Date: Tue, 13 Jan 2009 22:28:49 +0000 (UTC) From: Luigi Rizzo <luigi@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-7@freebsd.org Subject: svn commit: r187198 - in stable/7: sys/boot/i386/boot0 usr.sbin/boot0cfg Message-ID: <200901132228.n0DMSnai018184@svn.freebsd.org>
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Author: luigi Date: Tue Jan 13 22:28:48 2009 New Revision: 187198 URL: http://svn.freebsd.org/changeset/base/187198 Log: MFC: a number of small fixes and enhancements to the boot0 code, and matching modifications to boot0cfg. The most noticeable features are preserving the 4-byte volume ID that certain Windows versions put in the MBR, and an option (F6) to boot through INT18 that on some modern BIOSes invokes PXE. Modified: stable/7/sys/boot/i386/boot0/boot0.S stable/7/usr.sbin/boot0cfg/boot0cfg.8 stable/7/usr.sbin/boot0cfg/boot0cfg.c Modified: stable/7/sys/boot/i386/boot0/boot0.S ============================================================================== --- stable/7/sys/boot/i386/boot0/boot0.S Tue Jan 13 22:15:47 2009 (r187197) +++ stable/7/sys/boot/i386/boot0/boot0.S Tue Jan 13 22:28:48 2009 (r187198) @@ -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 +17,166 @@ * $FreeBSD$ */ -/* 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 */ +#define SAVE_MORE_MEMORY +#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 VOLUME_SERIAL /* support Volume serial number */ +#define B0_BASE 0x1ae /* move the internal data area */ +#define SAVE_MEMORY +#else +#define B0_BASE 0x1b2 +#endif + +#ifdef TEST /* enable some test code */ +#define SAVE_MEMORY +#define SAVE_MORE_MEMORY +#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 %si 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. Computed as a negative offset from 0x200 + * 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,(B0_BASE-0x200) # 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, B0_OFF+6 # Next drive + .set _OPT, B0_OFF+7 # Default option + .set _SETDRV, B0_OFF+8 # Drive to force + .set _FLAGS, B0_OFF+9 # Flags + .set SETDRV, 0x20 # the 'setdrv' flag + .set NOUPDATE, 0x40 # the 'noupdate' flag + .set USEPACKET, 0x80 # the 'packet' flag + + /* ticks is at a fixed position */ + .set _TICKS, (PRT_OFF - 0x200 - 2) # Timeout ticks + .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 @@ -69,7 +186,7 @@ start: cld # String ops inc 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 @@ -77,248 +194,301 @@ start: cld # String ops inc 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) + js save_curdrive # Possibly (0x80 set) +#endif /* - * Only update the boot-sector when there is a valid drive number or - * the drive number is set manually. + * Disable updates if the drive number is forced. */ - orb $0x40,_FLAGS(%bp) # Disable updates -main.1: movb _SETDRV(%bp),%dl # Drive number to use +disable_update: orb $NOUPDATE,_FLAGS(%bp) # Disable updates + movb _SETDRV(%bp),%dl # Use stored drive number + /* - * 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 + * 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 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. + * 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. + * pass a 256 byte boundary. */ -main.3: movb %ch,-0x4(%bx) # Zero active flag (ch == 0) +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 movb (%bx),%al # Load type - movw $tables,%di # Lookup tables - movb $TBL0SZ,%cl # Number of entries - repne # Exclude - scasb # partition? - je main.5 # Yes + test %al, %al # skip empty partition + jz next_entry /* - * Now scan the table of known types + * 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. We use a count of TLEN+1 so if we don't find a match + * within the first TLEN entries, we hit the 'unknown' entry. */ - movb $TBL1SZ+1,%cl # Number of entries + movw $bootable_ids,%di # Lookup tables + movb $(TLEN+1),%cl # Number of entries repne # Locate scasb # type /* * 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 $TBL1SZ-1, %di # Adjust + 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 + jnc read_entry # Till done /* - * Passed a 256 byte boundary; the table is finished. + * 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 + 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 + 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 + * 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. */ -main.6: addb $'0'|0x80,%al # Save next +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. + * Menu is complete, display a prompt followed by current selection. + * 'decw %si' makes the register point to the space after 'Boot: ' + * so we do not see an extra CRLF on the screen. */ -main.7: movw $prompt,%si # Display +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 + jmp start_input # Skip beep + /* - * Users's last try was bad, beep in