mirror of https://github.com/acidanthera/audk.git
88 lines
2.3 KiB
NASM
88 lines
2.3 KiB
NASM
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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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;#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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BITS 32
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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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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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; 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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; 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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jmp searchedForBfvHeaderAndItWasFound
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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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; 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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searchedForBfvHeaderAndItWasFound:
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mov ebp, eax
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debugShowPostCode POSTCODE_BFV_FOUND
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OneTimeCallRet Flat32SearchForBfvBase
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