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minix/kernel/arch/i386/klib.S
Erik van der Kouwe df0ba02a38 Multiboot support (contributed by Feiran "Fam" Zheng); 
keep in mind that GRUB needs to be patched to read MFS for now;
use /boot/image_latest to boot the last compiled image in GRUB
2010-07-23 14:24:34 +00:00

963 lines
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ArmAsm
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/* sections */
#include <minix/config.h>
#include <minix/const.h>
#include <machine/interrupt.h>
#include <i386/vm.h>
#include "archconst.h"
#include "kernel/const.h"
#include "sconst.h"
#include "multiboot.h"
/*
* This file contains a number of assembly code utility routines needed by the
* kernel. They are:
*/
.globl _monitor/* exit Minix and return to the monitor */
.globl _int86 /* let the monitor make an 8086 interrupt call */
#ifdef __ACK__
.globl _exit /* dummy for library routines */
.globl __exit /* dummy for library routines */
.globl ___exit /* dummy for library routines */
#endif
.globl ___main /* dummy for GCC */
.globl _phys_insw /* transfer data from (disk controller) port to memory */
.globl _phys_insb /* likewise byte by byte */
.globl _phys_outsw /* transfer data from memory to (disk controller) port */
.globl _phys_outsb /* likewise byte by byte */
.globl _phys_copy /* copy data from anywhere to anywhere in memory */
.globl _phys_copy_fault /* phys_copy pagefault */
.globl _phys_copy_fault_in_kernel /* phys_copy pagefault in kernel */
.globl _phys_memset /* write pattern anywhere in memory */
.globl _mem_rdw /* copy one word from [segment:offset] */
.globl _reset /* reset the system */
.globl _halt_cpu/* halts the current cpu when idle */
.globl _read_cpu_flags /* read the cpu flags */
.globl _read_cr0 /* read cr0 */
.globl _read_cr2 /* read cr2 */
.globl _getcr3val
.globl _write_cr0 /* write a value in cr0 */
.globl _read_cr3
.globl _write_cr3
.globl _read_cr4
.globl _write_cr4
.globl _catch_pagefaults
.globl _read_ds
.globl _read_cs
.globl _read_ss
.globl _idt_reload /* reload idt when returning to monitor. */
.globl _fninit /* non-waiting FPU initialization */
.globl _fnstsw /* store status word (non-waiting) */
.globl _fnstcw /* store control word (non-waiting) */
.globl _fxsave
.globl _fnsave
.globl _fxrstor
.globl _frstor
.globl _clts
/*
* The routines only guarantee to preserve the registers the C compiler
* expects to be preserved (ebx, esi, edi, ebp, esp, segment registers, and
* direction bit in the flags).
*/
.text
/*===========================================================================*/
/* monitor */
/*===========================================================================*/
/* PUBLIC void monitor(); */
/* Return to the monitor. */
_monitor:
movl _mon_sp, %esp /* restore monitor stack pointer */
movw $SS_SELECTOR, %dx /* monitor data segment */
mov %dx, %ds
mov %dx, %es
mov %dx, %fs
mov %dx, %gs
mov %dx, %ss
pop %edi
pop %esi
pop %ebp
lretw /* return to the monitor */
/*===========================================================================*/
/* int86 */
/*===========================================================================*/
/* PUBLIC void int86(); */
_int86:
cmpb $0, _mon_return /* is the monitor there? */
jne 0f
movb $0x01, %ah /* an int 13 error seems appropriate */
movb %ah, _reg86+0 /* reg86.w.f = 1 (set carry flag) */
movb %ah, _reg86+13 /* reg86.b.ah = 0x01 = "invalid command" */
ret
0:
push %ebp /* save C registers */
push %esi
push %edi
push %ebx
pushf /* save flags */
cli /* no interruptions */
inb $INT2_CTLMASK
movb %al, %ah
inb $INT_CTLMASK
push %eax /* save interrupt masks */
movl _irq_use, %eax /* map of in-use IRQ's */
and $~(1<<CLOCK_IRQ), %eax /* keep the clock ticking */
