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 static inline void uaccess_disable_privileged(void)
 140 {
 141         mte_disable_tco();
 142
 143         if (uaccess_ttbr0_disable())
 144                 return;
 145
 146         __uaccess_enable_hw_pan();
 147 }
 148
 149 static inline void uaccess_enable_privileged(void)
 150 {
 151         mte_enable_tco();
 152
 153         if (uaccess_ttbr0_enable())
 154                 return;
 155
 156         __uaccess_disable_hw_pan();
 157 }
 158
 159 /*
 160  * Sanitize a uaccess pointer such that it cannot reach any kernel address.
 161  *
 162  * Clearing bit 55 ensures the pointer cannot address any portion of the TTBR1
 163  * address range (i.e. any kernel address), and either the pointer falls within
 164  * the TTBR0 address range or must cause a fault.
 165  */
 166 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
 167 static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
 168 {
 169         void __user *safe_ptr;
 170
 171         asm volatile(
 172         "       bic     %0, %1, %2\n"
 173         : "=r" (safe_ptr)
 174         : "r" (ptr),
 175           "i" (BIT(55))
 176         );
 177
 178         return safe_ptr;
 179 }
 180
 181 /*
 182  * The "__xxx" versions of the user access functions do not verify the address
 183  * space - it must have been done previously with a separate "access_ok()"
 184  * call.
 185  *
 186  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 187  * occurs, and leave it unchanged on success.
 188  */
 189 #define __get_mem_asm(load, reg, x, addr, err, type)                    \
 190         asm volatile(                                                   \
 191         "1:     " load "        " reg "1, [%2]\n"                       \
 192         "2:\n"                                                          \
 193         _ASM_EXTABLE_##type##ACCESS_ERR_ZERO(1b, 2b, %w0, %w1)          \
 194         : "+r" (err), "=r" (x)                                          \
 195         : "r" (addr))
 196
 197 #define __raw_get_mem(ldr, x, ptr, err, type)                                   \
 198 do {                                                                            \
 199         unsigned long __gu_val;                                                 \
 200         switch (sizeof(*(ptr))) {                                               \
 201         case 1:                                                                 \
 202                 __get_mem_asm(ldr "b", "%w", __gu_val, (ptr), (err), type);     \
 203                 break;                                                          \
 204         case 2:                                                                 \
 205                 __get_mem_asm(ldr "h", "%w", __gu_val, (ptr), (err), type);     \
 206                 break;                                                          \
 207         case 4:                                                                 \
 208                 __get_mem_asm(ldr, "%w", __gu_val, (ptr), (err), type);         \
 209                 break;                                                          \
 210         case 8:                                                                 \
 211                 __get_mem_asm(ldr, "%x",  __gu_val, (ptr), (err), type);        \
 212                 break;                                                          \
 213         default:                                                                \
 214                 BUILD_BUG();                                                    \
 215         }                                                                       \
 216         (x) = (__force __typeof__(*(ptr)))__gu_val;                             \
 217 } while (0)
 218
 219 /*
 220  * We must not call into the scheduler between uaccess_ttbr0_enable() and
 221  * uaccess_ttbr0_disable(). As `x` and `ptr` could contain blocking functions,
 222  * we must evaluate these outside of the critical section.
