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/cpufeature.h>
  22 #include <asm/ptrace.h>
  23 #include <asm/memory.h>
  24 #include <asm/extable.h>
  25
  26 #define get_fs()        (current_thread_info()->addr_limit)
  27
  28 static inline void set_fs(mm_segment_t fs)
  29 {
  30         current_thread_info()->addr_limit = fs;
  31
  32         /*
  33          * Prevent a mispredicted conditional call to set_fs from forwarding
  34          * the wrong address limit to access_ok under speculation.
  35          */
  36         spec_bar();
  37
  38         /* On user-mode return, check fs is correct */
  39         set_thread_flag(TIF_FSCHECK);
  40
  41         /*
  42          * Enable/disable UAO so that copy_to_user() etc can access
  43          * kernel memory with the unprivileged instructions.
  44          */
  45         if (IS_ENABLED(CONFIG_ARM64_UAO) && fs == KERNEL_DS)
  46                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
  47         else
  48                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
  49                                 CONFIG_ARM64_UAO));
  50 }
  51
  52 #define segment_eq(a, b)        ((a) == (b))
  53
  54 /*
  55  * Test whether a block of memory is a valid user space address.
  56  * Returns 1 if the range is valid, 0 otherwise.
  57  *
  58  * This is equivalent to the following test:
  59  * (u65)addr + (u65)size <= (u65)current->addr_limit + 1
  60  */
  61 static inline unsigned long __range_ok(const void __user *addr, unsigned long size)
  62 {
  63         unsigned long ret, limit = current_thread_info()->addr_limit;
  64
  65         __chk_user_ptr(addr);
  66         asm volatile(
  67         // A + B <= C + 1 for all A,B,C, in four easy steps:
  68         // 1: X = A + B; X' = X % 2^64
  69         "       adds    %0, %3, %2\n"
  70         // 2: Set C = 0 if X > 2^64, to guarantee X' > C in step 4
  71         "       csel    %1, xzr, %1, hi\n"
  72         // 3: Set X' = ~0 if X >= 2^64. For X == 2^64, this decrements X'
  73         //    to compensate for the carry flag being set in step 4. For
  74         //    X > 2^64, X' merely has to remain nonzero, which it does.
  75         "       csinv   %0, %0, xzr, cc\n"
  76         // 4: For X < 2^64, this gives us X' - C - 1 <= 0, where the -1
  77         //    comes from the carry in being clear. Otherwise, we are
  78         //    testing X' - C == 0, subject to the previous adjustments.
  79         "       sbcs    xzr, %0, %1\n"
  80         "       cset    %0, ls\n"
  81         : "=&r" (ret), "+r" (limit) : "Ir" (size), "0" (addr) : "cc");
  82
  83         return ret;
  84 }
  85
  86 #define access_ok(addr, size)   __range_ok(addr, size)
  87 #define user_addr_max                   get_fs
  88
  89 #define _ASM_EXTABLE(from, to)                                          \
  90         "       .pushsection    __ex_table, \"a\"\n"                    \
  91         "       .align          3\n"                                    \
  92         "       .long           (" #from " - .), (" #to " - .)\n"       \
  93         "       .popsection\n"
  94
  95 /*
  96  * User access enabling/disabling.
  97  */
  98 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
  99 static inline void __uaccess_ttbr0_disable(void)
 100 {
 101         unsigned long flags, ttbr;
 102
 103         local_irq_save(flags);
 104         ttbr = read_sysreg(ttbr1_el1);
 105         ttbr &= ~TTBR_ASID_MASK;
 106         /* reserved_ttbr0 placed before swapper_pg_dir */
 107         write_sysreg(ttbr - RESERVED_TTBR0_SIZE, ttbr0_el1);
 108         isb();
 109         /* Set reserved ASID */
 110         write_sysreg(ttbr, ttbr1_el1);
 111         isb();
 112         local_irq_restore(flags);
 113 }
 114
 115 static inline void __uaccess_ttbr0_enable(void)
 116 {
 117         unsigned long flags, ttbr0, ttbr1;
 118
 119         /*
 120          * Disable interrupts to avoid preemption between reading the 'ttbr0'
 121          * variable and the MSR. A context switch could trigger an ASID
 122          * roll-over and an update of 'ttbr0'.
