MdePkg/Library/BaseLib/Ia32/SetJump.c

   1 /** @file
   2   Implementation of SetJump() 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   Worker function that checks ASSERT condition for JumpBuffer
  14
  15   Checks ASSERT condition for JumpBuffer.
  16
  17   If JumpBuffer is NULL, then ASSERT().
  18   For IPF CPUs, if JumpBuffer is not aligned on a 16-byte boundary, then ASSERT().
  19
  20   @param  JumpBuffer    A pointer to CPU context buffer.
  21
  22 **/
  23 VOID
  24 EFIAPI
  25 InternalAssertJumpBuffer (
  26   IN      BASE_LIBRARY_JUMP_BUFFER  *JumpBuffer
  27   );
  28
  29 /**
  30   Saves the current CPU context that can be restored with a call to LongJump()
  31   and returns 0.
  32
  33   Saves the current CPU context in the buffer specified by JumpBuffer and
  34   returns 0. The initial call to SetJump() must always return 0. Subsequent
  35   calls to LongJump() cause a non-zero value to be returned by SetJump().
  36
  37   If JumpBuffer is NULL, then ASSERT().
  38   For IPF CPUs, if JumpBuffer is not aligned on a 16-byte boundary, then ASSERT().
  39
  40   @param  JumpBuffer  A pointer to CPU context buffer.
  41
  42   @retval 0 Indicates a return from SetJump().
  43
  44 **/
  45 _declspec (naked)
  46 RETURNS_TWICE
  47 UINTN
  48 EFIAPI
  49 SetJump (
  50   OUT     BASE_LIBRARY_JUMP_BUFFER  *JumpBuffer
  51   )
  52 {
  53   _asm {
  54     push    [esp + 4]
  55     call    InternalAssertJumpBuffer
  56     pop     ecx
  57     pop     ecx
  58     mov     edx, [esp]
  59
  60     xor     eax, eax
  61     mov     [edx + 24], eax        ; save 0 to SSP
  62
  63     mov     eax, [PcdGet32 (PcdControlFlowEnforcementPropertyMask)]
  64     test    eax, eax
  65     jz      CetDone
  66     _emit      0x0F
  67     _emit      0x20
  68     _emit      0xE0                ; mov     eax, cr4
  69     bt      eax, 23                ; check if CET is enabled
  70     jnc     CetDone
  71
  72     mov     eax, 1
  73     _emit      0xF3
  74     _emit      0x0F
  75     _emit      0xAE
  76     _emit      0xE8                ; INCSSP EAX to read original SSP
  77     _emit      0xF3
  78     _emit      0x0F
  79     _emit      0x1E
  80     _emit      0xC8                ; READSSP EAX
  81     mov     [edx + 0x24], eax      ; save SSP
  82
  83 CetDone:
  84
  85     mov     [edx], ebx
  86     mov     [edx + 4], esi
  87     mov     [edx + 8], edi
  88     mov     [edx + 12], ebp
  89     mov     [edx + 16], esp
  90     mov     [edx + 20], ecx
  91     xor     eax, eax
  92     jmp     ecx
  93   }
  94 }
  95