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_map, 144 component_model_fixed_length_lists, 145 simd, 146 exceptions, 147 legacy_exceptions: _, 148 custom_descriptors: _, 149 150 hogs_memory: _, 151 nan_canonicalization: _, 152 gc_types: _, 153 stack_switching: _, 154 spec_test: _, 155 } = test.config; 156 157 // Enable/disable some proposals that aren't configurable in wasm-smith 158 // but are configurable in Wasmtime. 159 self.module_config.function_references_enabled = 160 function_references.or(gc).unwrap_or(false); 161 self.module_config.component_model_async = component_model_async.unwrap_or(false); 162 self.module_config.component_model_async_builtins = 163 component_model_async_builtins.unwrap_or(false); 164 self.module_config.component_model_async_stackful = 165 component_model_async_stackful.unwrap_or(false); 166 self.module_config.component_model_threading = component_model_threading.unwrap_or(false); 167 self.module_config.component_model_error_context = 168 component_model_error_context.unwrap_or(false); 169 self.module_config.component_model_gc = component_model_gc.unwrap_or(false); 170 self.module_config.component_model_map = component_model_map.unwrap_or(false); 171 self.module_config.component_model_fixed_length_lists = 172 component_model_fixed_length_lists.unwrap_or(false); 173 174 // Enable/disable proposals that wasm-smith has knobs for which will be 175 // read when creating `wasmtime::Config`. 176 let config = &mut self.module_config.config; 177 config.bulk_memory_enabled = true; 178 config.multi_value_enabled = true; 179 config.wide_arithmetic_enabled = wide_arithmetic.unwrap_or(false); 180 config.memory64_enabled = memory64.unwrap_or(false); 181 config.relaxed_simd_enabled = relaxed_simd.unwrap_or(false); 182 config.simd_enabled = config.relaxed_simd_enabled || simd.unwrap_or(false); 183 config.tail_call_enabled = tail_call.unwrap_or(false); 184 config.custom_page_sizes_enabled = custom_page_sizes.unwrap_or(false); 185 config.threads_enabled = threads.unwrap_or(false); 186 config.shared_everything_threads_enabled = shared_everything_threads.unwrap_or(false); 187 config.gc_enabled = gc.unwrap_or(false); 188 config.reference_types_enabled = config.gc_enabled 189 || self.module_config.function_references_enabled 190 || reference_types.unwrap_or(false); 191 config.extended_const_enabled = extended_const.unwrap_or(false); 192 config.exceptions_enabled = exceptions.unwrap_or(false); 193 if multi_memory.unwrap_or(false) { 194 config.max_memories = limits::MEMORIES_PER_MODULE as usize; 195 } else { 196 config.max_memories = 1; 197 } 198 199 if let Some(n) = &mut self.wasmtime.memory_config.memory_reservation { 200 *n = (*n).max(limits::MEMORY_SIZE as u64); 201 } 202 203 // FIXME: it might be more ideal to avoid the need for this entirely 204 // and to just let the test fail. If a test fails due to a pooling 205 // allocator resource limit being met we could ideally detect that and 206 // let the fuzz test case pass. That would avoid the need to hardcode 207 // so much here and in theory wouldn't reduce the usefulness of fuzzers 208 // all that much. At this time though we can't easily test this configuration. 209 if let InstanceAllocationStrategy::Pooling(pooling) = &mut self.wasmtime.strategy { 210 // Clamp protection keys between 1 & 2 to reduce the number of 211 // slots and then multiply the total memories by the number of keys 212 // we have since a single store has access to only one key. 213 pooling.max_memory_protection_keys = pooling.max_memory_protection_keys.max(1).min(2); 214 pooling.total_memories = pooling 215 .total_memories 216 .max(limits::MEMORIES * (pooling.max_memory_protection_keys as u32)); 217 218 // For other limits make sure they meet the minimum threshold 219 // required for our wast tests. 