Index: lld/trunk/ELF/Driver.cpp =================================================================== --- lld/trunk/ELF/Driver.cpp +++ lld/trunk/ELF/Driver.cpp @@ -1086,6 +1086,14 @@ if (!Config->Relocatable) InputSections.push_back(createCommentSection()); + // Create a .bss section for each common symbol and then replace the common + // symbol with a DefinedRegular symbol. As a result, all common symbols are + // "instantiated" as regular defined symbols, so that we don't need to care + // about common symbols beyond this point. Note that if -r is given, we just + // need to pass through common symbols as-is. + if (Config->DefineCommon) + createCommonSections(); + // Do size optimizations: garbage collection, merging of SHF_MERGE sections // and identical code folding. if (Config->GcSections) Index: lld/trunk/ELF/MarkLive.cpp =================================================================== --- lld/trunk/ELF/MarkLive.cpp +++ lld/trunk/ELF/MarkLive.cpp @@ -64,11 +64,6 @@ std::function Fn) { SymbolBody &B = Sec.getFile()->getRelocTargetSym(Rel); - if (auto *Sym = dyn_cast(&B)) { - Sym->Live = true; - return; - } - if (auto *D = dyn_cast(&B)) { if (!D->Section) return; @@ -223,13 +218,9 @@ }; auto MarkSymbol = [&](SymbolBody *Sym) { - if (auto *D = dyn_cast_or_null(Sym)) { + if (auto *D = dyn_cast_or_null(Sym)) if (auto *IS = cast_or_null(D->Section)) Enqueue(IS, D->Value); - return; - } - if (auto *S = dyn_cast_or_null(Sym)) - S->Live = true; }; // Add GC root symbols. Index: lld/trunk/ELF/Symbols.h =================================================================== --- lld/trunk/ELF/Symbols.h +++ lld/trunk/ELF/Symbols.h @@ -167,11 +167,6 @@ return S->kind() == SymbolBody::DefinedCommonKind; } - // True if this symbol is not GC'ed. Liveness is usually a notion of - // input sections and not of symbols, but since common symbols don't - // belong to any input section, their liveness is managed by this bit. - bool Live; - // The maximum alignment we have seen for this symbol. uint32_t Alignment; Index: lld/trunk/ELF/Symbols.cpp =================================================================== --- lld/trunk/ELF/Symbols.cpp +++ lld/trunk/ELF/Symbols.cpp @@ -99,14 +99,8 @@ } return VA; } - case SymbolBody::DefinedCommonKind: { - if (!Config->DefineCommon) - return 0; - auto DC = cast(Body); - if (!DC.Live) - return 0; - return DC.Section->getParent()->Addr + DC.Section->OutSecOff; - } + case SymbolBody::DefinedCommonKind: + llvm_unreachable("common are converted to bss"); case SymbolBody::SharedKind: { auto &SS = cast(Body); if (SS.CopyRelSec) @@ -286,7 +280,7 @@ uint8_t StOther, uint8_t Type) : Defined(SymbolBody::DefinedCommonKind, Name, /*IsLocal=*/false, StOther, Type), - Live(!Config->GcSections), Alignment(Alignment), Size(Size) {} + Alignment(Alignment), Size(Size) {} // If a shared symbol is referred via a copy relocation, its alignment // becomes part of the ABI. This function returns a symbol alignment. Index: lld/trunk/ELF/SyntheticSections.h =================================================================== --- lld/trunk/ELF/SyntheticSections.h +++ lld/trunk/ELF/SyntheticSections.h @@ -786,7 +786,7 @@ size_t Size = 0; }; -std::vector createCommonSections(); +template void createCommonSections(); InputSection *createInterpSection(); template MergeInputSection *createCommentSection(); void decompressAndMergeSections(); Index: lld/trunk/ELF/SyntheticSections.cpp =================================================================== --- lld/trunk/ELF/SyntheticSections.cpp +++ lld/trunk/ELF/SyntheticSections.cpp @@ -54,24 +54,28 @@ return 0; } -std::vector elf::createCommonSections() { - if (!Config->DefineCommon) - return {}; - - std::vector Ret; +// Create a .bss section for each common section and replace the common symbol +// with a DefinedRegular symbol. +template void elf::createCommonSections() { for (Symbol *S : Symtab->getSymbols()) { auto *Sym = dyn_cast(S->body()); - if (!Sym || !Sym->Live) + + if (!Sym) continue; - Sym->Section = make("COMMON"); - size_t Pos = Sym->Section->reserveSpace(Sym->Size, Sym->Alignment); - assert(Pos == 0); - (void)Pos; - Sym->Section->File = Sym->getFile(); - Ret.push_back(Sym->Section); + // Create a synthetic section for the common data. + auto *Section = make("COMMON"); + Section->File = Sym->getFile(); + Section->Live = !Config->GcSections; + Section->reserveSpace(Sym->Size, Sym->Alignment); + InputSections.push_back(Section); + + // Replace all DefinedCommon symbols with DefinedRegular symbols so that we + // don't have to care about DefinedCommon symbols beyond this point. + replaceBody(S, Sym->getFile(), Sym->getName(), + static_cast(Sym->IsLocal), Sym->StOther, + Sym->Type, 0, Sym->getSize(), Section); } - return Ret; } // Returns an LLD version string. @@ -2378,6 +2382,11 @@ template void PltSection::addEntry(SymbolBody &Sym); template void PltSection::addEntry(SymbolBody &Sym); +template void elf::createCommonSections(); +template void elf::createCommonSections(); +template void elf::createCommonSections(); +template void elf::createCommonSections(); + template MergeInputSection *elf::createCommentSection(); template MergeInputSection *elf::createCommentSection(); template MergeInputSection *elf::createCommentSection(); Index: lld/trunk/ELF/SyntheticSections.cpp~RF2791d30b.TMP =================================================================== --- lld/trunk/ELF/SyntheticSections.cpp~RF2791d30b.TMP +++ lld/trunk/ELF/SyntheticSections.cpp~RF2791d30b.TMP @@ -0,0 +1,2451 @@ +//===- SyntheticSections.cpp ----------------------------------------------===// +// +// The LLVM Linker +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file contains linker-synthesized sections. Currently, +// synthetic sections are created either output sections or input sections, +// but we are rewriting code so that all synthetic sections are created as +// input sections. +// +//===----------------------------------------------------------------------===// + +#include "SyntheticSections.h" +#include "Config.h" +#include "Error.h" +#include "InputFiles.h" +#include "LinkerScript.h" +#include "Memory.h" +#include "OutputSections.h" +#include "Strings.h" +#include "SymbolTable.h" +#include "Target.h" +#include "Threads.h" +#include "Writer.h" +#include "lld/Config/Version.h" +#include "llvm/BinaryFormat/Dwarf.h" +#include "llvm/DebugInfo/DWARF/DWARFDebugPubTable.h" +#include "llvm/Object/Decompressor.h" +#include "llvm/Object/ELFObjectFile.h" +#include "llvm/Support/Endian.h" +#include "llvm/Support/MD5.h" +#include "llvm/Support/RandomNumberGenerator.h" +#include "llvm/Support/SHA1.h" +#include "llvm/Support/xxhash.h" +#include + +using namespace llvm; +using namespace llvm::dwarf; +using namespace llvm::ELF; +using namespace llvm::object; +using namespace llvm::support; +using namespace llvm::support::endian; + +using namespace lld; +using namespace lld::elf; + +uint64_t SyntheticSection::getVA() const { + if (OutputSection *Sec = getParent()) + return Sec->Addr + OutSecOff; + return 0; +} + +// Create a .bss section for each common section and replace the common symbol +// with a DefinedRegular symbol. +template void elf::createCommonSections() { + for (Symbol *S : Symtab->getSymbols()) { + auto *Sym = dyn_cast(S->body()); + + if (!Sym) + continue; + + // Create a synthetic section for the common data. + auto *Section = make("COMMON"); + Section->File = Sym->getFile(); + Section->Live = !Config->GcSections; + Section->reserveSpace(Sym->Size, Sym->Alignment); + InputSections.push_back(Section); + + // Replace all DefinedCommon symbols with DefinedRegular symbols so that we + // don't have to care about DefinedCommon symbols beyond this point. + replaceBody(S, Sym->getFile(), Sym->getName(), Sym->IsLocal, + Sym->StOther, Sym->Type, 0, + Sym->getSize(), Section); + } +} + +// Returns an LLD version string. +static ArrayRef getVersion() { + // Check LLD_VERSION first for ease of testing. + // You can get consitent output by using the environment variable. + // This is only for testing. + StringRef S = getenv("LLD_VERSION"); + if (S.empty()) + S = Saver.save(Twine("Linker: ") + getLLDVersion()); + + // +1 to include the terminating '\0'. + return {(const uint8_t *)S.data(), S.size() + 1}; +} + +// Creates a .comment section containing LLD version info. +// With this feature, you can identify LLD-generated binaries easily +// by "readelf --string-dump .comment ". +// The returned object is a mergeable string section. +template MergeInputSection *elf::createCommentSection() { + typename ELFT::Shdr Hdr = {}; + Hdr.sh_flags = SHF_MERGE | SHF_STRINGS; + Hdr.sh_type = SHT_PROGBITS; + Hdr.sh_entsize = 1; + Hdr.sh_addralign = 1; + + auto *Ret = + make((ObjFile *)nullptr, &Hdr, ".comment"); + Ret->Data = getVersion(); + return Ret; +} + +// .MIPS.abiflags section. +template +MipsAbiFlagsSection::MipsAbiFlagsSection(Elf_Mips_ABIFlags Flags) + : SyntheticSection(SHF_ALLOC, SHT_MIPS_ABIFLAGS, 8, ".MIPS.abiflags"), + Flags(Flags) { + this->Entsize = sizeof(Elf_Mips_ABIFlags); +} + +template void MipsAbiFlagsSection::writeTo(uint8_t *Buf) { + memcpy(Buf, &Flags, sizeof(Flags)); +} + +template +MipsAbiFlagsSection *MipsAbiFlagsSection::create() { + Elf_Mips_ABIFlags Flags = {}; + bool Create = false; + + for (InputSectionBase *Sec : InputSections) { + if (Sec->Type != SHT_MIPS_ABIFLAGS) + continue; + Sec->Live = false; + Create = true; + + std::string Filename = toString(Sec->getFile()); + const size_t Size = Sec->Data.size(); + // Older version of BFD (such as the default FreeBSD linker) concatenate + // .MIPS.abiflags instead of merging. To allow for this case (or potential + // zero padding) we ignore everything after the first Elf_Mips_ABIFlags + if (Size < sizeof(Elf_Mips_ABIFlags)) { + error(Filename + ": invalid size of .MIPS.abiflags section: got " + + Twine(Size) + " instead of " + Twine(sizeof(Elf_Mips_ABIFlags))); + return nullptr; + } + auto *S = reinterpret_cast(Sec->Data.data()); + if (S->version != 0) { + error(Filename + ": unexpected .MIPS.abiflags version " + + Twine(S->version)); + return nullptr; + } + + // LLD checks ISA compatibility in getMipsEFlags(). Here we just + // select the highest number of ISA/Rev/Ext. + Flags.isa_level = std::max(Flags.isa_level, S->isa_level); + Flags.isa_rev = std::max(Flags.isa_rev, S->isa_rev); + Flags.isa_ext = std::max(Flags.isa_ext, S->isa_ext); + Flags.gpr_size = std::max(Flags.gpr_size, S->gpr_size); + Flags.cpr1_size = std::max(Flags.cpr1_size, S->cpr1_size); + Flags.cpr2_size = std::max(Flags.cpr2_size, S->cpr2_size); + Flags.ases |= S->ases; + Flags.flags1 |= S->flags1; + Flags.flags2 |= S->flags2; + Flags.fp_abi = elf::getMipsFpAbiFlag(Flags.fp_abi, S->fp_abi, Filename); + }; + + if (Create) + return make>(Flags); + return nullptr; +} + +// .MIPS.options section. +template +MipsOptionsSection::MipsOptionsSection(Elf_Mips_RegInfo Reginfo) + : SyntheticSection(SHF_ALLOC, SHT_MIPS_OPTIONS, 8, ".MIPS.options"), + Reginfo(Reginfo) { + this->Entsize = sizeof(Elf_Mips_Options) + sizeof(Elf_Mips_RegInfo); +} + +template void MipsOptionsSection::writeTo(uint8_t *Buf) { + auto *Options = reinterpret_cast(Buf); + Options->kind = ODK_REGINFO; + Options->size = getSize(); + + if (!Config->Relocatable) + Reginfo.ri_gp_value = InX::MipsGot->getGp(); + memcpy(Buf + sizeof(Elf_Mips_Options), &Reginfo, sizeof(Reginfo)); +} + +template +MipsOptionsSection *MipsOptionsSection::create() { + // N64 ABI only. + if (!ELFT::Is64Bits) + return nullptr; + + Elf_Mips_RegInfo Reginfo = {}; + bool Create = false; + + for (InputSectionBase *Sec : InputSections) { + if (Sec->Type != SHT_MIPS_OPTIONS) + continue; + Sec->Live = false; + Create = true; + + std::string Filename = toString(Sec->getFile()); + ArrayRef D = Sec->Data; + + while (!D.empty()) { + if (D.size() < sizeof(Elf_Mips_Options)) { + error(Filename + ": invalid size of .MIPS.options section"); + break; + } + + auto *Opt = reinterpret_cast(D.data()); + if (Opt->kind == ODK_REGINFO) { + if (Config->Relocatable && Opt->getRegInfo().ri_gp_value) + error(Filename + ": unsupported non-zero ri_gp_value"); + Reginfo.ri_gprmask |= Opt->getRegInfo().ri_gprmask; + Sec->getFile()->MipsGp0 = Opt->getRegInfo().ri_gp_value; + break; + } + + if (!Opt->size) + fatal(Filename + ": zero option descriptor size"); + D = D.slice(Opt->size); + } + }; + + if (Create) + return make>(Reginfo); + return nullptr; +} + +// MIPS .reginfo section. +template +MipsReginfoSection::MipsReginfoSection(Elf_Mips_RegInfo Reginfo) + : SyntheticSection(SHF_ALLOC, SHT_MIPS_REGINFO, 4, ".reginfo"), + Reginfo(Reginfo) { + this->Entsize = sizeof(Elf_Mips_RegInfo); +} + +template void MipsReginfoSection::writeTo(uint8_t *Buf) { + if (!Config->Relocatable) + Reginfo.ri_gp_value = InX::MipsGot->getGp(); + memcpy(Buf, &Reginfo, sizeof(Reginfo)); +} + +template +MipsReginfoSection *MipsReginfoSection::create() { + // Section should be alive for O32 and N32 ABIs only. + if (ELFT::Is64Bits) + return nullptr; + + Elf_Mips_RegInfo Reginfo = {}; + bool Create = false; + + for (InputSectionBase *Sec : InputSections) { + if (Sec->Type != SHT_MIPS_REGINFO) + continue; + Sec->Live = false; + Create = true; + + if (Sec->Data.size() != sizeof(Elf_Mips_RegInfo)) { + error(toString(Sec->getFile()) + + ": invalid size of .reginfo section"); + return nullptr; + } + auto *R = reinterpret_cast(Sec->Data.data()); + if (Config->Relocatable && R->ri_gp_value) + error(toString(Sec->getFile()) + + ": unsupported non-zero ri_gp_value"); + + Reginfo.ri_gprmask |= R->ri_gprmask; + Sec->getFile()->MipsGp0 = R->ri_gp_value; + }; + + if (Create) + return make>(Reginfo); + return nullptr; +} + +InputSection *elf::createInterpSection() { + // StringSaver guarantees that the returned string ends with '\0'. + StringRef S = Saver.save(Config->DynamicLinker); + ArrayRef Contents = {(const uint8_t *)S.data(), S.size() + 1}; + + auto *Sec = + make(SHF_ALLOC, SHT_PROGBITS, 1, Contents, ".interp"); + Sec->Live = true; + return Sec; +} + +SymbolBody *elf::addSyntheticLocal(StringRef Name, uint8_t Type, uint64_t Value, + uint64_t Size, InputSectionBase *Section) { + auto *S = make(Name, /*IsLocal*/ true, STV_DEFAULT, Type, + Value, Size, Section); + if (InX::SymTab) + InX::SymTab->addSymbol(S); + return S; +} + +static size_t getHashSize() { + switch (Config->BuildId) { + case BuildIdKind::Fast: + return 8; + case BuildIdKind::Md5: + case BuildIdKind::Uuid: + return 16; + case BuildIdKind::Sha1: + return 20; + case BuildIdKind::Hexstring: + return Config->BuildIdVector.size(); + default: + llvm_unreachable("unknown BuildIdKind"); + } +} + +BuildIdSection::BuildIdSection() + : SyntheticSection(SHF_ALLOC, SHT_NOTE, 1, ".note.gnu.build-id"), + HashSize(getHashSize()) {} + +void BuildIdSection::writeTo(uint8_t *Buf) { + endianness E = Config->Endianness; + write32(Buf, 4, E); // Name size + write32(Buf + 4, HashSize, E); // Content size + write32(Buf + 8, NT_GNU_BUILD_ID, E); // Type + memcpy(Buf + 12, "GNU", 4); // Name string + HashBuf = Buf + 16; +} + +// Split one uint8 array into small pieces of uint8 arrays. +static std::vector> split(ArrayRef Arr, + size_t ChunkSize) { + std::vector> Ret; + while (Arr.size() > ChunkSize) { + Ret.push_back(Arr.take_front(ChunkSize)); + Arr = Arr.drop_front(ChunkSize); + } + if (!Arr.empty()) + Ret.push_back(Arr); + return Ret; +} + +// Computes a hash value of Data using a given hash function. +// In order to utilize multiple cores, we first split data into 1MB +// chunks, compute a hash for each chunk, and then compute a hash value +// of the hash values. +void BuildIdSection::computeHash( + llvm::ArrayRef Data, + std::function Arr)> HashFn) { + std::vector> Chunks = split(Data, 1024 * 1024); + std::vector Hashes(Chunks.size() * HashSize); + + // Compute hash values. + parallelForEachN(0, Chunks.size(), [&](size_t I) { + HashFn(Hashes.data() + I * HashSize, Chunks[I]); + }); + + // Write to the final output buffer. + HashFn(HashBuf, Hashes); +} + +BssSection::BssSection(StringRef Name) + : SyntheticSection(SHF_ALLOC | SHF_WRITE, SHT_NOBITS, 0, Name) {} + +size_t BssSection::reserveSpace(uint64_t Size, uint32_t Alignment) { + if (OutputSection *Sec = getParent()) + Sec->updateAlignment(Alignment); + this->Size = alignTo(this->Size, Alignment) + Size; + this->Alignment = std::max(this->Alignment, Alignment); + return this->Size - Size; +} + +void BuildIdSection::writeBuildId(ArrayRef Buf) { + switch (Config->BuildId) { + case BuildIdKind::Fast: + computeHash(Buf, [](uint8_t *Dest, ArrayRef Arr) { + write64le(Dest, xxHash64(toStringRef(Arr))); + }); + break; + case BuildIdKind::Md5: + computeHash(Buf, [](uint8_t *Dest, ArrayRef Arr) { + memcpy(Dest, MD5::hash(Arr).data(), 16); + }); + break; + case BuildIdKind::Sha1: + computeHash(Buf, [](uint8_t *Dest, ArrayRef Arr) { + memcpy(Dest, SHA1::hash(Arr).data(), 20); + }); + break; + case BuildIdKind::Uuid: + if (getRandomBytes(HashBuf, HashSize)) + error("entropy source failure"); + break; + case BuildIdKind::Hexstring: + memcpy(HashBuf, Config->BuildIdVector.data(), Config->BuildIdVector.size()); + break; + default: + llvm_unreachable("unknown BuildIdKind"); + } +} + +template +EhFrameSection::EhFrameSection() + : SyntheticSection(SHF_ALLOC, SHT_PROGBITS, 1, ".eh_frame") {} + +// 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 +template +CieRecord *EhFrameSection::addCie(EhSectionPiece &Cie, + ArrayRef Rels) { + auto *Sec = cast(Cie.Sec); + const endianness E = ELFT::TargetEndianness; + if (read32(Cie.data().data() + 4) != 0) + fatal(toString(Sec) + ": CIE expected at beginning of .eh_frame"); + + SymbolBody *Personality = nullptr; + unsigned FirstRelI = Cie.FirstRelocation; + if (FirstRelI != (unsigned)-1) + Personality = + &Sec->template getFile()->getRelocTargetSym(Rels[FirstRelI]); + + // Search for an existing CIE by CIE contents/relocation target pair. + CieRecord *&Rec = CieMap[{Cie.data(), Personality}]; + + // If not found, create a new one. + if (!Rec) { + Rec = make(); + Rec->Cie = &Cie; + CieRecords.push_back(Rec); + } + return Rec; +} + +// There is one FDE per function. Returns true if a given FDE +// points to a live function. +template +template +bool EhFrameSection::isFdeLive(EhSectionPiece &Fde, + ArrayRef Rels) { + auto *Sec = cast(Fde.Sec); + unsigned FirstRelI = Fde.FirstRelocation; + + // An FDE should point to some function because FDEs are to describe + // functions. That's however not always the case due to an issue of + // ld.gold with -r. ld.gold may discard only functions and leave their + // corresponding FDEs, which results in creating bad .eh_frame sections. + // To deal with that, we ignore such FDEs. + if (FirstRelI == (unsigned)-1) + return false; + + const RelTy &Rel = Rels[FirstRelI]; + SymbolBody &B = Sec->template getFile()->getRelocTargetSym(Rel); + if (auto *D = dyn_cast(&B)) + if (D->Section) + return cast(D->Section)->Repl->Live; + return false; +} + +// .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 +template +void EhFrameSection::addSectionAux(EhInputSection *Sec, + ArrayRef Rels) { + const endianness E = ELFT::TargetEndianness; + + DenseMap 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(Piece.data().data() + 4); + if (ID == 0) { + OffsetToCie[Offset] = addCie(Piece, Rels); + continue; + } + + uint32_t CieOffset = Offset + 4 - ID; + CieRecord *Rec = OffsetToCie[CieOffset]; + if (!Rec) + fatal(toString(Sec) + ": invalid CIE reference"); + + if (!isFdeLive(Piece, Rels)) + continue; + Rec->Fdes.push_back(&Piece); + NumFdes++; + } +} + +template +void EhFrameSection::addSection(InputSectionBase *C) { + auto *Sec = cast(C); + Sec->Parent = this; + updateAlignment(Sec->Alignment); + Sections.push_back(Sec); + for (auto *DS : Sec->DependentSections) + DependentSections.push_back(DS); + + // .