/* * U-boot - i386 Startup Code * * Copyright (c) 2002, 2003 Omicron Ceti AB, Daniel Engström * * 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 $0x60000000,%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) */