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@oracle.com> (for mm bits)
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
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
"Alice Ryhl" <aliceryhl@google.com> writes: > 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@oracle.com> (for mm bits) > Signed-off-by: Alice Ryhl <aliceryhl@google.com> > --- > 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. Perhaps "Check whether the `VM_MIXEDMAP` flag is set. If so, return `Some`, otherwise `None` ? > + /// > + /// 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. Could we have a link to `VmAreaRef` and explain that this is a `VmAreaRef` with an additional requirement? > +/// > +/// # 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. Maybe something like this: "By the type invariant of `Self` caller has read access and has verified that `VM_MIXEDMAP` is set. By invariant on `Page` the page has order 0." > + to_result(unsafe { bindings::vm_insert_page(self.as_ptr(), address as _, page.as_ptr()) }) > + } > } > > /// The integer type used for vma flags. Best regards, Andreas Hindborg
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