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         /*
  66          * Asynchronous I/O running in a kernel thread does not have the
  67          * TIF_TAGGED_ADDR flag of the process owning the mm, so always untag
  68          * the user address before checking.
  69          */
  70         if (IS_ENABLED(CONFIG_ARM64_TAGGED_ADDR_ABI) &&
  71             (current->flags & PF_KTHREAD || test_thread_flag(TIF_TAGGED_ADDR)))
  72                 addr = untagged_addr(addr);
  73
  74         __chk_user_ptr(addr);
  75         asm volatile(
  76         // A + B <= C + 1 for all A,B,C, in four easy steps:
  77         // 1: X = A + B; X' = X % 2^64
  78         "       adds    %0, %3, %2\n"
  79         // 2: Set C = 0 if X > 2^64, to guarantee X' > C in step 4
  80         "       csel    %1, xzr, %1, hi\n"
  81         // 3: Set X' = ~0 if X >= 2^64. For X == 2^64, this decrements X'
  82         //    to compensate for the carry flag being set in step 4. For
  83         //    X > 2^64, X' merely has to remain nonzero, which it does.
  84         "       csinv   %0, %0, xzr, cc\n"
  85         // 4: For X < 2^64, this gives us X' - C - 1 <= 0, where the -1
  86         //    comes from the carry in being clear. Otherwise, we are
  87         //    testing X' - C == 0, subject to the previous adjustments.
  88         "       sbcs    xzr, %0, %1\n"
  89         "       cset    %0, ls\n"
  90         : "=&r" (ret), "+r" (limit) : "Ir" (size), "0" (addr) : "cc");
  91
  92         return ret;
  93 }
  94
  95 #define access_ok(addr, size)   __range_ok(addr, size)
  96 #define user_addr_max                   get_fs
  97
  98 #define _ASM_EXTABLE(from, to)                                          \
  99         "       .pushsection    __ex_table, \"a\"\n"                    \
 100         "       .align          3\n"                                    \
 101         "       .long           (" #from " - .), (" #to " - .)\n"       \
 102         "       .popsection\n"
 103
 104 /*
 105  * User access enabling/disabling.
 106  */
 107 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
 108 static inline void __uaccess_ttbr0_disable(void)
 109 {
 110         unsigned long flags, ttbr;
 111
 112         local_irq_save(flags);
 113         ttbr = read_sysreg(ttbr1_el1);
 114         ttbr &= ~TTBR_ASID_MASK;
 115         /* reserved_pg_dir placed before swapper_pg_dir */
 116         write_sysreg(ttbr - PAGE_SIZE, ttbr0_el1);
 117         isb();
 118         /* Set reserved ASID */
 119         write_sysreg(ttbr, ttbr1_el1);
 120         isb();
 121         local_irq_restore(flags);
 122 }
 123
 124 static inline void __uaccess_ttbr0_enable(void)
 125 {
 126         unsigned long flags, ttbr0, ttbr1;
 127
 128         /*
 129          * Disable interrupts to avoid preemption between reading the 'ttbr0'
 130          * variable and the MSR. A context switch could trigger an ASID
 131          * roll-over and an update of 'ttbr0'.
 132          */
 133         local_irq_save(flags);
 134         ttbr0 = READ_ONCE(current_thread_info()->ttbr0);
 135
 136         /* Restore active ASID */
 137         ttbr1 = read_sysreg(ttbr1_el1);
 138         ttbr1 &= ~TTBR_ASID_MASK;               /* safety measure */
 139         ttbr1 |= ttbr0 & TTBR_ASID_MASK;
 140         write_sysreg(ttbr1, ttbr1_el1);
 141         isb();
 142
 143         /* Restore user page table */
 144         write_sysreg(ttbr0, ttbr0_el1);
 145         isb();
 146         local_irq_restore(flags);
 147 }
 148
 149 static inline bool uaccess_ttbr0_disable(void)
 150 {
 151         if (!system_uses_ttbr0_pan())
 152                 return false;
 153         __uaccess_ttbr0_disable();
 154         return true;
 155 }
 156
 157 static inline bool uaccess_ttbr0_enable(void)
 158 {
 159         if (!system_uses_ttbr0_pan())
 160                 return false;
 161         __uaccess_ttbr0_enable();
 162         return true;
 163 }
 164 #else
 165 static inline bool uaccess_ttbr0_disable(void)
 166 {
 167         return false;
 168 }
 169
 170 static inline bool uaccess_ttbr0_enable(void)
 171 {
 172         return false;
 173 }
 174 #endif
 175
 176 static inline void __uaccess_disable_hw_pan(void)
 177 {
 178         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN,
 179                         CONFIG_ARM64_PAN));
 180 }
 181
 182 static inline void __uaccess_enable_hw_pan(void)
 183 {
 184         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,
 185                         CONFIG_ARM64_PAN));
 186 }
 187
 188 #define __uaccess_disable(alt)                                          \
 189 do {                                                                    \
 190         if (!uaccess_ttbr0_disable())                                   \
 191                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt,          \
 192                                 CONFIG_ARM64_PAN));                     \
 193 } while (0)
 194
 195 #define __uaccess_enable(alt)                                           \
 196 do {                                                                    \
 197         if (!uaccess_ttbr0_enable())                                    \
 198                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt,          \
 199                                 CONFIG_ARM64_PAN));                     \
 200 } while (0)
 201
 202 static inline void uaccess_disable(void)
 203 {
 204         __uaccess_disable(ARM64_HAS_PAN);
 205 }
 206
 207 static inline void uaccess_enable(void)
 208 {
 209         __uaccess_enable(ARM64_HAS_PAN);
 210 }
 211
 212 /*
 213  * These functions are no-ops when UAO is present.
