| 1 | /*
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| 2 | ** Copyright 2002, Michael Noisternig. All rights reserved.
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| 3 | ** Distributed under the terms of the NewOS License.
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| 4 | */
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| 5 | #include <boot/arch/i386/stage2.h>
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| 6 | #include <kernel/arch/cpu.h>
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| 7 | #include <kernel/smp.h>
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| 8 | #include <kernel/int.h>
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| 9 |
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| 10 | #include <kernel/arch/i386/selector.h>
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| 11 |
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| 12 | #define MAX_SELECTORS (GDT_LIMIT/8)
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| 13 | #define ENTRIES (MAX_SELECTORS/(sizeof(uint32)*8))
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| 14 |
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| 15 | static uint32 selector_bitmap[ENTRIES]
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| 16 | = { 0x000000ff }; // first 8 selectors reserved
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| 17 |
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| 18 | static selector_type *gdt_table;
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| 19 | static struct gdt_idt_descr descr = { GDT_LIMIT - 1, NULL };
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| 20 |
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| 21 | void i386_selector_init( void *gdt )
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| 22 | {
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| 23 | gdt_table = (selector_type *)gdt;
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| 24 | descr.b = (unsigned int *)gdt_table;
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| 25 | }
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| 26 |
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| 27 | // creates a new selector in the gdt of given type (use SELECTOR macro)
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| 28 | // IN: selector type
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| 29 | // RET: selector that can be directly used for segment registers
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| 30 | // 0 on error
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| 31 | selector_id i386_selector_add( selector_type type )
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| 32 | {
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| 33 | static int spinlock;
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| 34 | int state;
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| 35 | uint32 mask;
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| 36 | selector_id id = 0;
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| 37 | unsigned i;
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| 38 |
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| 39 | state = int_disable_interrupts();
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| 40 | acquire_spinlock( &spinlock );
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| 41 |
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| 42 | for ( i = 0; i < ENTRIES; i++ )
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| 43 | if ( selector_bitmap[i] != 0xffffffff ) { // found free place in there
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| 44 | id = i*sizeof(uint32)*8;
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| 45 | mask = 1;
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| 46 | while ( selector_bitmap[i] & mask ) {
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| 47 | mask <<= 1;
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| 48 | id++;
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| 49 | }
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| 50 | selector_bitmap[i] |= mask;
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| 51 | gdt_table[id] = type;
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| 52 | break;
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| 53 | }
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| 54 |
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| 55 | release_spinlock( &spinlock );
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| 56 | int_restore_interrupts( state );
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| 57 |
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| 58 | if ( id ) {
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| 59 | asm("lgdt %0;"
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| 60 | : : "m" (descr));
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| 61 | }
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| 62 |
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| 63 | return id*8;
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| 64 | }
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| 65 |
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| 66 | // removes a selector with given id from the gdt
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| 67 | void i386_selector_remove( selector_id id )
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| 68 | {
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| 69 | if ( id < 8*8 || id >= MAX_SELECTORS*8 )
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| 70 | return;
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| 71 |
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| 72 | id /= 8;
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| 73 | gdt_table[id] = 0;
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| 74 |
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| 75 | atomic_and( &selector_bitmap[id/32], ~(1<<(id&31)) );
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| 76 |
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| 77 | asm("lgdt %0;"
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| 78 | : : "m" (descr));
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| 79 | }
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| 80 |
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| 81 | // returns the selector type of a given id
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| 82 | selector_type i386_selector_get( selector_id id )
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| 83 | {
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| 84 | return gdt_table[id/8];
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| 85 | }
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