| //===- OutputSections.cpp -------------------------------------------------===// |
| // |
| // The LLVM Linker |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "OutputSections.h" |
| #include "Config.h" |
| #include "EhFrame.h" |
| #include "LinkerScript.h" |
| #include "Memory.h" |
| #include "Strings.h" |
| #include "SymbolTable.h" |
| #include "SyntheticSections.h" |
| #include "Target.h" |
| #include "Threads.h" |
| #include "llvm/Support/Dwarf.h" |
| #include "llvm/Support/MD5.h" |
| #include "llvm/Support/MathExtras.h" |
| #include "llvm/Support/SHA1.h" |
| |
| using namespace llvm; |
| using namespace llvm::dwarf; |
| using namespace llvm::object; |
| using namespace llvm::support::endian; |
| using namespace llvm::ELF; |
| |
| using namespace lld; |
| using namespace lld::elf; |
| |
| OutputSectionBase::OutputSectionBase(StringRef Name, uint32_t Type, |
| uint64_t Flags) |
| : Name(Name) { |
| this->Type = Type; |
| this->Flags = Flags; |
| this->Addralign = 1; |
| } |
| |
| uint32_t OutputSectionBase::getPhdrFlags() const { |
| uint32_t Ret = PF_R; |
| if (Flags & SHF_WRITE) |
| Ret |= PF_W; |
| if (Flags & SHF_EXECINSTR) |
| Ret |= PF_X; |
| return Ret; |
| } |
| |
| template <class ELFT> |
| void OutputSectionBase::writeHeaderTo(typename ELFT::Shdr *Shdr) { |
| Shdr->sh_entsize = Entsize; |
| Shdr->sh_addralign = Addralign; |
| Shdr->sh_type = Type; |
| Shdr->sh_offset = Offset; |
| Shdr->sh_flags = Flags; |
| Shdr->sh_info = Info; |
| Shdr->sh_link = Link; |
| Shdr->sh_addr = Addr; |
| Shdr->sh_size = Size; |
| Shdr->sh_name = ShName; |
| } |
| |
| template <class ELFT> static uint64_t getEntsize(uint32_t Type) { |
| switch (Type) { |
| case SHT_RELA: |
| return sizeof(typename ELFT::Rela); |
| case SHT_REL: |
| return sizeof(typename ELFT::Rel); |
| case SHT_MIPS_REGINFO: |
| return sizeof(Elf_Mips_RegInfo<ELFT>); |
| case SHT_MIPS_OPTIONS: |
| return sizeof(Elf_Mips_Options<ELFT>) + sizeof(Elf_Mips_RegInfo<ELFT>); |
| case SHT_MIPS_ABIFLAGS: |
| return sizeof(Elf_Mips_ABIFlags<ELFT>); |
| default: |
| return 0; |
| } |
| } |
| |
| template <class ELFT> |
| OutputSection<ELFT>::OutputSection(StringRef Name, uint32_t Type, uintX_t Flags) |
| : OutputSectionBase(Name, Type, Flags) { |
| this->Entsize = getEntsize<ELFT>(Type); |
| } |
| |
| template <typename ELFT> |
| static bool compareByFilePosition(InputSection<ELFT> *A, |
| InputSection<ELFT> *B) { |
| // Synthetic doesn't have link order dependecy, stable_sort will keep it last |
| if (A->kind() == InputSectionData::Synthetic || |
| B->kind() == InputSectionData::Synthetic) |
| return false; |
| auto *LA = cast<InputSection<ELFT>>(A->getLinkOrderDep()); |
| auto *LB = cast<InputSection<ELFT>>(B->getLinkOrderDep()); |
| OutputSectionBase *AOut = LA->OutSec; |
| OutputSectionBase *BOut = LB->OutSec; |
| if (AOut != BOut) |
| return AOut->SectionIndex < BOut->SectionIndex; |
| return LA->OutSecOff < LB->OutSecOff; |
| } |
| |
| template <class ELFT> void OutputSection<ELFT>::finalize() { |
| if ((this->Flags & SHF_LINK_ORDER) && !this->Sections.empty()) { |
| std::sort(Sections.begin(), Sections.end(), compareByFilePosition<ELFT>); |
| Size = 0; |
| assignOffsets(); |
| |
| // We must preserve the link order dependency of sections with the |
