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 #include <asm/purgatory.h>
  13
  14         .text
  15         .globl purgatory_start
  16         .balign 16
  17 purgatory_start:
  18         .code64
  19
  20         /* Load a gdt so I know what the segment registers are */
  21         lgdt    gdt(%rip)
  22
  23         /* load the data segments */
  24         movl    $0x18, %eax     /* data segment */
  25         movl    %eax, %ds
  26         movl    %eax, %es
  27         movl    %eax, %ss
  28         movl    %eax, %fs
  29         movl    %eax, %gs
  30
  31         /* Setup a stack */
  32         leaq    lstack_end(%rip), %rsp
  33
  34         /* Call the C code */
  35         call purgatory
  36         jmp     entry64
  37
  38         .section ".rodata"
  39         .balign 16
  40 gdt:    /* 0x00 unusable segment
  41          * 0x08 unused
  42          * so use them as the gdt ptr
  43          */
  44         .word   gdt_end - gdt - 1
  45         .quad   gdt
  46         .word   0, 0, 0
  47
  48         /* 0x10 4GB flat code segment */
  49         .word   0xFFFF, 0x0000, 0x9A00, 0x00AF
  50
  51         /* 0x18 4GB flat data segment */
  52         .word   0xFFFF, 0x0000, 0x9200, 0x00CF
  53 gdt_end:
  54
  55         .bss
  56         .balign 4096
  57 lstack:
  58         .skip 4096
  59 lstack_end: