1#
2# Copyright (c) 1998 Robert Nordier
3# All rights reserved.
4#
5# Redistribution and use in source and binary forms are freely
6# permitted provided that the above copyright notice and this
7# paragraph and the following disclaimer are duplicated in all
8# such forms.
9#
10# This software is provided "AS IS" and without any express or
11# implied warranties, including, without limitation, the implied
12# warranties of merchantability and fitness for a particular
13# purpose.
14#
15
16# $FreeBSD: head/sys/boot/i386/boot2/boot1.S 50477 1999-08-28 01:08:13Z peter $
17
18 .set MEM_REL,0x700 # Relocation address
19 .set MEM_ARG,0x900 # Arguments
20 .set MEM_ORG,0x7c00 # Origin
21 .set MEM_BUF,0x8c00 # Load area
22 .set MEM_BTX,0x9000 # BTX start
23 .set MEM_JMP,0x9010 # BTX entry point
24 .set MEM_USR,0xa000 # Client start
25
26 .set PRT_OFF,0x1be # Partition offset
27 .set PRT_NUM,0x4 # Partitions
28 .set PRT_BSD,0xa5 # Partition type
29
30 .set SIZ_PAG,0x1000 # Page size
31 .set SIZ_SEC,0x200 # Sector size
32
33 .globl start
34 .globl xread
35
36start: jmp main # Start recognizably
37
38 .org 0x4,0x90
39
40# External read from disk
41
42xread: pushl %ss # Address
43 popl %ds # data
44xread.1: o16 # Starting
45 pushb $0x0 # absolute
46 pushl %ecx # block
47 pushl %eax # number
48 pushl %es # Address of
49 pushl %ebx # transfer buffer
50 xorl %eax,%eax # Number of
51 movb %dh,%al # blocks to
52 pushl %eax # transfer
53 pushb $0x10 # Size of packet
54 movl %esp,%ebp # Packet pointer
55 callwi(read) # Read from disk
56 leaw1r(0x10,_bp_,_sp) # Clear stack
57 lret # To far caller
58
59# Bootstrap
60
61main: cld # String ops inc
62 xorl %ecx,%ecx # Zero
63 movl %cx,%es # Address
64 movl %cx,%ds # data
65 movl %cx,%ss # Set up
66 movwir(start,_sp) # stack
67 movl %esp,%esi # Source
68 movwir(MEM_REL,_di) # Destination
69 incb %ch # Word count
70 rep # Copy
71 movsl # code
72 movwir(part4,_si) # Partition
73 cmpb $0x80,%dl # Hard drive?
74 jb main.4 # No
75 movb $0x1,%dh # Block count
76 callwi(nread) # Read MBR
77 movwir(0x1,_cx) # Two passes
78main.1: movwir(MEM_BUF+PRT_OFF,_si) # Partition table
79 movb $0x1,%dh # Partition
80main.2: cmpbi1(PRT_BSD,0x4,_si_) # Our partition type?
81 jne main.3 # No
82 jecxz main.5 # If second pass
83 tstbi0(0x80,_si_) # Active?
84 jnz main.5 # Yes
85main.3: addl $0x10,%esi # Next entry
86 incb %dh # Partition
87 cmpb $0x1+PRT_NUM,%dh # In table?
88 jb main.2 # Yes
89 decl %ecx # Do two
90 jecxz main.1 # passes
91 movwir(msg_part,_si) # Message
92 jmp error # Error
93main.4: xorl %edx,%edx # Partition:drive
94main.5: movwrm(_dx,MEM_ARG) # Save args
95 movb $0x10,%dh # Sector count
96 callwi(nread) # Read disk
97 movwir(MEM_BTX,_bx) # BTX
98 movw1r(0xa,_bx_,_si) # Point past
99 addl %ebx,%esi # it
100 movwir(MEM_USR+SIZ_PAG,_di) # Client page 1
101 movwir(MEM_BTX+0xe*SIZ_SEC,_cx) # Byte
102 subl %esi,%ecx # count
103 rep # Relocate
104 movsb # client
105 subl %edi,%ecx # Byte count
106 xorb %al,%al # Zero
107 rep # assumed
108 stosb # bss
109 callwi(seta20) # Enable A20
110 jmpnwi(start+MEM_JMP-MEM_ORG) # Start BTX
111
112# Enable A20
113
114seta20: cli # Disable interrupts
115seta20.1: inb $0x64,%al # Get status
116 testb $0x2,%al # Busy?
117 jnz seta20.1 # Yes
118 movb $0xd1,%al # Command: Write
119 outb %al,$0x64 # output port
120seta20.2: inb $0x64,%al # Get status
121 testb $0x2,%al # Busy?
