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