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         IMAGE_SYM_UNDEFINED              = 0
  25         IMAGE_SYM_ABSOLUTE               = -1
  26         IMAGE_SYM_DEBUG                  = -2
  27         IMAGE_SYM_TYPE_NULL              = 0
  28         IMAGE_SYM_TYPE_VOID              = 1
  29         IMAGE_SYM_TYPE_CHAR              = 2
  30         IMAGE_SYM_TYPE_SHORT             = 3
  31         IMAGE_SYM_TYPE_INT               = 4
  32         IMAGE_SYM_TYPE_LONG              = 5
  33         IMAGE_SYM_TYPE_FLOAT             = 6
  34         IMAGE_SYM_TYPE_DOUBLE            = 7
  35         IMAGE_SYM_TYPE_STRUCT            = 8
  36         IMAGE_SYM_TYPE_UNION             = 9
  37         IMAGE_SYM_TYPE_ENUM              = 10
  38         IMAGE_SYM_TYPE_MOE               = 11
  39         IMAGE_SYM_TYPE_BYTE              = 12
  40         IMAGE_SYM_TYPE_WORD              = 13
  41         IMAGE_SYM_TYPE_UINT              = 14
  42         IMAGE_SYM_TYPE_DWORD             = 15
  43         IMAGE_SYM_TYPE_PCODE             = 32768
  44         IMAGE_SYM_DTYPE_NULL             = 0
  45         IMAGE_SYM_DTYPE_POINTER          = 1
  46         IMAGE_SYM_DTYPE_FUNCTION         = 2
  47         IMAGE_SYM_DTYPE_ARRAY            = 3
  48         IMAGE_SYM_CLASS_END_OF_FUNCTION  = -1
  49         IMAGE_SYM_CLASS_NULL             = 0
  50         IMAGE_SYM_CLASS_AUTOMATIC        = 1
  51         IMAGE_SYM_CLASS_EXTERNAL         = 2
  52         IMAGE_SYM_CLASS_STATIC           = 3
  53         IMAGE_SYM_CLASS_REGISTER         = 4
  54         IMAGE_SYM_CLASS_EXTERNAL_DEF     = 5
  55         IMAGE_SYM_CLASS_LABEL            = 6
  56         IMAGE_SYM_CLASS_UNDEFINED_LABEL  = 7
  57         IMAGE_SYM_CLASS_MEMBER_OF_STRUCT = 8
  58         IMAGE_SYM_CLASS_ARGUMENT         = 9
  59         IMAGE_SYM_CLASS_STRUCT_TAG       = 10
  60         IMAGE_SYM_CLASS_MEMBER_OF_UNION  = 11
  61         IMAGE_SYM_CLASS_UNION_TAG        = 12
  62         IMAGE_SYM_CLASS_TYPE_DEFINITION  = 13
  63         IMAGE_SYM_CLASS_UNDEFINED_STATIC = 14
  64         IMAGE_SYM_CLASS_ENUM_TAG         = 15
  65         IMAGE_SYM_CLASS_MEMBER_OF_ENUM   = 16
  66         IMAGE_SYM_CLASS_REGISTER_PARAM   = 17
  67         IMAGE_SYM_CLASS_BIT_FIELD        = 18
  68         IMAGE_SYM_CLASS_FAR_EXTERNAL     = 68 /* Not in PECOFF v8 spec */
  69         IMAGE_SYM_CLASS_BLOCK            = 100
  70         IMAGE_SYM_CLASS_FUNCTION         = 101
  71         IMAGE_SYM_CLASS_END_OF_STRUCT    = 102
  72         IMAGE_SYM_CLASS_FILE             = 103
  73         IMAGE_SYM_CLASS_SECTION          = 104
  74         IMAGE_SYM_CLASS_WEAK_EXTERNAL    = 105
  75         IMAGE_SYM_CLASS_CLR_TOKEN        = 107
  76         IMAGE_REL_I386_ABSOLUTE          = 0x0000
  77         IMAGE_REL_I386_DIR16             = 0x0001
  78         IMAGE_REL_I386_REL16             = 0x0002
  79         IMAGE_REL_I386_DIR32             = 0x0006
  80         IMAGE_REL_I386_DIR32NB           = 0x0007
  81         IMAGE_REL_I386_SEG12             = 0x0009
  82         IMAGE_REL_I386_SECTION           = 0x000A
  83         IMAGE_REL_I386_SECREL            = 0x000B
  84         IMAGE_REL_I386_TOKEN             = 0x000C
  85         IMAGE_REL_I386_SECREL7           = 0x000D
  86         IMAGE_REL_I386_REL32             = 0x0014
  87         IMAGE_REL_AMD64_ABSOLUTE         = 0x0000
  88         IMAGE_REL_AMD64_ADDR64           = 0x0001
  89         IMAGE_REL_AMD64_ADDR32           = 0x0002
  90         IMAGE_REL_AMD64_ADDR32NB         = 0x0003
  91         IMAGE_REL_AMD64_REL32            = 0x0004
  92         IMAGE_REL_AMD64_REL32_1          = 0x0005
  93         IMAGE_REL_AMD64_REL32_2          = 0x0006
  94         IMAGE_REL_AMD64_REL32_3          = 0x0007
  95         IMAGE_REL_AMD64_REL32_4          = 0x0008
  96         IMAGE_REL_AMD64_REL32_5          = 0x0009
  97         IMAGE_REL_AMD64_SECTION          = 0x000A
  98         IMAGE_REL_AMD64_SECREL           = 0x000B
  99         IMAGE_REL_AMD64_SECREL7          = 0x000C
 100         IMAGE_REL_AMD64_TOKEN            = 0x000D
 101         IMAGE_REL_AMD64_SREL32           = 0x000E
 102         IMAGE_REL_AMD64_PAIR             = 0x000F
 103         IMAGE_REL_AMD64_SSPAN32          = 0x0010
 104         IMAGE_REL_ARM_ABSOLUTE           = 0x0000
 105         IMAGE_REL_ARM_ADDR32             = 0x0001
 106         IMAGE_REL_ARM_ADDR32NB           = 0x0002
 107         IMAGE_REL_ARM_BRANCH24           = 0x0003
 108         IMAGE_REL_ARM_BRANCH11           = 0x0004
 109         IMAGE_REL_ARM_SECTION            = 0x000E
 110         IMAGE_REL_ARM_SECREL             = 0x000F
 111         IMAGE_REL_ARM_MOV32              = 0x0010
 112         IMAGE_REL_THUMB_MOV32            = 0x0011
 113         IMAGE_REL_THUMB_BRANCH20         = 0x0012
 114         IMAGE_REL_THUMB_BRANCH24         = 0x0014
 115         IMAGE_REL_THUMB_BLX23            = 0x0015
 116         IMAGE_REL_ARM_PAIR               = 0x0016
 117         IMAGE_REL_ARM64_ABSOLUTE         = 0x0000
 118         IMAGE_REL_ARM64_ADDR32           = 0x0001
 119         IMAGE_REL_ARM64_ADDR32NB         = 0x0002
 120         IMAGE_REL_ARM64_BRANCH26         = 0x0003
 121         IMAGE_REL_ARM64_PAGEBASE_REL21   = 0x0004
 122         IMAGE_REL_ARM64_REL21            = 0x0005
 123         IMAGE_REL_ARM64_PAGEOFFSET_12A   = 0x0006
 124         IMAGE_REL_ARM64_PAGEOFFSET_12L   = 0x0007
 125         IMAGE_REL_ARM64_SECREL           = 0x0008
 126         IMAGE_REL_ARM64_SECREL_LOW12A    = 0x0009
 127         IMAGE_REL_ARM64_SECREL_HIGH12A   = 0x000A
 128         IMAGE_REL_ARM64_SECREL_LOW12L    = 0x000B
 129         IMAGE_REL_ARM64_TOKEN            = 0x000C
 130         IMAGE_REL_ARM64_SECTION          = 0x000D
 131         IMAGE_REL_ARM64_ADDR64           = 0x000E
 132         IMAGE_REL_ARM64_BRANCH19         = 0x000F
 133         IMAGE_REL_ARM64_BRANCH14         = 0x0010
 134         IMAGE_REL_ARM64_REL32            = 0x0011
 135 )
 136
 137 const (
 138         // When stored into the PLT value for a symbol, this token tells
 139         // windynrelocsym to redirect direct references to this symbol to a stub
 140         // that loads from the corresponding import symbol and then does
 141         // a jump to the loaded value.
 142         CreateImportStubPltToken = -2
 143
 144         // When stored into the GOT value for an import symbol __imp_X this
 145         // token tells windynrelocsym to redirect references to the
 146         // underlying DYNIMPORT symbol X.
 147         RedirectToDynImportGotToken = -2
 148 )
 149
 150 // TODO(brainman): maybe just add ReadAt method to bio.Reader instead of creating peBiobuf
 151
 152 // peBiobuf makes bio.Reader look like io.ReaderAt.
 153 type peBiobuf bio.Reader
 154
 155 func (f *peBiobuf) ReadAt(p []byte, off int64) (int, error) {
 156         ret := ((*bio.Reader)(f)).MustSeek(off, 0)
 157         if ret < 0 {
 158                 return 0, errors.New("fail to seek")
 159         }
 160         n, err := f.Read(p)
 161         if err != nil {
 162                 return 0, err
 163         }
 164         return n, nil
 165 }
 166
 167 // makeUpdater creates a loader.SymbolBuilder if one hasn't been created previously.
