| Message ID | 20241211-vma-v11-7-466640428fc3@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Rust support for mm_struct, vm_area_struct, and mmap | expand |
"Alice Ryhl" <aliceryhl@google.com> writes: > Add the ability to write a file_operations->mmap hook in Rust when using > the miscdevice abstraction. The `vma` argument to the `mmap` hook uses > the `VmAreaNew` type from the previous commit; this type provides the > correct set of operations for a file_operations->mmap hook. > > Acked-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> (for mm bits) > Signed-off-by: Alice Ryhl <aliceryhl@google.com> > --- > rust/kernel/miscdevice.rs | 37 +++++++++++++++++++++++++++++++++++++ > 1 file changed, 37 insertions(+) > > diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs > index 7e2a79b3ae26..e5366f9c6d7f 100644 > --- a/rust/kernel/miscdevice.rs > +++ b/rust/kernel/miscdevice.rs > @@ -11,6 +11,8 @@ > use crate::{ > bindings, > error::{to_result, Error, Result, VTABLE_DEFAULT_ERROR}, > + fs::File, > + mm::virt::VmAreaNew, > prelude::*, > str::CStr, > types::{ForeignOwnable, Opaque}, > @@ -110,6 +112,15 @@ fn release(device: Self::Ptr) { > drop(device); > } > > + /// Handle for mmap. > + fn mmap( > + _device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>, > + _file: &File, > + _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 +167,7 @@ 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 +228,31 @@ 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. This safety comment seems unrelated to the safety requirements of `ForeignOwnable::borrow`. Best regards, Andreas Hindborg
diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs index 7e2a79b3ae26..e5366f9c6d7f 100644 --- a/rust/kernel/miscdevice.rs +++ b/rust/kernel/miscdevice.rs @@ -11,6 +11,8 @@ use crate::{ bindings, error::{to_result, Error, Result, VTABLE_DEFAULT_ERROR}, + fs::File, + mm::virt::VmAreaNew, prelude::*, str::CStr, types::{ForeignOwnable, Opaque}, @@ -110,6 +112,15 @@ fn release(device: Self::Ptr) { drop(device); } + /// Handle for mmap. + fn mmap( + _device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>, + _file: &File, + _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 +167,7 @@ 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 +228,31 @@ 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) }; + // SAFETY: + // * The file is valid for the duration of this call. + // * There is no active fdget_pos region on the file on this thread. + let file = unsafe { File::from_raw_file(file) }; + + match T::mmap(device, file, 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>`.