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

     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  // objSym represents a symbol in an object file. It is a tuple of
    95  // the object and the symbol's local index.
    96  // For external symbols, objidx is the index of l.extReader (extObj),
    97  // s is its index into the payload array.
    98  // {0, 0} represents the nil symbol.
    99  type objSym struct {
   100  	objidx uint32 // index of the object (in l.objs array)
   101  	s      uint32 // local index
   102  }
   103  
   104  type nameVer struct {
   105  	name string
   106  	v    int
   107  }
   108  
   109  type Bitmap []uint32
   110  
   111  // set the i-th bit.
   112  func (bm Bitmap) Set(i Sym) {
   113  	n, r := uint(i)/32, uint(i)%32
   114  	bm[n] |= 1 << r
   115  }
   116  
   117  // unset the i-th bit.
   118  func (bm Bitmap) Unset(i Sym) {
   119  	n, r := uint(i)/32, uint(i)%32
   120  	bm[n] &^= (1 << r)
   121  }
   122  
   123  // whether the i-th bit is set.
   124  func (bm Bitmap) Has(i Sym) bool {
   125  	n, r := uint(i)/32, uint(i)%32
   126  	return bm[n]&(1<<r) != 0
   127  }
   128  
   129  // return current length of bitmap in bits.
   130  func (bm Bitmap) Len() int {
   131  	return len(bm) * 32
   132  }
   133  
   134  // return the number of bits set.
   135  func (bm Bitmap) Count() int {
   136  	s := 0
   137  	for _, x := range bm {
   138  		s += bits.OnesCount32(x)
   139  	}
   140  	return s
   141  }
   142  
   143  func MakeBitmap(n int) Bitmap {
   144  	return make(Bitmap, (n+31)/32)
   145  }
   146  
   147  // growBitmap insures that the specified bitmap has enough capacity,
   148  // reallocating (doubling the size) if needed.
   149  func growBitmap(reqLen int, b Bitmap) Bitmap {
   150  	curLen := b.Len()
   151  	if reqLen > curLen {
   152  		b = append(b, MakeBitmap(reqLen+1-curLen)...)
   153  	}
   154  	return b
   155  }
   156  
   157  type symAndSize struct {
   158  	sym  Sym
   159  	size uint32
   160  }
   161  
   162  // A Loader loads new object files and resolves indexed symbol references.
   163  //
   164  // Notes on the layout of global symbol index space:
   165  //
   166  //   - Go object files are read before host object files; each Go object
   167  //     read adds its defined package symbols to the global index space.
   168  //     Nonpackage symbols are not yet added.
   169  //
   170  //   - In loader.LoadNonpkgSyms, add non-package defined symbols and
   171  //     references in all object files to the global index space.
   172  //
   173  //   - Host object file loading happens; the host object loader does a
   174  //     name/version lookup for each symbol it finds; this can wind up
   175  //     extending the external symbol index space range. The host object
   176  //     loader stores symbol payloads in loader.payloads using SymbolBuilder.
   177  //
   178  //   - Each symbol gets a unique global index. For duplicated and
   179  //     overwriting/overwritten symbols, the second (or later) appearance
   180  //     of the symbol gets the same global index as the first appearance.
   181  type Loader struct {
   182  	objs        []*oReader
   183  	extStart    Sym   // from this index on, the symbols are externally defined
   184  	builtinSyms []Sym // global index of builtin symbols
   185  
   186  	objSyms []objSym // global index mapping to local index
   187  
   188  	symsByName    [2]map[string]Sym // map symbol name to index, two maps are for ABI0 and ABIInternal
   189  	extStaticSyms map[nameVer]Sym   // externally defined static symbols, keyed by name
   190  
   191  	extReader    *oReader // a dummy oReader, for external symbols
   192  	payloadBatch []extSymPayload
   193  	payloads     []*extSymPayload // contents of linker-materialized external syms
   194  	values       []int64          // symbol values, indexed by global sym index
   195  
   196  	sects    []*sym.Section // sections
   197  	symSects []uint16       // symbol's section, index to sects array
   198  
   199  	align []uint8 // symbol 2^N alignment, indexed by global index
   200  
   201  	deferReturnTramp map[Sym]bool // whether the symbol is a trampoline of a deferreturn call
   202  
   203  	objByPkg map[string]uint32 // map package path to the index of its Go object reader
   204  
   205  	anonVersion int // most recently assigned ext static sym pseudo-version
   206  
   207  	// Bitmaps and other side structures used to store data used to store
   208  	// symbol flags/attributes; these are to be accessed via the
   209  	// corresponding loader "AttrXXX" and "SetAttrXXX" methods. Please
   210  	// visit the comments on these methods for more details on the
   211  	// semantics / interpretation of the specific flags or attribute.
   212  	attrReachable        Bitmap // reachable symbols, indexed by global index
   213  	attrOnList           Bitmap // "on list" symbols, indexed by global index
   214  	attrLocal            Bitmap // "local" symbols, indexed by global index
   215  	attrNotInSymbolTable Bitmap // "not in symtab" symbols, indexed by global idx
   216  	attrUsedInIface      Bitmap // "used in interface" symbols, indexed by global idx
   217  	attrSpecial          Bitmap // "special" frame symbols, indexed by global idx
   218  	attrVisibilityHidden Bitmap // hidden symbols, indexed by ext sym index
   219  	attrDuplicateOK      Bitmap // dupOK symbols, indexed by ext sym index
   220  	attrShared           Bitmap // shared symbols, indexed by ext sym index
   221  	attrExternal         Bitmap // external symbols, indexed by ext sym index
   222  	generatedSyms        Bitmap // symbols that generate their content, indexed by ext sym idx
   223  
   224  	attrReadOnly         map[Sym]bool     // readonly data for this sym
   225  	attrCgoExportDynamic map[Sym]struct{} // "cgo_export_dynamic" symbols
   226  	attrCgoExportStatic  map[Sym]struct{} // "cgo_export_static" symbols
   227  
   228  	// Outer and Sub relations for symbols.
   229  	outer []Sym // indexed by global index
   230  	sub   map[Sym]Sym
   231  
   232  	dynimplib   map[Sym]string      // stores Dynimplib symbol attribute
   233  	dynimpvers  map[Sym]string      // stores Dynimpvers symbol attribute
   234  	localentry  map[Sym]uint8       // stores Localentry symbol attribute
   235  	extname     map[Sym]string      // stores Extname symbol attribute
   236  	elfType     map[Sym]elf.SymType // stores elf type symbol property
   237  	elfSym      map[Sym]int32       // stores elf sym symbol property
   238  	localElfSym map[Sym]int32       // stores "local" elf sym symbol property
   239  	symPkg      map[Sym]string      // stores package for symbol, or library for shlib-derived syms
   240  	plt         map[Sym]int32       // stores dynimport for pe objects
   241  	got         map[Sym]int32       // stores got for pe objects
   242  	dynid       map[Sym]int32       // stores Dynid for symbol
   243  
   244  	relocVariant map[relocId]sym.RelocVariant // stores variant relocs
   245  
   246  	// Used to implement field tracking; created during deadcode if
   247  	// field tracking is enabled. Reachparent[K] contains the index of
   248  	// the symbol that triggered the marking of symbol K as live.
   249  	Reachparent []Sym
   250  
   251  	// CgoExports records cgo-exported symbols by SymName.
   252  	CgoExports map[string]Sym
   253  
   254  	WasmExports []Sym
   255  
   256  	// sizeFixups records symbols that we need to fix up the size
   257  	// after loading. It is very rarely needed, only for a DATA symbol
   258  	// and a BSS symbol with the same name, and the BSS symbol has
   259  	// larger size.
   260  	sizeFixups []symAndSize
   261  
   262  	flags uint32
   263  
   264  	strictDupMsgs int // number of strict-dup warning/errors, when FlagStrictDups is enabled
   265  
   266  	errorReporter *ErrorReporter
   267  
   268  	npkgsyms    int // number of package symbols, for accounting
   269  	nhashedsyms int // number of hashed symbols, for accounting
   270  }
   271  
   272  const (
   273  	pkgDef = iota
   274  	hashed64Def
   275  	hashedDef
   276  	nonPkgDef
   277  	nonPkgRef
   278  )
   279  
   280  // objidx
   281  const (
   282  	nilObj = iota
   283  	extObj
   284  	goObjStart
   285  )
   286  
   287  // extSymPayload holds the payload (data + relocations) for linker-synthesized
   288  // external symbols (note that symbol value is stored in a separate slice).
   289  type extSymPayload struct {
   290  	name   string // TODO: would this be better as offset into str table?
   291  	size   int64
   292  	ver    int
   293  	kind   sym.SymKind
   294  	objidx uint32 // index of original object if sym made by cloneToExternal
   295  	relocs []goobj.Reloc
   296  	data   []byte
   297  	auxs   []goobj.Aux
   298  }
   299  
   300  const (
   301  	// Loader.flags
   302  	FlagStrictDups = 1 << iota
   303  	FlagCheckLinkname
   304  )
   305  
   306  func NewLoader(flags uint32, reporter *ErrorReporter) *Loader {
   307  	nbuiltin := goobj.NBuiltin()
   308  	extReader := &oReader{objidx: extObj}
   309  	ldr := &Loader{
   310  		objs:                 []*oReader{nil, extReader}, // reserve index 0 for nil symbol, 1 for external symbols
   311  		objSyms:              make([]objSym, 1, 1),       // This will get overwritten later.
   312  		extReader:            extReader,
   313  		symsByName:           [2]map[string]Sym{make(map[string]Sym, 80000), make(map[string]Sym, 50000)}, // preallocate ~2MB for ABI0 and ~1MB for ABI1 symbols
   314  		objByPkg:             make(map[string]uint32),
   315  		sub:                  make(map[Sym]Sym),
   316  		dynimplib:            make(map[Sym]string),
   317  		dynimpvers:           make(map[Sym]string),
   318  		localentry:           make(map[Sym]uint8),
   319  		extname:              make(map[Sym]string),
   320  		attrReadOnly:         make(map[Sym]bool),
   321  		elfType:              make(map[Sym]elf.SymType),
   322  		elfSym:               make(map[Sym]int32),
   323  		localElfSym:          make(map[Sym]int32),
   324  		symPkg:               make(map[Sym]string),
   325  		plt:                  make(map[Sym]int32),
   326  		got:                  make(map[Sym]int32),
   327  		dynid:                make(map[Sym]int32),
   328  		attrCgoExportDynamic: make(map[Sym]struct{}),
   329  		attrCgoExportStatic:  make(map[Sym]struct{}),
   330  		deferReturnTramp:     make(map[Sym]bool),
   331  		extStaticSyms:        make(map[nameVer]Sym),
   332  		builtinSyms:          make([]Sym, nbuiltin),
   333  		flags:                flags,
   334  		errorReporter:        reporter,
   335  		sects:                []*sym.Section{nil}, // reserve index 0 for nil section
   336  	}
   337  	reporter.ldr = ldr
   338  	return ldr
   339  }
   340  
   341  // Add object file r
   342  func (l *Loader) addObj(pkg string, r *oReader) {
   343  	pkg = objabi.PathToPrefix(pkg) // the object file contains escaped package path
   344  	if _, ok := l.objByPkg[pkg]; !ok {
   345  		l.objByPkg[pkg] = r.objidx
   346  	}
   347  	l.objs = append(l.objs, r)
   348  }
   349  
   350  // Add a symbol from an object file, return the global index.
   351  // If the symbol already exist, it returns the index of that symbol.
   352  func (st *loadState) addSym(name string, ver int, r *oReader, li uint32, kind int, osym *goobj.Sym) Sym {
   353  	l := st.l
   354  	if l.extStart != 0 {
   355  		panic("addSym called after external symbol is created")
   356  	}
   357  	i := Sym(len(l.objSyms))
   358  	if int(i) != len(l.objSyms) { // overflow
   359  		panic("too many symbols")
   360  	}
   361  	addToGlobal := func() {
   362  		l.objSyms = append(l.objSyms, objSym{r.objidx, li})
   363  	}
   364  	if name == "" && kind != hashed64Def && kind != hashedDef {
   365  		addToGlobal()
   366  		return i // unnamed aux symbol
   367  	}
   368  	if ver == r.version {
   369  		// Static symbol. Add its global index but don't
   370  		// add to name lookup table, as it cannot be
   371  		// referenced by name.
   372  		addToGlobal()
   373  		return i
   374  	}
   375  	switch kind {
   376  	case pkgDef:
   377  		// Defined package symbols cannot be dup to each other.
   378  		// We load all the package symbols first, so we don't need
   379  		// to check dup here.
   380  		// We still add it to the lookup table, as it may still be
   381  		// referenced by name (e.g. through linkname).
   382  		l.symsByName[ver][name] = i
   383  		addToGlobal()
   384  		return i
   385  	case hashed64Def, hashedDef:
   386  		// Hashed (content-addressable) symbol. Check the hash
   387  		// but don't add to name lookup table, as they are not
   388  		// referenced by name. Also no need to do overwriting
   389  		// check, as same hash indicates same content.
   390  		var checkHash func() (symAndSize, bool)
   391  		var addToHashMap func(symAndSize)
   392  		var h64 uint64        // only used for hashed64Def
   393  		var h *goobj.HashType // only used for hashedDef
   394  		if kind == hashed64Def {
   395  			checkHash = func() (symAndSize, bool) {
   396  				h64 = r.Hash64(li - uint32(r.ndef))
   397  				s, existed := st.hashed64Syms[h64]
   398  				return s, existed
   399  			}
   400  			addToHashMap = func(ss symAndSize) { st.hashed64Syms[h64] = ss }
   401  		} else {
   402  			checkHash = func() (symAndSize, bool) {
   403  				h = r.Hash(li - uint32(r.ndef+r.nhashed64def))
   404  				s, existed := st.hashedSyms[*h]
   405  				return s, existed
   406  			}
   407  			addToHashMap = func(ss symAndSize) { st.hashedSyms[*h] = ss }
   408  		}
   409  		siz := osym.Siz()
   410  		if s, existed := checkHash(); existed {
   411  			// The content hash is built from symbol data and relocations. In the
   412  			// object file, the symbol data may not always contain trailing zeros,
   413  			// e.g. for [5]int{1,2,3} and [100]int{1,2,3}, the data is same
   414  			// (although the size is different).
   415  			// Also, for short symbols, the content hash is the identity function of
   416  			// the 8 bytes, and trailing zeros doesn't change the hash value, e.g.
   417  			// hash("A") == hash("A\0\0\0").
   418  			// So when two symbols have the same hash, we need to use the one with
   419  			// larger size.
   420  			if siz > s.size {
   421  				// New symbol has larger size, use the new one. Rewrite the index mapping.
   422  				l.objSyms[s.sym] = objSym{r.objidx, li}
   423  				addToHashMap(symAndSize{s.sym, siz})
   424  			}
   425  			return s.sym
   426  		}
   427  		addToHashMap(symAndSize{i, siz})
   428  		addToGlobal()
   429  		return i
   430  	}
   431  
   432  	// Non-package (named) symbol.
   433  	// Check if it already exists.
   434  	oldi, existed := l.symsByName[ver][name]
   435  	if !existed {
   436  		l.symsByName[ver][name] = i
   437  		addToGlobal()
   438  		return i
   439  	}
   440  	// symbol already exists
   441  	// Fix for issue #47185 -- given two dupok or BSS symbols with
   442  	// different sizes, favor symbol with larger size. See also
   443  	// issue #46653 and #72032.
