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@@ -0,0 +1,87 @@
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+;------------------------------------------------------------------------------
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+; @file
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+; Search for the Boot Firmware Volume (BFV) base address
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+;
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+; Copyright (c) 2008 - 2009, Intel Corporation. All rights reserved.<BR>
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+; Copyright (c) 2019, Citrix Systems, Inc.
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+;
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+; SPDX-License-Identifier: BSD-2-Clause-Patent
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+;
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+;------------------------------------------------------------------------------
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+
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+;#define EFI_FIRMWARE_FILE_SYSTEM2_GUID \
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+; { 0x8c8ce578, 0x8a3d, 0x4f1c, { 0x99, 0x35, 0x89, 0x61, 0x85, 0xc3, 0x2d, 0xd3 } }
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+%define FFS_GUID_DWORD0 0x8c8ce578
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+%define FFS_GUID_DWORD1 0x4f1c8a3d
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+%define FFS_GUID_DWORD2 0x61893599
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+%define FFS_GUID_DWORD3 0xd32dc385
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+
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+BITS 32
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+
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+;
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+; Modified: EAX, EBX, ECX
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+; Preserved: EDI, ESP
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+;
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+; @param[in] EAX Start search from here
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+; @param[out] EBP Address of Boot Firmware Volume (BFV)
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+;
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+Flat32SearchForBfvBase:
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+
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+ mov ecx, eax
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+searchingForBfvHeaderLoop:
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+ ;
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+ ; We check for a firmware volume at every 4KB address in the 16MB
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+ ; just below where we started, ECX.
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+ ;
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+ sub eax, 0x1000
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+ mov ebx, ecx
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+ sub ebx, eax
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+ cmp ebx, 0x01000000
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+ ; if ECX-EAX > 16MB; jump notfound
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+ ja searchedForBfvHeaderButNotFound
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+
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+ ;
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+ ; Check FFS GUID
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+ ;
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+ cmp dword [eax + 0x10], FFS_GUID_DWORD0
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+ jne searchingForBfvHeaderLoop
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+ cmp dword [eax + 0x14], FFS_GUID_DWORD1
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+ jne searchingForBfvHeaderLoop
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+ cmp dword [eax + 0x18], FFS_GUID_DWORD2
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+ jne searchingForBfvHeaderLoop
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+ cmp dword [eax + 0x1c], FFS_GUID_DWORD3
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+ jne searchingForBfvHeaderLoop
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+
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+ ;
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+ ; Check FV Length
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+ ;
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+ cmp dword [eax + 0x24], 0
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+ jne searchingForBfvHeaderLoop
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+ mov ebx, eax
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+ add ebx, dword [eax + 0x20]
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+ cmp ebx, ecx
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+ jnz searchingForBfvHeaderLoop
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+
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+ jmp searchedForBfvHeaderAndItWasFound
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+
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+searchedForBfvHeaderButNotFound:
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+ ;
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+ ; Hang if the SEC entry point was not found
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+ ;
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+ debugShowPostCode POSTCODE_BFV_NOT_FOUND
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+
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+ ;
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+ ; 0xbfbfbfbf in the EAX & EBP registers helps signal what failed
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+ ; for debugging purposes.
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+ ;
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+ mov eax, 0xBFBFBFBF
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+ mov ebp, eax
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+ jmp $
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+
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+searchedForBfvHeaderAndItWasFound:
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+ mov ebp, eax
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+
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+ debugShowPostCode POSTCODE_BFV_FOUND
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+
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+ OneTimeCallRet Flat32SearchForBfvBase
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+
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