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 *
| 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 * $FreeBSD: head/sys/boot/i386/boot2/boot1.S 128716 2004-04-28 14:31:44Z ru $
| 15 * $FreeBSD: head/sys/boot/i386/boot2/boot1.S 129240 2004-05-14 20:29:30Z ru $
|
16 */
17
18/* Memory Locations */
| 16 */
17
18/* Memory Locations */
|
19 .set MEM_REL,0x700 // Relocation address
20 .set MEM_ARG,0x900 // Arguments
21 .set MEM_ORG,0x7c00 // Origin
22 .set MEM_BUF,0x8cec // Load area
23 .set MEM_BTX,0x9000 // BTX start
24 .set MEM_JMP,0x9010 // BTX entry point
25 .set MEM_USR,0xa000 // Client start
26 .set BDA_BOOT,0x472 // Boot howto flag
| 19 .set MEM_REL,0x700 # Relocation address
20 .set MEM_ARG,0x900 # Arguments
21 .set MEM_ORG,0x7c00 # Origin
22 .set MEM_BUF,0x8cec # Load area
23 .set MEM_BTX,0x9000 # BTX start
24 .set MEM_JMP,0x9010 # BTX entry point
25 .set MEM_USR,0xa000 # Client start
26 .set BDA_BOOT,0x472 # Boot howto flag
|
27
28/* Partition Constants */
| 27
28/* Partition Constants */
|
29 .set PRT_OFF,0x1be // Partition offset
30 .set PRT_NUM,0x4 // Partitions
31 .set PRT_BSD,0xa5 // Partition type
| 29 .set PRT_OFF,0x1be # Partition offset
30 .set PRT_NUM,0x4 # Partitions
31 .set PRT_BSD,0xa5 # Partition type
|
32
33/* Flag Bits */
| 32
33/* Flag Bits */
|
34 .set FL_PACKET,0x80 // Packet mode
| 34 .set FL_PACKET,0x80 # Packet mode
|
35
36/* Misc. Constants */
| 35
36/* Misc. Constants */
|
37 .set SIZ_PAG,0x1000 // Page size
38 .set SIZ_SEC,0x200 // Sector size
| 37 .set SIZ_PAG,0x1000 # Page size
38 .set SIZ_SEC,0x200 # Sector size
|
39
40 .set NSECT,0x10
41 .globl start
42 .globl xread
43 .code16
44
| 39
40 .set NSECT,0x10
41 .globl start
42 .globl xread
43 .code16
44
|
45start: jmp main // Start recognizably
| 45start: jmp main # Start recognizably
|
46
47/*
48 * This is the start of a standard BIOS Parameter Block (BPB). Most bootable
49 * FAT disks have this at the start of their MBR. While normal BIOS's will
50 * work fine without this section, IBM's El Torito emulation "fixes" up the
51 * BPB by writing into the memory copy of the MBR. Rather than have data
52 * written into our xread routine, we'll define a BPB to work around it.
53 * The data marked with (T) indicates a field required for a ThinkPad to
54 * recognize the disk and (W) indicates fields written from IBM BIOS code.
55 * The use of the BPB is based on what OpenBSD and NetBSD implemented in
56 * their boot code but the required fields were determined by trial and error.
57 *
58 * Note: If additional space is needed in boot1, one solution would be to
59 * move the "prompt" message data (below) to replace the OEM ID.
60 */
61 .org 0x03, 0x00
| 46
47/*
48 * This is the start of a standard BIOS Parameter Block (BPB). Most bootable
49 * FAT disks have this at the start of their MBR. While normal BIOS's will
50 * work fine without this section, IBM's El Torito emulation "fixes" up the
51 * BPB by writing into the memory copy of the MBR. Rather than have data
52 * written into our xread routine, we'll define a BPB to work around it.
53 * The data marked with (T) indicates a field required for a ThinkPad to
54 * recognize the disk and (W) indicates fields written from IBM BIOS code.
55 * The use of the BPB is based on what OpenBSD and NetBSD implemented in
56 * their boot code but the required fields were determined by trial and error.
57 *
58 * Note: If additional space is needed in boot1, one solution would be to
59 * move the "prompt" message data (below) to replace the OEM ID.
60 */
61 .org 0x03, 0x00
|
62oemid: .space 0x08, 0x00 // OEM ID
| 62oemid: .space 0x08, 0x00 # OEM ID
|
63
64 .org 0x0b, 0x00
| 63
64 .org 0x0b, 0x00
|
65bpb: .word 512 // sector size (T)
66 .byte 0 // sectors/clustor
67 .word 0 // reserved sectors
68 .byte 0 // number of FATs
69 .word 0 // root entries
70 .word 0 // small sectors
71 .byte 0 // media type (W)
72 .word 0 // sectors/fat
73 .word 18 // sectors per track (T)
74 .word 2 // number of heads (T)
75 .long 0 // hidden sectors (W)
76 .long 0 // large sectors
| 65bpb: .word 512 # sector size (T)
66 .byte 0 # sectors/clustor
67 .word 0 # reserved sectors
68 .byte 0 # number of FATs
69 .word 0 # root entries
70 .word 0 # small sectors
71 .byte 0 # media type (W)
72 .word 0 # sectors/fat
73 .word 18 # sectors per track (T)
74 .word 2 # number of heads (T)
75 .long 0 # hidden sectors (W)
76 .long 0 # large sectors
|
77
78 .org 0x24, 0x00
| 77
78 .org 0x24, 0x00
|
79ebpb: .byte 0 // BIOS physical drive number (W)
| 79ebpb: .byte 0 # BIOS physical drive number (W)
|
80
81 .org 0x25,0x90
82/*
83 * Trampoline used by boot2 to call read to read data from the disk via
84 * the BIOS. Call with:
85 *
86 * %cx:%ax - long - LBA to read in
87 * %es:(%bx) - caddr_t - buffer to read data into
88 * %dl - byte - drive to read from
89 * %dh - byte - num sectors to read
90 */
91
| 80
81 .org 0x25,0x90
82/*
83 * Trampoline used by boot2 to call read to read data from the disk via
84 * the BIOS. Call with:
85 *
86 * %cx:%ax - long - LBA to read in
87 * %es:(%bx) - caddr_t - buffer to read data into
88 * %dl - byte - drive to read from
89 * %dh - byte - num sectors to read
90 */
91
|
92xread: push %ss // Address
93 pop %ds // data
| 92xread: push %ss # Address
93 pop %ds # data
|
94/*
95 * Setup an EDD disk packet and pass it to read
96 */
| 94/*
95 * Setup an EDD disk packet and pass it to read
96 */
|
97xread.1: // Starting
98 pushl $0x0 // absolute
99 push %cx // block
100 push %ax // number
101 push %es // Address of
102 push %bx // transfer buffer
103 xor %ax,%ax // Number of
104 movb %dh,%al // blocks to
105 push %ax // transfer
106 push $0x10 // Size of packet
107 mov %sp,%bp // Packet pointer
108 callw read // Read from disk
109 lea 0x10(%bp),%sp // Clear stack
110 lret // To far caller
| 97xread.1: # Starting
98 pushl $0x0 # absolute
99 push %cx # block
100 push %ax # number
101 push %es # Address of
102 push %bx # transfer buffer
103 xor %ax,%ax # Number of
104 movb %dh,%al # blocks to
105 push %ax # transfer
106 push $0x10 # Size of packet
107 mov %sp,%bp # Packet pointer
108 callw read # Read from disk
109 lea 0x10(%bp),%sp # Clear stack
110 lret # To far caller
|
111/*
112 * Load the rest of boot2 and BTX up, copy the parts to the right locations,
113 * and start it all up.
114 */
115
116/*
117 * Setup the segment registers to flat addressing (segment 0) and setup the
118 * stack to end just below the start of our code.
119 */
| 111/*
112 * Load the rest of boot2 and BTX up, copy the parts to the right locations,
113 * and start it all up.
114 */
115
116/*
117 * Setup the segment registers to flat addressing (segment 0) and setup the
118 * stack to end just below the start of our code.
