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 <asm/memory.h>
  16 #include <asm/domain.h>
  17 #include <asm/unified.h>
  18 #include <asm/compiler.h>
  19
  20 #include <asm/extable.h>
  21
  22 /*
  23  * These two functions allow hooking accesses to userspace to increase
  24  * system integrity by ensuring that the kernel can not inadvertantly
  25  * perform such accesses (eg, via list poison values) which could then
  26  * be exploited for priviledge escalation.
  27  */
  28 static inline unsigned int uaccess_save_and_enable(void)
  29 {
  30 #ifdef CONFIG_CPU_SW_DOMAIN_PAN
  31         unsigned int old_domain = get_domain();
  32
  33         /* Set the current domain access to permit user accesses */
  34         set_domain((old_domain & ~domain_mask(DOMAIN_USER)) |
  35                    domain_val(DOMAIN_USER, DOMAIN_CLIENT));
  36
  37         return old_domain;
  38 #else
  39         return 0;
  40 #endif
  41 }
  42
  43 static inline void uaccess_restore(unsigned int flags)
  44 {
  45 #ifdef CONFIG_CPU_SW_DOMAIN_PAN
  46         /* Restore the user access mask */
  47         set_domain(flags);
  48 #endif
  49 }
  50
  51 /*
  52  * These two are intentionally not defined anywhere - if the kernel
  53  * code generates any references to them, that's a bug.
  54  */
  55 extern int __get_user_bad(void);
  56 extern int __put_user_bad(void);
  57
  58 /*
  59  * Note that this is actually 0x1,0000,0000
  60  */
  61 #define KERNEL_DS       0x00000000
  62 #define get_ds()        (KERNEL_DS)
  63
  64 #ifdef CONFIG_MMU
  65
  66 #define USER_DS         TASK_SIZE
  67 #define get_fs()        (current_thread_info()->addr_limit)
  68
  69 static inline void set_fs(mm_segment_t fs)
  70 {
  71         current_thread_info()->addr_limit = fs;
  72
  73         /*
  74          * Prevent a mispredicted conditional call to set_fs from forwarding
  75          * the wrong address limit to access_ok under speculation.
  76          */
  77         dsb(nsh);
  78         isb();
  79
  80         modify_domain(DOMAIN_KERNEL, fs ? DOMAIN_CLIENT : DOMAIN_MANAGER);
  81 }
  82
  83 #define segment_eq(a, b)        ((a) == (b))
  84
  85 /* We use 33-bit arithmetic here... */
  86 #define __range_ok(addr, size) ({ \
  87         unsigned long flag, roksum; \
  88         __chk_user_ptr(addr);   \
  89         __asm__("adds %1, %2, %3; sbcccs %1, %1, %0; movcc %0, #0" \
  90                 : "=&r" (flag), "=&r" (roksum) \
  91                 : "r" (addr), "Ir" (size), "0" (current_thread_info()->addr_limit) \
  92                 : "cc"); \
  93         flag; })
  94
  95 /*
  96  * This is a type: either unsigned long, if the argument fits into
  97  * that type, or otherwise unsigned long long.
  98  */
  99 #define __inttype(x) \
 100         __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
 101
 102 /*
 103  * Sanitise a uaccess pointer such that it becomes NULL if addr+size
 104  * is above the current addr_limit.
 105  */
 106 #define uaccess_mask_range_ptr(ptr, size)                       \
 107         ((__typeof__(ptr))__uaccess_mask_range_ptr(ptr, size))
 108 static inline void __user *__uaccess_mask_range_ptr(const void __user *ptr,
 109                                                     size_t size)
 110 {
 111         void __user *safe_ptr = (void __user *)ptr;
 112         unsigned long tmp;
 113
 114         asm volatile(
 115         "       sub     %1, %3, #1\n"
 116         "       subs    %1, %1, %0\n"
 117         "       addhs   %1, %1, #1\n"
 118         "       subhss  %1, %1, %2\n"
 119         "       movlo   %0, #0\n"
 120         : "+r" (safe_ptr), "=&r" (tmp)
 121         : "r" (size), "r" (current_thread_info()->addr_limit)
 122         : "cc");
 123
 124         csdb();
 125         return safe_ptr;
 126 }
 127
 128 /*
 129  * Single-value transfer routines.  They automatically use the right
 130  * size if we just have the right pointer type.  Note that the functions
 131  * which read from user space (*get_*) need to take care not to leak
 132  * kernel data even if the calling code is buggy and fails to check
 133  * the return value.  This means zeroing out the destination variable
 134  * or buffer on error.  Normally this is done out of line by the
 135  * fixup code, but there are a few places where it intrudes on the
 136  * main code path.  When we only write to user space, there is no
 137  * problem.
