//===- DLL.cpp ------------------------------------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines various types of chunks for the DLL import or export
// descriptor tables. They are inherently Windows-specific.
// You need to read Microsoft PE/COFF spec to understand details
// about the data structures.
//
// If you are not particularly interested in linking against Windows
// DLL, you can skip this file, and you should still be able to
// understand the rest of the linker.
//
//===----------------------------------------------------------------------===//
#include "Chunks.h"
#include "DLL.h"
#include "llvm/Object/COFF.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/Path.h"
using namespace llvm;
using namespace llvm::object;
using namespace llvm::support::endian;
using namespace llvm::COFF;
namespace lld {
namespace coff {
namespace {
// Import table
static int ptrSize() { return Config->is64() ? 8 : 4; }
// A chunk for the import descriptor table.
class HintNameChunk : public Chunk {
public:
HintNameChunk(StringRef N, uint16_t H) : Name(N), Hint(H) {}
size_t getSize() const override {
// Starts with 2 byte Hint field, followed by a null-terminated string,
// ends with 0 or 1 byte padding.
return alignTo(Name.size() + 3, 2);
}
void writeTo(uint8_t *Buf) const override {
write16le(Buf + OutputSectionOff, Hint);
memcpy(Buf + OutputSectionOff + 2, Name.data(), Name.size());
}
private:
StringRef Name;
uint16_t Hint;
};
// A chunk for the import descriptor table.
class LookupChunk : public Chunk {
public:
explicit LookupChunk(Chunk *C) : HintName(C) {}
size_t getSize() const override { return ptrSize(); }
void writeTo(uint8_t *Buf) const override {
write32le(Buf + OutputSectionOff, HintName->getRVA());
}
Chunk *HintName;
};
// A chunk for the import descriptor table.
// This chunk represent import-by-ordinal symbols.
// See Microsoft PE/COFF spec 7.1. Import Header for details.
class OrdinalOnlyChunk : public Chunk {
public:
explicit OrdinalOnlyChunk(uint16_t V) : Ordinal(V) {}
size_t getSize() const override { return ptrSize(); }
void writeTo(uint8_t *Buf) const override {
// An import-by-ordinal slot has MSB 1 to indicate that
// this is import-by-ordinal (and not import-by-name).
if (Config->is64()) {
write64le(Buf + OutputSectionOff, (1ULL << 63) | Ordinal);
} else {
write32le(Buf + OutputSectionOff, (1ULL << 31) | Ordinal);
}
}
uint16_t Ordinal;
};
// A chunk for the import descriptor table.
class ImportDirectoryChunk : public Chunk {
public:
explicit ImportDirectoryChunk(Chunk *N) : DLLName(N) {}
size_t getSize() const override { return sizeof(ImportDirectoryTableEntry); }
void writeTo(uint8_t *Buf) const override {
auto *E = (coff_import_directory_table_entry *)(Buf + OutputSectionOff);
E->ImportLookupTableRVA = LookupTab->getRVA();
E->NameRVA = DLLName->getRVA();
E->ImportAddressTableRVA = AddressTab->getRVA();
}
Chunk *DLLName;
Chunk *LookupTab;
Chunk *AddressTab;
};
// A chunk representing null terminator in the import table.
// Contents of this chunk is always null bytes.
class NullChunk : public Chunk {
public:
explicit NullChunk(size_t N) : Size(N) {}
bool hasData() const override { return false; }
size_t getSize() const override { return Size; }
void setAlign(size_t N) { Align = N; }
private:
size_t Size;
};
static std::vector<std::vector<DefinedImportData *>>
binImports(const std::vector<DefinedImportData *> &Imports) {
// Group DLL-imported symbols by DLL name because that's how
// symbols are layed out in the import descriptor table.
auto Less = [](const std::string &A, const std::string &B) {
return Config->DLLOrder[A] < Config->DLLOrder[B];
};
std::map<std::string, std::vector<DefinedImportData *>,
bool(*)(const std::string &, const std::string &)> M(Less);
for (DefinedImportData *Sym : Imports)
M[Sym->getDLLName().lower()].push_back(Sym);
std::vector<std::vector<DefinedImportData *>> V;
for (auto &KV : M) {
// Sort symbols by name for each group.
std::vector<DefinedImportData *> &Syms = KV.second;
std::sort(Syms.begin(), Syms.end(),
[](DefinedImportData *A, DefinedImportData *B) {
return A->getName() < B->getName();
});
V.push_back(std::move(Syms));
}
return V;
}
// Export table
// See Microsoft PE/COFF spec 4.3 for details.