 168 // 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.
 169 func makeUpdater(l *loader.Loader, bld *loader.SymbolBuilder, s loader.Sym) *loader.SymbolBuilder {
 170         if bld != nil {
 171                 return bld
 172         }
 173         bld = l.MakeSymbolUpdater(s)
 174         return bld
 175 }
 176
 177 // peImportSymsState tracks the set of DLL import symbols we've seen
 178 // while reading host objects. We create a singleton instance of this
 179 // type, which will persist across multiple host objects.
 180 type peImportSymsState struct {
 181
 182         // Text and non-text sections read in by the host object loader.
 183         secSyms []loader.Sym
 184
 185         // SDYNIMPORT symbols encountered along the way
 186         dynimports map[loader.Sym]struct{}
 187
 188         // Loader and arch, for use in postprocessing.
 189         l    *loader.Loader
 190         arch *sys.Arch
 191 }
 192
 193 var importSymsState *peImportSymsState
 194
 195 func createImportSymsState(l *loader.Loader, arch *sys.Arch) {
 196         if importSymsState != nil {
 197                 return
 198         }
 199         importSymsState = &peImportSymsState{
 200                 dynimports: make(map[loader.Sym]struct{}),
 201                 l:          l,
 202                 arch:       arch,
 203         }
 204 }
 205
 206 // peLoaderState holds various bits of useful state information needed
 207 // while loading a single PE object file.
 208 type peLoaderState struct {
 209         l               *loader.Loader
 210         arch            *sys.Arch
 211         f               *pe.File
 212         pn              string
 213         sectsyms        map[*pe.Section]loader.Sym
 214         comdats         map[uint16]int64 // key is section index, val is size
 215         sectdata        map[*pe.Section][]byte
 216         localSymVersion int
 217 }
 218
 219 // comdatDefinitions records the names of symbols for which we've
 220 // previously seen a definition in COMDAT. Key is symbol name, value
 221 // is symbol size (or -1 if we're using the "any" strategy).
 222 var comdatDefinitions = make(map[string]int64)
 223
 224 // Load loads the PE file pn from input.
 225 // Symbols from the object file are created via the loader 'l', and
 226 // and a slice of the text symbols is returned.
 227 // If an .rsrc section or set of .rsrc$xx sections is found, its symbols are
 228 // returned as rsrc.
 229 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) {
 230         state := &peLoaderState{
 231                 l:               l,
 232                 arch:            arch,
 233                 sectsyms:        make(map[*pe.Section]loader.Sym),
 234                 sectdata:        make(map[*pe.Section][]byte),
 235                 localSymVersion: localSymVersion,
 236                 pn:              pn,
 237         }
 238         createImportSymsState(state.l, state.arch)
 239
 240         // Some input files are archives containing multiple of
 241         // object files, and pe.NewFile seeks to the start of
 242         // input file and get confused. Create section reader
 243         // to stop pe.NewFile looking before current position.
 244         sr := io.NewSectionReader((*peBiobuf)(input), input.Offset(), 1<<63-1)
 245
 246         // TODO: replace pe.NewFile with pe.Load (grep for "add Load function" in debug/pe for details)
 247         f, err := pe.NewFile(sr)
 248         if err != nil {
 249                 return nil, nil, err
 250         }
 251         defer f.Close()
 252         state.f = f
 253
 254         // TODO return error if found .cormeta
 255
 256         // create symbols for mapped sections
 257         for _, sect := range f.Sections {
 258                 if sect.Characteristics&pe.IMAGE_SCN_MEM_DISCARDABLE != 0 {
 259                         continue
 260                 }
 261
 262                 if sect.Characteristics&(pe.IMAGE_SCN_CNT_CODE|pe.IMAGE_SCN_CNT_INITIALIZED_DATA|pe.IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0 {
 263                         // This has been seen for .idata sections, which we
 264                         // want to ignore. See issues 5106 and 5273.
