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 #include <asm/extable.h>
  22
  23 /*
  24  * The fs value determines whether argument validity checking should
  25  * be performed or not.  If get_fs() == USER_DS, checking is
  26  * performed, with get_fs() == KERNEL_DS, checking is bypassed.
  27  *
  28  * For historical reasons (Data Segment Register?), these macros are
  29  * grossly misnamed.
  30  */
  31
  32 #define KERNEL_DS       ((mm_segment_t) { 0 })
  33 #define USER_DS         ((mm_segment_t) { 1 })
  34
  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(addr, size) __access_ok((unsigned long)(addr), (size))
  45
  46 #define user_addr_max() (uaccess_kernel() ? ~0UL : TASK_SIZE)
  47
  48 /*
  49  * These are the main single-value transfer routines.  They
  50  * automatically use the right size if we just have the right pointer
  51  * type.
  52  *
  53  * This gets kind of ugly. We want to return _two_ values in
  54  * "get_user()" and yet we don't want to do any pointers, because that
  55  * is too much of a performance impact. Thus we have a few rather ugly
  56  * macros here, and hide all the uglyness from the user.
  57  *
  58  * Careful to not
  59  * (a) re-use the arguments for side effects (sizeof is ok)
  60  * (b) require any knowledge of processes at this stage
  61  */
  62 #define put_user(x, ptr)        __put_user_check((x), (ptr), sizeof(*(ptr)))
  63 #define get_user(x, ptr) __get_user_check((x), (ptr), sizeof(*(ptr)))
  64
  65 /*
  66  * The "__xxx" versions of the user access functions are versions that
  67  * do not verify the address space, that must have been done previously
  68  * with a separate "access_ok()" call (this is used when we do multiple
  69  * accesses to the same area of user memory).
  70  */
  71 #define __put_user(x, ptr) __put_user_nocheck((x), (ptr), sizeof(*(ptr)))
  72 #define __get_user(x, ptr) __get_user_nocheck((x), (ptr), sizeof(*(ptr)))
  73
  74
  75 extern long __put_user_bad(void);
  76
  77 #define __put_user_nocheck(x, ptr, size)                \
  78 ({                                                      \
  79         long __pu_err;                                  \
  80         __put_user_size((x), (ptr), (size), __pu_err);  \
  81         __pu_err;                                       \
  82 })
  83
  84 #define __put_user_check(x, ptr, size)                                  \
  85 ({                                                                      \
  86         long __pu_err = -EFAULT;                                        \
  87         __typeof__(*(ptr)) *__pu_addr = (ptr);                          \
  88         if (access_ok(__pu_addr, size))                 \
  89                 __put_user_size((x), __pu_addr, (size), __pu_err);      \
  90         __pu_err;                                                       \
  91 })
  92
  93 #define __put_user_size(x, ptr, size, retval)                           \
  94 do {                                                                    \
  95         int __cb;                                                       \
  96         retval = 0;                                                     \
  97         switch (size) {                                                 \
  98         case 1: __put_user_asm(x, ptr, retval, 1, "s8i", __cb);  break; \
  99         case 2: __put_user_asm(x, ptr, retval, 2, "s16i", __cb); break; \
 100         case 4: __put_user_asm(x, ptr, retval, 4, "s32i", __cb); break; \
 101         case 8: {                                                       \
 102                      __typeof__(*ptr) __v64 = x;                        \
 103                      retval = __copy_to_user(ptr, &__v64, 8) ? -EFAULT : 0;     \
 104                      break;                                             \
 105                 }                                                       \
 106         default: __put_user_bad();                                      \
 107         }                                                               \
 108 } while (0)
 109
 110
 111 /*
 112  * Consider a case of a user single load/store would cause both an
 113  * unaligned exception and an MMU-related exception (unaligned
 114  * exceptions happen first):
 115  *
 116  * User code passes a bad variable ptr to a system call.
 117  * Kernel tries to access the variable.
 118  * Unaligned exception occurs.
 119  * Unaligned exception handler tries to make aligned accesses.
 120  * Double exception occurs for MMU-related cause (e.g., page not mapped).
