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/*
 *
 *      Trampoline.S    Derived from Setup.S by Linus Torvalds
 *
 *      4 Jan 1997 Michael Chastain: changed to gnu as.
 *
 *      Entry: CS:IP point to the start of our code, we are 
 *      in real mode with no stack, but the rest of the 
 *      trampoline page to make our stack and everything else
 *      is a mystery.
 *
 *      In fact we don't actually need a stack so we don't
 *      set one up.
 *
 *      On entry to trampoline_data, the processor is in real mode
 *      with 16-bit addressing and 16-bit data.  CS has some value
 *      and IP is zero.  Thus, data addresses need to be absolute
 *      (no relocation) and are taken with regard to r_base.
 *
 *      If you work on this file, check the object module with objdump
 *      --full-contents --reloc to make sure there are no relocation
 *      entries. For the GDT entry we do hand relocation in smpboot.c
 *      because of 64bit linker limitations.
 */

#include <linux/linkage.h>
#include <asm/segment.h>
#include <asm/page.h>

.data

.code16

ENTRY(trampoline_data)
r_base = .

        mov     %cs, %ax        # Code and data in the same place
        mov     %ax, %ds

        mov     $1, %bx         # Flag an SMP trampoline
        cli                     # We should be safe anyway

        movl    $0xA5A5A5A5, trampoline_data - r_base
                                # write marker for master knows we're running

        lidt    idt_48 - r_base # load idt with 0, 0
        lgdt    gdt_48 - r_base # load gdt with whatever is appropriate

        movw    $__KERNEL_DS,%ax
        movw    %ax,%ds
        movw    %ax,%es
        
        xor     %ax, %ax
        inc     %ax             # protected mode (PE) bit
        lmsw    %ax             # into protected mode
        jmp     flush_instr
flush_instr:
        ljmpl   $__KERNEL32_CS, $0x00100000
                        # jump to startup_32 in arch/x86_64/kernel/head.S

idt_48:
        .word   0                        # idt limit = 0
        .word   0, 0                    # idt base = 0L

gdt_48:
        .short  0x0800                  # gdt limit = 2048, 256 GDT entries
        .globl tramp_gdt_ptr
tramp_gdt_ptr:
        .long   0                        # gdt base = gdt (first SMP CPU)
                                        # this is filled in by C because the 64bit
                                        # linker doesn't support absolute 32bit
                                        # relocations.

        
.globl trampoline_end
trampoline_end: