[PATCH 1/2] rust: mm: add VmaRef range query helpers

From: liujinlong <[email protected]>

Add helpers on VmaRef to query the virtual address span and test
address membership:

  len(), is_empty()       - byte span and zero-length check
  contains()              - single-address membership in
                           [vm_start, vm_end)
  contains_range()        - sub-range membership, returns false
                           on overflow
  is_page_aligned()       - PAGE_SIZE alignment for one address
  is_page_aligned_range() - PAGE_SIZE alignment for addr and size

is_page_aligned() and is_page_aligned_range() are associated
functions rather than methods, since they do not reference any VMA
state.  They live here instead of a separate utility module to
keep the page-alignment helpers close to the range-checking code
that often uses them.

Signed-off-by: liujinlong <[email protected]>
---
 rust/kernel/mm/virt.rs | 41 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 40 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/mm/virt.rs b/rust/kernel/mm/virt.rs
index 63eb730b0b05..5fdc3c616ef3 100644
--- a/rust/kernel/mm/virt.rs
+++ b/rust/kernel/mm/virt.rs
@@ -18,7 +18,7 @@
     bindings,
     error::{code::EINVAL, to_result, Result},
     mm::MmWithUser,
-    page::Page,
+    page::{Page, PAGE_SIZE},
     types::Opaque,
 };
 
@@ -92,6 +92,45 @@ pub fn end(&self) -> usize {
         unsafe { (*self.as_ptr()).__bindgen_anon_1.__bindgen_anon_1.vm_end }
     }
 
+    /// Size in bytes (`vm_end - vm_start`).
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.end() - self.start()
+    }
+
+    /// True if `vm_start == vm_end`.
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.start() == self.end()
+    }
+
+    /// True if `addr` lies in `[vm_start, vm_end)`.
+    #[inline]
+    pub fn contains(&self, addr: usize) -> bool {
+        self.start() <= addr && addr < self.end()
+    }
+
+    /// True if `[addr, addr + size)` lies in `[vm_start, vm_end)`; false on overflow.
+    #[inline]
+    pub fn contains_range(&self, addr: usize, size: usize) -> bool {
+        let Some(end) = addr.checked_add(size) else {
+            return false;
+        };
+        self.start() <= addr && end <= self.end()
+    }
+
+    /// True if `addr` is `PAGE_SIZE`-aligned.
+    #[inline]
+    pub fn is_page_aligned(addr: usize) -> bool {
+        addr % PAGE_SIZE == 0
+    }
+
+    /// True if `addr` and `size` are both page-aligned.
+    #[inline]
+    pub fn is_page_aligned_range(addr: usize, size: usize) -> bool {
+        Self::is_page_aligned(addr) && Self::is_page_aligned(size)
+    }
+
     /// Zap pages in the given page range.
     ///
     /// This clears page table mappings for the range at the leaf level, leaving all other page
-- 
2.25.1