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 rnord...@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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