src/kernel_space.rs

// SPDX-FileCopyrightText: Copyright 2023 Arm Limited and/or its affiliates <open-source-office@arm.com>
// SPDX-License-Identifier: MIT OR Apache-2.0

//! Module for converting addresses between kernel virtual address space to physical address space

use core::ops::{Deref, DerefMut, Range};

use alloc::sync::Arc;
use spin::Mutex;

use super::{
    page_pool::{Page, PagePool},
    MemoryAccessRights, Xlat, XlatError,
};

static mut KERNEL_SPACE_INSTANCE: Option<KernelSpace> = None;

#[derive(Clone)]
pub struct KernelSpace {
    xlat: Arc<Mutex<Xlat>>,
}

/// # Kernel space memory mapping
///
/// This object handles the translation tables of the kernel address space. The main goal is to
/// limit the kernel's access to the memory and only map the ranges which are necessary for
/// operation.
/// The current implementation uses identity mapping into the upper virtual address range, e.g.
/// PA = 0x0000_0001_2345_0000 -> VA = 0xffff_fff1_2345_0000.
impl KernelSpace {
    pub const PAGE_SIZE: usize = Page::SIZE;

    /// Creates the kernel memory mapping instance. This should be called from the main core's init
    /// code.
    /// # Arguments
    /// * page_pool: Page pool for allocation kernel translation tables
    pub fn new(page_pool: PagePool) -> Self {
        Self {
            xlat: Arc::new(Mutex::new(Xlat::new(
                page_pool,
                0x0000_0000..0x10_0000_0000,
            ))),
        }
    }

    /// Maps the code (RX) and data (RW) segments of the SPMC itself.
    /// # Arguments
    /// * code_range: (start, end) addresses of the code segment
    /// * data_range: (start, end) addresses of the data segment
    /// # Return value
    /// * The result of the operation
    pub fn init(
        &self,
        code_range: Range<usize>,
        data_range: Range<usize>,
    ) -> Result<(), XlatError> {
        let mut xlat = self.xlat.lock();

        xlat.map_physical_address_range(
            Some(code_range.start),
            code_range.start,
            code_range.len(),
            MemoryAccessRights::RX | MemoryAccessRights::GLOBAL,
        )?;

        xlat.map_physical_address_range(
            Some(data_range.start),
            data_range.start,
            data_range.len(),
            MemoryAccessRights::RW | MemoryAccessRights::GLOBAL,
        )?;

        Ok(())
    }

    /// Map memory range into the kernel address space
    /// # Arguments
    /// * pa: Physical address of the memory
    /// * length: Length of the range in bytes
    /// * access_right: Memory access rights
    /// # Return value
    /// * Virtual address of the mapped memory or error
    pub fn map_memory(
        &self,
        pa: usize,
        length: usize,
        access_rights: MemoryAccessRights,
    ) -> Result<usize, XlatError> {
        let lower_va = self.xlat.lock().map_physical_address_range(
            Some(pa),
            pa,
            length,
            access_rights | MemoryAccessRights::GLOBAL,
        )?;

        Ok(Self::pa_to_kernel(lower_va as u64) as usize)
    }

    /// Unmap memory range from the kernel address space
    /// # Arguments
    /// * va: Virtual address of the memory
    /// * length: Length of the range in bytes
    /// # Return value
    /// The result of the operation
    pub fn unmap_memory(&self, va: usize, length: usize) -> Result<(), XlatError> {
        self.xlat
            .lock()
            .unmap_virtual_address_range(Self::kernel_to_pa(va as u64) as usize, length)
    }

    /// Activate kernel address space mapping
    pub fn activate(&self) {
        self.xlat.lock().activate(0, super::TTBR::TTBR1_EL1);
    }

    /// Rounds a value down to a kernel space page boundary
    pub const fn round_down_to_page_size(size: usize) -> usize {
        size & !(Self::PAGE_SIZE - 1)
    }

    /// Rounds a value up to a kernel space page boundary
    pub const fn round_up_to_page_size(size: usize) -> usize {
        (size + Self::PAGE_SIZE - 1) & !(Self::PAGE_SIZE - 1)
    }

    /// Returns the offset to the preceding page aligned address
    pub const fn offset_in_page(address: usize) -> usize {
        address & (Self::PAGE_SIZE - 1)
    }

