1/*
| 1/*
|
| 2 * Copyright (c) 2008 Luigi Rizzo (mostly documentation)
|
2 * Copyright (c) 2002 Bruce M. Simpson
3 * Copyright (c) 1998 Robert Nordier
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms are freely
7 * permitted provided that the above copyright notice and this
8 * paragraph and the following disclaimer are duplicated in all
9 * such forms.
10 *
11 * This software is provided "AS IS" and without any express or
12 * implied warranties, including, without limitation, the implied
13 * warranties of merchantability and fitness for a particular
14 * purpose.
15 *
| 3 * Copyright (c) 2002 Bruce M. Simpson
4 * Copyright (c) 1998 Robert Nordier
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms are freely
8 * permitted provided that the above copyright notice and this
9 * paragraph and the following disclaimer are duplicated in all
10 * such forms.
11 *
12 * This software is provided "AS IS" and without any express or
13 * implied warranties, including, without limitation, the implied
14 * warranties of merchantability and fitness for a particular
15 * purpose.
16 *
|
16 * $FreeBSD: head/sys/boot/i386/boot0/boot0.S 185346 2008-11-26 21:38:43Z luigi $
| 17 * $FreeBSD: head/sys/boot/i386/boot0/boot0.S 185562 2008-12-02 14:57:48Z luigi $
|
17 */
18
| 18 */
19
|
19/* A 512-byte boot manager. */
20#ifdef SIO
21/* ... using a serial console on COM1. */
| 20/* build options: */
21#ifdef SIO /* use serial console on COM1. */
|
22#endif
23
| 22#endif
23
|
| 24#ifdef PXE /* enable PXE/INT18 booting with F6 */
25#endif
26
27#ifdef CHECK_DRIVE /* make sure we boot from a HD. */
28#endif
29
30#ifdef ONLY_F_KEYS /* Only F1..F6, no digits on console */
31#endif
32
33#ifdef TEST /* enable some test code */
34#ifndef ONLY_F_KEYS
35#define ONLY_F_KEYS /* make room for the test code */
36#endif
37#endif
38
39/*
40 * Note - this code uses many tricks to save space and fit in one sector.
41 * This includes using side effects of certain instructions, reusing
42 * register values from previous operations, etc.
43 * Be extremely careful when changing the code, even for simple things.
44 */
45
46/*
47 * BOOT BLOCK STRUCTURE
48 *
49 * This code implements a Master Boot Record (MBR) for an Intel/PC disk.
50 * It is 512 bytes long and it is normally loaded by the BIOS (or another
51 * bootloader) at 0:0x7c00. This code depends on %cs:%ip being 0:0x7c00
52 *
53 * The initial chunk of instructions is used as a signature by external
54 * tools (e.g. boot0cfg) which can manipulate the block itself.
55 *
56 * The area at offset 0x1b2 contains a magic string ('Drive '), also
57 * used as a signature to detect the block, and some variables that can
58 * be updated by boot0cfg (and optionally written back to the disk).
59 * These variables control the operation of the bootloader itself,
60 * e.g. which partitions to enable, the timeout, the use of LBA
61 * (called 'packet') or CHS mode, whether to force a drive number,
62 * and whether to write back the user's selection back to disk.
63 *
64 * As in every Master Boot Record, the partition table is at 0x1be,
65 * made of four 16-byte entries each containing:
66 *
67 * OFF SIZE DESCRIPTION
68 * 0 1 status (0x80: bootable, 0: non bootable)
69 * 1 3 start sector CHS
70 * 8:head, 6:sector, 2:cyl bit 9..8, 8:cyl bit 7..0
71 * 4 1 partition type
72 * 5 3 end sector CHS
73 * 8 4 LBA of first sector
74 * 12 4 partition size in sectors
75 *
76 * and followed by the two bytes 0x55, 0xAA (MBR signature).
77 */
78
79
80/*
81 * BOOT BLOCK OPERATION
82 *
83 * On entry, the registers contain the following values:
84 *
85 * %cs:%ip 0:0x7c00
86 * %dl drive number (0x80, 0x81, ... )
87 * %si pointer to the partition table from which we were loaded.
88 * Some boot code (e.g. syslinux) use this info to relocate
89 * themselves, so we want to pass a valid one to the next stage.
90 * NOTE: the use of %is is not a standard.
91 *
92 * This boot block first relocates itself at a different address (0:0x600),
93 * to free the space at 0:0x7c00 for the next stage boot block.
94 *
95 * It then initializes some memory at 0:0x800 and above (pointed by %bp)
96 * to store the original drive number (%dl) passed to us, and to construct a
97 * fake partition entry. The latter is used by the disk I/O routine and,
98 * in some cases, passed in %si to the next stage boot code.
99 *
100 * The variables at 0x1b2 are accessed as negative offsets from %bp.
101 *
102 * After the relocation, the code scans the partition table printing
103 * out enabled partition or disks, and waits for user input.
104 *
105 * When a partition is selected, or a timeout expires, the currently
106 * selected partition is used to load the next stage boot code,
107 * %dl and %si are set appropriately as when we were called, and
108 * control is transferred to the newly loaded code at 0:0x7c00.
109 */
110
111/*
112 * CONSTANTS
113 *
114 * NHRDRV is the address in segment 0 where the BIOS writes the
115 * total number of hard disks in the system.
116 * LOAD is the original load address and cannot be changed.
117 * ORIGIN is the relocation address. If you change it, you also need
118 * to change the value passed to the linker in the Makefile
119 * PRT_OFF is the location of the partition table (from the MBR standard).
