MdePkg/BaseLib: Add Shadow Stack Support for X86.

[mirror_edk2.git] / MdePkg / Library / BaseLib / Ia32 / LongJump.c

/** @file\r
  Implementation of _LongJump() on IA-32.\r
\r
  Copyright (c) 2006 - 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
\r
#include "BaseLibInternals.h"\r
\r
\r
/**\r
  Restores the CPU context that was saved with SetJump().\r
\r
  Restores the CPU context from the buffer specified by JumpBuffer.\r
  This function never returns to the caller.\r
  Instead is resumes execution based on the state of JumpBuffer.\r
\r
  @param  JumpBuffer    A pointer to CPU context buffer.\r
  @param  Value         The value to return when the SetJump() context is restored.\r
\r
**/\r
__declspec (naked)\r
VOID\r
EFIAPI\r
InternalLongJump (\r
  IN      BASE_LIBRARY_JUMP_BUFFER  *JumpBuffer,\r
  IN      UINTN                     Value\r
  )\r
{\r
  _asm {\r
    mov     eax, [PcdGet32 (PcdControlFlowEnforcementPropertyMask)]\r
    test    eax, eax\r
    jz      CetDone\r
    _emit      0x0F\r
    _emit      0x20\r
    _emit      0xE0                ; mov     eax, cr4\r
    bt      eax, 23                ; check if CET is enabled\r
    jnc     CetDone\r
\r
    mov     edx, [esp + 4]         ; edx = JumpBuffer\r
    mov     edx, [edx + 24]        ; edx = target SSP\r
    _emit      0xF3\r
    _emit      0x0F\r
    _emit      0x1E\r
    _emit      0xC8                ; READSSP EAX\r
    sub     edx, eax               ; edx = delta\r
    mov     eax, edx               ; eax = delta\r
\r
    shr     eax, 2                 ; eax = delta/sizeof(UINT32)\r
    _emit      0xF3\r
    _emit      0x0F\r
    _emit      0xAE\r
    _emit      0xE8                ; INCSSP EAX\r
\r
CetDone:\r
\r
    pop     eax                         ; skip return address\r
    pop     edx                         ; edx <- JumpBuffer\r
    pop     eax                         ; eax <- Value\r
    mov     ebx, [edx]\r
    mov     esi, [edx + 4]\r
    mov     edi, [edx + 8]\r
    mov     ebp, [edx + 12]\r
    mov     esp, [edx + 16]\r
    jmp     dword ptr [edx + 20]\r
  }\r
}\r
\r