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 component_model_async_builtins, 143 component_model_async_stackful, 144 simd, 145 146 hogs_memory: _, 147 nan_canonicalization: _, 148 gc_types: _, 149 } = test.config; 150 151 // Enable/disable some proposals that aren't configurable in wasm-smith 152 // but are configurable in Wasmtime. 153 self.module_config.function_references_enabled = 154 function_references.or(gc).unwrap_or(false); 155 self.module_config.component_model_async = component_model_async.unwrap_or(false); 156 self.module_config.component_model_async_builtins = 157 component_model_async_builtins.unwrap_or(false); 158 self.module_config.component_model_async_stackful = 159 component_model_async_stackful.unwrap_or(false); 160 161 // Enable/disable proposals that wasm-smith has knobs for which will be 162 // read when creating `wasmtime::Config`. 163 let config = &mut self.module_config.config; 164 config.bulk_memory_enabled = true; 165 config.multi_value_enabled = true; 166 config.wide_arithmetic_enabled = wide_arithmetic.unwrap_or(false); 167 config.memory64_enabled = memory64.unwrap_or(false); 168 config.relaxed_simd_enabled = relaxed_simd.unwrap_or(false); 169 config.simd_enabled = config.relaxed_simd_enabled || simd.unwrap_or(false); 170 config.tail_call_enabled = tail_call.unwrap_or(false); 171 config.custom_page_sizes_enabled = custom_page_sizes.unwrap_or(false); 172 config.threads_enabled = threads.unwrap_or(false); 173 config.gc_enabled = gc.unwrap_or(false); 174 config.reference_types_enabled = config.gc_enabled 175 || self.module_config.function_references_enabled 176 || reference_types.unwrap_or(false); 177 config.extended_const_enabled = extended_const.unwrap_or(false); 178 if multi_memory.unwrap_or(false) { 179 config.max_memories = limits::MEMORIES_PER_MODULE as usize; 180 } else { 181 config.max_memories = 1; 182 } 183 184 match &mut self.wasmtime.memory_config { 185 MemoryConfig::Normal(config) => { 186 if let Some(n) = &mut config.memory_reservation { 187 *n = (*n).max(limits::MEMORY_SIZE as u64); 188 } 189 } 190 MemoryConfig::CustomUnaligned => {} 191 } 192 193 // FIXME: it might be more ideal to avoid the need for this entirely 194 // and to just let the test fail. If a test fails due to a pooling 195 // allocator resource limit being met we could ideally detect that and 196 // let the fuzz test case pass. That would avoid the need to hardcode 197 // so much here and in theory wouldn't reduce the usefulness of fuzzers 198 // all that much. At this time though we can't easily test this configuration. 199 if let InstanceAllocationStrategy::Pooling(pooling) = &mut self.wasmtime.strategy { 200 // Clamp protection keys between 1 & 2 to reduce the number of 201 // slots and then multiply the total memories by the number of keys 202 // we have since a single store has access to only one key. 203 pooling.max_memory_protection_keys = pooling.max_memory_protection_keys.max(1).min(2); 204 pooling.total_memories = pooling 205 .total_memories 206 .max(limits::MEMORIES * (pooling.max_memory_protection_keys as u32)); 207 208 // For other limits make sure they meet the minimum threshold 209 // required for our wast tests. 