ostd 0.8.4

Rust OS framework that facilitates the development of and innovation in OS kernels
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// SPDX-License-Identifier: MPL-2.0

//! Virtual memory (VM).

/// Virtual addresses.
pub type Vaddr = usize;

/// Physical addresses.
pub type Paddr = usize;

pub(crate) mod dma;
pub mod frame;
pub(crate) mod heap_allocator;
mod io;
pub(crate) mod kspace;
mod offset;
pub(crate) mod page;
pub(crate) mod page_prop;
pub(crate) mod page_table;
pub mod stat;
pub mod tlb;
pub mod vm_space;

use core::{fmt::Debug, ops::Range};

pub use self::{
    dma::{Daddr, DmaCoherent, DmaDirection, DmaStream, DmaStreamSlice, HasDaddr},
    frame::{options::FrameAllocOptions, Frame, Segment},
    io::{
        Fallible, FallibleVmRead, FallibleVmWrite, Infallible, PodOnce, VmIo, VmIoOnce, VmReader,
        VmWriter,
    },
    page_prop::{CachePolicy, PageFlags, PageProperty},
    vm_space::VmSpace,
};
pub(crate) use self::{
    kspace::paddr_to_vaddr, page::meta::init as init_page_meta, page_prop::PrivilegedPageFlags,
    page_table::PageTable,
};
use crate::arch::mm::PagingConsts;

/// The level of a page table node or a frame.
pub type PagingLevel = u8;

/// A minimal set of constants that determines the paging system.
/// This provides an abstraction over most paging modes in common architectures.
pub(crate) trait PagingConstsTrait: Clone + Debug + Default + Sync + 'static {
    /// The smallest page size.
    /// This is also the page size at level 1 page tables.
    const BASE_PAGE_SIZE: usize;

    /// The number of levels in the page table.
    /// The numbering of levels goes from deepest node to the root node. For example,
    /// the level 1 to 5 on AMD64 corresponds to Page Tables, Page Directory Tables,
    /// Page Directory Pointer Tables, Page-Map Level-4 Table, and Page-Map Level-5
    /// Table, respectively.
    const NR_LEVELS: PagingLevel;

    /// The highest level that a PTE can be directly used to translate a VA.
    /// This affects the the largest page size supported by the page table.
    const HIGHEST_TRANSLATION_LEVEL: PagingLevel;

    /// The size of a PTE.
    const PTE_SIZE: usize;

    /// The address width may be BASE_PAGE_SIZE.ilog2() + NR_LEVELS * IN_FRAME_INDEX_BITS.
    /// If it is shorter than that, the higher bits in the highest level are ignored.
    const ADDRESS_WIDTH: usize;
}

/// The page size
pub const PAGE_SIZE: usize = page_size::<PagingConsts>(1);

/// The page size at a given level.
pub(crate) const fn page_size<C: PagingConstsTrait>(level: PagingLevel) -> usize {
    C::BASE_PAGE_SIZE << (nr_subpage_per_huge::<C>().ilog2() as usize * (level as usize - 1))
}

/// The number of sub pages in a huge page.
pub(crate) const fn nr_subpage_per_huge<C: PagingConstsTrait>() -> usize {
    C::BASE_PAGE_SIZE / C::PTE_SIZE
}

/// The number of base pages in a huge page at a given level.
#[allow(dead_code)]
pub(crate) const fn nr_base_per_page<C: PagingConstsTrait>(level: PagingLevel) -> usize {
    page_size::<C>(level) / C::BASE_PAGE_SIZE
}

/// The maximum virtual address of user space (non inclusive).
///
/// Typical 64-bit systems have at least 48-bit virtual address space.
/// A typical way to reserve half of the address space for the kernel is
/// to use the highest 48-bit virtual address space.
///
/// Also, the top page is not regarded as usable since it's a workaround
/// for some x86_64 CPUs' bugs. See
/// <https://github.com/torvalds/linux/blob/480e035fc4c714fb5536e64ab9db04fedc89e910/arch/x86/include/asm/page_64.h#L68-L78>
/// for the rationale.
pub const MAX_USERSPACE_VADDR: Vaddr = 0x0000_8000_0000_0000 - PAGE_SIZE;

/// The kernel address space.
/// There are the high canonical addresses defined in most 48-bit width
/// architectures.
pub(crate) const KERNEL_VADDR_RANGE: Range<Vaddr> = 0xffff_8000_0000_0000..0xffff_ffff_ffff_0000;

/// Gets physical address trait
pub trait HasPaddr {
    /// Returns the physical address.
    fn paddr(&self) -> Paddr;
}

/// Checks if the given address is page-aligned.
pub const fn is_page_aligned(p: usize) -> bool {
    (p & (PAGE_SIZE - 1)) == 0
}