1 //! Generate a configuration for both Wasmtime and the Wasm module to execute. 2 3 use super::{AsyncConfig, CodegenSettings, InstanceAllocationStrategy, MemoryConfig, ModuleConfig}; 4 use crate::oracles::{StoreLimits, Timeout}; 5 use anyhow::Result; 6 use arbitrary::{Arbitrary, Unstructured}; 7 use std::time::Duration; 8 use wasmtime::{Enabled, Engine, Module, Store}; 9 use wasmtime_test_util::wast::{WastConfig, WastTest, limits}; 10 11 /// Configuration for `wasmtime::Config` and generated modules for a session of 12 /// fuzzing. 13 /// 14 /// This configuration guides what modules are generated, how wasmtime 15 /// configuration is generated, and is typically itself generated through a call 16 /// to `Arbitrary` which allows for a form of "swarm testing". 17 #[derive(Debug, Clone)] 18 pub struct Config { 19 /// Configuration related to the `wasmtime::Config`. 20 pub wasmtime: WasmtimeConfig, 21 /// Configuration related to generated modules. 22 pub module_config: ModuleConfig, 23 } 24 25 impl Config { 26 /// Indicates that this configuration is being used for differential 27 /// execution. 28 /// 29 /// The purpose of this function is to update the configuration which was 30 /// generated to be compatible with execution in multiple engines. The goal 31 /// is to produce the exact same result in all engines so we need to paper 32 /// over things like nan differences and memory/table behavior differences. 33 pub fn set_differential_config(&mut self) { 34 let config = &mut self.module_config.config; 35 36 // Make it more likely that there are types available to generate a 37 // function with. 38 config.min_types = config.min_types.max(1); 39 config.max_types = config.max_types.max(1); 40 41 // Generate at least one function 42 config.min_funcs = config.min_funcs.max(1); 43 config.max_funcs = config.max_funcs.max(1); 44 45 // Allow a memory to be generated, but don't let it get too large. 46 // Additionally require the maximum size to guarantee that the growth 47 // behavior is consistent across engines. 48 config.max_memory32_bytes = 10 << 16; 49 config.max_memory64_bytes = 10 << 16; 50 config.memory_max_size_required = true; 51 52 // If tables are generated make sure they don't get too large to avoid 53 // hitting any engine-specific limit. Additionally ensure that the 54 // maximum size is required to guarantee consistent growth across 55 // engines. 56 // 57 // Note that while reference types are disabled below, only allow one 58 // table. 59 config.max_table_elements = 1_000; 60 config.table_max_size_required = true; 61 62 // Don't allow any imports 63 config.max_imports = 0; 64 65 // Try to get the function and the memory exported 66 config.export_everything = true; 67 68 // NaN is canonicalized at the wasm level for differential fuzzing so we 69 // can paper over NaN differences between engines. 70 config.canonicalize_nans = true; 71 72 // If using the pooling allocator, update the instance limits too 73 if let InstanceAllocationStrategy::Pooling(pooling) = &mut self.wasmtime.strategy { 74 // One single-page memory 75 pooling.total_memories = config.max_memories as u32; 76 pooling.max_memory_size = 10 << 16; 77 pooling.max_memories_per_module = config.max_memories as u32; 78 if pooling.memory_protection_keys == Enabled::Auto 79 && pooling.max_memory_protection_keys > 1 80 { 81 pooling.total_memories = 82 pooling.total_memories * (pooling.max_memory_protection_keys as u32); 83 } 84 85 pooling.total_tables = config.max_tables as u32; 86 pooling.table_elements = 1_000; 87 pooling.max_tables_per_module = config.max_tables as u32; 88 89 pooling.core_instance_size = 1_000_000; 90 91 let cfg = &mut self.wasmtime.memory_config; 92 match &mut cfg.memory_reservation { 93 Some(size) => *size = (*size).max(pooling.max_memory_size as u64), 94 other @ None => *other = Some(pooling.max_memory_size as u64), 95 } 96 } 97 98 // These instructions are explicitly not expected to be exactly the same 99 // across engines. Don't fuzz them. 100 config.relaxed_simd_enabled = false; 101 } 102 103 /// Uses this configuration and the supplied source of data to generate 104 /// a wasm module. 105 /// 106 /// If a `default_fuel` is provided, the resulting module will be configured 107 /// to ensure termination; as doing so will add an additional global to the module, 108 /// the pooling allocator, if configured, will also have its globals limit updated. 