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/extable.h>
  36
  37 #define get_ds()        (KERNEL_DS)
  38 #define get_fs()        (current_thread_info()->addr_limit)
  39
  40 static inline void set_fs(mm_segment_t fs)
  41 {
  42         current_thread_info()->addr_limit = fs;
  43
  44         /*
  45          * Prevent a mispredicted conditional call to set_fs from forwarding
  46          * the wrong address limit to access_ok under speculation.
  47          */
  48         spec_bar();
  49
  50         /* On user-mode return, check fs is correct */
  51         set_thread_flag(TIF_FSCHECK);
  52
  53         /*
  54          * Enable/disable UAO so that copy_to_user() etc can access
  55          * kernel memory with the unprivileged instructions.
  56          */
  57         if (IS_ENABLED(CONFIG_ARM64_UAO) && fs == KERNEL_DS)
  58                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
  59         else
  60                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
  61                                 CONFIG_ARM64_UAO));
  62 }
  63
  64 #define segment_eq(a, b)        ((a) == (b))
  65
  66 /*
  67  * Test whether a block of memory is a valid user space address.
  68  * Returns 1 if the range is valid, 0 otherwise.
  69  *
  70  * This is equivalent to the following test:
  71  * (u65)addr + (u65)size <= (u65)current->addr_limit + 1
  72  */
  73 static inline unsigned long __range_ok(const void __user *addr, unsigned long size)
  74 {
  75         unsigned long ret, limit = current_thread_info()->addr_limit;
  76
  77         __chk_user_ptr(addr);
  78         asm volatile(
  79         // A + B <= C + 1 for all A,B,C, in four easy steps:
  80         // 1: X = A + B; X' = X % 2^64
  81         "       adds    %0, %3, %2\n"
  82         // 2: Set C = 0 if X > 2^64, to guarantee X' > C in step 4
  83         "       csel    %1, xzr, %1, hi\n"
  84         // 3: Set X' = ~0 if X >= 2^64. For X == 2^64, this decrements X'
  85         //    to compensate for the carry flag being set in step 4. For
  86         //    X > 2^64, X' merely has to remain nonzero, which it does.
  87         "       csinv   %0, %0, xzr, cc\n"
  88         // 4: For X < 2^64, this gives us X' - C - 1 <= 0, where the -1
  89         //    comes from the carry in being clear. Otherwise, we are
  90         //    testing X' - C == 0, subject to the previous adjustments.
  91         "       sbcs    xzr, %0, %1\n"
  92         "       cset    %0, ls\n"
  93         : "=&r" (ret), "+r" (limit) : "Ir" (size), "0" (addr) : "cc");
  94
  95         return ret;
  96 }
  97
  98 /*
  99  * When dealing with data aborts, watchpoints, or instruction traps we may end
 100  * up with a tagged userland pointer. Clear the tag to get a sane pointer to
 101  * pass on to access_ok(), for instance.
 102  */
 103 #define untagged_addr(addr)             sign_extend64(addr, 55)
 104
 105 #define access_ok(type, addr, size)     __range_ok(addr, size)
 106 #define user_addr_max                   get_fs
 107
 108 #define _ASM_EXTABLE(from, to)                                          \
 109         "       .pushsection    __ex_table, \"a\"\n"                    \
 110         "       .align          3\n"                                    \
 111         "       .long           (" #from " - .), (" #to " - .)\n"       \
 112         "       .popsection\n"
 113
 114 /*
 115  * User access enabling/disabling.
 116  */
 117 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
 118 static inline void __uaccess_ttbr0_disable(void)
 119 {
 120         unsigned long flags, ttbr;
 121
 122         local_irq_save(flags);
 123         ttbr = read_sysreg(ttbr1_el1);
 124         ttbr &= ~TTBR_ASID_MASK;
 125         /* reserved_ttbr0 placed before swapper_pg_dir */
 126         write_sysreg(ttbr - RESERVED_TTBR0_SIZE, ttbr0_el1);
 127         isb();
 128         /* Set reserved ASID */
 129         write_sysreg(ttbr, ttbr1_el1);
 130         isb();
 131         local_irq_restore(flags);
 132 }
 133
 134 static inline void __uaccess_ttbr0_enable(void)
 135 {
 136         unsigned long flags, ttbr0, ttbr1;
 137
 138         /*
 139          * Disable interrupts to avoid preemption between reading the 'ttbr0'
 140          * variable and the MSR. A context switch could trigger an ASID
 141          * roll-over and an update of 'ttbr0'.
 142          */
 143         local_irq_save(flags);
 144         ttbr0 = READ_ONCE(current_thread_info()->ttbr0);
 145
 146         /* Restore active ASID */
 147         ttbr1 = read_sysreg(ttbr1_el1);
 148         ttbr1 &= ~TTBR_ASID_MASK;               /* safety measure */
 149         ttbr1 |= ttbr0 & TTBR_ASID_MASK;
 150         write_sysreg(ttbr1, ttbr1_el1);
 151         isb();
 152
 153         /* Restore user page table */
 154         write_sysreg(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 static inline void __uaccess_disable_hw_pan(void)
 187 {
 188         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN,
 189                         CONFIG_ARM64_PAN));
 190 }
 191
 192 static inline void __uaccess_enable_hw_pan(void)
 193 {
 194         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,
 195                         CONFIG_ARM64_PAN));
 196 }
 197
 198 #define __uaccess_disable(alt)                                          \
 199 do {                                                                    \
 200         if (!uaccess_ttbr0_disable())                                   \
 201                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt,          \
 202                                 CONFIG_ARM64_PAN));                     \
 203 } while (0)
 204
 205 #define __uaccess_enable(alt)                                           \
 206 do {                                                                    \
 207         if (!uaccess_ttbr0_enable())                                    \
 208                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt,          \
 209                                 CONFIG_ARM64_PAN));                     \
 210 } while (0)
 211
 212 static inline void uaccess_disable(void)
 213 {
 214         __uaccess_disable(ARM64_HAS_PAN);
 215 }
 216
 217 static inline void uaccess_enable(void)
 218 {
 219         __uaccess_enable(ARM64_HAS_PAN);
 220 }
 221
 222 /*
 223  * These functions are no-ops when UAO is present.
 224  */
 225 static inline void uaccess_disable_not_uao(void)
 226 {
 227         __uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
 228 }
 229
 230 static inline void uaccess_enable_not_uao(void)
 231 {
 232         __uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
 233 }
 234
 235 /*
 236  * Sanitise a uaccess pointer such that it becomes NULL if above the
 237  * current addr_limit.
 238  */
 239 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
 240 static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
 241 {
 242         void __user *safe_ptr;
 243
 244         asm volatile(
 245         "       bics    xzr, %1, %2\n"
 246         "       csel    %0, %1, xzr, eq\n"
 247         : "=&r" (safe_ptr)
 248         : "r" (ptr), "r" (current_thread_info()->addr_limit)
 249         : "cc");
 250
 251         csdb();
 252         return safe_ptr;
 253 }
 254
 255 /*
 256  * The "__xxx" versions of the user access functions do not verify the address
 257  * space - it must have been done previously with a separate "access_ok()"
 258  * call.
 259  *
 260  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 261  * occurs, and leave it unchanged on success.
 262  */
 263 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 264         asm volatile(                                                   \
 265         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 266                         alt_instr " " reg "1, [%2]\n", feature)         \
 267         "2:\n"                                                          \
 268         "       .section .fixup, \"ax\"\n"                              \
 269         "       .align  2\n"                                            \
 270         "3:     mov     %w0, %3\n"                                      \
 271         "       mov     %1, #0\n"                                       \
 272         "       b       2b\n"                                           \
 273         "       .previous\n"                                            \
 274         _ASM_EXTABLE(1b, 3b)                                            \
 275         : "+r" (err), "=&r" (x)                                         \
 276         : "r" (addr), "i" (-EFAULT))
 277
 278 #define __get_user_err(x, ptr, err)                                     \
 279 do {                                                                    \
 280         unsigned long __gu_val;                                         \
 281         __chk_user_ptr(ptr);                                            \
 282         uaccess_enable_not_uao();                                       \
 283         switch (sizeof(*(ptr))) {                                       \
 284         case 1:                                                         \
 285                 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
 286                                (err), ARM64_HAS_UAO);                   \
 287                 break;                                                  \
 288         case 2:                                                         \
 289                 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
 290                                (err), ARM64_HAS_UAO);                   \
 291                 break;                                                  \
 292         case 4:                                                         \
 293                 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),    \
 294                                (err), ARM64_HAS_UAO);                   \
 295                 break;                                                  \
 296         case 8:                                                         \
 297                 __get_user_asm("ldr", "ldtr", "%x",  __gu_val, (ptr),   \
 298                                (err), ARM64_HAS_UAO);                   \
 299                 break;                                                  \
 300         default:                                                        \
 301                 BUILD_BUG();                                            \
 302         }                                                               \
 303         uaccess_disable_not_uao();                                      \
 304         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 305 } while (0)
 306
 307 #define __get_user_check(x, ptr, err)                                   \
 308 ({                                                                      \
 309         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 310         might_fault();                                                  \
 311         if (access_ok(VERIFY_READ, __p, sizeof(*__p))) {                \
 312                 __p = uaccess_mask_ptr(__p);                            \
 313                 __get_user_err((x), __p, (err));                        \
 314         } else {                                                        \
 315                 (x) = 0; (err) = -EFAULT;                               \
 316         }                                                               \
 317 })
 318
 319 #define __get_user_error(x, ptr, err)                                   \
 320 ({                                                                      \
