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         "bytes"
  10         "cmd/internal/bio"
  11         "cmd/internal/objabi"
  12         "cmd/internal/sys"
  13         "cmd/link/internal/loader"
  14         "cmd/link/internal/sym"
  15         "debug/pe"
  16         "encoding/binary"
  17         "errors"
  18         "fmt"
  19         "io"
  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 or set of .rsrc$xx sections is found, its symbols are
 161 // returned as rsrc.
 162 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) {
 163         lookup := func(name string, version int) (*loader.SymbolBuilder, loader.Sym) {
 164                 s := l.LookupOrCreateSym(name, version)
 165                 sb := l.MakeSymbolUpdater(s)
 166                 return sb, s
 167         }
 168         sectsyms := make(map[*pe.Section]loader.Sym)
 169         sectdata := make(map[*pe.Section][]byte)
 170
 171         // Some input files are archives containing multiple of
 172         // object files, and pe.NewFile seeks to the start of
 173         // input file and get confused. Create section reader
 174         // to stop pe.NewFile looking before current position.
 175         sr := io.NewSectionReader((*peBiobuf)(input), input.Offset(), 1<<63-1)
 176
 177         // TODO: replace pe.NewFile with pe.Load (grep for "add Load function" in debug/pe for details)
 178         f, err := pe.NewFile(sr)
 179         if err != nil {
 180                 return nil, nil, err
 181         }
 182         defer f.Close()
 183
 184         // TODO return error if found .cormeta
 185
 186         // create symbols for mapped sections
 187         for _, sect := range f.Sections {
 188                 if sect.Characteristics&IMAGE_SCN_MEM_DISCARDABLE != 0 {
 189                         continue
 190                 }
 191
 192                 if sect.Characteristics&(IMAGE_SCN_CNT_CODE|IMAGE_SCN_CNT_INITIALIZED_DATA|IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0 {
 193                         // This has been seen for .idata sections, which we
 194                         // want to ignore. See issues 5106 and 5273.
 195                         continue
 196                 }
 197
 198                 name := fmt.Sprintf("%s(%s)", pkg, sect.Name)
 199                 bld, s := lookup(name, localSymVersion)
 200
 201                 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) {
 202                 case IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ: //.rdata
 203                         bld.SetType(sym.SRODATA)
 204
 205                 case IMAGE_SCN_CNT_UNINITIALIZED_DATA | IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE: //.bss
 206                         bld.SetType(sym.SNOPTRBSS)
 207
 208                 case IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE: //.data
 209                         bld.SetType(sym.SNOPTRDATA)
 210
 211                 case IMAGE_SCN_CNT_CODE | IMAGE_SCN_MEM_EXECUTE | IMAGE_SCN_MEM_READ: //.text
 212                         bld.SetType(sym.STEXT)
 213
 214                 default:
 215                         return nil, nil, fmt.Errorf("unexpected flags %#06x for PE section %s", sect.Characteristics, sect.Name)
 216                 }
 217
 218                 if bld.Type() != sym.SNOPTRBSS {
 219                         data, err := sect.Data()
 220                         if err != nil {
 221                                 return nil, nil, err
 222                         }
 223                         sectdata[sect] = data
 224                         bld.SetData(data)
 225                 }
 226                 bld.SetSize(int64(sect.Size))
 227                 sectsyms[sect] = s
 228                 if sect.Name == ".rsrc" || strings.HasPrefix(sect.Name, ".rsrc$") {
 229                         rsrc = append(rsrc, s)
 230                 }
 231         }
 232
 233         // load relocations
 234         for _, rsect := range f.Sections {
 235                 if _, found := sectsyms[rsect]; !found {
 236                         continue
 237                 }
 238                 if rsect.NumberOfRelocations == 0 {
 239                         continue
 240                 }
 241                 if rsect.Characteristics&IMAGE_SCN_MEM_DISCARDABLE != 0 {
 242                         continue
 243                 }
 244                 if rsect.Characteristics&(IMAGE_SCN_CNT_CODE|IMAGE_SCN_CNT_INITIALIZED_DATA|IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0 {
 245                         // This has been seen for .idata sections, which we
 246                         // want to ignore. See issues 5106 and 5273.
