linux/arch/xtensa/include/asm/uaccess.h
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   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 uaccess_kernel() (get_fs().seg == KERNEL_DS.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
  75extern 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)) __user *__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)                           \
  94do {                                                                    \
  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)) __user *__gu_addr = (ptr);             \
 184        if (access_ok(__gu_addr, size))                                 \
 185                __get_user_size((x), __gu_addr, (size), __gu_err);      \
 186        else                                                            \
 187                (x) = (__typeof__(*(ptr)))0;                            \
 188        __gu_err;                                                       \
 189})
 190
 191extern long __get_user_bad(void);
 192
 193#define __get_user_size(x, ptr, size, retval)                           \
 194do {                                                                    \
 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) = (__typeof__(*(ptr)))0;                    \
 206                } else {                                                \
 207                        (x) = *(__force __typeof__(*(ptr)) *)&__x;      \
 208                }                                                       \
 209                break;                                                  \
 210        }                                                               \
 211        default:                                                        \
 212                (x) = (__typeof__(*(ptr)))0;                            \
 213                __get_user_bad();                                       \
 214        }                                                               \
 215} while (0)
 216
 217
 218/*
 219 * WARNING: If you modify this macro at all, verify that the
 220 * __check_align_* macros still work.
 221 */
 222#define __get_user_asm(x_, addr_, err_, align, insn, cb) \
 223do {                                                    \
 224        u32 __x = 0;                                    \
 225        __asm__ __volatile__(                           \
 226                __check_align_##align                   \
 227                "1: "insn"  %[x], %[mem]        \n"     \
 228                "2:                             \n"     \
 229                "   .section  .fixup,\"ax\"     \n"     \
 230                "   .align 4                    \n"     \
 231                "   .literal_position           \n"     \
 232                "5:                             \n"     \
 233                "   movi   %[tmp], 2b           \n"     \
 234                "   movi   %[err], %[efault]    \n"     \
 235                "   jx     %[tmp]               \n"     \
 236                "   .previous                   \n"     \
 237                "   .section  __ex_table,\"a\"  \n"     \
 238                "   .long       1b, 5b          \n"     \
 239                "   .previous"                          \
 240                :[err] "+r"(err_), [tmp] "=r"(cb), [x] "+r"(__x) \
 241                :[mem] "m"(*(addr_)), [efault] "i"(-EFAULT)); \
 242        (x_) = (__force __typeof__(*(addr_)))__x;       \
 243} while (0)
 244
 245
 246/*
 247 * Copy to/from user space
 248 */
 249
 250extern unsigned __xtensa_copy_user(void *to, const void *from, unsigned n);
 251
 252static inline unsigned long
 253raw_copy_from_user(void *to, const void __user *from, unsigned long n)
 254{
 255        prefetchw(to);
 256        return __xtensa_copy_user(to, (__force const void *)from, n);
 257}
 258static inline unsigned long
 259raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 260{
 261        prefetch(from);
 262        return __xtensa_copy_user((__force void *)to, from, n);
 263}
 264#define INLINE_COPY_FROM_USER
 265#define INLINE_COPY_TO_USER
 266
 267/*
 268 * We need to return the number of bytes not cleared.  Our memset()
 269 * returns zero if a problem occurs while accessing user-space memory.
 270 * In that event, return no memory cleared.  Otherwise, zero for
 271 * success.
 272 */
 273
 274static inline unsigned long
 275__xtensa_clear_user(void __user *addr, unsigned long size)
 276{
 277        if (!__memset((void __force *)addr, 0, size))
 278                return size;
 279        return 0;
 280}
 281
 282static inline unsigned long
 283clear_user(void __user *addr, unsigned long size)
 284{
 285        if (access_ok(addr, size))
 286                return __xtensa_clear_user(addr, size);
 287        return size ? -EFAULT : 0;
 288}
 289
 290#define __clear_user  __xtensa_clear_user
 291
 292
 293#ifndef CONFIG_GENERIC_STRNCPY_FROM_USER
 294
 295extern long __strncpy_user(char *dst, const char __user *src, long count);
 296
 297static inline long
 298strncpy_from_user(char *dst, const char __user *src, long count)
 299{
 300        if (access_ok(src, 1))
 301                return __strncpy_user(dst, src, count);
 302        return -EFAULT;
 303}
 304#else
 305long strncpy_from_user(char *dst, const char __user *src, long count);
 306#endif
 307
 308/*
 309 * Return the size of a string (including the ending 0!)
 310 */
 311extern long __strnlen_user(const char __user *str, long len);
 312
 313static inline long strnlen_user(const char __user *str, long len)
 314{
 315        if (!access_ok(str, 1))
 316                return 0;
 317        return __strnlen_user(str, len);
 318}
 319
 320#endif  /* _XTENSA_UACCESS_H */
 321