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