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/extable.h>
  36
  37 #define get_fs()        (current_thread_info()->addr_limit)
  38
  39 static inline void set_fs(mm_segment_t fs)
  40 {
  41         current_thread_info()->addr_limit = fs;
  42
  43         /*
  44          * Prevent a mispredicted conditional call to set_fs from forwarding
  45          * the wrong address limit to access_ok under speculation.
  46          */
  47         spec_bar();
  48
  49         /* On user-mode return, check fs is correct */
  50         set_thread_flag(TIF_FSCHECK);
  51
  52         /*
  53          * Enable/disable UAO so that copy_to_user() etc can access
  54          * kernel memory with the unprivileged instructions.
  55          */
  56         if (IS_ENABLED(CONFIG_ARM64_UAO) && fs == KERNEL_DS)
  57                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
  58         else
  59                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
  60                                 CONFIG_ARM64_UAO));
  61 }
  62
  63 #define segment_eq(a, b)        ((a) == (b))
  64
  65 /*
  66  * Test whether a block of memory is a valid user space address.
  67  * Returns 1 if the range is valid, 0 otherwise.
  68  *
  69  * This is equivalent to the following test:
  70  * (u65)addr + (u65)size <= (u65)current->addr_limit + 1
  71  */
  72 static inline unsigned long __range_ok(const void __user *addr, unsigned long size)
  73 {
  74         unsigned long ret, limit = current_thread_info()->addr_limit;
  75
  76         __chk_user_ptr(addr);
  77         asm volatile(
  78         // A + B <= C + 1 for all A,B,C, in four easy steps:
  79         // 1: X = A + B; X' = X % 2^64
  80         "       adds    %0, %3, %2\n"
  81         // 2: Set C = 0 if X > 2^64, to guarantee X' > C in step 4
  82         "       csel    %1, xzr, %1, hi\n"
  83         // 3: Set X' = ~0 if X >= 2^64. For X == 2^64, this decrements X'
  84         //    to compensate for the carry flag being set in step 4. For
  85         //    X > 2^64, X' merely has to remain nonzero, which it does.
  86         "       csinv   %0, %0, xzr, cc\n"
  87         // 4: For X < 2^64, this gives us X' - C - 1 <= 0, where the -1
  88         //    comes from the carry in being clear. Otherwise, we are
  89         //    testing X' - C == 0, subject to the previous adjustments.
  90         "       sbcs    xzr, %0, %1\n"
  91         "       cset    %0, ls\n"
  92         : "=&r" (ret), "+r" (limit) : "Ir" (size), "0" (addr) : "cc");
  93
  94         return ret;
  95 }
  96
  97 #define access_ok(addr, size)   __range_ok(addr, size)
  98 #define user_addr_max                   get_fs
  99
 100 #define _ASM_EXTABLE(from, to)                                          \
 101         "       .pushsection    __ex_table, \"a\"\n"                    \
 102         "       .align          3\n"                                    \
 103         "       .long           (" #from " - .), (" #to " - .)\n"       \
 104         "       .popsection\n"
 105
 106 /*
 107  * User access enabling/disabling.
 108  */
 109 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
 110 static inline void __uaccess_ttbr0_disable(void)
 111 {
 112         unsigned long flags, ttbr;
 113
 114         local_irq_save(flags);
 115         ttbr = read_sysreg(ttbr1_el1);
 116         ttbr &= ~TTBR_ASID_MASK;
 117         /* reserved_ttbr0 placed before swapper_pg_dir */
 118         write_sysreg(ttbr - RESERVED_TTBR0_SIZE, ttbr0_el1);
 119         isb();
 120         /* Set reserved ASID */
 121         write_sysreg(ttbr, ttbr1_el1);
 122         isb();
 123         local_irq_restore(flags);
 124 }
 125
 126 static inline void __uaccess_ttbr0_enable(void)
 127 {
 128         unsigned long flags, ttbr0, ttbr1;
 129
 130         /*
 131          * Disable interrupts to avoid preemption between reading the 'ttbr0'
 132          * variable and the MSR. A context switch could trigger an ASID
 133          * roll-over and an update of 'ttbr0'.
