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_ds()        (KERNEL_DS)
  36 #define get_fs()        (current->thread.current_ds)
  37 #define set_fs(val)     (current->thread.current_ds = (val))
  38
  39 #define segment_eq(a, b)        ((a).seg == (b).seg)
  40
  41 #define __kernel_ok (uaccess_kernel())
  42 #define __user_ok(addr, size) \
  43                 (((size) <= TASK_SIZE)&&((addr) <= TASK_SIZE-(size)))
  44 #define __access_ok(addr, size) (__kernel_ok || __user_ok((addr), (size)))
  45 #define access_ok(type, addr, size) __access_ok((unsigned long)(addr), (size))
  46
  47 /*
  48  * These are the main single-value transfer routines.  They
  49  * automatically use the right size if we just have the right pointer
  50  * type.
  51  *
  52  * This gets kind of ugly. We want to return _two_ values in
  53  * "get_user()" and yet we don't want to do any pointers, because that
  54  * is too much of a performance impact. Thus we have a few rather ugly
  55  * macros here, and hide all the uglyness from the user.
  56  *
  57  * Careful to not
  58  * (a) re-use the arguments for side effects (sizeof is ok)
  59  * (b) require any knowledge of processes at this stage
  60  */
  61 #define put_user(x, ptr)        __put_user_check((x), (ptr), sizeof(*(ptr)))
  62 #define get_user(x, ptr) __get_user_check((x), (ptr), sizeof(*(ptr)))
  63
  64 /*
  65  * The "__xxx" versions of the user access functions are versions that
  66  * do not verify the address space, that must have been done previously
  67  * with a separate "access_ok()" call (this is used when we do multiple
  68  * accesses to the same area of user memory).
  69  */
  70 #define __put_user(x, ptr) __put_user_nocheck((x), (ptr), sizeof(*(ptr)))
  71 #define __get_user(x, ptr) __get_user_nocheck((x), (ptr), sizeof(*(ptr)))
  72
  73
  74 extern long __put_user_bad(void);
  75
  76 #define __put_user_nocheck(x, ptr, size)                \
  77 ({                                                      \
  78         long __pu_err;                                  \
  79         __put_user_size((x), (ptr), (size), __pu_err);  \
  80         __pu_err;                                       \
  81 })
  82
  83 #define __put_user_check(x, ptr, size)                                  \
  84 ({                                                                      \
  85         long __pu_err = -EFAULT;                                        \
  86         __typeof__(*(ptr)) *__pu_addr = (ptr);                          \
  87         if (access_ok(VERIFY_WRITE, __pu_addr, size))                   \
  88                 __put_user_size((x), __pu_addr, (size), __pu_err);      \
  89         __pu_err;                                                       \
  90 })
  91
  92 #define __put_user_size(x, ptr, size, retval)                           \
  93 do {                                                                    \
  94         int __cb;                                                       \
  95         retval = 0;                                                     \
  96         switch (size) {                                                 \
  97         case 1: __put_user_asm(x, ptr, retval, 1, "s8i", __cb);  break; \
  98         case 2: __put_user_asm(x, ptr, retval, 2, "s16i", __cb); break; \
  99         case 4: __put_user_asm(x, ptr, retval, 4, "s32i", __cb); break; \
 100         case 8: {                                                       \
 101                      __typeof__(*ptr) __v64 = x;                        \
 102                      retval = __copy_to_user(ptr, &__v64, 8);           \
 103                      break;                                             \
 104                 }                                                       \
 105         default: __put_user_bad();                                      \
 106         }                                                               \
 107 } while (0)
 108
 109
 110 /*
 111  * Consider a case of a user single load/store would cause both an
 112  * unaligned exception and an MMU-related exception (unaligned
 113  * exceptions happen first):
 114  *
 115  * User code passes a bad variable ptr to a system call.
 116  * Kernel tries to access the variable.
 117  * Unaligned exception occurs.
 118  * Unaligned exception handler tries to make aligned accesses.
 119  * Double exception occurs for MMU-related cause (e.g., page not mapped).
 120  * do_page_fault() thinks the fault address belongs to the kernel, not the
 121  * user, and panics.
 122  *
 123  * The kernel currently prohibits user unaligned accesses.  We use the
 124  * __check_align_* macros to check for unaligned addresses before
 125  * accessing user space so we don't crash the kernel.  Both
 126  * __put_user_asm and __get_user_asm use these alignment macros, so
 127  * macro-specific labels such as 0f, 1f, %0, %2, and %3 must stay in
 128  * sync.
 129  */
 130
 131 #define __check_align_1  ""
 132
 133 #define __check_align_2                         \
 134         "   _bbci.l %3,  0, 1f          \n"     \
 135         "   movi    %0, %4              \n"     \
 136         "   _j      2f                  \n"
 137
 138 #define __check_align_4                         \
 139         "   _bbsi.l %3,  0, 0f          \n"     \
 140         "   _bbci.l %3,  1, 1f          \n"     \
 141         "0: movi    %0, %4              \n"     \
 142         "   _j      2f                  \n"
 143
 144
 145 /*
 146  * We don't tell gcc that we are accessing memory, but this is OK
 147  * because we do not write to any memory gcc knows about, so there
 148  * are no aliasing issues.
 149  *
 150  * WARNING: If you modify this macro at all, verify that the
 151  * __check_align_* macros still work.