109 pub fn generate( 110 &self, 111 input: &mut Unstructured<'_>, 112 default_fuel: Option<u32>, 113 ) -> arbitrary::Result<wasm_smith::Module> { 114 self.module_config.generate(input, default_fuel) 115 } 116 117 /// Updates this configuration to be able to run the `test` specified. 118 /// 119 /// This primarily updates `self.module_config` to ensure that it enables 120 /// all features and proposals necessary to execute the `test` specified. 121 /// This will additionally update limits in the pooling allocator to be able 122 /// to execute all tests. 123 pub fn make_wast_test_compliant(&mut self, test: &WastTest) -> WastConfig { 124 let wasmtime_test_util::wast::TestConfig { 125 memory64, 126 custom_page_sizes, 127 multi_memory, 128 threads, 129 shared_everything_threads, 130 gc, 131 function_references, 132 relaxed_simd, 133 reference_types, 134 tail_call, 135 extended_const, 136 wide_arithmetic, 137 component_model_async, 138 component_model_async_builtins, 139 component_model_async_stackful, 140 component_model_error_context, 141 component_model_gc, 142 simd, 143 exceptions, 144 legacy_exceptions: _, 145 146 hogs_memory: _, 147 nan_canonicalization: _, 148 gc_types: _, 149 stack_switching: _, 150 spec_test: _, 151 } = test.config; 152 153 // Enable/disable some proposals that aren't configurable in wasm-smith 154 // but are configurable in Wasmtime. 155 self.module_config.function_references_enabled = 156 function_references.or(gc).unwrap_or(false); 157 self.module_config.component_model_async = component_model_async.unwrap_or(false); 158 self.module_config.component_model_async_builtins = 159 component_model_async_builtins.unwrap_or(false); 160 self.module_config.component_model_async_stackful = 161 component_model_async_stackful.unwrap_or(false); 162 self.module_config.component_model_error_context = 163 component_model_error_context.unwrap_or(false); 164 self.module_config.component_model_gc = component_model_gc.unwrap_or(false); 165 166 // Enable/disable proposals that wasm-smith has knobs for which will be 167 // read when creating `wasmtime::Config`. 168 let config = &mut self.module_config.config; 169 config.bulk_memory_enabled = true; 170 config.multi_value_enabled = true; 171 config.wide_arithmetic_enabled = wide_arithmetic.unwrap_or(false); 172 config.memory64_enabled = memory64.unwrap_or(false); 173 config.relaxed_simd_enabled = relaxed_simd.unwrap_or(false); 174 config.simd_enabled = config.relaxed_simd_enabled || simd.unwrap_or(false); 175 config.tail_call_enabled = tail_call.unwrap_or(false); 176 config.custom_page_sizes_enabled = custom_page_sizes.unwrap_or(false); 177 config.threads_enabled = threads.unwrap_or(false); 178 config.shared_everything_threads_enabled = shared_everything_threads.unwrap_or(false); 179 config.gc_enabled = gc.unwrap_or(false); 180 config.reference_types_enabled = config.gc_enabled 181 || self.module_config.function_references_enabled 182 || reference_types.unwrap_or(false); 183 config.extended_const_enabled = extended_const.unwrap_or(false); 184 config.exceptions_enabled = exceptions.unwrap_or(false); 185 if multi_memory.unwrap_or(false) { 186 config.max_memories = limits::MEMORIES_PER_MODULE as usize; 187 } else { 188 config.max_memories = 1; 189 } 190 191 if let Some(n) = &mut self.wasmtime.memory_config.memory_reservation { 192 *n = (*n).max(limits::MEMORY_SIZE as u64); 193 } 194 195 // FIXME: it might be more ideal to avoid the need for this entirely 196 // and to just let the test fail. If a test fails due to a pooling 197 // allocator resource limit being met we could ideally detect that and 198 // let the fuzz test case pass. That would avoid the need to hardcode 199 // so much here and in theory wouldn't reduce the usefulness of fuzzers 200 // all that much. At this time though we can't easily test this configuration. 201 if let InstanceAllocationStrategy::Pooling(pooling) = &mut self.wasmtime.strategy { 202 // Clamp protection keys between 1 & 2 to reduce the number of 203 // slots and then multiply the total memories by the number of keys 204 // we have since a single store has access to only one key. 205 pooling.max_memory_protection_keys = pooling.max_memory_protection_keys.max(1).min(2); 206 pooling.total_memories = pooling 207 .total_memories 208 .max(limits::MEMORIES * (pooling.max_memory_protection_keys as u32)); 209 210 // For other limits make sure they meet the minimum threshold 211 // required for our wast tests. 212 pooling.total_component_instances = pooling 213 .total_component_instances 214 .max(limits::COMPONENT_INSTANCES); 215 pooling.total_tables = pooling.total_tables.max(limits::TABLES); 216 pooling.max_tables_per_module = 217 pooling.max_tables_per_module.max(limits::TABLES_PER_MODULE); 218 pooling.max_memories_per_module = pooling 219 .max_memories_per_module 220 .max(limits::MEMORIES_PER_MODULE); 221 pooling.max_memories_per_component = pooling 222 .max_memories_per_component 223 .max(limits::MEMORIES_PER_MODULE); 224 pooling.total_core_instances = pooling.total_core_instances.max(limits::CORE_INSTANCES); 225 pooling.max_memory_size = pooling.max_memory_size.max(limits::MEMORY_SIZE); 226 pooling.table_elements = pooling.table_elements.max(limits::TABLE_ELEMENTS); 227 pooling.core_instance_size = pooling.core_instance_size.max(limits::CORE_INSTANCE_SIZE); 228 pooling.component_instance_size = pooling 229 .component_instance_size 230 .max(limits::CORE_INSTANCE_SIZE); 231 pooling.total_stacks = pooling.total_stacks.max(limits::TOTAL_STACKS); 232 } 233 234 // Return the test configuration that this fuzz configuration represents 235 // which is used afterwards to test if the `test` here is expected to 236 // fail or not. 237 WastConfig { 238 collector: match self.wasmtime.collector { 239 Collector::Null => wasmtime_test_util::wast::Collector::Null, 240 Collector::DeferredReferenceCounting => { 241 wasmtime_test_util::wast::Collector::DeferredReferenceCounting 242 } 243 }, 244 pooling: matches!( 245 self.wasmtime.strategy, 246 InstanceAllocationStrategy::Pooling(_) 247 ), 248 compiler: match self.wasmtime.compiler_strategy { 249 CompilerStrategy::CraneliftNative => { 250 wasmtime_test_util::wast::Compiler::CraneliftNative 251 } 252 CompilerStrategy::CraneliftPulley => { 253 wasmtime_test_util::wast::Compiler::CraneliftPulley 254 } 255 CompilerStrategy::Winch => wasmtime_test_util::wast::Compiler::Winch, 256 }, 257 } 258 } 259 260 /// Converts this to a `wasmtime::Config` object 261 pub fn to_wasmtime(&self) -> wasmtime::Config { 262 crate::init_fuzzing(); 263 264 let mut cfg = wasmtime_cli_flags::CommonOptions::default(); 265 cfg.codegen.native_unwind_info = 266 Some(cfg!(target_os = "windows") || self.wasmtime.native_unwind_info); 267 cfg.codegen.parallel_compilation = Some(false); 268 269 cfg.debug.address_map = Some(self.wasmtime.generate_address_map); 270 cfg.opts.opt_level = Some(self.wasmtime.opt_level.to_wasmtime()); 271 cfg.opts.regalloc_algorithm = Some(self.wasmtime.regalloc_algorithm.to_wasmtime()); 272 cfg.opts.signals_based_traps = Some(self.wasmtime.signals_based_traps); 273 cfg.opts.memory_guaranteed_dense_image_size = Some(std::cmp::min( 274 // Clamp this at 16MiB so we don't get huge in-memory 275 // images during fuzzing. 276 16 << 20, 277 self.wasmtime.memory_guaranteed_dense_image_size, 278 )); 279 cfg.wasm.async_stack_zeroing = Some(self.wasmtime.async_stack_zeroing); 280 cfg.wasm.bulk_memory = Some(true); 281 cfg.wasm.component_model_async = Some(self.module_config.component_model_async); 282 cfg.wasm.component_model_async_builtins = 283 Some(self.module_config.component_model_async_builtins); 284 cfg.wasm.component_model_async_stackful = 285 Some(self.module_config.component_model_async_stackful); 286 cfg.wasm.component_model_error_context = 287 Some(self.module_config.component_model_error_context); 288 cfg.wasm.component_model_gc = Some(self.module_config.component_model_gc); 289 cfg.wasm.custom_page_sizes = Some(self.module_config.config.custom_page_sizes_enabled); 290 cfg.wasm.epoch_interruption = Some(self.wasmtime.epoch_interruption); 291 cfg.wasm.extended_const = Some(self.module_config.config.extended_const_enabled); 292 cfg.wasm.fuel = self.wasmtime.consume_fuel.then(|| u64::MAX); 293 cfg.wasm.function_references = Some(self.module_config.function_references_enabled); 294 cfg.wasm.gc = Some(self.module_config.config.gc_enabled); 295 cfg.wasm.memory64 = Some(self.module_config.config.memory64_enabled); 296 cfg.wasm.multi_memory = Some(self.module_config.config.max_memories > 1); 297 cfg.wasm.multi_value = Some(self.module_config.config.multi_value_enabled); 298 cfg.wasm.nan_canonicalization = Some(self.wasmtime.canonicalize_nans); 299 cfg.wasm.reference_types = Some(self.module_config.config.reference_types_enabled); 300 cfg.wasm.simd = Some(self.module_config.config.simd_enabled); 301 cfg.wasm.tail_call = Some(self.module_config.config.tail_call_enabled); 302 cfg.wasm.threads = Some(self.module_config.config.threads_enabled); 303 cfg.wasm.shared_everything_threads = 304 Some(self.module_config.config.shared_everything_threads_enabled); 305 cfg.wasm.wide_arithmetic = Some(self.module_config.config.wide_arithmetic_enabled); 306 cfg.wasm.exceptions = Some(self.module_config.config.exceptions_enabled); 307 if !self.module_config.config.simd_enabled { 308 cfg.wasm.relaxed_simd = Some(false); 309 } 310 cfg.codegen.collector = Some(self.wasmtime.collector.to_wasmtime()); 311 312 let compiler_strategy = &self.wasmtime.compiler_strategy; 313 let cranelift_strategy = match compiler_strategy { 314 CompilerStrategy::CraneliftNative | CompilerStrategy::CraneliftPulley => true, 315 CompilerStrategy::Winch => false, 316 }; 317 self.wasmtime.compiler_strategy.configure(&mut cfg); 318 319 self.wasmtime.codegen.configure(&mut cfg); 320 321 // Determine whether we will actually enable PCC -- this is 322 // disabled if the module requires memory64, which is not yet 323 // compatible (due to the need for dynamic checks). 324 let pcc = cfg!(feature = "fuzz-pcc") 325 && self.wasmtime.pcc 326 && !self.module_config.config.memory64_enabled; 327 328 cfg.codegen.inlining = self.wasmtime.inlining; 329 330 // Only set cranelift specific flags when the Cranelift strategy is 331 // chosen. 332 if cranelift_strategy { 333 if let Some(option) = self.wasmtime.inlining_intra_module { 334 cfg.codegen.cranelift.push(( 335 "wasmtime_inlining_intra_module".to_string(), 336 Some(option.to_string()), 337 )); 338 } 339 if let Some(size) = self.wasmtime.inlining_small_callee_size { 340 cfg.codegen.cranelift.push(( 341 "wasmtime_inlining_small_callee_size".to_string(), 342 // Clamp to avoid extreme code size blow up. 343 Some(std::cmp::min(1000, size).to_string()), 344 )); 345 } 346 if let Some(size) = self.wasmtime.inlining_sum_size_threshold { 347 cfg.codegen.cranelift.push(( 348 "wasmtime_inlining_sum_size_threshold".to_string(), 349 // Clamp to avoid extreme code size blow up. 350 Some(std::cmp::min(1000, size).to_string()), 351 )); 352 } 353 354 // If the wasm-smith-generated module use nan canonicalization then we 355 // don't need to enable it, but if it doesn't enable it already then we 356 // enable this codegen option. 357 cfg.wasm.nan_canonicalization = Some(!self.module_config.config.canonicalize_nans); 358 359 // Enabling the verifier will at-least-double compilation time, which 360 // with a 20-30x slowdown in fuzzing can cause issues related to 361 // timeouts. If generated modules can have more than a small handful of 362 // functions then disable the verifier when fuzzing to try to lessen the 363 // impact of timeouts. 364 if self.module_config.config.max_funcs > 10 { 365 cfg.codegen.cranelift_debug_verifier = Some(false); 366 } 367 368 if self.wasmtime.force_jump_veneers { 369 cfg.codegen.cranelift.push(( 370 "wasmtime_linkopt_force_jump_veneer".to_string(), 371 Some("true".to_string()), 372 )); 373 } 374 375 if let Some(pad) = self.wasmtime.padding_between_functions { 376 cfg.codegen.cranelift.push(( 377 "wasmtime_linkopt_padding_between_functions".to_string(), 378 Some(pad.to_string()), 379 )); 380 } 381 382 cfg.codegen.pcc = Some(pcc); 383 384 // Eager init is currently only supported on Cranelift, not Winch. 385 cfg.opts.table_lazy_init = Some(self.wasmtime.table_lazy_init); 386 } 387 388 self.wasmtime.strategy.configure(&mut cfg); 389 390 // Vary the memory configuration, but only if threads are not enabled. 391 // When the threads proposal is enabled we might generate shared memory, 392 // which is less amenable to different memory configurations: 393 // - shared memories are required to be "static" so fuzzing the various 394 // memory configurations will mostly result in uninteresting errors. 395 // The interesting part about shared memories is the runtime so we 396 // don't fuzz non-default settings. 397 // - shared memories are required to be aligned which means that the 398 // `CustomUnaligned` variant isn't actually safe to use with a shared 399 // memory. 400 if !self.module_config.config.threads_enabled { 401 // If PCC is enabled, force other options to be compatible: PCC is currently only 402 // supported when bounds checks are elided. 403 let memory_config = if pcc { 404 MemoryConfig { 405 memory_reservation: Some(4 << 30), // 4 GiB 406 memory_guard_size: Some(2 << 30), // 2 GiB 407 memory_reservation_for_growth: Some(0), 408 guard_before_linear_memory: false, 409 memory_init_cow: true, 410 // Doesn't matter, only using virtual memory. 