src/ld/passes/stubs/stubs.cpp

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  24
  25
  26
  27 #include <stdint.h>
  28 #include <math.h>
  29 #include <unistd.h>
  30 #include <assert.h>
  31 #include <libkern/OSByteOrder.h>
  32
  33 #include <vector>
  34 #include <set>
  35 #include <map>
  36
  37 #include "Options.h"
  38 #include "ld.hpp"
  39 #include "MachOFileAbstraction.hpp"
  40
  41 #include "make_stubs.h"
  42
  43
  44 namespace ld {
  45 namespace passes {
  46 namespace stubs {
  47
  48 class Pass {
  49 public:
  50                                                                 Pass(const Options& opts);
  51         void                                            process(ld::Internal& internal);
  52         void                                            addAtom(const ld::Atom& atom)   { _internal->addAtom(atom); }
  53         bool                                            usingCompressedLINKEDIT() const { return _compressedLINKEDIT; }
  54         ld::Internal*                           internal() { return _internal; }
  55
  56         Atom*                                           compressedHelperHelper;
  57         Atom*                                           compressedImageCache;
  58         Atom*                                           compressedFastBinderPointer;
  59
  60 private:
  61
  62         struct AtomByNameSorter
  63         {
  64                  bool operator()(const ld::Atom* left, const ld::Atom* right)
  65                  {
  66                           return (strcmp(left->name(), right->name()) < 0);
  67                  }
  68         };
  69
  70         const ld::Atom*                         stubableFixup(const ld::Fixup* fixup, ld::Internal&);
  71         ld::Atom*                                       makeStub(const ld::Atom& target, bool weakImport);
  72         void                                            verifyNoResolverFunctions(ld::Internal& state);
  73
  74         const Options&                          _options;
  75         const cpu_type_t                        _architecture;
  76         const bool                                      _lazyDylibsInUuse;
  77         const bool                                      _compressedLINKEDIT;
  78         const bool                                      _prebind;
  79         const bool                                      _mightBeInSharedRegion;
  80         const bool                                      _pic;
  81         const bool                                      _flatNamespace;
  82         ld::Internal*                           _internal;
  83         uint32_t                                        _stubCount;
  84         bool                                            _largeText;
  85 };
  86
  87 #include "stub_x86_64.hpp"
  88 #include "stub_x86_64_classic.hpp"
  89 #include "stub_x86.hpp"
  90 #include "stub_x86_classic.hpp"
  91 #include "stub_arm.hpp"
  92 #include "stub_arm_classic.hpp"
  93
  94
  95
  96 Pass::Pass(const Options& opts)
  97         :       compressedHelperHelper(NULL),
  98                 compressedImageCache(NULL),
  99                 compressedFastBinderPointer(NULL),
 100                 _options(opts),
 101                 _architecture(opts.architecture()),
 102                 _lazyDylibsInUuse(opts.usingLazyDylibLinking()),
 103                 _compressedLINKEDIT(opts.makeCompressedDyldInfo()),
 104                 _prebind(opts.prebind()),
 105                 _mightBeInSharedRegion(opts.sharedRegionEligible()),
 106                 _pic(opts.outputSlidable()),
 107                 _flatNamespace(opts.nameSpace() != Options::kTwoLevelNameSpace),
 108                 _internal(NULL), _stubCount(0), _largeText(false)
 109 {
 110
 111 }
 112
 113
 114 const ld::Atom* Pass::stubableFixup(const ld::Fixup* fixup, ld::Internal& state)
 115 {
 116         if ( fixup->binding == ld::Fixup::bindingsIndirectlyBound ) {
 117                 const ld::Atom* target = state.indirectBindingTable[fixup->u.bindingIndex];
 118                 switch ( fixup->kind ) {
 119                         case ld::Fixup::kindStoreTargetAddressX86BranchPCRel32:
 120                         case ld::Fixup::kindStoreTargetAddressARMBranch24:
 121                         case ld::Fixup::kindStoreTargetAddressThumbBranch22:
 122                 assert(target != NULL);
 123                                 // create stub if target is in a dylib
 124                                 if ( target->definition() == ld::Atom::definitionProxy )
 125                                         return target;
 126                                 // use stub if target is a resolver function in same linkage unit
 127                                 if ( target->contentType() == ld::Atom::typeResolver )
 128                                         return target;
 129                                 if ( target->scope() == ld::Atom::scopeGlobal ) {
 130                                         // create stub if target is global weak definition in symbol table
 131                                         if ( (target->definition() == ld::Atom::definitionRegular)
 132                                                 && (target->combine() == ld::Atom::combineByName)
 133                                                 && ((target->symbolTableInclusion() == ld::Atom::symbolTableIn)
 134                                                  || (target->symbolTableInclusion() == ld::Atom::symbolTableInAndNeverStrip)) )
 135                                                 return target;
 136                                         // create stub if target is interposable
 137                                         if ( _options.interposable(target->name()) )
 138                                                 return target;
 139                                         if ( _flatNamespace ) {
 140                                                 // flat namespace does not indirect calls within main exectuables
 141                                                 if ( _options.outputKind() == Options::kDynamicExecutable )
 142                                                         return NULL;
 143                                                 // create stub if target is global and building -flat dylib or bundle
 144                                                 return target;
 145                                         }
 146                                 }
 147                                 break;
 148                         default:
 149                                 if ( target->contentType() == ld::Atom::typeResolver ) {
 150                                         // any pointer to a resolver needs to change to pointer to stub
 151                                         return target;
 152                                 }
 153                                 break;
 154                 }
 155         }
 156         return NULL;
 157 }
 158
 159
 160
 161 ld::Atom* Pass::makeStub(const ld::Atom& target, bool weakImport)
 162 {
 163         //fprintf(stderr, "makeStub(target=%p %s in sect %s)\n", &target, target.name(), target.section().sectionName());
 164         bool stubToGlobalWeakDef = ( (target.scope() == ld::Atom::scopeGlobal)
 165                                                                 && (target.definition() == ld::Atom::definitionRegular)
 166                                                                 && (target.combine() == ld::Atom::combineByName) );
 167
 168         bool forLazyDylib = false;
 169         const ld::dylib::File* dylib = dynamic_cast<const ld::dylib::File*>(target.file());
 170         if ( (dylib != NULL) && dylib->willBeLazyLoadedDylib() )
 171                 forLazyDylib = true;
 172         bool stubToResolver = (target.contentType() == ld::Atom::typeResolver);
 173
 174         if ( usingCompressedLINKEDIT() && !forLazyDylib ) {
 175                 if ( _internal->compressedFastBinderProxy == NULL )
 176                         throwf("symbol dyld_stub_binder not found (normally in libSystem.dylib).  Needed to perform lazy binding to function %s", target.name());
 177         }
 178
 179         switch ( _architecture ) {
 180 #if SUPPORT_ARCH_i386
 181                 case CPU_TYPE_I386:
 182                         if ( usingCompressedLINKEDIT() && !forLazyDylib )
 183                                 return new ld::passes::stubs::x86::StubAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 184                         else
 185                                 return new ld::passes::stubs::x86::classic::StubAtom(*this, target, forLazyDylib, weakImport);
 186                         break;
 187 #endif
 188 #if SUPPORT_ARCH_x86_64
 189                 case CPU_TYPE_X86_64:
 190                         if ( (_options.outputKind() == Options::kKextBundle) && _options.kextsUseStubs() )
 191                                 return new ld::passes::stubs::x86_64::KextStubAtom(*this, target);
 192                         else if ( usingCompressedLINKEDIT() && !forLazyDylib )
 193                                 return new ld::passes::stubs::x86_64::StubAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 194                         else
 195                                 return new ld::passes::stubs::x86_64::classic::StubAtom(*this, target, forLazyDylib, weakImport);
 196                         break;
 197 #endif
 198 #if SUPPORT_ARCH_arm_any
 199                 case CPU_TYPE_ARM:
 200                         if ( (_options.outputKind() == Options::kKextBundle) && _options.kextsUseStubs() ) {
 201                                 // if text relocs are not allows in kext bundles, then linker must create a stub
 202                                 return new ld::passes::stubs::arm::StubPICKextAtom(*this, target);
 203                         }
 204                         else if ( usingCompressedLINKEDIT() && !forLazyDylib ) {
 205                                 if ( (_stubCount < 900) && !_mightBeInSharedRegion && !_largeText )
 206                                         return new ld::passes::stubs::arm::StubCloseAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 207                                 else if ( _pic )
 208                                         return new ld::passes::stubs::arm::StubPICAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 209                                 else
 210                                         return new ld::passes::stubs::arm::StubNoPICAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 211                         }
 212                         else {
 213                                 if ( _pic )
 214                                         return new ld::passes::stubs::arm::classic::StubPICAtom(*this, target, forLazyDylib, weakImport);
 215                                 else
 216                                         return new ld::passes::stubs::arm::classic::StubNoPICAtom(*this, target, forLazyDylib, weakImport);
 217                         }
 218                         break;
 219 #endif
 220         }
 221         throw "unsupported arch for stub";
 222 }
 223
 224
 225 void Pass::verifyNoResolverFunctions(ld::Internal& state)
 226 {
