From ca8bc76fd5319842954508484542f4beb6b591d0 Mon Sep 17 00:00:00 2001
From: Tianhao Wang <shrik3@mailbox.org>
Date: Wed, 5 Jun 2024 23:24:01 +0200
Subject: interrupt: set up dummy pagefault handler

Signed-off-by: Tianhao Wang <shrik3@mailbox.org>
---
 src/arch/x86_64/interrupt/mod.rs | 15 +++++++++++----
 src/arch/x86_64/paging/fault.rs  | 33 +++++++++++++++++++++++++++++++++
 src/arch/x86_64/paging/mod.rs    |  6 ++++++
 3 files changed, 50 insertions(+), 4 deletions(-)
 create mode 100644 src/arch/x86_64/paging/fault.rs

(limited to 'src/arch')

diff --git a/src/arch/x86_64/interrupt/mod.rs b/src/arch/x86_64/interrupt/mod.rs
index 6663b23..ed08223 100644
--- a/src/arch/x86_64/interrupt/mod.rs
+++ b/src/arch/x86_64/interrupt/mod.rs
@@ -1,6 +1,7 @@
 pub mod pic_8259;
 pub mod pit;
 use crate::arch::x86_64::arch_regs::TrapFrame;
+use crate::arch::x86_64::paging::fault;
 use crate::io::*;
 use core::arch::asm;
 use core::slice;
@@ -71,13 +72,19 @@ extern "C" fn trap_gate(_nr: u16, fp: u64) {
 	// able to release the lock if the interrupt handler blocks on it. Try
 	// spamming the keyboard with the following line of code uncommented: it
 	// will deadlock!
-	println!("interrupt received 0x{:x}", _nr);
-	if _nr < 0x20 {
-		let _frame = unsafe { &mut *(fp as *mut TrapFrame) };
-		println!("trap: @{:#X} {:#X?}", fp, _frame);
+	// TODO this is only a POC, use proper defines and match later
+	let _frame = unsafe { &mut *(fp as *mut TrapFrame) };
+	if _nr == 0xe {
+		// Pagefault
+		let fault_address = fault::get_fault_addr();
+		fault::page_fault_handler(_frame, fault_address)
+	} else if _nr < 0x20 {
+		println!("[trap[ {:#X?}", _frame);
 		unsafe {
 			asm!("hlt");
 		}
+	} else {
+		// deal with irq
 	}
 	interrupt_enable();
 }
diff --git a/src/arch/x86_64/paging/fault.rs b/src/arch/x86_64/paging/fault.rs
new file mode 100644
index 0000000..7b27649
--- /dev/null
+++ b/src/arch/x86_64/paging/fault.rs
@@ -0,0 +1,33 @@
+use crate::arch::x86_64::arch_regs::TrapFrame;
+use crate::io::*;
+use core::arch::asm;
+
+/// handle page fault: for now we only check if the faulting addr is within
+/// kernel heap range.
+/// TODO: improve this later
+pub fn page_fault_handler(frame: &mut TrapFrame, fault_addr: u64) {
+	let err_code = frame.err_code;
+	println!("pagefault @ {:#X}, err {:#X?}", fault_addr, err_code);
+	unsafe { asm!("hlt") };
+}
+
+/// for x86_64, return the CR3 register.
+/// TODO: use page root in task struct instead of raw cr3
+#[inline]
+pub fn get_root() -> u64 {
+	let cr3: u64;
+	unsafe {
+		asm!("mov {}, cr3", out(reg) cr3);
+	}
+	return cr3;
+}
+
+/// for x86_64, return the CR3 register.
+#[inline]
+pub fn get_fault_addr() -> u64 {
+	let cr2: u64;
+	unsafe {
+		asm!("mov {}, cr2", out(reg) cr2);
+	}
+	return cr2;
+}
diff --git a/src/arch/x86_64/paging/mod.rs b/src/arch/x86_64/paging/mod.rs
index ab93938..257b7b3 100644
--- a/src/arch/x86_64/paging/mod.rs
+++ b/src/arch/x86_64/paging/mod.rs
@@ -1,6 +1,7 @@
 // code derived from the x86_64 crate
 // https://docs.rs/x86_64/latest/src/x86_64/addr.rs.html
 // see ATTRIBUTIONS
+pub mod fault;
 use crate::defs::*;
 use bitflags::bitflags;
 #[repr(align(4096))]
@@ -98,6 +99,11 @@ impl Pagetable {
 	pub fn is_empty(&self) -> bool {
 		self.iter().all(|entry| entry.is_unused())
 	}
+
+	/// walk the page table, create missing tables, return mapped physical frame
+	pub fn map_page(&self, _va: VAddr) {
+		todo!()
+	}
 }
 
 impl VAddr {
-- 
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