--- /dev/null
+/* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
+ *
+ * Copyright (c) 2009 Apple Inc. All rights reserved.
+ *
+ * @APPLE_LICENSE_HEADER_START@
+ *
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ *
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ *
+ * @APPLE_LICENSE_HEADER_END@
+ */
+
+
+#include <stdint.h>
+#include <math.h>
+#include <unistd.h>
+#include <dlfcn.h>
+
+#include <vector>
+#include <map>
+#include <ext/hash_map>
+
+#include "ld.hpp"
+#include "got.h"
+
+namespace ld {
+namespace passes {
+namespace got {
+
+class File; // forward reference
+
+class GOTEntryAtom : public ld::Atom {
+public:
+ GOTEntryAtom(ld::Internal& internal, const ld::Atom* target, bool weakImport)
+ : ld::Atom(_s_section, ld::Atom::definitionRegular, ld::Atom::combineNever,
+ ld::Atom::scopeLinkageUnit, ld::Atom::typeNonLazyPointer,
+ symbolTableNotIn, false, false, false, ld::Atom::Alignment(3)),
+ _fixup(0, ld::Fixup::k1of1, ld::Fixup::kindStoreTargetAddressLittleEndian64, target),
+ _target(target)
+ { _fixup.weakImport = weakImport; internal.addAtom(*this); }
+
+ virtual const ld::File* file() const { return NULL; }
+ virtual bool translationUnitSource(const char** dir, const char**) const
+ { return false; }
+ virtual const char* name() const { return _target->name(); }
+ virtual uint64_t size() const { return 8; }
+ virtual uint64_t objectAddress() const { return 0; }
+ virtual void copyRawContent(uint8_t buffer[]) const { }
+ virtual void setScope(Scope) { }
+ virtual ld::Fixup::iterator fixupsBegin() const { return &_fixup; }
+ virtual ld::Fixup::iterator fixupsEnd() const { return &((ld::Fixup*)&_fixup)[1]; }
+
+private:
+ mutable ld::Fixup _fixup;
+ const ld::Atom* _target;
+
+ static ld::Section _s_section;
+};
+
+ld::Section GOTEntryAtom::_s_section("__DATA", "__got", ld::Section::typeNonLazyPointer);
+
+
+static bool gotFixup(const Options& opts, ld::Internal& internal, const ld::Atom* targetOfGOT, const ld::Fixup* fixup, bool* optimizable)
+{
+ switch (fixup->kind) {
+ case ld::Fixup::kindStoreTargetAddressX86PCRel32GOTLoad:
+ // start by assuming this can be optimized
+ *optimizable = true;
+ // cannot do LEA optimization if target is in another dylib
+ if ( targetOfGOT->definition() == ld::Atom::definitionProxy )
+ *optimizable = false;
+ // cannot do LEA optimization if target in __huge section
+ if ( internal.usingHugeSections && (targetOfGOT->size() > 1024*1024)
+ && ( (targetOfGOT->section().type() == ld::Section::typeZeroFill)
+ || (targetOfGOT->section().type() == ld::Section::typeTentativeDefs)) ) {
+ *optimizable = false;
+ }
+ if ( targetOfGOT->scope() == ld::Atom::scopeGlobal ) {
+ // cannot do LEA optimization if target is weak exported symbol
+ if ( (targetOfGOT->definition() == ld::Atom::definitionRegular) && (targetOfGOT->combine() == ld::Atom::combineByName) )
+ *optimizable = false;
+ // cannot do LEA optimization if target is interposable
+ if ( opts.interposable(targetOfGOT->name()) )
+ *optimizable = false;
+ // cannot do LEA optimization if target is resolver function
+ if ( targetOfGOT->contentType() == ld::Atom::typeResolver )
+ *optimizable = false;
+ // cannot do LEA optimization for flat-namespace
+ if ( opts.nameSpace() != Options::kTwoLevelNameSpace )
+ *optimizable = false;
+ }
+ return true;
+ case ld::Fixup::kindStoreX86PCRel32GOT:
+ *optimizable = false;
+ return true;
+ default:
+ break;
+ }
+
+ return false;
+}
+
+struct AtomByNameSorter
+{
+ bool operator()(const ld::Atom* left, const ld::Atom* right)
+ {
+ return (strcmp(left->name(), right->name()) < 0);
+ }
+};
+
+void doPass(const Options& opts, ld::Internal& internal)
+{
+ const bool log = false;
+
+ // only make got section in final linked images
+ if ( opts.outputKind() == Options::kObjectFile )
+ return;
+
+ // walk all atoms and fixups looking for stubable references
+ // don't create stubs inline because that could invalidate the sections walk
+ std::vector<const ld::Atom*> atomsReferencingGOT;
+ std::map<const ld::Atom*,ld::Atom*> gotMap;
+ std::map<const ld::Atom*,bool> weakImportMap;
+ atomsReferencingGOT.reserve(128);
+ for (std::vector<ld::Internal::FinalSection*>::iterator sit=internal.sections.begin(); sit != internal.sections.end(); ++sit) {
+ ld::Internal::FinalSection* sect = *sit;
+ for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin(); ait != sect->atoms.end(); ++ait) {
+ const ld::Atom* atom = *ait;
