1/* 2 * Multiboot Option ROM 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License as published by 6 * the Free Software Foundation; either version 2 of the License, or 7 * (at your option) any later version. 8 * 9 * This program is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 * GNU General Public License for more details. 13 * 14 * You should have received a copy of the GNU General Public License 15 * along with this program; if not, see <http://www.gnu.org/licenses/>. 16 * 17 * Copyright Novell Inc, 2009 18 * Authors: Alexander Graf <agraf@suse.de> 19 */ 20 21#include "optionrom.h" 22 23#define BOOT_ROM_PRODUCT "multiboot loader" 24 25#define MULTIBOOT_MAGIC 0x2badb002 26 27#define GS_PROT_JUMP 0 28#define GS_GDT_DESC 6 29 30 31BOOT_ROM_START 32 33run_multiboot: 34 35 cli 36 cld 37 38 mov %cs, %eax 39 shl $0x4, %eax 40 41 /* set up a long jump descriptor that is PC relative */ 42 43 /* move stack memory to %gs */ 44 mov %ss, %ecx 45 shl $0x4, %ecx 46 mov %esp, %ebx 47 add %ebx, %ecx 48 sub $0x20, %ecx 49 sub $0x30, %esp 50 shr $0x4, %ecx 51 mov %cx, %gs 52 53 /* now push the indirect jump descriptor there */ 54 mov (prot_jump), %ebx 55 add %eax, %ebx 56 movl %ebx, %gs:GS_PROT_JUMP 57 mov $8, %bx 58 movw %bx, %gs:GS_PROT_JUMP + 4 59 60 /* fix the gdt descriptor to be PC relative */ 61 movw (gdt_desc), %bx 62 movw %bx, %gs:GS_GDT_DESC 63 movl (gdt_desc+2), %ebx 64 add %eax, %ebx 65 movl %ebx, %gs:GS_GDT_DESC + 2 66 67 xor %eax, %eax 68 mov %eax, %es 69 70 /* Read the bootinfo struct into RAM */ 71 read_fw_blob(FW_CFG_INITRD) 72 73 /* FS = bootinfo_struct */ 74 read_fw FW_CFG_INITRD_ADDR 75 shr $4, %eax 76 mov %ax, %fs 77 78 /* ES = mmap_addr */ 79 mov %fs:48, %eax 80 shr $4, %eax 81 mov %ax, %es 82 83 /* Initialize multiboot mmap structs using int 0x15(e820) */ 84 xor %ebx, %ebx 85 /* mmap start after first size */ 86 movl $4, %edi 87 88mmap_loop: 89 /* entry size (mmap struct) & max buffer size (int15) */ 90 movl $20, %ecx 91 /* store entry size */ 92 /* old as(1) doesn't like this insn so emit the bytes instead: 93 movl %ecx, %es:-4(%edi) 94 */ 95 .dc.b 0x26,0x67,0x66,0x89,0x4f,0xfc 96 /* e820 */ 97 movl $0x0000e820, %eax 98 /* 'SMAP' magic */ 99 movl $0x534d4150, %edx 100 int $0x15 101 102mmap_check_entry: 103 /* last entry? then we're done */ 104 jb mmap_done 105 and %bx, %bx 106 jz mmap_done 107 /* valid entry, so let's loop on */ 108 109mmap_store_entry: 110 /* %ax = entry_number * 24 */ 111 mov $24, %ax 112 mul %bx 113 mov %ax, %di 114 movw %di, %fs:0x2c 115 /* %di = 4 + (entry_number * 24) */ 116 add $4, %di 117 jmp mmap_loop 118 119mmap_done: 120real_to_prot: 121 /* Load the GDT before going into protected mode */ 122lgdt: 123 data32 lgdt %gs:GS_GDT_DESC 124 125 /* get us to protected mode now */ 126 movl $1, %eax 127 movl %eax, %cr0 128 129 /* the LJMP sets CS for us and gets us to 32-bit */ 130ljmp: 131 data32 ljmp *%gs:GS_PROT_JUMP 132 133prot_mode: 134.code32 135 136 /* initialize all other segments */ 137 movl $0x10, %eax 138 movl %eax, %ss 139 movl %eax, %ds 140 movl %eax, %es 141 movl %eax, %fs 142 movl %eax, %gs 143 144 /* Read the kernel and modules into RAM */ 145 read_fw_blob(FW_CFG_KERNEL) 146 147 /* Jump off to the kernel */ 148 read_fw FW_CFG_KERNEL_ENTRY 149 mov %eax, %ecx 150 151 /* EBX contains a pointer to the bootinfo struct */ 152 read_fw FW_CFG_INITRD_ADDR 153 movl %eax, %ebx 154 155 /* EAX has to contain the magic */ 156 movl $MULTIBOOT_MAGIC, %eax 157ljmp2: 158 jmp *%ecx 159 160/* Variables */ 161.align 4, 0 162prot_jump: .long prot_mode 163 .short 8 164 165.align 4, 0 166gdt: 167 /* 0x00 */ 168.byte 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 169 170 /* 0x08: code segment (base=0, limit=0xfffff, type=32bit code exec/read, DPL=0, 4k) */ 171.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x9a, 0xcf, 0x00 172 173 /* 0x10: data segment (base=0, limit=0xfffff, type=32bit data read/write, DPL=0, 4k) */ 174.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0xcf, 0x00 175 176 /* 0x18: code segment (base=0, limit=0x0ffff, type=16bit code exec/read/conf, DPL=0, 1b) */ 177.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x9e, 0x00, 0x00 178 179 /* 0x20: data segment (base=0, limit=0x0ffff, type=16bit data read/write, DPL=0, 1b) */ 180.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0x00, 0x00 181 182gdt_desc: 183.short (5 * 8) - 1 184.long gdt 185 186BOOT_ROM_END 187