1 // SPDX-License-Identifier: GPL-2.0
2
3 //! Printing facilities.
4 //!
5 //! C header: [`include/linux/printk.h`](srctree/include/linux/printk.h)
6 //!
7 //! Reference: <https://docs.kernel.org/core-api/printk-basics.html>
8
9 use core::{
10 ffi::{c_char, c_void},
11 fmt,
12 };
13
14 use crate::str::RawFormatter;
15
16 // Called from `vsprintf` with format specifier `%pA`.
17 #[no_mangle]
18 unsafe extern "C" fn rust_fmt_argument(
19 buf: *mut c_char,
20 end: *mut c_char,
21 ptr: *const c_void,
22 ) -> *mut c_char {
23 use fmt::Write;
24 // SAFETY: The C contract guarantees that `buf` is valid if it's less than `end`.
25 let mut w = unsafe { RawFormatter::from_ptrs(buf.cast(), end.cast()) };
26 let _ = w.write_fmt(unsafe { *(ptr as *const fmt::Arguments<'_>) });
27 w.pos().cast()
28 }
29
30 /// Format strings.
31 ///
32 /// Public but hidden since it should only be used from public macros.
33 #[doc(hidden)]
34 pub mod format_strings {
35 /// The length we copy from the `KERN_*` kernel prefixes.
36 const LENGTH_PREFIX: usize = 2;
37
38 /// The length of the fixed format strings.
39 pub const LENGTH: usize = 10;
40
41 /// Generates a fixed format string for the kernel's [`_printk`].
42 ///
43 /// The format string is always the same for a given level, i.e. for a
44 /// given `prefix`, which are the kernel's `KERN_*` constants.
45 ///
46 /// [`_printk`]: srctree/include/linux/printk.h
47 const fn generate(is_cont: bool, prefix: &[u8; 3]) -> [u8; LENGTH] {
48 // Ensure the `KERN_*` macros are what we expect.
49 assert!(prefix[0] == b'\x01');
50 if is_cont {
51 assert!(prefix[1] == b'c');
52 } else {
53 assert!(prefix[1] >= b'0' && prefix[1] <= b'7');
54 }
55 assert!(prefix[2] == b'\x00');
56
57 let suffix: &[u8; LENGTH - LENGTH_PREFIX] = if is_cont {
58 b"%pA\0\0\0\0\0"
59 } else {
60 b"%s: %pA\0"
61 };
62
63 [
64 prefix[0], prefix[1], suffix[0], suffix[1], suffix[2], suffix[3], suffix[4], suffix[5],
65 suffix[6], suffix[7],
66 ]
67 }
68
69 // Generate the format strings at compile-time.
70 //
71 // This avoids the compiler generating the contents on the fly in the stack.
72 //
73 // Furthermore, `static` instead of `const` is used to share the strings
74 // for all the kernel.
75 pub static EMERG: [u8; LENGTH] = generate(false, bindings::KERN_EMERG);
76 pub static ALERT: [u8; LENGTH] = generate(false, bindings::KERN_ALERT);
77 pub static CRIT: [u8; LENGTH] = generate(false, bindings::KERN_CRIT);
78 pub static ERR: [u8; LENGTH] = generate(false, bindings::KERN_ERR);
79 pub static WARNING: [u8; LENGTH] = generate(false, bindings::KERN_WARNING);
80 pub static NOTICE: [u8; LENGTH] = generate(false, bindings::KERN_NOTICE);
81 pub static INFO: [u8; LENGTH] = generate(false, bindings::KERN_INFO);
82 pub static DEBUG: [u8; LENGTH] = generate(false, bindings::KERN_DEBUG);
83 pub static CONT: [u8; LENGTH] = generate(true, bindings::KERN_CONT);
84 }
85
86 /// Prints a message via the kernel's [`_printk`].
87 ///
88 /// Public but hidden since it should only be used from public macros.
89 ///
90 /// # Safety
91 ///
92 /// The format string must be one of the ones in [`format_strings`], and
93 /// the module name must be null-terminated.
94 ///
95 /// [`_printk`]: srctree/include/linux/_printk.h
96 #[doc(hidden)]
97 #[cfg_attr(not(CONFIG_PRINTK), allow(unused_variables))]
98 pub unsafe fn call_printk(
99 format_string: &[u8; format_strings::LENGTH],
100 module_name: &[u8],
101 args: fmt::Arguments<'_>,
102 ) {
103 // `_printk` does not seem to fail in any path.
104 #[cfg(CONFIG_PRINTK)]
105 unsafe {
106 bindings::_printk(
107 format_string.as_ptr() as _,
108 module_name.as_ptr(),
109 &args as *const _ as *const c_void,
110 );
111 }
112 }
113
114 /// Prints a message via the kernel's [`_printk`] for the `CONT` level.
115 ///
116 /// Public but hidden since it should only be used from public macros.