   444  	oldsz := l.SymSize(oldi)
   445  	sz := int64(r.Sym(li).Siz())
   446  	if osym.Dupok() {
   447  		if l.flags&FlagStrictDups != 0 {
   448  			l.checkdup(name, r, li, oldi)
   449  		}
   450  		if oldsz < sz {
   451  			// new symbol overwrites old symbol.
   452  			l.objSyms[oldi] = objSym{r.objidx, li}
   453  		}
   454  		return oldi
   455  	}
   456  	oldr, oldli := l.toLocal(oldi)
   457  	oldsym := oldr.Sym(oldli)
   458  	if oldsym.Dupok() {
   459  		return oldi
   460  	}
   461  	// If one is a DATA symbol (i.e. has content, DataSize != 0,
   462  	// including RODATA) and the other is BSS, the one with content wins.
   463  	// If both are BSS, the one with larger size wins.
   464  	//
   465  	// For a special case, we allow a TEXT symbol overwrites a BSS symbol
   466  	// even if the BSS symbol has larger size. This is because there is
   467  	// code like below to take the address of a function
   468  	//
   469  	//	//go:linkname fn
   470  	//	var fn uintptr
   471  	//	var fnAddr = uintptr(unsafe.Pointer(&fn))
   472  	//
   473  	// TODO: maybe limit this case to just pointer sized variable?
   474  	//
   475  	// In summary, the "overwrite" variable and the final result are
   476  	//
   477  	// new sym       old sym       result
   478  	// -------------------------------------------------------
   479  	// TEXT          BSS           new wins
   480  	// DATA          DATA          ERROR
   481  	// DATA lg/eq    BSS  sm/eq    new wins
   482  	// DATA small    BSS  large    merge: new with larger size
   483  	// BSS  large    DATA small    merge: old with larger size
   484  	// BSS  large    BSS  small    new wins
   485  	// BSS  sm/eq    D/B  lg/eq    old wins
   486  	// BSS           TEXT          old wins
   487  	oldtyp := sym.AbiSymKindToSymKind[objabi.SymKind(oldsym.Type())]
   488  	newtyp := sym.AbiSymKindToSymKind[objabi.SymKind(osym.Type())]
   489  	newIsText := newtyp.IsText()
   490  	oldHasContent := oldr.DataSize(oldli) != 0
   491  	newHasContent := r.DataSize(li) != 0
   492  	oldIsBSS := oldtyp.IsData() && !oldHasContent
   493  	newIsBSS := newtyp.IsData() && !newHasContent
   494  	switch {
   495  	case newIsText && oldIsBSS,
   496  		newHasContent && oldIsBSS,
   497  		newIsBSS && oldIsBSS && sz > oldsz:
   498  		// new symbol overwrites old symbol.
   499  		l.objSyms[oldi] = objSym{r.objidx, li}
   500  		if oldsz > sz {
   501  			// If the BSS symbol has a larger size, expand the data
   502  			// symbol's size so access from the BSS side cannot overrun.
   503  			// It is hard to modify the symbol size until all Go objects
   504  			// (potentially read-only) are loaded, so we record it in
   505  			// a fixup table and apply them later. This is very rare.
   506  			// One case is a global variable with a Go declaration and an
   507  			// assembly definition, which typically have the same size,
   508  			// but in ASAN mode the Go declaration has a larger size due
   509  			// to the inserted red zone.
   510  			l.sizeFixups = append(l.sizeFixups, symAndSize{oldi, uint32(oldsz)})
   511  		}
   512  	case newIsBSS:
   513  		// old win, just ignore the new symbol.
   514  		if sz > oldsz {
   515  			// See the comment above for sizeFixups.
   516  			l.sizeFixups = append(l.sizeFixups, symAndSize{oldi, uint32(sz)})
   517  		}
   518  	default:
   519  		log.Fatalf("duplicated definition of symbol %s, from %s (type %s size %d) and %s (type %s size %d)", name, r.unit.Lib.Pkg, newtyp, sz, oldr.unit.Lib.Pkg, oldtyp, oldsz)
   520  	}
   521  	return oldi
   522  }
   523  
   524  // newExtSym creates a new external sym with the specified
   525  // name/version.
   526  func (l *Loader) newExtSym(name string, ver int) Sym {
   527  	i := Sym(len(l.objSyms))
   528  	if int(i) != len(l.objSyms) { // overflow
   529  		panic("too many symbols")
   530  	}
   531  	if l.extStart == 0 {
   532  		l.extStart = i
   533  	}
   534  	l.growValues(int(i) + 1)
   535  	l.growOuter(int(i) + 1)
   536  	l.growAttrBitmaps(int(i) + 1)
   537  	pi := l.newPayload(name, ver)
   538  	l.objSyms = append(l.objSyms, objSym{l.extReader.objidx, uint32(pi)})
   539  	l.extReader.syms = append(l.extReader.syms, i)
   540  	return i
   541  }
   542  
   543  // LookupOrCreateSym looks up the symbol with the specified name/version,
   544  // returning its Sym index if found. If the lookup fails, a new external
   545  // Sym will be created, entered into the lookup tables, and returned.
   546  func (l *Loader) LookupOrCreateSym(name string, ver int) Sym {
   547  	i := l.Lookup(name, ver)
   548  	if i != 0 {
   549  		return i
   550  	}
   551  	i = l.newExtSym(name, ver)
   552  	static := ver >= sym.SymVerStatic || ver < 0
   553  	if static {
   554  		l.extStaticSyms[nameVer{name, ver}] = i
   555  	} else {
   556  		l.symsByName[ver][name] = i
   557  	}
   558  	return i
   559  }
   560  
   561  // AddCgoExport records a cgo-exported symbol in l.CgoExports.
   562  // This table is used to identify the correct Go symbol ABI to use
   563  // to resolve references from host objects (which don't have ABIs).
   564  func (l *Loader) AddCgoExport(s Sym) {
   565  	if l.CgoExports == nil {
   566  		l.CgoExports = make(map[string]Sym)
   567  	}
   568  	l.CgoExports[l.SymName(s)] = s
   569  }
   570  
   571  // LookupOrCreateCgoExport is like LookupOrCreateSym, but if ver
   572  // indicates a global symbol, it uses the CgoExport table to determine
   573  // the appropriate symbol version (ABI) to use. ver must be either 0
   574  // or a static symbol version.
   575  func (l *Loader) LookupOrCreateCgoExport(name string, ver int) Sym {
   576  	if ver >= sym.SymVerStatic {
   577  		return l.LookupOrCreateSym(name, ver)
   578  	}
   579  	if ver != 0 {
   580  		panic("ver must be 0 or a static version")
   581  	}
   582  	// Look for a cgo-exported symbol from Go.
   583  	if s, ok := l.CgoExports[name]; ok {
   584  		return s
   585  	}
   586  	// Otherwise, this must just be a symbol in the host object.
   587  	// Create a version 0 symbol for it.
   588  	return l.LookupOrCreateSym(name, 0)
   589  }
   590  
   591  func (l *Loader) IsExternal(i Sym) bool {
   592  	r, _ := l.toLocal(i)
   593  	return l.isExtReader(r)
   594  }
   595  
   596  func (l *Loader) isExtReader(r *oReader) bool {
   597  	return r == l.extReader
   598  }
   599  
   600  // For external symbol, return its index in the payloads array.
   601  // XXX result is actually not a global index. We (ab)use the Sym type
   602  // so we don't need conversion for accessing bitmaps.
   603  func (l *Loader) extIndex(i Sym) Sym {
   604  	_, li := l.toLocal(i)
   605  	return Sym(li)
   606  }
   607  
   608  // Get a new payload for external symbol, return its index in
   609  // the payloads array.
   610  func (l *Loader) newPayload(name string, ver int) int {
   611  	pi := len(l.payloads)
   612  	pp := l.allocPayload()
   613  	pp.name = name
   614  	pp.ver = ver
   615  	l.payloads = append(l.payloads, pp)
   616  	l.growExtAttrBitmaps()
   617  	return pi
   618  }
   619  
   620  // getPayload returns a pointer to the extSymPayload struct for an
   621  // external symbol if the symbol has a payload. Will panic if the
   622  // symbol in question is bogus (zero or not an external sym).
   623  func (l *Loader) getPayload(i Sym) *extSymPayload {
   624  	if !l.IsExternal(i) {
   625  		panic(fmt.Sprintf("bogus symbol index %d in getPayload", i))
   626  	}
   627  	pi := l.extIndex(i)
   628  	return l.payloads[pi]
   629  }
   630  
   631  // allocPayload allocates a new payload.
   632  func (l *Loader) allocPayload() *extSymPayload {
   633  	batch := l.payloadBatch
   634  	if len(batch) == 0 {
   635  		batch = make([]extSymPayload, 1000)
   636  	}
   637  	p := &batch[0]
   638  	l.payloadBatch = batch[1:]
   639  	return p
   640  }
   641  
   642  func (ms *extSymPayload) Grow(siz int64) {
   643  	if int64(int(siz)) != siz {
   644  		log.Fatalf("symgrow size %d too long", siz)
   645  	}
   646  	if int64(len(ms.data)) >= siz {
   647  		return
   648  	}
   649  	if cap(ms.data) < int(siz) {
   650  		cl := len(ms.data)
   651  		ms.data = append(ms.data, make([]byte, int(siz)+1-cl)...)
   652  		ms.data = ms.data[0:cl]
   653  	}
   654  	ms.data = ms.data[:siz]
   655  }
   656  
   657  // Convert a local index to a global index.
   658  func (l *Loader) toGlobal(r *oReader, i uint32) Sym {
   659  	return r.syms[i]
   660  }
   661  
   662  // Convert a global index to a local index.
   663  func (l *Loader) toLocal(i Sym) (*oReader, uint32) {
   664  	return l.objs[l.objSyms[i].objidx], l.objSyms[i].s
   665  }
   666  
   667  // Resolve a local symbol reference. Return global index.
   668  func (l *Loader) resolve(r *oReader, s goobj.SymRef) Sym {
   669  	var rr *oReader
   670  	switch p := s.PkgIdx; p {
   671  	case goobj.PkgIdxInvalid:
   672  		// {0, X} with non-zero X is never a valid sym reference from a Go object.
   673  		// We steal this space for symbol references from external objects.
   674  		// In this case, X is just the global index.
   675  		if l.isExtReader(r) {
   676  			return Sym(s.SymIdx)
   677  		}
   678  		if s.SymIdx != 0 {
   679  			panic("bad sym ref")
   680  		}
   681  		return 0
   682  	case goobj.PkgIdxHashed64:
   683  		i := int(s.SymIdx) + r.ndef
   684  		return r.syms[i]
   685  	case goobj.PkgIdxHashed:
   686  		i := int(s.SymIdx) + r.ndef + r.nhashed64def
   687  		return r.syms[i]
   688  	case goobj.PkgIdxNone:
   689  		i := int(s.SymIdx) + r.ndef + r.nhashed64def + r.nhasheddef
   690  		return r.syms[i]
   691  	case goobj.PkgIdxBuiltin:
   692  		if bi := l.builtinSyms[s.SymIdx]; bi != 0 {
   693  			return bi
   694  		}
   695  		l.reportMissingBuiltin(int(s.SymIdx), r.unit.Lib.Pkg)
   696  		return 0
   697  	case goobj.PkgIdxSelf:
   698  		rr = r
   699  	default:
   700  		rr = l.objs[r.pkg[p]]
   701  	}
   702  	return l.toGlobal(rr, s.SymIdx)
   703  }
   704  
   705  // reportMissingBuiltin issues an error in the case where we have a
   706  // relocation against a runtime builtin whose definition is not found
   707  // when the runtime package is built. The canonical example is
   708  // "runtime.racefuncenter" -- currently if you do something like
   709  //
   710  //	go build -gcflags=-race myprogram.go
   711  //
   712  // the compiler will insert calls to the builtin runtime.racefuncenter,
   713  // but the version of the runtime used for linkage won't actually contain
   714  // definitions of that symbol. See issue #42396 for details.
   715  //
   716  // As currently implemented, this is a fatal error. This has drawbacks
   717  // in that if there are multiple missing builtins, the error will only
   718  // cite the first one. On the plus side, terminating the link here has
   719  // advantages in that we won't run the risk of panics or crashes later
   720  // on in the linker due to R_CALL relocations with 0-valued target
   721  // symbols.
   722  func (l *Loader) reportMissingBuiltin(bsym int, reflib string) {
   723  	bname, _ := goobj.BuiltinName(bsym)
   724  	log.Fatalf("reference to undefined builtin %q from package %q",
   725  		bname, reflib)
   726  }
   727  
   728  // Look up a symbol by name, return global index, or 0 if not found.
   729  // This is more like Syms.ROLookup than Lookup -- it doesn't create
   730  // new symbol.
   731  func (l *Loader) Lookup(name string, ver int) Sym {
   732  	if ver >= sym.SymVerStatic || ver < 0 {
   733  		return l.extStaticSyms[nameVer{name, ver}]
   734  	}
   735  	return l.symsByName[ver][name]
   736  }
   737  
   738  // Check that duplicate symbols have same contents.
   739  func (l *Loader) checkdup(name string, r *oReader, li uint32, dup Sym) {
   740  	p := r.Data(li)
   741  	rdup, ldup := l.toLocal(dup)
   742  	pdup := rdup.Data(ldup)
   743  	reason := "same length but different contents"
   744  	if len(p) != len(pdup) {
   745  		reason = fmt.Sprintf("new length %d != old length %d", len(p), len(pdup))
   746  	} else if bytes.Equal(p, pdup) {
   747  		// For BSS symbols, we need to check size as well, see issue 46653.
   748  		szdup := l.SymSize(dup)
   749  		sz := int64(r.Sym(li).Siz())
   750  		if szdup == sz {
   751  			return
   752  		}
   753  		reason = fmt.Sprintf("different sizes: new size %d != old size %d",
   754  			sz, szdup)
   755  	}
   756  	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)
   757  
   758  	// For the moment, allow DWARF subprogram DIEs for
   759  	// auto-generated wrapper functions. What seems to happen
   760  	// here is that we get different line numbers on formal
   761  	// params; I am guessing that the pos is being inherited
   762  	// from the spot where the wrapper is needed.
   763  	allowed := strings.HasPrefix(name, "go:info.go.interface") ||
   764  		strings.HasPrefix(name, "go:info.go.builtin") ||
   765  		strings.HasPrefix(name, "go:debuglines")
   766  	if !allowed {
   767  		l.strictDupMsgs++
   768  	}
   769  }
   770  
   771  func (l *Loader) NStrictDupMsgs() int { return l.strictDupMsgs }
   772  
   773  // Number of total symbols.
   774  func (l *Loader) NSym() int {
   775  	return len(l.objSyms)
   776  }
   777  
   778  // Number of defined Go symbols.
   779  func (l *Loader) NDef() int {
   780  	return int(l.extStart)
   781  }
   782  
   783  // Number of reachable symbols.
   784  func (l *Loader) NReachableSym() int {
   785  	return l.attrReachable.Count()
   786  }
   787  
   788  // Returns the name of the i-th symbol.
   789  func (l *Loader) SymName(i Sym) string {
   790  	if l.IsExternal(i) {
   791  		pp := l.getPayload(i)
   792  		return pp.name
   793  	}
   794  	r, li := l.toLocal(i)
   795  	if r == nil {
   796  		return "?"
