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/mmu.h>
  24 #include <asm/sysreg.h>
  25
  26 #ifndef __ASSEMBLY__
  27
  28 /*
  29  * User space memory access functions
  30  */
  31 #include <linux/bitops.h>
  32 #include <linux/kasan-checks.h>
  33 #include <linux/string.h>
  34 #include <linux/thread_info.h>
  35
  36 #include <asm/cpufeature.h>
  37 #include <asm/ptrace.h>
  38 #include <asm/errno.h>
  39 #include <asm/memory.h>
  40 #include <asm/compiler.h>
  41
  42 #define VERIFY_READ 0
  43 #define VERIFY_WRITE 1
  44
  45 /*
  46  * The exception table consists of pairs of relative offsets: the first
  47  * is the relative offset to an instruction that is allowed to fault,
  48  * and the second is the relative offset at which the program should
  49  * continue. No registers are modified, so it is entirely up to the
  50  * continuation code to figure out what to do.
  51  *
  52  * All the routines below use bits of fixup code that are out of line
  53  * with the main instruction path.  This means when everything is well,
  54  * we don't even have to jump over them.  Further, they do not intrude
  55  * on our cache or tlb entries.
  56  */
  57
  58 struct exception_table_entry
  59 {
  60         int insn, fixup;
  61 };
  62
  63 #define ARCH_HAS_RELATIVE_EXTABLE
  64
  65 extern int fixup_exception(struct pt_regs *regs);
  66
  67 #define KERNEL_DS       (-1UL)
  68 #define get_ds()        (KERNEL_DS)
  69
  70 #define USER_DS         TASK_SIZE_64
  71 #define get_fs()        (current_thread_info()->addr_limit)
  72
  73 static inline void set_fs(mm_segment_t fs)
  74 {
  75         current_thread_info()->addr_limit = fs;
  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 <= current->addr_limit
  96  *
  97  * This needs 65-bit arithmetic.
  98  */
  99 #define __range_ok(addr, size)                                          \
 100 ({                                                                      \
 101         unsigned long __addr = (unsigned long __force)(addr);           \
 102         unsigned long flag, roksum;                                     \
 103         __chk_user_ptr(addr);                                           \
 104         asm("adds %1, %1, %3; ccmp %1, %4, #2, cc; cset %0, ls"         \
 105                 : "=&r" (flag), "=&r" (roksum)                          \
 106                 : "1" (__addr), "Ir" (size),                            \
 107                   "r" (current_thread_info()->addr_limit)               \
 108                 : "cc");                                                \
 109         flag;                                                           \
 110 })
 111
 112 /*
 113  * When dealing with data aborts, watchpoints, or instruction traps we may end
 114  * up with a tagged userland pointer. Clear the tag to get a sane pointer to
 115  * pass on to access_ok(), for instance.
 116  */
 117 #define untagged_addr(addr)             sign_extend64(addr, 55)
 118
 119 #define access_ok(type, addr, size)     __range_ok(addr, size)
 120 #define user_addr_max                   get_fs
 121
 122 #define _ASM_EXTABLE(from, to)                                          \
 123         "       .pushsection    __ex_table, \"a\"\n"                    \
 124         "       .align          3\n"                                    \
 125         "       .long           (" #from " - .), (" #to " - .)\n"       \
 126         "       .popsection\n"
 127
 128 /*
 129  * User access enabling/disabling.
 130  */
 131 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
 132 static inline void __uaccess_ttbr0_disable(void)
 133 {
 134         unsigned long flags, ttbr;
 135
 136         local_irq_save(flags);
 137         ttbr = read_sysreg(ttbr1_el1);
 138         ttbr &= ~TTBR_ASID_MASK;
 139         /* reserved_ttbr0 placed at the end of swapper_pg_dir */
 140         write_sysreg(ttbr + SWAPPER_DIR_SIZE, ttbr0_el1);
 141         isb();
 142         /* Set reserved ASID */
 143         write_sysreg(ttbr, ttbr1_el1);
 144         isb();
 145         local_irq_restore(flags);
 146 }
 147
 148 static inline void __uaccess_ttbr0_enable(void)
 149 {
 150         unsigned long flags, ttbr0, ttbr1;
 151
 152         /*
 153          * Disable interrupts to avoid preemption between reading the 'ttbr0'
 154          * variable and the MSR. A context switch could trigger an ASID
 155          * roll-over and an update of 'ttbr0'.
