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") {
101                 bail!(
102                     "Module was compiled with incompatible Wasmtime version '{}'",
103                     version
104                 );
105             }
106         }
107         ModuleVersionStrategy::Custom(v) => {
108             let version = core::str::from_utf8(&version)?;
109             if version != v {
110                 bail!(
111                     "Module was compiled with incompatible version '{}'",
112                     version
113                 );
114             }
115         }
116         ModuleVersionStrategy::None => { /* ignore the version info, accept all */ }
117     }
118     postcard::from_bytes::<Metadata<'_>>(data)?.check_compatible(engine)
119 }
120 
121 #[cfg(any(feature = "cranelift", feature = "winch"))]
122 pub fn append_compiler_info(engine: &Engine, obj: &mut Object<'_>, metadata: &Metadata<'_>) {
123     let section = obj.add_section(
124         obj.segment_name(StandardSegment::Data).to_vec(),
125         obj::ELF_WASM_ENGINE.as_bytes().to_vec(),
126         object::SectionKind::ReadOnlyData,
127     );
128     let mut data = Vec::new();
129     data.push(VERSION);
130     let version = match &engine.config().module_version {
131         ModuleVersionStrategy::WasmtimeVersion => env!("CARGO_PKG_VERSION"),
132         ModuleVersionStrategy::Custom(c) => c,
133         ModuleVersionStrategy::None => "",
134     };
135     // This precondition is checked in Config::module_version:
136     assert!(
137         version.len() < 256,
138         "package version must be less than 256 bytes"
139     );
140     data.push(version.len() as u8);
141     data.extend_from_slice(version.as_bytes());
142     data.extend(postcard::to_allocvec(metadata).unwrap());
143     obj.set_section_data(section, data, 1);
144 }
145 
146 fn detect_precompiled<'data, R: object::ReadRef<'data>>(
147     obj: ElfFile64<'data, Endianness, R>,
148 ) -> Option<Precompiled> {
149     match obj.flags() {
150         FileFlags::Elf {
151             os_abi: obj::ELFOSABI_WASMTIME,
152             abi_version: 0,
153             e_flags,
154         } if e_flags & obj::EF_WASMTIME_MODULE != 0 => Some(Precompiled::Module),
155         FileFlags::Elf {
156             os_abi: obj::ELFOSABI_WASMTIME,
157             abi_version: 0,
158             e_flags,
159         } if e_flags & obj::EF_WASMTIME_COMPONENT != 0 => Some(Precompiled::Component),
160         _ => None,
161     }
162 }
163 
164 pub fn detect_precompiled_bytes(bytes: &[u8]) -> Option<Precompiled> {
165     detect_precompiled(ElfFile64::parse(bytes).ok()?)
166 }
167 
168 #[cfg(feature = "std")]
169 pub fn detect_precompiled_file(path: impl AsRef<std::path::Path>) -> Result<Option<Precompiled>> {
170     let read_cache = object::ReadCache::new(std::fs::File::open(path)?);
171     let obj = ElfFile64::parse(&read_cache)?;
172     Ok(detect_precompiled(obj))
173 }
174 
175 #[derive(Serialize, Deserialize)]
176 pub struct Metadata<'a> {
177     target: String,
178     #[serde(borrow)]
179     shared_flags: Vec<(&'a str, FlagValue<'a>)>,
180     #[serde(borrow)]
181     isa_flags: Vec<(&'a str, FlagValue<'a>)>,
182     tunables: Tunables,
183     features: u64,
184 }
185 
186 impl Metadata<'_> {
187     #[cfg(any(feature = "cranelift", feature = "winch"))]
188     pub fn new(engine: &Engine) -> Metadata<'static> {
189         Metadata {
190             target: engine.compiler().triple().to_string(),
191             shared_flags: engine.compiler().flags(),
192             isa_flags: engine.compiler().isa_flags(),
193             tunables: engine.tunables().clone(),
194             features: engine.features().bits(),
195         }
196     }
197 
198     fn check_compatible(mut self, engine: &Engine) -> Result<()> {
199         self.check_triple(engine)?;
