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// SPDX-License-Identifier: GPL-2.0
use core::convert::{TryFrom, TryInto};
use core::{marker, mem, ptr};
use alloc::boxed::Box;
use crate::bindings;
use crate::c_types;
use crate::error::{Error, KernelResult};
use crate::user_ptr::{UserSlicePtr, UserSlicePtrReader, UserSlicePtrWriter};
bitflags::bitflags! {
pub struct FileFlags: c_types::c_uint {
const NONBLOCK = bindings::O_NONBLOCK;
}
}
pub struct File {
ptr: *const bindings::file,
}
impl File {
unsafe fn from_ptr(ptr: *const bindings::file) -> File {
File { ptr }
}
pub fn pos(&self) -> u64 {
unsafe { (*self.ptr).f_pos as u64 }
}
pub fn flags(&self) -> FileFlags {
FileFlags::from_bits_truncate(unsafe { (*self.ptr).f_flags })
}
}
// Matches std::io::SeekFrom in the Rust stdlib
pub enum SeekFrom {
Start(u64),
End(i64),
Current(i64),
}
unsafe extern "C" fn open_callback<T: FileOperations>(
_inode: *mut bindings::inode,
file: *mut bindings::file,
) -> c_types::c_int {
let f = match T::open() {
Ok(f) => Box::new(f),
Err(e) => return e.to_kernel_errno(),
};
(*file).private_data = Box::into_raw(f) as *mut c_types::c_void;
0
}
unsafe extern "C" fn read_callback<T: FileOperations>(
file: *mut bindings::file,
buf: *mut c_types::c_char,
len: c_types::c_size_t,
offset: *mut bindings::loff_t,
) -> c_types::c_ssize_t {
let mut data = match UserSlicePtr::new(buf as *mut c_types::c_void, len) {
Ok(ptr) => ptr.writer(),
Err(e) => return e.to_kernel_errno().try_into().unwrap(),
};
let f = &*((*file).private_data as *const T);
// No FMODE_UNSIGNED_OFFSET support, so offset must be in [0, 2^63).
// See discussion in #113
let positive_offset = match (*offset).try_into() {
Ok(v) => v,
Err(_) => return Error::EINVAL.to_kernel_errno().try_into().unwrap(),
};
let read = T::READ.unwrap();
match read(f, &File::from_ptr(file), &mut data, positive_offset) {
Ok(()) => {
let written = len - data.len();
(*offset) += bindings::loff_t::try_from(written).unwrap();
written.try_into().unwrap()
}
Err(e) => e.to_kernel_errno().try_into().unwrap(),
}
}
unsafe extern "C" fn write_callback<T: FileOperations>(
file: *mut bindings::file,
buf: *const c_types::c_char,
len: c_types::c_size_t,
offset: *mut bindings::loff_t,
) -> c_types::c_ssize_t {
let mut data = match UserSlicePtr::new(buf as *mut c_types::c_void, len) {
Ok(ptr) => ptr.reader(),
Err(e) => return e.to_kernel_errno().try_into().unwrap(),
};
let f = &*((*file).private_data as *const T);
// No FMODE_UNSIGNED_OFFSET support, so offset must be in [0, 2^63).
// See discussion in #113
let positive_offset = match (*offset).try_into() {
Ok(v) => v,
Err(_) => return Error::EINVAL.to_kernel_errno().try_into().unwrap(),
};
let write = T::WRITE.unwrap();
match write(f, &mut data, positive_offset) {
Ok(()) => {
let read = len - data.len();
(*offset) += bindings::loff_t::try_from(read).unwrap();
read.try_into().unwrap()
}
Err(e) => e.to_kernel_errno().try_into().unwrap(),
}
}
unsafe extern "C" fn release_callback<T: FileOperations>(
_inode: *mut bindings::inode,
file: *mut bindings::file,
) -> c_types::c_int {
let ptr = mem::replace(&mut (*file).private_data, ptr::null_mut());
drop(Box::from_raw(ptr as *mut T));
0
}
unsafe extern "C" fn llseek_callback<T: FileOperations>(
file: *mut bindings::file,
offset: bindings::loff_t,
whence: c_types::c_int,
) -> bindings::loff_t {
let off = match whence as u32 {
bindings::SEEK_SET => match offset.try_into() {
Ok(v) => SeekFrom::Start(v),
Err(_) => return Error::EINVAL.to_kernel_errno().into(),
},
bindings::SEEK_CUR => SeekFrom::Current(offset),
bindings::SEEK_END => SeekFrom::End(offset),
_ => return Error::EINVAL.to_kernel_errno().into(),
};
let f = &*((*file).private_data as *const T);
let seek = T::SEEK.unwrap();
match seek(f, &File::from_ptr(file), off) {
Ok(off) => off as bindings::loff_t,
Err(e) => e.to_kernel_errno().into(),
}
}
pub(crate) struct FileOperationsVtable<T>(marker::PhantomData<T>);
impl<T: FileOperations> FileOperationsVtable<T> {
pub(crate) const VTABLE: bindings::file_operations = bindings::file_operations {
open: Some(open_callback::<T>),
release: Some(release_callback::<T>),
read: if let Some(_) = T::READ {
Some(read_callback::<T>)
} else {
None
},
write: if let Some(_) = T::WRITE {
Some(write_callback::<T>)
} else {
None
},
llseek: if let Some(_) = T::SEEK {
Some(llseek_callback::<T>)
} else {
None
},
check_flags: None,
compat_ioctl: None,
copy_file_range: None,
fallocate: None,
fadvise: None,
fasync: None,
flock: None,
flush: None,
fsync: None,
get_unmapped_area: None,
iterate: None,
iterate_shared: None,
iopoll: None,
lock: None,
mmap: None,
mmap_supported_flags: 0,
owner: ptr::null_mut(),
poll: None,
read_iter: None,
remap_file_range: None,
sendpage: None,
setlease: None,
show_fdinfo: None,
splice_read: None,
splice_write: None,
unlocked_ioctl: None,
write_iter: None,
};
}
pub type ReadFn<T> = Option<fn(&T, &File, &mut UserSlicePtrWriter, u64) -> KernelResult<()>>;
pub type WriteFn<T> = Option<fn(&T, &mut UserSlicePtrReader, u64) -> KernelResult<()>>;
pub type SeekFn<T> = Option<fn(&T, &File, SeekFrom) -> KernelResult<u64>>;
/// `FileOperations` corresponds to the kernel's `struct file_operations`. You
/// implement this trait whenever you'd create a `struct file_operations`.
/// File descriptors may be used from multiple threads (or processes)
/// concurrently, so your type must be `Sync`.
pub trait FileOperations: Sync + Sized {
/// Creates a new instance of this file. Corresponds to the `open` function
/// pointer in `struct file_operations`.
fn open() -> KernelResult<Self>;
/// Reads data from this file to userspace. Corresponds to the `read`
/// function pointer in `struct file_operations`.
const READ: ReadFn<Self> = None;
/// Writes data from userspace o this file. Corresponds to the `write`
/// function pointer in `struct file_operations`.
const WRITE: WriteFn<Self> = None;
/// Changes the position of the file. Corresponds to the `llseek` function
/// pointer in `struct file_operations`.
const SEEK: SeekFn<Self> = None;
}
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