1/*
2 *
3 *	Trampoline.S	Derived from Setup.S by Linus Torvalds
4 *
5 *	4 Jan 1997 Michael Chastain: changed to gnu as.
6 *
7 *	Entry: CS:IP point to the start of our code, we are
8 *	in real mode with no stack, but the rest of the
9 *	trampoline page to make our stack and everything else
10 *	is a mystery.
11 *
12 *	In fact we don't actually need a stack so we don't
13 *	set one up.
14 *
15 *	We jump into the boot/compressed/head.S code. So you'd
16 *	better be running a compressed kernel image or you
17 *	won't get very far.
18 *
19 *	On entry to trampoline_data, the processor is in real mode
20 *	with 16-bit addressing and 16-bit data.  CS has some value
21 *	and IP is zero.  Thus, data addresses need to be absolute
22 *	(no relocation) and are taken with regard to r_base.
23 *
24 *	If you work on this file, check the object module with objdump
25 *	--full-contents --reloc to make sure there are no relocation
26 *	entries except for the gdt one..
27 */
28
29#include <linux/linkage.h>
30#include <asm/segment.h>
31#include <asm/page.h>
32
33.data
34
35.code16
36
37ENTRY(trampoline_data)
38r_base = .
39	wbinvd			# Needed for NUMA-Q should be harmless for others
40	mov	%cs, %ax	# Code and data in the same place
41	mov	%ax, %ds
42
43	mov	$1, %bx		# Flag an SMP trampoline
44	cli			# We should be safe anyway
45
46	movl	$0xA5A5A5A5, trampoline_data - r_base
47				# write marker for master knows we're running
48
49	lidt	idt_48 - r_base	# load idt with 0, 0
50	lgdt	gdt_48 - r_base	# load gdt with whatever is appropriate
51
52	xor	%ax, %ax
53	inc	%ax		# protected mode (PE) bit
54	lmsw	%ax		# into protected mode
55	jmp	flush_instr
56flush_instr:
57	ljmpl	$__KERNEL_CS, $0x00100000
58			# jump to startup_32 in arch/i386/kernel/head.S
59
60idt_48:
61	.word	0			# idt limit = 0
62	.word	0, 0			# idt base = 0L
63
64gdt_48:
65	.word	0x0800			# gdt limit = 2048, 256 GDT entries
66	.long	gdt_table-__PAGE_OFFSET	# gdt base = gdt (first SMP CPU)
67
68.globl SYMBOL_NAME(trampoline_end)
69SYMBOL_NAME_LABEL(trampoline_end)
70