123 lines
2.4 KiB
C
123 lines
2.4 KiB
C
#include "gdt.h"
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static struct gdt gdt = { 0 };
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static void create_kernel_ds(void)
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{
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struct gdt_entry *entry = gdt.entries + KERNEL_DS_INDEX;
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uint32_t limit = 0xfffff;
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uint32_t base = 0x0;
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entry->granularity = 1;
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entry->db = 1;
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entry->l = 0;
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entry->available = 0;
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entry->present = 1;
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entry->desc_priv = 0;
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entry->desc_type = 1;
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entry->ex = 0;
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entry->dc = 0;
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entry->rw = 1;
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entry->accessed = 0;
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entry->limit_1 = limit & 0xffff;
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entry->limit_2 = (limit >> 16) & 0xf;
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entry->base_1 = base & 0xffff;
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entry->base_2 = (base >> 16) & 0xff;
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entry->base_3 = (base >> 24) & 0xff;
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}
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static void create_kernel_cs(void)
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{
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struct gdt_entry *entry = gdt.entries + KERNEL_CS_INDEX;
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uint32_t limit = 0xfffff;
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uint32_t base = 0x0;
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entry->granularity = 1;
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entry->db = 1;
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entry->l = 0;
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entry->available = 0;
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entry->present = 1;
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entry->desc_priv = 0;
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entry->desc_type = 1;
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entry->ex = 1;
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entry->dc = 0;
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entry->rw = 1;
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entry->accessed = 0;
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entry->limit_1 = limit & 0xffff;
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entry->limit_2 = (limit >> 16) & 0xf;
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entry->base_1 = base & 0xffff;
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entry->base_2 = (base >> 16) & 0xff;
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entry->base_3 = (base >> 24) & 0xff;
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}
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static void create_gdt(void)
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{
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create_kernel_ds();
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create_kernel_cs();
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}
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static void load_gdt(void)
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{
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struct gdt_r gdtr;
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gdtr.addr = (uint32_t)&gdt;
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gdtr.limit = GDT_SIZE - 1;
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asm volatile("lgdt %0\n"
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:
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: "m" (gdtr)
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: "memory");
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}
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static void load_ds(void)
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{
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struct segment_selector selector;
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selector.index = KERNEL_DS_INDEX;
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selector.table_indicator = 0;
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selector.rpl = 0;
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asm volatile("movw %0, %%ax\n"
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"movw %%ax, %%ds\n"
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"movw %%ax, %%fs\n"
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"movw %%ax, %%gs\n"
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"movw %%ax, %%ss\n"
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:
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: "m" (selector)
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: "ax");
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}
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static void load_cs(void)
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{
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struct segment_selector selector;
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selector.index = KERNEL_CS_INDEX;
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selector.table_indicator = 0;
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selector.rpl = 0;
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asm volatile("pushl %0\n"
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"pushl $1f\n"
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"lret\n"
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"1:\n"
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:
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: "m" (selector));
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}
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static void reload_segment_selectors(void)
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{
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load_ds();
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load_cs();
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}
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void init_gdt(void)
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{
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create_gdt();
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load_gdt();
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reload_segment_selectors();
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}
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