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                 s := l.LookupOrCreateSym(name, version)
 164                 sb := l.MakeSymbolUpdater(s)
 165                 return sb, s
 166         }
 167         sectsyms := make(map[*pe.Section]loader.Sym)
 168         sectdata := make(map[*pe.Section][]byte)
 169
 170         // Some input files are archives containing multiple of
 171         // object files, and pe.NewFile seeks to the start of
 172         // input file and get confused. Create section reader
 173         // to stop pe.NewFile looking before current position.
 174         sr := io.NewSectionReader((*peBiobuf)(input), input.Offset(), 1<<63-1)
 175
 176         // TODO: replace pe.NewFile with pe.Load (grep for "add Load function" in debug/pe for details)
 177         f, err := pe.NewFile(sr)
 178         if err != nil {
 179                 return nil, 0, err
 180         }
 181         defer f.Close()
 182
 183         // TODO return error if found .cormeta
 184
 185         // create symbols for mapped sections
 186         for _, sect := range f.Sections {
 187                 if sect.Characteristics&IMAGE_SCN_MEM_DISCARDABLE != 0 {
 188                         continue
 189                 }
 190
 191                 if sect.Characteristics&(IMAGE_SCN_CNT_CODE|IMAGE_SCN_CNT_INITIALIZED_DATA|IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0 {
 192                         // This has been seen for .idata sections, which we
 193                         // want to ignore. See issues 5106 and 5273.
 194                         continue
 195                 }
 196
 197                 name := fmt.Sprintf("%s(%s)", pkg, sect.Name)
 198                 bld, s := lookup(name, localSymVersion)
 199
 200                 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) {
 201                 case IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ: //.rdata
 202                         bld.SetType(sym.SRODATA)
 203
 204                 case IMAGE_SCN_CNT_UNINITIALIZED_DATA | IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE: //.bss
 205                         bld.SetType(sym.SNOPTRBSS)
 206
 207                 case IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE: //.data
 208                         bld.SetType(sym.SNOPTRDATA)
 209
 210                 case IMAGE_SCN_CNT_CODE | IMAGE_SCN_MEM_EXECUTE | IMAGE_SCN_MEM_READ: //.text
 211                         bld.SetType(sym.STEXT)
 212
 213                 default:
 214                         return nil, 0, fmt.Errorf("unexpected flags %#06x for PE section %s", sect.Characteristics, sect.Name)
 215                 }
 216
 217                 if bld.Type() != sym.SNOPTRBSS {
 218                         data, err := sect.Data()
 219                         if err != nil {
 220                                 return nil, 0, err
 221                         }
 222                         sectdata[sect] = data
 223                         bld.SetData(data)
 224                 }
 225                 bld.SetSize(int64(sect.Size))
 226                 sectsyms[sect] = s
 227                 if sect.Name == ".rsrc" {
 228                         rsrc = s
 229                 }
 230         }
 231
 232         // load relocations
 233         for _, rsect := range f.Sections {
 234                 if _, found := sectsyms[rsect]; !found {
 235                         continue
 236                 }
 237                 if rsect.NumberOfRelocations == 0 {
 238                         continue
 239                 }
 240                 if rsect.Characteristics&IMAGE_SCN_MEM_DISCARDABLE != 0 {
 241                         continue
 242                 }
 243                 if rsect.Characteristics&(IMAGE_SCN_CNT_CODE|IMAGE_SCN_CNT_INITIALIZED_DATA|IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0 {
 244                         // This has been seen for .idata sections, which we
 245                         // want to ignore. See issues 5106 and 5273.
 246                         continue
 247                 }
 248
 249                 rs := make([]loader.Reloc, rsect.NumberOfRelocations)
 250                 for j, r := range rsect.Relocs {
 251                         rp := &rs[j]
 252                         if int(r.SymbolTableIndex) >= len(f.COFFSymbols) {
 253                                 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))
 254                         }
 255                         pesym := &f.COFFSymbols[r.SymbolTableIndex]
 256                         _, gosym, err := readpesym(l, arch, l.LookupOrCreateSym, f, pesym, sectsyms, localSymVersion)
 257                         if err != nil {
 258                                 return nil, 0, err
 259                         }
 260                         if gosym == 0 {
 261                                 name, err := pesym.FullName(f.StringTable)
 262                                 if err != nil {
 263                                         name = string(pesym.Name[:])
 264                                 }
 265                                 return nil, 0, fmt.Errorf("reloc of invalid sym %s idx=%d type=%d", name, r.SymbolTableIndex, pesym.Type)
 266                         }
 267
 268                         rp.Sym = gosym
 269                         rp.Size = 4
 270                         rp.Off = int32(r.VirtualAddress)
 271                         switch arch.Family {
 272                         default:
 273                                 return nil, 0, fmt.Errorf("%s: unsupported arch %v", pn, arch.Family)
 274                         case sys.I386, sys.AMD64:
 275                                 switch r.Type {
 276                                 default:
 277                                         return nil, 0, fmt.Errorf("%s: %v: unknown relocation type %v", pn, sectsyms[rsect], r.Type)
 278
 279                                 case IMAGE_REL_I386_REL32, IMAGE_REL_AMD64_REL32,
 280                                         IMAGE_REL_AMD64_ADDR32, // R_X86_64_PC32
 281                                         IMAGE_REL_AMD64_ADDR32NB:
 282                                         rp.Type = objabi.R_PCREL
 283
 284                                         rp.Add = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rp.Off:])))
 285
 286                                 case IMAGE_REL_I386_DIR32NB, IMAGE_REL_I386_DIR32:
 287                                         rp.Type = objabi.R_ADDR
 288
 289                                         // load addend from image
 290                                         rp.Add = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rp.Off:])))
 291
 292                                 case IMAGE_REL_AMD64_ADDR64: // R_X86_64_64
 293                                         rp.Size = 8
 294
 295                                         rp.Type = objabi.R_ADDR
 296
 297                                         // load addend from image
 298                                         rp.Add = int64(binary.LittleEndian.Uint64(sectdata[rsect][rp.Off:]))
 299                                 }
 300
 301                         case sys.ARM:
 302                                 switch r.Type {
 303                                 default:
 304                                         return nil, 0, fmt.Errorf("%s: %v: unknown ARM relocation type %v", pn, sectsyms[rsect], r.Type)
 305
 306                                 case IMAGE_REL_ARM_SECREL:
 307                                         rp.Type = objabi.R_PCREL
 308
 309                                         rp.Add = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rp.Off:])))
 310
 311                                 case IMAGE_REL_ARM_ADDR32:
 312                                         rp.Type = objabi.R_ADDR
 313
 314                                         rp.Add = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rp.Off:])))
 315
 316                                 case IMAGE_REL_ARM_BRANCH24:
 317                                         rp.Type = objabi.R_CALLARM
 318
 319                                         rp.Add = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rp.Off:])))
 320                                 }
 321                         }
 322
 323                         // ld -r could generate multiple section symbols for the
 324                         // same section but with different values, we have to take
 325                         // that into account
 326                         if issect(pesym) {
 327                                 rp.Add += int64(pesym.Value)
 328                         }
 329                 }
 330
 331                 sort.Sort(loader.RelocByOff(rs[:rsect.NumberOfRelocations]))
 332
 333                 bld := l.MakeSymbolUpdater(sectsyms[rsect])
 334                 bld.SetRelocs(rs[:rsect.NumberOfRelocations])
 335         }
 336
 337         // enter sub-symbols into symbol table.
 338         for i, numaux := 0, 0; i < len(f.COFFSymbols); i += numaux + 1 {
 339                 pesym := &f.COFFSymbols[i]
 340
 341                 numaux = int(pesym.NumberOfAuxSymbols)
 342
 343                 name, err := pesym.FullName(f.StringTable)
 344                 if err != nil {
 345                         return nil, 0, err
 346                 }
 347                 if name == "" {
 348                         continue
 349                 }
 350                 if issect(pesym) {
 351                         continue
 352                 }
 353                 if int(pesym.SectionNumber) > len(f.Sections) {
 354                         continue
 355                 }
 356                 if pesym.SectionNumber == IMAGE_SYM_DEBUG {
 357                         continue
 358                 }
 359                 var sect *pe.Section
 360                 if pesym.SectionNumber > 0 {
 361                         sect = f.Sections[pesym.SectionNumber-1]
 362                         if _, found := sectsyms[sect]; !found {
 363                                 continue
 364                         }
 365                 }
 366
 367                 bld, s, err := readpesym(l, arch, l.LookupOrCreateSym, f, pesym, sectsyms, localSymVersion)
 368                 if err != nil {
 369                         return nil, 0, err
 370                 }
 371
 372                 if pesym.SectionNumber == 0 { // extern
 373                         if l.SymType(s) == sym.SDYNIMPORT {
 374                                 bld = makeUpdater(l, bld, s)
 375                                 bld.SetPlt(-2) // flag for dynimport in PE object files.
 376                         }
 377                         if l.SymType(s) == sym.SXREF && pesym.Value > 0 { // global data
 378                                 bld = makeUpdater(l, bld, s)
 379                                 bld.SetType(sym.SNOPTRDATA)
 380                                 bld.SetSize(int64(pesym.Value))
 381                         }
 382
 383                         continue
 384                 } else if pesym.SectionNumber > 0 && int(pesym.SectionNumber) <= len(f.Sections) {
 385                         sect = f.Sections[pesym.SectionNumber-1]
 386                         if _, found := sectsyms[sect]; !found {
 387                                 return nil, 0, fmt.Errorf("%s: %v: missing sect.sym", pn, s)
 388                         }
 389                 } else {
 390                         return nil, 0, fmt.Errorf("%s: %v: sectnum < 0!", pn, s)
 391                 }
 392
 393                 if sect == nil {
 394                         return nil, 0, nil
 395                 }
 396
 397                 if l.OuterSym(s) != 0 {
 398                         if l.AttrDuplicateOK(s) {
 399                                 continue
 400                         }
 401                         outerName := l.SymName(l.OuterSym(s))
 402                         sectName := l.SymName(sectsyms[sect])
 403                         return nil, 0, fmt.Errorf("%s: duplicate symbol reference: %s in both %s and %s", pn, l.SymName(s), outerName, sectName)
 404                 }
 405
 406                 bld = makeUpdater(l, bld, s)
 407                 sectsym := sectsyms[sect]
 408                 bld.SetType(l.SymType(sectsym))
 409                 l.PrependSub(sectsym, s)
 410                 bld.SetValue(int64(pesym.Value))
 411                 bld.SetSize(4)
 412                 if l.SymType(sectsym) == sym.STEXT {
 413                         if bld.External() && !bld.DuplicateOK() {
 414                                 return nil, 0, fmt.Errorf("%s: duplicate symbol definition", l.SymName(s))
 415                         }
 416                         bld.SetExternal(true)
 417                 }
 418         }
 419
 420         // Sort outer lists by address, adding to textp.
