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Reuse wasmtime instances, the PR (#5567)
* Preserve a single wasmtime instance. * Sketch of wasm instance reusing. * Refactor and docs. * Rename state_snapshot to util module. * Renaming. * Comments. * Error handling * More fixes.
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#![warn(missing_docs)] | ||
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pub mod sandbox; | ||
pub mod error; | ||
pub mod sandbox; | ||
pub mod util; | ||
pub mod wasm_runtime; |
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// Copyright 2020 Parity Technologies (UK) Ltd. | ||
// This file is part of Substrate. | ||
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// Substrate 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. | ||
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// Substrate 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. | ||
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// You should have received a copy of the GNU General Public License | ||
// along with Substrate. If not, see <http://www.gnu.org/licenses/>. | ||
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//! A set of utilities for resetting a wasm instance to its initial state. | ||
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use crate::error::{self, Error}; | ||
use std::mem; | ||
use parity_wasm::elements::{deserialize_buffer, DataSegment, Instruction, Module as RawModule}; | ||
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/// A bunch of information collected from a WebAssembly module. | ||
pub struct WasmModuleInfo { | ||
raw_module: RawModule, | ||
} | ||
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impl WasmModuleInfo { | ||
/// Create `WasmModuleInfo` from the given wasm code. | ||
/// | ||
/// Returns `None` if the wasm code cannot be deserialized. | ||
pub fn new(wasm_code: &[u8]) -> Option<Self> { | ||
let raw_module: RawModule = deserialize_buffer(wasm_code).ok()?; | ||
Some(Self { raw_module }) | ||
} | ||
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/// Extract the data segments from the given wasm code. | ||
/// | ||
/// Returns `Err` if the given wasm code cannot be deserialized. | ||
fn data_segments(&self) -> Vec<DataSegment> { | ||
self.raw_module | ||
.data_section() | ||
.map(|ds| ds.entries()) | ||
.unwrap_or(&[]) | ||
.to_vec() | ||
} | ||
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/// The number of globals defined in locally in this module. | ||
pub fn declared_globals_count(&self) -> u32 { | ||
self.raw_module | ||
.global_section() | ||
.map(|gs| gs.entries().len() as u32) | ||
.unwrap_or(0) | ||
} | ||
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/// The number of imports of globals. | ||
pub fn imported_globals_count(&self) -> u32 { | ||
self.raw_module | ||
.import_section() | ||
.map(|is| is.globals() as u32) | ||
.unwrap_or(0) | ||
} | ||
} | ||
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/// This is a snapshot of data segments specialzied for a particular instantiation. | ||
/// | ||
/// Note that this assumes that no mutable globals are used. | ||
#[derive(Clone)] | ||
pub struct DataSegmentsSnapshot { | ||
/// The list of data segments represented by (offset, contents). | ||
data_segments: Vec<(u32, Vec<u8>)>, | ||
} | ||
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impl DataSegmentsSnapshot { | ||
/// Create a snapshot from the data segments from the module. | ||
pub fn take(module: &WasmModuleInfo) -> error::Result<Self> { | ||
let data_segments = module | ||
.data_segments() | ||
.into_iter() | ||
.map(|mut segment| { | ||
// Just replace contents of the segment since the segments will be discarded later | ||
// anyway. | ||
let contents = mem::replace(segment.value_mut(), vec![]); | ||
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let init_expr = match segment.offset() { | ||
Some(offset) => offset.code(), | ||
// Return if the segment is passive | ||
None => return Err(Error::from("Shared memory is not supported".to_string())), | ||
}; | ||
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// [op, End] | ||
if init_expr.len() != 2 { | ||
return Err(Error::from( | ||
"initializer expression can have only up to 2 expressions in wasm 1.0" | ||
.to_string(), | ||
)); | ||
} | ||
let offset = match &init_expr[0] { | ||
Instruction::I32Const(v) => *v as u32, | ||
Instruction::GetGlobal(_) => { | ||
// In a valid wasm file, initializer expressions can only refer imported | ||
// globals. | ||
// | ||
// At the moment of writing the Substrate Runtime Interface does not provide | ||
// any globals. There is nothing that prevents us from supporting this | ||
// if/when we gain those. | ||
return Err(Error::from( | ||
"Imported globals are not supported yet".to_string(), | ||
)); | ||
} | ||
insn => { | ||
return Err(Error::from(format!( | ||
"{:?} is not supported as initializer expression in wasm 1.0", | ||
insn | ||
))) | ||
} | ||
}; | ||
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Ok((offset, contents)) | ||
}) | ||
.collect::<error::Result<Vec<_>>>()?; | ||
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Ok(Self { data_segments }) | ||
} | ||
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/// Apply the given snapshot to a linear memory. | ||
/// | ||
/// Linear memory interface is represented by a closure `memory_set`. | ||
pub fn apply<E>( | ||
&self, | ||
mut memory_set: impl FnMut(u32, &[u8]) -> Result<(), E>, | ||
) -> Result<(), E> { | ||
for (offset, contents) in &self.data_segments { | ||
memory_set(*offset, contents)?; | ||
} | ||
Ok(()) | ||
} | ||
} |
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