/* * Copyright (c) 2003,2004 The DragonFly Project. All rights reserved. * * This code is derived from software contributed to The DragonFly Project * by Matthew Dillon * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * 3. Neither the name of The DragonFly Project nor the names of its * contributors may be used to endorse or promote products derived * from this software without specific, prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * 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: src/sys/boot/i386/boot0/boot0.s,v 1.26 2003/06/01 20:41:04 obrien Exp $ */ #include "../bootasm.h" #ifdef SIO /* ... using a serial console on COM1. */ #endif /* * A 512-byte boot manager. */ .set PRT_OFF,0x1be # Partition table .set TBL0SZ,0x3 # Table 0 size .set TBL1SZ,0xb # Table 1 size .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 .set ASCII_CR,0x0D # ASCII code for /* * Addresses in the sector of embedded data values. Accessed * with negative offsets from the end of the relocated sector * (%ebp). * * Note that %ebp is the base of our variable space and * points at the end of the sector (base + 0x200). The * fake partition and menu option is thus stored in the * memory just after the boot0 sector. */ .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 .set _SECTOR_FIELD_OFF,-0xe # Offset to Sector field # in the fake partition .set _DATA_OFF,PRT_OFF+_SECTOR_FIELD_OFF # Offset to boot0 variables # from partition table .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. */ start: cld # String ops inc xorw %ax,%ax # Zero movw %ax,%es # Address movw %ax,%ds # data movw %ax,%ss # Set up movw $MEM_BIOS_LADDR,%sp # stack /* * Copy this code to the address it was linked for. * Base address after relocation is - 0x600. */ 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. */ movw %di,%bp # Address variables movb $0x8,%cl # Words to clear rep # Zero stosw # them /* * Set C:H:S to 0:0:1 and relocate to the new copy of * the code. Do not make assumptions with regard to * a relative-PC near jump capability. */ incb _SECTOR_FIELD_OFF(%di) # Sector number pushw $main # Jump to relocated code retw main: #if defined(SIO) && COMSPEED != 0 /* * Initialize the serial port. * bioscom preserves the drive number in DX. */ movw $COMSPEED,%ax # defined by Makefile callw bioscom #endif /* * 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 $0x20,_FLAGS(%bp) # Set number drive? jnz main.1 # Yes testb %dl,%dl # Drive number valid? js main.2 # Possibly (0x80 set) 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) */ movw $(partbl+0x4),%bx # Partition table (+4 - type) xorw %dx,%dx # Partition entry item number /* * Loop around on the partition table, printing values until * we pass a 256 (4x 64 byte partitions) 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 BDA_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: #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) #endif /* SIO */ 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 $ASCII_BEL,%al # Signal callw putchr # error /* * Get the keystroke. */ main.11: #ifndef SIO xorb %ah,%ah # BIOS: Get int $0x16 # keypress movb %ah,%al # Scan code #else movb $0x02,%ah # BIOS: Receive call bioscom #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 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. 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 lea _FAKE(%bp),%si # Partition for write movb (%si),%dl # Drive number movw %si,%bx # Partition for read cmpb $0x4,%al # F5 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 $0x40,_FLAGS(%bp) # No updates? jnz main.14 # Yes movw $start,%bx # Data to write movb $0x3,%ah # Write sector callw intx13 # to disk main.14: popw %si # Restore partition popf # Restore eflags /* * 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 movb _NXTDRV(%bp),%dl # Next drive subb $'0',%dl # number /* * load selected bootsector to the MEM_BIOS_LADDR location * in RAM. If it fails to read or isn't marked bootable, * treat it as a bad selection. * XXX what does %si carry? */ main.15: movw $MEM_BIOS_LADDR,%bx # Address for read movb $0x2,%ah # Read sector callw intx13 # from disk jc main.10 # If error cmpw $MAGIC,0x1fe(%bx) # Bootable? jne main.10 # No pushw %si # Save movw $crlf,%si # Leave some callw puts # space popw %si # Restore jmp *%bx # Invoke bootstrap /* * Display routines */ 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.. */ 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 #ifndef SIO putchr: pusha # Save movw $0x7,%bx # Page:attribute movb $0xe,%ah # BIOS: Display int $0x10 # character popa # Restore retw # To caller #else /* SIO */ putchr: movb $0x01,%ah # BIOS: Send bioscom: pusha # Save drive number xorw %dx,%dx # Use COM1 int $0x14 # Character popa # Restore drive number retw # To caller #endif /* * One-sector disk I/O routine * * Setup for both the packet and non-packet interfaces * then select one or the other. * * Don't trust the BIOS to keep registers intact across * the call, use pusha/popa. */ intx13: movb 0x1(%si),%dh # (nonpkt) head movw 0x2(%si),%cx # (nonpkt) cylinder:sector movb $0x1,%al # (nonpkt) Sector count pusha # save: do not trust the bios pushl $0x0 # (pkt) LBA address pushl 0x8(%si) # (pkt) pushw %es # (pkt) xfer buffer address pushw %bx # (pkt) pushw $1 # (pkt) Block count pushw $16 # (pkt) Packet size testb $0x80,_FLAGS(%bp) # Use packet interface? jz intx13.1 movw %sp,%si # Yes, set packet pointer decw %ax # Verify off orb $0x40,%ah # Set pkt mode in command intx13.1: int $0x13 # BIOS: Disk I/O # WARNING: RETAIN CARRY AFTER BIOS CALL movw %sp,%si lea 16(%si),%sp # cleanup the stack popa # Restore registers retw /* * 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. */ .byte 0x0, 0x5, 0xf /* * These values indicate bootable types we know the names of. */ .byte 0x1, 0x6, 0x7, 0xc, 0xe, 0x6c, 0x83, 0x9f .byte 0xa5, 0xa6, 0xa9 /* * 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-. # Windows .byte os_dos-. # Windows .byte os_dos-. # Windows .byte os_dfbsd-. # DragonFly (new) .byte os_linux-. # Linux .byte os_bsd-. # BSD/OS .byte os_dfbsd-. # DragonFly (old) / FreeBSD .byte os_bsd-. # OpenBSD .byte os_bsd-. # 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 "?"; .byte '?'|0x80 os_dos: .ascii "DO"; .byte 'S'|0x80 os_linux: .ascii "Linu"; .byte 'x'|0x80 os_dfbsd: .ascii "DF/F" os_bsd: .ascii "BS"; .byte 'D'|0x80 .org _DATA_OFF,0x90 .word B0MAGIC # Magic number /* * 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. */ 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