From 81eba30a2934a8d676a87fc74f992b144876fc5a Mon Sep 17 00:00:00 2001
From: Simon Renblad <srenblad@m-labs.hk>
Date: Tue, 17 Dec 2024 11:46:36 +0800
Subject: [PATCH] prevent cursor r/w optimization

---
 src/libio/cursor.rs | 3 +++
 src/libio/lib.rs    | 1 +
 2 files changed, 4 insertions(+)

diff --git a/src/libio/cursor.rs b/src/libio/cursor.rs
index bd397ac..46ff6d6 100644
--- a/src/libio/cursor.rs
+++ b/src/libio/cursor.rs
@@ -2,6 +2,7 @@
 use alloc::vec::Vec;
 
 use core_io::{Error as IoError, Read, Write};
+use core::arch::asm;
 
 #[derive(Debug, Clone)]
 pub struct Cursor<T> {
@@ -47,6 +48,7 @@ impl<T: AsRef<[u8]>> Read for Cursor<T> {
         let len = buf.len().min(data.len());
         // ``copy_from_slice`` generates AXI bursts, use a regular loop instead
         for i in 0..len {
+            unsafe { asm!("", options(preserves_flags, nostack, readonly)); }            
             buf[i] = data[i];
         }
         self.pos += len;
@@ -59,6 +61,7 @@ impl Write for Cursor<&mut [u8]> {
         let data = &mut self.inner[self.pos..];
         let len = buf.len().min(data.len());
         for i in 0..len {
+            unsafe { asm!("", options(preserves_flags, nostack, readonly)); }            
             data[i] = buf[i];
         }
         self.pos += len;
diff --git a/src/libio/lib.rs b/src/libio/lib.rs
index 7abe5c1..70c2384 100644
--- a/src/libio/lib.rs
+++ b/src/libio/lib.rs
@@ -1,5 +1,6 @@
 #![no_std]
 #![feature(never_type)]
+#![feature(asm)]
 
 #[cfg(feature = "alloc")]
 extern crate alloc;