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::fmt;
27 use core::str::FromStr;
28 use object::endian::Endianness;
29 #[cfg(any(feature = "cranelift", feature = "winch"))]
30 use object::write::{Object, StandardSegment};
31 use object::{FileFlags, Object as _, ObjectSection, read::elf::ElfFile64};
32 use serde_derive::{Deserialize, Serialize};
33 use wasmtime_environ::obj;
34 use wasmtime_environ::{FlagValue, ObjectKind, Tunables};
35 
36 const VERSION: u8 = 0;
37 
38 /// Verifies that the serialized engine in `mmap` is compatible with the
39 /// `engine` provided.
40 ///
41 /// This function will verify that the `mmap` provided can be deserialized
42 /// successfully and that the contents are all compatible with the `engine`
43 /// provided here, notably compatible wasm features are enabled, compatible
44 /// compiler options, etc. If a mismatch is found and the compilation metadata
45 /// specified is incompatible then an error is returned.
46 pub fn check_compatible(engine: &Engine, mmap: &[u8], expected: ObjectKind) -> Result<()> {
47     // Parse the input `mmap` as an ELF file and see if the header matches the
48     // Wasmtime-generated header. This includes a Wasmtime-specific `os_abi` and
49     // the `e_flags` field should indicate whether `expected` matches or not.
50     //
51     // Note that errors generated here could mean that a precompiled module was
52     // loaded as a component, or vice versa, both of which aren't supposed to
53     // work.
54     //
55     // Ideally we'd only `File::parse` once and avoid the linear
56     // `section_by_name` search here but the general serialization code isn't
57     // structured well enough to make this easy and additionally it's not really
58     // a perf issue right now so doing that is left for another day's
59     // refactoring.
60     let obj = ElfFile64::<Endianness>::parse(mmap)
61         .map_err(obj::ObjectCrateErrorWrapper)
62         .context("failed to parse precompiled artifact as an ELF")?;
63     let expected_e_flags = match expected {
64         ObjectKind::Module => obj::EF_WASMTIME_MODULE,
65         ObjectKind::Component => obj::EF_WASMTIME_COMPONENT,
66     };
67     match obj.flags() {
68         FileFlags::Elf {
69             os_abi: obj::ELFOSABI_WASMTIME,
70             abi_version: 0,
71             e_flags,
72         } if e_flags & expected_e_flags == expected_e_flags => {}
73         _ => bail!("incompatible object file format"),
74     }
75 
76     let data = obj
77         .section_by_name(obj::ELF_WASM_ENGINE)
78         .ok_or_else(|| anyhow!("failed to find section `{}`", obj::ELF_WASM_ENGINE))?
79         .data()
80         .map_err(obj::ObjectCrateErrorWrapper)?;
81     let (first, data) = data
82         .split_first()
83         .ok_or_else(|| anyhow!("invalid engine section"))?;
84     if *first != VERSION {
85         bail!("mismatched version in engine section");
86     }
87     let (len, data) = data
88         .split_first()
89         .ok_or_else(|| anyhow!("invalid engine section"))?;
90     let len = usize::from(*len);
91     let (version, data) = if data.len() < len + 1 {
92         bail!("engine section too small")
93     } else {
94         data.split_at(len)
95     };
96 
97     match &engine.config().module_version {
98         ModuleVersionStrategy::WasmtimeVersion => {
99             let version = core::str::from_utf8(version)?;
100             if version != env!("CARGO_PKG_VERSION_MAJOR") {
101                 bail!("Module was compiled with incompatible Wasmtime version '{version}'");
102             }
103         }
104         ModuleVersionStrategy::Custom(v) => {
105             let version = core::str::from_utf8(&version)?;
106             if version != v {
107                 bail!("Module was compiled with incompatible version '{version}'");
108             }
109         }
110         ModuleVersionStrategy::None => { /* ignore the version info, accept all */ }
111     }
112     postcard::from_bytes::<Metadata<'_>>(data)?.check_compatible(engine)
113 }
114 
115 #[cfg(any(feature = "cranelift", feature = "winch"))]
116 pub fn append_compiler_info(engine: &Engine, obj: &mut Object<'_>, metadata: &Metadata<'_>) {
117     let section = obj.add_section(
118         obj.segment_name(StandardSegment::Data).to_vec(),
119         obj::ELF_WASM_ENGINE.as_bytes().to_vec(),
120         object::SectionKind::ReadOnlyData,
121     );
122     let mut data = Vec::new();
123     data.push(VERSION);
124     let version = match &engine.config().module_version {
125         ModuleVersionStrategy::WasmtimeVersion => env!("CARGO_PKG_VERSION_MAJOR"),
126         ModuleVersionStrategy::Custom(c) => c,
127         ModuleVersionStrategy::None => "",
128     };
129     // This precondition is checked in Config::module_version:
130     assert!(
131         version.len() < 256,
132         "package version must be less than 256 bytes"
133     );
134     data.push(version.len() as u8);
135     data.extend_from_slice(version.as_bytes());
136     data.extend(postcard::to_allocvec(metadata).unwrap());
137     obj.set_section_data(section, data, 1);
138 }
139 
140 fn detect_precompiled<'data, R: object::ReadRef<'data>>(
141     obj: ElfFile64<'data, Endianness, R>,
142 ) -> Option<Precompiled> {
143     match obj.flags() {
144         FileFlags::Elf {
145             os_abi: obj::ELFOSABI_WASMTIME,
146             abi_version: 0,
147             e_flags,
148         } if e_flags & obj::EF_WASMTIME_MODULE != 0 => Some(Precompiled::Module),
149         FileFlags::Elf {
150             os_abi: obj::ELFOSABI_WASMTIME,
151             abi_version: 0,
152             e_flags,
153         } if e_flags & obj::EF_WASMTIME_COMPONENT != 0 => Some(Precompiled::Component),
154         _ => None,
155     }
156 }
157 
158 pub fn detect_precompiled_bytes(bytes: &[u8]) -> Option<Precompiled> {
159     detect_precompiled(ElfFile64::parse(bytes).ok()?)
160 }
161 
162 #[cfg(feature = "std")]
163 pub fn detect_precompiled_file(path: impl AsRef<std::path::Path>) -> Result<Option<Precompiled>> {
164     let read_cache = object::ReadCache::new(std::fs::File::open(path)?);
165     let obj = ElfFile64::parse(&read_cache)?;
166     Ok(detect_precompiled(obj))
167 }
168 
169 #[derive(Serialize, Deserialize)]
170 pub struct Metadata<'a> {
171     target: String,
172     #[serde(borrow)]
173     shared_flags: Vec<(&'a str, FlagValue<'a>)>,
174     #[serde(borrow)]
175     isa_flags: Vec<(&'a str, FlagValue<'a>)>,
176     tunables: Tunables,
177     features: u64,
178 }
179 
180 impl Metadata<'_> {
181     #[cfg(any(feature = "cranelift", feature = "winch"))]
182     pub fn new(engine: &Engine) -> Result<Metadata<'static>> {
183         let compiler = engine.try_compiler()?;
184         Ok(Metadata {
185             target: compiler.triple().to_string(),
186             shared_flags: compiler.flags(),
187             isa_flags: compiler.isa_flags(),
188             tunables: engine.tunables().clone(),
189             features: engine.features().bits(),
190         })
191     }
192 
193     fn check_compatible(mut self, engine: &Engine) -> Result<()> {
194         self.check_triple(engine)?;
195         self.check_shared_flags(engine)?;
196         self.check_isa_flags(engine)?;
197         self.check_tunables(&engine.tunables())?;
198         self.check_features(&engine.features())?;
199         Ok(())
200     }
201 
202     fn check_triple(&self, engine: &Engine) -> Result<()> {
203         let engine_target = engine.target();
204         let module_target =
205             target_lexicon::Triple::from_str(&self.target).map_err(|e| anyhow!(e))?;
206 
207         if module_target.architecture != engine_target.architecture {
208             bail!(
209                 "Module was compiled for architecture '{}'",
210                 module_target.architecture
211             );
212         }
213 
214         if module_target.operating_system != engine_target.operating_system {
215             bail!(
216                 "Module was compiled for operating system '{}'",
217                 module_target.operating_system
218             );
219         }
220 
221         Ok(())
222     }
223 
224     fn check_shared_flags(&mut self, engine: &Engine) -> Result<()> {
225         for (name, val) in self.shared_flags.iter() {
226             engine
227                 .check_compatible_with_shared_flag(name, val)
228                 .map_err(|s| anyhow::Error::msg(s))
229                 .context("compilation settings of module incompatible with native host")?;
230         }
231         Ok(())
232     }
233 
234     fn check_isa_flags(&mut self, engine: &Engine) -> Result<()> {
235         for (name, val) in self.isa_flags.iter() {
236             engine
