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, NULL, 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         _kfifo_init(fifo, NULL, 0);
 101 }
 102 EXPORT_SYMBOL(kfifo_free);
 103
 104 /**
 105  * kfifo_skip - skip output data
 106  * @fifo: the fifo to be used.
 107  * @len: number of bytes to skip
 108  */
 109 void kfifo_skip(struct kfifo *fifo, unsigned int len)
 110 {
 111         if (len < kfifo_len(fifo)) {
 112                 __kfifo_add_out(fifo, len);
 113                 return;
 114         }
 115         kfifo_reset_out(fifo);
 116 }
 117 EXPORT_SYMBOL(kfifo_skip);
 118
 119 static inline void __kfifo_in_data(struct kfifo *fifo,
 120                 const void *from, unsigned int len, unsigned int off)
 121 {
 122         unsigned int l;
 123
 124         /*
 125          * Ensure that we sample the fifo->out index -before- we
 126          * start putting bytes into the kfifo.
 127          */
 128
 129         smp_mb();
 130
 131         off = __kfifo_off(fifo, fifo->in + off);
 132
 133         /* first put the data starting from fifo->in to buffer end */
 134         l = min(len, fifo->size - off);
 135         memcpy(fifo->buffer + off, from, l);
 136
 137         /* then put the rest (if any) at the beginning of the buffer */
 138         memcpy(fifo->buffer, from + l, len - l);
 139 }
 140
 141 static inline void __kfifo_out_data(struct kfifo *fifo,
 142                 void *to, unsigned int len, unsigned int off)
 143 {
 144         unsigned int l;
 145
 146         /*
 147          * Ensure that we sample the fifo->in index -before- we
 148          * start removing bytes from the kfifo.
 149          */
 150
 151         smp_rmb();
 152
 153         off = __kfifo_off(fifo, fifo->out + off);
 154
 155         /* first get the data from fifo->out until the end of the buffer */
 156         l = min(len, fifo->size - off);
 157         memcpy(to, fifo->buffer + off, l);
 158
 159         /* then get the rest (if any) from the beginning of the buffer */
 160         memcpy(to + l, fifo->buffer, len - l);
 161 }
 162
 163 static inline int __kfifo_from_user_data(struct kfifo *fifo,
 164          const void __user *from, unsigned int len, unsigned int off,
 165          unsigned *lenout)
 166 {
 167         unsigned int l;
 168         int ret;
 169
 170         /*
 171          * Ensure that we sample the fifo->out index -before- we
 172          * start putting bytes into the kfifo.
 173          */
 174
 175         smp_mb();
 176
 177         off = __kfifo_off(fifo, fifo->in + off);
 178
 179         /* first put the data starting from fifo->in to buffer end */
 180         l = min(len, fifo->size - off);
 181         ret = copy_from_user(fifo->buffer + off, from, l);
 182         if (unlikely(ret)) {
 183                 *lenout = ret;
 184                 return -EFAULT;
 185         }
 186         *lenout = l;
 187
 188         /* then put the rest (if any) at the beginning of the buffer */
 189         ret = copy_from_user(fifo->buffer, from + l, len - l);
 190         *lenout += ret ? ret : len - l;
 191         return ret ? -EFAULT : 0;
 192 }
 193
 194 static inline int __kfifo_to_user_data(struct kfifo *fifo,
 195                 void __user *to, unsigned int len, unsigned int off, unsigned *lenout)
 196 {
 197         unsigned int l;
 198         int ret;
 199
 200         /*
 201          * Ensure that we sample the fifo->in index -before- we
 202          * start removing bytes from the kfifo.
 203          */
 204
 205         smp_rmb();
 206
 207         off = __kfifo_off(fifo, fifo->out + off);
 208
 209         /* first get the data from fifo->out until the end of the buffer */
 210         l = min(len, fifo->size - off);
 211         ret = copy_to_user(to, fifo->buffer + off, l);
 212         *lenout = l;
 213         if (unlikely(ret)) {
 214                 *lenout -= ret;
 215                 return -EFAULT;
 216         }
 217
 218         /* then get the rest (if any) from the beginning of the buffer */
 219         len -= l;
 220         ret = copy_to_user(to + l, fifo->buffer, len);
 221         if (unlikely(ret)) {
 222                 *lenout += len - ret;
 223                 return -EFAULT;
 224         }
 225         *lenout += len;
 226         return 0;
 227 }
 228
 229 unsigned int __kfifo_in_n(struct kfifo *fifo,
 230         const void *from, unsigned int len, unsigned int recsize)
 231 {
 232         if (kfifo_avail(fifo) < len + recsize)
 233                 return len + 1;
 234
 235         __kfifo_in_data(fifo, from, len, recsize);
 236         return 0;
 237 }
 238 EXPORT_SYMBOL(__kfifo_in_n);
 239
 240 /**
 241  * kfifo_in - puts some data into the FIFO
 242  * @fifo: the fifo to be used.
