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, def=%d)\n", &target, target.name(), target.section().sectionName(), target.definition());
 168         bool stubToGlobalWeakDef = ( (target.combine() == ld::Atom::combineByName) &&
 169                                                                  (((target.definition() == ld::Atom::definitionRegular) && (target.scope() == ld::Atom::scopeGlobal))
 170                                                                   || (target.definition() == ld::Atom::definitionProxy)) );
 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         bool usingDataConst =  _options.useDataConstSegment();
 178
 179         if ( usingCompressedLINKEDIT() && !forLazyDylib ) {
 180                 if ( _internal->compressedFastBinderProxy == NULL )
 181                         throwf("symbol dyld_stub_binder not found (normally in libSystem.dylib).  Needed to perform lazy binding to function %s", target.name());
 182         }
 183
 184         switch ( _architecture ) {
 185 #if SUPPORT_ARCH_i386
 186                 case CPU_TYPE_I386:
 187                         if ( usingCompressedLINKEDIT() && !forLazyDylib )
 188                                 return new ld::passes::stubs::x86::StubAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 189                         else
 190                                 return new ld::passes::stubs::x86::classic::StubAtom(*this, target, forLazyDylib, weakImport);
 191                         break;
 192 #endif
 193 #if SUPPORT_ARCH_x86_64
 194                 case CPU_TYPE_X86_64:
 195                         if ( (_options.outputKind() == Options::kKextBundle) && _options.kextsUseStubs() )
 196                                 return new ld::passes::stubs::x86_64::KextStubAtom(*this, target);
 197                         else if ( usingCompressedLINKEDIT() && !forLazyDylib )
 198                                 return new ld::passes::stubs::x86_64::StubAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 199                         else
 200                                 return new ld::passes::stubs::x86_64::classic::StubAtom(*this, target, forLazyDylib, weakImport);
 201                         break;
 202 #endif
 203 #if SUPPORT_ARCH_arm_any
 204                 case CPU_TYPE_ARM:
 205                         if ( (_options.outputKind() == Options::kKextBundle) && _options.kextsUseStubs() ) {
 206                                 // if text relocs are not allows in kext bundles, then linker must create a stub
 207                                 return new ld::passes::stubs::arm::StubPICKextAtom(*this, target);
 208                         }
 209                         else if ( usingCompressedLINKEDIT() && !forLazyDylib ) {
 210                                 if ( (_stubCount < 900) && !_mightBeInSharedRegion && !_largeText )
 211                                         return new ld::passes::stubs::arm::StubCloseAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 212                                 else if ( _pic )
 213                                         return new ld::passes::stubs::arm::StubPICAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport, usingDataConst);
 214                                 else
 215                                         return new ld::passes::stubs::arm::StubNoPICAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 216                         }
 217                         else {
 218                                 if ( _pic )
 219                                         return new ld::passes::stubs::arm::classic::StubPICAtom(*this, target, forLazyDylib, weakImport);
 220                                 else
 221                                         return new ld::passes::stubs::arm::classic::StubNoPICAtom(*this, target, forLazyDylib, weakImport);
 222                         }
 223                         break;
 224 #endif
 225 #if SUPPORT_ARCH_arm64
 226                 case CPU_TYPE_ARM64:
 227                         if ( (_options.outputKind() == Options::kKextBundle) && _options.kextsUseStubs() )
 228                                 return new ld::passes::stubs::arm64::KextStubAtom(*this, target);
 229                         else
 230                                 return new ld::passes::stubs::arm64::StubAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport, usingDataConst);
 231                         break;
 232 #endif
 233         }
 234         throw "unsupported arch for stub";
 235 }
 236
 237
 238 void Pass::verifyNoResolverFunctions(ld::Internal& state)
 239 {
 240         for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 241                 ld::Internal::FinalSection* sect = *sit;
 242                 for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
 243                         const ld::Atom* atom = *ait;
 244                         if ( atom->contentType() == ld::Atom::typeResolver )
 245                                 throwf("resolver function '%s' not supported in type of output", atom->name());
 246                 }
 247         }
 248 }
 249
 250 void Pass::process(ld::Internal& state)
 251 {
 252         switch ( _options.outputKind() ) {
 253                 case Options::kObjectFile:
 254                         // these kinds don't use stubs and can have resolver functions
