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 #include "stub_ppc_classic.hpp"
  93
  94
  95
  96 Pass::Pass(const Options& opts)
  97         :       compressedHelperHelper(NULL),
  98                 compressedImageCache(NULL),
  99                 compressedFastBinderPointer(NULL),
 100                 _options(opts),
 101                 _architecture(opts.architecture()),
 102                 _lazyDylibsInUuse(opts.usingLazyDylibLinking()),
 103                 _compressedLINKEDIT(opts.makeCompressedDyldInfo()),
 104                 _prebind(opts.prebind()),
 105                 _mightBeInSharedRegion(opts.sharedRegionEligible()),
 106                 _pic(opts.outputSlidable()),
 107                 _flatNamespace(opts.nameSpace() != Options::kTwoLevelNameSpace),
 108                 _internal(NULL), _stubCount(0), _largeText(false)
 109 {
 110
 111 }
 112
 113
 114 const ld::Atom* Pass::stubableFixup(const ld::Fixup* fixup, ld::Internal& state)
 115 {
 116         if ( fixup->binding == ld::Fixup::bindingsIndirectlyBound ) {
 117                 const ld::Atom* target = state.indirectBindingTable[fixup->u.bindingIndex];
 118                 switch ( fixup->kind ) {
 119                         case ld::Fixup::kindStoreTargetAddressPPCBranch24:
 120                         case ld::Fixup::kindStoreTargetAddressX86BranchPCRel32:
 121                         case ld::Fixup::kindStoreTargetAddressARMBranch24:
 122                         case ld::Fixup::kindStoreTargetAddressThumbBranch22:
 123                                 // create stub if target is in a dylib
 124                                 if ( target->definition() == ld::Atom::definitionProxy )
 125                                         return target;
 126                                 // use stub if target is a resolver function in same linkage unit
 127                                 if ( target->contentType() == ld::Atom::typeResolver )
 128                                         return target;
 129                                 if ( target->scope() == ld::Atom::scopeGlobal ) {
 130                                         // create stub if target is global weak definition in symbol table
 131                                         if ( (target->definition() == ld::Atom::definitionRegular)
 132                                                 && (target->combine() == ld::Atom::combineByName)
 133                                                 && ((target->symbolTableInclusion() == ld::Atom::symbolTableIn)
 134                                                  || (target->symbolTableInclusion() == ld::Atom::symbolTableInAndNeverStrip)) )
 135                                                 return target;
 136                                         // create stub if target is interposable
 137                                         if ( _options.interposable(target->name()) )
 138                                                 return target;
 139                                         if ( _flatNamespace ) {
 140                                                 // flat namespace does not indirect calls within main exectuables
 141                                                 if ( _options.outputKind() == Options::kDynamicExecutable )
 142                                                         return NULL;
 143                                                 // create stub if target is global and building -flat dylib or bundle
 144                                                 return target;
 145                                         }
 146                                 }
 147                                 break;
 148                         default:
 149                                 if ( target->contentType() == ld::Atom::typeResolver ) {
 150                                         // any pointer to a resolver needs to change to pointer to stub
 151                                         return target;
 152                                 }
 153                                 break;
 154                 }
 155         }
 156         return NULL;
 157 }
 158
 159
 160
 161 ld::Atom* Pass::makeStub(const ld::Atom& target, bool weakImport)
 162 {
 163         //fprintf(stderr, "makeStub(target=%p %s in sect %s)\n", &target, target.name(), target.section().sectionName());
 164         bool stubToGlobalWeakDef = ( (target.scope() == ld::Atom::scopeGlobal)
 165                                                                 && (target.definition() == ld::Atom::definitionRegular)
 166                                                                 && (target.combine() == ld::Atom::combineByName) );
 167
 168         bool forLazyDylib = false;
 169         const ld::dylib::File* dylib = dynamic_cast<const ld::dylib::File*>(target.file());
 170         if ( (dylib != NULL) && dylib->willBeLazyLoadedDylib() )
 171                 forLazyDylib = true;
 172         bool stubToResolver = (target.contentType() == ld::Atom::typeResolver);
 173
 174         if ( usingCompressedLINKEDIT() && !forLazyDylib ) {
 175                 if ( _internal->compressedFastBinderProxy == NULL )
 176                         throwf("symbol dyld_stub_binder not found (normally in libSystem.dylib).  Needed to perform lazy binding to function %s", target.name());
 177         }
 178
 179         switch ( _architecture ) {
 180                 case CPU_TYPE_POWERPC:
 181                         if ( _pic )
 182                                 return new ld::passes::stubs::ppc::classic::StubPICAtom(*this, target, forLazyDylib, false, weakImport);
 183                         else
 184                                 return new ld::passes::stubs::ppc::classic::StubNoPICAtom(*this, target, forLazyDylib, false, weakImport);
 185                         break;
 186                 case CPU_TYPE_POWERPC64:
 187                         return new ld::passes::stubs::ppc::classic::StubPICAtom(*this, target, forLazyDylib, true, weakImport);
 188                         break;
 189                 case CPU_TYPE_I386:
 190                         if ( usingCompressedLINKEDIT() && !forLazyDylib )