// A chunk for the delay import descriptor table etnry.
class DelayDirectoryChunk : public Chunk {
public:
explicit DelayDirectoryChunk(Chunk *N) : DLLName(N) {}
size_t getSize() const override {
return sizeof(delay_import_directory_table_entry);
}
void writeTo(uint8_t *Buf) const override {
auto *E = (delay_import_directory_table_entry *)(Buf + OutputSectionOff);
E->Attributes = 1;
E->Name = DLLName->getRVA();
E->ModuleHandle = ModuleHandle->getRVA();
E->DelayImportAddressTable = AddressTab->getRVA();
E->DelayImportNameTable = NameTab->getRVA();
}
Chunk *DLLName;
Chunk *ModuleHandle;
Chunk *AddressTab;
Chunk *NameTab;
};
// Initial contents for delay-loaded functions.
// This code calls __delayLoadHelper2 function to resolve a symbol
// and then overwrites its jump table slot with the result
// for subsequent function calls.
static const uint8_t ThunkX64[] = {
0x51, // push rcx
0x52, // push rdx
0x41, 0x50, // push r8
0x41, 0x51, // push r9
0x48, 0x83, 0xEC, 0x48, // sub rsp, 48h
0x66, 0x0F, 0x7F, 0x04, 0x24, // movdqa xmmword ptr [rsp], xmm0
0x66, 0x0F, 0x7F, 0x4C, 0x24, 0x10, // movdqa xmmword ptr [rsp+10h], xmm1
0x66, 0x0F, 0x7F, 0x54, 0x24, 0x20, // movdqa xmmword ptr [rsp+20h], xmm2
0x66, 0x0F, 0x7F, 0x5C, 0x24, 0x30, // movdqa xmmword ptr [rsp+30h], xmm3
0x48, 0x8D, 0x15, 0, 0, 0, 0, // lea rdx, [__imp_<FUNCNAME>]
0x48, 0x8D, 0x0D, 0, 0, 0, 0, // lea rcx, [___DELAY_IMPORT_...]
0xE8, 0, 0, 0, 0, // call __delayLoadHelper2
0x66, 0x0F, 0x6F, 0x04, 0x24, // movdqa xmm0, xmmword ptr [rsp]
0x66, 0x0F, 0x6F, 0x4C, 0x24, 0x10, // movdqa xmm1, xmmword ptr [rsp+10h]
0x66, 0x0F, 0x6F, 0x54, 0x24, 0x20, // movdqa xmm2, xmmword ptr [rsp+20h]
0x66, 0x0F, 0x6F, 0x5C, 0x24, 0x30, // movdqa xmm3, xmmword ptr [rsp+30h]
0x48, 0x83, 0xC4, 0x48, // add rsp, 48h
0x41, 0x59, // pop r9
0x41, 0x58, // pop r8
0x5A, // pop rdx
0x59, // pop rcx
0xFF, 0xE0, // jmp rax
};
static const uint8_t ThunkX86[] = {
0x51, // push ecx
0x52, // push edx
0x68, 0, 0, 0, 0, // push offset ___imp__<FUNCNAME>
0x68, 0, 0, 0, 0, // push offset ___DELAY_IMPORT_DESCRIPTOR_<DLLNAME>_dll
0xE8, 0, 0, 0, 0, // call ___delayLoadHelper2@8
0x5A, // pop edx
0x59, // pop ecx
0xFF, 0xE0, // jmp eax
};
// A chunk for the delay import thunk.
