src/cmd/link/internal/loadpe/ldpe.go - go - Git at Google

 // Copyright 2010 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 // Package loadpe implements a PE/COFF file reader.
 package loadpe

 import (
 	"bytes"
 	"cmd/internal/bio"
 	"cmd/internal/objabi"
 	"cmd/internal/sys"
 	"cmd/link/internal/loader"
 	"cmd/link/internal/sym"
 	"debug/pe"
 	"encoding/binary"
 	"errors"
 	"fmt"
 	"io"
 	"strings"
 )

 const (
 	// TODO: the Microsoft doco says IMAGE_SYM_DTYPE_ARRAY is 3 (same with IMAGE_SYM_DTYPE_POINTER and IMAGE_SYM_DTYPE_FUNCTION)
 	IMAGE_SYM_UNDEFINED              = 0
 	IMAGE_SYM_ABSOLUTE               = -1
 	IMAGE_SYM_DEBUG                  = -2
 	IMAGE_SYM_TYPE_NULL              = 0
 	IMAGE_SYM_TYPE_VOID              = 1
 	IMAGE_SYM_TYPE_CHAR              = 2
 	IMAGE_SYM_TYPE_SHORT             = 3
 	IMAGE_SYM_TYPE_INT               = 4
 	IMAGE_SYM_TYPE_LONG              = 5
 	IMAGE_SYM_TYPE_FLOAT             = 6
 	IMAGE_SYM_TYPE_DOUBLE            = 7
 	IMAGE_SYM_TYPE_STRUCT            = 8
 	IMAGE_SYM_TYPE_UNION             = 9
 	IMAGE_SYM_TYPE_ENUM              = 10
 	IMAGE_SYM_TYPE_MOE               = 11
 	IMAGE_SYM_TYPE_BYTE              = 12
 	IMAGE_SYM_TYPE_WORD              = 13
 	IMAGE_SYM_TYPE_UINT              = 14
 	IMAGE_SYM_TYPE_DWORD             = 15
 	IMAGE_SYM_TYPE_PCODE             = 32768
 	IMAGE_SYM_DTYPE_NULL             = 0
 	IMAGE_SYM_DTYPE_POINTER          = 0x10
 	IMAGE_SYM_DTYPE_FUNCTION         = 0x20
 	IMAGE_SYM_DTYPE_ARRAY            = 0x30
 	IMAGE_SYM_CLASS_END_OF_FUNCTION  = -1
 	IMAGE_SYM_CLASS_NULL             = 0
 	IMAGE_SYM_CLASS_AUTOMATIC        = 1
 	IMAGE_SYM_CLASS_EXTERNAL         = 2
 	IMAGE_SYM_CLASS_STATIC           = 3
 	IMAGE_SYM_CLASS_REGISTER         = 4
 	IMAGE_SYM_CLASS_EXTERNAL_DEF     = 5
 	IMAGE_SYM_CLASS_LABEL            = 6
 	IMAGE_SYM_CLASS_UNDEFINED_LABEL  = 7
 	IMAGE_SYM_CLASS_MEMBER_OF_STRUCT = 8
 	IMAGE_SYM_CLASS_ARGUMENT         = 9
 	IMAGE_SYM_CLASS_STRUCT_TAG       = 10
 	IMAGE_SYM_CLASS_MEMBER_OF_UNION  = 11
 	IMAGE_SYM_CLASS_UNION_TAG        = 12
 	IMAGE_SYM_CLASS_TYPE_DEFINITION  = 13
 	IMAGE_SYM_CLASS_UNDEFINED_STATIC = 14
 	IMAGE_SYM_CLASS_ENUM_TAG         = 15
 	IMAGE_SYM_CLASS_MEMBER_OF_ENUM   = 16
 	IMAGE_SYM_CLASS_REGISTER_PARAM   = 17
 	IMAGE_SYM_CLASS_BIT_FIELD        = 18
 	IMAGE_SYM_CLASS_FAR_EXTERNAL     = 68 /* Not in PECOFF v8 spec */
 	IMAGE_SYM_CLASS_BLOCK            = 100
 	IMAGE_SYM_CLASS_FUNCTION         = 101
 	IMAGE_SYM_CLASS_END_OF_STRUCT    = 102
 	IMAGE_SYM_CLASS_FILE             = 103
 	IMAGE_SYM_CLASS_SECTION          = 104
 	IMAGE_SYM_CLASS_WEAK_EXTERNAL    = 105
 	IMAGE_SYM_CLASS_CLR_TOKEN        = 107
 	IMAGE_REL_I386_ABSOLUTE          = 0x0000
 	IMAGE_REL_I386_DIR16             = 0x0001
 	IMAGE_REL_I386_REL16             = 0x0002
 	IMAGE_REL_I386_DIR32             = 0x0006
 	IMAGE_REL_I386_DIR32NB           = 0x0007
 	IMAGE_REL_I386_SEG12             = 0x0009
 	IMAGE_REL_I386_SECTION           = 0x000A
 	IMAGE_REL_I386_SECREL            = 0x000B
 	IMAGE_REL_I386_TOKEN             = 0x000C
 	IMAGE_REL_I386_SECREL7           = 0x000D
 	IMAGE_REL_I386_REL32             = 0x0014
 	IMAGE_REL_AMD64_ABSOLUTE         = 0x0000
 	IMAGE_REL_AMD64_ADDR64           = 0x0001
 	IMAGE_REL_AMD64_ADDR32           = 0x0002
 	IMAGE_REL_AMD64_ADDR32NB         = 0x0003
 	IMAGE_REL_AMD64_REL32            = 0x0004
 	IMAGE_REL_AMD64_REL32_1          = 0x0005
 	IMAGE_REL_AMD64_REL32_2          = 0x0006
 	IMAGE_REL_AMD64_REL32_3          = 0x0007
 	IMAGE_REL_AMD64_REL32_4          = 0x0008
 	IMAGE_REL_AMD64_REL32_5          = 0x0009
 	IMAGE_REL_AMD64_SECTION          = 0x000A
 	IMAGE_REL_AMD64_SECREL           = 0x000B
 	IMAGE_REL_AMD64_SECREL7          = 0x000C
 	IMAGE_REL_AMD64_TOKEN            = 0x000D
 	IMAGE_REL_AMD64_SREL32           = 0x000E
 	IMAGE_REL_AMD64_PAIR             = 0x000F
 	IMAGE_REL_AMD64_SSPAN32          = 0x0010
 	IMAGE_REL_ARM_ABSOLUTE           = 0x0000
 	IMAGE_REL_ARM_ADDR32             = 0x0001
 	IMAGE_REL_ARM_ADDR32NB           = 0x0002
 	IMAGE_REL_ARM_BRANCH24           = 0x0003
 	IMAGE_REL_ARM_BRANCH11           = 0x0004
 	IMAGE_REL_ARM_SECTION            = 0x000E
 	IMAGE_REL_ARM_SECREL             = 0x000F
 	IMAGE_REL_ARM_MOV32              = 0x0010
 	IMAGE_REL_THUMB_MOV32            = 0x0011
 	IMAGE_REL_THUMB_BRANCH20         = 0x0012
 	IMAGE_REL_THUMB_BRANCH24         = 0x0014
 	IMAGE_REL_THUMB_BLX23            = 0x0015
 	IMAGE_REL_ARM_PAIR               = 0x0016
 	IMAGE_REL_ARM64_ABSOLUTE         = 0x0000
 	IMAGE_REL_ARM64_ADDR32           = 0x0001
 	IMAGE_REL_ARM64_ADDR32NB         = 0x0002
 	IMAGE_REL_ARM64_BRANCH26         = 0x0003
 	IMAGE_REL_ARM64_PAGEBASE_REL21   = 0x0004
 	IMAGE_REL_ARM64_REL21            = 0x0005
 	IMAGE_REL_ARM64_PAGEOFFSET_12A   = 0x0006
 	IMAGE_REL_ARM64_PAGEOFFSET_12L   = 0x0007
 	IMAGE_REL_ARM64_SECREL           = 0x0008
 	IMAGE_REL_ARM64_SECREL_LOW12A    = 0x0009
 	IMAGE_REL_ARM64_SECREL_HIGH12A   = 0x000A
 	IMAGE_REL_ARM64_SECREL_LOW12L    = 0x000B
 	IMAGE_REL_ARM64_TOKEN            = 0x000C
 	IMAGE_REL_ARM64_SECTION          = 0x000D
 	IMAGE_REL_ARM64_ADDR64           = 0x000E
 	IMAGE_REL_ARM64_BRANCH19         = 0x000F
 	IMAGE_REL_ARM64_BRANCH14         = 0x0010
 	IMAGE_REL_ARM64_REL32            = 0x0011
 )