411 cranelift_enable_heap_access_spectre_mitigations: None, 412 } 413 } else { 414 self.wasmtime.memory_config.clone() 415 }; 416 417 memory_config.configure(&mut cfg); 418 }; 419 420 // If malloc-based memory is going to be used, which requires these four 421 // options set to specific values (and Pulley auto-sets two of them) 422 // then be sure to cap `memory_reservation_for_growth` at a smaller 423 // value than the default. For malloc-based memory reservation beyond 424 // the end of memory isn't captured by `StoreLimiter` so we need to be 425 // sure it's small enough to not blow OOM limits while fuzzing. 426 if ((cfg.opts.signals_based_traps == Some(true) && cfg.opts.memory_guard_size == Some(0)) 427 || self.wasmtime.compiler_strategy == CompilerStrategy::CraneliftPulley) 428 && cfg.opts.memory_reservation == Some(0) 429 && cfg.opts.memory_init_cow == Some(false) 430 { 431 let growth = &mut cfg.opts.memory_reservation_for_growth; 432 let max = 1 << 20; 433 *growth = match *growth { 434 Some(n) => Some(n.min(max)), 435 None => Some(max), 436 }; 437 } 438 439 log::debug!("creating wasmtime config with CLI options:\n{cfg}"); 440 let mut cfg = cfg.config(None).expect("failed to create wasmtime::Config"); 441 442 if self.wasmtime.async_config != AsyncConfig::Disabled { 443 log::debug!("async config in use {:?}", self.wasmtime.async_config); 444 self.wasmtime.async_config.configure(&mut cfg); 445 } 446 447 return cfg; 448 } 449 450 /// Convenience function for generating a `Store<T>` using this 451 /// configuration. 452 pub fn to_store(&self) -> Store<StoreLimits> { 453 let engine = Engine::new(&self.to_wasmtime()).unwrap(); 454 let mut store = Store::new(&engine, StoreLimits::new()); 455 self.configure_store(&mut store); 456 store 457 } 458 459 /// Configures a store based on this configuration. 460 pub fn configure_store(&self, store: &mut Store<StoreLimits>) { 461 store.limiter(|s| s as &mut dyn wasmtime::ResourceLimiter); 462 463 // Configure the store to never abort by default, that is it'll have 464 // max fuel or otherwise trap on an epoch change but the epoch won't 465 // ever change. 466 // 467 // Afterwards though see what `AsyncConfig` is being used an further 468 // refine the store's configuration based on that. 469 if self.wasmtime.consume_fuel { 470 store.set_fuel(u64::MAX).unwrap(); 471 } 472 if self.wasmtime.epoch_interruption { 473 store.epoch_deadline_trap(); 474 store.set_epoch_deadline(1); 475 } 476 match self.wasmtime.async_config { 477 AsyncConfig::Disabled => {} 478 AsyncConfig::YieldWithFuel(amt) => { 479 assert!(self.wasmtime.consume_fuel); 480 store.fuel_async_yield_interval(Some(amt)).unwrap(); 481 } 482 AsyncConfig::YieldWithEpochs { ticks, .. } => { 483 assert!(self.wasmtime.epoch_interruption); 484 store.set_epoch_deadline(ticks); 485 store.epoch_deadline_async_yield_and_update(ticks); 486 } 487 } 488 } 489 490 /// Generates an arbitrary method of timing out an instance, ensuring that 491 /// this configuration supports the returned timeout. 492 pub fn generate_timeout(&mut self, u: &mut Unstructured<'_>) -> arbitrary::Result<Timeout> { 493 let time_duration = Duration::from_millis(100); 494 let timeout = u 495 .choose(&[Timeout::Fuel(100_000), Timeout::Epoch(time_duration)])? 496 .clone(); 497 match &timeout { 498 Timeout::Fuel(..) => { 499 self.wasmtime.consume_fuel = true; 500 } 501 Timeout::Epoch(..) => { 502 self.wasmtime.epoch_interruption = true; 503 } 504 Timeout::None => unreachable!("Not an option given to choose()"), 505 } 506 Ok(timeout) 507 } 508 509 /// Compiles the `wasm` within the `engine` provided. 510 /// 511 /// This notably will use `Module::{serialize,deserialize_file}` to 512 /// round-trip if configured in the fuzzer. 513 pub fn compile(&self, engine: &Engine, wasm: &[u8]) -> Result<Module> { 514 // Propagate this error in case the caller wants to handle 515 // valid-vs-invalid wasm. 516 let module = Module::new(engine, wasm)?; 517 if !self.wasmtime.use_precompiled_cwasm { 518 return Ok(module); 519 } 520 521 // Don't propagate these errors to prevent them from accidentally being 522 // interpreted as invalid wasm, these should never fail on a 523 // well-behaved host system. 524 let dir = tempfile::TempDir::new().unwrap(); 525 let file = dir.path().join("module.wasm"); 526 std::fs::write(&file, module.serialize().unwrap()).unwrap(); 527 unsafe { Ok(Module::deserialize_file(engine, &file).unwrap()) } 528 } 529 530 /// Updates this configuration to forcibly enable async support. Only useful 531 /// in fuzzers which do async calls. 