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/****************************************************************************
* arch/x86/src/qemu/qemu_lowsetup.c
*
* Copyright (C) 2011-2012 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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 and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX 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 COPYRIGHT HOLDERS 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.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <nuttx/arch.h>
#include <arch/board/board.h>
#include "up_internal.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Private Data
****************************************************************************/
static struct gdt_entry_s gdt_entries[5];
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: up_gdtentry
*
* Description:
* Set the value of one GDT entry.
*
****************************************************************************/
static void up_gdtentry(struct gdt_entry_s *entry, uint32_t base,
uint32_t limit, uint8_t access, uint8_t gran)
{
entry->lowbase = (base & 0xffff);
entry->midbase = (base >> 16) & 0xff;
entry->hibase = (base >> 24) & 0xff;
entry->lowlimit = (limit & 0xffff);
entry->granularity = (limit >> 16) & 0x0f;
entry->granularity |= gran & 0xf0;
entry->access = access;
}
/****************************************************************************
* Name: up_gdtinit
*
* Description:
* Initialize the GDT. The Global Descriptor Table or GDT is a data
* structure used by Intel x86-family processors starting with the 80286
* in order to define the characteristics of the various memory areas used
* during program execution, for example the base address, the size and
* access privileges like executability and writability. These memory areas
* are called segments in Intel terminology.
*
****************************************************************************/
static void up_gdtinit(void)
{
struct gdt_ptr_s gdt_ptr;
up_gdtentry(&gdt_entries[0], 0, 0, 0, 0); /* Null segment */
up_gdtentry(&gdt_entries[1], 0, 0xffffffff, 0x9a, 0xcf); /* Code segment */
up_gdtentry(&gdt_entries[2], 0, 0xffffffff, 0x92, 0xcf); /* Data segment */
up_gdtentry(&gdt_entries[3], 0, 0xffffffff, 0xfa, 0xcf); /* User mode code segment */
up_gdtentry(&gdt_entries[4], 0, 0xffffffff, 0xf2, 0xcf); /* User mode data segment */
gdt_ptr.limit = (sizeof(struct gdt_entry_s) * 5) - 1;
gdt_ptr.base = (uint32_t)gdt_entries;
gdt_flush((uint32_t )&gdt_ptr);
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: up_lowsetup
*
* Description:
* Called from qemu_head BEFORE starting the operating system in order
* perform any necessary, early initialization.
*
****************************************************************************/
void up_lowsetup(void)
{
/* Initialize the Global descriptor table */
up_gdtinit();
/* Early serial driver initialization */
#ifdef USE_EARLYSERIALINIT
up_earlyserialinit();
#endif
/* Now perform board-specific initializations */
up_boardinitialize();
}
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