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 extern bool debug_non_panic_cpus;
68
69 __printf(4, 0)
70 int vprintk_store(int facility, int level,
71 const struct dev_printk_info *dev_info,
72 const char *fmt, va_list args);
73
74 __printf(1, 0) int vprintk_default(const char *fmt, va_list args);
75 __printf(1, 0) int vprintk_deferred(const char *fmt, va_list args);
76
77 void __printk_safe_enter(void);
78 void __printk_safe_exit(void);
79
80 bool printk_percpu_data_ready(void);
81
82 #define printk_safe_enter_irqsave(flags) \
83 do { \
84 local_irq_save(flags); \
85 __printk_safe_enter(); \
86 } while (0)
87
88 #define printk_safe_exit_irqrestore(flags) \
89 do { \
90 __printk_safe_exit(); \
91 local_irq_restore(flags); \
92 } while (0)
93
94 void defer_console_output(void);
95 bool is_printk_legacy_deferred(void);
96 bool is_printk_force_console(void);
97
98 u16 printk_parse_prefix(const char *text, int *level,
99 enum printk_info_flags *flags);
100 void console_lock_spinning_enable(void);
101 int console_lock_spinning_disable_and_check(int cookie);
102
103 u64 nbcon_seq_read(struct console *con);
104 void nbcon_seq_force(struct console *con, u64 seq);
105 bool nbcon_alloc(struct console *con);
106 void nbcon_free(struct console *con);
107 enum nbcon_prio nbcon_get_default_prio(void);
108 void nbcon_atomic_flush_pending(void);
109 bool nbcon_legacy_emit_next_record(struct console *con, bool *handover,
110 int cookie, bool use_atomic);
111 bool nbcon_kthread_create(struct console *con);
112 void nbcon_kthread_stop(struct console *con);
113 void nbcon_kthreads_wake(void);
114
115 /*
116 * Check if the given console is currently capable and allowed to print
117 * records. Note that this function does not consider the current context,
118 * which can also play a role in deciding if @con can be used to print
119 * records.
120 */
console_is_usable(struct console * con,short flags,bool use_atomic)121 static inline bool console_is_usable(struct console *con, short flags, bool use_atomic)
122 {
123 if (!(flags & CON_ENABLED))
124 return false;
125
126 if ((flags & CON_SUSPENDED))
127 return false;
128
129 if (flags & CON_NBCON) {
130 /* The write_atomic() callback is optional. */
131 if (use_atomic && !con->write_atomic)
132 return false;
133
134 /*
135 * For the !use_atomic case, @printk_kthreads_running is not
136 * checked because the write_thread() callback is also used
137 * via the legacy loop when the printer threads are not
138 * available.
139 */
140 } else {
141 if (!con->write)
142 return false;
143 }
144
145 /*
146 * Console drivers may assume that per-cpu resources have been
147 * allocated. So unless they're explicitly marked as being able to
148 * cope (CON_ANYTIME) don't call them until this CPU is officially up.
149 */
150 if (!cpu_online(raw_smp_processor_id()) && !(flags & CON_ANYTIME))
151 return false;
152
153 return true;
154 }
155
156 /**
157 * nbcon_kthread_wake - Wake up a console printing thread
158 * @con: Console to operate on
159 */
nbcon_kthread_wake(struct console * con)160 static inline void nbcon_kthread_wake(struct console *con)
161 {
162 /*
163 * Guarantee any new records can be seen by tasks preparing to wait
164 * before this context checks if the rcuwait is empty.
165 *
166 * The full memory barrier in rcuwait_wake_up() pairs with the full
167 * memory barrier within set_current_state() of
168 * ___rcuwait_wait_event(), which is called after prepare_to_rcuwait()
169 * adds the waiter but before it has checked the wait condition.
170 *
171 * This pairs with nbcon_kthread_func:A.
172 */
173 rcuwait_wake_up(&con->rcuwait); /* LMM(nbcon_kthread_wake:A) */
174 }
175
176 #else
177
178 #define PRINTK_PREFIX_MAX 0
179 #define PRINTK_MESSAGE_MAX 0
180 #define PRINTKRB_RECORD_MAX 0
181
182 #define printk_kthreads_running (false)
183
184 /*
185 * In !PRINTK builds we still export console_sem
186 * semaphore and some of console functions (console_unlock()/etc.), so
187 * printk-safe must preserve the existing local IRQ guarantees.
