1 //! Generate a configuration for both Wasmtime and the Wasm module to execute. 2 3 use super::{AsyncConfig, CodegenSettings, InstanceAllocationStrategy, MemoryConfig, ModuleConfig}; 4 use crate::oracles::{StoreLimits, Timeout}; 5 use anyhow::Result; 6 use arbitrary::{Arbitrary, Unstructured}; 7 use std::time::Duration; 8 use wasmtime::{Enabled, Engine, Module, Store}; 9 use wasmtime_test_util::wast::{WastConfig, WastTest, limits}; 10 11 /// Configuration for `wasmtime::Config` and generated modules for a session of 12 /// fuzzing. 13 /// 14 /// This configuration guides what modules are generated, how wasmtime 15 /// configuration is generated, and is typically itself generated through a call 16 /// to `Arbitrary` which allows for a form of "swarm testing". 17 #[derive(Debug, Clone)] 18 pub struct Config { 19 /// Configuration related to the `wasmtime::Config`. 20 pub wasmtime: WasmtimeConfig, 21 /// Configuration related to generated modules. 22 pub module_config: ModuleConfig, 23 } 24 25 impl Config { 26 /// Indicates that this configuration is being used for differential 27 /// execution. 28 /// 29 /// The purpose of this function is to update the configuration which was 30 /// generated to be compatible with execution in multiple engines. The goal 31 /// is to produce the exact same result in all engines so we need to paper 32 /// over things like nan differences and memory/table behavior differences. 33 pub fn set_differential_config(&mut self) { 34 let config = &mut self.module_config.config; 35 36 // Make it more likely that there are types available to generate a 37 // function with. 38 config.min_types = config.min_types.max(1); 39 config.max_types = config.max_types.max(1); 40 41 // Generate at least one function 42 config.min_funcs = config.min_funcs.max(1); 43 config.max_funcs = config.max_funcs.max(1); 44 45 // Allow a memory to be generated, but don't let it get too large. 46 // Additionally require the maximum size to guarantee that the growth 47 // behavior is consistent across engines. 48 config.max_memory32_bytes = 10 << 16; 49 config.max_memory64_bytes = 10 << 16; 50 config.memory_max_size_required = true; 51 52 // If tables are generated make sure they don't get too large to avoid 53 // hitting any engine-specific limit. Additionally ensure that the 54 // maximum size is required to guarantee consistent growth across 55 // engines. 56 // 57 // Note that while reference types are disabled below, only allow one 58 // table. 59 config.max_table_elements = 1_000; 60 config.table_max_size_required = true; 61 62 // Don't allow any imports 63 config.max_imports = 0; 64 65 // Try to get the function and the memory exported 66 config.export_everything = true; 67 68 // NaN is canonicalized at the wasm level for differential fuzzing so we 69 // can paper over NaN differences between engines. 70 config.canonicalize_nans = true; 71 72 // If using the pooling allocator, update the instance limits too 73 if let InstanceAllocationStrategy::Pooling(pooling) = &mut self.wasmtime.strategy { 74 // One single-page memory 75 pooling.total_memories = config.max_memories as u32; 76 pooling.max_memory_size = 10 << 16; 77 pooling.max_memories_per_module = config.max_memories as u32; 78 if pooling.memory_protection_keys == Enabled::Auto 79 && pooling.max_memory_protection_keys > 1 80 { 81 pooling.total_memories = 82 pooling.total_memories * (pooling.max_memory_protection_keys as u32); 83 } 84 85 pooling.total_tables = config.max_tables as u32; 86 pooling.table_elements = 1_000; 87 pooling.max_tables_per_module = config.max_tables as u32; 88 89 pooling.core_instance_size = 1_000_000; 90 91 let cfg = &mut self.wasmtime.memory_config; 92 match &mut cfg.memory_reservation { 93 Some(size) => *size = (*size).max(pooling.max_memory_size as u64), 94 other @ None => *other = Some(pooling.max_memory_size as u64), 95 } 96 } 97 98 // These instructions are explicitly not expected to be exactly the same 99 // across engines. Don't fuzz them. 100 config.relaxed_simd_enabled = false; 101 } 102 103 /// Uses this configuration and the supplied source of data to generate 104 /// a wasm module. 105 /// 106 /// If a `default_fuel` is provided, the resulting module will be configured 107 /// to ensure termination; as doing so will add an additional global to the module, 108 /// the pooling allocator, if configured, will also have its globals limit updated. 109 pub fn generate( 110 &self, 111 input: &mut Unstructured<'_>, 112 default_fuel: Option<u32>, 113 ) -> arbitrary::Result<wasm_smith::Module> { 114 self.module_config.generate(input, default_fuel) 115 } 116 117 /// Updates this configuration to be able to run the `test` specified. 118 /// 119 /// This primarily updates `self.module_config` to ensure that it enables 120 /// all features and proposals necessary to execute the `test` specified. 121 /// This will additionally update limits in the pooling allocator to be able 122 /// to execute all tests. 123 pub fn make_wast_test_compliant(&mut self, test: &WastTest) -> WastConfig { 124 let wasmtime_test_util::wast::TestConfig { 125 memory64, 126 custom_page_sizes, 127 multi_memory, 128 threads, 129 shared_everything_threads, 130 gc, 131 function_references, 132 relaxed_simd, 133 reference_types, 134 tail_call, 135 extended_const, 136 wide_arithmetic, 137 component_model_async, 138 component_model_async_builtins, 139 component_model_async_stackful, 140 component_model_threading, 141 component_model_error_context, 142 component_model_gc, 143 simd, 144 exceptions, 145 legacy_exceptions: _, 146 custom_descriptors: _, 147 148 hogs_memory: _, 149 nan_canonicalization: _, 150 gc_types: _, 151 stack_switching: _, 152 spec_test: _, 153 } = test.config; 154 155 // Enable/disable some proposals that aren't configurable in wasm-smith 156 // but are configurable in Wasmtime. 157 self.module_config.function_references_enabled = 158 function_references.or(gc).unwrap_or(false); 159 self.module_config.component_model_async = component_model_async.unwrap_or(false); 160 self.module_config.component_model_async_builtins = 161 component_model_async_builtins.unwrap_or(false); 162 self.module_config.component_model_async_stackful = 163 component_model_async_stackful.unwrap_or(false); 164 self.module_config.component_model_threading = component_model_threading.unwrap_or(false); 165 self.module_config.component_model_error_context = 166 component_model_error_context.unwrap_or(false); 167 self.module_config.component_model_gc = component_model_gc.unwrap_or(false); 168 169 // Enable/disable proposals that wasm-smith has knobs for which will be 170 // read when creating `wasmtime::Config`. 171 let config = &mut self.module_config.config; 172 config.bulk_memory_enabled = true; 173 config.multi_value_enabled = true; 174 config.wide_arithmetic_enabled = wide_arithmetic.unwrap_or(false); 175 config.memory64_enabled = memory64.unwrap_or(false); 176 config.relaxed_simd_enabled = relaxed_simd.unwrap_or(false); 177 config.simd_enabled = config.relaxed_simd_enabled || simd.unwrap_or(false); 178 config.tail_call_enabled = tail_call.unwrap_or(false); 179 config.custom_page_sizes_enabled = custom_page_sizes.unwrap_or(false); 180 config.threads_enabled = threads.unwrap_or(false); 181 config.shared_everything_threads_enabled = shared_everything_threads.unwrap_or(false); 182 config.gc_enabled = gc.unwrap_or(false); 183 config.reference_types_enabled = config.gc_enabled 184 || self.module_config.function_references_enabled 185 || reference_types.unwrap_or(false); 186 config.extended_const_enabled = extended_const.unwrap_or(false); 187 config.exceptions_enabled = exceptions.unwrap_or(false); 188 if multi_memory.unwrap_or(false) { 189 config.max_memories = limits::MEMORIES_PER_MODULE as usize; 190 } else { 191 config.max_memories = 1; 192 } 193 194 if let Some(n) = &mut self.wasmtime.memory_config.memory_reservation { 195 *n = (*n).max(limits::MEMORY_SIZE as u64); 196 } 197 198 // FIXME: it might be more ideal to avoid the need for this entirely 199 // and to just let the test fail. If a test fails due to a pooling 200 // allocator resource limit being met we could ideally detect that and 201 // let the fuzz test case pass. That would avoid the need to hardcode 202 // so much here and in theory wouldn't reduce the usefulness of fuzzers 203 // all that much. At this time though we can't easily test this configuration. 204 if let InstanceAllocationStrategy::Pooling(pooling) = &mut self.wasmtime.strategy { 205 // Clamp protection keys between 1 & 2 to reduce the number of 206 // slots and then multiply the total memories by the number of keys 207 // we have since a single store has access to only one key. 208 pooling.max_memory_protection_keys = pooling.max_memory_protection_keys.max(1).min(2); 209 pooling.total_memories = pooling 210 .total_memories 211 .max(limits::MEMORIES * (pooling.max_memory_protection_keys as u32)); 212 213 // For other limits make sure they meet the minimum threshold 214 // required for our wast tests. 