arch/xtensa/include/asm/uaccess.h

   1 /*
   2  * include/asm-xtensa/uaccess.h
   3  *
   4  * User space memory access functions
   5  *
   6  * These routines provide basic accessing functions to the user memory
   7  * space for the kernel. This header file provides functions such as:
   8  *
   9  * This file is subject to the terms and conditions of the GNU General Public
  10  * License.  See the file "COPYING" in the main directory of this archive
  11  * for more details.
  12  *
  13  * Copyright (C) 2001 - 2005 Tensilica Inc.
  14  */
  15
  16 #ifndef _XTENSA_UACCESS_H
  17 #define _XTENSA_UACCESS_H
  18
  19 #include <linux/errno.h>
  20 #ifndef __ASSEMBLY__
  21 #include <linux/prefetch.h>
  22 #endif
  23 #include <asm/types.h>
  24
  25 #define VERIFY_READ    0
  26 #define VERIFY_WRITE   1
  27
  28 #ifdef __ASSEMBLY__
  29
  30 #include <asm/current.h>
  31 #include <asm/asm-offsets.h>
  32 #include <asm/processor.h>
  33
  34 /*
  35  * These assembly macros mirror the C macros that follow below.  They
  36  * should always have identical functionality.  See
  37  * arch/xtensa/kernel/sys.S for usage.
  38  */
  39
  40 #define KERNEL_DS       0
  41 #define USER_DS         1
  42
  43 #define get_ds          (KERNEL_DS)
  44
  45 /*
  46  * get_fs reads current->thread.current_ds into a register.
  47  * On Entry:
  48  *      <ad>    anything
  49  *      <sp>    stack
  50  * On Exit:
  51  *      <ad>    contains current->thread.current_ds
  52  */
  53         .macro  get_fs  ad, sp
  54         GET_CURRENT(\ad,\sp)
  55 #if THREAD_CURRENT_DS > 1020
  56         addi    \ad, \ad, TASK_THREAD
  57         l32i    \ad, \ad, THREAD_CURRENT_DS - TASK_THREAD
  58 #else
  59         l32i    \ad, \ad, THREAD_CURRENT_DS
  60 #endif
  61         .endm
  62
  63 /*
  64  * set_fs sets current->thread.current_ds to some value.
  65  * On Entry:
  66  *      <at>    anything (temp register)
  67  *      <av>    value to write
  68  *      <sp>    stack
  69  * On Exit:
  70  *      <at>    destroyed (actually, current)
  71  *      <av>    preserved, value to write
  72  */
  73         .macro  set_fs  at, av, sp
  74         GET_CURRENT(\at,\sp)
  75         s32i    \av, \at, THREAD_CURRENT_DS
  76         .endm
  77
  78 /*
  79  * kernel_ok determines whether we should bypass addr/size checking.
  80  * See the equivalent C-macro version below for clarity.
  81  * On success, kernel_ok branches to a label indicated by parameter
  82  * <success>.  This implies that the macro falls through to the next
  83  * insruction on an error.
  84  *
  85  * Note that while this macro can be used independently, we designed
  86  * in for optimal use in the access_ok macro below (i.e., we fall
  87  * through on error).
  88  *
  89  * On Entry:
  90  *      <at>            anything (temp register)
  91  *      <success>       label to branch to on success; implies
  92  *                      fall-through macro on error
  93  *      <sp>            stack pointer
  94  * On Exit:
  95  *      <at>            destroyed (actually, current->thread.current_ds)
  96  */
  97
  98 #if ((KERNEL_DS != 0) || (USER_DS == 0))
  99 # error Assembly macro kernel_ok fails
 100 #endif
 101         .macro  kernel_ok  at, sp, success
 102         get_fs  \at, \sp
 103         beqz    \at, \success
 104         .endm
 105
 106 /*
 107  * user_ok determines whether the access to user-space memory is allowed.
 108  * See the equivalent C-macro version below for clarity.
 109  *
 110  * On error, user_ok branches to a label indicated by parameter
 111  * <error>.  This implies that the macro falls through to the next
 112  * instruction on success.
