arch/x86/realmode/rm/trampoline_32.S

   1 /*
   2  *
   3  *      Trampoline.S    Derived from Setup.S by Linus Torvalds
   4  *
   5  *      4 Jan 1997 Michael Chastain: changed to gnu as.
   6  *
   7  *      This is only used for booting secondary CPUs in SMP machine
   8  *
   9  *      Entry: CS:IP point to the start of our code, we are
  10  *      in real mode with no stack, but the rest of the
  11  *      trampoline page to make our stack and everything else
  12  *      is a mystery.
  13  *
  14  *      We jump into arch/x86/kernel/head_32.S.
  15  *
  16  *      On entry to trampoline_start, the processor is in real mode
  17  *      with 16-bit addressing and 16-bit data.  CS has some value
  18  *      and IP is zero.  Thus, we load CS to the physical segment
  19  *      of the real mode code before doing anything further.
  20  */
  21
  22 #include <linux/linkage.h>
  23 #include <asm/segment.h>
  24 #include <asm/page_types.h>
  25 #include "realmode.h"
  26
  27         .text
  28         .code16
  29
  30         .balign PAGE_SIZE
  31 ENTRY(trampoline_start)
  32         wbinvd                  # Needed for NUMA-Q should be harmless for others
  33
  34         LJMPW_RM(1f)
  35 1:
  36         mov     %cs, %ax        # Code and data in the same place
  37         mov     %ax, %ds
  38
  39         cli                     # We should be safe anyway
  40
  41         movl    tr_start, %eax  # where we need to go
  42
  43         movl    $0xA5A5A5A5, trampoline_status
  44                                 # write marker for master knows we're running
  45
  46         /*
  47          * GDT tables in non default location kernel can be beyond 16MB and
  48          * lgdt will not be able to load the address as in real mode default
  49          * operand size is 16bit. Use lgdtl instead to force operand size
  50          * to 32 bit.
  51          */
  52         lidtl   tr_idt                  # load idt with 0, 0
  53         lgdtl   tr_gdt                  # load gdt with whatever is appropriate
  54
  55         movw    $1, %dx                 # protected mode (PE) bit
  56         lmsw    %dx                     # into protected mode
  57
  58         ljmpl   $__BOOT_CS, $pa_startup_32
  59
  60         .section ".text32","ax"
  61         .code32
  62 ENTRY(startup_32)                       # note: also used from wakeup_asm.S
  63         jmp     *%eax
  64
  65         .bss
  66         .balign 8
  67 GLOBAL(trampoline_header)
  68         tr_start:               .space  4
  69         tr_gdt_pad:             .space  2
  70         tr_gdt:                 .space  6
  71 END(trampoline_header)
  72
  73 #include "trampoline_common.S"