532 pub fn enable_async(&mut self, u: &mut Unstructured<'_>) -> arbitrary::Result<()> { 533 if self.wasmtime.consume_fuel || u.arbitrary()? { 534 self.wasmtime.async_config = 535 AsyncConfig::YieldWithFuel(u.int_in_range(1000..=100_000)?); 536 self.wasmtime.consume_fuel = true; 537 } else { 538 self.wasmtime.async_config = AsyncConfig::YieldWithEpochs { 539 dur: Duration::from_millis(u.int_in_range(1..=10)?), 540 ticks: u.int_in_range(1..=10)?, 541 }; 542 self.wasmtime.epoch_interruption = true; 543 } 544 Ok(()) 545 } 546 } 547 548 impl<'a> Arbitrary<'a> for Config { 549 fn arbitrary(u: &mut Unstructured<'a>) -> arbitrary::Result<Self> { 550 let mut config = Self { 551 wasmtime: u.arbitrary()?, 552 module_config: u.arbitrary()?, 553 }; 554 555 config 556 .wasmtime 557 .update_module_config(&mut config.module_config, u)?; 558 559 Ok(config) 560 } 561 } 562 563 /// Configuration related to `wasmtime::Config` and the various settings which 564 /// can be tweaked from within. 565 #[derive(Arbitrary, Clone, Debug, Eq, Hash, PartialEq)] 566 pub struct WasmtimeConfig { 567 opt_level: OptLevel, 568 regalloc_algorithm: RegallocAlgorithm, 569 debug_info: bool, 570 canonicalize_nans: bool, 571 interruptable: bool, 572 pub(crate) consume_fuel: bool, 573 pub(crate) epoch_interruption: bool, 574 /// The Wasmtime memory configuration to use. 575 pub memory_config: MemoryConfig, 576 force_jump_veneers: bool, 577 memory_init_cow: bool, 578 memory_guaranteed_dense_image_size: u64, 579 inlining: Option<bool>, 580 inlining_intra_module: Option<IntraModuleInlining>, 581 inlining_small_callee_size: Option<u32>, 582 inlining_sum_size_threshold: Option<u32>, 583 use_precompiled_cwasm: bool, 584 async_stack_zeroing: bool, 585 /// Configuration for the instance allocation strategy to use. 586 pub strategy: InstanceAllocationStrategy, 587 codegen: CodegenSettings, 588 padding_between_functions: Option<u16>, 589 generate_address_map: bool, 590 native_unwind_info: bool, 591 /// Configuration for the compiler to use. 592 pub compiler_strategy: CompilerStrategy, 593 collector: Collector, 594 table_lazy_init: bool, 595 596 /// Whether or not fuzzing should enable PCC. 597 pcc: bool, 598 599 /// Configuration for whether wasm is invoked in an async fashion and how 600 /// it's cooperatively time-sliced. 601 pub async_config: AsyncConfig, 602 603 /// Whether or not host signal handlers are enabled for this configuration, 604 /// aka whether signal handlers are supported. 605 signals_based_traps: bool, 606 } 607 608 impl WasmtimeConfig { 609 /// Force `self` to be a configuration compatible with `other`. This is 610 /// useful for differential execution to avoid unhelpful fuzz crashes when 611 /// one engine has a feature enabled and the other does not. 612 pub fn make_compatible_with(&mut self, other: &Self) { 613 // Use the same allocation strategy between the two configs. 614 // 615 // Ideally this wouldn't be necessary, but, during differential 616 // evaluation, if the `lhs` is using ondemand and the `rhs` is using the 617 // pooling allocator (or vice versa), then the module may have been 618 // generated in such a way that is incompatible with the other 619 // allocation strategy. 620 // 621 // We can remove this in the future when it's possible to access the 622 // fields of `wasm_smith::Module` to constrain the pooling allocator 623 // based on what was actually generated. 624 self.strategy = other.strategy.clone(); 625 if let InstanceAllocationStrategy::Pooling { .. } = &other.strategy { 626 // Also use the same memory configuration when using the pooling 627 // allocator. 628 self.memory_config = other.memory_config.clone(); 629 } 630 631 self.make_internally_consistent(); 632 } 633 634 /// Updates `config` to be compatible with `self` and the other way around 635 /// too. 636 pub fn update_module_config( 637 &mut self, 638 config: &mut ModuleConfig, 639 _u: &mut Unstructured<'_>, 640 ) -> arbitrary::Result<()> { 641 match self.compiler_strategy { 642 CompilerStrategy::CraneliftNative => {} 643 644 CompilerStrategy::Winch => { 645 // Winch is not complete on non-x64 targets, so just abandon this test 646 // case. We don't want to force Cranelift because we change what module 647 // config features are enabled based on the compiler strategy, and we 648 // don't want to make the same fuzz input DNA generate different test 649 // cases on different targets. 650 if cfg!(not(target_arch = "x86_64")) { 651 log::warn!