1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3 * internal.h - printk internal definitions
4 */
5 #include <linux/console.h>
6 #include <linux/percpu.h>
7 #include <linux/types.h>
8
9 #if defined(CONFIG_PRINTK) && defined(CONFIG_SYSCTL)
10 struct ctl_table;
11 void __init printk_sysctl_init(void);
12 int devkmsg_sysctl_set_loglvl(const struct ctl_table *table, int write,
13 void *buffer, size_t *lenp, loff_t *ppos);
14 #else
15 #define printk_sysctl_init() do { } while (0)
16 #endif
17
18 #define con_printk(lvl, con, fmt, ...) \
19 printk(lvl pr_fmt("%s%sconsole [%s%d] " fmt), \
20 (con->flags & CON_NBCON) ? "" : "legacy ", \
21 (con->flags & CON_BOOT) ? "boot" : "", \
22 con->name, con->index, ##__VA_ARGS__)
23
24 /*
25 * Identify if legacy printing is forced in a dedicated kthread. If
26 * true, all printing via console lock occurs within a dedicated
27 * legacy printer thread. The only exception is on panic, after the
28 * nbcon consoles have had their chance to print the panic messages
29 * first.
30 */
31 #ifdef CONFIG_PREEMPT_RT
32 # define force_legacy_kthread() (true)
33 #else
34 # define force_legacy_kthread() (false)
35 #endif
36
37 #ifdef CONFIG_PRINTK
38
39 #ifdef CONFIG_PRINTK_CALLER
40 #define PRINTK_PREFIX_MAX 48
41 #else
42 #define PRINTK_PREFIX_MAX 32
43 #endif
44
45 /*
46 * the maximum size of a formatted record (i.e. with prefix added
47 * per line and dropped messages or in extended message format)
48 */
49 #define PRINTK_MESSAGE_MAX 2048
50
51 /* the maximum size allowed to be reserved for a record */
52 #define PRINTKRB_RECORD_MAX 1024
53
54 /* Flags for a single printk record. */
55 enum printk_info_flags {
56 /* always show on console, ignore console_loglevel */
57 LOG_FORCE_CON = 1,
58 LOG_NEWLINE = 2, /* text ended with a newline */
59 LOG_CONT = 8, /* text is a fragment of a continuation line */
60 };
61
62 struct printk_ringbuffer;
63 struct dev_printk_info;
64
65 extern struct printk_ringbuffer *prb;
66 extern bool printk_kthreads_running;
67
68 __printf(4, 0)
69 int vprintk_store(int facility, int level,
70 const struct dev_printk_info *dev_info,
71 const char *fmt, va_list args);
72
73 __printf(1, 0) int vprintk_default(const char *fmt, va_list args);
74 __printf(1, 0) int vprintk_deferred(const char *fmt, va_list args);
75
76 void __printk_safe_enter(void);
77 void __printk_safe_exit(void);
78
79 bool printk_percpu_data_ready(void);
80
81 #define printk_safe_enter_irqsave(flags) \
82 do { \
83 local_irq_save(flags); \
84 __printk_safe_enter(); \
85 } while (0)
86
87 #define printk_safe_exit_irqrestore(flags) \
88 do { \
89 __printk_safe_exit(); \
90 local_irq_restore(flags); \
91 } while (0)
92
93 void defer_console_output(void);
94 bool is_printk_legacy_deferred(void);
95 bool is_printk_force_console(void);
96
97 u16 printk_parse_prefix(const char *text, int *level,
98 enum printk_info_flags *flags);
99 void console_lock_spinning_enable(void);
100 int console_lock_spinning_disable_and_check(int cookie);
101
102 u64 nbcon_seq_read(struct console *con);
103 void nbcon_seq_force(struct console *con, u64 seq);
104 bool nbcon_alloc(struct console *con);
105 void nbcon_free(struct console *con);
106 enum nbcon_prio nbcon_get_default_prio(void);
107 void nbcon_atomic_flush_pending(void);
108 bool nbcon_legacy_emit_next_record(struct console *con, bool *handover,
109 int cookie, bool use_atomic);
110 bool nbcon_kthread_create(struct console *con);
111 void nbcon_kthread_stop(struct console *con);
112 void nbcon_kthreads_wake(void);
113
114 /*
115 * Check if the given console is currently capable and allowed to print
116 * records. Note that this function does not consider the current context,
117 * which can also play a role in deciding if @con can be used to print
118 * records.