200         self.check_shared_flags(engine)?;
201         self.check_isa_flags(engine)?;
202         self.check_tunables(&engine.tunables())?;
203         self.check_features(&engine.features())?;
204         Ok(())
205     }
206 
207     fn check_triple(&self, engine: &Engine) -> Result<()> {
208         let engine_target = engine.target();
209         let module_target =
210             target_lexicon::Triple::from_str(&self.target).map_err(|e| anyhow!(e))?;
211 
212         if module_target.architecture != engine_target.architecture {
213             bail!(
214                 "Module was compiled for architecture '{}'",
215                 module_target.architecture
216             );
217         }
218 
219         if module_target.operating_system != engine_target.operating_system {
220             bail!(
221                 "Module was compiled for operating system '{}'",
222                 module_target.operating_system
223             );
224         }
225 
226         Ok(())
227     }
228 
229     fn check_shared_flags(&mut self, engine: &Engine) -> Result<()> {
230         for (name, val) in self.shared_flags.iter() {
231             engine
232                 .check_compatible_with_shared_flag(name, val)
233                 .map_err(|s| anyhow::Error::msg(s))
234                 .context("compilation settings of module incompatible with native host")?;
235         }
236         Ok(())
237     }
238 
239     fn check_isa_flags(&mut self, engine: &Engine) -> Result<()> {
240         for (name, val) in self.isa_flags.iter() {
241             engine
242                 .check_compatible_with_isa_flag(name, val)
243                 .map_err(|s| anyhow::Error::msg(s))
244                 .context("compilation settings of module incompatible with native host")?;
245         }
246         Ok(())
247     }
248 
249     fn check_int<T: Eq + fmt::Display>(found: T, expected: T, feature: &str) -> Result<()> {
250         if found == expected {
251             return Ok(());
252         }
253 
254         bail!(
255             "Module was compiled with a {} of '{}' but '{}' is expected for the host",
256             feature,
257             found,
258             expected
259         );
260     }
261 
262     fn check_bool(found: bool, expected: bool, feature: impl fmt::Display) -> Result<()> {
263         if found == expected {
264             return Ok(());
265         }
266 
267         bail!(
268             "Module was compiled {} {} but it {} enabled for the host",
269             if found { "with" } else { "without" },
270             feature,
271             if expected { "is" } else { "is not" }
272         );
273     }
274 
275     fn check_tunables(&mut self, other: &Tunables) -> Result<()> {
276         let Tunables {
277             collector,
278             memory_reservation,
279             memory_guard_size,
280             generate_native_debuginfo,
281             parse_wasm_debuginfo,
282             consume_fuel,
283             epoch_interruption,
284             memory_may_move,
285             guard_before_linear_memory,
286             table_lazy_init,
287             relaxed_simd_deterministic,
288             winch_callable,
289             signals_based_traps,
290             memory_init_cow,
291             // This doesn't affect compilation, it's just a runtime setting.
292             memory_reservation_for_growth: _,
293 
294             // This does technically affect compilation but modules with/without
295             // trap information can be loaded into engines with the opposite
296             // setting just fine (it's just a section in the compiled file and
297             // whether it's present or not)
298             generate_address_map: _,
299 
300             // Just a debugging aid, doesn't affect functionality at all.
301             debug_adapter_modules: _,
302         } = self.tunables;
303 
304         Self::check_collector(collector, other.collector)?;
305         Self::check_int(
306             memory_reservation,
307             other.memory_reservation,
308             "memory reservation",
309         )?;
310         Self::check_int(
311             memory_guard_size,
312             other.memory_guard_size,
313             "memory guard size",
314         )?;
315         Self::check_bool(
316             generate_native_debuginfo,
317             other.generate_native_debuginfo,
318             "debug information support",
319         )?;
320         Self::check_bool(
321             parse_wasm_debuginfo,
322             other.parse_wasm_debuginfo,
323             "WebAssembly backtrace support",
324         )?;
325         Self::check_bool(consume_fuel, other.consume_fuel, "fuel support")?;
326         Self::check_bool(
327             epoch_interruption,
328             other.epoch_interruption,
329             "epoch interruption",
330         )?;
331         Self::check_bool(memory_may_move, other.memory_may_move, "memory may move")?;
332         Self::check_bool(
333             guard_before_linear_memory,
334             other.guard_before_linear_memory,
335             "guard before linear memory",
336         )?;
337         Self::check_bool(table_lazy_init, other.table_lazy_init, "table lazy init")?;
338         Self::check_bool(
339             relaxed_simd_deterministic,
340             other.relaxed_simd_deterministic,
341             "relaxed simd deterministic semantics",
342         )?;
343         Self::check_bool(
344             winch_callable,
345             other.winch_callable,
346             "Winch calling convention",
347         )?;
348         Self::check_bool(
349             signals_based_traps,
350             other.signals_based_traps,
351             "Signals-based traps",
352         )?;
353         Self::check_bool(
354             memory_init_cow,
355             other.memory_init_cow,
356             "memory initialization with CoW",
357         )?;
358 
359         Ok(())
360     }
361 
362     fn check_cfg_bool(
363         cfg: bool,
364         cfg_str: &str,
365         found: bool,
366         expected: bool,
367         feature: impl fmt::Display,
368     ) -> Result<()> {
369         if cfg {
370             Self::check_bool(found, expected, feature)
371         } else {
372             assert!(!expected);
373             ensure!(
374                 !found,
375                 "Module was compiled with {feature} but support in the host \
376                  was disabled at compile time because the `{cfg_str}` Cargo \
377                  feature was not enabled",
378             );
379             Ok(())
380         }
381     }
382 
383     fn check_features(&mut self, other: &wasmparser::WasmFeatures) -> Result<()> {
384         let module_features = wasmparser::WasmFeatures::from_bits_truncate(self.features);
385         let difference = *other ^ module_features;
386         for (name, flag) in difference.iter_names() {
387             let found = module_features.contains(flag);
388             let expected = other.contains(flag);
389             // Give a slightly more specialized error message for the `GC_TYPES`
390             // feature which isn't actually part of wasm itself but is gated by
391             // compile-time crate features.
392             if flag == wasmparser::WasmFeatures::GC_TYPES {
393                 Self::check_cfg_bool(
394                     cfg!(feature = "gc"),
395                     "gc",
396                     found,
397                     expected,
398                     WasmFeature(name),
399                 )?;
400             } else {
401                 Self::check_bool(found, expected, WasmFeature(name))?;
402             }
403         }
404 
405         return Ok(());
406 
407         struct WasmFeature<'a>(&'a str);
408 
409         impl fmt::Display for WasmFeature<'_> {
410             fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
411                 write!(f, "support for WebAssembly feature `")?;
412                 for c in self.0.chars().map(|c| c.to_lowercase()) {
413                     write!(f, "{c}")?;
414                 }
415                 write!(f, "`")?;
416                 Ok(())
417             }
418         }
419     }
420 
421     fn check_collector(
422         module: Option<wasmtime_environ::Collector>,
423         host: Option<wasmtime_environ::Collector>,
424     ) -> Result<()> {
425         match (module, host) {
426             (None, None) => Ok(()),
427             (Some(module), Some(host)) if module == host => Ok(()),
428 
429             (None, Some(_)) => {
430                 bail!("module was compiled without GC but GC is enabled in the host")
431             }
432             (Some(_), None) => {
433                 bail!("module was compiled with GC however GC is disabled in the host")
434             }
435 
436             (Some(module), Some(host)) => {
437                 bail!(
438                     "module was compiled for the {module} collector but \
439                      the host is configured to use the {host} collector",
440                 )
441             }
442         }
443     }
444 }
445 
446 #[cfg(test)]
447 mod test {
448     use super::*;
449     use crate::{Cache, Config, Module, OptLevel};
450     use std::{
451         collections::hash_map::DefaultHasher,
452         hash::{Hash, Hasher},
453     };
454     use tempfile::TempDir;
455 
456     #[test]
457     fn test_architecture_mismatch() -> Result<()> {
458         let engine = Engine::default();
459         let mut metadata = Metadata::new(&engine);
460         metadata.target = "unknown-generic-linux".to_string();
461 
462         match metadata.check_compatible(&engine) {
463             Ok(_) => unreachable!(),
464             Err(e) => assert_eq!(
465                 e.to_string(),
466                 "Module was compiled for architecture 'unknown'",
467             ),
468         }
469 
470         Ok(())
471     }
472 
473     // Note that this test runs on a platform that is known to use Cranelift
474     #[test]
475     #[cfg(all(target_arch = "x86_64", not(miri)))]
476     fn test_os_mismatch() -> Result<()> {
477         let engine = Engine::default();
478         let mut metadata = Metadata::new(&engine);
479 
480         metadata.target = format!(
481             "{}-generic-unknown",
482             target_lexicon::Triple::host().architecture
483         );
484 
485         match metadata.check_compatible(&engine) {
486             Ok(_) => unreachable!(),
487             Err(e) => assert_eq!(
488                 e.to_string(),
489                 "Module was compiled for operating system 'unknown'",
490             ),
491         }
492 
493         Ok(())
494     }
495 
496     #[test]
497     fn test_cranelift_flags_mismatch() -> Result<()> {
498         let engine = Engine::default();
499         let mut metadata = Metadata::new(&engine);
500 
501         metadata
502             .shared_flags
503             .push(("preserve_frame_pointers", FlagValue::Bool(false)));
504 
505         match metadata.check_compatible(&engine) {
506             Ok(_) => unreachable!(),
507             Err(e) => assert!(format!("{e:?}").starts_with(
508                 "\
509 compilation settings of module incompatible with native host
510 
511 Caused by:
512     setting \"preserve_frame_pointers\" is configured to Bool(false) which is not supported"
513             )),
514         }
515 
516         Ok(())
517     }
518 
519     #[test]
520     fn test_isa_flags_mismatch() -> Result<()> {
521         let engine = Engine::default();
522         let mut metadata = Metadata::new(&engine);
523 
524         metadata
525             .isa_flags
526             .push(("not_a_flag", FlagValue::Bool(true)));
527 
528         match metadata.check_compatible(&engine) {
529             Ok(_) => unreachable!(),
530             Err(e) => assert!(
531                 format!("{e:?}").starts_with(
532                     "\
533 compilation settings of module incompatible with native host
534 
535 Caused by:
536     don't know how to test for target-specific flag \"not_a_flag\" at runtime",
537                 ),
538                 "bad error {e:?}",
539             ),
540         }
541 
542         Ok(())
543     }
544 
545     #[test]
546     #[cfg_attr(miri, ignore)]
547     #[cfg(target_pointer_width = "64")] // different defaults on 32-bit platforms
548     fn test_tunables_int_mismatch() -> Result<()> {
549         let engine = Engine::default();
550         let mut metadata = Metadata::new(&engine);
551 
552         metadata.tunables.memory_guard_size = 0;
553 
554         match metadata.check_compatible(&engine) {
555             Ok(_) => unreachable!(),
556             Err(e) => assert_eq!(
557                 e.to_string(),
558                 "Module was compiled with a memory guard size of '0' but '33554432' is expected for the host"
559             ),
560         }
561 
562         Ok(())
563     }
564 
565     #[test]
566     fn test_tunables_bool_mismatch() -> Result<()> {
567         let mut config = Config::new();
568         config.epoch_interruption(true);
569 
570         let engine = Engine::new(&config)?;
571         let mut metadata = Metadata::new(&engine);
572         metadata.tunables.epoch_interruption = false;
573 
574         match metadata.check_compatible(&engine) {
575             Ok(_) => unreachable!(),
576             Err(e) => assert_eq!(
577                 e.to_string(),
578                 "Module was compiled without epoch interruption but it is enabled for the host"
579             ),
580         }
581 
582         let mut config = Config::new();
583         config.epoch_interruption(false);
584 
585         let engine = Engine::new(&config)?;
586         let mut metadata = Metadata::new(&engine);
587         metadata.tunables.epoch_interruption = true;
588 
589         match metadata.check_compatible(&engine) {
590             Ok(_) => unreachable!(),
591             Err(e) => assert_eq!(
592                 e.to_string(),
593                 "Module was compiled with epoch interruption but it is not enabled for the host"
594             ),
595         }
596 
597         Ok(())
598     }
599 
600     /// This test is only run a platform that is known to implement threads
601     #[test]
602     #[cfg(all(target_arch = "x86_64", not(miri)))]
603     fn test_feature_mismatch() -> Result<()> {
604         let mut config = Config::new();
605         config.wasm_threads(true);
606 
607         let engine = Engine::new(&config)?;
608         let mut metadata = Metadata::new(&engine);
609         metadata.features &= !wasmparser::WasmFeatures::THREADS.bits();
610 
611         match metadata.check_compatible(&engine) {
612             Ok(_) => unreachable!(),
613             Err(e) => assert_eq!(
614                 e.to_string(),
615                 "Module was compiled without support for WebAssembly feature \
616                  `threads` but it is enabled for the host"
617             ),
618         }
619 
620         let mut config = Config::new();
621         config.wasm_threads(false);
622 
623         let engine = Engine::new(&config)?;
624         let mut metadata = Metadata::new(&engine);
625         metadata.features |= wasmparser::WasmFeatures::THREADS.bits();
626 
627         match metadata.check_compatible(&engine) {
628             Ok(_) => unreachable!(),
629             Err(e) => assert_eq!(
630                 e.to_string(),
631                 "Module was compiled with support for WebAssembly feature \
632                 `threads` but it is not enabled for the host"
633             ),
634         }
635 
636         Ok(())
637     }
638 
639     #[test]
640     fn engine_weak_upgrades() {
641         let engine = Engine::default();
642         let weak = engine.weak();
643         weak.upgrade()
644             .expect("engine is still alive, so weak reference can upgrade");
645         drop(engine);
646         assert!(
647             weak.upgrade().is_none(),
648             "engine was dropped, so weak reference cannot upgrade"
649         );
650     }
651 
652     #[test]
653     #[cfg_attr(miri, ignore)]
654     fn cache_accounts_for_opt_level() -> Result<()> {
655         let td = TempDir::new()?;
656         let config_path = td.path().join("config.toml");
657         std::fs::write(
658             &config_path,
659             &format!(
660                 "
661                     [cache]
662                     directory = '{}'
663                 ",
664                 td.path().join("cache").display()
665             ),
666         )?;
667         let mut cfg = Config::new();
668         cfg.cranelift_opt_level(OptLevel::None)
669             .cache(Some(Cache::from_file(Some(&config_path))?));
670         let engine = Engine::new(&cfg)?;
671         Module::new(&engine, "(module (func))")?;
672         let cache_config = engine
673             .config()
674             .cache
675             .as_ref()
676             .expect("Missing cache config");
677         assert_eq!(cache_config.cache_hits(), 0);
678         assert_eq!(cache_config.cache_misses(), 1);
679         Module::new(&engine, "(module (func))")?;
680         assert_eq!(cache_config.cache_hits(), 1);
681         assert_eq!(cache_config.cache_misses(), 1);
682 
683         let mut cfg = Config::new();
684         cfg.cranelift_opt_level(OptLevel::Speed)
685             .cache(Some(Cache::from_file(Some(&config_path))?));
686         let engine = Engine::new(&cfg)?;
687         let cache_config = engine
688             .config()
689             .cache
690             .as_ref()
691             .expect("Missing cache config");
692         Module::new(&engine, "(module (func))")?;
693         assert_eq!(cache_config.cache_hits(), 0);
694         assert_eq!(cache_config.cache_misses(), 1);
695         Module::new(&engine, "(module (func))")?;
696         assert_eq!(cache_config.cache_hits(), 1);
697         assert_eq!(cache_config.cache_misses(), 1);
698 
699         let mut cfg = Config::new();
