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
  32 #include <asm/cpufeature.h>
  33 #include <asm/ptrace.h>
  34 #include <asm/memory.h>
  35 #include <asm/compiler.h>
  36 #include <asm/extable.h>
  37
  38 #define get_ds()        (KERNEL_DS)
  39 #define get_fs()        (current_thread_info()->addr_limit)
  40
  41 static inline void set_fs(mm_segment_t fs)
  42 {
  43         current_thread_info()->addr_limit = fs;
  44
  45         /*
  46          * Prevent a mispredicted conditional call to set_fs from forwarding
  47          * the wrong address limit to access_ok under speculation.
  48          */
  49         dsb(nsh);
  50         isb();
  51
  52         /* On user-mode return, check fs is correct */
  53         set_thread_flag(TIF_FSCHECK);
  54
  55         /*
  56          * Enable/disable UAO so that copy_to_user() etc can access
  57          * kernel memory with the unprivileged instructions.
  58          */
  59         if (IS_ENABLED(CONFIG_ARM64_UAO) && fs == KERNEL_DS)
  60                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
  61         else
  62                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
  63                                 CONFIG_ARM64_UAO));
  64 }
  65
  66 #define segment_eq(a, b)        ((a) == (b))
  67
  68 /*
  69  * Test whether a block of memory is a valid user space address.
  70  * Returns 1 if the range is valid, 0 otherwise.
  71  *
  72  * This is equivalent to the following test:
  73  * (u65)addr + (u65)size <= (u65)current->addr_limit + 1
  74  */
  75 static inline unsigned long __range_ok(const void __user *addr, unsigned long size)
  76 {
  77         unsigned long ret, limit = current_thread_info()->addr_limit;
  78
  79         __chk_user_ptr(addr);
  80         asm volatile(
  81         // A + B <= C + 1 for all A,B,C, in four easy steps:
  82         // 1: X = A + B; X' = X % 2^64
  83         "       adds    %0, %3, %2\n"
  84         // 2: Set C = 0 if X > 2^64, to guarantee X' > C in step 4
  85         "       csel    %1, xzr, %1, hi\n"
  86         // 3: Set X' = ~0 if X >= 2^64. For X == 2^64, this decrements X'
  87         //    to compensate for the carry flag being set in step 4. For
  88         //    X > 2^64, X' merely has to remain nonzero, which it does.
  89         "       csinv   %0, %0, xzr, cc\n"
  90         // 4: For X < 2^64, this gives us X' - C - 1 <= 0, where the -1
  91         //    comes from the carry in being clear. Otherwise, we are
  92         //    testing X' - C == 0, subject to the previous adjustments.
  93         "       sbcs    xzr, %0, %1\n"
  94         "       cset    %0, ls\n"
  95         : "=&r" (ret), "+r" (limit) : "Ir" (size), "0" (addr) : "cc");
  96
  97         return ret;
  98 }
  99
 100 /*
 101  * When dealing with data aborts, watchpoints, or instruction traps we may end
 102  * up with a tagged userland pointer. Clear the tag to get a sane pointer to
 103  * pass on to access_ok(), for instance.
 104  */
 105 #define untagged_addr(addr)             sign_extend64(addr, 55)
 106
 107 #define access_ok(type, addr, size)     __range_ok(addr, size)
 108 #define user_addr_max                   get_fs
 109
 110 #define _ASM_EXTABLE(from, to)                                          \
 111         "       .pushsection    __ex_table, \"a\"\n"                    \
 112         "       .align          3\n"                                    \
 113         "       .long           (" #from " - .), (" #to " - .)\n"       \
 114         "       .popsection\n"
 115
 116 /*
 117  * User access enabling/disabling.
 118  */
 119 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
 120 static inline void __uaccess_ttbr0_disable(void)
 121 {
 122         unsigned long flags, ttbr;
 123
 124         local_irq_save(flags);
 125         ttbr = read_sysreg(ttbr1_el1);
 126         ttbr &= ~TTBR_ASID_MASK;
 127         /* reserved_ttbr0 placed before swapper_pg_dir */
 128         write_sysreg(ttbr - RESERVED_TTBR0_SIZE, ttbr0_el1);
 129         isb();
 130         /* Set reserved ASID */
 131         write_sysreg(ttbr, ttbr1_el1);
 132         isb();
 133         local_irq_restore(flags);
 134 }
 135
 136 static inline void __uaccess_ttbr0_enable(void)
 137 {
 138         unsigned long flags, ttbr0, ttbr1;
 139
 140         /*
 141          * Disable interrupts to avoid preemption between reading the 'ttbr0'
 142          * variable and the MSR. A context switch could trigger an ASID
 143          * roll-over and an update of 'ttbr0'.
