[deliverable/linux.git] / arch / x86_64 / boot / compressed / head.S

/*
 *  linux/boot/head.S
 *
 *  Copyright (C) 1991, 1992, 1993  Linus Torvalds
 *
 *  $Id: head.S,v 1.3 2001/04/20 00:59:28 ak Exp $	 		
 */

/*
 *  head.S contains the 32-bit startup code.
 *
 * NOTE!!! Startup happens at absolute address 0x00001000, which is also where
 * the page directory will exist. The startup code will be overwritten by
 * the page directory. [According to comments etc elsewhere on a compressed
 * kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC]
 *
 * Page 0 is deliberately kept safe, since System Management Mode code in 
 * laptops may need to access the BIOS data stored there.  This is also
 * useful for future device drivers that either access the BIOS via VM86 
 * mode.
 */

/*
 * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996	
 */
.code32
.text

#include <linux/linkage.h>
#include <asm/segment.h>
#include <asm/page.h>

	.code32
	.globl startup_32
	
startup_32:
	cld
	cli
	movl $(__KERNEL_DS),%eax
	movl %eax,%ds
	movl %eax,%es
	movl %eax,%fs
	movl %eax,%gs

	lss stack_start,%esp
	xorl %eax,%eax
1:	incl %eax		# check that A20 really IS enabled
	movl %eax,0x000000	# loop forever if it isn't
	cmpl %eax,0x100000
	je 1b

/*
 * Initialize eflags.  Some BIOS's leave bits like NT set.  This would
 * confuse the debugger if this code is traced.
 * XXX - best to initialize before switching to protected mode.
 */
	pushl $0
	popfl
/*
 * Clear BSS
 */
	xorl %eax,%eax
	movl $_edata,%edi
	movl $_end,%ecx
	subl %edi,%ecx
	cld
	rep
	stosb
/*
 * Do the decompression, and jump to the new kernel..
 */
	subl $16,%esp	# place for structure on the stack
	movl %esp,%eax
	pushl %esi	# real mode pointer as second arg
	pushl %eax	# address of structure as first arg
	call decompress_kernel
	orl  %eax,%eax 
	jnz  3f
	addl $8,%esp
	xorl %ebx,%ebx
	ljmp $(__KERNEL_CS), $__PHYSICAL_START

/*
 * We come here, if we were loaded high.
 * We need to move the move-in-place routine down to 0x1000
 * and then start it with the buffer addresses in registers,
 * which we got from the stack.
 */
3:
	movl %esi,%ebx	
	movl $move_routine_start,%esi
	movl $0x1000,%edi
	movl $move_routine_end,%ecx
	subl %esi,%ecx
	addl $3,%ecx
	shrl $2,%ecx
	cld
	rep
	movsl

	popl %esi	# discard the address
	addl $4,%esp	# real mode pointer
	popl %esi	# low_buffer_start
	popl %ecx	# lcount
	popl %edx	# high_buffer_start
	popl %eax	# hcount
	movl $__PHYSICAL_START,%edi
	cli		# make sure we don't get interrupted
	ljmp $(__KERNEL_CS), $0x1000 # and jump to the move routine

/*
 * Routine (template) for moving the decompressed kernel in place,
 * if we were high loaded. This _must_ PIC-code !
 */
move_routine_start:
	movl %ecx,%ebp
	shrl $2,%ecx
	rep
	movsl
	movl %ebp,%ecx
	andl $3,%ecx
	rep
	movsb
	movl %edx,%esi
	movl %eax,%ecx	# NOTE: rep movsb won't move if %ecx == 0
	addl $3,%ecx
	shrl $2,%ecx
	rep
	movsl
	movl %ebx,%esi	# Restore setup pointer
	xorl %ebx,%ebx
	ljmp $(__KERNEL_CS), $__PHYSICAL_START
move_routine_end:


