Kernel+Arch: Impl PIT timer interrupt

crates/arch/src/lib.rs

@@ -31,6 +31,7 @@ pub mod idt64;
 pub mod io;
 pub mod paging64;
 pub mod pic8259;
+pub mod pit825x;
 pub mod registers;
 
 pub mod interrupts {
@@ -43,6 +44,35 @@ pub mod interrupts {
     pub unsafe fn disable_interrupts() {
         core::arch::asm!("cli");
     }
+
+    pub fn assert_interrupts(enabled: bool) {
+        let int_state = crate::registers::eflags::is_interrupts_enable_set();
+        assert_eq!(
+            int_state,
+            enabled,
+            "Interrupts were {} when expected them to be {}",
+            if int_state { "on" } else { "off" },
+            if enabled { "on" } else { "off" }
+        );
+    }
+
+    #[macro_export]
+    macro_rules! critcal_section {
+        ($($tt:tt)*) => {
+            let _priv_interrupt_before_state =
+                ::arch::registers::eflags::is_interrupts_enable_set();
+
+            if _priv_interrupt_before_state {
+                unsafe { ::arch::interrupts::disable_interrupts() };
+            }
+
+            $($tt)*;
+
+            if _priv_interrupt_before_state {
+                unsafe { ::arch::interrupts::enable_interrupts() };
+            }
+        };
+    }
 }
 
 #[derive(Clone, Copy, Debug)]

crates/arch/src/pit825x.rs

@@ -0,0 +1,104 @@
+/*
+  ____                 __               __   _ __
+ / __ \__ _____ ____  / /___ ____ _    / /  (_) /
+/ /_/ / // / _ `/ _ \/ __/ // /  ' \  / /__/ / _ \
+\___\_\_,_/\_,_/_//_/\__/\_,_/_/_/_/ /____/_/_.__/
+    Part of the Quantum OS Project
+
+Copyright 2025 Gavin Kellam
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial
+portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+use crate::{interrupts::assert_interrupts, io::IOPort};
+
+const CHANNEL_0_DATA: IOPort = IOPort::new(0x40);
+const _CHANNEL_1_DATA: IOPort = IOPort::new(0x41);
+const _CHANNEL_2_DATA: IOPort = IOPort::new(0x42);
+const COMMAND: IOPort = IOPort::new(0x43);
+
+#[repr(u8)]
+#[derive(Clone, Copy, Debug)]
+pub enum PitSelectChannel {
+    Channel0 = 0,
+    Channel1 = 1,
+    Channel2 = 2,
+    ReadBack = 3,
+}
+
+#[repr(u8)]
+#[derive(Clone, Copy, Debug)]
+pub enum PitAccessMode {
+    LatchCount = 0,
+    AccessLoOnly = 1,
+    AccessHiOnly = 2,
+    AccessLoHi = 3,
+}
+
+#[repr(u8)]
+#[derive(Clone, Copy, Debug)]
+pub enum PitOperatingMode {
+    TerminalCount = 0,
+    RetriggerableOneShot = 1,
+    RateGenerator = 2,
+    SquareWave = 3,
+    SoftwareStrobe = 4,
+    HardwareStrobe = 5,
+}
+
+pub fn pit_command(
+    channel: PitSelectChannel,
+    access: PitAccessMode,
+    mode: PitOperatingMode,
+    bcd_mode: bool,
+) {
+    let bcd_bit = if bcd_mode { 1 } else { 0 };
+    let mode_bit = (mode as u8) << 1;
+    let access_bit = (access as u8) << 4;
+    let channel_bit = (channel as u8) << 6;
+
+    unsafe {
+        COMMAND.write_byte(bcd_bit | mode_bit | access_bit | channel_bit);
+    }
+}
+
+/// Set the pit reload count.
+///
+/// # Interrupts
+/// Interrupts must be disabled before calling this function!
+pub fn set_pit_reload(count: u16) {
+    assert_interrupts(false);
+
+    unsafe {
+        CHANNEL_0_DATA.write_byte((count & 0xFF) as u8);
+        CHANNEL_0_DATA.write_byte(((count >> 8) & 0xFF) as u8);
+    }
+}
+
+/// Set the pit reload count in HZ.
+///
+/// # Interrupts
+/// Interrupts must be disabled before calling this function!
+pub fn set_pit_hz(hz: f32) -> f32 {
+    assert_interrupts(false);
+
+    let div = 1193182_f32 / hz;
+    let int_div = div as u16;
+
+    set_pit_reload(int_div);
+
+    1193182_f32 / (int_div as f32)
+}

crates/arch/src/registers.rs

@@ -383,8 +383,12 @@ pub mod cr4 {
 pub mod eflags {
     #[inline(never)]
     pub fn read() -> u32 {
-        let mut flags;
+        #[cfg(not(target_pointer_width = "64"))]
+        let mut flags: u32;
+        #[cfg(target_pointer_width = "64")]
+        let mut flags: u64;
 