119 */
|
120main: cld // String ops inc
121 xor %cx,%cx // Zero
122 mov %cx,%es // Address
123 mov %cx,%ds // data
124 mov %cx,%ss // Set up
125 mov $start,%sp // stack
| 120main: cld # String ops inc
121 xor %cx,%cx # Zero
122 mov %cx,%es # Address
123 mov %cx,%ds # data
124 mov %cx,%ss # Set up
125 mov $start,%sp # stack
|
126/*
127 * Relocate ourself to MEM_REL. Since %cx == 0, the inc %ch sets
128 * %cx == 0x100.
129 */
| 126/*
127 * Relocate ourself to MEM_REL. Since %cx == 0, the inc %ch sets
128 * %cx == 0x100.
129 */
|
130 mov %sp,%si // Source
131 mov $MEM_REL,%di // Destination
132 incb %ch // Word count
133 rep // Copy
134 movsw // code
| 130 mov %sp,%si # Source
131 mov $MEM_REL,%di # Destination
132 incb %ch # Word count
133 rep # Copy
134 movsw # code
|
135/*
136 * If we are on a hard drive, then load the MBR and look for the first
137 * FreeBSD slice. We use the fake partition entry below that points to
138 * the MBR when we call nread. The first pass looks for the first active
139 * FreeBSD slice. The second pass looks for the first non-active FreeBSD
140 * slice if the first one fails.
141 */
| 135/*
136 * If we are on a hard drive, then load the MBR and look for the first
137 * FreeBSD slice. We use the fake partition entry below that points to
138 * the MBR when we call nread. The first pass looks for the first active
139 * FreeBSD slice. The second pass looks for the first non-active FreeBSD
140 * slice if the first one fails.
141 */
|
142 mov $part4,%si // Partition
143 cmpb $0x80,%dl // Hard drive?
144 jb main.4 // No
145 movb $0x1,%dh // Block count
146 callw nread // Read MBR
147 mov $0x1,%cx // Two passes
148main.1: mov $MEM_BUF+PRT_OFF,%si // Partition table
149 movb $0x1,%dh // Partition
150main.2: cmpb $PRT_BSD,0x4(%si) // Our partition type?
151 jne main.3 // No
152 jcxz main.5 // If second pass
153 testb $0x80,(%si) // Active?
154 jnz main.5 // Yes
155main.3: add $0x10,%si // Next entry
156 incb %dh // Partition
157 cmpb $0x1+PRT_NUM,%dh // In table?
158 jb main.2 // Yes
159 dec %cx // Do two
160 jcxz main.1 // passes
| 142 mov $part4,%si # Partition
143 cmpb $0x80,%dl # Hard drive?
144 jb main.4 # No
145 movb $0x1,%dh # Block count
146 callw nread # Read MBR
147 mov $0x1,%cx # Two passes
148main.1: mov $MEM_BUF+PRT_OFF,%si # Partition table
149 movb $0x1,%dh # Partition
150main.2: cmpb $PRT_BSD,0x4(%si) # Our partition type?
151 jne main.3 # No
152 jcxz main.5 # If second pass
153 testb $0x80,(%si) # Active?
154 jnz main.5 # Yes
155main.3: add $0x10,%si # Next entry
156 incb %dh # Partition
157 cmpb $0x1+PRT_NUM,%dh # In table?
158 jb main.2 # Yes
159 dec %cx # Do two
160 jcxz main.1 # passes
|
161/*
162 * If we get here, we didn't find any FreeBSD slices at all, so print an
163 * error message and die.
164 */
| 161/*
162 * If we get here, we didn't find any FreeBSD slices at all, so print an
163 * error message and die.
164 */
|
165 mov $msg_part,%si // Message
166 jmp error // Error
| 165 mov $msg_part,%si # Message
166 jmp error # Error
|
167/*
168 * Floppies use partition 0 of drive 0.
169 */
| 167/*
168 * Floppies use partition 0 of drive 0.
169 */
|
170main.4: xor %dx,%dx // Partition:drive
| 170main.4: xor %dx,%dx # Partition:drive
|
171/*
172 * Ok, we have a slice and drive in %dx now, so use that to locate and load
173 * boot2. %si references the start of the slice we are looking for, so go
174 * ahead and load up the first 16 sectors (boot1 + boot2) from that. When
175 * we read it in, we conveniently use 0x8cec as our transfer buffer. Thus,
176 * boot1 ends up at 0x8cec, and boot2 starts at 0x8cec + 0x200 = 0x8eec.
177 * The first part of boot2 is the disklabel, which is 0x114 bytes long.
178 * The second part is BTX, which is thus loaded into 0x9000, which is where
179 * it also runs from. The boot2.bin binary starts right after the end of
180 * BTX, so we have to figure out where the start of it is and then move the
181 * binary to 0xc000. Normally, BTX clients start at MEM_USR, or 0xa000, but
182 * when we use btxld to create boot2, we use an entry point of 0x2000. That
183 * entry point is relative to MEM_USR; thus boot2.bin starts at 0xc000.
184 */
| 171/*
172 * Ok, we have a slice and drive in %dx now, so use that to locate and load
173 * boot2. %si references the start of the slice we are looking for, so go
174 * ahead and load up the first 16 sectors (boot1 + boot2) from that. When
175 * we read it in, we conveniently use 0x8cec as our transfer buffer. Thus,
176 * boot1 ends up at 0x8cec, and boot2 starts at 0x8cec + 0x200 = 0x8eec.
177 * The first part of boot2 is the disklabel, which is 0x114 bytes long.
178 * The second part is BTX, which is thus loaded into 0x9000, which is where
179 * it also runs from. The boot2.bin binary starts right after the end of
180 * BTX, so we have to figure out where the start of it is and then move the
181 * binary to 0xc000. Normally, BTX clients start at MEM_USR, or 0xa000, but
182 * when we use btxld to create boot2, we use an entry point of 0x2000. That
183 * entry point is relative to MEM_USR; thus boot2.bin starts at 0xc000.
184 */
|
185main.5: mov %dx,MEM_ARG // Save args
186 movb $NSECT,%dh // Sector count
187 callw nread // Read disk
188 mov $MEM_BTX,%bx // BTX
189 mov 0xa(%bx),%si // Get BTX length and set
190 add %bx,%si // %si to start of boot2.bin
191 mov $MEM_USR+SIZ_PAG*2,%di // Client page 2
192 mov $MEM_BTX+(NSECT-1)*SIZ_SEC,%cx // Byte
193 sub %si,%cx // count
194 rep // Relocate
195 movsb // client
196 sub %di,%cx // Byte count
197 xorb %al,%al // Zero assumed bss from
198 rep // the end of boot2.bin
199 stosb // up to 0x10000
200 callw seta20 // Enable A20
201 jmp start+MEM_JMP-MEM_ORG // Start BTX
| 185main.5: mov %dx,MEM_ARG # Save args
186 movb $NSECT,%dh # Sector count
187 callw nread # Read disk
188 mov $MEM_BTX,%bx # BTX
189 mov 0xa(%bx),%si # Get BTX length and set
190 add %bx,%si # %si to start of boot2.bin
191 mov $MEM_USR+SIZ_PAG*2,%di # Client page 2
192 mov $MEM_BTX+(NSECT-1)*SIZ_SEC,%cx # Byte
193 sub %si,%cx # count
194 rep # Relocate
195 movsb # client
196 sub %di,%cx # Byte count
197 xorb %al,%al # Zero assumed bss from
198 rep # the end of boot2.bin
199 stosb # up to 0x10000
200 callw seta20 # Enable A20
201 jmp start+MEM_JMP-MEM_ORG # Start BTX
|
202/*
203 * Enable A20 so we can access memory above 1 meg.
204 */
| 202/*
203 * Enable A20 so we can access memory above 1 meg.
204 */
|
205seta20: cli // Disable interrupts
206seta20.1: inb $0x64,%al // Get status
207 testb $0x2,%al // Busy?
208 jnz seta20.1 // Yes
209 movb $0xd1,%al // Command: Write
210 outb %al,$0x64 // output port
211seta20.2: inb $0x64,%al // Get status
212 testb $0x2,%al // Busy?
