1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 *
4 *	Trampoline.S	Derived from Setup.S by Linus Torvalds
5 *
6 *	4 Jan 1997 Michael Chastain: changed to gnu as.
7 *
8 *	This is only used for booting secondary CPUs in SMP machine
9 *
10 *	Entry: CS:IP point to the start of our code, we are
11 *	in real mode with no stack, but the rest of the
12 *	trampoline page to make our stack and everything else
13 *	is a mystery.
14 *
15 *	We jump into arch/x86/kernel/head_32.S.
16 *
17 *	On entry to trampoline_start, the processor is in real mode
18 *	with 16-bit addressing and 16-bit data.  CS has some value
19 *	and IP is zero.  Thus, we load CS to the physical segment
20 *	of the real mode code before doing anything further.
21 */
22
23#include <linux/linkage.h>
24#include <asm/segment.h>
25#include <asm/page_types.h>
26#include "realmode.h"
27
28	.text
29	.code16
30
31	.balign	PAGE_SIZE
32SYM_CODE_START(trampoline_start)
33	wbinvd			# Needed for NUMA-Q should be harmless for others
34
35	LJMPW_RM(1f)
361:
37	mov	%cs, %ax	# Code and data in the same place
38	mov	%ax, %ds
39
40	cli			# We should be safe anyway
41
42	movl	tr_start, %eax	# where we need to go
43
44	/*
45	 * GDT tables in non default location kernel can be beyond 16MB and
46	 * lgdt will not be able to load the address as in real mode default
47	 * operand size is 16bit. Use lgdtl instead to force operand size
48	 * to 32 bit.
49	 */
50	lidtl	tr_idt			# load idt with 0, 0
51	lgdtl	tr_gdt			# load gdt with whatever is appropriate
52
53	movw	$1, %dx			# protected mode (PE) bit
54	lmsw	%dx			# into protected mode
55
56	ljmpl	$__BOOT_CS, $pa_startup_32
57SYM_CODE_END(trampoline_start)
58
59	.section ".text32","ax"
60	.code32
61SYM_CODE_START(startup_32)			# note: also used from wakeup_asm.S
62	jmp	*%eax
63SYM_CODE_END(startup_32)
64
65	.bss
66	.balign 8
67SYM_DATA_START(trampoline_header)
68	SYM_DATA_LOCAL(tr_start,	.space 4)
69	SYM_DATA_LOCAL(tr_gdt_pad,	.space 2)
70	SYM_DATA_LOCAL(tr_gdt,		.space 6)
71SYM_DATA_END(trampoline_header)
72
73#include "trampoline_common.S"
74