2 * Copyright (c) 2003,2004 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * Copyright (c) 1998 Robert Nordier
35 * All rights reserved.
37 * Redistribution and use in source and binary forms are freely
38 * permitted provided that the above copyright notice and this
39 * paragraph and the following disclaimer are duplicated in all
42 * This software is provided "AS IS" and without any express or
43 * implied warranties, including, without limitation, the implied
44 * warranties of merchantability and fitness for a particular
48 * $FreeBSD: src/sys/boot/i386/boot0/boot0.s,v 1.26 2003/06/01 20:41:04 obrien Exp $
49 * $DragonFly: src/sys/boot/i386/boot0/Attic/boot0.S,v 1.6 2004/07/19 23:30:31 dillon Exp $
52 #include "../bootasm.h"
55 * A 512-byte boot manager.
57 .set PRT_OFF,0x1be # Partition table
59 .set TBL0SZ,0x3 # Table 0 size
60 .set TBL1SZ,0xc # Table 1 size
62 .set MAGIC,0xaa55 # Magic: bootable
63 .set B0MAGIC,0xbb66 # Identification
65 .set KEY_ENTER,0x1c # Enter key scan code
66 .set KEY_F1,0x3b # F1 key scan code
67 .set KEY_1,0x02 # #1 key scan code
70 * Addresses in the sector of embedded data values. Accessed
71 * with negative offsets from the end of the relocated sector
74 * Note that %ebp is the base of our variable space and
75 * points at the end of the sector (base + 0x200). The
76 * fake partition and menu option is thus stored in the
77 * memory just after the boot0 sector.
79 .set _NXTDRV,-0x48 # Next drive
80 .set _OPT,-0x47 # Default option
81 .set _SETDRV,-0x46 # Drive to force
82 .set _FLAGS,-0x45 # Flags
83 .set _TICKS,-0x44 # Timeout ticks
84 .set _FAKE,0x0 # Fake partition entry
85 .set _MNUOPT,0xc # Menu options
87 .globl start # Entry point
88 .code16 # This runs in real mode
91 * Initialise segments and registers to known values.
92 * segments start at 0. The stack is immediately below the
93 * address we were loaded to.
95 start: cld # String ops inc
97 movw %ax,%es # Address
100 movw $MEM_BIOS_LADDR,%sp # stack
103 * Copy this code to the address it was linked for
105 movw %sp,%si # Source
106 movw $start,%di # Destination
107 movw $0x100,%cx # Word count
112 * Set address for variable space beyond code, and clear it.
113 * Notice that this is also used to point to the values
114 * embedded in the block, by using negative offsets.
116 movw %di,%bp # Address variables
117 movb $0x8,%cl # Words to clear
122 * Relocate to the new copy of the code. Do not make
123 * assumptions with regard to a relative-PC near jump
126 incb -0xe(%di) # Sector number
127 pushw $main # Jump to relocated code
131 * Check what flags were loaded with us, specifically, Use a
132 * predefined Drive. If what the bios gives us is bad, use
133 * the '0' in the block instead, as well.
135 main: testb $0x20,_FLAGS(%bp) # Set number drive?
137 testb %dl,%dl # Drive number valid?
138 js main.2 # Possibly (0x80 set)
139 main.1: movb _SETDRV(%bp),%dl # Drive number to use
142 * Whatever we decided to use, now store it into the fake
143 * partition entry that lives in the data space above us.
145 main.2: movb %dl,_FAKE(%bp) # Save drive number
146 callw putn # To new line
147 pushw %dx # Save drive number
150 * Start out with a pointer to the 4th byte of the first
151 * table entry so that after 4 iterations it's beyond the
152 * end of the sector. and beyond a 256 byte boundary and
153 * has overflowed 8 bits (see next comment). (remember
154 * that the table starts 2 bytes earlier than you would
155 * expect as the bootable flag is after it in the block)
157 movw $(partbl+0x4),%bx # Partition table (+4)
158 xorw %dx,%dx # Item number
161 * Loop around on the partition table, printing values until
162 * we pass a 256 byte boundary. The end of loop test is at
165 main.3: movb %ch,-0x4(%bx) # Zero active flag (ch == 0)
166 btw %dx,_FLAGS(%bp) # Entry enabled?
170 * If any of the entries in the table are the same as the
171 * 'type' in the slice table entry, then this is an empty
172 * or non bootable partition. Skip it.