220 pooling.total_component_instances = pooling 221 .total_component_instances 222 .max(limits::COMPONENT_INSTANCES); 223 pooling.total_tables = pooling.total_tables.max(limits::TABLES); 224 pooling.max_tables_per_module = 225 pooling.max_tables_per_module.max(limits::TABLES_PER_MODULE); 226 pooling.max_memories_per_module = pooling 227 .max_memories_per_module 228 .max(limits::MEMORIES_PER_MODULE); 229 pooling.max_memories_per_component = pooling 230 .max_memories_per_component 231 .max(limits::MEMORIES_PER_MODULE); 232 pooling.total_core_instances = pooling.total_core_instances.max(limits::CORE_INSTANCES); 233 pooling.max_memory_size = pooling.max_memory_size.max(limits::MEMORY_SIZE); 234 pooling.table_elements = pooling.table_elements.max(limits::TABLE_ELEMENTS); 235 pooling.core_instance_size = pooling.core_instance_size.max(limits::CORE_INSTANCE_SIZE); 236 pooling.component_instance_size = pooling 237 .component_instance_size 238 .max(limits::CORE_INSTANCE_SIZE); 239 pooling.total_stacks = pooling.total_stacks.max(limits::TOTAL_STACKS); 240 } 241 242 // Return the test configuration that this fuzz configuration represents 243 // which is used afterwards to test if the `test` here is expected to 244 // fail or not. 245 WastConfig { 246 collector: match self.wasmtime.collector { 247 Collector::Null => wasmtime_test_util::wast::Collector::Null, 248 Collector::DeferredReferenceCounting => { 249 wasmtime_test_util::wast::Collector::DeferredReferenceCounting 250 } 251 }, 252 pooling: matches!( 253 self.wasmtime.strategy, 254 InstanceAllocationStrategy::Pooling(_) 255 ), 256 compiler: match self.wasmtime.compiler_strategy { 257 CompilerStrategy::CraneliftNative => { 258 wasmtime_test_util::wast::Compiler::CraneliftNative 259 } 260 CompilerStrategy::CraneliftPulley => { 261 wasmtime_test_util::wast::Compiler::CraneliftPulley 262 } 263 CompilerStrategy::Winch => wasmtime_test_util::wast::Compiler::Winch, 264 }, 265 } 266 } 267 268 /// Converts this to a `wasmtime::Config` object 269 pub fn to_wasmtime(&self) -> wasmtime::Config { 270 crate::init_fuzzing(); 271 272 let mut cfg = wasmtime_cli_flags::CommonOptions::default(); 273 cfg.codegen.native_unwind_info = 274 Some(cfg!(target_os = "windows") || self.wasmtime.native_unwind_info); 275 cfg.codegen.parallel_compilation = Some(false); 276 277 cfg.debug.address_map = Some(self.wasmtime.generate_address_map); 278 cfg.opts.opt_level = Some(self.wasmtime.opt_level.to_wasmtime()); 279 cfg.opts.regalloc_algorithm = Some(self.wasmtime.regalloc_algorithm.to_wasmtime()); 280 cfg.opts.signals_based_traps = Some(self.wasmtime.signals_based_traps); 281 cfg.opts.memory_guaranteed_dense_image_size = Some(std::cmp::min( 282 // Clamp this at 16MiB so we don't get huge in-memory 283 // images during fuzzing. 284 16 << 20, 285 self.wasmtime.memory_guaranteed_dense_image_size, 286 )); 287 cfg.wasm.async_stack_zeroing = Some(self.wasmtime.async_stack_zeroing); 288 cfg.wasm.bulk_memory = Some(true); 289 cfg.wasm.component_model_async = Some(self.module_config.component_model_async); 290 cfg.wasm.component_model_async_builtins = 291 Some(self.module_config.component_model_async_builtins); 292 cfg.wasm.component_model_async_stackful = 293 Some(self.module_config.component_model_async_stackful); 294 cfg.wasm.component_model_threading = Some(self.module_config.component_model_threading); 295 cfg.wasm.component_model_error_context = 296 Some(self.module_config.component_model_error_context); 297 cfg.wasm.component_model_gc = Some(self.module_config.component_model_gc); 298 cfg.wasm.component_model_map = Some(self.module_config.component_model_map); 299 cfg.wasm.component_model_fixed_length_lists = 300 Some(self.module_config.component_model_fixed_length_lists); 301 cfg.wasm.custom_page_sizes = Some(self.module_config.config.custom_page_sizes_enabled); 302 cfg.wasm.epoch_interruption = Some(self.wasmtime.epoch_interruption); 303 cfg.wasm.extended_const = Some(self.module_config.config.extended_const_enabled); 304 cfg.wasm.fuel = self.wasmtime.consume_fuel.then(|| u64::MAX); 305 cfg.wasm.function_references = Some(self.module_config.function_references_enabled); 306 cfg.wasm.gc = Some(self.module_config.config.gc_enabled); 307 cfg.wasm.memory64 = Some(self.module_config.config.memory64_enabled); 308 cfg.wasm.multi_memory = Some(self.module_config.config.max_memories > 1); 309 cfg.wasm.multi_value = Some(self.module_config.config.multi_value_enabled); 310 cfg.wasm.nan_canonicalization = Some(self.wasmtime.canonicalize_nans); 311 cfg.wasm.reference_types = Some(self.module_config.config.reference_types_enabled); 312 cfg.wasm.simd = Some(self.module_config.config.simd_enabled); 313 cfg.wasm.tail_call = Some(self.module_config.config.tail_call_enabled); 314 cfg.wasm.threads = Some(self.module_config.config.threads_enabled); 315 cfg.wasm.shared_everything_threads = 316 Some(self.module_config.config.shared_everything_threads_enabled); 317 cfg.wasm.wide_arithmetic = Some(self.module_config.config.wide_arithmetic_enabled); 318 cfg.wasm.exceptions = Some(self.module_config.config.exceptions_enabled); 319 cfg.wasm.shared_memory = Some(self.module_config.shared_memory); 320 if !self.module_config.config.simd_enabled { 321 cfg.wasm.relaxed_simd = Some(false); 322 } 323 cfg.codegen.collector = Some(self.wasmtime.collector.to_wasmtime()); 324 325 let compiler_strategy = &self.wasmtime.compiler_strategy; 326 let cranelift_strategy = match compiler_strategy { 327 CompilerStrategy::CraneliftNative | CompilerStrategy::CraneliftPulley => true, 328 CompilerStrategy::Winch => false, 329 }; 330 self.wasmtime.compiler_strategy.configure(&mut cfg); 331 332 self.wasmtime.codegen.configure(&mut cfg); 333 334 // Determine whether we will actually enable PCC -- this is 335 // disabled if the module requires memory64, which is not yet 336 // compatible (due to the need for dynamic checks). 337 let pcc = cfg!(feature = "fuzz-pcc") 338 && self.wasmtime.pcc 339 && !self.module_config.config.memory64_enabled; 340 341 cfg.codegen.inlining = self.wasmtime.inlining; 342 343 // Only set cranelift specific flags when the Cranelift strategy is 344 // chosen. 345 if cranelift_strategy { 346 if let Some(option) = self.wasmtime.inlining_intra_module { 347 cfg.codegen.cranelift.push(( 348 "wasmtime_inlining_intra_module".to_string(), 349 Some(option.to_string()), 350 )); 351 } 352 if let Some(size) = self.wasmtime.inlining_small_callee_size { 353 cfg.codegen.cranelift.push(( 354 "wasmtime_inlining_small_callee_size".to_string(), 355 // Clamp to avoid extreme code size blow up. 356 Some(std::cmp::min(1000, size).to_string()), 357 )); 358 } 359 if let Some(size) = self.wasmtime.inlining_sum_size_threshold { 360 cfg.codegen.cranelift.push(( 361 "wasmtime_inlining_sum_size_threshold".to_string(), 362 // Clamp to avoid extreme code size blow up. 363 Some(std::cmp::min(1000, size).to_string()), 364 )); 365 } 366 367 // If the wasm-smith-generated module use nan canonicalization then we 368 // don't need to enable it, but if it doesn't enable it already then we 369 // enable this codegen option. 370 cfg.wasm.nan_canonicalization = Some(!self.module_config.config.canonicalize_nans); 371 372 // Enabling the verifier will at-least-double compilation time, which 373 // with a 20-30x slowdown in fuzzing can cause issues related to 374 // timeouts. If generated modules can have more than a small handful of 375 // functions then disable the verifier when fuzzing to try to lessen the 376 // impact of timeouts. 377 if self.module_config.config.max_funcs > 10 { 378 cfg.codegen.cranelift_debug_verifier = Some(false); 379 } 380 381 if self.wasmtime.force_jump_veneers { 382 cfg.codegen.cranelift.push(( 383 "wasmtime_linkopt_force_jump_veneer".to_string(), 384 Some("true".to_string()), 385 )); 386 } 387 388 if let Some(pad) = self.wasmtime.padding_between_functions { 389 cfg.codegen.cranelift.push(( 390 "wasmtime_linkopt_padding_between_functions".to_string(), 391 Some(pad.to_string()), 392 )); 393 } 394 395 cfg.codegen.pcc = Some(pcc); 396 397 // Eager init is currently only supported on Cranelift, not Winch. 398 cfg.opts.table_lazy_init = Some(self.wasmtime.table_lazy_init); 399 } 400 401 self.wasmtime.strategy.configure(&mut cfg); 402 403 // Vary the memory configuration, but only if threads are not enabled. 