ld64-134.9/src/ld/passes/tlvp.cpp

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  24
  25
  26 #include <stdint.h>
  27 #include <math.h>
  28 #include <unistd.h>
  29 #include <dlfcn.h>
  30
  31 #include <vector>
  32 #include <map>
  33 #include <ext/hash_map>
  34
  35 #include "ld.hpp"
  36 #include "tlvp.h"
  37
  38 namespace ld {
  39 namespace passes {
  40 namespace tlvp {
  41
  42 class File; // forward reference
  43
  44 class TLVEntryAtom : public ld::Atom {
  45 public:
  46                                                                                         TLVEntryAtom(ld::Internal& internal, const ld::Atom* target, bool weakImport)
  47                                 : ld::Atom(_s_section, ld::Atom::definitionRegular, ld::Atom::combineNever,
  48                                                         ld::Atom::scopeLinkageUnit, ld::Atom::typeNonLazyPointer,
  49                                                         symbolTableNotIn, false, false, false, ld::Atom::Alignment(3)),
  50                                 _fixup(0, ld::Fixup::k1of1, ld::Fixup::kindStoreTargetAddressLittleEndian64, target),
  51                                 _target(target)
  52                                         { _fixup.weakImport = weakImport; internal.addAtom(*this); }
  53
  54         virtual const ld::File*                                 file() const                                    { return NULL; }
  55         virtual const char*                                             name() const                                    { return _target->name(); }
  56         virtual uint64_t                                                size() const                                    { return 8; }
  57         virtual uint64_t                                                objectAddress() const                   { return 0; }
  58         virtual void                                                    copyRawContent(uint8_t buffer[]) const { }
  59         virtual void                                                    setScope(Scope)                                 { }
  60         virtual ld::Fixup::iterator                             fixupsBegin() const                             { return &_fixup; }
  61         virtual ld::Fixup::iterator                             fixupsEnd()     const                           { return &((ld::Fixup*)&_fixup)[1]; }
  62
  63 private:
  64         mutable ld::Fixup                                               _fixup;
  65         const ld::Atom*                                                 _target;
  66
  67         static ld::Section                                              _s_section;
  68 };
  69
  70 ld::Section TLVEntryAtom::_s_section("__DATA", "__thread_ptrs", ld::Section::typeTLVPointers);
  71
  72
  73 static bool optimizable(const Options& opts, const ld::Atom* targetOfTLV)
  74 {
  75         // cannot do LEA optimization if target is in another dylib
  76         if ( targetOfTLV->definition() == ld::Atom::definitionProxy )
  77                 return false;
  78         if ( targetOfTLV->scope() == ld::Atom::scopeGlobal ) {
  79                 // cannot do LEA optimization if target is weak exported symbol
  80                 if ( (targetOfTLV->definition() == ld::Atom::definitionRegular) && (targetOfTLV->combine() == ld::Atom::combineByName) )
  81                         return false;
  82                 // cannot do LEA optimization if target is interposable
  83                 if ( opts.interposable(targetOfTLV->name()) )
  84                         return false;
  85                 // cannot do LEA optimization for flat-namespace
  86                 if ( opts.nameSpace() != Options::kTwoLevelNameSpace )
  87                         return false;
  88         }
  89         return true;
  90 }
  91
  92 struct AtomByNameSorter
  93 {
  94          bool operator()(const ld::Atom* left, const ld::Atom* right)
  95          {
  96                   return (strcmp(left->name(), right->name()) < 0);
  97          }
  98 };
  99
 100 struct TlVReferenceCluster
 101 {
 102         const ld::Atom* targetOfTLV;
 103         ld::Fixup*              fixupWithTarget;
 104         ld::Fixup*              fixupWithTLVStore;
 105         bool                    optimizable;
 106 };
 107
 108 void doPass(const Options& opts, ld::Internal& internal)
 109 {
 110         const bool log = false;
 111
 112         // only make tlv section in final linked images
 113         if ( opts.outputKind() == Options::kObjectFile )
 114                 return;
 115
 116         // walk all atoms and fixups looking for TLV references and add them to list
 117         std::vector<TlVReferenceCluster>        references;
 118         for (std::vector<ld::Internal::FinalSection*>::iterator sit=internal.sections.begin(); sit != internal.sections.end(); ++sit) {
 119                 ld::Internal::FinalSection* sect = *sit;
 120                 for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin(); ait != sect->atoms.end(); ++ait) {
 121                         const ld::Atom* atom = *ait;
 122                         TlVReferenceCluster ref;
 123                         for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
 124                                 if ( fit->firstInCluster() ) {
 125                                         ref.targetOfTLV = NULL;
 126                                         ref.fixupWithTarget = NULL;
 127                                         ref.fixupWithTLVStore = NULL;
 128                                 }
 129                                 switch ( fit->binding ) {
 130                                         case ld::Fixup::bindingsIndirectlyBound:
