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 #include <asm/alternative.h>
  22 #include <asm/kernel-pgtable.h>
  23 #include <asm/sysreg.h>
  24
  25 /*
  26  * User space memory access functions
  27  */
  28 #include <linux/bitops.h>
  29 #include <linux/kasan-checks.h>
  30 #include <linux/string.h>
  31 #include <linux/thread_info.h>
  32
  33 #include <asm/cpufeature.h>
  34 #include <asm/ptrace.h>
  35 #include <asm/errno.h>
  36 #include <asm/memory.h>
  37 #include <asm/compiler.h>
  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 /*
 106  * When dealing with data aborts or instruction traps we may end up with
 107  * a tagged userland pointer. Clear the tag to get a sane pointer to pass
 108  * on to access_ok(), for instance.
 109  */
 110 #define untagged_addr(addr)             sign_extend64(addr, 55)
 111
 112 #define access_ok(type, addr, size)     __range_ok(addr, size)
 113 #define user_addr_max                   get_fs
 114
 115 #define _ASM_EXTABLE(from, to)                                          \
 116         "       .pushsection    __ex_table, \"a\"\n"                    \
 117         "       .align          3\n"                                    \
 118         "       .long           (" #from " - .), (" #to " - .)\n"       \
 119         "       .popsection\n"
 120
 121 /*
 122  * User access enabling/disabling.
 123  */
 124 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
 125 static inline void __uaccess_ttbr0_disable(void)
 126 {
 127         unsigned long ttbr;
 128
 129         /* reserved_ttbr0 placed at the end of swapper_pg_dir */
 130         ttbr = read_sysreg(ttbr1_el1) + SWAPPER_DIR_SIZE;
 131         write_sysreg(ttbr, ttbr0_el1);
 132         isb();
 133 }
 134
 135 static inline void __uaccess_ttbr0_enable(void)
 136 {
 137         unsigned long flags;
 138
 139         /*
 140          * Disable interrupts to avoid preemption between reading the 'ttbr0'
 141          * variable and the MSR. A context switch could trigger an ASID
 142          * roll-over and an update of 'ttbr0'.
 143          */
 144         local_irq_save(flags);
 145         write_sysreg(current_thread_info()->ttbr0, ttbr0_el1);
 146         isb();
 147         local_irq_restore(flags);
 148 }
 149
 150 static inline bool uaccess_ttbr0_disable(void)
 151 {
 152         if (!system_uses_ttbr0_pan())
 153                 return false;
 154         __uaccess_ttbr0_disable();
 155         return true;
 156 }
 157
 158 static inline bool uaccess_ttbr0_enable(void)
 159 {
 160         if (!system_uses_ttbr0_pan())
 161                 return false;
 162         __uaccess_ttbr0_enable();
 163         return true;
 164 }
 165 #else
 166 static inline bool uaccess_ttbr0_disable(void)
 167 {
 168         return false;
 169 }
 170
 171 static inline bool uaccess_ttbr0_enable(void)
 172 {
 173         return false;
 174 }
 175 #endif
 176
 177 #define __uaccess_disable(alt)                                          \
 178 do {                                                                    \
 179         if (!uaccess_ttbr0_disable())                                   \
 180                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt,          \
 181                                 CONFIG_ARM64_PAN));                     \
 182 } while (0)
 183
 184 #define __uaccess_enable(alt)                                           \
 185 do {                                                                    \
 186         if (!uaccess_ttbr0_enable())                                    \
 187                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt,          \
 188                                 CONFIG_ARM64_PAN));                     \
 189 } while (0)
 190
 191 static inline void uaccess_disable(void)
 192 {
 193         __uaccess_disable(ARM64_HAS_PAN);
 194 }
 195
 196 static inline void uaccess_enable(void)
 197 {
 198         __uaccess_enable(ARM64_HAS_PAN);
 199 }
 200
 201 /*
 202  * These functions are no-ops when UAO is present.