215 pooling.total_component_instances = pooling 216 .total_component_instances 217 .max(limits::COMPONENT_INSTANCES); 218 pooling.total_tables = pooling.total_tables.max(limits::TABLES); 219 pooling.max_tables_per_module = 220 pooling.max_tables_per_module.max(limits::TABLES_PER_MODULE); 221 pooling.max_memories_per_module = pooling 222 .max_memories_per_module 223 .max(limits::MEMORIES_PER_MODULE); 224 pooling.max_memories_per_component = pooling 225 .max_memories_per_component 226 .max(limits::MEMORIES_PER_MODULE); 227 pooling.total_core_instances = pooling.total_core_instances.max(limits::CORE_INSTANCES); 228 pooling.max_memory_size = pooling.max_memory_size.max(limits::MEMORY_SIZE); 229 pooling.table_elements = pooling.table_elements.max(limits::TABLE_ELEMENTS); 230 pooling.core_instance_size = pooling.core_instance_size.max(limits::CORE_INSTANCE_SIZE); 231 pooling.component_instance_size = pooling 232 .component_instance_size 233 .max(limits::CORE_INSTANCE_SIZE); 234 pooling.total_stacks = pooling.total_stacks.max(limits::TOTAL_STACKS); 235 } 236 237 // Return the test configuration that this fuzz configuration represents 238 // which is used afterwards to test if the `test` here is expected to 239 // fail or not. 240 WastConfig { 241 collector: match self.wasmtime.collector { 242 Collector::Null => wasmtime_test_util::wast::Collector::Null, 243 Collector::DeferredReferenceCounting => { 244 wasmtime_test_util::wast::Collector::DeferredReferenceCounting 245 } 246 }, 247 pooling: matches!( 248 self.wasmtime.strategy, 249 InstanceAllocationStrategy::Pooling(_) 250 ), 251 compiler: match self.wasmtime.compiler_strategy { 252 CompilerStrategy::CraneliftNative => { 253 wasmtime_test_util::wast::Compiler::CraneliftNative 254 } 255 CompilerStrategy::CraneliftPulley => { 256 wasmtime_test_util::wast::Compiler::CraneliftPulley 257 } 258 CompilerStrategy::Winch => wasmtime_test_util::wast::Compiler::Winch, 259 }, 260 } 261 } 262 263 /// Converts this to a `wasmtime::Config` object 264 pub fn to_wasmtime(&self) -> wasmtime::Config { 265 crate::init_fuzzing(); 266 267 let mut cfg = wasmtime_cli_flags::CommonOptions::default(); 268 cfg.codegen.native_unwind_info = 269 Some(cfg!(target_os = "windows") || self.wasmtime.native_unwind_info); 270 cfg.codegen.parallel_compilation = Some(false); 271 272 cfg.debug.address_map = Some(self.wasmtime.generate_address_map); 273 cfg.opts.opt_level = Some(self.wasmtime.opt_level.to_wasmtime()); 274 cfg.opts.regalloc_algorithm = Some(self.wasmtime.regalloc_algorithm.to_wasmtime()); 275 cfg.opts.signals_based_traps = Some(self.wasmtime.signals_based_traps); 276 cfg.opts.memory_guaranteed_dense_image_size = Some(std::cmp::min( 277 // Clamp this at 16MiB so we don't get huge in-memory 278 // images during fuzzing. 279 16 << 20, 280 self.wasmtime.memory_guaranteed_dense_image_size, 281 )); 282 cfg.wasm.async_stack_zeroing = Some(self.wasmtime.async_stack_zeroing); 283 cfg.wasm.bulk_memory = Some(true); 284 cfg.wasm.component_model_async = Some(self.module_config.component_model_async); 285 cfg.wasm.component_model_async_builtins = 286 Some(self.module_config.component_model_async_builtins); 287 cfg.wasm.component_model_async_stackful = 288 Some(self.module_config.component_model_async_stackful); 289 cfg.wasm.component_model_threading = Some(self.module_config.component_model_threading); 290 cfg.wasm.component_model_error_context = 291 Some(self.module_config.component_model_error_context); 292 cfg.wasm.component_model_gc = Some(self.module_config.component_model_gc); 293 cfg.wasm.custom_page_sizes = Some(self.module_config.config.custom_page_sizes_enabled); 294 cfg.wasm.epoch_interruption = Some(self.wasmtime.epoch_interruption); 295 cfg.wasm.extended_const = Some(self.module_config.config.extended_const_enabled); 296 cfg.wasm.fuel = self.wasmtime.consume_fuel.then(|| u64::MAX); 297 cfg.wasm.function_references = Some(self.module_config.function_references_enabled); 298 cfg.wasm.gc = Some(self.module_config.config.gc_enabled); 299 cfg.wasm.memory64 = Some(self.module_config.config.memory64_enabled); 300 cfg.wasm.multi_memory = Some(self.module_config.config.max_memories > 1); 301 cfg.wasm.multi_value = Some(self.module_config.config.multi_value_enabled); 302 cfg.wasm.nan_canonicalization = Some(self.wasmtime.canonicalize_nans); 303 cfg.wasm.reference_types = Some(self.module_config.config.reference_types_enabled); 304 cfg.wasm.simd = Some(self.module_config.config.simd_enabled); 305 cfg.wasm.tail_call = Some(self.module_config.config.tail_call_enabled); 306 cfg.wasm.threads = Some(self.module_config.config.threads_enabled); 307 cfg.wasm.shared_everything_threads = 308 Some(self.module_config.config.shared_everything_threads_enabled); 309 cfg.wasm.wide_arithmetic = Some(self.module_config.config.wide_arithmetic_enabled); 