1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
// This file is part of Substrate.

// Copyright (C) 2019-2022 Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.

//! Traits and accessor functions for calling into the Substrate Wasm runtime.
//!
//! The primary means of accessing the runtimes is through a cache which saves the reusable
//! components of the runtime that are expensive to initialize.

use crate::error::{Error, WasmError};
use codec::Decode;
use lru::LruCache;
use parking_lot::Mutex;
use sc_executor_common::{
	runtime_blob::RuntimeBlob,
	wasm_runtime::{WasmInstance, WasmModule},
};
use sp_core::traits::{Externalities, FetchRuntimeCode, RuntimeCode};
use sp_version::RuntimeVersion;
use std::{
	num::NonZeroUsize,
	panic::AssertUnwindSafe,
	path::{Path, PathBuf},
	sync::Arc,
};

use sp_wasm_interface::HostFunctions;

/// Specification of different methods of executing the runtime Wasm code.
#[derive(Debug, PartialEq, Eq, Hash, Copy, Clone)]
pub enum WasmExecutionMethod {
	/// Uses the Wasmi interpreter.
	Interpreted,
	/// Uses the Wasmtime compiled runtime.
	Compiled {
		/// The instantiation strategy to use.
		instantiation_strategy: sc_executor_wasmtime::InstantiationStrategy,
	},
}

impl Default for WasmExecutionMethod {
	fn default() -> WasmExecutionMethod {
		WasmExecutionMethod::Interpreted
	}
}

#[derive(Debug, PartialEq, Eq, Hash, Clone)]
struct VersionedRuntimeId {
	/// Runtime code hash.
	code_hash: Vec<u8>,
	/// Wasm runtime type.
	wasm_method: WasmExecutionMethod,
	/// The number of WebAssembly heap pages this instance was created with.
	heap_pages: u64,
}

/// A Wasm runtime object along with its cached runtime version.
struct VersionedRuntime {
	/// Shared runtime that can spawn instances.
	module: Arc<dyn WasmModule>,
	/// Runtime version according to `Core_version` if any.
	version: Option<RuntimeVersion>,

	// TODO: Remove this once the legacy instance reuse instantiation strategy
	//       for `wasmtime` is gone, as this only makes sense with that particular strategy.
	/// Cached instance pool.
	instances: Arc<Vec<Mutex<Option<Box<dyn WasmInstance>>>>>,
}

impl VersionedRuntime {
	/// Run the given closure `f` with an instance of this runtime.
	fn with_instance<R, F>(&self, ext: &mut dyn Externalities, f: F) -> Result<R, Error>
	where
		F: FnOnce(
			&Arc<dyn WasmModule>,
			&mut dyn WasmInstance,
			Option<&RuntimeVersion>,
			&mut dyn Externalities,
		) -> Result<R, Error>,
	{
		// Find a free instance
		let instance = self
			.instances
			.iter()
			.enumerate()
			.find_map(|(index, i)| i.try_lock().map(|i| (index, i)));

		match instance {
			Some((index, mut locked)) => {
				let (mut instance, new_inst) = locked
					.take()
					.map(|r| Ok((r, false)))
					.unwrap_or_else(|| self.module.new_instance().map(|i| (i, true)))?;

				let result = f(&self.module, &mut *instance, self.version.as_ref(), ext);
				if let Err(e) = &result {
					if new_inst {
						tracing::warn!(
							target: "wasm-runtime",
							error = %e,
							"Fresh runtime instance failed",
						)
					} else {
						tracing::warn!(
							target: "wasm-runtime",
							error = %e,
							"Evicting failed runtime instance",
						);
					}
				} else {
					*locked = Some(instance);

					if new_inst {
						tracing::debug!(
							target: "wasm-runtime",
							"Allocated WASM instance {}/{}",
							index + 1,
							self.instances.len(),
						);
					}
				}

				result
			},
			None => {
				tracing::warn!(target: "wasm-runtime", "Ran out of free WASM instances");

				// Allocate a new instance
				let mut instance = self.module.new_instance()?;

				f(&self.module, &mut *instance, self.version.as_ref(), ext)
			},
		}
	}
}

/// Cache for the runtimes.
///
/// When an instance is requested for the first time it is added to this cache. Metadata is kept
/// with the instance so that it can be efficiently reinitialized.
///
/// When using the Wasmi interpreter execution method, the metadata includes the initial memory and
/// values of mutable globals. Follow-up requests to fetch a runtime return this one instance with
/// the memory reset to the initial memory. So, one runtime instance is reused for every fetch
/// request.
///
/// The size of cache is configurable via the cli option `--runtime-cache-size`.
pub struct RuntimeCache {
	/// A cache of runtimes along with metadata.
	///
	/// Runtimes sorted by recent usage. The most recently used is at the front.
	runtimes: Mutex<LruCache<VersionedRuntimeId, Arc<VersionedRuntime>>>,
	/// The size of the instances cache for each runtime.
	max_runtime_instances: usize,
	cache_path: Option<PathBuf>,
}