outb $INT_CTLMASK /* enable all unused IRQ's and vv. */
movb %ah, %al
outb $INT2_CTLMASK
mov $SS_SELECTOR, %eax /* monitor data segment */
mov %ax, %ss
xchgl _mon_sp, %esp /* switch stacks */
push _reg86+36 /* parameters used in INT call */
push _reg86+32
push _reg86+28
push _reg86+24
push _reg86+20
push _reg86+16
push _reg86+12
push _reg86+8
push _reg86+4
push _reg86+0
mov %ax, %ds /* remaining data selectors */
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
push %cs
push $return /* kernel return address and selector */
ljmpw *20+2*4+10*4+2*4(%esp)
return:
pop _reg86+0
pop _reg86+4
pop _reg86+8
pop _reg86+12
pop _reg86+16
pop _reg86+20
pop _reg86+24
pop _reg86+28
pop _reg86+32
pop _reg86+36
lgdt _gdt+GDT_SELECTOR /* reload global descriptor table */
ljmp $CS_SELECTOR, $csinit
csinit:
mov $DS_SELECTOR, %eax
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
mov %ax, %ss
xchgl _mon_sp, %esp /* unswitch stacks */
lidt _gdt+IDT_SELECTOR /* reload interrupt descriptor table */
#ifdef CONFIG_APIC
cmpl $0x0, lapic_addr
jne 3f
mov $0, %ebx
jmp 4f
3:
mov $FLAT_DS_SELECTOR, %ebx
mov %bx, %fs
movl lapic_addr, %eax
add $0x20, %eax
.byte 0x64; mov (%eax), %ebx
and $0xFF000000, %ebx
shr $24, %ebx
movzb %bl, %ebx
4:
add $apicid2cpuid, %ebx
movzb (%ebx), %eax
shl $3, %eax
mov %eax, %ebx
add $TSS_SELECTOR, %eax
addl _gdt+DESC_ACCESS, %eax
and $~0x02, %eax
ltr %bx /* set TSS register */
mov $DS_SELECTOR, %eax
mov %ax, %fs
#endif /* CONFIG_APIC */
pop %eax
outb $INT_CTLMASK /* restore interrupt masks */
movb %ah, %al
outb $INT2_CTLMASK
6:
addl %ecx, _lost_ticks /* record lost clock ticks */
popf /* restore flags */
pop %ebx /* restore C registers */
pop %edi
pop %esi
pop %ebp
ret
/*===========================================================================*/
/* exit */
/*===========================================================================*/
/*
* PUBLIC void exit();
* Some library routines use exit, so provide a dummy version.
* Actual calls to exit cannot occur in the kernel.
* GNU CC likes to call ___main from main() for nonobvious reasons.
*/
#ifdef __ACK__
_exit:
__exit:
___exit:
sti
jmp ___exit
#endif
___main:
ret
/*===========================================================================*/
/* phys_insw */
/*===========================================================================*/
/*
* PUBLIC void phys_insw(Port_t port, phys_bytes buf, size_t count);
* Input an array from an I/O port. Absolute address version of insw().
*/
_phys_insw:
push %ebp
mov %esp, %ebp
cld
push %edi
push %es
mov $FLAT_DS_SELECTOR, %ecx
mov %cx, %es
mov 8(%ebp), %edx /* port to read from */
mov 12(%ebp), %edi /* destination addr */
mov 16(%ebp), %ecx /* byte count */
shr $1, %ecx /* word count */
rep insw /* input many words */
pop %es
pop %edi
pop %ebp
ret
/*===========================================================================*/
/* phys_insb */
/*===========================================================================*/
/*
* PUBLIC void phys_insb(Port_t port, phys_bytes buf, size_t count);
* Input an array from an I/O port. Absolute address version of insb().
*/
_phys_insb:
push %ebp
mov %esp, %ebp
cld
push %edi
push %es
mov $FLAT_DS_SELECTOR, %ecx
mov %cx, %es
mov 8(%ebp), %edx /* port to read from */
mov 12(%ebp), %edi /* destination addr */
mov 16(%ebp), %ecx /* byte count */
rep insb /* input many bytes */
pop %es
pop %edi
pop %ebp
ret
/*===========================================================================*/
/* phys_outsw */
/*===========================================================================*/
/*
* PUBLIC void phys_outsw(Port_t port, phys_bytes buf, size_t count);
* Output an array to an I/O port. Absolute address version of outsw().