   797  	}
   798  	return r.Sym(li).Name(r.Reader)
   799  }
   800  
   801  // Returns the version of the i-th symbol.
   802  func (l *Loader) SymVersion(i Sym) int {
   803  	if l.IsExternal(i) {
   804  		pp := l.getPayload(i)
   805  		return pp.ver
   806  	}
   807  	r, li := l.toLocal(i)
   808  	return int(abiToVer(r.Sym(li).ABI(), r.version))
   809  }
   810  
   811  func (l *Loader) IsFileLocal(i Sym) bool {
   812  	return l.SymVersion(i) >= sym.SymVerStatic
   813  }
   814  
   815  // IsFromAssembly returns true if this symbol is derived from an
   816  // object file generated by the Go assembler.
   817  func (l *Loader) IsFromAssembly(i Sym) bool {
   818  	if l.IsExternal(i) {
   819  		pp := l.getPayload(i)
   820  		if pp.objidx != 0 {
   821  			r := l.objs[pp.objidx]
   822  			return r.FromAssembly()
   823  		}
   824  		return false
   825  	}
   826  	r, _ := l.toLocal(i)
   827  	return r.FromAssembly()
   828  }
   829  
   830  // Returns the type of the i-th symbol.
   831  func (l *Loader) SymType(i Sym) sym.SymKind {
   832  	if l.IsExternal(i) {
   833  		pp := l.getPayload(i)
   834  		if pp != nil {
   835  			return pp.kind
   836  		}
   837  		return 0
   838  	}
   839  	r, li := l.toLocal(i)
   840  	return sym.AbiSymKindToSymKind[objabi.SymKind(r.Sym(li).Type())]
   841  }
   842  
   843  // Returns the attributes of the i-th symbol.
   844  func (l *Loader) SymAttr(i Sym) uint8 {
   845  	if l.IsExternal(i) {
   846  		// TODO: do something? External symbols have different representation of attributes.
   847  		// For now, ReflectMethod, NoSplit, GoType, and Typelink are used and they cannot be
   848  		// set by external symbol.
   849  		return 0
   850  	}
   851  	r, li := l.toLocal(i)
   852  	return r.Sym(li).Flag()
   853  }
   854  
   855  // Returns the size of the i-th symbol.
   856  func (l *Loader) SymSize(i Sym) int64 {
   857  	if l.IsExternal(i) {
   858  		pp := l.getPayload(i)
   859  		return pp.size
   860  	}
   861  	r, li := l.toLocal(i)
   862  	return int64(r.Sym(li).Siz())
   863  }
   864  
   865  // AttrReachable returns true for symbols that are transitively
   866  // referenced from the entry points. Unreachable symbols are not
   867  // written to the output.
   868  func (l *Loader) AttrReachable(i Sym) bool {
   869  	return l.attrReachable.Has(i)
   870  }
   871  
   872  // SetAttrReachable sets the reachability property for a symbol (see
   873  // AttrReachable).
   874  func (l *Loader) SetAttrReachable(i Sym, v bool) {
   875  	if v {
   876  		l.attrReachable.Set(i)
   877  	} else {
   878  		l.attrReachable.Unset(i)
   879  	}
   880  }
   881  
   882  // AttrOnList returns true for symbols that are on some list (such as
   883  // the list of all text symbols, or one of the lists of data symbols)
   884  // and is consulted to avoid bugs where a symbol is put on a list
   885  // twice.
   886  func (l *Loader) AttrOnList(i Sym) bool {
   887  	return l.attrOnList.Has(i)
   888  }
   889  
   890  // SetAttrOnList sets the "on list" property for a symbol (see
   891  // AttrOnList).
   892  func (l *Loader) SetAttrOnList(i Sym, v bool) {
   893  	if v {
   894  		l.attrOnList.Set(i)
   895  	} else {
   896  		l.attrOnList.Unset(i)
   897  	}
   898  }
   899  
   900  // AttrLocal returns true for symbols that are only visible within the
   901  // module (executable or shared library) being linked. This attribute
   902  // is applied to thunks and certain other linker-generated symbols.
   903  func (l *Loader) AttrLocal(i Sym) bool {
   904  	return l.attrLocal.Has(i)
   905  }
   906  
   907  // SetAttrLocal the "local" property for a symbol (see AttrLocal above).
   908  func (l *Loader) SetAttrLocal(i Sym, v bool) {
   909  	if v {
   910  		l.attrLocal.Set(i)
   911  	} else {
   912  		l.attrLocal.Unset(i)
   913  	}
   914  }
   915  
   916  // AttrUsedInIface returns true for a type symbol that is used in
   917  // an interface.
   918  func (l *Loader) AttrUsedInIface(i Sym) bool {
   919  	return l.attrUsedInIface.Has(i)
   920  }
   921  
   922  func (l *Loader) SetAttrUsedInIface(i Sym, v bool) {
   923  	if v {
   924  		l.attrUsedInIface.Set(i)
   925  	} else {
   926  		l.attrUsedInIface.Unset(i)
   927  	}
   928  }
   929  
   930  // SymAddr checks that a symbol is reachable, and returns its value.
   931  func (l *Loader) SymAddr(i Sym) int64 {
   932  	if !l.AttrReachable(i) {
   933  		panic("unreachable symbol in symaddr")
   934  	}
   935  	return l.values[i]
   936  }
   937  
   938  // AttrNotInSymbolTable returns true for symbols that should not be
   939  // added to the symbol table of the final generated load module.
   940  func (l *Loader) AttrNotInSymbolTable(i Sym) bool {
   941  	return l.attrNotInSymbolTable.Has(i)
   942  }
   943  
   944  // SetAttrNotInSymbolTable the "not in symtab" property for a symbol
   945  // (see AttrNotInSymbolTable above).
   946  func (l *Loader) SetAttrNotInSymbolTable(i Sym, v bool) {
   947  	if v {
   948  		l.attrNotInSymbolTable.Set(i)
   949  	} else {
   950  		l.attrNotInSymbolTable.Unset(i)
   951  	}
   952  }
   953  
   954  // AttrVisibilityHidden symbols returns true for ELF symbols with
   955  // visibility set to STV_HIDDEN. They become local symbols in
   956  // the final executable. Only relevant when internally linking
   957  // on an ELF platform.
   958  func (l *Loader) AttrVisibilityHidden(i Sym) bool {
   959  	if !l.IsExternal(i) {
   960  		return false
   961  	}
   962  	return l.attrVisibilityHidden.Has(l.extIndex(i))
   963  }
   964  
   965  // SetAttrVisibilityHidden sets the "hidden visibility" property for a
   966  // symbol (see AttrVisibilityHidden).
   967  func (l *Loader) SetAttrVisibilityHidden(i Sym, v bool) {
   968  	if !l.IsExternal(i) {
   969  		panic("tried to set visibility attr on non-external symbol")
   970  	}
   971  	if v {
   972  		l.attrVisibilityHidden.Set(l.extIndex(i))
   973  	} else {
   974  		l.attrVisibilityHidden.Unset(l.extIndex(i))
   975  	}
   976  }
   977  
   978  // AttrDuplicateOK returns true for a symbol that can be present in
   979  // multiple object files.
   980  func (l *Loader) AttrDuplicateOK(i Sym) bool {
   981  	if !l.IsExternal(i) {
   982  		// TODO: if this path winds up being taken frequently, it
   983  		// might make more sense to copy the flag value out of the object
   984  		// into a larger bitmap during preload.
   985  		r, li := l.toLocal(i)
   986  		return r.Sym(li).Dupok()
   987  	}
   988  	return l.attrDuplicateOK.Has(l.extIndex(i))
   989  }
   990  
   991  // SetAttrDuplicateOK sets the "duplicate OK" property for an external
   992  // symbol (see AttrDuplicateOK).
   993  func (l *Loader) SetAttrDuplicateOK(i Sym, v bool) {
   994  	if !l.IsExternal(i) {
   995  		panic("tried to set dupok attr on non-external symbol")
   996  	}
   997  	if v {
   998  		l.attrDuplicateOK.Set(l.extIndex(i))
   999  	} else {
  1000  		l.attrDuplicateOK.Unset(l.extIndex(i))
  1001  	}
  1002  }
  1003  
  1004  // AttrShared returns true for symbols compiled with the -shared option.
  1005  func (l *Loader) AttrShared(i Sym) bool {
  1006  	if !l.IsExternal(i) {
  1007  		// TODO: if this path winds up being taken frequently, it
  1008  		// might make more sense to copy the flag value out of the
  1009  		// object into a larger bitmap during preload.
  1010  		r, _ := l.toLocal(i)
  1011  		return r.Shared()
  1012  	}
  1013  	return l.attrShared.Has(l.extIndex(i))
  1014  }
  1015  
  1016  // SetAttrShared sets the "shared" property for an external
  1017  // symbol (see AttrShared).
  1018  func (l *Loader) SetAttrShared(i Sym, v bool) {
  1019  	if !l.IsExternal(i) {
  1020  		panic(fmt.Sprintf("tried to set shared attr on non-external symbol %d %s", i, l.SymName(i)))
  1021  	}
  1022  	if v {
  1023  		l.attrShared.Set(l.extIndex(i))
  1024  	} else {
  1025  		l.attrShared.Unset(l.extIndex(i))
  1026  	}
  1027  }
  1028  
  1029  // AttrExternal returns true for function symbols loaded from host
  1030  // object files.
  1031  func (l *Loader) AttrExternal(i Sym) bool {
  1032  	if !l.IsExternal(i) {
  1033  		return false
  1034  	}
  1035  	return l.attrExternal.Has(l.extIndex(i))
  1036  }
  1037  
  1038  // SetAttrExternal sets the "external" property for a host object
  1039  // symbol (see AttrExternal).
  1040  func (l *Loader) SetAttrExternal(i Sym, v bool) {
  1041  	if !l.IsExternal(i) {
  1042  		panic(fmt.Sprintf("tried to set external attr on non-external symbol %q", l.SymName(i)))
  1043  	}
  1044  	if v {
  1045  		l.attrExternal.Set(l.extIndex(i))
  1046  	} else {
  1047  		l.attrExternal.Unset(l.extIndex(i))
  1048  	}
  1049  }
  1050  
  1051  // AttrSpecial returns true for a symbols that do not have their
  1052  // address (i.e. Value) computed by the usual mechanism of
  1053  // data.go:dodata() & data.go:address().
  1054  func (l *Loader) AttrSpecial(i Sym) bool {
  1055  	return l.attrSpecial.Has(i)
  1056  }
  1057  
  1058  // SetAttrSpecial sets the "special" property for a symbol (see
  1059  // AttrSpecial).
  1060  func (l *Loader) SetAttrSpecial(i Sym, v bool) {
  1061  	if v {
  1062  		l.attrSpecial.Set(i)
  1063  	} else {
  1064  		l.attrSpecial.Unset(i)
  1065  	}
  1066  }
  1067  
  1068  // AttrCgoExportDynamic returns true for a symbol that has been
  1069  // specially marked via the "cgo_export_dynamic" compiler directive
  1070  // written by cgo (in response to //export directives in the source).
  1071  func (l *Loader) AttrCgoExportDynamic(i Sym) bool {
  1072  	_, ok := l.attrCgoExportDynamic[i]
  1073  	return ok
  1074  }
  1075  
  1076  // SetAttrCgoExportDynamic sets the "cgo_export_dynamic" for a symbol
  1077  // (see AttrCgoExportDynamic).
  1078  func (l *Loader) SetAttrCgoExportDynamic(i Sym, v bool) {
  1079  	if v {
  1080  		l.attrCgoExportDynamic[i] = struct{}{}
  1081  	} else {
  1082  		delete(l.attrCgoExportDynamic, i)
  1083  	}
  1084  }
  1085  
  1086  // ForAllCgoExportDynamic calls f for every symbol that has been
  1087  // marked with the "cgo_export_dynamic" compiler directive.
  1088  func (l *Loader) ForAllCgoExportDynamic(f func(Sym)) {
  1089  	for s := range l.attrCgoExportDynamic {
  1090  		f(s)
  1091  	}
  1092  }
  1093  
  1094  // AttrCgoExportStatic returns true for a symbol that has been
  1095  // specially marked via the "cgo_export_static" directive
  1096  // written by cgo.
  1097  func (l *Loader) AttrCgoExportStatic(i Sym) bool {
  1098  	_, ok := l.attrCgoExportStatic[i]
  1099  	return ok
  1100  }
  1101  
  1102  // SetAttrCgoExportStatic sets the "cgo_export_static" for a symbol
  1103  // (see AttrCgoExportStatic).
  1104  func (l *Loader) SetAttrCgoExportStatic(i Sym, v bool) {
  1105  	if v {
  1106  		l.attrCgoExportStatic[i] = struct{}{}
  1107  	} else {
  1108  		delete(l.attrCgoExportStatic, i)
  1109  	}
  1110  }
  1111  
  1112  // IsGeneratedSym returns true if a symbol's been previously marked as a
  1113  // generator symbol through the SetIsGeneratedSym. The functions for generator
  1114  // symbols are kept in the Link context.
  1115  func (l *Loader) IsGeneratedSym(i Sym) bool {
  1116  	if !l.IsExternal(i) {
  1117  		return false
  1118  	}
  1119  	return l.generatedSyms.Has(l.extIndex(i))
  1120  }
  1121  
  1122  // SetIsGeneratedSym marks symbols as generated symbols. Data shouldn't be
  1123  // stored in generated symbols, and a function is registered and called for
  1124  // each of these symbols.
  1125  func (l *Loader) SetIsGeneratedSym(i Sym, v bool) {
  1126  	if !l.IsExternal(i) {
  1127  		panic("only external symbols can be generated")
  1128  	}
  1129  	if v {
  1130  		l.generatedSyms.Set(l.extIndex(i))
  1131  	} else {
  1132  		l.generatedSyms.Unset(l.extIndex(i))
  1133  	}
  1134  }
  1135  
  1136  func (l *Loader) AttrCgoExport(i Sym) bool {
  1137  	return l.AttrCgoExportDynamic(i) || l.AttrCgoExportStatic(i)
  1138  }
  1139  
  1140  // AttrReadOnly returns true for a symbol whose underlying data
  1141  // is stored via a read-only mmap.
  1142  func (l *Loader) AttrReadOnly(i Sym) bool {
  1143  	if v, ok := l.attrReadOnly[i]; ok {
  1144  		return v
  1145  	}
  1146  	if l.IsExternal(i) {
  1147  		pp := l.getPayload(i)
  1148  		if pp.objidx != 0 {
  1149  			return l.objs[pp.objidx].ReadOnly()
  1150  		}
  1151  		return false
  1152  	}
  1153  	r, _ := l.toLocal(i)
  1154  	return r.ReadOnly()
  1155  }
  1156  
  1157  // SetAttrReadOnly sets the "data is read only" property for a symbol
  1158  // (see AttrReadOnly).
  1159  func (l *Loader) SetAttrReadOnly(i Sym, v bool) {
  1160  	l.attrReadOnly[i] = v
  1161  }
  1162  
  1163  // AttrSubSymbol returns true for symbols that are listed as a
  1164  // sub-symbol of some other outer symbol. The sub/outer mechanism is
  1165  // used when loading host objects (sections from the host object
  1166  // become regular linker symbols and symbols go on the Sub list of
  1167  // their section) and for constructing the global offset table when
  1168  // internally linking a dynamic executable.
  1169  //
  1170  // Note that in later stages of the linker, we set Outer(S) to some
  1171  // container symbol C, but don't set Sub(C). Thus we have two
  1172  // distinct scenarios:
  1173  //
  1174  // - Outer symbol covers the address ranges of its sub-symbols.
  1175  //   Outer.Sub is set in this case.
  1176  // - Outer symbol doesn't cover the address ranges. It is zero-sized
  1177  //   and doesn't have sub-symbols. In the case, the inner symbol is
  1178  //   not actually a "SubSymbol". (Tricky!)
  1179  //
  1180  // This method returns TRUE only for sub-symbols in the first scenario.
  1181  //
  1182  // FIXME: would be better to do away with this and have a better way
  1183  // to represent container symbols.
  1184  
  1185  func (l *Loader) AttrSubSymbol(i Sym) bool {
  1186  	// we don't explicitly store this attribute any more -- return
  1187  	// a value based on the sub-symbol setting.
  1188  	o := l.OuterSym(i)
  1189  	if o == 0 {
  1190  		return false
  1191  	}
  1192  	return l.SubSym(o) != 0
  1193  }
  1194  
  1195  // Note that we don't have a 'SetAttrSubSymbol' method in the loader;
  1196  // clients should instead use the AddInteriorSym method to establish
  1197  // containment relationships for host object symbols.
  1198  
  1199  // Returns whether the i-th symbol has ReflectMethod attribute set.
  1200  func (l *Loader) IsReflectMethod(i Sym) bool {
  1201  	return l.SymAttr(i)&goobj.SymFlagReflectMethod != 0
  1202  }
  1203  
  1204  // Returns whether the i-th symbol is nosplit.
  1205  func (l *Loader) IsNoSplit(i Sym) bool {
  1206  	return l.SymAttr(i)&goobj.SymFlagNoSplit != 0
  1207  }
  1208  
  1209  // Returns whether this is a Go type symbol.
  1210  func (l *Loader) IsGoType(i Sym) bool {
  1211  	return l.SymAttr(i)&goobj.SymFlagGoType != 0
  1212  }
  1213  
  1214  // Returns whether this symbol should be included in typelink.
  1215  func (l *Loader) IsTypelink(i Sym) bool {
  1216  	return l.SymAttr(i)&goobj.SymFlagTypelink != 0
  1217  }
  1218  
  1219  // Returns whether this symbol is an itab symbol.
  1220  func (l *Loader) IsItab(i Sym) bool {
  1221  	if l.IsExternal(i) {
  1222  		return false
  1223  	}
  1224  	r, li := l.toLocal(i)
  1225  	return r.Sym(li).IsItab()
  1226  }
  1227  
  1228  // Returns whether this symbol is a dictionary symbol.
  1229  func (l *Loader) IsDict(i Sym) bool {
  1230  	if l.IsExternal(i) {
  1231  		return false
  1232  	}
  1233  	r, li := l.toLocal(i)
  1234  	return r.Sym(li).IsDict()
  1235  }
  1236  
  1237  // Returns whether this symbol is a compiler-generated package init func.
  1238  func (l *Loader) IsPkgInit(i Sym) bool {
  1239  	if l.IsExternal(i) {
  1240  		return false
  1241  	}
  1242  	r, li := l.toLocal(i)
  1243  	return r.Sym(li).IsPkgInit()
  1244  }
  1245  
  1246  // Return whether this is a trampoline of a deferreturn call.
  1247  func (l *Loader) IsDeferReturnTramp(i Sym) bool {
  1248  	return l.deferReturnTramp[i]
  1249  }
  1250  
  1251  // Set that i is a trampoline of a deferreturn call.
  1252  func (l *Loader) SetIsDeferReturnTramp(i Sym, v bool) {
  1253  	l.deferReturnTramp[i] = v
  1254  }
  1255  
  1256  // growValues grows the slice used to store symbol values.
  1257  func (l *Loader) growValues(reqLen int) {
  1258  	curLen := len(l.values)
  1259  	if reqLen > curLen {
  1260  		l.values = append(l.values, make([]int64, reqLen+1-curLen)...)
  1261  	}
  1262  }
  1263  
  1264  // SymValue returns the value of the i-th symbol. i is global index.
  1265  func (l *Loader) SymValue(i Sym) int64 {
  1266  	return l.values[i]
  1267  }
  1268  
  1269  // SetSymValue sets the value of the i-th symbol. i is global index.
  1270  func (l *Loader) SetSymValue(i Sym, val int64) {
  1271  	l.values[i] = val
  1272  }
  1273  
  1274  // AddToSymValue adds to the value of the i-th symbol. i is the global index.
  1275  func (l *Loader) AddToSymValue(i Sym, val int64) {
  1276  	l.values[i] += val
  1277  }
  1278  
  1279  // Returns the symbol content of the i-th symbol. i is global index.
  1280  func (l *Loader) Data(i Sym) []byte {
  1281  	if l.IsExternal(i) {
  1282  		pp := l.getPayload(i)
  1283  		if pp != nil {
  1284  			return pp.data
  1285  		}
  1286  		return nil
  1287  	}
  1288  	r, li := l.toLocal(i)
  1289  	return r.Data(li)
  1290  }
  1291  
  1292  // Returns the symbol content of the i-th symbol as a string. i is global index.
  1293  func (l *Loader) DataString(i Sym) string {
  1294  	if l.IsExternal(i) {
  1295  		pp := l.getPayload(i)
  1296  		return string(pp.data)
  1297  	}
  1298  	r, li := l.toLocal(i)
  1299  	return r.DataString(li)
  1300  }
  1301  
  1302  // FreeData clears the symbol data of an external symbol, allowing the memory
  1303  // to be freed earlier. No-op for non-external symbols.
  1304  // i is global index.
  1305  func (l *Loader) FreeData(i Sym) {
  1306  	if l.IsExternal(i) {
  1307  		pp := l.getPayload(i)
  1308  		if pp != nil {
  1309  			pp.data = nil
  1310  		}
  1311  	}
  1312  }
  1313  
  1314  // SymAlign returns the alignment for a symbol.
  1315  func (l *Loader) SymAlign(i Sym) int32 {
  1316  	if int(i) >= len(l.align) {
  1317  		// align is extended lazily -- it the sym in question is
  1318  		// outside the range of the existing slice, then we assume its
  1319  		// alignment has not yet been set.
  1320  		return 0
  1321  	}
  1322  	// TODO: would it make sense to return an arch-specific
  1323  	// alignment depending on section type? E.g. STEXT => 32,
  1324  	// SDATA => 1, etc?
  1325  	abits := l.align[i]
  1326  	if abits == 0 {
  1327  		return 0
  1328  	}
  1329  	return int32(1 << (abits - 1))
  1330  }
  1331  
  1332  // SetSymAlign sets the alignment for a symbol.
  1333  func (l *Loader) SetSymAlign(i Sym, align int32) {
  1334  	// Reject nonsense alignments.
  1335  	if align < 0 || align&(align-1) != 0 {
  1336  		panic("bad alignment value")
  1337  	}
  1338  	if int(i) >= len(l.align) {
  1339  		l.align = append(l.align, make([]uint8, l.NSym()-len(l.align))...)
  1340  	}
  1341  	if align == 0 {
  1342  		l.align[i] = 0
  1343  	}
  1344  	l.align[i] = uint8(bits.Len32(uint32(align)))
  1345  }
  1346  
  1347  // SymSect returns the section of the i-th symbol. i is global index.
  1348  func (l *Loader) SymSect(i Sym) *sym.Section {
  1349  	if int(i) >= len(l.symSects) {
  1350  		// symSects is extended lazily -- it the sym in question is
  1351  		// outside the range of the existing slice, then we assume its
  1352  		// section has not yet been set.
  1353  		return nil
  1354  	}
  1355  	return l.sects[l.symSects[i]]
  1356  }
  1357  
  1358  // SetSymSect sets the section of the i-th symbol. i is global index.
  1359  func (l *Loader) SetSymSect(i Sym, sect *sym.Section) {
  1360  	if int(i) >= len(l.symSects) {
  1361  		l.symSects = append(l.symSects, make([]uint16, l.NSym()-len(l.symSects))...)
  1362  	}
  1363  	l.symSects[i] = sect.Index
  1364  }
  1365  
  1366  // NewSection creates a new (output) section.
  1367  func (l *Loader) NewSection() *sym.Section {
  1368  	sect := new(sym.Section)
  1369  	idx := len(l.sects)
  1370  	if idx != int(uint16(idx)) {
  1371  		panic("too many sections created")
  1372  	}
  1373  	sect.Index = uint16(idx)
  1374  	l.sects = append(l.sects, sect)
  1375  	return sect
  1376  }
  1377  
  1378  // SymDynimplib returns the "dynimplib" attribute for the specified
  1379  // symbol, making up a portion of the info for a symbol specified
  1380  // on a "cgo_import_dynamic" compiler directive.
  1381  func (l *Loader) SymDynimplib(i Sym) string {
  1382  	return l.dynimplib[i]
  1383  }
  1384  
  1385  // SetSymDynimplib sets the "dynimplib" attribute for a symbol.
  1386  func (l *Loader) SetSymDynimplib(i Sym, value string) {
  1387  	// reject bad symbols
  1388  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1389  		panic("bad symbol index in SetDynimplib")
  1390  	}
  1391  	if value == "" {
  1392  		delete(l.dynimplib, i)
  1393  	} else {
  1394  		l.dynimplib[i] = value
  1395  	}
  1396  }
  1397  
  1398  // SymDynimpvers returns the "dynimpvers" attribute for the specified
  1399  // symbol, making up a portion of the info for a symbol specified
  1400  // on a "cgo_import_dynamic" compiler directive.
  1401  func (l *Loader) SymDynimpvers(i Sym) string {
  1402  	return l.dynimpvers[i]
  1403  }
  1404  
  1405  // SetSymDynimpvers sets the "dynimpvers" attribute for a symbol.
  1406  func (l *Loader) SetSymDynimpvers(i Sym, value string) {
  1407  	// reject bad symbols
  1408  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1409  		panic("bad symbol index in SetDynimpvers")
  1410  	}
  1411  	if value == "" {
  1412  		delete(l.dynimpvers, i)
  1413  	} else {
  1414  		l.dynimpvers[i] = value
  1415  	}
  1416  }
  1417  
  1418  // SymExtname returns the "extname" value for the specified
  1419  // symbol.
  1420  func (l *Loader) SymExtname(i Sym) string {
  1421  	if s, ok := l.extname[i]; ok {
  1422  		return s
  1423  	}
  1424  	return l.SymName(i)
  1425  }
  1426  
  1427  // SetSymExtname sets the  "extname" attribute for a symbol.
  1428  func (l *Loader) SetSymExtname(i Sym, value string) {
  1429  	// reject bad symbols
  1430  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1431  		panic("bad symbol index in SetExtname")
  1432  	}
  1433  	if value == "" {
  1434  		delete(l.extname, i)
  1435  	} else {
  1436  		l.extname[i] = value
  1437  	}
  1438  }
  1439  
  1440  // SymElfType returns the previously recorded ELF type for a symbol
  1441  // (used only for symbols read from shared libraries by ldshlibsyms).
  1442  // It is not set for symbols defined by the packages being linked or
  1443  // by symbols read by ldelf (and so is left as elf.STT_NOTYPE).
  1444  func (l *Loader) SymElfType(i Sym) elf.SymType {
  1445  	if et, ok := l.elfType[i]; ok {
  1446  		return et
  1447  	}
  1448  	return elf.STT_NOTYPE
  1449  }
  1450  
  1451  // SetSymElfType sets the elf type attribute for a symbol.
  1452  func (l *Loader) SetSymElfType(i Sym, et elf.SymType) {
  1453  	// reject bad symbols
  1454  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1455  		panic("bad symbol index in SetSymElfType")
  1456  	}
  1457  	if et == elf.STT_NOTYPE {
  1458  		delete(l.elfType, i)
  1459  	} else {
  1460  		l.elfType[i] = et
  1461  	}
  1462  }
  1463  
  1464  // SymElfSym returns the ELF symbol index for a given loader
  1465  // symbol, assigned during ELF symtab generation.
  1466  func (l *Loader) SymElfSym(i Sym) int32 {
  1467  	return l.elfSym[i]
  1468  }
  1469  
  1470  // SetSymElfSym sets the elf symbol index for a symbol.
  1471  func (l *Loader) SetSymElfSym(i Sym, es int32) {
  1472  	if i == 0 {
  1473  		panic("bad sym index")
  1474  	}
  1475  	if es == 0 {
  1476  		delete(l.elfSym, i)
  1477  	} else {
  1478  		l.elfSym[i] = es
  1479  	}
  1480  }
  1481  
  1482  // SymLocalElfSym returns the "local" ELF symbol index for a given loader
  1483  // symbol, assigned during ELF symtab generation.
  1484  func (l *Loader) SymLocalElfSym(i Sym) int32 {
  1485  	return l.localElfSym[i]
  1486  }
  1487  
  1488  // SetSymLocalElfSym sets the "local" elf symbol index for a symbol.
  1489  func (l *Loader) SetSymLocalElfSym(i Sym, es int32) {
  1490  	if i == 0 {
  1491  		panic("bad sym index")
  1492  	}
  1493  	if es == 0 {
  1494  		delete(l.localElfSym, i)
  1495  	} else {
  1496  		l.localElfSym[i] = es
  1497  	}
  1498  }
  1499  
  1500  // SymPlt returns the PLT offset of symbol s.
  1501  func (l *Loader) SymPlt(s Sym) int32 {
  1502  	if v, ok := l.plt[s]; ok {
  1503  		return v
  1504  	}
  1505  	return -1
  1506  }
  1507  
  1508  // SetPlt sets the PLT offset of symbol i.
  1509  func (l *Loader) SetPlt(i Sym, v int32) {
  1510  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1511  		panic("bad symbol for SetPlt")
  1512  	}
  1513  	if v == -1 {
  1514  		delete(l.plt, i)
  1515  	} else {
  1516  		l.plt[i] = v
  1517  	}
  1518  }
  1519  
  1520  // SymGot returns the GOT offset of symbol s.
  1521  func (l *Loader) SymGot(s Sym) int32 {
  1522  	if v, ok := l.got[s]; ok {
  1523  		return v
  1524  	}
  1525  	return -1
  1526  }
  1527  
  1528  // SetGot sets the GOT offset of symbol i.
  1529  func (l *Loader) SetGot(i Sym, v int32) {
  1530  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1531  		panic("bad symbol for SetGot")
  1532  	}
  1533  	if v == -1 {
  1534  		delete(l.got, i)
  1535  	} else {
  1536  		l.got[i] = v
  1537  	}
  1538  }
  1539  
  1540  // SymDynid returns the "dynid" property for the specified symbol.
  1541  func (l *Loader) SymDynid(i Sym) int32 {
  1542  	if s, ok := l.dynid[i]; ok {
  1543  		return s
  1544  	}
  1545  	return -1
  1546  }
  1547  
  1548  // SetSymDynid sets the "dynid" property for a symbol.
