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// 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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//! Memory Management.
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use core::{
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fmt,
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ops::{Range, RangeInclusive},
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};
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/// Zero out a memory region.
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///
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/// # Safety
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///
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/// - `range.start` and `range.end` must be valid.
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/// - `range.start` and `range.end` must be `T` aligned.
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pub unsafe fn zero_volatile<T>(range: Range<*mut T>)
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where
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T: From<u8>,
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{
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let mut ptr = range.start;
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while ptr < range.end {
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core::ptr::write_volatile(ptr, T::from(0));
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ptr = ptr.offset(1);
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}
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}
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#[derive(Copy, Clone)]
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pub enum Translation {
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Identity,
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Offset(usize),
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}
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#[derive(Copy, Clone)]
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pub enum MemAttributes {
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CacheableDRAM,
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Device,
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}
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#[derive(Copy, Clone)]
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pub enum AccessPermissions {
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ReadOnly,
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ReadWrite,
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}
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#[derive(Copy, Clone)]
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pub struct AttributeFields {
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pub mem_attributes: MemAttributes,
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pub acc_perms: AccessPermissions,
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pub execute_never: bool,
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}
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impl Default for AttributeFields {
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fn default() -> AttributeFields {
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AttributeFields {
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mem_attributes: MemAttributes::CacheableDRAM,
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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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/// An architecture agnostic descriptor for a memory range.
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pub struct RangeDescriptor {
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pub name: &'static str,
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pub virtual_range: fn() -> RangeInclusive<usize>,
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pub translation: Translation,
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pub attribute_fields: AttributeFields,
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}
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/// Human-readable output of a RangeDescriptor.
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impl fmt::Display for RangeDescriptor {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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// Call the function to which self.range points, and dereference the result, which causes
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// Rust to copy the value.
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let start = *(self.virtual_range)().start();
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let end = *(self.virtual_range)().end();
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let size = end - start + 1;
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// log2(1024).
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const KIB_RSHIFT: u32 = 10;
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// log2(1024 * 1024).
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const MIB_RSHIFT: u32 = 20;
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let (size, unit) = if (size >> MIB_RSHIFT) > 0 {
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(size >> MIB_RSHIFT, "MiB")
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} else if (size >> KIB_RSHIFT) > 0 {
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(size >> KIB_RSHIFT, "KiB")
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} else {
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(size, "Byte")
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};
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let attr = match self.attribute_fields.mem_attributes {
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MemAttributes::CacheableDRAM => "C",
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MemAttributes::Device => "Dev",
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};
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let acc_p = match self.attribute_fields.acc_perms {
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AccessPermissions::ReadOnly => "RO",
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AccessPermissions::ReadWrite => "RW",
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};
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let xn = if self.attribute_fields.execute_never {
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"PXN"
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} else {
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"PX"
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};
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write!(
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f,
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" {:#010x} - {:#010x} | {: >3} {} | {: <3} {} {: <3} | {}",
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start, end, size, unit, attr, acc_p, xn, self.name
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)
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}
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}
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/// Type for expressing the kernel's virtual memory layout.
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pub struct KernelVirtualLayout<const NUM_SPECIAL_RANGES: usize> {
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max_virt_addr_inclusive: usize,
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inner: [RangeDescriptor; NUM_SPECIAL_RANGES],
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}
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impl<const NUM_SPECIAL_RANGES: usize> KernelVirtualLayout<{ NUM_SPECIAL_RANGES }> {
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pub const fn new(max: usize, layout: [RangeDescriptor; NUM_SPECIAL_RANGES]) -> Self {
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Self {
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max_virt_addr_inclusive: max,
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inner: layout,
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}
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}
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/// For a virtual address, find and return the output address and corresponding attributes.
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///
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/// If the address is not found in `inner`, return an identity mapped default with normal
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/// cacheable DRAM attributes.
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pub fn get_virt_addr_properties(
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&self,
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virt_addr: usize,
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) -> Result<(usize, AttributeFields), &'static str> {
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if virt_addr > self.max_virt_addr_inclusive {
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return Err("Address out of range");
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}
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for i in self.inner.iter() {
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if (i.virtual_range)().contains(&virt_addr) {
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let output_addr = match i.translation {
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Translation::Identity => virt_addr,
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Translation::Offset(a) => a + (virt_addr - (i.virtual_range)().start()),
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};
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return Ok((output_addr, i.attribute_fields));
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}
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}
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Ok((virt_addr, AttributeFields::default()))
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}
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/// Print the memory layout.
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pub fn print_layout(&self) {
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use crate::info;
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for i in self.inner.iter() {
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info!("{}", i);
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}
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}
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#[cfg(test)]
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pub fn inner(&self) -> &[RangeDescriptor; NUM_SPECIAL_RANGES] {
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&self.inner
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}
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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 `zero_volatile()`.
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#[kernel_test]
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fn zero_volatile_works() {
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let mut x: [usize; 3] = [10, 11, 12];
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let x_range = x.as_mut_ptr_range();
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unsafe { zero_volatile(x_range) };
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assert_eq!(x, [0, 0, 0]);
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}
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}
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