arch/mips/include/asm/uaccess.h

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 1996, 1997, 1998, 1999, 2000, 03, 04 by Ralf Baechle
   7  * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
   8  * Copyright (C) 2007  Maciej W. Rozycki
   9  * Copyright (C) 2014, Imagination Technologies Ltd.
  10  */
  11 #ifndef _ASM_UACCESS_H
  12 #define _ASM_UACCESS_H
  13
  14 #include <linux/kernel.h>
  15 #include <linux/string.h>
  16 #include <asm/asm-eva.h>
  17 #include <asm/extable.h>
  18
  19 #ifdef CONFIG_32BIT
  20
  21 #define __UA_LIMIT 0x80000000UL
  22
  23 #define __UA_ADDR       ".word"
  24 #define __UA_LA         "la"
  25 #define __UA_ADDU       "addu"
  26 #define __UA_t0         "$8"
  27 #define __UA_t1         "$9"
  28
  29 #endif /* CONFIG_32BIT */
  30
  31 #ifdef CONFIG_64BIT
  32
  33 extern u64 __ua_limit;
  34
  35 #define __UA_LIMIT      __ua_limit
  36
  37 #define __UA_ADDR       ".dword"
  38 #define __UA_LA         "dla"
  39 #define __UA_ADDU       "daddu"
  40 #define __UA_t0         "$12"
  41 #define __UA_t1         "$13"
  42
  43 #endif /* CONFIG_64BIT */
  44
  45 /*
  46  * Is a address valid? This does a straightforward calculation rather
  47  * than tests.
  48  *
  49  * Address valid if:
  50  *  - "addr" doesn't have any high-bits set
  51  *  - AND "size" doesn't have any high-bits set
  52  *  - AND "addr+size" doesn't have any high-bits set
  53  *  - OR we are in kernel mode.
  54  *
  55  * __ua_size() is a trick to avoid runtime checking of positive constant
  56  * sizes; for those we already know at compile time that the size is ok.
  57  */
  58 #define __ua_size(size)                                                 \
  59         ((__builtin_constant_p(size) && (signed long) (size) > 0) ? 0 : (size))
  60
  61 /*
  62  * access_ok: - Checks if a user space pointer is valid
  63  * @addr: User space pointer to start of block to check
  64  * @size: Size of block to check
  65  *
  66  * Context: User context only. This function may sleep if pagefaults are
  67  *          enabled.
  68  *
  69  * Checks if a pointer to a block of memory in user space is valid.
  70  *
  71  * Returns true (nonzero) if the memory block may be valid, false (zero)
  72  * if it is definitely invalid.
  73  *
  74  * Note that, depending on architecture, this function probably just
  75  * checks that the pointer is in the user space range - after calling
  76  * this function, memory access functions may still return -EFAULT.
  77  */
  78
  79 static inline int __access_ok(const void __user *p, unsigned long size)
  80 {
  81         unsigned long addr = (unsigned long)p;
  82         unsigned long end = addr + size - !!size;
  83
  84         return (__UA_LIMIT & (addr | end | __ua_size(size))) == 0;
  85 }
  86
  87 #define access_ok(addr, size)                                   \
  88         likely(__access_ok((addr), (size)))
  89
  90 /*
  91  * put_user: - Write a simple value into user space.
  92  * @x:   Value to copy to user space.
  93  * @ptr: Destination address, in user space.
  94  *
  95  * Context: User context only. This function may sleep if pagefaults are
  96  *          enabled.
  97  *
  98  * This macro copies a single simple value from kernel space to user
  99  * space.  It supports simple types like char and int, but not larger
 100  * data types like structures or arrays.
 101  *
 102  * @ptr must have pointer-to-simple-variable type, and @x must be assignable
 103  * to the result of dereferencing @ptr.
 104  *
 105  * Returns zero on success, or -EFAULT on error.
 106  */
 107 #define put_user(x, ptr)                                                \
 108 ({                                                                      \
 109         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 110                                                                         \
 111         might_fault();                                                  \
 112         access_ok(__p, sizeof(*__p)) ? __put_user((x), __p) : -EFAULT;  \
 113 })
 114
 115 /*
 116  * get_user: - Get a simple variable from user space.
 117  * @x:   Variable to store result.
 118  * @ptr: Source address, in user space.
 119  *
 120  * Context: User context only. This function may sleep if pagefaults are
 121  *          enabled.
