arch/x86/purgatory/setup-x86_64.S

   1 /*
   2  * purgatory:  setup code
   3  *
   4  * Copyright (C) 2003,2004  Eric Biederman (ebiederm@xmission.com)
   5  * Copyright (C) 2014 Red Hat Inc.
   6  *
   7  * This code has been taken from kexec-tools.
   8  *
   9  * This source code is licensed under the GNU General Public License,
  10  * Version 2.  See the file COPYING for more details.
  11  */
  12
  13         .text
  14         .globl purgatory_start
  15         .balign 16
  16 purgatory_start:
  17         .code64
  18
  19         /* Load a gdt so I know what the segment registers are */
  20         lgdt    gdt(%rip)
  21
  22         /* load the data segments */
  23         movl    $0x18, %eax     /* data segment */
  24         movl    %eax, %ds
  25         movl    %eax, %es
  26         movl    %eax, %ss
  27         movl    %eax, %fs
  28         movl    %eax, %gs
  29
  30         /* Setup a stack */
  31         leaq    lstack_end(%rip), %rsp
  32
  33         /* Call the C code */
  34         call purgatory
  35         jmp     entry64
  36
  37         .section ".rodata"
  38         .balign 16
  39 gdt:    /* 0x00 unusable segment
  40          * 0x08 unused
  41          * so use them as the gdt ptr
  42          */
  43         .word   gdt_end - gdt - 1
  44         .quad   gdt
  45         .word   0, 0, 0
  46
  47         /* 0x10 4GB flat code segment */
  48         .word   0xFFFF, 0x0000, 0x9A00, 0x00AF
  49
  50         /* 0x18 4GB flat data segment */
  51         .word   0xFFFF, 0x0000, 0x9200, 0x00CF
  52 gdt_end:
  53
  54         .bss
  55         .balign 4096
  56 lstack:
  57         .skip 4096
  58 lstack_end: