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 /*
  22  * User space memory access functions
  23  */
  24 #include <linux/bitops.h>
  25 #include <linux/kasan-checks.h>
  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  * Test whether a block of memory is a valid user space address.
  87  * Returns 1 if the range is valid, 0 otherwise.
  88  *
  89  * This is equivalent to the following test:
  90  * (u65)addr + (u65)size <= current->addr_limit
  91  *
  92  * This needs 65-bit arithmetic.
  93  */
  94 #define __range_ok(addr, size)                                          \
  95 ({                                                                      \
  96         unsigned long flag, roksum;                                     \
  97         __chk_user_ptr(addr);                                           \
  98         asm("adds %1, %1, %3; ccmp %1, %4, #2, cc; cset %0, ls"         \
  99                 : "=&r" (flag), "=&r" (roksum)                          \
 100                 : "1" (addr), "Ir" (size),                              \
 101                   "r" (current_thread_info()->addr_limit)               \
 102                 : "cc");                                                \
 103         flag;                                                           \
 104 })
 105
 106 /*
 107  * When dealing with data aborts or instruction traps we may end up with
 108  * a tagged userland pointer. Clear the tag to get a sane pointer to pass
 109  * on to access_ok(), for instance.
 110  */
 111 #define untagged_addr(addr)             sign_extend64(addr, 55)
 112
 113 #define access_ok(type, addr, size)     __range_ok(addr, size)
 114 #define user_addr_max                   get_fs
 115
 116 #define _ASM_EXTABLE(from, to)                                          \
 117         "       .pushsection    __ex_table, \"a\"\n"                    \
 118         "       .align          3\n"                                    \
 119         "       .long           (" #from " - .), (" #to " - .)\n"       \
 120         "       .popsection\n"
 121
 122 /*
 123  * The "__xxx" versions of the user access functions do not verify the address
 124  * space - it must have been done previously with a separate "access_ok()"
 125  * call.
 126  *
 127  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 128  * occurs, and leave it unchanged on success.
 129  */
 130 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 131         asm volatile(                                                   \
 132         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 133                         alt_instr " " reg "1, [%2]\n", feature)         \
 134         "2:\n"                                                          \
 135         "       .section .fixup, \"ax\"\n"                              \
 136         "       .align  2\n"                                            \
 137         "3:     mov     %w0, %3\n"                                      \
 138         "       mov     %1, #0\n"                                       \
 139         "       b       2b\n"                                           \
 140         "       .previous\n"                                            \
 141         _ASM_EXTABLE(1b, 3b)                                            \
 142         : "+r" (err), "=&r" (x)                                         \
 143         : "r" (addr), "i" (-EFAULT))
 144
 145 #define __get_user_err(x, ptr, err)                                     \
 146 do {                                                                    \
 147         unsigned long __gu_val;                                         \
 148         __chk_user_ptr(ptr);                                            \
 149         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_ALT_PAN_NOT_UAO,\
 150                         CONFIG_ARM64_PAN));                             \
 151         switch (sizeof(*(ptr))) {                                       \
 152         case 1:                                                         \
 153                 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
 154                                (err), ARM64_HAS_UAO);                   \
 155                 break;                                                  \
 156         case 2:                                                         \
 157                 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
 158                                (err), ARM64_HAS_UAO);                   \
 159                 break;                                                  \
 160         case 4:                                                         \
 161                 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),    \
 162                                (err), ARM64_HAS_UAO);                   \
 163                 break;                                                  \
 164         case 8:                                                         \
 165                 __get_user_asm("ldr", "ldtr", "%",  __gu_val, (ptr),    \
 166                                (err), ARM64_HAS_UAO);                   \
 167                 break;                                                  \
 168         default:                                                        \
 169                 BUILD_BUG();                                            \
 170         }                                                               \
 171         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 172         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_ALT_PAN_NOT_UAO,\
 173                         CONFIG_ARM64_PAN));                             \
 174 } while (0)
 175
 176 #define __get_user(x, ptr)                                              \
 177 ({                                                                      \
 178         int __gu_err = 0;                                               \
 179         __get_user_err((x), (ptr), __gu_err);                           \
 180         __gu_err;                                                       \
 181 })
 182
 183 #define __get_user_error(x, ptr, err)                                   \
 184 ({                                                                      \
 185         __get_user_err((x), (ptr), (err));                              \
 186         (void)0;                                                        \
 187 })
 188
 189 #define __get_user_unaligned __get_user
 190
 191 #define get_user(x, ptr)                                                \
 192 ({                                                                      \
 193         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 194         might_fault();                                                  \
 195         access_ok(VERIFY_READ, __p, sizeof(*__p)) ?                     \
 196                 __get_user((x), __p) :                                  \
 197                 ((x) = 0, -EFAULT);                                     \
 198 })
 199
