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"
28 using namespace llvm::COFF;
29 using namespace llvm::object;
35 static bool is32bit(MachineTypes Machine) {
38 llvm_unreachable("unsupported machine");
39 case IMAGE_FILE_MACHINE_AMD64:
41 case IMAGE_FILE_MACHINE_ARMNT:
42 case IMAGE_FILE_MACHINE_I386:
47 static uint16_t getImgRelRelocation(MachineTypes Machine) {
50 llvm_unreachable("unsupported machine");
51 case IMAGE_FILE_MACHINE_AMD64:
52 return IMAGE_REL_AMD64_ADDR32NB;
53 case IMAGE_FILE_MACHINE_ARMNT:
54 return IMAGE_REL_ARM_ADDR32NB;
55 case IMAGE_FILE_MACHINE_I386:
56 return IMAGE_REL_I386_DIR32NB;
60 template <class T> static void append(std::vector<uint8_t> &B, const T &Data) {
62 B.resize(S + sizeof(T));
63 memcpy(&B[S], &Data, sizeof(T));
66 static void writeStringTable(std::vector<uint8_t> &B,
67 ArrayRef<const std::string> Strings) {
68 // The COFF string table consists of a 4-byte value which is the size of the
69 // table, including the length field itself. This value is followed by the
70 // string content itself, which is an array of null-terminated C-style
71 // strings. The termination is important as they are referenced to by offset
72 // by the symbol entity in the file format.
74 size_t Pos = B.size();
75 size_t Offset = B.size();
77 // Skip over the length field, we will fill it in later as we will have
78 // computed the length while emitting the string content itself.
79 Pos += sizeof(uint32_t);
81 for (const auto &S : Strings) {
82 B.resize(Pos + S.length() + 1);
83 strcpy(reinterpret_cast<char *>(&B[Pos]), S.c_str());
84 Pos += S.length() + 1;
87 // Backfill the length of the table now that it has been computed.
88 support::ulittle32_t Length(B.size() - Offset);
89 support::endian::write32le(&B[Offset], Length);
92 static ImportNameType getNameType(StringRef Sym, StringRef ExtName,
93 MachineTypes Machine) {
95 return IMPORT_NAME_UNDECORATE;
96 if (Machine == IMAGE_FILE_MACHINE_I386 && Sym.startswith("_"))
97 return IMPORT_NAME_NOPREFIX;
101 static Expected<std::string> replace(StringRef S, StringRef From,
103 size_t Pos = S.find(From);
105 // From and To may be mangled, but substrings in S may not.
106 if (Pos == StringRef::npos && From.startswith("_") && To.startswith("_")) {
107 From = From.substr(1);
112 if (Pos == StringRef::npos) {
113 return make_error<StringError>(
114 StringRef(Twine(S + ": replacing '" + From +
115 "' with '" + To + "' failed").str()), object_error::parse_failed);
118 return (Twine(S.substr(0, Pos)) + To + S.substr(Pos + From.size())).str();
121 static const std::string NullImportDescriptorSymbolName =
122 "__NULL_IMPORT_DESCRIPTOR";
125 // This class constructs various small object files necessary to support linking
126 // symbols imported from a DLL. The contents are pretty strictly defined and
127 // nearly entirely static. The details of the structures files are defined in
128 // WINNT.h and the PE/COFF specification.
129 class ObjectFactory {
130 using u16 = support::ulittle16_t;
131 using u32 = support::ulittle32_t;
132 MachineTypes Machine;
133 BumpPtrAllocator Alloc;
136 std::string ImportDescriptorSymbolName;
137 std::string NullThunkSymbolName;
140 ObjectFactory(StringRef S, MachineTypes M)
141 : Machine(M), DLLName(S), Library(S.drop_back(4)),
142 ImportDescriptorSymbolName(("__IMPORT_DESCRIPTOR_" + Library).str()),
143 NullThunkSymbolName(("\x7f" + Library + "_NULL_THUNK_DATA").str()) {}
145 // Creates an Import Descriptor. This is a small object file which contains a
146 // reference to the terminators and contains the library name (entry) for the
147 // import name table. It will force the linker to construct the necessary
148 // structure to import symbols from the DLL.