310 cfg.wasm.exceptions = Some(self.module_config.config.exceptions_enabled); 311 if !self.module_config.config.simd_enabled { 312 cfg.wasm.relaxed_simd = Some(false); 313 } 314 cfg.codegen.collector = Some(self.wasmtime.collector.to_wasmtime()); 315 316 let compiler_strategy = &self.wasmtime.compiler_strategy; 317 let cranelift_strategy = match compiler_strategy { 318 CompilerStrategy::CraneliftNative | CompilerStrategy::CraneliftPulley => true, 319 CompilerStrategy::Winch => false, 320 }; 321 self.wasmtime.compiler_strategy.configure(&mut cfg); 322 323 self.wasmtime.codegen.configure(&mut cfg); 324 325 // Determine whether we will actually enable PCC -- this is 326 // disabled if the module requires memory64, which is not yet 327 // compatible (due to the need for dynamic checks). 328 let pcc = cfg!(feature = "fuzz-pcc") 329 && self.wasmtime.pcc 330 && !self.module_config.config.memory64_enabled; 331 332 cfg.codegen.inlining = self.wasmtime.inlining; 333 334 // Only set cranelift specific flags when the Cranelift strategy is 335 // chosen. 336 if cranelift_strategy { 337 if let Some(option) = self.wasmtime.inlining_intra_module { 338 cfg.codegen.cranelift.push(( 339 "wasmtime_inlining_intra_module".to_string(), 340 Some(option.to_string()), 341 )); 342 } 343 if let Some(size) = self.wasmtime.inlining_small_callee_size { 344 cfg.codegen.cranelift.push(( 345 "wasmtime_inlining_small_callee_size".to_string(), 346 // Clamp to avoid extreme code size blow up. 347 Some(std::cmp::min(1000, size).to_string()), 348 )); 349 } 350 if let Some(size) = self.wasmtime.inlining_sum_size_threshold { 351 cfg.codegen.cranelift.push(( 352 "wasmtime_inlining_sum_size_threshold".to_string(), 353 // Clamp to avoid extreme code size blow up. 354 Some(std::cmp::min(1000, size).to_string()), 355 )); 356 } 357 358 // If the wasm-smith-generated module use nan canonicalization then we 359 // don't need to enable it, but if it doesn't enable it already then we 360 // enable this codegen option. 361 cfg.wasm.nan_canonicalization = Some(!self.module_config.config.canonicalize_nans); 362 363 // Enabling the verifier will at-least-double compilation time, which 364 // with a 20-30x slowdown in fuzzing can cause issues related to 365 // timeouts. If generated modules can have more than a small handful of 366 // functions then disable the verifier when fuzzing to try to lessen the 367 // impact of timeouts. 368 if self.module_config.config.max_funcs > 10 { 369 cfg.codegen.cranelift_debug_verifier = Some(false); 370 } 371 372 if self.wasmtime.force_jump_veneers { 373 cfg.codegen.cranelift.push(( 374 "wasmtime_linkopt_force_jump_veneer".to_string(), 375 Some("true".to_string()), 376 )); 377 } 378 379 if let Some(pad) = self.wasmtime.padding_between_functions { 380 cfg.codegen.cranelift.push(( 381 "wasmtime_linkopt_padding_between_functions".to_string(), 382 Some(pad.to_string()), 383 )); 384 } 385 386 cfg.codegen.pcc = Some(pcc); 387 388 // Eager init is currently only supported on Cranelift, not Winch. 389 cfg.opts.table_lazy_init = Some(self.wasmtime.table_lazy_init); 390 } 391 392 self.wasmtime.strategy.configure(&mut cfg); 393 394 // Vary the memory configuration, but only if threads are not enabled. 395 // When the threads proposal is enabled we might generate shared memory, 396 // which is less amenable to different memory configurations: 397 // - shared memories are required to be "static" so fuzzing the various 398 // memory configurations will mostly result in uninteresting errors. 399 // The interesting part about shared memories is the runtime so we 400 // don't fuzz non-default settings. 401 // - shared memories are required to be aligned which means that the 402 // `CustomUnaligned` variant isn't actually safe to use with a shared 403 // memory. 404 if !self.module_config.config.threads_enabled { 405 // If PCC is enabled, force other options to be compatible: PCC is currently only 406 // supported when bounds checks are elided. 407 let memory_config = if pcc { 408 MemoryConfig { 409 memory_reservation: Some(4 << 30), // 4 GiB 410 memory_guard_size: Some(2 << 30), // 2 GiB 411 memory_reservation_for_growth: Some(0), 412 guard_before_linear_memory: false, 413 memory_init_cow: true, 414 // Doesn't matter, only using virtual memory. 415 cranelift_enable_heap_access_spectre_mitigations: None, 416 } 417 } else { 418 self.wasmtime.memory_config.clone() 419 }; 420 421 memory_config.configure(&mut cfg); 422 }; 423 424 // If malloc-based memory is going to be used, which requires these four 425 // options set to specific values (and Pulley auto-sets two of them) 426 // then be sure to cap `memory_reservation_for_growth` at a smaller 427 // value than the default. For malloc-based memory reservation beyond 428 // the end of memory isn't captured by `StoreLimiter` so we need to be 429 // sure it's small enough to not blow OOM limits while fuzzing. 