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 == 0) + addSectionAux(Sec, makeArrayRef(nullptr, nullptr)); + else if (Sec->AreRelocsRela) + addSectionAux(Sec, Sec->template relas()); + else + addSectionAux(Sec, Sec->template rels()); +} + +template +static void writeCieFde(uint8_t *Buf, ArrayRef D) { + memcpy(Buf, D.data(), D.size()); + + size_t Aligned = alignTo(D.size(), sizeof(typename ELFT::uint)); + + // Zero-clear trailing padding if it exists. + memset(Buf + D.size(), 0, Aligned - D.size()); + + // Fix the size field. -4 since size does not include the size field itself. + const endianness E = ELFT::TargetEndianness; + write32(Buf, Aligned - 4); +} + +template void EhFrameSection::finalizeContents() { + if (this->Size) + return; // Already finalized. + + size_t Off = 0; + for (CieRecord *Rec : CieRecords) { + Rec->Cie->OutputOff = Off; + Off += alignTo(Rec->Cie->Size, Config->Wordsize); + + for (EhSectionPiece *Fde : Rec->Fdes) { + Fde->OutputOff = Off; + Off += alignTo(Fde->Size, Config->Wordsize); + } + } + + // The LSB standard does not allow a .eh_frame section with zero + // Call Frame Information records. Therefore add a CIE record length + // 0 as a terminator if this .eh_frame section is empty. + if (Off == 0) + Off = 4; + + this->Size = Off; +} + +template static uint64_t readFdeAddr(uint8_t *Buf, int Size) { + const endianness E = ELFT::TargetEndianness; + switch (Size) { + case DW_EH_PE_udata2: + return read16(Buf); + case DW_EH_PE_udata4: + return read32(Buf); + case DW_EH_PE_udata8: + return read64(Buf); + case DW_EH_PE_absptr: + if (ELFT::Is64Bits) + return read64(Buf); + return read32(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 +uint64_t EhFrameSection::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(Buf + Off, Enc & 0x7); + if ((Enc & 0x70) == DW_EH_PE_absptr) + return Addr; + if ((Enc & 0x70) == DW_EH_PE_pcrel) + return Addr + getParent()->Addr + Off; + fatal("unknown FDE size relative encoding"); +} + +template void EhFrameSection::writeTo(uint8_t *Buf) { + const endianness E = ELFT::TargetEndianness; + for (CieRecord *Rec : CieRecords) { + size_t CieOffset = Rec->Cie->OutputOff; + writeCieFde(Buf + CieOffset, Rec->Cie->data()); + + for (EhSectionPiece *Fde : Rec->Fdes) { + size_t Off = Fde->OutputOff; + writeCieFde(Buf + Off, Fde->data()); + + // FDE's second word should have the offset to an associated CIE. + // Write it. + write32(Buf + Off + 4, Off + 4 - CieOffset); + } + } + + for (EhInputSection *S : Sections) + S->relocateAlloc(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::EhFrameHdr) { + for (CieRecord *Rec : CieRecords) { + uint8_t Enc = getFdeEncoding(Rec->Cie); + for (EhSectionPiece *Fde : Rec->Fdes) { + uint64_t Pc = getFdePc(Buf, Fde->OutputOff, Enc); + uint64_t FdeVA = getParent()->Addr + Fde->OutputOff; + In::EhFrameHdr->addFde(Pc, FdeVA); + } + } + } +} + +GotSection::GotSection() + : SyntheticSection(SHF_ALLOC | SHF_WRITE, SHT_PROGBITS, + Target->GotEntrySize, ".got") {} + +void GotSection::addEntry(SymbolBody &Sym) { + Sym.GotIndex = NumEntries; + ++NumEntries; +} + +bool GotSection::addDynTlsEntry(SymbolBody &Sym) { + if (Sym.GlobalDynIndex != -1U) + return false; + Sym.GlobalDynIndex = NumEntries; + // Global Dynamic TLS entries take two GOT slots. + NumEntries += 2; + return true; +} + +// Reserves TLS entries for a TLS module ID and a TLS block offset. +// In total it takes two GOT slots. +bool GotSection::addTlsIndex() { + if (TlsIndexOff != uint32_t(-1)) + return false; + TlsIndexOff = NumEntries * Config->Wordsize; + NumEntries += 2; + return true; +} + +uint64_t GotSection::getGlobalDynAddr(const SymbolBody &B) const { + return this->getVA() + B.GlobalDynIndex * Config->Wordsize; +} + +uint64_t GotSection::getGlobalDynOffset(const SymbolBody &B) const { + return B.GlobalDynIndex * Config->Wordsize; +} + +void GotSection::finalizeContents() { Size = NumEntries * Config->Wordsize; } + +bool GotSection::empty() const { + // We need to emit a GOT even if it's empty if there's a relocation that is + // relative to GOT(such as GOTOFFREL) or there's a symbol that points to a GOT + // (i.e. _GLOBAL_OFFSET_TABLE_). + return NumEntries == 0 && !HasGotOffRel && !ElfSym::GlobalOffsetTable; +} + +void GotSection::writeTo(uint8_t *Buf) { + // Buf points to the start of this section's buffer, + // whereas InputSectionBase::relocateAlloc() expects its argument + // to point to the start of the output section. + relocateAlloc(Buf - OutSecOff, Buf - OutSecOff + Size); +} + +MipsGotSection::MipsGotSection() + : SyntheticSection(SHF_ALLOC | SHF_WRITE | SHF_MIPS_GPREL, SHT_PROGBITS, 16, + ".got") {} + +void MipsGotSection::addEntry(SymbolBody &Sym, int64_t Addend, RelExpr Expr) { + // For "true" local symbols which can be referenced from the same module + // only compiler creates two instructions for address loading: + // + // lw $8, 0($gp) # R_MIPS_GOT16 + // addi $8, $8, 0 # R_MIPS_LO16 + // + // The first instruction loads high 16 bits of the symbol address while + // the second adds an offset. That allows to reduce number of required + // GOT entries because only one global offset table entry is necessary + // for every 64 KBytes of local data. So for local symbols we need to + // allocate number of GOT entries to hold all required "page" addresses. + // + // All global symbols (hidden and regular) considered by compiler uniformly. + // It always generates a single `lw` instruction and R_MIPS_GOT16 relocation + // to load address of the symbol. So for each such symbol we need to + // allocate dedicated GOT entry to store its address. + // + // If a symbol is preemptible we need help of dynamic linker to get its + // final address. The corresponding GOT entries are allocated in the + // "global" part of GOT. Entries for non preemptible global symbol allocated + // in the "local" part of GOT. + // + // See "Global Offset Table" in Chapter 5: + // ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf + if (Expr == R_MIPS_GOT_LOCAL_PAGE) { + // At this point we do not know final symbol value so to reduce number + // of allocated GOT entries do the following trick. Save all output + // sections referenced by GOT relocations. Then later in the `finalize` + // method calculate number of "pages" required to cover all saved output + // section and allocate appropriate number of GOT entries. + PageIndexMap.insert({Sym.getOutputSection(), 0}); + return; + } + if (Sym.isTls()) { + // GOT entries created for MIPS TLS relocations behave like + // almost GOT entries from other ABIs. They go to the end + // of the global offset table. + Sym.GotIndex = TlsEntries.size(); + TlsEntries.push_back(&Sym); + return; + } + auto AddEntry = [&](SymbolBody &S, uint64_t A, GotEntries &Items) { + if (S.isInGot() && !A) + return; + size_t NewIndex = Items.size(); + if (!EntryIndexMap.insert({{&S, A}, NewIndex}).second) + return; + Items.emplace_back(&S, A); + if (!A) + S.GotIndex = NewIndex; + }; + if (Sym.isPreemptible()) { + // Ignore addends for preemptible symbols. They got single GOT entry anyway. + AddEntry(Sym, 0, GlobalEntries); + Sym.IsInGlobalMipsGot = true; + } else if (Expr == R_MIPS_GOT_OFF32) { + AddEntry(Sym, Addend, LocalEntries32); + Sym.Is32BitMipsGot = true; + } else { + // Hold local GOT entries accessed via a 16-bit index separately. + // That allows to write them in the beginning of the GOT and keep + // their indexes as less as possible to escape relocation's overflow. + AddEntry(Sym, Addend, LocalEntries); + } +} + +bool MipsGotSection::addDynTlsEntry(SymbolBody &Sym) { + if (Sym.GlobalDynIndex != -1U) + return false; + Sym.GlobalDynIndex = TlsEntries.size(); + // Global Dynamic TLS entries take two GOT slots. + TlsEntries.push_back(nullptr); + TlsEntries.push_back(&Sym); + return true; +} + +// Reserves TLS entries for a TLS module ID and a TLS block offset. +// In total it takes two GOT slots. +bool MipsGotSection::addTlsIndex() { + if (TlsIndexOff != uint32_t(-1)) + return false; + TlsIndexOff = TlsEntries.size() * Config->Wordsize; + TlsEntries.push_back(nullptr); + TlsEntries.push_back(nullptr); + return true; +} + +static uint64_t getMipsPageAddr(uint64_t Addr) { + return (Addr + 0x8000) & ~0xffff; +} + +static uint64_t getMipsPageCount(uint64_t Size) { + return (Size + 0xfffe) / 0xffff + 1; +} + +uint64_t MipsGotSection::getPageEntryOffset(const SymbolBody &B, + int64_t Addend) const { + const OutputSection *OutSec = B.getOutputSection(); + uint64_t SecAddr = getMipsPageAddr(OutSec->Addr); + uint64_t SymAddr = getMipsPageAddr(B.getVA(Addend)); + uint64_t Index = PageIndexMap.lookup(OutSec) + (SymAddr - SecAddr) / 0xffff; + assert(Index < PageEntriesNum); + return (HeaderEntriesNum + Index) * Config->Wordsize; +} + +uint64_t MipsGotSection::getBodyEntryOffset(const SymbolBody &B, + int64_t Addend) const { + // Calculate offset of the GOT entries block: TLS, global, local. + uint64_t Index = HeaderEntriesNum + PageEntriesNum; + if (B.isTls()) + Index += LocalEntries.size() + LocalEntries32.size() + GlobalEntries.size(); + else if (B.IsInGlobalMipsGot) + Index += LocalEntries.size() + LocalEntries32.size(); + else if (B.Is32BitMipsGot) + Index += LocalEntries.size(); + // Calculate offset of the GOT entry in the block. + if (B.isInGot()) + Index += B.GotIndex; + else { + auto It = EntryIndexMap.find({&B, Addend}); + assert(It != EntryIndexMap.end()); + Index += It->second; + } + return Index * Config->Wordsize; +} + +uint64_t MipsGotSection::getTlsOffset() const { + return (getLocalEntriesNum() + GlobalEntries.size()) * Config->Wordsize; +} + +uint64_t MipsGotSection::getGlobalDynOffset(const SymbolBody &B) const { + return B.GlobalDynIndex * Config->Wordsize; +} + +const SymbolBody *MipsGotSection::getFirstGlobalEntry() const { + return GlobalEntries.empty() ? nullptr : GlobalEntries.front().first; +} + +unsigned MipsGotSection::getLocalEntriesNum() const { + return HeaderEntriesNum + PageEntriesNum + LocalEntries.size() + + LocalEntries32.size(); +} + +void MipsGotSection::finalizeContents() { updateAllocSize(); } + +void MipsGotSection::updateAllocSize() { + PageEntriesNum = 0; + for (std::pair &P : PageIndexMap) { + // For each output section referenced by GOT page relocations calculate + // and save into PageIndexMap an upper bound of MIPS GOT entries required + // to store page addresses of local symbols. We assume the worst case - + // each 64kb page of the output section has at least one GOT relocation + // against it. And take in account the case when the section intersects + // page boundaries. + P.second = PageEntriesNum; + PageEntriesNum += getMipsPageCount(P.first->Size); + } + Size = (getLocalEntriesNum() + GlobalEntries.size() + TlsEntries.size()) * + Config->Wordsize; +} + +bool MipsGotSection::empty() const { + // We add the .got section to the result for dynamic MIPS target because + // its address and properties are mentioned in the .dynamic section. + return Config->Relocatable; +} + +uint64_t MipsGotSection::getGp() const { return ElfSym::MipsGp->getVA(0); } + +static uint64_t readUint(uint8_t *Buf) { + if (Config->Is64) + return read64(Buf, Config->Endianness); + return read32(Buf, Config->Endianness); +} + +static void writeUint(uint8_t *Buf, uint64_t Val) { + if (Config->Is64) + write64(Buf, Val, Config->Endianness); + else + write32(Buf, Val, Config->Endianness); +} + +void MipsGotSection::writeTo(uint8_t *Buf) { + // Set the MSB of the second GOT slot. This is not required by any + // MIPS ABI documentation, though. + // + // There is a comment in glibc saying that "The MSB of got[1] of a + // gnu object is