diff options
Diffstat (limited to 'sys/boot')
| -rw-r--r-- | sys/boot/i386/boot0/Makefile | 28 | ||||
| -rw-r--r-- | sys/boot/i386/boot0/boot0.S | 696 |
2 files changed, 476 insertions, 248 deletions
diff --git a/sys/boot/i386/boot0/Makefile b/sys/boot/i386/boot0/Makefile index e02b102..4eb8435 100644 --- a/sys/boot/i386/boot0/Makefile +++ b/sys/boot/i386/boot0/Makefile @@ -6,11 +6,29 @@ BINMODE=${NOBINMODE} NO_MAN= SRCS= ${PROG}.S -# The default set of flags compiled into boot0. This enables update (writing -# the modified boot0 back to disk after running so that the selection made is -# saved), packet mode (detect and use the BIOS EDD extensions if we try to -# boot past the 1024 cylinder liimt), and booting from all valid slices. -BOOT_BOOT0_FLAGS?= 0x8f +# Additional options that you can specify with make OPTS="..." +# (these only apply to boot0.S) +# +# -DSIO do I/O using COM1: +# -DPXE fallback to INT18/PXE with F6 +# -DCHECK_DRIVE enable checking drive number +# -DONLY_F_KEYS accept only Fx keys in console +# -DTEST print drive number on entry +# +CFLAGS += ${OPTS} + +# Flags used in the boot0.S code: +# 0x0f all valid partitions enabled. +# 0x80 'packet', use BIOS EDD (LBA) extensions instead of CHS +# to read from disk. boot0.S does not check that the extensions +# are supported, but all modern BIOSes should have them. +# 0x40 'noupdate', disable writing boot0 back to disk so that +# the current selection is not preserved across reboots. +# 0x20 'setdrv', override the drive number supplied by the bios +# with the one in the boot sector. + +# Default boot flags: +BOOT_BOOT0_FLAGS?= 0xcf # The number of timer ticks to wait for a keypress before assuming the default # selection. Since there are 18.2 ticks per second, the default value of diff --git a/sys/boot/i386/boot0/boot0.S b/sys/boot/i386/boot0/boot0.S index 78c5345..33e950b 100644 --- a/sys/boot/i386/boot0/boot0.S +++ b/sys/boot/i386/boot0/boot0.S @@ -1,4 +1,5 @@ /* + * Copyright (c) 2008 Luigi Rizzo (mostly documentation) * Copyright (c) 2002 Bruce M. Simpson * Copyright (c) 1998 Robert Nordier * All rights reserved. @@ -16,50 +17,158 @@ * $FreeBSD$ */ -/* A 512-byte boot manager. */ -#ifdef SIO -/* ... using a serial console on COM1. */ +/* build options: */ +#ifdef SIO /* use serial console on COM1. */ #endif +#ifdef PXE /* enable PXE/INT18 booting with F6 */ +#endif + +#ifdef CHECK_DRIVE /* make sure we boot from a HD. */ +#endif + +#ifdef ONLY_F_KEYS /* Only F1..F6, no digits on console */ +#endif + +#ifdef TEST /* enable some test code */ +#ifndef ONLY_F_KEYS +#define ONLY_F_KEYS /* make room for the test code */ +#endif +#endif + +/* + * Note - this code uses many tricks to save space and fit in one sector. + * This includes using side effects of certain instructions, reusing + * register values from previous operations, etc. + * Be extremely careful when changing the code, even for simple things. + */ + +/* + * BOOT BLOCK STRUCTURE + * + * This code implements a Master Boot Record (MBR) for an Intel/PC disk. + * It is 512 bytes long and it is normally loaded by the BIOS (or another + * bootloader) at 0:0x7c00. This code depends on %cs:%ip being 0:0x7c00 + * + * The initial chunk of instructions is used as a signature by external + * tools (e.g. boot0cfg) which can manipulate the block itself. + * + * The area at offset 0x1b2 contains a magic string ('Drive '), also + * used as a signature to detect the block, and some variables that can + * be updated by boot0cfg (and optionally written back to the disk). + * These variables control the operation of the bootloader itself, + * e.g. which partitions to enable, the timeout, the use of LBA + * (called 