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/*
* (C) Copyright 2014 Google, Inc
* Copyright (C) 1991, 1992, 1993 Linus Torvalds
*
* Parts of this copied from Linux arch/x86/boot/compressed/head_64.S
*
* SPDX-License-Identifier: GPL-2.0+
*/
#include <asm/global_data.h>
#include <asm/msr-index.h>
#include <asm/processor-flags.h>
.code32
.globl cpu_call64
cpu_call64:
/*
* cpu_call64(ulong pgtable, ulong setup_base, ulong target)
*
* eax - pgtable
* edx - setup_base
* ecx - target
*/
cli
push %ecx /* arg2 = target */
push %edx /* arg1 = setup_base */
mov %eax, %ebx
/* Load new GDT with the 64bit segments using 32bit descriptor */
leal gdt, %eax
movl %eax, gdt+2
lgdt gdt
/* Enable PAE mode */
movl $(X86_CR4_PAE), %eax
movl %eax, %cr4
/* Enable the boot page tables */
leal (%ebx), %eax
movl %eax, %cr3
/* Enable Long mode in EFER (Extended Feature Enable Register) */
movl $MSR_EFER, %ecx
rdmsr
btsl $_EFER_LME, %eax
wrmsr
/* After gdt is loaded */
xorl %eax, %eax
lldt %ax
movl $0x20, %eax
ltr %ax
/*
* Setup for the jump to 64bit mode
*
* When the jump is performed we will be in long mode but
* in 32bit compatibility mode with EFER.LME = 1, CS.L = 0, CS.D = 1
* (and in turn EFER.LMA = 1). To jump into 64bit mode we use
* the new gdt/idt that has __KERNEL_CS with CS.L = 1.
* We place all of the values on our mini stack so lret can
* used to perform that far jump. See the gdt below.
*/
pop %esi /* setup_base */
pushl $0x10
leal lret_target, %eax
pushl %eax
/* Enter paged protected Mode, activating Long Mode */
movl $(X86_CR0_PG | X86_CR0_PE), %eax
movl %eax, %cr0
/* Jump from 32bit compatibility mode into 64bit mode. */
lret
code64:
lret_target:
pop %eax /* target */
mov %eax, %eax /* Clear bits 63:32 */
jmp *%eax /* Jump to the 64-bit target */
.data
gdt:
.word gdt_end - gdt
.long gdt
.word 0
.quad 0x0000000000000000 /* NULL descriptor */
.quad 0x00af9a000000ffff /* __KERNEL_CS */
.quad 0x00cf92000000ffff /* __KERNEL_DS */
.quad 0x0080890000000000 /* TS descriptor */
.quad 0x0000000000000000 /* TS continued */
gdt_end:
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