1 //! This module implements serialization and deserialization of `Engine`
2 //! configuration data which is embedded into compiled artifacts of Wasmtime.
3 //!
4 //! The data serialized here is used to double-check that when a module is
5 //! loaded from one host onto another that it's compatible with the target host.
6 //! Additionally though this data is the first data read from a precompiled
7 //! artifact so it's "extra hardened" to provide reasonable-ish error messages
8 //! for mismatching wasmtime versions. Once something successfully deserializes
9 //! here it's assumed it's meant for this wasmtime so error messages are in
10 //! general much worse afterwards.
11 //!
12 //! Wasmtime AOT artifacts are ELF files so the data for the engine here is
13 //! stored into a section of the output file. The structure of this section is:
14 //!
15 //! 1. A version byte, currently `VERSION`.
16 //! 2. A byte indicating how long the next field is.
17 //! 3. A version string of the length of the previous byte value.
18 //! 4. A `postcard`-encoded `Metadata` structure.
19 //!
20 //! This is hoped to help distinguish easily Wasmtime-based ELF files from
21 //! other random ELF files, as well as provide better error messages for
22 //! using wasmtime artifacts across versions.
23 
24 use crate::prelude::*;
25 use crate::{Engine, ModuleVersionStrategy, Precompiled};
26 use core::str::FromStr;
27 use object::endian::Endianness;
28 #[cfg(any(feature = "cranelift", feature = "winch"))]
29 use object::write::{Object, StandardSegment};
30 use object::{read::elf::ElfFile64, FileFlags, Object as _, ObjectSection, SectionKind};
31 use serde_derive::{Deserialize, Serialize};
32 use wasmtime_environ::obj;
33 use wasmtime_environ::{FlagValue, ObjectKind, Tunables};
34 
35 const VERSION: u8 = 0;
36 
37 /// Verifies that the serialized engine in `mmap` is compatible with the
38 /// `engine` provided.
39 ///
40 /// This function will verify that the `mmap` provided can be deserialized
41 /// successfully and that the contents are all compatible with the `engine`
42 /// provided here, notably compatible wasm features are enabled, compatible
43 /// compiler options, etc. If a mismatch is found and the compilation metadata
44 /// specified is incompatible then an error is returned.
45 pub fn check_compatible(engine: &Engine, mmap: &[u8], expected: ObjectKind) -> Result<()> {
46     // Parse the input `mmap` as an ELF file and see if the header matches the
47     // Wasmtime-generated header. This includes a Wasmtime-specific `os_abi` and
48     // the `e_flags` field should indicate whether `expected` matches or not.
49     //
50     // Note that errors generated here could mean that a precompiled module was
51     // loaded as a component, or vice versa, both of which aren't supposed to
52     // work.
53     //
54     // Ideally we'd only `File::parse` once and avoid the linear
55     // `section_by_name` search here but the general serialization code isn't
56     // structured well enough to make this easy and additionally it's not really
57     // a perf issue right now so doing that is left for another day's
58     // refactoring.
59     let obj = ElfFile64::<Endianness>::parse(mmap)
60         .map_err(obj::ObjectCrateErrorWrapper)
61         .context("failed to parse precompiled artifact as an ELF")?;
62     let expected_e_flags = match expected {
63         ObjectKind::Module => obj::EF_WASMTIME_MODULE,
64         ObjectKind::Component => obj::EF_WASMTIME_COMPONENT,
65     };
66     match obj.flags() {
67         FileFlags::Elf {
68             os_abi: obj::ELFOSABI_WASMTIME,
69             abi_version: 0,
70             e_flags,
71         } if e_flags == expected_e_flags => {}
72         _ => bail!("incompatible object file format"),
73     }
74 
75     let data = obj
76         .section_by_name(obj::ELF_WASM_ENGINE)
77         .ok_or_else(|| anyhow!("failed to find section `{}`", obj::ELF_WASM_ENGINE))?
