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                                                 // don't make stubs for auto-hide symbols
 140                                                 if ( target->autoHide() && (!_options.hasExportMaskList() || !_options.shouldExport(target->name())) )
 141                                                         return NULL;
 142                                                 return target;
 143                                         }
 144                                         // create stub if target is interposable
 145                                         if ( _options.interposable(target->name()) )
 146                                                 return target;
 147                                         if ( _flatNamespace ) {
 148                                                 // flat namespace does not indirect calls within main exectuables
 149                                                 if ( _options.outputKind() == Options::kDynamicExecutable )
 150                                                         return NULL;
 151                                                 // create stub if target is global and building -flat dylib or bundle
 152                                                 return target;
 153                                         }
 154                                 }
 155                                 break;
 156                         default:
 157                                 if ( target->contentType() == ld::Atom::typeResolver ) {
 158                                         // any pointer to a resolver needs to change to pointer to stub
 159                                         return target;
 160                                 }
 161                                 break;
 162                 }
 163         }
 164         return NULL;
 165 }
 166
 167
 168
 169 ld::Atom* Pass::makeStub(const ld::Atom& target, bool weakImport)
 170 {
 171         //fprintf(stderr, "makeStub(target=%p %s in sect %s, def=%d)\n", &target, target.name(), target.section().sectionName(), target.definition());
 172         bool stubToGlobalWeakDef = ( (target.combine() == ld::Atom::combineByName) &&
 173                                                                  (((target.definition() == ld::Atom::definitionRegular) && (target.scope() == ld::Atom::scopeGlobal))
 174                                                                   || (target.definition() == ld::Atom::definitionProxy)) );
 175
 176         bool forLazyDylib = false;
 177         const ld::dylib::File* dylib = dynamic_cast<const ld::dylib::File*>(target.file());
 178         if ( (dylib != NULL) && dylib->willBeLazyLoadedDylib() )
 179                 forLazyDylib = true;
 180         bool stubToResolver = (target.contentType() == ld::Atom::typeResolver);
 181 #if SUPPORT_ARCH_arm_any || SUPPORT_ARCH_arm64
 182         bool usingDataConst =  _options.useDataConstSegment();
 183 #endif
 184
 185         if ( usingCompressedLINKEDIT() && !forLazyDylib ) {
 186                 if ( _internal->compressedFastBinderProxy == NULL )
 187                         throwf("symbol dyld_stub_binder not found (normally in libSystem.dylib).  Needed to perform lazy binding to function %s", target.name());
 188         }
 189
 190         switch ( _architecture ) {
 191 #if SUPPORT_ARCH_i386
 192                 case CPU_TYPE_I386:
 193                         if ( usingCompressedLINKEDIT() && !forLazyDylib )
 194                                 return new ld::passes::stubs::x86::StubAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 195                         else
 196                                 return new ld::passes::stubs::x86::classic::StubAtom(*this, target, forLazyDylib, weakImport);
 197                         break;
 198 #endif
 199 #if SUPPORT_ARCH_x86_64
 200                 case CPU_TYPE_X86_64:
 201                         if ( (_options.outputKind() == Options::kKextBundle) && _options.kextsUseStubs() )
 202                                 return new ld::passes::stubs::x86_64::KextStubAtom(*this, target);
 203                         else if ( usingCompressedLINKEDIT() && !forLazyDylib )
 204                                 return new ld::passes::stubs::x86_64::StubAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 205                         else
 206                                 return new ld::passes::stubs::x86_64::classic::StubAtom(*this, target, forLazyDylib, weakImport);
 207                         break;
 208 #endif
 209 #if SUPPORT_ARCH_arm_any
 210                 case CPU_TYPE_ARM:
 211                         if ( (_options.outputKind() == Options::kKextBundle) && _options.kextsUseStubs() ) {
 212                                 // if text relocs are not allows in kext bundles, then linker must create a stub
 213                                 return new ld::passes::stubs::arm::StubPICKextAtom(*this, target);
 214                         }
 215                         else if ( usingCompressedLINKEDIT() && !forLazyDylib ) {
 216                                 if ( (_stubCount < 900) && !_mightBeInSharedRegion && !_largeText && !_options.makeEncryptable() )
 217                                         return new ld::passes::stubs::arm::StubCloseAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 218                                 else if ( _pic )
 219                                         return new ld::passes::stubs::arm::StubPICAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport, usingDataConst);
 220                                 else
 221                                         return new ld::passes::stubs::arm::StubNoPICAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 222                         }
 223                         else {
 224                                 if ( _pic )
 225                                         return new ld::passes::stubs::arm::classic::StubPICAtom(*this, target, forLazyDylib, weakImport);
 226                                 else