  1549  func (l *Loader) SetSymDynid(i Sym, val int32) {
  1550  	// reject bad symbols
  1551  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1552  		panic("bad symbol index in SetSymDynid")
  1553  	}
  1554  	if val == -1 {
  1555  		delete(l.dynid, i)
  1556  	} else {
  1557  		l.dynid[i] = val
  1558  	}
  1559  }
  1560  
  1561  // DynidSyms returns the set of symbols for which dynID is set to an
  1562  // interesting (non-default) value. This is expected to be a fairly
  1563  // small set.
  1564  func (l *Loader) DynidSyms() []Sym {
  1565  	sl := make([]Sym, 0, len(l.dynid))
  1566  	for s := range l.dynid {
  1567  		sl = append(sl, s)
  1568  	}
  1569  	sort.Slice(sl, func(i, j int) bool { return sl[i] < sl[j] })
  1570  	return sl
  1571  }
  1572  
  1573  // SymGoType returns the 'Gotype' property for a given symbol (set by
  1574  // the Go compiler for variable symbols). This version relies on
  1575  // reading aux symbols for the target sym -- it could be that a faster
  1576  // approach would be to check for gotype during preload and copy the
  1577  // results in to a map (might want to try this at some point and see
  1578  // if it helps speed things up).
  1579  func (l *Loader) SymGoType(i Sym) Sym { return l.aux1(i, goobj.AuxGotype) }
  1580  
  1581  // SymUnit returns the compilation unit for a given symbol (which will
  1582  // typically be nil for external or linker-manufactured symbols).
  1583  func (l *Loader) SymUnit(i Sym) *sym.CompilationUnit {
  1584  	if l.IsExternal(i) {
  1585  		pp := l.getPayload(i)
  1586  		if pp.objidx != 0 {
  1587  			r := l.objs[pp.objidx]
  1588  			return r.unit
  1589  		}
  1590  		return nil
  1591  	}
  1592  	r, _ := l.toLocal(i)
  1593  	return r.unit
  1594  }
  1595  
  1596  // SymPkg returns the package where the symbol came from (for
  1597  // regular compiler-generated Go symbols), but in the case of
  1598  // building with "-linkshared" (when a symbol is read from a
  1599  // shared library), will hold the library name.
  1600  // NOTE: this corresponds to sym.Symbol.File field.
  1601  func (l *Loader) SymPkg(i Sym) string {
  1602  	if f, ok := l.symPkg[i]; ok {
  1603  		return f
  1604  	}
  1605  	if l.IsExternal(i) {
  1606  		pp := l.getPayload(i)
  1607  		if pp.objidx != 0 {
  1608  			r := l.objs[pp.objidx]
  1609  			return r.unit.Lib.Pkg
  1610  		}
  1611  		return ""
  1612  	}
  1613  	r, _ := l.toLocal(i)
  1614  	return r.unit.Lib.Pkg
  1615  }
  1616  
  1617  // SetSymPkg sets the package/library for a symbol. This is
  1618  // needed mainly for external symbols, specifically those imported
  1619  // from shared libraries.
  1620  func (l *Loader) SetSymPkg(i Sym, pkg string) {
  1621  	// reject bad symbols
  1622  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1623  		panic("bad symbol index in SetSymPkg")
  1624  	}
  1625  	l.symPkg[i] = pkg
  1626  }
  1627  
  1628  // SymLocalentry returns an offset in bytes of the "local entry" of a symbol.
  1629  //
  1630  // On PPC64, a value of 1 indicates the symbol does not use or preserve a TOC
  1631  // pointer in R2, nor does it have a distinct local entry.
  1632  func (l *Loader) SymLocalentry(i Sym) uint8 {
  1633  	return l.localentry[i]
  1634  }
  1635  
  1636  // SetSymLocalentry sets the "local entry" offset attribute for a symbol.
  1637  func (l *Loader) SetSymLocalentry(i Sym, value uint8) {
  1638  	// reject bad symbols
  1639  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1640  		panic("bad symbol index in SetSymLocalentry")
  1641  	}
  1642  	if value == 0 {
  1643  		delete(l.localentry, i)
  1644  	} else {
  1645  		l.localentry[i] = value
  1646  	}
  1647  }
  1648  
  1649  // Returns the number of aux symbols given a global index.
  1650  func (l *Loader) NAux(i Sym) int {
  1651  	if l.IsExternal(i) {
  1652  		return 0
  1653  	}
  1654  	r, li := l.toLocal(i)
  1655  	return r.NAux(li)
  1656  }
  1657  
  1658  // Returns the "handle" to the j-th aux symbol of the i-th symbol.
  1659  func (l *Loader) Aux(i Sym, j int) Aux {
  1660  	if l.IsExternal(i) {
  1661  		return Aux{}
  1662  	}
  1663  	r, li := l.toLocal(i)
  1664  	if j >= r.NAux(li) {
  1665  		return Aux{}
  1666  	}
  1667  	return Aux{r.Aux(li, j), r, l}
  1668  }
  1669  
  1670  // WasmImportSym returns the auxiliary WebAssembly import symbol associated with
  1671  // a given function symbol. The aux sym only exists for Go function stubs that
  1672  // have been annotated with the //go:wasmimport directive.  The aux sym
  1673  // contains the information necessary for the linker to add a WebAssembly
  1674  // import statement.
  1675  // (https://webassembly.github.io/spec/core/syntax/modules.html#imports)
  1676  func (l *Loader) WasmImportSym(fnSymIdx Sym) Sym {
  1677  	if !l.SymType(fnSymIdx).IsText() {
  1678  		log.Fatalf("error: non-function sym %d/%s t=%s passed to WasmImportSym", fnSymIdx, l.SymName(fnSymIdx), l.SymType(fnSymIdx).String())
  1679  	}
  1680  	return l.aux1(fnSymIdx, goobj.AuxWasmImport)
  1681  }
  1682  
  1683  func (l *Loader) WasmTypeSym(s Sym) Sym {
  1684  	return l.aux1(s, goobj.AuxWasmType)
  1685  }
  1686  
  1687  // SEHUnwindSym returns the auxiliary SEH unwind symbol associated with
  1688  // a given function symbol.
  1689  func (l *Loader) SEHUnwindSym(fnSymIdx Sym) Sym {
  1690  	if !l.SymType(fnSymIdx).IsText() {
  1691  		log.Fatalf("error: non-function sym %d/%s t=%s passed to SEHUnwindSym", fnSymIdx, l.SymName(fnSymIdx), l.SymType(fnSymIdx).String())
  1692  	}
  1693  
  1694  	return l.aux1(fnSymIdx, goobj.AuxSehUnwindInfo)
  1695  }
  1696  
  1697  // GetFuncDwarfAuxSyms collects and returns the auxiliary DWARF
  1698  // symbols associated with a given function symbol.  Prior to the
  1699  // introduction of the loader, this was done purely using name
  1700  // lookups, e.f. for function with name XYZ we would then look up
  1701  // go.info.XYZ, etc.
  1702  func (l *Loader) GetFuncDwarfAuxSyms(fnSymIdx Sym) (auxDwarfInfo, auxDwarfLoc, auxDwarfRanges, auxDwarfLines Sym) {
  1703  	if !l.SymType(fnSymIdx).IsText() {
  1704  		log.Fatalf("error: non-function sym %d/%s t=%s passed to GetFuncDwarfAuxSyms", fnSymIdx, l.SymName(fnSymIdx), l.SymType(fnSymIdx).String())
  1705  	}
  1706  	r, auxs := l.auxs(fnSymIdx)
  1707  
  1708  	for i := range auxs {
  1709  		a := &auxs[i]
  1710  		switch a.Type() {
  1711  		case goobj.AuxDwarfInfo:
  1712  			auxDwarfInfo = l.resolve(r, a.Sym())
  1713  			if l.SymType(auxDwarfInfo) != sym.SDWARFFCN {
  1714  				panic("aux dwarf info sym with wrong type")
  1715  			}
  1716  		case goobj.AuxDwarfLoc:
  1717  			auxDwarfLoc = l.resolve(r, a.Sym())
  1718  			if l.SymType(auxDwarfLoc) != sym.SDWARFLOC {
  1719  				panic("aux dwarf loc sym with wrong type")
  1720  			}
  1721  		case goobj.AuxDwarfRanges:
  1722  			auxDwarfRanges = l.resolve(r, a.Sym())
  1723  			if l.SymType(auxDwarfRanges) != sym.SDWARFRANGE {
  1724  				panic("aux dwarf ranges sym with wrong type")
  1725  			}
  1726  		case goobj.AuxDwarfLines:
  1727  			auxDwarfLines = l.resolve(r, a.Sym())
  1728  			if l.SymType(auxDwarfLines) != sym.SDWARFLINES {
  1729  				panic("aux dwarf lines sym with wrong type")
  1730  			}
  1731  		}
  1732  	}
  1733  	return
  1734  }
  1735  
  1736  func (l *Loader) GetVarDwarfAuxSym(i Sym) Sym {
  1737  	aux := l.aux1(i, goobj.AuxDwarfInfo)
  1738  	if aux != 0 && l.SymType(aux) != sym.SDWARFVAR {
  1739  		fmt.Println(l.SymName(i), l.SymType(i), l.SymType(aux), sym.SDWARFVAR)
  1740  		panic("aux dwarf info sym with wrong type")
  1741  	}
  1742  	return aux
  1743  }
  1744  
  1745  // AddInteriorSym sets up 'interior' as an interior symbol of
  1746  // container/payload symbol 'container'. An interior symbol does not
  1747  // itself have data, but gives a name to a subrange of the data in its
  1748  // container symbol. The container itself may or may not have a name.
  1749  // This method is intended primarily for use in the host object
  1750  // loaders, to capture the semantics of symbols and sections in an
  1751  // object file. When reading a host object file, we'll typically
  1752  // encounter a static section symbol (ex: ".text") containing content
  1753  // for a collection of functions, then a series of ELF (or macho, etc)
  1754  // symbol table entries each of which points into a sub-section
  1755  // (offset and length) of its corresponding container symbol. Within
  1756  // the go linker we create a loader.Sym for the container (which is
  1757  // expected to have the actual content/payload) and then a set of
  1758  // interior loader.Sym's that point into a portion of the container.
  1759  func (l *Loader) AddInteriorSym(container Sym, interior Sym) {
  1760  	// Container symbols are expected to have content/data.
  1761  	// NB: this restriction may turn out to be too strict (it's possible
  1762  	// to imagine a zero-sized container with an interior symbol pointing
  1763  	// into it); it's ok to relax or remove it if we counter an
  1764  	// oddball host object that triggers this.
  1765  	if l.SymSize(container) == 0 && len(l.Data(container)) == 0 {
  1766  		panic("unexpected empty container symbol")
  1767  	}
  1768  	// The interior symbols for a container are not expected to have
  1769  	// content/data or relocations.
  1770  	if len(l.Data(interior)) != 0 {
  1771  		panic("unexpected non-empty interior symbol")
  1772  	}
  1773  	// Interior symbol is expected to be in the symbol table.
  1774  	if l.AttrNotInSymbolTable(interior) {
  1775  		panic("interior symbol must be in symtab")
  1776  	}
  1777  	// Only a single level of containment is allowed.
  1778  	if l.OuterSym(container) != 0 {
  1779  		panic("outer has outer itself")
  1780  	}
  1781  	// Interior sym should not already have a sibling.
  1782  	if l.SubSym(interior) != 0 {
  1783  		panic("sub set for subsym")
  1784  	}
  1785  	// Interior sym should not already point at a container.
  1786  	if l.OuterSym(interior) != 0 {
  1787  		panic("outer already set for subsym")
  1788  	}
  1789  	l.sub[interior] = l.sub[container]
  1790  	l.sub[container] = interior
  1791  	l.outer[interior] = container
  1792  }
  1793  
  1794  // OuterSym gets the outer/container symbol.
  1795  func (l *Loader) OuterSym(i Sym) Sym {
  1796  	return l.outer[i]
  1797  }
  1798  
  1799  // SubSym gets the subsymbol for host object loaded symbols.
  1800  func (l *Loader) SubSym(i Sym) Sym {
  1801  	return l.sub[i]
  1802  }
  1803  
  1804  // growOuter grows the slice used to store outer symbol.
  1805  func (l *Loader) growOuter(reqLen int) {
  1806  	curLen := len(l.outer)
  1807  	if reqLen > curLen {
  1808  		l.outer = append(l.outer, make([]Sym, reqLen-curLen)...)
  1809  	}
  1810  }
  1811  
  1812  // SetCarrierSym declares that 'c' is the carrier or container symbol
  1813  // for 's'. Carrier symbols are used in the linker to as a container
  1814  // for a collection of sub-symbols where the content of the
  1815  // sub-symbols is effectively concatenated to form the content of the
  1816  // carrier. The carrier is given a name in the output symbol table
  1817  // while the sub-symbol names are not. For example, the Go compiler
  1818  // emits named string symbols (type SGOSTRING) when compiling a
  1819  // package; after being deduplicated, these symbols are collected into
  1820  // a single unit by assigning them a new carrier symbol named
  1821  // "go:string.*" (which appears in the final symbol table for the
  1822  // output load module).
  1823  func (l *Loader) SetCarrierSym(s Sym, c Sym) {
  1824  	if c == 0 {
  1825  		panic("invalid carrier in SetCarrierSym")
  1826  	}
  1827  	if s == 0 {
  1828  		panic("invalid sub-symbol in SetCarrierSym")
  1829  	}
  1830  	// Carrier symbols are not expected to have content/data. It is
  1831  	// ok for them to have non-zero size (to allow for use of generator
  1832  	// symbols).
  1833  	if len(l.Data(c)) != 0 {
  1834  		panic("unexpected non-empty carrier symbol")
  1835  	}
  1836  	l.outer[s] = c
  1837  	// relocsym's foldSubSymbolOffset requires that we only
  1838  	// have a single level of containment-- enforce here.
  1839  	if l.outer[c] != 0 {
  1840  		panic("invalid nested carrier sym")
  1841  	}
  1842  }
  1843  
  1844  // Initialize Reachable bitmap and its siblings for running deadcode pass.
  1845  func (l *Loader) InitReachable() {
  1846  	l.growAttrBitmaps(l.NSym() + 1)
  1847  }
  1848  
  1849  type symWithVal struct {
  1850  	s Sym
  1851  	v int64
  1852  }
  1853  type bySymValue []symWithVal
  1854  
  1855  func (s bySymValue) Len() int           { return len(s) }
  1856  func (s bySymValue) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
  1857  func (s bySymValue) Less(i, j int) bool { return s[i].v < s[j].v }
  1858  
  1859  // SortSub walks through the sub-symbols for 's' and sorts them
  1860  // in place by increasing value. Return value is the new
  1861  // sub symbol for the specified outer symbol.
  1862  func (l *Loader) SortSub(s Sym) Sym {
  1863  
  1864  	if s == 0 || l.sub[s] == 0 {
  1865  		return s
  1866  	}
  1867  
  1868  	// Sort symbols using a slice first. Use a stable sort on the off
  1869  	// chance that there's more than once symbol with the same value,
  1870  	// so as to preserve reproducible builds.
  1871  	sl := []symWithVal{}
  1872  	for ss := l.sub[s]; ss != 0; ss = l.sub[ss] {
  1873  		sl = append(sl, symWithVal{s: ss, v: l.SymValue(ss)})
  1874  	}
  1875  	sort.Stable(bySymValue(sl))
  1876  
  1877  	// Then apply any changes needed to the sub map.
