summaryrefslogtreecommitdiff
path: root/src/cpu/x86/64bit/entry64.inc
blob: 65c0fdc929250ffa43e02eb995ef6fe2cd2b94e5 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
/* SPDX-License-Identifier: GPL-2.0-only */

/*
 * For starting coreboot in long mode.
 *
 * For reference see "AMD64 ArchitectureProgrammer's Manual Volume 2",
 * Document 24593-Rev. 3.31-July 2019 Chapter 5.3
 *
 * Clobbers: eax, ecx, edx
 */

#if defined(__x86_64__)
	.code32
#if (CONFIG_ARCH_X86_64_PGTBL_LOC & 0xfff) > 0
#error pagetables must be 4KiB aligned!
#endif

#include <cpu/x86/msr.h>
#include <arch/rom_segs.h>

setup_longmode:
	/* Get page table address */
	movl	$(CONFIG_ARCH_X86_64_PGTBL_LOC), %eax

	/* load identity mapped page tables */
	movl	%eax, %cr3

	/* enable PAE */
	movl	%cr4, %eax
	btsl	$5, %eax
	movl	%eax, %cr4

	/* enable long mode */
	movl	$(IA32_EFER), %ecx
	rdmsr
	btsl	$8, %eax
	wrmsr

	/* enable paging */
	movl	%cr0, %eax
	btsl	$31, %eax
	movl	%eax, %cr0

	/* use long jump to switch to 64-bit code segment */
	ljmp $ROM_CODE_SEG64, $__longmode_start
.code64
__longmode_start:

#endif