119 */
console_is_usable(struct console * con,short flags,bool use_atomic)120 static inline bool console_is_usable(struct console *con, short flags, bool use_atomic)
121 {
122 if (!(flags & CON_ENABLED))
123 return false;
124
125 if ((flags & CON_SUSPENDED))
126 return false;
127
128 if (flags & CON_NBCON) {
129 /* The write_atomic() callback is optional. */
130 if (use_atomic && !con->write_atomic)
131 return false;
132
133 /*
134 * For the !use_atomic case, @printk_kthreads_running is not
135 * checked because the write_thread() callback is also used
136 * via the legacy loop when the printer threads are not
137 * available.
138 */
139 } else {
140 if (!con->write)
141 return false;
142 }
143
144 /*
145 * Console drivers may assume that per-cpu resources have been
146 * allocated. So unless they're explicitly marked as being able to
147 * cope (CON_ANYTIME) don't call them until this CPU is officially up.
148 */
149 if (!cpu_online(raw_smp_processor_id()) && !(flags & CON_ANYTIME))
150 return false;
151
152 return true;
153 }
154
155 /**
156 * nbcon_kthread_wake - Wake up a console printing thread
157 * @con: Console to operate on
158 */
nbcon_kthread_wake(struct console * con)159 static inline void nbcon_kthread_wake(struct console *con)
160 {
161 /*
162 * Guarantee any new records can be seen by tasks preparing to wait
163 * before this context checks if the rcuwait is empty.
164 *
165 * The full memory barrier in rcuwait_wake_up() pairs with the full
166 * memory barrier within set_current_state() of
167 * ___rcuwait_wait_event(), which is called after prepare_to_rcuwait()
168 * adds the waiter but before it has checked the wait condition.
169 *
170 * This pairs with nbcon_kthread_func:A.
171 */
172 rcuwait_wake_up(&con->rcuwait); /* LMM(nbcon_kthread_wake:A) */
173 }
174
175 #else
176
177 #define PRINTK_PREFIX_MAX 0
178 #define PRINTK_MESSAGE_MAX 0
179 #define PRINTKRB_RECORD_MAX 0
180
181 #define printk_kthreads_running (false)
182
183 /*
184 * In !PRINTK builds we still export console_sem
185 * semaphore and some of console functions (console_unlock()/etc.), so
186 * printk-safe must preserve the existing local IRQ guarantees.
187 */
188 #define printk_safe_enter_irqsave(flags) local_irq_save(flags)
189 #define printk_safe_exit_irqrestore(flags) local_irq_restore(flags)
190
printk_percpu_data_ready(void)191 static inline bool printk_percpu_data_ready(void) { return false; }
defer_console_output(void)192 static inline void defer_console_output(void) { }
is_printk_legacy_deferred(void)193 static inline bool is_printk_legacy_deferred(void) { return false; }
nbcon_seq_read(struct console * con)194 static inline u64 nbcon_seq_read(struct console *con) { return 0; }
nbcon_seq_force(struct console * con,u64 seq)195 static inline void nbcon_seq_force(struct console *con, u64 seq) { }
nbcon_alloc(struct console * con)196 static inline bool nbcon_alloc(struct console *con) { return false; }
nbcon_free(struct console * con)197 static inline void nbcon_free(struct console *con) { }
nbcon_get_default_prio(void)198 static inline enum nbcon_prio nbcon_get_default_prio(void) { return NBCON_PRIO_NONE; }
nbcon_atomic_flush_pending(void)199 static inline void nbcon_atomic_flush_pending(void) { }
nbcon_legacy_emit_next_record(struct console * con,bool * handover,int cookie,bool use_atomic)200 static inline bool nbcon_legacy_emit_next_record(struct console *con, bool *handover,
201 int cookie, bool use_atomic) { return false; }
nbcon_kthread_wake(struct console * con)202 static inline void nbcon_kthread_wake(struct console *con) { }
nbcon_kthreads_wake(void)203 static inline void nbcon_kthreads_wake(void) { }
204
console_is_usable(struct console * con,short flags,bool use_atomic)205 static inline bool console_is_usable(struct console *con, short flags,
206 bool use_atomic) { return false; }
207
208 #endif /* CONFIG_PRINTK */
209
210 extern bool have_boot_console;
211 extern bool have_nbcon_console;
212 extern bool have_legacy_console;
213 extern bool legacy_allow_panic_sync;
214
215 /**
216 * struct console_flush_type - Define available console flush methods
217 * @nbcon_atomic: Flush directly using nbcon_atomic() callback
218 * @nbcon_offload: Offload flush to printer thread
219 * @legacy_direct: Call the legacy loop in this context
220 * @legacy_offload: Offload the legacy loop into IRQ or legacy thread
221 *
222 * Note that the legacy loop also flushes the nbcon consoles.
223 */
224 struct console_flush_type {
225 bool nbcon_atomic;
226 bool nbcon_offload;
227 bool legacy_direct;
228 bool legacy_offload;
229 };
230
231 /*
232 * Identify which console flushing methods should be used in the context of
233 * the caller.
234 */
printk_get_console_flush_type(struct console_flush_type * ft)235 static inline void printk_get_console_flush_type(struct console_flush_type *ft)
236 {
237 memset(ft, 0, sizeof(*ft));
238
239 switch (nbcon_get_default_prio()) {
240 case NBCON_PRIO_NORMAL:
241 if (have_nbcon_console && !have_boot_console) {
242 if (printk_kthreads_running)
243 ft->nbcon_offload = true;
244 else
245 ft->nbcon_atomic = true;
246 }
247
248 /* Legacy consoles are flushed directly when possible. */
249 if (have_legacy_console || have_boot_console) {
250 if (!is_printk_legacy_deferred())
251 ft->legacy_direct = true;
252 else
253 ft->legacy_offload = true;
254 }
255 break;
256
257 case NBCON_PRIO_EMERGENCY:
258 if (have_nbcon_console && !have_boot_console)
259 ft->nbcon_atomic = true;
260
261 /* Legacy consoles are flushed directly when possible. */
262 if (have_legacy_console || have_boot_console) {
263 if (!is_printk_legacy_deferred())
264 ft->legacy_direct = true;
265 else
266 ft->legacy_offload = true;
267 }
268 break;
269
270 case NBCON_PRIO_PANIC:
271 /*
272 * In panic, the nbcon consoles will directly print. But
273 * only allowed if there are no boot consoles.
274 */
275 if (have_nbcon_console && !have_boot_console)
276 ft->nbcon_atomic = true;
277
278 if (have_legacy_console || have_boot_console) {
279 /*
280 * This is the same decision as NBCON_PRIO_NORMAL
281 * except that offloading never occurs in panic.
282 *
283 * Note that console_flush_on_panic() will flush
284 * legacy consoles anyway, even if unsafe.
285 */
286 if (!is_printk_legacy_deferred())
287 ft->legacy_direct = true;
288
289 /*
290 * In panic, if nbcon atomic printing occurs,
291 * the legacy consoles must remain silent until
292 * explicitly allowed.
293 */
294 if (ft->nbcon_atomic && !legacy_allow_panic_sync)
295 ft->legacy_direct = false;
296 }
297 break;
298
299 default:
300 WARN_ON_ONCE(1);
301 break;
302 }
303 }
304
305 extern struct printk_buffers printk_shared_pbufs;
306
307 /**
308 * struct printk_buffers - Buffers to read/format/output printk messages.
309 * @outbuf: After formatting, contains text to output.
310 * @scratchbuf: Used as temporary ringbuffer reading and string-print space.
311 */
312 struct printk_buffers {
313 char outbuf[PRINTK_MESSAGE_MAX];
314 char scratchbuf[PRINTKRB_RECORD_MAX];
315 };
316
317 /**
318 * struct printk_message - Container for a prepared printk message.
319 * @pbufs: printk buffers used to prepare the message.
320 * @outbuf_len: The length of prepared text in @pbufs->outbuf to output. This
321 * does not count the terminator. A value of 0 means there is
322 * nothing to output and this record should be skipped.
323 * @seq: The sequence number of the record used for @pbufs->outbuf.
324 * @dropped: The number of dropped records from reading @seq.
325 */
326 struct printk_message {
327 struct printk_buffers *pbufs;
328 unsigned int outbuf_len;
329 u64 seq;
330 unsigned long dropped;
331 };
332
333 bool other_cpu_in_panic(void);
334 bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
335 bool is_extended, bool may_supress);
336
337 #ifdef CONFIG_PRINTK
338 void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped);
339 void console_prepend_replay(struct printk_message *pmsg);
340 #endif
341