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023dd287ea
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).
113 lines
3.6 KiB
C++
113 lines
3.6 KiB
C++
//===------- EHFrameSupportImpl.h - JITLink eh-frame utils ------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// EHFrame registration support for JITLink.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIB_EXECUTIONENGINE_JITLINK_EHFRAMESUPPORTIMPL_H
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#define LLVM_LIB_EXECUTIONENGINE_JITLINK_EHFRAMESUPPORTIMPL_H
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#include "llvm/ExecutionEngine/JITLink/EHFrameSupport.h"
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#include "llvm/ExecutionEngine/JITLink/JITLink.h"
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#include "llvm/Support/BinaryStreamReader.h"
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namespace llvm {
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namespace jitlink {
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/// A LinkGraph pass that splits blocks in an eh-frame section into sub-blocks
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/// representing individual eh-frames.
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/// EHFrameSplitter should not be run without EHFrameEdgeFixer, which is
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/// responsible for adding FDE-to-CIE edges.
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class EHFrameSplitter {
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public:
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EHFrameSplitter(StringRef EHFrameSectionName);
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Error operator()(LinkGraph &G);
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private:
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Error processBlock(LinkGraph &G, Block &B, LinkGraph::SplitBlockCache &Cache);
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StringRef EHFrameSectionName;
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};
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/// A LinkGraph pass that adds missing FDE-to-CIE, FDE-to-PC and FDE-to-LSDA
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/// edges.
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class EHFrameEdgeFixer {
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public:
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EHFrameEdgeFixer(StringRef EHFrameSectionName, Edge::Kind FDEToCIE,
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Edge::Kind FDEToPCBegin, Edge::Kind FDEToLSDA);
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Error operator()(LinkGraph &G);
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private:
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struct AugmentationInfo {
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bool AugmentationDataPresent = false;
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bool EHDataFieldPresent = false;
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uint8_t Fields[4] = {0x0, 0x0, 0x0, 0x0};
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};
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struct CIEInformation {
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CIEInformation() = default;
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CIEInformation(Symbol &CIESymbol) : CIESymbol(&CIESymbol) {}
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Symbol *CIESymbol = nullptr;
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bool FDEsHaveLSDAField = false;
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};
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struct EdgeTarget {
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EdgeTarget() = default;
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EdgeTarget(const Edge &E) : Target(&E.getTarget()), Addend(E.getAddend()) {}
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Symbol *Target = nullptr;
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Edge::AddendT Addend = 0;
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};
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using BlockEdgeMap = DenseMap<Edge::OffsetT, EdgeTarget>;
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using CIEInfosMap = DenseMap<JITTargetAddress, CIEInformation>;
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struct ParseContext {
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ParseContext(LinkGraph &G) : G(G) {}
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Expected<CIEInformation *> findCIEInfo(JITTargetAddress Address) {
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auto I = CIEInfos.find(Address);
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if (I == CIEInfos.end())
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return make_error<JITLinkError>("No CIE found at address " +
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formatv("{0:x16}", Address));
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return &I->second;
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}
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LinkGraph &G;
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CIEInfosMap CIEInfos;
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BlockAddressMap AddrToBlock;
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SymbolAddressMap AddrToSyms;
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};
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Error processBlock(ParseContext &PC, Block &B);
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Error processCIE(ParseContext &PC, Block &B, size_t RecordOffset,
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size_t RecordLength, size_t CIEDeltaFieldOffset);
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Error processFDE(ParseContext &PC, Block &B, size_t RecordOffset,
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size_t RecordLength, size_t CIEDeltaFieldOffset,
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uint32_t CIEDelta, BlockEdgeMap &BlockEdges);
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Expected<AugmentationInfo>
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parseAugmentationString(BinaryStreamReader &RecordReader);
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Expected<JITTargetAddress>
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readAbsolutePointer(LinkGraph &G, BinaryStreamReader &RecordReader);
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Expected<Symbol &> getOrCreateSymbol(ParseContext &PC, JITTargetAddress Addr);
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StringRef EHFrameSectionName;
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Edge::Kind FDEToCIE;
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Edge::Kind FDEToPCBegin;
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Edge::Kind FDEToLSDA;
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};
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} // end namespace jitlink
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} // end namespace llvm
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#endif // LLVM_LIB_EXECUTIONENGINE_JITLINK_EHFRAMESUPPORTIMPL_H
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