UefiCpuPkg/ResetVector/Vtf0/Ia32/SearchForBfvBase.asm

   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
  23 BITS    32
  24
  25 ;
  26 ; Modified:  EAX, EBX
  27 ; Preserved: EDI, ESP
  28 ;
  29 ; @param[out]  EBP  Address of Boot Firmware Volume (BFV)
  30 ;
  31 Flat32SearchForBfvBase:
  32
  33     xor     eax, eax
  34 searchingForBfvHeaderLoop:
  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
  66 searchedForBfvHeaderButNotFound:
  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
  80 searchedForBfvHeaderAndItWasFound:
  81     mov     ebp, eax
  82
  83     debugShowPostCode POSTCODE_BFV_FOUND
  84
  85     OneTimeCallRet Flat32SearchForBfvBase
  86