kernel/kfifo.c

   1 /*
   2  * A generic kernel FIFO implementation.
   3  *
   4  * Copyright (C) 2009 Stefani Seibold <stefani@seibold.net>
   5  * Copyright (C) 2004 Stelian Pop <stelian@popies.net>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  *
  21  */
  22
  23 #include <linux/kernel.h>
  24 #include <linux/module.h>
  25 #include <linux/slab.h>
  26 #include <linux/err.h>
  27 #include <linux/kfifo.h>
  28 #include <linux/log2.h>
  29 #include <linux/uaccess.h>
  30
  31 static void _kfifo_init(struct kfifo *fifo, void *buffer,
  32                 unsigned int size)
  33 {
  34         fifo->buffer = buffer;
  35         fifo->size = size;
  36
  37         kfifo_reset(fifo);
  38 }
  39
  40 /**
  41  * kfifo_init - initialize a FIFO using a preallocated buffer
  42  * @fifo: the fifo to assign the buffer
  43  * @buffer: the preallocated buffer to be used.
  44  * @size: the size of the internal buffer, this has to be a power of 2.
  45  *
  46  */
  47 void kfifo_init(struct kfifo *fifo, void *buffer, unsigned int size)
  48 {
  49         /* size must be a power of 2 */
  50         BUG_ON(!is_power_of_2(size));
  51
  52         _kfifo_init(fifo, buffer, size);
  53 }
  54 EXPORT_SYMBOL(kfifo_init);
  55
  56 /**
  57  * kfifo_alloc - allocates a new FIFO internal buffer
  58  * @fifo: the fifo to assign then new buffer
  59  * @size: the size of the buffer to be allocated, this have to be a power of 2.
  60  * @gfp_mask: get_free_pages mask, passed to kmalloc()
  61  *
  62  * This function dynamically allocates a new fifo internal buffer
  63  *
  64  * The size will be rounded-up to a power of 2.
  65  * The buffer will be release with kfifo_free().
  66  * Return 0 if no error, otherwise the an error code
  67  */
  68 int kfifo_alloc(struct kfifo *fifo, unsigned int size, gfp_t gfp_mask)
  69 {
  70         unsigned char *buffer;
  71
  72         /*
  73          * round up to the next power of 2, since our 'let the indices
  74          * wrap' technique works only in this case.
  75          */
  76         if (!is_power_of_2(size)) {
  77                 BUG_ON(size > 0x80000000);
  78                 size = roundup_pow_of_two(size);
  79         }
  80
  81         buffer = kmalloc(size, gfp_mask);
  82         if (!buffer) {
  83                 _kfifo_init(fifo, 0, 0);
  84                 return -ENOMEM;
  85         }
  86
  87         _kfifo_init(fifo, buffer, size);
  88
  89         return 0;
  90 }
  91 EXPORT_SYMBOL(kfifo_alloc);
  92
  93 /**
  94  * kfifo_free - frees the FIFO internal buffer
  95  * @fifo: the fifo to be freed.
  96  */
  97 void kfifo_free(struct kfifo *fifo)
  98 {
  99         kfree(fifo->buffer);
 100 }
 101 EXPORT_SYMBOL(kfifo_free);
 102
 103 /**
 104  * kfifo_skip - skip output data
 105  * @fifo: the fifo to be used.
 106  * @len: number of bytes to skip
 107  */
 108 void kfifo_skip(struct kfifo *fifo, unsigned int len)
 109 {
 110         if (len < kfifo_len(fifo)) {
 111                 __kfifo_add_out(fifo, len);
 112                 return;
 113         }
 114         kfifo_reset_out(fifo);
 115 }
 116 EXPORT_SYMBOL(kfifo_skip);
 117
 118 static inline void __kfifo_in_data(struct kfifo *fifo,
 119                 const void *from, unsigned int len, unsigned int off)
 120 {
 121         unsigned int l;
 122
 123         /*
 124          * Ensure that we sample the fifo->out index -before- we
 125          * start putting bytes into the kfifo.