 134          */
 135         local_irq_save(flags);
 136         ttbr0 = READ_ONCE(current_thread_info()->ttbr0);
 137
 138         /* Restore active ASID */
 139         ttbr1 = read_sysreg(ttbr1_el1);
 140         ttbr1 &= ~TTBR_ASID_MASK;               /* safety measure */
 141         ttbr1 |= ttbr0 & TTBR_ASID_MASK;
 142         write_sysreg(ttbr1, ttbr1_el1);
 143         isb();
 144
 145         /* Restore user page table */
 146         write_sysreg(ttbr0, ttbr0_el1);
 147         isb();
 148         local_irq_restore(flags);
 149 }
 150
 151 static inline bool uaccess_ttbr0_disable(void)
 152 {
 153         if (!system_uses_ttbr0_pan())
 154                 return false;
 155         __uaccess_ttbr0_disable();
 156         return true;
 157 }
 158
 159 static inline bool uaccess_ttbr0_enable(void)
 160 {
 161         if (!system_uses_ttbr0_pan())
 162                 return false;
 163         __uaccess_ttbr0_enable();
 164         return true;
 165 }
 166 #else
 167 static inline bool uaccess_ttbr0_disable(void)
 168 {
 169         return false;
 170 }
 171
 172 static inline bool uaccess_ttbr0_enable(void)
 173 {
 174         return false;
 175 }
 176 #endif
 177
 178 static inline void __uaccess_disable_hw_pan(void)
 179 {
 180         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN,
 181                         CONFIG_ARM64_PAN));
 182 }
 183
 184 static inline void __uaccess_enable_hw_pan(void)
 185 {
 186         asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,
 187                         CONFIG_ARM64_PAN));
 188 }
 189
 190 #define __uaccess_disable(alt)                                          \
 191 do {                                                                    \
 192         if (!uaccess_ttbr0_disable())                                   \
 193                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt,          \
 194                                 CONFIG_ARM64_PAN));                     \
 195 } while (0)
 196
 197 #define __uaccess_enable(alt)                                           \
 198 do {                                                                    \
 199         if (!uaccess_ttbr0_enable())                                    \
 200                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt,          \
 201                                 CONFIG_ARM64_PAN));                     \
 202 } while (0)
 203
 204 static inline void uaccess_disable(void)
 205 {
 206         __uaccess_disable(ARM64_HAS_PAN);
 207 }
 208
 209 static inline void uaccess_enable(void)
 210 {
 211         __uaccess_enable(ARM64_HAS_PAN);
 212 }
 213
 214 /*
 215  * These functions are no-ops when UAO is present.
 216  */
 217 static inline void uaccess_disable_not_uao(void)
 218 {
 219         __uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
 220 }
 221
 222 static inline void uaccess_enable_not_uao(void)
 223 {
 224         __uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
 225 }
 226
 227 /*
 228  * Sanitise a uaccess pointer such that it becomes NULL if above the
 229  * current addr_limit.
 230  */
 231 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
 232 static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
 233 {
 234         void __user *safe_ptr;
 235
 236         asm volatile(
 237         "       bics    xzr, %1, %2\n"
 238         "       csel    %0, %1, xzr, eq\n"
 239         : "=&r" (safe_ptr)
 240         : "r" (ptr), "r" (current_thread_info()->addr_limit)
 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         __arch_copy_from_user((to), __uaccess_mask_ptr(from), (n));     \
 387 })
 388
 389 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 390 #define raw_copy_to_user(to, from, n)                                   \
 391 ({                                                                      \
 392         __arch_copy_to_user(__uaccess_mask_ptr(to), (from), (n));       \
 393 })
 394
 395 extern unsigned long __must_check __arch_copy_in_user(void __user *to, const void __user *from, unsigned long n);
 396 #define raw_copy_in_user(to, from, n)                                   \
 397 ({                                                                      \
 398         __arch_copy_in_user(__uaccess_mask_ptr(to),                     \
 399                             __uaccess_mask_ptr(from), (n));             \
 400 })
 401
 402 #define INLINE_COPY_TO_USER
 403 #define INLINE_COPY_FROM_USER
 404
 405 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
 406 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
 407 {
 408         if (access_ok(to, n))
 409                 n = __arch_clear_user(__uaccess_mask_ptr(to), n);
 410         return n;
 411 }
 412 #define clear_user      __clear_user
 413
 414 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 415
 416 extern __must_check long strnlen_user(const char __user *str, long n);
 417
 418 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
 419 struct page;
 420 void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len);
 421 extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n);
 422
 423 static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
 424 {
 425         kasan_check_write(dst, size);
 426         return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size);
 427 }
 428 #endif
 429
 430 #endif /* __ASM_UACCESS_H */