 247                         continue
 248                 }
 249
 250                 splitResources := strings.HasPrefix(rsect.Name, ".rsrc$")
 251                 sb := l.MakeSymbolUpdater(sectsyms[rsect])
 252                 for j, r := range rsect.Relocs {
 253                         if int(r.SymbolTableIndex) >= len(f.COFFSymbols) {
 254                                 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))
 255                         }
 256                         pesym := &f.COFFSymbols[r.SymbolTableIndex]
 257                         _, gosym, err := readpesym(l, arch, l.LookupOrCreateSym, f, pesym, sectsyms, localSymVersion)
 258                         if err != nil {
 259                                 return nil, nil, err
 260                         }
 261                         if gosym == 0 {
 262                                 name, err := pesym.FullName(f.StringTable)
 263                                 if err != nil {
 264                                         name = string(pesym.Name[:])
 265                                 }
 266                                 return nil, nil, fmt.Errorf("reloc of invalid sym %s idx=%d type=%d", name, r.SymbolTableIndex, pesym.Type)
 267                         }
 268
 269                         rSym := gosym
 270                         rSize := uint8(4)
 271                         rOff := int32(r.VirtualAddress)
 272                         var rAdd int64
 273                         var rType objabi.RelocType
 274                         switch arch.Family {
 275                         default:
 276                                 return nil, nil, fmt.Errorf("%s: unsupported arch %v", pn, arch.Family)
 277                         case sys.I386, sys.AMD64:
 278                                 switch r.Type {
 279                                 default:
 280                                         return nil, nil, fmt.Errorf("%s: %v: unknown relocation type %v", pn, sectsyms[rsect], r.Type)
 281
 282                                 case IMAGE_REL_I386_REL32, IMAGE_REL_AMD64_REL32,
 283                                         IMAGE_REL_AMD64_ADDR32, // R_X86_64_PC32
 284                                         IMAGE_REL_AMD64_ADDR32NB:
 285                                         rType = objabi.R_PCREL
 286
 287                                         rAdd = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rOff:])))
 288
 289                                 case IMAGE_REL_I386_DIR32NB, IMAGE_REL_I386_DIR32:
 290                                         rType = objabi.R_ADDR
 291
 292                                         // load addend from image
 293                                         rAdd = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rOff:])))
 294
 295                                 case IMAGE_REL_AMD64_ADDR64: // R_X86_64_64
 296                                         rSize = 8
 297
 298                                         rType = objabi.R_ADDR
 299
 300                                         // load addend from image
 301                                         rAdd = int64(binary.LittleEndian.Uint64(sectdata[rsect][rOff:]))
 302                                 }
 303
 304                         case sys.ARM:
 305                                 switch r.Type {
 306                                 default:
 307                                         return nil, nil, fmt.Errorf("%s: %v: unknown ARM relocation type %v", pn, sectsyms[rsect], r.Type)
 308
 309                                 case IMAGE_REL_ARM_SECREL:
 310                                         rType = objabi.R_PCREL
 311
 312                                         rAdd = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rOff:])))
 313
 314                                 case IMAGE_REL_ARM_ADDR32, IMAGE_REL_ARM_ADDR32NB:
 315                                         rType = objabi.R_ADDR
 316
 317                                         rAdd = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rOff:])))
 318
 319                                 case IMAGE_REL_ARM_BRANCH24:
 320                                         rType = objabi.R_CALLARM
 321
 322                                         rAdd = int64(int32(binary.LittleEndian.Uint32(sectdata[rsect][rOff:])))
 323                                 }
 324                         }
 325
 326                         // ld -r could generate multiple section symbols for the
 327                         // same section but with different values, we have to take
 328                         // that into account, or in the case of split resources,
 329                         // the section and its symbols are split into two sections.
 330                         if issect(pesym) || splitResources {
 331                                 rAdd += int64(pesym.Value)
 332                         }
 333
 334                         rel, _ := sb.AddRel(rType)
 335                         rel.SetOff(rOff)
 336                         rel.SetSiz(rSize)
 337                         rel.SetSym(rSym)
 338                         rel.SetAdd(rAdd)
 339                 }
 340
 341                 sb.SortRelocs()
 342         }
 343
 344         // enter sub-symbols into symbol table.