 138  */
 139 extern int __get_user_1(void *);
 140 extern int __get_user_2(void *);
 141 extern int __get_user_4(void *);
 142 extern int __get_user_32t_8(void *);
 143 extern int __get_user_8(void *);
 144 extern int __get_user_64t_1(void *);
 145 extern int __get_user_64t_2(void *);
 146 extern int __get_user_64t_4(void *);
 147
 148 #define __GUP_CLOBBER_1 "lr", "cc"
 149 #ifdef CONFIG_CPU_USE_DOMAINS
 150 #define __GUP_CLOBBER_2 "ip", "lr", "cc"
 151 #else
 152 #define __GUP_CLOBBER_2 "lr", "cc"
 153 #endif
 154 #define __GUP_CLOBBER_4 "lr", "cc"
 155 #define __GUP_CLOBBER_32t_8 "lr", "cc"
 156 #define __GUP_CLOBBER_8 "lr", "cc"
 157
 158 #define __get_user_x(__r2, __p, __e, __l, __s)                          \
 159            __asm__ __volatile__ (                                       \
 160                 __asmeq("%0", "r0") __asmeq("%1", "r2")                 \
 161                 __asmeq("%3", "r1")                                     \
 162                 "bl     __get_user_" #__s                               \
 163                 : "=&r" (__e), "=r" (__r2)                              \
 164                 : "0" (__p), "r" (__l)                                  \
 165                 : __GUP_CLOBBER_##__s)
 166
 167 /* narrowing a double-word get into a single 32bit word register: */
 168 #ifdef __ARMEB__
 169 #define __get_user_x_32t(__r2, __p, __e, __l, __s)                      \
 170         __get_user_x(__r2, __p, __e, __l, 32t_8)
 171 #else
 172 #define __get_user_x_32t __get_user_x
 173 #endif
 174
 175 /*
 176  * storing result into proper least significant word of 64bit target var,
 177  * different only for big endian case where 64 bit __r2 lsw is r3:
 178  */
 179 #ifdef __ARMEB__
 180 #define __get_user_x_64t(__r2, __p, __e, __l, __s)                      \
 181            __asm__ __volatile__ (                                       \
 182                 __asmeq("%0", "r0") __asmeq("%1", "r2")                 \
 183                 __asmeq("%3", "r1")                                     \
 184                 "bl     __get_user_64t_" #__s                           \
 185                 : "=&r" (__e), "=r" (__r2)                              \
 186                 : "0" (__p), "r" (__l)                                  \
 187                 : __GUP_CLOBBER_##__s)
 188 #else
 189 #define __get_user_x_64t __get_user_x
 190 #endif
 191
 192
 193 #define __get_user_check(x, p)                                          \
 194         ({                                                              \
 195                 unsigned long __limit = current_thread_info()->addr_limit - 1; \
 196                 register typeof(*(p)) __user *__p asm("r0") = (p);      \
 197                 register __inttype(x) __r2 asm("r2");                   \
 198                 register unsigned long __l asm("r1") = __limit;         \
 199                 register int __e asm("r0");                             \
 200                 unsigned int __ua_flags = uaccess_save_and_enable();    \
 201                 switch (sizeof(*(__p))) {                               \
 202                 case 1:                                                 \
 203                         if (sizeof((x)) >= 8)                           \
 204                                 __get_user_x_64t(__r2, __p, __e, __l, 1); \
 205                         else                                            \
 206                                 __get_user_x(__r2, __p, __e, __l, 1);   \
 207                         break;                                          \
 208                 case 2:                                                 \
 209                         if (sizeof((x)) >= 8)                           \
 210                                 __get_user_x_64t(__r2, __p, __e, __l, 2); \
 211                         else                                            \
 212                                 __get_user_x(__r2, __p, __e, __l, 2);   \
 213                         break;                                          \
 214                 case 4:                                                 \
 215                         if (sizeof((x)) >= 8)                           \
