331 lines
7.2 KiB
ArmAsm
331 lines
7.2 KiB
ArmAsm
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/* -----------------------------------------------------------------------
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*
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* Copyright 2007-2009 H. Peter Anvin - All Rights Reserved
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* Copyright 2009-2010 Intel Corporation; author: H. Peter Anvin
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*
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* Permission is hereby granted, free of charge, to any person
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* obtaining a copy of this software and associated documentation
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* files (the "Software"), to deal in the Software without
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* restriction, including without limitation the rights to use,
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* copy, modify, merge, publish, distribute, sublicense, and/or
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* sell copies of the Software, and to permit persons to whom
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* the Software is furnished to do so, subject to the following
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* conditions:
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*
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* The above copyright notice and this permission notice shall
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* be included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*
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* ----------------------------------------------------------------------- */
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#include <machine/asm.h>
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#include <sys/bootblock.h>
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#ifdef CTRL_80
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.macro ADJUST_DRIVE
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testb $0x04, BIOS_kbdflags
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jz 1f
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movb $0x80, %dl
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1:
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.endm
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#elif defined(FORCE_80)
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.macro ADJUST_DRIVE
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movb $0x80, %dl
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.endm
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#else
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.macro ADJUST_DRIVE
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.endm
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#endif
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.code16
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.text
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.globl bootsec
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stack = 0x7c00
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/* Partition table header here */
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phdr = stack /* Above the stack, overwritten by bootsect */
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/* Partition table sector here */
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/* To handle > 32K we need to play segment tricks... */
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psec = _phdr + 512
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/* Where we put DS:SI */
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dssi_out = start + 0x1be
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BIOS_kbdflags = 0x417
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BIOS_page = 0x462
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/* gas/ld has issues with doing this as absolute addresses... */
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.section ".bootsec", "a", @nobits
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.globl bootsec
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bootsec:
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.space 512
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.text
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.globl start
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start:
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cli
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xorw %ax, %ax
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movw %ax, %ds
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movw %ax, %ss
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movw $stack, %sp
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movw %sp, %si
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pushw %es /* 4(%bp) es:di -> $PnP header */
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pushw %di /* 2(%bp) */
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movw %ax, %es
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sti
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cld
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/* Copy down to 0:0x600 */
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movw $start, %di
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movw $(512/2), %cx
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rep; movsw
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ljmpw $0, $next
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next:
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ADJUST_DRIVE
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pushw %dx /* 0(%bp) = %dl -> drive number */
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/* Check to see if we have EBIOS */
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pushw %dx /* drive number */
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movb $0x41, %ah /* %al == 0 already */
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movw $0x55aa, %bx
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xorw %cx, %cx
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xorb %dh, %dh
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stc
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int $0x13
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jc 1f
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cmpw $0xaa55, %bx
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jne 1f
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shrw %cx /* Bit 0 = fixed disk subset */
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jnc 1f
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/* We have EBIOS; patch in the following code at
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read_sector_cbios: movb $0x42, %ah ; jmp read_common */
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movl $0xeb42b4+((read_common-read_sector_cbios-4) << 24), \
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(read_sector_cbios)
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1:
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popw %dx
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/* Get (C)HS geometry */
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movb $0x08, %ah
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int $0x13
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andw $0x3f, %cx /* Sector count */
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movw %sp, %bp /* %bp -> frame pointer: LEAVE UNCHANGED */
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pushw %cx /* -2(%bp) Save sectors on the stack */
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movzbw %dh, %ax /* dh = max head */
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incw %ax /* From 0-based max to count */
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mulw %cx /* Heads*sectors -> sectors per cylinder */
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/* Save sectors/cylinder on the stack */
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pushw %dx /* -4(%bp) High word */
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pushw %ax /* -6(%bp) Low word */
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/* Load partition table header */
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xorl %eax,%eax
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cltd
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incw %ax /* %edx:%eax = 1 */
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movw $phdr, %bx
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pushw %bx /* -8(%bp) phdr == bootsect */
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call read_sector
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/* Number of partition sectors */
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/* We assume the partition table is 32K or less, and that
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the sector size is 512. */
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/* Note: phdr == 6(%bp) */
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movw (80+6)(%bp),%cx /* NumberOfPartitionEntries */
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movw (84+6)(%bp),%ax /* SizeOfPartitionEntry */
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pushw %ax
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pushw %cx
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mulw %cx
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shrw $9,%ax
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xchgw %ax,%cx
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incw %cx
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/* Starting LBA of partition array */
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movl (72+6)(%bp),%eax
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movl (76+6)(%bp),%edx
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pushw %bx
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get_ptab:
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call read_sector
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call inc64
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loopw get_ptab
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/* Find the boot partition */
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xorw %si,%si /* Nothing found yet */
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popw %di /* Partition table in memory */