404 // When the threads proposal is enabled we might generate shared memory, 405 // which is less amenable to different memory configurations: 406 // - shared memories are required to be "static" so fuzzing the various 407 // memory configurations will mostly result in uninteresting errors. 408 // The interesting part about shared memories is the runtime so we 409 // don't fuzz non-default settings. 410 // - shared memories are required to be aligned which means that the 411 // `CustomUnaligned` variant isn't actually safe to use with a shared 412 // memory. 413 if !self.module_config.config.threads_enabled { 414 // If PCC is enabled, force other options to be compatible: PCC is currently only 415 // supported when bounds checks are elided. 416 let memory_config = if pcc { 417 MemoryConfig { 418 memory_reservation: Some(4 << 30), // 4 GiB 419 memory_guard_size: Some(2 << 30), // 2 GiB 420 memory_reservation_for_growth: Some(0), 421 guard_before_linear_memory: false, 422 memory_init_cow: true, 423 // Doesn't matter, only using virtual memory. 424 cranelift_enable_heap_access_spectre_mitigations: None, 425 } 426 } else { 427 self.wasmtime.memory_config.clone() 428 }; 429 430 memory_config.configure(&mut cfg); 431 }; 432 433 // If malloc-based memory is going to be used, which requires these four 434 // options set to specific values (and Pulley auto-sets two of them) 435 // then be sure to cap `memory_reservation_for_growth` at a smaller 436 // value than the default. For malloc-based memory reservation beyond 437 // the end of memory isn't captured by `StoreLimiter` so we need to be 438 // sure it's small enough to not blow OOM limits while fuzzing. 439 if ((cfg.opts.signals_based_traps == Some(true) && cfg.opts.memory_guard_size == Some(0)) 440 || self.wasmtime.compiler_strategy == CompilerStrategy::CraneliftPulley) 441 && cfg.opts.memory_reservation == Some(0) 442 && cfg.opts.memory_init_cow == Some(false) 443 { 444 let growth = &mut cfg.opts.memory_reservation_for_growth; 445 let max = 1 << 20; 446 *growth = match *growth { 447 Some(n) => Some(n.min(max)), 448 None => Some(max), 449 }; 450 } 451 452 log::debug!("creating wasmtime config with CLI options:\n{cfg}"); 453 let mut cfg = cfg.config(None).expect("failed to create wasmtime::Config"); 454 455 if self.wasmtime.async_config != AsyncConfig::Disabled { 456 log::debug!("async config in use {:?}", self.wasmtime.async_config); 457 self.wasmtime.async_config.configure(&mut cfg); 458 } 459 460 // Fuzzing on macOS with mach ports seems to sometimes bypass the mach 461 // port handling thread entirely and go straight to asan's or fuzzing's 462 // signal handler. No idea why and for me at least it's just easier to 463 // disable mach ports when fuzzing because there's no need to use that 464 // over signal handlers. 465 if cfg!(target_vendor = "apple") { 466 cfg.macos_use_mach_ports(false); 467 } 468 469 return cfg; 470 } 471 472 /// Convenience function for generating a `Store<T>` using this 473 /// configuration. 474 pub fn to_store(&self) -> Store<StoreLimits> { 475 let engine = Engine::new(&self.to_wasmtime()).unwrap(); 476 let mut store = Store::new(&engine, StoreLimits::new()); 477 self.configure_store(&mut store); 478 store 479 } 480 481 /// Configures a store based on this configuration. 482 pub fn configure_store(&self, store: &mut Store<StoreLimits>) { 483 store.limiter(|s| s as &mut dyn wasmtime::ResourceLimiter); 484 self.configure_store_epoch_and_fuel(store); 485 } 486 487 /// Configures everything unrelated to `T` in a store, such as epochs and 488 /// fuel. 489 pub fn configure_store_epoch_and_fuel<T>(&self, store: &mut Store<T>) { 490 // Configure the store to never abort by default, that is it'll have 491 // max fuel or otherwise trap on an epoch change but the epoch won't 492 // ever change. 