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 #ifndef __ASSEMBLY__
  26
  27 /*
  28  * User space memory access functions
  29  */
  30 #include <linux/bitops.h>
  31 #include <linux/kasan-checks.h>
  32 #include <linux/string.h>
  33 #include <linux/thread_info.h>
  34
  35 #include <asm/cpufeature.h>
  36 #include <asm/ptrace.h>
  37 #include <asm/errno.h>
  38 #include <asm/memory.h>
  39 #include <asm/compiler.h>
  40
  41 #define VERIFY_READ 0
  42 #define VERIFY_WRITE 1
  43
  44 /*
  45  * The exception table consists of pairs of relative offsets: the first
  46  * is the relative offset to an instruction that is allowed to fault,
  47  * and the second is the relative offset at which the program should
  48  * continue. No registers are modified, so it is entirely up to the
  49  * continuation code to figure out what to do.
  50  *
  51  * All the routines below use bits of fixup code that are out of line
  52  * with the main instruction path.  This means when everything is well,
  53  * we don't even have to jump over them.  Further, they do not intrude
  54  * on our cache or tlb entries.
  55  */
  56
  57 struct exception_table_entry
  58 {
  59         int insn, fixup;
  60 };
  61
  62 #define ARCH_HAS_RELATIVE_EXTABLE
  63
  64 extern int fixup_exception(struct pt_regs *regs);
  65
  66 #define KERNEL_DS       (-1UL)
  67 #define get_ds()        (KERNEL_DS)
  68
  69 #define USER_DS         TASK_SIZE_64
  70 #define get_fs()        (current_thread_info()->addr_limit)
  71
  72 static inline void set_fs(mm_segment_t fs)
  73 {
  74         current_thread_info()->addr_limit = fs;
  75
  76         /*
  77          * Enable/disable UAO so that copy_to_user() etc can access
  78          * kernel memory with the unprivileged instructions.
  79          */
  80         if (IS_ENABLED(CONFIG_ARM64_UAO) && fs == KERNEL_DS)
  81                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
  82         else
  83                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
  84                                 CONFIG_ARM64_UAO));
  85 }
  86
  87 #define segment_eq(a, b)        ((a) == (b))
  88
  89 /*
  90  * Test whether a block of memory is a valid user space address.
  91  * Returns 1 if the range is valid, 0 otherwise.
  92  *
  93  * This is equivalent to the following test:
  94  * (u65)addr + (u65)size <= current->addr_limit
  95  *
  96  * This needs 65-bit arithmetic.
  97  */
  98 #define __range_ok(addr, size)                                          \
  99 ({                                                                      \
 100         unsigned long flag, roksum;                                     \
 101         __chk_user_ptr(addr);                                           \
 102         asm("adds %1, %1, %3; ccmp %1, %4, #2, cc; cset %0, ls"         \
 103                 : "=&r" (flag), "=&r" (roksum)                          \
 104                 : "1" (addr), "Ir" (size),                              \
 105                   "r" (current_thread_info()->addr_limit)               \
 106                 : "cc");                                                \
 107         flag;                                                           \
 108 })
 109
 110 /*
 111  * When dealing with data aborts or instruction traps we may end up with
 112  * a tagged userland pointer. Clear the tag to get a sane pointer to pass
 113  * on to access_ok(), for instance.
 114  */
 115 #define untagged_addr(addr)             sign_extend64(addr, 55)
 116
 117 #define access_ok(type, addr, size)     __range_ok(addr, size)
 118 #define user_addr_max                   get_fs
 119
 120 #define _ASM_EXTABLE(from, to)                                          \
 121         "       .pushsection    __ex_table, \"a\"\n"                    \
 122         "       .align          3\n"                                    \
 123         "       .long           (" #from " - .), (" #to " - .)\n"       \
 124         "       .popsection\n"
 125
 126 /*
 127  * User access enabling/disabling.
 128  */
 129 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
 130 static inline void __uaccess_ttbr0_disable(void)
 131 {
 132         unsigned long ttbr;
 133
 134         /* reserved_ttbr0 placed at the end of swapper_pg_dir */
 135         ttbr = read_sysreg(ttbr1_el1) + SWAPPER_DIR_SIZE;
 136         write_sysreg(ttbr, ttbr0_el1);
 137         isb();
 138 }
 139
 140 static inline void __uaccess_ttbr0_enable(void)
 141 {
 142         unsigned long flags;
 143
 144         /*
 145          * Disable interrupts to avoid preemption between reading the 'ttbr0'
 146          * variable and the MSR. A context switch could trigger an ASID
 147          * roll-over and an update of 'ttbr0'.