set to identify gnu objects," and in GNU gold it + // says "the second entry will be used by some runtime loaders". + // But how this field is being used is unclear. + // + // We are not really willing to mimic other linkers behaviors + // without understanding why they do that, but because all files + // generated by GNU tools have this special GOT value, and because + // we've been doing this for years, it is probably a safe bet to + // keep doing this for now. We really need to revisit this to see + // if we had to do this. + writeUint(Buf + Config->Wordsize, (uint64_t)1 << (Config->Wordsize * 8 - 1)); + Buf += HeaderEntriesNum * Config->Wordsize; + // Write 'page address' entries to the local part of the GOT. + for (std::pair &L : PageIndexMap) { + size_t PageCount = getMipsPageCount(L.first->Size); + uint64_t FirstPageAddr = getMipsPageAddr(L.first->Addr); + for (size_t PI = 0; PI < PageCount; ++PI) { + uint8_t *Entry = Buf + (L.second + PI) * Config->Wordsize; + writeUint(Entry, FirstPageAddr + PI * 0x10000); + } + } + Buf += PageEntriesNum * Config->Wordsize; + auto AddEntry = [&](const GotEntry &SA) { + uint8_t *Entry = Buf; + Buf += Config->Wordsize; + const SymbolBody *Body = SA.first; + uint64_t VA = Body->getVA(SA.second); + writeUint(Entry, VA); + }; + std::for_each(std::begin(LocalEntries), std::end(LocalEntries), AddEntry); + std::for_each(std::begin(LocalEntries32), std::end(LocalEntries32), AddEntry); + std::for_each(std::begin(GlobalEntries), std::end(GlobalEntries), AddEntry); + // Initialize TLS-related GOT entries. If the entry has a corresponding + // dynamic relocations, leave it initialized by zero. Write down adjusted + // TLS symbol's values otherwise. To calculate the adjustments use offsets + // for thread-local storage. + // https://www.linux-mips.org/wiki/NPTL + if (TlsIndexOff != -1U && !Config->Pic) + writeUint(Buf + TlsIndexOff, 1); + for (const SymbolBody *B : TlsEntries) { + if (!B || B->isPreemptible()) + continue; + uint64_t VA = B->getVA(); + if (B->GotIndex != -1U) { + uint8_t *Entry = Buf + B->GotIndex * Config->Wordsize; + writeUint(Entry, VA - 0x7000); + } + if (B->GlobalDynIndex != -1U) { + uint8_t *Entry = Buf + B->GlobalDynIndex * Config->Wordsize; + writeUint(Entry, 1); + Entry += Config->Wordsize; + writeUint(Entry, VA - 0x8000); + } + } +} + +GotPltSection::GotPltSection() + : SyntheticSection(SHF_ALLOC | SHF_WRITE, SHT_PROGBITS, + Target->GotPltEntrySize, ".got.plt") {} + +void GotPltSection::addEntry(SymbolBody &Sym) { + Sym.GotPltIndex = Target->GotPltHeaderEntriesNum + Entries.size(); + Entries.push_back(&Sym); +} + +size_t GotPltSection::getSize() const { + return (Target->GotPltHeaderEntriesNum + Entries.size()) * + Target->GotPltEntrySize; +} + +void GotPltSection::writeTo(uint8_t *Buf) { + Target->writeGotPltHeader(Buf); + Buf += Target->GotPltHeaderEntriesNum * Target->GotPltEntrySize; + for (const SymbolBody *B : Entries) { + Target->writeGotPlt(Buf, *B); + Buf += Config->Wordsize; + } +} + +// On ARM the IgotPltSection is part of the GotSection, on other Targets it is +// part of the .got.plt +IgotPltSection::IgotPltSection() + : SyntheticSection(SHF_ALLOC | SHF_WRITE, SHT_PROGBITS, + Target->GotPltEntrySize, + Config->EMachine == EM_ARM ? ".got" : ".got.plt") {} + +void IgotPltSection::addEntry(SymbolBody &Sym) { + Sym.IsInIgot = true; + Sym.GotPltIndex = Entries.size(); + Entries.push_back(&Sym); +} + +size_t IgotPltSection::getSize() const { + return Entries.size() * Target->GotPltEntrySize; +} + +void IgotPltSection::writeTo(uint8_t *Buf) { + for (const SymbolBody *B : Entries) { + Target->writeIgotPlt(Buf, *B); + Buf += Config->Wordsize; + } +} + +StringTableSection::StringTableSection(StringRef Name, bool Dynamic) + : SyntheticSection(Dynamic ? (uint64_t)SHF_ALLOC : 0, SHT_STRTAB, 1, Name), + Dynamic(Dynamic) { + // ELF string tables start with a NUL byte. + addString(""); +} + +// Adds a string to the string table. If HashIt is true we hash and check for +// duplicates. It is optional because the name of global symbols are already +// uniqued and hashing them again has a big cost for a small value: uniquing +// them with some other string that happens to be the same. +unsigned StringTableSection::addString(StringRef S, bool HashIt) { + if (HashIt) { + auto R = StringMap.insert(std::make_pair(S, this->Size)); + if (!R.second) + return R.first->second; + } + unsigned Ret = this->Size; + this->Size = this->Size + S.size() + 1; + Strings.push_back(S); + return Ret; +} + +void StringTableSection::writeTo(uint8_t *Buf) { + for (StringRef S : Strings) { + memcpy(Buf, S.data(), S.size()); + Buf[S.size()] = '\0'; + Buf += S.size() + 1; + } +} + +// Returns the number of version definition entries. Because the first entry +// is for the version definition itself, it is the number of versioned symbols +// plus one. Note that we don't support multiple versions yet. +static unsigned getVerDefNum() { return Config->VersionDefinitions.size() + 1; } + +template +DynamicSection::DynamicSection() + : SyntheticSection(SHF_ALLOC | SHF_WRITE, SHT_DYNAMIC, Config->Wordsize, + ".dynamic") { + this->Entsize = ELFT::Is64Bits ? 16 : 8; + + // .dynamic section is not writable on MIPS and on Fuchsia OS + // which passes -z rodynamic. + // See "Special Section" in Chapter 4 in the following document: + // ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf + if (Config->EMachine == EM_MIPS || Config->ZRodynamic) + this->Flags = SHF_ALLOC; + + addEntries(); +} + +// There are some dynamic entries that don't depend on other sections. +// Such entries can be set early. +template void DynamicSection::addEntries() { + // Add strings to .dynstr early so that .dynstr's size will be + // fixed early. + for (StringRef S : Config->FilterList) + add({DT_FILTER, InX::DynStrTab->addString(S)}); + for (StringRef S : Config->AuxiliaryList) + add({DT_AUXILIARY, InX::DynStrTab->addString(S)}); + if (!Config->Rpath.empty()) + add({Config->EnableNewDtags ? DT_RUNPATH : DT_RPATH, + InX::DynStrTab->addString(Config->Rpath)}); + for (InputFile *File : SharedFiles) { + SharedFile *F = cast>(File); + if (F->isNeeded()) + add({DT_NEEDED, InX::DynStrTab->addString(F->SoName)}); + } + if (!Config->SoName.empty()) + add({DT_SONAME, InX::DynStrTab->addString(Config->SoName)}); + + // Set DT_FLAGS and DT_FLAGS_1. + uint32_t DtFlags = 0; + uint32_t DtFlags1 = 0; + if (Config->Bsymbolic) + DtFlags |= DF_SYMBOLIC; + if (Config->ZNodelete) + DtFlags1 |= DF_1_NODELETE; + if (Config->ZNodlopen) + DtFlags1 |= DF_1_NOOPEN; + if (Config->ZNow) { + DtFlags |= DF_BIND_NOW; + DtFlags1 |= DF_1_NOW; + } + if (Config->ZOrigin) { + DtFlags |= DF_ORIGIN; + DtFlags1 |= DF_1_ORIGIN; + } + + if (DtFlags) + add({DT_FLAGS, DtFlags}); + if (DtFlags1) + add({DT_FLAGS_1, DtFlags1}); + + // DT_DEBUG is a pointer to debug informaion used by debuggers at runtime. We + // need it for each process, so we don't write it for DSOs. The loader writes + // the pointer into this entry. + // + // DT_DEBUG is the only .dynamic entry that needs to be written to. Some + // systems (currently only Fuchsia OS) provide other means to give the + // debugger this information. Such systems may choose make .dynamic read-only. + // If the target is such a system (used -z rodynamic) don't write DT_DEBUG. + if (!Config->Shared && !Config->Relocatable && !Config->ZRodynamic) + add({DT_DEBUG, (uint64_t)0}); +} + +// Add remaining entries to complete .dynamic contents. +template void DynamicSection::finalizeContents() { + if (this->Size) + return; // Already finalized. + + this->Link = InX::DynStrTab->getParent()->SectionIndex; + if (In::RelaDyn->getParent() && !In::RelaDyn->empty()) { + bool IsRela = Config->IsRela; + add({IsRela ? DT_RELA : DT_REL, In::RelaDyn}); + add({IsRela ? DT_RELASZ : DT_RELSZ, In::RelaDyn->getParent(), + Entry::SecSize}); + add({IsRela ? DT_RELAENT : DT_RELENT, + uint64_t(IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel))}); + + // MIPS dynamic loader does not support RELCOUNT tag. + // The problem is in the tight relation between dynamic + // relocations and GOT. So do not emit this tag on MIPS. + if (Config->EMachine != EM_MIPS) { + size_t NumRelativeRels = In::RelaDyn->getRelativeRelocCount(); + if (Config->ZCombreloc && NumRelativeRels) + add({IsRela ? DT_RELACOUNT : DT_RELCOUNT, NumRelativeRels}); + } + } + if (In::RelaPlt->getParent() && !In::RelaPlt->empty()) { + add({DT_JMPREL, In::RelaPlt}); + add({DT_PLTRELSZ, In::RelaPlt->getParent(), Entry::SecSize}); + switch (Config->EMachine) { + case EM_MIPS: + add({DT_MIPS_PLTGOT, In::GotPlt}); + break; + case EM_SPARCV9: + add({DT_PLTGOT, In::Plt}); + break; + default: + add({DT_PLTGOT, In::GotPlt}); + break; + } + add({DT_PLTREL, uint64_t(Config->IsRela ? DT_RELA : DT_REL)}); + } + + add({DT_SYMTAB, InX::DynSymTab}); + add({DT_SYMENT, sizeof(Elf_Sym)}); + add({DT_STRTAB, InX::DynStrTab}); + add({DT_STRSZ, InX::DynStrTab->getSize()}); + if (!Config->ZText) + add({DT_TEXTREL, (uint64_t)0}); + if (InX::GnuHashTab) + add({DT_GNU_HASH, InX::GnuHashTab}); + if (In::HashTab) + add({DT_HASH, In::HashTab}); + + if (Out::PreinitArray) { + add({DT_PREINIT_ARRAY, Out::PreinitArray}); + add({DT_PREINIT_ARRAYSZ, Out::PreinitArray, Entry::SecSize}); + } + if (Out::InitArray) { + add({DT_INIT_ARRAY, Out::InitArray}); + add({DT_INIT_ARRAYSZ, Out::InitArray, Entry::SecSize}); + } + if (Out::FiniArray) { + add({DT_FINI_ARRAY, Out::FiniArray}); + add({DT_FINI_ARRAYSZ, Out::FiniArray, Entry::SecSize}); + } + + if (SymbolBody *B = Symtab->find(Config->Init)) + if (B->isInCurrentDSO()) + add({DT_INIT, B}); + if (SymbolBody *B = Symtab->find(Config->Fini)) + if (B->isInCurrentDSO()) + add({DT_FINI, B}); + + bool HasVerNeed = In::VerNeed->getNeedNum() != 0; + if (HasVerNeed || In::VerDef) + add({DT_VERSYM, In::VerSym}); + if (In::VerDef) { + add({DT_VERDEF, In::VerDef}); + add({DT_VERDEFNUM, getVerDefNum()}); + } + if (HasVerNeed) { + add({DT_VERNEED, In::VerNeed}); + add({DT_VERNEEDNUM, In::VerNeed->getNeedNum()}); + } + + if (Config->EMachine == EM_MIPS) { + add({DT_MIPS_RLD_VERSION, 1}); + add({DT_MIPS_FLAGS, RHF_NOTPOT}); + add({DT_MIPS_BASE_ADDRESS, Config->ImageBase}); + add({DT_MIPS_SYMTABNO, InX::DynSymTab->getNumSymbols()}); + add({DT_MIPS_LOCAL_GOTNO, InX::MipsGot->getLocalEntriesNum()}); + if (const SymbolBody *B = InX::MipsGot->getFirstGlobalEntry()) + add({DT_MIPS_GOTSYM, B->DynsymIndex}); + else + add({DT_MIPS_GOTSYM, InX::DynSymTab->getNumSymbols()}); + add({DT_PLTGOT, InX::MipsGot}); + if (InX::MipsRldMap) + add({DT_MIPS_RLD_MAP, InX::MipsRldMap}); + } + + getParent()->Link = this->Link; + + // +1 for DT_NULL + this->Size = (Entries.size() + 1) * this->Entsize; +} + +template void DynamicSection::writeTo(uint8_t *Buf) { + auto *P = reinterpret_cast(Buf); + + for (const Entry &E : Entries) { + P->d_tag = E.Tag; + switch (E.Kind) { + case Entry::SecAddr: + P->d_un.d_ptr = E.OutSec->Addr; + break; + case Entry::InSecAddr: + P->d_un.d_ptr = E.InSec->getParent()->Addr + E.InSec->OutSecOff; + break; + case Entry::SecSize: + P->d_un.d_val = E.OutSec->Size; + break; + case Entry::SymAddr: + P->d_un.d_ptr = E.Sym->getVA(); + break; + case Entry::PlainInt: + P->d_un.d_val = E.Val; + break; + } + ++P; + } +} + +uint64_t DynamicReloc::getOffset() const { + return InputSec->getOutputSection()->Addr + InputSec->getOffset(OffsetInSec); +} + +int64_t DynamicReloc::getAddend() const { + if (UseSymVA) + return Sym->getVA(Addend); + return Addend; +} + +uint32_t DynamicReloc::getSymIndex() const { + if (Sym && !UseSymVA) + return Sym->DynsymIndex; + return 0; +} + +template +RelocationSection::RelocationSection(StringRef Name, bool Sort) + : SyntheticSection(SHF_ALLOC, Config->IsRela ? SHT_RELA : SHT_REL, + Config->Wordsize, Name), + Sort(Sort) { + this->Entsize = Config->IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel); +} + +template +void RelocationSection::addReloc(const DynamicReloc &Reloc) { + if (Reloc.Type == Target->RelativeRel) + ++NumRelativeRelocs; + Relocs.push_back(Reloc); +} + +template +static bool compRelocations(const RelTy &A, const RelTy &B) { + bool AIsRel = A.getType(Config->IsMips64EL) == Target->RelativeRel; + bool BIsRel = B.getType(Config->IsMips64EL) == Target->RelativeRel; + if (AIsRel != BIsRel) + return AIsRel; + + return A.getSymbol(Config->IsMips64EL) < B.getSymbol(Config->IsMips64EL); +} + +template void RelocationSection::writeTo(uint8_t *Buf) { + uint8_t *BufBegin = Buf; + for (const DynamicReloc &Rel : Relocs) { + auto *P = reinterpret_cast(Buf); + Buf += Config->IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel); + + if (Config->IsRela) + P->r_addend = Rel.getAddend(); + P->r_offset = Rel.getOffset(); + if (Config->EMachine == EM_MIPS && Rel.getInputSec() == InX::MipsGot) + // Dynamic relocation against MIPS GOT section make deal TLS entries + // allocated in the end of the GOT. We need to adjust the offset to take + // in account 'local' and 'global' GOT entries. + P->r_offset += InX::MipsGot->getTlsOffset(); + P->setSymbolAndType(Rel.getSymIndex(), Rel.Type, Config->IsMips64EL); + } + + if (Sort) { + if (Config->IsRela) + std::stable_sort((Elf_Rela *)BufBegin, + (Elf_Rela *)BufBegin + Relocs.size(), + compRelocations); + else + std::stable_sort((Elf_Rel *)BufBegin, (Elf_Rel *)BufBegin + Relocs.size(), + compRelocations); + } +} + +template unsigned RelocationSection::getRelocOffset() { + return this->Entsize * Relocs.size(); +} + +template void RelocationSection::finalizeContents() { + this->Link = InX::DynSymTab ? InX::DynSymTab->getParent()->SectionIndex + : InX::SymTab->getParent()->SectionIndex; + + // Set required output section properties. + getParent()->Link = this->Link; +} + +SymbolTableBaseSection::SymbolTableBaseSection(StringTableSection &StrTabSec) + : SyntheticSection(StrTabSec.isDynamic() ? (uint64_t)SHF_ALLOC : 0, + StrTabSec.isDynamic() ? SHT_DYNSYM : SHT_SYMTAB, + Config->Wordsize, + StrTabSec.isDynamic() ? ".dynsym" : ".symtab"), + StrTabSec(StrTabSec) {} + +// Orders symbols according to their positions in the GOT, +// in compliance with MIPS ABI rules. +// See "Global Offset Table" in Chapter 5 in the following document +// for detailed description: +// ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf +static bool sortMipsSymbols(const SymbolTableEntry &L, + const SymbolTableEntry &R) { + // Sort entries related to non-local preemptible symbols by GOT indexes. + // All other entries go to the first part of GOT in arbitrary order. + bool LIsInLocalGot = !L.Symbol->IsInGlobalMipsGot; + bool RIsInLocalGot = !R.Symbol->IsInGlobalMipsGot; + if (LIsInLocalGot || RIsInLocalGot) + return !RIsInLocalGot; + return L.Symbol->GotIndex < R.Symbol->GotIndex; +} + +// Finalize a symbol table. The ELF spec requires that all local +// symbols precede global symbols, so we sort symbol entries in this +// function. (For .dynsym, we don't do that because symbols for +// dynamic linking are inherently all globals.) +void SymbolTableBaseSection::finalizeContents() { + getParent()->Link = StrTabSec.getParent()->SectionIndex; + + // If it is a .dynsym, there should be no local symbols, but we need + // to do a few things for the dynamic linker. + if (this->Type == SHT_DYNSYM) { + // Section's Info field has the index of the first non-local symbol. + // Because the first symbol entry is a null entry, 1 is the first. + getParent()->Info = 1; + + if (InX::GnuHashTab) { + // NB: It also sorts Symbols to meet the GNU hash table requirements. + InX::GnuHashTab->addSymbols(Symbols); + } else if (Config->EMachine == EM_MIPS) { + std::stable_sort(Symbols.begin(), Symbols.end(), sortMipsSymbols); + } + + size_t I = 0; + for (const SymbolTableEntry &S : Symbols) + S.Symbol->DynsymIndex = ++I; + return; + } +} + +void SymbolTableBaseSection::postThunkContents() { + if (this->Type == SHT_DYNSYM) + return; + // move all local symbols before global symbols. + auto It = std::stable_partition( + Symbols.begin(), Symbols.end(), [](const SymbolTableEntry &S) { + return S.Symbol->isLocal() || + S.Symbol->symbol()->computeBinding() == STB_LOCAL; + }); + size_t NumLocals = It - Symbols.begin(); + getParent()->Info = NumLocals + 1; +} + +void SymbolTableBaseSection::addSymbol(SymbolBody *B) { + // Adding a local symbol to a .dynsym is a bug. + assert(this->Type != SHT_DYNSYM || !B->isLocal()); + + bool HashIt = B->isLocal(); + Symbols.push_back({B, StrTabSec.addString(B->getName(), HashIt)}); +} + +size_t SymbolTableBaseSection::getSymbolIndex(SymbolBody *Body) { + auto I = llvm::find_if(Symbols, [&](const SymbolTableEntry &E) { + if (E.Symbol == Body) + return true; + // This is used for -r, so we have to handle multiple section + // symbols being combined. + if (Body->Type == STT_SECTION && E.Symbol->Type == STT_SECTION) + return Body->getOutputSection() == E.Symbol->getOutputSection(); + return false; + }); + if (I == Symbols.end()) + return 0; + return I - Symbols.begin() + 1; +} + +template +SymbolTableSection::SymbolTableSection(StringTableSection &StrTabSec) + : SymbolTableBaseSection(StrTabSec) { + this->Entsize = sizeof(Elf_Sym); +} + +// Write the internal symbol table contents to the output symbol table. +template void SymbolTableSection::writeTo(uint8_t *Buf) { + // The first entry is a null entry as per the ELF spec. + Buf += sizeof(Elf_Sym); + + auto *ESym = reinterpret_cast(Buf); + + for (SymbolTableEntry &Ent : Symbols) { + SymbolBody *Body = Ent.Symbol; + + // Set st_info and st_other. + if (Body->isLocal()) { + ESym->setBindingAndType(STB_LOCAL, Body->Type); + } else { + ESym->setBindingAndType(Body->symbol()->computeBinding(), Body->Type); + ESym->setVisibility(Body->symbol()->Visibility); + } + + ESym->st_name = Ent.StrTabOffset; + + // Set a section index. + if (const OutputSection *OutSec = Body->getOutputSection()) + ESym->st_shndx = OutSec->SectionIndex; + else if (isa(Body)) + ESym->st_shndx = SHN_ABS; + else if (isa(Body)) + ESym->st_shndx = SHN_COMMON; + + // Copy symbol size if it is a defined symbol. st_size is not significant + // for undefined symbols, so whether copying it or not is up to us if that's + // the case. We'll leave it as zero because by not setting a value, we can + // get the exact same outputs for two sets of input files that differ only + // in undefined symbol size in DSOs. + if (ESym->st_shndx != SHN_UNDEF) + ESym->st_size = Body->getSize(); + + // st_value is usually an address of a symbol, but that has a + // special meaining for uninstantiated common symbols (this can + // occur if -r is given). + if (!Config->DefineCommon && isa(Body)) + ESym->st_value = cast(Body)->Alignment; + else + ESym->st_value = Body->getVA(); + + ++ESym; + } + + // On MIPS we need to mark symbol which has a PLT entry and requires + // pointer equality by STO_MIPS_PLT flag. That is necessary to help + // dynamic linker distinguish such symbols and MIPS lazy-binding stubs. + // https://sourceware.org/ml/binutils/2008-07/txt00000.txt + if (Config->EMachine == EM_MIPS) { + auto *ESym = reinterpret_cast(Buf); + + for (SymbolTableEntry &Ent : Symbols) { + SymbolBody *Body = Ent.Symbol; + if (Body->isInPlt() && Body->NeedsPltAddr) + ESym->st_other |= STO_MIPS_PLT; + + if (Config->Relocatable) + if (auto *D = dyn_cast(Body)) + if (D->isMipsPIC()) + ESym->st_other |= STO_MIPS_PIC; + ++ESym; + } + } +} + +// .hash and .gnu.hash sections contain on-disk hash tables that map +// symbol names to their dynamic symbol table indices. Their purpose +// is to help the dynamic linker resolve symbols quickly. If ELF files +// don't have them, the dynamic linker has to do linear search on all +// dynamic symbols, which makes programs slower. Therefore, a .hash +// section is added to a DSO by default. A .gnu.hash is added if you +// give the -hash-style=gnu or -hash-style=both option. +// +// The Unix semantics of resolving dynamic symbols is somewhat expensive. +// Each ELF file has a list of DSOs that the ELF file depends on and a +// list of dynamic symbols that need to be resolved from any of the +// DSOs. That means resolving all dynamic symbols takes O(m)*O(n) +// where m is the number of DSOs and n is the number of dynamic +// symbols. For modern large programs, both m and n are large. So +// making each step faster by using hash tables substiantially +// improves time to load programs. +// +// (Note that this is not the only way to design the shared library. +// For instance, the Windows DLL takes a different approach. On +// Windows, each dynamic symbol has a name of DLL from which the symbol +// has to be resolved. That makes the cost of symbol resolution O(n). +// This disables some hacky techniques you can use on Unix such as +// LD_PRELOAD, but this is arguably better semantics than the Unix ones.) +// +// Due to historical reasons, we have two different hash tables, .hash +// and .gnu.hash. They are for the same purpose, and .gnu.hash is a new +// and better version of .hash. .hash is just