mirror of
https://github.com/pezkuwichain/pezkuwi-subxt.git
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Kian Paimani
abd08e29ce
* reformat everything again * manual formatting * last manual fix * Fix build
59 lines
2.6 KiB
Rust
59 lines
2.6 KiB
Rust
// This file is part of Substrate.
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// Copyright (C) 2021 Parity Technologies (UK) Ltd.
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// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <https://www.gnu.org/licenses/>.
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//! This module allows for inspection and instrumentation, i.e. modifying the module to alter it's
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//! structure or behavior, of a wasm module.
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//!
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//! ## Instrumentation
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//!
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//! In ideal world, there would be no instrumentation. However, in the real world the execution
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//! engines we use are somewhat limited in their APIs or abilities.
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//!
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//! To give you some examples:
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//!
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//! - wasmi allows reaching to non-exported mutable globals so that we could reset them. Wasmtime
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//! doesn’t support that.
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//!
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//! We need to reset the globals because when we
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//! execute the Substrate Runtime, we do not drop and create the instance anew, instead
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//! we restore some selected parts of the state.
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//!
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//! - stack depth metering can be performed via instrumentation or deferred to the engine and say be
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//! added directly in machine code. Implementing this in machine code is rather cumbersome so
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//! instrumentation looks like a good solution.
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//!
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//! Stack depth metering is needed to make a wasm blob
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//! execution deterministic, which in turn is needed by the Parachain Validation Function in
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//! Polkadot.
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//!
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//! ## Inspection
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//!
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//! Inspection of a wasm module may be needed to extract some useful information, such as to extract
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//! data segment snapshot, which is helpful for quickly restoring the initial state of instances.
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//! Inspection can be also useful to prove that a wasm module possesses some properties, such as,
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//! is free of any floating point operations, which is a useful step towards making instances
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//! produced from such a module deterministic.
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mod data_segments_snapshot;
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mod globals_snapshot;
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mod runtime_blob;
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pub use data_segments_snapshot::DataSegmentsSnapshot;
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pub use globals_snapshot::{ExposedMutableGlobalsSet, GlobalsSnapshot, InstanceGlobals};
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pub use runtime_blob::RuntimeBlob;
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