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Merge pull request #54 from google/static
Add Translation for pregenerating a static pagetable for some target
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,196 @@ | ||
| // Copyright 2024 The aarch64-paging Authors. | ||
| // This project is dual-licensed under Apache 2.0 and MIT terms. | ||
| // See LICENSE-APACHE and LICENSE-MIT for details. | ||
|
|
||
| //! Types for building a static pagetable for some separate target device. | ||
| //! | ||
| //! See [`TargetAllocator`] for details on how to use it. | ||
| use crate::paging::{deallocate, PageTable, PhysicalAddress, Translation}; | ||
| use alloc::{vec, vec::Vec}; | ||
| use core::{mem::size_of, ptr::NonNull}; | ||
| #[cfg(feature = "zerocopy")] | ||
| use zerocopy::AsBytes; | ||
|
|
||
| /// An implementation of `Translation` which builds a static pagetable to be built into a binary for | ||
| /// some target device. | ||
| /// | ||
| /// # Example | ||
| /// | ||
| /// ``` | ||
| /// use aarch64_paging::{ | ||
| /// paging::{ | ||
| /// Attributes, Constraints, MemoryRegion, PhysicalAddress, RootTable, TranslationRegime, | ||
| /// VaRange, | ||
| /// }, | ||
| /// target::TargetAllocator, | ||
| /// }; | ||
| /// | ||
| /// const ROOT_LEVEL: usize = 1; | ||
| /// | ||
| /// let mut map = RootTable::new( | ||
| /// TargetAllocator::new(0x1_0000), | ||
| /// ROOT_LEVEL, | ||
| /// TranslationRegime::El1And0, | ||
| /// VaRange::Lower, | ||
| /// ); | ||
| /// map.map_range( | ||
| /// &MemoryRegion::new(0x0, 0x1000), | ||
| /// PhysicalAddress(0x4_2000), | ||
| /// Attributes::VALID | ||
| /// | Attributes::ATTRIBUTE_INDEX_0 | ||
| /// | Attributes::INNER_SHAREABLE | ||
| /// | Attributes::UXN, | ||
| /// Constraints::empty(), | ||
| /// ) | ||
| /// .unwrap(); | ||
| /// | ||
| /// let bytes = map.translation().as_bytes(); | ||
| /// // Build the bytes into a binary image for the target device... | ||
| /// ``` | ||
| #[derive(Debug)] | ||
| pub struct TargetAllocator { | ||
| base_address: u64, | ||
| allocations: Vec<Option<NonNull<PageTable>>>, | ||
| } | ||
|
|
||
| impl TargetAllocator { | ||
| /// Creates a new `TargetAllocator` for a page table which will be loaded on the target in a | ||
| /// contiguous block of memory starting at the given address. | ||
| pub fn new(base_address: u64) -> Self { | ||
| Self { | ||
| base_address, | ||
| allocations: vec![], | ||
| } | ||
| } | ||
|
|
||
| fn add_allocation(&mut self, page_table: NonNull<PageTable>) -> usize { | ||
| for (i, allocation) in self.allocations.iter_mut().enumerate() { | ||
| if allocation.is_none() { | ||
| *allocation = Some(page_table); | ||
| return i; | ||
| } | ||
| } | ||
| self.allocations.push(Some(page_table)); | ||
| self.allocations.len() - 1 | ||
| } | ||
|
|
||
| fn remove_allocation(&mut self, page_table: NonNull<PageTable>) -> bool { | ||
| for allocation in &mut self.allocations { | ||
| if *allocation == Some(page_table) { | ||
| *allocation = None; | ||
| return true; | ||
| } | ||
| } | ||
| false | ||
| } | ||
|
|
||
| /// Returns the full page table as bytes to be loaded into the target device's memory. | ||
| /// | ||
| /// This could be embedded in a binary image for the target. | ||
| #[cfg(feature = "zerocopy")] | ||
| pub fn as_bytes(&self) -> Vec<u8> { | ||
| let mut bytes = vec![0; self.allocations.len() * size_of::<PageTable>()]; | ||
| for (chunk, allocation) in bytes | ||
