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 arbitrary::{Arbitrary, Unstructured}; 6 use std::time::Duration; 7 use wasmtime::Result; 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_threading, 141 component_model_error_context, 142 component_model_gc, 143 component_model_fixed_length_lists, 144 simd, 145 exceptions, 146 legacy_exceptions: _, 147 custom_descriptors: _, 148 149 hogs_memory: _, 150 nan_canonicalization: _, 151 gc_types: _, 152 stack_switching: _, 153 spec_test: _, 154 } = test.config; 155 156 // Enable/disable some proposals that aren't configurable in wasm-smith 157 // but are configurable in Wasmtime. 158 self.module_config.function_references_enabled = 159 function_references.or(gc).unwrap_or(false); 160 self.module_config.component_model_async = component_model_async.unwrap_or(false); 161 self.module_config.component_model_async_builtins = 162 component_model_async_builtins.unwrap_or(false); 163 self.module_config.component_model_async_stackful = 164 component_model_async_stackful.unwrap_or(false); 165 self.module_config.component_model_threading = component_model_threading.unwrap_or(false); 166 self.module_config.component_model_error_context = 167 component_model_error_context.unwrap_or(false); 168 self.module_config.component_model_gc = component_model_gc.unwrap_or(false); 169 self.module_config.component_model_fixed_length_lists = 170 component_model_fixed_length_lists.unwrap_or(false); 171 172 // Enable/disable proposals that wasm-smith has knobs for which will be 173 // read when creating `wasmtime::Config`. 174 let config = &mut self.module_config.config; 175 config.bulk_memory_enabled = true; 176 config.multi_value_enabled = true; 177 config.wide_arithmetic_enabled = wide_arithmetic.unwrap_or(false); 178 config.memory64_enabled = memory64.unwrap_or(false); 179 config.relaxed_simd_enabled = relaxed_simd.unwrap_or(false); 180 config.simd_enabled = config.relaxed_simd_enabled || simd.unwrap_or(false); 181 config.tail_call_enabled = tail_call.unwrap_or(false); 182 config.custom_page_sizes_enabled = custom_page_sizes.unwrap_or(false); 183 config.threads_enabled = threads.unwrap_or(false); 184 config.shared_everything_threads_enabled = shared_everything_threads.unwrap_or(false); 185 config.gc_enabled = gc.unwrap_or(false); 186 config.reference_types_enabled = config.gc_enabled 187 || self.module_config.function_references_enabled 188 || reference_types.unwrap_or(false); 189 config.extended_const_enabled = extended_const.unwrap_or(false); 190 config.exceptions_enabled = exceptions.unwrap_or(false); 191 if multi_memory.unwrap_or(false) { 192 config.max_memories = limits::MEMORIES_PER_MODULE as usize; 193 } else { 194 config.max_memories = 1; 195 } 196 197 if let Some(n) = &mut self.wasmtime.memory_config.memory_reservation { 198 *n = (*n).max(limits::MEMORY_SIZE as u64); 199 } 200 201 // FIXME: it might be more ideal to avoid the need for this entirely 202 // and to just let the test fail. If a test fails due to a pooling 203 // allocator resource limit being met we could ideally detect that and 204 // let the fuzz test case pass. That would avoid the need to hardcode 205 // so much here and in theory wouldn't reduce the usefulness of fuzzers 206 // all that much. At this time though we can't easily test this configuration. 207 if let InstanceAllocationStrategy::Pooling(pooling) = &mut self.wasmtime.strategy { 208 // Clamp protection keys between 1 & 2 to reduce the number of 209 // slots and then multiply the total memories by the number of keys 210 // we have since a single store has access to only one key. 211 pooling.max_memory_protection_keys = pooling.max_memory_protection_keys.max(1).min(2); 212 pooling.total_memories = pooling 213 .total_memories 214 .max(limits::MEMORIES * (pooling.max_memory_protection_keys as u32)); 215 216 // For other limits make sure they meet the minimum threshold 217 // required for our wast tests. 218 pooling.total_component_instances = pooling 219 .total_component_instances 220 .max(limits::COMPONENT_INSTANCES); 221 pooling.total_tables = pooling.total_tables.max(limits::TABLES); 222 pooling.max_tables_per_module = 223 pooling.max_tables_per_module.max(limits::TABLES_PER_MODULE); 224 pooling.max_memories_per_module = pooling 225 .max_memories_per_module 226 .max(limits::MEMORIES_PER_MODULE); 227 pooling.max_memories_per_component = pooling 228 .max_memories_per_component 229 .max(limits::MEMORIES_PER_MODULE); 230 pooling.total_core_instances = pooling.total_core_instances.max(limits::CORE_INSTANCES); 231 pooling.max_memory_size = pooling.max_memory_size.max(limits::MEMORY_SIZE); 232 pooling.table_elements = pooling.table_elements.max(limits::TABLE_ELEMENTS); 233 pooling.core_instance_size = pooling.core_instance_size.max(limits::CORE_INSTANCE_SIZE); 234 pooling.component_instance_size = pooling 235 .component_instance_size 236 .max(limits::CORE_INSTANCE_SIZE); 237 pooling.total_stacks = pooling.total_stacks.max(limits::TOTAL_STACKS); 238 } 239 240 // Return the test configuration that this fuzz configuration represents 241 // which is used afterwards to test if the `test` here is expected to 242 // fail or not. 243 WastConfig { 244 collector: match self.wasmtime.collector { 245 Collector::Null => wasmtime_test_util::wast::Collector::Null, 246 Collector::DeferredReferenceCounting => { 247 wasmtime_test_util::wast::Collector::DeferredReferenceCounting 248 } 249 }, 250 pooling: matches!( 251 self.wasmtime.strategy, 252 InstanceAllocationStrategy::Pooling(_) 253 ), 254 compiler: match self.wasmtime.compiler_strategy { 255 CompilerStrategy::CraneliftNative => { 256 wasmtime_test_util::wast::Compiler::CraneliftNative 257 } 258 CompilerStrategy::CraneliftPulley => { 259 wasmtime_test_util::wast::Compiler::CraneliftPulley 260 } 261 CompilerStrategy::Winch => wasmtime_test_util::wast::Compiler::Winch, 262 }, 263 } 264 } 265 266 /// Converts this to a `wasmtime::Config` object 267 pub fn to_wasmtime(&self) -> wasmtime::Config { 268 crate::init_fuzzing(); 269 270 let mut cfg = wasmtime_cli_flags::CommonOptions::default(); 271 cfg.codegen.native_unwind_info = 272 Some(cfg!(target_os = "windows") || self.wasmtime.native_unwind_info); 273 cfg.codegen.parallel_compilation = Some(false); 274 275 cfg.debug.address_map = Some(self.wasmtime.generate_address_map); 276 cfg.opts.opt_level = Some(self.wasmtime.opt_level.to_wasmtime()); 277 cfg.opts.regalloc_algorithm = Some(self.wasmtime.regalloc_algorithm.to_wasmtime()); 278 cfg.opts.signals_based_traps = Some(self.wasmtime.signals_based_traps); 279 cfg.opts.memory_guaranteed_dense_image_size = Some(std::cmp::min( 280 // Clamp this at 16MiB so we don't get huge in-memory 281 // images during fuzzing. 282 16 << 20, 283 self.wasmtime.memory_guaranteed_dense_image_size, 284 )); 285 cfg.wasm.async_stack_zeroing = Some(self.wasmtime.async_stack_zeroing); 286 cfg.wasm.bulk_memory = Some(true); 287 cfg.wasm.component_model_async = Some(self.module_config.component_model_async); 288 cfg.wasm.component_model_async_builtins = 289 Some(self.module_config.component_model_async_builtins); 290 cfg.wasm.component_model_async_stackful = 291 Some(self.module_config.component_model_async_stackful); 292 cfg.wasm.component_model_threading = Some(self.module_config.component_model_threading); 293 cfg.wasm.component_model_error_context = 294 Some(self.module_config.component_model_error_context); 295 cfg.wasm.component_model_gc = Some(self.module_config.component_model_gc); 296 cfg.wasm.component_model_fixed_length_lists = 297 Some(self.module_config.component_model_fixed_length_lists); 298 cfg.wasm.custom_page_sizes = Some(self.module_config.config.custom_page_sizes_enabled); 299 cfg.wasm.epoch_interruption = Some(self.wasmtime.epoch_interruption); 300 cfg.wasm.extended_const = Some(self.module_config.config.extended_const_enabled); 301 cfg.wasm.fuel = self.wasmtime.consume_fuel.then(|| u64::MAX); 302 cfg.wasm.function_references = Some(self.module_config.function_references_enabled); 303 cfg.wasm.gc = Some(self.module_config.config.gc_enabled); 304 cfg.wasm.memory64 = Some(self.module_config.config.memory64_enabled); 305 cfg.wasm.multi_memory = Some(self.module_config.config.max_memories > 1); 306 cfg.wasm.multi_value = Some(self.module_config.config.multi_value_enabled); 307 cfg.wasm.nan_canonicalization = Some(self.wasmtime.canonicalize_nans); 308 cfg.wasm.reference_types = Some(self.module_config.config.reference_types_enabled); 309 cfg.wasm.simd = Some(self.module_config.config.simd_enabled); 310 cfg.wasm.tail_call = Some(self.module_config.config.tail_call_enabled); 311 cfg.wasm.threads = Some(self.module_config.config.threads_enabled); 312 cfg.wasm.shared_everything_threads = 313 Some(self.module_config.config.shared_everything_threads_enabled); 314 cfg.wasm.wide_arithmetic = Some(self.module_config.config.wide_arithmetic_enabled); 315 cfg.wasm.exceptions = Some(self.module_config.config.exceptions_enabled); 316 cfg.wasm.shared_memory = Some(self.module_config.shared_memory); 317 if !self.module_config.config.simd_enabled { 318 cfg.wasm.relaxed_simd = Some(false); 319 } 320 cfg.codegen.collector = Some(self.wasmtime.collector.to_wasmtime()); 321 322 let compiler_strategy = &self.wasmtime.compiler_strategy; 323 let cranelift_strategy = match compiler_strategy { 324 CompilerStrategy::CraneliftNative | CompilerStrategy::CraneliftPulley => true, 325 CompilerStrategy::Winch => false, 326 }; 327 self.wasmtime.compiler_strategy.configure(&mut cfg); 328 329 self.wasmtime.codegen.configure(&mut cfg); 330 331 // Determine whether we will actually enable PCC -- this is 332 // disabled if the module requires memory64, which is not yet 333 // compatible (due to the need for dynamic checks). 334 let pcc = cfg!(feature = "fuzz-pcc") 335 && self.wasmtime.pcc 336 && !self.module_config.config.memory64_enabled; 337 338 cfg.codegen.inlining = self.wasmtime.inlining; 339 340 // Only set cranelift specific flags when the Cranelift strategy is 341 // chosen. 342 if cranelift_strategy { 343 if let Some(option) = self.wasmtime.inlining_intra_module { 344 cfg.codegen.cranelift.push(( 345 "wasmtime_inlining_intra_module".to_string(), 346 Some(option.to_string()), 347 )); 348 } 349 if let Some(size) = self.wasmtime.inlining_small_callee_size { 350 cfg.codegen.cranelift.push(( 351 "wasmtime_inlining_small_callee_size".to_string(), 352 // Clamp to avoid extreme code size blow up. 353 Some(std::cmp::min(1000, size).to_string()), 354 )); 355 } 356 if let Some(size) = self.wasmtime.inlining_sum_size_threshold { 357 cfg.codegen.cranelift.push(( 358 "wasmtime_inlining_sum_size_threshold".to_string(), 359 // Clamp to avoid extreme code size blow up. 360 Some(std::cmp::min(1000, size).to_string()), 361 )); 362 } 363 364 // If the wasm-smith-generated module use nan canonicalization then we 365 // don't need to enable it, but if it doesn't enable it already then we 366 // enable this codegen option. 367 cfg.wasm.nan_canonicalization = Some(!self.module_config.config.canonicalize_nans); 368 369 // Enabling the verifier will at-least-double compilation time, which 370 // with a 20-30x slowdown in fuzzing can cause issues related to 371 // timeouts. If generated modules can have more than a small handful of 372 // functions then disable the verifier when fuzzing to try to lessen the 373 // impact of timeouts. 374 if self.module_config.config.max_funcs > 10 { 375 cfg.codegen.cranelift_debug_verifier = Some(false); 376 } 377 378 if self.wasmtime.force_jump_veneers { 379 cfg.codegen.cranelift.push(( 380 "wasmtime_linkopt_force_jump_veneer".to_string(), 381 Some("true".to_string()), 382 )); 383 } 384 385 if let Some(pad) = self.wasmtime.padding_between_functions { 386 cfg.codegen.cranelift.push(( 387 "wasmtime_linkopt_padding_between_functions".to_string(), 388 Some(pad.to_string()), 389 )); 390 } 391 392 cfg.codegen.pcc = Some(pcc); 393 394 // Eager init is currently only supported on Cranelift, not Winch. 395 cfg.opts.table_lazy_init = Some(self.wasmtime.table_lazy_init); 396 } 397 398 self.wasmtime.strategy.configure(&mut cfg); 399 400 // Vary the memory configuration, but only if threads are not enabled. 