arch/arm64/include/asm/uaccess.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  * Based on arch/arm/include/asm/uaccess.h
   4  *
   5  * Copyright (C) 2012 ARM Ltd.
   6  */
   7 #ifndef __ASM_UACCESS_H
   8 #define __ASM_UACCESS_H
   9
  10 #include <asm/alternative.h>
  11 #include <asm/kernel-pgtable.h>
  12 #include <asm/sysreg.h>
  13
  14 /*
  15  * User space memory access functions
  16  */
  17 #include <linux/bitops.h>
  18 #include <linux/kasan-checks.h>
  19 #include <linux/string.h>
  20
  21 #include <asm/asm-extable.h>
  22 #include <asm/cpufeature.h>
  23 #include <asm/mmu.h>
  24 #include <asm/mte.h>
  25 #include <asm/ptrace.h>
  26 #include <asm/memory.h>
  27 #include <asm/extable.h>
  28
  29 static inline int __access_ok(const void __user *ptr, unsigned long size);
  30
  31 /*
  32  * Test whether a block of memory is a valid user space address.
  33  * Returns 1 if the range is valid, 0 otherwise.
  34  *
  35  * This is equivalent to the following test:
  36  * (u65)addr + (u65)size <= (u65)TASK_SIZE_MAX
  37  */
  38 static inline int access_ok(const void __user *addr, unsigned long size)
  39 {
  40         /*
  41          * Asynchronous I/O running in a kernel thread does not have the
  42          * TIF_TAGGED_ADDR flag of the process owning the mm, so always untag
  43          * the user address before checking.
  44          */
  45         if (IS_ENABLED(CONFIG_ARM64_TAGGED_ADDR_ABI) &&
  46             (current->flags & PF_KTHREAD || test_thread_flag(TIF_TAGGED_ADDR)))
  47                 addr = untagged_addr(addr);
  48
  49         return likely(__access_ok(addr, size));
  50 }
  51 #define access_ok access_ok
  52
  53 #include <asm-generic/access_ok.h>
  54
  55 /*
  56  * User access enabling/disabling.
  57  */
  58 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
  59 static inline void __uaccess_ttbr0_disable(void)
  60 {
  61         unsigned long flags, ttbr;
  62
  63         local_irq_save(flags);
  64         ttbr = read_sysreg(ttbr1_el1);
  65         ttbr &= ~TTBR_ASID_MASK;
  66         /* reserved_pg_dir placed before swapper_pg_dir */
  67         write_sysreg(ttbr - RESERVED_SWAPPER_OFFSET, ttbr0_el1);
  68         isb();
  69         /* Set reserved ASID */
  70         write_sysreg(ttbr, ttbr1_el1);
  71         isb();
  72         local_irq_restore(flags);
  73 }
  74
  75 static inline void __uaccess_ttbr0_enable(void)
  76 {
  77         unsigned long flags, ttbr0, ttbr1;
  78
  79         /*
  80          * Disable interrupts to avoid preemption between reading the 'ttbr0'
  81          * variable and the MSR. A context switch could trigger an ASID
  82          * roll-over and an update of 'ttbr0'.
  83          */
  84         local_irq_save(flags);
  85         ttbr0 = READ_ONCE(current_thread_info()->ttbr0);
  86
  87         /* Restore active ASID */
  88         ttbr1 = read_sysreg(ttbr1_el1);
  89         ttbr1 &= ~TTBR_ASID_MASK;               /* safety measure */
  90         ttbr1 |= ttbr0 & TTBR_ASID_MASK;
  91         write_sysreg(ttbr1, ttbr1_el1);
  92         isb();
  93
  94         /* Restore user page table */
  95         write_sysreg(ttbr0, ttbr0_el1);
  96         isb();
  97         local_irq_restore(flags);
  98 }
  99
 100 static inline bool uaccess_ttbr0_disable(void)
 101 {
 102         if (!system_uses_ttbr0_pan())
 103                 return false;
 104         __uaccess_ttbr0_disable();
 105         return true;
 106 }
 107
 108 static inline bool uaccess_ttbr0_enable(void)
 109 {
 110         if (!system_uses_ttbr0_pan())
 111                 return false;
 112         __uaccess_ttbr0_enable();
 113         return true;
 114 }
 115 #else
 116 static inline bool uaccess_ttbr0_disable(void)
 117 {
 118         return false;
 119 }
 120
 121 static inline bool uaccess_ttbr0_enable(void)
 122 {
 123         return false;
 124 }
 125 #endif
 126
 127 static inline void __uaccess_disable_hw_pan(void)
 128 {
 129         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN,
 130                         CONFIG_ARM64_PAN));
 131 }
 132
 133 static inline void __uaccess_enable_hw_pan(void)
 134 {
 135         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,
 136                         CONFIG_ARM64_PAN));
 137 }
 138
 139 /*
 140  * The Tag Check Flag (TCF) mode for MTE is per EL, hence TCF0
 141  * affects EL0 and TCF affects EL1 irrespective of which TTBR is
 142  * used.
