diff options
Diffstat (limited to 'src/cmd/link/internal/loadpe/ldpe.go')
| -rw-r--r-- | src/cmd/link/internal/loadpe/ldpe.go | 777 |
1 files changed, 777 insertions, 0 deletions
diff --git a/src/cmd/link/internal/loadpe/ldpe.go b/src/cmd/link/internal/loadpe/ldpe.go new file mode 100644 index 0000000..0d33823 --- /dev/null +++ b/src/cmd/link/internal/loadpe/ldpe.go @@ -0,0 +1,777 @@ +// 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 +) + +const ( + // When stored into the PLT value for a symbol, this token tells + // windynrelocsym to redirect direct references to this symbol to a stub + // that loads from the corresponding import symbol and then does + // a jump to the loaded value. + CreateImportStubPltToken = -2 + + // When stored into the GOT value for a import symbol __imp_X this + // token tells windynrelocsym to redirect references to the + // underlying DYNIMPORT symbol X. + RedirectToDynImportGotToken = -2 +) + +// 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 +} + +// peImportSymsState tracks the set of DLL import symbols we've seen +// while reading host objects. We create a singleton instance of this +// type, which will persist across multiple host objects. +type peImportSymsState struct { + + // Text and non-text sections read in by the host object loader. + secSyms []loader.Sym + + // SDYNIMPORT symbols encountered along the way + dynimports map[loader.Sym]struct{} + + // Loader and arch, for use in postprocessing. + l *loader.Loader + arch *sys.Arch +} + +var importSymsState *peImportSymsState + +func createImportSymsState(l *loader.Loader, arch *sys.Arch) { + if importSymsState != nil { + return + } + importSymsState = &peImportSymsState{ + dynimports: make(map[loader.Sym]struct{}), + l: l, + arch: arch, + } +} + +// peLoaderState holds various bits of useful state information needed +// while loading a single PE object file. +type peLoaderState struct { + l *loader.Loader + arch *sys.Arch + f *pe.File + pn string + sectsyms map[*pe.Section]loader.Sym + 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 from the object file are created via the loader 'l', and +// 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, + } + createImportSymsState(state.l, state.arch) + + // 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 collect info about COMDAT symbols. + 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.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) + importSymsState.secSyms = append(importSymsState.secSyms, 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 +} + +// PostProcessImports works to resolve inconsistencies with DLL import +// symbols; it is needed when building with more "modern" C compilers +// with internal linkage. +// +// Background: DLL import symbols are data (SNOPTRDATA) symbols whose +// name is of the form "__imp_XXX", which contain a pointer/reference +// to symbol XXX. It's possible to have import symbols for both data +// symbols ("__imp__fmode") and text symbols ("__imp_CreateEventA"). +// In some case import symbols are just references to some external +// thing, and in other cases we see actual definitions of import +// symbols when reading host objects. +// +// Previous versions of the linker would in most cases immediately +// "forward" import symbol references, e.g. treat a references to +// "__imp_XXX" a references to "XXX", however this doesn't work well +// with more modern compilers, where you can sometimes see import +// symbols that are defs (as opposed to external refs). +// +// The main actions taken below are to search for references to +// SDYNIMPORT symbols in host object text/data sections and flag the +// symbols for later fixup. When we see a reference to an import +// symbol __imp_XYZ where XYZ corresponds to some SDYNIMPORT symbol, +// we flag the symbol (via GOT setting) so that it can be redirected +// to XYZ later in windynrelocsym. When we see a direct reference to +// an SDYNIMPORT symbol XYZ, we also flag the symbol (via PLT setting) +// to indicated that the reference will need to be redirected to a +// stub. +func PostProcessImports() error { + ldr := importSymsState.l + arch := importSymsState.arch + keeprelocneeded := make(map[loader.Sym]loader.Sym) + for _, s := range importSymsState.secSyms { + isText := ldr.SymType(s) == sym.STEXT + relocs := ldr.Relocs(s) + for i := 0; i < relocs.Count(); i++ { + r := relocs.At(i) + rs := r.Sym() + if ldr.SymType(rs) == sym.SDYNIMPORT { + // Tag the symbol for later stub generation. + ldr.SetPlt(rs, CreateImportStubPltToken) + continue + } + isym, err := LookupBaseFromImport(rs, ldr, arch) + if err != nil { + return err + } + if isym == 0 { + continue + } + if ldr.SymType(isym) != sym.SDYNIMPORT { + continue + } + // For non-text symbols, forward the reference from __imp_X to + // X immediately. + if !isText { + r.SetSym(isym) + continue + } + // Flag this imp symbol to be processed later in windynrelocsym. + ldr.SetGot(rs, RedirectToDynImportGotToken) + // Consistency check: should be no PLT token here. + splt := ldr.SymPlt(rs) + if splt != -1 { + return fmt.Errorf("internal error: import symbol %q has invalid PLT setting %d", ldr.SymName(rs), splt) + } + // Flag for dummy relocation. + keeprelocneeded[rs] = isym + } + } + for k, v := range keeprelocneeded { + sb := ldr.MakeSymbolUpdater(k) + r, _ := sb.AddRel(objabi.R_KEEP) + r.SetSym(v) + } + importSymsState = nil + return 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 + // A note on the "_main" exclusion below: the main routine + // defined by the Go runtime is named "_main", not "main", so + // when reading references to _main from a host object we want + // to avoid rewriting "_main" to "main" in this specific + // instance. See #issuecomment-1143698749 on #35006 for more + // details on this problem. + if state.arch.Family == sys.I386 && name[0] == '_' && name != "_main" && !strings.HasPrefix(name, "__imp_") { + 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) + } + + 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. + 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 + } + 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) + } + } + return nil +} + +// LookupBaseFromImport examines the symbol "s" to see if it +// corresponds to an import symbol (name of the form "__imp_XYZ") and +// if so, it looks up the underlying target of the import symbol and +// returns it. An error is returned if the symbol is of the form +// "__imp_XYZ" but no XYZ can be found. +func LookupBaseFromImport(s loader.Sym, ldr *loader.Loader, arch *sys.Arch) (loader.Sym, error) { + sname := ldr.SymName(s) + if !strings.HasPrefix(sname, "__imp_") { + return 0, nil + } + basename := sname[len("__imp_"):] + if arch.Family == sys.I386 && basename[0] == '_' { + basename = basename[1:] // _Name => Name + } + isym := ldr.Lookup(basename, 0) + if isym == 0 { + return 0, fmt.Errorf("internal error: import symbol %q with no underlying sym", sname) + } + return isym, nil +} |