src/ld/passes/tlvp.cpp

   1 /* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
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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
  34 #include "ld.hpp"
  35 #include "tlvp.h"
  36
  37 namespace ld {
  38 namespace passes {
  39 namespace tlvp {
  40
  41 class File; // forward reference
  42
  43 class TLVEntryAtom : public ld::Atom {
  44 public:
  45                                                                                         TLVEntryAtom(ld::Internal& internal, const ld::Atom* target, bool weakImport)
  46                                 : ld::Atom(_s_section, ld::Atom::definitionRegular, ld::Atom::combineNever,
  47                                                         ld::Atom::scopeLinkageUnit, ld::Atom::typeNonLazyPointer,
  48                                                         symbolTableNotIn, false, false, false, ld::Atom::Alignment(3)),
  49                                 _fixup(0, ld::Fixup::k1of1, ld::Fixup::kindStoreTargetAddressLittleEndian64, target),
  50                                 _target(target)
  51                                         { _fixup.weakImport = weakImport; internal.addAtom(*this); }
  52
  53         virtual const ld::File*                                 file() const                                    { return NULL; }
  54         virtual const char*                                             name() const                                    { return _target->name(); }
  55         virtual uint64_t                                                size() const                                    { return 8; }
  56         virtual uint64_t                                                objectAddress() const                   { return 0; }
  57         virtual void                                                    copyRawContent(uint8_t buffer[]) const { }
  58         virtual void                                                    setScope(Scope)                                 { }
  59         virtual ld::Fixup::iterator                             fixupsBegin() const                             { return &_fixup; }
  60         virtual ld::Fixup::iterator                             fixupsEnd()     const                           { return &((ld::Fixup*)&_fixup)[1]; }
  61
  62 private:
  63         mutable ld::Fixup                                               _fixup;
  64         const ld::Atom*                                                 _target;
  65
  66         static ld::Section                                              _s_section;
  67 };
  68
  69 ld::Section TLVEntryAtom::_s_section("__DATA", "__thread_ptrs", ld::Section::typeTLVPointers);
  70
  71
  72 static bool optimizable(const Options& opts, const ld::Atom* targetOfTLV)
  73 {
  74         // cannot do LEA optimization if target is in another dylib
  75         if ( targetOfTLV->definition() == ld::Atom::definitionProxy )
  76                 return false;
  77         if ( targetOfTLV->scope() == ld::Atom::scopeGlobal ) {
  78                 // cannot do LEA optimization if target is weak exported symbol
  79                 if ( (targetOfTLV->definition() == ld::Atom::definitionRegular) && (targetOfTLV->combine() == ld::Atom::combineByName) )
  80                         return false;
  81                 // cannot do LEA optimization if target is interposable
  82                 if ( opts.interposable(targetOfTLV->name()) )
  83                         return false;
  84                 // cannot do LEA optimization for flat-namespace
  85                 if ( opts.nameSpace() != Options::kTwoLevelNameSpace )
  86                         return false;
  87         }
  88         return true;
  89 }
  90
  91 struct AtomByNameSorter
  92 {
  93          bool operator()(const ld::Atom* left, const ld::Atom* right)
  94          {
  95                   return (strcmp(left->name(), right->name()) < 0);
  96          }
  97 };
  98
  99 struct TlVReferenceCluster
 100 {
 101         const ld::Atom* targetOfTLV;
 102         ld::Fixup*              fixupWithTarget;
 103         ld::Fixup*              fixupWithTLVStore;
 104         bool                    optimizable;
 105 };
 106
 107 void doPass(const Options& opts, ld::Internal& internal)
 108 {
 109         const bool log = false;
 110
 111         // only make tlv section in final linked images
 112         if ( opts.outputKind() == Options::kObjectFile )
 113                 return;
 114
 115         // walk all atoms and fixups looking for TLV references and add them to list
 116         std::vector<TlVReferenceCluster>        references;
 117         for (std::vector<ld::Internal::FinalSection*>::iterator sit=internal.sections.begin(); sit != internal.sections.end(); ++sit) {
 118                 ld::Internal::FinalSection* sect = *sit;
 119                 for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin(); ait != sect->atoms.end(); ++ait) {
 120                         const ld::Atom* atom = *ait;
 121                         TlVReferenceCluster ref;
 122                         for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
 123                                 if ( fit->firstInCluster() ) {
 124                                         ref.targetOfTLV = NULL;
 125                                         ref.fixupWithTarget = NULL;
 126                                         ref.fixupWithTLVStore = NULL;
 127                                 }
 128                                 switch ( fit->binding ) {
 129                                         case ld::Fixup::bindingsIndirectlyBound:
