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Linux/arch/arm/include/asm/uaccess.h

  1 /*
  2  *  arch/arm/include/asm/uaccess.h
  3  *
  4  * This program is free software; you can redistribute it and/or modify
  5  * it under the terms of the GNU General Public License version 2 as
  6  * published by the Free Software Foundation.
  7  */
  8 #ifndef _ASMARM_UACCESS_H
  9 #define _ASMARM_UACCESS_H
 10 
 11 /*
 12  * User space memory access functions
 13  */
 14 #include <linux/string.h>
 15 #include <linux/thread_info.h>
 16 #include <asm/errno.h>
 17 #include <asm/memory.h>
 18 #include <asm/domain.h>
 19 #include <asm/unified.h>
 20 #include <asm/compiler.h>
 21 
 22 #ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
 23 #include <asm-generic/uaccess-unaligned.h>
 24 #else
 25 #define __get_user_unaligned __get_user
 26 #define __put_user_unaligned __put_user
 27 #endif
 28 
 29 #define VERIFY_READ 0
 30 #define VERIFY_WRITE 1
 31 
 32 /*
 33  * The exception table consists of pairs of addresses: the first is the
 34  * address of an instruction that is allowed to fault, and the second is
 35  * the address at which the program should continue.  No registers are
 36  * modified, so it is entirely up to the continuation code to figure out
 37  * what to do.
 38  *
 39  * All the routines below use bits of fixup code that are out of line
 40  * with the main instruction path.  This means when everything is well,
 41  * we don't even have to jump over them.  Further, they do not intrude
 42  * on our cache or tlb entries.
 43  */
 44 
 45 struct exception_table_entry
 46 {
 47         unsigned long insn, fixup;
 48 };
 49 
 50 extern int fixup_exception(struct pt_regs *regs);
 51 
 52 /*
 53  * These two functions allow hooking accesses to userspace to increase
 54  * system integrity by ensuring that the kernel can not inadvertantly
 55  * perform such accesses (eg, via list poison values) which could then
 56  * be exploited for priviledge escalation.
 57  */
 58 static inline unsigned int uaccess_save_and_enable(void)
 59 {
 60 #ifdef CONFIG_CPU_SW_DOMAIN_PAN
 61         unsigned int old_domain = get_domain();
 62 
 63         /* Set the current domain access to permit user accesses */
 64         set_domain((old_domain & ~domain_mask(DOMAIN_USER)) |
 65                    domain_val(DOMAIN_USER, DOMAIN_CLIENT));
 66 
 67         return old_domain;
 68 #else
 69         return 0;
 70 #endif
 71 }
 72 
 73 static inline void uaccess_restore(unsigned int flags)
 74 {
 75 #ifdef CONFIG_CPU_SW_DOMAIN_PAN
 76         /* Restore the user access mask */
 77         set_domain(flags);
 78 #endif
 79 }
 80 
 81 /*
 82  * These two are intentionally not defined anywhere - if the kernel
 83  * code generates any references to them, that's a bug.
 84  */
 85 extern int __get_user_bad(void);
 86 extern int __put_user_bad(void);
 87 
 88 /*
 89  * Note that this is actually 0x1,0000,0000
 90  */
 91 #define KERNEL_DS       0x00000000
 92 #define get_ds()        (KERNEL_DS)
 93 
 94 #ifdef CONFIG_MMU
 95 
 96 #define USER_DS         TASK_SIZE
 97 #define get_fs()        (current_thread_info()->addr_limit)
 98 
 99 static inline void set_fs(mm_segment_t fs)
100 {
101         current_thread_info()->addr_limit = fs;
102         modify_domain(DOMAIN_KERNEL, fs ? DOMAIN_CLIENT : DOMAIN_MANAGER);
103 }
104 
105 #define segment_eq(a, b)        ((a) == (b))
106 
107 /* We use 33-bit arithmetic here... */
108 #define __range_ok(addr, size) ({ \
109         unsigned long flag, roksum; \
110         __chk_user_ptr(addr);   \
111         __asm__("adds %1, %2, %3; sbcccs %1, %1, %0; movcc %0, #0" \
112                 : "=&r" (flag), "=&r" (roksum) \
113                 : "r" (addr), "Ir" (size), "" (current_thread_info()->addr_limit) \
114                 : "cc"); \
115         flag; })
116 
117 /*
118  * Single-value transfer routines.  They automatically use the right
119  * size if we just have the right pointer type.  Note that the functions
120  * which read from user space (*get_*) need to take care not to leak
121  * kernel data even if the calling code is buggy and fails to check
122  * the return value.  This means zeroing out the destination variable
123  * or buffer on error.  Normally this is done out of line by the
124  * fixup code, but there are a few places where it intrudes on the
125  * main code path.  When we only write to user space, there is no
126  * problem.
127  */
128 extern int __get_user_1(void *);
129 extern int __get_user_2(void *);
130 extern int __get_user_4(void *);
131 extern int __get_user_32t_8(void *);
132 extern int __get_user_8(void *);
133 extern int __get_user_64t_1(void *);
134 extern int __get_user_64t_2(void *);
135 extern int __get_user_64t_4(void *);
136 
137 #define __GUP_CLOBBER_1 "lr", "cc"
138 #ifdef CONFIG_CPU_USE_DOMAINS
139 #define __GUP_CLOBBER_2 "ip", "lr", "cc"
140 #else
141 #define __GUP_CLOBBER_2 "lr", "cc"
142 #endif
143 #define __GUP_CLOBBER_4 "lr", "cc"
144 #define __GUP_CLOBBER_32t_8 "lr", "cc"
145 #define __GUP_CLOBBER_8 "lr", "cc"
146 
147 #define __get_user_x(__r2, __p, __e, __l, __s)                          \
148            __asm__ __volatile__ (                                       \
149                 __asmeq("%0", "r0") __asmeq("%1", "r2")                 \
150                 __asmeq("%3", "r1")                                     \
151                 "bl     __get_user_" #__s                               \
152                 : "=&r" (__e), "=r" (__r2)                              \
153                 : "" (__p), "r" (__l)                                  \
154                 : __GUP_CLOBBER_##__s)
155 
156 /* narrowing a double-word get into a single 32bit word register: */
157 #ifdef __ARMEB__
158 #define __get_user_x_32t(__r2, __p, __e, __l, __s)                      \
159         __get_user_x(__r2, __p, __e, __l, 32t_8)
160 #else
161 #define __get_user_x_32t __get_user_x
162 #endif
163 
164 /*
165  * storing result into proper least significant word of 64bit target var,
166  * different only for big endian case where 64 bit __r2 lsw is r3:
167  */
168 #ifdef __ARMEB__
169 #define __get_user_x_64t(__r2, __p, __e, __l, __s)                      \
170            __asm__ __volatile__ (                                       \
171                 __asmeq("%0", "r0") __asmeq("%1", "r2")                 \
172                 __asmeq("%3", "r1")                                     \
173                 "bl     __get_user_64t_" #__s                           \
174                 : "=&r" (__e), "=r" (__r2)                              \
175                 : "" (__p), "r" (__l)                                  \
176                 : __GUP_CLOBBER_##__s)
177 #else
178 #define __get_user_x_64t __get_user_x
179 #endif
180 
181 
182 #define __get_user_check(x, p)                                          \
183         ({                                                              \
184                 unsigned long __limit = current_thread_info()->addr_limit - 1; \
185                 register const typeof(*(p)) __user *__p asm("r0") = (p);\
186                 register typeof(x) __r2 asm("r2");                      \
187                 register unsigned long __l asm("r1") = __limit;         \
188                 register int __e asm("r0");                             \
189                 unsigned int __ua_flags = uaccess_save_and_enable();    \
190                 switch (sizeof(*(__p))) {                               \
191                 case 1:                                                 \
192                         if (sizeof((x)) >= 8)                           \
193                                 __get_user_x_64t(__r2, __p, __e, __l, 1); \
194                         else                                            \
195                                 __get_user_x(__r2, __p, __e, __l, 1);   \
196                         break;                                          \
197                 case 2:                                                 \
198                         if (sizeof((x)) >= 8)                           \
199                                 __get_user_x_64t(__r2, __p, __e, __l, 2); \
200                         else                                            \
201                                 __get_user_x(__r2, __p, __e, __l, 2);   \
202                         break;                                          \
203                 case 4:                                                 \
204                         if (sizeof((x)) >= 8)                           \
205                                 __get_user_x_64t(__r2, __p, __e, __l, 4); \
206                         else                                            \
207                                 __get_user_x(__r2, __p, __e, __l, 4);   \
208                         break;                                          \
209                 case 8:                                                 \
210                         if (sizeof((x)) < 8)                            \
211                                 __get_user_x_32t(__r2, __p, __e, __l, 4); \
212                         else                                            \
213                                 __get_user_x(__r2, __p, __e, __l, 8);   \
214                         break;                                          \
215                 default: __e = __get_user_bad(); break;                 \
216                 }                                                       \
217                 uaccess_restore(__ua_flags);                            \
218                 x = (typeof(*(p))) __r2;                                \
219                 __e;                                                    \
220         })
221 
222 #define get_user(x, p)                                                  \
223         ({                                                              \
224                 might_fault();                                          \
225                 __get_user_check(x, p);                                 \
226          })
227 
228 extern int __put_user_1(void *, unsigned int);
229 extern int __put_user_2(void *, unsigned int);
230 extern int __put_user_4(void *, unsigned int);
231 extern int __put_user_8(void *, unsigned long long);
232 
233 #define __put_user_check(__pu_val, __ptr, __err, __s)                   \
234         ({                                                              \
235                 unsigned long __limit = current_thread_info()->addr_limit - 1; \
236                 register typeof(__pu_val) __r2 asm("r2") = __pu_val;    \
237                 register const void __user *__p asm("r0") = __ptr;      \
238                 register unsigned long __l asm("r1") = __limit;         \
239                 register int __e asm("r0");                             \
240                 __asm__ __volatile__ (                                  \
241                         __asmeq("%0", "r0") __asmeq("%2", "r2")         \
242                         __asmeq("%3", "r1")                             \
243                         "bl     __put_user_" #__s                       \
244                         : "=&r" (__e)                                   \
245                         : "" (__p), "r" (__r2), "r" (__l)              \
246                         : "ip", "lr", "cc");                            \
247                 __err = __e;                                            \
248         })
249 
250 #else /* CONFIG_MMU */
251 
252 /*
253  * uClinux has only one addr space, so has simplified address limits.
254  */
255 #define USER_DS                 KERNEL_DS
256 
257 #define segment_eq(a, b)                (1)
258 #define __addr_ok(addr)         ((void)(addr), 1)
259 #define __range_ok(addr, size)  ((void)(addr), 0)
260 #define get_fs()                (KERNEL_DS)
261 
262 static inline void set_fs(mm_segment_t fs)
263 {
264 }
265 
266 #define get_user(x, p)  __get_user(x, p)
267 #define __put_user_check __put_user_nocheck
268 
269 #endif /* CONFIG_MMU */
270 
271 #define access_ok(type, addr, size)     (__range_ok(addr, size) == 0)
272 
273 #define user_addr_max() \
274         (segment_eq(get_fs(), KERNEL_DS) ? ~0UL : get_fs())
275 
276 /*
277  * The "__xxx" versions of the user access functions do not verify the
278  * address space - it must have been done previously with a separate
279  * "access_ok()" call.
280  *
281  * The "xxx_error" versions set the third argument to EFAULT if an
282  * error occurs, and leave it unchanged on success.  Note that these
283  * versions are void (ie, don't return a value as such).
