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/*
* U-boot - i386 Startup Code
*
* Copyright (c) 2002 Omicron Ceti AB, Daniel Engström <denaiel@omicron.se>
*
* See file CREDITS for list of people who contributed to this
* project.
*
* 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 (at your option) 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., 59 Temple Place, Suite 330, Boston,
* MA 02111-1307 USA
*/
#define BOOT_SEG 0xffff0000 /* linear segment of boot code */
#define a32 .byte 0x67;
#define o32 .byte 0x66;
.section .start16, "ax"
.code16
.globl start16
start16:
/* First we let the BSP do some early initialization
* this code have to map the flash to its final position
*/
mov $board_init16_ret, %bp
jmp board_init16
board_init16_ret:
/* Turn of cache (this might require a 486-class CPU) */
movl %cr0, %eax
orl $060000000,%eax
movl %eax, %cr0
wbinvd
/* load the descriptor tables */
o32 cs lidt idt_ptr
o32 cs lgdt gdt_ptr
/* Now, we enter protected mode */
movl %cr0, %eax
orl $1,%eax
movl %eax, %cr0
/* Flush the prefetch queue */
jmp ff
ff:
/* Finally jump to the 32bit initialization code */
movw $code32start, %ax
movw %ax,%bp
o32 cs ljmp *(%bp)
/* 48-bit far pointer */
code32start:
.long _start /* offset */
.word 0x10 /* segment */
idt_ptr:
.word 0 /* limit */
.long 0 /* base */
gdt_ptr:
.word 0x30 /* limit (48 bytes = 6 GDT entries) */
.long BOOT_SEG + gdt /* base */
/* The GDT table ...
*
* Selector Type
* 0x00 NULL
* 0x08 Unused
* 0x10 32bit code
* 0x18 32bit data/stack
* 0x20 16bit code
* 0x28 16bit data/stack
*/
gdt:
.word 0, 0, 0, 0 /* NULL */
.word 0, 0, 0, 0 /* unused */
.word 0xFFFF /* 4Gb - (0x100000*0x1000 = 4Gb) */
.word 0 /* base address = 0 */
.word 0x9B00 /* code read/exec */
.word 0x00CF /* granularity = 4096, 386 (+5th nibble of limit) */
.word 0xFFFF /* 4Gb - (0x100000*0x1000 = 4Gb) */
.word 0x0 /* base address = 0 */
.word 0x9300 /* data read/write */
.word 0x00CF /* granularity = 4096, 386 (+5th nibble of limit) */
.word 0xFFFF /* 64kb */
.word 0 /* base address = 0 */
.word 0x9b00 /* data read/write */
.word 0x0010 /* granularity = 1 (+5th nibble of limit) */
.word 0xFFFF /* 64kb */
.word 0 /* base address = 0 */
.word 0x9300 /* data read/write */
.word 0x0010 /* granularity = 1 (+5th nibble of limit) */
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