122 jnz seta20.2 # Yes
123 movb $0xdf,%al # Enable
124 outb %al,$0x60 # A20
125 sti # Enable interrupts
126 ret # To caller
127
128# Local read from disk
129
130nread: movwir(MEM_BUF,_bx) # Transfer buffer
131 movw1r(0x8,_si_,_ax) # Get
132 movw1r(0xa,_si_,_cx) # LBA
133 pushl %cs # Read from
134 callwi(xread.1) # disk
135 jnc return # If success
136 movwir(msg_read,_si) # Message
137
138# Error exit
139
140error: callwi(putstr) # Display message
141 movwir(prompt,_si) # Display
142 callwi(putstr) # prompt
143 xorb %ah,%ah # BIOS: Get
144 int $0x16 # keypress
145 int $0x19 # BIOS: Reboot
146
147# Display string
148
149putstr.0: movwir(0x7,_bx) # Page:attribute
150 movb $0xe,%ah # BIOS: Display
151 int $0x10 # character
152putstr: lodsb # Get char
153 testb %al,%al # End of string?
154 jne putstr.0 # No
155
156ereturn: movb $0x1,%ah # Invalid
157 stc # argument
158return: ret # To caller
159
160# Read from disk
161
162read: cs_ # LBA support
163 tstbim(0x80,MEM_REL+flags-start)# enabled?
164 jz read.1 # No
165 movwir(0x55aa,_bx) # Magic
166 pushl %edx # Save
167 movb $0x41,%ah # BIOS: Check
168 int $0x13 # extensions present
169 popl %edx # Restore
170 jc read.1 # If error
171 cmpwir(0xaa55,_bx) # Magic?
172 jne read.1 # No
173 testb $0x1,%cl # Packet interface?
174 jz read.1 # No
175 movl %ebp,%esi # Disk packet
176 movb $0x42,%ah # BIOS: Extended
177 int $0x13 # read
178 ret # To caller
179
180read.1: pushl %edx # Save
181 movb $0x8,%ah # BIOS: Get drive
182 int $0x13 # parameters
183 movb %dh,%ch # Max head number
184 popl %edx # Restore
185 jc return # If error
186 andb $0x3f,%cl # Sectors per track
187 jz ereturn # If zero
188 cli # Disable interrupts
189 o16 # Get
190 movw1r(0x8,_bp_,_ax) # LBA
191 pushl %edx # Save
192 movzbw %cl,%bx # Divide by
193 xorw %dx,%dx # sectors
194 divw %bx,%ax # per track
195 movb %ch,%bl # Max head number
196 movb %dl,%ch # Sector number
197 incl %ebx # Divide by
198 xorb %dl,%dl # number
199 divw %bx,%ax # of heads
200 movb %dl,%bh # Head number
201 popl %edx # Restore
202 o16 # Cylinder number
203 cmpl $0x3ff,%eax # supportable?
204 sti # Enable interrupts
205 ja ereturn # No
206 xchgb %al,%ah # Set up cylinder
207 rorb $0x2,%al # number
208 orb %ch,%al # Merge
209 incl %eax # sector
210 xchgl %eax,%ecx # number
211 movb %bh,%dh # Head number
212 subb %ah,%al # Sectors this track
213 movb1r(0x2,_bp_,_ah) # Blocks to read
214 cmpb %ah,%al # To read
215 jb read.2 # this
216 movb %ah,%al # track
217read.2: movwir(0x5,_di) # Try count
218read.3: lesw1r(0x4,_bp_,_bx) # Transfer buffer
219 pushl %eax # Save
220 movb $0x2,%ah # BIOS: Read
221 int $0x13 # from disk
222 popl %ebx # Restore
223 jnc read.4 # If success
224 decl %edi # Retry?
225 jz read.6 # No
226 xorb %ah,%ah # BIOS: Reset
227 int $0x13 # disk system
228 xchgl %ebx,%eax # Block count
229 jmp read.3 # Continue
230read.4: movzbl %bl,%eax # Sectors read
231 addwr1(_ax,0x8,_bp_) # Adjust
232 jnc read.5 # LBA,
233 incw1(0xa,_bp_) # transfer
234read.5: shlb %bl # buffer
235 addbr1(_bl,0x5,_bp_) # pointer,
236 subbr1(_al,0x2,_bp_) # block count
237 ja read.1 # If not done
238read.6: ret # To caller
239
240# Messages
241
242msg_read: .asciz "Read"
243msg_part: .asciz "Boot"
244
245prompt: .asciz " error\r\n"
246
--- 13 unchanged lines hidden ---
2# Copyright (c) 1998 Robert Nordier
3# All rights reserved.
