linux-kernel - Re: [PATCH v2 2/5] rust: dma: add DMA addressing capabilities

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-Id: <442B2871-4512-4C5B-A394-C9CA14FF4C3C@collabora.com>
Date: Wed, 16 Jul 2025 19:19:49 -0300
From: Daniel Almeida <daniel.almeida@...labora.com>
To: Danilo Krummrich <dakr@...nel.org>
Cc: abdiel.janulgue@...il.com,
 robin.murphy@....com,
 a.hindborg@...nel.org,
 ojeda@...nel.org,
 alex.gaynor@...il.com,
 boqun.feng@...il.com,
 gary@...yguo.net,
 bjorn3_gh@...tonmail.com,
 lossin@...nel.org,
 aliceryhl@...gle.com,
 tmgross@...ch.edu,
 bhelgaas@...gle.com,
 kwilczynski@...nel.org,
 gregkh@...uxfoundation.org,
 rafael@...nel.org,
 rust-for-linux@...r.kernel.org,
 linux-pci@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/5] rust: dma: add DMA addressing capabilities

For some reason this diff did not apply on top of your latest commit (corrupt
patch on line 6)

> 
> diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs
> index afd3ba538e3c..ad69ef316295 100644
> --- a/rust/kernel/dma.rs
> +++ b/rust/kernel/dma.rs
> @@ -81,25 +81,6 @@ unsafe fn dma_set_mask_and_coherent(&self, mask: DmaMask) -> Result {
> /// never exceed the bit width of `u64`.
> ///
> /// This is the Rust equivalent of the C macro `DMA_BIT_MASK()`.
> -///
> -/// # Examples
> -///
> -/// ```
> -/// use kernel::dma::DmaMask;
> -///
> -/// let mask0 = DmaMask::new(0)?;
> -/// assert_eq!(mask0.value(), 0);
> -///
> -/// let mask1 = DmaMask::new(1)?;
> -/// assert_eq!(mask1.value(), 0b1);
> -///
> -/// let mask64 = DmaMask::new(64)?;
> -/// assert_eq!(mask64.value(), u64::MAX);
> -///
> -/// let mask_overflow = DmaMask::new(100);
> -/// assert!(mask_overflow.is_err());
> -/// # Ok::<(), Error>(())
> -/// ```
> #[derive(Debug, Clone, Copy, PartialEq, Eq)]
> pub struct DmaMask(u64);
> 
> @@ -108,8 +89,27 @@ impl DmaMask {
>     ///
>     /// For `n <= 64`, sets exactly the lowest `n` bits.
>     /// For `n > 64`, returns [`EINVAL`].
> +    ///
> +    /// # Examples
> +    ///
> +    /// ```
> +    /// use kernel::dma::DmaMask;
> +    ///
> +    /// let mask0 = DmaMask::try_new(0)?;
> +    /// assert_eq!(mask0.value(), 0);
> +    ///
> +    /// let mask1 = DmaMask::try_new(1)?;
> +    /// assert_eq!(mask1.value(), 0b1);
> +    ///
> +    /// let mask64 = DmaMask::try_new(64)?;
> +    /// assert_eq!(mask64.value(), u64::MAX);
> +    ///
> +    /// let mask_overflow = DmaMask::try_new(100);
> +    /// assert!(mask_overflow.is_err());
> +    /// # Ok::<(), Error>(())
> +    /// ```
>     #[inline]
> -    pub const fn new(n: usize) -> Result<Self> {
> +    pub const fn try_new(n: u32) -> Result<Self> {
>         Ok(Self(match n {
>             0 => 0,
>             1..=64 => u64::MAX >> (64 - n),
> @@ -117,6 +117,38 @@ pub const fn new(n: usize) -> Result<Self> {
>         }))
>     }
> 
> +    /// Constructs a `DmaMask` with the lowest `n` bits set to `1`.
> +    ///
> +    /// For `n <= 64`, sets exactly the lowest `n` bits.
> +    /// For `n > 64`, results in a build error.
> +    ///
> +    /// # Examples
> +    ///
> +    /// ```
> +    /// use kernel::dma::DmaMask;
> +    /// use kernel::bits::genmask_u64;

There is also this, which is not upstream (nor used in the patch)

> +    ///
> +    /// let mask0 = DmaMask::new::<0>();
> +    /// assert_eq!(mask0.value(), 0);
> +    ///
> +    /// let mask1 = DmaMask::new::<1>();
> +    /// assert_eq!(mask1.value(), 0b1);
> +    ///
> +    /// let mask64 = DmaMask::new::<64>();
> +    /// assert_eq!(mask64.value(), u64::MAX);
> +    ///
> +    /// // Build failure.
> +    /// // let mask_overflow = DmaMask::new::<100>();
> +    /// ```
> +    #[inline(always)]
> +    pub const fn new<const N: u32>() -> Self {
> +        let Ok(mask) = Self::try_new(N) else {
> +            build_error!("Invalid DMA Mask.");
> +        };
> +
> +        mask
> +    }
> +
>     /// Returns the underlying `u64` bitmask value.
>     #[inline]
>     pub const fn value(&self) -> u64 {
> diff --git a/samples/rust/rust_dma.rs b/samples/rust/rust_dma.rs
> index 9422ac68c139..c5e7cce68654 100644
> --- a/samples/rust/rust_dma.rs
> +++ b/samples/rust/rust_dma.rs
> @@ -58,7 +58,7 @@ impl pci::Driver for DmaSampleDriver {
>     fn probe(pdev: &pci::Device<Core>, _info: &Self::IdInfo) -> Result<Pin<KBox<Self>>> {
>         dev_info!(pdev.as_ref(), "Probe DMA test driver.\n");
> 
> -        let mask = DmaMask::new(64)?;
> +        let mask = DmaMask::new::<64>();
> 
>         // SAFETY: There are no concurrent calls to DMA allocation and mapping primitives.
>         unsafe { pdev.dma_set_mask_and_coherent(mask)? };
> 
> 

I hand-applied this and fixed the issue above. All doctests pass FYI.

— Daniel