 265                         continue
 266                 }
 267
 268                 name := fmt.Sprintf("%s(%s)", pkg, sect.Name)
 269                 s := state.l.LookupOrCreateCgoExport(name, localSymVersion)
 270                 bld := l.MakeSymbolUpdater(s)
 271
 272                 switch sect.Characteristics & (pe.IMAGE_SCN_CNT_UNINITIALIZED_DATA | pe.IMAGE_SCN_CNT_INITIALIZED_DATA | pe.IMAGE_SCN_MEM_READ | pe.IMAGE_SCN_MEM_WRITE | pe.IMAGE_SCN_CNT_CODE | pe.IMAGE_SCN_MEM_EXECUTE) {
 273                 case pe.IMAGE_SCN_CNT_INITIALIZED_DATA | pe.IMAGE_SCN_MEM_READ: //.rdata
 274                         bld.SetType(sym.SRODATA)
 275
 276                 case pe.IMAGE_SCN_CNT_UNINITIALIZED_DATA | pe.IMAGE_SCN_MEM_READ | pe.IMAGE_SCN_MEM_WRITE: //.bss
 277                         bld.SetType(sym.SNOPTRBSS)
 278
 279                 case pe.IMAGE_SCN_CNT_INITIALIZED_DATA | pe.IMAGE_SCN_MEM_READ | pe.IMAGE_SCN_MEM_WRITE: //.data
 280                         bld.SetType(sym.SNOPTRDATA)
 281
 282                 case pe.IMAGE_SCN_CNT_CODE | pe.IMAGE_SCN_MEM_EXECUTE | pe.IMAGE_SCN_MEM_READ: //.text
 283                         bld.SetType(sym.STEXT)
 284
 285                 default:
 286                         return nil, nil, fmt.Errorf("unexpected flags %#06x for PE section %s", sect.Characteristics, sect.Name)
 287                 }
 288
 289                 if bld.Type() != sym.SNOPTRBSS {
 290                         data, err := sect.Data()
 291                         if err != nil {
 292                                 return nil, nil, err
 293                         }
 294                         state.sectdata[sect] = data
 295                         bld.SetData(data)
 296                 }
 297                 bld.SetSize(int64(sect.Size))
 298                 state.sectsyms[sect] = s
 299                 if sect.Name == ".rsrc" || strings.HasPrefix(sect.Name, ".rsrc$") {
 300                         rsrc = append(rsrc, s)
 301                 }
 302         }
 303
 304         // Make a prepass over the symbols to collect info about COMDAT symbols.
 305         if err := state.preprocessSymbols(); err != nil {
 306                 return nil, nil, err
 307         }
 308
 309         // load relocations
 310         for _, rsect := range f.Sections {
 311                 if _, found := state.sectsyms[rsect]; !found {
 312                         continue
 313                 }
 314                 if rsect.NumberOfRelocations == 0 {
 315                         continue
 316                 }
 317                 if rsect.Characteristics&pe.IMAGE_SCN_MEM_DISCARDABLE != 0 {
 318                         continue
 319                 }
 320                 if rsect.Characteristics&(pe.IMAGE_SCN_CNT_CODE|pe.IMAGE_SCN_CNT_INITIALIZED_DATA|pe.IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0 {
 321                         // This has been seen for .idata sections, which we
 322                         // want to ignore. See issues 5106 and 5273.
 323                         continue
 324                 }
 325
 326                 splitResources := strings.HasPrefix(rsect.Name, ".rsrc$")
 327                 sb := l.MakeSymbolUpdater(state.sectsyms[rsect])
 328                 for j, r := range rsect.Relocs {
 329                         if int(r.SymbolTableIndex) >= len(f.COFFSymbols) {
 330                                 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))
 331                         }
 332                         pesym := &f.COFFSymbols[r.SymbolTableIndex]
 333                         _, gosym, err := state.readpesym(pesym)
 334                         if err != nil {
 335                                 return nil, nil, err
 336                         }
 337                         if gosym == 0 {
 338                                 name, err := pesym.FullName(f.StringTable)
 339                                 if err != nil {
 340                                         name = string(pesym.Name[:])
 341                                 }
 342                                 return nil, nil, fmt.Errorf("reloc of invalid sym %s idx=%d type=%d", name, r.SymbolTableIndex, pesym.Type)
 343                         }
 344
 345                         rSym := gosym
 346                         rSize := uint8(4)
 347                         rOff := int32(r.VirtualAddress)
 348                         var rAdd int64
 349                         var rType objabi.RelocType
 350                         switch arch.Family {
 351                         default:
 352                                 return nil, nil, fmt.Errorf("%s: unsupported arch %v", pn, arch.Family)
 353                         case sys.I386, sys.AMD64:
 354                                 switch r.Type {
 355                                 default:
 356                                         return nil, nil, fmt.Errorf("%s: %v: unknown relocation type %v", pn, state.sectsyms[rsect], r.Type)
 357
 358                                 case IMAGE_REL_I386_REL32, IMAGE_REL_AMD64_REL32,
 359                                         IMAGE_REL_AMD64_ADDR32, // R_X86_64_PC32
 360                                         IMAGE_REL_AMD64_ADDR32NB:
 361                                         rType = objabi.R_PCREL
 362
 363                                         rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))
 364
