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 bulk_memory, 126 memory64, 127 custom_page_sizes, 128 multi_memory, 129 threads, 130 shared_everything_threads, 131 gc, 132 function_references, 133 relaxed_simd, 134 reference_types, 135 tail_call, 136 extended_const, 137 wide_arithmetic, 138 component_model_async, 139 component_model_async_builtins, 140 component_model_async_stackful, 141 component_model_threading, 142 component_model_error_context, 143 component_model_gc, 144 component_model_map, 145 component_model_fixed_length_lists, 146 simd, 147 exceptions, 148 legacy_exceptions: _, 149 custom_descriptors: _, 150 151 hogs_memory: _, 152 nan_canonicalization: _, 153 gc_types: _, 154 stack_switching: _, 155 spec_test: _, 156 } = test.config; 157 158 // Enable/disable some proposals that aren't configurable in wasm-smith 159 // but are configurable in Wasmtime. 160 self.module_config.function_references_enabled = 161 function_references.or(gc).unwrap_or(false); 162 self.module_config.component_model_async = component_model_async.unwrap_or(false); 163 self.module_config.component_model_async_builtins = 164 component_model_async_builtins.unwrap_or(false); 165 self.module_config.component_model_async_stackful = 166 component_model_async_stackful.unwrap_or(false); 167 self.module_config.component_model_threading = component_model_threading.unwrap_or(false); 168 self.module_config.component_model_error_context = 169 component_model_error_context.unwrap_or(false); 170 self.module_config.component_model_gc = component_model_gc.unwrap_or(false); 171 self.module_config.component_model_map = component_model_map.unwrap_or(false); 172 self.module_config.component_model_fixed_length_lists = 173 component_model_fixed_length_lists.unwrap_or(false); 174 175 // Enable/disable proposals that wasm-smith has knobs for which will be 176 // read when creating `wasmtime::Config`. 177 let config = &mut self.module_config.config; 178 config.bulk_memory_enabled = bulk_memory.unwrap_or(false); 179 config.multi_value_enabled = true; 180 config.wide_arithmetic_enabled = wide_arithmetic.unwrap_or(false); 181 config.memory64_enabled = memory64.unwrap_or(false); 182 config.relaxed_simd_enabled = relaxed_simd.unwrap_or(false); 183 config.simd_enabled = config.relaxed_simd_enabled || simd.unwrap_or(false); 184 config.tail_call_enabled = tail_call.unwrap_or(false); 185 config.custom_page_sizes_enabled = custom_page_sizes.unwrap_or(false); 186 config.threads_enabled = threads.unwrap_or(false); 187 config.shared_everything_threads_enabled = shared_everything_threads.unwrap_or(false); 188 config.gc_enabled = gc.unwrap_or(false); 189 config.reference_types_enabled = config.gc_enabled 190 || self.module_config.function_references_enabled 191 || reference_types.unwrap_or(false); 192 config.extended_const_enabled = extended_const.unwrap_or(false); 193 config.exceptions_enabled = exceptions.unwrap_or(false); 194 if multi_memory.unwrap_or(false) { 195 config.max_memories = limits::MEMORIES_PER_MODULE as usize; 196 } else { 197 config.max_memories = 1; 198 } 199 200 if let Some(n) = &mut self.wasmtime.memory_config.memory_reservation { 201 *n = (*n).max(limits::MEMORY_SIZE as u64); 202 } 203 204 // FIXME: it might be more ideal to avoid the need for this entirely 205 // and to just let the test fail. If a test fails due to a pooling 206 // allocator resource limit being met we could ideally detect that and 207 // let the fuzz test case pass. That would avoid the need to hardcode 208 // so much here and in theory wouldn't reduce the usefulness of fuzzers 209 // all that much. At this time though we can't easily test this configuration. 210 if let InstanceAllocationStrategy::Pooling(pooling) = &mut self.wasmtime.strategy { 211 // Clamp protection keys between 1 & 2 to reduce the number of 212 // slots and then multiply the total memories by the number of keys 213 // we have since a single store has access to only one key. 214 pooling.max_memory_protection_keys = pooling.max_memory_protection_keys.max(1).min(2); 215 pooling.total_memories = pooling 216 .total_memories 217 .max(limits::MEMORIES * (pooling.max_memory_protection_keys as u32)); 218 219 // For other limits make sure they meet the minimum threshold 220 // required for our wast tests. 