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

Boqun Feng
2024-10-14T15:24:05Z

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@google.com>

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