arch/arm/include/asm/uaccess.h

   1 /*
   2  *  arch/arm/include/asm/uaccess.h
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8 #ifndef _ASMARM_UACCESS_H
   9 #define _ASMARM_UACCESS_H
  10
  11 /*
  12  * User space memory access functions
  13  */
  14 #include <linux/string.h>
  15 #include <asm/memory.h>
  16 #include <asm/domain.h>
  17 #include <asm/unified.h>
  18 #include <asm/compiler.h>
  19
  20 #include <asm/extable.h>
  21
  22 /*
  23  * These two functions allow hooking accesses to userspace to increase
  24  * system integrity by ensuring that the kernel can not inadvertantly
  25  * perform such accesses (eg, via list poison values) which could then
  26  * be exploited for priviledge escalation.
  27  */
  28 static inline unsigned int uaccess_save_and_enable(void)
  29 {
  30 #ifdef CONFIG_CPU_SW_DOMAIN_PAN
  31         unsigned int old_domain = get_domain();
  32
  33         /* Set the current domain access to permit user accesses */
  34         set_domain((old_domain & ~domain_mask(DOMAIN_USER)) |
  35                    domain_val(DOMAIN_USER, DOMAIN_CLIENT));
  36
  37         return old_domain;
  38 #else
  39         return 0;
  40 #endif
  41 }
  42
  43 static inline void uaccess_restore(unsigned int flags)
  44 {
  45 #ifdef CONFIG_CPU_SW_DOMAIN_PAN
  46         /* Restore the user access mask */
  47         set_domain(flags);
  48 #endif
  49 }
  50
  51 /*
  52  * These two are intentionally not defined anywhere - if the kernel
  53  * code generates any references to them, that's a bug.
  54  */
  55 extern int __get_user_bad(void);
  56 extern int __put_user_bad(void);
  57
  58 /*
  59  * Note that this is actually 0x1,0000,0000
  60  */
  61 #define KERNEL_DS       0x00000000
  62
  63 #ifdef CONFIG_MMU
  64
  65 #define USER_DS         TASK_SIZE
  66 #define get_fs()        (current_thread_info()->addr_limit)
  67
  68 static inline void set_fs(mm_segment_t fs)
  69 {
  70         current_thread_info()->addr_limit = fs;
  71
  72         /*
  73          * Prevent a mispredicted conditional call to set_fs from forwarding
  74          * the wrong address limit to access_ok under speculation.
  75          */
  76         dsb(nsh);
  77         isb();
  78
  79         modify_domain(DOMAIN_KERNEL, fs ? DOMAIN_CLIENT : DOMAIN_MANAGER);
  80 }
  81
  82 #define segment_eq(a, b)        ((a) == (b))
  83
  84 /* We use 33-bit arithmetic here... */
  85 #define __range_ok(addr, size) ({ \
  86         unsigned long flag, roksum; \
  87         __chk_user_ptr(addr);   \
  88         __asm__(".syntax unified\n" \
  89                 "adds %1, %2, %3; sbcscc %1, %1, %0; movcc %0, #0" \
  90                 : "=&r" (flag), "=&r" (roksum) \
  91                 : "r" (addr), "Ir" (size), "0" (current_thread_info()->addr_limit) \
  92                 : "cc"); \
  93         flag; })
  94
  95 /*
  96  * This is a type: either unsigned long, if the argument fits into
  97  * that type, or otherwise unsigned long long.
  98  */
  99 #define __inttype(x) \
 100         __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
 101
 102 /*
 103  * Sanitise a uaccess pointer such that it becomes NULL if addr+size
 104  * is above the current addr_limit.
