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 #[expect(clippy::missing_safety_doc)] 18 #[no_mangle] 19 unsafe extern "C" fn rust_fmt_argument( 20 buf: *mut c_char, 21 end: *mut c_char, 22 ptr: *const c_void, 23 ) -> *mut c_char { 24 use fmt::Write; 25 // SAFETY: The C contract guarantees that `buf` is valid if it's less than `end`. 26 let mut w = unsafe { RawFormatter::from_ptrs(buf.cast(), end.cast()) }; 27 // SAFETY: TODO. 28 let _ = w.write_fmt(unsafe { *(ptr as *const fmt::Arguments<'_>) }); 29 w.pos().cast() 30 } 31 32 /// Format strings. 33 /// 34 /// Public but hidden since it should only be used from public macros. 35 #[doc(hidden)] 36 pub mod format_strings { 37 /// The length we copy from the `KERN_*` kernel prefixes. 38 const LENGTH_PREFIX: usize = 2; 39 40 /// The length of the fixed format strings. 41 pub const LENGTH: usize = 10; 42 43 /// Generates a fixed format string for the kernel's [`_printk`]. 44 /// 45 /// The format string is always the same for a given level, i.e. for a 46 /// given `prefix`, which are the kernel's `KERN_*` constants. 47 /// 48 /// [`_printk`]: srctree/include/linux/printk.h 49 const fn generate(is_cont: bool, prefix: &[u8; 3]) -> [u8; LENGTH] { 50 // Ensure the `KERN_*` macros are what we expect. 51 assert!(prefix[0] == b'\x01'); 52 if is_cont { 53 assert!(prefix[1] == b'c'); 54 } else { 55 assert!(prefix[1] >= b'0' && prefix[1] <= b'7'); 56 } 57 assert!(prefix[2] == b'\x00'); 58 59 let suffix: &[u8; LENGTH - LENGTH_PREFIX] = if is_cont { 60 b"%pA\0\0\0\0\0" 61 } else { 62 b"%s: %pA\0" 63 }; 64 65 [ 66 prefix[0], prefix[1], suffix[0], suffix[1], suffix[2], suffix[3], suffix[4], suffix[5], 67 suffix[6], suffix[7], 68 ] 69 } 70 71 // Generate the format strings at compile-time. 72 // 73 // This avoids the compiler generating the contents on the fly in the stack. 74 // 75 // Furthermore, `static` instead of `const` is used to share the strings 76 // for all the kernel. 77 pub static EMERG: [u8; LENGTH] = generate(false, bindings::KERN_EMERG); 78 pub static ALERT: [u8; LENGTH] = generate(false, bindings::KERN_ALERT); 79 pub static CRIT: [u8; LENGTH] = generate(false, bindings::KERN_CRIT); 80 pub static ERR: [u8; LENGTH] = generate(false, bindings::KERN_ERR); 81 pub static WARNING: [u8; LENGTH] = generate(false, bindings::KERN_WARNING); 82 pub static NOTICE: [u8; LENGTH] = generate(false, bindings::KERN_NOTICE); 83 pub static INFO: [u8; LENGTH] = generate(false, bindings::KERN_INFO); 84 pub static DEBUG: [u8; LENGTH] = generate(false, bindings::KERN_DEBUG); 85 pub static CONT: [u8; LENGTH] = generate(true, bindings::KERN_CONT); 86 } 87 88 /// Prints a message via the kernel's [`_printk`]. 89 /// 90 /// Public but hidden since it should only be used from public macros. 91 /// 92 /// # Safety 93 /// 94 /// The format string must be one of the ones in [`format_strings`], and 95 /// the module name must be null-terminated. 96 /// 97 /// [`_printk`]: srctree/include/linux/_printk.h 98 #[doc(hidden)] 99 #[cfg_attr(not(CONFIG_PRINTK), allow(unused_variables))] 100 pub unsafe fn call_printk( 101 format_string: &[u8; format_strings::LENGTH], 102 module_name: &[u8], 103 args: fmt::Arguments<'_>, 104 ) { 105 // `_printk` does not seem to fail in any path. 106 #[cfg(CONFIG_PRINTK)] 107 // SAFETY: TODO. 108 unsafe { 109 bindings::_printk( 110 format_string.as_ptr() as _, 111 module_name.as_ptr(), 112 &args as *const _ as *const c_void, 113 ); 114 } 115 } 116 117 /// Prints a message via the kernel's [`_printk`] for the `CONT` level. 118 /// 119 /// Public but hidden since it should only be used from public macros. 120 /// 121 /// [`_printk`]: srctree/include/linux/printk.h 122 #[doc(hidden)] 123 #[cfg_attr(not(CONFIG_PRINTK), allow(unused_variables))] 124 pub fn call_printk_cont(args: fmt::Arguments<'_>) { 125 // `_printk` does not seem to fail in any path. 126 // 127 // SAFETY: The format string is fixed. 128 #[cfg(CONFIG_PRINTK)] 129 unsafe { 130 bindings::_printk( 131 format_strings::CONT.as_ptr() as _, 132 &args as *const _ as *const c_void, 133 ); 134 } 135 } 136 137 /// Performs formatting and forwards the string to [`call_printk`]. 138 /// 139 /// Public but hidden since it should only be used from public macros. 140 #[doc(hidden)] 141 #[cfg(not(testlib))] 142 #[macro_export] 143 #[expect(clippy::crate_in_macro_def)] 144 macro_rules! print_macro ( 145 // The non-continuation cases (most of them, e.g. `INFO`). 146 ($format_string:path, false, $($arg:tt)+) => ( 147 // To remain sound, `arg`s must be expanded outside the `unsafe` block. 148 // Typically one would use a `let` binding for that; however, `format_args!` 149 // takes borrows on the arguments, but does not extend the scope of temporaries. 150 // Therefore, a `match` expression is used to keep them around, since 151 // the scrutinee is kept until the end of the `match`. 152 match format_args!($($arg)+) { 153 // SAFETY: This hidden macro should only be called by the documented 154 // printing macros which ensure the format string is one of the fixed 155 // ones. All `__LOG_PREFIX`s are null-terminated as they are generated 156 // by the `module!` proc macro or fixed values defined in a kernel 157 // crate. 158 args => unsafe { 159 $crate::print::call_printk( 160 &$format_string, 161 crate::__LOG_PREFIX, 162 args, 163 ); 164 } 165 } 166 ); 167 168 // The `CONT` case. 169 ($format_string:path, true, $($arg:tt)+) => ( 170 $crate::print::call_printk_cont( 171 format_args!($($arg)+), 172 ); 173 ); 174 ); 175 176 /// Stub for doctests 177 #[cfg(testlib)] 178 #[macro_export] 179 macro_rules! print_macro ( 180 ($format_string:path, $e:expr, $($arg:tt)+) => ( 181 () 182 ); 183 ); 184 185 // We could use a macro to generate these macros. However, doing so ends 186 // up being a bit ugly: it requires the dollar token trick to escape `$` as 187 // well as playing with the `doc` attribute. Furthermore, they cannot be easily 188 // imported in the prelude due to [1]. So, for the moment, we just write them 189 // manually, like in the C side; while keeping most of the logic in another 190 // macro, i.e. [`print_macro`]. 191 // 192 // [1]: https://github.com/rust-lang/rust/issues/52234 193 194 /// Prints an emergency-level message (level 0). 195 /// 196 /// Use this level if the system is unusable. 197 /// 198 /// Equivalent to the kernel's [`pr_emerg`] macro. 199 /// 200 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and 201 /// `alloc::format!` for information about the formatting syntax. 202 /// 203 /// [`pr_emerg`]: https://docs.kernel.org/core-api/printk-basics.html#c.pr_emerg 204 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html 205 /// 206 /// # Examples 207 /// 208 /// ``` 209 /// pr_emerg!("hello {}\n", "there"); 210 /// ``` 211 #[macro_export] 212 macro_rules! pr_emerg ( 213 ($($arg:tt)*) => ( 214 $crate::print_macro!($crate::print::format_strings::EMERG, false, $($arg)*) 215 ) 216 ); 217 218 /// Prints an alert-level message (level 1). 219 /// 220 /// Use this level if action must be taken immediately. 221 /// 222 /// Equivalent to the kernel's [`pr_alert`] macro. 223 /// 224 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and 225 /// `alloc::format!` for information about the formatting syntax. 226 /// 227 /// [`pr_alert`]: https://docs.kernel.org/core-api/printk-basics.html#c.pr_alert 228 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html 229 /// 230 /// # Examples 231 /// 232 /// ``` 233 /// pr_alert!("hello {}\n", "there"); 234 /// ``` 235 #[macro_export] 236 macro_rules! pr_alert ( 237 ($($arg:tt)*) => ( 238 $crate::print_macro!($crate::print::format_strings::ALERT, false, $($arg)*) 239 ) 240 ); 241 242 /// Prints a critical-level message (level 2). 243 /// 244 /// Use this level for critical conditions. 245 /// 246 /// Equivalent to the kernel's [`pr_crit`] macro. 247 /// 248 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and 249 /// `alloc::format!` for information about the formatting syntax. 250 /// 251 /// [`pr_crit`]: https://docs.kernel.org/core-api/printk-basics.html#c.pr_crit 252 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html 253 /// 254 /// # Examples 255 /// 256 /// ``` 257 /// pr_crit!("hello {}\n", "there"); 258 /// ``` 259 #[macro_export] 260 macro_rules! pr_crit ( 261 ($($arg:tt)*) => ( 262 $crate::print_macro!($crate::print::format_strings::CRIT, false, $($arg)*) 263 ) 264 ); 265 266 /// Prints an error-level message (level 3). 267 /// 268 /// Use this level for error conditions. 269 /// 270 /// Equivalent to the kernel's [`pr_err`] macro. 271 /// 272 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and 273 /// `alloc::format!` for information about the formatting syntax. 