ostd/mm/frame/
untyped.rs

1// SPDX-License-Identifier: MPL-2.0
2
3//! Untyped physical memory management.
4//!
5//! As detailed in [`crate::mm::frame`], untyped memory can be accessed with
6//! relaxed rules but we cannot create references to them. This module provides
7//! the declaration of untyped frames and segments, and the implementation of
8//! extra functionalities (such as [`VmIo`]) for them.
9//!
10//! [`VmIo`]: crate::mm::VmIo
11
12use super::{Frame, Segment, meta::AnyFrameMeta};
13use crate::mm::{
14    HasPaddr, HasSize, Infallible,
15    io::{VmReader, VmWriter},
16    io_util::{HasVmReaderWriter, VmReaderWriterIdentity},
17    paddr_to_vaddr,
18};
19
20/// The metadata of untyped frame.
21///
22/// If a structure `M` implements [`AnyUFrameMeta`], it can be used as the
23/// metadata of a type of untyped frames [`Frame<M>`]. All frames of such type
24/// will be accessible as untyped memory.
25pub trait AnyUFrameMeta: AnyFrameMeta {}
26
27/// A smart pointer to an untyped frame with any metadata.
28///
29/// The metadata of the frame is not known at compile time but the frame must
30/// be an untyped one. An [`UFrame`] as a parameter accepts any type of
31/// untyped frame metadata.
32///
33/// The usage of this frame will not be changed while this object is alive.
34pub type UFrame = Frame<dyn AnyUFrameMeta>;
35
36/// Makes a structure usable as untyped frame metadata.
37///
38/// If this macro is used for built-in typed frame metadata, it won't compile.
39#[macro_export]
40macro_rules! impl_untyped_frame_meta_for {
41    // Implement without specifying the drop behavior.
42    ($t:ty) => {
43        // SAFETY: Untyped frames can be safely read.
44        unsafe impl $crate::mm::frame::meta::AnyFrameMeta for $t {
45            fn is_untyped(&self) -> bool {
46                true
47            }
48        }
49        impl $crate::mm::frame::untyped::AnyUFrameMeta for $t {}
50
51        $crate::check_frame_meta_layout!($t);
52    };
53    // Implement with a customized drop function.
54    ($t:ty, $body:expr) => {
55        // SAFETY: Untyped frames can be safely read.
56        unsafe impl $crate::mm::frame::meta::AnyFrameMeta for $t {
57            fn on_drop(&mut self, reader: &mut $crate::mm::VmReader<$crate::mm::Infallible>) {
58                $body
59            }
60
61            fn is_untyped(&self) -> bool {
62                true
63            }
64        }
65        impl $crate::mm::frame::untyped::AnyUFrameMeta for $t {}
66
67        $crate::check_frame_meta_layout!($t);
68    };
69}
70
71// A special case of untyped metadata is the unit type.
72impl_untyped_frame_meta_for!(());
73
74macro_rules! impl_untyped_for {
75    ($t:ident) => {
76        impl<UM: AnyUFrameMeta + ?Sized> HasVmReaderWriter for $t<UM> {
77            type Types = VmReaderWriterIdentity;
78
79            fn reader(&self) -> VmReader<'_, Infallible> {
80                let ptr = paddr_to_vaddr(self.paddr()) as *const u8;
81                // SAFETY:
82                // - The memory range points to untyped memory.
83                // - The frame/segment is alive during the lifetime `'_`.
84                // - Using `VmReader` and `VmWriter` is the only way to access the frame/segment.
85                unsafe { VmReader::from_kernel_space(ptr, self.size()) }
86            }
87
88            fn writer(&self) -> VmWriter<'_, Infallible> {
89                let ptr = paddr_to_vaddr(self.paddr()) as *mut u8;
90                // SAFETY:
91                // - The memory range points to untyped memory.
92                // - The frame/segment is alive during the lifetime `'_`.
93                // - Using `VmReader` and `VmWriter` is the only way to access the frame/segment.
94                unsafe { VmWriter::from_kernel_space(ptr, self.size()) }
95            }
96        }
97    };
98}
99
100impl_untyped_for!(Frame);
101impl_untyped_for!(Segment);
ostd/mm/frame/untyped.rs

ostd/mm/frame/
untyped.rs