*/
.balign 16
_phys_outsw:
push %ebp
mov %esp, %ebp
cld
push %esi
push %ds
mov $FLAT_DS_SELECTOR, %ecx
mov %cx, %ds
mov 8(%ebp), %edx /* port to write to */
mov 12(%ebp), %esi /* source addr */
mov 16(%ebp), %ecx /* byte count */
shr $1, %ecx /* word count */
rep outsw /* output many words */
pop %ds
pop %esi
pop %ebp
ret
/*===========================================================================*/
/* phys_outsb */
/*===========================================================================*/
/*
* PUBLIC void phys_outsb(Port_t port, phys_bytes buf, size_t count);
* Output an array to an I/O port. Absolute address version of outsb().
*/
.balign 16
_phys_outsb:
push %ebp
mov %esp, %ebp
cld
push %esi
push %ds
mov $FLAT_DS_SELECTOR, %ecx
mov %cx, %ds
mov 8(%ebp), %edx /* port to write to */
mov 12(%ebp), %esi /* source addr */
mov 16(%ebp), %ecx /* byte count */
rep outsb /* output many bytes */
pop %ds
pop %esi
pop %ebp
ret
/*===========================================================================*/
/* phys_copy */
/*===========================================================================*/
/*
* PUBLIC phys_bytes phys_copy(phys_bytes source, phys_bytes destination,
* phys_bytes bytecount);
* Copy a block of physical memory.
*/
PC_ARGS = 4+4+4+4 /* 4 + 4 + 4 */
/* es edi esi eip src dst len */
.balign 16
_phys_copy:
cld
push %esi
push %edi
push %es
mov $FLAT_DS_SELECTOR, %eax
mov %ax, %es
mov PC_ARGS(%esp), %esi
mov PC_ARGS+4(%esp), %edi
mov PC_ARGS+4+4(%esp), %eax
cmp $10, %eax /* avoid align overhead for small counts */
jb pc_small
mov %esi, %ecx /* align source, hope target is too */
neg %ecx
and $3, %ecx /* count for alignment */
sub %ecx, %eax
rep movsb %es:(%esi), %es:(%edi)
mov %eax, %ecx
shr $2, %ecx /* count of dwords */
rep movsl %es:(%esi), %es:(%edi)
and $3, %eax
pc_small:
xchg %eax, %ecx /* remainder */
rep movsb %es:(%esi), %es:(%edi)
mov $0, %eax /* 0 means: no fault */
_phys_copy_fault: /* kernel can send us here */
pop %es
pop %edi
pop %esi
ret
_phys_copy_fault_in_kernel: /* kernel can send us here */
pop %es
pop %edi
pop %esi
mov %cr2, %eax
ret
/*===========================================================================*/
/* copy_msg_from_user */
/*===========================================================================*/
/*
* int copy_msg_from_user(struct proc * p, message * user_mbuf, message * dst);
*
* Copies a message of 36 bytes from user process space to a kernel buffer. This
* function assumes that the process address space is installed (cr3 loaded) and
* the local descriptor table of this process is loaded too.
*
* The %gs segment register is used to access the userspace memory. We load the
* process' data segment in this register.
*
* This function from the callers point of view either succeeds or returns an
* error which gives the caller a chance to respond accordingly. In fact it
* either succeeds or if it generates a pagefault, general protection or other
* exception, the trap handler has to redirect the execution to
* __user_copy_msg_pointer_failure where the error is reported to the caller
* without resolving the pagefault. It is not kernel's problem to deal with
* wrong pointers from userspace and the caller should return an error to
* userspace as if wrong values or request were passed to the kernel
*/
.balign 16
.globl _copy_msg_from_user
_copy_msg_from_user:
push %gs
mov 8(%esp), %eax
movw DSREG(%eax), %gs
/* load the source pointer */
mov 12(%esp), %ecx
/* load the destination pointer */
mov 16(%esp), %edx
mov %gs:0*4(%ecx), %eax
mov %eax, 0*4(%edx)
mov %gs:1*4(%ecx), %eax
mov %eax, 1*4(%edx)
mov %gs:2*4(%ecx), %eax
mov %eax, 2*4(%edx)
mov %gs:3*4(%ecx), %eax
mov %eax, 3*4(%edx)
mov %gs:4*4(%ecx), %eax
mov %eax, 4*4(%edx)
mov %gs:5*4(%ecx), %eax
mov %eax, 5*4(%edx)
mov %gs:6*4(%ecx), %eax
mov %eax, 6*4(%edx)
mov %gs:7*4(%ecx), %eax
mov %eax, 7*4(%edx)
mov %gs:8*4(%ecx), %eax
mov %eax, 8*4(%edx)
.globl ___copy_msg_from_user_end
___copy_msg_from_user_end:
pop %gs
movl $0, %eax
ret
/*===========================================================================*/
/* copy_msg_to_user */
/*===========================================================================*/
/*
* void copy_msg_to_user(struct proc * p, message * src, message * user_mbuf);
*
* Copies a message of 36 bytes to user process space from a kernel buffer. This
* function assumes that the process address space is installed (cr3 loaded) and
* the local descriptor table of this process is loaded too.
