/*--------------------------------------------------------------------------+
* start16.s v1.0 - PC386 BSP - 1998/04/13
* startAP.s 05/2019
*--------------------------------------------------------------------------+
* This file contains the initialization code for application processors (AP)
* for i386 based board support packages in SMP configuration.
* The APs start in 16 bit real mode. The goal is to:
* 1. Initialize the CPU registers
* 2. Load the global descriptor table
* 3. Switch to protected mode
* 4. Setup the stack pointers
* 5. Switch to the higher level initialization routine
*
*--------------------------------------------------------------------------+
* (C) Copyright 1997 -
* - NavIST Group - Real-Time Distributed Systems and Industrial Automation
*
* http://pandora.ist.utl.pt
*
* Instituto Superior Tecnico * Lisboa * PORTUGAL
*--------------------------------------------------------------------------+
* Disclaimer:
*
* This file is provided "AS IS" without warranty of any kind, either
* expressed or implied.
*--------------------------------------------------------------------------+
*/
/*
* COPYRIGHT (c) 2011.
* On-Line Applications Research Corporation (OAR).
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.org/license/LICENSE.
*/
#include <bspopts.h>
/*---------------------------------------------------------------------------+
| Constants
+----------------------------------------------------------------------------*/
.set PROT_CODE_SEG, 0x08 # offset of code segment descriptor into GDT
.set PROT_DATA_SEG, 0x10 # offset of code segment descriptor into GDT
.set CR0_PE, 1 # protected mode flag on CR0 register
.set HDRSTART, HEADERADDR # address of start of bin2boot header
.set HDROFF, 0x24 # offset into bin2boot header of start32 addr
.set STACKOFF, 0x200-0x10 # offset to load into %esp, from start of image
/* #define NEW_GAS */
#ifdef NEW_GAS
#define LJMPL ljmpl
#else
#define LJMPL ljmp
#endif
/*----------------------------------------------------------------------------+
| CODE section
+----------------------------------------------------------------------------*/
.text
.globl app_processor_start # entry point
app_processor_start:
.code16
cli # DISABLE INTERRUPTS!!!
jmp setup_processor
/*
* Placeholder to copy information from boot_cpu()
* Do NOT move or add asm instruction before
*/
.align 4
app_cpu_start:
.long 0
app_cpu_stack:
.long 0
setup_processor:
movw %cs, %ax # Initialize the rest of
movw %ax, %ds # segment registers
movw %ax, %es
movw %ax, %ss
/*---------------------------------------------------------------------+
| Bare PC machines boot in real mode! We have to turn protected mode on.
+---------------------------------------------------------------------*/
lgdt gdtptr - app_processor_start # load Global Descriptor Table
movl %cr0, %eax
orl $CR0_PE, %eax
movl %eax, %cr0 # turn on protected mode
LJMPL $PROT_CODE_SEG, $start_32bit # flush prefetch queue, and reload %cs
.code32
start_32bit:
/*---------------------------------------------------------------------+
| load the other segment registers
+---------------------------------------------------------------------*/
movl $PROT_DATA_SEG, %eax
movw %ax, %ds
movw %ax, %es
movw %ax, %ss
/* Prepare stack pointers */
movl app_cpu_stack, %esp # stack pointer
movl app_cpu_stack, %ebp # base pointer
movl app_cpu_start, %eax # jump to app CPU start
pushl %eax
/* Clear stack pointer to signal that the we jump to the kernel */
movl $0, app_cpu_stack
/* Switch to the higher level initialization routines */
ret
/*----------------------------------------------------------------------------+
| DATA section
+----------------------------------------------------------------------------*/
/**************************
* GLOBAL DESCRIPTOR TABLE *
**************************/
.p2align 4
gdtptr:
/* we use the NULL descriptor to store the GDT pointer - a trick quite
nifty due to: Robert Collins (rcollins@x86.org) */
.word gdtlen - 1
.long gdtptr
.word 0x0000
/* code segment */
.word 0xffff, 0
.byte 0, 0x9f, 0xcf, 0
/* data segment */
.word 0xffff, 0
.byte 0, 0x93, 0xcf, 0
/* gs segment */
.word 0xffff, 0
.byte 0, 0x92, 0xcf, 0
.set gdtlen, . - gdtptr # length of GDT
