zephyr/arch/x86/include/gdt.h

76 lines
2.0 KiB
C

/*
* Copyright (c) 2011-2012, 2014 Wind River Systems, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* @file
* @brief IA-32 Global Descriptor Table (GDT) definitions
*
* This file provides definitions for the Global Descriptor Table (GDT) for the
* IA-32 architecture.
*/
#ifndef _GDT_H
#define _GDT_H
#include <arch/x86/arch.h>
#ifdef __cplusplus
extern "C" {
#endif
#ifndef _ASMLANGUAGE
#include <stdint.h>
#include <toolchain.h>
/* a generic GDT entry structure definition */
typedef struct s_gdtDesc {
uint16_t limitLowerWord; /* bits 0:15 of segment limit */
uint16_t baseAdrsLowerWord; /* bits 0:15 of segment base address */
uint8_t baseAdrsMidByte; /* bits 16:23 of segment base address */
uint8_t descType; /* descriptor type fields */
uint8_t limitUpperByte; /* bits 16:19 of limit + more type fields */
uint8_t baseAdrsUpperByte; /* bits 24:31 of segment base address */
} tGdtDesc;
/*
* structure definition for the GDT "header"
* (does not include the GDT entries).
* The structure is packed to force the structure to appear "as is".
* Unfortunately, this appears to remove any alignment restrictions
* so the aligned attribute is used.
*/
typedef struct __packed s_gdtHeader
{
uint16_t limit; /* GDT limit */
tGdtDesc *pEntries; /* pointer to the GDT entries */
} tGdtHeader __aligned(4);
/* externs */
extern tGdtHeader _gdt; /* GDT is implemented in arch/x86/core/gdt.c */
#endif /* _ASMLANGUAGE */
#ifdef __cplusplus
}
#endif
#endif /* _GDT_H */