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         if (IS_ENABLED(CONFIG_ARM64_TAGGED_ADDR_ABI) &&
  66             test_thread_flag(TIF_TAGGED_ADDR))
  67                 addr = untagged_addr(addr);
  68
  69         __chk_user_ptr(addr);
  70         asm volatile(
  71         // A + B <= C + 1 for all A,B,C, in four easy steps:
  72         // 1: X = A + B; X' = X % 2^64
  73         "       adds    %0, %3, %2\n"
  74         // 2: Set C = 0 if X > 2^64, to guarantee X' > C in step 4
  75         "       csel    %1, xzr, %1, hi\n"
  76         // 3: Set X' = ~0 if X >= 2^64. For X == 2^64, this decrements X'
  77         //    to compensate for the carry flag being set in step 4. For
  78         //    X > 2^64, X' merely has to remain nonzero, which it does.
  79         "       csinv   %0, %0, xzr, cc\n"
  80         // 4: For X < 2^64, this gives us X' - C - 1 <= 0, where the -1
  81         //    comes from the carry in being clear. Otherwise, we are
  82         //    testing X' - C == 0, subject to the previous adjustments.
  83         "       sbcs    xzr, %0, %1\n"
  84         "       cset    %0, ls\n"
  85         : "=&r" (ret), "+r" (limit) : "Ir" (size), "0" (addr) : "cc");
  86
  87         return ret;
  88 }
  89
  90 #define access_ok(addr, size)   __range_ok(addr, size)
  91 #define user_addr_max                   get_fs
  92
  93 #define _ASM_EXTABLE(from, to)                                          \
  94         "       .pushsection    __ex_table, \"a\"\n"                    \
  95         "       .align          3\n"                                    \
  96         "       .long           (" #from " - .), (" #to " - .)\n"       \
  97         "       .popsection\n"
  98
  99 /*
 100  * User access enabling/disabling.
 101  */
 102 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
 103 static inline void __uaccess_ttbr0_disable(void)
 104 {
 105         unsigned long flags, ttbr;
 106
 107         local_irq_save(flags);
 108         ttbr = read_sysreg(ttbr1_el1);
 109         ttbr &= ~TTBR_ASID_MASK;
 110         /* reserved_ttbr0 placed before swapper_pg_dir */
 111         write_sysreg(ttbr - RESERVED_TTBR0_SIZE, ttbr0_el1);
 112         isb();
 113         /* Set reserved ASID */
 114         write_sysreg(ttbr, ttbr1_el1);
 115         isb();
 116         local_irq_restore(flags);
 117 }
 118
 119 static inline void __uaccess_ttbr0_enable(void)
 120 {
 121         unsigned long flags, ttbr0, ttbr1;
 122
 123         /*
 124          * Disable interrupts to avoid preemption between reading the 'ttbr0'
 125          * variable and the MSR. A context switch could trigger an ASID
 126          * roll-over and an update of 'ttbr0'.
 127          */
 128         local_irq_save(flags);
 129         ttbr0 = READ_ONCE(current_thread_info()->ttbr0);
 130
 131         /* Restore active ASID */
 132         ttbr1 = read_sysreg(ttbr1_el1);
 133         ttbr1 &= ~TTBR_ASID_MASK;               /* safety measure */
 134         ttbr1 |= ttbr0 & TTBR_ASID_MASK;
 135         write_sysreg(ttbr1, ttbr1_el1);
 136         isb();
 137
 138         /* Restore user page table */
 139         write_sysreg(ttbr0, ttbr0_el1);
 140         isb();
 141         local_irq_restore(flags);
 142 }
 143
 144 static inline bool uaccess_ttbr0_disable(void)
 145 {
 146         if (!system_uses_ttbr0_pan())
 147                 return false;
 148         __uaccess_ttbr0_disable();
 149         return true;
 150 }
 151
 152 static inline bool uaccess_ttbr0_enable(void)
 153 {
 154         if (!system_uses_ttbr0_pan())
 155                 return false;
 156         __uaccess_ttbr0_enable();
 157         return true;
 158 }
 159 #else
 160 static inline bool uaccess_ttbr0_disable(void)
 161 {
 162         return false;
 163 }
 164
 165 static inline bool uaccess_ttbr0_enable(void)
 166 {
 167         return false;
 168 }
 169 #endif
 170
 171 static inline void __uaccess_disable_hw_pan(void)
 172 {
 173         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN,
 174                         CONFIG_ARM64_PAN));
 175 }
 176
 177 static inline void __uaccess_enable_hw_pan(void)
 178 {
 179         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,
 180                         CONFIG_ARM64_PAN));
 181 }
 182
 183 #define __uaccess_disable(alt)                                          \
 184 do {                                                                    \
 185         if (!uaccess_ttbr0_disable())                                   \
 186                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt,          \
 187                                 CONFIG_ARM64_PAN));                     \
 188 } while (0)
 189
 190 #define __uaccess_enable(alt)                                           \
 191 do {                                                                    \
 192         if (!uaccess_ttbr0_enable())                                    \
 193                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt,          \
 194                                 CONFIG_ARM64_PAN));                     \
 195 } while (0)
 196
 197 static inline void uaccess_disable(void)
 198 {
 199         __uaccess_disable(ARM64_HAS_PAN);
 200 }
 201
 202 static inline void uaccess_enable(void)
 203 {
 204         __uaccess_enable(ARM64_HAS_PAN);
 205 }
 206
 207 /*
 208  * These functions are no-ops when UAO is present.