401 // When the threads proposal is enabled we might generate shared memory, 402 // which is less amenable to different memory configurations: 403 // - shared memories are required to be "static" so fuzzing the various 404 // memory configurations will mostly result in uninteresting errors. 405 // The interesting part about shared memories is the runtime so we 406 // don't fuzz non-default settings. 407 // - shared memories are required to be aligned which means that the 408 // `CustomUnaligned` variant isn't actually safe to use with a shared 409 // memory. 410 if !self.module_config.config.threads_enabled { 411 // If PCC is enabled, force other options to be compatible: PCC is currently only 412 // supported when bounds checks are elided. 413 let memory_config = if pcc { 414 MemoryConfig { 415 memory_reservation: Some(4 << 30), // 4 GiB 416 memory_guard_size: Some(2 << 30), // 2 GiB 417 memory_reservation_for_growth: Some(0), 418 guard_before_linear_memory: false, 419 memory_init_cow: true, 420 // Doesn't matter, only using virtual memory. 421 cranelift_enable_heap_access_spectre_mitigations: None, 422 } 423 } else { 424 self.wasmtime.memory_config.clone() 425 }; 426 427 memory_config.configure(&mut cfg); 428 }; 429 430 // If malloc-based memory is going to be used, which requires these four 431 // options set to specific values (and Pulley auto-sets two of them) 432 // then be sure to cap `memory_reservation_for_growth` at a smaller 433 // value than the default. For malloc-based memory reservation beyond 434 // the end of memory isn't captured by `StoreLimiter` so we need to be 435 // sure it's small enough to not blow OOM limits while fuzzing. 436 if ((cfg.opts.signals_based_traps == Some(true) && cfg.opts.memory_guard_size == Some(0)) 437 || self.wasmtime.compiler_strategy == CompilerStrategy::CraneliftPulley) 438 && cfg.opts.memory_reservation == Some(0) 439 && cfg.opts.memory_init_cow == Some(false) 440 { 441 let growth = &mut cfg.opts.memory_reservation_for_growth; 442 let max = 1 << 20; 443 *growth = match *growth { 444 Some(n) => Some(n.min(max)), 445 None => Some(max), 446 }; 447 } 448 449 log::debug!("creating wasmtime config with CLI options:\n{cfg}"); 450 let mut cfg = cfg.config(None).expect("failed to create wasmtime::Config"); 451 452 if self.wasmtime.async_config != AsyncConfig::Disabled { 453 log::debug!("async config in use {:?}", self.wasmtime.async_config); 454 self.wasmtime.async_config.configure(&mut cfg); 455 } 456 457 // Fuzzing on macOS with mach ports seems to sometimes bypass the mach 458 // port handling thread entirely and go straight to asan's or fuzzing's 459 // signal handler. No idea why and for me at least it's just easier to 460 // disable mach ports when fuzzing because there's no need to use that 461 // over signal handlers. 462 if cfg!(target_vendor = "apple") { 463 cfg.macos_use_mach_ports(false); 464 } 465 466 return cfg; 467 } 468 469 /// Convenience function for generating a `Store<T>` using this 470 /// configuration. 471 pub fn to_store(&self) -> Store<StoreLimits> { 472 let engine = Engine::new(&self.to_wasmtime()).unwrap(); 473 let mut store = Store::new(&engine, StoreLimits::new()); 474 self.configure_store(&mut store); 475 store 476 } 477 478 /// Configures a store based on this configuration. 479 pub fn configure_store(&self, store: &mut Store<StoreLimits>) { 480 store.limiter(|s| s as &mut dyn wasmtime::ResourceLimiter); 481 self.configure_store_epoch_and_fuel(store); 482 } 483 484 /// Configures everything unrelated to `T` in a store, such as epochs and 485 /// fuel. 486 pub fn configure_store_epoch_and_fuel<T>(&self, store: &mut Store<T>) { 487 // Configure the store to never abort by default, that is it'll have 488 // max fuel or otherwise trap on an epoch change but the epoch won't 489 // ever change. 