+        #[cfg(not(target_pointer_width = "64"))]
         unsafe {
             core::arch::asm!("
                 pushf
@@ -394,7 +398,20 @@ pub mod eflags {
             )
         }
 
-        flags
+        #[cfg(target_pointer_width = "64")]
+        unsafe {
+            core::arch::asm!("
+                pushf
+                pop rax
+            ",
+                out("rax") flags
+            )
+        }
+
+        #[cfg(not(target_pointer_width = "64"))]
+        return flags;
+        #[cfg(target_pointer_width = "64")]
+        return flags as u32;
     }
 }
 

crates/mem/src/vmm.rs

@@ -22,3 +22,5 @@ NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FO
 DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
 OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
+
+pub struct Vmm {}

kernel/src/int.rs

@@ -24,7 +24,7 @@ OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWA
 */
 
 use arch::{
-    attach_irq,
+    attach_irq, critcal_section,
     idt64::{
         ExceptionKind, InterruptDescTable, InterruptFlags, InterruptInfo, fire_debug_int, interrupt,
     },
@@ -34,16 +34,19 @@ use arch::{
 use lldebug::{logln, sync::Mutex};
 
 static INTERRUPT_TABLE: Mutex<InterruptDescTable> = Mutex::new(InterruptDescTable::new());
+static IRQ_HANDLERS: Mutex<[Option<fn(&InterruptInfo)>; 32]> = Mutex::new([None; 32]);
 
 #[interrupt(0..256)]
 fn main_handler(args: InterruptInfo) {
     match args.flags {
         // IRQ
         InterruptFlags::Irq(irq_num) if irq_num - PIC_IRQ_OFFSET <= 16 => {
+            call_attached_irq(irq_num - PIC_IRQ_OFFSET, &args);
             unsafe { pic_eoi(irq_num - PIC_IRQ_OFFSET) };
         }
+        InterruptFlags::Debug => (),
         exception => {
-            logln!("{:#?}", exception)
+            panic!("UNHANDLED FAULT\n{:#016x?}", args)
         }
         _ => (),
     }
@@ -53,6 +56,29 @@ fn main_handler(args: InterruptInfo) {
     }
 }
 
+fn call_attached_irq(irq_id: u8, args: &InterruptInfo) {
+    let irq_handler = IRQ_HANDLERS.lock();
+
+    if let Some(handler) = irq_handler
+        .get((irq_id) as usize)
+        .and_then(|&handler| handler)
+    {
+        handler(args);
+    }
+}
+
+/// Set a function to be called whenever an irq is triggered.
+pub fn attach_irq_handler(handler_fn: fn(&InterruptInfo), irq: u8) {
+    critcal_section! {
+        let mut irq_handler = IRQ_HANDLERS.lock();
+        let Some(handler) = irq_handler.get_mut(irq as usize) else {
+            return;
+        };
+
+        *handler = Some(handler_fn);
+    }
+}
+
 pub fn attach_interrupts() {
     let mut idt = INTERRUPT_TABLE.lock();
     attach_irq!(idt, main_handler);

kernel/src/main.rs

@@ -31,6 +31,7 @@ OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWA
 
 mod int;
 mod panic;
+mod timer;
 extern crate alloc;
 
 use bootloader::KernelBootHeader;
@@ -66,6 +67,7 @@ fn main(kbh: &KernelBootHeader) {
 
     int::attach_interrupts();
     int::enable_pic();
+    timer::init_timer();
 
     logln!(
         "Init Heap Region ({})",

kernel/src/timer.rs

@@ -0,0 +1,57 @@
+/*
+  ____                 __               __ __                 __
+ / __ \__ _____ ____  / /___ ____ _    / //_/__ _______  ___ / /
+/ /_/ / // / _ `/ _ \/ __/ // /  ' \  / ,< / -_) __/ _ \/ -_) /
+\___\_\_,_/\_,_/_//_/\__/\_,_/_/_/_/ /_/|_|\__/_/ /_//_/\__/_/
+  Part of the Quantum OS Kernel
+
+Copyright 2025 Gavin Kellam
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial
+portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+use arch::{
+    critcal_section,
+    idt64::InterruptInfo,
+    pit825x::{PitAccessMode, PitOperatingMode, PitSelectChannel, pit_command, set_pit_hz},
+};
+use lldebug::{log, logln};
+
+use crate::int::attach_irq_handler;
+
+const TIMER_HZ: f32 = 1000_f32;
+
+pub fn init_timer() {
+    log!("Enabling PIT...");
+    critcal_section! {
+        // Put the pit in repeted trigger mode
+        pit_command(
+            PitSelectChannel::Channel0,
+            PitAccessMode::AccessLoHi,
+            PitOperatingMode::SquareWave,
+            false,
+        );
+
+        // Set the trigger time
+        logln!("({}Hz)", set_pit_hz(TIMER_HZ));
+
+        // Attach our IRQ
+        attach_irq_handler(pit_interrupt_handler, 0);
+    }
+    logln!("OK");
+}
+
+fn pit_interrupt_handler(_args: &InterruptInfo) {}