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Diffstat (limited to 'qemu/roms/ipxe/src/arch/i386/transitions/liba20.S')
| -rw-r--r-- | qemu/roms/ipxe/src/arch/i386/transitions/liba20.S | 309 |
1 files changed, 309 insertions, 0 deletions
diff --git a/qemu/roms/ipxe/src/arch/i386/transitions/liba20.S b/qemu/roms/ipxe/src/arch/i386/transitions/liba20.S new file mode 100644 index 000000000..684697525 --- /dev/null +++ b/qemu/roms/ipxe/src/arch/i386/transitions/liba20.S @@ -0,0 +1,309 @@ +/* + * 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 |