Add a more complex physalloc syscall.

src/call.rs

@@ -251,7 +251,7 @@ pub fn open<T: AsRef<[u8]>>(path: T, flags: usize) -> Result<usize> {
     unsafe { syscall3(SYS_OPEN, path.as_ref().as_ptr() as usize, path.as_ref().len(), flags) }
 }
 
-/// Allocate pages, linearly in physical memory
+/// Allocate frames, linearly in physical memory.
 ///
 /// # Errors
 ///
@@ -261,6 +261,37 @@ pub unsafe fn physalloc(size: usize) -> Result<usize> {
     syscall1(SYS_PHYSALLOC, size)
 }
 
+/// Allocate frames, linearly in physical memory, with an extra set of flags. If the flags contain
+/// [`PARTIAL_ALLOC`], this will result in `physalloc3` with `min = 1`.
+///
+/// Refer to the simpler [`physalloc`] and the more complex [`physalloc3`], that this convenience
+/// function is based on.
+///
+/// # Errors
+///
+/// * `EPERM` - `uid != 0`
+/// * `ENOMEM` - the system has run out of available memory
+pub unsafe fn physalloc2(size: usize, flags: usize) -> Result<usize> {
+    let mut ret = 1usize;
+    physalloc3(size, flags, &mut ret)
+}
+
+/// Allocate frames, linearly in physical memory, with an extra set of flags. If the flags contain
+/// [`PARTIAL_ALLOC`], the `min` parameter specifies the number of frames that have to be allocated
+/// for this operation to succeed. The return value is the offset of the first frame, and `min` is
+/// overwritten with the number of frames actually allocated.
+///
+/// Refer to the simpler [`physalloc`] and the simpler library function [`physalloc2`].
+///
+/// # Errors
+///
+/// * `EPERM` - `uid != 0`
+/// * `ENOMEM` - the system has run out of available memory
+/// * `EINVAL` - `min = 0`
+pub unsafe fn physalloc3(size: usize, flags: usize, min: &mut usize) -> Result<usize> {
+    syscall3(SYS_PHYSALLOC3, size, flags, min as *mut usize as usize)
+}
+
 /// Free physically allocated pages
 ///
 /// # Errors

src/flag.rs

@@ -114,6 +114,70 @@ bitflags! {
         const PHYSMAP_NO_CACHE = 0x0000_0004;
     }
 }
+bitflags! {
+    /// Extra flags for [`physalloc2`] or [`physalloc3`].
+    ///
+    /// [`physalloc2`]: ../call/fn.physalloc2.html
+    /// [`physalloc3`]: ../call/fn.physalloc3.html
+    pub struct PhysallocFlags: usize {
+        /// Only allocate memory within the 32-bit physical memory space. This is necessary for
+        /// some devices may not support 64-bit memory.
+        const SPACE_32 =        0x0000_0001;
+
+        /// The frame that will be allocated, is going to reside anywhere in 64-bit space. This
+        /// flag is redundant for the most part, except when overriding some other default.
+        const SPACE_64 =        0x0000_0002;
+
+        /// Do a "partial allocation", which means that not all of the frames specified in the
+        /// frame count `size` actually have to be allocated. This means that if the allocator was
+        /// unable to find a physical memory range large enough, it can instead return whatever
+        /// range it decides is optimal. Thus, instead of letting one driver get an expensive
+        /// 128MiB physical memory range when the physical memory has become fragmented, and
+        /// failing, it can instead be given a more optimal range. If the device supports
+        /// scatter-gather lists, then the driver only has to allocate more ranges, and the device
+        /// will do vectored I/O.
+        ///
+        /// PARTIAL_ALLOC supports different allocation strategies, refer to
+        /// [`Optimal`], [`GreatestRange`].
+        ///
+        /// [`Optimal`]: ./enum.PartialAllocStrategy.html
+        /// [`GreatestRange`]: ./enum.PartialAllocStrategy.html
+        const PARTIAL_ALLOC =   0x0000_0004;
+    }
+}
+
+/// The bitmask of the partial allocation strategy. Currently four different strategies are
+/// supported. If [`PARTIAL_ALLOC`] is not set, this bitmask is no longer reserved.
+pub const PARTIAL_ALLOC_STRATEGY_MASK: usize = 0x0003_0000;
+
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+#[repr(usize)]
+pub enum PartialAllocStrategy {
+    /// The allocator decides itself the size of the memory range, based on e.g. free memory ranges
+    /// and other processes which require large physical memory chunks.
+    Optimal = 0x0001_0000,
+
+    /// The allocator returns the absolute greatest range it can find.
+    GreatestRange = 0x0002_0000,
+
+    /// The allocator returns the first range that fits the minimum count, without searching extra.
+    Greedy = 0x0003_0000,
+}
+impl Default for PartialAllocStrategy {
+    fn default() -> Self {
+        Self::Optimal
+    }
+}
+
+impl PartialAllocStrategy {
+    pub fn from_raw(raw: usize) -> Option<Self> {
+        match raw {
+            0x0001_0000 => Some(Self::Optimal),
+            0x0002_0000 => Some(Self::GreatestRange),
+            _ => None,
+        }
+    }
+}
 
