arch/arm64/include/asm/uaccess.h

   1 /*
   2  * Based on arch/arm/include/asm/uaccess.h
   3  *
   4  * Copyright (C) 2012 ARM Ltd.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18 #ifndef __ASM_UACCESS_H
  19 #define __ASM_UACCESS_H
  20
  21 #include <asm/alternative.h>
  22 #include <asm/kernel-pgtable.h>
  23 #include <asm/sysreg.h>
  24
  25 /*
  26  * User space memory access functions
  27  */
  28 #include <linux/bitops.h>
  29 #include <linux/kasan-checks.h>
  30 #include <linux/string.h>
  31
  32 #include <asm/cpufeature.h>
  33 #include <asm/ptrace.h>
  34 #include <asm/memory.h>
  35 #include <asm/compiler.h>
  36 #include <asm/extable.h>
  37
  38 #define get_ds()        (KERNEL_DS)
  39 #define get_fs()        (current_thread_info()->addr_limit)
  40
  41 static inline void set_fs(mm_segment_t fs)
  42 {
  43         current_thread_info()->addr_limit = fs;
  44
  45         /*
  46          * Prevent a mispredicted conditional call to set_fs from forwarding
  47          * the wrong address limit to access_ok under speculation.
  48          */
  49         dsb(nsh);
  50         isb();
  51
  52         /* On user-mode return, check fs is correct */
  53         set_thread_flag(TIF_FSCHECK);
  54
  55         /*
  56          * Enable/disable UAO so that copy_to_user() etc can access
  57          * kernel memory with the unprivileged instructions.
  58          */
  59         if (IS_ENABLED(CONFIG_ARM64_UAO) && fs == KERNEL_DS)
  60                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
  61         else
  62                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
  63                                 CONFIG_ARM64_UAO));
  64 }
  65
  66 #define segment_eq(a, b)        ((a) == (b))
  67
  68 /*
  69  * Test whether a block of memory is a valid user space address.
  70  * Returns 1 if the range is valid, 0 otherwise.
  71  *
  72  * This is equivalent to the following test:
  73  * (u65)addr + (u65)size <= (u65)current->addr_limit + 1
  74  */
  75 static inline unsigned long __range_ok(unsigned long addr, unsigned long size)
  76 {
  77         unsigned long limit = current_thread_info()->addr_limit;
  78
  79         __chk_user_ptr(addr);
  80         asm volatile(
  81         // A + B <= C + 1 for all A,B,C, in four easy steps:
  82         // 1: X = A + B; X' = X % 2^64
  83         "       adds    %0, %0, %2\n"
  84         // 2: Set C = 0 if X > 2^64, to guarantee X' > C in step 4
  85         "       csel    %1, xzr, %1, hi\n"
  86         // 3: Set X' = ~0 if X >= 2^64. For X == 2^64, this decrements X'
  87         //    to compensate for the carry flag being set in step 4. For
  88         //    X > 2^64, X' merely has to remain nonzero, which it does.
  89         "       csinv   %0, %0, xzr, cc\n"
  90         // 4: For X < 2^64, this gives us X' - C - 1 <= 0, where the -1
  91         //    comes from the carry in being clear. Otherwise, we are
  92         //    testing X' - C == 0, subject to the previous adjustments.
  93         "       sbcs    xzr, %0, %1\n"
  94         "       cset    %0, ls\n"
  95         : "+r" (addr), "+r" (limit) : "Ir" (size) : "cc");
  96
  97         return addr;
  98 }
  99
 100 /*
 101  * When dealing with data aborts, watchpoints, or instruction traps we may end
 102  * up with a tagged userland pointer. Clear the tag to get a sane pointer to
 103  * pass on to access_ok(), for instance.
 104  */
 105 #define untagged_addr(addr)             sign_extend64(addr, 55)
 106
 107 #define access_ok(type, addr, size)     __range_ok((unsigned long)(addr), size)
 108 #define user_addr_max                   get_fs
 109
 110 #define _ASM_EXTABLE(from, to)                                          \
 111         "       .pushsection    __ex_table, \"a\"\n"                    \
 112         "       .align          3\n"                                    \
 113         "       .long           (" #from " - .), (" #to " - .)\n"       \
 114         "       .popsection\n"
 115
 116 /*
 117  * User access enabling/disabling.