impl RuntimeCache {
	/// Creates a new instance of a runtimes cache.
	///
	/// `max_runtime_instances` specifies the number of instances per runtime preserved in an
	/// in-memory cache.
	///
	/// `cache_path` allows to specify an optional directory where the executor can store files
	/// for caching.
	///
	/// `runtime_cache_size` specifies the number of different runtimes versions preserved in an
	/// in-memory cache, must always be at least 1.
	pub fn new(
		max_runtime_instances: usize,
		cache_path: Option<PathBuf>,
		runtime_cache_size: u8,
	) -> RuntimeCache {
		let cap =
			NonZeroUsize::new(runtime_cache_size.max(1) as usize).expect("cache size is not zero");
		RuntimeCache { runtimes: Mutex::new(LruCache::new(cap)), max_runtime_instances, cache_path }
	}

	/// Prepares a WASM module instance and executes given function for it.
	///
	/// This uses internal cache to find available instance or create a new one.
	/// # Parameters
	///
	/// `runtime_code` - The runtime wasm code used setup the runtime.
	///
	/// `default_heap_pages` - Number of 64KB pages to allocate for Wasm execution.
	///
	/// `wasm_method` - Type of WASM backend to use.
	///
	/// `allow_missing_func_imports` - Ignore missing function imports.
	///
	/// `f` - Function to execute.
	///
	/// `H` - A compile-time list of host functions to expose to the runtime.
	///
	/// # Returns result of `f` wrapped in an additional result.
	/// In case of failure one of two errors can be returned:
	///
	/// `Err::RuntimeConstruction` is returned for runtime construction issues.
	///
	/// `Error::InvalidMemoryReference` is returned if no memory export with the
	/// identifier `memory` can be found in the runtime.
	pub fn with_instance<'c, H, R, F>(
		&self,
		runtime_code: &'c RuntimeCode<'c>,
		ext: &mut dyn Externalities,
		wasm_method: WasmExecutionMethod,
		default_heap_pages: u64,
		allow_missing_func_imports: bool,
		f: F,
	) -> Result<Result<R, Error>, Error>
	where
		H: HostFunctions,
		F: FnOnce(
			&Arc<dyn WasmModule>,
			&mut dyn WasmInstance,
			Option<&RuntimeVersion>,
			&mut dyn Externalities,
		) -> Result<R, Error>,
	{
		let code_hash = &runtime_code.hash;
		let heap_pages = runtime_code.heap_pages.unwrap_or(default_heap_pages);

		let versioned_runtime_id =
			VersionedRuntimeId { code_hash: code_hash.clone(), heap_pages, wasm_method };

		let mut runtimes = self.runtimes.lock(); // this must be released prior to calling f
		let versioned_runtime = if let Some(versioned_runtime) = runtimes.get(&versioned_runtime_id)
		{
			versioned_runtime.clone()
		} else {
			let code = runtime_code.fetch_runtime_code().ok_or(WasmError::CodeNotFound)?;

			let time = std::time::Instant::now();

			let result = create_versioned_wasm_runtime::<H>(
				&code,
				ext,
				wasm_method,
				heap_pages,
				allow_missing_func_imports,
				self.max_runtime_instances,
				self.cache_path.as_deref(),
			);

			match result {
				Ok(ref result) => {
					tracing::debug!(
						target: "wasm-runtime",
						"Prepared new runtime version {:?} in {} ms.",
						result.version,
						time.elapsed().as_millis(),
					);
				},
				Err(ref err) => {
					tracing::warn!(target: "wasm-runtime", error = ?err, "Cannot create a runtime");
				},
			}

			let versioned_runtime = Arc::new(result?);

			// Save new versioned wasm runtime in cache
			runtimes.put(versioned_runtime_id, versioned_runtime.clone());

			versioned_runtime
		};

		// Lock must be released prior to calling f
		drop(runtimes);