 191                                 return new ld::passes::stubs::x86::StubAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 192                         else
 193                                 return new ld::passes::stubs::x86::classic::StubAtom(*this, target, forLazyDylib, weakImport);
 194                         break;
 195                 case CPU_TYPE_X86_64:
 196                         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                 case CPU_TYPE_ARM:
 202                         if ( usingCompressedLINKEDIT() && !forLazyDylib ) {
 203                                 if ( (_stubCount < 900) && !_mightBeInSharedRegion && !_largeText )
 204                                         return new ld::passes::stubs::arm::StubCloseAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 205                                 else if ( _pic )
 206                                         return new ld::passes::stubs::arm::StubPICAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 207                                 else
 208                                         return new ld::passes::stubs::arm::StubNoPICAtom(*this, target, stubToGlobalWeakDef, stubToResolver, weakImport);
 209                         }
 210                         else {
 211                                 if ( _pic )
 212                                         return new ld::passes::stubs::arm::classic::StubPICAtom(*this, target, forLazyDylib, weakImport);
 213                                 else
 214                                         return new ld::passes::stubs::arm::classic::StubNoPICAtom(*this, target, forLazyDylib, weakImport);
 215                         }
 216                         break;
 217         }
 218         throw "unsupported arch for stub";
 219 }
 220
 221
 222 void Pass::verifyNoResolverFunctions(ld::Internal& state)
 223 {
 224         for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 225                 ld::Internal::FinalSection* sect = *sit;
 226                 for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
 227                         const ld::Atom* atom = *ait;
 228                         if ( atom->contentType() == ld::Atom::typeResolver )
 229                                 throwf("resolver function '%s' not supported in type of output", atom->name());
 230                 }
 231         }
 232 }
 233
 234 void Pass::process(ld::Internal& state)
 235 {
 236         switch ( _options.outputKind() ) {
 237                 case Options::kObjectFile:
 238                         // these kinds don't use stubs and can have resolver functions
 239                         return;
 240                 case Options::kKextBundle:
 241                 case Options::kStaticExecutable:
 242                 case Options::kPreload:
 243                 case Options::kDyld:
 244                         // these kinds don't use stubs and cannot have resolver functions
 245                         verifyNoResolverFunctions(state);
 246                         return;
 247                 case Options::kDynamicLibrary:
 248                         // uses stubs and can have resolver functions
 249                         break;
 250                 case Options::kDynamicExecutable:
 251                 case Options::kDynamicBundle:
 252                         // these kinds do use stubs and cannot have resolver functions
 253                         verifyNoResolverFunctions(state);
 254                         break;
 255         }
 256
 257         // walk all atoms and fixups looking for stubable references
 258         // don't create stubs inline because that could invalidate the sections iterator
 259         std::vector<const ld::Atom*> atomsCallingStubs;
 260         std::map<const ld::Atom*,ld::Atom*> stubFor;
 261         std::map<const ld::Atom*,bool>          weakImportMap;
 262         atomsCallingStubs.reserve(128);
 263         uint64_t codeSize = 0;
 264         for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 265                 ld::Internal::FinalSection* sect = *sit;
 266                 for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
 267                         const ld::Atom* atom = *ait;
 268                         codeSize += atom->size();
 269                         bool atomNeedsStub = false;
 270                         for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
 271                                 const ld::Atom* stubableTargetOfFixup = stubableFixup(fit, state);
 272                                 if ( stubableTargetOfFixup != NULL ) {
 273                                         if ( !atomNeedsStub ) {
 274                                                 atomsCallingStubs.push_back(atom);
 275                                                 atomNeedsStub = true;
 276                                         }
 277                                         stubFor[stubableTargetOfFixup] = NULL;
 278                                         // record weak_import attribute
 279                                         std::map<const ld::Atom*,bool>::iterator pos = weakImportMap.find(stubableTargetOfFixup);
 280                                         if ( pos == weakImportMap.end() ) {
 281                                                 // target not in weakImportMap, so add
 282                                                 weakImportMap[stubableTargetOfFixup] = fit->weakImport;
 283                                         }
 284                                         else {
 285                                                 // target in weakImportMap, check for weakness mismatch
 286                                                 if ( pos->second != fit->weakImport ) {
 287                                                         // found mismatch
 288                                                         switch ( _options.weakReferenceMismatchTreatment() ) {
 289                                                                 case Options::kWeakReferenceMismatchError:
 290                                                                         throwf("mismatching weak references for symbol: %s", stubableTargetOfFixup->name());
