[mirror_edk2.git] / DuetPkg / BootSector / bs32.S

#------------------------------------------------------------------------------\r
#*\r
#*   Copyright 2006 - 2007, Intel Corporation                                                         \r
#*   All rights reserved. This program and the accompanying materials                          \r
#*   are licensed and made available under the terms and conditions of the BSD License         \r
#*   which accompanies this distribution.  The full text of the license may be found at        \r
#*   http://opensource.org/licenses/bsd-license.php                                            \r
#*                                                                                             \r
#*   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,                     \r
#*   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.             \r
#*   \r
#*    bs32.asm\r
#*  \r
#*   Abstract:\r
#*\r
#------------------------------------------------------------------------------\r
\r
        #.MODEL small\r
        .stack: \r
        .486p: \r
        .code16\r
\r
.equ                      FAT_DIRECTORY_ENTRY_SIZE, 0x0020\r
.equ                      FAT_DIRECTORY_ENTRY_SHIFT, 5\r
.equ                      BLOCK_SIZE, 0x0200\r
.equ                      BLOCK_MASK, 0x01ff\r
.equ                      BLOCK_SHIFT, 9\r
                                               # "EFILDR_____"\r
.equ                      LOADER_FILENAME_PART1, 0x4c494645    # "EFIL"\r
.equ                      LOADER_FILENAME_PART2, 0x30325244    # "DR20"\r
.equ                      LOADER_FILENAME_PART3, 0x20202030    # "0___"\r
\r
        .org 0x0\r
.global _start\r\r
_start:\r
Ia32Jump: \r
  jmp   BootSectorEntryPoint  # JMP inst                  - 3 bytes\r
  nop\r
\r
OemId:             .ascii  "INTEL   "   # OemId               - 8 bytes\r
# BPB data below will be fixed by tool\r
SectorSize:        .word  0             # Sector Size         - 16 bits\r
SectorsPerCluster: .byte  0             # Sector Per Cluster  - 8 bits\r
ReservedSectors:   .word  0             # Reserved Sectors    - 16 bits\r
NoFats:            .byte  0             # Number of FATs      - 8 bits\r
RootEntries:       .word  0             # Root Entries        - 16 bits\r
Sectors:           .word  0             # Number of Sectors   - 16 bits\r
Media:             .byte  0             # Media               - 8 bits  - ignored\r
SectorsPerFat:     .word  0             # Sectors Per FAT     - 16 bits\r
SectorsPerTrack:   .word  0             # Sectors Per Track   - 16 bits - ignored\r
Heads:             .word  0             # Heads               - 16 bits - ignored\r
HiddenSectors:     .long  0             # Hidden Sectors      - 32 bits - ignored\r
LargeSectors:      .long  0             # Large Sectors       - 32 bits \r
\r
#******************************************************************************\r
#\r
#The structure for FAT32 starting at offset 36 of the boot sector. (At this point, \r
#the BPB/boot sector for FAT12 and FAT16 differs from the BPB/boot sector for FAT32.)\r
#\r
#******************************************************************************\r
\r
SectorsPerFat32:   .long  0              # Sectors Per FAT for FAT32       - 4 bytes\r
