Less useless allocs for monitor display (#1874)

* Less useless allocs for monitor display

* More less String

* Lol who needs generics

* clippy

* remove &String

libafl/src/events/centralized.rs

@@ -446,7 +446,7 @@ where
     fn add_custom_buf_handler(
         &mut self,
         handler: Box<
-            dyn FnMut(&mut Self::State, &String, &[u8]) -> Result<CustomBufEventResult, Error>,
+            dyn FnMut(&mut Self::State, &str, &[u8]) -> Result<CustomBufEventResult, Error>,
         >,
     ) {
         self.inner.add_custom_buf_handler(handler);

libafl/src/events/llmp.rs

@@ -1,10 +1,6 @@
 //! LLMP-backed event manager for scalable multi-processed fuzzing
 
-use alloc::{
+use alloc::{boxed::Box, vec::Vec};
-    boxed::Box,
-    string::{String, ToString},
-    vec::Vec,
-};
 #[cfg(all(unix, not(miri), feature = "std"))]
 use core::ptr::addr_of_mut;
 #[cfg(feature = "std")]
@@ -208,7 +204,7 @@ where
                         Ok(llmp::LlmpMsgHookResult::ForwardToClients)
                     }
                 } else {
-                    monitor.display("Broker".into(), ClientId(0));
+                    monitor.display("Broker", ClientId(0));
                     Ok(llmp::LlmpMsgHookResult::Handled)
                 }
             },
@@ -254,7 +250,7 @@ where
                     // as a forwarded msg with a lower executions may arrive after a stats msg with an higher executions
                     client.update_executions(*executions as u64, *time);
                 }
-                monitor.display(event.name().to_string(), id);
+                monitor.display(event.name(), id);
                 Ok(BrokerEventResult::Forward)
             }
             Event::UpdateExecStats {
@@ -266,7 +262,7 @@ where
                 monitor.client_stats_insert(client_id);
                 let client = monitor.client_stats_mut_for(client_id);
                 client.update_executions(*executions as u64, *time);
-                monitor.display(event.name().to_string(), client_id);
+                monitor.display(event.name(), client_id);
                 Ok(BrokerEventResult::Handled)
             }
             Event::UpdateUserStats {
@@ -278,7 +274,7 @@ where
                 let client = monitor.client_stats_mut_for(client_id);
                 client.update_user_stats(name.clone(), value.clone());
                 monitor.aggregate(name);
-                monitor.display(event.name().to_string(), client_id);
+                monitor.display(event.name(), client_id);
                 Ok(BrokerEventResult::Handled)
             }
             #[cfg(feature = "introspection")]
@@ -301,7 +297,7 @@ where
                 client.update_introspection_monitor((**introspection_monitor).clone());
 
                 // Display the monitor via `.display` only on core #1
-                monitor.display(event.name().to_string(), client_id);
+                monitor.display(event.name(), client_id);
 
                 // Correctly handled the event
                 Ok(BrokerEventResult::Handled)
@@ -310,7 +306,7 @@ where
                 monitor.client_stats_insert(client_id);
                 let client = monitor.client_stats_mut_for(client_id);
                 client.update_objective_size(*objective_size as u64);
-                monitor.display(event.name().to_string(), client_id);
+                monitor.display(event.name(), client_id);
                 Ok(BrokerEventResult::Handled)
             }
             Event::Log {
@@ -826,7 +822,7 @@ where
 {
     fn add_custom_buf_handler(
         &mut self,
-        handler: Box<dyn FnMut(&mut S, &String, &[u8]) -> Result<CustomBufEventResult, Error>>,
+        handler: Box<dyn FnMut(&mut S, &str, &[u8]) -> Result<CustomBufEventResult, Error>>,
     ) {
         self.custom_buf_handlers.push(handler);
     }

libafl/src/events/mod.rs

@@ -598,8 +598,7 @@ where
 }
 
 /// The handler function for custom buffers exchanged via [`EventManager`]
-type CustomBufHandlerFn<S> =
+type CustomBufHandlerFn<S> = dyn FnMut(&mut S, &str, &[u8]) -> Result<CustomBufEventResult, Error>;
-    dyn FnMut(&mut S, &String, &[u8]) -> Result<CustomBufEventResult, Error>;
 
