faces_pfm/
frame.rs

1use crate::PageFlags;
2
3/// Metadata associated with a single physical page frame.
4///
5/// This structure stores per‑frame information required by the page frame
6/// manager, such as flags, allocation order, linked list pointers for free
7/// lists, reference count, and a pointer to the kernel virtual address of
8/// the freelist header (if any). It is guaranteed to be 32‑byte aligned.
9#[derive(Debug, Default)]
10#[repr(C, align(32))]
11pub struct PageFrame {
12    /// Page state flags (locked, dirty, reserved, etc.).
13    pub flags: PageFlags,
14    /// Allocation order (2^order pages). 0 means a single 4 KiB page.
15    pub order: u8,
16    /// Index of the next page frame in a linked list (e.g., free list).
17    pub next: u32,
18    /// Index of the previous page frame in a linked list.
19    pub prev: u32,
20    /// Size class index for slab allocators (if used).
21    pub size_class: u8,
22    /// Reference count: number of users of this page frame.
23    pub rc: u16,
24    /// Kernel virtual address of the freelist header (or 0 if none).
25    pub freelist_va: usize,
26    /// Padding to maintain alignment and reserved for future use.
27    pub _pad: u8,
28}
29
30impl PageFrame {
31    /// Creates a new, zeroed (default) page frame metadata structure.
32    ///
33    /// All fields are initialised with their default values. The `flags`
34    /// field is cloned from a zeroed instance of `F`.
35    ///
36    /// # Panics
37    /// This function is `const` and will not panic.
38    pub const fn new() -> Self {
39        Self {
40            flags: (*unsafe { core::mem::transmute::<&usize, &PageFlags>(&0) }).clone(),
41            order: 0,
42            next: 0,
43            prev: 0,
44            size_class: 0,
45            rc: 0,
46            freelist_va: 0,
47            _pad: 0,
48        }
49    }
50
51    /// Resets the page frame metadata to its default state.
52    ///
53    /// This is equivalent to `*self = PageFrame::new()`. After calling this,
54    /// all flags are cleared, and counters are set to zero.
55    pub fn reset(&mut self) {
56        self.flags = (*unsafe { core::mem::transmute::<&usize, &PageFlags>(&0) }).clone();
57        self.order = 0;
58        self.next = 0;
59        self.prev = 0;
60        self.freelist_va = 0;
61        self.rc = 0;
62        self.size_class = 0;
63    }
64}
faces_pfm/frame.rs

faces_pfm/
frame.rs
