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

#------------------------------------------------------------------------------
#*
#*   Copyright 2006 - 2007, Intel Corporation                                                         
#*   All rights reserved. This program and the accompanying materials
#*   are licensed and made available under the terms and conditions of the BSD License
#*   which accompanies this distribution.  The full text of the license may be found at
#*   http://opensource.org/licenses/bsd-license.php
#*
#*   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
#*   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
#*
#*    Mbr.asm
#*
#*   Abstract:
#*
#------------------------------------------------------------------------------

.equ                      BLOCK_SIZE, 0x0200
.equ                      BLOCK_MASK, 0x01ff
.equ                      BLOCK_SHIFT, 9

# ****************************************************************************
# Code loaded by BIOS at 0x0000:0x7C00
# ****************************************************************************

.org 0x0
Start: 

# ****************************************************************************
# Start Print
# ****************************************************************************

        movw $0xb800, %ax
        movw %ax, %es
        movw $0x7c0, %ax
        movw %ax, %ds
        leaw %cs:StartString, %si
        movw $10, %cx
        movw $160, %di
        rep 
        movsw

# ****************************************************************************
# Print over
# ****************************************************************************

# ****************************************************************************
# Initialize segment registers and copy code at 0x0000:0x7c00 to 0x0000:0x0600
# ****************************************************************************
        xorw  %ax, %ax                            # AX = 0x0000
        movw  $0x7c00, %bx                        # BX = 0x7C00
        movw  $0x600, %bp                         # BP = 0x0600
        movw  RelocatedStart, %si                 # SI = Offset(RelocatedStart)
        movw  $0x200, %cx                         # CX = 0x0200
        subw  %si, %cx                            # CS = 0x0200 - Offset(RelocatedStart)
        leaw  (%bp,%si,), %di                     # DI = 0x0600 + Offset(RelocatedStart)
        leaw  (%bx,%si,), %si                     # BX = 0x7C00 + Offset(RelocatedStart)
        movw  %ax, %ss                            # SS = 0x0000
        movw  %bx, %sp                            # SP = 0x7C00
        movw  %ax, %es                            # ES = 0x0000
        movw  %ax, %ds                            # DS = 0x0000
        pushw %ax                                 # PUSH 0x0000
        pushw %di                                 # PUSH 0x0600 + Offset(RelocatedStart)
        cld                                       # Clear the direction flag
        rep
        movsb                                     # Copy 0x0200 bytes from 0x7C00 to 0x0600
        retl                                      # JMP 0x0000:0x0600 + Offset(RelocatedStart)

# ****************************************************************************
# Code relocated to 0x0000:0x0600
# ****************************************************************************

RelocatedStart: 
# ****************************************************************************
# Get Driver Parameters to 0x0000:0x7BFC
# ****************************************************************************

        xorw  %ax, %ax                            # AX = 0
        movw  %ax, %ss                            # SS = 0
        addw  $0x1000, %ax
        movw  %ax, %ds

        movw  $0x7c00, %sp                        # SP = 0x7c00
        movw  %sp, %bp                            # BP = 0x7c00

        movb  $8, %ah                             # AH = 8 - Get Drive Parameters Function
        movb  %dl, PhysicalDrive(%bp)             # BBS defines that BIOS would pass the booting driver number to the loader through DL
        int   $0x13                               # Get Drive Parameters
        xorw  %ax, %ax                            # AX = 0
        movb  %dh, %al                            # AL = DH
        incb  %al                                 # MaxHead = AL + 1
        pushw %ax                                 # 0000:7bfe = MaxHead
        movb  %cl, %al                            # AL = CL
        andb  $0x3f, %al                          # MaxSector = AL & 0x3f
        pushw %ax                                 # 0000:7bfc = MaxSector

# ****************************************************************************
# Read Target DBR from hard disk to 0x0000:0x7C00
# ****************************************************************************

        xorw  %ax, %ax
        movb  MbrPartitionIndicator(%bp), %al          # AX = MbrPartitionIndex
        cmpb  $0xff, %al                               # 0xFF means do legacy MBR boot
        jnz   EfiDbr
LegacyMbr: 
        movl  $0x0000600, %eax                    # Assume LegacyMBR is backuped in Sector 6
        jmp   StartReadTo7C00                     # EAX = Header/Sector/Tracker/Zero

EfiDbr: 
        cmpb  $4, %al                             # MbrPartitionIndex should < 4
        jae   BadDbr
        shlw  $4, %ax                             # AX  = MBREntrySize * Index
        addw  $0x1be, %ax                         # AX  = MBREntryOffset
        movw  %ax, %di                            # DI  = MBREntryOffset

        # Here we don't use the C/H/S information provided by Partition table
        #  but calculate C/H/S from LBA ourselves
        #       Ci: Cylinder number
        #       Hi: Header number
        #       Si: Sector number
        movl  %es:8(%bp,%di,), %eax               # Start LBA
        movl  %eax, %edx
        shrl  $16, %edx                           # DX:AX = Start LBA
                                                  #       = Ci * (H * S) + Hi * S + (Si - 1)

        # Calculate C/H/S according to LBA
        movw  $0x7bfa, %bp
        divw  2(%bp)                              # AX = Hi + H*Ci
                                                  # DX = Si - 1
        incw  %dx                                 # DX = Si
        pushw %dx                                 # 0000:7bfa = Si  <----
        xorw  %dx, %dx                            # DX:AX = Hi + H*Ci
        divw  4(%bp)                              # AX = Ci         <----
                                                  # DX = Hi         <----

StartReadTo7C00: 

        movb  (%bp), %cl                          # Si
        movb  %al, %ch                            # Ci[0-7]
        orb   %ah, %cl                            # Ci[8,9]
        movw  $0x7c00, %bx                        # ES:BX = 0000:7C00h
        movb  $0x2, %ah                           # Function 02h
        movb  $1, %al                             # 1 Sector
        movb  %dl, %dh                            # Hi
        movw  $0x600, %bp
        movb  PhysicalDrive(%bp), %dl             # Drive number
        int   $0x13
        jc    BadDbr


# ****************************************************************************
# Transfer control to BootSector - Jump to 0x0000:0x7C00
# ****************************************************************************
        xorw  %ax, %ax
        pushw %ax                                 # PUSH 0x0000 - Segment
        movw  $0x7c00, %di
        pushw %di                                 # PUSH 0x7C00 - Offset
        retl                                      # JMP 0x0000:0x7C00

# ****************************************************************************
# ERROR Condition:
# ****************************************************************************

BadDbr: 
    pushw %ax
    movw $0xb800, %ax
    movw %ax, %es
    movw $0x60, %ax
    movw %ax, %ds
    leaw %cs:ErrorString, %si
    movw $320, %di
    popw %ax
    call A2C
    movb %ah, 16(%si)
    movb %al, 18(%si)
    movw $10, %cx
    rep
    movsw
Halt: 
    jmp   Halt

StartString: 
.byte 'M', 0x0c, 'B', 0x0c, 'R', 0x0c, ' ', 0x0c, 'S', 0x0c, 't', 0x0c, 'a', 0x0c, 'r', 0x0c, 't', 0x0c, '!', 0x0c
ErrorString: 
.byte 'M', 0x0c, 'B', 0x0c, 'R', 0x0c, ' ', 0x0c, 'E', 0x0c, 'r', 0x0c, 'r', 0x0c, ':', 0x0c, '?', 0x0c, '?', 0x0c

# ****************************************************************************
# A2C - convert Ascii code stored in AH to character stored in AX
# ****************************************************************************
A2C: 
    movb %ah, %al
    shrb $4, %ah
    andb $0xF, %al
    addb '0', %ah
    addb '0', %al

    cmpb '9', %ah
    jle  A2C_L1
    addb $7, %ah
A2C_L1: 

    cmpb '9', %al
    jle A2C_L2
    addb $7, %al
A2C_L2: 
    ret


# ****************************************************************************
# PhysicalDrive - Used to indicate which disk to be boot
#                 Can be patched by tool
# ****************************************************************************
.org   0x01B6
PhysicalDrive:        .byte 0x80

# ****************************************************************************
# MbrPartitionIndicator - Used to indicate which MBR partition to be boot
#                         Can be patched by tool
#                         OxFF means boot to legacy MBR. (LBA OFFSET 6)
# ****************************************************************************
.org   0x01B7
MbrPartitionIndicator: .byte 0

# ****************************************************************************
# Unique MBR signature
# ****************************************************************************
.org   0x01B8
    .ascii "DUET"

# ****************************************************************************
# Unknown
# ****************************************************************************
.org   0x01BC
    .word 0

# ****************************************************************************
# MBR Entry - To be patched
# ****************************************************************************
.org   0x01BE
    .long 0,0,0,0
.org   0x01CE
    .long 0,0,0,0
.org   0x01DE
    .long 0,0,0,0
.org   0x01EE
    .long 0,0,0,0

# ****************************************************************************
# Sector Signature
# ****************************************************************************

