llvm-project/lld/lib/ReaderWriter/ELF/Mips/MipsRelocationPass.cpp

568 lines
16 KiB
C++

//===- lib/ReaderWriter/ELF/Mips/MipsRelocationPass.cpp -------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "MipsLinkingContext.h"
#include "MipsRelocationPass.h"
#include "Atoms.h"
#include "MipsELFFile.h"
using namespace lld;
using namespace lld::elf;
using namespace llvm::ELF;
// Lazy resolver
static const uint8_t mipsGot0AtomContent[] = { 0x00, 0x00, 0x00, 0x00 };
// Module pointer
static const uint8_t mipsGotModulePointerAtomContent[] = { 0x00, 0x00, 0x00, 0x80 };
// PLT0 entry
static const uint8_t mipsPlt0AtomContent[] = {
0x00, 0x00, 0x1c, 0x3c, // lui $28, %hi(&GOTPLT[0])
0x00, 0x00, 0x99, 0x8f, // lw $25, %lo(&GOTPLT[0])($28)
0x00, 0x00, 0x9c, 0x27, // addiu $28, $28, %lo(&GOTPLT[0])
0x23, 0xc0, 0x1c, 0x03, // subu $24, $24, $28
0x21, 0x78, 0xe0, 0x03, // move $15, $31
0x82, 0xc0, 0x18, 0x00, // srl $24, $24, 2
0x09, 0xf8, 0x20, 0x03, // jalr $25
0xfe, 0xff, 0x18, 0x27 // subu $24, $24, 2
};
// Regular PLT entry
static const uint8_t mipsPltAAtomContent[] = {
0x00, 0x00, 0x0f, 0x3c, // lui $15, %hi(.got.plt entry)
0x00, 0x00, 0xf9, 0x8d, // l[wd] $25, %lo(.got.plt entry)($15)
0x08, 0x00, 0x20, 0x03, // jr $25
0x00, 0x00, 0xf8, 0x25 // addiu $24, $15, %lo(.got.plt entry)
};
// LA25 stub entry
static const uint8_t mipsLA25AtomContent[] = {
0x00, 0x00, 0x19, 0x3c, // lui $25, %hi(func)
0x00, 0x00, 0x00, 0x08, // j func
0x00, 0x00, 0x39, 0x27, // addiu $25, $25, %lo(func)
0x00, 0x00, 0x00, 0x00 // nop
};
namespace {
/// \brief Abstract base class represent MIPS GOT entries.
class MipsGOTAtom : public GOTAtom {
public:
MipsGOTAtom(const File &f) : GOTAtom(f, ".got") {}
Alignment alignment() const override { return Alignment(2); }
};
/// \brief MIPS GOT entry initialized by zero.
class GOT0Atom : public MipsGOTAtom {
public:
GOT0Atom(const File &f) : MipsGOTAtom(f) {}
ArrayRef<uint8_t> rawContent() const override {
return llvm::makeArrayRef(mipsGot0AtomContent);
}
};
/// \brief MIPS GOT entry initialized by zero.
class GOTModulePointerAtom : public MipsGOTAtom {
public:
GOTModulePointerAtom(const File &f) : MipsGOTAtom(f) {}
ArrayRef<uint8_t> rawContent() const override {
return llvm::makeArrayRef(mipsGotModulePointerAtomContent);
}
};
class PLT0Atom : public PLTAtom {
public:
PLT0Atom(const File &f) : PLTAtom(f, ".plt") {}
ArrayRef<uint8_t> rawContent() const override {
return llvm::makeArrayRef(mipsPlt0AtomContent);
}
};
class PLTAAtom : public PLTAtom {
public:
PLTAAtom(const File &f) : PLTAtom(f, ".plt") {}
ArrayRef<uint8_t> rawContent() const override {
return llvm::makeArrayRef(mipsPltAAtomContent);
}
};
/// \brief MIPS GOT PLT entry
class GOTPLTAtom : public GOTAtom {
public:
GOTPLTAtom(const File &f) : GOTAtom(f, ".got.plt") {}
Alignment alignment() const override { return Alignment(2); }
ArrayRef<uint8_t> rawContent() const override {
return llvm::makeArrayRef(mipsGot0AtomContent);
}
};
/// \brief LA25 stub atom
class LA25Atom : public PLTAtom {
public:
LA25Atom(const File &f) : PLTAtom(f, ".text") {}
ArrayRef<uint8_t> rawContent() const override {
return llvm::makeArrayRef(mipsLA25AtomContent);
}
};
class RelocationPassFile : public SimpleFile {
public:
RelocationPassFile(const ELFLinkingContext &ctx)
: SimpleFile("RelocationPassFile") {
setOrdinal(ctx.getNextOrdinalAndIncrement());
}
llvm::BumpPtrAllocator _alloc;
};
template <typename ELFT> class RelocationPass : public Pass {
public:
RelocationPass(MipsLinkingContext &context);
void perform(std::unique_ptr<MutableFile> &mf) override;
private:
/// \brief Reference to the linking context.
