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) (((size) <= TASK_SIZE)&&((addr) <= TASK_SIZE-(size)))
 184 #define __access_ok(addr,size) (__kernel_ok || __user_ok((addr),(size)))
 185 #define access_ok(type,addr,size) __access_ok((unsigned long)(addr),(size))
 186
 187 /*
 188  * These are the main single-value transfer routines.  They
 189  * automatically use the right size if we just have the right pointer
 190  * type.
 191  *
 192  * This gets kind of ugly. We want to return _two_ values in
 193  * "get_user()" and yet we don't want to do any pointers, because that
 194  * is too much of a performance impact. Thus we have a few rather ugly
 195  * macros here, and hide all the uglyness from the user.
 196  *
 197  * Careful to not
 198  * (a) re-use the arguments for side effects (sizeof is ok)
 199  * (b) require any knowledge of processes at this stage
 200  */
 201 #define put_user(x,ptr) __put_user_check((x),(ptr),sizeof(*(ptr)))
 202 #define get_user(x,ptr) __get_user_check((x),(ptr),sizeof(*(ptr)))
 203
 204 /*
 205  * The "__xxx" versions of the user access functions are versions that
 206  * do not verify the address space, that must have been done previously
 207  * with a separate "access_ok()" call (this is used when we do multiple
 208  * accesses to the same area of user memory).
 209  */
 210 #define __put_user(x,ptr) __put_user_nocheck((x),(ptr),sizeof(*(ptr)))
 211 #define __get_user(x,ptr) __get_user_nocheck((x),(ptr),sizeof(*(ptr)))
 212
 213
 214 extern long __put_user_bad(void);
 215
 216 #define __put_user_nocheck(x,ptr,size)                  \
 217 ({                                                      \
 218         long __pu_err;                                  \
 219         __put_user_size((x),(ptr),(size),__pu_err);     \
 220         __pu_err;                                       \
 221 })
 222
 223 #define __put_user_check(x,ptr,size)                            \
 224 ({                                                              \
 225         long __pu_err = -EFAULT;                                \
 226         __typeof__(*(ptr)) *__pu_addr = (ptr);                  \
 227         if (access_ok(VERIFY_WRITE,__pu_addr,size))             \
 228                 __put_user_size((x),__pu_addr,(size),__pu_err); \
 229         __pu_err;                                               \
 230 })
 231
 232 #define __put_user_size(x,ptr,size,retval)                              \
 233 do {                                                                    \
 234         int __cb;                                                       \
 235         retval = 0;                                                     \
 236         switch (size) {                                                 \
 237         case 1: __put_user_asm(x,ptr,retval,1,"s8i",__cb);  break;      \
 238         case 2: __put_user_asm(x,ptr,retval,2,"s16i",__cb); break;      \
 239         case 4: __put_user_asm(x,ptr,retval,4,"s32i",__cb); break;      \
 240         case 8: {                                                       \
 241                      __typeof__(*ptr) __v64 = x;                        \
 242                      retval = __copy_to_user(ptr,&__v64,8);             \
 243                      break;                                             \
 244                 }                                                       \
 245         default: __put_user_bad();                                      \
 246         }                                                               \
 247 } while (0)
 248
 249
 250 /*
 251  * Consider a case of a user single load/store would cause both an
 252  * unaligned exception and an MMU-related exception (unaligned
 253  * exceptions happen first):
 254  *
 255  * User code passes a bad variable ptr to a system call.
 256  * Kernel tries to access the variable.
 257  * Unaligned exception occurs.
 258  * Unaligned exception handler tries to make aligned accesses.
 259  * Double exception occurs for MMU-related cause (e.g., page not mapped).
 260  * do_page_fault() thinks the fault address belongs to the kernel, not the
 261  * user, and panics.
 262  *
 263  * The kernel currently prohibits user unaligned accesses.  We use the
 264  * __check_align_* macros to check for unaligned addresses before
 265  * accessing user space so we don't crash the kernel.  Both
 266  * __put_user_asm and __get_user_asm use these alignment macros, so
 267  * macro-specific labels such as 0f, 1f, %0, %2, and %3 must stay in
 268  * sync.