213 jnz seta20.2 // Yes
214 movb $0xdf,%al // Enable
215 outb %al,$0x60 // A20
216 sti // Enable interrupts
217 retw // To caller
| 205seta20: cli # Disable interrupts
206seta20.1: inb $0x64,%al # Get status
207 testb $0x2,%al # Busy?
208 jnz seta20.1 # Yes
209 movb $0xd1,%al # Command: Write
210 outb %al,$0x64 # output port
211seta20.2: inb $0x64,%al # Get status
212 testb $0x2,%al # Busy?
213 jnz seta20.2 # Yes
214 movb $0xdf,%al # Enable
215 outb %al,$0x60 # A20
216 sti # Enable interrupts
217 retw # To caller
|
218/*
219 * Trampoline used to call read from within boot1.
220 */
| 218/*
219 * Trampoline used to call read from within boot1.
220 */
|
221nread: mov $MEM_BUF,%bx // Transfer buffer
222 mov 0x8(%si),%ax // Get
223 mov 0xa(%si),%cx // LBA
224 push %cs // Read from
225 callw xread.1 // disk
226 jnc return // If success, return
227 mov $msg_read,%si // Otherwise, set the error
228 // message and fall through to
229 // the error routine
| 221nread: mov $MEM_BUF,%bx # Transfer buffer
222 mov 0x8(%si),%ax # Get
223 mov 0xa(%si),%cx # LBA
224 push %cs # Read from
225 callw xread.1 # disk
226 jnc return # If success, return
227 mov $msg_read,%si # Otherwise, set the error
228 # message and fall through to
229 # the error routine
|
230/*
231 * Print out the error message pointed to by %ds:(%si) followed
232 * by a prompt, wait for a keypress, and then reboot the machine.
233 */
| 230/*
231 * Print out the error message pointed to by %ds:(%si) followed
232 * by a prompt, wait for a keypress, and then reboot the machine.
233 */
|
234error: callw putstr // Display message
235 mov $prompt,%si // Display
236 callw putstr // prompt
237 xorb %ah,%ah // BIOS: Get
238 int $0x16 // keypress
239 movw $0x1234, BDA_BOOT // Do a warm boot
240 ljmp $0xffff,$0x0 // reboot the machine
| 234error: callw putstr # Display message
235 mov $prompt,%si # Display
236 callw putstr # prompt
237 xorb %ah,%ah # BIOS: Get
238 int $0x16 # keypress
239 movw $0x1234, BDA_BOOT # Do a warm boot
240 ljmp $0xffff,$0x0 # reboot the machine
|
241/*
242 * Display a null-terminated string using the BIOS output.
243 */
| 241/*
242 * Display a null-terminated string using the BIOS output.
243 */
|
244putstr.0: mov $0x7,%bx // Page:attribute
245 movb $0xe,%ah // BIOS: Display
246 int $0x10 // character
247putstr: lodsb // Get char
248 testb %al,%al // End of string?
249 jne putstr.0 // No
| 244putstr.0: mov $0x7,%bx # Page:attribute
245 movb $0xe,%ah # BIOS: Display
246 int $0x10 # character
247putstr: lodsb # Get char
248 testb %al,%al # End of string?
249 jne putstr.0 # No
|
250
251/*
252 * Overused return code. ereturn is used to return an error from the
253 * read function. Since we assume putstr succeeds, we (ab)use the
254 * same code when we return from putstr.
255 */
| 250
251/*
252 * Overused return code. ereturn is used to return an error from the
253 * read function. Since we assume putstr succeeds, we (ab)use the
254 * same code when we return from putstr.
255 */
|
256ereturn: movb $0x1,%ah // Invalid
257 stc // argument
258return: retw // To caller
| 256ereturn: movb $0x1,%ah # Invalid
257 stc # argument
258return: retw # To caller
|
259/*
260 * Reads sectors from the disk. If EDD is enabled, then check if it is
261 * installed and use it if it is. If it is not installed or not enabled, then
262 * fall back to using CHS. Since we use a LBA, if we are using CHS, we have to
263 * fetch the drive parameters from the BIOS and divide it out ourselves.
