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uaccess.h
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1 /*
2  * Based on arch/arm/include/asm/uaccess.h
3  *
4  * Copyright (C) 2012 ARM Ltd.
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 as
8  * published by the Free Software Foundation.
9  *
10  * This program is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13  * GNU General Public License for more details.
14  *
15  * You should have received a copy of the GNU General Public License
16  * along with this program. If not, see <http://www.gnu.org/licenses/>.
17  */
18 #ifndef __ASM_UACCESS_H
19 #define __ASM_UACCESS_H
20 
21 /*
22  * User space memory access functions
23  */
24 #include <linux/string.h>
25 #include <linux/thread_info.h>
26 
27 #include <asm/ptrace.h>
28 #include <asm/errno.h>
29 #include <asm/memory.h>
30 #include <asm/compiler.h>
31 
32 #define VERIFY_READ 0
33 #define VERIFY_WRITE 1
34 
35 /*
36  * The exception table consists of pairs of addresses: the first is the
37  * address of an instruction that is allowed to fault, and the second is
38  * the address at which the program should continue. No registers are
39  * modified, so it is entirely up to the continuation code to figure out
40  * what to do.
41  *
42  * All the routines below use bits of fixup code that are out of line
43  * with the main instruction path. This means when everything is well,
44  * we don't even have to jump over them. Further, they do not intrude
45  * on our cache or tlb entries.
46  */
47 
48 struct exception_table_entry
49 {
50  unsigned long insn, fixup;
51 };
52 
53 extern int fixup_exception(struct pt_regs *regs);
54 
55 #define KERNEL_DS (-1UL)
56 #define get_ds() (KERNEL_DS)
57 
58 #define USER_DS TASK_SIZE_64
59 #define get_fs() (current_thread_info()->addr_limit)
60 
61 static inline void set_fs(mm_segment_t fs)
62 {
63  current_thread_info()->addr_limit = fs;
64 }
65 
66 #define segment_eq(a,b) ((a) == (b))
67 
68 /*
69  * Return 1 if addr < current->addr_limit, 0 otherwise.
70  */
71 #define __addr_ok(addr) \
72 ({ \
73  unsigned long flag; \
74  asm("cmp %1, %0; cset %0, lo" \
75  : "=&r" (flag) \
76  : "r" (addr), "0" (current_thread_info()->addr_limit) \
77  : "cc"); \
78  flag; \
79 })
80 
81 /*
82  * Test whether a block of memory is a valid user space address.
83  * Returns 1 if the range is valid, 0 otherwise.
84  *
85  * This is equivalent to the following test:
86  * (u65)addr + (u65)size < (u65)current->addr_limit
87  *
88  * This needs 65-bit arithmetic.
89  */
90 #define __range_ok(addr, size) \
91 ({ \
92  unsigned long flag, roksum; \
93  __chk_user_ptr(addr); \
94  asm("adds %1, %1, %3; ccmp %1, %4, #2, cc; cset %0, cc" \
95  : "=&r" (flag), "=&r" (roksum) \
96  : "1" (addr), "Ir" (size), \
97  "r" (current_thread_info()->addr_limit) \
98  : "cc"); \
99  flag; \
100 })
101 
102 #define access_ok(type, addr, size) __range_ok(addr, size)
103 
104 /*
105  * The "__xxx" versions of the user access functions do not verify the address
106  * space - it must have been done previously with a separate "access_ok()"
107  * call.
108  *
109  * The "__xxx_error" versions set the third argument to -EFAULT if an error
110  * occurs, and leave it unchanged on success.
111  */
112 #define __get_user_asm(instr, reg, x, addr, err) \
113  asm volatile( \
114  "1: " instr " " reg "1, [%2]\n" \
115  "2:\n" \
116  " .section .fixup, \"ax\"\n" \
117  " .align 2\n" \
118  "3: mov %w0, %3\n" \
119  " mov %1, #0\n" \
120  " b 2b\n" \
121  " .previous\n" \
122  " .section __ex_table,\"a\"\n" \
123  " .align 3\n" \
124  " .quad 1b, 3b\n" \
125  " .previous" \
126  : "+r" (err), "=&r" (x) \
127  : "r" (addr), "i" (-EFAULT))
128 
129 #define __get_user_err(x, ptr, err) \
130 do { \
131  unsigned long __gu_val; \
132  __chk_user_ptr(ptr); \
133  switch (sizeof(*(ptr))) { \
134  case 1: \
135  __get_user_asm("ldrb", "%w", __gu_val, (ptr), (err)); \
136  break; \
137  case 2: \
138  __get_user_asm("ldrh", "%w", __gu_val, (ptr), (err)); \
139  break; \
140  case 4: \
141  __get_user_asm("ldr", "%w", __gu_val, (ptr), (err)); \
142  break; \
143  case 8: \
144  __get_user_asm("ldr", "%", __gu_val, (ptr), (err)); \
145  break; \
146  default: \
147  BUILD_BUG(); \
148  } \
149  (x) = (__typeof__(*(ptr)))__gu_val; \
150 } while (0)
151 
152 #define __get_user(x, ptr) \
153 ({ \
154  int __gu_err = 0; \
155  __get_user_err((x), (ptr), __gu_err); \
156  __gu_err; \
157 })
158 
159 #define __get_user_error(x, ptr, err) \
160 ({ \
161  __get_user_err((x), (ptr), (err)); \
162  (void)0; \
163 })
164 
165 #define __get_user_unaligned __get_user
166 
167 #define get_user(x, ptr) \
168 ({ \
169  might_sleep(); \
170  access_ok(VERIFY_READ, (ptr), sizeof(*(ptr))) ? \
171  __get_user((x), (ptr)) : \
172  ((x) = 0, -EFAULT); \
173 })
174 
175 #define __put_user_asm(instr, reg, x, addr, err) \
176  asm volatile( \
177  "1: " instr " " reg "1, [%2]\n" \
178  "2:\n" \
179  " .section .fixup,\"ax\"\n" \
180  " .align 2\n" \
181  "3: mov %w0, %3\n" \
182  " b 2b\n" \
183  " .previous\n" \
184  " .section __ex_table,\"a\"\n" \
185  " .align 3\n" \
186  " .quad 1b, 3b\n" \
187  " .previous" \
188  : "+r" (err) \
189  : "r" (x), "r" (addr), "i" (-EFAULT))
190 
191 #define __put_user_err(x, ptr, err) \
192 do { \
193  __typeof__(*(ptr)) __pu_val = (x); \
194  __chk_user_ptr(ptr); \
195  switch (sizeof(*(ptr))) { \
196  case 1: \
197  __put_user_asm("strb", "%w", __pu_val, (ptr), (err)); \
198  break; \
199  case 2: \
200  __put_user_asm("strh", "%w", __pu_val, (ptr), (err)); \
201  break; \
202  case 4: \
203  __put_user_asm("str", "%w", __pu_val, (ptr), (err)); \
204  break; \
205  case 8: \
206  __put_user_asm("str", "%", __pu_val, (ptr), (err)); \
207  break; \
208  default: \
209  BUILD_BUG(); \
210  } \
211 } while (0)
212 
213 #define __put_user(x, ptr) \
214 ({ \
215  int __pu_err = 0; \
216  __put_user_err((x), (ptr), __pu_err); \
217  __pu_err; \
218 })
219 
220 #define __put_user_error(x, ptr, err) \
221 ({ \
222  __put_user_err((x), (ptr), (err)); \
223  (void)0; \
224 })
225 
226 #define __put_user_unaligned __put_user
227 
228 #define put_user(x, ptr) \
229 ({ \
230  might_sleep(); \
231  access_ok(VERIFY_WRITE, (ptr), sizeof(*(ptr))) ? \
232  __put_user((x), (ptr)) : \
233  -EFAULT; \
234 })
235 
236 extern unsigned long __must_check __copy_from_user(void *to, const void __user *from, unsigned long n);
237 extern unsigned long __must_check __copy_to_user(void __user *to, const void *from, unsigned long n);
238 extern unsigned long __must_check __copy_in_user(void __user *to, const void __user *from, unsigned long n);
239 extern unsigned long __must_check __clear_user(void __user *addr, unsigned long n);
240 
241 extern unsigned long __must_check __strncpy_from_user(char *to, const char __user *from, unsigned long count);
242 extern unsigned long __must_check __strnlen_user(const char __user *s, long n);
243 
244 static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n)
245 {
246  if (access_ok(VERIFY_READ, from, n))
247  n = __copy_from_user(to, from, n);
248  else /* security hole - plug it */
249  memset(to, 0, n);
250  return n;
251 }
252 
253 static inline unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n)
254 {
255  if (access_ok(VERIFY_WRITE, to, n))
256  n = __copy_to_user(to, from, n);
257  return n;
258 }
259 
260 static inline unsigned long __must_check copy_in_user(void __user *to, const void __user *from, unsigned long n)
261 {
262  if (access_ok(VERIFY_READ, from, n) && access_ok(VERIFY_WRITE, to, n))
263  n = __copy_in_user(to, from, n);
264  return n;
265 }
266 
267 #define __copy_to_user_inatomic __copy_to_user
268 #define __copy_from_user_inatomic __copy_from_user
269 
270 static inline unsigned long __must_check clear_user(void __user *to, unsigned long n)
271 {
272  if (access_ok(VERIFY_WRITE, to, n))
273  n = __clear_user(to, n);
274  return n;
275 }
276 
277 static inline long __must_check strncpy_from_user(char *dst, const char __user *src, long count)
278 {
279  long res = -EFAULT;
280  if (access_ok(VERIFY_READ, src, 1))
281  res = __strncpy_from_user(dst, src, count);
282  return res;
283 }
284 
285 #define strlen_user(s) strnlen_user(s, ~0UL >> 1)
286 
287 static inline long __must_check strnlen_user(const char __user *s, long n)
288 {
289  unsigned long res = 0;
290 
291  if (__addr_ok(s))
292  res = __strnlen_user(s, n);
293 
294  return res;
295 }
296 
297 #endif /* __ASM_UACCESS_H */
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