1 #ifndef _LIB_RING_BUFFER_BACKEND_H
2 #define _LIB_RING_BUFFER_BACKEND_H
5 * lib/ringbuffer/backend.h
7 * Ring buffer backend (API).
9 * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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.
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.
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
25 * Credits to Steven Rostedt for proposing to use an extra-subbuffer owned by
26 * the reader in flight recorder mode.
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>
37 #include <linux/uaccess.h>
39 /* Internal helpers */
40 #include "../../wrapper/ringbuffer/backend_internal.h"
41 #include "../../wrapper/ringbuffer/frontend_internal.h"
43 /* Ring buffer backend API */
45 /* Ring buffer backend access (read/write) */
47 extern size_t lib_ring_buffer_read(struct lib_ring_buffer_backend *bufb,
48 size_t offset, void *dest, size_t len);
50 extern int __lib_ring_buffer_copy_to_user(struct lib_ring_buffer_backend *bufb,
51 size_t offset, void __user *dest,
54 extern int lib_ring_buffer_read_cstr(struct lib_ring_buffer_backend *bufb,
55 size_t offset, void *dest, size_t len);
58 lib_ring_buffer_read_get_page(struct lib_ring_buffer_backend *bufb, size_t offset,
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.
68 lib_ring_buffer_offset_address(struct lib_ring_buffer_backend *bufb,
71 lib_ring_buffer_read_offset_address(struct lib_ring_buffer_backend *bufb,
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
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.
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)
91 struct lib_ring_buffer_backend *bufb = &ctx->buf->backend;
92 struct channel_backend *chanb = &ctx->chan->backend;
94 size_t offset = ctx->buf_offset;
96 struct lib_ring_buffer_backend_pages *rpages;
97 unsigned long sb_bindex, id;
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),
117 _lib_ring_buffer_write(bufb, offset, src, len, 0);
118 ctx->buf_offset += len;
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
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
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)
139 struct lib_ring_buffer_backend *bufb = &ctx->buf->backend;
140 struct channel_backend *chanb = &ctx->chan->backend;
142 size_t offset = ctx->buf_offset;
144 struct lib_ring_buffer_backend_pages *rpages;
145 unsigned long sb_bindex, id;
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),
164 _lib_ring_buffer_memset(bufb, offset, c, len, 0);
165 ctx->buf_offset += len;
169 * lib_ring_buffer_copy_from_user_inatomic - write userspace data to a buffer backend
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
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
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.
182 void lib_ring_buffer_copy_from_user_inatomic(const struct lib_ring_buffer_config *config,
183 struct lib_ring_buffer_ctx *ctx,
184 const void __user *src, size_t len)
186 struct lib_ring_buffer_backend *bufb = &ctx->buf->backend;
187 struct channel_backend *chanb = &ctx->chan->backend;
189 size_t offset = ctx->buf_offset;
191 struct lib_ring_buffer_backend_pages *rpages;
192 unsigned long sb_bindex, id;
194 mm_segment_t old_fs = get_fs();
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));
211 if (unlikely(!access_ok(VERIFY_READ, src, len)))
214 if (likely(pagecpy == len)) {
215 ret = lib_ring_buffer_do_copy_from_user_inatomic(
216 rpages->p[index].virt + (offset & ~PAGE_MASK),
218 if (unlikely(ret > 0)) {
219 len -= (pagecpy - ret);
220 offset += (pagecpy - ret);
224 _lib_ring_buffer_copy_from_user_inatomic(bufb, offset, src, len, 0);
228 ctx->buf_offset += len;
236 * In the error path we call the slow path version to avoid
237 * the pollution of static inline code.
239 _lib_ring_buffer_memset(bufb, offset, 0, len, 0);
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
248 unsigned long lib_ring_buffer_get_records_unread(
249 const struct lib_ring_buffer_config *config,
250 struct lib_ring_buffer *buf)
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;
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);
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);
269 return records_unread;
272 #endif /* _LIB_RING_BUFFER_BACKEND_H */