264 * Call with:
265 *
266 * %dl - byte - drive number
267 * stack - 10 bytes - EDD Packet
268 */
| 259/*
260 * Reads sectors from the disk. If EDD is enabled, then check if it is
261 * installed and use it if it is. If it is not installed or not enabled, then
262 * fall back to using CHS. Since we use a LBA, if we are using CHS, we have to
263 * fetch the drive parameters from the BIOS and divide it out ourselves.
264 * Call with:
265 *
266 * %dl - byte - drive number
267 * stack - 10 bytes - EDD Packet
268 */
|
269read: push %dx // Save
270 movb $0x8,%ah // BIOS: Get drive
271 int $0x13 // parameters
272 movb %dh,%ch // Max head number
273 pop %dx // Restore
274 jc return // If error
275 andb $0x3f,%cl // Sectors per track
276 jz ereturn // If zero
277 cli // Disable interrupts
278 mov 0x8(%bp),%eax // Get LBA
279 push %dx // Save
280 movzbl %cl,%ebx // Divide by
281 xor %edx,%edx // sectors
282 div %ebx // per track
283 movb %ch,%bl // Max head number
284 movb %dl,%ch // Sector number
285 inc %bx // Divide by
286 xorb %dl,%dl // number
287 div %ebx // of heads
288 movb %dl,%bh // Head number
289 pop %dx // Restore
290 cmpl $0x3ff,%eax // Cylinder number supportable?
291 sti // Enable interrupts
292 ja read.7 // No, try EDD
293 xchgb %al,%ah // Set up cylinder
294 rorb $0x2,%al // number
295 orb %ch,%al // Merge
296 inc %ax // sector
297 xchg %ax,%cx // number
298 movb %bh,%dh // Head number
299 subb %ah,%al // Sectors this track
300 mov 0x2(%bp),%ah // Blocks to read
301 cmpb %ah,%al // To read
302 jb read.2 // this
| 269read: push %dx # Save
270 movb $0x8,%ah # BIOS: Get drive
271 int $0x13 # parameters
272 movb %dh,%ch # Max head number
273 pop %dx # Restore
274 jc return # If error
275 andb $0x3f,%cl # Sectors per track
276 jz ereturn # If zero
277 cli # Disable interrupts
278 mov 0x8(%bp),%eax # Get LBA
279 push %dx # Save
280 movzbl %cl,%ebx # Divide by
281 xor %edx,%edx # sectors
282 div %ebx # per track
283 movb %ch,%bl # Max head number
284 movb %dl,%ch # Sector number
285 inc %bx # Divide by
286 xorb %dl,%dl # number
287 div %ebx # of heads
288 movb %dl,%bh # Head number
289 pop %dx # Restore
290 cmpl $0x3ff,%eax # Cylinder number supportable?
291 sti # Enable interrupts
292 ja read.7 # No, try EDD
293 xchgb %al,%ah # Set up cylinder
294 rorb $0x2,%al # number
295 orb %ch,%al # Merge
296 inc %ax # sector
297 xchg %ax,%cx # number
298 movb %bh,%dh # Head number
299 subb %ah,%al # Sectors this track
300 mov 0x2(%bp),%ah # Blocks to read
301 cmpb %ah,%al # To read
302 jb read.2 # this
|
303#ifdef TRACK_AT_A_TIME
| 303#ifdef TRACK_AT_A_TIME
|
304 movb %ah,%al // track
| 304 movb %ah,%al # track
|
305#else
| 305#else
|
306 movb $1,%al // one sector
| 306 movb $1,%al # one sector
|
307#endif
| 307#endif
|
308read.2: mov $0x5,%di // Try count
309read.3: les 0x4(%bp),%bx // Transfer buffer
310 push %ax // Save
311 movb $0x2,%ah // BIOS: Read
312 int $0x13 // from disk
313 pop %bx // Restore
314 jnc read.4 // If success
315 dec %di // Retry?
