1 files changed, 22 insertions, 0 deletions
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 112d3b98a3b6..001dd7dc829f 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -680,6 +680,28 @@ static void __init memory_map_bottom_up(unsigned long map_start,
 	}
 }
 
+/*
+ * The real mode trampoline, which is required for bootstrapping CPUs
+ * occupies only a small area under the low 1MB.  See reserve_real_mode()
+ * for details.
+ *
+ * If KASLR is disabled the first PGD entry of the direct mapping is copied
+ * to map the real mode trampoline.
+ *
+ * If KASLR is enabled, copy only the PUD which covers the low 1MB
+ * area. This limits the randomization granularity to 1GB for both 4-level
+ * and 5-level paging.
+ */
+static void __init init_trampoline(void)
+{
+#ifdef CONFIG_X86_64
+	if (!kaslr_memory_enabled())
+		trampoline_pgd_entry = init_top_pgt[pgd_index(__PAGE_OFFSET)];
+	else
+		init_trampoline_kaslr();
+#endif
+}
+
 void __init init_mem_mapping(void)
 {
 	unsigned long end;