 216                                 __get_user_x_64t(__r2, __p, __e, __l, 4); \
 217                         else                                            \
 218                                 __get_user_x(__r2, __p, __e, __l, 4);   \
 219                         break;                                          \
 220                 case 8:                                                 \
 221                         if (sizeof((x)) < 8)                            \
 222                                 __get_user_x_32t(__r2, __p, __e, __l, 4); \
 223                         else                                            \
 224                                 __get_user_x(__r2, __p, __e, __l, 8);   \
 225                         break;                                          \
 226                 default: __e = __get_user_bad(); break;                 \
 227                 }                                                       \
 228                 uaccess_restore(__ua_flags);                            \
 229                 x = (typeof(*(p))) __r2;                                \
 230                 __e;                                                    \
 231         })
 232
 233 #define get_user(x, p)                                                  \
 234         ({                                                              \
 235                 might_fault();                                          \
 236                 __get_user_check(x, p);                                 \
 237          })
 238
 239 extern int __put_user_1(void *, unsigned int);
 240 extern int __put_user_2(void *, unsigned int);
 241 extern int __put_user_4(void *, unsigned int);
 242 extern int __put_user_8(void *, unsigned long long);
 243
 244 #define __put_user_check(__pu_val, __ptr, __err, __s)                   \
 245         ({                                                              \
 246                 unsigned long __limit = current_thread_info()->addr_limit - 1; \
 247                 register typeof(__pu_val) __r2 asm("r2") = __pu_val;    \
 248                 register const void __user *__p asm("r0") = __ptr;      \
 249                 register unsigned long __l asm("r1") = __limit;         \
 250                 register int __e asm("r0");                             \
 251                 __asm__ __volatile__ (                                  \
 252                         __asmeq("%0", "r0") __asmeq("%2", "r2")         \
 253                         __asmeq("%3", "r1")                             \
 254                         "bl     __put_user_" #__s                       \
 255                         : "=&r" (__e)                                   \
 256                         : "0" (__p), "r" (__r2), "r" (__l)              \
 257                         : "ip", "lr", "cc");                            \
 258                 __err = __e;                                            \
 259         })
 260
 261 #else /* CONFIG_MMU */
 262
 263 /*
 264  * uClinux has only one addr space, so has simplified address limits.
 265  */
 266 #define USER_DS                 KERNEL_DS
 267
 268 #define segment_eq(a, b)                (1)
 269 #define __addr_ok(addr)         ((void)(addr), 1)
 270 #define __range_ok(addr, size)  ((void)(addr), 0)
 271 #define get_fs()                (KERNEL_DS)
 272
 273 static inline void set_fs(mm_segment_t fs)
 274 {
 275 }
 276
 277 #define get_user(x, p)  __get_user(x, p)
 278 #define __put_user_check __put_user_nocheck
 279
 280 #endif /* CONFIG_MMU */
 281
 282 #define access_ok(type, addr, size)     (__range_ok(addr, size) == 0)
 283
 284 #define user_addr_max() \
 285         (uaccess_kernel() ? ~0UL : get_fs())
 286
 287 #ifdef CONFIG_CPU_SPECTRE
 288 /*
 289  * When mitigating Spectre variant 1, it is not worth fixing the non-
 290  * verifying accessors, because we need to add verification of the
 291  * address space there.  Force these to use the standard get_user()
 292  * version instead.
 293  */
 294 #define __get_user(x, ptr) get_user(x, ptr)
 295 #else
 296
 297 /*
 298  * The "__xxx" versions of the user access functions do not verify the
 299  * address space - it must have been done previously with a separate
 300  * "access_ok()" call.
