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charset="utf-8" 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 --- This could not land with the base miscdevice abstractions due to the dependency on SeqFile. As for the dependency on File, please see: https://lore.kernel.org/r/20241203-miscdevice-file-param-v1-1-1d6622978480@google.com --- rust/kernel/miscdevice.rs | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs index 7e2a79b3ae26..190d7f477346 100644 --- a/rust/kernel/miscdevice.rs +++ b/rust/kernel/miscdevice.rs @@ -11,7 +11,9 @@ use crate::{ bindings, error::{to_result, Error, Result, VTABLE_DEFAULT_ERROR}, + fs::File, prelude::*, + seq_file::SeqFile, str::CStr, types::{ForeignOwnable, Opaque}, }; @@ -138,6 +140,15 @@ fn compat_ioctl( ) -> Result { kernel::build_error(VTABLE_DEFAULT_ERROR) } + + /// Show info for this fd. + fn show_fdinfo( + _device: ::Borrowed<'_>, + _m: &SeqFile, + _file: &File, + ) { + kernel::build_error(VTABLE_DEFAULT_ERROR) + } } const fn create_vtable() -> &'static bindings::file_operations { @@ -165,6 +176,7 @@ impl VtableHelper { } else { None }, + show_fdinfo: maybe_fn(T::HAS_SHOW_FDINFO, fops_show_fdinfo::), // SAFETY: All zeros is a valid value for `bindings::file_operations`. ..unsafe { MaybeUninit::zeroed().assume_init() } }; @@ -254,3 +266,26 @@ impl VtableHelper { Err(err) => err.to_errno() as c_long, } } + +/// # Safety +/// +/// - `file` must be a valid file that is associated with a `MiscDeviceRegistration`. +/// - `seq_file` must be a valid `struct seq_file` that we can write to. +unsafe extern "C" fn fops_show_fdinfo( + 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 { ::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); +} --- base-commit: 40384c840ea1944d7c5a392e8975ed088ecf0b37 change-id: 20241203-miscdevice-showfdinfo-1147802f403e Best regards, -- Alice Ryhl