qemu/pc-bios/optionrom/linuxboot.S
Gleb Natapov 75b9f69057 fix linuxboot.bin and multiboot.bin to not hijack int19
Currently linuxboot.bin and multiboot.bin option roms override int19
vector to intercept boot process. No sane option rom should do that.
Provide bev entry instead that will be called by BIOS if option rom
is selected for booting.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Acked-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
2011-03-22 07:00:58 +01:00

140 lines
2.9 KiB
ArmAsm

/*
* Linux Boot 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>
*
* Based on code in hw/pc.c.
*/
#include "optionrom.h"
#define BOOT_ROM_PRODUCT "Linux loader"
BOOT_ROM_START
run_linuxboot:
cli
cld
jmp copy_kernel
boot_kernel:
read_fw FW_CFG_SETUP_ADDR
mov %eax, %ebx
shr $4, %ebx
/* All segments contain real_addr */
mov %bx, %ds
mov %bx, %es
mov %bx, %fs
mov %bx, %gs
mov %bx, %ss
/* CX = CS we want to jump to */
add $0x20, %bx
mov %bx, %cx
/* SP = cmdline_addr-real_addr-16 */
read_fw FW_CFG_CMDLINE_ADDR
mov %eax, %ebx
read_fw FW_CFG_SETUP_ADDR
sub %eax, %ebx
sub $16, %ebx
mov %ebx, %esp
/* Build indirect lret descriptor */
pushw %cx /* CS */
xor %ax, %ax
pushw %ax /* IP = 0 */
/* Clear registers */
xor %eax, %eax
xor %ebx, %ebx
xor %ecx, %ecx
xor %edx, %edx
xor %edi, %edi
xor %ebp, %ebp
/* Jump to Linux */
lret
copy_kernel:
/* We need to load the kernel into memory we can't access in 16 bit
mode, so let's get into 32 bit mode, write the kernel and jump
back again. */
/* Reserve space on the stack for our GDT descriptor. */
mov %esp, %ebp
sub $16, %esp
/* Now create the GDT descriptor */
movw $((3 * 8) - 1), -16(%bp)
mov %cs, %eax
movzwl %ax, %eax
shl $4, %eax
addl $gdt, %eax
movl %eax, -14(%bp)
/* And load the GDT */
data32 lgdt -16(%bp)
mov %ebp, %esp
/* Get us to protected mode now */
mov $1, %eax
mov %eax, %cr0
/* So we can set ES to a 32-bit segment */
mov $0x10, %eax
mov %eax, %es
/* We're now running in 16-bit CS, but 32-bit ES! */
/* Load kernel and initrd */
read_fw_blob_addr32(FW_CFG_KERNEL)
read_fw_blob_addr32(FW_CFG_INITRD)
read_fw_blob_addr32(FW_CFG_CMDLINE)
read_fw_blob_addr32(FW_CFG_SETUP)
/* And now jump into Linux! */
mov $0, %eax
mov %eax, %cr0
/* ES = CS */
mov %cs, %ax
mov %ax, %es
jmp boot_kernel
/* Variables */
.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
BOOT_ROM_END