| .chunks_exact_mut(size_of::<PageTable>()) | ||
| .zip(self.allocations.iter()) | ||
| { | ||
| if let Some(page_table) = allocation { | ||
| // SAFETY: The pointer is valid because we allocated it in `allocate_table`, and has | ||
| // no aliases for this block. | ||
| let page_table = unsafe { page_table.as_ref() }; | ||
| page_table.write_to(chunk).unwrap(); | ||
| } | ||
| } | ||
| bytes | ||
| } | ||
| } | ||
|
|
||
| impl Translation for TargetAllocator { | ||
| fn allocate_table(&mut self) -> (NonNull<PageTable>, PhysicalAddress) { | ||
| let page_table = PageTable::new(); | ||
| let index = self.add_allocation(page_table); | ||
| let address = PhysicalAddress( | ||
| usize::try_from(self.base_address).unwrap() + index * size_of::<PageTable>(), | ||
| ); | ||
| (page_table, address) | ||
| } | ||
|
|
||
| unsafe fn deallocate_table(&mut self, page_table: NonNull<PageTable>) { | ||
| if !self.remove_allocation(page_table) { | ||
| panic!( | ||
| "dealloc_table called for page table {:?} which isn't in allocations.", | ||
| page_table | ||
| ); | ||
| } | ||
| // SAFETY: Our caller promises that the memory was allocated by `allocate_table` on this | ||
| // `TargetAllocator` and not yet deallocated. `allocate_table` used the global allocator | ||
| // and appropriate layout by calling `PageTable::new()`. | ||
| unsafe { | ||
| deallocate(page_table); | ||
| } | ||
| } | ||
|
|
||
| fn physical_to_virtual(&self, pa: PhysicalAddress) -> NonNull<PageTable> { | ||
| self.allocations | ||
| [(pa.0 - usize::try_from(self.base_address).unwrap()) / size_of::<PageTable>()] | ||
| .unwrap() | ||
| } | ||
| } | ||
|
|
||
| #[cfg(test)] | ||
| mod tests { | ||
| use super::*; | ||
| use crate::paging::{ | ||
| Attributes, Constraints, MemoryRegion, RootTable, TranslationRegime, VaRange, | ||
| }; | ||
|
|
||
| const ROOT_LEVEL: usize = 1; | ||
|
|
||
| #[test] | ||
| fn map_one_page() { | ||
| let mut map = RootTable::new( | ||
| TargetAllocator::new(0x1_0000), | ||
| ROOT_LEVEL, | ||
| TranslationRegime::El1And0, | ||
| VaRange::Lower, | ||
| ); | ||
| map.map_range( | ||
| &MemoryRegion::new(0x0, 0x1000), | ||
| PhysicalAddress(0x4_2000), | ||
| Attributes::VALID | ||
| | Attributes::ATTRIBUTE_INDEX_0 | ||
| | Attributes::INNER_SHAREABLE | ||
| | Attributes::UXN, | ||
| Constraints::empty(), | ||
| ) | ||
| .unwrap(); | ||
|
|
||
| let bytes = map.translation().as_bytes(); | ||
| assert_eq!(bytes.len(), 3 * size_of::<PageTable>()); | ||
| // Table mapping for table at 0x01_1000 | ||
| assert_eq!( | ||
| bytes[0..8], | ||
| [0x03, 0x10, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00] | ||
| ); | ||
| for byte in &bytes[8..size_of::<PageTable>()] { | ||
| assert_eq!(*byte, 0); | ||
| } | ||
| // Table mapping for table at 0x01_2000 | ||
| assert_eq!( | ||
| bytes[size_of::<PageTable>()..size_of::<PageTable>() + 8], | ||
| [0x03, 0x20, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00] | ||
| ); | ||
| for byte in &bytes[size_of::<PageTable>() + 8..2 * size_of::<PageTable>()] { | ||
| assert_eq!(*byte, 0); | ||
| } | ||
| // Page mapping for 0x04_2000 with the attributes given above. | ||
| assert_eq!( | ||
| bytes[2 * size_of::<PageTable>()..2 * size_of::<PageTable>() + 8], | ||
| [0x03, 0x23, 0x04, 0x00, 0x00, 0x00, 0x40, 0x00] | ||
| ); | ||
| for byte in &bytes[2 * size_of::<PageTable>() + 8..3 * size_of::<PageTable>()] { | ||
| assert_eq!(*byte, 0); | ||
| } | ||
| } | ||
| } |