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/processor.h>
  32 #include <asm/ptrace.h>
  33 #include <asm/sysreg.h>
  34 #include <asm/errno.h>
  35 #include <asm/memory.h>
  36 #include <asm/compiler.h>
  37
  38 #define VERIFY_READ 0
  39 #define VERIFY_WRITE 1
  40
  41 /*
  42  * The exception table consists of pairs of relative offsets: the first
  43  * is the relative offset to an instruction that is allowed to fault,
  44  * and the second is the relative offset at which the program should
  45  * continue. No registers are modified, so it is entirely up to the
  46  * continuation code to figure out what to do.
  47  *
  48  * All the routines below use bits of fixup code that are out of line
  49  * with the main instruction path.  This means when everything is well,
  50  * we don't even have to jump over them.  Further, they do not intrude
  51  * on our cache or tlb entries.
  52  */
  53
  54 struct exception_table_entry
  55 {
  56         int insn, fixup;
  57 };
  58
  59 #define ARCH_HAS_RELATIVE_EXTABLE
  60
  61 extern int fixup_exception(struct pt_regs *regs);
  62
  63 #define get_ds()        (KERNEL_DS)
  64 #define get_fs()        (current_thread_info()->addr_limit)
  65
  66 static inline void set_fs(mm_segment_t fs)
  67 {
  68         current_thread_info()->addr_limit = fs;
  69
  70         /*
  71          * Prevent a mispredicted conditional call to set_fs from forwarding
  72          * the wrong address limit to access_ok under speculation.
  73          */
  74         dsb(nsh);
  75         isb();
  76
  77         /*
  78          * Enable/disable UAO so that copy_to_user() etc can access
  79          * kernel memory with the unprivileged instructions.
  80          */
  81         if (IS_ENABLED(CONFIG_ARM64_UAO) && fs == KERNEL_DS)
  82                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
  83         else
  84                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
  85                                 CONFIG_ARM64_UAO));
  86 }
  87
  88 #define segment_eq(a, b)        ((a) == (b))
  89
  90 /*
  91  * Test whether a block of memory is a valid user space address.
  92  * Returns 1 if the range is valid, 0 otherwise.
  93  *
  94  * This is equivalent to the following test:
  95  * (u65)addr + (u65)size <= (u65)current->addr_limit + 1
  96  */
  97 static inline unsigned long __range_ok(unsigned long addr, unsigned long size)
  98 {
  99         unsigned long limit = current_thread_info()->addr_limit;
 100
 101         __chk_user_ptr(addr);
 102         asm volatile(
 103         // A + B <= C + 1 for all A,B,C, in four easy steps:
 104         // 1: X = A + B; X' = X % 2^64
 105         "       adds    %0, %0, %2\n"
 106         // 2: Set C = 0 if X > 2^64, to guarantee X' > C in step 4
 107         "       csel    %1, xzr, %1, hi\n"
 108         // 3: Set X' = ~0 if X >= 2^64. For X == 2^64, this decrements X'
 109         //    to compensate for the carry flag being set in step 4. For
 110         //    X > 2^64, X' merely has to remain nonzero, which it does.
 111         "       csinv   %0, %0, xzr, cc\n"
 112         // 4: For X < 2^64, this gives us X' - C - 1 <= 0, where the -1
 113         //    comes from the carry in being clear. Otherwise, we are
 114         //    testing X' - C == 0, subject to the previous adjustments.
 115         "       sbcs    xzr, %0, %1\n"
 116         "       cset    %0, ls\n"
 117         : "+r" (addr), "+r" (limit) : "Ir" (size) : "cc");
 118
 119         return addr;
 120 }
 121
 122 /*
 123  * When dealing with data aborts, watchpoints, or instruction traps we may end
 124  * up with a tagged userland pointer. Clear the tag to get a sane pointer to
 125  * pass on to access_ok(), for instance.
 126  */
 127 #define untagged_addr(addr)             sign_extend64(addr, 55)
 128
 129 #define access_ok(type, addr, size)     __range_ok((unsigned long)(addr), size)
 130 #define user_addr_max                   get_fs
 131
 132 #define _ASM_EXTABLE(from, to)                                          \
 133         "       .pushsection    __ex_table, \"a\"\n"                    \
 134         "       .align          3\n"                                    \
 135         "       .long           (" #from " - .), (" #to " - .)\n"       \
 136         "       .popsection\n"
 137
 138 /*
 139  * Sanitise a uaccess pointer such that it becomes NULL if above the
 140  * current addr_limit.
 141  */
 142 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
 143 static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
 144 {
 145         void __user *safe_ptr;
 146
 147         asm volatile(
 148         "       bics    xzr, %1, %2\n"
 149         "       csel    %0, %1, xzr, eq\n"
 150         : "=&r" (safe_ptr)
 151         : "r" (ptr), "r" (current_thread_info()->addr_limit)
 152         : "cc");
 153
 154         csdb();
 155         return safe_ptr;
 156 }
 157
 158 /*
 159  * The "__xxx" versions of the user access functions do not verify the address
 160  * space - it must have been done previously with a separate "access_ok()"
 161  * call.
 162  *
 163  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 164  * occurs, and leave it unchanged on success.
 165  */
 166 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 167         asm volatile(                                                   \
 168         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 169                         alt_instr " " reg "1, [%2]\n", feature)         \
 170         "2:\n"                                                          \
 171         "       .section .fixup, \"ax\"\n"                              \
 172         "       .align  2\n"                                            \
 173         "3:     mov     %w0, %3\n"                                      \
 174         "       mov     %1, #0\n"                                       \
 175         "       b       2b\n"                                           \
 176         "       .previous\n"                                            \
 177         _ASM_EXTABLE(1b, 3b)                                            \
 178         : "+r" (err), "=&r" (x)                                         \
 179         : "r" (addr), "i" (-EFAULT))
 180
 181 #define __get_user_err(x, ptr, err)                                     \
 182 do {                                                                    \
 183         unsigned long __gu_val;                                         \
 184         __chk_user_ptr(ptr);                                            \
 185         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_ALT_PAN_NOT_UAO,\
 186                         CONFIG_ARM64_PAN));                             \
 187         switch (sizeof(*(ptr))) {                                       \
 188         case 1:                                                         \
 189                 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
 190                                (err), ARM64_HAS_UAO);                   \
 191                 break;                                                  \
 192         case 2:                                                         \
 193                 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
 194                                (err), ARM64_HAS_UAO);                   \
 195                 break;                                                  \
 196         case 4:                                                         \
 197                 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),    \
 198                                (err), ARM64_HAS_UAO);                   \
 199                 break;                                                  \
 200         case 8:                                                         \
 201                 __get_user_asm("ldr", "ldtr", "%",  __gu_val, (ptr),    \
 202                                (err), ARM64_HAS_UAO);                   \
 203                 break;                                                  \
 204         default:                                                        \
 205                 BUILD_BUG();                                            \
 206         }                                                               \
 207         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 208         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_ALT_PAN_NOT_UAO,\
 209                         CONFIG_ARM64_PAN));                             \
 210 } while (0)
 211
 212 #define __get_user_check(x, ptr, err)                                   \
 213 ({                                                                      \
 214         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 215         might_fault();                                                  \
 216         if (access_ok(VERIFY_READ, __p, sizeof(*__p))) {                \
 217                 __p = uaccess_mask_ptr(__p);                            \
 218                 __get_user_err((x), __p, (err));                        \
 219         } else {                                                        \
 220                 (x) = 0; (err) = -EFAULT;                               \
 221         }                                                               \
 222 })
 223
 224 #define __get_user_error(x, ptr, err)                                   \
 225 ({                                                                      \
 226         __get_user_check((x), (ptr), (err));                            \
 227         (void)0;                                                        \
 228 })
 229
 230 #define __get_user(x, ptr)                                              \
 231 ({                                                                      \
 232         int __gu_err = 0;                                               \
 233         __get_user_check((x), (ptr), __gu_err);                         \
 234         __gu_err;                                                       \
 235 })
 236
 237 #define __get_user_unaligned __get_user
 238
 239 #define get_user        __get_user
 240
 241 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 242         asm volatile(                                                   \
