85 lines
2.3 KiB
Zig
85 lines
2.3 KiB
Zig
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// Zig version: 0.4.0
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const gdt = @import("gdt.zig");
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const arch = @import("arch.zig");
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const NUMBER_OF_ENTRIES: u16 = 256;
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const TABLE_SIZE: u16 = @sizeOf(IdtEntry) * NUMBER_OF_ENTRIES - 1;
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// The different gate types
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const TASK_GATE_32BIT: u4 = 0x5;
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const INTERRUPT_GATE_16BIT: u4 = 0x6;
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const TRAP_GATE_16BIT: u4 = 0x7;
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const INTERRUPT_GATE_32BIT: u4 = 0xE;
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const TRAP_GATE_32BIT: u4 = 0xF;
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const PRIVILEGE_RING_0: u2 = 0x0;
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const PRIVILEGE_RING_1: u2 = 0x1;
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const PRIVILEGE_RING_2: u2 = 0x2;
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const PRIVILEGE_RING_3: u2 = 0x3;
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const IdtEntry = packed struct {
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/// The lower 16 bits of the base address of the interrupt handler offset.
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base_low: u16,
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/// The code segment in the GDT which the handlers will be held.
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selector: u16,
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/// Must be zero, unused.
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zero: u8,
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/// The IDT gate type.
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gate_type: u4,
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/// Must be 0 for interrupt and trap gates.
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storage_segment: u1,
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/// The minimum ring level that the calling code must have to run the handler. So user code may not be able to run some interrupts.
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privilege: u2,
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/// Whether the IDT entry is present.
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present: u1,
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/// The upper 16 bits of the base address of the interrupt handler offset.
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base_high: u16,
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};
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pub const IdtPtr = packed struct {
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/// The total size of the IDT (minus 1) in bytes.
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limit: u16,
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/// The base address where the IDT is located.
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base: *IdtEntry,
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};
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var idt: [NUMBER_OF_ENTRIES]IdtEntry = []IdtEntry{makeEntry(0, 0, 0, 0, 0)} ** NUMBER_OF_ENTRIES;
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const idt_ptr: IdtPtr = IdtPtr {
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.limit = TABLE_SIZE,
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.base = &idt[0],
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};
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fn makeEntry(base: u32, selector: u16, gate_type: u4, privilege: u2, present: u1) IdtEntry {
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return IdtEntry {
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.base_low = @truncate(u16, base),
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.selector = selector,
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.zero = 0,
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.gate_type = gate_type,
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.storage_segment = 0,
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.privilege = privilege,
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.present = present,
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.base_high = @truncate(u16, base >> 16),
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};
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}
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pub fn openInterruptGate(index: u8, base: extern fn()void) void {
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idt[index] = makeEntry(@ptrToInt(base), gdt.KERNEL_CODE_OFFSET, INTERRUPT_GATE_32BIT, PRIVILEGE_RING_0, 1);
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}
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pub fn closeInterruptGate(index: u8) void {
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idt[index] = makeEntry(0, 0, 0, 0, 0);
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}
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pub fn init() void {
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arch.lidt(&idt_ptr);
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}
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