 243  * @from: the data to be added.
 244  * @len: the length of the data to be added.
 245  *
 246  * This function copies at most @len bytes from the @from buffer into
 247  * the FIFO depending on the free space, and returns the number of
 248  * bytes copied.
 249  *
 250  * Note that with only one concurrent reader and one concurrent
 251  * writer, you don't need extra locking to use these functions.
 252  */
 253 unsigned int kfifo_in(struct kfifo *fifo, const void *from,
 254                                 unsigned int len)
 255 {
 256         len = min(kfifo_avail(fifo), len);
 257
 258         __kfifo_in_data(fifo, from, len, 0);
 259         __kfifo_add_in(fifo, len);
 260         return len;
 261 }
 262 EXPORT_SYMBOL(kfifo_in);
 263
 264 unsigned int __kfifo_in_generic(struct kfifo *fifo,
 265         const void *from, unsigned int len, unsigned int recsize)
 266 {
 267         return __kfifo_in_rec(fifo, from, len, recsize);
 268 }
 269 EXPORT_SYMBOL(__kfifo_in_generic);
 270
 271 unsigned int __kfifo_out_n(struct kfifo *fifo,
 272         void *to, unsigned int len, unsigned int recsize)
 273 {
 274         if (kfifo_len(fifo) < len + recsize)
 275                 return len;
 276
 277         __kfifo_out_data(fifo, to, len, recsize);
 278         __kfifo_add_out(fifo, len + recsize);
 279         return 0;
 280 }
 281 EXPORT_SYMBOL(__kfifo_out_n);
 282
 283 /**
 284  * kfifo_out - gets some data from the FIFO
 285  * @fifo: the fifo to be used.
 286  * @to: where the data must be copied.
 287  * @len: the size of the destination buffer.
 288  *
 289  * This function copies at most @len bytes from the FIFO into the
 290  * @to buffer and returns the number of copied bytes.
 291  *
 292  * Note that with only one concurrent reader and one concurrent
 293  * writer, you don't need extra locking to use these functions.
 294  */
 295 unsigned int kfifo_out(struct kfifo *fifo, void *to, unsigned int len)
 296 {
 297         len = min(kfifo_len(fifo), len);
 298
 299         __kfifo_out_data(fifo, to, len, 0);
 300         __kfifo_add_out(fifo, len);
 301
 302         return len;
 303 }
 304 EXPORT_SYMBOL(kfifo_out);
 305
 306 /**
 307  * kfifo_out_peek - copy some data from the FIFO, but do not remove it
 308  * @fifo: the fifo to be used.
 309  * @to: where the data must be copied.
 310  * @len: the size of the destination buffer.
 311  * @offset: offset into the fifo
 312  *
 313  * This function copies at most @len bytes at @offset from the FIFO
 314  * into the @to buffer and returns the number of copied bytes.
 315  * The data is not removed from the FIFO.
 316  */
 317 unsigned int kfifo_out_peek(struct kfifo *fifo, void *to, unsigned int len,
 318                             unsigned offset)
 319 {
 320         len = min(kfifo_len(fifo), len + offset);
 321
 322         __kfifo_out_data(fifo, to, len, offset);
 323         return len;
 324 }
 325 EXPORT_SYMBOL(kfifo_out_peek);
 326
 327 unsigned int __kfifo_out_generic(struct kfifo *fifo,
 328         void *to, unsigned int len, unsigned int recsize,
 329         unsigned int *total)
 330 {
 331         return __kfifo_out_rec(fifo, to, len, recsize, total);
 332 }
 333 EXPORT_SYMBOL(__kfifo_out_generic);
 334
 335 unsigned int __kfifo_from_user_n(struct kfifo *fifo,
 336         const void __user *from, unsigned int len, unsigned int recsize)
 337 {
 338         unsigned total;
 339
 340         if (kfifo_avail(fifo) < len + recsize)
 341                 return len + 1;
 342
 343         __kfifo_from_user_data(fifo, from, len, recsize, &total);
 344         return total;
 345 }
 346 EXPORT_SYMBOL(__kfifo_from_user_n);
 347
 348 /**
 349  * kfifo_from_user - puts some data from user space into the FIFO
 350  * @fifo: the fifo to be used.
