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         // Loader and arch, for use in postprocessing.
 186         l    *loader.Loader
 187         arch *sys.Arch
 188 }
 189
 190 var importSymsState *peImportSymsState
 191
 192 func createImportSymsState(l *loader.Loader, arch *sys.Arch) {
 193         if importSymsState != nil {
 194                 return
 195         }
 196         importSymsState = &peImportSymsState{
 197                 l:    l,
 198                 arch: arch,
 199         }
 200 }
 201
 202 // peLoaderState holds various bits of useful state information needed
 203 // while loading a single PE object file.
 204 type peLoaderState struct {
 205         l               *loader.Loader
 206         arch            *sys.Arch
 207         f               *pe.File
 208         pn              string
 209         sectsyms        map[*pe.Section]loader.Sym
 210         comdats         map[uint16]int64 // key is section index, val is size
 211         sectdata        map[*pe.Section][]byte
 212         localSymVersion int
 213 }
 214
 215 // comdatDefinitions records the names of symbols for which we've
 216 // previously seen a definition in COMDAT. Key is symbol name, value
 217 // is symbol size (or -1 if we're using the "any" strategy).
 218 var comdatDefinitions map[string]int64
 219
 220 // Symbols contains the symbols that can be loaded from a PE file.
 221 type Symbols struct {
 222         Textp     []loader.Sym // text symbols
 223         Resources []loader.Sym // .rsrc section or set of .rsrc$xx sections
 224         PData     loader.Sym
 225         XData     loader.Sym
 226 }
 227
 228 // Load loads the PE file pn from input.
 229 // Symbols from the object file are created via the loader 'l'.
 230 func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, input *bio.Reader, pkg string, length int64, pn string) (*Symbols, 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         if comdatDefinitions == nil {
 241                 comdatDefinitions = make(map[string]int64)
 242         }
 243
 244         // Some input files are archives containing multiple of
 245         // object files, and pe.NewFile seeks to the start of
 246         // input file and get confused. Create section reader
 247         // to stop pe.NewFile looking before current position.
 248         sr := io.NewSectionReader((*peBiobuf)(input), input.Offset(), 1<<63-1)
 249
 250         // TODO: replace pe.NewFile with pe.Load (grep for "add Load function" in debug/pe for details)
 251         f, err := pe.NewFile(sr)
 252         if err != nil {
 253                 return nil, err
 254         }
 255         defer f.Close()
 256         state.f = f
 257
 258         var ls Symbols
 259
 260         // TODO return error if found .cormeta
 261
 262         // create symbols for mapped sections
 263         for _, sect := range f.Sections {
 264                 if sect.Characteristics&pe.IMAGE_SCN_MEM_DISCARDABLE != 0 {
 265                         continue
 266                 }
 267
 268                 if sect.Characteristics&(pe.IMAGE_SCN_CNT_CODE|pe.IMAGE_SCN_CNT_INITIALIZED_DATA|pe.IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0 {
 269                         // This has been seen for .idata sections, which we
 270                         // want to ignore. See issues 5106 and 5273.
 271                         continue
 272                 }
 273
 274                 name := fmt.Sprintf("%s(%s)", pkg, sect.Name)
 275                 s := state.l.LookupOrCreateCgoExport(name, localSymVersion)
 276                 bld := l.MakeSymbolUpdater(s)
 277
 278                 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) {
 279                 case pe.IMAGE_SCN_CNT_INITIALIZED_DATA | pe.IMAGE_SCN_MEM_READ: //.rdata
 280                         if issehsect(arch, sect) {
 281                                 bld.SetType(sym.SSEHSECT)
 282                                 bld.SetAlign(4)
 283                         } else {
 284                                 bld.SetType(sym.SRODATA)
 285                         }
 286
 287                 case pe.IMAGE_SCN_CNT_UNINITIALIZED_DATA | pe.IMAGE_SCN_MEM_READ | pe.IMAGE_SCN_MEM_WRITE: //.bss
 288                         bld.SetType(sym.SNOPTRBSS)
 289
 290                 case pe.IMAGE_SCN_CNT_INITIALIZED_DATA | pe.IMAGE_SCN_MEM_READ | pe.IMAGE_SCN_MEM_WRITE: //.data
 291                         bld.SetType(sym.SNOPTRDATA)
 292
 293                 case pe.IMAGE_SCN_CNT_CODE | pe.IMAGE_SCN_MEM_EXECUTE | pe.IMAGE_SCN_MEM_READ: //.text
 294                         bld.SetType(sym.STEXT)
 295
 296                 default:
 297                         return nil, fmt.Errorf("unexpected flags %#06x for PE section %s", sect.Characteristics, sect.Name)
 298                 }
 299
 300                 if bld.Type() != sym.SNOPTRBSS {
 301                         data, err := sect.Data()
 302                         if err != nil {
 303                                 return nil, err
 304                         }
 305                         state.sectdata[sect] = data
 306                         bld.SetData(data)
 307                 }
 308                 bld.SetSize(int64(sect.Size))
 309                 state.sectsyms[sect] = s
 310                 if sect.Name == ".rsrc" || strings.HasPrefix(sect.Name, ".rsrc$") {
 311                         ls.Resources = append(ls.Resources, s)
 312                 } else if bld.Type() == sym.SSEHSECT {
 313                         if sect.Name == ".pdata" {
 314                                 ls.PData = s
 315                         } else if sect.Name == ".xdata" {
 316                                 ls.XData = s
 317                         }
 318                 }
 319         }
 320
 321         // Make a prepass over the symbols to collect info about COMDAT symbols.
 322         if err := state.preprocessSymbols(); err != nil {
 323                 return nil, err
 324         }
 325
 326         // load relocations
 327         for _, rsect := range f.Sections {
 328                 if _, found := state.sectsyms[rsect]; !found {
 329                         continue
 330                 }
 331                 if rsect.NumberOfRelocations == 0 {
 332                         continue
 333                 }
 334                 if rsect.Characteristics&pe.IMAGE_SCN_MEM_DISCARDABLE != 0 {
 335                         continue
 336                 }
 337                 if rsect.Characteristics&(pe.IMAGE_SCN_CNT_CODE|pe.IMAGE_SCN_CNT_INITIALIZED_DATA|pe.IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0 {
 338                         // This has been seen for .idata sections, which we
 339                         // want to ignore. See issues 5106 and 5273.
 340                         continue
 341                 }
 342
 343                 splitResources := strings.HasPrefix(rsect.Name, ".rsrc$")
 344                 issehsect := issehsect(arch, rsect)
 345                 sb := l.MakeSymbolUpdater(state.sectsyms[rsect])
 346                 for j, r := range rsect.Relocs {
 347                         if int(r.SymbolTableIndex) >= len(f.COFFSymbols) {
 348                                 return nil, fmt.Errorf("relocation number %d symbol index idx=%d cannot be large then number of symbols %d", j, r.SymbolTableIndex, len(f.COFFSymbols))
 349                         }
 350                         pesym := &f.COFFSymbols[r.SymbolTableIndex]
 351                         _, gosym, err := state.readpesym(pesym)
 352                         if err != nil {
 353                                 return nil, err
 354                         }
 355                         if gosym == 0 {
 356                                 name, err := pesym.FullName(f.StringTable)
 357                                 if err != nil {
 358                                         name = string(pesym.Name[:])
 359                                 }
 360                                 return nil, fmt.Errorf("reloc of invalid sym %s idx=%d type=%d", name, r.SymbolTableIndex, pesym.Type)
 361                         }
 362
 363                         rSym := gosym
 364                         rSize := uint8(4)
 365                         rOff := int32(r.VirtualAddress)
 366                         var rAdd int64
 367                         var rType objabi.RelocType
 368                         switch arch.Family {
 369                         default:
 370                                 return nil, fmt.Errorf("%s: unsupported arch %v", pn, arch.Family)
 371                         case sys.I386, sys.AMD64:
 372                                 switch r.Type {
 373                                 default:
 374                                         return nil, fmt.Errorf("%s: %v: unknown relocation type %v", pn, state.sectsyms[rsect], r.Type)
 375
 376                                 case IMAGE_REL_I386_REL32, IMAGE_REL_AMD64_REL32,
 377                                         IMAGE_REL_AMD64_ADDR32, // R_X86_64_PC32
 378                                         IMAGE_REL_AMD64_ADDR32NB:
 379                                         if r.Type == IMAGE_REL_AMD64_ADDR32NB {
 380                                                 rType = objabi.R_PEIMAGEOFF
 381                                         } else {
 382                                                 rType = objabi.R_PCREL
 383                                         }
 384
 385                                         rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))
 386
 387                                 case IMAGE_REL_I386_DIR32NB, IMAGE_REL_I386_DIR32:
 388                                         if r.Type == IMAGE_REL_I386_DIR32NB {
 389                                                 rType = objabi.R_PEIMAGEOFF
 390                                         } else {
 391                                                 rType = objabi.R_ADDR
 392                                         }
 393
 394                                         // load addend from image
 395                                         rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))
 396
 397                                 case IMAGE_REL_AMD64_ADDR64: // R_X86_64_64
 398                                         rSize = 8
 399
 400                                         rType = objabi.R_ADDR
 401
 402                                         // load addend from image
 403                                         rAdd = int64(binary.LittleEndian.Uint64(state.sectdata[rsect][rOff:]))
 404                                 }
 405
 406                         case sys.ARM:
 407                                 switch r.Type {
 408                                 default:
 409                                         return nil, fmt.Errorf("%s: %v: unknown ARM relocation type %v", pn, state.sectsyms[rsect], r.Type)
 410
 411                                 case IMAGE_REL_ARM_SECREL:
 412                                         rType = objabi.R_PCREL
 413
 414                                         rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))
 415
 416                                 case IMAGE_REL_ARM_ADDR32, IMAGE_REL_ARM_ADDR32NB:
 417                                         if r.Type == IMAGE_REL_ARM_ADDR32NB {
 418                                                 rType = objabi.R_PEIMAGEOFF
 419                                         } else {
 420                                                 rType = objabi.R_ADDR
 421                                         }
 422
 423                                         rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))
 424
 425                                 case IMAGE_REL_ARM_BRANCH24:
 426                                         rType = objabi.R_CALLARM
 427
 428                                         rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))
 429                                 }
 430
 431                         case sys.ARM64:
 432                                 switch r.Type {
 433                                 default:
 434                                         return nil, fmt.Errorf("%s: %v: unknown ARM64 relocation type %v", pn, state.sectsyms[rsect], r.Type)
 435
 436                                 case IMAGE_REL_ARM64_ADDR32, IMAGE_REL_ARM64_ADDR32NB:
 437                                         if r.Type == IMAGE_REL_ARM64_ADDR32NB {
 438                                                 rType = objabi.R_PEIMAGEOFF
 439                                         } else {
 440                                                 rType = objabi.R_ADDR
 441                                         }
 442
 443                                         rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))
 444                                 }
 445                         }
 446
 447                         // ld -r could generate multiple section symbols for the
 448                         // same section but with different values, we have to take
 449                         // that into account, or in the case of split resources,
 450                         // the section and its symbols are split into two sections.
 451                         if issect(pesym) || splitResources {
 452                                 rAdd += int64(pesym.Value)
 453                         }
 454                         if issehsect {
 455                                 // .pdata and .xdata sections can contain records
 456                                 // associated to functions that won't be used in
 457                                 // the final binary, in which case the relocation
 458                                 // target symbol won't be reachable.
 459                                 rType |= objabi.R_WEAK
 460                         }
 461
 462                         rel, _ := sb.AddRel(rType)
 463                         rel.SetOff(rOff)
 464                         rel.SetSiz(rSize)
 465                         rel.SetSym(rSym)
 466                         rel.SetAdd(rAdd)
 467
 468                 }
 469
 470                 sb.SortRelocs()
 471         }
 472
 473         // enter sub-symbols into symbol table.
