310 lines
6.7 KiB
ArmAsm
310 lines
6.7 KiB
ArmAsm
/*
|
|
* Copyright (C) 2010 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., 51 Franklin Street, Fifth Floor, Boston, MA
|
|
* 02110-1301, USA.
|
|
*
|
|
*/
|
|
|
|
FILE_LICENCE ( GPL2_OR_LATER )
|
|
|
|
.arch i386
|
|
|
|
/****************************************************************************
|
|
* test_a20_short, test_a20_long
|
|
*
|
|
* Check to see if A20 line is enabled
|
|
*
|
|
* Parameters:
|
|
* none
|
|
* Returns:
|
|
* CF set if A20 line is not enabled
|
|
* Corrupts:
|
|
* none
|
|
****************************************************************************
|
|
*/
|
|
#define TEST_A20_SHORT_MAX_RETRIES 0x20
|
|
#define TEST_A20_LONG_MAX_RETRIES 0x200000
|
|
.section ".text16.early", "awx", @progbits
|
|
.code16
|
|
test_a20_short:
|
|
pushl %ecx
|
|
movl $TEST_A20_SHORT_MAX_RETRIES, %ecx
|
|
jmp 1f
|
|
.size test_a20_short, . - test_a20_short
|
|
test_a20_long:
|
|
pushl %ecx
|
|
movl $TEST_A20_LONG_MAX_RETRIES, %ecx
|
|
1: pushw %ax
|
|
pushw %ds
|
|
pushw %es
|
|
|
|
/* Set up segment registers for access across the 1MB boundary */
|
|
xorw %ax, %ax
|
|
movw %ax, %ds
|
|
decw %ax
|
|
movw %ax, %es
|
|
|
|
2: /* Modify and check test pattern; succeed if we see a difference */
|
|
pushfw
|
|
cli
|
|
xchgw %ds:0, %cx
|
|
movw %es:0x10, %ax
|
|
xchgw %ds:0, %cx
|
|
popfw
|
|
cmpw %ax, %cx
|
|
clc
|
|
jnz 99f
|
|
|
|
/* Delay and retry */
|
|
outb %al, $0x80
|
|
addr32 loop 2b
|
|
stc
|
|
|
|
99: /* Restore registers and return */
|
|
popw %es
|
|
popw %ds
|
|
popw %ax
|
|
popl %ecx
|
|
ret
|
|
.size test_a20_long, . - test_a20_long
|
|
|
|
/****************************************************************************
|
|
* enable_a20_bios
|
|
*
|
|
* Try enabling A20 line via BIOS
|
|
*
|
|
* Parameters:
|
|
* none
|
|
* Returns:
|
|
* CF set if A20 line is not enabled
|
|
* Corrupts:
|
|
* none
|
|
****************************************************************************
|
|
*/
|
|
.section ".text16.early", "awx", @progbits
|
|
.code16
|
|
enable_a20_bios:
|
|
|
|
/* Preserve registers. Be very paranoid, since some BIOSes
|
|
* are reported to clobber %ebx
|
|
*/
|
|
pushal
|
|
|
|
/* Attempt INT 15,2401 */
|
|
movw $0x2401, %ax
|
|
int $0x15
|
|
jc 99f
|
|
|
|
/* Check that success was really successful */
|
|
call test_a20_short
|
|
|
|
99: /* Restore registers and return */
|
|
popal
|
|
ret
|
|
.size enable_a20_bios, . - enable_a20_bios
|
|
|
|
/****************************************************************************
|
|
* enable_a20_kbc
|
|
*
|
|
* Try enabling A20 line via keyboard controller
|
|
*
|
|
* Parameters:
|
|
* none
|
|
* Returns:
|
|
* CF set if A20 line is not enabled
|
|
* Corrupts:
|
|
* none
|
|
****************************************************************************
|
|
*/
|
|
#define KC_RDWR 0x60
|
|
#define KC_RDWR_SET_A20 0xdf
|
|
#define KC_CMD 0x64
|
|
#define KC_CMD_WOUT 0xd1
|
|
#define KC_CMD_NULL 0xff
|
|
#define KC_STATUS 0x64
|
|
#define KC_STATUS_OBUF_FULL 0x01
|
|
#define KC_STATUS_IBUF_FULL 0x02
|
|
#define KC_MAX_RETRIES 100000
|
|
.section ".text16.early", "awx", @progbits
|
|
.code16
|
|
enable_a20_kbc:
|
|
/* Preserve registers */
|
|
pushw %ax
|
|
|
|
/* Try keyboard controller */
|
|
call empty_kbc
|
|
movb $KC_CMD_WOUT, %al
|
|
outb %al, $KC_CMD
|
|
call empty_kbc
|
|
movb $KC_RDWR_SET_A20, %al
|
|
outb %al, $KC_RDWR
|
|
call empty_kbc
|
|
movb $KC_CMD_NULL, %al
|
|
outb %al, $KC_CMD
|
|
call empty_kbc
|
|
|
|
/* Check to see if it worked */
|
|
call test_a20_long
|
|
|
|
/* Restore registers and return */
|
|
popw %ax
|
|
ret
|
|
.size enable_a20_kbc, . - enable_a20_kbc
|
|
|
|
.section ".text16.early", "awx", @progbits
|
|
.code16
|
|
empty_kbc:
|
|
/* Preserve registers */
|
|
pushl %ecx
|
|
pushw %ax
|
|
|
|
/* Wait for KBC to become empty */
|
|
movl $KC_MAX_RETRIES, %ecx
|
|
1: outb %al, $0x80
|
|
inb $KC_STATUS, %al
|
|
testb $( KC_STATUS_OBUF_FULL | KC_STATUS_IBUF_FULL ), %al
|
|
jz 99f
|
|
testb $KC_STATUS_OBUF_FULL, %al
|
|
jz 2f
|
|
outb %al, $0x80
|
|
inb $KC_RDWR, %al
|
|
2: addr32 loop 1b
|
|
|
|
99: /* Restore registers and return */
|
|
popw %ax
|
|
popl %ecx
|
|
ret
|
|
.size empty_kbc, . - empty_kbc
|
|
|
|
/****************************************************************************
|
|
* enable_a20_fast
|
|
*
|
|
* Try enabling A20 line via "Fast Gate A20"
|
|
*
|
|
* Parameters:
|
|
* none
|
|
* Returns:
|
|
* CF set if A20 line is not enabled
|
|
* Corrupts:
|
|
* none
|
|
****************************************************************************
|
|
*/
|
|
#define SCP_A 0x92
|
|
.section ".text16.early", "awx", @progbits
|
|
.code16
|
|
enable_a20_fast:
|
|
/* Preserve registers */
|
|
pushw %ax
|
|
|
|
/* Try "Fast Gate A20" */
|
|
inb $SCP_A, %al
|
|
orb $0x02, %al
|
|
andb $~0x01, %al
|
|
outb %al, $SCP_A
|
|
|
|
/* Check to see if it worked */
|
|
call test_a20_long
|
|
|
|
/* Restore registers and return */
|
|
popw %ax
|
|
ret
|
|
.size enable_a20_fast, . - enable_a20_fast
|
|
|
|
/****************************************************************************
|
|
* enable_a20
|
|
*
|
|
* Try enabling A20 line via any available method
|
|
*
|
|
* Parameters:
|
|
* none
|
|
* Returns:
|
|
* CF set if A20 line is not enabled
|
|
* Corrupts:
|
|
* none
|
|
****************************************************************************
|
|
*/
|
|
#define ENABLE_A20_RETRIES 255
|
|
.section ".text16.early", "awx", @progbits
|
|
.code16
|
|
.globl enable_a20
|
|
enable_a20:
|
|
/* Preserve registers */
|
|
pushl %ecx
|
|
pushw %ax
|
|
|
|
/* Check to see if A20 is already enabled */
|
|
call test_a20_short
|
|
jnc 99f
|
|
|
|
/* Use known working method, if we have one */
|
|
movw %cs:enable_a20_method, %ax
|
|
testw %ax, %ax
|
|
jz 1f
|
|
call *%ax
|
|
jmp 99f
|
|
1:
|
|
/* Try all methods in turn until one works */
|
|
movl $ENABLE_A20_RETRIES, %ecx
|
|
2: movw $enable_a20_bios, %ax
|
|
movw %ax, %cs:enable_a20_method
|
|
call *%ax
|
|
jnc 99f
|
|
movw $enable_a20_kbc, %ax
|
|
movw %ax, %cs:enable_a20_method
|
|
call *%ax
|
|
jnc 99f
|
|
movw $enable_a20_fast, %ax
|
|
movw %ax, %cs:enable_a20_method
|
|
call *%ax
|
|
jnc 99f
|
|
addr32 loop 2b
|
|
/* Failure; exit with carry set */
|
|
movw $0, %cs:enable_a20_method
|
|
stc
|
|
|
|
99: /* Restore registers and return */
|
|
popw %ax
|
|
popl %ecx
|
|
ret
|
|
|
|
.section ".text16.early.data", "aw", @progbits
|
|
.align 2
|
|
enable_a20_method:
|
|
.word 0
|
|
.size enable_a20_method, . - enable_a20_method
|
|
|
|
/****************************************************************************
|
|
* access_highmem (real mode far call)
|
|
*
|
|
* Open up access to high memory with A20 enabled
|
|
*
|
|
* Parameters:
|
|
* none
|
|
* Returns:
|
|
* CF set if high memory could not be accessed
|
|
* Corrupts:
|
|
* none
|
|
****************************************************************************
|
|
*/
|
|
.section ".text16.early", "awx", @progbits
|
|
.code16
|
|
.globl access_highmem
|
|
access_highmem:
|
|
/* Enable A20 line */
|
|
call enable_a20
|
|
lret
|
|
.size access_highmem, . - access_highmem
|