		Ok(versioned_runtime.with_instance(ext, f))
	}
}

/// Create a wasm runtime with the given `code`.
pub fn create_wasm_runtime_with_code<H>(
	wasm_method: WasmExecutionMethod,
	heap_pages: u64,
	blob: RuntimeBlob,
	allow_missing_func_imports: bool,
	cache_path: Option<&Path>,
) -> Result<Arc<dyn WasmModule>, WasmError>
where
	H: HostFunctions,
{
	match wasm_method {
		WasmExecutionMethod::Interpreted => {
			// Wasmi doesn't have any need in a cache directory.
			//
			// We drop the cache_path here to silence warnings that cache_path is not used if
			// compiling without the `wasmtime` flag.
			let _ = cache_path;

			sc_executor_wasmi::create_runtime(
				blob,
				heap_pages,
				H::host_functions(),
				allow_missing_func_imports,
			)
			.map(|runtime| -> Arc<dyn WasmModule> { Arc::new(runtime) })
		},
		WasmExecutionMethod::Compiled { instantiation_strategy } =>
			sc_executor_wasmtime::create_runtime::<H>(
				blob,
				sc_executor_wasmtime::Config {
					allow_missing_func_imports,
					cache_path: cache_path.map(ToOwned::to_owned),
					semantics: sc_executor_wasmtime::Semantics {
						extra_heap_pages: heap_pages,
						instantiation_strategy,
						deterministic_stack_limit: None,
						canonicalize_nans: false,
						parallel_compilation: true,
						max_memory_size: None,
					},
				},
			)
			.map(|runtime| -> Arc<dyn WasmModule> { Arc::new(runtime) }),
	}
}

fn decode_version(mut version: &[u8]) -> Result<RuntimeVersion, WasmError> {
	Decode::decode(&mut version).map_err(|_| {
		WasmError::Instantiation(
			"failed to decode \"Core_version\" result using old runtime version".into(),
		)
	})
}

fn decode_runtime_apis(apis: &[u8]) -> Result<Vec<([u8; 8], u32)>, WasmError> {
	use sp_api::RUNTIME_API_INFO_SIZE;

	apis.chunks(RUNTIME_API_INFO_SIZE)
		.map(|chunk| {
			// `chunk` can be less than `RUNTIME_API_INFO_SIZE` if the total length of `apis`
			// doesn't completely divide by `RUNTIME_API_INFO_SIZE`.
			<[u8; RUNTIME_API_INFO_SIZE]>::try_from(chunk)
				.map(sp_api::deserialize_runtime_api_info)
				.map_err(|_| WasmError::Other("a clipped runtime api info declaration".to_owned()))
		})
		.collect::<Result<Vec<_>, WasmError>>()
}

/// Take the runtime blob and scan it for the custom wasm sections containing the version
/// information and construct the `RuntimeVersion` from them.
///
/// If there are no such sections, it returns `None`. If there is an error during decoding those
/// sections, `Err` will be returned.
pub fn read_embedded_version(blob: &RuntimeBlob) -> Result<Option<RuntimeVersion>, WasmError> {
	if let Some(mut version_section) = blob.custom_section_contents("runtime_version") {
		let apis = blob
			.custom_section_contents("runtime_apis")
			.map(decode_runtime_apis)
			.transpose()?
			.map(Into::into);

		let core_version = apis.as_ref().and_then(sp_version::core_version_from_apis);
		// We do not use `RuntimeVersion::decode` here because that `decode_version` relies on
		// presence of a special API in the `apis` field to treat the input as a non-legacy version.
		// However the structure found in the `runtime_version` always contain an empty `apis`
		// field. Therefore the version read will be mistakenly treated as an legacy one.
		let mut decoded_version = sp_version::RuntimeVersion::decode_with_version_hint(
			&mut version_section,
			core_version,
		)
		.map_err(|_| WasmError::Instantiation("failed to decode version section".into()))?;

		if let Some(apis) = apis {
			decoded_version.apis = apis;
		}

		Ok(Some(decoded_version))
	} else {
		Ok(None)
	}
}

fn create_versioned_wasm_runtime<H>(
	code: &[u8],
	ext: &mut dyn Externalities,
	wasm_method: WasmExecutionMethod,
	heap_pages: u64,
	allow_missing_func_imports: bool,
	max_instances: usize,
	cache_path: Option<&Path>,
) -> Result<VersionedRuntime, WasmError>
where
	H: HostFunctions,
{
	// The incoming code may be actually compressed. We decompress it here and then work with
	// the uncompressed code from now on.
	let blob = sc_executor_common::runtime_blob::RuntimeBlob::uncompress_if_needed(code)?;

	// Use the runtime blob to scan if there is any metadata embedded into the wasm binary
	// pertaining to runtime version. We do it before consuming the runtime blob for creating the
	// runtime.
	let mut version: Option<_> = read_embedded_version(&blob)?;

	let runtime = create_wasm_runtime_with_code::<H>(
		wasm_method,
		heap_pages,
		blob,
		allow_missing_func_imports,
		cache_path,
	)?;

	// If the runtime blob doesn't embed the runtime version then use the legacy version query
	// mechanism: call the runtime.
	if version.is_none() {
		// Call to determine runtime version.
		let version_result = {
			// `ext` is already implicitly handled as unwind safe, as we store it in a global
			// variable.
			let mut ext = AssertUnwindSafe(ext);