class ThunkChunkX64 : public Chunk {
public:
ThunkChunkX64(Defined *I, Chunk *D, Defined *H)
: Imp(I), Desc(D), Helper(H) {}
size_t getSize() const override { return sizeof(ThunkX64); }
void writeTo(uint8_t *Buf) const override {
memcpy(Buf + OutputSectionOff, ThunkX64, sizeof(ThunkX64));
write32le(Buf + OutputSectionOff + 36, Imp->getRVA() - RVA - 40);
write32le(Buf + OutputSectionOff + 43, Desc->getRVA() - RVA - 47);
write32le(Buf + OutputSectionOff + 48, Helper->getRVA() - RVA - 52);
}
Defined *Imp = nullptr;
Chunk *Desc = nullptr;
Defined *Helper = nullptr;
};
class ThunkChunkX86 : public Chunk {
public:
ThunkChunkX86(Defined *I, Chunk *D, Defined *H)
: Imp(I), Desc(D), Helper(H) {}
size_t getSize() const override { return sizeof(ThunkX86); }
void writeTo(uint8_t *Buf) const override {
memcpy(Buf + OutputSectionOff, ThunkX86, sizeof(ThunkX86));
write32le(Buf + OutputSectionOff + 3, Imp->getRVA() + Config->ImageBase);
write32le(Buf + OutputSectionOff + 8, Desc->getRVA() + Config->ImageBase);
write32le(Buf + OutputSectionOff + 13, Helper->getRVA() - RVA - 17);
}
void getBaserels(std::vector<Baserel> *Res) override {
Res->emplace_back(RVA + 3);
Res->emplace_back(RVA + 8);
}
Defined *Imp = nullptr;
Chunk *Desc = nullptr;
Defined *Helper = nullptr;
};
// A chunk for the import descriptor table.
class DelayAddressChunk : public Chunk {
public:
explicit DelayAddressChunk(Chunk *C) : Thunk(C) {}
size_t getSize() const override { return ptrSize(); }
void writeTo(uint8_t *Buf) const override {
if (Config->is64()) {
write64le(Buf + OutputSectionOff, Thunk->getRVA() + Config->ImageBase);
} else {
write32le(Buf + OutputSectionOff, Thunk->getRVA() + Config->ImageBase);
}
}
void getBaserels(std::vector<Baserel> *Res) override {
Res->emplace_back(RVA);
}
Chunk *Thunk;
};
// Export table
// Read Microsoft PE/COFF spec 5.3 for details.
// A chunk for the export descriptor table.
class ExportDirectoryChunk : public Chunk {
public:
ExportDirectoryChunk(int I, int J, Chunk *D, Chunk *A, Chunk *N, Chunk *O)
: MaxOrdinal(I), NameTabSize(J), DLLName(D), AddressTab(A), NameTab(N),
OrdinalTab(O) {}
size_t getSize() const override {
return sizeof(export_directory_table_entry);
}
void writeTo(uint8_t *Buf) const override {
auto *E = (export_directory_table_entry *)(Buf + OutputSectionOff);
E->NameRVA = DLLName->getRVA();
E->OrdinalBase = 0;
E->AddressTableEntries = MaxOrdinal + 1;
E->NumberOfNamePointers = NameTabSize;
E->ExportAddressTableRVA = AddressTab->getRVA();
E->NamePointerRVA = NameTab->getRVA();
E->OrdinalTableRVA = OrdinalTab->getRVA();
}
uint16_t MaxOrdinal;
uint16_t NameTabSize;
Chunk *DLLName;
Chunk *AddressTab;
Chunk *NameTab;
Chunk *OrdinalTab;
};
class AddressTableChunk : public Chunk {
public:
explicit AddressTableChunk(size_t MaxOrdinal) : Size(MaxOrdinal + 1) {}
size_t getSize() const override { return Size * 4; }
void writeTo(uint8_t *Buf) const override {
for (Export &E : Config->Exports) {