 345         for i, numaux := 0, 0; i < len(f.COFFSymbols); i += numaux + 1 {
 346                 pesym := &f.COFFSymbols[i]
 347
 348                 numaux = int(pesym.NumberOfAuxSymbols)
 349
 350                 name, err := pesym.FullName(f.StringTable)
 351                 if err != nil {
 352                         return nil, nil, err
 353                 }
 354                 if name == "" {
 355                         continue
 356                 }
 357                 if issect(pesym) {
 358                         continue
 359                 }
 360                 if int(pesym.SectionNumber) > len(f.Sections) {
 361                         continue
 362                 }
 363                 if pesym.SectionNumber == IMAGE_SYM_DEBUG {
 364                         continue
 365                 }
 366                 if pesym.SectionNumber == IMAGE_SYM_ABSOLUTE && bytes.Equal(pesym.Name[:], []byte("@feat.00")) {
 367                         // Microsoft's linker looks at whether all input objects have an empty
 368                         // section called @feat.00. If all of them do, then it enables SEH;
 369                         // otherwise it doesn't enable that feature. So, since around the Windows
 370                         // XP SP2 era, most tools that make PE objects just tack on that section,
 371                         // so that it won't gimp Microsoft's linker logic. Go doesn't support SEH,
 372                         // so in theory, none of this really matters to us. But actually, if the
 373                         // linker tries to ingest an object with @feat.00 -- which are produced by
 374                         // LLVM's resource compiler, for example -- it chokes because of the
 375                         // IMAGE_SYM_ABSOLUTE section that it doesn't know how to deal with. Since
 376                         // @feat.00 is just a marking anyway, skip IMAGE_SYM_ABSOLUTE sections that
 377                         // are called @feat.00.
 378                         continue
 379                 }
 380                 var sect *pe.Section
 381                 if pesym.SectionNumber > 0 {
 382                         sect = f.Sections[pesym.SectionNumber-1]
 383                         if _, found := sectsyms[sect]; !found {
 384                                 continue
 385                         }
 386                 }
 387
 388                 bld, s, err := readpesym(l, arch, l.LookupOrCreateSym, f, pesym, sectsyms, localSymVersion)
 389                 if err != nil {
 390                         return nil, nil, err
 391                 }
 392
 393                 if pesym.SectionNumber == 0 { // extern
 394                         if l.SymType(s) == sym.SDYNIMPORT {
 395                                 bld = makeUpdater(l, bld, s)
 396                                 bld.SetPlt(-2) // flag for dynimport in PE object files.
 397                         }
 398                         if l.SymType(s) == sym.SXREF && pesym.Value > 0 { // global data
 399                                 bld = makeUpdater(l, bld, s)
 400                                 bld.SetType(sym.SNOPTRDATA)
 401                                 bld.SetSize(int64(pesym.Value))
 402                         }
 403
 404                         continue
 405                 } else if pesym.SectionNumber > 0 && int(pesym.SectionNumber) <= len(f.Sections) {
 406                         sect = f.Sections[pesym.SectionNumber-1]
 407                         if _, found := sectsyms[sect]; !found {
 408                                 return nil, nil, fmt.Errorf("%s: %v: missing sect.sym", pn, s)
 409                         }
 410                 } else {
 411                         return nil, nil, fmt.Errorf("%s: %v: sectnum < 0!", pn, s)
 412                 }
 413
 414                 if sect == nil {
 415                         return nil, nil, nil
 416                 }
 417
 418                 if l.OuterSym(s) != 0 {
 419                         if l.AttrDuplicateOK(s) {
 420                                 continue
 421                         }
 422                         outerName := l.SymName(l.OuterSym(s))
 423                         sectName := l.SymName(sectsyms[sect])
 424                         return nil, nil, fmt.Errorf("%s: duplicate symbol reference: %s in both %s and %s", pn, l.SymName(s), outerName, sectName)
 425                 }
 426
 427                 bld = makeUpdater(l, bld, s)
 428                 sectsym := sectsyms[sect]
 429                 bld.SetType(l.SymType(sectsym))
 430                 l.AddInteriorSym(sectsym, s)
 431                 bld.SetValue(int64(pesym.Value))
 432                 bld.SetSize(4)
 433                 if l.SymType(sectsym) == sym.STEXT {
 434                         if bld.External() && !bld.DuplicateOK() {
 435                                 return nil, nil, fmt.Errorf("%s: duplicate symbol definition", l.SymName(s))
 436                         }
 437                         bld.SetExternal(true)
 438                 }
 439         }
 440
 441         // Sort outer lists by address, adding to textp.