493 // 494 // Afterwards though see what `AsyncConfig` is being used an further 495 // refine the store's configuration based on that. 496 if self.wasmtime.consume_fuel { 497 store.set_fuel(u64::MAX).unwrap(); 498 } 499 if self.wasmtime.epoch_interruption { 500 store.epoch_deadline_trap(); 501 store.set_epoch_deadline(1); 502 } 503 match self.wasmtime.async_config { 504 AsyncConfig::Disabled => {} 505 AsyncConfig::YieldWithFuel(amt) => { 506 assert!(self.wasmtime.consume_fuel); 507 store.fuel_async_yield_interval(Some(amt)).unwrap(); 508 } 509 AsyncConfig::YieldWithEpochs { ticks, .. } => { 510 assert!(self.wasmtime.epoch_interruption); 511 store.set_epoch_deadline(ticks); 512 store.epoch_deadline_async_yield_and_update(ticks); 513 } 514 } 515 } 516 517 /// Generates an arbitrary method of timing out an instance, ensuring that 518 /// this configuration supports the returned timeout. 519 pub fn generate_timeout(&mut self, u: &mut Unstructured<'_>) -> arbitrary::Result<Timeout> { 520 let time_duration = Duration::from_millis(100); 521 let timeout = u 522 .choose(&[Timeout::Fuel(100_000), Timeout::Epoch(time_duration)])? 523 .clone(); 524 match &timeout { 525 Timeout::Fuel(..) => { 526 self.wasmtime.consume_fuel = true; 527 } 528 Timeout::Epoch(..) => { 529 self.wasmtime.epoch_interruption = true; 530 } 531 Timeout::None => unreachable!("Not an option given to choose()"), 532 } 533 Ok(timeout) 534 } 535 536 /// Compiles the `wasm` within the `engine` provided. 537 /// 538 /// This notably will use `Module::{serialize,deserialize_file}` to 539 /// round-trip if configured in the fuzzer. 540 pub fn compile(&self, engine: &Engine, wasm: &[u8]) -> Result<Module> { 541 // Propagate this error in case the caller wants to handle 542 // valid-vs-invalid wasm. 543 let module = Module::new(engine, wasm)?; 544 if !self.wasmtime.use_precompiled_cwasm { 545 return Ok(module); 546 } 547 548 // Don't propagate these errors to prevent them from accidentally being 549 // interpreted as invalid wasm, these should never fail on a 550 // well-behaved host system. 551 let dir = tempfile::TempDir::new().unwrap(); 552 let file = dir.path().join("module.wasm"); 553 std::fs::write(&file, module.serialize().unwrap()).unwrap(); 554 unsafe { Ok(Module::deserialize_file(engine, &file).unwrap()) } 555 } 556 557 /// Updates this configuration to forcibly enable async support. Only useful 558 /// in fuzzers which do async calls. 559 pub fn enable_async(&mut self, u: &mut Unstructured<'_>) -> arbitrary::Result<()> { 560 if self.wasmtime.consume_fuel || u.arbitrary()? { 561 self.wasmtime.async_config = 562 AsyncConfig::YieldWithFuel(u.int_in_range(1000..=100_000)?); 563 self.wasmtime.consume_fuel = true; 564 } else { 565 self.wasmtime.async_config = AsyncConfig::YieldWithEpochs { 566 dur: Duration::from_millis(u.int_in_range(1..=10)?), 567 ticks: u.int_in_range(1..=10)?, 568 }; 569 self.wasmtime.epoch_interruption = true; 570 } 571 Ok(()) 572 } 573 } 574 575 impl<'a> Arbitrary<'a> for Config { 576 fn arbitrary(u: &mut Unstructured<'a>) -> arbitrary::Result<Self> { 577 let mut config = Self { 578 wasmtime: u.arbitrary()?, 579 module_config: u.arbitrary()?, 580 }; 581 582 config 583 .wasmtime 584 .update_module_config(&mut config.module_config, u)?; 585 586 Ok(config) 587 } 588 } 589 590 /// Configuration related to `wasmtime::Config` and the various settings which 591 /// can be tweaked from within. 592 #[derive(Arbitrary, Clone, Debug, Eq, Hash, PartialEq)] 593 pub struct WasmtimeConfig { 594 opt_level: OptLevel, 595 regalloc_algorithm: RegallocAlgorithm, 596 debug_info: bool, 597 canonicalize_nans: bool, 598 interruptible: bool, 599 pub(crate) consume_fuel: bool, 600 pub(crate) epoch_interruption: bool, 601 /// The Wasmtime memory configuration to use. 602 pub memory_config: MemoryConfig, 603 force_jump_veneers: bool, 604 memory_init_cow: bool, 605 memory_guaranteed_dense_image_size: u64, 606 inlining: Option<bool>, 607 inlining_intra_module: Option<IntraModuleInlining>, 608 inlining_small_callee_size: Option<u32>, 609 inlining_sum_size_threshold: Option<u32>, 610 use_precompiled_cwasm: bool, 611 async_stack_zeroing: bool, 612 /// Configuration for the instance allocation strategy to use. 613 pub strategy: InstanceAllocationStrategy, 614 codegen: CodegenSettings, 615 padding_between_functions: Option<u16>, 616 generate_address_map: bool, 617 native_unwind_info: bool, 618 /// Configuration for the compiler to use. 619 pub compiler_strategy: CompilerStrategy, 620 collector: Collector, 621 table_lazy_init: bool, 622 623 /// Whether or not fuzzing should enable PCC. 624 pcc: bool, 625 626 /// Configuration for whether wasm is invoked in an async fashion and how 627 /// it's cooperatively time-sliced. 628 pub async_config: AsyncConfig, 629 630 /// Whether or not host signal handlers are enabled for this configuration, 631 /// aka whether signal handlers are supported. 632 signals_based_traps: bool, 633 } 634 635 impl WasmtimeConfig { 636 /// Force `self` to be a configuration compatible with `other`. This is 637 /// useful for differential execution to avoid unhelpful fuzz crashes when 638 /// one engine has a feature enabled and the other does not. 639 pub fn make_compatible_with(&mut self, other: &Self) { 640 // Use the same allocation strategy between the two configs. 641 // 642 // Ideally this wouldn't be necessary, but, during differential 643 // evaluation, if the `lhs` is using ondemand and the `rhs` is using the 644 // pooling allocator (or vice versa), then the module may have been 645 // generated in such a way that is incompatible with the other 646 // allocation strategy. 647 // 648 // We can remove this in the future when it's possible to access the 649 // fields of `wasm_smith::Module` to constrain the pooling allocator 650 // based on what was actually generated. 651 self.strategy = other.strategy.clone(); 652 if let InstanceAllocationStrategy::Pooling { .. } = &other.strategy { 653 // Also use the same memory configuration when using the pooling 654 // allocator. 655 self.memory_config = other.memory_config.clone(); 656 } 657 658 self.make_internally_consistent(); 659 } 660 661 /// Updates `config` to be compatible with `self` and the other way around 662 /// too. 663 pub fn update_module_config( 664 &mut self, 665 config: &mut ModuleConfig, 666 _u: &mut Unstructured<'_>, 667 ) -> arbitrary::Result<()> { 668 match self.compiler_strategy { 669 CompilerStrategy::CraneliftNative => {} 670 671 CompilerStrategy::Winch => { 672 // Winch is not complete on non-x64 targets, so just abandon this test 673 // case. We don't want to force Cranelift because we change what module 674 // config features are enabled based on the compiler strategy, and we 675 // don't want to make the same fuzz input DNA generate different test 676 // cases on different targets. 677 if cfg!(not(any(target_arch = "x86_64", target_arch = "aarch64"))) { 678 log::warn!( 679 "want to compile with Winch but host architecture does not support it" 680 ); 681 return Err(arbitrary::Error::IncorrectFormat); 682 } 683 684 // Winch doesn't support the same set of wasm proposal as Cranelift 685 // at this time, so if winch is selected be sure to disable wasm 686 // proposals in `Config` to ensure that Winch can compile the 687 // module that wasm-smith generates. 688 config.config.relaxed_simd_enabled = false; 689 config.config.gc_enabled = false; 690 config.config.tail_call_enabled = false; 691 config.config.reference_types_enabled = false; 692 config.config.exceptions_enabled = false; 693 config.function_references_enabled = false; 694 695 // Winch's SIMD implementations require AVX and AVX2. 696 if self 697 .codegen_flag("has_avx") 698 .is_some_and(|value| value == "false") 699 || self 700 .codegen_flag("has_avx2") 701 .is_some_and(|value| value == "false") 702 { 703 config.config.simd_enabled = false; 704 } 705 706 // Account for the proposals that are currently only 707 // supported on x64. 708 if cfg!(target_arch = "aarch64") { 709 config.config.simd_enabled = false; 710 config.config.wide_arithmetic_enabled = false; 711 config.config.threads_enabled = false; 712 } 713 714 // Tuning the following engine options is currently not supported 715 // by Winch. 