149 NewArchiveMember createImportDescriptor(std::vector<uint8_t> &Buffer);
151 // Creates a NULL import descriptor. This is a small object file whcih
152 // contains a NULL import descriptor. It is used to terminate the imports
153 // from a specific DLL.
154 NewArchiveMember createNullImportDescriptor(std::vector<uint8_t> &Buffer);
156 // Create a NULL Thunk Entry. This is a small object file which contains a
157 // NULL Import Address Table entry and a NULL Import Lookup Table Entry. It
158 // is used to terminate the IAT and ILT.
159 NewArchiveMember createNullThunk(std::vector<uint8_t> &Buffer);
161 // Create a short import file which is described in PE/COFF spec 7. Import
163 NewArchiveMember createShortImport(StringRef Sym, uint16_t Ordinal,
164 ImportType Type, ImportNameType NameType);
169 ObjectFactory::createImportDescriptor(std::vector<uint8_t> &Buffer) {
170 static const uint32_t NumberOfSections = 2;
171 static const uint32_t NumberOfSymbols = 7;
172 static const uint32_t NumberOfRelocations = 3;
175 coff_file_header Header{
177 u16(NumberOfSections),
179 u32(sizeof(Header) + (NumberOfSections * sizeof(coff_section)) +
181 sizeof(coff_import_directory_table_entry) +
182 NumberOfRelocations * sizeof(coff_relocation) +
184 (DLLName.size() + 1)),
185 u32(NumberOfSymbols),
187 u16(is32bit(Machine) ? IMAGE_FILE_32BIT_MACHINE : 0),
189 append(Buffer, Header);
191 // Section Header Table
192 static const coff_section SectionTable[NumberOfSections] = {
193 {{'.', 'i', 'd', 'a', 't', 'a', '$', '2'},
196 u32(sizeof(coff_import_directory_table_entry)),
197 u32(sizeof(coff_file_header) + NumberOfSections * sizeof(coff_section)),
198 u32(sizeof(coff_file_header) + NumberOfSections * sizeof(coff_section) +
199 sizeof(coff_import_directory_table_entry)),
201 u16(NumberOfRelocations),
203 u32(IMAGE_SCN_ALIGN_4BYTES | IMAGE_SCN_CNT_INITIALIZED_DATA |
204 IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE)},
205 {{'.', 'i', 'd', 'a', 't', 'a', '$', '6'},
208 u32(DLLName.size() + 1),
209 u32(sizeof(coff_file_header) + NumberOfSections * sizeof(coff_section) +
210 sizeof(coff_import_directory_table_entry) +
211 NumberOfRelocations * sizeof(coff_relocation)),
216 u32(IMAGE_SCN_ALIGN_2BYTES | IMAGE_SCN_CNT_INITIALIZED_DATA |
217 IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE)},
219 append(Buffer, SectionTable);
222 static const coff_import_directory_table_entry ImportDescriptor{
223 u32(0), u32(0), u32(0), u32(0), u32(0),
225 append(Buffer, ImportDescriptor);
227 static const coff_relocation RelocationTable[NumberOfRelocations] = {
228 {u32(offsetof(coff_import_directory_table_entry, NameRVA)), u32(2),
229 u16(getImgRelRelocation(Machine))},
230 {u32(offsetof(coff_import_directory_table_entry, ImportLookupTableRVA)),
231 u32(3), u16(getImgRelRelocation(Machine))},
232 {u32(offsetof(coff_import_directory_table_entry, ImportAddressTableRVA)),
233 u32(4), u16(getImgRelRelocation(Machine))},
235 append(Buffer, RelocationTable);
238 auto S = Buffer.size();
239 Buffer.resize(S + DLLName.size() + 1);
240 memcpy(&Buffer[S], DLLName.data(), DLLName.size());
241 Buffer[S + DLLName.size()] = '\0';
244 coff_symbol16 SymbolTable[NumberOfSymbols] = {
245 {{{0, 0, 0, 0, 0, 0, 0, 0}},
249 IMAGE_SYM_CLASS_EXTERNAL,
251 {{{'.', 'i', 'd', 'a', 't', 'a', '$', '2'}},
255 IMAGE_SYM_CLASS_SECTION,
257 {{{'.', 'i', 'd', 'a', 't', 'a', '$', '6'}},
261 IMAGE_SYM_CLASS_STATIC,
263 {{{'.', 'i', 'd', 'a', 't', 'a', '$', '4'}},
267 IMAGE_SYM_CLASS_SECTION,
269 {{{'.', 'i', 'd', 'a', 't', 'a', '$', '5'}},
273 IMAGE_SYM_CLASS_SECTION,
275 {{{0, 0, 0, 0, 0, 0, 0, 0}},
279 IMAGE_SYM_CLASS_EXTERNAL,
281 {{{0, 0, 0, 0, 0, 0, 0, 0}},
285 IMAGE_SYM_CLASS_EXTERNAL,
288 // TODO: Name.Offset.Offset here and in the all similar places below
289 // suggests a names refactoring. Maybe StringTableOffset.Value?