( 652 "want to compile with Winch but host architecture does not support it" 653 ); 654 return Err(arbitrary::Error::IncorrectFormat); 655 } 656 657 // Winch doesn't support the same set of wasm proposal as Cranelift 658 // at this time, so if winch is selected be sure to disable wasm 659 // proposals in `Config` to ensure that Winch can compile the 660 // module that wasm-smith generates. 661 config.config.relaxed_simd_enabled = false; 662 config.config.gc_enabled = false; 663 config.config.tail_call_enabled = false; 664 config.config.reference_types_enabled = false; 665 config.config.exceptions_enabled = false; 666 config.function_references_enabled = false; 667 668 // Winch's SIMD implementations require AVX and AVX2. 669 if self 670 .codegen_flag("has_avx") 671 .is_some_and(|value| value == "false") 672 || self 673 .codegen_flag("has_avx2") 674 .is_some_and(|value| value == "false") 675 { 676 config.config.simd_enabled = false; 677 } 678 679 // Tuning the following engine options is currently not supported 680 // by Winch. 681 self.signals_based_traps = true; 682 self.table_lazy_init = true; 683 self.debug_info = false; 684 } 685 686 CompilerStrategy::CraneliftPulley => { 687 config.config.threads_enabled = false; 688 } 689 } 690 691 // If using the pooling allocator, constrain the memory and module configurations 692 // to the module limits. 693 if let InstanceAllocationStrategy::Pooling(pooling) = &mut self.strategy { 694 // If the pooling allocator is used, do not allow shared memory to 695 // be created. FIXME: see 696 // https://github.com/bytecodealliance/wasmtime/issues/4244. 697 config.config.threads_enabled = false; 698 699 // Ensure the pooling allocator can support the maximal size of 700 // memory, picking the smaller of the two to win. 701 let min_bytes = config 702 .config 703 .max_memory32_bytes 704 // memory64_bytes is a u128, but since we are taking the min 705 // we can truncate it down to a u64. 706 .min( 707 config 708 .config 709 .max_memory64_bytes 710 .try_into() 711 .unwrap_or(u64::MAX), 712 ); 713 let min = min_bytes 714 .min(pooling.max_memory_size as u64) 715 .min(self.memory_config.memory_reservation.unwrap_or(0)); 716 pooling.max_memory_size = min as usize; 717 config.config.max_memory32_bytes = min; 718 config.config.max_memory64_bytes = min as u128; 719 720 // If traps are disallowed then memories must have at least one page 721 // of memory so if we still are only allowing 0 pages of memory then 722 // increase that to one here. 723 if config.config.disallow_traps { 724 if pooling.max_memory_size < (1 << 16) { 725 pooling.max_memory_size = 1 << 16; 726 config.config.max_memory32_bytes = 1 << 16; 727 config.config.max_memory64_bytes = 1 << 16; 728 let cfg = &mut self.memory_config; 729 match &mut cfg.memory_reservation { 730 Some(size) => *size = (*size).max(pooling.max_memory_size as u64), 731 size @ None => *size = Some(pooling.max_memory_size as u64), 732 } 733 } 734 // .. additionally update tables 735 if pooling.table_elements == 0 { 736 pooling.table_elements = 1; 737 } 738 } 739 740 // Don't allow too many linear memories per instance since massive 741 // virtual mappings can fail to get allocated. 742 config.config.min_memories = config.config.min_memories.min(10); 743 config.config.max_memories = config.config.max_memories.min(10); 744 745 // Force this pooling allocator to always be able to accommodate the 746 // module that may be generated. 747 pooling.total_memories = config.config.max_memories as u32; 748 pooling.total_tables = config.config.max_tables as u32; 749 } 750 751 if !self.signals_based_traps { 752 // At this time shared memories require a "static" memory 753 // configuration but when signals-based traps are disabled all 754 // memories are forced to the "dynamic" configuration. This is 755 // fixable with some more work on the bounds-checks side of things 756 // to do a full bounds check even on static memories, but that's 757 // left for a future PR. 758 config.config.threads_enabled = false; 759 760 // Spectre-based heap mitigations require signal handlers so this 761 // must always be disabled if signals-based traps are disabled. 762 self.memory_config 763 .cranelift_enable_heap_access_spectre_mitigations = None; 764 } 765 766 self.make_internally_consistent(); 767 768 Ok(()) 769 } 770 771 /// Returns the codegen flag value, if any, for `name`. 