 123          */
 124         local_irq_save(flags);
 125         ttbr0 = READ_ONCE(current_thread_info()->ttbr0);
 126
 127         /* Restore active ASID */
 128         ttbr1 = read_sysreg(ttbr1_el1);
 129         ttbr1 &= ~TTBR_ASID_MASK;               /* safety measure */
 130         ttbr1 |= ttbr0 & TTBR_ASID_MASK;
 131         write_sysreg(ttbr1, ttbr1_el1);
 132         isb();
 133
 134         /* Restore user page table */
 135         write_sysreg(ttbr0, ttbr0_el1);
 136         isb();
 137         local_irq_restore(flags);
 138 }
 139
 140 static inline bool uaccess_ttbr0_disable(void)
 141 {
 142         if (!system_uses_ttbr0_pan())
 143                 return false;
 144         __uaccess_ttbr0_disable();
 145         return true;
 146 }
 147
 148 static inline bool uaccess_ttbr0_enable(void)
 149 {
 150         if (!system_uses_ttbr0_pan())
 151                 return false;
 152         __uaccess_ttbr0_enable();
 153         return true;
 154 }
 155 #else
 156 static inline bool uaccess_ttbr0_disable(void)
 157 {
 158         return false;
 159 }
 160
 161 static inline bool uaccess_ttbr0_enable(void)
 162 {
 163         return false;
 164 }
 165 #endif
 166
 167 static inline void __uaccess_disable_hw_pan(void)
 168 {
 169         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN,
 170                         CONFIG_ARM64_PAN));
 171 }
 172
 173 static inline void __uaccess_enable_hw_pan(void)
 174 {
 175         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,
 176                         CONFIG_ARM64_PAN));
 177 }
 178
 179 #define __uaccess_disable(alt)                                          \
 180 do {                                                                    \
 181         if (!uaccess_ttbr0_disable())                                   \
 182                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt,          \
 183                                 CONFIG_ARM64_PAN));                     \
 184 } while (0)
 185
 186 #define __uaccess_enable(alt)                                           \
 187 do {                                                                    \
 188         if (!uaccess_ttbr0_enable())                                    \
 189                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt,          \
 190                                 CONFIG_ARM64_PAN));                     \
 191 } while (0)
 192
 193 static inline void uaccess_disable(void)
 194 {
 195         __uaccess_disable(ARM64_HAS_PAN);
 196 }
 197
 198 static inline void uaccess_enable(void)
 199 {
 200         __uaccess_enable(ARM64_HAS_PAN);
 201 }
 202
 203 /*
 204  * These functions are no-ops when UAO is present.
 205  */
 206 static inline void uaccess_disable_not_uao(void)
 207 {
 208         __uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
 209 }
 210
 211 static inline void uaccess_enable_not_uao(void)
 212 {
 213         __uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
 214 }
 215
 216 /*
 217  * Sanitise a uaccess pointer such that it becomes NULL if above the
 218  * current addr_limit.
 219  */
 220 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
 221 static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
 222 {
 223         void __user *safe_ptr;
 224
 225         asm volatile(
 226         "       bics    xzr, %1, %2\n"
 227         "       csel    %0, %1, xzr, eq\n"
 228         : "=&r" (safe_ptr)
 229         : "r" (ptr), "r" (current_thread_info()->addr_limit)
 230         : "cc");
 231
 232         csdb();
 233         return safe_ptr;
 234 }
 235
 236 /*
 237  * The "__xxx" versions of the user access functions do not verify the address
 238  * space - it must have been done previously with a separate "access_ok()"
 239  * call.
 240  *
 241  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 242  * occurs, and leave it unchanged on success.
 243  */
 244 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 245         asm volatile(                                                   \
 246         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 247                         alt_instr " " reg "1, [%2]\n", feature)         \
 248         "2:\n"                                                          \
 249         "       .section .fixup, \"ax\"\n"                              \
 250         "       .align  2\n"                                            \
 251         "3:     mov     %w0, %3\n"                                      \
 252         "       mov     %1, #0\n"                                       \
 253         "       b       2b\n"                                           \
 254         "       .previous\n"                                            \
 255         _ASM_EXTABLE(1b, 3b)                                            \
 256         : "+r" (err), "=&r" (x)                                         \
 257         : "r" (addr), "i" (-EFAULT))
 258
 259 #define __raw_get_user(x, ptr, err)                                     \
 260 do {                                                                    \
 261         unsigned long __gu_val;                                         \
 262         __chk_user_ptr(ptr);                                            \
 263         uaccess_enable_not_uao();                                       \
 264         switch (sizeof(*(ptr))) {                                       \
 265         case 1:                                                         \
 266                 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
 267                                (err), ARM64_HAS_UAO);                   \
 268                 break;                                                  \
 269         case 2:                                                         \
 270                 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
 271                                (err), ARM64_HAS_UAO);                   \
 272                 break;                                                  \
 273         case 4:                                                         \
 274                 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),    \
 275                                (err), ARM64_HAS_UAO);                   \
 276                 break;                                                  \
 277         case 8:                                                         \
 278                 __get_user_asm("ldr", "ldtr", "%x",  __gu_val, (ptr),   \
 279                                (err), ARM64_HAS_UAO);                   \
 280                 break;                                                  \
 281         default:                                                        \
 282                 BUILD_BUG();                                            \
 283         }                                                               \
 284         uaccess_disable_not_uao();                                      \
 285         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 286 } while (0)
 287
 288 #define __get_user_error(x, ptr, err)                                   \
 289 do {                                                                    \
 290         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 291         might_fault();                                                  \
