boot0.S revision 185562
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 185562 2008-12-02 14:57:48Z 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 33185562Sluigi#ifdef TEST /* enable some test code */ 34185562Sluigi#ifndef ONLY_F_KEYS 35185562Sluigi#define ONLY_F_KEYS /* make room for the test code */ 36185562Sluigi#endif 37185562Sluigi#endif 38185562Sluigi 39185562Sluigi/* 40185562Sluigi * Note - this code uses many tricks to save space and fit in one sector. 41185562Sluigi * This includes using side effects of certain instructions, reusing 42185562Sluigi * register values from previous operations, etc. 43185562Sluigi * Be extremely careful when changing the code, even for simple things. 44185562Sluigi */ 45185562Sluigi 46185562Sluigi/* 47185562Sluigi * BOOT BLOCK STRUCTURE 48185562Sluigi * 49185562Sluigi * This code implements a Master Boot Record (MBR) for an Intel/PC disk. 50185562Sluigi * It is 512 bytes long and it is normally loaded by the BIOS (or another 51185562Sluigi * bootloader) at 0:0x7c00. This code depends on %cs:%ip being 0:0x7c00 52185562Sluigi * 53185562Sluigi * The initial chunk of instructions is used as a signature by external 54185562Sluigi * tools (e.g. boot0cfg) which can manipulate the block itself. 55185562Sluigi * 56185562Sluigi * The area at offset 0x1b2 contains a magic string ('Drive '), also 57185562Sluigi * used as a signature to detect the block, and some variables that can 58185562Sluigi * be updated by boot0cfg (and optionally written back to the disk). 59185562Sluigi * These variables control the operation of the bootloader itself, 60185562Sluigi * e.g. which partitions to enable, the timeout, the use of LBA 61185562Sluigi * (called 'packet') or CHS mode, whether to force a drive number, 62185562Sluigi * and whether to write back the user's selection back to disk. 63185562Sluigi * 64185562Sluigi * As in every Master Boot Record, the partition table is at 0x1be, 65185562Sluigi * made of four 16-byte entries each containing: 66185562Sluigi * 67185562Sluigi * OFF SIZE DESCRIPTION 68185562Sluigi * 0 1 status (0x80: bootable, 0: non bootable) 69185562Sluigi * 1 3 start sector CHS 70185562Sluigi * 8:head, 6:sector, 2:cyl bit 9..8, 8:cyl bit 7..0 71185562Sluigi * 4 1 partition type 72185562Sluigi * 5 3 end sector CHS 73185562Sluigi * 8 4 LBA of first sector 74185562Sluigi * 12 4 partition size in sectors 75185562Sluigi * 76185562Sluigi * and followed by the two bytes 0x55, 0xAA (MBR signature). 77185562Sluigi */ 78185562Sluigi 79185562Sluigi 80185562Sluigi/* 81185562Sluigi * BOOT BLOCK OPERATION 82185562Sluigi * 83185562Sluigi * On entry, the registers contain the following values: 84185562Sluigi * 85185562Sluigi * %cs:%ip 0:0x7c00 86185562Sluigi * %dl drive number (0x80, 0x81, ... ) 87185562Sluigi * %si pointer to the partition table from which we were loaded. 88185562Sluigi * Some boot code (e.g. syslinux) use this info to relocate 89185562Sluigi * themselves, so we want to pass a valid one to the next stage. 90185562Sluigi * NOTE: the use of %is is not a standard. 91185562Sluigi * 92185562Sluigi * This boot block first relocates itself at a different address (0:0x600), 93185562Sluigi * to free the space at 0:0x7c00 for the next stage boot block. 94185562Sluigi * 95185562Sluigi * It then initializes some memory at 0:0x800 and above (pointed by %bp) 96185562Sluigi * to store the original drive number (%dl) passed to us, and to construct a 97185562Sluigi * fake partition entry. The latter is used by the disk I/O routine and, 98185562Sluigi * in some cases, passed in %si to the next stage boot code. 99185562Sluigi * 100185562Sluigi * The variables at 0x1b2 are accessed as negative offsets from %bp. 101185562Sluigi * 102185562Sluigi * After the relocation, the code scans the partition table printing 103185562Sluigi * out enabled partition or disks, and waits for user input. 104185562Sluigi * 105185562Sluigi * When a partition is selected, or a timeout expires, the currently 106185562Sluigi * selected partition is used to load the next stage boot code, 107185562Sluigi * %dl and %si are set appropriately as when we were called, and 108185562Sluigi * control is transferred to the newly loaded code at 0:0x7c00. 109185562Sluigi */ 110185562Sluigi 111185562Sluigi/* 112185562Sluigi * CONSTANTS 113185562Sluigi * 114185562Sluigi * NHRDRV is the address in segment 0 where the BIOS writes the 115185562Sluigi * total number of hard disks in the system. 116185562Sluigi * LOAD is the original load address and cannot be changed. 117185562Sluigi * ORIGIN is the relocation address. If you change it, you also need 118185562Sluigi * to change the value passed to the linker in the Makefile 119185562Sluigi * PRT_OFF is the location of the partition table (from the MBR standard). 120185562Sluigi * B0_OFF is the location of the data area, known to boot0cfg so 121185562Sluigi * it cannot be changed. 122185562Sluigi * MAGIC is the signature of a boot block. 123185562Sluigi */ 124185562Sluigi 125129239Sru .set NHRDRV,0x475 # Number of hard drives 126129239Sru .set ORIGIN,0x600 # Execution address 127129239Sru .set LOAD,0x7c00 # Load address 128128722Sru 129129239Sru .set PRT_OFF,0x1be # Partition table 130185562Sluigi .set B0_OFF,0x1b2 # Offset of boot0 data 131128722Sru 132129239Sru .set MAGIC,0xaa55 # Magic: bootable 133128722Sru 134129239Sru .set KEY_ENTER,0x1c # Enter key scan code 135129239Sru .set KEY_F1,0x3b # F1 key scan code 136129239Sru .set KEY_1,0x02 # #1 key scan code 137128722Sru 138185562Sluigi .set ASCII_BEL,'#' # ASCII code for <BEL> 139129239Sru .set ASCII_CR,0x0D # ASCII code for <CR> 140128722Sru 141128723Sru/* 142185562Sluigi * Offsets of variables in the block at B0_OFF, and in the volatile 143185562Sluigi * data area, computed as displacement from %bp. 144185562Sluigi * We need to define them as constant as the assembler cannot 145185562Sluigi * compute them in its single pass. 146128723Sru */ 147185562Sluigi .set _NXTDRV, -0x48 # Next drive 148185562Sluigi .set _OPT, -0x47 # Default option 149185562Sluigi .set _SETDRV, -0x46 # Drive to force 150185562Sluigi .set _FLAGS, -0x45 # Flags 151185562Sluigi .set SETDRV, 0x20 # the 'setdrv' flag 152185562Sluigi .set NOUPDATE, 0x40 # the 'noupdate' flag 153185562Sluigi .set USEPACKET, 0x80 # the 'packet' flag 154185562Sluigi .set _TICKS, -0x44 # Timeout ticks 155185562Sluigi .set _FAKE,0x0 # Fake partition table 156185562Sluigi .set _MNUOPT, 0x10 # Saved menu entries 157128722Sru 158185562Sluigi .set TLEN, (desc_ofs - bootable_ids) # size of bootable ids 159129239Sru .globl start # Entry point 160129239Sru .code16 # This runs in real mode 161128722Sru 162128723Sru/* 163185562Sluigi * MAIN ENTRY POINT 164128723Sru * Initialise segments and registers to known values. 165128723Sru * segments start at 0. 166128723Sru * The stack is immediately below the address we were loaded to. 167185562Sluigi * NOTE: the initial section of the code (up to movw $LOAD,%sp) 168185562Sluigi * is used by boot0cfg, together with the 'Drive ' string and 169185562Sluigi * the 0x55, 0xaa at the end, as an identifier for version 1.0 170185562Sluigi * of the boot code. Do not change it. 171185562Sluigi * In version 1.0 the parameter table (_NEXTDRV etc) is at 0x1b9 172128723Sru */ 173129239Srustart: cld # String ops inc 174129239Sru xorw %ax,%ax # Zero 175129239Sru movw %ax,%es # Address 176129239Sru movw %ax,%ds # data 177129239Sru movw %ax,%ss # Set up 178129239Sru movw $LOAD,%sp # stack 179128722Sru 180185562Sluigi /* 181185562Sluigi * Copy this code to the address it was linked for, 0x600 by default. 182185562Sluigi */ 183129239Sru movw %sp,%si # Source 184129239Sru movw $start,%di # Destination 185129239Sru movw $0x100,%cx # Word count 186129239Sru rep # Relocate 187129239Sru movsw # code 188185562Sluigi /* 189185562Sluigi * After the code, (i.e. at %di+0, 0x800) create a partition entry, 190185562Sluigi * initialized to LBA 0 / CHS 0:0:1. 191185562Sluigi * Set %bp to point to the partition and also, with negative offsets, 192185562Sluigi * to the variables embedded in the bootblock (nextdrv and so on). 193185562Sluigi */ 194129239Sru movw %di,%bp # Address variables 195129239Sru movb $0x8,%cl # Words to clear 196129239Sru rep # Zero 197129239Sru stosw # them 198185562Sluigi incb -0xe(%di) # Set the S field to 1 199128722Sru 200185562Sluigi jmp main-LOAD+ORIGIN # Jump to relocated code 201185562Sluigi 202128722Srumain: 203138048Sjhb#if defined(SIO) && COMSPEED != 0 204185562Sluigi /* 205185562Sluigi * Init the serial port. bioscom preserves the driver number in DX. 206185562Sluigi */ 207167914Sthomas movw $COMSPEED,%ax # defined by Makefile 208130632Sphk callw bioscom 209138048Sjhb#endif 210185562Sluigi 211185562Sluigi /* 212185562Sluigi * If the 'setdrv' flag is set in the boot sector, use the drive 213185562Sluigi * number from the boot sector at 'setdrv_num'. 214185562Sluigi * Optionally, do the same if the BIOS gives us an invalid number 215185562Sluigi * (note though that the override prevents booting from a floppy 216185562Sluigi * or a ZIP/flash drive in floppy emulation). 217185562Sluigi * The test costs 4 bytes of code so it is disabled by default. 218185562Sluigi */ 219185562Sluigi testb $SETDRV,_FLAGS(%bp) # Set drive number? 220185562Sluigi#ifndef CHECK_DRIVE /* disable drive checks */ 221185562Sluigi jz save_curdrive # no, use the default 222185562Sluigi#else 223185562Sluigi jnz disable_update # Yes 224129239Sru testb %dl,%dl # Drive number valid? 225185562Sluigi js save_curdrive # Possibly (0x80 set) 226185562Sluigi#endif 227185562Sluigi /* 228185562Sluigi * Disable updates if the drive number is forced. 229185562Sluigi */ 230185562Sluigidisable_update: orb $NOUPDATE,_FLAGS(%bp) # Disable updates 231185562Sluigi movb _SETDRV(%bp),%dl # Use stored drive number 232185562Sluigi 233185562Sluigi /* 234185562Sluigi * Whatever drive we decided to use, store it at (%bp). The byte 235185562Sluigi * is normally used for the state of the partition (0x80 or 0x00), 236185562Sluigi * but we abuse it as it is very convenient to access at offset 0. 237185562Sluigi * The value is read back after 'check_selection' 238185562Sluigi */ 239185562Sluigisave_curdrive: movb %dl, (%bp) # Save drive number 240185562Sluigi pushw %dx # Also in the stack 241185562Sluigi#ifdef TEST /* test code, print internal bios drive */ 242185562Sluigi rolb $1, %dl 243185562Sluigi movw $drive, %si 244185562Sluigi call putkey 245185562Sluigi#endif 246185562Sluigi callw putn # Print a newline 247185562Sluigi /* 248185562Sluigi * Start out with a pointer to the 4th byte of the first table entry 249185562Sluigi * so that after 4 iterations it's beyond the end of the sector 250185562Sluigi * and beyond a 256 byte boundary. We use the latter trick to check for 251185562Sluigi * end of the loop without using an extra register (see start.5). 