 143  * The kernel accesses TTBR0 usually with LDTR/STTR instructions
 144  * when UAO is available, so these would act as EL0 accesses using
 145  * TCF0.
 146  * However futex.h code uses exclusives which would be executed as
 147  * EL1, this can potentially cause a tag check fault even if the
 148  * user disables TCF0.
 149  *
 150  * To address the problem we set the PSTATE.TCO bit in uaccess_enable()
 151  * and reset it in uaccess_disable().
 152  *
 153  * The Tag check override (TCO) bit disables temporarily the tag checking
 154  * preventing the issue.
 155  */
 156 static inline void __uaccess_disable_tco(void)
 157 {
 158         asm volatile(ALTERNATIVE("nop", SET_PSTATE_TCO(0),
 159                                  ARM64_MTE, CONFIG_KASAN_HW_TAGS));
 160 }
 161
 162 static inline void __uaccess_enable_tco(void)
 163 {
 164         asm volatile(ALTERNATIVE("nop", SET_PSTATE_TCO(1),
 165                                  ARM64_MTE, CONFIG_KASAN_HW_TAGS));
 166 }
 167
 168 /*
 169  * These functions disable tag checking only if in MTE async mode
 170  * since the sync mode generates exceptions synchronously and the
 171  * nofault or load_unaligned_zeropad can handle them.
 172  */
 173 static inline void __uaccess_disable_tco_async(void)
 174 {
 175         if (system_uses_mte_async_or_asymm_mode())
 176                  __uaccess_disable_tco();
 177 }
 178
 179 static inline void __uaccess_enable_tco_async(void)
 180 {
 181         if (system_uses_mte_async_or_asymm_mode())
 182                 __uaccess_enable_tco();
 183 }
 184
 185 static inline void uaccess_disable_privileged(void)
 186 {
 187         __uaccess_disable_tco();
 188
 189         if (uaccess_ttbr0_disable())
 190                 return;
 191
 192         __uaccess_enable_hw_pan();
 193 }
 194
 195 static inline void uaccess_enable_privileged(void)
 196 {
 197         __uaccess_enable_tco();
 198
 199         if (uaccess_ttbr0_enable())
 200                 return;
 201
 202         __uaccess_disable_hw_pan();
 203 }
 204
 205 /*
 206  * Sanitise a uaccess pointer such that it becomes NULL if above the maximum
 207  * user address. In case the pointer is tagged (has the top byte set), untag
 208  * the pointer before checking.
 209  */
 210 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
 211 static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
 212 {
 213         void __user *safe_ptr;
 214
 215         asm volatile(
 216         "       bics    xzr, %3, %2\n"
 217         "       csel    %0, %1, xzr, eq\n"
 218         : "=&r" (safe_ptr)
 219         : "r" (ptr), "r" (TASK_SIZE_MAX - 1),
 220           "r" (untagged_addr(ptr))
 221         : "cc");
 222
 223         csdb();
 224         return safe_ptr;
 225 }
 226
 227 /*
 228  * The "__xxx" versions of the user access functions do not verify the address
 229  * space - it must have been done previously with a separate "access_ok()"
 230  * call.
 231  *
 232  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 233  * occurs, and leave it unchanged on success.
 234  */
 235 #define __get_mem_asm(load, reg, x, addr, err, type)                    \
 236         asm volatile(                                                   \
 237         "1:     " load "        " reg "1, [%2]\n"                       \
 238         "2:\n"                                                          \
 239         _ASM_EXTABLE_##type##ACCESS_ERR_ZERO(1b, 2b, %w0, %w1)          \
 240         : "+r" (err), "=&r" (x)                                         \
 241         : "r" (addr))
 242
 243 #define __raw_get_mem(ldr, x, ptr, err, type)                                   \
 244 do {                                                                            \
 245         unsigned long __gu_val;                                                 \
 246         switch (sizeof(*(ptr))) {                                               \
 247         case 1:                                                                 \
 248                 __get_mem_asm(ldr "b", "%w", __gu_val, (ptr), (err), type);     \
 249                 break;                                                          \
 250         case 2:                                                                 \
 251                 __get_mem_asm(ldr "h", "%w", __gu_val, (ptr), (err), type);     \
 252                 break;                                                          \
 253         case 4:                                                                 \
 254                 __get_mem_asm(ldr, "%w", __gu_val, (ptr), (err), type);         \
 255                 break;                                                          \
 256         case 8:                                                                 \
 257                 __get_mem_asm(ldr, "%x",  __gu_val, (ptr), (err), type);        \
 258                 break;                                                          \
 259         default:                                                                \
 260                 BUILD_BUG();                                                    \
 261         }                                                                       \
 262         (x) = (__force __typeof__(*(ptr)))__gu_val;                             \
 263 } while (0)
 264
 265 /*
 266  * We must not call into the scheduler between uaccess_ttbr0_enable() and
 267  * uaccess_ttbr0_disable(). As `x` and `ptr` could contain blocking functions,
 268  * we must evaluate these outside of the critical section.