displeasure. + * Here we have the code waiting for user input or a timeout. */ -main.10: movb $ASCII_BEL,%al # Signal - callw putchr # beep! +beep: movb $ASCII_BEL,%al # Input error, print or beep + callw putchr + +start_input: /* - * Start of input loop. Take note of time + * Actual Start of input loop. Take note of time */ -main.7_1: xorb %ah,%ah # BIOS: Get + xorb %ah,%ah # BIOS: Get int $0x1a # system time movw %dx,%di # Ticks when addw _TICKS(%bp),%di # timeout +read_key: /* * Busy loop, looking for keystrokes but keeping one eye on the time. */ -main.8: #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 + jb read_key # No + /* - * If timed out or defaulting, come here. + * Timed out or default selection */ -main.9: movb _OPT(%bp),%al # Load default - jmp main.12 # Join common code +use_default: movb _OPT(%bp),%al # Load default + orb $NOUPDATE,_FLAGS(%bp) # Disable updates + 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. */ -main.11: +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 + je use_default # enter -> default /* - * 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 + * 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 + 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. */ -main.12: cbtw # Option - btw %ax,_MNUOPT(%bp) # enabled? - jnc main.10 # No + 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. + * Around the call, save the partition pointer to %bx and + * restore to %si which is where the next stage expects it. */ -main.13: pushw %bx # Save - testb $0x40,_FLAGS(%bp) # No updates? - jnz main.14 # Yes + 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 + 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! */ - jne main.15 # If not F5/#5 + 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. + * Load selected bootsector to the LOAD location in RAM. If read + * fails or there is no 0x55aa marker, treat it as a bad selection. */ -main.15: movw $LOAD,%bx # Address for read + 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 @@ -326,64 +496,80 @@ main.15: movw $LOAD,%bx # Address for /* * 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. + * putn: print a crlf + * putstr: print the string at %si + * putchr: print the char in al */ -putkey: -#ifndef SIO - movb $'F',%al # Display - callw putchr # 'F' -#endif - movb $'1',%al # Prepare - addb %dl,%al # digit - 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 callw putkey # key movw %di,%si # Display the rest - -puts: callw putstr # Display string + callw putstr # Display string putn: movw $crlf,%si # To next line + jmp putstr + +putkey: +#ifndef SIO + movb $'F',%al # Display + callw putchr # 'F' +#endif + movb $'1',%al # Prepare + addb %dl,%al # digit +putstr.1: callw putchr # Display char putstr: lodsb # Get byte testb $0x80,%al # End of string? - jnz putstr.2 # Yes -putstr.1: callw putchr # Display char - jmp putstr # Continue -putstr.2: andb $~0x80,%al # Clear MSB + jz putstr.1 # No + andb $~0x80,%al # Clear MSB then print last -#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 +579,104 @@ 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. + */ +prompt: +#ifdef PXE + .ascii "\nF6 PXE\r" +#endif + .ascii "\nBoot:" item: .ascii " "; .byte ' '|0x80 -prompt: .ascii "\nDefault:"; .byte ' '|0x80 crlf: .ascii "\r"; .byte '\n'|0x80 /* Partition type tables */ -tables: +bootable_ids: /* - * These entries identify invalid or NON BOOT types and partitions. - */ - .byte 0x0, 0x5, 0xf + * These values indicate bootable types we know about. + * Corresponding descriptions are at desc_ofs: + * Entries don't need to be sorted. + */ + .byte 0x83, 0xa5, 0xa6, 0xa9, 0x06, 0x07, 0x0b +#ifndef SAVE_MORE_MEMORY + .byte 0x05 # extended partition +#endif +#ifndef SAVE_MEMORY /* other DOS partitions */ + .byte 0x01 # FAT12 + .byte 0x04 # FAT16 < 32M +#endif + +desc_ofs: /* - * These values indicate bootable types we know the names of. - */ - .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 + * 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_linux-. # 131, Linux + .byte os_freebsd-. # 165, FreeBSD + .byte os_bsd-. # 166, OpenBSD + .byte os_bsd-. # 169, NetBSD + .byte os_dos-. # 6, FAT16 >= 32M + .byte os_win-. # 7, NTFS + .byte os_win-. # 11, FAT32 + +#ifndef SAVE_MORE_MEMORY + .byte os_ext-. # 5, DOS Ext +#endif +#ifndef SAVE_MEMORY + .byte os_dos-. # 1, FAT12 DOS + .byte os_dos-. # 4, FAT16 <32M +#endif .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...) + * And here are the strings themselves. The last byte of + * the string has bit 7 set. */ -os_misc: .ascii "?"; .byte '?'|0x80 -os_dos: .ascii "DO"; .byte 'S'|0x80 +os_misc: .byte '?'