700         cfg.cranelift_opt_level(OptLevel::SpeedAndSize)
701             .cache(Some(Cache::from_file(Some(&config_path))?));
702         let engine = Engine::new(&cfg)?;
703         let cache_config = engine
704             .config()
705             .cache
706             .as_ref()
707             .expect("Missing cache config");
708         Module::new(&engine, "(module (func))")?;
709         assert_eq!(cache_config.cache_hits(), 0);
710         assert_eq!(cache_config.cache_misses(), 1);
711         Module::new(&engine, "(module (func))")?;
712         assert_eq!(cache_config.cache_hits(), 1);
713         assert_eq!(cache_config.cache_misses(), 1);
714 
715         let mut cfg = Config::new();
716         cfg.debug_info(true)
717             .cache(Some(Cache::from_file(Some(&config_path))?));
718         let engine = Engine::new(&cfg)?;
719         let cache_config = engine
720             .config()
721             .cache
722             .as_ref()
723             .expect("Missing cache config");
724         Module::new(&engine, "(module (func))")?;
725         assert_eq!(cache_config.cache_hits(), 0);
726         assert_eq!(cache_config.cache_misses(), 1);
727         Module::new(&engine, "(module (func))")?;
728         assert_eq!(cache_config.cache_hits(), 1);
729         assert_eq!(cache_config.cache_misses(), 1);
730 
731         Ok(())
732     }
733 
734     #[test]
735     fn precompile_compatibility_key_accounts_for_opt_level() {
736         fn hash_for_config(cfg: &Config) -> u64 {
737             let engine = Engine::new(cfg).expect("Config should be valid");
738             let mut hasher = DefaultHasher::new();
739             engine.precompile_compatibility_hash().hash(&mut hasher);
740             hasher.finish()
741         }
742         let mut cfg = Config::new();
743         cfg.cranelift_opt_level(OptLevel::None);
744         let opt_none_hash = hash_for_config(&cfg);
745         cfg.cranelift_opt_level(OptLevel::Speed);
746         let opt_speed_hash = hash_for_config(&cfg);
747         assert_ne!(opt_none_hash, opt_speed_hash)
748     }
749 
750     #[test]
751     fn precompile_compatibility_key_accounts_for_module_version_strategy() -> Result<()> {
752         fn hash_for_config(cfg: &Config) -> u64 {
753             let engine = Engine::new(cfg).expect("Config should be valid");
754             let mut hasher = DefaultHasher::new();
755             engine.precompile_compatibility_hash().hash(&mut hasher);
756             hasher.finish()
757         }
758         let mut cfg_custom_version = Config::new();
759         cfg_custom_version.module_version(ModuleVersionStrategy::Custom("1.0.1111".to_string()))?;
760         let custom_version_hash = hash_for_config(&cfg_custom_version);
761 
762         let mut cfg_default_version = Config::new();
763         cfg_default_version.module_version(ModuleVersionStrategy::WasmtimeVersion)?;
764         let default_version_hash = hash_for_config(&cfg_default_version);
765 
766         let mut cfg_none_version = Config::new();
767         cfg_none_version.module_version(ModuleVersionStrategy::None)?;
768         let none_version_hash = hash_for_config(&cfg_none_version);
769 
770         assert_ne!(custom_version_hash, default_version_hash);
771         assert_ne!(custom_version_hash, none_version_hash);
772         assert_ne!(default_version_hash, none_version_hash);
773 
774         Ok(())
775     }
776 
777     #[test]
778     #[cfg_attr(miri, ignore)]
779     #[cfg(feature = "component-model")]
780     fn components_are_cached() -> Result<()> {
781         use crate::component::Component;
782 
783         let td = TempDir::new()?;
784         let config_path = td.path().join("config.toml");
785         std::fs::write(
786             &config_path,
787             &format!(
788                 "
789                     [cache]
790                     directory = '{}'
791                 ",
792                 td.path().join("cache").display()
793             ),
794         )?;
795         let mut cfg = Config::new();
796         cfg.cache(Some(Cache::from_file(Some(&config_path))?));
797         let engine = Engine::new(&cfg)?;
798         let cache_config = engine
799             .config()
800             .cache
801             .as_ref()
802             .expect("Missing cache config");
803         Component::new(&engine, "(component (core module (func)))")?;
804         assert_eq!(cache_config.cache_hits(), 0);
805         assert_eq!(cache_config.cache_misses(), 1);
806         Component::new(&engine, "(component (core module (func)))")?;
807         assert_eq!(cache_config.cache_hits(), 1);
808         assert_eq!(cache_config.cache_misses(), 1);
809 
810         Ok(())
811     }
812 }
813