x86-64: Early TLS initialization

Allow early boot code to use thread local storage
when it is enabled.

Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>

arch/x86/core/intel64.cmake

@@ -17,5 +17,5 @@ zephyr_library_sources(
 )
 
 zephyr_library_sources_ifdef(CONFIG_USERSPACE	intel64/userspace.S)
-
+zephyr_library_sources_ifdef(CONFIG_THREAD_LOCAL_STORAGE	intel64/tls.c)
 zephyr_library_sources_ifdef(CONFIG_DEBUG_COREDUMP	intel64/coredump.c)

arch/x86/core/intel64/locore.S

@@ -261,6 +261,11 @@ enter_code64:
 
 	/* Enter C domain now that we have a stack set up, never to return */
 	movq %rbp, %rdi
+#ifdef CONFIG_STACK_CANARIES_TLS
+	pushq %rsp
+	call z_x86_early_tls_update_gdt
+	popq %rsp
+#endif
 	call z_x86_cpu_init
 
 	/* 64 bit OS entry point, used by EFI support.  UEFI

arch/x86/core/intel64/tls.c

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2023 Intel Corporation.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <kernel_internal.h>
+
+FUNC_NO_STACK_PROTECTOR
+void z_x86_early_tls_update_gdt(char *stack_ptr)
+{
+	uintptr_t *self_ptr;
+	uint32_t fs_base = X86_FS_BASE;
+
+	/*
+	 * Since we are populating things backwards, store
+	 * the pointer to the TLS area at top of stack.
+	 */
+	stack_ptr -= sizeof(uintptr_t);
+	self_ptr = (void *)stack_ptr;
+	*self_ptr = POINTER_TO_UINT(stack_ptr);
+
+	__asm__ volatile(
+		"movl %0, %%ecx;\n\t"
+		"movq %1, %%rax;\n\t"
+		"movq %1, %%rdx;\n\t"
+		"shrq $32, %%rdx;\n\t"
+		"wrmsr;\n\t"
+		:
+		: "r"(fs_base), "r"(POINTER_TO_UINT(self_ptr)));
+}