kernel

commit 97ff1cf15e62e17652fbd4b789e7c07f711c155b
parent 706e95f994b9d474d9a784683273b55a63c24b2f
Author: evenfri <evenfri256@gmail.com>
Date:   Mon,  3 Aug 2026 01:41:33 +0800

feat: pit

Diffstat:
M
dat.h
 | 
5
+++++
M
fns.h
 | 
4
++++
M
idt.c
 | 
16
+++++++---------
M
init.c
 | 
5
+++++
A
isr_stub.asm
 | 
25
+++++++++++++++++++++++++
M
mkfile
 | 
2
++
A
pit.c
 | 
36
++++++++++++++++++++++++++++++++++++

7 files changed, 84 insertions(+), 9 deletions(-)
diff --git a/dat.h b/dat.h
@@ -66,4 +66,9 @@ typedef void (*int_handler)();
 #define sys_read 0
 #define sys_write 1
 
+/* pit */
+#define pit_chan0 0x40
+#define pit_comm 0x43
+#define pit_base_freq 1193182
+
 #endif /* dat_h */
diff --git a/fns.h b/fns.h
@@ -60,4 +60,8 @@ size_t vfs_write(unsigned int fd, void *buf, size_t size);
 /* syscall */
 void syscall_init();
 
+/* pit */
+void pit_init(uint32_t freq);
+void pit_sleep(uint32_t ticks_to_wait);
+
 #endif /* fns_h */
diff --git a/idt.c b/idt.c
@@ -22,10 +22,8 @@ void pic_remap() {
   outb(pic_1_data, 0x01); io_wait();
   outb(pic_2_data, 0x01); io_wait();
 
-  outb(pic_1_data, 0b11111101); io_wait();
+  outb(pic_1_data, 0xFC); io_wait();
   outb(pic_2_data, 0xff); io_wait();
-
-  asm volatile ("sti");
 }
 
 void idt_load() {
@@ -36,8 +34,6 @@ void idt_load() {
 }
 
 void idt_register(unsigned char vec, int_handler handler) {
-  asm volatile ("cli");
-
   unsigned int addr = (unsigned int) handler;
 
   idt[vec].isr_low = addr & 0xffff;
@@ -45,12 +41,14 @@ void idt_register(unsigned char vec, int_handler handler) {
   idt[vec].reserved = 0;
   idt[vec].attr = 0x8e;
   idt[vec].isr_high = addr >> 16;
-
-  idt_load();
-
-  asm volatile ("sti");
 }
 
 void idt_init(void) {
+  asm volatile ("cli");
+  for (int i = 0; i < 256; i++) {
+    idt_register(i, excp_handler);
+  }
+
   pic_remap();
+  idt_load();
 }
diff --git a/init.c b/init.c
@@ -21,12 +21,17 @@ void init() {
 
   idt_init();
   vfs_write(stdout, "idt initialized\n", 16);
+  
+  pit_init(1000);
+  vfs_write(stdout, "pit initialized (freq = 1000)\n", 30);
 
   syscall_init();
   vfs_write(stdout, "syscalls initialized\n", 21);
 
   keyboard_init();
   vfs_write(stdout, "keyboard initialized\n", 21);
+
+  asm volatile ("sti");
 }
 
 void bin_init_prog() {
diff --git a/isr_stub.asm b/isr_stub.asm
@@ -0,0 +1,25 @@
+bits 32
+
+global irq0_stub
+extern pit_handler
+
+section .text
+
+irq0_stub:
+  pusha
+
+  mov ax, ds
+  push eax
+
+  mov ax, 0x10
+  mov ds, ax
+  mov es, ax
+
+  call pit_handler
+
+  pop eax
+  mov ds, ax
+  mov es, ax
+
+  popa
+  iret
diff --git a/mkfile b/mkfile
@@ -14,11 +14,13 @@ ofiles =  boot.$o \
           vga.$o \
           gdt.$o \
           idt.$o \
+          isr_stub.$o \
           ints.$o \
           tty.$o \
           vfs.$o \
           syscall_entry.$o \
           syscall.$o \
+          pit.$o \
           init.$o \
           strlen.$o
 
diff --git a/pit.c b/pit.c
@@ -0,0 +1,36 @@
+#include <dat.h>
+#include <fns.h>
+
+volatile uint64_t g_ticks = 0;
+
+extern void irq0_stub(void);
+
+void pit_handler(void) {
+  g_ticks++;
+  outb(0x20, 0x20);
+}
+
+void pit_init(uint32_t freq) {
+  /* calc divisor */
+  uint32_t divisor = pit_base_freq / freq;
+
+  /* limit */
+  if (divisor > 0xffff) divisor = 0xffff;
+  if (divisor < 1) divisor = 1;
+
+  /* command byte */
+  outb(pit_comm, 0x36);
+  /* lsb */
+  outb(pit_chan0, (uint8_t)(divisor & 0xff));
+  /* msb */
+  outb(pit_chan0, (uint8_t)((divisor >> 8) & 0xff));
+
+  idt_register(0x20, irq0_stub);
+}
+
+void pit_sleep(uint32_t ticks_to_wait) {
+  uint64_t target_ticks = g_ticks + ticks_to_wait;
+  while (g_ticks < target_ticks) {
+    asm volatile ("hlt");
+  }
+}