 144          */
 145         local_irq_save(flags);
 146         ttbr0 = READ_ONCE(current_thread_info()->ttbr0);
 147
 148         /* Restore active ASID */
 149         ttbr1 = read_sysreg(ttbr1_el1);
 150         ttbr1 &= ~TTBR_ASID_MASK;               /* safety measure */
 151         ttbr1 |= ttbr0 & TTBR_ASID_MASK;
 152         write_sysreg(ttbr1, ttbr1_el1);
 153         isb();
 154
 155         /* Restore user page table */
 156         write_sysreg(ttbr0, ttbr0_el1);
 157         isb();
 158         local_irq_restore(flags);
 159 }
 160
 161 static inline bool uaccess_ttbr0_disable(void)
 162 {
 163         if (!system_uses_ttbr0_pan())
 164                 return false;
 165         __uaccess_ttbr0_disable();
 166         return true;
 167 }
 168
 169 static inline bool uaccess_ttbr0_enable(void)
 170 {
 171         if (!system_uses_ttbr0_pan())
 172                 return false;
 173         __uaccess_ttbr0_enable();
 174         return true;
 175 }
 176 #else
 177 static inline bool uaccess_ttbr0_disable(void)
 178 {
 179         return false;
 180 }
 181
 182 static inline bool uaccess_ttbr0_enable(void)
 183 {
 184         return false;
 185 }
 186 #endif
 187
 188 static inline void __uaccess_disable_hw_pan(void)
 189 {
 190         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN,
 191                         CONFIG_ARM64_PAN));
 192 }
 193
 194 static inline void __uaccess_enable_hw_pan(void)
 195 {
 196         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,
 197                         CONFIG_ARM64_PAN));
 198 }
 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  * Sanitise a uaccess pointer such that it becomes NULL if above the
 239  * current addr_limit.
 240  */
 241 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
 242 static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
 243 {
 244         void __user *safe_ptr;
 245
 246         asm volatile(
 247         "       bics    xzr, %1, %2\n"
 248         "       csel    %0, %1, xzr, eq\n"
 249         : "=&r" (safe_ptr)
 250         : "r" (ptr), "r" (current_thread_info()->addr_limit)
 251         : "cc");
 252
 253         csdb();
 254         return safe_ptr;
 255 }
 256
 257 /*
 258  * The "__xxx" versions of the user access functions do not verify the address
 259  * space - it must have been done previously with a separate "access_ok()"
 260  * call.
 261  *
 262  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 263  * occurs, and leave it unchanged on success.
 264  */
 265 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 266         asm volatile(                                                   \
 267         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 268                         alt_instr " " reg "1, [%2]\n", feature)         \
 269         "2:\n"                                                          \
 270         "       .section .fixup, \"ax\"\n"                              \
 271         "       .align  2\n"                                            \
 272         "3:     mov     %w0, %3\n"                                      \
 273         "       mov     %1, #0\n"                                       \
 274         "       b       2b\n"                                           \
 275         "       .previous\n"                                            \
 276         _ASM_EXTABLE(1b, 3b)                                            \
 277         : "+r" (err), "=&r" (x)                                         \
 278         : "r" (addr), "i" (-EFAULT))
 279
 280 #define __get_user_err(x, ptr, err)                                     \
 281 do {                                                                    \
 282         unsigned long __gu_val;                                         \
 283         __chk_user_ptr(ptr);                                            \
 284         uaccess_enable_not_uao();                                       \
 285         switch (sizeof(*(ptr))) {                                       \
 286         case 1:                                                         \
 287                 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
 288                                (err), ARM64_HAS_UAO);                   \
 289                 break;                                                  \
 290         case 2:                                                         \
 291                 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
 292                                (err), ARM64_HAS_UAO);                   \
 293                 break;                                                  \
 294         case 4:                                                         \
 295                 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),    \
 296                                (err), ARM64_HAS_UAO);                   \
 297                 break;                                                  \
 298         case 8:                                                         \
 299                 __get_user_asm("ldr", "ldtr", "%x",  __gu_val, (ptr),   \
 300                                (err), ARM64_HAS_UAO);                   \
 301                 break;                                                  \
 302         default:                                                        \
 303                 BUILD_BUG();                                            \
 304         }                                                               \
 305         uaccess_disable_not_uao();                                      \
 306         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 307 } while (0)
 308
 309 #define __get_user_check(x, ptr, err)                                   \
 310 ({                                                                      \
 311         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 312         might_fault();                                                  \
 313         if (access_ok(VERIFY_READ, __p, sizeof(*__p))) {                \
 314                 __p = uaccess_mask_ptr(__p);                            \
 315                 __get_user_err((x), __p, (err));                        \
 316         } else {                                                        \
 317                 (x) = 0; (err) = -EFAULT;                               \
 318         }                                                               \
 319 })
 320
 321 #define __get_user_error(x, ptr, err)                                   \
 322 ({                                                                      \
 323         __get_user_check((x), (ptr), (err));                            \
 324         (void)0;                                                        \
 325 })
 326
 327 #define __get_user(x, ptr)                                              \
 328 ({                                                                      \