const MipsLinkingContext &_context;
/// \brief Owner of all the Atoms created by this pass.
RelocationPassFile _file;
/// \brief Map Atoms and addend to local GOT entries.
typedef std::pair<const Atom *, int64_t> LocalGotMapKeyT;
llvm::DenseMap<LocalGotMapKeyT, GOTAtom *> _gotLocalMap;
/// \brief Map Atoms to global GOT entries.
llvm::DenseMap<const Atom *, GOTAtom *> _gotGlobalMap;
/// \brief the list of local GOT atoms.
std::vector<GOTAtom *> _localGotVector;
/// \brief the list of global GOT atoms.
std::vector<GOTAtom *> _globalGotVector;
/// \brief Map Atoms to their PLT entries.
llvm::DenseMap<const Atom *, PLTAtom *> _pltMap;
/// \brief Map Atoms to their Object entries.
llvm::DenseMap<const Atom *, ObjectAtom *> _objectMap;
/// \brief Map Atoms to their LA25 entries.
llvm::DenseMap<const Atom *, LA25Atom *> _la25Map;
/// \brief the list of PLT atoms.
std::vector<PLTAtom *> _pltVector;
/// \brief the list of GOTPLT atoms.
std::vector<GOTAtom *> _gotpltVector;
/// \brief the list of Object entries.
std::vector<ObjectAtom *> _objectVector;
/// \brief the list of LA25 entries.
std::vector<LA25Atom *> _la25Vector;
/// \brief Handle a specific reference.
void handleReference(Reference &ref);
/// \brief Calculate AHL addendums for the atom's references.
void calculateAHLs(const DefinedAtom &atom);
void handlePlain(Reference &ref);
void handlePLT(Reference &ref);
void handleGOT(Reference &ref);
const GOTAtom *getLocalGOTEntry(const Reference &ref);
const GOTAtom *getGlobalGOTEntry(const Atom *a);
const PLTAtom *getPLTEntry(const Atom *a);
const LA25Atom *getLA25Entry(const Atom *a);
const ObjectAtom *getObjectEntry(const SharedLibraryAtom *a);
bool isLocal(const Atom *a) const;
bool requireLocalGOT(const Atom *a);
bool requireLA25Stub(const Atom *a);
void createPLTHeader();
};
template <typename ELFT>
RelocationPass<ELFT>::RelocationPass(MipsLinkingContext &context)
: _context(context), _file(context) {
_localGotVector.push_back(new (_file._alloc) GOT0Atom(_file));
_localGotVector.push_back(new (_file._alloc) GOTModulePointerAtom(_file));
}
template <typename ELFT>
void RelocationPass<ELFT>::perform(std::unique_ptr<MutableFile> &mf) {
// Process all references.