290 SymbolTable[0].Name.Offset.Offset =
292 SymbolTable[5].Name.Offset.Offset =
293 sizeof(uint32_t) + ImportDescriptorSymbolName.length() + 1;
294 SymbolTable[6].Name.Offset.Offset =
295 sizeof(uint32_t) + ImportDescriptorSymbolName.length() + 1 +
296 NullImportDescriptorSymbolName.length() + 1;
297 append(Buffer, SymbolTable);
300 writeStringTable(Buffer,
301 {ImportDescriptorSymbolName, NullImportDescriptorSymbolName,
302 NullThunkSymbolName});
304 StringRef F{reinterpret_cast<const char *>(Buffer.data()), Buffer.size()};
305 return {MemoryBufferRef(F, DLLName)};
309 ObjectFactory::createNullImportDescriptor(std::vector<uint8_t> &Buffer) {
310 static const uint32_t NumberOfSections = 1;
311 static const uint32_t NumberOfSymbols = 1;
314 coff_file_header Header{
316 u16(NumberOfSections),
318 u32(sizeof(Header) + (NumberOfSections * sizeof(coff_section)) +
320 sizeof(coff_import_directory_table_entry)),
321 u32(NumberOfSymbols),
323 u16(is32bit(Machine) ? IMAGE_FILE_32BIT_MACHINE : 0),
325 append(Buffer, Header);
327 // Section Header Table
328 static const coff_section SectionTable[NumberOfSections] = {
329 {{'.', 'i', 'd', 'a', 't', 'a', '$', '3'},
332 u32(sizeof(coff_import_directory_table_entry)),
333 u32(sizeof(coff_file_header) +
334 (NumberOfSections * sizeof(coff_section))),
339 u32(IMAGE_SCN_ALIGN_4BYTES | IMAGE_SCN_CNT_INITIALIZED_DATA |
340 IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE)},
342 append(Buffer, SectionTable);
345 static const coff_import_directory_table_entry ImportDescriptor{
346 u32(0), u32(0), u32(0), u32(0), u32(0),
348 append(Buffer, ImportDescriptor);
351 coff_symbol16 SymbolTable[NumberOfSymbols] = {
352 {{{0, 0, 0, 0, 0, 0, 0, 0}},
356 IMAGE_SYM_CLASS_EXTERNAL,
359 SymbolTable[0].Name.Offset.Offset = sizeof(uint32_t);
360 append(Buffer, SymbolTable);
363 writeStringTable(Buffer, {NullImportDescriptorSymbolName});
365 StringRef F{reinterpret_cast<const char *>(Buffer.data()), Buffer.size()};
366 return {MemoryBufferRef(F, DLLName)};
369 NewArchiveMember ObjectFactory::createNullThunk(std::vector<uint8_t> &Buffer) {
370 static const uint32_t NumberOfSections = 2;
371 static const uint32_t NumberOfSymbols = 1;
372 uint32_t VASize = is32bit(Machine) ? 4 : 8;
375 coff_file_header Header{
377 u16(NumberOfSections),
379 u32(sizeof(Header) + (NumberOfSections * sizeof(coff_section)) +
384 u32(NumberOfSymbols),
386 u16(is32bit(Machine) ? IMAGE_FILE_32BIT_MACHINE : 0),
388 append(Buffer, Header);
390 // Section Header Table
391 static const coff_section SectionTable[NumberOfSections] = {
392 {{'.', 'i', 'd', 'a', 't', 'a', '$', '5'},
396 u32(sizeof(coff_file_header) + NumberOfSections * sizeof(coff_section)),
401 u32((is32bit(Machine) ? IMAGE_SCN_ALIGN_4BYTES
402 : IMAGE_SCN_ALIGN_8BYTES) |
403 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ |
404 IMAGE_SCN_MEM_WRITE)},
