1 //! Generate a configuration for both Wasmtime and the Wasm module to execute. 2 3 use super::{ 4 AsyncConfig, CodegenSettings, InstanceAllocationStrategy, MemoryConfig, ModuleConfig, 5 NormalMemoryConfig, UnalignedMemoryCreator, 6 }; 7 use crate::oracles::{StoreLimits, Timeout}; 8 use anyhow::Result; 9 use arbitrary::{Arbitrary, Unstructured}; 10 use std::sync::Arc; 11 use std::time::Duration; 12 use wasmtime::{Engine, Module, MpkEnabled, Store}; 13 use wasmtime_test_util::wast::{limits, WastConfig, WastTest}; 14 15 /// Configuration for `wasmtime::Config` and generated modules for a session of 16 /// fuzzing. 17 /// 18 /// This configuration guides what modules are generated, how wasmtime 19 /// configuration is generated, and is typically itself generated through a call 20 /// to `Arbitrary` which allows for a form of "swarm testing". 21 #[derive(Debug, Clone)] 22 pub struct Config { 23 /// Configuration related to the `wasmtime::Config`. 24 pub wasmtime: WasmtimeConfig, 25 /// Configuration related to generated modules. 26 pub module_config: ModuleConfig, 27 } 28 29 impl Config { 30 /// Indicates that this configuration is being used for differential 31 /// execution. 32 /// 33 /// The purpose of this function is to update the configuration which was 34 /// generated to be compatible with execution in multiple engines. The goal 35 /// is to produce the exact same result in all engines so we need to paper 36 /// over things like nan differences and memory/table behavior differences. 37 pub fn set_differential_config(&mut self) { 38 let config = &mut self.module_config.config; 39 40 // Make it more likely that there are types available to generate a 41 // function with. 42 config.min_types = config.min_types.max(1); 43 config.max_types = config.max_types.max(1); 44 45 // Generate at least one function 46 config.min_funcs = config.min_funcs.max(1); 47 config.max_funcs = config.max_funcs.max(1); 48 49 // Allow a memory to be generated, but don't let it get too large. 50 // Additionally require the maximum size to guarantee that the growth 51 // behavior is consistent across engines. 52 config.max_memory32_bytes = 10 << 16; 53 config.max_memory64_bytes = 10 << 16; 54 config.memory_max_size_required = true; 55 56 // If tables are generated make sure they don't get too large to avoid 57 // hitting any engine-specific limit. Additionally ensure that the 58 // maximum size is required to guarantee consistent growth across 59 // engines. 60 // 61 // Note that while reference types are disabled below, only allow one 62 // table. 63 config.max_table_elements = 1_000; 64 config.table_max_size_required = true; 65 66 // Don't allow any imports 67 config.max_imports = 0; 68 69 // Try to get the function and the memory exported 70 config.export_everything = true; 71 72 // NaN is canonicalized at the wasm level for differential fuzzing so we 73 // can paper over NaN differences between engines. 74 config.canonicalize_nans = true; 75 76 // If using the pooling allocator, update the instance limits too 77 if let InstanceAllocationStrategy::Pooling(pooling) = &mut self.wasmtime.strategy { 78 // One single-page memory 79 pooling.total_memories = config.max_memories as u32; 80 pooling.max_memory_size = 10 << 16; 81 pooling.max_memories_per_module = config.max_memories as u32; 82 if pooling.memory_protection_keys == MpkEnabled::Auto 83 && pooling.max_memory_protection_keys > 1 84 { 85 pooling.total_memories = 86 pooling.total_memories * (pooling.max_memory_protection_keys as u32); 87 } 88 89 pooling.total_tables = config.max_tables as u32; 90 pooling.table_elements = 1_000; 91 pooling.max_tables_per_module = config.max_tables as u32; 92 93 pooling.core_instance_size = 1_000_000; 94 95 if let MemoryConfig::Normal(cfg) = &mut self.wasmtime.memory_config { 96 match &mut cfg.memory_reservation { 97 Some(size) => *size = (*size).max(pooling.max_memory_size as u64), 98 other @ None => *other = Some(pooling.max_memory_size as u64), 99 } 100 } 101 } 102 103 // These instructions are explicitly not expected to be exactly the same 104 // across engines. Don't fuzz them. 105 config.relaxed_simd_enabled = false; 106 } 107 108 /// Uses this configuration and the supplied source of data to generate 109 /// a wasm module. 