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/prefetch.h>
  20 #include <asm/types.h>
  21
  22 /*
  23  * The fs value determines whether argument validity checking should
  24  * be performed or not.  If get_fs() == USER_DS, checking is
  25  * performed, with get_fs() == KERNEL_DS, checking is bypassed.
  26  *
  27  * For historical reasons (Data Segment Register?), these macros are
  28  * grossly misnamed.
  29  */
  30
  31 #define KERNEL_DS       ((mm_segment_t) { 0 })
  32 #define USER_DS         ((mm_segment_t) { 1 })
  33
  34 #define get_ds()        (KERNEL_DS)
  35 #define get_fs()        (current->thread.current_ds)
  36 #define set_fs(val)     (current->thread.current_ds = (val))
  37
  38 #define segment_eq(a, b)        ((a).seg == (b).seg)
  39
  40 #define __kernel_ok (uaccess_kernel())
  41 #define __user_ok(addr, size) \
  42                 (((size) <= TASK_SIZE)&&((addr) <= TASK_SIZE-(size)))
  43 #define __access_ok(addr, size) (__kernel_ok || __user_ok((addr), (size)))
  44 #define access_ok(type, addr, size) __access_ok((unsigned long)(addr), (size))
  45
  46 /*
  47  * These are the main single-value transfer routines.  They
  48  * automatically use the right size if we just have the right pointer
  49  * type.
  50  *
  51  * This gets kind of ugly. We want to return _two_ values in
  52  * "get_user()" and yet we don't want to do any pointers, because that
  53  * is too much of a performance impact. Thus we have a few rather ugly
  54  * macros here, and hide all the uglyness from the user.
  55  *
  56  * Careful to not
  57  * (a) re-use the arguments for side effects (sizeof is ok)
  58  * (b) require any knowledge of processes at this stage
  59  */
  60 #define put_user(x, ptr)        __put_user_check((x), (ptr), sizeof(*(ptr)))
  61 #define get_user(x, ptr) __get_user_check((x), (ptr), sizeof(*(ptr)))
  62
  63 /*
  64  * The "__xxx" versions of the user access functions are versions that
  65  * do not verify the address space, that must have been done previously
  66  * with a separate "access_ok()" call (this is used when we do multiple
  67  * accesses to the same area of user memory).
  68  */
  69 #define __put_user(x, ptr) __put_user_nocheck((x), (ptr), sizeof(*(ptr)))
  70 #define __get_user(x, ptr) __get_user_nocheck((x), (ptr), sizeof(*(ptr)))
  71
  72
  73 extern long __put_user_bad(void);
  74
  75 #define __put_user_nocheck(x, ptr, size)                \
  76 ({                                                      \
  77         long __pu_err;                                  \
  78         __put_user_size((x), (ptr), (size), __pu_err);  \
  79         __pu_err;                                       \
  80 })
  81
  82 #define __put_user_check(x, ptr, size)                                  \
  83 ({                                                                      \
  84         long __pu_err = -EFAULT;                                        \
  85         __typeof__(*(ptr)) *__pu_addr = (ptr);                          \
  86         if (access_ok(VERIFY_WRITE, __pu_addr, size))                   \
  87                 __put_user_size((x), __pu_addr, (size), __pu_err);      \
  88         __pu_err;                                                       \
  89 })
  90
  91 #define __put_user_size(x, ptr, size, retval)                           \
  92 do {                                                                    \
  93         int __cb;                                                       \
  94         retval = 0;                                                     \
  95         switch (size) {                                                 \
  96         case 1: __put_user_asm(x, ptr, retval, 1, "s8i", __cb);  break; \
  97         case 2: __put_user_asm(x, ptr, retval, 2, "s16i", __cb); break; \
  98         case 4: __put_user_asm(x, ptr, retval, 4, "s32i", __cb); break; \
  99         case 8: {                                                       \
 100                      __typeof__(*ptr) __v64 = x;                        \
 101                      retval = __copy_to_user(ptr, &__v64, 8);           \
 102                      break;                                             \
 103                 }                                                       \
 104         default: __put_user_bad();                                      \
 105         }                                                               \
 106 } while (0)
 107
 108
 109 /*
 110  * Consider a case of a user single load/store would cause both an
 111  * unaligned exception and an MMU-related exception (unaligned
 112  * exceptions happen first):
 113  *
 114  * User code passes a bad variable ptr to a system call.
 115  * Kernel tries to access the variable.
 116  * Unaligned exception occurs.
 117  * Unaligned exception handler tries to make aligned accesses.
 118  * Double exception occurs for MMU-related cause (e.g., page not mapped).
 119  * do_page_fault() thinks the fault address belongs to the kernel, not the
 120  * user, and panics.
