src/cmd/link/internal/loadpe/ldpe.go

   1 // Copyright 2010 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 loadpe implements a PE/COFF file reader.
   6 package loadpe
   7
   8 import (
   9         "cmd/internal/bio"
  10         "cmd/internal/objabi"
  11         "cmd/internal/sys"
  12         "cmd/link/internal/loader"
  13         "cmd/link/internal/sym"
  14         "debug/pe"
  15         "encoding/binary"
  16         "errors"
  17         "fmt"
  18         "io"
  19         "sort"
  20         "strings"
  21 )
  22
  23 const (
  24         // TODO: the Microsoft doco says IMAGE_SYM_DTYPE_ARRAY is 3 (same with IMAGE_SYM_DTYPE_POINTER and IMAGE_SYM_DTYPE_FUNCTION)
  25         IMAGE_SYM_UNDEFINED              = 0
  26         IMAGE_SYM_ABSOLUTE               = -1
  27         IMAGE_SYM_DEBUG                  = -2
  28         IMAGE_SYM_TYPE_NULL              = 0
  29         IMAGE_SYM_TYPE_VOID              = 1
  30         IMAGE_SYM_TYPE_CHAR              = 2
  31         IMAGE_SYM_TYPE_SHORT             = 3
  32         IMAGE_SYM_TYPE_INT               = 4
  33         IMAGE_SYM_TYPE_LONG              = 5
  34         IMAGE_SYM_TYPE_FLOAT             = 6
  35         IMAGE_SYM_TYPE_DOUBLE            = 7
  36         IMAGE_SYM_TYPE_STRUCT            = 8
  37         IMAGE_SYM_TYPE_UNION             = 9
  38         IMAGE_SYM_TYPE_ENUM              = 10
  39         IMAGE_SYM_TYPE_MOE               = 11
  40         IMAGE_SYM_TYPE_BYTE              = 12
  41         IMAGE_SYM_TYPE_WORD              = 13
  42         IMAGE_SYM_TYPE_UINT              = 14
  43         IMAGE_SYM_TYPE_DWORD             = 15
  44         IMAGE_SYM_TYPE_PCODE             = 32768
  45         IMAGE_SYM_DTYPE_NULL             = 0
  46         IMAGE_SYM_DTYPE_POINTER          = 0x10
  47         IMAGE_SYM_DTYPE_FUNCTION         = 0x20
  48         IMAGE_SYM_DTYPE_ARRAY            = 0x30
  49         IMAGE_SYM_CLASS_END_OF_FUNCTION  = -1
  50         IMAGE_SYM_CLASS_NULL             = 0
  51         IMAGE_SYM_CLASS_AUTOMATIC        = 1
  52         IMAGE_SYM_CLASS_EXTERNAL         = 2
  53         IMAGE_SYM_CLASS_STATIC           = 3
  54         IMAGE_SYM_CLASS_REGISTER         = 4
  55         IMAGE_SYM_CLASS_EXTERNAL_DEF     = 5
  56         IMAGE_SYM_CLASS_LABEL            = 6
  57         IMAGE_SYM_CLASS_UNDEFINED_LABEL  = 7
  58         IMAGE_SYM_CLASS_MEMBER_OF_STRUCT = 8
  59         IMAGE_SYM_CLASS_ARGUMENT         = 9
  60         IMAGE_SYM_CLASS_STRUCT_TAG       = 10
  61         IMAGE_SYM_CLASS_MEMBER_OF_UNION  = 11
  62         IMAGE_SYM_CLASS_UNION_TAG        = 12
  63         IMAGE_SYM_CLASS_TYPE_DEFINITION  = 13
  64         IMAGE_SYM_CLASS_UNDEFINED_STATIC = 14
  65         IMAGE_SYM_CLASS_ENUM_TAG         = 15
  66         IMAGE_SYM_CLASS_MEMBER_OF_ENUM   = 16
  67         IMAGE_SYM_CLASS_REGISTER_PARAM   = 17
  68         IMAGE_SYM_CLASS_BIT_FIELD        = 18
  69         IMAGE_SYM_CLASS_FAR_EXTERNAL     = 68 /* Not in PECOFF v8 spec */
  70         IMAGE_SYM_CLASS_BLOCK            = 100
  71         IMAGE_SYM_CLASS_FUNCTION         = 101
  72         IMAGE_SYM_CLASS_END_OF_STRUCT    = 102