 126          */
 127
 128         smp_mb();
 129
 130         off = __kfifo_off(fifo, fifo->in + off);
 131
 132         /* first put the data starting from fifo->in to buffer end */
 133         l = min(len, fifo->size - off);
 134         memcpy(fifo->buffer + off, from, l);
 135
 136         /* then put the rest (if any) at the beginning of the buffer */
 137         memcpy(fifo->buffer, from + l, len - l);
 138 }
 139
 140 static inline void __kfifo_out_data(struct kfifo *fifo,
 141                 void *to, unsigned int len, unsigned int off)
 142 {
 143         unsigned int l;
 144
 145         /*
 146          * Ensure that we sample the fifo->in index -before- we
 147          * start removing bytes from the kfifo.
 148          */
 149
 150         smp_rmb();
 151
 152         off = __kfifo_off(fifo, fifo->out + off);
 153
 154         /* first get the data from fifo->out until the end of the buffer */
 155         l = min(len, fifo->size - off);
 156         memcpy(to, fifo->buffer + off, l);
 157
 158         /* then get the rest (if any) from the beginning of the buffer */
 159         memcpy(to + l, fifo->buffer, len - l);
 160 }
 161
 162 static inline int __kfifo_from_user_data(struct kfifo *fifo,
 163          const void __user *from, unsigned int len, unsigned int off,
 164          unsigned *lenout)
 165 {
 166         unsigned int l;
 167         int ret;
 168
 169         /*
 170          * Ensure that we sample the fifo->out index -before- we
 171          * start putting bytes into the kfifo.
 172          */
 173
 174         smp_mb();
 175
 176         off = __kfifo_off(fifo, fifo->in + off);
 177
 178         /* first put the data starting from fifo->in to buffer end */
 179         l = min(len, fifo->size - off);
 180         ret = copy_from_user(fifo->buffer + off, from, l);
 181         if (unlikely(ret)) {
 182                 *lenout = ret;
 183                 return -EFAULT;
 184         }
 185         *lenout = l;
 186
 187         /* then put the rest (if any) at the beginning of the buffer */
 188         ret = copy_from_user(fifo->buffer, from + l, len - l);
 189         *lenout += ret ? ret : len - l;
 190         return ret ? -EFAULT : 0;
 191 }
 192
 193 static inline int __kfifo_to_user_data(struct kfifo *fifo,
 194                 void __user *to, unsigned int len, unsigned int off, unsigned *lenout)
 195 {
 196         unsigned int l;
 197         int ret;
 198
 199         /*
 200          * Ensure that we sample the fifo->in index -before- we
 201          * start removing bytes from the kfifo.
 202          */
 203
 204         smp_rmb();
 205
 206         off = __kfifo_off(fifo, fifo->out + off);
 207
 208         /* first get the data from fifo->out until the end of the buffer */
 209         l = min(len, fifo->size - off);
 210         ret = copy_to_user(to, fifo->buffer + off, l);
 211         *lenout = l;
 212         if (unlikely(ret)) {
 213                 *lenout -= ret;
 214                 return -EFAULT;
 215         }
 216
 217         /* then get the rest (if any) from the beginning of the buffer */
 218         len -= l;
 219         ret = copy_to_user(to + l, fifo->buffer, len);
 220         if (unlikely(ret)) {
 221                 *lenout += len - ret;
 222                 return -EFAULT;
 223         }
 224         *lenout += len;
 225         return 0;
 226 }
 227
 228 unsigned int __kfifo_in_n(struct kfifo *fifo,
 229         const void *from, unsigned int len, unsigned int recsize)
 230 {
 231         if (kfifo_avail(fifo) < len + recsize)
 232                 return len + 1;
 233
 234         __kfifo_in_data(fifo, from, len, recsize);
 235         return 0;
 236 }
 237 EXPORT_SYMBOL(__kfifo_in_n);
 238
 239 /**
 240  * kfifo_in - puts some data into the FIFO
 241  * @fifo: the fifo to be used.
 242  * @from: the data to be added.