 // TODO(brainman): maybe just add ReadAt method to bio.Reader instead of creating peBiobuf

 // peBiobuf makes bio.Reader look like io.ReaderAt.
 type peBiobuf bio.Reader

 func (f *peBiobuf) ReadAt(p []byte, off int64) (int, error) {
 	ret := ((*bio.Reader)(f)).MustSeek(off, 0)
 	if ret < 0 {
 		return 0, errors.New("fail to seek")
 	}
 	n, err := f.Read(p)
 	if err != nil {
 		return 0, err
 	}
 	return n, nil
 }

 // makeUpdater creates a loader.SymbolBuilder if one hasn't been created previously.
 // 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.
 func makeUpdater(l *loader.Loader, bld *loader.SymbolBuilder, s loader.Sym) *loader.SymbolBuilder {
 	if bld != nil {
 		return bld
 	}
 	bld = l.MakeSymbolUpdater(s)
 	return bld
 }

 // peLoaderState holds various bits of useful state information needed
 // while loading a PE object file.
 type peLoaderState struct {
 	l               *loader.Loader
 	arch            *sys.Arch
 	f               *pe.File
 	pn              string
 	sectsyms        map[*pe.Section]loader.Sym
 	defWithImp      map[string]struct{}
 	comdats         map[uint16]int64 // key is section index, val is size
 	sectdata        map[*pe.Section][]byte
 	localSymVersion int
 }

 // comdatDefinitions records the names of symbols for which we've
 // previously seen a definition in COMDAT. Key is symbol name, value
 // is symbol size (or -1 if we're using the "any" strategy).
 var comdatDefinitions = make(map[string]int64)

 // Load loads the PE file pn from input.
 // Symbols are written into syms, and a slice of the text symbols is returned.
 // If an .rsrc section or set of .rsrc$xx sections is found, its symbols are
 // returned as rsrc.
 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) {
 	state := &peLoaderState{
 		l:               l,
 		arch:            arch,
 		sectsyms:        make(map[*pe.Section]loader.Sym),
 		sectdata:        make(map[*pe.Section][]byte),
 		localSymVersion: localSymVersion,
 		pn:              pn,
 	}

 	// Some input files are archives containing multiple of
 	// object files, and pe.NewFile seeks to the start of
 	// input file and get confused. Create section reader
 	// to stop pe.NewFile looking before current position.
 	sr := io.NewSectionReader((*peBiobuf)(input), input.Offset(), 1<<63-1)

 	// TODO: replace pe.NewFile with pe.Load (grep for "add Load function" in debug/pe for details)
 	f, err := pe.NewFile(sr)
 	if err != nil {
 		return nil, nil, err
 	}
 	defer f.Close()
 	state.f = f

 	// TODO return error if found .cormeta

 	// create symbols for mapped sections
 	for _, sect := range f.Sections {
 		if sect.Characteristics&pe.IMAGE_SCN_MEM_DISCARDABLE != 0 {
 			continue
 		}

 		if sect.Characteristics&(pe.IMAGE_SCN_CNT_CODE|pe.IMAGE_SCN_CNT_INITIALIZED_DATA|pe.IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0 {
 			// This has been seen for .idata sections, which we
 			// want to ignore. See issues 5106 and 5273.
 			continue
 		}

 		name := fmt.Sprintf("%s(%s)", pkg, sect.Name)
 		s := state.l.LookupOrCreateCgoExport(name, localSymVersion)
 		bld := l.MakeSymbolUpdater(s)

 		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) {
 		case pe.IMAGE_SCN_CNT_INITIALIZED_DATA | pe.IMAGE_SCN_MEM_READ: //.rdata
 			bld.SetType(sym.SRODATA)

 		case pe.IMAGE_SCN_CNT_UNINITIALIZED_DATA | pe.IMAGE_SCN_MEM_READ | pe.IMAGE_SCN_MEM_WRITE: //.bss
 			bld.SetType(sym.SNOPTRBSS)

 		case pe.IMAGE_SCN_CNT_INITIALIZED_DATA | pe.IMAGE_SCN_MEM_READ | pe.IMAGE_SCN_MEM_WRITE: //.data
 			bld.SetType(sym.SNOPTRDATA)

 		case pe.IMAGE_SCN_CNT_CODE | pe.IMAGE_SCN_MEM_EXECUTE | pe.IMAGE_SCN_MEM_READ: //.text
 			bld.SetType(sym.STEXT)

 		default:
 			return nil, nil, fmt.Errorf("unexpected flags %#06x for PE section %s", sect.Characteristics, sect.Name)
 		}

 		if bld.Type() != sym.SNOPTRBSS {
 			data, err := sect.Data()
 			if err != nil {
 				return nil, nil, err
 			}
 			state.sectdata[sect] = data
 			bld.SetData(data)
 		}
 		bld.SetSize(int64(sect.Size))
 		state.sectsyms[sect] = s
 		if sect.Name == ".rsrc" || strings.HasPrefix(sect.Name, ".rsrc$") {
 			rsrc = append(rsrc, s)
 		}
 	}

 	// Make a prepass over the symbols to detect situations where
 	// we have both a defined symbol X and an import symbol __imp_X
 	// (needed by readpesym()).
 	if err := state.preprocessSymbols(); err != nil {
 		return nil, nil, err
 	}

