1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 /* 3 * arch/arm/include/asm/uaccess.h 4 */ 5 #ifndef _ASMARM_UACCESS_H 6 #define _ASMARM_UACCESS_H 7 8 /* 9 * User space memory access functions 10 */ 11 #include <linux/kernel.h> 12 #include <linux/string.h> 13 #include <asm/page.h> 14 #include <asm/domain.h> 15 #include <linux/unaligned.h> 16 #include <asm/unified.h> 17 #include <asm/pgtable.h> 18 #include <asm/proc-fns.h> 19 #include <asm/compiler.h> 20 21 #include <asm/extable.h> 22 23 /* 24 * These two functions allow hooking accesses to userspace to increase 25 * system integrity by ensuring that the kernel can not inadvertantly 26 * perform such accesses (eg, via list poison values) which could then 27 * be exploited for priviledge escalation. 28 */ 29 #if defined(CONFIG_CPU_SW_DOMAIN_PAN) 30 31 static __always_inline unsigned int uaccess_save_and_enable(void) 32 { 33 unsigned int old_domain = get_domain(); 34 35 /* Set the current domain access to permit user accesses */ 36 set_domain((old_domain & ~domain_mask(DOMAIN_USER)) | 37 domain_val(DOMAIN_USER, DOMAIN_CLIENT)); 38 39 return old_domain; 40 } 41 42 static __always_inline void uaccess_restore(unsigned int flags) 43 { 44 /* Restore the user access mask */ 45 set_domain(flags); 46 } 47 48 #elif defined(CONFIG_CPU_TTBR0_PAN) 49 50 static __always_inline unsigned int uaccess_save_and_enable(void) 51 { 52 unsigned int old_ttbcr = cpu_get_ttbcr(); 53 54 /* 55 * Enable TTBR0 page table walks (T0SZ = 0, EDP0 = 0) and ASID from 56 * TTBR0 (A1 = 0). 57 */ 58 cpu_set_ttbcr(old_ttbcr & ~(TTBCR_A1 | TTBCR_EPD0 | TTBCR_T0SZ_MASK)); 59 isb(); 60 61 return old_ttbcr; 62 } 63 64 static inline void uaccess_restore(unsigned int flags) 65 { 66 cpu_set_ttbcr(flags); 67 isb(); 68 } 69 70 #else 71 72 static inline unsigned int uaccess_save_and_enable(void) 73 { 74 return 0; 75 } 76 77 static inline void uaccess_restore(unsigned int flags) 78 { 79 } 80 81 #endif 82 83 /* 84 * These two are intentionally not defined anywhere - if the kernel 85 * code generates any references to them, that's a bug. 86 */ 87 extern int __get_user_bad(void); 88 extern int __put_user_bad(void); 89 90 #ifdef CONFIG_MMU 91 92 /* 93 * This is a type: either unsigned long, if the argument fits into 94 * that type, or otherwise unsigned long long. 95 */ 96 #define __inttype(x) \ 97 __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL)) 98 99 /* 100 * Sanitise a uaccess pointer such that it becomes NULL if addr+size 101 * is above the current addr_limit. 102 */ 103 #define uaccess_mask_range_ptr(ptr, size) \ 104 ((__typeof__(ptr))__uaccess_mask_range_ptr(ptr, size)) 105 static inline void __user *__uaccess_mask_range_ptr(const void __user *ptr, 106 size_t size) 107 { 108 void __user *safe_ptr = (void __user *)ptr; 109 unsigned long tmp; 110 111 asm volatile( 112 " .syntax unified\n" 113 " sub %1, %3, #1\n" 114 " subs %1, %1, %0\n" 115 " addhs %1, %1, #1\n" 116 " subshs %1, %1, %2\n" 117 " movlo %0, #0\n" 118 : "+r" (safe_ptr), "=&r" (tmp) 119 : "r" (size), "r" (TASK_SIZE) 120 : "cc"); 121 122 csdb(); 123 return safe_ptr; 124 } 125 126 /* 127 * Single-value transfer routines. They automatically use the right 128 * size if we just have the right pointer type. Note that the functions 129 * which read from user space (*get_*) need to take care not to leak 130 * kernel data even if the calling code is buggy and fails to check 131 * the return value. This means zeroing out the destination variable 132 * or buffer on error. Normally this is done out of line by the 133 * fixup code, but there are a few places where it intrudes on the 134 * main code path. When we only write to user space, there is no 135 * problem. 136 */ 137 extern int __get_user_1(void *); 138 extern int __get_user_2(void *); 139 extern int __get_user_4(void *); 140 extern int __get_user_32t_8(void *); 141 extern int __get_user_8(void *); 142 extern int __get_user_64t_1(void *); 143 extern int __get_user_64t_2(void *); 144 extern int __get_user_64t_4(void *); 145 146 #define __get_user_x(__r2, __p, __e, __l, __s) \ 147 __asm__ __volatile__ ( \ 148 __asmeq("%0", "r0") __asmeq("%1", "r2") \ 149 __asmeq("%3", "r1") \ 150 "bl __get_user_" #__s \ 151 : "=&r" (__e), "=r" (__r2) \ 152 : "0" (__p), "r" (__l) \ 153 : "ip", "lr", "cc") 154 155 /* narrowing a double-word get into a single 32bit word register: */ 156 #ifdef __ARMEB__ 157 #define __get_user_x_32t(__r2, __p, __e, __l, __s) \ 158 __get_user_x(__r2, __p, __e, __l, 32t_8) 159 #else 160 #define __get_user_x_32t __get_user_x 161 #endif 162 163 /* 164 * storing result into proper least significant word of 64bit target var, 165 * different only for big endian case where 64 bit __r2 lsw is r3: 166 */ 167 #ifdef __ARMEB__ 168 #define __get_user_x_64t(__r2, __p, __e, __l, __s) \ 169 __asm__ __volatile__ ( \ 170 __asmeq("%0", "r0") __asmeq("%1", "r2") \ 171 __asmeq("%3", "r1") \ 172 "bl __get_user_64t_" #__s \ 173 : "=&r" (__e), "=r" (__r2) \ 174 : "0" (__p), "r" (__l) \ 175 : "ip", "lr", "cc") 176 #else 177 #define __get_user_x_64t __get_user_x 178 #endif 179 180 181 #define __get_user_check(x, p) \ 182 ({ \ 183 unsigned long __limit = TASK_SIZE - 1; \ 184 register typeof(*(p)) __user *__p asm("r0") = (p); \ 185 register __inttype(x) __r2 asm("r2"); \ 186 register unsigned long __l asm("r1") = __limit; \ 187 register int __e asm("r0"); \ 188 unsigned int __ua_flags = uaccess_save_and_enable(); \ 189 int __tmp_e; \ 190 switch (sizeof(*(__p))) { \ 191 case 1: \ 192 if (sizeof((x)) >= 8) \ 193 __get_user_x_64t(__r2, __p, __e, __l, 1); \ 194 else \ 195 __get_user_x(__r2, __p, __e, __l, 1); \ 196 break; \ 197 case 2: \ 198 if (sizeof((x)) >= 8) \ 199 __get_user_x_64t(__r2, __p, __e, __l, 2); \ 200 else \ 201 __get_user_x(__r2, __p, __e, __l, 2); \ 202 break; \ 203 case 4: \ 204 if (sizeof((x)) >= 8) \ 205 __get_user_x_64t(__r2, __p, __e, __l, 4); \ 206 else \ 207 __get_user_x(__r2, __p, __e, __l, 4); \ 208 break; \ 209 case 8: \ 210 if (sizeof((x)) < 8) \ 211 __get_user_x_32t(__r2, __p, __e, __l, 4); \ 212 else \ 213 __get_user_x(__r2, __p, __e, __l, 8); \ 214 break; \ 215 default: __e = __get_user_bad(); break; \ 216 } \ 217 __tmp_e = __e; \ 218 uaccess_restore(__ua_flags); \ 219 x = (typeof(*(p))) __r2; \ 220 __tmp_e; \ 221 }) 222 223 #define get_user(x, p) \ 224 ({ \ 225 might_fault(); \ 226 __get_user_check(x, p); \ 227 }) 228 229 