[PATCH v8 1/2] rust: alloc: add alignment tests for allocators

[Hui Zhu]

From: Hui Zhu <zhuhui@xxxxxxxxxx>

Add unit tests to verify alignment guarantees of Kmalloc, Vmalloc,
and KVmallocallocators. Tests create types with explicit alignment
requirements (128B and 8192B) and validate allocations meet alignment.
Includes two test blobs with custom alignments and helper struct
TestAlignto abstract allocation and alignment checks.

Also updates kvec test macro name from rust_kvec_kunitto rust_kvec
for consistency with other test modules.

Co-developed-by: Geliang Tang <geliang@xxxxxxxxxx>
Signed-off-by: Geliang Tang <geliang@xxxxxxxxxx>
Signed-off-by: Hui Zhu <zhuhui@xxxxxxxxxx>
Reviewed-by: Kunwu Chan <chentao@xxxxxxxxxx>
Reviewed-by: David Gow <davidgow@xxxxxxxxxx>
---
 rust/kernel/alloc/allocator.rs | 56 ++++++++++++++++++++++++++++++++++
 rust/kernel/alloc/kvec.rs      |  2 +-
 2 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index 63f271624428..a20111b40529 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -184,3 +184,59 @@ unsafe fn realloc(
         unsafe { ReallocFunc::KVREALLOC.call(ptr, layout, old_layout, flags, nid) }
     }
 }
+
+#[macros::kunit_tests(rust_allocator)]
+mod tests {
+    use super::*;
+    use core::mem::MaybeUninit;
+    use kernel::prelude::*;
+
+    #[test]
+    fn test_alignment() -> Result {
+        const TEST_SIZE: usize = 1024;
+        const TEST_LARGE_ALIGN_SIZE: usize = kernel::page::PAGE_SIZE * 4;
+
+        // These two structs are used to test allocating aligned memory.
+        // they don't need to be accessed, so they're marked as dead_code.
+        #[expect(dead_code)]
+        #[repr(align(128))]
+        struct Blob([u8; TEST_SIZE]);
+        #[expect(dead_code)]
+        #[repr(align(8192))]
+        struct LargeAlignBlob([u8; TEST_LARGE_ALIGN_SIZE]);
+
+        struct TestAlign<T, A: Allocator>(Box<MaybeUninit<T>, A>);
+        impl<T, A: Allocator> TestAlign<T, A> {
+            fn new() -> Result<Self> {
+                Ok(Self(Box::<_, A>::new_uninit(GFP_KERNEL)?))
+            }
+
+            fn is_aligned_to(&self, align: usize) -> bool {
+                assert!(align.is_power_of_two());
+
+                let addr = self.0.as_ptr() as usize;
+                addr & (align - 1) == 0
+            }
+        }
+
+        let ta = TestAlign::<Blob, Kmalloc>::new()?;
+        assert!(ta.is_aligned_to(128));
+
+        let ta = TestAlign::<LargeAlignBlob, Kmalloc>::new()?;
+        assert!(ta.is_aligned_to(8192));
+
+        let ta = TestAlign::<Blob, Vmalloc>::new()?;
+        assert!(ta.is_aligned_to(128));
+
+        let ta = TestAlign::<LargeAlignBlob, Vmalloc>::new()?;
+        assert!(ta.is_aligned_to(8192));
+
+        let ta = TestAlign::<Blob, KVmalloc>::new()?;
+        assert!(ta.is_aligned_to(128));
+
+        let ta = TestAlign::<LargeAlignBlob, KVmalloc>::new()?;
+        assert!(ta.is_aligned_to(8192));
+
+        Ok(())
+    }
+}
diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs
index 92d0ed3f302e..f912a9642969 100644
--- a/rust/kernel/alloc/kvec.rs
+++ b/rust/kernel/alloc/kvec.rs
@@ -1301,7 +1301,7 @@ fn drop(&mut self) {
     }
 }
 
-#[macros::kunit_tests(rust_kvec_kunit)]
+#[macros::kunit_tests(rust_kvec)]
 mod tests {
     use super::*;
     use crate::prelude::*;
-- 
2.43.0