316 jz read.6 // No
317 xorb %ah,%ah // BIOS: Reset
318 int $0x13 // disk system
319 xchg %bx,%ax // Block count
320 jmp read.3 // Continue
321read.4: movzbw %bl,%ax // Sectors read
322 add %ax,0x8(%bp) // Adjust
323 jnc read.5 // LBA,
324 incw 0xa(%bp) // transfer
325read.5: shlb %bl // buffer
326 add %bl,0x5(%bp) // pointer,
327 sub %al,0x2(%bp) // block count
328 ja read // If not done
329read.6: retw // To caller
330read.7: testb $FL_PACKET,%cs:MEM_REL+flags-start // LBA support enabled?
331 jz ereturn // No, so return an error
332 mov $0x55aa,%bx // Magic
333 push %dx // Save
334 movb $0x41,%ah // BIOS: Check
335 int $0x13 // extensions present
336 pop %dx // Restore
337 jc return // If error, return an error
338 cmp $0xaa55,%bx // Magic?
339 jne ereturn // No, so return an error
340 testb $0x1,%cl // Packet interface?
341 jz ereturn // No, so return an error
342 mov %bp,%si // Disk packet
343 movb $0x42,%ah // BIOS: Extended
344 int $0x13 // read
345 retw // To caller
| 308read.2: mov $0x5,%di # Try count
309read.3: les 0x4(%bp),%bx # Transfer buffer
310 push %ax # Save
311 movb $0x2,%ah # BIOS: Read
312 int $0x13 # from disk
313 pop %bx # Restore
314 jnc read.4 # If success
315 dec %di # Retry?
316 jz read.6 # No
317 xorb %ah,%ah # BIOS: Reset
318 int $0x13 # disk system
319 xchg %bx,%ax # Block count
320 jmp read.3 # Continue
321read.4: movzbw %bl,%ax # Sectors read
322 add %ax,0x8(%bp) # Adjust
323 jnc read.5 # LBA,
324 incw 0xa(%bp) # transfer
325read.5: shlb %bl # buffer
326 add %bl,0x5(%bp) # pointer,
327 sub %al,0x2(%bp) # block count
328 ja read # If not done
329read.6: retw # To caller
330read.7: testb $FL_PACKET,%cs:MEM_REL+flags-start # LBA support enabled?
331 jz ereturn # No, so return an error
332 mov $0x55aa,%bx # Magic
333 push %dx # Save
334 movb $0x41,%ah # BIOS: Check
335 int $0x13 # extensions present
336 pop %dx # Restore
337 jc return # If error, return an error
338 cmp $0xaa55,%bx # Magic?
339 jne ereturn # No, so return an error
340 testb $0x1,%cl # Packet interface?
341 jz ereturn # No, so return an error
342 mov %bp,%si # Disk packet
343 movb $0x42,%ah # BIOS: Extended
344 int $0x13 # read
345 retw # To caller
|
346
347/* Messages */
348
349msg_read: .asciz "Read"
350msg_part: .asciz "Boot"
351
352prompt: .asciz " error\r\n"
353
| 346
347/* Messages */
348
349msg_read: .asciz "Read"
350msg_part: .asciz "Boot"
351
352prompt: .asciz " error\r\n"
353
|
354flags: .byte FLAGS // Flags
| 354flags: .byte FLAGS # Flags
|
355
356 .org PRT_OFF,0x90
357
358/* Partition table */
359
360 .fill 0x30,0x1,0x0
361part4: .byte 0x80, 0x00, 0x01, 0x00
362 .byte 0xa5, 0xfe, 0xff, 0xff
363 .byte 0x00, 0x00, 0x00, 0x00
| 355
356 .org PRT_OFF,0x90
357
358/* Partition table */
359
360 .fill 0x30,0x1,0x0
361part4: .byte 0x80, 0x00, 0x01, 0x00
362 .byte 0xa5, 0xfe, 0xff, 0xff
363 .byte 0x00, 0x00, 0x00, 0x00
|
364 .byte 0x50, 0xc3, 0x00, 0x00 // 50000 sectors long, bleh
| 364 .byte 0x50, 0xc3, 0x00, 0x00 # 50000 sectors long, bleh
|
365
| 365
|
366 .word 0xaa55 // Magic number
| 366 .word 0xaa55 # Magic number
|
| |