extern int __put_user_1(void *, unsigned int); 230 extern int __put_user_2(void *, unsigned int); 231 extern int __put_user_4(void *, unsigned int); 232 extern int __put_user_8(void *, unsigned long long); 233 234 #define __put_user_check(__pu_val, __ptr, __err, __s) \ 235 ({ \ 236 unsigned long __limit = TASK_SIZE - 1; \ 237 register typeof(__pu_val) __r2 asm("r2") = __pu_val; \ 238 register const void __user *__p asm("r0") = __ptr; \ 239 register unsigned long __l asm("r1") = __limit; \ 240 register int __e asm("r0"); \ 241 __asm__ __volatile__ ( \ 242 __asmeq("%0", "r0") __asmeq("%2", "r2") \ 243 __asmeq("%3", "r1") \ 244 "bl __put_user_" #__s \ 245 : "=&r" (__e) \ 246 : "0" (__p), "r" (__r2), "r" (__l) \ 247 : "ip", "lr", "cc"); \ 248 __err = __e; \ 249 }) 250 251 #else /* CONFIG_MMU */ 252 253 #define get_user(x, p) __get_user(x, p) 254 #define __put_user_check __put_user_nocheck 255 256 #endif /* CONFIG_MMU */ 257 258 #include <asm-generic/access_ok.h> 259 260 #ifdef CONFIG_CPU_SPECTRE 261 /* 262 * When mitigating Spectre variant 1, it is not worth fixing the non- 263 * verifying accessors, because we need to add verification of the 264 * address space there. Force these to use the standard get_user() 265 * version instead. 266 */ 267 #define __get_user(x, ptr) get_user(x, ptr) 268 #else 269 270 /* 271 * The "__xxx" versions of the user access functions do not verify the 272 * address space - it must have been done previously with a separate 273 * "access_ok()" call. 274 * 275 * The "xxx_error" versions set the third argument to EFAULT if an 276 * error occurs, and leave it unchanged on success. Note that these 277 * versions are void (ie, don't return a value as such). 278 */ 279 #define __get_user(x, ptr) \ 280 ({ \ 281 long __gu_err = 0; \ 282 __get_user_err((x), (ptr), __gu_err, TUSER()); \ 283 __gu_err; \ 284 }) 285 286 /* 287 * This is a type: either unsigned long, if the argument fits into 288 * that type, or otherwise unsigned long long. 289 */ 290 #define __long_type(x) \ 291 __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL)) 292 293 #define __get_user_err(x, ptr, err, __t) \ 294 do { \ 295 unsigned long __gu_addr = (unsigned long)(ptr); \ 296 __long_type(x) __gu_val; \ 297 unsigned int __ua_flags; \ 298 __chk_user_ptr(ptr); \ 299 might_fault(); \ 300 __ua_flags = uaccess_save_and_enable(); \ 301 switch (sizeof(*(ptr))) { \ 302 case 1: __get_user_asm_byte(__gu_val, __gu_addr, err, __t); break; \ 303 case 2: __get_user_asm_half(__gu_val, __gu_addr, err, __t); break; \ 304 case 4: __get_user_asm_word(__gu_val, __gu_addr, err, __t); break; \ 305 case 8: __get_user_asm_dword(__gu_val, __gu_addr, err, __t); break; \ 306 default: (__gu_val) = __get_user_bad(); \ 307 } \ 308 uaccess_restore(__ua_flags); \ 309 (x) = (__typeof__(*(ptr)))__gu_val; \ 310 } while (0) 311 #endif 312 313 #define __get_user_asm(x, addr, err, instr) \ 314 __asm__ __volatile__( \ 315 "1: " instr " %1, [%2], #0\n" \ 316 "2:\n" \ 317 " .pushsection .text.fixup,\"ax\"\n" \ 318 " .align 2\n" \ 319 "3: mov %0, %3\n" \ 320 " mov %1, #0\n" \ 321 " b 2b\n" \ 322 " .popsection\n" \ 323 " .pushsection __ex_table,\"a\"\n" \ 324 " .align 3\n" \ 325 " .long 1b, 3b\n" \ 326 " .popsection" \ 327 : "+r" (err), "=&r" (x) \ 328 : "r" (addr), "i" (-EFAULT) \ 329 : "cc") 330 331 #define __get_user_asm_byte(x, addr, err, __t) \ 332 __get_user_asm(x, addr, err, "ldrb" __t) 333 334 #if __LINUX_ARM_ARCH__ >= 6 335 336 #define __get_user_asm_half(x, addr, err, __t) \ 337 __get_user_asm(x, addr, err, "ldrh" __t) 338 339 #else 340 341 #ifndef __ARMEB__ 342 #define __get_user_asm_half(x, __gu_addr, err, __t) \ 343 ({ \ 344 unsigned long __b1, __b2; \ 345 __get_user_asm_byte(__b1, __gu_addr, err, __t); \ 346 __get_user_asm_byte(__b2, __gu_addr + 1, err, __t); \ 347 (x) = __b1 | (__b2 << 8); \ 348 }) 349 #else 350 #define __get_user_asm_half(x, __gu_addr, err, __t) \ 351 ({ \ 352 unsigned long __b1, __b2; \ 353 __get_user_asm_byte(__b1, __gu_addr, err, __t); \ 354 __get_user_asm_byte(__b2, __gu_addr + 1, err, __t); \ 355 (x) = (__b1 << 8) | __b2; \ 356 }) 357 #endif 358 359 #endif /* __LINUX_ARM_ARCH__ >= 6 */ 360 361 #define __get_user_asm_word(x, addr, err, __t) \ 362 __get_user_asm(x, addr, err, "ldr" __t) 363 364 #ifdef __ARMEB__ 365 #define __WORD0_OFFS 4 366 #define __WORD1_OFFS 0 367 #else 368 #define __WORD0_OFFS 0 369 #define __WORD1_OFFS 4 370 #endif 371 372 #define __get_user_asm_dword(x, addr, err, __t) \ 373 ({ \ 374 unsigned long __w0, __w1; \ 375 __get_user_asm(__w0, addr + __WORD0_OFFS, err, "ldr" __t); \ 376 __get_user_asm(__w1, addr + __WORD1_OFFS, err, "ldr" __t); \ 377 (x) = ((u64)__w1 << 32) | (u64) __w0; \ 378 }) 379 380 #define __put_user_switch(x, ptr, __err, __fn) \ 381 do { \ 382 const __typeof__(*(ptr)) __user *__pu_ptr = (ptr); \ 383 __typeof__(*(ptr)) __pu_val = (x); \ 384 unsigned int __ua_flags; \ 385 might_fault(); \ 386 __ua_flags = uaccess_save_and_enable(); \ 387 switch (sizeof(*(ptr))) { \ 388 case 1: __fn(__pu_val, __pu_ptr, __err, 1); break; \ 389 case 2: __fn(__pu_val, __pu_ptr, __err, 2); break; \ 390 case 4: __fn(__pu_val, __pu_ptr, __err, 4); break; \ 391 case 8: __fn(__pu_val, __pu_ptr, __err, 8); break; \ 392 default: __err = __put_user_bad(); break; \ 393 } \ 394 uaccess_restore(__ua_flags); \ 395 } while (0) 396 397 #define put_user(x, ptr) \ 398 ({ \ 399 int __pu_err = 0; \ 400 __put_user_switch((x), (ptr), __pu_err, __put_user_check); \ 401 __pu_err; \ 402 }) 403 404 #ifdef CONFIG_CPU_SPECTRE 405 /* 406 * When mitigating Spectre variant 1.1, all accessors need to include 407 * verification of the address space. 408 */ 409 #define __put_user(x, ptr) put_user(x, ptr) 410 411 #else 412 #define __put_user(x, ptr) \ 413 ({ \ 414 long __pu_err = 0; \ 415 __put_user_switch((x), (ptr), __pu_err, __put_user_nocheck); \ 416 __pu_err; \ 417 }) 418 419 #define __put_user_nocheck(x, __pu_ptr, __err, __size) \ 420 do { \ 421 unsigned long __pu_addr = (unsigned long)__pu_ptr; \ 422 __put_user_nocheck_##__size(x, __pu_addr, __err, TUSER());\ 423 } while (0) 424 425 #define __put_user_nocheck_1 __put_user_asm_byte 426 #define __put_user_nocheck_2 __put_user_asm_half 427 #define __put_user_nocheck_4 __put_user_asm_word 428 #define __put_user_nocheck_8 __put_user_asm_dword 429 430 #endif /* !CONFIG_CPU_SPECTRE */ 431 432 #define __put_user_asm(x, __pu_addr, err, instr) \ 