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

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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: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20241203-miscdevice-showfdinfo-v1-1-7e990732d430@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alice Ryhl 2024-12-03 12:34:38 +00:00 committed by Greg Kroah-Hartman
parent 8d9b095b8f
commit 5bcc8bfe84
1 changed files with 34 additions and 0 deletions
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34
rust/kernel/miscdevice.rs
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@ -14,6 +14,7 @@ use crate::{
error::{to_result, Error, Result, VTABLE_DEFAULT_ERROR},
fs::File,
prelude::*,
seq_file::SeqFile,
str::CStr,
types::{ForeignOwnable, Opaque},
};
@ -152,6 +153,15 @@ pub trait MiscDevice: Sized {
) -> 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 @@ const fn create_vtable<T: MiscDevice>() -> &'static bindings::file_operations {
} 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 @@ unsafe extern "C" fn fops_compat_ioctl<T: MiscDevice>(
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);
}