  73         IMAGE_SYM_CLASS_FILE             = 103
  74         IMAGE_SYM_CLASS_SECTION          = 104
  75         IMAGE_SYM_CLASS_WEAK_EXTERNAL    = 105
  76         IMAGE_SYM_CLASS_CLR_TOKEN        = 107
  77         IMAGE_REL_I386_ABSOLUTE          = 0x0000
  78         IMAGE_REL_I386_DIR16             = 0x0001
  79         IMAGE_REL_I386_REL16             = 0x0002
  80         IMAGE_REL_I386_DIR32             = 0x0006
  81         IMAGE_REL_I386_DIR32NB           = 0x0007
  82         IMAGE_REL_I386_SEG12             = 0x0009
  83         IMAGE_REL_I386_SECTION           = 0x000A
  84         IMAGE_REL_I386_SECREL            = 0x000B
  85         IMAGE_REL_I386_TOKEN             = 0x000C
  86         IMAGE_REL_I386_SECREL7           = 0x000D
  87         IMAGE_REL_I386_REL32             = 0x0014
  88         IMAGE_REL_AMD64_ABSOLUTE         = 0x0000
  89         IMAGE_REL_AMD64_ADDR64           = 0x0001
  90         IMAGE_REL_AMD64_ADDR32           = 0x0002
  91         IMAGE_REL_AMD64_ADDR32NB         = 0x0003
  92         IMAGE_REL_AMD64_REL32            = 0x0004
  93         IMAGE_REL_AMD64_REL32_1          = 0x0005
  94         IMAGE_REL_AMD64_REL32_2          = 0x0006
  95         IMAGE_REL_AMD64_REL32_3          = 0x0007
  96         IMAGE_REL_AMD64_REL32_4          = 0x0008
  97         IMAGE_REL_AMD64_REL32_5          = 0x0009
  98         IMAGE_REL_AMD64_SECTION          = 0x000A
  99         IMAGE_REL_AMD64_SECREL           = 0x000B
 100         IMAGE_REL_AMD64_SECREL7          = 0x000C
 101         IMAGE_REL_AMD64_TOKEN            = 0x000D
 102         IMAGE_REL_AMD64_SREL32           = 0x000E
 103         IMAGE_REL_AMD64_PAIR             = 0x000F
 104         IMAGE_REL_AMD64_SSPAN32          = 0x0010
 105         IMAGE_REL_ARM_ABSOLUTE           = 0x0000
 106         IMAGE_REL_ARM_ADDR32             = 0x0001
 107         IMAGE_REL_ARM_ADDR32NB           = 0x0002
 108         IMAGE_REL_ARM_BRANCH24           = 0x0003
 109         IMAGE_REL_ARM_BRANCH11           = 0x0004
 110         IMAGE_REL_ARM_SECTION            = 0x000E
 111         IMAGE_REL_ARM_SECREL             = 0x000F
 112         IMAGE_REL_ARM_MOV32              = 0x0010
 113         IMAGE_REL_THUMB_MOV32            = 0x0011
 114         IMAGE_REL_THUMB_BRANCH20         = 0x0012
 115         IMAGE_REL_THUMB_BRANCH24         = 0x0014
 116         IMAGE_REL_THUMB_BLX23            = 0x0015
 117         IMAGE_REL_ARM_PAIR               = 0x0016
 118 )
 119
 120 // TODO(crawshaw): de-duplicate these symbols with cmd/internal/ld, ideally in debug/pe.
 121 const (
 122         IMAGE_SCN_CNT_CODE               = 0x00000020
 123         IMAGE_SCN_CNT_INITIALIZED_DATA   = 0x00000040
 124         IMAGE_SCN_CNT_UNINITIALIZED_DATA = 0x00000080
 125         IMAGE_SCN_MEM_DISCARDABLE        = 0x02000000
 126         IMAGE_SCN_MEM_EXECUTE            = 0x20000000
 127         IMAGE_SCN_MEM_READ               = 0x40000000
 128         IMAGE_SCN_MEM_WRITE              = 0x80000000
 129 )
 130
 131 // TODO(brainman): maybe just add ReadAt method to bio.Reader instead of creating peBiobuf
 132
 133 // peBiobuf makes bio.Reader look like io.ReaderAt.
 134 type peBiobuf bio.Reader
 135
 136 func (f *peBiobuf) ReadAt(p []byte, off int64) (int, error) {
 137         ret := ((*bio.Reader)(f)).MustSeek(off, 0)
 138         if ret < 0 {
 139                 return 0, errors.New("fail to seek")
 140         }
 141         n, err := f.Read(p)
 142         if err != nil {
 143                 return 0, err
 144         }
 145         return n, nil
 146 }
 147
 148 // makeUpdater creates a loader.SymbolBuilder if one hasn't been created previously.
 149 // We use this to lazily make SymbolBuilders as we don't always need a builder, and creating them for all symbols might be an error.
 150 func makeUpdater(l *loader.Loader, bld *loader.SymbolBuilder, s loader.Sym) *loader.SymbolBuilder {
 151         if bld != nil {
 152                 return bld
 153         }
 154         bld, _ = l.MakeSymbolUpdater(s)
 155         return bld
 156 }
 157
 158 // Load loads the PE file pn from input.
 159 // Symbols are written into syms, and a slice of the text symbols is returned.
 160 // If an .rsrc section is found, its symbol is returned as rsrc.
 161 func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, input *bio.Reader, pkg string, length int64, pn string) (textp []loader.Sym, rsrc loader.Sym, err error) {
 162         lookup := func(name string, version int) (*loader.SymbolBuilder, loader.Sym) {
 163                 return l.MakeSymbolUpdater(l.LookupOrCreateSym(name, version))
 164         }
 165         sectsyms := make(map[*pe.Section]loader.Sym)
 166         sectdata := make(map[*pe.Section][]byte)
 167
 168         // Some input files are archives containing multiple of
 169         // object files, and pe.NewFile seeks to the start of
 170         // input file and get confused. Create section reader
 171         // to stop pe.NewFile looking before current position.
 172         sr := io.NewSectionReader((*peBiobuf)(input), input.Offset(), 1<<63-1)
 173
 174         // TODO: replace pe.NewFile with pe.Load (grep for "add Load function" in debug/pe for details)
 175         f, err := pe.NewFile(sr)
 176         if err != nil {
 177                 return nil, 0, err
 178         }
 179         defer f.Close()
 180
 181         // TODO return error if found .cormeta
 182
 183         // create symbols for mapped sections
 184         for _, sect := range f.Sections {
 185                 if sect.Characteristics&IMAGE_SCN_MEM_DISCARDABLE != 0 {
 186                         continue
 187                 }
 188
 189                 if sect.Characteristics&(IMAGE_SCN_CNT_CODE|IMAGE_SCN_CNT_INITIALIZED_DATA|IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0 {
 190                         // This has been seen for .idata sections, which we
 191                         // want to ignore. See issues 5106 and 5273.
 192                         continue
 193                 }
 194
 195                 name := fmt.Sprintf("%s(%s)", pkg, sect.Name)
 196                 bld, s := lookup(name, localSymVersion)
 197
 198                 switch sect.Characteristics & (IMAGE_SCN_CNT_UNINITIALIZED_DATA | IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE | IMAGE_SCN_CNT_CODE | IMAGE_SCN_MEM_EXECUTE) {
 199                 case IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ: //.rdata
 200                         bld.SetType(sym.SRODATA)
 201
 202                 case IMAGE_SCN_CNT_UNINITIALIZED_DATA | IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE: //.bss
 203                         bld.SetType(sym.SNOPTRBSS)
 204
 205                 case IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE: //.data
 206                         bld.SetType(sym.SNOPTRDATA)
 207
 208                 case IMAGE_SCN_CNT_CODE | IMAGE_SCN_MEM_EXECUTE | IMAGE_SCN_MEM_READ: //.text
 209                         bld.SetType(sym.STEXT)
 210
 211                 default:
 212                         return nil, 0, fmt.Errorf("unexpected flags %#06x for PE section %s", sect.Characteristics, sect.Name)
 213                 }
 214
 215                 if bld.Type() != sym.SNOPTRBSS {
 216                         data, err := sect.Data()
 217                         if err != nil {
 218                                 return nil, 0, err
 219                         }
 220                         sectdata[sect] = data
 221                         bld.SetData(data)
 222                 }
 223                 bld.SetSize(int64(sect.Size))
 224                 sectsyms[sect] = s
 225                 if sect.Name == ".rsrc" {
 226                         rsrc = s
 227                 }
 228         }
 229
 230         // load relocations
 231         for _, rsect := range f.Sections {
 232                 if _, found := sectsyms[rsect]; !found {
 233                         continue
 234                 }
 235                 if rsect.NumberOfRelocations == 0 {
 236                         continue
 237                 }
 238                 if rsect.Characteristics&IMAGE_SCN_MEM_DISCARDABLE != 0 {
 239                         continue
 240                 }
 241                 if rsect.Characteristics&(IMAGE_SCN_CNT_CODE|IMAGE_SCN_CNT_INITIALIZED_DATA|IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0 {
 242                         // This has been seen for .idata sections, which we
 243                         // want to ignore. See issues 5106 and 5273.
 244                         continue
 245                 }
 246
 247                 rs := make([]loader.Reloc, rsect.NumberOfRelocations)
 248                 for j, r := range rsect.Relocs {
 249                         rp := &rs[j]
 250                         if int(r.SymbolTableIndex) >= len(f.COFFSymbols) {
 251                                 return nil, 0, fmt.Errorf("relocation number %d symbol index idx=%d cannot be large then number of symbols %d", j, r.SymbolTableIndex, len(f.COFFSymbols))
 252                         }
 253                         pesym := &f.COFFSymbols[r.SymbolTableIndex]
 254                         _, gosym, err := readpesym(l, arch, l.LookupOrCreateSym, f, pesym, sectsyms, localSymVersion)
 255                         if err != nil {
 256                                 return nil, 0, err
 257                         }
 258                         if gosym == 0 {
 259                                 name, err := pesym.FullName(f.StringTable)
 260                                 if err != nil {
 261                                         name = string(pesym.Name[:])
 262                                 }
 263                                 return nil, 0, fmt.Errorf("reloc of invalid sym %s idx=%d type=%d", name, r.SymbolTableIndex, pesym.Type)
 264                         }
 265
 266                         rp.Sym = gosym
 267                         rp.Size = 4
 268                         rp.Off = int32(r.VirtualAddress)
 269                         switch arch.Family {
 270                         default:
 271                                 return nil, 0, fmt.Errorf("%s: unsupported arch %v", pn, arch.Family)
 272                         case sys.I386, sys.AMD64:
 273                                 switch r.Type {
 274                                 default:
 275                                         return nil, 0, fmt.Errorf("%s: %v: unknown relocation type %v", pn, sectsyms[rsect], r.Type)
 276
 277                                 case IMAGE_REL_I386_REL32, IMAGE_REL_AMD64_REL32,
 278                                         IMAGE_REL_AMD64_ADDR32, // R_X86_64_PC32
 279                                         IMAGE_REL_AMD64_ADDR32NB:
 280                                         rp.Type = objabi.R_PCREL
 281
 282                                         rp.Add = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rp.Off:])))
 283
 284                                 case IMAGE_REL_I386_DIR32NB, IMAGE_REL_I386_DIR32:
 285                                         rp.Type = objabi.R_ADDR
 286
 287                                         // load addend from image
 288                                         rp.Add = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rp.Off:])))
 289
 290                                 case IMAGE_REL_AMD64_ADDR64: // R_X86_64_64
 291                                         rp.Size = 8
 292
 293                                         rp.Type = objabi.R_ADDR
 294
 295                                         // load addend from image
 296                                         rp.Add = int64(binary.LittleEndian.Uint64(sectdata[rsect][rp.Off:]))
 297                                 }
 298
 299                         case sys.ARM:
 300                                 switch r.Type {
 301                                 default:
 302                                         return nil, 0, fmt.Errorf("%s: %v: unknown ARM relocation type %v", pn, sectsyms[rsect], r.Type)
 303
 304                                 case IMAGE_REL_ARM_SECREL:
 305                                         rp.Type = objabi.R_PCREL
 306
 307                                         rp.Add = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rp.Off:])))
 308
 309                                 case IMAGE_REL_ARM_ADDR32:
 310                                         rp.Type = objabi.R_ADDR
 311
 312                                         rp.Add = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rp.Off:])))
 313
 314                                 case IMAGE_REL_ARM_BRANCH24:
 315                                         rp.Type = objabi.R_CALLARM
 316
 317                                         rp.Add = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rp.Off:])))
 318                                 }
 319                         }
 320
 321                         // ld -r could generate multiple section symbols for the
 322                         // same section but with different values, we have to take
 323                         // that into account
 324                         if issect(pesym) {
 325                                 rp.Add += int64(pesym.Value)
 326                         }
 327                 }
 328
 329                 sort.Sort(loader.RelocByOff(rs[:rsect.NumberOfRelocations]))
 330
 331                 bld, _ := l.MakeSymbolUpdater(sectsyms[rsect])
 332                 bld.SetRelocs(rs[:rsect.NumberOfRelocations])
 333         }
 334
 335         // enter sub-symbols into symbol table.
