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uaccess.h
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1 #ifndef __ASM_GENERIC_UACCESS_H
2 #define __ASM_GENERIC_UACCESS_H
3 
4 /*
5  * User space memory access functions, these should work
6  * on a ny machine that has kernel and user data in the same
7  * address space, e.g. all NOMMU machines.
8  */
9 #include <linux/sched.h>
10 #include <linux/mm.h>
11 #include <linux/string.h>
12 
13 #include <asm/segment.h>
14 
15 #define MAKE_MM_SEG(s) ((mm_segment_t) { (s) })
16 
17 #ifndef KERNEL_DS
18 #define KERNEL_DS MAKE_MM_SEG(~0UL)
19 #endif
20 
21 #ifndef USER_DS
22 #define USER_DS MAKE_MM_SEG(TASK_SIZE - 1)
23 #endif
24 
25 #ifndef get_fs
26 #define get_ds() (KERNEL_DS)
27 #define get_fs() (current_thread_info()->addr_limit)
28 
29 static inline void set_fs(mm_segment_t fs)
30 {
31  current_thread_info()->addr_limit = fs;
32 }
33 #endif
34 
35 #define segment_eq(a, b) ((a).seg == (b).seg)
36 
37 #define VERIFY_READ 0
38 #define VERIFY_WRITE 1
39 
40 #define access_ok(type, addr, size) __access_ok((unsigned long)(addr),(size))
41 
42 /*
43  * The architecture should really override this if possible, at least
44  * doing a check on the get_fs()
45  */
46 #ifndef __access_ok
47 static inline int __access_ok(unsigned long addr, unsigned long size)
48 {
49  return 1;
50 }
51 #endif
52 
53 /*
54  * The exception table consists of pairs of addresses: the first is the
55  * address of an instruction that is allowed to fault, and the second is
56  * the address at which the program should continue. No registers are
57  * modified, so it is entirely up to the continuation code to figure out
58  * what to do.
59  *
60  * All the routines below use bits of fixup code that are out of line
61  * with the main instruction path. This means when everything is well,
62  * we don't even have to jump over them. Further, they do not intrude
63  * on our cache or tlb entries.
64  */
65 
67 {
68  unsigned long insn, fixup;
69 };
70 
71 /* Returns 0 if exception not found and fixup otherwise. */
72 extern unsigned long search_exception_table(unsigned long);
73 
74 /*
75  * architectures with an MMU should override these two
76  */
77 #ifndef __copy_from_user
78 static inline __must_check long __copy_from_user(void *to,
79  const void __user * from, unsigned long n)
80 {
81  if (__builtin_constant_p(n)) {
82  switch(n) {
83  case 1:
84  *(u8 *)to = *(u8 __force *)from;
85  return 0;
86  case 2:
87  *(u16 *)to = *(u16 __force *)from;
88  return 0;
89  case 4:
90  *(u32 *)to = *(u32 __force *)from;
91  return 0;
92 #ifdef CONFIG_64BIT
93  case 8:
94  *(u64 *)to = *(u64 __force *)from;
95  return 0;
96 #endif
97  default:
98  break;
99  }
100  }
101 
102  memcpy(to, (const void __force *)from, n);
103  return 0;
104 }
105 #endif
106 
107 #ifndef __copy_to_user
108 static inline __must_check long __copy_to_user(void __user *to,
109  const void *from, unsigned long n)
110 {
111  if (__builtin_constant_p(n)) {
112  switch(n) {
113  case 1:
114  *(u8 __force *)to = *(u8 *)from;
115  return 0;
116  case 2:
117  *(u16 __force *)to = *(u16 *)from;
118  return 0;
119  case 4:
120  *(u32 __force *)to = *(u32 *)from;
121  return 0;
122 #ifdef CONFIG_64BIT
123  case 8:
124  *(u64 __force *)to = *(u64 *)from;
125  return 0;
126 #endif
127  default:
128  break;
129  }
130  }
131 
132  memcpy((void __force *)to, from, n);
133  return 0;
134 }
135 #endif
136 
137 /*
138  * These are the main single-value transfer routines. They automatically
139  * use the right size if we just have the right pointer type.
140  * This version just falls back to copy_{from,to}_user, which should
141  * provide a fast-path for small values.
