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