120 * B0_OFF is the location of the data area, known to boot0cfg so
121 * it cannot be changed.
122 * MAGIC is the signature of a boot block.
123 */
124
|
24 .set NHRDRV,0x475 # Number of hard drives
25 .set ORIGIN,0x600 # Execution address
| 125 .set NHRDRV,0x475 # Number of hard drives
126 .set ORIGIN,0x600 # Execution address
|
26 .set FAKE,0x800 # Partition entry
| |
27 .set LOAD,0x7c00 # Load address
28
29 .set PRT_OFF,0x1be # Partition table
| 127 .set LOAD,0x7c00 # Load address
128
129 .set PRT_OFF,0x1be # Partition table
|
| 130 .set B0_OFF,0x1b2 # Offset of boot0 data
|
30
| 131
|
31 .set TBL0SZ,0x3 # Table 0 size
32 .set TBL1SZ,0xa # Table 1 size
33
| |
34 .set MAGIC,0xaa55 # Magic: bootable
| 132 .set MAGIC,0xaa55 # Magic: bootable
|
35 .set B0MAGIC,0xbb66 # Identification
| |
36
37 .set KEY_ENTER,0x1c # Enter key scan code
38 .set KEY_F1,0x3b # F1 key scan code
39 .set KEY_1,0x02 # #1 key scan code
40
| 133
134 .set KEY_ENTER,0x1c # Enter key scan code
135 .set KEY_F1,0x3b # F1 key scan code
136 .set KEY_1,0x02 # #1 key scan code
137
|
41 .set ASCII_BEL,0x07 # ASCII code for <BEL>
| 138 .set ASCII_BEL,'#' # ASCII code for <BEL>
|
42 .set ASCII_CR,0x0D # ASCII code for <CR>
43
44/*
| 139 .set ASCII_CR,0x0D # ASCII code for <CR>
140
141/*
|
45 * Addresses in the sector of embedded data values.
46 * Accessed with negative offsets from the end of the relocated sector (%ebp).
| 142 * Offsets of variables in the block at B0_OFF, and in the volatile
143 * data area, computed as displacement from %bp.
144 * We need to define them as constant as the assembler cannot
145 * compute them in its single pass.
|
47 */
| 146 */
|
48 .set _NXTDRV,-0x48 # Next drive
49 .set _OPT,-0x47 # Default option
50 .set _SETDRV,-0x46 # Drive to force
51 .set _FLAGS,-0x45 # Flags
52 .set _TICKS,-0x44 # Timeout ticks
53 .set _FAKE,0x0 # Fake partition entry
54 .set _MNUOPT,0xc # Menu options
| 147 .set _NXTDRV, -0x48 # Next drive
148 .set _OPT, -0x47 # Default option
149 .set _SETDRV, -0x46 # Drive to force
150 .set _FLAGS, -0x45 # Flags
151 .set SETDRV, 0x20 # the 'setdrv' flag
152 .set NOUPDATE, 0x40 # the 'noupdate' flag
153 .set USEPACKET, 0x80 # the 'packet' flag
154 .set _TICKS, -0x44 # Timeout ticks
155 .set _FAKE,0x0 # Fake partition table
156 .set _MNUOPT, 0x10 # Saved menu entries
|
55
| 157
|
| 158 .set TLEN, (desc_ofs - bootable_ids) # size of bootable ids
|
56 .globl start # Entry point
57 .code16 # This runs in real mode
58
59/*
| 159 .globl start # Entry point
160 .code16 # This runs in real mode
161
162/*
|
| 163 * MAIN ENTRY POINT
|
60 * Initialise segments and registers to known values.
61 * segments start at 0.
62 * The stack is immediately below the address we were loaded to.
| 164 * Initialise segments and registers to known values.
165 * segments start at 0.
166 * The stack is immediately below the address we were loaded to.
|
| 167 * NOTE: the initial section of the code (up to movw $LOAD,%sp)
168 * is used by boot0cfg, together with the 'Drive ' string and
169 * the 0x55, 0xaa at the end, as an identifier for version 1.0
170 * of the boot code. Do not change it.
171 * In version 1.0 the parameter table (_NEXTDRV etc) is at 0x1b9
|
63 */
64start: cld # String ops inc
65 xorw %ax,%ax # Zero
66 movw %ax,%es # Address
67 movw %ax,%ds # data
68 movw %ax,%ss # Set up
69 movw $LOAD,%sp # stack
70
| 172 */
173start: cld # String ops inc
174 xorw %ax,%ax # Zero
175 movw %ax,%es # Address
176 movw %ax,%ds # data
177 movw %ax,%ss # Set up
178 movw $LOAD,%sp # stack
179
|
71/*
72 * Copy this code to the address it was linked for
73 */
| 180 /*
181 * Copy this code to the address it was linked for, 0x600 by default.
182 */
|
74 movw %sp,%si # Source
75 movw $start,%di # Destination
76 movw $0x100,%cx # Word count
77 rep # Relocate
78 movsw # code
| 183 movw %sp,%si # Source
184 movw $start,%di # Destination
185 movw $0x100,%cx # Word count
186 rep # Relocate
187 movsw # code
|
79/*
80 * Set address for variable space beyond code, and clear it.
81 * Notice that this is also used to point to the values embedded in the block,
82 * by using negative offsets.
83 */
| 188 /*
189 * After the code, (i.e. at %di+0, 0x800) create a partition entry,
190 * initialized to LBA 0 / CHS 0:0:1.
191 * Set %bp to point to the partition and also, with negative offsets,
192 * to the variables embedded in the bootblock (nextdrv and so on).