716 self.signals_based_traps = true; 717 self.table_lazy_init = true; 718 self.debug_info = false; 719 } 720 721 CompilerStrategy::CraneliftPulley => { 722 config.config.threads_enabled = false; 723 } 724 } 725 726 // If using the pooling allocator, constrain the memory and module configurations 727 // to the module limits. 728 if let InstanceAllocationStrategy::Pooling(pooling) = &mut self.strategy { 729 // If the pooling allocator is used, do not allow shared memory to 730 // be created. FIXME: see 731 // https://github.com/bytecodealliance/wasmtime/issues/4244. 732 config.config.threads_enabled = false; 733 734 // Ensure the pooling allocator can support the maximal size of 735 // memory, picking the smaller of the two to win. 736 let min_bytes = config 737 .config 738 .max_memory32_bytes 739 // memory64_bytes is a u128, but since we are taking the min 740 // we can truncate it down to a u64. 741 .min( 742 config 743 .config 744 .max_memory64_bytes 745 .try_into() 746 .unwrap_or(u64::MAX), 747 ); 748 let min = min_bytes 749 .min(pooling.max_memory_size as u64) 750 .min(self.memory_config.memory_reservation.unwrap_or(0)); 751 pooling.max_memory_size = min as usize; 752 config.config.max_memory32_bytes = min; 753 config.config.max_memory64_bytes = min as u128; 754 755 // If traps are disallowed then memories must have at least one page 756 // of memory so if we still are only allowing 0 pages of memory then 757 // increase that to one here. 758 if config.config.disallow_traps { 759 if pooling.max_memory_size < (1 << 16) { 760 pooling.max_memory_size = 1 << 16; 761 config.config.max_memory32_bytes = 1 << 16; 762 config.config.max_memory64_bytes = 1 << 16; 763 let cfg = &mut self.memory_config; 764 match &mut cfg.memory_reservation { 765 Some(size) => *size = (*size).max(pooling.max_memory_size as u64), 766 size @ None => *size = Some(pooling.max_memory_size as u64), 767 } 768 } 769 // .. additionally update tables 770 if pooling.table_elements == 0 { 771 pooling.table_elements = 1; 772 } 773 } 774 775 // Don't allow too many linear memories per instance since massive 776 // virtual mappings can fail to get allocated. 777 config.config.min_memories = config.config.min_memories.min(10); 778 config.config.max_memories = config.config.max_memories.min(10); 779 780 // Force this pooling allocator to always be able to accommodate the 781 // module that may be generated. 782 pooling.total_memories = config.config.max_memories as u32; 783 pooling.total_tables = config.config.max_tables as u32; 784 } 785 786 if !self.signals_based_traps { 787 // At this time shared memories require a "static" memory 788 // configuration but when signals-based traps are disabled all 789 // memories are forced to the "dynamic" configuration. This is 790 // fixable with some more work on the bounds-checks side of things 791 // to do a full bounds check even on static memories, but that's 792 // left for a future PR. 793 config.config.threads_enabled = false; 794 795 // Spectre-based heap mitigations require signal handlers so this 796 // must always be disabled if signals-based traps are disabled. 797 self.memory_config 798 .cranelift_enable_heap_access_spectre_mitigations = None; 799 } 800 801 self.make_internally_consistent(); 802 803 Ok(()) 804 } 805 806 /// Returns the codegen flag value, if any, for `name`. 807 pub(crate) fn codegen_flag(&self, name: &str) -> Option<&str> { 808 self.codegen.flags().iter().find_map(|(n, value)| { 809 if n == name { 810 Some(value.as_str()) 811 } else { 812 None 813 } 814 }) 815 } 816 817 /// Helper method to handle some dependencies between various configuration 818 /// options. This is intended to be called whenever a `Config` is created or 819 /// modified to ensure that the final result is an instantiable `Config`. 820 /// 821 /// Note that in general this probably shouldn't exist and anything here can 822 /// be considered a "TODO" to go implement more stuff in Wasmtime to accept 823 /// these sorts of configurations. For now though it's intended to reflect 824 /// the current state of the engine's development. 