 // The top 48 bits of PTRACE_* are reserved, for now
 

src/io/dma.rs

@@ -1,19 +1,76 @@
-use core::{mem, ptr};
+use core::mem::{self, MaybeUninit};
 use core::ops::{Deref, DerefMut};
+use core::{ptr, slice};
 
 use crate::Result;
+use crate::{PartialAllocStrategy, PhysallocFlags};
 
-struct PhysBox {
+/// 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 {
-    fn new(size: usize) -> Result<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(PhysBox {
-            address: address,
-            size: size
+        Ok(Self {
+            address,
+            size,
         })
     }
 }
@@ -26,53 +83,100 @@ impl Drop for PhysBox {
 
 pub struct Dma<T: ?Sized> {
     phys: PhysBox,
-    virt: *mut T
+    virt: *mut T,
 }
 
 impl<T> Dma<T> {
-    pub fn new(value: T) -> Result<Dma<T>> {
-        let phys = PhysBox::new(mem::size_of::<T>())?;
-        let virt = unsafe { crate::physmap(phys.address, phys.size, crate::PHYSMAP_WRITE)? } as *mut T;
-        unsafe { ptr::write(virt, value); }
-        Ok(Dma {
-            phys: phys,
-            virt: virt
-        })
-    }
-
-    pub fn zeroed() -> Result<Dma<T>> {
-        let phys = PhysBox::new(mem::size_of::<T>())?;
-        let virt = unsafe { crate::physmap(phys.address, phys.size, crate::PHYSMAP_WRITE)? } as *mut T;
-        unsafe { ptr::write_bytes(virt as *mut u8, 0, phys.size); }
-        Ok(Dma {
-            phys: phys,
-            virt: virt
-        })
-    }
-}
-impl<T: ?Sized> Dma<T> {
-    pub fn physical(&self) -> usize {
-        self.phys.address
-    }
-}
-
-impl<T> Dma<[T]> {
-    /// Crates 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)?;
-        let virt_ptr = crate::physmap(phys.address, phys.size, crate::PHYSMAP_WRITE)? as *mut T;
-        ptr::write_bytes(virt_ptr, 0, count);
-
-        let virt = core::slice::from_raw_parts_mut(virt_ptr, count);
+    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> {

src/number.rs

@@ -59,6 +59,7 @@ pub const SYS_MPROTECT: usize = 125;
 pub const SYS_MKNS: usize =     984;
 pub const SYS_NANOSLEEP: usize =162;
 pub const SYS_PHYSALLOC: usize =945;
+pub const SYS_PHYSALLOC3: usize=9453;
 pub const SYS_PHYSFREE: usize = 946;
 pub const SYS_PHYSMAP: usize =  947;
 pub const SYS_PHYSUNMAP: usize =948;