252185562Sluigi */ 253129239Sru movw $(partbl+0x4),%bx # Partition table (+4) 254129239Sru xorw %dx,%dx # Item number 255185562Sluigi 256185562Sluigi /* 257185562Sluigi * Loop around on the partition table, printing values until we 258185562Sluigi * pass a 256 byte boundary. 259185562Sluigi */ 260185562Sluigiread_entry: movb %ch,-0x4(%bx) # Zero active flag (ch == 0) 261129239Sru btw %dx,_FLAGS(%bp) # Entry enabled? 262185562Sluigi jnc next_entry # No 263185562Sluigi /* 264185562Sluigi * Lookup type in the 'non_bootable_ids' table, skip matching entries. 265185562Sluigi * This is implemented is by setting %di to the start of the 266185562Sluigi * exclude table, and %cl to the length of the table itself. After the 267185562Sluigi * 'repne scasb' the zero flag is set if we found a match. 268185562Sluigi * If not, %di points to the beginning of the 'valid' types, 269185562Sluigi * which is what we need for the next check. 270185562Sluigi */ 271129239Sru movb (%bx),%al # Load type 272185562Sluigi movw $non_bootable_ids,%di # Lookup tables 273185562Sluigi movb $(bootable_ids-non_bootable_ids),%cl # length 274129239Sru repne # Exclude 275129239Sru scasb # partition? 276185562Sluigi je next_entry # Yes, ignore it 277185562Sluigi /* 278185562Sluigi * Now scan the table of bootable ids, which starts at %di and has 279185562Sluigi * length TLEN. On a match, %di points to the element following the 280185562Sluigi * match; the corresponding offset to the description is $(TLEN-1) 281185562Sluigi * bytes ahead. If we don't find a match, we hit the 'unknown' entry. 282185562Sluigi */ 283185562Sluigi movb $(TLEN),%cl # Number of entries 284139948Speadar repne # Locate 285139948Speadar scasb # type 286185562Sluigi /* 287185562Sluigi * Get the matching element in the next array. 288185562Sluigi * The byte at $(TLEN-1)(%di) contains the offset of the description 289185562Sluigi * string from %di, so we add the number and print the string. 290185562Sluigi */ 291185562Sluigi addw $(TLEN-1), %di # Adjust 292139948Speadar movb (%di),%cl # Partition 293129239Sru addw %cx,%di # description 294129239Sru callw putx # Display it 295185562Sluigi 296185562Sluiginext_entry: incw %dx # Next item 297129239Sru addb $0x10,%bl # Next entry 298185562Sluigi jnc read_entry # Till done 299185562Sluigi /* 300185562Sluigi * We are past a 256 byte boundary: the partition table is finished. 301185562Sluigi * Add one to the drive number and check it is valid. 302185562Sluigi * Note that if we started from a floppy, %dl was 0 so we still 303185562Sluigi * get an entry for the next drive, which is the first Hard Disk. 304185562Sluigi */ 305129239Sru popw %ax # Drive number 306129239Sru subb $0x80-0x1,%al # Does next 307129239Sru cmpb NHRDRV,%al # drive exist? (from BIOS?) 308185562Sluigi jb print_drive # Yes 309185562Sluigi /* 310185562Sluigi * If this is the only drive, don't display it as an option. 311185562Sluigi */ 312129239Sru decw %ax # Already drive 0? 313185562Sluigi jz print_prompt # Yes 314185562Sluigi /* 315185562Sluigi * If it was illegal or we cycled through them, go back to drive 0. 316185562Sluigi */ 317129239Sru xorb %al,%al # Drive 0 318185562Sluigi /* 319185562Sluigi * Whatever drive we selected, make it an ascii digit and save it 320185562Sluigi * back to the "nxtdrv" location in case we want to save it to disk. 321185562Sluigi * This digit is also part of the printed drive string, so add 0x80 322185562Sluigi * to indicate end of string. 323185562Sluigi */ 324185562Sluigiprint_drive: addb $'0'|0x80,%al # Save next 325129239Sru movb %al,_NXTDRV(%bp) # drive number 326129239Sru movw $drive,%di # Display 327129239Sru callw putx # item 328185562Sluigi /* 329185562Sluigi * Menu is complete, display a prompt followed by current selection. 330185562Sluigi * 'decw %si' makes the register point to the space after 'Default: ' 331185562Sluigi * so we do not see an extra CRLF on the screen. 332185562Sluigi */ 333185562Sluigiprint_prompt: movw $prompt,%si # Display 334129239Sru callw putstr # prompt 335129239Sru movb _OPT(%bp),%dl # Display 336129239Sru decw %si # default 337129239Sru callw putkey # key 338185562Sluigi jmp start_input # Skip beep 339185562Sluigi 340130343Sphk/* 341185562Sluigi * Here we have the code waiting for user input or a timeout. 342130343Sphk */ 343185562Sluigibeep: movb $ASCII_BEL,%al # Input error, print or beep 344185562Sluigi callw putchr 345185562Sluigi 346185562Sluigistart_input: 347185562Sluigi /* 348185562Sluigi * Actual Start of input loop. Take note of time 349185562Sluigi */ 350185562Sluigi xorb %ah,%ah # BIOS: Get 351129239Sru int $0x1a # system time 352129239Sru movw %dx,%di # Ticks when 353130343Sphk addw _TICKS(%bp),%di # timeout 354185562Sluigiread_key: 355185562Sluigi /* 356185562Sluigi * Busy loop, looking for keystrokes but keeping one eye on the time. 357185562Sluigi */ 358128722Sru#ifndef SIO 359129239Sru movb $0x1,%ah # BIOS: Check 360129239Sru int $0x16 # for keypress 361128722Sru#else /* SIO */ 362129239Sru movb $0x03,%ah # BIOS: Read COM 363130343Sphk call bioscom 364129239Sru testb $0x01,%ah # Check line status 365185562Sluigi # (bit 1 indicates input) 366128722Sru#endif /* SIO */ 367185562Sluigi jnz got_key # Have input 368185562Sluigi xorb %ah,%ah # BIOS: int 0x1a, 00 369185562Sluigi int $0x1a # get system time 370129239Sru cmpw %di,%dx # Timeout? 371185562Sluigi jb read_key # No 372185562Sluigi 373185562Sluigi /* 374185562Sluigi * Timed out or default selection 375185562Sluigi */ 376185562Sluigiuse_default: movb _OPT(%bp),%al # Load default 377185562Sluigi jmp check_selection # Join common code 378185562Sluigi 379185562Sluigi /* 380185562Sluigi * Get the keystroke. 381185562Sluigi * ENTER or CR confirm the current selection (same as a timeout). 382185562Sluigi * Otherwise convert F1..F6 (or '1'..'6') to 0..5 and check if the 383185562Sluigi * selection is valid. 384185562Sluigi * The SIO code uses ascii chars, the console code uses scancodes. 385185562Sluigi */ 386185562Sluigigot_key: 387128722Sru#ifndef SIO 388185562Sluigi xorb %ah,%ah # BIOS: int 0x16, 00 389185562Sluigi int $0x16 # get keypress 390185562Sluigi movb %ah,%al # move scan code to %al 391185562Sluigi cmpb $KEY_ENTER,%al 392138048Sjhb#else 393129239Sru movb $0x02,%ah # BIOS: Receive 394130343Sphk call bioscom 395185562Sluigi cmpb $ASCII_CR,%al 396138048Sjhb#endif 397185562Sluigi je use_default # enter -> default 398185562Sluigi /* 399185562Sluigi * Check if the key is acceptable, and loop back if not. 400185562Sluigi * The console (non-SIO) code looks at scancodes and accepts 401185562Sluigi * both F1..F6 and 1..6 (the latter costs 6 bytes of code), 402185562Sluigi * relying on the fact that F1..F6 have higher scancodes than 1..6 403185562Sluigi * The SIO code only takes 1..6 404185562Sluigi */ 405185562Sluigi#ifdef SIO /* SIO mode, use ascii values */ 406185562Sluigi subb $'1',%al # Subtract '1' ascii code 407185562Sluigi#else /* console mode -- use scancodes */ 408185562Sluigi subb $KEY_F1,%al /* Subtract F1 scan code */ 409185562Sluigi#if !defined(ONLY_F_KEYS) 410185562Sluigi cmpb $0x5,%al # F1..F6 411185562Sluigi jna 3f # Yes 412129239Sru subb $(KEY_1 - KEY_F1),%al # Less #1 scan code 413185562Sluigi 3: 414185562Sluigi#endif /* ONLY_F_KEYS */ 415185562Sluigi#endif /* SIO */ 416185562Sluigi cmpb $0x5,%al # F1..F6 or 1..6 ? 417185562Sluigi#ifdef PXE /* enable PXE/INT18 using F6 */ 418185562Sluigi jne 1f; 419185562Sluigi int $0x18 # found F6, try INT18 420185562Sluigi 1: 421185562Sluigi#endif /* PXE */ 422185562Sluigi jae beep # Not in F1..F5, beep 423185562Sluigi 424185562Sluigicheck_selection: 425185562Sluigi /* 426185562Sluigi * We have a selection. If it's a bad selection go back to complain. 427185562Sluigi * The bits in MNUOPT were set when the options were printed. 428185562Sluigi * Anything not printed is not an option. 429185562Sluigi */ 430185562Sluigi cbtw # Extend (%ah=0 used later) 431185562Sluigi btw %ax,_MNUOPT(%bp) # Option enabled? 432185562Sluigi jnc beep # No 433185562Sluigi /* 434185562Sluigi * Save the info in the original tables 435185562Sluigi * for rewriting to the disk. 436185562Sluigi */ 437129239Sru movb %al,_OPT(%bp) # Save option 438185562Sluigi 439185562Sluigi /* 440185562Sluigi * Make %si and %bx point to the fake partition at LBA 0 (CHS 0:0:1). 441185562Sluigi * Because the correct address is already in %bp, just use it. 442185562Sluigi * Set %dl with the drive number saved in byte 0. 443185562Sluigi * If we have pressed F5 or 5, then this is a good, fake value 444185562Sluigi * to present to the next stage boot code. 445185562Sluigi */ 446185562Sluigi movw %bp,%si # Partition for write 447185562Sluigi movb (%si),%dl # Drive number, saved above 448129239Sru movw %si,%bx # Partition for read 449129239Sru cmpb $0x4,%al # F5/#5 pressed? 450185562Sluigi pushf # Save results for later 451185562Sluigi je 1f # Yes, F5 452185562Sluigi 453185562Sluigi /* 454185562Sluigi * F1..F4 was pressed, so make %bx point to the currently 455185562Sluigi * selected partition, and leave the drive number unchanged. 456185562Sluigi */ 457129239Sru shlb $0x4,%al # Point to 458129239Sru addw $partbl,%ax # selected 459129239Sru xchgw %bx,%ax # partition 460129239Sru movb $0x80,(%bx) # Flag active 461185562Sluigi /* 462185562Sluigi * If not asked to do a write-back (flags 0x40) don't do one. 463185562Sluigi * Around the call, save the partition pointer to %bx and 464185562Sluigi * restore to %si which is where the next stage expects it. 465185562Sluigi */ 466185562Sluigi 1: pushw %bx # Save 467185562Sluigi testb $NOUPDATE,_FLAGS(%bp) # No updates? 468185562Sluigi jnz 2f # skip update 469129239Sru movw $start,%bx # Data to write 470129239Sru movb $0x3,%ah # Write sector 471129239Sru callw intx13 # to disk 472185562Sluigi 2: popw %si # Restore 473185562Sluigi 474185562Sluigi /* 475185562Sluigi * If going to next drive, replace drive with selected one. 476185562Sluigi * Remember to un-ascii it. Hey 0x80 is already set, cool! 477185562Sluigi */ 478185562Sluigi popf # Restore %al test results 479185562Sluigi jne 3f # If not F5/#5 480129239Sru movb _NXTDRV(%bp),%dl # Next drive 481129239Sru subb $'0',%dl # number 482185562Sluigi /* 483185562Sluigi * Load selected bootsector to the LOAD location in RAM. If read 484185562Sluigi * fails or there is no 0x55aa marker, treat it as a bad selection. 485185562Sluigi */ 486185562Sluigi 3: movw $LOAD,%bx # Address for read 487129239Sru movb $0x2,%ah # Read sector 488129239Sru callw intx13 # from disk 489185562Sluigi jc beep # If error 490129239Sru cmpw $MAGIC,0x1fe(%bx) # Bootable? 491185562Sluigi jne beep # No 492185339Sluigi pushw %si # Save ptr to selected part. 493185346Sluigi callw putn # Leave some space 494185339Sluigi popw %si # Restore, next stage uses it 495129239Sru jmp *%bx # Invoke bootstrap 496128722Sru 497128723Sru/* 498128723Sru * Display routines 499185562Sluigi * putkey prints the option selected in %dl (F1..F5 or 1..5) followed by 500185562Sluigi * the string at %si 501185562Sluigi * putx: print the option in %dl followed by the string at %di 502185562Sluigi * also record the drive as valid. 