110 /// 111 /// If a `default_fuel` is provided, the resulting module will be configured 112 /// to ensure termination; as doing so will add an additional global to the module, 113 /// the pooling allocator, if configured, will also have its globals limit updated. 114 pub fn generate( 115 &self, 116 input: &mut Unstructured<'_>, 117 default_fuel: Option<u32>, 118 ) -> arbitrary::Result<wasm_smith::Module> { 119 self.module_config.generate(input, default_fuel) 120 } 121 122 /// Updates this configuration to be able to run the `test` specified. 123 /// 124 /// This primarily updates `self.module_config` to ensure that it enables 125 /// all features and proposals necessary to execute the `test` specified. 126 /// This will additionally update limits in the pooling allocator to be able 127 /// to execute all tests. 128 pub fn make_wast_test_compliant(&mut self, test: &WastTest) -> WastConfig { 129 let wasmtime_test_util::wast::TestConfig { 130 memory64, 131 custom_page_sizes, 132 multi_memory, 133 threads, 134 gc, 135 function_references, 136 relaxed_simd, 137 reference_types, 138 tail_call, 139 extended_const, 140 wide_arithmetic, 141 component_model_async, 142 simd, 143 144 hogs_memory: _, 145 nan_canonicalization: _, 146 gc_types: _, 147 } = test.config; 148 149 // Enable/disable some proposals that aren't configurable in wasm-smith 150 // but are configurable in Wasmtime. 151 self.module_config.function_references_enabled = 152 function_references.or(gc).unwrap_or(false); 153 self.module_config.component_model_async = component_model_async.unwrap_or(false); 154 155 // Enable/disable proposals that wasm-smith has knobs for which will be 156 // read when creating `wasmtime::Config`. 157 let config = &mut self.module_config.config; 158 config.bulk_memory_enabled = true; 159 config.multi_value_enabled = true; 160 config.wide_arithmetic_enabled = wide_arithmetic.unwrap_or(false); 161 config.memory64_enabled = memory64.unwrap_or(false); 162 config.relaxed_simd_enabled = relaxed_simd.unwrap_or(false); 163 config.simd_enabled = config.relaxed_simd_enabled || simd.unwrap_or(false); 164 config.tail_call_enabled = tail_call.unwrap_or(false); 165 config.custom_page_sizes_enabled = custom_page_sizes.unwrap_or(false); 166 config.threads_enabled = threads.unwrap_or(false); 167 config.gc_enabled = gc.unwrap_or(false); 168 config.reference_types_enabled = config.gc_enabled 169 || self.module_config.function_references_enabled 170 || reference_types.unwrap_or(false); 171 config.extended_const_enabled = extended_const.unwrap_or(false); 172 if multi_memory.unwrap_or(false) { 173 config.max_memories = limits::MEMORIES_PER_MODULE as usize; 174 } else { 175 config.max_memories = 1; 176 } 177 178 match &mut self.wasmtime.memory_config { 179 MemoryConfig::Normal(config) => { 180 if let Some(n) = &mut config.memory_reservation { 181 *n = (*n).max(limits::MEMORY_SIZE as u64); 182 } 183 } 184 MemoryConfig::CustomUnaligned => {} 185 } 186 187 // FIXME: it might be more ideal to avoid the need for this entirely 188 // and to just let the test fail. If a test fails due to a pooling 189 // allocator resource limit being met we could ideally detect that and 190 // let the fuzz test case pass. That would avoid the need to hardcode 191 // so much here and in theory wouldn't reduce the usefulness of fuzzers 192 // all that much. At this time though we can't easily test this configuration. 193 if let InstanceAllocationStrategy::Pooling(pooling) = &mut self.wasmtime.strategy { 194 // Clamp protection keys between 1 & 2 to reduce the number of 195 // slots and then multiply the total memories by the number of keys 196 // we have since a single store has access to only one key. 197 pooling.max_memory_protection_keys = pooling.max_memory_protection_keys.max(1).min(2); 198 pooling.total_memories = pooling 199 .total_memories 200 .max(limits::MEMORIES * (pooling.max_memory_protection_keys as u32)); 201 202 // For other limits make sure they meet the minimum threshold 203 // required for our wast tests. 