;------------------------------------------------------------------------------
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;
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; Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
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; SPDX-License-Identifier: BSD-2-Clause-Patent
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;
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; Module Name:
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;
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; LongJump.Asm
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;
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; Abstract:
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;
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; Implementation of _LongJump() on IA-32.
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;
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;------------------------------------------------------------------------------
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%include "Nasm.inc"
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SECTION .text
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extern ASM_PFX(PcdGet32 (PcdControlFlowEnforcementPropertyMask))
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;------------------------------------------------------------------------------
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; VOID
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; EFIAPI
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; InternalLongJump (
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; IN BASE_LIBRARY_JUMP_BUFFER *JumpBuffer,
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; IN UINTN Value
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; );
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;------------------------------------------------------------------------------
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global ASM_PFX(InternalLongJump)
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ASM_PFX(InternalLongJump):
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mov eax, [ASM_PFX(PcdGet32 (PcdControlFlowEnforcementPropertyMask))]
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test eax, eax
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jz CetDone
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mov eax, cr4
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bt eax, 23 ; check if CET is enabled
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jnc CetDone
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mov edx, [esp + 4] ; edx = JumpBuffer
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mov edx, [edx + 24] ; edx = target SSP
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READSSP_EAX
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sub edx, eax ; edx = delta
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mov eax, edx ; eax = delta
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shr eax, 2 ; eax = delta/sizeof(UINT32)
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INCSSP_EAX
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CetDone:
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pop eax ; skip return address
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pop edx ; edx <- JumpBuffer
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pop eax ; eax <- Value
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mov ebx, [edx]
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mov esi, [edx + 4]
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mov edi, [edx + 8]
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mov ebp, [edx + 12]
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mov esp, [edx + 16]
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jmp dword [edx + 20] ; restore "eip"
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