193 */
|
84 movw %di,%bp # Address variables
85 movb $0x8,%cl # Words to clear
86 rep # Zero
87 stosw # them
| 194 movw %di,%bp # Address variables
195 movb $0x8,%cl # Words to clear
196 rep # Zero
197 stosw # them
|
88/*
89 * Relocate to the new copy of the code.
90 */
91 incb -0xe(%di) # Sector number
92 jmp main-LOAD+ORIGIN # To relocated code
| 198 incb -0xe(%di) # Set the S field to 1
|
93
| 199
|
| 200 jmp main-LOAD+ORIGIN # Jump to relocated code
201
|
94main:
95#if defined(SIO) && COMSPEED != 0
| 202main:
203#if defined(SIO) && COMSPEED != 0
|
96/*
97 * Initialize the serial port. bioscom preserves the driver number in DX.
98 */
| 204 /*
205 * Init the serial port. bioscom preserves the driver number in DX.
206 */
|
99 movw $COMSPEED,%ax # defined by Makefile
100 callw bioscom
101#endif
| 207 movw $COMSPEED,%ax # defined by Makefile
208 callw bioscom
209#endif
|
102/*
103 * Check what flags were loaded with us, specifically if a predefined drive
104 * number should be used. If what the bios gives us is bad, use the '0' in
105 * the block instead.
106 */
107 testb $0x20,_FLAGS(%bp) # Set drive number?
108 jnz main.1 # Yes
| 210
211 /*
212 * If the 'setdrv' flag is set in the boot sector, use the drive
213 * number from the boot sector at 'setdrv_num'.
214 * Optionally, do the same if the BIOS gives us an invalid number
215 * (note though that the override prevents booting from a floppy
216 * or a ZIP/flash drive in floppy emulation).
217 * The test costs 4 bytes of code so it is disabled by default.
218 */
219 testb $SETDRV,_FLAGS(%bp) # Set drive number?
220#ifndef CHECK_DRIVE /* disable drive checks */
221 jz save_curdrive # no, use the default
222#else
223 jnz disable_update # Yes
|
109 testb %dl,%dl # Drive number valid?
| 224 testb %dl,%dl # Drive number valid?
|
110 js main.2 # Possibly (0x80 set)
111/*
112 * Only update the boot-sector when there is a valid drive number or
113 * the drive number is set manually.
114 */
115 orb $0x40,_FLAGS(%bp) # Disable updates
116main.1: movb _SETDRV(%bp),%dl # Drive number to use
117/*
118 * Whatever we decided to use, now store it into the fake
119 * partition entry that lives in the data space above us.
120 */
121main.2: movb %dl,_FAKE(%bp) # Save drive number
122 callw putn # To new line
123 pushw %dx # Save drive number
124/*
125 * Start out with a pointer to the 4th byte of the first table entry
126 * so that after 4 iterations it's beyond the end of the sector
127 * and beyond a 256 byte boundary and has overflowed 8 bits (see next comment).
128 * Remember that the table starts 2 bytes earlier than you would expect
129 * as the bootable flag is after it in the block.
130 */
| 225 js save_curdrive # Possibly (0x80 set)
226#endif
227 /*
228 * Disable updates if the drive number is forced.
229 */
230disable_update: orb $NOUPDATE,_FLAGS(%bp) # Disable updates
231 movb _SETDRV(%bp),%dl # Use stored drive number
232
233 /*
234 * Whatever drive we decided to use, store it at (%bp). The byte
235 * is normally used for the state of the partition (0x80 or 0x00),
236 * but we abuse it as it is very convenient to access at offset 0.
237 * The value is read back after 'check_selection'
238 */
239save_curdrive: movb %dl, (%bp) # Save drive number
240 pushw %dx # Also in the stack
241#ifdef TEST /* test code, print internal bios drive */
242 rolb $1, %dl
243 movw $drive, %si
244 call putkey
245#endif
246 callw putn # Print a newline
247 /*
248 * Start out with a pointer to the 4th byte of the first table entry
249 * so that after 4 iterations it's beyond the end of the sector
250 * and beyond a 256 byte boundary. We use the latter trick to check for
251 * end of the loop without using an extra register (see start.5).
252 */
|
131 movw $(partbl+0x4),%bx # Partition table (+4)
132 xorw %dx,%dx # Item number
| 253 movw $(partbl+0x4),%bx # Partition table (+4)
254 xorw %dx,%dx # Item number
|
133/*
134 * Loop around on the partition table, printing values until we
135 * pass a 256 byte boundary. The end of loop test is at main.5.
136 */
137main.3: movb %ch,-0x4(%bx) # Zero active flag (ch == 0)
| 255
256 /*
257 * Loop around on the partition table, printing values until we
258 * pass a 256 byte boundary.
259 */
260read_entry: movb %ch,-0x4(%bx) # Zero active flag (ch == 0)
|
138 btw %dx,_FLAGS(%bp) # Entry enabled?
| 261 btw %dx,_FLAGS(%bp) # Entry enabled?
|
139 jnc main.5 # No
140/*
141 * If any of the entries in the table are the same as the 'type' in the slice
142 * table entry, then this is an empty or non bootable partition. Skip it.
143 */
| 262 jnc next_entry # No
263 /*
264 * Lookup type in the 'non_bootable_ids' table, skip matching entries.
265 * This is implemented is by setting %di to the start of the
266 * exclude table, and %cl to the length of the table itself. After the
267 * 'repne scasb' the zero flag is set if we found a match.
