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1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | ||
3 | #ifndef _KERNEL_PRINTK_RINGBUFFER_H | |
4 | #define _KERNEL_PRINTK_RINGBUFFER_H | |
5 | ||
6 | #include <linux/atomic.h> | |
74caba7f | 7 | #include <linux/dev_printk.h> |
b6cf8b3f JO |
8 | |
9 | /* | |
10 | * Meta information about each stored message. | |
11 | * | |
f35efc78 JO |
12 | * All fields are set by the printk code except for @seq, which is |
13 | * set by the ringbuffer code. | |
b6cf8b3f JO |
14 | */ |
15 | struct printk_info { | |
16 | u64 seq; /* sequence number */ | |
17 | u64 ts_nsec; /* timestamp in nanoseconds */ | |
18 | u16 text_len; /* length of text message */ | |
b6cf8b3f JO |
19 | u8 facility; /* syslog facility */ |
20 | u8 flags:5; /* internal record flags */ | |
21 | u8 level:3; /* syslog level */ | |
22 | u32 caller_id; /* thread id or processor id */ | |
74caba7f JO |
23 | |
24 | struct dev_printk_info dev_info; | |
b6cf8b3f JO |
25 | }; |
26 | ||
27 | /* | |
28 | * A structure providing the buffers, used by writers and readers. | |
29 | * | |
30 | * Writers: | |
f35efc78 JO |
31 | * Using prb_rec_init_wr(), a writer sets @text_buf_size before calling |
32 | * prb_reserve(). On success, prb_reserve() sets @info and @text_buf to | |
33 | * buffers reserved for that writer. | |
b6cf8b3f JO |
34 | * |
35 | * Readers: | |
36 | * Using prb_rec_init_rd(), a reader sets all fields before calling | |
f35efc78 JO |
37 | * prb_read_valid(). Note that the reader provides the @info and @text_buf, |
38 | * buffers. On success, the struct pointed to by @info will be filled and | |
39 | * the char array pointed to by @text_buf will be filled with text data. | |
b6cf8b3f JO |
40 | */ |
41 | struct printk_record { | |
42 | struct printk_info *info; | |
43 | char *text_buf; | |
b6cf8b3f | 44 | unsigned int text_buf_size; |
b6cf8b3f JO |
45 | }; |
46 | ||
47 | /* Specifies the logical position and span of a data block. */ | |
48 | struct prb_data_blk_lpos { | |
49 | unsigned long begin; | |
50 | unsigned long next; | |
51 | }; | |
52 | ||
53 | /* | |
54 | * A descriptor: the complete meta-data for a record. | |
55 | * | |
56 | * @state_var: A bitwise combination of descriptor ID and descriptor state. | |
57 | */ | |
58 | struct prb_desc { | |
b6cf8b3f JO |
59 | atomic_long_t state_var; |
60 | struct prb_data_blk_lpos text_blk_lpos; | |
b6cf8b3f JO |
61 | }; |
62 | ||
63 | /* A ringbuffer of "ID + data" elements. */ | |
64 | struct prb_data_ring { | |
65 | unsigned int size_bits; | |
66 | char *data; | |
67 | atomic_long_t head_lpos; | |
68 | atomic_long_t tail_lpos; | |
69 | }; | |
70 | ||
71 | /* A ringbuffer of "struct prb_desc" elements. */ | |
72 | struct prb_desc_ring { | |
73 | unsigned int count_bits; | |
74 | struct prb_desc *descs; | |
cfe2790b | 75 | struct printk_info *infos; |
b6cf8b3f JO |
76 | atomic_long_t head_id; |
77 | atomic_long_t tail_id; | |
78 | }; | |
79 | ||
80 | /* | |
81 | * The high level structure representing the printk ringbuffer. | |
82 | * | |
83 | * @fail: Count of failed prb_reserve() calls where not even a data-less | |
84 | * record was created. | |
85 | */ | |
86 | struct printk_ringbuffer { | |
87 | struct prb_desc_ring desc_ring; | |
88 | struct prb_data_ring text_data_ring; | |
b6cf8b3f JO |
89 | atomic_long_t fail; |
90 | }; | |
91 | ||
92 | /* | |
93 | * Used by writers as a reserve/commit handle. | |
94 | * | |
95 | * @rb: Ringbuffer where the entry is reserved. | |
96 | * @irqflags: Saved irq flags to restore on entry commit. | |