 227                                         return new ld::passes::stubs::arm::classic::StubNoPICAtom(*this, target, forLazyDylib, weakImport);
 228                         }
 229                         break;
 230 #endif
 231 #if SUPPORT_ARCH_arm64
 232                 case CPU_TYPE_ARM64:
 233                         if ( (_options.outputKind() == Options::kKextBundle) && _options.kextsUseStubs() )
 234                                 return new ld::passes::stubs::arm64::KextStubAtom(*this, target);
 235                         else
 236                                 return new ld::passes::stubs::arm64::StubAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport, usingDataConst);
 237                         break;
 238 #endif
 239         }
 240         throw "unsupported arch for stub";
 241 }
 242
 243
 244 void Pass::verifyNoResolverFunctions(ld::Internal& state)
 245 {
 246         for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 247                 ld::Internal::FinalSection* sect = *sit;
 248                 for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
 249                         const ld::Atom* atom = *ait;
 250                         if ( atom->contentType() == ld::Atom::typeResolver )
 251                                 throwf("resolver function '%s' not supported in type of output", atom->name());
 252                 }
 253         }
 254 }
 255
 256 void Pass::process(ld::Internal& state)
 257 {
 258         switch ( _options.outputKind() ) {
 259                 case Options::kObjectFile:
 260                         // these kinds don't use stubs and can have resolver functions
 261                         return;
 262                 case Options::kStaticExecutable:
 263                 case Options::kPreload:
 264                 case Options::kDyld:
 265                         // these kinds don't use stubs and cannot have resolver functions
 266                         verifyNoResolverFunctions(state);
 267                         return;
 268                 case Options::kDynamicLibrary:
 269                         // uses stubs and can have resolver functions
 270                         break;
 271                 case Options::kKextBundle:
 272                         verifyNoResolverFunctions(state);
 273                         // if kext don't use stubs, don't do this pass
 274                         if ( !_options.kextsUseStubs() )
 275                                 return;
 276                         break;
 277                 case Options::kDynamicExecutable:
 278                 case Options::kDynamicBundle:
 279                         // these kinds do use stubs and cannot have resolver functions
 280                         verifyNoResolverFunctions(state);
 281                         break;
 282         }
 283
 284         // walk all atoms and fixups looking for stubable references
 285         // don't create stubs inline because that could invalidate the sections iterator
 286         std::vector<const ld::Atom*> atomsCallingStubs;
 287         std::map<const ld::Atom*,ld::Atom*> stubFor;
 288         std::map<const ld::Atom*,bool>          weakImportMap;
 289         atomsCallingStubs.reserve(128);
 290         uint64_t codeSize = 0;
 291         for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 292                 ld::Internal::FinalSection* sect = *sit;
 293                 for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
 294                         const ld::Atom* atom = *ait;
 295                         codeSize += atom->size();
 296                         bool atomNeedsStub = false;
 297                         for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
 298                                 const ld::Atom* stubableTargetOfFixup = stubableFixup(fit, state);
 299                                 if ( stubableTargetOfFixup != NULL ) {
 300                                         if ( !atomNeedsStub ) {
 301                                                 atomsCallingStubs.push_back(atom);
 302                                                 atomNeedsStub = true;
 303                                         }
 304                                         stubFor[stubableTargetOfFixup] = NULL;
 305                                         // record weak_import attribute
 306                                         std::map<const ld::Atom*,bool>::iterator pos = weakImportMap.find(stubableTargetOfFixup);
 307                                         if ( pos == weakImportMap.end() ) {
 308                                                 // target not in weakImportMap, so add
 309                                                 weakImportMap[stubableTargetOfFixup] = fit->weakImport;
 310                                         }
 311                                         else {
 312                                                 // target in weakImportMap, check for weakness mismatch
 313                                                 if ( pos->second != fit->weakImport ) {
 314                                                         // found mismatch
 315                                                         switch ( _options.weakReferenceMismatchTreatment() ) {
 316                                                                 case Options::kWeakReferenceMismatchError:
 317                                                                         throwf("mismatching weak references for symbol: %s", stubableTargetOfFixup->name());
 318                                                                 case Options::kWeakReferenceMismatchWeak:
 319                                                                         pos->second = true;
 320                                                                         break;
 321                                                                 case Options::kWeakReferenceMismatchNonWeak:
 322                                                                         pos->second = false;
 323                                                                         break;
 324                                                         }
