1 //===- COFFImportFile.cpp - COFF short import file implementation ---------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the writeImportLibrary function.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/Object/COFFImportFile.h"
15 #include "llvm/ADT/ArrayRef.h"
16 #include "llvm/Object/Archive.h"
17 #include "llvm/Object/ArchiveWriter.h"
18 #include "llvm/Object/COFF.h"
19 #include "llvm/Support/Error.h"
20 #include "llvm/Support/Path.h"
26 using namespace llvm::COFF;
27 using namespace llvm::object;
33 static bool is32bit(MachineTypes Machine) {
36 llvm_unreachable("unsupported machine");
37 case IMAGE_FILE_MACHINE_ARM64:
38 case IMAGE_FILE_MACHINE_AMD64:
40 case IMAGE_FILE_MACHINE_ARMNT:
41 case IMAGE_FILE_MACHINE_I386:
46 static uint16_t getImgRelRelocation(MachineTypes Machine) {
49 llvm_unreachable("unsupported machine");
50 case IMAGE_FILE_MACHINE_AMD64:
51 return IMAGE_REL_AMD64_ADDR32NB;
52 case IMAGE_FILE_MACHINE_ARMNT:
53 return IMAGE_REL_ARM_ADDR32NB;
54 case IMAGE_FILE_MACHINE_ARM64:
55 return IMAGE_REL_ARM64_ADDR32NB;
56 case IMAGE_FILE_MACHINE_I386:
57 return IMAGE_REL_I386_DIR32NB;
61 template <class T> static void append(std::vector<uint8_t> &B, const T &Data) {
63 B.resize(S + sizeof(T));
64 memcpy(&B[S], &Data, sizeof(T));
67 static void writeStringTable(std::vector<uint8_t> &B,
68 ArrayRef<const std::string> Strings) {
69 // The COFF string table consists of a 4-byte value which is the size of the
70 // table, including the length field itself. This value is followed by the
71 // string content itself, which is an array of null-terminated C-style
72 // strings. The termination is important as they are referenced to by offset
73 // by the symbol entity in the file format.
75 size_t Pos = B.size();
76 size_t Offset = B.size();
78 // Skip over the length field, we will fill it in later as we will have
79 // computed the length while emitting the string content itself.
80 Pos += sizeof(uint32_t);
82 for (const auto &S : Strings) {
83 B.resize(Pos + S.length() + 1);
84 strcpy(reinterpret_cast<char *>(&B[Pos]), S.c_str());
85 Pos += S.length() + 1;
88 // Backfill the length of the table now that it has been computed.
89 support::ulittle32_t Length(B.size() - Offset);
90 support::endian::write32le(&B[Offset], Length);
93 static ImportNameType getNameType(StringRef Sym, StringRef ExtName,
94 MachineTypes Machine, bool MinGW) {
95 // A decorated stdcall function in MSVC is exported with the
96 // type IMPORT_NAME, and the exported function name includes the
97 // the leading underscore. In MinGW on the other hand, a decorated
98 // stdcall function still omits the underscore (IMPORT_NAME_NOPREFIX).
99 // See the comment in isDecorated in COFFModuleDefinition.cpp for more
101 if (ExtName.startswith("_") && ExtName.contains('@') && !MinGW)
104 return IMPORT_NAME_UNDECORATE;
105 if (Machine == IMAGE_FILE_MACHINE_I386 && Sym.startswith("_"))
106 return IMPORT_NAME_NOPREFIX;
110 static Expected<std::string> replace(StringRef S, StringRef From,
112 size_t Pos = S.find(From);
114 // From and To may be mangled, but substrings in S may not.
115 if (Pos == StringRef::npos && From.startswith("_") && To.startswith("_")) {
116 From = From.substr(1);
121 if (Pos == StringRef::npos) {
122 return make_error<StringError>(
123 StringRef(Twine(S + ": replacing '" + From +
124 "' with '" + To + "' failed").str()), object_error::parse_failed);
127 return (Twine(S.substr(0, Pos)) + To + S.substr(Pos + From.size())).str();
130 static const std::string NullImportDescriptorSymbolName =
131 "__NULL_IMPORT_DESCRIPTOR";
134 // This class constructs various small object files necessary to support linking
135 // symbols imported from a DLL. The contents are pretty strictly defined and
136 // nearly entirely static. The details of the structures files are defined in
137 // WINNT.h and the PE/COFF specification.