 223  */
 224 #define __raw_get_user(x, ptr, err)                                     \
 225 do {                                                                    \
 226         __typeof__(*(ptr)) __user *__rgu_ptr = (ptr);                   \
 227         __typeof__(x) __rgu_val;                                        \
 228         __chk_user_ptr(ptr);                                            \
 229                                                                         \
 230         uaccess_ttbr0_enable();                                         \
 231         __raw_get_mem("ldtr", __rgu_val, __rgu_ptr, err, U);            \
 232         uaccess_ttbr0_disable();                                        \
 233                                                                         \
 234         (x) = __rgu_val;                                                \
 235 } while (0)
 236
 237 #define __get_user_error(x, ptr, err)                                   \
 238 do {                                                                    \
 239         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 240         might_fault();                                                  \
 241         if (access_ok(__p, sizeof(*__p))) {                             \
 242                 __p = uaccess_mask_ptr(__p);                            \
 243                 __raw_get_user((x), __p, (err));                        \
 244         } else {                                                        \
 245                 (x) = (__force __typeof__(x))0; (err) = -EFAULT;        \
 246         }                                                               \
 247 } while (0)
 248
 249 #define __get_user(x, ptr)                                              \
 250 ({                                                                      \
 251         int __gu_err = 0;                                               \
 252         __get_user_error((x), (ptr), __gu_err);                         \
 253         __gu_err;                                                       \
 254 })
 255
 256 #define get_user        __get_user
 257
 258 /*
 259  * We must not call into the scheduler between __mte_enable_tco_async() and
 260  * __mte_disable_tco_async(). As `dst` and `src` may contain blocking
 261  * functions, we must evaluate these outside of the critical section.
 262  */
 263 #define __get_kernel_nofault(dst, src, type, err_label)                 \
 264 do {                                                                    \
 265         __typeof__(dst) __gkn_dst = (dst);                              \
 266         __typeof__(src) __gkn_src = (src);                              \
 267         int __gkn_err = 0;                                              \
 268                                                                         \
 269         __mte_enable_tco_async();                                       \
 270         __raw_get_mem("ldr", *((type *)(__gkn_dst)),                    \
 271                       (__force type *)(__gkn_src), __gkn_err, K);       \
 272         __mte_disable_tco_async();                                      \
 273                                                                         \
 274         if (unlikely(__gkn_err))                                        \
 275                 goto err_label;                                         \
 276 } while (0)
 277
 278 #define __put_mem_asm(store, reg, x, addr, err, type)                   \
 279         asm volatile(                                                   \
 280         "1:     " store "       " reg "1, [%2]\n"                       \
 281         "2:\n"                                                          \
 282         _ASM_EXTABLE_##type##ACCESS_ERR(1b, 2b, %w0)                    \
 283         : "+r" (err)                                                    \
 284         : "rZ" (x), "r" (addr))
 285
 286 #define __raw_put_mem(str, x, ptr, err, type)                                   \
 287 do {                                                                            \
 288         __typeof__(*(ptr)) __pu_val = (x);                                      \
 289         switch (sizeof(*(ptr))) {                                               \
 290         case 1:                                                                 \
 291                 __put_mem_asm(str "b", "%w", __pu_val, (ptr), (err), type);     \
 292                 break;                                                          \
 293         case 2:                                                                 \
 294                 __put_mem_asm(str "h", "%w", __pu_val, (ptr), (err), type);     \
 295                 break;                                                          \
 296         case 4:                                                                 \
 297                 __put_mem_asm(str, "%w", __pu_val, (ptr), (err), type);         \
 298                 break;                                                          \
 299         case 8:                                                                 \
 300                 __put_mem_asm(str, "%x", __pu_val, (ptr), (err), type);         \
 301                 break;                                                          \
 302         default:                                                                \
 303                 BUILD_BUG();                                                    \
 304         }                                                                       \
 305 } while (0)
 306
 307 /*
 308  * We must not call into the scheduler between uaccess_ttbr0_enable() and
 309  * uaccess_ttbr0_disable(). As `x` and `ptr` could contain blocking functions,
 310  * we must evaluate these outside of the critical section.