 365                                 case IMAGE_REL_I386_DIR32NB, IMAGE_REL_I386_DIR32:
 366                                         rType = objabi.R_ADDR
 367
 368                                         // load addend from image
 369                                         rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))
 370
 371                                 case IMAGE_REL_AMD64_ADDR64: // R_X86_64_64
 372                                         rSize = 8
 373
 374                                         rType = objabi.R_ADDR
 375
 376                                         // load addend from image
 377                                         rAdd = int64(binary.LittleEndian.Uint64(state.sectdata[rsect][rOff:]))
 378                                 }
 379
 380                         case sys.ARM:
 381                                 switch r.Type {
 382                                 default:
 383                                         return nil, nil, fmt.Errorf("%s: %v: unknown ARM relocation type %v", pn, state.sectsyms[rsect], r.Type)
 384
 385                                 case IMAGE_REL_ARM_SECREL:
 386                                         rType = objabi.R_PCREL
 387
 388                                         rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))
 389
 390                                 case IMAGE_REL_ARM_ADDR32, IMAGE_REL_ARM_ADDR32NB:
 391                                         rType = objabi.R_ADDR
 392
 393                                         rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))
 394
 395                                 case IMAGE_REL_ARM_BRANCH24:
 396                                         rType = objabi.R_CALLARM
 397
 398                                         rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))
 399                                 }
 400
 401                         case sys.ARM64:
 402                                 switch r.Type {
 403                                 default:
 404                                         return nil, nil, fmt.Errorf("%s: %v: unknown ARM64 relocation type %v", pn, state.sectsyms[rsect], r.Type)
 405
 406                                 case IMAGE_REL_ARM64_ADDR32, IMAGE_REL_ARM64_ADDR32NB:
 407                                         rType = objabi.R_ADDR
 408
 409                                         rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))
 410                                 }
 411                         }
 412
 413                         // ld -r could generate multiple section symbols for the
 414                         // same section but with different values, we have to take
 415                         // that into account, or in the case of split resources,
 416                         // the section and its symbols are split into two sections.
 417                         if issect(pesym) || splitResources {
 418                                 rAdd += int64(pesym.Value)
 419                         }
 420
 421                         rel, _ := sb.AddRel(rType)
 422                         rel.SetOff(rOff)
 423                         rel.SetSiz(rSize)
 424                         rel.SetSym(rSym)
 425                         rel.SetAdd(rAdd)
 426                 }
 427
 428                 sb.SortRelocs()
 429         }
 430
 431         // enter sub-symbols into symbol table.
 432         for i, numaux := 0, 0; i < len(f.COFFSymbols); i += numaux + 1 {
 433                 pesym := &f.COFFSymbols[i]
 434
 435                 numaux = int(pesym.NumberOfAuxSymbols)
 436
 437                 name, err := pesym.FullName(f.StringTable)
 438                 if err != nil {
 439                         return nil, nil, err
 440                 }
 441                 if name == "" {
 442                         continue
 443                 }
 444                 if issect(pesym) {
 445                         continue
 446                 }
 447                 if int(pesym.SectionNumber) > len(f.Sections) {
 448                         continue
 449                 }
 450                 if pesym.SectionNumber == IMAGE_SYM_DEBUG {
 451                         continue
 452                 }
 453                 if pesym.SectionNumber == IMAGE_SYM_ABSOLUTE && bytes.Equal(pesym.Name[:], []byte("@feat.00")) {
 454                         // Microsoft's linker looks at whether all input objects have an empty
 455                         // section called @feat.00. If all of them do, then it enables SEH;
 456                         // otherwise it doesn't enable that feature. So, since around the Windows
 457                         // XP SP2 era, most tools that make PE objects just tack on that section,
 458                         // so that it won't gimp Microsoft's linker logic. Go doesn't support SEH,
 459                         // so in theory, none of this really matters to us. But actually, if the
 460                         // linker tries to ingest an object with @feat.00 -- which are produced by
 461                         // LLVM's resource compiler, for example -- it chokes because of the
 462                         // IMAGE_SYM_ABSOLUTE section that it doesn't know how to deal with. Since
 463                         // @feat.00 is just a marking anyway, skip IMAGE_SYM_ABSOLUTE sections that
 464                         // are called @feat.00.