 214  */
 215 static inline void uaccess_disable_not_uao(void)
 216 {
 217         __uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
 218 }
 219
 220 static inline void uaccess_enable_not_uao(void)
 221 {
 222         __uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
 223 }
 224
 225 /*
 226  * Sanitise a uaccess pointer such that it becomes NULL if above the
 227  * current addr_limit. In case the pointer is tagged (has the top byte set),
 228  * untag the pointer before checking.
 229  */
 230 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
 231 static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
 232 {
 233         void __user *safe_ptr;
 234
 235         asm volatile(
 236         "       bics    xzr, %3, %2\n"
 237         "       csel    %0, %1, xzr, eq\n"
 238         : "=&r" (safe_ptr)
 239         : "r" (ptr), "r" (current_thread_info()->addr_limit),
 240           "r" (untagged_addr(ptr))
 241         : "cc");
 242
 243         csdb();
 244         return safe_ptr;
 245 }
 246
 247 /*
 248  * The "__xxx" versions of the user access functions do not verify the address
 249  * space - it must have been done previously with a separate "access_ok()"
 250  * call.
 251  *
 252  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 253  * occurs, and leave it unchanged on success.
 254  */
 255 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 256         asm volatile(                                                   \
 257         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 258                         alt_instr " " reg "1, [%2]\n", feature)         \
 259         "2:\n"                                                          \
 260         "       .section .fixup, \"ax\"\n"                              \
 261         "       .align  2\n"                                            \
 262         "3:     mov     %w0, %3\n"                                      \
 263         "       mov     %1, #0\n"                                       \
 264         "       b       2b\n"                                           \
 265         "       .previous\n"                                            \
 266         _ASM_EXTABLE(1b, 3b)                                            \
 267         : "+r" (err), "=&r" (x)                                         \
 268         : "r" (addr), "i" (-EFAULT))
 269
 270 #define __raw_get_user(x, ptr, err)                                     \
 271 do {                                                                    \
 272         unsigned long __gu_val;                                         \
 273         __chk_user_ptr(ptr);                                            \
 274         uaccess_enable_not_uao();                                       \
 275         switch (sizeof(*(ptr))) {                                       \
 276         case 1:                                                         \
 277                 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
 278                                (err), ARM64_HAS_UAO);                   \
 279                 break;                                                  \
 280         case 2:                                                         \
 281                 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
 282                                (err), ARM64_HAS_UAO);                   \
 283                 break;                                                  \
 284         case 4:                                                         \
 285                 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),    \
 286                                (err), ARM64_HAS_UAO);                   \
 287                 break;                                                  \
 288         case 8:                                                         \
 289                 __get_user_asm("ldr", "ldtr", "%x",  __gu_val, (ptr),   \
 290                                (err), ARM64_HAS_UAO);                   \
 291                 break;                                                  \
 292         default:                                                        \
 293                 BUILD_BUG();                                            \
 294         }                                                               \
 295         uaccess_disable_not_uao();                                      \
 296         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 297 } while (0)
 298
 299 #define __get_user_error(x, ptr, err)                                   \
 300 do {                                                                    \
 301         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 302         might_fault();                                                  \
 303         if (access_ok(__p, sizeof(*__p))) {                             \
 304                 __p = uaccess_mask_ptr(__p);                            \
 305                 __raw_get_user((x), __p, (err));                        \
 306         } else {                                                        \
 307                 (x) = 0; (err) = -EFAULT;                               \
 308         }                                                               \
 309 } while (0)
 310
 311 #define __get_user(x, ptr)                                              \
 312 ({                                                                      \
 313         int __gu_err = 0;                                               \
 314         __get_user_error((x), (ptr), __gu_err);                         \
 315         __gu_err;                                                       \
 316 })
 317
 318 #define get_user        __get_user
 319
 320 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 321         asm volatile(                                                   \
 322         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 323                         alt_instr " " reg "1, [%2]\n", feature)         \
 324         "2:\n"                                                          \
 325         "       .section .fixup,\"ax\"\n"                               \
 326         "       .align  2\n"                                            \
 327         "3:     mov     %w0, %3\n"                                      \
 328         "       b       2b\n"                                           \
 329         "       .previous\n"                                            \
 330         _ASM_EXTABLE(1b, 3b)                                            \
 331         : "+r" (err)                                                    \