'packet') or CHS mode, whether to force a drive number, + * and whether to write back the user's selection back to disk. + * + * As in every Master Boot Record, the partition table is at 0x1be, + * made of four 16-byte entries each containing: + * + * OFF SIZE DESCRIPTION + * 0 1 status (0x80: bootable, 0: non bootable) + * 1 3 start sector CHS + * 8:head, 6:sector, 2:cyl bit 9..8, 8:cyl bit 7..0 + * 4 1 partition type + * 5 3 end sector CHS + * 8 4 LBA of first sector + * 12 4 partition size in sectors + * + * and followed by the two bytes 0x55, 0xAA (MBR signature). + */ + + +/* + * BOOT BLOCK OPERATION + * + * On entry, the registers contain the following values: + * + * %cs:%ip 0:0x7c00 + * %dl drive number (0x80, 0x81, ... ) + * %si pointer to the partition table from which we were loaded. + * Some boot code (e.g. syslinux) use this info to relocate + * themselves, so we want to pass a valid one to the next stage. + * NOTE: the use of %is is not a standard. + * + * This boot block first relocates itself at a different address (0:0x600), + * to free the space at 0:0x7c00 for the next stage boot block. + * + * It then initializes some memory at 0:0x800 and above (pointed by %bp) + * to store the original drive number (%dl) passed to us, and to construct a + * fake partition entry. The latter is used by the disk I/O routine and, + * in some cases, passed in %si to the next stage boot code. + * + * The variables at 0x1b2 are accessed as negative offsets from %bp. + * + * After the relocation, the code scans the partition table printing + * out enabled partition or disks, and waits for user input. + * + * When a partition is selected, or a timeout expires, the currently + * selected partition is used to load the next stage boot code, + * %dl and %si are set appropriately as when we were called, and + * control is transferred to the newly loaded code at 0:0x7c00. + */ + +/* + * CONSTANTS + * + * NHRDRV is the address in segment 0 where the BIOS writes the + * total number of hard disks in the system. + * LOAD is the original load address and cannot be changed. + * ORIGIN is the relocation address. If you change it, you also need + * to change the value passed to the linker in the Makefile + * PRT_OFF is the location of the partition table (from the MBR standard). + * B0_OFF is the location of the data area, known to boot0cfg so + * it cannot be changed. + * MAGIC is the signature of a boot block. + */ + .set NHRDRV,0x475 # Number of hard drives .set ORIGIN,0x600 # Execution address - .set FAKE,0x800 # Partition entry .set LOAD,0x7c00 # Load address .set PRT_OFF,0x1be # Partition table - - .set TBL0SZ,0x3 # Table 0 size - .set TBL1SZ,0xa # Table 1 size + .set B0_OFF,0x1b2 # Offset of boot0 data .set MAGIC,0xaa55 # Magic: bootable - .set B0MAGIC,0xbb66 # Identification .set KEY_ENTER,0x1c # Enter key scan code .set KEY_F1,0x3b # F1 key scan code .set KEY_1,0x02 # #1 key scan code - .set ASCII_BEL,0x07 # ASCII code for <BEL> + .set ASCII_BEL,'#' # ASCII code for <BEL> .set ASCII_CR,0x0D # ASCII code for <CR> /* - * Addresses in the sector of embedded data values. - * Accessed with negative offsets from the end of the relocated sector (%ebp). - */ - .set _NXTDRV,-0x48 # Next drive - .set _OPT,-0x47 # Default option - .set _SETDRV,-0x46 # Drive to force - .set _FLAGS,-0x45 # Flags - .set _TICKS,-0x44 # Timeout ticks - .set _FAKE,0x0 # Fake partition entry - .set _MNUOPT,0xc # Menu options + * Offsets of variables in the block at B0_OFF, and in the volatile + * data area, computed as displacement from %bp. + * We need to define them as constant as the assembler cannot + * compute them in its single pass. + */ + .set _NXTDRV, -0x48 # Next drive + .set _OPT, -0x47 # Default option + .set _SETDRV, -0x46 # Drive to force + .set _FLAGS, -0x45 # Flags + .set SETDRV, 0x20 # the 'setdrv' flag + .set NOUPDATE, 0x40 # the 'noupdate' flag + .set USEPACKET, 0x80 # the 'packet' flag + .set _TICKS, -0x44 # Timeout ticks + .set _FAKE,0x0 # Fake partition table + .set _MNUOPT, 0x10 # Saved menu entries + .set TLEN, (desc_ofs - bootable_ids) # size of bootable ids .globl start # Entry point .code16 # This runs in real mode /* + * MAIN ENTRY POINT * Initialise segments and registers to known values. * segments start at 0. * The stack is immediately below the address we were loaded to. + * NOTE: the initial section of the code (up to movw $LOAD,%sp) + * is used by boot0cfg, together with the 'Drive ' string and + * the 0x55, 0xaa at the end, as an identifier for version 1.0 + * of the boot code. Do not change it. + * In version 1.0 the parameter table (_NEXTDRV etc) is at 0x1b9 */ start: cld # String ops inc xorw %ax,%ax # Zero @@ -68,257 +177,318 @@ start: cld # String ops inc movw %ax,%ss # Set up movw $LOAD,%sp # stack -/* - * Copy this code to the address it was linked for - */ + /* + * Copy this code to the address it was linked for, 0x600 by default. + */ movw %sp,%si # Source movw $start,%di # Destination movw $0x100,%cx # Word count rep # Relocate movsw # code -/* - * Set address for variable space beyond code, and clear it. - * Notice that this is also used to point to the values embedded in the block, - * by using negative offsets. - */ + /* + * After the code, (i.e. at %di+0, 0x800) create a partition entry, + * initialized to LBA 0 / CHS 0:0:1. + * Set %bp to point to the partition and also, with negative offsets, + * to the variables embedded in the bootblock (nextdrv and so on). + */ movw %di,%bp # Address variables movb $0x8,%cl # Words to clear rep # Zero stosw # them -/* - * Relocate to the new copy of the code. - */ - incb -0xe(%di) # Sector number - jmp main-LOAD+ORIGIN # To relocated code + incb -0xe(%di) # Set the S field to 1 + + jmp main-LOAD+ORIGIN # Jump to relocated code main: #if defined(SIO) && COMSPEED != 0 -/* - * Initialize the serial port. bioscom preserves the driver number in DX. - */ + /* + * Init the serial port. bioscom preserves the driver number in DX. + */ movw $COMSPEED,%ax # defined by Makefile callw bioscom #endif -/* - * Check what flags were loaded with us, specifically if a predefined drive - * number should be used. If what the bios gives us is bad, use the '0' in - * the block instead. - */ - testb $0x20,_FLAGS(%bp) # Set drive number? - jnz main.1 # Yes + + /* + * If the 'setdrv' flag is set in the boot sector, use the drive + * number from the boot sector at 'setdrv_num'. + * Optionally, do the same if the BIOS gives us an invalid number + * (note though that the override prevents booting from a floppy + * or a ZIP/flash drive in floppy emulation). + * The test costs 4 bytes of code so it is disabled by default. + */ + testb $SETDRV,_FLAGS(%bp) # Set drive number? +#ifndef CHECK_DRIVE /* disable drive checks */ + jz save_curdrive # no, use the default +#else + jnz disable_update # Yes testb %dl,%dl # Drive number valid? - js main.2 # Possibly (0x80 set) -/* - * Only update the boot-sector when there is a valid drive number or - * the drive number is set manually. - */ - orb $0x40,_FLAGS(%bp) # Disable updates -main.1: movb _SETDRV(%bp),%dl # Drive number to use -/* - * Whatever we decided to use, now store it into the fake - * partition entry that lives in the data space above us. - */ -main.2: movb %dl,_FAKE(%bp) # Save drive number - callw putn # To new line - pushw %dx # Save drive number -/* - * Start out