 255                         return;
 256                 case Options::kStaticExecutable:
 257                 case Options::kPreload:
 258                 case Options::kDyld:
 259                         // these kinds don't use stubs and cannot have resolver functions
 260                         verifyNoResolverFunctions(state);
 261                         return;
 262                 case Options::kDynamicLibrary:
 263                         // uses stubs and can have resolver functions
 264                         break;
 265                 case Options::kKextBundle:
 266                         verifyNoResolverFunctions(state);
 267                         // if kext don't use stubs, don't do this pass
 268                         if ( !_options.kextsUseStubs() )
 269                                 return;
 270                         break;
 271                 case Options::kDynamicExecutable:
 272                 case Options::kDynamicBundle:
 273                         // these kinds do use stubs and cannot have resolver functions
 274                         verifyNoResolverFunctions(state);
 275                         break;
 276         }
 277
 278         // walk all atoms and fixups looking for stubable references
 279         // don't create stubs inline because that could invalidate the sections iterator
 280         std::vector<const ld::Atom*> atomsCallingStubs;
 281         std::map<const ld::Atom*,ld::Atom*> stubFor;
 282         std::map<const ld::Atom*,bool>          weakImportMap;
 283         atomsCallingStubs.reserve(128);
 284         uint64_t codeSize = 0;
 285         for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 286                 ld::Internal::FinalSection* sect = *sit;
 287                 for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
 288                         const ld::Atom* atom = *ait;
 289                         codeSize += atom->size();
 290                         bool atomNeedsStub = false;
 291                         for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
 292                                 const ld::Atom* stubableTargetOfFixup = stubableFixup(fit, state);
 293                                 if ( stubableTargetOfFixup != NULL ) {
 294                                         if ( !atomNeedsStub ) {
 295                                                 atomsCallingStubs.push_back(atom);
 296                                                 atomNeedsStub = true;
 297                                         }
 298                                         stubFor[stubableTargetOfFixup] = NULL;
 299                                         // record weak_import attribute
 300                                         std::map<const ld::Atom*,bool>::iterator pos = weakImportMap.find(stubableTargetOfFixup);
 301                                         if ( pos == weakImportMap.end() ) {
 302                                                 // target not in weakImportMap, so add
 303                                                 weakImportMap[stubableTargetOfFixup] = fit->weakImport;
 304                                         }
 305                                         else {
 306                                                 // target in weakImportMap, check for weakness mismatch
 307                                                 if ( pos->second != fit->weakImport ) {
 308                                                         // found mismatch
 309                                                         switch ( _options.weakReferenceMismatchTreatment() ) {
 310                                                                 case Options::kWeakReferenceMismatchError:
 311                                                                         throwf("mismatching weak references for symbol: %s", stubableTargetOfFixup->name());
 312                                                                 case Options::kWeakReferenceMismatchWeak:
 313                                                                         pos->second = true;
 314                                                                         break;
 315                                                                 case Options::kWeakReferenceMismatchNonWeak:
 316                                                                         pos->second = false;
 317                                                                         break;
 318                                                         }
 319                                                 }
 320                                         }
 321                                 }
 322                         }
 323                         // all resolver functions must have a corresponding stub
 324                         if ( atom->contentType() == ld::Atom::typeResolver ) {
 325                                 if ( _options.outputKind() != Options::kDynamicLibrary )
 326                                         throwf("resolver functions (%s) can only be used in dylibs", atom->name());
 327                                 if ( !_options.makeCompressedDyldInfo() ) {
 328                                         if ( _options.architecture() == CPU_TYPE_ARM )