490 // 491 // Afterwards though see what `AsyncConfig` is being used an further 492 // refine the store's configuration based on that. 493 if self.wasmtime.consume_fuel { 494 store.set_fuel(u64::MAX).unwrap(); 495 } 496 if self.wasmtime.epoch_interruption { 497 store.epoch_deadline_trap(); 498 store.set_epoch_deadline(1); 499 } 500 match self.wasmtime.async_config { 501 AsyncConfig::Disabled => {} 502 AsyncConfig::YieldWithFuel(amt) => { 503 assert!(self.wasmtime.consume_fuel); 504 store.fuel_async_yield_interval(Some(amt)).unwrap(); 505 } 506 AsyncConfig::YieldWithEpochs { ticks, .. } => { 507 assert!(self.wasmtime.epoch_interruption); 508 store.set_epoch_deadline(ticks); 509 store.epoch_deadline_async_yield_and_update(ticks); 510 } 511 } 512 } 513 514 /// Generates an arbitrary method of timing out an instance, ensuring that 515 /// this configuration supports the returned timeout. 516 pub fn generate_timeout(&mut self, u: &mut Unstructured<'_>) -> arbitrary::Result<Timeout> { 517 let time_duration = Duration::from_millis(100); 518 let timeout = u 519 .choose(&[Timeout::Fuel(100_000), Timeout::Epoch(time_duration)])? 520 .clone(); 521 match &timeout { 522 Timeout::Fuel(..) => { 523 self.wasmtime.consume_fuel = true; 524 } 525 Timeout::Epoch(..) => { 526 self.wasmtime.epoch_interruption = true; 527 } 528 Timeout::None => unreachable!("Not an option given to choose()"), 529 } 530 Ok(timeout) 531 } 532 533 /// Compiles the `wasm` within the `engine` provided. 534 /// 535 /// This notably will use `Module::{serialize,deserialize_file}` to 536 /// round-trip if configured in the fuzzer. 537 pub fn compile(&self, engine: &Engine, wasm: &[u8]) -> Result<Module> { 538 // Propagate this error in case the caller wants to handle 539 // valid-vs-invalid wasm. 540 let module = Module::new(engine, wasm)?; 541 if !self.wasmtime.use_precompiled_cwasm { 542 return Ok(module); 543 } 544 545 // Don't propagate these errors to prevent them from accidentally being 546 // interpreted as invalid wasm, these should never fail on a 547 // well-behaved host system. 548 let dir = tempfile::TempDir::new().unwrap(); 549 let file = dir.path().join("module.wasm"); 550 std::fs::write(&file, module.serialize().unwrap()).unwrap(); 551 unsafe { Ok(Module::deserialize_file(engine, &file).unwrap()) } 552 } 553 554 /// Updates this configuration to forcibly enable async support. Only useful 555 /// in fuzzers which do async calls. 556 pub fn enable_async(&mut self, u: &mut Unstructured<'_>) -> arbitrary::Result<()> { 557 if self.wasmtime.consume_fuel || u.arbitrary()? { 558 self.wasmtime.async_config = 559 AsyncConfig::YieldWithFuel(u.int_in_range(1000..=100_000)?); 560 self.wasmtime.consume_fuel = true; 561 } else { 562 self.wasmtime.async_config = AsyncConfig::YieldWithEpochs { 563 dur: Duration::from_millis(u.int_in_range(1..=10)?), 564 ticks: u.int_in_range(1..=10)?, 565 }; 566 self.wasmtime.epoch_interruption = true; 567 } 568 Ok(()) 569 } 570 } 571 572 impl<'a> Arbitrary<'a> for Config { 573 fn arbitrary(u: &mut Unstructured<'a>) -> arbitrary::Result<Self> { 574 let mut config = Self { 575 wasmtime: u.arbitrary()?, 576 module_config: u.arbitrary()?, 577 }; 578 579 config 580 .wasmtime 581 .update_module_config(&mut config.module_config, u)?; 582 583 Ok(config) 584 } 585 } 586 587 /// Configuration related to `wasmtime::Config` and the various settings which 588 /// can be tweaked from within. 589 #[derive(Arbitrary, Clone, Debug, Eq, Hash, PartialEq)] 590 pub struct WasmtimeConfig { 591 opt_level: OptLevel, 592 regalloc_algorithm: RegallocAlgorithm, 593 debug_info: bool, 594 canonicalize_nans: bool, 595 interruptible: bool, 596 pub(crate) consume_fuel: bool, 597 pub(crate) epoch_interruption: bool, 598 /// The Wasmtime memory configuration to use. 599 pub memory_config: MemoryConfig, 600 force_jump_veneers: bool, 601 memory_init_cow: bool, 602 memory_guaranteed_dense_image_size: u64, 603 inlining: Option<bool>, 604 inlining_intra_module: Option<IntraModuleInlining>, 605 inlining_small_callee_size: Option<u32>, 606 inlining_sum_size_threshold: Option<u32>, 607 use_precompiled_cwasm: bool, 608 async_stack_zeroing: bool, 609 /// Configuration for the instance allocation strategy to use. 610 pub strategy: InstanceAllocationStrategy, 611 codegen: CodegenSettings, 612 padding_between_functions: Option<u16>, 613 generate_address_map: bool, 614 native_unwind_info: bool, 615 /// Configuration for the compiler to use. 616 pub compiler_strategy: CompilerStrategy, 617 collector: Collector, 618 table_lazy_init: bool, 619 620 /// Whether or not fuzzing should enable PCC. 621 pcc: bool, 622 623 /// Configuration for whether wasm is invoked in an async fashion and how 624 /// it's cooperatively time-sliced. 