From db7ce822dc8b0ee7f72e81d39ced930a32844430 Mon Sep 17 00:00:00 2001
From: lazymio <mio@lazym.io>
Date: Thu, 3 Apr 2025 23:25:11 +0800
Subject: [PATCH] QoL Types and Changes (#3124)

* Nop executor

* Qol types

* no stage

* A new() for NopStage

* clippy

* clippy again

---------

Co-authored-by: Dongjia "toka" Zhang <tokazerkje@outlook.com>
---
 libafl/src/executors/mod.rs  |  1 +
 libafl/src/executors/nop.rs  | 75 ++++++++++++++++++++++++++++++++++++
 libafl/src/stages/dynamic.rs | 51 ++++++++++++++++++++++++
 libafl/src/stages/mod.rs     |  2 +
 libafl/src/stages/nop.rs     | 37 ++++++++++++++++++
 5 files changed, 166 insertions(+)
 create mode 100644 libafl/src/executors/nop.rs
 create mode 100644 libafl/src/stages/dynamic.rs
 create mode 100644 libafl/src/stages/nop.rs

diff --git a/libafl/src/executors/mod.rs b/libafl/src/executors/mod.rs
index 2e5754908c..3754e5c156 100644
--- a/libafl/src/executors/mod.rs
+++ b/libafl/src/executors/mod.rs
@@ -28,6 +28,7 @@ pub mod differential;
 #[cfg(all(feature = "std", feature = "fork", unix))]
 pub mod forkserver;
 pub mod inprocess;
+pub mod nop;
 /// SAND(<https://github.com/wtdcode/sand-aflpp>) implementation
 pub mod sand;
 
