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