Add random memory writes

fuzz/fuzz_targets/snapshot2.rs

@@ -55,9 +55,7 @@ impl DataSource<u32> for DummyData {
         let data = match *id {
             DATA_SOURCE_PROGRAM => &self.program,
             DATA_SOURCE_CONTENT => &self.content,
-            _ => {
-                panic!("invalid id")
-            }
+            _ => unreachable!(),
         };
         Ok((
             data.slice(offset as usize..offset as usize + length as usize),
@@ -91,7 +89,7 @@ fuzz_target!(|data: [u8; 32]| {
     let mut loading_action_vec: Vec<LoadingAction> = Vec::new();
     for i in 0..2 + deque.u8() as usize % 3 {
         let segsize = deque.u16() as u64 % 1024;
-        let p_vaddr = i as u64 * 1024 * 1024;
+        let p_vaddr = i as u64 * 1024 * 256;
         let p_memsz = segsize;
         let p_offset = deque.u32() as u64 % (dummy_data.program.len() as u64 - segsize);
         let p_filesz = segsize;
@@ -121,6 +119,19 @@ fuzz_target!(|data: [u8; 32]| {
         .load_program_with_metadata(&dummy_data.program, &metadata, &vec![])
         .unwrap();
     ctx.mark_program(&mut machine1, &metadata, &0, 0).unwrap();
+    for i in 0..2 + deque.u8() as usize % 3 {
+        let id = i as u32 % 2;
+        let data = match id {
+            DATA_SOURCE_PROGRAM => &dummy_data.program,
+            DATA_SOURCE_CONTENT => &dummy_data.content,
+            _ => unreachable!(),
+        };
+        let length = deque.u16() as u64 % 1024;
+        let offset = deque.u32() as u64 % (data.len() as u64 - length);
+        let addr = 1024 * 1024 + (deque.u8() as u64 % 4) * 1024 * 256;
+        ctx.store_bytes(&mut machine1, addr, &id, offset, length)
+            .unwrap();
+    }
     let snapshot = ctx.make_snapshot(&mut machine1).unwrap();
     ctx.resume(&mut machine2, &snapshot).unwrap();
     let mem1 = machine1