 269  */
 270 #define __raw_get_user(x, ptr, err)                                     \
 271 do {                                                                    \
 272         __typeof__(*(ptr)) __user *__rgu_ptr = (ptr);                   \
 273         __typeof__(x) __rgu_val;                                        \
 274         __chk_user_ptr(ptr);                                            \
 275                                                                         \
 276         uaccess_ttbr0_enable();                                         \
 277         __raw_get_mem("ldtr", __rgu_val, __rgu_ptr, err, U);            \
 278         uaccess_ttbr0_disable();                                        \
 279                                                                         \
 280         (x) = __rgu_val;                                                \
 281 } while (0)
 282
 283 #define __get_user_error(x, ptr, err)                                   \
 284 do {                                                                    \
 285         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 286         might_fault();                                                  \
 287         if (access_ok(__p, sizeof(*__p))) {                             \
 288                 __p = uaccess_mask_ptr(__p);                            \
 289                 __raw_get_user((x), __p, (err));                        \
 290         } else {                                                        \
 291                 (x) = (__force __typeof__(x))0; (err) = -EFAULT;        \
 292         }                                                               \
 293 } while (0)
 294
 295 #define __get_user(x, ptr)                                              \
 296 ({                                                                      \
 297         int __gu_err = 0;                                               \
 298         __get_user_error((x), (ptr), __gu_err);                         \
 299         __gu_err;                                                       \
 300 })
 301
 302 #define get_user        __get_user
 303
 304 /*
 305  * We must not call into the scheduler between __uaccess_enable_tco_async() and
 306  * __uaccess_disable_tco_async(). As `dst` and `src` may contain blocking
 307  * functions, we must evaluate these outside of the critical section.
 308  */
 309 #define __get_kernel_nofault(dst, src, type, err_label)                 \
 310 do {                                                                    \
 311         __typeof__(dst) __gkn_dst = (dst);                              \
 312         __typeof__(src) __gkn_src = (src);                              \
 313         int __gkn_err = 0;                                              \
 314                                                                         \
 315         __uaccess_enable_tco_async();                                   \
 316         __raw_get_mem("ldr", *((type *)(__gkn_dst)),                    \
 317                       (__force type *)(__gkn_src), __gkn_err, K);       \
 318         __uaccess_disable_tco_async();                                  \
 319                                                                         \
 320         if (unlikely(__gkn_err))                                        \
 321                 goto err_label;                                         \
 322 } while (0)
 323
 324 #define __put_mem_asm(store, reg, x, addr, err, type)                   \
 325         asm volatile(                                                   \
 326         "1:     " store "       " reg "1, [%2]\n"                       \
 327         "2:\n"                                                          \
 328         _ASM_EXTABLE_##type##ACCESS_ERR(1b, 2b, %w0)                    \
 329         : "+r" (err)                                                    \
 330         : "r" (x), "r" (addr))
 331
 332 #define __raw_put_mem(str, x, ptr, err, type)                                   \
 333 do {                                                                            \
 334         __typeof__(*(ptr)) __pu_val = (x);                                      \
 335         switch (sizeof(*(ptr))) {                                               \
 336         case 1:                                                                 \
 337                 __put_mem_asm(str "b", "%w", __pu_val, (ptr), (err), type);     \
 338                 break;                                                          \
 339         case 2:                                                                 \
 340                 __put_mem_asm(str "h", "%w", __pu_val, (ptr), (err), type);     \
 341                 break;                                                          \
 342         case 4:                                                                 \
 343                 __put_mem_asm(str, "%w", __pu_val, (ptr), (err), type);         \
 344                 break;                                                          \
 345         case 8:                                                                 \
 346                 __put_mem_asm(str, "%x", __pu_val, (ptr), (err), type);         \
 347                 break;                                                          \
 348         default:                                                                \
 349                 BUILD_BUG();                                                    \
 350         }                                                                       \
 351 } while (0)
 352
 353 /*
 354  * We must not call into the scheduler between uaccess_ttbr0_enable() and
 355  * uaccess_ttbr0_disable(). As `x` and `ptr` could contain blocking functions,
 356  * we must evaluate these outside of the critical section.