ExtFlags:          .word  0              # Mirror Flag                     - 2 bytes\r
FSVersion:         .word  0              # File System Version             - 2 bytes\r
RootCluster:       .long  0              # 1st Cluster Number of Root Dir  - 4 bytes\r
FSInfo:            .word  0              # Sector Number of FSINFO         - 2 bytes\r
BkBootSector:      .word  0              # Sector Number of Bk BootSector  - 2 bytes\r
Reserved:          .fill  12, 1, 0       # Reserved Field                  - 12 bytes\r
PhysicalDrive:     .byte  0              # Physical Drive Number           - 1 byte\r
Reserved1:         .byte  0              # Reserved Field                  - 1 byte\r
Signature:         .byte  0              # Extended Boot Signature         - 1 byte\r
VolId:             .ascii  "    "        # Volume Serial Number            - 4 bytes\r
FatLabel:          .ascii  "           " # Volume Label                    - 11 bytes\r
FileSystemType:    .ascii  "FAT32   "    # File System Type                - 8 bytes\r
BootSectorEntryPoint: \r
        #ASSUME ds:@code\r
        #ASSUME ss:@code\r
\r
# ****************************************************************************\r
# Start Print\r
# ****************************************************************************\r
  movw $StartString, %si\r
  call PrintString\r
\r
# ****************************************************************************\r
# Print over\r
# ****************************************************************************\r
\r
  movw  %cs, %ax      # ax = 0\r
  movw  %ax, %ss      # ss = 0\r
  addw  $0x1000, %ax\r
  movw  %ax, %ds\r
\r
  movw  $0x7c00, %sp  # sp = 0x7c00\r
  movw  %sp, %bp      # bp = 0x7c00\r
\r
  movb  $8, %ah                             # ah = 8 - Get Drive Parameters Function\r
  movb  %dl, PhysicalDrive(%bp)             # BBS defines that BIOS would pass the booting driver number to the loader through DL\r
  int   $0x13                               # Get Drive Parameters\r
  xorw  %ax, %ax                # ax = 0\r
  movb  %dh, %al                # al = dh\r
  incb  %al                     # MaxHead = al + 1\r
  pushw %ax                     # 0000:7bfe = MaxHead\r
  movb  %cl, %al                # al = cl\r
  andb  $0x3f, %al              # MaxSector = al & 0x3f\r
  pushw %ax                     # 0000:7bfc = MaxSector\r
\r
  cmpw  $0xaa55, SectorSignature(%bp)         # Verify Boot Sector Signature\r
  jne   BadBootSector\r
  movw  RootEntries(%bp), %cx             # cx = RootEntries\r
  shlw  $FAT_DIRECTORY_ENTRY_SHIFT, %cx   # cx = cx * 32 = cx * sizeof(FAT_DIRECTORY_ENTRY) = Size of Root Directory in bytes\r
  movw  %cx, %bx                          # bx = size of the Root Directory in bytes\r
  andw  $BLOCK_MASK, %bx                  # See if it is an even number of sectors long\r
  jne   BadBootSector                     # If is isn't, then the boot sector is bad.\r
  movw  %cx, %bx                          # bx = size of the Root Directory in bytes\r
  shrw  $BLOCK_SHIFT, %bx                 # bx = size of Root Directory in sectors\r
  movb  NoFats(%bp), %al                  # al = NoFats\r
  xorb  %ah, %ah                          # ah = 0  ==> ax = NoFats\r
  mulw  SectorsPerFat32(%bp)              # ax = NoFats * SectorsPerFat\r