204 pooling.total_component_instances = pooling 205 .total_component_instances 206 .max(limits::COMPONENT_INSTANCES); 207 pooling.total_tables = pooling.total_tables.max(limits::TABLES); 208 pooling.max_tables_per_module = 209 pooling.max_tables_per_module.max(limits::TABLES_PER_MODULE); 210 pooling.max_memories_per_module = pooling 211 .max_memories_per_module 212 .max(limits::MEMORIES_PER_MODULE); 213 pooling.max_memories_per_component = pooling 214 .max_memories_per_component 215 .max(limits::MEMORIES_PER_MODULE); 216 pooling.total_core_instances = pooling.total_core_instances.max(limits::CORE_INSTANCES); 217 pooling.max_memory_size = pooling.max_memory_size.max(limits::MEMORY_SIZE); 218 pooling.table_elements = pooling.table_elements.max(limits::TABLE_ELEMENTS); 219 pooling.core_instance_size = pooling.core_instance_size.max(limits::CORE_INSTANCE_SIZE); 220 pooling.component_instance_size = pooling 221 .component_instance_size 222 .max(limits::CORE_INSTANCE_SIZE); 223 } 224 225 // Return the test configuration that this fuzz configuration represents 226 // which is used afterwards to test if the `test` here is expected to 227 // fail or not. 228 WastConfig { 229 collector: match self.wasmtime.collector { 230 Collector::Null => wasmtime_test_util::wast::Collector::Null, 231 Collector::DeferredReferenceCounting => { 232 wasmtime_test_util::wast::Collector::DeferredReferenceCounting 233 } 234 }, 235 pooling: matches!( 236 self.wasmtime.strategy, 237 InstanceAllocationStrategy::Pooling(_) 238 ), 239 compiler: match self.wasmtime.compiler_strategy { 240 CompilerStrategy::CraneliftNative => { 241 wasmtime_test_util::wast::Compiler::CraneliftNative 242 } 243 CompilerStrategy::CraneliftPulley => { 244 wasmtime_test_util::wast::Compiler::CraneliftPulley 245 } 246 CompilerStrategy::Winch => wasmtime_test_util::wast::Compiler::Winch, 247 }, 248 } 249 } 250 251 /// Converts this to a `wasmtime::Config` object 252 pub fn to_wasmtime(&self) -> wasmtime::Config { 253 crate::init_fuzzing(); 254 255 let mut cfg = wasmtime_cli_flags::CommonOptions::default(); 256 cfg.codegen.native_unwind_info = 257 Some(cfg!(target_os = "windows") || self.wasmtime.native_unwind_info); 258 cfg.codegen.parallel_compilation = Some(false); 259 cfg.debug.address_map = Some(self.wasmtime.generate_address_map); 260 cfg.opts.opt_level = Some(self.wasmtime.opt_level.to_wasmtime()); 261 cfg.opts.regalloc_algorithm = Some(self.wasmtime.regalloc_algorithm.to_wasmtime()); 262 cfg.opts.signals_based_traps = Some(self.wasmtime.signals_based_traps); 263 cfg.opts.memory_guaranteed_dense_image_size = Some(std::cmp::min( 264 // Clamp this at 16MiB so we don't get huge in-memory 265 // images during fuzzing. 266 16 << 20, 267 self.wasmtime.memory_guaranteed_dense_image_size, 268 )); 269 cfg.wasm.async_stack_zeroing = Some(self.wasmtime.async_stack_zeroing); 270 cfg.wasm.bulk_memory = Some(true); 271 cfg.wasm.component_model_async = Some(self.module_config.component_model_async); 272 cfg.wasm.custom_page_sizes = Some(self.module_config.config.custom_page_sizes_enabled); 273 cfg.wasm.epoch_interruption = Some(self.wasmtime.epoch_interruption); 274 cfg.wasm.extended_const = Some(self.module_config.config.extended_const_enabled); 275 cfg.wasm.fuel = self.wasmtime.consume_fuel.then(|| u64::MAX); 276 cfg.wasm.function_references = Some(self.module_config.function_references_enabled); 277 cfg.wasm.gc = Some(self.module_config.config.gc_enabled); 278 cfg.wasm.memory64 = Some(self.module_config.config.memory64_enabled); 279 cfg.wasm.multi_memory = Some(self.module_config.config.max_memories > 1); 280 cfg.wasm.multi_value = Some(self.module_config.config.multi_value_enabled); 281 cfg.wasm.nan_canonicalization = Some(self.wasmtime.canonicalize_nans); 282 cfg.wasm.reference_types = Some(self.module_config.config.reference_types_enabled); 283 cfg.wasm.simd = Some(self.module_config.config.simd_enabled); 284 cfg.wasm.tail_call = Some(self.module_config.config.tail_call_enabled); 285 cfg.wasm.threads = Some(self.module_config.config.threads_enabled); 286 cfg.wasm.wide_arithmetic = Some(self.module_config.config.wide_arithmetic_enabled); 287 if !self.module_config.config.simd_enabled { 288 cfg.wasm.relaxed_simd = Some(false); 289 } 290 cfg.codegen.collector = Some(self.wasmtime.collector.to_wasmtime()); 291 292 let compiler_strategy = &self.wasmtime.compiler_strategy; 293 let cranelift_strategy = match compiler_strategy { 294 CompilerStrategy::CraneliftNative | CompilerStrategy::CraneliftPulley => true, 295 CompilerStrategy::Winch => false, 296 }; 297 self.wasmtime.compiler_strategy.configure(&mut cfg); 298 299 self.wasmtime.codegen.configure(&mut cfg); 300 301 // Determine whether we will actually enable PCC -- this is 302 // disabled if the module requires memory64, which is not yet 303 // compatible (due to the need for dynamic checks). 