diff options
Diffstat (limited to 'stand/i386/gptboot/gptldr.S')
| -rw-r--r-- | stand/i386/gptboot/gptldr.S | 142 |
1 files changed, 142 insertions, 0 deletions
diff --git a/stand/i386/gptboot/gptldr.S b/stand/i386/gptboot/gptldr.S new file mode 100644 index 0000000..088122f --- /dev/null +++ b/stand/i386/gptboot/gptldr.S @@ -0,0 +1,142 @@ +/*- + * 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. + * + * $FreeBSD$ + * + * 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 + .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 128kB so we'll copy 4 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 MEM_JMP # Start BTX +end: |