 291                                                                 case Options::kWeakReferenceMismatchWeak:
 292                                                                         pos->second = true;
 293                                                                         break;
 294                                                                 case Options::kWeakReferenceMismatchNonWeak:
 295                                                                         pos->second = false;
 296                                                                         break;
 297                                                         }
 298                                                 }
 299                                         }
 300                                 }
 301                         }
 302                         // all resolver functions must have a corresponding stub
 303                         if ( atom->contentType() == ld::Atom::typeResolver ) {
 304                                 if ( _options.outputKind() != Options::kDynamicLibrary )
 305                                         throwf("resolver functions (%s) can only be used in dylibs", atom->name());
 306                                 if ( !_options.makeCompressedDyldInfo() ) {
 307                                         if ( _options.architecture() == CPU_TYPE_POWERPC )
 308                                                 throwf("resolver functions (%s) not supported for PowerPC", atom->name());
 309                                         else if ( _options.architecture() == CPU_TYPE_ARM )
 310                                                 throwf("resolver functions (%s) can only be used when targeting iOS 4.2 or later", atom->name());
 311                                         else
 312                                                 throwf("resolver functions (%s) can only be used when targeting Mac OS X 10.6 or later", atom->name());
 313                                 }
 314                                 stubFor[atom] = NULL;
 315                         }
 316                 }
 317         }
 318
 319         // short circuit if no stubs needed
 320         _internal = &state;
 321         _stubCount = stubFor.size();
 322         if ( _stubCount == 0 )
 323                 return;
 324
 325         // <rdar://problem/8553283> lazily check for helper
 326         if ( !_options.makeCompressedDyldInfo() && (state.classicBindingHelper == NULL) )
 327                 throw "symbol dyld_stub_binding_helper not found, normally in crt1.o/dylib1.o/bundle1.o";
 328
 329         // disable arm close stubs in some cases
 330         if ( _architecture == CPU_TYPE_ARM ) {
 331         if ( codeSize > 4*1024*1024 )
 332             _largeText = true;
 333         else {
 334             for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 335                 ld::Internal::FinalSection* sect = *sit;
 336                 if ( sect->type() == ld::Section::typeMachHeader )
 337                     continue;
 338                 if ( strcmp(sect->segmentName(), "__TEXT") == 0) {
 339                     for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
 340                         const ld::Atom* atom = *ait;
 341                         if ( atom->alignment().powerOf2 > 10 ) {
 342                             // overaligned section means might not be able to keep closestubs sect pushed to end of __TEXT
 343                             //warning("alignment 1<<%d in atom %s in section %s disables close stubs optimization",
 344                             //        atom->alignment().powerOf2, atom->name(), sect->segmentName());
 345                             _largeText = true;
 346                             break;
 347                         }
 348                     }
 349                 }
 350             }
 351         }
 352     }
 353
 354         // make stub atoms
 355         for (std::map<const ld::Atom*,ld::Atom*>::iterator it = stubFor.begin(); it != stubFor.end(); ++it) {
 356                 it->second = makeStub(*it->first, weakImportMap[it->first]);
 357         }
 358
 359         // updated atoms to use stubs
 360         for (std::vector<const ld::Atom*>::iterator it=atomsCallingStubs.begin(); it != atomsCallingStubs.end(); ++it) {
 361                 const ld::Atom* atom = *it;
 362                 for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
 363                         const ld::Atom* stubableTargetOfFixup = stubableFixup(fit, state);
 364                         if ( stubableTargetOfFixup != NULL ) {
 365                                 ld::Atom* stub = stubFor[stubableTargetOfFixup];
 366                                 assert(stub != NULL && "stub not created");
 367                                 fit->binding = ld::Fixup::bindingDirectlyBound;
 368                                 fit->u.target = stub;
 369                         }
 370                 }
 371         }
 372
 373         // sort new atoms so links are consistent
 374         for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
 375                 ld::Internal::FinalSection* sect = *sit;
 376                 switch ( sect->type() ) {
 377                         case ld::Section::typeStubHelper:
 378                         case ld::Section::typeStub:
 379                         case ld::Section::typeStubClose:
 380                         case ld::Section::typeLazyPointer:
 381                         case ld::Section::typeLazyPointerClose:
 382                                 std::sort(sect->atoms.begin(), sect->atoms.end(), AtomByNameSorter());
 383                                 break;
 384                         default:
 385                                 break;
 386                 }
 387         }
 388
 389 }
 390
 391
 392 void doPass(const Options& opts, ld::Internal& internal)
 393 {
 394         Pass  pass(opts);
 395         pass.process(internal);
 396 }
 397
 398
 399
 400 } // namespace stubs
 401 } // namespace passes
 402 } // namespace ld
 403