 301  *
 302  * The "xxx_error" versions set the third argument to EFAULT if an
 303  * error occurs, and leave it unchanged on success.  Note that these
 304  * versions are void (ie, don't return a value as such).
 305  */
 306 #define __get_user(x, ptr)                                              \
 307 ({                                                                      \
 308         long __gu_err = 0;                                              \
 309         __get_user_err((x), (ptr), __gu_err);                           \
 310         __gu_err;                                                       \
 311 })
 312
 313 #define __get_user_err(x, ptr, err)                                     \
 314 do {                                                                    \
 315         unsigned long __gu_addr = (unsigned long)(ptr);                 \
 316         unsigned long __gu_val;                                         \
 317         unsigned int __ua_flags;                                        \
 318         __chk_user_ptr(ptr);                                            \
 319         might_fault();                                                  \
 320         __ua_flags = uaccess_save_and_enable();                         \
 321         switch (sizeof(*(ptr))) {                                       \
 322         case 1: __get_user_asm_byte(__gu_val, __gu_addr, err);  break;  \
 323         case 2: __get_user_asm_half(__gu_val, __gu_addr, err);  break;  \
 324         case 4: __get_user_asm_word(__gu_val, __gu_addr, err);  break;  \
 325         default: (__gu_val) = __get_user_bad();                         \
 326         }                                                               \
 327         uaccess_restore(__ua_flags);                                    \
 328         (x) = (__typeof__(*(ptr)))__gu_val;                             \
 329 } while (0)
 330
 331 #define __get_user_asm(x, addr, err, instr)                     \
 332         __asm__ __volatile__(                                   \
 333         "1:     " TUSER(instr) " %1, [%2], #0\n"                \
 334         "2:\n"                                                  \
 335         "       .pushsection .text.fixup,\"ax\"\n"              \
 336         "       .align  2\n"                                    \
 337         "3:     mov     %0, %3\n"                               \
 338         "       mov     %1, #0\n"                               \
 339         "       b       2b\n"                                   \
 340         "       .popsection\n"                                  \
 341         "       .pushsection __ex_table,\"a\"\n"                \
 342         "       .align  3\n"                                    \
 343         "       .long   1b, 3b\n"                               \
 344         "       .popsection"                                    \
 345         : "+r" (err), "=&r" (x)                                 \
 346         : "r" (addr), "i" (-EFAULT)                             \
 347         : "cc")
 348
 349 #define __get_user_asm_byte(x, addr, err)                       \
 350         __get_user_asm(x, addr, err, ldrb)
 351
 352 #ifndef __ARMEB__
 353 #define __get_user_asm_half(x, __gu_addr, err)                  \
 354 ({                                                              \
 355         unsigned long __b1, __b2;                               \
 356         __get_user_asm_byte(__b1, __gu_addr, err);              \
 357         __get_user_asm_byte(__b2, __gu_addr + 1, err);          \
 358         (x) = __b1 | (__b2 << 8);                               \
 359 })
 360 #else
 361 #define __get_user_asm_half(x, __gu_addr, err)                  \
 362 ({                                                              \
 363         unsigned long __b1, __b2;                               \
 364         __get_user_asm_byte(__b1, __gu_addr, err);              \
 365         __get_user_asm_byte(__b2, __gu_addr + 1, err);          \
 366         (x) = (__b1 << 8) | __b2;                               \
 367 })
 368 #endif
 369
 370 #define __get_user_asm_word(x, addr, err)                       \
 371         __get_user_asm(x, addr, err, ldr)
 372 #endif
 373
 374
 375 #define __put_user_switch(x, ptr, __err, __fn)                          \
 376         do {                                                            \
 377                 const __typeof__(*(ptr)) __user *__pu_ptr = (ptr);      \
 378                 __typeof__(*(ptr)) __pu_val = (x);                      \
 379                 unsigned int __ua_flags;                                \
 380                 might_fault();                                          \
 381                 __ua_flags = uaccess_save_and_enable();                 \
 382                 switch (sizeof(*(ptr))) {                               \
 383                 case 1: __fn(__pu_val, __pu_ptr, __err, 1); break;      \
 384                 case 2: __fn(__pu_val, __pu_ptr, __err, 2); break;      \
 385                 case 4: __fn(__pu_val, __pu_ptr, __err, 4); break;      \
 386                 case 8: __fn(__pu_val, __pu_ptr, __err, 8); break;      \
 387                 default: __err = __put_user_bad(); break;               \
 388                 }                                                       \
 389                 uaccess_restore(__ua_flags);                            \
 390         } while (0)
 391
 392 #define put_user(x, ptr)                                                \
 393 ({                                                                      \
 394         int __pu_err = 0;                                               \
 395         __put_user_switch((x), (ptr), __pu_err, __put_user_check);      \
 396         __pu_err;                                                       \
 397 })
 398
 399 #ifdef CONFIG_CPU_SPECTRE
 400 /*
 401  * When mitigating Spectre variant 1.1, all accessors need to include
 402  * verification of the address space.