304 let pcc = cfg!(feature = "fuzz-pcc") 305 && self.wasmtime.pcc 306 && !self.module_config.config.memory64_enabled; 307 308 // Only set cranelift specific flags when the Cranelift strategy is 309 // chosen. 310 if cranelift_strategy { 311 // If the wasm-smith-generated module use nan canonicalization then we 312 // don't need to enable it, but if it doesn't enable it already then we 313 // enable this codegen option. 314 cfg.wasm.nan_canonicalization = Some(!self.module_config.config.canonicalize_nans); 315 316 // Enabling the verifier will at-least-double compilation time, which 317 // with a 20-30x slowdown in fuzzing can cause issues related to 318 // timeouts. If generated modules can have more than a small handful of 319 // functions then disable the verifier when fuzzing to try to lessen the 320 // impact of timeouts. 321 if self.module_config.config.max_funcs > 10 { 322 cfg.codegen.cranelift_debug_verifier = Some(false); 323 } 324 325 if self.wasmtime.force_jump_veneers { 326 cfg.codegen.cranelift.push(( 327 "wasmtime_linkopt_force_jump_veneer".to_string(), 328 Some("true".to_string()), 329 )); 330 } 331 332 if let Some(pad) = self.wasmtime.padding_between_functions { 333 cfg.codegen.cranelift.push(( 334 "wasmtime_linkopt_padding_between_functions".to_string(), 335 Some(pad.to_string()), 336 )); 337 } 338 339 cfg.codegen.pcc = Some(pcc); 340 341 // Eager init is currently only supported on Cranelift, not Winch. 342 cfg.opts.table_lazy_init = Some(self.wasmtime.table_lazy_init); 343 } 344 345 self.wasmtime.strategy.configure(&mut cfg); 346 347 // Vary the memory configuration, but only if threads are not enabled. 348 // When the threads proposal is enabled we might generate shared memory, 349 // which is less amenable to different memory configurations: 350 // - shared memories are required to be "static" so fuzzing the various 351 // memory configurations will mostly result in uninteresting errors. 352 // The interesting part about shared memories is the runtime so we 353 // don't fuzz non-default settings. 354 // - shared memories are required to be aligned which means that the 355 // `CustomUnaligned` variant isn't actually safe to use with a shared 356 // memory. 357 let host_memory = if !self.module_config.config.threads_enabled { 358 // If PCC is enabled, force other options to be compatible: PCC is currently only 359 // supported when bounds checks are elided. 360 let memory_config = if pcc { 361 MemoryConfig::Normal(NormalMemoryConfig { 362 memory_reservation: Some(4 << 30), // 4 GiB 363 memory_guard_size: Some(2 << 30), // 2 GiB 364 memory_reservation_for_growth: Some(0), 365 guard_before_linear_memory: false, 366 memory_init_cow: true, 367 // Doesn't matter, only using virtual memory. 368 cranelift_enable_heap_access_spectre_mitigations: None, 369 }) 370 } else { 371 self.wasmtime.memory_config.clone() 372 }; 373 374 match &memory_config { 375 MemoryConfig::Normal(memory_config) => { 376 memory_config.configure(&mut cfg); 377 None 378 } 379 MemoryConfig::CustomUnaligned => { 380 cfg.opts.memory_reservation = Some(0); 381 cfg.opts.memory_guard_size = Some(0); 382 cfg.opts.memory_reservation_for_growth = Some(0); 383 cfg.opts.guard_before_linear_memory = Some(false); 384 cfg.opts.memory_init_cow = Some(false); 385 log::debug!("a custom unaligned host memory will be in use"); 386 Some(Arc::new(UnalignedMemoryCreator)) 387 } 388 } 389 } else { 390 None 391 }; 392 393 // If malloc-based memory is going to be used, which requires these four 394 // options set to specific values (and Pulley auto-sets two of them) 395 // then be sure to cap `memory_reservation_for_growth` at a smaller 396 // value than the default. For malloc-based memory reservation beyond 397 // the end of memory isn't captured by `StoreLimiter` so we need to be 398 // sure it's small enough to not blow OOM limits while fuzzing. 399 if ((cfg.opts.signals_based_traps == Some(true) && cfg.opts.memory_guard_size == Some(0)) 400 || self.wasmtime.compiler_strategy == CompilerStrategy::CraneliftPulley) 401 && cfg.opts.memory_reservation == Some(0) 402 && cfg.opts.memory_init_cow == Some(false) 403 { 404 let growth = &mut cfg.opts.memory_reservation_for_growth; 405 let max = 1 << 20; 406 *growth = match *growth { 407 Some(n) => Some(n.min(max)), 408 None => Some(max), 409 }; 410 } 411 412 log::debug!