Fixes, load and parse relocations.

src/emucore/CartELF.cxx

@@ -60,6 +60,38 @@ namespace {
 	  0xd0, 0xfb,			  // bne WaitForCart
 	  0x4c, 0x00, 0x10	// jmp $1000
   };
+
+#ifdef DUMP_ELF
+  void dumpElf(const ElfParser& elfParser) {
+    cout << "ELF sections:" << std::endl << std::endl;
+
+    size_t i = 0;
+    for (auto& section: elfParser.getSections()) {
+      if (section.type != 0x00) cout << i << " " << section << std::endl;
+      i++;
+    }
+
+    auto symbols = elfParser.getSymbols();
+    cout << std::endl << "ELF symbols:" << std::endl << std::endl;
+    if (symbols.size() > 0) {
+      i = 0;
+      for (auto& symbol: symbols)
+        cout << (i++) << " " << symbol << std::endl;
+    }
+
+    i = 0;
+    for (auto& section: elfParser.getSections()) {
+      auto rels = elfParser.getRelocations(i++);
+      if (!rels) continue;
+
+      cout
+        << std::endl << "ELF relocations for section "
+        << section.name << ":" << std::endl << std::endl;
+
+      for (auto& rel: *rels) cout << rel << std::endl;
+    }
+  }
+#endif
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -81,23 +113,9 @@ CartridgeELF::CartridgeELF(const ByteBuffer& image, size_t size, string_view md5
 
   createRomAccessArrays(0x1000);
 
-  #ifdef DUMP_ELF
+#ifdef DUMP_ELF
-    cout << "ELF sections:" << std::endl << std::endl;
+  dumpElf(elfParser);
-
+#endif
-    size_t i = 0;
-    for (auto& section: elfParser.getSections()) {
-      if (section.type != 0x00) cout << i << " " << section << std::endl;
-      i++;
-    }
-
-    auto symbols = elfParser.getSymbols();
-    cout << std::endl << "ELF symbols:" << std::endl << std::endl;
-    if (symbols.size() > 0) {
-      i = 0;
-      for (auto& symbol: symbols)
-        cout << (i++) << " " << symbol << std::endl;
-    }
-  #endif
 }
 
 

src/emucore/elf/ElfParser.cxx

@@ -7,6 +7,8 @@ namespace {
   constexpr uInt8 ELF_CLASS_32 = 1;
   constexpr uInt8 ELF_VERSION = 1;
   constexpr uInt32 SYMBOL_ENTRY_SIZE = 16;
+  constexpr uInt32 REL_ENTRY_SIZE = 8;
+  constexpr uInt32 RELA_ENTRY_SIZE = 12;
 } // namespace
 
 void ElfParser::parse(const uInt8 *elfData, size_t size)
@@ -50,6 +52,7 @@ void ElfParser::parse(const uInt8 *elfData, size_t size)
       section.name = getName(shrstrtab, section.nameOffset);
 
     const Section* symtab = getSymtab();
+
     if (symtab) {
       const Section* strtab = getStrtab();
       if (!strtab) EInvalidElf::raise("no string table to resolve symbol names");
@@ -59,6 +62,25 @@ void ElfParser::parse(const uInt8 *elfData, size_t size)
       for (size_t i = 0; i < symtab->size / SYMBOL_ENTRY_SIZE; i++)
         symbols.push_back(readSymbol(i, *symtab, *strtab));
     }
+
+    for (auto& section: sections) {
+      if (section.type != SHT_REL && section.type != SHT_RELA) continue;
+      if (section.info >= sections.size()) EInvalidElf::raise("relocation table for invalid section");
+
+      vector<Relocation> rels;
+      rels.reserve(section.size / (section.type == SHT_REL ? REL_ENTRY_SIZE : RELA_ENTRY_SIZE));
+
+      for (size_t i = 0; i < rels.capacity(); i++) {
+        Relocation rel = readRelocation(i, section);
+
+        if (rel.symbol >= symbols.size()) EInvalidElf::raise("invalid relocation symbol");
+        rel.symbolName = symbols[rel.symbol].name;
+
+        rels.push_back(rel);
+      }
+
+      relocations[section.info] = rels;
+    }
   } catch (const EInvalidElf &e) {
     EInvalidElf::raise("failed to parse ELF: " + string(e.what()));
   }
@@ -87,6 +109,11 @@ ElfParser::getSection(const string &name) const {
   return optional<Section>();
 }
 
+const optional<vector<ElfParser::Relocation>> ElfParser::getRelocations(size_t section) const
+{
+  return relocations.contains(section) ? relocations.at(section) : optional<vector<ElfParser::Relocation>>();
+}
+
 uInt8 ElfParser::read8(uInt32 offset) const
 {
   if (offset >= size)
@@ -133,12 +160,12 @@ ElfParser::Section ElfParser::readSection(uInt32 offset) const {
 
 ElfParser::Symbol ElfParser::readSymbol(uInt32 index, const Section& symSec, const Section& strSec) const
 {
-  Symbol sym;
-
   uInt32 offset = index * SYMBOL_ENTRY_SIZE;
   if (offset + SYMBOL_ENTRY_SIZE > symSec.size) EInvalidElf::raise("symbol is beyond section");
   offset += symSec.offset;
 
+  Symbol sym;
+
   sym.nameOffset = read32(offset);
   sym.value = read32(offset + 0x04);
   sym.size = read32(offset + 0x08);
@@ -146,13 +173,43 @@ ElfParser::Symbol ElfParser::readSymbol(uInt32 index, const Section& symSec, con
   sym.visibility = read8(offset + 0x0d);
   sym.section = read16(offset + 0x0e);
 
-  sym.name = getName(strSec, sym.nameOffset);
+  if (
+      ((sym.section != SHN_ABS && sym.section != SHN_UND) || sym.type == STT_SECTION) &&
+      sym.section >= sections.size()
+  )
+    EInvalidElf::raise("symbol: section index out of range");
+
   sym.bind = sym.info >> 4;
   sym.type = sym.info & 0x0f;
 
+  sym.name = sym.type == STT_SECTION ? sections[sym.section].name : getName(strSec, sym.nameOffset);
+
   return sym;
 }
 
+ElfParser::Relocation ElfParser::readRelocation(uInt32 index, const Section& sec) const
+{
+  if (sec.type != SHT_REL && sec.type != SHT_RELA)
+    throw runtime_error("section is not RELA or REL");
+
+  const size_t size = sec.type == SHT_REL ? REL_ENTRY_SIZE : RELA_ENTRY_SIZE;
+  uInt32 offset = index * size;
+
+  if (offset + size > sec.size) EInvalidElf::raise("relocation is beyond bounds");
+
+  offset += sec.offset;
+  Relocation rel;
+
+  rel.address = read32(offset);
+  rel.info = read32(offset + 0x04);
+  rel.addend = sec.type == SHT_RELA ? read32(offset + 0x08) :  0;
+
+  rel.symbol = rel.info >> 8;
+  rel.type = rel.info & 0x0f;
+
+  return rel;
+}
+
 const char* ElfParser::getName(const Section& section, uInt32 offset) const
 {
   if (offset >= section.size) EInvalidElf::raise("name out of bounds");
@@ -220,6 +277,7 @@ ostream& operator<<(ostream& os, const ElfParser::Symbol symbol)
   reset.copyfmt(os);
 
   os
+    << symbol.nameOffset << " "
     << symbol.name
     << std::hex << std::setw(4) << std::setfill('0')
     << " value=0x" << symbol.value
@@ -234,3 +292,23 @@ ostream& operator<<(ostream& os, const ElfParser::Symbol symbol)
 
   return os;
 }
+
+ostream& operator<<(ostream& os, const ElfParser::Relocation rel)
+{
+  std::ios reset(nullptr);
+  reset.copyfmt(os);
+
+  os
+    << rel.symbolName << " :"
+    << std::hex << std::setw(4) << std::setfill('0')
+    << " address=0x" << rel.address
+    << " info=0x" << rel.info
+    << " addend=0x" << rel.addend
+    << " type=0x" << (int)rel.type;
+
+  os.copyfmt(reset);
+
+  os << " symbol=" << (int)rel.symbol;
+
+  return os;
+}

src/emucore/elf/ElfParser.hxx

@@ -18,6 +18,8 @@
 #ifndef ELF_PARSER
 #define ELF_PARSER
 
+#include <unordered_map>
+
 #include "bspf.hxx"
 
 class ElfParser {
@@ -78,6 +80,16 @@ class ElfParser {
       uInt8 type;
     };
 
+    struct Relocation {
+      uInt32 address;
+      uInt32 info;
+      uInt32 addend;
+
+      uInt32 symbol;
+      uInt8 type;
+      string symbolName;
+    };
+
   public:
     static constexpr uInt8 ENDIAN_LITTLE_ENDIAN = 0x01;
     static constexpr uInt8 ENDIAN_BIG_ENDIAN = 0x02;
@@ -99,6 +111,8 @@ class ElfParser {
     static constexpr uInt32 SHN_ABS = 0xfff1;
     static constexpr uInt32 SHN_UND = 0x00;
 
+    static constexpr uInt32 STT_SECTION = 0x03;
+
   public:
     ElfParser() = default;
 
@@ -111,6 +125,7 @@ class ElfParser {
     const vector<Section>& getSections() const;
     const vector<Symbol>& getSymbols() const;
     const optional<Section> getSection(const std::string &name) const;
+    const optional<vector<Relocation>> getRelocations(size_t section) const;
 
   private:
     uInt8 read8(uInt32 offset) const;
@@ -119,6 +134,7 @@ class ElfParser {
 
     Section readSection(uInt32 offset) const;
     Symbol readSymbol(uInt32 index, const Section& symSec, const Section& strSec) const;
+    Relocation readRelocation(uInt32 index, const Section& sec) const;
     const char* getName(const Section& section, uInt32 offset) const;
 
     const Section* getSymtab() const;
@@ -133,9 +149,11 @@ class ElfParser {
     Header header;
     vector<Section> sections;
     vector<Symbol> symbols;
+    std::unordered_map<size_t, vector<Relocation>> relocations;
 };
 
 ostream& operator<<(ostream& os, const ElfParser::Section& section);
 ostream& operator<<(ostream& os, const ElfParser::Symbol symbol);
+ostream& operator<<(ostream& os, const ElfParser::Relocation relocation);
 
 #endif // ELF_PARSER