arch/x86/include/asm/uaccess_32.h

   1 #ifndef _ASM_X86_UACCESS_32_H
   2 #define _ASM_X86_UACCESS_32_H
   3
   4 /*
   5  * User space memory access functions
   6  */
   7 #include <linux/errno.h>
   8 #include <linux/thread_info.h>
   9 #include <linux/string.h>
  10 #include <asm/asm.h>
  11 #include <asm/page.h>
  12
  13 unsigned long __must_check __copy_to_user_ll
  14                 (void __user *to, const void *from, unsigned long n);
  15 unsigned long __must_check __copy_from_user_ll
  16                 (void *to, const void __user *from, unsigned long n);
  17 unsigned long __must_check __copy_from_user_ll_nozero
  18                 (void *to, const void __user *from, unsigned long n);
  19 unsigned long __must_check __copy_from_user_ll_nocache
  20                 (void *to, const void __user *from, unsigned long n);
  21 unsigned long __must_check __copy_from_user_ll_nocache_nozero
  22                 (void *to, const void __user *from, unsigned long n);
  23
  24 /**
  25  * __copy_to_user_inatomic: - Copy a block of data into user space, with less checking.
  26  * @to:   Destination address, in user space.
  27  * @from: Source address, in kernel space.
  28  * @n:    Number of bytes to copy.
  29  *
  30  * Context: User context only.
  31  *
  32  * Copy data from kernel space to user space.  Caller must check
  33  * the specified block with access_ok() before calling this function.
  34  * The caller should also make sure he pins the user space address
  35  * so that we don't result in page fault and sleep.
  36  *
  37  * Here we special-case 1, 2 and 4-byte copy_*_user invocations.  On a fault
  38  * we return the initial request size (1, 2 or 4), as copy_*_user should do.
  39  * If a store crosses a page boundary and gets a fault, the x86 will not write
  40  * anything, so this is accurate.
  41  */
  42
  43 static __always_inline unsigned long __must_check
  44 __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
  45 {
  46         if (__builtin_constant_p(n)) {
  47                 unsigned long ret;
  48
  49                 switch (n) {
  50                 case 1:
  51                         __put_user_size(*(u8 *)from, (u8 __user *)to,
  52                                         1, ret, 1);
  53                         return ret;
  54                 case 2:
  55                         __put_user_size(*(u16 *)from, (u16 __user *)to,
  56                                         2, ret, 2);
  57                         return ret;
  58                 case 4:
  59                         __put_user_size(*(u32 *)from, (u32 __user *)to,
  60                                         4, ret, 4);
  61                         return ret;
  62                 }
  63         }
  64         return __copy_to_user_ll(to, from, n);
  65 }
  66
  67 /**
  68  * __copy_to_user: - Copy a block of data into user space, with less checking.
  69  * @to:   Destination address, in user space.
  70  * @from: Source address, in kernel space.
  71  * @n:    Number of bytes to copy.
  72  *
  73  * Context: User context only.  This function may sleep.
  74  *
  75  * Copy data from kernel space to user space.  Caller must check
  76  * the specified block with access_ok() before calling this function.
  77  *
  78  * Returns number of bytes that could not be copied.
  79  * On success, this will be zero.
  80  */
  81 static __always_inline unsigned long __must_check
  82 __copy_to_user(void __user *to, const void *from, unsigned long n)
  83 {
  84         might_fault();
  85         return __copy_to_user_inatomic(to, from, n);
  86 }
  87
  88 static __always_inline unsigned long
  89 __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
  90 {
  91         /* Avoid zeroing the tail if the copy fails..
  92          * If 'n' is constant and 1, 2, or 4, we do still zero on a failure,
  93          * but as the zeroing behaviour is only significant when n is not
  94          * constant, that shouldn't be a problem.
  95          */
  96         if (__builtin_constant_p(n)) {
  97                 unsigned long ret;
  98
  99                 switch (n) {
 100                 case 1:
 101                         __get_user_size(*(u8 *)to, from, 1, ret, 1);
 102                         return ret;
 103                 case 2:
 104                         __get_user_size(*(u16 *)to, from, 2, ret, 2);
 105                         return ret;
 106                 case 4:
 107                         __get_user_size(*(u32 *)to, from, 4, ret, 4);
 108                         return ret;
 109                 }
 110         }
 111         return __copy_from_user_ll_nozero(to, from, n);
 112 }
 113
 114 /**
 115  * __copy_from_user: - Copy a block of data from user space, with less checking.
 116  * @to:   Destination address, in kernel space.
 117  * @from: Source address, in user space.
 118  * @n:    Number of bytes to copy.
 119  *
 120  * Context: User context only.  This function may sleep.
 121  *
 122  * Copy data from user space to kernel space.  Caller must check
 123  * the specified block with access_ok() before calling this function.
 124  *
 125  * Returns number of bytes that could not be copied.
 126  * On success, this will be zero.
 127  *
 128  * If some data could not be copied, this function will pad the copied
 129  * data to the requested size using zero bytes.
 130  *
 131  * An alternate version - __copy_from_user_inatomic() - may be called from
 132  * atomic context and will fail rather than sleep.  In this case the
 133  * uncopied bytes will *NOT* be padded with zeros.  See fs/filemap.h
 134  * for explanation of why this is needed.
 135  */
 136 static __always_inline unsigned long
 137 __copy_from_user(void *to, const void __user *from, unsigned long n)
 138 {
 139         might_fault();
 140         if (__builtin_constant_p(n)) {
 141                 unsigned long ret;
 142
 143                 switch (n) {
 144                 case 1:
 145                         __get_user_size(*(u8 *)to, from, 1, ret, 1);
 146                         return ret;
 147                 case 2:
 148                         __get_user_size(*(u16 *)to, from, 2, ret, 2);
 149                         return ret;
 150                 case 4:
 151                         __get_user_size(*(u32 *)to, from, 4, ret, 4);
 152                         return ret;
 153                 }
 154         }
 155         return __copy_from_user_ll(to, from, n);
 156 }
 157
 158 static __always_inline unsigned long __copy_from_user_nocache(void *to,
 159                                 const void __user *from, unsigned long n)
 160 {
 161         might_fault();
 162         if (__builtin_constant_p(n)) {
 163                 unsigned long ret;
 164
 165                 switch (n) {
 166                 case 1:
 167                         __get_user_size(*(u8 *)to, from, 1, ret, 1);
 168                         return ret;
 169                 case 2:
 170                         __get_user_size(*(u16 *)to, from, 2, ret, 2);
 171                         return ret;
 172                 case 4:
 173                         __get_user_size(*(u32 *)to, from, 4, ret, 4);
 174                         return ret;
 175                 }
 176         }
 177         return __copy_from_user_ll_nocache(to, from, n);
 178 }
 179
 180 static __always_inline unsigned long
 181 __copy_from_user_inatomic_nocache(void *to, const void __user *from,
 182                                   unsigned long n)
 183 {
 184        return __copy_from_user_ll_nocache_nozero(to, from, n);
 185 }
 186
 187 unsigned long __must_check copy_to_user(void __user *to,
 188                                         const void *from, unsigned long n);
 189 unsigned long __must_check _copy_from_user(void *to,
 190                                           const void __user *from,
 191                                           unsigned long n);
 192
 193
 194 extern void copy_from_user_overflow(void)
 195 #ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
 196         __compiletime_error("copy_from_user() buffer size is not provably correct")
 197 #else
 198         __compiletime_warning("copy_from_user() buffer size is not provably correct")
 199 #endif
 200 ;
 201
 202 static inline unsigned long __must_check copy_from_user(void *to,
 203                                           const void __user *from,
 204                                           unsigned long n)
 205 {
 206         int sz = __compiletime_object_size(to);
 207
 208         if (likely(sz == -1 || sz >= n))
 209                 n = _copy_from_user(to, from, n);
 210         else
 211                 copy_from_user_overflow();
 212
 213         return n;
 214 }
 215
 216 #endif /* _ASM_X86_UACCESS_32_H */