 /// Supports custom buf handlers to handle `CustomBuf` events.
 pub trait HasCustomBufHandlers: UsesState {
@@ -677,7 +676,7 @@ where
     fn add_custom_buf_handler(
         &mut self,
         _handler: Box<
-            dyn FnMut(&mut Self::State, &String, &[u8]) -> Result<CustomBufEventResult, Error>,
+            dyn FnMut(&mut Self::State, &str, &[u8]) -> Result<CustomBufEventResult, Error>,
         >,
     ) {
     }
@@ -808,7 +807,7 @@ where
     fn add_custom_buf_handler(
         &mut self,
         handler: Box<
-            dyn FnMut(&mut Self::State, &String, &[u8]) -> Result<CustomBufEventResult, Error>,
+            dyn FnMut(&mut Self::State, &str, &[u8]) -> Result<CustomBufEventResult, Error>,
         >,
     ) {
         self.inner.add_custom_buf_handler(handler);

libafl/src/events/simple.rs

@@ -1,10 +1,6 @@
 //! A very simple event manager, that just supports log outputs, but no multiprocessing
 
-use alloc::{
+use alloc::{boxed::Box, vec::Vec};
-    boxed::Box,
-    string::{String, ToString},
-    vec::Vec,
-};
 #[cfg(all(unix, not(miri), feature = "std"))]
 use core::ptr::addr_of_mut;
 use core::{fmt::Debug, marker::PhantomData};
@@ -146,7 +142,7 @@ where
     fn add_custom_buf_handler(
         &mut self,
         handler: Box<
-            dyn FnMut(&mut Self::State, &String, &[u8]) -> Result<CustomBufEventResult, Error>,
+            dyn FnMut(&mut Self::State, &str, &[u8]) -> Result<CustomBufEventResult, Error>,
         >,
     ) {
         self.custom_buf_handlers.push(handler);
@@ -221,7 +217,7 @@ where
                 monitor
                     .client_stats_mut_for(ClientId(0))
                     .update_executions(*executions as u64, *time);
-                monitor.display(event.name().to_string(), ClientId(0));
+                monitor.display(event.name(), ClientId(0));
                 Ok(BrokerEventResult::Handled)
             }
             Event::UpdateExecStats {
@@ -235,7 +231,7 @@ where
 
                 client.update_executions(*executions as u64, *time);
 
-                monitor.display(event.name().to_string(), ClientId(0));
+                monitor.display(event.name(), ClientId(0));
                 Ok(BrokerEventResult::Handled)
             }
             Event::UpdateUserStats {
@@ -248,7 +244,7 @@ where
                     .client_stats_mut_for(ClientId(0))
                     .update_user_stats(name.clone(), value.clone());
                 monitor.aggregate(name);
-                monitor.display(event.name().to_string(), ClientId(0));
+                monitor.display(event.name(), ClientId(0));
                 Ok(BrokerEventResult::Handled)
             }
             #[cfg(feature = "introspection")]
@@ -263,7 +259,7 @@ where
                 let client = monitor.client_stats_mut_for(ClientId(0));
                 client.update_executions(*executions as u64, *time);
                 client.update_introspection_monitor((**introspection_monitor).clone());
-                monitor.display(event.name().to_string(), ClientId(0));
+                monitor.display(event.name(), ClientId(0));
                 Ok(BrokerEventResult::Handled)
             }
             Event::Objective { objective_size } => {
@@ -271,7 +267,7 @@ where
                 monitor
                     .client_stats_mut_for(ClientId(0))
                     .update_objective_size(*objective_size as u64);
-                monitor.display(event.name().to_string(), ClientId(0));
+                monitor.display(event.name(), ClientId(0));
                 Ok(BrokerEventResult::Handled)
             }
             Event::Log {
@@ -407,7 +403,7 @@ where
 {
     fn add_custom_buf_handler(
         &mut self,
-        handler: Box<dyn FnMut(&mut S, &String, &[u8]) -> Result<CustomBufEventResult, Error>>,
+        handler: Box<dyn FnMut(&mut S, &str, &[u8]) -> Result<CustomBufEventResult, Error>>,
     ) {
         self.simple_event_mgr.add_custom_buf_handler(handler);
     }

libafl/src/events/tcp.rs

@@ -1,10 +1,6 @@
 //! TCP-backed event manager for scalable multi-processed fuzzing
 