 351  * @from: pointer to the data to be added.
 352  * @len: the length of the data to be added.
 353  * @total: the actual returned data length.
 354  *
 355  * This function copies at most @len bytes from the @from into the
 356  * FIFO depending and returns -EFAULT/0.
 357  *
 358  * Note that with only one concurrent reader and one concurrent
 359  * writer, you don't need extra locking to use these functions.
 360  */
 361 int kfifo_from_user(struct kfifo *fifo,
 362         const void __user *from, unsigned int len, unsigned *total)
 363 {
 364         int ret;
 365         len = min(kfifo_avail(fifo), len);
 366         ret = __kfifo_from_user_data(fifo, from, len, 0, total);
 367         if (ret)
 368                 return ret;
 369         __kfifo_add_in(fifo, len);
 370         return 0;
 371 }
 372 EXPORT_SYMBOL(kfifo_from_user);
 373
 374 unsigned int __kfifo_from_user_generic(struct kfifo *fifo,
 375         const void __user *from, unsigned int len, unsigned int recsize)
 376 {
 377         return __kfifo_from_user_rec(fifo, from, len, recsize);
 378 }
 379 EXPORT_SYMBOL(__kfifo_from_user_generic);
 380
 381 unsigned int __kfifo_to_user_n(struct kfifo *fifo,
 382         void __user *to, unsigned int len, unsigned int reclen,
 383         unsigned int recsize)
 384 {
 385         unsigned int ret, total;
 386
 387         if (kfifo_len(fifo) < reclen + recsize)
 388                 return len;
 389
 390         ret = __kfifo_to_user_data(fifo, to, reclen, recsize, &total);
 391
 392         if (likely(ret == 0))
 393                 __kfifo_add_out(fifo, reclen + recsize);
 394
 395         return total;
 396 }
 397 EXPORT_SYMBOL(__kfifo_to_user_n);
 398
 399 /**
 400  * kfifo_to_user - gets data from the FIFO and write it to user space
 401  * @fifo: the fifo to be used.
 402  * @to: where the data must be copied.
 403  * @len: the size of the destination buffer.
 404  * @lenout: pointer to output variable with copied data
 405  *
 406  * This function copies at most @len bytes from the FIFO into the
 407  * @to buffer and 0 or -EFAULT.
 408  *
 409  * Note that with only one concurrent reader and one concurrent
 410  * writer, you don't need extra locking to use these functions.
 411  */
 412 int kfifo_to_user(struct kfifo *fifo,
 413         void __user *to, unsigned int len, unsigned *lenout)
 414 {
 415         int ret;
 416         len = min(kfifo_len(fifo), len);
 417         ret = __kfifo_to_user_data(fifo, to, len, 0, lenout);
 418         __kfifo_add_out(fifo, *lenout);
 419         return ret;
 420 }
 421 EXPORT_SYMBOL(kfifo_to_user);
 422
 423 unsigned int __kfifo_to_user_generic(struct kfifo *fifo,
 424         void __user *to, unsigned int len, unsigned int recsize,
 425         unsigned int *total)
 426 {
 427         return __kfifo_to_user_rec(fifo, to, len, recsize, total);
 428 }
 429 EXPORT_SYMBOL(__kfifo_to_user_generic);
 430
 431 unsigned int __kfifo_peek_generic(struct kfifo *fifo, unsigned int recsize)
 432 {
 433         if (recsize == 0)
 434                 return kfifo_avail(fifo);
 435
 436         return __kfifo_peek_n(fifo, recsize);
 437 }
 438 EXPORT_SYMBOL(__kfifo_peek_generic);
 439
 440 void __kfifo_skip_generic(struct kfifo *fifo, unsigned int recsize)
 441 {
 442         __kfifo_skip_rec(fifo, recsize);
 443 }
 444 EXPORT_SYMBOL(__kfifo_skip_generic);
 445