From e3ecc6a91241affd1d93615e0c9569794b016a00 Mon Sep 17 00:00:00 2001
From: Fangrui Song <i@maskray.me>
Date: Thu, 29 Sep 2022 00:50:19 -0700
Subject: [PATCH] [ELF] Make symAux[0] a sentinel

And default auxIdx to 0.
---
 lld/ELF/Driver.cpp            |  2 ++
 lld/ELF/InputFiles.cpp        |  1 -
 lld/ELF/Relocations.cpp       |  2 +-
 lld/ELF/SymbolTable.cpp       |  1 -
 lld/ELF/Symbols.h             | 19 +++++--------------
 lld/ELF/SyntheticSections.cpp |  4 ++--
 6 files changed, 10 insertions(+), 19 deletions(-)

diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index 74b16e0..d5e9e8f 100644
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -118,6 +118,8 @@ bool elf::link(ArrayRef<const char *> args, llvm::raw_ostream &stdoutOS,
   script = std::make_unique<LinkerScript>();
   symtab = std::make_unique<SymbolTable>();
 
+  symAux.emplace_back();
+
   partitions.clear();
   partitions.emplace_back();
 
diff --git a/lld/ELF/InputFiles.cpp b/lld/ELF/InputFiles.cpp
index 2f2d40b..d5faefe 100644
--- a/lld/ELF/InputFiles.cpp
+++ b/lld/ELF/InputFiles.cpp
@@ -1131,7 +1131,6 @@ void ObjFile<ELFT>::initSectionsAndLocalSyms(bool ignoreComdats) {
                                eSym.st_value, eSym.st_size, sec);
     symbols[i]->partition = 1;
     symbols[i]->isUsedInRegularObj = true;
-    symbols[i]->auxIdx = -1;
   }
 }
 
diff --git a/lld/ELF/Relocations.cpp b/lld/ELF/Relocations.cpp
index 6590d91..e2e7a5e 100644
--- a/lld/ELF/Relocations.cpp
+++ b/lld/ELF/Relocations.cpp
@@ -1748,7 +1748,7 @@ void elf::postScanRelocations() {
           {R_ADDEND, target->symbolicRel, in.got->getTlsIndexOff(), 1, &dummy});
   }
 
-  assert(symAux.empty());
+  assert(symAux.size() == 1);
   for (Symbol *sym : symtab->getSymbols())
     fn(*sym);
 
diff --git a/lld/ELF/SymbolTable.cpp b/lld/ELF/SymbolTable.cpp
index baa085c..7852127 100644
--- a/lld/ELF/SymbolTable.cpp
+++ b/lld/ELF/SymbolTable.cpp
@@ -91,7 +91,6 @@ Symbol *SymbolTable::insert(StringRef name) {
   memset(sym, 0, sizeof(Symbol));
   sym->setName(name);
   sym->partition = 1;
-  sym->auxIdx = -1;
   sym->verdefIndex = -1;
   sym->versionId = VER_NDX_GLOBAL;
   if (pos != StringRef::npos)
diff --git a/lld/ELF/Symbols.h b/lld/ELF/Symbols.h
index 6e8f0a0..5ef08a6 100644
--- a/lld/ELF/Symbols.h
+++ b/lld/ELF/Symbols.h
@@ -201,18 +201,10 @@ public:
   // truncated by Symbol::parseSymbolVersion().
   const char *getVersionSuffix() const { return nameData + nameSize; }
 
-  uint32_t getGotIdx() const {
-    return auxIdx == uint32_t(-1) ? uint32_t(-1) : symAux[auxIdx].gotIdx;
-  }
-  uint32_t getPltIdx() const {
-    return auxIdx == uint32_t(-1) ? uint32_t(-1) : symAux[auxIdx].pltIdx;
-  }
-  uint32_t getTlsDescIdx() const {
-    return auxIdx == uint32_t(-1) ? uint32_t(-1) : symAux[auxIdx].tlsDescIdx;
-  }
-  uint32_t getTlsGdIdx() const {
-    return auxIdx == uint32_t(-1) ? uint32_t(-1) : symAux[auxIdx].tlsGdIdx;
-  }
+  uint32_t getGotIdx() const { return symAux[auxIdx].gotIdx; }
+  uint32_t getPltIdx() const { return symAux[auxIdx].pltIdx; }
+  uint32_t getTlsDescIdx() const { return symAux[auxIdx].tlsDescIdx; }
+  uint32_t getTlsGdIdx() const { return symAux[auxIdx].tlsGdIdx; }
 
   bool isInGot() const { return getGotIdx() != uint32_t(-1); }
   bool isInPlt() const { return getPltIdx() != uint32_t(-1); }
@@ -328,7 +320,7 @@ public:
             NEEDS_TLSGD_TO_IE | NEEDS_GOT_DTPREL | NEEDS_TLSIE);
   }
   void allocateAux() {
-    assert(auxIdx == uint32_t(-1));
+    assert(auxIdx == 0);
     auxIdx = symAux.size();
     symAux.emplace_back();
   }
@@ -548,7 +540,6 @@ template <typename... T> Defined *makeDefined(T &&...args) {
   auto *sym = getSpecificAllocSingleton<SymbolUnion>().Allocate();
   memset(sym, 0, sizeof(Symbol));
   auto &s = *new (reinterpret_cast<Defined *>(sym)) Defined(std::forward<T>(args)...);
-  s.auxIdx = -1;
   return &s;
 }
 
diff --git a/lld/ELF/SyntheticSections.cpp b/lld/ELF/SyntheticSections.cpp
index eb70c1d..24336fd 100644
--- a/lld/ELF/SyntheticSections.cpp
+++ b/lld/ELF/SyntheticSections.cpp
@@ -960,12 +960,12 @@ void MipsGotSection::build() {
   // Update SymbolAux::gotIdx field to use this
   // value later in the `sortMipsSymbols` function.
   for (auto &p : primGot->global) {
-    if (p.first->auxIdx == uint32_t(-1))
+    if (p.first->auxIdx == 0)
       p.first->allocateAux();
     symAux.back().gotIdx = p.second;
   }
   for (auto &p : primGot->relocs) {
-    if (p.first->auxIdx == uint32_t(-1))
+    if (p.first->auxIdx == 0)
       p.first->allocateAux();
     symAux.back().gotIdx = p.second;
   }
-- 
2.7.4