268 * If not, %di points to the beginning of the 'valid' types,
269 * which is what we need for the next check.
270 */
|
144 movb (%bx),%al # Load type
| 271 movb (%bx),%al # Load type
|
145 movw $tables,%di # Lookup tables
146 movb $TBL0SZ,%cl # Number of entries
| 272 movw $non_bootable_ids,%di # Lookup tables
273 movb $(bootable_ids-non_bootable_ids),%cl # length
|
147 repne # Exclude
148 scasb # partition?
| 274 repne # Exclude
275 scasb # partition?
|
149 je main.5 # Yes
150/*
151 * Now scan the table of known types
152 */
153 movb $TBL1SZ+1,%cl # Number of entries
| 276 je next_entry # Yes, ignore it
277 /*
278 * Now scan the table of bootable ids, which starts at %di and has
279 * length TLEN. On a match, %di points to the element following the
280 * match; the corresponding offset to the description is $(TLEN-1)
281 * bytes ahead. If we don't find a match, we hit the 'unknown' entry.
282 */
283 movb $(TLEN),%cl # Number of entries
|
154 repne # Locate
155 scasb # type
| 284 repne # Locate
285 scasb # type
|
156/*
157 * Get the matching element in the next array.
158 */
159 addw $TBL1SZ-1, %di # Adjust
| 286 /*
287 * Get the matching element in the next array.
288 * The byte at $(TLEN-1)(%di) contains the offset of the description
289 * string from %di, so we add the number and print the string.
290 */
291 addw $(TLEN-1), %di # Adjust
|
160 movb (%di),%cl # Partition
161 addw %cx,%di # description
162 callw putx # Display it
| 292 movb (%di),%cl # Partition
293 addw %cx,%di # description
294 callw putx # Display it
|
163main.5: incw %dx # Next item
| 295
296next_entry: incw %dx # Next item
|
164 addb $0x10,%bl # Next entry
| 297 addb $0x10,%bl # Next entry
|
165 jnc main.3 # Till done
166/*
167 * Passed a 256 byte boundary; the table is finished.
168 * Add one to the drive number and check it is valid.
169 */
| 298 jnc read_entry # Till done
299 /*
300 * We are past a 256 byte boundary: the partition table is finished.
301 * Add one to the drive number and check it is valid.
302 * Note that if we started from a floppy, %dl was 0 so we still
303 * get an entry for the next drive, which is the first Hard Disk.
304 */
|
170 popw %ax # Drive number
171 subb $0x80-0x1,%al # Does next
172 cmpb NHRDRV,%al # drive exist? (from BIOS?)
| 305 popw %ax # Drive number
306 subb $0x80-0x1,%al # Does next
307 cmpb NHRDRV,%al # drive exist? (from BIOS?)
|
173 jb main.6 # Yes
174/*
175 * If this is the only drive, don't display it as an option.
176 */
| 308 jb print_drive # Yes
309 /*
310 * If this is the only drive, don't display it as an option.
311 */
|
177 decw %ax # Already drive 0?
| 312 decw %ax # Already drive 0?
|
178 jz main.7 # Yes
179/*
180 * If it was illegal or we cycled through them, go back to drive 0.
181 */
| 313 jz print_prompt # Yes
314 /*
315 * If it was illegal or we cycled through them, go back to drive 0.
316 */
|
182 xorb %al,%al # Drive 0
| 317 xorb %al,%al # Drive 0
|
183/*
184 * Whatever drive we selected, make it an ascii digit and save it back to the
185 * "next drive" location in the loaded block in case we want to save it later
186 * for next time. This also is part of the printed drive string so add 0x80
187 * to indicate end of string.
188 */
189main.6: addb $'0'|0x80,%al # Save next
| 318 /*
319 * Whatever drive we selected, make it an ascii digit and save it
320 * back to the "nxtdrv" location in case we want to save it to disk.
321 * This digit is also part of the printed drive string, so add 0x80
322 * to indicate end of string.
323 */
324print_drive: addb $'0'|0x80,%al # Save next
|
190 movb %al,_NXTDRV(%bp) # drive number
191 movw $drive,%di # Display
192 callw putx # item
| 325 movb %al,_NXTDRV(%bp) # drive number
326 movw $drive,%di # Display
327 callw putx # item
|
193/*
194 * Now that we've printed the drive (if we needed to), display a prompt.
195 */
196main.7: movw $prompt,%si # Display
| 328 /*
329 * Menu is complete, display a prompt followed by current selection.
330 * 'decw %si' makes the register point to the space after 'Default: '
331 * so we do not see an extra CRLF on the screen.
332 */
333print_prompt: movw $prompt,%si # Display
|
197 callw putstr # prompt
198 movb _OPT(%bp),%dl # Display
199 decw %si # default
200 callw putkey # key
| 334 callw putstr # prompt
335 movb _OPT(%bp),%dl # Display
336 decw %si # default
337 callw putkey # key
|
201 jmp main.7_1 # Skip beep
| 338 jmp start_input # Skip beep
339
|
202/*
| 340/*
|
203 * Users's last try was bad, beep in displeasure.
| 341 * Here we have the code waiting for user input or a timeout.
|
204 */
| 342 */
|
205main.10: movb $ASCII_BEL,%al # Signal
206 callw putchr # beep!
