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Date: Wed, 12 Feb 2025 21:58:23 +0100
From: Danilo Krummrich <dakr@kernel.org>
To: Tamir Duberstein <tamird@gmail.com>
Cc: Gary Guo <gary@garyguo.net>, Miguel Ojeda <ojeda@kernel.org>,
	DJ Delorie <dj@redhat.com>, Eric Blake <eblake@redhat.com>,
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	Boqun Feng <boqun.feng@gmail.com>,
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	Alice Ryhl <aliceryhl@google.com>, Trevor Gross <tmgross@umich.edu>,
	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
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On Wed, Feb 12, 2025 at 03:47:11PM -0500, Tamir Duberstein wrote:
> Looks like I wasn't the only one to fall into the trap (rust/kernel/io.rs):
> 
>     #[inline]
>     const fn io_addr_assert<U>(&self, offset: usize) -> usize {
>         build_assert!(Self::offset_valid::<U>(offset, SIZE));
> 
>         self.addr() + offset
>     }
> 
> since offset isn't known at compile time, this can easily be misused?

Well, that's intentional.

iomem.readb(0x0)     // succeeds if SIZE >=1
iomem.readb(foo)     // fails if foo is not known at compile time
iomem.try_readb(foo) // succeeds if self.maxsize() >= 1