forked from OSchip/llvm-project
803 lines
28 KiB
C++
803 lines
28 KiB
C++
//===- InputSection.cpp ---------------------------------------------------===//
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//
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// The LLVM Linker
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "InputSection.h"
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#include "Config.h"
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#include "EhFrame.h"
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#include "Error.h"
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#include "InputFiles.h"
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#include "LinkerScript.h"
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#include "Memory.h"
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#include "OutputSections.h"
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#include "Relocations.h"
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#include "SyntheticSections.h"
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#include "Target.h"
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#include "Thunks.h"
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#include "llvm/Object/Decompressor.h"
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#include "llvm/Support/Compression.h"
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#include "llvm/Support/Endian.h"
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#include <mutex>
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using namespace llvm;
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using namespace llvm::ELF;
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using namespace llvm::object;
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using namespace llvm::support;
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using namespace llvm::support::endian;
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using namespace lld;
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using namespace lld::elf;
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// Returns a string to construct an error message.
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template <class ELFT>
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std::string lld::toString(const InputSectionBase<ELFT> *Sec) {
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// File can be absent if section is synthetic.
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std::string FileName =
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Sec->getFile() ? Sec->getFile()->getName() : "<internal>";
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return (FileName + ":(" + Sec->Name + ")").str();
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}
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template <class ELFT>
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static ArrayRef<uint8_t> getSectionContents(elf::ObjectFile<ELFT> *File,
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const typename ELFT::Shdr *Hdr) {
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if (!File || Hdr->sh_type == SHT_NOBITS)
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return makeArrayRef<uint8_t>(nullptr, Hdr->sh_size);
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return check(File->getObj().getSectionContents(Hdr));
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}
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template <class ELFT>
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InputSectionBase<ELFT>::InputSectionBase(elf::ObjectFile<ELFT> *File,
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uintX_t Flags, uint32_t Type,
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uintX_t Entsize, uint32_t Link,
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uint32_t Info, uintX_t Addralign,
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ArrayRef<uint8_t> Data, StringRef Name,
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Kind SectionKind)
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: InputSectionData(SectionKind, Name, Data,
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!Config->GcSections || !(Flags & SHF_ALLOC)),
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File(File), Flags(Flags), Entsize(Entsize), Type(Type), Link(Link),
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Info(Info), Repl(this) {
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NumRelocations = 0;
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AreRelocsRela = false;
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// The ELF spec states that a value of 0 means the section has
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// no alignment constraits.
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uint64_t V = std::max<uint64_t>(Addralign, 1);
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if (!isPowerOf2_64(V))
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fatal(toString(File) + ": section sh_addralign is not a power of 2");
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// We reject object files having insanely large alignments even though
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// they are allowed by the spec. I think 4GB is a reasonable limitation.
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// We might want to relax this in the future.
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if (V > UINT32_MAX)
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fatal(toString(File) + ": section sh_addralign is too large");
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Alignment = V;
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// If it is not a mergeable section, overwrite the flag so that the flag
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// is consistent with the class. This inconsistency could occur when
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// string merging is disabled using -O0 flag.
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if (!Config->Relocatable && !isa<MergeInputSection<ELFT>>(this))
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this->Flags &= ~(SHF_MERGE | SHF_STRINGS);
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}
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template <class ELFT>
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InputSectionBase<ELFT>::InputSectionBase(elf::ObjectFile<ELFT> *File,
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const Elf_Shdr *Hdr, StringRef Name,
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Kind SectionKind)
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: InputSectionBase(File, Hdr->sh_flags & ~SHF_INFO_LINK, Hdr->sh_type,
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Hdr->sh_entsize, Hdr->sh_link, Hdr->sh_info,
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Hdr->sh_addralign, getSectionContents(File, Hdr), Name,
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SectionKind) {
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this->Offset = Hdr->sh_offset;
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}
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template <class ELFT> size_t InputSectionBase<ELFT>::getSize() const {
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if (auto *S = dyn_cast<SyntheticSection<ELFT>>(this))
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return S->getSize();
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if (auto *D = dyn_cast<InputSection<ELFT>>(this))
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if (D->getThunksSize() > 0)
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return D->getThunkOff() + D->getThunksSize();
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return Data.size();
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}
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template <class ELFT>
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typename ELFT::uint InputSectionBase<ELFT>::getOffset(uintX_t Offset) const {
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switch (kind()) {
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case Regular:
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return cast<InputSection<ELFT>>(this)->OutSecOff + Offset;
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case Synthetic:
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// For synthetic sections we treat offset -1 as the end of the section.
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// The same approach is used for synthetic symbols (DefinedSynthetic).
