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