117 ///
118 /// [`_printk`]: srctree/include/linux/printk.h
119 #[doc(hidden)]
120 #[cfg_attr(not(CONFIG_PRINTK), allow(unused_variables))]
121 pub fn call_printk_cont(args: fmt::Arguments<'_>) {
122 // `_printk` does not seem to fail in any path.
123 //
124 // SAFETY: The format string is fixed.
125 #[cfg(CONFIG_PRINTK)]
126 unsafe {
127 bindings::_printk(
128 format_strings::CONT.as_ptr() as _,
129 &args as *const _ as *const c_void,
130 );
131 }
132 }
133
134 /// Performs formatting and forwards the string to [`call_printk`].
135 ///
136 /// Public but hidden since it should only be used from public macros.
137 #[doc(hidden)]
138 #[cfg(not(testlib))]
139 #[macro_export]
140 #[allow(clippy::crate_in_macro_def)]
141 macro_rules! print_macro (
142 // The non-continuation cases (most of them, e.g. `INFO`).
143 ($format_string:path, false, $($arg:tt)+) => (
144 // To remain sound, `arg`s must be expanded outside the `unsafe` block.
145 // Typically one would use a `let` binding for that; however, `format_args!`
146 // takes borrows on the arguments, but does not extend the scope of temporaries.
147 // Therefore, a `match` expression is used to keep them around, since
148 // the scrutinee is kept until the end of the `match`.
149 match format_args!($($arg)+) {
150 // SAFETY: This hidden macro should only be called by the documented
151 // printing macros which ensure the format string is one of the fixed
152 // ones. All `__LOG_PREFIX`s are null-terminated as they are generated
153 // by the `module!` proc macro or fixed values defined in a kernel
154 // crate.
155 args => unsafe {
156 $crate::print::call_printk(
157 &$format_string,
158 crate::__LOG_PREFIX,
159 args,
160 );
161 }
162 }
163 );
164
165 // The `CONT` case.
166 ($format_string:path, true, $($arg:tt)+) => (
167 $crate::print::call_printk_cont(
168 format_args!($($arg)+),
169 );
170 );
171 );
172
173 /// Stub for doctests
174 #[cfg(testlib)]
175 #[macro_export]
176 macro_rules! print_macro (
177 ($format_string:path, $e:expr, $($arg:tt)+) => (
178 ()
179 );
180 );
181
182 // We could use a macro to generate these macros. However, doing so ends
183 // up being a bit ugly: it requires the dollar token trick to escape `$` as
184 // well as playing with the `doc` attribute. Furthermore, they cannot be easily
185 // imported in the prelude due to [1]. So, for the moment, we just write them
186 // manually, like in the C side; while keeping most of the logic in another
187 // macro, i.e. [`print_macro`].
188 //
189 // [1]: https://github.com/rust-lang/rust/issues/52234
190
191 /// Prints an emergency-level message (level 0).
192 ///
193 /// Use this level if the system is unusable.
194 ///
195 /// Equivalent to the kernel's [`pr_emerg`] macro.
196 ///
197 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
198 /// `alloc::format!` for information about the formatting syntax.
199 ///
200 /// [`pr_emerg`]: https://docs.kernel.org/core-api/printk-basics.html#c.pr_emerg
201 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
202 ///
203 /// # Examples
204 ///
205 /// ```
206 /// pr_emerg!("hello {}\n", "there");
207 /// ```
208 #[macro_export]
209 macro_rules! pr_emerg (
210 ($($arg:tt)*) => (
211 $crate::print_macro!($crate::print::format_strings::EMERG, false, $($arg)*)
212 )
213 );
214
215 /// Prints an alert-level message (level 1).
216 ///
217 /// Use this level if action must be taken immediately.
218 ///
219 /// Equivalent to the kernel's [`pr_alert`] macro.
220 ///
221 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
222 /// `alloc::format!` for information about the formatting syntax.
223 ///
224 /// [`pr_alert`]: https://docs.kernel.org/core-api/printk-basics.html#c.pr_alert
225 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
226 ///
227 /// # Examples
228 ///
229 /// ```
230 /// pr_alert!("hello {}\n", "there");
231 /// ```
232 #[macro_export]
233 macro_rules! pr_alert (
234 ($($arg:tt)*) => (
235 $crate::print_macro!($crate::print::format_strings::ALERT, false, $($arg)*)
236 )
237 );
238
239 /// Prints a critical-level message (level 2).
240 ///
241 /// Use this level for critical conditions.
242 ///
243 /// Equivalent to the kernel's [`pr_crit`] macro.
244 ///
245 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
246 /// `alloc::format!` for information about the formatting syntax.
247 ///
248 /// [`pr_crit`]: https://docs.kernel.org/core-api/printk-basics.html#c.pr_crit
249 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
250 ///
251 /// # Examples
252 ///
253 /// ```
254 /// pr_crit!("hello {}\n", "there");
255 /// ```
256 #[macro_export]
257 macro_rules! pr_crit (
258 ($($arg:tt)*) => (
259 $crate::print_macro!($crate::print::format_strings::CRIT, false, $($arg)*)
260 )
261 );
262
263 /// Prints an error-level message (level 3).
