blob: 9bc2905e683e67c5220ff725e8b73acef65e8d20 [file] [log] [blame]
/*
* Switch back to real mode and call the BIOS reboot vector.
* This is a trampoline copied around in process.c
* Written 2003 by Andi Kleen, SuSE Labs.
*/
#include <asm/msr.h>
#define R(x) x-warm_reboot(%ebx)
#define R64(x) x-warm_reboot(%rbx)
/* running in identity mapping and in the first 64k of memory
and in compatibility mode. This must be position independent */
/* Follows 14.7 "Leaving Long Mode" in the AMD x86-64 manual, volume 2
and 8.9.2 "Switching Back to Real-Address Mode" in the Intel IA32
manual, volume 2 */
/* ebx: self pointer to warm_reboot */
.globl warm_reboot
warm_reboot:
addl %ebx, R64(real_mode_desc) /* relocate tables */
addl %ebx,2+R64(warm_gdt_desc)
movq %cr0,%rax
btr $31,%rax
movq %rax,%cr0 /* disable paging */
jmp 1f /* flush prefetch queue */
.code32
1: movl $MSR_EFER,%ecx
rdmsr
andl $~((1<<_EFER_LME)|(1<<_EFER_SCE)|(1<<_EFER_NX)),%eax
wrmsr /* disable long mode in EFER */
xorl %eax,%eax
movl %eax,%cr3 /* flush tlb */
/* Running protected mode without paging now */
wbinvd /* flush caches. Needed? */
lidt R(warm_idt_desc)
lgdt R(warm_gdt_desc)
movl $0x10,%ecx /* load segment registers with real mode settings */
movl %ecx,%ds
movl %ecx,%es
movl %ecx,%fs
movl %ecx,%gs
movl %ecx,%ss
lea R(real_mode_desc),%eax
ljmp *(%eax)
.code16:
real_mode:
xorl %eax,%eax
movl %eax,%cr0
/* some people claim $0xf000,0xfff0 is better. Use what 32bit linux uses. */
/* code as bytes because gas has problems with it */
.byte 0xea,0xf0,0xff,0x00,0xf0 /* ljmp 0xf000:0xfff0 */
real_mode_desc:
.long real_mode - warm_reboot
.short 8
warm_gdt_desc:
.short 8*3
.long warm_gdt - warm_reboot
warm_gdt:
.quad 0
.quad 0x00009a000000ffff /* 16-bit real-mode 64k code at 0x00000000 */
.quad 0x000092000100ffff /* 16-bit real-mode 64k data at 0x00000100 */
warm_idt_desc:
.short 0x3ff
.long 0
.globl warm_reboot_end
warm_reboot_end: