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 #define access_ok(addr, size)   __range_ok(addr, size)
  99 #define user_addr_max                   get_fs
 100
 101 #define _ASM_EXTABLE(from, to)                                          \
 102         "       .pushsection    __ex_table, \"a\"\n"                    \
 103         "       .align          3\n"                                    \
 104         "       .long           (" #from " - .), (" #to " - .)\n"       \
 105         "       .popsection\n"
 106
 107 /*
 108  * User access enabling/disabling.
 109  */
 110 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
 111 static inline void __uaccess_ttbr0_disable(void)
 112 {
 113         unsigned long flags, ttbr;
 114
 115         local_irq_save(flags);
 116         ttbr = read_sysreg(ttbr1_el1);
 117         ttbr &= ~TTBR_ASID_MASK;
 118         /* reserved_ttbr0 placed before swapper_pg_dir */
 119         write_sysreg(ttbr - RESERVED_TTBR0_SIZE, ttbr0_el1);
 120         isb();
 121         /* Set reserved ASID */
 122         write_sysreg(ttbr, ttbr1_el1);
 123         isb();
 124         local_irq_restore(flags);
 125 }
 126
 127 static inline void __uaccess_ttbr0_enable(void)
 128 {
 129         unsigned long flags, ttbr0, ttbr1;
 130
 131         /*
 132          * Disable interrupts to avoid preemption between reading the 'ttbr0'
 133          * variable and the MSR. A context switch could trigger an ASID
 134          * roll-over and an update of 'ttbr0'.
 135          */
 136         local_irq_save(flags);
 137         ttbr0 = READ_ONCE(current_thread_info()->ttbr0);
 138
 139         /* Restore active ASID */
 140         ttbr1 = read_sysreg(ttbr1_el1);
 141         ttbr1 &= ~TTBR_ASID_MASK;               /* safety measure */
 142         ttbr1 |= ttbr0 & TTBR_ASID_MASK;
 143         write_sysreg(ttbr1, ttbr1_el1);
 144         isb();
 145
 146         /* Restore user page table */
 147         write_sysreg(ttbr0, ttbr0_el1);
 148         isb();
 149         local_irq_restore(flags);
 150 }
 151
 152 static inline bool uaccess_ttbr0_disable(void)
 153 {
 154         if (!system_uses_ttbr0_pan())
 155                 return false;
 156         __uaccess_ttbr0_disable();
 157         return true;
 158 }
 159
 160 static inline bool uaccess_ttbr0_enable(void)
 161 {
 162         if (!system_uses_ttbr0_pan())
 163                 return false;
 164         __uaccess_ttbr0_enable();
 165         return true;
 166 }
 167 #else
 168 static inline bool uaccess_ttbr0_disable(void)
 169 {
 170         return false;
 171 }
 172
 173 static inline bool uaccess_ttbr0_enable(void)
 174 {
 175         return false;
 176 }
 177 #endif
 178
 179 static inline void __uaccess_disable_hw_pan(void)
 180 {
 181         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN,
 182                         CONFIG_ARM64_PAN));
 183 }
 184
 185 static inline void __uaccess_enable_hw_pan(void)
 186 {
 187         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,
 188                         CONFIG_ARM64_PAN));
 189 }
 190
 191 #define __uaccess_disable(alt)                                          \
 192 do {                                                                    \
 193         if (!uaccess_ttbr0_disable())                                   \
 194                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt,          \
 195                                 CONFIG_ARM64_PAN));                     \
 196 } while (0)
 197
 198 #define __uaccess_enable(alt)                                           \
 199 do {                                                                    \
 200         if (!uaccess_ttbr0_enable())                                    \
 201                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt,          \
 202                                 CONFIG_ARM64_PAN));                     \
 203 } while (0)
 204
 205 static inline void uaccess_disable(void)
 206 {
 207         __uaccess_disable(ARM64_HAS_PAN);
 208 }
 209
 210 static inline void uaccess_enable(void)
 211 {
 212         __uaccess_enable(ARM64_HAS_PAN);
 213 }
 214
 215 /*
 216  * These functions are no-ops when UAO is present.
 217  */
 218 static inline void uaccess_disable_not_uao(void)
 219 {
 220         __uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
 221 }
 222
 223 static inline void uaccess_enable_not_uao(void)
 224 {
 225         __uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
 226 }
 227
 228 /*
 229  * Sanitise a uaccess pointer such that it becomes NULL if above the
 230  * current addr_limit.
 231  */
 232 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
 233 static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
 234 {
 235         void __user *safe_ptr;
 236
 237         asm volatile(
 238         "       bics    xzr, %1, %2\n"
 239         "       csel    %0, %1, xzr, eq\n"
 240         : "=&r" (safe_ptr)
 241         : "r" (ptr), "r" (current_thread_info()->addr_limit)
 242         : "cc");
 243
 244         csdb();
 245         return safe_ptr;
 246 }
 247
 248 /*
 249  * The "__xxx" versions of the user access functions do not verify the address
 250  * space - it must have been done previously with a separate "access_ok()"
 251  * call.
 252  *
 253  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 254  * occurs, and leave it unchanged on success.
 255  */
 256 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 257         asm volatile(                                                   \
 258         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 259                         alt_instr " " reg "1, [%2]\n", feature)         \
 260         "2:\n"                                                          \
 261         "       .section .fixup, \"ax\"\n"                              \
 262         "       .align  2\n"                                            \
 263         "3:     mov     %w0, %3\n"                                      \
 264         "       mov     %1, #0\n"                                       \
 265         "       b       2b\n"                                           \
 266         "       .previous\n"                                            \
 267         _ASM_EXTABLE(1b, 3b)                                            \
 268         : "+r" (err), "=&r" (x)                                         \
 269         : "r" (addr), "i" (-EFAULT))
 270
 271 #define __get_user_err(x, ptr, err)                                     \
 272 do {                                                                    \
 273         unsigned long __gu_val;                                         \
 274         __chk_user_ptr(ptr);                                            \
 275         uaccess_enable_not_uao();                                       \
 276         switch (sizeof(*(ptr))) {                                       \
 277         case 1:                                                         \
 278                 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
 279                                (err), ARM64_HAS_UAO);                   \
 280                 break;                                                  \
 281         case 2:                                                         \
 282                 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
 283                                (err), ARM64_HAS_UAO);                   \
 284                 break;                                                  \
 285         case 4:                                                         \
 286                 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),    \
 287                                (err), ARM64_HAS_UAO);                   \
 288                 break;                                                  \
 289         case 8:                                                         \
 290                 __get_user_asm("ldr", "ldtr", "%x",  __gu_val, (ptr),   \
 291                                (err), ARM64_HAS_UAO);                   \
 292                 break;                                                  \
 293         default:                                                        \
 294                 BUILD_BUG();                                            \
 295         }                                                               \
 296         uaccess_disable_not_uao();                                      \
 297         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 298 } while (0)
 299
 300 #define __get_user_check(x, ptr, err)                                   \
 301 ({                                                                      \
 302         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 303         might_fault();                                                  \
 304         if (access_ok(__p, sizeof(*__p))) {                             \
 305                 __p = uaccess_mask_ptr(__p);                            \
 306                 __get_user_err((x), __p, (err));                        \
 307         } else {                                                        \
 308                 (x) = 0; (err) = -EFAULT;                               \
 309         }                                                               \
 310 })
 311
 312 #define __get_user_error(x, ptr, err)                                   \
 313 ({                                                                      \
 314         __get_user_check((x), (ptr), (err));                            \
 315         (void)0;                                                        \
 316 })
 317
 318 #define __get_user(x, ptr)                                              \
 319 ({                                                                      \
 320         int __gu_err = 0;                                               \
 321         __get_user_check((x), (ptr), __gu_err);                         \
 322         __gu_err;                                                       \
 323 })
 324
 325 #define get_user        __get_user
 326
 327 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 328         asm volatile(                                                   \
 329         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 330                         alt_instr " " reg "1, [%2]\n", feature)         \
 331         "2:\n"                                                          \
