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 KERNEL_DS       (-1UL)
  39 #define get_ds()        (KERNEL_DS)
  40
  41 #define USER_DS         TASK_SIZE_64
  42 #define get_fs()        (current_thread_info()->addr_limit)
  43
  44 static inline void set_fs(mm_segment_t fs)
  45 {
  46         current_thread_info()->addr_limit = fs;
  47
  48         /*
  49          * Enable/disable UAO so that copy_to_user() etc can access
  50          * kernel memory with the unprivileged instructions.
  51          */
  52         if (IS_ENABLED(CONFIG_ARM64_UAO) && fs == KERNEL_DS)
  53                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
  54         else
  55                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
  56                                 CONFIG_ARM64_UAO));
  57 }
  58
  59 #define segment_eq(a, b)        ((a) == (b))
  60
  61 /*
  62  * Test whether a block of memory is a valid user space address.
  63  * Returns 1 if the range is valid, 0 otherwise.
  64  *
  65  * This is equivalent to the following test:
  66  * (u65)addr + (u65)size <= current->addr_limit
  67  *
  68  * This needs 65-bit arithmetic.
  69  */
  70 #define __range_ok(addr, size)                                          \
  71 ({                                                                      \
  72         unsigned long __addr = (unsigned long)(addr);                   \
  73         unsigned long flag, roksum;                                     \
  74         __chk_user_ptr(addr);                                           \
  75         asm("adds %1, %1, %3; ccmp %1, %4, #2, cc; cset %0, ls"         \
  76                 : "=&r" (flag), "=&r" (roksum)                          \
  77                 : "1" (__addr), "Ir" (size),                            \
  78                   "r" (current_thread_info()->addr_limit)               \
  79                 : "cc");                                                \
  80         flag;                                                           \
  81 })
  82
  83 /*
  84  * When dealing with data aborts, watchpoints, or instruction traps we may end
  85  * up with a tagged userland pointer. Clear the tag to get a sane pointer to
  86  * pass on to access_ok(), for instance.
  87  */
  88 #define untagged_addr(addr)             sign_extend64(addr, 55)
  89
  90 #define access_ok(type, 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 ttbr;
 106
 107         /* reserved_ttbr0 placed at the end of swapper_pg_dir */
 108         ttbr = read_sysreg(ttbr1_el1) + SWAPPER_DIR_SIZE;
 109         write_sysreg(ttbr, ttbr0_el1);
 110         isb();
 111 }
 112
 113 static inline void __uaccess_ttbr0_enable(void)
 114 {
 115         unsigned long flags;
 116
 117         /*
 118          * Disable interrupts to avoid preemption between reading the 'ttbr0'
 119          * variable and the MSR. A context switch could trigger an ASID
 120          * roll-over and an update of 'ttbr0'.
 121          */
 122         local_irq_save(flags);
 123         write_sysreg(current_thread_info()->ttbr0, ttbr0_el1);
 124         isb();
 125         local_irq_restore(flags);
 126 }
 127
 128 static inline bool uaccess_ttbr0_disable(void)
 129 {
 130         if (!system_uses_ttbr0_pan())
 131                 return false;
 132         __uaccess_ttbr0_disable();
 133         return true;
 134 }
 135
 136 static inline bool uaccess_ttbr0_enable(void)
 137 {
 138         if (!system_uses_ttbr0_pan())
 139                 return false;
 140         __uaccess_ttbr0_enable();
 141         return true;
 142 }
 143 #else
 144 static inline bool uaccess_ttbr0_disable(void)
 145 {
 146         return false;
 147 }
 148
 149 static inline bool uaccess_ttbr0_enable(void)
 150 {
 151         return false;
 152 }
 153 #endif
 154
 155 #define __uaccess_disable(alt)                                          \
 156 do {                                                                    \
 157         if (!uaccess_ttbr0_disable())                                   \
 158                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt,          \
 159                                 CONFIG_ARM64_PAN));                     \
 160 } while (0)
 161
 162 #define __uaccess_enable(alt)                                           \
 163 do {                                                                    \
 164         if (!uaccess_ttbr0_enable())                                    \
 165                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt,          \
 166                                 CONFIG_ARM64_PAN));                     \
 167 } while (0)
 168
 169 static inline void uaccess_disable(void)
 170 {
 171         __uaccess_disable(ARM64_HAS_PAN);
 172 }
 173
 174 static inline void uaccess_enable(void)
 175 {
 176         __uaccess_enable(ARM64_HAS_PAN);
 177 }
 178
 179 /*
 180  * These functions are no-ops when UAO is present.
 181  */
 182 static inline void uaccess_disable_not_uao(void)
 183 {
 184         __uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
 185 }
 186
 187 static inline void uaccess_enable_not_uao(void)
 188 {
 189         __uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
 190 }
 191
 192 /*
 193  * The "__xxx" versions of the user access functions do not verify the address
 194  * space - it must have been done previously with a separate "access_ok()"
 195  * call.
 196  *
 197  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 198  * occurs, and leave it unchanged on success.