uint8_t *P = Buf + OutputSectionOff + E.Ordinal * 4;
if (E.ForwardChunk) {
write32le(P, E.ForwardChunk->getRVA());
} else {
write32le(P, cast<Defined>(E.Sym)->getRVA());
}
}
}
private:
size_t Size;
};
class NamePointersChunk : public Chunk {
public:
explicit NamePointersChunk(std::vector<Chunk *> &V) : Chunks(V) {}
size_t getSize() const override { return Chunks.size() * 4; }
void writeTo(uint8_t *Buf) const override {
uint8_t *P = Buf + OutputSectionOff;
for (Chunk *C : Chunks) {
write32le(P, C->getRVA());
P += 4;
}
}
private:
std::vector<Chunk *> Chunks;
};
class ExportOrdinalChunk : public Chunk {
public:
explicit ExportOrdinalChunk(size_t I) : Size(I) {}
size_t getSize() const override { return Size * 2; }
void writeTo(uint8_t *Buf) const override {
uint8_t *P = Buf + OutputSectionOff;
for (Export &E : Config->Exports) {
if (E.Noname)
continue;
write16le(P, E.Ordinal);
P += 2;
}
}
private:
size_t Size;
};
} // anonymous namespace
uint64_t IdataContents::getDirSize() {
return Dirs.size() * sizeof(ImportDirectoryTableEntry);
}
uint64_t IdataContents::getIATSize() {
return Addresses.size() * ptrSize();
}
// Returns a list of .idata contents.
// See Microsoft PE/COFF spec 5.4 for details.
std::vector<Chunk *> IdataContents::getChunks() {
create();
// The loader assumes a specific order of data.
// Add each type in the correct order.
std::vector<Chunk *> V;
V.insert(V.end(), Dirs.begin(), Dirs.end());
V.insert(V.end(), Lookups.begin(), Lookups.end());
V.insert(V.end(), Addresses.begin(), Addresses.end());
V.insert(V.end(), Hints.begin(), Hints.end());
V.insert(V.end(), DLLNames.begin(), DLLNames.end());
return V;
}
void IdataContents::create() {
std::vector<std::vector<DefinedImportData *>> V = binImports(Imports);
// Create .idata contents for each DLL.
for (std::vector<DefinedImportData *> &Syms : V) {
// Create lookup and address tables. If they have external names,
// we need to create HintName chunks to store the names.
// If they don't (if they are import-by-ordinals), we store only
// ordinal values to the table.
size_t Base = Lookups.size();
for (DefinedImportData *S : Syms) {
uint16_t Ord = S->getOrdinal();
if (S->getExternalName().empty()) {
Lookups.push_back(make<OrdinalOnlyChunk>(Ord));
Addresses.push_back(make<OrdinalOnlyChunk>(Ord));
continue;
}
auto *C = make<HintNameChunk>(S->getExternalName(), Ord);
Lookups.push_back(make<LookupChunk>(C));
Addresses.push_back(make<LookupChunk>(C));
Hints.push_back(C);
}
// Terminate with null values.
Lookups.push_back(make<NullChunk>(ptrSize()));
Addresses.push_back(make<NullChunk>(ptrSize()));
for (int I = 0, E = Syms.size(); I < E; ++I)
Syms[I]->setLocation(Addresses[Base + I]);
// Create the import table header.
DLLNames.push_back(make<StringChunk>(Syms[0]->getDLLName()));
auto *Dir = make<ImportDirectoryChunk>(DLLNames.back());
Dir->LookupTab = Lookups[Base];
Dir->AddressTab = Addresses[Base];
Dirs.push_back(Dir);
}
// Add null terminator.