*
* All the other copy_msg_from_user() comments apply here as well!
*/
.balign 16
.globl _copy_msg_to_user
_copy_msg_to_user:
push %gs
mov 8(%esp), %eax
movw DSREG(%eax), %gs
/* load the source pointer */
mov 12(%esp), %ecx
/* load the destination pointer */
mov 16(%esp), %edx
mov 0*4(%ecx), %eax
mov %eax, %gs:0*4(%edx)
mov 1*4(%ecx), %eax
mov %eax, %gs:1*4(%edx)
mov 2*4(%ecx), %eax
mov %eax, %gs:2*4(%edx)
mov 3*4(%ecx), %eax
mov %eax, %gs:3*4(%edx)
mov 4*4(%ecx), %eax
mov %eax, %gs:4*4(%edx)
mov 5*4(%ecx), %eax
mov %eax, %gs:5*4(%edx)
mov 6*4(%ecx), %eax
mov %eax, %gs:6*4(%edx)
mov 7*4(%ecx), %eax
mov %eax, %gs:7*4(%edx)
mov 8*4(%ecx), %eax
mov %eax, %gs:8*4(%edx)
.globl ___copy_msg_to_user_end
___copy_msg_to_user_end:
pop %gs
movl $0, %eax
ret
/*
* if a function from a selected set of copies from or to userspace fails, it is
* because of a wrong pointer supplied by the userspace. We have to clean up and
* and return -1 to indicated that something wrong has happend. The place it was
* called from has to handle this situation. The exception handler redirect us
* here to continue, clean up and report the error
*/
.balign 16
.globl ___user_copy_msg_pointer_failure
___user_copy_msg_pointer_failure:
pop %gs
movl $-1, %eax
ret
/*===========================================================================*/
/* phys_memset */
/*===========================================================================*/
/*
* PUBLIC void phys_memset(phys_bytes source, unsigned long pattern,
* phys_bytes bytecount);
* Fill a block of physical memory with pattern.
*/
.balign 16
_phys_memset:
push %ebp
mov %esp, %ebp
push %esi
push %ebx
push %ds
mov 8(%ebp), %esi
mov 16(%ebp), %eax
mov $FLAT_DS_SELECTOR, %ebx
mov %bx, %ds
mov 12(%ebp), %ebx
shr $2, %eax
fill_start:
mov %ebx, (%esi)
add $4, %esi
dec %eax
jne fill_start
/* Any remaining bytes? */
mov 16(%ebp), %eax
and $3, %eax
remain_fill:
cmp $0, %eax
je fill_done
movb 12(%ebp), %bl
movb %bl, (%esi)
add $1, %esi
inc %ebp
dec %eax
jmp remain_fill
fill_done:
pop %ds
pop %ebx
pop %esi
pop %ebp
ret
/*===========================================================================*/
/* mem_rdw */
/*===========================================================================*/
/*
* PUBLIC u16_t mem_rdw(U16_t segment, u16_t *offset);
* Load and return word at far pointer segment:offset.
*/
.balign 16
_mem_rdw:
mov %ds, %cx
mov 4(%esp), %ds
mov 4+4(%esp), %eax /* offset */
movzwl (%eax), %eax /* word to return */
mov %cx, %ds
ret
/*===========================================================================*/
/* reset */
/*===========================================================================*/
/*
* PUBLIC void reset();
* Reset the system by loading IDT with offset 0 and interrupting.