 121  *
 122  * The kernel currently prohibits user unaligned accesses.  We use the
 123  * __check_align_* macros to check for unaligned addresses before
 124  * accessing user space so we don't crash the kernel.  Both
 125  * __put_user_asm and __get_user_asm use these alignment macros, so
 126  * macro-specific labels such as 0f, 1f, %0, %2, and %3 must stay in
 127  * sync.
 128  */
 129
 130 #define __check_align_1  ""
 131
 132 #define __check_align_2                         \
 133         "   _bbci.l %3,  0, 1f          \n"     \
 134         "   movi    %0, %4              \n"     \
 135         "   _j      2f                  \n"
 136
 137 #define __check_align_4                         \
 138         "   _bbsi.l %3,  0, 0f          \n"     \
 139         "   _bbci.l %3,  1, 1f          \n"     \
 140         "0: movi    %0, %4              \n"     \
 141         "   _j      2f                  \n"
 142
 143
 144 /*
 145  * We don't tell gcc that we are accessing memory, but this is OK
 146  * because we do not write to any memory gcc knows about, so there
 147  * are no aliasing issues.
 148  *
 149  * WARNING: If you modify this macro at all, verify that the
 150  * __check_align_* macros still work.
 151  */
 152 #define __put_user_asm(x, addr, err, align, insn, cb)   \
 153 __asm__ __volatile__(                                   \
 154         __check_align_##align                           \
 155         "1: "insn"  %2, %3, 0           \n"             \
 156         "2:                             \n"             \
 157         "   .section  .fixup,\"ax\"     \n"             \
 158         "   .align 4                    \n"             \
 159         "4:                             \n"             \
 160         "   .long  2b                   \n"             \
 161         "5:                             \n"             \
 162         "   l32r   %1, 4b               \n"             \
 163         "   movi   %0, %4               \n"             \
 164         "   jx     %1                   \n"             \
 165         "   .previous                   \n"             \
 166         "   .section  __ex_table,\"a\"  \n"             \
 167         "   .long       1b, 5b          \n"             \
 168         "   .previous"                                  \
 169         :"=r" (err), "=r" (cb)                          \
 170         :"r" ((int)(x)), "r" (addr), "i" (-EFAULT), "0" (err))
 171
 172 #define __get_user_nocheck(x, ptr, size)                        \
 173 ({                                                              \
 174         long __gu_err, __gu_val;                                \
 175         __get_user_size(__gu_val, (ptr), (size), __gu_err);     \
 176         (x) = (__force __typeof__(*(ptr)))__gu_val;             \
 177         __gu_err;                                               \
 178 })
 179
 180 #define __get_user_check(x, ptr, size)                                  \
 181 ({                                                                      \
 182         long __gu_err = -EFAULT, __gu_val = 0;                          \
 183         const __typeof__(*(ptr)) *__gu_addr = (ptr);                    \
 184         if (access_ok(VERIFY_READ, __gu_addr, size))                    \
 185                 __get_user_size(__gu_val, __gu_addr, (size), __gu_err); \
 186         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 187         __gu_err;                                                       \
 188 })
 189
 190 extern long __get_user_bad(void);
 191
 192 #define __get_user_size(x, ptr, size, retval)                           \
 193 do {                                                                    \
 194         int __cb;                                                       \
 195         retval = 0;                                                     \
 196         switch (size) {                                                 \
 197         case 1: __get_user_asm(x, ptr, retval, 1, "l8ui", __cb);  break;\
 198         case 2: __get_user_asm(x, ptr, retval, 2, "l16ui", __cb); break;\
 199         case 4: __get_user_asm(x, ptr, retval, 4, "l32i", __cb);  break;\
 200         case 8: retval = __copy_from_user(&x, ptr, 8);    break;        \
 201         default: (x) = __get_user_bad();                                \
 202         }                                                               \
 203 } while (0)
 204
 205
 206 /*
 207  * WARNING: If you modify this macro at all, verify that the
 208  * __check_align_* macros still work.