 421         // This keeps textp in increasing address order.
 422         for _, sect := range f.Sections {
 423                 s := sectsyms[sect]
 424                 if s == 0 {
 425                         continue
 426                 }
 427                 l.SortSub(s)
 428                 if l.SymType(s) == sym.STEXT {
 429                         for ; s != 0; s = l.SubSym(s) {
 430                                 if l.AttrOnList(s) {
 431                                         return nil, 0, fmt.Errorf("symbol %s listed multiple times", l.SymName(s))
 432                                 }
 433                                 l.SetAttrOnList(s, true)
 434                                 textp = append(textp, s)
 435                         }
 436                 }
 437         }
 438
 439         return textp, rsrc, nil
 440 }
 441
 442 func issect(s *pe.COFFSymbol) bool {
 443         return s.StorageClass == IMAGE_SYM_CLASS_STATIC && s.Type == 0 && s.Name[0] == '.'
 444 }
 445
 446 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) {
 447         symname, err := pesym.FullName(f.StringTable)
 448         if err != nil {
 449                 return nil, 0, err
 450         }
 451         var name string
 452         if issect(pesym) {
 453                 name = l.SymName(sectsyms[f.Sections[pesym.SectionNumber-1]])
 454         } else {
 455                 name = symname
 456                 switch arch.Family {
 457                 case sys.AMD64:
 458                         if name == "__imp___acrt_iob_func" {
 459                                 // Do not rename __imp___acrt_iob_func into __acrt_iob_func,
 460                                 // because __imp___acrt_iob_func symbol is real
 461                                 // (see commit b295099 from git://git.code.sf.net/p/mingw-w64/mingw-w64 for details).
 462                         } else {
 463                                 name = strings.TrimPrefix(name, "__imp_") // __imp_Name => Name
 464                         }
 465                 case sys.I386:
 466                         if name == "__imp____acrt_iob_func" {
 467                                 // Do not rename __imp____acrt_iob_func into ___acrt_iob_func,
 468                                 // because __imp____acrt_iob_func symbol is real
 469                                 // (see commit b295099 from git://git.code.sf.net/p/mingw-w64/mingw-w64 for details).
 470                         } else {
 471                                 name = strings.TrimPrefix(name, "__imp_") // __imp_Name => Name
 472                         }
 473                         if name[0] == '_' {
 474                                 name = name[1:] // _Name => Name
 475                         }
 476                 }
 477         }
 478
 479         // remove last @XXX
 480         if i := strings.LastIndex(name, "@"); i >= 0 {
 481                 name = name[:i]
 482         }
 483
 484         var s loader.Sym
 485         var bld *loader.SymbolBuilder
 486         switch pesym.Type {
 487         default:
 488                 return nil, 0, fmt.Errorf("%s: invalid symbol type %d", symname, pesym.Type)
 489
 490         case IMAGE_SYM_DTYPE_FUNCTION, IMAGE_SYM_DTYPE_NULL:
 491                 switch pesym.StorageClass {
 492                 case IMAGE_SYM_CLASS_EXTERNAL: //global
 493                         s = lookup(name, 0)
 494
 495                 case IMAGE_SYM_CLASS_NULL, IMAGE_SYM_CLASS_STATIC, IMAGE_SYM_CLASS_LABEL:
 496                         s = lookup(name, localSymVersion)
 497                         bld = makeUpdater(l, bld, s)
 498                         bld.SetDuplicateOK(true)
 499
 500                 default:
 501                         return nil, 0, fmt.Errorf("%s: invalid symbol binding %d", symname, pesym.StorageClass)
 502                 }
 503         }
 504
 505         if s != 0 && l.SymType(s) == 0 && (pesym.StorageClass != IMAGE_SYM_CLASS_STATIC || pesym.Value != 0) {
 506                 bld = makeUpdater(l, bld, s)
 507                 bld.SetType(sym.SXREF)
 508         }
 509         if strings.HasPrefix(symname, "__imp_") {
 510                 bld = makeUpdater(l, bld, s)
 511                 bld.SetGot(-2) // flag for __imp_
 512         }
 513
 514         return bld, s, nil
 515 }