[𝘀𝗽𝗿] initial version

Created using spr 1.3.5

Author: jrtc27

lld/ELF/Arch/Mips.cpp

@@ -40,6 +40,10 @@ template <class ELFT> class MIPS final : public TargetInfo {
 };
 } // namespace
 
+uint64_t elf::getMipsPageAddr(uint64_t addr) {
+  return (addr + 0x8000) & ~0xffff;
+}
+
 template <class ELFT> MIPS<ELFT>::MIPS(Ctx &ctx) : TargetInfo(ctx) {
   gotPltHeaderEntriesNum = 2;
   defaultMaxPageSize = 65536;

lld/ELF/Config.h

@@ -701,6 +701,8 @@ struct Ctx : CommonLinkerContext {
   std::unique_ptr<llvm::TarWriter> tar;
   // InputFile for linker created symbols with no source location.
   InputFile *internalFile = nullptr;
+  // Dummy Undefined for relocations without a symbol.
+  Undefined *dummySym = nullptr;
   // True if symbols can be exported (isExported) or preemptible.
   bool hasDynsym = false;
   // True if SHT_LLVM_SYMPART is used.

lld/ELF/Driver.cpp

@@ -3138,6 +3138,7 @@ template <class ELFT> void LinkerDriver::link(opt::InputArgList &args) {
     ctx.symtab->insert(arg->getValue())->traced = true;
 
   ctx.internalFile = createInternalFile(ctx, "<internal>");
+  ctx.dummySym = make<Undefined>(ctx.internalFile, "", STB_LOCAL, 0, 0);
 
   // Handle -u/--undefined before input files. If both a.a and b.so define foo,
   // -u foo a.a b.so will extract a.a.

lld/ELF/InputSection.cpp

@@ -861,6 +861,11 @@ uint64_t InputSectionBase::getRelocTargetVA(Ctx &ctx, const Relocation &r,
     return ctx.in.mipsGot->getVA() +
            ctx.in.mipsGot->getPageEntryOffset(file, *r.sym, a) -
            ctx.in.mipsGot->getGp(file);
+  case RE_MIPS_OSEC_LOCAL_PAGE:
+    // This is used by the MIPS multi-GOT implementation. It relocates
+    // addresses of 64kb pages that lie inside the output section that sym is
+    // a representative for.
+    return getMipsPageAddr(r.sym->getOutputSection()->addr) + a;
   case RE_MIPS_GOT_OFF:
   case RE_MIPS_GOT_OFF32:
     // In case of MIPS if a GOT relocation has non-zero addend this addend

lld/ELF/Relocations.cpp

@@ -885,10 +885,12 @@ static void addPltEntry(Ctx &ctx, PltSection &plt, GotPltSection &gotPlt,
                         RelocationBaseSection &rel, RelType type, Symbol &sym) {
   plt.addEntry(sym);
   gotPlt.addEntry(sym);
-  rel.addReloc({type, &gotPlt, sym.getGotPltOffset(ctx),
-                sym.isPreemptible ? DynamicReloc::AgainstSymbol
-                                  : DynamicReloc::AddendOnlyWithTargetVA,
-                sym, 0, R_ABS});
+  if (sym.isPreemptible)
+    rel.addReloc(
+        {type, &gotPlt, sym.getGotPltOffset(ctx), true, sym, 0, R_ADDEND});
+  else
+    rel.addReloc(
+        {type, &gotPlt, sym.getGotPltOffset(ctx), false, sym, 0, R_ABS});
 }
 
 void elf::addGotEntry(Ctx &ctx, Symbol &sym) {
@@ -897,9 +899,8 @@ void elf::addGotEntry(Ctx &ctx, Symbol &sym) {
 
   // If preemptible, emit a GLOB_DAT relocation.
   if (sym.isPreemptible) {
-    ctx.mainPart->relaDyn->addReloc({ctx.target->gotRel, ctx.in.got.get(), off,
-                                     DynamicReloc::AgainstSymbol, sym, 0,
-                                     R_ABS});
+    ctx.mainPart->relaDyn->addReloc(
+        {ctx.target->gotRel, ctx.in.got.get(), off, true, sym, 0, R_ADDEND});
     return;
   }
 
@@ -920,15 +921,13 @@ static void addGotAuthEntry(Ctx &ctx, Symbol &sym) {
   // If preemptible, emit a GLOB_DAT relocation.
   if (sym.isPreemptible) {
     ctx.mainPart->relaDyn->addReloc({R_AARCH64_AUTH_GLOB_DAT, ctx.in.got.get(),
-                                     off, DynamicReloc::AgainstSymbol, sym, 0,
-                                     R_ABS});
+                                     off, true, sym, 0, R_ADDEND});
     return;
   }
 
   // Signed GOT requires dynamic relocation.
   ctx.in.got->getPartition(ctx).relaDyn->addReloc(
-      {R_AARCH64_AUTH_RELATIVE, ctx.in.got.get(), off,
-       DynamicReloc::AddendOnlyWithTargetVA, sym, 0, R_ABS});
+      {R_AARCH64_AUTH_RELATIVE, ctx.in.got.get(), off, false, sym, 0, R_ABS});
 }
 
 static void addTpOffsetGotEntry(Ctx &ctx, Symbol &sym) {
@@ -1159,9 +1158,8 @@ void RelocationScanner::processAux(RelExpr expr, RelType type, uint64_t offset,
           sec->addReloc({expr, type, offset, addend, &sym});
           part.relrAuthDyn->relocs.push_back({sec, sec->relocs().size() - 1});
         } else {
-          part.relaDyn->addReloc({R_AARCH64_AUTH_RELATIVE, sec, offset,
-                                  DynamicReloc::AddendOnlyWithTargetVA, sym,
-                                  addend, R_ABS});
+          part.relaDyn->addReloc({R_AARCH64_AUTH_RELATIVE, sec, offset, false,
+                                  sym, addend, R_ABS});
         }
         return;
       }
@@ -1948,13 +1946,12 @@ void elf::postScanRelocations(Ctx &ctx) {
 
   GotSection *got = ctx.in.got.get();
   if (ctx.needsTlsLd.load(std::memory_order_relaxed) && got->addTlsIndex()) {
-    static Undefined dummy(ctx.internalFile, "", STB_LOCAL, 0, 0);
     if (ctx.arg.shared)
       ctx.mainPart->relaDyn->addReloc(
           {ctx.target->tlsModuleIndexRel, got, got->getTlsIndexOff()});
     else
       got->addConstant({R_ADDEND, ctx.target->symbolicRel,
-                        got->getTlsIndexOff(), 1, &dummy});
+                        got->getTlsIndexOff(), 1, ctx.dummySym});
   }
 
   assert(ctx.symAux.size() == 1);

lld/ELF/Relocations.h

@@ -110,6 +110,7 @@ enum RelExpr {
   RE_MIPS_GOT_LOCAL_PAGE,
   RE_MIPS_GOT_OFF,
   RE_MIPS_GOT_OFF32,
+  RE_MIPS_OSEC_LOCAL_PAGE,
   RE_MIPS_TLSGD,
   RE_MIPS_TLSLD,
   RE_PPC32_PLTREL,

lld/ELF/SyntheticSections.cpp

@@ -769,10 +769,6 @@ void GotSection::writeTo(uint8_t *buf) {
   }
 }
 
-static uint64_t getMipsPageAddr(uint64_t addr) {
-  return (addr + 0x8000) & ~0xffff;
-}
-
 static uint64_t getMipsPageCount(uint64_t size) {
   return (size + 0xfffe) / 0xffff + 1;
 }
@@ -786,7 +782,7 @@ void MipsGotSection::addEntry(InputFile &file, Symbol &sym, int64_t addend,
   FileGot &g = getGot(file);
   if (expr == RE_MIPS_GOT_LOCAL_PAGE) {
     if (const OutputSection *os = sym.getOutputSection())
-      g.pagesMap.insert({os, {}});
+      g.pagesMap.insert({os, {&sym}});
     else
       g.local16.insert({{nullptr, getMipsPageAddr(sym.getVA(ctx, addend))}, 0});
   } else if (sym.isTls())
@@ -1066,8 +1062,7 @@ void MipsGotSection::build() {
       // be allocated before us in the static TLS block.
       if (s->isPreemptible || ctx.arg.shared)
         ctx.mainPart->relaDyn->addReloc(
-            {ctx.target->tlsGotRel, this, offset,
-             DynamicReloc::AgainstSymbolWithTargetVA, *s, 0, R_ABS});
+            {ctx.target->tlsGotRel, this, offset, true, *s, 0, R_ABS});
     }
     for (std::pair<Symbol *, size_t> &p : got.dynTlsSymbols) {
       Symbol *s = p.first;
@@ -1115,15 +1110,16 @@ void MipsGotSection::build() {
       size_t pageCount = l.second.count;
       for (size_t pi = 0; pi < pageCount; ++pi) {
         uint64_t offset = (l.second.firstIndex + pi) * ctx.arg.wordsize;
-        ctx.mainPart->relaDyn->addReloc({ctx.target->relativeRel, this, offset,
-                                         l.first, int64_t(pi * 0x10000)});
+        ctx.mainPart->relaDyn->addReloc(
+            {ctx.target->relativeRel, this, offset, false, *l.second.repSym,
+             int64_t(pi * 0x10000), RE_MIPS_OSEC_LOCAL_PAGE});
       }
     }
     for (const std::pair<GotEntry, size_t> &p : got.local16) {
       uint64_t offset = p.second * ctx.arg.wordsize;
       ctx.mainPart->relaDyn->addReloc({ctx.target->relativeRel, this, offset,
-                                       DynamicReloc::AddendOnlyWithTargetVA,
-                                       *p.first.first, p.first.second, R_ABS});
+                                       false, *p.first.first, p.first.second,
+                                       R_ABS});
     }
   }
 }
@@ -1646,24 +1642,10 @@ uint64_t DynamicReloc::getOffset() const {
 }
 
