forked from OSchip/llvm-project
127 lines
4.4 KiB
C++
127 lines
4.4 KiB
C++
//===--------------- PerGraphGOTAndPLTStubBuilder.h -------------*- 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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// Construct GOT and PLT entries for each graph.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_EXECUTIONENGINE_JITLINK_PERGRAPHGOTANDPLTSTUBSBUILDER_H
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#define LLVM_EXECUTIONENGINE_JITLINK_PERGRAPHGOTANDPLTSTUBSBUILDER_H
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#include "llvm/ExecutionEngine/JITLink/JITLink.h"
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#include "llvm/Support/Debug.h"
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#define DEBUG_TYPE "jitlink"
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namespace llvm {
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namespace jitlink {
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/// Per-object GOT and PLT Stub builder.
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///
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/// Constructs GOT entries and PLT stubs in every graph for referenced symbols.
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/// Building these blocks in every graph is likely to lead to duplicate entries
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/// in the JITLinkDylib, but allows graphs to be trivially removed independently
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/// without affecting other graphs (since those other graphs will have their own
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/// copies of any required entries).
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template <typename BuilderImplT>
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class PerGraphGOTAndPLTStubsBuilder {
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public:
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PerGraphGOTAndPLTStubsBuilder(LinkGraph &G) : G(G) {}
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static Error asPass(LinkGraph &G) { return BuilderImplT(G).run(); }
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Error run() {
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LLVM_DEBUG(dbgs() << "Running Per-Graph GOT and Stubs builder:\n");
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// We're going to be adding new blocks, but we don't want to iterate over
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// the new ones, so build a worklist.
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std::vector<Block *> Worklist(G.blocks().begin(), G.blocks().end());
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for (auto *B : Worklist)
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for (auto &E : B->edges()) {
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if (impl().isGOTEdgeToFix(E)) {
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LLVM_DEBUG({
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dbgs() << " Fixing " << G.getEdgeKindName(E.getKind())
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<< " edge at " << formatv("{0:x}", B->getFixupAddress(E))
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<< " (" << formatv("{0:x}", B->getAddress()) << " + "
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<< formatv("{0:x}", E.getOffset()) << ")\n";
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});
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impl().fixGOTEdge(E, getGOTEntry(E.getTarget()));
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} else if (impl().isExternalBranchEdge(E)) {
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LLVM_DEBUG({
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dbgs() << " Fixing " << G.getEdgeKindName(E.getKind())
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<< " edge at " << formatv("{0:x}", B->getFixupAddress(E))
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<< " (" << formatv("{0:x}", B->getAddress()) << " + "
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<< formatv("{0:x}", E.getOffset()) << ")\n";
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});
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impl().fixPLTEdge(E, getPLTStub(E.getTarget()));
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}
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}
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return Error::success();
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}
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protected:
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Symbol &getGOTEntry(Symbol &Target) {
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assert(Target.hasName() && "GOT edge cannot point to anonymous target");
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auto GOTEntryI = GOTEntries.find(Target.getName());
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// Build the entry if it doesn't exist.
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if (GOTEntryI == GOTEntries.end()) {
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auto &GOTEntry = impl().createGOTEntry(Target);
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LLVM_DEBUG({
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dbgs() << " Created GOT entry for " << Target.getName() << ": "
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<< GOTEntry << "\n";
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});
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GOTEntryI =
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GOTEntries.insert(std::make_pair(Target.getName(), &GOTEntry)).first;
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}
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assert(GOTEntryI != GOTEntries.end() && "Could not get GOT entry symbol");
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LLVM_DEBUG(
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{ dbgs() << " Using GOT entry " << *GOTEntryI->second << "\n"; });
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return *GOTEntryI->second;
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}
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Symbol &getPLTStub(Symbol &Target) {
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assert(Target.hasName() &&
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"External branch edge can not point to an anonymous target");
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auto StubI = PLTStubs.find(Target.getName());
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if (StubI == PLTStubs.end()) {
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auto &StubSymbol = impl().createPLTStub(Target);
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LLVM_DEBUG({
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dbgs() << " Created PLT stub for " << Target.getName() << ": "
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<< StubSymbol << "\n";
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});
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StubI =
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PLTStubs.insert(std::make_pair(Target.getName(), &StubSymbol)).first;
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}
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assert(StubI != PLTStubs.end() && "Count not get stub symbol");
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LLVM_DEBUG({ dbgs() << " Using PLT stub " << *StubI->second << "\n"; });
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return *StubI->second;
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}
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LinkGraph &G;
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private:
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BuilderImplT &impl() { return static_cast<BuilderImplT &>(*this); }
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DenseMap<StringRef, Symbol *> GOTEntries;
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DenseMap<StringRef, Symbol *> PLTStubs;
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};
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} // end namespace jitlink
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} // end namespace llvm
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#undef DEBUG_TYPE
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#endif // LLVM_EXECUTIONENGINE_JITLINK_PERGRAPHGOTANDPLTSTUBSBUILDER_H
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