1;------------------------------------------------------------------------------
2; @file
3; Search for the Boot Firmware Volume (BFV) base address
4;
5; Copyright (c) 2008 - 2009, Intel Corporation. All rights reserved.<BR>
6; This program and the accompanying materials
7; are licensed and made available under the terms and conditions of the BSD License
8; which accompanies this distribution.  The full text of the license may be found at
9; http://opensource.org/licenses/bsd-license.php
10;
11; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
12; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
13;
14;------------------------------------------------------------------------------
15
16;#define EFI_FIRMWARE_FILE_SYSTEM2_GUID \
17;  { 0x8c8ce578, 0x8a3d, 0x4f1c, { 0x99, 0x35, 0x89, 0x61, 0x85, 0xc3, 0x2d, 0xd3 } }
18%define FFS_GUID_DWORD0 0x8c8ce578
19%define FFS_GUID_DWORD1 0x4f1c8a3d
20%define FFS_GUID_DWORD2 0x61893599
21%define FFS_GUID_DWORD3 0xd32dc385
22
23BITS    32
24
25;
26; Modified:  EAX, EBX
27; Preserved: EDI, ESP
28;
29; @param[out]  EBP  Address of Boot Firmware Volume (BFV)
30;
31Flat32SearchForBfvBase:
32
33    xor     eax, eax
34searchingForBfvHeaderLoop:
35    ;
36    ; We check for a firmware volume at every 4KB address in the top 16MB
37    ; just below 4GB.  (Addresses at 0xffHHH000 where H is any hex digit.)
38    ;
39    sub     eax, 0x1000
40    cmp     eax, 0xff000000
41    jb      searchedForBfvHeaderButNotFound
42
43    ;
44    ; Check FFS GUID
45    ;
46    cmp     dword [eax + 0x10], FFS_GUID_DWORD0
47    jne     searchingForBfvHeaderLoop
48    cmp     dword [eax + 0x14], FFS_GUID_DWORD1
49    jne     searchingForBfvHeaderLoop
50    cmp     dword [eax + 0x18], FFS_GUID_DWORD2
51    jne     searchingForBfvHeaderLoop
52    cmp     dword [eax + 0x1c], FFS_GUID_DWORD3
53    jne     searchingForBfvHeaderLoop
54
55    ;
56    ; Check FV Length
57    ;
58    cmp     dword [eax + 0x24], 0
59    jne     searchingForBfvHeaderLoop
60    mov     ebx, eax
61    add     ebx, dword [eax + 0x20]
62    jnz     searchingForBfvHeaderLoop
63
64    jmp     searchedForBfvHeaderAndItWasFound
65
66searchedForBfvHeaderButNotFound:
67    ;
68    ; Hang if the SEC entry point was not found
69    ;
70    debugShowPostCode POSTCODE_BFV_NOT_FOUND
71
72    ;
73    ; 0xbfbfbfbf in the EAX & EBP registers helps signal what failed
74    ; for debugging purposes.
75    ;
76    mov     eax, 0xBFBFBFBF
77    mov     ebp, eax
78    jmp     $
79
80searchedForBfvHeaderAndItWasFound:
81    mov     ebp, eax
82
83    debugShowPostCode POSTCODE_BFV_FOUND
84
85    OneTimeCallRet Flat32SearchForBfvBase
86
87