feat(mm): add DeviceAlloc for communicating with devices

Signed-off-by: Martin Kröning <martin.kroening@eonerc.rwth-aachen.de>

src/mm/device_alloc.rs

@@ -0,0 +1,28 @@
+use core::alloc::{AllocError, Allocator, Layout};
+use core::ptr::{self, NonNull};
+
+use align_address::Align;
+
+use crate::arch::mm::paging::{BasePageSize, PageSize};
+
+/// An [`Allocator`] for memory that is used to communicate with devices.
+/// 
+/// Allocations from this allocator always correspond to contiguous physical memory.
+pub struct DeviceAlloc;
+
+unsafe impl Allocator for DeviceAlloc {
+	fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
+		assert!(layout.align() <= BasePageSize::SIZE as usize);
+		let size = layout.size().align_up(BasePageSize::SIZE as usize);
+		let ptr = super::allocate(size, true).as_mut_ptr::<u8>();
+		let slice = ptr::slice_from_raw_parts_mut(ptr, size);
+		Ok(NonNull::new(slice).unwrap())
+	}
+
+	unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
+		assert!(layout.align() <= BasePageSize::SIZE as usize);
+		let size = layout.size().align_up(BasePageSize::SIZE as usize);
+		let addr = ptr.as_ptr().expose_provenance().into();
+		super::deallocate(addr, size);
+	}
+}

src/mm/mod.rs

@@ -1,4 +1,5 @@
 pub mod allocator;
+pub mod device_alloc;
 pub mod freelist;
 
 use core::mem;
@@ -307,7 +308,7 @@ pub(crate) fn print_information() {
 	arch::mm::virtualmem::print_information();
 }
 
-#[allow(dead_code)]
+/// Soft-deprecated in favor of `DeviceAlloc`
 pub(crate) fn allocate(sz: usize, no_execution: bool) -> VirtAddr {
 	let size = sz.align_up(BasePageSize::SIZE as usize);
 	let physical_address = arch::mm::physicalmem::allocate(size).unwrap();
@@ -324,7 +325,7 @@ pub(crate) fn allocate(sz: usize, no_execution: bool) -> VirtAddr {
 	virtual_address
 }
 
-#[allow(dead_code)]
+/// Soft-deprecated in favor of `DeviceAlloc`
 pub(crate) fn deallocate(virtual_address: VirtAddr, sz: usize) {
 	let size = sz.align_up(BasePageSize::SIZE as usize);