 332         : "r" (x), "r" (addr), "i" (-EFAULT))
 333
 334 #define __raw_put_user(x, ptr, err)                                     \
 335 do {                                                                    \
 336         __typeof__(*(ptr)) __pu_val = (x);                              \
 337         __chk_user_ptr(ptr);                                            \
 338         uaccess_enable_not_uao();                                       \
 339         switch (sizeof(*(ptr))) {                                       \
 340         case 1:                                                         \
 341                 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr),  \
 342                                (err), ARM64_HAS_UAO);                   \
 343                 break;                                                  \
 344         case 2:                                                         \
 345                 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr),  \
 346                                (err), ARM64_HAS_UAO);                   \
 347                 break;                                                  \
 348         case 4:                                                         \
 349                 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr),    \
 350                                (err), ARM64_HAS_UAO);                   \
 351                 break;                                                  \
 352         case 8:                                                         \
 353                 __put_user_asm("str", "sttr", "%x", __pu_val, (ptr),    \
 354                                (err), ARM64_HAS_UAO);                   \
 355                 break;                                                  \
 356         default:                                                        \
 357                 BUILD_BUG();                                            \
 358         }                                                               \
 359         uaccess_disable_not_uao();                                      \
 360 } while (0)
 361
 362 #define __put_user_error(x, ptr, err)                                   \
 363 do {                                                                    \
 364         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 365         might_fault();                                                  \
 366         if (access_ok(__p, sizeof(*__p))) {                             \
 367                 __p = uaccess_mask_ptr(__p);                            \
 368                 __raw_put_user((x), __p, (err));                        \
 369         } else  {                                                       \
 370                 (err) = -EFAULT;                                        \
 371         }                                                               \
 372 } while (0)
 373
 374 #define __put_user(x, ptr)                                              \
 375 ({                                                                      \
 376         int __pu_err = 0;                                               \
 377         __put_user_error((x), (ptr), __pu_err);                         \
 378         __pu_err;                                                       \
 379 })
 380
 381 #define put_user        __put_user
 382
 383 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 384 #define raw_copy_from_user(to, from, n)                                 \
 385 ({                                                                      \
 386         unsigned long __acfu_ret;                                       \
 387         uaccess_enable_not_uao();                                       \
 388         __acfu_ret = __arch_copy_from_user((to),                        \
 389                                       __uaccess_mask_ptr(from), (n));   \
 390         uaccess_disable_not_uao();                                      \
 391         __acfu_ret;                                                     \
 392 })
 393
 394 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 395 #define raw_copy_to_user(to, from, n)                                   \
 396 ({                                                                      \
 397         unsigned long __actu_ret;                                       \
 398         uaccess_enable_not_uao();                                       \
 399         __actu_ret = __arch_copy_to_user(__uaccess_mask_ptr(to),        \
 400                                     (from), (n));                       \
 401         uaccess_disable_not_uao();                                      \
 402         __actu_ret;                                                     \
 403 })
 404
 405 extern unsigned long __must_check __arch_copy_in_user(void __user *to, const void __user *from, unsigned long n);
 406 #define raw_copy_in_user(to, from, n)                                   \
 407 ({                                                                      \
 408         unsigned long __aciu_ret;                                       \
 409         uaccess_enable_not_uao();                                       \
 410         __aciu_ret = __arch_copy_in_user(__uaccess_mask_ptr(to),        \
 411                                     __uaccess_mask_ptr(from), (n));     \
 412         uaccess_disable_not_uao();                                      \
 413         __aciu_ret;                                                     \
 414 })
 415
 416 #define INLINE_COPY_TO_USER
 417 #define INLINE_COPY_FROM_USER
 418
 419 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
 420 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
 421 {
 422         if (access_ok(to, n)) {
 423                 uaccess_enable_not_uao();
 424                 n = __arch_clear_user(__uaccess_mask_ptr(to), n);
 425                 uaccess_disable_not_uao();
 426         }
 427         return n;
 428 }
 429 #define clear_user      __clear_user
 430
 431 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 432
 433 extern __must_check long strnlen_user(const char __user *str, long n);
 434
 435 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
 436 struct page;
 437 void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len);
 438 extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n);
 439
 440 static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
 441 {
 442         kasan_check_write(dst, size);
 443         return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size);
 444 }
 445 #endif
 446
 447 #endif /* __ASM_UACCESS_H */