mm/alloc: add GlobalBox implementation

Add a new type, GlobalBox, which wraps around the TryBox type but uses
the global SvsmAllocator transparently. The new type implements
AsRef<TryBox> and Into<TryBox>, so regular TryBox methods can also be
used on the new type.

Signed-off-by: Carlos López <[email protected]>

src/mm/alloc.rs

@@ -1314,7 +1314,7 @@ unsafe impl Allocator for SvsmAllocator {
 
 #[cfg_attr(any(target_os = "none"), global_allocator)]
 #[cfg_attr(not(target_os = "none"), allow(dead_code))]
-static ALLOCATOR: SvsmAllocator = SvsmAllocator::new();
+pub(super) static ALLOCATOR: SvsmAllocator = SvsmAllocator::new();
 
 pub fn root_mem_init(pstart: PhysAddr, vstart: VirtAddr, page_count: usize) {
     {

src/mm/boxed.rs

@@ -0,0 +1,88 @@
+use super::alloc::{SvsmAllocator, ALLOCATOR};
+use crate::alloc::boxed::TryBox;
+use crate::alloc::TryAllocError;
+use crate::error::SvsmError;
+use core::mem::MaybeUninit;
+use core::ops::{Deref, DerefMut};
+
+impl From<TryAllocError> for SvsmError {
+    fn from(err: TryAllocError) -> Self {
+        SvsmError::TryAlloc(err)
+    }
+}
+
+/// A [`TryBox`] wrapper which uses the global memory allocator.
+#[derive(Debug)]
+pub struct GlobalBox<T>(TryBox<T, &'static SvsmAllocator>);
+
+impl<T> GlobalBox<T> {
+    pub fn try_new(val: T) -> Result<Self, SvsmError> {
+        let inner = TryBox::try_new_in(val, &ALLOCATOR)?;
+        Ok(Self(inner))
+    }
+
+    pub fn try_new_uninit() -> Result<GlobalBox<MaybeUninit<T>>, SvsmError> {
+        let inner = TryBox::try_new_uninit_in(&ALLOCATOR)?;
+        Ok(GlobalBox(inner))
+    }
+
+    pub fn try_new_zeroed() -> Result<GlobalBox<MaybeUninit<T>>, SvsmError> {
+        let inner = TryBox::try_new_zeroed_in(&ALLOCATOR)?;
+        Ok(GlobalBox(inner))
+    }
+
+    pub fn into_inner(self) -> T {
+        TryBox::into_inner(self.0)
+    }
+
+    /// # Safety
+    ///
+    /// See the safety requirements for [`TryBox::from_raw_in()`].
+    #[inline]
+    pub unsafe fn from_raw(raw: *mut T) -> Self {
+        Self(TryBox::from_raw_in(raw, &ALLOCATOR))
+    }
+}
+
+impl<T> From<TryBox<T, &'static SvsmAllocator>> for GlobalBox<T> {
+    fn from(boxed: TryBox<T, &'static SvsmAllocator>) -> Self {
+        Self(boxed)
+    }
+}
+
+impl<T> From<GlobalBox<T>> for TryBox<T, &'static SvsmAllocator> {
+    fn from(boxed: GlobalBox<T>) -> Self {
+        let ptr = TryBox::into_raw(boxed.0);
+        // SAFETY: if this GlobalBox was constructed correctly then the inner
+        // pointer is guaranteed to belong to the global allocator. This
+        // function also consumes the GlobalBox, so the inner pointer will
+        // not be used twice.
+        unsafe { TryBox::from_raw_in(ptr, &ALLOCATOR) }
+    }
+}
+
+impl<T> AsRef<TryBox<T, &'static SvsmAllocator>> for GlobalBox<T> {
+    fn as_ref(&self) -> &TryBox<T, &'static SvsmAllocator> {
+        &self.0
+    }
+}
+
+impl<T> AsMut<TryBox<T, &'static SvsmAllocator>> for GlobalBox<T> {
+    fn as_mut(&mut self) -> &mut TryBox<T, &'static SvsmAllocator> {
+        &mut self.0
+    }
+}
+
+impl<T> Deref for GlobalBox<T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        TryBox::deref(self.as_ref())
+    }
+}
+
+impl<T> DerefMut for GlobalBox<T> {
+    fn deref_mut(&mut self) -> &mut T {
+        TryBox::deref_mut(self.as_mut())
+    }
+}

src/mm/mod.rs

@@ -6,6 +6,7 @@
 
 pub mod address_space;
 pub mod alloc;
+mod boxed;
 pub mod guestmem;
 pub mod memory;
 pub mod page_visibility;
@@ -17,6 +18,7 @@ pub mod virtualrange;
 pub mod vm;
 
 pub use address_space::*;
+pub use boxed::GlobalBox;
 pub use guestmem::GuestPtr;
 pub use memory::{valid_phys_address, writable_phys_addr};
 pub use ptguards::*;