 int64_t DynamicReloc::computeAddend(Ctx &ctx) const {
-  switch (kind) {
-  case AddendOnly:
-    assert(sym == nullptr);
-    return addend;
-  case AgainstSymbol:
-    assert(sym != nullptr);
-    return addend;
-  case AddendOnlyWithTargetVA:
-  case AgainstSymbolWithTargetVA: {
-    uint64_t ca = inputSec->getRelocTargetVA(
-        ctx, Relocation{expr, type, 0, addend, sym}, getOffset());
-    return ctx.arg.is64 ? ca : SignExtend64<32>(ca);
-  }
-  case MipsMultiGotPage:
-    assert(sym == nullptr);
-    return getMipsPageAddr(outputSec->addr) + addend;
-  }
-  llvm_unreachable("Unknown DynamicReloc::Kind enum");
+  assert(!isFinal && "addend already computed");
+  uint64_t ca = inputSec->getRelocTargetVA(
+      ctx, Relocation{expr, type, 0, addend, sym}, getOffset());
+  return ctx.arg.is64 ? ca : SignExtend64<32>(ca);
 }
 
 uint32_t DynamicReloc::getSymIndex(SymbolTableBaseSection *symTab) const {
@@ -1691,20 +1673,18 @@ RelocationBaseSection::RelocationBaseSection(Ctx &ctx, StringRef name,
 void RelocationBaseSection::addSymbolReloc(
     RelType dynType, InputSectionBase &isec, uint64_t offsetInSec, Symbol &sym,
     int64_t addend, std::optional<RelType> addendRelType) {
-  addReloc(DynamicReloc::AgainstSymbol, dynType, isec, offsetInSec, sym, addend,
-           R_ADDEND, addendRelType ? *addendRelType : ctx.target->noneRel);
+  addReloc(true, dynType, isec, offsetInSec, sym, addend, R_ADDEND,
+           addendRelType ? *addendRelType : ctx.target->noneRel);
 }
 
 void RelocationBaseSection::addAddendOnlyRelocIfNonPreemptible(
     RelType dynType, InputSectionBase &isec, uint64_t offsetInSec, Symbol &sym,
     RelType addendRelType) {
   // No need to write an addend to the section for preemptible symbols.
   if (sym.isPreemptible)
-    addReloc({dynType, &isec, offsetInSec, DynamicReloc::AgainstSymbol, sym, 0,
-              R_ABS});
+    addReloc({dynType, &isec, offsetInSec, true, sym, 0, R_ADDEND});
   else
-    addReloc(DynamicReloc::AddendOnlyWithTargetVA, dynType, isec, offsetInSec,
-             sym, 0, R_ABS, addendRelType);
+    addReloc(false, dynType, isec, offsetInSec, sym, 0, R_ABS, addendRelType);
 }
 
 void RelocationBaseSection::mergeRels() {
@@ -1744,17 +1724,17 @@ void RelocationBaseSection::finalizeContents() {
   }
 }
 
