141 lines
5.2 KiB
C
141 lines
5.2 KiB
C
/****************************************************************************
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* arch/x86/src/qemu/qemu_lowsetup.c
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*
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* Copyright (C) 2011-2012 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <nuttx/arch.h>
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#include <arch/board/board.h>
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#include "up_internal.h"
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/****************************************************************************
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* Private Data
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****************************************************************************/
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static struct gdt_entry_s gdt_entries[5];
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: up_gdtentry
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*
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* Description:
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* Set the value of one GDT entry.
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*
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****************************************************************************/
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static void up_gdtentry(struct gdt_entry_s *entry, uint32_t base,
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uint32_t limit, uint8_t access, uint8_t gran)
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{
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entry->lowbase = (base & 0xffff);
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entry->midbase = (base >> 16) & 0xff;
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entry->hibase = (base >> 24) & 0xff;
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entry->lowlimit = (limit & 0xffff);
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entry->granularity = (limit >> 16) & 0x0f;
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entry->granularity |= gran & 0xf0;
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entry->access = access;
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}
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/****************************************************************************
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* Name: up_gdtinit
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*
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* Description:
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* Initialize the GDT. The Global Descriptor Table or GDT is a data
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* structure used by Intel x86-family processors starting with the 80286
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* in order to define the characteristics of the various memory areas used
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* during program execution, for example the base address, the size and
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* access privileges like executability and writability. These memory areas
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* are called segments in Intel terminology.
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*
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****************************************************************************/
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static void up_gdtinit(void)
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{
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struct gdt_ptr_s gdt_ptr;
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up_gdtentry(&gdt_entries[0], 0, 0, 0, 0); /* Null segment */
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up_gdtentry(&gdt_entries[1], 0, 0xffffffff, 0x9a, 0xcf); /* Code segment */
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up_gdtentry(&gdt_entries[2], 0, 0xffffffff, 0x92, 0xcf); /* Data segment */
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up_gdtentry(&gdt_entries[3], 0, 0xffffffff, 0xfa, 0xcf); /* User mode code segment */
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up_gdtentry(&gdt_entries[4], 0, 0xffffffff, 0xf2, 0xcf); /* User mode data segment */
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gdt_ptr.limit = (sizeof(struct gdt_entry_s) * 5) - 1;
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gdt_ptr.base = (uint32_t)gdt_entries;
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gdt_flush((uint32_t )&gdt_ptr);
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}
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: up_lowsetup
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*
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* Description:
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* Called from qemu_head BEFORE starting the operating system in order
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* perform any necessary, early initialization.
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*
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****************************************************************************/
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void up_lowsetup(void)
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{
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/* Initialize the Global descriptor table */
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up_gdtinit();
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/* Early serial driver initialization */
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#ifdef USE_EARLYSERIALINIT
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up_earlyserialinit();
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#endif
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/* Now perform board-specific initializations */
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up_boardinitialize();
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}
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