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

Documentation: cmd/link/internal/loader

     1  // Copyright 2019 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package loader
     6  
     7  import (
     8  	"bytes"
     9  	"cmd/internal/bio"
    10  	"cmd/internal/goobj"
    11  	"cmd/internal/obj"
    12  	"cmd/internal/objabi"
    13  	"cmd/internal/sys"
    14  	"cmd/link/internal/sym"
    15  	"debug/elf"
    16  	"fmt"
    17  	"internal/abi"
    18  	"io"
    19  	"log"
    20  	"math/bits"
    21  	"os"
    22  	"sort"
    23  	"strings"
    24  )
    25  
    26  var _ = fmt.Print
    27  
    28  // Sym encapsulates a global symbol index, used to identify a specific
    29  // Go symbol. The 0-valued Sym is corresponds to an invalid symbol.
    30  type Sym = sym.LoaderSym
    31  
    32  // Relocs encapsulates the set of relocations on a given symbol; an
    33  // instance of this type is returned by the Loader Relocs() method.
    34  type Relocs struct {
    35  	rs []goobj.Reloc
    36  
    37  	li uint32   // local index of symbol whose relocs we're examining
    38  	r  *oReader // object reader for containing package
    39  	l  *Loader  // loader
    40  }
    41  
    42  // ExtReloc contains the payload for an external relocation.
    43  type ExtReloc struct {
    44  	Xsym Sym
    45  	Xadd int64
    46  	Type objabi.RelocType
    47  	Size uint8
    48  }
    49  
    50  // Reloc holds a "handle" to access a relocation record from an
    51  // object file.
    52  type Reloc struct {
    53  	*goobj.Reloc
    54  	r *oReader
    55  	l *Loader
    56  }
    57  
    58  func (rel Reloc) Type() objabi.RelocType     { return objabi.RelocType(rel.Reloc.Type()) &^ objabi.R_WEAK }
    59  func (rel Reloc) Weak() bool                 { return objabi.RelocType(rel.Reloc.Type())&objabi.R_WEAK != 0 }
    60  func (rel Reloc) SetType(t objabi.RelocType) { rel.Reloc.SetType(uint16(t)) }
    61  func (rel Reloc) Sym() Sym                   { return rel.l.resolve(rel.r, rel.Reloc.Sym()) }
    62  func (rel Reloc) SetSym(s Sym)               { rel.Reloc.SetSym(goobj.SymRef{PkgIdx: 0, SymIdx: uint32(s)}) }
    63  func (rel Reloc) IsMarker() bool             { return rel.Siz() == 0 }
    64  
    65  // Aux holds a "handle" to access an aux symbol record from an
    66  // object file.
    67  type Aux struct {
    68  	*goobj.Aux
    69  	r *oReader
    70  	l *Loader
    71  }
    72  
    73  func (a Aux) Sym() Sym { return a.l.resolve(a.r, a.Aux.Sym()) }
    74  
    75  // oReader is a wrapper type of obj.Reader, along with some
    76  // extra information.
    77  type oReader struct {
    78  	*goobj.Reader
    79  	unit         *sym.CompilationUnit
    80  	version      int // version of static symbol
    81  	pkgprefix    string
    82  	syms         []Sym    // Sym's global index, indexed by local index
    83  	pkg          []uint32 // indices of referenced package by PkgIdx (index into loader.objs array)
    84  	ndef         int      // cache goobj.Reader.NSym()
    85  	nhashed64def int      // cache goobj.Reader.NHashed64Def()
    86  	nhasheddef   int      // cache goobj.Reader.NHashedDef()
    87  	objidx       uint32   // index of this reader in the objs slice
    88  }
    89  
    90  // Total number of defined symbols (package symbols, hashed symbols, and
    91  // non-package symbols).
    92  func (r *oReader) NAlldef() int { return r.ndef + r.nhashed64def + r.nhasheddef + r.NNonpkgdef() }
    93  
    94  // 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  	flags uint32
   255  
   256  	strictDupMsgs int // number of strict-dup warning/errors, when FlagStrictDups is enabled
   257  
   258  	errorReporter *ErrorReporter
   259  
   260  	npkgsyms    int // number of package symbols, for accounting
   261  	nhashedsyms int // number of hashed symbols, for accounting
   262  }
   263  
   264  const (
   265  	pkgDef = iota
   266  	hashed64Def
   267  	hashedDef
   268  	nonPkgDef
   269  	nonPkgRef
   270  )
   271  
   272  // objidx
   273  const (
   274  	nilObj = iota
   275  	extObj
   276  	goObjStart
   277  )
   278  
   279  // extSymPayload holds the payload (data + relocations) for linker-synthesized
   280  // external symbols (note that symbol value is stored in a separate slice).
   281  type extSymPayload struct {
   282  	name   string // TODO: would this be better as offset into str table?
   283  	size   int64
   284  	ver    int
   285  	kind   sym.SymKind
   286  	objidx uint32 // index of original object if sym made by cloneToExternal
   287  	relocs []goobj.Reloc
   288  	data   []byte
   289  	auxs   []goobj.Aux
   290  }
   291  
   292  const (
   293  	// Loader.flags
   294  	FlagStrictDups = 1 << iota
   295  	FlagCheckLinkname
   296  )
   297  
   298  func NewLoader(flags uint32, reporter *ErrorReporter) *Loader {
   299  	nbuiltin := goobj.NBuiltin()
   300  	extReader := &oReader{objidx: extObj}
   301  	ldr := &Loader{
   302  		objs:                 []*oReader{nil, extReader}, // reserve index 0 for nil symbol, 1 for external symbols
   303  		objSyms:              make([]objSym, 1, 1),       // This will get overwritten later.
   304  		extReader:            extReader,
   305  		symsByName:           [2]map[string]Sym{make(map[string]Sym, 80000), make(map[string]Sym, 50000)}, // preallocate ~2MB for ABI0 and ~1MB for ABI1 symbols
   306  		objByPkg:             make(map[string]uint32),
   307  		sub:                  make(map[Sym]Sym),
   308  		dynimplib:            make(map[Sym]string),
   309  		dynimpvers:           make(map[Sym]string),
   310  		localentry:           make(map[Sym]uint8),
   311  		extname:              make(map[Sym]string),
   312  		attrReadOnly:         make(map[Sym]bool),
   313  		elfType:              make(map[Sym]elf.SymType),
   314  		elfSym:               make(map[Sym]int32),
   315  		localElfSym:          make(map[Sym]int32),
   316  		symPkg:               make(map[Sym]string),
   317  		plt:                  make(map[Sym]int32),
   318  		got:                  make(map[Sym]int32),
   319  		dynid:                make(map[Sym]int32),
   320  		attrCgoExportDynamic: make(map[Sym]struct{}),
   321  		attrCgoExportStatic:  make(map[Sym]struct{}),
   322  		deferReturnTramp:     make(map[Sym]bool),
   323  		extStaticSyms:        make(map[nameVer]Sym),
   324  		builtinSyms:          make([]Sym, nbuiltin),
   325  		flags:                flags,
   326  		errorReporter:        reporter,
   327  		sects:                []*sym.Section{nil}, // reserve index 0 for nil section
   328  	}
   329  	reporter.ldr = ldr
   330  	return ldr
   331  }
   332  
   333  // Add object file r
   334  func (l *Loader) addObj(pkg string, r *oReader) {
   335  	pkg = objabi.PathToPrefix(pkg) // the object file contains escaped package path
   336  	if _, ok := l.objByPkg[pkg]; !ok {
   337  		l.objByPkg[pkg] = r.objidx
   338  	}
   339  	l.objs = append(l.objs, r)
   340  }
   341  
   342  // Add a symbol from an object file, return the global index.
   343  // If the symbol already exist, it returns the index of that symbol.
   344  func (st *loadState) addSym(name string, ver int, r *oReader, li uint32, kind int, osym *goobj.Sym) Sym {
   345  	l := st.l
   346  	if l.extStart != 0 {
   347  		panic("addSym called after external symbol is created")
   348  	}
   349  	i := Sym(len(l.objSyms))
   350  	if int(i) != len(l.objSyms) { // overflow
   351  		panic("too many symbols")
   352  	}
   353  	addToGlobal := func() {
   354  		l.objSyms = append(l.objSyms, objSym{r.objidx, li})
   355  	}
   356  	if name == "" && kind != hashed64Def && kind != hashedDef {
   357  		addToGlobal()
   358  		return i // unnamed aux symbol
   359  	}
   360  	if ver == r.version {
   361  		// Static symbol. Add its global index but don't
   362  		// add to name lookup table, as it cannot be
   363  		// referenced by name.
   364  		addToGlobal()
   365  		return i
   366  	}
   367  	switch kind {
   368  	case pkgDef:
   369  		// Defined package symbols cannot be dup to each other.
   370  		// We load all the package symbols first, so we don't need
   371  		// to check dup here.
   372  		// We still add it to the lookup table, as it may still be
   373  		// referenced by name (e.g. through linkname).
   374  		l.symsByName[ver][name] = i
   375  		addToGlobal()
   376  		return i
   377  	case hashed64Def, hashedDef:
   378  		// Hashed (content-addressable) symbol. Check the hash
   379  		// but don't add to name lookup table, as they are not
   380  		// referenced by name. Also no need to do overwriting
   381  		// check, as same hash indicates same content.
   382  		var checkHash func() (symAndSize, bool)
   383  		var addToHashMap func(symAndSize)
   384  		var h64 uint64        // only used for hashed64Def
   385  		var h *goobj.HashType // only used for hashedDef
   386  		if kind == hashed64Def {
   387  			checkHash = func() (symAndSize, bool) {
   388  				h64 = r.Hash64(li - uint32(r.ndef))
   389  				s, existed := st.hashed64Syms[h64]
   390  				return s, existed
   391  			}
   392  			addToHashMap = func(ss symAndSize) { st.hashed64Syms[h64] = ss }
   393  		} else {
   394  			checkHash = func() (symAndSize, bool) {
   395  				h = r.Hash(li - uint32(r.ndef+r.nhashed64def))
   396  				s, existed := st.hashedSyms[*h]
   397  				return s, existed
   398  			}
   399  			addToHashMap = func(ss symAndSize) { st.hashedSyms[*h] = ss }
   400  		}
   401  		siz := osym.Siz()
   402  		if s, existed := checkHash(); existed {
   403  			// The content hash is built from symbol data and relocations. In the
   404  			// object file, the symbol data may not always contain trailing zeros,
   405  			// e.g. for [5]int{1,2,3} and [100]int{1,2,3}, the data is same
   406  			// (although the size is different).
   407  			// Also, for short symbols, the content hash is the identity function of
   408  			// the 8 bytes, and trailing zeros doesn't change the hash value, e.g.
   409  			// hash("A") == hash("A\0\0\0").
   410  			// So when two symbols have the same hash, we need to use the one with
   411  			// larger size.
   412  			if siz > s.size {
   413  				// New symbol has larger size, use the new one. Rewrite the index mapping.
   414  				l.objSyms[s.sym] = objSym{r.objidx, li}
   415  				addToHashMap(symAndSize{s.sym, siz})
   416  			}
   417  			return s.sym
   418  		}
   419  		addToHashMap(symAndSize{i, siz})
   420  		addToGlobal()
   421  		return i
   422  	}
   423  
   424  	// Non-package (named) symbol.
   425  	// Check if it already exists.
   426  	oldi, existed := l.symsByName[ver][name]
   427  	if !existed {
   428  		l.symsByName[ver][name] = i
   429  		addToGlobal()
   430  		return i
   431  	}
   432  	// symbol already exists
   433  	if osym.Dupok() {
   434  		if l.flags&FlagStrictDups != 0 {
   435  			l.checkdup(name, r, li, oldi)
   436  		}
   437  		// Fix for issue #47185 -- given two dupok symbols with
   438  		// different sizes, favor symbol with larger size. See
   439  		// also issue #46653.
   440  		szdup := l.SymSize(oldi)
   441  		sz := int64(r.Sym(li).Siz())
   442  		if szdup < sz {
   443  			// new symbol overwrites old symbol.
   444  			l.objSyms[oldi] = objSym{r.objidx, li}
   445  		}
   446  		return oldi
   447  	}
   448  	oldr, oldli := l.toLocal(oldi)
   449  	oldsym := oldr.Sym(oldli)
   450  	if oldsym.Dupok() {
   451  		return oldi
   452  	}
   453  	overwrite := r.DataSize(li) != 0
   454  	if overwrite {
   455  		// new symbol overwrites old symbol.
   456  		oldtyp := sym.AbiSymKindToSymKind[objabi.SymKind(oldsym.Type())]
   457  		if !(oldtyp.IsData() && oldr.DataSize(oldli) == 0) {
   458  			log.Fatalf("duplicated definition of symbol %s, from %s and %s", name, r.unit.Lib.Pkg, oldr.unit.Lib.Pkg)
   459  		}
   460  		l.objSyms[oldi] = objSym{r.objidx, li}
   461  	} else {
   462  		// old symbol overwrites new symbol.
   463  		typ := sym.AbiSymKindToSymKind[objabi.SymKind(oldsym.Type())]
   464  		if !typ.IsData() { // only allow overwriting data symbol
   465  			log.Fatalf("duplicated definition of symbol %s, from %s and %s", name, r.unit.Lib.Pkg, oldr.unit.Lib.Pkg)
   466  		}
   467  	}
   468  	return oldi
   469  }
   470  
   471  // newExtSym creates a new external sym with the specified
   472  // name/version.
   473  func (l *Loader) newExtSym(name string, ver int) Sym {
   474  	i := Sym(len(l.objSyms))
   475  	if int(i) != len(l.objSyms) { // overflow
   476  		panic("too many symbols")
   477  	}
   478  	if l.extStart == 0 {
   479  		l.extStart = i
   480  	}
   481  	l.growValues(int(i) + 1)
   482  	l.growOuter(int(i) + 1)
   483  	l.growAttrBitmaps(int(i) + 1)
   484  	pi := l.newPayload(name, ver)
   485  	l.objSyms = append(l.objSyms, objSym{l.extReader.objidx, uint32(pi)})
   486  	l.extReader.syms = append(l.extReader.syms, i)
   487  	return i
   488  }
   489  
   490  // LookupOrCreateSym looks up the symbol with the specified name/version,
   491  // returning its Sym index if found. If the lookup fails, a new external
   492  // Sym will be created, entered into the lookup tables, and returned.
