1 files changed, 373 insertions, 0 deletions
diff --git a/lib/ReaderWriter/ELF/ARM/ARMRelocationPass.cpp b/lib/ReaderWriter/ELF/ARM/ARMRelocationPass.cpp
new file mode 100644
index 000000000000..27ec66ac5557
--- /dev/null
+++ b/lib/ReaderWriter/ELF/ARM/ARMRelocationPass.cpp
@@ -0,0 +1,373 @@
+//===--------- lib/ReaderWriter/ELF/ARM/ARMRelocationPass.cpp -------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief Defines the relocation processing pass for ARM. This includes
+///   GOT and PLT entries, TLS, COPY, and ifunc.
+///
+/// This also includes additional behavior that gnu-ld and gold implement but
+/// which is not specified anywhere.
+///
+//===----------------------------------------------------------------------===//
+
+#include "ARMRelocationPass.h"
+#include "ARMLinkingContext.h"
+#include "Atoms.h"
+#include "lld/Core/Simple.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/Support/Debug.h"
+
+using namespace lld;
+using namespace lld::elf;
+using namespace llvm::ELF;
+
+// ARM B/BL instructions of static relocation veneer.
+// TODO: consider different instruction set for archs below ARMv5
+// (one as for Thumb may be used though it's less optimal).
+static const uint8_t Veneer_ARM_B_BL_StaticAtomContent[8] = {
+    0x04, 0xf0, 0x1f, 0xe5,  // ldr pc, [pc, #-4]
+    0x00, 0x00, 0x00, 0x00   // <target_symbol_address>
+};
+
+// Thumb B/BL instructions of static relocation veneer.
+// TODO: consider different instruction set for archs above ARMv5
+// (one as for ARM may be used since it's more optimal).
+static const uint8_t Veneer_THM_B_BL_StaticAtomContent[8] = {
+    0x78, 0x47,              // bx pc
+    0x00, 0x00,              // nop
+    0xfe, 0xff, 0xff, 0xea   // b <target_symbol_address>
+};
+
+// .got values
+static const uint8_t ARMGotAtomContent[4] = {0};
+
+namespace {
+/// \brief Atoms that hold veneer code.
+class VeneerAtom : public SimpleELFDefinedAtom {
+  StringRef _section;
+
+public:
+  VeneerAtom(const File &f, StringRef secName)
+      : SimpleELFDefinedAtom(f), _section(secName) {}
+
+  Scope scope() const override { return DefinedAtom::scopeTranslationUnit; }
+
+  SectionChoice sectionChoice() const override {
+    return DefinedAtom::sectionBasedOnContent;
+  }
+
+  StringRef customSectionName() const override { return _section; }
+
+  ContentType contentType() const override {
+    return DefinedAtom::typeCode;
+  }
+
+  uint64_t size() const override { return rawContent().size(); }
+
+  ContentPermissions permissions() const override { return permR_X; }
+
+  Alignment alignment() const override { return Alignment(2); }
+
+  StringRef name() const override { return _name; }
+  std::string _name;
+};
+
+/// \brief Atoms that hold veneer for statically relocated
+/// ARM B/BL instructions.
+class Veneer_ARM_B_BL_StaticAtom : public VeneerAtom {
+public:
+  Veneer_ARM_B_BL_StaticAtom(const File &f, StringRef secName)
+      : VeneerAtom(f, secName) {}
+
+  ArrayRef<uint8_t> rawContent() const override {
+    return llvm::makeArrayRef(Veneer_ARM_B_BL_StaticAtomContent);
+  }
+};
+
+/// \brief Atoms that hold veneer for statically relocated
+/// Thumb B/BL instructions.
+class Veneer_THM_B_BL_StaticAtom : public VeneerAtom {
+public:
+  Veneer_THM_B_BL_StaticAtom(const File &f, StringRef secName)
+      : VeneerAtom(f, secName) {}
+
+  DefinedAtom::CodeModel codeModel() const override {
+    return DefinedAtom::codeARMThumb;
+  }
+
+  ArrayRef<uint8_t> rawContent() const override {
+    return llvm::makeArrayRef(Veneer_THM_B_BL_StaticAtomContent);
+  }
+};
+
+/// \brief Atoms that are used by ARM dynamic linking
+class ARMGOTAtom : public GOTAtom {
+public:
+  ARMGOTAtom(const File &f, StringRef secName) : GOTAtom(f, secName) {}
+
+  ArrayRef<uint8_t> rawContent() const override {
+    return llvm::makeArrayRef(ARMGotAtomContent);
+  }
+
+  Alignment alignment() const override { return Alignment(2); }
+};
+
+class ELFPassFile : public SimpleFile {
+public:
+  ELFPassFile(const ELFLinkingContext &eti) : SimpleFile("ELFPassFile") {
+    setOrdinal(eti.getNextOrdinalAndIncrement());
+  }
+
+  llvm::BumpPtrAllocator _alloc;
+};
+
+/// \brief CRTP base for handling relocations.