97 | * @id: ID of the reserved descriptor. | |
98 | * @text_space: Total occupied buffer space in the text data ring, including | |
99 | * ID, alignment padding, and wrapping data blocks. | |
100 | * | |
101 | * This structure is an opaque handle for writers. Its contents are only | |
102 | * to be used by the ringbuffer implementation. | |
103 | */ | |
104 | struct prb_reserved_entry { | |
105 | struct printk_ringbuffer *rb; | |
106 | unsigned long irqflags; | |
107 | unsigned long id; | |
108 | unsigned int text_space; | |
109 | }; | |
110 | ||
10dcb06d JO |
111 | /* The possible responses of a descriptor state-query. */ |
112 | enum desc_state { | |
113 | desc_miss = -1, /* ID mismatch (pseudo state) */ | |
114 | desc_reserved = 0x0, /* reserved, in use by writer */ | |
4cfc7258 JO |
115 | desc_committed = 0x1, /* committed by writer, could get reopened */ |
116 | desc_finalized = 0x2, /* committed, no further modification allowed */ | |
10dcb06d JO |
117 | desc_reusable = 0x3, /* free, not yet used by any writer */ |
118 | }; | |
119 | ||
120 | #define _DATA_SIZE(sz_bits) (1UL << (sz_bits)) | |
121 | #define _DESCS_COUNT(ct_bits) (1U << (ct_bits)) | |
122 | #define DESC_SV_BITS (sizeof(unsigned long) * 8) | |
123 | #define DESC_FLAGS_SHIFT (DESC_SV_BITS - 2) | |
124 | #define DESC_FLAGS_MASK (3UL << DESC_FLAGS_SHIFT) | |
125 | #define DESC_STATE(sv) (3UL & (sv >> DESC_FLAGS_SHIFT)) | |
126 | #define DESC_SV(id, state) (((unsigned long)state << DESC_FLAGS_SHIFT) | id) | |
127 | #define DESC_ID_MASK (~DESC_FLAGS_MASK) | |
128 | #define DESC_ID(sv) ((sv) & DESC_ID_MASK) | |
129 | #define FAILED_LPOS 0x1 | |
130 | #define NO_LPOS 0x3 | |
b6cf8b3f | 131 | |
d397820f | 132 | #define FAILED_BLK_LPOS \ |
b6cf8b3f | 133 | { \ |
d397820f JO |
134 | .begin = FAILED_LPOS, \ |
135 | .next = FAILED_LPOS, \ | |
b6cf8b3f JO |
136 | } |
137 | ||
138 | /* | |
139 | * Descriptor Bootstrap | |
140 | * | |
141 | * The descriptor array is minimally initialized to allow immediate usage | |
142 | * by readers and writers. The requirements that the descriptor array | |
143 | * initialization must satisfy: | |
144 | * | |
145 | * Req1 | |
146 | * The tail must point to an existing (committed or reusable) descriptor. | |
147 | * This is required by the implementation of prb_first_seq(). | |
148 | * | |
149 | * Req2 | |
150 | * Readers must see that the ringbuffer is initially empty. | |
151 | * | |
152 | * Req3 | |
153 | * The first record reserved by a writer is assigned sequence number 0. | |
154 | * | |
155 | * To satisfy Req1, the tail initially points to a descriptor that is | |
156 | * minimally initialized (having no data block, i.e. data-less with the | |
d397820f | 157 | * data block's lpos @begin and @next values set to FAILED_LPOS). |
b6cf8b3f JO |
158 | * |
159 | * To satisfy Req2, the initial tail descriptor is initialized to the | |
160 | * reusable state. Readers recognize reusable descriptors as existing | |
161 | * records, but skip over them. | |
162 | * | |
163 | * To satisfy Req3, the last descriptor in the array is used as the initial | |
164 | * head (and tail) descriptor. This allows the first record reserved by a | |
165 | * writer (head + 1) to be the first descriptor in the array. (Only the first | |
166 | * descriptor in the array could have a valid sequence number of 0.) | |
167 | * | |
168 | * The first time a descriptor is reserved, it is assigned a sequence number | |
169 | * with the value of the array index. A "first time reserved" descriptor can | |
