable(i) {
   886  		panic("unreachable symbol in symaddr")
   887  	}
   888  	return l.values[i]
   889  }
   890  
   891  // AttrNotInSymbolTable returns true for symbols that should not be
   892  // added to the symbol table of the final generated load module.
   893  func (l *Loader) AttrNotInSymbolTable(i Sym) bool {
   894  	return l.attrNotInSymbolTable.Has(i)
   895  }
   896  
   897  // SetAttrNotInSymbolTable the "not in symtab" property for a symbol
   898  // (see AttrNotInSymbolTable above).
   899  func (l *Loader) SetAttrNotInSymbolTable(i Sym, v bool) {
   900  	if v {
   901  		l.attrNotInSymbolTable.Set(i)
   902  	} else {
   903  		l.attrNotInSymbolTable.Unset(i)
   904  	}
   905  }
   906  
   907  // AttrVisibilityHidden symbols returns true for ELF symbols with
   908  // visibility set to STV_HIDDEN. They become local symbols in
   909  // the final executable. Only relevant when internally linking
   910  // on an ELF platform.
   911  func (l *Loader) AttrVisibilityHidden(i Sym) bool {
   912  	if !l.IsExternal(i) {
   913  		return false
   914  	}
   915  	return l.attrVisibilityHidden.Has(l.extIndex(i))
   916  }
   917  
   918  // SetAttrVisibilityHidden sets the "hidden visibility" property for a
   919  // symbol (see AttrVisibilityHidden).
   920  func (l *Loader) SetAttrVisibilityHidden(i Sym, v bool) {
   921  	if !l.IsExternal(i) {
   922  		panic("tried to set visibility attr on non-external symbol")
   923  	}
   924  	if v {
   925  		l.attrVisibilityHidden.Set(l.extIndex(i))
   926  	} else {
   927  		l.attrVisibilityHidden.Unset(l.extIndex(i))
   928  	}
   929  }
   930  
   931  // AttrDuplicateOK returns true for a symbol that can be present in
   932  // multiple object files.
   933  func (l *Loader) AttrDuplicateOK(i Sym) bool {
   934  	if !l.IsExternal(i) {
   935  		// TODO: if this path winds up being taken frequently, it
   936  		// might make more sense to copy the flag value out of the object
   937  		// into a larger bitmap during preload.
   938  		r, li := l.toLocal(i)
   939  		return r.Sym(li).Dupok()
   940  	}
   941  	return l.attrDuplicateOK.Has(l.extIndex(i))
   942  }
   943  
   944  // SetAttrDuplicateOK sets the "duplicate OK" property for an external
   945  // symbol (see AttrDuplicateOK).
   946  func (l *Loader) SetAttrDuplicateOK(i Sym, v bool) {
   947  	if !l.IsExternal(i) {
   948  		panic("tried to set dupok attr on non-external symbol")
   949  	}
   950  	if v {
   951  		l.attrDuplicateOK.Set(l.extIndex(i))
   952  	} else {
   953  		l.attrDuplicateOK.Unset(l.extIndex(i))
   954  	}
   955  }
   956  
   957  // AttrShared returns true for symbols compiled with the -shared option.
   958  func (l *Loader) AttrShared(i Sym) bool {
   959  	if !l.IsExternal(i) {
   960  		// TODO: if this path winds up being taken frequently, it
   961  		// might make more sense to copy the flag value out of the
   962  		// object into a larger bitmap during preload.
   963  		r, _ := l.toLocal(i)
   964  		return r.Shared()
   965  	}
   966  	return l.attrShared.Has(l.extIndex(i))
   967  }
   968  
   969  // SetAttrShared sets the "shared" property for an external
   970  // symbol (see AttrShared).
   971  func (l *Loader) SetAttrShared(i Sym, v bool) {
   972  	if !l.IsExternal(i) {
   973  		panic(fmt.Sprintf("tried to set shared attr on non-external symbol %d %s", i, l.SymName(i)))
   974  	}
   975  	if v {
   976  		l.attrShared.Set(l.extIndex(i))
   977  	} else {
   978  		l.attrShared.Unset(l.extIndex(i))
   979  	}
   980  }
   981  
   982  // AttrExternal returns true for function symbols loaded from host
   983  // object files.
   984  func (l *Loader) AttrExternal(i Sym) bool {
   985  	if !l.IsExternal(i) {
   986  		return false
   987  	}
   988  	return l.attrExternal.Has(l.extIndex(i))
   989  }
   990  
   991  // SetAttrExternal sets the "external" property for a host object
   992  // symbol (see AttrExternal).
   993  func (l *Loader) SetAttrExternal(i Sym, v bool) {
   994  	if !l.IsExternal(i) {
   995  		panic(fmt.Sprintf("tried to set external attr on non-external symbol %q", l.SymName(i)))
   996  	}
   997  	if v {
   998  		l.attrExternal.Set(l.extIndex(i))
   999  	} else {
  1000  		l.attrExternal.Unset(l.extIndex(i))
  1001  	}
  1002  }
  1003  
  1004  // AttrSpecial returns true for a symbols that do not have their
  1005  // address (i.e. Value) computed by the usual mechanism of
  1006  // data.go:dodata() & data.go:address().
  1007  func (l *Loader) AttrSpecial(i Sym) bool {
  1008  	return l.attrSpecial.Has(i)
  1009  }
  1010  
  1011  // SetAttrSpecial sets the "special" property for a symbol (see
  1012  // AttrSpecial).
  1013  func (l *Loader) SetAttrSpecial(i Sym, v bool) {
  1014  	if v {
  1015  		l.attrSpecial.Set(i)
  1016  	} else {
  1017  		l.attrSpecial.Unset(i)
  1018  	}
  1019  }
  1020  
  1021  // AttrCgoExportDynamic returns true for a symbol that has been
  1022  // specially marked via the "cgo_export_dynamic" compiler directive
  1023  // written by cgo (in response to //export directives in the source).
  1024  func (l *Loader) AttrCgoExportDynamic(i Sym) bool {
  1025  	_, ok := l.attrCgoExportDynamic[i]
  1026  	return ok
  1027  }
  1028  
  1029  // SetAttrCgoExportDynamic sets the "cgo_export_dynamic" for a symbol
  1030  // (see AttrCgoExportDynamic).
  1031  func (l *Loader) SetAttrCgoExportDynamic(i Sym, v bool) {
  1032  	if v {
  1033  		l.attrCgoExportDynamic[i] = struct{}{}
  1034  	} else {
  1035  		delete(l.attrCgoExportDynamic, i)
  1036  	}
  1037  }
  1038  
  1039  // ForAllCgoExportDynamic calls f for every symbol that has been
  1040  // marked with the "cgo_export_dynamic" compiler directive.
  1041  func (l *Loader) ForAllCgoExportDynamic(f func(Sym)) {
  1042  	for s := range l.attrCgoExportDynamic {
  1043  		f(s)
  1044  	}
  1045  }
  1046  
  1047  // AttrCgoExportStatic returns true for a symbol that has been
  1048  // specially marked via the "cgo_export_static" directive
  1049  // written by cgo.
  1050  func (l *Loader) AttrCgoExportStatic(i Sym) bool {
  1051  	_, ok := l.attrCgoExportStatic[i]
  1052  	return ok
  1053  }
  1054  
  1055  // SetAttrCgoExportStatic sets the "cgo_export_static" for a symbol
  1056  // (see AttrCgoExportStatic).
  1057  func (l *Loader) SetAttrCgoExportStatic(i Sym, v bool) {
  1058  	if v {
  1059  		l.attrCgoExportStatic[i] = struct{}{}
  1060  	} else {
  1061  		delete(l.attrCgoExportStatic, i)
  1062  	}
  1063  }
  1064  
  1065  // IsGeneratedSym returns true if a symbol's been previously marked as a
  1066  // generator symbol through the SetIsGeneratedSym. The functions for generator
  1067  // symbols are kept in the Link context.
  1068  func (l *Loader) IsGeneratedSym(i Sym) bool {
  1069  	if !l.IsExternal(i) {
  1070  		return false
  1071  	}
  1072  	return l.generatedSyms.Has(l.extIndex(i))
  1073  }
  1074  
  1075  // SetIsGeneratedSym marks symbols as generated symbols. Data shouldn't be
  1076  // stored in generated symbols, and a function is registered and called for
  1077  // each of these symbols.
  1078  func (l *Loader) SetIsGeneratedSym(i Sym, v bool) {
  1079  	if !l.IsExternal(i) {
  1080  		panic("only external symbols can be generated")
  1081  	}
  1082  	if v {
  1083  		l.generatedSyms.Set(l.extIndex(i))
  1084  	} else {
  1085  		l.generatedSyms.Unset(l.extIndex(i))
  1086  	}
  1087  }
  1088  
  1089  func (l *Loader) AttrCgoExport(i Sym) bool {
  1090  	return l.AttrCgoExportDynamic(i) || l.AttrCgoExportStatic(i)
  1091  }
  1092  
  1093  // AttrReadOnly returns true for a symbol whose underlying data
  1094  // is stored via a read-only mmap.
  1095  func (l *Loader) AttrReadOnly(i Sym) bool {
  1096  	if v, ok := l.attrReadOnly[i]; ok {
  1097  		return v
  1098  	}
  1099  	if l.IsExternal(i) {
  1100  		pp := l.getPayload(i)
  1101  		if pp.objidx != 0 {
  1102  			return l.objs[pp.objidx].r.ReadOnly()
  1103  		}
  1104  		return false
  1105  	}
  1106  	r, _ := l.toLocal(i)
  1107  	return r.ReadOnly()
  1108  }
  1109  
  1110  // SetAttrReadOnly sets the "data is read only" property for a symbol
  1111  // (see AttrReadOnly).
  1112  func (l *Loader) SetAttrReadOnly(i Sym, v bool) {
  1113  	l.attrReadOnly[i] = v
  1114  }
  1115  
  1116  // AttrSubSymbol returns true for symbols that are listed as a
  1117  // sub-symbol of some other outer symbol. The sub/outer mechanism is
  1118  // used when loading host objects (sections from the host object
  1119  // become regular linker symbols and symbols go on the Sub list of
  1120  // their section) and for constructing the global offset table when
  1121  // internally linking a dynamic executable.
