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clang-p2996/llvm/lib/ExecutionEngine/JITLink/MachO_x86_64.cpp
Lang Hames 76aee8a389 [JITLink] Refactor EH-frame handling to support eh-frames with existing relocs. 
Some targets (E.g. MachO/arm64) use relocations to fix some CFI record fields
in the eh-frame section. When relocations are used the initial (pre-relocation)
content of the eh-frame section can no longer be interpreted by following the
eh-frame specification. This causes errors in the existing eh-frame parser.

This patch moves eh-frame handling into two LinkGraph passes that are run after
relocations have been parsed (but before they are applied). The first] pass
breaks up blocks in the eh-frame section into per-CFI-record blocks, and the
second parses blocks of (potentially multiple) CFI records and adds the
appropriate edges to any CFI fields that do not have existing relocations.
These passes can be run independently of one another. By handling eh-frame
splitting/fixing with LinkGraph passes we can both re-use existing relocations
for CFI record fields and avoid applying eh-frame fixups before parsing the
section (which would complicate the linker and require extra temporary
allocations of working memory).
2019-11-06 14:30:26 -08:00

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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 "MachOLinkGraphBuilder.h"
#define DEBUG_TYPE "jitlink"
using namespace llvm;
using namespace llvm::jitlink;
using namespace llvm::jitlink::MachO_x86_64_Edges;
namespace {
class MachOLinkGraphBuilder_x86_64 : public MachOLinkGraphBuilder {
public:
MachOLinkGraphBuilder_x86_64(const object::MachOObjectFile &Obj)
: MachOLinkGraphBuilder(Obj) {}
private:
static Expected<MachOX86RelocationKind>
getRelocationKind(const MachO::relocation_info &RI) {
switch (RI.r_type) {
case MachO::X86_64_RELOC_UNSIGNED:
if (!RI.r_pcrel) {
if (RI.r_length == 3)
return RI.r_extern ? Pointer64 : Pointer64Anon;
else if (RI.r_extern && RI.r_length == 2)
return Pointer32;
}
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));
}
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, Symbol *, uint64_t>;
// Parses paired SUBTRACTOR/UNSIGNED relocations and, on success,
// returns the edge kind and addend to be used.
Expected<PairRelocInfo>
parsePairRelocation(Block &BlockToFix, 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");
Symbol *FromSymbol;
if (auto FromSymbolOrErr = findSymbolByIndex(SubRI.r_symbolnum))
FromSymbol = FromSymbolOrErr->GraphSymbol;
else
return FromSymbolOrErr.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 'ToSymbol' using symbol number or address, depending on whether the
// paired UNSIGNED relocation is extern.
Symbol *ToSymbol = nullptr;
if (UnsignedRI.r_extern) {
// Find target symbol by symbol index.
if (auto ToSymbolOrErr = findSymbolByIndex(UnsignedRI.r_symbolnum))
ToSymbol = ToSymbolOrErr->GraphSymbol;
else
return ToSymbolOrErr.takeError();
} else {
if (auto ToSymbolOrErr = findSymbolByAddress(FixupValue))
ToSymbol = &*ToSymbolOrErr;
else
return ToSymbolOrErr.takeError();
FixupValue -= ToSymbol->getAddress();
}
MachOX86RelocationKind DeltaKind;
Symbol *TargetSymbol;
uint64_t Addend;
if (&BlockToFix == &FromSymbol->getAddressable()) {
TargetSymbol = ToSymbol;
DeltaKind = (SubRI.r_length == 3) ? Delta64 : Delta32;
Addend = FixupValue + (FixupAddress - FromSymbol->getAddress());
// FIXME: handle extern 'from'.
} else if (&BlockToFix == &ToSymbol->getAddressable()) {
TargetSymbol = FromSymbol;
DeltaKind = (SubRI.r_length == 3) ? NegDelta64 : NegDelta32;
Addend = FixupValue - (FixupAddress - ToSymbol->getAddress());
} else {
// BlockToFix was neither FromSymbol nor ToSymbol.
return make_error<JITLinkError>("SUBTRACTOR relocation must fix up "
"either 'A' or 'B' (or a symbol in one "
"of their alt-entry chains)");
}
return PairRelocInfo(DeltaKind, TargetSymbol, Addend);
}
Error addRelocations() override {
using namespace support;
auto &Obj = getObject();
for (auto &S : Obj.sections()) {
JITTargetAddress SectionAddress = S.getAddress();
if (S.isVirtual()) {
if (S.relocation_begin() != S.relocation_end())
return make_error<JITLinkError>("Virtual section contains "
"relocations");
continue;
}
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 block that the fixup points to.
Block *BlockToFix = nullptr;
{
auto SymbolToFixOrErr = findSymbolByAddress(FixupAddress);
if (!SymbolToFixOrErr)
return SymbolToFixOrErr.takeError();
BlockToFix = &SymbolToFixOrErr->getBlock();
}
if (FixupAddress + static_cast<JITTargetAddress>(1ULL << RI.r_length) >
BlockToFix->getAddress() + BlockToFix->getContent().size())
return make_error<JITLinkError>(
"Relocation extends past end of fixup block");
// Get a pointer to the fixup content.
const char *FixupContent = BlockToFix->getContent().data() +
(FixupAddress - BlockToFix->getAddress());
// The target symbol and addend will be populated by the switch below.
Symbol *TargetSymbol = nullptr;
uint64_t Addend = 0;
switch (*Kind) {
case Branch32:
case PCRel32:
case PCRel32GOTLoad:
case PCRel32GOT:
if (auto TargetSymbolOrErr = findSymbolByIndex(RI.r_symbolnum))
TargetSymbol = TargetSymbolOrErr->GraphSymbol;
else
return TargetSymbolOrErr.takeError();
Addend = *(const ulittle32_t *)FixupContent;
break;
case Pointer32:
if (auto TargetSymbolOrErr = findSymbolByIndex(RI.r_symbolnum))
TargetSymbol = TargetSymbolOrErr->GraphSymbol;
else
return TargetSymbolOrErr.takeError();
Addend = *(const ulittle32_t *)FixupContent;
break;
case Pointer64:
if (auto TargetSymbolOrErr = findSymbolByIndex(RI.r_symbolnum))
TargetSymbol = TargetSymbolOrErr->GraphSymbol;
else
return TargetSymbolOrErr.takeError();
Addend = *(const ulittle64_t *)FixupContent;
break;
case Pointer64Anon: {
JITTargetAddress TargetAddress = *(const ulittle64_t *)FixupContent;
if (auto TargetSymbolOrErr = findSymbolByAddress(TargetAddress))
TargetSymbol = &*TargetSymbolOrErr;
else
return TargetSymbolOrErr.takeError();
Addend = TargetAddress - TargetSymbol->getAddress();
break;
}
case PCRel32Minus1:
case PCRel32Minus2:
case PCRel32Minus4:
if (auto TargetSymbolOrErr = findSymbolByIndex(RI.r_symbolnum))
TargetSymbol = TargetSymbolOrErr->GraphSymbol;
else
return TargetSymbolOrErr.takeError();
Addend = *(const ulittle32_t *)FixupContent +
(1 << (*Kind - PCRel32Minus1));
break;
case PCRel32Anon: {
JITTargetAddress TargetAddress =
FixupAddress + 4 + *(const ulittle32_t *)FixupContent;
if (auto TargetSymbolOrErr = findSymbolByAddress(TargetAddress))
TargetSymbol = &*TargetSymbolOrErr;
else
return TargetSymbolOrErr.takeError();
Addend = TargetAddress - TargetSymbol->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 TargetSymbolOrErr = findSymbolByAddress(TargetAddress))
TargetSymbol = &*TargetSymbolOrErr;
else
return TargetSymbolOrErr.takeError();
Addend = TargetAddress - TargetSymbol->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(*BlockToFix, *Kind, RI, FixupAddress,
FixupContent, ++RelItr, RelEnd);
if (!PairInfo)
return PairInfo.takeError();
std::tie(*Kind, TargetSymbol, Addend) = *PairInfo;
assert(TargetSymbol && "No target symbol from parsePairRelocation?");
break;
}
default:
llvm_unreachable("Special relocation kind should not appear in "
"mach-o file");
}
LLVM_DEBUG({
Edge GE(*Kind, FixupAddress - BlockToFix->getAddress(), *TargetSymbol,
Addend);
printEdge(dbgs(), *BlockToFix, GE,
getMachOX86RelocationKindName(*Kind));
dbgs() << "\n";
});
BlockToFix->addEdge(*Kind, FixupAddress - BlockToFix->getAddress(),
*TargetSymbol, Addend);
}
}
return Error::success();
}
};
class MachO_x86_64_GOTAndStubsBuilder
: public BasicGOTAndStubsBuilder<MachO_x86_64_GOTAndStubsBuilder> {
public:
MachO_x86_64_GOTAndStubsBuilder(LinkGraph &G)
: BasicGOTAndStubsBuilder<MachO_x86_64_GOTAndStubsBuilder>(G) {}