207/*
208 * Start of input loop. Take note of time
209 */
210main.7_1: xorb %ah,%ah # BIOS: Get
| 343beep: movb $ASCII_BEL,%al # Input error, print or beep
344 callw putchr
345
346start_input:
347 /*
348 * Actual Start of input loop. Take note of time
349 */
350 xorb %ah,%ah # BIOS: Get
|
211 int $0x1a # system time
212 movw %dx,%di # Ticks when
213 addw _TICKS(%bp),%di # timeout
| 351 int $0x1a # system time
352 movw %dx,%di # Ticks when
353 addw _TICKS(%bp),%di # timeout
|
214/*
215 * Busy loop, looking for keystrokes but keeping one eye on the time.
216 */
217main.8:
| 354read_key:
355 /*
356 * Busy loop, looking for keystrokes but keeping one eye on the time.
357 */
|
218#ifndef SIO
219 movb $0x1,%ah # BIOS: Check
220 int $0x16 # for keypress
| 358#ifndef SIO
359 movb $0x1,%ah # BIOS: Check
360 int $0x16 # for keypress
|
221 jnz main.11 # Have one
| |
222#else /* SIO */
223 movb $0x03,%ah # BIOS: Read COM
224 call bioscom
225 testb $0x01,%ah # Check line status
| 361#else /* SIO */
362 movb $0x03,%ah # BIOS: Read COM
363 call bioscom
364 testb $0x01,%ah # Check line status
|
226 jnz main.11 # (bit 1 indicates input)
| 365 # (bit 1 indicates input)
|
227#endif /* SIO */
| 366#endif /* SIO */
|
228 xorb %ah,%ah # BIOS: Get
229 int $0x1a # system time
| 367 jnz got_key # Have input
368 xorb %ah,%ah # BIOS: int 0x1a, 00
369 int $0x1a # get system time
|
230 cmpw %di,%dx # Timeout?
| 370 cmpw %di,%dx # Timeout?
|
231 jb main.8 # No
232/*
233 * If timed out or defaulting, come here.
234 */
235main.9: movb _OPT(%bp),%al # Load default
236 jmp main.12 # Join common code
237/*
238 * Get the keystroke.
239 */
240main.11:
| 371 jb read_key # No
372
373 /*
374 * Timed out or default selection
375 */
376use_default: movb _OPT(%bp),%al # Load default
377 jmp check_selection # Join common code
378
379 /*
380 * Get the keystroke.
381 * ENTER or CR confirm the current selection (same as a timeout).
382 * Otherwise convert F1..F6 (or '1'..'6') to 0..5 and check if the
383 * selection is valid.
384 * The SIO code uses ascii chars, the console code uses scancodes.
385 */
386got_key:
|
241#ifndef SIO
| 387#ifndef SIO
|
242 xorb %ah,%ah # BIOS: Get
243 int $0x16 # keypress
244 movb %ah,%al # Scan code
| 388 xorb %ah,%ah # BIOS: int 0x16, 00
389 int $0x16 # get keypress
390 movb %ah,%al # move scan code to %al
391 cmpb $KEY_ENTER,%al
|
245#else
246 movb $0x02,%ah # BIOS: Receive
247 call bioscom
| 392#else
393 movb $0x02,%ah # BIOS: Receive
394 call bioscom
|
| 395 cmpb $ASCII_CR,%al
|
248#endif
| 396#endif
|
249/*
250 * If it's CR act as if timed out.
251 */
252#ifndef SIO
253 cmpb $KEY_ENTER,%al # Enter pressed?
254#else
255 cmpb $ASCII_CR,%al # Enter pressed?
256#endif
257 je main.9 # Yes
258/*
259 * Otherwise check if legal. If not ask again.
260 */
261#ifndef SIO
262 subb $KEY_F1,%al # Less F1 scan code
263 cmpb $0x4,%al # F1..F5?
264 jna main.12 # Yes
| 397 je use_default # enter -> default
398 /*
399 * Check if the key is acceptable, and loop back if not.
400 * The console (non-SIO) code looks at scancodes and accepts
401 * both F1..F6 and 1..6 (the latter costs 6 bytes of code),
402 * relying on the fact that F1..F6 have higher scancodes than 1..6
403 * The SIO code only takes 1..6
404 */
405#ifdef SIO /* SIO mode, use ascii values */
406 subb $'1',%al # Subtract '1' ascii code
407#else /* console mode -- use scancodes */
408 subb $KEY_F1,%al /* Subtract F1 scan code */
409#if !defined(ONLY_F_KEYS)
410 cmpb $0x5,%al # F1..F6
411 jna 3f # Yes
|
265 subb $(KEY_1 - KEY_F1),%al # Less #1 scan code
| 412 subb $(KEY_1 - KEY_F1),%al # Less #1 scan code
|
266#else
267 subb $'1',%al # Less '1' ascii character
268#endif
269 cmpb $0x4,%al # #1..#5?
270 ja main.10 # No
271/*
272 * We have a selection. If it's a bad selection go back to complain.
273 * The bits in MNUOPT were set when the options were printed.
274 * Anything not printed is not an option.
275 */
276main.12: cbtw # Option
277 btw %ax,_MNUOPT(%bp) # enabled?
278 jnc main.10 # No
279/*
280 * Save the info in the original tables
281 * for rewriting to the disk.
282 */
| 413 3:
414#endif /* ONLY_F_KEYS */
415#endif /* SIO */
416 cmpb $0x5,%al # F1..F6 or 1..6 ?
417#ifdef PXE /* enable PXE/INT18 using F6 */
418 jne 1f;
419 int $0x18 # found F6, try INT18
420 1:
421#endif /* PXE */
422 jae beep # Not in F1..F5, beep
423
424check_selection:
425 /*
426 * We have a selection. If it's a bad selection go back to complain.
427 * The bits in MNUOPT were set when the options were printed.