  1122  //
  1123  // Note that in later stages of the linker, we set Outer(S) to some
  1124  // container symbol C, but don't set Sub(C). Thus we have two
  1125  // distinct scenarios:
  1126  //
  1127  // - Outer symbol covers the address ranges of its sub-symbols.
  1128  //   Outer.Sub is set in this case.
  1129  // - Outer symbol doesn't cover the address ranges. It is zero-sized
  1130  //   and doesn't have sub-symbols. In the case, the inner symbol is
  1131  //   not actually a "SubSymbol". (Tricky!)
  1132  //
  1133  // This method returns TRUE only for sub-symbols in the first scenario.
  1134  //
  1135  // FIXME: would be better to do away with this and have a better way
  1136  // to represent container symbols.
  1137  
  1138  func (l *Loader) AttrSubSymbol(i Sym) bool {
  1139  	// we don't explicitly store this attribute any more -- return
  1140  	// a value based on the sub-symbol setting.
  1141  	o := l.OuterSym(i)
  1142  	if o == 0 {
  1143  		return false
  1144  	}
  1145  	return l.SubSym(o) != 0
  1146  }
  1147  
  1148  // Note that we don't have a 'SetAttrSubSymbol' method in the loader;
  1149  // clients should instead use the AddInteriorSym method to establish
  1150  // containment relationships for host object symbols.
  1151  
  1152  // Returns whether the i-th symbol has ReflectMethod attribute set.
  1153  func (l *Loader) IsReflectMethod(i Sym) bool {
  1154  	return l.SymAttr(i)&goobj.SymFlagReflectMethod != 0
  1155  }
  1156  
  1157  // Returns whether the i-th symbol is nosplit.
  1158  func (l *Loader) IsNoSplit(i Sym) bool {
  1159  	return l.SymAttr(i)&goobj.SymFlagNoSplit != 0
  1160  }
  1161  
  1162  // Returns whether this is a Go type symbol.
  1163  func (l *Loader) IsGoType(i Sym) bool {
  1164  	return l.SymAttr(i)&goobj.SymFlagGoType != 0
  1165  }
  1166  
  1167  // Returns whether this symbol should be included in typelink.
  1168  func (l *Loader) IsTypelink(i Sym) bool {
  1169  	return l.SymAttr(i)&goobj.SymFlagTypelink != 0
  1170  }
  1171  
  1172  // Returns whether this symbol is an itab symbol.
  1173  func (l *Loader) IsItab(i Sym) bool {
  1174  	if l.IsExternal(i) {
  1175  		return false
  1176  	}
  1177  	r, li := l.toLocal(i)
  1178  	return r.Sym(li).IsItab()
  1179  }
  1180  
  1181  // Returns whether this symbol is a dictionary symbol.
  1182  func (l *Loader) IsDict(i Sym) bool {
  1183  	if l.IsExternal(i) {
  1184  		return false
  1185  	}
  1186  	r, li := l.toLocal(i)
  1187  	return r.Sym(li).IsDict()
  1188  }
  1189  
  1190  // Returns whether this symbol is a compiler-generated package init func.
  1191  func (l *Loader) IsPkgInit(i Sym) bool {
  1192  	if l.IsExternal(i) {
  1193  		return false
  1194  	}
  1195  	r, li := l.toLocal(i)
  1196  	return r.Sym(li).IsPkgInit()
  1197  }
  1198  
  1199  // Return whether this is a trampoline of a deferreturn call.
  1200  func (l *Loader) IsDeferReturnTramp(i Sym) bool {
  1201  	return l.deferReturnTramp[i]
  1202  }
  1203  
  1204  // Set that i is a trampoline of a deferreturn call.
  1205  func (l *Loader) SetIsDeferReturnTramp(i Sym, v bool) {
  1206  	l.deferReturnTramp[i] = v
  1207  }
  1208  
  1209  // growValues grows the slice used to store symbol values.
  1210  func (l *Loader) growValues(reqLen int) {
  1211  	curLen := len(l.values)
  1212  	if reqLen > curLen {
  1213  		l.values = append(l.values, make([]int64, reqLen+1-curLen)...)
  1214  	}
  1215  }
  1216  
  1217  // SymValue returns the value of the i-th symbol. i is global index.
  1218  func (l *Loader) SymValue(i Sym) int64 {
  1219  	return l.values[i]
  1220  }
  1221  
  1222  // SetSymValue sets the value of the i-th symbol. i is global index.
  1223  func (l *Loader) SetSymValue(i Sym, val int64) {
  1224  	l.values[i] = val
  1225  }
  1226  
  1227  // AddToSymValue adds to the value of the i-th symbol. i is the global index.
  1228  func (l *Loader) AddToSymValue(i Sym, val int64) {
  1229  	l.values[i] += val
  1230  }
  1231  
  1232  // Returns the symbol content of the i-th symbol. i is global index.
  1233  func (l *Loader) Data(i Sym) []byte {
  1234  	if l.IsExternal(i) {
  1235  		pp := l.getPayload(i)
  1236  		if pp != nil {
  1237  			return pp.data
  1238  		}
  1239  		return nil
  1240  	}
  1241  	r, li := l.toLocal(i)
  1242  	return r.Data(li)
  1243  }
  1244  
  1245  // Returns the symbol content of the i-th symbol as a string. i is global index.
  1246  func (l *Loader) DataString(i Sym) string {
  1247  	if l.IsExternal(i) {
  1248  		pp := l.getPayload(i)
  1249  		return string(pp.data)
  1250  	}
  1251  	r, li := l.toLocal(i)
  1252  	return r.DataString(li)
  1253  }
  1254  
  1255  // FreeData clears the symbol data of an external symbol, allowing the memory
  1256  // to be freed earlier. No-op for non-external symbols.
  1257  // i is global index.
  1258  func (l *Loader) FreeData(i Sym) {
  1259  	if l.IsExternal(i) {
  1260  		pp := l.getPayload(i)
  1261  		if pp != nil {
  1262  			pp.data = nil
  1263  		}
  1264  	}
  1265  }
  1266  
  1267  // SymAlign returns the alignment for a symbol.
  1268  func (l *Loader) SymAlign(i Sym) int32 {
  1269  	if int(i) >= len(l.align) {
  1270  		// align is extended lazily -- it the sym in question is
  1271  		// outside the range of the existing slice, then we assume its
  1272  		// alignment has not yet been set.
  1273  		return 0
  1274  	}
  1275  	// TODO: would it make sense to return an arch-specific
  1276  	// alignment depending on section type? E.g. STEXT => 32,
  1277  	// SDATA => 1, etc?
  1278  	abits := l.align[i]
  1279  	if abits == 0 {
  1280  		return 0
  1281  	}
  1282  	return int32(1 << (abits - 1))
  1283  }
  1284  
  1285  // SetSymAlign sets the alignment for a symbol.
  1286  func (l *Loader) SetSymAlign(i Sym, align int32) {
  1287  	// Reject nonsense alignments.
  1288  	if align < 0 || align&(align-1) != 0 {
  1289  		panic("bad alignment value")
  1290  	}
  1291  	if int(i) >= len(l.align) {
  1292  		l.align = append(l.align, make([]uint8, l.NSym()-len(l.align))...)
  1293  	}
  1294  	if align == 0 {
  1295  		l.align[i] = 0
  1296  	}
  1297  	l.align[i] = uint8(bits.Len32(uint32(align)))
  1298  }
  1299  
  1300  // SymSect returns the section of the i-th symbol. i is global index.
  1301  func (l *Loader) SymSect(i Sym) *sym.Section {
  1302  	if int(i) >= len(l.symSects) {
  1303  		// symSects is extended lazily -- it the sym in question is
  1304  		// outside the range of the existing slice, then we assume its
  1305  		// section has not yet been set.
  1306  		return nil
  1307  	}
  1308  	return l.sects[l.symSects[i]]
  1309  }
  1310  
  1311  // SetSymSect sets the section of the i-th symbol. i is global index.
  1312  func (l *Loader) SetSymSect(i Sym, sect *sym.Section) {
  1313  	if int(i) >= len(l.symSects) {
  1314  		l.symSects = append(l.symSects, make([]uint16, l.NSym()-len(l.symSects))...)
  1315  	}
  1316  	l.symSects[i] = sect.Index
  1317  }
  1318  
  1319  // NewSection creates a new (output) section.
  1320  func (l *Loader) NewSection() *sym.Section {
  1321  	sect := new(sym.Section)
  1322  	idx := len(l.sects)
  1323  	if idx != int(uint16(idx)) {
  1324  		panic("too many sections created")
  1325  	}
  1326  	sect.Index = uint16(idx)
  1327  	l.sects = append(l.sects, sect)
  1328  	return sect
  1329  }
  1330  
  1331  // SymDynimplib returns the "dynimplib" attribute for the specified
  1332  // symbol, making up a portion of the info for a symbol specified
  1333  // on a "cgo_import_dynamic" compiler directive.
  1334  func (l *Loader) SymDynimplib(i Sym) string {
  1335  	return l.dynimplib[i]
  1336  }
  1337  
  1338  // SetSymDynimplib sets the "dynimplib" attribute for a symbol.
  1339  func (l *Loader) SetSymDynimplib(i Sym, value string) {
  1340  	// reject bad symbols
  1341  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1342  		panic("bad symbol index in SetDynimplib")
  1343  	}
  1344  	if value == "" {
  1345  		delete(l.dynimplib, i)
  1346  	} else {
  1347  		l.dynimplib[i] = value
  1348  	}
  1349  }
  1350  
  1351  // SymDynimpvers returns the "dynimpvers" attribute for the specified
  1352  // symbol, making up a portion of the info for a symbol specified
  1353  // on a "cgo_import_dynamic" compiler directive.