 329                                                 throwf("resolver functions (%s) can only be used when targeting iOS 4.2 or later", atom->name());
 330                                         else
 331                                                 throwf("resolver functions (%s) can only be used when targeting Mac OS X 10.6 or later", atom->name());
 332                                 }
 333                                 stubFor[atom] = NULL;
 334                         }
 335                 }
 336         }
 337
 338         const bool needStubForMain = _options.needsEntryPointLoadCommand()
 339                                                                 && (state.entryPoint != NULL)
 340                                                                 && (state.entryPoint->definition() == ld::Atom::definitionProxy);
 341         if ( needStubForMain ) {
 342                 // _main not found in any .o files.  Currently have proxy to dylib
 343                 // Add to map, so that a stub will be made
 344                 stubFor[state.entryPoint] = NULL;
 345         }
 346
 347         // short circuit if no stubs needed
 348         _internal = &state;
 349         _stubCount = stubFor.size();
 350         if ( _stubCount == 0 )
 351                 return;
 352
 353         // <rdar://problem/8553283> lazily check for helper
 354         if ( !_options.makeCompressedDyldInfo() && (state.classicBindingHelper == NULL) && (_options.outputKind() != Options::kKextBundle) )
 355                 throw "symbol dyld_stub_binding_helper not found, normally in crt1.o/dylib1.o/bundle1.o";
 356
 357         // disable arm close stubs in some cases
 358         if ( _architecture == CPU_TYPE_ARM ) {
 359         if ( codeSize > 4*1024*1024 )
 360             _largeText = true;
 361         else {
 362             for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 363                 ld::Internal::FinalSection* sect = *sit;
 364                 if ( sect->type() == ld::Section::typeMachHeader )
 365                     continue;
 366                 if ( strcmp(sect->segmentName(), "__TEXT") == 0) {
 367                     for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
 368                         const ld::Atom* atom = *ait;
 369                         if ( atom->alignment().powerOf2 > 10 ) {
 370                             // overaligned section means might not be able to keep closestubs sect pushed to end of __TEXT
 371                             //warning("alignment 1<<%d in atom %s in section %s disables close stubs optimization",
 372                             //        atom->alignment().powerOf2, atom->name(), sect->segmentName());
 373                             _largeText = true;
 374                             break;
 375                         }
 376                     }
 377                 }
 378             }
 379         }
 380     }
 381
 382         // make stub atoms
 383         for (std::map<const ld::Atom*,ld::Atom*>::iterator it = stubFor.begin(); it != stubFor.end(); ++it) {
 384                 it->second = makeStub(*it->first, weakImportMap[it->first]);
 385         }
 386
 387         // updated atoms to use stubs
 388         for (std::vector<const ld::Atom*>::iterator it=atomsCallingStubs.begin(); it != atomsCallingStubs.end(); ++it) {
 389                 const ld::Atom* atom = *it;
 390                 for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
 391                         const ld::Atom* stubableTargetOfFixup = stubableFixup(fit, state);
 392                         if ( stubableTargetOfFixup != NULL ) {
 393                                 ld::Atom* stub = stubFor[stubableTargetOfFixup];
 394                                 assert(stub != NULL && "stub not created");
 395                                 fit->binding = ld::Fixup::bindingDirectlyBound;
 396                                 fit->u.target = stub;
 397                         }
 398                 }
 399         }
 400
 401         // switch entry point from proxy to stub
 402         if ( needStubForMain ) {
 403                 const ld::Atom* mainStub = stubFor[state.entryPoint];
 404                 assert(mainStub != NULL);
 405                 state.entryPoint = mainStub;
 406         }
 407
 408         // sort new atoms so links are consistent
 409         for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 410                 ld::Internal::FinalSection* sect = *sit;
 411                 switch ( sect->type() ) {
 412                         case ld::Section::typeStubHelper:
 413                         case ld::Section::typeStub:
 414                         case ld::Section::typeStubClose:
 415                         case ld::Section::typeLazyPointer:
 416                         case ld::Section::typeLazyPointerClose:
 417                                 std::sort(sect->atoms.begin(), sect->atoms.end(), AtomByNameSorter());
 418                                 break;
 419                         default:
 420                                 break;
 421                 }
 422         }
 423
 424 }
 425
 426
 427 void doPass(const Options& opts, ld::Internal& internal)
 428 {
 429         Pass  pass(opts);
 430         pass.process(internal);
 431 }
 432
 433
 434
 435 } // namespace stubs
 436 } // namespace passes
 437 } // namespace ld
 438