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return cast<InputSection<ELFT>>(this)->OutSecOff +
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(Offset == uintX_t(-1) ? getSize() : Offset);
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case EHFrame:
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// The file crtbeginT.o has relocations pointing to the start of an empty
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// .eh_frame that is known to be the first in the link. It does that to
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// identify the start of the output .eh_frame.
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return Offset;
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case Merge:
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return cast<MergeInputSection<ELFT>>(this)->getOffset(Offset);
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}
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llvm_unreachable("invalid section kind");
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}
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// Uncompress section contents. Note that this function is called
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// from parallel_for_each, so it must be thread-safe.
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template <class ELFT> void InputSectionBase<ELFT>::uncompress() {
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Decompressor Dec = check(Decompressor::create(
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Name, toStringRef(Data), ELFT::TargetEndianness == llvm::support::little,
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ELFT::Is64Bits));
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size_t Size = Dec.getDecompressedSize();
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char *OutputBuf;
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{
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static std::mutex Mu;
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std::lock_guard<std::mutex> Lock(Mu);
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OutputBuf = BAlloc.Allocate<char>(Size);
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}
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if (Error E = Dec.decompress({OutputBuf, Size}))
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fatal(toString(this) +
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": decompress failed: " + llvm::toString(std::move(E)));
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Data = ArrayRef<uint8_t>((uint8_t *)OutputBuf, Size);
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}
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template <class ELFT>
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typename ELFT::uint
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InputSectionBase<ELFT>::getOffset(const DefinedRegular<ELFT> &Sym) const {
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return getOffset(Sym.Value);
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}
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template <class ELFT>
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InputSectionBase<ELFT> *InputSectionBase<ELFT>::getLinkOrderDep() const {
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if ((Flags & SHF_LINK_ORDER) && Link != 0)
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return getFile()->getSections()[Link];
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return nullptr;
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}
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// Returns a source location string. Used to construct an error message.
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template <class ELFT>
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std::string InputSectionBase<ELFT>::getLocation(typename ELFT::uint Offset) {
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// First check if we can get desired values from debugging information.
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std::string LineInfo = File->getLineInfo(this, Offset);
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if (!LineInfo.empty())
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return LineInfo;
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// File->SourceFile contains STT_FILE symbol that contains a
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// source file name. If it's missing, we use an object file name.
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std::string SrcFile = File->SourceFile;
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if (SrcFile.empty())
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SrcFile = toString(File);
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// Find a function symbol that encloses a given location.
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for (SymbolBody *B : File->getSymbols())
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if (auto *D = dyn_cast<DefinedRegular<ELFT>>(B))
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if (D->Section == this && D->Type == STT_FUNC)
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if (D->Value <= Offset && Offset < D->Value + D->Size)
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return SrcFile + ":(function " + toString(*D) + ")";
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// If there's no symbol, print out the offset in the section.
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return (SrcFile + ":(" + Name + "+0x" + utohexstr(Offset) + ")").str();
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}
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template <class ELFT>
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InputSection<ELFT>::InputSection() : InputSectionBase<ELFT>() {}
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template <class ELFT>
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InputSection<ELFT>::InputSection(uintX_t Flags, uint32_t Type,
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uintX_t Addralign, ArrayRef<uint8_t> Data,
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StringRef Name, Kind K)
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: InputSectionBase<ELFT>(nullptr, Flags, Type,
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/*Entsize*/ 0, /*Link*/ 0, /*Info*/ 0, Addralign,
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Data, Name, K) {}
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template <class ELFT>
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InputSection<ELFT>::InputSection(elf::ObjectFile<ELFT> *F,
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const Elf_Shdr *Header, StringRef Name)
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: InputSectionBase<ELFT>(F, Header, Name, Base::Regular) {}
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template <class ELFT>
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bool InputSection<ELFT>::classof(const InputSectionData *S) {
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return S->kind() == Base::Regular || S->kind() == Base::Synthetic;
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}
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template <class ELFT>
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InputSectionBase<ELFT> *InputSection<ELFT>::getRelocatedSection() {
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assert(this->Type == SHT_RELA || this->Type == SHT_REL);
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ArrayRef<InputSectionBase<ELFT> *> Sections = this->File->getSections();
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return Sections[this->Info];
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}
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template <class ELFT> void InputSection<ELFT>::addThunk(const Thunk<ELFT> *T) {
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Thunks.push_back(T);
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}
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template <class ELFT> uint64_t InputSection<ELFT>::getThunkOff() const {
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return this->Data.size();
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}
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template <class ELFT> uint64_t InputSection<ELFT>::getThunksSize() const {
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uint64_t Total = 0;
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for (const Thunk<ELFT> *T : Thunks)
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Total += T->size();
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return Total;
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}
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// This is used for -r. We can't use memcpy to copy relocations because we need
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// to update symbol table offset and section index for each relocation. So we
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// copy relocations one by one.
