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::Range;

use alloc::string::String;
use spin::Mutex;

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

static mut KERNEL_SPACE_INSTANCE: Option<KernelSpace> = None;

pub struct KernelSpace {
    xlat: 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 create_instance(page_pool: PagePool) {
        unsafe {
            assert!(KERNEL_SPACE_INSTANCE.is_none());

            KERNEL_SPACE_INSTANCE = Some(Self {
                xlat: 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(code_range: Range<usize>, data_range: Range<usize>) -> Result<(), XlatError> {
        if let Some(kernel_space) = unsafe { &KERNEL_SPACE_INSTANCE } {
            let mut xlat = kernel_space.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(())
        } else {
            Err(XlatError::InvalidOperation(String::from(
                "KernelSpace is not initialized",
            )))
        }
    }

    /// 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(
        pa: usize,
        length: usize,
        access_rights: MemoryAccessRights,
    ) -> Result<usize, XlatError> {
        if let Some(kernel_space) = unsafe { &KERNEL_SPACE_INSTANCE } {
            let lower_va = kernel_space.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)
        } else {
            Err(XlatError::InvalidOperation(String::from(
                "KernelSpace is not initialized",
            )))
        }
    }

    /// 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(va: usize, length: usize) -> Result<(), XlatError> {
        if let Some(kernel_space) = unsafe { &KERNEL_SPACE_INSTANCE } {
            kernel_space
                .xlat
                .lock()
                .unmap_virtual_address_range(Self::kernel_to_pa(va as u64) as usize, length)
        } else {
            Err(XlatError::InvalidOperation(String::from(
                "KernelSpace is not initialized",
            )))
        }
    }

    /// Activate kernel address space mapping
    pub fn activate() {
        if let Some(kernel_space) = unsafe { &KERNEL_SPACE_INSTANCE } {
            kernel_space.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
    }
}