78         .data()
79         .map_err(obj::ObjectCrateErrorWrapper)?;
80     let (first, data) = data
81         .split_first()
82         .ok_or_else(|| anyhow!("invalid engine section"))?;
83     if *first != VERSION {
84         bail!("mismatched version in engine section");
85     }
86     let (len, data) = data
87         .split_first()
88         .ok_or_else(|| anyhow!("invalid engine section"))?;
89     let len = usize::from(*len);
90     let (version, data) = if data.len() < len + 1 {
91         bail!("engine section too small")
92     } else {
93         data.split_at(len)
94     };
95 
96     match &engine.config().module_version {
97         ModuleVersionStrategy::WasmtimeVersion => {
98             let version = core::str::from_utf8(version)?;
99             if version != env!("CARGO_PKG_VERSION") {
100                 bail!(
101                     "Module was compiled with incompatible Wasmtime version '{}'",
102                     version
103                 );
104             }
105         }
106         ModuleVersionStrategy::Custom(v) => {
107             let version = core::str::from_utf8(&version)?;
108             if version != v {
109                 bail!(
110                     "Module was compiled with incompatible version '{}'",
111                     version
112                 );
113             }
114         }
115         ModuleVersionStrategy::None => { /* ignore the version info, accept all */ }
116     }
117     postcard::from_bytes::<Metadata<'_>>(data)?.check_compatible(engine)
118 }
119 
120 #[cfg(any(feature = "cranelift", feature = "winch"))]
121 pub fn append_compiler_info(engine: &Engine, obj: &mut Object<'_>, metadata: &Metadata<'_>) {
122     let section = obj.add_section(
123         obj.segment_name(StandardSegment::Data).to_vec(),
124         obj::ELF_WASM_ENGINE.as_bytes().to_vec(),
125         SectionKind::ReadOnlyData,
126     );
127     let mut data = Vec::new();
128     data.push(VERSION);
129     let version = match &engine.config().module_version {
130         ModuleVersionStrategy::WasmtimeVersion => env!("CARGO_PKG_VERSION"),
131         ModuleVersionStrategy::Custom(c) => c,
132         ModuleVersionStrategy::None => "",
133     };
134     // This precondition is checked in Config::module_version:
135     assert!(
136         version.len() < 256,
137         "package version must be less than 256 bytes"
138     );
139     data.push(version.len() as u8);
140     data.extend_from_slice(version.as_bytes());
141     data.extend(postcard::to_allocvec(metadata).unwrap());
142     obj.set_section_data(section, data, 1);
143 }
144 
145 fn detect_precompiled<'data, R: object::ReadRef<'data>>(
146     obj: ElfFile64<'data, Endianness, R>,
147 ) -> Option<Precompiled> {
148     match obj.flags() {
149         FileFlags::Elf {
150             os_abi: obj::ELFOSABI_WASMTIME,
151             abi_version: 0,
152             e_flags: obj::EF_WASMTIME_MODULE,
153         } => Some(Precompiled::Module),
154         FileFlags::Elf {
155             os_abi: obj::ELFOSABI_WASMTIME,
156             abi_version: 0,
157             e_flags: obj::EF_WASMTIME_COMPONENT,
158         } => Some(Precompiled::Component),
159         _ => None,
160     }
161 }
162 
163 pub fn detect_precompiled_bytes(bytes: &[u8]) -> Option<Precompiled> {
164     detect_precompiled(ElfFile64::parse(bytes).ok()?)
165 }
166 
167 #[cfg(feature = "std")]
168 pub fn detect_precompiled_file(path: impl AsRef<std::path::Path>) -> Result<Option<Precompiled>> {
169     let read_cache = object::ReadCache::new(std::fs::File::open(path)?);
170     let obj = ElfFile64::parse(&read_cache)?;
171     Ok(detect_precompiled(obj))
172 }
173 
174 #[derive(Serialize, Deserialize)]
175 pub struct Metadata<'a> {
176     target: String,
177     #[serde(borrow)]
178     shared_flags: Vec<(&'a str, FlagValue<'a>)>,
179     #[serde(borrow)]
180     isa_flags: Vec<(&'a str, FlagValue<'a>)>,
181     tunables: Tunables,
182     features: WasmFeatures,
183 }
184 
185 // This exists because `wasmparser::WasmFeatures` isn't serializable
186 #[derive(Debug, Copy, Clone, Serialize, Deserialize)]
187 struct WasmFeatures {
188     reference_types: bool,
189     multi_value: bool,
190     bulk_memory: bool,
191     component_model: bool,
192     simd: bool,
193     tail_call: bool,
194     threads: bool,
195     multi_memory: bool,
196     exceptions: bool,
197     memory64: bool,
198     relaxed_simd: bool,
199     extended_const: bool,
200     function_references: bool,
201     gc: bool,
202     custom_page_sizes: bool,
203     component_model_more_flags: bool,
204     component_model_multiple_returns: bool,
205     gc_types: bool,
206     wide_arithmetic: bool,
207 }
208 
209 impl Metadata<'_> {
210     #[cfg(any(feature = "cranelift", feature = "winch"))]
211     pub fn new(engine: &Engine) -> Metadata<'static> {
212         let wasmparser::WasmFeaturesInflated {
213             reference_types,
214             multi_value,
215             bulk_memory,
216             component_model,
217             simd,
218             threads,
219             tail_call,
220             multi_memory,
221             exceptions,
222             memory64,
223             relaxed_simd,
224             extended_const,
225             memory_control,
226             function_references,
227             gc,
228             custom_page_sizes,
229             shared_everything_threads,
230             component_model_values,
231             component_model_nested_names,
232             component_model_more_flags,
233             component_model_multiple_returns,
234             component_model_async,
235             legacy_exceptions,
236             gc_types,
237             stack_switching,
238             wide_arithmetic,
239 
240             // Always on; we don't currently have knobs for these.
241             mutable_global: _,
242             saturating_float_to_int: _,
243             sign_extension: _,
244             floats: _,
245         } = engine.features().inflate();
246 
247         // These features are not implemented in Wasmtime yet. We match on them
248         // above so that once we do implement support for them, we won't
249         // silently ignore them during serialization.
250         assert!(!memory_control);
251         assert!(!component_model_values);
252         assert!(!component_model_nested_names);
253         assert!(!shared_everything_threads);
254         assert!(!legacy_exceptions);
255         assert!(!stack_switching);
256         assert!(!component_model_async);
257 
258         Metadata {
259             target: engine.compiler().triple().to_string(),
260             shared_flags: engine.compiler().flags(),
261             isa_flags: engine.compiler().isa_flags(),
262             tunables: engine.tunables().clone(),
263             features: WasmFeatures {
264                 reference_types,
265                 multi_value,
266                 bulk_memory,
267                 component_model,
268                 simd,
269                 threads,
270                 tail_call,
271                 multi_memory,
272                 exceptions,
273                 memory64,
274                 relaxed_simd,
275                 extended_const,
276                 function_references,
277                 gc,
278                 custom_page_sizes,
279                 component_model_more_flags,
280                 component_model_multiple_returns,
281                 gc_types,
282                 wide_arithmetic,
283             },
284         }
285     }
286 
287     fn check_compatible(mut self, engine: &Engine) -> Result<()> {
288         self.check_triple(engine)?;
289         self.check_shared_flags(engine)?;
290         self.check_isa_flags(engine)?;
291         self.check_tunables(&engine.tunables())?;
292         self.check_features(&engine.features())?;
293         Ok(())
294     }
295 
296     fn check_triple(&self, engine: &Engine) -> Result<()> {
297         let engine_target = engine.target();
298         let module_target =
299             target_lexicon::Triple::from_str(&self.target).map_err(|e| anyhow!(e))?;
300 
301         if module_target.architecture != engine_target.architecture {
302             bail!(
303                 "Module was compiled for architecture '{}'",
304                 module_target.architecture
305             );
306         }
307 
308         if module_target.operating_system != engine_target.operating_system {
309             bail!(
310                 "Module was compiled for operating system '{}'",
311                 module_target.operating_system
312             );
313         }
314 
315         Ok(())
316     }
317 
318     fn check_shared_flags(&mut self, engine: &Engine) -> Result<()> {
319         for (name, val) in self.shared_flags.iter() {
320             engine
321                 .check_compatible_with_shared_flag(name, val)
322                 .map_err(|s| anyhow::Error::msg(s))
323                 .context("compilation settings of module incompatible with native host")?;
324         }
325         Ok(())
326     }
327 
328     fn check_isa_flags(&mut self, engine: &Engine) -> Result<()> {
329         for (name, val) in self.isa_flags.iter() {
330             engine
331                 .check_compatible_with_isa_flag(name, val)
332                 .map_err(|s| anyhow::Error::msg(s))
333                 .context("compilation settings of module incompatible with native host")?;
334         }
335         Ok(())
336     }
337 
338     fn check_int<T: Eq + core::fmt::Display>(found: T, expected: T, feature: &str) -> Result<()> {
339         if found == expected {
340             return Ok(());
341         }
342 
343         bail!(
344             "Module was compiled with a {} of '{}' but '{}' is expected for the host",
345             feature,
346             found,
347             expected
348         );
349     }
350 
351     fn check_bool(found: bool, expected: bool, feature: &str) -> Result<()> {
352         if found == expected {
353             return Ok(());
354         }
355 
356         bail!(
357             "Module was compiled {} {} but it {} enabled for the host",
358             if found { "with" } else { "without" },
359             feature,
360             if expected { "is" } else { "is not" }
361         );
362     }
363 
364     fn check_tunables(&mut self, other: &Tunables) -> Result<()> {
365         let Tunables {
366             collector,
367             memory_reservation,
368             memory_guard_size,
369             generate_native_debuginfo,
370             parse_wasm_debuginfo,
371             consume_fuel,
372             epoch_interruption,
373             memory_may_move,
374             guard_before_linear_memory,
375             table_lazy_init,
376             relaxed_simd_deterministic,
377             winch_callable,
378             signals_based_traps,
379             memory_init_cow,
380             // This doesn't affect compilation, it's just a runtime setting.
381             memory_reservation_for_growth: _,
382 
383             // This does technically affect compilation but modules with/without
384             // trap information can be loaded into engines with the opposite
385             // setting just fine (it's just a section in the compiled file and
386             // whether it's present or not)
387             generate_address_map: _,
388 
389             // Just a debugging aid, doesn't affect functionality at all.
390             debug_adapter_modules: _,
391         } = self.tunables;
392 
393         Self::check_collector(collector, other.collector)?;
394         Self::check_int(
395             memory_reservation,
396             other.memory_reservation,
397             "memory reservation",
398         )?;
399         Self::check_int(
400             memory_guard_size,
401             other.memory_guard_size,
402             "memory guard size",
403         )?;
404         Self::check_bool(
405             generate_native_debuginfo,
406             other.generate_native_debuginfo,
407             "debug information support",
408         )?;
409         Self::check_bool(
410             parse_wasm_debuginfo,
411             other.parse_wasm_debuginfo,
412             "WebAssembly backtrace support",
413         )?;
414         Self::check_bool(consume_fuel, other.consume_fuel, "fuel support")?;
415         Self::check_bool(
416             epoch_interruption,
417             other.epoch_interruption,
418             "epoch interruption",
419         )?;
420         Self::check_bool(memory_may_move, other.memory_may_move, "memory may move")?;
421         Self::check_bool(
422             guard_before_linear_memory,
423             other.guard_before_linear_memory,
424             "guard before linear memory",
425         )?;
426         Self::check_bool(table_lazy_init, other.table_lazy_init, "table lazy init")?;
427         Self::check_bool(
428             relaxed_simd_deterministic,
