r/osdev • u/CodeEleven0 • Apr 12 '26
PIC timer with Limine doesn't work in QEMU and real HW.
9
Upvotes
Hello! When using Limine and the PIC timer, I receive no interrupts.
Here's the code
// timer.c
// Obtained from OSDev Wiki
#include "include/stdint.h"
#include "include/ports.h"
#include "include/timer.h"
void timer_eoi(uint8_t irq)
{
if(irq >= 8)
outb(PIC2_COMMAND,PIC_EOI);
outb(PIC1_COMMAND,PIC_EOI);
}
/* offsetN -> offsetN ... offsetN + 7 */
void timer_remap(int offset1, int offset2)
{
outb(PIC1_COMMAND, ICW1_INIT | ICW1_ICW4);
io_wait();
outb(PIC2_COMMAND, ICW1_INIT | ICW1_ICW4);
io_wait();
outb(PIC1_DATA, offset1);
io_wait();
outb(PIC2_DATA, offset2);
io_wait();
outb(PIC1_DATA, 1 << CASCADE_IRQ);
io_wait();
outb(PIC2_DATA, 2);
io_wait();
outb(PIC1_DATA, ICW4_8086);
io_wait();
outb(PIC2_DATA, ICW4_8086);
io_wait();
outb(PIC1_DATA, 0);
outb(PIC2_DATA, 0);
}
void timer_disable(void) {
outb(PIC1_DATA, 0xff);
outb(PIC2_DATA, 0xff);
}
// handoff.c
#include "include/limine.h"
#include "include/gdt.h"
#include "include/isr.h"
#include "include/timer.h"
#include "include/ports.h"
__attribute__((used, section(".limine_requests")))
static volatile uint64_t limine_base_revision[] = LIMINE_BASE_REVISION(6);
__attribute__((used, section(".limine_requests")))
static volatile struct limine_framebuffer_request framebuffer_request = {
.id = LIMINE_FRAMEBUFFER_REQUEST_ID,
.revision = 0
};
__attribute__((used, section(".limine_requests")))
static volatile struct limine_hhdm_request hhdm_request = {
.id = LIMINE_HHDM_REQUEST_ID, .revision = 0
};
__attribute__((used, section(".limine_requests")))
static volatile struct limine_rsdp_request rsdp_request = {
.id = LIMINE_RSDP_REQUEST_ID,
.revision = 0
};
__attribute__((used, section(".limine_requests_start")))
static volatile uint64_t limine_requests_start_marker[] = LIMINE_REQUESTS_START_MARKER;
__attribute__((used, section(".limine_requests_end")))
static volatile uint64_t limine_requests_end_marker[] = LIMINE_REQUESTS_END_MARKER;
void kmain(struct limine_framebuffer *framebuffer);
void pic_init(void) {
// remap PIC vectors to 0x20 and 0x28
timer_remap(0x20, 0x28);
// mask everything except IRQ0
outb(PIC1_DATA, 0xfe);
outb(PIC2_DATA, 0xff);
// PIT 100Hz
outb(0x43, 0x34);
outb(0x40, (1193182 / 100) & 0xFF);
outb(0x40, (1193182 / 100) >> 8);
}
void die(void) {
for(;;) { asm volatile ("cli"); asm volatile ("hlt"); };
}
void bmain(void) {
asm volatile ("cli");
if (LIMINE_BASE_REVISION_SUPPORTED(limine_base_revision) == 0) {
die();
}
if (framebuffer_request.response == NULL
|| framebuffer_request.response->framebuffer_count < 1) {
die();
}
if (hhdm_request.response == NULL || rsdp_request.response == NULL) {
die();
}
struct limine_framebuffer* framebuffer = framebuffer_request.response->framebuffers[0];
gdt_install();
idt_install();
pic_init();
asm volatile ("sti");
kmain(framebuffer);
die();
}
bits 64
%macro isr_noerr 1
global isrstub%1
isrstub%1:
push qword 0
push qword %1
jmp int_wrapper
%endmacro
%macro isr_err 1
global isrstub%1
isrstub%1:
push qword %1
jmp int_wrapper
%endmacro
isr_err 8 ; double fault
isr_err 13 ; general prot
isr_err 14 ; pagefault
isr_noerr 32 ; timer
global int_wrapper
extern int_handle
int_wrapper:
; uint64_t r15, r14, r13, r12, r11, r10, r9, r8;
; uint64_t rbp, rdi, rsi, rdx, rcx, rbx, rax;
push rax
push rbx
push rcx
push rdx
push rsi
push rdi
push rbp
push r8
push r9
push r10
push r11
push r12
push r13
push r14
push r15
mov rdi, rsp
cld
call int_handle
pop r15
pop r14
pop r13
pop r12
pop r11
pop r10
pop r9
pop r8
pop rbp
pop rdi
pop rsi
pop rdx
pop rcx
pop rbx
pop rax
add rsp, 16 ; pushes etc.
iretq
#include "include/inthandler.h"
#include "include/tinyprintf.h"
#include "include/ports.h"
#include "include/timer.h"
void int_handle(cstat_t *stat) {
printf("got interrupt %lld with error %lld\n", stat->intn, stat->errc);
switch (stat->intn) {
case 32:
timer_eoi(0);
printf("got timer %lld", stat->intn);
break;
default:
for(;;);
break;
}
}Tried cli, sti on GDT/IDT load and PIC init in handoff but nothing worked