  1354  func (l *Loader) SymDynimpvers(i Sym) string {
  1355  	return l.dynimpvers[i]
  1356  }
  1357  
  1358  // SetSymDynimpvers sets the "dynimpvers" attribute for a symbol.
  1359  func (l *Loader) SetSymDynimpvers(i Sym, value string) {
  1360  	// reject bad symbols
  1361  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1362  		panic("bad symbol index in SetDynimpvers")
  1363  	}
  1364  	if value == "" {
  1365  		delete(l.dynimpvers, i)
  1366  	} else {
  1367  		l.dynimpvers[i] = value
  1368  	}
  1369  }
  1370  
  1371  // SymExtname returns the "extname" value for the specified
  1372  // symbol.
  1373  func (l *Loader) SymExtname(i Sym) string {
  1374  	if s, ok := l.extname[i]; ok {
  1375  		return s
  1376  	}
  1377  	return l.SymName(i)
  1378  }
  1379  
  1380  // SetSymExtname sets the  "extname" attribute for a symbol.
  1381  func (l *Loader) SetSymExtname(i Sym, value string) {
  1382  	// reject bad symbols
  1383  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1384  		panic("bad symbol index in SetExtname")
  1385  	}
  1386  	if value == "" {
  1387  		delete(l.extname, i)
  1388  	} else {
  1389  		l.extname[i] = value
  1390  	}
  1391  }
  1392  
  1393  // SymElfType returns the previously recorded ELF type for a symbol
  1394  // (used only for symbols read from shared libraries by ldshlibsyms).
  1395  // It is not set for symbols defined by the packages being linked or
  1396  // by symbols read by ldelf (and so is left as elf.STT_NOTYPE).
  1397  func (l *Loader) SymElfType(i Sym) elf.SymType {
  1398  	if et, ok := l.elfType[i]; ok {
  1399  		return et
  1400  	}
  1401  	return elf.STT_NOTYPE
  1402  }
  1403  
  1404  // SetSymElfType sets the elf type attribute for a symbol.
  1405  func (l *Loader) SetSymElfType(i Sym, et elf.SymType) {
  1406  	// reject bad symbols
  1407  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1408  		panic("bad symbol index in SetSymElfType")
  1409  	}
  1410  	if et == elf.STT_NOTYPE {
  1411  		delete(l.elfType, i)
  1412  	} else {
  1413  		l.elfType[i] = et
  1414  	}
  1415  }
  1416  
  1417  // SymElfSym returns the ELF symbol index for a given loader
  1418  // symbol, assigned during ELF symtab generation.
  1419  func (l *Loader) SymElfSym(i Sym) int32 {
  1420  	return l.elfSym[i]
  1421  }
  1422  
  1423  // SetSymElfSym sets the elf symbol index for a symbol.
  1424  func (l *Loader) SetSymElfSym(i Sym, es int32) {
  1425  	if i == 0 {
  1426  		panic("bad sym index")
  1427  	}
  1428  	if es == 0 {
  1429  		delete(l.elfSym, i)
  1430  	} else {
  1431  		l.elfSym[i] = es
  1432  	}
  1433  }
  1434  
  1435  // SymLocalElfSym returns the "local" ELF symbol index for a given loader
  1436  // symbol, assigned during ELF symtab generation.
  1437  func (l *Loader) SymLocalElfSym(i Sym) int32 {
  1438  	return l.localElfSym[i]
  1439  }
  1440  
  1441  // SetSymLocalElfSym sets the "local" elf symbol index for a symbol.
  1442  func (l *Loader) SetSymLocalElfSym(i Sym, es int32) {
  1443  	if i == 0 {
  1444  		panic("bad sym index")
  1445  	}
  1446  	if es == 0 {
  1447  		delete(l.localElfSym, i)
  1448  	} else {
  1449  		l.localElfSym[i] = es
  1450  	}
  1451  }
  1452  
  1453  // SymPlt returns the PLT offset of symbol s.
  1454  func (l *Loader) SymPlt(s Sym) int32 {
  1455  	if v, ok := l.plt[s]; ok {
  1456  		return v
  1457  	}
  1458  	return -1
  1459  }
  1460  
  1461  // SetPlt sets the PLT offset of symbol i.
  1462  func (l *Loader) SetPlt(i Sym, v int32) {
  1463  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1464  		panic("bad symbol for SetPlt")
  1465  	}
  1466  	if v == -1 {
  1467  		delete(l.plt, i)
  1468  	} else {
  1469  		l.plt[i] = v
  1470  	}
  1471  }
  1472  
  1473  // SymGot returns the GOT offset of symbol s.
  1474  func (l *Loader) SymGot(s Sym) int32 {
  1475  	if v, ok := l.got[s]; ok {
  1476  		return v
  1477  	}
  1478  	return -1
  1479  }
  1480  
  1481  // SetGot sets the GOT offset of symbol i.
  1482  func (l *Loader) SetGot(i Sym, v int32) {
  1483  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1484  		panic("bad symbol for SetGot")
  1485  	}
  1486  	if v == -1 {
  1487  		delete(l.got, i)
  1488  	} else {
  1489  		l.got[i] = v
  1490  	}
  1491  }
  1492  
  1493  // SymDynid returns the "dynid" property for the specified symbol.
  1494  func (l *Loader) SymDynid(i Sym) int32 {
  1495  	if s, ok := l.dynid[i]; ok {
  1496  		return s
  1497  	}
  1498  	return -1
  1499  }
  1500  
  1501  // SetSymDynid sets the "dynid" property for a symbol.
  1502  func (l *Loader) SetSymDynid(i Sym, val int32) {
  1503  	// reject bad symbols
  1504  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1505  		panic("bad symbol index in SetSymDynid")
  1506  	}
  1507  	if val == -1 {
  1508  		delete(l.dynid, i)
  1509  	} else {
  1510  		l.dynid[i] = val
  1511  	}
  1512  }
  1513  
  1514  // DynidSyms returns the set of symbols for which dynID is set to an
  1515  // interesting (non-default) value. This is expected to be a fairly
  1516  // small set.
  1517  func (l *Loader) DynidSyms() []Sym {
  1518  	sl := make([]Sym, 0, len(l.dynid))
  1519  	for s := range l.dynid {
  1520  		sl = append(sl, s)
  1521  	}
  1522  	sort.Slice(sl, func(i, j int) bool { return sl[i] < sl[j] })
  1523  	return sl
  1524  }
  1525  
  1526  // SymGoType returns the 'Gotype' property for a given symbol (set by
  1527  // the Go compiler for variable symbols). This version relies on
  1528  // reading aux symbols for the target sym -- it could be that a faster
  1529  // approach would be to check for gotype during preload and copy the
  1530  // results in to a map (might want to try this at some point and see
  1531  // if it helps speed things up).
  1532  func (l *Loader) SymGoType(i Sym) Sym { return l.aux1(i, goobj.AuxGotype) }
  1533  
  1534  // SymUnit returns the compilation unit for a given symbol (which will
  1535  // typically be nil for external or linker-manufactured symbols).
  1536  func (l *Loader) SymUnit(i Sym) *sym.CompilationUnit {
  1537  	if l.IsExternal(i) {
  1538  		pp := l.getPayload(i)
  1539  		if pp.objidx != 0 {
  1540  			r := l.objs[pp.objidx].r
  1541  			return r.unit
  1542  		}
  1543  		return nil
  1544  	}
  1545  	r, _ := l.toLocal(i)
  1546  	return r.unit
  1547  }
  1548  
  1549  // SymPkg returns the package where the symbol came from (for
  1550  // regular compiler-generated Go symbols), but in the case of
  1551  // building with "-linkshared" (when a symbol is read from a
  1552  // shared library), will hold the library name.
  1553  // NOTE: this corresponds to sym.Symbol.File field.
  1554  func (l *Loader) SymPkg(i Sym) string {
  1555  	if f, ok := l.symPkg[i]; ok {
  1556  		return f
  1557  	}
  1558  	if l.IsExternal(i) {
  1559  		pp := l.getPayload(i)
  1560  		if pp.objidx != 0 {
  1561  			r := l.objs[pp.objidx].r
  1562  			return r.unit.Lib.Pkg
  1563  		}
  1564  		return ""
  1565  	}
  1566  	r, _ := l.toLocal(i)
  1567  	return r.unit.Lib.Pkg
  1568  }
  1569  
  1570  // SetSymPkg sets the package/library for a symbol. This is
  1571  // needed mainly for external symbols, specifically those imported
  1572  // from shared libraries.
  1573  func (l *Loader) SetSymPkg(i Sym, pkg string) {
  1574  	// reject bad symbols
  1575  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1576  		panic("bad symbol index in SetSymPkg")
  1577  	}
  1578  	l.symPkg[i] = pkg
  1579  }
  1580  
  1581  // SymLocalentry returns an offset in bytes of the "local entry" of a symbol.
  1582  //
  1583  // On PPC64, a value of 1 indicates the symbol does not use or preserve a TOC
  1584  // pointer in R2, nor does it have a distinct local entry.
  1585  func (l *Loader) SymLocalentry(i Sym) uint8 {
  1586  	return l.localentry[i]
  1587  }
  1588  
  1589  // SetSymLocalentry sets the "local entry" offset attribute for a symbol.
  1590  func (l *Loader) SetSymLocalentry(i Sym, value uint8) {
  1591  	// reject bad symbols
  1592  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1593  		panic("bad symbol index in SetSymLocalentry")
  1594  	}
  1595  	if value == 0 {
  1596  		delete(l.localentry, i)
  1597  	} else {
  1598  		l.localentry[i] = value
  1599  	}
  1600  }
  1601  
  1602  // Returns the number of aux symbols given a global index.
  1603  func (l *Loader) NAux(i Sym) int {
  1604  	if l.IsExternal(i) {
  1605  		return 0
  1606  	}
  1607  	r, li := l.toLocal(i)
  1608  	return r.NAux(li)
  1609  }
  1610  
  1611  // Returns the "handle" to the j-th aux symbol of the i-th symbol.