-use alloc::{
+use alloc::{boxed::Box, vec::Vec};
-    boxed::Box,
-    string::{String, ToString},
-    vec::Vec,
-};
 #[cfg(all(unix, feature = "std", not(miri)))]
 use core::ptr::addr_of_mut;
 use core::{
@@ -337,7 +333,7 @@ where
                 let client = monitor.client_stats_mut_for(id);
                 client.update_corpus_size(*corpus_size as u64);
                 client.update_executions(*executions as u64, *time);
-                monitor.display(event.name().to_string(), id);
+                monitor.display(event.name(), id);
                 Ok(BrokerEventResult::Forward)
             }
             Event::UpdateExecStats {
@@ -349,7 +345,7 @@ where
                 monitor.client_stats_insert(client_id);
                 let client = monitor.client_stats_mut_for(client_id);
                 client.update_executions(*executions as u64, *time);
-                monitor.display(event.name().to_string(), client_id);
+                monitor.display(event.name(), client_id);
                 Ok(BrokerEventResult::Handled)
             }
             Event::UpdateUserStats {
@@ -361,7 +357,7 @@ where
                 let client = monitor.client_stats_mut_for(client_id);
                 client.update_user_stats(name.clone(), value.clone());
                 monitor.aggregate(name);
-                monitor.display(event.name().to_string(), client_id);
+                monitor.display(event.name(), client_id);
                 Ok(BrokerEventResult::Handled)
             }
             #[cfg(feature = "introspection")]
@@ -384,7 +380,7 @@ where
                 client.update_introspection_monitor((**introspection_monitor).clone());
 
                 // Display the monitor via `.display` only on core #1
-                monitor.display(event.name().to_string(), client_id);
+                monitor.display(event.name(), client_id);
 
                 // Correctly handled the event
                 Ok(BrokerEventResult::Handled)
@@ -393,7 +389,7 @@ where
                 monitor.client_stats_insert(client_id);
                 let client = monitor.client_stats_mut_for(client_id);
                 client.update_objective_size(*objective_size as u64);
-                monitor.display(event.name().to_string(), client_id);
+                monitor.display(event.name(), client_id);
                 Ok(BrokerEventResult::Handled)
             }
             Event::Log {
@@ -759,7 +755,7 @@ where
 {
     fn add_custom_buf_handler(
         &mut self,
-        handler: Box<dyn FnMut(&mut S, &String, &[u8]) -> Result<CustomBufEventResult, Error>>,
+        handler: Box<dyn FnMut(&mut S, &str, &[u8]) -> Result<CustomBufEventResult, Error>>,
     ) {
         self.custom_buf_handlers.push(handler);
     }

libafl/src/monitors/disk.rs

@@ -52,7 +52,7 @@ where
         self.base.aggregate(name);
     }
 
-    fn display(&mut self, event_msg: String, sender_id: ClientId) {
+    fn display(&mut self, event_msg: &str, sender_id: ClientId) {
         let cur_time = current_time();
 
         if (cur_time - self.last_update).as_secs() >= 60 {
@@ -201,7 +201,7 @@ where
         self.base.set_start_time(time);
     }
 
-    fn display(&mut self, event_msg: String, sender_id: ClientId) {
+    fn display(&mut self, event_msg: &str, sender_id: ClientId) {
         if (self.log_record)(&mut self.base) {
             let file = OpenOptions::new()
                 .append(true)

libafl/src/monitors/mod.rs

@@ -497,7 +497,7 @@ pub trait Monitor {
     fn set_start_time(&mut self, time: Duration);
 
     /// Show the monitor to the user
-    fn display(&mut self, event_msg: String, sender_id: ClientId);
+    fn display(&mut self, event_msg: &str, sender_id: ClientId);
 
     /// Amount of elements in the corpus (combined for all children)
     fn corpus_size(&self) -> u64 {
@@ -591,7 +591,8 @@ impl Monitor for NopMonitor {
         self.start_time = time;
     }
 
-    fn display(&mut self, _event_msg: String, _sender_id: ClientId) {}
+    #[inline]
+    fn display(&mut self, _event_msg: &str, _sender_id: ClientId) {}
 }
 
 impl NopMonitor {
@@ -660,7 +661,7 @@ impl Monitor for SimplePrintingMonitor {
         self.start_time = time;
     }
 