138 class ObjectFactory {
139 using u16 = support::ulittle16_t;
140 using u32 = support::ulittle32_t;
141 MachineTypes Machine;
142 BumpPtrAllocator Alloc;
143 StringRef ImportName;
145 std::string ImportDescriptorSymbolName;
146 std::string NullThunkSymbolName;
149 ObjectFactory(StringRef S, MachineTypes M)
150 : Machine(M), ImportName(S), Library(S.drop_back(4)),
151 ImportDescriptorSymbolName(("__IMPORT_DESCRIPTOR_" + Library).str()),
152 NullThunkSymbolName(("\x7f" + Library + "_NULL_THUNK_DATA").str()) {}
154 // Creates an Import Descriptor. This is a small object file which contains a
155 // reference to the terminators and contains the library name (entry) for the
156 // import name table. It will force the linker to construct the necessary
157 // structure to import symbols from the DLL.
158 NewArchiveMember createImportDescriptor(std::vector<uint8_t> &Buffer);
160 // Creates a NULL import descriptor. This is a small object file whcih
161 // contains a NULL import descriptor. It is used to terminate the imports
162 // from a specific DLL.
163 NewArchiveMember createNullImportDescriptor(std::vector<uint8_t> &Buffer);
165 // Create a NULL Thunk Entry. This is a small object file which contains a
166 // NULL Import Address Table entry and a NULL Import Lookup Table Entry. It
167 // is used to terminate the IAT and ILT.
168 NewArchiveMember createNullThunk(std::vector<uint8_t> &Buffer);
170 // Create a short import file which is described in PE/COFF spec 7. Import
172 NewArchiveMember createShortImport(StringRef Sym, uint16_t Ordinal,
173 ImportType Type, ImportNameType NameType);
175 // Create a weak external file which is described in PE/COFF Aux Format 3.
176 NewArchiveMember createWeakExternal(StringRef Sym, StringRef Weak, bool Imp);
181 ObjectFactory::createImportDescriptor(std::vector<uint8_t> &Buffer) {
182 const uint32_t NumberOfSections = 2;
183 const uint32_t NumberOfSymbols = 7;
184 const uint32_t NumberOfRelocations = 3;
187 coff_file_header Header{
189 u16(NumberOfSections),
191 u32(sizeof(Header) + (NumberOfSections * sizeof(coff_section)) +
193 sizeof(coff_import_directory_table_entry) +
194 NumberOfRelocations * sizeof(coff_relocation) +
196 (ImportName.size() + 1)),
197 u32(NumberOfSymbols),
199 u16(is32bit(Machine) ? IMAGE_FILE_32BIT_MACHINE : C_Invalid),
201 append(Buffer, Header);
203 // Section Header Table
204 const coff_section SectionTable[NumberOfSections] = {
205 {{'.', 'i', 'd', 'a', 't', 'a', '$', '2'},
208 u32(sizeof(coff_import_directory_table_entry)),
209 u32(sizeof(coff_file_header) + NumberOfSections * sizeof(coff_section)),
210 u32(sizeof(coff_file_header) + NumberOfSections * sizeof(coff_section) +
211 sizeof(coff_import_directory_table_entry)),
213 u16(NumberOfRelocations),
215 u32(IMAGE_SCN_ALIGN_4BYTES | IMAGE_SCN_CNT_INITIALIZED_DATA |
216 IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE)},
217 {{'.', 'i', 'd', 'a', 't', 'a', '$', '6'},
220 u32(ImportName.size() + 1),
221 u32(sizeof(coff_file_header) + NumberOfSections * sizeof(coff_section) +
