blob: 27ee37efb1b22a5d79d354f8a97f446e7e5a874b [file] [log] [blame]
/*
* Copyright (c) 2009 Corey Tabaka
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files
* (the "Software"), to deal in the Software without restriction,
* including without limitation the rights to use, copy, modify, merge,
* publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#include <compiler.h>
#include <arch/x86/descriptor.h>
/* not the best way to do this, but easy for now */
typedef struct {
uint16_t limit_15_0;
uint16_t base_15_0;
uint8_t base_23_16;
uint8_t type : 4;
uint8_t s : 1;
uint8_t dpl : 2;
uint8_t p : 1;
uint8_t limit_19_16 : 4;
uint8_t avl : 1;
uint8_t reserved_0 : 1;
uint8_t d_b : 1;
uint8_t g : 1;
uint8_t base_31_24;
} __PACKED seg_desc_t;
extern seg_desc_t _gdt[];
void set_global_desc(seg_sel_t sel, void *base, uint32_t limit,
uint8_t present, uint8_t ring, uint8_t sys, uint8_t type, uint8_t gran, uint8_t bits)
{
// convert selector into index
uint16_t index = sel >> 3;
_gdt[index].limit_15_0 = limit & 0x0000ffff;
_gdt[index].limit_19_16 = (limit & 0x000f0000) >> 16;
_gdt[index].base_15_0 = ((uint32_t) base) & 0x0000ffff;
_gdt[index].base_23_16 = (((uint32_t) base) & 0x00ff0000) >> 16;
_gdt[index].base_31_24 = ((uint32_t) base) >> 24;
_gdt[index].type = type & 0x0f; // segment type
_gdt[index].p = present != 0; // present
_gdt[index].dpl = ring & 0x03; // descriptor privilege level
_gdt[index].g = gran != 0; // granularity
_gdt[index].s = sys != 0; // system / non-system
_gdt[index].d_b = bits != 0; // 16 / 32 bit
}