772 pub(crate) fn codegen_flag(&self, name: &str) -> Option<&str> { 773 self.codegen.flags().iter().find_map(|(n, value)| { 774 if n == name { 775 Some(value.as_str()) 776 } else { 777 None 778 } 779 }) 780 } 781 782 /// Helper method to handle some dependencies between various configuration 783 /// options. This is intended to be called whenever a `Config` is created or 784 /// modified to ensure that the final result is an instantiable `Config`. 785 /// 786 /// Note that in general this probably shouldn't exist and anything here can 787 /// be considered a "TODO" to go implement more stuff in Wasmtime to accept 788 /// these sorts of configurations. For now though it's intended to reflect 789 /// the current state of the engine's development. 790 fn make_internally_consistent(&mut self) { 791 if !self.signals_based_traps { 792 let cfg = &mut self.memory_config; 793 // Spectre-based heap mitigations require signal handlers so 794 // this must always be disabled if signals-based traps are 795 // disabled. 796 cfg.cranelift_enable_heap_access_spectre_mitigations = None; 797 798 // With configuration settings that match the use of malloc for 799 // linear memories cap the `memory_reservation_for_growth` value 800 // to something reasonable to avoid OOM in fuzzing. 801 if !cfg.memory_init_cow 802 && cfg.memory_guard_size == Some(0) 803 && cfg.memory_reservation == Some(0) 804 { 805 let min = 10 << 20; // 10 MiB 806 if let Some(val) = &mut cfg.memory_reservation_for_growth { 807 *val = (*val).min(min); 808 } else { 809 cfg.memory_reservation_for_growth = Some(min); 810 } 811 } 812 } 813 } 814 } 815 816 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 817 enum OptLevel { 818 None, 819 Speed, 820 SpeedAndSize, 821 } 822 823 impl OptLevel { 824 fn to_wasmtime(&self) -> wasmtime::OptLevel { 825 match self { 826 OptLevel::None => wasmtime::OptLevel::None, 827 OptLevel::Speed => wasmtime::OptLevel::Speed, 828 OptLevel::SpeedAndSize => wasmtime::OptLevel::SpeedAndSize, 829 } 830 } 831 } 832 833 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 834 enum RegallocAlgorithm { 835 Backtracking, 836 // FIXME(#11544 and #11545): rename back to `SinglePass` and handle below 837 // when those issues are fixed 838 TemporarilyDisabledSinglePass, 839 } 840 841 impl RegallocAlgorithm { 842 fn to_wasmtime(&self) -> wasmtime::RegallocAlgorithm { 843 match self { 844 RegallocAlgorithm::Backtracking => wasmtime::RegallocAlgorithm::Backtracking, 845 RegallocAlgorithm::TemporarilyDisabledSinglePass => { 846 wasmtime::RegallocAlgorithm::Backtracking 847 } 848 } 849 } 850 } 851 852 #[derive(Arbitrary, Clone, Copy, Debug, PartialEq, Eq, Hash)] 853 enum IntraModuleInlining { 854 Yes, 855 No, 856 WhenUsingGc, 857 } 858 859 impl std::fmt::Display for IntraModuleInlining { 860 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { 861 match self { 862 IntraModuleInlining::Yes => write!(f, "yes"), 863 IntraModuleInlining::No => write!(f, "no"), 864 IntraModuleInlining::WhenUsingGc => write!(f, "gc"), 865 } 866 } 867 } 868 869 #[derive(Clone, Debug, PartialEq, Eq, Hash)] 870 /// Compiler to use. 871 pub enum CompilerStrategy { 872 /// Cranelift compiler for the native architecture. 873 CraneliftNative, 874 /// Winch compiler. 875 Winch, 876 /// Cranelift compiler for the native architecture. 877 CraneliftPulley, 878 } 879 880 impl CompilerStrategy { 881 /// Configures `config` to use this compilation strategy 882 pub fn configure(&self, config: &mut wasmtime_cli_flags::CommonOptions) { 883 match self { 884 CompilerStrategy::CraneliftNative => { 885 config.codegen.compiler = Some(wasmtime::Strategy::Cranelift); 886 } 887 CompilerStrategy::Winch => { 888 config.codegen.compiler = Some(wasmtime::Strategy::Winch); 889 } 890 CompilerStrategy::CraneliftPulley => { 891 config.codegen.compiler = Some(wasmtime::Strategy::Cranelift); 892 config.target = Some("pulley64".to_string()); 893 } 894 } 895 } 896 } 897 898 impl Arbitrary<'_> for CompilerStrategy { 899 fn arbitrary(u: &mut Unstructured<'_>) -> arbitrary::Result<Self> { 900 // Favor fuzzing native cranelift, but if allowed also enable 901 // winch/pulley. 902 match u.int_in_range(0..=19)? { 903 1 => Ok(Self::CraneliftPulley), 904 2 => Ok(Self::Winch), 905 _ => Ok(Self::CraneliftNative), 906 } 907 } 908 } 909 910 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 911 pub enum Collector { 912 DeferredReferenceCounting, 913 Null, 914 } 915 916 impl Collector { 917 fn to_wasmtime(&self) -> wasmtime::Collector { 918 match self { 919 Collector::DeferredReferenceCounting => wasmtime::Collector::DeferredReferenceCounting, 920 Collector::Null => wasmtime::Collector::Null, 921 } 922 } 923 } 924