428 * Anything not printed is not an option.
429 */
430 cbtw # Extend (%ah=0 used later)
431 btw %ax,_MNUOPT(%bp) # Option enabled?
432 jnc beep # No
433 /*
434 * Save the info in the original tables
435 * for rewriting to the disk.
436 */
|
283 movb %al,_OPT(%bp) # Save option
| 437 movb %al,_OPT(%bp) # Save option
|
284 movw $FAKE,%si # Partition for write
285 movb (%si),%dl # Drive number
| 438
439 /*
440 * Make %si and %bx point to the fake partition at LBA 0 (CHS 0:0:1).
441 * Because the correct address is already in %bp, just use it.
442 * Set %dl with the drive number saved in byte 0.
443 * If we have pressed F5 or 5, then this is a good, fake value
444 * to present to the next stage boot code.
445 */
446 movw %bp,%si # Partition for write
447 movb (%si),%dl # Drive number, saved above
|
286 movw %si,%bx # Partition for read
287 cmpb $0x4,%al # F5/#5 pressed?
| 448 movw %si,%bx # Partition for read
449 cmpb $0x4,%al # F5/#5 pressed?
|
288 pushf # Save
289 je main.13 # Yes
| 450 pushf # Save results for later
451 je 1f # Yes, F5
452
453 /*
454 * F1..F4 was pressed, so make %bx point to the currently
455 * selected partition, and leave the drive number unchanged.
456 */
|
290 shlb $0x4,%al # Point to
291 addw $partbl,%ax # selected
292 xchgw %bx,%ax # partition
293 movb $0x80,(%bx) # Flag active
| 457 shlb $0x4,%al # Point to
458 addw $partbl,%ax # selected
459 xchgw %bx,%ax # partition
460 movb $0x80,(%bx) # Flag active
|
294/*
295 * If not asked to do a write-back (flags 0x40) don't do one.
296 */
297main.13: pushw %bx # Save
298 testb $0x40,_FLAGS(%bp) # No updates?
299 jnz main.14 # Yes
| 461 /*
462 * If not asked to do a write-back (flags 0x40) don't do one.
463 * Around the call, save the partition pointer to %bx and
464 * restore to %si which is where the next stage expects it.
465 */
466 1: pushw %bx # Save
467 testb $NOUPDATE,_FLAGS(%bp) # No updates?
468 jnz 2f # skip update
|
300 movw $start,%bx # Data to write
301 movb $0x3,%ah # Write sector
302 callw intx13 # to disk
| 469 movw $start,%bx # Data to write
470 movb $0x3,%ah # Write sector
471 callw intx13 # to disk
|
303main.14: popw %si # Restore
304 popf # Restore
305/*
306 * If going to next drive, replace drive with selected one.
307 * Remember to un-ascii it. Hey 0x80 is already set, cool!
308 */
309 jne main.15 # If not F5/#5
| 472 2: popw %si # Restore
473
474 /*
475 * If going to next drive, replace drive with selected one.
476 * Remember to un-ascii it. Hey 0x80 is already set, cool!
477 */
478 popf # Restore %al test results
479 jne 3f # If not F5/#5
|
310 movb _NXTDRV(%bp),%dl # Next drive
311 subb $'0',%dl # number
| 480 movb _NXTDRV(%bp),%dl # Next drive
481 subb $'0',%dl # number
|
312/*
313 * Load selected bootsector to the LOAD location in RAM.
314 * If it fails to read or isn't marked bootable, treat it as a bad selection.
315 */
316main.15: movw $LOAD,%bx # Address for read
| 482 /*
483 * Load selected bootsector to the LOAD location in RAM. If read
484 * fails or there is no 0x55aa marker, treat it as a bad selection.
485 */
486 3: movw $LOAD,%bx # Address for read
|
317 movb $0x2,%ah # Read sector
318 callw intx13 # from disk
| 487 movb $0x2,%ah # Read sector
488 callw intx13 # from disk
|
319 jc main.10 # If error
| 489 jc beep # If error
|
320 cmpw $MAGIC,0x1fe(%bx) # Bootable?
| 490 cmpw $MAGIC,0x1fe(%bx) # Bootable?
|
321 jne main.10 # No
| 491 jne beep # No
|
322 pushw %si # Save ptr to selected part.
323 callw putn # Leave some space
324 popw %si # Restore, next stage uses it
325 jmp *%bx # Invoke bootstrap
326
327/*
328 * Display routines
| 492 pushw %si # Save ptr to selected part.
493 callw putn # Leave some space
494 popw %si # Restore, next stage uses it
495 jmp *%bx # Invoke bootstrap
496
497/*
498 * Display routines
|
| 499 * putkey prints the option selected in %dl (F1..F5 or 1..5) followed by
500 * the string at %si
501 * putx: print the option in %dl followed by the string at %di
502 * also record the drive as valid.
503 * puts: print the string at %si followed by a crlf
504 * putn: print a crlf
505 * putstr: print the string at %si
506 * putchr: print the char in al
|
329 */
330putkey:
331#ifndef SIO
332 movb $'F',%al # Display
333 callw putchr # 'F'
334#endif
335 movb $'1',%al # Prepare
336 addb %dl,%al # digit
337 jmp putstr.1 # Display the rest
338
339/*
| 507 */
508putkey:
509#ifndef SIO
510 movb $'F',%al # Display
511 callw putchr # 'F'
512#endif
513 movb $'1',%al # Prepare
514 addb %dl,%al # digit
515 jmp putstr.1 # Display the rest
516
517/*
|
340 * Display the option and note that it is a valid option.
