1 files changed, 34 insertions, 0 deletions
diff --git a/src/VBox/Devices/EFI/Firmware/UefiCpuPkg/PiSmmCpuDxeSmm/X64/Cet.nasm b/src/VBox/Devices/EFI/Firmware/UefiCpuPkg/PiSmmCpuDxeSmm/X64/Cet.nasm
new file mode 100644
index 00000000..99172364
--- /dev/null
+++ b/src/VBox/Devices/EFI/Firmware/UefiCpuPkg/PiSmmCpuDxeSmm/X64/Cet.nasm
@@ -0,0 +1,34 @@
+;------------------------------------------------------------------------------ ;
+; Copyright (c) 2019, Intel Corporation. All rights reserved.<BR>
+; SPDX-License-Identifier: BSD-2-Clause-Patent
+;
+;-------------------------------------------------------------------------------
+
+%include "Nasm.inc"
+
+DEFAULT REL
+SECTION .text
+
+global ASM_PFX(DisableCet)
+ASM_PFX(DisableCet):
+
+    ; Skip the pushed data for call
+    mov     rax, 1
+    INCSSP_RAX
+
+    mov     rax, cr4
+    btr     eax, 23                      ; clear CET
+    mov     cr4, rax
+    ret
+
+global ASM_PFX(EnableCet)
+ASM_PFX(EnableCet):
+
+    mov     rax, cr4
+    bts     eax, 23                      ; set CET
+    mov     cr4, rax
+
+    ; use jmp to skip the check for ret
+    pop     rax
+    jmp     rax
+