430 if ((cfg.opts.signals_based_traps == Some(true) && cfg.opts.memory_guard_size == Some(0)) 431 || self.wasmtime.compiler_strategy == CompilerStrategy::CraneliftPulley) 432 && cfg.opts.memory_reservation == Some(0) 433 && cfg.opts.memory_init_cow == Some(false) 434 { 435 let growth = &mut cfg.opts.memory_reservation_for_growth; 436 let max = 1 << 20; 437 *growth = match *growth { 438 Some(n) => Some(n.min(max)), 439 None => Some(max), 440 }; 441 } 442 443 log::debug!("creating wasmtime config with CLI options:\n{cfg}"); 444 let mut cfg = cfg.config(None).expect("failed to create wasmtime::Config"); 445 446 if self.wasmtime.async_config != AsyncConfig::Disabled { 447 log::debug!("async config in use {:?}", self.wasmtime.async_config); 448 self.wasmtime.async_config.configure(&mut cfg); 449 } 450 451 // Fuzzing on macOS with mach ports seems to sometimes bypass the mach 452 // port handling thread entirely and go straight to asan's or fuzzing's 453 // signal handler. No idea why and for me at least it's just easier to 454 // disable mach ports when fuzzing because there's no need to use that 455 // over signal handlers. 456 if cfg!(target_vendor = "apple") { 457 cfg.macos_use_mach_ports(false); 458 } 459 460 return cfg; 461 } 462 463 /// Convenience function for generating a `Store<T>` using this 464 /// configuration. 465 pub fn to_store(&self) -> Store<StoreLimits> { 466 let engine = Engine::new(&self.to_wasmtime()).unwrap(); 467 let mut store = Store::new(&engine, StoreLimits::new()); 468 self.configure_store(&mut store); 469 store 470 } 471 472 /// Configures a store based on this configuration. 473 pub fn configure_store(&self, store: &mut Store<StoreLimits>) { 474 store.limiter(|s| s as &mut dyn wasmtime::ResourceLimiter); 475 self.configure_store_epoch_and_fuel(store); 476 } 477 478 /// Configures everything unrelated to `T` in a store, such as epochs and 479 /// fuel. 480 pub fn configure_store_epoch_and_fuel<T>(&self, store: &mut Store<T>) { 481 // Configure the store to never abort by default, that is it'll have 482 // max fuel or otherwise trap on an epoch change but the epoch won't 483 // ever change. 484 // 485 // Afterwards though see what `AsyncConfig` is being used an further 486 // refine the store's configuration based on that. 487 if self.wasmtime.consume_fuel { 488 store.set_fuel(u64::MAX).unwrap(); 489 } 490 if self.wasmtime.epoch_interruption { 491 store.epoch_deadline_trap(); 492 store.set_epoch_deadline(1); 493 } 494 match self.wasmtime.async_config { 495 AsyncConfig::Disabled => {} 496 AsyncConfig::YieldWithFuel(amt) => { 497 assert!(self.wasmtime.consume_fuel); 498 store.fuel_async_yield_interval(Some(amt)).unwrap(); 499 } 500 AsyncConfig::YieldWithEpochs { ticks, .. } => { 501 assert!(self.wasmtime.epoch_interruption); 502 store.set_epoch_deadline(ticks); 503 store.epoch_deadline_async_yield_and_update(ticks); 504 } 505 } 506 } 507 508 /// Generates an arbitrary method of timing out an instance, ensuring that 509 /// this configuration supports the returned timeout. 510 pub fn generate_timeout(&mut self, u: &mut Unstructured<'_>) -> arbitrary::Result<Timeout> { 511 let time_duration = Duration::from_millis(100); 512 let timeout = u 513 .choose(&[Timeout::Fuel(100_000), Timeout::Epoch(time_duration)])? 514 .clone(); 515 match &timeout { 516 Timeout::Fuel(..) => { 517 self.wasmtime.consume_fuel = true; 518 } 519 Timeout::Epoch(..) => { 520 self.wasmtime.epoch_interruption = true; 521 } 522 Timeout::None => unreachable!("Not an option given to choose()"), 523 } 524 Ok(timeout) 525 } 526 527 /// Compiles the `wasm` within the `engine` provided. 528 /// 529 /// This notably will use `Module::{serialize,deserialize_file}` to 530 /// round-trip if configured in the fuzzer. 531 pub fn compile(&self, engine: &Engine, wasm: &[u8]) -> Result<Module> { 532 // Propagate this error in case the caller wants to handle 533 // valid-vs-invalid wasm. 534 let module = Module::new(engine, wasm)?; 535 if !self.wasmtime.use_precompiled_cwasm { 536 return Ok(module); 537 } 538 539 // Don't propagate these errors to prevent them from accidentally being 540 // interpreted as invalid wasm, these should never fail on a 541 // well-behaved host system. 542 let dir = tempfile::TempDir::new().unwrap(); 543 let file = dir.path().join("module.wasm"); 544 std::fs::write(&file, module.serialize().unwrap()).unwrap(); 545 unsafe { Ok(Module::deserialize_file(engine, &file).unwrap()) } 546 } 547 548 /// Updates this configuration to forcibly enable async support. Only useful 549 /// in fuzzers which do async calls. 550 pub fn enable_async(&mut self, u: &mut Unstructured<'_>) -> arbitrary::Result<()> { 551 if self.wasmtime.consume_fuel || u.arbitrary()? { 552 self.wasmtime.async_config = 553 AsyncConfig::YieldWithFuel(u.int_in_range(1000..=100_000)?); 554 self.wasmtime.consume_fuel = true; 555 } else { 556 self.wasmtime.async_config = AsyncConfig::YieldWithEpochs { 557 dur: Duration::from_millis(u.int_in_range(1..=10)?), 558 ticks: u.int_in_range(1..=10)?, 559 }; 560 self.wasmtime.epoch_interruption = true; 561 } 562 Ok(()) 563 } 564 } 565 566 impl<'a> Arbitrary<'a> for Config { 567 fn arbitrary(u: &mut Unstructured<'a>) -> arbitrary::Result<Self> { 568 let mut config = Self { 569 wasmtime: u.arbitrary()?, 570 module_config: u.arbitrary()?, 571 }; 572 573 config 574 .wasmtime 575 .update_module_config(&mut config.module_config, u)?; 576 577 Ok(config) 578 } 579 } 580 581 /// Configuration related to `wasmtime::Config` and the various settings which 582 /// can be tweaked from within. 583 #[derive(Arbitrary, Clone, Debug, Eq, Hash, PartialEq)] 584 pub struct WasmtimeConfig { 585 opt_level: OptLevel, 586 regalloc_algorithm: RegallocAlgorithm, 587 debug_info: bool, 588 canonicalize_nans: bool, 589 interruptible: bool, 590 pub(crate) consume_fuel: bool, 591 pub(crate) epoch_interruption: bool, 592 /// The Wasmtime memory configuration to use. 593 pub memory_config: MemoryConfig, 594 force_jump_veneers: bool, 595 memory_init_cow: bool, 596 memory_guaranteed_dense_image_size: u64, 597 inlining: Option<bool>, 598 inlining_intra_module: Option<IntraModuleInlining>, 599 inlining_small_callee_size: Option<u32>, 600 inlining_sum_size_threshold: Option<u32>, 601 use_precompiled_cwasm: bool, 602 async_stack_zeroing: bool, 603 /// Configuration for the instance allocation strategy to use. 604 pub strategy: InstanceAllocationStrategy, 605 codegen: CodegenSettings, 606 padding_between_functions: Option<u16>, 607 generate_address_map: bool, 608 native_unwind_info: bool, 609 /// Configuration for the compiler to use. 610 pub compiler_strategy: CompilerStrategy, 611 collector: Collector, 612 table_lazy_init: bool, 613 614 /// Whether or not fuzzing should enable PCC. 615 pcc: bool, 616 617 /// Configuration for whether wasm is invoked in an async fashion and how 618 /// it's cooperatively time-sliced. 619 pub async_config: AsyncConfig, 620 621 /// Whether or not host signal handlers are enabled for this configuration, 622 /// aka whether signal handlers are supported. 623 signals_based_traps: bool, 624 } 625 626 impl WasmtimeConfig { 627 /// Force `self` to be a configuration compatible with `other`. This is 628 /// useful for differential execution to avoid unhelpful fuzz crashes when 629 /// one engine has a feature enabled and the other does not. 630 pub fn make_compatible_with(&mut self, other: &Self) { 631 // Use the same allocation strategy between the two configs. 632 // 633 // Ideally this wouldn't be necessary, but, during differential 634 // evaluation, if the `lhs` is using ondemand and the `rhs` is using the 635 // pooling allocator (or vice versa), then the module may have been 636 // generated in such a way that is incompatible with the other 637 // allocation strategy. 638 // 639 // We can remove this in the future when it's possible to access the 640 // fields of `wasm_smith::Module` to constrain the pooling allocator 641 // based on what was actually generated. 642 self.strategy = other.strategy.clone(); 643 if let InstanceAllocationStrategy::Pooling { .. } = &other.strategy { 644 // Also use the same memory configuration when using the pooling 645 // allocator. 646 self.memory_config = other.memory_config.clone(); 647 } 648 649 self.make_internally_consistent(); 650 } 651 652 /// Updates `config` to be compatible with `self` and the other way around 653 /// too. 654 pub fn update_module_config( 655 &mut self, 656 config: &mut ModuleConfig, 657 _u: &mut Unstructured<'_>, 658 ) -> arbitrary::Result<()> { 659 match self.compiler_strategy { 660 CompilerStrategy::CraneliftNative => {} 661 662 CompilerStrategy::Winch => { 663 // Winch is not complete on non-x64 targets, so just abandon this test 664 // case. We don't want to force Cranelift because we change what module 665 // config features are enabled based on the compiler strategy, and we 666 // don't want to make the same fuzz input DNA generate different test 667 // cases on different targets. 668 if cfg!(not(target_arch = "x86_64")) { 669 log::warn!( 670 "want to compile with Winch but host architecture does not support it" 671 ); 672 return Err(arbitrary::Error::IncorrectFormat); 673 } 674 675 // Winch doesn't support the same set of wasm proposal as Cranelift 676 // at this time, so if winch is selected be sure to disable wasm 677 // proposals in `Config` to ensure that Winch can compile the 678 // module that wasm-smith generates. 679 config.config.relaxed_simd_enabled = false; 680 config.config.gc_enabled = false; 681 config.config.tail_call_enabled = false; 682 config.config.reference_types_enabled = false; 683 config.config.exceptions_enabled = false; 684 config.function_references_enabled = false; 685 686 // Winch's SIMD implementations require AVX and AVX2. 687 if self 688 .codegen_flag("has_avx") 689 .is_some_and(|value| value == "false") 690 || self 691 .codegen_flag("has_avx2") 692 .is_some_and(|value| value == "false") 693 { 694 config.config.simd_enabled = false; 695 } 696 697 // Tuning the following engine options is currently not supported 698 // by Winch. 699 self.signals_based_traps = true; 700 self.table_lazy_init = true; 701 self.debug_info = false; 702 } 703 704 CompilerStrategy::CraneliftPulley => { 705 config.config.threads_enabled = false; 706 } 707 } 708 709 // If using the pooling allocator, constrain the memory and module configurations 710 // to the module limits. 711 if let InstanceAllocationStrategy::Pooling(pooling) = &mut self.strategy { 712 // If the pooling allocator is used, do not allow shared memory to 713 // be created. FIXME: see 714 // https://github.com/bytecodealliance/wasmtime/issues/4244. 715 config.config.threads_enabled = false; 716 717 // Ensure the pooling allocator can support the maximal size of 718 // memory, picking the smaller of the two to win. 719 let min_bytes = config 720 .config 721 .max_memory32_bytes 722 // memory64_bytes is a u128, but since we are taking the min 723 // we can truncate it down to a u64. 724 .min( 725 config 726 .config 727 .max_memory64_bytes 728 .try_into() 729 .unwrap_or(u64::MAX), 730 ); 731 let min = min_bytes 732 .min(pooling.max_memory_size as u64) 733 .min(self.memory_config.memory_reservation.unwrap_or(0)); 734 pooling.max_memory_size = min as usize; 735 config.config.max_memory32_bytes = min; 736 config.config.max_memory64_bytes = min as u128; 737 738 // If traps are disallowed then memories must have at least one page 739 // of memory so if we still are only allowing 0 pages of memory then 740 // increase that to one here. 741 if config.config.disallow_traps { 742 if pooling.max_memory_size < (1 << 16) { 743 pooling.max_memory_size = 1 << 16; 744 config.config.max_memory32_bytes = 1 << 16; 745 config.config.max_memory64_bytes = 1 << 16; 746 let cfg = &mut self.memory_config; 747 match &mut cfg.memory_reservation { 748 Some(size) => *size = (*size).max(pooling.max_memory_size as u64), 749 size @ None => *size = Some(pooling.max_memory_size as u64), 750 } 751 } 752 // .. additionally update tables 753 if pooling.table_elements == 0 { 754 pooling.table_elements = 1; 755 } 756 } 757 758 // Don't allow too many linear memories per instance since massive 759 // virtual mappings can fail to get allocated. 760 config.config.min_memories = config.config.min_memories.min(10); 761 config.config.max_memories = config.config.max_memories.min(10); 762 763 // Force this pooling allocator to always be able to accommodate the 764 // module that may be generated. 765 pooling.total_memories = config.config.max_memories as u32; 766 pooling.total_tables = config.config.max_tables as u32; 767 } 768 769 if !self.signals_based_traps { 770 // At this time shared memories require a "static" memory 771 // configuration but when signals-based traps are disabled all 772 // memories are forced to the "dynamic" configuration. This is 773 // fixable with some more work on the bounds-checks side of things 774 // to do a full bounds check even on static memories, but that's 775 // left for a future PR. 776 config.config.threads_enabled = false; 777 778 // Spectre-based heap mitigations require signal handlers so this 779 // must always be disabled if signals-based traps are disabled. 780 self.memory_config 781 .cranelift_enable_heap_access_spectre_mitigations = None; 782 } 783 784 self.make_internally_consistent(); 785 786 Ok(()) 787 } 788 789 /// Returns the codegen flag value, if any, for `name`. 