  addw  ReservedSectors(%bp), %ax         # ax = NoFats * SectorsPerFat + ReservedSectors = RootLBA\r
  addw  %bx, %ax                          # ax = NoFats * SectorsPerFat + ReservedSectors + RootDirSectors = FirstClusterLBA\r
  movw  %ax, (%bp)                        # Save FirstClusterLBA for later use\r
\r
  movw  RootCluster(%bp), %ax             # ax = StartCluster of Root Directory\r
  subw  $2, %ax                           # ax = StartCluster - 2\r
  xorb  %bh, %bh\r
  movb  SectorsPerCluster(%bp), %bl       # bx = SectorsPerCluster\r
  mulw  %bx                               # ax = (StartCluster - 2) * SectorsPerCluster\r
  addw  (%bp), %ax                        # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster\r
  pushw %ds\r
  popw  %es\r
  xorw  %di, %di                          # Store directory in es:di = 1000:0000\r
  call  ReadBlocks                        # Read StartCluster of Root Directory\r
\r
  # dx - variable storage (initial value is 0)\r
  # bx - loader (initial value is 0)\r
  xorw  %dx, %dx\r
  xorw  %bx, %bx\r
\r
FindEFILDR: \r
  cmpl  $LOADER_FILENAME_PART1, (%di)\r
  jne   FindVARSTORE\r
  cmpl  $LOADER_FILENAME_PART2, 4(%di)\r
  jne   FindVARSTORE\r
  cmpl  $LOADER_FILENAME_PART3, 7(%di)\r
  jne   FindVARSTORE\r
  movw  26(%di), %bx                      # bx = Start Cluster for EFILDR  <----------------------------------\r
  testw %dx, %dx\r
  je    FindNext                          # Efivar.bin is not loaded\r
  jmp   FoundAll\r
\r
FindVARSTORE: \r
  ## if the file is not loader file, see if it's "EFIVAR  BIN"\r
  cmpl  $0x56494645, (%di)                # Compare to "EFIV"\r
  jne   FindNext\r
  cmpl  $0x20205241, 4(%di)               # Compare to "AR  "\r
  jne   FindNext\r
  cmpl  $0x4e494220, 7(%di)               # Compare to " BIN"\r
  jne   FindNext\r
  movw  %di, %dx                          # dx = Offset of Start Cluster for Efivar.bin <---------------------\r
  addw  $26, %dx\r
  testw %bx, %bx\r
  je    FindNext                          # Efildr is not loaded\r
  jmp   FoundAll\r
\r
FindNext: \r
  # go to next find\r
  addw  $FAT_DIRECTORY_ENTRY_SIZE, %di    # Increment di\r
  subw  $FAT_DIRECTORY_ENTRY_SIZE, %cx    # Decrement cx\r
  # TODO: jump to FindVarStore if ...\r
  jne   FindEFILDR\r
  jmp   NotFoundAll\r
\r
FoundAll: \r
FoundEFILDR: \r
  movw    %bx, %cx                            # cx = Start Cluster for EFILDR  <----------------------------------\r
  movw    %cs, %ax                            # Destination = 2000:0000\r
  addw    $0x2000, %ax\r
  movw    %ax, %es\r
  xorw    %di, %di\r
ReadFirstClusterOfEFILDR: \r
  movw    %cx, %ax                            # ax = StartCluster\r
  subw    $2, %ax                             # ax = StartCluster - 2\r
  xorb    %bh, %bh\r
  movb    SectorsPerCluster(%bp), %bl         # bx = SectorsPerCluster\r
  pushw   %dx\r
  mulw    %bx\r
  popw    %dx                                 # ax = (StartCluster - 2) * SectorsPerCluster\r
  addw    (%bp), %ax                          # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster\r
  xorb    %bh, %bh\r
  movb    SectorsPerCluster(%bp), %bl         # bx = Number of Sectors in a cluster\r
  pushw   %es\r
  call    ReadBlocks\r
  popw    %ax\r
JumpIntoFirstSectorOfEFILDR: \r
  movw    %ax, JumpSegment(%bp)\r