+template <class Derived> class ARMRelocationPass : public Pass {
+  /// \brief Handle a specific reference.
+  void handleReference(const DefinedAtom &atom, const Reference &ref) {
+    DEBUG_WITH_TYPE(
+        "ARM", llvm::dbgs() << "\t" << LLVM_FUNCTION_NAME << "()"
+            << ":   Name of Defined Atom: " << atom.name().str();
+        llvm::dbgs() << "   kindValue: " << ref.kindValue() << "\n");
+    if (ref.kindNamespace() != Reference::KindNamespace::ELF)
+      return;
+    assert(ref.kindArch() == Reference::KindArch::ARM);
+    switch (ref.kindValue()) {
+    case R_ARM_JUMP24:
+    case R_ARM_THM_JUMP24:
+      static_cast<Derived *>(this)->handleVeneer(atom, ref);
+      break;
+    case R_ARM_TLS_IE32:
+      static_cast<Derived *>(this)->handleTLSIE32(ref);
+      break;
+    }
+  }
+
+protected:
+  std::error_code handleVeneer(const DefinedAtom &atom, const Reference &ref) {
+    // Target symbol and relocated place should have different
+    // instruction sets in order a veneer to be generated in between.
+    const auto *target = dyn_cast<DefinedAtom>(ref.target());
+    if (!target || target->codeModel() == atom.codeModel())
+      return std::error_code();
+
+    // TODO: For unconditional jump instructions (R_ARM_CALL and R_ARM_THM_CALL)
+    // fixup isn't possible without veneer generation for archs below ARMv5.
+
+    // Veneers may only be generated for STT_FUNC target symbols
+    // or for symbols located in sections different to the place of relocation.
+    const auto kindValue = ref.kindValue();
+    StringRef secName = atom.customSectionName();
+    if (DefinedAtom::typeCode != target->contentType() &&
+        !target->customSectionName().equals(secName)) {
+      StringRef kindValStr;
+      if (!this->_ctx.registry().referenceKindToString(
+              ref.kindNamespace(), ref.kindArch(), kindValue, kindValStr)) {
+        kindValStr = "unknown";
+      }
+
+      std::string errStr =
+          (Twine("Reference of type ") + Twine(kindValue) + " (" + kindValStr +
+           ") from " + atom.name() + "+" + Twine(ref.offsetInAtom()) + " to " +
+           ref.target()->name() + "+" + Twine(ref.addend()) +
+           " cannot be effected without a veneer").str();
+
+      llvm_unreachable(errStr.c_str());
+    }
+
+    const Atom *veneer = nullptr;
+    switch (kindValue) {
+    case R_ARM_JUMP24:
+      veneer = static_cast<Derived *>(this)
+                   ->getVeneer_ARM_B_BL(target, secName);
+      break;
+    case R_ARM_THM_JUMP24:
+      veneer = static_cast<Derived *>(this)
+                   ->getVeneer_THM_B_BL(target, secName);
+      break;
+    default:
+      llvm_unreachable("Unhandled reference type for veneer generation");
+    }
+
+    assert(veneer && "The veneer is not set");
+    const_cast<Reference &>(ref).setTarget(veneer);
+    return std::error_code();
+  }
+
+  std::error_code handleTLSIE32(const Reference &ref) {
+    if (const auto *target = dyn_cast<DefinedAtom>(ref.target())) {
+      const_cast<Reference &>(ref).setTarget(
+          static_cast<Derived *>(this)->getTLSTPOFF32(target));
+      return std::error_code();
+    }
+    llvm_unreachable("R_ARM_TLS_IE32 reloc targets wrong atom type");
+  }
+
+  /// \brief Create a GOT entry for TLS with reloc type and addend specified.
+  template <Reference::KindValue R_ARM_TLS, Reference::Addend A = 0>
+  const GOTAtom *getGOTTLSEntry(const DefinedAtom *da) {
+    auto got = _gotMap.find(da);
+    if (got != _gotMap.end())
+      return got->second;
+    auto g = new (_file._alloc) ARMGOTAtom(_file, ".got");
+    g->addReferenceELF_ARM(R_ARM_TLS, 0, da, A);
+#ifndef NDEBUG
+    g->_name = "__got_tls_";
+    g->_name += da->name();
+#endif
+    _gotMap[da] = g;
+    _gotVector.push_back(g);
+    return g;
+  }
+
+public:
+  ARMRelocationPass(const ELFLinkingContext &ctx) : _file(ctx), _ctx(ctx) {}
+
+  /// \brief Do the pass.
+  ///
+  /// The goal here is to first process each reference individually. Each call
+  /// to handleReference may modify the reference itself and/or create new
+  /// atoms which must be stored in one of the maps below.
+  ///
+  /// After all references are handled, the atoms created during that are all
+  /// added to mf.