221 pooling.total_component_instances = pooling 222 .total_component_instances 223 .max(limits::COMPONENT_INSTANCES); 224 pooling.total_tables = pooling.total_tables.max(limits::TABLES); 225 pooling.max_tables_per_module = 226 pooling.max_tables_per_module.max(limits::TABLES_PER_MODULE); 227 pooling.max_memories_per_module = pooling 228 .max_memories_per_module 229 .max(limits::MEMORIES_PER_MODULE); 230 pooling.max_memories_per_component = pooling 231 .max_memories_per_component 232 .max(limits::MEMORIES_PER_MODULE); 233 pooling.total_core_instances = pooling.total_core_instances.max(limits::CORE_INSTANCES); 234 pooling.max_memory_size = pooling.max_memory_size.max(limits::MEMORY_SIZE); 235 pooling.table_elements = pooling.table_elements.max(limits::TABLE_ELEMENTS); 236 pooling.core_instance_size = pooling.core_instance_size.max(limits::CORE_INSTANCE_SIZE); 237 pooling.component_instance_size = pooling 238 .component_instance_size 239 .max(limits::CORE_INSTANCE_SIZE); 240 pooling.total_stacks = pooling.total_stacks.max(limits::TOTAL_STACKS); 241 } 242 243 // Return the test configuration that this fuzz configuration represents 244 // which is used afterwards to test if the `test` here is expected to 245 // fail or not. 246 WastConfig { 247 collector: match self.wasmtime.collector { 248 Collector::Null => wasmtime_test_util::wast::Collector::Null, 249 Collector::DeferredReferenceCounting => { 250 wasmtime_test_util::wast::Collector::DeferredReferenceCounting 251 } 252 }, 253 pooling: matches!( 254 self.wasmtime.strategy, 255 InstanceAllocationStrategy::Pooling(_) 256 ), 257 compiler: match self.wasmtime.compiler_strategy { 258 CompilerStrategy::CraneliftNative => { 259 wasmtime_test_util::wast::Compiler::CraneliftNative 260 } 261 CompilerStrategy::CraneliftPulley => { 262 wasmtime_test_util::wast::Compiler::CraneliftPulley 263 } 264 CompilerStrategy::Winch => wasmtime_test_util::wast::Compiler::Winch, 265 }, 266 } 267 } 268 269 /// Converts this to a `wasmtime::Config` object 270 pub fn to_wasmtime(&self) -> wasmtime::Config { 271 crate::init_fuzzing(); 272 273 let mut cfg = wasmtime_cli_flags::CommonOptions::default(); 274 cfg.codegen.native_unwind_info = 275 Some(cfg!(target_os = "windows") || self.wasmtime.native_unwind_info); 276 cfg.codegen.parallel_compilation = Some(false); 277 278 cfg.debug.address_map = Some(self.wasmtime.generate_address_map); 279 cfg.opts.opt_level = Some(self.wasmtime.opt_level.to_wasmtime()); 280 cfg.opts.regalloc_algorithm = Some(self.wasmtime.regalloc_algorithm.to_wasmtime()); 281 cfg.opts.signals_based_traps = Some(self.wasmtime.signals_based_traps); 282 cfg.opts.memory_guaranteed_dense_image_size = Some(std::cmp::min( 283 // Clamp this at 16MiB so we don't get huge in-memory 284 // images during fuzzing. 285 16 << 20, 286 self.wasmtime.memory_guaranteed_dense_image_size, 287 )); 288 cfg.wasm.async_stack_zeroing = Some(self.wasmtime.async_stack_zeroing); 289 cfg.wasm.bulk_memory = Some(self.module_config.config.bulk_memory_enabled); 290 cfg.wasm.component_model_async = Some(self.module_config.component_model_async); 291 cfg.wasm.component_model_async_builtins = 292 Some(self.module_config.component_model_async_builtins); 293 cfg.wasm.component_model_async_stackful = 294 Some(self.module_config.component_model_async_stackful); 295 cfg.wasm.component_model_threading = Some(self.module_config.component_model_threading); 296 cfg.wasm.component_model_error_context = 297 Some(self.module_config.component_model_error_context); 298 cfg.wasm.component_model_gc = Some(self.module_config.component_model_gc); 299 cfg.wasm.component_model_map = Some(self.module_config.component_model_map); 300 cfg.wasm.component_model_fixed_length_lists = 301 Some(self.module_config.component_model_fixed_length_lists); 302 cfg.wasm.custom_page_sizes = Some(self.module_config.config.custom_page_sizes_enabled); 303 cfg.wasm.epoch_interruption = Some(self.wasmtime.epoch_interruption); 304 cfg.wasm.extended_const = Some(self.module_config.config.extended_const_enabled); 305 cfg.wasm.fuel = self.wasmtime.consume_fuel.then(|| u64::MAX); 306 cfg.wasm.function_references = Some(self.module_config.function_references_enabled); 307 cfg.wasm.gc = Some(self.module_config.config.gc_enabled); 308 cfg.wasm.memory64 = Some(self.module_config.config.memory64_enabled); 309 cfg.wasm.multi_memory = Some(self.module_config.config.max_memories > 1); 310 cfg.wasm.multi_value = Some(self.module_config.config.multi_value_enabled); 311 cfg.wasm.nan_canonicalization = Some(self.wasmtime.canonicalize_nans); 312 cfg.wasm.reference_types = Some(self.module_config.config.reference_types_enabled); 313 cfg.wasm.simd = Some(self.module_config.config.simd_enabled); 314 cfg.wasm.tail_call = Some(self.module_config.config.tail_call_enabled); 315 cfg.wasm.threads = Some(self.module_config.config.threads_enabled); 316 cfg.wasm.shared_everything_threads = 317 Some(self.module_config.config.shared_everything_threads_enabled); 318 cfg.wasm.wide_arithmetic = Some(self.module_config.config.wide_arithmetic_enabled); 319 cfg.wasm.exceptions = Some(self.module_config.config.exceptions_enabled); 320 cfg.wasm.shared_memory = Some(self.module_config.shared_memory); 321 if !self.module_config.config.simd_enabled { 322 cfg.wasm.relaxed_simd = Some(false); 323 } 324 cfg.codegen.collector = Some(self.wasmtime.collector.to_wasmtime()); 325 326 let compiler_strategy = &self.wasmtime.compiler_strategy; 327 let cranelift_strategy = match compiler_strategy { 328 CompilerStrategy::CraneliftNative | CompilerStrategy::CraneliftPulley => true, 329 CompilerStrategy::Winch => false, 330 }; 331 self.wasmtime.compiler_strategy.configure(&mut cfg); 332 333 self.wasmtime.codegen.configure(&mut cfg); 334 335 // Determine whether we will actually enable PCC -- this is 336 // disabled if the module requires memory64, which is not yet 337 // compatible (due to the need for dynamic checks). 338 let pcc = cfg!(feature = "fuzz-pcc") 339 && self.wasmtime.pcc 340 && !self.module_config.config.memory64_enabled; 341 342 cfg.codegen.inlining = self.wasmtime.inlining; 343 344 // Only set cranelift specific flags when the Cranelift strategy is 345 // chosen. 346 if cranelift_strategy { 347 if let Some(option) = self.wasmtime.inlining_intra_module { 348 cfg.codegen.cranelift.push(( 349 "wasmtime_inlining_intra_module".to_string(), 350 Some(option.to_string()), 351 )); 352 } 353 if let Some(size) = self.wasmtime.inlining_small_callee_size { 354 cfg.codegen.cranelift.push(( 355 "wasmtime_inlining_small_callee_size".to_string(), 356 // Clamp to avoid extreme code size blow up. 357 Some(std::cmp::min(1000, size).to_string()), 358 )); 359 } 360 if let Some(size) = self.wasmtime.inlining_sum_size_threshold { 361 cfg.codegen.cranelift.push(( 362 "wasmtime_inlining_sum_size_threshold".to_string(), 363 // Clamp to avoid extreme code size blow up. 364 Some(std::cmp::min(1000, size).to_string()), 365 )); 366 } 367 368 // If the wasm-smith-generated module use nan canonicalization then we 369 // don't need to enable it, but if it doesn't enable it already then we 370 // enable this codegen option. 371 cfg.wasm.nan_canonicalization = Some(!self.module_config.config.canonicalize_nans); 372 373 // Enabling the verifier will at-least-double compilation time, which 374 // with a 20-30x slowdown in fuzzing can cause issues related to 375 // timeouts. If generated modules can have more than a small handful of 376 // functions then disable the verifier when fuzzing to try to lessen the 377 // impact of timeouts. 378 if self.module_config.config.max_funcs > 10 { 379 cfg.codegen.cranelift_debug_verifier = Some(false); 380 } 381 382 if self.wasmtime.force_jump_veneers { 383 cfg.codegen.cranelift.push(( 384 "wasmtime_linkopt_force_jump_veneer".to_string(), 385 Some("true".to_string()), 386 )); 387 } 388 389 if let Some(pad) = self.wasmtime.padding_between_functions { 390 cfg.codegen.cranelift.push(( 391 "wasmtime_linkopt_padding_between_functions".to_string(), 392 Some(pad.to_string()), 393 )); 394 } 395 396 cfg.codegen.pcc = Some(pcc); 397 398 // Eager init is currently only supported on Cranelift, not Winch. 399 cfg.opts.table_lazy_init = Some(self.wasmtime.table_lazy_init); 400 } 401 402 self.wasmtime.strategy.configure(&mut cfg); 403 404 // Vary the memory configuration, but only if threads are not enabled. 405 // When the threads proposal is enabled we might generate shared memory, 406 // which is less amenable to different memory configurations: 407 // - shared memories are required to be "static" so fuzzing the various 408 // memory configurations will mostly result in uninteresting errors. 409 // The interesting part about shared memories is the runtime so we 410 // don't fuzz non-default settings. 411 // - shared memories are required to be aligned which means that the 412 // `CustomUnaligned` variant isn't actually safe to use with a shared 413 // memory. 414 if !self.module_config.config.threads_enabled { 415 // If PCC is enabled, force other options to be compatible: PCC is currently only 416 // supported when bounds checks are elided. 417 let memory_config = if pcc { 418 MemoryConfig { 419 memory_reservation: Some(4 << 30), // 4 GiB 420 memory_guard_size: Some(2 << 30), // 2 GiB 421 memory_reservation_for_growth: Some(0), 422 guard_before_linear_memory: false, 423 memory_init_cow: true, 424 // Doesn't matter, only using virtual memory. 425 cranelift_enable_heap_access_spectre_mitigations: None, 426 } 427 } else { 428 self.wasmtime.memory_config.clone() 429 }; 430 431 memory_config.configure(&mut cfg); 432 }; 433 434 // If malloc-based memory is going to be used, which requires these four 435 // options set to specific values (and Pulley auto-sets two of them) 436 // then be sure to cap `memory_reservation_for_growth` at a smaller 437 // value than the default. For malloc-based memory reservation beyond 438 // the end of memory isn't captured by `StoreLimiter` so we need to be 439 // sure it's small enough to not blow OOM limits while fuzzing. 440 if ((cfg.opts.signals_based_traps == Some(true) && cfg.opts.memory_guard_size == Some(0)) 441 || self.wasmtime.compiler_strategy == CompilerStrategy::CraneliftPulley) 442 && cfg.opts.memory_reservation == Some(0) 443 && cfg.opts.memory_init_cow == Some(false) 444 { 445 let growth = &mut cfg.opts.memory_reservation_for_growth; 446 let max = 1 << 20; 447 *growth = match *growth { 448 Some(n) => Some(n.min(max)), 449 None => Some(max), 450 }; 451 } 452 453 log::debug!("creating wasmtime config with CLI options:\n{cfg}"); 454 let mut cfg = cfg.config(None).expect("failed to create wasmtime::Config"); 455 456 if self.wasmtime.async_config != AsyncConfig::Disabled { 457 log::debug!("async config in use {:?}", self.wasmtime.async_config); 458 self.wasmtime.async_config.configure(&mut cfg); 459 } 460 461 // Fuzzing on macOS with mach ports seems to sometimes bypass the mach 462 // port handling thread entirely and go straight to asan's or fuzzing's 463 // signal handler. No idea why and for me at least it's just easier to 464 // disable mach ports when fuzzing because there's no need to use that 465 // over signal handlers. 466 if cfg!(target_vendor = "apple") { 467 cfg.macos_use_mach_ports(false); 468 } 469 470 return cfg; 471 } 472 473 /// Convenience function for generating a `Store<T>` using this 474 /// configuration. 475 pub fn to_store(&self) -> Store<StoreLimits> { 476 let engine = Engine::new(&self.to_wasmtime()).unwrap(); 477 let mut store = Store::new(&engine, StoreLimits::new()); 478 self.configure_store(&mut store); 479 store 480 } 481 482 /// Configures a store based on this configuration. 483 pub fn configure_store(&self, store: &mut Store<StoreLimits>) { 484 store.limiter(|s| s as &mut dyn wasmtime::ResourceLimiter); 485 self.configure_store_epoch_and_fuel(store); 486 } 487 488 /// Configures everything unrelated to `T` in a store, such as epochs and 489 /// fuel. 490 pub fn configure_store_epoch_and_fuel<T>(&self, store: &mut Store<T>) { 491 // Configure the store to never abort by default, that is it'll have 492 // max fuel or otherwise trap on an epoch change but the epoch won't 493 // ever change. 