 311  */
 312 #define __raw_put_user(x, ptr, err)                                     \
 313 do {                                                                    \
 314         __typeof__(*(ptr)) __user *__rpu_ptr = (ptr);                   \
 315         __typeof__(*(ptr)) __rpu_val = (x);                             \
 316         __chk_user_ptr(__rpu_ptr);                                      \
 317                                                                         \
 318         uaccess_ttbr0_enable();                                         \
 319         __raw_put_mem("sttr", __rpu_val, __rpu_ptr, err, U);            \
 320         uaccess_ttbr0_disable();                                        \
 321 } while (0)
 322
 323 #define __put_user_error(x, ptr, err)                                   \
 324 do {                                                                    \
 325         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 326         might_fault();                                                  \
 327         if (access_ok(__p, sizeof(*__p))) {                             \
 328                 __p = uaccess_mask_ptr(__p);                            \
 329                 __raw_put_user((x), __p, (err));                        \
 330         } else  {                                                       \
 331                 (err) = -EFAULT;                                        \
 332         }                                                               \
 333 } while (0)
 334
 335 #define __put_user(x, ptr)                                              \
 336 ({                                                                      \
 337         int __pu_err = 0;                                               \
 338         __put_user_error((x), (ptr), __pu_err);                         \
 339         __pu_err;                                                       \
 340 })
 341
 342 #define put_user        __put_user
 343
 344 /*
 345  * We must not call into the scheduler between __mte_enable_tco_async() and
 346  * __mte_disable_tco_async(). As `dst` and `src` may contain blocking
 347  * functions, we must evaluate these outside of the critical section.
 348  */
 349 #define __put_kernel_nofault(dst, src, type, err_label)                 \
 350 do {                                                                    \
 351         __typeof__(dst) __pkn_dst = (dst);                              \
 352         __typeof__(src) __pkn_src = (src);                              \
 353         int __pkn_err = 0;                                              \
 354                                                                         \
 355         __mte_enable_tco_async();                                       \
 356         __raw_put_mem("str", *((type *)(__pkn_src)),                    \
 357                       (__force type *)(__pkn_dst), __pkn_err, K);       \
 358         __mte_disable_tco_async();                                      \
 359                                                                         \
 360         if (unlikely(__pkn_err))                                        \
 361                 goto err_label;                                         \
 362 } while(0)
 363
 364 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 365 #define raw_copy_from_user(to, from, n)                                 \
 366 ({                                                                      \
 367         unsigned long __acfu_ret;                                       \
 368         uaccess_ttbr0_enable();                                         \
 369         __acfu_ret = __arch_copy_from_user((to),                        \
 370                                       __uaccess_mask_ptr(from), (n));   \
 371         uaccess_ttbr0_disable();                                        \
 372         __acfu_ret;                                                     \
 373 })
 374
 375 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 376 #define raw_copy_to_user(to, from, n)                                   \
 377 ({                                                                      \
 378         unsigned long __actu_ret;                                       \
 379         uaccess_ttbr0_enable();                                         \
 380         __actu_ret = __arch_copy_to_user(__uaccess_mask_ptr(to),        \
 381                                     (from), (n));                       \
 382         uaccess_ttbr0_disable();                                        \
 383         __actu_ret;                                                     \
 384 })
 385
 386 #define INLINE_COPY_TO_USER
 387 #define INLINE_COPY_FROM_USER
 388
 389 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
 390 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
 391 {
 392         if (access_ok(to, n)) {
 393                 uaccess_ttbr0_enable();
 394                 n = __arch_clear_user(__uaccess_mask_ptr(to), n);
 395                 uaccess_ttbr0_disable();
 396         }
 397         return n;
 398 }
 399 #define clear_user      __clear_user
 400
 401 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 402
 403 extern __must_check long strnlen_user(const char __user *str, long n);
 404
 405 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
 406 extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n);
 407
 408 static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
 409 {
 410         kasan_check_write(dst, size);
 411         return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size);
 412 }
 413 #endif
 414
 415 #ifdef CONFIG_ARCH_HAS_SUBPAGE_FAULTS
 416
 417 /*
 418  * Return 0 on success, the number of bytes not probed otherwise.
 419  */
 420 static inline size_t probe_subpage_writeable(const char __user *uaddr,
 421                                              size_t size)
 422 {
 423         if (!system_supports_mte())
 424                 return 0;
 425         return mte_probe_user_range(uaddr, size);
 426 }
 427
 428 #endif /* CONFIG_ARCH_HAS_SUBPAGE_FAULTS */
 429
 430 #endif /* __ASM_UACCESS_H */