 131                                                 ref.targetOfTLV = internal.indirectBindingTable[fit->u.bindingIndex];
 132                                                 ref.fixupWithTarget = fit;
 133                                                 break;
 134                                         case ld::Fixup::bindingDirectlyBound:
 135                                                 ref.targetOfTLV = fit->u.target;
 136                                                 ref.fixupWithTarget = fit;
 137                                                 break;
 138                     default:
 139                         break;
 140                                 }
 141                                 switch ( fit->kind ) {
 142                                         case ld::Fixup::kindStoreTargetAddressX86PCRel32TLVLoad:
 143                                         case ld::Fixup::kindStoreTargetAddressX86Abs32TLVLoad:
 144                                         case ld::Fixup::kindStoreX86PCRel32TLVLoad:
 145                                         case ld::Fixup::kindStoreX86Abs32TLVLoad:
 146                                                 ref.fixupWithTLVStore = fit;
 147                                                 break;
 148                                         default:
 149                                                 break;
 150                                 }
 151                                 if ( fit->lastInCluster() && (ref.fixupWithTLVStore != NULL) ) {
 152                                         ref.optimizable = optimizable(opts, ref.targetOfTLV);
 153                                         if (log) fprintf(stderr, "found reference to TLV at %s+0x%X to %s\n",
 154                                                                         atom->name(), ref.fixupWithTLVStore->offsetInAtom, ref.targetOfTLV->name());
 155                                         if ( ! opts.canUseThreadLocalVariables() ) {
 156                                                 throwf("targeted OS version does not support use of thread local variables in %s", atom->name());
 157                                         }
 158                                         references.push_back(ref);
 159                                 }
 160                         }
 161                 }
 162         }
 163
 164         // compute which TLV references will be weak_imports
 165         std::map<const ld::Atom*,bool>          weakImportMap;
 166         for(std::vector<TlVReferenceCluster>::iterator it=references.begin(); it != references.end(); ++it) {
 167                 if ( !it->optimizable ) {
 168                         // record weak_import attribute
 169                         std::map<const ld::Atom*,bool>::iterator pos = weakImportMap.find(it->targetOfTLV);
 170                         if ( pos == weakImportMap.end() ) {
 171                                 // target not in weakImportMap, so add
 172                                 weakImportMap[it->targetOfTLV] = it->fixupWithTarget->weakImport;
 173                         }
 174                         else {
 175                                 // target in weakImportMap, check for weakness mismatch
 176                                 if ( pos->second != it->fixupWithTarget->weakImport ) {
 177                                         // found mismatch
 178                                         switch ( opts.weakReferenceMismatchTreatment() ) {
 179                                                 case Options::kWeakReferenceMismatchError:
 180                                                         throwf("mismatching weak references for symbol: %s", it->targetOfTLV->name());
 181                                                 case Options::kWeakReferenceMismatchWeak:
 182                                                         pos->second = true;
 183                                                         break;
 184                                                 case Options::kWeakReferenceMismatchNonWeak:
 185                                                         pos->second = false;
 186                                                         break;
 187                                         }
 188                                 }
 189                         }
 190                 }
 191         }
 192
 193         // create TLV pointers for TLV references that cannot be optimized
 194         std::map<const ld::Atom*,ld::Atom*> variableToPointerMap;
 195         for(std::map<const ld::Atom*,bool>::iterator it=weakImportMap.begin(); it != weakImportMap.end(); ++it) {
 196                 std::map<const ld::Atom*,ld::Atom*>::iterator pos = variableToPointerMap.find(it->first);
 197                 if ( pos == variableToPointerMap.end() ) {
 198                         if (log) fprintf(stderr, "make TLV pointer for %s\n", it->first->name());
 199                         if ( it->first->contentType() != ld::Atom::typeTLV )
 200                                 throwf("illegal thread local variable reference to regular symbol %s", it->first->name());
 201                         TLVEntryAtom* tlvp = new TLVEntryAtom(internal, it->first, it->second);
 202                         variableToPointerMap[it->first] = tlvp;
 203                 }
 204         }
 205
 206         // sort new tvlp atoms so links are consistent
 207         for (std::vector<ld::Internal::FinalSection*>::iterator sit=internal.sections.begin(); sit != internal.sections.end(); ++sit) {
 208                 ld::Internal::FinalSection* sect = *sit;
 209                 if ( sect->type() == ld::Section::typeTLVPointers ) {
 210                         std::sort(sect->atoms.begin(), sect->atoms.end(), AtomByNameSorter());