210 pooling.total_component_instances = pooling 211 .total_component_instances 212 .max(limits::COMPONENT_INSTANCES); 213 pooling.total_tables = pooling.total_tables.max(limits::TABLES); 214 pooling.max_tables_per_module = 215 pooling.max_tables_per_module.max(limits::TABLES_PER_MODULE); 216 pooling.max_memories_per_module = pooling 217 .max_memories_per_module 218 .max(limits::MEMORIES_PER_MODULE); 219 pooling.max_memories_per_component = pooling 220 .max_memories_per_component 221 .max(limits::MEMORIES_PER_MODULE); 222 pooling.total_core_instances = pooling.total_core_instances.max(limits::CORE_INSTANCES); 223 pooling.max_memory_size = pooling.max_memory_size.max(limits::MEMORY_SIZE); 224 pooling.table_elements = pooling.table_elements.max(limits::TABLE_ELEMENTS); 225 pooling.core_instance_size = pooling.core_instance_size.max(limits::CORE_INSTANCE_SIZE); 226 pooling.component_instance_size = pooling 227 .component_instance_size 228 .max(limits::CORE_INSTANCE_SIZE); 229 } 230 231 // Return the test configuration that this fuzz configuration represents 232 // which is used afterwards to test if the `test` here is expected to 233 // fail or not. 234 WastConfig { 235 collector: match self.wasmtime.collector { 236 Collector::Null => wasmtime_test_util::wast::Collector::Null, 237 Collector::DeferredReferenceCounting => { 238 wasmtime_test_util::wast::Collector::DeferredReferenceCounting 239 } 240 }, 241 pooling: matches!( 242 self.wasmtime.strategy, 243 InstanceAllocationStrategy::Pooling(_) 244 ), 245 compiler: match self.wasmtime.compiler_strategy { 246 CompilerStrategy::CraneliftNative => { 247 wasmtime_test_util::wast::Compiler::CraneliftNative 248 } 249 CompilerStrategy::CraneliftPulley => { 250 wasmtime_test_util::wast::Compiler::CraneliftPulley 251 } 252 CompilerStrategy::Winch => wasmtime_test_util::wast::Compiler::Winch, 253 }, 254 } 255 } 256 257 /// Converts this to a `wasmtime::Config` object 258 pub fn to_wasmtime(&self) -> wasmtime::Config { 259 crate::init_fuzzing(); 260 261 let mut cfg = wasmtime_cli_flags::CommonOptions::default(); 262 cfg.codegen.native_unwind_info = 263 Some(cfg!(target_os = "windows") || self.wasmtime.native_unwind_info); 264 cfg.codegen.parallel_compilation = Some(false); 265 cfg.debug.address_map = Some(self.wasmtime.generate_address_map); 266 cfg.opts.opt_level = Some(self.wasmtime.opt_level.to_wasmtime()); 267 cfg.opts.regalloc_algorithm = Some(self.wasmtime.regalloc_algorithm.to_wasmtime()); 268 cfg.opts.signals_based_traps = Some(self.wasmtime.signals_based_traps); 269 cfg.opts.memory_guaranteed_dense_image_size = Some(std::cmp::min( 270 // Clamp this at 16MiB so we don't get huge in-memory 271 // images during fuzzing. 272 16 << 20, 273 self.wasmtime.memory_guaranteed_dense_image_size, 274 )); 275 cfg.wasm.async_stack_zeroing = Some(self.wasmtime.async_stack_zeroing); 276 cfg.wasm.bulk_memory = Some(true); 277 cfg.wasm.component_model_async = Some(self.module_config.component_model_async); 278 cfg.wasm.component_model_async_builtins = 279 Some(self.module_config.component_model_async_builtins); 280 cfg.wasm.component_model_async_stackful = 281 Some(self.module_config.component_model_async_stackful); 282 cfg.wasm.custom_page_sizes = Some(self.module_config.config.custom_page_sizes_enabled); 283 cfg.wasm.epoch_interruption = Some(self.wasmtime.epoch_interruption); 284 cfg.wasm.extended_const = Some(self.module_config.config.extended_const_enabled); 285 cfg.wasm.fuel = self.wasmtime.consume_fuel.then(|| u64::MAX); 286 cfg.wasm.function_references = Some(self.module_config.function_references_enabled); 287 cfg.wasm.gc = Some(self.module_config.config.gc_enabled); 288 cfg.wasm.memory64 = Some(self.module_config.config.memory64_enabled); 289 cfg.wasm.multi_memory = Some(self.module_config.config.max_memories > 1); 290 cfg.wasm.multi_value = Some(self.module_config.config.multi_value_enabled); 291 cfg.wasm.nan_canonicalization = Some(self.wasmtime.canonicalize_nans); 292 cfg.wasm.reference_types = Some(self.module_config.config.reference_types_enabled); 293 cfg.wasm.simd = Some(self.module_config.config.simd_enabled); 294 cfg.wasm.tail_call = Some(self.module_config.config.tail_call_enabled); 295 cfg.wasm.threads = Some(self.module_config.config.threads_enabled); 296 cfg.wasm.wide_arithmetic = Some(self.module_config.config.wide_arithmetic_enabled); 297 if !self.module_config.config.simd_enabled { 298 cfg.wasm.relaxed_simd = Some(false); 299 } 300 cfg.codegen.collector = Some(self.wasmtime.collector.to_wasmtime()); 301 302 let compiler_strategy = &self.wasmtime.compiler_strategy; 303 let cranelift_strategy = match compiler_strategy { 304 CompilerStrategy::CraneliftNative | CompilerStrategy::CraneliftPulley => true, 305 CompilerStrategy::Winch => false, 306 }; 307 self.wasmtime.compiler_strategy.configure(&mut cfg); 308 309 self.wasmtime.codegen.configure(&mut cfg); 310 311 // Determine whether we will actually enable PCC -- this is 312 // disabled if the module requires memory64, which is not yet 313 // compatible (due to the need for dynamic checks). 314 let pcc = cfg!(feature = "fuzz-pcc") 315 && self.wasmtime.pcc 316 && !self.module_config.config.memory64_enabled; 317 318 // Only set cranelift specific flags when the Cranelift strategy is 319 // chosen. 320 if cranelift_strategy { 321 // If the wasm-smith-generated module use nan canonicalization then we 322 // don't need to enable it, but if it doesn't enable it already then we 323 // enable this codegen option. 324 cfg.wasm.nan_canonicalization = Some(!self.module_config.config.canonicalize_nans); 325 326 // Enabling the verifier will at-least-double compilation time, which 327 // with a 20-30x slowdown in fuzzing can cause issues related to 328 // timeouts. If generated modules can have more than a small handful of 329 // functions then disable the verifier when fuzzing to try to lessen the 330 // impact of timeouts. 331 if self.module_config.config.max_funcs > 10 { 332 cfg.codegen.cranelift_debug_verifier = Some(false); 333 } 334 335 if self.wasmtime.force_jump_veneers { 336 cfg.codegen.cranelift.push(( 337 "wasmtime_linkopt_force_jump_veneer".to_string(), 338 Some("true".to_string()), 339 )); 340 } 341 342 if let Some(pad) = self.wasmtime.padding_between_functions { 343 cfg.codegen.cranelift.push(( 344 "wasmtime_linkopt_padding_between_functions".to_string(), 345 Some(pad.to_string()), 346 )); 347 } 348 349 cfg.codegen.pcc = Some(pcc); 350 351 // Eager init is currently only supported on Cranelift, not Winch. 352 cfg.opts.table_lazy_init = Some(self.wasmtime.table_lazy_init); 353 } 354 355 self.wasmtime.strategy.configure(&mut cfg); 356 357 // Vary the memory configuration, but only if threads are not enabled. 358 // When the threads proposal is enabled we might generate shared memory, 359 // which is less amenable to different memory configurations: 360 // - shared memories are required to be "static" so fuzzing the various 361 // memory configurations will mostly result in uninteresting errors. 362 // The interesting part about shared memories is the runtime so we 363 // don't fuzz non-default settings. 364 // - shared memories are required to be aligned which means that the 365 // `CustomUnaligned` variant isn't actually safe to use with a shared 366 // memory. 367 let host_memory = if !self.module_config.config.threads_enabled { 368 // If PCC is enabled, force other options to be compatible: PCC is currently only 369 // supported when bounds checks are elided. 370 let memory_config = if pcc { 371 MemoryConfig::Normal(NormalMemoryConfig { 372 memory_reservation: Some(4 << 30), // 4 GiB 373 memory_guard_size: Some(2 << 30), // 2 GiB 374 memory_reservation_for_growth: Some(0), 375 guard_before_linear_memory: false, 376 memory_init_cow: true, 377 // Doesn't matter, only using virtual memory. 378 cranelift_enable_heap_access_spectre_mitigations: None, 379 }) 380 } else { 381 self.wasmtime.memory_config.clone() 382 }; 383 384 match &memory_config { 385 MemoryConfig::Normal(memory_config) => { 386 memory_config.configure(&mut cfg); 387 None 388 } 389 MemoryConfig::CustomUnaligned => { 390 cfg.opts.memory_reservation = Some(0); 391 cfg.opts.memory_guard_size = Some(0); 392 cfg.opts.memory_reservation_for_growth = Some(0); 393 cfg.opts.guard_before_linear_memory = Some(false); 394 cfg.opts.memory_init_cow = Some(false); 395 log::debug!("a custom unaligned host memory will be in use"); 396 Some(Arc::new(UnalignedMemoryCreator)) 397 } 398 } 399 } else { 400 None 401 }; 402 403 // If malloc-based memory is going to be used, which requires these four 404 // options set to specific values (and Pulley auto-sets two of them) 405 // then be sure to cap `memory_reservation_for_growth` at a smaller 406 // value than the default. For malloc-based memory reservation beyond 407 // the end of memory isn't captured by `StoreLimiter` so we need to be 408 // sure it's small enough to not blow OOM limits while fuzzing. 409 if ((cfg.opts.signals_based_traps == Some(true) && cfg.opts.memory_guard_size == Some(0)) 410 || self.wasmtime.compiler_strategy == CompilerStrategy::CraneliftPulley) 411 && cfg.opts.memory_reservation == Some(0) 412 && cfg.opts.memory_init_cow == Some(false) 413 { 414 let growth = &mut cfg.opts.memory_reservation_for_growth; 415 let max = 1 << 20; 416 *growth = match *growth { 417 Some(n) => Some(n.min(max)), 418 None => Some(max), 419 }; 420 } 421 422 log::debug!("creating wasmtime config with CLI options:\n{cfg}"); 423 let mut cfg = cfg.config(None).expect("failed to create wasmtime::Config"); 424 425 if let Some(host_memory) = host_memory { 426 cfg.with_host_memory(host_memory); 427 } 428 429 if self.wasmtime.async_config != AsyncConfig::Disabled { 430 log::debug!("async config in use {:?}", self.wasmtime.async_config); 431 self.wasmtime.async_config.configure(&mut cfg); 432 } 433 434 return cfg; 435 } 436 437 /// Convenience function for generating a `Store<T>` using this 438 /// configuration. 439 pub fn to_store(&self) -> Store<StoreLimits> { 440 let engine = Engine::new(&self.to_wasmtime()).unwrap(); 441 let mut store = Store::new(&engine, StoreLimits::new()); 442 self.configure_store(&mut store); 443 store 444 } 445 446 /// Configures a store based on this configuration. 447 pub fn configure_store(&self, store: &mut Store<StoreLimits>) { 448 store.limiter(|s| s as &mut dyn wasmtime::ResourceLimiter); 449 450 // Configure the store to never abort by default, that is it'll have 451 // max fuel or otherwise trap on an epoch change but the epoch won't 452 // ever change. 453 // 454 // Afterwards though see what `AsyncConfig` is being used an further 455 // refine the store's configuration based on that. 456 if self.wasmtime.consume_fuel { 457 store.set_fuel(u64::MAX).unwrap(); 458 } 459 if self.wasmtime.epoch_interruption { 460 store.epoch_deadline_trap(); 461 store.set_epoch_deadline(1); 462 } 463 match self.wasmtime.async_config { 464 AsyncConfig::Disabled => {} 465 AsyncConfig::YieldWithFuel(amt) => { 466 assert!(self.wasmtime.consume_fuel); 467 store.fuel_async_yield_interval(Some(amt)).unwrap(); 468 } 469 AsyncConfig::YieldWithEpochs { ticks, .. } => { 470 assert!(self.wasmtime.epoch_interruption); 471 store.set_epoch_deadline(ticks); 472 store.epoch_deadline_async_yield_and_update(ticks); 473 } 474 } 475 } 476 477 /// Generates an arbitrary method of timing out an instance, ensuring that 478 /// this configuration supports the returned timeout. 479 pub fn generate_timeout(&mut self, u: &mut Unstructured<'_>) -> arbitrary::Result<Timeout> { 480 let time_duration = Duration::from_millis(100); 481 let timeout = u 482 .choose(&[Timeout::Fuel(100_000), Timeout::Epoch(time_duration)])? 483 .clone(); 484 match &timeout { 485 Timeout::Fuel(..) => { 486 self.wasmtime.consume_fuel = true; 487 } 488 Timeout::Epoch(..) => { 489 self.wasmtime.epoch_interruption = true; 490 } 491 Timeout::None => unreachable!("Not an option given to choose()"), 492 } 493 Ok(timeout) 494 } 495 496 /// Compiles the `wasm` within the `engine` provided. 497 /// 498 /// This notably will use `Module::{serialize,deserialize_file}` to 499 /// round-trip if configured in the fuzzer. 500 pub fn compile(&self, engine: &Engine, wasm: &[u8]) -> Result<Module> { 501 // Propagate this error in case the caller wants to handle 502 // valid-vs-invalid wasm. 503 let module = Module::new(engine, wasm)?; 504 if !self.wasmtime.use_precompiled_cwasm { 505 return Ok(module); 506 } 507 508 // Don't propagate these errors to prevent them from accidentally being 509 // interpreted as invalid wasm, these should never fail on a 510 // well-behaved host system. 511 let dir = tempfile::TempDir::new().unwrap(); 512 let file = dir.path().join("module.wasm"); 513 std::fs::write(&file, module.serialize().unwrap()).unwrap(); 514 unsafe { Ok(Module::deserialize_file(engine, &file).unwrap()) } 515 } 516 517 /// Updates this configuration to forcibly enable async support. Only useful 518 /// in fuzzers which do async calls. 519 pub fn enable_async(&mut self, u: &mut Unstructured<'_>) -> arbitrary::Result<()> { 520 if self.wasmtime.consume_fuel || u.arbitrary()? { 521 self.wasmtime.async_config = 522 AsyncConfig::YieldWithFuel(u.int_in_range(1000..=100_000)?); 523 self.wasmtime.consume_fuel = true; 524 } else { 525 self.wasmtime.async_config = AsyncConfig::YieldWithEpochs { 526 dur: Duration::from_millis(u.int_in_range(1..=10)?), 527 ticks: u.int_in_range(1..=10)?, 528 }; 529 self.wasmtime.epoch_interruption = true; 530 } 531 Ok(()) 532 } 533 } 534 535 impl<'a> Arbitrary<'a> for Config { 536 fn arbitrary(u: &mut Unstructured<'a>) -> arbitrary::Result<Self> { 537 let mut config = Self { 538 wasmtime: u.arbitrary()?, 539 module_config: u.arbitrary()?, 540 }; 541 542 config 543 .wasmtime 544 .update_module_config(&mut config.module_config, u)?; 545 546 Ok(config) 547 } 548 } 549 550 /// Configuration related to `wasmtime::Config` and the various settings which 551 /// can be tweaked from within. 552 #[derive(Arbitrary, Clone, Debug, Eq, Hash, PartialEq)] 553 pub struct WasmtimeConfig { 554 opt_level: OptLevel, 555 regalloc_algorithm: RegallocAlgorithm, 556 debug_info: bool, 557 canonicalize_nans: bool, 558 interruptable: bool, 559 pub(crate) consume_fuel: bool, 560 pub(crate) epoch_interruption: bool, 561 /// The Wasmtime memory configuration to use. 562 pub memory_config: MemoryConfig, 563 force_jump_veneers: bool, 564 memory_init_cow: bool, 565 memory_guaranteed_dense_image_size: u64, 566 use_precompiled_cwasm: bool, 567 async_stack_zeroing: bool, 568 /// Configuration for the instance allocation strategy to use. 569 pub strategy: InstanceAllocationStrategy, 570 codegen: CodegenSettings, 571 padding_between_functions: Option<u16>, 572 generate_address_map: bool, 573 native_unwind_info: bool, 574 /// Configuration for the compiler to use. 575 pub compiler_strategy: CompilerStrategy, 576 collector: Collector, 577 table_lazy_init: bool, 578 579 /// Whether or not fuzzing should enable PCC. 580 pcc: bool, 581 582 /// Configuration for whether wasm is invoked in an async fashion and how 583 /// it's cooperatively time-sliced. 584 pub async_config: AsyncConfig, 585 586 /// Whether or not host signal handlers are enabled for this configuration, 587 /// aka whether signal handlers are supported. 588 signals_based_traps: bool, 589 } 590 591 impl WasmtimeConfig { 592 /// Force `self` to be a configuration compatible with `other`. This is 593 /// useful for differential execution to avoid unhelpful fuzz crashes when 594 /// one engine has a feature enabled and the other does not. 595 pub fn make_compatible_with(&mut self, other: &Self) { 596 // Use the same allocation strategy between the two configs. 