projects/linux·blob v6.2 · refs

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