 321         __get_user_check((x), (ptr), (err));                            \
 322         (void)0;                                                        \
 323 })
 324
 325 #define __get_user(x, ptr)                                              \
 326 ({                                                                      \
 327         int __gu_err = 0;                                               \
 328         __get_user_check((x), (ptr), __gu_err);                         \
 329         __gu_err;                                                       \
 330 })
 331
 332 #define get_user        __get_user
 333
 334 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 335         asm volatile(                                                   \
 336         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 337                         alt_instr " " reg "1, [%2]\n", feature)         \
 338         "2:\n"                                                          \
 339         "       .section .fixup,\"ax\"\n"                               \
 340         "       .align  2\n"                                            \
 341         "3:     mov     %w0, %3\n"                                      \
 342         "       b       2b\n"                                           \
 343         "       .previous\n"                                            \
 344         _ASM_EXTABLE(1b, 3b)                                            \
 345         : "+r" (err)                                                    \
 346         : "r" (x), "r" (addr), "i" (-EFAULT))
 347
 348 #define __put_user_err(x, ptr, err)                                     \
 349 do {                                                                    \
 350         __typeof__(*(ptr)) __pu_val = (x);                              \
 351         __chk_user_ptr(ptr);                                            \
 352         uaccess_enable_not_uao();                                       \
 353         switch (sizeof(*(ptr))) {                                       \
 354         case 1:                                                         \
 355                 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr),  \
 356                                (err), ARM64_HAS_UAO);                   \
 357                 break;                                                  \
 358         case 2:                                                         \
 359                 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr),  \
 360                                (err), ARM64_HAS_UAO);                   \
 361                 break;                                                  \
 362         case 4:                                                         \
 363                 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr),    \
 364                                (err), ARM64_HAS_UAO);                   \
 365                 break;                                                  \
 366         case 8:                                                         \
 367                 __put_user_asm("str", "sttr", "%x", __pu_val, (ptr),    \
 368                                (err), ARM64_HAS_UAO);                   \
 369                 break;                                                  \
 370         default:                                                        \
 371                 BUILD_BUG();                                            \
 372         }                                                               \
 373         uaccess_disable_not_uao();                                      \
 374 } while (0)
 375
 376 #define __put_user_check(x, ptr, err)                                   \
 377 ({                                                                      \
 378         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 379         might_fault();                                                  \
 380         if (access_ok(VERIFY_WRITE, __p, sizeof(*__p))) {               \
 381                 __p = uaccess_mask_ptr(__p);                            \
 382                 __put_user_err((x), __p, (err));                        \
 383         } else  {                                                       \
 384                 (err) = -EFAULT;                                        \
 385         }                                                               \
 386 })
 387
 388 #define __put_user_error(x, ptr, err)                                   \
 389 ({                                                                      \
 390         __put_user_check((x), (ptr), (err));                            \
 391         (void)0;                                                        \
 392 })
 393
 394 #define __put_user(x, ptr)                                              \
 395 ({                                                                      \
 396         int __pu_err = 0;                                               \
 397         __put_user_check((x), (ptr), __pu_err);                         \
 398         __pu_err;                                                       \
 399 })
 400
 401 #define put_user        __put_user
 402
 403 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 404 #define raw_copy_from_user(to, from, n)                                 \
 405 ({                                                                      \
 406         __arch_copy_from_user((to), __uaccess_mask_ptr(from), (n));     \
 407 })
 408
 409 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 410 #define raw_copy_to_user(to, from, n)                                   \
 411 ({                                                                      \
 412         __arch_copy_to_user(__uaccess_mask_ptr(to), (from), (n));       \
 413 })
 414
 415 extern unsigned long __must_check __arch_copy_in_user(void __user *to, const void __user *from, unsigned long n);
 416 #define raw_copy_in_user(to, from, n)                                   \
 417 ({                                                                      \
 418         __arch_copy_in_user(__uaccess_mask_ptr(to),                     \
 419                             __uaccess_mask_ptr(from), (n));             \
 420 })
 421
 422 #define INLINE_COPY_TO_USER
 423 #define INLINE_COPY_FROM_USER
 424
 425 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
 426 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
 427 {
 428         if (access_ok(VERIFY_WRITE, to, n))
 429                 n = __arch_clear_user(__uaccess_mask_ptr(to), n);
 430         return n;
 431 }
 432 #define clear_user      __clear_user
 433
 434 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 435
 436 extern __must_check long strnlen_user(const char __user *str, long n);
 437
 438 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
 439 struct page;
 440 void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len);
 441 extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n);
 442
 443 static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
 444 {
 445         kasan_check_write(dst, size);
 446         return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size);
 447 }
 448 #endif
 449
 450 #endif /* __ASM_UACCESS_H */