fix: Snapshot2 should untrack cached pages in case of repeated memory…

… writes (#418)

Test case is provided by @mohanson

src/snapshot2.rs

@@ -2,7 +2,7 @@ use crate::{
     bits::roundup,
     elf::{LoadingAction, ProgramMetadata},
     machine::SupportMachine,
-    memory::{Memory, FLAG_DIRTY},
+    memory::{get_page_indices, Memory, FLAG_DIRTY},
     Error, Register, RISCV_GENERAL_REGISTER_NUMBER, RISCV_PAGESIZE,
 };
 use bytes::Bytes;
@@ -125,6 +125,7 @@ impl<I: Clone + PartialEq, D: DataSource<I>> Snapshot2Context<I, D> {
         length: u64,
     ) -> Result<(u64, u64), Error> {
         let (data, full_length) = self.data_source.load_data(id, offset, length)?;
+        self.untrack_pages(machine, addr, data.len() as u64)?;
         machine.memory_mut().store_bytes(addr, &data)?;
         self.track_pages(machine, addr, data.len() as u64, id, offset)?;
         Ok((data.len() as u64, full_length))
@@ -231,7 +232,7 @@ impl<I: Clone + PartialEq, D: DataSource<I>> Snapshot2Context<I, D> {
         self.track_pages(machine, start, length, id, offset + action.source.start)
     }
 
-    /// This is only made public for advanced usages, but make sure to exercise more
+    /// The followings are only made public for advanced usages, but make sure to exercise more
     /// cautions when calling it!
     pub fn track_pages<M: SupportMachine>(
         &mut self,
@@ -259,6 +260,20 @@ impl<I: Clone + PartialEq, D: DataSource<I>> Snapshot2Context<I, D> {
         }
         Ok(())
     }
+
+    pub fn untrack_pages<M: SupportMachine>(
+        &mut self,
+        machine: &mut M,
+        start: u64,
+        length: u64,
+    ) -> Result<(), Error> {
+        let page_indices = get_page_indices(start, length);
+        for page in page_indices.0..=page_indices.1 {
+            machine.memory_mut().set_flag(page, FLAG_DIRTY)?;
+            self.pages.remove(&page);
+        }
+        Ok(())
+    }
 }
 
 #[derive(Clone, Debug, Deserialize, Serialize)]

tests/test_resume2.rs

@@ -309,7 +309,11 @@ fn load_program(name: &str) -> TestSource {
     file.read_to_end(&mut buffer).unwrap();
     let program = buffer.into();
 
-    let data = vec![7; 16 * 4096];
+    let mut data = vec![0; 16 * 4096];
+    for i in 0..data.len() {
+        data[i] = i as u8;
+    }
+
     let mut m = HashMap::default();
     m.insert(DATA_ID, data.into());
     m.insert(PROGRAM_ID, program);
@@ -622,3 +626,36 @@ pub fn test_sc_after_snapshot2() {
     assert!(result2.is_ok());
     assert_eq!(result2.unwrap(), 0);
 }
+
+#[cfg(not(feature = "enable-chaos-mode-by-default"))]
+#[test]
+pub fn test_store_bytes_twice() {
+    let data_source = load_program("tests/programs/sc_after_snapshot");
+
+    let mut machine = MachineTy::Asm.build(data_source.clone(), VERSION2);
+    machine.set_max_cycles(u64::MAX);
+    machine.load_program(&vec!["main".into()]).unwrap();
+
+    match machine {
+        Machine::Asm(ref mut inner, ref ctx) => {
+            ctx.lock()
+                .unwrap()
+                .store_bytes(&mut inner.machine, 0, &DATA_ID, 2, 29186)
+                .unwrap();
+            ctx.lock()
+                .unwrap()
+                .store_bytes(&mut inner.machine, 0, &DATA_ID, 0, 11008)
+                .unwrap();
+        }
+        _ => unimplemented!(),
+    }
+    let a = machine.full_memory().unwrap()[4096 * 2];
+
+    let snapshot = machine.snapshot().unwrap();
+    let mut machine2 = MachineTy::Asm.build(data_source.clone(), VERSION2);
+    machine2.resume(snapshot).unwrap();
+    machine2.set_max_cycles(u64::MAX);
+    let b = machine2.full_memory().unwrap()[4096 * 2];
+
+    assert_eq!(a, b);
+}