| // SHF_LINK_ORDER flag. The dependency is indicated by the sh_link field. We |
| // need to translate the InputSection sh_link to the OutputSection sh_link, |
| // all InputSections in the OutputSection have the same dependency. |
| if (auto *D = this->Sections.front()->getLinkOrderDep()) |
| this->Link = D->OutSec->SectionIndex; |
| } |
| |
| uint32_t Type = this->Type; |
| if (!Config->Relocatable || (Type != SHT_RELA && Type != SHT_REL)) |
| return; |
| |
| this->Link = In<ELFT>::SymTab->OutSec->SectionIndex; |
| // sh_info for SHT_REL[A] sections should contain the section header index of |
| // the section to which the relocation applies. |
| InputSectionBase<ELFT> *S = Sections[0]->getRelocatedSection(); |
| this->Info = S->OutSec->SectionIndex; |
| } |
| |
| template <class ELFT> |
| void OutputSection<ELFT>::addSection(InputSectionData *C) { |
| assert(C->Live); |
| auto *S = cast<InputSection<ELFT>>(C); |
| Sections.push_back(S); |
| S->OutSec = this; |
| this->updateAlignment(S->Alignment); |
| // Keep sh_entsize value of the input section to be able to perform merging |
| // later during a final linking using the generated relocatable object. |
| if (Config->Relocatable && (S->Flags & SHF_MERGE)) |
| this->Entsize = S->Entsize; |
| } |
| |
| // This function is called after we sort input sections |
| // and scan relocations to setup sections' offsets. |
| template <class ELFT> void OutputSection<ELFT>::assignOffsets() { |
| uintX_t Off = this->Size; |
| for (InputSection<ELFT> *S : Sections) { |
| Off = alignTo(Off, S->Alignment); |
| S->OutSecOff = Off; |
| Off += S->getSize(); |
| } |
| this->Size = Off; |
| } |
| |
| template <class ELFT> |
| void OutputSection<ELFT>::sort( |
| std::function<int(InputSection<ELFT> *S)> Order) { |
| typedef std::pair<unsigned, InputSection<ELFT> *> Pair; |
| auto Comp = [](const Pair &A, const Pair &B) { return A.first < B.first; }; |
| |
| std::vector<Pair> V; |
| for (InputSection<ELFT> *S : Sections) |
| V.push_back({Order(S), S}); |
| std::stable_sort(V.begin(), V.end(), Comp); |
| Sections.clear(); |
| for (Pair &P : V) |
| Sections.push_back(P.second); |
| } |
| |
| // Sorts input sections by section name suffixes, so that .foo.N comes |
| // before .foo.M if N < M. Used to sort .{init,fini}_array.N sections. |
| // We want to keep the original order if the priorities are the same |
| // because the compiler keeps the original initialization order in a |
| // translation unit and we need to respect that. |
| // For more detail, read the section of the GCC's manual about init_priority. |
| template <class ELFT> void OutputSection<ELFT>::sortInitFini() { |
| // Sort sections by priority. |
| sort([](InputSection<ELFT> *S) { return getPriority(S->Name); }); |
| } |
| |
| // Returns true if S matches /Filename.?\.o$/. |
| static bool isCrtBeginEnd(StringRef S, StringRef Filename) { |
| if (!S.endswith(".o")) |
| return false; |
| S = S.drop_back(2); |
| if (S.endswith(Filename)) |
| return true; |
| return !S.empty() && S.drop_back().endswith(Filename); |
| } |
| |
| static bool isCrtbegin(StringRef S) { return isCrtBeginEnd(S, "crtbegin"); } |
| static bool isCrtend(StringRef S) { return isCrtBeginEnd(S, "crtend"); } |
| |
| // .ctors and .dtors are sorted by this priority from highest to lowest. |
| // |
| // 1. The section was contained in crtbegin (crtbegin contains |
| // some sentinel value in its .ctors and .dtors so that the runtime |
| // can find the beginning of the sections.) |
| // |
| // 2. The section has an optional priority value in the form of ".ctors.N" |
| // or ".dtors.N" where N is a number. Unlike .{init,fini}_array, |
| // they are compared as string rather than number. |
| // |
| // 3. The section is just ".ctors" or ".dtors". |
| // |
| // 4. The section was contained in crtend, which contains an end marker. |
| // |
| // In an ideal world, we don't need this function because .init_array and |
| // .ctors are duplicate features (and .init_array is newer.) However, there |
| // are too many real-world use cases of .ctors, so we had no choice to |
| // support that with this rather ad-hoc semantics. |
| template <class ELFT> |
| static bool compCtors(const InputSection<ELFT> *A, |
| const InputSection<ELFT> *B) { |
| bool BeginA = isCrtbegin(A->getFile()->getName()); |
| bool BeginB = isCrtbegin(B->getFile()->getName()); |
| if (BeginA != BeginB) |
| return BeginA; |
| bool EndA = isCrtend(A->getFile()->getName()); |
| bool EndB = isCrtend(B->getFile()->getName()); |
| if (EndA != EndB) |
| return EndB; |
| StringRef X = A->Name; |
| StringRef Y = B->Name; |
| assert(X.startswith(".ctors") || X.startswith(".dtors")); |
| assert(Y.startswith(".ctors") || Y.startswith(".dtors")); |
| X = X.substr(6); |
| Y = Y.substr(6); |
| if (X.empty() && Y.empty()) |
| return false; |
| return X < Y; |
| } |
| |
| // Sorts input sections by the special rules for .ctors and .dtors. |
| // Unfortunately, the rules are different from the one for .{init,fini}_array. |
| // Read the comment above. |
| template <class ELFT> void OutputSection<ELFT>::sortCtorsDtors() { |
| std::stable_sort(Sections.begin(), Sections.end(), compCtors<ELFT>); |
| } |
| |
| // Fill [Buf, Buf + Size) with Filler. Filler is written in big |
| // endian order. This is used for linker script "=fillexp" command. |
| void fill(uint8_t *Buf, size_t Size, uint32_t Filler) { |
| uint8_t V[4]; |
| write32be(V, Filler); |
| size_t I = 0; |
| for (; I + 4 < Size; I += 4) |
| memcpy(Buf + I, V, 4); |
| memcpy(Buf + I, V, Size - I); |
| } |
| |
| template <class ELFT> void OutputSection<ELFT>::writeTo(uint8_t *Buf) { |
| Loc = Buf; |
| if (uint32_t Filler = Script<ELFT>::X->getFiller(this->Name)) |
| fill(Buf, this->Size, Filler); |
| |
| auto Fn = [=](InputSection<ELFT> *IS) { IS->writeTo(Buf); }; |
| forEach(Sections.begin(), Sections.end(), Fn); |
| |
| // Linker scripts may have BYTE()-family commands with which you |
| // can write arbitrary bytes to the output. Process them if any. |
| Script<ELFT>::X->writeDataBytes(this->Name, Buf); |
| } |
| |
| template <class ELFT> |
| EhOutputSection<ELFT>::EhOutputSection() |
| : OutputSectionBase(".eh_frame", SHT_PROGBITS, SHF_ALLOC) {} |
| |
| // Search for an existing CIE record or create a new one. |
| // CIE records from input object files are uniquified by their contents |
| // and where their relocations point to. |
| template <class ELFT> |
