Break on timeout in QEMU system mode (#1619)

* Break on timeout in QEMU system mode

* fix

* fix

* fix

fuzzers/qemu_systemmode/Cargo.toml

@@ -18,3 +18,4 @@ codegen-units = 1
 libafl = { path = "../../libafl/" }
 libafl_bolts = { path = "../../libafl_bolts/" }
 libafl_qemu = { path = "../../libafl_qemu/", features = ["arm", "systemmode"] }
+env_logger = "*"

fuzzers/qemu_systemmode/example/main.c

@@ -1,12 +1,11 @@
-int BREAKPOINT() {
+int __attribute__ ((noinline)) BREAKPOINT() {
   for (;;) {}
 }
 
 int LLVMFuzzerTestOneInput(unsigned int *Data, unsigned int Size) {
-  // if (Data[3] == 0) {while(1){}}  // cause a timeout
+  if (Data[3] == 0) {while(1){}}  // cause a timeout
   for (int i = 0; i < Size; i++) {
-    // if (Data[i] > 0xFFd0 && Data[i] < 0xFFFF) {return 1;}    // cause qemu to
-    // crash
+    // if (Data[i] > 0xFFd0 && Data[i] < 0xFFFF) {return 1;}    // cause qemu to crash
     for (int j = i + 1; j < Size; j++) {
       if (Data[j] == 0) { continue; }
       if (Data[j] > Data[i]) {

fuzzers/qemu_systemmode/src/fuzzer.rs

@@ -37,6 +37,8 @@ use libafl_qemu::{
 pub static mut MAX_INPUT_SIZE: usize = 50;
 
 pub fn fuzz() {
+    env_logger::init();
+
     if let Ok(s) = env::var("FUZZ_SIZE") {
         str::parse::<usize>(&s).expect("FUZZ_SIZE was not a number");
     };
@@ -193,7 +195,7 @@ pub fn fuzz() {
         let mut hooks = QemuHooks::new(&emu, tuple_list!(QemuEdgeCoverageHelper::default()));
 
         // Create a QEMU in-process executor
-        let executor = QemuExecutor::new(
+        let mut executor = QemuExecutor::new(
             &mut hooks,
             &mut harness,
             tuple_list!(edges_observer, time_observer),
@@ -203,6 +205,9 @@ pub fn fuzz() {
         )
         .expect("Failed to create QemuExecutor");
 
+        // Instead of calling the timeout handler and restart the process, trigger a breakpoint ASAP
+        executor.break_on_timeout();
+
         // Wrap the executor to keep track of the timeout
         let mut executor = TimeoutExecutor::new(executor, timeout);
 

libafl_bolts/src/minibsod.rs

@@ -845,7 +845,7 @@ pub fn generate_minibsod<W: Write>(
         writeln!(writer, "{:━^100}", " REGISTERS ")?;
         dump_registers(writer, uctx)?;
     } else {
-        writeln!(writer, "Received signal {}", signal)?;
+        writeln!(writer, "Received signal {signal}")?;
     }
     writeln!(writer, "{:━^100}", " BACKTRACE ")?;
     writeln!(writer, "{:?}", backtrace::Backtrace::new())?;

libafl_qemu/src/executor.rs

@@ -1,10 +1,9 @@
 //! A `QEMU`-based executor for binary-only instrumentation in `LibAFL`
-#[cfg(emulation_mode = "usermode")]
-use core::ffi::c_void;
-use core::fmt::{self, Debug, Formatter};
+use core::{
+    ffi::c_void,
+    fmt::{self, Debug, Formatter},
+};
 