 336         for i, numaux := 0, 0; i < len(f.COFFSymbols); i += numaux + 1 {
 337                 pesym := &f.COFFSymbols[i]
 338
 339                 numaux = int(pesym.NumberOfAuxSymbols)
 340
 341                 name, err := pesym.FullName(f.StringTable)
 342                 if err != nil {
 343                         return nil, 0, err
 344                 }
 345                 if name == "" {
 346                         continue
 347                 }
 348                 if issect(pesym) {
 349                         continue
 350                 }
 351                 if int(pesym.SectionNumber) > len(f.Sections) {
 352                         continue
 353                 }
 354                 if pesym.SectionNumber == IMAGE_SYM_DEBUG {
 355                         continue
 356                 }
 357                 var sect *pe.Section
 358                 if pesym.SectionNumber > 0 {
 359                         sect = f.Sections[pesym.SectionNumber-1]
 360                         if _, found := sectsyms[sect]; !found {
 361                                 continue
 362                         }
 363                 }
 364
 365                 bld, s, err := readpesym(l, arch, l.LookupOrCreateSym, f, pesym, sectsyms, localSymVersion)
 366                 if err != nil {
 367                         return nil, 0, err
 368                 }
 369
 370                 if pesym.SectionNumber == 0 { // extern
 371                         if l.SymType(s) == sym.SDYNIMPORT {
 372                                 bld = makeUpdater(l, bld, s)
 373                                 bld.SetPlt(-2) // flag for dynimport in PE object files.
 374                         }
 375                         if l.SymType(s) == sym.SXREF && pesym.Value > 0 { // global data
 376                                 bld = makeUpdater(l, bld, s)
 377                                 bld.SetType(sym.SNOPTRDATA)
 378                                 bld.SetSize(int64(pesym.Value))
 379                         }
 380
 381                         continue
 382                 } else if pesym.SectionNumber > 0 && int(pesym.SectionNumber) <= len(f.Sections) {
 383                         sect = f.Sections[pesym.SectionNumber-1]
 384                         if _, found := sectsyms[sect]; !found {
 385                                 return nil, 0, fmt.Errorf("%s: %v: missing sect.sym", pn, s)
 386                         }
 387                 } else {
 388                         return nil, 0, fmt.Errorf("%s: %v: sectnum < 0!", pn, s)
 389                 }
 390
 391                 if sect == nil {
 392                         return nil, 0, nil
 393                 }
 394
 395                 if l.OuterSym(s) != 0 {
 396                         if l.AttrDuplicateOK(s) {
 397                                 continue
 398                         }
 399                         outerName := l.SymName(l.OuterSym(s))
 400                         sectName := l.SymName(sectsyms[sect])
 401                         return nil, 0, fmt.Errorf("%s: duplicate symbol reference: %s in both %s and %s", pn, l.SymName(s), outerName, sectName)
 402                 }
 403
 404                 bld = makeUpdater(l, bld, s)
 405                 sectsym := sectsyms[sect]
 406                 bld.SetType(l.SymType(sectsym))
 407                 l.PrependSub(sectsym, s)
 408                 bld.SetValue(int64(pesym.Value))
 409                 bld.SetSize(4)
 410                 if l.SymType(sectsym) == sym.STEXT {
 411                         if bld.External() && !bld.DuplicateOK() {
 412                                 return nil, 0, fmt.Errorf("%s: duplicate symbol definition", l.SymName(s))
 413                         }
 414                         bld.SetExternal(true)
 415                 }
 416         }
 417
 418         // Sort outer lists by address, adding to textp.
 419         // This keeps textp in increasing address order.