274 /// 275 /// [`pr_err`]: https://docs.kernel.org/core-api/printk-basics.html#c.pr_err 276 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html 277 /// 278 /// # Examples 279 /// 280 /// ``` 281 /// pr_err!("hello {}\n", "there"); 282 /// ``` 283 #[macro_export] 284 macro_rules! pr_err ( 285 ($($arg:tt)*) => ( 286 $crate::print_macro!($crate::print::format_strings::ERR, false, $($arg)*) 287 ) 288 ); 289 290 /// Prints a warning-level message (level 4). 291 /// 292 /// Use this level for warning conditions. 293 /// 294 /// Equivalent to the kernel's [`pr_warn`] macro. 295 /// 296 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and 297 /// `alloc::format!` for information about the formatting syntax. 298 /// 299 /// [`pr_warn`]: https://docs.kernel.org/core-api/printk-basics.html#c.pr_warn 300 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html 301 /// 302 /// # Examples 303 /// 304 /// ``` 305 /// pr_warn!("hello {}\n", "there"); 306 /// ``` 307 #[macro_export] 308 macro_rules! pr_warn ( 309 ($($arg:tt)*) => ( 310 $crate::print_macro!($crate::print::format_strings::WARNING, false, $($arg)*) 311 ) 312 ); 313 314 /// Prints a notice-level message (level 5). 315 /// 316 /// Use this level for normal but significant conditions. 317 /// 318 /// Equivalent to the kernel's [`pr_notice`] macro. 319 /// 320 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and 321 /// `alloc::format!` for information about the formatting syntax. 322 /// 323 /// [`pr_notice`]: https://docs.kernel.org/core-api/printk-basics.html#c.pr_notice 324 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html 325 /// 326 /// # Examples 327 /// 328 /// ``` 329 /// pr_notice!("hello {}\n", "there"); 330 /// ``` 331 #[macro_export] 332 macro_rules! pr_notice ( 333 ($($arg:tt)*) => ( 334 $crate::print_macro!($crate::print::format_strings::NOTICE, false, $($arg)*) 335 ) 336 ); 337 338 /// Prints an info-level message (level 6). 339 /// 340 /// Use this level for informational messages. 341 /// 342 /// Equivalent to the kernel's [`pr_info`] macro. 343 /// 344 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and 345 /// `alloc::format!` for information about the formatting syntax. 346 /// 347 /// [`pr_info`]: https://docs.kernel.org/core-api/printk-basics.html#c.pr_info 348 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html 349 /// 350 /// # Examples 351 /// 352 /// ``` 353 /// pr_info!("hello {}\n", "there"); 354 /// ``` 355 #[macro_export] 356 #[doc(alias = "print")] 357 macro_rules! pr_info ( 358 ($($arg:tt)*) => ( 359 $crate::print_macro!($crate::print::format_strings::INFO, false, $($arg)*) 360 ) 361 ); 362 363 /// Prints a debug-level message (level 7). 364 /// 365 /// Use this level for debug messages. 366 /// 367 /// Equivalent to the kernel's [`pr_debug`] macro, except that it doesn't support dynamic debug 368 /// yet. 369 /// 370 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and 371 /// `alloc::format!` for information about the formatting syntax. 372 /// 373 /// [`pr_debug`]: https://docs.kernel.org/core-api/printk-basics.html#c.pr_debug 374 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html 375 /// 376 /// # Examples 377 /// 378 /// ``` 379 /// pr_debug!("hello {}\n", "there"); 380 /// ``` 381 #[macro_export] 382 #[doc(alias = "print")] 383 macro_rules! pr_debug ( 384 ($($arg:tt)*) => ( 385 if cfg!(debug_assertions) { 386 $crate::print_macro!($crate::print::format_strings::DEBUG, false, $($arg)*) 387 } 388 ) 389 ); 390 391 /// Continues a previous log message in the same line. 392 /// 393 /// Use only when continuing a previous `pr_*!` macro (e.g. [`pr_info!`]). 394 /// 395 /// Equivalent to the kernel's [`pr_cont`] macro. 396 /// 397 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and 398 /// `alloc::format!` for information about the formatting syntax. 399 /// 400 /// [`pr_info!`]: crate::pr_info! 401 /// [`pr_cont`]: https://docs.kernel.org/core-api/printk-basics.html#c.pr_cont 402 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html 403 /// 404 /// # Examples 405 /// 406 /// ``` 407 /// # use kernel::pr_cont; 408 /// pr_info!("hello"); 409 /// pr_cont!(" {}\n", "there"); 410 /// ``` 411 #[macro_export] 412 macro_rules! pr_cont ( 413 ($($arg:tt)*) => ( 414 $crate::print_macro!($crate::print::format_strings::CONT, true, $($arg)*) 415 ) 416 ); 417