104 lines
3.2 KiB
C
104 lines
3.2 KiB
C
/* gdt.c - Global Descriptor Table support */
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/*
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* Copyright (c) 2011-2014 Wind River Systems, Inc.
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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 are met:
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*
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* 1) Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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*
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* 2) Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* 3) Neither the name of Wind River Systems nor the names of its contributors
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* may be used to endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN 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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DESCRIPTION
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This module contains routines for updating the global descriptor table (GDT)
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for the IA-32 architecture.
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*/
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/* includes */
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#include <linker-defs.h>
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#include <toolchain.h>
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#include <sections.h>
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#include <nanok.h>
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#include <nanokernel/cpu.h>
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#include <gdt.h>
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/* defines */
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#if (CONFIG_NUM_GDT_SPARE_ENTRIES < 0)
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#error "**** CONFIG_NUM_GDT_SPARE_ENTRIES must be at least 0\n\n"
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#endif
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#define NUM_BASE_GDT_ENTRIES 3
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#define MAX_GDT_ENTRIES \
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(NUM_BASE_GDT_ENTRIES + CONFIG_NUM_GDT_SPARE_ENTRIES)
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/* locals */
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/*
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* The RAM based global descriptor table. It is aligned on an 8 byte boundary
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* as the Intel manuals recommend this for best performance.
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*/
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/*
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* For MM_POMS, _gdt_entries must be global so the linker script can
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* generate a _GdtEntriesP for crt0.s
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*/
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static
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tGdtDesc
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_gdt_entries[MAX_GDT_ENTRIES]
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__attribute__((aligned(8))) = {
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{/* Entry 0 (selector=0x0000): The "NULL descriptor" */
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0x0000, 0x0000, 0x00, 0x00, 0x00, 0x00},
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{ /* Entry 1 (selector=0x0008): Code descriptor: DPL0 */
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0xffff, /* limit: xffff */
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0x0000, /* base : xxxx0000 */
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0x00, /* base : xx00xxxx */
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0x9b, /* Code e/r, Present, DPL0, Accessed=1 */
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0xcf, /* limit: fxxxx, Page Gra, 32 bit */
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0x00 /* base : 00xxxxxx */
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},
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{ /* Entry 2 (selector=0x0010): Data descriptor: DPL0 */
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0xffff, /* limit: xffff */
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0x0000, /* base : xxxx0000 */
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0x00, /* base : xx00xxxx */
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0x93, /* Data r/w, Present, DPL0, Accessed=1 */
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0xcf, /* limit: fxxxx, Page Gra, 32 bit */
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0x00 /* base : 00xxxxxx */
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},
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};
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/* globals */
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tGdtHeader _gdt = {
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sizeof(tGdtDesc[MAX_GDT_ENTRIES - CONFIG_NUM_GDT_SPARE_ENTRIES]) -
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1,
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&_gdt_entries[0]};
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