 	// load relocations
 	for _, rsect := range f.Sections {
 		if _, found := state.sectsyms[rsect]; !found {
 			continue
 		}
 		if rsect.NumberOfRelocations == 0 {
 			continue
 		}
 		if rsect.Characteristics&pe.IMAGE_SCN_MEM_DISCARDABLE != 0 {
 			continue
 		}
 		if rsect.Characteristics&(pe.IMAGE_SCN_CNT_CODE|pe.IMAGE_SCN_CNT_INITIALIZED_DATA|pe.IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0 {
 			// This has been seen for .idata sections, which we
 			// want to ignore. See issues 5106 and 5273.
 			continue
 		}

 		splitResources := strings.HasPrefix(rsect.Name, ".rsrc$")
 		sb := l.MakeSymbolUpdater(state.sectsyms[rsect])
 		for j, r := range rsect.Relocs {
 			if int(r.SymbolTableIndex) >= len(f.COFFSymbols) {
 				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))
 			}
 			pesym := &f.COFFSymbols[r.SymbolTableIndex]
 			_, gosym, err := state.readpesym(pesym)
 			if err != nil {
 				return nil, nil, err
 			}
 			if gosym == 0 {
 				name, err := pesym.FullName(f.StringTable)
 				if err != nil {
 					name = string(pesym.Name[:])
 				}
 				return nil, nil, fmt.Errorf("reloc of invalid sym %s idx=%d type=%d", name, r.SymbolTableIndex, pesym.Type)
 			}

 			rSym := gosym
 			rSize := uint8(4)
 			rOff := int32(r.VirtualAddress)
 			var rAdd int64
 			var rType objabi.RelocType
 			switch arch.Family {
 			default:
 				return nil, nil, fmt.Errorf("%s: unsupported arch %v", pn, arch.Family)
 			case sys.I386, sys.AMD64:
 				switch r.Type {
 				default:
 					return nil, nil, fmt.Errorf("%s: %v: unknown relocation type %v", pn, state.sectsyms[rsect], r.Type)

 				case IMAGE_REL_I386_REL32, IMAGE_REL_AMD64_REL32,
 					IMAGE_REL_AMD64_ADDR32, // R_X86_64_PC32
 					IMAGE_REL_AMD64_ADDR32NB:
 					rType = objabi.R_PCREL

 					rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))

 				case IMAGE_REL_I386_DIR32NB, IMAGE_REL_I386_DIR32:
 					rType = objabi.R_ADDR

 					// load addend from image
 					rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))

 				case IMAGE_REL_AMD64_ADDR64: // R_X86_64_64
 					rSize = 8

 					rType = objabi.R_ADDR

 					// load addend from image
 					rAdd = int64(binary.LittleEndian.Uint64(state.sectdata[rsect][rOff:]))
 				}

 			case sys.ARM:
 				switch r.Type {
 				default:
 					return nil, nil, fmt.Errorf("%s: %v: unknown ARM relocation type %v", pn, state.sectsyms[rsect], r.Type)

 				case IMAGE_REL_ARM_SECREL:
 					rType = objabi.R_PCREL

 					rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))

 				case IMAGE_REL_ARM_ADDR32, IMAGE_REL_ARM_ADDR32NB:
 					rType = objabi.R_ADDR

 					rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))

 				case IMAGE_REL_ARM_BRANCH24:
 					rType = objabi.R_CALLARM

 					rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))
 				}

 			case sys.ARM64:
 				switch r.Type {
 				default:
 					return nil, nil, fmt.Errorf("%s: %v: unknown ARM64 relocation type %v", pn, state.sectsyms[rsect], r.Type)

 				case IMAGE_REL_ARM64_ADDR32, IMAGE_REL_ARM64_ADDR32NB:
 					rType = objabi.R_ADDR

 					rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))
 				}
 			}

 			// ld -r could generate multiple section symbols for the
 			// same section but with different values, we have to take
 			// that into account, or in the case of split resources,
 			// the section and its symbols are split into two sections.
 			if issect(pesym) || splitResources {
 				rAdd += int64(pesym.Value)
 			}

 			rel, _ := sb.AddRel(rType)
 			rel.SetOff(rOff)
 			rel.SetSiz(rSize)
 			rel.SetSym(rSym)
 			rel.SetAdd(rAdd)
 		}

 		sb.SortRelocs()
 	}

 	// enter sub-symbols into symbol table.
 	for i, numaux := 0, 0; i < len(f.COFFSymbols); i += numaux + 1 {
 		pesym := &f.COFFSymbols[i]

 		numaux = int(pesym.NumberOfAuxSymbols)

 		name, err := pesym.FullName(f.StringTable)
 		if err != nil {
 			return nil, nil, err
 		}
 		if name == "" {
 			continue
 		}
 		if issect(pesym) {
 			continue
 		}
 		if int(pesym.SectionNumber) > len(f.Sections) {
 			continue
 		}
 		if pesym.SectionNumber == IMAGE_SYM_DEBUG {
 			continue
 		}
 		if pesym.SectionNumber == IMAGE_SYM_ABSOLUTE && bytes.Equal(pesym.Name[:], []byte("@feat.00")) {
 			// Microsoft's linker looks at whether all input objects have an empty
 			// section called @feat.00. If all of them do, then it enables SEH;
 			// otherwise it doesn't enable that feature. So, since around the Windows
 			// XP SP2 era, most tools that make PE objects just tack on that section,
 			// so that it won't gimp Microsoft's linker logic. Go doesn't support SEH,
 			// so in theory, none of this really matters to us. But actually, if the
 			// linker tries to ingest an object with @feat.00 -- which are produced by
 			// LLVM's resource compiler, for example -- it chokes because of the
 			// IMAGE_SYM_ABSOLUTE section that it doesn't know how to deal with. Since
 			// @feat.00 is just a marking anyway, skip IMAGE_SYM_ABSOLUTE sections that
 			// are called @feat.00.
 			continue
 		}
 		var sect *pe.Section
 		if pesym.SectionNumber > 0 {
 			sect = f.Sections[pesym.SectionNumber-1]
 			if _, found := state.sectsyms[sect]; !found {
 				continue
 			}
 		}

 		bld, s, err := state.readpesym(pesym)
 		if err != nil {
 			return nil, nil, err
 		}

 		if pesym.SectionNumber == 0 { // extern
 			if l.SymType(s) == sym.SDYNIMPORT {
 				bld = makeUpdater(l, bld, s)
 				bld.SetPlt(-2) // flag for dynimport in PE object files.
 			}
 			if l.SymType(s) == sym.SXREF && pesym.Value > 0 { // global data
 				bld = makeUpdater(l, bld, s)
 				bld.SetType(sym.SNOPTRDATA)
 				bld.SetSize(int64(pesym.Value))
 			}

 			continue
 		} else if pesym.SectionNumber > 0 && int(pesym.SectionNumber) <= len(f.Sections) {
 			sect = f.Sections[pesym.SectionNumber-1]
 			if _, found := state.sectsyms[sect]; !found {
 				return nil, nil, fmt.Errorf("%s: %v: missing sect.sym", pn, s)
 			}
 		} else {
 			return nil, nil, fmt.Errorf("%s: %v: sectnum < 0!", pn, s)
 		}