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popw %cx /* NumberOfPartitionEntries */
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popw %ax /* SizeOfPartitionEntry */
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find_part:
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/* If the PartitionTypeGUID is all zero, it's an empty slot */
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movl (%di),%edx
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orl 4(%di),%edx
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orl 8(%di),%edx
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orl 12(%di),%edx
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jz not_this
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testb $0x04,48(%di)
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jz not_this
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andw %si,%si
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jnz found_multiple
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movw %di,%si
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not_this:
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addw %ax,%di
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loopw find_part
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andw %si,%si
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jnz found_part
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missing_os:
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call error
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.ascii "Missing OS\r\n"
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found_multiple:
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call error
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.ascii "Multiple active partitions\r\n"
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found_part:
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xchgw %ax,%cx /* Set up %cx for rep movsb further down */
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movw $dssi_out,%di
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pushw %di
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/* 80 00 00 00 ee 00 00 00
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- bootable partition, type EFI (EE), no CHS information */
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xorl %eax,%eax
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movb $0x80,%al
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stosl
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movb $0xed,%al
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stosl
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movl 32(%si),%eax
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movl 36(%si),%edx
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call saturate_stosl /* Partition start */
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movl 40(%si),%eax
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movl 44(%si),%edx
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subl 32(%si),%eax
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sbbl 36(%si),%edx
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call inc64
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call saturate_stosl /* Partition length */
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movzwl %cx,%eax /* Length of GPT entry */
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stosl
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rep; movsb /* GPT entry follows MBR entry */
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popw %si
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/*
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* boot: invoke the actual bootstrap. %ds:%si points to the
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* partition information in memory. The top word on the stack
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* is phdr == 0x7c00 == the address of the boot sector.
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*/
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boot:
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movl (32+20)(%si),%eax
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movl (36+20)(%si),%edx
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popw %bx
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call read_sector
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cmpw $0xaa55, -2(%bx)
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jne missing_os /* Not a valid boot sector */
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movw %bp, %sp /* driveno == bootsec-6 */
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popw %dx /* dl -> drive number */
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popw %di /* es:di -> $PnP vector */
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popw %es
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movl $0x54504721,%eax /* !GPT magic number */
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cli
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jmpw *%sp /* %sp == bootsec */
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/*
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* Store the value in %eax to %di iff %edx == 0, otherwise store -1.
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* Returns the value that was actually written in %eax.
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*/
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saturate_stosl:
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andl %edx,%edx
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jz 1f
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orl $-1,%eax
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1: stosl
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ret
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/*
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* Increment %edx:%eax
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*/
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inc64:
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addl $1,%eax
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adcl $0,%edx
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ret
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/*
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* read_sector: read a single sector pointed to by %edx:%eax to
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* %es:%bx. CF is set on error. All registers saved.
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*/
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read_sector:
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pushal
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pushl %edx /* MSW of LBA */
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pushl %eax /* LSW of LBA */
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pushw %es /* Buffer segment */
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pushw %bx /* Buffer offset */
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pushw $1 /* Sector count */
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pushw $16 /* Size of packet */
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movw %sp, %si
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/* This chunk is skipped if we have ebios */
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/* Do not clobber %es:%bx or %edx:%eax before this chunk! */
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read_sector_cbios:
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divl -6(%bp) /* secpercyl */
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shlb $6, %ah
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movb %ah, %cl
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movb %al, %ch
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xchgw %dx, %ax
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divb -2(%bp) /* sectors */
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movb %al, %dh
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orb %ah, %cl
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incw %cx /* Sectors are 1-based */
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movw $0x0201, %ax
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read_common:
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movb (%bp), %dl /* driveno */
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int $0x13
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leaw 16(%si), %sp /* Drop DAPA */
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popal
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jc disk_error
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addb $2, %bh /* bx += 512: point to the next buffer */
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ret
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disk_error:
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call error
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.ascii "Disk error on boot\r\n"
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/*
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* Print error messages. This is invoked with "call", with the
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* error message at the return address.
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*/
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error:
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popw %si
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2:
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lodsb
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movb $0x0e, %ah
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movb (BIOS_page), %bh
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movb $0x07, %bl
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int $0x10 /* May destroy %bp */
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cmpb $10, %al /* Newline? */
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jne 2b
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int $0x18 /* Boot failure */
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die:
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hlt
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jmp die
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mbr_space = end - .
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. = MBR_DSN_OFFSET
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end:
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