JumpFarInstruction: \r
  .byte   0xea\r
JumpOffset: \r
  .word   0x000\r
JumpSegment: \r
  .word   0x2000\r
\r
\r
PrintString: \r
  movw $0xb800, %ax\r
  movw %ax, %es\r
  movw $0x7c0, %ax\r
  movw %ax, %ds\r
  movw $7, %cx\r
  movw $160, %di\r
  rep\r
  movsw\r
  ret\r
# ****************************************************************************\r
# ReadBlocks - Reads a set of blocks from a block device\r
#\r
# AX    = Start LBA\r
# BX    = Number of Blocks to Read\r
# ES:DI = Buffer to store sectors read from disk\r
# ****************************************************************************\r
\r
# cx = Blocks\r
# bx = NumberOfBlocks\r
# si = StartLBA\r
\r
ReadBlocks: \r
  pusha\r
  addl    LBAOffsetForBootSector(%bp), %eax            # Add LBAOffsetForBootSector to Start LBA\r
  addl    HiddenSectors(%bp), %eax            # Add HiddenSectors to Start LBA\r
  movl    %eax, %esi                          # esi = Start LBA\r
  movw    %bx, %cx                            # cx = Number of blocks to read\r
ReadCylinderLoop: \r
  movw    $0x7bfc, %bp                        # bp = 0x7bfc\r
  movl    %esi, %eax                          # eax = Start LBA\r
  xorl    %edx, %edx                          # edx = 0\r
  movzwl  (%bp), %ebx                         # bx = MaxSector\r
  divl    %ebx                                # ax = StartLBA / MaxSector\r
  incw    %dx                                 # dx = (StartLBA % MaxSector) + 1\r
  subw    %dx, %bx                            # bx = MaxSector - Sector\r
  incw    %bx                                 # bx = MaxSector - Sector + 1\r
  cmpw    %bx, %cx                            # Compare (Blocks) to (MaxSector - Sector + 1)\r
  jg      LimitTransfer\r
  movw    %cx, %bx                            # bx = Blocks\r
LimitTransfer: \r
  pushw   %cx\r
  movb    %dl, %cl                            # cl = (StartLBA % MaxSector) + 1 = Sector\r
  xorw    %dx, %dx                            # dx = 0\r
  divw    2(%bp)                              # ax = ax / (MaxHead + 1) = Cylinder  \r
                                              # dx = ax % (MaxHead + 1) = Head\r
\r
  pushw   %bx                                 # Save number of blocks to transfer\r
  movb    %dl, %dh                            # dh = Head\r
  movw    $0x7c00, %bp                        # bp = 0x7c00\r
  movb    PhysicalDrive(%bp), %dl             # dl = Drive Number\r
  movb    %al, %ch                            # ch = Cylinder\r
  movb    %bl, %al                            # al = Blocks\r
  movb    $2, %ah                             # ah = Function 2\r
  movw    %di, %bx                            # es:bx = Buffer address\r
  int     $0x13\r
  jc      DiskError\r
  popw    %bx\r
  popw    %cx\r
  movzwl  %bx, %ebx\r
  addl    %ebx, %esi                          # StartLBA = StartLBA + NumberOfBlocks\r
  subw    %bx, %cx                            # Blocks = Blocks - NumberOfBlocks\r
  movw    %es, %ax\r
  shlw    $(BLOCK_SHIFT-4), %bx\r
  addw    %bx, %ax\r
  movw    %ax, %es                            # es:di = es:di + NumberOfBlocks*BLOCK_SIZE\r
  cmpw    $0, %cx\r
  jne     ReadCylinderLoop\r
  popa\r
  ret\r
\r
# ****************************************************************************\r
# ERROR Condition:\r
# ****************************************************************************\r
NotFoundAll: \r