 148          */
 149         local_irq_save(flags);
 150         write_sysreg(current_thread_info()->ttbr0, ttbr0_el1);
 151         isb();
 152         local_irq_restore(flags);
 153 }
 154
 155 static inline bool uaccess_ttbr0_disable(void)
 156 {
 157         if (!system_uses_ttbr0_pan())
 158                 return false;
 159         __uaccess_ttbr0_disable();
 160         return true;
 161 }
 162
 163 static inline bool uaccess_ttbr0_enable(void)
 164 {
 165         if (!system_uses_ttbr0_pan())
 166                 return false;
 167         __uaccess_ttbr0_enable();
 168         return true;
 169 }
 170 #else
 171 static inline bool uaccess_ttbr0_disable(void)
 172 {
 173         return false;
 174 }
 175
 176 static inline bool uaccess_ttbr0_enable(void)
 177 {
 178         return false;
 179 }
 180 #endif
 181
 182 #define __uaccess_disable(alt)                                          \
 183 do {                                                                    \
 184         if (!uaccess_ttbr0_disable())                                   \
 185                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt,          \
 186                                 CONFIG_ARM64_PAN));                     \
 187 } while (0)
 188
 189 #define __uaccess_enable(alt)                                           \
 190 do {                                                                    \
 191         if (!uaccess_ttbr0_enable())                                    \
 192                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt,          \
 193                                 CONFIG_ARM64_PAN));                     \
 194 } while (0)
 195
 196 static inline void uaccess_disable(void)
 197 {
 198         __uaccess_disable(ARM64_HAS_PAN);
 199 }
 200
 201 static inline void uaccess_enable(void)
 202 {
 203         __uaccess_enable(ARM64_HAS_PAN);
 204 }
 205
 206 /*
 207  * These functions are no-ops when UAO is present.
 208  */
 209 static inline void uaccess_disable_not_uao(void)
 210 {
 211         __uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
 212 }
 213
 214 static inline void uaccess_enable_not_uao(void)
 215 {
 216         __uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
 217 }
 218
 219 /*
 220  * The "__xxx" versions of the user access functions do not verify the address
 221  * space - it must have been done previously with a separate "access_ok()"
 222  * call.
 223  *
 224  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 225  * occurs, and leave it unchanged on success.
 226  */
 227 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 228         asm volatile(                                                   \
 229         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 230                         alt_instr " " reg "1, [%2]\n", feature)         \
 231         "2:\n"                                                          \
 232         "       .section .fixup, \"ax\"\n"                              \
 233         "       .align  2\n"                                            \
 234         "3:     mov     %w0, %3\n"                                      \
 235         "       mov     %1, #0\n"                                       \
 236         "       b       2b\n"                                           \
 237         "       .previous\n"                                            \
 238         _ASM_EXTABLE(1b, 3b)                                            \
 239         : "+r" (err), "=&r" (x)                                         \
 240         : "r" (addr), "i" (-EFAULT))
 241
 242 #define __get_user_err(x, ptr, err)                                     \
 243 do {                                                                    \
 244         unsigned long __gu_val;                                         \
 245         __chk_user_ptr(ptr);                                            \
 246         uaccess_enable_not_uao();                                       \
 247         switch (sizeof(*(ptr))) {                                       \
 248         case 1:                                                         \
 249                 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
 250                                (err), ARM64_HAS_UAO);                   \
 251                 break;                                                  \
 252         case 2:                                                         \
 253                 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
 254                                (err), ARM64_HAS_UAO);                   \
 255                 break;                                                  \
 256         case 4:                                                         \
 257                 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),    \
 258                                (err), ARM64_HAS_UAO);                   \
 259                 break;                                                  \
 260         case 8:                                                         \
 261                 __get_user_asm("ldr", "ldtr", "%",  __gu_val, (ptr),    \
 262                                (err), ARM64_HAS_UAO);                   \
 263                 break;                                                  \
