linux-kernel - [PATCH v6 1/2] rust: allocator: add KUnit tests for alignment guarantees

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Message-ID: <3ad14f15b6d2639d6e998ecd03158313414b69dd.1753841900.git.zhuhui@kylinos.cn>
Date: Wed, 30 Jul 2025 11:35:21 +0800
From: Hui Zhu <hui.zhu@...ux.dev>
To: Danilo Krummrich <dakr@...nel.org>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	"Liam R . Howlett" <Liam.Howlett@...cle.com>,
	Uladzislau Rezki <urezki@...il.com>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	bjorn3_gh@...tonmail.com,
	Benno Lossin <lossin@...nel.org>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Trevor Gross <tmgross@...ch.edu>,
	rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org,
	vitaly.wool@...sulko.se
Cc: Hui Zhu <zhuhui@...inos.cn>,
	Geliang Tang <geliang@...nel.org>
Subject: [PATCH v6 1/2] rust: allocator: add KUnit tests for alignment guarantees

From: Hui Zhu <zhuhui@...inos.cn>

Add a test module to verify memory alignment guarantees for Rust kernel
allocators.
The tests cover `Kmalloc`, `Vmalloc` and `KVmalloc` allocators
with both standard and large page-aligned allocations.

Key features of the tests:
1. Creates alignment-constrained types:
   - 128-byte aligned `Blob`
   - 8192-byte (4-page) aligned `LargeAlignBlob`
2. Validates allocators using `TestAlign` helper which:
   - Checks address alignment masks
   - Supports uninitialized allocations
3. Tests all three allocators with both alignment requirements:
   - Kmalloc with 128B and 8192B
   - Vmalloc with 128B and 8192B
   - KVmalloc with 128B and 8192B

Co-developed-by: Geliang Tang <geliang@...nel.org>
Signed-off-by: Geliang Tang <geliang@...nel.org>
Signed-off-by: Hui Zhu <zhuhui@...inos.cn>
---
 rust/kernel/alloc/allocator.rs | 56 ++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index 63f271624428..1f173038cec9 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_kunit)]
+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 alignment_valid(&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.alignment_valid(128));
+
+        let ta = TestAlign::<LargeAlignBlob, Kmalloc>::new()?;
+        assert!(ta.alignment_valid(8192));
+
+        let ta = TestAlign::<Blob, Vmalloc>::new()?;
+        assert!(ta.alignment_valid(128));
+
+        let ta = TestAlign::<LargeAlignBlob, Vmalloc>::new()?;
+        assert!(ta.alignment_valid(8192));
+
+        let ta = TestAlign::<Blob, KVmalloc>::new()?;
+        assert!(ta.alignment_valid(128));
+
+        let ta = TestAlign::<LargeAlignBlob, KVmalloc>::new()?;
+        assert!(ta.alignment_valid(8192));
+
+        Ok(())
+    }
+}
-- 
2.43.0