  1612  func (l *Loader) Aux(i Sym, j int) Aux {
  1613  	if l.IsExternal(i) {
  1614  		return Aux{}
  1615  	}
  1616  	r, li := l.toLocal(i)
  1617  	if j >= r.NAux(li) {
  1618  		return Aux{}
  1619  	}
  1620  	return Aux{r.Aux(li, j), r, l}
  1621  }
  1622  
  1623  // WasmImportSym returns the auxiliary WebAssembly import symbol associated with
  1624  // a given function symbol. The aux sym only exists for Go function stubs that
  1625  // have been annotated with the //go:wasmimport directive.  The aux sym
  1626  // contains the information necessary for the linker to add a WebAssembly
  1627  // import statement.
  1628  // (https://webassembly.github.io/spec/core/syntax/modules.html#imports)
  1629  func (l *Loader) WasmImportSym(fnSymIdx Sym) (Sym, bool) {
  1630  	if l.SymType(fnSymIdx) != sym.STEXT {
  1631  		log.Fatalf("error: non-function sym %d/%s t=%s passed to WasmImportSym", fnSymIdx, l.SymName(fnSymIdx), l.SymType(fnSymIdx).String())
  1632  	}
  1633  	r, li := l.toLocal(fnSymIdx)
  1634  	auxs := r.Auxs(li)
  1635  	for i := range auxs {
  1636  		a := &auxs[i]
  1637  		switch a.Type() {
  1638  		case goobj.AuxWasmImport:
  1639  			return l.resolve(r, a.Sym()), true
  1640  		}
  1641  	}
  1642  
  1643  	return 0, false
  1644  }
  1645  
  1646  // SEHUnwindSym returns the auxiliary SEH unwind symbol associated with
  1647  // a given function symbol.
  1648  func (l *Loader) SEHUnwindSym(fnSymIdx Sym) Sym {
  1649  	if l.SymType(fnSymIdx) != sym.STEXT {
  1650  		log.Fatalf("error: non-function sym %d/%s t=%s passed to SEHUnwindSym", fnSymIdx, l.SymName(fnSymIdx), l.SymType(fnSymIdx).String())
  1651  	}
  1652  
  1653  	return l.aux1(fnSymIdx, goobj.AuxSehUnwindInfo)
  1654  }
  1655  
  1656  // GetFuncDwarfAuxSyms collects and returns the auxiliary DWARF
  1657  // symbols associated with a given function symbol.  Prior to the
  1658  // introduction of the loader, this was done purely using name
  1659  // lookups, e.f. for function with name XYZ we would then look up
  1660  // go.info.XYZ, etc.
  1661  func (l *Loader) GetFuncDwarfAuxSyms(fnSymIdx Sym) (auxDwarfInfo, auxDwarfLoc, auxDwarfRanges, auxDwarfLines Sym) {
  1662  	if l.SymType(fnSymIdx) != sym.STEXT {
  1663  		log.Fatalf("error: non-function sym %d/%s t=%s passed to GetFuncDwarfAuxSyms", fnSymIdx, l.SymName(fnSymIdx), l.SymType(fnSymIdx).String())
  1664  	}
  1665  	r, auxs := l.auxs(fnSymIdx)
  1666  
  1667  	for i := range auxs {
  1668  		a := &auxs[i]
  1669  		switch a.Type() {
  1670  		case goobj.AuxDwarfInfo:
  1671  			auxDwarfInfo = l.resolve(r, a.Sym())
  1672  			if l.SymType(auxDwarfInfo) != sym.SDWARFFCN {
  1673  				panic("aux dwarf info sym with wrong type")
  1674  			}
  1675  		case goobj.AuxDwarfLoc:
  1676  			auxDwarfLoc = l.resolve(r, a.Sym())
  1677  			if l.SymType(auxDwarfLoc) != sym.SDWARFLOC {
  1678  				panic("aux dwarf loc sym with wrong type")
  1679  			}
  1680  		case goobj.AuxDwarfRanges:
  1681  			auxDwarfRanges = l.resolve(r, a.Sym())
  1682  			if l.SymType(auxDwarfRanges) != sym.SDWARFRANGE {
  1683  				panic("aux dwarf ranges sym with wrong type")
  1684  			}
  1685  		case goobj.AuxDwarfLines:
  1686  			auxDwarfLines = l.resolve(r, a.Sym())
  1687  			if l.SymType(auxDwarfLines) != sym.SDWARFLINES {
  1688  				panic("aux dwarf lines sym with wrong type")
  1689  			}
  1690  		}
  1691  	}
  1692  	return
  1693  }
  1694  
  1695  func (l *Loader) GetVarDwarfAuxSym(i Sym) Sym {
  1696  	aux := l.aux1(i, goobj.AuxDwarfInfo)
  1697  	if aux != 0 && l.SymType(aux) != sym.SDWARFVAR {
  1698  		fmt.Println(l.SymName(i), l.SymType(i), l.SymType(aux), sym.SDWARFVAR)
  1699  		panic("aux dwarf info sym with wrong type")
  1700  	}
  1701  	return aux
  1702  }
  1703  
  1704  // AddInteriorSym sets up 'interior' as an interior symbol of
  1705  // container/payload symbol 'container'. An interior symbol does not
  1706  // itself have data, but gives a name to a subrange of the data in its
  1707  // container symbol. The container itself may or may not have a name.
  1708  // This method is intended primarily for use in the host object
  1709  // loaders, to capture the semantics of symbols and sections in an
  1710  // object file. When reading a host object file, we'll typically
  1711  // encounter a static section symbol (ex: ".text") containing content
  1712  // for a collection of functions, then a series of ELF (or macho, etc)
  1713  // symbol table entries each of which points into a sub-section
  1714  // (offset and length) of its corresponding container symbol. Within
  1715  // the go linker we create a loader.Sym for the container (which is
  1716  // expected to have the actual content/payload) and then a set of
  1717  // interior loader.Sym's that point into a portion of the container.
  1718  func (l *Loader) AddInteriorSym(container Sym, interior Sym) {
  1719  	// Container symbols are expected to have content/data.
  1720  	// NB: this restriction may turn out to be too strict (it's possible
  1721  	// to imagine a zero-sized container with an interior symbol pointing
  1722  	// into it); it's ok to relax or remove it if we counter an
  1723  	// oddball host object that triggers this.
  1724  	if l.SymSize(container) == 0 && len(l.Data(container)) == 0 {
  1725  		panic("unexpected empty container symbol")
  1726  	}
  1727  	// The interior symbols for a container are not expected to have
  1728  	// content/data or relocations.
  1729  	if len(l.Data(interior)) != 0 {
  1730  		panic("unexpected non-empty interior symbol")
  1731  	}
  1732  	// Interior symbol is expected to be in the symbol table.
  1733  	if l.AttrNotInSymbolTable(interior) {
  1734  		panic("interior symbol must be in symtab")
  1735  	}
  1736  	// Only a single level of containment is allowed.
  1737  	if l.OuterSym(container) != 0 {
  1738  		panic("outer has outer itself")
  1739  	}
  1740  	// Interior sym should not already have a sibling.
  1741  	if l.SubSym(interior) != 0 {
  1742  		panic("sub set for subsym")
  1743  	}
  1744  	// Interior sym should not already point at a container.
  1745  	if l.OuterSym(interior) != 0 {
  1746  		panic("outer already set for subsym")
  1747  	}
  1748  	l.sub[interior] = l.sub[container]
  1749  	l.sub[container] = interior
  1750  	l.outer[interior] = container
  1751  }
  1752  
  1753  // OuterSym gets the outer/container symbol.
  1754  func (l *Loader) OuterSym(i Sym) Sym {
  1755  	return l.outer[i]
  1756  }
  1757  
  1758  // SubSym gets the subsymbol for host object loaded symbols.
  1759  func (l *Loader) SubSym(i Sym) Sym {
  1760  	return l.sub[i]
  1761  }
  1762  
  1763  // growOuter grows the slice used to store outer symbol.
  1764  func (l *Loader) growOuter(reqLen int) {
  1765  	curLen := len(l.outer)
  1766  	if reqLen > curLen {
  1767  		l.outer = append(l.outer, make([]Sym, reqLen-curLen)...)
  1768  	}
  1769  }
  1770  
  1771  // SetCarrierSym declares that 'c' is the carrier or container symbol
  1772  // for 's'. Carrier symbols are used in the linker to as a container
  1773  // for a collection of sub-symbols where the content of the
  1774  // sub-symbols is effectively concatenated to form the content of the
  1775  // carrier. The carrier is given a name in the output symbol table
  1776  // while the sub-symbol names are not. For example, the Go compiler
  1777  // emits named string symbols (type SGOSTRING) when compiling a
  1778  // package; after being deduplicated, these symbols are collected into
  1779  // a single unit by assigning them a new carrier symbol named
  1780  // "go:string.*" (which appears in the final symbol table for the
  1781  // output load module).
  1782  func (l *Loader) SetCarrierSym(s Sym, c Sym) {
  1783  	if c == 0 {
  1784  		panic("invalid carrier in SetCarrierSym")
  1785  	}
  1786  	if s == 0 {
  1787  		panic("invalid sub-symbol in SetCarrierSym")
  1788  	}
  1789  	// Carrier symbols are not expected to have content/data. It is
  1790  	// ok for them to have non-zero size (to allow for use of generator
  1791  	// symbols).
  1792  	if len(l.Data(c)) != 0 {
  1793  		panic("unexpected non-empty carrier symbol")
  1794  	}
  1795  	l.outer[s] = c
  1796  	// relocsym's foldSubSymbolOffset requires that we only
  1797  	// have a single level of containment-- enforce here.
  1798  	if l.outer[c] != 0 {
  1799  		panic("invalid nested carrier sym")
  1800  	}
  1801  }
  1802  
  1803  // Initialize Reachable bitmap and its siblings for running deadcode pass.
