forked from OSchip/llvm-project
72 lines
2.4 KiB
C++
72 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. The platform object does the work of creating the platform-specific
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// StubAtom.
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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/Platform.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() {
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// Skip this pass if output format uses text relocations instead of stubs.
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if ( !_platform.noTextRelocs() )
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return;
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// Scan all references in all atoms.
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for(const DefinedAtom *atom : _file.defined()) {
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for (const Reference *ref : *atom) {
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// Look at call-sites.
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if ( _platform.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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// Ask platform to make stub and other support atoms.
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const DefinedAtom* stub = _platform.getStub(*target, _file);
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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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// Tell platform to add all created stubs and support Atoms to file.
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_platform.addStubAtoms(_file);
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}
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}
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