 105  */
 106 #define uaccess_mask_range_ptr(ptr, size)                       \
 107         ((__typeof__(ptr))__uaccess_mask_range_ptr(ptr, size))
 108 static inline void __user *__uaccess_mask_range_ptr(const void __user *ptr,
 109                                                     size_t size)
 110 {
 111         void __user *safe_ptr = (void __user *)ptr;
 112         unsigned long tmp;
 113
 114         asm volatile(
 115         "       .syntax unified\n"
 116         "       sub     %1, %3, #1\n"
 117         "       subs    %1, %1, %0\n"
 118         "       addhs   %1, %1, #1\n"
 119         "       subshs  %1, %1, %2\n"
 120         "       movlo   %0, #0\n"
 121         : "+r" (safe_ptr), "=&r" (tmp)
 122         : "r" (size), "r" (current_thread_info()->addr_limit)
 123         : "cc");
 124
 125         csdb();
 126         return safe_ptr;
 127 }
 128
 129 /*
 130  * Single-value transfer routines.  They automatically use the right
 131  * size if we just have the right pointer type.  Note that the functions
 132  * which read from user space (*get_*) need to take care not to leak
 133  * kernel data even if the calling code is buggy and fails to check
 134  * the return value.  This means zeroing out the destination variable
 135  * or buffer on error.  Normally this is done out of line by the
 136  * fixup code, but there are a few places where it intrudes on the
 137  * main code path.  When we only write to user space, there is no
 138  * problem.
 139  */
 140 extern int __get_user_1(void *);
 141 extern int __get_user_2(void *);
 142 extern int __get_user_4(void *);
 143 extern int __get_user_32t_8(void *);
 144 extern int __get_user_8(void *);
 145 extern int __get_user_64t_1(void *);
 146 extern int __get_user_64t_2(void *);
 147 extern int __get_user_64t_4(void *);
 148
 149 #define __GUP_CLOBBER_1 "lr", "cc"
 150 #ifdef CONFIG_CPU_USE_DOMAINS
 151 #define __GUP_CLOBBER_2 "ip", "lr", "cc"
 152 #else
 153 #define __GUP_CLOBBER_2 "lr", "cc"
 154 #endif
 155 #define __GUP_CLOBBER_4 "lr", "cc"
 156 #define __GUP_CLOBBER_32t_8 "lr", "cc"
 157 #define __GUP_CLOBBER_8 "lr", "cc"
 158
 159 #define __get_user_x(__r2, __p, __e, __l, __s)                          \
 160            __asm__ __volatile__ (                                       \
 161                 __asmeq("%0", "r0") __asmeq("%1", "r2")                 \
 162                 __asmeq("%3", "r1")                                     \
 163                 "bl     __get_user_" #__s                               \
 164                 : "=&r" (__e), "=r" (__r2)                              \
 165                 : "0" (__p), "r" (__l)                                  \
 166                 : __GUP_CLOBBER_##__s)
 167
 168 /* narrowing a double-word get into a single 32bit word register: */
 169 #ifdef __ARMEB__
 170 #define __get_user_x_32t(__r2, __p, __e, __l, __s)                      \
 171         __get_user_x(__r2, __p, __e, __l, 32t_8)
 172 #else
 173 #define __get_user_x_32t __get_user_x
 174 #endif
 175
 176 /*
 177  * storing result into proper least significant word of 64bit target var,
 178  * different only for big endian case where 64 bit __r2 lsw is r3:
 179  */
 180 #ifdef __ARMEB__
 181 #define __get_user_x_64t(__r2, __p, __e, __l, __s)                      \
 182            __asm__ __volatile__ (                                       \
 183                 __asmeq("%0", "r0") __asmeq("%1", "r2")                 \
 184                 __asmeq("%3", "r1")                                     \
 185                 "bl     __get_user_64t_" #__s                           \
 186                 : "=&r" (__e), "=r" (__r2)                              \
 187                 : "0" (__p), "r" (__l)                                  \
 188                 : __GUP_CLOBBER_##__s)
 189 #else
 190 #define __get_user_x_64t __get_user_x
 191 #endif
 192
 193
 194 #define __get_user_check(x, p)                                          \
 195         ({                                                              \
 196                 unsigned long __limit = current_thread_info()->addr_limit - 1; \
 197                 register typeof(*(p)) __user *__p asm("r0") = (p);      \
 198                 register __inttype(x) __r2 asm("r2");                   \
 199                 register unsigned long __l asm("r1") = __limit;         \
 200                 register int __e asm("r0");                             \
 201                 unsigned int __ua_flags = uaccess_save_and_enable();    \
 202                 switch (sizeof(*(__p))) {                               \
 203                 case 1:                                                 \
 204                         if (sizeof((x)) >= 8)                           \
 205                                 __get_user_x_64t(__r2, __p, __e, __l, 1); \
 206                         else                                            \
 207                                 __get_user_x(__r2, __p, __e, __l, 1);   \
 208                         break;                                          \