| template <class RelTy> |
| CieRecord *EhOutputSection<ELFT>::addCie(EhSectionPiece &Piece, |
| ArrayRef<RelTy> Rels) { |
| auto *Sec = cast<EhInputSection<ELFT>>(Piece.ID); |
| const endianness E = ELFT::TargetEndianness; |
| if (read32<E>(Piece.data().data() + 4) != 0) |
| fatal(toString(Sec) + ": CIE expected at beginning of .eh_frame"); |
| |
| SymbolBody *Personality = nullptr; |
| unsigned FirstRelI = Piece.FirstRelocation; |
| if (FirstRelI != (unsigned)-1) |
| Personality = &Sec->getFile()->getRelocTargetSym(Rels[FirstRelI]); |
| |
| // Search for an existing CIE by CIE contents/relocation target pair. |
| CieRecord *Cie = &CieMap[{Piece.data(), Personality}]; |
| |
| // If not found, create a new one. |
| if (Cie->Piece == nullptr) { |
| Cie->Piece = &Piece; |
| Cies.push_back(Cie); |
| } |
| return Cie; |
| } |
| |
| // There is one FDE per function. Returns true if a given FDE |
| // points to a live function. |
| template <class ELFT> |
| template <class RelTy> |
| bool EhOutputSection<ELFT>::isFdeLive(EhSectionPiece &Piece, |
| ArrayRef<RelTy> Rels) { |
| auto *Sec = cast<EhInputSection<ELFT>>(Piece.ID); |
| unsigned FirstRelI = Piece.FirstRelocation; |
| if (FirstRelI == (unsigned)-1) |
| fatal(toString(Sec) + ": FDE doesn't reference another section"); |
| const RelTy &Rel = Rels[FirstRelI]; |
| SymbolBody &B = Sec->getFile()->getRelocTargetSym(Rel); |
| auto *D = dyn_cast<DefinedRegular<ELFT>>(&B); |
| if (!D || !D->Section) |
| return false; |
| InputSectionBase<ELFT> *Target = D->Section->Repl; |
| return Target && Target->Live; |
| } |
| |
| // .eh_frame is a sequence of CIE or FDE records. In general, there |
| // is one CIE record per input object file which is followed by |
| // a list of FDEs. This function searches an existing CIE or create a new |
| // one and associates FDEs to the CIE. |
| template <class ELFT> |
| template <class RelTy> |
| void EhOutputSection<ELFT>::addSectionAux(EhInputSection<ELFT> *Sec, |
| ArrayRef<RelTy> Rels) { |
| const endianness E = ELFT::TargetEndianness; |
| |
| DenseMap<size_t, CieRecord *> OffsetToCie; |
| for (EhSectionPiece &Piece : Sec->Pieces) { |
| // The empty record is the end marker. |
| if (Piece.size() == 4) |
| return; |
| |
| size_t Offset = Piece.InputOff; |
| uint32_t ID = read32<E>(Piece.data().data() + 4); |
| if (ID == 0) { |
| OffsetToCie[Offset] = addCie(Piece, Rels); |
| continue; |
| } |
| |
| uint32_t CieOffset = Offset + 4 - ID; |
| CieRecord *Cie = OffsetToCie[CieOffset]; |
| if (!Cie) |
| fatal(toString(Sec) + ": invalid CIE reference"); |
| |
| if (!isFdeLive(Piece, Rels)) |
| continue; |
| Cie->FdePieces.push_back(&Piece); |
| NumFdes++; |
| } |
| } |
| |
| template <class ELFT> |
| void EhOutputSection<ELFT>::addSection(InputSectionData *C) { |
| auto *Sec = cast<EhInputSection<ELFT>>(C); |
| Sec->OutSec = this; |
| this->updateAlignment(Sec->Alignment); |
| Sections.push_back(Sec); |
| |
| // .eh_frame is a sequence of CIE or FDE records. This function |
| // splits it into pieces so that we can call |
| // SplitInputSection::getSectionPiece on the section. |
| Sec->split(); |
| if (Sec->Pieces.empty()) |
| return; |
| |
| if (Sec->NumRelocations) { |
| if (Sec->AreRelocsRela) |