("creating wasmtime config with CLI options:\n{cfg}"); 413 let mut cfg = cfg.config(None).expect("failed to create wasmtime::Config"); 414 415 if let Some(host_memory) = host_memory { 416 cfg.with_host_memory(host_memory); 417 } 418 419 if self.wasmtime.async_config != AsyncConfig::Disabled { 420 log::debug!("async config in use {:?}", self.wasmtime.async_config); 421 self.wasmtime.async_config.configure(&mut cfg); 422 } 423 424 return cfg; 425 } 426 427 /// Convenience function for generating a `Store<T>` using this 428 /// configuration. 429 pub fn to_store(&self) -> Store<StoreLimits> { 430 let engine = Engine::new(&self.to_wasmtime()).unwrap(); 431 let mut store = Store::new(&engine, StoreLimits::new()); 432 self.configure_store(&mut store); 433 store 434 } 435 436 /// Configures a store based on this configuration. 437 pub fn configure_store(&self, store: &mut Store<StoreLimits>) { 438 store.limiter(|s| s as &mut dyn wasmtime::ResourceLimiter); 439 440 // Configure the store to never abort by default, that is it'll have 441 // max fuel or otherwise trap on an epoch change but the epoch won't 442 // ever change. 443 // 444 // Afterwards though see what `AsyncConfig` is being used an further 445 // refine the store's configuration based on that. 446 if self.wasmtime.consume_fuel { 447 store.set_fuel(u64::MAX).unwrap(); 448 } 449 if self.wasmtime.epoch_interruption { 450 store.epoch_deadline_trap(); 451 store.set_epoch_deadline(1); 452 } 453 match self.wasmtime.async_config { 454 AsyncConfig::Disabled => {} 455 AsyncConfig::YieldWithFuel(amt) => { 456 assert!(self.wasmtime.consume_fuel); 457 store.fuel_async_yield_interval(Some(amt)).unwrap(); 458 } 459 AsyncConfig::YieldWithEpochs { ticks, .. } => { 460 assert!(self.wasmtime.epoch_interruption); 461 store.set_epoch_deadline(ticks); 462 store.epoch_deadline_async_yield_and_update(ticks); 463 } 464 } 465 } 466 467 /// Generates an arbitrary method of timing out an instance, ensuring that 468 /// this configuration supports the returned timeout. 469 pub fn generate_timeout(&mut self, u: &mut Unstructured<'_>) -> arbitrary::Result<Timeout> { 470 let time_duration = Duration::from_millis(100); 471 let timeout = u 472 .choose(&[Timeout::Fuel(100_000), Timeout::Epoch(time_duration)])? 473 .clone(); 474 match &timeout { 475 Timeout::Fuel(..) => { 476 self.wasmtime.consume_fuel = true; 477 } 478 Timeout::Epoch(..) => { 479 self.wasmtime.epoch_interruption = true; 480 } 481 Timeout::None => unreachable!("Not an option given to choose()"), 482 } 483 Ok(timeout) 484 } 485 486 /// Compiles the `wasm` within the `engine` provided. 487 /// 488 /// This notably will use `Module::{serialize,deserialize_file}` to 489 /// round-trip if configured in the fuzzer. 490 pub fn compile(&self, engine: &Engine, wasm: &[u8]) -> Result<Module> { 491 // Propagate this error in case the caller wants to handle 492 // valid-vs-invalid wasm. 493 let module = Module::new(engine, wasm)?; 494 if !self.wasmtime.use_precompiled_cwasm { 495 return Ok(module); 496 } 497 498 // Don't propagate these errors to prevent them from accidentally being 499 // interpreted as invalid wasm, these should never fail on a 500 // well-behaved host system. 501 let dir = tempfile::TempDir::new().unwrap(); 502 let file = dir.path().join("module.wasm"); 503 std::fs::write(&file, module.serialize().unwrap()).unwrap(); 504 unsafe { Ok(Module::deserialize_file(engine, &file).unwrap()) } 505 } 506 507 /// Updates this configuration to forcibly enable async support. Only useful 508 /// in fuzzers which do async calls. 509 pub fn enable_async(&mut self, u: &mut Unstructured<'_>) -> arbitrary::Result<()> { 510 if self.wasmtime.consume_fuel || u.arbitrary()? { 511 self.wasmtime.async_config = 512 AsyncConfig::YieldWithFuel(u.int_in_range(1000..=100_000)?); 513 self.wasmtime.consume_fuel = true; 514 } else { 515 self.wasmtime.async_config = AsyncConfig::YieldWithEpochs { 516 dur: Duration::from_millis(u.int_in_range(1..=10)?), 517 ticks: u.int_in_range(1..=10)?, 518 }; 519 self.wasmtime.epoch_interruption = true; 520 } 521 Ok(()) 522 } 523 } 524 525 impl<'a> Arbitrary<'a> for Config { 526 fn arbitrary(u: &mut Unstructured<'a>) -> arbitrary::Result<Self> { 527 let mut config = Self { 528 wasmtime: u.arbitrary()?, 529 module_config: u.arbitrary()?, 530 }; 531 532 config 533 .wasmtime 534 .update_module_config(&mut config.module_config, u)?; 535 536 Ok(config) 537 } 538 } 539 540 /// Configuration related to `wasmtime::Config` and the various settings which 541 /// can be tweaked from within. 