 209  */
 210 #define __get_user_asm(x, addr, err, align, insn, cb) \
 211 __asm__ __volatile__(                   \
 212         __check_align_##align                   \
 213         "1: "insn"  %2, %3, 0           \n"     \
 214         "2:                             \n"     \
 215         "   .section  .fixup,\"ax\"     \n"     \
 216         "   .align 4                    \n"     \
 217         "4:                             \n"     \
 218         "   .long  2b                   \n"     \
 219         "5:                             \n"     \
 220         "   l32r   %1, 4b               \n"     \
 221         "   movi   %2, 0                \n"     \
 222         "   movi   %0, %4               \n"     \
 223         "   jx     %1                   \n"     \
 224         "   .previous                   \n"     \
 225         "   .section  __ex_table,\"a\"  \n"     \
 226         "   .long       1b, 5b          \n"     \
 227         "   .previous"                          \
 228         :"=r" (err), "=r" (cb), "=r" (x)        \
 229         :"r" (addr), "i" (-EFAULT), "0" (err))
 230
 231
 232 /*
 233  * Copy to/from user space
 234  */
 235
 236 /*
 237  * We use a generic, arbitrary-sized copy subroutine.  The Xtensa
 238  * architecture would cause heavy code bloat if we tried to inline
 239  * these functions and provide __constant_copy_* equivalents like the
 240  * i386 versions.  __xtensa_copy_user is quite efficient.  See the
 241  * .fixup section of __xtensa_copy_user for a discussion on the
 242  * X_zeroing equivalents for Xtensa.
 243  */
 244
 245 extern unsigned __xtensa_copy_user(void *to, const void *from, unsigned n);
 246 #define __copy_user(to, from, size) __xtensa_copy_user(to, from, size)
 247
 248
 249 static inline unsigned long
 250 __generic_copy_from_user_nocheck(void *to, const void *from, unsigned long n)
 251 {
 252         return __copy_user(to, from, n);
 253 }
 254
 255 static inline unsigned long
 256 __generic_copy_to_user_nocheck(void *to, const void *from, unsigned long n)
 257 {
 258         return __copy_user(to, from, n);
 259 }
 260
 261 static inline unsigned long
 262 __generic_copy_to_user(void *to, const void *from, unsigned long n)
 263 {
 264         prefetch(from);
 265         if (access_ok(VERIFY_WRITE, to, n))
 266                 return __copy_user(to, from, n);
 267         return n;
 268 }
 269
 270 static inline unsigned long
 271 __generic_copy_from_user(void *to, const void *from, unsigned long n)
 272 {
 273         prefetchw(to);
 274         if (access_ok(VERIFY_READ, from, n))
 275                 return __copy_user(to, from, n);
 276         else
 277                 memset(to, 0, n);
 278         return n;
 279 }
 280
 281 #define copy_to_user(to, from, n) __generic_copy_to_user((to), (from), (n))
 282 #define copy_from_user(to, from, n) __generic_copy_from_user((to), (from), (n))
 283 #define __copy_to_user(to, from, n) \
 284         __generic_copy_to_user_nocheck((to), (from), (n))
 285 #define __copy_from_user(to, from, n) \
 286         __generic_copy_from_user_nocheck((to), (from), (n))
 287 #define __copy_to_user_inatomic __copy_to_user
 288 #define __copy_from_user_inatomic __copy_from_user
 289
 290
 291 /*
 292  * We need to return the number of bytes not cleared.  Our memset()
 293  * returns zero if a problem occurs while accessing user-space memory.
 294  * In that event, return no memory cleared.  Otherwise, zero for
 295  * success.
 296  */
 297
 298 static inline unsigned long
 299 __xtensa_clear_user(void *addr, unsigned long size)
 300 {
 301         if ( ! memset(addr, 0, size) )
 302                 return size;
 303         return 0;
 304 }
 305
 306 static inline unsigned long
 307 clear_user(void *addr, unsigned long size)
 308 {
 309         if (access_ok(VERIFY_WRITE, addr, size))
 310                 return __xtensa_clear_user(addr, size);
 311         return size ? -EFAULT : 0;
 312 }
 313
 314 #define __clear_user  __xtensa_clear_user
 315
 316
 317 extern long __strncpy_user(char *, const char *, long);
 318 #define __strncpy_from_user __strncpy_user
 319
 320 static inline long
 321 strncpy_from_user(char *dst, const char *src, long count)
 322 {
 323         if (access_ok(VERIFY_READ, src, 1))
 324                 return __strncpy_from_user(dst, src, count);
 325         return -EFAULT;
 326 }
 327
 328
 329 #define strlen_user(str) strnlen_user((str), TASK_SIZE - 1)
 330
 331 /*
 332  * Return the size of a string (including the ending 0!)
 333  */
 334 extern long __strnlen_user(const char *, long);
 335
 336 static inline long strnlen_user(const char *str, long len)
 337 {
 338         unsigned long top = __kernel_ok ? ~0UL : TASK_SIZE - 1;
 339
 340         if ((unsigned long)str > top)
 341                 return 0;
 342         return __strnlen_user(str, len);
 343 }
 344
 345
 346 struct exception_table_entry
 347 {
 348         unsigned long insn, fixup;
 349 };
 350
 351 #endif  /* _XTENSA_UACCESS_H */