 442         // This keeps textp in increasing address order.
 443         for _, sect := range f.Sections {
 444                 s := sectsyms[sect]
 445                 if s == 0 {
 446                         continue
 447                 }
 448                 l.SortSub(s)
 449                 if l.SymType(s) == sym.STEXT {
 450                         for ; s != 0; s = l.SubSym(s) {
 451                                 if l.AttrOnList(s) {
 452                                         return nil, nil, fmt.Errorf("symbol %s listed multiple times", l.SymName(s))
 453                                 }
 454                                 l.SetAttrOnList(s, true)
 455                                 textp = append(textp, s)
 456                         }
 457                 }
 458         }
 459
 460         return textp, rsrc, nil
 461 }
 462
 463 func issect(s *pe.COFFSymbol) bool {
 464         return s.StorageClass == IMAGE_SYM_CLASS_STATIC && s.Type == 0 && s.Name[0] == '.'
 465 }
 466
 467 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) {
 468         symname, err := pesym.FullName(f.StringTable)
 469         if err != nil {
 470                 return nil, 0, err
 471         }
 472         var name string
 473         if issect(pesym) {
 474                 name = l.SymName(sectsyms[f.Sections[pesym.SectionNumber-1]])
 475         } else {
 476                 name = symname
 477                 switch arch.Family {
 478                 case sys.AMD64:
 479                         if name == "__imp___acrt_iob_func" {
 480                                 // Do not rename __imp___acrt_iob_func into __acrt_iob_func,
 481                                 // because __imp___acrt_iob_func symbol is real
 482                                 // (see commit b295099 from git://git.code.sf.net/p/mingw-w64/mingw-w64 for details).
 483                         } else {
 484                                 name = strings.TrimPrefix(name, "__imp_") // __imp_Name => Name
 485                         }
 486                 case sys.I386:
 487                         if name == "__imp____acrt_iob_func" {
 488                                 // Do not rename __imp____acrt_iob_func into ___acrt_iob_func,
 489                                 // because __imp____acrt_iob_func symbol is real
 490                                 // (see commit b295099 from git://git.code.sf.net/p/mingw-w64/mingw-w64 for details).
 491                         } else {
 492                                 name = strings.TrimPrefix(name, "__imp_") // __imp_Name => Name
 493                         }
 494                         if name[0] == '_' {
 495                                 name = name[1:] // _Name => Name
 496                         }
 497                 }
 498         }
 499
 500         // remove last @XXX
 501         if i := strings.LastIndex(name, "@"); i >= 0 {
 502                 name = name[:i]
 503         }
 504
 505         var s loader.Sym
 506         var bld *loader.SymbolBuilder
 507         switch pesym.Type {
 508         default:
 509                 return nil, 0, fmt.Errorf("%s: invalid symbol type %d", symname, pesym.Type)
 510
 511         case IMAGE_SYM_DTYPE_FUNCTION, IMAGE_SYM_DTYPE_NULL:
 512                 switch pesym.StorageClass {
 513                 case IMAGE_SYM_CLASS_EXTERNAL: //global
 514                         s = lookup(name, 0)
 515
 516                 case IMAGE_SYM_CLASS_NULL, IMAGE_SYM_CLASS_STATIC, IMAGE_SYM_CLASS_LABEL:
 517                         s = lookup(name, localSymVersion)
 518                         bld = makeUpdater(l, bld, s)
 519                         bld.SetDuplicateOK(true)
 520
 521                 default:
 522                         return nil, 0, fmt.Errorf("%s: invalid symbol binding %d", symname, pesym.StorageClass)
 523                 }
 524         }
 525
 526         if s != 0 && l.SymType(s) == 0 && (pesym.StorageClass != IMAGE_SYM_CLASS_STATIC || pesym.Value != 0) {
 527                 bld = makeUpdater(l, bld, s)
 528                 bld.SetType(sym.SXREF)
 529         }
 530         if strings.HasPrefix(symname, "__imp_") {
 531                 bld = makeUpdater(l, bld, s)
 532                 bld.SetGot(-2) // flag for __imp_
 533         }
 534
 535         return bld, s, nil
 536 }