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llvm-project/llvm/lib/ExecutionEngine/JITLink/MachO_x86_64.cpp

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//===---- MachO_x86_64.cpp -JIT linker implementation for MachO/x86-64 ----===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// MachO/x86-64 jit-link implementation.
//
//===----------------------------------------------------------------------===//
#include "llvm/ExecutionEngine/JITLink/MachO_x86_64.h"
#include "BasicGOTAndStubsBuilder.h"
#include "MachOAtomGraphBuilder.h"
#define DEBUG_TYPE "jitlink"
using namespace llvm;
using namespace llvm::jitlink;
using namespace llvm::jitlink::MachO_x86_64_Edges;
namespace {
class MachOAtomGraphBuilder_x86_64 : public MachOAtomGraphBuilder {
public:
MachOAtomGraphBuilder_x86_64(const object::MachOObjectFile &Obj)
: MachOAtomGraphBuilder(Obj),
NumSymbols(Obj.getSymtabLoadCommand().nsyms) {
addCustomAtomizer("__eh_frame", [this](MachOSection &EHFrameSection) {
return addEHFrame(getGraph(), EHFrameSection.getGenericSection(),
EHFrameSection.getContent(),
EHFrameSection.getAddress(), NegDelta32, Delta64);
});
}
private:
static Expected<MachOX86RelocationKind>
getRelocationKind(const MachO::relocation_info &RI) {
switch (RI.r_type) {
case MachO::X86_64_RELOC_UNSIGNED:
if (!RI.r_pcrel && RI.r_length == 3)
return RI.r_extern ? Pointer64 : Pointer64Anon;
break;
case MachO::X86_64_RELOC_SIGNED:
if (RI.r_pcrel && RI.r_length == 2)
return RI.r_extern ? PCRel32 : PCRel32Anon;
break;
case MachO::X86_64_RELOC_BRANCH:
if (RI.r_pcrel && RI.r_extern && RI.r_length == 2)
return Branch32;
break;
case MachO::X86_64_RELOC_GOT_LOAD:
if (RI.r_pcrel && RI.r_extern && RI.r_length == 2)
return PCRel32GOTLoad;
break;
case MachO::X86_64_RELOC_GOT:
if (RI.r_pcrel && RI.r_extern && RI.r_length == 2)
return PCRel32GOT;
break;
case MachO::X86_64_RELOC_SUBTRACTOR:
// SUBTRACTOR must be non-pc-rel, extern, with length 2 or 3.
// Initially represent SUBTRACTOR relocations with 'Delta<W>'. They may
// be turned into NegDelta<W> by parsePairRelocation.
if (!RI.r_pcrel && RI.r_extern) {
if (RI.r_length == 2)
return Delta32;
else if (RI.r_length == 3)
return Delta64;
}
break;
case MachO::X86_64_RELOC_SIGNED_1:
if (RI.r_pcrel && RI.r_length == 2)
return RI.r_extern ? PCRel32Minus1 : PCRel32Minus1Anon;
break;
case MachO::X86_64_RELOC_SIGNED_2:
if (RI.r_pcrel && RI.r_length == 2)
return RI.r_extern ? PCRel32Minus2 : PCRel32Minus2Anon;
break;
case MachO::X86_64_RELOC_SIGNED_4:
if (RI.r_pcrel && RI.r_length == 2)
return RI.r_extern ? PCRel32Minus4 : PCRel32Minus4Anon;
break;
case MachO::X86_64_RELOC_TLV:
if (RI.r_pcrel && RI.r_extern && RI.r_length == 2)
return PCRel32TLV;
break;
}
return make_error<JITLinkError>(
"Unsupported x86-64 relocation: address=" +
formatv("{0:x8}", RI.r_address) +
", symbolnum=" + formatv("{0:x6}", RI.r_symbolnum) +
", kind=" + formatv("{0:x1}", RI.r_type) +
", pc_rel=" + (RI.r_pcrel ? "true" : "false") +
", extern= " + (RI.r_extern ? "true" : "false") +
", length=" + formatv("{0:d}", RI.r_length));
}
Expected<Atom &> findAtomBySymbolIndex(const MachO::relocation_info &RI) {
auto &Obj = getObject();
if (RI.r_symbolnum >= NumSymbols)
return make_error<JITLinkError>("Symbol index out of range");
auto SymI = Obj.getSymbolByIndex(RI.r_symbolnum);
auto Name = SymI->getName();
if (!Name)
return Name.takeError();
return getGraph().getAtomByName(*Name);
}
MachO::relocation_info
getRelocationInfo(const object::relocation_iterator RelItr) {
MachO::any_relocation_info ARI =
getObject().getRelocation(RelItr->getRawDataRefImpl());
MachO::relocation_info RI;
memcpy(&RI, &ARI, sizeof(MachO::relocation_info));
return RI;
}
using PairRelocInfo = std::tuple<MachOX86RelocationKind, Atom *, uint64_t>;
// Parses paired SUBTRACTOR/UNSIGNED relocations and, on success,
// returns the edge kind and addend to be used.
Expected<PairRelocInfo>
parsePairRelocation(DefinedAtom &AtomToFix, Edge::Kind SubtractorKind,
const MachO::relocation_info &SubRI,
JITTargetAddress FixupAddress, const char *FixupContent,
object::relocation_iterator &UnsignedRelItr,
object::relocation_iterator &RelEnd) {
using namespace support;
assert(((SubtractorKind == Delta32 && SubRI.r_length == 2) ||
(SubtractorKind == Delta64 && SubRI.r_length == 3)) &&
"Subtractor kind should match length");
assert(SubRI.r_extern && "SUBTRACTOR reloc symbol should be extern");
assert(!SubRI.r_pcrel && "SUBTRACTOR reloc should not be PCRel");
if (UnsignedRelItr == RelEnd)
return make_error<JITLinkError>("x86_64 SUBTRACTOR without paired "
"UNSIGNED relocation");
auto UnsignedRI = getRelocationInfo(UnsignedRelItr);
if (SubRI.r_address != UnsignedRI.r_address)
return make_error<JITLinkError>("x86_64 SUBTRACTOR and paired UNSIGNED "
"point to different addresses");
if (SubRI.r_length != UnsignedRI.r_length)
return make_error<JITLinkError>("length of x86_64 SUBTRACTOR and paired "
"UNSIGNED reloc must match");
auto FromAtom = findAtomBySymbolIndex(SubRI);
if (!FromAtom)
return FromAtom.takeError();
// Read the current fixup value.
uint64_t FixupValue = 0;
if (SubRI.r_length == 3)
FixupValue = *(const little64_t *)FixupContent;
else
FixupValue = *(const little32_t *)FixupContent;
// Find 'ToAtom' using symbol number or address, depending on whether the
// paired UNSIGNED relocation is extern.
Atom *ToAtom = nullptr;
if (UnsignedRI.r_extern) {
// Find target atom by symbol index.
if (auto ToAtomOrErr = findAtomBySymbolIndex(UnsignedRI))
ToAtom = &*ToAtomOrErr;
else
return ToAtomOrErr.takeError();
} else {
if (auto ToAtomOrErr = getGraph().findAtomByAddress(FixupValue))
ToAtom = &*ToAtomOrErr;
else
return ToAtomOrErr.takeError();
FixupValue -= ToAtom->getAddress();
}
MachOX86RelocationKind DeltaKind;
Atom *TargetAtom;
uint64_t Addend;
if (areLayoutLocked(AtomToFix, *FromAtom)) {
TargetAtom = ToAtom;
DeltaKind = (SubRI.r_length == 3) ? Delta64 : Delta32;
Addend = FixupValue + (FixupAddress - FromAtom->getAddress());
// FIXME: handle extern 'from'.
} else if (areLayoutLocked(AtomToFix, *ToAtom)) {
TargetAtom = &*FromAtom;
DeltaKind = (SubRI.r_length == 3) ? NegDelta64 : NegDelta32;
Addend = FixupValue - (FixupAddress - ToAtom->getAddress());
} else {
// AtomToFix was neither FromAtom nor ToAtom.
return make_error<JITLinkError>("SUBTRACTOR relocation must fix up "
"either 'A' or 'B' (or an atom in one "
"of their alt-entry groups)");
}
return PairRelocInfo(DeltaKind, TargetAtom, Addend);
}
Error addRelocations() override {
using namespace support;
auto &G = getGraph();
auto &Obj = getObject();
for (auto &S : Obj.sections()) {
JITTargetAddress SectionAddress = S.getAddress();
for (auto RelItr = S.relocation_begin(), RelEnd = S.relocation_end();
RelItr != RelEnd; ++RelItr) {
MachO::relocation_info RI = getRelocationInfo(RelItr);
// Sanity check the relocation kind.
auto Kind = getRelocationKind(RI);
if (!Kind)
return Kind.takeError();
// Find the address of the value to fix up.
JITTargetAddress FixupAddress = SectionAddress + (uint32_t)RI.r_address;
LLVM_DEBUG({
dbgs() << "Processing relocation at "
<< format("0x%016" PRIx64, FixupAddress) << "\n";
});
// Find the atom that the fixup points to.