-#[cfg(emulation_mode = "usermode")]
-use libafl::executors::inprocess::InProcessExecutorHandlerData;
 #[cfg(feature = "fork")]
 use libafl::{
     events::EventManager,
@@ -13,7 +12,10 @@ use libafl::{
 };
 use libafl::{
     events::{EventFirer, EventRestarter},
-    executors::{inprocess::InProcessExecutor, Executor, ExitKind, HasObservers},
+    executors::{
+        inprocess::{InProcessExecutor, InProcessExecutorHandlerData},
+        Executor, ExitKind, HasObservers,
+    },
     feedbacks::Feedback,
     fuzzer::HasObjective,
     inputs::UsesInput,
@@ -21,7 +23,6 @@ use libafl::{
     state::{HasClientPerfMonitor, HasCorpus, HasExecutions, HasSolutions, State, UsesState},
     Error,
 };
-#[cfg(emulation_mode = "usermode")]
 use libafl_bolts::os::unix_signals::{siginfo_t, ucontext_t, Signal};
 #[cfg(feature = "fork")]
 use libafl_bolts::shmem::ShMemProvider;
@@ -74,7 +75,7 @@ pub unsafe extern "C" fn libafl_executor_reinstall_handlers() {
 pub unsafe fn inproc_qemu_crash_handler<E, EM, OF, Z>(
     signal: Signal,
     info: &mut siginfo_t,
-    context: &mut ucontext_t,
+    mut context: Option<&mut ucontext_t>,
     data: &mut InProcessExecutorHandlerData,
 ) where
     E: Executor<EM, Z> + HasObservers,
@@ -86,7 +87,11 @@ pub unsafe fn inproc_qemu_crash_handler<E, EM, OF, Z>(
     let real_crash = if USE_LIBAFL_CRASH_HANDLER {
         true
     } else {
-        libafl_qemu_handle_crash(signal as i32, info, context as *mut _ as *mut c_void) != 0
+        let puc = match &mut context {
+            Some(v) => (*v) as *mut ucontext_t as *mut c_void,
+            None => core::ptr::null_mut(),
+        };
+        libafl_qemu_handle_crash(signal as i32, info, puc) != 0
     };
     if real_crash {
         libafl::executors::inprocess::unix_signal_handler::inproc_crash_handler::<E, EM, OF, Z>(
@@ -95,6 +100,36 @@ pub unsafe fn inproc_qemu_crash_handler<E, EM, OF, Z>(
     }
 }
 
+#[cfg(emulation_mode = "systemmode")]
+static mut BREAK_ON_TMOUT: bool = false;
+
+#[cfg(emulation_mode = "systemmode")]
+extern "C" {
+    fn qemu_system_debug_request();
+}
+
+#[cfg(emulation_mode = "systemmode")]
+pub unsafe fn inproc_qemu_timeout_handler<E, EM, OF, Z>(
+    signal: Signal,
+    info: &mut siginfo_t,
+    context: Option<&mut ucontext_t>,
+    data: &mut InProcessExecutorHandlerData,
+) where
+    E: Executor<EM, Z> + HasObservers,
+    EM: EventFirer<State = E::State> + EventRestarter<State = E::State>,
+    OF: Feedback<E::State>,
+    E::State: HasSolutions + HasClientPerfMonitor + HasCorpus,
+    Z: HasObjective<Objective = OF, State = E::State>,
+{
+    if BREAK_ON_TMOUT {
+        qemu_system_debug_request();
+    } else {
+        libafl::executors::inprocess::unix_signal_handler::inproc_timeout_handler::<E, EM, OF, Z>(
+            signal, info, context, data,
+        );
+    }
+}
+
 impl<'a, H, OT, QT, S> QemuExecutor<'a, H, OT, QT, S>
 where
     H: FnMut(&S::Input) -> ExitKind,
@@ -116,24 +151,23 @@ where
         S: State + HasExecutions + HasCorpus + HasSolutions + HasClientPerfMonitor,
         Z: HasObjective<Objective = OF, State = S>,
     {
+        let mut inner = InProcessExecutor::new(harness_fn, observers, fuzzer, state, event_mgr)?;
         #[cfg(emulation_mode = "usermode")]
         {
-            let mut inner =
-                InProcessExecutor::new(harness_fn, observers, fuzzer, state, event_mgr)?;
             inner.handlers_mut().crash_handler =
                 inproc_qemu_crash_handler::<InProcessExecutor<'a, H, OT, S>, EM, OF, Z>
                     as *const c_void;
-            Ok(Self {
-                first_exec: true,
-                hooks,
-                inner,
-            })
         }
-        #[cfg(not(emulation_mode = "usermode"))]
+        #[cfg(emulation_mode = "systemmode")]
+        {
+            inner.handlers_mut().timeout_handler =
+                inproc_qemu_timeout_handler::<InProcessExecutor<'a, H, OT, S>, EM, OF, Z>
+                    as *const c_void;
+        }
         Ok(Self {
             first_exec: true,
             hooks,
-            inner: InProcessExecutor::new(harness_fn, observers, fuzzer, state, event_mgr)?,
+            inner,
         })
     }
 
@@ -141,6 +175,13 @@ where
         &self.inner
     }
 
+    #[cfg(emulation_mode = "systemmode")]
+    pub fn break_on_timeout(&mut self) {
+        unsafe {
+            BREAK_ON_TMOUT = true;
+        }
+    }
+
     pub fn inner_mut(&mut self) -> &mut InProcessExecutor<'a, H, OT, S> {
         &mut self.inner
     }