 474         for i, numaux := 0, 0; i < len(f.COFFSymbols); i += numaux + 1 {
 475                 pesym := &f.COFFSymbols[i]
 476
 477                 numaux = int(pesym.NumberOfAuxSymbols)
 478
 479                 name, err := pesym.FullName(f.StringTable)
 480                 if err != nil {
 481                         return nil, err
 482                 }
 483                 if name == "" {
 484                         continue
 485                 }
 486                 if issect(pesym) {
 487                         continue
 488                 }
 489                 if int(pesym.SectionNumber) > len(f.Sections) {
 490                         continue
 491                 }
 492                 if pesym.SectionNumber == IMAGE_SYM_DEBUG {
 493                         continue
 494                 }
 495                 if pesym.SectionNumber == IMAGE_SYM_ABSOLUTE && bytes.Equal(pesym.Name[:], []byte("@feat.00")) {
 496                         // Microsoft's linker looks at whether all input objects have an empty
 497                         // section called @feat.00. If all of them do, then it enables SEH;
 498                         // otherwise it doesn't enable that feature. So, since around the Windows
 499                         // XP SP2 era, most tools that make PE objects just tack on that section,
 500                         // so that it won't gimp Microsoft's linker logic. Go doesn't support SEH,
 501                         // so in theory, none of this really matters to us. But actually, if the
 502                         // linker tries to ingest an object with @feat.00 -- which are produced by
 503                         // LLVM's resource compiler, for example -- it chokes because of the
 504                         // IMAGE_SYM_ABSOLUTE section that it doesn't know how to deal with. Since
 505                         // @feat.00 is just a marking anyway, skip IMAGE_SYM_ABSOLUTE sections that
 506                         // are called @feat.00.
 507                         continue
 508                 }
 509                 var sect *pe.Section
 510                 if pesym.SectionNumber > 0 {
 511                         sect = f.Sections[pesym.SectionNumber-1]
 512                         if _, found := state.sectsyms[sect]; !found {
 513                                 continue
 514                         }
 515                 }
 516
 517                 bld, s, err := state.readpesym(pesym)
 518                 if err != nil {
 519                         return nil, err
 520                 }
 521
 522                 if pesym.SectionNumber == 0 { // extern
 523                         if l.SymType(s) == sym.SXREF && pesym.Value > 0 { // global data
 524                                 bld = makeUpdater(l, bld, s)
 525                                 bld.SetType(sym.SNOPTRDATA)
 526                                 bld.SetSize(int64(pesym.Value))
 527                         }
 528
 529                         continue
 530                 } else if pesym.SectionNumber > 0 && int(pesym.SectionNumber) <= len(f.Sections) {
 531                         sect = f.Sections[pesym.SectionNumber-1]
 532                         if _, found := state.sectsyms[sect]; !found {
 533                                 return nil, fmt.Errorf("%s: %v: missing sect.sym", pn, s)
 534                         }
 535                 } else {
 536                         return nil, fmt.Errorf("%s: %v: sectnum < 0!", pn, s)
 537                 }
 538
 539                 if sect == nil {
 540                         return nil, nil
 541                 }
 542
 543                 // Check for COMDAT symbol.
 544                 if sz, ok1 := state.comdats[uint16(pesym.SectionNumber-1)]; ok1 {
 545                         if psz, ok2 := comdatDefinitions[l.SymName(s)]; ok2 {
 546                                 if sz == psz {
 547                                         //  OK to discard, we've seen an instance
 548                                         // already.
 549                                         continue
 550                                 }
 551                         }
 552                 }
 553                 if l.OuterSym(s) != 0 {
 554                         if l.AttrDuplicateOK(s) {
 555                                 continue
 556                         }
 557                         outerName := l.SymName(l.OuterSym(s))
 558                         sectName := l.SymName(state.sectsyms[sect])
 559                         return nil, fmt.Errorf("%s: duplicate symbol reference: %s in both %s and %s", pn, l.SymName(s), outerName, sectName)
 560                 }
 561
 562                 bld = makeUpdater(l, bld, s)
 563                 sectsym := state.sectsyms[sect]
 564                 bld.SetType(l.SymType(sectsym))
 565                 l.AddInteriorSym(sectsym, s)
 566                 bld.SetValue(int64(pesym.Value))
 567                 bld.SetSize(4)
 568                 if l.SymType(sectsym) == sym.STEXT {
 569                         if bld.External() && !bld.DuplicateOK() {
 570                                 return nil, fmt.Errorf("%s: duplicate symbol definition", l.SymName(s))
 571                         }
 572                         bld.SetExternal(true)
 573                 }
 574                 if sz, ok := state.comdats[uint16(pesym.SectionNumber-1)]; ok {
 575                         // This is a COMDAT definition. Record that we're picking
 576                         // this instance so that we can ignore future defs.