   493  func (l *Loader) LookupOrCreateSym(name string, ver int) Sym {
   494  	i := l.Lookup(name, ver)
   495  	if i != 0 {
   496  		return i
   497  	}
   498  	i = l.newExtSym(name, ver)
   499  	static := ver >= sym.SymVerStatic || ver < 0
   500  	if static {
   501  		l.extStaticSyms[nameVer{name, ver}] = i
   502  	} else {
   503  		l.symsByName[ver][name] = i
   504  	}
   505  	return i
   506  }
   507  
   508  // AddCgoExport records a cgo-exported symbol in l.CgoExports.
   509  // This table is used to identify the correct Go symbol ABI to use
   510  // to resolve references from host objects (which don't have ABIs).
   511  func (l *Loader) AddCgoExport(s Sym) {
   512  	if l.CgoExports == nil {
   513  		l.CgoExports = make(map[string]Sym)
   514  	}
   515  	l.CgoExports[l.SymName(s)] = s
   516  }
   517  
   518  // LookupOrCreateCgoExport is like LookupOrCreateSym, but if ver
   519  // indicates a global symbol, it uses the CgoExport table to determine
   520  // the appropriate symbol version (ABI) to use. ver must be either 0
   521  // or a static symbol version.
   522  func (l *Loader) LookupOrCreateCgoExport(name string, ver int) Sym {
   523  	if ver >= sym.SymVerStatic {
   524  		return l.LookupOrCreateSym(name, ver)
   525  	}
   526  	if ver != 0 {
   527  		panic("ver must be 0 or a static version")
   528  	}
   529  	// Look for a cgo-exported symbol from Go.
   530  	if s, ok := l.CgoExports[name]; ok {
   531  		return s
   532  	}
   533  	// Otherwise, this must just be a symbol in the host object.
   534  	// Create a version 0 symbol for it.
   535  	return l.LookupOrCreateSym(name, 0)
   536  }
   537  
   538  func (l *Loader) IsExternal(i Sym) bool {
   539  	r, _ := l.toLocal(i)
   540  	return l.isExtReader(r)
   541  }
   542  
   543  func (l *Loader) isExtReader(r *oReader) bool {
   544  	return r == l.extReader
   545  }
   546  
   547  // For external symbol, return its index in the payloads array.
   548  // XXX result is actually not a global index. We (ab)use the Sym type
   549  // so we don't need conversion for accessing bitmaps.
   550  func (l *Loader) extIndex(i Sym) Sym {
   551  	_, li := l.toLocal(i)
   552  	return Sym(li)
   553  }
   554  
   555  // Get a new payload for external symbol, return its index in
   556  // the payloads array.
   557  func (l *Loader) newPayload(name string, ver int) int {
   558  	pi := len(l.payloads)
   559  	pp := l.allocPayload()
   560  	pp.name = name
   561  	pp.ver = ver
   562  	l.payloads = append(l.payloads, pp)
   563  	l.growExtAttrBitmaps()
   564  	return pi
   565  }
   566  
   567  // getPayload returns a pointer to the extSymPayload struct for an
   568  // external symbol if the symbol has a payload. Will panic if the
   569  // symbol in question is bogus (zero or not an external sym).
   570  func (l *Loader) getPayload(i Sym) *extSymPayload {
   571  	if !l.IsExternal(i) {
   572  		panic(fmt.Sprintf("bogus symbol index %d in getPayload", i))
   573  	}
   574  	pi := l.extIndex(i)
   575  	return l.payloads[pi]
   576  }
   577  
   578  // allocPayload allocates a new payload.
   579  func (l *Loader) allocPayload() *extSymPayload {
   580  	batch := l.payloadBatch
   581  	if len(batch) == 0 {
   582  		batch = make([]extSymPayload, 1000)
   583  	}
   584  	p := &batch[0]
   585  	l.payloadBatch = batch[1:]
   586  	return p
   587  }
   588  
   589  func (ms *extSymPayload) Grow(siz int64) {
   590  	if int64(int(siz)) != siz {
   591  		log.Fatalf("symgrow size %d too long", siz)
   592  	}
   593  	if int64(len(ms.data)) >= siz {
   594  		return
   595  	}
   596  	if cap(ms.data) < int(siz) {
   597  		cl := len(ms.data)
   598  		ms.data = append(ms.data, make([]byte, int(siz)+1-cl)...)
   599  		ms.data = ms.data[0:cl]
   600  	}
   601  	ms.data = ms.data[:siz]
   602  }
   603  
   604  // Convert a local index to a global index.
   605  func (l *Loader) toGlobal(r *oReader, i uint32) Sym {
   606  	return r.syms[i]
   607  }
   608  
   609  // Convert a global index to a local index.
   610  func (l *Loader) toLocal(i Sym) (*oReader, uint32) {
   611  	return l.objs[l.objSyms[i].objidx], l.objSyms[i].s
   612  }
   613  
   614  // Resolve a local symbol reference. Return global index.
   615  func (l *Loader) resolve(r *oReader, s goobj.SymRef) Sym {
   616  	var rr *oReader
   617  	switch p := s.PkgIdx; p {
   618  	case goobj.PkgIdxInvalid:
   619  		// {0, X} with non-zero X is never a valid sym reference from a Go object.
   620  		// We steal this space for symbol references from external objects.
   621  		// In this case, X is just the global index.
   622  		if l.isExtReader(r) {
   623  			return Sym(s.SymIdx)
   624  		}
   625  		if s.SymIdx != 0 {
   626  			panic("bad sym ref")
   627  		}
   628  		return 0
   629  	case goobj.PkgIdxHashed64:
   630  		i := int(s.SymIdx) + r.ndef
   631  		return r.syms[i]
   632  	case goobj.PkgIdxHashed:
   633  		i := int(s.SymIdx) + r.ndef + r.nhashed64def
   634  		return r.syms[i]
   635  	case goobj.PkgIdxNone:
   636  		i := int(s.SymIdx) + r.ndef + r.nhashed64def + r.nhasheddef
   637  		return r.syms[i]
   638  	case goobj.PkgIdxBuiltin:
   639  		if bi := l.builtinSyms[s.SymIdx]; bi != 0 {
   640  			return bi
   641  		}
   642  		l.reportMissingBuiltin(int(s.SymIdx), r.unit.Lib.Pkg)
   643  		return 0
   644  	case goobj.PkgIdxSelf:
   645  		rr = r
   646  	default:
   647  		rr = l.objs[r.pkg[p]]
   648  	}
   649  	return l.toGlobal(rr, s.SymIdx)
   650  }
   651  
   652  // reportMissingBuiltin issues an error in the case where we have a
   653  // relocation against a runtime builtin whose definition is not found
   654  // when the runtime package is built. The canonical example is
   655  // "runtime.racefuncenter" -- currently if you do something like
   656  //
   657  //	go build -gcflags=-race myprogram.go
   658  //
   659  // the compiler will insert calls to the builtin runtime.racefuncenter,
   660  // but the version of the runtime used for linkage won't actually contain
   661  // definitions of that symbol. See issue #42396 for details.
   662  //
   663  // As currently implemented, this is a fatal error. This has drawbacks
   664  // in that if there are multiple missing builtins, the error will only
   665  // cite the first one. On the plus side, terminating the link here has
   666  // advantages in that we won't run the risk of panics or crashes later
   667  // on in the linker due to R_CALL relocations with 0-valued target
   668  // symbols.
   669  func (l *Loader) reportMissingBuiltin(bsym int, reflib string) {
   670  	bname, _ := goobj.BuiltinName(bsym)
   671  	log.Fatalf("reference to undefined builtin %q from package %q",
   672  		bname, reflib)
   673  }
   674  
   675  // Look up a symbol by name, return global index, or 0 if not found.
   676  // This is more like Syms.ROLookup than Lookup -- it doesn't create
   677  // new symbol.
   678  func (l *Loader) Lookup(name string, ver int) Sym {
   679  	if ver >= sym.SymVerStatic || ver < 0 {
   680  		return l.extStaticSyms[nameVer{name, ver}]
   681  	}
   682  	return l.symsByName[ver][name]
   683  }
   684  
   685  // Check that duplicate symbols have same contents.
   686  func (l *Loader) checkdup(name string, r *oReader, li uint32, dup Sym) {
   687  	p := r.Data(li)
   688  	rdup, ldup := l.toLocal(dup)
   689  	pdup := rdup.Data(ldup)
   690  	reason := "same length but different contents"
   691  	if len(p) != len(pdup) {
   692  		reason = fmt.Sprintf("new length %d != old length %d", len(p), len(pdup))
   693  	} else if bytes.Equal(p, pdup) {
   694  		// For BSS symbols, we need to check size as well, see issue 46653.
   695  		szdup := l.SymSize(dup)
   696  		sz := int64(r.Sym(li).Siz())
   697  		if szdup == sz {
   698  			return
   699  		}
   700  		reason = fmt.Sprintf("different sizes: new size %d != old size %d",
   701  			sz, szdup)
   702  	}
   703  	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)
   704  
   705  	// For the moment, allow DWARF subprogram DIEs for
   706  	// auto-generated wrapper functions. What seems to happen
   707  	// here is that we get different line numbers on formal
   708  	// params; I am guessing that the pos is being inherited
   709  	// from the spot where the wrapper is needed.
   710  	allowed := strings.HasPrefix(name, "go:info.go.interface") ||
   711  		strings.HasPrefix(name, "go:info.go.builtin") ||
   712  		strings.HasPrefix(name, "go:debuglines")
   713  	if !allowed {
   714  		l.strictDupMsgs++
   715  	}
   716  }
   717  
   718  func (l *Loader) NStrictDupMsgs() int { return l.strictDupMsgs }
   719  
   720  // Number of total symbols.
   721  func (l *Loader) NSym() int {
   722  	return len(l.objSyms)
   723  }
   724  
   725  // Number of defined Go symbols.
   726  func (l *Loader) NDef() int {
   727  	return int(l.extStart)
   728  }
   729  
   730  // Number of reachable symbols.
   731  func (l *Loader) NReachableSym() int {
   732  	return l.attrReachable.Count()
   733  }
   734  
   735  // Returns the name of the i-th symbol.
   736  func (l *Loader) SymName(i Sym) string {
   737  	if l.IsExternal(i) {
   738  		pp := l.getPayload(i)
   739  		return pp.name
   740  	}
   741  	r, li := l.toLocal(i)
   742  	if r == nil {
   743  		return "?"
   744  	}
   745  	return r.Sym(li).Name(r.Reader)
   746  }
   747  
   748  // Returns the version of the i-th symbol.
   749  func (l *Loader) SymVersion(i Sym) int {
   750  	if l.IsExternal(i) {
   751  		pp := l.getPayload(i)
   752  		return pp.ver
   753  	}
   754  	r, li := l.toLocal(i)
   755  	return int(abiToVer(r.Sym(li).ABI(), r.version))
   756  }
   757  
   758  func (l *Loader) IsFileLocal(i Sym) bool {
   759  	return l.SymVersion(i) >= sym.SymVerStatic
   760  }
   761  
   762  // IsFromAssembly returns true if this symbol is derived from an
   763  // object file generated by the Go assembler.
   764  func (l *Loader) IsFromAssembly(i Sym) bool {
   765  	if l.IsExternal(i) {
   766  		pp := l.getPayload(i)
   767  		if pp.objidx != 0 {
   768  			r := l.objs[pp.objidx]
   769  			return r.FromAssembly()
   770  		}
   771  		return false
   772  	}
   773  	r, _ := l.toLocal(i)
   774  	return r.FromAssembly()
   775  }
   776  
   777  // Returns the type of the i-th symbol.
   778  func (l *Loader) SymType(i Sym) sym.SymKind {
   779  	if l.IsExternal(i) {
   780  		pp := l.getPayload(i)
   781  		if pp != nil {
   782  			return pp.kind
   783  		}
   784  		return 0
   785  	}
   786  	r, li := l.toLocal(i)
   787  	return sym.AbiSymKindToSymKind[objabi.SymKind(r.Sym(li).Type())]
   788  }
   789  
   790  // Returns the attributes of the i-th symbol.
   791  func (l *Loader) SymAttr(i Sym) uint8 {
   792  	if l.IsExternal(i) {
   793  		// TODO: do something? External symbols have different representation of attributes.
   794  		// For now, ReflectMethod, NoSplit, GoType, and Typelink are used and they cannot be
   795  		// set by external symbol.
   796  		return 0
   797  	}
   798  	r, li := l.toLocal(i)
   799  	return r.Sym(li).Flag()
   800  }
   801  
   802  // Returns the size of the i-th symbol.
   803  func (l *Loader) SymSize(i Sym) int64 {
   804  	if l.IsExternal(i) {
   805  		pp := l.getPayload(i)
   806  		return pp.size
   807  	}
   808  	r, li := l.toLocal(i)
   809  	return int64(r.Sym(li).Siz())
   810  }
   811  
   812  // AttrReachable returns true for symbols that are transitively
   813  // referenced from the entry points. Unreachable symbols are not
   814  // written to the output.
   815  func (l *Loader) AttrReachable(i Sym) bool {
   816  	return l.attrReachable.Has(i)
   817  }
   818  
   819  // SetAttrReachable sets the reachability property for a symbol (see
   820  // AttrReachable).
   821  func (l *Loader) SetAttrReachable(i Sym, v bool) {
   822  	if v {
   823  		l.attrReachable.Set(i)
   824  	} else {
   825  		l.attrReachable.Unset(i)
   826  	}
   827  }
   828  
   829  // AttrOnList returns true for symbols that are on some list (such as
   830  // the list of all text symbols, or one of the lists of data symbols)
   831  // and is consulted to avoid bugs where a symbol is put on a list
   832  // twice.
   833  func (l *Loader) AttrOnList(i Sym) bool {
   834  	return l.attrOnList.Has(i)
   835  }
   836  
   837  // SetAttrOnList sets the "on list" property for a symbol (see
   838  // AttrOnList).