			// The following unwind safety assertion is OK because if the method call panics, the
			// runtime will be dropped.
			let runtime = AssertUnwindSafe(runtime.as_ref());
			crate::native_executor::with_externalities_safe(&mut **ext, move || {
				runtime.new_instance()?.call("Core_version".into(), &[])
			})
			.map_err(|_| WasmError::Instantiation("panic in call to get runtime version".into()))?
		};

		if let Ok(version_buf) = version_result {
			version = Some(decode_version(&version_buf)?)
		}
	}

	let mut instances = Vec::with_capacity(max_instances);
	instances.resize_with(max_instances, || Mutex::new(None));

	Ok(VersionedRuntime { module: runtime, version, instances: Arc::new(instances) })
}

#[cfg(test)]
mod tests {
	use super::*;
	use codec::Encode;
	use sp_api::{Core, RuntimeApiInfo};
	use sp_runtime::RuntimeString;
	use sp_wasm_interface::HostFunctions;
	use substrate_test_runtime::Block;

	#[derive(Encode)]
	pub struct OldRuntimeVersion {
		pub spec_name: RuntimeString,
		pub impl_name: RuntimeString,
		pub authoring_version: u32,
		pub spec_version: u32,
		pub impl_version: u32,
		pub apis: sp_version::ApisVec,
	}

	#[test]
	fn host_functions_are_equal() {
		let host_functions = sp_io::SubstrateHostFunctions::host_functions();

		let equal = &host_functions[..] == &host_functions[..];
		assert!(equal, "Host functions are not equal");
	}

	#[test]
	fn old_runtime_version_decodes() {
		let old_runtime_version = OldRuntimeVersion {
			spec_name: "test".into(),
			impl_name: "test".into(),
			authoring_version: 1,
			spec_version: 1,
			impl_version: 1,
			apis: sp_api::create_apis_vec!([(<dyn Core::<Block>>::ID, 1)]),
		};

		let version = decode_version(&old_runtime_version.encode()).unwrap();
		assert_eq!(1, version.transaction_version);
		assert_eq!(0, version.state_version);
	}

	#[test]
	fn old_runtime_version_decodes_fails_with_version_3() {
		let old_runtime_version = OldRuntimeVersion {
			spec_name: "test".into(),
			impl_name: "test".into(),
			authoring_version: 1,
			spec_version: 1,
			impl_version: 1,
			apis: sp_api::create_apis_vec!([(<dyn Core::<Block>>::ID, 3)]),
		};

		decode_version(&old_runtime_version.encode()).unwrap_err();
	}

	#[test]
	fn new_runtime_version_decodes() {
		let old_runtime_version = sp_api::RuntimeVersion {
			spec_name: "test".into(),
			impl_name: "test".into(),
			authoring_version: 1,
			spec_version: 1,
			impl_version: 1,
			apis: sp_api::create_apis_vec!([(<dyn Core::<Block>>::ID, 3)]),
			transaction_version: 3,
			state_version: 4,
		};

		let version = decode_version(&old_runtime_version.encode()).unwrap();
		assert_eq!(3, version.transaction_version);
		assert_eq!(0, version.state_version);

		let old_runtime_version = sp_api::RuntimeVersion {
			spec_name: "test".into(),
			impl_name: "test".into(),
			authoring_version: 1,
			spec_version: 1,
			impl_version: 1,
			apis: sp_api::create_apis_vec!([(<dyn Core::<Block>>::ID, 4)]),
			transaction_version: 3,
			state_version: 4,
		};

		let version = decode_version(&old_runtime_version.encode()).unwrap();
		assert_eq!(3, version.transaction_version);
		assert_eq!(4, version.state_version);
	}

	#[test]
	fn embed_runtime_version_works() {
		let wasm = sp_maybe_compressed_blob::decompress(
			substrate_test_runtime::wasm_binary_unwrap(),
			sp_maybe_compressed_blob::CODE_BLOB_BOMB_LIMIT,
		)
		.expect("Decompressing works");
		let runtime_version = RuntimeVersion {
			spec_name: "test_replace".into(),
			impl_name: "test_replace".into(),
			authoring_version: 100,
			spec_version: 100,
			impl_version: 100,
			apis: sp_api::create_apis_vec!([(<dyn Core::<Block>>::ID, 4)]),
			transaction_version: 100,
			state_version: 1,
		};

		let embedded = sp_version::embed::embed_runtime_version(&wasm, runtime_version.clone())
			.expect("Embedding works");

		let blob = RuntimeBlob::new(&embedded).expect("Embedded blob is valid");
		let read_version = read_embedded_version(&blob)
			.ok()
			.flatten()
			.expect("Reading embedded version works");

		assert_eq!(runtime_version, read_version);
	}
}