ap-boot.S

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/*-
 * Copyright (c) 2002-2018 The UbixOS Project.
 * All rights reserved.
 *
 * This was developed by Christopher W. Olsen for the UbixOS Project.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted
 * provided that the following conditions are met:
 *
 * 1) Redistributions of source code must retain the above copyright notice, this list of
 *    conditions, the following disclaimer and the list of authors.
 * 2) Redistributions in binary form must reproduce the above copyright notice, this list of
 *    conditions, the following disclaimer and the list of authors in the documentation and/or
 *    other materials provided with the distribution.
 * 3) Neither the name of the UbixOS Project nor the names of its contributors may be used to
 *    endorse or promote products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * Okay, this file contains the code that's going to bootstrap the AP cpus
 */


   .globl  ap_trampoline_start,ap_trampoline_end
   .text
   .code16
ap_trampoline_start:
   cli
   cld

   movw    %cs,%ax         // The CPU knows its CS already, so lets use it for the other segments
   movw    %ax,%ds
   movw    %ax,%es
   movw    %ax,%ss

   // Do some bochs-specific bullshit
   mov     $0x31,%al // '1'
   mov     $0xe9,%dx
   outb    %al,%dx
        //lgdt    ap_gdt;  
   lgdt    ap_trampoline_gdt_limit - ap_trampoline_start
   movl    %cr0,%eax
   orl     $0x1,%eax
   movl    %eax,%cr0       // PMODE!

.code32
   .byte 0x66
   ljmp    $0x08,$(ap_trampoline_32 - ap_trampoline_start)         // 0x08 == KERNEL_CS

ap_trampoline_32:
   mov     $0x32,%al // '2'
   mov     $0xe9,%dx
   outb    %al,%dx

   mov     $0x10,%ax
   mov     %ax,%ds
   mov     %ax,%es
   mov     %ax,%fs
   mov     %ax,%gs
   mov     %ax,%ss

   // Spinlock
   mov     ap_trampoline_spl - ap_trampoline_start,%edi
ap_spl:
   //cmp   $1,(%edi)
   //je    ap_spl

   mov     $1,%eax      // Value to be set
   xchgl   (%edi),%eax
   cmp     $0,%eax
   je      ap_spl
   // /Spinlock

   mov     $0x30,%al // '0'
   mov     $0xe9,%dx
   outb    %al,%dx
           
   mov     ap_trampoline_stackptr - ap_trampoline_start,%ebx
   mov     %ebx,%esp
   add     $0x1000,%ebx
   mov     %ebx,ap_trampoline_stackptr - ap_trampoline_start

   mov     $0x31,%al // '1'
   mov     $0xe9,%dx
   outb    %al,%dx

   // spinunlock
   mov     $0,%eax
   mov     ap_trampoline_spl - ap_trampoline_start,%edi
   xchgl   (%edi),%eax
   // /spinunlock

   mov     $0x33,%al // '3'
   mov     $0xe9,%dx
   outb    %al,%dx

   mov     ap_trampoline_epoint,%eax
   call    *%eax
1:
   hlt
   jmp     1b              // Halt if we ever get here somehow

   // Stack.. This sucks, since CPU initialization isn't serialized
ap_trampoline_stackptr:
   .long   0x10000         // 256KB
ap_trampoline_epoint:
   .long   c_ap_boot

ap_trampoline_spl:
   .long   0
ap_gdt:
   .long ubixGDT
   
   // GDT
ap_trampoline_gdt:
   .word   0
ap_trampoline_gdt_limit:
   .word   128     // Room for 32 descriptors
ap_trampoline_gdt_base:
   .long   0x20000         // 128KB (move this later)


ap_trampoline_end: