1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
//! Unsafe `ioctl` API.
//!
//! Unix systems expose a number of `ioctl`'s. `ioctl`s have been adopted as a
//! general purpose system call for making calls into the kernel. In addition
//! to the wide variety of system calls that are included by default in the
//! kernel, many drivers expose their own `ioctl`'s for controlling their
//! behavior, some of which are proprietary. Therefore it is impossible to make
//! a safe interface for every `ioctl` call, as they all have wildly varying
//! semantics.
//!
//! This module provides an unsafe interface to write your own `ioctl` API. To
//! start, create a type that implements [`Ioctl`]. Then, pass it to [`ioctl`]
//! to make the `ioctl` call.

#![allow(unsafe_code)]

use crate::backend::c;
use crate::fd::{AsFd, BorrowedFd};
use crate::io::Result;

#[cfg(any(linux_kernel, bsd))]
use core::mem;

pub use patterns::*;

mod patterns;

#[cfg(linux_kernel)]
mod linux;

#[cfg(bsd)]
mod bsd;

#[cfg(linux_kernel)]
use linux as platform;

#[cfg(bsd)]
use bsd as platform;

/// Perform an `ioctl` call.
///
/// `ioctl` was originally intended to act as a way of modifying the behavior
/// of files, but has since been adopted as a general purpose system call for
/// making calls into the kernel. In addition to the default calls exposed by
/// generic file descriptors, many drivers expose their own `ioctl` calls for
/// controlling their behavior, some of which are proprietary.
///
/// This crate exposes many other `ioctl` interfaces with safe and idiomatic
/// wrappers, like [`ioctl_fionbio`] and [`ioctl_fionread`]. It is recommended
/// to use those instead of this function, as they are safer and more
/// idiomatic. For other cases, implement the [`Ioctl`] API and pass it to this
/// function.
///
/// See documentation for [`Ioctl`] for more information.
///
/// [`ioctl_fionbio`]: crate::io::ioctl_fionbio
/// [`ioctl_fionread`]: crate::io::ioctl_fionread
///
/// # Safety
///
/// While [`Ioctl`] takes much of the unsafety out of `ioctl` calls, it is
/// still unsafe to call this code with arbitrary device drivers, as it is up
/// to the device driver to implement the `ioctl` call correctly. It is on the
/// onus of the protocol between the user and the driver to ensure that the
/// `ioctl` call is safe to make.
///
/// # References
///  - [Linux]
///  - [Winsock]
///  - [FreeBSD]
///  - [NetBSD]
///  - [OpenBSD]
///  - [Apple]
///  - [Solaris]
///  - [illumos]
///
/// [Linux]: https://man7.org/linux/man-pages/man2/ioctl.2.html
/// [Winsock]: https://learn.microsoft.com/en-us/windows/win32/api/winsock/nf-winsock-ioctlsocket
/// [FreeBSD]: https://man.freebsd.org/cgi/man.cgi?query=ioctl&sektion=2
/// [NetBSD]: https://man.netbsd.org/ioctl.2
/// [OpenBSD]: https://man.openbsd.org/ioctl.2
/// [Apple]: https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/ioctl.2.html
/// [Solaris]: https://docs.oracle.com/cd/E23824_01/html/821-1463/ioctl-2.html
/// [illumos]: https://illumos.org/man/2/ioctl
#[inline]
pub unsafe fn ioctl<F: AsFd, I: Ioctl>(fd: F, mut ioctl: I) -> Result<I::Output> {
    let fd = fd.as_fd();
    let request = I::OPCODE.raw();
    let arg = ioctl.as_ptr();

    // SAFETY: The variant of `Ioctl` asserts that this is a valid IOCTL call
    // to make.
    let output = if I::IS_MUTATING {
        _ioctl(fd, request, arg)?
    } else {
        _ioctl_readonly(fd, request, arg)?
    };

