From f5aeb0b43a05c8173dcd9f56e8264c453ee2b90c Mon Sep 17 00:00:00 2001
From: Ivan Tan <ivantan1524@gmail.com>
Date: Tue, 13 May 2025 15:30:45 +0800
Subject: [PATCH] implement monotonic for aarch64

---
 src/arch/aarch64/time.rs | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/arch/aarch64/time.rs b/src/arch/aarch64/time.rs
index 8bf457db66..54e2354b9f 100644
--- a/src/arch/aarch64/time.rs
+++ b/src/arch/aarch64/time.rs
@@ -1,4 +1,11 @@
+use crate::time::NANOS_PER_SEC;
+
 pub fn monotonic_absolute() -> u128 {
     //TODO: aarch64 generic timer counter
-    *crate::time::OFFSET.lock()
+    let ticks: usize;
+    unsafe { core::arch::asm!("mrs {}, cntpct_el0", out(reg) ticks) };
+    let freq: usize;
+    unsafe { core::arch::asm!("mrs {}, cntfrq_el0", out(reg) freq) };
+
+    ticks as u128 * NANOS_PER_SEC / freq as u128
 }