| 1 | #ifndef _LIB_RING_BUFFER_BACKEND_H |
| 2 | #define _LIB_RING_BUFFER_BACKEND_H |
| 3 | |
| 4 | /* |
| 5 | * lib/ringbuffer/backend.h |
| 6 | * |
| 7 | * Ring buffer backend (API). |
| 8 | * |
| 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 |
| 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> |
| 37 | #include <linux/uaccess.h> |
| 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 | |
| 99 | offset &= chanb->buf_size - 1; |
| 100 | sbidx = offset >> chanb->subbuf_size_order; |
| 101 | index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT; |
| 102 | pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK); |
| 103 | id = bufb->buf_wsb[sbidx].id; |
| 104 | sb_bindex = subbuffer_id_get_index(config, id); |
| 105 | rpages = bufb->array[sb_bindex]; |
| 106 | CHAN_WARN_ON(ctx->chan, |
| 107 | config->mode == RING_BUFFER_OVERWRITE |
| 108 | && subbuffer_id_is_noref(config, id)); |
| 109 | if (likely(pagecpy == len)) |
| 110 | lib_ring_buffer_do_copy(config, |
| 111 | rpages->p[index].virt |
| 112 | + (offset & ~PAGE_MASK), |
| 113 | src, len); |
| 114 | else |
| 115 | _lib_ring_buffer_write(bufb, offset, src, len, 0); |
| 116 | ctx->buf_offset += len; |
| 117 | } |
| 118 | |
| 119 | /** |
| 120 | * lib_ring_buffer_memset - write len bytes of c to a buffer backend |
| 121 | * @config : ring buffer instance configuration |
| 122 | * @bufb : ring buffer backend |
| 123 | * @offset : offset within the buffer |
| 124 | * @c : the byte to copy |
| 125 | * @len : number of bytes to copy |
| 126 | * |
| 127 | * This function writes "len" bytes of "c" to a buffer backend, at a specific |
| 128 | * offset. This is more or less a buffer backend-specific memset() operation. |
| 129 | * Calls the slow path (_ring_buffer_memset) if write is crossing a page |
| 130 | * boundary. |
| 131 | */ |
| 132 | static inline |
| 133 | void lib_ring_buffer_memset(const struct lib_ring_buffer_config *config, |
| 134 | struct lib_ring_buffer_ctx *ctx, int c, size_t len) |
| 135 | { |
| 136 | |
| 137 | struct lib_ring_buffer_backend *bufb = &ctx->buf->backend; |
| 138 | struct channel_backend *chanb = &ctx->chan->backend; |
| 139 | size_t sbidx, index; |
| 140 | size_t offset = ctx->buf_offset; |
| 141 | ssize_t pagecpy; |
| 142 | struct lib_ring_buffer_backend_pages *rpages; |
| 143 | unsigned long sb_bindex, id; |
| 144 | |
| 145 | offset &= chanb->buf_size - 1; |
| 146 | sbidx = offset >> chanb->subbuf_size_order; |
| 147 | index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT; |
| 148 | pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK); |
| 149 | id = bufb->buf_wsb[sbidx].id; |
| 150 | sb_bindex = subbuffer_id_get_index(config, id); |
| 151 | rpages = bufb->array[sb_bindex]; |
| 152 | CHAN_WARN_ON(ctx->chan, |
| 153 | config->mode == RING_BUFFER_OVERWRITE |
| 154 | && subbuffer_id_is_noref(config, id)); |
| 155 | if (likely(pagecpy == len)) |
| 156 | lib_ring_buffer_do_memset(rpages->p[index].virt |
| 157 | + (offset & ~PAGE_MASK), |
| 158 | c, len); |
| 159 | else |
| 160 | _lib_ring_buffer_memset(bufb, offset, c, len, 0); |
| 161 | ctx->buf_offset += len; |
| 162 | } |
| 163 | |
| 164 | /** |
| 165 | * lib_ring_buffer_copy_from_user_inatomic - write userspace data to a buffer backend |
| 166 | * @config : ring buffer instance configuration |
| 167 | * @ctx: ring buffer context. (input arguments only) |
| 168 | * @src : userspace source pointer to copy from |
| 169 | * @len : length of data to copy |
| 170 | * |
| 171 | * This function copies "len" bytes of data from a userspace pointer to a |
| 172 | * buffer backend, at the current context offset. This is more or less a buffer |
| 173 | * backend-specific memcpy() operation. Calls the slow path |