170 | * be recognized because it has a sequence number of 0 but does not have an | |
171 | * index of 0. (Only the first descriptor in the array could have a valid | |
172 | * sequence number of 0.) After the first reservation, all future reservations | |
173 | * (recycling) simply involve incrementing the sequence number by the array | |
174 | * count. | |
175 | * | |
176 | * Hack #1 | |
177 | * Only the first descriptor in the array is allowed to have the sequence | |
178 | * number 0. In this case it is not possible to recognize if it is being | |
179 | * reserved the first time (set to index value) or has been reserved | |
180 | * previously (increment by the array count). This is handled by _always_ | |
181 | * incrementing the sequence number by the array count when reserving the | |
182 | * first descriptor in the array. In order to satisfy Req3, the sequence | |
183 | * number of the first descriptor in the array is initialized to minus | |
184 | * the array count. Then, upon the first reservation, it is incremented | |
185 | * to 0, thus satisfying Req3. | |
186 | * | |
187 | * Hack #2 | |
188 | * prb_first_seq() can be called at any time by readers to retrieve the | |
189 | * sequence number of the tail descriptor. However, due to Req2 and Req3, | |
190 | * initially there are no records to report the sequence number of | |
191 | * (sequence numbers are u64 and there is nothing less than 0). To handle | |
192 | * this, the sequence number of the initial tail descriptor is initialized | |
193 | * to 0. Technically this is incorrect, because there is no record with | |
194 | * sequence number 0 (yet) and the tail descriptor is not the first | |
195 | * descriptor in the array. But it allows prb_read_valid() to correctly | |
196 | * report the existence of a record for _any_ given sequence number at all | |
197 | * times. Bootstrapping is complete when the tail is pushed the first | |
198 | * time, thus finally pointing to the first descriptor reserved by a | |
199 | * writer, which has the assigned sequence number 0. | |
200 | */ | |
201 | ||
202 | /* | |
203 | * Initiating Logical Value Overflows | |
204 | * | |
205 | * Both logical position (lpos) and ID values can be mapped to array indexes | |
206 | * but may experience overflows during the lifetime of the system. To ensure | |
207 | * that printk_ringbuffer can handle the overflows for these types, initial | |
208 | * values are chosen that map to the correct initial array indexes, but will | |
209 | * result in overflows soon. | |
210 | * | |
211 | * BLK0_LPOS | |
212 | * The initial @head_lpos and @tail_lpos for data rings. It is at index | |
213 | * 0 and the lpos value is such that it will overflow on the first wrap. | |
214 | * | |
215 | * DESC0_ID | |
216 | * The initial @head_id and @tail_id for the desc ring. It is at the last | |
217 | * index of the descriptor array (see Req3 above) and the ID value is such | |
218 | * that it will overflow on the second wrap. | |
219 | */ | |
220 | #define BLK0_LPOS(sz_bits) (-(_DATA_SIZE(sz_bits))) | |
221 | #define DESC0_ID(ct_bits) DESC_ID(-(_DESCS_COUNT(ct_bits) + 1)) | |
10dcb06d | 222 | #define DESC0_SV(ct_bits) DESC_SV(DESC0_ID(ct_bits), desc_reusable) |
b6cf8b3f JO |
223 | |
224 | /* | |
225 | * Define a ringbuffer with an external text data buffer. The same as | |
226 | * DEFINE_PRINTKRB() but requires specifying an external buffer for the | |
227 | * text data. | |
228 | * | |
229 | * Note: The specified external buffer must be of the size: | |
230 | * 2 ^ (descbits + avgtextbits) | |