625 pub async_config: AsyncConfig, 626 627 /// Whether or not host signal handlers are enabled for this configuration, 628 /// aka whether signal handlers are supported. 629 signals_based_traps: bool, 630 } 631 632 impl WasmtimeConfig { 633 /// Force `self` to be a configuration compatible with `other`. This is 634 /// useful for differential execution to avoid unhelpful fuzz crashes when 635 /// one engine has a feature enabled and the other does not. 636 pub fn make_compatible_with(&mut self, other: &Self) { 637 // Use the same allocation strategy between the two configs. 638 // 639 // Ideally this wouldn't be necessary, but, during differential 640 // evaluation, if the `lhs` is using ondemand and the `rhs` is using the 641 // pooling allocator (or vice versa), then the module may have been 642 // generated in such a way that is incompatible with the other 643 // allocation strategy. 644 // 645 // We can remove this in the future when it's possible to access the 646 // fields of `wasm_smith::Module` to constrain the pooling allocator 647 // based on what was actually generated. 648 self.strategy = other.strategy.clone(); 649 if let InstanceAllocationStrategy::Pooling { .. } = &other.strategy { 650 // Also use the same memory configuration when using the pooling 651 // allocator. 652 self.memory_config = other.memory_config.clone(); 653 } 654 655 self.make_internally_consistent(); 656 } 657 658 /// Updates `config` to be compatible with `self` and the other way around 659 /// too. 660 pub fn update_module_config( 661 &mut self, 662 config: &mut ModuleConfig, 663 _u: &mut Unstructured<'_>, 664 ) -> arbitrary::Result<()> { 665 match self.compiler_strategy { 666 CompilerStrategy::CraneliftNative => {} 667 668 CompilerStrategy::Winch => { 669 // Winch is not complete on non-x64 targets, so just abandon this test 670 // case. We don't want to force Cranelift because we change what module 671 // config features are enabled based on the compiler strategy, and we 672 // don't want to make the same fuzz input DNA generate different test 673 // cases on different targets. 674 if cfg!(not(any(target_arch = "x86_64", target_arch = "aarch64"))) { 675 log::warn!( 676 "want to compile with Winch but host architecture does not support it" 677 ); 678 return Err(arbitrary::Error::IncorrectFormat); 679 } 680 681 // Winch doesn't support the same set of wasm proposal as Cranelift 682 // at this time, so if winch is selected be sure to disable wasm 683 // proposals in `Config` to ensure that Winch can compile the 684 // module that wasm-smith generates. 685 config.config.relaxed_simd_enabled = false; 686 config.config.gc_enabled = false; 687 config.config.tail_call_enabled = false; 688 config.config.reference_types_enabled = false; 689 config.config.exceptions_enabled = false; 690 config.function_references_enabled = false; 691 692 // Winch's SIMD implementations require AVX and AVX2. 693 if self 694 .codegen_flag("has_avx") 695 .is_some_and(|value| value == "false") 696 || self 697 .codegen_flag("has_avx2") 698 .is_some_and(|value| value == "false") 699 { 700 config.config.simd_enabled = false; 701 } 702 703 // Account for the proposals that are currently only 704 // supported on x64. 705 if cfg!(target_arch = "aarch64") { 706 config.config.simd_enabled = false; 707 config.config.wide_arithmetic_enabled = false; 708 config.config.threads_enabled = false; 709 } 710 711 // Tuning the following engine options is currently not supported 712 // by Winch. 713 self.signals_based_traps = true; 714 self.table_lazy_init = true; 715 self.debug_info = false; 716 } 717 718 CompilerStrategy::CraneliftPulley => { 719 config.config.threads_enabled = false; 720 } 721 } 722 723 // If using the pooling allocator, constrain the memory and module configurations 724 // to the module limits. 725 if let InstanceAllocationStrategy::Pooling(pooling) = &mut self.strategy { 726 // If the pooling allocator is used, do not allow shared memory to 727 // be created. FIXME: see 728 // https://github.com/bytecodealliance/wasmtime/issues/4244. 729 config.config.threads_enabled = false; 730 731 // Ensure the pooling allocator can support the maximal size of 732 // memory, picking the smaller of the two to win. 733 let min_bytes = config 734 .config 735 .max_memory32_bytes 736 // memory64_bytes is a u128, but since we are taking the min 737 // we can truncate it down to a u64. 738 .min( 739 config 740 .config 741 .max_memory64_bytes 742 .try_into() 743 .unwrap_or(u64::MAX), 744 ); 745 let min = min_bytes 746 .min(pooling.max_memory_size as u64) 747 .min(self.memory_config.memory_reservation.unwrap_or(0)); 748 pooling.max_memory_size = min as usize; 749 config.config.max_memory32_bytes = min; 750 config.config.max_memory64_bytes = min as u128; 751 752 // If traps are disallowed then memories must have at least one page 753 // of memory so if we still are only allowing 0 pages of memory then 754 // increase that to one here. 755 if config.config.disallow_traps { 756 if pooling.max_memory_size < (1 << 16) { 757 pooling.max_memory_size = 1 << 16; 758 config.config.max_memory32_bytes = 1 << 16; 759 config.config.max_memory64_bytes = 1 << 16; 760 let cfg = &mut self.memory_config; 761 match &mut cfg.memory_reservation { 762 Some(size) => *size = (*size).max(pooling.max_memory_size as u64), 763 size @ None => *size = Some(pooling.max_memory_size as u64), 764 } 765 } 766 // .. additionally update tables 767 if pooling.table_elements == 0 { 768 pooling.table_elements = 1; 769 } 770 } 771 772 // Don't allow too many linear memories per instance since massive 773 // virtual mappings can fail to get allocated. 774 config.config.min_memories = config.config.min_memories.min(10); 775 config.config.max_memories = config.config.max_memories.min(10); 776 777 // Force this pooling allocator to always be able to accommodate the 778 // module that may be generated. 779 pooling.total_memories = config.config.max_memories as u32; 780 pooling.total_tables = config.config.max_tables as u32; 781 } 782 783 if !self.signals_based_traps { 784 // At this time shared memories require a "static" memory 785 // configuration but when signals-based traps are disabled all 786 // memories are forced to the "dynamic" configuration. This is 787 // fixable with some more work on the bounds-checks side of things 788 // to do a full bounds check even on static memories, but that's 789 // left for a future PR. 790 config.config.threads_enabled = false; 791 792 // Spectre-based heap mitigations require signal handlers so this 793 // must always be disabled if signals-based traps are disabled. 794 self.memory_config 795 .cranelift_enable_heap_access_spectre_mitigations = None; 796 } 797 798 self.make_internally_consistent(); 799 800 Ok(()) 801 } 802 803 /// Returns the codegen flag value, if any, for `name`. 804 pub(crate) fn codegen_flag(&self, name: &str) -> Option<&str> { 805 self.codegen.flags().iter().find_map(|(n, value)| { 806 if n == name { 807 Some(value.as_str()) 808 } else { 809 None 810 } 811 }) 812 } 813 814 /// Helper method to handle some dependencies between various configuration 815 /// options. This is intended to be called whenever a `Config` is created or 816 /// modified to ensure that the final result is an instantiable `Config`. 817 /// 818 /// Note that in general this probably shouldn't exist and anything here can 819 /// be considered a "TODO" to go implement more stuff in Wasmtime to accept 820 /// these sorts of configurations. For now though it's intended to reflect 821 /// the current state of the engine's development. 