| 174 | * (_ring_buffer_write_from_user_inatomic) if copy is crossing a page boundary. |
| 175 | * Disable the page fault handler to ensure we never try to take the mmap_sem. |
| 176 | */ |
| 177 | static inline |
| 178 | void lib_ring_buffer_copy_from_user_inatomic(const struct lib_ring_buffer_config *config, |
| 179 | struct lib_ring_buffer_ctx *ctx, |
| 180 | const void __user *src, size_t len) |
| 181 | { |
| 182 | struct lib_ring_buffer_backend *bufb = &ctx->buf->backend; |
| 183 | struct channel_backend *chanb = &ctx->chan->backend; |
| 184 | size_t sbidx, index; |
| 185 | size_t offset = ctx->buf_offset; |
| 186 | ssize_t pagecpy; |
| 187 | struct lib_ring_buffer_backend_pages *rpages; |
| 188 | unsigned long sb_bindex, id; |
| 189 | unsigned long ret; |
| 190 | mm_segment_t old_fs = get_fs(); |
| 191 | |
| 192 | offset &= chanb->buf_size - 1; |
| 193 | sbidx = offset >> chanb->subbuf_size_order; |
| 194 | index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT; |
| 195 | pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK); |
| 196 | id = bufb->buf_wsb[sbidx].id; |
| 197 | sb_bindex = subbuffer_id_get_index(config, id); |
| 198 | rpages = bufb->array[sb_bindex]; |
| 199 | CHAN_WARN_ON(ctx->chan, |
| 200 | config->mode == RING_BUFFER_OVERWRITE |
| 201 | && subbuffer_id_is_noref(config, id)); |
| 202 | |
| 203 | set_fs(KERNEL_DS); |
| 204 | pagefault_disable(); |
| 205 | if (unlikely(!access_ok(VERIFY_READ, src, len))) |
| 206 | goto fill_buffer; |
| 207 | |
| 208 | if (likely(pagecpy == len)) { |
| 209 | ret = lib_ring_buffer_do_copy_from_user_inatomic( |
| 210 | rpages->p[index].virt + (offset & ~PAGE_MASK), |
| 211 | src, len); |
| 212 | if (unlikely(ret > 0)) { |
| 213 | len -= (pagecpy - ret); |
| 214 | offset += (pagecpy - ret); |
| 215 | goto fill_buffer; |
| 216 | } |
| 217 | } else { |
| 218 | _lib_ring_buffer_copy_from_user_inatomic(bufb, offset, src, len, 0); |
| 219 | } |
| 220 | pagefault_enable(); |
| 221 | set_fs(old_fs); |
| 222 | ctx->buf_offset += len; |
| 223 | |
| 224 | return; |
| 225 | |
| 226 | fill_buffer: |
| 227 | pagefault_enable(); |
| 228 | set_fs(old_fs); |
| 229 | /* |
| 230 | * In the error path we call the slow path version to avoid |
| 231 | * the pollution of static inline code. |
| 232 | */ |
| 233 | _lib_ring_buffer_memset(bufb, offset, 0, len, 0); |
| 234 | } |
| 235 | |
| 236 | /* |
| 237 | * This accessor counts the number of unread records in a buffer. |
| 238 | * It only provides a consistent value if no reads not writes are performed |
| 239 | * concurrently. |
| 240 | */ |
| 241 | static inline |
| 242 | unsigned long lib_ring_buffer_get_records_unread( |
| 243 | const struct lib_ring_buffer_config *config, |
| 244 | struct lib_ring_buffer *buf) |
| 245 | { |
| 246 | struct lib_ring_buffer_backend *bufb = &buf->backend; |
| 247 | struct lib_ring_buffer_backend_pages *pages; |
| 248 | unsigned long records_unread = 0, sb_bindex, id; |
| 249 | unsigned int i; |
| 250 | |
| 251 | for (i = 0; i < bufb->chan->backend.num_subbuf; i++) { |
| 252 | id = bufb->buf_wsb[i].id; |
| 253 | sb_bindex = subbuffer_id_get_index(config, id); |
| 254 | pages = bufb->array[sb_bindex]; |
| 255 | records_unread += v_read(config, &pages->records_unread); |
| 256 | } |
| 257 | if (config->mode == RING_BUFFER_OVERWRITE) { |
| 258 | id = bufb->buf_rsb.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 | return records_unread; |
| 264 | } |
| 265 | |
| 266 | ssize_t lib_ring_buffer_file_splice_read(struct file *in, loff_t *ppos, |
| 267 | struct pipe_inode_info *pipe, |
| 268 | size_t len, unsigned int flags); |
| 269 | loff_t lib_ring_buffer_no_llseek(struct file *file, loff_t offset, int origin); |
| 270 | |
| 271 | #endif /* _LIB_RING_BUFFER_BACKEND_H */ |