with a pointer to the 4th byte of the first table entry - * so that after 4 iterations it's beyond the end of the sector - * and beyond a 256 byte boundary and has overflowed 8 bits (see next comment). - * Remember that the table starts 2 bytes earlier than you would expect - * as the bootable flag is after it in the block. - */ + js save_curdrive # Possibly (0x80 set) +#endif + /* + * Disable updates if the drive number is forced. + */ +disable_update: orb $NOUPDATE,_FLAGS(%bp) # Disable updates + movb _SETDRV(%bp),%dl # Use stored drive number + + /* + * Whatever drive we decided to use, store it at (%bp). The byte + * is normally used for the state of the partition (0x80 or 0x00), + * but we abuse it as it is very convenient to access at offset 0. + * The value is read back after 'check_selection' + */ +save_curdrive: movb %dl, (%bp) # Save drive number + pushw %dx # Also in the stack +#ifdef TEST /* test code, print internal bios drive */ + rolb $1, %dl + movw $drive, %si + call putkey +#endif + callw putn # Print a newline + /* + * Start out with a pointer to the 4th byte of the first table entry + * so that after 4 iterations it's beyond the end of the sector + * and beyond a 256 byte boundary. We use the latter trick to check for + * end of the loop without using an extra register (see start.5). + */ movw $(partbl+0x4),%bx # Partition table (+4) xorw %dx,%dx # Item number -/* - * Loop around on the partition table, printing values until we - * pass a 256 byte boundary. The end of loop test is at main.5. - */ -main.3: movb %ch,-0x4(%bx) # Zero active flag (ch == 0) + + /* + * Loop around on the partition table, printing values until we + * pass a 256 byte boundary. + */ +read_entry: movb %ch,-0x4(%bx) # Zero active flag (ch == 0) btw %dx,_FLAGS(%bp) # Entry enabled? - jnc main.5 # No -/* - * If any of the entries in the table are the same as the 'type' in the slice - * table entry, then this is an empty or non bootable partition. Skip it. - */ + jnc next_entry # No + /* + * Lookup type in the 'non_bootable_ids' table, skip matching entries. + * This is implemented is by setting %di to the start of the + * exclude table, and %cl to the length of the table itself. After the + * 'repne scasb' the zero flag is set if we found a match. + * If not, %di points to the beginning of the 'valid' types, + * which is what we need for the next check. + */ movb (%bx),%al # Load type - movw $tables,%di # Lookup tables - movb $TBL0SZ,%cl # Number of entries + movw $non_bootable_ids,%di # Lookup tables + movb $(bootable_ids-non_bootable_ids),%cl # length repne # Exclude scasb # partition? - je main.5 # Yes -/* - * Now scan the table of known types - */ - movb $TBL1SZ+1,%cl # Number of entries + je next_entry # Yes, ignore it + /* + * Now scan the table of bootable ids, which starts at %di and has + * length TLEN. On a match, %di points to the element following the + * match; the corresponding offset to the description is $(TLEN-1) + * bytes ahead. If we don't find a match, we hit the 'unknown' entry. + */ + movb $(TLEN),%cl # Number of entries repne # Locate scasb # type -/* - * Get the matching element in the next array. - */ - addw $TBL1SZ-1, %di # Adjust + /* + * Get the matching element in the next array. + * The byte at $(TLEN-1)(%di) contains the offset of the description + * string from %di, so we add the number and print the string. + */ + addw $(TLEN-1), %di # Adjust movb (%di),%cl # Partition addw %cx,%di # description callw putx # Display it -main.5: incw %dx # Next item + +next_entry: incw %dx # Next item addb $0x10,%bl # Next entry - jnc main.3 # Till done -/* - * Passed a 256 byte boundary; the table is finished. - * Add