 156          */
 157         local_irq_save(flags);
 158         ttbr0 = READ_ONCE(current_thread_info()->ttbr0);
 159
 160         /* Restore active ASID */
 161         ttbr1 = read_sysreg(ttbr1_el1);
 162         ttbr1 &= ~TTBR_ASID_MASK;               /* safety measure */
 163         ttbr1 |= ttbr0 & TTBR_ASID_MASK;
 164         write_sysreg(ttbr1, ttbr1_el1);
 165         isb();
 166
 167         /* Restore user page table */
 168         write_sysreg(ttbr0, ttbr0_el1);
 169         isb();
 170         local_irq_restore(flags);
 171 }
 172
 173 static inline bool uaccess_ttbr0_disable(void)
 174 {
 175         if (!system_uses_ttbr0_pan())
 176                 return false;
 177         __uaccess_ttbr0_disable();
 178         return true;
 179 }
 180
 181 static inline bool uaccess_ttbr0_enable(void)
 182 {
 183         if (!system_uses_ttbr0_pan())
 184                 return false;
 185         __uaccess_ttbr0_enable();
 186         return true;
 187 }
 188 #else
 189 static inline bool uaccess_ttbr0_disable(void)
 190 {
 191         return false;
 192 }
 193
 194 static inline bool uaccess_ttbr0_enable(void)
 195 {
 196         return false;
 197 }
 198 #endif
 199
 200 #define __uaccess_disable(alt)                                          \
 201 do {                                                                    \
 202         if (!uaccess_ttbr0_disable())                                   \
 203                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt,          \
 204                                 CONFIG_ARM64_PAN));                     \
 205 } while (0)
 206
 207 #define __uaccess_enable(alt)                                           \
 208 do {                                                                    \
 209         if (!uaccess_ttbr0_enable())                                    \
 210                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt,          \
 211                                 CONFIG_ARM64_PAN));                     \
 212 } while (0)
 213
 214 static inline void uaccess_disable(void)
 215 {
 216         __uaccess_disable(ARM64_HAS_PAN);
 217 }
 218
 219 static inline void uaccess_enable(void)
 220 {
 221         __uaccess_enable(ARM64_HAS_PAN);
 222 }
 223
 224 /*
 225  * These functions are no-ops when UAO is present.
 226  */
 227 static inline void uaccess_disable_not_uao(void)
 228 {
 229         __uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
 230 }
 231
 232 static inline void uaccess_enable_not_uao(void)
 233 {
 234         __uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
 235 }
 236
 237 /*
 238  * The "__xxx" versions of the user access functions do not verify the address
 239  * space - it must have been done previously with a separate "access_ok()"
 240  * call.
 241  *
 242  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 243  * occurs, and leave it unchanged on success.
 244  */
 245 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 246         asm volatile(                                                   \
 247         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 248                         alt_instr " " reg "1, [%2]\n", feature)         \
 249         "2:\n"                                                          \
 250         "       .section .fixup, \"ax\"\n"                              \
 251         "       .align  2\n"                                            \
 252         "3:     mov     %w0, %3\n"                                      \
 253         "       mov     %1, #0\n"                                       \
 254         "       b       2b\n"                                           \
 255         "       .previous\n"                                            \
 256         _ASM_EXTABLE(1b, 3b)                                            \
 257         : "+r" (err), "=&r" (x)                                         \
 258         : "r" (addr), "i" (-EFAULT))
 259
 260 #define __get_user_err(x, ptr, err)                                     \
 261 do {                                                                    \
 262         unsigned long __gu_val;                                         \
 263         __chk_user_ptr(ptr);                                            \
 264         uaccess_enable_not_uao();                                       \
 265         switch (sizeof(*(ptr))) {                                       \
 266         case 1:                                                         \
 267                 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
 268                                (err), ARM64_HAS_UAO);                   \
 269                 break;                                                  \
 270         case 2:                                                         \
 271                 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
 272                                (err), ARM64_HAS_UAO);                   \
 273                 break;                                                  \
 274         case 4:                                                         \
 275                 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),    \
 276                                (err), ARM64_HAS_UAO);                   \
 277                 break;                                                  \
 278         case 8:                                                         \
 279                 __get_user_asm("ldr", "ldtr", "%",  __gu_val, (ptr),    \
 280                                (err), ARM64_HAS_UAO);                   \
 281                 break;                                                  \
 282         default:                                                        \
 283                 BUILD_BUG();                                            \
 284         }                                                               \
 285         uaccess_disable_not_uao();                                      \
 286         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 287 } while (0)
 288
 289 #define __get_user(x, ptr)                                              \
 290 ({                                                                      \
 291         int __gu_err = 0;                                               \
 292         __get_user_err((x), (ptr), __gu_err);                           \
 293         __gu_err;                                                       \
 294 })
 295
 296 #define __get_user_error(x, ptr, err)                                   \
 297 ({                                                                      \
 298         __get_user_err((x), (ptr), (err));                              \
 299         (void)0;                                                        \
 300 })
 301
 302 #define __get_user_unaligned __get_user
 303
 304 #define get_user(x, ptr)                                                \
 305 ({                                                                      \
 306         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 307         might_fault();                                                  \
 308         access_ok(VERIFY_READ, __p, sizeof(*__p)) ?                     \
 309                 __get_user((x), __p) :                                  \
 310                 ((x) = 0, -EFAULT);                                     \
 311 })
 312
 313 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 314         asm volatile(                                                   \
 315         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 316                         alt_instr " " reg "1, [%2]\n", feature)         \
 317         "2:\n"                                                          \
 318         "       .section .fixup,\"ax\"\n"                               \
 319         "       .align  2\n"                                            \
 320         "3:     mov     %w0, %3\n"                                      \
 321         "       b       2b\n"                                           \
 322         "       .previous\n"                                            \
 323         _ASM_EXTABLE(1b, 3b)                                            \
 324         : "+r" (err)                                                    \
 325         : "r" (x), "r" (addr), "i" (-EFAULT))
 326
 327 #define __put_user_err(x, ptr, err)                                     \
 328 do {                                                                    \
 329         __typeof__(*(ptr)) __pu_val = (x);                              \
 330         __chk_user_ptr(ptr);                                            \
 331         uaccess_enable_not_uao();                                       \
 332         switch (sizeof(*(ptr))) {                                       \
 333         case 1:                                                         \
 334                 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr),  \
 335                                (err), ARM64_HAS_UAO);                   \
 336                 break;                                                  \
 337         case 2:                                                         \
 338                 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr),  \
 339                                (err), ARM64_HAS_UAO);                   \
 340                 break;                                                  \
 341         case 4:                                                         \
 342                 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr),    \
 343                                (err), ARM64_HAS_UAO);                   \
 344                 break;                                                  \
 345         case 8:                                                         \
 346                 __put_user_asm("str", "sttr", "%", __pu_val, (ptr),     \
 347                                (err), ARM64_HAS_UAO);                   \
 348                 break;                                                  \
 349         default:                                                        \
 350                 BUILD_BUG();                                            \
 351         }                                                               \
 352         uaccess_disable_not_uao();                                      \
 353 } while (0)
 354
 355 #define __put_user(x, ptr)                                              \
 356 ({                                                                      \
 357         int __pu_err = 0;                                               \
 358         __put_user_err((x), (ptr), __pu_err);                           \
 359         __pu_err;                                                       \
 360 })
 361
 362 #define __put_user_error(x, ptr, err)                                   \
 363 ({                                                                      \
 364         __put_user_err((x), (ptr), (err));                              \
 365         (void)0;                                                        \
 366 })
 367
 368 #define __put_user_unaligned __put_user
 369
 370 #define put_user(x, ptr)                                                \
 371 ({                                                                      \
 372         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 373         might_fault();                                                  \
 374         access_ok(VERIFY_WRITE, __p, sizeof(*__p)) ?                    \
 375                 __put_user((x), __p) :                                  \
 376                 -EFAULT;                                                \
 377 })
 378
 379 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 380 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 381 extern unsigned long __must_check __copy_in_user(void __user *to, const void __user *from, unsigned long n);
 382 extern unsigned long __must_check __clear_user(void __user *addr, unsigned long n);
 383
 384 static inline unsigned long __must_check __copy_from_user(void *to, const void __user *from, unsigned long n)
 385 {
 386         kasan_check_write(to, n);
 387         check_object_size(to, n, false);
 388         return __arch_copy_from_user(to, from, n);
 389 }
 390
 391 static inline unsigned long __must_check __copy_to_user(void __user *to, const void *from, unsigned long n)
 392 {
 393         kasan_check_read(from, n);
 394         check_object_size(from, n, true);
 395         return __arch_copy_to_user(to, from, n);
 396 }
 397
 398 static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n)
 399 {
 400         unsigned long res = n;
 401         kasan_check_write(to, n);
 402
 403         if (access_ok(VERIFY_READ, from, n)) {
 404                 check_object_size(to, n, false);
 405                 res = __arch_copy_from_user(to, from, n);
 406         }
 407         if (unlikely(res))
 408                 memset(to + (n - res), 0, res);
 409         return res;
 410 }
 411
 412 static inline unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n)
 413 {
 414         kasan_check_read(from, n);
 415
 416         if (access_ok(VERIFY_WRITE, to, n)) {
 417                 check_object_size(from, n, true);
 418                 n = __arch_copy_to_user(to, from, n);
 419         }
 420         return n;
 421 }
 422
 423 static inline unsigned long __must_check copy_in_user(void __user *to, const void __user *from, unsigned long n)
 424 {
 425         if (access_ok(VERIFY_READ, from, n) && access_ok(VERIFY_WRITE, to, n))
 426                 n = __copy_in_user(to, from, n);
 427         return n;
 428 }
 429
 430 #define __copy_to_user_inatomic __copy_to_user
 431 #define __copy_from_user_inatomic __copy_from_user
 432
 433 static inline unsigned long __must_check clear_user(void __user *to, unsigned long n)
 434 {
 435         if (access_ok(VERIFY_WRITE, to, n))
 436                 n = __clear_user(to, n);
 437         return n;
 438 }
 439
 440 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 441
 442 extern __must_check long strlen_user(const char __user *str);
 443 extern __must_check long strnlen_user(const char __user *str, long n);
 444
 445 #else   /* __ASSEMBLY__ */
 446
 447 #include <asm/assembler.h>
 448
 449 /*
 450  * User access enabling/disabling macros.