822 fn make_internally_consistent(&mut self) { 823 if !self.signals_based_traps { 824 let cfg = &mut self.memory_config; 825 // Spectre-based heap mitigations require signal handlers so 826 // this must always be disabled if signals-based traps are 827 // disabled. 828 cfg.cranelift_enable_heap_access_spectre_mitigations = None; 829 830 // With configuration settings that match the use of malloc for 831 // linear memories cap the `memory_reservation_for_growth` value 832 // to something reasonable to avoid OOM in fuzzing. 833 if !cfg.memory_init_cow 834 && cfg.memory_guard_size == Some(0) 835 && cfg.memory_reservation == Some(0) 836 { 837 let min = 10 << 20; // 10 MiB 838 if let Some(val) = &mut cfg.memory_reservation_for_growth { 839 *val = (*val).min(min); 840 } else { 841 cfg.memory_reservation_for_growth = Some(min); 842 } 843 } 844 } 845 } 846 } 847 848 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 849 enum OptLevel { 850 None, 851 Speed, 852 SpeedAndSize, 853 } 854 855 impl OptLevel { 856 fn to_wasmtime(&self) -> wasmtime::OptLevel { 857 match self { 858 OptLevel::None => wasmtime::OptLevel::None, 859 OptLevel::Speed => wasmtime::OptLevel::Speed, 860 OptLevel::SpeedAndSize => wasmtime::OptLevel::SpeedAndSize, 861 } 862 } 863 } 864 865 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 866 enum RegallocAlgorithm { 867 Backtracking, 868 SinglePass, 869 } 870 871 impl RegallocAlgorithm { 872 fn to_wasmtime(&self) -> wasmtime::RegallocAlgorithm { 873 match self { 874 RegallocAlgorithm::Backtracking => wasmtime::RegallocAlgorithm::Backtracking, 875 RegallocAlgorithm::SinglePass => { 876 // FIXME(#11850) 877 const SINGLE_PASS_KNOWN_BUGGY_AT_THIS_TIME: bool = true; 878 if SINGLE_PASS_KNOWN_BUGGY_AT_THIS_TIME { 879 wasmtime::RegallocAlgorithm::Backtracking 880 } else { 881 wasmtime::RegallocAlgorithm::SinglePass 882 } 883 } 884 } 885 } 886 } 887 888 #[derive(Arbitrary, Clone, Copy, Debug, PartialEq, Eq, Hash)] 889 enum IntraModuleInlining { 890 Yes, 891 No, 892 WhenUsingGc, 893 } 894 895 impl std::fmt::Display for IntraModuleInlining { 896 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { 897 match self { 898 IntraModuleInlining::Yes => write!(f, "yes"), 899 IntraModuleInlining::No => write!(f, "no"), 900 IntraModuleInlining::WhenUsingGc => write!(f, "gc"), 901 } 902 } 903 } 904 905 #[derive(Clone, Debug, PartialEq, Eq, Hash)] 906 /// Compiler to use. 907 pub enum CompilerStrategy { 908 /// Cranelift compiler for the native architecture. 909 CraneliftNative, 910 /// Winch compiler. 911 Winch, 912 /// Cranelift compiler for the native architecture. 913 CraneliftPulley, 914 } 915 916 impl CompilerStrategy { 917 /// Configures `config` to use this compilation strategy 918 pub fn configure(&self, config: &mut wasmtime_cli_flags::CommonOptions) { 919 match self { 920 CompilerStrategy::CraneliftNative => { 921 config.codegen.compiler = Some(wasmtime::Strategy::Cranelift); 922 } 923 CompilerStrategy::Winch => { 924 config.codegen.compiler = Some(wasmtime::Strategy::Winch); 925 } 926 CompilerStrategy::CraneliftPulley => { 927 config.codegen.compiler = Some(wasmtime::Strategy::Cranelift); 928 config.target = Some("pulley64".to_string()); 929 } 930 } 931 } 932 } 933 934 impl Arbitrary<'_> for CompilerStrategy { 935 fn arbitrary(u: &mut Unstructured<'_>) -> arbitrary::Result<Self> { 936 // Favor fuzzing native cranelift, but if allowed also enable 937 // winch/pulley. 938 match u.int_in_range(0..=19)? { 939 1 => Ok(Self::CraneliftPulley), 940 2 => Ok(Self::Winch), 941 _ => Ok(Self::CraneliftNative), 942 } 943 } 944 } 945 946 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 947 pub enum Collector { 948 DeferredReferenceCounting, 949 Null, 950 } 951 952 impl Collector { 953 fn to_wasmtime(&self) -> wasmtime::Collector { 954 match self { 955 Collector::DeferredReferenceCounting => wasmtime::Collector::DeferredReferenceCounting, 956 Collector::Null => wasmtime::Collector::Null, 957 } 958 } 959 } 960