67 lines
2.4 KiB
C++
67 lines
2.4 KiB
C++
//===- Passes/StubsPass.cpp - Adds stubs ----------------------------------===//
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//
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// The LLVM Linker
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This linker pass updates call-sites which have references to shared library
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// atoms to instead have a reference to a stub (PLT entry) for the specified
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// symbol. Each file format defines a subclass of StubsPass which implements
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// the abstract methods for creating the file format specific StubAtoms.
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//
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//===----------------------------------------------------------------------===//
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#include "lld/Core/DefinedAtom.h"
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#include "lld/Core/File.h"
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#include "lld/Core/LLVM.h"
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#include "lld/Core/Pass.h"
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#include "lld/Core/Reference.h"
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#include "llvm/ADT/DenseMap.h"
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namespace lld {
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void StubsPass::perform(MutableFile &mergedFile) {
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// Skip this pass if output format uses text relocations instead of stubs.
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if ( ! this->noTextRelocs() )
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return;
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// Scan all references in all atoms.
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for(const DefinedAtom *atom : mergedFile.defined()) {
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for (const Reference *ref : *atom) {
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// Look at call-sites.
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if (this->isCallSite(ref->kind()) ) {
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const Atom* target = ref->target();
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assert(target != nullptr);
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bool replaceCalleeWithStub = false;
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if ( target->definition() == Atom::definitionSharedLibrary ) {
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// Calls to shared libraries go through stubs.
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replaceCalleeWithStub = true;
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}
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else if (const DefinedAtom* defTarget =
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dyn_cast<DefinedAtom>(target)) {
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if ( defTarget->interposable() != DefinedAtom::interposeNo ) {
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// Calls to interposable functions in same linkage unit
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// must also go through a stub.
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assert(defTarget->scope() != DefinedAtom::scopeTranslationUnit);
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replaceCalleeWithStub = true;
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}
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}
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if ( replaceCalleeWithStub ) {
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// Make file-format specific stub and other support atoms.
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const DefinedAtom* stub = this->getStub(*target);
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assert(stub != nullptr);
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// Switch call site to reference stub atom instead.
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(const_cast<Reference*>(ref))->setTarget(stub);
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}
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}
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}
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}
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// Add all created stubs and support Atoms.
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this->addStubAtoms(mergedFile);
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}
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}
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