.org 0x01FE
SectorSignature: 
  .word     0xaa55      # Boot Sector Signature
Commit	Line	Data
819958c6	1	#------------------------------------------------------------------------------
	2	#*
	3	#* Copyright 2006 - 2007, Intel Corporation
	4	#* All rights reserved. This program and the accompanying materials
	5	#* are licensed and made available under the terms and conditions of the BSD License
	6	#* which accompanies this distribution. The full text of the license may be found at
	7	#* http://opensource.org/licenses/bsd-license.php
	8	#*
	9	#* THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
	10	#* WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
	11	#*
	12	#* Mbr.asm
	13	#*
	14	#* Abstract:
	15	#*
	16	#------------------------------------------------------------------------------
	17
	18	.equ BLOCK_SIZE, 0x0200
	19	.equ BLOCK_MASK, 0x01ff
	20	.equ BLOCK_SHIFT, 9
	21
	22	# ****************************************************************************
	23	# Code loaded by BIOS at 0x0000:0x7C00
	24	# ****************************************************************************
	25
	26	.org 0x0
	27	Start:
	28
	29	# ****************************************************************************
	30	# Start Print
	31	# ****************************************************************************
	32
	33	movw $0xb800, %ax
	34	movw %ax, %es
	35	movw $0x7c0, %ax
	36	movw %ax, %ds
	37	leaw %cs:StartString, %si
	38	movw $10, %cx
	39	movw $160, %di
	40	rep
	41	movsw
	42
	43	# ****************************************************************************
	44	# Print over
	45	# ****************************************************************************
	46
	47	# ****************************************************************************
	48	# Initialize segment registers and copy code at 0x0000:0x7c00 to 0x0000:0x0600
	49	# ****************************************************************************
	50	xorw %ax, %ax # AX = 0x0000
	51	movw $0x7c00, %bx # BX = 0x7C00
	52	movw $0x600, %bp # BP = 0x0600
	53	movw RelocatedStart, %si # SI = Offset(RelocatedStart)
	54	movw $0x200, %cx # CX = 0x0200
	55	subw %si, %cx # CS = 0x0200 - Offset(RelocatedStart)
	56	leaw (%bp,%si,), %di # DI = 0x0600 + Offset(RelocatedStart)
	57	leaw (%bx,%si,), %si # BX = 0x7C00 + Offset(RelocatedStart)
	58	movw %ax, %ss # SS = 0x0000
	59	movw %bx, %sp # SP = 0x7C00
	60	movw %ax, %es # ES = 0x0000
	61	movw %ax, %ds # DS = 0x0000
	62	pushw %ax # PUSH 0x0000
	63	pushw %di # PUSH 0x0600 + Offset(RelocatedStart)
	64	cld # Clear the direction flag
65	rep
66	movsb # Copy 0x0200 bytes from 0x7C00 to 0x0600
67	retl # JMP 0x0000:0x0600 + Offset(RelocatedStart)
68
69	# ****************************************************************************
70	# Code relocated to 0x0000:0x0600
71	# ****************************************************************************
72
73	RelocatedStart:
74	# ****************************************************************************
75	# Get Driver Parameters to 0x0000:0x7BFC
76	# ****************************************************************************
77
78	xorw %ax, %ax # AX = 0
79	movw %ax, %ss # SS = 0
80	addw $0x1000, %ax
81	movw %ax, %ds
82
83	movw $0x7c00, %sp # SP = 0x7c00
84	movw %sp, %bp # BP = 0x7c00
85
86	movb $8, %ah # AH = 8 - Get Drive Parameters Function
87	movb %dl, PhysicalDrive(%bp) # BBS defines that BIOS would pass the booting driver number to the loader through DL
88	int $0x13 # Get Drive Parameters
89	xorw %ax, %ax # AX = 0
90	movb %dh, %al # AL = DH
91	incb %al # MaxHead = AL + 1
92	pushw %ax # 0000:7bfe = MaxHead
93	movb %cl, %al # AL = CL
94	andb $0x3f, %al # MaxSector = AL & 0x3f
95	pushw %ax # 0000:7bfc = MaxSector
96
97	# ****************************************************************************
98	# Read Target DBR from hard disk to 0x0000:0x7C00
99	# ****************************************************************************
100
101	xorw %ax, %ax
102	movb MbrPartitionIndicator(%bp), %al # AX = MbrPartitionIndex
103	cmpb $0xff, %al # 0xFF means do legacy MBR boot
104	jnz EfiDbr
105	LegacyMbr:
106	movl $0x0000600, %eax # Assume LegacyMBR is backuped in Sector 6
107	jmp StartReadTo7C00 # EAX = Header/Sector/Tracker/Zero
108
109	EfiDbr:
110	cmpb $4, %al # MbrPartitionIndex should < 4
111	jae BadDbr
112	shlw $4, %ax # AX = MBREntrySize * Index
113	addw $0x1be, %ax # AX = MBREntryOffset
