gptldr.S revision 267654
1341825Sdim/*- 2277325Sdim * Copyright (c) 2007 Yahoo!, Inc. 3353358Sdim * All rights reserved. 4353358Sdim * Written by: John Baldwin <jhb@FreeBSD.org> 5353358Sdim * 6277325Sdim * Redistribution and use in source and binary forms, with or without 7277325Sdim * modification, are permitted provided that the following conditions 8277325Sdim * are met: 9277325Sdim * 1. Redistributions of source code must retain the above copyright 10277325Sdim * notice, this list of conditions and the following disclaimer. 11277325Sdim * 2. Redistributions in binary form must reproduce the above copyright 12341825Sdim * notice, this list of conditions and the following disclaimer in the 13277325Sdim * documentation and/or other materials provided with the distribution. 14353358Sdim * 3. Neither the name of the author nor the names of any co-contributors 15288943Sdim * may be used to endorse or promote products derived from this software 16277325Sdim * without specific prior written permission. 17277325Sdim * 18277325Sdim * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 19353358Sdim * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20353358Sdim * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21353358Sdim * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 22353358Sdim * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23353358Sdim * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24353358Sdim * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25353358Sdim * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26353358Sdim * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27288943Sdim * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28288943Sdim * SUCH DAMAGE. 29288943Sdim * 30288943Sdim * $FreeBSD: releng/9.3/sys/boot/i386/gptboot/gptldr.S 173957 2007-11-26 21:29:59Z jhb $ 31353358Sdim * 32288943Sdim * Partly from: src/sys/boot/i386/boot2/boot1.S 1.31 33353358Sdim */ 34288943Sdim 35277325Sdim/* Memory Locations */ 36277325Sdim .set MEM_REL,0x700 # Relocation address 37288943Sdim .set MEM_ARG,0x900 # Arguments 38288943Sdim .set MEM_ORG,0x7c00 # Origin 39288943Sdim .set MEM_BUF,0x8cec # Load area 40288943Sdim .set MEM_BTX,0x9000 # BTX start 41288943Sdim .set MEM_JMP,0x9010 # BTX entry point 42288943Sdim .set MEM_USR,0xa000 # Client start 43288943Sdim .set BDA_BOOT,0x472 # Boot howto flag 44277325Sdim 45353358Sdim/* Misc. Constants */ 46353358Sdim .set SIZ_PAG,0x1000 # Page size 47353358Sdim .set SIZ_SEC,0x200 # Sector size 48353358Sdim 49353358Sdim .globl start 50353358Sdim .code16 51353358Sdim 52353358Sdim/* 53353358Sdim * Copy BTX and boot2 to the right locations and start it all up. 54353358Sdim */ 55 56/* 57 * Setup the segment registers to flat addressing (segment 0) and setup the 58 * stack to end just below the start of our code. 59 */ 60start: xor %cx,%cx # Zero 61 mov %cx,%es # Address 62 mov %cx,%ds # data 63 mov %cx,%ss # Set up 64 mov $start,%sp # stack 65 66/* 67 * BTX is right after us at 'end'. We read the length of BTX out of 68 * its header to find boot2. We need to copy boot2 to MEM_USR and BTX 69 * to MEM_BTX. Since those might overlap, we have to copy boot2 70 * backwards first and then copy BTX. We aren't sure exactly how long 71 * boot2 is, but we assume it can't be longer than 64k, so we just always 72 * copy 64k. 73 */ 74 mov $end,%bx # BTX 75 mov 0xa(%bx),%si # Get BTX length and set 76 add %bx,%si # %si to start of boot2 77 mov %si,%ax # Align %ds:%si on a 78 shr $4,%ax # paragraph boundary 79 and $0xf,%si # with the smallest 80 mov %ax,%ds # possible %si 81 add $(64 * 1024 - 16),%si 82 mov $MEM_USR/16,%ax # Point %es:%di at end of 83 mov $(64 * 1024 - 16),%di # largest boot2 range 84 mov %ax,%es 85 std 86 mov %di,%cx # Copy 64k - paragraph + 1 87 inc %cx # bytes 88 rep movsb 89 mov %cx,%ds # Reset %ds and %es 90 mov %cx,%es 91 mov 0xa(%bx),%cx # Get BTX length and set 92 mov %bx,%si # %si to end of BTX 93 mov $MEM_BTX,%di # %di -> end of BTX at 94 add %cx,%si # MEM_BTX 95 add %cx,%di 96 dec %si 97 dec %di 98 rep movsb # Move BTX 99 cld # String ops inc 100/* 101 * Enable A20 so we can access memory above 1 meg. 102 * Use the zero-valued %cx as a timeout for embedded hardware which do not 103 * have a keyboard controller. 104 */ 105seta20: cli # Disable interrupts 106seta20.1: dec %cx # Timeout? 107 jz seta20.3 # Yes 108 inb $0x64,%al # Get status 109 testb $0x2,%al # Busy? 110 jnz seta20.1 # Yes 111 movb $0xd1,%al # Command: Write 112 outb %al,$0x64 # output port 113seta20.2: inb $0x64,%al # Get status 114 testb $0x2,%al # Busy? 115 jnz seta20.2 # Yes 116 movb $0xdf,%al # Enable 117 outb %al,$0x60 # A20 118seta20.3: sti # Enable interrupts 119 120/* 121 * Save drive number from BIOS so boot2 can see it and start BTX. 122 */ 123 movb %dl,MEM_ARG 124 jmp MEM_JMP # Start BTX 125end: 126