+  void perform(std::unique_ptr<MutableFile> &mf) override {
+    ScopedTask task(getDefaultDomain(), "ARM GOT/PLT Pass");
+    DEBUG_WITH_TYPE(
+        "ARM", llvm::dbgs() << "Undefined Atoms" << "\n";
+        for (const auto &atom
+             : mf->undefined()) {
+          llvm::dbgs() << " Name of Atom: " << atom->name().str() << "\n";
+        }
+
+        llvm::dbgs() << "Shared Library Atoms" << "\n";
+        for (const auto &atom
+             : mf->sharedLibrary()) {
+          llvm::dbgs() << " Name of Atom: " << atom->name().str() << "\n";
+        }
+
+        llvm::dbgs() << "Absolute Atoms" << "\n";
+        for (const auto &atom
+             : mf->absolute()) {
+          llvm::dbgs() << " Name of Atom: " << atom->name().str() << "\n";
+        }
+
+        llvm::dbgs() << "Defined Atoms" << "\n";
+        for (const auto &atom
+             : mf->defined()) {
+          llvm::dbgs() << " Name of Atom: " << atom->name().str() << "\n";
+        });
+
+    // Process all references.
+    for (const auto &atom : mf->defined()) {
+      for (const auto &ref : *atom) {
+        handleReference(*atom, *ref);
+      }
+    }
+
+    // Add all created atoms to the link.
+    uint64_t ordinal = 0;
+    for (auto &got : _gotVector) {
+      got->setOrdinal(ordinal++);
+      mf->addAtom(*got);
+    }
+    for (auto &veneer : _veneerVector) {
+      veneer->setOrdinal(ordinal++);
+      mf->addAtom(*veneer);
+    }
+  }
+
+protected:
+  /// \brief Owner of all the Atoms created by this pass.
+  ELFPassFile _file;
+  const ELFLinkingContext &_ctx;
+
+  /// \brief Map Atoms to their GOT entries.
+  llvm::DenseMap<const Atom *, GOTAtom *> _gotMap;
+
+  /// \brief Map Atoms to their veneers.
+  llvm::DenseMap<const Atom *, VeneerAtom *> _veneerMap;
+
+  /// \brief the list of GOT/PLT atoms
+  std::vector<GOTAtom *> _gotVector;
+
+  /// \brief the list of veneer atoms.
+  std::vector<VeneerAtom *> _veneerVector;
+};
+
+/// This implements the static relocation model. Meaning GOT and PLT entries are
+/// not created for references that can be directly resolved. These are
+/// converted to a direct relocation. For entries that do require a GOT or PLT
+/// entry, that entry is statically bound.
+///
+/// TLS always assumes module 1 and attempts to remove indirection.
+class ARMStaticRelocationPass final
+    : public ARMRelocationPass<ARMStaticRelocationPass> {
+public:
+  ARMStaticRelocationPass(const elf::ARMLinkingContext &ctx)
+      : ARMRelocationPass(ctx) {}
+
+  /// \brief Get the veneer for ARM B/BL instructions.
+  const VeneerAtom *getVeneer_ARM_B_BL(const DefinedAtom *da,
+                                       StringRef secName) {
+    auto veneer = _veneerMap.find(da);
+    if (_veneerMap.end() != veneer)
+      return veneer->second;
+
+    auto v = new (_file._alloc) Veneer_ARM_B_BL_StaticAtom(_file, secName);
+    v->addReferenceELF_ARM(R_ARM_ABS32, 4, da, 0);
+
+    v->_name = "__";
+    v->_name += da->name();
+    v->_name += "_from_arm";
+
+    _veneerMap[da] = v;
+    _veneerVector.push_back(v);
+    return v;
+  }
+
+  /// \brief Get the veneer for Thumb B/BL instructions.
+  const VeneerAtom *getVeneer_THM_B_BL(const DefinedAtom *da,
+                                       StringRef secName) {
+    auto veneer = _veneerMap.find(da);
+    if (_veneerMap.end() != veneer)
+      return veneer->second;
+
+    auto v = new (_file._alloc) Veneer_THM_B_BL_StaticAtom(_file, secName);
+    v->addReferenceELF_ARM(R_ARM_JUMP24, 4, da, 0);
+
+    v->_name = "__";
+    v->_name += da->name();
+    v->_name += "_from_thumb";
+
+    _veneerMap[da] = v;
+    _veneerVector.push_back(v);
+    return v;
+  }
+
+  /// \brief Create a GOT entry for R_ARM_TLS_TPOFF32 reloc.
+  const GOTAtom *getTLSTPOFF32(const DefinedAtom *da) {
+    return getGOTTLSEntry<R_ARM_TLS_LE32>(da);
+  }
+};
+
+} // end of anon namespace
+
+std::unique_ptr<Pass>
+lld::elf::createARMRelocationPass(const ARMLinkingContext &ctx) {
+  switch (ctx.getOutputELFType()) {
+  case llvm::ELF::ET_EXEC:
+    if (ctx.isDynamic())
+      llvm_unreachable("Unhandled output file type");
+    return llvm::make_unique<ARMStaticRelocationPass>(ctx);
+  default:
+    llvm_unreachable("Unhandled output file type");
+  }
+}