 130                                                 ref.targetOfTLV = internal.indirectBindingTable[fit->u.bindingIndex];
 131                                                 ref.fixupWithTarget = fit;
 132                                                 break;
 133                                         case ld::Fixup::bindingDirectlyBound:
 134                                                 ref.targetOfTLV = fit->u.target;
 135                                                 ref.fixupWithTarget = fit;
 136                                                 break;
 137                     default:
 138                         break;
 139                                 }
 140                                 switch ( fit->kind ) {
 141                                         case ld::Fixup::kindStoreTargetAddressX86PCRel32TLVLoad:
 142                                         case ld::Fixup::kindStoreTargetAddressX86Abs32TLVLoad:
 143                                         case ld::Fixup::kindStoreX86PCRel32TLVLoad:
 144                                         case ld::Fixup::kindStoreX86Abs32TLVLoad:
 145                                                 ref.fixupWithTLVStore = fit;
 146                                                 break;
 147                                         default:
 148                                                 break;
 149                                 }
 150                                 if ( fit->lastInCluster() && (ref.fixupWithTLVStore != NULL) ) {
 151                                         ref.optimizable = optimizable(opts, ref.targetOfTLV);
 152                                         if (log) fprintf(stderr, "found reference to TLV at %s+0x%X to %s\n",
 153                                                                         atom->name(), ref.fixupWithTLVStore->offsetInAtom, ref.targetOfTLV->name());
 154                                         if ( ! opts.canUseThreadLocalVariables() ) {
 155                                                 throwf("targeted OS version does not support use of thread local variables in %s", atom->name());
 156                                         }
 157                                         references.push_back(ref);
 158                                 }
 159                         }
 160                 }
 161         }
 162
 163         // compute which TLV references will be weak_imports
 164         std::map<const ld::Atom*,bool>          weakImportMap;
 165         for(std::vector<TlVReferenceCluster>::iterator it=references.begin(); it != references.end(); ++it) {
 166                 if ( !it->optimizable ) {
 167                         // record weak_import attribute
 168                         std::map<const ld::Atom*,bool>::iterator pos = weakImportMap.find(it->targetOfTLV);
 169                         if ( pos == weakImportMap.end() ) {
 170                                 // target not in weakImportMap, so add
 171                                 weakImportMap[it->targetOfTLV] = it->fixupWithTarget->weakImport;
 172                         }
 173                         else {
 174                                 // target in weakImportMap, check for weakness mismatch
 175                                 if ( pos->second != it->fixupWithTarget->weakImport ) {
 176                                         // found mismatch
 177                                         switch ( opts.weakReferenceMismatchTreatment() ) {
 178                                                 case Options::kWeakReferenceMismatchError:
 179                                                         throwf("mismatching weak references for symbol: %s", it->targetOfTLV->name());
 180                                                 case Options::kWeakReferenceMismatchWeak:
 181                                                         pos->second = true;
 182                                                         break;
 183                                                 case Options::kWeakReferenceMismatchNonWeak:
 184                                                         pos->second = false;
 185                                                         break;
 186                                         }
 187                                 }
 188                         }
 189                 }
 190         }
 191
 192         // create TLV pointers for TLV references that cannot be optimized
 193         std::map<const ld::Atom*,ld::Atom*> variableToPointerMap;
 194         for(std::map<const ld::Atom*,bool>::iterator it=weakImportMap.begin(); it != weakImportMap.end(); ++it) {
 195                 std::map<const ld::Atom*,ld::Atom*>::iterator pos = variableToPointerMap.find(it->first);
 196                 if ( pos == variableToPointerMap.end() ) {
 197                         if (log) fprintf(stderr, "make TLV pointer for %s\n", it->first->name());
 198                         if ( it->first->contentType() != ld::Atom::typeTLV )
 199                                 throwf("illegal thread local variable reference to regular symbol %s", it->first->name());
 200                         TLVEntryAtom* tlvp = new TLVEntryAtom(internal, it->first, it->second);
 201                         variableToPointerMap[it->first] = tlvp;
 202                 }
 203         }
 204
 205         // sort new tvlp atoms so links are consistent
 206         for (std::vector<ld::Internal::FinalSection*>::iterator sit=internal.sections.begin(); sit != internal.sections.end(); ++sit) {
 207                 ld::Internal::FinalSection* sect = *sit;
 208                 if ( sect->type() == ld::Section::typeTLVPointers ) {
 209                         std::sort(sect->atoms.begin(), sect->atoms.end(), AtomByNameSorter());