 243         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 244                         alt_instr " " reg "1, [%2]\n", feature)         \
 245         "2:\n"                                                          \
 246         "       .section .fixup,\"ax\"\n"                               \
 247         "       .align  2\n"                                            \
 248         "3:     mov     %w0, %3\n"                                      \
 249         "       b       2b\n"                                           \
 250         "       .previous\n"                                            \
 251         _ASM_EXTABLE(1b, 3b)                                            \
 252         : "+r" (err)                                                    \
 253         : "r" (x), "r" (addr), "i" (-EFAULT))
 254
 255 #define __put_user_err(x, ptr, err)                                     \
 256 do {                                                                    \
 257         __typeof__(*(ptr)) __pu_val = (x);                              \
 258         __chk_user_ptr(ptr);                                            \
 259         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_ALT_PAN_NOT_UAO,\
 260                         CONFIG_ARM64_PAN));                             \
 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         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_ALT_PAN_NOT_UAO,\
 282                         CONFIG_ARM64_PAN));                             \
 283 } while (0)
 284
 285 #define __put_user_check(x, ptr, err)                                   \
 286 ({                                                                      \
 287         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 288         might_fault();                                                  \
 289         if (access_ok(VERIFY_WRITE, __p, sizeof(*__p))) {               \
 290                 __p = uaccess_mask_ptr(__p);                            \
 291                 __put_user_err((x), __p, (err));                        \
 292         } else  {                                                       \
 293                 (err) = -EFAULT;                                        \
 294         }                                                               \
 295 })
 296
 297 #define __put_user_error(x, ptr, err)                                   \
 298 ({                                                                      \
 299         __put_user_check((x), (ptr), (err));                            \
 300         (void)0;                                                        \
 301 })
 302
 303 #define __put_user(x, ptr)                                              \
 304 ({                                                                      \
 305         int __pu_err = 0;                                               \
 306         __put_user_check((x), (ptr), __pu_err);                         \
 307         __pu_err;                                                       \
 308 })
 309
 310 #define __put_user_unaligned __put_user
 311
 312 #define put_user        __put_user
 313
 314 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 315 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 316 extern unsigned long __must_check __arch_copy_in_user(void __user *to, const void __user *from, unsigned long n);
 317
 318 static inline unsigned long __must_check __copy_from_user(void *to, const void __user *from, unsigned long n)
 319 {
 320         kasan_check_write(to, n);
 321         check_object_size(to, n, false);
 322         return __arch_copy_from_user(to, __uaccess_mask_ptr(from), n);
 323 }
 324
 325 static inline unsigned long __must_check __copy_to_user(void __user *to, const void *from, unsigned long n)
 326 {
 327         kasan_check_read(from, n);
 328         check_object_size(from, n, true);
 329         return __arch_copy_to_user(__uaccess_mask_ptr(to), from, n);
 330 }
 331
 332 static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n)
 333 {
 334         unsigned long res = n;
 335         kasan_check_write(to, n);
 336
 337         if (access_ok(VERIFY_READ, from, n)) {
 338                 check_object_size(to, n, false);
 339                 res = __arch_copy_from_user(to, from, n);
 340         }
 341         if (unlikely(res))
 342                 memset(to + (n - res), 0, res);
 343         return res;
 344 }
 345
 346 static inline unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n)
 347 {
 348         kasan_check_read(from, n);
 349
 350         if (access_ok(VERIFY_WRITE, to, n)) {
 351                 check_object_size(from, n, true);
 352                 n = __arch_copy_to_user(to, from, n);
 353         }
 354         return n;
 355 }
 356
 357 static inline unsigned long __must_check __copy_in_user(void __user *to, const void __user *from, unsigned long n)
 358 {
 359         if (access_ok(VERIFY_READ, from, n) && access_ok(VERIFY_WRITE, to, n))
 360                 n = __arch_copy_in_user(__uaccess_mask_ptr(to), __uaccess_mask_ptr(from), n);
 361         return n;
 362 }
 363 #define copy_in_user __copy_in_user
 364
 365 #define __copy_to_user_inatomic __copy_to_user
 366 #define __copy_from_user_inatomic __copy_from_user
 367
 368 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
 369 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
 370 {
 371         if (access_ok(VERIFY_WRITE, to, n))
 372                 n = __arch_clear_user(__uaccess_mask_ptr(to), n);
 373         return n;
 374 }
 375 #define clear_user      __clear_user
 376
 377 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 378
 379 extern __must_check long strlen_user(const char __user *str);
 380 extern __must_check long strnlen_user(const char __user *str, long n);
 381
 382 #endif /* __ASM_UACCESS_H */