284  */
285 #define __get_user(x, ptr)                                              \
286 ({                                                                      \
287         long __gu_err = 0;                                              \
288         __get_user_err((x), (ptr), __gu_err);                           \
289         __gu_err;                                                       \
290 })
291 
292 #define __get_user_error(x, ptr, err)                                   \
293 ({                                                                      \
294         __get_user_err((x), (ptr), err);                                \
295         (void) 0;                                                       \
296 })
297 
298 #define __get_user_err(x, ptr, err)                                     \
299 do {                                                                    \
300         unsigned long __gu_addr = (unsigned long)(ptr);                 \
301         unsigned long __gu_val;                                         \
302         unsigned int __ua_flags;                                        \
303         __chk_user_ptr(ptr);                                            \
304         might_fault();                                                  \
305         __ua_flags = uaccess_save_and_enable();                         \
306         switch (sizeof(*(ptr))) {                                       \
307         case 1: __get_user_asm_byte(__gu_val, __gu_addr, err);  break;  \
308         case 2: __get_user_asm_half(__gu_val, __gu_addr, err);  break;  \
309         case 4: __get_user_asm_word(__gu_val, __gu_addr, err);  break;  \
310         default: (__gu_val) = __get_user_bad();                         \
311         }                                                               \
312         uaccess_restore(__ua_flags);                                    \
313         (x) = (__typeof__(*(ptr)))__gu_val;                             \
314 } while (0)
315 
316 #define __get_user_asm(x, addr, err, instr)                     \
317         __asm__ __volatile__(                                   \
318         "1:     " TUSER(instr) " %1, [%2], #0\n"                \
319         "2:\n"                                                  \
320         "       .pushsection .text.fixup,\"ax\"\n"              \
321         "       .align  2\n"                                    \
322         "3:     mov     %0, %3\n"                               \
323         "       mov     %1, #0\n"                               \
324         "       b       2b\n"                                   \
325         "       .popsection\n"                                  \
326         "       .pushsection __ex_table,\"a\"\n"                \
327         "       .align  3\n"                                    \
328         "       .long   1b, 3b\n"                               \
329         "       .popsection"                                    \
330         : "+r" (err), "=&r" (x)                                 \
331         : "r" (addr), "i" (-EFAULT)                             \
332         : "cc")
333 
334 #define __get_user_asm_byte(x, addr, err)                       \
335         __get_user_asm(x, addr, err, ldrb)
336 
337 #ifndef __ARMEB__
338 #define __get_user_asm_half(x, __gu_addr, err)                  \
339 ({                                                              \
340         unsigned long __b1, __b2;                               \
341         __get_user_asm_byte(__b1, __gu_addr, err);              \
342         __get_user_asm_byte(__b2, __gu_addr + 1, err);          \
343         (x) = __b1 | (__b2 << 8);                               \
344 })
345 #else
346 #define __get_user_asm_half(x, __gu_addr, err)                  \
347 ({                                                              \
348         unsigned long __b1, __b2;                               \
349         __get_user_asm_byte(__b1, __gu_addr, err);              \
350         __get_user_asm_byte(__b2, __gu_addr + 1, err);          \
351         (x) = (__b1 << 8) | __b2;                               \
352 })
353 #endif
354 
355 #define __get_user_asm_word(x, addr, err)                       \
356         __get_user_asm(x, addr, err, ldr)
357 
358 
359 #define __put_user_switch(x, ptr, __err, __fn)                          \
360         do {                                                            \
361                 const __typeof__(*(ptr)) __user *__pu_ptr = (ptr);      \
362                 __typeof__(*(ptr)) __pu_val = (x);                      \
363                 unsigned int __ua_flags;                                \