for (const auto &atom : mf->defined()) {
calculateAHLs(*atom);
for (const auto &ref : *atom)
handleReference(const_cast<Reference &>(*ref));
}
uint64_t ordinal = 0;
for (auto &got : _localGotVector) {
DEBUG_WITH_TYPE("MipsGOT", llvm::dbgs() << "[ GOT ] Adding L "
<< got->name() << "\n");
got->setOrdinal(ordinal++);
mf->addAtom(*got);
}
for (auto &got : _globalGotVector) {
DEBUG_WITH_TYPE("MipsGOT", llvm::dbgs() << "[ GOT ] Adding G "
<< got->name() << "\n");
got->setOrdinal(ordinal++);
mf->addAtom(*got);
}
for (auto &plt : _pltVector) {
DEBUG_WITH_TYPE("MipsGOT", llvm::dbgs() << "[ PLT ] Adding " << plt->name()
<< "\n");
plt->setOrdinal(ordinal++);
mf->addAtom(*plt);
}
for (auto &gotplt : _gotpltVector) {
DEBUG_WITH_TYPE("MipsGOT", llvm::dbgs() << "[ GOTPLT ] Adding "
<< gotplt->name() << "\n");
gotplt->setOrdinal(ordinal++);
mf->addAtom(*gotplt);
}
for (auto obj : _objectVector) {
obj->setOrdinal(ordinal++);
mf->addAtom(*obj);
}
for (auto la25 : _la25Vector) {
la25->setOrdinal(ordinal++);
mf->addAtom(*la25);
}
}
/// \brief Calculate AHL value combines addends from 'hi' and 'lo' relocations.
inline int64_t calcAHL(int64_t AHI, int64_t ALO) {
AHI &= 0xffff;
ALO &= 0xffff;
return (AHI << 16) + (int16_t)ALO;
}
template <typename ELFT>
void RelocationPass<ELFT>::calculateAHLs(const DefinedAtom &atom) {
std::vector<const Reference *> lo16Refs;
std::vector<Reference *> hi16Refs;
for (const auto &ref : atom) {
if (ref->kindNamespace() != lld::Reference::KindNamespace::ELF)
continue;
assert(ref->kindArch() == Reference::KindArch::Mips);
switch (ref->kindValue()) {
case R_MIPS_HI16:
hi16Refs.push_back(const_cast<Reference *>(ref));
case R_MIPS_LO16:
lo16Refs.push_back(ref);
break;
case R_MIPS_GOT16:
if (isLocal(ref->target()))
hi16Refs.push_back(const_cast<Reference *>(ref));
break;
}
}
std::sort(lo16Refs.begin(), lo16Refs.end(),
[](const Reference *a, const Reference *b) {
return a->offsetInAtom() < b->offsetInAtom();
});
std::sort(hi16Refs.begin(), hi16Refs.end(),
[](const Reference *a, const Reference *b) {
return a->offsetInAtom() < b->offsetInAtom();
});
// Iterate over R_MIPS_LO16 relocations sorted by theirs offsets in the atom.
// Calculate AHL addend for each R_MIPS_HI16 amd R_MIPS_GOT16 relocation
// precedes the current R_MIPS_LO16 one.
auto hic = hi16Refs.begin();
for (const auto &lo : lo16Refs) {
for (; hic != hi16Refs.end(); ++hic) {
if ((*hic)->offsetInAtom() > lo->offsetInAtom())
break;
(*hic)->setAddend(calcAHL((*hic)->addend(), lo->addend()));
}
}
assert(hic == hi16Refs.end());
}
template <typename ELFT>
void RelocationPass<ELFT>::handleReference(Reference &ref) {
if (ref.kindNamespace() != lld::Reference::KindNamespace::ELF)
return;
assert(ref.kindArch() == Reference::KindArch::Mips);
switch (ref.kindValue()) {
case R_MIPS_32:
case R_MIPS_HI16:
case R_MIPS_LO16:
// FIXME (simon): Handle dynamic/static linking differently.