 152  */
 153 #define __put_user_asm(x, addr, err, align, insn, cb)   \
 154 __asm__ __volatile__(                                   \
 155         __check_align_##align                           \
 156         "1: "insn"  %2, %3, 0           \n"             \
 157         "2:                             \n"             \
 158         "   .section  .fixup,\"ax\"     \n"             \
 159         "   .align 4                    \n"             \
 160         "4:                             \n"             \
 161         "   .long  2b                   \n"             \
 162         "5:                             \n"             \
 163         "   l32r   %1, 4b               \n"             \
 164         "   movi   %0, %4               \n"             \
 165         "   jx     %1                   \n"             \
 166         "   .previous                   \n"             \
 167         "   .section  __ex_table,\"a\"  \n"             \
 168         "   .long       1b, 5b          \n"             \
 169         "   .previous"                                  \
 170         :"=r" (err), "=r" (cb)                          \
 171         :"r" ((int)(x)), "r" (addr), "i" (-EFAULT), "0" (err))
 172
 173 #define __get_user_nocheck(x, ptr, size)                        \
 174 ({                                                              \
 175         long __gu_err, __gu_val;                                \
 176         __get_user_size(__gu_val, (ptr), (size), __gu_err);     \
 177         (x) = (__force __typeof__(*(ptr)))__gu_val;             \
 178         __gu_err;                                               \
 179 })
 180
 181 #define __get_user_check(x, ptr, size)                                  \
 182 ({                                                                      \
 183         long __gu_err = -EFAULT, __gu_val = 0;                          \
 184         const __typeof__(*(ptr)) *__gu_addr = (ptr);                    \
 185         if (access_ok(VERIFY_READ, __gu_addr, size))                    \
 186                 __get_user_size(__gu_val, __gu_addr, (size), __gu_err); \
 187         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 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: retval = __copy_from_user(&x, ptr, 8);    break;        \
 202         default: (x) = __get_user_bad();                                \
 203         }                                                               \
 204 } while (0)
 205
 206
 207 /*
 208  * WARNING: If you modify this macro at all, verify that the
 209  * __check_align_* macros still work.
 210  */
 211 #define __get_user_asm(x, addr, err, align, insn, cb) \
 212 __asm__ __volatile__(                   \
 213         __check_align_##align                   \
 214         "1: "insn"  %2, %3, 0           \n"     \
 215         "2:                             \n"     \
 216         "   .section  .fixup,\"ax\"     \n"     \
 217         "   .align 4                    \n"     \
 218         "4:                             \n"     \
 219         "   .long  2b                   \n"     \
 220         "5:                             \n"     \
 221         "   l32r   %1, 4b               \n"     \
 222         "   movi   %2, 0                \n"     \
 223         "   movi   %0, %4               \n"     \
 224         "   jx     %1                   \n"     \
 225         "   .previous                   \n"     \
 226         "   .section  __ex_table,\"a\"  \n"     \
 227         "   .long       1b, 5b          \n"     \
 228         "   .previous"                          \
 229         :"=r" (err), "=r" (cb), "=r" (x)        \
 230         :"r" (addr), "i" (-EFAULT), "0" (err))
 231
 232
 233 /*
 234  * Copy to/from user space
 235  */
 236
 237 extern unsigned __xtensa_copy_user(void *to, const void *from, unsigned n);
 238
 239 static inline unsigned long
 240 raw_copy_from_user(void *to, const void __user *from, unsigned long n)
 241 {
 242         prefetchw(to);
 243         return __xtensa_copy_user(to, (__force const void *)from, n);
 244 }
 245 static inline unsigned long
 246 raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 247 {
 248         prefetch(from);
 249         return __xtensa_copy_user((__force void *)to, from, n);
 250 }
 251 #define INLINE_COPY_FROM_USER
 252 #define INLINE_COPY_TO_USER
 253
 254 /*
 255  * We need to return the number of bytes not cleared.  Our memset()
 256  * returns zero if a problem occurs while accessing user-space memory.
 257  * In that event, return no memory cleared.  Otherwise, zero for
 258  * success.
 259  */
 260
 261 static inline unsigned long
 262 __xtensa_clear_user(void *addr, unsigned long size)
 263 {
 264         if ( ! memset(addr, 0, size) )
 265                 return size;
 266         return 0;
 267 }
 268
 269 static inline unsigned long
 270 clear_user(void *addr, unsigned long size)
 271 {
 272         if (access_ok(VERIFY_WRITE, addr, size))
 273                 return __xtensa_clear_user(addr, size);
 274         return size ? -EFAULT : 0;
 275 }
 276
 277 #define __clear_user  __xtensa_clear_user
 278
 279
 280 extern long __strncpy_user(char *, const char *, long);
 281
 282 static inline long
 283 strncpy_from_user(char *dst, const char *src, long count)
 284 {
 285         if (access_ok(VERIFY_READ, src, 1))
 286                 return __strncpy_user(dst, src, count);
 287         return -EFAULT;
 288 }
 289
 290 /*
 291  * Return the size of a string (including the ending 0!)
 292  */
 293 extern long __strnlen_user(const char *, long);
 294
 295 static inline long strnlen_user(const char *str, long len)
 296 {
 297         unsigned long top = __kernel_ok ? ~0UL : TASK_SIZE - 1;
 298
 299         if ((unsigned long)str > top)
 300                 return 0;
 301         return __strnlen_user(str, len);
 302 }
 303
 304 #endif  /* _XTENSA_UACCESS_H */