 113  *
 114  * Note that while this macro can be used independently, we designed
 115  * in for optimal use in the access_ok macro below (i.e., we fall
 116  * through on success).
 117  *
 118  * On Entry:
 119  *      <aa>    register containing memory address
 120  *      <as>    register containing memory size
 121  *      <at>    temp register
 122  *      <error> label to branch to on error; implies fall-through
 123  *              macro on success
 124  * On Exit:
 125  *      <aa>    preserved
 126  *      <as>    preserved
 127  *      <at>    destroyed (actually, (TASK_SIZE + 1 - size))
 128  */
 129         .macro  user_ok aa, as, at, error
 130         movi    \at, __XTENSA_UL_CONST(TASK_SIZE)
 131         bgeu    \as, \at, \error
 132         sub     \at, \at, \as
 133         bgeu    \aa, \at, \error
 134         .endm
 135
 136 /*
 137  * access_ok determines whether a memory access is allowed.  See the
 138  * equivalent C-macro version below for clarity.
 139  *
 140  * On error, access_ok branches to a label indicated by parameter
 141  * <error>.  This implies that the macro falls through to the next
 142  * instruction on success.
 143  *
 144  * Note that we assume success is the common case, and we optimize the
 145  * branch fall-through case on success.
 146  *
 147  * On Entry:
 148  *      <aa>    register containing memory address
 149  *      <as>    register containing memory size
 150  *      <at>    temp register
 151  *      <sp>
 152  *      <error> label to branch to on error; implies fall-through
 153  *              macro on success
 154  * On Exit:
 155  *      <aa>    preserved
 156  *      <as>    preserved
 157  *      <at>    destroyed
 158  */
 159         .macro  access_ok  aa, as, at, sp, error
 160         kernel_ok  \at, \sp, .Laccess_ok_\@
 161         user_ok    \aa, \as, \at, \error
 162 .Laccess_ok_\@:
 163         .endm
 164
 165 #else /* __ASSEMBLY__ not defined */
 166
 167 #include <linux/sched.h>
 168
 169 /*
 170  * The fs value determines whether argument validity checking should
 171  * be performed or not.  If get_fs() == USER_DS, checking is
 172  * performed, with get_fs() == KERNEL_DS, checking is bypassed.
 173  *
 174  * For historical reasons (Data Segment Register?), these macros are
 175  * grossly misnamed.
 176  */
 177
 178 #define KERNEL_DS       ((mm_segment_t) { 0 })
 179 #define USER_DS         ((mm_segment_t) { 1 })
 180
 181 #define get_ds()        (KERNEL_DS)
 182 #define get_fs()        (current->thread.current_ds)
 183 #define set_fs(val)     (current->thread.current_ds = (val))
 184
 185 #define segment_eq(a,b) ((a).seg == (b).seg)
 186
 187 #define __kernel_ok (segment_eq(get_fs(), KERNEL_DS))
 188 #define __user_ok(addr,size) \
 189                 (((size) <= TASK_SIZE)&&((addr) <= TASK_SIZE-(size)))
 190 #define __access_ok(addr,size) (__kernel_ok || __user_ok((addr),(size)))
 191 #define access_ok(type,addr,size) __access_ok((unsigned long)(addr),(size))
 192
 193 /*
 194  * These are the main single-value transfer routines.  They
 195  * automatically use the right size if we just have the right pointer
 196  * type.
 197  *
 198  * This gets kind of ugly. We want to return _two_ values in
 199  * "get_user()" and yet we don't want to do any pointers, because that
 200  * is too much of a performance impact. Thus we have a few rather ugly
 201  * macros here, and hide all the uglyness from the user.
 202  *
 203  * Careful to not
 204  * (a) re-use the arguments for side effects (sizeof is ok)
 205  * (b) require any knowledge of processes at this stage
 206  */
 207 #define put_user(x,ptr) __put_user_check((x),(ptr),sizeof(*(ptr)))
 208 #define get_user(x,ptr) __get_user_check((x),(ptr),sizeof(*(ptr)))
 209
 210 /*
 211  * The "__xxx" versions of the user access functions are versions that
 212  * do not verify the address space, that must have been done previously
 213  * with a separate "access_ok()" call (this is used when we do multiple
 214  * accesses to the same area of user memory).
 215  */
 216 #define __put_user(x,ptr) __put_user_nocheck((x),(ptr),sizeof(*(ptr)))
 217 #define __get_user(x,ptr) __get_user_nocheck((x),(ptr),sizeof(*(ptr)))
 218
 219
 220 extern long __put_user_bad(void);
 221
 222 #define __put_user_nocheck(x,ptr,size)                  \
 223 ({                                                      \
 224         long __pu_err;                                  \
 225         __put_user_size((x),(ptr),(size),__pu_err);     \
 226         __pu_err;                                       \
 227 })
 228
 229 #define __put_user_check(x,ptr,size)                            \
 230 ({                                                              \
 231         long __pu_err = -EFAULT;                                \
 232         __typeof__(*(ptr)) *__pu_addr = (ptr);                  \
 233         if (access_ok(VERIFY_WRITE,__pu_addr,size))             \
 234                 __put_user_size((x),__pu_addr,(size),__pu_err); \
 235         __pu_err;                                               \
 236 })
 237
 238 #define __put_user_size(x,ptr,size,retval)                              \
 239 do {                                                                    \
 240         int __cb;                                                       \
 241         retval = 0;                                                     \
 242         switch (size) {                                                 \
 243         case 1: __put_user_asm(x,ptr,retval,1,"s8i",__cb);  break;      \
 244         case 2: __put_user_asm(x,ptr,retval,2,"s16i",__cb); break;      \
 245         case 4: __put_user_asm(x,ptr,retval,4,"s32i",__cb); break;      \
 246         case 8: {                                                       \
 247                      __typeof__(*ptr) __v64 = x;                        \
 248                      retval = __copy_to_user(ptr,&__v64,8);             \
 249                      break;                                             \
 250                 }                                                       \
 251         default: __put_user_bad();                                      \
 252         }                                                               \
 253 } while (0)
 254
 255
 256 /*
 257  * Consider a case of a user single load/store would cause both an
 258  * unaligned exception and an MMU-related exception (unaligned
 259  * exceptions happen first):
 260  *
 261  * User code passes a bad variable ptr to a system call.
 262  * Kernel tries to access the variable.
 263  * Unaligned exception occurs.
 264  * Unaligned exception handler tries to make aligned accesses.
 265  * Double exception occurs for MMU-related cause (e.g., page not mapped).
 266  * do_page_fault() thinks the fault address belongs to the kernel, not the
 267  * user, and panics.
 268  *
 269  * The kernel currently prohibits user unaligned accesses.  We use the
 270  * __check_align_* macros to check for unaligned addresses before
 271  * accessing user space so we don't crash the kernel.  Both
 272  * __put_user_asm and __get_user_asm use these alignment macros, so
 273  * macro-specific labels such as 0f, 1f, %0, %2, and %3 must stay in
 274  * sync.
 275  */
 276
 277 #define __check_align_1  ""
 278
 279 #define __check_align_2                         \
 280         "   _bbci.l %3,  0, 1f          \n"     \
 281         "   movi    %0, %4              \n"     \
 282         "   _j      2f                  \n"
 283
 284 #define __check_align_4                         \
 285         "   _bbsi.l %3,  0, 0f          \n"     \
 286         "   _bbci.l %3,  1, 1f          \n"     \
 287         "0: movi    %0, %4              \n"     \
 288         "   _j      2f                  \n"
 289
 290
 291 /*
 292  * We don't tell gcc that we are accessing memory, but this is OK
 293  * because we do not write to any memory gcc knows about, so there
 294  * are no aliasing issues.
 295  *
 296  * WARNING: If you modify this macro at all, verify that the
 297  * __check_align_* macros still work.
 298  */
 299 #define __put_user_asm(x, addr, err, align, insn, cb)   \
 300 __asm__ __volatile__(                                   \
 301         __check_align_##align                           \
 302         "1: "insn"  %2, %3, 0           \n"             \
 303         "2:                             \n"             \
 304         "   .section  .fixup,\"ax\"     \n"             \
 305         "   .align 4                    \n"             \
 306         "4:                             \n"             \
 307         "   .long  2b                   \n"             \
 308         "5:                             \n"             \
 309         "   l32r   %1, 4b               \n"             \
 310         "   movi   %0, %4               \n"             \
 311         "   jx     %1                   \n"             \
 312         "   .previous                   \n"             \
 313         "   .section  __ex_table,\"a\"  \n"             \
 314         "   .long       1b, 5b          \n"             \
 315         "   .previous"                                  \
 316         :"=r" (err), "=r" (cb)                          \
 317         :"r" ((int)(x)), "r" (addr), "i" (-EFAULT), "0" (err))
 318
 319 #define __get_user_nocheck(x,ptr,size)                          \
 320 ({                                                              \
 321         long __gu_err, __gu_val;                                \
 322         __get_user_size(__gu_val,(ptr),(size),__gu_err);        \
 323         (x) = (__typeof__(*(ptr)))__gu_val;                     \
 324         __gu_err;                                               \
 325 })
 326
 327 #define __get_user_check(x,ptr,size)                                    \
 328 ({                                                                      \
 329         long __gu_err = -EFAULT, __gu_val = 0;                          \
 330         const __typeof__(*(ptr)) *__gu_addr = (ptr);                    \
 331         if (access_ok(VERIFY_READ,__gu_addr,size))                      \
 332                 __get_user_size(__gu_val,__gu_addr,(size),__gu_err);    \
 333         (x) = (__typeof__(*(ptr)))__gu_val;                             \
 334         __gu_err;                                                       \
 335 })
 336
 337 extern long __get_user_bad(void);
 338
 339 #define __get_user_size(x,ptr,size,retval)                              \
 340 do {                                                                    \
 341         int __cb;                                                       \
 342         retval = 0;                                                     \
 343         switch (size) {                                                 \
 344         case 1: __get_user_asm(x,ptr,retval,1,"l8ui",__cb);  break;     \
 345         case 2: __get_user_asm(x,ptr,retval,2,"l16ui",__cb); break;     \
 346         case 4: __get_user_asm(x,ptr,retval,4,"l32i",__cb);  break;     \
 347         case 8: retval = __copy_from_user(&x,ptr,8);    break;  \
 348         default: (x) = __get_user_bad();                                \
 349         }                                                               \
 350 } while (0)
 351
 352
 353 /*
 354  * WARNING: If you modify this macro at all, verify that the
 355  * __check_align_* macros still work.
 356  */
 357 #define __get_user_asm(x, addr, err, align, insn, cb) \
 358 __asm__ __volatile__(                   \
 359         __check_align_##align                   \
 360         "1: "insn"  %2, %3, 0           \n"     \
 361         "2:                             \n"     \
 362         "   .section  .fixup,\"ax\"     \n"     \
 363         "   .align 4                    \n"     \
 364         "4:                             \n"     \
 365         "   .long  2b                   \n"     \
 366         "5:                             \n"     \
 367         "   l32r   %1, 4b               \n"     \
 368         "   movi   %2, 0                \n"     \
 369         "   movi   %0, %4               \n"     \
 370         "   jx     %1                   \n"     \
 371         "   .previous                   \n"     \
 372         "   .section  __ex_table,\"a\"  \n"     \
 373         "   .long       1b, 5b          \n"     \
 374         "   .previous"                          \
 375         :"=r" (err), "=r" (cb), "=r" (x)        \
 376         :"r" (addr), "i" (-EFAULT), "0" (err))
 377
 378
 379 /*
 380  * Copy to/from user space
 381  */
 382
 383 /*
 384  * We use a generic, arbitrary-sized copy subroutine.  The Xtensa
 385  * architecture would cause heavy code bloat if we tried to inline
 386  * these functions and provide __constant_copy_* equivalents like the
 387  * i386 versions.  __xtensa_copy_user is quite efficient.  See the
 388  * .fixup section of __xtensa_copy_user for a discussion on the
 389  * X_zeroing equivalents for Xtensa.
