[qemu.git] / pc-bios / optionrom / linuxboot.S

/*
 * 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"

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
Commit	Line	Data
57a46d05 AG	1	/*
	2	* Linux Boot 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	* Based on code in hw/pc.c.
	21	*/
	22
	23	#include "optionrom.h"
	24
	25	BOOT_ROM_START
	26
	27	run_linuxboot:
	28
	29	cli
	30	cld
	31
	32	jmp copy_kernel
	33	boot_kernel:
	34
	35	read_fw FW_CFG_SETUP_ADDR
	36
	37	mov %eax, %ebx
	38	shr $4, %ebx
	39
	40	/* All segments contain real_addr */
	41	mov %bx, %ds
	42	mov %bx, %es
	43	mov %bx, %fs
	44	mov %bx, %gs
	45	mov %bx, %ss
	46
	47	/* CX = CS we want to jump to */
	48	add $0x20, %bx
	49	mov %bx, %cx
	50
	51	/* SP = cmdline_addr-real_addr-16 */
	52	read_fw FW_CFG_CMDLINE_ADDR
	53	mov %eax, %ebx
	54	read_fw FW_CFG_SETUP_ADDR
	55	sub %eax, %ebx
	56	sub $16, %ebx
	57	mov %ebx, %esp
	58
	59	/* Build indirect lret descriptor */
	60	pushw %cx /* CS */
	61	xor %ax, %ax
	62	pushw %ax /* IP = 0 */
	63
	64	/* Clear registers */
65	xor %eax, %eax
66	xor %ebx, %ebx
67	xor %ecx, %ecx
68	xor %edx, %edx
69	xor %edi, %edi
70	xor %ebp, %ebp
71
72	/* Jump to Linux */
73	lret
74
75
76	copy_kernel:
77
78	/* We need to load the kernel into memory we can't access in 16 bit
79	mode, so let's get into 32 bit mode, write the kernel and jump
80	back again. */
81
36ecd7c0 PB	82	/* Reserve space on the stack for our GDT descriptor. */
	83	mov %esp, %ebp
	84	sub $16, %esp
57a46d05 AG	85
57a46d05 AG	86	/* Now create the GDT descriptor */
36ecd7c0	87	movw $((3 * 8) - 1), -16(%bp)
57a46d05	88	mov %cs, %eax
d0652aa8	89	movzwl %ax, %eax
57a46d05	90	shl $4, %eax
d0652aa8 AK	91	addl $gdt, %eax
d0652aa8 AK	92	movl %eax, -14(%bp)
57a46d05 AG	93
57a46d05 AG	94	/* And load the GDT */
36ecd7c0 PB	95	data32 lgdt -16(%bp)
36ecd7c0 PB	96	mov %ebp, %esp
57a46d05 AG	97
	98	/* Get us to protected mode now */
	99	mov $1, %eax
	100	mov %eax, %cr0
	101
dc61b0dc	102	/* So we can set ES to a 32-bit segment */
57a46d05	103	mov $0x10, %eax
dc61b0dc	104	mov %eax, %es
57a46d05	105
dc61b0dc	106	/* We're now running in 16-bit CS, but 32-bit ES! */
57a46d05 AG	107
57a46d05 AG	108	/* Load kernel and initrd */
590bf491 AG	109	read_fw_blob_addr32(FW_CFG_KERNEL)
	110	read_fw_blob_addr32(FW_CFG_INITRD)
	111	read_fw_blob_addr32(FW_CFG_CMDLINE)
	112	read_fw_blob_addr32(FW_CFG_SETUP)
57a46d05 AG	113
	114	/* And now jump into Linux! */
	115	mov $0, %eax
	116	mov %eax, %cr0
	117
dc61b0dc	118	/* ES = CS */
57a46d05	119	mov %cs, %ax
dc61b0dc	120	mov %ax, %es
57a46d05 AG	121
	122	jmp boot_kernel
	123
	124	/* Variables */
	125
	126	.align 4, 0
	127	gdt:
	128	/* 0x00 */
	129	.byte 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
	130
	131	/* 0x08: code segment (base=0, limit=0xfffff, type=32bit code exec/read, DPL=0, 4k) */
	132	.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x9a, 0xcf, 0x00
	133
	134	/* 0x10: data segment (base=0, limit=0xfffff, type=32bit data read/write, DPL=0, 4k) */
	135	.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0xcf, 0x00
	136
	137	BOOT_ROM_END