vm_memory/
volatile_memory.rs

1// Portions Copyright 2019 Red Hat, Inc.
2//
3// Copyright 2017 The Chromium OS Authors. All rights reserved.
4// Use of this source code is governed by a BSD-style license that can be
5// found in the THIRT-PARTY file.
6//
7// SPDX-License-Identifier: Apache-2.0 OR BSD-3-Clause
8
9//! Types for volatile access to memory.
10//!
11//! Two of the core rules for safe rust is no data races and no aliased mutable references.
12//! `VolatileRef` and `VolatileSlice`, along with types that produce those which implement
13//! `VolatileMemory`, allow us to sidestep that rule by wrapping pointers that absolutely have to be
14//! accessed volatile. Some systems really do need to operate on shared memory and can't have the
15//! compiler reordering or eliding access because it has no visibility into what other systems are
16//! doing with that hunk of memory.
17//!
18//! For the purposes of maintaining safety, volatile memory has some rules of its own:
19//!
20//! 1. No references or slices to volatile memory (`&` or `&mut`).
21//!
22//! 2. Access should always been done with a volatile read or write.
23//!
24//! The First rule is because having references of any kind to memory considered volatile would
25//! violate pointer aliasing. The second is because unvolatile accesses are inherently undefined if
26//! done concurrently without synchronization. With volatile access we know that the compiler has
27//! not reordered or elided the access.
28
29pub use vm_memory_new::volatile_memory::{
30    compute_offset, Error, PtrGuard, PtrGuardMut, Result, VolatileArrayRef, VolatileMemory,
31    VolatileRef, VolatileSlice,
32};
vm_memory/volatile_memory.rs

vm_memory/
volatile_memory.rs