4#
5# Redistribution and use in source and binary forms are freely
6# permitted provided that the above copyright notice and this
7# paragraph and the following disclaimer are duplicated in all
8# such forms.
9#
10# This software is provided "AS IS" and without any express or
11# implied warranties, including, without limitation, the implied
12# warranties of merchantability and fitness for a particular
13# purpose.
14#
15
16# $FreeBSD: head/sys/boot/i386/boot2/boot1.S 50477 1999-08-28 01:08:13Z peter $
17
18 .set MEM_REL,0x700 # Relocation address
19 .set MEM_ARG,0x900 # Arguments
20 .set MEM_ORG,0x7c00 # Origin
21 .set MEM_BUF,0x8c00 # Load area
22 .set MEM_BTX,0x9000 # BTX start
23 .set MEM_JMP,0x9010 # BTX entry point
24 .set MEM_USR,0xa000 # Client start
25
26 .set PRT_OFF,0x1be # Partition offset
27 .set PRT_NUM,0x4 # Partitions
28 .set PRT_BSD,0xa5 # Partition type
29
30 .set SIZ_PAG,0x1000 # Page size
31 .set SIZ_SEC,0x200 # Sector size
32
33 .globl start
34 .globl xread
35
36start: jmp main # Start recognizably
37
38 .org 0x4,0x90
39
40# External read from disk
41
42xread: pushl %ss # Address
43 popl %ds # data
44xread.1: o16 # Starting
45 pushb $0x0 # absolute
46 pushl %ecx # block
47 pushl %eax # number
48 pushl %es # Address of
49 pushl %ebx # transfer buffer
50 xorl %eax,%eax # Number of
51 movb %dh,%al # blocks to
52 pushl %eax # transfer
53 pushb $0x10 # Size of packet
54 movl %esp,%ebp # Packet pointer
55 callwi(read) # Read from disk
56 leaw1r(0x10,_bp_,_sp) # Clear stack
57 lret # To far caller
58
59# Bootstrap
60
61main: cld # String ops inc
62 xorl %ecx,%ecx # Zero
63 movl %cx,%es # Address
64 movl %cx,%ds # data
65 movl %cx,%ss # Set up
66 movwir(start,_sp) # stack
67 movl %esp,%esi # Source
68 movwir(MEM_REL,_di) # Destination
69 incb %ch # Word count
70 rep # Copy
71 movsl # code
72 movwir(part4,_si) # Partition
73 cmpb $0x80,%dl # Hard drive?
74 jb main.4 # No
75 movb $0x1,%dh # Block count
76 callwi(nread) # Read MBR
77 movwir(0x1,_cx) # Two passes
78main.1: movwir(MEM_BUF+PRT_OFF,_si) # Partition table
79 movb $0x1,%dh # Partition
80main.2: cmpbi1(PRT_BSD,0x4,_si_) # Our partition type?
81 jne main.3 # No
82 jecxz main.5 # If second pass
83 tstbi0(0x80,_si_) # Active?
84 jnz main.5 # Yes
85main.3: addl $0x10,%esi # Next entry
86 incb %dh # Partition
87 cmpb $0x1+PRT_NUM,%dh # In table?
88 jb main.2 # Yes
89 decl %ecx # Do two
90 jecxz main.1 # passes
91 movwir(msg_part,_si) # Message
92 jmp error # Error
93main.4: xorl %edx,%edx # Partition:drive
94main.5: movwrm(_dx,MEM_ARG) # Save args
95 movb $0x10,%dh # Sector count
96 callwi(nread) # Read disk
97 movwir(MEM_BTX,_bx) # BTX
98 movw1r(0xa,_bx_,_si) # Point past
99 addl %ebx,%esi # it
100 movwir(MEM_USR+SIZ_PAG,_di) # Client page 1
101 movwir(MEM_BTX+0xe*SIZ_SEC,_cx) # Byte
102 subl %esi,%ecx # count
103 rep # Relocate
104 movsb # client
105 subl %edi,%ecx # Byte count
106 xorb %al,%al # Zero
107 rep # assumed
108 stosb # bss
109 callwi(seta20) # Enable A20
110 jmpnwi(start+MEM_JMP-MEM_ORG) # Start BTX
111
112# Enable A20
113
114seta20: cli # Disable interrupts
115seta20.1: inb $0x64,%al # Get status
116 testb $0x2,%al # Busy?
117 jnz seta20.1 # Yes
118 movb $0xd1,%al # Command: Write
119 outb %al,$0x64 # output port
120seta20.2: inb $0x64,%al # Get status
121 testb $0x2,%al # Busy?