 121  * do_page_fault() thinks the fault address belongs to the kernel, not the
 122  * user, and panics.
 123  *
 124  * The kernel currently prohibits user unaligned accesses.  We use the
 125  * __check_align_* macros to check for unaligned addresses before
 126  * accessing user space so we don't crash the kernel.  Both
 127  * __put_user_asm and __get_user_asm use these alignment macros, so
 128  * macro-specific labels such as 0f, 1f, %0, %2, and %3 must stay in
 129  * sync.
 130  */
 131
 132 #define __check_align_1  ""
 133
 134 #define __check_align_2                         \
 135         "   _bbci.l %[mem] * 0, 1f      \n"     \
 136         "   movi    %[err], %[efault]   \n"     \
 137         "   _j      2f                  \n"
 138
 139 #define __check_align_4                         \
 140         "   _bbsi.l %[mem] * 0, 0f      \n"     \
 141         "   _bbci.l %[mem] * 0 + 1, 1f  \n"     \
 142         "0: movi    %[err], %[efault]   \n"     \
 143         "   _j      2f                  \n"
 144
 145
 146 /*
 147  * We don't tell gcc that we are accessing memory, but this is OK
 148  * because we do not write to any memory gcc knows about, so there
 149  * are no aliasing issues.
 150  *
 151  * WARNING: If you modify this macro at all, verify that the
 152  * __check_align_* macros still work.
 153  */
 154 #define __put_user_asm(x_, addr_, err_, align, insn, cb)\
 155 __asm__ __volatile__(                                   \
 156         __check_align_##align                           \
 157         "1: "insn"  %[x], %[mem]        \n"             \
 158         "2:                             \n"             \
 159         "   .section  .fixup,\"ax\"     \n"             \
 160         "   .align 4                    \n"             \
 161         "   .literal_position           \n"             \
 162         "5:                             \n"             \
 163         "   movi   %[tmp], 2b           \n"             \
 164         "   movi   %[err], %[efault]    \n"             \
 165         "   jx     %[tmp]               \n"             \
 166         "   .previous                   \n"             \
 167         "   .section  __ex_table,\"a\"  \n"             \
 168         "   .long       1b, 5b          \n"             \
 169         "   .previous"                                  \
 170         :[err] "+r"(err_), [tmp] "=r"(cb), [mem] "=m"(*(addr_))         \
 171         :[x] "r"(x_), [efault] "i"(-EFAULT))
 172
 173 #define __get_user_nocheck(x, ptr, size)                        \
 174 ({                                                              \
 175         long __gu_err;                                          \
 176         __get_user_size((x), (ptr), (size), __gu_err);          \
 177         __gu_err;                                               \
 178 })
 179
 180 #define __get_user_check(x, ptr, size)                                  \
 181 ({                                                                      \
 182         long __gu_err = -EFAULT;                                        \
 183         const __typeof__(*(ptr)) *__gu_addr = (ptr);                    \
 184         if (access_ok(__gu_addr, size))                                 \
 185                 __get_user_size((x), __gu_addr, (size), __gu_err);      \
 186         else                                                            \
 187                 (x) = 0;                                                \
 188         __gu_err;                                                       \
 189 })
 190
 191 extern long __get_user_bad(void);
 192
 193 #define __get_user_size(x, ptr, size, retval)                           \
 194 do {                                                                    \
 195         int __cb;                                                       \
 196         retval = 0;                                                     \
 197         switch (size) {                                                 \
 198         case 1: __get_user_asm(x, ptr, retval, 1, "l8ui", __cb);  break;\
 199         case 2: __get_user_asm(x, ptr, retval, 2, "l16ui", __cb); break;\
 200         case 4: __get_user_asm(x, ptr, retval, 4, "l32i", __cb);  break;\
 201         case 8: {                                                       \
 202                 u64 __x;                                                \
 203                 if (unlikely(__copy_from_user(&__x, ptr, 8))) {         \
 204                         retval = -EFAULT;                               \
 205                         (x) = 0;                                        \
 206                 } else {                                                \
 207                         (x) = *(__force __typeof__((ptr)))&__x;         \
 208                 }                                                       \
 209                 break;                                                  \
 210         }                                                               \
 211         default: (x) = 0; __get_user_bad();                             \
 212         }                                                               \
 213 } while (0)
 214
 215
 216 /*
 217  * WARNING: If you modify this macro at all, verify that the
 218  * __check_align_* macros still work.