    /// Kernel virtual address to physical address
    #[cfg(not(test))]
    pub const fn kernel_to_pa(kernel_address: u64) -> u64 {
        kernel_address & 0x0000_000f_ffff_ffff
    }
    /// Physical address to kernel virtual address
    #[cfg(not(test))]
    pub const fn pa_to_kernel(pa: u64) -> u64 {
        // TODO: make this consts assert_eq!(pa & 0xffff_fff0_0000_0000, 0);
        pa | 0xffff_fff0_0000_0000
    }

    // Do not use any mapping in test build
    #[cfg(test)]
    pub const fn kernel_to_pa(kernel_address: u64) -> u64 {
        kernel_address
    }

    #[cfg(test)]
    pub const fn pa_to_kernel(pa: u64) -> u64 {
        pa
    }
}

/// # Kernel mapping wrapper
///
/// Objects in the physical address space can be wrapped into a KernelMapper which maps it to the
/// virtual kernel address space and provides the same access to the object via the Deref trait.
/// When the mapper is dropped it unmaps the mapped object from the virtual kernel space.
pub struct KernelMapper<T>
where
    T: Deref,
    T::Target: Sized,
{
    physical_instance: T,
    va: *const T::Target,
    kernel_space: KernelSpace,
}

impl<T> KernelMapper<T>
where
    T: Deref,
    T::Target: Sized,
{
    /// Create new mapped object
    /// The access_rights parameter must contain read access
    pub fn new(
        physical_instance: T,
        kernel_space: KernelSpace,
        access_rights: MemoryAccessRights,
    ) -> Self {
        assert!(access_rights.contains(MemoryAccessRights::R));

        let pa = physical_instance.deref() as *const _ as usize;
        let length = KernelSpace::round_up_to_page_size(core::mem::size_of::<T::Target>());

        let va = kernel_space
            .map_memory(pa, length, access_rights)
            .expect("Failed to map area");

        Self {
            physical_instance,
            va: va as *const T::Target,
            kernel_space,
        }
    }
}

impl<T> Deref for KernelMapper<T>
where
    T: Deref,
    T::Target: Sized,
{
    type Target = T::Target;

    #[inline(always)]
    fn deref(&self) -> &Self::Target {
        unsafe { &*self.va }
    }
}

impl<T> Drop for KernelMapper<T>
where
    T: Deref,
    T::Target: Sized,
{
    fn drop(&mut self) {
        let length = KernelSpace::round_up_to_page_size(core::mem::size_of::<T::Target>());
        self.kernel_space
            .unmap_memory(self.va as usize, length)
            .expect("Failed to unmap area");
    }
}

unsafe impl<T> Send for KernelMapper<T>
where
    T: Deref + Send,
    T::Target: Sized,
{
}

/// # Mutable version of kernel mapping wrapper
pub struct KernelMapperMut<T>
where
    T: DerefMut,
    T::Target: Sized,
{
    physical_instance: T,
    va: *mut T::Target,
    kernel_space: KernelSpace,
}

impl<T> KernelMapperMut<T>
where
    T: DerefMut,
    T::Target: Sized,
{
    /// Create new mapped object
    /// The access_rights parameter must contain read and write access
    pub fn new(
        physical_instance: T,
        kernel_space: KernelSpace,
        access_rights: MemoryAccessRights,
    ) -> Self {
        assert!(access_rights.contains(MemoryAccessRights::RW));

        let pa = physical_instance.deref() as *const _ as usize;
        let length = KernelSpace::round_up_to_page_size(core::mem::size_of::<T::Target>());

        let va = kernel_space
            .map_memory(pa, length, access_rights)
            .expect("Failed to map area");

        Self {
            physical_instance,
            va: va as *mut T::Target,
            kernel_space,
        }
    }
}

impl<T> Deref for KernelMapperMut<T>
where
    T: DerefMut,
    T::Target: Sized,
{
    type Target = T::Target;

    #[inline(always)]
    fn deref(&self) -> &Self::Target {
        unsafe { &*self.va }
    }
}

impl<T> DerefMut for KernelMapperMut<T>
where
    T: DerefMut,
    T::Target: Sized,
{
    #[inline(always)]
    fn deref_mut(&mut self) -> &mut Self::Target {
        unsafe { &mut *self.va }
    }
}

impl<T> Drop for KernelMapperMut<T>
where
    T: DerefMut,
    T::Target: Sized,
{
    fn drop(&mut self) {
        let length = KernelSpace::round_up_to_page_size(core::mem::size_of::<T::Target>());
        self.kernel_space
            .unmap_memory(self.va as usize, length)
            .expect("Failed to unmap area");
    }
}

unsafe impl<T> Send for KernelMapperMut<T>
where
    T: DerefMut + Send,
    T::Target: Sized,
{
}