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