So I tried to write a basic PIT timer but the interrupt doesn't get called. When I call the handler manually by int command it does work but it doesn't do anything automatically. I am sure my main function never returns as I have set a infinite loop. (I have set up the GDT, IDT and PIC and exceptions does work)
#include <stdint.h>
#include <arch/x86/idt.h>
#include <arch/x86/regs.h>
#include <arch/x86/pic.h>
#include <sys/kprint.h>
struct InterruptDescriptor {
uint16_t offset_low; //Offset bits 0 to 15
uint16_t selector; //A code segment selector in GDT or LDT
uint8_t zero; //Just a gap, always set to zero
uint8_t type_attributes; //Gate type, DPL and present bit fields
uint16_t offset_high; //Offset bits 16 to 31
} __attribute__((packed));
struct IDTPointer{
uint16_t limit;
void* base;
} __attribute__((packed));
static struct IDTPointer idt_pointer;
struct InterruptDescriptor idt[256];
static void (*irq_handler_table[16]) (void);
void idt_set_gate(uint8_t num, void* handler, uint16_t selector, uint8_t type_attributes){
idt[num].offset_low = (uint32_t) handler & 0xFFFF;
idt[num].selector = selector;
idt[num].type_attributes = type_attributes;
idt[num].offset_high = ((uint32_t)handler >> 16) & 0xFFFF;
}
void irq_set_handler(uint8_t irq, void* handler){
irq_handler_table[irq] = handler;
}
void initialize_idt(void){
idt_pointer.limit = sizeof(idt);
idt_pointer.base = &idt;
void* isr_handlers[] = {_isr0, _isr1, _isr2, _isr3, _isr4, _isr5,
_isr6, _isr7, _isr8, _isr9, _isr10, _isr11, _isr12, _isr13, _isr14, _isr15, _isr16,
_isr17, _isr18, _isr19, _isr20, _isr21, _isr22, _isr23, _isr24, _isr25, _isr26, _isr27,
_isr28, _isr29, _isr30, _isr31};
for(int i = 0; i < 32; ++i){
idt_set_gate(i, isr_handlers[i], 0x08, 0x8E);
}
void* irq_handlers[] = {_irq0, _irq1, _irq2, _irq3, _irq4, _irq5, _irq6, _irq7, _irq8, _irq9,
_irq10, _irq11, _irq12, _irq13, _irq14, _irq15};
for(int i = 0; i < 16; ++i){
idt_set_gate(i + 32, irq_handlers[i], 0x08, 0x8E); //There are 32 entries before the first IRQ entry
}
//Load the new IDT
asm volatile ("lidt %0" :: "m"(idt_pointer));
}
static void _exception(char* message, struct x86Registers* regs){
kprintf(message);
kprintf("EAX : 0x%x EBX : 0x%x ECX : 0x%x EDX : 0x%x\n", regs->eax, regs->ebx, regs->ecx, regs->edx);
kprintf("ESP : 0x%x EBP : 0x%x ESI : 0x%x EDI : 0x%x\n", regs->esp, regs->ebp, regs->esi, regs->edi);
kprintf("EIP : 0x%x CS : 0x%x EFLAGS : 0x%x SS : 0x%x\n", regs->eip, regs->cs, regs->eflags, regs->ss);
asm volatile("hlt");
}
static void _handle_irq(struct x86Registers* regs, int irq){
irq_handler_table[irq]();
acknowledge_irq(irq);
}
struct x86Registers* isr_handler(struct x86Registers* regs){
switch (regs->interrupt_no){
case 0: _exception("Division by zero\n", regs); break;
case 3: _exception("Breakpoint\n", regs); break;
case 4: _exception("Overflow\n", regs); break;
case 5: _exception("Range exceeded\n", regs); break;
case 6: _exception("Invalid opcode\n", regs); break;
case 7: _exception("Device not available\n", regs); break;
case 8: _exception("Double fault\n", regs); break;
case 32: _handle_irq(regs, 0); break;
case 33: _handle_irq(regs, 1); break;
case 34: _handle_irq(regs, 2); break;
case 35: _handle_irq(regs, 3); break;
case 36: _handle_irq(regs, 4); break;
case 37: _handle_irq(regs, 5); break;
case 38: _handle_irq(regs, 6); break;
case 39: _handle_irq(regs, 7); break;
case 40: _handle_irq(regs, 8); break;
case 41: _handle_irq(regs, 9); break;
case 42: _handle_irq(regs, 10); break;
case 43: _handle_irq(regs, 11); break;
case 44: _handle_irq(regs, 12); break;
case 45: _handle_irq(regs, 13); break;
case 46: _handle_irq(regs, 14); break;
case 47: _handle_irq(regs, 15); break;
default: kprintf("Interrupt!"); break;
}
return regs;
}
#include <stdint.h>
#include <arch/x86/ports.h>
#define PIC1_COMMAND 0x20
#define PIC1_DATA 0x21
#define PIC2_COMMAND 0xA0
#define PIC2_DATA 0xA1
void remap_pic(uint32_t offset1, uint32_t offset2){
uint8_t p1, p2;
p1 = inb(PIC1_DATA);
p2 = inb(PIC2_DATA);
outb(PIC1_COMMAND, 0x11);
iowait();
outb(PIC2_COMMAND, 0x11);
iowait();
outb(PIC1_DATA, offset1);
iowait();
outb(PIC2_DATA, offset2);
iowait();
outb(PIC1_DATA, 4);
iowait();
outb(PIC2_DATA, 2);
iowait();
outb(PIC1_DATA, 0x01);
iowait();
outb(PIC2_DATA, 0x01);
iowait();
outb(PIC1_DATA, p1);
outb(PIC2_DATA, p2);
}
void unmask_irq(uint8_t irq){
uint16_t port = PIC1_DATA;
uint8_t value;
if(irq >= 8){
port = PIC2_DATA;
irq -= 8;
}
value = inb(port) & ~(1 << irq);
outb(port, value);
}
void acknowledge_irq(uint8_t irq_no){
if (irq_no >= 8)
outb(PIC2_COMMAND, 0x20);
outb(PIC1_COMMAND, 0x20);
}
Thanks for any help.
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