/* Stack for uncompression */ 	
	.align 32
user_stack:	 	
	.fill 4096,4,0
stack_start:	
	.long user_stack+4096
	.word __KERNEL_DS
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/boot/head.S
	3	*
	4	* Copyright (C) 1991, 1992, 1993 Linus Torvalds
	5	*
	6	* $Id: head.S,v 1.3 2001/04/20 00:59:28 ak Exp $
	7	*/
	8
	9	/*
	10	* head.S contains the 32-bit startup code.
	11	*
	12	* NOTE!!! Startup happens at absolute address 0x00001000, which is also where
	13	* the page directory will exist. The startup code will be overwritten by
	14	* the page directory. [According to comments etc elsewhere on a compressed
	15	* kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC]
	16	*
	17	* Page 0 is deliberately kept safe, since System Management Mode code in
	18	* laptops may need to access the BIOS data stored there. This is also
	19	* useful for future device drivers that either access the BIOS via VM86
	20	* mode.
	21	*/
	22
	23	/*
	24	* High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
	25	*/
	26	.code32
	27	.text
	28
	29	#include <linux/linkage.h>
	30	#include <asm/segment.h>
d0537508	31	#include <asm/page.h>
1da177e4 LT	32
	33	.code32
	34	.globl startup_32
	35
	36	startup_32:
	37	cld
	38	cli
	39	movl $(__KERNEL_DS),%eax
	40	movl %eax,%ds
	41	movl %eax,%es
	42	movl %eax,%fs
	43	movl %eax,%gs
	44
	45	lss stack_start,%esp
	46	xorl %eax,%eax
	47	1: incl %eax # check that A20 really IS enabled
	48	movl %eax,0x000000 # loop forever if it isn't
	49	cmpl %eax,0x100000
	50	je 1b
	51
	52	/*
	53	* Initialize eflags. Some BIOS's leave bits like NT set. This would
	54	* confuse the debugger if this code is traced.
	55	* XXX - best to initialize before switching to protected mode.
	56	*/
	57	pushl $0
	58	popfl
	59	/*
	60	* Clear BSS
	61	*/
	62	xorl %eax,%eax
	63	movl $_edata,%edi
	64	movl $_end,%ecx
	65	subl %edi,%ecx
	66	cld
	67	rep
	68	stosb
	69	/*
	70	* Do the decompression, and jump to the new kernel..
	71	*/
	72	subl $16,%esp # place for structure on the stack
	73	movl %esp,%eax
	74	pushl %esi # real mode pointer as second arg
	75	pushl %eax # address of structure as first arg
	76	call decompress_kernel
	77	orl %eax,%eax
	78	jnz 3f
	79	addl $8,%esp
	80	xorl %ebx,%ebx
d0537508	81	ljmp $(__KERNEL_CS), $__PHYSICAL_START
1da177e4 LT	82
	83	/*
	84	* We come here, if we were loaded high.
	85	* We need to move the move-in-place routine down to 0x1000
	86	* and then start it with the buffer addresses in registers,
	87	* which we got from the stack.
	88	*/
	89	3:
	90	movl %esi,%ebx
	91	movl $move_routine_start,%esi
	92	movl $0x1000,%edi
	93	movl $move_routine_end,%ecx
	94	subl %esi,%ecx
	95	addl $3,%ecx
	96	shrl $2,%ecx
	97	cld
	98	rep
	99	movsl
	100
	101	popl %esi # discard the address
	102	addl $4,%esp # real mode pointer
	103	popl %esi # low_buffer_start
	104	popl %ecx # lcount
	105	popl %edx # high_buffer_start
	106	popl %eax # hcount
d0537508	107	movl $__PHYSICAL_START,%edi
1da177e4 LT	108	cli # make sure we don't get interrupted
	109	ljmp $(__KERNEL_CS), $0x1000 # and jump to the move routine
	110
	111	/*
	112	* Routine (template) for moving the decompressed kernel in place,
	113	* if we were high loaded. This _must_ PIC-code !
	114	*/
	115	move_routine_start:
	116	movl %ecx,%ebp
	117	shrl $2,%ecx
	118	rep
	119	movsl
	120	movl %ebp,%ecx
	121	andl $3,%ecx
	122	rep
	123	movsb
	124	movl %edx,%esi
	125	movl %eax,%ecx # NOTE: rep movsb won't move if %ecx == 0
	126	addl $3,%ecx
	127	shrl $2,%ecx
	128	rep
	129	movsl
	130	movl %ebx,%esi # Restore setup pointer
	131	xorl %ebx,%ebx
d0537508	132	ljmp $(__KERNEL_CS), $__PHYSICAL_START
1da177e4 LT	133	move_routine_end:
	134
	135
	136	/* Stack for uncompression */
	137	.align 32
	138	user_stack:
	139	.fill 4096,4,0
	140	stack_start:
	141	.long user_stack+4096
	142	.word __KERNEL_DS
	143