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         /* Set reserved ASID */
  69         write_sysreg(ttbr, ttbr1_el1);
  70         isb();
  71         local_irq_restore(flags);
  72 }
  73
  74 static inline void __uaccess_ttbr0_enable(void)
  75 {
  76         unsigned long flags, ttbr0, ttbr1;
  77
  78         /*
  79          * Disable interrupts to avoid preemption between reading the 'ttbr0'
  80          * variable and the MSR. A context switch could trigger an ASID
  81          * roll-over and an update of 'ttbr0'.
  82          */
  83         local_irq_save(flags);
  84         ttbr0 = READ_ONCE(current_thread_info()->ttbr0);
  85
  86         /* Restore active ASID */
  87         ttbr1 = read_sysreg(ttbr1_el1);
  88         ttbr1 &= ~TTBR_ASID_MASK;               /* safety measure */
  89         ttbr1 |= ttbr0 & TTBR_ASID_MASK;
  90         write_sysreg(ttbr1, ttbr1_el1);
  91
  92         /* Restore user page table */
  93         write_sysreg(ttbr0, ttbr0_el1);
  94         isb();
  95         local_irq_restore(flags);
  96 }
  97
  98 static inline bool uaccess_ttbr0_disable(void)
  99 {
 100         if (!system_uses_ttbr0_pan())
 101                 return false;
 102         __uaccess_ttbr0_disable();
 103         return true;
 104 }
 105
 106 static inline bool uaccess_ttbr0_enable(void)
 107 {
 108         if (!system_uses_ttbr0_pan())
 109                 return false;
 110         __uaccess_ttbr0_enable();
 111         return true;
 112 }
 113 #else
 114 static inline bool uaccess_ttbr0_disable(void)
 115 {
 116         return false;
 117 }
 118
 119 static inline bool uaccess_ttbr0_enable(void)
 120 {
 121         return false;
 122 }
 123 #endif
 124
 125 static inline void __uaccess_disable_hw_pan(void)
 126 {
 127         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN,
 128                         CONFIG_ARM64_PAN));
 129 }
 130
 131 static inline void __uaccess_enable_hw_pan(void)
 132 {
 133         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,
 134                         CONFIG_ARM64_PAN));
 135 }
 136
 137 static inline void uaccess_disable_privileged(void)
 138 {
 139         mte_disable_tco();
 140
 141         if (uaccess_ttbr0_disable())
 142                 return;
 143
 144         __uaccess_enable_hw_pan();
 145 }
 146
 147 static inline void uaccess_enable_privileged(void)
 148 {
 149         mte_enable_tco();
 150
 151         if (uaccess_ttbr0_enable())
 152                 return;
 153
 154         __uaccess_disable_hw_pan();
 155 }
 156
 157 /*
 158  * Sanitize a uaccess pointer such that it cannot reach any kernel address.
 159  *
 160  * Clearing bit 55 ensures the pointer cannot address any portion of the TTBR1
 161  * address range (i.e. any kernel address), and either the pointer falls within
 162  * the TTBR0 address range or must cause a fault.
 163  */
 164 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
 165 static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
 166 {
 167         void __user *safe_ptr;
 168
 169         asm volatile(
 170         "       bic     %0, %1, %2\n"
 171         : "=r" (safe_ptr)
 172         : "r" (ptr),
 173           "i" (BIT(55))
 174         );
 175
 176         return safe_ptr;
 177 }
 178
 179 /*
 180  * The "__xxx" versions of the user access functions do not verify the address
 181  * space - it must have been done previously with a separate "access_ok()"
 182  * call.
 183  *
 184  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 185  * occurs, and leave it unchanged on success.
 186  */
 187 #define __get_mem_asm(load, reg, x, addr, err, type)                    \
 188         asm volatile(                                                   \
 189         "1:     " load "        " reg "1, [%2]\n"                       \
 190         "2:\n"                                                          \
 191         _ASM_EXTABLE_##type##ACCESS_ERR_ZERO(1b, 2b, %w0, %w1)          \
 192         : "+r" (err), "=r" (x)                                          \
 193         : "r" (addr))
 194
 195 #define __raw_get_mem(ldr, x, ptr, err, type)                                   \
 196 do {                                                                            \
 197         unsigned long __gu_val;                                                 \
 198         switch (sizeof(*(ptr))) {                                               \
 199         case 1:                                                                 \
 200                 __get_mem_asm(ldr "b", "%w", __gu_val, (ptr), (err), type);     \
 201                 break;                                                          \
 202         case 2:                                                                 \
 203                 __get_mem_asm(ldr "h", "%w", __gu_val, (ptr), (err), type);     \
 204                 break;                                                          \
 205         case 4:                                                                 \
 206                 __get_mem_asm(ldr, "%w", __gu_val, (ptr), (err), type);         \
 207                 break;                                                          \
 208         case 8:                                                                 \
 209                 __get_mem_asm(ldr, "%x",  __gu_val, (ptr), (err), type);        \
 210                 break;                                                          \
 211         default:                                                                \
 212                 BUILD_BUG();                                                    \
 213         }                                                                       \
 214         (x) = (__force __typeof__(*(ptr)))__gu_val;                             \
 215 } while (0)
 216
 217 /*
 218  * We must not call into the scheduler between uaccess_ttbr0_enable() and
 219  * uaccess_ttbr0_disable(). As `x` and `ptr` could contain blocking functions,
 220  * we must evaluate these outside of the critical section.