  1804  func (l *Loader) InitReachable() {
  1805  	l.growAttrBitmaps(l.NSym() + 1)
  1806  }
  1807  
  1808  type symWithVal struct {
  1809  	s Sym
  1810  	v int64
  1811  }
  1812  type bySymValue []symWithVal
  1813  
  1814  func (s bySymValue) Len() int           { return len(s) }
  1815  func (s bySymValue) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
  1816  func (s bySymValue) Less(i, j int) bool { return s[i].v < s[j].v }
  1817  
  1818  // SortSub walks through the sub-symbols for 's' and sorts them
  1819  // in place by increasing value. Return value is the new
  1820  // sub symbol for the specified outer symbol.
  1821  func (l *Loader) SortSub(s Sym) Sym {
  1822  
  1823  	if s == 0 || l.sub[s] == 0 {
  1824  		return s
  1825  	}
  1826  
  1827  	// Sort symbols using a slice first. Use a stable sort on the off
  1828  	// chance that there's more than once symbol with the same value,
  1829  	// so as to preserve reproducible builds.
  1830  	sl := []symWithVal{}
  1831  	for ss := l.sub[s]; ss != 0; ss = l.sub[ss] {
  1832  		sl = append(sl, symWithVal{s: ss, v: l.SymValue(ss)})
  1833  	}
  1834  	sort.Stable(bySymValue(sl))
  1835  
  1836  	// Then apply any changes needed to the sub map.
  1837  	ns := Sym(0)
  1838  	for i := len(sl) - 1; i >= 0; i-- {
  1839  		s := sl[i].s
  1840  		l.sub[s] = ns
  1841  		ns = s
  1842  	}
  1843  
  1844  	// Update sub for outer symbol, then return
  1845  	l.sub[s] = sl[0].s
  1846  	return sl[0].s
  1847  }
  1848  
  1849  // SortSyms sorts a list of symbols by their value.
  1850  func (l *Loader) SortSyms(ss []Sym) {
  1851  	sort.SliceStable(ss, func(i, j int) bool { return l.SymValue(ss[i]) < l.SymValue(ss[j]) })
  1852  }
  1853  
  1854  // Insure that reachable bitmap and its siblings have enough size.
  1855  func (l *Loader) growAttrBitmaps(reqLen int) {
  1856  	if reqLen > l.attrReachable.Len() {
  1857  		// These are indexed by global symbol
  1858  		l.attrReachable = growBitmap(reqLen, l.attrReachable)
  1859  		l.attrOnList = growBitmap(reqLen, l.attrOnList)
  1860  		l.attrLocal = growBitmap(reqLen, l.attrLocal)
  1861  		l.attrNotInSymbolTable = growBitmap(reqLen, l.attrNotInSymbolTable)
  1862  		l.attrUsedInIface = growBitmap(reqLen, l.attrUsedInIface)
  1863  		l.attrSpecial = growBitmap(reqLen, l.attrSpecial)
  1864  	}
  1865  	l.growExtAttrBitmaps()
  1866  }
  1867  
  1868  func (l *Loader) growExtAttrBitmaps() {
  1869  	// These are indexed by external symbol index (e.g. l.extIndex(i))
  1870  	extReqLen := len(l.payloads)
  1871  	if extReqLen > l.attrVisibilityHidden.Len() {
  1872  		l.attrVisibilityHidden = growBitmap(extReqLen, l.attrVisibilityHidden)
  1873  		l.attrDuplicateOK = growBitmap(extReqLen, l.attrDuplicateOK)
  1874  		l.attrShared = growBitmap(extReqLen, l.attrShared)
  1875  		l.attrExternal = growBitmap(extReqLen, l.attrExternal)
  1876  		l.generatedSyms = growBitmap(extReqLen, l.generatedSyms)
  1877  	}
  1878  }
  1879  
  1880  func (relocs *Relocs) Count() int { return len(relocs.rs) }
  1881  
  1882  // At returns the j-th reloc for a global symbol.
  1883  func (relocs *Relocs) At(j int) Reloc {
  1884  	if relocs.l.isExtReader(relocs.r) {
  1885  		return Reloc{&relocs.rs[j], relocs.r, relocs.l}
  1886  	}
  1887  	return Reloc{&relocs.rs[j], relocs.r, relocs.l}
  1888  }
  1889  
  1890  // Relocs returns a Relocs object for the given global sym.
  1891  func (l *Loader) Relocs(i Sym) Relocs {
  1892  	r, li := l.toLocal(i)
  1893  	if r == nil {
  1894  		panic(fmt.Sprintf("trying to get oreader for invalid sym %d\n\n", i))
  1895  	}
  1896  	return l.relocs(r, li)
  1897  }
  1898  
  1899  // relocs returns a Relocs object given a local sym index and reader.
  1900  func (l *Loader) relocs(r *oReader, li uint32) Relocs {
  1901  	var rs []goobj.Reloc
  1902  	if l.isExtReader(r) {
  1903  		pp := l.payloads[li]
  1904  		rs = pp.relocs
  1905  	} else {
  1906  		rs = r.Relocs(li)
  1907  	}
  1908  	return Relocs{
  1909  		rs: rs,
  1910  		li: li,
  1911  		r:  r,
  1912  		l:  l,
  1913  	}
  1914  }
  1915  
  1916  func (l *Loader) auxs(i Sym) (*oReader, []goobj.Aux) {
  1917  	if l.IsExternal(i) {
  1918  		pp := l.getPayload(i)
  1919  		return l.objs[pp.objidx].r, pp.auxs
  1920  	} else {
  1921  		r, li := l.toLocal(i)
  1922  		return r, r.Auxs(li)
  1923  	}
  1924  }
  1925  
  1926  // Returns a specific aux symbol of type t for symbol i.
  1927  func (l *Loader) aux1(i Sym, t uint8) Sym {
  1928  	r, auxs := l.auxs(i)
  1929  	for j := range auxs {
  1930  		a := &auxs[j]
  1931  		if a.Type() == t {
  1932  			return l.resolve(r, a.Sym())
  1933  		}
  1934  	}
  1935  	return 0
  1936  }
  1937  
  1938  func (l *Loader) Pcsp(i Sym) Sym { return l.aux1(i, goobj.AuxPcsp) }
  1939  
  1940  // Returns all aux symbols of per-PC data for symbol i.
  1941  // tmp is a scratch space for the pcdata slice.
  1942  func (l *Loader) PcdataAuxs(i Sym, tmp []Sym) (pcsp, pcfile, pcline, pcinline Sym, pcdata []Sym) {
  1943  	pcdata = tmp[:0]
  1944  	r, auxs := l.auxs(i)
  1945  	for j := range auxs {
  1946  		a := &auxs[j]
  1947  		switch a.Type() {
  1948  		case goobj.AuxPcsp:
  1949  			pcsp = l.resolve(r, a.Sym())
  1950  		case goobj.AuxPcline:
  1951  			pcline = l.resolve(r, a.Sym())
  1952  		case goobj.AuxPcfile:
  1953  			pcfile = l.resolve(r, a.Sym())
  1954  		case goobj.AuxPcinline:
  1955  			pcinline = l.resolve(r, a.Sym())
  1956  		case goobj.AuxPcdata:
  1957  			pcdata = append(pcdata, l.resolve(r, a.Sym()))
  1958  		}
  1959  	}
  1960  	return
  1961  }
  1962  
  1963  // Returns the number of pcdata for symbol i.
  1964  func (l *Loader) NumPcdata(i Sym) int {
  1965  	n := 0
  1966  	_, auxs := l.auxs(i)
  1967  	for j := range auxs {
  1968  		a := &auxs[j]
  1969  		if a.Type() == goobj.AuxPcdata {
  1970  			n++
  1971  		}
  1972  	}
  1973  	return n
  1974  }
  1975  
  1976  // Returns all funcdata symbols of symbol i.
  1977  // tmp is a scratch space.
  1978  func (l *Loader) Funcdata(i Sym, tmp []Sym) []Sym {
  1979  	fd := tmp[:0]
  1980  	r, auxs := l.auxs(i)
  1981  	for j := range auxs {
  1982  		a := &auxs[j]
  1983  		if a.Type() == goobj.AuxFuncdata {
  1984  			fd = append(fd, l.resolve(r, a.Sym()))
  1985  		}
  1986  	}
  1987  	return fd
  1988  }
  1989  
  1990  // Returns the number of funcdata for symbol i.
  1991  func (l *Loader) NumFuncdata(i Sym) int {
  1992  	n := 0
  1993  	_, auxs := l.auxs(i)
  1994  	for j := range auxs {
  1995  		a := &auxs[j]
  1996  		if a.Type() == goobj.AuxFuncdata {
  1997  			n++
  1998  		}
  1999  	}
  2000  	return n
  2001  }
  2002  
  2003  // FuncInfo provides hooks to access goobj.FuncInfo in the objects.
  2004  type FuncInfo struct {
  2005  	l       *Loader
  2006  	r       *oReader
  2007  	data    []byte
  2008  	lengths goobj.FuncInfoLengths
  2009  }
  2010  
  2011  func (fi *FuncInfo) Valid() bool { return fi.r != nil }
  2012  
  2013  func (fi *FuncInfo) Args() int {
  2014  	return int((*goobj.FuncInfo)(nil).ReadArgs(fi.data))
  2015  }
  2016  
  2017  func (fi *FuncInfo) Locals() int {
  2018  	return int((*goobj.FuncInfo)(nil).ReadLocals(fi.data))
  2019  }
  2020  
  2021  func (fi *FuncInfo) FuncID() abi.FuncID {
  2022  	return (*goobj.FuncInfo)(nil).ReadFuncID(fi.data)
  2023  }
  2024  
  2025  func (fi *FuncInfo) FuncFlag() abi.FuncFlag {
  2026  	return (*goobj.FuncInfo)(nil).ReadFuncFlag(fi.data)
  2027  }
  2028  
  2029  func (fi *FuncInfo) StartLine() int32 {
  2030  	return (*goobj.FuncInfo)(nil).ReadStartLine(fi.data)
  2031  }
  2032  
  2033  // Preload has to be called prior to invoking the various methods
  2034  // below related to pcdata, funcdataoff, files, and inltree nodes.