 209                 case 2:                                                 \
 210                         if (sizeof((x)) >= 8)                           \
 211                                 __get_user_x_64t(__r2, __p, __e, __l, 2); \
 212                         else                                            \
 213                                 __get_user_x(__r2, __p, __e, __l, 2);   \
 214                         break;                                          \
 215                 case 4:                                                 \
 216                         if (sizeof((x)) >= 8)                           \
 217                                 __get_user_x_64t(__r2, __p, __e, __l, 4); \
 218                         else                                            \
 219                                 __get_user_x(__r2, __p, __e, __l, 4);   \
 220                         break;                                          \
 221                 case 8:                                                 \
 222                         if (sizeof((x)) < 8)                            \
 223                                 __get_user_x_32t(__r2, __p, __e, __l, 4); \
 224                         else                                            \
 225                                 __get_user_x(__r2, __p, __e, __l, 8);   \
 226                         break;                                          \
 227                 default: __e = __get_user_bad(); break;                 \
 228                 }                                                       \
 229                 uaccess_restore(__ua_flags);                            \
 230                 x = (typeof(*(p))) __r2;                                \
 231                 __e;                                                    \
 232         })
 233
 234 #define get_user(x, p)                                                  \
 235         ({                                                              \
 236                 might_fault();                                          \
 237                 __get_user_check(x, p);                                 \
 238          })
 239
 240 extern int __put_user_1(void *, unsigned int);
 241 extern int __put_user_2(void *, unsigned int);
 242 extern int __put_user_4(void *, unsigned int);
 243 extern int __put_user_8(void *, unsigned long long);
 244
 245 #define __put_user_check(__pu_val, __ptr, __err, __s)                   \
 246         ({                                                              \
 247                 unsigned long __limit = current_thread_info()->addr_limit - 1; \
 248                 register typeof(__pu_val) __r2 asm("r2") = __pu_val;    \
 249                 register const void __user *__p asm("r0") = __ptr;      \
 250                 register unsigned long __l asm("r1") = __limit;         \
 251                 register int __e asm("r0");                             \
 252                 __asm__ __volatile__ (                                  \
 253                         __asmeq("%0", "r0") __asmeq("%2", "r2")         \
 254                         __asmeq("%3", "r1")                             \
 255                         "bl     __put_user_" #__s                       \
 256                         : "=&r" (__e)                                   \
 257                         : "0" (__p), "r" (__r2), "r" (__l)              \
 258                         : "ip", "lr", "cc");                            \
 259                 __err = __e;                                            \
 260         })
 261
 262 #else /* CONFIG_MMU */
 263
 264 /*
 265  * uClinux has only one addr space, so has simplified address limits.
 266  */
 267 #define USER_DS                 KERNEL_DS
 268
 269 #define segment_eq(a, b)                (1)
 270 #define __addr_ok(addr)         ((void)(addr), 1)
 271 #define __range_ok(addr, size)  ((void)(addr), 0)
 272 #define get_fs()                (KERNEL_DS)
 273
 274 static inline void set_fs(mm_segment_t fs)
 275 {
 276 }
 277
 278 #define get_user(x, p)  __get_user(x, p)
 279 #define __put_user_check __put_user_nocheck
 280
 281 #endif /* CONFIG_MMU */
 282
 283 #define access_ok(addr, size)   (__range_ok(addr, size) == 0)
 284
 285 #define user_addr_max() \
 286         (uaccess_kernel() ? ~0UL : get_fs())
 287
 288 #ifdef CONFIG_CPU_SPECTRE
 289 /*
 290  * When mitigating Spectre variant 1, it is not worth fixing the non-
 291  * verifying accessors, because we need to add verification of the
 292  * address space there.  Force these to use the standard get_user()
 293  * version instead.
 294  */
 295 #define __get_user(x, ptr) get_user(x, ptr)
 296 #else
 297
 298 /*
 299  * The "__xxx" versions of the user access functions do not verify the
 300  * address space - it must have been done previously with a separate
 301  * "access_ok()" call.
 302  *
 303  * The "xxx_error" versions set the third argument to EFAULT if an
 304  * error occurs, and leave it unchanged on success.  Note that these
 305  * versions are void (ie, don't return a value as such).
 306  */
 307 #define __get_user(x, ptr)                                              \
 308 ({                                                                      \
 309         long __gu_err = 0;                                              \
 310         __get_user_err((x), (ptr), __gu_err);                           \
 311         __gu_err;                                                       \
 312 })
 313
 314 #define __get_user_err(x, ptr, err)                                     \
 315 do {                                                                    \
 316         unsigned long __gu_addr = (unsigned long)(ptr);                 \
 317         unsigned long __gu_val;                                         \
 318         unsigned int __ua_flags;                                        \
 319         __chk_user_ptr(ptr);                                            \
 320         might_fault();                                                  \
 321         __ua_flags = uaccess_save_and_enable();                         \
 322         switch (sizeof(*(ptr))) {                                       \
 323         case 1: __get_user_asm_byte(__gu_val, __gu_addr, err);  break;  \
 324         case 2: __get_user_asm_half(__gu_val, __gu_addr, err);  break;  \
 325         case 4: __get_user_asm_word(__gu_val, __gu_addr, err);  break;  \
 326         default: (__gu_val) = __get_user_bad();                         \
 327         }                                                               \
 328         uaccess_restore(__ua_flags);                                    \
 329         (x) = (__typeof__(*(ptr)))__gu_val;                             \
 330 } while (0)
 331
 332 #define __get_user_asm(x, addr, err, instr)                     \
 333         __asm__ __volatile__(                                   \
 334         "1:     " TUSER(instr) " %1, [%2], #0\n"                \
 335         "2:\n"                                                  \
 336         "       .pushsection .text.fixup,\"ax\"\n"              \
 337         "       .align  2\n"                                    \
 338         "3:     mov     %0, %3\n"                               \
 339         "       mov     %1, #0\n"                               \
 340         "       b       2b\n"                                   \
 341         "       .popsection\n"                                  \
 342         "       .pushsection __ex_table,\"a\"\n"                \
 343         "       .align  3\n"                                    \
 344         "       .long   1b, 3b\n"                               \
 345         "       .popsection"                                    \
 346         : "+r" (err), "=&r" (x)                                 \
 347         : "r" (addr), "i" (-EFAULT)                             \
 348         : "cc")
 349
 350 #define __get_user_asm_byte(x, addr, err)                       \
 351         __get_user_asm(x, addr, err, ldrb)
 352
 353 #if __LINUX_ARM_ARCH__ >= 6
 354
 355 #define __get_user_asm_half(x, addr, err)                       \
 356         __get_user_asm(x, addr, err, ldrh)
 357
 358 #else
 359
 360 #ifndef __ARMEB__
 361 #define __get_user_asm_half(x, __gu_addr, err)                  \
 362 ({                                                              \
 363         unsigned long __b1, __b2;                               \
 364         __get_user_asm_byte(__b1, __gu_addr, err);              \
 365         __get_user_asm_byte(__b2, __gu_addr + 1, err);          \
 366         (x) = __b1 | (__b2 << 8);                               \
 367 })
 368 #else
 369 #define __get_user_asm_half(x, __gu_addr, err)                  \
 370 ({                                                              \
 371         unsigned long __b1, __b2;                               \
 372         __get_user_asm_byte(__b1, __gu_addr, err);              \
 373         __get_user_asm_byte(__b2, __gu_addr + 1, err);          \
 374         (x) = (__b1 << 8) | __b2;                               \
 375 })
 376 #endif
 377
 378 #endif /* __LINUX_ARM_ARCH__ >= 6 */
 379
 380 #define __get_user_asm_word(x, addr, err)                       \
 381         __get_user_asm(x, addr, err, ldr)
 382 #endif
 383
 384
 385 #define __put_user_switch(x, ptr, __err, __fn)                          \
 386         do {                                                            \
 387                 const __typeof__(*(ptr)) __user *__pu_ptr = (ptr);      \
 388                 __typeof__(*(ptr)) __pu_val = (x);                      \
 389                 unsigned int __ua_flags;                                \
 390                 might_fault();                                          \
 391                 __ua_flags = uaccess_save_and_enable();                 \
 392                 switch (sizeof(*(ptr))) {                               \
 393                 case 1: __fn(__pu_val, __pu_ptr, __err, 1); break;      \
 394                 case 2: __fn(__pu_val, __pu_ptr, __err, 2); break;      \
 395                 case 4: __fn(__pu_val, __pu_ptr, __err, 4); break;      \
 396                 case 8: __fn(__pu_val, __pu_ptr, __err, 8); break;      \
 397                 default: __err = __put_user_bad(); break;               \
 398                 }                                                       \
 399                 uaccess_restore(__ua_flags);                            \
 400         } while (0)
 401
 402 #define put_user(x, ptr)                                                \
 403 ({                                                                      \
 404         int __pu_err = 0;                                               \
 405         __put_user_switch((x), (ptr), __pu_err, __put_user_check);      \
 406         __pu_err;                                                       \
 407 })
 408
 409 #ifdef CONFIG_CPU_SPECTRE
 410 /*
 411  * When mitigating Spectre variant 1.1, all accessors need to include
 412  * verification of the address space.
