Rebased on #150798

jrtc27 · jrtc27 · commit ddcb9eea493f · 2025-07-26T22:17:52.000+01:00
Created using spr 1.3.5
diff --git a/lld/ELF/Config.h b/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.
diff --git a/lld/ELF/Driver.cpp b/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.
diff --git a/lld/ELF/Relocations.cpp b/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),
+                  DynamicReloc::AgainstSymbol, sym, 0, R_ADDEND});
+  else
+    rel.addReloc({type, &gotPlt, sym.getGotPltOffset(ctx),
+                  DynamicReloc::AddendOnly, sym, 0, R_ABS});
 }
 
 void elf::addGotEntry(Ctx &ctx, Symbol &sym) {
@@ -899,7 +901,7 @@ void elf::addGotEntry(Ctx &ctx, Symbol &sym) {
   if (sym.isPreemptible) {
     ctx.mainPart->relaDyn->addReloc({ctx.target->gotRel, ctx.in.got.get(), off,
                                      DynamicReloc::AgainstSymbol, sym, 0,
-                                     R_ABS});
+                                     R_ADDEND});
     return;
   }
 
@@ -921,14 +923,14 @@ static void addGotAuthEntry(Ctx &ctx, Symbol &sym) {
   if (sym.isPreemptible) {
     ctx.mainPart->relaDyn->addReloc({R_AARCH64_AUTH_GLOB_DAT, ctx.in.got.get(),
                                      off, DynamicReloc::AgainstSymbol, sym, 0,
-                                     R_ABS});
+                                     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, DynamicReloc::AddendOnly,
+       sym, 0, R_ABS});
 }
 
 static void addTpOffsetGotEntry(Ctx &ctx, Symbol &sym) {
@@ -1160,8 +1162,8 @@ void RelocationScanner::processAux(RelExpr expr, RelType type, uint64_t offset,
           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});
+                                  DynamicReloc::AddendOnly, sym, addend,
+                                  R_ABS});
         }
         return;
       }
@@ -1948,13 +1950,12 @@ 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);
diff --git a/lld/ELF/SyntheticSections.cpp b/lld/ELF/SyntheticSections.cpp
@@ -1121,8 +1121,8 @@ void MipsGotSection::build() {
     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});
+                                       DynamicReloc::AddendOnly, *p.first.first,
+                                       p.first.second, R_ABS});
     }
   }
 }
@@ -1648,13 +1648,10 @@ uint64_t DynamicReloc::getOffset() const {
 
 int64_t DynamicReloc::computeAddend(Ctx &ctx) const {
   switch (kind) {
+  case Computed:
+    llvm_unreachable("addend already computed");
   case AddendOnly:
-    assert(sym == nullptr);
-    return addend;
-  case AgainstSymbol:
-    assert(sym != nullptr);
-    return addend;
-  case AddendOnlyWithTargetVA: {
+  case AgainstSymbol: {
     uint64_t ca = inputSec->getRelocTargetVA(
         ctx, Relocation{expr, type, 0, addend, sym}, getOffset());
     return ctx.arg.is64 ? ca : SignExtend64<32>(ca);
@@ -1701,10 +1698,10 @@ void RelocationBaseSection::addAddendOnlyRelocIfNonPreemptible(
   // 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});
+              R_ADDEND});
   else
-    addReloc(DynamicReloc::AddendOnlyWithTargetVA, dynType, isec, offsetInSec,
-             sym, 0, R_ABS, addendRelType);
+    addReloc(DynamicReloc::AddendOnly, dynType, isec, offsetInSec, sym, 0,
+             R_ABS, addendRelType);
 }
 
 void RelocationBaseSection::mergeRels() {
@@ -1748,7 +1745,7 @@ void DynamicReloc::computeRaw(Ctx &ctx, SymbolTableBaseSection *symt) {
   r_offset = getOffset();
   r_sym = getSymIndex(symt);
   addend = computeAddend(ctx);
-  kind = AddendOnly; // Catch errors
+  kind = Computed; // Catch errors
 }
 
 void RelocationBaseSection::computeRels() {
diff --git a/lld/ELF/SyntheticSections.h b/lld/ELF/SyntheticSections.h
@@ -419,21 +419,22 @@ 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 has already had its addend computed.
+    /// Calling computeAddend() is an error. Only for internal use.
+    Computed,
     /// 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,
+    AddendOnly,
     /// The resulting dynamic relocation references symbol #sym from the dynamic
-    /// symbol table and uses #addend as the value of computeAddend(ctx).
+    /// symbol table and uses InputSection::getRelocTargetVA() for the final
+    /// addend.
     AgainstSymbol,
     /// 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)
@@ -442,8 +443,9 @@ class DynamicReloc {
   /// 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) {}
+      : sym(inputSec->getCtx().dummySym), 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,
@@ -455,7 +457,10 @@ class DynamicReloc {
 
   uint64_t getOffset() const;
   uint32_t getSymIndex(SymbolTableBaseSection *symTab) const;
-  bool needsDynSymIndex() const { return kind == AgainstSymbol; }
+  bool needsDynSymIndex() const {
+    assert(kind != Computed && "cannot check kind after computeRaw");
+    return kind == AgainstSymbol;
+  }
 
   /// 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
@@ -521,8 +526,8 @@ 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>(DynamicReloc::AddendOnly, 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.
diff --git a/lld/ELF/Target.cpp b/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())};
     }
   }
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
@@ -1573,8 +1573,7 @@ template <class ELFT> void Writer<ELFT>::finalizeAddressDependentContent() {
               if (isInt<32>(reloc.sym->getVA(ctx, reloc.addend)))
                 return false;
               part.relaDyn->addReloc({R_AARCH64_AUTH_RELATIVE, elem.inputSec,
-                                      reloc.offset,
-                                      DynamicReloc::AddendOnlyWithTargetVA,
+                                      reloc.offset, DynamicReloc::AddendOnly,
                                       *reloc.sym, reloc.addend, R_ABS});
               return true;
             });

Original file line number	Diff line number	Diff line change
`@@ -105,10 +105,9 @@ ErrorPlace elf::getErrorPlace(Ctx &ctx, const uint8_t *loc) {`
`105`	`105`	`if (isecLoc <= loc && loc < isecLoc + isec->getSize()) {`
`106`	`106`	`std::string objLoc = isec->getLocation(loc - isecLoc);`
`107`	`107`	`// Return object file location and source file location.`
`108`		`- Undefined dummy(ctx.internalFile, "", STB_LOCAL, 0, 0);`
`109`	`108`	`ELFSyncStream msg(ctx, DiagLevel::None);`
`110`	`109`	`if (isec->file)`
`111`		`- msg << isec->getSrcMsg(dummy, loc - isecLoc);`
	`110`	`+ msg << isec->getSrcMsg(*ctx.dummySym, loc - isecLoc);`
`112`	`111`	`return {isec, objLoc + ": ", std::string(msg.str())};`
`113`	`112`	`}`
`114`	`113`	`}`