[SharedCache] Add mutex to guard m_namedSymbols

It is modified on a worker thread so if a user tries to call `GetSymbolWithName` after view init but before the processing on the worker thread finishes, there would have been issues!

Author: emesare

view/sharedcache/core/SharedCache.cpp

@@ -149,6 +149,7 @@ SharedCache::SharedCache(uint64_t addressSize)
 {
 	m_addressSize = addressSize;
 	m_vm = std::make_shared<VirtualMemory>();
+	m_namedSymMutex = std::make_unique<std::shared_mutex>();
 }
 
 
@@ -437,6 +438,7 @@ void SharedCache::ProcessEntrySlideInfo(const CacheEntry& entry) const
 
 void SharedCache::ProcessSymbols()
 {
+	std::unique_lock<std::shared_mutex> lock(*m_namedSymMutex);
 	// Populate the named symbols from the regular symbols map.
 	m_namedSymbols.reserve(m_symbols.size());
 	for (const auto& [address, symbol] : m_symbols)
@@ -520,8 +522,9 @@ std::optional<CacheSymbol> SharedCache::GetSymbolAt(uint64_t address) const
 	return it->second;
 }
 
-std::optional<CacheSymbol> SharedCache::GetSymbolWithName(const std::string& name) const
+std::optional<CacheSymbol> SharedCache::GetSymbolWithName(const std::string& name)
 {
+	std::shared_lock<std::shared_mutex> lock(*m_namedSymMutex);
 	const auto it = m_namedSymbols.find(name);
 	if (it == m_namedSymbols.end())
 		return std::nullopt;

view/sharedcache/core/SharedCache.h

@@ -203,6 +203,9 @@ class SharedCache
 	// Quickly lookup a symbol by name, populated by `FinalizeSymbols`.
 	// `m_namedSymbols` is modified in a worker thread spawned by view init so we must not get a symbol until its populated.
 	std::unordered_map<std::string, uint64_t> m_namedSymbols {};
+	// Used to guard `m_namedSymbols` as it's accessed on multiple threads.
+	// NOTE: Wrapped in unique_ptr to keep SharedCache movable.
+	std::unique_ptr<std::shared_mutex> m_namedSymMutex;
 
 	bool ProcessEntryImage(const std::string& path, const dyld_cache_image_info& info);
 
@@ -225,7 +228,6 @@ class SharedCache
 	const AddressRangeMap<CacheRegion>& GetRegions() const { return m_regions; }
 	const std::unordered_map<uint64_t, CacheImage>& GetImages() const { return m_images; }
 	const std::unordered_map<uint64_t, CacheSymbol>& GetSymbols() const { return m_symbols; }
-	const std::unordered_map<std::string, uint64_t>& GetNamedSymbols() const { return m_namedSymbols; }
 
 	void AddImage(CacheImage&& image);
 
@@ -266,7 +268,7 @@ class SharedCache
 
 	std::optional<CacheSymbol> GetSymbolAt(uint64_t address) const;
 
-	std::optional<CacheSymbol> GetSymbolWithName(const std::string& name) const;
+	std::optional<CacheSymbol> GetSymbolWithName(const std::string& name);
 };
 
 // This constructs a Cache, give it a file path, and it will add all relevant cache entries.