[Lldb-commits] [lldb] [lldb] Adjust DynamicLoaderDarwin::GetThreadLocalData to support changes to TLS on macOS (PR #77854)

[Felipe de Azevedo Piovezan via lldb-commits]

================
@@ -1048,70 +1048,107 @@ DynamicLoaderDarwin::GetThreadLocalData(const lldb::ModuleSP module_sp,
 
   std::lock_guard<std::recursive_mutex> guard(m_mutex);
 
-  const uint32_t addr_size = m_process->GetAddressByteSize();
+  lldb_private::Address tls_addr;
+  if (!module_sp->ResolveFileAddress(tls_file_addr, tls_addr))
+    return LLDB_INVALID_ADDRESS;
+
+  Target &target = m_process->GetTarget();
   uint8_t buf[sizeof(lldb::addr_t) * 3];
+  const uint32_t addr_size = m_process->GetAddressByteSize();
+  const size_t tls_data_size = addr_size * 3;
+  Status error;
+  const size_t bytes_read = target.ReadMemory(
+      tls_addr, buf, tls_data_size, error, /*force_live_memory = */ true);
+  if (bytes_read != tls_data_size || error.Fail())
+    return LLDB_INVALID_ADDRESS;
 
-  lldb_private::Address tls_addr;
-  if (module_sp->ResolveFileAddress(tls_file_addr, tls_addr)) {
-    Status error;
-    const size_t tsl_data_size = addr_size * 3;
-    Target &target = m_process->GetTarget();
-    if (target.ReadMemory(tls_addr, buf, tsl_data_size, error, true) ==
-        tsl_data_size) {
-      const ByteOrder byte_order = m_process->GetByteOrder();
-      DataExtractor data(buf, sizeof(buf), byte_order, addr_size);
-      lldb::offset_t offset = addr_size; // Skip the first pointer
-      const lldb::addr_t pthread_key = data.GetAddress(&offset);
-      const lldb::addr_t tls_offset = data.GetAddress(&offset);
-      if (pthread_key != 0) {
-        // First check to see if we have already figured out the location of
-        // TLS data for the pthread_key on a specific thread yet. If we have we
-        // can re-use it since its location will not change unless the process
-        // execs.
-        const tid_t tid = thread_sp->GetID();
-        auto tid_pos = m_tid_to_tls_map.find(tid);
-        if (tid_pos != m_tid_to_tls_map.end()) {
-          auto tls_pos = tid_pos->second.find(pthread_key);
-          if (tls_pos != tid_pos->second.end()) {
-            return tls_pos->second + tls_offset;
-          }
+  DataExtractor data(buf, sizeof(buf), m_process->GetByteOrder(), addr_size);
+  lldb::offset_t offset = 0;
+  const lldb::addr_t thunk_addr = data.GetAddress(&offset);
+  const lldb::addr_t key = data.GetAddress(&offset);
+  const lldb::addr_t tls_offset = data.GetAddress(&offset);
+
+  TypeSystemClangSP scratch_ts_sp =
+      ScratchTypeSystemClang::GetForTarget(target);
+  if (!scratch_ts_sp)
+    return LLVM_INVALID_ADDRESS;
+  CompilerType clang_void_ptr_type =
+      scratch_ts_sp->GetBasicType(eBasicTypeVoid).GetPointerType();
+  EvaluateExpressionOptions options;
+  DiagnosticManager execution_errors;
+  ExecutionContext exe_ctx(thread_sp);
+
+  // On modern apple platforms, there is a small data structure that looks
+  // approximately like this:
+  // struct TLS_Thunk {
+  //  void *(*get_addr)(struct TLS_Thunk *);
+  //  size_t key;
+  //  size_t offset;
+  // }
----------------
felipepiovezan wrote:

Do you think this comment would be more appropriate a few lines above? It seems like we are trying to find these fields around line 1067

https://github.com/llvm/llvm-project/pull/77854