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 // Load loads the PE file pn from input.
 149 // Symbols are written into syms, and a slice of the text symbols is returned.
 150 // If an .rsrc section is found, its symbol is returned as rsrc.
 151 func Load(l *loader.Loader, arch *sys.Arch, syms *sym.Symbols, input *bio.Reader, pkg string, length int64, pn string) (textp []*sym.Symbol, rsrc *sym.Symbol, err error) {
 152         lookup := func(name string, version int) *sym.Symbol {
 153                 return l.LookupOrCreate(name, version, syms)
 154         }
 155         localSymVersion := syms.IncVersion()
 156         sectsyms := make(map[*pe.Section]*sym.Symbol)
 157         sectdata := make(map[*pe.Section][]byte)
 158
 159         // Some input files are archives containing multiple of
 160         // object files, and pe.NewFile seeks to the start of
 161         // input file and get confused. Create section reader
 162         // to stop pe.NewFile looking before current position.
 163         sr := io.NewSectionReader((*peBiobuf)(input), input.Offset(), 1<<63-1)
 164
 165         // TODO: replace pe.NewFile with pe.Load (grep for "add Load function" in debug/pe for details)
 166         f, err := pe.NewFile(sr)
 167         if err != nil {
 168                 return nil, nil, err
 169         }
 170         defer f.Close()
 171
 172         // TODO return error if found .cormeta
 173
 174         // create symbols for mapped sections
 175         for _, sect := range f.Sections {
 176                 if sect.Characteristics&IMAGE_SCN_MEM_DISCARDABLE != 0 {
 177                         continue
 178                 }
 179
 180                 if sect.Characteristics&(IMAGE_SCN_CNT_CODE|IMAGE_SCN_CNT_INITIALIZED_DATA|IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0 {
 181                         // This has been seen for .idata sections, which we
 182                         // want to ignore. See issues 5106 and 5273.
 183                         continue
 184                 }
 185
 186                 name := fmt.Sprintf("%s(%s)", pkg, sect.Name)
 187                 s := lookup(name, localSymVersion)
 188
 189                 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) {
 190                 case IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ: //.rdata
 191                         s.Type = sym.SRODATA
 192
 193                 case IMAGE_SCN_CNT_UNINITIALIZED_DATA | IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE: //.bss
 194                         s.Type = sym.SNOPTRBSS
 195
 196                 case IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE: //.data
 197                         s.Type = sym.SNOPTRDATA
 198
 199                 case IMAGE_SCN_CNT_CODE | IMAGE_SCN_MEM_EXECUTE | IMAGE_SCN_MEM_READ: //.text
 200                         s.Type = sym.STEXT
 201
 202                 default:
 203                         return nil, nil, fmt.Errorf("unexpected flags %#06x for PE section %s", sect.Characteristics, sect.Name)
 204                 }
 205
 206                 if s.Type != sym.SNOPTRBSS {
 207                         data, err := sect.Data()
 208                         if err != nil {
 209                                 return nil, nil, err
 210                         }
 211                         sectdata[sect] = data
 212                         s.P = data
 213                 }
 214                 s.Size = int64(sect.Size)
 215                 sectsyms[sect] = s
 216                 if sect.Name == ".rsrc" {
 217                         rsrc = s
 218                 }
 219         }
 220
 221         // load relocations
 222         for _, rsect := range f.Sections {
 223                 if _, found := sectsyms[rsect]; !found {
 224                         continue
 225                 }
 226                 if rsect.NumberOfRelocations == 0 {
 227                         continue
 228                 }
 229                 if rsect.Characteristics&IMAGE_SCN_MEM_DISCARDABLE != 0 {
 230                         continue
 231                 }
 232                 if rsect.Characteristics&(IMAGE_SCN_CNT_CODE|IMAGE_SCN_CNT_INITIALIZED_DATA|IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0 {
 233                         // This has been seen for .idata sections, which we
 234                         // want to ignore. See issues 5106 and 5273.
 235                         continue
 236                 }
 237
 238                 rs := make([]sym.Reloc, rsect.NumberOfRelocations)
 239                 for j, r := range rsect.Relocs {
 240                         rp := &rs[j]
 241                         if int(r.SymbolTableIndex) >= len(f.COFFSymbols) {
 242                                 return nil, nil, fmt.Errorf("relocation number %d symbol index idx=%d cannot be large then number of symbols %d", j, r.SymbolTableIndex, len(f.COFFSymbols))
 243                         }
 244                         pesym := &f.COFFSymbols[r.SymbolTableIndex]
 245                         gosym, err := readpesym(arch, lookup, f, pesym, sectsyms, localSymVersion)
 246                         if err != nil {
 247                                 return nil, nil, err
 248                         }
 249                         if gosym == nil {
 250                                 name, err := pesym.FullName(f.StringTable)
 251                                 if err != nil {
 252                                         name = string(pesym.Name[:])
 253                                 }
 254                                 return nil, nil, fmt.Errorf("reloc of invalid sym %s idx=%d type=%d", name, r.SymbolTableIndex, pesym.Type)
 255                         }
 256
 257                         rp.Sym = gosym
 258                         rp.Siz = 4
 259                         rp.Off = int32(r.VirtualAddress)
 260                         switch arch.Family {
 261                         default:
 262                                 return nil, nil, fmt.Errorf("%s: unsupported arch %v", pn, arch.Family)
 263                         case sys.I386, sys.AMD64:
 264                                 switch r.Type {
 265                                 default:
 266                                         return nil, nil, fmt.Errorf("%s: %v: unknown relocation type %v", pn, sectsyms[rsect], r.Type)
 267
 268                                 case IMAGE_REL_I386_REL32, IMAGE_REL_AMD64_REL32,
 269                                         IMAGE_REL_AMD64_ADDR32, // R_X86_64_PC32
 270                                         IMAGE_REL_AMD64_ADDR32NB:
 271                                         rp.Type = objabi.R_PCREL
 272
 273                                         rp.Add = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rp.Off:])))
 274
 275                                 case IMAGE_REL_I386_DIR32NB, IMAGE_REL_I386_DIR32:
 276                                         rp.Type = objabi.R_ADDR
 277
 278                                         // load addend from image
 279                                         rp.Add = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rp.Off:])))
 280
 281                                 case IMAGE_REL_AMD64_ADDR64: // R_X86_64_64
 282                                         rp.Siz = 8
 283
 284                                         rp.Type = objabi.R_ADDR
 285
 286                                         // load addend from image
 287                                         rp.Add = int64(binary.LittleEndian.Uint64(sectdata[rsect][rp.Off:]))
 288                                 }
 289
 290                         case sys.ARM:
 291                                 switch r.Type {
 292                                 default:
 293                                         return nil, nil, fmt.Errorf("%s: %v: unknown ARM relocation type %v", pn, sectsyms[rsect], r.Type)
 294
 295                                 case IMAGE_REL_ARM_SECREL:
 296                                         rp.Type = objabi.R_PCREL
 297
 298                                         rp.Add = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rp.Off:])))
 299
 300                                 case IMAGE_REL_ARM_ADDR32:
 301                                         rp.Type = objabi.R_ADDR
 302
 303                                         rp.Add = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rp.Off:])))
 304
 305                                 case IMAGE_REL_ARM_BRANCH24:
 306                                         rp.Type = objabi.R_CALLARM
 307
 308                                         rp.Add = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rp.Off:])))
 309                                 }
 310                         }
 311
 312                         // ld -r could generate multiple section symbols for the
 313                         // same section but with different values, we have to take
 314                         // that into account
 315                         if issect(pesym) {
 316                                 rp.Add += int64(pesym.Value)
 317                         }
 318                 }
 319
 320                 sort.Sort(sym.RelocByOff(rs[:rsect.NumberOfRelocations]))
 321
 322                 s := sectsyms[rsect]
 323                 s.R = rs
 324                 s.R = s.R[:rsect.NumberOfRelocations]
 325         }
 326
 327         // enter sub-symbols into symbol table.
 328         for i, numaux := 0, 0; i < len(f.COFFSymbols); i += numaux + 1 {
 329                 pesym := &f.COFFSymbols[i]
 330
 331                 numaux = int(pesym.NumberOfAuxSymbols)
 332
 333                 name, err := pesym.FullName(f.StringTable)
 334                 if err != nil {
 335                         return nil, nil, err
 336                 }
 337                 if name == "" {
 338                         continue
 339                 }
 340                 if issect(pesym) {
 341                         continue
 342                 }
 343                 if int(pesym.SectionNumber) > len(f.Sections) {
 344                         continue
 345                 }
 346                 if pesym.SectionNumber == IMAGE_SYM_DEBUG {
 347                         continue
 348                 }
 349                 var sect *pe.Section
 350                 if pesym.SectionNumber > 0 {
 351                         sect = f.Sections[pesym.SectionNumber-1]
 352                         if _, found := sectsyms[sect]; !found {
 353                                 continue
 354                         }
 355                 }
 356
 357                 s, err := readpesym(arch, lookup, f, pesym, sectsyms, localSymVersion)
 358                 if err != nil {
 359                         return nil, nil, err
 360                 }
 361
 362                 if pesym.SectionNumber == 0 { // extern
 363                         if s.Type == sym.SDYNIMPORT {
 364                                 s.SetPlt(-2) // flag for dynimport in PE object files.
 365                         }
 366                         if s.Type == sym.SXREF && pesym.Value > 0 { // global data
 367                                 s.Type = sym.SNOPTRDATA
 368                                 s.Size = int64(pesym.Value)
 369                         }
 370
 371                         continue
 372                 } else if pesym.SectionNumber > 0 && int(pesym.SectionNumber) <= len(f.Sections) {
 373                         sect = f.Sections[pesym.SectionNumber-1]
 374                         if _, found := sectsyms[sect]; !found {
 375                                 return nil, nil, fmt.Errorf("%s: %v: missing sect.sym", pn, s)
 376                         }
 377                 } else {
 378                         return nil, nil, fmt.Errorf("%s: %v: sectnum < 0!", pn, s)
 379                 }
 380
 381                 if sect == nil {
 382                         return nil, rsrc, nil
 383                 }
 384
 385                 if s.Outer != nil {
 386                         if s.Attr.DuplicateOK() {
 387                                 continue
 388                         }
 389                         return nil, nil, fmt.Errorf("%s: duplicate symbol reference: %s in both %s and %s", pn, s.Name, s.Outer.Name, sectsyms[sect].Name)
 390                 }
 391
 392                 sectsym := sectsyms[sect]
 393                 s.Sub = sectsym.Sub
 394                 sectsym.Sub = s
 395                 s.Type = sectsym.Type
 396                 s.Attr |= sym.AttrSubSymbol
 397                 s.Value = int64(pesym.Value)
 398                 s.Size = 4
 399                 s.Outer = sectsym
 400                 if sectsym.Type == sym.STEXT {
 401                         if s.Attr.External() && !s.Attr.DuplicateOK() {
 402                                 return nil, nil, fmt.Errorf("%s: duplicate symbol definition", s.Name)
 403                         }
 404                         s.Attr |= sym.AttrExternal
 405                 }
 406         }
 407
 408         // Sort outer lists by address, adding to textp.
 409         // This keeps textp in increasing address order.