 269  */
 270
 271 #define __check_align_1  ""
 272
 273 #define __check_align_2                         \
 274         "   _bbci.l %3,  0, 1f          \n"     \
 275         "   movi    %0, %4              \n"     \
 276         "   _j      2f                  \n"
 277
 278 #define __check_align_4                         \
 279         "   _bbsi.l %3,  0, 0f          \n"     \
 280         "   _bbci.l %3,  1, 1f          \n"     \
 281         "0: movi    %0, %4              \n"     \
 282         "   _j      2f                  \n"
 283
 284
 285 /*
 286  * We don't tell gcc that we are accessing memory, but this is OK
 287  * because we do not write to any memory gcc knows about, so there
 288  * are no aliasing issues.
 289  *
 290  * WARNING: If you modify this macro at all, verify that the
 291  * __check_align_* macros still work.
 292  */
 293 #define __put_user_asm(x, addr, err, align, insn, cb)   \
 294    __asm__ __volatile__(                                \
 295         __check_align_##align                           \
 296         "1: "insn"  %2, %3, 0           \n"             \
 297         "2:                             \n"             \
 298         "   .section  .fixup,\"ax\"     \n"             \
 299         "   .align 4                    \n"             \
 300         "4:                             \n"             \
 301         "   .long  2b                   \n"             \
 302         "5:                             \n"             \
 303         "   l32r   %1, 4b               \n"             \
 304         "   movi   %0, %4               \n"             \
 305         "   jx     %1                   \n"             \
 306         "   .previous                   \n"             \
 307         "   .section  __ex_table,\"a\"  \n"             \
 308         "   .long       1b, 5b          \n"             \
 309         "   .previous"                                  \
 310         :"=r" (err), "=r" (cb)                          \
 311         :"r" ((int)(x)), "r" (addr), "i" (-EFAULT), "0" (err))
 312
 313 #define __get_user_nocheck(x,ptr,size)                          \
 314 ({                                                              \
 315         long __gu_err, __gu_val;                                \
 316         __get_user_size(__gu_val,(ptr),(size),__gu_err);        \
 317         (x) = (__typeof__(*(ptr)))__gu_val;                     \
 318         __gu_err;                                               \
 319 })
 320
 321 #define __get_user_check(x,ptr,size)                                    \
 322 ({                                                                      \
 323         long __gu_err = -EFAULT, __gu_val = 0;                          \
 324         const __typeof__(*(ptr)) *__gu_addr = (ptr);                    \
 325         if (access_ok(VERIFY_READ,__gu_addr,size))                      \
 326                 __get_user_size(__gu_val,__gu_addr,(size),__gu_err);    \
 327         (x) = (__typeof__(*(ptr)))__gu_val;                             \
 328         __gu_err;                                                       \
 329 })
 330
 331 extern long __get_user_bad(void);
 332
 333 #define __get_user_size(x,ptr,size,retval)                              \
 334 do {                                                                    \
 335         int __cb;                                                       \
 336         retval = 0;                                                     \
 337         switch (size) {                                                 \
 338           case 1: __get_user_asm(x,ptr,retval,1,"l8ui",__cb);  break;   \
 339           case 2: __get_user_asm(x,ptr,retval,2,"l16ui",__cb); break;   \
 340           case 4: __get_user_asm(x,ptr,retval,4,"l32i",__cb);  break;   \
 341           case 8: retval = __copy_from_user(&x,ptr,8);    break;        \
 342           default: (x) = __get_user_bad();                              \
 343         }                                                               \
 344 } while (0)
 345
 346
 347 /*
 348  * WARNING: If you modify this macro at all, verify that the
 349  * __check_align_* macros still work.
 350  */
 351 #define __get_user_asm(x, addr, err, align, insn, cb) \
 352    __asm__ __volatile__(                        \
 353         __check_align_##align                   \
 354         "1: "insn"  %2, %3, 0           \n"     \
 355         "2:                             \n"     \
 356         "   .section  .fixup,\"ax\"     \n"     \
 357         "   .align 4                    \n"     \
 358         "4:                             \n"     \
 359         "   .long  2b                   \n"     \
 360         "5:                             \n"     \
 361         "   l32r   %1, 4b               \n"     \
 362         "   movi   %2, 0                \n"     \
 363         "   movi   %0, %4               \n"     \
 364         "   jx     %1                   \n"     \
 365         "   .previous                   \n"     \
 366         "   .section  __ex_table,\"a\"  \n"     \
 367         "   .long       1b, 5b          \n"     \
 368         "   .previous"                          \
 369         :"=r" (err), "=r" (cb), "=r" (x)        \
 370         :"r" (addr), "i" (-EFAULT), "0" (err))
 371
 372
 373 /*
 374  * Copy to/from user space
 375  */
 376
 377 /*
 378  * We use a generic, arbitrary-sized copy subroutine.  The Xtensa
 379  * architecture would cause heavy code bloat if we tried to inline
 380  * these functions and provide __constant_copy_* equivalents like the
 381  * i386 versions.  __xtensa_copy_user is quite efficient.  See the
 382  * .fixup section of __xtensa_copy_user for a discussion on the
 383  * X_zeroing equivalents for Xtensa.