494 // 495 // Afterwards though see what `AsyncConfig` is being used an further 496 // refine the store's configuration based on that. 497 if self.wasmtime.consume_fuel { 498 store.set_fuel(u64::MAX).unwrap(); 499 } 500 if self.wasmtime.epoch_interruption { 501 store.epoch_deadline_trap(); 502 store.set_epoch_deadline(1); 503 } 504 match self.wasmtime.async_config { 505 AsyncConfig::Disabled => {} 506 AsyncConfig::YieldWithFuel(amt) => { 507 assert!(self.wasmtime.consume_fuel); 508 store.fuel_async_yield_interval(Some(amt)).unwrap(); 509 } 510 AsyncConfig::YieldWithEpochs { ticks, .. } => { 511 assert!(self.wasmtime.epoch_interruption); 512 store.set_epoch_deadline(ticks); 513 store.epoch_deadline_async_yield_and_update(ticks); 514 } 515 } 516 } 517 518 /// Generates an arbitrary method of timing out an instance, ensuring that 519 /// this configuration supports the returned timeout. 520 pub fn generate_timeout(&mut self, u: &mut Unstructured<'_>) -> arbitrary::Result<Timeout> { 521 let time_duration = Duration::from_millis(100); 522 let timeout = u 523 .choose(&[Timeout::Fuel(100_000), Timeout::Epoch(time_duration)])? 524 .clone(); 525 match &timeout { 526 Timeout::Fuel(..) => { 527 self.wasmtime.consume_fuel = true; 528 } 529 Timeout::Epoch(..) => { 530 self.wasmtime.epoch_interruption = true; 531 } 532 Timeout::None => unreachable!("Not an option given to choose()"), 533 } 534 Ok(timeout) 535 } 536 537 /// Compiles the `wasm` within the `engine` provided. 538 /// 539 /// This notably will use `Module::{serialize,deserialize_file}` to 540 /// round-trip if configured in the fuzzer. 541 pub fn compile(&self, engine: &Engine, wasm: &[u8]) -> Result<Module> { 542 // Propagate this error in case the caller wants to handle 543 // valid-vs-invalid wasm. 544 let module = Module::new(engine, wasm)?; 545 if !self.wasmtime.use_precompiled_cwasm { 546 return Ok(module); 547 } 548 549 // Don't propagate these errors to prevent them from accidentally being 550 // interpreted as invalid wasm, these should never fail on a 551 // well-behaved host system. 552 let dir = tempfile::TempDir::new().unwrap(); 553 let file = dir.path().join("module.wasm"); 554 std::fs::write(&file, module.serialize().unwrap()).unwrap(); 555 unsafe { Ok(Module::deserialize_file(engine, &file).unwrap()) } 556 } 557 558 /// Updates this configuration to forcibly enable async support. Only useful 559 /// in fuzzers which do async calls. 560 pub fn enable_async(&mut self, u: &mut Unstructured<'_>) -> arbitrary::Result<()> { 561 if self.wasmtime.consume_fuel || u.arbitrary()? { 562 self.wasmtime.async_config = 563 AsyncConfig::YieldWithFuel(u.int_in_range(1000..=100_000)?); 564 self.wasmtime.consume_fuel = true; 565 } else { 566 self.wasmtime.async_config = AsyncConfig::YieldWithEpochs { 567 dur: Duration::from_millis(u.int_in_range(1..=10)?), 568 ticks: u.int_in_range(1..=10)?, 569 }; 570 self.wasmtime.epoch_interruption = true; 571 } 572 Ok(()) 573 } 574 } 575 576 impl<'a> Arbitrary<'a> for Config { 577 fn arbitrary(u: &mut Unstructured<'a>) -> arbitrary::Result<Self> { 578 let mut config = Self { 579 wasmtime: u.arbitrary()?, 580 module_config: u.arbitrary()?, 581 }; 582 583 config 584 .wasmtime 585 .update_module_config(&mut config.module_config, u)?; 586 587 Ok(config) 588 } 589 } 590 591 /// Configuration related to `wasmtime::Config` and the various settings which 592 /// can be tweaked from within. 