 332         "       .section .fixup,\"ax\"\n"                               \
 333         "       .align  2\n"                                            \
 334         "3:     mov     %w0, %3\n"                                      \
 335         "       b       2b\n"                                           \
 336         "       .previous\n"                                            \
 337         _ASM_EXTABLE(1b, 3b)                                            \
 338         : "+r" (err)                                                    \
 339         : "r" (x), "r" (addr), "i" (-EFAULT))
 340
 341 #define __put_user_err(x, ptr, err)                                     \
 342 do {                                                                    \
 343         __typeof__(*(ptr)) __pu_val = (x);                              \
 344         __chk_user_ptr(ptr);                                            \
 345         uaccess_enable_not_uao();                                       \
 346         switch (sizeof(*(ptr))) {                                       \
 347         case 1:                                                         \
 348                 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr),  \
 349                                (err), ARM64_HAS_UAO);                   \
 350                 break;                                                  \
 351         case 2:                                                         \
 352                 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr),  \
 353                                (err), ARM64_HAS_UAO);                   \
 354                 break;                                                  \
 355         case 4:                                                         \
 356                 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr),    \
 357                                (err), ARM64_HAS_UAO);                   \
 358                 break;                                                  \
 359         case 8:                                                         \
 360                 __put_user_asm("str", "sttr", "%x", __pu_val, (ptr),    \
 361                                (err), ARM64_HAS_UAO);                   \
 362                 break;                                                  \
 363         default:                                                        \
 364                 BUILD_BUG();                                            \
 365         }                                                               \
 366         uaccess_disable_not_uao();                                      \
 367 } while (0)
 368
 369 #define __put_user_check(x, ptr, err)                                   \
 370 ({                                                                      \
 371         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 372         might_fault();                                                  \
 373         if (access_ok(__p, sizeof(*__p))) {                             \
 374                 __p = uaccess_mask_ptr(__p);                            \
 375                 __put_user_err((x), __p, (err));                        \
 376         } else  {                                                       \
 377                 (err) = -EFAULT;                                        \
 378         }                                                               \
 379 })
 380
 381 #define __put_user_error(x, ptr, err)                                   \
 382 ({                                                                      \
 383         __put_user_check((x), (ptr), (err));                            \
 384         (void)0;                                                        \
 385 })
 386
 387 #define __put_user(x, ptr)                                              \
 388 ({                                                                      \
 389         int __pu_err = 0;                                               \
 390         __put_user_check((x), (ptr), __pu_err);                         \
 391         __pu_err;                                                       \
 392 })
 393
 394 #define put_user        __put_user
 395
 396 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 397 #define raw_copy_from_user(to, from, n)                                 \
 398 ({                                                                      \
 399         __arch_copy_from_user((to), __uaccess_mask_ptr(from), (n));     \
 400 })
 401
 402 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 403 #define raw_copy_to_user(to, from, n)                                   \
 404 ({                                                                      \
 405         __arch_copy_to_user(__uaccess_mask_ptr(to), (from), (n));       \
 406 })
 407
 408 extern unsigned long __must_check __arch_copy_in_user(void __user *to, const void __user *from, unsigned long n);
 409 #define raw_copy_in_user(to, from, n)                                   \
 410 ({                                                                      \
 411         __arch_copy_in_user(__uaccess_mask_ptr(to),                     \
 412                             __uaccess_mask_ptr(from), (n));             \
 413 })
 414
 415 #define INLINE_COPY_TO_USER
 416 #define INLINE_COPY_FROM_USER
 417
 418 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
 419 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
 420 {
 421         if (access_ok(to, n))
 422                 n = __arch_clear_user(__uaccess_mask_ptr(to), n);
 423         return n;
 424 }
 425 #define clear_user      __clear_user
 426
 427 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 428
 429 extern __must_check long strnlen_user(const char __user *str, long n);
 430
 431 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
 432 struct page;
 433 void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len);
 434 extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n);
 435
 436 static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
 437 {
 438         kasan_check_write(dst, size);
 439         return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size);
 440 }
 441 #endif
 442
 443 #endif /* __ASM_UACCESS_H */