 203  */
 204 static inline void uaccess_disable_not_uao(void)
 205 {
 206         __uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
 207 }
 208
 209 static inline void uaccess_enable_not_uao(void)
 210 {
 211         __uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
 212 }
 213
 214 /*
 215  * The "__xxx" versions of the user access functions do not verify the address
 216  * space - it must have been done previously with a separate "access_ok()"
 217  * call.
 218  *
 219  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 220  * occurs, and leave it unchanged on success.
 221  */
 222 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 223         asm volatile(                                                   \
 224         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 225                         alt_instr " " reg "1, [%2]\n", feature)         \
 226         "2:\n"                                                          \
 227         "       .section .fixup, \"ax\"\n"                              \
 228         "       .align  2\n"                                            \
 229         "3:     mov     %w0, %3\n"                                      \
 230         "       mov     %1, #0\n"                                       \
 231         "       b       2b\n"                                           \
 232         "       .previous\n"                                            \
 233         _ASM_EXTABLE(1b, 3b)                                            \
 234         : "+r" (err), "=&r" (x)                                         \
 235         : "r" (addr), "i" (-EFAULT))
 236
 237 #define __get_user_err(x, ptr, err)                                     \
 238 do {                                                                    \
 239         unsigned long __gu_val;                                         \
 240         __chk_user_ptr(ptr);                                            \
 241         uaccess_enable_not_uao();                                       \
 242         switch (sizeof(*(ptr))) {                                       \
 243         case 1:                                                         \
 244                 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
 245                                (err), ARM64_HAS_UAO);                   \
 246                 break;                                                  \
 247         case 2:                                                         \
 248                 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
 249                                (err), ARM64_HAS_UAO);                   \
 250                 break;                                                  \
 251         case 4:                                                         \
 252                 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),    \
 253                                (err), ARM64_HAS_UAO);                   \
 254                 break;                                                  \
 255         case 8:                                                         \
 256                 __get_user_asm("ldr", "ldtr", "%",  __gu_val, (ptr),    \
 257                                (err), ARM64_HAS_UAO);                   \
 258                 break;                                                  \
 259         default:                                                        \
 260                 BUILD_BUG();                                            \
 261         }                                                               \
 262         uaccess_disable_not_uao();                                      \
 263         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 264 } while (0)
 265
 266 #define __get_user(x, ptr)                                              \
 267 ({                                                                      \
 268         int __gu_err = 0;                                               \
 269         __get_user_err((x), (ptr), __gu_err);                           \
 270         __gu_err;                                                       \
 271 })
 272
 273 #define __get_user_error(x, ptr, err)                                   \
 274 ({                                                                      \
 275         __get_user_err((x), (ptr), (err));                              \
 276         (void)0;                                                        \
 277 })
 278
 279 #define __get_user_unaligned __get_user
 280
 281 #define get_user(x, ptr)                                                \
 282 ({                                                                      \
 283         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 284         might_fault();                                                  \
 285         access_ok(VERIFY_READ, __p, sizeof(*__p)) ?                     \
 286                 __get_user((x), __p) :                                  \
 287                 ((x) = 0, -EFAULT);                                     \
 288 })
 289
 290 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 291         asm volatile(                                                   \
 292         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 293                         alt_instr " " reg "1, [%2]\n", feature)         \
 294         "2:\n"                                                          \
 295         "       .section .fixup,\"ax\"\n"                               \
 296         "       .align  2\n"                                            \
 297         "3:     mov     %w0, %3\n"                                      \
 298         "       b       2b\n"                                           \
 299         "       .previous\n"                                            \
 300         _ASM_EXTABLE(1b, 3b)                                            \
 301         : "+r" (err)                                                    \
 302         : "r" (x), "r" (addr), "i" (-EFAULT))
 303
 304 #define __put_user_err(x, ptr, err)                                     \
 305 do {                                                                    \
 306         __typeof__(*(ptr)) __pu_val = (x);                              \
 307         __chk_user_ptr(ptr);                                            \
 308         uaccess_enable_not_uao();                                       \
 309         switch (sizeof(*(ptr))) {                                       \
 310         case 1:                                                         \
 311                 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr),  \
 312                                (err), ARM64_HAS_UAO);                   \
 313                 break;                                                  \
 314         case 2:                                                         \
 315                 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr),  \
 316                                (err), ARM64_HAS_UAO);                   \
 317                 break;                                                  \
 318         case 4:                                                         \
 319                 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr),    \
 320                                (err), ARM64_HAS_UAO);                   \
 321                 break;                                                  \
 322         case 8:                                                         \
 323                 __put_user_asm("str", "sttr", "%", __pu_val, (ptr),     \
 324                                (err), ARM64_HAS_UAO);                   \
 325                 break;                                                  \
 326         default:                                                        \
 327                 BUILD_BUG();                                            \
 328         }                                                               \
 329         uaccess_disable_not_uao();                                      \
 330 } while (0)
 331
 332 #define __put_user(x, ptr)                                              \
 333 ({                                                                      \
 334         int __pu_err = 0;                                               \
 335         __put_user_err((x), (ptr), __pu_err);                           \
 336         __pu_err;                                                       \
 337 })
 338
 339 #define __put_user_error(x, ptr, err)                                   \
 340 ({                                                                      \
 341         __put_user_err((x), (ptr), (err));                              \
 342         (void)0;                                                        \
 343 })
 344
 345 #define __put_user_unaligned __put_user
 346
 347 #define put_user(x, ptr)                                                \
 348 ({                                                                      \
 349         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 350         might_fault();                                                  \
 351         access_ok(VERIFY_WRITE, __p, sizeof(*__p)) ?                    \
 352                 __put_user((x), __p) :                                  \
 353                 -EFAULT;                                                \
 354 })
 355
 356 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 357 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 358 extern unsigned long __must_check __copy_in_user(void __user *to, const void __user *from, unsigned long n);
 359 extern unsigned long __must_check __clear_user(void __user *addr, unsigned long n);
 360
 361 static inline unsigned long __must_check __copy_from_user(void *to, const void __user *from, unsigned long n)
 362 {
 363         kasan_check_write(to, n);
 364         check_object_size(to, n, false);
 365         return __arch_copy_from_user(to, from, n);
 366 }
 367
 368 static inline unsigned long __must_check __copy_to_user(void __user *to, const void *from, unsigned long n)
 369 {
 370         kasan_check_read(from, n);
 371         check_object_size(from, n, true);
 372         return __arch_copy_to_user(to, from, n);
 373 }
 374
 375 static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n)
 376 {
 377         unsigned long res = n;
 378         kasan_check_write(to, n);
 379         check_object_size(to, n, false);
 380
 381         if (access_ok(VERIFY_READ, from, n)) {
 382                 res = __arch_copy_from_user(to, from, n);
 383         }
 384         if (unlikely(res))
 385                 memset(to + (n - res), 0, res);
 386         return res;
 387 }
 388
 389 static inline unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n)
 390 {
 391         kasan_check_read(from, n);
 392         check_object_size(from, n, true);
 393
 394         if (access_ok(VERIFY_WRITE, to, n)) {
 395                 n = __arch_copy_to_user(to, from, n);
 396         }
 397         return n;
 398 }
 399
 400 static inline unsigned long __must_check copy_in_user(void __user *to, const void __user *from, unsigned long n)
 401 {
 402         if (access_ok(VERIFY_READ, from, n) && access_ok(VERIFY_WRITE, to, n))
 403                 n = __copy_in_user(to, from, n);
 404         return n;
 405 }
 406
 407 #define __copy_to_user_inatomic __copy_to_user
 408 #define __copy_from_user_inatomic __copy_from_user
 409
 410 static inline unsigned long __must_check clear_user(void __user *to, unsigned long n)
 411 {
 412         if (access_ok(VERIFY_WRITE, to, n))
 413                 n = __clear_user(to, n);
 414         return n;
 415 }
 416
 417 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 418
 419 extern __must_check long strlen_user(const char __user *str);
 420 extern __must_check long strnlen_user(const char __user *str, long n);
 421
 422 #endif /* __ASM_UACCESS_H */