 		if sect == nil {
 			return nil, nil, nil
 		}

 		// Check for COMDAT symbol.
 		if sz, ok1 := state.comdats[uint16(pesym.SectionNumber-1)]; ok1 {
 			if psz, ok2 := comdatDefinitions[l.SymName(s)]; ok2 {
 				if sz == psz {
 					//  OK to discard, we've seen an instance
 					// already.
 					continue
 				}
 			}
 		}
 		if l.OuterSym(s) != 0 {
 			if l.AttrDuplicateOK(s) {
 				continue
 			}
 			outerName := l.SymName(l.OuterSym(s))
 			sectName := l.SymName(state.sectsyms[sect])
 			return nil, nil, fmt.Errorf("%s: duplicate symbol reference: %s in both %s and %s", pn, l.SymName(s), outerName, sectName)
 		}

 		bld = makeUpdater(l, bld, s)
 		sectsym := state.sectsyms[sect]
 		bld.SetType(l.SymType(sectsym))
 		l.AddInteriorSym(sectsym, s)
 		bld.SetValue(int64(pesym.Value))
 		bld.SetSize(4)
 		if l.SymType(sectsym) == sym.STEXT {
 			if bld.External() && !bld.DuplicateOK() {
 				return nil, nil, fmt.Errorf("%s: duplicate symbol definition", l.SymName(s))
 			}
 			bld.SetExternal(true)
 		}
 		if sz, ok := state.comdats[uint16(pesym.SectionNumber-1)]; ok {
 			// This is a COMDAT definition. Record that we're picking
 			// this instance so that we can ignore future defs.
 			if _, ok := comdatDefinitions[l.SymName(s)]; ok {
 				return nil, nil, fmt.Errorf("internal error: preexisting COMDAT definition for %q", name)
 			}
 			comdatDefinitions[l.SymName(s)] = sz
 		}
 	}

 	// Sort outer lists by address, adding to textp.
 	// This keeps textp in increasing address order.
 	for _, sect := range f.Sections {
 		s := state.sectsyms[sect]
 		if s == 0 {
 			continue
 		}
 		l.SortSub(s)
 		if l.SymType(s) == sym.STEXT {
 			for ; s != 0; s = l.SubSym(s) {
 				if l.AttrOnList(s) {
 					return nil, nil, fmt.Errorf("symbol %s listed multiple times", l.SymName(s))
 				}
 				l.SetAttrOnList(s, true)
 				textp = append(textp, s)
 			}
 		}
 	}

 	return textp, rsrc, nil
 }

 func issect(s *pe.COFFSymbol) bool {
 	return s.StorageClass == IMAGE_SYM_CLASS_STATIC && s.Type == 0 && s.Name[0] == '.'
 }

 func (state *peLoaderState) readpesym(pesym *pe.COFFSymbol) (*loader.SymbolBuilder, loader.Sym, error) {
 	symname, err := pesym.FullName(state.f.StringTable)
 	if err != nil {
 		return nil, 0, err
 	}
 	var name string
 	if issect(pesym) {
 		name = state.l.SymName(state.sectsyms[state.f.Sections[pesym.SectionNumber-1]])
 	} else {
 		name = symname
 		if strings.HasPrefix(symname, "__imp_") {
 			orig := symname[len("__imp_"):]
 			if _, ok := state.defWithImp[orig]; ok {
 				// Don't rename __imp_XXX to XXX, since if we do this
 				// we'll wind up with a duplicate definition. One
 				// example is "__acrt_iob_func"; see commit b295099
 				// from git://git.code.sf.net/p/mingw-w64/mingw-w64
 				// for details.
 			} else {
 				name = strings.TrimPrefix(name, "__imp_") // __imp_Name => Name
 			}
 		}
 		if state.arch.Family == sys.I386 && name[0] == '_' {
 			name = name[1:] // _Name => Name
 		}
 	}

 	// remove last @XXX
 	if i := strings.LastIndex(name, "@"); i >= 0 {
 		name = name[:i]
 	}

 	var s loader.Sym
 	var bld *loader.SymbolBuilder
 	switch pesym.Type {
 	default:
 		return nil, 0, fmt.Errorf("%s: invalid symbol type %d", symname, pesym.Type)

 	case IMAGE_SYM_DTYPE_FUNCTION, IMAGE_SYM_DTYPE_NULL:
 		switch pesym.StorageClass {
 		case IMAGE_SYM_CLASS_EXTERNAL: //global
 			s = state.l.LookupOrCreateCgoExport(name, 0)

 		case IMAGE_SYM_CLASS_NULL, IMAGE_SYM_CLASS_STATIC, IMAGE_SYM_CLASS_LABEL:
 			s = state.l.LookupOrCreateCgoExport(name, state.localSymVersion)
 			bld = makeUpdater(state.l, bld, s)
 			bld.SetDuplicateOK(true)

 		default:
 			return nil, 0, fmt.Errorf("%s: invalid symbol binding %d", symname, pesym.StorageClass)
 		}
 	}

 	if s != 0 && state.l.SymType(s) == 0 && (pesym.StorageClass != IMAGE_SYM_CLASS_STATIC || pesym.Value != 0) {
 		bld = makeUpdater(state.l, bld, s)
 		bld.SetType(sym.SXREF)
 	}
 	if strings.HasPrefix(symname, "__imp_") {
 		bld = makeUpdater(state.l, bld, s)
 		bld.SetGot(-2) // flag for __imp_
 	}

 	return bld, s, nil
 }

 // preprocessSymbols walks the COFF symbols for the PE file we're
 // reading and looks for cases where we have both a symbol definition
 // for "XXX" and an "__imp_XXX" symbol, recording these cases in a map
 // in the state struct. This information will be used in readpesym()
 // above to give such symbols special treatment. This function also
 // gathers information about COMDAT sections/symbols for later use
 // in readpesym().
 func (state *peLoaderState) preprocessSymbols() error {

 	// Locate comdat sections.
 	state.comdats = make(map[uint16]int64)
 	for i, s := range state.f.Sections {
 		if s.Characteristics&uint32(pe.IMAGE_SCN_LNK_COMDAT) != 0 {
 			state.comdats[uint16(i)] = int64(s.Size)
 		}
 	}

 	// Examine symbol defs.
 	imp := make(map[string]struct{})
 	def := make(map[string]struct{})
 	for i, numaux := 0, 0; i < len(state.f.COFFSymbols); i += numaux + 1 {
 		pesym := &state.f.COFFSymbols[i]
 		numaux = int(pesym.NumberOfAuxSymbols)
 		if pesym.SectionNumber == 0 { // extern
 			continue
 		}
 		symname, err := pesym.FullName(state.f.StringTable)
 		if err != nil {
 			return err
 		}
 		def[symname] = struct{}{}
 		if strings.HasPrefix(symname, "__imp_") {
 			imp[strings.TrimPrefix(symname, "__imp_")] = struct{}{}
 		}
 		if _, isc := state.comdats[uint16(pesym.SectionNumber-1)]; !isc {
 			continue
 		}
 		if pesym.StorageClass != uint8(IMAGE_SYM_CLASS_STATIC) {
 			continue
 		}
 		// This symbol corresponds to a COMDAT section. Read the
 		// aux data for it.
 		auxsymp, err := state.f.COFFSymbolReadSectionDefAux(i)
 		if err != nil {
 			return fmt.Errorf("unable to read aux info for section def symbol %d %s: pe.COFFSymbolReadComdatInfo returns %v", i, symname, err)
 		}
 		if auxsymp.Selection == pe.IMAGE_COMDAT_SELECT_SAME_SIZE {
 			// This is supported.
 		} else if auxsymp.Selection == pe.IMAGE_COMDAT_SELECT_ANY {
 			// Also supported.
 			state.comdats[uint16(pesym.SectionNumber-1)] = int64(-1)
 		} else {
 			// We don't support any of the other strategies at the
 			// moment. I suspect that we may need to also support
 			// "associative", we'll see.
 			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)
 		}
 	}
 	state.defWithImp = make(map[string]struct{})
 	for n := range imp {
 		if _, ok := def[n]; ok {
 			state.defWithImp[n] = struct{}{}
 		}
 	}
 	return nil
 }
	// Copyright 2010 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	// Package loadpe implements a PE/COFF file reader.
	package loadpe

	import (
	"bytes"
	"cmd/internal/bio"
	"cmd/internal/objabi"
	"cmd/internal/sys"
	"cmd/link/internal/loader"
	"cmd/link/internal/sym"
	"debug/pe"
	"encoding/binary"
	"errors"
	"fmt"
	"io"
	"strings"
	)

	const (
	// TODO: the Microsoft doco says IMAGE_SYM_DTYPE_ARRAY is 3 (same with IMAGE_SYM_DTYPE_POINTER and IMAGE_SYM_DTYPE_FUNCTION)
	IMAGE_SYM_UNDEFINED = 0
	IMAGE_SYM_ABSOLUTE = -1
	IMAGE_SYM_DEBUG = -2
	IMAGE_SYM_TYPE_NULL = 0
	IMAGE_SYM_TYPE_VOID = 1
	IMAGE_SYM_TYPE_CHAR = 2
	IMAGE_SYM_TYPE_SHORT = 3
	IMAGE_SYM_TYPE_INT = 4
	IMAGE_SYM_TYPE_LONG = 5
	IMAGE_SYM_TYPE_FLOAT = 6
	IMAGE_SYM_TYPE_DOUBLE = 7
	IMAGE_SYM_TYPE_STRUCT = 8
	IMAGE_SYM_TYPE_UNION = 9
	IMAGE_SYM_TYPE_ENUM = 10
	IMAGE_SYM_TYPE_MOE = 11
	IMAGE_SYM_TYPE_BYTE = 12
	IMAGE_SYM_TYPE_WORD = 13
	IMAGE_SYM_TYPE_UINT = 14
	IMAGE_SYM_TYPE_DWORD = 15
	IMAGE_SYM_TYPE_PCODE = 32768
	IMAGE_SYM_DTYPE_NULL = 0
	IMAGE_SYM_DTYPE_POINTER = 0x10
	IMAGE_SYM_DTYPE_FUNCTION = 0x20
	IMAGE_SYM_DTYPE_ARRAY = 0x30
	IMAGE_SYM_CLASS_END_OF_FUNCTION = -1
	IMAGE_SYM_CLASS_NULL = 0
	IMAGE_SYM_CLASS_AUTOMATIC = 1
	IMAGE_SYM_CLASS_EXTERNAL = 2
	IMAGE_SYM_CLASS_STATIC = 3
	IMAGE_SYM_CLASS_REGISTER = 4
	IMAGE_SYM_CLASS_EXTERNAL_DEF = 5
	IMAGE_SYM_CLASS_LABEL = 6
	IMAGE_SYM_CLASS_UNDEFINED_LABEL = 7
	IMAGE_SYM_CLASS_MEMBER_OF_STRUCT = 8
	IMAGE_SYM_CLASS_ARGUMENT = 9
	IMAGE_SYM_CLASS_STRUCT_TAG = 10
	IMAGE_SYM_CLASS_MEMBER_OF_UNION = 11
	IMAGE_SYM_CLASS_UNION_TAG = 12
	IMAGE_SYM_CLASS_TYPE_DEFINITION = 13
	IMAGE_SYM_CLASS_UNDEFINED_STATIC = 14
	IMAGE_SYM_CLASS_ENUM_TAG = 15
	IMAGE_SYM_CLASS_MEMBER_OF_ENUM = 16
	IMAGE_SYM_CLASS_REGISTER_PARAM = 17
	IMAGE_SYM_CLASS_BIT_FIELD = 18
	IMAGE_SYM_CLASS_FAR_EXTERNAL = 68 /* Not in PECOFF v8 spec */
	IMAGE_SYM_CLASS_BLOCK = 100
	IMAGE_SYM_CLASS_FUNCTION = 101
	IMAGE_SYM_CLASS_END_OF_STRUCT = 102
	IMAGE_SYM_CLASS_FILE = 103
	IMAGE_SYM_CLASS_SECTION = 104
	IMAGE_SYM_CLASS_WEAK_EXTERNAL = 105
	IMAGE_SYM_CLASS_CLR_TOKEN = 107
	IMAGE_REL_I386_ABSOLUTE = 0x0000
	IMAGE_REL_I386_DIR16 = 0x0001
	IMAGE_REL_I386_REL16 = 0x0002
	IMAGE_REL_I386_DIR32 = 0x0006
	IMAGE_REL_I386_DIR32NB = 0x0007
	IMAGE_REL_I386_SEG12 = 0x0009
	IMAGE_REL_I386_SECTION = 0x000A
	IMAGE_REL_I386_SECREL = 0x000B
	IMAGE_REL_I386_TOKEN = 0x000C
	IMAGE_REL_I386_SECREL7 = 0x000D
	IMAGE_REL_I386_REL32 = 0x0014
	IMAGE_REL_AMD64_ABSOLUTE = 0x0000
	IMAGE_REL_AMD64_ADDR64 = 0x0001
	IMAGE_REL_AMD64_ADDR32 = 0x0002
	IMAGE_REL_AMD64_ADDR32NB = 0x0003
	IMAGE_REL_AMD64_REL32 = 0x0004
	IMAGE_REL_AMD64_REL32_1 = 0x0005
	IMAGE_REL_AMD64_REL32_2 = 0x0006
	IMAGE_REL_AMD64_REL32_3 = 0x0007
	IMAGE_REL_AMD64_REL32_4 = 0x0008
	IMAGE_REL_AMD64_REL32_5 = 0x0009
	IMAGE_REL_AMD64_SECTION = 0x000A
	IMAGE_REL_AMD64_SECREL = 0x000B
	IMAGE_REL_AMD64_SECREL7 = 0x000C
	IMAGE_REL_AMD64_TOKEN = 0x000D
	IMAGE_REL_AMD64_SREL32 = 0x000E
	IMAGE_REL_AMD64_PAIR = 0x000F
	IMAGE_REL_AMD64_SSPAN32 = 0x0010
	IMAGE_REL_ARM_ABSOLUTE = 0x0000
	IMAGE_REL_ARM_ADDR32 = 0x0001
	IMAGE_REL_ARM_ADDR32NB = 0x0002
	IMAGE_REL_ARM_BRANCH24 = 0x0003
	IMAGE_REL_ARM_BRANCH11 = 0x0004
	IMAGE_REL_ARM_SECTION = 0x000E
	IMAGE_REL_ARM_SECREL = 0x000F
	IMAGE_REL_ARM_MOV32 = 0x0010
	IMAGE_REL_THUMB_MOV32 = 0x0011
	IMAGE_REL_THUMB_BRANCH20 = 0x0012
	IMAGE_REL_THUMB_BRANCH24 = 0x0014
	IMAGE_REL_THUMB_BLX23 = 0x0015
	IMAGE_REL_ARM_PAIR = 0x0016
	IMAGE_REL_ARM64_ABSOLUTE = 0x0000
	IMAGE_REL_ARM64_ADDR32 = 0x0001
	IMAGE_REL_ARM64_ADDR32NB = 0x0002
	IMAGE_REL_ARM64_BRANCH26 = 0x0003
	IMAGE_REL_ARM64_PAGEBASE_REL21 = 0x0004
	IMAGE_REL_ARM64_REL21 = 0x0005
	IMAGE_REL_ARM64_PAGEOFFSET_12A = 0x0006
	IMAGE_REL_ARM64_PAGEOFFSET_12L = 0x0007
	IMAGE_REL_ARM64_SECREL = 0x0008
	IMAGE_REL_ARM64_SECREL_LOW12A = 0x0009
	IMAGE_REL_ARM64_SECREL_HIGH12A = 0x000A
	IMAGE_REL_ARM64_SECREL_LOW12L = 0x000B
	IMAGE_REL_ARM64_TOKEN = 0x000C
	IMAGE_REL_ARM64_SECTION = 0x000D
	IMAGE_REL_ARM64_ADDR64 = 0x000E
	IMAGE_REL_ARM64_BRANCH19 = 0x000F
	IMAGE_REL_ARM64_BRANCH14 = 0x0010
	IMAGE_REL_ARM64_REL32 = 0x0011
	)