 325                                                 }
 326                                         }
 327                                 }
 328                         }
 329                         // all resolver functions must have a corresponding stub
 330                         if ( atom->contentType() == ld::Atom::typeResolver ) {
 331                                 if ( _options.outputKind() != Options::kDynamicLibrary )
 332                                         throwf("resolver functions (%s) can only be used in dylibs", atom->name());
 333                                 if ( !_options.makeCompressedDyldInfo() ) {
 334                                         if ( _options.architecture() == CPU_TYPE_ARM )
 335                                                 throwf("resolver functions (%s) can only be used when targeting iOS 4.2 or later", atom->name());
 336                                         else
 337                                                 throwf("resolver functions (%s) can only be used when targeting Mac OS X 10.6 or later", atom->name());
 338                                 }
 339                                 stubFor[atom] = NULL;
 340                         }
 341                 }
 342         }
 343
 344         const bool needStubForMain = _options.needsEntryPointLoadCommand()
 345                                                                 && (state.entryPoint != NULL)
 346                                                                 && (state.entryPoint->definition() == ld::Atom::definitionProxy);
 347         if ( needStubForMain ) {
 348                 // _main not found in any .o files.  Currently have proxy to dylib
 349                 // Add to map, so that a stub will be made
 350                 stubFor[state.entryPoint] = NULL;
 351         }
 352
 353         // short circuit if no stubs needed
 354         _internal = &state;
 355         _stubCount = stubFor.size();
 356         if ( _stubCount == 0 )
 357                 return;
 358
 359         // <rdar://problem/8553283> lazily check for helper
 360         if ( !_options.makeCompressedDyldInfo() && (state.classicBindingHelper == NULL) && (_options.outputKind() != Options::kKextBundle) )
 361                 throw "symbol dyld_stub_binding_helper not found, normally in crt1.o/dylib1.o/bundle1.o";
 362
 363         // disable arm close stubs in some cases
 364         if ( _architecture == CPU_TYPE_ARM ) {
 365         if ( codeSize > 4*1024*1024 )
 366             _largeText = true;
 367         else {
 368             for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 369                 ld::Internal::FinalSection* sect = *sit;
 370                 if ( sect->type() == ld::Section::typeMachHeader )
 371                     continue;
 372                 if ( strcmp(sect->segmentName(), "__TEXT") == 0) {
 373                     for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
 374                         const ld::Atom* atom = *ait;
 375                         if ( atom->alignment().powerOf2 > 10 ) {
 376                             // overaligned section means might not be able to keep closestubs sect pushed to end of __TEXT
 377                             //warning("alignment 1<<%d in atom %s in section %s disables close stubs optimization",
 378                             //        atom->alignment().powerOf2, atom->name(), sect->segmentName());
 379                             _largeText = true;
 380                             break;
 381                         }
 382                     }
 383                 }
 384             }
 385         }
 386     }
 387
 388         // make stub atoms
 389         for (std::map<const ld::Atom*,ld::Atom*>::iterator it = stubFor.begin(); it != stubFor.end(); ++it) {
 390                 it->second = makeStub(*it->first, weakImportMap[it->first]);
 391         }
 392
 393         // updated atoms to use stubs
 394         for (std::vector<const ld::Atom*>::iterator it=atomsCallingStubs.begin(); it != atomsCallingStubs.end(); ++it) {
 395                 const ld::Atom* atom = *it;
 396                 for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
 397                         const ld::Atom* stubableTargetOfFixup = stubableFixup(fit, state);
 398                         if ( stubableTargetOfFixup != NULL ) {
 399                                 ld::Atom* stub = stubFor[stubableTargetOfFixup];
 400                                 assert(stub != NULL && "stub not created");
 401                                 fit->binding = ld::Fixup::bindingDirectlyBound;
 402                                 fit->u.target = stub;
 403                         }
 404                 }
 405         }
 406
 407         // switch entry point from proxy to stub
 408         if ( needStubForMain ) {
 409                 const ld::Atom* mainStub = stubFor[state.entryPoint];
 410                 assert(mainStub != NULL);
 411                 state.entryPoint = mainStub;
 412         }
 413
 414         // sort new atoms so links are consistent
 415         for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 416                 ld::Internal::FinalSection* sect = *sit;
 417                 switch ( sect->type() ) {
 418                         case ld::Section::typeStubHelper:
 419                         case ld::Section::typeStub:
 420                         case ld::Section::typeStubClose:
 421                         case ld::Section::typeLazyPointer:
 422                         case ld::Section::typeLazyPointerClose:
 423                                 std::sort(sect->atoms.begin(), sect->atoms.end(), AtomByNameSorter());
 424                                 break;
 425                         default:
 426                                 break;
 427                 }
 428         }
 429
 430 }
 431
 432
 433 void doPass(const Options& opts, ld::Internal& internal)
 434 {
 435         Pass  pass(opts);
 436         pass.process(internal);
 437 }
 438
 439
 440
 441 } // namespace stubs
 442 } // namespace passes
 443 } // namespace ld
 444