 243  * @len: the length of the data to be added.
 244  *
 245  * This function copies at most @len bytes from the @from buffer into
 246  * the FIFO depending on the free space, and returns the number of
 247  * bytes copied.
 248  *
 249  * Note that with only one concurrent reader and one concurrent
 250  * writer, you don't need extra locking to use these functions.
 251  */
 252 unsigned int kfifo_in(struct kfifo *fifo, const void *from,
 253                                 unsigned int len)
 254 {
 255         len = min(kfifo_avail(fifo), len);
 256
 257         __kfifo_in_data(fifo, from, len, 0);
 258         __kfifo_add_in(fifo, len);
 259         return len;
 260 }
 261 EXPORT_SYMBOL(kfifo_in);
 262
 263 unsigned int __kfifo_in_generic(struct kfifo *fifo,
 264         const void *from, unsigned int len, unsigned int recsize)
 265 {
 266         return __kfifo_in_rec(fifo, from, len, recsize);
 267 }
 268 EXPORT_SYMBOL(__kfifo_in_generic);
 269
 270 unsigned int __kfifo_out_n(struct kfifo *fifo,
 271         void *to, unsigned int len, unsigned int recsize)
 272 {
 273         if (kfifo_len(fifo) < len + recsize)
 274                 return len;
 275
 276         __kfifo_out_data(fifo, to, len, recsize);
 277         __kfifo_add_out(fifo, len + recsize);
 278         return 0;
 279 }
 280 EXPORT_SYMBOL(__kfifo_out_n);
 281
 282 /**
 283  * kfifo_out - gets some data from the FIFO
 284  * @fifo: the fifo to be used.
 285  * @to: where the data must be copied.
 286  * @len: the size of the destination buffer.
 287  *
 288  * This function copies at most @len bytes from the FIFO into the
 289  * @to buffer and returns the number of copied bytes.
 290  *
 291  * Note that with only one concurrent reader and one concurrent
 292  * writer, you don't need extra locking to use these functions.
 293  */
 294 unsigned int kfifo_out(struct kfifo *fifo, void *to, unsigned int len)
 295 {
 296         len = min(kfifo_len(fifo), len);
 297
 298         __kfifo_out_data(fifo, to, len, 0);
 299         __kfifo_add_out(fifo, len);
 300
 301         return len;
 302 }
 303 EXPORT_SYMBOL(kfifo_out);
 304
 305 /**
 306  * kfifo_out_peek - copy some data from the FIFO, but do not remove it
 307  * @fifo: the fifo to be used.
 308  * @to: where the data must be copied.
 309  * @len: the size of the destination buffer.
 310  * @offset: offset into the fifo
 311  *
 312  * This function copies at most @len bytes at @offset from the FIFO
 313  * into the @to buffer and returns the number of copied bytes.
 314  * The data is not removed from the FIFO.
 315  */
 316 unsigned int kfifo_out_peek(struct kfifo *fifo, void *to, unsigned int len,
 317                             unsigned offset)
 318 {
 319         len = min(kfifo_len(fifo), len + offset);
 320
 321         __kfifo_out_data(fifo, to, len, offset);
 322         return len;
 323 }
 324 EXPORT_SYMBOL(kfifo_out_peek);
 325
 326 unsigned int __kfifo_out_generic(struct kfifo *fifo,
 327         void *to, unsigned int len, unsigned int recsize,
 328         unsigned int *total)
 329 {
 330         return __kfifo_out_rec(fifo, to, len, recsize, total);
 331 }
 332 EXPORT_SYMBOL(__kfifo_out_generic);
 333
 334 unsigned int __kfifo_from_user_n(struct kfifo *fifo,
 335         const void __user *from, unsigned int len, unsigned int recsize)
 336 {
 337         unsigned total;
 338
 339         if (kfifo_avail(fifo) < len + recsize)
 340                 return len + 1;
 341
 342         __kfifo_from_user_data(fifo, from, len, recsize, &total);
 343         return total;
 344 }
 345 EXPORT_SYMBOL(__kfifo_from_user_n);
 346
 347 /**
 348  * kfifo_from_user - puts some data from user space into the FIFO
 349  * @fifo: the fifo to be used.
 350  * @from: pointer to the data to be added.
 351  * @len: the length of the data to be added.
 352  *
 353  * This function copies at most @len bytes from the @from into the
 354  * FIFO depending and returns -EFAULT/0.
 355  *
 356  * Note that with only one concurrent reader and one concurrent
 357  * writer, you don't need extra locking to use these functions.
 358  */
 359 int kfifo_from_user(struct kfifo *fifo,
 360         const void __user *from, unsigned int len, unsigned *total)
 361 {
 362         int ret;
 363         len = min(kfifo_avail(fifo), len);
 364         ret = __kfifo_from_user_data(fifo, from, len, 0, total);
 365         if (ret)
 366                 return ret;
 367         __kfifo_add_in(fifo, len);
 368         return 0;
 369 }
 370 EXPORT_SYMBOL(kfifo_from_user);
 371
 372 unsigned int __kfifo_from_user_generic(struct kfifo *fifo,
 373         const void __user *from, unsigned int len, unsigned int recsize)
 374 {
 375         return __kfifo_from_user_rec(fifo, from, len, recsize);
 376 }
 377 EXPORT_SYMBOL(__kfifo_from_user_generic);
 378
 379 unsigned int __kfifo_to_user_n(struct kfifo *fifo,
 380         void __user *to, unsigned int len, unsigned int reclen,
 381         unsigned int recsize)
 382 {
 383         unsigned int ret, total;
 384
 385         if (kfifo_len(fifo) < reclen + recsize)
 386                 return len;
 387
 388         ret = __kfifo_to_user_data(fifo, to, reclen, recsize, &total);
 389
 390         if (likely(ret == 0))
 391                 __kfifo_add_out(fifo, reclen + recsize);
 392
 393         return total;
 394 }
 395 EXPORT_SYMBOL(__kfifo_to_user_n);
 396
 397 /**
 398  * kfifo_to_user - gets data from the FIFO and write it to user space
 399  * @fifo: the fifo to be used.
 400  * @to: where the data must be copied.
 401  * @len: the size of the destination buffer.
 402  @ @lenout: pointer to output variable with copied data
 403  *
 404  * This function copies at most @len bytes from the FIFO into the
 405  * @to buffer and 0 or -EFAULT.
 406  *
 407  * Note that with only one concurrent reader and one concurrent
 408  * writer, you don't need extra locking to use these functions.
 409  */
 410 int kfifo_to_user(struct kfifo *fifo,
 411         void __user *to, unsigned int len, unsigned *lenout)
 412 {
 413         int ret;
 414         len = min(kfifo_len(fifo), len);
 415         ret = __kfifo_to_user_data(fifo, to, len, 0, lenout);
 416         __kfifo_add_out(fifo, *lenout);
 417         return ret;
 418 }
 419 EXPORT_SYMBOL(kfifo_to_user);
 420
 421 unsigned int __kfifo_to_user_generic(struct kfifo *fifo,
 422         void __user *to, unsigned int len, unsigned int recsize,
 423         unsigned int *total)
 424 {
 425         return __kfifo_to_user_rec(fifo, to, len, recsize, total);
 426 }
 427 EXPORT_SYMBOL(__kfifo_to_user_generic);
 428
 429 unsigned int __kfifo_peek_generic(struct kfifo *fifo, unsigned int recsize)
 430 {
 431         if (recsize == 0)
 432                 return kfifo_avail(fifo);
 433
 434         return __kfifo_peek_n(fifo, recsize);
 435 }
 436 EXPORT_SYMBOL(__kfifo_peek_generic);
 437
 438 void __kfifo_skip_generic(struct kfifo *fifo, unsigned int recsize)
 439 {
 440         __kfifo_skip_rec(fifo, recsize);
 441 }
 442 EXPORT_SYMBOL(__kfifo_skip_generic);
 443