174 movb (%bx),%al # Load type
175 movw $tables,%di # Lookup tables
176 movb $TBL0SZ,%cl # Number of entries
182 * Now scan the table of known types
184 movb $TBL1SZ,%cl # Number of entries
190 * If it matches get the matching element in the
191 * next array. if it doesn't, we are already
192 * pointing at its first element which points to a "?".
194 addw $TBL1SZ,%di # Adjust
195 main.4: movb (%di),%cl # Partition
196 addw %cx,%di # description
197 callw putx # Display it
198 main.5: incw %dx # Next item
199 addb $0x10,%bl # Next entry
200 jnc main.3 # Till done
203 * Passed a 256 byte boundary..
205 * Add one to the drive number and check it is valid,
207 popw %ax # Drive number
208 subb $0x80-0x1,%al # Does next
209 cmpb BDA_NHRDRV,%al # drive exist? (from BIOS?)
213 * If not then if there is only one drive,
214 * Don't display drive as an option.
216 decw %ax # Already drive 0?
220 * If it was illegal or we cycled through them,
221 * then go back to drive 0.
223 xorb %al,%al # Drive 0
226 * Whatever drive we selected, make it an ascii digit and
227 * save it back to the "next drive" location in the loaded
228 * block in case we want to save it for next time. This also
229 * is part of the printed drive string so add 0x80 to indicate
232 main.6: addb $'0'|0x80,%al # Save next
233 movb %al,_NXTDRV(%bp) # drive number
234 movw $drive,%di # Display
238 * Now that we've printed the drive (if we needed to),
239 * display a prompt. Get ready for the input by noting the
242 main.7: movw $prompt,%si # Display
243 callw putstr # prompt
244 movb _OPT(%bp),%dl # Display
247 xorb %ah,%ah # BIOS: Get
248 int $0x1a # system time
249 movw %dx,%di # Ticks when
250 addw _TICKS(%bp),%di # timeout
253 * Busy loop, looking for keystrokes but
254 * keeping one eye on the time.
256 main.8: movb $0x1,%ah # BIOS: Check
257 int $0x16 # for keypress
258 jnz main.11 # Have one
259 xorb %ah,%ah # BIOS: Get
260 int $0x1a # system time
261 cmpw %di,%dx # Timeout?
265 * If timed out or defaulting, come here.
267 main.9: movb _OPT(%bp),%al # Load default
268 jmp main.12 # Join common code
271 * User's last try was bad, beep in displeasure.
272 * Since nothing was printed, just continue on as if the
273 * user hadn't done anything. This gives the effect of the
274 * user getting a beep for all bad keystrokes but no action
275 * until either the timeout occurs or the user hits a good
278 main.10: movb $0x7,%al # Signal
284 main.11: xorb %ah,%ah # BIOS: Get
286 movb %ah,%al # Scan code
289 * If it's CR act as if timed out.
291 cmpb $KEY_ENTER,%al # Enter pressed?
295 * Otherwise check if legal
298 subb $KEY_F1,%al # Less F1 scan code
299 cmpb $0x4,%al # F1..F5?
301 subb $(KEY_1 - KEY_F1),%al # Less #1 scan code
302 cmpb $0x4,%al # #1..#5?
306 * We have a selection. But if it's a bad selection go back
307 * to complain. The bits in MNUOPT were set when the options
308 * were printed. Anything not printed is not an option.
310 main.12: cbtw # Option
311 btw %ax,_MNUOPT(%bp) # enabled?
315 * Save the info in the original tables
316 * for rewriting to the disk.
318 movb %al,_OPT(%bp) # Save option
319 lea _FAKE(%bp),%si # Partition for write
320 movb (%si),%dl # Drive number
321 movw %si,%bx # Partition for read
322 cmpb $0x4,%al # F5 pressed?
325 shlb $0x4,%al # Point to
326 addw $partbl,%ax # selected
327 xchgw %bx,%ax # partition
328 movb $0x80,(%bx) # Flag active
331 * If not asked to do a write-back (flags 0x40) don't do one.
333 main.13: pushw %bx # Save
334 testb $0x40,_FLAGS(%bp) # No updates?
336 movw $start,%bx # Data to write
337 movb $0x3,%ah # Write sector
338 callw intx13 # to disk
339 main.14: popw %si # Restore
343 * If going to next drive, replace drive with selected one.
344 * Remember to un-ascii it. Hey 0x80 is already set, cool!
346 jne main.15 # If not F5
347 movb _NXTDRV(%bp),%dl # Next drive
348 subb $'0',%dl # number
351 * load selected bootsector to the MEM_BIOS_LADDR location
352 * in RAM. If it fails to read or isn't marked bootable,
353 * treat it as a bad selection.