 329         int __gu_err = 0;                                               \
 330         __get_user_check((x), (ptr), __gu_err);                         \
 331         __gu_err;                                                       \
 332 })
 333
 334 #define get_user        __get_user
 335
 336 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 337         asm volatile(                                                   \
 338         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 339                         alt_instr " " reg "1, [%2]\n", feature)         \
 340         "2:\n"                                                          \
 341         "       .section .fixup,\"ax\"\n"                               \
 342         "       .align  2\n"                                            \
 343         "3:     mov     %w0, %3\n"                                      \
 344         "       b       2b\n"                                           \
 345         "       .previous\n"                                            \
 346         _ASM_EXTABLE(1b, 3b)                                            \
 347         : "+r" (err)                                                    \
 348         : "r" (x), "r" (addr), "i" (-EFAULT))
 349
 350 #define __put_user_err(x, ptr, err)                                     \
 351 do {                                                                    \
 352         __typeof__(*(ptr)) __pu_val = (x);                              \
 353         __chk_user_ptr(ptr);                                            \
 354         uaccess_enable_not_uao();                                       \
 355         switch (sizeof(*(ptr))) {                                       \
 356         case 1:                                                         \
 357                 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr),  \
 358                                (err), ARM64_HAS_UAO);                   \
 359                 break;                                                  \
 360         case 2:                                                         \
 361                 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr),  \
 362                                (err), ARM64_HAS_UAO);                   \
 363                 break;                                                  \
 364         case 4:                                                         \
 365                 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr),    \
 366                                (err), ARM64_HAS_UAO);                   \
 367                 break;                                                  \
 368         case 8:                                                         \
 369                 __put_user_asm("str", "sttr", "%x", __pu_val, (ptr),    \
 370                                (err), ARM64_HAS_UAO);                   \
 371                 break;                                                  \
 372         default:                                                        \
 373                 BUILD_BUG();                                            \
 374         }                                                               \
 375         uaccess_disable_not_uao();                                      \
 376 } while (0)
 377
 378 #define __put_user_check(x, ptr, err)                                   \
 379 ({                                                                      \
 380         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 381         might_fault();                                                  \
 382         if (access_ok(VERIFY_WRITE, __p, sizeof(*__p))) {               \
 383                 __p = uaccess_mask_ptr(__p);                            \
 384                 __put_user_err((x), __p, (err));                        \
 385         } else  {                                                       \
 386                 (err) = -EFAULT;                                        \
 387         }                                                               \
 388 })
 389
 390 #define __put_user_error(x, ptr, err)                                   \
 391 ({                                                                      \
 392         __put_user_check((x), (ptr), (err));                            \
 393         (void)0;                                                        \
 394 })
 395
 396 #define __put_user(x, ptr)                                              \
 397 ({                                                                      \
 398         int __pu_err = 0;                                               \
 399         __put_user_check((x), (ptr), __pu_err);                         \
 400         __pu_err;                                                       \
 401 })
 402
 403 #define put_user        __put_user
 404
 405 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 406 #define raw_copy_from_user(to, from, n)                                 \
 407 ({                                                                      \
 408         __arch_copy_from_user((to), __uaccess_mask_ptr(from), (n));     \
 409 })
 410
 411 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 412 #define raw_copy_to_user(to, from, n)                                   \
 413 ({                                                                      \
 414         __arch_copy_to_user(__uaccess_mask_ptr(to), (from), (n));       \
 415 })
 416
 417 extern unsigned long __must_check __arch_copy_in_user(void __user *to, const void __user *from, unsigned long n);
 418 #define raw_copy_in_user(to, from, n)                                   \
 419 ({                                                                      \
 420         __arch_copy_in_user(__uaccess_mask_ptr(to),                     \
 421                             __uaccess_mask_ptr(from), (n));             \
 422 })
 423
 424 #define INLINE_COPY_TO_USER
 425 #define INLINE_COPY_FROM_USER
 426
 427 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
 428 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
 429 {
 430         if (access_ok(VERIFY_WRITE, to, n))
 431                 n = __arch_clear_user(__uaccess_mask_ptr(to), n);
 432         return n;
 433 }
 434 #define clear_user      __clear_user
 435
 436 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 437
 438 extern __must_check long strnlen_user(const char __user *str, long n);
 439
 440 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
 441 struct page;
 442 void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len);
 443 extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n);
 444
 445 static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
 446 {
 447         kasan_check_write(dst, size);
 448         return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size);
 449 }
 450 #endif
 451
 452 #endif /* __ASM_UACCESS_H */