542 #[derive(Arbitrary, Clone, Debug, Eq, Hash, PartialEq)] 543 pub struct WasmtimeConfig { 544 opt_level: OptLevel, 545 regalloc_algorithm: RegallocAlgorithm, 546 debug_info: bool, 547 canonicalize_nans: bool, 548 interruptable: bool, 549 pub(crate) consume_fuel: bool, 550 pub(crate) epoch_interruption: bool, 551 /// The Wasmtime memory configuration to use. 552 pub memory_config: MemoryConfig, 553 force_jump_veneers: bool, 554 memory_init_cow: bool, 555 memory_guaranteed_dense_image_size: u64, 556 use_precompiled_cwasm: bool, 557 async_stack_zeroing: bool, 558 /// Configuration for the instance allocation strategy to use. 559 pub strategy: InstanceAllocationStrategy, 560 codegen: CodegenSettings, 561 padding_between_functions: Option<u16>, 562 generate_address_map: bool, 563 native_unwind_info: bool, 564 /// Configuration for the compiler to use. 565 pub compiler_strategy: CompilerStrategy, 566 collector: Collector, 567 table_lazy_init: bool, 568 569 /// Whether or not fuzzing should enable PCC. 570 pcc: bool, 571 572 /// Configuration for whether wasm is invoked in an async fashion and how 573 /// it's cooperatively time-sliced. 574 pub async_config: AsyncConfig, 575 576 /// Whether or not host signal handlers are enabled for this configuration, 577 /// aka whether signal handlers are supported. 578 signals_based_traps: bool, 579 } 580 581 impl WasmtimeConfig { 582 /// Force `self` to be a configuration compatible with `other`. This is 583 /// useful for differential execution to avoid unhelpful fuzz crashes when 584 /// one engine has a feature enabled and the other does not. 585 pub fn make_compatible_with(&mut self, other: &Self) { 586 // Use the same allocation strategy between the two configs. 587 // 588 // Ideally this wouldn't be necessary, but, during differential 589 // evaluation, if the `lhs` is using ondemand and the `rhs` is using the 590 // pooling allocator (or vice versa), then the module may have been 591 // generated in such a way that is incompatible with the other 592 // allocation strategy. 593 // 594 // We can remove this in the future when it's possible to access the 595 // fields of `wasm_smith::Module` to constrain the pooling allocator 596 // based on what was actually generated. 597 self.strategy = other.strategy.clone(); 598 if let InstanceAllocationStrategy::Pooling { .. } = &other.strategy { 599 // Also use the same memory configuration when using the pooling 600 // allocator. 601 self.memory_config = other.memory_config.clone(); 602 } 603 604 self.make_internally_consistent(); 605 } 606 607 /// Updates `config` to be compatible with `self` and the other way around 608 /// too. 609 pub fn update_module_config( 610 &mut self, 611 config: &mut ModuleConfig, 612 u: &mut Unstructured<'_>, 613 ) -> arbitrary::Result<()> { 614 match self.compiler_strategy { 615 CompilerStrategy::CraneliftNative => {} 616 617 CompilerStrategy::Winch => { 618 // Winch is not complete on non-x64 targets, so just abandon this test 619 // case. We don't want to force Cranelift because we change what module 620 // config features are enabled based on the compiler strategy, and we 621 // don't want to make the same fuzz input DNA generate different test 622 // cases on different targets. 623 if cfg!(not(target_arch = "x86_64")) { 624 log::warn!( 625 "want to compile with Winch but host architecture does not support it" 626 ); 627 return Err(arbitrary::Error::IncorrectFormat); 628 } 629 630 // Winch doesn't support the same set of wasm proposal as Cranelift 631 // at this time, so if winch is selected be sure to disable wasm 632 // proposals in `Config` to ensure that Winch can compile the 633 // module that wasm-smith generates. 634 config.config.relaxed_simd_enabled = false; 635 config.config.gc_enabled = false; 636 config.config.tail_call_enabled = false; 637 config.config.reference_types_enabled = false; 638 config.function_references_enabled = false; 639 640 // Winch's SIMD implementations require AVX and AVX2. 