 465                         continue
 466                 }
 467                 var sect *pe.Section
 468                 if pesym.SectionNumber > 0 {
 469                         sect = f.Sections[pesym.SectionNumber-1]
 470                         if _, found := state.sectsyms[sect]; !found {
 471                                 continue
 472                         }
 473                 }
 474
 475                 bld, s, err := state.readpesym(pesym)
 476                 if err != nil {
 477                         return nil, nil, err
 478                 }
 479
 480                 if pesym.SectionNumber == 0 { // extern
 481                         if l.SymType(s) == sym.SXREF && pesym.Value > 0 { // global data
 482                                 bld = makeUpdater(l, bld, s)
 483                                 bld.SetType(sym.SNOPTRDATA)
 484                                 bld.SetSize(int64(pesym.Value))
 485                         }
 486
 487                         continue
 488                 } else if pesym.SectionNumber > 0 && int(pesym.SectionNumber) <= len(f.Sections) {
 489                         sect = f.Sections[pesym.SectionNumber-1]
 490                         if _, found := state.sectsyms[sect]; !found {
 491                                 return nil, nil, fmt.Errorf("%s: %v: missing sect.sym", pn, s)
 492                         }
 493                 } else {
 494                         return nil, nil, fmt.Errorf("%s: %v: sectnum < 0!", pn, s)
 495                 }
 496
 497                 if sect == nil {
 498                         return nil, nil, nil
 499                 }
 500
 501                 // Check for COMDAT symbol.
 502                 if sz, ok1 := state.comdats[uint16(pesym.SectionNumber-1)]; ok1 {
 503                         if psz, ok2 := comdatDefinitions[l.SymName(s)]; ok2 {
 504                                 if sz == psz {
 505                                         //  OK to discard, we've seen an instance
 506                                         // already.
 507                                         continue
 508                                 }
 509                         }
 510                 }
 511                 if l.OuterSym(s) != 0 {
 512                         if l.AttrDuplicateOK(s) {
 513                                 continue
 514                         }
 515                         outerName := l.SymName(l.OuterSym(s))
 516                         sectName := l.SymName(state.sectsyms[sect])
 517                         return nil, nil, fmt.Errorf("%s: duplicate symbol reference: %s in both %s and %s", pn, l.SymName(s), outerName, sectName)
 518                 }
 519
 520                 bld = makeUpdater(l, bld, s)
 521                 sectsym := state.sectsyms[sect]
 522                 bld.SetType(l.SymType(sectsym))
 523                 l.AddInteriorSym(sectsym, s)
 524                 bld.SetValue(int64(pesym.Value))
 525                 bld.SetSize(4)
 526                 if l.SymType(sectsym) == sym.STEXT {
 527                         if bld.External() && !bld.DuplicateOK() {
 528                                 return nil, nil, fmt.Errorf("%s: duplicate symbol definition", l.SymName(s))
 529                         }
 530                         bld.SetExternal(true)
 531                 }
 532                 if sz, ok := state.comdats[uint16(pesym.SectionNumber-1)]; ok {
 533                         // This is a COMDAT definition. Record that we're picking
 534                         // this instance so that we can ignore future defs.
 535                         if _, ok := comdatDefinitions[l.SymName(s)]; ok {
 536                                 return nil, nil, fmt.Errorf("internal error: preexisting COMDAT definition for %q", name)
 537                         }
 538                         comdatDefinitions[l.SymName(s)] = sz
 539                 }
 540         }
 541
 542         // Sort outer lists by address, adding to textp.
 543         // This keeps textp in increasing address order.
 544         for _, sect := range f.Sections {
 545                 s := state.sectsyms[sect]
 546                 if s == 0 {
 547                         continue
 548                 }
 549                 l.SortSub(s)
 550                 importSymsState.secSyms = append(importSymsState.secSyms, s)
 551                 if l.SymType(s) == sym.STEXT {
 552                         for ; s != 0; s = l.SubSym(s) {
 553                                 if l.AttrOnList(s) {
 554                                         return nil, nil, fmt.Errorf("symbol %s listed multiple times", l.SymName(s))
 555                                 }
 556                                 l.SetAttrOnList(s, true)
 557                                 textp = append(textp, s)
 558                         }
 559                 }
 560         }
 561
 562         return textp, rsrc, nil
 563 }
 564
 565 // PostProcessImports works to resolve inconsistencies with DLL import
 566 // symbols; it is needed when building with more "modern" C compilers
 567 // with internal linkage.
 568 //
 569 // Background: DLL import symbols are data (SNOPTRDATA) symbols whose
 570 // name is of the form "__imp_XXX", which contain a pointer/reference
 571 // to symbol XXX. It's possible to have import symbols for both data
 572 // symbols ("__imp__fmode") and text symbols ("__imp_CreateEventA").
 573 // In some case import symbols are just references to some external
 574 // thing, and in other cases we see actual definitions of import
 575 // symbols when reading host objects.
 576 //
 577 // Previous versions of the linker would in most cases immediately
 578 // "forward" import symbol references, e.g. treat a references to
 579 // "__imp_XXX" a references to "XXX", however this doesn't work well
 580 // with more modern compilers, where you can sometimes see import
 581 // symbols that are defs (as opposed to external refs).