503185562Sluigi * puts: print the string at %si followed by a crlf 504185562Sluigi * putn: print a crlf 505185562Sluigi * putstr: print the string at %si 506185562Sluigi * putchr: print the char in al 507128723Sru */ 508128722Sruputkey: 509128722Sru#ifndef SIO 510129239Sru movb $'F',%al # Display 511129239Sru callw putchr # 'F' 512138048Sjhb#endif 513129239Sru movb $'1',%al # Prepare 514129239Sru addb %dl,%al # digit 515129239Sru jmp putstr.1 # Display the rest 516128722Sru 517128723Sru/* 518185562Sluigi * Display the option and record the drive as valid in the options. 519185562Sluigi * That last point is done using the btsw instruction which does 520185562Sluigi * a test and set. We don't care for the test part. 521128723Sru */ 522129239Sruputx: btsw %dx,_MNUOPT(%bp) # Enable menu option 523129239Sru movw $item,%si # Display 524129239Sru callw putkey # key 525129239Sru movw %di,%si # Display the rest 526128722Sru 527129239Sruputs: callw putstr # Display string 528128722Sru 529129239Sruputn: movw $crlf,%si # To next line 530128722Sru 531129239Sruputstr: lodsb # Get byte 532129239Sru testb $0x80,%al # End of string? 533129239Sru jnz putstr.2 # Yes 534129239Sruputstr.1: callw putchr # Display char 535129239Sru jmp putstr # Continue 536129239Sruputstr.2: andb $~0x80,%al # Clear MSB 537128722Sru 538185562Sluigiputchr: 539130343Sphk#ifndef SIO 540129239Sru pushw %bx # Save 541129239Sru movw $0x7,%bx # Page:attribute 542129239Sru movb $0xe,%ah # BIOS: Display 543129239Sru int $0x10 # character 544129239Sru popw %bx # Restore 545128722Sru#else /* SIO */ 546130343Sphk movb $0x01,%ah # BIOS: Send 547130343Sphkbioscom: 548129239Sru pushw %dx # Save 549129239Sru xorw %dx,%dx # Use COM1 550129239Sru int $0x14 # Character 551129239Sru popw %dx # Restore 552185562Sluigi#endif /* SIO */ 553130343Sphk retw # To caller 554128722Sru 555128723Sru/* One-sector disk I/O routine */ 556128722Sru 557185562Sluigi/* 558185562Sluigi * %dl: drive, %si partition entry, %es:%bx transfer buffer. 559185562Sluigi * Load the CHS values and possibly the LBA address from the block 560185562Sluigi * at %si, and use the appropriate method to load the sector. 561185562Sluigi * Don't use packet mode for a floppy. 562185562Sluigi */ 563185562Sluigiintx13: # Prepare CHS parameters 564185562Sluigi movb 0x1(%si),%dh # Load head 565129239Sru movw 0x2(%si),%cx # Load cylinder:sector 566129239Sru movb $0x1,%al # Sector count 567129239Sru pushw %si # Save 568129239Sru movw %sp,%di # Save 569185562Sluigi#ifndef CHECK_DRIVE /* floppy support */ 570185562Sluigi testb %dl, %dl # is this a floppy ? 571185562Sluigi jz 1f # Yes, use CHS mode 572185562Sluigi#endif 573185562Sluigi testb $USEPACKET,_FLAGS(%bp) # Use packet interface? 574185562Sluigi jz 1f # No 575129239Sru pushl $0x0 # Set the 576129239Sru pushl 0x8(%si) # LBA address 577129239Sru pushw %es # Set the transfer 578129239Sru pushw %bx # buffer address 579129239Sru push $0x1 # Block count 580129239Sru push $0x10 # Packet size 581129239Sru movw %sp,%si # Packet pointer 582129239Sru decw %ax # Verify off 583129239Sru orb $0x40,%ah # Use disk packet 584185562Sluigi 1: int $0x13 # BIOS: Disk I/O 585129239Sru movw %di,%sp # Restore 586129239Sru popw %si # Restore 587129239Sru retw # To caller 588128722Sru 589185562Sluigi/* 590185562Sluigi * Various menu strings. 'item' goes after 'prompt' to save space. 