 210                 }
 211         }
 212
 213         // update references to use TLV pointers or TLV object directly
 214         for(std::vector<TlVReferenceCluster>::iterator it=references.begin(); it != references.end(); ++it) {
 215                 if ( it->optimizable ) {
 216                         // change store to be LEA instead load (mov)
 217                         if (log) fprintf(stderr, "optimizing load of TLV to %s into an LEA\n", it->targetOfTLV->name());
 218                         it->fixupWithTLVStore->binding = ld::Fixup::bindingDirectlyBound;
 219                         it->fixupWithTLVStore->u.target = it->targetOfTLV;
 220                         switch ( it->fixupWithTLVStore->kind ) {
 221                                 case ld::Fixup::kindStoreTargetAddressX86PCRel32TLVLoad:
 222                                         it->fixupWithTLVStore->kind = ld::Fixup::kindStoreTargetAddressX86PCRel32TLVLoadNowLEA;
 223                                         break;
 224                                 case ld::Fixup::kindStoreTargetAddressX86Abs32TLVLoad:
 225                                         it->fixupWithTLVStore->kind = ld::Fixup::kindStoreTargetAddressX86Abs32TLVLoadNowLEA;
 226                                         break;
 227                                 case ld::Fixup::kindStoreX86PCRel32TLVLoad:
 228                                         it->fixupWithTLVStore->kind = ld::Fixup::kindStoreX86PCRel32TLVLoadNowLEA;
 229                                         break;
 230                                 case ld::Fixup::kindStoreX86Abs32TLVLoad:
 231                                         it->fixupWithTLVStore->kind = ld::Fixup::kindStoreX86Abs32TLVLoadNowLEA;
 232                                         break;
 233                                 default:
 234                                         assert(0 && "bad store kind for TLV optimization");
 235                         }
 236                 }
 237                 else {
 238                         // change target to be new TLV pointer atom
 239                         if (log) fprintf(stderr, "updating load of TLV to %s to load from TLV pointer\n", it->targetOfTLV->name());
 240                         const ld::Atom* tlvpAtom = variableToPointerMap[it->targetOfTLV];
 241                         assert(tlvpAtom != NULL);
 242                         it->fixupWithTarget->binding = ld::Fixup::bindingDirectlyBound;
 243                         it->fixupWithTarget->u.target = tlvpAtom;
 244                 }
 245         }
 246
 247
 248
 249         // alter tlv definitions to have an offset as third field
 250         for (std::vector<ld::Internal::FinalSection*>::iterator sit=internal.sections.begin(); sit != internal.sections.end(); ++sit) {
 251                 ld::Internal::FinalSection* sect = *sit;
 252                 if ( sect->type() != ld::Section::typeTLVDefs )
 253                         continue;
 254                 for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
 255                         const ld::Atom* atom = *ait;
 256                         for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
 257                                 if ( fit->offsetInAtom != 0 ) {
 258                                         assert(fit->binding == ld::Fixup::bindingDirectlyBound && "thread variable def contains pointer to global");
 259                                         switch( fit->u.target->contentType() ) {
 260                                                 case ld::Atom::typeTLVZeroFill:
 261                                                 case ld::Atom::typeTLVInitialValue:
 262                                                         switch ( fit->kind ) {
 263                                                                 case ld::Fixup::kindSetTargetAddress:
 264                                                                         fit->kind = ld::Fixup::kindSetTargetTLVTemplateOffset;
 265                                                                         break;
 266                                                                 case ld::Fixup::kindStoreTargetAddressLittleEndian32:
 267                                                                         fit->kind = ld::Fixup::kindSetTargetTLVTemplateOffsetLittleEndian32;
 268                                                                         break;
 269                                                                 case ld::Fixup::kindStoreTargetAddressLittleEndian64:
 270                                                                         fit->kind = ld::Fixup::kindSetTargetTLVTemplateOffsetLittleEndian64;
 271                                                                         break;
 272                                                                 default:
 273                                                                         assert(0 && "bad kind for target in tlv defs");
 274                                                                         break;
 275                                                         }
 276                                                         break;
 277                                                 default:
 278                                                         assert(0 && "wrong content type for target in tlv defs");
 279                                                         break;
 280                                         }
 281                                 }
 282                         }
 283                 }
 284         }
 285
 286 }
 287
 288
 289
 290 } // namespace tlvp
 291 } // namespace passes
 292 } // namespace ld