-void DynamicReloc::computeRaw(Ctx &ctx, SymbolTableBaseSection *symt) {
+void DynamicReloc::finalize(Ctx &ctx, SymbolTableBaseSection *symt) {
   r_offset = getOffset();
   r_sym = getSymIndex(symt);
   addend = computeAddend(ctx);
-  kind = AddendOnly; // Catch errors
+  isFinal = true; // Catch errors
 }
 
 void RelocationBaseSection::computeRels() {
   SymbolTableBaseSection *symTab = getPartition(ctx).dynSymTab.get();
   parallelForEach(relocs, [&ctx = ctx, symTab](DynamicReloc &rel) {
-    rel.computeRaw(ctx, symTab);
+    rel.finalize(ctx, symTab);
   });
 
   auto irelative = std::stable_partition(

lld/ELF/SyntheticSections.h

@@ -327,9 +327,11 @@ class MipsGotSection final : public SyntheticSection {
     size_t startIndex = 0;
 
     struct PageBlock {
+      Symbol *repSym; // Representative symbol for the OutputSection
       size_t firstIndex;
       size_t count;
-      PageBlock() : firstIndex(0), count(0) {}
+      PageBlock(Symbol *repSym = nullptr)
+          : repSym(repSym), firstIndex(0), count(0) {}
     };
 
     // Map output sections referenced by MIPS GOT relocations
@@ -418,61 +420,31 @@ class StringTableSection final : public SyntheticSection {
 
 class DynamicReloc {
 public:
-  enum Kind {
-    /// The resulting dynamic relocation does not reference a symbol (#sym must
-    /// be nullptr) and uses #addend as the result of computeAddend(ctx).
-    AddendOnly,
-    /// The resulting dynamic relocation will not reference a symbol: #sym is
-    /// only used to compute the addend with InputSection::getRelocTargetVA().
-    /// Useful for various relative and TLS relocations (e.g. R_X86_64_TPOFF64).
-    AddendOnlyWithTargetVA,
-    /// The resulting dynamic relocation references symbol #sym from the dynamic
-    /// symbol table and uses #addend as the value of computeAddend(ctx).
-    AgainstSymbol,
-    /// The resulting dynamic relocation references symbol #sym from the dynamic
-    /// symbol table and uses InputSection::getRelocTargetVA() + #addend for the
-    /// final addend. It can be used for relocations that write the symbol VA as
-    // the addend (e.g. R_MIPS_TLS_TPREL64) but still reference the symbol.
-    AgainstSymbolWithTargetVA,
-    /// This is used by the MIPS multi-GOT implementation. It relocates
-    /// addresses of 64kb pages that lie inside the output section.
-    MipsMultiGotPage,
-  };
-  /// This constructor records a relocation against a symbol.
+  /// This constructor records a normal relocation.
   DynamicReloc(RelType type, const InputSectionBase *inputSec,
-               uint64_t offsetInSec, Kind kind, Symbol &sym, int64_t addend,
-               RelExpr expr)
+               uint64_t offsetInSec, bool isAgainstSymbol, Symbol &sym,
+               int64_t addend, RelExpr expr)
       : sym(&sym), inputSec(inputSec), offsetInSec(offsetInSec), type(type),
-        addend(addend), kind(kind), expr(expr) {}
+        addend(addend), isAgainstSymbol(isAgainstSymbol), isFinal(false),
+        expr(expr) {}
   /// This constructor records a relative relocation with no symbol.
   DynamicReloc(RelType type, const InputSectionBase *inputSec,
                uint64_t offsetInSec, int64_t addend = 0)
-      : sym(nullptr), inputSec(inputSec), offsetInSec(offsetInSec), type(type),
-        addend(addend), kind(AddendOnly), expr(R_ADDEND) {}
-  /// This constructor records dynamic relocation settings used by the MIPS
-  /// multi-GOT implementation.
-  DynamicReloc(RelType type, const InputSectionBase *inputSec,
-               uint64_t offsetInSec, const OutputSection *outputSec,
-               int64_t addend)
-      : sym(nullptr), outputSec(outputSec), inputSec(inputSec),
-        offsetInSec(offsetInSec), type(type), addend(addend),
-        kind(MipsMultiGotPage), expr(R_ADDEND) {}
+      : DynamicReloc(type, inputSec, offsetInSec, false,
+                     *inputSec->getCtx().dummySym, addend, R_ADDEND) {}
 
   uint64_t getOffset() const;
   uint32_t getSymIndex(SymbolTableBaseSection *symTab) const;
-  bool needsDynSymIndex() const {
-    return kind == AgainstSymbol || kind == AgainstSymbolWithTargetVA;
-  }
+  bool needsDynSymIndex() const { return isAgainstSymbol; }
 