597 // 598 // Ideally this wouldn't be necessary, but, during differential 599 // evaluation, if the `lhs` is using ondemand and the `rhs` is using the 600 // pooling allocator (or vice versa), then the module may have been 601 // generated in such a way that is incompatible with the other 602 // allocation strategy. 603 // 604 // We can remove this in the future when it's possible to access the 605 // fields of `wasm_smith::Module` to constrain the pooling allocator 606 // based on what was actually generated. 607 self.strategy = other.strategy.clone(); 608 if let InstanceAllocationStrategy::Pooling { .. } = &other.strategy { 609 // Also use the same memory configuration when using the pooling 610 // allocator. 611 self.memory_config = other.memory_config.clone(); 612 } 613 614 self.make_internally_consistent(); 615 } 616 617 /// Updates `config` to be compatible with `self` and the other way around 618 /// too. 619 pub fn update_module_config( 620 &mut self, 621 config: &mut ModuleConfig, 622 u: &mut Unstructured<'_>, 623 ) -> arbitrary::Result<()> { 624 match self.compiler_strategy { 625 CompilerStrategy::CraneliftNative => {} 626 627 CompilerStrategy::Winch => { 628 // Winch is not complete on non-x64 targets, so just abandon this test 629 // case. We don't want to force Cranelift because we change what module 630 // config features are enabled based on the compiler strategy, and we 631 // don't want to make the same fuzz input DNA generate different test 632 // cases on different targets. 633 if cfg!(not(target_arch = "x86_64")) { 634 log::warn!( 635 "want to compile with Winch but host architecture does not support it" 636 ); 637 return Err(arbitrary::Error::IncorrectFormat); 638 } 639 640 // Winch doesn't support the same set of wasm proposal as Cranelift 641 // at this time, so if winch is selected be sure to disable wasm 642 // proposals in `Config` to ensure that Winch can compile the 643 // module that wasm-smith generates. 644 config.config.relaxed_simd_enabled = false; 645 config.config.gc_enabled = false; 646 config.config.tail_call_enabled = false; 647 config.config.reference_types_enabled = false; 648 config.function_references_enabled = false; 649 650 // Winch's SIMD implementations require AVX and AVX2. 651 if self 652 .codegen_flag("has_avx") 653 .is_some_and(|value| value == "false") 654 || self 655 .codegen_flag("has_avx2") 656 .is_some_and(|value| value == "false") 657 { 658 config.config.simd_enabled = false; 659 } 660 661 // Tuning the following engine options is currently not supported 662 // by Winch. 663 self.signals_based_traps = true; 664 self.table_lazy_init = true; 665 self.debug_info = false; 666 } 667 668 CompilerStrategy::CraneliftPulley => { 669 config.config.threads_enabled = false; 670 } 671 } 672 673 // Forcibly don't use the `CustomUnaligned` memory configuration when 674 // wasm threads are enabled or when the pooling allocator is used. For 675 // the pooling allocator it doesn't use custom memory creators anyway 676 // and for wasm threads that will require some refactoring of the 677 // `LinearMemory` trait to bubble up the request that the linear memory 678 // not move. Otherwise that just generates a panic right now. 679 if config.config.threads_enabled 680 || matches!(self.strategy, InstanceAllocationStrategy::Pooling(_)) 681 { 682 self.avoid_custom_unaligned_memory(u)?; 683 } 684 685 // If using the pooling allocator, constrain the memory and module configurations 686 // to the module limits. 