   839  func (l *Loader) SetAttrOnList(i Sym, v bool) {
   840  	if v {
   841  		l.attrOnList.Set(i)
   842  	} else {
   843  		l.attrOnList.Unset(i)
   844  	}
   845  }
   846  
   847  // AttrLocal returns true for symbols that are only visible within the
   848  // module (executable or shared library) being linked. This attribute
   849  // is applied to thunks and certain other linker-generated symbols.
   850  func (l *Loader) AttrLocal(i Sym) bool {
   851  	return l.attrLocal.Has(i)
   852  }
   853  
   854  // SetAttrLocal the "local" property for a symbol (see AttrLocal above).
   855  func (l *Loader) SetAttrLocal(i Sym, v bool) {
   856  	if v {
   857  		l.attrLocal.Set(i)
   858  	} else {
   859  		l.attrLocal.Unset(i)
   860  	}
   861  }
   862  
   863  // AttrUsedInIface returns true for a type symbol that is used in
   864  // an interface.
   865  func (l *Loader) AttrUsedInIface(i Sym) bool {
   866  	return l.attrUsedInIface.Has(i)
   867  }
   868  
   869  func (l *Loader) SetAttrUsedInIface(i Sym, v bool) {
   870  	if v {
   871  		l.attrUsedInIface.Set(i)
   872  	} else {
   873  		l.attrUsedInIface.Unset(i)
   874  	}
   875  }
   876  
   877  // SymAddr checks that a symbol is reachable, and returns its value.
   878  func (l *Loader) SymAddr(i Sym) int64 {
   879  	if !l.AttrReachable(i) {
   880  		panic("unreachable symbol in symaddr")
   881  	}
   882  	return l.values[i]
   883  }
   884  
   885  // AttrNotInSymbolTable returns true for symbols that should not be
   886  // added to the symbol table of the final generated load module.
   887  func (l *Loader) AttrNotInSymbolTable(i Sym) bool {
   888  	return l.attrNotInSymbolTable.Has(i)
   889  }
   890  
   891  // SetAttrNotInSymbolTable the "not in symtab" property for a symbol
   892  // (see AttrNotInSymbolTable above).
   893  func (l *Loader) SetAttrNotInSymbolTable(i Sym, v bool) {
   894  	if v {
   895  		l.attrNotInSymbolTable.Set(i)
   896  	} else {
   897  		l.attrNotInSymbolTable.Unset(i)
   898  	}
   899  }
   900  
   901  // AttrVisibilityHidden symbols returns true for ELF symbols with
   902  // visibility set to STV_HIDDEN. They become local symbols in
   903  // the final executable. Only relevant when internally linking
   904  // on an ELF platform.
   905  func (l *Loader) AttrVisibilityHidden(i Sym) bool {
   906  	if !l.IsExternal(i) {
   907  		return false
   908  	}
   909  	return l.attrVisibilityHidden.Has(l.extIndex(i))
   910  }
   911  
   912  // SetAttrVisibilityHidden sets the "hidden visibility" property for a
   913  // symbol (see AttrVisibilityHidden).
   914  func (l *Loader) SetAttrVisibilityHidden(i Sym, v bool) {
   915  	if !l.IsExternal(i) {
   916  		panic("tried to set visibility attr on non-external symbol")
   917  	}
   918  	if v {
   919  		l.attrVisibilityHidden.Set(l.extIndex(i))
   920  	} else {
   921  		l.attrVisibilityHidden.Unset(l.extIndex(i))
   922  	}
   923  }
   924  
   925  // AttrDuplicateOK returns true for a symbol that can be present in
   926  // multiple object files.
   927  func (l *Loader) AttrDuplicateOK(i Sym) bool {
   928  	if !l.IsExternal(i) {
   929  		// TODO: if this path winds up being taken frequently, it
   930  		// might make more sense to copy the flag value out of the object
   931  		// into a larger bitmap during preload.
   932  		r, li := l.toLocal(i)
   933  		return r.Sym(li).Dupok()
   934  	}
   935  	return l.attrDuplicateOK.Has(l.extIndex(i))
   936  }
   937  
   938  // SetAttrDuplicateOK sets the "duplicate OK" property for an external
   939  // symbol (see AttrDuplicateOK).
   940  func (l *Loader) SetAttrDuplicateOK(i Sym, v bool) {
   941  	if !l.IsExternal(i) {
   942  		panic("tried to set dupok attr on non-external symbol")
   943  	}
   944  	if v {
   945  		l.attrDuplicateOK.Set(l.extIndex(i))
   946  	} else {
   947  		l.attrDuplicateOK.Unset(l.extIndex(i))
   948  	}
   949  }
   950  
   951  // AttrShared returns true for symbols compiled with the -shared option.
   952  func (l *Loader) AttrShared(i Sym) bool {
   953  	if !l.IsExternal(i) {
   954  		// TODO: if this path winds up being taken frequently, it
   955  		// might make more sense to copy the flag value out of the
   956  		// object into a larger bitmap during preload.
   957  		r, _ := l.toLocal(i)
   958  		return r.Shared()
   959  	}
   960  	return l.attrShared.Has(l.extIndex(i))
   961  }
   962  
   963  // SetAttrShared sets the "shared" property for an external
   964  // symbol (see AttrShared).
   965  func (l *Loader) SetAttrShared(i Sym, v bool) {
   966  	if !l.IsExternal(i) {
   967  		panic(fmt.Sprintf("tried to set shared attr on non-external symbol %d %s", i, l.SymName(i)))
   968  	}
   969  	if v {
   970  		l.attrShared.Set(l.extIndex(i))
   971  	} else {
   972  		l.attrShared.Unset(l.extIndex(i))
   973  	}
   974  }
   975  
   976  // AttrExternal returns true for function symbols loaded from host
   977  // object files.
   978  func (l *Loader) AttrExternal(i Sym) bool {
   979  	if !l.IsExternal(i) {
   980  		return false
   981  	}
   982  	return l.attrExternal.Has(l.extIndex(i))
   983  }
   984  
   985  // SetAttrExternal sets the "external" property for a host object
   986  // symbol (see AttrExternal).
   987  func (l *Loader) SetAttrExternal(i Sym, v bool) {
   988  	if !l.IsExternal(i) {
   989  		panic(fmt.Sprintf("tried to set external attr on non-external symbol %q", l.SymName(i)))
   990  	}
   991  	if v {
   992  		l.attrExternal.Set(l.extIndex(i))
   993  	} else {
   994  		l.attrExternal.Unset(l.extIndex(i))
   995  	}
   996  }
   997  
   998  // AttrSpecial returns true for a symbols that do not have their
   999  // address (i.e. Value) computed by the usual mechanism of
  1000  // data.go:dodata() & data.go:address().
  1001  func (l *Loader) AttrSpecial(i Sym) bool {
  1002  	return l.attrSpecial.Has(i)
  1003  }
  1004  
  1005  // SetAttrSpecial sets the "special" property for a symbol (see
  1006  // AttrSpecial).
  1007  func (l *Loader) SetAttrSpecial(i Sym, v bool) {
  1008  	if v {
  1009  		l.attrSpecial.Set(i)
  1010  	} else {
  1011  		l.attrSpecial.Unset(i)
  1012  	}
  1013  }
  1014  
  1015  // AttrCgoExportDynamic returns true for a symbol that has been
  1016  // specially marked via the "cgo_export_dynamic" compiler directive
  1017  // written by cgo (in response to //export directives in the source).
  1018  func (l *Loader) AttrCgoExportDynamic(i Sym) bool {
  1019  	_, ok := l.attrCgoExportDynamic[i]
  1020  	return ok
  1021  }
  1022  
  1023  // SetAttrCgoExportDynamic sets the "cgo_export_dynamic" for a symbol
  1024  // (see AttrCgoExportDynamic).
  1025  func (l *Loader) SetAttrCgoExportDynamic(i Sym, v bool) {
  1026  	if v {
  1027  		l.attrCgoExportDynamic[i] = struct{}{}
  1028  	} else {
  1029  		delete(l.attrCgoExportDynamic, i)
  1030  	}
  1031  }
  1032  
  1033  // ForAllCgoExportDynamic calls f for every symbol that has been
  1034  // marked with the "cgo_export_dynamic" compiler directive.
  1035  func (l *Loader) ForAllCgoExportDynamic(f func(Sym)) {
  1036  	for s := range l.attrCgoExportDynamic {
  1037  		f(s)
  1038  	}
  1039  }
  1040  
  1041  // AttrCgoExportStatic returns true for a symbol that has been
  1042  // specially marked via the "cgo_export_static" directive
  1043  // written by cgo.
  1044  func (l *Loader) AttrCgoExportStatic(i Sym) bool {
  1045  	_, ok := l.attrCgoExportStatic[i]
  1046  	return ok
  1047  }
  1048  
  1049  // SetAttrCgoExportStatic sets the "cgo_export_static" for a symbol
  1050  // (see AttrCgoExportStatic).
  1051  func (l *Loader) SetAttrCgoExportStatic(i Sym, v bool) {
  1052  	if v {
  1053  		l.attrCgoExportStatic[i] = struct{}{}
  1054  	} else {
  1055  		delete(l.attrCgoExportStatic, i)
  1056  	}
  1057  }
  1058  
  1059  // IsGeneratedSym returns true if a symbol's been previously marked as a
  1060  // generator symbol through the SetIsGeneratedSym. The functions for generator
  1061  // symbols are kept in the Link context.
  1062  func (l *Loader) IsGeneratedSym(i Sym) bool {
  1063  	if !l.IsExternal(i) {
  1064  		return false
  1065  	}
  1066  	return l.generatedSyms.Has(l.extIndex(i))
  1067  }
  1068  
  1069  // SetIsGeneratedSym marks symbols as generated symbols. Data shouldn't be
  1070  // stored in generated symbols, and a function is registered and called for
  1071  // each of these symbols.
  1072  func (l *Loader) SetIsGeneratedSym(i Sym, v bool) {
  1073  	if !l.IsExternal(i) {
  1074  		panic("only external symbols can be generated")
  1075  	}
  1076  	if v {
  1077  		l.generatedSyms.Set(l.extIndex(i))
  1078  	} else {
  1079  		l.generatedSyms.Unset(l.extIndex(i))
  1080  	}
  1081  }
  1082  
  1083  func (l *Loader) AttrCgoExport(i Sym) bool {
  1084  	return l.AttrCgoExportDynamic(i) || l.AttrCgoExportStatic(i)
  1085  }
  1086  
  1087  // AttrReadOnly returns true for a symbol whose underlying data
  1088  // is stored via a read-only mmap.
  1089  func (l *Loader) AttrReadOnly(i Sym) bool {
  1090  	if v, ok := l.attrReadOnly[i]; ok {
  1091  		return v
  1092  	}
  1093  	if l.IsExternal(i) {
  1094  		pp := l.getPayload(i)
  1095  		if pp.objidx != 0 {
  1096  			return l.objs[pp.objidx].ReadOnly()
  1097  		}
  1098  		return false
  1099  	}
  1100  	r, _ := l.toLocal(i)
  1101  	return r.ReadOnly()
  1102  }
  1103  
  1104  // SetAttrReadOnly sets the "data is read only" property for a symbol
  1105  // (see AttrReadOnly).
  1106  func (l *Loader) SetAttrReadOnly(i Sym, v bool) {
  1107  	l.attrReadOnly[i] = v
  1108  }
  1109  
  1110  // AttrSubSymbol returns true for symbols that are listed as a
  1111  // sub-symbol of some other outer symbol. The sub/outer mechanism is
  1112  // used when loading host objects (sections from the host object
  1113  // become regular linker symbols and symbols go on the Sub list of
  1114  // their section) and for constructing the global offset table when
  1115  // internally linking a dynamic executable.
  1116  //
  1117  // Note that in later stages of the linker, we set Outer(S) to some
  1118  // container symbol C, but don't set Sub(C). Thus we have two
  1119  // distinct scenarios:
  1120  //
  1121  // - Outer symbol covers the address ranges of its sub-symbols.
  1122  //   Outer.Sub is set in this case.
  1123  // - Outer symbol doesn't cover the address ranges. It is zero-sized
  1124  //   and doesn't have sub-symbols. In the case, the inner symbol is
  1125  //   not actually a "SubSymbol". (Tricky!)
  1126  //
  1127  // This method returns TRUE only for sub-symbols in the first scenario.
  1128  //
  1129  // FIXME: would be better to do away with this and have a better way
  1130  // to represent container symbols.
  1131  
  1132  func (l *Loader) AttrSubSymbol(i Sym) bool {
  1133  	// we don't explicitly store this attribute any more -- return
  1134  	// a value based on the sub-symbol setting.
  1135  	o := l.OuterSym(i)
  1136  	if o == 0 {
  1137  		return false
  1138  	}
  1139  	return l.SubSym(o) != 0
  1140  }
  1141  
  1142  // Note that we don't have a 'SetAttrSubSymbol' method in the loader;
  1143  // clients should instead use the AddInteriorSym method to establish
  1144  // containment relationships for host object symbols.
  1145  
  1146  // Returns whether the i-th symbol has ReflectMethod attribute set.
  1147  func (l *Loader) IsReflectMethod(i Sym) bool {
  1148  	return l.SymAttr(i)&goobj.SymFlagReflectMethod != 0
  1149  }
  1150  
  1151  // Returns whether the i-th symbol is nosplit.
  1152  func (l *Loader) IsNoSplit(i Sym) bool {
  1153  	return l.SymAttr(i)&goobj.SymFlagNoSplit != 0
  1154  }
  1155  
  1156  // Returns whether this is a Go type symbol.
  1157  func (l *Loader) IsGoType(i Sym) bool {
  1158  	return l.SymAttr(i)&goobj.SymFlagGoType != 0
  1159  }
  1160  
  1161  // Returns whether this symbol should be included in typelink.
  1162  func (l *Loader) IsTypelink(i Sym) bool {
  1163  	return l.SymAttr(i)&goobj.SymFlagTypelink != 0
  1164  }
  1165  
  1166  // Returns whether this symbol is an itab symbol.