 403  */
 404 #define __put_user(x, ptr) put_user(x, ptr)
 405
 406 #else
 407 #define __put_user(x, ptr)                                              \
 408 ({                                                                      \
 409         long __pu_err = 0;                                              \
 410         __put_user_switch((x), (ptr), __pu_err, __put_user_nocheck);    \
 411         __pu_err;                                                       \
 412 })
 413
 414 #define __put_user_nocheck(x, __pu_ptr, __err, __size)                  \
 415         do {                                                            \
 416                 unsigned long __pu_addr = (unsigned long)__pu_ptr;      \
 417                 __put_user_nocheck_##__size(x, __pu_addr, __err);       \
 418         } while (0)
 419
 420 #define __put_user_nocheck_1 __put_user_asm_byte
 421 #define __put_user_nocheck_2 __put_user_asm_half
 422 #define __put_user_nocheck_4 __put_user_asm_word
 423 #define __put_user_nocheck_8 __put_user_asm_dword
 424
 425 #define __put_user_asm(x, __pu_addr, err, instr)                \
 426         __asm__ __volatile__(                                   \
 427         "1:     " TUSER(instr) " %1, [%2], #0\n"                \
 428         "2:\n"                                                  \
 429         "       .pushsection .text.fixup,\"ax\"\n"              \
 430         "       .align  2\n"                                    \
 431         "3:     mov     %0, %3\n"                               \
 432         "       b       2b\n"                                   \
 433         "       .popsection\n"                                  \
 434         "       .pushsection __ex_table,\"a\"\n"                \
 435         "       .align  3\n"                                    \
 436         "       .long   1b, 3b\n"                               \
 437         "       .popsection"                                    \
 438         : "+r" (err)                                            \
 439         : "r" (x), "r" (__pu_addr), "i" (-EFAULT)               \
 440         : "cc")
 441
 442 #define __put_user_asm_byte(x, __pu_addr, err)                  \
 443         __put_user_asm(x, __pu_addr, err, strb)
 444
 445 #ifndef __ARMEB__
 446 #define __put_user_asm_half(x, __pu_addr, err)                  \
 447 ({                                                              \
 448         unsigned long __temp = (__force unsigned long)(x);      \
 449         __put_user_asm_byte(__temp, __pu_addr, err);            \
 450         __put_user_asm_byte(__temp >> 8, __pu_addr + 1, err);   \
 451 })
 452 #else
 453 #define __put_user_asm_half(x, __pu_addr, err)                  \
 454 ({                                                              \
 455         unsigned long __temp = (__force unsigned long)(x);      \
 456         __put_user_asm_byte(__temp >> 8, __pu_addr, err);       \
 457         __put_user_asm_byte(__temp, __pu_addr + 1, err);        \
 458 })
 459 #endif
 460
 461 #define __put_user_asm_word(x, __pu_addr, err)                  \
 462         __put_user_asm(x, __pu_addr, err, str)
 463
 464 #ifndef __ARMEB__
 465 #define __reg_oper0     "%R2"
 466 #define __reg_oper1     "%Q2"
 467 #else
 468 #define __reg_oper0     "%Q2"
 469 #define __reg_oper1     "%R2"
 470 #endif
 471
 472 #define __put_user_asm_dword(x, __pu_addr, err)                 \
 473         __asm__ __volatile__(                                   \
 474  ARM(   "1:     " TUSER(str) "  " __reg_oper1 ", [%1], #4\n"    ) \
 475  ARM(   "2:     " TUSER(str) "  " __reg_oper0 ", [%1]\n"        ) \
 476  THUMB( "1:     " TUSER(str) "  " __reg_oper1 ", [%1]\n"        ) \