DefinedAtom *AtomToFix = nullptr;
{
auto AtomToFixOrErr = G.findAtomByAddress(FixupAddress);
if (!AtomToFixOrErr)
return AtomToFixOrErr.takeError();
AtomToFix = &*AtomToFixOrErr;
}
if (FixupAddress + static_cast<JITTargetAddress>(1ULL << RI.r_length) >
AtomToFix->getAddress() + AtomToFix->getContent().size())
return make_error<JITLinkError>(
"Relocation content extends past end of fixup atom");
// Get a pointer to the fixup content.
const char *FixupContent = AtomToFix->getContent().data() +
(FixupAddress - AtomToFix->getAddress());
// The target atom and addend will be populated by the switch below.
Atom *TargetAtom = nullptr;
uint64_t Addend = 0;
switch (*Kind) {
case Branch32:
case PCRel32:
case PCRel32GOTLoad:
case PCRel32GOT:
if (auto TargetAtomOrErr = findAtomBySymbolIndex(RI))
TargetAtom = &*TargetAtomOrErr;
else
return TargetAtomOrErr.takeError();
Addend = *(const ulittle32_t *)FixupContent;
break;
case Pointer64:
if (auto TargetAtomOrErr = findAtomBySymbolIndex(RI))
TargetAtom = &*TargetAtomOrErr;
else
return TargetAtomOrErr.takeError();
Addend = *(const ulittle64_t *)FixupContent;
break;
case Pointer64Anon: {
JITTargetAddress TargetAddress = *(const ulittle64_t *)FixupContent;
if (auto TargetAtomOrErr = G.findAtomByAddress(TargetAddress))
TargetAtom = &*TargetAtomOrErr;
else
return TargetAtomOrErr.takeError();
Addend = TargetAddress - TargetAtom->getAddress();
break;
}
case PCRel32Minus1:
case PCRel32Minus2:
case PCRel32Minus4:
if (auto TargetAtomOrErr = findAtomBySymbolIndex(RI))
TargetAtom = &*TargetAtomOrErr;
else
return TargetAtomOrErr.takeError();
Addend = *(const ulittle32_t *)FixupContent +
(1 << (*Kind - PCRel32Minus1));
break;
case PCRel32Anon: {
JITTargetAddress TargetAddress =
FixupAddress + 4 + *(const ulittle32_t *)FixupContent;
if (auto TargetAtomOrErr = G.findAtomByAddress(TargetAddress))
TargetAtom = &*TargetAtomOrErr;
else
return TargetAtomOrErr.takeError();
Addend = TargetAddress - TargetAtom->getAddress();
break;
}
case PCRel32Minus1Anon:
case PCRel32Minus2Anon:
case PCRel32Minus4Anon: {
JITTargetAddress Delta =
static_cast<JITTargetAddress>(1ULL << (*Kind - PCRel32Minus1Anon));
JITTargetAddress TargetAddress =
FixupAddress + 4 + Delta + *(const ulittle32_t *)FixupContent;
if (auto TargetAtomOrErr = G.findAtomByAddress(TargetAddress))
TargetAtom = &*TargetAtomOrErr;
else
return TargetAtomOrErr.takeError();
Addend = TargetAddress - TargetAtom->getAddress();
break;
}
case Delta32:
case Delta64: {
// We use Delta32/Delta64 to represent SUBTRACTOR relocations.
// parsePairRelocation handles the paired reloc, and returns the
// edge kind to be used (either Delta32/Delta64, or
// NegDelta32/NegDelta64, depending on the direction of the
// subtraction) along with the addend.
