e4cc638a8d
This commit adds GDT initialization with proper code/data segments and reloads CS. It also adds the initial IDT structure and loads an empty IDT. Build configuration updated to disable SSE/MMX to prevent compiler generation of unsupported instructions in early boot.
47 lines
1.2 KiB
C
47 lines
1.2 KiB
C
#include "idt.h"
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#include <stdint.h>
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#include <stddef.h> /* for memset */
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idt_entry_t idt_entries[256];
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idt_ptr_t idt_ptr;
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extern void idt_load();
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static void idt_set_gate(uint8_t num, uint32_t base, uint16_t sel, uint8_t flags)
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{
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idt_entries[num].base_lo = base & 0xFFFF;
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idt_entries[num].base_hi = (base >> 16) & 0xFFFF;
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idt_entries[num].sel = sel;
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idt_entries[num].always0 = 0;
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// We must uncomment the OR below when we get to using user-mode.
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// It sets the interrupt gate's privilege level to 3.
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idt_entries[num].flags = flags /* | 0x60 */;
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}
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/* Note: memset implementation because we don't link with libc */
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static void *memset(void *s, int c, size_t n)
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{
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unsigned char *p = s;
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while(n--)
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*p++ = (unsigned char)c;
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return s;
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}
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void init_idt()
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{
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idt_ptr.limit = sizeof(idt_entry_t) * 256 - 1;
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idt_ptr.base = (uint32_t)&idt_entries;
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memset(&idt_entries, 0, sizeof(idt_entry_t) * 256);
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/* Determine valid flags:
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* 0x8E = 1000 1110
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* P=1, DPL=00, S=0 (System), Type=1110 (32-bit Interrupt Gate) */
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/* For now, just load the IDT without any entries to verify loading works without crashing.
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Later we will set up ISRs. */
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idt_load((uint32_t)&idt_ptr);
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}
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