+ bool atomUsesGOT = false;
+ const ld::Atom* targetOfGOT = NULL;
+ for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
+ if ( fit->firstInCluster() )
+ targetOfGOT = NULL;
+ switch ( fit->binding ) {
+ case ld::Fixup::bindingsIndirectlyBound:
+ targetOfGOT = internal.indirectBindingTable[fit->u.bindingIndex];
+ break;
+ case ld::Fixup::bindingDirectlyBound:
+ targetOfGOT = fit->u.target;
+ break;
+ default:
+ break;
+ }
+ bool optimizable;
+ if ( !gotFixup(opts, internal, targetOfGOT, fit, &optimizable) )
+ continue;
+ if ( optimizable ) {
+ // change from load of GOT entry to lea of target
+ if ( log ) fprintf(stderr, "optimized GOT usage in %s to %s\n", atom->name(), targetOfGOT->name());
+ switch ( fit->binding ) {
+ case ld::Fixup::bindingsIndirectlyBound:
+ case ld::Fixup::bindingDirectlyBound:
+ fit->binding = ld::Fixup::bindingDirectlyBound;
+ fit->u.target = targetOfGOT;
+ fit->kind = ld::Fixup::kindStoreTargetAddressX86PCRel32GOTLoadNowLEA;
+ break;
+ default:
+ assert(0 && "unsupported GOT reference");
+ break;
+ }
+ }
+ else {
+ // remember that we need to use GOT in this function
+ if ( log ) fprintf(stderr, "found GOT use in %s to %s\n", atom->name(), targetOfGOT->name());
+ if ( !atomUsesGOT ) {
+ atomsReferencingGOT.push_back(atom);
+ atomUsesGOT = true;
+ }
+ gotMap[targetOfGOT] = NULL;
+ // record weak_import attribute
+ std::map<const ld::Atom*,bool>::iterator pos = weakImportMap.find(targetOfGOT);
+ if ( pos == weakImportMap.end() ) {
+ // target not in weakImportMap, so add
+ weakImportMap[targetOfGOT] = fit->weakImport;
+ // <rdar://problem/5529626> If only weak_import symbols are used, linker should use LD_LOAD_WEAK_DYLIB
+ const ld::dylib::File* dylib = dynamic_cast<const ld::dylib::File*>(targetOfGOT->file());
+ if ( dylib != NULL ) {
+ if ( fit->weakImport )
+ (const_cast<ld::dylib::File*>(dylib))->setUsingWeakImportedSymbols();
+ else
+ (const_cast<ld::dylib::File*>(dylib))->setUsingNonWeakImportedSymbols();
+ }
+ }
+ else {
+ // target in weakImportMap, check for weakness mismatch
+ if ( pos->second != fit->weakImport ) {
+ // found mismatch
+ switch ( opts.weakReferenceMismatchTreatment() ) {
+ case Options::kWeakReferenceMismatchError:
+ throwf("mismatching weak references for symbol: %s", targetOfGOT->name());
+ case Options::kWeakReferenceMismatchWeak:
+ pos->second = true;
+ break;
+ case Options::kWeakReferenceMismatchNonWeak:
+ pos->second = false;
+ break;
+ }
+ }
+ }
+ }
+ }
+ }
+ }
+
+ // make GOT entries
+ for (std::map<const ld::Atom*,ld::Atom*>::iterator it = gotMap.begin(); it != gotMap.end(); ++it) {
+ it->second = new GOTEntryAtom(internal, it->first, weakImportMap[it->first]);
+ }
+
+ // update atoms to use GOT entries
+ for (std::vector<const ld::Atom*>::iterator it=atomsReferencingGOT.begin(); it != atomsReferencingGOT.end(); ++it) {
+ const ld::Atom* atom = *it;
+ const ld::Atom* targetOfGOT = NULL;
+ ld::Fixup::iterator fitThatSetTarget = NULL;
+ for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
+ if ( fit->firstInCluster() ) {
+ targetOfGOT = NULL;
+ fitThatSetTarget = NULL;
+ }
+ switch ( fit->binding ) {
+ case ld::Fixup::bindingsIndirectlyBound:
+ targetOfGOT = internal.indirectBindingTable[fit->u.bindingIndex];
+ fitThatSetTarget = fit;
+ break;
+ case ld::Fixup::bindingDirectlyBound:
+ targetOfGOT = fit->u.target;
+ fitThatSetTarget = fit;
+ break;
+ default:
+ break;
+ }
+ bool optimizable;
+ if ( (targetOfGOT == NULL) || !gotFixup(opts, internal, targetOfGOT, fit, &optimizable) )
+ continue;
+ if ( !optimizable ) {
+ // GOT use not optimized away, update to bind to GOT entry
+ assert(fitThatSetTarget != NULL);
+ switch ( fitThatSetTarget->binding ) {
+ case ld::Fixup::bindingsIndirectlyBound:
+ case ld::Fixup::bindingDirectlyBound:
+ fitThatSetTarget->binding = ld::Fixup::bindingDirectlyBound;
+ fitThatSetTarget->u.target = gotMap[targetOfGOT];
+ break;
+ default:
+ assert(0 && "unsupported GOT reference");
+ break;
+ }
+ }
+ }
+ }
+
+ // sort new atoms so links are consistent
+ for (std::vector<ld::Internal::FinalSection*>::iterator sit=internal.sections.begin(); sit != internal.sections.end(); ++sit) {
+ ld::Internal::FinalSection* sect = *sit;
+ if ( sect->type() == ld::Section::typeNonLazyPointer ) {
+ std::sort(sect->atoms.begin(), sect->atoms.end(), AtomByNameSorter());
+ }
+ }
+}
+
+
+} // namespace got
+} // namespace passes
+} // namespace ld
projects / apple / ld64.git / blobdiff