Refactor ELF reader class

also properly interpet the mmap failure condition

src/Common/ExceptionHandler/ELFSymbolTable.cpp

@@ -5,31 +5,19 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
-uint16 ELFSymbolTable::FindSection(int type, const std::string_view& name)
+template <typename T>
+std::span<T> ELFSymbolTable::SectionAsArray(const Elf64_Shdr* section)
 {
-	if (!shTable || !shStrTable)
-		return 0;
+	if (section == nullptr)
+		return {};
+	if (section->sh_size < sizeof(T))
+		return {};
+	if (section->sh_entsize != 0 && section->sh_entsize != sizeof(T))
+		return {};
 
-	for (uint16 i = 0; i < header->e_shnum; ++i)
-	{
-		auto& entry = shTable[i];
-		if(entry.sh_type == type && std::string_view{&shStrTable[entry.sh_name]} == name)
-		{
-			return i;
-		}
-	}
-	return 0;
+	return {(T*)(mappedExecutable + section->sh_offset), section->sh_size / sizeof(T)};
 }
 
-void* ELFSymbolTable::SectionPointer(uint16 index)
-{
-	return SectionPointer(shTable[index]);
-}
-
-void* ELFSymbolTable::SectionPointer(const Elf64_Shdr& section)
-{
-	return (void*)(mappedExecutable + section.sh_offset);
-}
 
 ELFSymbolTable::ELFSymbolTable()
 {
@@ -40,7 +28,7 @@ ELFSymbolTable::ELFSymbolTable()
 
 	// retrieve file size.
 	struct stat filestats;
-	if (fstat(fd, &filestats))
+	if (fstat(fd, &filestats) != 0)
 	{
 		close(fd);
 		return;
@@ -48,9 +36,9 @@ ELFSymbolTable::ELFSymbolTable()
 	mappedExecutableSize = filestats.st_size;
 
 	// attempt to map the file
-	mappedExecutable = (uint8*)(mmap(nullptr, mappedExecutableSize, PROT_READ, MAP_PRIVATE, fd, 0));
+	mappedExecutable = static_cast<uint8*>(mmap(nullptr, mappedExecutableSize, PROT_READ, MAP_PRIVATE, fd, 0));
 	close(fd);
-	if (!mappedExecutable)
+	if (mappedExecutable == MAP_FAILED)
 		return;
 
 	// verify signature
@@ -64,19 +52,11 @@ ELFSymbolTable::ELFSymbolTable()
 		}
 	}
 
-	shTable = (Elf64_Shdr*)(mappedExecutable + header->e_shoff);
+	shTable = {(Elf64_Shdr*)(mappedExecutable + header->e_shoff), header->e_shnum};
 
-	Elf64_Shdr& shStrn = shTable[header->e_shstrndx];
-	shStrTable = (char*)(mappedExecutable + shStrn.sh_offset);
-
-	strTable = (char*)SectionPointer(FindSection(SHT_STRTAB, ".strtab"));
-
-	Elf64_Shdr& symTabShdr = shTable[FindSection(SHT_SYMTAB, ".symtab")];
-	if (symTabShdr.sh_entsize == 0)
-		return;
-
-	symTableLen = symTabShdr.sh_size / symTabShdr.sh_entsize;
-	symTable = (Elf64_Sym*)(SectionPointer(symTabShdr));
+	shStrTable = SectionAsArray<char>(&shTable[header->e_shstrndx]);
+	strTable = SectionAsArray<char>(FindSection(SHT_STRTAB, ".strtab"));
+	symTable = SectionAsArray<Elf64_Sym>(FindSection(SHT_SYMTAB, ".symtab"));
 }
 
 ELFSymbolTable::~ELFSymbolTable()
@@ -85,15 +65,30 @@ ELFSymbolTable::~ELFSymbolTable()
 		munmap(mappedExecutable, mappedExecutableSize);
 }
 
+Elf64_Shdr* ELFSymbolTable::FindSection(Elf64_Word type, const std::string_view& name)
+{
+	if (shTable.empty() || shStrTable.empty())
+		return nullptr;
+
+	for (auto& entry : shTable)
+	{
+		if(entry.sh_type == type && std::string_view{&shStrTable[entry.sh_name]} == name)
+		{
+			return &entry;
+		}
+	}
+	return nullptr;
+}
+
 std::string_view ELFSymbolTable::OffsetToSymbol(uint64 ptr, uint64& fromStart) const
 {
-	if(!symTable || !strTable)
+	if(symTable.empty() || strTable.empty())
 	{
 		fromStart = -1;
 		return {};
 	}
 
-	for (auto entry = symTable+1; entry < symTable+symTableLen; ++entry)
+	for (auto entry = symTable.begin()+1; entry != symTable.end(); ++entry)
 	{
 		if (ELF64_ST_TYPE(entry->st_info) != STT_FUNC)
 			continue;

src/Common/ExceptionHandler/ELFSymbolTable.h

@@ -15,17 +15,16 @@ private:
 
 	Elf64_Ehdr* header = nullptr;
 
-	Elf64_Shdr* shTable = nullptr;
-	char* shStrTable = nullptr;
+	std::span<Elf64_Shdr> shTable{};
+	std::span<char> shStrTable{};
 
-	Elf64_Sym* symTable = nullptr;
-	uint64 symTableLen = 0;
-	char* strTable = nullptr;
+	std::span<Elf64_Sym> symTable{};
+	std::span<char> strTable{};
 
-	uint16 FindSection(int type, const std::string_view& name);
+	Elf64_Shdr* FindSection(Elf64_Word type, const std::string_view& name);
 
-	void* SectionPointer (uint16 index);
-	void* SectionPointer(const Elf64_Shdr& section);
+	template <typename T>
+	std::span<T> SectionAsArray(const Elf64_Shdr* section);
 
 	// ownership of mapped memory, cannot copy.
 	ELFSymbolTable(const ELFSymbolTable&) = delete;