1/* 2 * Copyright (c) 2003,2004 The DragonFly Project. All rights reserved. 3 * 4 * This code is derived from software contributed to The DragonFly Project 5 * by Matthew Dillon <dillon@backplane.com> 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 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 16 * distribution. 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. 20 * 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 32 * SUCH DAMAGE. 33 * 34 * Copyright (c) 1998 Robert Nordier 35 * All rights reserved. 36 * 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 40 * such forms. 41 * 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 45 * purpose. 46 * 47 * 48 * $FreeBSD: src/sys/boot/i386/boot0/boot0.s,v 1.26 2003/06/01 20:41:04 obrien Exp $ 49 */ 50 51#include "../bootasm.h" 52 53#ifdef SIO 54/* ... using a serial console on COM1. */ 55#endif 56 57 /* 58 * A 512-byte boot manager. 59 */ 60 .set PRT_OFF,0x1be # Partition table 61 62 .set TBL0SZ,0x3 # Table 0 size 63 .set TBL1SZ,0xb # Table 1 size 64 65 .set MAGIC,0xaa55 # Magic: bootable 66 .set B0MAGIC,0xbb66 # Identification 67 68 .set KEY_ENTER,0x1c # Enter key scan code 69 .set KEY_F1,0x3b # F1 key scan code 70 .set KEY_1,0x02 # #1 key scan code 71 72 .set ASCII_BEL,0x07 # ASCII code for <BEL> 73 .set ASCII_CR,0x0D # ASCII code for <CR> 74 75 /* 76 * Addresses in the sector of embedded data values. Accessed 77 * with negative offsets from the end of the relocated sector 78 * (%ebp). 79 * 80 * Note that %ebp is the base of our variable space and 81 * points at the end of the sector (base + 0x200). The 82 * fake partition and menu option is thus stored in the 83 * memory just after the boot0 sector. 84 */ 85 .set _NXTDRV,-0x48 # Next drive 86 .set _OPT,-0x47 # Default option 87 .set _SETDRV,-0x46 # Drive to force 88 .set _FLAGS,-0x45 # Flags 89 .set _TICKS,-0x44 # Timeout ticks 90 .set _FAKE,0x0 # Fake partition entry 91 .set _MNUOPT,0xc # Menu options 92 93 .set _SECTOR_FIELD_OFF,-0xe # Offset to Sector field 94 # in the fake partition 95 .set _DATA_OFF,PRT_OFF+_SECTOR_FIELD_OFF 96 # Offset to boot0 variables 97 # from partition table 98 99 .globl start # Entry point 100 .code16 # This runs in real mode 101 102 /* 103 * Initialise segments and registers to known values. 104 * segments start at 0. The stack is immediately below the 105 * address we were loaded to. 106 */ 107start: cld # String ops inc 108 xorw %ax,%ax # Zero 109 movw %ax,%es # Address 110 movw %ax,%ds # data 111 movw %ax,%ss # Set up 112 movw $MEM_BIOS_LADDR,%sp # stack 113 114 /* 115 * Copy this code to the address it was linked for. 116 * Base address after relocation is - 0x600. 117 */ 118 movw %sp,%si # Source 119 movw $start,%di # Destination 120 movw $0x100,%cx # Word count 121 rep # Relocate 122 movsw # code 123 124 /* 125 * Set address for variable space beyond code, and clear it. 126 * Notice that this is also used to point to the values 127 * embedded in the block, by using negative offsets. 128 */ 129 movw %di,%bp # Address variables 130 movb $0x8,%cl # Words to clear 131 rep # Zero 132 stosw # them 133 134 /* 135 * Set C:H:S to 0:0:1 and relocate to the new copy of 136 * the code. Do not make assumptions with regard to 137 * a relative-PC near jump capability. 138 */ 139 incb _SECTOR_FIELD_OFF(%di) # Sector number 140 pushw $main # Jump to relocated code 141 retw 142 143main: 144#if defined(SIO) && COMSPEED != 0 145 /* 146 * Initialize the serial port. 147 * bioscom preserves the drive number in DX. 148 */ 149 movw $COMSPEED,%ax # defined by Makefile 150 callw bioscom 151#endif 152 /* 153 * Check what flags were loaded with us, specifically, Use a 154 * predefined Drive. If what the bios gives us is bad, use 155 * the '0' in the block instead, as well. 156 */ 157 testb $0x20,_FLAGS(%bp) # Set number drive? 158 jnz main.1 # Yes 159 testb %dl,%dl # Drive number valid? 160 js main.2 # Possibly (0x80 set) 161 162main.1: movb _SETDRV(%bp),%dl # Drive number to use 163 164 /* 165 * Whatever we decided to use, now store it into the fake 166 * partition entry that lives in the data space above us. 167 */ 168main.2: movb %dl,_FAKE(%bp) # Save drive number 169 callw putn # To new line 170 pushw %dx # Save drive number 171 172 /* 173 * Start out with a pointer to the 4th byte of the first 174 * table entry so that after 4 iterations it's beyond the 175 * end of the sector. and beyond a 256 byte boundary and 176 * has overflowed 8 bits (see next comment). (remember 177 * that the table starts 2 bytes earlier than you would 178 * expect as the bootable flag is after it in the block) 179 */ 180 movw $(partbl+0x4),%bx # Partition table (+4 - type) 181 xorw %dx,%dx # Partition entry item number 182 183 /* 184 * Loop around on the partition table, printing values until 185 * we pass a 256 (4x 64 byte partitions) byte boundary. The 186 * end of loop test is at 187 * main.5. 188 */ 189main.3: movb %ch,-0x4(%bx) # Zero active flag (ch == 0) 190 btw %dx,_FLAGS(%bp) # Entry enabled? 191 jnc main.5 # No 192 193 /* 194 * If any of the entries in the table are the same as the 195 * 'type' in the slice table entry, then this is an empty 196 * or non bootable partition. Skip it. 197 */ 198 movb (%bx),%al # Load type 199 movw $tables,%di # Lookup tables 200 movb $TBL0SZ,%cl # Number of entries 201 repne # Exclude 202 scasb # partition? 203 je main.5 # Yes 204 205 /* 206 * Now scan the table of known types 207 */ 208 movb $TBL1SZ,%cl # Number of entries 209 repne # Known 210 scasb # type? 211 jne main.4 # No 212 213 /* 214 * If it matches get the matching element in the 215 * next array. if it doesn't, we are already 216 * pointing at its first element which points to a "?". 217 */ 218 addw $TBL1SZ,%di # Adjust 219main.4: movb (%di),%cl # Partition 220 addw %cx,%di # description 221 callw putx # Display it 222main.5: incw %dx # Next item 223 addb $0x10,%bl # Next entry 224 jnc main.3 # Till done 225 226 /* 227 * Passed a 256 byte boundary.. 228 * table is finished. 229 * Add one to the drive number and check it is valid, 230 */ 231 popw %ax # Drive number 232 subb $0x80-0x1,%al # Does next 233 cmpb BDA_NHRDRV,%al # drive exist? (from BIOS?) 234 jb main.6 # Yes 235 236 /* 237 * If not then if there is only one drive, 238 * Don't display drive as an option. 239 */ 240 decw %ax # Already drive 0? 241 jz main.7 # Yes 242 243 /* 244 * If it was illegal or we cycled through them, 245 * then go back to drive 0. 246 */ 247 xorb %al,%al # Drive 0 248 249 /* 250 * Whatever drive we selected, make it an ascii digit and 251 * save it back to the "next drive" location in the loaded 252 * block in case we want to save it for next time. This also 253 * is part of the printed drive string so add 0x80 to indicate 254 * end of string. 255 */ 256main.6: addb $'0'|0x80,%al # Save next 257 movb %al,_NXTDRV(%bp) # drive number 258 movw $drive,%di # Display 259 callw putx # item 260 261 /* 262 * Now that we've printed the drive (if we needed to), 263 * display a prompt. Get ready for the input by noting the 264 * time. 265 */ 266main.7: movw $prompt,%si # Display 267 callw putstr # prompt 268 movb _OPT(%bp),%dl # Display 269 decw %si # default 270 callw putkey # key 271 xorb %ah,%ah # BIOS: Get 272 int $0x1a # system time 273 movw %dx,%di # Ticks when 274 addw _TICKS(%bp),%di # timeout 275 276 /* 277 * Busy loop, looking for keystrokes but 278 * keeping one eye on the time. 279 */ 280main.8: 281#ifndef SIO 282 movb $0x1,%ah # BIOS: Check 283 int $0x16 # for keypress 284 jnz main.11 # Have one 285#else /* SIO */ 286 movb $0x03,%ah # BIOS: Read COM 287 call bioscom 288 testb $0x01,%ah # Check line status 289 jnz main.11 # (bit 1 indicates input) 290#endif /* SIO */ 291 xorb %ah,%ah # BIOS: Get 292 int $0x1a # system time 293 cmpw %di,%dx # Timeout? 