  ## if we found EFILDR, continue\r
  testw %bx, %bx\r
  jne  FoundEFILDR\r
BadBootSector: \r
DiskError: \r
  movw $ErrorString, %si\r
  call PrintString\r
Halt: \r
  jmp   Halt\r
\r
StartString: \r
  .byte 'B', 0x0c, 'S', 0x0c, 't', 0x0c, 'a', 0x0c, 'r', 0x0c, 't', 0x0c, '!', 0x0c\r
ErrorString: \r
  .byte 'B', 0x0c, 'E', 0x0c, 'r', 0x0c, 'r', 0x0c, 'o', 0x0c, 'r', 0x0c, '!', 0x0c\r
\r
# ****************************************************************************\r
# LBA Offset for BootSector, need patched by tool for HD boot.\r
# ****************************************************************************\r
\r
  #.org 0x01fa\r
LBAOffsetForBootSector: \r
  .long     0x0\r
\r
# ****************************************************************************\r
# Sector Signature\r
# ****************************************************************************\r
\r
  #.org 0x01fe\r
SectorSignature: \r
  .word     0xaa55      # Boot Sector Signature\r
\r
\r
\r
Commit	Line	Data
32f9b796	1	#------------------------------------------------------------------------------\r
	2	#*\r
	3	#* Copyright 2006 - 2007, Intel Corporation \r
	4	#* All rights reserved. This program and the accompanying materials \r
	5	#* are licensed and made available under the terms and conditions of the BSD License \r
	6	#* which accompanies this distribution. The full text of the license may be found at \r
	7	#* http://opensource.org/licenses/bsd-license.php \r
	8	#* \r
	9	#* THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, \r
	10	#* WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED. \r
	11	#* \r
	12	#* bs32.asm\r
	13	#* \r
	14	#* Abstract:\r
	15	#*\r
	16	#------------------------------------------------------------------------------\r
	17	\r
	18	#.MODEL small\r
20193e01	19	.stack: \r
	20	.486p: \r
	21	.code16\r
32f9b796	22	\r
	23	.equ FAT_DIRECTORY_ENTRY_SIZE, 0x0020\r
	24	.equ FAT_DIRECTORY_ENTRY_SHIFT, 5\r
	25	.equ BLOCK_SIZE, 0x0200\r
	26	.equ BLOCK_MASK, 0x01ff\r
	27	.equ BLOCK_SHIFT, 9\r
	28	# "EFILDR_____"\r
	29	.equ LOADER_FILENAME_PART1, 0x4c494645 # "EFIL"\r
	30	.equ LOADER_FILENAME_PART2, 0x30325244 # "DR20"\r
	31	.equ LOADER_FILENAME_PART3, 0x20202030 # "0___"\r
	32	\r
d5172f91	33	.org 0x0\r
ae3d1e91	34	.global _start\r\r
fd549a4d	35	_start:\r
32f9b796	36	Ia32Jump: \r
	37	jmp BootSectorEntryPoint # JMP inst - 3 bytes\r
	38	nop\r
	39	\r
9ffd16fb	40	OemId: .ascii "INTEL " # OemId - 8 bytes\r
32f9b796	41	# BPB data below will be fixed by tool\r
	42	SectorSize: .word 0 # Sector Size - 16 bits\r
	43	SectorsPerCluster: .byte 0 # Sector Per Cluster - 8 bits\r
	44	ReservedSectors: .word 0 # Reserved Sectors - 16 bits\r
	45	NoFats: .byte 0 # Number of FATs - 8 bits\r
	46	RootEntries: .word 0 # Root Entries - 16 bits\r
	47	Sectors: .word 0 # Number of Sectors - 16 bits\r
	48	Media: .byte 0 # Media - 8 bits - ignored\r
	49	SectorsPerFat: .word 0 # Sectors Per FAT - 16 bits\r
	50	SectorsPerTrack: .word 0 # Sectors Per Track - 16 bits - ignored\r
	51	Heads: .word 0 # Heads - 16 bits - ignored\r
	52	HiddenSectors: .long 0 # Hidden Sectors - 32 bits - ignored\r
	53	LargeSectors: .long 0 # Large Sectors - 32 bits \r
	54	\r
	55	#******************************************************************************\r