one to the drive number and check it is valid. - */ + jnc read_entry # Till done + /* + * We are past a 256 byte boundary: the partition table is finished. + * Add one to the drive number and check it is valid. + * Note that if we started from a floppy, %dl was 0 so we still + * get an entry for the next drive, which is the first Hard Disk. + */ popw %ax # Drive number subb $0x80-0x1,%al # Does next cmpb NHRDRV,%al # drive exist? (from BIOS?) - jb main.6 # Yes -/* - * If this is the only drive, don't display it as an option. - */ + jb print_drive # Yes + /* + * If this is the only drive, don't display it as an option. + */ decw %ax # Already drive 0? - jz main.7 # Yes -/* - * If it was illegal or we cycled through them, go back to drive 0. - */ + jz print_prompt # Yes + /* + * If it was illegal or we cycled through them, go back to drive 0. + */ xorb %al,%al # Drive 0 -/* - * Whatever drive we selected, make it an ascii digit and save it back to the - * "next drive" location in the loaded block in case we want to save it later - * for next time. This also is part of the printed drive string so add 0x80 - * to indicate end of string. - */ -main.6: addb $'0'|0x80,%al # Save next + /* + * Whatever drive we selected, make it an ascii digit and save it + * back to the "nxtdrv" location in case we want to save it to disk. + * This digit is also part of the printed drive string, so add 0x80 + * to indicate end of string. + */ +print_drive: addb $'0'|0x80,%al # Save next movb %al,_NXTDRV(%bp) # drive number movw $drive,%di # Display callw putx # item -/* - * Now that we've printed the drive (if we needed to), display a prompt. - */ -main.7: movw $prompt,%si # Display + /* + * Menu is complete, display a prompt followed by current selection. + * 'decw %si' makes the register point to the space after 'Default: ' + * so we do not see an extra CRLF on the screen. + */ +print_prompt: movw $prompt,%si # Display callw putstr # prompt movb _OPT(%bp),%dl # Display decw %si # default callw putkey # key - jmp main.7_1 # Skip beep -/* - * Users's last try was bad, beep in displeasure. - */ -main.10: movb $ASCII_BEL,%al # Signal - callw putchr # beep! + jmp start_input # Skip beep + /* - * Start of input loop. Take note of time + * Here we have the code waiting for user input or a timeout. */ -main.7_1: xorb %ah,%ah # BIOS: Get +beep: movb $ASCII_BEL,%al # Input error, print or beep + callw putchr + +start_input: + /* + * Actual Start of input loop. Take note of time + */ + xorb %ah,%ah # BIOS: Get int $0x1a # system time movw %dx,%di # Ticks when addw _TICKS(%bp),%di # timeout -/* - * Busy loop, looking for keystrokes but keeping one eye on the time. - */ -main.8: +read_key: + /* + * Busy loop, looking for keystrokes but keeping one eye on the time. + */ #ifndef SIO movb $0x1,%ah # BIOS: Check int $0x16 # for keypress - jnz main.11 # Have one #else /* SIO */ movb $0x03,%ah # BIOS: Read COM call bioscom testb $0x01,%ah # Check line status - jnz main.11 # (bit 1 indicates input) + # (bit 1 indicates input) #endif /* SIO */ - xorb %ah,%ah # BIOS: Get - int $0x1a # system time + jnz got_key # Have input + xorb %ah,%ah # BIOS: int 0x1a, 00 + int $0x1a # get system time cmpw %di,%dx # Timeout? - jb main.8 # No -/* - * If timed out or defaulting, come here. - */ -main.9: movb _OPT(%bp),%al # Load default - jmp main.12 # Join common code -/* - * Get the keystroke. - */ -main.11: + jb read_key # No + + /* + * Timed out or default selection + */ +use_default: movb _OPT(%bp),%al # Load default + jmp check_selection # Join common code + + /* + * Get the keystroke. + * ENTER or CR confirm the current selection (same as a timeout). + * Otherwise