222 sizeof(coff_import_directory_table_entry) +
223 NumberOfRelocations * sizeof(coff_relocation)),
228 u32(IMAGE_SCN_ALIGN_2BYTES | IMAGE_SCN_CNT_INITIALIZED_DATA |
229 IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE)},
231 append(Buffer, SectionTable);
234 const coff_import_directory_table_entry ImportDescriptor{
235 u32(0), u32(0), u32(0), u32(0), u32(0),
237 append(Buffer, ImportDescriptor);
239 const coff_relocation RelocationTable[NumberOfRelocations] = {
240 {u32(offsetof(coff_import_directory_table_entry, NameRVA)), u32(2),
241 u16(getImgRelRelocation(Machine))},
242 {u32(offsetof(coff_import_directory_table_entry, ImportLookupTableRVA)),
243 u32(3), u16(getImgRelRelocation(Machine))},
244 {u32(offsetof(coff_import_directory_table_entry, ImportAddressTableRVA)),
245 u32(4), u16(getImgRelRelocation(Machine))},
247 append(Buffer, RelocationTable);
250 auto S = Buffer.size();
251 Buffer.resize(S + ImportName.size() + 1);
252 memcpy(&Buffer[S], ImportName.data(), ImportName.size());
253 Buffer[S + ImportName.size()] = '\0';
256 coff_symbol16 SymbolTable[NumberOfSymbols] = {
257 {{{0, 0, 0, 0, 0, 0, 0, 0}},
261 IMAGE_SYM_CLASS_EXTERNAL,
263 {{{'.', 'i', 'd', 'a', 't', 'a', '$', '2'}},
267 IMAGE_SYM_CLASS_SECTION,
269 {{{'.', 'i', 'd', 'a', 't', 'a', '$', '6'}},
273 IMAGE_SYM_CLASS_STATIC,
275 {{{'.', 'i', 'd', 'a', 't', 'a', '$', '4'}},
279 IMAGE_SYM_CLASS_SECTION,
281 {{{'.', 'i', 'd', 'a', 't', 'a', '$', '5'}},
285 IMAGE_SYM_CLASS_SECTION,
287 {{{0, 0, 0, 0, 0, 0, 0, 0}},
291 IMAGE_SYM_CLASS_EXTERNAL,
293 {{{0, 0, 0, 0, 0, 0, 0, 0}},
297 IMAGE_SYM_CLASS_EXTERNAL,
300 // TODO: Name.Offset.Offset here and in the all similar places below
301 // suggests a names refactoring. Maybe StringTableOffset.Value?
302 SymbolTable[0].Name.Offset.Offset =
304 SymbolTable[5].Name.Offset.Offset =
305 sizeof(uint32_t) + ImportDescriptorSymbolName.length() + 1;
306 SymbolTable[6].Name.Offset.Offset =
307 sizeof(uint32_t) + ImportDescriptorSymbolName.length() + 1 +
308 NullImportDescriptorSymbolName.length() + 1;
309 append(Buffer, SymbolTable);
312 writeStringTable(Buffer,
313 {ImportDescriptorSymbolName, NullImportDescriptorSymbolName,
314 NullThunkSymbolName});
316 StringRef F{reinterpret_cast<const char *>(Buffer.data()), Buffer.size()};
317 return {MemoryBufferRef(F, ImportName)};
321 ObjectFactory::createNullImportDescriptor(std::vector<uint8_t> &Buffer) {
322 const uint32_t NumberOfSections = 1;
323 const uint32_t NumberOfSymbols = 1;
326 coff_file_header Header{
328 u16(NumberOfSections),
330 u32(sizeof(Header) + (NumberOfSections * sizeof(coff_section)) +
332 sizeof(coff_import_directory_table_entry)),
333 u32(NumberOfSymbols),
335 u16(is32bit(Machine) ? IMAGE_FILE_32BIT_MACHINE : C_Invalid),
337 append(Buffer, Header);
339 // Section Header Table
340 const coff_section SectionTable[NumberOfSections] = {
341 {{'.', 'i', 'd', 'a', 't', 'a', '$', '3'},
344 u32(sizeof(coff_import_directory_table_entry)),
345 u32(sizeof(coff_file_header) +
346 (NumberOfSections * sizeof(coff_section))),