| addSectionAux(Sec, Sec->relas()); |
| else |
| addSectionAux(Sec, Sec->rels()); |
| return; |
| } |
| addSectionAux(Sec, makeArrayRef<Elf_Rela>(nullptr, nullptr)); |
| } |
| |
| template <class ELFT> |
| static void writeCieFde(uint8_t *Buf, ArrayRef<uint8_t> D) { |
| memcpy(Buf, D.data(), D.size()); |
| |
| // Fix the size field. -4 since size does not include the size field itself. |
| const endianness E = ELFT::TargetEndianness; |
| write32<E>(Buf, alignTo(D.size(), sizeof(typename ELFT::uint)) - 4); |
| } |
| |
| template <class ELFT> void EhOutputSection<ELFT>::finalize() { |
| if (this->Size) |
| return; // Already finalized. |
| |
| size_t Off = 0; |
| for (CieRecord *Cie : Cies) { |
| Cie->Piece->OutputOff = Off; |
| Off += alignTo(Cie->Piece->size(), sizeof(uintX_t)); |
| |
| for (EhSectionPiece *Fde : Cie->FdePieces) { |
| Fde->OutputOff = Off; |
| Off += alignTo(Fde->size(), sizeof(uintX_t)); |
| } |
| } |
| this->Size = Off; |
| } |
| |
| template <class ELFT> static uint64_t readFdeAddr(uint8_t *Buf, int Size) { |
| const endianness E = ELFT::TargetEndianness; |
| switch (Size) { |
| case DW_EH_PE_udata2: |
| return read16<E>(Buf); |
| case DW_EH_PE_udata4: |
| return read32<E>(Buf); |
| case DW_EH_PE_udata8: |
| return read64<E>(Buf); |
| case DW_EH_PE_absptr: |
| if (ELFT::Is64Bits) |
| return read64<E>(Buf); |
| return read32<E>(Buf); |
| } |
| fatal("unknown FDE size encoding"); |
| } |
| |
| // Returns the VA to which a given FDE (on a mmap'ed buffer) is applied to. |
| // We need it to create .eh_frame_hdr section. |
| template <class ELFT> |
| typename ELFT::uint EhOutputSection<ELFT>::getFdePc(uint8_t *Buf, size_t FdeOff, |
| uint8_t Enc) { |
| // The starting address to which this FDE applies is |
| // stored at FDE + 8 byte. |
| size_t Off = FdeOff + 8; |
| uint64_t Addr = readFdeAddr<ELFT>(Buf + Off, Enc & 0x7); |
| if ((Enc & 0x70) == DW_EH_PE_absptr) |
| return Addr; |
| if ((Enc & 0x70) == DW_EH_PE_pcrel) |
| return Addr + this->Addr + Off; |
| fatal("unknown FDE size relative encoding"); |
| } |
| |
| template <class ELFT> void EhOutputSection<ELFT>::writeTo(uint8_t *Buf) { |
| const endianness E = ELFT::TargetEndianness; |
| for (CieRecord *Cie : Cies) { |
| size_t CieOffset = Cie->Piece->OutputOff; |
| writeCieFde<ELFT>(Buf + CieOffset, Cie->Piece->data()); |
| |
| for (EhSectionPiece *Fde : Cie->FdePieces) { |
| size_t Off = Fde->OutputOff; |
| writeCieFde<ELFT>(Buf + Off, Fde->data()); |
| |
| // FDE's second word should have the offset to an associated CIE. |
| // Write it. |
| write32<E>(Buf + Off + 4, Off + 4 - CieOffset); |
| } |
| } |
| |
| for (EhInputSection<ELFT> *S : Sections) |
| S->relocate(Buf, nullptr); |
| |
| // Construct .eh_frame_hdr. .eh_frame_hdr is a binary search table |
| // to get a FDE from an address to which FDE is applied. So here |
| // we obtain two addresses and pass them to EhFrameHdr object. |
| if (In<ELFT>::EhFrameHdr) { |
| for (CieRecord *Cie : Cies) { |
| uint8_t Enc = getFdeEncoding<ELFT>(Cie->Piece); |
| for (SectionPiece *Fde : Cie->FdePieces) { |
| uintX_t Pc = getFdePc(Buf, Fde->OutputOff, Enc); |
| uintX_t FdeVA = this->Addr + Fde->OutputOff; |
| In<ELFT>::EhFrameHdr->addFde(Pc, FdeVA); |
| } |
| } |
| } |
| } |