433 __asm__ __volatile__( \ 434 "1: " instr " %1, [%2], #0\n" \ 435 "2:\n" \ 436 " .pushsection .text.fixup,\"ax\"\n" \ 437 " .align 2\n" \ 438 "3: mov %0, %3\n" \ 439 " b 2b\n" \ 440 " .popsection\n" \ 441 " .pushsection __ex_table,\"a\"\n" \ 442 " .align 3\n" \ 443 " .long 1b, 3b\n" \ 444 " .popsection" \ 445 : "+r" (err) \ 446 : "r" (x), "r" (__pu_addr), "i" (-EFAULT) \ 447 : "cc") 448 449 #define __put_user_asm_byte(x, __pu_addr, err, __t) \ 450 __put_user_asm(x, __pu_addr, err, "strb" __t) 451 452 #if __LINUX_ARM_ARCH__ >= 6 453 454 #define __put_user_asm_half(x, __pu_addr, err, __t) \ 455 __put_user_asm(x, __pu_addr, err, "strh" __t) 456 457 #else 458 459 #ifndef __ARMEB__ 460 #define __put_user_asm_half(x, __pu_addr, err, __t) \ 461 ({ \ 462 unsigned long __temp = (__force unsigned long)(x); \ 463 __put_user_asm_byte(__temp, __pu_addr, err, __t); \ 464 __put_user_asm_byte(__temp >> 8, __pu_addr + 1, err, __t);\ 465 }) 466 #else 467 #define __put_user_asm_half(x, __pu_addr, err, __t) \ 468 ({ \ 469 unsigned long __temp = (__force unsigned long)(x); \ 470 __put_user_asm_byte(__temp >> 8, __pu_addr, err, __t); \ 471 __put_user_asm_byte(__temp, __pu_addr + 1, err, __t); \ 472 }) 473 #endif 474 475 #endif /* __LINUX_ARM_ARCH__ >= 6 */ 476 477 #define __put_user_asm_word(x, __pu_addr, err, __t) \ 478 __put_user_asm(x, __pu_addr, err, "str" __t) 479 480 #ifndef __ARMEB__ 481 #define __reg_oper0 "%R2" 482 #define __reg_oper1 "%Q2" 483 #else 484 #define __reg_oper0 "%Q2" 485 #define __reg_oper1 "%R2" 486 #endif 487 488 #define __put_user_asm_dword(x, __pu_addr, err, __t) \ 489 __asm__ __volatile__( \ 490 ARM( "1: str" __t " " __reg_oper1 ", [%1], #4\n" ) \ 491 ARM( "2: str" __t " " __reg_oper0 ", [%1]\n" ) \ 492 THUMB( "1: str" __t " " __reg_oper1 ", [%1]\n" ) \ 493 THUMB( "2: str" __t " " __reg_oper0 ", [%1, #4]\n" ) \ 494 "3:\n" \ 495 " .pushsection .text.fixup,\"ax\"\n" \ 496 " .align 2\n" \ 497 "4: mov %0, %3\n" \ 498 " b 3b\n" \ 499 " .popsection\n" \ 500 " .pushsection __ex_table,\"a\"\n" \ 501 " .align 3\n" \ 502 " .long 1b, 4b\n" \ 503 " .long 2b, 4b\n" \ 504 " .popsection" \ 505 : "+r" (err), "+r" (__pu_addr) \ 506 : "r" (x), "i" (-EFAULT) \ 507 : "cc") 508 509 #define __get_kernel_nofault(dst, src, type, err_label) \ 510 do { \ 511 const type *__pk_ptr = (src); \ 512 unsigned long __src = (unsigned long)(__pk_ptr); \ 513 type __val; \ 514 int __err = 0; \ 515 switch (sizeof(type)) { \ 516 case 1: __get_user_asm_byte(__val, __src, __err, ""); break; \ 517 case 2: __get_user_asm_half(__val, __src, __err, ""); break; \ 518 case 4: __get_user_asm_word(__val, __src, __err, ""); break; \ 519 case 8: { \ 520 u32 *__v32 = (u32*)&__val; \ 521 __get_user_asm_word(__v32[0], __src, __err, ""); \ 522 if (__err) \ 523 break; \ 524 __get_user_asm_word(__v32[1], __src+4, __err, ""); \ 525 break; \ 526 } \ 527 default: __err = __get_user_bad(); break; \ 528 } \ 529 if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) \ 530 put_unaligned(__val, (type *)(dst)); \ 531 else \ 532 *(type *)(dst) = __val; /* aligned by caller */ \ 533 if (__err) \ 534 goto err_label; \ 535 } while (0) 536 537 #define __put_kernel_nofault(dst, src, type, err_label) \ 