 420         for _, sect := range f.Sections {
 421                 s := sectsyms[sect]
 422                 if s == 0 {
 423                         continue
 424                 }
 425                 l.SortSub(s)
 426                 if l.SymType(s) == sym.STEXT {
 427                         for ; s != 0; s = l.SubSym(s) {
 428                                 if l.AttrOnList(s) {
 429                                         return nil, 0, fmt.Errorf("symbol %s listed multiple times", l.SymName(s))
 430                                 }
 431                                 l.SetAttrOnList(s, true)
 432                                 textp = append(textp, s)
 433                         }
 434                 }
 435         }
 436
 437         return textp, rsrc, nil
 438 }
 439
 440 func issect(s *pe.COFFSymbol) bool {
 441         return s.StorageClass == IMAGE_SYM_CLASS_STATIC && s.Type == 0 && s.Name[0] == '.'
 442 }
 443
 444 func readpesym(l *loader.Loader, arch *sys.Arch, lookup func(string, int) loader.Sym, f *pe.File, pesym *pe.COFFSymbol, sectsyms map[*pe.Section]loader.Sym, localSymVersion int) (*loader.SymbolBuilder, loader.Sym, error) {
 445         symname, err := pesym.FullName(f.StringTable)
 446         if err != nil {
 447                 return nil, 0, err
 448         }
 449         var name string
 450         if issect(pesym) {
 451                 name = l.SymName(sectsyms[f.Sections[pesym.SectionNumber-1]])
 452         } else {
 453                 name = symname
 454                 switch arch.Family {
 455                 case sys.AMD64:
 456                         if name == "__imp___acrt_iob_func" {
 457                                 // Do not rename __imp___acrt_iob_func into __acrt_iob_func,
 458                                 // because __imp___acrt_iob_func symbol is real
 459                                 // (see commit b295099 from git://git.code.sf.net/p/mingw-w64/mingw-w64 for details).
 460                         } else {
 461                                 name = strings.TrimPrefix(name, "__imp_") // __imp_Name => Name
 462                         }
 463                 case sys.I386:
 464                         if name == "__imp____acrt_iob_func" {
 465                                 // Do not rename __imp____acrt_iob_func into ___acrt_iob_func,
 466                                 // because __imp____acrt_iob_func symbol is real
 467                                 // (see commit b295099 from git://git.code.sf.net/p/mingw-w64/mingw-w64 for details).
 468                         } else {
 469                                 name = strings.TrimPrefix(name, "__imp_") // __imp_Name => Name
 470                         }
 471                         if name[0] == '_' {
 472                                 name = name[1:] // _Name => Name
 473                         }
 474                 }
 475         }
 476
 477         // remove last @XXX
 478         if i := strings.LastIndex(name, "@"); i >= 0 {
 479                 name = name[:i]
 480         }
 481
 482         var s loader.Sym
 483         var bld *loader.SymbolBuilder
 484         switch pesym.Type {
 485         default:
 486                 return nil, 0, fmt.Errorf("%s: invalid symbol type %d", symname, pesym.Type)
 487
 488         case IMAGE_SYM_DTYPE_FUNCTION, IMAGE_SYM_DTYPE_NULL:
 489                 switch pesym.StorageClass {
 490                 case IMAGE_SYM_CLASS_EXTERNAL: //global
 491                         s = lookup(name, 0)
 492
 493                 case IMAGE_SYM_CLASS_NULL, IMAGE_SYM_CLASS_STATIC, IMAGE_SYM_CLASS_LABEL:
 494                         s = lookup(name, localSymVersion)
 495                         bld = makeUpdater(l, bld, s)
 496                         bld.SetDuplicateOK(true)
 497
 498                 default:
 499                         return nil, 0, fmt.Errorf("%s: invalid symbol binding %d", symname, pesym.StorageClass)
 500                 }
 501         }
 502
 503         if s != 0 && l.SymType(s) == 0 && (pesym.StorageClass != IMAGE_SYM_CLASS_STATIC || pesym.Value != 0) {
 504                 bld = makeUpdater(l, bld, s)
 505                 bld.SetType(sym.SXREF)
 506         }
 507         if strings.HasPrefix(symname, "__imp_") {
 508                 bld = makeUpdater(l, bld, s)
 509                 bld.SetGot(-2) // flag for __imp_
 510         }
 511
 512         return bld, s, nil
 513 }