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template <class ELFT>
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template <class RelTy>
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void InputSection<ELFT>::copyRelocations(uint8_t *Buf, ArrayRef<RelTy> Rels) {
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InputSectionBase<ELFT> *RelocatedSection = getRelocatedSection();
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for (const RelTy &Rel : Rels) {
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uint32_t Type = Rel.getType(Config->Mips64EL);
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SymbolBody &Body = this->File->getRelocTargetSym(Rel);
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Elf_Rela *P = reinterpret_cast<Elf_Rela *>(Buf);
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Buf += sizeof(RelTy);
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if (Config->Rela)
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P->r_addend = getAddend<ELFT>(Rel);
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P->r_offset = RelocatedSection->getOffset(Rel.r_offset);
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P->setSymbolAndType(Body.DynsymIndex, Type, Config->Mips64EL);
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}
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}
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static uint32_t getARMUndefinedRelativeWeakVA(uint32_t Type, uint32_t A,
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uint32_t P) {
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switch (Type) {
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case R_ARM_THM_JUMP11:
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return P + 2;
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case R_ARM_CALL:
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case R_ARM_JUMP24:
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case R_ARM_PC24:
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case R_ARM_PLT32:
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case R_ARM_PREL31:
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case R_ARM_THM_JUMP19:
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case R_ARM_THM_JUMP24:
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return P + 4;
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case R_ARM_THM_CALL:
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// We don't want an interworking BLX to ARM
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return P + 5;
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default:
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return A;
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}
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}
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static uint64_t getAArch64UndefinedRelativeWeakVA(uint64_t Type, uint64_t A,
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uint64_t P) {
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switch (Type) {
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case R_AARCH64_CALL26:
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case R_AARCH64_CONDBR19:
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case R_AARCH64_JUMP26:
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case R_AARCH64_TSTBR14:
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return P + 4;
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default:
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return A;
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}
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}
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template <class ELFT>
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static typename ELFT::uint
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getRelocTargetVA(uint32_t Type, typename ELFT::uint A, typename ELFT::uint P,
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const SymbolBody &Body, RelExpr Expr) {
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switch (Expr) {
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case R_HINT:
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case R_TLSDESC_CALL:
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llvm_unreachable("cannot relocate hint relocs");
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case R_TLSLD:
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return In<ELFT>::Got->getTlsIndexOff() + A - In<ELFT>::Got->getSize();
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case R_TLSLD_PC:
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return In<ELFT>::Got->getTlsIndexVA() + A - P;
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case R_THUNK_ABS:
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return Body.getThunkVA<ELFT>() + A;
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case R_THUNK_PC:
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case R_THUNK_PLT_PC:
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return Body.getThunkVA<ELFT>() + A - P;
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case R_PPC_TOC:
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return getPPC64TocBase() + A;
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case R_TLSGD:
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return In<ELFT>::Got->getGlobalDynOffset(Body) + A -
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In<ELFT>::Got->getSize();
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case R_TLSGD_PC:
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return In<ELFT>::Got->getGlobalDynAddr(Body) + A - P;
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case R_TLSDESC:
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return In<ELFT>::Got->getGlobalDynAddr(Body) + A;
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case R_TLSDESC_PAGE:
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return getAArch64Page(In<ELFT>::Got->getGlobalDynAddr(Body) + A) -
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getAArch64Page(P);
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case R_PLT:
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return Body.getPltVA<ELFT>() + A;
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case R_PLT_PC:
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case R_PPC_PLT_OPD:
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return Body.getPltVA<ELFT>() + A - P;
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case R_SIZE:
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return Body.getSize<ELFT>() + A;
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case R_GOTREL:
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return Body.getVA<ELFT>(A) - In<ELFT>::Got->getVA();
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case R_GOTREL_FROM_END:
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return Body.getVA<ELFT>(A) - In<ELFT>::Got->getVA() -
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In<ELFT>::Got->getSize();
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case R_RELAX_TLS_GD_TO_IE_END:
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case R_GOT_FROM_END:
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return Body.getGotOffset<ELFT>() + A - In<ELFT>::Got->getSize();
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case R_RELAX_TLS_GD_TO_IE_ABS:
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case R_GOT:
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return Body.getGotVA<ELFT>() + A;
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case R_RELAX_TLS_GD_TO_IE_PAGE_PC:
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case R_GOT_PAGE_PC:
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return getAArch64Page(Body.getGotVA<ELFT>() + A) - getAArch64Page(P);
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case R_RELAX_TLS_GD_TO_IE:
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case R_GOT_PC:
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return Body.getGotVA<ELFT>() + A - P;
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case R_GOTONLY_PC:
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return In<ELFT>::Got->getVA() + A - P;
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case R_GOTONLY_PC_FROM_END:
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return In<ELFT>::Got->getVA() + A - P + In<ELFT>::Got->getSize();
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case R_RELAX_TLS_LD_TO_LE:
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case R_RELAX_TLS_IE_TO_LE:
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case R_RELAX_TLS_GD_TO_LE:
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case R_TLS:
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// A weak undefined TLS symbol resolves to the base of the TLS
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// block, i.e. gets a value of zero. If we pass --gc-sections to
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// lld and .tbss is not referenced, it gets reclaimed and we don't
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// create a TLS program header. Therefore, we resolve this
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// statically to zero.
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if (Body.isTls() && (Body.isLazy() || Body.isUndefined()) &&
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Body.symbol()->isWeak())
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return 0;
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if (Target->TcbSize)
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return Body.getVA<ELFT>(A) +
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alignTo(Target->TcbSize, Out<ELFT>::TlsPhdr->p_align);
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return Body.getVA<ELFT>(A) - Out<ELFT>::TlsPhdr->p_memsz;
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case R_RELAX_TLS_GD_TO_LE_NEG:
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case R_NEG_TLS:
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return Out<ELF32LE>::TlsPhdr->p_memsz - Body.getVA<ELFT>(A);
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case R_ABS:
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case R_RELAX_GOT_PC_NOPIC:
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return Body.getVA<ELFT>(A);
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case R_GOT_OFF:
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return Body.getGotOffset<ELFT>() + A;
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case R_MIPS_GOT_LOCAL_PAGE:
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// If relocation against MIPS local symbol requires GOT entry, this entry
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// should be initialized by 'page address'. This address is high 16-bits
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// of sum the symbol's value and the addend.
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return In<ELFT>::MipsGot->getVA() +
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In<ELFT>::MipsGot->getPageEntryOffset(Body, A) -
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In<ELFT>::MipsGot->getGp();
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case R_MIPS_GOT_OFF:
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case R_MIPS_GOT_OFF32:
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// In case of MIPS if a GOT relocation has non-zero addend this addend
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// should be applied to the GOT entry content not to the GOT entry offset.
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// That is why we use separate expression type.
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return In<ELFT>::MipsGot->getVA() +
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In<ELFT>::MipsGot->getBodyEntryOffset(Body, A) -
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In<ELFT>::MipsGot->getGp();
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case R_MIPS_GOTREL:
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return Body.getVA<ELFT>(A) - In<ELFT>::MipsGot->getGp();
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case R_MIPS_TLSGD:
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return In<ELFT>::MipsGot->getVA() + In<ELFT>::MipsGot->getTlsOffset() +
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In<ELFT>::MipsGot->getGlobalDynOffset(Body) -
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In<ELFT>::MipsGot->getGp();
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case R_MIPS_TLSLD:
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return In<ELFT>::MipsGot->getVA() + In<ELFT>::MipsGot->getTlsOffset() +
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In<ELFT>::MipsGot->getTlsIndexOff() - In<ELFT>::MipsGot->getGp();
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case R_PPC_OPD: {
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uint64_t SymVA = Body.getVA<ELFT>(A);
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// If we have an undefined weak symbol, we might get here with a symbol
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// address of zero. That could overflow, but the code must be unreachable,
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// so don't bother doing anything at all.
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if (!SymVA)
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return 0;
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if (Out<ELF64BE>::Opd) {
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// If this is a local call, and we currently have the address of a
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// function-descriptor, get the underlying code address instead.
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uint64_t OpdStart = Out<ELF64BE>::Opd->Addr;
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uint64_t OpdEnd = OpdStart + Out<ELF64BE>::Opd->Size;
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bool InOpd = OpdStart <= SymVA && SymVA < OpdEnd;
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if (InOpd)
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SymVA = read64be(&Out<ELF64BE>::OpdBuf[SymVA - OpdStart]);
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}
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return SymVA - P;
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}
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case R_PC:
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if (Body.isUndefined() && !Body.isLocal() && Body.symbol()->isWeak()) {
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// On ARM and AArch64 a branch to an undefined weak resolves to the
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// next instruction, otherwise the place.
