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 "MachOFileAbstraction.hpp"
  39 #include "ld.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 #if SUPPORT_ARCH_arm64
  94 #include "stub_arm64.hpp"
  95 #endif
  96
  97 Pass::Pass(const Options& opts)
  98         :       compressedHelperHelper(NULL),
  99                 compressedImageCache(NULL),
 100                 compressedFastBinderPointer(NULL),
 101                 _options(opts),
 102                 _architecture(opts.architecture()),
 103                 _lazyDylibsInUuse(opts.usingLazyDylibLinking()),
 104                 _compressedLINKEDIT(opts.makeCompressedDyldInfo()),
 105                 _prebind(opts.prebind()),
 106                 _mightBeInSharedRegion(opts.sharedRegionEligible()),
 107                 _pic(opts.outputSlidable()),
 108                 _flatNamespace(opts.nameSpace() != Options::kTwoLevelNameSpace),
 109                 _internal(NULL), _stubCount(0), _largeText(false)
 110 {
 111
 112 }
 113
 114
 115 const ld::Atom* Pass::stubableFixup(const ld::Fixup* fixup, ld::Internal& state)
 116 {
 117         if ( fixup->binding == ld::Fixup::bindingsIndirectlyBound ) {
 118                 const ld::Atom* target = state.indirectBindingTable[fixup->u.bindingIndex];
 119                 switch ( fixup->kind ) {
 120                         case ld::Fixup::kindStoreTargetAddressX86BranchPCRel32:
 121                         case ld::Fixup::kindStoreTargetAddressARMBranch24:
 122                         case ld::Fixup::kindStoreTargetAddressThumbBranch22:
 123 #if SUPPORT_ARCH_arm64
 124                         case ld::Fixup::kindStoreTargetAddressARM64Branch26:
 125 #endif
 126                 assert(target != NULL);
 127                                 // create stub if target is in a dylib
 128                                 if ( target->definition() == ld::Atom::definitionProxy )
 129                                         return target;
 130                                 // use stub if target is a resolver function in same linkage unit
 131                                 if ( target->contentType() == ld::Atom::typeResolver )
 132                                         return target;
 133                                 if ( target->scope() == ld::Atom::scopeGlobal ) {
 134                                         // create stub if target is global weak definition in symbol table
 135                                         if ( (target->definition() == ld::Atom::definitionRegular)
 136                                                 && (target->combine() == ld::Atom::combineByName)
 137                                                 && ((target->symbolTableInclusion() == ld::Atom::symbolTableIn)
 138                                                  || (target->symbolTableInclusion() == ld::Atom::symbolTableInAndNeverStrip)) )
 139                                                 return target;
 140                                         // create stub if target is interposable
 141                                         if ( _options.interposable(target->name()) )
 142                                                 return target;
 143                                         if ( _flatNamespace ) {
 144                                                 // flat namespace does not indirect calls within main exectuables
 145                                                 if ( _options.outputKind() == Options::kDynamicExecutable )
 146                                                         return NULL;
 147                                                 // create stub if target is global and building -flat dylib or bundle
 148                                                 return target;
 149                                         }
 150                                 }
 151                                 break;
 152                         default:
 153                                 if ( target->contentType() == ld::Atom::typeResolver ) {
 154                                         // any pointer to a resolver needs to change to pointer to stub
 155                                         return target;
 156                                 }
 157                                 break;
 158                 }
 159         }
 160         return NULL;
 161 }
 162
 163
 164
 165 ld::Atom* Pass::makeStub(const ld::Atom& target, bool weakImport)
 166 {
 167         //fprintf(stderr, "makeStub(target=%p %s in sect %s)\n", &target, target.name(), target.section().sectionName());
 168         bool stubToGlobalWeakDef = ( (target.scope() == ld::Atom::scopeGlobal)
 169                                                                 && (target.definition() == ld::Atom::definitionRegular)
 170                                                                 && (target.combine() == ld::Atom::combineByName) );
 171
 172         bool forLazyDylib = false;
 173         const ld::dylib::File* dylib = dynamic_cast<const ld::dylib::File*>(target.file());
 174         if ( (dylib != NULL) && dylib->willBeLazyLoadedDylib() )
 175                 forLazyDylib = true;