 384  */
 385
 386 extern unsigned __xtensa_copy_user(void *to, const void *from, unsigned n);
 387 #define __copy_user(to,from,size) __xtensa_copy_user(to,from,size)
 388
 389
 390 static inline unsigned long
 391 __generic_copy_from_user_nocheck(void *to, const void *from, unsigned long n)
 392 {
 393         return __copy_user(to,from,n);
 394 }
 395
 396 static inline unsigned long
 397 __generic_copy_to_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(void *to, const void *from, unsigned long n)
 404 {
 405         prefetch(from);
 406         if (access_ok(VERIFY_WRITE, to, n))
 407                 return __copy_user(to,from,n);
 408         return n;
 409 }
 410
 411 static inline unsigned long
 412 __generic_copy_from_user(void *to, const void *from, unsigned long n)
 413 {
 414         prefetchw(to);
 415         if (access_ok(VERIFY_READ, from, n))
 416                 return __copy_user(to,from,n);
 417         else
 418                 memset(to, 0, n);
 419         return n;
 420 }
 421
 422 #define copy_to_user(to,from,n) __generic_copy_to_user((to),(from),(n))
 423 #define copy_from_user(to,from,n) __generic_copy_from_user((to),(from),(n))
 424 #define __copy_to_user(to,from,n) __generic_copy_to_user_nocheck((to),(from),(n))
 425 #define __copy_from_user(to,from,n) __generic_copy_from_user_nocheck((to),(from),(n))
 426 #define __copy_to_user_inatomic __copy_to_user
 427 #define __copy_from_user_inatomic __copy_from_user
 428
 429
 430 /*
 431  * We need to return the number of bytes not cleared.  Our memset()
 432  * returns zero if a problem occurs while accessing user-space memory.
 433  * In that event, return no memory cleared.  Otherwise, zero for
 434  * success.
 435  */
 436
 437 static inline unsigned long
 438 __xtensa_clear_user(void *addr, unsigned long size)
 439 {
 440         if ( ! memset(addr, 0, size) )
 441                 return size;
 442         return 0;
 443 }
 444
 445 static inline unsigned long
 446 clear_user(void *addr, unsigned long size)
 447 {
 448         if (access_ok(VERIFY_WRITE, addr, size))
 449                 return __xtensa_clear_user(addr, size);
 450         return size ? -EFAULT : 0;
 451 }
 452
 453 #define __clear_user  __xtensa_clear_user
 454
 455
 456 extern long __strncpy_user(char *, const char *, long);
 457 #define __strncpy_from_user __strncpy_user
 458
 459 static inline long
 460 strncpy_from_user(char *dst, const char *src, long count)
 461 {
 462         if (access_ok(VERIFY_READ, src, 1))
 463                 return __strncpy_from_user(dst, src, count);
 464         return -EFAULT;
 465 }
 466
 467
 468 #define strlen_user(str) strnlen_user((str), TASK_SIZE - 1)
 469
 470 /*
 471  * Return the size of a string (including the ending 0!)
 472  */
 473 extern long __strnlen_user(const char *, long);
 474
 475 static inline long strnlen_user(const char *str, long len)
 476 {
 477         unsigned long top = __kernel_ok ? ~0UL : TASK_SIZE - 1;
 478
 479         if ((unsigned long)str > top)
 480                 return 0;
 481         return __strnlen_user(str, len);
 482 }
 483
 484
 485 struct exception_table_entry
 486 {
 487         unsigned long insn, fixup;
 488 };
 489
 490 /* Returns 0 if exception not found and fixup.unit otherwise.  */
 491
 492 extern unsigned long search_exception_table(unsigned long addr);
 493 extern void sort_exception_table(void);
 494
 495 /* Returns the new pc */
 496 #define fixup_exception(map_reg, fixup_unit, pc)                \
 497 ({                                                              \
 498         fixup_unit;                                             \
 499 })
 500
 501 #endif  /* __ASSEMBLY__ */
 502 #endif  /* _XTENSA_UACCESS_H */