 582 //
 583 // The main actions taken below are to search for references to
 584 // SDYNIMPORT symbols in host object text/data sections and flag the
 585 // symbols for later fixup. When we see a reference to an import
 586 // symbol __imp_XYZ where XYZ corresponds to some SDYNIMPORT symbol,
 587 // we flag the symbol (via GOT setting) so that it can be redirected
 588 // to XYZ later in windynrelocsym. When we see a direct reference to
 589 // an SDYNIMPORT symbol XYZ, we also flag the symbol (via PLT setting)
 590 // to indicated that the reference will need to be redirected to a
 591 // stub.
 592 func PostProcessImports() error {
 593         ldr := importSymsState.l
 594         arch := importSymsState.arch
 595         keeprelocneeded := make(map[loader.Sym]loader.Sym)
 596         for _, s := range importSymsState.secSyms {
 597                 isText := ldr.SymType(s) == sym.STEXT
 598                 relocs := ldr.Relocs(s)
 599                 for i := 0; i < relocs.Count(); i++ {
 600                         r := relocs.At(i)
 601                         rs := r.Sym()
 602                         if ldr.SymType(rs) == sym.SDYNIMPORT {
 603                                 // Tag the symbol for later stub generation.
 604                                 ldr.SetPlt(rs, CreateImportStubPltToken)
 605                                 continue
 606                         }
 607                         isym, err := LookupBaseFromImport(rs, ldr, arch)
 608                         if err != nil {
 609                                 return err
 610                         }
 611                         if isym == 0 {
 612                                 continue
 613                         }
 614                         if ldr.SymType(isym) != sym.SDYNIMPORT {
 615                                 continue
 616                         }
 617                         // For non-text symbols, forward the reference from __imp_X to
 618                         // X immediately.
 619                         if !isText {
 620                                 r.SetSym(isym)
 621                                 continue
 622                         }
 623                         // Flag this imp symbol to be processed later in windynrelocsym.
 624                         ldr.SetGot(rs, RedirectToDynImportGotToken)
 625                         // Consistency check: should be no PLT token here.
 626                         splt := ldr.SymPlt(rs)
 627                         if splt != -1 {
 628                                 return fmt.Errorf("internal error: import symbol %q has invalid PLT setting %d", ldr.SymName(rs), splt)
 629                         }
 630                         // Flag for dummy relocation.
 631                         keeprelocneeded[rs] = isym
 632                 }
 633         }
 634         for k, v := range keeprelocneeded {
 635                 sb := ldr.MakeSymbolUpdater(k)
 636                 r, _ := sb.AddRel(objabi.R_KEEP)
 637                 r.SetSym(v)
 638         }
 639         importSymsState = nil
 640         return nil
 641 }
 642
 643 func issect(s *pe.COFFSymbol) bool {
 644         return s.StorageClass == IMAGE_SYM_CLASS_STATIC && s.Type == 0 && s.Name[0] == '.'
 645 }
 646
 647 func (state *peLoaderState) readpesym(pesym *pe.COFFSymbol) (*loader.SymbolBuilder, loader.Sym, error) {
 648         symname, err := pesym.FullName(state.f.StringTable)
 649         if err != nil {
 650                 return nil, 0, err
 651         }
 652         var name string
 653         if issect(pesym) {
 654                 name = state.l.SymName(state.sectsyms[state.f.Sections[pesym.SectionNumber-1]])
 655         } else {
 656                 name = symname
 657                 // A note on the "_main" exclusion below: the main routine
 658                 // defined by the Go runtime is named "_main", not "main", so
 659                 // when reading references to _main from a host object we want
 660                 // to avoid rewriting "_main" to "main" in this specific
 661                 // instance. See #issuecomment-1143698749 on #35006 for more
 662                 // details on this problem.
 663                 if state.arch.Family == sys.I386 && name[0] == '_' && name != "_main" && !strings.HasPrefix(name, "__imp_") {
 664                         name = name[1:] // _Name => Name
 665                 }
 666         }
 667
 668         // remove last @XXX
 669         if i := strings.LastIndex(name, "@"); i >= 0 {
 670                 name = name[:i]
 671         }
 672
 673         var s loader.Sym
 674         var bld *loader.SymbolBuilder
 675         // Microsoft's PE documentation is contradictory. It says that the symbol's complex type
 676         // is stored in the pesym.Type most significant byte, but MSVC, LLVM, and mingw store it
 677         // in the 4 high bits of the less significant byte.