294 jb main.8 # No 295 296 /* 297 * If timed out or defaulting, come here. 298 */ 299main.9: movb _OPT(%bp),%al # Load default 300 jmp main.12 # Join common code 301 302 /* 303 * User's last try was bad, beep in displeasure. 304 * Since nothing was printed, just continue on as if the 305 * user hadn't done anything. This gives the effect of the 306 * user getting a beep for all bad keystrokes but no action 307 * until either the timeout occurs or the user hits a good 308 * key. 309 */ 310main.10: movb $ASCII_BEL,%al # Signal 311 callw putchr # error 312 313 /* 314 * Get the keystroke. 315 */ 316main.11: 317#ifndef SIO 318 xorb %ah,%ah # BIOS: Get 319 int $0x16 # keypress 320 movb %ah,%al # Scan code 321#else 322 movb $0x02,%ah # BIOS: Receive 323 call bioscom 324#endif 325 326 /* 327 * If it's CR act as if timed out. 328 */ 329#ifndef SIO 330 cmpb $KEY_ENTER,%al # Enter pressed? 331#else 332 cmpb $ASCII_CR,%al # Enter pressed? 333#endif 334 je main.9 # Yes 335 336 /* 337 * Otherwise check if legal 338 * If not ask again. 339 */ 340#ifndef SIO 341 subb $KEY_F1,%al # Less F1 scan code 342 cmpb $0x4,%al # F1..F5? 343 jna main.12 # Yes 344 subb $(KEY_1 - KEY_F1),%al # Less #1 scan code 345#else 346 subb $'1',%al # Less '1' ascii character 347#endif 348 cmpb $0x4,%al # #1..#5? 349 ja main.10 # No 350 351 /* 352 * We have a selection. But if it's a bad selection go back 353 * to complain. The bits in MNUOPT were set when the options 354 * were printed. Anything not printed is not an option. 355 */ 356main.12: cbtw # Option 357 btw %ax,_MNUOPT(%bp) # enabled? 358 jnc main.10 # No 359 360 /* 361 * Save the info in the original tables 362 * for rewriting to the disk. 363 */ 364 movb %al,_OPT(%bp) # Save option 365 lea _FAKE(%bp),%si # Partition for write 366 movb (%si),%dl # Drive number 367 movw %si,%bx # Partition for read 368 cmpb $0x4,%al # F5 pressed? 369 pushf # Save 370 je main.13 # Yes 371 shlb $0x4,%al # Point to 372 addw $partbl,%ax # selected 373 xchgw %bx,%ax # partition 374 movb $0x80,(%bx) # Flag active 375 376 /* 377 * If not asked to do a write-back (flags 0x40) don't do one. 378 */ 379main.13: pushw %bx # Save 380 testb $0x40,_FLAGS(%bp) # No updates? 381 jnz main.14 # Yes 382 movw $start,%bx # Data to write 383 movb $0x3,%ah # Write sector 384 callw intx13 # to disk 385main.14: popw %si # Restore partition 386 popf # Restore eflags 387 388 /* 389 * If going to next drive, replace drive with selected one. 390 * Remember to un-ascii it. Hey 0x80 is already set, cool! 391 */ 392 jne main.15 # If not F5 393 movb _NXTDRV(%bp),%dl # Next drive 394 subb $'0',%dl # number 395 396 /* 397 * load selected bootsector to the MEM_BIOS_LADDR location 398 * in RAM. If it fails to read or isn't marked bootable, 399 * treat it as a bad selection. 400 * XXX what does %si carry? 401 */ 402main.15: movw $MEM_BIOS_LADDR,%bx # Address for read 403 movb $0x2,%ah # Read sector 404 callw intx13 # from disk 405 jc main.10 # If error 406 cmpw $MAGIC,0x1fe(%bx) # Bootable? 407 jne main.10 # No 408 pushw %si # Save 409 movw $crlf,%si # Leave some 410 callw puts # space 411 popw %si # Restore 412 jmp *%bx # Invoke bootstrap 413 414 /* 415 * Display routines 416 */ 417putkey: 418#ifndef SIO 419 movb $'F',%al # Display 420 callw putchr # 'F' 421#endif 422 movb $'1',%al # Prepare 423 addb %dl,%al # digit 424 jmp putstr.1 # Display the rest 425 426 /* 427 * Display the option and note that it is a valid option. 428 * That last point is a bit tricky.. 