From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8BB6121E097; Wed, 12 Feb 2025 15:40:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739374844; cv=none; b=jyzxPWLQJQBeJojfij5QC10+HuE8aYMd1iwFN5EUN5zFpJHE4qQuQq800Sxam7y2hIKW8Gy40076sXUyx/dbIAbJY0b0R/jU7cSo99TGIgnI5TNhUX1199jJgAnwbPnzGVuPDJouEX5/bWiU30rItjNUISNiQCpSHjJTBJzo4ww= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739374844; c=relaxed/simple; bh=zriqMxxivzJ+e+SRUhbYjcGx6tySbbLJ8Jprrig86VM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ogya9S0/mVQVHs04h8BDwFvWyjslLyN+Wa8slcst/RUKcgzfHEjyMnrjy9WUzWiZvQ5nnhQXdndzVKJV0MO9lf9VY9Jtnip+wfY2Xgf9TixcdFhTQzeqLViZnQziXBtcOG3WU/HVo5fn5QWdEskfIT8Xf51r2ew/kV2mq//URsI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NlzXXs60; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="NlzXXs60" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A04A2C4CEDF; Wed, 12 Feb 2025 15:40:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1739374844; bh=zriqMxxivzJ+e+SRUhbYjcGx6tySbbLJ8Jprrig86VM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=NlzXXs60MAUomwoBgs1NCPoADrVw0Ssbfuk0Xy9+tnfyQifq3TUvT8ghgxN7Zt5Vg q88KvhPsjWtGhfHC5ISbe/9ky9Hy10O/MpsywIdrh9ADdWJqCyui/mgEbhh1civiBF I8DnC5nO17K2h9fTGf91THDhI+paJr7nBYSEIklyVbv7sKvNA8/DuGjOOhPhmK5qQ7 FShFV7TdJrkJa7wWJH4rYjYjjWj+tC3oF4l+CFeBn6MjBK5NayzpYU6jHpXUt5loTe OD/CrQftFVgXqT2Kudxa3rl2MvZK7cOEcGNF4XZCep25n91LlW/92WiuF9ogVfQKHr bl3kN9ysNohBg== Date: Wed, 12 Feb 2025 16:40:37 +0100 From: Danilo Krummrich To: Tamir Duberstein Cc: Miguel Ojeda , DJ Delorie , Eric Blake , Paul Eggert , Alex Gaynor , Boqun Feng , Gary Guo , =?iso-8859-1?Q?Bj=F6rn?= Roy Baron , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , rust-for-linux@vger.kernel.org, linux-man@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5] rust: alloc: satisfy POSIX alignment requirement Message-ID: References: <20250212-aligned-alloc-v5-1-c51e0b17dee9@gmail.com> Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250212-aligned-alloc-v5-1-c51e0b17dee9@gmail.com> On Wed, Feb 12, 2025 at 09:43:02AM -0500, Tamir Duberstein wrote: > diff --git a/rust/kernel/alloc/allocator_test.rs b/rust/kernel/alloc/allocator_test.rs > index e3240d16040b..17a475380253 100644 > --- a/rust/kernel/alloc/allocator_test.rs > +++ b/rust/kernel/alloc/allocator_test.rs > @@ -62,6 +62,26 @@ unsafe fn realloc( > )); > } > > + // 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).unwrap_or_else(|_err| { > + crate::build_error!("invalid alignment") That's not what I thought this patch will look like. I thought you'll directly follow Gary's proposal, which is why I said you can keep the ACK. build_error!() doesn't work here, there is no guarantee that this can be evaluated at compile time. I think this should just be: let layout = layout.align_to(min_align).map_err(|_| AllocError)?.pad_to_align(); - Danilo > + }); > + 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;