diff --git a/libafl/src/executors/nop.rs b/libafl/src/executors/nop.rs
new file mode 100644
index 0000000000..208f7f5929
--- /dev/null
+++ b/libafl/src/executors/nop.rs
@@ -0,0 +1,75 @@
+//! Trivial Constant Executor
+
+use core::time::Duration;
+
+use libafl_bolts::tuples::RefIndexable;
+
+use super::{Executor, ExitKind, HasObservers, HasTimeout};
+
+/// [`NopExecutor`] is an executor that does nothing
+pub type NopExecutor = ConstantExecutor<()>;
+
+/// Constant Executor that returns a fixed value. Mostly helpful
+/// when you need it to satisfy some bounds like [`crate::fuzzer::NopFuzzer`]
+#[derive(Debug)]
+pub struct ConstantExecutor<OT = ()> {
+    exit: ExitKind,
+    tm: Duration,
+    ot: OT,
+}
+
+impl<OT> ConstantExecutor<OT> {
+    /// Construct a [`ConstantExecutor`]
+    #[must_use]
+    pub fn new(exit: ExitKind, tm: Duration, ot: OT) -> Self {
+        Self { exit, tm, ot }
+    }
+}
+
+impl ConstantExecutor<()> {
+    /// Construct a [`ConstantExecutor`] that always returns Ok
+    #[must_use]
+    pub fn ok() -> Self {
+        Self::new(ExitKind::Ok, Duration::default(), ())
+    }
+
+    /// Construct a [`ConstantExecutor`] that always returns Crash
+    #[must_use]
+    pub fn crash() -> Self {
+        Self::new(ExitKind::Crash, Duration::default(), ())
+    }
+}
+
+/// These are important to allow [`ConstantExecutor`] to be used with other components
+impl<OT> HasObservers for ConstantExecutor<OT> {
+    type Observers = OT;
+    fn observers(&self) -> RefIndexable<&Self::Observers, Self::Observers> {
+        RefIndexable::from(&self.ot)
+    }
+
+    fn observers_mut(&mut self) -> RefIndexable<&mut Self::Observers, Self::Observers> {
+        RefIndexable::from(&mut self.ot)
+    }
+}
+
+impl<OT> HasTimeout for ConstantExecutor<OT> {
+    fn timeout(&self) -> Duration {
+        self.tm
+    }
+
+    fn set_timeout(&mut self, timeout: Duration) {
+        self.tm = timeout;
+    }
+}
+
+impl<OT, EM, I, S, Z> Executor<EM, I, S, Z> for ConstantExecutor<OT> {
+    fn run_target(
+        &mut self,
+        _fuzzer: &mut Z,
+        _state: &mut S,
+        _mgr: &mut EM,
+        _input: &I,
+    ) -> Result<ExitKind, libafl_bolts::Error> {
+        Ok(self.exit)
+    }
+}
diff --git a/libafl/src/stages/dynamic.rs b/libafl/src/stages/dynamic.rs
new file mode 100644
index 0000000000..9e08864844
--- /dev/null
+++ b/libafl/src/stages/dynamic.rs
@@ -0,0 +1,51 @@
+//! A stage implementation that can have dynamic stage runtime
+
+use super::{Restartable, Stage};
+
+/// A dynamic stage implementation. This explicity uses enum so that rustc can better
+/// reason about the bounds.
+#[derive(Debug)]
+pub enum DynamicStage<T1, T2> {
+    /// One stage
+    Stage1(T1),
+    /// The alernative stage
+    Stage2(T2),
+}
+
+impl<T1, T2, E, EM, S, Z> Stage<E, EM, S, Z> for DynamicStage<T1, T2>
+where
+    T1: Stage<E, EM, S, Z>,
+    T2: Stage<E, EM, S, Z>,
+{
+    fn perform(
+        &mut self,
+        fuzzer: &mut Z,
+        executor: &mut E,
+        state: &mut S,
+        manager: &mut EM,
+    ) -> Result<(), libafl_bolts::Error> {
+        match self {
+            Self::Stage1(st1) => st1.perform(fuzzer, executor, state, manager),
+            Self::Stage2(st2) => st2.perform(fuzzer, executor, state, manager),
+        }
+    }
+}
+
+impl<T1, T2, S> Restartable<S> for DynamicStage<T1, T2>
+where
+    T1: Restartable<S>,
+    T2: Restartable<S>,
+{
+    fn should_restart(&mut self, state: &mut S) -> Result<bool, libafl_bolts::Error> {
+        match self {
+            Self::Stage1(st1) => st1.should_restart(state),
+            Self::Stage2(st2) => st2.should_restart(state),
+        }
+    }
+    fn clear_progress(&mut self, state: &mut S) -> Result<(), libafl_bolts::Error> {
+        match self {
+            Self::Stage1(st1) => st1.clear_progress(state),
+            Self::Stage2(st2) => st2.clear_progress(state),
+        }
+    }
+}
diff --git a/libafl/src/stages/mod.rs b/libafl/src/stages/mod.rs
index dbddebc8d5..e57c3c76d8 100644
--- a/libafl/src/stages/mod.rs
+++ b/libafl/src/stages/mod.rs
@@ -71,9 +71,11 @@ pub mod colorization;
 pub mod concolic;
 #[cfg(feature = "std")]
 pub mod dump;
+pub mod dynamic;
 pub mod generalization;
 pub mod generation;
 pub mod logics;
+pub mod nop;
 pub mod power;
 #[cfg(feature = "std")]
 pub mod sync;
diff --git a/libafl/src/stages/nop.rs b/libafl/src/stages/nop.rs
new file mode 100644
index 0000000000..3f2e21a021
--- /dev/null
+++ b/libafl/src/stages/nop.rs
@@ -0,0 +1,37 @@
+//! A nop stage does nothing
+
+use super::{Restartable, Stage};
+
+/// A stage that does nothing
+#[derive(Debug, Default)]
+pub struct NopStage {}
+
+impl NopStage {
+    /// Create a [`NopStage`]
+    #[must_use]
+    pub fn new() -> Self {
+        Self {}
+    }
+}
+
+impl<E, EM, S, Z> Stage<E, EM, S, Z> for NopStage {
+    fn perform(
+        &mut self,
+        _fuzzer: &mut Z,
+        _executor: &mut E,
+        _state: &mut S,
+        _manager: &mut EM,
+    ) -> Result<(), libafl_bolts::Error> {
+        Ok(())
+    }
+}
+
+impl<S> Restartable<S> for NopStage {
+    fn clear_progress(&mut self, _state: &mut S) -> Result<(), libafl_bolts::Error> {
+        Ok(())
+    }
+
+    fn should_restart(&mut self, _state: &mut S) -> Result<bool, libafl_bolts::Error> {
+        Ok(true)
+    }
+}