429             other.relaxed_simd_deterministic,
430             "relaxed simd deterministic semantics",
431         )?;
432         Self::check_bool(
433             winch_callable,
434             other.winch_callable,
435             "Winch calling convention",
436         )?;
437         Self::check_bool(
438             signals_based_traps,
439             other.signals_based_traps,
440             "Signals-based traps",
441         )?;
442         Self::check_bool(
443             memory_init_cow,
444             other.memory_init_cow,
445             "memory initialization with CoW",
446         )?;
447 
448         Ok(())
449     }
450 
451     fn check_cfg_bool(
452         cfg: bool,
453         cfg_str: &str,
454         found: bool,
455         expected: bool,
456         feature: &str,
457     ) -> Result<()> {
458         if cfg {
459             Self::check_bool(found, expected, feature)
460         } else {
461             assert!(!expected);
462             ensure!(
463                 !found,
464                 "Module was compiled with {feature} but support in the host \
465                  was disabled at compile time because the `{cfg_str}` Cargo \
466                  feature was not enabled",
467             );
468             Ok(())
469         }
470     }
471 
472     fn check_features(&mut self, other: &wasmparser::WasmFeatures) -> Result<()> {
473         let WasmFeatures {
474             reference_types,
475             multi_value,
476             bulk_memory,
477             component_model,
478             simd,
479             tail_call,
480             threads,
481             multi_memory,
482             exceptions,
483             memory64,
484             relaxed_simd,
485             extended_const,
486             function_references,
487             gc,
488             custom_page_sizes,
489             component_model_more_flags,
490             component_model_multiple_returns,
491             gc_types,
492             wide_arithmetic,
493         } = self.features;
494 
495         use wasmparser::WasmFeatures as F;
496         Self::check_bool(
497             reference_types,
498             other.contains(F::REFERENCE_TYPES),
499             "WebAssembly reference types support",
500         )?;
501         Self::check_bool(
502             function_references,
503             other.contains(F::FUNCTION_REFERENCES),
504             "WebAssembly function-references support",
505         )?;
506         Self::check_bool(
507             gc,
508             other.contains(F::GC),
509             "WebAssembly garbage collection support",
510         )?;
511         Self::check_bool(
512             multi_value,
513             other.contains(F::MULTI_VALUE),
514             "WebAssembly multi-value support",
515         )?;
516         Self::check_bool(
517             bulk_memory,
518             other.contains(F::BULK_MEMORY),
519             "WebAssembly bulk memory support",
520         )?;
521         Self::check_bool(
522             component_model,
523             other.contains(F::COMPONENT_MODEL),
524             "WebAssembly component model support",
525         )?;
526         Self::check_bool(simd, other.contains(F::SIMD), "WebAssembly SIMD support")?;
527         Self::check_bool(
528             tail_call,
529             other.contains(F::TAIL_CALL),
530             "WebAssembly tail calls support",
531         )?;
532         Self::check_bool(
533             threads,
534             other.contains(F::THREADS),
535             "WebAssembly threads support",
536         )?;
537         Self::check_bool(
538             multi_memory,
539             other.contains(F::MULTI_MEMORY),
540             "WebAssembly multi-memory support",
541         )?;
542         Self::check_bool(
543             exceptions,
544             other.contains(F::EXCEPTIONS),
545             "WebAssembly exceptions support",
546         )?;
547         Self::check_bool(
548             memory64,
549             other.contains(F::MEMORY64),
550             "WebAssembly 64-bit memory support",
551         )?;
552         Self::check_bool(
553             extended_const,
554             other.contains(F::EXTENDED_CONST),
555             "WebAssembly extended-const support",
556         )?;
557         Self::check_bool(
558             relaxed_simd,
559             other.contains(F::RELAXED_SIMD),
560             "WebAssembly relaxed-simd support",
561         )?;
562         Self::check_bool(
563             custom_page_sizes,
564             other.contains(F::CUSTOM_PAGE_SIZES),
565             "WebAssembly custom-page-sizes support",
566         )?;
567         Self::check_bool(
568             component_model_more_flags,
569             other.contains(F::COMPONENT_MODEL_MORE_FLAGS),
570             "WebAssembly component model support for more than 32 flags",
571         )?;
572         Self::check_bool(
573             component_model_multiple_returns,
574             other.contains(F::COMPONENT_MODEL_MULTIPLE_RETURNS),
575             "WebAssembly component model support for multiple returns",
576         )?;
577         Self::check_cfg_bool(
578             cfg!(feature = "gc"),
579             "gc",
580             gc_types,
581             other.contains(F::GC_TYPES),
582             "support for WebAssembly gc types",
583         )?;
584         Self::check_bool(
585             wide_arithmetic,
586             other.contains(F::WIDE_ARITHMETIC),
587             "WebAssembly wide-arithmetic support",
588         )?;
589 
590         Ok(())
591     }
592 
593     fn check_collector(
594         module: Option<wasmtime_environ::Collector>,
595         host: Option<wasmtime_environ::Collector>,
596     ) -> Result<()> {
597         match (module, host) {
598             (None, None) => Ok(()),
599             (Some(module), Some(host)) if module == host => Ok(()),
600 
601             (None, Some(_)) => {
602                 bail!("module was compiled without GC but GC is enabled in the host")
603             }
604             (Some(_), None) => {
605                 bail!("module was compiled with GC however GC is disabled in the host")
606             }
607 
608             (Some(module), Some(host)) => {
609                 bail!(
610                     "module was compiled for the {module} collector but \
611                      the host is configured to use the {host} collector",
612                 )
613             }
614         }
615     }
616 }
617 
618 #[cfg(test)]
619 mod test {
620     use super::*;
621     use crate::{Config, Module, OptLevel};
622     use std::{
623         collections::hash_map::DefaultHasher,
624         hash::{Hash, Hasher},
625     };
626     use tempfile::TempDir;
627 
628     #[test]
629     fn test_architecture_mismatch() -> Result<()> {
630         let engine = Engine::default();
631         let mut metadata = Metadata::new(&engine);
632         metadata.target = "unknown-generic-linux".to_string();
633 
634         match metadata.check_compatible(&engine) {
635             Ok(_) => unreachable!(),
636             Err(e) => assert_eq!(
637                 e.to_string(),
638                 "Module was compiled for architecture 'unknown'",
639             ),
640         }
641 
642         Ok(())
643     }
644 
645     #[test]
646     #[cfg(target_arch = "x86_64")] // test on a platform that is known to use
647                                    // Cranelift
648     fn test_os_mismatch() -> Result<()> {
649         let engine = Engine::default();
650         let mut metadata = Metadata::new(&engine);
651 
652         metadata.target = format!(
653             "{}-generic-unknown",
654             target_lexicon::Triple::host().architecture
655         );
656 
657         match metadata.check_compatible(&engine) {
658             Ok(_) => unreachable!(),
659             Err(e) => assert_eq!(
660                 e.to_string(),
661                 "Module was compiled for operating system 'unknown'",
662             ),
663         }
664 
665         Ok(())
666     }
667 
668     #[test]
669     fn test_cranelift_flags_mismatch() -> Result<()> {
670         let engine = Engine::default();
671         let mut metadata = Metadata::new(&engine);
672 
673         metadata
674             .shared_flags
675             .push(("preserve_frame_pointers", FlagValue::Bool(false)));
676 
677         match metadata.check_compatible(&engine) {
678             Ok(_) => unreachable!(),
679             Err(e) => assert!(format!("{e:?}").starts_with(
680                 "\
681 compilation settings of module incompatible with native host
682 
683 Caused by:
684     setting \"preserve_frame_pointers\" is configured to Bool(false) which is not supported"
685             )),
686         }
687 
688         Ok(())
689     }
690 
691     #[test]
692     fn test_isa_flags_mismatch() -> Result<()> {
693         let engine = Engine::default();
694         let mut metadata = Metadata::new(&engine);
695 
696         metadata
697             .isa_flags
698             .push(("not_a_flag", FlagValue::Bool(true)));
699 
700         match metadata.check_compatible(&engine) {
701             Ok(_) => unreachable!(),
702             Err(e) => assert!(
703                 format!("{e:?}").starts_with(
704                     "\
705 compilation settings of module incompatible with native host
706 
707 Caused by:
708     don't know how to test for target-specific flag \"not_a_flag\" at runtime",
709                 ),
710                 "bad error {e:?}",
711             ),
712         }
713 
714         Ok(())
715     }
716 
717     #[test]
718     #[cfg_attr(miri, ignore)]
719     #[cfg(target_pointer_width = "64")] // different defaults on 32-bit platforms
720     fn test_tunables_int_mismatch() -> Result<()> {
721         let engine = Engine::default();
722         let mut metadata = Metadata::new(&engine);
723 
724         metadata.tunables.memory_guard_size = 0;
725 
726         match metadata.check_compatible(&engine) {
727             Ok(_) => unreachable!(),
728             Err(e) => assert_eq!(e.to_string(), "Module was compiled with a memory guard size of '0' but '33554432' is expected for the host"),
729         }
730 
731         Ok(())
732     }
733 
734     #[test]
735     fn test_tunables_bool_mismatch() -> Result<()> {
736         let mut config = Config::new();
737         config.epoch_interruption(true);
738 
739         let engine = Engine::new(&config)?;
740         let mut metadata = Metadata::new(&engine);
741         metadata.tunables.epoch_interruption = false;
742 
743         match metadata.check_compatible(&engine) {
744             Ok(_) => unreachable!(),
745             Err(e) => assert_eq!(
746                 e.to_string(),
747                 "Module was compiled without epoch interruption but it is enabled for the host"
748             ),
749         }
750 
751         let mut config = Config::new();
752         config.epoch_interruption(false);
753 
754         let engine = Engine::new(&config)?;
755         let mut metadata = Metadata::new(&engine);
756         metadata.tunables.epoch_interruption = true;
757 
758         match metadata.check_compatible(&engine) {
759             Ok(_) => unreachable!(),
760             Err(e) => assert_eq!(
761                 e.to_string(),
762                 "Module was compiled with epoch interruption but it is not enabled for the host"
763             ),
764         }
765 
766         Ok(())
767     }
768 
769     #[test]
770     #[cfg(target_arch = "x86_64")] // test on a platform that is known to
771                                    // implement threads
772     fn test_feature_mismatch() -> Result<()> {
773         let mut config = Config::new();
774         config.wasm_threads(true);
775 
776         let engine = Engine::new(&config)?;
777         let mut metadata = Metadata::new(&engine);
778         metadata.features.threads = false;
779 
780         match metadata.check_compatible(&engine) {
781             Ok(_) => unreachable!(),
782             Err(e) => assert_eq!(e.to_string(), "Module was compiled without WebAssembly threads support but it is enabled for the host"),
783         }
784 
785         let mut config = Config::new();
786         config.wasm_threads(false);
787 
788         let engine = Engine::new(&config)?;
789         let mut metadata = Metadata::new(&engine);
790         metadata.features.threads = true;
791 
792         match metadata.check_compatible(&engine) {
793             Ok(_) => unreachable!(),
794             Err(e) => assert_eq!(e.to_string(), "Module was compiled with WebAssembly threads support but it is not enabled for the host"),
795         }
796 
797         Ok(())
798     }
799 
800     #[test]
801     fn engine_weak_upgrades() {
802         let engine = Engine::default();
803         let weak = engine.weak();
804         weak.upgrade()
805             .expect("engine is still alive, so weak reference can upgrade");
806         drop(engine);
807         assert!(
808             weak.upgrade().is_none(),
809             "engine was dropped, so weak reference cannot upgrade"
810         );
811     }
812 
813     #[test]
814     #[cfg_attr(miri, ignore)]
815     fn cache_accounts_for_opt_level() -> Result<()> {
816         let td = TempDir::new()?;
817         let config_path = td.path().join("config.toml");
818         std::fs::write(
819             &config_path,
820             &format!(
821                 "
822                     [cache]
823                     enabled = true
824                     directory = '{}'
825                 ",
826                 td.path().join("cache").display()
827             ),
828         )?;
829         let mut cfg = Config::new();
830         cfg.cranelift_opt_level(OptLevel::None)
831             .cache_config_load(&config_path)?;
832         let engine = Engine::new(&cfg)?;
833         Module::new(&engine, "(module (func))")?;
834         assert_eq!(engine.config().cache_config.cache_hits(), 0);
835         assert_eq!(engine.config().cache_config.cache_misses(), 1);
836         Module::new(&engine, "(module (func))")?;
837         assert_eq!(engine.config().cache_config.cache_hits(), 1);
838         assert_eq!(engine.config().cache_config.cache_misses(), 1);
839 
840         let mut cfg = Config::new();
841         cfg.cranelift_opt_level(OptLevel::Speed)
842             .cache_config_load(&config_path)?;
843         let engine = Engine::new(&cfg)?;
