SAFE public projects git trees. - safe/jmp/linux-2.6/blob - arch/i386/lib/usercopy.c

   1 /*
   2  * User address space access functions.
   3  * The non inlined parts of asm-i386/uaccess.h are here.
   4  *
   5  * Copyright 1997 Andi Kleen <ak@muc.de>
   6  * Copyright 1997 Linus Torvalds
   7  */
   8 #include <linux/config.h>
   9 #include <linux/mm.h>
  10 #include <linux/highmem.h>
  11 #include <linux/blkdev.h>
  12 #include <linux/module.h>
  13 #include <asm/uaccess.h>
  14 #include <asm/mmx.h>
  15
  16 static inline int __movsl_is_ok(unsigned long a1, unsigned long a2, unsigned long n)
  17 {
  18 #ifdef CONFIG_X86_INTEL_USERCOPY
  19         if (n >= 64 && ((a1 ^ a2) & movsl_mask.mask))
  20                 return 0;
  21 #endif
  22         return 1;
  23 }
  24 #define movsl_is_ok(a1,a2,n) \
  25         __movsl_is_ok((unsigned long)(a1),(unsigned long)(a2),(n))
  26
  27 /*
  28  * Copy a null terminated string from userspace.
  29  */
  30
  31 #define __do_strncpy_from_user(dst,src,count,res)                          \
  32 do {                                                                       \
  33         int __d0, __d1, __d2;                                              \
  34         might_sleep();                                                     \
  35         __asm__ __volatile__(                                              \
  36                 "       testl %1,%1\n"                                     \
  37                 "       jz 2f\n"                                           \
  38                 "0:     lodsb\n"                                           \
  39                 "       stosb\n"                                           \
  40                 "       testb %%al,%%al\n"                                 \
  41                 "       jz 1f\n"                                           \
  42                 "       decl %1\n"                                         \
  43                 "       jnz 0b\n"                                          \
  44                 "1:     subl %1,%0\n"                                      \
  45                 "2:\n"                                                     \
  46                 ".section .fixup,\"ax\"\n"                                 \
  47                 "3:     movl %5,%0\n"                                      \
  48                 "       jmp 2b\n"                                          \
  49                 ".previous\n"                                              \
  50                 ".section __ex_table,\"a\"\n"                              \
  51                 "       .align 4\n"                                        \
  52                 "       .long 0b,3b\n"                                     \
  53                 ".previous"                                                \
  54                 : "=d"(res), "=c"(count), "=&a" (__d0), "=&S" (__d1),      \
  55                   "=&D" (__d2)                                             \
  56                 : "i"(-EFAULT), "0"(count), "1"(count), "3"(src), "4"(dst) \
  57                 : "memory");                                               \
  58 } while (0)
  59
  60 /**
  61  * __strncpy_from_user: - Copy a NUL terminated string from userspace, with less checking.
  62  * @dst:   Destination address, in kernel space.  This buffer must be at
  63  *         least @count bytes long.
  64  * @src:   Source address, in user space.
  65  * @count: Maximum number of bytes to copy, including the trailing NUL.
  66  *
  67  * Copies a NUL-terminated string from userspace to kernel space.
  68  * Caller must check the specified block with access_ok() before calling
  69  * this function.
  70  *
  71  * On success, returns the length of the string (not including the trailing
  72  * NUL).
  73  *
  74  * If access to userspace fails, returns -EFAULT (some data may have been
  75  * copied).
  76  *
  77  * If @count is smaller than the length of the string, copies @count bytes
  78  * and returns @count.
  79  */
  80 long
  81 __strncpy_from_user(char *dst, const char __user *src, long count)
  82 {
  83         long res;
  84         __do_strncpy_from_user(dst, src, count, res);
  85         return res;
  86 }
  87
  88 /**
  89  * strncpy_from_user: - Copy a NUL terminated string from userspace.
  90  * @dst:   Destination address, in kernel space.  This buffer must be at
  91  *         least @count bytes long.