122 jnz seta20.2 # Yes
123 movb $0xdf,%al # Enable
124 outb %al,$0x60 # A20
125 sti # Enable interrupts
126 ret # To caller
127
128# Local read from disk
129
130nread: movwir(MEM_BUF,_bx) # Transfer buffer
131 movw1r(0x8,_si_,_ax) # Get
132 movw1r(0xa,_si_,_cx) # LBA
133 pushl %cs # Read from
134 callwi(xread.1) # disk
135 jnc return # If success
136 movwir(msg_read,_si) # Message
137
138# Error exit
139
140error: callwi(putstr) # Display message
141 movwir(prompt,_si) # Display
142 callwi(putstr) # prompt
143 xorb %ah,%ah # BIOS: Get
144 int $0x16 # keypress
145 int $0x19 # BIOS: Reboot
146
147# Display string
148
149putstr.0: movwir(0x7,_bx) # Page:attribute
150 movb $0xe,%ah # BIOS: Display
151 int $0x10 # character
152putstr: lodsb # Get char
153 testb %al,%al # End of string?
154 jne putstr.0 # No
155
156ereturn: movb $0x1,%ah # Invalid
157 stc # argument
158return: ret # To caller
159
160# Read from disk
161
162read: cs_ # LBA support
163 tstbim(0x80,MEM_REL+flags-start)# enabled?
164 jz read.1 # No
165 movwir(0x55aa,_bx) # Magic
166 pushl %edx # Save
167 movb $0x41,%ah # BIOS: Check
168 int $0x13 # extensions present
169 popl %edx # Restore
170 jc read.1 # If error
171 cmpwir(0xaa55,_bx) # Magic?
172 jne read.1 # No
173 testb $0x1,%cl # Packet interface?
174 jz read.1 # No
175 movl %ebp,%esi # Disk packet
176 movb $0x42,%ah # BIOS: Extended
177 int $0x13 # read
178 ret # To caller
179
180read.1: pushl %edx # Save
181 movb $0x8,%ah # BIOS: Get drive
182 int $0x13 # parameters
183 movb %dh,%ch # Max head number
184 popl %edx # Restore
185 jc return # If error
186 andb $0x3f,%cl # Sectors per track
187 jz ereturn # If zero
188 cli # Disable interrupts
189 o16 # Get
190 movw1r(0x8,_bp_,_ax) # LBA
191 pushl %edx # Save
192 movzbw %cl,%bx # Divide by
193 xorw %dx,%dx # sectors
194 divw %bx,%ax # per track
195 movb %ch,%bl # Max head number
196 movb %dl,%ch # Sector number
197 incl %ebx # Divide by
198 xorb %dl,%dl # number
199 divw %bx,%ax # of heads
200 movb %dl,%bh # Head number
201 popl %edx # Restore
202 o16 # Cylinder number
203 cmpl $0x3ff,%eax # supportable?
204 sti # Enable interrupts
205 ja ereturn # No
206 xchgb %al,%ah # Set up cylinder
207 rorb $0x2,%al # number
208 orb %ch,%al # Merge
209 incl %eax # sector
210 xchgl %eax,%ecx # number
211 movb %bh,%dh # Head number
212 subb %ah,%al # Sectors this track
213 movb1r(0x2,_bp_,_ah) # Blocks to read
214 cmpb %ah,%al # To read
215 jb read.2 # this
216 movb %ah,%al # track
217read.2: movwir(0x5,_di) # Try count
218read.3: lesw1r(0x4,_bp_,_bx) # Transfer buffer
219 pushl %eax # Save
220 movb $0x2,%ah # BIOS: Read
221 int $0x13 # from disk
222 popl %ebx # Restore
223 jnc read.4 # If success
224 decl %edi # Retry?
225 jz read.6 # No
226 xorb %ah,%ah # BIOS: Reset
227 int $0x13 # disk system
228 xchgl %ebx,%eax # Block count
229 jmp read.3 # Continue
230read.4: movzbl %bl,%eax # Sectors read
231 addwr1(_ax,0x8,_bp_) # Adjust
232 jnc read.5 # LBA,
233 incw1(0xa,_bp_) # transfer
234read.5: shlb %bl # buffer
235 addbr1(_bl,0x5,_bp_) # pointer,
236 subbr1(_al,0x2,_bp_) # block count
237 ja read.1 # If not done
238read.6: ret # To caller
239
240# Messages
241
242msg_read: .asciz "Read"
243msg_part: .asciz "Boot"
244
245prompt: .asciz " error\r\n"
246
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