364                 might_fault();                                          \
365                 __ua_flags = uaccess_save_and_enable();                 \
366                 switch (sizeof(*(ptr))) {                               \
367                 case 1: __fn(__pu_val, __pu_ptr, __err, 1); break;      \
368                 case 2: __fn(__pu_val, __pu_ptr, __err, 2); break;      \
369                 case 4: __fn(__pu_val, __pu_ptr, __err, 4); break;      \
370                 case 8: __fn(__pu_val, __pu_ptr, __err, 8); break;      \
371                 default: __err = __put_user_bad(); break;               \
372                 }                                                       \
373                 uaccess_restore(__ua_flags);                            \
374         } while (0)
375 
376 #define put_user(x, ptr)                                                \
377 ({                                                                      \
378         int __pu_err = 0;                                               \
379         __put_user_switch((x), (ptr), __pu_err, __put_user_check);      \
380         __pu_err;                                                       \
381 })
382 
383 #define __put_user(x, ptr)                                              \
384 ({                                                                      \
385         long __pu_err = 0;                                              \
386         __put_user_switch((x), (ptr), __pu_err, __put_user_nocheck);    \
387         __pu_err;                                                       \
388 })
389 
390 #define __put_user_error(x, ptr, err)                                   \
391 ({                                                                      \
392         __put_user_switch((x), (ptr), (err), __put_user_nocheck);       \
393         (void) 0;                                                       \
394 })
395 
396 #define __put_user_nocheck(x, __pu_ptr, __err, __size)                  \
397         do {                                                            \
398                 unsigned long __pu_addr = (unsigned long)__pu_ptr;      \
399                 __put_user_nocheck_##__size(x, __pu_addr, __err);       \
400         } while (0)
401 
402 #define __put_user_nocheck_1 __put_user_asm_byte
403 #define __put_user_nocheck_2 __put_user_asm_half
404 #define __put_user_nocheck_4 __put_user_asm_word
405 #define __put_user_nocheck_8 __put_user_asm_dword
406 
407 #define __put_user_asm(x, __pu_addr, err, instr)                \
408         __asm__ __volatile__(                                   \
409         "1:     " TUSER(instr) " %1, [%2], #0\n"                \
410         "2:\n"                                                  \
411         "       .pushsection .text.fixup,\"ax\"\n"              \
412         "       .align  2\n"                                    \
413         "3:     mov     %0, %3\n"                               \
414         "       b       2b\n"                                   \
415         "       .popsection\n"                                  \
416         "       .pushsection __ex_table,\"a\"\n"                \
417         "       .align  3\n"                                    \
418         "       .long   1b, 3b\n"                               \
419         "       .popsection"                                    \
420         : "+r" (err)                                            \
421         : "r" (x), "r" (__pu_addr), "i" (-EFAULT)               \
422         : "cc")
423 
424 #define __put_user_asm_byte(x, __pu_addr, err)                  \
425         __put_user_asm(x, __pu_addr, err, strb)
426 
427 #ifndef __ARMEB__
428 #define __put_user_asm_half(x, __pu_addr, err)                  \
429 ({                                                              \
430         unsigned long __temp = (__force unsigned long)(x);      \
431         __put_user_asm_byte(__temp, __pu_addr, err);            \
432         __put_user_asm_byte(__temp >> 8, __pu_addr + 1, err);   \
433 })
434 #else
435 #define __put_user_asm_half(x, __pu_addr, err)                  \
436 ({                                                              \
437         unsigned long __temp = (__force unsigned long)(x);      \
438         __put_user_asm_byte(__temp >> 8, __pu_addr, err);       \
439         __put_user_asm_byte(__temp, __pu_addr + 1, err);        \
440 })
441 #endif
442 
443 #define __put_user_asm_word(x, __pu_addr, err)                  \
444         __put_user_asm(x, __pu_addr, err, str)
445 
446 #ifndef __ARMEB__
447 #define __reg_oper0     "%R2"
448 #define __reg_oper1     "%Q2"
449 #else
450 #define __reg_oper0     "%Q2"