 122  *
 123  * This macro copies a single simple variable from user space to kernel
 124  * space.  It supports simple types like char and int, but not larger
 125  * data types like structures or arrays.
 126  *
 127  * @ptr must have pointer-to-simple-variable type, and the result of
 128  * dereferencing @ptr must be assignable to @x without a cast.
 129  *
 130  * Returns zero on success, or -EFAULT on error.
 131  * On error, the variable @x is set to zero.
 132  */
 133 #define get_user(x, ptr)                                                \
 134 ({                                                                      \
 135         const __typeof__(*(ptr)) __user *__p = (ptr);                   \
 136                                                                         \
 137         might_fault();                                                  \
 138         access_ok(__p, sizeof(*__p)) ? __get_user((x), __p) :           \
 139                                        ((x) = 0, -EFAULT);              \
 140 })
 141
 142 /*
 143  * __put_user: - Write a simple value into user space, with less checking.
 144  * @x:   Value to copy to user space.
 145  * @ptr: Destination address, in user space.
 146  *
 147  * Context: User context only. This function may sleep if pagefaults are
 148  *          enabled.
 149  *
 150  * This macro copies a single simple value from kernel space to user
 151  * space.  It supports simple types like char and int, but not larger
 152  * data types like structures or arrays.
 153  *
 154  * @ptr must have pointer-to-simple-variable type, and @x must be assignable
 155  * to the result of dereferencing @ptr.
 156  *
 157  * Caller must check the pointer with access_ok() before calling this
 158  * function.
 159  *
 160  * Returns zero on success, or -EFAULT on error.
 161  */
 162 #define __put_user(x, ptr)                                              \
 163 ({                                                                      \
 164         __typeof__(*(ptr)) __user *__pu_ptr = (ptr);                    \
 165         __typeof__(*(ptr)) __pu_val = (x);                              \
 166         int __pu_err = 0;                                               \
 167                                                                         \
 168         __chk_user_ptr(__pu_ptr);                                       \
 169         switch (sizeof(*__pu_ptr)) {                                    \
 170         case 1:                                                         \
 171                 __put_data_asm(user_sb, __pu_ptr);                      \
 172                 break;                                                  \
 173         case 2:                                                         \
 174                 __put_data_asm(user_sh, __pu_ptr);                      \
 175                 break;                                                  \
 176         case 4:                                                         \
 177                 __put_data_asm(user_sw, __pu_ptr);                      \
 178                 break;                                                  \
 179         case 8:                                                         \
 180                 __PUT_DW(user_sd, __pu_ptr);                            \
 181                 break;                                                  \
 182         default:                                                        \
 183                 BUILD_BUG();                                            \
 184         }                                                               \
 185                                                                         \
 186         __pu_err;                                                       \
 187 })
 188
 189 /*
 190  * __get_user: - Get a simple variable from user space, with less checking.
 191  * @x:   Variable to store result.
 192  * @ptr: Source address, in user space.
 193  *
 194  * Context: User context only. This function may sleep if pagefaults are
 195  *          enabled.
 196  *
 197  * This macro copies a single simple variable from user space to kernel
 198  * space.  It supports simple types like char and int, but not larger
 199  * data types like structures or arrays.
 200  *
 201  * @ptr must have pointer-to-simple-variable type, and the result of
 202  * dereferencing @ptr must be assignable to @x without a cast.
 203  *
 204  * Caller must check the pointer with access_ok() before calling this
 205  * function.
 206  *
 207  * Returns zero on success, or -EFAULT on error.
 208  * On error, the variable @x is set to zero.