Dirs.push_back(make<NullChunk>(sizeof(ImportDirectoryTableEntry)));
}
std::vector<Chunk *> DelayLoadContents::getChunks() {
std::vector<Chunk *> V;
V.insert(V.end(), Dirs.begin(), Dirs.end());
V.insert(V.end(), Names.begin(), Names.end());
V.insert(V.end(), HintNames.begin(), HintNames.end());
V.insert(V.end(), DLLNames.begin(), DLLNames.end());
return V;
}
std::vector<Chunk *> DelayLoadContents::getDataChunks() {
std::vector<Chunk *> V;
V.insert(V.end(), ModuleHandles.begin(), ModuleHandles.end());
V.insert(V.end(), Addresses.begin(), Addresses.end());
return V;
}
uint64_t DelayLoadContents::getDirSize() {
return Dirs.size() * sizeof(delay_import_directory_table_entry);
}
void DelayLoadContents::create(Defined *H) {
Helper = H;
std::vector<std::vector<DefinedImportData *>> V = binImports(Imports);
// Create .didat contents for each DLL.
for (std::vector<DefinedImportData *> &Syms : V) {
// Create the delay import table header.
DLLNames.push_back(make<StringChunk>(Syms[0]->getDLLName()));
auto *Dir = make<DelayDirectoryChunk>(DLLNames.back());
size_t Base = Addresses.size();
for (DefinedImportData *S : Syms) {
Chunk *T = newThunkChunk(S, Dir);
auto *A = make<DelayAddressChunk>(T);
Addresses.push_back(A);
Thunks.push_back(T);
StringRef ExtName = S->getExternalName();
if (ExtName.empty()) {
Names.push_back(make<OrdinalOnlyChunk>(S->getOrdinal()));
} else {
auto *C = make<HintNameChunk>(ExtName, 0);
Names.push_back(make<LookupChunk>(C));
HintNames.push_back(C);
}
}
// Terminate with null values.
Addresses.push_back(make<NullChunk>(8));
Names.push_back(make<NullChunk>(8));
for (int I = 0, E = Syms.size(); I < E; ++I)
Syms[I]->setLocation(Addresses[Base + I]);
auto *MH = make<NullChunk>(8);
MH->setAlign(8);
ModuleHandles.push_back(MH);
// Fill the delay import table header fields.
Dir->ModuleHandle = MH;
Dir->AddressTab = Addresses[Base];
Dir->NameTab = Names[Base];
Dirs.push_back(Dir);
}
// Add null terminator.
Dirs.push_back(make<NullChunk>(sizeof(delay_import_directory_table_entry)));
}
Chunk *DelayLoadContents::newThunkChunk(DefinedImportData *S, Chunk *Dir) {
switch (Config->Machine) {
case AMD64:
return make<ThunkChunkX64>(S, Dir, Helper);
case I386:
return make<ThunkChunkX86>(S, Dir, Helper);
default:
llvm_unreachable("unsupported machine type");
}
}
EdataContents::EdataContents() {
uint16_t MaxOrdinal = 0;
for (Export &E : Config->Exports)
MaxOrdinal = std::max(MaxOrdinal, E.Ordinal);
auto *DLLName = make<StringChunk>(sys::path::filename(Config->OutputFile));
auto *AddressTab = make<AddressTableChunk>(MaxOrdinal);
std::vector<Chunk *> Names;
for (Export &E : Config->Exports)
if (!E.Noname)
Names.push_back(make<StringChunk>(E.ExportName));
std::vector<Chunk *> Forwards;
for (Export &E : Config->Exports) {
if (E.ForwardTo.empty())
continue;
E.ForwardChunk = make<StringChunk>(E.ForwardTo);
Forwards.push_back(E.ForwardChunk);
}
auto *NameTab = make<NamePointersChunk>(Names);
auto *OrdinalTab = make<ExportOrdinalChunk>(Names.size());
auto *Dir = make<ExportDirectoryChunk>(MaxOrdinal, Names.size(), DLLName,
AddressTab, NameTab, OrdinalTab);
Chunks.push_back(Dir);
Chunks.push_back(DLLName);
Chunks.push_back(AddressTab);
Chunks.push_back(NameTab);
Chunks.push_back(OrdinalTab);
Chunks.insert(Chunks.end(), Names.begin(), Names.end());
Chunks.insert(Chunks.end(), Forwards.begin(), Forwards.end());
}
} // namespace coff
} // namespace lld