 451  */
 452 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
 453         .macro  __uaccess_ttbr0_disable, tmp1
 454         mrs     \tmp1, ttbr1_el1                // swapper_pg_dir
 455         bic     \tmp1, \tmp1, #TTBR_ASID_MASK
 456         add     \tmp1, \tmp1, #SWAPPER_DIR_SIZE // reserved_ttbr0 at the end of swapper_pg_dir
 457         msr     ttbr0_el1, \tmp1                // set reserved TTBR0_EL1
 458         isb
 459         sub     \tmp1, \tmp1, #SWAPPER_DIR_SIZE
 460         msr     ttbr1_el1, \tmp1                // set reserved ASID
 461         isb
 462         .endm
 463
 464         .macro  __uaccess_ttbr0_enable, tmp1, tmp2
 465         get_thread_info \tmp1
 466         ldr     \tmp1, [\tmp1, #TSK_TI_TTBR0]   // load saved TTBR0_EL1
 467         mrs     \tmp2, ttbr1_el1
 468         extr    \tmp2, \tmp2, \tmp1, #48
 469         ror     \tmp2, \tmp2, #16
 470         msr     ttbr1_el1, \tmp2                // set the active ASID
 471         isb
 472         msr     ttbr0_el1, \tmp1                // set the non-PAN TTBR0_EL1
 473         isb
 474         .endm
 475
 476         .macro  uaccess_ttbr0_disable, tmp1, tmp2
 477 alternative_if_not ARM64_HAS_PAN
 478         save_and_disable_irq \tmp2              // avoid preemption
 479         __uaccess_ttbr0_disable \tmp1
 480         restore_irq \tmp2
 481 alternative_else_nop_endif
 482         .endm
 483
 484         .macro  uaccess_ttbr0_enable, tmp1, tmp2, tmp3
 485 alternative_if_not ARM64_HAS_PAN
 486         save_and_disable_irq \tmp3              // avoid preemption
 487         __uaccess_ttbr0_enable \tmp1, \tmp2
 488         restore_irq \tmp3
 489 alternative_else_nop_endif
 490         .endm
 491 #else
 492         .macro  uaccess_ttbr0_disable, tmp1, tmp2
 493         .endm
 494
 495         .macro  uaccess_ttbr0_enable, tmp1, tmp2, tmp3
 496         .endm
 497 #endif
 498
 499 /*
 500  * These macros are no-ops when UAO is present.
 501  */
 502         .macro  uaccess_disable_not_uao, tmp1, tmp2
 503         uaccess_ttbr0_disable \tmp1, \tmp2
 504 alternative_if ARM64_ALT_PAN_NOT_UAO
 505         SET_PSTATE_PAN(1)
 506 alternative_else_nop_endif
 507         .endm
 508
 509         .macro  uaccess_enable_not_uao, tmp1, tmp2, tmp3
 510         uaccess_ttbr0_enable \tmp1, \tmp2, \tmp3
 511 alternative_if ARM64_ALT_PAN_NOT_UAO
 512         SET_PSTATE_PAN(0)
 513 alternative_else_nop_endif
 514         .endm
 515
 516 #endif  /* __ASSEMBLY__ */
 517
 518 #endif /* __ASM_UACCESS_H */