 209  */
 210 #define __get_user(x, ptr)                                              \
 211 ({                                                                      \
 212         const __typeof__(*(ptr)) __user *__gu_ptr = (ptr);              \
 213         int __gu_err = 0;                                               \
 214                                                                         \
 215         __chk_user_ptr(__gu_ptr);                                       \
 216         switch (sizeof(*__gu_ptr)) {                                    \
 217         case 1:                                                         \
 218                 __get_data_asm((x), user_lb, __gu_ptr);                 \
 219                 break;                                                  \
 220         case 2:                                                         \
 221                 __get_data_asm((x), user_lh, __gu_ptr);                 \
 222                 break;                                                  \
 223         case 4:                                                         \
 224                 __get_data_asm((x), user_lw, __gu_ptr);                 \
 225                 break;                                                  \
 226         case 8:                                                         \
 227                 __GET_DW((x), user_ld, __gu_ptr);                       \
 228                 break;                                                  \
 229         default:                                                        \
 230                 BUILD_BUG();                                            \
 231         }                                                               \
 232                                                                         \
 233         __gu_err;                                                       \
 234 })
 235
 236 struct __large_struct { unsigned long buf[100]; };
 237 #define __m(x) (*(struct __large_struct __user *)(x))
 238
 239 #ifdef CONFIG_32BIT
 240 #define __GET_DW(val, insn, ptr) __get_data_asm_ll32(val, insn, ptr)
 241 #endif
 242 #ifdef CONFIG_64BIT
 243 #define __GET_DW(val, insn, ptr) __get_data_asm(val, insn, ptr)
 244 #endif
 245
 246 #define __get_data_asm(val, insn, addr)                                 \
 247 {                                                                       \
 248         long __gu_tmp;                                                  \
 249                                                                         \
 250         __asm__ __volatile__(                                           \
 251         "1:     "insn("%1", "%3")"                              \n"     \
 252         "2:                                                     \n"     \
 253         "       .insn                                           \n"     \
 254         "       .section .fixup,\"ax\"                          \n"     \
 255         "3:     li      %0, %4                                  \n"     \
 256         "       move    %1, $0                                  \n"     \
 257         "       j       2b                                      \n"     \
 258         "       .previous                                       \n"     \
 259         "       .section __ex_table,\"a\"                       \n"     \
 260         "       "__UA_ADDR "\t1b, 3b                            \n"     \
 261         "       .previous                                       \n"     \
 262         : "=r" (__gu_err), "=r" (__gu_tmp)                              \
 263         : "0" (0), "o" (__m(addr)), "i" (-EFAULT));                     \
 264                                                                         \
 265         (val) = (__typeof__(*(addr))) __gu_tmp;                         \
 266 }
 267
 268 /*
 269  * Get a long long 64 using 32 bit registers.
 270  */
 271 #define __get_data_asm_ll32(val, insn, addr)                            \
 272 {                                                                       \
 273         union {                                                         \
 274                 unsigned long long      l;                              \
 275                 __typeof__(*(addr))     t;                              \
 276         } __gu_tmp;                                                     \
 277                                                                         \
 278         __asm__ __volatile__(                                           \
 279         "1:     " insn("%1", "(%3)")"                           \n"     \
 280         "2:     " insn("%D1", "4(%3)")"                         \n"     \
 281         "3:                                                     \n"     \
 282         "       .insn                                           \n"     \
 283         "       .section        .fixup,\"ax\"                   \n"     \
 284         "4:     li      %0, %4                                  \n"     \
 285         "       move    %1, $0                                  \n"     \
 286         "       move    %D1, $0                                 \n"     \
 287         "       j       3b                                      \n"     \
 288         "       .previous                                       \n"     \
 289         "       .section        __ex_table,\"a\"                \n"     \
 290         "       " __UA_ADDR "   1b, 4b                          \n"     \
 291         "       " __UA_ADDR "   2b, 4b                          \n"     \
 292         "       .previous                                       \n"     \
 293         : "=r" (__gu_err), "=&r" (__gu_tmp.l)                           \
 294         : "0" (0), "r" (addr), "i" (-EFAULT));                          \
 295                                                                         \
 296         (val) = __gu_tmp.t;                                             \
 297 }
 298
 299 #define HAVE_GET_KERNEL_NOFAULT
 300
 301 #define __get_kernel_nofault(dst, src, type, err_label)                 \
 302 do {                                                                    \
 303         int __gu_err;                                                   \
 304                                                                         \
 305         switch (sizeof(type)) {                                         \
 306         case 1:                                                         \
 307                 __get_data_asm(*(type *)(dst), kernel_lb,               \
 308                                (__force type *)(src));                  \
 309                 break;                                                  \
 310         case 2:                                                         \
 311                 __get_data_asm(*(type *)(dst), kernel_lh,               \
 312                                (__force type *)(src));                  \
 313                 break;                                                  \
 314         case 4:                                                         \
 315                  __get_data_asm(*(type *)(dst), kernel_lw,              \
 316                                (__force type *)(src));                  \
 317                 break;                                                  \
 318         case 8:                                                         \
 319                 __GET_DW(*(type *)(dst), kernel_ld,                     \
 320                          (__force type *)(src));                        \
 321                 break;                                                  \
 322         default:                                                        \
 323                 BUILD_BUG();                                            \
 324                 break;                                                  \
 325         }                                                               \
 326         if (unlikely(__gu_err))                                         \
 327                 goto err_label;                                         \
 328 } while (0)
 329
 330 /*
 331  * Yuck.  We need two variants, one for 64bit operation and one
 332  * for 32 bit mode and old iron.