231 | */ | |
f35efc78 | 232 | #define _DEFINE_PRINTKRB(name, descbits, avgtextbits, text_buf) \ |
b6cf8b3f | 233 | static struct prb_desc _##name##_descs[_DESCS_COUNT(descbits)] = { \ |
b6cf8b3f JO |
234 | /* the initial head and tail */ \ |
235 | [_DESCS_COUNT(descbits) - 1] = { \ | |
b6cf8b3f JO |
236 | /* reusable */ \ |
237 | .state_var = ATOMIC_INIT(DESC0_SV(descbits)), \ | |
238 | /* no associated data block */ \ | |
d397820f | 239 | .text_blk_lpos = FAILED_BLK_LPOS, \ |
b6cf8b3f JO |
240 | }, \ |
241 | }; \ | |
cfe2790b JO |
242 | static struct printk_info _##name##_infos[_DESCS_COUNT(descbits)] = { \ |
243 | /* this will be the first record reserved by a writer */ \ | |
244 | [0] = { \ | |
245 | /* will be incremented to 0 on the first reservation */ \ | |
246 | .seq = -(u64)_DESCS_COUNT(descbits), \ | |
247 | }, \ | |
248 | /* the initial head and tail */ \ | |
249 | [_DESCS_COUNT(descbits) - 1] = { \ | |
250 | /* reports the first seq value during the bootstrap phase */ \ | |
251 | .seq = 0, \ | |
252 | }, \ | |
253 | }; \ | |
b6cf8b3f JO |
254 | static struct printk_ringbuffer name = { \ |
255 | .desc_ring = { \ | |
256 | .count_bits = descbits, \ | |
257 | .descs = &_##name##_descs[0], \ | |
cfe2790b | 258 | .infos = &_##name##_infos[0], \ |
b6cf8b3f JO |
259 | .head_id = ATOMIC_INIT(DESC0_ID(descbits)), \ |
260 | .tail_id = ATOMIC_INIT(DESC0_ID(descbits)), \ | |
261 | }, \ | |
262 | .text_data_ring = { \ | |
263 | .size_bits = (avgtextbits) + (descbits), \ | |
264 | .data = text_buf, \ | |
265 | .head_lpos = ATOMIC_LONG_INIT(BLK0_LPOS((avgtextbits) + (descbits))), \ | |
266 | .tail_lpos = ATOMIC_LONG_INIT(BLK0_LPOS((avgtextbits) + (descbits))), \ | |
267 | }, \ | |
b6cf8b3f JO |
268 | .fail = ATOMIC_LONG_INIT(0), \ |
269 | } | |
270 | ||
271 | /** | |
272 | * DEFINE_PRINTKRB() - Define a ringbuffer. | |
273 | * | |
274 | * @name: The name of the ringbuffer variable. | |
275 | * @descbits: The number of descriptors as a power-of-2 value. | |
276 | * @avgtextbits: The average text data size per record as a power-of-2 value. | |
b6cf8b3f JO |
277 | * |
278 | * This is a macro for defining a ringbuffer and all internal structures | |
279 | * such that it is ready for immediate use. See _DEFINE_PRINTKRB() for a | |
280 | * variant where the text data buffer can be specified externally. | |
281 | */ | |
f35efc78 | 282 | #define DEFINE_PRINTKRB(name, descbits, avgtextbits) \ |
b6cf8b3f JO |
283 | static char _##name##_text[1U << ((avgtextbits) + (descbits))] \ |
284 | __aligned(__alignof__(unsigned long)); \ | |
f35efc78 | 285 | _DEFINE_PRINTKRB(name, descbits, avgtextbits, &_##name##_text[0]) |
b6cf8b3f JO |
286 | |
287 | /* Writer Interface */ | |
288 | ||
289 | /** | |
9bc284ca | 290 | * prb_rec_init_wr() - Initialize a buffer for writing records. |
b6cf8b3f JO |
291 | * |
292 | * @r: The record to initialize. | |
293 | * @text_buf_size: The needed text buffer size. | |
b6cf8b3f JO |
294 | */ |
295 | static inline void prb_rec_init_wr(struct printk_record *r, | |
f35efc78 | 296 | unsigned int text_buf_size) |
b6cf8b3f JO |
297 | { |
298 | r->info = NULL; | |
299 | r->text_buf = NULL; | |
b6cf8b3f | 300 | r->text_buf_size = text_buf_size; |
b6cf8b3f JO |
301 | } |
302 | ||
303 | bool prb_reserve(struct prb_reserved_entry *e, struct printk_ringbuffer *rb, | |
304 | struct printk_record *r); | |
4cfc7258 | 305 | bool prb_reserve_in_last(struct prb_reserved_entry *e, struct printk_ringbuffer *rb, |
59f8bcca | 306 | struct printk_record *r, u32 caller_id, unsigned int max_size); |