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if (Config->EMachine == EM_ARM)
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return getARMUndefinedRelativeWeakVA(Type, A, P);
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if (Config->EMachine == EM_AARCH64)
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return getAArch64UndefinedRelativeWeakVA(Type, A, P);
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}
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case R_RELAX_GOT_PC:
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return Body.getVA<ELFT>(A) - P;
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case R_PLT_PAGE_PC:
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case R_PAGE_PC:
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if (Body.isUndefined() && !Body.isLocal() && Body.symbol()->isWeak())
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return getAArch64Page(A);
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return getAArch64Page(Body.getVA<ELFT>(A)) - getAArch64Page(P);
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}
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llvm_unreachable("Invalid expression");
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}
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// This function applies relocations to sections without SHF_ALLOC bit.
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// Such sections are never mapped to memory at runtime. Debug sections are
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// an example. Relocations in non-alloc sections are much easier to
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// handle than in allocated sections because it will never need complex
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// treatement such as GOT or PLT (because at runtime no one refers them).
|
|
// So, we handle relocations for non-alloc sections directly in this
|
|
// function as a performance optimization.
|
|
template <class ELFT>
|
|
template <class RelTy>
|
|
void InputSection<ELFT>::relocateNonAlloc(uint8_t *Buf, ArrayRef<RelTy> Rels) {
|
|
for (const RelTy &Rel : Rels) {
|
|
uint32_t Type = Rel.getType(Config->Mips64EL);
|
|
uintX_t Offset = this->getOffset(Rel.r_offset);
|
|
uint8_t *BufLoc = Buf + Offset;
|
|
uintX_t Addend = getAddend<ELFT>(Rel);
|
|
if (!RelTy::IsRela)
|
|
Addend += Target->getImplicitAddend(BufLoc, Type);
|
|
|
|
SymbolBody &Sym = this->File->getRelocTargetSym(Rel);
|
|
if (Target->getRelExpr(Type, Sym) != R_ABS) {
|
|
error(this->getLocation(Offset) + ": has non-ABS reloc");
|
|
return;
|
|
}
|
|
|
|
uintX_t AddrLoc = this->OutSec->Addr + Offset;
|
|
uint64_t SymVA = 0;
|
|
if (!Sym.isTls() || Out<ELFT>::TlsPhdr)
|
|
SymVA = SignExtend64<sizeof(uintX_t) * 8>(
|
|
getRelocTargetVA<ELFT>(Type, Addend, AddrLoc, Sym, R_ABS));
|
|
Target->relocateOne(BufLoc, Type, SymVA);
|
|
}
|
|
}
|
|
|
|
template <class ELFT>
|
|
void InputSectionBase<ELFT>::relocate(uint8_t *Buf, uint8_t *BufEnd) {
|
|
// scanReloc function in Writer.cpp constructs Relocations
|
|
// vector only for SHF_ALLOC'ed sections. For other sections,
|
|
// we handle relocations directly here.
|
|
auto *IS = dyn_cast<InputSection<ELFT>>(this);
|
|
if (IS && !(IS->Flags & SHF_ALLOC)) {
|
|
if (IS->AreRelocsRela)
|
|
IS->relocateNonAlloc(Buf, IS->relas());
|
|
else
|
|
IS->relocateNonAlloc(Buf, IS->rels());
|
|
return;
|
|
}
|
|
|
|
const unsigned Bits = sizeof(uintX_t) * 8;
|
|
for (const Relocation &Rel : Relocations) {
|
|
uintX_t Offset = getOffset(Rel.Offset);
|
|
uint8_t *BufLoc = Buf + Offset;
|
|
uint32_t Type = Rel.Type;
|
|
uintX_t A = Rel.Addend;
|
|
|
|
uintX_t AddrLoc = OutSec->Addr + Offset;
|
|
RelExpr Expr = Rel.Expr;
|
|
uint64_t TargetVA = SignExtend64<Bits>(
|
|
getRelocTargetVA<ELFT>(Type, A, AddrLoc, *Rel.Sym, Expr));
|
|
|
|
switch (Expr) {
|
|
case R_RELAX_GOT_PC:
|
|
case R_RELAX_GOT_PC_NOPIC:
|
|
Target->relaxGot(BufLoc, TargetVA);
|
|
break;
|
|
case R_RELAX_TLS_IE_TO_LE:
|
|
Target->relaxTlsIeToLe(BufLoc, Type, TargetVA);
|
|
break;
|
|
case R_RELAX_TLS_LD_TO_LE:
|
|
Target->relaxTlsLdToLe(BufLoc, Type, TargetVA);
|
|
break;
|
|
case R_RELAX_TLS_GD_TO_LE:
|
|
case R_RELAX_TLS_GD_TO_LE_NEG:
|
|
Target->relaxTlsGdToLe(BufLoc, Type, TargetVA);
|
|
break;
|
|
case R_RELAX_TLS_GD_TO_IE:
|
|
case R_RELAX_TLS_GD_TO_IE_ABS:
|
|
case R_RELAX_TLS_GD_TO_IE_PAGE_PC:
|
|
case R_RELAX_TLS_GD_TO_IE_END:
|
|
Target->relaxTlsGdToIe(BufLoc, Type, TargetVA);
|
|
break;
|
|
case R_PPC_PLT_OPD:
|
|
// Patch a nop (0x60000000) to a ld.