114	movw %ax, %di # DI = MBREntryOffset
115
116	# Here we don't use the C/H/S information provided by Partition table
117	# but calculate C/H/S from LBA ourselves
118	# Ci: Cylinder number
119	# Hi: Header number
120	# Si: Sector number
121	movl %es:8(%bp,%di,), %eax # Start LBA
122	movl %eax, %edx
123	shrl $16, %edx # DX:AX = Start LBA
124	# = Ci * (H * S) + Hi * S + (Si - 1)
125
126	# Calculate C/H/S according to LBA
127	movw $0x7bfa, %bp
128	divw 2(%bp) # AX = Hi + H*Ci
129	# DX = Si - 1
130	incw %dx # DX = Si
131	pushw %dx # 0000:7bfa = Si <----
132	xorw %dx, %dx # DX:AX = Hi + H*Ci
133	divw 4(%bp) # AX = Ci <----
134	# DX = Hi <----
135
136	StartReadTo7C00:
137
138	movb (%bp), %cl # Si
139	movb %al, %ch # Ci[0-7]
140	orb %ah, %cl # Ci[8,9]
141	movw $0x7c00, %bx # ES:BX = 0000:7C00h
142	movb $0x2, %ah # Function 02h
143	movb $1, %al # 1 Sector
144	movb %dl, %dh # Hi
145	movw $0x600, %bp
146	movb PhysicalDrive(%bp), %dl # Drive number
147	int $0x13
148	jc BadDbr
149
150
151
152	# ****************************************************************************
153	# Transfer control to BootSector - Jump to 0x0000:0x7C00
154	# ****************************************************************************
155	xorw %ax, %ax
156	pushw %ax # PUSH 0x0000 - Segment
157	movw $0x7c00, %di
158	pushw %di # PUSH 0x7C00 - Offset
159	retl # JMP 0x0000:0x7C00
160
161	# ****************************************************************************
162	# ERROR Condition:
163	# ****************************************************************************
164
165	BadDbr:
166	pushw %ax
167	movw $0xb800, %ax
168	movw %ax, %es
169	movw $0x60, %ax
170	movw %ax, %ds
171	leaw %cs:ErrorString, %si
172	movw $320, %di
173	popw %ax
174	call A2C
175	movb %ah, 16(%si)
176	movb %al, 18(%si)
177	movw $10, %cx
178	rep
179	movsw
180	Halt:
181	jmp Halt
182
183	StartString:
184	.byte 'M', 0x0c, 'B', 0x0c, 'R', 0x0c, ' ', 0x0c, 'S', 0x0c, 't', 0x0c, 'a', 0x0c, 'r', 0x0c, 't', 0x0c, '!', 0x0c
185	ErrorString:
186	.byte 'M', 0x0c, 'B', 0x0c, 'R', 0x0c, ' ', 0x0c, 'E', 0x0c, 'r', 0x0c, 'r', 0x0c, ':', 0x0c, '?', 0x0c, '?', 0x0c
187
188	# ****************************************************************************
189	# A2C - convert Ascii code stored in AH to character stored in AX
190	# ****************************************************************************
191	A2C:
192	movb %ah, %al
193	shrb $4, %ah
194	andb $0xF, %al
195	addb '0', %ah
196	addb '0', %al
197
198	cmpb '9', %ah
199	jle A2C_L1
200	addb $7, %ah
201	A2C_L1:
202
203	cmpb '9', %al
204	jle A2C_L2
205	addb $7, %al
206	A2C_L2:
207	ret
208
209
210	# ****************************************************************************
211	# PhysicalDrive - Used to indicate which disk to be boot
212	# Can be patched by tool
213	# ****************************************************************************
214	.org 0x01B6
215	PhysicalDrive: .byte 0x80
216
217	# ****************************************************************************
218	# MbrPartitionIndicator - Used to indicate which MBR partition to be boot
219	# Can be patched by tool
220	# OxFF means boot to legacy MBR. (LBA OFFSET 6)
221	# ****************************************************************************
222	.org 0x01B7
223	MbrPartitionIndicator: .byte 0
224
225	# ****************************************************************************
226	# Unique MBR signature
227	# ****************************************************************************
228	.org 0x01B8
229	.ascii "DUET"
230
231	# ****************************************************************************
232	# Unknown
233	# ****************************************************************************
234	.org 0x01BC
235	.word 0
236
237	# ****************************************************************************
238	# MBR Entry - To be patched
239	# ****************************************************************************
240	.org 0x01BE
241	.long 0,0,0,0
242	.org 0x01CE
243	.long 0,0,0,0
244	.org 0x01DE
245	.long 0,0,0,0
246	.org 0x01EE
247	.long 0,0,0,0
248
249	# ****************************************************************************
250	# Sector Signature
251	# ****************************************************************************
252
253	.org 0x01FE
254	SectorSignature:
255	.word 0xaa55 # Boot Sector Signature
256
257
258