boot0.S revision 185579
1128723Sru/* 2185562Sluigi * Copyright (c) 2008 Luigi Rizzo (mostly documentation) 3128723Sru * Copyright (c) 2002 Bruce M. Simpson 4128723Sru * Copyright (c) 1998 Robert Nordier 5128723Sru * All rights reserved. 6128723Sru * 7128723Sru * Redistribution and use in source and binary forms are freely 8128723Sru * permitted provided that the above copyright notice and this 9128723Sru * paragraph and the following disclaimer are duplicated in all 10128723Sru * such forms. 11128723Sru * 12128723Sru * This software is provided "AS IS" and without any express or 13128723Sru * implied warranties, including, without limitation, the implied 14128723Sru * warranties of merchantability and fitness for a particular 15128723Sru * purpose. 16128723Sru * 17128723Sru * $FreeBSD: head/sys/boot/i386/boot0/boot0.S 185579 2008-12-03 14:53:59Z luigi $ 18128723Sru */ 19128722Sru 20185562Sluigi/* build options: */ 21185562Sluigi#ifdef SIO /* use serial console on COM1. */ 22138048Sjhb#endif 23128722Sru 24185562Sluigi#ifdef PXE /* enable PXE/INT18 booting with F6 */ 25185562Sluigi#endif 26185562Sluigi 27185562Sluigi#ifdef CHECK_DRIVE /* make sure we boot from a HD. */ 28185562Sluigi#endif 29185562Sluigi 30185562Sluigi#ifdef ONLY_F_KEYS /* Only F1..F6, no digits on console */ 31185562Sluigi#endif 32185562Sluigi 33185579Sluigi#ifdef VOLUME_SERIAL /* support Volume serial number */ 34185579Sluigi#define B0_BASE 0x1ae /* move the internal data area */ 35185579Sluigi#define SAVE_MEMORY 36185579Sluigi#else 37185579Sluigi#define B0_BASE 0x1b2 38185579Sluigi#endif 39185579Sluigi 40185562Sluigi#ifdef TEST /* enable some test code */ 41185579Sluigi#define SAVE_MEMORY 42185579Sluigi#define SAVE_MORE_MEMORY 43185562Sluigi#endif 44185562Sluigi 45185562Sluigi/* 46185562Sluigi * Note - this code uses many tricks to save space and fit in one sector. 47185562Sluigi * This includes using side effects of certain instructions, reusing 48185562Sluigi * register values from previous operations, etc. 49185562Sluigi * Be extremely careful when changing the code, even for simple things. 50185562Sluigi */ 51185562Sluigi 52185562Sluigi/* 53185562Sluigi * BOOT BLOCK STRUCTURE 54185562Sluigi * 55185562Sluigi * This code implements a Master Boot Record (MBR) for an Intel/PC disk. 56185562Sluigi * It is 512 bytes long and it is normally loaded by the BIOS (or another 57185562Sluigi * bootloader) at 0:0x7c00. This code depends on %cs:%ip being 0:0x7c00 58185562Sluigi * 59185562Sluigi * The initial chunk of instructions is used as a signature by external 60185562Sluigi * tools (e.g. boot0cfg) which can manipulate the block itself. 61185562Sluigi * 62185562Sluigi * The area at offset 0x1b2 contains a magic string ('Drive '), also 63185562Sluigi * used as a signature to detect the block, and some variables that can 64185562Sluigi * be updated by boot0cfg (and optionally written back to the disk). 65185562Sluigi * These variables control the operation of the bootloader itself, 66185562Sluigi * e.g. which partitions to enable, the timeout, the use of LBA 67185562Sluigi * (called 'packet') or CHS mode, whether to force a drive number, 68185562Sluigi * and whether to write back the user's selection back to disk. 69185562Sluigi * 70185562Sluigi * As in every Master Boot Record, the partition table is at 0x1be, 71185562Sluigi * made of four 16-byte entries each containing: 72185562Sluigi * 73185562Sluigi * OFF SIZE DESCRIPTION 74185562Sluigi * 0 1 status (0x80: bootable, 0: non bootable) 75185562Sluigi * 1 3 start sector CHS 76185562Sluigi * 8:head, 6:sector, 2:cyl bit 9..8, 8:cyl bit 7..0 77185562Sluigi * 4 1 partition type 78185562Sluigi * 5 3 end sector CHS 79185562Sluigi * 8 4 LBA of first sector 80185562Sluigi * 12 4 partition size in sectors 81185562Sluigi * 82185562Sluigi * and followed by the two bytes 0x55, 0xAA (MBR signature). 