78dd963c1f
skip past an empty region, otherwise we end up generating an infinitely long e820 map. (Yes, there *are* real systems that provide e820 maps with a zero-length region at the end...)
467 lines
11 KiB
ArmAsm
467 lines
11 KiB
ArmAsm
/*
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* Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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.text
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.arch i386
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.section ".text16", "ax", @progbits
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.section ".data16", "aw", @progbits
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.section ".text16.data", "aw", @progbits
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.code16
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#define SMAP 0x534d4150
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/****************************************************************************
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* Check for overlap
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*
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* Parameters:
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* %edx:%eax Region start
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* %ecx:%ebx Region end
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* %si Pointer to hidden region descriptor
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* Returns:
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* CF set Region overlaps
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* CF clear No overlap
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****************************************************************************
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*/
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.section ".text16"
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check_overlap:
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/* If start >= hidden_end, there is no overlap. */
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testl %edx, %edx
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jnz no_overlap
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cmpl 4(%si), %eax
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jae no_overlap
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/* If end <= hidden_start, there is no overlap; equivalently,
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* if end > hidden_start, there is overlap.
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*/
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testl %ecx, %ecx
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jnz overlap
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cmpl 0(%si), %ebx
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ja overlap
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no_overlap:
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clc
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ret
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overlap:
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stc
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ret
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.size check_overlap, . - check_overlap
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/****************************************************************************
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* Check for overflow/underflow
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*
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* Parameters:
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* %edx:%eax Region start
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* %ecx:%ebx Region end
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* Returns:
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* CF set start < end
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* CF clear start >= end
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****************************************************************************
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*/
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.section ".text16"
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check_overflow:
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pushl %ecx
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pushl %ebx
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subl %eax, %ebx
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sbbl %edx, %ecx
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popl %ebx
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popl %ecx
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ret
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.size check_overflow, . - check_overflow
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/****************************************************************************
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* Truncate towards start of region
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*
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* Parameters:
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* %edx:%eax Region start
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* %ecx:%ebx Region end
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* %si Pointer to hidden region descriptor
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* Returns:
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* %edx:%eax Modified region start
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* %ecx:%ebx Modified region end
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* CF set Region was truncated
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* CF clear Region was not truncated
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****************************************************************************
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*/
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.section ".text16"
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truncate_to_start:
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/* If overlaps, set region end = hidden region start */
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call check_overlap
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jnc 99f
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movl 0(%si), %ebx
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xorl %ecx, %ecx
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/* If region end < region start, set region end = region start */
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call check_overflow
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jnc 1f
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movl %eax, %ebx
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movl %edx, %ecx
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1: stc
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99: ret
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.size truncate_to_start, . - truncate_to_start
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/****************************************************************************
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* Truncate towards end of region
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*
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* Parameters:
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* %edx:%eax Region start
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* %ecx:%ebx Region end
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* %si Pointer to hidden region descriptor
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* Returns:
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* %edx:%eax Modified region start
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* %ecx:%ebx Modified region end
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* CF set Region was truncated
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* CF clear Region was not truncated
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****************************************************************************
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*/
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.section ".text16"
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truncate_to_end:
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/* If overlaps, set region start = hidden region end */
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call check_overlap
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jnc 99f
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movl 4(%si), %eax
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xorl %edx, %edx
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/* If region start > region end, set region start = region end */
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call check_overflow
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jnc 1f
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movl %ebx, %eax
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movl %ecx, %edx
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1: stc
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99: ret
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.size truncate_to_end, . - truncate_to_end
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/****************************************************************************
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* Truncate region
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*
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* Parameters:
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* %edx:%eax Region start
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* %ecx:%ebx Region length (*not* region end)
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* %bp truncate_to_start or truncate_to_end
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* Returns:
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* %edx:%eax Modified region start
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* %ecx:%ebx Modified region length
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* CF set Region was truncated
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* CF clear Region was not truncated
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****************************************************************************
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*/
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.section ".text16"
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truncate:
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pushw %si
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pushfw
