1a6615dc88
Add first linker pass (StubsPass) which looks for calls to shared library symbols and replaces them with calls to a StubAtom. On ELF system, a "stub" is a PLT entry. Added a simple test case. Pass a Platform object to YAML reader and writer for converting fixup kinds between names and values. Change output of Resolver to be a File object instead of a vector of Atoms. Thus, passes operate on a File instead of just Atoms. Rework how to walk through a File's Atoms. Now iterator based instead of a method that visits each atom. llvm-svn: 152269
80 lines
2.3 KiB
C++
80 lines
2.3 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 is
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//
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//
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//
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//
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#include "llvm/ADT/DenseMap.h"
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#include "lld/Core/Pass.h"
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#include "lld/Core/File.h"
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#include "lld/Core/Reference.h"
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#include "lld/Platform/Platform.h"
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namespace lld {
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void StubsPass::perform() {
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// Skip this pass if output format does not need stubs.
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if ( !_platform.outputUsesStubs() )
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return;
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// Use map so all call sites to same shlib symbol use same stub
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llvm::DenseMap<const SharedLibraryAtom*, const Atom*> shlibToStub;
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// Scan all references in all atoms.
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for(auto ait=_file.definedAtomsBegin(), aend=_file.definedAtomsEnd();
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ait != aend; ++ait) {
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const DefinedAtom* atom = *ait;
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for (auto rit=atom->referencesBegin(), rend=atom->referencesEnd();
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rit != rend; ++rit) {
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const Reference* ref = *rit;
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const Atom* target = ref->target();
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assert(target != NULL);
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// If the target of this reference is in a shared library
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if ( const SharedLibraryAtom* shlbTarget = target->sharedLibraryAtom() ) {
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// and this is a call to that shared library symbol.
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if ( _platform.isBranch(ref) ) {
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const Atom* stub;
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// Replace the target with a reference to a stub
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auto pos = shlibToStub.find(shlbTarget);
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if ( pos == shlibToStub.end() ) {
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// This is no existing stub. Create a new one.
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stub = _platform.makeStub(*shlbTarget, _file);
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shlibToStub[shlbTarget] = stub;
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}
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else {
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// Reuse and existing stub
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stub = pos->second;
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}
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assert(stub != NULL);
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// Switch call site in atom to refrence stub instead of shlib atom.
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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 to file
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for (auto it=shlibToStub.begin(), end=shlibToStub.end(); it != end; ++it) {
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_file.addAtom(*it->second);
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}
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}
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}
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