687 if let InstanceAllocationStrategy::Pooling(pooling) = &mut self.strategy { 688 // If the pooling allocator is used, do not allow shared memory to 689 // be created. FIXME: see 690 // https://github.com/bytecodealliance/wasmtime/issues/4244. 691 config.config.threads_enabled = false; 692 693 // Ensure the pooling allocator can support the maximal size of 694 // memory, picking the smaller of the two to win. 695 let min_bytes = config 696 .config 697 .max_memory32_bytes 698 // memory64_bytes is a u128, but since we are taking the min 699 // we can truncate it down to a u64. 700 .min( 701 config 702 .config 703 .max_memory64_bytes 704 .try_into() 705 .unwrap_or(u64::MAX), 706 ); 707 let mut min = min_bytes.min(pooling.max_memory_size as u64); 708 if let MemoryConfig::Normal(cfg) = &self.memory_config { 709 min = min.min(cfg.memory_reservation.unwrap_or(0)); 710 } 711 pooling.max_memory_size = min as usize; 712 config.config.max_memory32_bytes = min; 713 config.config.max_memory64_bytes = min as u128; 714 715 // If traps are disallowed then memories must have at least one page 716 // of memory so if we still are only allowing 0 pages of memory then 717 // increase that to one here. 718 if config.config.disallow_traps { 719 if pooling.max_memory_size < (1 << 16) { 720 pooling.max_memory_size = 1 << 16; 721 config.config.max_memory32_bytes = 1 << 16; 722 config.config.max_memory64_bytes = 1 << 16; 723 if let MemoryConfig::Normal(cfg) = &mut self.memory_config { 724 match &mut cfg.memory_reservation { 725 Some(size) => *size = (*size).max(pooling.max_memory_size as u64), 726 size @ None => *size = Some(pooling.max_memory_size as u64), 727 } 728 } 729 } 730 // .. additionally update tables 731 if pooling.table_elements == 0 { 732 pooling.table_elements = 1; 733 } 734 } 735 736 // Don't allow too many linear memories per instance since massive 737 // virtual mappings can fail to get allocated. 738 config.config.min_memories = config.config.min_memories.min(10); 739 config.config.max_memories = config.config.max_memories.min(10); 740 741 // Force this pooling allocator to always be able to accommodate the 742 // module that may be generated. 743 pooling.total_memories = config.config.max_memories as u32; 744 pooling.total_tables = config.config.max_tables as u32; 745 } 746 747 if !self.signals_based_traps { 748 // At this time shared memories require a "static" memory 749 // configuration but when signals-based traps are disabled all 750 // memories are forced to the "dynamic" configuration. This is 751 // fixable with some more work on the bounds-checks side of things 752 // to do a full bounds check even on static memories, but that's 753 // left for a future PR. 754 config.config.threads_enabled = false; 755 756 // Spectre-based heap mitigations require signal handlers so this 757 // must always be disabled if signals-based traps are disabled. 758 if let MemoryConfig::Normal(cfg) = &mut self.memory_config { 759 cfg.cranelift_enable_heap_access_spectre_mitigations = None; 760 } 761 } 762 763 self.make_internally_consistent(); 764 765 Ok(()) 766 } 767 768 /// Returns the codegen flag value, if any, for `name`. 769 pub(crate) fn codegen_flag(&self, name: &str) -> Option<&str> { 770 self.codegen.flags().iter().find_map(|(n, value)| { 771 if n == name { 772 Some(value.as_str()) 773 } else { 774 None 775 } 776 }) 777 } 778 779 /// Helper to switch `MemoryConfig::CustomUnaligned` to 780 /// `MemoryConfig::Normal` 781 fn avoid_custom_unaligned_memory(&mut self, u: &mut Unstructured<'_>) -> arbitrary::Result<()> { 782 if let MemoryConfig::CustomUnaligned = self.memory_config { 783 self.memory_config = MemoryConfig::Normal(u.arbitrary()?); 784 } 785 Ok(()) 786 } 787 788 /// Helper method to handle some dependencies between various configuration 789 /// options. This is intended to be called whenever a `Config` is created or 790 /// modified to ensure that the final result is an instantiable `Config`. 