/*- * Copyright (c) 2007 Yahoo!, Inc. * All rights reserved. * Written by: John Baldwin <jhb@FreeBSD.org> * * 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 author nor the names of any co-contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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. * * Partly from: src/sys/boot/i386/boot2/boot1.S 1.31 */ /* Memory Locations */ .set MEM_REL,0x700 # Relocation address .set MEM_ARG,0x900 # Arguments .set MEM_ORG,0x7c00 # Origin .set MEM_BUF,0x8cec # Load area .set MEM_BTX,0x9000 # BTX start .set MEM_JMP,0x9010 # BTX entry point .set MEM_USR,0xa000 # Client start .set BDA_BOOT,0x472 # Boot howto flag /* Misc. Constants */ .set SIZ_PAG,0x1000 # Page size .set SIZ_SEC,0x200 # Sector size .set COPY_BLKS,0x8 # Number of blocks # to copy for boot2 (<= 15) .set COPY_BLK_SZ,0x8000 # Copy in 32k blocks; must be # a multiple of 16 bytes .globl start .code16 /* * Copy BTX and boot2 to the right locations and start it all up. */ /* * Setup the segment registers to flat addressing (segment 0) and setup the * stack to end just below the start of our code. */ start: xor %cx,%cx # Zero mov %cx,%es # Address mov %cx,%ds # data mov %cx,%ss # Set up mov $start,%sp # stack /* * BTX is right after us at 'end'. We read the length of BTX out of * its header to find boot2. We need to copy boot2 to MEM_USR and BTX * to MEM_BTX. Since those might overlap, we have to copy boot2 * backwards first and then copy BTX. We aren't sure exactly how long * boot2 is, but it's currently under 256kB so we'll copy 8 blocks of 32kB * each; this can be adjusted via COPY_BLK and COPY_BLK_SZ above. */ mov $end,%bx # BTX mov 0xa(%bx),%si # Get BTX length and set add %bx,%si # %si to start of boot2 dec %si # Set %ds:%si to point at the mov %si,%ax # last byte we want to copy shr $4,%ax # from boot2, with %si made as add $(COPY_BLKS*COPY_BLK_SZ/16),%ax # small as possible. and $0xf,%si # mov %ax,%ds # mov $MEM_USR/16,%ax # Set %es:(-1) to point at add $(COPY_BLKS*COPY_BLK_SZ/16),%ax # the last byte we mov %ax,%es # want to copy boot2 into. mov $COPY_BLKS,%bx # Copy COPY_BLKS 32k blocks copyloop: add $COPY_BLK_SZ,%si # Adjust %ds:%si to point at mov %ds,%ax # the end of the next 32k to sub $COPY_BLK_SZ/16,%ax # copy from boot2 mov %ax,%ds mov $COPY_BLK_SZ-1,%di # Adjust %es:%di to point at mov %es,%ax # the end of the next 32k into sub $COPY_BLK_SZ/16,%ax # which we want boot2 copied mov %ax,%es mov $COPY_BLK_SZ,%cx # Copy 32k std rep movsb dec %bx jnz copyloop mov %cx,%ds # Reset %ds and %es mov %cx,%es mov $end,%bx # BTX mov 0xa(%bx),%cx # Get BTX length and set mov %bx,%si # %si to end of BTX mov $MEM_BTX,%di # %di -> end of BTX at add %cx,%si # MEM_BTX add %cx,%di dec %si dec %di rep movsb # Move BTX cld # String ops inc /* * Enable A20 so we can access memory above 1 meg. * Use the zero-valued %cx as a timeout for embedded hardware which do not * have a keyboard controller. */ seta20: cli # Disable interrupts seta20.1: dec %cx # Timeout? jz seta20.3 # Yes inb $0x64,%al # Get status testb $0x2,%al # Busy? jnz seta20.1 # Yes movb $0xd1,%al # Command: Write outb %al,$0x64 # output port seta20.2: inb $0x64,%al # Get status testb $0x2,%al # Busy? jnz seta20.2 # Yes movb $0xdf,%al # Enable outb %al,$0x60 # A20 seta20.3: sti # Enable interrupts /* * Save drive number from BIOS so boot2 can see it and start BTX. */ movb %dl,MEM_ARG jmp start+MEM_JMP-MEM_ORG # Start BTX end:
