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886d51a3 MD |
1 | #ifndef _LIB_RING_BUFFER_BACKEND_H |
2 | #define _LIB_RING_BUFFER_BACKEND_H | |
f3bc08c5 MD |
3 | |
4 | /* | |
886d51a3 | 5 | * lib/ringbuffer/backend.h |
f3bc08c5 MD |
6 | * |
7 | * Ring buffer backend (API). | |
8 | * | |
886d51a3 MD |
9 | * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
10 | * | |
11 | * This library is free software; you can redistribute it and/or | |
12 | * modify it under the terms of the GNU Lesser General Public | |
13 | * License as published by the Free Software Foundation; only | |
14 | * version 2.1 of the License. | |
15 | * | |
16 | * This library is distributed in the hope that it will be useful, | |
17 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
18 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
19 | * Lesser General Public License for more details. | |
20 | * | |
21 | * You should have received a copy of the GNU Lesser General Public | |
22 | * License along with this library; if not, write to the Free Software | |
23 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
f3bc08c5 MD |
24 | * |
25 | * Credits to Steven Rostedt for proposing to use an extra-subbuffer owned by | |
26 | * the reader in flight recorder mode. | |
27 | */ | |
28 | ||
29 | #include <linux/types.h> | |
30 | #include <linux/sched.h> | |
31 | #include <linux/timer.h> | |
32 | #include <linux/wait.h> | |
33 | #include <linux/poll.h> | |
34 | #include <linux/list.h> | |
35 | #include <linux/fs.h> | |
36 | #include <linux/mm.h> | |
7b8ea3a5 | 37 | #include <linux/uaccess.h> |
f3bc08c5 MD |
38 | |
39 | /* Internal helpers */ | |
40 | #include "../../wrapper/ringbuffer/backend_internal.h" | |
41 | #include "../../wrapper/ringbuffer/frontend_internal.h" | |
42 | ||
43 | /* Ring buffer backend API */ | |
44 | ||
45 | /* Ring buffer backend access (read/write) */ | |
46 | ||
47 | extern size_t lib_ring_buffer_read(struct lib_ring_buffer_backend *bufb, | |
48 | size_t offset, void *dest, size_t len); | |
49 | ||
50 | extern int __lib_ring_buffer_copy_to_user(struct lib_ring_buffer_backend *bufb, | |
51 | size_t offset, void __user *dest, | |
52 | size_t len); | |
53 | ||
54 | extern int lib_ring_buffer_read_cstr(struct lib_ring_buffer_backend *bufb, | |
55 | size_t offset, void *dest, size_t len); | |
56 | ||
57 | extern struct page ** | |
58 | lib_ring_buffer_read_get_page(struct lib_ring_buffer_backend *bufb, size_t offset, | |
59 | void ***virt); | |
60 | ||
61 | /* | |
62 | * Return the address where a given offset is located. | |
63 | * Should be used to get the current subbuffer header pointer. Given we know | |
64 | * it's never on a page boundary, it's safe to write directly to this address, | |
65 | * as long as the write is never bigger than a page size. | |
66 | */ | |
67 | extern void * | |
68 | lib_ring_buffer_offset_address(struct lib_ring_buffer_backend *bufb, | |
69 | size_t offset); | |
70 | extern void * | |
71 | lib_ring_buffer_read_offset_address(struct lib_ring_buffer_backend *bufb, | |
72 | size_t offset); | |
73 | ||
74 | /** | |
75 | * lib_ring_buffer_write - write data to a buffer backend | |
76 | * @config : ring buffer instance configuration | |
77 | * @ctx: ring buffer context. (input arguments only) | |
78 | * @src : source pointer to copy from | |
79 | * @len : length of data to copy | |
80 | * | |
81 | * This function copies "len" bytes of data from a source pointer to a buffer | |
82 | * backend, at the current context offset. This is more or less a buffer | |
83 | * backend-specific memcpy() operation. Calls the slow path (_ring_buffer_write) | |
84 | * if copy is crossing a page boundary. | |
85 | */ | |
86 | static inline | |
87 | void lib_ring_buffer_write(const struct lib_ring_buffer_config *config, | |
88 | struct lib_ring_buffer_ctx *ctx, | |
89 | const void *src, size_t len) | |