  92  * @src:   Source address, in user space.
  93  * @count: Maximum number of bytes to copy, including the trailing NUL.
  94  *
  95  * Copies a NUL-terminated string from userspace to kernel space.
  96  *
  97  * On success, returns the length of the string (not including the trailing
  98  * NUL).
  99  *
 100  * If access to userspace fails, returns -EFAULT (some data may have been
 101  * copied).
 102  *
 103  * If @count is smaller than the length of the string, copies @count bytes
 104  * and returns @count.
 105  */
 106 long
 107 strncpy_from_user(char *dst, const char __user *src, long count)
 108 {
 109         long res = -EFAULT;
 110         if (access_ok(VERIFY_READ, src, 1))
 111                 __do_strncpy_from_user(dst, src, count, res);
 112         return res;
 113 }
 114
 115
 116 /*
 117  * Zero Userspace
 118  */
 119
 120 #define __do_clear_user(addr,size)                                      \
 121 do {                                                                    \
 122         int __d0;                                                       \
 123         might_sleep();                                                  \
 124         __asm__ __volatile__(                                           \
 125                 "0:     rep; stosl\n"                                   \
 126                 "       movl %2,%0\n"                                   \
 127                 "1:     rep; stosb\n"                                   \
 128                 "2:\n"                                                  \
 129                 ".section .fixup,\"ax\"\n"                              \
 130                 "3:     lea 0(%2,%0,4),%0\n"                            \
 131                 "       jmp 2b\n"                                       \
 132                 ".previous\n"                                           \
 133                 ".section __ex_table,\"a\"\n"                           \
 134                 "       .align 4\n"                                     \
 135                 "       .long 0b,3b\n"                                  \
 136                 "       .long 1b,2b\n"                                  \
 137                 ".previous"                                             \
 138                 : "=&c"(size), "=&D" (__d0)                             \
 139                 : "r"(size & 3), "0"(size / 4), "1"(addr), "a"(0));     \
 140 } while (0)
 141
 142 /**
 143  * clear_user: - Zero a block of memory in user space.
 144  * @to:   Destination address, in user space.
 145  * @n:    Number of bytes to zero.
 146  *
 147  * Zero a block of memory in user space.
 148  *
 149  * Returns number of bytes that could not be cleared.
 150  * On success, this will be zero.
 151  */
 152 unsigned long
 153 clear_user(void __user *to, unsigned long n)
 154 {
 155         might_sleep();
 156         if (access_ok(VERIFY_WRITE, to, n))
 157                 __do_clear_user(to, n);
 158         return n;
 159 }
 160
 161 /**
 162  * __clear_user: - Zero a block of memory in user space, with less checking.
 163  * @to:   Destination address, in user space.
 164  * @n:    Number of bytes to zero.
 165  *
 166  * Zero a block of memory in user space.  Caller must check
 167  * the specified block with access_ok() before calling this function.
 168  *
 169  * Returns number of bytes that could not be cleared.
 170  * On success, this will be zero.
 171  */
 172 unsigned long
 173 __clear_user(void __user *to, unsigned long n)
 174 {
 175         __do_clear_user(to, n);
 176         return n;
 177 }
 178
 179 /**
 180  * strlen_user: - Get the size of a string in user space.
 181  * @s: The string to measure.
 182  * @n: The maximum valid length
 183  *
 184  * Get the size of a NUL-terminated string in user space.
 185  *
 186  * Returns the size of the string INCLUDING the terminating NUL.
 187  * On exception, returns 0.
 188  * If the string is too long, returns a value greater than @n.
