qemu/pc-bios/optionrom/linuxboot.S

196 lines
4.4 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:
/* Read info block in low memory (0x10000 or 0x90000) */
read_fw FW_CFG_SETUP_ADDR
shr $4, %eax
mov %eax, %es
xor %edi, %edi
read_fw_blob_addr32_edi(FW_CFG_SETUP)
cmpw $0x203, %es:0x206 // if protocol >= 0x203
jae 1f // have initrd_max
movl $0x37ffffff, %es:0x22c // else assume 0x37ffffff
1:
/* Check if using kernel-specified initrd address */
read_fw FW_CFG_INITRD_ADDR
mov %eax, %edi // (load_kernel wants it in %edi)
read_fw FW_CFG_INITRD_SIZE // find end of initrd
add %edi, %eax
xor %es:0x22c, %eax // if it matches es:0x22c
and $-4096, %eax // (apart from padding for page)
jz load_kernel // then initrd is not at top
// of memory
/* pc.c placed the initrd at end of memory. Compute a better
* initrd address based on e801 data.
*/
mov $0xe801, %ax
xor %cx, %cx
xor %dx, %dx
int $0x15
/* Output could be in AX/BX or CX/DX */
or %cx, %cx
jnz 1f
or %dx, %dx
jnz 1f
mov %ax, %cx
mov %bx, %dx
1:
or %dx, %dx
jnz 2f
addw $1024, %cx /* add 1 MB */
movzwl %cx, %edi
shll $10, %edi /* convert to bytes */
jmp 3f
2:
addw $16777216 >> 16, %dx /* add 16 MB */
movzwl %dx, %edi
shll $16, %edi /* convert to bytes */
3:
read_fw FW_CFG_INITRD_SIZE
subl %eax, %edi
andl $-4096, %edi /* EDI = start of initrd */
movl %edi, %es:0x218 /* put it in the header */
load_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_edi(FW_CFG_INITRD)
read_fw_blob_addr32(FW_CFG_KERNEL)
read_fw_blob_addr32(FW_CFG_CMDLINE)
/* 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