-    fn display(&mut self, event_msg: String, sender_id: ClientId) {
+    fn display(&mut self, event_msg: &str, sender_id: ClientId) {
         let mut userstats = self.client_stats()[sender_id.0 as usize]
             .user_monitor
             .iter()
@@ -698,7 +699,7 @@ impl Monitor for SimplePrintingMonitor {
 #[derive(Clone)]
 pub struct SimpleMonitor<F>
 where
-    F: FnMut(String),
+    F: FnMut(&str),
 {
     print_fn: F,
     start_time: Duration,
@@ -708,7 +709,7 @@ where
 
 impl<F> Debug for SimpleMonitor<F>
 where
-    F: FnMut(String),
+    F: FnMut(&str),
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("SimpleMonitor")
@@ -720,7 +721,7 @@ where
 
 impl<F> Monitor for SimpleMonitor<F>
 where
-    F: FnMut(String),
+    F: FnMut(&str),
 {
     /// the client monitor, mutable
     fn client_stats_mut(&mut self) -> &mut Vec<ClientStats> {
@@ -742,7 +743,7 @@ where
         self.start_time = time;
     }
 
-    fn display(&mut self, event_msg: String, sender_id: ClientId) {
+    fn display(&mut self, event_msg: &str, sender_id: ClientId) {
         let mut fmt = format!(
             "[{} #{}] run time: {}, clients: {}, corpus: {}, objectives: {}, executions: {}, exec/sec: {}",
             event_msg,
@@ -763,7 +764,7 @@ where
             }
         }
 
-        (self.print_fn)(fmt);
+        (self.print_fn)(&fmt);
 
         // Only print perf monitor if the feature is enabled
         #[cfg(feature = "introspection")]
@@ -773,17 +774,17 @@ where
                 "Client {:03}:\n{}",
                 sender_id.0, self.client_stats[sender_id.0 as usize].introspection_monitor
             );
-            (self.print_fn)(fmt);
+            (self.print_fn)(&fmt);
 
             // Separate the spacing just a bit
-            (self.print_fn)(String::new());
+            (self.print_fn)("");
         }
     }
 }
 
 impl<F> SimpleMonitor<F>
 where
-    F: FnMut(String),
+    F: FnMut(&str),
 {
     /// Creates the monitor, using the `current_time` as `start_time`.
     pub fn new(print_fn: F) -> Self {
@@ -1293,7 +1294,7 @@ impl Default for ClientPerfMonitor {
 #[allow(clippy::unnecessary_fallible_conversions)]
 #[allow(missing_docs)]
 pub mod pybind {
-    use alloc::{boxed::Box, string::String, vec::Vec};
+    use alloc::{boxed::Box, vec::Vec};
     use core::time::Duration;
 
     use libafl_bolts::ClientId;
@@ -1302,13 +1303,16 @@ pub mod pybind {
     use super::ClientStats;
     use crate::monitors::{Monitor, SimpleMonitor};
 
+    /// A [`SimpleMonitor`] type with a boxed `FnMut` for printing
+    pub type SimpleBoxedFnMonitor = SimpleMonitor<Box<dyn FnMut(&str)>>;
+
     // TODO create a PyObjectFnMut to pass, track stabilization of https://github.com/rust-lang/rust/issues/29625
 
     #[pyclass(unsendable, name = "SimpleMonitor")]
     /// Python class for SimpleMonitor
     pub struct PythonSimpleMonitor {
         /// Rust wrapped SimpleMonitor object
-        pub inner: SimpleMonitor<Box<dyn FnMut(String)>>,
+        pub inner: SimpleBoxedFnMonitor,
         print_fn: PyObject,
     }
 
