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