 221  */
 222 #define __raw_get_user(x, ptr, err)                                     \
 223 do {                                                                    \
 224         __typeof__(*(ptr)) __user *__rgu_ptr = (ptr);                   \
 225         __typeof__(x) __rgu_val;                                        \
 226         __chk_user_ptr(ptr);                                            \
 227                                                                         \
 228         uaccess_ttbr0_enable();                                         \
 229         __raw_get_mem("ldtr", __rgu_val, __rgu_ptr, err, U);            \
 230         uaccess_ttbr0_disable();                                        \
 231                                                                         \
 232         (x) = __rgu_val;                                                \
 233 } while (0)
 234
 235 #define __get_user_error(x, ptr, err)                                   \
 236 do {                                                                    \
 237         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 238         might_fault();                                                  \
 239         if (access_ok(__p, sizeof(*__p))) {                             \
 240                 __p = uaccess_mask_ptr(__p);                            \
 241                 __raw_get_user((x), __p, (err));                        \
 242         } else {                                                        \
 243                 (x) = (__force __typeof__(x))0; (err) = -EFAULT;        \
 244         }                                                               \
 245 } while (0)
 246
 247 #define __get_user(x, ptr)                                              \
 248 ({                                                                      \
 249         int __gu_err = 0;                                               \
 250         __get_user_error((x), (ptr), __gu_err);                         \
 251         __gu_err;                                                       \
 252 })
 253
 254 #define get_user        __get_user
 255
 256 /*
 257  * We must not call into the scheduler between __mte_enable_tco_async() and
 258  * __mte_disable_tco_async(). As `dst` and `src` may contain blocking
 259  * functions, we must evaluate these outside of the critical section.
 260  */
 261 #define __get_kernel_nofault(dst, src, type, err_label)                 \
 262 do {                                                                    \
 263         __typeof__(dst) __gkn_dst = (dst);                              \
 264         __typeof__(src) __gkn_src = (src);                              \
 265         int __gkn_err = 0;                                              \
 266                                                                         \
 267         __mte_enable_tco_async();                                       \
 268         __raw_get_mem("ldr", *((type *)(__gkn_dst)),                    \
 269                       (__force type *)(__gkn_src), __gkn_err, K);       \
 270         __mte_disable_tco_async();                                      \
 271                                                                         \
 272         if (unlikely(__gkn_err))                                        \
 273                 goto err_label;                                         \
 274 } while (0)
 275
 276 #define __put_mem_asm(store, reg, x, addr, err, type)                   \
 277         asm volatile(                                                   \
 278         "1:     " store "       " reg "1, [%2]\n"                       \
 279         "2:\n"                                                          \
 280         _ASM_EXTABLE_##type##ACCESS_ERR(1b, 2b, %w0)                    \
 281         : "+r" (err)                                                    \
 282         : "rZ" (x), "r" (addr))
 283
 284 #define __raw_put_mem(str, x, ptr, err, type)                                   \
 285 do {                                                                            \
 286         __typeof__(*(ptr)) __pu_val = (x);                                      \
 287         switch (sizeof(*(ptr))) {                                               \
 288         case 1:                                                                 \
 289                 __put_mem_asm(str "b", "%w", __pu_val, (ptr), (err), type);     \
 290                 break;                                                          \
 291         case 2:                                                                 \
 292                 __put_mem_asm(str "h", "%w", __pu_val, (ptr), (err), type);     \
 293                 break;                                                          \
 294         case 4:                                                                 \
 295                 __put_mem_asm(str, "%w", __pu_val, (ptr), (err), type);         \
 296                 break;                                                          \
 297         case 8:                                                                 \
 298                 __put_mem_asm(str, "%x", __pu_val, (ptr), (err), type);         \
 299                 break;                                                          \
 300         default:                                                                \
 301                 BUILD_BUG();                                                    \
 302         }                                                                       \
 303 } while (0)
 304
 305 /*
 306  * We must not call into the scheduler between uaccess_ttbr0_enable() and
 307  * uaccess_ttbr0_disable(). As `x` and `ptr` could contain blocking functions,
 308  * we must evaluate these outside of the critical section.
