From: Tamir Duberstein <tamird@xxxxxxxxx>
commit ff64846bee0e7e3e7bc9363ebad3bab42dd27e24 upstream.
ISO C's `aligned_alloc` is partially implementation-defined; on some
systems it inherits stricter requirements from POSIX's `posix_memalign`.
This causes the call added in commit dd09538fb409 ("rust: alloc:
implement `Cmalloc` in module allocator_test") to fail on macOS because
it doesn't meet the requirements of `posix_memalign`.
Adjust the call to meet the POSIX requirement and add a comment. This
fixes failures in `make rusttest` on macOS.
Acked-by: Danilo Krummrich <dakr@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Fixes: dd09538fb409 ("rust: alloc: implement `Cmalloc` in module allocator_test")
Signed-off-by: Tamir Duberstein <tamird@xxxxxxxxx>
Reviewed-by: Gary Guo <gary@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20250213-aligned-alloc-v7-1-d2a2d0be164b@xxxxxxxxx
[ Added Cc: stable. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
rust/kernel/alloc/allocator_test.rs | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
--- a/rust/kernel/alloc/allocator_test.rs
+++ b/rust/kernel/alloc/allocator_test.rs
@@ -62,6 +62,24 @@ unsafe impl Allocator for Cmalloc {
));
}
+ // ISO C (ISO/IEC 9899:2011) defines `aligned_alloc`:
+ //
+ // > The value of alignment shall be a valid alignment supported by the implementation
+ // [...].
+ //
+ // As an example of the "supported by the implementation" requirement, POSIX.1-2001 (IEEE
+ // 1003.1-2001) defines `posix_memalign`:
+ //
+ // > The value of alignment shall be a power of two multiple of sizeof (void *).
+ //
+ // and POSIX-based implementations of `aligned_alloc` inherit this requirement. At the time
+ // of writing, this is known to be the case on macOS (but not in glibc).
+ //
+ // Satisfy the stricter requirement to avoid spurious test failures on some platforms.
+ let min_align = core::mem::size_of::<*const crate::ffi::c_void>();
+ let layout = layout.align_to(min_align).map_err(|_| AllocError)?;
+ let layout = layout.pad_to_align();
+
// SAFETY: Returns either NULL or a pointer to a memory allocation that satisfies or
// exceeds the given size and alignment requirements.
let dst = unsafe { libc_aligned_alloc(layout.align(), layout.size()) } as *mut u8;
Patches currently in stable-queue which might be from tamird@xxxxxxxxx are
queue-6.12/rust-alloc-satisfy-posix-alignment-requirement.patch