354 * XXX what does %si carry?
356 main.15: movw $MEM_BIOS_LADDR,%bx # Address for read
357 movb $0x2,%ah # Read sector
358 callw intx13 # from disk
359 jc main.10 # If error
360 cmpw $MAGIC,0x1fe(%bx) # Bootable?
363 movw $crlf,%si # Leave some
366 jmp *%bx # Invoke bootstrap
371 putkey: movb $'F',%al # Display
373 movb $'1',%al # Prepare
375 jmp putstr.1 # Display the rest
378 * Display the option and note that it is a valid option.
379 * That last point is a bit tricky..
381 putx: btsw %dx,_MNUOPT(%bp) # Enable menu option
382 movw $item,%si # Display
384 movw %di,%si # Display the rest
386 puts: callw putstr # Display string
388 putn: movw $crlf,%si # To next line
390 putstr: lodsb # Get byte
391 testb $0x80,%al # End of string?
393 putstr.1: callw putchr # Display char
394 jmp putstr # Continue
395 putstr.2: andb $~0x80,%al # Clear MSB
398 movw $0x7,%bx # Page:attribute
399 movb $0xe,%ah # BIOS: Display
400 int $0x10 # character
405 * One-sector disk I/O routine
407 * Setup for both the packet and non-packet interfaces
408 * then select one or the other.
410 * Don't trust the BIOS to keep registers intact across
411 * the call, use pusha/popa.
413 intx13: movb 0x1(%si),%dh # (nonpkt) head
414 movw 0x2(%si),%cx # (nonpkt) cylinder:sector
415 movb $0x1,%al # (nonpkt) Sector count
416 pusha # save: do not trust the bios
417 pushl $0x0 # (pkt) LBA address
418 pushl 0x8(%si) # (pkt)
419 pushw %es # (pkt) xfer buffer address
421 pushw $1 # (pkt) Block count
422 pushw $16 # (pkt) Packet size
423 testb $0x80,_FLAGS(%bp) # Use packet interface?
425 movw %sp,%si # Yes, set packet pointer
426 decw %ax # Verify off
427 orb $0x40,%ah # Set pkt mode in command
428 intx13.1: int $0x13 # BIOS: Disk I/O
429 # WARNING: RETAIN CARRY AFTER BIOS CALL
431 lea 16(%si),%sp # cleanup the stack
432 popa # Restore registers
439 item: .ascii " "; .byte ' '|0x80
440 prompt: .ascii "\nDefault:"; .byte ' '|0x80
441 crlf: .ascii "\r"; .byte '\n'|0x80
444 * Partition type tables
449 * These entries identify invalid or NON BOOT types and
455 * These values indicate bootable types we know the names of.
457 .byte 0x1, 0x4, 0x6, 0xb, 0xc, 0xe, 0x83
458 .byte 0x9f, 0xa5, 0xa6, 0xa9
461 * These are offsets that match the known names above and
462 * point to the strings that will be printed.
464 .byte os_misc-. # Unknown
468 .byte os_dos-. # Windows
469 .byte os_dos-. # Windows
470 .byte os_dos-. # Windows
471 .byte os_linux-. # Linux
472 .byte os_bsd-. # BSD/OS
473 .byte os_freebsd-. # FreeBSD
474 .byte os_bsd-. # OpenBSD
475 .byte os_bsd-. # NetBSD
478 * And here are the strings themselves. 0x80 or'd into a
479 * byte indicates the end of the string. (not so great for
482 os_misc: .ascii "?"; .byte '?'|0x80
483 os_dos: .ascii "DO"; .byte 'S'|0x80
484 os_linux: .ascii "Linu"; .byte 'x'|0x80
485 os_freebsd: .ascii "Free"
486 os_bsd: .ascii "BS"; .byte 'D'|0x80
488 .org PRT_OFF-0xe,0x90
490 .word B0MAGIC # Magic number
493 * These values are sometimes changed before writing back
494 * to the drive. Be especially careful that nxtdrv: must
495 * come after drive:, as it is part of the same string.
497 drive: .ascii "Drive "
498 nxtdrv: .byte 0x0 # Next drive number
499 opt: .byte 0x0 # Option
500 setdrv: .byte 0x80 # Drive to force
501 flags: .byte FLAGS # Flags
502 ticks: .word TICKS # Delay
505 * here is the 64 byte partition table that fdisk would
508 partbl: .fill 0x40,0x1,0x0 # Partition table
509 .word MAGIC # Magic number