641 if self 642 .codegen_flag("has_avx") 643 .is_some_and(|value| value == "false") 644 || self 645 .codegen_flag("has_avx2") 646 .is_some_and(|value| value == "false") 647 { 648 config.config.simd_enabled = false; 649 } 650 651 // Tuning the following engine options is currently not supported 652 // by Winch. 653 self.signals_based_traps = true; 654 self.table_lazy_init = true; 655 self.debug_info = false; 656 } 657 658 CompilerStrategy::CraneliftPulley => { 659 config.config.threads_enabled = false; 660 } 661 } 662 663 // Forcibly don't use the `CustomUnaligned` memory configuration when 664 // wasm threads are enabled or when the pooling allocator is used. For 665 // the pooling allocator it doesn't use custom memory creators anyway 666 // and for wasm threads that will require some refactoring of the 667 // `LinearMemory` trait to bubble up the request that the linear memory 668 // not move. Otherwise that just generates a panic right now. 669 if config.config.threads_enabled 670 || matches!(self.strategy, InstanceAllocationStrategy::Pooling(_)) 671 { 672 self.avoid_custom_unaligned_memory(u)?; 673 } 674 675 // If using the pooling allocator, constrain the memory and module configurations 676 // to the module limits. 677 if let InstanceAllocationStrategy::Pooling(pooling) = &mut self.strategy { 678 // If the pooling allocator is used, do not allow shared memory to 679 // be created. FIXME: see 680 // https://github.com/bytecodealliance/wasmtime/issues/4244. 681 config.config.threads_enabled = false; 682 683 // Ensure the pooling allocator can support the maximal size of 684 // memory, picking the smaller of the two to win. 685 let min_bytes = config 686 .config 687 .max_memory32_bytes 688 // memory64_bytes is a u128, but since we are taking the min 689 // we can truncate it down to a u64. 690 .min( 691 config 692 .config 693 .max_memory64_bytes 694 .try_into() 695 .unwrap_or(u64::MAX), 696 ); 697 let mut min = min_bytes.min(pooling.max_memory_size as u64); 698 if let MemoryConfig::Normal(cfg) = &self.memory_config { 699 min = min.min(cfg.memory_reservation.unwrap_or(0)); 700 } 701 pooling.max_memory_size = min as usize; 702 config.config.max_memory32_bytes = min; 703 config.config.max_memory64_bytes = min as u128; 704 705 // If traps are disallowed then memories must have at least one page 706 // of memory so if we still are only allowing 0 pages of memory then 707 // increase that to one here. 708 if config.config.disallow_traps { 709 if pooling.max_memory_size < (1 << 16) { 710 pooling.max_memory_size = 1 << 16; 711 config.config.max_memory32_bytes = 1 << 16; 712 config.config.max_memory64_bytes = 1 << 16; 713 if let MemoryConfig::Normal(cfg) = &mut self.memory_config { 714 match &mut cfg.memory_reservation { 715 Some(size) => *size = (*size).max(pooling.max_memory_size as u64), 716 size @ None => *size = Some(pooling.max_memory_size as u64), 717 } 718 } 719 } 720 // .. additionally update tables 721 if pooling.table_elements == 0 { 722 pooling.table_elements = 1; 723 } 724 } 725 726 // Don't allow too many linear memories per instance since massive 727 // virtual mappings can fail to get allocated. 728 config.config.min_memories = config.config.min_memories.min(10); 729 config.config.max_memories = config.config.max_memories.min(10); 730 731 // Force this pooling allocator to always be able to accommodate the 732 // module that may be generated. 733 pooling.total_memories = config.config.max_memories as u32; 734 pooling.total_tables = config.config.max_tables as u32; 735 } 736 737 if !self.signals_based_traps { 738 // At this time shared memories require a "static" memory 739 // configuration but when signals-based traps are disabled all 740 // memories are forced to the "dynamic" configuration. This is 741 // fixable with some more work on the bounds-checks side of things 742 // to do a full bounds check even on static memories, but that's 743 // left for a future PR. 744 config.config.threads_enabled = false; 745 746 // Spectre-based heap mitigations require signal handlers so this 747 // must always be disabled if signals-based traps are disabled. 748 if let MemoryConfig::Normal(cfg) = &mut self.memory_config { 749 cfg.cranelift_enable_heap_access_spectre_mitigations = None; 750 } 751 } 752 753 self.make_internally_consistent(); 754 755 Ok(()) 756 } 757 758 /// Returns the codegen flag value, if any, for `name`. 