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