LXR linux/arch/x86/realmode/rm/trampoline

   1/* SPDX-License-Identifier: GPL-2.0 */
   2/*
   3 *
   4 *      Trampoline.S    Derived from Setup.S by Linus Torvalds
   5 *
   6 *      4 Jan 1997 Michael Chastain: changed to gnu as.
   7 *
   8 *      This is only used for booting secondary CPUs in SMP machine
   9 *
  10 *      Entry: CS:IP point to the start of our code, we are
  11 *      in real mode with no stack, but the rest of the
  12 *      trampoline page to make our stack and everything else
  13 *      is a mystery.
  14 *
  15 *      We jump into arch/x86/kernel/head_32.S.
  16 *
  17 *      On entry to trampoline_start, the processor is in real mode
  18 *      with 16-bit addressing and 16-bit data.  CS has some value
  19 *      and IP is zero.  Thus, we load CS to the physical segment
  20 *      of the real mode code before doing anything further.
  21 */
  22
  23#include <linux/linkage.h>
  24#include <asm/segment.h>
  25#include <asm/page_types.h>
  26#include "realmode.h"
  27
  28        .text
  29        .code16
  30
  31        .balign PAGE_SIZE
  32SYM_CODE_START(trampoline_start)
  33        wbinvd                  # Needed for NUMA-Q should be harmless for others
  34
  35        LJMPW_RM(1f)
  361:
  37        mov     %cs, %ax        # Code and data in the same place
  38        mov     %ax, %ds
  39
  40        cli                     # We should be safe anyway
  41
  42        movl    tr_start, %eax  # where we need to go
  43
  44        /*
  45         * GDT tables in non default location kernel can be beyond 16MB and
  46         * lgdt will not be able to load the address as in real mode default
  47         * operand size is 16bit. Use lgdtl instead to force operand size
  48         * to 32 bit.
  49         */
  50        lidtl   tr_idt                  # load idt with 0, 0
  51        lgdtl   tr_gdt                  # load gdt with whatever is appropriate
  52
  53        movw    $1, %dx                 # protected mode (PE) bit
  54        lmsw    %dx                     # into protected mode
  55
  56        ljmpl   $__BOOT_CS, $pa_startup_32
  57SYM_CODE_END(trampoline_start)
  58
  59        .section ".text32","ax"
  60        .code32
  61SYM_CODE_START(startup_32)                      # note: also used from wakeup_asm.S
  62        jmp     *%eax
  63SYM_CODE_END(startup_32)
  64
  65        .bss
  66        .balign 8
  67SYM_DATA_START(trampoline_header)
  68        SYM_DATA_LOCAL(tr_start,        .space 4)
  69        SYM_DATA_LOCAL(tr_gdt_pad,      .space 2)
  70        SYM_DATA_LOCAL(tr_gdt,          .space 6)
  71SYM_DATA_END(trampoline_header)
  72        
  73#include "trampoline_common.S"
  74