759 pub(crate) fn codegen_flag(&self, name: &str) -> Option<&str> { 760 self.codegen.flags().iter().find_map(|(n, value)| { 761 if n == name { 762 Some(value.as_str()) 763 } else { 764 None 765 } 766 }) 767 } 768 769 /// Helper to switch `MemoryConfig::CustomUnaligned` to 770 /// `MemoryConfig::Normal` 771 fn avoid_custom_unaligned_memory(&mut self, u: &mut Unstructured<'_>) -> arbitrary::Result<()> { 772 if let MemoryConfig::CustomUnaligned = self.memory_config { 773 self.memory_config = MemoryConfig::Normal(u.arbitrary()?); 774 } 775 Ok(()) 776 } 777 778 /// Helper method to handle some dependencies between various configuration 779 /// options. This is intended to be called whenever a `Config` is created or 780 /// modified to ensure that the final result is an instantiable `Config`. 781 /// 782 /// Note that in general this probably shouldn't exist and anything here can 783 /// be considered a "TODO" to go implement more stuff in Wasmtime to accept 784 /// these sorts of configurations. For now though it's intended to reflect 785 /// the current state of the engine's development. 786 fn make_internally_consistent(&mut self) { 787 if !self.signals_based_traps { 788 if let MemoryConfig::Normal(cfg) = &mut self.memory_config { 789 // Spectre-based heap mitigations require signal handlers so 790 // this must always be disabled if signals-based traps are 791 // disabled. 792 cfg.cranelift_enable_heap_access_spectre_mitigations = None; 793 794 // With configuration settings that match the use of malloc for 795 // linear memories cap the `memory_reservation_for_growth` value 796 // to something reasonable to avoid OOM in fuzzing. 797 if !cfg.memory_init_cow 798 && cfg.memory_guard_size == Some(0) 799 && cfg.memory_reservation == Some(0) 800 { 801 let min = 10 << 20; // 10 MiB 802 if let Some(val) = &mut cfg.memory_reservation_for_growth { 803 *val = (*val).min(min); 804 } else { 805 cfg.memory_reservation_for_growth = Some(min); 806 } 807 } 808 } 809 } 810 } 811 } 812 813 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 814 enum OptLevel { 815 None, 816 Speed, 817 SpeedAndSize, 818 } 819 820 impl OptLevel { 821 fn to_wasmtime(&self) -> wasmtime::OptLevel { 822 match self { 823 OptLevel::None => wasmtime::OptLevel::None, 824 OptLevel::Speed => wasmtime::OptLevel::Speed, 825 OptLevel::SpeedAndSize => wasmtime::OptLevel::SpeedAndSize, 826 } 827 } 828 } 829 830 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 831 enum RegallocAlgorithm { 832 Backtracking, 833 SinglePass, 834 } 835 836 impl RegallocAlgorithm { 837 fn to_wasmtime(&self) -> wasmtime::RegallocAlgorithm { 838 match self { 839 RegallocAlgorithm::Backtracking => wasmtime::RegallocAlgorithm::Backtracking, 840 RegallocAlgorithm::SinglePass => wasmtime::RegallocAlgorithm::SinglePass, 841 } 842 } 843 } 844 845 #[derive(Clone, Debug, PartialEq, Eq, Hash)] 846 /// Compiler to use. 847 pub enum CompilerStrategy { 848 /// Cranelift compiler for the native architecture. 849 CraneliftNative, 850 /// Winch compiler. 851 Winch, 852 /// Cranelift compiler for the native architecture. 853 CraneliftPulley, 854 } 855 856 impl CompilerStrategy { 857 /// Configures `config` to use this compilation strategy 858 pub fn configure(&self, config: &mut wasmtime_cli_flags::CommonOptions) { 859 match self { 860 CompilerStrategy::CraneliftNative => { 861 config.codegen.compiler = Some(wasmtime::Strategy::Cranelift); 862 } 863 CompilerStrategy::Winch => { 864 config.codegen.compiler = Some(wasmtime::Strategy::Winch); 865 } 866 CompilerStrategy::CraneliftPulley => { 867 config.codegen.compiler = Some(wasmtime::Strategy::Cranelift); 868 config.target = Some("pulley64".to_string()); 869 } 870 } 871 } 872 } 873 874 impl Arbitrary<'_> for CompilerStrategy { 875 fn arbitrary(u: &mut Unstructured<'_>) -> arbitrary::Result<Self> { 876 // Favor fuzzing native cranelift, but if allowed also enable 877 // winch/pulley. 878 match u.int_in_range(0..=19)? { 879 1 => Ok(Self::CraneliftPulley), 880 2 => Ok(Self::Winch), 881 _ => Ok(Self::CraneliftNative), 882 } 883 } 884 } 885 886 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 887 pub enum Collector { 888 DeferredReferenceCounting, 889 Null, 890 } 891 892 impl Collector { 893 fn to_wasmtime(&self) -> wasmtime::Collector { 894 match self { 895 Collector::DeferredReferenceCounting => wasmtime::Collector::DeferredReferenceCounting, 896 Collector::Null => wasmtime::Collector::Null, 897 } 898 } 899 } 900