rust-raspberrypi-OS-tutorials/10_privilege_level/src/bsp/raspberrypi/memory.rs

// SPDX-License-Identifier: MIT OR Apache-2.0
//
// Copyright (c) 2018-2021 Andre Richter <andre.o.richter@gmail.com>

//! BSP Memory Management.

use core::{cell::UnsafeCell, ops::RangeInclusive};

//--------------------------------------------------------------------------------------------------
// Private Definitions
//--------------------------------------------------------------------------------------------------

// Symbols from the linker script.
extern "Rust" {
    static __rx_start: UnsafeCell<()>;

    static __bss_start: UnsafeCell<u64>;
    static __bss_end_inclusive: UnsafeCell<u64>;
}

//--------------------------------------------------------------------------------------------------
// Public Definitions
//--------------------------------------------------------------------------------------------------

/// The board's physical memory map.
#[rustfmt::skip]
pub(super) mod map {

    pub const GPIO_OFFSET:         usize = 0x0020_0000;
    pub const UART_OFFSET:         usize = 0x0020_1000;

    /// Physical devices.
    #[cfg(feature = "bsp_rpi3")]
    pub mod mmio {
        use super::*;

        pub const START:            usize =         0x3F00_0000;
        pub const GPIO_START:       usize = START + GPIO_OFFSET;
        pub const PL011_UART_START: usize = START + UART_OFFSET;
    }

    /// Physical devices.
    #[cfg(feature = "bsp_rpi4")]
    pub mod mmio {
        use super::*;

        pub const START:            usize =         0xFE00_0000;
        pub const GPIO_START:       usize = START + GPIO_OFFSET;
        pub const PL011_UART_START: usize = START + UART_OFFSET;
    }
}

//--------------------------------------------------------------------------------------------------
// Private Code
//--------------------------------------------------------------------------------------------------

/// Start address of the Read+Execute (RX) range.
///
/// # Safety
///
/// - Value is provided by the linker script and must be trusted as-is.
#[inline(always)]
fn rx_start() -> usize {
    unsafe { __rx_start.get() as usize }
}

//--------------------------------------------------------------------------------------------------
// Public Code
//--------------------------------------------------------------------------------------------------

/// Exclusive end address of the boot core's stack.
#[inline(always)]
pub fn boot_core_stack_end() -> usize {
    rx_start()
}

/// Return the inclusive range spanning the .bss section.
///
/// # Safety
///
/// - Values are provided by the linker script and must be trusted as-is.
/// - The linker-provided addresses must be u64 aligned.
pub fn bss_range_inclusive() -> RangeInclusive<*mut u64> {
    let range;
    unsafe {
        range = RangeInclusive::new(__bss_start.get(), __bss_end_inclusive.get());
    }
    assert!(!range.is_empty());

    range
}