From d960909d1bc496d7dd4b4998b0810356c2ea91b3 Mon Sep 17 00:00:00 2001
From: Max Wash <mbswash@gmail.com>
Date: Thu, 9 Feb 2023 21:38:06 +0000
Subject: [PATCH] x86_64: pmap: enable NX protection during bootstrap

---
 arch/x86_64/include/arch/paging.h |  1 +
 arch/x86_64/pmap.c                |  2 ++
 arch/x86_64/pmap_ctrl.S           | 11 +++++++++++
 3 files changed, 14 insertions(+)

diff --git a/arch/x86_64/include/arch/paging.h b/arch/x86_64/include/arch/paging.h
index 7335e31..d3fd4e0 100644
--- a/arch/x86_64/include/arch/paging.h
+++ b/arch/x86_64/include/arch/paging.h
@@ -50,5 +50,6 @@ typedef enum page_size {
 /* returns 1 if gigabyte pages are supported by the CPU, 0 otherwise.
    defined in pmap_ctrl.S */
 extern int gigabyte_pages(void);
+extern int enable_nx(void);
 
 #endif
diff --git a/arch/x86_64/pmap.c b/arch/x86_64/pmap.c
index 6f93c48..f1636ea 100644
--- a/arch/x86_64/pmap.c
+++ b/arch/x86_64/pmap.c
@@ -226,6 +226,8 @@ void pmap_bootstrap(void)
 {
 	can_use_gbpages = gigabyte_pages();
 	printk("pmap: gigabyte pages %sabled", can_use_gbpages == 1 ? "en" : "dis");
+	enable_nx();
+	printk("pmap: NX protection enabled");
 
 	page_size_t hugepage = PS_2M;
 	if (can_use_gbpages) {
diff --git a/arch/x86_64/pmap_ctrl.S b/arch/x86_64/pmap_ctrl.S
index 28c9b67..a8416f2 100644
--- a/arch/x86_64/pmap_ctrl.S
+++ b/arch/x86_64/pmap_ctrl.S
@@ -29,3 +29,14 @@ gigabyte_pages:
 3:	pop %rbx
 	pop %rbp
 	ret
+
+	.global enable_nx
+	.type enable_nx, @function
+
+enable_nx:
+	mov $0xC0000080, %ecx
+	rdmsr
+	or $0x800, %eax
+	wrmsr
+
+	ret