Re: linux-next: manual merge of the rust tree with the driver-core tree

Stephen Rothwell
2025-01-23T03:30:27Z

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Hi all,

On Tue, 14 Jan 2025 15:46:23 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
> Today's linux-next merge of the rust tree got a conflict in:
>
> rust/kernel/miscdevice.rs
>
> between commit:
>
> 88441d5c6d17 ("rust: miscdevice: access the `struct miscdevice` from fops->open()")
>
> from the driver-core tree and commit:
>
> 14686571a914 ("rust: kernel: change `ForeignOwnable` pointer to mut")
>
> from the rust tree.
>
> I fixed it up (see below) and can carry the fix as necessary. This
> is now fixed as far as linux-next is concerned, but any non trivial
> conflicts should be mentioned to your upstream maintainer when your tree
> is submitted for merging. You may also want to consider cooperating
> with the maintainer of the conflicting tree to minimise any particularly
> complex conflicts.
>
> diff --cc rust/kernel/miscdevice.rs
> index dfb363630c70,b3a6cc50b240..000000000000
> --- a/rust/kernel/miscdevice.rs
> +++ b/rust/kernel/miscdevice.rs
> @@@ -10,11 -10,9 +10,12 @@@
>
> use crate::{
> bindings,
> + device::Device,
> error::{to_result, Error, Result, VTABLE_DEFAULT_ERROR},
> + ffi::{c_int, c_long, c_uint, c_ulong},
> + fs::File,
> prelude::*,
> + seq_file::SeqFile,
> str::CStr,
> types::{ForeignOwnable, Opaque},
> };
> @@@ -151,17 -132,8 +147,17 @@@ pub trait MiscDevice: Sized
> _cmd: u32,
> _arg: usize,
> ) -> Result<isize> {
> - kernel::build_error!(VTABLE_DEFAULT_ERROR)
> + build_error!(VTABLE_DEFAULT_ERROR)
> }
> +
> + /// Show info for this fd.
> + fn show_fdinfo(
> + _device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,
> + _m: &SeqFile,
> + _file: &File,
> + ) {
> - kernel::build_error!(VTABLE_DEFAULT_ERROR)
> ++ build_error!(VTABLE_DEFAULT_ERROR)
> + }
> }
>
> const fn create_vtable<T: MiscDevice>() -> &'static bindings::file_operations {
> @@@ -230,12 -188,8 +226,12 @@@ unsafe extern "C" fn fops_open<T: MiscD
> Err(err) => return err.to_errno(),
> };
>
> - // SAFETY: The open call of a file owns the private data.
> - unsafe { (*file).private_data = ptr.into_foreign() };
> + // This overwrites the private data with the value specified by the user, changing the type of
> + // this file's private data. All future accesses to the private data is performed by other
> + // fops_* methods in this file, which all correctly cast the private data to the new type.
> + //
> + // SAFETY: The open call of a file can access the private data.
> - unsafe { (*raw_file).private_data = ptr.into_foreign().cast_mut() };
> ++ unsafe { (*raw_file).private_data = ptr.into_foreign() };
>
> 0
> }
> @@@ -274,12 -225,7 +270,12 @@@ unsafe extern "C" fn fops_ioctl<T: Misc
> // SAFETY: Ioctl calls can borrow the private data of the file.
> let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };
>
> - match T::ioctl(device, cmd, arg) {
> + // 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::ioctl(device, file, cmd, arg as usize) {
> ++ match T::ioctl(device, file, cmd, arg) {
> Ok(ret) => ret as c_long,
> Err(err) => err.to_errno() as c_long,
> }
> @@@ -299,12 -245,7 +295,12 @@@ unsafe extern "C" fn fops_compat_ioctl<
> // SAFETY: Ioctl calls can borrow the private data of the file.
> let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };
>
> - match T::compat_ioctl(device, cmd, arg) {
> + // 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::compat_ioctl(device, file, cmd, arg as usize) {
> ++ match T::compat_ioctl(device, file, cmd, arg) {
> Ok(ret) => ret as c_long,
> Err(err) => err.to_errno() as c_long,
> }

This is now a conflict between the driver-core tree and Linus' tree.