341 * That last point is a bit tricky..
| 518 * Display the option and record the drive as valid in the options.
519 * That last point is done using the btsw instruction which does
520 * a test and set. We don't care for the test part.
|
342 */
343putx: btsw %dx,_MNUOPT(%bp) # Enable menu option
344 movw $item,%si # Display
345 callw putkey # key
346 movw %di,%si # Display the rest
347
348puts: callw putstr # Display string
349
350putn: movw $crlf,%si # To next line
351
352putstr: lodsb # Get byte
353 testb $0x80,%al # End of string?
354 jnz putstr.2 # Yes
355putstr.1: callw putchr # Display char
356 jmp putstr # Continue
357putstr.2: andb $~0x80,%al # Clear MSB
358
| 521 */
522putx: btsw %dx,_MNUOPT(%bp) # Enable menu option
523 movw $item,%si # Display
524 callw putkey # key
525 movw %di,%si # Display the rest
526
527puts: callw putstr # Display string
528
529putn: movw $crlf,%si # To next line
530
531putstr: lodsb # Get byte
532 testb $0x80,%al # End of string?
533 jnz putstr.2 # Yes
534putstr.1: callw putchr # Display char
535 jmp putstr # Continue
536putstr.2: andb $~0x80,%al # Clear MSB
537
|
359#ifndef SIO
| |
360putchr:
| 538putchr:
|
| 539#ifndef SIO
|
361 pushw %bx # Save
362 movw $0x7,%bx # Page:attribute
363 movb $0xe,%ah # BIOS: Display
364 int $0x10 # character
365 popw %bx # Restore
| 540 pushw %bx # Save
541 movw $0x7,%bx # Page:attribute
542 movb $0xe,%ah # BIOS: Display
543 int $0x10 # character
544 popw %bx # Restore
|
366 retw # To caller
| |
367#else /* SIO */
| 545#else /* SIO */
|
368putchr:
| |
369 movb $0x01,%ah # BIOS: Send
370bioscom:
371 pushw %dx # Save
372 xorw %dx,%dx # Use COM1
373 int $0x14 # Character
374 popw %dx # Restore
| 546 movb $0x01,%ah # BIOS: Send
547bioscom:
548 pushw %dx # Save
549 xorw %dx,%dx # Use COM1
550 int $0x14 # Character
551 popw %dx # Restore
|
375 retw # To caller
| |
376#endif /* SIO */
| 552#endif /* SIO */
|
| 553 retw # To caller
|
377
378/* One-sector disk I/O routine */
379
| 554
555/* One-sector disk I/O routine */
556
|
380intx13: movb 0x1(%si),%dh # Load head
| 557/*
558 * %dl: drive, %si partition entry, %es:%bx transfer buffer.
559 * Load the CHS values and possibly the LBA address from the block
560 * at %si, and use the appropriate method to load the sector.
561 * Don't use packet mode for a floppy.
562 */
563intx13: # Prepare CHS parameters
564 movb 0x1(%si),%dh # Load head
|
381 movw 0x2(%si),%cx # Load cylinder:sector
382 movb $0x1,%al # Sector count
383 pushw %si # Save
384 movw %sp,%di # Save
| 565 movw 0x2(%si),%cx # Load cylinder:sector
566 movb $0x1,%al # Sector count
567 pushw %si # Save
568 movw %sp,%di # Save
|
385 testb $0x80,_FLAGS(%bp) # Use packet interface?
386 jz intx13.1 # No
| 569#ifndef CHECK_DRIVE /* floppy support */
570 testb %dl, %dl # is this a floppy ?
571 jz 1f # Yes, use CHS mode
572#endif
573 testb $USEPACKET,_FLAGS(%bp) # Use packet interface?
574 jz 1f # No
|
387 pushl $0x0 # Set the
388 pushl 0x8(%si) # LBA address
389 pushw %es # Set the transfer
390 pushw %bx # buffer address
391 push $0x1 # Block count
392 push $0x10 # Packet size
393 movw %sp,%si # Packet pointer
394 decw %ax # Verify off
395 orb $0x40,%ah # Use disk packet
| 575 pushl $0x0 # Set the
576 pushl 0x8(%si) # LBA address
577 pushw %es # Set the transfer
578 pushw %bx # buffer address
579 push $0x1 # Block count
580 push $0x10 # Packet size
581 movw %sp,%si # Packet pointer
582 decw %ax # Verify off
583 orb $0x40,%ah # Use disk packet
|
396intx13.1: int $0x13 # BIOS: Disk I/O
| 584 1: int $0x13 # BIOS: Disk I/O
|
397 movw %di,%sp # Restore
398 popw %si # Restore
399 retw # To caller
400
| 585 movw %di,%sp # Restore
586 popw %si # Restore
587 retw # To caller
588
|
401/* Menu strings */
402
| 589/*
590 * Various menu strings. 'item' goes after 'prompt' to save space.
591 * Also use shorter versions to make room for the PXE/INT18 code.
592 */
593#ifdef PXE
594prompt: .ascii "\nBoot:"
595item: .ascii " "; .byte ' '|0x80
596#else
597prompt: .ascii "\nDefault:"
|
403item: .ascii " "; .byte ' '|0x80
| 598item: .ascii " "; .byte ' '|0x80
|
404prompt: .ascii "\nDefault:"; .byte ' '|0x80
| 599#endif
|
405crlf: .ascii "\r"; .byte '\n'|0x80
406
407/* Partition type tables */
408
| 600crlf: .ascii "\r"; .byte '\n'|0x80
601
602/* Partition type tables */
603
|
409tables:
410/*
411 * These entries identify invalid or NON BOOT types and partitions.
