Commit 5bcc8bfe authored by Alice Ryhl's avatar Alice Ryhl Committed by Greg Kroah-Hartman
Browse files

rust: miscdevice: add fops->show_fdinfo() hook 



File descriptors should generally provide a fops->show_fdinfo() hook for
debugging purposes. Thus, add such a hook to the miscdevice
abstractions.

Signed-off-by: default avatarAlice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20241203-miscdevice-showfdinfo-v1-1-7e990732d430@google.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 8d9b095b

rust/kernel/miscdevice.rs

+34 −0
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
    error::{to_result, Error, Result, VTABLE_DEFAULT_ERROR},

    fs::File,

    prelude::*,

    seq_file::SeqFile,

    str::CStr,

    types::{ForeignOwnable, Opaque},

};
@@ -152,6 +153,15 @@ fn compat_ioctl( 
    ) -> Result<isize> {

        kernel::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)

    }

}



const fn create_vtable<T: MiscDevice>() -> &'static bindings::file_operations {
@@ -179,6 +189,7 @@ impl<T: MiscDevice> VtableHelper<T> { 
            } else {

                None

            },

            show_fdinfo: maybe_fn(T::HAS_SHOW_FDINFO, fops_show_fdinfo::<T>),

            // SAFETY: All zeros is a valid value for `bindings::file_operations`.

            ..unsafe { MaybeUninit::zeroed().assume_init() }

        };
@@ -298,3 +309,26 @@ impl<T: MiscDevice> VtableHelper<T> { 
        Err(err) => err.to_errno() as c_long,

    }

}



/// # Safety

///

/// - `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.

/// - `seq_file` must be a valid `struct seq_file` that we can write to.

unsafe extern "C" fn fops_show_fdinfo<T: MiscDevice>(

    seq_file: *mut bindings::seq_file,

    file: *mut bindings::file,

) {

    // SAFETY: The release call of a file owns the private data.

    let private = unsafe { (*file).private_data };

    // SAFETY: Ioctl calls can borrow the private data of the file.

    let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };

    // 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) };

    // SAFETY: The caller ensures that the pointer is valid and exclusive for the duration in which

    // this method is called.

    let m = unsafe { SeqFile::from_raw(seq_file) };



    T::show_fdinfo(device, m, file);

}