Add vsyscall emulation

kernel/src/arch/x86_64/interrupt/handler.rs

@@ -133,6 +133,10 @@ fn page_fault(tf: &mut TrapFrame) {
         asm!("mov %cr2, $0" : "=r" (addr));
     }
 
+    if vsyscall(addr, tf) {
+        return;
+    }
+
     bitflags! {
         struct PageError: u8 {
             const PRESENT = 1 << 0;
@@ -162,6 +166,20 @@ fn page_fault(tf: &mut TrapFrame) {
     error(tf);
 }
 
+fn vsyscall(addr: usize, tf: &mut TrapFrame) -> bool {
+    let id: usize = match addr {
+        0xffffffffff600000 => 96,
+        _ => return false
+    };
+    debug!("vsyscall emulation");
+    let caller = unsafe { (tf.rsp as *mut u32).read() };
+    let ret = crate::syscall::syscall(id, [tf.rdi, tf.rsi, tf.rdx, tf.r10, tf.r8, tf.r9], tf);
+    tf.rip = caller as usize;
+    tf.rax = ret as usize;
+    tf.rsp += 8;
+    true
+}
+
 fn keyboard() {
     use crate::arch::driver::keyboard;
     use pc_keyboard::{DecodedKey, KeyCode};