bool isGOTEdge(Edge &E) const {
return E.getKind() == PCRel32GOT || E.getKind() == PCRel32GOTLoad;
}
Symbol &createGOTEntry(Symbol &Target) {
auto &GOTEntryBlock = G.createContentBlock(
getGOTSection(), getGOTEntryBlockContent(), 0, 8, 0);
GOTEntryBlock.addEdge(Pointer64, 0, Target, 0);
return G.addAnonymousSymbol(GOTEntryBlock, 0, 8, false, false);
}
void fixGOTEdge(Edge &E, Symbol &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();
}
Symbol &createStub(Symbol &Target) {
auto &StubContentBlock =
G.createContentBlock(getStubsSection(), getStubBlockContent(), 0, 1, 0);
// Re-use GOT entries for stub targets.
auto &GOTEntrySymbol = getGOTEntrySymbol(Target);
StubContentBlock.addEdge(PCRel32, 2, GOTEntrySymbol, 0);
return G.addAnonymousSymbol(StubContentBlock, 0, 6, true, false);
}
void fixExternalBranchEdge(Edge &E, Symbol &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("$__GOT", sys::Memory::MF_READ);
return *GOTSection;
}
Section &getStubsSection() {
if (!StubsSection) {
auto StubsProt = static_cast<sys::Memory::ProtectionFlags>(
sys::Memory::MF_READ | sys::Memory::MF_EXEC);
StubsSection = &G.createSection("$__STUBS", StubsProt);
}
return *StubsSection;
}
StringRef getGOTEntryBlockContent() {
return StringRef(reinterpret_cast<const char *>(NullGOTEntryContent),
sizeof(NullGOTEntryContent));
}
StringRef getStubBlockContent() {
return StringRef(reinterpret_cast<const char *>(StubContent),
sizeof(StubContent));
}
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<LinkGraph>>
buildGraph(MemoryBufferRef ObjBuffer) override {
auto MachOObj = object::ObjectFile::createMachOObjectFile(ObjBuffer);
if (!MachOObj)
return MachOObj.takeError();
return MachOLinkGraphBuilder_x86_64(**MachOObj).buildGraph();
}
static Error targetOutOfRangeError(const Block &B, const Edge &E) {
std::string ErrMsg;
{
raw_string_ostream ErrStream(ErrMsg);
ErrStream << "Relocation target out of range: ";
printEdge(ErrStream, B, E, getMachOX86RelocationKindName(E.getKind()));
ErrStream << "\n";
}
return make_error<JITLinkError>(std::move(ErrMsg));
}
Error applyFixup(Block &B, const Edge &E, char *BlockWorkingMem) const {
using namespace support;
char *FixupPtr = BlockWorkingMem + E.getOffset();
JITTargetAddress FixupAddress = B.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(B, 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(B, 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(B, 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(B, E);
*(little32_t *)FixupPtr = Value;
} else
*(little64_t *)FixupPtr = Value;
break;
}
case Pointer32: {
uint64_t Value = E.getTarget().getAddress() + E.getAddend();
if (Value > std::numeric_limits<uint32_t>::max())
return targetOutOfRangeError(B, E);
*(ulittle32_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 eh-frame passses.
Config.PrePrunePasses.push_back(EHFrameSplitter("__eh_frame"));
Config.PrePrunePasses.push_back(
EHFrameEdgeFixer("__eh_frame", NegDelta32, Delta64, Delta64));
// Add a mark-live pass.
if (auto MarkLive = Ctx->getMarkLivePass(TT))
Config.PrePrunePasses.push_back(std::move(MarkLive));
else
Config.PrePrunePasses.push_back(markAllSymbolsLive);
// Add an in-place GOT/Stubs pass.
Config.PostPrunePasses.push_back([](LinkGraph &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 Pointer32:
return "Pointer32";
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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