 577                         if _, ok := comdatDefinitions[l.SymName(s)]; ok {
 578                                 return nil, fmt.Errorf("internal error: preexisting COMDAT definition for %q", name)
 579                         }
 580                         comdatDefinitions[l.SymName(s)] = sz
 581                 }
 582         }
 583
 584         // Sort outer lists by address, adding to textp.
 585         // This keeps textp in increasing address order.
 586         for _, sect := range f.Sections {
 587                 s := state.sectsyms[sect]
 588                 if s == 0 {
 589                         continue
 590                 }
 591                 l.SortSub(s)
 592                 importSymsState.secSyms = append(importSymsState.secSyms, s)
 593                 if l.SymType(s) == sym.STEXT {
 594                         for ; s != 0; s = l.SubSym(s) {
 595                                 if l.AttrOnList(s) {
 596                                         return nil, fmt.Errorf("symbol %s listed multiple times", l.SymName(s))
 597                                 }
 598                                 l.SetAttrOnList(s, true)
 599                                 ls.Textp = append(ls.Textp, s)
 600                         }
 601                 }
 602         }
 603
 604         if ls.PData != 0 {
 605                 processSEH(l, arch, ls.PData, ls.XData)
 606         }
 607
 608         return &ls, nil
 609 }
 610
 611 // PostProcessImports works to resolve inconsistencies with DLL import
 612 // symbols; it is needed when building with more "modern" C compilers
 613 // with internal linkage.
 614 //
 615 // Background: DLL import symbols are data (SNOPTRDATA) symbols whose
 616 // name is of the form "__imp_XXX", which contain a pointer/reference
 617 // to symbol XXX. It's possible to have import symbols for both data
 618 // symbols ("__imp__fmode") and text symbols ("__imp_CreateEventA").
 619 // In some case import symbols are just references to some external
 620 // thing, and in other cases we see actual definitions of import
 621 // symbols when reading host objects.
 622 //
 623 // Previous versions of the linker would in most cases immediately
 624 // "forward" import symbol references, e.g. treat a references to
 625 // "__imp_XXX" a references to "XXX", however this doesn't work well
 626 // with more modern compilers, where you can sometimes see import
 627 // symbols that are defs (as opposed to external refs).
 628 //
 629 // The main actions taken below are to search for references to
 630 // SDYNIMPORT symbols in host object text/data sections and flag the
 631 // symbols for later fixup. When we see a reference to an import
 632 // symbol __imp_XYZ where XYZ corresponds to some SDYNIMPORT symbol,
 633 // we flag the symbol (via GOT setting) so that it can be redirected
 634 // to XYZ later in windynrelocsym. When we see a direct reference to
 635 // an SDYNIMPORT symbol XYZ, we also flag the symbol (via PLT setting)
 636 // to indicated that the reference will need to be redirected to a
 637 // stub.
 638 func PostProcessImports() error {
 639         ldr := importSymsState.l
 640         arch := importSymsState.arch
 641         keeprelocneeded := make(map[loader.Sym]loader.Sym)
 642         for _, s := range importSymsState.secSyms {
 643                 isText := ldr.SymType(s) == sym.STEXT
 644                 relocs := ldr.Relocs(s)
 645                 for i := 0; i < relocs.Count(); i++ {
 646                         r := relocs.At(i)
 647                         rs := r.Sym()
 648                         if ldr.SymType(rs) == sym.SDYNIMPORT {
 649                                 // Tag the symbol for later stub generation.