 333  */
 334 #ifdef CONFIG_32BIT
 335 #define __PUT_DW(insn, ptr) __put_data_asm_ll32(insn, ptr)
 336 #endif
 337 #ifdef CONFIG_64BIT
 338 #define __PUT_DW(insn, ptr) __put_data_asm(insn, ptr)
 339 #endif
 340
 341 #define __put_data_asm(insn, ptr)                                       \
 342 {                                                                       \
 343         __asm__ __volatile__(                                           \
 344         "1:     "insn("%z2", "%3")"     # __put_data_asm        \n"     \
 345         "2:                                                     \n"     \
 346         "       .insn                                           \n"     \
 347         "       .section        .fixup,\"ax\"                   \n"     \
 348         "3:     li      %0, %4                                  \n"     \
 349         "       j       2b                                      \n"     \
 350         "       .previous                                       \n"     \
 351         "       .section        __ex_table,\"a\"                \n"     \
 352         "       " __UA_ADDR "   1b, 3b                          \n"     \
 353         "       .previous                                       \n"     \
 354         : "=r" (__pu_err)                                               \
 355         : "0" (0), "Jr" (__pu_val), "o" (__m(ptr)),                     \
 356           "i" (-EFAULT));                                               \
 357 }
 358
 359 #define __put_data_asm_ll32(insn, ptr)                                  \
 360 {                                                                       \
 361         __asm__ __volatile__(                                           \
 362         "1:     "insn("%2", "(%3)")"    # __put_data_asm_ll32   \n"     \
 363         "2:     "insn("%D2", "4(%3)")"                          \n"     \
 364         "3:                                                     \n"     \
 365         "       .insn                                           \n"     \
 366         "       .section        .fixup,\"ax\"                   \n"     \
 367         "4:     li      %0, %4                                  \n"     \
 368         "       j       3b                                      \n"     \
 369         "       .previous                                       \n"     \
 370         "       .section        __ex_table,\"a\"                \n"     \
 371         "       " __UA_ADDR "   1b, 4b                          \n"     \
 372         "       " __UA_ADDR "   2b, 4b                          \n"     \
 373         "       .previous"                                              \
 374         : "=r" (__pu_err)                                               \
 375         : "0" (0), "r" (__pu_val), "r" (ptr),                           \
 376           "i" (-EFAULT));                                               \
 377 }
 378
 379 #define __put_kernel_nofault(dst, src, type, err_label)                 \
 380 do {                                                                    \
 381         type __pu_val;                                  \
 382         int __pu_err = 0;                                               \
 383                                                                         \
 384         __pu_val = *(__force type *)(src);                              \
 385         switch (sizeof(type)) {                                         \
 386         case 1:                                                         \
 387                 __put_data_asm(kernel_sb, (type *)(dst));               \
 388                 break;                                                  \
 389         case 2:                                                         \
 390                 __put_data_asm(kernel_sh, (type *)(dst));               \
 391                 break;                                                  \
 392         case 4:                                                         \
 393                 __put_data_asm(kernel_sw, (type *)(dst))                \
 394                 break;                                                  \
 395         case 8:                                                         \
 396                 __PUT_DW(kernel_sd, (type *)(dst));                     \
 397                 break;                                                  \
 398         default:                                                        \
 399                 BUILD_BUG();                                            \
 400                 break;                                                  \
