linux-kernel - Re: [PATCH v7 2/2] rust: miscdevice: add mmap support

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Message-ID: <Zw03kpgOYA1GbvAD@Boquns-Mac-mini.local>
Date: Mon, 14 Oct 2024 08:24:02 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, Matthew Wilcox <willy@...radead.org>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	John Hubbard <jhubbard@...dia.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Arnd Bergmann <arnd@...db.de>, Alex Gaynor <alex.gaynor@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, rust-for-linux@...r.kernel.org,
	Andreas Hindborg <a.hindborg@...nel.org>
Subject: Re: [PATCH v7 2/2] rust: miscdevice: add mmap support

On Mon, Oct 14, 2024 at 09:29:52AM +0000, Alice Ryhl wrote:
> Using the vma support introduced by the previous commit, introduce mmap
> support for miscdevices. The mmap call is given a vma that is undergoing
> initial setup, so the VmAreaNew type is used.
> 
> Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>

Acked-by: Boqun Feng <boqun.feng@...il.com>

Regards,
Boqun

> ---
>  rust/kernel/miscdevice.rs | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs
> index cbd5249b5b45..c9428a6154e3 100644
> --- a/rust/kernel/miscdevice.rs
> +++ b/rust/kernel/miscdevice.rs
> @@ -11,6 +11,7 @@
>  use crate::{
>      bindings,
>      error::{to_result, Error, Result, VTABLE_DEFAULT_ERROR},
> +    mm::virt::VmAreaNew,
>      prelude::*,
>      str::CStr,
>      types::{ForeignOwnable, Opaque},
> @@ -110,6 +111,11 @@ fn release(device: Self::Ptr) {
>          drop(device);
>      }
>  
> +    /// Handle for mmap.
> +    fn mmap(_device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>, _vma: &VmAreaNew) -> Result {
> +        kernel::build_error(VTABLE_DEFAULT_ERROR)
> +    }
> +
>      /// Handler for ioctls.
>      ///
>      /// The `cmd` argument is usually manipulated using the utilties in [`kernel::ioctl`].
> @@ -156,6 +162,7 @@ impl<T: MiscDevice> VtableHelper<T> {
>          const VTABLE: bindings::file_operations = bindings::file_operations {
>              open: Some(fops_open::<T>),
>              release: Some(fops_release::<T>),
> +            mmap: maybe_fn(T::HAS_MMAP, fops_mmap::<T>),
>              unlocked_ioctl: maybe_fn(T::HAS_IOCTL, fops_ioctl::<T>),
>              #[cfg(CONFIG_COMPAT)]
>              compat_ioctl: if T::HAS_COMPAT_IOCTL {
> @@ -207,6 +214,23 @@ impl<T: MiscDevice> VtableHelper<T> {
>      0
>  }
>  
> +unsafe extern "C" fn fops_mmap<T: MiscDevice>(
> +    file: *mut bindings::file,
> +    vma: *mut bindings::vm_area_struct,
> +) -> c_int {
> +    // SAFETY: The mmap call of a file can access the private data.
> +    let private = unsafe { (*file).private_data };
> +    // SAFETY: Mmap calls can borrow the private data of the file.
> +    let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };
> +    // SAFETY: The caller provides a vma that is undergoing initial VMA setup.
> +    let area = unsafe { kernel::mm::virt::VmAreaNew::from_raw(vma) };
> +
> +    match T::mmap(device, area) {
> +        Ok(()) => 0,
> +        Err(err) => err.to_errno() as c_int,
> +    }
> +}
> +
>  unsafe extern "C" fn fops_ioctl<T: MiscDevice>(
>      file: *mut bindings::file,
>      cmd: c_uint,
> 
> -- 
> 2.47.0.rc1.288.g06298d1525-goog
>