b6cf8b3f | 307 | void prb_commit(struct prb_reserved_entry *e); |
4cfc7258 | 308 | void prb_final_commit(struct prb_reserved_entry *e); |
b6cf8b3f JO |
309 | |
310 | void prb_init(struct printk_ringbuffer *rb, | |
311 | char *text_buf, unsigned int text_buf_size, | |
cfe2790b JO |
312 | struct prb_desc *descs, unsigned int descs_count_bits, |
313 | struct printk_info *infos); | |
b6cf8b3f JO |
314 | unsigned int prb_record_text_space(struct prb_reserved_entry *e); |
315 | ||
316 | /* Reader Interface */ | |
317 | ||
318 | /** | |
319 | * prb_rec_init_rd() - Initialize a buffer for reading records. | |
320 | * | |
321 | * @r: The record to initialize. | |
322 | * @info: A buffer to store record meta-data. | |
323 | * @text_buf: A buffer to store text data. | |
324 | * @text_buf_size: The size of @text_buf. | |
b6cf8b3f JO |
325 | * |
326 | * Initialize all the fields that a reader is interested in. All arguments | |
327 | * (except @r) are optional. Only record data for arguments that are | |
328 | * non-NULL or non-zero will be read. | |
329 | */ | |
330 | static inline void prb_rec_init_rd(struct printk_record *r, | |
331 | struct printk_info *info, | |
f35efc78 | 332 | char *text_buf, unsigned int text_buf_size) |
b6cf8b3f JO |
333 | { |
334 | r->info = info; | |
335 | r->text_buf = text_buf; | |
b6cf8b3f | 336 | r->text_buf_size = text_buf_size; |
b6cf8b3f JO |
337 | } |
338 | ||
339 | /** | |
340 | * prb_for_each_record() - Iterate over the records of a ringbuffer. | |
341 | * | |
342 | * @from: The sequence number to begin with. | |
343 | * @rb: The ringbuffer to iterate over. | |
344 | * @s: A u64 to store the sequence number on each iteration. | |
345 | * @r: A printk_record to store the record on each iteration. | |
346 | * | |
347 | * This is a macro for conveniently iterating over a ringbuffer. | |
348 | * Note that @s may not be the sequence number of the record on each | |
349 | * iteration. For the sequence number, @r->info->seq should be checked. | |
350 | * | |
351 | * Context: Any context. | |
352 | */ | |
353 | #define prb_for_each_record(from, rb, s, r) \ | |
354 | for ((s) = from; prb_read_valid(rb, s, r); (s) = (r)->info->seq + 1) | |
355 | ||
356 | /** | |
357 | * prb_for_each_info() - Iterate over the meta data of a ringbuffer. | |
358 | * | |
359 | * @from: The sequence number to begin with. | |
360 | * @rb: The ringbuffer to iterate over. | |
361 | * @s: A u64 to store the sequence number on each iteration. | |
362 | * @i: A printk_info to store the record meta data on each iteration. | |
363 | * @lc: An unsigned int to store the text line count of each record. | |
364 | * | |
365 | * This is a macro for conveniently iterating over a ringbuffer. | |
366 | * Note that @s may not be the sequence number of the record on each | |
367 | * iteration. For the sequence number, @r->info->seq should be checked. | |
368 | * | |
369 | * Context: Any context. | |
370 | */ | |
371 | #define prb_for_each_info(from, rb, s, i, lc) \ | |
372 | for ((s) = from; prb_read_valid_info(rb, s, i, lc); (s) = (i)->seq + 1) | |
373 | ||
374 | bool prb_read_valid(struct printk_ringbuffer *rb, u64 seq, | |
375 | struct printk_record *r); | |
376 | bool prb_read_valid_info(struct printk_ringbuffer *rb, u64 seq, | |
377 | struct printk_info *info, unsigned int *line_count); | |
378 | ||
379 | u64 prb_first_valid_seq(struct printk_ringbuffer *rb); | |
380 | u64 prb_next_seq(struct printk_ringbuffer *rb); | |
381 | ||
382 | #endif /* _KERNEL_PRINTK_RINGBUFFER_H */ |