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/*
* Multiboot Option ROM
*
* 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, see <http://www.gnu.org/licenses/>.
*
* Copyright Novell Inc, 2009
* Authors: Alexander Graf <agraf@suse.de>
*/
#define NO_QEMU_PROTOS
#include "../../hw/fw_cfg.h"
#define BIOS_CFG_IOPORT_CFG 0x510
#define BIOS_CFG_IOPORT_DATA 0x511
#define MULTIBOOT_MAGIC 0x2badb002
/* Read a variable from the fw_cfg device.
Clobbers: %edx
Out: %eax */
.macro read_fw VAR
mov $\VAR, %ax
mov $BIOS_CFG_IOPORT_CFG, %dx
outw %ax, (%dx)
mov $BIOS_CFG_IOPORT_DATA, %dx
inb (%dx), %al
shl $8, %eax
inb (%dx), %al
shl $8, %eax
inb (%dx), %al
shl $8, %eax
inb (%dx), %al
bswap %eax
.endm
.code16
.text
.global _start
_start:
.short 0xaa55
.byte 1 /* (_end - _start) / 512 */
push %eax
push %ds
/* setup ds so we can access the IVT */
xor %ax, %ax
mov %ax, %ds
/* save old int 19 */
mov (0x19*4), %eax
mov %eax, %cs:old_int19
/* install our int 19 handler */
movw $int19_handler, (0x19*4)
mov %cs, (0x19*4+2)
pop %ds
pop %eax
lret
int19_handler:
/* DS = CS */
movw %cs, %ax
movw %ax, %ds
/* fall through */
run_multiboot:
cli
cld
mov %cs, %eax
shl $0x4, %eax
/* fix the gdt descriptor to be PC relative */
mov (gdt_desc+2), %ebx
add %eax, %ebx
mov %ebx, (gdt_desc+2)
/* fix the prot mode indirect jump to be PC relative */
mov (prot_jump), %ebx
add %eax, %ebx
mov %ebx, (prot_jump)
/* FS = bootinfo_struct */
read_fw FW_CFG_INITRD_ADDR
shr $4, %eax
mov %ax, %fs
/* ES = mmap_addr */
read_fw FW_CFG_INITRD_SIZE
shr $4, %eax
mov %ax, %es
/* Initialize multiboot mmap structs using int 0x15(e820) */
xor %ebx, %ebx
/* mmap start after first size */
movl $4, %edi
mmap_loop:
/* entry size (mmap struct) & max buffer size (int15) */
movl $20, %ecx
/* store entry size */
/* old as(1) doesn't like this insn so emit the bytes instead:
movl %ecx, %es:-4(%edi)
*/
.dc.b 0x26,0x67,0x66,0x89,0x4f,0xfc
/* e820 */
movl $0x0000e820, %eax
/* 'SMAP' magic */
movl $0x534d4150, %edx
int $0x15
mmap_check_entry:
/* last entry? then we're done */
jb mmap_done
and %bx, %bx
jz mmap_done
/* valid entry, so let's loop on */
mmap_store_entry:
/* %ax = entry_number * 24 */
mov $24, %ax
mul %bx
mov %ax, %di
movw %di, %fs:0x2c
/* %di = 4 + (entry_number * 24) */
add $4, %di
jmp mmap_loop
mmap_done:
real_to_prot:
/* Load the GDT before going into protected mode */
lgdt:
data32 lgdt %cs:gdt_desc
/* get us to protected mode now */
movl $1, %eax
movl %eax, %cr0
/* the LJMP sets CS for us and gets us to 32-bit */
ljmp:
data32 ljmp *%cs:prot_jump
prot_mode:
.code32
/* initialize all other segments */
movl $0x10, %eax
movl %eax, %ss
movl %eax, %ds
movl %eax, %es
movl %eax, %fs
movl %eax, %gs
/* Jump off to the kernel */
read_fw FW_CFG_KERNEL_ADDR
mov %eax, %ecx
/* EBX contains a pointer to the bootinfo struct */
read_fw FW_CFG_INITRD_ADDR
movl %eax, %ebx
/* EAX has to contain the magic */
movl $MULTIBOOT_MAGIC, %eax
ljmp2:
jmp *%ecx
/* Variables */
.align 4, 0
old_int19: .long 0
prot_jump: .long prot_mode
.short 8
.align 4, 0
gdt:
/* 0x00 */
.byte 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
/* 0x08: code segment (base=0, limit=0xfffff, type=32bit code exec/read, DPL=0, 4k) */
.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x9a, 0xcf, 0x00
/* 0x10: data segment (base=0, limit=0xfffff, type=32bit data read/write, DPL=0, 4k) */
.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0xcf, 0x00
/* 0x18: code segment (base=0, limit=0x0ffff, type=16bit code exec/read/conf, DPL=0, 1b) */
.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x9e, 0x00, 0x00
/* 0x20: data segment (base=0, limit=0x0ffff, type=16bit data read/write, DPL=0, 1b) */
.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0x00, 0x00
gdt_desc:
.short (5 * 8) - 1
.long gdt
.align 512, 0
_end:
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