 357  */
 358 #define __raw_put_user(x, ptr, err)                                     \
 359 do {                                                                    \
 360         __typeof__(*(ptr)) __user *__rpu_ptr = (ptr);                   \
 361         __typeof__(*(ptr)) __rpu_val = (x);                             \
 362         __chk_user_ptr(__rpu_ptr);                                      \
 363                                                                         \
 364         uaccess_ttbr0_enable();                                         \
 365         __raw_put_mem("sttr", __rpu_val, __rpu_ptr, err, U);            \
 366         uaccess_ttbr0_disable();                                        \
 367 } while (0)
 368
 369 #define __put_user_error(x, ptr, err)                                   \
 370 do {                                                                    \
 371         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 372         might_fault();                                                  \
 373         if (access_ok(__p, sizeof(*__p))) {                             \
 374                 __p = uaccess_mask_ptr(__p);                            \
 375                 __raw_put_user((x), __p, (err));                        \
 376         } else  {                                                       \
 377                 (err) = -EFAULT;                                        \
 378         }                                                               \
 379 } while (0)
 380
 381 #define __put_user(x, ptr)                                              \
 382 ({                                                                      \
 383         int __pu_err = 0;                                               \
 384         __put_user_error((x), (ptr), __pu_err);                         \
 385         __pu_err;                                                       \
 386 })
 387
 388 #define put_user        __put_user
 389
 390 /*
 391  * We must not call into the scheduler between __uaccess_enable_tco_async() and
 392  * __uaccess_disable_tco_async(). As `dst` and `src` may contain blocking
 393  * functions, we must evaluate these outside of the critical section.
 394  */
 395 #define __put_kernel_nofault(dst, src, type, err_label)                 \
 396 do {                                                                    \
 397         __typeof__(dst) __pkn_dst = (dst);                              \
 398         __typeof__(src) __pkn_src = (src);                              \
 399         int __pkn_err = 0;                                              \
 400                                                                         \
 401         __uaccess_enable_tco_async();                                   \
 402         __raw_put_mem("str", *((type *)(__pkn_src)),                    \
 403                       (__force type *)(__pkn_dst), __pkn_err, K);       \
 404         __uaccess_disable_tco_async();                                  \
 405                                                                         \
 406         if (unlikely(__pkn_err))                                        \
 407                 goto err_label;                                         \
 408 } while(0)
 409
 410 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 411 #define raw_copy_from_user(to, from, n)                                 \
 412 ({                                                                      \
 413         unsigned long __acfu_ret;                                       \
 414         uaccess_ttbr0_enable();                                         \
 415         __acfu_ret = __arch_copy_from_user((to),                        \
 416                                       __uaccess_mask_ptr(from), (n));   \
 417         uaccess_ttbr0_disable();                                        \
 418         __acfu_ret;                                                     \
 419 })
 420
 421 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 422 #define raw_copy_to_user(to, from, n)                                   \
 423 ({                                                                      \
 424         unsigned long __actu_ret;                                       \
 425         uaccess_ttbr0_enable();                                         \
 426         __actu_ret = __arch_copy_to_user(__uaccess_mask_ptr(to),        \
 427                                     (from), (n));                       \
 428         uaccess_ttbr0_disable();                                        \
 429         __actu_ret;                                                     \
 430 })
 431
 432 #define INLINE_COPY_TO_USER
 433 #define INLINE_COPY_FROM_USER
 434
 435 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
 436 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
 437 {
 438         if (access_ok(to, n)) {
 439                 uaccess_ttbr0_enable();
 440                 n = __arch_clear_user(__uaccess_mask_ptr(to), n);
 441                 uaccess_ttbr0_disable();
 442         }
 443         return n;
 444 }
 445 #define clear_user      __clear_user
 446
 447 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 448
 449 extern __must_check long strnlen_user(const char __user *str, long n);
 450
 451 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
 452 struct page;
 453 void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len);
 454 extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n);
 455
 456 static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
 457 {
 458         kasan_check_write(dst, size);
 459         return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size);
 460 }
 461 #endif
 462
 463 #ifdef CONFIG_ARCH_HAS_SUBPAGE_FAULTS
 464
 465 /*
 466  * Return 0 on success, the number of bytes not probed otherwise.
 467  */
 468 static inline size_t probe_subpage_writeable(const char __user *uaddr,
 469                                              size_t size)
 470 {
 471         if (!system_supports_mte())
 472                 return 0;
 473         return mte_probe_user_range(uaddr, size);
 474 }
 475
 476 #endif /* CONFIG_ARCH_HAS_SUBPAGE_FAULTS */
 477
 478 #endif /* __ASM_UACCESS_H */