 650                                 ldr.SetPlt(rs, CreateImportStubPltToken)
 651                                 continue
 652                         }
 653                         isym, err := LookupBaseFromImport(rs, ldr, arch)
 654                         if err != nil {
 655                                 return err
 656                         }
 657                         if isym == 0 {
 658                                 continue
 659                         }
 660                         if ldr.SymType(isym) != sym.SDYNIMPORT {
 661                                 continue
 662                         }
 663                         // For non-text symbols, forward the reference from __imp_X to
 664                         // X immediately.
 665                         if !isText {
 666                                 r.SetSym(isym)
 667                                 continue
 668                         }
 669                         // Flag this imp symbol to be processed later in windynrelocsym.
 670                         ldr.SetGot(rs, RedirectToDynImportGotToken)
 671                         // Consistency check: should be no PLT token here.
 672                         splt := ldr.SymPlt(rs)
 673                         if splt != -1 {
 674                                 return fmt.Errorf("internal error: import symbol %q has invalid PLT setting %d", ldr.SymName(rs), splt)
 675                         }
 676                         // Flag for dummy relocation.
 677                         keeprelocneeded[rs] = isym
 678                 }
 679         }
 680         for k, v := range keeprelocneeded {
 681                 sb := ldr.MakeSymbolUpdater(k)
 682                 r, _ := sb.AddRel(objabi.R_KEEP)
 683                 r.SetSym(v)
 684         }
 685         importSymsState = nil
 686         return nil
 687 }
 688
 689 func issehsect(arch *sys.Arch, s *pe.Section) bool {
 690         return arch.Family == sys.AMD64 && (s.Name == ".pdata" || s.Name == ".xdata")
 691 }
 692
 693 func issect(s *pe.COFFSymbol) bool {
 694         return s.StorageClass == IMAGE_SYM_CLASS_STATIC && s.Type == 0 && s.Name[0] == '.'
 695 }
 696
 697 func (state *peLoaderState) readpesym(pesym *pe.COFFSymbol) (*loader.SymbolBuilder, loader.Sym, error) {
 698         symname, err := pesym.FullName(state.f.StringTable)
 699         if err != nil {
 700                 return nil, 0, err
 701         }
 702         var name string
 703         if issect(pesym) {
 704                 name = state.l.SymName(state.sectsyms[state.f.Sections[pesym.SectionNumber-1]])
 705         } else {
 706                 name = symname
 707                 // A note on the "_main" exclusion below: the main routine
 708                 // defined by the Go runtime is named "_main", not "main", so
 709                 // when reading references to _main from a host object we want
 710                 // to avoid rewriting "_main" to "main" in this specific
 711                 // instance. See #issuecomment-1143698749 on #35006 for more
 712                 // details on this problem.
 713                 if state.arch.Family == sys.I386 && name[0] == '_' && name != "_main" && !strings.HasPrefix(name, "__imp_") {
 714                         name = name[1:] // _Name => Name
 715                 }
 716         }
 717
 718         // remove last @XXX
 719         if i := strings.LastIndex(name, "@"); i >= 0 {
 720                 name = name[:i]
 721         }
 722
 723         var s loader.Sym
 724         var bld *loader.SymbolBuilder
 725         // Microsoft's PE documentation is contradictory. It says that the symbol's complex type
 726         // is stored in the pesym.Type most significant byte, but MSVC, LLVM, and mingw store it
 727         // in the 4 high bits of the less significant byte.
 728         switch uint8(pesym.Type&0xf0) >> 4 {
 729         default:
 730                 return nil, 0, fmt.Errorf("%s: invalid symbol type %d", symname, pesym.Type)
 731
 732         case IMAGE_SYM_DTYPE_FUNCTION, IMAGE_SYM_DTYPE_NULL:
 733                 switch pesym.StorageClass {
 734                 case IMAGE_SYM_CLASS_EXTERNAL: //global
 735                         s = state.l.LookupOrCreateCgoExport(name, 0)
 736
 737                 case IMAGE_SYM_CLASS_NULL, IMAGE_SYM_CLASS_STATIC, IMAGE_SYM_CLASS_LABEL:
 738                         s = state.l.LookupOrCreateCgoExport(name, state.localSymVersion)
 739                         bld = makeUpdater(state.l, bld, s)
 740                         bld.SetDuplicateOK(true)
 741
 742                 default:
 743                         return nil, 0, fmt.Errorf("%s: invalid symbol binding %d", symname, pesym.StorageClass)
 744                 }
 745         }
 746
 747         if s != 0 && state.l.SymType(s) == 0 && (pesym.StorageClass != IMAGE_SYM_CLASS_STATIC || pesym.Value != 0) {
 748                 bld = makeUpdater(state.l, bld, s)
 749                 bld.SetType(sym.SXREF)
 750         }
 751
 752         return bld, s, nil
 753 }
 754
 755 // preprocessSymbols walks the COFF symbols for the PE file we're
 756 // reading and looks for cases where we have both a symbol definition
 757 // for "XXX" and an "__imp_XXX" symbol, recording these cases in a map
 758 // in the state struct. This information will be used in readpesym()
 759 // above to give such symbols special treatment. This function also
 760 // gathers information about COMDAT sections/symbols for later use
 761 // in readpesym().