| |
| template <class ELFT> |
| MergeOutputSection<ELFT>::MergeOutputSection(StringRef Name, uint32_t Type, |
| uintX_t Flags, uintX_t Alignment) |
| : OutputSectionBase(Name, Type, Flags), |
| Builder(StringTableBuilder::RAW, Alignment) {} |
| |
| template <class ELFT> void MergeOutputSection<ELFT>::writeTo(uint8_t *Buf) { |
| Builder.write(Buf); |
| } |
| |
| template <class ELFT> |
| void MergeOutputSection<ELFT>::addSection(InputSectionData *C) { |
| auto *Sec = cast<MergeInputSection<ELFT>>(C); |
| Sec->OutSec = this; |
| this->updateAlignment(Sec->Alignment); |
| this->Entsize = Sec->Entsize; |
| Sections.push_back(Sec); |
| } |
| |
| template <class ELFT> bool MergeOutputSection<ELFT>::shouldTailMerge() const { |
| return (this->Flags & SHF_STRINGS) && Config->Optimize >= 2; |
| } |
| |
| template <class ELFT> void MergeOutputSection<ELFT>::finalizeTailMerge() { |
| // Add all string pieces to the string table builder to create section |
| // contents. |
| for (MergeInputSection<ELFT> *Sec : Sections) |
| for (size_t I = 0, E = Sec->Pieces.size(); I != E; ++I) |
| if (Sec->Pieces[I].Live) |
| Builder.add(Sec->getData(I)); |
| |
| // Fix the string table content. After this, the contents will never change. |
| Builder.finalize(); |
| this->Size = Builder.getSize(); |
| |
| // finalize() fixed tail-optimized strings, so we can now get |
| // offsets of strings. Get an offset for each string and save it |
| // to a corresponding StringPiece for easy access. |
| for (MergeInputSection<ELFT> *Sec : Sections) |
| for (size_t I = 0, E = Sec->Pieces.size(); I != E; ++I) |
| if (Sec->Pieces[I].Live) |
| Sec->Pieces[I].OutputOff = Builder.getOffset(Sec->getData(I)); |
| } |
| |
| template <class ELFT> void MergeOutputSection<ELFT>::finalizeNoTailMerge() { |
| // Add all string pieces to the string table builder to create section |
| // contents. Because we are not tail-optimizing, offsets of strings are |
| // fixed when they are added to the builder (string table builder contains |
| // a hash table from strings to offsets). |
| for (MergeInputSection<ELFT> *Sec : Sections) |
| for (size_t I = 0, E = Sec->Pieces.size(); I != E; ++I) |
| if (Sec->Pieces[I].Live) |
| Sec->Pieces[I].OutputOff = Builder.add(Sec->getData(I)); |
| |
| Builder.finalizeInOrder(); |
| this->Size = Builder.getSize(); |
| } |
| |
| template <class ELFT> void MergeOutputSection<ELFT>::finalize() { |
| if (shouldTailMerge()) |
| finalizeTailMerge(); |
| else |
| finalizeNoTailMerge(); |
| } |
| |
| template <class ELFT> |
| static typename ELFT::uint getOutFlags(InputSectionBase<ELFT> *S) { |
| return S->Flags & ~SHF_GROUP & ~SHF_COMPRESSED; |
| } |
| |
| namespace llvm { |
| template <> struct DenseMapInfo<lld::elf::SectionKey> { |
| static lld::elf::SectionKey getEmptyKey(); |
| static lld::elf::SectionKey getTombstoneKey(); |
| static unsigned getHashValue(const lld::elf::SectionKey &Val); |
| static bool isEqual(const lld::elf::SectionKey &LHS, |
| const lld::elf::SectionKey &RHS); |
| }; |
| } |
| |
| template <class ELFT> |
| static SectionKey createKey(InputSectionBase<ELFT> *C, StringRef OutsecName) { |
| // The ELF spec just says |
| // ---------------------------------------------------------------- |