429 */ 430putx: btsw %dx,_MNUOPT(%bp) # Enable menu option 431 movw $item,%si # Display 432 callw putkey # key 433 movw %di,%si # Display the rest 434 435puts: callw putstr # Display string 436 437putn: movw $crlf,%si # To next line 438 439putstr: lodsb # Get byte 440 testb $0x80,%al # End of string? 441 jnz putstr.2 # Yes 442putstr.1: callw putchr # Display char 443 jmp putstr # Continue 444putstr.2: andb $~0x80,%al # Clear MSB 445 446#ifndef SIO 447putchr: 448 pusha # Save 449 movw $0x7,%bx # Page:attribute 450 movb $0xe,%ah # BIOS: Display 451 int $0x10 # character 452 popa # Restore 453 retw # To caller 454#else /* SIO */ 455putchr: 456 movb $0x01,%ah # BIOS: Send 457bioscom: 458 pusha # Save drive number 459 xorw %dx,%dx # Use COM1 460 int $0x14 # Character 461 popa # Restore drive number 462 retw # To caller 463#endif 464 465 466 /* 467 * One-sector disk I/O routine 468 * 469 * Setup for both the packet and non-packet interfaces 470 * then select one or the other. 471 * 472 * Don't trust the BIOS to keep registers intact across 473 * the call, use pusha/popa. 474 */ 475intx13: movb 0x1(%si),%dh # (nonpkt) head 476 movw 0x2(%si),%cx # (nonpkt) cylinder:sector 477 movb $0x1,%al # (nonpkt) Sector count 478 pusha # save: do not trust the bios 479 pushl $0x0 # (pkt) LBA address 480 pushl 0x8(%si) # (pkt) 481 pushw %es # (pkt) xfer buffer address 482 pushw %bx # (pkt) 483 pushw $1 # (pkt) Block count 484 pushw $16 # (pkt) Packet size 485 testb $0x80,_FLAGS(%bp) # Use packet interface? 486 jz intx13.1 487 movw %sp,%si # Yes, set packet pointer 488 decw %ax # Verify off 489 orb $0x40,%ah # Set pkt mode in command 490intx13.1: int $0x13 # BIOS: Disk I/O 491 # WARNING: RETAIN CARRY AFTER BIOS CALL 492 movw %sp,%si 493 lea 16(%si),%sp # cleanup the stack 494 popa # Restore registers 495 retw 496 497 /* 498 * Menu strings 499 */ 500 501item: .ascii " "; .byte ' '|0x80 502prompt: .ascii "\nDefault:"; .byte ' '|0x80 503crlf: .ascii "\r"; .byte '\n'|0x80 504 505 /* 506 * Partition type tables 507 */ 508 509tables: 510 /* 511 * These entries identify invalid or NON BOOT types and 512 * partitions. 513 */ 514 .byte 0x0, 0x5, 0xf 515 516 /* 517 * These values indicate bootable types we know the names of. 518 */ 519 .byte 0x1, 0x6, 0x7, 0xc, 0xe, 0x6c, 0x83, 0x9f 520 .byte 0xa5, 0xa6, 0xa9 521 522 /* 523 * These are offsets that match the known names above and 524 * point to the strings that will be printed. 525 */ 526 .byte os_misc-. # Unknown 527 .byte os_dos-. # DOS 528 .byte os_dos-. # DOS 529 .byte os_dos-. # Windows 530 .byte os_dos-. # Windows 531 .byte os_dos-. # Windows 532 .byte os_dfbsd-. # DragonFly (new) 533 .byte os_linux-. # Linux 534 .byte os_bsd-. # BSD/OS 535 .byte os_dfbsd-. # DragonFly (old) / FreeBSD 536 .byte os_bsd-. # OpenBSD 537 .byte os_bsd-. # NetBSD 538 539 /* 540 * And here are the strings themselves. 0x80 or'd into a 541 * byte indicates the end of the string. (not so great for 542 * Russians but...) 543 */ 544os_misc: .ascii "?"; .byte '?'|0x80 545os_dos: .ascii "DO"; .byte 'S'|0x80 546os_linux: .ascii "Linu"; .byte 'x'|0x80 547os_dfbsd: .ascii "DF/F" 548os_bsd: .ascii "BS"; .byte 'D'|0x80 549 550 .org _DATA_OFF,0x90 551 552 .word B0MAGIC # Magic number 553 554 /* 555 * These values are sometimes changed before writing back 556 * to the drive. Be especially careful that nxtdrv: must 557 * come after drive:, as it is part of the same string. 558 */ 559drive: .ascii "Drive " 560nxtdrv: .byte 0x0 # Next drive number 561opt: .byte 0x0 # Option 562setdrv: .byte 0x80 # Drive to force 563flags: .byte FLAGS # Flags 564ticks: .word TICKS # Delay 565 566 /* 567 * here is the 64 byte partition table that fdisk would 568 * fiddle with. 569 */ 570partbl: .fill 0x40,0x1,0x0 # Partition table 571 .word MAGIC # Magic number 572