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/* Some CPUs are picky about GDT alignment... */ 93.align 16 94gdt: 95 /* 96 * The GDT table ... 97 * 98 * Selector Type 99 * 0x00 NULL 100 * 0x08 Unused 101 * 0x10 32bit code 102 * 0x18 32bit data/stack 103 */ 104 /* The NULL Desciptor - Mandatory */ 105 .word 0x0000 /* limit_low */ 106 .word 0x0000 /* base_low */ 107 .byte 0x00 /* base_middle */ 108 .byte 0x00 /* access */ 109 .byte 0x00 /* flags + limit_high */ 110 .byte 0x00 /* base_high */ 111 112 /* Unused Desciptor - (matches Linux) */ 113 .word 0x0000 /* limit_low */ 114 .word 0x0000 /* base_low */ 115 .byte 0x00 /* base_middle */ 116 .byte 0x00 /* access */ 117 .byte 0x00 /* flags + limit_high */ 118 .byte 0x00 /* base_high */ 119 120 /* 121 * The Code Segment Descriptor: 122 * - Base = 0x00000000 123 * - Size = 4GB 124 * - Access = Present, Ring 0, Exec (Code), Readable 125 * - Flags = 4kB Granularity, 32-bit 126 */ 127 .word 0xffff /* limit_low */ 128 .word 0x0000 /* base_low */ 129 .byte 0x00 /* base_middle */ 130 .byte 0x9b /* access */ 131 .byte 0xcf /* flags + limit_high */ 132 .byte 0x00 /* base_high */ 133 134 /* 135 * The Data Segment Descriptor: 136 * - Base = 0x00000000 137 * - Size = 4GB 138 * - Access = Present, Ring 0, Non-Exec (Data), Writable 139 * - Flags = 4kB Granularity, 32-bit 140 */ 141 .word 0xffff /* limit_low */ 142 .word 0x0000 /* base_low */ 143 .byte 0x00 /* base_middle */ 144 .byte 0x93 /* access */ 145 .byte 0xcf /* flags + limit_high */ 146 .byte 0x00 /* base_high */ 147