xref: /DragonOS/kernel/crates/rust-slabmalloc/src/lib.rs (revision 40db1e61da60c695b425bdff8889504613a7f09d)
1 //! A slab allocator implementation for objects less than a page-size (4 KiB or 2MiB).
2 //!
3 //! # Overview
4 //!
5 //! The organization is as follows:
6 //!
7 //!  * A `ZoneAllocator` manages many `SCAllocator` and can
8 //!    satisfy requests for different allocation sizes.
9 //!  * A `SCAllocator` allocates objects of exactly one size.
10 //!    It stores the objects and meta-data in one or multiple `AllocablePage` objects.
11 //!  * A trait `AllocablePage` that defines the page-type from which we allocate objects.
12 //!
13 //! Lastly, it provides two default `AllocablePage` implementations `ObjectPage` and `LargeObjectPage`:
14 //!  * A `ObjectPage` that is 4 KiB in size and contains allocated objects and associated meta-data.
15 //!  * A `LargeObjectPage` that is 2 MiB in size and contains allocated objects and associated meta-data.
16 //!
17 //!
18 //! # Implementing GlobalAlloc
19 //! See the [global alloc](https://github.com/gz/rust-slabmalloc/tree/master/examples/global_alloc.rs) example.
20 #![allow(unused_features)]
21 #![cfg_attr(feature = "unstable", feature(const_mut_refs))]
22 #![no_std]
23 #![crate_name = "slabmalloc"]
24 #![crate_type = "lib"]
25 #![feature(new_uninit)]
26 #![feature(maybe_uninit_as_bytes)]
27 
28 extern crate alloc;
29 
30 mod pages;
31 mod sc;
32 mod zone;
33 
34 pub use pages::*;
35 pub use sc::*;
36 pub use zone::*;
37 
38 use core::alloc::Layout;
39 use core::fmt;
40 use core::ptr::{self, NonNull};
41 
42 use log::trace;
43 
44 /// How many bytes in the page are used by allocator meta-data.
45 const OBJECT_PAGE_METADATA_OVERHEAD: usize = 80;
46 
47 /// How many bytes a [`ObjectPage`] is.
48 const OBJECT_PAGE_SIZE: usize = 4096;
49 
50 type VAddr = usize;
51 
52 /// Error that can be returned for `allocation` and `deallocation` requests.
53 #[derive(Debug)]
54 pub enum AllocationError {
55     /// Can't satisfy the allocation request for Layout because the allocator
56     /// does not have enough memory (you may be able to `refill` it).
57     OutOfMemory,
58     /// Allocator can't deal with the provided size of the Layout.
59     InvalidLayout,
60 }
61 
62 /// Allocator trait to be implemented by users of slabmalloc to provide memory to slabmalloc.
63 ///
64 /// # Safety
65 /// Needs to adhere to safety requirements of a rust allocator (see GlobalAlloc et. al.).
66 pub unsafe trait Allocator<'a> {
67     fn allocate(&mut self, layout: Layout) -> Result<NonNull<u8>, AllocationError>;
68     unsafe fn deallocate(
69         &mut self,
70         ptr: NonNull<u8>,
71         layout: Layout,
72         slab_callback: &'static dyn CallBack,
73     ) -> Result<(), AllocationError>;
74 
75     /// Refill the allocator with a [`ObjectPage`].
76     ///
77     /// # Safety
78     /// TBD (this API needs to change anyways, likely new page should be a raw pointer)
79     unsafe fn refill(
80         &mut self,
81         layout: Layout,
82         new_page: &'a mut ObjectPage<'a>,
83     ) -> Result<(), AllocationError>;
84 }
85 
86 /// 将slab_page归还Buddy的回调函数
87 pub trait CallBack: Send + Sync {
88     unsafe fn free_slab_page(&self, _: *mut u8, _: usize) {}
89 }
90