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

Alice Ryhl
2024-10-14T09:30:17Z

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>
---
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