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