 264         default:                                                        \
 265                 BUILD_BUG();                                            \
 266         }                                                               \
 267         uaccess_disable_not_uao();                                      \
 268         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 269 } while (0)
 270
 271 #define __get_user(x, ptr)                                              \
 272 ({                                                                      \
 273         int __gu_err = 0;                                               \
 274         __get_user_err((x), (ptr), __gu_err);                           \
 275         __gu_err;                                                       \
 276 })
 277
 278 #define __get_user_error(x, ptr, err)                                   \
 279 ({                                                                      \
 280         __get_user_err((x), (ptr), (err));                              \
 281         (void)0;                                                        \
 282 })
 283
 284 #define __get_user_unaligned __get_user
 285
 286 #define get_user(x, ptr)                                                \
 287 ({                                                                      \
 288         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 289         might_fault();                                                  \
 290         access_ok(VERIFY_READ, __p, sizeof(*__p)) ?                     \
 291                 __get_user((x), __p) :                                  \
 292                 ((x) = 0, -EFAULT);                                     \
 293 })
 294
 295 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 296         asm volatile(                                                   \
 297         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 298                         alt_instr " " reg "1, [%2]\n", feature)         \
 299         "2:\n"                                                          \
 300         "       .section .fixup,\"ax\"\n"                               \
 301         "       .align  2\n"                                            \
 302         "3:     mov     %w0, %3\n"                                      \
 303         "       b       2b\n"                                           \
 304         "       .previous\n"                                            \
 305         _ASM_EXTABLE(1b, 3b)                                            \
 306         : "+r" (err)                                                    \
 307         : "r" (x), "r" (addr), "i" (-EFAULT))
 308
 309 #define __put_user_err(x, ptr, err)                                     \
 310 do {                                                                    \
 311         __typeof__(*(ptr)) __pu_val = (x);                              \
 312         __chk_user_ptr(ptr);                                            \
 313         uaccess_enable_not_uao();                                       \
 314         switch (sizeof(*(ptr))) {                                       \
 315         case 1:                                                         \
 316                 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr),  \
 317                                (err), ARM64_HAS_UAO);                   \
 318                 break;                                                  \
 319         case 2:                                                         \
 320                 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr),  \
 321                                (err), ARM64_HAS_UAO);                   \
 322                 break;                                                  \
 323         case 4:                                                         \
 324                 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr),    \
 325                                (err), ARM64_HAS_UAO);                   \
 326                 break;                                                  \
 327         case 8:                                                         \
 328                 __put_user_asm("str", "sttr", "%", __pu_val, (ptr),     \
 329                                (err), ARM64_HAS_UAO);                   \
 330                 break;                                                  \
 331         default:                                                        \
 332                 BUILD_BUG();                                            \
 333         }                                                               \
 334         uaccess_disable_not_uao();                                      \
 335 } while (0)
 336
 337 #define __put_user(x, ptr)                                              \
 338 ({                                                                      \
 339         int __pu_err = 0;                                               \
 340         __put_user_err((x), (ptr), __pu_err);                           \
 341         __pu_err;                                                       \
 342 })
 343
 344 #define __put_user_error(x, ptr, err)                                   \
 345 ({                                                                      \