351 u32(IMAGE_SCN_ALIGN_4BYTES | IMAGE_SCN_CNT_INITIALIZED_DATA |
352 IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE)},
354 append(Buffer, SectionTable);
357 const coff_import_directory_table_entry ImportDescriptor{
358 u32(0), u32(0), u32(0), u32(0), u32(0),
360 append(Buffer, ImportDescriptor);
363 coff_symbol16 SymbolTable[NumberOfSymbols] = {
364 {{{0, 0, 0, 0, 0, 0, 0, 0}},
368 IMAGE_SYM_CLASS_EXTERNAL,
371 SymbolTable[0].Name.Offset.Offset = sizeof(uint32_t);
372 append(Buffer, SymbolTable);
375 writeStringTable(Buffer, {NullImportDescriptorSymbolName});
377 StringRef F{reinterpret_cast<const char *>(Buffer.data()), Buffer.size()};
378 return {MemoryBufferRef(F, ImportName)};
381 NewArchiveMember ObjectFactory::createNullThunk(std::vector<uint8_t> &Buffer) {
382 const uint32_t NumberOfSections = 2;
383 const uint32_t NumberOfSymbols = 1;
384 uint32_t VASize = is32bit(Machine) ? 4 : 8;
387 coff_file_header Header{
389 u16(NumberOfSections),
391 u32(sizeof(Header) + (NumberOfSections * sizeof(coff_section)) +
396 u32(NumberOfSymbols),
398 u16(is32bit(Machine) ? IMAGE_FILE_32BIT_MACHINE : C_Invalid),
400 append(Buffer, Header);
402 // Section Header Table
403 const coff_section SectionTable[NumberOfSections] = {
404 {{'.', 'i', 'd', 'a', 't', 'a', '$', '5'},
408 u32(sizeof(coff_file_header) + NumberOfSections * sizeof(coff_section)),
413 u32((is32bit(Machine) ? IMAGE_SCN_ALIGN_4BYTES
414 : IMAGE_SCN_ALIGN_8BYTES) |
415 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ |
416 IMAGE_SCN_MEM_WRITE)},
417 {{'.', 'i', 'd', 'a', 't', 'a', '$', '4'},
421 u32(sizeof(coff_file_header) + NumberOfSections * sizeof(coff_section) +
427 u32((is32bit(Machine) ? IMAGE_SCN_ALIGN_4BYTES
428 : IMAGE_SCN_ALIGN_8BYTES) |
429 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ |
430 IMAGE_SCN_MEM_WRITE)},
432 append(Buffer, SectionTable);
435 append(Buffer, u32(0));
436 if (!is32bit(Machine))
437 append(Buffer, u32(0));
440 append(Buffer, u32(0));
441 if (!is32bit(Machine))
442 append(Buffer, u32(0));
445 coff_symbol16 SymbolTable[NumberOfSymbols] = {
446 {{{0, 0, 0, 0, 0, 0, 0, 0}},
450 IMAGE_SYM_CLASS_EXTERNAL,
453 SymbolTable[0].Name.Offset.Offset = sizeof(uint32_t);
454 append(Buffer, SymbolTable);
457 writeStringTable(Buffer, {NullThunkSymbolName});
459 StringRef F{reinterpret_cast<const char *>(Buffer.data()), Buffer.size()};
460 return {MemoryBufferRef{F, ImportName}};
463 NewArchiveMember ObjectFactory::createShortImport(StringRef Sym,
465 ImportType ImportType,
466 ImportNameType NameType) {
467 size_t ImpSize = ImportName.size() + Sym.size() + 2; // +2 for NULs
468 size_t Size = sizeof(coff_import_header) + ImpSize;
469 char *Buf = Alloc.Allocate<char>(Size);
470 memset(Buf, 0, Size);
473 // Write short import library.
474 auto *Imp = reinterpret_cast<coff_import_header *>(P);
477 Imp->Machine = Machine;
478 Imp->SizeOfData = ImpSize;
480 Imp->OrdinalHint = Ordinal;
481 Imp->TypeInfo = (NameType << 2) | ImportType;
483 // Write symbol name and DLL name.
484 memcpy(P, Sym.data(), Sym.size());
486 memcpy(P, ImportName.data(), ImportName.size());
488 return {MemoryBufferRef(StringRef(Buf, Size), ImportName)};
491 NewArchiveMember ObjectFactory::createWeakExternal(StringRef Sym,
492 StringRef Weak, bool Imp) {
493 std::vector<uint8_t> Buffer;
494 const uint32_t NumberOfSections = 1;
495 const uint32_t NumberOfSymbols = 5;
498 coff_file_header Header{
500 u16(NumberOfSections),
502 u32(sizeof(Header) + (NumberOfSections * sizeof(coff_section))),
503 u32(NumberOfSymbols),
507 append(Buffer, Header);
509 // Section Header Table
510 const coff_section SectionTable[NumberOfSections] = {
511 {{'.', 'd', 'r', 'e', 'c', 't', 'v', 'e'},
520 u32(IMAGE_SCN_LNK_INFO | IMAGE_SCN_LNK_REMOVE)}};
521 append(Buffer, SectionTable);
524 coff_symbol16 SymbolTable[NumberOfSymbols] = {
525 {{{'@', 'c', 'o', 'm', 'p', '.', 'i', 'd'}},
529 IMAGE_SYM_CLASS_STATIC,
531 {{{'@', 'f', 'e', 'a', 't', '.', '0', '0'}},
535 IMAGE_SYM_CLASS_STATIC,
537 {{{0, 0, 0, 0, 0, 0, 0, 0}},
541 IMAGE_SYM_CLASS_EXTERNAL,
543 {{{0, 0, 0, 0, 0, 0, 0, 0}},
547 IMAGE_SYM_CLASS_WEAK_EXTERNAL,
549 {{{2, 0, 0, 0, IMAGE_WEAK_EXTERN_SEARCH_ALIAS, 0, 0, 0}},
553 IMAGE_SYM_CLASS_NULL,
556 SymbolTable[2].Name.Offset.Offset = sizeof(uint32_t);
558 //__imp_ String Table
559 StringRef Prefix = Imp ? "__imp_" : "";
560 SymbolTable[3].Name.Offset.Offset =
561 sizeof(uint32_t) + Sym.size() + Prefix.size() + 1;
562 append(Buffer, SymbolTable);
563 writeStringTable(Buffer, {(Prefix + Sym).str(),
564 (Prefix + Weak).str()});
566 // Copied here so we can still use writeStringTable
567 char *Buf = Alloc.Allocate<char>(Buffer.size());
568 memcpy(Buf, Buffer.data(), Buffer.size());
569 return {MemoryBufferRef(StringRef(Buf, Buffer.size()), ImportName)};
572 Error writeImportLibrary(StringRef ImportName, StringRef Path,
573 ArrayRef<COFFShortExport> Exports,
574 MachineTypes Machine, bool MinGW) {
576 std::vector<NewArchiveMember> Members;
577 ObjectFactory OF(llvm::sys::path::filename(ImportName), Machine);
579 std::vector<uint8_t> ImportDescriptor;
580 Members.push_back(OF.createImportDescriptor(ImportDescriptor));
582 std::vector<uint8_t> NullImportDescriptor;
583 Members.push_back(OF.createNullImportDescriptor(NullImportDescriptor));
585 std::vector<uint8_t> NullThunk;
586 Members.push_back(OF.createNullThunk(NullThunk));
588 for (COFFShortExport E : Exports) {
592 ImportType ImportType = IMPORT_CODE;
594 ImportType = IMPORT_DATA;
596 ImportType = IMPORT_CONST;
598 StringRef SymbolName = E.SymbolName.empty() ? E.Name : E.SymbolName;
599 ImportNameType NameType = getNameType(SymbolName, E.Name, Machine, MinGW);
600 Expected<std::string> Name = E.ExtName.empty()
602 : replace(SymbolName, E.Name, E.ExtName);
605 return Name.takeError();
607 if (!E.AliasTarget.empty() && *Name != E.AliasTarget) {
608 Members.push_back(OF.createWeakExternal(E.AliasTarget, *Name, false));
609 Members.push_back(OF.createWeakExternal(E.AliasTarget, *Name, true));
614 OF.createShortImport(*Name, E.Ordinal, ImportType, NameType));
617 return writeArchive(Path, Members, /*WriteSymtab*/ true,
618 object::Archive::K_GNU,
619 /*Deterministic*/ true, /*Thin*/ false);
622 } // namespace object