	// TODO(brainman): maybe just add ReadAt method to bio.Reader instead of creating peBiobuf

	// peBiobuf makes bio.Reader look like io.ReaderAt.
	type peBiobuf bio.Reader

	func (f *peBiobuf) ReadAt(p []byte, off int64) (int, error) {
	ret := ((*bio.Reader)(f)).MustSeek(off, 0)
	if ret < 0 {
	return 0, errors.New("fail to seek")
	}
	n, err := f.Read(p)
	if err != nil {
	return 0, err
	}
	return n, nil
	}

	// makeUpdater creates a loader.SymbolBuilder if one hasn't been created previously.
	// 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.
	func makeUpdater(l loader.Loader, bld loader.SymbolBuilder, s loader.Sym) *loader.SymbolBuilder {
	if bld != nil {
	return bld
	}
	bld = l.MakeSymbolUpdater(s)
	return bld
	}

	// peLoaderState holds various bits of useful state information needed
	// while loading a PE object file.
	type peLoaderState struct {
	l *loader.Loader
	arch *sys.Arch
	f *pe.File
	pn string
	sectsyms map[*pe.Section]loader.Sym
	defWithImp map[string]struct{}
	comdats map[uint16]int64 // key is section index, val is size
	sectdata map[*pe.Section][]byte
	localSymVersion int
	}

	// comdatDefinitions records the names of symbols for which we've
	// previously seen a definition in COMDAT. Key is symbol name, value
	// is symbol size (or -1 if we're using the "any" strategy).
	var comdatDefinitions = make(map[string]int64)

	// Load loads the PE file pn from input.
	// Symbols are written into syms, and a slice of the text symbols is returned.
	// If an .rsrc section or set of .rsrc$xx sections is found, its symbols are
	// returned as rsrc.
	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) {
	state := &peLoaderState{
	l: l,
	arch: arch,
	sectsyms: make(map[*pe.Section]loader.Sym),
	sectdata: make(map[*pe.Section][]byte),
	localSymVersion: localSymVersion,
	pn: pn,
	}

	// Some input files are archives containing multiple of
	// object files, and pe.NewFile seeks to the start of
	// input file and get confused. Create section reader
	// to stop pe.NewFile looking before current position.
	sr := io.NewSectionReader((*peBiobuf)(input), input.Offset(), 1<<63-1)

	// TODO: replace pe.NewFile with pe.Load (grep for "add Load function" in debug/pe for details)
	f, err := pe.NewFile(sr)
	if err != nil {
	return nil, nil, err
	}
	defer f.Close()
	state.f = f

	// TODO return error if found .cormeta

	// create symbols for mapped sections
	for _, sect := range f.Sections {
	if sect.Characteristics&pe.IMAGE_SCN_MEM_DISCARDABLE != 0 {
	continue
	}

	if sect.Characteristics&(pe.IMAGE_SCN_CNT_CODE\|pe.IMAGE_SCN_CNT_INITIALIZED_DATA\|pe.IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0 {
	// This has been seen for .idata sections, which we
	// want to ignore. See issues 5106 and 5273.
	continue
	}

	name := fmt.Sprintf("%s(%s)", pkg, sect.Name)
	s := state.l.LookupOrCreateCgoExport(name, localSymVersion)
	bld := l.MakeSymbolUpdater(s)

	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) {
	case pe.IMAGE_SCN_CNT_INITIALIZED_DATA \| pe.IMAGE_SCN_MEM_READ: //.rdata
	bld.SetType(sym.SRODATA)

	case pe.IMAGE_SCN_CNT_UNINITIALIZED_DATA \| pe.IMAGE_SCN_MEM_READ \| pe.IMAGE_SCN_MEM_WRITE: //.bss
	bld.SetType(sym.SNOPTRBSS)

	case pe.IMAGE_SCN_CNT_INITIALIZED_DATA \| pe.IMAGE_SCN_MEM_READ \| pe.IMAGE_SCN_MEM_WRITE: //.data
	bld.SetType(sym.SNOPTRDATA)

	case pe.IMAGE_SCN_CNT_CODE \| pe.IMAGE_SCN_MEM_EXECUTE \| pe.IMAGE_SCN_MEM_READ: //.text
	bld.SetType(sym.STEXT)

	default:
	return nil, nil, fmt.Errorf("unexpected flags %#06x for PE section %s", sect.Characteristics, sect.Name)
	}

	if bld.Type() != sym.SNOPTRBSS {
	data, err := sect.Data()
	if err != nil {
	return nil, nil, err
	}
	state.sectdata[sect] = data
	bld.SetData(data)
	}
	bld.SetSize(int64(sect.Size))
	state.sectsyms[sect] = s
	if sect.Name == ".rsrc" \|\| strings.HasPrefix(sect.Name, ".rsrc$") {
	rsrc = append(rsrc, s)
	}
	}

	// Make a prepass over the symbols to detect situations where
	// we have both a defined symbol X and an import symbol __imp_X
	// (needed by readpesym()).
	if err := state.preprocessSymbols(); err != nil {
	return nil, nil, err
	}