591185562Sluigi * Also use shorter versions to make room for the PXE/INT18 code. 592185562Sluigi */ 593185562Sluigi#ifdef PXE 594185562Sluigiprompt: .ascii "\nBoot:" 595185562Sluigiitem: .ascii " "; .byte ' '|0x80 596185562Sluigi#else 597185562Sluigiprompt: .ascii "\nDefault:" 598128722Sruitem: .ascii " "; .byte ' '|0x80 599185562Sluigi#endif 600128722Srucrlf: .ascii "\r"; .byte '\n'|0x80 601128722Sru 602128723Sru/* Partition type tables */ 603128722Sru 604185562Sluiginon_bootable_ids: 605185562Sluigi /* 606185562Sluigi * These entries identify invalid or NON BOOT types and partitions. 607185562Sluigi * 0: empty, 5: DOS3 ext. partition, 0xf: WIN95 ext partition 608185562Sluigi */ 609128722Sru .byte 0x0, 0x5, 0xf 610185562Sluigibootable_ids: 611185562Sluigi /* 612185562Sluigi * These values indicate bootable types we know the names of. 613185562Sluigi * 1: FAT12, 4: FAT16 <32M, 6: FAT16 > 32M, 7: NTFS 614185562Sluigi * 0xb: FAT32, 0xc: FAT32-LBA, 0xe: FAT16-LBA, 615185562Sluigi * 0x83: linux, 0xa5: FreeBSD, 0xa6: netbsd, 0xa9:openbsd 616185562Sluigi */ 617141540Sdes .byte 0x1, 0x6, 0x7, 0xb, 0xc, 0xe, 0x83 618185562Sluigi .byte 0xa5, 0xa6, 0xa9, 0x4 619185562Sluigidesc_ofs: 620185562Sluigi /* 621185562Sluigi * Offsets that match the known types above, used to point to the 622185562Sluigi * actual partition name. The last entry must point to os_misc, 623185562Sluigi * which is used for non-matching names. 624185562Sluigi */ 625185562Sluigi .byte os_dos-. # 1, DOS 626185562Sluigi .byte os_dos-. # 6, DOS/WIN 627185562Sluigi .byte os_win-. # 7, Windows 628185562Sluigi .byte os_win-. # 11, Windows 629185562Sluigi .byte os_win-. # 12, Windows 630185562Sluigi .byte os_win-. # 14, Windows 631185562Sluigi .byte os_linux-. # 131, Linux 632185562Sluigi .byte os_freebsd-. # 165, FreeBSD 633185562Sluigi .byte os_bsd-. # 166, OpenBSD 634185562Sluigi .byte os_bsd-. # 169, NetBSD 635185562Sluigi .byte os_dos-. # 4, DOS 636139948Speadar .byte os_misc-. # Unknown 637185562Sluigi 638185562Sluigi /* 639185562Sluigi * And here are the strings themselves. The last byte of 640185562Sluigi * the string has bit 7 set. 641185562Sluigi */ 642185562Sluigios_misc: .byte '?'|0x80 643185562Sluigios_dos: 644185562Sluigi#if !defined(TEST) /* DOS string only if room */ 645185562Sluigi .ascii "DO"; .byte 'S'|0x80 646185562Sluigi#endif 647185562Sluigios_win: .ascii "WI"; .byte 'N'|0x80 648128722Sruos_linux: .ascii "Linu"; .byte 'x'|0x80 649128722Sruos_freebsd: .ascii "Free" 650128722Sruos_bsd: .ascii "BS"; .byte 'D'|0x80 651128722Sru 652185562Sluigi .org B0_OFF,0x90 653128723Sru/* 654185562Sluigi * The boot0 version 1.0 parameter table. 655185562Sluigi * Do not move it nor change the "Drive " string, boot0cfg 656185562Sluigi * uses its offset and content to identify the boot sector. 657185562Sluigi * The other fields are sometimes changed before writing back to the drive 658128723Sru * Be especially careful that nxtdrv: must come after drive:, as it 659128723Sru * is part of the same string. 660128723Sru */ 661128722Srudrive: .ascii "Drive " 662129239Srunxtdrv: .byte 0x0 # Next drive number 663129239Sruopt: .byte 0x0 # Option 664185562Sluigisetdrv_num: .byte 0x80 # Drive to force 665129239Sruflags: .byte FLAGS # Flags 666129239Sruticks: .word TICKS # Delay 667128722Sru 668185562Sluigi .org PRT_OFF 669128723Sru/* 670137298Skeramida * Here is the 64 byte partition table that fdisk would fiddle with. 671128723Sru */ 672129239Srupartbl: .fill 0x40,0x1,0x0 # Partition table 673129239Sru .word MAGIC # Magic number 674185562Sluigi .org 0x200 # again, safety check 675185562Sluigiendblock: 676