593 #[derive(Arbitrary, Clone, Debug, Eq, Hash, PartialEq)] 594 pub struct WasmtimeConfig { 595 opt_level: OptLevel, 596 regalloc_algorithm: RegallocAlgorithm, 597 debug_info: bool, 598 canonicalize_nans: bool, 599 interruptible: bool, 600 pub(crate) consume_fuel: bool, 601 pub(crate) epoch_interruption: bool, 602 /// The Wasmtime memory configuration to use. 603 pub memory_config: MemoryConfig, 604 force_jump_veneers: bool, 605 memory_init_cow: bool, 606 memory_guaranteed_dense_image_size: u64, 607 inlining: Option<bool>, 608 inlining_intra_module: Option<IntraModuleInlining>, 609 inlining_small_callee_size: Option<u32>, 610 inlining_sum_size_threshold: Option<u32>, 611 use_precompiled_cwasm: bool, 612 async_stack_zeroing: bool, 613 /// Configuration for the instance allocation strategy to use. 614 pub strategy: InstanceAllocationStrategy, 615 codegen: CodegenSettings, 616 padding_between_functions: Option<u16>, 617 generate_address_map: bool, 618 native_unwind_info: bool, 619 /// Configuration for the compiler to use. 620 pub compiler_strategy: CompilerStrategy, 621 collector: Collector, 622 table_lazy_init: bool, 623 624 /// Whether or not fuzzing should enable PCC. 625 pcc: bool, 626 627 /// Configuration for whether wasm is invoked in an async fashion and how 628 /// it's cooperatively time-sliced. 629 pub async_config: AsyncConfig, 630 631 /// Whether or not host signal handlers are enabled for this configuration, 632 /// aka whether signal handlers are supported. 633 signals_based_traps: bool, 634 } 635 636 impl WasmtimeConfig { 637 /// Force `self` to be a configuration compatible with `other`. This is 638 /// useful for differential execution to avoid unhelpful fuzz crashes when 639 /// one engine has a feature enabled and the other does not. 640 pub fn make_compatible_with(&mut self, other: &Self) { 641 // Use the same allocation strategy between the two configs. 642 // 643 // Ideally this wouldn't be necessary, but, during differential 644 // evaluation, if the `lhs` is using ondemand and the `rhs` is using the 645 // pooling allocator (or vice versa), then the module may have been 646 // generated in such a way that is incompatible with the other 647 // allocation strategy. 648 // 649 // We can remove this in the future when it's possible to access the 650 // fields of `wasm_smith::Module` to constrain the pooling allocator 651 // based on what was actually generated. 652 self.strategy = other.strategy.clone(); 653 if let InstanceAllocationStrategy::Pooling { .. } = &other.strategy { 654 // Also use the same memory configuration when using the pooling 655 // allocator. 656 self.memory_config = other.memory_config.clone(); 657 } 658 659 self.make_internally_consistent(); 660 } 661 662 /// Updates `config` to be compatible with `self` and the other way around 663 /// too. 664 pub fn update_module_config( 665 &mut self, 666 config: &mut ModuleConfig, 667 _u: &mut Unstructured<'_>, 668 ) -> arbitrary::Result<()> { 669 match self.compiler_strategy { 670 CompilerStrategy::CraneliftNative => {} 671 672 CompilerStrategy::Winch => { 673 // Winch is not complete on non-x64 targets, so just abandon this test 674 // case. We don't want to force Cranelift because we change what module 675 // config features are enabled based on the compiler strategy, and we 676 // don't want to make the same fuzz input DNA generate different test 677 // cases on different targets. 678 if cfg!(not(any(target_arch = "x86_64", target_arch = "aarch64"))) { 679 log::warn!( 680 "want to compile with Winch but host architecture does not support it" 681 ); 682 return Err(arbitrary::Error::IncorrectFormat); 683 } 684 685 // Winch doesn't support the same set of wasm proposal as Cranelift 686 // at this time, so if winch is selected be sure to disable wasm 687 // proposals in `Config` to ensure that Winch can compile the 688 // module that wasm-smith generates. 689 config.config.relaxed_simd_enabled = false; 690 config.config.gc_enabled = false; 691 config.config.tail_call_enabled = false; 692 config.config.reference_types_enabled = false; 693 config.config.exceptions_enabled = false; 694 config.function_references_enabled = false; 695 696 // Winch's SIMD implementations require AVX and AVX2. 697 if self 698 .codegen_flag("has_avx") 699 .is_some_and(|value| value == "false") 700 || self 701 .codegen_flag("has_avx2") 702 .is_some_and(|value| value == "false") 703 { 704 config.config.simd_enabled = false; 705 } 706 707 // Account for the proposals that are currently only 708 // supported on x64. 709 if cfg!(target_arch = "aarch64") { 710 config.config.simd_enabled = false; 711 config.config.wide_arithmetic_enabled = false; 712 config.config.threads_enabled = false; 713 } 714 715 // Tuning the following engine options is currently not supported 716 // by Winch. 