	// load relocations
	for _, rsect := range f.Sections {
	if _, found := state.sectsyms[rsect]; !found {
	continue
	}
	if rsect.NumberOfRelocations == 0 {
	continue
	}
	if rsect.Characteristics&pe.IMAGE_SCN_MEM_DISCARDABLE != 0 {
	continue
	}
	if rsect.Characteristics&(pe.IMAGE_SCN_CNT_CODE\|pe.IMAGE_SCN_CNT_INITIALIZED_DATA\|pe.IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0 {
	// This has been seen for .idata sections, which we
	// want to ignore. See issues 5106 and 5273.
	continue
	}

	splitResources := strings.HasPrefix(rsect.Name, ".rsrc$")
	sb := l.MakeSymbolUpdater(state.sectsyms[rsect])
	for j, r := range rsect.Relocs {
	if int(r.SymbolTableIndex) >= len(f.COFFSymbols) {
	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))
	}
	pesym := &f.COFFSymbols[r.SymbolTableIndex]
	_, gosym, err := state.readpesym(pesym)
	if err != nil {
	return nil, nil, err
	}
	if gosym == 0 {
	name, err := pesym.FullName(f.StringTable)
	if err != nil {
	name = string(pesym.Name[:])
	}
	return nil, nil, fmt.Errorf("reloc of invalid sym %s idx=%d type=%d", name, r.SymbolTableIndex, pesym.Type)
	}

	rSym := gosym
	rSize := uint8(4)
	rOff := int32(r.VirtualAddress)
	var rAdd int64
	var rType objabi.RelocType
	switch arch.Family {
	default:
	return nil, nil, fmt.Errorf("%s: unsupported arch %v", pn, arch.Family)
	case sys.I386, sys.AMD64:
	switch r.Type {
	default:
	return nil, nil, fmt.Errorf("%s: %v: unknown relocation type %v", pn, state.sectsyms[rsect], r.Type)

	case IMAGE_REL_I386_REL32, IMAGE_REL_AMD64_REL32,
	IMAGE_REL_AMD64_ADDR32, // R_X86_64_PC32
	IMAGE_REL_AMD64_ADDR32NB:
	rType = objabi.R_PCREL

	rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))

	case IMAGE_REL_I386_DIR32NB, IMAGE_REL_I386_DIR32:
	rType = objabi.R_ADDR

	// load addend from image
	rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))

	case IMAGE_REL_AMD64_ADDR64: // R_X86_64_64
	rSize = 8

	rType = objabi.R_ADDR

	// load addend from image
	rAdd = int64(binary.LittleEndian.Uint64(state.sectdata[rsect][rOff:]))
	}

	case sys.ARM:
	switch r.Type {
	default:
	return nil, nil, fmt.Errorf("%s: %v: unknown ARM relocation type %v", pn, state.sectsyms[rsect], r.Type)

	case IMAGE_REL_ARM_SECREL:
	rType = objabi.R_PCREL

	rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))

	case IMAGE_REL_ARM_ADDR32, IMAGE_REL_ARM_ADDR32NB:
	rType = objabi.R_ADDR

	rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))

	case IMAGE_REL_ARM_BRANCH24:
	rType = objabi.R_CALLARM

	rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))
	}

	case sys.ARM64:
	switch r.Type {
	default:
	return nil, nil, fmt.Errorf("%s: %v: unknown ARM64 relocation type %v", pn, state.sectsyms[rsect], r.Type)

	case IMAGE_REL_ARM64_ADDR32, IMAGE_REL_ARM64_ADDR32NB:
	rType = objabi.R_ADDR

	rAdd = int64(int32(binary.LittleEndian.Uint32(state.sectdata[rsect][rOff:])))
	}
	}

	// ld -r could generate multiple section symbols for the
	// same section but with different values, we have to take
	// that into account, or in the case of split resources,
	// the section and its symbols are split into two sections.
	if issect(pesym) \|\| splitResources {
	rAdd += int64(pesym.Value)
	}

	rel, _ := sb.AddRel(rType)
	rel.SetOff(rOff)
	rel.SetSiz(rSize)
	rel.SetSym(rSym)
	rel.SetAdd(rAdd)
	}

	sb.SortRelocs()
	}

	// enter sub-symbols into symbol table.
	for i, numaux := 0, 0; i < len(f.COFFSymbols); i += numaux + 1 {
	pesym := &f.COFFSymbols[i]

	numaux = int(pesym.NumberOfAuxSymbols)

	name, err := pesym.FullName(f.StringTable)
	if err != nil {
	return nil, nil, err
	}
	if name == "" {
	continue
	}
	if issect(pesym) {
	continue
	}
	if int(pesym.SectionNumber) > len(f.Sections) {
	continue
	}
	if pesym.SectionNumber == IMAGE_SYM_DEBUG {
	continue
	}
	if pesym.SectionNumber == IMAGE_SYM_ABSOLUTE && bytes.Equal(pesym.Name[:], []byte("@feat.00")) {
	// Microsoft's linker looks at whether all input objects have an empty
	// section called @feat.00. If all of them do, then it enables SEH;
	// otherwise it doesn't enable that feature. So, since around the Windows
	// XP SP2 era, most tools that make PE objects just tack on that section,
	// so that it won't gimp Microsoft's linker logic. Go doesn't support SEH,
	// so in theory, none of this really matters to us. But actually, if the
	// linker tries to ingest an object with @feat.00 -- which are produced by
	// LLVM's resource compiler, for example -- it chokes because of the
	// IMAGE_SYM_ABSOLUTE section that it doesn't know how to deal with. Since
	// @feat.00 is just a marking anyway, skip IMAGE_SYM_ABSOLUTE sections that
	// are called @feat.00.
	continue
	}
	var sect *pe.Section
	if pesym.SectionNumber > 0 {
	sect = f.Sections[pesym.SectionNumber-1]
	if _, found := state.sectsyms[sect]; !found {
	continue
	}
	}

	bld, s, err := state.readpesym(pesym)
	if err != nil {
	return nil, nil, err
	}

	if pesym.SectionNumber == 0 { // extern
	if l.SymType(s) == sym.SDYNIMPORT {
	bld = makeUpdater(l, bld, s)
	bld.SetPlt(-2) // flag for dynimport in PE object files.
	}
	if l.SymType(s) == sym.SXREF && pesym.Value > 0 { // global data
	bld = makeUpdater(l, bld, s)
	bld.SetType(sym.SNOPTRDATA)
	bld.SetSize(int64(pesym.Value))
	}

	continue
	} else if pesym.SectionNumber > 0 && int(pesym.SectionNumber) <= len(f.Sections) {
	sect = f.Sections[pesym.SectionNumber-1]
	if _, found := state.sectsyms[sect]; !found {
	return nil, nil, fmt.Errorf("%s: %v: missing sect.sym", pn, s)
	}
	} else {
	return nil, nil, fmt.Errorf("%s: %v: sectnum < 0!", pn, s)
	}

	if sect == nil {
	return nil, nil, nil
	}

	// Check for COMDAT symbol.
	if sz, ok1 := state.comdats[uint16(pesym.SectionNumber-1)]; ok1 {
	if psz, ok2 := comdatDefinitions[l.SymName(s)]; ok2 {
	if sz == psz {
	// OK to discard, we've seen an instance
	// already.
	continue
	}
	}
	}
	if l.OuterSym(s) != 0 {
	if l.AttrDuplicateOK(s) {
	continue
	}
	outerName := l.SymName(l.OuterSym(s))
	sectName := l.SymName(state.sectsyms[sect])
	return nil, nil, fmt.Errorf("%s: duplicate symbol reference: %s in both %s and %s", pn, l.SymName(s), outerName, sectName)
	}