237                 .check_compatible_with_isa_flag(name, val)
238                 .map_err(|s| anyhow::Error::msg(s))
239                 .context("compilation settings of module incompatible with native host")?;
240         }
241         Ok(())
242     }
243 
244     fn check_int<T: Eq + fmt::Display>(found: T, expected: T, feature: &str) -> Result<()> {
245         if found == expected {
246             return Ok(());
247         }
248 
249         bail!(
250             "Module was compiled with a {feature} of '{found}' but '{expected}' is expected for the host"
251         );
252     }
253 
254     fn check_bool(found: bool, expected: bool, feature: impl fmt::Display) -> Result<()> {
255         if found == expected {
256             return Ok(());
257         }
258 
259         bail!(
260             "Module was compiled {} {} but it {} enabled for the host",
261             if found { "with" } else { "without" },
262             feature,
263             if expected { "is" } else { "is not" }
264         );
265     }
266 
267     fn check_tunables(&mut self, other: &Tunables) -> Result<()> {
268         let Tunables {
269             collector,
270             memory_reservation,
271             memory_guard_size,
272             debug_native,
273             debug_guest,
274             parse_wasm_debuginfo,
275             consume_fuel,
276             epoch_interruption,
277             memory_may_move,
278             guard_before_linear_memory,
279             table_lazy_init,
280             relaxed_simd_deterministic,
281             winch_callable,
282             signals_based_traps,
283             memory_init_cow,
284             inlining,
285             inlining_intra_module,
286             inlining_small_callee_size,
287             inlining_sum_size_threshold,
288 
289             // This doesn't affect compilation, it's just a runtime setting.
290             memory_reservation_for_growth: _,
291 
292             // This does technically affect compilation but modules with/without
293             // trap information can be loaded into engines with the opposite
294             // setting just fine (it's just a section in the compiled file and
295             // whether it's present or not)
296             generate_address_map: _,
297 
298             // Just a debugging aid, doesn't affect functionality at all.
299             debug_adapter_modules: _,
300         } = self.tunables;
301 
302         Self::check_collector(collector, other.collector)?;
303         Self::check_int(
304             memory_reservation,
305             other.memory_reservation,
306             "memory reservation",
307         )?;
308         Self::check_int(
309             memory_guard_size,
310             other.memory_guard_size,
311             "memory guard size",
312         )?;
313         Self::check_bool(
314             debug_native,
315             other.debug_native,
316             "native debug information support",
317         )?;
318         Self::check_bool(debug_guest, other.debug_guest, "guest debug")?;
319         Self::check_bool(
320             parse_wasm_debuginfo,
321             other.parse_wasm_debuginfo,
322             "WebAssembly backtrace support",
323         )?;
324         Self::check_bool(consume_fuel, other.consume_fuel, "fuel support")?;
325         Self::check_bool(
326             epoch_interruption,
327             other.epoch_interruption,
328             "epoch interruption",
329         )?;
330         Self::check_bool(memory_may_move, other.memory_may_move, "memory may move")?;
331         Self::check_bool(
332             guard_before_linear_memory,
333             other.guard_before_linear_memory,
334             "guard before linear memory",
335         )?;
336         Self::check_bool(table_lazy_init, other.table_lazy_init, "table lazy init")?;
337         Self::check_bool(
338             relaxed_simd_deterministic,
339             other.relaxed_simd_deterministic,
340             "relaxed simd deterministic semantics",
341         )?;
342         Self::check_bool(
343             winch_callable,
344             other.winch_callable,
345             "Winch calling convention",
346         )?;
347         Self::check_bool(
348             signals_based_traps,
349             other.signals_based_traps,
350             "Signals-based traps",
351         )?;
352         Self::check_bool(