412 */
| 604non_bootable_ids:
605 /*
606 * These entries identify invalid or NON BOOT types and partitions.
607 * 0: empty, 5: DOS3 ext. partition, 0xf: WIN95 ext partition
608 */
|
413 .byte 0x0, 0x5, 0xf
| 609 .byte 0x0, 0x5, 0xf
|
414/*
415 * These values indicate bootable types we know the names of.
416 */
| 610bootable_ids:
611 /*
612 * These values indicate bootable types we know the names of.
613 * 1: FAT12, 4: FAT16 <32M, 6: FAT16 > 32M, 7: NTFS
614 * 0xb: FAT32, 0xc: FAT32-LBA, 0xe: FAT16-LBA,
615 * 0x83: linux, 0xa5: FreeBSD, 0xa6: netbsd, 0xa9:openbsd
616 */
|
417 .byte 0x1, 0x6, 0x7, 0xb, 0xc, 0xe, 0x83
| 617 .byte 0x1, 0x6, 0x7, 0xb, 0xc, 0xe, 0x83
|
418 .byte 0xa5, 0xa6, 0xa9
419/*
420 * These are offsets that match the known names above and point to the strings
421 * that will be printed. os_misc will be used if the search of the above table
422 * runs over.
423 */
424 .byte os_dos-. # DOS
425 .byte os_dos-. # DOS
426 .byte os_dos-. # Windows
427 .byte os_dos-. # Windows
428 .byte os_dos-. # Windows
429 .byte os_dos-. # Windows
430 .byte os_linux-. # Linux
431 .byte os_freebsd-. # FreeBSD
432 .byte os_bsd-. # OpenBSD
433 .byte os_bsd-. # NetBSD
| 618 .byte 0xa5, 0xa6, 0xa9, 0x4
619desc_ofs:
620 /*
621 * Offsets that match the known types above, used to point to the
622 * actual partition name. The last entry must point to os_misc,
623 * which is used for non-matching names.
624 */
625 .byte os_dos-. # 1, DOS
626 .byte os_dos-. # 6, DOS/WIN
627 .byte os_win-. # 7, Windows
628 .byte os_win-. # 11, Windows
629 .byte os_win-. # 12, Windows
630 .byte os_win-. # 14, Windows
631 .byte os_linux-. # 131, Linux
632 .byte os_freebsd-. # 165, FreeBSD
633 .byte os_bsd-. # 166, OpenBSD
634 .byte os_bsd-. # 169, NetBSD
635 .byte os_dos-. # 4, DOS
|
434 .byte os_misc-. # Unknown
| 636 .byte os_misc-. # Unknown
|
435/*
436 * And here are the strings themselves. 0x80 or'd into a byte indicates
437 * the end of the string. (not so great for Russians but...)
438 */
439os_misc: .ascii "?"; .byte '?'|0x80
440os_dos: .ascii "DO"; .byte 'S'|0x80
| 637
638 /*
639 * And here are the strings themselves. The last byte of
640 * the string has bit 7 set.
641 */
642os_misc: .byte '?'|0x80
643os_dos:
644#if !defined(TEST) /* DOS string only if room */
645 .ascii "DO"; .byte 'S'|0x80
646#endif
647os_win: .ascii "WI"; .byte 'N'|0x80
|
441os_linux: .ascii "Linu"; .byte 'x'|0x80
442os_freebsd: .ascii "Free"
443os_bsd: .ascii "BS"; .byte 'D'|0x80
444
| 648os_linux: .ascii "Linu"; .byte 'x'|0x80
649os_freebsd: .ascii "Free"
650os_bsd: .ascii "BS"; .byte 'D'|0x80
651
|
445 .org PRT_OFF-0xe,0x90
446
447 .word B0MAGIC # Magic number
448
| 652 .org B0_OFF,0x90
|
449/*
| 653/*
|
450 * These values are sometimes changed before writing back to the drive
| 654 * The boot0 version 1.0 parameter table.
655 * Do not move it nor change the "Drive " string, boot0cfg
656 * uses its offset and content to identify the boot sector.
657 * The other fields are sometimes changed before writing back to the drive
|
451 * Be especially careful that nxtdrv: must come after drive:, as it
452 * is part of the same string.
453 */
454drive: .ascii "Drive "
455nxtdrv: .byte 0x0 # Next drive number
456opt: .byte 0x0 # Option
| 658 * Be especially careful that nxtdrv: must come after drive:, as it
659 * is part of the same string.
660 */
661drive: .ascii "Drive "
662nxtdrv: .byte 0x0 # Next drive number
663opt: .byte 0x0 # Option
|
457setdrv: .byte 0x80 # Drive to force
| 664setdrv_num: .byte 0x80 # Drive to force
|
458flags: .byte FLAGS # Flags
459ticks: .word TICKS # Delay
460
| 665flags: .byte FLAGS # Flags
666ticks: .word TICKS # Delay
667
|
| 668 .org PRT_OFF
|
461/*
462 * Here is the 64 byte partition table that fdisk would fiddle with.
463 */
464partbl: .fill 0x40,0x1,0x0 # Partition table
465 .word MAGIC # Magic number
| 669/*
670 * Here is the 64 byte partition table that fdisk would fiddle with.
671 */
672partbl: .fill 0x40,0x1,0x0 # Partition table
673 .word MAGIC # Magic number
|
| 674 .org 0x200 # again, safety check
675endblock:
|
| |