MdePkg/Library/BaseLib/Ia32/LongJump.c

   1 /** @file
   2   Implementation of _LongJump() on IA-32.
   3
   4   Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
   5   This program and the accompanying materials
   6   are licensed and made available under the terms and conditions of the BSD License
   7   which accompanies this distribution.  The full text of the license may be found at
   8   http://opensource.org/licenses/bsd-license.php.
   9
  10   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  11   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  12
  13 **/
  14
  15
  16 #include "BaseLibInternals.h"
  17
  18
  19 /**
  20   Restores the CPU context that was saved with SetJump().
  21
  22   Restores the CPU context from the buffer specified by JumpBuffer.
  23   This function never returns to the caller.
  24   Instead is resumes execution based on the state of JumpBuffer.
  25
  26   @param  JumpBuffer    A pointer to CPU context buffer.
  27   @param  Value         The value to return when the SetJump() context is restored.
  28
  29 **/
  30 __declspec (naked)
  31 VOID
  32 EFIAPI
  33 InternalLongJump (
  34   IN      BASE_LIBRARY_JUMP_BUFFER  *JumpBuffer,
  35   IN      UINTN                     Value
  36   )
  37 {
  38   _asm {
  39     mov     eax, [PcdGet32 (PcdControlFlowEnforcementPropertyMask)]
  40     test    eax, eax
  41     jz      CetDone
  42     _emit      0x0F
  43     _emit      0x20
  44     _emit      0xE0                ; mov     eax, cr4
  45     bt      eax, 23                ; check if CET is enabled
  46     jnc     CetDone
  47
  48     mov     edx, [esp + 4]         ; edx = JumpBuffer
  49     mov     edx, [edx + 24]        ; edx = target SSP
  50     _emit      0xF3
  51     _emit      0x0F
  52     _emit      0x1E
  53     _emit      0xC8                ; READSSP EAX
  54     sub     edx, eax               ; edx = delta
  55     mov     eax, edx               ; eax = delta
  56
  57     shr     eax, 2                 ; eax = delta/sizeof(UINT32)
  58     _emit      0xF3
  59     _emit      0x0F
  60     _emit      0xAE
  61     _emit      0xE8                ; INCSSP EAX
  62
  63 CetDone:
  64
  65     pop     eax                         ; skip return address
  66     pop     edx                         ; edx <- JumpBuffer
  67     pop     eax                         ; eax <- Value
  68     mov     ebx, [edx]
  69     mov     esi, [edx + 4]
  70     mov     edi, [edx + 8]
  71     mov     ebp, [edx + 12]
  72     mov     esp, [edx + 16]
  73     jmp     dword ptr [edx + 20]
  74   }
  75 }
  76