 390  */
 391
 392 extern unsigned __xtensa_copy_user(void *to, const void *from, unsigned n);
 393 #define __copy_user(to,from,size) __xtensa_copy_user(to,from,size)
 394
 395
 396 static inline unsigned long
 397 __generic_copy_from_user_nocheck(void *to, const void *from, unsigned long n)
 398 {
 399         return __copy_user(to,from,n);
 400 }
 401
 402 static inline unsigned long
 403 __generic_copy_to_user_nocheck(void *to, const void *from, unsigned long n)
 404 {
 405         return __copy_user(to,from,n);
 406 }
 407
 408 static inline unsigned long
 409 __generic_copy_to_user(void *to, const void *from, unsigned long n)
 410 {
 411         prefetch(from);
 412         if (access_ok(VERIFY_WRITE, to, n))
 413                 return __copy_user(to,from,n);
 414         return n;
 415 }
 416
 417 static inline unsigned long
 418 __generic_copy_from_user(void *to, const void *from, unsigned long n)
 419 {
 420         prefetchw(to);
 421         if (access_ok(VERIFY_READ, from, n))
 422                 return __copy_user(to,from,n);
 423         else
 424                 memset(to, 0, n);
 425         return n;
 426 }
 427
 428 #define copy_to_user(to,from,n) __generic_copy_to_user((to),(from),(n))
 429 #define copy_from_user(to,from,n) __generic_copy_from_user((to),(from),(n))
 430 #define __copy_to_user(to,from,n) \
 431         __generic_copy_to_user_nocheck((to),(from),(n))
 432 #define __copy_from_user(to,from,n) \
 433         __generic_copy_from_user_nocheck((to),(from),(n))
 434 #define __copy_to_user_inatomic __copy_to_user
 435 #define __copy_from_user_inatomic __copy_from_user
 436
 437
 438 /*
 439  * We need to return the number of bytes not cleared.  Our memset()
 440  * returns zero if a problem occurs while accessing user-space memory.
 441  * In that event, return no memory cleared.  Otherwise, zero for
 442  * success.
 443  */
 444
 445 static inline unsigned long
 446 __xtensa_clear_user(void *addr, unsigned long size)
 447 {
 448         if ( ! memset(addr, 0, size) )
 449                 return size;
 450         return 0;
 451 }
 452
 453 static inline unsigned long
 454 clear_user(void *addr, unsigned long size)
 455 {
 456         if (access_ok(VERIFY_WRITE, addr, size))
 457                 return __xtensa_clear_user(addr, size);
 458         return size ? -EFAULT : 0;
 459 }
 460
 461 #define __clear_user  __xtensa_clear_user
 462
 463
 464 extern long __strncpy_user(char *, const char *, long);
 465 #define __strncpy_from_user __strncpy_user
 466
 467 static inline long
 468 strncpy_from_user(char *dst, const char *src, long count)
 469 {
 470         if (access_ok(VERIFY_READ, src, 1))
 471                 return __strncpy_from_user(dst, src, count);
 472         return -EFAULT;
 473 }
 474
 475
 476 #define strlen_user(str) strnlen_user((str), TASK_SIZE - 1)
 477
 478 /*
 479  * Return the size of a string (including the ending 0!)
 480  */
 481 extern long __strnlen_user(const char *, long);
 482
 483 static inline long strnlen_user(const char *str, long len)
 484 {
 485         unsigned long top = __kernel_ok ? ~0UL : TASK_SIZE - 1;
 486
 487         if ((unsigned long)str > top)
 488                 return 0;
 489         return __strnlen_user(str, len);
 490 }
 491
 492
 493 struct exception_table_entry
 494 {
 495         unsigned long insn, fixup;
 496 };
 497
 498 /* Returns 0 if exception not found and fixup.unit otherwise.  */
 499
 500 extern unsigned long search_exception_table(unsigned long addr);
 501 extern void sort_exception_table(void);
 502
 503 /* Returns the new pc */
 504 #define fixup_exception(map_reg, fixup_unit, pc)                \
 505 ({                                                              \
 506         fixup_unit;                                             \
 507 })
 508
 509 #endif  /* __ASSEMBLY__ */
 510 #endif  /* _XTENSA_UACCESS_H */