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