 292         if (access_ok(__p, sizeof(*__p))) {                             \
 293                 __p = uaccess_mask_ptr(__p);                            \
 294                 __raw_get_user((x), __p, (err));                        \
 295         } else {                                                        \
 296                 (x) = 0; (err) = -EFAULT;                               \
 297         }                                                               \
 298 } while (0)
 299
 300 #define __get_user(x, ptr)                                              \
 301 ({                                                                      \
 302         int __gu_err = 0;                                               \
 303         __get_user_error((x), (ptr), __gu_err);                         \
 304         __gu_err;                                                       \
 305 })
 306
 307 #define get_user        __get_user
 308
 309 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 310         asm volatile(                                                   \
 311         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 312                         alt_instr " " reg "1, [%2]\n", feature)         \
 313         "2:\n"                                                          \
 314         "       .section .fixup,\"ax\"\n"                               \
 315         "       .align  2\n"                                            \
 316         "3:     mov     %w0, %3\n"                                      \
 317         "       b       2b\n"                                           \
 318         "       .previous\n"                                            \
 319         _ASM_EXTABLE(1b, 3b)                                            \
 320         : "+r" (err)                                                    \
 321         : "r" (x), "r" (addr), "i" (-EFAULT))
 322
 323 #define __raw_put_user(x, ptr, err)                                     \
 324 do {                                                                    \
 325         __typeof__(*(ptr)) __pu_val = (x);                              \
 326         __chk_user_ptr(ptr);                                            \
 327         uaccess_enable_not_uao();                                       \
 328         switch (sizeof(*(ptr))) {                                       \
 329         case 1:                                                         \
 330                 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr),  \
 331                                (err), ARM64_HAS_UAO);                   \
 332                 break;                                                  \
 333         case 2:                                                         \
 334                 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr),  \
 335                                (err), ARM64_HAS_UAO);                   \
 336                 break;                                                  \
 337         case 4:                                                         \
 338                 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr),    \
 339                                (err), ARM64_HAS_UAO);                   \
 340                 break;                                                  \
 341         case 8:                                                         \
 342                 __put_user_asm("str", "sttr", "%x", __pu_val, (ptr),    \
 343                                (err), ARM64_HAS_UAO);                   \
 344                 break;                                                  \
 345         default:                                                        \
 346                 BUILD_BUG();                                            \
 347         }                                                               \
 348         uaccess_disable_not_uao();                                      \
 349 } while (0)
 350
 351 #define __put_user_error(x, ptr, err)                                   \
 352 do {                                                                    \
 353         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 354         might_fault();                                                  \
 355         if (access_ok(__p, sizeof(*__p))) {                             \
 356                 __p = uaccess_mask_ptr(__p);                            \
 357                 __raw_put_user((x), __p, (err));                        \
 358         } else  {                                                       \
 359                 (err) = -EFAULT;                                        \
 360         }                                                               \
 361 } while (0)
 362
 363 #define __put_user(x, ptr)                                              \
 364 ({                                                                      \
 365         int __pu_err = 0;                                               \
 366         __put_user_error((x), (ptr), __pu_err);                         \
 367         __pu_err;                                                       \
 368 })
 369
 370 #define put_user        __put_user
 371
 372 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 373 #define raw_copy_from_user(to, from, n)                                 \
 374 ({                                                                      \
 375         __arch_copy_from_user((to), __uaccess_mask_ptr(from), (n));     \
 376 })
 377
 378 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 379 #define raw_copy_to_user(to, from, n)                                   \
 380 ({                                                                      \
 381         __arch_copy_to_user(__uaccess_mask_ptr(to), (from), (n));       \
 382 })
 383
 384 extern unsigned long __must_check __arch_copy_in_user(void __user *to, const void __user *from, unsigned long n);
 385 #define raw_copy_in_user(to, from, n)                                   \
 386 ({                                                                      \
 387         __arch_copy_in_user(__uaccess_mask_ptr(to),                     \
 388                             __uaccess_mask_ptr(from), (n));             \
 389 })
 390
 391 #define INLINE_COPY_TO_USER
 392 #define INLINE_COPY_FROM_USER
 393
 394 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
 395 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
 396 {
 397         if (access_ok(to, n))
 398                 n = __arch_clear_user(__uaccess_mask_ptr(to), n);
 399         return n;
 400 }
 401 #define clear_user      __clear_user
 402
 403 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 404
 405 extern __must_check long strnlen_user(const char __user *str, long n);
 406
 407 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
 408 struct page;
 409 void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len);
 410 extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n);
 411
 412 static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
 413 {
 414         kasan_check_write(dst, size);
 415         return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size);
 416 }
 417 #endif
 418
 419 #endif /* __ASM_UACCESS_H */