791 /// 792 /// Note that in general this probably shouldn't exist and anything here can 793 /// be considered a "TODO" to go implement more stuff in Wasmtime to accept 794 /// these sorts of configurations. For now though it's intended to reflect 795 /// the current state of the engine's development. 796 fn make_internally_consistent(&mut self) { 797 if !self.signals_based_traps { 798 if let MemoryConfig::Normal(cfg) = &mut self.memory_config { 799 // Spectre-based heap mitigations require signal handlers so 800 // this must always be disabled if signals-based traps are 801 // disabled. 802 cfg.cranelift_enable_heap_access_spectre_mitigations = None; 803 804 // With configuration settings that match the use of malloc for 805 // linear memories cap the `memory_reservation_for_growth` value 806 // to something reasonable to avoid OOM in fuzzing. 807 if !cfg.memory_init_cow 808 && cfg.memory_guard_size == Some(0) 809 && cfg.memory_reservation == Some(0) 810 { 811 let min = 10 << 20; // 10 MiB 812 if let Some(val) = &mut cfg.memory_reservation_for_growth { 813 *val = (*val).min(min); 814 } else { 815 cfg.memory_reservation_for_growth = Some(min); 816 } 817 } 818 } 819 } 820 } 821 } 822 823 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 824 enum OptLevel { 825 None, 826 Speed, 827 SpeedAndSize, 828 } 829 830 impl OptLevel { 831 fn to_wasmtime(&self) -> wasmtime::OptLevel { 832 match self { 833 OptLevel::None => wasmtime::OptLevel::None, 834 OptLevel::Speed => wasmtime::OptLevel::Speed, 835 OptLevel::SpeedAndSize => wasmtime::OptLevel::SpeedAndSize, 836 } 837 } 838 } 839 840 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 841 enum RegallocAlgorithm { 842 Backtracking, 843 SinglePass, 844 } 845 846 impl RegallocAlgorithm { 847 fn to_wasmtime(&self) -> wasmtime::RegallocAlgorithm { 848 match self { 849 RegallocAlgorithm::Backtracking => wasmtime::RegallocAlgorithm::Backtracking, 850 RegallocAlgorithm::SinglePass => wasmtime::RegallocAlgorithm::SinglePass, 851 } 852 } 853 } 854 855 #[derive(Clone, Debug, PartialEq, Eq, Hash)] 856 /// Compiler to use. 857 pub enum CompilerStrategy { 858 /// Cranelift compiler for the native architecture. 859 CraneliftNative, 860 /// Winch compiler. 861 Winch, 862 /// Cranelift compiler for the native architecture. 863 CraneliftPulley, 864 } 865 866 impl CompilerStrategy { 867 /// Configures `config` to use this compilation strategy 868 pub fn configure(&self, config: &mut wasmtime_cli_flags::CommonOptions) { 869 match self { 870 CompilerStrategy::CraneliftNative => { 871 config.codegen.compiler = Some(wasmtime::Strategy::Cranelift); 872 } 873 CompilerStrategy::Winch => { 874 config.codegen.compiler = Some(wasmtime::Strategy::Winch); 875 } 876 CompilerStrategy::CraneliftPulley => { 877 config.codegen.compiler = Some(wasmtime::Strategy::Cranelift); 878 config.target = Some("pulley64".to_string()); 879 } 880 } 881 } 882 } 883 884 impl Arbitrary<'_> for CompilerStrategy { 885 fn arbitrary(u: &mut Unstructured<'_>) -> arbitrary::Result<Self> { 886 // Favor fuzzing native cranelift, but if allowed also enable 887 // winch/pulley. 888 match u.int_in_range(0..=19)? { 889 1 => Ok(Self::CraneliftPulley), 890 2 => Ok(Self::Winch), 891 _ => Ok(Self::CraneliftNative), 892 } 893 } 894 } 895 896 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 897 pub enum Collector { 898 DeferredReferenceCounting, 899 Null, 900 } 901 902 impl Collector { 903 fn to_wasmtime(&self) -> wasmtime::Collector { 904 match self { 905 Collector::DeferredReferenceCounting => wasmtime::Collector::DeferredReferenceCounting, 906 Collector::Null => wasmtime::Collector::Null, 907 } 908 } 909 } 910