 199  */
 200 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 201         asm volatile(                                                   \
 202         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 203                         alt_instr " " reg "1, [%2]\n", feature)         \
 204         "2:\n"                                                          \
 205         "       .section .fixup, \"ax\"\n"                              \
 206         "       .align  2\n"                                            \
 207         "3:     mov     %w0, %3\n"                                      \
 208         "       mov     %1, #0\n"                                       \
 209         "       b       2b\n"                                           \
 210         "       .previous\n"                                            \
 211         _ASM_EXTABLE(1b, 3b)                                            \
 212         : "+r" (err), "=&r" (x)                                         \
 213         : "r" (addr), "i" (-EFAULT))
 214
 215 #define __get_user_err(x, ptr, err)                                     \
 216 do {                                                                    \
 217         unsigned long __gu_val;                                         \
 218         __chk_user_ptr(ptr);                                            \
 219         uaccess_enable_not_uao();                                       \
 220         switch (sizeof(*(ptr))) {                                       \
 221         case 1:                                                         \
 222                 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
 223                                (err), ARM64_HAS_UAO);                   \
 224                 break;                                                  \
 225         case 2:                                                         \
 226                 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
 227                                (err), ARM64_HAS_UAO);                   \
 228                 break;                                                  \
 229         case 4:                                                         \
 230                 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),    \
 231                                (err), ARM64_HAS_UAO);                   \
 232                 break;                                                  \
 233         case 8:                                                         \
 234                 __get_user_asm("ldr", "ldtr", "%x",  __gu_val, (ptr),   \
 235                                (err), ARM64_HAS_UAO);                   \
 236                 break;                                                  \
 237         default:                                                        \
 238                 BUILD_BUG();                                            \
 239         }                                                               \
 240         uaccess_disable_not_uao();                                      \
 241         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 242 } while (0)
 243
 244 #define __get_user(x, ptr)                                              \
 245 ({                                                                      \
 246         int __gu_err = 0;                                               \
 247         __get_user_err((x), (ptr), __gu_err);                           \
 248         __gu_err;                                                       \
 249 })
 250
 251 #define __get_user_error(x, ptr, err)                                   \
 252 ({                                                                      \
 253         __get_user_err((x), (ptr), (err));                              \
 254         (void)0;                                                        \
 255 })
 256
 257 #define get_user(x, ptr)                                                \
 258 ({                                                                      \
 259         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 260         might_fault();                                                  \
 261         access_ok(VERIFY_READ, __p, sizeof(*__p)) ?                     \
 262                 __get_user((x), __p) :                                  \
 263                 ((x) = 0, -EFAULT);                                     \
 264 })
 265
 266 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 267         asm volatile(                                                   \
 268         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 269                         alt_instr " " reg "1, [%2]\n", feature)         \
 270         "2:\n"                                                          \
 271         "       .section .fixup,\"ax\"\n"                               \
 272         "       .align  2\n"                                            \
 273         "3:     mov     %w0, %3\n"                                      \
 274         "       b       2b\n"                                           \
 275         "       .previous\n"                                            \
 276         _ASM_EXTABLE(1b, 3b)                                            \
 277         : "+r" (err)                                                    \
 278         : "r" (x), "r" (addr), "i" (-EFAULT))
 279
 280 #define __put_user_err(x, ptr, err)                                     \
 281 do {                                                                    \
 282         __typeof__(*(ptr)) __pu_val = (x);                              \
 283         __chk_user_ptr(ptr);                                            \
 284         uaccess_enable_not_uao();                                       \
 285         switch (sizeof(*(ptr))) {                                       \
 286         case 1:                                                         \
 287                 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr),  \
 288                                (err), ARM64_HAS_UAO);                   \
 289                 break;                                                  \
 290         case 2:                                                         \
 291                 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr),  \
 292                                (err), ARM64_HAS_UAO);                   \
 293                 break;                                                  \
 294         case 4:                                                         \
 295                 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr),    \
 296                                (err), ARM64_HAS_UAO);                   \
 297                 break;                                                  \
 298         case 8:                                                         \
 299                 __put_user_asm("str", "sttr", "%x", __pu_val, (ptr),    \
 300                                (err), ARM64_HAS_UAO);                   \
 301                 break;                                                  \
 302         default:                                                        \
 303                 BUILD_BUG();                                            \
 304         }                                                               \
 305         uaccess_disable_not_uao();                                      \
 306 } while (0)
 307
 308 #define __put_user(x, ptr)                                              \
 309 ({                                                                      \
 310         int __pu_err = 0;                                               \
 311         __put_user_err((x), (ptr), __pu_err);                           \
 312         __pu_err;                                                       \
 313 })
 314
 315 #define __put_user_error(x, ptr, err)                                   \
 316 ({                                                                      \
 317         __put_user_err((x), (ptr), (err));                              \
 318         (void)0;                                                        \
 319 })
 320
 321 #define put_user(x, ptr)                                                \
 322 ({                                                                      \
 323         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 324         might_fault();                                                  \
 325         access_ok(VERIFY_WRITE, __p, sizeof(*__p)) ?                    \
 326                 __put_user((x), __p) :                                  \
 327                 -EFAULT;                                                \
 328 })
 329
 330 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 331 #define raw_copy_from_user __arch_copy_from_user
 332 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 333 #define raw_copy_to_user __arch_copy_to_user
 334 extern unsigned long __must_check raw_copy_in_user(void __user *to, const void __user *from, unsigned long n);
 335 extern unsigned long __must_check __clear_user(void __user *addr, unsigned long n);
 336 #define INLINE_COPY_TO_USER
 337 #define INLINE_COPY_FROM_USER
 338
 339 static inline unsigned long __must_check clear_user(void __user *to, unsigned long n)
 340 {
 341         if (access_ok(VERIFY_WRITE, to, n))
 342                 n = __clear_user(to, n);
 343         return n;
 344 }
 345
 346 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 347
 348 extern __must_check long strnlen_user(const char __user *str, long n);
 349
 350 #endif /* __ASM_UACCESS_H */