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
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
|
// SPDX-License-Identifier: GPL-2.0
//! Extensions to the [`alloc`] crate.
#[cfg(not(any(test, testlib)))]
pub mod allocator;
pub mod kbox;
pub mod kvec;
pub mod vec_ext;
#[cfg(any(test, testlib))]
pub mod allocator_test;
#[cfg(any(test, testlib))]
pub use self::allocator_test as allocator;
pub use self::kbox::Box;
pub use self::kbox::KBox;
pub use self::kbox::KVBox;
pub use self::kbox::VBox;
pub use self::kvec::KVVec;
pub use self::kvec::KVec;
pub use self::kvec::VVec;
pub use self::kvec::Vec;
/// Indicates an allocation error.
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub struct AllocError;
use core::{alloc::Layout, ptr::NonNull};
/// Flags to be used when allocating memory.
///
/// They can be combined with the operators `|`, `&`, and `!`.
///
/// Values can be used from the [`flags`] module.
#[derive(Clone, Copy)]
pub struct Flags(u32);
impl Flags {
/// Get the raw representation of this flag.
pub(crate) fn as_raw(self) -> u32 {
self.0
}
}
impl core::ops::BitOr for Flags {
type Output = Self;
fn bitor(self, rhs: Self) -> Self::Output {
Self(self.0 | rhs.0)
}
}
impl core::ops::BitAnd for Flags {
type Output = Self;
fn bitand(self, rhs: Self) -> Self::Output {
Self(self.0 & rhs.0)
}
}
impl core::ops::Not for Flags {
type Output = Self;
fn not(self) -> Self::Output {
Self(!self.0)
}
}
/// Allocation flags.
///
/// These are meant to be used in functions that can allocate memory.
pub mod flags {
use super::Flags;
/// Zeroes out the allocated memory.
///
/// This is normally or'd with other flags.
pub const __GFP_ZERO: Flags = Flags(bindings::__GFP_ZERO);
/// Allow the allocation to be in high memory.
///
/// Allocations in high memory may not be mapped into the kernel's address space, so this can't
/// be used with `kmalloc` and other similar methods.
///
/// This is normally or'd with other flags.
pub const __GFP_HIGHMEM: Flags = Flags(bindings::__GFP_HIGHMEM);
/// Users can not sleep and need the allocation to succeed.
///
/// A lower watermark is applied to allow access to "atomic reserves". The current
/// implementation doesn't support NMI and few other strict non-preemptive contexts (e.g.
/// raw_spin_lock). The same applies to [`GFP_NOWAIT`].
pub const GFP_ATOMIC: Flags = Flags(bindings::GFP_ATOMIC);
/// Typical for kernel-internal allocations. The caller requires ZONE_NORMAL or a lower zone
/// for direct access but can direct reclaim.
pub const GFP_KERNEL: Flags = Flags(bindings::GFP_KERNEL);
/// The same as [`GFP_KERNEL`], except the allocation is accounted to kmemcg.
pub const GFP_KERNEL_ACCOUNT: Flags = Flags(bindings::GFP_KERNEL_ACCOUNT);
/// For kernel allocations that should not stall for direct reclaim, start physical IO or
/// use any filesystem callback. It is very likely to fail to allocate memory, even for very
/// small allocations.
pub const GFP_NOWAIT: Flags = Flags(bindings::GFP_NOWAIT);
/// Suppresses allocation failure reports.
///
/// This is normally or'd with other flags.
pub const __GFP_NOWARN: Flags = Flags(bindings::__GFP_NOWARN);
}
/// The kernel's [`Allocator`] trait.
///
/// An implementation of [`Allocator`] can allocate, re-allocate and free memory buffer described
/// via [`Layout`].
///
/// [`Allocator`] is designed to be implemented as a ZST; [`Allocator`] functions do not operate on
/// an object instance.
///
/// In order to be able to support `#[derive(SmartPointer)]` later on, we need to avoid a design
/// that requires an `Allocator` to be instantiated, hence its functions must not contain any kind
/// of `self` parameter.
///
/// # Safety
///
/// Memory returned from an allocator must point to a valid memory buffer and remain valid until
/// it is explicitly freed.
///
/// Any pointer to a memory buffer which is currently allocated must be valid to be passed to any
/// other [`Allocator`] function of the same type.
///
/// If `realloc` is called with:
/// - a size of zero, the given memory allocation, if any, must be freed
/// - `None`, a new memory allocation must be created
pub unsafe trait Allocator {
/// Allocate memory based on `layout` and `flags`.
///
/// On success, returns a buffer represented as `NonNull<[u8]>` that satisfies the layout
/// constraints (i.e. minimum size and alignment as specified by `layout`).
///
/// This function is equivalent to `realloc` when called with `None`.
fn alloc(layout: Layout, flags: Flags) -> Result<NonNull<[u8]>, AllocError> {
// SAFETY: Passing `None` to `realloc` is valid by it's safety requirements and asks for a
// new memory allocation.
unsafe { Self::realloc(None, layout, flags) }
}
/// Re-allocate an existing memory allocation to satisfy the requested `layout`. If the
/// requested size is zero, `realloc` behaves equivalent to `free`.
///
/// If the requested size is larger than the size of the existing allocation, a successful call
/// to `realloc` guarantees that the new or grown buffer has at least `Layout::size` bytes, but
/// may also be larger.
///
/// If the requested size is smaller than the size of the existing allocation, `realloc` may or
/// may not shrink the buffer; this is implementation specific to the allocator.
///
/// On allocation failure, the existing buffer, if any, remains valid.
///
/// The buffer is represented as `NonNull<[u8]>`.
///
/// # Safety
///
/// If `ptr = Some(p)`, then `p` must point to an existing and valid memory allocation created
/// by this allocator. The alignment encoded in `layout` must be smaller than or equal to the
/// alignment requested in the previous `alloc` or `realloc` call of the same allocation.
///
/// Additionally, `ptr` is allowed to be `None`; in this case a new memory allocation is
/// created.
unsafe fn realloc(
ptr: Option<NonNull<u8>>,
layout: Layout,
flags: Flags,
) -> Result<NonNull<[u8]>, AllocError>;
/// Free an existing memory allocation.
///
/// # Safety
///
/// `ptr` must point to an existing and valid memory allocation created by this `Allocator` and
/// must not be a dangling pointer.
///
/// The memory allocation at `ptr` must never again be read from or written to.
unsafe fn free(ptr: NonNull<u8>) {
// SAFETY: The caller guarantees that `ptr` points at a valid allocation created by this
// allocator. We are passing a `Layout` with the smallest possible alignment, so it is
// smaller than or equal to the alignment previously used with this allocation.
let _ = unsafe { Self::realloc(Some(ptr), Layout::new::<()>(), Flags(0)) };
}
}
|