717 self.signals_based_traps = true; 718 self.table_lazy_init = true; 719 self.debug_info = false; 720 } 721 722 CompilerStrategy::CraneliftPulley => { 723 config.config.threads_enabled = false; 724 } 725 } 726 727 // If using the pooling allocator, constrain the memory and module configurations 728 // to the module limits. 729 if let InstanceAllocationStrategy::Pooling(pooling) = &mut self.strategy { 730 // If the pooling allocator is used, do not allow shared memory to 731 // be created. FIXME: see 732 // https://github.com/bytecodealliance/wasmtime/issues/4244. 733 config.config.threads_enabled = false; 734 735 // Ensure the pooling allocator can support the maximal size of 736 // memory, picking the smaller of the two to win. 737 let min_bytes = config 738 .config 739 .max_memory32_bytes 740 // memory64_bytes is a u128, but since we are taking the min 741 // we can truncate it down to a u64. 742 .min( 743 config 744 .config 745 .max_memory64_bytes 746 .try_into() 747 .unwrap_or(u64::MAX), 748 ); 749 let min = min_bytes 750 .min(pooling.max_memory_size as u64) 751 .min(self.memory_config.memory_reservation.unwrap_or(0)); 752 pooling.max_memory_size = min as usize; 753 config.config.max_memory32_bytes = min; 754 config.config.max_memory64_bytes = min as u128; 755 756 // If traps are disallowed then memories must have at least one page 757 // of memory so if we still are only allowing 0 pages of memory then 758 // increase that to one here. 759 if config.config.disallow_traps { 760 if pooling.max_memory_size < (1 << 16) { 761 pooling.max_memory_size = 1 << 16; 762 config.config.max_memory32_bytes = 1 << 16; 763 config.config.max_memory64_bytes = 1 << 16; 764 let cfg = &mut self.memory_config; 765 match &mut cfg.memory_reservation { 766 Some(size) => *size = (*size).max(pooling.max_memory_size as u64), 767 size @ None => *size = Some(pooling.max_memory_size as u64), 768 } 769 } 770 // .. additionally update tables 771 if pooling.table_elements == 0 { 772 pooling.table_elements = 1; 773 } 774 } 775 776 // Don't allow too many linear memories per instance since massive 777 // virtual mappings can fail to get allocated. 778 config.config.min_memories = config.config.min_memories.min(10); 779 config.config.max_memories = config.config.max_memories.min(10); 780 781 // Force this pooling allocator to always be able to accommodate the 782 // module that may be generated. 783 pooling.total_memories = config.config.max_memories as u32; 784 pooling.total_tables = config.config.max_tables as u32; 785 } 786 787 if !self.signals_based_traps { 788 // At this time shared memories require a "static" memory 789 // configuration but when signals-based traps are disabled all 790 // memories are forced to the "dynamic" configuration. This is 791 // fixable with some more work on the bounds-checks side of things 792 // to do a full bounds check even on static memories, but that's 793 // left for a future PR. 794 config.config.threads_enabled = false; 795 796 // Spectre-based heap mitigations require signal handlers so this 797 // must always be disabled if signals-based traps are disabled. 798 self.memory_config 799 .cranelift_enable_heap_access_spectre_mitigations = None; 800 } 801 802 self.make_internally_consistent(); 803 804 Ok(()) 805 } 806 807 /// Returns the codegen flag value, if any, for `name`. 808 pub(crate) fn codegen_flag(&self, name: &str) -> Option<&str> { 809 self.codegen.flags().iter().find_map(|(n, value)| { 810 if n == name { 811 Some(value.as_str()) 812 } else { 813 None 814 } 815 }) 816 } 817 818 /// Helper method to handle some dependencies between various configuration 819 /// options. This is intended to be called whenever a `Config` is created or 820 /// modified to ensure that the final result is an instantiable `Config`. 821 /// 822 /// Note that in general this probably shouldn't exist and anything here can 823 /// be considered a "TODO" to go implement more stuff in Wasmtime to accept 824 /// these sorts of configurations. For now though it's intended to reflect 825 /// the current state of the engine's development. 