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 __addr = (unsigned long __force)(addr);           \
 101         unsigned long flag, roksum;                                     \
 102         __chk_user_ptr(addr);                                           \
 103         asm("adds %1, %1, %3; ccmp %1, %4, #2, cc; cset %0, ls"         \
 104                 : "=&r" (flag), "=&r" (roksum)                          \
 105                 : "1" (__addr), "Ir" (size),                            \
 106                   "r" (current_thread_info()->addr_limit)               \
 107                 : "cc");                                                \
 108         flag;                                                           \
 109 })
 110
 111 /*
 112  * When dealing with data aborts, watchpoints, or instruction traps we may end
 113  * up with a tagged userland pointer. Clear the tag to get a sane pointer to
 114  * pass on to access_ok(), for instance.
 115  */
 116 #define untagged_addr(addr)             sign_extend64(addr, 55)
 117
 118 #define access_ok(type, addr, size)     __range_ok(addr, size)
 119 #define user_addr_max                   get_fs
 120
 121 #define _ASM_EXTABLE(from, to)                                          \
 122         "       .pushsection    __ex_table, \"a\"\n"                    \
 123         "       .align          3\n"                                    \
 124         "       .long           (" #from " - .), (" #to " - .)\n"       \
 125         "       .popsection\n"
 126
 127 /*
 128  * User access enabling/disabling.
 129  */
 130 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
 131 static inline void __uaccess_ttbr0_disable(void)
 132 {
 133         unsigned long ttbr;
 134
 135         /* reserved_ttbr0 placed at the end of swapper_pg_dir */
 136         ttbr = read_sysreg(ttbr1_el1) + SWAPPER_DIR_SIZE;
 137         write_sysreg(ttbr, ttbr0_el1);
 138         isb();
 139 }
 140
 141 static inline void __uaccess_ttbr0_enable(void)
 142 {
 143         unsigned long flags;
 144
 145         /*
 146          * Disable interrupts to avoid preemption between reading the 'ttbr0'
 147          * variable and the MSR. A context switch could trigger an ASID
 148          * roll-over and an update of 'ttbr0'.
 149          */
 150         local_irq_save(flags);
 151         write_sysreg(current_thread_info()->ttbr0, ttbr0_el1);
 152         isb();
 153         local_irq_restore(flags);
 154 }
 155
 156 static inline bool uaccess_ttbr0_disable(void)
 157 {
 158         if (!system_uses_ttbr0_pan())
 159                 return false;
 160         __uaccess_ttbr0_disable();
 161         return true;
 162 }
 163
 164 static inline bool uaccess_ttbr0_enable(void)
 165 {
 166         if (!system_uses_ttbr0_pan())
 167                 return false;
 168         __uaccess_ttbr0_enable();
 169         return true;
 170 }
 171 #else
 172 static inline bool uaccess_ttbr0_disable(void)
 173 {
 174         return false;
 175 }
 176
 177 static inline bool uaccess_ttbr0_enable(void)
 178 {
 179         return false;
 180 }
 181 #endif
 182
 183 #define __uaccess_disable(alt)                                          \
 184 do {                                                                    \
 185         if (!uaccess_ttbr0_disable())                                   \
 186                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt,          \
 187                                 CONFIG_ARM64_PAN));                     \
 188 } while (0)
 189
 190 #define __uaccess_enable(alt)                                           \
 191 do {                                                                    \
 192         if (!uaccess_ttbr0_enable())                                    \
 193                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt,          \
 194                                 CONFIG_ARM64_PAN));                     \
 195 } while (0)
 196
 197 static inline void uaccess_disable(void)
 198 {
 199         __uaccess_disable(ARM64_HAS_PAN);
 200 }
 201
 202 static inline void uaccess_enable(void)
 203 {
 204         __uaccess_enable(ARM64_HAS_PAN);
 205 }
 206
 207 /*
 208  * These functions are no-ops when UAO is present.
 209  */
 210 static inline void uaccess_disable_not_uao(void)
 211 {
 212         __uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
 213 }
 214
 215 static inline void uaccess_enable_not_uao(void)
 216 {
 217         __uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
 218 }
 219
 220 /*
 221  * The "__xxx" versions of the user access functions do not verify the address
 222  * space - it must have been done previously with a separate "access_ok()"
 223  * call.
 224  *
 225  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 226  * occurs, and leave it unchanged on success.