 118  */
 119 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
 120 static inline void __uaccess_ttbr0_disable(void)
 121 {
 122         unsigned long flags, ttbr;
 123
 124         local_irq_save(flags);
 125         ttbr = read_sysreg(ttbr1_el1);
 126         ttbr &= ~TTBR_ASID_MASK;
 127         /* reserved_ttbr0 placed at the end of swapper_pg_dir */
 128         write_sysreg(ttbr + SWAPPER_DIR_SIZE, ttbr0_el1);
 129         isb();
 130         /* Set reserved ASID */
 131         write_sysreg(ttbr, ttbr1_el1);
 132         isb();
 133         local_irq_restore(flags);
 134 }
 135
 136 static inline void __uaccess_ttbr0_enable(void)
 137 {
 138         unsigned long flags, ttbr0, ttbr1;
 139
 140         /*
 141          * Disable interrupts to avoid preemption between reading the 'ttbr0'
 142          * variable and the MSR. A context switch could trigger an ASID
 143          * roll-over and an update of 'ttbr0'.
 144          */
 145         local_irq_save(flags);
 146         ttbr0 = READ_ONCE(current_thread_info()->ttbr0);
 147
 148         /* Restore active ASID */
 149         ttbr1 = read_sysreg(ttbr1_el1);
 150         ttbr1 &= ~TTBR_ASID_MASK;               /* safety measure */
 151         ttbr1 |= ttbr0 & TTBR_ASID_MASK;
 152         write_sysreg(ttbr1, ttbr1_el1);
 153         isb();
 154
 155         /* Restore user page table */
 156         write_sysreg(ttbr0, ttbr0_el1);
 157         isb();
 158         local_irq_restore(flags);
 159 }
 160
 161 static inline bool uaccess_ttbr0_disable(void)
 162 {
 163         if (!system_uses_ttbr0_pan())
 164                 return false;
 165         __uaccess_ttbr0_disable();
 166         return true;
 167 }
 168
 169 static inline bool uaccess_ttbr0_enable(void)
 170 {
 171         if (!system_uses_ttbr0_pan())
 172                 return false;
 173         __uaccess_ttbr0_enable();
 174         return true;
 175 }
 176 #else
 177 static inline bool uaccess_ttbr0_disable(void)
 178 {
 179         return false;
 180 }
 181
 182 static inline bool uaccess_ttbr0_enable(void)
 183 {
 184         return false;
 185 }
 186 #endif
 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.
 228  */
 229 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
 230 static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
 231 {
 232         void __user *safe_ptr;
 233
 234         asm volatile(
 235         "       bics    xzr, %1, %2\n"
 236         "       csel    %0, %1, xzr, eq\n"
 237         : "=&r" (safe_ptr)
 238         : "r" (ptr), "r" (current_thread_info()->addr_limit)
 239         : "cc");
 240
 241         csdb();
 242         return safe_ptr;
 243 }
 244
 245 /*
 246  * The "__xxx" versions of the user access functions do not verify the address
 247  * space - it must have been done previously with a separate "access_ok()"
 248  * call.
 249  *
 250  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 251  * occurs, and leave it unchanged on success.
 252  */
 253 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 254         asm volatile(                                                   \
 255         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 256                         alt_instr " " reg "1, [%2]\n", feature)         \
 257         "2:\n"                                                          \
 258         "       .section .fixup, \"ax\"\n"                              \
 259         "       .align  2\n"                                            \
 260         "3:     mov     %w0, %3\n"                                      \
 261         "       mov     %1, #0\n"                                       \
 262         "       b       2b\n"                                           \
 263         "       .previous\n"                                            \
 264         _ASM_EXTABLE(1b, 3b)                                            \
 265         : "+r" (err), "=&r" (x)                                         \
 266         : "r" (addr), "i" (-EFAULT))
 267
 268 #define __get_user_err(x, ptr, err)                                     \
 269 do {                                                                    \
 270         unsigned long __gu_val;                                         \
 271         __chk_user_ptr(ptr);                                            \
 272         uaccess_enable_not_uao();                                       \
 273         switch (sizeof(*(ptr))) {                                       \
 274         case 1:                                                         \
 275                 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
 276                                (err), ARM64_HAS_UAO);                   \
 277                 break;                                                  \
 278         case 2:                                                         \
 279                 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
 280                                (err), ARM64_HAS_UAO);                   \
 281                 break;                                                  \
 282         case 4:                                                         \
 283                 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),    \
 284                                (err), ARM64_HAS_UAO);                   \
 285                 break;                                                  \
 286         case 8:                                                         \
 287                 __get_user_asm("ldr", "ldtr", "%x",  __gu_val, (ptr),   \
 288                                (err), ARM64_HAS_UAO);                   \
 289                 break;                                                  \
 290         default:                                                        \
 291                 BUILD_BUG();                                            \
 292         }                                                               \
 293         uaccess_disable_not_uao();                                      \
 294         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 295 } while (0)
 296
 297 #define __get_user_check(x, ptr, err)                                   \
 298 ({                                                                      \
 299         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 300         might_fault();                                                  \
 301         if (access_ok(VERIFY_READ, __p, sizeof(*__p))) {                \
 302                 __p = uaccess_mask_ptr(__p);                            \
 303                 __get_user_err((x), __p, (err));                        \
 304         } else {                                                        \
 305                 (x) = 0; (err) = -EFAULT;                               \
 306         }                                                               \
 307 })
 308
 309 #define __get_user_error(x, ptr, err)                                   \
 310 ({                                                                      \