 413  */
 414 #define __put_user(x, ptr) put_user(x, ptr)
 415
 416 #else
 417 #define __put_user(x, ptr)                                              \
 418 ({                                                                      \
 419         long __pu_err = 0;                                              \
 420         __put_user_switch((x), (ptr), __pu_err, __put_user_nocheck);    \
 421         __pu_err;                                                       \
 422 })
 423
 424 #define __put_user_nocheck(x, __pu_ptr, __err, __size)                  \
 425         do {                                                            \
 426                 unsigned long __pu_addr = (unsigned long)__pu_ptr;      \
 427                 __put_user_nocheck_##__size(x, __pu_addr, __err);       \
 428         } while (0)
 429
 430 #define __put_user_nocheck_1 __put_user_asm_byte
 431 #define __put_user_nocheck_2 __put_user_asm_half
 432 #define __put_user_nocheck_4 __put_user_asm_word
 433 #define __put_user_nocheck_8 __put_user_asm_dword
 434
 435 #define __put_user_asm(x, __pu_addr, err, instr)                \
 436         __asm__ __volatile__(                                   \
 437         "1:     " TUSER(instr) " %1, [%2], #0\n"                \
 438         "2:\n"                                                  \
 439         "       .pushsection .text.fixup,\"ax\"\n"              \
 440         "       .align  2\n"                                    \
 441         "3:     mov     %0, %3\n"                               \
 442         "       b       2b\n"                                   \
 443         "       .popsection\n"                                  \
 444         "       .pushsection __ex_table,\"a\"\n"                \
 445         "       .align  3\n"                                    \
 446         "       .long   1b, 3b\n"                               \
 447         "       .popsection"                                    \
 448         : "+r" (err)                                            \
 449         : "r" (x), "r" (__pu_addr), "i" (-EFAULT)               \
 450         : "cc")
 451
 452 #define __put_user_asm_byte(x, __pu_addr, err)                  \
 453         __put_user_asm(x, __pu_addr, err, strb)
 454
 455 #if __LINUX_ARM_ARCH__ >= 6
 456
 457 #define __put_user_asm_half(x, __pu_addr, err)                  \
 458         __put_user_asm(x, __pu_addr, err, strh)
 459
 460 #else
 461
 462 #ifndef __ARMEB__
 463 #define __put_user_asm_half(x, __pu_addr, err)                  \
 464 ({                                                              \
 465         unsigned long __temp = (__force unsigned long)(x);      \
 466         __put_user_asm_byte(__temp, __pu_addr, err);            \
 467         __put_user_asm_byte(__temp >> 8, __pu_addr + 1, err);   \
 468 })
 469 #else
 470 #define __put_user_asm_half(x, __pu_addr, err)                  \
 471 ({                                                              \
 472         unsigned long __temp = (__force unsigned long)(x);      \
 473         __put_user_asm_byte(__temp >> 8, __pu_addr, err);       \
 474         __put_user_asm_byte(__temp, __pu_addr + 1, err);        \
 475 })
 476 #endif
 477
 478 #endif /* __LINUX_ARM_ARCH__ >= 6 */
 479
 480 #define __put_user_asm_word(x, __pu_addr, err)                  \
 481         __put_user_asm(x, __pu_addr, err, str)
 482
 483 #ifndef __ARMEB__
 484 #define __reg_oper0     "%R2"
 485 #define __reg_oper1     "%Q2"
 486 #else
 487 #define __reg_oper0     "%Q2"
 488 #define __reg_oper1     "%R2"
 489 #endif
 490
 491 #define __put_user_asm_dword(x, __pu_addr, err)                 \
 492         __asm__ __volatile__(                                   \
 493  ARM(   "1:     " TUSER(str) "  " __reg_oper1 ", [%1], #4\n"    ) \
 494  ARM(   "2:     " TUSER(str) "  " __reg_oper0 ", [%1]\n"        ) \