  1167  func (l *Loader) IsItab(i Sym) bool {
  1168  	if l.IsExternal(i) {
  1169  		return false
  1170  	}
  1171  	r, li := l.toLocal(i)
  1172  	return r.Sym(li).IsItab()
  1173  }
  1174  
  1175  // Returns whether this symbol is a dictionary symbol.
  1176  func (l *Loader) IsDict(i Sym) bool {
  1177  	if l.IsExternal(i) {
  1178  		return false
  1179  	}
  1180  	r, li := l.toLocal(i)
  1181  	return r.Sym(li).IsDict()
  1182  }
  1183  
  1184  // Returns whether this symbol is a compiler-generated package init func.
  1185  func (l *Loader) IsPkgInit(i Sym) bool {
  1186  	if l.IsExternal(i) {
  1187  		return false
  1188  	}
  1189  	r, li := l.toLocal(i)
  1190  	return r.Sym(li).IsPkgInit()
  1191  }
  1192  
  1193  // Return whether this is a trampoline of a deferreturn call.
  1194  func (l *Loader) IsDeferReturnTramp(i Sym) bool {
  1195  	return l.deferReturnTramp[i]
  1196  }
  1197  
  1198  // Set that i is a trampoline of a deferreturn call.
  1199  func (l *Loader) SetIsDeferReturnTramp(i Sym, v bool) {
  1200  	l.deferReturnTramp[i] = v
  1201  }
  1202  
  1203  // growValues grows the slice used to store symbol values.
  1204  func (l *Loader) growValues(reqLen int) {
  1205  	curLen := len(l.values)
  1206  	if reqLen > curLen {
  1207  		l.values = append(l.values, make([]int64, reqLen+1-curLen)...)
  1208  	}
  1209  }
  1210  
  1211  // SymValue returns the value of the i-th symbol. i is global index.
  1212  func (l *Loader) SymValue(i Sym) int64 {
  1213  	return l.values[i]
  1214  }
  1215  
  1216  // SetSymValue sets the value of the i-th symbol. i is global index.
  1217  func (l *Loader) SetSymValue(i Sym, val int64) {
  1218  	l.values[i] = val
  1219  }
  1220  
  1221  // AddToSymValue adds to the value of the i-th symbol. i is the global index.
  1222  func (l *Loader) AddToSymValue(i Sym, val int64) {
  1223  	l.values[i] += val
  1224  }
  1225  
  1226  // Returns the symbol content of the i-th symbol. i is global index.
  1227  func (l *Loader) Data(i Sym) []byte {
  1228  	if l.IsExternal(i) {
  1229  		pp := l.getPayload(i)
  1230  		if pp != nil {
  1231  			return pp.data
  1232  		}
  1233  		return nil
  1234  	}
  1235  	r, li := l.toLocal(i)
  1236  	return r.Data(li)
  1237  }
  1238  
  1239  // Returns the symbol content of the i-th symbol as a string. i is global index.
  1240  func (l *Loader) DataString(i Sym) string {
  1241  	if l.IsExternal(i) {
  1242  		pp := l.getPayload(i)
  1243  		return string(pp.data)
  1244  	}
  1245  	r, li := l.toLocal(i)
  1246  	return r.DataString(li)
  1247  }
  1248  
  1249  // FreeData clears the symbol data of an external symbol, allowing the memory
  1250  // to be freed earlier. No-op for non-external symbols.
  1251  // i is global index.
  1252  func (l *Loader) FreeData(i Sym) {
  1253  	if l.IsExternal(i) {
  1254  		pp := l.getPayload(i)
  1255  		if pp != nil {
  1256  			pp.data = nil
  1257  		}
  1258  	}
  1259  }
  1260  
  1261  // SymAlign returns the alignment for a symbol.
  1262  func (l *Loader) SymAlign(i Sym) int32 {
  1263  	if int(i) >= len(l.align) {
  1264  		// align is extended lazily -- it the sym in question is
  1265  		// outside the range of the existing slice, then we assume its
  1266  		// alignment has not yet been set.
  1267  		return 0
  1268  	}
  1269  	// TODO: would it make sense to return an arch-specific
  1270  	// alignment depending on section type? E.g. STEXT => 32,
  1271  	// SDATA => 1, etc?
  1272  	abits := l.align[i]
  1273  	if abits == 0 {
  1274  		return 0
  1275  	}
  1276  	return int32(1 << (abits - 1))
  1277  }
  1278  
  1279  // SetSymAlign sets the alignment for a symbol.
  1280  func (l *Loader) SetSymAlign(i Sym, align int32) {
  1281  	// Reject nonsense alignments.
  1282  	if align < 0 || align&(align-1) != 0 {
  1283  		panic("bad alignment value")
  1284  	}
  1285  	if int(i) >= len(l.align) {
  1286  		l.align = append(l.align, make([]uint8, l.NSym()-len(l.align))...)
  1287  	}
  1288  	if align == 0 {
  1289  		l.align[i] = 0
  1290  	}
  1291  	l.align[i] = uint8(bits.Len32(uint32(align)))
  1292  }
  1293  
  1294  // SymSect returns the section of the i-th symbol. i is global index.
  1295  func (l *Loader) SymSect(i Sym) *sym.Section {
  1296  	if int(i) >= len(l.symSects) {
  1297  		// symSects is extended lazily -- it the sym in question is
  1298  		// outside the range of the existing slice, then we assume its
  1299  		// section has not yet been set.
  1300  		return nil
  1301  	}
  1302  	return l.sects[l.symSects[i]]
  1303  }
  1304  
  1305  // SetSymSect sets the section of the i-th symbol. i is global index.
  1306  func (l *Loader) SetSymSect(i Sym, sect *sym.Section) {
  1307  	if int(i) >= len(l.symSects) {
  1308  		l.symSects = append(l.symSects, make([]uint16, l.NSym()-len(l.symSects))...)
  1309  	}
  1310  	l.symSects[i] = sect.Index
  1311  }
  1312  
  1313  // NewSection creates a new (output) section.
  1314  func (l *Loader) NewSection() *sym.Section {
  1315  	sect := new(sym.Section)
  1316  	idx := len(l.sects)
  1317  	if idx != int(uint16(idx)) {
  1318  		panic("too many sections created")
  1319  	}
  1320  	sect.Index = uint16(idx)
  1321  	l.sects = append(l.sects, sect)
  1322  	return sect
  1323  }
  1324  
  1325  // SymDynimplib returns the "dynimplib" attribute for the specified
  1326  // symbol, making up a portion of the info for a symbol specified
  1327  // on a "cgo_import_dynamic" compiler directive.
  1328  func (l *Loader) SymDynimplib(i Sym) string {
  1329  	return l.dynimplib[i]
  1330  }
  1331  
  1332  // SetSymDynimplib sets the "dynimplib" attribute for a symbol.
  1333  func (l *Loader) SetSymDynimplib(i Sym, value string) {
  1334  	// reject bad symbols
  1335  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1336  		panic("bad symbol index in SetDynimplib")
  1337  	}
  1338  	if value == "" {
  1339  		delete(l.dynimplib, i)
  1340  	} else {
  1341  		l.dynimplib[i] = value
  1342  	}
  1343  }
  1344  
  1345  // SymDynimpvers returns the "dynimpvers" attribute for the specified
  1346  // symbol, making up a portion of the info for a symbol specified
  1347  // on a "cgo_import_dynamic" compiler directive.
  1348  func (l *Loader) SymDynimpvers(i Sym) string {
  1349  	return l.dynimpvers[i]
  1350  }
  1351  
  1352  // SetSymDynimpvers sets the "dynimpvers" attribute for a symbol.
  1353  func (l *Loader) SetSymDynimpvers(i Sym, value string) {
  1354  	// reject bad symbols
  1355  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1356  		panic("bad symbol index in SetDynimpvers")
  1357  	}
  1358  	if value == "" {
  1359  		delete(l.dynimpvers, i)
  1360  	} else {
  1361  		l.dynimpvers[i] = value
  1362  	}
  1363  }
  1364  
  1365  // SymExtname returns the "extname" value for the specified
  1366  // symbol.
  1367  func (l *Loader) SymExtname(i Sym) string {
  1368  	if s, ok := l.extname[i]; ok {
  1369  		return s
  1370  	}
  1371  	return l.SymName(i)
  1372  }
  1373  
  1374  // SetSymExtname sets the  "extname" attribute for a symbol.
  1375  func (l *Loader) SetSymExtname(i Sym, value string) {
  1376  	// reject bad symbols
  1377  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1378  		panic("bad symbol index in SetExtname")
  1379  	}
  1380  	if value == "" {
  1381  		delete(l.extname, i)
  1382  	} else {
  1383  		l.extname[i] = value
  1384  	}
  1385  }
  1386  
  1387  // SymElfType returns the previously recorded ELF type for a symbol
  1388  // (used only for symbols read from shared libraries by ldshlibsyms).
  1389  // It is not set for symbols defined by the packages being linked or
  1390  // by symbols read by ldelf (and so is left as elf.STT_NOTYPE).
  1391  func (l *Loader) SymElfType(i Sym) elf.SymType {
  1392  	if et, ok := l.elfType[i]; ok {
  1393  		return et
  1394  	}
  1395  	return elf.STT_NOTYPE
  1396  }
  1397  
  1398  // SetSymElfType sets the elf type attribute for a symbol.
  1399  func (l *Loader) SetSymElfType(i Sym, et elf.SymType) {
  1400  	// reject bad symbols
  1401  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1402  		panic("bad symbol index in SetSymElfType")
  1403  	}
  1404  	if et == elf.STT_NOTYPE {
  1405  		delete(l.elfType, i)
  1406  	} else {
  1407  		l.elfType[i] = et
  1408  	}
  1409  }
  1410  
  1411  // SymElfSym returns the ELF symbol index for a given loader
  1412  // symbol, assigned during ELF symtab generation.
  1413  func (l *Loader) SymElfSym(i Sym) int32 {
  1414  	return l.elfSym[i]
  1415  }
  1416  
  1417  // SetSymElfSym sets the elf symbol index for a symbol.
  1418  func (l *Loader) SetSymElfSym(i Sym, es int32) {
  1419  	if i == 0 {
  1420  		panic("bad sym index")
  1421  	}
  1422  	if es == 0 {
  1423  		delete(l.elfSym, i)
  1424  	} else {
  1425  		l.elfSym[i] = es
  1426  	}
  1427  }
  1428  
  1429  // SymLocalElfSym returns the "local" ELF symbol index for a given loader
  1430  // symbol, assigned during ELF symtab generation.
  1431  func (l *Loader) SymLocalElfSym(i Sym) int32 {
  1432  	return l.localElfSym[i]
  1433  }
  1434  
  1435  // SetSymLocalElfSym sets the "local" elf symbol index for a symbol.
  1436  func (l *Loader) SetSymLocalElfSym(i Sym, es int32) {
  1437  	if i == 0 {
  1438  		panic("bad sym index")
  1439  	}
  1440  	if es == 0 {
  1441  		delete(l.localElfSym, i)
  1442  	} else {
  1443  		l.localElfSym[i] = es
  1444  	}
  1445  }
  1446  
  1447  // SymPlt returns the PLT offset of symbol s.
  1448  func (l *Loader) SymPlt(s Sym) int32 {
  1449  	if v, ok := l.plt[s]; ok {
  1450  		return v
  1451  	}
  1452  	return -1
  1453  }
  1454  
  1455  // SetPlt sets the PLT offset of symbol i.
  1456  func (l *Loader) SetPlt(i Sym, v int32) {
  1457  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1458  		panic("bad symbol for SetPlt")
  1459  	}
  1460  	if v == -1 {
  1461  		delete(l.plt, i)
  1462  	} else {
  1463  		l.plt[i] = v
  1464  	}
  1465  }
  1466  
  1467  // SymGot returns the GOT offset of symbol s.
  1468  func (l *Loader) SymGot(s Sym) int32 {
  1469  	if v, ok := l.got[s]; ok {
  1470  		return v
  1471  	}
  1472  	return -1
  1473  }
  1474  
  1475  // SetGot sets the GOT offset of symbol i.
  1476  func (l *Loader) SetGot(i Sym, v int32) {
  1477  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1478  		panic("bad symbol for SetGot")
  1479  	}
  1480  	if v == -1 {
  1481  		delete(l.got, i)
  1482  	} else {
  1483  		l.got[i] = v
  1484  	}
  1485  }
  1486  
  1487  // SymDynid returns the "dynid" property for the specified symbol.
  1488  func (l *Loader) SymDynid(i Sym) int32 {
  1489  	if s, ok := l.dynid[i]; ok {
  1490  		return s
  1491  	}
  1492  	return -1
  1493  }
  1494  
  1495  // SetSymDynid sets the "dynid" property for a symbol.
  1496  func (l *Loader) SetSymDynid(i Sym, val int32) {
  1497  	// reject bad symbols
  1498  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1499  		panic("bad symbol index in SetSymDynid")
  1500  	}
  1501  	if val == -1 {
  1502  		delete(l.dynid, i)
  1503  	} else {
  1504  		l.dynid[i] = val
  1505  	}
  1506  }
  1507  
  1508  // DynidSyms returns the set of symbols for which dynID is set to an
  1509  // interesting (non-default) value. This is expected to be a fairly
  1510  // small set.
  1511  func (l *Loader) DynidSyms() []Sym {
  1512  	sl := make([]Sym, 0, len(l.dynid))
  1513  	for s := range l.dynid {
  1514  		sl = append(sl, s)
  1515  	}
  1516  	sort.Slice(sl, func(i, j int) bool { return sl[i] < sl[j] })
  1517  	return sl
  1518  }
  1519  
  1520  // SymGoType returns the 'Gotype' property for a given symbol (set by
  1521  // the Go compiler for variable symbols). This version relies on
  1522  // reading aux symbols for the target sym -- it could be that a faster
  1523  // approach would be to check for gotype during preload and copy the
  1524  // results in to a map (might want to try this at some point and see
  1525  // if it helps speed things up).
  1526  func (l *Loader) SymGoType(i Sym) Sym { return l.aux1(i, goobj.AuxGotype) }
  1527  
  1528  // SymUnit returns the compilation unit for a given symbol (which will
  1529  // typically be nil for external or linker-manufactured symbols).