|
|
if (BufLoc + 8 <= BufEnd && read32be(BufLoc + 4) == 0x60000000)
|
|
write32be(BufLoc + 4, 0xe8410028); // ld %r2, 40(%r1)
|
|
// fallthrough
|
|
default:
|
|
Target->relocateOne(BufLoc, Type, TargetVA);
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
template <class ELFT> void InputSection<ELFT>::writeTo(uint8_t *Buf) {
|
|
if (this->Type == SHT_NOBITS)
|
|
return;
|
|
|
|
if (auto *S = dyn_cast<SyntheticSection<ELFT>>(this)) {
|
|
S->writeTo(Buf + OutSecOff);
|
|
return;
|
|
}
|
|
|
|
// If -r is given, then an InputSection may be a relocation section.
|
|
if (this->Type == SHT_RELA) {
|
|
copyRelocations(Buf + OutSecOff, this->template getDataAs<Elf_Rela>());
|
|
return;
|
|
}
|
|
if (this->Type == SHT_REL) {
|
|
copyRelocations(Buf + OutSecOff, this->template getDataAs<Elf_Rel>());
|
|
return;
|
|
}
|
|
|
|
// Copy section contents from source object file to output file.
|
|
ArrayRef<uint8_t> Data = this->Data;
|
|
memcpy(Buf + OutSecOff, Data.data(), Data.size());
|
|
|
|
// Iterate over all relocation sections that apply to this section.
|
|
uint8_t *BufEnd = Buf + OutSecOff + Data.size();
|
|
this->relocate(Buf, BufEnd);
|
|
|
|
// The section might have a data/code generated by the linker and need
|
|
// to be written after the section. Usually these are thunks - small piece
|
|
// of code used to jump between "incompatible" functions like PIC and non-PIC
|
|
// or if the jump target too far and its address does not fit to the short
|
|
// jump istruction.
|
|
if (!Thunks.empty()) {
|
|
Buf += OutSecOff + getThunkOff();
|
|
for (const Thunk<ELFT> *T : Thunks) {
|
|
T->writeTo(Buf);
|
|
Buf += T->size();
|
|
}
|
|
}
|
|
}
|
|
|
|
template <class ELFT>
|
|
void InputSection<ELFT>::replace(InputSection<ELFT> *Other) {
|
|
this->Alignment = std::max(this->Alignment, Other->Alignment);
|
|
Other->Repl = this->Repl;
|
|
Other->Live = false;
|
|
}
|
|
|
|
template <class ELFT>
|
|
EhInputSection<ELFT>::EhInputSection(elf::ObjectFile<ELFT> *F,
|
|
const Elf_Shdr *Header, StringRef Name)
|
|
: InputSectionBase<ELFT>(F, Header, Name, InputSectionBase<ELFT>::EHFrame) {
|
|
// Mark .eh_frame sections as live by default because there are
|
|
// usually no relocations that point to .eh_frames. Otherwise,
|
|
// the garbage collector would drop all .eh_frame sections.
|
|
this->Live = true;
|
|
}
|
|
|
|
template <class ELFT>
|
|
bool EhInputSection<ELFT>::classof(const InputSectionData *S) {
|
|
return S->kind() == InputSectionBase<ELFT>::EHFrame;
|
|
}
|
|
|
|
// Returns the index of the first relocation that points to a region between
|
|
// Begin and Begin+Size.
|
|
template <class IntTy, class RelTy>
|
|
static unsigned getReloc(IntTy Begin, IntTy Size, const ArrayRef<RelTy> &Rels,
|
|
unsigned &RelocI) {
|
|
// Start search from RelocI for fast access. That works because the
|
|
// relocations are sorted in .eh_frame.
|
|
for (unsigned N = Rels.size(); RelocI < N; ++RelocI) {
|
|
const RelTy &Rel = Rels[RelocI];
|
|
if (Rel.r_offset < Begin)
|
|
continue;
|
|
|
|
if (Rel.r_offset < Begin + Size)
|
|
return RelocI;
|
|
return -1;
|
|
}
|
|
return -1;
|
|
}
|
|
|
|
// .eh_frame is a sequence of CIE or FDE records.