  1878  	ns := Sym(0)
  1879  	for i := len(sl) - 1; i >= 0; i-- {
  1880  		s := sl[i].s
  1881  		l.sub[s] = ns
  1882  		ns = s
  1883  	}
  1884  
  1885  	// Update sub for outer symbol, then return
  1886  	l.sub[s] = sl[0].s
  1887  	return sl[0].s
  1888  }
  1889  
  1890  // SortSyms sorts a list of symbols by their value.
  1891  func (l *Loader) SortSyms(ss []Sym) {
  1892  	sort.SliceStable(ss, func(i, j int) bool { return l.SymValue(ss[i]) < l.SymValue(ss[j]) })
  1893  }
  1894  
  1895  // Insure that reachable bitmap and its siblings have enough size.
  1896  func (l *Loader) growAttrBitmaps(reqLen int) {
  1897  	if reqLen > l.attrReachable.Len() {
  1898  		// These are indexed by global symbol
  1899  		l.attrReachable = growBitmap(reqLen, l.attrReachable)
  1900  		l.attrOnList = growBitmap(reqLen, l.attrOnList)
  1901  		l.attrLocal = growBitmap(reqLen, l.attrLocal)
  1902  		l.attrNotInSymbolTable = growBitmap(reqLen, l.attrNotInSymbolTable)
  1903  		l.attrUsedInIface = growBitmap(reqLen, l.attrUsedInIface)
  1904  		l.attrSpecial = growBitmap(reqLen, l.attrSpecial)
  1905  	}
  1906  	l.growExtAttrBitmaps()
  1907  }
  1908  
  1909  func (l *Loader) growExtAttrBitmaps() {
  1910  	// These are indexed by external symbol index (e.g. l.extIndex(i))
  1911  	extReqLen := len(l.payloads)
  1912  	if extReqLen > l.attrVisibilityHidden.Len() {
  1913  		l.attrVisibilityHidden = growBitmap(extReqLen, l.attrVisibilityHidden)
  1914  		l.attrDuplicateOK = growBitmap(extReqLen, l.attrDuplicateOK)
  1915  		l.attrShared = growBitmap(extReqLen, l.attrShared)
  1916  		l.attrExternal = growBitmap(extReqLen, l.attrExternal)
  1917  		l.generatedSyms = growBitmap(extReqLen, l.generatedSyms)
  1918  	}
  1919  }
  1920  
  1921  func (relocs *Relocs) Count() int { return len(relocs.rs) }
  1922  
  1923  // At returns the j-th reloc for a global symbol.
  1924  func (relocs *Relocs) At(j int) Reloc {
  1925  	if relocs.l.isExtReader(relocs.r) {
  1926  		return Reloc{&relocs.rs[j], relocs.r, relocs.l}
  1927  	}
  1928  	return Reloc{&relocs.rs[j], relocs.r, relocs.l}
  1929  }
  1930  
  1931  // Relocs returns a Relocs object for the given global sym.
  1932  func (l *Loader) Relocs(i Sym) Relocs {
  1933  	r, li := l.toLocal(i)
  1934  	if r == nil {
  1935  		panic(fmt.Sprintf("trying to get oreader for invalid sym %d\n\n", i))
  1936  	}
  1937  	return l.relocs(r, li)
  1938  }
  1939  
  1940  // relocs returns a Relocs object given a local sym index and reader.
  1941  func (l *Loader) relocs(r *oReader, li uint32) Relocs {
  1942  	var rs []goobj.Reloc
  1943  	if l.isExtReader(r) {
  1944  		pp := l.payloads[li]
  1945  		rs = pp.relocs
  1946  	} else {
  1947  		rs = r.Relocs(li)
  1948  	}
  1949  	return Relocs{
  1950  		rs: rs,
  1951  		li: li,
  1952  		r:  r,
  1953  		l:  l,
  1954  	}
  1955  }
  1956  
  1957  func (l *Loader) auxs(i Sym) (*oReader, []goobj.Aux) {
  1958  	if l.IsExternal(i) {
  1959  		pp := l.getPayload(i)
  1960  		return l.objs[pp.objidx], pp.auxs
  1961  	} else {
  1962  		r, li := l.toLocal(i)
  1963  		return r, r.Auxs(li)
  1964  	}
  1965  }
  1966  
  1967  // Returns a specific aux symbol of type t for symbol i.
  1968  func (l *Loader) aux1(i Sym, t uint8) Sym {
  1969  	r, auxs := l.auxs(i)
  1970  	for j := range auxs {
  1971  		a := &auxs[j]
  1972  		if a.Type() == t {
  1973  			return l.resolve(r, a.Sym())
  1974  		}
  1975  	}
  1976  	return 0
  1977  }
  1978  
  1979  func (l *Loader) Pcsp(i Sym) Sym { return l.aux1(i, goobj.AuxPcsp) }
  1980  
  1981  // Returns all aux symbols of per-PC data for symbol i.
  1982  // tmp is a scratch space for the pcdata slice.
  1983  func (l *Loader) PcdataAuxs(i Sym, tmp []Sym) (pcsp, pcfile, pcline, pcinline Sym, pcdata []Sym) {
  1984  	pcdata = tmp[:0]
  1985  	r, auxs := l.auxs(i)
  1986  	for j := range auxs {
  1987  		a := &auxs[j]
  1988  		switch a.Type() {
  1989  		case goobj.AuxPcsp:
  1990  			pcsp = l.resolve(r, a.Sym())
  1991  		case goobj.AuxPcline:
  1992  			pcline = l.resolve(r, a.Sym())
  1993  		case goobj.AuxPcfile:
  1994  			pcfile = l.resolve(r, a.Sym())
  1995  		case goobj.AuxPcinline:
  1996  			pcinline = l.resolve(r, a.Sym())
  1997  		case goobj.AuxPcdata:
  1998  			pcdata = append(pcdata, l.resolve(r, a.Sym()))
  1999  		}
  2000  	}
  2001  	return
  2002  }
  2003  
  2004  // Returns the number of pcdata for symbol i.
  2005  func (l *Loader) NumPcdata(i Sym) int {
  2006  	n := 0
  2007  	_, auxs := l.auxs(i)
  2008  	for j := range auxs {
  2009  		a := &auxs[j]
  2010  		if a.Type() == goobj.AuxPcdata {
  2011  			n++
  2012  		}
  2013  	}
  2014  	return n
  2015  }
  2016  
  2017  // Returns all funcdata symbols of symbol i.
  2018  // tmp is a scratch space.
  2019  func (l *Loader) Funcdata(i Sym, tmp []Sym) []Sym {
  2020  	fd := tmp[:0]
  2021  	r, auxs := l.auxs(i)
  2022  	for j := range auxs {
  2023  		a := &auxs[j]
  2024  		if a.Type() == goobj.AuxFuncdata {
  2025  			fd = append(fd, l.resolve(r, a.Sym()))
  2026  		}
  2027  	}
  2028  	return fd
  2029  }
  2030  
  2031  // Returns the number of funcdata for symbol i.
  2032  func (l *Loader) NumFuncdata(i Sym) int {
  2033  	n := 0
  2034  	_, auxs := l.auxs(i)
  2035  	for j := range auxs {
  2036  		a := &auxs[j]
  2037  		if a.Type() == goobj.AuxFuncdata {
  2038  			n++
  2039  		}
  2040  	}
  2041  	return n
  2042  }
  2043  
  2044  // FuncInfo provides hooks to access goobj.FuncInfo in the objects.
  2045  type FuncInfo struct {
  2046  	l       *Loader
  2047  	r       *oReader
  2048  	data    []byte
  2049  	lengths goobj.FuncInfoLengths
  2050  }
  2051  
  2052  func (fi *FuncInfo) Valid() bool { return fi.r != nil }
  2053  
  2054  func (fi *FuncInfo) Args() int {
  2055  	return int((*goobj.FuncInfo)(nil).ReadArgs(fi.data))
  2056  }
  2057  
  2058  func (fi *FuncInfo) Locals() int {
  2059  	return int((*goobj.FuncInfo)(nil).ReadLocals(fi.data))
  2060  }
  2061  
  2062  func (fi *FuncInfo) FuncID() abi.FuncID {
  2063  	return (*goobj.FuncInfo)(nil).ReadFuncID(fi.data)
  2064  }
  2065  
  2066  func (fi *FuncInfo) FuncFlag() abi.FuncFlag {
  2067  	return (*goobj.FuncInfo)(nil).ReadFuncFlag(fi.data)
  2068  }
  2069  
  2070  func (fi *FuncInfo) StartLine() int32 {
  2071  	return (*goobj.FuncInfo)(nil).ReadStartLine(fi.data)
  2072  }
  2073  
  2074  // Preload has to be called prior to invoking the various methods
  2075  // below related to pcdata, funcdataoff, files, and inltree nodes.
  2076  func (fi *FuncInfo) Preload() {
  2077  	fi.lengths = (*goobj.FuncInfo)(nil).ReadFuncInfoLengths(fi.data)
  2078  }
  2079  
  2080  func (fi *FuncInfo) NumFile() uint32 {
  2081  	if !fi.lengths.Initialized {
  2082  		panic("need to call Preload first")
  2083  	}
  2084  	return fi.lengths.NumFile
  2085  }
  2086  
  2087  func (fi *FuncInfo) File(k int) goobj.CUFileIndex {
  2088  	if !fi.lengths.Initialized {
  2089  		panic("need to call Preload first")
  2090  	}
  2091  	return (*goobj.FuncInfo)(nil).ReadFile(fi.data, fi.lengths.FileOff, uint32(k))
  2092  }
  2093  
  2094  // TopFrame returns true if the function associated with this FuncInfo
  2095  // is an entry point, meaning that unwinders should stop when they hit
  2096  // this function.
  2097  func (fi *FuncInfo) TopFrame() bool {
  2098  	return (fi.FuncFlag() & abi.FuncFlagTopFrame) != 0
  2099  }
  2100  
  2101  type InlTreeNode struct {
  2102  	Parent   int32
  2103  	File     goobj.CUFileIndex
  2104  	Line     int32
  2105  	Func     Sym
  2106  	ParentPC int32
  2107  }
  2108  
  2109  func (fi *FuncInfo) NumInlTree() uint32 {
  2110  	if !fi.lengths.Initialized {
  2111  		panic("need to call Preload first")
  2112  	}
  2113  	return fi.lengths.NumInlTree
  2114  }
  2115  
  2116  func (fi *FuncInfo) InlTree(k int) InlTreeNode {
  2117  	if !fi.lengths.Initialized {
  2118  		panic("need to call Preload first")
  2119  	}
  2120  	node := (*goobj.FuncInfo)(nil).ReadInlTree(fi.data, fi.lengths.InlTreeOff, uint32(k))
  2121  	return InlTreeNode{
  2122  		Parent:   node.Parent,
  2123  		File:     node.File,
  2124  		Line:     node.Line,
  2125  		Func:     fi.l.resolve(fi.r, node.Func),
  2126  		ParentPC: node.ParentPC,
  2127  	}
  2128  }
  2129  
  2130  func (l *Loader) FuncInfo(i Sym) FuncInfo {
  2131  	r, auxs := l.auxs(i)
  2132  	for j := range auxs {
  2133  		a := &auxs[j]
  2134  		if a.Type() == goobj.AuxFuncInfo {
  2135  			b := r.Data(a.Sym().SymIdx)
  2136  			return FuncInfo{l, r, b, goobj.FuncInfoLengths{}}
  2137  		}
  2138  	}
  2139  	return FuncInfo{}
  2140  }
  2141  
  2142  // Preload a package: adds autolib.
  2143  // Does not add defined package or non-packaged symbols to the symbol table.
  2144  // These are done in LoadSyms.
  2145  // Does not read symbol data.
  2146  // Returns the fingerprint of the object.
  2147  func (l *Loader) Preload(localSymVersion int, f *bio.Reader, lib *sym.Library, unit *sym.CompilationUnit, length int64) goobj.FingerprintType {
  2148  	roObject, readonly, err := f.Slice(uint64(length)) // TODO: no need to map blocks that are for tools only (e.g. RefName)
  2149  	if err != nil {
  2150  		log.Fatal("cannot read object file:", err)
  2151  	}
  2152  	r := goobj.NewReaderFromBytes(roObject, readonly)
  2153  	if r == nil {
  2154  		if len(roObject) >= 8 && bytes.Equal(roObject[:8], []byte("\x00go114ld")) {
  2155  			log.Fatalf("found object file %s in old format", f.File().Name())
  2156  		}
  2157  		panic("cannot read object file")
  2158  	}
  2159  	pkgprefix := objabi.PathToPrefix(lib.Pkg) + "."
  2160  	ndef := r.NSym()
  2161  	nhashed64def := r.NHashed64def()
  2162  	nhasheddef := r.NHasheddef()
  2163  	or := &oReader{
  2164  		Reader:       r,
  2165  		unit:         unit,
  2166  		version:      localSymVersion,
  2167  		pkgprefix:    pkgprefix,
  2168  		syms:         make([]Sym, ndef+nhashed64def+nhasheddef+r.NNonpkgdef()+r.NNonpkgref()),
  2169  		ndef:         ndef,
  2170  		nhasheddef:   nhasheddef,
  2171  		nhashed64def: nhashed64def,
  2172  		objidx:       uint32(len(l.objs)),
  2173  	}
  2174  
  2175  	if r.Unlinkable() {
  2176  		log.Fatalf("link: unlinkable object (from package %s) - compiler requires -p flag", lib.Pkg)
  2177  	}
  2178  
  2179  	// Autolib
  2180  	lib.Autolib = append(lib.Autolib, r.Autolib()...)
  2181  
  2182  	// DWARF file table
  2183  	nfile := r.NFile()
  2184  	unit.FileTable = make([]string, nfile)
  2185  	for i := range unit.FileTable {
  2186  		unit.FileTable[i] = r.File(i)
  2187  	}
  2188  
  2189  	l.addObj(lib.Pkg, or)
  2190  
  2191  	// The caller expects us consuming all the data
  2192  	f.MustSeek(length, io.SeekCurrent)
  2193  
  2194  	return r.Fingerprint()
  2195  }
  2196  
  2197  // Holds the loader along with temporary states for loading symbols.
  2198  type loadState struct {
  2199  	l            *Loader
  2200  	hashed64Syms map[uint64]symAndSize         // short hashed (content-addressable) symbols, keyed by content hash
  2201  	hashedSyms   map[goobj.HashType]symAndSize // hashed (content-addressable) symbols, keyed by content hash
  2202  
  2203  	linknameVarRefs []linknameVarRef // linknamed var refererces
  2204  }
  2205  
  2206  type linknameVarRef struct {
  2207  	pkg  string // package of reference (not definition)
  2208  	name string
  2209  	sym  Sym
  2210  }
  2211  
  2212  // Preload symbols of given kind from an object.