353             memory_init_cow,
354             other.memory_init_cow,
355             "memory initialization with CoW",
356         )?;
357         Self::check_bool(inlining, other.inlining, "function inlining")?;
358         Self::check_int(
359             inlining_small_callee_size,
360             other.inlining_small_callee_size,
361             "function inlining small-callee size",
362         )?;
363         Self::check_int(
364             inlining_sum_size_threshold,
365             other.inlining_sum_size_threshold,
366             "function inlining sum-size threshold",
367         )?;
368         Self::check_intra_module_inlining(inlining_intra_module, other.inlining_intra_module)?;
369 
370         Ok(())
371     }
372 
373     fn check_features(&mut self, other: &wasmparser::WasmFeatures) -> Result<()> {
374         let module_features = wasmparser::WasmFeatures::from_bits_truncate(self.features);
375         let missing_features = (*other & module_features) ^ module_features;
376         for (name, _) in missing_features.iter_names() {
377             let name = name.to_ascii_lowercase();
378             bail!(
379                 "Module was compiled with support for WebAssembly feature \
380                 `{name}` but it is not enabled for the host",
381             );
382         }
383         Ok(())
384     }
385 
386     fn check_collector(
387         module: Option<wasmtime_environ::Collector>,
388         host: Option<wasmtime_environ::Collector>,
389     ) -> Result<()> {
390         match (module, host) {
391             // If the module doesn't require GC support it doesn't matter
392             // whether the host has GC support enabled or not.
393             (None, _) => Ok(()),
394             (Some(module), Some(host)) if module == host => Ok(()),
395 
396             (Some(_), None) => {
397                 bail!("module was compiled with GC however GC is disabled in the host")
398             }
399 
400             (Some(module), Some(host)) => {
401                 bail!(
402                     "module was compiled for the {module} collector but \
403                      the host is configured to use the {host} collector",
404                 )
405             }
406         }
407     }
408 
409     fn check_intra_module_inlining(
410         module: wasmtime_environ::IntraModuleInlining,
411         host: wasmtime_environ::IntraModuleInlining,
412     ) -> Result<()> {
413         if module == host {
414             return Ok(());
415         }
416 
417         let desc = |cfg| match cfg {
418             wasmtime_environ::IntraModuleInlining::No => "without intra-module inlining",
419             wasmtime_environ::IntraModuleInlining::Yes => "with intra-module inlining",
420             wasmtime_environ::IntraModuleInlining::WhenUsingGc => {
421                 "with intra-module inlining only when using GC"
422             }
423         };
424 
425         let module = desc(module);
426         let host = desc(host);
427 
428         bail!("module was compiled {module} however the host is configured {host}")
429     }
430 }
431 
432 #[cfg(test)]
433 mod test {
434     use super::*;
435     use crate::{Cache, Config, Module, OptLevel};
436     use std::{
437         collections::hash_map::DefaultHasher,
438         hash::{Hash, Hasher},
439     };
440     use tempfile::TempDir;
441 
442     #[test]
443     fn test_architecture_mismatch() -> Result<()> {
444         let engine = Engine::default();
445         let mut metadata = Metadata::new(&engine)?;
446         metadata.target = "unknown-generic-linux".to_string();
447 
448         match metadata.check_compatible(&engine) {
449             Ok(_) => unreachable!(),
450             Err(e) => assert_eq!(
451                 e.to_string(),
452                 "Module was compiled for architecture 'unknown'",
453             ),
454         }
455 
456         Ok(())
457     }
458 
459     // Note that this test runs on a platform that is known to use Cranelift
460     #[test]
461     #[cfg(all(target_arch = "x86_64", not(miri)))]
462     fn test_os_mismatch() -> Result<()> {
463         let engine = Engine::default();
464         let mut metadata = Metadata::new(&engine)?;
465 
466         metadata.target = format!(
467             "{}-generic-unknown",
468             target_lexicon::Triple::host().architecture
469         );
470 
471         match metadata.check_compatible(&engine) {
472             Ok(_) => unreachable!(),
473             Err(e) => assert_eq!(
474                 e.to_string(),
475                 "Module was compiled for operating system 'unknown'",
476             ),
477         }
478 
479         Ok(())
480     }
481 
482     #[test]
483     fn test_cranelift_flags_mismatch() -> Result<()> {
484         let engine = Engine::default();
485         let mut metadata = Metadata::new(&engine)?;
486 
487         metadata
488             .shared_flags
489             .push(("preserve_frame_pointers", FlagValue::Bool(false)));
490 
491         match metadata.check_compatible(&engine) {
492             Ok(_) => unreachable!(),
493             Err(e) => assert!(format!("{e:?}").starts_with(
494                 "\
495 compilation settings of module incompatible with native host
496 
497 Caused by:
498     setting \"preserve_frame_pointers\" is configured to Bool(false) which is not supported"
499             )),
500         }
501 
502         Ok(())
503     }
504 
505     #[test]
506     fn test_isa_flags_mismatch() -> Result<()> {
507         let engine = Engine::default();
508         let mut metadata = Metadata::new(&engine)?;
509 
510         metadata
511             .isa_flags
512             .push(("not_a_flag", FlagValue::Bool(true)));
513 
514         match metadata.check_compatible(&engine) {
515             Ok(_) => unreachable!(),
516             Err(e) => assert!(
517                 format!("{e:?}").starts_with(
518                     "\
519 compilation settings of module incompatible with native host
520 
521 Caused by:
522     don't know how to test for target-specific flag \"not_a_flag\" at runtime",
523                 ),
524                 "bad error {e:?}",
525             ),
526         }
527 
528         Ok(())
529     }
530 
531     #[test]
532     #[cfg_attr(miri, ignore)]
533     #[cfg(target_pointer_width = "64")] // different defaults on 32-bit platforms
534     fn test_tunables_int_mismatch() -> Result<()> {
535         let engine = Engine::default();
536         let mut metadata = Metadata::new(&engine)?;
537 
538         metadata.tunables.memory_guard_size = 0;
539 
540         match metadata.check_compatible(&engine) {
541             Ok(_) => unreachable!(),
542             Err(e) => assert_eq!(
543                 e.to_string(),
544                 "Module was compiled with a memory guard size of '0' but '33554432' is expected for the host"
545             ),
546         }
547 
548         Ok(())
549     }
550 
551     #[test]
552     fn test_tunables_bool_mismatch() -> Result<()> {
553         let mut config = Config::new();
554         config.epoch_interruption(true);
555 
556         let engine = Engine::new(&config)?;
557         let mut metadata = Metadata::new(&engine)?;
558         metadata.tunables.epoch_interruption = false;
559 
560         match metadata.check_compatible(&engine) {
561             Ok(_) => unreachable!(),
562             Err(e) => assert_eq!(
563                 e.to_string(),
564                 "Module was compiled without epoch interruption but it is enabled for the host"
565             ),
566         }
567 
568         let mut config = Config::new();
569         config.epoch_interruption(false);
570 
571         let engine = Engine::new(&config)?;
572         let mut metadata = Metadata::new(&engine)?;
573         metadata.tunables.epoch_interruption = true;
574 
575         match metadata.check_compatible(&engine) {
576             Ok(_) => unreachable!(),
577             Err(e) => assert_eq!(
578                 e.to_string(),
579                 "Module was compiled with epoch interruption but it is not enabled for the host"
580             ),
581         }
582 
583         Ok(())
584     }
585 
586     /// This test is only run a platform that is known to implement threads
587     #[test]
588     #[cfg(all(target_arch = "x86_64", not(miri)))]
589     fn test_feature_mismatch() -> Result<()> {
590         let mut config = Config::new();
591         config.wasm_threads(true);
592 
593         let engine = Engine::new(&config)?;
594         let mut metadata = Metadata::new(&engine)?;
595         metadata.features &= !wasmparser::WasmFeatures::THREADS.bits();
596 
597         // If a feature is disabled in the module and enabled in the host,
598         // that's always ok.
599         metadata.check_compatible(&engine)?;
600 
601         let mut config = Config::new();
602         config.wasm_threads(false);
603 
604         let engine = Engine::new(&config)?;
605         let mut metadata = Metadata::new(&engine)?;
606         metadata.features |= wasmparser::WasmFeatures::THREADS.bits();
607 
608         match metadata.check_compatible(&engine) {
609             Ok(_) => unreachable!(),
610             Err(e) => assert_eq!(
611                 e.to_string(),
612                 "Module was compiled with support for WebAssembly feature \
613                 `threads` but it is not enabled for the host"
614             ),
615         }
616 
617         Ok(())
618     }
619 
620     #[test]
621     fn engine_weak_upgrades() {
622         let engine = Engine::default();
623         let weak = engine.weak();
624         weak.upgrade()
625             .expect("engine is still alive, so weak reference can upgrade");
626         drop(engine);
627         assert!(
628             weak.upgrade().is_none(),
629             "engine was dropped, so weak reference cannot upgrade"
630         );
631     }
632 
633     #[test]
634     #[cfg_attr(miri, ignore)]
635     fn cache_accounts_for_opt_level() -> Result<()> {
636         let _ = env_logger::try_init();
637 
638         let td = TempDir::new()?;
639         let config_path = td.path().join("config.toml");
640         std::fs::write(
641             &config_path,
642             &format!(
643                 "
644                     [cache]
645                     directory = '{}'
646                 ",
647                 td.path().join("cache").display()
648             ),
649         )?;
650         let mut cfg = Config::new();
651         cfg.cranelift_opt_level(OptLevel::None)
652             .cache(Some(Cache::from_file(Some(&config_path))?));
653         let engine = Engine::new(&cfg)?;
654         Module::new(&engine, "(module (func))")?;
655         let cache_config = engine
656             .config()
657             .cache
658             .as_ref()
659             .expect("Missing cache config");
660         assert_eq!(cache_config.cache_hits(), 0);
661         assert_eq!(cache_config.cache_misses(), 1);
662         Module::new(&engine, "(module (func))")?;
663         assert_eq!(cache_config.cache_hits(), 1);
664         assert_eq!(cache_config.cache_misses(), 1);
665 
666         let mut cfg = Config::new();
667         cfg.cranelift_opt_level(OptLevel::Speed)
668             .cache(Some(Cache::from_file(Some(&config_path))?));
669         let engine = Engine::new(&cfg)?;
670         let cache_config = engine
671             .config()
672             .cache
673             .as_ref()
674             .expect("Missing cache config");
675         Module::new(&engine, "(module (func))")?;
676         assert_eq!(cache_config.cache_hits(), 0);
677         assert_eq!(cache_config.cache_misses(), 1);
678         Module::new(&engine, "(module (func))")?;
679         assert_eq!(cache_config.cache_hits(), 1);
680         assert_eq!(cache_config.cache_misses(), 1);
681 
682         let mut cfg = Config::new();
683         cfg.cranelift_opt_level(OptLevel::SpeedAndSize)
684             .cache(Some(Cache::from_file(Some(&config_path))?));
685         let engine = Engine::new(&cfg)?;
686         let cache_config = engine
687             .config()
688             .cache
689             .as_ref()
690             .expect("Missing cache config");
691         Module::new(&engine, "(module (func))")?;
692         assert_eq!(cache_config.cache_hits(), 0);
693         assert_eq!(cache_config.cache_misses(), 1);
694         Module::new(&engine, "(module (func))")?;
695         assert_eq!(cache_config.cache_hits(), 1);
696         assert_eq!(cache_config.cache_misses(), 1);
697 
698         let mut cfg = Config::new();
699         cfg.debug_info(true)
700             .cache(Some(Cache::from_file(Some(&config_path))?));