  2035  func (fi *FuncInfo) Preload() {
  2036  	fi.lengths = (*goobj.FuncInfo)(nil).ReadFuncInfoLengths(fi.data)
  2037  }
  2038  
  2039  func (fi *FuncInfo) NumFile() uint32 {
  2040  	if !fi.lengths.Initialized {
  2041  		panic("need to call Preload first")
  2042  	}
  2043  	return fi.lengths.NumFile
  2044  }
  2045  
  2046  func (fi *FuncInfo) File(k int) goobj.CUFileIndex {
  2047  	if !fi.lengths.Initialized {
  2048  		panic("need to call Preload first")
  2049  	}
  2050  	return (*goobj.FuncInfo)(nil).ReadFile(fi.data, fi.lengths.FileOff, uint32(k))
  2051  }
  2052  
  2053  // TopFrame returns true if the function associated with this FuncInfo
  2054  // is an entry point, meaning that unwinders should stop when they hit
  2055  // this function.
  2056  func (fi *FuncInfo) TopFrame() bool {
  2057  	return (fi.FuncFlag() & abi.FuncFlagTopFrame) != 0
  2058  }
  2059  
  2060  type InlTreeNode struct {
  2061  	Parent   int32
  2062  	File     goobj.CUFileIndex
  2063  	Line     int32
  2064  	Func     Sym
  2065  	ParentPC int32
  2066  }
  2067  
  2068  func (fi *FuncInfo) NumInlTree() uint32 {
  2069  	if !fi.lengths.Initialized {
  2070  		panic("need to call Preload first")
  2071  	}
  2072  	return fi.lengths.NumInlTree
  2073  }
  2074  
  2075  func (fi *FuncInfo) InlTree(k int) InlTreeNode {
  2076  	if !fi.lengths.Initialized {
  2077  		panic("need to call Preload first")
  2078  	}
  2079  	node := (*goobj.FuncInfo)(nil).ReadInlTree(fi.data, fi.lengths.InlTreeOff, uint32(k))
  2080  	return InlTreeNode{
  2081  		Parent:   node.Parent,
  2082  		File:     node.File,
  2083  		Line:     node.Line,
  2084  		Func:     fi.l.resolve(fi.r, node.Func),
  2085  		ParentPC: node.ParentPC,
  2086  	}
  2087  }
  2088  
  2089  func (l *Loader) FuncInfo(i Sym) FuncInfo {
  2090  	r, auxs := l.auxs(i)
  2091  	for j := range auxs {
  2092  		a := &auxs[j]
  2093  		if a.Type() == goobj.AuxFuncInfo {
  2094  			b := r.Data(a.Sym().SymIdx)
  2095  			return FuncInfo{l, r, b, goobj.FuncInfoLengths{}}
  2096  		}
  2097  	}
  2098  	return FuncInfo{}
  2099  }
  2100  
  2101  // Preload a package: adds autolib.
  2102  // Does not add defined package or non-packaged symbols to the symbol table.
  2103  // These are done in LoadSyms.
  2104  // Does not read symbol data.
  2105  // Returns the fingerprint of the object.
  2106  func (l *Loader) Preload(localSymVersion int, f *bio.Reader, lib *sym.Library, unit *sym.CompilationUnit, length int64) goobj.FingerprintType {
  2107  	roObject, readonly, err := f.Slice(uint64(length)) // TODO: no need to map blocks that are for tools only (e.g. RefName)
  2108  	if err != nil {
  2109  		log.Fatal("cannot read object file:", err)
  2110  	}
  2111  	r := goobj.NewReaderFromBytes(roObject, readonly)
  2112  	if r == nil {
  2113  		if len(roObject) >= 8 && bytes.Equal(roObject[:8], []byte("\x00go114ld")) {
  2114  			log.Fatalf("found object file %s in old format", f.File().Name())
  2115  		}
  2116  		panic("cannot read object file")
  2117  	}
  2118  	pkgprefix := objabi.PathToPrefix(lib.Pkg) + "."
  2119  	ndef := r.NSym()
  2120  	nhashed64def := r.NHashed64def()
  2121  	nhasheddef := r.NHasheddef()
  2122  	or := &oReader{
  2123  		Reader:       r,
  2124  		unit:         unit,
  2125  		version:      localSymVersion,
  2126  		pkgprefix:    pkgprefix,
  2127  		syms:         make([]Sym, ndef+nhashed64def+nhasheddef+r.NNonpkgdef()+r.NNonpkgref()),
  2128  		ndef:         ndef,
  2129  		nhasheddef:   nhasheddef,
  2130  		nhashed64def: nhashed64def,
  2131  		objidx:       uint32(len(l.objs)),
  2132  	}
  2133  
  2134  	if r.Unlinkable() {
  2135  		log.Fatalf("link: unlinkable object (from package %s) - compiler requires -p flag", lib.Pkg)
  2136  	}
  2137  
  2138  	// Autolib
  2139  	lib.Autolib = append(lib.Autolib, r.Autolib()...)
  2140  
  2141  	// DWARF file table
  2142  	nfile := r.NFile()
  2143  	unit.FileTable = make([]string, nfile)
  2144  	for i := range unit.FileTable {
  2145  		unit.FileTable[i] = r.File(i)
  2146  	}
  2147  
  2148  	l.addObj(lib.Pkg, or)
  2149  
  2150  	// The caller expects us consuming all the data
  2151  	f.MustSeek(length, io.SeekCurrent)
  2152  
  2153  	return r.Fingerprint()
  2154  }
  2155  
  2156  // Holds the loader along with temporary states for loading symbols.
  2157  type loadState struct {
  2158  	l            *Loader
  2159  	hashed64Syms map[uint64]symAndSize         // short hashed (content-addressable) symbols, keyed by content hash
  2160  	hashedSyms   map[goobj.HashType]symAndSize // hashed (content-addressable) symbols, keyed by content hash
  2161  }
  2162  
  2163  // Preload symbols of given kind from an object.
  2164  func (st *loadState) preloadSyms(r *oReader, kind int) {
  2165  	l := st.l
  2166  	var start, end uint32
  2167  	switch kind {
  2168  	case pkgDef:
  2169  		start = 0
  2170  		end = uint32(r.ndef)
  2171  	case hashed64Def:
  2172  		start = uint32(r.ndef)
  2173  		end = uint32(r.ndef + r.nhashed64def)
  2174  	case hashedDef:
  2175  		start = uint32(r.ndef + r.nhashed64def)
  2176  		end = uint32(r.ndef + r.nhashed64def + r.nhasheddef)
  2177  	case nonPkgDef:
  2178  		start = uint32(r.ndef + r.nhashed64def + r.nhasheddef)
  2179  		end = uint32(r.ndef + r.nhashed64def + r.nhasheddef + r.NNonpkgdef())
  2180  	default:
  2181  		panic("preloadSyms: bad kind")
  2182  	}
  2183  	l.growAttrBitmaps(len(l.objSyms) + int(end-start))
  2184  	loadingRuntimePkg := r.unit.Lib.Pkg == "runtime"
  2185  	for i := start; i < end; i++ {
  2186  		osym := r.Sym(i)
  2187  		var name string
  2188  		var v int
  2189  		if kind != hashed64Def && kind != hashedDef { // we don't need the name, etc. for hashed symbols
  2190  			name = osym.Name(r.Reader)
  2191  			v = abiToVer(osym.ABI(), r.version)
  2192  		}
  2193  		gi := st.addSym(name, v, r, i, kind, osym)
  2194  		r.syms[i] = gi
  2195  		if osym.Local() {
  2196  			l.SetAttrLocal(gi, true)
  2197  		}
  2198  		if osym.UsedInIface() {
  2199  			l.SetAttrUsedInIface(gi, true)
  2200  		}
  2201  		if strings.HasPrefix(name, "runtime.") ||
  2202  			(loadingRuntimePkg && strings.HasPrefix(name, "type:")) {
  2203  			if bi := goobj.BuiltinIdx(name, int(osym.ABI())); bi != -1 {
  2204  				// This is a definition of a builtin symbol. Record where it is.
  2205  				l.builtinSyms[bi] = gi
  2206  			}
  2207  		}
  2208  		if a := int32(osym.Align()); a != 0 && a > l.SymAlign(gi) {
  2209  			l.SetSymAlign(gi, a)
  2210  		}
  2211  	}
  2212  }
  2213  
  2214  // Add syms, hashed (content-addressable) symbols, non-package symbols, and
  2215  // references to external symbols (which are always named).
  2216  func (l *Loader) LoadSyms(arch *sys.Arch) {
  2217  	// Allocate space for symbols, making a guess as to how much space we need.
  2218  	// This function was determined empirically by looking at the cmd/compile on
  2219  	// Darwin, and picking factors for hashed and hashed64 syms.
  2220  	var symSize, hashedSize, hashed64Size int
  2221  	for _, o := range l.objs[goObjStart:] {
  2222  		symSize += o.r.ndef + o.r.nhasheddef/2 + o.r.nhashed64def/2 + o.r.NNonpkgdef()
  2223  		hashedSize += o.r.nhasheddef / 2
  2224  		hashed64Size += o.r.nhashed64def / 2
  2225  	}
  2226  	// Index 0 is invalid for symbols.
