The vm_insert_page method is only usable on vmas with the VM_MIXEDMAP
flag, so we introduce a new type to keep track of such vmas.
The approach used in this patch assumes that we will not need to encode
many flag combinations in the type. I don't think we need to encode more
than VM_MIXEDMAP and VM_PFNMAP as things are now. However, if that
becomes necessary, using generic parameters in a single type would scale
better as the number of flags increases.
Acked-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx> (for mm bits)
Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
---
rust/kernel/mm/virt.rs | 71 +++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 70 insertions(+), 1 deletion(-)
diff --git a/rust/kernel/mm/virt.rs b/rust/kernel/mm/virt.rs
index 68c763169cf0..3a23854e14f4 100644
--- a/rust/kernel/mm/virt.rs
+++ b/rust/kernel/mm/virt.rs
@@ -4,7 +4,15 @@
//! Virtual memory.
-use crate::{bindings, mm::MmWithUser, types::Opaque};
+use crate::{
+ bindings,
+ error::{to_result, Result},
+ mm::MmWithUser,
+ page::Page,
+ types::Opaque,
+};
+
+use core::ops::Deref;
/// A wrapper for the kernel's `struct vm_area_struct` with read access.
///
@@ -100,6 +108,67 @@ pub fn zap_page_range_single(&self, address: usize, size: usize) {
)
};
}
+
+ /// Check whether the `VM_MIXEDMAP` flag is set.
+ ///
+ /// This can be used to access methods that require `VM_MIXEDMAP` to be set.
+ #[inline]
+ pub fn as_mixedmap_vma(&self) -> Option<&VmAreaMixedMap> {
+ if self.flags() & flags::MIXEDMAP != 0 {
+ // SAFETY: We just checked that `VM_MIXEDMAP` is set. All other requirements are
+ // satisfied by the type invariants of `VmAreaRef`.
+ Some(unsafe { VmAreaMixedMap::from_raw(self.as_ptr()) })
+ } else {
+ None
+ }
+ }
+}
+
+/// A wrapper for the kernel's `struct vm_area_struct` with read access and `VM_MIXEDMAP` set.
+///
+/// It represents an area of virtual memory.
+///
+/// # Invariants
+///
+/// The caller must hold the mmap read lock or the vma read lock. The `VM_MIXEDMAP` flag must be
+/// set.
+#[repr(transparent)]
+pub struct VmAreaMixedMap {
+ vma: VmAreaRef,
+}
+
+// Make all `VmAreaRef` methods available on `VmAreaMixedMap`.
+impl Deref for VmAreaMixedMap {
+ type Target = VmAreaRef;
+
+ #[inline]
+ fn deref(&self) -> &VmAreaRef {
+ &self.vma
+ }
+}
+
+impl VmAreaMixedMap {
+ /// Access a virtual memory area given a raw pointer.
+ ///
+ /// # Safety
+ ///
+ /// Callers must ensure that `vma` is valid for the duration of 'a, and that the mmap read lock
+ /// (or stronger) is held for at least the duration of 'a. The `VM_MIXEDMAP` flag must be set.
+ #[inline]
+ pub unsafe fn from_raw<'a>(vma: *const bindings::vm_area_struct) -> &'a Self {
+ // SAFETY: The caller ensures that the invariants are satisfied for the duration of 'a.
+ unsafe { &*vma.cast() }
+ }
+
+ /// Maps a single page at the given address within the virtual memory area.
+ ///
+ /// This operation does not take ownership of the page.
+ #[inline]
+ pub fn vm_insert_page(&self, address: usize, page: &Page) -> Result {
+ // SAFETY: The caller has read access and has verified that `VM_MIXEDMAP` is set. The page
+ // is order 0. The address is checked on the C side so it can take any value.
+ to_result(unsafe { bindings::vm_insert_page(self.as_ptr(), address as _, page.as_ptr()) })
+ }
}
/// The integer type used for vma flags.
--
2.47.1.613.gc27f4b7a9f-goog