 477  THUMB( "2:     " TUSER(str) "  " __reg_oper0 ", [%1, #4]\n"    ) \
 478         "3:\n"                                                  \
 479         "       .pushsection .text.fixup,\"ax\"\n"              \
 480         "       .align  2\n"                                    \
 481         "4:     mov     %0, %3\n"                               \
 482         "       b       3b\n"                                   \
 483         "       .popsection\n"                                  \
 484         "       .pushsection __ex_table,\"a\"\n"                \
 485         "       .align  3\n"                                    \
 486         "       .long   1b, 4b\n"                               \
 487         "       .long   2b, 4b\n"                               \
 488         "       .popsection"                                    \
 489         : "+r" (err), "+r" (__pu_addr)                          \
 490         : "r" (x), "i" (-EFAULT)                                \
 491         : "cc")
 492
 493 #endif /* !CONFIG_CPU_SPECTRE */
 494
 495 #ifdef CONFIG_MMU
 496 extern unsigned long __must_check
 497 arm_copy_from_user(void *to, const void __user *from, unsigned long n);
 498
 499 static inline unsigned long __must_check
 500 raw_copy_from_user(void *to, const void __user *from, unsigned long n)
 501 {
 502         unsigned int __ua_flags;
 503
 504         __ua_flags = uaccess_save_and_enable();
 505         n = arm_copy_from_user(to, from, n);
 506         uaccess_restore(__ua_flags);
 507         return n;
 508 }
 509
 510 extern unsigned long __must_check
 511 arm_copy_to_user(void __user *to, const void *from, unsigned long n);
 512 extern unsigned long __must_check
 513 __copy_to_user_std(void __user *to, const void *from, unsigned long n);
 514
 515 static inline unsigned long __must_check
 516 raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 517 {
 518 #ifndef CONFIG_UACCESS_WITH_MEMCPY
 519         unsigned int __ua_flags;
 520         __ua_flags = uaccess_save_and_enable();
 521         n = arm_copy_to_user(to, from, n);
 522         uaccess_restore(__ua_flags);
 523         return n;
 524 #else
 525         return arm_copy_to_user(to, from, n);
 526 #endif
 527 }
 528
 529 extern unsigned long __must_check
 530 arm_clear_user(void __user *addr, unsigned long n);
 531 extern unsigned long __must_check
 532 __clear_user_std(void __user *addr, unsigned long n);
 533
 534 static inline unsigned long __must_check
 535 __clear_user(void __user *addr, unsigned long n)
 536 {
 537         unsigned int __ua_flags = uaccess_save_and_enable();
 538         n = arm_clear_user(addr, n);
 539         uaccess_restore(__ua_flags);
 540         return n;
 541 }
 542
 543 #else
 544 static inline unsigned long
 545 raw_copy_from_user(void *to, const void __user *from, unsigned long n)
 546 {
 547         memcpy(to, (const void __force *)from, n);
 548         return 0;
 549 }
 550 static inline unsigned long
 551 raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 552 {
 553         memcpy((void __force *)to, from, n);
 554         return 0;
 555 }
 556 #define __clear_user(addr, n)           (memset((void __force *)addr, 0, n), 0)
 557 #endif
 558 #define INLINE_COPY_TO_USER
 559 #define INLINE_COPY_FROM_USER
 560
 561 static inline unsigned long __must_check clear_user(void __user *to, unsigned long n)
 562 {
 563         if (access_ok(VERIFY_WRITE, to, n))
 564                 n = __clear_user(to, n);
 565         return n;
 566 }
 567
 568 /* These are from lib/ code, and use __get_user() and friends */
 569 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 570
 571 extern __must_check long strnlen_user(const char __user *str, long n);
 572
 573 #endif /* _ASMARM_UACCESS_H */