    // SAFETY: The variant of `Ioctl` asserts that this is a valid pointer to
    // the output data.
    I::output_from_ptr(output, arg)
}

unsafe fn _ioctl(
    fd: BorrowedFd<'_>,
    request: RawOpcode,
    arg: *mut c::c_void,
) -> Result<IoctlOutput> {
    crate::backend::io::syscalls::ioctl(fd, request, arg)
}

unsafe fn _ioctl_readonly(
    fd: BorrowedFd<'_>,
    request: RawOpcode,
    arg: *mut c::c_void,
) -> Result<IoctlOutput> {
    crate::backend::io::syscalls::ioctl_readonly(fd, request, arg)
}

/// A trait defining the properties of an `ioctl` command.
///
/// Objects implementing this trait can be passed to [`ioctl`] to make an
/// `ioctl` call. The contents of the object represent the inputs to the
/// `ioctl` call. The inputs must be convertible to a pointer through the
/// `as_ptr` method. In most cases, this involves either casting a number to a
/// pointer, or creating a pointer to the actual data. The latter case is
/// necessary for `ioctl` calls that modify userspace data.
///
/// # Safety
///
/// This trait is unsafe to implement because it is impossible to guarantee
/// that the `ioctl` call is safe. The `ioctl` call may be proprietary, or it
/// may be unsafe to call in certain circumstances.
///
/// By implementing this trait, you guarantee that:
///
/// - The `ioctl` call expects the input provided by `as_ptr` and produces the
///   output as indicated by `output`.
/// - That `output_from_ptr` can safely take the pointer from `as_ptr` and cast
///   it to the correct type, *only* after the `ioctl` call.
/// - That `OPCODE` uniquely identifies the `ioctl` call.
/// - That, for whatever platforms you are targeting, the `ioctl` call is safe
///   to make.
/// - If `IS_MUTATING` is false, that no userspace data will be modified by the
///   `ioctl` call.
pub unsafe trait Ioctl {
    /// The type of the output data.
    ///
    /// Given a pointer, one should be able to construct an instance of this
    /// type.
    type Output;

    /// The opcode used by this `ioctl` command.
    ///
    /// There are different types of opcode depending on the operation. See
    /// documentation for the [`Opcode`] struct for more information.
    const OPCODE: Opcode;

    /// Does the `ioctl` mutate any data in the userspace?
    ///
    /// If the `ioctl` call does not mutate any data in the userspace, then
    /// making this `false` enables optimizations that can make the call
    /// faster. When in doubt, set this to `true`.
    ///
    /// # Safety
    ///
    /// This should only be set to `false` if the `ioctl` call does not mutate
    /// any data in the userspace. Undefined behavior may occur if this is set
    /// to `false` when it should be `true`.
    const IS_MUTATING: bool;

    /// Get a pointer to the data to be passed to the `ioctl` command.
    ///
    /// See trait-level documentation for more information.
    fn as_ptr(&mut self) -> *mut c::c_void;

    /// Cast the output data to the correct type.
    ///
    /// # Safety
    ///
    /// The `extract_output` value must be the resulting value after a
    /// successful `ioctl` call, and `out` is the direct return value of an
    /// `ioctl` call that did not fail. In this case `extract_output` is the
    /// pointer that was passed to the `ioctl` call.
    unsafe fn output_from_ptr(
        out: IoctlOutput,
        extract_output: *mut c::c_void,
    ) -> Result<Self::Output>;
}

/// The opcode used by an `Ioctl`.
#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Opcode {
    /// The raw opcode.
    raw: RawOpcode,
}

impl Opcode {
    /// Create a new old `Opcode` from a raw opcode.
    ///
    /// Rather than being a composition of several attributes, old opcodes are
    /// just numbers. In general most drivers follow stricter conventions, but
    /// older drivers may still use this strategy.
    #[inline]
    pub const fn old(raw: RawOpcode) -> Self {
        Self { raw }
    }

    /// Create a new opcode from a direction, group, number, and size.
    ///
    /// This corresponds to the C macro `_IOC(direction, group, number, size)`
    #[cfg(any(linux_kernel, bsd))]
    #[inline]
    pub const fn from_components(
        direction: Direction,
        group: u8,
        number: u8,
        data_size: usize,
    ) -> Self {
        assert!(
            data_size <= RawOpcode::MAX as usize,
            "data size is too large"
        );