  2213  func (st *loadState) preloadSyms(r *oReader, kind int) {
  2214  	l := st.l
  2215  	var start, end uint32
  2216  	switch kind {
  2217  	case pkgDef:
  2218  		start = 0
  2219  		end = uint32(r.ndef)
  2220  	case hashed64Def:
  2221  		start = uint32(r.ndef)
  2222  		end = uint32(r.ndef + r.nhashed64def)
  2223  	case hashedDef:
  2224  		start = uint32(r.ndef + r.nhashed64def)
  2225  		end = uint32(r.ndef + r.nhashed64def + r.nhasheddef)
  2226  	case nonPkgDef:
  2227  		start = uint32(r.ndef + r.nhashed64def + r.nhasheddef)
  2228  		end = uint32(r.ndef + r.nhashed64def + r.nhasheddef + r.NNonpkgdef())
  2229  	default:
  2230  		panic("preloadSyms: bad kind")
  2231  	}
  2232  	l.growAttrBitmaps(len(l.objSyms) + int(end-start))
  2233  	loadingRuntimePkg := r.unit.Lib.Pkg == "runtime"
  2234  	for i := start; i < end; i++ {
  2235  		osym := r.Sym(i)
  2236  		var name string
  2237  		var v int
  2238  		if kind != hashed64Def && kind != hashedDef { // we don't need the name, etc. for hashed symbols
  2239  			name = osym.Name(r.Reader)
  2240  			v = abiToVer(osym.ABI(), r.version)
  2241  		}
  2242  		gi := st.addSym(name, v, r, i, kind, osym)
  2243  		r.syms[i] = gi
  2244  		if kind == nonPkgDef && osym.IsLinkname() && r.DataSize(i) == 0 && strings.Contains(name, ".") {
  2245  			// This is a linknamed "var" "reference" (var x T with no data and //go:linkname x).
  2246  			// We want to check if a linkname reference is allowed. Here we haven't loaded all
  2247  			// symbol definitions, so we don't yet know all the push linknames. So we add to a
  2248  			// list and check later after all symbol defs are loaded. Linknamed vars are rare,
  2249  			// so this list won't be long.
  2250  			// Only check references (pull), not definitions (push, with non-zero size),
  2251  			// so push is always allowed.
  2252  			// This use of linkname is usually for referencing C symbols, so allow symbols
  2253  			// with no "." in its name (not a regular Go symbol).
  2254  			// Linkname is always a non-package reference.
  2255  			st.linknameVarRefs = append(st.linknameVarRefs, linknameVarRef{r.unit.Lib.Pkg, name, gi})
  2256  		}
  2257  		if osym.Local() {
  2258  			l.SetAttrLocal(gi, true)
  2259  		}
  2260  		if osym.UsedInIface() {
  2261  			l.SetAttrUsedInIface(gi, true)
  2262  		}
  2263  		if strings.HasPrefix(name, "runtime.") ||
  2264  			(loadingRuntimePkg && strings.HasPrefix(name, "type:")) {
  2265  			if bi := goobj.BuiltinIdx(name, int(osym.ABI())); bi != -1 {
  2266  				// This is a definition of a builtin symbol. Record where it is.
  2267  				l.builtinSyms[bi] = gi
  2268  			}
  2269  		}
  2270  		if a := int32(osym.Align()); a != 0 && a > l.SymAlign(gi) {
  2271  			l.SetSymAlign(gi, a)
  2272  		}
  2273  		if osym.WasmExport() {
  2274  			l.WasmExports = append(l.WasmExports, gi)
  2275  		}
  2276  	}
  2277  }
  2278  
  2279  // Add syms, hashed (content-addressable) symbols, non-package symbols, and
  2280  // references to external symbols (which are always named).
  2281  func (l *Loader) LoadSyms(arch *sys.Arch) {
  2282  	// Allocate space for symbols, making a guess as to how much space we need.
  2283  	// This function was determined empirically by looking at the cmd/compile on
  2284  	// Darwin, and picking factors for hashed and hashed64 syms.
  2285  	var symSize, hashedSize, hashed64Size int
  2286  	for _, r := range l.objs[goObjStart:] {
  2287  		symSize += r.ndef + r.nhasheddef/2 + r.nhashed64def/2 + r.NNonpkgdef()
  2288  		hashedSize += r.nhasheddef / 2
  2289  		hashed64Size += r.nhashed64def / 2
  2290  	}
  2291  	// Index 0 is invalid for symbols.
  2292  	l.objSyms = make([]objSym, 1, symSize)
  2293  
  2294  	st := loadState{
  2295  		l:            l,
  2296  		hashed64Syms: make(map[uint64]symAndSize, hashed64Size),
  2297  		hashedSyms:   make(map[goobj.HashType]symAndSize, hashedSize),
  2298  	}
  2299  
  2300  	for _, r := range l.objs[goObjStart:] {
  2301  		st.preloadSyms(r, pkgDef)
  2302  	}
  2303  	l.npkgsyms = l.NSym()
  2304  	for _, r := range l.objs[goObjStart:] {
  2305  		st.preloadSyms(r, hashed64Def)
  2306  		st.preloadSyms(r, hashedDef)
  2307  		st.preloadSyms(r, nonPkgDef)
  2308  	}
  2309  	for _, sf := range l.sizeFixups {
  2310  		pp := l.cloneToExternal(sf.sym)
  2311  		pp.size = int64(sf.size)
  2312  	}
  2313  	for _, vr := range st.linknameVarRefs {
  2314  		l.checkLinkname(vr.pkg, vr.name, vr.sym)
  2315  	}
  2316  	l.nhashedsyms = len(st.hashed64Syms) + len(st.hashedSyms)
  2317  	for _, r := range l.objs[goObjStart:] {
  2318  		loadObjRefs(l, r, arch)
  2319  	}
  2320  	l.values = make([]int64, l.NSym(), l.NSym()+1000) // +1000 make some room for external symbols
  2321  	l.outer = make([]Sym, l.NSym(), l.NSym()+1000)
  2322  }
  2323  
  2324  func loadObjRefs(l *Loader, r *oReader, arch *sys.Arch) {
  2325  	// load non-package refs
  2326  	ndef := uint32(r.NAlldef())
  2327  	for i, n := uint32(0), uint32(r.NNonpkgref()); i < n; i++ {
  2328  		osym := r.Sym(ndef + i)
  2329  		name := osym.Name(r.Reader)
  2330  		v := abiToVer(osym.ABI(), r.version)
  2331  		gi := l.LookupOrCreateSym(name, v)
  2332  		r.syms[ndef+i] = gi
  2333  		if osym.IsLinkname() {
  2334  			// Check if a linkname reference is allowed.
  2335  			// Only check references (pull), not definitions (push),
  2336  			// so push is always allowed.
  2337  			// Linkname is always a non-package reference.
  2338  			l.checkLinkname(r.unit.Lib.Pkg, name, gi)
  2339  		}
  2340  		if osym.Local() {
  2341  			l.SetAttrLocal(gi, true)
  2342  		}
  2343  		if osym.UsedInIface() {
  2344  			l.SetAttrUsedInIface(gi, true)
  2345  		}
  2346  	}
  2347  
  2348  	// referenced packages
  2349  	npkg := r.NPkg()
  2350  	r.pkg = make([]uint32, npkg)
  2351  	for i := 1; i < npkg; i++ { // PkgIdx 0 is a dummy invalid package
  2352  		pkg := r.Pkg(i)
  2353  		objidx, ok := l.objByPkg[pkg]
  2354  		if !ok {
  2355  			log.Fatalf("%v: reference to nonexistent package %s", r.unit.Lib, pkg)
  2356  		}
  2357  		r.pkg[i] = objidx
  2358  	}
  2359  
  2360  	// load flags of package refs
  2361  	for i, n := 0, r.NRefFlags(); i < n; i++ {
  2362  		rf := r.RefFlags(i)
  2363  		gi := l.resolve(r, rf.Sym())
  2364  		if rf.Flag2()&goobj.SymFlagUsedInIface != 0 {
  2365  			l.SetAttrUsedInIface(gi, true)
  2366  		}
  2367  	}
  2368  }
  2369  
  2370  func abiToVer(abi uint16, localSymVersion int) int {
  2371  	var v int
  2372  	if abi == goobj.SymABIstatic {
  2373  		// Static
  2374  		v = localSymVersion
  2375  	} else if abiver := sym.ABIToVersion(obj.ABI(abi)); abiver != -1 {
  2376  		// Note that data symbols are "ABI0", which maps to version 0.
  2377  		v = abiver
  2378  	} else {
  2379  		log.Fatalf("invalid symbol ABI: %d", abi)
  2380  	}
  2381  	return v
  2382  }
  2383  
  2384  // A list of blocked linknames. Some linknames are allowed only
  2385  // in specific packages. This maps symbol names to allowed packages.
  2386  // If a name is not in this map, it is allowed iff the definition
  2387  // has a linkname (push).
  2388  // If a name is in this map, it is allowed only in listed packages,
  2389  // even if it has a linknamed definition.
  2390  var blockedLinknames = map[string][]string{
  2391  	// coroutines
  2392  	"runtime.coroswitch": {"iter"},
  2393  	"runtime.newcoro":    {"iter"},
  2394  	// fips info
  2395  	"go:fipsinfo": {"crypto/internal/fips140/check"},
  2396  	// New internal linknames in Go 1.24
  2397  	// Pushed from runtime
  2398  	"crypto/internal/fips140.fatal":         {"crypto/internal/fips140"},
  2399  	"crypto/internal/fips140.getIndicator":  {"crypto/internal/fips140"},
  2400  	"crypto/internal/fips140.setIndicator":  {"crypto/internal/fips140"},
  2401  	"crypto/internal/sysrand.fatal":         {"crypto/internal/sysrand"},
  2402  	"crypto/rand.fatal":                     {"crypto/rand"},
  2403  	"internal/runtime/maps.errNilAssign":    {"internal/runtime/maps"},
  2404  	"internal/runtime/maps.fatal":           {"internal/runtime/maps"},
  2405  	"internal/runtime/maps.mapKeyError":     {"internal/runtime/maps"},
  2406  	"internal/runtime/maps.newarray":        {"internal/runtime/maps"},
  2407  	"internal/runtime/maps.newobject":       {"internal/runtime/maps"},
  2408  	"internal/runtime/maps.typedmemclr":     {"internal/runtime/maps"},
  2409  	"internal/runtime/maps.typedmemmove":    {"internal/runtime/maps"},
  2410  	"internal/sync.fatal":                   {"internal/sync"},
  2411  	"internal/sync.runtime_canSpin":         {"internal/sync"},
  2412  	"internal/sync.runtime_doSpin":          {"internal/sync"},
  2413  	"internal/sync.runtime_nanotime":        {"internal/sync"},
  2414  	"internal/sync.runtime_Semrelease":      {"internal/sync"},
  2415  	"internal/sync.runtime_SemacquireMutex": {"internal/sync"},
  2416  	"internal/sync.throw":                   {"internal/sync"},
  2417  	"internal/synctest.Run":                 {"internal/synctest"},
  2418  	"internal/synctest.Wait":                {"internal/synctest"},
  2419  	"internal/synctest.acquire":             {"internal/synctest"},
  2420  	"internal/synctest.release":             {"internal/synctest"},
  2421  	"internal/synctest.inBubble":            {"internal/synctest"},
  2422  	"runtime.getStaticuint64s":              {"reflect"},
  2423  	"sync.runtime_SemacquireWaitGroup":      {"sync"},
  2424  	"time.runtimeNow":                       {"time"},
  2425  	"time.runtimeNano":                      {"time"},
  2426  	// Pushed to runtime from internal/runtime/maps
  2427  	// (other map functions are already linknamed in Go 1.23)
  2428  	"runtime.mapaccess1":         {"runtime"},
  2429  	"runtime.mapaccess1_fast32":  {"runtime"},
  2430  	"runtime.mapaccess1_fast64":  {"runtime"},
  2431  	"runtime.mapaccess1_faststr": {"runtime"},
  2432  	"runtime.mapdelete_fast32":   {"runtime"},
  2433  	"runtime.mapdelete_fast64":   {"runtime"},
  2434  	"runtime.mapdelete_faststr":  {"runtime"},
  2435  }
  2436  
  2437  // check if a linkname reference to symbol s from pkg is allowed
  2438  func (l *Loader) checkLinkname(pkg, name string, s Sym) {
  2439  	if l.flags&FlagCheckLinkname == 0 {
  2440  		return
  2441  	}
  2442  
  2443  	error := func() {
  2444  		log.Fatalf("%s: invalid reference to %s", pkg, name)
  2445  	}
  2446  	pkgs, ok := blockedLinknames[name]
  2447  	if ok {
  2448  		for _, p := range pkgs {
  2449  			if pkg == p {
  2450  				return // pkg is allowed
  2451  			}
  2452  			// crypto/internal/fips140/vX.Y.Z/... is the frozen version of
  2453  			// crypto/internal/fips140/... and is similarly allowed.
  2454  			if strings.HasPrefix(pkg, "crypto/internal/fips140/v") {
  2455  				parts := strings.Split(pkg, "/")
  2456  				parts = append(parts[:3], parts[4:]...)
  2457  				pkg := strings.Join(parts, "/")
  2458  				if pkg == p {
  2459  					return
  2460  				}
  2461  			}
  2462  		}
  2463  		error()
  2464  	}
  2465  	r, li := l.toLocal(s)
  2466  	if r == l.extReader { // referencing external symbol is okay
  2467  		return
  2468  	}
  2469  	if !r.Std() { // For now, only check for symbols defined in std
  2470  		return
  2471  	}
  2472  	if r.unit.Lib.Pkg == pkg { // assembly reference from same package
  2473  		return
  2474  	}
  2475  	osym := r.Sym(li)
  2476  	if osym.IsLinkname() || osym.ABIWrapper() {
  2477  		// Allow if the def has a linkname (push).
  2478  		// ABI wrapper usually wraps an assembly symbol, a linknamed symbol,
  2479  		// or an external symbol, or provide access of a Go symbol to assembly.
  2480  		// For now, allow ABI wrappers.
  2481  		// TODO: check the wrapped symbol?
  2482  		return
  2483  	}
  2484  	error()
  2485  }
  2486  
  2487  // TopLevelSym tests a symbol (by name and kind) to determine whether
  2488  // the symbol first class sym (participating in the link) or is an
  2489  // anonymous aux or sub-symbol containing some sub-part or payload of
  2490  // another symbol.
  2491  func (l *Loader) TopLevelSym(s Sym) bool {
  2492  	return topLevelSym(l.SymName(s), l.SymType(s))
  2493  }
  2494  
  2495  // topLevelSym tests a symbol name and kind to determine whether
  2496  // the symbol first class sym (participating in the link) or is an
  2497  // anonymous aux or sub-symbol containing some sub-part or payload of
  2498  // another symbol.
  2499  func topLevelSym(sname string, skind sym.SymKind) bool {
  2500  	if sname != "" {
  2501  		return true
  2502  	}
  2503  	switch skind {
  2504  	case sym.SDWARFFCN, sym.SDWARFABSFCN, sym.SDWARFTYPE, sym.SDWARFCONST, sym.SDWARFCUINFO, sym.SDWARFRANGE, sym.SDWARFLOC, sym.SDWARFLINES, sym.SGOFUNC:
  2505  		return true
  2506  	default:
  2507  		return false
  2508  	}
  2509  }
  2510  
  2511  // cloneToExternal takes the existing object file symbol (symIdx)
  2512  // and creates a new external symbol payload that is a clone with
  2513  // respect to name, version, type, relocations, etc. The idea here
  2514  // is that if the linker decides it wants to update the contents of
  2515  // a symbol originally discovered as part of an object file, it's
  2516  // easier to do this if we make the updates to an external symbol
  2517  // payload.
  2518  func (l *Loader) cloneToExternal(symIdx Sym) *extSymPayload {
  2519  	if l.IsExternal(symIdx) {
  2520  		panic("sym is already external, no need for clone")
  2521  	}
  2522  
  2523  	// Read the particulars from object.