|0x80 +os_dos: +#ifndef SAVE_MORE_MEMORY /* 'DOS' remapped to 'WIN' if no 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 +#ifndef SAVE_MORE_MEMORY +os_ext: .ascii "EX"; .byte 'T'|0x80 +#endif - .org PRT_OFF-0xe,0x90 - - .word B0MAGIC # Magic number - + .org (0x200 + 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 +#ifdef VOLUME_SERIAL + .byte 0xa8,0xa8,0xa8,0xa8 # Volume Serial Number +#endif 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: Modified: stable/7/usr.sbin/boot0cfg/boot0cfg.8 ============================================================================== --- stable/7/usr.sbin/boot0cfg/boot0cfg.8 Tue Jan 13 22:15:47 2009 (r187197) +++ stable/7/usr.sbin/boot0cfg/boot0cfg.8 Tue Jan 13 22:28:48 2009 (r187198) @@ -24,7 +24,7 @@ .\" .\" $FreeBSD$ .\" -.Dd June 7, 2007 +.Dd January 13, 2009 .Dt BOOT0CFG 8 .Os .Sh NAME @@ -35,7 +35,9 @@ .Op Fl Bv .Op Fl b Ar boot0 .Op Fl d Ar drive +.Op Fl e Ar bell character .Op Fl f Ar file +.Op Fl i Ar volume-id .Op Fl m Ar mask .Op Fl o Ar options .Op Fl s Ar slice @@ -96,10 +98,17 @@ which contains the specified Typically this will be 0x80 for the first hard drive, 0x81 for the second hard drive, and so on; however any integer between 0 and 0xff is acceptable here. +.It Fl e Ar bell character +Set the character to be printed in case of input error. .It Fl f Ar file Specify that a backup copy of the preexisting MBR should be written to .Ar file . This file is created if it does not exist, and replaced if it does. +.It Fl i Ar volume-id +Specifies a volume-id (in the form XXXX-XXXX) to be saved at location +0x1b8 in the MBR. This information is sometimes used by NT, XP and Vista +to identify the disk drive. The option is only compatible with version 2.00 +of the 512-byte boot block. .It Fl m Ar mask Specify slices to be enabled/disabled, where .Ar mask @@ -144,6 +153,21 @@ Set the timeout value to .It Fl v Verbose: display information about the slices defined, etc. .El +.Sh NOTE +Protection mechanisms in the +.Xr geom 4 +subsystem might prevent +.Nm +from being able to update the MBR on a mounted disk. +Instructions for temporarily disabling these protection mechanisms +can be found in the +.Xr geom 4 +manpage. Specifically, do a +.Pp +.Dl sysctl kern.geom.debugflags=0x10 +.Pp +to allow writing to the MBR, and restore it to 0 afterwards. +.Pp .Sh FILES .Bl -tag -width /boot/boot0sio -compact .It Pa /boot/boot0 @@ -177,16 +201,6 @@ to install the default MBR: .Sh AUTHORS .An Robert Nordier Aq rnordier@FreeBSD.org . .Sh BUGS -Protection mechanisms in the -.Xr geom 4 -subsystem might prevent -.Nm -from being able to update the MBR on a mounted disk. -Instructions for temporarily disabling these protection mechanisms -can be found in the -.Xr geom 4 -manpage. -.Pp Use of the .Sq packet option may cause @@ -195,6 +209,6 @@ to fail, depending on the nature of BIOS .Pp Use of the .Sq setdrv -option with an incorrect -d operand may cause the MBR to be written -to the wrong disk. -Be careful! +option with an incorrect -d operand may cause the boot0 code +to write the MBR to the wrong disk, thus trashing its previous +content. Be careful. Modified: stable/7/usr.sbin/boot0cfg/boot0cfg.c ============================================================================== --- stable/7/usr.sbin/boot0cfg/boot0cfg.c Tue Jan 13 22:15:47 2009 (r187197) +++ stable/7/usr.sbin/boot0cfg/boot0cfg.c Tue Jan 13 22:28:48 2009 (r187198) @@ -1,4 +1,5 @@ /* + * Copyright (c) 2008 Luigi Rizzo * Copyright (c) 1999 Robert Nordier * All rights reserved. * @@ -44,13 +45,34 @@ __FBSDID("$FreeBSD$"); #define MBRSIZE 512 /* master boot record size */ -#define OFF_VERSION 0x1b0 /* offset: version number */ -#define OFF_OPT 0x1b9 /* offset: default boot option */ -#define OFF_DRIVE 0x1ba /* offset: setdrv drive */ -#define OFF_FLAGS 0x1bb /* offset: option flags */ -#define OFF_TICKS 0x1bc /* offset: clock ticks */ +#define OFF_VERSION 0x1b0 /* offset: version number, only boot0version */ +#define OFF_SERIAL 0x1b8 /* offset: volume serial number */ #define OFF_PTBL 0x1be /* offset: partition table */ #define OFF_MAGIC 0x1fe /* offset: magic number */ +/* + * Offsets to the parameters of the 512-byte boot block. + * For historical reasons they are set as macros + */ +struct opt_offsets { + int opt; + int drive; + int flags; + int ticks; +}; + +struct opt_offsets b0_ofs[] = { + { 0x0, 0x0, 0x0, 0x0 }, /* no boot block */ + { 0x1b9, 0x1ba, 0x1bb, 0x1bc }, /* original block */ + { 0x1b5, 0x1b6, 0x1b7, 0x1bc }, /* NT_SERIAL block */ +}; + +int b0_ver; /* boot block version set by boot0bs */ + +#define OFF_OPT (b0_ofs[b0_ver].opt) /* default boot option */ +#define OFF_DRIVE (b0_ofs[b0_ver].drive) /* setdrv drive */ +#define OFF_FLAGS (b0_ofs[b0_ver].flags) /* option flags */ +#define OFF_TICKS (b0_ofs[b0_ver].ticks) /* clock ticks */ + #define cv2(p) ((p)[0] | (p)[1] << 010) @@ -82,8 +104,12 @@ static int boot0bs(const u_int8_t *); *** DIFF OUTPUT TRUNCATED AT 1000 LINES ***
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