188 */
189 #define printk_safe_enter_irqsave(flags) local_irq_save(flags)
190 #define printk_safe_exit_irqrestore(flags) local_irq_restore(flags)
191
printk_percpu_data_ready(void)192 static inline bool printk_percpu_data_ready(void) { return false; }
defer_console_output(void)193 static inline void defer_console_output(void) { }
is_printk_legacy_deferred(void)194 static inline bool is_printk_legacy_deferred(void) { return false; }
nbcon_seq_read(struct console * con)195 static inline u64 nbcon_seq_read(struct console *con) { return 0; }
nbcon_seq_force(struct console * con,u64 seq)196 static inline void nbcon_seq_force(struct console *con, u64 seq) { }
nbcon_alloc(struct console * con)197 static inline bool nbcon_alloc(struct console *con) { return false; }
nbcon_free(struct console * con)198 static inline void nbcon_free(struct console *con) { }
nbcon_get_default_prio(void)199 static inline enum nbcon_prio nbcon_get_default_prio(void) { return NBCON_PRIO_NONE; }
nbcon_atomic_flush_pending(void)200 static inline void nbcon_atomic_flush_pending(void) { }
nbcon_legacy_emit_next_record(struct console * con,bool * handover,int cookie,bool use_atomic)201 static inline bool nbcon_legacy_emit_next_record(struct console *con, bool *handover,
202 int cookie, bool use_atomic) { return false; }
nbcon_kthread_wake(struct console * con)203 static inline void nbcon_kthread_wake(struct console *con) { }
nbcon_kthreads_wake(void)204 static inline void nbcon_kthreads_wake(void) { }
205
console_is_usable(struct console * con,short flags,bool use_atomic)206 static inline bool console_is_usable(struct console *con, short flags,
207 bool use_atomic) { return false; }
208
209 #endif /* CONFIG_PRINTK */
210
211 extern bool have_boot_console;
212 extern bool have_nbcon_console;
213 extern bool have_legacy_console;
214 extern bool legacy_allow_panic_sync;
215
216 /**
217 * struct console_flush_type - Define available console flush methods
218 * @nbcon_atomic: Flush directly using nbcon_atomic() callback
219 * @nbcon_offload: Offload flush to printer thread
220 * @legacy_direct: Call the legacy loop in this context
221 * @legacy_offload: Offload the legacy loop into IRQ or legacy thread
222 *
223 * Note that the legacy loop also flushes the nbcon consoles.
224 */
225 struct console_flush_type {
226 bool nbcon_atomic;
227 bool nbcon_offload;
228 bool legacy_direct;
229 bool legacy_offload;
230 };
231
232 /*
233 * Identify which console flushing methods should be used in the context of
234 * the caller.
235 */
printk_get_console_flush_type(struct console_flush_type * ft)236 static inline void printk_get_console_flush_type(struct console_flush_type *ft)
237 {
238 memset(ft, 0, sizeof(*ft));
239
240 switch (nbcon_get_default_prio()) {
241 case NBCON_PRIO_NORMAL:
242 if (have_nbcon_console && !have_boot_console) {
243 if (printk_kthreads_running)
244 ft->nbcon_offload = true;
245 else
246 ft->nbcon_atomic = true;
247 }
248
249 /* Legacy consoles are flushed directly when possible. */
250 if (have_legacy_console || have_boot_console) {
251 if (!is_printk_legacy_deferred())
252 ft->legacy_direct = true;
253 else
254 ft->legacy_offload = true;
255 }
256 break;
257
258 case NBCON_PRIO_EMERGENCY:
259 if (have_nbcon_console && !have_boot_console)
260 ft->nbcon_atomic = true;
261
262 /* Legacy consoles are flushed directly when possible. */
263 if (have_legacy_console || have_boot_console) {
264 if (!is_printk_legacy_deferred())
265 ft->legacy_direct = true;
266 else
267 ft->legacy_offload = true;
268 }
269 break;
270
271 case NBCON_PRIO_PANIC:
272 /*
273 * In panic, the nbcon consoles will directly print. But
274 * only allowed if there are no boot consoles.
275 */
276 if (have_nbcon_console && !have_boot_console)
277 ft->nbcon_atomic = true;
278
279 if (have_legacy_console || have_boot_console) {
280 /*
281 * This is the same decision as NBCON_PRIO_NORMAL
282 * except that offloading never occurs in panic.
283 *
284 * Note that console_flush_on_panic() will flush
285 * legacy consoles anyway, even if unsafe.
286 */
287 if (!is_printk_legacy_deferred())
288 ft->legacy_direct = true;
289
290 /*
291 * In panic, if nbcon atomic printing occurs,
292 * the legacy consoles must remain silent until
293 * explicitly allowed.
294 */
295 if (ft->nbcon_atomic && !legacy_allow_panic_sync)
296 ft->legacy_direct = false;
297 }
298 break;
299
300 default:
301 WARN_ON_ONCE(1);
302 break;
303 }
304 }
305
306 extern struct printk_buffers printk_shared_pbufs;
307
308 /**
309 * struct printk_buffers - Buffers to read/format/output printk messages.
310 * @outbuf: After formatting, contains text to output.
311 * @scratchbuf: Used as temporary ringbuffer reading and string-print space.
312 */
313 struct printk_buffers {
314 char outbuf[PRINTK_MESSAGE_MAX];
315 char scratchbuf[PRINTKRB_RECORD_MAX];
316 };
317
318 /**
319 * struct printk_message - Container for a prepared printk message.
320 * @pbufs: printk buffers used to prepare the message.
321 * @outbuf_len: The length of prepared text in @pbufs->outbuf to output. This
322 * does not count the terminator. A value of 0 means there is
323 * nothing to output and this record should be skipped.
324 * @seq: The sequence number of the record used for @pbufs->outbuf.
325 * @dropped: The number of dropped records from reading @seq.
326 */
327 struct printk_message {
328 struct printk_buffers *pbufs;
329 unsigned int outbuf_len;
330 u64 seq;
331 unsigned long dropped;
332 };
333
334 bool other_cpu_in_panic(void);
335 bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
336 bool is_extended, bool may_supress);
337
338 #ifdef CONFIG_PRINTK
339 void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped);
340 void console_prepend_replay(struct printk_message *pmsg);
341 #endif
342
343 #ifdef CONFIG_SMP
344 bool is_printk_cpu_sync_owner(void);
345 #else
is_printk_cpu_sync_owner(void)346 static inline bool is_printk_cpu_sync_owner(void) { return false; }
347 #endif
348