handlePlain(ref);
break;
case R_MIPS_26:
handlePLT(ref);
break;
case R_MIPS_GOT16:
case R_MIPS_CALL16:
handleGOT(ref);
break;
}
}
template <typename ELFT>
bool RelocationPass<ELFT>::isLocal(const Atom *a) const {
if (auto *da = dyn_cast<DefinedAtom>(a))
return da->scope() == Atom::scopeTranslationUnit;
return false;
}
template <typename ELFT>
void RelocationPass<ELFT>::handlePlain(Reference &ref) {
if (!ref.target())
return;
auto sla = dyn_cast<SharedLibraryAtom>(ref.target());
if (sla && sla->type() == SharedLibraryAtom::Type::Data)
ref.setTarget(getObjectEntry(sla));
}
template <typename ELFT> void RelocationPass<ELFT>::handlePLT(Reference &ref) {
if (ref.kindValue() == R_MIPS_26 && !isLocal(ref.target())) {
ref.setKindValue(LLD_R_MIPS_GLOBAL_26);
if (requireLA25Stub(ref.target()))
const_cast<Reference &>(ref).setTarget(getLA25Entry(ref.target()));
}
if (isa<SharedLibraryAtom>(ref.target()))
ref.setTarget(getPLTEntry(ref.target()));
}
template <typename ELFT> void RelocationPass<ELFT>::handleGOT(Reference &ref) {
if (requireLocalGOT(ref.target()))
ref.setTarget(getLocalGOTEntry(ref));
else
ref.setTarget(getGlobalGOTEntry(ref.target()));
}
template <typename ELFT>
bool RelocationPass<ELFT>::requireLocalGOT(const Atom *a) {
Atom::Scope scope;
if (auto *da = dyn_cast<DefinedAtom>(a))
scope = da->scope();
else if (auto *aa = dyn_cast<AbsoluteAtom>(a))
scope = aa->scope();
else
return false;
// Local and hidden symbols must be local.
if (scope == Atom::scopeTranslationUnit || scope == Atom::scopeLinkageUnit)
return true;
// External symbol defined in an executable file requires a local GOT entry.
if (_context.getOutputELFType() == llvm::ELF::ET_EXEC)
return true;
return false;
}
template <typename ELFT>
bool RelocationPass<ELFT>::requireLA25Stub(const Atom *a) {
if (auto *da = dyn_cast<DefinedAtom>(a))
return static_cast<const MipsELFDefinedAtom<ELFT> *>(da)->file().isPIC();
return false;
}
template <typename ELFT>
const GOTAtom *RelocationPass<ELFT>::getLocalGOTEntry(const Reference &ref) {
const Atom *a = ref.target();
LocalGotMapKeyT key(a, ref.addend());
auto got = _gotLocalMap.find(key);
if (got != _gotLocalMap.end())
return got->second;
auto ga = new (_file._alloc) GOT0Atom(_file);
_gotLocalMap[key] = ga;
_localGotVector.push_back(ga);
if (isLocal(a))
ga->addReferenceELF_Mips(LLD_R_MIPS_32_HI16, 0, a, ref.addend());
else
ga->addReferenceELF_Mips(R_MIPS_32, 0, a, 0);
DEBUG_WITH_TYPE("MipsGOT", {
ga->_name = "__got_";
ga->_name += a->name();
llvm::dbgs() << "[ GOT ] Create L " << a->name() << "\n";
});
return ga;
}
template <typename ELFT>
const GOTAtom *RelocationPass<ELFT>::getGlobalGOTEntry(const Atom *a) {
auto got = _gotGlobalMap.find(a);
if (got != _gotGlobalMap.end())
return got->second;
auto ga = new (_file._alloc) GOT0Atom(_file);
_gotGlobalMap[a] = ga;
_globalGotVector.push_back(ga);
ga->addReferenceELF_Mips(LLD_R_MIPS_GLOBAL_GOT, 0, a, 0);
if (const DefinedAtom *da = dyn_cast<DefinedAtom>(a))
ga->addReferenceELF_Mips(R_MIPS_32, 0, da, 0);
DEBUG_WITH_TYPE("MipsGOT", {
ga->_name = "__got_";
ga->_name += a->name();
llvm::dbgs() << "[ GOT ] Create G " << a->name() << "\n";
});
return ga;
}
template <typename ELFT> void RelocationPass<ELFT>::createPLTHeader() {
assert(_pltVector.empty() && _gotpltVector.empty());
auto pa = new (_file._alloc) PLT0Atom(_file);
_pltVector.push_back(pa);
auto ga0 = new (_file._alloc) GOTPLTAtom(_file);
_gotpltVector.push_back(ga0);
auto ga1 = new (_file._alloc) GOTPLTAtom(_file);
_gotpltVector.push_back(ga1);
// Setup reference to fixup the PLT0 entry.
