| Current Path : /sys/boot/i386/boot0/ |
FreeBSD hs32.drive.ne.jp 9.1-RELEASE FreeBSD 9.1-RELEASE #1: Wed Jan 14 12:18:08 JST 2015 root@hs32.drive.ne.jp:/sys/amd64/compile/hs32 amd64 |
| Current File : //sys/boot/i386/boot0/boot0ext.S |
/* * Copyright (c) 1998 Robert Nordier * All rights reserved. * * Redistribution and use in source and binary forms are freely * permitted provided that the above copyright notice and this * paragraph and the following disclaimer are duplicated in all * such forms. * * This software is provided "AS IS" and without any express or * implied warranties, including, without limitation, the implied * warranties of merchantability and fitness for a particular * purpose. * * $FreeBSD: release/9.1.0/sys/boot/i386/boot0/boot0ext.S 128741 2004-04-29 18:58:38Z ru $ */ /* A 1024-byte boot manager. */ .set NHRDRV,0x475 # Number of hard drives .set ORIGIN,0x600 # Execution address .set SECTOR_SIZE,0x200 # Length of a sector .set NUM_SECTORS,2 # Total length in sectors .set FAKE,ORIGIN+(SECTOR_SIZE*NUM_SECTORS) # Partition entry .set LOAD,0x7c00 # Load address .set PRT_OFF,0x1be # Partition table .set TBL0SZ,table0_end-table0 # Table 0 size .set TBL1SZ,table1_end-table1 # Table 1 size .set MAGIC,0xaa55 # Magic: bootable .set KEY_ENTER,0x1c # Enter key scan code .set KEY_F1,0x3b # F1 key scan code .set KEY_1,0x02 # #1 key scan code /* * Flag bits */ .set FL_PACKET,0x80 # Packet mode .set FL_NOUPDATE,0x40 # Don't save selection .set FL_SETDRV,0x20 # Override drive number /* * Addresses in the sector of embedded data values. * Accessed with negative offsets from the end of the relocated sectors (%bp). */ .set _PRT_END,(FAKE-(ORIGIN+SECTOR_SIZE*(NUM_SECTORS-1))) .set _NXTDRV,-(_PRT_END+0x48) # Next drive .set _OPT,-(_PRT_END+0x47) # Default option .set _SETDRV,-(_PRT_END+0x46) # Drive to force .set _FLAGS,-(_PRT_END+0x45) # Flags .set _TICKS,-(_PRT_END+0x44) # Timeout ticks .set _FAKE,0x0 # Fake partition entry .set _MNUOPT,0xc # Menu options .globl start # Entry point .code16 # This runs in real mode /* * Initialise segments and registers to known values. * segments start at 0. * The stack is immediately below the address we were loaded to. * * Note that this section of code is used as the first signature check in * boot0cfg(8). */ start: cld # String ops inc xorw %ax,%ax # Zero movw %ax,%es # Address movw %ax,%ds # data movw %ax,%ss # Set up movw $LOAD,%sp # stack /* * End signature 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. */ movw $fake,%bp # Address variables movw %bp,%di # %di used in stosw movw $0x8,%cx # Words to clear rep # Zero stosw # them incb -0xe(%di) # Sector number 1 /* * Check what flags were loaded with us; specifically, use a predefined Drive. * If what the bios gives us is bad, use the '0' in the block instead, as well. */ testb $FL_SETDRV,LOAD+flags-start # Set number drive? jnz boot.1 # Yes testb %dl,%dl # Drive number valid? js boot.2 # Possibly (0x80 set) boot.1: movb LOAD+setdrv-start,%dl # Drive number to use boot.2: /* * Reload all of boot0 (including the extra sectors) into memory at the * relocation address. */ push %dx # Save drive number movw $start,%bx # Origin we were linked for movw %bp,%si # Fake PTE movw $0x200+NUM_SECTORS,%ax # Read in all callw intx13 # of boot0 pop %dx # Restore /* * Relocate to the new copy of the code. */ jmp main+ORIGIN-LOAD # To relocated code /* * Whatever we decided to use, now store it into the fake * partition entry that lives in the data space above us. */ main: 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) */ 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) 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. */ movb (%bx),%al # Load type movw $tables,%di # Lookup tables movb $TBL0SZ,%cl # Number of entries repne # Exclude scasb # partition? je main.5 # Yes /* * Now scan the table of known types */ movb $TBL1SZ,%cl # Number of entries repne # Known scasb # type? jne main.4 # No /* * If it matches get the matching element in the * next array. If it doesn't, we are already * pointing at its first element which points to a "?". */ addw $TBL1SZ,%di # Adjust main.4: movb (%di),%cl # Partition addw %cx,%di # description callw putx # Display it main.5: incw %dx # Next item addb $0x10,%bl # Next entry jnc main.3 # Till done /* * Passed a 256 byte boundary.. * table is finished. * Add one to the drive number and check it is valid, */ popw %ax # Drive number subb $0x80-0x1,%al # Does next cmpb NHRDRV,%al # drive exist? (from BIOS?) jb main.6 # Yes /* * If not then if there is only one drive, * Don't display drive as an option. */ decw %ax # Already drive 0? jz main.7 # Yes /* * If it was illegal or we cycled through them, * then 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 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 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. * Get ready for the input by noting the time. */ main.7: movw $prompt,%si # Display callw putstr # prompt movb _OPT(%bp),%dl # Display decw %si # default callw putkey # key 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: movb $0x1,%ah # BIOS: Check int $0x16 # for keypress jnz main.11 # Have one xorb %ah,%ah # BIOS: Get int $0x1a # 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 /* * User's last try was bad, beep in displeasure. * Since nothing was printed, just continue on as if the user * hadn't done anything. This gives the effect of the user getting a beep * for all bad keystrokes but no action until either the timeout * occurs or the user hits a good key. */ main.10: movb $0x7,%al # Signal callw putchr # error /* * Get the keystroke. */ main.11: xorb %ah,%ah # BIOS: Get int $0x16 # keypress movb %ah,%al # Scan code /* * If it's CR act as if timed out. */ cmpb $KEY_ENTER,%al # Enter pressed? je main.9 # Yes /* * Otherwise check if legal * If not ask again. */ subb $KEY_F1,%al # Less F1 scan code cmpb $0x4,%al # F1..F5? jna main.12 # Yes subb $(KEY_1 - KEY_F1),%al # Less #1 scan code cmpb $0x4,%al # #1..#5? ja main.10 # No /* * We have a selection. * but 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. */ movb %al,_OPT(%bp) # Save option movw $fake,%si # Partition for write movb (%si),%dl # Drive number movw %si,%bx # Partition for read cmpb $0x4,%al # F5/#5 pressed? pushf # Save je main.13 # Yes 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 $FL_NOUPDATE,_FLAGS(%bp) # Skip update? jnz main.14 # Yes movw $start,%bx # Data to write movw $0x301,%ax # Write 1 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 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 movw $0x201,%ax # Read 1 sector callw intx13 # from disk jc main.10 # If error cmpw $MAGIC,0x1fe(%bx) # Bootable? jne main.10 # No callw putn # Leave some space jmp *%bx # Invoke bootstrap /* * Display routines */ putkey: movb $'F',%al # Display callw putchr # 'F' 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.. */ 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 putn: movw $crlf,%si # To next line 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 putchr: pushw %bx # Save movw $0x7,%bx # Page:attribute movb $0xe,%ah # BIOS: Display int $0x10 # character popw %bx # Restore retw # To caller /* * One-sector disk I/O routine * * Calling conventions: (assumes %si -> partition table entry) * * 0x1(%si) - byte - head * 0x2(%si) - word - cylinder/sector * 0x8(%si) - long - LBA to use if needed * %ah - byte - operation, 2 = read, 3 = write * %al - byte - sector count * %dl - byte - drive number * %es:(%bx) - void - buffer to use for transfer * * If the head == 0xff, and cylinder/sector == 0xffff, then try * to use the EDD stuff with the LBA offset instead of CHS. However, * use CHS if at all possible. */ intx13: movb 0x1(%si),%dh # Load head movw 0x2(%si),%cx # Load cylinder:sector pushw %si # Save movw %sp,%di # Save cmpb $0xff,%dh # Might we need LBA? jne intx13.2 # No, just use CHS cmpw $0xffff,%cx # Do we need LBA? jne intx13.2 # No testb $FL_PACKET,_FLAGS(%bp) # Try the packet interface? jz intx13.2 # No pushw %cx # Save pushw %bx # Save movw $0x55aa,%bx # Magic pushw %ax # Save movb $0x41,%ah # BIOS: EDD extensions int $0x13 # present? popw %ax # Restore jc intx13.1 # Not present, use CHS cmpw $0xaa55,%bx # Magic? jne intx13.1 # Not present, use CHS testb $0x1,%cl # Packet mode available? jz intx13.1 # No, use CHS orb $0x40,%ah # Use disk packet intx13.1: popw %bx # Restore popw %cx # Restore testb $0x40,%ah # Using packet mode? jz intx13.2 # No, so skip the rest pushl $0x0 # Set the pushl 0x8(%si) # LBA address pushw %es # Set the transfer pushw %bx # buffer address push $0x0 # Punch a hole in the stack push $0x10 # Packet size movw %sp,%si # Packet pointer xchgb %al,0x2(%si) # Set the block count in the # packet and zero %al, # turning verify off for writes intx13.2: int $0x13 # BIOS: Disk I/O movw %di,%sp # Restore popw %si # Restore retw # To caller .org PRT_OFF-0xe,0x90 /* * These values 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. * * Note that the 'drive' string variable is used as the second signature * check in boot0cfg(8). */ version_minor: .byte 0x1 # minor version version_major: .byte 0x1 # major version drive: .ascii "Drive " nxtdrv: .byte 0x0 # Next drive number opt: .byte 0x0 # Option setdrv: .byte 0x80 # Drive to force flags: .byte FLAGS # Flags ticks: .word TICKS # Delay /* * here is the 64 byte partition table that fdisk would fiddle with. */ partbl: .fill 0x40,0x1,0x0 # Partition table .word MAGIC # Magic number /* * start of sector two.. ugh */ .org SECTOR_SIZE,0x90 /* Menu strings */ item: .ascii " "; .byte ' '|0x80 prompt: .ascii "\nDefault:"; .byte ' '|0x80 crlf: .ascii "\r"; .byte '\n'|0x80 /* Partition type tables */ tables: /* * These entries identify invalid or NON BOOT types and partitions. */ table0: .byte 0x0, 0x5, 0xf table0_end: /* * These values indicate bootable types we know the names of */ table1: .byte 0x1, 0x4, 0x6, 0x7, 0xb, 0xc, 0xe, 0x42, 0x63, 0x83 .byte 0x9f, 0xa5, 0xa6, 0xa9 table1_end: /* * These are offsets that match the known names above and point to the strings * that will be printed. */ .byte os_misc-. # Unknown .byte os_dos-. # DOS .byte os_dos-. # DOS .byte os_dos-. # DOS .byte os_nt-. # NT/XP or OS/2 .byte os_windows-. # Windows 32-bit FAT .byte os_windows-. # Windows 32-bit FAT ext int 13 .byte os_windows-. # Windows .byte os_windows-. # Windows 2000 dyn ext .byte os_unix-. # UNIX .byte os_linux-. # Linux .byte os_bsdos-. # BSD/OS .byte os_freebsd-. # FreeBSD .byte os_openbsd-. # OpenBSD .byte os_netbsd-. # NetBSD /* * 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 "Unknow"; .byte 'n'|0x80 os_dos: .ascii "DO"; .byte 'S'|0x80 os_nt: .ascii "Windows NT/X"; .byte 'P'|0x80 os_windows: .ascii "Window"; .byte 's'|0x80 os_unix: .ascii "UNI"; .byte 'X'|0x80 os_linux: .ascii "Linu"; .byte 'x'|0x80 os_freebsd: .ascii "FreeBS"; .byte 'D'|0x80 os_openbsd: .ascii "OpenBS"; .byte 'D'|0x80 os_netbsd: .ascii "NetBS"; .byte 'D'|0x80 os_bsdos: .ascii "BSD/O"; .byte 'S'|0x80 /* * Fake partition entry created at the end of the table used when loading * boot0 at the very beginning and when loading an MBR from another disk when * F5 is pressed. */ .org SECTOR_SIZE*NUM_SECTORS, 0x0 fake: