multiboot.S (5170B)
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 31 BOOT_ROM_START 32 33 run_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_dma(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 /* Account for the EBDA in the multiboot structure's e801 79 * map. 80 */ 81 int $0x12 82 cwtl 83 movl %eax, %fs:4 84 85 /* ES = mmap_addr */ 86 mov %fs:48, %eax 87 shr $4, %eax 88 mov %ax, %es 89 90 /* Initialize multiboot mmap structs using int 0x15(e820) */ 91 xor %ebx, %ebx 92 /* Start storing mmap data at %es:0 */ 93 xor %edi, %edi 94 95 mmap_loop: 96 /* The multiboot entry size has offset -4, so leave some space */ 97 add $4, %di 98 /* entry size (mmap struct) & max buffer size (int15) */ 99 movl $20, %ecx 100 /* e820 */ 101 movl $0x0000e820, %eax 102 /* 'SMAP' magic */ 103 movl $0x534d4150, %edx 104 int $0x15 105 106 mmap_check_entry: 107 /* Error or last entry already done? */ 108 jb mmap_done 109 110 mmap_store_entry: 111 /* store entry size */ 112 /* old as(1) doesn't like this insn so emit the bytes instead: 113 movl %ecx, %es:-4(%edi) 114 */ 115 .dc.b 0x26,0x67,0x66,0x89,0x4f,0xfc 116 117 /* %edi += entry_size, store as mbs_mmap_length */ 118 add %ecx, %edi 119 movw %di, %fs:0x2c 120 121 /* Continuation value 0 means last entry */ 122 test %ebx, %ebx 123 jnz mmap_loop 124 125 mmap_done: 126 /* Calculate upper_mem field: The amount of memory between 1 MB and 127 the first upper memory hole. Get it from the mmap. */ 128 xor %di, %di 129 mov $0x100000, %edx 130 upper_mem_entry: 131 cmp %fs:0x2c, %di 132 je upper_mem_done 133 add $4, %di 134 135 /* Skip if type != 1 */ 136 cmpl $1, %es:16(%di) 137 jne upper_mem_next 138 139 /* Skip if > 4 GB */ 140 movl %es:4(%di), %eax 141 test %eax, %eax 142 jnz upper_mem_next 143 144 /* Check for contiguous extension (base <= %edx < base + length) */ 145 movl %es:(%di), %eax 146 cmp %eax, %edx 147 jb upper_mem_next 148 addl %es:8(%di), %eax 149 cmp %eax, %edx 150 jae upper_mem_next 151 152 /* If so, update %edx, and restart the search (mmap isn't ordered) */ 153 mov %eax, %edx 154 xor %di, %di 155 jmp upper_mem_entry 156 157 upper_mem_next: 158 addl %es:-4(%di), %edi 159 jmp upper_mem_entry 160 161 upper_mem_done: 162 sub $0x100000, %edx 163 shr $10, %edx 164 mov %edx, %fs:0x8 165 166 real_to_prot: 167 /* Load the GDT before going into protected mode */ 168 lgdt: 169 data32 lgdt %gs:GS_GDT_DESC 170 171 /* get us to protected mode now */ 172 movl $1, %eax 173 movl %eax, %cr0 174 175 /* the LJMP sets CS for us and gets us to 32-bit */ 176 ljmp: 177 data32 ljmp *%gs:GS_PROT_JUMP 178 179 prot_mode: 180 .code32 181 182 /* initialize all other segments */ 183 movl $0x10, %eax 184 movl %eax, %ss 185 movl %eax, %ds 186 movl %eax, %es 187 movl %eax, %fs 188 movl %eax, %gs 189 190 /* Read the kernel and modules into RAM */ 191 read_fw_blob_dma(FW_CFG_KERNEL) 192 193 /* Jump off to the kernel */ 194 read_fw FW_CFG_KERNEL_ENTRY 195 mov %eax, %ecx 196 197 /* EBX contains a pointer to the bootinfo struct */ 198 read_fw FW_CFG_INITRD_ADDR 199 movl %eax, %ebx 200 201 /* EAX has to contain the magic */ 202 movl $MULTIBOOT_MAGIC, %eax 203 ljmp2: 204 jmp *%ecx 205 206 /* Variables */ 207 .align 4, 0 208 prot_jump: .long prot_mode 209 .short 8 210 211 .align 4, 0 212 gdt: 213 /* 0x00 */ 214 .byte 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 215 216 /* 0x08: code segment (base=0, limit=0xfffff, type=32bit code exec/read, DPL=0, 4k) */ 217 .byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x9a, 0xcf, 0x00 218 219 /* 0x10: data segment (base=0, limit=0xfffff, type=32bit data read/write, DPL=0, 4k) */ 220 .byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0xcf, 0x00 221 222 /* 0x18: code segment (base=0, limit=0x0ffff, type=16bit code exec/read/conf, DPL=0, 1b) */ 223 .byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x9e, 0x00, 0x00 224 225 /* 0x20: data segment (base=0, limit=0x0ffff, type=16bit data read/write, DPL=0, 1b) */ 226 .byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0x00, 0x00 227 228 gdt_desc: 229 .short (5 * 8) - 1 230 .long gdt 231 232 BOOT_ROM_END