 346         __put_user_err((x), (ptr), (err));                              \
 347         (void)0;                                                        \
 348 })
 349
 350 #define __put_user_unaligned __put_user
 351
 352 #define put_user(x, ptr)                                                \
 353 ({                                                                      \
 354         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 355         might_fault();                                                  \
 356         access_ok(VERIFY_WRITE, __p, sizeof(*__p)) ?                    \
 357                 __put_user((x), __p) :                                  \
 358                 -EFAULT;                                                \
 359 })
 360
 361 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 362 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 363 extern unsigned long __must_check __copy_in_user(void __user *to, const void __user *from, unsigned long n);
 364 extern unsigned long __must_check __clear_user(void __user *addr, unsigned long n);
 365
 366 static inline unsigned long __must_check __copy_from_user(void *to, const void __user *from, unsigned long n)
 367 {
 368         kasan_check_write(to, n);
 369         check_object_size(to, n, false);
 370         return __arch_copy_from_user(to, from, n);
 371 }
 372
 373 static inline unsigned long __must_check __copy_to_user(void __user *to, const void *from, unsigned long n)
 374 {
 375         kasan_check_read(from, n);
 376         check_object_size(from, n, true);
 377         return __arch_copy_to_user(to, from, n);
 378 }
 379
 380 static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n)
 381 {
 382         unsigned long res = n;
 383         kasan_check_write(to, n);
 384
 385         if (access_ok(VERIFY_READ, from, n)) {
 386                 check_object_size(to, n, false);
 387                 res = __arch_copy_from_user(to, from, n);
 388         }
 389         if (unlikely(res))
 390                 memset(to + (n - res), 0, res);
 391         return res;
 392 }
 393
 394 static inline unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n)
 395 {
 396         kasan_check_read(from, n);
 397
 398         if (access_ok(VERIFY_WRITE, to, n)) {
 399                 check_object_size(from, n, true);
 400                 n = __arch_copy_to_user(to, from, n);
 401         }
 402         return n;
 403 }
 404
 405 static inline unsigned long __must_check copy_in_user(void __user *to, const void __user *from, unsigned long n)
 406 {
 407         if (access_ok(VERIFY_READ, from, n) && access_ok(VERIFY_WRITE, to, n))
 408                 n = __copy_in_user(to, from, n);
 409         return n;
 410 }
 411
 412 #define __copy_to_user_inatomic __copy_to_user
 413 #define __copy_from_user_inatomic __copy_from_user
 414
 415 static inline unsigned long __must_check clear_user(void __user *to, unsigned long n)
 416 {
 417         if (access_ok(VERIFY_WRITE, to, n))
 418                 n = __clear_user(to, n);
 419         return n;
 420 }
 421
 422 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 423
 424 extern __must_check long strlen_user(const char __user *str);
 425 extern __must_check long strnlen_user(const char __user *str, long n);
 426
 427 #else   /* __ASSEMBLY__ */
 428
 429 #include <asm/assembler.h>
 430
 431 /*
 432  * User access enabling/disabling macros.
 433  */
 434 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
 435         .macro  __uaccess_ttbr0_disable, tmp1
 436         mrs     \tmp1, ttbr1_el1                // swapper_pg_dir
 437         add     \tmp1, \tmp1, #SWAPPER_DIR_SIZE // reserved_ttbr0 at the end of swapper_pg_dir
 438         msr     ttbr0_el1, \tmp1                // set reserved TTBR0_EL1
 439         isb
 440         .endm
 441
 442         .macro  __uaccess_ttbr0_enable, tmp1
 443         get_thread_info \tmp1
 444         ldr     \tmp1, [\tmp1, #TSK_TI_TTBR0]   // load saved TTBR0_EL1
 445         msr     ttbr0_el1, \tmp1                // set the non-PAN TTBR0_EL1
 446         isb
 447         .endm
 448
 449         .macro  uaccess_ttbr0_disable, tmp1
 450 alternative_if_not ARM64_HAS_PAN
 451         __uaccess_ttbr0_disable \tmp1
 452 alternative_else_nop_endif
 453         .endm
 454
 455         .macro  uaccess_ttbr0_enable, tmp1, tmp2
 456 alternative_if_not ARM64_HAS_PAN
 457         save_and_disable_irq \tmp2              // avoid preemption
 458         __uaccess_ttbr0_enable \tmp1
 459         restore_irq \tmp2
 460 alternative_else_nop_endif
 461         .endm
 462 #else
 463         .macro  uaccess_ttbr0_disable, tmp1
 464         .endm
 465
 466         .macro  uaccess_ttbr0_enable, tmp1, tmp2
 467         .endm
 468 #endif
 469
 470 /*
 471  * These macros are no-ops when UAO is present.
 472  */
 473         .macro  uaccess_disable_not_uao, tmp1
 474         uaccess_ttbr0_disable \tmp1
 475 alternative_if ARM64_ALT_PAN_NOT_UAO
 476         SET_PSTATE_PAN(1)
 477 alternative_else_nop_endif
 478         .endm
 479
 480         .macro  uaccess_enable_not_uao, tmp1, tmp2
 481         uaccess_ttbr0_enable \tmp1, \tmp2
 482 alternative_if ARM64_ALT_PAN_NOT_UAO
 483         SET_PSTATE_PAN(0)
 484 alternative_else_nop_endif
 485         .endm
 486
 487 #endif  /* __ASSEMBLY__ */
 488
 489 #endif /* __ASM_UACCESS_H */