@@ -1323,9 +1327,9 @@ pub mod pybind {
     impl Clone for PythonSimpleMonitor {
         fn clone(&self) -> PythonSimpleMonitor {
             let py_print_fn = self.print_fn.clone();
-            let closure = move |s: String| {
+            let closure = move |s: &str| {
                 Python::with_gil(|py| -> PyResult<()> {
-                    py_print_fn.call1(py, (PyUnicode::new(py, &s),))?;
+                    py_print_fn.call1(py, (PyUnicode::new(py, s),))?;
                     Ok(())
                 })
                 .unwrap();
@@ -1348,9 +1352,9 @@ pub mod pybind {
         #[new]
         fn new(py_print_fn: PyObject) -> Self {
             let py_print_fn1 = py_print_fn.clone();
-            let closure = move |s: String| {
+            let closure = move |s: &str| {
                 Python::with_gil(|py| -> PyResult<()> {
-                    py_print_fn1.call1(py, (PyUnicode::new(py, &s),))?;
+                    py_print_fn1.call1(py, (PyUnicode::new(py, s),))?;
                     Ok(())
                 })
                 .unwrap();
@@ -1427,7 +1431,7 @@ pub mod pybind {
             unwrap_me_mut!(self.wrapper, m, { m.set_start_time(time) });
         }
 
-        fn display(&mut self, event_msg: String, sender_id: ClientId) {
+        fn display(&mut self, event_msg: &str, sender_id: ClientId) {
             unwrap_me_mut!(self.wrapper, m, { m.display(event_msg, sender_id) });
         }
     }

libafl/src/monitors/multi.rs

@@ -1,7 +1,5 @@
 //! Monitor to display both cumulative and per-client monitor
 
-#[cfg(feature = "introspection")]
-use alloc::string::ToString;
 use alloc::{string::String, vec::Vec};
 use core::{
     fmt::{Debug, Formatter, Write},
@@ -17,7 +15,7 @@ use crate::monitors::{ClientStats, Monitor};
 #[derive(Clone)]
 pub struct MultiMonitor<F>
 where
-    F: FnMut(String),
+    F: FnMut(&str),
 {
     print_fn: F,
     start_time: Duration,
@@ -27,7 +25,7 @@ where
 
 impl<F> Debug for MultiMonitor<F>
 where
-    F: FnMut(String),
+    F: FnMut(&str),
 {
     fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
         f.debug_struct("MultiMonitor")
@@ -39,7 +37,7 @@ where
 
 impl<F> Monitor for MultiMonitor<F>
 where
-    F: FnMut(String),
+    F: FnMut(&str),
 {
     /// the client monitor, mutable
     fn client_stats_mut(&mut self) -> &mut Vec<ClientStats> {
@@ -65,7 +63,7 @@ where
         self.aggregator.aggregate(name, &self.client_stats);
     }
 
-    fn display(&mut self, event_msg: String, sender_id: ClientId) {
+    fn display(&mut self, event_msg: &str, sender_id: ClientId) {
         let sender = format!("#{}", sender_id.0);
         let pad = if event_msg.len() + sender.len() < 13 {
             " ".repeat(13 - event_msg.len() - sender.len())
@@ -87,7 +85,7 @@ where
             write!(global_fmt, ", {key}: {val}").unwrap();
         }
 
-        (self.print_fn)(global_fmt);
+        (self.print_fn)(&global_fmt);
 
         self.client_stats_insert(sender_id);
         let client = self.client_stats_mut_for(sender_id);
@@ -102,7 +100,7 @@ where
         for (key, val) in &client.user_monitor {
             write!(fmt, ", {key}: {val}").unwrap();
         }
-        (self.print_fn)(fmt);
+        (self.print_fn)(&fmt);
 
         // Only print perf monitor if the feature is enabled
         #[cfg(feature = "introspection")]
@@ -110,18 +108,18 @@ where
             // Print the client performance monitor. Skip the Client 0 which is the broker
             for (i, client) in self.client_stats.iter().skip(1).enumerate() {
                 let fmt = format!("Client {:03}:\n{}", i + 1, client.introspection_monitor);
-                (self.print_fn)(fmt);
+                (self.print_fn)(&fmt);
             }
 