  2227  	l.objSyms = make([]objSym, 1, symSize)
  2228  
  2229  	st := loadState{
  2230  		l:            l,
  2231  		hashed64Syms: make(map[uint64]symAndSize, hashed64Size),
  2232  		hashedSyms:   make(map[goobj.HashType]symAndSize, hashedSize),
  2233  	}
  2234  
  2235  	for _, o := range l.objs[goObjStart:] {
  2236  		st.preloadSyms(o.r, pkgDef)
  2237  	}
  2238  	l.npkgsyms = l.NSym()
  2239  	for _, o := range l.objs[goObjStart:] {
  2240  		st.preloadSyms(o.r, hashed64Def)
  2241  		st.preloadSyms(o.r, hashedDef)
  2242  		st.preloadSyms(o.r, nonPkgDef)
  2243  	}
  2244  	l.nhashedsyms = len(st.hashed64Syms) + len(st.hashedSyms)
  2245  	for _, o := range l.objs[goObjStart:] {
  2246  		loadObjRefs(l, o.r, arch)
  2247  	}
  2248  	l.values = make([]int64, l.NSym(), l.NSym()+1000) // +1000 make some room for external symbols
  2249  	l.outer = make([]Sym, l.NSym(), l.NSym()+1000)
  2250  }
  2251  
  2252  func loadObjRefs(l *Loader, r *oReader, arch *sys.Arch) {
  2253  	// load non-package refs
  2254  	ndef := uint32(r.NAlldef())
  2255  	for i, n := uint32(0), uint32(r.NNonpkgref()); i < n; i++ {
  2256  		osym := r.Sym(ndef + i)
  2257  		name := osym.Name(r.Reader)
  2258  		v := abiToVer(osym.ABI(), r.version)
  2259  		r.syms[ndef+i] = l.LookupOrCreateSym(name, v)
  2260  		gi := r.syms[ndef+i]
  2261  		if osym.Local() {
  2262  			l.SetAttrLocal(gi, true)
  2263  		}
  2264  		if osym.UsedInIface() {
  2265  			l.SetAttrUsedInIface(gi, true)
  2266  		}
  2267  	}
  2268  
  2269  	// referenced packages
  2270  	npkg := r.NPkg()
  2271  	r.pkg = make([]uint32, npkg)
  2272  	for i := 1; i < npkg; i++ { // PkgIdx 0 is a dummy invalid package
  2273  		pkg := r.Pkg(i)
  2274  		objidx, ok := l.objByPkg[pkg]
  2275  		if !ok {
  2276  			log.Fatalf("%v: reference to nonexistent package %s", r.unit.Lib, pkg)
  2277  		}
  2278  		r.pkg[i] = objidx
  2279  	}
  2280  
  2281  	// load flags of package refs
  2282  	for i, n := 0, r.NRefFlags(); i < n; i++ {
  2283  		rf := r.RefFlags(i)
  2284  		gi := l.resolve(r, rf.Sym())
  2285  		if rf.Flag2()&goobj.SymFlagUsedInIface != 0 {
  2286  			l.SetAttrUsedInIface(gi, true)
  2287  		}
  2288  	}
  2289  }
  2290  
  2291  func abiToVer(abi uint16, localSymVersion int) int {
  2292  	var v int
  2293  	if abi == goobj.SymABIstatic {
  2294  		// Static
  2295  		v = localSymVersion
  2296  	} else if abiver := sym.ABIToVersion(obj.ABI(abi)); abiver != -1 {
  2297  		// Note that data symbols are "ABI0", which maps to version 0.
  2298  		v = abiver
  2299  	} else {
  2300  		log.Fatalf("invalid symbol ABI: %d", abi)
  2301  	}
  2302  	return v
  2303  }
  2304  
  2305  // TopLevelSym tests a symbol (by name and kind) to determine whether
  2306  // the symbol first class sym (participating in the link) or is an
  2307  // anonymous aux or sub-symbol containing some sub-part or payload of
  2308  // another symbol.
  2309  func (l *Loader) TopLevelSym(s Sym) bool {
  2310  	return topLevelSym(l.SymName(s), l.SymType(s))
  2311  }
  2312  
  2313  // topLevelSym tests a symbol name and kind to determine whether
  2314  // the symbol first class sym (participating in the link) or is an
  2315  // anonymous aux or sub-symbol containing some sub-part or payload of
  2316  // another symbol.
  2317  func topLevelSym(sname string, skind sym.SymKind) bool {
  2318  	if sname != "" {
  2319  		return true
  2320  	}
  2321  	switch skind {
  2322  	case sym.SDWARFFCN, sym.SDWARFABSFCN, sym.SDWARFTYPE, sym.SDWARFCONST, sym.SDWARFCUINFO, sym.SDWARFRANGE, sym.SDWARFLOC, sym.SDWARFLINES, sym.SGOFUNC:
  2323  		return true
  2324  	default:
  2325  		return false
  2326  	}
  2327  }
  2328  
  2329  // cloneToExternal takes the existing object file symbol (symIdx)
  2330  // and creates a new external symbol payload that is a clone with
  2331  // respect to name, version, type, relocations, etc. The idea here
  2332  // is that if the linker decides it wants to update the contents of
  2333  // a symbol originally discovered as part of an object file, it's
  2334  // easier to do this if we make the updates to an external symbol
  2335  // payload.
  2336  func (l *Loader) cloneToExternal(symIdx Sym) {
  2337  	if l.IsExternal(symIdx) {
  2338  		panic("sym is already external, no need for clone")
  2339  	}
  2340  
  2341  	// Read the particulars from object.
  2342  	r, li := l.toLocal(symIdx)
  2343  	osym := r.Sym(li)
  2344  	sname := osym.Name(r.Reader)
  2345  	sver := abiToVer(osym.ABI(), r.version)
  2346  	skind := sym.AbiSymKindToSymKind[objabi.SymKind(osym.Type())]
  2347  
  2348  	// Create new symbol, update version and kind.
  2349  	pi := l.newPayload(sname, sver)
  2350  	pp := l.payloads[pi]
  2351  	pp.kind = skind
  2352  	pp.ver = sver
  2353  	pp.size = int64(osym.Siz())
  2354  	pp.objidx = r.objidx
  2355  
  2356  	// If this is a def, then copy the guts. We expect this case
  2357  	// to be very rare (one case it may come up is with -X).
  2358  	if li < uint32(r.NAlldef()) {
  2359  
  2360  		// Copy relocations
  2361  		relocs := l.Relocs(symIdx)
  2362  		pp.relocs = make([]goobj.Reloc, relocs.Count())
  2363  		for i := range pp.relocs {
  2364  			// Copy the relocs slice.
  2365  			// Convert local reference to global reference.
  2366  			rel := relocs.At(i)
  2367  			pp.relocs[i].Set(rel.Off(), rel.Siz(), uint16(rel.Type()), rel.Add(), goobj.SymRef{PkgIdx: 0, SymIdx: uint32(rel.Sym())})
  2368  		}
  2369  
  2370  		// Copy data
  2371  		pp.data = r.Data(li)
  2372  	}
  2373  
  2374  	// If we're overriding a data symbol, collect the associated
  2375  	// Gotype, so as to propagate it to the new symbol.
  2376  	auxs := r.Auxs(li)
  2377  	pp.auxs = auxs
  2378  
  2379  	// Install new payload to global index space.
  2380  	// (This needs to happen at the end, as the accessors above
  2381  	// need to access the old symbol content.)
  2382  	l.objSyms[symIdx] = objSym{l.extReader.objidx, uint32(pi)}
  2383  	l.extReader.syms = append(l.extReader.syms, symIdx)
  2384  
  2385  	// Some attributes were encoded in the object file. Copy them over.
  2386  	l.SetAttrDuplicateOK(symIdx, r.Sym(li).Dupok())
  2387  	l.SetAttrShared(symIdx, r.Shared())
  2388  }
  2389  
  2390  // Copy the payload of symbol src to dst. Both src and dst must be external
  2391  // symbols.
  2392  // The intended use case is that when building/linking against a shared library,
  2393  // where we do symbol name mangling, the Go object file may have reference to
  2394  // the original symbol name whereas the shared library provides a symbol with
  2395  // the mangled name. When we do mangling, we copy payload of mangled to original.
  2396  func (l *Loader) CopySym(src, dst Sym) {
  2397  	if !l.IsExternal(dst) {
  2398  		panic("dst is not external") //l.newExtSym(l.SymName(dst), l.SymVersion(dst))
  2399  	}
  2400  	if !l.IsExternal(src) {
  2401  		panic("src is not external") //l.cloneToExternal(src)
  2402  	}
  2403  	l.payloads[l.extIndex(dst)] = l.payloads[l.extIndex(src)]
  2404  	l.SetSymPkg(dst, l.SymPkg(src))
  2405  	// TODO: other attributes?
  2406  }
  2407  
  2408  // CreateExtSym creates a new external symbol with the specified name
  2409  // without adding it to any lookup tables, returning a Sym index for it.
  2410  func (l *Loader) CreateExtSym(name string, ver int) Sym {
  2411  	return l.newExtSym(name, ver)
  2412  }
  2413  
  2414  // CreateStaticSym creates a new static symbol with the specified name
  2415  // without adding it to any lookup tables, returning a Sym index for it.
  2416  func (l *Loader) CreateStaticSym(name string) Sym {
  2417  	// Assign a new unique negative version -- this is to mark the
  2418  	// symbol so that it is not included in the name lookup table.
  2419  	l.anonVersion--
  2420  	return l.newExtSym(name, l.anonVersion)
  2421  }
  2422  
  2423  func (l *Loader) FreeSym(i Sym) {
  2424  	if l.IsExternal(i) {
  2425  		pp := l.getPayload(i)
  2426  		*pp = extSymPayload{}
  2427  	}
  2428  }
  2429  
  2430  // relocId is essentially a <S,R> tuple identifying the Rth
  2431  // relocation of symbol S.
  2432  type relocId struct {
  2433  	sym  Sym
  2434  	ridx int
  2435  }
  2436  
  2437  // SetRelocVariant sets the 'variant' property of a relocation on
  2438  // some specific symbol.
  2439  func (l *Loader) SetRelocVariant(s Sym, ri int, v sym.RelocVariant) {
  2440  	// sanity check
  2441  	if relocs := l.Relocs(s); ri >= relocs.Count() {
  2442  		panic("invalid relocation ID")
  2443  	}
  2444  	if l.relocVariant == nil {
  2445  		l.relocVariant = make(map[relocId]sym.RelocVariant)
  2446  	}
  2447  	if v != 0 {
  2448  		l.relocVariant[relocId{s, ri}] = v
  2449  	} else {
  2450  		delete(l.relocVariant, relocId{s, ri})
  2451  	}
  2452  }
  2453  
  2454  // RelocVariant returns the 'variant' property of a relocation on
  2455  // some specific symbol.
