arch/arm64/include/asm/uaccess.h

   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 #ifndef __ASSEMBLY__
  22
  23 /*
  24  * User space memory access functions
  25  */
  26 #include <linux/string.h>
  27 #include <linux/thread_info.h>
  28
  29 #include <asm/alternative.h>
  30 #include <asm/cpufeature.h>
  31 #include <asm/ptrace.h>
  32 #include <asm/sysreg.h>
  33 #include <asm/errno.h>
  34 #include <asm/memory.h>
  35 #include <asm/compiler.h>
  36
  37 #define VERIFY_READ 0
  38 #define VERIFY_WRITE 1
  39
  40 /*
  41  * The exception table consists of pairs of relative offsets: the first
  42  * is the relative offset to an instruction that is allowed to fault,
  43  * and the second is the relative offset at which the program should
  44  * continue. No registers are modified, so it is entirely up to the
  45  * continuation code to figure out what to do.
  46  *
  47  * All the routines below use bits of fixup code that are out of line
  48  * with the main instruction path.  This means when everything is well,
  49  * we don't even have to jump over them.  Further, they do not intrude
  50  * on our cache or tlb entries.
  51  */
  52
  53 struct exception_table_entry
  54 {
  55         int insn, fixup;
  56 };
  57
  58 #define ARCH_HAS_RELATIVE_EXTABLE
  59
  60 extern int fixup_exception(struct pt_regs *regs);
  61
  62 #define KERNEL_DS       (-1UL)
  63 #define get_ds()        (KERNEL_DS)
  64
  65 #define USER_DS         TASK_SIZE_64
  66 #define get_fs()        (current_thread_info()->addr_limit)
  67
  68 static inline void set_fs(mm_segment_t fs)
  69 {
  70         current_thread_info()->addr_limit = fs;
  71
  72         /*
  73          * Enable/disable UAO so that copy_to_user() etc can access
  74          * kernel memory with the unprivileged instructions.
  75          */
  76         if (IS_ENABLED(CONFIG_ARM64_UAO) && fs == KERNEL_DS)
  77                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
  78         else
  79                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
  80                                 CONFIG_ARM64_UAO));
  81 }
  82
  83 #define segment_eq(a, b)        ((a) == (b))
  84
  85 /*
  86  * Return 1 if addr < current->addr_limit, 0 otherwise.
  87  */
  88 #define __addr_ok(addr)                                                 \
  89 ({                                                                      \
  90         unsigned long flag;                                             \
  91         asm("cmp %1, %0; cset %0, lo"                                   \
  92                 : "=&r" (flag)                                          \
  93                 : "r" (addr), "0" (current_thread_info()->addr_limit)   \
  94                 : "cc");                                                \
  95         flag;                                                           \
  96 })
  97
  98 /*
  99  * Test whether a block of memory is a valid user space address.
 100  * Returns 1 if the range is valid, 0 otherwise.
 101  *
 102  * This is equivalent to the following test:
 103  * (u65)addr + (u65)size <= current->addr_limit
 104  *
 105  * This needs 65-bit arithmetic.
 106  */
 107 #define __range_ok(addr, size)                                          \
 108 ({                                                                      \
 109         unsigned long flag, roksum;                                     \
 110         __chk_user_ptr(addr);                                           \
 111         asm("adds %1, %1, %3; ccmp %1, %4, #2, cc; cset %0, ls"         \
 112                 : "=&r" (flag), "=&r" (roksum)                          \
 113                 : "1" (addr), "Ir" (size),                              \
 114                   "r" (current_thread_info()->addr_limit)               \
 115                 : "cc");                                                \
 116         flag;                                                           \
 117 })
 118
 119 #define access_ok(type, addr, size)     __range_ok(addr, size)
 120 #define user_addr_max                   get_fs
 121
 122 #define _ASM_EXTABLE(from, to)                                          \
 123         "       .pushsection    __ex_table, \"a\"\n"                    \
 124         "       .align          3\n"                                    \
 125         "       .long           (" #from " - .), (" #to " - .)\n"       \
 126         "       .popsection\n"
 127
 128 /*
 129  * User access enabling/disabling.
 130  */
 131 #define __uaccess_disable(alt)                                          \
 132 do {                                                                    \
 133         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt,                  \
 134                         CONFIG_ARM64_PAN));                             \
 135 } while (0)
 136
 137 #define __uaccess_enable(alt)                                           \
 138 do {                                                                    \
 139         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt,                  \
 140                         CONFIG_ARM64_PAN));                             \
 141 } while (0)
 142
 143 static inline void uaccess_disable(void)
 144 {
 145         __uaccess_disable(ARM64_HAS_PAN);
 146 }
 147
 148 static inline void uaccess_enable(void)
 149 {
 150         __uaccess_enable(ARM64_HAS_PAN);
 151 }
 152
 153 /*
 154  * These functions are no-ops when UAO is present.
