summaryrefslogtreecommitdiff
path: root/rust/kernel/print.rs
blob: a78aa3514a0af0925913a9dbad1aec1c279db791 (plain)
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
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
// SPDX-License-Identifier: GPL-2.0

//! Printing facilities.
//!
//! C header: [`include/linux/printk.h`](srctree/include/linux/printk.h)
//!
//! Reference: <https://www.kernel.org/doc/html/latest/core-api/printk-basics.html>

use core::{
    ffi::{c_char, c_void},
    fmt,
};

use crate::str::RawFormatter;

// Called from `vsprintf` with format specifier `%pA`.
#[no_mangle]
unsafe extern "C" fn rust_fmt_argument(
    buf: *mut c_char,
    end: *mut c_char,
    ptr: *const c_void,
) -> *mut c_char {
    use fmt::Write;
    // SAFETY: The C contract guarantees that `buf` is valid if it's less than `end`.
    let mut w = unsafe { RawFormatter::from_ptrs(buf.cast(), end.cast()) };
    let _ = w.write_fmt(unsafe { *(ptr as *const fmt::Arguments<'_>) });
    w.pos().cast()
}

/// Format strings.
///
/// Public but hidden since it should only be used from public macros.
#[doc(hidden)]
pub mod format_strings {
    /// The length we copy from the `KERN_*` kernel prefixes.
    const LENGTH_PREFIX: usize = 2;

    /// The length of the fixed format strings.
    pub const LENGTH: usize = 10;

    /// Generates a fixed format string for the kernel's [`_printk`].
    ///
    /// The format string is always the same for a given level, i.e. for a
    /// given `prefix`, which are the kernel's `KERN_*` constants.
    ///
    /// [`_printk`]: srctree/include/linux/printk.h
    const fn generate(is_cont: bool, prefix: &[u8; 3]) -> [u8; LENGTH] {
        // Ensure the `KERN_*` macros are what we expect.
        assert!(prefix[0] == b'\x01');
        if is_cont {
            assert!(prefix[1] == b'c');
        } else {
            assert!(prefix[1] >= b'0' && prefix[1] <= b'7');
        }
        assert!(prefix[2] == b'\x00');

        let suffix: &[u8; LENGTH - LENGTH_PREFIX] = if is_cont {
            b"%pA\0\0\0\0\0"
        } else {
            b"%s: %pA\0"
        };

        [
            prefix[0], prefix[1], suffix[0], suffix[1], suffix[2], suffix[3], suffix[4], suffix[5],
            suffix[6], suffix[7],
        ]
    }

    // Generate the format strings at compile-time.
    //
    // This avoids the compiler generating the contents on the fly in the stack.
    //
    // Furthermore, `static` instead of `const` is used to share the strings
    // for all the kernel.
    pub static EMERG: [u8; LENGTH] = generate(false, bindings::KERN_EMERG);
    pub static ALERT: [u8; LENGTH] = generate(false, bindings::KERN_ALERT);
    pub static CRIT: [u8; LENGTH] = generate(false, bindings::KERN_CRIT);
    pub static ERR: [u8; LENGTH] = generate(false, bindings::KERN_ERR);
    pub static WARNING: [u8; LENGTH] = generate(false, bindings::KERN_WARNING);
    pub static NOTICE: [u8; LENGTH] = generate(false, bindings::KERN_NOTICE);
    pub static INFO: [u8; LENGTH] = generate(false, bindings::KERN_INFO);
    pub static DEBUG: [u8; LENGTH] = generate(false, bindings::KERN_DEBUG);
    pub static CONT: [u8; LENGTH] = generate(true, bindings::KERN_CONT);
}

/// Prints a message via the kernel's [`_printk`].
///
/// Public but hidden since it should only be used from public macros.
///
/// # Safety
///
/// The format string must be one of the ones in [`format_strings`], and
/// the module name must be null-terminated.
///
/// [`_printk`]: srctree/include/linux/_printk.h
#[doc(hidden)]
#[cfg_attr(not(CONFIG_PRINTK), allow(unused_variables))]
pub unsafe fn call_printk(
    format_string: &[u8; format_strings::LENGTH],
    module_name: &[u8],
    args: fmt::Arguments<'_>,
) {
    // `_printk` does not seem to fail in any path.
    #[cfg(CONFIG_PRINTK)]
    unsafe {
        bindings::_printk(
            format_string.as_ptr() as _,
            module_name.as_ptr(),
            &args as *const _ as *const c_void,
        );
    }
}

/// Prints a message via the kernel's [`_printk`] for the `CONT` level.
///
/// Public but hidden since it should only be used from public macros.
///
/// [`_printk`]: srctree/include/linux/printk.h
#[doc(hidden)]
#[cfg_attr(not(CONFIG_PRINTK), allow(unused_variables))]
pub fn call_printk_cont(args: fmt::Arguments<'_>) {
    // `_printk` does not seem to fail in any path.
    //
    // SAFETY: The format string is fixed.
    #[cfg(CONFIG_PRINTK)]
    unsafe {
        bindings::_printk(
            format_strings::CONT.as_ptr() as _,
            &args as *const _ as *const c_void,
        );
    }
}

/// Performs formatting and forwards the string to [`call_printk`].
///
/// Public but hidden since it should only be used from public macros.
#[doc(hidden)]
#[cfg(not(testlib))]
#[macro_export]
#[allow(clippy::crate_in_macro_def)]
macro_rules! print_macro (
    // The non-continuation cases (most of them, e.g. `INFO`).
    ($format_string:path, false, $($arg:tt)+) => (
        // To remain sound, `arg`s must be expanded outside the `unsafe` block.
        // Typically one would use a `let` binding for that; however, `format_args!`
        // takes borrows on the arguments, but does not extend the scope of temporaries.
        // Therefore, a `match` expression is used to keep them around, since
        // the scrutinee is kept until the end of the `match`.
        match format_args!($($arg)+) {
            // SAFETY: This hidden macro should only be called by the documented
            // printing macros which ensure the format string is one of the fixed
            // ones. All `__LOG_PREFIX`s are null-terminated as they are generated
            // by the `module!` proc macro or fixed values defined in a kernel
            // crate.
            args => unsafe {
                $crate::print::call_printk(
                    &$format_string,
                    crate::__LOG_PREFIX,
                    args,
                );
            }
        }
    );

    // The `CONT` case.
    ($format_string:path, true, $($arg:tt)+) => (
        $crate::print::call_printk_cont(
            format_args!($($arg)+),
        );
    );
);

/// Stub for doctests
#[cfg(testlib)]
#[macro_export]
macro_rules! print_macro (
    ($format_string:path, $e:expr, $($arg:tt)+) => (
        ()
    );
);

// We could use a macro to generate these macros. However, doing so ends
// up being a bit ugly: it requires the dollar token trick to escape `$` as
// well as playing with the `doc` attribute. Furthermore, they cannot be easily
// imported in the prelude due to [1]. So, for the moment, we just write them
// manually, like in the C side; while keeping most of the logic in another
// macro, i.e. [`print_macro`].
//
// [1]: https://github.com/rust-lang/rust/issues/52234

/// Prints an emergency-level message (level 0).
///
/// Use this level if the system is unusable.
///
/// Equivalent to the kernel's [`pr_emerg`] macro.
///
/// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
/// `alloc::format!` for information about the formatting syntax.
///
/// [`pr_emerg`]: https://www.kernel.org/doc/html/latest/core-api/printk-basics.html#c.pr_emerg
/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
///
/// # Examples
///
/// ```
/// pr_emerg!("hello {}\n", "there");
/// ```
#[macro_export]
macro_rules! pr_emerg (
    ($($arg:tt)*) => (
        $crate::print_macro!($crate::print::format_strings::EMERG, false, $($arg)*)
    )
);

/// Prints an alert-level message (level 1).
///
/// Use this level if action must be taken immediately.
///
/// Equivalent to the kernel's [`pr_alert`] macro.
///
/// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
/// `alloc::format!` for information about the formatting syntax.
///
/// [`pr_alert`]: https://www.kernel.org/doc/html/latest/core-api/printk-basics.html#c.pr_alert
/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
///
/// # Examples
///
/// ```
/// pr_alert!("hello {}\n", "there");
/// ```
#[macro_export]
macro_rules! pr_alert (
    ($($arg:tt)*) => (
        $crate::print_macro!($crate::print::format_strings::ALERT, false, $($arg)*)
    )
);

/// Prints a critical-level message (level 2).
///
/// Use this level for critical conditions.
///
/// Equivalent to the kernel's [`pr_crit`] macro.
///
/// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
/// `alloc::format!` for information about the formatting syntax.
///
/// [`pr_crit`]: https://www.kernel.org/doc/html/latest/core-api/printk-basics.html#c.pr_crit
/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
///
/// # Examples
///
/// ```
/// pr_crit!("hello {}\n", "there");
/// ```
#[macro_export]
macro_rules! pr_crit (
    ($($arg:tt)*) => (
        $crate::print_macro!($crate::print::format_strings::CRIT, false, $($arg)*)
    )
);

/// Prints an error-level message (level 3).
///
/// Use this level for error conditions.
///
/// Equivalent to the kernel's [`pr_err`] macro.
///
/// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
/// `alloc::format!` for information about the formatting syntax.
///
/// [`pr_err`]: https://www.kernel.org/doc/html/latest/core-api/printk-basics.html#c.pr_err
/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
///
/// # Examples
///
/// ```
/// pr_err!("hello {}\n", "there");
/// ```
#[macro_export]
macro_rules! pr_err (
    ($($arg:tt)*) => (
        $crate::print_macro!($crate::print::format_strings::ERR, false, $($arg)*)
    )
);

/// Prints a warning-level message (level 4).
///
/// Use this level for warning conditions.
///
/// Equivalent to the kernel's [`pr_warn`] macro.
///
/// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
/// `alloc::format!` for information about the formatting syntax.
///
/// [`pr_warn`]: https://www.kernel.org/doc/html/latest/core-api/printk-basics.html#c.pr_warn
/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
///
/// # Examples
///
/// ```
/// pr_warn!("hello {}\n", "there");
/// ```
#[macro_export]
macro_rules! pr_warn (
    ($($arg:tt)*) => (
        $crate::print_macro!($crate::print::format_strings::WARNING, false, $($arg)*)
    )
);

/// Prints a notice-level message (level 5).
///
/// Use this level for normal but significant conditions.
///
/// Equivalent to the kernel's [`pr_notice`] macro.
///
/// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
/// `alloc::format!` for information about the formatting syntax.
///
/// [`pr_notice`]: https://www.kernel.org/doc/html/latest/core-api/printk-basics.html#c.pr_notice
/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
///
/// # Examples
///
/// ```
/// pr_notice!("hello {}\n", "there");
/// ```
#[macro_export]
macro_rules! pr_notice (
    ($($arg:tt)*) => (
        $crate::print_macro!($crate::print::format_strings::NOTICE, false, $($arg)*)
    )
);

/// Prints an info-level message (level 6).
///
/// Use this level for informational messages.
///
/// Equivalent to the kernel's [`pr_info`] macro.
///
/// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
/// `alloc::format!` for information about the formatting syntax.
///
/// [`pr_info`]: https://www.kernel.org/doc/html/latest/core-api/printk-basics.html#c.pr_info
/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
///
/// # Examples
///
/// ```
/// pr_info!("hello {}\n", "there");
/// ```
#[macro_export]
#[doc(alias = "print")]
macro_rules! pr_info (
    ($($arg:tt)*) => (
        $crate::print_macro!($crate::print::format_strings::INFO, false, $($arg)*)
    )
);

/// Prints a debug-level message (level 7).
///
/// Use this level for debug messages.
///
/// Equivalent to the kernel's [`pr_debug`] macro, except that it doesn't support dynamic debug
/// yet.
///
/// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
/// `alloc::format!` for information about the formatting syntax.
///
/// [`pr_debug`]: https://www.kernel.org/doc/html/latest/core-api/printk-basics.html#c.pr_debug
/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
///
/// # Examples
///
/// ```
/// pr_debug!("hello {}\n", "there");
/// ```
#[macro_export]
#[doc(alias = "print")]
macro_rules! pr_debug (
    ($($arg:tt)*) => (
        if cfg!(debug_assertions) {
            $crate::print_macro!($crate::print::format_strings::DEBUG, false, $($arg)*)
        }
    )
);

/// Continues a previous log message in the same line.
///
/// Use only when continuing a previous `pr_*!` macro (e.g. [`pr_info!`]).
///
/// Equivalent to the kernel's [`pr_cont`] macro.
///
/// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
/// `alloc::format!` for information about the formatting syntax.
///
/// [`pr_info!`]: crate::pr_info!
/// [`pr_cont`]: https://www.kernel.org/doc/html/latest/core-api/printk-basics.html#c.pr_cont
/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
///
/// # Examples
///
/// ```
/// # use kernel::pr_cont;
/// pr_info!("hello");
/// pr_cont!(" {}\n", "there");
/// ```
#[macro_export]
macro_rules! pr_cont (
    ($($arg:tt)*) => (
        $crate::print_macro!($crate::print::format_strings::CONT, true, $($arg)*)
    )
);