an on-disk hash table, but +// .gnu.hash has a bloom filter in addition to a hash table to skip +// DSOs very quickly. If you are sure that your dynamic linker knows +// about .gnu.hash, you want to specify -hash-style=gnu. Otherwise, a +// safe bet is to specify -hash-style=both for backward compatibilty. +GnuHashTableSection::GnuHashTableSection() + : SyntheticSection(SHF_ALLOC, SHT_GNU_HASH, Config->Wordsize, ".gnu.hash") { +} + +void GnuHashTableSection::finalizeContents() { + getParent()->Link = InX::DynSymTab->getParent()->SectionIndex; + + // Computes bloom filter size in word size. We want to allocate 8 + // bits for each symbol. It must be a power of two. + if (Symbols.empty()) + MaskWords = 1; + else + MaskWords = NextPowerOf2((Symbols.size() - 1) / Config->Wordsize); + + Size = 16; // Header + Size += Config->Wordsize * MaskWords; // Bloom filter + Size += NBuckets * 4; // Hash buckets + Size += Symbols.size() * 4; // Hash values +} + +void GnuHashTableSection::writeTo(uint8_t *Buf) { + // Write a header. + write32(Buf, NBuckets, Config->Endianness); + write32(Buf + 4, InX::DynSymTab->getNumSymbols() - Symbols.size(), + Config->Endianness); + write32(Buf + 8, MaskWords, Config->Endianness); + write32(Buf + 12, getShift2(), Config->Endianness); + Buf += 16; + + // Write a bloom filter and a hash table. + writeBloomFilter(Buf); + Buf += Config->Wordsize * MaskWords; + writeHashTable(Buf); +} + +// This function writes a 2-bit bloom filter. This bloom filter alone +// usually filters out 80% or more of all symbol lookups [1]. +// The dynamic linker uses the hash table only when a symbol is not +// filtered out by a bloom filter. +// +// [1] Ulrich Drepper (2011), "How To Write Shared Libraries" (Ver. 4.1.2), +// p.9, https://www.akkadia.org/drepper/dsohowto.pdf +void GnuHashTableSection::writeBloomFilter(uint8_t *Buf) { + const unsigned C = Config->Wordsize * 8; + for (const Entry &Sym : Symbols) { + size_t I = (Sym.Hash / C) & (MaskWords - 1); + uint64_t Val = readUint(Buf + I * Config->Wordsize); + Val |= uint64_t(1) << (Sym.Hash % C); + Val |= uint64_t(1) << ((Sym.Hash >> getShift2()) % C); + writeUint(Buf + I * Config->Wordsize, Val); + } +} + +void GnuHashTableSection::writeHashTable(uint8_t *Buf) { + // Group symbols by hash value. + std::vector> Syms(NBuckets); + for (const Entry &Ent : Symbols) + Syms[Ent.Hash % NBuckets].push_back(Ent); + + // Write hash buckets. Hash buckets contain indices in the following + // hash value table. + uint32_t *Buckets = reinterpret_cast(Buf); + for (size_t I = 0; I < NBuckets; ++I) + if (!Syms[I].empty()) + write32(Buckets + I, Syms[I][0].Body->DynsymIndex, Config->Endianness); + + // Write a hash value table. It represents a sequence of chains that + // share the same hash modulo value. The last element of each chain + // is terminated by LSB 1. + uint32_t *Values = Buckets + NBuckets; + size_t I = 0; + for (std::vector &Vec : Syms) { + if (Vec.empty()) + continue; + for (const Entry &Ent : makeArrayRef(Vec).drop_back()) + write32(Values + I++, Ent.Hash & ~1, Config->Endianness); + write32(Values + I++, Vec.back().Hash | 1, Config->Endianness); + } +} + +static uint32_t hashGnu(StringRef Name) { + uint32_t H = 5381; + for (uint8_t C : Name) + H = (H << 5) + H + C; + return H; +} + +// Returns a number of hash buckets to accomodate given number of elements. +// We want to choose a moderate number that is not too small (which +// causes too many hash collisions) and not too large (which wastes +// disk space.) +// +// We return a prime number because it (is believed to) achieve good +// hash distribution. +static size_t getBucketSize(size_t NumSymbols) { + // List of largest prime numbers that are not greater than 2^n + 1. + for (size_t N : {131071, 65521, 32749, 16381, 8191, 4093, 2039, 1021, 509, + 251, 127, 61, 31, 13, 7, 3, 1}) + if (N <= NumSymbols) + return N; + return 0; +} + +// Add symbols to this symbol hash table. Note that this function +// destructively sort a given vector -- which is needed because +// GNU-style hash table places some sorting requirements. +void GnuHashTableSection::addSymbols(std::vector &V) { + // We cannot use 'auto' for Mid because GCC 6.1 cannot deduce + // its type correctly. + std::vector::iterator Mid = + std::stable_partition(V.begin(), V.end(), [](const SymbolTableEntry &S) { + return S.Symbol->isUndefined(); + }); + if (Mid == V.end()) + return; + + for (SymbolTableEntry &Ent : llvm::make_range(Mid, V.end())) { + SymbolBody *B = Ent.Symbol; + Symbols.push_back({B, Ent.StrTabOffset, hashGnu(B->getName())}); + } + + NBuckets = getBucketSize(Symbols.size()); + std::stable_sort(Symbols.begin(), Symbols.end(), + [&](const Entry &L, const Entry &R) { + return L.Hash % NBuckets < R.Hash % NBuckets; + }); + + V.erase(Mid, V.end()); + for (const Entry &Ent : Symbols) + V.push_back({Ent.Body, Ent.StrTabOffset}); +} + +template +HashTableSection::HashTableSection() + : SyntheticSection(SHF_ALLOC, SHT_HASH, 4, ".hash") { + this->Entsize = 4; +} + +template void HashTableSection::finalizeContents() { + getParent()->Link = InX::DynSymTab->getParent()->SectionIndex; + + unsigned NumEntries = 2; // nbucket and nchain. + NumEntries += InX::DynSymTab->getNumSymbols(); // The chain entries. + + // Create as many buckets as there are symbols. + // FIXME: This is simplistic. We can try to optimize it, but implementing + // support for SHT_GNU_HASH is probably even more profitable. + NumEntries += InX::DynSymTab->getNumSymbols(); + this->Size = NumEntries * 4; +} + +template void HashTableSection::writeTo(uint8_t *Buf) { + // A 32-bit integer type in the target endianness. + typedef typename ELFT::Word Elf_Word; + + unsigned NumSymbols = InX::DynSymTab->getNumSymbols(); + + auto *P = reinterpret_cast(Buf); + *P++ = NumSymbols; // nbucket + *P++ = NumSymbols; // nchain + + Elf_Word *Buckets = P; + Elf_Word *Chains = P + NumSymbols; + + for (const SymbolTableEntry &S : InX::DynSymTab->getSymbols()) { + SymbolBody *Body = S.Symbol; + StringRef Name = Body->getName(); + unsigned I = Body->DynsymIndex; + uint32_t Hash = hashSysV(Name) % NumSymbols; + Chains[I] = Buckets[Hash]; + Buckets[Hash] = I; + } +} + +PltSection::PltSection(size_t S) + : SyntheticSection(SHF_ALLOC | SHF_EXECINSTR, SHT_PROGBITS, 16, ".plt"), + HeaderSize(S) { + // The PLT needs to be writable on SPARC as the dynamic linker will + // modify the instructions in the PLT entries. + if (Config->EMachine == EM_SPARCV9) + this->Flags |= SHF_WRITE; +} + +void PltSection::writeTo(uint8_t *Buf) { + // At beginning of PLT but not the IPLT, we have code to call the dynamic + // linker to resolve dynsyms at runtime. Write such code. + if (HeaderSize != 0) + Target->writePltHeader(Buf); + size_t Off = HeaderSize; + // The IPlt is immediately after the Plt, account for this in RelOff + unsigned PltOff = getPltRelocOff(); + + for (auto &I : Entries) { + const SymbolBody *B = I.first; + unsigned RelOff = I.second + PltOff; + uint64_t Got = B->getGotPltVA(); + uint64_t Plt = this->getVA() + Off; + Target->writePlt(Buf + Off, Got, Plt, B->PltIndex, RelOff); + Off += Target->PltEntrySize; + } +} + +template void PltSection::addEntry(SymbolBody &Sym) { + Sym.PltIndex = Entries.size(); + RelocationSection *PltRelocSection = In::RelaPlt; + if (HeaderSize == 0) { + PltRelocSection = In::RelaIplt; + Sym.IsInIplt = true; + } + unsigned RelOff = PltRelocSection->getRelocOffset(); + Entries.push_back(std::make_pair(&Sym, RelOff)); +} + +size_t PltSection::getSize() const { + return HeaderSize + Entries.size() * Target->PltEntrySize; +} + +// Some architectures such as additional symbols in the PLT section. For +// example ARM uses mapping symbols to aid disassembly +void PltSection::addSymbols() { + // The PLT may have symbols defined for the Header, the IPLT has no header + if (HeaderSize != 0) + Target->addPltHeaderSymbols(this); + size_t Off = HeaderSize; + for (size_t I = 0; I < Entries.size(); ++I) { + Target->addPltSymbols(this, Off); + Off += Target->PltEntrySize; + } +} + +unsigned PltSection::getPltRelocOff() const { + return (HeaderSize == 0) ? InX::Plt->getSize() : 0; +} + +// The string hash function for .gdb_index. +static uint32_t computeGdbHash(StringRef S) { + uint32_t H = 0; + for (uint8_t C : S) + H = H * 67 + tolower(C) - 113; + return H; +} + +static std::vector readCuList(DWARFContext &Dwarf) { + std::vector Ret; + for (std::unique_ptr &Cu : Dwarf.compile_units()) + Ret.push_back({Cu->getOffset(), Cu->getLength() + 4}); + return Ret; +} + +static std::vector +readAddressAreas(DWARFContext &Dwarf, InputSection *Sec) { + std::vector Ret; + + uint32_t CuIdx = 0; + for (std::unique_ptr &Cu : Dwarf.compile_units()) { + DWARFAddressRangesVector Ranges; + Cu->collectAddressRanges(Ranges); + + ArrayRef Sections = Sec->File->getSections(); + for (DWARFAddressRange &R : Ranges) { + InputSectionBase *S = Sections[R.SectionIndex]; + if (!S || S == &InputSection::Discarded || !S->Live) + continue; + // Range list with zero size has no effect. + if (R.LowPC == R.HighPC) + continue; + auto *IS = cast(S); + uint64_t Offset = IS->getOffsetInFile(); + Ret.push_back({IS, R.LowPC - Offset, R.HighPC - Offset, CuIdx}); + } + ++CuIdx; + } + return Ret; +} + +static std::vector +readPubNamesAndTypes(DWARFContext &Dwarf) { + StringRef Sec1 = Dwarf.getDWARFObj().getGnuPubNamesSection(); + StringRef Sec2 = Dwarf.getDWARFObj().getGnuPubTypesSection(); + + std::vector Ret; + for (StringRef Sec : {Sec1, Sec2}) { + DWARFDebugPubTable Table(Sec, Config->IsLE, true); + for (const DWARFDebugPubTable::Set &Set : Table.getData()) { + for (const DWARFDebugPubTable::Entry &Ent : Set.Entries) { + CachedHashStringRef S(Ent.Name, computeGdbHash(Ent.Name)); + Ret.push_back({S, Ent.Descriptor.toBits()}); + } + } + } + return Ret; +} + +static std::vector getDebugInfoSections() { + std::vector Ret; + for (InputSectionBase *S : InputSections) + if (InputSection *IS = dyn_cast(S)) + if (IS->Name == ".debug_info") + Ret.push_back(IS); + return Ret; +} + +void GdbIndexSection::fixCuIndex() { + uint32_t Idx = 0; + for (GdbIndexChunk &Chunk : Chunks) { + for (GdbIndexChunk::AddressEntry &Ent : Chunk.AddressAreas) + Ent.CuIndex += Idx; + Idx += Chunk.CompilationUnits.size(); + } +} + +std::vector> GdbIndexSection::createCuVectors() { + std::vector> Ret; + uint32_t Idx = 0; + uint32_t Off = 0; + + for (GdbIndexChunk &Chunk : Chunks) { + for (GdbIndexChunk::NameTypeEntry &Ent : Chunk.NamesAndTypes) { + GdbSymbol *&Sym = Symbols[Ent.Name]; + if (!Sym) { + Sym = make(GdbSymbol{Ent.Name.hash(), Off, Ret.size()}); + Off += Ent.Name.size() + 1; + Ret.push_back({}); + } + + // gcc 5.4.1 produces a buggy .debug_gnu_pubnames that contains + // duplicate entries, so we want to dedup them. + std::vector &Vec = Ret[Sym->CuVectorIndex]; + uint32_t Val = (Ent.Type << 24) | Idx; + if (Vec.empty() || Vec.back() != Val) + Vec.push_back(Val); + } + Idx += Chunk.CompilationUnits.size(); + } + + StringPoolSize = Off; + return Ret; +} + +template GdbIndexSection *elf::createGdbIndex() { + std::vector Sections = getDebugInfoSections(); + std::vector Chunks(Sections.size()); + + parallelForEachN(0, Chunks.size(), [&](size_t I) { + ObjFile *File = Sections[I]->getFile(); + DWARFContext Dwarf(make_unique>(File)); + + Chunks[I].DebugInfoSec = Sections[I]; + Chunks[I].CompilationUnits = readCuList(Dwarf); + Chunks[I].AddressAreas = readAddressAreas(Dwarf, Sections[I]); + Chunks[I].NamesAndTypes = readPubNamesAndTypes(Dwarf); + }); + + return make(std::move(Chunks)); +} + +static size_t getCuSize(ArrayRef Arr) { + size_t Ret = 0; + for (const GdbIndexChunk &D : Arr) + Ret += D.CompilationUnits.size(); + return Ret; +} + +static size_t getAddressAreaSize(ArrayRef Arr) { + size_t Ret = 0; + for (const GdbIndexChunk &D : Arr) + Ret += D.AddressAreas.size(); + return Ret; +} + +std::vector GdbIndexSection::createGdbSymtab() { + uint32_t Size = NextPowerOf2(Symbols.size() * 4 / 3); + if (Size < 1024) + Size = 1024; + + uint32_t Mask = Size - 1; + std::vector Ret(Size); + + for (auto &KV : Symbols) { + GdbSymbol *Sym = KV.second; + uint32_t I = Sym->NameHash & Mask; + uint32_t Step = ((Sym->NameHash * 17) & Mask) | 1; + + while (Ret[I]) + I = (I + Step) & Mask; + Ret[I] = Sym; + } + return Ret; +} + +GdbIndexSection::GdbIndexSection(std::vector &&C) + : SyntheticSection(0, SHT_PROGBITS, 1, ".gdb_index"), Chunks(std::move(C)) { + fixCuIndex(); + CuVectors = createCuVectors(); + GdbSymtab = createGdbSymtab(); + + // Compute offsets early to know the section size. + // Each chunk size needs to be in sync with what we write in writeTo. + CuTypesOffset = CuListOffset + getCuSize(Chunks) * 16; + SymtabOffset = CuTypesOffset + getAddressAreaSize(Chunks) * 20; + ConstantPoolOffset = SymtabOffset + GdbSymtab.size() * 8; + + size_t Off = 0; + for (ArrayRef Vec : CuVectors) { + CuVectorOffsets.push_back(Off); + Off += (Vec.size() + 1) * 4; + } + StringPoolOffset = ConstantPoolOffset + Off; +} + +size_t GdbIndexSection::getSize() const { + return StringPoolOffset + StringPoolSize; +} + +void GdbIndexSection::writeTo(uint8_t *Buf) { + // Write the section header. + write32le(Buf, 7); + write32le(Buf + 4, CuListOffset); + write32le(Buf + 8, CuTypesOffset); + write32le(Buf + 12, CuTypesOffset); + write32le(Buf + 16, SymtabOffset); + write32le(Buf + 20, ConstantPoolOffset); + Buf += 24; + + // Write the CU list. + for (GdbIndexChunk &D : Chunks) { + for (GdbIndexChunk::CuEntry &Cu : D.CompilationUnits) { + write64le(Buf, D.DebugInfoSec->OutSecOff + Cu.CuOffset); + write64le(Buf + 8, Cu.CuLength); + Buf += 16; + } + } + + // Write the address area. + for (GdbIndexChunk &D : Chunks) { + for (GdbIndexChunk::AddressEntry &E : D.AddressAreas) { + uint64_t BaseAddr = + E.Section->getParent()->Addr + E.Section->getOffset(0); + write64le(Buf, BaseAddr + E.LowAddress); + write64le(Buf + 8, BaseAddr + E.HighAddress); + write32le(Buf + 16, E.CuIndex); + Buf += 20; + } + } + + // Write the symbol table. + for (GdbSymbol *Sym : GdbSymtab) { + if (Sym) { + write32le(Buf, Sym->NameOffset + StringPoolOffset - ConstantPoolOffset); + write32le(Buf + 4, CuVectorOffsets[Sym->CuVectorIndex]); + } + Buf += 8; + } + + // Write the CU vectors. + for (ArrayRef Vec : CuVectors) { + write32le(Buf, Vec.size()); + Buf += 4; + for (uint32_t Val : Vec) { + write32le(Buf, Val); + Buf += 4; + } + } + + // Write the string pool. + for (auto &KV : Symbols) { + CachedHashStringRef S = KV.first; + GdbSymbol *Sym = KV.second; + size_t Off = Sym->NameOffset; + memcpy(Buf + Off, S.val().data(), S.size()); + Buf[Off + S.size()] = '\0'; + } +} + +bool GdbIndexSection::empty() const { return !Out::DebugInfo; } + +template +EhFrameHeader::EhFrameHeader() + : SyntheticSection(SHF_ALLOC, SHT_PROGBITS, 1, ".eh_frame_hdr") {} + +// .eh_frame_hdr contains a binary search table of pointers to FDEs. +// Each entry of the search table consists of two values, +// the starting PC from where FDEs covers, and the FDE's address. +// It is sorted by PC. +template void EhFrameHeader::writeTo(uint8_t *Buf) { + const endianness E = ELFT::TargetEndianness; + + // Sort the FDE list by their PC and uniqueify. Usually there is only + // one FDE for a PC (i.e. function), but if ICF merges two functions + // into one, there can be more than one FDEs pointing to the address. + auto Less = [](const FdeData &A, const FdeData &B) { return A.Pc < B.Pc; }; + std::stable_sort(Fdes.begin(), Fdes.end(), Less); + auto Eq = [](const FdeData &A, const FdeData &B) { return A.Pc == B.Pc; }; + Fdes.erase(std::unique(Fdes.begin(), Fdes.end(), Eq), Fdes.end()); + + Buf[0] = 1; + Buf[1] = DW_EH_PE_pcrel | DW_EH_PE_sdata4; + Buf[2] = DW_EH_PE_udata4; + Buf[3] = DW_EH_PE_datarel | DW_EH_PE_sdata4; + write32(Buf + 4, In::EhFrame->getParent()->Addr - this->getVA() - 4); + write32(Buf + 8, Fdes.size()); + Buf += 12; + + uint64_t VA = this->getVA(); + for (FdeData &Fde : Fdes) { + write32(Buf, Fde.Pc - VA); + write32(Buf + 4, Fde.FdeVA - VA); + Buf += 8; + } +} + +template size_t EhFrameHeader::getSize() const { + // .eh_frame_hdr has a 12 bytes header followed by an array of FDEs. + return 12 + In::EhFrame->NumFdes * 8; +} + +template +void EhFrameHeader::addFde(uint32_t Pc, uint32_t FdeVA) { + Fdes.push_back({Pc, FdeVA}); +} + +template bool EhFrameHeader::empty() const { + return In::EhFrame->empty(); +} + +template +VersionDefinitionSection::VersionDefinitionSection() + : SyntheticSection(SHF_ALLOC, SHT_GNU_verdef, sizeof(uint32_t), + ".gnu.version_d") {} + +static StringRef getFileDefName() { + if (!Config->SoName.empty()) + return Config->SoName; + return Config->OutputFile; +} + +template void VersionDefinitionSection::finalizeContents() { + FileDefNameOff = InX::DynStrTab->addString(getFileDefName()); + for (VersionDefinition &V : Config->VersionDefinitions) + V.NameOff = InX::DynStrTab->addString(V.Name); + + getParent()->Link = InX::DynStrTab->getParent()->SectionIndex; + + // sh_info should be set to the number of definitions. This fact is missed in + // documentation, but confirmed by binutils community: + // https://sourceware.org/ml/binutils/2014-11/msg00355.html + getParent()->Info = getVerDefNum(); +} + +template +void VersionDefinitionSection::writeOne(uint8_t *Buf, uint32_t Index, + StringRef Name, size_t NameOff) { + auto *Verdef = reinterpret_cast(Buf); + Verdef->vd_version = 1; + Verdef->vd_cnt = 1; + Verdef->vd_aux = sizeof(Elf_Verdef); + Verdef->vd_next = sizeof(Elf_Verdef) + sizeof(Elf_Verdaux); + Verdef->vd_flags = (Index == 1 ? VER_FLG_BASE : 0); + Verdef->vd_ndx = Index; + Verdef->vd_hash = hashSysV(Name); + + auto *Verdaux = reinterpret_cast(Buf + sizeof(Elf_Verdef)); + Verdaux->vda_name = NameOff; + Verdaux->vda_next = 0; +} + +template +void VersionDefinitionSection::writeTo(uint8_t *Buf) { + writeOne(Buf, 1, getFileDefName(), FileDefNameOff); + + for (VersionDefinition &V : Config->VersionDefinitions) { + Buf += sizeof(Elf_Verdef) + sizeof(Elf_Verdaux); + writeOne(Buf, V.Id, V.Name, V.NameOff); + } + + // Need to terminate the last version definition. + Elf_Verdef *Verdef = reinterpret_cast(Buf); + Verdef->vd_next = 0; +} + +template size_t VersionDefinitionSection::getSize() const { + return (sizeof(Elf_Verdef) + sizeof(Elf_Verdaux)) * getVerDefNum(); +} + +template +VersionTableSection::VersionTableSection() + : SyntheticSection(SHF_ALLOC, SHT_GNU_versym, sizeof(uint16_t), + ".gnu.version") { + this->Entsize = sizeof(Elf_Versym); +} + +template void VersionTableSection::finalizeContents() { + // At the moment of june 2016 GNU docs does not mention that sh_link field + // should be set, but Sun docs do. Also readelf relies on this field. + getParent()->Link = InX::DynSymTab->getParent()->SectionIndex; +} + +template size_t VersionTableSection::getSize() const { + return sizeof(Elf_Versym) * (InX::DynSymTab->getSymbols().size() + 1); +} + +template void VersionTableSection::writeTo(uint8_t *Buf) { + auto *OutVersym = reinterpret_cast(Buf) + 1; + for (const SymbolTableEntry &S : InX::DynSymTab->getSymbols()) { + OutVersym->vs_index = S.Symbol->symbol()->VersionId; + ++OutVersym; + } +} + +template bool VersionTableSection::empty() const { + return !In::VerDef && In::VerNeed->empty(); +} + +template +VersionNeedSection::VersionNeedSection() + : SyntheticSection(SHF_ALLOC, SHT_GNU_verneed, sizeof(uint32_t), + ".gnu.version_r") { + // Identifiers in verneed section start at 2 because 0 and 1 are reserved + // for VER_NDX_LOCAL and VER_NDX_GLOBAL. + // First identifiers are reserved by verdef section if it exist. + NextIndex = getVerDefNum() + 1; +} + +template +void VersionNeedSection::addSymbol(SharedSymbol *SS) { + auto *Ver = reinterpret_cast(SS->Verdef); + if (!Ver) { + SS->symbol()->VersionId = VER_NDX_GLOBAL; + return; + } + + SharedFile *File = SS->getFile(); + + // If we don't already know that we need an Elf_Verneed for this DSO, prepare + // to create one by adding it to our needed list and creating a dynstr entry + // for the soname. + if (File->VerdefMap.empty()) + Needed.push_back({File, InX::DynStrTab->addString(File->SoName)}); + typename SharedFile::NeededVer &NV = File->VerdefMap[Ver]; + // If we don't already know that we need an Elf_Vernaux for this Elf_Verdef, + // prepare to create one by allocating a version identifier and creating a + // dynstr entry for the version name. + if (NV.Index == 0) { + NV.StrTab = InX::DynStrTab->addString(File->getStringTable().data() + + Ver->getAux()->vda_name); + NV.Index = NextIndex++; + } + SS->symbol()->VersionId = NV.Index; +} + +template void VersionNeedSection::writeTo(uint8_t *Buf) { + // The Elf_Verneeds need to appear first, followed by the Elf_Vernauxs. + auto *Verneed = reinterpret_cast(Buf); + auto *Vernaux = reinterpret_cast(Verneed + Needed.size()); + + for (std::pair *, size_t> &P : Needed) { + // Create an Elf_Verneed for this DSO. + Verneed->vn_version = 1; + Verneed->vn_cnt = P.first->VerdefMap.size(); + Verneed->vn_file = P.second; + Verneed->vn_aux = + reinterpret_cast(Vernaux) - reinterpret_cast(Verneed); + Verneed->vn_next = sizeof(Elf_Verneed); + ++Verneed; + + // Create the Elf_Vernauxs for this Elf_Verneed. The loop iterates over + // VerdefMap, which will only contain references to needed version + // definitions. Each Elf_Vernaux is based on the information contained in + // the Elf_Verdef in the source DSO. This loop iterates over a std::map of + // pointers, but is deterministic because the pointers refer to Elf_Verdef + // data structures within a single input file. + for (auto &NV : P.first->VerdefMap) { + Vernaux->vna_hash = NV.first->vd_hash; + Vernaux->vna_flags = 0; + Vernaux->vna_other = NV.second.Index; + Vernaux->vna_name = NV.second.StrTab; + Vernaux->vna_next = sizeof(Elf_Vernaux); + ++Vernaux; + } + + Vernaux[-1].vna_next = 0; + } + Verneed[-1].vn_next = 0; +} + +template void VersionNeedSection::finalizeContents() { + getParent()->Link = InX::DynStrTab->getParent()->SectionIndex; + getParent()->Info = Needed.size(); +} + +template size_t VersionNeedSection::getSize() const { + unsigned Size = Needed.size() * sizeof(Elf_Verneed); + for (const std::pair *, size_t> &P : Needed) + Size += P.first->VerdefMap.size() * sizeof(Elf_Vernaux); + return Size; +} + +template bool VersionNeedSection::empty() const { + return getNeedNum() == 0; +} + +MergeSyntheticSection::MergeSyntheticSection(StringRef Name, uint32_t Type, + uint64_t Flags, uint32_t Alignment) + : SyntheticSection(Flags, Type, Alignment, Name), + Builder(StringTableBuilder::RAW, Alignment) {} + +void MergeSyntheticSection::addSection(MergeInputSection *MS) { + MS->Parent = this; + Sections.push_back(MS); +} + +void MergeSyntheticSection::writeTo(uint8_t *Buf) { Builder.write(Buf); } + +bool MergeSyntheticSection::shouldTailMerge() const { + return (this->Flags & SHF_STRINGS) && Config->Optimize >= 2; +} + +void MergeSyntheticSection::finalizeTailMerge() { + // Add all string pieces to the string table builder to create section + // contents. + for (MergeInputSection *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(); + + // 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 *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)); +} + +void MergeSyntheticSection::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 *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(); +} + +void MergeSyntheticSection::finalizeContents() { + if (shouldTailMerge()) + finalizeTailMerge(); + else + finalizeNoTailMerge(); +} + +size_t MergeSyntheticSection::getSize() const { return Builder.getSize(); } + +// This function decompresses compressed sections and scans over the input +// sections to create mergeable synthetic sections. It removes +// MergeInputSections from the input section array and adds new synthetic +// sections at the location of the first input section that it replaces. It then +// finalizes each synthetic section in order to compute an output offset for +// each piece of each input section. +void elf::decompressAndMergeSections() { + // splitIntoPieces needs to be called on each MergeInputSection before calling + // finalizeContents(). Do that first. + parallelForEach(InputSections, [](InputSectionBase *S) { + if (!S->Live) + return; + if (Decompressor::isCompressedELFSection(S->Flags, S->Name)) + S->uncompress(); + if (auto *MS = dyn_cast(S)) + MS->splitIntoPieces(); + }); + + std::vector MergeSections; + for (InputSectionBase *&S : InputSections) { + MergeInputSection *MS = dyn_cast(S); + if (!MS) + continue; + + // We do not want to handle sections that are not alive, so just remove + // them instead of trying to merge. + if (!MS->Live) + continue; + + StringRef OutsecName = getOutputSectionName(MS->Name); + uint32_t Alignment = std::max(MS->Alignment, MS->Entsize); + + auto I = llvm::find_if(MergeSections, [=](MergeSyntheticSection *Sec) { + return Sec->Name == OutsecName && Sec->Flags == MS->Flags && + Sec->Alignment == Alignment; + }); + if (I == MergeSections.end()) { + MergeSyntheticSection *Syn = make( + OutsecName, MS->Type, MS->Flags, Alignment); + MergeSections.push_back(Syn); + I = std::prev(MergeSections.end()); + S = Syn; + } else { + S = nullptr; + } + (*I)->addSection(MS); + } + for (auto *MS : MergeSections) + MS->finalizeContents(); + + std::vector &V = InputSections; + V.erase(std::remove(V.begin(), V.end(), nullptr), V.end()); +} + +MipsRldMapSection::MipsRldMapSection() + : SyntheticSection(SHF_ALLOC | SHF_WRITE, SHT_PROGBITS, Config->Wordsize, + ".rld_map") {} + +ARMExidxSentinelSection::ARMExidxSentinelSection() + : SyntheticSection(SHF_ALLOC | SHF_LINK_ORDER, SHT_ARM_EXIDX, + Config->Wordsize, ".ARM.exidx") {} + +// Write a terminating sentinel entry to the end of the .ARM.exidx table. +// This section will have been sorted last in the .ARM.exidx table. +// This table entry will have the form: +// | PREL31 upper bound of code that has exception tables | EXIDX_CANTUNWIND | +// The sentinel must have the PREL31 value of an address higher than any +// address described by any other table entry. +void ARMExidxSentinelSection::writeTo(uint8_t *Buf) { + // The Sections are sorted in order of ascending PREL31 address with the + // sentinel last. We need to find the InputSection that precedes the + // sentinel. By construction the Sentinel is in the last + // InputSectionDescription as the InputSection that precedes it. + OutputSection *C = getParent(); + auto ISD = std::find_if(C->Commands.rbegin(), C->Commands.rend(), + [](const BaseCommand *Base) { + return isa(Base); + }); + auto L = cast(*ISD); + InputSection *Highest = L->Sections[L->Sections.size() - 2]; + InputSection *LS = Highest->getLinkOrderDep(); + uint64_t S = LS->getParent()->Addr + LS->getOffset(LS->getSize()); + uint64_t P = getVA(); + Target->relocateOne(Buf, R_ARM_PREL31, S - P); + write32le(Buf + 4, 0x1); +} + +ThunkSection::ThunkSection(OutputSection *OS, uint64_t Off) + : SyntheticSection(SHF_ALLOC | SHF_EXECINSTR, SHT_PROGBITS, + Config->Wordsize, ".text.thunk") { + this->Parent = OS; + this->OutSecOff = Off; +} + +void ThunkSection::addThunk(Thunk *T) { + uint64_t Off = alignTo(Size, T->Alignment); + T->Offset = Off; + Thunks.push_back(T); + T->addSymbols(*this); + Size = Off + T->size(); +} + +void ThunkSection::writeTo(uint8_t *Buf) { + for (const Thunk *T : Thunks) + T->writeTo(Buf + T->Offset, *this); +} + +InputSection *ThunkSection::getTargetInputSection() const { + const Thunk *T = Thunks.front(); + return T->getTargetInputSection(); +} + +InputSection *InX::ARMAttributes; +BssSection *InX::Bss; +BssSection *InX::BssRelRo; +BuildIdSection *InX::BuildId; +SyntheticSection *InX::Dynamic; +StringTableSection *InX::DynStrTab; +SymbolTableBaseSection *InX::DynSymTab; +InputSection *InX::Interp; +GdbIndexSection *InX::GdbIndex; +GotSection *InX::Got; +GotPltSection *InX::GotPlt; +GnuHashTableSection *InX::GnuHashTab; +IgotPltSection *InX::IgotPlt; +MipsGotSection *InX::MipsGot; +MipsRldMapSection *InX::MipsRldMap; +PltSection *InX::Plt; +PltSection *InX::Iplt; +StringTableSection *InX::ShStrTab; +StringTableSection *InX::StrTab; +SymbolTableBaseSection *InX::SymTab; + +template GdbIndexSection *elf::createGdbIndex(); +template GdbIndexSection *elf::createGdbIndex(); +template GdbIndexSection *elf::createGdbIndex(); +template GdbIndexSection *elf::createGdbIndex(); + +template void PltSection::addEntry(SymbolBody &Sym); +template void PltSection::addEntry(SymbolBody &Sym); +template void PltSection::addEntry(SymbolBody &Sym); +template void PltSection::addEntry(SymbolBody &Sym); + +template void elf::createCommonSections(); +template void elf::createCommonSections(); +template void elf::createCommonSections(); +template void elf::createCommonSections(); + +template MergeInputSection *elf::createCommentSection(); +template MergeInputSection *elf::createCommentSection(); +template MergeInputSection *elf::createCommentSection(); +template MergeInputSection *elf::createCommentSection(); + +template class elf::MipsAbiFlagsSection; +template class elf::MipsAbiFlagsSection; +template class elf::MipsAbiFlagsSection; +template class elf::MipsAbiFlagsSection; + +template class elf::MipsOptionsSection; +template class elf::MipsOptionsSection; +template class elf::MipsOptionsSection; +template class elf::MipsOptionsSection; + +template class elf::MipsReginfoSection; +template class elf::MipsReginfoSection; +template class elf::MipsReginfoSection; +template class elf::MipsReginfoSection; + +template class elf::DynamicSection; +template class elf::DynamicSection; +template class elf::DynamicSection; +template class elf::DynamicSection; + +template class elf::RelocationSection; +template class elf::RelocationSection; +template class elf::RelocationSection; +template class elf::RelocationSection; + +template class elf::SymbolTableSection; +template class elf::SymbolTableSection; +template class elf::SymbolTableSection; +template class elf::SymbolTableSection; + +template class elf::HashTableSection; +template class elf::HashTableSection; +template class elf::HashTableSection; +template class elf::HashTableSection; + +template class elf::EhFrameHeader; +template class elf::EhFrameHeader; +template class elf::EhFrameHeader; +template class elf::EhFrameHeader; + +template class elf::VersionTableSection; +template class elf::VersionTableSection; +template class elf::VersionTableSection; +template class elf::VersionTableSection; + +template class elf::VersionNeedSection; +template class elf::VersionNeedSection; +template class elf::VersionNeedSection; +template class elf::VersionNeedSection; + +template class elf::VersionDefinitionSection; +template class elf::VersionDefinitionSection; +template class elf::VersionDefinitionSection; +template class elf::VersionDefinitionSection; + +template class elf::EhFrameSection; +template class elf::EhFrameSection; +template class elf::EhFrameSection; +template class elf::EhFrameSection; Index: lld/trunk/ELF/Writer.cpp =================================================================== --- lld/trunk/ELF/Writer.cpp +++ lld/trunk/ELF/Writer.cpp @@ -290,9 +290,6 @@ Add(InX::BuildId); } - for (InputSection *S : createCommonSections()) - Add(S); - InX::Bss = make(".bss"); Add(InX::Bss); InX::BssRelRo = make(".bss.rel.ro"); @@ -441,11 +438,7 @@ if (auto *S = dyn_cast(Sec)) if (!S->getSectionPiece(D->Value)->Live) return false; - return true; } - - if (auto *Sym = dyn_cast(&B)) - return Sym->Live; return true; }