142  */
143 #define __put_user(x, ptr) \
144 ({ \
145  __typeof__(*(ptr)) __x = (x); \
146  int __pu_err = -EFAULT; \
147  __chk_user_ptr(ptr); \
148  switch (sizeof (*(ptr))) { \
149  case 1: \
150  case 2: \
151  case 4: \
152  case 8: \
153  __pu_err = __put_user_fn(sizeof (*(ptr)), \
154  ptr, &__x); \
155  break; \
156  default: \
157  __put_user_bad(); \
158  break; \
159  } \
160  __pu_err; \
161 })
162 
163 #define put_user(x, ptr) \
164 ({ \
165  might_sleep(); \
166  access_ok(VERIFY_WRITE, ptr, sizeof(*ptr)) ? \
167  __put_user(x, ptr) : \
168  -EFAULT; \
169 })
170 
171 static inline int __put_user_fn(size_t size, void __user *ptr, void *x)
172 {
173  size = __copy_to_user(ptr, x, size);
174  return size ? -EFAULT : size;
175 }
176 
177 extern int __put_user_bad(void) __attribute__((noreturn));
178 
179 #define __get_user(x, ptr) \
180 ({ \
181  int __gu_err = -EFAULT; \
182  __chk_user_ptr(ptr); \
183  switch (sizeof(*(ptr))) { \
184  case 1: { \
185  unsigned char __x; \
186  __gu_err = __get_user_fn(sizeof (*(ptr)), \
187  ptr, &__x); \
188  (x) = *(__force __typeof__(*(ptr)) *) &__x; \
189  break; \
190  }; \
191  case 2: { \
192  unsigned short __x; \
193  __gu_err = __get_user_fn(sizeof (*(ptr)), \
194  ptr, &__x); \
195  (x) = *(__force __typeof__(*(ptr)) *) &__x; \
196  break; \
197  }; \
198  case 4: { \
199  unsigned int __x; \
200  __gu_err = __get_user_fn(sizeof (*(ptr)), \
201  ptr, &__x); \
202  (x) = *(__force __typeof__(*(ptr)) *) &__x; \
203  break; \
204  }; \
205  case 8: { \
206  unsigned long long __x; \
207  __gu_err = __get_user_fn(sizeof (*(ptr)), \
208  ptr, &__x); \
209  (x) = *(__force __typeof__(*(ptr)) *) &__x; \
210  break; \
211  }; \
212  default: \
213  __get_user_bad(); \
214  break; \
215  } \
216  __gu_err; \
217 })
218 
219 #define get_user(x, ptr) \
220 ({ \
221  might_sleep(); \
222  access_ok(VERIFY_READ, ptr, sizeof(*ptr)) ? \
223  __get_user(x, ptr) : \
224  -EFAULT; \
225 })
226 
227 static inline int __get_user_fn(size_t size, const void __user *ptr, void *x)
228 {
229  size = __copy_from_user(x, ptr, size);
230  return size ? -EFAULT : size;
231 }
232 
233 extern int __get_user_bad(void) __attribute__((noreturn));
234 
235 #ifndef __copy_from_user_inatomic
236 #define __copy_from_user_inatomic __copy_from_user
237 #endif
238 
239 #ifndef __copy_to_user_inatomic
240 #define __copy_to_user_inatomic __copy_to_user
241 #endif
242 
243 static inline long copy_from_user(void *to,
244  const void __user * from, unsigned long n)
245 {
246  might_sleep();
247  if (access_ok(VERIFY_READ, from, n))
248  return __copy_from_user(to, from, n);
249  else
250  return n;
251 }
252 
253 static inline long copy_to_user(void __user *to,
254  const void *from, unsigned long n)
255 {
256  might_sleep();
257  if (access_ok(VERIFY_WRITE, to, n))
258  return __copy_to_user(to, from, n);
259  else
260  return n;
261 }
262 
263 /*
264  * Copy a null terminated string from userspace.
265  */
266 #ifndef __strncpy_from_user
267 static inline long
268 __strncpy_from_user(char *dst, const char __user *src, long count)
269 {
270  char *tmp;
271  strncpy(dst, (const char __force *)src, count);
272  for (tmp = dst; *tmp && count > 0; tmp++, count--)
273  ;
274  return (tmp - dst);
275 }
276 #endif
277 
278 static inline long
279 strncpy_from_user(char *dst, const char __user *src, long count)
280 {
281  if (!access_ok(VERIFY_READ, src, 1))
282  return -EFAULT;
283  return __strncpy_from_user(dst, src, count);
284 }
285 
286 /*
287  * Return the size of a string (including the ending 0)
288  *
289  * Return 0 on exception, a value greater than N if too long
290  */
291 #ifndef __strnlen_user
292 #define __strnlen_user(s, n) (strnlen((s), (n)) + 1)
293 #endif
294 
295 /*
296  * Unlike strnlen, strnlen_user includes the nul terminator in
297  * its returned count. Callers should check for a returned value
298  * greater than N as an indication the string is too long.
299  */
300 static inline long strnlen_user(const char __user *src, long n)
301 {
302  if (!access_ok(VERIFY_READ, src, 1))
303  return 0;
304  return __strnlen_user(src, n);
305 }
306 
307 static inline long strlen_user(const char __user *src)
308 {
309  return strnlen_user(src, 32767);
310 }
311 
312 /*
313  * Zero Userspace
314  */
315 #ifndef __clear_user
316 static inline __must_check unsigned long
317 __clear_user(void __user *to, unsigned long n)
318 {
319  memset((void __force *)to, 0, n);
320  return 0;
321 }
322 #endif
323 
324 static inline __must_check unsigned long
325 clear_user(void __user *to, unsigned long n)
326 {
327  might_sleep();
328  if (!access_ok(VERIFY_WRITE, to, n))
329  return n;
330 
331  return __clear_user(to, n);
332 }
333 
334 #endif /* __ASM_GENERIC_UACCESS_H */