451 #define __reg_oper1     "%R2"
452 #endif
453 
454 #define __put_user_asm_dword(x, __pu_addr, err)                 \
455         __asm__ __volatile__(                                   \
456  ARM(   "1:     " TUSER(str) "  " __reg_oper1 ", [%1], #4\n"    ) \
457  ARM(   "2:     " TUSER(str) "  " __reg_oper0 ", [%1]\n"        ) \
458  THUMB( "1:     " TUSER(str) "  " __reg_oper1 ", [%1]\n"        ) \
459  THUMB( "2:     " TUSER(str) "  " __reg_oper0 ", [%1, #4]\n"    ) \
460         "3:\n"                                                  \
461         "       .pushsection .text.fixup,\"ax\"\n"              \
462         "       .align  2\n"                                    \
463         "4:     mov     %0, %3\n"                               \
464         "       b       3b\n"                                   \
465         "       .popsection\n"                                  \
466         "       .pushsection __ex_table,\"a\"\n"                \
467         "       .align  3\n"                                    \
468         "       .long   1b, 4b\n"                               \
469         "       .long   2b, 4b\n"                               \
470         "       .popsection"                                    \
471         : "+r" (err), "+r" (__pu_addr)                          \
472         : "r" (x), "i" (-EFAULT)                                \
473         : "cc")
474 
475 
476 #ifdef CONFIG_MMU
477 extern unsigned long __must_check
478 arm_copy_from_user(void *to, const void __user *from, unsigned long n);
479 
480 static inline unsigned long __must_check
481 __copy_from_user(void *to, const void __user *from, unsigned long n)
482 {
483         unsigned int __ua_flags;
484 
485         check_object_size(to, n, false);
486         __ua_flags = uaccess_save_and_enable();
487         n = arm_copy_from_user(to, from, n);
488         uaccess_restore(__ua_flags);
489         return n;
490 }
491 
492 extern unsigned long __must_check
493 arm_copy_to_user(void __user *to, const void *from, unsigned long n);
494 extern unsigned long __must_check
495 __copy_to_user_std(void __user *to, const void *from, unsigned long n);
496 
497 static inline unsigned long __must_check
498 __copy_to_user(void __user *to, const void *from, unsigned long n)
499 {
500 #ifndef CONFIG_UACCESS_WITH_MEMCPY
501         unsigned int __ua_flags;
502 
503         check_object_size(from, n, true);
504         __ua_flags = uaccess_save_and_enable();
505         n = arm_copy_to_user(to, from, n);
506         uaccess_restore(__ua_flags);
507         return n;
508 #else
509         check_object_size(from, n, true);
510         return arm_copy_to_user(to, from, n);
511 #endif
512 }
513 
514 extern unsigned long __must_check
515 arm_clear_user(void __user *addr, unsigned long n);
516 extern unsigned long __must_check
517 __clear_user_std(void __user *addr, unsigned long n);
518 
519 static inline unsigned long __must_check
520 __clear_user(void __user *addr, unsigned long n)
521 {
522         unsigned int __ua_flags = uaccess_save_and_enable();
523         n = arm_clear_user(addr, n);
524         uaccess_restore(__ua_flags);
525         return n;
526 }
527 
528 #else
529 #define __copy_from_user(to, from, n)   (memcpy(to, (void __force *)from, n), 0)
530 #define __copy_to_user(to, from, n)     (memcpy((void __force *)to, from, n), 0)
531 #define __clear_user(addr, n)           (memset((void __force *)addr, 0, n), 0)
532 #endif
533 
534 static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n)
535 {
536         if (access_ok(VERIFY_READ, from, n))
537                 n = __copy_from_user(to, from, n);
538         else /* security hole - plug it */
539                 memset(to, 0, n);
540         return n;
541 }
542 
543 static inline unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n)
544 {
545         if (access_ok(VERIFY_WRITE, to, n))
546                 n = __copy_to_user(to, from, n);
547         return n;
548 }
549 
550 #define __copy_to_user_inatomic __copy_to_user
551 #define __copy_from_user_inatomic __copy_from_user
552 
553 static inline unsigned long __must_check clear_user(void __user *to, unsigned long n)
554 {
555         if (access_ok(VERIFY_WRITE, to, n))
556                 n = __clear_user(to, n);
557         return n;
558 }
559 
560 /* These are from lib/ code, and use __get_user() and friends */
561 extern long strncpy_from_user(char *dest, const char __user *src, long count);
562 
563 extern __must_check long strlen_user(const char __user *str);
564 extern __must_check long strnlen_user(const char __user *str, long n);
565 
566 #endif /* _ASMARM_UACCESS_H */
567 

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