 176         bool stubToResolver = (target.contentType() == ld::Atom::typeResolver);
 177
 178         if ( usingCompressedLINKEDIT() && !forLazyDylib ) {
 179                 if ( _internal->compressedFastBinderProxy == NULL )
 180                         throwf("symbol dyld_stub_binder not found (normally in libSystem.dylib).  Needed to perform lazy binding to function %s", target.name());
 181         }
 182
 183         switch ( _architecture ) {
 184 #if SUPPORT_ARCH_i386
 185                 case CPU_TYPE_I386:
 186                         if ( usingCompressedLINKEDIT() && !forLazyDylib )
 187                                 return new ld::passes::stubs::x86::StubAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 188                         else
 189                                 return new ld::passes::stubs::x86::classic::StubAtom(*this, target, forLazyDylib, weakImport);
 190                         break;
 191 #endif
 192 #if SUPPORT_ARCH_x86_64
 193                 case CPU_TYPE_X86_64:
 194                         if ( (_options.outputKind() == Options::kKextBundle) && _options.kextsUseStubs() )
 195                                 return new ld::passes::stubs::x86_64::KextStubAtom(*this, target);
 196                         else if ( usingCompressedLINKEDIT() && !forLazyDylib )
 197                                 return new ld::passes::stubs::x86_64::StubAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 198                         else
 199                                 return new ld::passes::stubs::x86_64::classic::StubAtom(*this, target, forLazyDylib, weakImport);
 200                         break;
 201 #endif
 202 #if SUPPORT_ARCH_arm_any
 203                 case CPU_TYPE_ARM:
 204                         if ( (_options.outputKind() == Options::kKextBundle) && _options.kextsUseStubs() ) {
 205                                 // if text relocs are not allows in kext bundles, then linker must create a stub
 206                                 return new ld::passes::stubs::arm::StubPICKextAtom(*this, target);
 207                         }
 208                         else if ( usingCompressedLINKEDIT() && !forLazyDylib ) {
 209                                 if ( (_stubCount < 900) && !_mightBeInSharedRegion && !_largeText )
 210                                         return new ld::passes::stubs::arm::StubCloseAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 211                                 else if ( _pic )
 212                                         return new ld::passes::stubs::arm::StubPICAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 213                                 else
 214                                         return new ld::passes::stubs::arm::StubNoPICAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 215                         }
 216                         else {
 217                                 if ( _pic )
 218                                         return new ld::passes::stubs::arm::classic::StubPICAtom(*this, target, forLazyDylib, weakImport);
 219                                 else
 220                                         return new ld::passes::stubs::arm::classic::StubNoPICAtom(*this, target, forLazyDylib, weakImport);
 221                         }
 222                         break;
 223 #endif
 224 #if SUPPORT_ARCH_arm64
 225                 case CPU_TYPE_ARM64:
 226                         if ( (_options.outputKind() == Options::kKextBundle) && _options.kextsUseStubs() )
 227                                 return new ld::passes::stubs::arm64::KextStubAtom(*this, target);
 228                         else
 229                                 return new ld::passes::stubs::arm64::StubAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 230                         break;
 231 #endif
 232         }
 233         throw "unsupported arch for stub";
 234 }
 235
 236
 237 void Pass::verifyNoResolverFunctions(ld::Internal& state)
 238 {
 239         for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 240                 ld::Internal::FinalSection* sect = *sit;
 241                 for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
 242                         const ld::Atom* atom = *ait;
 243                         if ( atom->contentType() == ld::Atom::typeResolver )
 244                                 throwf("resolver function '%s' not supported in type of output", atom->name());
 245                 }
 246         }
 247 }
 248
 249 void Pass::process(ld::Internal& state)
 250 {
 251         switch ( _options.outputKind() ) {
 252                 case Options::kObjectFile:
 253                         // these kinds don't use stubs and can have resolver functions
 254                         return;
 255                 case Options::kStaticExecutable:
 256                 case Options::kPreload:
 257                 case Options::kDyld:
 258                         // these kinds don't use stubs and cannot have resolver functions
 259                         verifyNoResolverFunctions(state);
 260                         return;
 261                 case Options::kDynamicLibrary:
 262                         // uses stubs and can have resolver functions
 263                         break;
 264                 case Options::kKextBundle:
 265                         verifyNoResolverFunctions(state);
 266                         // if kext don't use stubs, don't do this pass
 267                         if ( !_options.kextsUseStubs() )
 268                                 return;
 269                         break;
 270                 case Options::kDynamicExecutable:
 271                 case Options::kDynamicBundle:
 272                         // these kinds do use stubs and cannot have resolver functions
 273                         verifyNoResolverFunctions(state);
 274                         break;
 275         }
 276
 277         // walk all atoms and fixups looking for stubable references
 278         // don't create stubs inline because that could invalidate the sections iterator
 279         std::vector<const ld::Atom*> atomsCallingStubs;
 280         std::map<const ld::Atom*,ld::Atom*> stubFor;
 281         std::map<const ld::Atom*,bool>          weakImportMap;
 282         atomsCallingStubs.reserve(128);
 283         uint64_t codeSize = 0;
 284         for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 285                 ld::Internal::FinalSection* sect = *sit;
 286                 for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
 287                         const ld::Atom* atom = *ait;
 288                         codeSize += atom->size();
 289                         bool atomNeedsStub = false;
 290                         for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
 291                                 const ld::Atom* stubableTargetOfFixup = stubableFixup(fit, state);
 292                                 if ( stubableTargetOfFixup != NULL ) {
 293                                         if ( !atomNeedsStub ) {
 294                                                 atomsCallingStubs.push_back(atom);
 295                                                 atomNeedsStub = true;
 296                                         }
 297                                         stubFor[stubableTargetOfFixup] = NULL;
 298                                         // record weak_import attribute
 299                                         std::map<const ld::Atom*,bool>::iterator pos = weakImportMap.find(stubableTargetOfFixup);
 300                                         if ( pos == weakImportMap.end() ) {
 301                                                 // target not in weakImportMap, so add
 302                                                 weakImportMap[stubableTargetOfFixup] = fit->weakImport;
 303                                         }
 304                                         else {
 305                                                 // target in weakImportMap, check for weakness mismatch
 306                                                 if ( pos->second != fit->weakImport ) {
 307                                                         // found mismatch
 308                                                         switch ( _options.weakReferenceMismatchTreatment() ) {
 309                                                                 case Options::kWeakReferenceMismatchError:
 310                                                                         throwf("mismatching weak references for symbol: %s", stubableTargetOfFixup->name());
 311                                                                 case Options::kWeakReferenceMismatchWeak:
 312                                                                         pos->second = true;
 313                                                                         break;
 314                                                                 case Options::kWeakReferenceMismatchNonWeak:
 315                                                                         pos->second = false;
 316                                                                         break;
 317                                                         }
 318                                                 }
 319                                         }
 320                                 }
 321                         }
 322                         // all resolver functions must have a corresponding stub
 323                         if ( atom->contentType() == ld::Atom::typeResolver ) {
 324                                 if ( _options.outputKind() != Options::kDynamicLibrary )
 325                                         throwf("resolver functions (%s) can only be used in dylibs", atom->name());
 326                                 if ( !_options.makeCompressedDyldInfo() ) {
 327                                         if ( _options.architecture() == CPU_TYPE_ARM )
 328                                                 throwf("resolver functions (%s) can only be used when targeting iOS 4.2 or later", atom->name());
 329                                         else