701         let engine = Engine::new(&cfg)?;
702         let cache_config = engine
703             .config()
704             .cache
705             .as_ref()
706             .expect("Missing cache config");
707         Module::new(&engine, "(module (func))")?;
708         assert_eq!(cache_config.cache_hits(), 0);
709         assert_eq!(cache_config.cache_misses(), 1);
710         Module::new(&engine, "(module (func))")?;
711         assert_eq!(cache_config.cache_hits(), 1);
712         assert_eq!(cache_config.cache_misses(), 1);
713 
714         Ok(())
715     }
716 
717     #[test]
718     fn precompile_compatibility_key_accounts_for_opt_level() {
719         fn hash_for_config(cfg: &Config) -> u64 {
720             let engine = Engine::new(cfg).expect("Config should be valid");
721             let mut hasher = DefaultHasher::new();
722             engine.precompile_compatibility_hash().hash(&mut hasher);
723             hasher.finish()
724         }
725         let mut cfg = Config::new();
726         cfg.cranelift_opt_level(OptLevel::None);
727         let opt_none_hash = hash_for_config(&cfg);
728         cfg.cranelift_opt_level(OptLevel::Speed);
729         let opt_speed_hash = hash_for_config(&cfg);
730         assert_ne!(opt_none_hash, opt_speed_hash)
731     }
732 
733     #[test]
734     fn precompile_compatibility_key_accounts_for_module_version_strategy() -> Result<()> {
735         fn hash_for_config(cfg: &Config) -> u64 {
736             let engine = Engine::new(cfg).expect("Config should be valid");
737             let mut hasher = DefaultHasher::new();
738             engine.precompile_compatibility_hash().hash(&mut hasher);
739             hasher.finish()
740         }
741         let mut cfg_custom_version = Config::new();
742         cfg_custom_version.module_version(ModuleVersionStrategy::Custom("1.0.1111".to_string()))?;
743         let custom_version_hash = hash_for_config(&cfg_custom_version);
744 
745         let mut cfg_default_version = Config::new();
746         cfg_default_version.module_version(ModuleVersionStrategy::WasmtimeVersion)?;
747         let default_version_hash = hash_for_config(&cfg_default_version);
748 
749         let mut cfg_none_version = Config::new();
750         cfg_none_version.module_version(ModuleVersionStrategy::None)?;
751         let none_version_hash = hash_for_config(&cfg_none_version);
752 
753         assert_ne!(custom_version_hash, default_version_hash);
754         assert_ne!(custom_version_hash, none_version_hash);
755         assert_ne!(default_version_hash, none_version_hash);
756 
757         Ok(())
758     }
759 
760     #[test]
761     #[cfg_attr(miri, ignore)]
762     #[cfg(feature = "component-model")]
763     fn components_are_cached() -> Result<()> {
764         use crate::component::Component;
765 
766         let td = TempDir::new()?;
767         let config_path = td.path().join("config.toml");
768         std::fs::write(
769             &config_path,
770             &format!(
771                 "
772                     [cache]
773                     directory = '{}'
774                 ",
775                 td.path().join("cache").display()
776             ),
777         )?;
778         let mut cfg = Config::new();
779         cfg.cache(Some(Cache::from_file(Some(&config_path))?));
780         let engine = Engine::new(&cfg)?;
781         let cache_config = engine
782             .config()
783             .cache
784             .as_ref()
785             .expect("Missing cache config");
786         Component::new(&engine, "(component (core module (func)))")?;
787         assert_eq!(cache_config.cache_hits(), 0);
788         assert_eq!(cache_config.cache_misses(), 1);
789         Component::new(&engine, "(component (core module (func)))")?;
790         assert_eq!(cache_config.cache_hits(), 1);
791         assert_eq!(cache_config.cache_misses(), 1);
792 
793         Ok(())
794     }
795 }
796