 189  */
 190 long strnlen_user(const char __user *s, long n)
 191 {
 192         unsigned long mask = -__addr_ok(s);
 193         unsigned long res, tmp;
 194
 195         might_sleep();
 196
 197         __asm__ __volatile__(
 198                 "       testl %0, %0\n"
 199                 "       jz 3f\n"
 200                 "       andl %0,%%ecx\n"
 201                 "0:     repne; scasb\n"
 202                 "       setne %%al\n"
 203                 "       subl %%ecx,%0\n"
 204                 "       addl %0,%%eax\n"
 205                 "1:\n"
 206                 ".section .fixup,\"ax\"\n"
 207                 "2:     xorl %%eax,%%eax\n"
 208                 "       jmp 1b\n"
 209                 "3:     movb $1,%%al\n"
 210                 "       jmp 1b\n"
 211                 ".previous\n"
 212                 ".section __ex_table,\"a\"\n"
 213                 "       .align 4\n"
 214                 "       .long 0b,2b\n"
 215                 ".previous"
 216                 :"=r" (n), "=D" (s), "=a" (res), "=c" (tmp)
 217                 :"0" (n), "1" (s), "2" (0), "3" (mask)
 218                 :"cc");
 219         return res & mask;
 220 }
 221
 222 #ifdef CONFIG_X86_INTEL_USERCOPY
 223 static unsigned long
 224 __copy_user_intel(void __user *to, const void *from, unsigned long size)
 225 {
 226         int d0, d1;
 227         __asm__ __volatile__(
 228                        "       .align 2,0x90\n"
 229                        "1:     movl 32(%4), %%eax\n"
 230                        "       cmpl $67, %0\n"
 231                        "       jbe 3f\n"
 232                        "2:     movl 64(%4), %%eax\n"
 233                        "       .align 2,0x90\n"
 234                        "3:     movl 0(%4), %%eax\n"
 235                        "4:     movl 4(%4), %%edx\n"
 236                        "5:     movl %%eax, 0(%3)\n"
 237                        "6:     movl %%edx, 4(%3)\n"
 238                        "7:     movl 8(%4), %%eax\n"
 239                        "8:     movl 12(%4),%%edx\n"
 240                        "9:     movl %%eax, 8(%3)\n"
 241                        "10:    movl %%edx, 12(%3)\n"
 242                        "11:    movl 16(%4), %%eax\n"
 243                        "12:    movl 20(%4), %%edx\n"
 244                        "13:    movl %%eax, 16(%3)\n"
 245                        "14:    movl %%edx, 20(%3)\n"
 246                        "15:    movl 24(%4), %%eax\n"
 247                        "16:    movl 28(%4), %%edx\n"
 248                        "17:    movl %%eax, 24(%3)\n"
 249                        "18:    movl %%edx, 28(%3)\n"
 250                        "19:    movl 32(%4), %%eax\n"
 251                        "20:    movl 36(%4), %%edx\n"
 252                        "21:    movl %%eax, 32(%3)\n"
 253                        "22:    movl %%edx, 36(%3)\n"
 254                        "23:    movl 40(%4), %%eax\n"
 255                        "24:    movl 44(%4), %%edx\n"
 256                        "25:    movl %%eax, 40(%3)\n"
 257                        "26:    movl %%edx, 44(%3)\n"
 258                        "27:    movl 48(%4), %%eax\n"
 259                        "28:    movl 52(%4), %%edx\n"
 260                        "29:    movl %%eax, 48(%3)\n"
 261                        "30:    movl %%edx, 52(%3)\n"
 262                        "31:    movl 56(%4), %%eax\n"
 263                        "32:    movl 60(%4), %%edx\n"
 264                        "33:    movl %%eax, 56(%3)\n"
 265                        "34:    movl %%edx, 60(%3)\n"
 266                        "       addl $-64, %0\n"
 267                        "       addl $64, %4\n"
 268                        "       addl $64, %3\n"
 269                        "       cmpl $63, %0\n"
 270                        "       ja  1b\n"
 271                        "35:    movl  %0, %%eax\n"
 272                        "       shrl  $2, %0\n"
 273                        "       andl  $3, %%eax\n"
 274                        "       cld\n"
 275                        "99:    rep; movsl\n"
 276                        "36:    movl %%eax, %0\n"
 277                        "37:    rep; movsb\n"
 278                        "100:\n"
 279                        ".section .fixup,\"ax\"\n"
 280                        "101:   lea 0(%%eax,%0,4),%0\n"
 281                        "       jmp 100b\n"
 282                        ".previous\n"
 283                        ".section __ex_table,\"a\"\n"
 284                        "       .align 4\n"
 285                        "       .long 1b,100b\n"
 286                        "       .long 2b,100b\n"
 287                        "       .long 3b,100b\n"
