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charset="utf-8" Add the ability to write a file_operations->llseek hook in Rust when using the miscdevice abstraction. Signed-off-by: Ryosuke Yasuoka --- rust/kernel/miscdevice.rs | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs index 6373fe183b27..597e7b66e493 100644 --- a/rust/kernel/miscdevice.rs +++ b/rust/kernel/miscdevice.rs @@ -125,6 +125,16 @@ fn release(device: Self::Ptr, _file: &File) { drop(device); } =20 + /// Handler for llseek. + fn llseek( + _device: ::Borrowed<'_>, + _file: &File, + _offset: i64, + _whence: i32, + ) -> Result { + build_error!(VTABLE_DEFAULT_ERROR) + } + /// Handle for mmap. /// /// This function is invoked when a user space process invokes the `mm= ap` system call on @@ -245,6 +255,27 @@ impl MiscdeviceVTable { 0 } =20 + /// # Safety + /// + /// `file` must be a valid file that is associated with a `MiscDeviceR= egistration`. + unsafe extern "C" fn llseek(file: *mut bindings::file, offset: i64, wh= ence: c_int) -> i64 { + // SAFETY: The llseek call of a file can access the private data. + let private =3D unsafe { (*file).private_data }; + // SAFETY: This is a Rust Miscdevice, so we call `into_foreign` in= `open` and + // `from_foreign` in `release`, and `fops_llseek` is guaranteed to= be called between those + // two operations. + let device =3D 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 threa= d. + let file =3D unsafe { File::from_raw_file(file) }; + + match T::llseek(device, file, offset, whence) { + Ok(res) =3D> res as i64, + Err(err) =3D> i64::from(err.to_errno()), + } + } + /// # Safety /// /// `file` must be a valid file that is associated with a `MiscDeviceR= egistration`. @@ -340,6 +371,11 @@ impl MiscdeviceVTable { const VTABLE: bindings::file_operations =3D bindings::file_operations { open: Some(Self::open), release: Some(Self::release), + llseek: if T::HAS_LLSEEK { + Some(Self::llseek) + } else { + None + }, mmap: if T::HAS_MMAP { Some(Self::mmap) } else { None }, unlocked_ioctl: if T::HAS_IOCTL { Some(Self::ioctl) --=20 2.50.1 From nobody Sat Oct 4 09:37:56 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2BE54322A2F for ; 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charset="utf-8" Add lseek samples in Rust MiscDevice samples Signed-off-by: Ryosuke Yasuoka --- samples/rust/rust_misc_device.rs | 68 ++++++++++++++++++++++++++++++++ 1 file changed, 68 insertions(+) diff --git a/samples/rust/rust_misc_device.rs b/samples/rust/rust_misc_devi= ce.rs index e7ab77448f75..991a59a3ea16 100644 --- a/samples/rust/rust_misc_device.rs +++ b/samples/rust/rust_misc_device.rs @@ -86,6 +86,33 @@ //! return -1; //! } //! +//! // Set a file offset +//! printf("Call lseek SEEK_SET\n"); +//! ret =3D lseek(fd, 10, SEEK_SET); +//! if (ret =3D=3D 10) +//! printf("lseek: Succeed to SEEK_SET\n"); +//! else +//! printf("lseek: Failed to SEEK_SET\n"); +//! +//! // Change the file offset from the initial value +//! printf("Call lseek SEEK_CUR\n"); +//! ret =3D lseek(fd, 10, SEEK_CUR); +//! if (ret =3D=3D 20) +//! printf("lseek: Succeed to SEEK_CUR\n"); +//! else +//! printf("lseek: Failed to SEEK_CUR\n"); +//! +//! // i_size is 0. So the following task always should fail. +//! printf("Call lseek SEEK_END\n"); +//! ret =3D lseek(fd, -10, SEEK_END); +//! if (ret < 0) +//! perror("lseek: Succeeded to fail - this was expected"); +//! else { +//! printf("lseek: Failed to fail SEEK_END\n"); +//! close(fd); +//! return -1; +//! } +//! //! // Close the device file //! printf("Closing /dev/rust-misc-device\n"); //! close(fd); @@ -114,6 +141,10 @@ const RUST_MISC_DEV_GET_VALUE: u32 =3D _IOR::('|' as u32, 0x81); const RUST_MISC_DEV_SET_VALUE: u32 =3D _IOW::('|' as u32, 0x82); =20 +const SEEK_SET: i32 =3D 0; +const SEEK_CUR: i32 =3D 1; +const SEEK_END: i32 =3D 2; + module! { type: RustMiscDeviceModule, name: "rust_misc_device", @@ -173,6 +204,43 @@ fn open(_file: &File, misc: &MiscDeviceRegistration) -> Result, file: &File, offset: i64, whence: = i32) -> Result { + dev_info!(me.dev, "LLSEEK Rust Misc Device Sample\n"); + let pos: i64; + let eof: i64; + + // SAFETY: + // * The file is valid for the duration of this call. + // * f_inode must be valid while the file is valid. + unsafe { + pos =3D (*file.as_ptr()).f_pos; + eof =3D (*(*file.as_ptr()).f_inode).i_size; + } + + let new_pos =3D match whence { + SEEK_SET =3D> offset, + SEEK_CUR =3D> pos + offset, + SEEK_END =3D> eof + offset, + _ =3D> { + dev_err!(me.dev, "LLSEEK does not recognised: {}.\n", when= ce); + return Err(EINVAL); + } + }; + + if new_pos < 0 { + dev_err!(me.dev, "The file offset becomes negative: {}.\n", ne= w_pos); + return Err(EINVAL); + } + + // SAFETY: The file is valid for the duration of this call. + let ret: isize =3D unsafe { + (*file.as_ptr()).f_pos =3D new_pos; + new_pos as isize + }; + + Ok(ret) + } + fn ioctl(me: Pin<&RustMiscDevice>, _file: &File, cmd: u32, arg: usize)= -> Result { dev_info!(me.dev, "IOCTLing Rust Misc Device Sample\n"); =20 --=20 2.50.1