 219  */
 220 #define __get_user_asm(x_, addr_, err_, align, insn, cb) \
 221 do {                                                    \
 222         u32 __x = 0;                                    \
 223         __asm__ __volatile__(                           \
 224                 __check_align_##align                   \
 225                 "1: "insn"  %[x], %[mem]        \n"     \
 226                 "2:                             \n"     \
 227                 "   .section  .fixup,\"ax\"     \n"     \
 228                 "   .align 4                    \n"     \
 229                 "   .literal_position           \n"     \
 230                 "5:                             \n"     \
 231                 "   movi   %[tmp], 2b           \n"     \
 232                 "   movi   %[err], %[efault]    \n"     \
 233                 "   jx     %[tmp]               \n"     \
 234                 "   .previous                   \n"     \
 235                 "   .section  __ex_table,\"a\"  \n"     \
 236                 "   .long       1b, 5b          \n"     \
 237                 "   .previous"                          \
 238                 :[err] "+r"(err_), [tmp] "=r"(cb), [x] "+r"(__x) \
 239                 :[mem] "m"(*(addr_)), [efault] "i"(-EFAULT)); \
 240         (x_) = (__force __typeof__(*(addr_)))__x;       \
 241 } while (0)
 242
 243
 244 /*
 245  * Copy to/from user space
 246  */
 247
 248 extern unsigned __xtensa_copy_user(void *to, const void *from, unsigned n);
 249
 250 static inline unsigned long
 251 raw_copy_from_user(void *to, const void __user *from, unsigned long n)
 252 {
 253         prefetchw(to);
 254         return __xtensa_copy_user(to, (__force const void *)from, n);
 255 }
 256 static inline unsigned long
 257 raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 258 {
 259         prefetch(from);
 260         return __xtensa_copy_user((__force void *)to, from, n);
 261 }
 262 #define INLINE_COPY_FROM_USER
 263 #define INLINE_COPY_TO_USER
 264
 265 /*
 266  * We need to return the number of bytes not cleared.  Our memset()
 267  * returns zero if a problem occurs while accessing user-space memory.
 268  * In that event, return no memory cleared.  Otherwise, zero for
 269  * success.
 270  */
 271
 272 static inline unsigned long
 273 __xtensa_clear_user(void *addr, unsigned long size)
 274 {
 275         if (!__memset(addr, 0, size))
 276                 return size;
 277         return 0;
 278 }
 279
 280 static inline unsigned long
 281 clear_user(void *addr, unsigned long size)
 282 {
 283         if (access_ok(addr, size))
 284                 return __xtensa_clear_user(addr, size);
 285         return size ? -EFAULT : 0;
 286 }
 287
 288 #define __clear_user  __xtensa_clear_user
 289
 290
 291 #ifndef CONFIG_GENERIC_STRNCPY_FROM_USER
 292
 293 extern long __strncpy_user(char *, const char *, long);
 294
 295 static inline long
 296 strncpy_from_user(char *dst, const char *src, long count)
 297 {
 298         if (access_ok(src, 1))
 299                 return __strncpy_user(dst, src, count);
 300         return -EFAULT;
 301 }
 302 #else
 303 long strncpy_from_user(char *dst, const char *src, long count);
 304 #endif
 305
 306 /*
 307  * Return the size of a string (including the ending 0!)
 308  */
 309 extern long __strnlen_user(const char *, long);
 310
 311 static inline long strnlen_user(const char *str, long len)
 312 {
 313         unsigned long top = __kernel_ok ? ~0UL : TASK_SIZE - 1;
 314
 315         if ((unsigned long)str > top)
 316                 return 0;
 317         return __strnlen_user(str, len);
 318 }
 319
 320 #endif  /* _XTENSA_UACCESS_H */