	56	#\r
	57	#The structure for FAT32 starting at offset 36 of the boot sector. (At this point, \r
	58	#the BPB/boot sector for FAT12 and FAT16 differs from the BPB/boot sector for FAT32.)\r
	59	#\r
	60	#******************************************************************************\r
	61	\r
	62	SectorsPerFat32: .long 0 # Sectors Per FAT for FAT32 - 4 bytes\r
	63	ExtFlags: .word 0 # Mirror Flag - 2 bytes\r
	64	FSVersion: .word 0 # File System Version - 2 bytes\r
	65	RootCluster: .long 0 # 1st Cluster Number of Root Dir - 4 bytes\r
	66	FSInfo: .word 0 # Sector Number of FSINFO - 2 bytes\r
	67	BkBootSector: .word 0 # Sector Number of Bk BootSector - 2 bytes\r
	68	Reserved: .fill 12, 1, 0 # Reserved Field - 12 bytes\r
	69	PhysicalDrive: .byte 0 # Physical Drive Number - 1 byte\r
	70	Reserved1: .byte 0 # Reserved Field - 1 byte\r
	71	Signature: .byte 0 # Extended Boot Signature - 1 byte\r
	72	VolId: .ascii " " # Volume Serial Number - 4 bytes\r
	73	FatLabel: .ascii " " # Volume Label - 11 bytes\r
	74	FileSystemType: .ascii "FAT32 " # File System Type - 8 bytes\r
	75	BootSectorEntryPoint: \r
	76	#ASSUME ds:@code\r
	77	#ASSUME ss:@code\r
	78	\r
	79	# ****************************************************************************\r
	80	# Start Print\r
	81	# ****************************************************************************\r
20193e01	82	movw $StartString, %si\r
32f9b796	83	call PrintString\r
	84	\r
	85	# ****************************************************************************\r
	86	# Print over\r
	87	# ****************************************************************************\r
	88	\r
	89	movw %cs, %ax # ax = 0\r
	90	movw %ax, %ss # ss = 0\r
	91	addw $0x1000, %ax\r
	92	movw %ax, %ds\r
	93	\r
	94	movw $0x7c00, %sp # sp = 0x7c00\r
	95	movw %sp, %bp # bp = 0x7c00\r
	96	\r
	97	movb $8, %ah # ah = 8 - Get Drive Parameters Function\r
	98	movb %dl, PhysicalDrive(%bp) # BBS defines that BIOS would pass the booting driver number to the loader through DL\r
	99	int $0x13 # Get Drive Parameters\r
	100	xorw %ax, %ax # ax = 0\r
	101	movb %dh, %al # al = dh\r
	102	incb %al # MaxHead = al + 1\r
	103	pushw %ax # 0000:7bfe = MaxHead\r
	104	movb %cl, %al # al = cl\r
	105	andb $0x3f, %al # MaxSector = al & 0x3f\r
	106	pushw %ax # 0000:7bfc = MaxSector\r
	107	\r
	108	cmpw $0xaa55, SectorSignature(%bp) # Verify Boot Sector Signature\r
	109	jne BadBootSector\r
	110	movw RootEntries(%bp), %cx # cx = RootEntries\r
	111	shlw $FAT_DIRECTORY_ENTRY_SHIFT, %cx # cx = cx * 32 = cx * sizeof(FAT_DIRECTORY_ENTRY) = Size of Root Directory in bytes\r
	112	movw %cx, %bx # bx = size of the Root Directory in bytes\r
	113	andw $BLOCK_MASK, %bx # See if it is an even number of sectors long\r
	114	jne BadBootSector # If is isn't, then the boot sector is bad.\r
	115	movw %cx, %bx # bx = size of the Root Directory in bytes\r
	116	shrw $BLOCK_SHIFT, %bx # bx = size of Root Directory in sectors\r
	117	movb NoFats(%bp), %al # al = NoFats\r
	118	xorb %ah, %ah # ah = 0 ==> ax = NoFats\r
	119	mulw SectorsPerFat32(%bp) # ax = NoFats * SectorsPerFat\r
	120	addw ReservedSectors(%bp), %ax # ax = NoFats * SectorsPerFat + ReservedSectors = RootLBA\r
	121	addw %bx, %ax # ax = NoFats * SectorsPerFat + ReservedSectors + RootDirSectors = FirstClusterLBA\r
	122	movw %ax, (%bp) # Save FirstClusterLBA for later use\r