  1530  func (l *Loader) SymUnit(i Sym) *sym.CompilationUnit {
  1531  	if l.IsExternal(i) {
  1532  		pp := l.getPayload(i)
  1533  		if pp.objidx != 0 {
  1534  			r := l.objs[pp.objidx]
  1535  			return r.unit
  1536  		}
  1537  		return nil
  1538  	}
  1539  	r, _ := l.toLocal(i)
  1540  	return r.unit
  1541  }
  1542  
  1543  // SymPkg returns the package where the symbol came from (for
  1544  // regular compiler-generated Go symbols), but in the case of
  1545  // building with "-linkshared" (when a symbol is read from a
  1546  // shared library), will hold the library name.
  1547  // NOTE: this corresponds to sym.Symbol.File field.
  1548  func (l *Loader) SymPkg(i Sym) string {
  1549  	if f, ok := l.symPkg[i]; ok {
  1550  		return f
  1551  	}
  1552  	if l.IsExternal(i) {
  1553  		pp := l.getPayload(i)
  1554  		if pp.objidx != 0 {
  1555  			r := l.objs[pp.objidx]
  1556  			return r.unit.Lib.Pkg
  1557  		}
  1558  		return ""
  1559  	}
  1560  	r, _ := l.toLocal(i)
  1561  	return r.unit.Lib.Pkg
  1562  }
  1563  
  1564  // SetSymPkg sets the package/library for a symbol. This is
  1565  // needed mainly for external symbols, specifically those imported
  1566  // from shared libraries.
  1567  func (l *Loader) SetSymPkg(i Sym, pkg string) {
  1568  	// reject bad symbols
  1569  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1570  		panic("bad symbol index in SetSymPkg")
  1571  	}
  1572  	l.symPkg[i] = pkg
  1573  }
  1574  
  1575  // SymLocalentry returns an offset in bytes of the "local entry" of a symbol.
  1576  //
  1577  // On PPC64, a value of 1 indicates the symbol does not use or preserve a TOC
  1578  // pointer in R2, nor does it have a distinct local entry.
  1579  func (l *Loader) SymLocalentry(i Sym) uint8 {
  1580  	return l.localentry[i]
  1581  }
  1582  
  1583  // SetSymLocalentry sets the "local entry" offset attribute for a symbol.
  1584  func (l *Loader) SetSymLocalentry(i Sym, value uint8) {
  1585  	// reject bad symbols
  1586  	if i >= Sym(len(l.objSyms)) || i == 0 {
  1587  		panic("bad symbol index in SetSymLocalentry")
  1588  	}
  1589  	if value == 0 {
  1590  		delete(l.localentry, i)
  1591  	} else {
  1592  		l.localentry[i] = value
  1593  	}
  1594  }
  1595  
  1596  // Returns the number of aux symbols given a global index.
  1597  func (l *Loader) NAux(i Sym) int {
  1598  	if l.IsExternal(i) {
  1599  		return 0
  1600  	}
  1601  	r, li := l.toLocal(i)
  1602  	return r.NAux(li)
  1603  }
  1604  
  1605  // Returns the "handle" to the j-th aux symbol of the i-th symbol.
  1606  func (l *Loader) Aux(i Sym, j int) Aux {
  1607  	if l.IsExternal(i) {
  1608  		return Aux{}
  1609  	}
  1610  	r, li := l.toLocal(i)
  1611  	if j >= r.NAux(li) {
  1612  		return Aux{}
  1613  	}
  1614  	return Aux{r.Aux(li, j), r, l}
  1615  }
  1616  
  1617  // WasmImportSym returns the auxiliary WebAssembly import symbol associated with
  1618  // a given function symbol. The aux sym only exists for Go function stubs that
  1619  // have been annotated with the //go:wasmimport directive.  The aux sym
  1620  // contains the information necessary for the linker to add a WebAssembly
  1621  // import statement.
  1622  // (https://webassembly.github.io/spec/core/syntax/modules.html#imports)
  1623  func (l *Loader) WasmImportSym(fnSymIdx Sym) (Sym, bool) {
  1624  	if l.SymType(fnSymIdx) != sym.STEXT {
  1625  		log.Fatalf("error: non-function sym %d/%s t=%s passed to WasmImportSym", fnSymIdx, l.SymName(fnSymIdx), l.SymType(fnSymIdx).String())
  1626  	}
  1627  	r, li := l.toLocal(fnSymIdx)
  1628  	auxs := r.Auxs(li)
  1629  	for i := range auxs {
  1630  		a := &auxs[i]
  1631  		switch a.Type() {
  1632  		case goobj.AuxWasmImport:
  1633  			return l.resolve(r, a.Sym()), true
  1634  		}
  1635  	}
  1636  
  1637  	return 0, false
  1638  }
  1639  
  1640  // SEHUnwindSym returns the auxiliary SEH unwind symbol associated with
  1641  // a given function symbol.
  1642  func (l *Loader) SEHUnwindSym(fnSymIdx Sym) Sym {
  1643  	if l.SymType(fnSymIdx) != sym.STEXT {
  1644  		log.Fatalf("error: non-function sym %d/%s t=%s passed to SEHUnwindSym", fnSymIdx, l.SymName(fnSymIdx), l.SymType(fnSymIdx).String())
  1645  	}
  1646  
  1647  	return l.aux1(fnSymIdx, goobj.AuxSehUnwindInfo)
  1648  }
  1649  
  1650  // GetFuncDwarfAuxSyms collects and returns the auxiliary DWARF
  1651  // symbols associated with a given function symbol.  Prior to the
  1652  // introduction of the loader, this was done purely using name
  1653  // lookups, e.f. for function with name XYZ we would then look up
  1654  // go.info.XYZ, etc.
  1655  func (l *Loader) GetFuncDwarfAuxSyms(fnSymIdx Sym) (auxDwarfInfo, auxDwarfLoc, auxDwarfRanges, auxDwarfLines Sym) {
  1656  	if l.SymType(fnSymIdx) != sym.STEXT {
  1657  		log.Fatalf("error: non-function sym %d/%s t=%s passed to GetFuncDwarfAuxSyms", fnSymIdx, l.SymName(fnSymIdx), l.SymType(fnSymIdx).String())
  1658  	}
  1659  	r, auxs := l.auxs(fnSymIdx)
  1660  
  1661  	for i := range auxs {
  1662  		a := &auxs[i]
  1663  		switch a.Type() {
  1664  		case goobj.AuxDwarfInfo:
  1665  			auxDwarfInfo = l.resolve(r, a.Sym())
  1666  			if l.SymType(auxDwarfInfo) != sym.SDWARFFCN {
  1667  				panic("aux dwarf info sym with wrong type")
  1668  			}
  1669  		case goobj.AuxDwarfLoc:
  1670  			auxDwarfLoc = l.resolve(r, a.Sym())
  1671  			if l.SymType(auxDwarfLoc) != sym.SDWARFLOC {
  1672  				panic("aux dwarf loc sym with wrong type")
  1673  			}
  1674  		case goobj.AuxDwarfRanges:
  1675  			auxDwarfRanges = l.resolve(r, a.Sym())
  1676  			if l.SymType(auxDwarfRanges) != sym.SDWARFRANGE {
  1677  				panic("aux dwarf ranges sym with wrong type")
  1678  			}
  1679  		case goobj.AuxDwarfLines:
  1680  			auxDwarfLines = l.resolve(r, a.Sym())
  1681  			if l.SymType(auxDwarfLines) != sym.SDWARFLINES {
  1682  				panic("aux dwarf lines sym with wrong type")
  1683  			}
  1684  		}
  1685  	}
  1686  	return
  1687  }
  1688  
  1689  func (l *Loader) GetVarDwarfAuxSym(i Sym) Sym {
  1690  	aux := l.aux1(i, goobj.AuxDwarfInfo)
  1691  	if aux != 0 && l.SymType(aux) != sym.SDWARFVAR {
  1692  		fmt.Println(l.SymName(i), l.SymType(i), l.SymType(aux), sym.SDWARFVAR)
  1693  		panic("aux dwarf info sym with wrong type")
  1694  	}
  1695  	return aux
  1696  }
  1697  
  1698  // AddInteriorSym sets up 'interior' as an interior symbol of
  1699  // container/payload symbol 'container'. An interior symbol does not
  1700  // itself have data, but gives a name to a subrange of the data in its
  1701  // container symbol. The container itself may or may not have a name.
  1702  // This method is intended primarily for use in the host object
  1703  // loaders, to capture the semantics of symbols and sections in an
  1704  // object file. When reading a host object file, we'll typically
  1705  // encounter a static section symbol (ex: ".text") containing content
  1706  // for a collection of functions, then a series of ELF (or macho, etc)
  1707  // symbol table entries each of which points into a sub-section
  1708  // (offset and length) of its corresponding container symbol. Within
  1709  // the go linker we create a loader.Sym for the container (which is
  1710  // expected to have the actual content/payload) and then a set of
  1711  // interior loader.Sym's that point into a portion of the container.
  1712  func (l *Loader) AddInteriorSym(container Sym, interior Sym) {
  1713  	// Container symbols are expected to have content/data.
  1714  	// NB: this restriction may turn out to be too strict (it's possible
  1715  	// to imagine a zero-sized container with an interior symbol pointing
  1716  	// into it); it's ok to relax or remove it if we counter an
  1717  	// oddball host object that triggers this.
  1718  	if l.SymSize(container) == 0 && len(l.Data(container)) == 0 {
  1719  		panic("unexpected empty container symbol")
  1720  	}
  1721  	// The interior symbols for a container are not expected to have
  1722  	// content/data or relocations.
  1723  	if len(l.Data(interior)) != 0 {
  1724  		panic("unexpected non-empty interior symbol")
  1725  	}
  1726  	// Interior symbol is expected to be in the symbol table.
  1727  	if l.AttrNotInSymbolTable(interior) {
  1728  		panic("interior symbol must be in symtab")
  1729  	}
  1730  	// Only a single level of containment is allowed.
  1731  	if l.OuterSym(container) != 0 {
  1732  		panic("outer has outer itself")
  1733  	}
  1734  	// Interior sym should not already have a sibling.
  1735  	if l.SubSym(interior) != 0 {
  1736  		panic("sub set for subsym")
  1737  	}
  1738  	// Interior sym should not already point at a container.
  1739  	if l.OuterSym(interior) != 0 {
  1740  		panic("outer already set for subsym")
  1741  	}
  1742  	l.sub[interior] = l.sub[container]
  1743  	l.sub[container] = interior
  1744  	l.outer[interior] = container
  1745  }
  1746  
  1747  // OuterSym gets the outer/container symbol.
  1748  func (l *Loader) OuterSym(i Sym) Sym {
  1749  	return l.outer[i]
  1750  }
  1751  
  1752  // SubSym gets the subsymbol for host object loaded symbols.
  1753  func (l *Loader) SubSym(i Sym) Sym {
  1754  	return l.sub[i]
  1755  }
  1756  
  1757  // growOuter grows the slice used to store outer symbol.
  1758  func (l *Loader) growOuter(reqLen int) {
  1759  	curLen := len(l.outer)
  1760  	if reqLen > curLen {
  1761  		l.outer = append(l.outer, make([]Sym, reqLen-curLen)...)
  1762  	}
  1763  }
  1764  
  1765  // SetCarrierSym declares that 'c' is the carrier or container symbol
  1766  // for 's'. Carrier symbols are used in the linker to as a container
  1767  // for a collection of sub-symbols where the content of the
  1768  // sub-symbols is effectively concatenated to form the content of the
  1769  // carrier. The carrier is given a name in the output symbol table
  1770  // while the sub-symbol names are not. For example, the Go compiler
  1771  // emits named string symbols (type SGOSTRING) when compiling a
  1772  // package; after being deduplicated, these symbols are collected into
  1773  // a single unit by assigning them a new carrier symbol named
  1774  // "go:string.*" (which appears in the final symbol table for the
  1775  // output load module).
  1776  func (l *Loader) SetCarrierSym(s Sym, c Sym) {
  1777  	if c == 0 {
  1778  		panic("invalid carrier in SetCarrierSym")
  1779  	}
  1780  	if s == 0 {
  1781  		panic("invalid sub-symbol in SetCarrierSym")
  1782  	}
  1783  	// Carrier symbols are not expected to have content/data. It is
  1784  	// ok for them to have non-zero size (to allow for use of generator
  1785  	// symbols).
  1786  	if len(l.Data(c)) != 0 {
  1787  		panic("unexpected non-empty carrier symbol")
  1788  	}
  1789  	l.outer[s] = c
  1790  	// relocsym's foldSubSymbolOffset requires that we only
  1791  	// have a single level of containment-- enforce here.
  1792  	if l.outer[c] != 0 {
  1793  		panic("invalid nested carrier sym")
  1794  	}
  1795  }
  1796  
  1797  // Initialize Reachable bitmap and its siblings for running deadcode pass.
  1798  func (l *Loader) InitReachable() {
  1799  	l.growAttrBitmaps(l.NSym() + 1)
  1800  }
  1801  
  1802  type symWithVal struct {
  1803  	s Sym
  1804  	v int64
  1805  }
  1806  type bySymValue []symWithVal
  1807  
  1808  func (s bySymValue) Len() int           { return len(s) }
  1809  func (s bySymValue) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
  1810  func (s bySymValue) Less(i, j int) bool { return s[i].v < s[j].v }
  1811  
  1812  // SortSub walks through the sub-symbols for 's' and sorts them
  1813  // in place by increasing value. Return value is the new
  1814  // sub symbol for the specified outer symbol.
  1815  func (l *Loader) SortSub(s Sym) Sym {
  1816  
  1817  	if s == 0 || l.sub[s] == 0 {
  1818  		return s
  1819  	}
  1820  
  1821  	// Sort symbols using a slice first. Use a stable sort on the off
  1822  	// chance that there's more than once symbol with the same value,
  1823  	// so as to preserve reproducible builds.
  1824  	sl := []symWithVal{}
  1825  	for ss := l.sub[s]; ss != 0; ss = l.sub[ss] {
  1826  		sl = append(sl, symWithVal{s: ss, v: l.SymValue(ss)})
  1827  	}
  1828  	sort.Stable(bySymValue(sl))
  1829  
  1830  	// Then apply any changes needed to the sub map.