83185562Sluigi */ 84185562Sluigi 85185562Sluigi 86185562Sluigi/* 87185562Sluigi * BOOT BLOCK OPERATION 88185562Sluigi * 89185562Sluigi * On entry, the registers contain the following values: 90185562Sluigi * 91185562Sluigi * %cs:%ip 0:0x7c00 92185562Sluigi * %dl drive number (0x80, 0x81, ... ) 93185562Sluigi * %si pointer to the partition table from which we were loaded. 94185562Sluigi * Some boot code (e.g. syslinux) use this info to relocate 95185562Sluigi * themselves, so we want to pass a valid one to the next stage. 96185562Sluigi * NOTE: the use of %is is not a standard. 97185562Sluigi * 98185562Sluigi * This boot block first relocates itself at a different address (0:0x600), 99185562Sluigi * to free the space at 0:0x7c00 for the next stage boot block. 100185562Sluigi * 101185562Sluigi * It then initializes some memory at 0:0x800 and above (pointed by %bp) 102185562Sluigi * to store the original drive number (%dl) passed to us, and to construct a 103185562Sluigi * fake partition entry. The latter is used by the disk I/O routine and, 104185562Sluigi * in some cases, passed in %si to the next stage boot code. 105185562Sluigi * 106185562Sluigi * The variables at 0x1b2 are accessed as negative offsets from %bp. 107185562Sluigi * 108185562Sluigi * After the relocation, the code scans the partition table printing 109185562Sluigi * out enabled partition or disks, and waits for user input. 110185562Sluigi * 111185562Sluigi * When a partition is selected, or a timeout expires, the currently 112185562Sluigi * selected partition is used to load the next stage boot code, 113185562Sluigi * %dl and %si are set appropriately as when we were called, and 114185562Sluigi * control is transferred to the newly loaded code at 0:0x7c00. 115185562Sluigi */ 116185562Sluigi 117185562Sluigi/* 118185562Sluigi * CONSTANTS 119185562Sluigi * 120185562Sluigi * NHRDRV is the address in segment 0 where the BIOS writes the 121185562Sluigi * total number of hard disks in the system. 122185562Sluigi * LOAD is the original load address and cannot be changed. 123185562Sluigi * ORIGIN is the relocation address. If you change it, you also need 124185562Sluigi * to change the value passed to the linker in the Makefile 125185562Sluigi * PRT_OFF is the location of the partition table (from the MBR standard). 126185562Sluigi * B0_OFF is the location of the data area, known to boot0cfg so 127185579Sluigi * it cannot be changed. Computed as a negative offset from 0x200 128185562Sluigi * MAGIC is the signature of a boot block. 129185562Sluigi */ 130185562Sluigi 131129239Sru .set NHRDRV,0x475 # Number of hard drives 132129239Sru .set ORIGIN,0x600 # Execution address 133129239Sru .set LOAD,0x7c00 # Load address 134128722Sru 135129239Sru .set PRT_OFF,0x1be # Partition table 136185579Sluigi .set B0_OFF,(B0_BASE-0x200) # Offset of boot0 data 137128722Sru 138129239Sru .set MAGIC,0xaa55 # Magic: bootable 139128722Sru 140129239Sru .set KEY_ENTER,0x1c # Enter key scan code 141129239Sru .set KEY_F1,0x3b # F1 key scan code 142129239Sru .set KEY_1,0x02 # #1 key scan code 143128722Sru 144185562Sluigi .set ASCII_BEL,'#' # ASCII code for <BEL> 145129239Sru .set ASCII_CR,0x0D # ASCII code for <CR> 146128722Sru 147128723Sru/* 148185562Sluigi * Offsets of variables in the block at B0_OFF, and in the volatile 149185562Sluigi * data area, computed as displacement from %bp. 150185562Sluigi * We need to define them as constant as the assembler cannot 151185562Sluigi * compute them in its single pass. 152128723Sru */ 153185579Sluigi .set _NXTDRV, B0_OFF+6 # Next drive 154185579Sluigi .set _OPT, B0_OFF+7 # Default option 155185579Sluigi .set _SETDRV, B0_OFF+8 # Drive to force 156185579Sluigi .set _FLAGS, B0_OFF+9 # Flags 157185562Sluigi .set SETDRV, 0x20 # the 'setdrv' flag 158185562Sluigi .set NOUPDATE, 0x40 # the 'noupdate' flag 159185562Sluigi .set USEPACKET, 0x80 # the 'packet' flag 160185579Sluigi 161185579Sluigi /* ticks is at a fixed position */ 162185579Sluigi .set _TICKS, (PRT_OFF - 0x200 - 2) # Timeout ticks 163185562Sluigi .set _MNUOPT, 0x10 # Saved menu entries 164128722Sru 165185562Sluigi .set TLEN, (desc_ofs - bootable_ids) # size of bootable ids 166129239Sru .globl start # Entry point 167129239Sru .code16 # This runs in real mode 168128722Sru 169128723Sru/* 170185562Sluigi * MAIN ENTRY POINT 171128723Sru * Initialise segments and registers to known values. 172128723Sru * segments start at 0. 173128723Sru * The stack is immediately below the address we were loaded to. 174185562Sluigi * NOTE: the initial section of the code (up to movw $LOAD,%sp) 175185562Sluigi * is used by boot0cfg, together with the 'Drive ' string and 176185562Sluigi * the 0x55, 0xaa at the end, as an identifier for version 1.0 177185562Sluigi * of the boot code. Do not change it. 178185562Sluigi * In version 1.0 the parameter table (_NEXTDRV etc) is at 0x1b9 179128723Sru */ 180129239Srustart: cld # String ops inc 181129239Sru xorw %ax,%ax # Zero 182129239Sru movw %ax,%es # Address 183129239Sru movw %ax,%ds # data 184129239Sru movw %ax,%ss # Set up 185129239Sru movw $LOAD,%sp # stack 186128722Sru 187185562Sluigi /* 188185562Sluigi * Copy this code to the address it was linked for, 0x600 by default. 189185562Sluigi */ 190129239Sru movw %sp,%si # Source 191129239Sru movw $start,%di # Destination 192129239Sru movw $0x100,%cx # Word count 193129239Sru rep # Relocate 194129239Sru movsw # code 195185562Sluigi /* 196185562Sluigi * After the code, (i.e. at %di+0, 0x800) create a partition entry, 197185562Sluigi * initialized to LBA 0 / CHS 0:0:1. 198185562Sluigi * Set %bp to point to the partition and also, with negative offsets, 199185562Sluigi * to the variables embedded in the bootblock (nextdrv and so on). 200185562Sluigi */ 201129239Sru movw %di,%bp # Address variables 202129239Sru movb $0x8,%cl # Words to clear 203129239Sru rep # Zero 204129239Sru stosw # them 205185562Sluigi incb -0xe(%di) # Set the S field to 1 206128722Sru 207185562Sluigi jmp main-LOAD+ORIGIN # Jump to relocated code 208185562Sluigi 209128722Srumain: 210138048Sjhb#if defined(SIO) && COMSPEED != 0 211185562Sluigi /* 212185562Sluigi * Init the serial port. bioscom preserves the driver number in DX. 213185562Sluigi */ 214167914Sthomas movw $COMSPEED,%ax # defined by Makefile 215130632Sphk callw bioscom 216138048Sjhb#endif 217185562Sluigi 218185562Sluigi /* 219185562Sluigi * If the 'setdrv' flag is set in the boot sector, use the drive 220185562Sluigi * number from the boot sector at 'setdrv_num'. 221185562Sluigi * Optionally, do the same if the BIOS gives us an invalid number 222185562Sluigi * (note though that the override prevents booting from a floppy 223185562Sluigi * or a ZIP/flash drive in floppy emulation). 224185562Sluigi * The test costs 4 bytes of code so it is disabled by default. 225185562Sluigi */ 226185562Sluigi testb $SETDRV,_FLAGS(%bp) # Set drive number? 227185562Sluigi#ifndef CHECK_DRIVE /* disable drive checks */ 228185562Sluigi jz save_curdrive # no, use the default 229185562Sluigi#else 230185562Sluigi jnz disable_update # Yes 231129239Sru testb %dl,%dl # Drive number valid? 232185562Sluigi js save_curdrive # Possibly (0x80 set) 233185562Sluigi#endif 234185562Sluigi /* 235185562Sluigi * Disable updates if the drive number is forced. 