844         Module::new(&engine, "(module (func))")?;
845         assert_eq!(engine.config().cache_config.cache_hits(), 0);
846         assert_eq!(engine.config().cache_config.cache_misses(), 1);
847         Module::new(&engine, "(module (func))")?;
848         assert_eq!(engine.config().cache_config.cache_hits(), 1);
849         assert_eq!(engine.config().cache_config.cache_misses(), 1);
850 
851         let mut cfg = Config::new();
852         cfg.cranelift_opt_level(OptLevel::SpeedAndSize)
853             .cache_config_load(&config_path)?;
854         let engine = Engine::new(&cfg)?;
855         Module::new(&engine, "(module (func))")?;
856         assert_eq!(engine.config().cache_config.cache_hits(), 0);
857         assert_eq!(engine.config().cache_config.cache_misses(), 1);
858         Module::new(&engine, "(module (func))")?;
859         assert_eq!(engine.config().cache_config.cache_hits(), 1);
860         assert_eq!(engine.config().cache_config.cache_misses(), 1);
861 
862         let mut cfg = Config::new();
863         cfg.debug_info(true).cache_config_load(&config_path)?;
864         let engine = Engine::new(&cfg)?;
865         Module::new(&engine, "(module (func))")?;
866         assert_eq!(engine.config().cache_config.cache_hits(), 0);
867         assert_eq!(engine.config().cache_config.cache_misses(), 1);
868         Module::new(&engine, "(module (func))")?;
869         assert_eq!(engine.config().cache_config.cache_hits(), 1);
870         assert_eq!(engine.config().cache_config.cache_misses(), 1);
871 
872         Ok(())
873     }
874 
875     #[test]
876     fn precompile_compatibility_key_accounts_for_opt_level() {
877         fn hash_for_config(cfg: &Config) -> u64 {
878             let engine = Engine::new(cfg).expect("Config should be valid");
879             let mut hasher = DefaultHasher::new();
880             engine.precompile_compatibility_hash().hash(&mut hasher);
881             hasher.finish()
882         }
883         let mut cfg = Config::new();
884         cfg.cranelift_opt_level(OptLevel::None);
885         let opt_none_hash = hash_for_config(&cfg);
886         cfg.cranelift_opt_level(OptLevel::Speed);
887         let opt_speed_hash = hash_for_config(&cfg);
888         assert_ne!(opt_none_hash, opt_speed_hash)
889     }
890 
891     #[test]
892     fn precompile_compatibility_key_accounts_for_module_version_strategy() -> Result<()> {
893         fn hash_for_config(cfg: &Config) -> u64 {
894             let engine = Engine::new(cfg).expect("Config should be valid");
895             let mut hasher = DefaultHasher::new();
896             engine.precompile_compatibility_hash().hash(&mut hasher);
897             hasher.finish()
898         }
899         let mut cfg_custom_version = Config::new();
900         cfg_custom_version.module_version(ModuleVersionStrategy::Custom("1.0.1111".to_string()))?;
901         let custom_version_hash = hash_for_config(&cfg_custom_version);
902 
903         let mut cfg_default_version = Config::new();
904         cfg_default_version.module_version(ModuleVersionStrategy::WasmtimeVersion)?;
905         let default_version_hash = hash_for_config(&cfg_default_version);
906 
907         let mut cfg_none_version = Config::new();
908         cfg_none_version.module_version(ModuleVersionStrategy::None)?;
909         let none_version_hash = hash_for_config(&cfg_none_version);
910 
911         assert_ne!(custom_version_hash, default_version_hash);
912         assert_ne!(custom_version_hash, none_version_hash);
913         assert_ne!(default_version_hash, none_version_hash);
914 
915         Ok(())
916     }
917 
918     #[test]
919     #[cfg_attr(miri, ignore)]
920     #[cfg(feature = "component-model")]
921     fn components_are_cached() -> Result<()> {
922         use crate::component::Component;
923 
924         let td = TempDir::new()?;
925         let config_path = td.path().join("config.toml");
926         std::fs::write(
927             &config_path,
928             &format!(
929                 "
930                     [cache]
931                     enabled = true
932                     directory = '{}'
933                 ",
934                 td.path().join("cache").display()
935             ),
936         )?;
937         let mut cfg = Config::new();
938         cfg.cache_config_load(&config_path)?;
939         let engine = Engine::new(&cfg)?;
940         Component::new(&engine, "(component (core module (func)))")?;
941         assert_eq!(engine.config().cache_config.cache_hits(), 0);
942         assert_eq!(engine.config().cache_config.cache_misses(), 1);
943         Component::new(&engine, "(component (core module (func)))")?;
944         assert_eq!(engine.config().cache_config.cache_hits(), 1);
945         assert_eq!(engine.config().cache_config.cache_misses(), 1);
946 
947         Ok(())
948     }
949 }
950