1/* 2 * U-boot - x86 Startup Code 3 * 4 * (C) Copyright 2008-2011 5 * Graeme Russ, <graeme.russ@gmail.com> 6 * 7 * (C) Copyright 2002,2003 8 * Daniel Engström, Omicron Ceti AB, <daniel@omicron.se> 9 * 10 * See file CREDITS for list of people who contributed to this 11 * project. 12 * 13 * This program is free software; you can redistribute it and/or 14 * modify it under the terms of the GNU General Public License as 15 * published by the Free Software Foundation; either version 2 of 16 * the License, or (at your option) any later version. 17 * 18 * This program is distributed in the hope that it will be useful, 19 * but WITHOUT ANY WARRANTY; without even the implied warranty of 20 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 21 * GNU General Public License for more details. 22 * 23 * You should have received a copy of the GNU General Public License 24 * along with this program; if not, write to the Free Software 25 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, 26 * MA 02111-1307 USA 27 */ 28 29#include <asm/global_data.h> 30#include <asm/processor-flags.h> 31 32#define BOOT_SEG 0xffff0000 /* linear segment of boot code */ 33#define a32 .byte 0x67; 34#define o32 .byte 0x66; 35 36.section .start16, "ax" 37.code16 38.globl start16 39start16: 40 /* Set the Cold Boot / Hard Reset flag */ 41 movl $GD_FLG_COLD_BOOT, %ebx 42 43 /* 44 * First we let the BSP do some early initialization 45 * this code have to map the flash to its final position 46 */ 47 jmp board_init16 48.globl board_init16_ret 49board_init16_ret: 50 51 /* Turn of cache (this might require a 486-class CPU) */ 52 movl %cr0, %eax 53 orl $(X86_CR0_NW | X86_CR0_CD), %eax 54 movl %eax, %cr0 55 wbinvd 56 57 /* load the temporary Global Descriptor Table */ 58o32 cs lidt idt_ptr 59o32 cs lgdt gdt_ptr 60 61 /* Now, we enter protected mode */ 62 movl %cr0, %eax 63 orl $X86_CR0_PE, %eax 64 movl %eax, %cr0 65 66 /* Flush the prefetch queue */ 67 jmp ff 68ff: 69 /* Finally jump to the 32bit initialization code */ 70 movw $code32start, %ax 71 movw %ax, %bp 72o32 cs ljmp *(%bp) 73 74 /* 48-bit far pointer */ 75code32start: 76 .long _start /* offset */ 77 .word 0x10 /* segment */ 78 79idt_ptr: 80 .word 0 /* limit */ 81 .long 0 /* base */ 82 83/* 84 * The following Global Descriptor Table is just enough to get us into 85 * 'Flat Protected Mode' - It will be discarded as soon as the final 86 * GDT is setup in a safe location in RAM 87 */ 88gdt_ptr: 89 .word 0x20 /* limit (32 bytes = 4 GDT entries) */ 90 .long BOOT_SEG + gdt /* base */ 91 92 /* The GDT table ... 93 * 94 * Selector Type 95 * 0x00 NULL 96 * 0x08 Unused 97 * 0x10 32bit code 98 * 0x18 32bit data/stack 99 */ 100 101gdt: 102 .word 0, 0, 0, 0 /* NULL */ 103 .word 0, 0, 0, 0 /* unused */ 104 105 .word 0xFFFF /* 4Gb - (0x100000*0x1000 = 4Gb) */ 106 .word 0 /* base address = 0 */ 107 .word 0x9B00 /* code read/exec */ 108 .word 0x00CF /* granularity = 4096, 386 (+5th nibble of limit) */ 109 110 .word 0xFFFF /* 4Gb - (0x100000*0x1000 = 4Gb) */ 111 .word 0x0 /* base address = 0 */ 112 .word 0x9300 /* data read/write */ 113 .word 0x00CF /* granularity = 4096, 386 (+5th nibble of limit) */ 114