	123	\r
	124	movw RootCluster(%bp), %ax # ax = StartCluster of Root Directory\r
	125	subw $2, %ax # ax = StartCluster - 2\r
	126	xorb %bh, %bh\r
	127	movb SectorsPerCluster(%bp), %bl # bx = SectorsPerCluster\r
	128	mulw %bx # ax = (StartCluster - 2) * SectorsPerCluster\r
	129	addw (%bp), %ax # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster\r
	130	pushw %ds\r
	131	popw %es\r
	132	xorw %di, %di # Store directory in es:di = 1000:0000\r
	133	call ReadBlocks # Read StartCluster of Root Directory\r
	134	\r
	135	# dx - variable storage (initial value is 0)\r
	136	# bx - loader (initial value is 0)\r
	137	xorw %dx, %dx\r
	138	xorw %bx, %bx\r
	139	\r
	140	FindEFILDR: \r
	141	cmpl $LOADER_FILENAME_PART1, (%di)\r
	142	jne FindVARSTORE\r
	143	cmpl $LOADER_FILENAME_PART2, 4(%di)\r
	144	jne FindVARSTORE\r
	145	cmpl $LOADER_FILENAME_PART3, 7(%di)\r
	146	jne FindVARSTORE\r
147	movw 26(%di), %bx # bx = Start Cluster for EFILDR <----------------------------------\r
148	testw %dx, %dx\r
149	je FindNext # Efivar.bin is not loaded\r
150	jmp FoundAll\r
151	\r
152	FindVARSTORE: \r
fd549a4d	153	## if the file is not loader file, see if it's "EFIVAR BIN"\r
32f9b796	154	cmpl $0x56494645, (%di) # Compare to "EFIV"\r
	155	jne FindNext\r
	156	cmpl $0x20205241, 4(%di) # Compare to "AR "\r
	157	jne FindNext\r
	158	cmpl $0x4e494220, 7(%di) # Compare to " BIN"\r
	159	jne FindNext\r
	160	movw %di, %dx # dx = Offset of Start Cluster for Efivar.bin <---------------------\r
	161	addw $26, %dx\r
	162	testw %bx, %bx\r
	163	je FindNext # Efildr is not loaded\r
	164	jmp FoundAll\r
	165	\r
	166	FindNext: \r
	167	# go to next find\r
	168	addw $FAT_DIRECTORY_ENTRY_SIZE, %di # Increment di\r
	169	subw $FAT_DIRECTORY_ENTRY_SIZE, %cx # Decrement cx\r
	170	# TODO: jump to FindVarStore if ...\r
	171	jne FindEFILDR\r
	172	jmp NotFoundAll\r
	173	\r
	174	FoundAll: \r
	175	FoundEFILDR: \r
	176	movw %bx, %cx # cx = Start Cluster for EFILDR <----------------------------------\r
	177	movw %cs, %ax # Destination = 2000:0000\r
	178	addw $0x2000, %ax\r
	179	movw %ax, %es\r
	180	xorw %di, %di\r
	181	ReadFirstClusterOfEFILDR: \r
	182	movw %cx, %ax # ax = StartCluster\r
	183	subw $2, %ax # ax = StartCluster - 2\r
	184	xorb %bh, %bh\r
	185	movb SectorsPerCluster(%bp), %bl # bx = SectorsPerCluster\r
	186	pushw %dx\r
	187	mulw %bx\r
	188	popw %dx # ax = (StartCluster - 2) * SectorsPerCluster\r
	189	addw (%bp), %ax # ax = FirstClusterLBA + (StartCluster-2)*SectorsPerCluster\r
	190	xorb %bh, %bh\r
	191	movb SectorsPerCluster(%bp), %bl # bx = Number of Sectors in a cluster\r
	192	pushw %es\r
	193	call ReadBlocks\r
	194	popw %ax\r
	195	JumpIntoFirstSectorOfEFILDR: \r
	196	movw %ax, JumpSegment(%bp)\r
	197	JumpFarInstruction: \r
	198	.byte 0xea\r
	199	JumpOffset: \r
	200	.word 0x000\r
	201	JumpSegment: \r
	202	.word 0x2000\r
	203	\r
	204	\r
	205	PrintString: \r
	206	movw $0xb800, %ax\r
	207	movw %ax, %es\r
	208	movw $0x7c0, %ax\r
	209	movw %ax, %ds\r
	210	movw $7, %cx\r
	211	movw $160, %di\r
	212	rep\r
	213	movsw\r
	214	ret\r
	215	# ****************************************************************************\r
	216	# ReadBlocks - Reads a set of blocks from a block device\r
	217	#\r
218	# AX = Start LBA\r
219	# BX = Number of Blocks to Read\r
220	# ES:DI = Buffer to store sectors read from disk\r
