linux-kernel - Re: [PATCH v2 2/3] rust: dma: convert the read/write macros to return Result

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Z_exjZ9xEntlL9FC@pollux>
Date: Thu, 10 Apr 2025 13:54:53 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: Abdiel Janulgue <abdiel.janulgue@...il.com>
Cc: a.hindborg@...nel.org, benno.lossin@...ton.me,
	rust-for-linux@...r.kernel.org, Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	Valentin Obst <kernel@...entinobst.de>,
	open list <linux-kernel@...r.kernel.org>,
	Christoph Hellwig <hch@....de>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Robin Murphy <robin.murphy@....com>, airlied@...hat.com,
	"open list:DMA MAPPING HELPERS" <iommu@...ts.linux.dev>
Subject: Re: [PATCH v2 2/3] rust: dma: convert the read/write macros to
 return Result

On Thu, Apr 10, 2025 at 11:58:17AM +0300, Abdiel Janulgue wrote:
> diff --git a/samples/rust/rust_dma.rs b/samples/rust/rust_dma.rs
> index 874c2c964afa..1e610545e100 100644
> --- a/samples/rust/rust_dma.rs
> +++ b/samples/rust/rust_dma.rs
> @@ -54,13 +54,9 @@ fn probe(pdev: &pci::Device<Core>, _info: &Self::IdInfo) -> Result<Pin<KBox<Self
>          let ca: CoherentAllocation<MyStruct> =
>              CoherentAllocation::alloc_coherent(pdev.as_ref(), TEST_VALUES.len(), GFP_KERNEL)?;
>  
> -        || -> Result {
> -            for (i, value) in TEST_VALUES.into_iter().enumerate() {
> -                kernel::dma_write!(ca[i] = MyStruct::new(value.0, value.1));
> -            }
> -
> -            Ok(())
> -        }()?;
> +        for (i, value) in TEST_VALUES.into_iter().enumerate() {
> +            kernel::dma_write!(ca[i] = MyStruct::new(value.0, value.1))?;
> +        }
>  
>          let drvdata = KBox::new(
>              Self {
> @@ -78,13 +74,14 @@ impl Drop for DmaSampleDriver {
>      fn drop(&mut self) {
>          dev_info!(self.pdev.as_ref(), "Unload DMA test driver.\n");
>  
> -        let _ = || -> Result {
> -            for (i, value) in TEST_VALUES.into_iter().enumerate() {
> -                assert_eq!(kernel::dma_read!(self.ca[i].h), value.0);
> -                assert_eq!(kernel::dma_read!(self.ca[i].b), value.1);
> -            }
> -            Ok(())
> -        }();
> +        for (i, value) in TEST_VALUES.into_iter().enumerate() {
> +            let val0 = kernel::dma_read!(self.ca[i].h);
> +            let val1 = kernel::dma_read!(self.ca[i].b);
> +            assert!(val0.is_ok());
> +            assert!(val1.is_ok());
> +            assert_eq!(val0.unwrap(), value.0);
> +            assert_eq!(val1.unwrap(), value.1);

Maybe use if-let to avoid the unwrap?

	if let Ok(val0) = val0 {
	   assert_eq!(val0, value.0);
	}

I know it's a bit pointless, since we know it must be ok, but the educational
message of the example should be to check and not to unwrap, so maybe that's
better.