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use core::mem::{self, MaybeUninit};
use core::ops::{Deref, DerefMut};
use core::{ptr, slice};
use crate::Result;
use crate::{PartialAllocStrategy, PhysallocFlags};
/// An RAII guard of a physical memory allocation. Currently all physically allocated memory are
/// page-aligned and take up at least 4k of space (on x86_64).
#[derive(Debug)]
pub struct PhysBox {
address: usize,
size: usize
}
impl PhysBox {
/// Construct a PhysBox from an address and a size.
///
/// # Safety
/// This function is unsafe because when dropping, Self has to a valid allocation.
pub unsafe fn from_raw_parts(address: usize, size: usize) -> Self {
Self {
address,
size,
}
}
/// Retrieve the byte address in physical memory, of this allocation.
pub fn address(&self) -> usize {
self.address
}
/// Retrieve the size in bytes of the alloc.
pub fn size(&self) -> usize {
self.size
}
/// Allocate physical memory that must reside in 32-bit space.
pub fn new_in_32bit_space(size: usize) -> Result<Self> {
Self::new_with_flags(size, PhysallocFlags::SPACE_32)
}
pub fn new_with_flags(size: usize, flags: PhysallocFlags) -> Result<Self> {
assert!(!flags.contains(PhysallocFlags::PARTIAL_ALLOC));
let address = unsafe { crate::physalloc2(size, flags.bits())? };
Ok(Self {
address,
size,
})
}
/// "Partially" allocate physical memory, in the sense that the allocation may be smaller than
/// expected, but still with a minimum limit. This is particularly useful when the physical
/// memory space is fragmented, and a device supports scatter-gather I/O. In that case, the
/// driver can optimistically request e.g. 1 alloc of 1 MiB, with the minimum of 512 KiB. If
/// that first allocation only returns half the size, the driver can do another allocation
/// and then let the device use both buffers.
pub fn new_partial_allocation(size: usize, flags: PhysallocFlags, strategy: Option<PartialAllocStrategy>, mut min: usize) -> Result<Self> {
debug_assert!(!(flags.contains(PhysallocFlags::PARTIAL_ALLOC) && strategy.is_none()));
let address = unsafe { crate::physalloc3(size, flags.bits() | strategy.map(|s| s as usize).unwrap_or(0), &mut min)? };
Ok(Self {
address,
size: min,
})
}
pub fn new(size: usize) -> Result<Self> {
let address = unsafe { crate::physalloc(size)? };
Ok(Self {
address,
size,
})
}
}
impl Drop for PhysBox {
fn drop(&mut self) {
let _ = unsafe { crate::physfree(self.address, self.size) };
}
}
pub struct Dma<T: ?Sized> {
phys: PhysBox,
virt: *mut T,
}
impl<T> Dma<T> {
pub fn from_physbox_uninit(phys: PhysBox) -> Result<Dma<MaybeUninit<T>>> {
let virt = unsafe { crate::physmap(phys.address, phys.size, crate::PHYSMAP_WRITE)? } as *mut MaybeUninit<T>;
Ok(Dma {
phys,
virt,
})
}
pub fn from_physbox_zeroed(phys: PhysBox) -> Result<Dma<MaybeUninit<T>>> {
let this = Self::from_physbox_uninit(phys)?;
unsafe { ptr::write_bytes(this.virt as *mut MaybeUninit<u8>, 0, this.phys.size) }
Ok(this)
}
pub fn from_physbox(phys: PhysBox, value: T) -> Result<Self> {
let this = Self::from_physbox_uninit(phys)?;
Ok(unsafe {
ptr::write(this.virt, MaybeUninit::new(value));
this.assume_init()
})
}
pub fn new(value: T) -> Result<Self> {
let phys = PhysBox::new(mem::size_of::<T>())?;
Self::from_physbox(phys, value)
}
pub fn zeroed() -> Result<Dma<MaybeUninit<T>>> {
let phys = PhysBox::new(mem::size_of::<T>())?;
Self::from_physbox_zeroed(phys)
}
}
impl<T> Dma<MaybeUninit<T>> {
pub unsafe fn assume_init(self) -> Dma<T> {
let &Dma { phys: PhysBox { address, size }, virt } = &self;
mem::forget(self);
Dma {
phys: PhysBox { address, size },
virt: virt as *mut T,
}
}
}
impl<T: ?Sized> Dma<T> {
pub fn physical(&self) -> usize {
self.phys.address()
}
pub fn size(&self) -> usize {
self.phys.size()
}
pub fn phys(&self) -> &PhysBox {
&self.phys
}
}
impl<T> Dma<[T]> {
pub fn from_physbox_uninit_unsized(phys: PhysBox, len: usize) -> Result<Dma<[MaybeUninit<T>]>> {
let max_len = phys.size() / mem::size_of::<T>();
assert!(len <= max_len);
Ok(Dma {
virt: unsafe { slice::from_raw_parts_mut(crate::physmap(phys.address, phys.size, crate::PHYSMAP_WRITE)? as *mut MaybeUninit<T>, len) } as *mut [MaybeUninit<T>],
phys,
})
}
pub fn from_physbox_zeroed_unsized(phys: PhysBox, len: usize) -> Result<Dma<[MaybeUninit<T>]>> {
let this = Self::from_physbox_uninit_unsized(phys, len)?;
unsafe { ptr::write_bytes(this.virt as *mut MaybeUninit<u8>, 0, this.phys.size()) }
Ok(this)
}
/// Creates a new DMA buffer with a size only known at runtime.
/// ## Safety
/// * `T` must be properly aligned.
/// * `T` must be valid as zeroed (i.e. no NonNull pointers).
pub unsafe fn zeroed_unsized(count: usize) -> Result<Self> {
let phys = PhysBox::new(mem::size_of::<T>() * count)?;
Ok(Self::from_physbox_zeroed_unsized(phys, count)?.assume_init())
}
}
impl<T> Dma<[MaybeUninit<T>]> {
pub unsafe fn assume_init(self) -> Dma<[T]> {
let &Dma { phys: PhysBox { address, size }, virt } = &self;
mem::forget(self);
Dma {
phys: PhysBox { address, size },
virt: virt as *mut [T],
}
}
}
impl<T: ?Sized> Deref for Dma<T> {
type Target = T;
fn deref(&self) -> &T {
unsafe { &*self.virt }
}
}
impl<T: ?Sized> DerefMut for Dma<T> {
fn deref_mut(&mut self) -> &mut T {
unsafe { &mut *self.virt }
}
}
impl<T: ?Sized> Drop for Dma<T> {
fn drop(&mut self) {
unsafe { ptr::drop_in_place(self.virt) }
let _ = unsafe { crate::physunmap(self.virt as *mut u8 as usize) };
}
}
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