             // Separate the spacing just a bit
-            (self.print_fn)("\n".to_string());
+            (self.print_fn)("\n");
         }
     }
 }
 
 impl<F> MultiMonitor<F>
 where
-    F: FnMut(String),
+    F: FnMut(&str),
 {
     /// Creates the monitor, using the `current_time` as `start_time`.
     pub fn new(print_fn: F) -> Self {

libafl/src/monitors/prometheus.rs

@@ -47,7 +47,7 @@ use crate::monitors::{ClientStats, Monitor, UserStatsValue};
 #[derive(Clone)]
 pub struct PrometheusMonitor<F>
 where
-    F: FnMut(String),
+    F: FnMut(&str),
 {
     print_fn: F,
     start_time: Duration,
@@ -63,7 +63,7 @@ where
 
 impl<F> Debug for PrometheusMonitor<F>
 where
-    F: FnMut(String),
+    F: FnMut(&str),
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("PrometheusMonitor")
@@ -75,7 +75,7 @@ where
 
 impl<F> Monitor for PrometheusMonitor<F>
 where
-    F: FnMut(String),
+    F: FnMut(&str),
 {
     /// the client monitor, mutable
     fn client_stats_mut(&mut self) -> &mut Vec<ClientStats> {
@@ -98,7 +98,7 @@ where
     }
 
     #[allow(clippy::cast_sign_loss)]
-    fn display(&mut self, event_msg: String, sender_id: ClientId) {
+    fn display(&mut self, event_msg: &str, sender_id: ClientId) {
         // Update the prometheus metrics
         // Label each metric with the sender / client_id
         // The gauges must take signed i64's, with max value of 2^63-1 so it is
@@ -162,7 +162,7 @@ where
             self.total_execs(),
             self.execs_per_sec_pretty()
         );
-        (self.print_fn)(fmt);
+        (self.print_fn)(&fmt);
 
         self.client_stats_insert(sender_id);
         let cur_client = self.client_stats_mut_for(sender_id);
@@ -192,7 +192,7 @@ where
 
 impl<F> PrometheusMonitor<F>
 where
-    F: FnMut(String),
+    F: FnMut(&str),
 {
     pub fn new(listener: String, print_fn: F) -> Self {
         // Gauge's implementation of clone uses Arc

libafl/src/monitors/tui/mod.rs

@@ -357,7 +357,7 @@ impl Monitor for TuiMonitor {
     }
 
     #[allow(clippy::cast_sign_loss)]
-    fn display(&mut self, event_msg: String, sender_id: ClientId) {
+    fn display(&mut self, event_msg: &str, sender_id: ClientId) {
         let cur_time = current_time();
 
         {

libafl/src/schedulers/mod.rs

@@ -1,9 +1,6 @@
 //! Schedule the access to the Corpus.
 
-use alloc::{
+use alloc::{borrow::ToOwned, string::ToString};
-    borrow::ToOwned,
-    string::{String, ToString},
-};
 use core::marker::PhantomData;
 
 pub mod testcase_score;
@@ -155,7 +152,7 @@ where
     fn set_last_hash(&mut self, value: usize);
 
     /// Get the observer map observer name
-    fn map_observer_name(&self) -> &String;
+    fn map_observer_name(&self) -> &str;
 
     /// Called when a [`Testcase`] is added to the corpus
     fn on_add_metadata(&self, state: &mut Self::State, idx: CorpusId) -> Result<(), Error> {

libafl/src/schedulers/powersched.rs

@@ -230,7 +230,7 @@ where
         self.last_hash = hash;
     }
 
-    fn map_observer_name(&self) -> &String {
+    fn map_observer_name(&self) -> &str {
         &self.map_observer_name
     }
 }

libafl/src/schedulers/weighted.rs

@@ -274,7 +274,7 @@ where
         self.last_hash = hash;
     }
 
-    fn map_observer_name(&self) -> &String {
+    fn map_observer_name(&self) -> &str {
         &self.map_observer_name
     }
 }

libafl_libfuzzer/libafl_libfuzzer_runtime/src/fuzz.rs

@@ -175,7 +175,7 @@ where
     })
 }
 
-fn create_monitor_closure() -> impl Fn(String) + Clone {
+fn create_monitor_closure() -> impl Fn(&str) + Clone {
     #[cfg(unix)]
     let stderr_fd =
         std::os::fd::RawFd::from_str(&std::env::var(crate::STDERR_FD_VAR).unwrap()).unwrap(); // set in main

libafl_qemu/src/injections.rs

@@ -394,7 +394,7 @@ where
 
 fn find_function(
     emu: &Emulator,
-    file: &String,
+    file: &str,
     function: &str,
     loadaddr: GuestAddr,
 ) -> Result<Option<GuestAddr>, Error> {