*/
_reset:
lidt idt_zero
int $3 /* anything goes, the 386 will not like it */
.data
idt_zero:
.long 0, 0
.text
/*===========================================================================*/
/* halt_cpu */
/*===========================================================================*/
/*
* PUBLIC void halt_cpu(void);
* reanables interrupts and puts the cpu in the halts state. Once an interrupt
* is handled the execution resumes by disabling interrupts and continues
*/
_halt_cpu:
sti
hlt /* interrupts enabled only after this instruction is executed! */
/*
* interrupt handlers make sure that the interrupts are disabled when we
* get here so we take only _one_ interrupt after halting the CPU
*/
ret
/*===========================================================================*/
/* read_flags */
/*===========================================================================*/
/*
* PUBLIC unsigned long read_cpu_flags(void);
* Read CPU status flags from C.
*/
.balign 16
_read_cpu_flags:
pushf
mov (%esp), %eax
add $4, %esp
ret
_read_ds:
mov $0, %eax
mov %ds, %ax
ret
_read_cs:
mov $0, %eax
mov %cs, %ax
ret
_read_ss:
mov $0, %eax
mov %ss, %ax
ret
/*===========================================================================*/
/* fpu_routines */
/*===========================================================================*/
_fninit:
fninit
ret
_clts:
clts
ret
_fnstsw:
xor %eax, %eax
/* DO NOT CHANGE THE OPERAND!!! gas2ack does not handle it yet */
fnstsw %ax
ret
_fnstcw:
push %eax
mov 8(%esp), %eax
/* DO NOT CHANGE THE OPERAND!!! gas2ack does not handle it yet */
fnstcw (%eax)
pop %eax
ret
/*===========================================================================*/
/* fxsave */
/*===========================================================================*/
_fxsave:
mov 4(%esp), %eax
fxsave (%eax) /* Do not change the operand! (gas2ack) */
ret
/*===========================================================================*/
/* fnsave */
/*===========================================================================*/
_fnsave:
mov 4(%esp), %eax
fnsave (%eax) /* Do not change the operand! (gas2ack) */
fwait /* required for compatibility with processors prior pentium */
ret
/*===========================================================================*/
/* fxrstor */
/*===========================================================================*/
_fxrstor:
mov 4(%esp), %eax
fxrstor (%eax) /* Do not change the operand! (gas2ack) */
ret
/*===========================================================================*/
/* frstor */
/*===========================================================================*/
_frstor:
mov 4(%esp), %eax
frstor (%eax) /* Do not change the operand! (gas2ack) */
ret
/*===========================================================================*/
/* read_cr0 */
/*===========================================================================*/
/* PUBLIC unsigned long read_cr0(void); */
_read_cr0:
push %ebp
mov %esp, %ebp
mov %cr0, %eax
pop %ebp
ret
/*===========================================================================*/
/* write_cr0 */
/*===========================================================================*/
/* PUBLIC void write_cr0(unsigned long value); */
_write_cr0:
push %ebp
mov %esp, %ebp
mov 8(%ebp), %eax
mov %eax, %cr0
jmp 0f /* A jump is required for some flags */
0:
pop %ebp
ret
/*===========================================================================*/
/* read_cr2 */
/*===========================================================================*/
/* PUBLIC reg_t read_cr2(void); */
_read_cr2:
mov %cr2, %eax
ret
/*===========================================================================*/
/* read_cr3 */
/*===========================================================================*/
/* PUBLIC unsigned long read_cr3(void); */
_read_cr3:
push %ebp
mov %esp, %ebp
/* DO NOT CHANGE THE OPERAND!!! gas2ack does not handle it yet */
mov %cr3, %eax
pop %ebp
ret
/*===========================================================================*/
/* read_cr4 */
/*===========================================================================*/
/* PUBLIC unsigned long read_cr4(void); */
_read_cr4:
push %ebp
mov %esp, %ebp
/* DO NOT CHANGE THE OPERAND!!! gas2ack does not handle it yet */
mov %cr4, %eax
pop %ebp
ret
/*===========================================================================*/
/* write_cr4 */
/*===========================================================================*/
/* PUBLIC void write_cr4(unsigned long value); */
_write_cr4:
push %ebp
mov %esp, %ebp
mov 8(%ebp), %eax
/* DO NOT CHANGE THE OPERAND!!! gas2ack does not handle it yet */
mov %eax, %cr4
jmp 0f
0:
pop %ebp
ret
/*===========================================================================*/
/* write_cr3 */
/*===========================================================================*/
/* PUBLIC void write_cr3(unsigned long value); */
_write_cr3:
push %ebp
mov %esp, %ebp
mov 8(%ebp), %eax
/* DO NOT CHANGE THE OPERAND!!! gas2ack does not handle it yet */
mov %eax, %cr3
pop %ebp
ret
/*===========================================================================*/
/* getcr3val */
/*===========================================================================*/
/* PUBLIC unsigned long getcr3val(void); */
_getcr3val:
mov %cr3, %eax
ret
/*
* Read the Model Specific Register (MSR) of IA32 architecture
*
* void ia32_msr_read(u32_t reg, u32_t * hi, u32_t * lo)
*/
.globl _ia32_msr_read
_ia32_msr_read:
push %ebp
mov %esp, %ebp
mov 8(%ebp), %ecx
rdmsr
mov 12(%ebp), %ecx
mov %edx, (%ecx)
mov 16(%ebp), %ecx
mov %eax, (%ecx)
pop %ebp
ret
/*
* Write the Model Specific Register (MSR) of IA32 architecture
*
* void ia32_msr_write(u32_t reg, u32_t hi, u32_t lo)
*/
.globl _ia32_msr_write
_ia32_msr_write:
push %ebp
mov %esp, %ebp
mov 12(%ebp), %edx
mov 16(%ebp), %eax
mov 8(%ebp), %ecx
wrmsr
pop %ebp
ret
/*===========================================================================*/
/* idt_reload */
/*===========================================================================*/
/* PUBLIC void idt_reload (void); */
.balign 16
_idt_reload:
lidt _gdt+IDT_SELECTOR /* reload interrupt descriptor table */
ret
/*
* void reload_segment_regs(void)
*/
#define RELOAD_SEG_REG(reg) \
mov reg, %ax ;\
mov %ax, reg ;
.globl _reload_ds
_reload_ds:
RELOAD_SEG_REG(%ds)
ret
/*===========================================================================*/
/* switch_address_space */
/*===========================================================================*/
/* PUBLIC void switch_address_space(struct proc *p)
*
* sets the %cr3 register to the supplied value if it is not already set to the
* same value in which case it would only result in an extra TLB flush which is
* not desirable
*/
.balign 16
.globl _switch_address_space
_switch_address_space:
/* read the process pointer */
mov 4(%esp), %edx
/* enable process' segment descriptors */
lldt P_LDT_SEL(%edx)
/* get the new cr3 value */
movl P_CR3(%edx), %eax
/* test if the new cr3 != NULL */
cmpl $0, %eax
je 0f
/*
* test if the cr3 is loaded with the current value to avoid unnecessary
* TLB flushes
*/
mov %cr3, %ecx
cmp %ecx, %eax
je 0f
mov %eax, %cr3
mov %edx, _ptproc
0:
ret
/*===========================================================================*/
/* poweroff */
/*===========================================================================*/
/* PUBLIC void poweroff(); */
/* Jump to 16-bit poweroff code */
.globl _poweroff_jmp
_poweroff_jmp:
cli
/* Make real mode descriptor */
mov $(_gdt + SS_SELECTOR), %edi
mov $0x100, %eax
movw %ax, 2(%edi)
shr $16, %eax
movb %al, 4(%edi)
and $0xff00, %ax
andw $0xff, 6(%edi)
or %ax, 6(%edi)
mov $0xffff, %eax
movw %ax, (%edi)
shr $16, %eax
and $0xf, %ax
andb $0xf0, 6(%edi)
or %ax, 6(%edi)
/* Flush TLB */
xor %eax, %eax
mov %eax, %cr3
xor %esp, %esp /* clear esp for real mode*/
/* Reset IDTR */
lidt idt_ptr
mov $SS_SELECTOR, %ax
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
mov %ax, %ss
/* Save real mode cr0 in eax */
mov %cr0, %eax
andl $~I386_CR0_PE, %eax
/* Jump to 16-bit code that is copied to below 1MB */
ljmp $MON_CS_SELECTOR, $0
.data
idt_ptr:
.short 0x3ff
.long 0x0
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