Kernel: Disable __thread and TLS on x86_64 for now

They're not yet properly supported.

CMakeLists.txt

@@ -93,6 +93,11 @@ set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 
+if("${SERENITY_ARCH}" STREQUAL "x86_64")
+    # FIXME: Implement TLS support and get rid of this
+    add_compile_definitions(NO_TLS X86_64_NO_TLS)
+endif()
+
 add_compile_options(-Wno-literal-suffix)
 if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
     add_compile_options(-fconcepts)

Kernel/Syscalls/mmap.cpp

@@ -612,7 +612,7 @@ KResultOr<FlatPtr> Process::sys$allocate_tls(Userspace<const char*> initial_data
     tls_descriptor.set_base(main_thread->thread_specific_data());
     tls_descriptor.set_limit(main_thread->thread_specific_region_size());
 #else
-    TODO();
+    dbgln("FIXME: Not setting FS_BASE for process.");
 #endif
 
     return m_master_tls_region.unsafe_ptr()->vaddr().get();

Userland/Libraries/LibC/pthread_tls.cpp

@@ -26,7 +26,10 @@ struct SpecificTable {
 
 static KeyTable s_keys;
 
-__thread SpecificTable t_specifics;
+#    ifndef X86_64_NO_TLS
+__thread
+#    endif
+    SpecificTable t_specifics;
 
 int __pthread_key_create(pthread_key_t* key, KeyDestructor destructor)
 {

Userland/Libraries/LibDl/dlfcn.cpp

@@ -11,8 +11,16 @@
 #include <string.h>
 
 // FIXME: use thread_local and a String once TLS works
-__thread char* s_dlerror_text = NULL;
-__thread bool s_dlerror_retrieved = false;
+#ifndef X86_64_NO_TLS
+__thread
+#endif
+    char* s_dlerror_text
+    = NULL;
+#ifndef X86_64_NO_TLS
+__thread
+#endif
+    bool s_dlerror_retrieved
+    = false;
 
 static void store_error(const String& error)
 {

Userland/Libraries/LibPthread/pthread.cpp

@@ -33,8 +33,14 @@ static constexpr size_t required_stack_alignment = 4 * MiB;
 static constexpr size_t highest_reasonable_guard_size = 32 * PAGE_SIZE;
 static constexpr size_t highest_reasonable_stack_size = 8 * MiB; // That's the default in Ubuntu?
 
-__thread void* s_stack_location;
-__thread size_t s_stack_size;
+#ifndef X86_64_NO_TLS
+__thread
+#endif
+    void* s_stack_location;
+#ifndef X86_64_NO_TLS
+__thread
+#endif
+    size_t s_stack_size;
 
 #define __RETURN_PTHREAD_ERROR(rc) \
     return ((rc) < 0 ? -(rc) : 0)