 288                        "       .long 4b,100b\n"
 289                        "       .long 5b,100b\n"
 290                        "       .long 6b,100b\n"
 291                        "       .long 7b,100b\n"
 292                        "       .long 8b,100b\n"
 293                        "       .long 9b,100b\n"
 294                        "       .long 10b,100b\n"
 295                        "       .long 11b,100b\n"
 296                        "       .long 12b,100b\n"
 297                        "       .long 13b,100b\n"
 298                        "       .long 14b,100b\n"
 299                        "       .long 15b,100b\n"
 300                        "       .long 16b,100b\n"
 301                        "       .long 17b,100b\n"
 302                        "       .long 18b,100b\n"
 303                        "       .long 19b,100b\n"
 304                        "       .long 20b,100b\n"
 305                        "       .long 21b,100b\n"
 306                        "       .long 22b,100b\n"
 307                        "       .long 23b,100b\n"
 308                        "       .long 24b,100b\n"
 309                        "       .long 25b,100b\n"
 310                        "       .long 26b,100b\n"
 311                        "       .long 27b,100b\n"
 312                        "       .long 28b,100b\n"
 313                        "       .long 29b,100b\n"
 314                        "       .long 30b,100b\n"
 315                        "       .long 31b,100b\n"
 316                        "       .long 32b,100b\n"
 317                        "       .long 33b,100b\n"
 318                        "       .long 34b,100b\n"
 319                        "       .long 35b,100b\n"
 320                        "       .long 36b,100b\n"
 321                        "       .long 37b,100b\n"
 322                        "       .long 99b,101b\n"
 323                        ".previous"
 324                        : "=&c"(size), "=&D" (d0), "=&S" (d1)
 325                        :  "1"(to), "2"(from), "0"(size)
 326                        : "eax", "edx", "memory");
 327         return size;
 328 }
 329
 330 static unsigned long
 331 __copy_user_zeroing_intel(void *to, const void __user *from, unsigned long size)
 332 {
 333         int d0, d1;
 334         __asm__ __volatile__(
 335                        "        .align 2,0x90\n"
 336                        "0:      movl 32(%4), %%eax\n"
 337                        "        cmpl $67, %0\n"
 338                        "        jbe 2f\n"
 339                        "1:      movl 64(%4), %%eax\n"
 340                        "        .align 2,0x90\n"
 341                        "2:      movl 0(%4), %%eax\n"
 342                        "21:     movl 4(%4), %%edx\n"
 343                        "        movl %%eax, 0(%3)\n"
 344                        "        movl %%edx, 4(%3)\n"
 345                        "3:      movl 8(%4), %%eax\n"
 346                        "31:     movl 12(%4),%%edx\n"
 347                        "        movl %%eax, 8(%3)\n"
 348                        "        movl %%edx, 12(%3)\n"
 349                        "4:      movl 16(%4), %%eax\n"
 350                        "41:     movl 20(%4), %%edx\n"
 351                        "        movl %%eax, 16(%3)\n"
 352                        "        movl %%edx, 20(%3)\n"
 353                        "10:     movl 24(%4), %%eax\n"
 354                        "51:     movl 28(%4), %%edx\n"
 355                        "        movl %%eax, 24(%3)\n"
 356                        "        movl %%edx, 28(%3)\n"
 357                        "11:     movl 32(%4), %%eax\n"
 358                        "61:     movl 36(%4), %%edx\n"
 359                        "        movl %%eax, 32(%3)\n"
 360                        "        movl %%edx, 36(%3)\n"
 361                        "12:     movl 40(%4), %%eax\n"
 362                        "71:     movl 44(%4), %%edx\n"
 363                        "        movl %%eax, 40(%3)\n"
 364                        "        movl %%edx, 44(%3)\n"
 365                        "13:     movl 48(%4), %%eax\n"
 366                        "81:     movl 52(%4), %%edx\n"
 367                        "        movl %%eax, 48(%3)\n"
 368                        "        movl %%edx, 52(%3)\n"
 369                        "14:     movl 56(%4), %%eax\n"
 370                        "91:     movl 60(%4), %%edx\n"
 371                        "        movl %%eax, 56(%3)\n"
 372                        "        movl %%edx, 60(%3)\n"
 373                        "        addl $-64, %0\n"
 374                        "        addl $64, %4\n"
 375                        "        addl $64, %3\n"
 376                        "        cmpl $63, %0\n"
 377                        "        ja  0b\n"
 378                        "5:      movl  %0, %%eax\n"
 379                        "        shrl  $2, %0\n"
 380                        "        andl $3, %%eax\n"
 381                        "        cld\n"
 382                        "6:      rep; movsl\n"
 383                        "        movl %%eax,%0\n"
 384                        "7:      rep; movsb\n"
 385                        "8:\n"
 386                        ".section .fixup,\"ax\"\n"
 387                        "9:      lea 0(%%eax,%0,4),%0\n"
 388                        "16:     pushl %0\n"
 389                        "        pushl %%eax\n"
 390                        "        xorl %%eax,%%eax\n"
 391                        "        rep; stosb\n"
 392                        "        popl %%eax\n"
 393                        "        popl %0\n"
 394                        "        jmp 8b\n"
 395                        ".previous\n"
 396                        ".section __ex_table,\"a\"\n"
 397                        "        .align 4\n"
 398                        "        .long 0b,16b\n"
 399                        "        .long 1b,16b\n"
 400                        "        .long 2b,16b\n"
 401                        "        .long 21b,16b\n"
 402                        "        .long 3b,16b\n"
 403                        "        .long 31b,16b\n"
 404                        "        .long 4b,16b\n"
 405                        "        .long 41b,16b\n"
 406                        "        .long 10b,16b\n"
 407                        "        .long 51b,16b\n"
 408                        "        .long 11b,16b\n"
 409                        "        .long 61b,16b\n"
 410                        "        .long 12b,16b\n"
 411                        "        .long 71b,16b\n"
 412                        "        .long 13b,16b\n"
 413                        "        .long 81b,16b\n"
 414                        "        .long 14b,16b\n"
 415                        "        .long 91b,16b\n"
 416                        "        .long 6b,9b\n"
 417                        "        .long 7b,16b\n"
 418                        ".previous"
 419                        : "=&c"(size), "=&D" (d0), "=&S" (d1)
 420                        :  "1"(to), "2"(from), "0"(size)
 421                        : "eax", "edx", "memory");
 422         return size;
 423 }
 424 #else
 425 /*
 426  * Leave these declared but undefined.  They should not be any references to
 427  * them
 428  */
 429 unsigned long
 430 __copy_user_zeroing_intel(void *to, const void __user *from, unsigned long size);
 431 unsigned long
 432 __copy_user_intel(void __user *to, const void *from, unsigned long size);
 433 #endif /* CONFIG_X86_INTEL_USERCOPY */
 434
 435 /* Generic arbitrary sized copy.  */
 436 #define __copy_user(to,from,size)                                       \
 437 do {                                                                    \
 438         int __d0, __d1, __d2;                                           \
 439         __asm__ __volatile__(                                           \
 440                 "       cmp  $7,%0\n"                                   \
 441                 "       jbe  1f\n"                                      \
 442                 "       movl %1,%0\n"                                   \
 443                 "       negl %0\n"                                      \
 444                 "       andl $7,%0\n"                                   \
 445                 "       subl %0,%3\n"                                   \
 446                 "4:     rep; movsb\n"                                   \
 447                 "       movl %3,%0\n"                                   \
 448                 "       shrl $2,%0\n"                                   \
 449                 "       andl $3,%3\n"                                   \
 450                 "       .align 2,0x90\n"                                \
 451                 "0:     rep; movsl\n"                                   \
 452                 "       movl %3,%0\n"                                   \
 453                 "1:     rep; movsb\n"                                   \
 454                 "2:\n"                                                  \
 455                 ".section .fixup,\"ax\"\n"                              \
 456                 "5:     addl %3,%0\n"                                   \
 457                 "       jmp 2b\n"                                       \
