From c51b49a8cb8901eb36860718495cccf2d5f05eea Mon Sep 17 00:00:00 2001
From: Gunnar Beutner <gbeutner@serenityos.org>
Date: Sat, 3 Jul 2021 00:25:44 +0200
Subject: [PATCH] Kernel: Implement TLS support for x86_64

---
 Kernel/Arch/x86/common/Processor.cpp | 3 +++
 Kernel/Syscalls/mmap.cpp             | 4 +++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/Kernel/Arch/x86/common/Processor.cpp b/Kernel/Arch/x86/common/Processor.cpp
index 90a2b3af3bc..263cb6803b4 100644
--- a/Kernel/Arch/x86/common/Processor.cpp
+++ b/Kernel/Arch/x86/common/Processor.cpp
@@ -1214,6 +1214,9 @@ extern "C" void enter_thread_context(Thread* from_thread, Thread* to_thread)
     auto& tls_descriptor = processor.get_gdt_entry(GDT_SELECTOR_TLS);
     tls_descriptor.set_base(to_thread->thread_specific_data());
     tls_descriptor.set_limit(to_thread->thread_specific_region_size());
+#else
+    MSR fs_base_msr(MSR_FS_BASE);
+    fs_base_msr.set(to_thread->thread_specific_data().get());
 #endif
 
     if (from_regs.cr3 != to_regs.cr3)
diff --git a/Kernel/Syscalls/mmap.cpp b/Kernel/Syscalls/mmap.cpp
index 3a44c41b1c2..cc6cc1fa1f9 100644
--- a/Kernel/Syscalls/mmap.cpp
+++ b/Kernel/Syscalls/mmap.cpp
@@ -6,6 +6,7 @@
  */
 
 #include <Kernel/Arch/x86/InterruptDisabler.h>
+#include <Kernel/Arch/x86/MSR.h>
 #include <Kernel/Arch/x86/SmapDisabler.h>
 #include <Kernel/FileSystem/FileDescription.h>
 #include <Kernel/PerformanceEventBuffer.h>
@@ -618,7 +619,8 @@ 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
-    dbgln("FIXME: Not setting FS_BASE for process.");
+    MSR fs_base_msr(MSR_FS_BASE);
+    fs_base_msr.set(main_thread->thread_specific_data().get());
 #endif
 
     return m_master_tls_region.unsafe_ptr()->vaddr().get();