 155  */
 156 static inline void uaccess_disable_not_uao(void)
 157 {
 158         __uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
 159 }
 160
 161 static inline void uaccess_enable_not_uao(void)
 162 {
 163         __uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
 164 }
 165
 166 /*
 167  * The "__xxx" versions of the user access functions do not verify the address
 168  * space - it must have been done previously with a separate "access_ok()"
 169  * call.
 170  *
 171  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 172  * occurs, and leave it unchanged on success.
 173  */
 174 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 175         asm volatile(                                                   \
 176         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 177                         alt_instr " " reg "1, [%2]\n", feature)         \
 178         "2:\n"                                                          \
 179         "       .section .fixup, \"ax\"\n"                              \
 180         "       .align  2\n"                                            \
 181         "3:     mov     %w0, %3\n"                                      \
 182         "       mov     %1, #0\n"                                       \
 183         "       b       2b\n"                                           \
 184         "       .previous\n"                                            \
 185         _ASM_EXTABLE(1b, 3b)                                            \
 186         : "+r" (err), "=&r" (x)                                         \
 187         : "r" (addr), "i" (-EFAULT))
 188
 189 #define __get_user_err(x, ptr, err)                                     \
 190 do {                                                                    \
 191         unsigned long __gu_val;                                         \
 192         __chk_user_ptr(ptr);                                            \
 193         uaccess_enable_not_uao();                                       \
 194         switch (sizeof(*(ptr))) {                                       \
 195         case 1:                                                         \
 196                 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
 197                                (err), ARM64_HAS_UAO);                   \
 198                 break;                                                  \
 199         case 2:                                                         \
 200                 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
 201                                (err), ARM64_HAS_UAO);                   \
 202                 break;                                                  \
 203         case 4:                                                         \
 204                 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),    \
 205                                (err), ARM64_HAS_UAO);                   \
 206                 break;                                                  \
 207         case 8:                                                         \
 208                 __get_user_asm("ldr", "ldtr", "%",  __gu_val, (ptr),    \
 209                                (err), ARM64_HAS_UAO);                   \
 210                 break;                                                  \
 211         default:                                                        \
 212                 BUILD_BUG();                                            \
 213         }                                                               \
 214         uaccess_disable_not_uao();                                      \
 215         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 216 } while (0)
 217
 218 #define __get_user(x, ptr)                                              \
 219 ({                                                                      \
 220         int __gu_err = 0;                                               \
 221         __get_user_err((x), (ptr), __gu_err);                           \
 222         __gu_err;                                                       \
 223 })
 224
 225 #define __get_user_error(x, ptr, err)                                   \
 226 ({                                                                      \
 227         __get_user_err((x), (ptr), (err));                              \
 228         (void)0;                                                        \
 229 })
 230
 231 #define __get_user_unaligned __get_user
 232
 233 #define get_user(x, ptr)                                                \
 234 ({                                                                      \
 235         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 236         might_fault();                                                  \
 237         access_ok(VERIFY_READ, __p, sizeof(*__p)) ?                     \
 238                 __get_user((x), __p) :                                  \
 239                 ((x) = 0, -EFAULT);                                     \
 240 })
 241
 242 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 243         asm volatile(                                                   \
 244         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 245                         alt_instr " " reg "1, [%2]\n", feature)         \
 246         "2:\n"                                                          \
 247         "       .section .fixup,\"ax\"\n"                               \
 248         "       .align  2\n"                                            \
 249         "3:     mov     %w0, %3\n"                                      \
 250         "       b       2b\n"                                           \
 251         "       .previous\n"                                            \
 252         _ASM_EXTABLE(1b, 3b)                                            \
 253         : "+r" (err)                                                    \
 254         : "r" (x), "r" (addr), "i" (-EFAULT))
 255
 256 #define __put_user_err(x, ptr, err)                                     \
 257 do {                                                                    \
 258         __typeof__(*(ptr)) __pu_val = (x);                              \
 259         __chk_user_ptr(ptr);                                            \
 260         uaccess_enable_not_uao();                                       \
 261         switch (sizeof(*(ptr))) {                                       \
 262         case 1:                                                         \
 263                 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr),  \
 264                                (err), ARM64_HAS_UAO);                   \
 265                 break;                                                  \
 266         case 2:                                                         \
 267                 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr),  \
 268                                (err), ARM64_HAS_UAO);                   \
 269                 break;                                                  \
 270         case 4:                                                         \
 271                 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr),    \
 272                                (err), ARM64_HAS_UAO);                   \
 273                 break;                                                  \
 274         case 8:                                                         \
 275                 __put_user_asm("str", "sttr", "%", __pu_val, (ptr),     \
 276                                (err), ARM64_HAS_UAO);                   \
 277                 break;                                                  \
 278         default:                                                        \
 279                 BUILD_BUG();                                            \
 280         }                                                               \
 281         uaccess_disable_not_uao();                                      \
 282 } while (0)
 283
 284 #define __put_user(x, ptr)                                              \
 285 ({                                                                      \
 286         int __pu_err = 0;                                               \
 287         __put_user_err((x), (ptr), __pu_err);                           \
 288         __pu_err;                                                       \
 289 })
 290
 291 #define __put_user_error(x, ptr, err)                                   \
 292 ({                                                                      \
 293         __put_user_err((x), (ptr), (err));                              \
 294         (void)0;                                                        \
 295 })
 296
 297 #define __put_user_unaligned __put_user
 298
 299 #define put_user(x, ptr)                                                \
 300 ({                                                                      \
 301         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 302         might_fault();                                                  \
 303         access_ok(VERIFY_WRITE, __p, sizeof(*__p)) ?                    \
 304                 __put_user((x), __p) :                                  \
 305                 -EFAULT;                                                \
 306 })
 307
 308 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 309 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 310 extern unsigned long __must_check __copy_in_user(void __user *to, const void __user *from, unsigned long n);
 311 extern unsigned long __must_check __clear_user(void __user *addr, unsigned long n);
 312
 313 static inline unsigned long __must_check __copy_from_user(void *to, const void __user *from, unsigned long n)
 314 {
 315         check_object_size(to, n, false);
 316         return __arch_copy_from_user(to, from, n);
 317 }
 318
 319 static inline unsigned long __must_check __copy_to_user(void __user *to, const void *from, unsigned long n)
 320 {
 321         check_object_size(from, n, true);
 322         return __arch_copy_to_user(to, from, n);
 323 }
 324
 325 static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n)
 326 {
 327         if (access_ok(VERIFY_READ, from, n)) {
 328                 check_object_size(to, n, false);
 329                 n = __arch_copy_from_user(to, from, n);
 330         } else /* security hole - plug it */
 331                 memset(to, 0, n);
 332         return n;
 333 }
 334
 335 static inline unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n)
 336 {
 337         if (access_ok(VERIFY_WRITE, to, n)) {
 338                 check_object_size(from, n, true);
 339                 n = __arch_copy_to_user(to, from, n);
 340         }
 341         return n;
 342 }
 343
 344 static inline unsigned long __must_check copy_in_user(void __user *to, const void __user *from, unsigned long n)
 345 {
 346         if (access_ok(VERIFY_READ, from, n) && access_ok(VERIFY_WRITE, to, n))
 347                 n = __copy_in_user(to, from, n);
 348         return n;
 349 }
 350
 351 #define __copy_to_user_inatomic __copy_to_user
 352 #define __copy_from_user_inatomic __copy_from_user
 353
 354 static inline unsigned long __must_check clear_user(void __user *to, unsigned long n)
 355 {
 356         if (access_ok(VERIFY_WRITE, to, n))
 357                 n = __clear_user(to, n);
 358         return n;
 359 }
 360
 361 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 362
 363 extern __must_check long strlen_user(const char __user *str);
 364 extern __must_check long strnlen_user(const char __user *str, long n);
 365
 366 #else   /* __ASSEMBLY__ */
 367
 368 #include <asm/alternative.h>
 369 #include <asm/assembler.h>
 370
 371 /*
 372  * User access enabling/disabling macros. These are no-ops when UAO is
 373  * present.
 374  */
 375         .macro  uaccess_disable_not_uao, tmp1
 376 alternative_if_not ARM64_ALT_PAN_NOT_UAO
 377         nop
 378 alternative_else
 379         SET_PSTATE_PAN(1)
 380 alternative_endif
 381         .endm
 382
 383         .macro  uaccess_enable_not_uao, tmp1, tmp2
 384 alternative_if_not ARM64_ALT_PAN_NOT_UAO
 385         nop
 386 alternative_else
 387         SET_PSTATE_PAN(0)
 388 alternative_endif
 389         .endm
 390
 391 #endif  /* __ASSEMBLY__ */
 392
 393 #endif /* __ASM_UACCESS_H */