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1//===--------------- PerGraphGOTAndPLTStubBuilder.h -------------*- C++ -*-===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// Construct GOT and PLT entries for each graph.10//11//===----------------------------------------------------------------------===//12 13#ifndef LLVM_EXECUTIONENGINE_JITLINK_PERGRAPHGOTANDPLTSTUBSBUILDER_H14#define LLVM_EXECUTIONENGINE_JITLINK_PERGRAPHGOTANDPLTSTUBSBUILDER_H15 16#include "llvm/ExecutionEngine/JITLink/JITLink.h"17#include "llvm/Support/Debug.h"18 19#define DEBUG_TYPE "jitlink"20 21namespace llvm {22namespace jitlink {23 24/// Per-object GOT and PLT Stub builder.25///26/// Constructs GOT entries and PLT stubs in every graph for referenced symbols.27/// Building these blocks in every graph is likely to lead to duplicate entries28/// in the JITLinkDylib, but allows graphs to be trivially removed independently29/// without affecting other graphs (since those other graphs will have their own30/// copies of any required entries).31template <typename BuilderImplT>32class PerGraphGOTAndPLTStubsBuilder {33public:34 PerGraphGOTAndPLTStubsBuilder(LinkGraph &G) : G(G) {}35 36 static Error asPass(LinkGraph &G) { return BuilderImplT(G).run(); }37 38 Error run() {39 LLVM_DEBUG(dbgs() << "Running Per-Graph GOT and Stubs builder:\n");40 41 // We're going to be adding new blocks, but we don't want to iterate over42 // the new ones, so build a worklist.43 std::vector<Block *> Worklist(G.blocks().begin(), G.blocks().end());44 45 for (auto *B : Worklist)46 for (auto &E : B->edges()) {47 if (impl().isGOTEdgeToFix(E)) {48 LLVM_DEBUG({49 dbgs() << " Fixing " << G.getEdgeKindName(E.getKind())50 << " edge at " << B->getFixupAddress(E) << " ("51 << B->getAddress() << " + "52 << formatv("{0:x}", E.getOffset()) << ")\n";53 });54 impl().fixGOTEdge(E, getGOTEntry(E.getTarget()));55 } else if (impl().isExternalBranchEdge(E)) {56 LLVM_DEBUG({57 dbgs() << " Fixing " << G.getEdgeKindName(E.getKind())58 << " edge at " << B->getFixupAddress(E) << " ("59 << B->getAddress() << " + "60 << formatv("{0:x}", E.getOffset()) << ")\n";61 });62 impl().fixPLTEdge(E, getPLTStub(E.getTarget()));63 }64 }65 66 return Error::success();67 }68 69protected:70 Symbol &getGOTEntry(Symbol &Target) {71 assert(Target.hasName() && "GOT edge cannot point to anonymous target");72 73 auto GOTEntryI = GOTEntries.find(Target.getName());74 75 // Build the entry if it doesn't exist.76 if (GOTEntryI == GOTEntries.end()) {77 auto &GOTEntry = impl().createGOTEntry(Target);78 LLVM_DEBUG({79 dbgs() << " Created GOT entry for " << Target.getName() << ": "80 << GOTEntry << "\n";81 });82 GOTEntryI =83 GOTEntries.insert(std::make_pair(Target.getName(), &GOTEntry)).first;84 }85 86 assert(GOTEntryI != GOTEntries.end() && "Could not get GOT entry symbol");87 LLVM_DEBUG(88 { dbgs() << " Using GOT entry " << *GOTEntryI->second << "\n"; });89 return *GOTEntryI->second;90 }91 92 Symbol &getPLTStub(Symbol &Target) {93 assert(Target.hasName() &&94 "External branch edge can not point to an anonymous target");95 auto StubI = PLTStubs.find(Target.getName());96 97 if (StubI == PLTStubs.end()) {98 auto &StubSymbol = impl().createPLTStub(Target);99 LLVM_DEBUG({100 dbgs() << " Created PLT stub for " << Target.getName() << ": "101 << StubSymbol << "\n";102 });103 StubI =104 PLTStubs.insert(std::make_pair(Target.getName(), &StubSymbol)).first;105 }106 107 assert(StubI != PLTStubs.end() && "Count not get stub symbol");108 LLVM_DEBUG({ dbgs() << " Using PLT stub " << *StubI->second << "\n"; });109 return *StubI->second;110 }111 112 LinkGraph &G;113 114private:115 BuilderImplT &impl() { return static_cast<BuilderImplT &>(*this); }116 117 DenseMap<orc::SymbolStringPtr, Symbol *> GOTEntries;118 DenseMap<orc::SymbolStringPtr, Symbol *> PLTStubs;119};120 121} // end namespace jitlink122} // end namespace llvm123 124#undef DEBUG_TYPE125 126#endif // LLVM_EXECUTIONENGINE_JITLINK_PERGRAPHGOTANDPLTSTUBSBUILDER_H127