  1831  	ns := Sym(0)
  1832  	for i := len(sl) - 1; i >= 0; i-- {
  1833  		s := sl[i].s
  1834  		l.sub[s] = ns
  1835  		ns = s
  1836  	}
  1837  
  1838  	// Update sub for outer symbol, then return
  1839  	l.sub[s] = sl[0].s
  1840  	return sl[0].s
  1841  }
  1842  
  1843  // SortSyms sorts a list of symbols by their value.
  1844  func (l *Loader) SortSyms(ss []Sym) {
  1845  	sort.SliceStable(ss, func(i, j int) bool { return l.SymValue(ss[i]) < l.SymValue(ss[j]) })
  1846  }
  1847  
  1848  // Insure that reachable bitmap and its siblings have enough size.
  1849  func (l *Loader) growAttrBitmaps(reqLen int) {
  1850  	if reqLen > l.attrReachable.Len() {
  1851  		// These are indexed by global symbol
  1852  		l.attrReachable = growBitmap(reqLen, l.attrReachable)
  1853  		l.attrOnList = growBitmap(reqLen, l.attrOnList)
  1854  		l.attrLocal = growBitmap(reqLen, l.attrLocal)
  1855  		l.attrNotInSymbolTable = growBitmap(reqLen, l.attrNotInSymbolTable)
  1856  		l.attrUsedInIface = growBitmap(reqLen, l.attrUsedInIface)
  1857  		l.attrSpecial = growBitmap(reqLen, l.attrSpecial)
  1858  	}
  1859  	l.growExtAttrBitmaps()
  1860  }
  1861  
  1862  func (l *Loader) growExtAttrBitmaps() {
  1863  	// These are indexed by external symbol index (e.g. l.extIndex(i))
  1864  	extReqLen := len(l.payloads)
  1865  	if extReqLen > l.attrVisibilityHidden.Len() {
  1866  		l.attrVisibilityHidden = growBitmap(extReqLen, l.attrVisibilityHidden)
  1867  		l.attrDuplicateOK = growBitmap(extReqLen, l.attrDuplicateOK)
  1868  		l.attrShared = growBitmap(extReqLen, l.attrShared)
  1869  		l.attrExternal = growBitmap(extReqLen, l.attrExternal)
  1870  		l.generatedSyms = growBitmap(extReqLen, l.generatedSyms)
  1871  	}
  1872  }
  1873  
  1874  func (relocs *Relocs) Count() int { return len(relocs.rs) }
  1875  
  1876  // At returns the j-th reloc for a global symbol.
  1877  func (relocs *Relocs) At(j int) Reloc {
  1878  	if relocs.l.isExtReader(relocs.r) {
  1879  		return Reloc{&relocs.rs[j], relocs.r, relocs.l}
  1880  	}
  1881  	return Reloc{&relocs.rs[j], relocs.r, relocs.l}
  1882  }
  1883  
  1884  // Relocs returns a Relocs object for the given global sym.
  1885  func (l *Loader) Relocs(i Sym) Relocs {
  1886  	r, li := l.toLocal(i)
  1887  	if r == nil {
  1888  		panic(fmt.Sprintf("trying to get oreader for invalid sym %d\n\n", i))
  1889  	}
  1890  	return l.relocs(r, li)
  1891  }
  1892  
  1893  // relocs returns a Relocs object given a local sym index and reader.
  1894  func (l *Loader) relocs(r *oReader, li uint32) Relocs {
  1895  	var rs []goobj.Reloc
  1896  	if l.isExtReader(r) {
  1897  		pp := l.payloads[li]
  1898  		rs = pp.relocs
  1899  	} else {
  1900  		rs = r.Relocs(li)
  1901  	}
  1902  	return Relocs{
  1903  		rs: rs,
  1904  		li: li,
  1905  		r:  r,
  1906  		l:  l,
  1907  	}
  1908  }
  1909  
  1910  func (l *Loader) auxs(i Sym) (*oReader, []goobj.Aux) {
  1911  	if l.IsExternal(i) {
  1912  		pp := l.getPayload(i)
  1913  		return l.objs[pp.objidx], pp.auxs
  1914  	} else {
  1915  		r, li := l.toLocal(i)
  1916  		return r, r.Auxs(li)
  1917  	}
  1918  }
  1919  
  1920  // Returns a specific aux symbol of type t for symbol i.
  1921  func (l *Loader) aux1(i Sym, t uint8) Sym {
  1922  	r, auxs := l.auxs(i)
  1923  	for j := range auxs {
  1924  		a := &auxs[j]
  1925  		if a.Type() == t {
  1926  			return l.resolve(r, a.Sym())
  1927  		}
  1928  	}
  1929  	return 0
  1930  }
  1931  
  1932  func (l *Loader) Pcsp(i Sym) Sym { return l.aux1(i, goobj.AuxPcsp) }
  1933  
  1934  // Returns all aux symbols of per-PC data for symbol i.
  1935  // tmp is a scratch space for the pcdata slice.
  1936  func (l *Loader) PcdataAuxs(i Sym, tmp []Sym) (pcsp, pcfile, pcline, pcinline Sym, pcdata []Sym) {
  1937  	pcdata = tmp[:0]
  1938  	r, auxs := l.auxs(i)
  1939  	for j := range auxs {
  1940  		a := &auxs[j]
  1941  		switch a.Type() {
  1942  		case goobj.AuxPcsp:
  1943  			pcsp = l.resolve(r, a.Sym())
  1944  		case goobj.AuxPcline:
  1945  			pcline = l.resolve(r, a.Sym())
  1946  		case goobj.AuxPcfile:
  1947  			pcfile = l.resolve(r, a.Sym())
  1948  		case goobj.AuxPcinline:
  1949  			pcinline = l.resolve(r, a.Sym())
  1950  		case goobj.AuxPcdata:
  1951  			pcdata = append(pcdata, l.resolve(r, a.Sym()))
  1952  		}
  1953  	}
  1954  	return
  1955  }
  1956  
  1957  // Returns the number of pcdata for symbol i.
  1958  func (l *Loader) NumPcdata(i Sym) int {
  1959  	n := 0
  1960  	_, auxs := l.auxs(i)
  1961  	for j := range auxs {
  1962  		a := &auxs[j]
  1963  		if a.Type() == goobj.AuxPcdata {
  1964  			n++
  1965  		}
  1966  	}
  1967  	return n
  1968  }
  1969  
  1970  // Returns all funcdata symbols of symbol i.
  1971  // tmp is a scratch space.
  1972  func (l *Loader) Funcdata(i Sym, tmp []Sym) []Sym {
  1973  	fd := tmp[:0]
  1974  	r, auxs := l.auxs(i)
  1975  	for j := range auxs {
  1976  		a := &auxs[j]
  1977  		if a.Type() == goobj.AuxFuncdata {
  1978  			fd = append(fd, l.resolve(r, a.Sym()))
  1979  		}
  1980  	}
  1981  	return fd
  1982  }
  1983  
  1984  // Returns the number of funcdata for symbol i.
  1985  func (l *Loader) NumFuncdata(i Sym) int {
  1986  	n := 0
  1987  	_, auxs := l.auxs(i)
  1988  	for j := range auxs {
  1989  		a := &auxs[j]
  1990  		if a.Type() == goobj.AuxFuncdata {
  1991  			n++
  1992  		}
  1993  	}
  1994  	return n
  1995  }
  1996  
  1997  // FuncInfo provides hooks to access goobj.FuncInfo in the objects.
  1998  type FuncInfo struct {
  1999  	l       *Loader
  2000  	r       *oReader
  2001  	data    []byte
  2002  	lengths goobj.FuncInfoLengths
  2003  }
  2004  
  2005  func (fi *FuncInfo) Valid() bool { return fi.r != nil }
  2006  
  2007  func (fi *FuncInfo) Args() int {
  2008  	return int((*goobj.FuncInfo)(nil).ReadArgs(fi.data))
  2009  }
  2010  
  2011  func (fi *FuncInfo) Locals() int {
  2012  	return int((*goobj.FuncInfo)(nil).ReadLocals(fi.data))
  2013  }
  2014  
  2015  func (fi *FuncInfo) FuncID() abi.FuncID {
  2016  	return (*goobj.FuncInfo)(nil).ReadFuncID(fi.data)
  2017  }
  2018  
  2019  func (fi *FuncInfo) FuncFlag() abi.FuncFlag {
  2020  	return (*goobj.FuncInfo)(nil).ReadFuncFlag(fi.data)
  2021  }
  2022  
  2023  func (fi *FuncInfo) StartLine() int32 {
  2024  	return (*goobj.FuncInfo)(nil).ReadStartLine(fi.data)
  2025  }
  2026  
  2027  // Preload has to be called prior to invoking the various methods
  2028  // below related to pcdata, funcdataoff, files, and inltree nodes.
  2029  func (fi *FuncInfo) Preload() {
  2030  	fi.lengths = (*goobj.FuncInfo)(nil).ReadFuncInfoLengths(fi.data)
  2031  }
  2032  
  2033  func (fi *FuncInfo) NumFile() uint32 {
  2034  	if !fi.lengths.Initialized {
  2035  		panic("need to call Preload first")
  2036  	}
  2037  	return fi.lengths.NumFile
  2038  }
  2039  
  2040  func (fi *FuncInfo) File(k int) goobj.CUFileIndex {
  2041  	if !fi.lengths.Initialized {
  2042  		panic("need to call Preload first")
  2043  	}
  2044  	return (*goobj.FuncInfo)(nil).ReadFile(fi.data, fi.lengths.FileOff, uint32(k))
  2045  }
  2046  
  2047  // TopFrame returns true if the function associated with this FuncInfo
  2048  // is an entry point, meaning that unwinders should stop when they hit
  2049  // this function.
  2050  func (fi *FuncInfo) TopFrame() bool {
  2051  	return (fi.FuncFlag() & abi.FuncFlagTopFrame) != 0
  2052  }
  2053  
  2054  type InlTreeNode struct {
  2055  	Parent   int32
  2056  	File     goobj.CUFileIndex
  2057  	Line     int32
  2058  	Func     Sym
  2059  	ParentPC int32
  2060  }
  2061  
  2062  func (fi *FuncInfo) NumInlTree() uint32 {
  2063  	if !fi.lengths.Initialized {
  2064  		panic("need to call Preload first")
  2065  	}
  2066  	return fi.lengths.NumInlTree
  2067  }
  2068  
  2069  func (fi *FuncInfo) InlTree(k int) InlTreeNode {
  2070  	if !fi.lengths.Initialized {
  2071  		panic("need to call Preload first")
  2072  	}
  2073  	node := (*goobj.FuncInfo)(nil).ReadInlTree(fi.data, fi.lengths.InlTreeOff, uint32(k))
  2074  	return InlTreeNode{
  2075  		Parent:   node.Parent,
  2076  		File:     node.File,
  2077  		Line:     node.Line,
  2078  		Func:     fi.l.resolve(fi.r, node.Func),
  2079  		ParentPC: node.ParentPC,
  2080  	}
  2081  }
  2082  
  2083  func (l *Loader) FuncInfo(i Sym) FuncInfo {
  2084  	r, auxs := l.auxs(i)
  2085  	for j := range auxs {
  2086  		a := &auxs[j]
  2087  		if a.Type() == goobj.AuxFuncInfo {
  2088  			b := r.Data(a.Sym().SymIdx)
  2089  			return FuncInfo{l, r, b, goobj.FuncInfoLengths{}}
  2090  		}
  2091  	}
  2092  	return FuncInfo{}
  2093  }
  2094  
  2095  // Preload a package: adds autolib.
  2096  // Does not add defined package or non-packaged symbols to the symbol table.
  2097  // These are done in LoadSyms.
  2098  // Does not read symbol data.
  2099  // Returns the fingerprint of the object.
  2100  func (l *Loader) Preload(localSymVersion int, f *bio.Reader, lib *sym.Library, unit *sym.CompilationUnit, length int64) goobj.FingerprintType {
  2101  	roObject, readonly, err := f.Slice(uint64(length)) // TODO: no need to map blocks that are for tools only (e.g. RefName)
  2102  	if err != nil {
  2103  		log.Fatal("cannot read object file:", err)
  2104  	}
  2105  	r := goobj.NewReaderFromBytes(roObject, readonly)
  2106  	if r == nil {
  2107  		if len(roObject) >= 8 && bytes.Equal(roObject[:8], []byte("\x00go114ld")) {
  2108  			log.Fatalf("found object file %s in old format", f.File().Name())
  2109  		}
  2110  		panic("cannot read object file")
  2111  	}
  2112  	pkgprefix := objabi.PathToPrefix(lib.Pkg) + "."
  2113  	ndef := r.NSym()
  2114  	nhashed64def := r.NHashed64def()
  2115  	nhasheddef := r.NHasheddef()
  2116  	or := &oReader{
  2117  		Reader:       r,
  2118  		unit:         unit,
  2119  		version:      localSymVersion,
  2120  		pkgprefix:    pkgprefix,
  2121  		syms:         make([]Sym, ndef+nhashed64def+nhasheddef+r.NNonpkgdef()+r.NNonpkgref()),
  2122  		ndef:         ndef,
  2123  		nhasheddef:   nhasheddef,
  2124  		nhashed64def: nhashed64def,
  2125  		objidx:       uint32(len(l.objs)),
  2126  	}
  2127  
  2128  	if r.Unlinkable() {
  2129  		log.Fatalf("link: unlinkable object (from package %s) - compiler requires -p flag", lib.Pkg)
  2130  	}
  2131  
  2132  	// Autolib
  2133  	lib.Autolib = append(lib.Autolib, r.Autolib()...)
  2134  
  2135  	// DWARF file table
  2136  	nfile := r.NFile()
  2137  	unit.FileTable = make([]string, nfile)
  2138  	for i := range unit.FileTable {
  2139  		unit.FileTable[i] = r.File(i)
  2140  	}
  2141  
  2142  	l.addObj(lib.Pkg, or)
  2143  
  2144  	// The caller expects us consuming all the data
  2145  	f.MustSeek(length, io.SeekCurrent)
  2146  
  2147  	return r.Fingerprint()
  2148  }
  2149  
  2150  // Holds the loader along with temporary states for loading symbols.