 200 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 201         asm volatile(                                                   \
 202         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 203                         alt_instr " " reg "1, [%2]\n", feature)         \
 204         "2:\n"                                                          \
 205         "       .section .fixup,\"ax\"\n"                               \
 206         "       .align  2\n"                                            \
 207         "3:     mov     %w0, %3\n"                                      \
 208         "       b       2b\n"                                           \
 209         "       .previous\n"                                            \
 210         _ASM_EXTABLE(1b, 3b)                                            \
 211         : "+r" (err)                                                    \
 212         : "r" (x), "r" (addr), "i" (-EFAULT))
 213
 214 #define __put_user_err(x, ptr, err)                                     \
 215 do {                                                                    \
 216         __typeof__(*(ptr)) __pu_val = (x);                              \
 217         __chk_user_ptr(ptr);                                            \
 218         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_ALT_PAN_NOT_UAO,\
 219                         CONFIG_ARM64_PAN));                             \
 220         switch (sizeof(*(ptr))) {                                       \
 221         case 1:                                                         \
 222                 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr),  \
 223                                (err), ARM64_HAS_UAO);                   \
 224                 break;                                                  \
 225         case 2:                                                         \
 226                 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr),  \
 227                                (err), ARM64_HAS_UAO);                   \
 228                 break;                                                  \
 229         case 4:                                                         \
 230                 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr),    \
 231                                (err), ARM64_HAS_UAO);                   \
 232                 break;                                                  \
 233         case 8:                                                         \
 234                 __put_user_asm("str", "sttr", "%", __pu_val, (ptr),     \
 235                                (err), ARM64_HAS_UAO);                   \
 236                 break;                                                  \
 237         default:                                                        \
 238                 BUILD_BUG();                                            \
 239         }                                                               \
 240         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_ALT_PAN_NOT_UAO,\
 241                         CONFIG_ARM64_PAN));                             \
 242 } while (0)
 243
 244 #define __put_user(x, ptr)                                              \
 245 ({                                                                      \
 246         int __pu_err = 0;                                               \
 247         __put_user_err((x), (ptr), __pu_err);                           \
 248         __pu_err;                                                       \
 249 })
 250
 251 #define __put_user_error(x, ptr, err)                                   \
 252 ({                                                                      \
 253         __put_user_err((x), (ptr), (err));                              \
 254         (void)0;                                                        \
 255 })
 256
 257 #define __put_user_unaligned __put_user
 258
 259 #define put_user(x, ptr)                                                \
 260 ({                                                                      \
 261         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 262         might_fault();                                                  \
 263         access_ok(VERIFY_WRITE, __p, sizeof(*__p)) ?                    \
 264                 __put_user((x), __p) :                                  \
 265                 -EFAULT;                                                \
 266 })
 267
 268 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 269 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 270 extern unsigned long __must_check __copy_in_user(void __user *to, const void __user *from, unsigned long n);
 271 extern unsigned long __must_check __clear_user(void __user *addr, unsigned long n);
 272
 273 static inline unsigned long __must_check __copy_from_user(void *to, const void __user *from, unsigned long n)
 274 {
 275         kasan_check_write(to, n);
 276         check_object_size(to, n, false);
 277         return __arch_copy_from_user(to, from, n);
 278 }
 279
 280 static inline unsigned long __must_check __copy_to_user(void __user *to, const void *from, unsigned long n)
 281 {
 282         kasan_check_read(from, n);
 283         check_object_size(from, n, true);
 284         return __arch_copy_to_user(to, from, n);
 285 }
 286
 287 static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n)
 288 {
 289         unsigned long res = n;
 290         kasan_check_write(to, n);
 291
 292         if (access_ok(VERIFY_READ, from, n)) {
 293                 check_object_size(to, n, false);
 294                 res = __arch_copy_from_user(to, from, n);
 295         }
 296         if (unlikely(res))
 297                 memset(to + (n - res), 0, res);
 298         return res;
 299 }
 300
 301 static inline unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n)
 302 {
 303         kasan_check_read(from, n);
 304
 305         if (access_ok(VERIFY_WRITE, to, n)) {
 306                 check_object_size(from, n, true);
 307                 n = __arch_copy_to_user(to, from, n);
 308         }
 309         return n;
 310 }
 311
 312 static inline unsigned long __must_check copy_in_user(void __user *to, const void __user *from, unsigned long n)
 313 {
 314         if (access_ok(VERIFY_READ, from, n) && access_ok(VERIFY_WRITE, to, n))
 315                 n = __copy_in_user(to, from, n);
 316         return n;
 317 }
 318
 319 #define __copy_to_user_inatomic __copy_to_user
 320 #define __copy_from_user_inatomic __copy_from_user
 321
 322 static inline unsigned long __must_check clear_user(void __user *to, unsigned long n)
 323 {
 324         if (access_ok(VERIFY_WRITE, to, n))
 325                 n = __clear_user(to, n);
 326         return n;
 327 }
 328
 329 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 330
 331 extern __must_check long strlen_user(const char __user *str);
 332 extern __must_check long strnlen_user(const char __user *str, long n);
 333
 334 #endif /* __ASM_UACCESS_H */