	bld = makeUpdater(l, bld, s)
	sectsym := state.sectsyms[sect]
	bld.SetType(l.SymType(sectsym))
	l.AddInteriorSym(sectsym, s)
	bld.SetValue(int64(pesym.Value))
	bld.SetSize(4)
	if l.SymType(sectsym) == sym.STEXT {
	if bld.External() && !bld.DuplicateOK() {
	return nil, nil, fmt.Errorf("%s: duplicate symbol definition", l.SymName(s))
	}
	bld.SetExternal(true)
	}
	if sz, ok := state.comdats[uint16(pesym.SectionNumber-1)]; ok {
	// This is a COMDAT definition. Record that we're picking
	// this instance so that we can ignore future defs.
	if _, ok := comdatDefinitions[l.SymName(s)]; ok {
	return nil, nil, fmt.Errorf("internal error: preexisting COMDAT definition for %q", name)
	}
	comdatDefinitions[l.SymName(s)] = sz
	}
	}

	// Sort outer lists by address, adding to textp.
	// This keeps textp in increasing address order.
	for _, sect := range f.Sections {
	s := state.sectsyms[sect]
	if s == 0 {
	continue
	}
	l.SortSub(s)
	if l.SymType(s) == sym.STEXT {
	for ; s != 0; s = l.SubSym(s) {
	if l.AttrOnList(s) {
	return nil, nil, fmt.Errorf("symbol %s listed multiple times", l.SymName(s))
	}
	l.SetAttrOnList(s, true)
	textp = append(textp, s)
	}
	}
	}

	return textp, rsrc, nil
	}

	func issect(s *pe.COFFSymbol) bool {
	return s.StorageClass == IMAGE_SYM_CLASS_STATIC && s.Type == 0 && s.Name[0] == '.'
	}

	func (state peLoaderState) readpesym(pesym pe.COFFSymbol) (*loader.SymbolBuilder, loader.Sym, error) {
	symname, err := pesym.FullName(state.f.StringTable)
	if err != nil {
	return nil, 0, err
	}
	var name string
	if issect(pesym) {
	name = state.l.SymName(state.sectsyms[state.f.Sections[pesym.SectionNumber-1]])
	} else {
	name = symname
	if strings.HasPrefix(symname, "__imp_") {
	orig := symname[len("__imp_"):]
	if _, ok := state.defWithImp[orig]; ok {
	// Don't rename __imp_XXX to XXX, since if we do this
	// we'll wind up with a duplicate definition. One
	// example is "__acrt_iob_func"; see commit b295099
	// from git://git.code.sf.net/p/mingw-w64/mingw-w64
	// for details.
	} else {
	name = strings.TrimPrefix(name, "__imp_") // __imp_Name => Name
	}
	}
	if state.arch.Family == sys.I386 && name[0] == '_' {
	name = name[1:] // _Name => Name
	}
	}

	// remove last @XXX
	if i := strings.LastIndex(name, "@"); i >= 0 {
	name = name[:i]
	}

	var s loader.Sym
	var bld *loader.SymbolBuilder
	switch pesym.Type {
	default:
	return nil, 0, fmt.Errorf("%s: invalid symbol type %d", symname, pesym.Type)

	case IMAGE_SYM_DTYPE_FUNCTION, IMAGE_SYM_DTYPE_NULL:
	switch pesym.StorageClass {
	case IMAGE_SYM_CLASS_EXTERNAL: //global
	s = state.l.LookupOrCreateCgoExport(name, 0)

	case IMAGE_SYM_CLASS_NULL, IMAGE_SYM_CLASS_STATIC, IMAGE_SYM_CLASS_LABEL:
	s = state.l.LookupOrCreateCgoExport(name, state.localSymVersion)
	bld = makeUpdater(state.l, bld, s)
	bld.SetDuplicateOK(true)

	default:
	return nil, 0, fmt.Errorf("%s: invalid symbol binding %d", symname, pesym.StorageClass)
	}
	}

	if s != 0 && state.l.SymType(s) == 0 && (pesym.StorageClass != IMAGE_SYM_CLASS_STATIC \|\| pesym.Value != 0) {
	bld = makeUpdater(state.l, bld, s)
	bld.SetType(sym.SXREF)
	}
	if strings.HasPrefix(symname, "__imp_") {
	bld = makeUpdater(state.l, bld, s)
	bld.SetGot(-2) // flag for __imp_
	}

	return bld, s, nil
	}

	// preprocessSymbols walks the COFF symbols for the PE file we're
	// reading and looks for cases where we have both a symbol definition
	// for "XXX" and an "__imp_XXX" symbol, recording these cases in a map
	// in the state struct. This information will be used in readpesym()
	// above to give such symbols special treatment. This function also
	// gathers information about COMDAT sections/symbols for later use
	// in readpesym().
	func (state *peLoaderState) preprocessSymbols() error {

	// Locate comdat sections.
	state.comdats = make(map[uint16]int64)
	for i, s := range state.f.Sections {
	if s.Characteristics&uint32(pe.IMAGE_SCN_LNK_COMDAT) != 0 {
	state.comdats[uint16(i)] = int64(s.Size)
	}
	}

	// Examine symbol defs.
	imp := make(map[string]struct{})
	def := make(map[string]struct{})
	for i, numaux := 0, 0; i < len(state.f.COFFSymbols); i += numaux + 1 {
	pesym := &state.f.COFFSymbols[i]
	numaux = int(pesym.NumberOfAuxSymbols)
	if pesym.SectionNumber == 0 { // extern
	continue
	}
	symname, err := pesym.FullName(state.f.StringTable)
	if err != nil {
	return err
	}
	def[symname] = struct{}{}
	if strings.HasPrefix(symname, "__imp_") {
	imp[strings.TrimPrefix(symname, "__imp_")] = struct{}{}
	}
	if _, isc := state.comdats[uint16(pesym.SectionNumber-1)]; !isc {
	continue
	}
	if pesym.StorageClass != uint8(IMAGE_SYM_CLASS_STATIC) {
	continue
	}
	// This symbol corresponds to a COMDAT section. Read the
	// aux data for it.
	auxsymp, err := state.f.COFFSymbolReadSectionDefAux(i)
	if err != nil {
	return fmt.Errorf("unable to read aux info for section def symbol %d %s: pe.COFFSymbolReadComdatInfo returns %v", i, symname, err)
	}
	if auxsymp.Selection == pe.IMAGE_COMDAT_SELECT_SAME_SIZE {
	// This is supported.
	} else if auxsymp.Selection == pe.IMAGE_COMDAT_SELECT_ANY {
	// Also supported.
	state.comdats[uint16(pesym.SectionNumber-1)] = int64(-1)
	} else {
	// We don't support any of the other strategies at the
	// moment. I suspect that we may need to also support
	// "associative", we'll see.
	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)
	}
	}
	state.defWithImp = make(map[string]struct{})
	for n := range imp {
	if _, ok := def[n]; ok {
	state.defWithImp[n] = struct{}{}
	}
	}
	return nil
	}