538 do { \ 539 const type *__pk_ptr = (dst); \ 540 unsigned long __dst = (unsigned long)__pk_ptr; \ 541 int __err = 0; \ 542 type __val = IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) \ 543 ? get_unaligned((type *)(src)) \ 544 : *(type *)(src); /* aligned by caller */ \ 545 switch (sizeof(type)) { \ 546 case 1: __put_user_asm_byte(__val, __dst, __err, ""); break; \ 547 case 2: __put_user_asm_half(__val, __dst, __err, ""); break; \ 548 case 4: __put_user_asm_word(__val, __dst, __err, ""); break; \ 549 case 8: __put_user_asm_dword(__val, __dst, __err, ""); break; \ 550 default: __err = __put_user_bad(); break; \ 551 } \ 552 if (__err) \ 553 goto err_label; \ 554 } while (0) 555 556 #ifdef CONFIG_MMU 557 extern unsigned long __must_check 558 arm_copy_from_user(void *to, const void __user *from, unsigned long n); 559 560 static inline unsigned long __must_check 561 raw_copy_from_user(void *to, const void __user *from, unsigned long n) 562 { 563 unsigned int __ua_flags; 564 565 __ua_flags = uaccess_save_and_enable(); 566 n = arm_copy_from_user(to, from, n); 567 uaccess_restore(__ua_flags); 568 return n; 569 } 570 571 extern unsigned long __must_check 572 arm_copy_to_user(void __user *to, const void *from, unsigned long n); 573 extern unsigned long __must_check 574 __copy_to_user_std(void __user *to, const void *from, unsigned long n); 575 576 static inline unsigned long __must_check 577 raw_copy_to_user(void __user *to, const void *from, unsigned long n) 578 { 579 #ifndef CONFIG_UACCESS_WITH_MEMCPY 580 unsigned int __ua_flags; 581 __ua_flags = uaccess_save_and_enable(); 582 n = arm_copy_to_user(to, from, n); 583 uaccess_restore(__ua_flags); 584 return n; 585 #else 586 return arm_copy_to_user(to, from, n); 587 #endif 588 } 589 590 extern unsigned long __must_check 591 arm_clear_user(void __user *addr, unsigned long n); 592 extern unsigned long __must_check 593 __clear_user_std(void __user *addr, unsigned long n); 594 595 static inline unsigned long __must_check 596 __clear_user(void __user *addr, unsigned long n) 597 { 598 unsigned int __ua_flags = uaccess_save_and_enable(); 599 n = arm_clear_user(addr, n); 600 uaccess_restore(__ua_flags); 601 return n; 602 } 603 604 #else 605 static inline unsigned long 606 raw_copy_from_user(void *to, const void __user *from, unsigned long n) 607 { 608 memcpy(to, (const void __force *)from, n); 609 return 0; 610 } 611 static inline unsigned long 612 raw_copy_to_user(void __user *to, const void *from, unsigned long n) 613 { 614 memcpy((void __force *)to, from, n); 615 return 0; 616 } 617 #define __clear_user(addr, n) (memset((void __force *)addr, 0, n), 0) 618 #endif 619 #define INLINE_COPY_TO_USER 620 #define INLINE_COPY_FROM_USER 621 622 static inline unsigned long __must_check clear_user(void __user *to, unsigned long n) 623 { 624 if (access_ok(to, n)) 625 n = __clear_user(to, n); 626 return n; 627 } 628 629 /* These are from lib/ code, and use __get_user() and friends */ 630 extern long strncpy_from_user(char *dest, const char __user *src, long count); 631 632 extern __must_check long strnlen_user(const char __user *str, long n); 633 634 #endif /* _ASMARM_UACCESS_H */ 635