auto PairInfo =
parsePairRelocation(*AtomToFix, *Kind, RI, FixupAddress,
FixupContent, ++RelItr, RelEnd);
if (!PairInfo)
return PairInfo.takeError();
std::tie(*Kind, TargetAtom, Addend) = *PairInfo;
assert(TargetAtom && "No target atom from parsePairRelocation?");
break;
}
default:
llvm_unreachable("Special relocation kind should not appear in "
"mach-o file");
}
LLVM_DEBUG({
Edge GE(*Kind, FixupAddress - AtomToFix->getAddress(), *TargetAtom,
Addend);
printEdge(dbgs(), *AtomToFix, GE,
getMachOX86RelocationKindName(*Kind));
dbgs() << "\n";
});
AtomToFix->addEdge(*Kind, FixupAddress - AtomToFix->getAddress(),
*TargetAtom, Addend);
}
}
return Error::success();
}
unsigned NumSymbols = 0;
};
class MachO_x86_64_GOTAndStubsBuilder
: public BasicGOTAndStubsBuilder<MachO_x86_64_GOTAndStubsBuilder> {
public:
MachO_x86_64_GOTAndStubsBuilder(AtomGraph &G)
: BasicGOTAndStubsBuilder<MachO_x86_64_GOTAndStubsBuilder>(G) {}
bool isGOTEdge(Edge &E) const {
return E.getKind() == PCRel32GOT || E.getKind() == PCRel32GOTLoad;
}
DefinedAtom &createGOTEntry(Atom &Target) {
auto &GOTEntryAtom = G.addAnonymousAtom(getGOTSection(), 0x0, 8);
GOTEntryAtom.setContent(
StringRef(reinterpret_cast<const char *>(NullGOTEntryContent), 8));
GOTEntryAtom.addEdge(Pointer64, 0, Target, 0);
return GOTEntryAtom;
}
void fixGOTEdge(Edge &E, Atom &GOTEntry) {
assert((E.getKind() == PCRel32GOT || E.getKind() == PCRel32GOTLoad) &&
"Not a GOT edge?");
E.setKind(PCRel32);
E.setTarget(GOTEntry);
// Leave the edge addend as-is.
}
bool isExternalBranchEdge(Edge &E) {
return E.getKind() == Branch32 && !E.getTarget().isDefined();
}
DefinedAtom &createStub(Atom &Target) {
auto &StubAtom = G.addAnonymousAtom(getStubsSection(), 0x0, 2);
StubAtom.setContent(
StringRef(reinterpret_cast<const char *>(StubContent), 6));
// Re-use GOT entries for stub targets.
auto &GOTEntryAtom = getGOTEntryAtom(Target);
StubAtom.addEdge(PCRel32, 2, GOTEntryAtom, 0);
return StubAtom;
}
void fixExternalBranchEdge(Edge &E, Atom &Stub) {
assert(E.getKind() == Branch32 && "Not a Branch32 edge?");
assert(E.getAddend() == 0 && "Branch32 edge has non-zero addend?");
E.setTarget(Stub);
}
private:
Section &getGOTSection() {
if (!GOTSection)
GOTSection = &G.createSection("$__GOT", 8, sys::Memory::MF_READ, false);
return *GOTSection;
}
Section &getStubsSection() {
if (!StubsSection) {
auto StubsProt = static_cast<sys::Memory::ProtectionFlags>(
sys::Memory::MF_READ | sys::Memory::MF_EXEC);
StubsSection = &G.createSection("$__STUBS", 8, StubsProt, false);
}
return *StubsSection;
}
static const uint8_t NullGOTEntryContent[8];
static const uint8_t StubContent[6];
Section *GOTSection = nullptr;
Section *StubsSection = nullptr;
};
const uint8_t MachO_x86_64_GOTAndStubsBuilder::NullGOTEntryContent[8] = {
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
const uint8_t MachO_x86_64_GOTAndStubsBuilder::StubContent[6] = {
0xFF, 0x25, 0x00, 0x00, 0x00, 0x00};
} // namespace
namespace llvm {
namespace jitlink {
class MachOJITLinker_x86_64 : public JITLinker<MachOJITLinker_x86_64> {
friend class JITLinker<MachOJITLinker_x86_64>;
public:
MachOJITLinker_x86_64(std::unique_ptr<JITLinkContext> Ctx,
PassConfiguration PassConfig)
: JITLinker(std::move(Ctx), std::move(PassConfig)) {}
private:
StringRef getEdgeKindName(Edge::Kind R) const override {
return getMachOX86RelocationKindName(R);
}
Expected<std::unique_ptr<AtomGraph>>
buildGraph(MemoryBufferRef ObjBuffer) override {
auto MachOObj = object::ObjectFile::createMachOObjectFile(ObjBuffer);
if (!MachOObj)
return MachOObj.takeError();
return MachOAtomGraphBuilder_x86_64(**MachOObj).buildGraph();
}
static Error targetOutOfRangeError(const Atom &A, const Edge &E) {
std::string ErrMsg;
{
raw_string_ostream ErrStream(ErrMsg);
ErrStream << "Relocation target out of range: ";
printEdge(ErrStream, A, E, getMachOX86RelocationKindName(E.getKind()));
ErrStream << "\n";