   /// Computes the addend of the dynamic relocation. Note that this is not the
   /// same as the #addend member variable as it may also include the symbol
   /// address/the address of the corresponding GOT entry/etc.
   int64_t computeAddend(Ctx &) const;
 
-  void computeRaw(Ctx &, SymbolTableBaseSection *symt);
+  void finalize(Ctx &, SymbolTableBaseSection *symt);
 
   Symbol *sym;
-  const OutputSection *outputSec = nullptr;
   const InputSectionBase *inputSec;
   uint64_t offsetInSec;
   uint64_t r_offset;
@@ -483,7 +455,15 @@ class DynamicReloc {
   int64_t addend;
 
 private:
-  Kind kind;
+  /// Whether this was constructed with a Kind of AgainstSymbol.
+  LLVM_PREFERRED_TYPE(bool)
+  uint8_t isAgainstSymbol : 1;
+
+  /// The resulting dynamic relocation has already had its addend computed.
+  /// Calling computeAddend() is an error.
+  LLVM_PREFERRED_TYPE(bool)
+  uint8_t isFinal : 1;
+
   // The kind of expression used to calculate the added (required e.g. for
   // relative GOT relocations).
   RelExpr expr;
@@ -528,8 +508,8 @@ class RelocationBaseSection : public SyntheticSection {
                         uint64_t offsetInSec, Symbol &sym, int64_t addend,
                         RelType addendRelType, RelExpr expr) {
     assert(expr != R_ADDEND && "expected non-addend relocation expression");
-    addReloc<shard>(DynamicReloc::AddendOnlyWithTargetVA, dynType, isec,
-                    offsetInSec, sym, addend, expr, addendRelType);
+    addReloc<shard>(false, dynType, isec, offsetInSec, sym, addend, expr,
+                    addendRelType);
   }
   /// Add a dynamic relocation using the target address of \p sym as the addend
   /// if \p sym is non-preemptible. Otherwise add a relocation against \p sym.
@@ -538,14 +518,15 @@ class RelocationBaseSection : public SyntheticSection {
                                           uint64_t offsetInSec, Symbol &sym,
                                           RelType addendRelType);
   template <bool shard = false>
-  void addReloc(DynamicReloc::Kind kind, RelType dynType, InputSectionBase &sec,
+  void addReloc(bool isAgainstSymbol, RelType dynType, InputSectionBase &sec,
                 uint64_t offsetInSec, Symbol &sym, int64_t addend, RelExpr expr,
                 RelType addendRelType) {
     // Write the addends to the relocated address if required. We skip
     // it if the written value would be zero.
     if (ctx.arg.writeAddends && (expr != R_ADDEND || addend != 0))
       sec.addReloc({expr, addendRelType, offsetInSec, addend, &sym});
-    addReloc<shard>({dynType, &sec, offsetInSec, kind, sym, addend, expr});
+    addReloc<shard>(
+        {dynType, &sec, offsetInSec, isAgainstSymbol, sym, addend, expr});
   }
   bool isNeeded() const override {
     return !relocs.empty() ||

lld/ELF/Target.cpp

@@ -105,10 +105,9 @@ ErrorPlace elf::getErrorPlace(Ctx &ctx, const uint8_t *loc) {
     if (isecLoc <= loc && loc < isecLoc + isec->getSize()) {
       std::string objLoc = isec->getLocation(loc - isecLoc);
       // Return object file location and source file location.
-      Undefined dummy(ctx.internalFile, "", STB_LOCAL, 0, 0);
       ELFSyncStream msg(ctx, DiagLevel::None);
       if (isec->file)
-        msg << isec->getSrcMsg(dummy, loc - isecLoc);
+        msg << isec->getSrcMsg(*ctx.dummySym, loc - isecLoc);
       return {isec, objLoc + ": ", std::string(msg.str())};
     }
   }

lld/ELF/Target.h

@@ -214,6 +214,7 @@ void processArmCmseSymbols(Ctx &);
 template <class ELFT> uint32_t calcMipsEFlags(Ctx &);
 uint8_t getMipsFpAbiFlag(Ctx &, InputFile *file, uint8_t oldFlag,
                          uint8_t newFlag);
+uint64_t getMipsPageAddr(uint64_t addr);
 bool isMipsN32Abi(Ctx &, const InputFile &f);
 bool isMicroMips(Ctx &);
 bool isMipsR6(Ctx &);