 211                 }
 212         }
 213
 214         // update references to use TLV pointers or TLV object directly
 215         for(std::vector<TlVReferenceCluster>::iterator it=references.begin(); it != references.end(); ++it) {
 216                 if ( it->optimizable ) {
 217                         // change store to be LEA instead load (mov)
 218                         if (log) fprintf(stderr, "optimizing load of TLV to %s into an LEA\n", it->targetOfTLV->name());
 219                         it->fixupWithTLVStore->binding = ld::Fixup::bindingDirectlyBound;
 220                         it->fixupWithTLVStore->u.target = it->targetOfTLV;
 221                         switch ( it->fixupWithTLVStore->kind ) {
 222                                 case ld::Fixup::kindStoreTargetAddressX86PCRel32TLVLoad:
 223                                         it->fixupWithTLVStore->kind = ld::Fixup::kindStoreTargetAddressX86PCRel32TLVLoadNowLEA;
 224                                         break;
 225                                 case ld::Fixup::kindStoreTargetAddressX86Abs32TLVLoad:
 226                                         it->fixupWithTLVStore->kind = ld::Fixup::kindStoreTargetAddressX86Abs32TLVLoadNowLEA;
 227                                         break;
 228                                 case ld::Fixup::kindStoreX86PCRel32TLVLoad:
 229                                         it->fixupWithTLVStore->kind = ld::Fixup::kindStoreX86PCRel32TLVLoadNowLEA;
 230                                         break;
 231                                 case ld::Fixup::kindStoreX86Abs32TLVLoad:
 232                                         it->fixupWithTLVStore->kind = ld::Fixup::kindStoreX86Abs32TLVLoadNowLEA;
 233                                         break;
 234                                 default:
 235                                         assert(0 && "bad store kind for TLV optimization");
 236                         }
 237                 }
 238                 else {
 239                         // change target to be new TLV pointer atom
 240                         if (log) fprintf(stderr, "updating load of TLV to %s to load from TLV pointer\n", it->targetOfTLV->name());
 241                         const ld::Atom* tlvpAtom = variableToPointerMap[it->targetOfTLV];
 242                         assert(tlvpAtom != NULL);
 243                         it->fixupWithTarget->binding = ld::Fixup::bindingDirectlyBound;
 244                         it->fixupWithTarget->u.target = tlvpAtom;
 245                 }
 246         }
 247
 248
 249
 250         // alter tlv definitions to have an offset as third field
 251         for (std::vector<ld::Internal::FinalSection*>::iterator sit=internal.sections.begin(); sit != internal.sections.end(); ++sit) {
 252                 ld::Internal::FinalSection* sect = *sit;
 253                 if ( sect->type() != ld::Section::typeTLVDefs )
 254                         continue;
 255                 for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
 256                         const ld::Atom* atom = *ait;
 257                         for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
 258                                 if ( fit->offsetInAtom != 0 ) {
 259                                         assert(fit->binding == ld::Fixup::bindingDirectlyBound && "thread variable def contains pointer to global");
 260                                         switch( fit->u.target->contentType() ) {
 261                                                 case ld::Atom::typeTLVZeroFill:
 262                                                 case ld::Atom::typeTLVInitialValue:
 263                                                         switch ( fit->kind ) {
 264                                                                 case ld::Fixup::kindSetTargetAddress:
 265                                                                         fit->kind = ld::Fixup::kindSetTargetTLVTemplateOffset;
 266                                                                         break;
 267                                                                 case ld::Fixup::kindStoreTargetAddressLittleEndian32:
 268                                                                         fit->kind = ld::Fixup::kindSetTargetTLVTemplateOffsetLittleEndian32;
 269                                                                         break;
 270                                                                 case ld::Fixup::kindStoreTargetAddressLittleEndian64:
 271                                                                         fit->kind = ld::Fixup::kindSetTargetTLVTemplateOffsetLittleEndian64;
 272                                                                         break;
 273                                                                 default:
 274                                                                         assert(0 && "bad kind for target in tlv defs");
 275                                                                         break;
 276                                                         }
 277                                                         break;
 278                                                 default:
 279                                                         assert(0 && "wrong content type for target in tlv defs");
 280                                                         break;
 281                                         }
 282                                 }
 283                         }
 284                 }
 285         }
 286
 287 }
 288
 289
 290
 291 } // namespace tlvp
 292 } // namespace passes
 293 } // namespace ld