On Wed, Nov 20, 2024 at 02:50:01PM +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.
Again, I'd be explicit about the VMA being passed to a struct
file_operations->mmap() hook on mmap. Otherwise this seems super vague to
me!
>
> Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
> ---
> rust/kernel/miscdevice.rs | 28 ++++++++++++++++++++++++++++
> 1 file changed, 28 insertions(+)
>
> diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs
> index 7e2a79b3ae26..4e4b9476e092 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 {
You will have to help me with this :) ForeignOwnable, Borrowed<'_>, _vma I'm a
bit lost here!
> + kernel::build_error(VTABLE_DEFAULT_ERROR)
What is this? Is this not yet implemented or something, and this is a
placeholder or something?
> + }
> +
> /// 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 {
> @@ -216,6 +223,27 @@ impl<T: MiscDevice> VtableHelper<T> {
> 0
> }
>
> +/// # Safety
> +///
> +/// `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.
> +/// `vma` must be a vma that is currently being mmap'ed with this file.
> +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 { VmAreaNew::from_raw(vma) };
> +
> + match T::mmap(device, area) {
> + Ok(()) => 0,
> + Err(err) => err.to_errno() as c_int,
> + }
> +}
> +
> /// # Safety
> ///
> /// `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.
>
> --
> 2.47.0.371.ga323438b13-goog
>