 410         for _, sect := range f.Sections {
 411                 s := sectsyms[sect]
 412                 if s == nil {
 413                         continue
 414                 }
 415                 if s.Sub != nil {
 416                         s.Sub = sym.SortSub(s.Sub)
 417                 }
 418                 if s.Type == sym.STEXT {
 419                         if s.Attr.OnList() {
 420                                 return nil, nil, fmt.Errorf("symbol %s listed multiple times", s.Name)
 421                         }
 422                         s.Attr |= sym.AttrOnList
 423                         textp = append(textp, s)
 424                         for s = s.Sub; s != nil; s = s.Sub {
 425                                 if s.Attr.OnList() {
 426                                         return nil, nil, fmt.Errorf("symbol %s listed multiple times", s.Name)
 427                                 }
 428                                 s.Attr |= sym.AttrOnList
 429                                 textp = append(textp, s)
 430                         }
 431                 }
 432         }
 433
 434         return textp, rsrc, nil
 435 }
 436
 437 func issect(s *pe.COFFSymbol) bool {
 438         return s.StorageClass == IMAGE_SYM_CLASS_STATIC && s.Type == 0 && s.Name[0] == '.'
 439 }
 440
 441 func readpesym(arch *sys.Arch, lookup func(string, int) *sym.Symbol, f *pe.File, pesym *pe.COFFSymbol, sectsyms map[*pe.Section]*sym.Symbol, localSymVersion int) (*sym.Symbol, error) {
 442         symname, err := pesym.FullName(f.StringTable)
 443         if err != nil {
 444                 return nil, err
 445         }
 446         var name string
 447         if issect(pesym) {
 448                 name = sectsyms[f.Sections[pesym.SectionNumber-1]].Name
 449         } else {
 450                 name = symname
 451                 switch arch.Family {
 452                 case sys.AMD64:
 453                         if name == "__imp___acrt_iob_func" {
 454                                 // Do not rename __imp___acrt_iob_func into __acrt_iob_func,
 455                                 // becasue __imp___acrt_iob_func symbol is real
 456                                 // (see commit b295099 from git://git.code.sf.net/p/mingw-w64/mingw-w64 for detials).
 457                         } else {
 458                                 name = strings.TrimPrefix(name, "__imp_") // __imp_Name => Name
 459                         }
 460                 case sys.I386:
 461                         if name == "__imp____acrt_iob_func" {
 462                                 // Do not rename __imp____acrt_iob_func into ___acrt_iob_func,
 463                                 // becasue __imp____acrt_iob_func symbol is real
 464                                 // (see commit b295099 from git://git.code.sf.net/p/mingw-w64/mingw-w64 for detials).
 465                         } else {
 466                                 name = strings.TrimPrefix(name, "__imp_") // __imp_Name => Name
 467                         }
 468                         if name[0] == '_' {
 469                                 name = name[1:] // _Name => Name
 470                         }
 471                 }
 472         }
 473
 474         // remove last @XXX
 475         if i := strings.LastIndex(name, "@"); i >= 0 {
 476                 name = name[:i]
 477         }
 478
 479         var s *sym.Symbol
 480         switch pesym.Type {
 481         default:
 482                 return nil, fmt.Errorf("%s: invalid symbol type %d", symname, pesym.Type)
 483
 484         case IMAGE_SYM_DTYPE_FUNCTION, IMAGE_SYM_DTYPE_NULL:
 485                 switch pesym.StorageClass {
 486                 case IMAGE_SYM_CLASS_EXTERNAL: //global
 487                         s = lookup(name, 0)
 488
 489                 case IMAGE_SYM_CLASS_NULL, IMAGE_SYM_CLASS_STATIC, IMAGE_SYM_CLASS_LABEL:
 490                         s = lookup(name, localSymVersion)
 491                         s.Attr |= sym.AttrDuplicateOK
 492
 493                 default:
 494                         return nil, fmt.Errorf("%s: invalid symbol binding %d", symname, pesym.StorageClass)
 495                 }
 496         }
 497
 498         if s != nil && s.Type == 0 && (pesym.StorageClass != IMAGE_SYM_CLASS_STATIC || pesym.Value != 0) {
 499                 s.Type = sym.SXREF
 500         }
 501         if strings.HasPrefix(symname, "__imp_") {
 502                 s.SetGot(-2) // flag for __imp_
 503         }
 504
 505         return s, nil
 506 }