convert F1..F6 (or '1'..'6') to 0..5 and check if the + * selection is valid. + * The SIO code uses ascii chars, the console code uses scancodes. + */ +got_key: #ifndef SIO - xorb %ah,%ah # BIOS: Get - int $0x16 # keypress - movb %ah,%al # Scan code + xorb %ah,%ah # BIOS: int 0x16, 00 + int $0x16 # get keypress + movb %ah,%al # move scan code to %al + cmpb $KEY_ENTER,%al #else movb $0x02,%ah # BIOS: Receive call bioscom + cmpb $ASCII_CR,%al #endif -/* - * If it's CR act as if timed out. - */ -#ifndef SIO - cmpb $KEY_ENTER,%al # Enter pressed? -#else - cmpb $ASCII_CR,%al # Enter pressed? -#endif - je main.9 # Yes -/* - * Otherwise check if legal. If not ask again. - */ -#ifndef SIO - subb $KEY_F1,%al # Less F1 scan code - cmpb $0x4,%al # F1..F5? - jna main.12 # Yes + je use_default # enter -> default + /* + * Check if the key is acceptable, and loop back if not. + * The console (non-SIO) code looks at scancodes and accepts + * both F1..F6 and 1..6 (the latter costs 6 bytes of code), + * relying on the fact that F1..F6 have higher scancodes than 1..6 + * The SIO code only takes 1..6 + */ +#ifdef SIO /* SIO mode, use ascii values */ + subb $'1',%al # Subtract '1' ascii code +#else /* console mode -- use scancodes */ + subb $KEY_F1,%al /* Subtract F1 scan code */ +#if !defined(ONLY_F_KEYS) + cmpb $0x5,%al # F1..F6 + jna 3f # Yes subb $(KEY_1 - KEY_F1),%al # Less #1 scan code -#else - subb $'1',%al # Less '1' ascii character -#endif - cmpb $0x4,%al # #1..#5? - ja main.10 # No -/* - * We have a selection. If it's a bad selection go back to complain. - * The bits in MNUOPT were set when the options were printed. - * Anything not printed is not an option. - */ -main.12: cbtw # Option - btw %ax,_MNUOPT(%bp) # enabled? - jnc main.10 # No -/* - * Save the info in the original tables - * for rewriting to the disk. - */ + 3: +#endif /* ONLY_F_KEYS */ +#endif /* SIO */ + cmpb $0x5,%al # F1..F6 or 1..6 ? +#ifdef PXE /* enable PXE/INT18 using F6 */ + jne 1f; + int $0x18 # found F6, try INT18 + 1: +#endif /* PXE */ + jae beep # Not in F1..F5, beep + +check_selection: + /* + * We have a selection. If it's a bad selection go back to complain. + * The bits in MNUOPT were set when the options were printed. + * Anything not printed is not an option. + */ + cbtw # Extend (%ah=0 used later) + btw %ax,_MNUOPT(%bp) # Option enabled? + jnc beep # No + /* + * Save the info in the original tables + * for rewriting to the disk. + */ movb %al,_OPT(%bp) # Save option - movw $FAKE,%si # Partition for write - movb (%si),%dl # Drive number + + /* + * Make %si and %bx point to the fake partition at LBA 0 (CHS 0:0:1). + * Because the correct address is already in %bp, just use it. + * Set %dl with the drive number saved in byte 0. + * If we have pressed F5 or 5, then this is a good, fake value + * to present to the next stage boot code. + */ + movw %bp,%si # Partition for write + movb (%si),%dl # Drive number, saved above movw %si,%bx # Partition for read cmpb $0x4,%al # F5/#5 pressed? - pushf # Save - je main.13 # Yes + pushf # Save results for later + je 1f # Yes, F5 + + /* + * F1..F4 was pressed, so make %bx point to the currently + * selected partition, and leave the drive number unchanged. + */ shlb $0x4,%al # Point to addw $partbl,%ax # selected xchgw %bx,%ax # partition movb $0x80,(%bx) # Flag active -/* - * If not asked to do a write-back (flags 0x40) don't do one. - */ -main.13: pushw %bx # Save - testb $0x40,_FLAGS(%bp) # No updates? - jnz main.14 # Yes + /* + * If not asked to do a write-back (flags 0x40) don't do one. + * Around the call, save the partition pointer to %bx and + * restore to %si which is where the next stage expects it. + */ + 1: pushw %bx # Save + testb $NOUPDATE,_FLAGS(%bp) # No updates? + jnz 2f # skip update movw $start,%bx # Data to write movb $0x3,%ah # Write sector callw intx13 # to disk -main.14: popw %si # Restore - popf # Restore -/* - * If going to next drive, replace drive with selected one. - * Remember to un-ascii it. Hey 0x80 is already set, cool! - */ - jne main.15 # If not F5/#5 + 2: popw %si # Restore + + /* + * If going to next drive, replace drive with selected one. + * Remember to un-ascii it. Hey 0x80 is already set, cool! + */ + popf # Restore %al test results + jne 3f # If not F5/#5 movb _NXTDRV(%bp),%dl # Next drive subb $'0',%dl # number -/* - * Load selected bootsector to the LOAD location in RAM. - * If it fails to read or isn't marked bootable, treat it as a bad selection. - */ -main.15: movw $LOAD,%bx # Address for read + /* + * Load selected bootsector to the LOAD location in RAM. If read + * fails or there is no 0x55aa marker, treat it as a bad selection. + */ + 3: movw $LOAD,%bx # Address for read movb $0x2,%ah # Read sector callw intx13 # from disk - jc main.10 # If error + jc beep # If error cmpw $MAGIC,0x1fe(%bx) # Bootable? - jne main.10 # No + jne beep # No pushw %si # Save ptr to selected part. callw putn # Leave some space popw %si # Restore, next stage uses it @@ -326,6 +496,14 @@ main.15: movw $LOAD,%bx # Address for read /* * Display routines + * putkey prints the option selected in %dl (F1..F5 or 1..5) followed by + * the string at %si + * putx: print the option in %dl followed by the string at %di + * also record the drive as valid. + * puts: print the string at %si followed by a crlf + * putn: print a crlf + * putstr: print the string at %si + * putchr: print the char in al */ putkey: #ifndef SIO @@ -337,8 +515,9 @@ putkey: jmp putstr.1 # Display the rest /* - * Display the option and note that it is a valid option. - * That last point is a bit tricky.. + * Display the option and record the drive as valid in the options. + * That last point is done using the btsw instruction which does + * a test and set. We don't care for the test part. */ putx: btsw %dx,_MNUOPT(%bp) # Enable menu option movw $item,%si # Display @@ -356,34 +535,43 @@ putstr.1: callw putchr # Display char jmp putstr # Continue putstr.2: andb $~0x80,%al # Clear MSB -#ifndef SIO putchr: +#ifndef SIO pushw %bx # Save movw $0x7,%bx # Page:attribute movb $0xe,%ah # BIOS: Display int $0x10 # character popw %bx # Restore - retw # To caller #else /* SIO */ -putchr: movb $0x01,%ah # BIOS: Send bioscom: pushw %dx # Save xorw %dx,%dx # Use COM1 int $0x14 # Character popw %dx # Restore - retw # To caller #endif /* SIO */ + retw # To caller /* One-sector disk I/O routine */ -intx13: movb 0x1(%si),%dh # Load head +/* + * %dl: drive, %si partition entry, %es:%bx transfer buffer. + * Load the CHS values and possibly the LBA address from the block + * at %si, and use the appropriate method to load the sector. + * Don't use packet mode for a floppy. + */ +intx13: # Prepare CHS parameters + movb 0x1(%si),%dh # Load head movw 0x2(%si),%cx # Load cylinder:sector movb $0x1,%al # Sector count pushw %si # Save movw %sp,%di # Save - testb $0x80,_FLAGS(%bp) # Use packet interface? - jz intx13.1 # No +#ifndef CHECK_DRIVE /* floppy support */ + testb %dl, %dl # is this a floppy ? + jz 1f # Yes, use CHS mode +#endif + testb $USEPACKET,_FLAGS(%bp) # Use packet interface? + jz 1f # No pushl $0x0 # Set the pushl 0x8(%si) # LBA address pushw %es # Set the transfer @@ -393,73 +581,95 @@ intx13: movb 0x1(%si),%dh # Load head movw %sp,%si # Packet pointer decw %ax # Verify off orb $0x40,%ah # Use disk packet -intx13.1: int $0x13 # BIOS: Disk I/O + 1: int $0x13 # BIOS: Disk I/O movw %di,%sp # Restore popw %si # Restore retw # To caller -/* Menu strings */ - +/* + * Various menu strings. 