|
|
// This function splits an input section into records and returns them.
|
|
template <class ELFT> void EhInputSection<ELFT>::split() {
|
|
// Early exit if already split.
|
|
if (!this->Pieces.empty())
|
|
return;
|
|
|
|
if (this->NumRelocations) {
|
|
if (this->AreRelocsRela)
|
|
split(this->relas());
|
|
else
|
|
split(this->rels());
|
|
return;
|
|
}
|
|
split(makeArrayRef<typename ELFT::Rela>(nullptr, nullptr));
|
|
}
|
|
|
|
template <class ELFT>
|
|
template <class RelTy>
|
|
void EhInputSection<ELFT>::split(ArrayRef<RelTy> Rels) {
|
|
ArrayRef<uint8_t> Data = this->Data;
|
|
unsigned RelI = 0;
|
|
for (size_t Off = 0, End = Data.size(); Off != End;) {
|
|
size_t Size = readEhRecordSize<ELFT>(this, Off);
|
|
this->Pieces.emplace_back(Off, this, Size, getReloc(Off, Size, Rels, RelI));
|
|
// The empty record is the end marker.
|
|
if (Size == 4)
|
|
break;
|
|
Off += Size;
|
|
}
|
|
}
|
|
|
|
static size_t findNull(ArrayRef<uint8_t> A, size_t EntSize) {
|
|
// Optimize the common case.
|
|
StringRef S((const char *)A.data(), A.size());
|
|
if (EntSize == 1)
|
|
return S.find(0);
|
|
|
|
for (unsigned I = 0, N = S.size(); I != N; I += EntSize) {
|
|
const char *B = S.begin() + I;
|
|
if (std::all_of(B, B + EntSize, [](char C) { return C == 0; }))
|
|
return I;
|
|
}
|
|
return StringRef::npos;
|
|
}
|
|
|
|
// Split SHF_STRINGS section. Such section is a sequence of
|
|
// null-terminated strings.
|
|
template <class ELFT>
|
|
void MergeInputSection<ELFT>::splitStrings(ArrayRef<uint8_t> Data,
|
|
size_t EntSize) {
|
|
size_t Off = 0;
|
|
bool IsAlloc = this->Flags & SHF_ALLOC;
|
|
while (!Data.empty()) {
|
|
size_t End = findNull(Data, EntSize);
|
|
if (End == StringRef::npos)
|
|
fatal(toString(this) + ": string is not null terminated");
|
|
size_t Size = End + EntSize;
|
|
Pieces.emplace_back(Off, !IsAlloc);
|
|
Hashes.push_back(hash_value(toStringRef(Data.slice(0, Size))));
|
|
Data = Data.slice(Size);
|
|
Off += Size;
|
|
}
|
|
}
|
|
|
|
// Split non-SHF_STRINGS section. Such section is a sequence of
|
|
// fixed size records.
|
|
template <class ELFT>
|
|
void MergeInputSection<ELFT>::splitNonStrings(ArrayRef<uint8_t> Data,
|
|
size_t EntSize) {
|
|
size_t Size = Data.size();
|
|
assert((Size % EntSize) == 0);
|
|
bool IsAlloc = this->Flags & SHF_ALLOC;
|
|
for (unsigned I = 0, N = Size; I != N; I += EntSize) {
|
|
Hashes.push_back(hash_value(toStringRef(Data.slice(I, EntSize))));
|
|
Pieces.emplace_back(I, !IsAlloc);
|
|
}
|
|
}
|
|
|
|
template <class ELFT>
|
|
MergeInputSection<ELFT>::MergeInputSection(elf::ObjectFile<ELFT> *F,
|
|
const Elf_Shdr *Header,
|
|
StringRef Name)
|
|
: InputSectionBase<ELFT>(F, Header, Name, InputSectionBase<ELFT>::Merge) {}
|
|
|
|
// This function is called after we obtain a complete list of input sections
|
|
// that need to be linked. This is responsible to split section contents
|
|
// into small chunks for further processing.
|
|
//
|
|
// Note that this function is called from parallel_for_each. This must be
|
|
// thread-safe (i.e. no memory allocation from the pools).
|
|
template <class ELFT> void MergeInputSection<ELFT>::splitIntoPieces() {
|
|
ArrayRef<uint8_t> Data = this->Data;
|
|
uintX_t EntSize = this->Entsize;
|
|
if (this->Flags & SHF_STRINGS)
|
|
splitStrings(Data, EntSize);
|
|
else
|
|
splitNonStrings(Data, EntSize);
|
|
|
|
if (Config->GcSections && (this->Flags & SHF_ALLOC))
|
|
for (uintX_t Off : LiveOffsets)
|
|
this->getSectionPiece(Off)->Live = true;
|
|
}
|
|
|
|
template <class ELFT>
|
|
bool MergeInputSection<ELFT>::classof(const InputSectionData *S) {
|
|
return S->kind() == InputSectionBase<ELFT>::Merge;
|
|
}
|
|
|
|
// Do binary search to get a section piece at a given input offset.