236185562Sluigi */ 237185562Sluigidisable_update: orb $NOUPDATE,_FLAGS(%bp) # Disable updates 238185562Sluigi movb _SETDRV(%bp),%dl # Use stored drive number 239185562Sluigi 240185562Sluigi /* 241185562Sluigi * Whatever drive we decided to use, store it at (%bp). The byte 242185562Sluigi * is normally used for the state of the partition (0x80 or 0x00), 243185562Sluigi * but we abuse it as it is very convenient to access at offset 0. 244185562Sluigi * The value is read back after 'check_selection' 245185562Sluigi */ 246185562Sluigisave_curdrive: movb %dl, (%bp) # Save drive number 247185562Sluigi pushw %dx # Also in the stack 248185562Sluigi#ifdef TEST /* test code, print internal bios drive */ 249185562Sluigi rolb $1, %dl 250185562Sluigi movw $drive, %si 251185562Sluigi call putkey 252185562Sluigi#endif 253185562Sluigi callw putn # Print a newline 254185562Sluigi /* 255185562Sluigi * Start out with a pointer to the 4th byte of the first table entry 256185562Sluigi * so that after 4 iterations it's beyond the end of the sector 257185562Sluigi * and beyond a 256 byte boundary. We use the latter trick to check for 258185562Sluigi * end of the loop without using an extra register (see start.5). 259185562Sluigi */ 260129239Sru movw $(partbl+0x4),%bx # Partition table (+4) 261129239Sru xorw %dx,%dx # Item number 262185562Sluigi 263185562Sluigi /* 264185562Sluigi * Loop around on the partition table, printing values until we 265185562Sluigi * pass a 256 byte boundary. 266185562Sluigi */ 267185562Sluigiread_entry: movb %ch,-0x4(%bx) # Zero active flag (ch == 0) 268129239Sru btw %dx,_FLAGS(%bp) # Entry enabled? 269185562Sluigi jnc next_entry # No 270129239Sru movb (%bx),%al # Load type 271185579Sluigi test %al, %al # skip empty partition 272185579Sluigi jz next_entry 273185562Sluigi /* 274185579Sluigi * Scan the table of bootable ids, which starts at %di and has 275185562Sluigi * length TLEN. On a match, %di points to the element following the 276185562Sluigi * match; the corresponding offset to the description is $(TLEN-1) 277185562Sluigi * bytes ahead. If we don't find a match, we hit the 'unknown' entry. 278185562Sluigi */ 279185579Sluigi movw $bootable_ids,%di # Lookup tables 280185562Sluigi movb $(TLEN),%cl # Number of entries 281139948Speadar repne # Locate 282139948Speadar scasb # type 283185562Sluigi /* 284185562Sluigi * Get the matching element in the next array. 285185562Sluigi * The byte at $(TLEN-1)(%di) contains the offset of the description 286185562Sluigi * string from %di, so we add the number and print the string. 287185562Sluigi */ 288185562Sluigi addw $(TLEN-1), %di # Adjust 289139948Speadar movb (%di),%cl # Partition 290129239Sru addw %cx,%di # description 291129239Sru callw putx # Display it 292185562Sluigi 293185562Sluiginext_entry: incw %dx # Next item 294129239Sru addb $0x10,%bl # Next entry 295185562Sluigi jnc read_entry # Till done 296185562Sluigi /* 297185562Sluigi * We are past a 256 byte boundary: the partition table is finished. 298185562Sluigi * Add one to the drive number and check it is valid. 299185562Sluigi * Note that if we started from a floppy, %dl was 0 so we still 300185562Sluigi * get an entry for the next drive, which is the first Hard Disk. 301185562Sluigi */ 302129239Sru popw %ax # Drive number 303129239Sru subb $0x80-0x1,%al # Does next 304129239Sru cmpb NHRDRV,%al # drive exist? (from BIOS?) 305185562Sluigi jb print_drive # Yes 306185562Sluigi /* 307185562Sluigi * If this is the only drive, don't display it as an option. 308185562Sluigi */ 309129239Sru decw %ax # Already drive 0? 310185562Sluigi jz print_prompt # Yes 311185562Sluigi /* 312185562Sluigi * If it was illegal or we cycled through them, go back to drive 0. 313185562Sluigi */ 314129239Sru xorb %al,%al # Drive 0 315185562Sluigi /* 316185562Sluigi * Whatever drive we selected, make it an ascii digit and save it 317185562Sluigi * back to the "nxtdrv" location in case we want to save it to disk. 318185562Sluigi * This digit is also part of the printed drive string, so add 0x80 319185562Sluigi * to indicate end of string. 320185562Sluigi */ 321185562Sluigiprint_drive: addb $'0'|0x80,%al # Save next 322129239Sru movb %al,_NXTDRV(%bp) # drive number 323129239Sru movw $drive,%di # Display 324129239Sru callw putx # item 325185562Sluigi /* 326185562Sluigi * Menu is complete, display a prompt followed by current selection. 327185562Sluigi * 'decw %si' makes the register point to the space after 'Default: ' 328185562Sluigi * so we do not see an extra CRLF on the screen. 329185562Sluigi */ 330185562Sluigiprint_prompt: movw $prompt,%si # Display 331129239Sru callw putstr # prompt 332129239Sru movb _OPT(%bp),%dl # Display 333129239Sru decw %si # default 334129239Sru callw putkey # key 335185562Sluigi jmp start_input # Skip beep 336185562Sluigi 337130343Sphk/* 338185562Sluigi * Here we have the code waiting for user input or a timeout. 339130343Sphk */ 340185562Sluigibeep: movb $ASCII_BEL,%al # Input error, print or beep 341185562Sluigi callw putchr 342185562Sluigi 343185562Sluigistart_input: 344185562Sluigi /* 345185562Sluigi * Actual Start of input loop. Take note of time 346185562Sluigi */ 347185562Sluigi xorb %ah,%ah # BIOS: Get 348129239Sru int $0x1a # system time 349129239Sru movw %dx,%di # Ticks when 350130343Sphk addw _TICKS(%bp),%di # timeout 351185562Sluigiread_key: 352185562Sluigi /* 353185562Sluigi * Busy loop, looking for keystrokes but keeping one eye on the time. 354185562Sluigi */ 355128722Sru#ifndef SIO 356129239Sru movb $0x1,%ah # BIOS: Check 357129239Sru int $0x16 # for keypress 358128722Sru#else /* SIO */ 359129239Sru movb $0x03,%ah # BIOS: Read COM 360130343Sphk call bioscom 361129239Sru testb $0x01,%ah # Check line status 362185562Sluigi # (bit 1 indicates input) 363128722Sru#endif /* SIO */ 364185562Sluigi jnz got_key # Have input 365185562Sluigi xorb %ah,%ah # BIOS: int 0x1a, 00 366185562Sluigi int $0x1a # get system time 367129239Sru cmpw %di,%dx # Timeout? 368185562Sluigi jb read_key # No 369185562Sluigi 370185562Sluigi /* 371185562Sluigi * Timed out or default selection 372185562Sluigi */ 373185562Sluigiuse_default: movb _OPT(%bp),%al # Load default 374185562Sluigi jmp check_selection # Join common code 375185562Sluigi 376185562Sluigi /* 377185562Sluigi * Get the keystroke. 378185562Sluigi * ENTER or CR confirm the current selection (same as a timeout). 379185562Sluigi * Otherwise convert F1..F6 (or '1'..'6') to 0..5 and check if the 380185562Sluigi * selection is valid. 381185562Sluigi * The SIO code uses ascii chars, the console code uses scancodes. 382185562Sluigi */ 383185562Sluigigot_key: 384128722Sru#ifndef SIO 385185562Sluigi xorb %ah,%ah # BIOS: int 0x16, 00 386185562Sluigi int $0x16 # get keypress 387185562Sluigi movb %ah,%al # move scan code to %al 388185562Sluigi cmpb $KEY_ENTER,%al 389138048Sjhb#else 390129239Sru movb $0x02,%ah # BIOS: Receive 391130343Sphk call bioscom 392185562Sluigi cmpb $ASCII_CR,%al 393138048Sjhb#endif 394185562Sluigi je use_default # enter -> default 395185562Sluigi /* 396185562Sluigi * Check if the key is acceptable, and loop back if not. 397185562Sluigi * The console (non-SIO) code looks at scancodes and accepts 398185562Sluigi * both F1..F6 and 1..6 (the latter costs 6 bytes of code), 399185562Sluigi * relying on the fact that F1..F6 have higher scancodes than 1..6 400185562Sluigi * The SIO code only takes 1..6 401185562Sluigi */ 402185562Sluigi#ifdef SIO /* SIO mode, use ascii values */ 403185562Sluigi subb $'1',%al # Subtract '1' ascii code 404185562Sluigi#else /* console mode -- use scancodes */ 405185562Sluigi subb $KEY_F1,%al /* Subtract F1 scan code */ 406185562Sluigi#if !defined(ONLY_F_KEYS) 407185562Sluigi cmpb $0x5,%al # F1..F6 408185562Sluigi jna 3f # Yes 409129239Sru subb $(KEY_1 - KEY_F1),%al # Less #1 scan code 410185562Sluigi 3: 411185562Sluigi#endif /* ONLY_F_KEYS */ 412185562Sluigi#endif /* SIO */ 413185562Sluigi cmpb $0x5,%al # F1..F6 or 1..6 ? 414185562Sluigi#ifdef PXE /* enable PXE/INT18 using F6 */ 415185562Sluigi jne 1f; 416185562Sluigi int $0x18 # found F6, try INT18 417185562Sluigi 1: 418185562Sluigi#endif /* PXE */ 419185562Sluigi jae beep # Not in F1..F5, beep 420185562Sluigi 421185562Sluigicheck_selection: 422185562Sluigi /* 423185562Sluigi * We have a selection. If it's a bad selection go back to complain. 424185562Sluigi * The bits in MNUOPT were set when the options were printed. 425185562Sluigi * Anything not printed is not an option. 426185562Sluigi */ 427185562Sluigi cbtw # Extend (%ah=0 used later) 428185562Sluigi btw %ax,_MNUOPT(%bp) # Option enabled? 429185562Sluigi jnc beep # No 430185562Sluigi /* 431185562Sluigi * Save the info in the original tables 432185562Sluigi * for rewriting to the disk. 433185562Sluigi */ 434129239Sru movb %al,_OPT(%bp) # Save option 435185562Sluigi 436185562Sluigi /* 437185562Sluigi * Make %si and %bx point to the fake partition at LBA 0 (CHS 0:0:1). 438185562Sluigi * Because the correct address is already in %bp, just use it. 439185562Sluigi * Set %dl with the drive number saved in byte 0. 440185562Sluigi * If we have pressed F5 or 5, then this is a good, fake value 441185562Sluigi * to present to the next stage boot code. 442185562Sluigi */ 443185562Sluigi movw %bp,%si # Partition for write 444185562Sluigi movb (%si),%dl # Drive number, saved above 445129239Sru movw %si,%bx # Partition for read 446129239Sru cmpb $0x4,%al # F5/#5 pressed? 447185562Sluigi pushf # Save results for later 448185562Sluigi je 1f # Yes, F5 449185562Sluigi 450185562Sluigi /* 451185562Sluigi * F1..F4 was pressed, so make %bx point to the currently 452185562Sluigi * selected partition, and leave the drive number unchanged. 453185562Sluigi */ 454129239Sru shlb $0x4,%al # Point to 455129239Sru addw $partbl,%ax # selected 456129239Sru xchgw %bx,%ax # partition 457129239Sru movb $0x80,(%bx) # Flag active 458185562Sluigi /* 459185562Sluigi * If not asked to do a write-back (flags 0x40) don't do one. 460185562Sluigi * Around the call, save the partition pointer to %bx and 461185562Sluigi * restore to %si which is where the next stage expects it. 462185562Sluigi */ 463185562Sluigi 1: pushw %bx # Save 464185562Sluigi testb $NOUPDATE,_FLAGS(%bp) # No updates? 465185562Sluigi jnz 2f # skip update 466129239Sru movw $start,%bx # Data to write 467129239Sru movb $0x3,%ah # Write sector 468129239Sru callw intx13 # to disk 469185562Sluigi 2: popw %si # Restore 470185562Sluigi 471185562Sluigi /* 472185562Sluigi * If going to next drive, replace drive with selected one. 473185562Sluigi * Remember to un-ascii it. Hey 0x80 is already set, cool! 474185562Sluigi */ 475185562Sluigi popf # Restore %al test results 476185562Sluigi jne 3f # If not F5/#5 477129239Sru movb _NXTDRV(%bp),%dl # Next drive 478129239Sru subb $'0',%dl # number 479185562Sluigi /* 480185562Sluigi * Load selected bootsector to the LOAD location in RAM. If read 481185562Sluigi * fails or there is no 0x55aa marker, treat it as a bad selection. 482185562Sluigi */ 483185562Sluigi 3: movw $LOAD,%bx # Address for read 484129239Sru movb $0x2,%ah # Read sector 485129239Sru callw intx13 # from disk 486185562Sluigi jc beep # If error 487129239Sru cmpw $MAGIC,0x1fe(%bx) # Bootable? 488185562Sluigi jne beep # No 489185339Sluigi pushw %si # Save ptr to selected part. 490185346Sluigi callw putn # Leave some space 491185339Sluigi popw %si # Restore, next stage uses it 492129239Sru jmp *%bx # Invoke bootstrap 493128722Sru 494128723Sru/* 495128723Sru * Display routines 496185562Sluigi * putkey prints the option selected in %dl (F1..F5 or 1..5) followed by 497185562Sluigi * the string at %si 498185562Sluigi * putx: print the option in %dl followed by the string at %di 499185562Sluigi * also record the drive as valid. 500185562Sluigi * putn: print a crlf 501185562Sluigi * putstr: print the string at %si 502185562Sluigi * putchr: print the char in al 503128723Sru */ 504128722Sru 505128723Sru/* 506185562Sluigi * Display the option and record the drive as valid in the options. 507185562Sluigi * That last point is done using the btsw instruction which does 508185562Sluigi * a test and set. We don't care for the test part. 509128723Sru */ 510129239Sruputx: btsw %dx,_MNUOPT(%bp) # Enable menu option 511129239Sru movw $item,%si # Display 512129239Sru callw putkey # key 513129239Sru movw %di,%si # Display the rest 514185579Sluigi callw putstr # Display string 515128722Sru 516129239Sruputn: movw $crlf,%si # To next line 517185579Sluigi jmp putstr 518128722Sru 519185579Sluigiputkey: 520185579Sluigi#ifndef SIO 521185579Sluigi movb $'F',%al # Display 522185579Sluigi callw putchr # 'F' 523185579Sluigi#endif 524185579Sluigi movb $'1',%al # Prepare 525185579Sluigi addb %dl,%al # digit 526185579Sluigi 527185579Sluigiputstr.1: callw putchr # Display char 528129239Sruputstr: lodsb # Get byte 529129239Sru testb $0x80,%al # End of string? 530185579Sluigi jz putstr.1 # No 531185579Sluigi andb $~0x80,%al # Clear MSB then print last 532128722Sru 533185562Sluigiputchr: 534130343Sphk#ifndef SIO 535129239Sru pushw %bx # Save 536129239Sru movw $0x7,%bx # Page:attribute 537129239Sru movb $0xe,%ah # BIOS: Display 538129239Sru int $0x10 # character 539129239Sru popw %bx # Restore 540128722Sru#else /* SIO */ 541130343Sphk movb $0x01,%ah # BIOS: Send 542130343Sphkbioscom: 543129239Sru pushw %dx # Save 544129239Sru xorw %dx,%dx # Use COM1 545129239Sru int $0x14 # Character 546129239Sru popw %dx # Restore 547185562Sluigi#endif /* SIO */ 548130343Sphk retw # To caller 549128722Sru 550128723Sru/* One-sector disk I/O routine */ 551128722Sru 552185562Sluigi/* 553185562Sluigi * %dl: drive, %si partition entry, %es:%bx transfer buffer. 554185562Sluigi * Load the CHS values and possibly the LBA address from the block 555185562Sluigi * at %si, and use the appropriate method to load the sector. 556185562Sluigi * Don't use packet mode for a floppy. 557185562Sluigi */ 558185562Sluigiintx13: # Prepare CHS parameters 559185562Sluigi movb 0x1(%si),%dh # Load head 560129239Sru movw 0x2(%si),%cx # Load cylinder:sector 561129239Sru movb $0x1,%al # Sector count 562129239Sru pushw %si # Save 563129239Sru movw %sp,%di # Save 564185562Sluigi#ifndef CHECK_DRIVE /* floppy support */ 565185562Sluigi testb %dl, %dl # is this a floppy ? 566185562Sluigi jz 1f # Yes, use CHS mode 567185562Sluigi#endif 568185562Sluigi testb $USEPACKET,_FLAGS(%bp) # Use packet interface? 569185562Sluigi jz 1f # No 570129239Sru pushl $0x0 # Set the 571129239Sru pushl 0x8(%si) # LBA address 572129239Sru pushw %es # Set the transfer 573129239Sru pushw %bx # buffer address 574129239Sru push $0x1 # Block count 575129239Sru push $0x10 # Packet size 576129239Sru movw %sp,%si # Packet pointer 577129239Sru decw %ax # Verify off 578129239Sru orb $0x40,%ah # Use disk packet 579185562Sluigi 1: int $0x13 # BIOS: Disk I/O 580129239Sru movw %di,%sp # Restore 581129239Sru popw %si # Restore 582129239Sru retw # To caller 583128722Sru 584185562Sluigi/* 585185562Sluigi * Various menu strings. 'item' goes after 'prompt' to save space. 586185562Sluigi * Also use shorter versions to make room for the PXE/INT18 code. 587185562Sluigi */ 588185562Sluigi#ifdef PXE 589185562Sluigiprompt: .ascii "\nBoot:" 590185562Sluigiitem: .ascii " "; .byte ' '|0x80 591185562Sluigi#else 592185562Sluigiprompt: .ascii "\nDefault:" 593128722Sruitem: .ascii " "; .byte ' '|0x80 594185562Sluigi#endif 595128722Srucrlf: .ascii "\r"; .byte '\n'|0x80 596128722Sru 597128723Sru/* Partition type tables */ 598128722Sru 599185562Sluigibootable_ids: 600185562Sluigi /* 601185579Sluigi * These values indicate bootable types we know about. 602185579Sluigi * Corresponding descriptions are at desc_ofs: 603185579Sluigi * Entries don't need to be sorted. 604185562Sluigi */ 605185579Sluigi .byte 0x1, 0x6, 0x7, 0xb, 0xc 606185579Sluigi#ifndef SAVE_MEMORY 607185579Sluigi .byte 0xe 608185579Sluigi#endif 609185579Sluigi .byte 0x83, 0xa5, 0xa6, 0xa9, 0x4 610185579Sluigi#ifndef SAVE_MORE_MEMORY 611185579Sluigi .byte 0x5, 0xf 612185579Sluigi#endif 613185579Sluigi 614185562Sluigidesc_ofs: 615185562Sluigi /* 616185562Sluigi * Offsets that match the known types above, used to point to the 617185562Sluigi * actual partition name. The last entry must point to os_misc, 618185562Sluigi * which is used for non-matching names. 619185562Sluigi */ 620185579Sluigi .byte os_dos-. # 1, FAT12 DOS 621185579Sluigi .byte os_dos-. # 6, FAT16 <32M, DOS/WIN 622185579Sluigi .byte os_win-. # 7, FAT16 >=32M Windows 623185579Sluigi .byte os_win-. # 11, FAT32 624185579Sluigi .byte os_win-. # 12, FAT32-LBA 625185579Sluigi#ifndef SAVE_MEMORY 626185579Sluigi .byte os_win-. # 14, FAT16-LBA 627185579Sluigi#endif 628185562Sluigi .byte os_linux-. # 131, Linux 629185562Sluigi .byte os_freebsd-. # 165, FreeBSD 630185562Sluigi .byte os_bsd-. # 166, OpenBSD 631185562Sluigi .byte os_bsd-. # 169, NetBSD 632185579Sluigi .byte os_dos-. # 4, FAT16 < 32M 633185579Sluigi#ifndef SAVE_MORE_MEMORY 634185579Sluigi .byte os_ext-. # 5, DOS Ext 635185579Sluigi .byte os_ext-. # 15, DOS Ext-LBA 636185579Sluigi#endif 637185579Sluigi 638139948Speadar .byte os_misc-. # Unknown 639185562Sluigi 640185562Sluigi /* 641185562Sluigi * And here are the strings themselves. The last byte of 642185562Sluigi * the string has bit 7 set. 643185562Sluigi */ 644185562Sluigios_misc: .byte '?'|0x80 645185562Sluigios_dos: 646185579Sluigi#ifndef SAVE_MEMORY /* DOS string only if room */ 647185562Sluigi .ascii "DO"; .byte 'S'|0x80 648185562Sluigi#endif 649185562Sluigios_win: .ascii "WI"; .byte 'N'|0x80 650128722Sruos_linux: .ascii "Linu"; .byte 'x'|0x80 651128722Sruos_freebsd: .ascii "Free" 652128722Sruos_bsd: .ascii "BS"; .byte 'D'|0x80 653185579Sluigi#ifndef SAVE_MORE_MEMORY 654185579Sluigios_ext: .ascii "EX"; .byte 'T'|0x80 655185579Sluigi#endif 656128722Sru 657185579Sluigi .org (0x200 + B0_OFF),0x90 658128723Sru/* 659185562Sluigi * The boot0 version 1.0 parameter table. 660185562Sluigi * Do not move it nor change the "Drive " string, boot0cfg 661185562Sluigi * uses its offset and content to identify the boot sector. 662185562Sluigi * The other fields are sometimes changed before writing back to the drive 663128723Sru * Be especially careful that nxtdrv: must come after drive:, as it 664128723Sru * is part of the same string. 665128723Sru */ 666128722Srudrive: .ascii "Drive " 667129239Srunxtdrv: .byte 0x0 # Next drive number 668129239Sruopt: .byte 0x0 # Option 669185562Sluigisetdrv_num: .byte 0x80 # Drive to force 670129239Sruflags: .byte FLAGS # Flags 671185579Sluigi#ifdef VOLUME_SERIAL 672185579Sluigi .byte 0xa8,0xa8,0xa8,0xa8 # Volume Serial Number 673185579Sluigi#endif 674129239Sruticks: .word TICKS # Delay 675128722Sru 676185562Sluigi .org PRT_OFF 677128723Sru/* 678137298Skeramida * Here is the 64 byte partition table that fdisk would fiddle with. 679128723Sru */ 680129239Srupartbl: .fill 0x40,0x1,0x0 # Partition table 681129239Sru .word MAGIC # Magic number 682185562Sluigi .org 0x200 # again, safety check 683185562Sluigiendblock: 684