825 fn make_internally_consistent(&mut self) { 826 if !self.signals_based_traps { 827 let cfg = &mut self.memory_config; 828 // Spectre-based heap mitigations require signal handlers so 829 // this must always be disabled if signals-based traps are 830 // disabled. 831 cfg.cranelift_enable_heap_access_spectre_mitigations = None; 832 833 // With configuration settings that match the use of malloc for 834 // linear memories cap the `memory_reservation_for_growth` value 835 // to something reasonable to avoid OOM in fuzzing. 836 if !cfg.memory_init_cow 837 && cfg.memory_guard_size == Some(0) 838 && cfg.memory_reservation == Some(0) 839 { 840 let min = 10 << 20; // 10 MiB 841 if let Some(val) = &mut cfg.memory_reservation_for_growth { 842 *val = (*val).min(min); 843 } else { 844 cfg.memory_reservation_for_growth = Some(min); 845 } 846 } 847 } 848 } 849 } 850 851 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 852 enum OptLevel { 853 None, 854 Speed, 855 SpeedAndSize, 856 } 857 858 impl OptLevel { 859 fn to_wasmtime(&self) -> wasmtime::OptLevel { 860 match self { 861 OptLevel::None => wasmtime::OptLevel::None, 862 OptLevel::Speed => wasmtime::OptLevel::Speed, 863 OptLevel::SpeedAndSize => wasmtime::OptLevel::SpeedAndSize, 864 } 865 } 866 } 867 868 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 869 enum RegallocAlgorithm { 870 Backtracking, 871 SinglePass, 872 } 873 874 impl RegallocAlgorithm { 875 fn to_wasmtime(&self) -> wasmtime::RegallocAlgorithm { 876 match self { 877 RegallocAlgorithm::Backtracking => wasmtime::RegallocAlgorithm::Backtracking, 878 RegallocAlgorithm::SinglePass => { 879 // FIXME(#11850) 880 const SINGLE_PASS_KNOWN_BUGGY_AT_THIS_TIME: bool = true; 881 if SINGLE_PASS_KNOWN_BUGGY_AT_THIS_TIME { 882 wasmtime::RegallocAlgorithm::Backtracking 883 } else { 884 wasmtime::RegallocAlgorithm::SinglePass 885 } 886 } 887 } 888 } 889 } 890 891 #[derive(Arbitrary, Clone, Copy, Debug, PartialEq, Eq, Hash)] 892 enum IntraModuleInlining { 893 Yes, 894 No, 895 WhenUsingGc, 896 } 897 898 impl std::fmt::Display for IntraModuleInlining { 899 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { 900 match self { 901 IntraModuleInlining::Yes => write!(f, "yes"), 902 IntraModuleInlining::No => write!(f, "no"), 903 IntraModuleInlining::WhenUsingGc => write!(f, "gc"), 904 } 905 } 906 } 907 908 #[derive(Clone, Debug, PartialEq, Eq, Hash)] 909 /// Compiler to use. 910 pub enum CompilerStrategy { 911 /// Cranelift compiler for the native architecture. 912 CraneliftNative, 913 /// Winch compiler. 914 Winch, 915 /// Cranelift compiler for the native architecture. 916 CraneliftPulley, 917 } 918 919 impl CompilerStrategy { 920 /// Configures `config` to use this compilation strategy 921 pub fn configure(&self, config: &mut wasmtime_cli_flags::CommonOptions) { 922 match self { 923 CompilerStrategy::CraneliftNative => { 924 config.codegen.compiler = Some(wasmtime::Strategy::Cranelift); 925 } 926 CompilerStrategy::Winch => { 927 config.codegen.compiler = Some(wasmtime::Strategy::Winch); 928 } 929 CompilerStrategy::CraneliftPulley => { 930 config.codegen.compiler = Some(wasmtime::Strategy::Cranelift); 931 config.target = Some("pulley64".to_string()); 932 } 933 } 934 } 935 } 936 937 impl Arbitrary<'_> for CompilerStrategy { 938 fn arbitrary(u: &mut Unstructured<'_>) -> arbitrary::Result<Self> { 939 // Favor fuzzing native cranelift, but if allowed also enable 940 // winch/pulley. 941 match u.int_in_range(0..=19)? { 942 1 => Ok(Self::CraneliftPulley), 943 2 => Ok(Self::Winch), 944 _ => Ok(Self::CraneliftNative), 945 } 946 } 947 } 948 949 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 950 pub enum Collector { 951 DeferredReferenceCounting, 952 Null, 953 } 954 955 impl Collector { 956 fn to_wasmtime(&self) -> wasmtime::Collector { 957 match self { 958 Collector::DeferredReferenceCounting => wasmtime::Collector::DeferredReferenceCounting, 959 Collector::Null => wasmtime::Collector::Null, 960 } 961 } 962 } 963