790 pub(crate) fn codegen_flag(&self, name: &str) -> Option<&str> { 791 self.codegen.flags().iter().find_map(|(n, value)| { 792 if n == name { 793 Some(value.as_str()) 794 } else { 795 None 796 } 797 }) 798 } 799 800 /// Helper method to handle some dependencies between various configuration 801 /// options. This is intended to be called whenever a `Config` is created or 802 /// modified to ensure that the final result is an instantiable `Config`. 803 /// 804 /// Note that in general this probably shouldn't exist and anything here can 805 /// be considered a "TODO" to go implement more stuff in Wasmtime to accept 806 /// these sorts of configurations. For now though it's intended to reflect 807 /// the current state of the engine's development. 808 fn make_internally_consistent(&mut self) { 809 if !self.signals_based_traps { 810 let cfg = &mut self.memory_config; 811 // Spectre-based heap mitigations require signal handlers so 812 // this must always be disabled if signals-based traps are 813 // disabled. 814 cfg.cranelift_enable_heap_access_spectre_mitigations = None; 815 816 // With configuration settings that match the use of malloc for 817 // linear memories cap the `memory_reservation_for_growth` value 818 // to something reasonable to avoid OOM in fuzzing. 819 if !cfg.memory_init_cow 820 && cfg.memory_guard_size == Some(0) 821 && cfg.memory_reservation == Some(0) 822 { 823 let min = 10 << 20; // 10 MiB 824 if let Some(val) = &mut cfg.memory_reservation_for_growth { 825 *val = (*val).min(min); 826 } else { 827 cfg.memory_reservation_for_growth = Some(min); 828 } 829 } 830 } 831 } 832 } 833 834 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 835 enum OptLevel { 836 None, 837 Speed, 838 SpeedAndSize, 839 } 840 841 impl OptLevel { 842 fn to_wasmtime(&self) -> wasmtime::OptLevel { 843 match self { 844 OptLevel::None => wasmtime::OptLevel::None, 845 OptLevel::Speed => wasmtime::OptLevel::Speed, 846 OptLevel::SpeedAndSize => wasmtime::OptLevel::SpeedAndSize, 847 } 848 } 849 } 850 851 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 852 enum RegallocAlgorithm { 853 Backtracking, 854 SinglePass, 855 } 856 857 impl RegallocAlgorithm { 858 fn to_wasmtime(&self) -> wasmtime::RegallocAlgorithm { 859 match self { 860 RegallocAlgorithm::Backtracking => wasmtime::RegallocAlgorithm::Backtracking, 861 RegallocAlgorithm::SinglePass => { 862 // FIXME(#11850) 863 const SINGLE_PASS_KNOWN_BUGGY_AT_THIS_TIME: bool = true; 864 if SINGLE_PASS_KNOWN_BUGGY_AT_THIS_TIME { 865 wasmtime::RegallocAlgorithm::Backtracking 866 } else { 867 wasmtime::RegallocAlgorithm::SinglePass 868 } 869 } 870 } 871 } 872 } 873 874 #[derive(Arbitrary, Clone, Copy, Debug, PartialEq, Eq, Hash)] 875 enum IntraModuleInlining { 876 Yes, 877 No, 878 WhenUsingGc, 879 } 880 881 impl std::fmt::Display for IntraModuleInlining { 882 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { 883 match self { 884 IntraModuleInlining::Yes => write!(f, "yes"), 885 IntraModuleInlining::No => write!(f, "no"), 886 IntraModuleInlining::WhenUsingGc => write!(f, "gc"), 887 } 888 } 889 } 890 891 #[derive(Clone, Debug, PartialEq, Eq, Hash)] 892 /// Compiler to use. 893 pub enum CompilerStrategy { 894 /// Cranelift compiler for the native architecture. 895 CraneliftNative, 896 /// Winch compiler. 897 Winch, 898 /// Cranelift compiler for the native architecture. 899 CraneliftPulley, 900 } 901 902 impl CompilerStrategy { 903 /// Configures `config` to use this compilation strategy 904 pub fn configure(&self, config: &mut wasmtime_cli_flags::CommonOptions) { 905 match self { 906 CompilerStrategy::CraneliftNative => { 907 config.codegen.compiler = Some(wasmtime::Strategy::Cranelift); 908 } 909 CompilerStrategy::Winch => { 910 config.codegen.compiler = Some(wasmtime::Strategy::Winch); 911 } 912 CompilerStrategy::CraneliftPulley => { 913 config.codegen.compiler = Some(wasmtime::Strategy::Cranelift); 914 config.target = Some("pulley64".to_string()); 915 } 916 } 917 } 918 } 919 920 impl Arbitrary<'_> for CompilerStrategy { 921 fn arbitrary(u: &mut Unstructured<'_>) -> arbitrary::Result<Self> { 922 // Favor fuzzing native cranelift, but if allowed also enable 923 // winch/pulley. 924 match u.int_in_range(0..=19)? { 925 1 => Ok(Self::CraneliftPulley), 926 2 => Ok(Self::Winch), 927 _ => Ok(Self::CraneliftNative), 928 } 929 } 930 } 931 932 #[derive(Arbitrary, Clone, Debug, PartialEq, Eq, Hash)] 933 pub enum Collector { 934 DeferredReferenceCounting, 935 Null, 936 } 937 938 impl Collector { 939 fn to_wasmtime(&self) -> wasmtime::Collector { 940 match self { 941 Collector::DeferredReferenceCounting => wasmtime::Collector::DeferredReferenceCounting, 942 Collector::Null => wasmtime::Collector::Null, 943 } 944 } 945 } 946