 227  */
 228 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 229         asm volatile(                                                   \
 230         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 231                         alt_instr " " reg "1, [%2]\n", feature)         \
 232         "2:\n"                                                          \
 233         "       .section .fixup, \"ax\"\n"                              \
 234         "       .align  2\n"                                            \
 235         "3:     mov     %w0, %3\n"                                      \
 236         "       mov     %1, #0\n"                                       \
 237         "       b       2b\n"                                           \
 238         "       .previous\n"                                            \
 239         _ASM_EXTABLE(1b, 3b)                                            \
 240         : "+r" (err), "=&r" (x)                                         \
 241         : "r" (addr), "i" (-EFAULT))
 242
 243 #define __get_user_err(x, ptr, err)                                     \
 244 do {                                                                    \
 245         unsigned long __gu_val;                                         \
 246         __chk_user_ptr(ptr);                                            \
 247         uaccess_enable_not_uao();                                       \
 248         switch (sizeof(*(ptr))) {                                       \
 249         case 1:                                                         \
 250                 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
 251                                (err), ARM64_HAS_UAO);                   \
 252                 break;                                                  \
 253         case 2:                                                         \
 254                 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
 255                                (err), ARM64_HAS_UAO);                   \
 256                 break;                                                  \
 257         case 4:                                                         \
 258                 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),    \
 259                                (err), ARM64_HAS_UAO);                   \
 260                 break;                                                  \
 261         case 8:                                                         \
 262                 __get_user_asm("ldr", "ldtr", "%",  __gu_val, (ptr),    \
 263                                (err), ARM64_HAS_UAO);                   \
 264                 break;                                                  \
 265         default:                                                        \
 266                 BUILD_BUG();                                            \
 267         }                                                               \
 268         uaccess_disable_not_uao();                                      \
 269         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 270 } while (0)
 271
 272 #define __get_user(x, ptr)                                              \
 273 ({                                                                      \
 274         int __gu_err = 0;                                               \
 275         __get_user_err((x), (ptr), __gu_err);                           \
 276         __gu_err;                                                       \
 277 })
 278
 279 #define __get_user_error(x, ptr, err)                                   \
 280 ({                                                                      \
 281         __get_user_err((x), (ptr), (err));                              \
 282         (void)0;                                                        \
 283 })
 284
 285 #define __get_user_unaligned __get_user
 286
 287 #define get_user(x, ptr)                                                \
 288 ({                                                                      \
 289         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 290         might_fault();                                                  \
 291         access_ok(VERIFY_READ, __p, sizeof(*__p)) ?                     \
 292                 __get_user((x), __p) :                                  \
 293                 ((x) = 0, -EFAULT);                                     \
 294 })
 295
 296 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 297         asm volatile(                                                   \
 298         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 299                         alt_instr " " reg "1, [%2]\n", feature)         \
 300         "2:\n"                                                          \
 301         "       .section .fixup,\"ax\"\n"                               \
 302         "       .align  2\n"                                            \
 303         "3:     mov     %w0, %3\n"                                      \
 304         "       b       2b\n"                                           \
 305         "       .previous\n"                                            \
 306         _ASM_EXTABLE(1b, 3b)                                            \
 307         : "+r" (err)                                                    \
 308         : "r" (x), "r" (addr), "i" (-EFAULT))
 309
 310 #define __put_user_err(x, ptr, err)                                     \
 311 do {                                                                    \
 312         __typeof__(*(ptr)) __pu_val = (x);                              \
 313         __chk_user_ptr(ptr);                                            \
 314         uaccess_enable_not_uao();                                       \
 315         switch (sizeof(*(ptr))) {                                       \
 316         case 1:                                                         \
 317                 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr),  \
 318                                (err), ARM64_HAS_UAO);                   \
 319                 break;                                                  \
 320         case 2:                                                         \
 321                 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr),  \
 322                                (err), ARM64_HAS_UAO);                   \
 323                 break;                                                  \
 324         case 4:                                                         \
 325                 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr),    \