405 {{'.', 'i', 'd', 'a', 't', 'a', '$', '4'},
409 u32(sizeof(coff_file_header) + NumberOfSections * sizeof(coff_section) +
415 u32((is32bit(Machine) ? IMAGE_SCN_ALIGN_4BYTES
416 : IMAGE_SCN_ALIGN_8BYTES) |
417 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ |
418 IMAGE_SCN_MEM_WRITE)},
420 append(Buffer, SectionTable);
423 append(Buffer, u32(0));
424 if (!is32bit(Machine))
425 append(Buffer, u32(0));
428 append(Buffer, u32(0));
429 if (!is32bit(Machine))
430 append(Buffer, u32(0));
433 coff_symbol16 SymbolTable[NumberOfSymbols] = {
434 {{{0, 0, 0, 0, 0, 0, 0, 0}},
438 IMAGE_SYM_CLASS_EXTERNAL,
441 SymbolTable[0].Name.Offset.Offset = sizeof(uint32_t);
442 append(Buffer, SymbolTable);
445 writeStringTable(Buffer, {NullThunkSymbolName});
447 StringRef F{reinterpret_cast<const char *>(Buffer.data()), Buffer.size()};
448 return {MemoryBufferRef{F, DLLName}};
451 NewArchiveMember ObjectFactory::createShortImport(StringRef Sym,
453 ImportType ImportType,
454 ImportNameType NameType) {
455 size_t ImpSize = DLLName.size() + Sym.size() + 2; // +2 for NULs
456 size_t Size = sizeof(coff_import_header) + ImpSize;
457 char *Buf = Alloc.Allocate<char>(Size);
458 memset(Buf, 0, Size);
461 // Write short import library.
462 auto *Imp = reinterpret_cast<coff_import_header *>(P);
465 Imp->Machine = Machine;
466 Imp->SizeOfData = ImpSize;
468 Imp->OrdinalHint = Ordinal;
469 Imp->TypeInfo = (NameType << 2) | ImportType;
471 // Write symbol name and DLL name.
472 memcpy(P, Sym.data(), Sym.size());
474 memcpy(P, DLLName.data(), DLLName.size());
476 return {MemoryBufferRef(StringRef(Buf, Size), DLLName)};
479 std::error_code writeImportLibrary(StringRef DLLName, StringRef Path,
480 ArrayRef<COFFShortExport> Exports,
481 MachineTypes Machine) {
483 std::vector<NewArchiveMember> Members;
484 ObjectFactory OF(llvm::sys::path::filename(DLLName), Machine);
486 std::vector<uint8_t> ImportDescriptor;
487 Members.push_back(OF.createImportDescriptor(ImportDescriptor));
489 std::vector<uint8_t> NullImportDescriptor;
490 Members.push_back(OF.createNullImportDescriptor(NullImportDescriptor));
492 std::vector<uint8_t> NullThunk;
493 Members.push_back(OF.createNullThunk(NullThunk));
495 for (COFFShortExport E : Exports) {
499 ImportType ImportType = IMPORT_CODE;
501 ImportType = IMPORT_DATA;
503 ImportType = IMPORT_CONST;
505 StringRef SymbolName = E.isWeak() ? E.ExtName : E.Name;
506 ImportNameType NameType = getNameType(SymbolName, E.Name, Machine);
507 Expected<std::string> Name = E.ExtName.empty()
509 : replace(SymbolName, E.Name, E.ExtName);
512 return errorToErrorCode(Name.takeError());
516 OF.createShortImport(*Name, E.Ordinal, ImportType, NameType));
519 std::pair<StringRef, std::error_code> Result =
520 writeArchive(Path, Members, /*WriteSymtab*/ true, object::Archive::K_GNU,
521 /*Deterministic*/ true, /*Thin*/ false);
523 return Result.second;
526 } // namespace object