264 ///
265 /// Use this level for error conditions.
266 ///
267 /// Equivalent to the kernel's [`pr_err`] macro.
268 ///
269 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
270 /// `alloc::format!` for information about the formatting syntax.
271 ///
272 /// [`pr_err`]: https://docs.kernel.org/core-api/printk-basics.html#c.pr_err
273 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
274 ///
275 /// # Examples
276 ///
277 /// ```
278 /// pr_err!("hello {}\n", "there");
279 /// ```
280 #[macro_export]
281 macro_rules! pr_err (
282 ($($arg:tt)*) => (
283 $crate::print_macro!($crate::print::format_strings::ERR, false, $($arg)*)
284 )
285 );
286
287 /// Prints a warning-level message (level 4).
288 ///
289 /// Use this level for warning conditions.
290 ///
291 /// Equivalent to the kernel's [`pr_warn`] macro.
292 ///
293 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
294 /// `alloc::format!` for information about the formatting syntax.
295 ///
296 /// [`pr_warn`]: https://docs.kernel.org/core-api/printk-basics.html#c.pr_warn
297 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
298 ///
299 /// # Examples
300 ///
301 /// ```
302 /// pr_warn!("hello {}\n", "there");
303 /// ```
304 #[macro_export]
305 macro_rules! pr_warn (
306 ($($arg:tt)*) => (
307 $crate::print_macro!($crate::print::format_strings::WARNING, false, $($arg)*)
308 )
309 );
310
311 /// Prints a notice-level message (level 5).
312 ///
313 /// Use this level for normal but significant conditions.
314 ///
315 /// Equivalent to the kernel's [`pr_notice`] macro.
316 ///
317 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
318 /// `alloc::format!` for information about the formatting syntax.
319 ///
320 /// [`pr_notice`]: https://docs.kernel.org/core-api/printk-basics.html#c.pr_notice
321 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
322 ///
323 /// # Examples
324 ///
325 /// ```
326 /// pr_notice!("hello {}\n", "there");
327 /// ```
328 #[macro_export]
329 macro_rules! pr_notice (
330 ($($arg:tt)*) => (
331 $crate::print_macro!($crate::print::format_strings::NOTICE, false, $($arg)*)
332 )
333 );
334
335 /// Prints an info-level message (level 6).
336 ///
337 /// Use this level for informational messages.
338 ///
339 /// Equivalent to the kernel's [`pr_info`] macro.
340 ///
341 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
342 /// `alloc::format!` for information about the formatting syntax.
343 ///
344 /// [`pr_info`]: https://docs.kernel.org/core-api/printk-basics.html#c.pr_info
345 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
346 ///
347 /// # Examples
348 ///
349 /// ```
350 /// pr_info!("hello {}\n", "there");
351 /// ```
352 #[macro_export]
353 #[doc(alias = "print")]
354 macro_rules! pr_info (
355 ($($arg:tt)*) => (
356 $crate::print_macro!($crate::print::format_strings::INFO, false, $($arg)*)
357 )
358 );
359
360 /// Prints a debug-level message (level 7).
361 ///
362 /// Use this level for debug messages.
363 ///
364 /// Equivalent to the kernel's [`pr_debug`] macro, except that it doesn't support dynamic debug
365 /// yet.
366 ///
367 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
368 /// `alloc::format!` for information about the formatting syntax.
369 ///
370 /// [`pr_debug`]: https://docs.kernel.org/core-api/printk-basics.html#c.pr_debug
371 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
372 ///
373 /// # Examples
374 ///
375 /// ```
376 /// pr_debug!("hello {}\n", "there");
377 /// ```
378 #[macro_export]
379 #[doc(alias = "print")]
380 macro_rules! pr_debug (
381 ($($arg:tt)*) => (
382 if cfg!(debug_assertions) {
383 $crate::print_macro!($crate::print::format_strings::DEBUG, false, $($arg)*)
384 }
385 )
386 );
387
388 /// Continues a previous log message in the same line.
389 ///
390 /// Use only when continuing a previous `pr_*!` macro (e.g. [`pr_info!`]).
391 ///
392 /// Equivalent to the kernel's [`pr_cont`] macro.
393 ///
394 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
395 /// `alloc::format!` for information about the formatting syntax.
396 ///
397 /// [`pr_info!`]: crate::pr_info!
398 /// [`pr_cont`]: https://docs.kernel.org/core-api/printk-basics.html#c.pr_cont
399 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
400 ///
401 /// # Examples
402 ///
403 /// ```
404 /// # use kernel::pr_cont;
405 /// pr_info!("hello");
406 /// pr_cont!(" {}\n", "there");
407 /// ```
408 #[macro_export]
409 macro_rules! pr_cont (
410 ($($arg:tt)*) => (
411 $crate::print_macro!($crate::print::format_strings::CONT, true, $($arg)*)
412 )
413 );
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