826 fn make_internally_consistent(&mut self) { 827 if !self.signals_based_traps { 828 let cfg = &mut self.memory_config; 829 // Spectre-based heap mitigations require signal handlers so 830 // this must always be disabled if signals-based traps are 831 // disabled. 832 cfg.cranelift_enable_heap_access_spectre_mitigations = None; 833 834 // With configuration settings that match the use of malloc for 835 // linear memories cap the `memory_reservation_for_growth` value 836 // to something reasonable to avoid OOM in fuzzing. 837 if !cfg.memory_init_cow 838 && cfg.memory_guard_size == Some(0) 839 && cfg.memory_reservation == Some(0) 840 { 841 let min = 10 << 20; // 10 MiB 842 if let Some(val) = &mut cfg.memory_reservation_for_growth { 843 *val = (*val).min(min); 844 } else { 845 cfg.memory_reservation_for_growth = Some(min); 846 } 847 } 848 } 849 } 850 } 851 852 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 853 enum OptLevel { 854 None, 855 Speed, 856 SpeedAndSize, 857 } 858 859 impl OptLevel { 860 fn to_wasmtime(&self) -> wasmtime::OptLevel { 861 match self { 862 OptLevel::None => wasmtime::OptLevel::None, 863 OptLevel::Speed => wasmtime::OptLevel::Speed, 864 OptLevel::SpeedAndSize => wasmtime::OptLevel::SpeedAndSize, 865 } 866 } 867 } 868 869 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 870 enum RegallocAlgorithm { 871 Backtracking, 872 SinglePass, 873 } 874 875 impl RegallocAlgorithm { 876 fn to_wasmtime(&self) -> wasmtime::RegallocAlgorithm { 877 match self { 878 RegallocAlgorithm::Backtracking => wasmtime::RegallocAlgorithm::Backtracking, 879 RegallocAlgorithm::SinglePass => { 880 // FIXME(#11850) 881 const SINGLE_PASS_KNOWN_BUGGY_AT_THIS_TIME: bool = true; 882 if SINGLE_PASS_KNOWN_BUGGY_AT_THIS_TIME { 883 wasmtime::RegallocAlgorithm::Backtracking 884 } else { 885 wasmtime::RegallocAlgorithm::SinglePass 886 } 887 } 888 } 889 } 890 } 891 892 #[derive(Arbitrary, Clone, Copy, Debug, PartialEq, Eq, Hash)] 893 enum IntraModuleInlining { 894 Yes, 895 No, 896 WhenUsingGc, 897 } 898 899 impl std::fmt::Display for IntraModuleInlining { 900 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { 901 match self { 902 IntraModuleInlining::Yes => write!(f, "yes"), 903 IntraModuleInlining::No => write!(f, "no"), 904 IntraModuleInlining::WhenUsingGc => write!(f, "gc"), 905 } 906 } 907 } 908 909 #[derive(Clone, Debug, PartialEq, Eq, Hash)] 910 /// Compiler to use. 911 pub enum CompilerStrategy { 912 /// Cranelift compiler for the native architecture. 913 CraneliftNative, 914 /// Winch compiler. 915 Winch, 916 /// Cranelift compiler for the native architecture. 917 CraneliftPulley, 918 } 919 920 impl CompilerStrategy { 921 /// Configures `config` to use this compilation strategy 922 pub fn configure(&self, config: &mut wasmtime_cli_flags::CommonOptions) { 923 match self { 924 CompilerStrategy::CraneliftNative => { 925 config.codegen.compiler = Some(wasmtime::Strategy::Cranelift); 926 } 927 CompilerStrategy::Winch => { 928 config.codegen.compiler = Some(wasmtime::Strategy::Winch); 929 } 930 CompilerStrategy::CraneliftPulley => { 931 config.codegen.compiler = Some(wasmtime::Strategy::Cranelift); 932 config.target = Some("pulley64".to_string()); 933 } 934 } 935 } 936 } 937 938 impl Arbitrary<'_> for CompilerStrategy { 939 fn arbitrary(u: &mut Unstructured<'_>) -> arbitrary::Result<Self> { 940 // Favor fuzzing native cranelift, but if allowed also enable 941 // winch/pulley. 942 match u.int_in_range(0..=19)? { 943 1 => Ok(Self::CraneliftPulley), 944 2 => Ok(Self::Winch), 945 _ => Ok(Self::CraneliftNative), 946 } 947 } 948 } 949 950 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 951 pub enum Collector { 952 DeferredReferenceCounting, 953 Null, 954 } 955 956 impl Collector { 957 fn to_wasmtime(&self) -> wasmtime::Collector { 958 match self { 959 Collector::DeferredReferenceCounting => wasmtime::Collector::DeferredReferenceCounting, 960 Collector::Null => wasmtime::Collector::Null, 961 } 962 } 963 } 964