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