 401         }                                                               \
 402         if (unlikely(__pu_err))                                         \
 403                 goto err_label;                                         \
 404 } while (0)
 405
 406
 407 /*
 408  * We're generating jump to subroutines which will be outside the range of
 409  * jump instructions
 410  */
 411 #ifdef MODULE
 412 #define __MODULE_JAL(destination)                                       \
 413         ".set\tnoat\n\t"                                                \
 414         __UA_LA "\t$1, " #destination "\n\t"                            \
 415         "jalr\t$1\n\t"                                                  \
 416         ".set\tat\n\t"
 417 #else
 418 #define __MODULE_JAL(destination)                                       \
 419         "jal\t" #destination "\n\t"
 420 #endif
 421
 422 #if defined(CONFIG_CPU_DADDI_WORKAROUNDS) || (defined(CONFIG_EVA) &&    \
 423                                               defined(CONFIG_CPU_HAS_PREFETCH))
 424 #define DADDI_SCRATCH "$3"
 425 #else
 426 #define DADDI_SCRATCH "$0"
 427 #endif
 428
 429 extern size_t __raw_copy_from_user(void *__to, const void *__from, size_t __n);
 430 extern size_t __raw_copy_to_user(void *__to, const void *__from, size_t __n);
 431 extern size_t __raw_copy_in_user(void *__to, const void *__from, size_t __n);
 432
 433 static inline unsigned long
 434 raw_copy_from_user(void *to, const void __user *from, unsigned long n)
 435 {
 436         register void *__cu_to_r __asm__("$4");
 437         register const void __user *__cu_from_r __asm__("$5");
 438         register long __cu_len_r __asm__("$6");
 439
 440         __cu_to_r = to;
 441         __cu_from_r = from;
 442         __cu_len_r = n;
 443
 444         __asm__ __volatile__(
 445                 ".set\tnoreorder\n\t"
 446                 __MODULE_JAL(__raw_copy_from_user)
 447                 ".set\tnoat\n\t"
 448                 __UA_ADDU "\t$1, %1, %2\n\t"
 449                 ".set\tat\n\t"
 450                 ".set\treorder"
 451                 : "+r" (__cu_to_r), "+r" (__cu_from_r), "+r" (__cu_len_r)
 452                 :
 453                 : "$8", "$9", "$10", "$11", "$12", "$14", "$15", "$24", "$31",
 454                   DADDI_SCRATCH, "memory");
 455
 456         return __cu_len_r;
 457 }
 458
 459 static inline unsigned long
 460 raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 461 {
 462         register void __user *__cu_to_r __asm__("$4");
 463         register const void *__cu_from_r __asm__("$5");
 464         register long __cu_len_r __asm__("$6");
 465
 466         __cu_to_r = (to);
 467         __cu_from_r = (from);
 468         __cu_len_r = (n);
 469
 470         __asm__ __volatile__(
 471                 __MODULE_JAL(__raw_copy_to_user)
 472                 : "+r" (__cu_to_r), "+r" (__cu_from_r), "+r" (__cu_len_r)
 473                 :
 474                 : "$8", "$9", "$10", "$11", "$12", "$14", "$15", "$24", "$31",
 475                   DADDI_SCRATCH, "memory");
 476
 477         return __cu_len_r;
 478 }
 479
 480 #define INLINE_COPY_FROM_USER
 481 #define INLINE_COPY_TO_USER
 482
 483 static inline unsigned long
 484 raw_copy_in_user(void __user *to, const void __user *from, unsigned long n)
 485 {
 486         register void __user *__cu_to_r __asm__("$4");
 487         register const void __user *__cu_from_r __asm__("$5");
 488         register long __cu_len_r __asm__("$6");
 489
 490         __cu_to_r = to;
 491         __cu_from_r = from;
 492         __cu_len_r = n;
 493
 494         __asm__ __volatile__(
 495                 ".set\tnoreorder\n\t"
 496                 __MODULE_JAL(__raw_copy_in_user)
 497                 ".set\tnoat\n\t"
 498                 __UA_ADDU "\t$1, %1, %2\n\t"
 499                 ".set\tat\n\t"
 500                 ".set\treorder"
 501                 : "+r" (__cu_to_r), "+r" (__cu_from_r), "+r" (__cu_len_r)
 502                 :
 503                 : "$8", "$9", "$10", "$11", "$12", "$14", "$15", "$24", "$31",
 504                   DADDI_SCRATCH, "memory");
 505         return __cu_len_r;
 506 }
 507
 508 extern __kernel_size_t __bzero(void __user *addr, __kernel_size_t size);
 509
 510 /*
 511  * __clear_user: - Zero a block of memory in user space, with less checking.
 512  * @to:   Destination address, in user space.
 513  * @n:    Number of bytes to zero.
 514  *
 515  * Zero a block of memory in user space.  Caller must check
 516  * the specified block with access_ok() before calling this function.
 517  *
 518  * Returns number of bytes that could not be cleared.
 519  * On success, this will be zero.
 520  */
 521 static inline __kernel_size_t
 522 __clear_user(void __user *addr, __kernel_size_t size)
 523 {
 524         __kernel_size_t res;
 525
 526 #ifdef CONFIG_CPU_MICROMIPS
 527 /* micromips memset / bzero also clobbers t7 & t8 */
 528 #define bzero_clobbers "$4", "$5", "$6", __UA_t0, __UA_t1, "$15", "$24", "$31"
 529 #else
 530 #define bzero_clobbers "$4", "$5", "$6", __UA_t0, __UA_t1, "$31"
 531 #endif /* CONFIG_CPU_MICROMIPS */
 532
 533         might_fault();
 534         __asm__ __volatile__(
 535                 "move\t$4, %1\n\t"
 536                 "move\t$5, $0\n\t"
 537                 "move\t$6, %2\n\t"
 538                 __MODULE_JAL(__bzero)
 539                 "move\t%0, $6"
 540                 : "=r" (res)
 541                 : "r" (addr), "r" (size)
 542                 : bzero_clobbers);
 543
 544         return res;
 545 }
 546
 547 #define clear_user(addr,n)                                              \
 548 ({                                                                      \
 549         void __user * __cl_addr = (addr);                               \
 550         unsigned long __cl_size = (n);                                  \
 551         if (__cl_size && access_ok(__cl_addr, __cl_size))               \
 552                 __cl_size = __clear_user(__cl_addr, __cl_size);         \
 553         __cl_size;                                                      \
 554 })
 555
 556 extern long __strncpy_from_user_asm(char *__to, const char __user *__from, long __len);
 557
 558 /*
 559  * strncpy_from_user: - Copy a NUL terminated string from userspace.
 560  * @dst:   Destination address, in kernel space.  This buffer must be at
 561  *         least @count bytes long.
 562  * @src:   Source address, in user space.
 563  * @count: Maximum number of bytes to copy, including the trailing NUL.
 564  *
 565  * Copies a NUL-terminated string from userspace to kernel space.
 566  *
 567  * On success, returns the length of the string (not including the trailing
 568  * NUL).
 569  *
 570  * If access to userspace fails, returns -EFAULT (some data may have been
 571  * copied).
 572  *
 573  * If @count is smaller than the length of the string, copies @count bytes
 574  * and returns @count.
 575  */
 576 static inline long
 577 strncpy_from_user(char *__to, const char __user *__from, long __len)
 578 {
 579         long res;
 580
 581         if (!access_ok(__from, __len))
 582                 return -EFAULT;
 583
 584         might_fault();
 585         __asm__ __volatile__(
 586                 "move\t$4, %1\n\t"
 587                 "move\t$5, %2\n\t"
 588                 "move\t$6, %3\n\t"
 589                 __MODULE_JAL(__strncpy_from_user_asm)
 590                 "move\t%0, $2"
 591                 : "=r" (res)
 592                 : "r" (__to), "r" (__from), "r" (__len)
 593                 : "$2", "$3", "$4", "$5", "$6", __UA_t0, "$31", "memory");
 594
 595         return res;
 596 }
 597
 598 extern long __strnlen_user_asm(const char __user *s, long n);
 599
 600 /*
 601  * strnlen_user: - Get the size of a string in user space.
 602  * @str: The string to measure.
 603  *
 604  * Context: User context only. This function may sleep if pagefaults are
 605  *          enabled.
 606  *
 607  * Get the size of a NUL-terminated string in user space.
 608  *
 609  * Returns the size of the string INCLUDING the terminating NUL.
 610  * On exception, returns 0.
 611  * If the string is too long, returns a value greater than @n.
 612  */
 613 static inline long strnlen_user(const char __user *s, long n)
 614 {
 615         long res;
 616
 617         if (!access_ok(s, 1))
 618                 return 0;
 619
 620         might_fault();
 621         __asm__ __volatile__(
 622                 "move\t$4, %1\n\t"
 623                 "move\t$5, %2\n\t"
 624                 __MODULE_JAL(__strnlen_user_asm)
 625                 "move\t%0, $2"
 626                 : "=r" (res)
 627                 : "r" (s), "r" (n)
 628                 : "$2", "$4", "$5", __UA_t0, "$31");
 629
 630         return res;
 631 }
 632
 633 #endif /* _ASM_UACCESS_H */