| // In the first phase, input sections that match in name, type and |
| // attribute flags should be concatenated into single sections. |
| // ---------------------------------------------------------------- |
| // |
| // However, it is clear that at least some flags have to be ignored for |
| // section merging. At the very least SHF_GROUP and SHF_COMPRESSED have to be |
| // ignored. We should not have two output .text sections just because one was |
| // in a group and another was not for example. |
| // |
| // It also seems that that wording was a late addition and didn't get the |
| // necessary scrutiny. |
| // |
| // Merging sections with different flags is expected by some users. One |
| // reason is that if one file has |
| // |
| // int *const bar __attribute__((section(".foo"))) = (int *)0; |
| // |
| // gcc with -fPIC will produce a read only .foo section. But if another |
| // file has |
| // |
| // int zed; |
| // int *const bar __attribute__((section(".foo"))) = (int *)&zed; |
| // |
| // gcc with -fPIC will produce a read write section. |
| // |
| // Last but not least, when using linker script the merge rules are forced by |
| // the script. Unfortunately, linker scripts are name based. This means that |
| // expressions like *(.foo*) can refer to multiple input sections with |
| // different flags. We cannot put them in different output sections or we |
| // would produce wrong results for |
| // |
| // start = .; *(.foo.*) end = .; *(.bar) |
| // |
| // and a mapping of .foo1 and .bar1 to one section and .foo2 and .bar2 to |
| // another. The problem is that there is no way to layout those output |
| // sections such that the .foo sections are the only thing between the start |
| // and end symbols. |
| // |
| // Given the above issues, we instead merge sections by name and error on |
| // incompatible types and flags. |
| // |
| // The exception being SHF_MERGE, where we create different output sections |
| // for each alignment. This makes each output section simple. In case of |
| // relocatable object generation we do not try to perform merging and treat |
| // SHF_MERGE sections as regular ones, but also create different output |
| // sections for them to allow merging at final linking stage. |
| // |
| // Fortunately, creating symbols in the middle of a merge section is not |
| // supported by bfd or gold, so the SHF_MERGE exception should not cause |
| // problems with most linker scripts. |
| |
| typedef typename ELFT::uint uintX_t; |
| uintX_t Flags = C->Flags & (SHF_MERGE | SHF_STRINGS); |
| |
| uintX_t Alignment = 0; |
| if (isa<MergeInputSection<ELFT>>(C) || |
| (Config->Relocatable && (C->Flags & SHF_MERGE))) |
| Alignment = std::max<uintX_t>(C->Alignment, C->Entsize); |
| |
| return SectionKey{OutsecName, Flags, Alignment}; |
| } |
| |
| template <class ELFT> OutputSectionFactory<ELFT>::OutputSectionFactory() {} |
| |
| template <class ELFT> OutputSectionFactory<ELFT>::~OutputSectionFactory() {} |
| |
| template <class ELFT> |
| std::pair<OutputSectionBase *, bool> |
| OutputSectionFactory<ELFT>::create(InputSectionBase<ELFT> *C, |
| StringRef OutsecName) { |
| SectionKey Key = createKey(C, OutsecName); |
| return create(Key, C); |
| } |
| |
