From 200f18b425f6b39c840998035e021e6abcb0fea2 Mon Sep 17 00:00:00 2001
From: Mark Poliakov <mark@alnyan.me>
Date: Tue, 22 Mar 2022 18:44:10 +0200
Subject: [PATCH] feature: x86_64 user pf handling

---
 kernel/src/arch/x86_64/exception.rs | 31 ++++++++++++++++++++++++++---
 kernel/src/proc/process.rs          | 14 ++++++-------
 2 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/kernel/src/arch/x86_64/exception.rs b/kernel/src/arch/x86_64/exception.rs
index f0d8e65..39a8edf 100644
--- a/kernel/src/arch/x86_64/exception.rs
+++ b/kernel/src/arch/x86_64/exception.rs
@@ -2,6 +2,9 @@ use crate::arch::x86_64;
 use crate::debug::Level;
 use crate::dev::irq::{IntController, IrqContext};
 use core::arch::{asm, global_asm};
+use libsys::{error::Errno, signal::Signal};
+use crate::mem::{self, virt::table::Space};
+use crate::proc::{Thread, sched};
 
 #[derive(Debug)]
 struct ExceptionFrame {
@@ -48,7 +51,7 @@ fn pfault_access_type(code: u64) -> &'static str {
     }
 }
 
-fn pfault_dump(level: Level, frame: &ExceptionFrame, cr2: u64) {
+fn pfault_dump(level: Level, frame: &ExceptionFrame, cr2: usize) {
     println!(level, "\x1B[41;1mPage fault:");
     println!(
         level,
@@ -61,8 +64,30 @@ fn pfault_dump(level: Level, frame: &ExceptionFrame, cr2: u64) {
 #[no_mangle]
 extern "C" fn __x86_64_exception_handler(frame: &mut ExceptionFrame) {
     if frame.err_no == 14 {
-        // TODO userspace page faults
-        let cr2 = pfault_read_cr2();
+        let cr2 = pfault_read_cr2() as usize;
+
+        if cr2 < mem::KERNEL_OFFSET && sched::is_ready() {
+            let thread = Thread::current();
+            let proc = thread.owner().unwrap();
+
+            let res = proc.manipulate_space(|space| {
+                space.try_cow_copy(cr2)?;
+                // unsafe {
+                //     intrin::flush_tlb_asid(asid);
+                // }
+                Result::<(), Errno>::Ok(())
+            });
+
+            if res.is_err() {
+                errorln!("Page fault at {:#x} in user {:?}", frame.rip, thread.owner_id());
+                pfault_dump(Level::Error, frame, cr2);
+                proc.enter_fault_signal(thread, Signal::SegmentationFault);
+            }
+
+            return;
+        }
+
+        errorln!("Unresolved page fault:");
         pfault_dump(Level::Error, frame, cr2);
     }
 
diff --git a/kernel/src/proc/process.rs b/kernel/src/proc/process.rs
index 94c0436..6a0f653 100644
--- a/kernel/src/proc/process.rs
+++ b/kernel/src/proc/process.rs
@@ -152,13 +152,13 @@ impl Process {
         }
     }
 
-    // /// Immediately delivers a signal to requested thread
-    // pub fn enter_fault_signal(&self, thread: ThreadRef, signal: Signal) {
-    //     let mut lock = self.inner.lock();
-    //     let table = Self::space_phys(&lock);
-    //     drop(lock);
-    //     thread.enter_signal(signal, table);
-    // }
+    /// Immediately delivers a signal to requested thread
+    pub fn enter_fault_signal(&self, thread: ThreadRef, signal: Signal) {
+        let mut lock = self.inner.lock();
+        let table = Self::space_phys(&mut lock);
+        drop(lock);
+        thread.enter_signal(signal, table);
+    }
 
     /// Crates a new thread in the process
     pub fn new_user_thread(&self, entry: usize, stack: usize, arg: usize) -> Result<Tid, Errno> {