pa->addReferenceELF_Mips(LLD_R_MIPS_HI16, 0, ga0, 0);
pa->addReferenceELF_Mips(LLD_R_MIPS_LO16, 4, ga0, 0);
pa->addReferenceELF_Mips(LLD_R_MIPS_LO16, 8, ga0, 0);
DEBUG_WITH_TYPE("MipsGOT", {
pa->_name = "__plt0";
llvm::dbgs() << "[ PLT ] Create PLT0\n";
ga0->_name = "__gotplt0";
llvm::dbgs() << "[ GOTPLT ] Create GOTPLT0\n";
ga1->_name = "__gotplt1";
llvm::dbgs() << "[ GOTPLT ] Create GOTPLT1\n";
});
}
template <typename ELFT>
const PLTAtom *RelocationPass<ELFT>::getPLTEntry(const Atom *a) {
auto plt = _pltMap.find(a);
if (plt != _pltMap.end())
return plt->second;
if (_pltVector.empty())
createPLTHeader();
auto pa = new (_file._alloc) PLTAAtom(_file);
_pltMap[a] = pa;
_pltVector.push_back(pa);
auto ga = new (_file._alloc) GOTPLTAtom(_file);
_gotpltVector.push_back(ga);
// Setup reference to fixup the PLT entry.
pa->addReferenceELF_Mips(LLD_R_MIPS_HI16, 0, ga, 0);
pa->addReferenceELF_Mips(LLD_R_MIPS_LO16, 4, ga, 0);
pa->addReferenceELF_Mips(LLD_R_MIPS_LO16, 12, ga, 0);
// Setup reference to assign initial value to the .got.plt entry.
ga->addReferenceELF_Mips(R_MIPS_32, 0, _pltVector.front(), 0);
// Create dynamic relocation to adjust the .got.plt entry at runtime.
ga->addReferenceELF_Mips(R_MIPS_JUMP_SLOT, 0, a, 0);
DEBUG_WITH_TYPE("MipsGOT", {
pa->_name = "__plt_";
pa->_name += a->name();
llvm::dbgs() << "[ PLT ] Create " << a->name() << "\n";
ga->_name = "__got_plt_";
ga->_name += a->name();
llvm::dbgs() << "[ GOTPLT ] Create " << a->name() << "\n";
});
return pa;
}
template <typename ELFT>
const LA25Atom *RelocationPass<ELFT>::getLA25Entry(const Atom *a) {
auto la25 = _la25Map.find(a);
if (la25 != _la25Map.end())
return la25->second;
auto sa = new (_file._alloc) LA25Atom(_file);
_la25Map[a] = sa;
_la25Vector.push_back(sa);
// Setup reference to fixup the LA25 stub entry.
sa->addReferenceELF_Mips(R_MIPS_HI16, 0, a, 0);
sa->addReferenceELF_Mips(R_MIPS_26, 4, a, 0);
sa->addReferenceELF_Mips(R_MIPS_LO16, 8, a, 0);
DEBUG_WITH_TYPE("MipsGOT", {
sa->_name = ".pic.";
sa->_name += a->name();
});
return sa;
}
template <typename ELFT>
const ObjectAtom *
RelocationPass<ELFT>::getObjectEntry(const SharedLibraryAtom *a) {
auto obj = _objectMap.find(a);
if (obj != _objectMap.end())
return obj->second;
auto oa = new (_file._alloc) ObjectAtom(_file);
oa->addReferenceELF_Mips(R_MIPS_COPY, 0, oa, 0);
oa->_name = a->name();
oa->_size = a->size();
_objectMap[a] = oa;
_objectVector.push_back(oa);
return oa;
}
} // end anon namespace
std::unique_ptr<Pass>
lld::elf::createMipsRelocationPass(MipsLinkingContext &ctx) {
switch (ctx.getOutputELFType()) {
case llvm::ELF::ET_EXEC:
case llvm::ELF::ET_DYN:
return std::unique_ptr<Pass>(new RelocationPass<Mips32ElELFType>(ctx));
case llvm::ELF::ET_REL:
return std::unique_ptr<Pass>();
default:
llvm_unreachable("Unhandled output file type");
}
}