 458                 "3:     lea 0(%3,%0,4),%0\n"                            \
 459                 "       jmp 2b\n"                                       \
 460                 ".previous\n"                                           \
 461                 ".section __ex_table,\"a\"\n"                           \
 462                 "       .align 4\n"                                     \
 463                 "       .long 4b,5b\n"                                  \
 464                 "       .long 0b,3b\n"                                  \
 465                 "       .long 1b,2b\n"                                  \
 466                 ".previous"                                             \
 467                 : "=&c"(size), "=&D" (__d0), "=&S" (__d1), "=r"(__d2)   \
 468                 : "3"(size), "0"(size), "1"(to), "2"(from)              \
 469                 : "memory");                                            \
 470 } while (0)
 471
 472 #define __copy_user_zeroing(to,from,size)                               \
 473 do {                                                                    \
 474         int __d0, __d1, __d2;                                           \
 475         __asm__ __volatile__(                                           \
 476                 "       cmp  $7,%0\n"                                   \
 477                 "       jbe  1f\n"                                      \
 478                 "       movl %1,%0\n"                                   \
 479                 "       negl %0\n"                                      \
 480                 "       andl $7,%0\n"                                   \
 481                 "       subl %0,%3\n"                                   \
 482                 "4:     rep; movsb\n"                                   \
 483                 "       movl %3,%0\n"                                   \
 484                 "       shrl $2,%0\n"                                   \
 485                 "       andl $3,%3\n"                                   \
 486                 "       .align 2,0x90\n"                                \
 487                 "0:     rep; movsl\n"                                   \
 488                 "       movl %3,%0\n"                                   \
 489                 "1:     rep; movsb\n"                                   \
 490                 "2:\n"                                                  \
 491                 ".section .fixup,\"ax\"\n"                              \
 492                 "5:     addl %3,%0\n"                                   \
 493                 "       jmp 6f\n"                                       \
 494                 "3:     lea 0(%3,%0,4),%0\n"                            \
 495                 "6:     pushl %0\n"                                     \
 496                 "       pushl %%eax\n"                                  \
 497                 "       xorl %%eax,%%eax\n"                             \
 498                 "       rep; stosb\n"                                   \
 499                 "       popl %%eax\n"                                   \
 500                 "       popl %0\n"                                      \
 501                 "       jmp 2b\n"                                       \
 502                 ".previous\n"                                           \
 503                 ".section __ex_table,\"a\"\n"                           \
 504                 "       .align 4\n"                                     \
 505                 "       .long 4b,5b\n"                                  \
 506                 "       .long 0b,3b\n"                                  \
 507                 "       .long 1b,6b\n"                                  \
 508                 ".previous"                                             \
 509                 : "=&c"(size), "=&D" (__d0), "=&S" (__d1), "=r"(__d2)   \
 510                 : "3"(size), "0"(size), "1"(to), "2"(from)              \
 511                 : "memory");                                            \
 512 } while (0)
 513
 514
 515 unsigned long __copy_to_user_ll(void __user *to, const void *from, unsigned long n)
 516 {
 517         BUG_ON((long) n < 0);
 518 #ifndef CONFIG_X86_WP_WORKS_OK
 519         if (unlikely(boot_cpu_data.wp_works_ok == 0) &&
 520                         ((unsigned long )to) < TASK_SIZE) {
 521                 /*
 522                  * CPU does not honor the WP bit when writing
 523                  * from supervisory mode, and due to preemption or SMP,
 524                  * the page tables can change at any time.
 525                  * Do it manually.      Manfred <manfred@colorfullife.com>
 526                  */
 527                 while (n) {
 528                         unsigned long offset = ((unsigned long)to)%PAGE_SIZE;
 529                         unsigned long len = PAGE_SIZE - offset;
 530                         int retval;
 531                         struct page *pg;
 532                         void *maddr;
 533
 534                         if (len > n)
 535                                 len = n;
 536
 537 survive:
 538                         down_read(&current->mm->mmap_sem);
 539                         retval = get_user_pages(current, current->mm,
 540                                         (unsigned long )to, 1, 1, 0, &pg, NULL);
 541
 542                         if (retval == -ENOMEM && current->pid == 1) {
 543                                 up_read(&current->mm->mmap_sem);
 544                                 blk_congestion_wait(WRITE, HZ/50);
 545                                 goto survive;
 546                         }
 547
 548                         if (retval != 1) {
 549                                 up_read(&current->mm->mmap_sem);
 550                                 break;
 551                         }
 552
 553                         maddr = kmap_atomic(pg, KM_USER0);
 554                         memcpy(maddr + offset, from, len);
 555                         kunmap_atomic(maddr, KM_USER0);
 556                         set_page_dirty_lock(pg);
 557                         put_page(pg);
 558                         up_read(&current->mm->mmap_sem);
 559
 560                         from += len;
 561                         to += len;
 562                         n -= len;
 563                 }
 564                 return n;
 565         }
 566 #endif
 567         if (movsl_is_ok(to, from, n))
 568                 __copy_user(to, from, n);
 569         else
 570                 n = __copy_user_intel(to, from, n);
 571         return n;
 572 }
 573
 574 unsigned long
 575 __copy_from_user_ll(void *to, const void __user *from, unsigned long n)
 576 {
 577         BUG_ON((long)n < 0);
 578         if (movsl_is_ok(to, from, n))
 579                 __copy_user_zeroing(to, from, n);
 580         else
 581                 n = __copy_user_zeroing_intel(to, from, n);
 582         return n;
 583 }
 584
 585 /**
 586  * copy_to_user: - Copy a block of data into user space.
 587  * @to:   Destination address, in user space.
 588  * @from: Source address, in kernel space.
 589  * @n:    Number of bytes to copy.
 590  *
 591  * Context: User context only.  This function may sleep.
 592  *
 593  * Copy data from kernel space to user space.
 594  *
 595  * Returns number of bytes that could not be copied.
 596  * On success, this will be zero.
 597  */
 598 unsigned long
 599 copy_to_user(void __user *to, const void *from, unsigned long n)
 600 {
 601         might_sleep();
 602         BUG_ON((long) n < 0);
 603         if (access_ok(VERIFY_WRITE, to, n))
 604                 n = __copy_to_user(to, from, n);
 605         return n;
 606 }
 607 EXPORT_SYMBOL(copy_to_user);
 608
 609 /**
 610  * copy_from_user: - Copy a block of data from user space.
 611  * @to:   Destination address, in kernel space.
 612  * @from: Source address, in user space.
 613  * @n:    Number of bytes to copy.
 614  *
 615  * Context: User context only.  This function may sleep.
 616  *
 617  * Copy data from user space to kernel space.
 618  *
 619  * Returns number of bytes that could not be copied.
 620  * On success, this will be zero.
 621  *
 622  * If some data could not be copied, this function will pad the copied
 623  * data to the requested size using zero bytes.
 624  */
 625 unsigned long
 626 copy_from_user(void *to, const void __user *from, unsigned long n)
 627 {
 628         might_sleep();
 629         BUG_ON((long) n < 0);
 630         if (access_ok(VERIFY_READ, from, n))
 631                 n = __copy_from_user(to, from, n);
 632         else
 633                 memset(to, 0, n);
 634         return n;
 635 }
 636 EXPORT_SYMBOL(copy_from_user);