        Self::old(platform::compose_opcode(
            direction,
            group as RawOpcode,
            number as RawOpcode,
            data_size as RawOpcode,
        ))
    }

    /// Create a new non-mutating opcode from a group, a number, and the type
    /// of data.
    ///
    /// This corresponds to the C macro `_IO(group, number)` when `T` is zero
    /// sized.
    #[cfg(any(linux_kernel, bsd))]
    #[inline]
    pub const fn none<T>(group: u8, number: u8) -> Self {
        Self::from_components(Direction::None, group, number, mem::size_of::<T>())
    }

    /// Create a new reading opcode from a group, a number and the type of
    /// data.
    ///
    /// This corresponds to the C macro `_IOR(group, number, T)`.
    #[cfg(any(linux_kernel, bsd))]
    #[inline]
    pub const fn read<T>(group: u8, number: u8) -> Self {
        Self::from_components(Direction::Read, group, number, mem::size_of::<T>())
    }

    /// Create a new writing opcode from a group, a number and the type of
    /// data.
    ///
    /// This corresponds to the C macro `_IOW(group, number, T)`.
    #[cfg(any(linux_kernel, bsd))]
    #[inline]
    pub const fn write<T>(group: u8, number: u8) -> Self {
        Self::from_components(Direction::Write, group, number, mem::size_of::<T>())
    }

    /// Create a new reading and writing opcode from a group, a number and the
    /// type of data.
    ///
    /// This corresponds to the C macro `_IOWR(group, number, T)`.
    #[cfg(any(linux_kernel, bsd))]
    #[inline]
    pub const fn read_write<T>(group: u8, number: u8) -> Self {
        Self::from_components(Direction::ReadWrite, group, number, mem::size_of::<T>())
    }

    /// Get the raw opcode.
    #[inline]
    pub fn raw(self) -> RawOpcode {
        self.raw
    }
}

/// The direction that an `ioctl` is going.
///
/// Note that this is relative to userspace. `Read` means reading data from the
/// kernel, and write means the kernel writing data to userspace.
#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum Direction {
    /// None of the above.
    None,

    /// Read data from the kernel.
    Read,

    /// Write data to the kernel.
    Write,

    /// Read and write data to the kernel.
    ReadWrite,
}

/// The type used by the `ioctl` to signify the output.
pub type IoctlOutput = c::c_int;

/// The type used by the `ioctl` to signify the command.
pub type RawOpcode = _RawOpcode;

// Under raw Linux, this is an `unsigned int`.
#[cfg(linux_raw)]
type _RawOpcode = c::c_uint;

// On libc Linux with GNU libc or uclibc, this is an `unsigned long`.
#[cfg(all(
    not(linux_raw),
    target_os = "linux",
    any(target_env = "gnu", target_env = "uclibc")
))]
type _RawOpcode = c::c_ulong;

// Musl uses `c_int`.
#[cfg(all(
    not(linux_raw),
    target_os = "linux",
    not(target_env = "gnu"),
    not(target_env = "uclibc")
))]
type _RawOpcode = c::c_int;

// Android uses `c_int`.
#[cfg(all(not(linux_raw), target_os = "android"))]
type _RawOpcode = c::c_int;

// BSD, Haiku, Hurd, Redox, and Vita use `unsigned long`.
#[cfg(any(
    bsd,
    target_os = "redox",
    target_os = "haiku",
    target_os = "horizon",
    target_os = "hurd",
    target_os = "vita"
))]
type _RawOpcode = c::c_ulong;

// AIX, Emscripten, Fuchsia, Solaris, and WASI use a `int`.
#[cfg(any(
    solarish,
    target_os = "aix",
    target_os = "fuchsia",
    target_os = "emscripten",
    target_os = "wasi",
    target_os = "nto"
))]
type _RawOpcode = c::c_int;

// ESP-IDF uses a `c_uint`.
#[cfg(target_os = "espidf")]
type _RawOpcode = c::c_uint;

// Windows has `ioctlsocket`, which uses `i32`.
#[cfg(windows)]
type _RawOpcode = i32;