wasmtime_fuzzing/
oracles.rs

1//! Oracles.
2//!
3//! Oracles take a test case and determine whether we have a bug. For example,
4//! one of the simplest oracles is to take a Wasm binary as our input test case,
5//! validate and instantiate it, and (implicitly) check that no assertions
6//! failed or segfaults happened. A more complicated oracle might compare the
7//! result of executing a Wasm file with and without optimizations enabled, and
8//! make sure that the two executions are observably identical.
9//!
10//! When an oracle finds a bug, it should report it to the fuzzing engine by
11//! panicking.
12
13#[cfg(feature = "fuzz-spec-interpreter")]
14pub mod diff_spec;
15pub mod diff_wasmi;
16pub mod diff_wasmtime;
17pub mod dummy;
18pub mod engine;
19pub mod memory;
20mod stacks;
21
22use self::diff_wasmtime::WasmtimeInstance;
23use self::engine::{DiffEngine, DiffInstance};
24use crate::generators::{self, CompilerStrategy, DiffValue, DiffValueType};
25use crate::single_module_fuzzer::KnownValid;
26use arbitrary::Arbitrary;
27pub use stacks::check_stacks;
28use std::future::Future;
29use std::pin::Pin;
30use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering::SeqCst};
31use std::sync::{Arc, Condvar, Mutex};
32use std::task::{Context, Poll, Waker};
33use std::time::{Duration, Instant};
34use wasmtime::*;
35use wasmtime_wast::WastContext;
36
37#[cfg(not(any(windows, target_arch = "s390x", target_arch = "riscv64")))]
38mod diff_v8;
39
40static CNT: AtomicUsize = AtomicUsize::new(0);
41
42/// Logs a wasm file to the filesystem to make it easy to figure out what wasm
43/// was used when debugging.
44pub fn log_wasm(wasm: &[u8]) {
45    super::init_fuzzing();
46
47    if !log::log_enabled!(log::Level::Debug) {
48        return;
49    }
50
51    let i = CNT.fetch_add(1, SeqCst);
52    let name = format!("testcase{i}.wasm");
53    std::fs::write(&name, wasm).expect("failed to write wasm file");
54    log::debug!("wrote wasm file to `{}`", name);
55    let wat = format!("testcase{i}.wat");
56    match wasmprinter::print_bytes(wasm) {
57        Ok(s) => std::fs::write(&wat, s).expect("failed to write wat file"),
58        // If wasmprinter failed remove a `*.wat` file, if any, to avoid
59        // confusing a preexisting one with this wasm which failed to get
60        // printed.
61        Err(_) => drop(std::fs::remove_file(&wat)),
62    }
63}
64
65/// The `T` in `Store<T>` for fuzzing stores, used to limit resource
66/// consumption during fuzzing.
67#[derive(Clone)]
68pub struct StoreLimits(Arc<LimitsState>);
69
70struct LimitsState {
71    /// Remaining memory, in bytes, left to allocate
72    remaining_memory: AtomicUsize,
73    /// Remaining amount of memory that's allowed to be copied via a growth.
74    remaining_copy_allowance: AtomicUsize,
75    /// Whether or not an allocation request has been denied
76    oom: AtomicBool,
77}
78
79/// Allow up to 1G which is well below the 2G limit on OSS-Fuzz and should allow
80/// most interesting behavior.
81const MAX_MEMORY: usize = 1 << 30;
82
83/// Allow up to 4G of bytes to be copied (conservatively) which should enable
84/// growth up to `MAX_MEMORY` or at least up to a relatively large amount.
85const MAX_MEMORY_MOVED: usize = 4 << 30;
86
87impl StoreLimits {
88    /// Creates the default set of limits for all fuzzing stores.
89    pub fn new() -> StoreLimits {
90        StoreLimits(Arc::new(LimitsState {
91            remaining_memory: AtomicUsize::new(MAX_MEMORY),
92            remaining_copy_allowance: AtomicUsize::new(MAX_MEMORY_MOVED),
93            oom: AtomicBool::new(false),
94        }))
95    }
96
97    fn alloc(&mut self, amt: usize) -> bool {
98        log::trace!("alloc {amt:#x} bytes");
99
100        // Assume that on each allocation of memory that all previous
101        // allocations of memory are moved. This is pretty coarse but is used to
102        // help prevent against fuzz test cases that just move tons of bytes
103        // around continuously. This assumes that all previous memory was
104        // allocated in a single linear memory and growing by `amt` will require
105        // moving all the bytes to a new location. This isn't actually required
106        // all the time nor does it accurately reflect what happens all the
107        // time, but it's a coarse approximation that should be "good enough"
108        // for allowing interesting fuzz behaviors to happen while not timing
109        // out just copying bytes around.
110        let prev_size = MAX_MEMORY - self.0.remaining_memory.load(SeqCst);
111        if self
112            .0
113            .remaining_copy_allowance
114            .fetch_update(SeqCst, SeqCst, |remaining| remaining.checked_sub(prev_size))
115            .is_err()
116        {
117            self.0.oom.store(true, SeqCst);
118            log::debug!("-> too many bytes moved, rejecting allocation");
119            return false;
120        }
121
122        // If we're allowed to move the bytes, then also check if we're allowed
123        // to actually have this much residence at once.
124        match self
125            .0
126            .remaining_memory
127            .fetch_update(SeqCst, SeqCst, |remaining| remaining.checked_sub(amt))
128        {
129            Ok(_) => true,
130            Err(_) => {
131                self.0.oom.store(true, SeqCst);
132                log::debug!("-> OOM hit");
133                false
134            }
135        }
136    }
137
138    fn is_oom(&self) -> bool {
139        self.0.oom.load(SeqCst)
140    }
141}
142
143impl ResourceLimiter for StoreLimits {
144    fn memory_growing(
145        &mut self,
146        current: usize,
147        desired: usize,
148        _maximum: Option<usize>,
149    ) -> Result<bool> {
150        Ok(self.alloc(desired - current))
151    }
152
153    fn table_growing(
154        &mut self,
155        current: usize,
156        desired: usize,
157        _maximum: Option<usize>,
158    ) -> Result<bool> {
159        let delta = (desired - current).saturating_mul(std::mem::size_of::<usize>());
160        Ok(self.alloc(delta))
161    }
162}
163
164/// Methods of timing out execution of a WebAssembly module
165#[derive(Clone, Debug)]
166pub enum Timeout {
167    /// No timeout is used, it should be guaranteed via some other means that
168    /// the input does not infinite loop.
169    None,
170    /// Fuel-based timeouts are used where the specified fuel is all that the
171    /// provided wasm module is allowed to consume.
172    Fuel(u64),
173    /// An epoch-interruption-based timeout is used with a sleeping
174    /// thread bumping the epoch counter after the specified duration.
175    Epoch(Duration),
176}
177
178/// Instantiate the Wasm buffer, and implicitly fail if we have an unexpected
179/// panic or segfault or anything else that can be detected "passively".
180///
181/// The engine will be configured using provided config.
182pub fn instantiate(
183    wasm: &[u8],
184    known_valid: KnownValid,
185    config: &generators::Config,
186    timeout: Timeout,
187) {
188    let mut store = config.to_store();
189
190    let module = match compile_module(store.engine(), wasm, known_valid, config) {
191        Some(module) => module,
192        None => return,
193    };
194
195    let mut timeout_state = HelperThread::default();
196    match timeout {
197        Timeout::Fuel(fuel) => store.set_fuel(fuel).unwrap(),
198
199        // If a timeout is requested then we spawn a helper thread to wait for
200        // the requested time and then send us a signal to get interrupted. We
201        // also arrange for the thread's sleep to get interrupted if we return
202        // early (or the wasm returns within the time limit), which allows the
203        // thread to get torn down.
204        //
205        // This prevents us from creating a huge number of sleeping threads if
206        // this function is executed in a loop, like it does on nightly fuzzing
207        // infrastructure.
208        Timeout::Epoch(timeout) => {
209            let engine = store.engine().clone();
210            timeout_state.run_periodically(timeout, move || engine.increment_epoch());
211        }
212        Timeout::None => {}
213    }
214
215    instantiate_with_dummy(&mut store, &module);
216}
217
218/// Represents supported commands to the `instantiate_many` function.
219#[derive(Arbitrary, Debug)]
220pub enum Command {
221    /// Instantiates a module.
222    ///
223    /// The value is the index of the module to instantiate.
224    ///
225    /// The module instantiated will be this value modulo the number of modules provided to `instantiate_many`.
226    Instantiate(usize),
227    /// Terminates a "running" instance.
228    ///
229    /// The value is the index of the instance to terminate.
230    ///
231    /// The instance terminated will be this value modulo the number of currently running
232    /// instances.
233    ///
234    /// If no instances are running, the command will be ignored.
235    Terminate(usize),
236}
237
238/// Instantiates many instances from the given modules.
239///
240/// The engine will be configured using the provided config.
241///
242/// The modules are expected to *not* have start functions as no timeouts are configured.
243pub fn instantiate_many(
244    modules: &[Vec<u8>],
245    known_valid: KnownValid,
246    config: &generators::Config,
247    commands: &[Command],
248) {
249    log::debug!("instantiate_many: {commands:#?}");
250
251    assert!(!config.module_config.config.allow_start_export);
252
253    let engine = Engine::new(&config.to_wasmtime()).unwrap();
254
255    let modules = modules
256        .iter()
257        .enumerate()
258        .filter_map(
259            |(i, bytes)| match compile_module(&engine, bytes, known_valid, config) {
260                Some(m) => {
261                    log::debug!("successfully compiled module {i}");
262                    Some(m)
263                }
264                None => {
265                    log::debug!("failed to compile module {i}");
266                    None
267                }
268            },
269        )
270        .collect::<Vec<_>>();
271
272    // If no modules were valid, we're done
273    if modules.is_empty() {
274        return;
275    }
276
277    // This stores every `Store` where a successful instantiation takes place
278    let mut stores = Vec::new();
279    let limits = StoreLimits::new();
280
281    for command in commands {
282        match command {
283            Command::Instantiate(index) => {
284                let index = *index % modules.len();
285                log::info!("instantiating {}", index);
286                let module = &modules[index];
287                let mut store = Store::new(&engine, limits.clone());
288                config.configure_store(&mut store);
289
290                if instantiate_with_dummy(&mut store, module).is_some() {
291                    stores.push(Some(store));
292                } else {
293                    log::warn!("instantiation failed");
294                }
295            }
296            Command::Terminate(index) => {
297                if stores.is_empty() {
298                    continue;
299                }
300                let index = *index % stores.len();
301
302                log::info!("dropping {}", index);
303                stores.swap_remove(index);
304            }
305        }
306    }
307}
308
309fn compile_module(
310    engine: &Engine,
311    bytes: &[u8],
312    known_valid: KnownValid,
313    config: &generators::Config,
314) -> Option<Module> {
315    log_wasm(bytes);
316
317    fn is_pcc_error(e: &anyhow::Error) -> bool {
318        // NOTE: please keep this predicate in sync with the display format of CodegenError,
319        // defined in `wasmtime/cranelift/codegen/src/result.rs`
320        e.to_string().to_lowercase().contains("proof-carrying-code")
321    }
322
323    match config.compile(engine, bytes) {
324        Ok(module) => Some(module),
325        Err(e) if is_pcc_error(&e) => {
326            panic!("pcc error in input: {e:#?}");
327        }
328        Err(_) if known_valid == KnownValid::No => None,
329        Err(e) => {
330            if let generators::InstanceAllocationStrategy::Pooling(c) = &config.wasmtime.strategy {
331                // When using the pooling allocator, accept failures to compile
332                // when arbitrary table element limits have been exceeded as
333                // there is currently no way to constrain the generated module
334                // table types.
335                let string = format!("{e:?}");
336                if string.contains("minimum element size") {
337                    return None;
338                }
339
340                // Allow modules-failing-to-compile which exceed the requested
341                // size for each instance. This is something that is difficult
342                // to control and ensure it always succeeds, so we simply have a
343                // "random" instance size limit and if a module doesn't fit we
344                // move on to the next fuzz input.
345                if string.contains("instance allocation for this module requires") {
346                    return None;
347                }
348
349                // If the pooling allocator is more restrictive on the number of
350                // tables and memories than we allowed wasm-smith to generate
351                // then allow compilation errors along those lines.
352                if c.max_tables_per_module < (config.module_config.config.max_tables as u32)
353                    && string.contains("defined tables count")
354                    && string.contains("exceeds the per-instance limit")
355                {
356                    return None;
357                }
358
359                if c.max_memories_per_module < (config.module_config.config.max_memories as u32)
360                    && string.contains("defined memories count")
361                    && string.contains("exceeds the per-instance limit")
362                {
363                    return None;
364                }
365            }
366
367            panic!("failed to compile module: {e:?}");
368        }
369    }
370}
371
372/// Create a Wasmtime [`Instance`] from a [`Module`] and fill in all imports
373/// with dummy values (e.g., zeroed values, immediately-trapping functions).
374/// Also, this function catches certain fuzz-related instantiation failures and
375/// returns `None` instead of panicking.
376///
377/// TODO: we should implement tracing versions of these dummy imports that
378/// record a trace of the order that imported functions were called in and with
379/// what values. Like the results of exported functions, calls to imports should
380/// also yield the same values for each configuration, and we should assert
381/// that.
382pub fn instantiate_with_dummy(store: &mut Store<StoreLimits>, module: &Module) -> Option<Instance> {
383    // Creation of imports can fail due to resource limit constraints, and then
384    // instantiation can naturally fail for a number of reasons as well. Bundle
385    // the two steps together to match on the error below.
386    let linker = dummy::dummy_linker(store, module);
387    if let Err(e) = &linker {
388        log::warn!("failed to create dummy linker: {e:?}");
389    }
390    let instance = linker.and_then(|l| l.instantiate(&mut *store, module));
391    unwrap_instance(store, instance)
392}
393
394fn unwrap_instance(
395    store: &Store<StoreLimits>,
396    instance: anyhow::Result<Instance>,
397) -> Option<Instance> {
398    let e = match instance {
399        Ok(i) => return Some(i),
400        Err(e) => e,
401    };
402
403    log::debug!("failed to instantiate: {e:?}");
404
405    // If the instantiation hit OOM for some reason then that's ok, it's
406    // expected that fuzz-generated programs try to allocate lots of
407    // stuff.
408    if store.data().is_oom() {
409        return None;
410    }
411
412    // Allow traps which can happen normally with `unreachable` or a timeout or
413    // such.
414    if e.is::<Trap>()
415        // Also allow failures to instantiate as a result of hitting pooling
416        // limits.
417        || e.is::<wasmtime::PoolConcurrencyLimitError>()
418        // And GC heap OOMs.
419        || e.is::<wasmtime::GcHeapOutOfMemory<()>>()
420    {
421        return None;
422    }
423
424    let string = e.to_string();
425
426    // Currently we instantiate with a `Linker` which can't instantiate
427    // every single module under the sun due to using name-based resolution
428    // rather than positional-based resolution
429    if string.contains("incompatible import type") {
430        return None;
431    }
432
433    // Everything else should be a bug in the fuzzer or a bug in wasmtime
434    panic!("failed to instantiate: {e:?}");
435}
436
437/// Evaluate the function identified by `name` in two different engine
438/// instances--`lhs` and `rhs`.
439///
440/// Returns `Ok(true)` if more evaluations can happen or `Ok(false)` if the
441/// instances may have drifted apart and no more evaluations can happen.
442///
443/// # Panics
444///
445/// This will panic if the evaluation is different between engines (e.g.,
446/// results are different, hashed instance is different, one side traps, etc.).
447pub fn differential(
448    lhs: &mut dyn DiffInstance,
449    lhs_engine: &dyn DiffEngine,
450    rhs: &mut WasmtimeInstance,
451    name: &str,
452    args: &[DiffValue],
453    result_tys: &[DiffValueType],
454) -> anyhow::Result<bool> {
455    log::debug!("Evaluating: `{}` with {:?}", name, args);
456    let lhs_results = match lhs.evaluate(name, args, result_tys) {
457        Ok(Some(results)) => Ok(results),
458        Err(e) => Err(e),
459        // this engine couldn't execute this type signature, so discard this
460        // execution by returning success.
461        Ok(None) => return Ok(true),
462    };
463    log::debug!(" -> lhs results on {}: {:?}", lhs.name(), &lhs_results);
464
465    let rhs_results = rhs
466        .evaluate(name, args, result_tys)
467        // wasmtime should be able to invoke any signature, so unwrap this result
468        .map(|results| results.unwrap());
469    log::debug!(" -> rhs results on {}: {:?}", rhs.name(), &rhs_results);
470
471    // If Wasmtime hit its OOM condition, which is possible since it's set
472    // somewhat low while fuzzing, then don't return an error but return
473    // `false` indicating that differential fuzzing must stop. There's no
474    // guarantee the other engine has the same OOM limits as Wasmtime, and
475    // it's assumed that Wasmtime is configured to have a more conservative
476    // limit than the other engine.
477    if rhs.is_oom() {
478        return Ok(false);
479    }
480
481    match DiffEqResult::new(lhs_engine, lhs_results, rhs_results) {
482        DiffEqResult::Success(lhs, rhs) => assert_eq!(lhs, rhs),
483        DiffEqResult::Poisoned => return Ok(false),
484        DiffEqResult::Failed => {}
485    }
486
487    for (global, ty) in rhs.exported_globals() {
488        log::debug!("Comparing global `{global}`");
489        let lhs = match lhs.get_global(&global, ty) {
490            Some(val) => val,
491            None => continue,
492        };
493        let rhs = rhs.get_global(&global, ty).unwrap();
494        assert_eq!(lhs, rhs);
495    }
496    for (memory, shared) in rhs.exported_memories() {
497        log::debug!("Comparing memory `{memory}`");
498        let lhs = match lhs.get_memory(&memory, shared) {
499            Some(val) => val,
500            None => continue,
501        };
502        let rhs = rhs.get_memory(&memory, shared).unwrap();
503        if lhs == rhs {
504            continue;
505        }
506        eprintln!("differential memory is {} bytes long", lhs.len());
507        eprintln!("wasmtime memory is     {} bytes long", rhs.len());
508        panic!("memories have differing values");
509    }
510
511    Ok(true)
512}
513
514/// Result of comparing the result of two operations during differential
515/// execution.
516pub enum DiffEqResult<T, U> {
517    /// Both engines succeeded.
518    Success(T, U),
519    /// The result has reached the state where engines may have diverged and
520    /// results can no longer be compared.
521    Poisoned,
522    /// Both engines failed with the same error message, and internal state
523    /// should still match between the two engines.
524    Failed,
525}
526
527fn wasmtime_trap_is_non_deterministic(trap: &Trap) -> bool {
528    match trap {
529        // Allocations being too large for the GC are
530        // implementation-defined.
531        Trap::AllocationTooLarge |
532        // Stack size, and therefore when overflow happens, is
533        // implementation-defined.
534        Trap::StackOverflow => true,
535        _ => false,
536    }
537}
538
539fn wasmtime_error_is_non_deterministic(error: &wasmtime::Error) -> bool {
540    match error.downcast_ref::<Trap>() {
541        Some(trap) => wasmtime_trap_is_non_deterministic(trap),
542
543        // For general, unknown errors, we can't rely on this being
544        // a deterministic Wasm failure that both engines handled
545        // identically, leaving Wasm in identical states. We could
546        // just as easily be hitting engine-specific failures, like
547        // different implementation-defined limits. So simply poison
548        // this execution and move on to the next test.
549        None => true,
550    }
551}
552
553impl<T, U> DiffEqResult<T, U> {
554    /// Computes the differential result from executing in two different
555    /// engines.
556    pub fn new(
557        lhs_engine: &dyn DiffEngine,
558        lhs_result: Result<T>,
559        rhs_result: Result<U>,
560    ) -> DiffEqResult<T, U> {
561        match (lhs_result, rhs_result) {
562            (Ok(lhs_result), Ok(rhs_result)) => DiffEqResult::Success(lhs_result, rhs_result),
563
564            // Handle all non-deterministic errors by poisoning this execution's
565            // state, so that we simply move on to the next test.
566            (Err(lhs), _) if lhs_engine.is_non_deterministic_error(&lhs) => {
567                log::debug!("lhs failed non-deterministically: {lhs:?}");
568                DiffEqResult::Poisoned
569            }
570            (_, Err(rhs)) if wasmtime_error_is_non_deterministic(&rhs) => {
571                log::debug!("rhs failed non-deterministically: {rhs:?}");
572                DiffEqResult::Poisoned
573            }
574
575            // Both sides failed deterministically. Check that the trap and
576            // state at the time of failure is the same.
577            (Err(lhs), Err(rhs)) => {
578                let rhs = rhs
579                    .downcast::<Trap>()
580                    .expect("non-traps handled in earlier match arm");
581
582                debug_assert!(
583                    !lhs_engine.is_non_deterministic_error(&lhs),
584                    "non-deterministic traps handled in earlier match arm",
585                );
586                debug_assert!(
587                    !wasmtime_trap_is_non_deterministic(&rhs),
588                    "non-deterministic traps handled in earlier match arm",
589                );
590
591                lhs_engine.assert_error_match(&lhs, &rhs);
592                DiffEqResult::Failed
593            }
594
595            // A real bug is found if only one side fails.
596            (Ok(_), Err(err)) => panic!("only the `rhs` failed for this input: {err:?}"),
597            (Err(err), Ok(_)) => panic!("only the `lhs` failed for this input: {err:?}"),
598        }
599    }
600}
601
602/// Invoke the given API calls.
603pub fn make_api_calls(api: generators::api::ApiCalls) {
604    use crate::generators::api::ApiCall;
605    use std::collections::HashMap;
606
607    let mut store: Option<Store<StoreLimits>> = None;
608    let mut modules: HashMap<usize, Module> = Default::default();
609    let mut instances: HashMap<usize, Instance> = Default::default();
610
611    for call in api.calls {
612        match call {
613            ApiCall::StoreNew(config) => {
614                log::trace!("creating store");
615                assert!(store.is_none());
616                store = Some(config.to_store());
617            }
618
619            ApiCall::ModuleNew { id, wasm } => {
620                log::debug!("creating module: {}", id);
621                log_wasm(&wasm);
622                let module = match Module::new(store.as_ref().unwrap().engine(), &wasm) {
623                    Ok(m) => m,
624                    Err(_) => continue,
625                };
626                let old = modules.insert(id, module);
627                assert!(old.is_none());
628            }
629
630            ApiCall::ModuleDrop { id } => {
631                log::trace!("dropping module: {}", id);
632                drop(modules.remove(&id));
633            }
634
635            ApiCall::InstanceNew { id, module } => {
636                log::trace!("instantiating module {} as {}", module, id);
637                let module = match modules.get(&module) {
638                    Some(m) => m,
639                    None => continue,
640                };
641
642                let store = store.as_mut().unwrap();
643                if let Some(instance) = instantiate_with_dummy(store, module) {
644                    instances.insert(id, instance);
645                }
646            }
647
648            ApiCall::InstanceDrop { id } => {
649                log::trace!("dropping instance {}", id);
650                instances.remove(&id);
651            }
652
653            ApiCall::CallExportedFunc { instance, nth } => {
654                log::trace!("calling instance export {} / {}", instance, nth);
655                let instance = match instances.get(&instance) {
656                    Some(i) => i,
657                    None => {
658                        // Note that we aren't guaranteed to instantiate valid
659                        // modules, see comments in `InstanceNew` for details on
660                        // that. But the API call generator can't know if
661                        // instantiation failed, so we might not actually have
662                        // this instance. When that's the case, just skip the
663                        // API call and keep going.
664                        continue;
665                    }
666                };
667                let store = store.as_mut().unwrap();
668
669                let funcs = instance
670                    .exports(&mut *store)
671                    .filter_map(|e| match e.into_extern() {
672                        Extern::Func(f) => Some(f),
673                        _ => None,
674                    })
675                    .collect::<Vec<_>>();
676
677                if funcs.is_empty() {
678                    continue;
679                }
680
681                let nth = nth % funcs.len();
682                let f = &funcs[nth];
683                let ty = f.ty(&store);
684                if let Some(params) = ty
685                    .params()
686                    .map(|p| p.default_value())
687                    .collect::<Option<Vec<_>>>()
688                {
689                    let mut results = vec![Val::I32(0); ty.results().len()];
690                    let _ = f.call(store, &params, &mut results);
691                }
692            }
693        }
694    }
695}
696
697/// Executes the wast `test` with the `config` specified.
698///
699/// Ensures that wast tests pass regardless of the `Config`.
700pub fn wast_test(u: &mut arbitrary::Unstructured<'_>) -> arbitrary::Result<()> {
701    crate::init_fuzzing();
702
703    let mut fuzz_config: generators::Config = u.arbitrary()?;
704    let test: generators::WastTest = u.arbitrary()?;
705    if u.arbitrary()? {
706        fuzz_config.enable_async(u)?;
707    }
708
709    let test = &test.test;
710
711    // Discard tests that allocate a lot of memory as we don't want to OOM the
712    // fuzzer and we also limit memory growth which would cause the test to
713    // fail.
714    if test.config.hogs_memory.unwrap_or(false) {
715        return Err(arbitrary::Error::IncorrectFormat);
716    }
717
718    // Transform `fuzz_config` to be valid for `test` and make sure that this
719    // test is supposed to pass.
720    let wast_config = fuzz_config.make_wast_test_compliant(test);
721    if test.should_fail(&wast_config) {
722        return Err(arbitrary::Error::IncorrectFormat);
723    }
724
725    // Winch requires AVX and AVX2 for SIMD tests to pass so don't run the test
726    // if either isn't enabled.
727    if fuzz_config.wasmtime.compiler_strategy == CompilerStrategy::Winch
728        && test.config.simd()
729        && (fuzz_config
730            .wasmtime
731            .codegen_flag("has_avx")
732            .is_some_and(|value| value == "false")
733            || fuzz_config
734                .wasmtime
735                .codegen_flag("has_avx2")
736                .is_some_and(|value| value == "false"))
737    {
738        log::warn!(
739            "Skipping Wast test because Winch doesn't support SIMD tests with AVX or AVX2 disabled"
740        );
741        return Err(arbitrary::Error::IncorrectFormat);
742    }
743
744    // Fuel and epochs don't play well with threads right now, so exclude any
745    // thread-spawning test if it looks like threads are spawned in that case.
746    if fuzz_config.wasmtime.consume_fuel || fuzz_config.wasmtime.epoch_interruption {
747        if test.contents.contains("(thread") {
748            return Err(arbitrary::Error::IncorrectFormat);
749        }
750    }
751
752    log::debug!("running {:?}", test.path);
753    let async_ = if fuzz_config.wasmtime.async_config == generators::AsyncConfig::Disabled {
754        wasmtime_wast::Async::No
755    } else {
756        wasmtime_wast::Async::Yes
757    };
758    let mut wast_context = WastContext::new(fuzz_config.to_store(), async_);
759    wast_context
760        .register_spectest(&wasmtime_wast::SpectestConfig {
761            use_shared_memory: true,
762            suppress_prints: true,
763        })
764        .unwrap();
765    wast_context
766        .run_buffer(test.path.to_str().unwrap(), test.contents.as_bytes())
767        .unwrap();
768    Ok(())
769}
770
771/// Execute a series of `table.get` and `table.set` operations.
772///
773/// Returns the number of `gc` operations which occurred throughout the test
774/// case -- used to test below that gc happens reasonably soon and eventually.
775pub fn table_ops(
776    mut fuzz_config: generators::Config,
777    ops: generators::table_ops::TableOps,
778) -> Result<usize> {
779    let expected_drops = Arc::new(AtomicUsize::new(0));
780    let num_dropped = Arc::new(AtomicUsize::new(0));
781
782    let num_gcs = Arc::new(AtomicUsize::new(0));
783    {
784        fuzz_config.wasmtime.consume_fuel = true;
785        let mut store = fuzz_config.to_store();
786        store.set_fuel(1_000).unwrap();
787
788        let wasm = ops.to_wasm_binary();
789        log_wasm(&wasm);
790        let module = match compile_module(store.engine(), &wasm, KnownValid::No, &fuzz_config) {
791            Some(m) => m,
792            None => return Ok(0),
793        };
794
795        let mut linker = Linker::new(store.engine());
796
797        // To avoid timeouts, limit the number of explicit GCs we perform per
798        // test case.
799        const MAX_GCS: usize = 5;
800
801        let func_ty = FuncType::new(
802            store.engine(),
803            vec![],
804            vec![ValType::EXTERNREF, ValType::EXTERNREF, ValType::EXTERNREF],
805        );
806        let func = Func::new(&mut store, func_ty, {
807            let num_dropped = num_dropped.clone();
808            let expected_drops = expected_drops.clone();
809            let num_gcs = num_gcs.clone();
810            move |mut caller: Caller<'_, StoreLimits>, _params, results| {
811                log::info!("table_ops: GC");
812                if num_gcs.fetch_add(1, SeqCst) < MAX_GCS {
813                    caller.gc(None);
814                }
815
816                let a = ExternRef::new(
817                    &mut caller,
818                    CountDrops::new(&expected_drops, num_dropped.clone()),
819                )?;
820                let b = ExternRef::new(
821                    &mut caller,
822                    CountDrops::new(&expected_drops, num_dropped.clone()),
823                )?;
824                let c = ExternRef::new(
825                    &mut caller,
826                    CountDrops::new(&expected_drops, num_dropped.clone()),
827                )?;
828
829                log::info!("table_ops: gc() -> ({:?}, {:?}, {:?})", a, b, c);
830                results[0] = Some(a).into();
831                results[1] = Some(b).into();
832                results[2] = Some(c).into();
833                Ok(())
834            }
835        });
836        linker.define(&store, "", "gc", func).unwrap();
837
838        linker
839            .func_wrap("", "take_refs", {
840                let expected_drops = expected_drops.clone();
841                move |caller: Caller<'_, StoreLimits>,
842                      a: Option<Rooted<ExternRef>>,
843                      b: Option<Rooted<ExternRef>>,
844                      c: Option<Rooted<ExternRef>>|
845                      -> Result<()> {
846                    log::info!("table_ops: take_refs({a:?}, {b:?}, {c:?})",);
847
848                    // Do the assertion on each ref's inner data, even though it
849                    // all points to the same atomic, so that if we happen to
850                    // run into a use-after-free bug with one of these refs we
851                    // are more likely to trigger a segfault.
852                    if let Some(a) = a {
853                        let a = a
854                            .data(&caller)?
855                            .unwrap()
856                            .downcast_ref::<CountDrops>()
857                            .unwrap();
858                        assert!(a.0.load(SeqCst) <= expected_drops.load(SeqCst));
859                    }
860                    if let Some(b) = b {
861                        let b = b
862                            .data(&caller)?
863                            .unwrap()
864                            .downcast_ref::<CountDrops>()
865                            .unwrap();
866                        assert!(b.0.load(SeqCst) <= expected_drops.load(SeqCst));
867                    }
868                    if let Some(c) = c {
869                        let c = c
870                            .data(&caller)?
871                            .unwrap()
872                            .downcast_ref::<CountDrops>()
873                            .unwrap();
874                        assert!(c.0.load(SeqCst) <= expected_drops.load(SeqCst));
875                    }
876                    Ok(())
877                }
878            })
879            .unwrap();
880
881        let func_ty = FuncType::new(
882            store.engine(),
883            vec![],
884            vec![ValType::EXTERNREF, ValType::EXTERNREF, ValType::EXTERNREF],
885        );
886        let func = Func::new(&mut store, func_ty, {
887            let num_dropped = num_dropped.clone();
888            let expected_drops = expected_drops.clone();
889            move |mut caller, _params, results| {
890                log::info!("table_ops: make_refs");
891
892                let a = ExternRef::new(
893                    &mut caller,
894                    CountDrops::new(&expected_drops, num_dropped.clone()),
895                )?;
896                let b = ExternRef::new(
897                    &mut caller,
898                    CountDrops::new(&expected_drops, num_dropped.clone()),
899                )?;
900                let c = ExternRef::new(
901                    &mut caller,
902                    CountDrops::new(&expected_drops, num_dropped.clone()),
903                )?;
904
905                log::info!("table_ops: make_refs() -> ({:?}, {:?}, {:?})", a, b, c);
906
907                results[0] = Some(a).into();
908                results[1] = Some(b).into();
909                results[2] = Some(c).into();
910
911                Ok(())
912            }
913        });
914        linker.define(&store, "", "make_refs", func).unwrap();
915
916        let instance = linker.instantiate(&mut store, &module).unwrap();
917        let run = instance.get_func(&mut store, "run").unwrap();
918
919        {
920            let mut scope = RootScope::new(&mut store);
921
922            log::info!(
923                "table_ops: begin allocating {} externref arguments",
924                ops.num_globals
925            );
926            let args: Vec<_> = (0..ops.num_params)
927                .map(|_| {
928                    Ok(Val::ExternRef(Some(ExternRef::new(
929                        &mut scope,
930                        CountDrops::new(&expected_drops, num_dropped.clone()),
931                    )?)))
932                })
933                .collect::<Result<_>>()?;
934            log::info!(
935                "table_ops: end allocating {} externref arguments",
936                ops.num_globals
937            );
938
939            // The generated function should always return a trap. The only two
940            // valid traps are table-out-of-bounds which happens through `table.get`
941            // and `table.set` generated or an out-of-fuel trap. Otherwise any other
942            // error is unexpected and should fail fuzzing.
943            log::info!("table_ops: calling into Wasm `run` function");
944            let err = run.call(&mut scope, &args, &mut []).unwrap_err();
945            match err.downcast::<GcHeapOutOfMemory<CountDrops>>() {
946                Ok(_oom) => {}
947                Err(err) => {
948                    let trap = err
949                        .downcast::<Trap>()
950                        .expect("if not GC oom, error should be a Wasm trap");
951                    match trap {
952                        Trap::TableOutOfBounds | Trap::OutOfFuel => {}
953                        _ => panic!("unexpected trap: {trap}"),
954                    }
955                }
956            }
957        }
958
959        // Do a final GC after running the Wasm.
960        store.gc(None);
961    }
962
963    assert_eq!(num_dropped.load(SeqCst), expected_drops.load(SeqCst));
964    return Ok(num_gcs.load(SeqCst));
965
966    struct CountDrops(Arc<AtomicUsize>);
967
968    impl CountDrops {
969        fn new(expected_drops: &AtomicUsize, num_dropped: Arc<AtomicUsize>) -> Self {
970            let expected = expected_drops.fetch_add(1, SeqCst);
971            log::info!(
972                "CountDrops::new: expected drops: {expected} -> {}",
973                expected + 1
974            );
975            Self(num_dropped)
976        }
977    }
978
979    impl Drop for CountDrops {
980        fn drop(&mut self) {
981            let drops = self.0.fetch_add(1, SeqCst);
982            log::info!("CountDrops::drop: actual drops: {drops} -> {}", drops + 1);
983        }
984    }
985}
986
987#[derive(Default)]
988struct HelperThread {
989    state: Arc<HelperThreadState>,
990    thread: Option<std::thread::JoinHandle<()>>,
991}
992
993#[derive(Default)]
994struct HelperThreadState {
995    should_exit: Mutex<bool>,
996    should_exit_cvar: Condvar,
997}
998
999impl HelperThread {
1000    fn run_periodically(&mut self, dur: Duration, mut closure: impl FnMut() + Send + 'static) {
1001        let state = self.state.clone();
1002        self.thread = Some(std::thread::spawn(move || {
1003            // Using our mutex/condvar we wait here for the first of `dur` to
1004            // pass or the `HelperThread` instance to get dropped.
1005            let mut should_exit = state.should_exit.lock().unwrap();
1006            while !*should_exit {
1007                let (lock, result) = state
1008                    .should_exit_cvar
1009                    .wait_timeout(should_exit, dur)
1010                    .unwrap();
1011                should_exit = lock;
1012                // If we timed out for sure then there's no need to continue
1013                // since we'll just abort on the next `checked_sub` anyway.
1014                if result.timed_out() {
1015                    closure();
1016                }
1017            }
1018        }));
1019    }
1020}
1021
1022impl Drop for HelperThread {
1023    fn drop(&mut self) {
1024        let thread = match self.thread.take() {
1025            Some(thread) => thread,
1026            None => return,
1027        };
1028        // Signal our thread that it should exit and wake it up in case it's
1029        // sleeping.
1030        *self.state.should_exit.lock().unwrap() = true;
1031        self.state.should_exit_cvar.notify_one();
1032
1033        // ... and then wait for the thread to exit to ensure we clean up
1034        // after ourselves.
1035        thread.join().unwrap();
1036    }
1037}
1038
1039/// Generate and execute a `crate::generators::component_types::TestCase` using the specified `input` to create
1040/// arbitrary types and values.
1041pub fn dynamic_component_api_target(input: &mut arbitrary::Unstructured) -> arbitrary::Result<()> {
1042    use crate::generators::component_types;
1043    use wasmtime::component::{Component, Linker, Val};
1044    use wasmtime_test_util::component::FuncExt;
1045    use wasmtime_test_util::component_fuzz::{
1046        EXPORT_FUNCTION, IMPORT_FUNCTION, MAX_TYPE_DEPTH, TestCase, Type,
1047    };
1048
1049    crate::init_fuzzing();
1050
1051    let mut types = Vec::new();
1052    let mut type_fuel = 500;
1053
1054    for _ in 0..5 {
1055        types.push(Type::generate(input, MAX_TYPE_DEPTH, &mut type_fuel)?);
1056    }
1057    let params = (0..input.int_in_range(0..=5)?)
1058        .map(|_| input.choose(&types))
1059        .collect::<arbitrary::Result<Vec<_>>>()?;
1060    let result = if input.arbitrary()? {
1061        Some(input.choose(&types)?)
1062    } else {
1063        None
1064    };
1065
1066    let case = TestCase {
1067        params,
1068        result,
1069        encoding1: input.arbitrary()?,
1070        encoding2: input.arbitrary()?,
1071    };
1072
1073    let mut config = wasmtime_test_util::component::config();
1074    config.debug_adapter_modules(input.arbitrary()?);
1075    let engine = Engine::new(&config).unwrap();
1076    let mut store = Store::new(&engine, (Vec::new(), None));
1077    let wat = case.declarations().make_component();
1078    let wat = wat.as_bytes();
1079    log_wasm(wat);
1080    let component = Component::new(&engine, wat).unwrap();
1081    let mut linker = Linker::new(&engine);
1082
1083    linker
1084        .root()
1085        .func_new(IMPORT_FUNCTION, {
1086            move |mut cx: StoreContextMut<'_, (Vec<Val>, Option<Vec<Val>>)>,
1087                  params: &[Val],
1088                  results: &mut [Val]|
1089                  -> Result<()> {
1090                log::trace!("received params {params:?}");
1091                let (expected_args, expected_results) = cx.data_mut();
1092                assert_eq!(params.len(), expected_args.len());
1093                for (expected, actual) in expected_args.iter().zip(params) {
1094                    assert_eq!(expected, actual);
1095                }
1096                results.clone_from_slice(&expected_results.take().unwrap());
1097                log::trace!("returning results {results:?}");
1098                Ok(())
1099            }
1100        })
1101        .unwrap();
1102
1103    let instance = linker.instantiate(&mut store, &component).unwrap();
1104    let func = instance.get_func(&mut store, EXPORT_FUNCTION).unwrap();
1105    let param_tys = func.params(&store);
1106    let result_tys = func.results(&store);
1107
1108    while input.arbitrary()? {
1109        let params = param_tys
1110            .iter()
1111            .map(|(_, ty)| component_types::arbitrary_val(ty, input))
1112            .collect::<arbitrary::Result<Vec<_>>>()?;
1113        let results = result_tys
1114            .iter()
1115            .map(|ty| component_types::arbitrary_val(ty, input))
1116            .collect::<arbitrary::Result<Vec<_>>>()?;
1117
1118        *store.data_mut() = (params.clone(), Some(results.clone()));
1119
1120        log::trace!("passing params {params:?}");
1121        let mut actual = vec![Val::Bool(false); results.len()];
1122        func.call_and_post_return(&mut store, &params, &mut actual)
1123            .unwrap();
1124        log::trace!("received results {actual:?}");
1125        assert_eq!(actual, results);
1126    }
1127
1128    Ok(())
1129}
1130
1131/// Instantiates a wasm module and runs its exports with dummy values, all in
1132/// an async fashion.
1133///
1134/// Attempts to stress yields in host functions to ensure that exiting and
1135/// resuming a wasm function call works.
1136pub fn call_async(wasm: &[u8], config: &generators::Config, mut poll_amts: &[u32]) {
1137    let mut store = config.to_store();
1138    let module = match compile_module(store.engine(), wasm, KnownValid::Yes, config) {
1139        Some(module) => module,
1140        None => return,
1141    };
1142
1143    // Configure a helper thread to periodically increment the epoch to
1144    // forcibly enable yields-via-epochs if epochs are in use. Note that this
1145    // is required because the wasm isn't otherwise guaranteed to necessarily
1146    // call any imports which will also increment the epoch.
1147    let mut helper_thread = HelperThread::default();
1148    if let generators::AsyncConfig::YieldWithEpochs { dur, .. } = &config.wasmtime.async_config {
1149        let engine = store.engine().clone();
1150        helper_thread.run_periodically(*dur, move || engine.increment_epoch());
1151    }
1152
1153    // Generate a `Linker` where all function imports are custom-built to yield
1154    // periodically and additionally increment the epoch.
1155    let mut imports = Vec::new();
1156    for import in module.imports() {
1157        let item = match import.ty() {
1158            ExternType::Func(ty) => {
1159                let poll_amt = take_poll_amt(&mut poll_amts);
1160                Func::new_async(&mut store, ty.clone(), move |caller, _, results| {
1161                    let ty = ty.clone();
1162                    Box::new(async move {
1163                        caller.engine().increment_epoch();
1164                        log::info!("yielding {} times in import", poll_amt);
1165                        YieldN(poll_amt).await;
1166                        for (ret_ty, result) in ty.results().zip(results) {
1167                            *result = ret_ty.default_value().unwrap();
1168                        }
1169                        Ok(())
1170                    })
1171                })
1172                .into()
1173            }
1174            other_ty => match other_ty.default_value(&mut store) {
1175                Ok(item) => item,
1176                Err(e) => {
1177                    log::warn!("couldn't create import for {import:?}: {e:?}");
1178                    return;
1179                }
1180            },
1181        };
1182        imports.push(item);
1183    }
1184
1185    // Run the instantiation process, asynchronously, and if everything
1186    // succeeds then pull out the instance.
1187    // log::info!("starting instantiation");
1188    let instance = run(Timeout {
1189        future: Instance::new_async(&mut store, &module, &imports),
1190        polls: take_poll_amt(&mut poll_amts),
1191        end: Instant::now() + Duration::from_millis(2_000),
1192    });
1193    let instance = match instance {
1194        Ok(instantiation_result) => match unwrap_instance(&store, instantiation_result) {
1195            Some(instance) => instance,
1196            None => {
1197                log::info!("instantiation hit a nominal error");
1198                return; // resource exhaustion or limits met
1199            }
1200        },
1201        Err(_) => {
1202            log::info!("instantiation failed to complete");
1203            return; // Timed out or ran out of polls
1204        }
1205    };
1206
1207    // Run each export of the instance in the same manner as instantiation
1208    // above. Dummy values are passed in for argument values here:
1209    //
1210    // TODO: this should probably be more clever about passing in arguments for
1211    // example they might be used as pointers or something and always using 0
1212    // isn't too interesting.
1213    let funcs = instance
1214        .exports(&mut store)
1215        .filter_map(|e| {
1216            let name = e.name().to_string();
1217            let func = e.into_extern().into_func()?;
1218            Some((name, func))
1219        })
1220        .collect::<Vec<_>>();
1221    for (name, func) in funcs {
1222        let ty = func.ty(&store);
1223        let params = ty
1224            .params()
1225            .map(|ty| ty.default_value().unwrap())
1226            .collect::<Vec<_>>();
1227        let mut results = ty
1228            .results()
1229            .map(|ty| ty.default_value().unwrap())
1230            .collect::<Vec<_>>();
1231
1232        log::info!("invoking export {:?}", name);
1233        let future = func.call_async(&mut store, &params, &mut results);
1234        match run(Timeout {
1235            future,
1236            polls: take_poll_amt(&mut poll_amts),
1237            end: Instant::now() + Duration::from_millis(2_000),
1238        }) {
1239            // On success or too many polls, try the next export.
1240            Ok(_) | Err(Exhausted::Polls) => {}
1241
1242            // If time ran out then stop the current test case as we might have
1243            // already sucked up a lot of time for this fuzz test case so don't
1244            // keep it going.
1245            Err(Exhausted::Time) => return,
1246        }
1247    }
1248
1249    fn take_poll_amt(polls: &mut &[u32]) -> u32 {
1250        match polls.split_first() {
1251            Some((a, rest)) => {
1252                *polls = rest;
1253                *a
1254            }
1255            None => 0,
1256        }
1257    }
1258
1259    /// Helper future to yield N times before resolving.
1260    struct YieldN(u32);
1261
1262    impl Future for YieldN {
1263        type Output = ();
1264
1265        fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<()> {
1266            if self.0 == 0 {
1267                Poll::Ready(())
1268            } else {
1269                self.0 -= 1;
1270                cx.waker().wake_by_ref();
1271                Poll::Pending
1272            }
1273        }
1274    }
1275
1276    /// Helper future for applying a timeout to `future` up to either when `end`
1277    /// is the current time or `polls` polls happen.
1278    ///
1279    /// Note that this helps to time out infinite loops in wasm, for example.
1280    struct Timeout<F> {
1281        future: F,
1282        /// If the future isn't ready by this time then the `Timeout<F>` future
1283        /// will return `None`.
1284        end: Instant,
1285        /// If the future doesn't resolve itself in this many calls to `poll`
1286        /// then the `Timeout<F>` future will return `None`.
1287        polls: u32,
1288    }
1289
1290    enum Exhausted {
1291        Time,
1292        Polls,
1293    }
1294
1295    impl<F: Future> Future for Timeout<F> {
1296        type Output = Result<F::Output, Exhausted>;
1297
1298        fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
1299            let (end, polls, future) = unsafe {
1300                let me = self.get_unchecked_mut();
1301                (me.end, &mut me.polls, Pin::new_unchecked(&mut me.future))
1302            };
1303            match future.poll(cx) {
1304                Poll::Ready(val) => Poll::Ready(Ok(val)),
1305                Poll::Pending => {
1306                    if Instant::now() >= end {
1307                        log::warn!("future operation timed out");
1308                        return Poll::Ready(Err(Exhausted::Time));
1309                    }
1310                    if *polls == 0 {
1311                        log::warn!("future operation ran out of polls");
1312                        return Poll::Ready(Err(Exhausted::Polls));
1313                    }
1314                    *polls -= 1;
1315                    Poll::Pending
1316                }
1317            }
1318        }
1319    }
1320
1321    fn run<F: Future>(future: F) -> F::Output {
1322        let mut f = Box::pin(future);
1323        let mut cx = Context::from_waker(Waker::noop());
1324        loop {
1325            match f.as_mut().poll(&mut cx) {
1326                Poll::Ready(val) => break val,
1327                Poll::Pending => {}
1328            }
1329        }
1330    }
1331}
1332
1333#[cfg(test)]
1334mod tests {
1335    use super::*;
1336    use arbitrary::Unstructured;
1337    use rand::prelude::*;
1338    use wasmparser::{Validator, WasmFeatures};
1339
1340    fn gen_until_pass<T: for<'a> Arbitrary<'a>>(
1341        mut f: impl FnMut(T, &mut Unstructured<'_>) -> Result<bool>,
1342    ) -> bool {
1343        let mut rng = SmallRng::seed_from_u64(0);
1344        let mut buf = vec![0; 2048];
1345        let n = 3000;
1346        for _ in 0..n {
1347            rng.fill_bytes(&mut buf);
1348            let mut u = Unstructured::new(&buf);
1349
1350            if let Ok(config) = u.arbitrary() {
1351                if f(config, &mut u).unwrap() {
1352                    return true;
1353                }
1354            }
1355        }
1356        false
1357    }
1358
1359    /// Runs `f` with random data until it returns `Ok(())` `iters` times.
1360    fn test_n_times<T: for<'a> Arbitrary<'a>>(
1361        iters: u32,
1362        mut f: impl FnMut(T, &mut Unstructured<'_>) -> arbitrary::Result<()>,
1363    ) {
1364        let mut to_test = 0..iters;
1365        let ok = gen_until_pass(|a, b| {
1366            if f(a, b).is_ok() {
1367                Ok(to_test.next().is_none())
1368            } else {
1369                Ok(false)
1370            }
1371        });
1372        assert!(ok);
1373    }
1374
1375    // Test that the `table_ops` fuzzer eventually runs the gc function in the host.
1376    // We've historically had issues where this fuzzer accidentally wasn't fuzzing
1377    // anything for a long time so this is an attempt to prevent that from happening
1378    // again.
1379    #[test]
1380    fn table_ops_eventually_gcs() {
1381        // Skip if we're under emulation because some fuzz configurations will do
1382        // large address space reservations that QEMU doesn't handle well.
1383        if std::env::var("WASMTIME_TEST_NO_HOG_MEMORY").is_ok() {
1384            return;
1385        }
1386
1387        let ok = gen_until_pass(|(config, test), _| {
1388            let result = table_ops(config, test)?;
1389            Ok(result > 0)
1390        });
1391
1392        if !ok {
1393            panic!("gc was never found");
1394        }
1395    }
1396
1397    #[test]
1398    fn module_generation_uses_expected_proposals() {
1399        // Proposals that Wasmtime supports. Eventually a module should be
1400        // generated that needs these proposals.
1401        let mut expected = WasmFeatures::MUTABLE_GLOBAL
1402            | WasmFeatures::FLOATS
1403            | WasmFeatures::SIGN_EXTENSION
1404            | WasmFeatures::SATURATING_FLOAT_TO_INT
1405            | WasmFeatures::MULTI_VALUE
1406            | WasmFeatures::BULK_MEMORY
1407            | WasmFeatures::REFERENCE_TYPES
1408            | WasmFeatures::SIMD
1409            | WasmFeatures::MULTI_MEMORY
1410            | WasmFeatures::RELAXED_SIMD
1411            | WasmFeatures::THREADS
1412            | WasmFeatures::TAIL_CALL
1413            | WasmFeatures::WIDE_ARITHMETIC
1414            | WasmFeatures::MEMORY64
1415            | WasmFeatures::FUNCTION_REFERENCES
1416            | WasmFeatures::GC
1417            | WasmFeatures::GC_TYPES
1418            | WasmFeatures::CUSTOM_PAGE_SIZES
1419            | WasmFeatures::EXTENDED_CONST;
1420
1421        // All other features that wasmparser supports, which is presumably a
1422        // superset of the features that wasm-smith supports, are listed here as
1423        // unexpected. This means, for example, that if wasm-smith updates to
1424        // include a new proposal by default that wasmtime implements then it
1425        // will be required to be listed above.
1426        let unexpected = WasmFeatures::all() ^ expected;
1427
1428        let ok = gen_until_pass(|config: generators::Config, u| {
1429            let wasm = config.generate(u, None)?.to_bytes();
1430
1431            // Double-check the module is valid
1432            Validator::new_with_features(WasmFeatures::all()).validate_all(&wasm)?;
1433
1434            // If any of the unexpected features are removed then this module
1435            // should always be valid, otherwise something went wrong.
1436            for feature in unexpected.iter() {
1437                let ok =
1438                    Validator::new_with_features(WasmFeatures::all() ^ feature).validate_all(&wasm);
1439                if ok.is_err() {
1440                    anyhow::bail!("generated a module with {feature:?} but that wasn't expected");
1441                }
1442            }
1443
1444            // If any of `expected` is removed and the module fails to validate,
1445            // then that means the module requires that feature. Remove that
1446            // from the set of features we're then expecting.
1447            for feature in expected.iter() {
1448                let ok =
1449                    Validator::new_with_features(WasmFeatures::all() ^ feature).validate_all(&wasm);
1450                if ok.is_err() {
1451                    expected ^= feature;
1452                }
1453            }
1454
1455            Ok(expected.is_empty())
1456        });
1457
1458        if !ok {
1459            panic!("never generated wasm module using {expected:?}");
1460        }
1461    }
1462
1463    #[test]
1464    fn wast_smoke_test() {
1465        test_n_times(50, |(), u| super::wast_test(u));
1466    }
1467}