  2524  	r, li := l.toLocal(symIdx)
  2525  	osym := r.Sym(li)
  2526  	sname := osym.Name(r.Reader)
  2527  	sver := abiToVer(osym.ABI(), r.version)
  2528  	skind := sym.AbiSymKindToSymKind[objabi.SymKind(osym.Type())]
  2529  
  2530  	// Create new symbol, update version and kind.
  2531  	pi := l.newPayload(sname, sver)
  2532  	pp := l.payloads[pi]
  2533  	pp.kind = skind
  2534  	pp.ver = sver
  2535  	pp.size = int64(osym.Siz())
  2536  	pp.objidx = r.objidx
  2537  
  2538  	// If this is a def, then copy the guts. We expect this case
  2539  	// to be very rare (one case it may come up is with -X).
  2540  	if li < uint32(r.NAlldef()) {
  2541  
  2542  		// Copy relocations
  2543  		relocs := l.Relocs(symIdx)
  2544  		pp.relocs = make([]goobj.Reloc, relocs.Count())
  2545  		for i := range pp.relocs {
  2546  			// Copy the relocs slice.
  2547  			// Convert local reference to global reference.
  2548  			rel := relocs.At(i)
  2549  			pp.relocs[i].Set(rel.Off(), rel.Siz(), uint16(rel.Type()), rel.Add(), goobj.SymRef{PkgIdx: 0, SymIdx: uint32(rel.Sym())})
  2550  		}
  2551  
  2552  		// Copy data
  2553  		pp.data = r.Data(li)
  2554  	}
  2555  
  2556  	// If we're overriding a data symbol, collect the associated
  2557  	// Gotype, so as to propagate it to the new symbol.
  2558  	auxs := r.Auxs(li)
  2559  	pp.auxs = auxs
  2560  
  2561  	// Install new payload to global index space.
  2562  	// (This needs to happen at the end, as the accessors above
  2563  	// need to access the old symbol content.)
  2564  	l.objSyms[symIdx] = objSym{l.extReader.objidx, uint32(pi)}
  2565  	l.extReader.syms = append(l.extReader.syms, symIdx)
  2566  
  2567  	// Some attributes were encoded in the object file. Copy them over.
  2568  	l.SetAttrDuplicateOK(symIdx, r.Sym(li).Dupok())
  2569  	l.SetAttrShared(symIdx, r.Shared())
  2570  
  2571  	return pp
  2572  }
  2573  
  2574  // Copy the payload of symbol src to dst. Both src and dst must be external
  2575  // symbols.
  2576  // The intended use case is that when building/linking against a shared library,
  2577  // where we do symbol name mangling, the Go object file may have reference to
  2578  // the original symbol name whereas the shared library provides a symbol with
  2579  // the mangled name. When we do mangling, we copy payload of mangled to original.
  2580  func (l *Loader) CopySym(src, dst Sym) {
  2581  	if !l.IsExternal(dst) {
  2582  		panic("dst is not external") //l.newExtSym(l.SymName(dst), l.SymVersion(dst))
  2583  	}
  2584  	if !l.IsExternal(src) {
  2585  		panic("src is not external") //l.cloneToExternal(src)
  2586  	}
  2587  	l.payloads[l.extIndex(dst)] = l.payloads[l.extIndex(src)]
  2588  	l.SetSymPkg(dst, l.SymPkg(src))
  2589  	// TODO: other attributes?
  2590  }
  2591  
  2592  // CreateExtSym creates a new external symbol with the specified name
  2593  // without adding it to any lookup tables, returning a Sym index for it.
  2594  func (l *Loader) CreateExtSym(name string, ver int) Sym {
  2595  	return l.newExtSym(name, ver)
  2596  }
  2597  
  2598  // CreateStaticSym creates a new static symbol with the specified name
  2599  // without adding it to any lookup tables, returning a Sym index for it.
  2600  func (l *Loader) CreateStaticSym(name string) Sym {
  2601  	// Assign a new unique negative version -- this is to mark the
  2602  	// symbol so that it is not included in the name lookup table.
  2603  	l.anonVersion--
  2604  	return l.newExtSym(name, l.anonVersion)
  2605  }
  2606  
  2607  func (l *Loader) FreeSym(i Sym) {
  2608  	if l.IsExternal(i) {
  2609  		pp := l.getPayload(i)
  2610  		*pp = extSymPayload{}
  2611  	}
  2612  }
  2613  
  2614  // relocId is essentially a <S,R> tuple identifying the Rth
  2615  // relocation of symbol S.
  2616  type relocId struct {
  2617  	sym  Sym
  2618  	ridx int
  2619  }
  2620  
  2621  // SetRelocVariant sets the 'variant' property of a relocation on
  2622  // some specific symbol.
  2623  func (l *Loader) SetRelocVariant(s Sym, ri int, v sym.RelocVariant) {
  2624  	// sanity check
  2625  	if relocs := l.Relocs(s); ri >= relocs.Count() {
  2626  		panic("invalid relocation ID")
  2627  	}
  2628  	if l.relocVariant == nil {
  2629  		l.relocVariant = make(map[relocId]sym.RelocVariant)
  2630  	}
  2631  	if v != 0 {
  2632  		l.relocVariant[relocId{s, ri}] = v
  2633  	} else {
  2634  		delete(l.relocVariant, relocId{s, ri})
  2635  	}
  2636  }
  2637  
  2638  // RelocVariant returns the 'variant' property of a relocation on
  2639  // some specific symbol.
  2640  func (l *Loader) RelocVariant(s Sym, ri int) sym.RelocVariant {
  2641  	return l.relocVariant[relocId{s, ri}]
  2642  }
  2643  
  2644  // UndefinedRelocTargets iterates through the global symbol index
  2645  // space, looking for symbols with relocations targeting undefined
  2646  // references. The linker's loadlib method uses this to determine if
  2647  // there are unresolved references to functions in system libraries
  2648  // (for example, libgcc.a), presumably due to CGO code. Return value
  2649  // is a pair of lists of loader.Sym's. First list corresponds to the
  2650  // corresponding to the undefined symbols themselves, the second list
  2651  // is the symbol that is making a reference to the undef. The "limit"
  2652  // param controls the maximum number of results returned; if "limit"
  2653  // is -1, then all undefs are returned.
  2654  func (l *Loader) UndefinedRelocTargets(limit int) ([]Sym, []Sym) {
  2655  	result, fromr := []Sym{}, []Sym{}
  2656  outerloop:
  2657  	for si := Sym(1); si < Sym(len(l.objSyms)); si++ {
  2658  		relocs := l.Relocs(si)
  2659  		for ri := 0; ri < relocs.Count(); ri++ {
  2660  			r := relocs.At(ri)
  2661  			rs := r.Sym()
  2662  			if rs != 0 && l.SymType(rs) == sym.SXREF && l.SymName(rs) != ".got" {
  2663  				result = append(result, rs)
  2664  				fromr = append(fromr, si)
  2665  				if limit != -1 && len(result) >= limit {
  2666  					break outerloop
  2667  				}
  2668  			}
  2669  		}
  2670  	}
  2671  	return result, fromr
  2672  }
  2673  
  2674  // AssignTextSymbolOrder populates the Textp slices within each
  2675  // library and compilation unit, insuring that packages are laid down
  2676  // in dependency order (internal first, then everything else). Return value
  2677  // is a slice of all text syms.
  2678  func (l *Loader) AssignTextSymbolOrder(libs []*sym.Library, intlibs []bool, extsyms []Sym) []Sym {
  2679  
  2680  	// Library Textp lists should be empty at this point.
  2681  	for _, lib := range libs {
  2682  		if len(lib.Textp) != 0 {
  2683  			panic("expected empty Textp slice for library")
  2684  		}
  2685  		if len(lib.DupTextSyms) != 0 {
  2686  			panic("expected empty DupTextSyms slice for library")
  2687  		}
  2688  	}
  2689  
  2690  	// Used to record which dupok symbol we've assigned to a unit.
  2691  	// Can't use the onlist attribute here because it will need to
  2692  	// clear for the later assignment of the sym.Symbol to a unit.
  2693  	// NB: we can convert to using onList once we no longer have to
  2694  	// call the regular addToTextp.
  2695  	assignedToUnit := MakeBitmap(l.NSym() + 1)
  2696  
  2697  	// Start off textp with reachable external syms.
  2698  	textp := []Sym{}
  2699  	for _, sym := range extsyms {
  2700  		if !l.attrReachable.Has(sym) {
  2701  			continue
  2702  		}
  2703  		textp = append(textp, sym)
  2704  	}
  2705  
  2706  	// Walk through all text symbols from Go object files and append
  2707  	// them to their corresponding library's textp list.
  2708  	for _, r := range l.objs[goObjStart:] {
  2709  		lib := r.unit.Lib
  2710  		for i, n := uint32(0), uint32(r.NAlldef()); i < n; i++ {
  2711  			gi := l.toGlobal(r, i)
  2712  			if !l.attrReachable.Has(gi) {
  2713  				continue
  2714  			}
  2715  			osym := r.Sym(i)
  2716  			st := sym.AbiSymKindToSymKind[objabi.SymKind(osym.Type())]
  2717  			if !st.IsText() {
  2718  				continue
  2719  			}
  2720  			dupok := osym.Dupok()
  2721  			if r2, i2 := l.toLocal(gi); r2 != r || i2 != i {
  2722  				// A dupok text symbol is resolved to another package.
  2723  				// We still need to record its presence in the current
  2724  				// package, as the trampoline pass expects packages
  2725  				// are laid out in dependency order.
  2726  				lib.DupTextSyms = append(lib.DupTextSyms, sym.LoaderSym(gi))
  2727  				continue // symbol in different object
  2728  			}
  2729  			if dupok {
  2730  				lib.DupTextSyms = append(lib.DupTextSyms, sym.LoaderSym(gi))
  2731  				continue
  2732  			}
  2733  
  2734  			lib.Textp = append(lib.Textp, sym.LoaderSym(gi))
  2735  		}
  2736  	}
  2737  
  2738  	// Now assemble global textp, and assign text symbols to units.
  2739  	for _, doInternal := range [2]bool{true, false} {
  2740  		for idx, lib := range libs {
  2741  			if intlibs[idx] != doInternal {
  2742  				continue
  2743  			}
  2744  			lists := [2][]sym.LoaderSym{lib.Textp, lib.DupTextSyms}
  2745  			for i, list := range lists {
  2746  				for _, s := range list {
  2747  					sym := Sym(s)
  2748  					if !assignedToUnit.Has(sym) {
  2749  						textp = append(textp, sym)
  2750  						unit := l.SymUnit(sym)
  2751  						if unit != nil {
  2752  							unit.Textp = append(unit.Textp, s)
  2753  							assignedToUnit.Set(sym)
  2754  						}
  2755  						// Dupok symbols may be defined in multiple packages; the
  2756  						// associated package for a dupok sym is chosen sort of
  2757  						// arbitrarily (the first containing package that the linker
  2758  						// loads). Canonicalizes its Pkg to the package with which
  2759  						// it will be laid down in text.
  2760  						if i == 1 /* DupTextSyms2 */ && l.SymPkg(sym) != lib.Pkg {
  2761  							l.SetSymPkg(sym, lib.Pkg)
  2762  						}
  2763  					}
  2764  				}
  2765  			}
  2766  			lib.Textp = nil
  2767  			lib.DupTextSyms = nil
  2768  		}
  2769  	}
  2770  
  2771  	return textp
  2772  }
  2773  
  2774  // ErrorReporter is a helper class for reporting errors.
  2775  type ErrorReporter struct {
  2776  	ldr              *Loader
  2777  	AfterErrorAction func()
  2778  }
  2779  
  2780  // Errorf method logs an error message.
  2781  //
  2782  // After each error, the error actions function will be invoked; this
  2783  // will either terminate the link immediately (if -h option given)
  2784  // or it will keep a count and exit if more than 20 errors have been printed.
  2785  //
  2786  // Logging an error means that on exit cmd/link will delete any
  2787  // output file and return a non-zero error code.
  2788  func (reporter *ErrorReporter) Errorf(s Sym, format string, args ...interface{}) {
  2789  	if s != 0 && reporter.ldr.SymName(s) != "" {
  2790  		// Note: Replace is needed here because symbol names might have % in them,
  2791  		// due to the use of LinkString for names of instantiating types.
  2792  		format = strings.Replace(reporter.ldr.SymName(s), "%", "%%", -1) + ": " + format
  2793  	} else {
  2794  		format = fmt.Sprintf("sym %d: %s", s, format)
  2795  	}
  2796  	format += "\n"
  2797  	fmt.Fprintf(os.Stderr, format, args...)
  2798  	reporter.AfterErrorAction()
  2799  }
  2800  
  2801  // GetErrorReporter returns the loader's associated error reporter.
  2802  func (l *Loader) GetErrorReporter() *ErrorReporter {
  2803  	return l.errorReporter
  2804  }
  2805  
  2806  // Errorf method logs an error message. See ErrorReporter.Errorf for details.
  2807  func (l *Loader) Errorf(s Sym, format string, args ...interface{}) {
  2808  	l.errorReporter.Errorf(s, format, args...)
  2809  }
  2810  
  2811  // Symbol statistics.
  2812  func (l *Loader) Stat() string {
  2813  	s := fmt.Sprintf("%d symbols, %d reachable\n", l.NSym(), l.NReachableSym())
  2814  	s += fmt.Sprintf("\t%d package symbols, %d hashed symbols, %d non-package symbols, %d external symbols\n",
  2815  		l.npkgsyms, l.nhashedsyms, int(l.extStart)-l.npkgsyms-l.nhashedsyms, l.NSym()-int(l.extStart))
  2816  	return s
  2817  }
  2818  
  2819  // For debugging.
  2820  func (l *Loader) Dump() {
  2821  	fmt.Println("objs")
  2822  	for _, r := range l.objs[goObjStart:] {
  2823  		if r != nil {
  2824  			fmt.Println(r.unit.Lib)
  2825  		}
  2826  	}
  2827  	fmt.Println("extStart:", l.extStart)
  2828  	fmt.Println("Nsyms:", len(l.objSyms))
  2829  	fmt.Println("syms")
  2830  	for i := Sym(1); i < Sym(len(l.objSyms)); i++ {
  2831  		pi := ""
  2832  		if l.IsExternal(i) {
  2833  			pi = fmt.Sprintf("<ext %d>", l.extIndex(i))
  2834  		}
  2835  		sect := ""
  2836  		if l.SymSect(i) != nil {
  2837  			sect = l.SymSect(i).Name
  2838  		}
  2839  		fmt.Printf("%v %v %v %v %x %v\n", i, l.SymName(i), l.SymType(i), pi, l.SymValue(i), sect)
  2840  	}
  2841  	fmt.Println("symsByName")
  2842  	for name, i := range l.symsByName[0] {
  2843  		fmt.Println(i, name, 0)
  2844  	}
  2845  	for name, i := range l.symsByName[1] {
  2846  		fmt.Println(i, name, 1)
  2847  	}
  2848  	fmt.Println("payloads:")
  2849  	for i := range l.payloads {
  2850  		pp := l.payloads[i]
  2851  		fmt.Println(i, pp.name, pp.ver, pp.kind)
  2852  	}
  2853  }
  2854  

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