221	# ****************************************************************************\r
222	\r
223	# cx = Blocks\r
224	# bx = NumberOfBlocks\r
225	# si = StartLBA\r
226	\r
227	ReadBlocks: \r
228	pusha\r
229	addl LBAOffsetForBootSector(%bp), %eax # Add LBAOffsetForBootSector to Start LBA\r
230	addl HiddenSectors(%bp), %eax # Add HiddenSectors to Start LBA\r
231	movl %eax, %esi # esi = Start LBA\r
232	movw %bx, %cx # cx = Number of blocks to read\r
233	ReadCylinderLoop: \r
234	movw $0x7bfc, %bp # bp = 0x7bfc\r
235	movl %esi, %eax # eax = Start LBA\r
236	xorl %edx, %edx # edx = 0\r
237	movzwl (%bp), %ebx # bx = MaxSector\r
238	divl %ebx # ax = StartLBA / MaxSector\r
239	incw %dx # dx = (StartLBA % MaxSector) + 1\r
240	subw %dx, %bx # bx = MaxSector - Sector\r
241	incw %bx # bx = MaxSector - Sector + 1\r
242	cmpw %bx, %cx # Compare (Blocks) to (MaxSector - Sector + 1)\r
243	jg LimitTransfer\r
244	movw %cx, %bx # bx = Blocks\r
245	LimitTransfer: \r
246	pushw %cx\r
247	movb %dl, %cl # cl = (StartLBA % MaxSector) + 1 = Sector\r
248	xorw %dx, %dx # dx = 0\r
249	divw 2(%bp) # ax = ax / (MaxHead + 1) = Cylinder \r
250	# dx = ax % (MaxHead + 1) = Head\r
251	\r
252	pushw %bx # Save number of blocks to transfer\r
253	movb %dl, %dh # dh = Head\r
254	movw $0x7c00, %bp # bp = 0x7c00\r
255	movb PhysicalDrive(%bp), %dl # dl = Drive Number\r
256	movb %al, %ch # ch = Cylinder\r
257	movb %bl, %al # al = Blocks\r
258	movb $2, %ah # ah = Function 2\r
259	movw %di, %bx # es:bx = Buffer address\r
260	int $0x13\r
261	jc DiskError\r
262	popw %bx\r
263	popw %cx\r
264	movzwl %bx, %ebx\r
265	addl %ebx, %esi # StartLBA = StartLBA + NumberOfBlocks\r
266	subw %bx, %cx # Blocks = Blocks - NumberOfBlocks\r
267	movw %es, %ax\r
268	shlw $(BLOCK_SHIFT-4), %bx\r
269	addw %bx, %ax\r
270	movw %ax, %es # es:di = es:di + NumberOfBlocks*BLOCK_SIZE\r
271	cmpw $0, %cx\r
272	jne ReadCylinderLoop\r
273	popa\r
274	ret\r
275	\r
276	# ****************************************************************************\r
277	# ERROR Condition:\r
278	# ****************************************************************************\r
279	NotFoundAll: \r
fd549a4d	280	## if we found EFILDR, continue\r
32f9b796	281	testw %bx, %bx\r
	282	jne FoundEFILDR\r
	283	BadBootSector: \r
	284	DiskError: \r
20193e01	285	movw $ErrorString, %si\r
32f9b796	286	call PrintString\r
	287	Halt: \r
	288	jmp Halt\r
	289	\r
	290	StartString: \r
	291	.byte 'B', 0x0c, 'S', 0x0c, 't', 0x0c, 'a', 0x0c, 'r', 0x0c, 't', 0x0c, '!', 0x0c\r
	292	ErrorString: \r
	293	.byte 'B', 0x0c, 'E', 0x0c, 'r', 0x0c, 'r', 0x0c, 'o', 0x0c, 'r', 0x0c, '!', 0x0c\r
	294	\r
	295	# ****************************************************************************\r
	296	# LBA Offset for BootSector, need patched by tool for HD boot.\r
	297	# ****************************************************************************\r
	298	\r
20193e01	299	#.org 0x01fa\r
32f9b796	300	LBAOffsetForBootSector: \r
	301	.long 0x0\r
	302	\r
	303	# ****************************************************************************\r
	304	# Sector Signature\r
	305	# ****************************************************************************\r
	306	\r
20193e01	307	#.org 0x01fe\r
32f9b796	308	SectorSignature: \r
	309	.word 0xaa55 # Boot Sector Signature\r
	310	\r
	311	\r
	312	\r