  2456  func (l *Loader) RelocVariant(s Sym, ri int) sym.RelocVariant {
  2457  	return l.relocVariant[relocId{s, ri}]
  2458  }
  2459  
  2460  // UndefinedRelocTargets iterates through the global symbol index
  2461  // space, looking for symbols with relocations targeting undefined
  2462  // references. The linker's loadlib method uses this to determine if
  2463  // there are unresolved references to functions in system libraries
  2464  // (for example, libgcc.a), presumably due to CGO code. Return value
  2465  // is a pair of lists of loader.Sym's. First list corresponds to the
  2466  // corresponding to the undefined symbols themselves, the second list
  2467  // is the symbol that is making a reference to the undef. The "limit"
  2468  // param controls the maximum number of results returned; if "limit"
  2469  // is -1, then all undefs are returned.
  2470  func (l *Loader) UndefinedRelocTargets(limit int) ([]Sym, []Sym) {
  2471  	result, fromr := []Sym{}, []Sym{}
  2472  outerloop:
  2473  	for si := Sym(1); si < Sym(len(l.objSyms)); si++ {
  2474  		relocs := l.Relocs(si)
  2475  		for ri := 0; ri < relocs.Count(); ri++ {
  2476  			r := relocs.At(ri)
  2477  			rs := r.Sym()
  2478  			if rs != 0 && l.SymType(rs) == sym.SXREF && l.SymName(rs) != ".got" {
  2479  				result = append(result, rs)
  2480  				fromr = append(fromr, si)
  2481  				if limit != -1 && len(result) >= limit {
  2482  					break outerloop
  2483  				}
  2484  			}
  2485  		}
  2486  	}
  2487  	return result, fromr
  2488  }
  2489  
  2490  // AssignTextSymbolOrder populates the Textp slices within each
  2491  // library and compilation unit, insuring that packages are laid down
  2492  // in dependency order (internal first, then everything else). Return value
  2493  // is a slice of all text syms.
  2494  func (l *Loader) AssignTextSymbolOrder(libs []*sym.Library, intlibs []bool, extsyms []Sym) []Sym {
  2495  
  2496  	// Library Textp lists should be empty at this point.
  2497  	for _, lib := range libs {
  2498  		if len(lib.Textp) != 0 {
  2499  			panic("expected empty Textp slice for library")
  2500  		}
  2501  		if len(lib.DupTextSyms) != 0 {
  2502  			panic("expected empty DupTextSyms slice for library")
  2503  		}
  2504  	}
  2505  
  2506  	// Used to record which dupok symbol we've assigned to a unit.
  2507  	// Can't use the onlist attribute here because it will need to
  2508  	// clear for the later assignment of the sym.Symbol to a unit.
  2509  	// NB: we can convert to using onList once we no longer have to
  2510  	// call the regular addToTextp.
  2511  	assignedToUnit := MakeBitmap(l.NSym() + 1)
  2512  
  2513  	// Start off textp with reachable external syms.
  2514  	textp := []Sym{}
  2515  	for _, sym := range extsyms {
  2516  		if !l.attrReachable.Has(sym) {
  2517  			continue
  2518  		}
  2519  		textp = append(textp, sym)
  2520  	}
  2521  
  2522  	// Walk through all text symbols from Go object files and append
  2523  	// them to their corresponding library's textp list.
  2524  	for _, o := range l.objs[goObjStart:] {
  2525  		r := o.r
  2526  		lib := r.unit.Lib
  2527  		for i, n := uint32(0), uint32(r.NAlldef()); i < n; i++ {
  2528  			gi := l.toGlobal(r, i)
  2529  			if !l.attrReachable.Has(gi) {
  2530  				continue
  2531  			}
  2532  			osym := r.Sym(i)
  2533  			st := sym.AbiSymKindToSymKind[objabi.SymKind(osym.Type())]
  2534  			if st != sym.STEXT {
  2535  				continue
  2536  			}
  2537  			dupok := osym.Dupok()
  2538  			if r2, i2 := l.toLocal(gi); r2 != r || i2 != i {
  2539  				// A dupok text symbol is resolved to another package.
  2540  				// We still need to record its presence in the current
  2541  				// package, as the trampoline pass expects packages
  2542  				// are laid out in dependency order.
  2543  				lib.DupTextSyms = append(lib.DupTextSyms, sym.LoaderSym(gi))
  2544  				continue // symbol in different object
  2545  			}
  2546  			if dupok {
  2547  				lib.DupTextSyms = append(lib.DupTextSyms, sym.LoaderSym(gi))
  2548  				continue
  2549  			}
  2550  
  2551  			lib.Textp = append(lib.Textp, sym.LoaderSym(gi))
  2552  		}
  2553  	}
  2554  
  2555  	// Now assemble global textp, and assign text symbols to units.
  2556  	for _, doInternal := range [2]bool{true, false} {
  2557  		for idx, lib := range libs {
  2558  			if intlibs[idx] != doInternal {
  2559  				continue
  2560  			}
  2561  			lists := [2][]sym.LoaderSym{lib.Textp, lib.DupTextSyms}
  2562  			for i, list := range lists {
  2563  				for _, s := range list {
  2564  					sym := Sym(s)
  2565  					if !assignedToUnit.Has(sym) {
  2566  						textp = append(textp, sym)
  2567  						unit := l.SymUnit(sym)
  2568  						if unit != nil {
  2569  							unit.Textp = append(unit.Textp, s)
  2570  							assignedToUnit.Set(sym)
  2571  						}
  2572  						// Dupok symbols may be defined in multiple packages; the
  2573  						// associated package for a dupok sym is chosen sort of
  2574  						// arbitrarily (the first containing package that the linker
  2575  						// loads). Canonicalizes its Pkg to the package with which
  2576  						// it will be laid down in text.
  2577  						if i == 1 /* DupTextSyms2 */ && l.SymPkg(sym) != lib.Pkg {
  2578  							l.SetSymPkg(sym, lib.Pkg)
  2579  						}
  2580  					}
  2581  				}
  2582  			}
  2583  			lib.Textp = nil
  2584  			lib.DupTextSyms = nil
  2585  		}
  2586  	}
  2587  
  2588  	return textp
  2589  }
  2590  
  2591  // ErrorReporter is a helper class for reporting errors.
  2592  type ErrorReporter struct {
  2593  	ldr              *Loader
  2594  	AfterErrorAction func()
  2595  }
  2596  
  2597  // Errorf method logs an error message.
  2598  //
  2599  // After each error, the error actions function will be invoked; this
  2600  // will either terminate the link immediately (if -h option given)
  2601  // or it will keep a count and exit if more than 20 errors have been printed.
  2602  //
  2603  // Logging an error means that on exit cmd/link will delete any
  2604  // output file and return a non-zero error code.
  2605  func (reporter *ErrorReporter) Errorf(s Sym, format string, args ...interface{}) {
  2606  	if s != 0 && reporter.ldr.SymName(s) != "" {
  2607  		// Note: Replace is needed here because symbol names might have % in them,
  2608  		// due to the use of LinkString for names of instantiating types.
  2609  		format = strings.Replace(reporter.ldr.SymName(s), "%", "%%", -1) + ": " + format
  2610  	} else {
  2611  		format = fmt.Sprintf("sym %d: %s", s, format)
  2612  	}
  2613  	format += "\n"
  2614  	fmt.Fprintf(os.Stderr, format, args...)
  2615  	reporter.AfterErrorAction()
  2616  }
  2617  
  2618  // GetErrorReporter returns the loader's associated error reporter.
  2619  func (l *Loader) GetErrorReporter() *ErrorReporter {
  2620  	return l.errorReporter
  2621  }
  2622  
  2623  // Errorf method logs an error message. See ErrorReporter.Errorf for details.
  2624  func (l *Loader) Errorf(s Sym, format string, args ...interface{}) {
  2625  	l.errorReporter.Errorf(s, format, args...)
  2626  }
  2627  
  2628  // Symbol statistics.
  2629  func (l *Loader) Stat() string {
  2630  	s := fmt.Sprintf("%d symbols, %d reachable\n", l.NSym(), l.NReachableSym())
  2631  	s += fmt.Sprintf("\t%d package symbols, %d hashed symbols, %d non-package symbols, %d external symbols\n",
  2632  		l.npkgsyms, l.nhashedsyms, int(l.extStart)-l.npkgsyms-l.nhashedsyms, l.NSym()-int(l.extStart))
  2633  	return s
  2634  }
  2635  
  2636  // For debugging.
  2637  func (l *Loader) Dump() {
  2638  	fmt.Println("objs")
  2639  	for _, obj := range l.objs[goObjStart:] {
  2640  		if obj.r != nil {
  2641  			fmt.Println(obj.i, obj.r.unit.Lib)
  2642  		}
  2643  	}
  2644  	fmt.Println("extStart:", l.extStart)
  2645  	fmt.Println("Nsyms:", len(l.objSyms))
  2646  	fmt.Println("syms")
  2647  	for i := Sym(1); i < Sym(len(l.objSyms)); i++ {
  2648  		pi := ""
  2649  		if l.IsExternal(i) {
  2650  			pi = fmt.Sprintf("<ext %d>", l.extIndex(i))
  2651  		}
  2652  		sect := ""
  2653  		if l.SymSect(i) != nil {
  2654  			sect = l.SymSect(i).Name
  2655  		}
  2656  		fmt.Printf("%v %v %v %v %x %v\n", i, l.SymName(i), l.SymType(i), pi, l.SymValue(i), sect)
  2657  	}
  2658  	fmt.Println("symsByName")
  2659  	for name, i := range l.symsByName[0] {
  2660  		fmt.Println(i, name, 0)
  2661  	}
  2662  	for name, i := range l.symsByName[1] {
  2663  		fmt.Println(i, name, 1)
  2664  	}
  2665  	fmt.Println("payloads:")
  2666  	for i := range l.payloads {
  2667  		pp := l.payloads[i]
  2668  		fmt.Println(i, pp.name, pp.ver, pp.kind)
  2669  	}
  2670  }
  2671  

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