  2151  type loadState struct {
  2152  	l            *Loader
  2153  	hashed64Syms map[uint64]symAndSize         // short hashed (content-addressable) symbols, keyed by content hash
  2154  	hashedSyms   map[goobj.HashType]symAndSize // hashed (content-addressable) symbols, keyed by content hash
  2155  
  2156  	linknameVarRefs []linknameVarRef // linknamed var refererces
  2157  }
  2158  
  2159  type linknameVarRef struct {
  2160  	pkg  string // package of reference (not definition)
  2161  	name string
  2162  	sym  Sym
  2163  }
  2164  
  2165  // Preload symbols of given kind from an object.
  2166  func (st *loadState) preloadSyms(r *oReader, kind int) {
  2167  	l := st.l
  2168  	var start, end uint32
  2169  	switch kind {
  2170  	case pkgDef:
  2171  		start = 0
  2172  		end = uint32(r.ndef)
  2173  	case hashed64Def:
  2174  		start = uint32(r.ndef)
  2175  		end = uint32(r.ndef + r.nhashed64def)
  2176  	case hashedDef:
  2177  		start = uint32(r.ndef + r.nhashed64def)
  2178  		end = uint32(r.ndef + r.nhashed64def + r.nhasheddef)
  2179  	case nonPkgDef:
  2180  		start = uint32(r.ndef + r.nhashed64def + r.nhasheddef)
  2181  		end = uint32(r.ndef + r.nhashed64def + r.nhasheddef + r.NNonpkgdef())
  2182  	default:
  2183  		panic("preloadSyms: bad kind")
  2184  	}
  2185  	l.growAttrBitmaps(len(l.objSyms) + int(end-start))
  2186  	loadingRuntimePkg := r.unit.Lib.Pkg == "runtime"
  2187  	for i := start; i < end; i++ {
  2188  		osym := r.Sym(i)
  2189  		var name string
  2190  		var v int
  2191  		if kind != hashed64Def && kind != hashedDef { // we don't need the name, etc. for hashed symbols
  2192  			name = osym.Name(r.Reader)
  2193  			v = abiToVer(osym.ABI(), r.version)
  2194  		}
  2195  		gi := st.addSym(name, v, r, i, kind, osym)
  2196  		r.syms[i] = gi
  2197  		if kind == nonPkgDef && osym.IsLinkname() && r.DataSize(i) == 0 && strings.Contains(name, ".") {
  2198  			// This is a linknamed "var" "reference" (var x T with no data and //go:linkname x).
  2199  			// We want to check if a linkname reference is allowed. Here we haven't loaded all
  2200  			// symbol definitions, so we don't yet know all the push linknames. So we add to a
  2201  			// list and check later after all symbol defs are loaded. Linknamed vars are rare,
  2202  			// so this list won't be long.
  2203  			// Only check references (pull), not definitions (push, with non-zero size),
  2204  			// so push is always allowed.
  2205  			// This use of linkname is usually for referencing C symbols, so allow symbols
  2206  			// with no "." in its name (not a regular Go symbol).
  2207  			// Linkname is always a non-package reference.
  2208  			st.linknameVarRefs = append(st.linknameVarRefs, linknameVarRef{r.unit.Lib.Pkg, name, gi})
  2209  		}
  2210  		if osym.Local() {
  2211  			l.SetAttrLocal(gi, true)
  2212  		}
  2213  		if osym.UsedInIface() {
  2214  			l.SetAttrUsedInIface(gi, true)
  2215  		}
  2216  		if strings.HasPrefix(name, "runtime.") ||
  2217  			(loadingRuntimePkg && strings.HasPrefix(name, "type:")) {
  2218  			if bi := goobj.BuiltinIdx(name, int(osym.ABI())); bi != -1 {
  2219  				// This is a definition of a builtin symbol. Record where it is.
  2220  				l.builtinSyms[bi] = gi
  2221  			}
  2222  		}
  2223  		if a := int32(osym.Align()); a != 0 && a > l.SymAlign(gi) {
  2224  			l.SetSymAlign(gi, a)
  2225  		}
  2226  	}
  2227  }
  2228  
  2229  // Add syms, hashed (content-addressable) symbols, non-package symbols, and
  2230  // references to external symbols (which are always named).
  2231  func (l *Loader) LoadSyms(arch *sys.Arch) {
  2232  	// Allocate space for symbols, making a guess as to how much space we need.
  2233  	// This function was determined empirically by looking at the cmd/compile on
  2234  	// Darwin, and picking factors for hashed and hashed64 syms.
  2235  	var symSize, hashedSize, hashed64Size int
  2236  	for _, r := range l.objs[goObjStart:] {
  2237  		symSize += r.ndef + r.nhasheddef/2 + r.nhashed64def/2 + r.NNonpkgdef()
  2238  		hashedSize += r.nhasheddef / 2
  2239  		hashed64Size += r.nhashed64def / 2
  2240  	}
  2241  	// Index 0 is invalid for symbols.
  2242  	l.objSyms = make([]objSym, 1, symSize)
  2243  
  2244  	st := loadState{
  2245  		l:            l,
  2246  		hashed64Syms: make(map[uint64]symAndSize, hashed64Size),
  2247  		hashedSyms:   make(map[goobj.HashType]symAndSize, hashedSize),
  2248  	}
  2249  
  2250  	for _, r := range l.objs[goObjStart:] {
  2251  		st.preloadSyms(r, pkgDef)
  2252  	}
  2253  	l.npkgsyms = l.NSym()
  2254  	for _, r := range l.objs[goObjStart:] {
  2255  		st.preloadSyms(r, hashed64Def)
  2256  		st.preloadSyms(r, hashedDef)
  2257  		st.preloadSyms(r, nonPkgDef)
  2258  	}
  2259  	for _, vr := range st.linknameVarRefs {
  2260  		l.checkLinkname(vr.pkg, vr.name, vr.sym)
  2261  	}
  2262  	l.nhashedsyms = len(st.hashed64Syms) + len(st.hashedSyms)
  2263  	for _, r := range l.objs[goObjStart:] {
  2264  		loadObjRefs(l, r, arch)
  2265  	}
  2266  	l.values = make([]int64, l.NSym(), l.NSym()+1000) // +1000 make some room for external symbols
  2267  	l.outer = make([]Sym, l.NSym(), l.NSym()+1000)
  2268  }
  2269  
  2270  func loadObjRefs(l *Loader, r *oReader, arch *sys.Arch) {
  2271  	// load non-package refs
  2272  	ndef := uint32(r.NAlldef())
  2273  	for i, n := uint32(0), uint32(r.NNonpkgref()); i < n; i++ {
  2274  		osym := r.Sym(ndef + i)
  2275  		name := osym.Name(r.Reader)
  2276  		v := abiToVer(osym.ABI(), r.version)
  2277  		gi := l.LookupOrCreateSym(name, v)
  2278  		r.syms[ndef+i] = gi
  2279  		if osym.IsLinkname() {
  2280  			// Check if a linkname reference is allowed.
  2281  			// Only check references (pull), not definitions (push),
  2282  			// so push is always allowed.
  2283  			// Linkname is always a non-package reference.
  2284  			l.checkLinkname(r.unit.Lib.Pkg, name, gi)
  2285  		}
  2286  		if osym.Local() {
  2287  			l.SetAttrLocal(gi, true)
  2288  		}
  2289  		if osym.UsedInIface() {
  2290  			l.SetAttrUsedInIface(gi, true)
  2291  		}
  2292  	}
  2293  
  2294  	// referenced packages
  2295  	npkg := r.NPkg()
  2296  	r.pkg = make([]uint32, npkg)
  2297  	for i := 1; i < npkg; i++ { // PkgIdx 0 is a dummy invalid package
  2298  		pkg := r.Pkg(i)
  2299  		objidx, ok := l.objByPkg[pkg]
  2300  		if !ok {
  2301  			log.Fatalf("%v: reference to nonexistent package %s", r.unit.Lib, pkg)
  2302  		}
  2303  		r.pkg[i] = objidx
  2304  	}
  2305  
  2306  	// load flags of package refs
  2307  	for i, n := 0, r.NRefFlags(); i < n; i++ {
  2308  		rf := r.RefFlags(i)
  2309  		gi := l.resolve(r, rf.Sym())
  2310  		if rf.Flag2()&goobj.SymFlagUsedInIface != 0 {
  2311  			l.SetAttrUsedInIface(gi, true)
  2312  		}
  2313  	}
  2314  }
  2315  
  2316  func abiToVer(abi uint16, localSymVersion int) int {
  2317  	var v int
  2318  	if abi == goobj.SymABIstatic {
  2319  		// Static
  2320  		v = localSymVersion
  2321  	} else if abiver := sym.ABIToVersion(obj.ABI(abi)); abiver != -1 {
  2322  		// Note that data symbols are "ABI0", which maps to version 0.
  2323  		v = abiver
  2324  	} else {
  2325  		log.Fatalf("invalid symbol ABI: %d", abi)
  2326  	}
  2327  	return v
  2328  }
  2329  
  2330  // A list of blocked linknames. Some linknames are allowed only
  2331  // in specific packages. This maps symbol names to allowed packages.
  2332  // If a name is not in this map, it is allowed iff the definition
  2333  // has a linkname (push).
  2334  // If a name is in this map, it is allowed only in listed packages,
  2335  // even if it has a linknamed definition.
  2336  var blockedLinknames = map[string][]string{
  2337  	// coroutines
  2338  	"runtime.coroswitch": {"iter"},
  2339  	"runtime.newcoro":    {"iter"},
  2340  	// weak references
  2341  	"internal/weak.runtime_registerWeakPointer": {"internal/weak"},
  2342  	"internal/weak.runtime_makeStrongFromWeak":  {"internal/weak"},
  2343  }
  2344  
  2345  // check if a linkname reference to symbol s from pkg is allowed
  2346  func (l *Loader) checkLinkname(pkg, name string, s Sym) {
  2347  	if l.flags&FlagCheckLinkname == 0 {
  2348  		return
  2349  	}
  2350  
  2351  	error := func() {
  2352  		log.Fatalf("%s: invalid reference to %s", pkg, name)
  2353  	}
  2354  	pkgs, ok := blockedLinknames[name]
  2355  	if ok {
  2356  		for _, p := range pkgs {
  2357  			if pkg == p {
  2358  				return // pkg is allowed
  2359  			}
  2360  		}
  2361  		error()
  2362  	}
  2363  	r, li := l.toLocal(s)
  2364  	if r == l.extReader { // referencing external symbol is okay
  2365  		return
  2366  	}
  2367  	if !r.Std() { // For now, only check for symbols defined in std
  2368  		return
  2369  	}
  2370  	if r.unit.Lib.Pkg == pkg { // assembly reference from same package
  2371  		return
  2372  	}
  2373  	osym := r.Sym(li)
  2374  	if osym.IsLinkname() || osym.ABIWrapper() {
  2375  		// Allow if the def has a linkname (push).
  2376  		// ABI wrapper usually wraps an assembly symbol, a linknamed symbol,
  2377  		// or an external symbol, or provide access of a Go symbol to assembly.
  2378  		// For now, allow ABI wrappers.
  2379  		// TODO: check the wrapped symbol?
  2380  		return
  2381  	}
  2382  	error()
  2383  }
  2384  
  2385  // TopLevelSym tests a symbol (by name and kind) to determine whether
  2386  // the symbol first class sym (participating in the link) or is an
  2387  // anonymous aux or sub-symbol containing some sub-part or payload of
  2388  // another symbol.
  2389  func (l *Loader) TopLevelSym(s Sym) bool {
  2390  	return topLevelSym(l.SymName(s), l.SymType(s))
  2391  }
  2392  
  2393  // topLevelSym tests a symbol name and kind to determine whether
  2394  // the symbol first class sym (participating in the link) or is an
  2395  // anonymous aux or sub-symbol containing some sub-part or payload of
  2396  // another symbol.
  2397  func topLevelSym(sname string, skind sym.SymKind) bool {
  2398  	if sname != "" {
  2399  		return true
  2400  	}
  2401  	switch skind {
  2402  	case sym.SDWARFFCN, sym.SDWARFABSFCN, sym.SDWARFTYPE, sym.SDWARFCONST, sym.SDWARFCUINFO, sym.SDWARFRANGE, sym.SDWARFLOC, sym.SDWARFLINES, sym.SGOFUNC:
  2403  		return true
  2404  	default:
  2405  		return false
  2406  	}
  2407  }
  2408  
  2409  // cloneToExternal takes the existing object file symbol (symIdx)
  2410  // and creates a new external symbol payload that is a clone with
  2411  // respect to name, version, type, relocations, etc. The idea here
  2412  // is that if the linker decides it wants to update the contents of
  2413  // a symbol originally discovered as part of an object file, it's
  2414  // easier to do this if we make the updates to an external symbol
  2415  // payload.
  2416  func (l *Loader) cloneToExternal(symIdx Sym) {
  2417  	if l.IsExternal(symIdx) {
  2418  		panic("sym is already external, no need for clone")
  2419  	}
  2420  
  2421  	// Read the particulars from object.
  2422  	r, li := l.toLocal(symIdx)
  2423  	osym := r.Sym(li)
  2424  	sname := osym.Name(r.Reader)
  2425  	sver := abiToVer(osym.ABI(), r.version)
  2426  	skind := sym.AbiSymKindToSymKind[objabi.SymKind(osym.Type())]
  2427  
  2428  	// Create new symbol, update version and kind.
  2429  	pi := l.newPayload(sname, sver)
  2430  	pp := l.payloads[pi]
  2431  	pp.kind = skind
  2432  	pp.ver = sver
  2433  	pp.size = int64(osym.Siz())
  2434  	pp.objidx = r.objidx
  2435  
  2436  	// If this is a def, then copy the guts. We expect this case
  2437  	// to be very rare (one case it may come up is with -X).
  2438  	if li < uint32(r.NAlldef()) {
  2439  
  2440  		// Copy relocations
  2441  		relocs := l.Relocs(symIdx)
  2442  		pp.relocs = make([]goobj.Reloc, relocs.Count())
  2443  		for i := range pp.relocs {
  2444  			// Copy the relocs slice.
