/* SPDX-License-Identifier: GPL-2.0 */
/*
 *
 *      Trampoline.S    Derived from Setup.S by Linus Torvalds
 *
 *      4 Jan 1997 Michael Chastain: changed to gnu as.
 *
 *      This is only used for booting secondary CPUs in SMP machine
 *
 *      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.
 *
 *      We jump into arch/x86/kernel/head_32.S.
 *
 *      On entry to trampoline_start, the processor is in real mode
 *      with 16-bit addressing and 16-bit data.  CS has some value
 *      and IP is zero.  Thus, we load CS to the physical segment
 *      of the real mode code before doing anything further.
 */

#include <linux/linkage.h>
#include <asm/segment.h>
#include <asm/page_types.h>
#include "realmode.h"

        .text
        .code16

        .balign PAGE_SIZE
SYM_CODE_START(trampoline_start)
        wbinvd                  # Needed for NUMA-Q should be harmless for others

        LJMPW_RM(1f)
1:
        mov     %cs, %ax        # Code and data in the same place
        mov     %ax, %ds

        cli                     # We should be safe anyway

        movl    tr_start, %eax  # where we need to go

        /*
         * GDT tables in non default location kernel can be beyond 16MB and
         * lgdt will not be able to load the address as in real mode default
         * operand size is 16bit. Use lgdtl instead to force operand size
         * to 32 bit.
         */
        lidtl   tr_idt                  # load idt with 0, 0
        lgdtl   tr_gdt                  # load gdt with whatever is appropriate

        movw    $1, %dx                 # protected mode (PE) bit
        lmsw    %dx                     # into protected mode

        ljmpl   $__BOOT_CS, $pa_startup_32
SYM_CODE_END(trampoline_start)

        .section ".text32","ax"
        .code32
SYM_CODE_START(startup_32)                      # note: also used from wakeup_asm.S
        jmp     *%eax
SYM_CODE_END(startup_32)

        .bss
        .balign 8
SYM_DATA_START(trampoline_header)
        SYM_DATA_LOCAL(tr_start,        .space 4)
        SYM_DATA_LOCAL(tr_gdt_pad,      .space 2)
        SYM_DATA_LOCAL(tr_gdt,          .space 6)
SYM_DATA_END(trampoline_header)
        
#include "trampoline_common.S"