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