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110 lines
3.9 KiB
Rust
110 lines
3.9 KiB
Rust
// SPDX-License-Identifier: MIT OR Apache-2.0
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//
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// Copyright (c) 2018-2020 Andre Richter <andre.o.richter@gmail.com>
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//! BSP Memory Management Unit.
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use super::map as memory_map;
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use crate::memory::mmu::*;
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use core::ops::RangeInclusive;
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//--------------------------------------------------------------------------------------------------
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// Public Definitions
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//--------------------------------------------------------------------------------------------------
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const NUM_MEM_RANGES: usize = 2;
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/// The virtual memory layout.
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///
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/// The layout must contain only special ranges, aka anything that is _not_ normal cacheable DRAM.
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/// It is agnostic of the paging granularity that the architecture's MMU will use.
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pub static LAYOUT: KernelVirtualLayout<{ NUM_MEM_RANGES }> = KernelVirtualLayout::new(
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memory_map::END_INCLUSIVE,
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[
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RangeDescriptor {
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name: "Kernel code and RO data",
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virtual_range: || {
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// Using the linker script, we ensure that the RO area is consecutive and 64 KiB
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// aligned, and we export the boundaries via symbols:
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//
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// [__ro_start, __ro_end)
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extern "C" {
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// The inclusive start of the read-only area, aka the address of the first
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// byte of the area.
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static __ro_start: usize;
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// The exclusive end of the read-only area, aka the address of the first
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// byte _after_ the RO area.
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static __ro_end: usize;
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}
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unsafe {
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// Notice the subtraction to turn the exclusive end into an inclusive end.
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#[allow(clippy::range_minus_one)]
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RangeInclusive::new(
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&__ro_start as *const _ as usize,
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&__ro_end as *const _ as usize - 1,
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)
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}
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},
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translation: Translation::Identity,
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attribute_fields: AttributeFields {
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mem_attributes: MemAttributes::CacheableDRAM,
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acc_perms: AccessPermissions::ReadOnly,
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execute_never: false,
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},
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},
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RangeDescriptor {
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name: "Device MMIO",
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virtual_range: || {
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RangeInclusive::new(memory_map::mmio::BASE, memory_map::mmio::END_INCLUSIVE)
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},
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translation: Translation::Identity,
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attribute_fields: AttributeFields {
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mem_attributes: MemAttributes::Device,
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acc_perms: AccessPermissions::ReadWrite,
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execute_never: true,
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},
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},
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],
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);
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//--------------------------------------------------------------------------------------------------
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// Public Code
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//--------------------------------------------------------------------------------------------------
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/// Return the address space size in bytes.
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pub const fn addr_space_size() -> usize {
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memory_map::END_INCLUSIVE + 1
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}
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/// Return a reference to the virtual memory layout.
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pub fn virt_mem_layout() -> &'static KernelVirtualLayout<{ NUM_MEM_RANGES }> {
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&LAYOUT
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}
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//--------------------------------------------------------------------------------------------------
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// Testing
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//--------------------------------------------------------------------------------------------------
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#[cfg(test)]
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mod tests {
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use super::*;
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use test_macros::kernel_test;
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/// Check 64 KiB alignment of the kernel's virtual memory layout sections.
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#[kernel_test]
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fn virt_mem_layout_sections_are_64KiB_aligned() {
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const SIXTYFOUR_KIB: usize = 65536;
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for i in LAYOUT.inner().iter() {
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let start: usize = *(i.virtual_range)().start();
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let end: usize = *(i.virtual_range)().end() + 1;
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assert_eq!(start % SIXTYFOUR_KIB, 0);
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assert_eq!(end % SIXTYFOUR_KIB, 0);
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assert!(end >= start);
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}
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}
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}
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