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/* Convert (start,len) to (start,end) */
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addl %eax, %ebx
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adcl %edx, %ecx
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/* Hide all hidden regions, truncating as directed */
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movw $hidden_regions, %si
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1: call *%bp
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jnc 2f
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popfw /* If CF was set, set stored CF in flags word on stack */
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stc
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pushfw
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2: addw $8, %si
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cmpl $0, 0(%si)
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jne 1b
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/* Convert modified (start,end) back to (start,len) */
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subl %eax, %ebx
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sbbl %edx, %ecx
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popfw
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popw %si
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ret
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.size truncate, . - truncate
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/****************************************************************************
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* Patch "memory above 1MB" figure
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*
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* Parameters:
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* %ax Memory above 1MB, in 1kB blocks
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* Returns:
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* %ax Modified memory above 1M in 1kB blocks
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* CF set Region was truncated
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* CF clear Region was not truncated
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****************************************************************************
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*/
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.section ".text16"
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patch_1m:
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pushal
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/* Convert to (start,len) format and call truncate */
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movw $truncate_to_start, %bp
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xorl %ecx, %ecx
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movzwl %ax, %ebx
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shll $10, %ebx
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xorl %edx, %edx
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movl $0x100000, %eax
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call truncate
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/* Convert back to "memory above 1MB" format and return via %ax */
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pushfw
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shrl $10, %ebx
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popfw
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movw %sp, %bp
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movw %bx, 28(%bp)
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popal
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ret
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.size patch_1m, . - patch_1m
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/****************************************************************************
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* Patch "memory above 16MB" figure
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*
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* Parameters:
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* %bx Memory above 16MB, in 64kB blocks
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* Returns:
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* %bx Modified memory above 16M in 64kB blocks
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* CF set Region was truncated
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* CF clear Region was not truncated
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****************************************************************************
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*/
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.section ".text16"
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patch_16m:
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pushal
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/* Convert to (start,len) format and call truncate */
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movw $truncate_to_start, %bp
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xorl %ecx, %ecx
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shll $16, %ebx
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xorl %edx, %edx
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movl $0x1000000, %eax
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call truncate
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/* Convert back to "memory above 16MB" format and return via %bx */
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pushfw
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shrl $16, %ebx
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popfw
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movw %sp, %bp
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movw %bx, 16(%bp)
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popal
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ret
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.size patch_16m, . - patch_16m
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/****************************************************************************
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* Patch "memory between 1MB and 16MB" and "memory above 16MB" figures
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*
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* Parameters:
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* %ax Memory between 1MB and 16MB, in 1kB blocks
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* %bx Memory above 16MB, in 64kB blocks
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* Returns:
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* %ax Modified memory between 1MB and 16MB, in 1kB blocks
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* %bx Modified memory above 16MB, in 64kB blocks
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* CF set Region was truncated
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* CF clear Region was not truncated
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****************************************************************************
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*/
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.section ".text16"
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patch_1m_16m:
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call patch_1m
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jc 1f
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call patch_16m
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ret
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1: /* 1m region was truncated; kill the 16m region */
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xorw %bx, %bx
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ret
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.size patch_1m_16m, . - patch_1m_16m
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/****************************************************************************
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* Patch E820 memory map entry
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*
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* Parameters:
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* %es:di Pointer to E820 memory map descriptor
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* %bp truncate_to_start or truncate_to_end
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* Returns:
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* %es:di Pointer to now-modified E820 memory map descriptor
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* CF set Region was truncated
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* CF clear Region was not truncated
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****************************************************************************
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*/
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.section ".text16"
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patch_e820:
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pushal
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movl %es:0(%di), %eax
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movl %es:4(%di), %edx
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movl %es:8(%di), %ebx
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movl %es:12(%di), %ecx
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call truncate
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movl %eax, %es:0(%di)
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movl %edx, %es:4(%di)
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movl %ebx, %es:8(%di)
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movl %ecx, %es:12(%di)
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popal
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ret
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.size patch_e820, . - patch_e820
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/****************************************************************************
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* Split E820 memory map entry if necessary
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*
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* Parameters:
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* As for INT 15,e820
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* Returns:
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* As for INT 15,e820
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*
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* Calls the underlying INT 15,e820 and returns a modified memory map.
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* Regions will be split around any hidden regions.
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****************************************************************************
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*/
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.section ".text16"
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split_e820:
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pushw %si
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pushw %bp
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/* Caller's %bx => %si, real %ebx to %ebx, call previous handler */
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pushfw
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movw %bx, %si
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testl %ebx, %ebx
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jnz 1f
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movl %ebx, %cs:real_ebx
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1: movl %cs:real_ebx, %ebx
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lcall *%cs:int15_vector
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pushfw
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/* Edit result */
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pushw %ds
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pushw %cs:rm_ds
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popw %ds
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movw $truncate_to_start, %bp
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incw %si
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jns 2f
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movw $truncate_to_end, %bp
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2: call patch_e820
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jnc 3f
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xorw $0x8000, %si
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3: testw %si, %si
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js 4f
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movl %ebx, %cs:real_ebx
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testl %ebx, %ebx
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jz 5f
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4: movw %si, %bx
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5: popw %ds
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/* Restore flags returned by previous handler and return */
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popfw
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popw %bp
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popw %si
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ret
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.size split_e820, . - split_e820
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.section ".text16.data"
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real_ebx:
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.long 0
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.size real_ebx, . - real_ebx
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/****************************************************************************
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* INT 15,e820 handler
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****************************************************************************
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*/
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.section ".text16"
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int15_e820:
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pushl %eax
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pushl %ecx
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pushl %edx
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call split_e820
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pushfw
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/* Skip empty region checking if we've reached the end of the
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* map or hit an error, to avoid a potential endless loop.
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*/
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jc 1f
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testl %ebx, %ebx
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jz 1f
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/* Check for an empty region */
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pushl %eax
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movl %es:8(%di), %eax
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orl %es:12(%di), %eax
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popl %eax
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jnz 1f
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/* Strip empty regions out of the returned map */
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popfw
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popl %edx
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popl %ecx
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popl %eax
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jmp int15_e820
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/* Restore flags from original INT 15,e820 call and return */
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1: popfw
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addr32 leal 12(%esp), %esp /* avoid changing flags */
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lret $2
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.size int15_e820, . - int15_e820
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/****************************************************************************
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* INT 15,e801 handler
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****************************************************************************
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*/
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.section ".text16"
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int15_e801:
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/* Call previous handler */
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pushfw
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lcall *%cs:int15_vector
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pushfw
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/* Edit result */
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pushw %ds
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pushw %cs:rm_ds
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popw %ds
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call patch_1m_16m
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xchgw %ax, %cx
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xchgw %bx, %dx
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call patch_1m_16m
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xchgw %ax, %cx
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xchgw %bx, %dx
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popw %ds
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/* Restore flags returned by previous handler and return */
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popfw
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lret $2
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.size int15_e801, . - int15_e801
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/****************************************************************************
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* INT 15,88 handler
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****************************************************************************
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*/
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.section ".text16"
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int15_88:
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/* Call previous handler */
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pushfw
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lcall *%cs:int15_vector
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pushfw
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/* Edit result */
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pushw %ds
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pushw %cs:rm_ds
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popw %ds
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call patch_1m
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popw %ds
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/* Restore flags returned by previous handler and return */
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popfw
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lret $2
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.size int15_88, . - int15_88
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/****************************************************************************
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* INT 15 handler
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****************************************************************************
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*/
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.section ".text16"
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.globl int15
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int15:
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/* See if we want to intercept this call */
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pushfw
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cmpw $0xe820, %ax
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jne 1f
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cmpl $SMAP, %edx
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jne 1f
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popfw
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jmp int15_e820
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1: cmpw $0xe801, %ax
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jne 2f
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popfw
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jmp int15_e801
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2: cmpb $0x88, %ah
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jne 3f
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popfw
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jmp int15_88
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3: popfw
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ljmp *%cs:int15_vector
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.size int15, . - int15
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.section ".text16.data"
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.globl int15_vector
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int15_vector:
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.long 0
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.size int15_vector, . - int15_vector
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