'item' goes after 'prompt' to save space. + * Also use shorter versions to make room for the PXE/INT18 code. + */ +#ifdef PXE +prompt: .ascii "\nBoot:" +item: .ascii " "; .byte ' '|0x80 +#else +prompt: .ascii "\nDefault:" item: .ascii " "; .byte ' '|0x80 -prompt: .ascii "\nDefault:"; .byte ' '|0x80 +#endif crlf: .ascii "\r"; .byte '\n'|0x80 /* Partition type tables */ -tables: -/* - * These entries identify invalid or NON BOOT types and partitions. - */ +non_bootable_ids: + /* + * These entries identify invalid or NON BOOT types and partitions. + * 0: empty, 5: DOS3 ext. partition, 0xf: WIN95 ext partition + */ .byte 0x0, 0x5, 0xf -/* - * These values indicate bootable types we know the names of. - */ +bootable_ids: + /* + * These values indicate bootable types we know the names of. + * 1: FAT12, 4: FAT16 <32M, 6: FAT16 > 32M, 7: NTFS + * 0xb: FAT32, 0xc: FAT32-LBA, 0xe: FAT16-LBA, + * 0x83: linux, 0xa5: FreeBSD, 0xa6: netbsd, 0xa9:openbsd + */ .byte 0x1, 0x6, 0x7, 0xb, 0xc, 0xe, 0x83 - .byte 0xa5, 0xa6, 0xa9 -/* - * These are offsets that match the known names above and point to the strings - * that will be printed. os_misc will be used if the search of the above table - * runs over. - */ - .byte os_dos-. # DOS - .byte os_dos-. # DOS - .byte os_dos-. # Windows - .byte os_dos-. # Windows - .byte os_dos-. # Windows - .byte os_dos-. # Windows - .byte os_linux-. # Linux - .byte os_freebsd-. # FreeBSD - .byte os_bsd-. # OpenBSD - .byte os_bsd-. # NetBSD + .byte 0xa5, 0xa6, 0xa9, 0x4 +desc_ofs: + /* + * Offsets that match the known types above, used to point to the + * actual partition name. The last entry must point to os_misc, + * which is used for non-matching names. + */ + .byte os_dos-. # 1, DOS + .byte os_dos-. # 6, DOS/WIN + .byte os_win-. # 7, Windows + .byte os_win-. # 11, Windows + .byte os_win-. # 12, Windows + .byte os_win-. # 14, Windows + .byte os_linux-. # 131, Linux + .byte os_freebsd-. # 165, FreeBSD + .byte os_bsd-. # 166, OpenBSD + .byte os_bsd-. # 169, NetBSD + .byte os_dos-. # 4, DOS .byte os_misc-. # Unknown -/* - * And here are the strings themselves. 0x80 or'd into a byte indicates - * the end of the string. (not so great for Russians but...) - */ -os_misc: .ascii "?"; .byte '?'|0x80 -os_dos: .ascii "DO"; .byte 'S'|0x80 + + /* + * And here are the strings themselves. The last byte of + * the string has bit 7 set. + */ +os_misc: .byte '?'|0x80 +os_dos: +#if !defined(TEST) /* DOS string only if room */ + .ascii "DO"; .byte 'S'|0x80 +#endif +os_win: .ascii "WI"; .byte 'N'|0x80 os_linux: .ascii "Linu"; .byte 'x'|0x80 os_freebsd: .ascii "Free" os_bsd: .ascii "BS"; .byte 'D'|0x80 - .org PRT_OFF-0xe,0x90 - - .word B0MAGIC # Magic number - + .org B0_OFF,0x90 /* - * These values are sometimes changed before writing back to the drive + * The boot0 version 1.0 parameter table. + * Do not move it nor change the "Drive " string, boot0cfg + * uses its offset and content to identify the boot sector. + * The other fields are sometimes changed before writing back to the drive * Be especially careful that nxtdrv: must come after drive:, as it * is part of the same string. */ drive: .ascii "Drive " nxtdrv: .byte 0x0 # Next drive number opt: .byte 0x0 # Option -setdrv: .byte 0x80 # Drive to force +setdrv_num: .byte 0x80 # Drive to force flags: .byte FLAGS # Flags ticks: .word TICKS # Delay + .org PRT_OFF /* * Here is the 64 byte partition table that fdisk would fiddle with. */ partbl: .fill 0x40,0x1,0x0 # Partition table .word MAGIC # Magic number + .org 0x200 # again, safety check +endblock: |
