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