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