65 lines
1.7 KiB
C
65 lines
1.7 KiB
C
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#include "../include/description_table.h"
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#include "../include/memory.h"
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#include "../include/io.h"
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extern void tss_flush();
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extern uint32_t stack;
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gdt_entry_t gdt_entries[GDT_LENGTH];
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gdt_ptr_t gdt_ptr;
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tss_entry tss;
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void gdt_set_gate(uint32_t num, uint32_t base, uint32_t limit, uint8_t access, uint8_t gran) {
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gdt_entries[num].base_low = (base & 0xFFFF);
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gdt_entries[num].base_middle = (base >> 16) & 0xFF;
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gdt_entries[num].base_high = (base >> 24) & 0xFF;
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gdt_entries[num].limit_low = (limit & 0xFFFF);
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gdt_entries[num].granularity = (limit >> 16) & 0x0F;
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gdt_entries[num].granularity |= gran & 0xF0;
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gdt_entries[num].access = access;
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}
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void write_tss(int32_t num, uint16_t ss0, uint32_t esp0) {
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uintptr_t base = (uintptr_t) & tss;
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uintptr_t limit = base + sizeof(tss);
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gdt_set_gate(num, base, limit, 0xE9, 0x00);
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memset((uint8_t * ) & tss, 0x0, sizeof(tss));
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tss.ss0 = ss0;
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tss.esp0 = esp0;
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tss.cs = 0x0b;
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tss.ss = 0x13;
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tss.ds = 0x13;
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tss.es = 0x13;
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tss.fs = 0x13;
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tss.gs = 0x13;
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tss.iomap_base = sizeof(tss);
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}
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void set_kernel_stack(uintptr_t stack) {
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tss.esp0 = stack;
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}
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void gdt_install() {
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gdt_ptr.limit = sizeof(gdt_entry_t) * GDT_LENGTH - 1;
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gdt_ptr.base = (uint32_t)&gdt_entries;
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gdt_set_gate(0, 0, 0, 0, 0); // 按照 Intel 文档要求，第一个描述符必须全 0
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gdt_set_gate(1, 0, 0xFFFFFFFF, 0x9A, 0xCF); // 指令段
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gdt_set_gate(2, 0, 0xFFFFFFFF, 0x92, 0xCF); // 数据段
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gdt_set_gate(3, 0, 0xFFFFFFFF, 0xFA, 0xCF); // 用户模式代码段
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gdt_set_gate(4, 0, 0xFFFFFFFF, 0xF2, 0xCF); // 用户模式数据段
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gdt_flush((uint32_t)&gdt_ptr);
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write_tss(5, 0x10, 0x0);
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tss_flush();
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}
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