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

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

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