|
|
template <class ELFT>
|
|
SectionPiece *MergeInputSection<ELFT>::getSectionPiece(uintX_t Offset) {
|
|
auto *This = static_cast<const MergeInputSection<ELFT> *>(this);
|
|
return const_cast<SectionPiece *>(This->getSectionPiece(Offset));
|
|
}
|
|
|
|
template <class It, class T, class Compare>
|
|
static It fastUpperBound(It First, It Last, const T &Value, Compare Comp) {
|
|
size_t Size = std::distance(First, Last);
|
|
assert(Size != 0);
|
|
while (Size != 1) {
|
|
size_t H = Size / 2;
|
|
const It MI = First + H;
|
|
Size -= H;
|
|
First = Comp(Value, *MI) ? First : First + H;
|
|
}
|
|
return Comp(Value, *First) ? First : First + 1;
|
|
}
|
|
|
|
template <class ELFT>
|
|
const SectionPiece *
|
|
MergeInputSection<ELFT>::getSectionPiece(uintX_t Offset) const {
|
|
uintX_t Size = this->Data.size();
|
|
if (Offset >= Size)
|
|
fatal(toString(this) + ": entry is past the end of the section");
|
|
|
|
// Find the element this offset points to.
|
|
auto I = fastUpperBound(
|
|
Pieces.begin(), Pieces.end(), Offset,
|
|
[](const uintX_t &A, const SectionPiece &B) { return A < B.InputOff; });
|
|
--I;
|
|
return &*I;
|
|
}
|
|
|
|
// Returns the offset in an output section for a given input offset.
|
|
// Because contents of a mergeable section is not contiguous in output,
|
|
// it is not just an addition to a base output offset.
|
|
template <class ELFT>
|
|
typename ELFT::uint MergeInputSection<ELFT>::getOffset(uintX_t Offset) const {
|
|
// Initialize OffsetMap lazily.
|
|
std::call_once(InitOffsetMap, [&] {
|
|
OffsetMap.reserve(Pieces.size());
|
|
for (const SectionPiece &Piece : Pieces)
|
|
OffsetMap[Piece.InputOff] = Piece.OutputOff;
|
|
});
|
|
|
|
// Find a string starting at a given offset.
|
|
auto It = OffsetMap.find(Offset);
|
|
if (It != OffsetMap.end())
|
|
return It->second;
|
|
|
|
if (!this->Live)
|
|
return 0;
|
|
|
|
// If Offset is not at beginning of a section piece, it is not in the map.
|
|
// In that case we need to search from the original section piece vector.
|
|
const SectionPiece &Piece = *this->getSectionPiece(Offset);
|
|
if (!Piece.Live)
|
|
return 0;
|
|
|
|
uintX_t Addend = Offset - Piece.InputOff;
|
|
return Piece.OutputOff + Addend;
|
|
}
|
|
|
|
template class elf::InputSectionBase<ELF32LE>;
|
|
template class elf::InputSectionBase<ELF32BE>;
|
|
template class elf::InputSectionBase<ELF64LE>;
|
|
template class elf::InputSectionBase<ELF64BE>;
|
|
|
|
template class elf::InputSection<ELF32LE>;
|
|
template class elf::InputSection<ELF32BE>;
|
|
template class elf::InputSection<ELF64LE>;
|
|
template class elf::InputSection<ELF64BE>;
|
|
|
|
template class elf::EhInputSection<ELF32LE>;
|
|
template class elf::EhInputSection<ELF32BE>;
|
|
template class elf::EhInputSection<ELF64LE>;
|
|
template class elf::EhInputSection<ELF64BE>;
|
|
|
|
template class elf::MergeInputSection<ELF32LE>;
|
|
template class elf::MergeInputSection<ELF32BE>;
|
|
template class elf::MergeInputSection<ELF64LE>;
|
|
template class elf::MergeInputSection<ELF64BE>;
|
|
|
|
template std::string lld::toString(const InputSectionBase<ELF32LE> *);
|
|
template std::string lld::toString(const InputSectionBase<ELF32BE> *);
|
|
template std::string lld::toString(const InputSectionBase<ELF64LE> *);
|
|
template std::string lld::toString(const InputSectionBase<ELF64BE> *);
|