  2445  			// Convert local reference to global reference.
  2446  			rel := relocs.At(i)
  2447  			pp.relocs[i].Set(rel.Off(), rel.Siz(), uint16(rel.Type()), rel.Add(), goobj.SymRef{PkgIdx: 0, SymIdx: uint32(rel.Sym())})
  2448  		}
  2449  
  2450  		// Copy data
  2451  		pp.data = r.Data(li)
  2452  	}
  2453  
  2454  	// If we're overriding a data symbol, collect the associated
  2455  	// Gotype, so as to propagate it to the new symbol.
  2456  	auxs := r.Auxs(li)
  2457  	pp.auxs = auxs
  2458  
  2459  	// Install new payload to global index space.
  2460  	// (This needs to happen at the end, as the accessors above
  2461  	// need to access the old symbol content.)
  2462  	l.objSyms[symIdx] = objSym{l.extReader.objidx, uint32(pi)}
  2463  	l.extReader.syms = append(l.extReader.syms, symIdx)
  2464  
  2465  	// Some attributes were encoded in the object file. Copy them over.
  2466  	l.SetAttrDuplicateOK(symIdx, r.Sym(li).Dupok())
  2467  	l.SetAttrShared(symIdx, r.Shared())
  2468  }
  2469  
  2470  // Copy the payload of symbol src to dst. Both src and dst must be external
  2471  // symbols.
  2472  // The intended use case is that when building/linking against a shared library,
  2473  // where we do symbol name mangling, the Go object file may have reference to
  2474  // the original symbol name whereas the shared library provides a symbol with
  2475  // the mangled name. When we do mangling, we copy payload of mangled to original.
  2476  func (l *Loader) CopySym(src, dst Sym) {
  2477  	if !l.IsExternal(dst) {
  2478  		panic("dst is not external") //l.newExtSym(l.SymName(dst), l.SymVersion(dst))
  2479  	}
  2480  	if !l.IsExternal(src) {
  2481  		panic("src is not external") //l.cloneToExternal(src)
  2482  	}
  2483  	l.payloads[l.extIndex(dst)] = l.payloads[l.extIndex(src)]
  2484  	l.SetSymPkg(dst, l.SymPkg(src))
  2485  	// TODO: other attributes?
  2486  }
  2487  
  2488  // CreateExtSym creates a new external symbol with the specified name
  2489  // without adding it to any lookup tables, returning a Sym index for it.
  2490  func (l *Loader) CreateExtSym(name string, ver int) Sym {
  2491  	return l.newExtSym(name, ver)
  2492  }
  2493  
  2494  // CreateStaticSym creates a new static symbol with the specified name
  2495  // without adding it to any lookup tables, returning a Sym index for it.
  2496  func (l *Loader) CreateStaticSym(name string) Sym {
  2497  	// Assign a new unique negative version -- this is to mark the
  2498  	// symbol so that it is not included in the name lookup table.
  2499  	l.anonVersion--
  2500  	return l.newExtSym(name, l.anonVersion)
  2501  }
  2502  
  2503  func (l *Loader) FreeSym(i Sym) {
  2504  	if l.IsExternal(i) {
  2505  		pp := l.getPayload(i)
  2506  		*pp = extSymPayload{}
  2507  	}
  2508  }
  2509  
  2510  // relocId is essentially a <S,R> tuple identifying the Rth
  2511  // relocation of symbol S.
  2512  type relocId struct {
  2513  	sym  Sym
  2514  	ridx int
  2515  }
  2516  
  2517  // SetRelocVariant sets the 'variant' property of a relocation on
  2518  // some specific symbol.
  2519  func (l *Loader) SetRelocVariant(s Sym, ri int, v sym.RelocVariant) {
  2520  	// sanity check
  2521  	if relocs := l.Relocs(s); ri >= relocs.Count() {
  2522  		panic("invalid relocation ID")
  2523  	}
  2524  	if l.relocVariant == nil {
  2525  		l.relocVariant = make(map[relocId]sym.RelocVariant)
  2526  	}
  2527  	if v != 0 {
  2528  		l.relocVariant[relocId{s, ri}] = v
  2529  	} else {
  2530  		delete(l.relocVariant, relocId{s, ri})
  2531  	}
  2532  }
  2533  
  2534  // RelocVariant returns the 'variant' property of a relocation on
  2535  // some specific symbol.
  2536  func (l *Loader) RelocVariant(s Sym, ri int) sym.RelocVariant {
  2537  	return l.relocVariant[relocId{s, ri}]
  2538  }
  2539  
  2540  // UndefinedRelocTargets iterates through the global symbol index
  2541  // space, looking for symbols with relocations targeting undefined
  2542  // references. The linker's loadlib method uses this to determine if
  2543  // there are unresolved references to functions in system libraries
  2544  // (for example, libgcc.a), presumably due to CGO code. Return value
  2545  // is a pair of lists of loader.Sym's. First list corresponds to the
  2546  // corresponding to the undefined symbols themselves, the second list
  2547  // is the symbol that is making a reference to the undef. The "limit"
  2548  // param controls the maximum number of results returned; if "limit"
  2549  // is -1, then all undefs are returned.
  2550  func (l *Loader) UndefinedRelocTargets(limit int) ([]Sym, []Sym) {
  2551  	result, fromr := []Sym{}, []Sym{}
  2552  outerloop:
  2553  	for si := Sym(1); si < Sym(len(l.objSyms)); si++ {
  2554  		relocs := l.Relocs(si)
  2555  		for ri := 0; ri < relocs.Count(); ri++ {
  2556  			r := relocs.At(ri)
  2557  			rs := r.Sym()
  2558  			if rs != 0 && l.SymType(rs) == sym.SXREF && l.SymName(rs) != ".got" {
  2559  				result = append(result, rs)
  2560  				fromr = append(fromr, si)
  2561  				if limit != -1 && len(result) >= limit {
  2562  					break outerloop
  2563  				}
  2564  			}
  2565  		}
  2566  	}
  2567  	return result, fromr
  2568  }
  2569  
  2570  // AssignTextSymbolOrder populates the Textp slices within each
  2571  // library and compilation unit, insuring that packages are laid down
  2572  // in dependency order (internal first, then everything else). Return value
  2573  // is a slice of all text syms.
  2574  func (l *Loader) AssignTextSymbolOrder(libs []*sym.Library, intlibs []bool, extsyms []Sym) []Sym {
  2575  
  2576  	// Library Textp lists should be empty at this point.
  2577  	for _, lib := range libs {
  2578  		if len(lib.Textp) != 0 {
  2579  			panic("expected empty Textp slice for library")
  2580  		}
  2581  		if len(lib.DupTextSyms) != 0 {
  2582  			panic("expected empty DupTextSyms slice for library")
  2583  		}
  2584  	}
  2585  
  2586  	// Used to record which dupok symbol we've assigned to a unit.
  2587  	// Can't use the onlist attribute here because it will need to
  2588  	// clear for the later assignment of the sym.Symbol to a unit.
  2589  	// NB: we can convert to using onList once we no longer have to
  2590  	// call the regular addToTextp.
  2591  	assignedToUnit := MakeBitmap(l.NSym() + 1)
  2592  
  2593  	// Start off textp with reachable external syms.
  2594  	textp := []Sym{}
  2595  	for _, sym := range extsyms {
  2596  		if !l.attrReachable.Has(sym) {
  2597  			continue
  2598  		}
  2599  		textp = append(textp, sym)
  2600  	}
  2601  
  2602  	// Walk through all text symbols from Go object files and append
  2603  	// them to their corresponding library's textp list.
  2604  	for _, r := range l.objs[goObjStart:] {
  2605  		lib := r.unit.Lib
  2606  		for i, n := uint32(0), uint32(r.NAlldef()); i < n; i++ {
  2607  			gi := l.toGlobal(r, i)
  2608  			if !l.attrReachable.Has(gi) {
  2609  				continue
  2610  			}
  2611  			osym := r.Sym(i)
  2612  			st := sym.AbiSymKindToSymKind[objabi.SymKind(osym.Type())]
  2613  			if st != sym.STEXT {
  2614  				continue
  2615  			}
  2616  			dupok := osym.Dupok()
  2617  			if r2, i2 := l.toLocal(gi); r2 != r || i2 != i {
  2618  				// A dupok text symbol is resolved to another package.
  2619  				// We still need to record its presence in the current
  2620  				// package, as the trampoline pass expects packages
  2621  				// are laid out in dependency order.
  2622  				lib.DupTextSyms = append(lib.DupTextSyms, sym.LoaderSym(gi))
  2623  				continue // symbol in different object
  2624  			}
  2625  			if dupok {
  2626  				lib.DupTextSyms = append(lib.DupTextSyms, sym.LoaderSym(gi))
  2627  				continue
  2628  			}
  2629  
  2630  			lib.Textp = append(lib.Textp, sym.LoaderSym(gi))
  2631  		}
  2632  	}
  2633  
  2634  	// Now assemble global textp, and assign text symbols to units.
  2635  	for _, doInternal := range [2]bool{true, false} {
  2636  		for idx, lib := range libs {
  2637  			if intlibs[idx] != doInternal {
  2638  				continue
  2639  			}
  2640  			lists := [2][]sym.LoaderSym{lib.Textp, lib.DupTextSyms}
  2641  			for i, list := range lists {
  2642  				for _, s := range list {
  2643  					sym := Sym(s)
  2644  					if !assignedToUnit.Has(sym) {
  2645  						textp = append(textp, sym)
  2646  						unit := l.SymUnit(sym)
  2647  						if unit != nil {
  2648  							unit.Textp = append(unit.Textp, s)
  2649  							assignedToUnit.Set(sym)
  2650  						}
  2651  						// Dupok symbols may be defined in multiple packages; the
  2652  						// associated package for a dupok sym is chosen sort of
  2653  						// arbitrarily (the first containing package that the linker
  2654  						// loads). Canonicalizes its Pkg to the package with which
  2655  						// it will be laid down in text.
  2656  						if i == 1 /* DupTextSyms2 */ && l.SymPkg(sym) != lib.Pkg {
  2657  							l.SetSymPkg(sym, lib.Pkg)
  2658  						}
  2659  					}
  2660  				}
  2661  			}
  2662  			lib.Textp = nil
  2663  			lib.DupTextSyms = nil
  2664  		}
  2665  	}
  2666  
  2667  	return textp
  2668  }
  2669  
  2670  // ErrorReporter is a helper class for reporting errors.
  2671  type ErrorReporter struct {
  2672  	ldr              *Loader
  2673  	AfterErrorAction func()
  2674  }
  2675  
  2676  // Errorf method logs an error message.
  2677  //
  2678  // After each error, the error actions function will be invoked; this
  2679  // will either terminate the link immediately (if -h option given)
  2680  // or it will keep a count and exit if more than 20 errors have been printed.
  2681  //
  2682  // Logging an error means that on exit cmd/link will delete any
  2683  // output file and return a non-zero error code.
  2684  func (reporter *ErrorReporter) Errorf(s Sym, format string, args ...interface{}) {
  2685  	if s != 0 && reporter.ldr.SymName(s) != "" {
  2686  		// Note: Replace is needed here because symbol names might have % in them,
  2687  		// due to the use of LinkString for names of instantiating types.
  2688  		format = strings.Replace(reporter.ldr.SymName(s), "%", "%%", -1) + ": " + format
  2689  	} else {
  2690  		format = fmt.Sprintf("sym %d: %s", s, format)
  2691  	}
  2692  	format += "\n"
  2693  	fmt.Fprintf(os.Stderr, format, args...)
  2694  	reporter.AfterErrorAction()
  2695  }
  2696  
  2697  // GetErrorReporter returns the loader's associated error reporter.
  2698  func (l *Loader) GetErrorReporter() *ErrorReporter {
  2699  	return l.errorReporter
  2700  }
  2701  
  2702  // Errorf method logs an error message. See ErrorReporter.Errorf for details.
  2703  func (l *Loader) Errorf(s Sym, format string, args ...interface{}) {
  2704  	l.errorReporter.Errorf(s, format, args...)
  2705  }
  2706  
  2707  // Symbol statistics.
  2708  func (l *Loader) Stat() string {
  2709  	s := fmt.Sprintf("%d symbols, %d reachable\n", l.NSym(), l.NReachableSym())
  2710  	s += fmt.Sprintf("\t%d package symbols, %d hashed symbols, %d non-package symbols, %d external symbols\n",
  2711  		l.npkgsyms, l.nhashedsyms, int(l.extStart)-l.npkgsyms-l.nhashedsyms, l.NSym()-int(l.extStart))
  2712  	return s
  2713  }
  2714  
  2715  // For debugging.
  2716  func (l *Loader) Dump() {
  2717  	fmt.Println("objs")
  2718  	for _, r := range l.objs[goObjStart:] {
  2719  		if r != nil {
  2720  			fmt.Println(r.unit.Lib)
  2721  		}
  2722  	}
  2723  	fmt.Println("extStart:", l.extStart)
  2724  	fmt.Println("Nsyms:", len(l.objSyms))
  2725  	fmt.Println("syms")
  2726  	for i := Sym(1); i < Sym(len(l.objSyms)); i++ {
  2727  		pi := ""
  2728  		if l.IsExternal(i) {
  2729  			pi = fmt.Sprintf("<ext %d>", l.extIndex(i))
  2730  		}
  2731  		sect := ""
  2732  		if l.SymSect(i) != nil {
  2733  			sect = l.SymSect(i).Name
  2734  		}
  2735  		fmt.Printf("%v %v %v %v %x %v\n", i, l.SymName(i), l.SymType(i), pi, l.SymValue(i), sect)
  2736  	}
  2737  	fmt.Println("symsByName")
  2738  	for name, i := range l.symsByName[0] {
  2739  		fmt.Println(i, name, 0)
  2740  	}
  2741  	for name, i := range l.symsByName[1] {
  2742  		fmt.Println(i, name, 1)
  2743  	}
  2744  	fmt.Println("payloads:")
  2745  	for i := range l.payloads {
  2746  		pp := l.payloads[i]
  2747  		fmt.Println(i, pp.name, pp.ver, pp.kind)
  2748  	}
  2749  }
  2750  

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