90 | { | |
91 | struct lib_ring_buffer_backend *bufb = &ctx->buf->backend; | |
92 | struct channel_backend *chanb = &ctx->chan->backend; | |
93 | size_t sbidx, index; | |
94 | size_t offset = ctx->buf_offset; | |
95 | ssize_t pagecpy; | |
96 | struct lib_ring_buffer_backend_pages *rpages; | |
97 | unsigned long sb_bindex, id; | |
98 | ||
61eb4c39 MD |
99 | if (unlikely(!len)) |
100 | return; | |
f3bc08c5 MD |
101 | offset &= chanb->buf_size - 1; |
102 | sbidx = offset >> chanb->subbuf_size_order; | |
103 | index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT; | |
104 | pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK); | |
105 | id = bufb->buf_wsb[sbidx].id; | |
106 | sb_bindex = subbuffer_id_get_index(config, id); | |
107 | rpages = bufb->array[sb_bindex]; | |
108 | CHAN_WARN_ON(ctx->chan, | |
109 | config->mode == RING_BUFFER_OVERWRITE | |
110 | && subbuffer_id_is_noref(config, id)); | |
111 | if (likely(pagecpy == len)) | |
112 | lib_ring_buffer_do_copy(config, | |
113 | rpages->p[index].virt | |
114 | + (offset & ~PAGE_MASK), | |
115 | src, len); | |
116 | else | |
117 | _lib_ring_buffer_write(bufb, offset, src, len, 0); | |
118 | ctx->buf_offset += len; | |
119 | } | |
120 | ||
4ea00e4f JD |
121 | /** |
122 | * lib_ring_buffer_memset - write len bytes of c to a buffer backend | |
123 | * @config : ring buffer instance configuration | |
124 | * @bufb : ring buffer backend | |
125 | * @offset : offset within the buffer | |
126 | * @c : the byte to copy | |
127 | * @len : number of bytes to copy | |
128 | * | |
129 | * This function writes "len" bytes of "c" to a buffer backend, at a specific | |
130 | * offset. This is more or less a buffer backend-specific memset() operation. | |
131 | * Calls the slow path (_ring_buffer_memset) if write is crossing a page | |
132 | * boundary. | |
133 | */ | |
134 | static inline | |
135 | void lib_ring_buffer_memset(const struct lib_ring_buffer_config *config, | |
136 | struct lib_ring_buffer_ctx *ctx, int c, size_t len) | |
137 | { | |
138 | ||
139 | struct lib_ring_buffer_backend *bufb = &ctx->buf->backend; | |
140 | struct channel_backend *chanb = &ctx->chan->backend; | |
141 | size_t sbidx, index; | |
142 | size_t offset = ctx->buf_offset; | |
143 | ssize_t pagecpy; | |
144 | struct lib_ring_buffer_backend_pages *rpages; | |
145 | unsigned long sb_bindex, id; | |
146 | ||
61eb4c39 MD |
147 | if (unlikely(!len)) |
148 | return; | |
4ea00e4f JD |
149 | offset &= chanb->buf_size - 1; |
150 | sbidx = offset >> chanb->subbuf_size_order; | |
151 | index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT; | |
152 | pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK); | |
153 | id = bufb->buf_wsb[sbidx].id; | |
154 | sb_bindex = subbuffer_id_get_index(config, id); | |
155 | rpages = bufb->array[sb_bindex]; | |
156 | CHAN_WARN_ON(ctx->chan, | |
157 | config->mode == RING_BUFFER_OVERWRITE | |
158 | && subbuffer_id_is_noref(config, id)); | |
159 | if (likely(pagecpy == len)) | |
160 | lib_ring_buffer_do_memset(rpages->p[index].virt | |
161 | + (offset & ~PAGE_MASK), | |
162 | c, len); | |
163 | else | |
164 | _lib_ring_buffer_memset(bufb, offset, c, len, 0); | |
165 | ctx->buf_offset += len; | |
166 | } | |
167 | ||
168 | /** | |
7b8ea3a5 | 169 | * lib_ring_buffer_copy_from_user_inatomic - write userspace data to a buffer backend |
4ea00e4f JD |
170 | * @config : ring buffer instance configuration |
171 | * @ctx: ring buffer context. (input arguments only) | |
172 | * @src : userspace source pointer to copy from | |
173 | * @len : length of data to copy | |
174 | * | |
175 | * This function copies "len" bytes of data from a userspace pointer to a | |
176 | * buffer backend, at the current context offset. This is more or less a buffer | |
177 | * backend-specific memcpy() operation. Calls the slow path | |
7b8ea3a5 MD |
178 | * (_ring_buffer_write_from_user_inatomic) if copy is crossing a page boundary. |
179 | * Disable the page fault handler to ensure we never try to take the mmap_sem. | |
4ea00e4f JD |
180 | */ |
181 | static inline | |
7b8ea3a5 | 182 | void lib_ring_buffer_copy_from_user_inatomic(const struct lib_ring_buffer_config *config, |
4ea00e4f JD |
183 | struct lib_ring_buffer_ctx *ctx, |
184 | const void __user *src, size_t len) | |
185 | { | |
186 | struct lib_ring_buffer_backend *bufb = &ctx->buf->backend; | |
187 | struct channel_backend *chanb = &ctx->chan->backend; | |
188 | size_t sbidx, index; | |
189 | size_t offset = ctx->buf_offset; | |
190 | ssize_t pagecpy; | |
191 | struct lib_ring_buffer_backend_pages *rpages; | |
192 | unsigned long sb_bindex, id; | |
193 | unsigned long ret; | |
7b8ea3a5 | 194 | mm_segment_t old_fs = get_fs(); |
4ea00e4f | 195 | |
61eb4c39 MD |
196 | if (unlikely(!len)) |
197 | return; | |
4ea00e4f JD |
198 | offset &= chanb->buf_size - 1; |
199 | sbidx = offset >> chanb->subbuf_size_order; | |
200 | index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT; | |
201 | pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK); | |
202 | id = bufb->buf_wsb[sbidx].id; | |
203 | sb_bindex = subbuffer_id_get_index(config, id); | |
204 | rpages = bufb->array[sb_bindex]; | |
205 | CHAN_WARN_ON(ctx->chan, | |
206 | config->mode == RING_BUFFER_OVERWRITE | |
207 | && subbuffer_id_is_noref(config, id)); | |
208 | ||
7b8ea3a5 MD |
209 | set_fs(KERNEL_DS); |
210 | pagefault_disable(); | |
4ea00e4f JD |
211 | if (unlikely(!access_ok(VERIFY_READ, src, len))) |
212 | goto fill_buffer; | |
213 | ||
214 | if (likely(pagecpy == len)) { | |
7b8ea3a5 | 215 | ret = lib_ring_buffer_do_copy_from_user_inatomic( |
4ea00e4f JD |
216 | rpages->p[index].virt + (offset & ~PAGE_MASK), |
217 | src, len); | |
218 | if (unlikely(ret > 0)) { | |
219 | len -= (pagecpy - ret); | |
220 | offset += (pagecpy - ret); | |
221 | goto fill_buffer; | |
222 | } | |
223 | } else { | |
7b8ea3a5 | 224 | _lib_ring_buffer_copy_from_user_inatomic(bufb, offset, src, len, 0); |
4ea00e4f | 225 | } |
7b8ea3a5 MD |
226 | pagefault_enable(); |
227 | set_fs(old_fs); | |
4ea00e4f JD |
228 | ctx->buf_offset += len; |
229 | ||
230 | return; | |
231 | ||
232 | fill_buffer: | |
7b8ea3a5 MD |
233 | pagefault_enable(); |
234 | set_fs(old_fs); | |
4ea00e4f JD |
235 | /* |
236 | * In the error path we call the slow path version to avoid | |
237 | * the pollution of static inline code. | |
238 | */ | |
239 | _lib_ring_buffer_memset(bufb, offset, 0, len, 0); | |
240 | } | |
241 | ||
f3bc08c5 MD |
242 | /* |
243 | * This accessor counts the number of unread records in a buffer. | |
244 | * It only provides a consistent value if no reads not writes are performed | |
245 | * concurrently. | |
246 | */ | |
247 | static inline | |
248 | unsigned long lib_ring_buffer_get_records_unread( | |
249 | const struct lib_ring_buffer_config *config, | |
250 | struct lib_ring_buffer *buf) | |
251 | { | |
252 | struct lib_ring_buffer_backend *bufb = &buf->backend; | |
253 | struct lib_ring_buffer_backend_pages *pages; | |
254 | unsigned long records_unread = 0, sb_bindex, id; | |
255 | unsigned int i; | |
256 | ||
257 | for (i = 0; i < bufb->chan->backend.num_subbuf; i++) { | |
258 | id = bufb->buf_wsb[i].id; | |
259 | sb_bindex = subbuffer_id_get_index(config, id); | |
260 | pages = bufb->array[sb_bindex]; | |
261 | records_unread += v_read(config, &pages->records_unread); | |
262 | } | |
263 | if (config->mode == RING_BUFFER_OVERWRITE) { | |
264 | id = bufb->buf_rsb.id; | |
265 | sb_bindex = subbuffer_id_get_index(config, id); | |
266 | pages = bufb->array[sb_bindex]; | |
267 | records_unread += v_read(config, &pages->records_unread); | |
268 | } | |
269 | return records_unread; | |
270 | } | |
271 | ||
886d51a3 | 272 | #endif /* _LIB_RING_BUFFER_BACKEND_H */ |