 495  THUMB( "1:     " TUSER(str) "  " __reg_oper1 ", [%1]\n"        ) \
 496  THUMB( "2:     " TUSER(str) "  " __reg_oper0 ", [%1, #4]\n"    ) \
 497         "3:\n"                                                  \
 498         "       .pushsection .text.fixup,\"ax\"\n"              \
 499         "       .align  2\n"                                    \
 500         "4:     mov     %0, %3\n"                               \
 501         "       b       3b\n"                                   \
 502         "       .popsection\n"                                  \
 503         "       .pushsection __ex_table,\"a\"\n"                \
 504         "       .align  3\n"                                    \
 505         "       .long   1b, 4b\n"                               \
 506         "       .long   2b, 4b\n"                               \
 507         "       .popsection"                                    \
 508         : "+r" (err), "+r" (__pu_addr)                          \
 509         : "r" (x), "i" (-EFAULT)                                \
 510         : "cc")
 511
 512 #endif /* !CONFIG_CPU_SPECTRE */
 513
 514 #ifdef CONFIG_MMU
 515 extern unsigned long __must_check
 516 arm_copy_from_user(void *to, const void __user *from, unsigned long n);
 517
 518 static inline unsigned long __must_check
 519 raw_copy_from_user(void *to, const void __user *from, unsigned long n)
 520 {
 521         unsigned int __ua_flags;
 522
 523         __ua_flags = uaccess_save_and_enable();
 524         n = arm_copy_from_user(to, from, n);
 525         uaccess_restore(__ua_flags);
 526         return n;
 527 }
 528
 529 extern unsigned long __must_check
 530 arm_copy_to_user(void __user *to, const void *from, unsigned long n);
 531 extern unsigned long __must_check
 532 __copy_to_user_std(void __user *to, const void *from, unsigned long n);
 533
 534 static inline unsigned long __must_check
 535 raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 536 {
 537 #ifndef CONFIG_UACCESS_WITH_MEMCPY
 538         unsigned int __ua_flags;
 539         __ua_flags = uaccess_save_and_enable();
 540         n = arm_copy_to_user(to, from, n);
 541         uaccess_restore(__ua_flags);
 542         return n;
 543 #else
 544         return arm_copy_to_user(to, from, n);
 545 #endif
 546 }
 547
 548 extern unsigned long __must_check
 549 arm_clear_user(void __user *addr, unsigned long n);
 550 extern unsigned long __must_check
 551 __clear_user_std(void __user *addr, unsigned long n);
 552
 553 static inline unsigned long __must_check
 554 __clear_user(void __user *addr, unsigned long n)
 555 {
 556         unsigned int __ua_flags = uaccess_save_and_enable();
 557         n = arm_clear_user(addr, n);
 558         uaccess_restore(__ua_flags);
 559         return n;
 560 }
 561
 562 #else
 563 static inline unsigned long
 564 raw_copy_from_user(void *to, const void __user *from, unsigned long n)
 565 {
 566         memcpy(to, (const void __force *)from, n);
 567         return 0;
 568 }
 569 static inline unsigned long
 570 raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 571 {
 572         memcpy((void __force *)to, from, n);
 573         return 0;
 574 }
 575 #define __clear_user(addr, n)           (memset((void __force *)addr, 0, n), 0)
 576 #endif
 577 #define INLINE_COPY_TO_USER
 578 #define INLINE_COPY_FROM_USER
 579
 580 static inline unsigned long __must_check clear_user(void __user *to, unsigned long n)
 581 {
 582         if (access_ok(to, n))
 583                 n = __clear_user(to, n);
 584         return n;
 585 }
 586
 587 /* These are from lib/ code, and use __get_user() and friends */
 588 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 589
 590 extern __must_check long strnlen_user(const char __user *str, long n);
 591
 592 #endif /* _ASMARM_UACCESS_H */