 309  */
 310 #define __raw_put_user(x, ptr, err)                                     \
 311 do {                                                                    \
 312         __typeof__(*(ptr)) __user *__rpu_ptr = (ptr);                   \
 313         __typeof__(*(ptr)) __rpu_val = (x);                             \
 314         __chk_user_ptr(__rpu_ptr);                                      \
 315                                                                         \
 316         uaccess_ttbr0_enable();                                         \
 317         __raw_put_mem("sttr", __rpu_val, __rpu_ptr, err, U);            \
 318         uaccess_ttbr0_disable();                                        \
 319 } while (0)
 320
 321 #define __put_user_error(x, ptr, err)                                   \
 322 do {                                                                    \
 323         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 324         might_fault();                                                  \
 325         if (access_ok(__p, sizeof(*__p))) {                             \
 326                 __p = uaccess_mask_ptr(__p);                            \
 327                 __raw_put_user((x), __p, (err));                        \
 328         } else  {                                                       \
 329                 (err) = -EFAULT;                                        \
 330         }                                                               \
 331 } while (0)
 332
 333 #define __put_user(x, ptr)                                              \
 334 ({                                                                      \
 335         int __pu_err = 0;                                               \
 336         __put_user_error((x), (ptr), __pu_err);                         \
 337         __pu_err;                                                       \
 338 })
 339
 340 #define put_user        __put_user
 341
 342 /*
 343  * We must not call into the scheduler between __mte_enable_tco_async() and
 344  * __mte_disable_tco_async(). As `dst` and `src` may contain blocking
 345  * functions, we must evaluate these outside of the critical section.
 346  */
 347 #define __put_kernel_nofault(dst, src, type, err_label)                 \
 348 do {                                                                    \
 349         __typeof__(dst) __pkn_dst = (dst);                              \
 350         __typeof__(src) __pkn_src = (src);                              \
 351         int __pkn_err = 0;                                              \
 352                                                                         \
 353         __mte_enable_tco_async();                                       \
 354         __raw_put_mem("str", *((type *)(__pkn_src)),                    \
 355                       (__force type *)(__pkn_dst), __pkn_err, K);       \
 356         __mte_disable_tco_async();                                      \
 357                                                                         \
 358         if (unlikely(__pkn_err))                                        \
 359                 goto err_label;                                         \
 360 } while(0)
 361
 362 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 363 #define raw_copy_from_user(to, from, n)                                 \
 364 ({                                                                      \
 365         unsigned long __acfu_ret;                                       \
 366         uaccess_ttbr0_enable();                                         \
 367         __acfu_ret = __arch_copy_from_user((to),                        \
 368                                       __uaccess_mask_ptr(from), (n));   \
 369         uaccess_ttbr0_disable();                                        \
 370         __acfu_ret;                                                     \
 371 })
 372
 373 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 374 #define raw_copy_to_user(to, from, n)                                   \
 375 ({                                                                      \
 376         unsigned long __actu_ret;                                       \
 377         uaccess_ttbr0_enable();                                         \
 378         __actu_ret = __arch_copy_to_user(__uaccess_mask_ptr(to),        \
 379                                     (from), (n));                       \
 380         uaccess_ttbr0_disable();                                        \
 381         __actu_ret;                                                     \
 382 })
 383
 384 #define INLINE_COPY_TO_USER
 385 #define INLINE_COPY_FROM_USER
 386
 387 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
 388 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
 389 {
 390         if (access_ok(to, n)) {
 391                 uaccess_ttbr0_enable();
 392                 n = __arch_clear_user(__uaccess_mask_ptr(to), n);
 393                 uaccess_ttbr0_disable();
 394         }
 395         return n;
 396 }
 397 #define clear_user      __clear_user
 398
 399 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 400
 401 extern __must_check long strnlen_user(const char __user *str, long n);
 402
 403 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
 404 extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n);
 405
 406 static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
 407 {
 408         kasan_check_write(dst, size);
 409         return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size);
 410 }
 411 #endif
 412
 413 #ifdef CONFIG_ARCH_HAS_SUBPAGE_FAULTS
 414
 415 /*
 416  * Return 0 on success, the number of bytes not probed otherwise.
 417  */
 418 static inline size_t probe_subpage_writeable(const char __user *uaddr,
 419                                              size_t size)
 420 {
 421         if (!system_supports_mte())
 422                 return 0;
 423         return mte_probe_user_range(uaddr, size);
 424 }
 425
 426 #endif /* CONFIG_ARCH_HAS_SUBPAGE_FAULTS */
 427
 428 #endif /* __ASM_UACCESS_H */