UefiCpuPkg/PiSmmCpu: Add Shadow Stack Support for X86 SMM.

[mirror_edk2.git] / UefiCpuPkg / PiSmmCpuDxeSmm / Ia32 / Cet.nasm

;------------------------------------------------------------------------------ ;\r
; Copyright (c) 2019, Intel Corporation. All rights reserved.<BR>\r
; This program and the accompanying materials\r
; are licensed and made available under the terms and conditions of the BSD License\r
; which accompanies this distribution.  The full text of the license may be found at\r
; http://opensource.org/licenses/bsd-license.php.\r
;\r
; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
;\r
;-------------------------------------------------------------------------------\r
\r
%include "Nasm.inc"\r
\r
SECTION .text\r
\r
global ASM_PFX(DisableCet)\r
ASM_PFX(DisableCet):\r
\r
    ; Skip the pushed data for call\r
    mov     eax, 1\r
    INCSSP_EAX\r
\r
    mov     eax, cr4\r
    btr     eax, 23                      ; clear CET\r
    mov     cr4, eax\r
    ret\r
\r
global ASM_PFX(EnableCet)\r
ASM_PFX(EnableCet):\r
\r
    mov     eax, cr4\r
    bts     eax, 23                      ; set CET\r
    mov     cr4, eax\r
\r
    ; use jmp to skip the check for ret\r
    pop     eax\r
    jmp     eax\r
\r