 326                                (err), ARM64_HAS_UAO);                   \
 327                 break;                                                  \
 328         case 8:                                                         \
 329                 __put_user_asm("str", "sttr", "%", __pu_val, (ptr),     \
 330                                (err), ARM64_HAS_UAO);                   \
 331                 break;                                                  \
 332         default:                                                        \
 333                 BUILD_BUG();                                            \
 334         }                                                               \
 335         uaccess_disable_not_uao();                                      \
 336 } while (0)
 337
 338 #define __put_user(x, ptr)                                              \
 339 ({                                                                      \
 340         int __pu_err = 0;                                               \
 341         __put_user_err((x), (ptr), __pu_err);                           \
 342         __pu_err;                                                       \
 343 })
 344
 345 #define __put_user_error(x, ptr, err)                                   \
 346 ({                                                                      \
 347         __put_user_err((x), (ptr), (err));                              \
 348         (void)0;                                                        \
 349 })
 350
 351 #define __put_user_unaligned __put_user
 352
 353 #define put_user(x, ptr)                                                \
 354 ({                                                                      \
 355         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 356         might_fault();                                                  \
 357         access_ok(VERIFY_WRITE, __p, sizeof(*__p)) ?                    \
 358                 __put_user((x), __p) :                                  \
 359                 -EFAULT;                                                \
 360 })
 361
 362 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 363 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 364 extern unsigned long __must_check __copy_in_user(void __user *to, const void __user *from, unsigned long n);
 365 extern unsigned long __must_check __clear_user(void __user *addr, unsigned long n);
 366
 367 static inline unsigned long __must_check __copy_from_user(void *to, const void __user *from, unsigned long n)
 368 {
 369         kasan_check_write(to, n);
 370         check_object_size(to, n, false);
 371         return __arch_copy_from_user(to, from, n);
 372 }
 373
 374 static inline unsigned long __must_check __copy_to_user(void __user *to, const void *from, unsigned long n)
 375 {
 376         kasan_check_read(from, n);
 377         check_object_size(from, n, true);
 378         return __arch_copy_to_user(to, from, n);
 379 }
 380
 381 static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n)
 382 {
 383         unsigned long res = n;
 384         kasan_check_write(to, n);
 385
 386         if (access_ok(VERIFY_READ, from, n)) {
 387                 check_object_size(to, n, false);
 388                 res = __arch_copy_from_user(to, from, n);
 389         }
 390         if (unlikely(res))
 391                 memset(to + (n - res), 0, res);
 392         return res;
 393 }
 394
 395 static inline unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n)
 396 {
 397         kasan_check_read(from, n);
 398
 399         if (access_ok(VERIFY_WRITE, to, n)) {
 400                 check_object_size(from, n, true);
 401                 n = __arch_copy_to_user(to, from, n);
 402         }
 403         return n;
 404 }
 405
 406 static inline unsigned long __must_check copy_in_user(void __user *to, const void __user *from, unsigned long n)
 407 {
 408         if (access_ok(VERIFY_READ, from, n) && access_ok(VERIFY_WRITE, to, n))
 409                 n = __copy_in_user(to, from, n);
 410         return n;
 411 }
 412
 413 #define __copy_to_user_inatomic __copy_to_user
 414 #define __copy_from_user_inatomic __copy_from_user
 415
 416 static inline unsigned long __must_check clear_user(void __user *to, unsigned long n)
 417 {
 418         if (access_ok(VERIFY_WRITE, to, n))
 419                 n = __clear_user(to, n);
 420         return n;
 421 }
 422
 423 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 424
 425 extern __must_check long strlen_user(const char __user *str);
 426 extern __must_check long strnlen_user(const char __user *str, long n);
 427
 428 #else   /* __ASSEMBLY__ */
 429
 430 #include <asm/assembler.h>
 431
 432 /*
 433  * User access enabling/disabling macros.
 434  */
 435 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
 436         .macro  __uaccess_ttbr0_disable, tmp1
 437         mrs     \tmp1, ttbr1_el1                // swapper_pg_dir
 438         add     \tmp1, \tmp1, #SWAPPER_DIR_SIZE // reserved_ttbr0 at the end of swapper_pg_dir
 439         msr     ttbr0_el1, \tmp1                // set reserved TTBR0_EL1
 440         isb
 441         .endm
 442
 443         .macro  __uaccess_ttbr0_enable, tmp1
 444         get_thread_info \tmp1
 445         ldr     \tmp1, [\tmp1, #TSK_TI_TTBR0]   // load saved TTBR0_EL1
 446         msr     ttbr0_el1, \tmp1                // set the non-PAN TTBR0_EL1
 447         isb
 448         .endm
 449
 450         .macro  uaccess_ttbr0_disable, tmp1
 451 alternative_if_not ARM64_HAS_PAN
 452         __uaccess_ttbr0_disable \tmp1
 453 alternative_else_nop_endif
 454         .endm
 455
 456         .macro  uaccess_ttbr0_enable, tmp1, tmp2
 457 alternative_if_not ARM64_HAS_PAN
 458         save_and_disable_irq \tmp2              // avoid preemption
 459         __uaccess_ttbr0_enable \tmp1
 460         restore_irq \tmp2
 461 alternative_else_nop_endif
 462         .endm
 463 #else
 464         .macro  uaccess_ttbr0_disable, tmp1
 465         .endm
 466
 467         .macro  uaccess_ttbr0_enable, tmp1, tmp2
 468         .endm
 469 #endif
 470
 471 /*
 472  * These macros are no-ops when UAO is present.
 473  */
 474         .macro  uaccess_disable_not_uao, tmp1
 475         uaccess_ttbr0_disable \tmp1
 476 alternative_if ARM64_ALT_PAN_NOT_UAO
 477         SET_PSTATE_PAN(1)
 478 alternative_else_nop_endif
 479         .endm
 480
 481         .macro  uaccess_enable_not_uao, tmp1, tmp2
 482         uaccess_ttbr0_enable \tmp1, \tmp2
 483 alternative_if ARM64_ALT_PAN_NOT_UAO
 484         SET_PSTATE_PAN(0)
 485 alternative_else_nop_endif
 486         .endm
 487
 488 #endif  /* __ASSEMBLY__ */
 489
 490 #endif /* __ASM_UACCESS_H */