| static uint64_t getIncompatibleFlags(uint64_t Flags) { |
| return Flags & (SHF_ALLOC | SHF_TLS); |
| } |
| |
| template <class ELFT> |
| std::pair<OutputSectionBase *, bool> |
| OutputSectionFactory<ELFT>::create(const SectionKey &Key, |
| InputSectionBase<ELFT> *C) { |
| uintX_t Flags = getOutFlags(C); |
| OutputSectionBase *&Sec = Map[Key]; |
| if (Sec) { |
| if (getIncompatibleFlags(Sec->Flags) != getIncompatibleFlags(C->Flags)) |
| error("Section has flags incompatible with others with the same name " + |
| toString(C)); |
| // Convert notbits to progbits if they are mixed. This happens is some |
| // linker scripts. |
| if (Sec->Type == SHT_NOBITS && C->Type == SHT_PROGBITS) |
| Sec->Type = SHT_PROGBITS; |
| if (Sec->Type != C->Type && |
| !(Sec->Type == SHT_PROGBITS && C->Type == SHT_NOBITS)) |
| error("Section has different type from others with the same name " + |
| toString(C)); |
| Sec->Flags |= Flags; |
| return {Sec, false}; |
| } |
| |
| uint32_t Type = C->Type; |
| switch (C->kind()) { |
| case InputSectionBase<ELFT>::Regular: |
| case InputSectionBase<ELFT>::Synthetic: |
| Sec = make<OutputSection<ELFT>>(Key.Name, Type, Flags); |
| break; |
| case InputSectionBase<ELFT>::EHFrame: |
| return {Out<ELFT>::EhFrame, false}; |
| case InputSectionBase<ELFT>::Merge: |
| Sec = make<MergeOutputSection<ELFT>>(Key.Name, Type, Flags, Key.Alignment); |
| break; |
| } |
| return {Sec, true}; |
| } |
| |
| SectionKey DenseMapInfo<SectionKey>::getEmptyKey() { |
| return SectionKey{DenseMapInfo<StringRef>::getEmptyKey(), 0, 0}; |
| } |
| |
| SectionKey DenseMapInfo<SectionKey>::getTombstoneKey() { |
| return SectionKey{DenseMapInfo<StringRef>::getTombstoneKey(), 0, 0}; |
| } |
| |
| unsigned DenseMapInfo<SectionKey>::getHashValue(const SectionKey &Val) { |
| return hash_combine(Val.Name, Val.Flags, Val.Alignment); |
| } |
| |
| bool DenseMapInfo<SectionKey>::isEqual(const SectionKey &LHS, |
| const SectionKey &RHS) { |
| return DenseMapInfo<StringRef>::isEqual(LHS.Name, RHS.Name) && |
| LHS.Flags == RHS.Flags && LHS.Alignment == RHS.Alignment; |
| } |
| |
| namespace lld { |
| namespace elf { |
| |
| template void OutputSectionBase::writeHeaderTo<ELF32LE>(ELF32LE::Shdr *Shdr); |
| template void OutputSectionBase::writeHeaderTo<ELF32BE>(ELF32BE::Shdr *Shdr); |
| template void OutputSectionBase::writeHeaderTo<ELF64LE>(ELF64LE::Shdr *Shdr); |
| template void OutputSectionBase::writeHeaderTo<ELF64BE>(ELF64BE::Shdr *Shdr); |
| |
| template class OutputSection<ELF32LE>; |
| template class OutputSection<ELF32BE>; |
| template class OutputSection<ELF64LE>; |
| template class OutputSection<ELF64BE>; |
| |
| template class EhOutputSection<ELF32LE>; |
| template class EhOutputSection<ELF32BE>; |
| template class EhOutputSection<ELF64LE>; |
| template class EhOutputSection<ELF64BE>; |
| |
| template class MergeOutputSection<ELF32LE>; |
| template class MergeOutputSection<ELF32BE>; |
| template class MergeOutputSection<ELF64LE>; |
| template class MergeOutputSection<ELF64BE>; |
| |
| template class OutputSectionFactory<ELF32LE>; |
| template class OutputSectionFactory<ELF32BE>; |
| template class OutputSectionFactory<ELF64LE>; |
| template class OutputSectionFactory<ELF64BE>; |
| } |
| } |