 330                                                 throwf("resolver functions (%s) can only be used when targeting Mac OS X 10.6 or later", atom->name());
 331                                 }
 332                                 stubFor[atom] = NULL;
 333                         }
 334                 }
 335         }
 336
 337         const bool needStubForMain = _options.needsEntryPointLoadCommand()
 338                                                                 && (state.entryPoint != NULL)
 339                                                                 && (state.entryPoint->definition() == ld::Atom::definitionProxy);
 340         if ( needStubForMain ) {
 341                 // _main not found in any .o files.  Currently have proxy to dylib
 342                 // Add to map, so that a stub will be made
 343                 stubFor[state.entryPoint] = NULL;
 344         }
 345
 346         // short circuit if no stubs needed
 347         _internal = &state;
 348         _stubCount = stubFor.size();
 349         if ( _stubCount == 0 )
 350                 return;
 351
 352         // <rdar://problem/8553283> lazily check for helper
 353         if ( !_options.makeCompressedDyldInfo() && (state.classicBindingHelper == NULL) && (_options.outputKind() != Options::kKextBundle) )
 354                 throw "symbol dyld_stub_binding_helper not found, normally in crt1.o/dylib1.o/bundle1.o";
 355
 356         // disable arm close stubs in some cases
 357         if ( _architecture == CPU_TYPE_ARM ) {
 358         if ( codeSize > 4*1024*1024 )
 359             _largeText = true;
 360         else {
 361             for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 362                 ld::Internal::FinalSection* sect = *sit;
 363                 if ( sect->type() == ld::Section::typeMachHeader )
 364                     continue;
 365                 if ( strcmp(sect->segmentName(), "__TEXT") == 0) {
 366                     for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
 367                         const ld::Atom* atom = *ait;
 368                         if ( atom->alignment().powerOf2 > 10 ) {
 369                             // overaligned section means might not be able to keep closestubs sect pushed to end of __TEXT
 370                             //warning("alignment 1<<%d in atom %s in section %s disables close stubs optimization",
 371                             //        atom->alignment().powerOf2, atom->name(), sect->segmentName());
 372                             _largeText = true;
 373                             break;
 374                         }
 375                     }
 376                 }
 377             }
 378         }
 379     }
 380
 381         // make stub atoms
 382         for (std::map<const ld::Atom*,ld::Atom*>::iterator it = stubFor.begin(); it != stubFor.end(); ++it) {
 383                 it->second = makeStub(*it->first, weakImportMap[it->first]);
 384         }
 385
 386         // updated atoms to use stubs
 387         for (std::vector<const ld::Atom*>::iterator it=atomsCallingStubs.begin(); it != atomsCallingStubs.end(); ++it) {
 388                 const ld::Atom* atom = *it;
 389                 for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
 390                         const ld::Atom* stubableTargetOfFixup = stubableFixup(fit, state);
 391                         if ( stubableTargetOfFixup != NULL ) {
 392                                 ld::Atom* stub = stubFor[stubableTargetOfFixup];
 393                                 assert(stub != NULL && "stub not created");
 394                                 fit->binding = ld::Fixup::bindingDirectlyBound;
 395                                 fit->u.target = stub;
 396                         }
 397                 }
 398         }
 399
 400         // switch entry point from proxy to stub
 401         if ( needStubForMain ) {
 402                 const ld::Atom* mainStub = stubFor[state.entryPoint];
 403                 assert(mainStub != NULL);
 404                 state.entryPoint = mainStub;
 405         }
 406
 407         // sort new atoms so links are consistent
 408         for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 409                 ld::Internal::FinalSection* sect = *sit;
 410                 switch ( sect->type() ) {
 411                         case ld::Section::typeStubHelper:
 412                         case ld::Section::typeStub:
 413                         case ld::Section::typeStubClose:
 414                         case ld::Section::typeLazyPointer:
 415                         case ld::Section::typeLazyPointerClose:
 416                                 std::sort(sect->atoms.begin(), sect->atoms.end(), AtomByNameSorter());
 417                                 break;
 418                         default:
 419                                 break;
 420                 }
 421         }
 422
 423 }
 424
 425
 426 void doPass(const Options& opts, ld::Internal& internal)
 427 {
 428         Pass  pass(opts);
 429         pass.process(internal);
 430 }
 431
 432
 433
 434 } // namespace stubs
 435 } // namespace passes
 436 } // namespace ld
 437