95 lines
2.0 KiB
C
95 lines
2.0 KiB
C
#include <stdint.h>
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#include <stddef.h>
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#include "compiler/attr.h"
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#include "hal/hal.h"
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#define GDT_SIZE 5
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typedef struct {
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uint16_t limitlow;
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uint16_t baselow;
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uint8_t basemid;
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uint8_t access;
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uint8_t gran;
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uint8_t basehigh;
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} PACKED GdtEntry;
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typedef struct {
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uint16_t limit;
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uint64_t base;
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} PACKED GdtPtr;
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typedef struct {
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GdtEntry old[5];
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GdtEntry tsslow;
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GdtEntry tsshigh;
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} PACKED ExtendedGdt;
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typedef struct {
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uint32_t resv0;
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uint64_t rsp0;
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uint64_t rsp1;
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uint64_t rsp2;
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uint64_t resv1;
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uint64_t ist[7];
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uint64_t resv2;
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uint16_t resv3;
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uint16_t iopb_off;
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} PACKED Tss;
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static Tss tss = {0};
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static ExtendedGdt *curgdt = NULL;
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#define KCODE 0x08
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#define KDATA 0x10
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#define UCODE 0x18
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#define UDATA 0x20
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#define TSS 0x28
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#define GDT_PRESENT 0x80
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#define GDT_TSS 0x89
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static uint64_t gdt_curretbase(void) {
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GdtPtr gdtr;
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asm volatile("sgdt %0" : "=m"(gdtr));
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return gdtr.base;
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}
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void gdt_setenty(GdtEntry *entry, uint32_t base, uint32_t limit, uint8_t access, uint8_t gran) {
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entry->baselow = base & 0xffff;
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entry->basemid = (base >> 16) & 0xff;
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entry->basehigh = (base >> 24) & 0xff;
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entry->limitlow = limit & 0xffff;
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entry->gran = (limit >> 16) & 0x0f | (gran & 0xf0);
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entry->access = access;
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}
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void gdt_init(void) {
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uint64_t base = gdt_curretbase();
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curgdt = (ExtendedGdt *)base;
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HAL_MEMSET(&tss, 0, sizeof(tss));
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tss.iopb_off = sizeof(tss);
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uint64_t tss_base = (uint64_t)&tss;
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uint32_t tss_limit = sizeof(tss) - 1;
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gdt_setenty(&curgdt->tsslow, tss_base & 0xFFFFFFFF, tss_limit, GDT_PRESENT | GDT_TSS, 0x0);
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GdtEntry *tsshigh = &curgdt->tsshigh;
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tsshigh->baselow = (tss_base >> 32) & 0xffff;
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tsshigh->basemid = (tss_base >> 48) & 0xff;
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tsshigh->basehigh = (tss_base >> 56) & 0xff;
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tsshigh->access = 0;
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tsshigh->gran = 0;
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tsshigh->limitlow = 0;
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GdtPtr gdtr;
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asm volatile("sgdt %0" : "=m"(gdtr));
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gdtr.limit = sizeof(ExtendedGdt) - 1;
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asm volatile("lgdt %0" :: "m"(gdtr));
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asm volatile("ltr %0" :: "r"((uint16_t)0x28));
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}
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