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   SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9
  10 #include "BaseLibInternals.h"
  11
  12
  13 /**
  14   Restores the CPU context that was saved with SetJump().
  15
  16   Restores the CPU context from the buffer specified by JumpBuffer.
  17   This function never returns to the caller.
  18   Instead is resumes execution based on the state of JumpBuffer.
  19
  20   @param  JumpBuffer    A pointer to CPU context buffer.
  21   @param  Value         The value to return when the SetJump() context is restored.
  22
  23 **/
  24 __declspec (naked)
  25 VOID
  26 EFIAPI
  27 InternalLongJump (
  28   IN      BASE_LIBRARY_JUMP_BUFFER  *JumpBuffer,
  29   IN      UINTN                     Value
  30   )
  31 {
  32   _asm {
  33     mov     eax, [PcdGet32 (PcdControlFlowEnforcementPropertyMask)]
  34     test    eax, eax
  35     jz      CetDone
  36     _emit      0x0F
  37     _emit      0x20
  38     _emit      0xE0                ; mov     eax, cr4
  39     bt      eax, 23                ; check if CET is enabled
  40     jnc     CetDone
  41
  42     mov     edx, [esp + 4]         ; edx = JumpBuffer
  43     mov     edx, [edx + 24]        ; edx = target SSP
  44     _emit      0xF3
  45     _emit      0x0F
  46     _emit      0x1E
  47     _emit      0xC8                ; READSSP EAX
  48     sub     edx, eax               ; edx = delta
  49     mov     eax, edx               ; eax = delta
  50
  51     shr     eax, 2                 ; eax = delta/sizeof(UINT32)
  52     _emit      0xF3
  53     _emit      0x0F
  54     _emit      0xAE
  55     _emit      0xE8                ; INCSSP EAX
  56
  57 CetDone:
  58
  59     pop     eax                         ; skip return address
  60     pop     edx                         ; edx <- JumpBuffer
  61     pop     eax                         ; eax <- Value
  62     mov     ebx, [edx]
  63     mov     esi, [edx + 4]
  64     mov     edi, [edx + 8]
  65     mov     ebp, [edx + 12]
  66     mov     esp, [edx + 16]
  67     jmp     dword ptr [edx + 20]
  68   }
  69 }
  70