 678         switch uint8(pesym.Type&0xf0) >> 4 {
 679         default:
 680                 return nil, 0, fmt.Errorf("%s: invalid symbol type %d", symname, pesym.Type)
 681
 682         case IMAGE_SYM_DTYPE_FUNCTION, IMAGE_SYM_DTYPE_NULL:
 683                 switch pesym.StorageClass {
 684                 case IMAGE_SYM_CLASS_EXTERNAL: //global
 685                         s = state.l.LookupOrCreateCgoExport(name, 0)
 686
 687                 case IMAGE_SYM_CLASS_NULL, IMAGE_SYM_CLASS_STATIC, IMAGE_SYM_CLASS_LABEL:
 688                         s = state.l.LookupOrCreateCgoExport(name, state.localSymVersion)
 689                         bld = makeUpdater(state.l, bld, s)
 690                         bld.SetDuplicateOK(true)
 691
 692                 default:
 693                         return nil, 0, fmt.Errorf("%s: invalid symbol binding %d", symname, pesym.StorageClass)
 694                 }
 695         }
 696
 697         if s != 0 && state.l.SymType(s) == 0 && (pesym.StorageClass != IMAGE_SYM_CLASS_STATIC || pesym.Value != 0) {
 698                 bld = makeUpdater(state.l, bld, s)
 699                 bld.SetType(sym.SXREF)
 700         }
 701
 702         return bld, s, nil
 703 }
 704
 705 // preprocessSymbols walks the COFF symbols for the PE file we're
 706 // reading and looks for cases where we have both a symbol definition
 707 // for "XXX" and an "__imp_XXX" symbol, recording these cases in a map
 708 // in the state struct. This information will be used in readpesym()
 709 // above to give such symbols special treatment. This function also
 710 // gathers information about COMDAT sections/symbols for later use
 711 // in readpesym().
 712 func (state *peLoaderState) preprocessSymbols() error {
 713
 714         // Locate comdat sections.
 715         state.comdats = make(map[uint16]int64)
 716         for i, s := range state.f.Sections {
 717                 if s.Characteristics&uint32(pe.IMAGE_SCN_LNK_COMDAT) != 0 {
 718                         state.comdats[uint16(i)] = int64(s.Size)
 719                 }
 720         }
 721
 722         // Examine symbol defs.
 723         for i, numaux := 0, 0; i < len(state.f.COFFSymbols); i += numaux + 1 {
 724                 pesym := &state.f.COFFSymbols[i]
 725                 numaux = int(pesym.NumberOfAuxSymbols)
 726                 if pesym.SectionNumber == 0 { // extern
 727                         continue
 728                 }
 729                 symname, err := pesym.FullName(state.f.StringTable)
 730                 if err != nil {
 731                         return err
 732                 }
 733                 if _, isc := state.comdats[uint16(pesym.SectionNumber-1)]; !isc {
 734                         continue
 735                 }
 736                 if pesym.StorageClass != uint8(IMAGE_SYM_CLASS_STATIC) {
 737                         continue
 738                 }
 739                 // This symbol corresponds to a COMDAT section. Read the
 740                 // aux data for it.
 741                 auxsymp, err := state.f.COFFSymbolReadSectionDefAux(i)
 742                 if err != nil {
 743                         return fmt.Errorf("unable to read aux info for section def symbol %d %s: pe.COFFSymbolReadComdatInfo returns %v", i, symname, err)
 744                 }
 745                 if auxsymp.Selection == pe.IMAGE_COMDAT_SELECT_SAME_SIZE {
 746                         // This is supported.
 747                 } else if auxsymp.Selection == pe.IMAGE_COMDAT_SELECT_ANY {
 748                         // Also supported.
 749                         state.comdats[uint16(pesym.SectionNumber-1)] = int64(-1)
 750                 } else {
 751                         // We don't support any of the other strategies at the
 752                         // moment. I suspect that we may need to also support
 753                         // "associative", we'll see.
 754                         return fmt.Errorf("internal error: unsupported COMDAT selection strategy found in path=%s sec=%d strategy=%d idx=%d, please file a bug", state.pn, auxsymp.SecNum, auxsymp.Selection, i)
 755                 }
 756         }
 757         return nil
 758 }
 759
 760 // LookupBaseFromImport examines the symbol "s" to see if it
 761 // corresponds to an import symbol (name of the form "__imp_XYZ") and
 762 // if so, it looks up the underlying target of the import symbol and
 763 // returns it. An error is returned if the symbol is of the form
 764 // "__imp_XYZ" but no XYZ can be found.
 765 func LookupBaseFromImport(s loader.Sym, ldr *loader.Loader, arch *sys.Arch) (loader.Sym, error) {
 766         sname := ldr.SymName(s)
 767         if !strings.HasPrefix(sname, "__imp_") {
 768                 return 0, nil
 769         }
 770         basename := sname[len("__imp_"):]
 771         if arch.Family == sys.I386 && basename[0] == '_' {
 772                 basename = basename[1:] // _Name => Name
 773         }
 774         isym := ldr.Lookup(basename, 0)
 775         if isym == 0 {
 776                 return 0, fmt.Errorf("internal error: import symbol %q with no underlying sym", sname)
 777         }
 778         return isym, nil
 779 }