}
return make_error<JITLinkError>(std::move(ErrMsg));
}
Error applyFixup(DefinedAtom &A, const Edge &E, char *AtomWorkingMem) const {
using namespace support;
char *FixupPtr = AtomWorkingMem + E.getOffset();
JITTargetAddress FixupAddress = A.getAddress() + E.getOffset();
switch (E.getKind()) {
case Branch32:
case PCRel32:
case PCRel32Anon: {
int64_t Value =
E.getTarget().getAddress() - (FixupAddress + 4) + E.getAddend();
if (Value < std::numeric_limits<int32_t>::min() ||
Value > std::numeric_limits<int32_t>::max())
return targetOutOfRangeError(A, E);
*(little32_t *)FixupPtr = Value;
break;
}
case Pointer64:
case Pointer64Anon: {
uint64_t Value = E.getTarget().getAddress() + E.getAddend();
*(ulittle64_t *)FixupPtr = Value;
break;
}
case PCRel32Minus1:
case PCRel32Minus2:
case PCRel32Minus4: {
int Delta = 4 + (1 << (E.getKind() - PCRel32Minus1));
int64_t Value =
E.getTarget().getAddress() - (FixupAddress + Delta) + E.getAddend();
if (Value < std::numeric_limits<int32_t>::min() ||
Value > std::numeric_limits<int32_t>::max())
return targetOutOfRangeError(A, E);
*(little32_t *)FixupPtr = Value;
break;
}
case PCRel32Minus1Anon:
case PCRel32Minus2Anon:
case PCRel32Minus4Anon: {
int Delta = 4 + (1 << (E.getKind() - PCRel32Minus1Anon));
int64_t Value =
E.getTarget().getAddress() - (FixupAddress + Delta) + E.getAddend();
if (Value < std::numeric_limits<int32_t>::min() ||
Value > std::numeric_limits<int32_t>::max())
return targetOutOfRangeError(A, E);
*(little32_t *)FixupPtr = Value;
break;
}
case Delta32:
case Delta64:
case NegDelta32:
case NegDelta64: {
int64_t Value;
if (E.getKind() == Delta32 || E.getKind() == Delta64)
Value = E.getTarget().getAddress() - FixupAddress + E.getAddend();
else
Value = FixupAddress - E.getTarget().getAddress() + E.getAddend();
if (E.getKind() == Delta32 || E.getKind() == NegDelta32) {
if (Value < std::numeric_limits<int32_t>::min() ||
Value > std::numeric_limits<int32_t>::max())
return targetOutOfRangeError(A, E);
*(little32_t *)FixupPtr = Value;
} else
*(little64_t *)FixupPtr = Value;
break;
}
default:
llvm_unreachable("Unrecognized edge kind");
}
return Error::success();
}
uint64_t NullValue = 0;
};
void jitLink_MachO_x86_64(std::unique_ptr<JITLinkContext> Ctx) {
PassConfiguration Config;
Triple TT("x86_64-apple-macosx");
if (Ctx->shouldAddDefaultTargetPasses(TT)) {
// Add a mark-live pass.
if (auto MarkLive = Ctx->getMarkLivePass(TT))
Config.PrePrunePasses.push_back(std::move(MarkLive));
else
Config.PrePrunePasses.push_back(markAllAtomsLive);
// Add an in-place GOT/Stubs pass.
Config.PostPrunePasses.push_back([](AtomGraph &G) -> Error {
MachO_x86_64_GOTAndStubsBuilder(G).run();
return Error::success();
});
}
if (auto Err = Ctx->modifyPassConfig(TT, Config))
return Ctx->notifyFailed(std::move(Err));
// Construct a JITLinker and run the link function.
MachOJITLinker_x86_64::link(std::move(Ctx), std::move(Config));
}
StringRef getMachOX86RelocationKindName(Edge::Kind R) {
switch (R) {
case Branch32:
return "Branch32";
case Pointer64:
return "Pointer64";
case Pointer64Anon:
return "Pointer64Anon";
case PCRel32:
return "PCRel32";
case PCRel32Minus1:
return "PCRel32Minus1";
case PCRel32Minus2:
return "PCRel32Minus2";
case PCRel32Minus4:
return "PCRel32Minus4";
case PCRel32Anon:
return "PCRel32Anon";
case PCRel32Minus1Anon:
return "PCRel32Minus1Anon";
case PCRel32Minus2Anon:
return "PCRel32Minus2Anon";
case PCRel32Minus4Anon:
return "PCRel32Minus4Anon";
case PCRel32GOTLoad:
return "PCRel32GOTLoad";
case PCRel32GOT:
return "PCRel32GOT";
case PCRel32TLV:
return "PCRel32TLV";
case Delta32:
return "Delta32";
case Delta64:
return "Delta64";
case NegDelta32:
return "NegDelta32";
case NegDelta64:
return "NegDelta64";
default:
return getGenericEdgeKindName(static_cast<Edge::Kind>(R));
}
}
} // end namespace jitlink
} // end namespace llvm
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