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
// This file is part of Substrate.
// Copyright (C) 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/>.
//! This module defines `HostState` and `HostContext` structs which provide logic and state
//! required for execution of host.
use wasmtime::Caller;
use sc_allocator::{AllocationStats, FreeingBumpHeapAllocator};
use sp_wasm_interface::{Pointer, WordSize};
use crate::{instance_wrapper::MemoryWrapper, runtime::StoreData, util};
/// The state required to construct a HostContext context. The context only lasts for one host
/// call, whereas the state is maintained for the duration of a Wasm runtime call, which may make
/// many different host calls that must share state.
pub struct HostState {
/// The allocator instance to keep track of allocated memory.
///
/// This is stored as an `Option` as we need to temporarily set this to `None` when we are
/// allocating/deallocating memory. The problem being that we can only mutable access `caller`
/// once.
allocator: Option<FreeingBumpHeapAllocator>,
panic_message: Option<String>,
}
impl HostState {
/// Constructs a new `HostState`.
pub fn new(allocator: FreeingBumpHeapAllocator) -> Self {
HostState { allocator: Some(allocator), panic_message: None }
}
/// Takes the error message out of the host state, leaving a `None` in its place.
pub fn take_panic_message(&mut self) -> Option<String> {
self.panic_message.take()
}
pub(crate) fn allocation_stats(&self) -> AllocationStats {
self.allocator.as_ref()
.expect("Allocator is always set and only unavailable when doing an allocation/deallocation; qed")
.stats()
}
}
/// A `HostContext` implements `FunctionContext` for making host calls from a Wasmtime
/// runtime. The `HostContext` exists only for the lifetime of the call and borrows state from
/// a longer-living `HostState`.
pub(crate) struct HostContext<'a> {
pub(crate) caller: Caller<'a, StoreData>,
}
impl<'a> HostContext<'a> {
fn host_state_mut(&mut self) -> &mut HostState {
self.caller
.data_mut()
.host_state_mut()
.expect("host state is not empty when calling a function in wasm; qed")
}
}
impl<'a> sp_wasm_interface::FunctionContext for HostContext<'a> {
fn read_memory_into(
&self,
address: Pointer<u8>,
dest: &mut [u8],
) -> sp_wasm_interface::Result<()> {
util::read_memory_into(&self.caller, address, dest).map_err(|e| e.to_string())
}
fn write_memory(&mut self, address: Pointer<u8>, data: &[u8]) -> sp_wasm_interface::Result<()> {
util::write_memory_from(&mut self.caller, address, data).map_err(|e| e.to_string())
}
fn allocate_memory(&mut self, size: WordSize) -> sp_wasm_interface::Result<Pointer<u8>> {
let memory = self.caller.data().memory();
let mut allocator = self
.host_state_mut()
.allocator
.take()
.expect("allocator is not empty when calling a function in wasm; qed");
// We can not return on error early, as we need to store back allocator.
let res = allocator
.allocate(&mut MemoryWrapper(&memory, &mut self.caller), size)
.map_err(|e| e.to_string());
self.host_state_mut().allocator = Some(allocator);
res
}
fn deallocate_memory(&mut self, ptr: Pointer<u8>) -> sp_wasm_interface::Result<()> {
let memory = self.caller.data().memory();
let mut allocator = self
.host_state_mut()
.allocator
.take()
.expect("allocator is not empty when calling a function in wasm; qed");
// We can not return on error early, as we need to store back allocator.
let res = allocator
.deallocate(&mut MemoryWrapper(&memory, &mut self.caller), ptr)
.map_err(|e| e.to_string());
self.host_state_mut().allocator = Some(allocator);
res
}
fn register_panic_error_message(&mut self, message: &str) {
self.host_state_mut().panic_message = Some(message.to_owned());
}
}