 209  */
 210 static inline void uaccess_disable_not_uao(void)
 211 {
 212         __uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
 213 }
 214
 215 static inline void uaccess_enable_not_uao(void)
 216 {
 217         __uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
 218 }
 219
 220 /*
 221  * Sanitise a uaccess pointer such that it becomes NULL if above the
 222  * current addr_limit. In case the pointer is tagged (has the top byte set),
 223  * untag the pointer before checking.
 224  */
 225 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
 226 static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
 227 {
 228         void __user *safe_ptr;
 229
 230         asm volatile(
 231         "       bics    xzr, %3, %2\n"
 232         "       csel    %0, %1, xzr, eq\n"
 233         : "=&r" (safe_ptr)
 234         : "r" (ptr), "r" (current_thread_info()->addr_limit),
 235           "r" (untagged_addr(ptr))
 236         : "cc");
 237
 238         csdb();
 239         return safe_ptr;
 240 }
 241
 242 /*
 243  * The "__xxx" versions of the user access functions do not verify the address
 244  * space - it must have been done previously with a separate "access_ok()"
 245  * call.
 246  *
 247  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 248  * occurs, and leave it unchanged on success.
 249  */
 250 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 251         asm volatile(                                                   \
 252         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 253                         alt_instr " " reg "1, [%2]\n", feature)         \
 254         "2:\n"                                                          \
 255         "       .section .fixup, \"ax\"\n"                              \
 256         "       .align  2\n"                                            \
 257         "3:     mov     %w0, %3\n"                                      \
 258         "       mov     %1, #0\n"                                       \
 259         "       b       2b\n"                                           \
 260         "       .previous\n"                                            \
 261         _ASM_EXTABLE(1b, 3b)                                            \
 262         : "+r" (err), "=&r" (x)                                         \
 263         : "r" (addr), "i" (-EFAULT))
 264
 265 #define __raw_get_user(x, ptr, err)                                     \
 266 do {                                                                    \
 267         unsigned long __gu_val;                                         \
 268         __chk_user_ptr(ptr);                                            \
 269         uaccess_enable_not_uao();                                       \
 270         switch (sizeof(*(ptr))) {                                       \
 271         case 1:                                                         \
 272                 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
 273                                (err), ARM64_HAS_UAO);                   \
 274                 break;                                                  \
 275         case 2:                                                         \
 276                 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
 277                                (err), ARM64_HAS_UAO);                   \
 278                 break;                                                  \
 279         case 4:                                                         \
 280                 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),    \
 281                                (err), ARM64_HAS_UAO);                   \
 282                 break;                                                  \
 283         case 8:                                                         \
 284                 __get_user_asm("ldr", "ldtr", "%x",  __gu_val, (ptr),   \
 285                                (err), ARM64_HAS_UAO);                   \
 286                 break;                                                  \
 287         default:                                                        \
 288                 BUILD_BUG();                                            \
 289         }                                                               \
 290         uaccess_disable_not_uao();                                      \
 291         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 292 } while (0)
 293
 294 #define __get_user_error(x, ptr, err)                                   \
 295 do {                                                                    \
 296         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 297         might_fault();                                                  \
 298         if (access_ok(__p, sizeof(*__p))) {                             \
 299                 __p = uaccess_mask_ptr(__p);                            \
 300                 __raw_get_user((x), __p, (err));                        \
 301         } else {                                                        \
 302                 (x) = 0; (err) = -EFAULT;                               \
 303         }                                                               \
 304 } while (0)
 305
 306 #define __get_user(x, ptr)                                              \
 307 ({                                                                      \
 308         int __gu_err = 0;                                               \
 309         __get_user_error((x), (ptr), __gu_err);                         \
 310         __gu_err;                                                       \
 311 })
 312
 313 #define get_user        __get_user
 314
 315 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 316         asm volatile(                                                   \
 317         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 318                         alt_instr " " reg "1, [%2]\n", feature)         \
 319         "2:\n"                                                          \
 320         "       .section .fixup,\"ax\"\n"                               \
 321         "       .align  2\n"                                            \
 322         "3:     mov     %w0, %3\n"                                      \
 323         "       b       2b\n"                                           \
 324         "       .previous\n"                                            \
 325         _ASM_EXTABLE(1b, 3b)                                            \
 326         : "+r" (err)                                                    \
 327         : "r" (x), "r" (addr), "i" (-EFAULT))
 328
 329 #define __raw_put_user(x, ptr, err)                                     \
 330 do {                                                                    \
 331         __typeof__(*(ptr)) __pu_val = (x);                              \
 332         __chk_user_ptr(ptr);                                            \
 333         uaccess_enable_not_uao();                                       \
 334         switch (sizeof(*(ptr))) {                                       \
 335         case 1:                                                         \
 336                 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr),  \
 337                                (err), ARM64_HAS_UAO);                   \
 338                 break;                                                  \
 339         case 2:                                                         \
 340                 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr),  \
 341                                (err), ARM64_HAS_UAO);                   \
 342                 break;                                                  \
 343         case 4:                                                         \
 344                 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr),    \
 345                                (err), ARM64_HAS_UAO);                   \
 346                 break;                                                  \
 347         case 8:                                                         \
 348                 __put_user_asm("str", "sttr", "%x", __pu_val, (ptr),    \
 349                                (err), ARM64_HAS_UAO);                   \
 350                 break;                                                  \
 351         default:                                                        \
 352                 BUILD_BUG();                                            \
 353         }                                                               \
 354         uaccess_disable_not_uao();                                      \
 355 } while (0)
 356
 357 #define __put_user_error(x, ptr, err)                                   \
 358 do {                                                                    \
 359         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 360         might_fault();                                                  \
 361         if (access_ok(__p, sizeof(*__p))) {                             \
 362                 __p = uaccess_mask_ptr(__p);                            \
 363                 __raw_put_user((x), __p, (err));                        \
 364         } else  {                                                       \
 365                 (err) = -EFAULT;                                        \
 366         }                                                               \
 367 } while (0)
 368
 369 #define __put_user(x, ptr)                                              \
 370 ({                                                                      \
 371         int __pu_err = 0;                                               \
 372         __put_user_error((x), (ptr), __pu_err);                         \
 373         __pu_err;                                                       \
 374 })
 375
 376 #define put_user        __put_user
 377
 378 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 379 #define raw_copy_from_user(to, from, n)                                 \
 380 ({                                                                      \
 381         __arch_copy_from_user((to), __uaccess_mask_ptr(from), (n));     \
 382 })
 383
 384 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 385 #define raw_copy_to_user(to, from, n)                                   \
 386 ({                                                                      \
 387         __arch_copy_to_user(__uaccess_mask_ptr(to), (from), (n));       \
 388 })
 389
 390 extern unsigned long __must_check __arch_copy_in_user(void __user *to, const void __user *from, unsigned long n);
 391 #define raw_copy_in_user(to, from, n)                                   \
 392 ({                                                                      \
 393         __arch_copy_in_user(__uaccess_mask_ptr(to),                     \
 394                             __uaccess_mask_ptr(from), (n));             \
 395 })
 396
 397 #define INLINE_COPY_TO_USER
 398 #define INLINE_COPY_FROM_USER
 399
 400 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
 401 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
 402 {
 403         if (access_ok(to, n))
 404                 n = __arch_clear_user(__uaccess_mask_ptr(to), n);
 405         return n;
 406 }
 407 #define clear_user      __clear_user
 408
 409 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 410
 411 extern __must_check long strnlen_user(const char __user *str, long n);
 412
 413 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
 414 struct page;
 415 void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len);
 416 extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n);
 417
 418 static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
 419 {
 420         kasan_check_write(dst, size);
 421         return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size);
 422 }
 423 #endif
 424
 425 #endif /* __ASM_UACCESS_H */