 227         for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 228                 ld::Internal::FinalSection* sect = *sit;
 229                 for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
 230                         const ld::Atom* atom = *ait;
 231                         if ( atom->contentType() == ld::Atom::typeResolver )
 232                                 throwf("resolver function '%s' not supported in type of output", atom->name());
 233                 }
 234         }
 235 }
 236
 237 void Pass::process(ld::Internal& state)
 238 {
 239         switch ( _options.outputKind() ) {
 240                 case Options::kObjectFile:
 241                         // these kinds don't use stubs and can have resolver functions
 242                         return;
 243                 case Options::kStaticExecutable:
 244                 case Options::kPreload:
 245                 case Options::kDyld:
 246                         // these kinds don't use stubs and cannot have resolver functions
 247                         verifyNoResolverFunctions(state);
 248                         return;
 249                 case Options::kDynamicLibrary:
 250                         // uses stubs and can have resolver functions
 251                         break;
 252                 case Options::kKextBundle:
 253                         verifyNoResolverFunctions(state);
 254                         // if kext don't use stubs, don't do this pass
 255                         if ( !_options.kextsUseStubs() )
 256                                 return;
 257                         break;
 258                 case Options::kDynamicExecutable:
 259                 case Options::kDynamicBundle:
 260                         // these kinds do use stubs and cannot have resolver functions
 261                         verifyNoResolverFunctions(state);
 262                         break;
 263         }
 264
 265         // walk all atoms and fixups looking for stubable references
 266         // don't create stubs inline because that could invalidate the sections iterator
 267         std::vector<const ld::Atom*> atomsCallingStubs;
 268         std::map<const ld::Atom*,ld::Atom*> stubFor;
 269         std::map<const ld::Atom*,bool>          weakImportMap;
 270         atomsCallingStubs.reserve(128);
 271         uint64_t codeSize = 0;
 272         for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 273                 ld::Internal::FinalSection* sect = *sit;
 274                 for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
 275                         const ld::Atom* atom = *ait;
 276                         codeSize += atom->size();
 277                         bool atomNeedsStub = false;
 278                         for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
 279                                 const ld::Atom* stubableTargetOfFixup = stubableFixup(fit, state);
 280                                 if ( stubableTargetOfFixup != NULL ) {
 281                                         if ( !atomNeedsStub ) {
 282                                                 atomsCallingStubs.push_back(atom);
 283                                                 atomNeedsStub = true;
 284                                         }
 285                                         stubFor[stubableTargetOfFixup] = NULL;
 286                                         // record weak_import attribute
 287                                         std::map<const ld::Atom*,bool>::iterator pos = weakImportMap.find(stubableTargetOfFixup);
 288                                         if ( pos == weakImportMap.end() ) {
 289                                                 // target not in weakImportMap, so add
 290                                                 weakImportMap[stubableTargetOfFixup] = fit->weakImport;
 291                                         }
 292                                         else {
 293                                                 // target in weakImportMap, check for weakness mismatch
 294                                                 if ( pos->second != fit->weakImport ) {
 295                                                         // found mismatch
 296                                                         switch ( _options.weakReferenceMismatchTreatment() ) {
 297                                                                 case Options::kWeakReferenceMismatchError:
 298                                                                         throwf("mismatching weak references for symbol: %s", stubableTargetOfFixup->name());
 299                                                                 case Options::kWeakReferenceMismatchWeak:
 300                                                                         pos->second = true;
 301                                                                         break;
 302                                                                 case Options::kWeakReferenceMismatchNonWeak:
 303                                                                         pos->second = false;
 304                                                                         break;
 305                                                         }
 306                                                 }
 307                                         }
 308                                 }
 309                         }
 310                         // all resolver functions must have a corresponding stub
 311                         if ( atom->contentType() == ld::Atom::typeResolver ) {
 312                                 if ( _options.outputKind() != Options::kDynamicLibrary )
 313                                         throwf("resolver functions (%s) can only be used in dylibs", atom->name());
 314                                 if ( !_options.makeCompressedDyldInfo() ) {
 315                                         if ( _options.architecture() == CPU_TYPE_ARM )
 316                                                 throwf("resolver functions (%s) can only be used when targeting iOS 4.2 or later", atom->name());
 317                                         else
 318                                                 throwf("resolver functions (%s) can only be used when targeting Mac OS X 10.6 or later", atom->name());
 319                                 }
 320                                 stubFor[atom] = NULL;
 321                         }
 322                 }
 323         }
 324
 325         const bool needStubForMain = _options.needsEntryPointLoadCommand()
 326                                                                 && (state.entryPoint != NULL)
 327                                                                 && (state.entryPoint->definition() == ld::Atom::definitionProxy);
 328         if ( needStubForMain ) {
 329                 // _main not found in any .o files.  Currently have proxy to dylib
 330                 // Add to map, so that a stub will be made
 331                 stubFor[state.entryPoint] = NULL;
 332         }
 333
 334         // short circuit if no stubs needed
 335         _internal = &state;
 336         _stubCount = stubFor.size();
 337         if ( _stubCount == 0 )
 338                 return;
 339
 340         // <rdar://problem/8553283> lazily check for helper
 341         if ( !_options.makeCompressedDyldInfo() && (state.classicBindingHelper == NULL) && (_options.outputKind() != Options::kKextBundle) )
 342                 throw "symbol dyld_stub_binding_helper not found, normally in crt1.o/dylib1.o/bundle1.o";
 343
 344         // disable arm close stubs in some cases
 345         if ( _architecture == CPU_TYPE_ARM ) {
 346         if ( codeSize > 4*1024*1024 )
 347             _largeText = true;
 348         else {
 349             for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 350                 ld::Internal::FinalSection* sect = *sit;
 351                 if ( sect->type() == ld::Section::typeMachHeader )
 352                     continue;
 353                 if ( strcmp(sect->segmentName(), "__TEXT") == 0) {
 354                     for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
 355                         const ld::Atom* atom = *ait;
 356                         if ( atom->alignment().powerOf2 > 10 ) {
 357                             // overaligned section means might not be able to keep closestubs sect pushed to end of __TEXT
 358                             //warning("alignment 1<<%d in atom %s in section %s disables close stubs optimization",
 359                             //        atom->alignment().powerOf2, atom->name(), sect->segmentName());
 360                             _largeText = true;
 361                             break;
 362                         }
 363                     }
 364                 }
 365             }
 366         }
 367     }
 368
 369         // make stub atoms
 370         for (std::map<const ld::Atom*,ld::Atom*>::iterator it = stubFor.begin(); it != stubFor.end(); ++it) {
 371                 it->second = makeStub(*it->first, weakImportMap[it->first]);
 372         }
 373
 374         // updated atoms to use stubs
 375         for (std::vector<const ld::Atom*>::iterator it=atomsCallingStubs.begin(); it != atomsCallingStubs.end(); ++it) {
 376                 const ld::Atom* atom = *it;
 377                 for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
 378                         const ld::Atom* stubableTargetOfFixup = stubableFixup(fit, state);
 379                         if ( stubableTargetOfFixup != NULL ) {
 380                                 ld::Atom* stub = stubFor[stubableTargetOfFixup];
 381                                 assert(stub != NULL && "stub not created");
 382                                 fit->binding = ld::Fixup::bindingDirectlyBound;
 383                                 fit->u.target = stub;
 384                         }
 385                 }
 386         }
 387
 388         // switch entry point from proxy to stub
 389         if ( needStubForMain ) {
 390                 const ld::Atom* mainStub = stubFor[state.entryPoint];
 391                 assert(mainStub != NULL);
 392                 state.entryPoint = mainStub;
 393         }
 394
 395         // sort new atoms so links are consistent
 396         for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 397                 ld::Internal::FinalSection* sect = *sit;
 398                 switch ( sect->type() ) {
 399                         case ld::Section::typeStubHelper:
 400                         case ld::Section::typeStub:
 401                         case ld::Section::typeStubClose:
 402                         case ld::Section::typeLazyPointer:
 403                         case ld::Section::typeLazyPointerClose:
 404                                 std::sort(sect->atoms.begin(), sect->atoms.end(), AtomByNameSorter());
 405                                 break;
 406                         default:
 407                                 break;
 408                 }
 409         }
 410
 411 }
 412
 413
 414 void doPass(const Options& opts, ld::Internal& internal)
 415 {
 416         Pass  pass(opts);
 417         pass.process(internal);
 418 }
 419
 420
 421
 422 } // namespace stubs
 423 } // namespace passes
 424 } // namespace ld
 425