 762 func (state *peLoaderState) preprocessSymbols() error {
 763
 764         // Locate comdat sections.
 765         state.comdats = make(map[uint16]int64)
 766         for i, s := range state.f.Sections {
 767                 if s.Characteristics&uint32(pe.IMAGE_SCN_LNK_COMDAT) != 0 {
 768                         state.comdats[uint16(i)] = int64(s.Size)
 769                 }
 770         }
 771
 772         // Examine symbol defs.
 773         for i, numaux := 0, 0; i < len(state.f.COFFSymbols); i += numaux + 1 {
 774                 pesym := &state.f.COFFSymbols[i]
 775                 numaux = int(pesym.NumberOfAuxSymbols)
 776                 if pesym.SectionNumber == 0 { // extern
 777                         continue
 778                 }
 779                 symname, err := pesym.FullName(state.f.StringTable)
 780                 if err != nil {
 781                         return err
 782                 }
 783                 if _, isc := state.comdats[uint16(pesym.SectionNumber-1)]; !isc {
 784                         continue
 785                 }
 786                 if pesym.StorageClass != uint8(IMAGE_SYM_CLASS_STATIC) {
 787                         continue
 788                 }
 789                 // This symbol corresponds to a COMDAT section. Read the
 790                 // aux data for it.
 791                 auxsymp, err := state.f.COFFSymbolReadSectionDefAux(i)
 792                 if err != nil {
 793                         return fmt.Errorf("unable to read aux info for section def symbol %d %s: pe.COFFSymbolReadComdatInfo returns %v", i, symname, err)
 794                 }
 795                 if auxsymp.Selection == pe.IMAGE_COMDAT_SELECT_SAME_SIZE {
 796                         // This is supported.
 797                 } else if auxsymp.Selection == pe.IMAGE_COMDAT_SELECT_ANY {
 798                         // Also supported.
 799                         state.comdats[uint16(pesym.SectionNumber-1)] = int64(-1)
 800                 } else {
 801                         // We don't support any of the other strategies at the
 802                         // moment. I suspect that we may need to also support
 803                         // "associative", we'll see.
 804                         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)
 805                 }
 806         }
 807         return nil
 808 }
 809
 810 // LookupBaseFromImport examines the symbol "s" to see if it
 811 // corresponds to an import symbol (name of the form "__imp_XYZ") and
 812 // if so, it looks up the underlying target of the import symbol and
 813 // returns it. An error is returned if the symbol is of the form
 814 // "__imp_XYZ" but no XYZ can be found.
 815 func LookupBaseFromImport(s loader.Sym, ldr *loader.Loader, arch *sys.Arch) (loader.Sym, error) {
 816         sname := ldr.SymName(s)
 817         if !strings.HasPrefix(sname, "__imp_") {
 818                 return 0, nil
 819         }
 820         basename := sname[len("__imp_"):]
 821         if arch.Family == sys.I386 && basename[0] == '_' {
 822                 basename = basename[1:] // _Name => Name
 823         }
 824         isym := ldr.Lookup(basename, 0)
 825         if isym == 0 {
 826                 return 0, fmt.Errorf("internal error: import symbol %q with no underlying sym", sname)
 827         }
 828         return isym, nil
 829 }