 311         __get_user_check((x), (ptr), (err));                            \
 312         (void)0;                                                        \
 313 })
 314
 315 #define __get_user(x, ptr)                                              \
 316 ({                                                                      \
 317         int __gu_err = 0;                                               \
 318         __get_user_check((x), (ptr), __gu_err);                         \
 319         __gu_err;                                                       \
 320 })
 321
 322 #define get_user        __get_user
 323
 324 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 325         asm volatile(                                                   \
 326         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 327                         alt_instr " " reg "1, [%2]\n", feature)         \
 328         "2:\n"                                                          \
 329         "       .section .fixup,\"ax\"\n"                               \
 330         "       .align  2\n"                                            \
 331         "3:     mov     %w0, %3\n"                                      \
 332         "       b       2b\n"                                           \
 333         "       .previous\n"                                            \
 334         _ASM_EXTABLE(1b, 3b)                                            \
 335         : "+r" (err)                                                    \
 336         : "r" (x), "r" (addr), "i" (-EFAULT))
 337
 338 #define __put_user_err(x, ptr, err)                                     \
 339 do {                                                                    \
 340         __typeof__(*(ptr)) __pu_val = (x);                              \
 341         __chk_user_ptr(ptr);                                            \
 342         uaccess_enable_not_uao();                                       \
 343         switch (sizeof(*(ptr))) {                                       \
 344         case 1:                                                         \
 345                 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr),  \
 346                                (err), ARM64_HAS_UAO);                   \
 347                 break;                                                  \
 348         case 2:                                                         \
 349                 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr),  \
 350                                (err), ARM64_HAS_UAO);                   \
 351                 break;                                                  \
 352         case 4:                                                         \
 353                 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr),    \
 354                                (err), ARM64_HAS_UAO);                   \
 355                 break;                                                  \
 356         case 8:                                                         \
 357                 __put_user_asm("str", "sttr", "%x", __pu_val, (ptr),    \
 358                                (err), ARM64_HAS_UAO);                   \
 359                 break;                                                  \
 360         default:                                                        \
 361                 BUILD_BUG();                                            \
 362         }                                                               \
 363         uaccess_disable_not_uao();                                      \
 364 } while (0)
 365
 366 #define __put_user_check(x, ptr, err)                                   \
 367 ({                                                                      \
 368         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 369         might_fault();                                                  \
 370         if (access_ok(VERIFY_WRITE, __p, sizeof(*__p))) {               \
 371                 __p = uaccess_mask_ptr(__p);                            \
 372                 __put_user_err((x), __p, (err));                        \
 373         } else  {                                                       \
 374                 (err) = -EFAULT;                                        \
 375         }                                                               \
 376 })
 377
 378 #define __put_user_error(x, ptr, err)                                   \
 379 ({                                                                      \
 380         __put_user_check((x), (ptr), (err));                            \
 381         (void)0;                                                        \
 382 })
 383
 384 #define __put_user(x, ptr)                                              \
 385 ({                                                                      \
 386         int __pu_err = 0;                                               \
 387         __put_user_check((x), (ptr), __pu_err);                         \
 388         __pu_err;                                                       \
 389 })
 390
 391 #define put_user        __put_user
 392
 393 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 394 #define raw_copy_from_user(to, from, n)                                 \
 395 ({                                                                      \
 396         __arch_copy_from_user((to), __uaccess_mask_ptr(from), (n));     \
 397 })
 398
 399 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 400 #define raw_copy_to_user(to, from, n)                                   \
 401 ({                                                                      \
 402         __arch_copy_to_user(__uaccess_mask_ptr(to), (from), (n));       \
 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         __arch_copy_in_user(__uaccess_mask_ptr(to),                     \
 409                             __uaccess_mask_ptr(from), (n));             \
 410 })
 411
 412 #define INLINE_COPY_TO_USER
 413 #define INLINE_COPY_FROM_USER
 414
 415 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
 416 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
 417 {
 418         if (access_ok(VERIFY_WRITE, to, n))
 419                 n = __arch_clear_user(__uaccess_mask_ptr(to), n);
 420         return n;
 421 }
 422 #define clear_user      __clear_user
 423
 424 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 425
 426 extern __must_check long strnlen_user(const char __user *str, long n);
 427
 428 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
 429 struct page;
 430 void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len);
 431 extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n);
 432
 433 static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
 434 {
 435         kasan_check_write(dst, size);
 436         return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size);
 437 }
 438 #endif
 439
 440 #endif /* __ASM_UACCESS_H */