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         /* On user-mode return, check fs is correct */
  49         set_thread_flag(TIF_FSCHECK);
  50
  51         /*
  52          * Enable/disable UAO so that copy_to_user() etc can access
  53          * kernel memory with the unprivileged instructions.
  54          */
  55         if (IS_ENABLED(CONFIG_ARM64_UAO) && fs == KERNEL_DS)
  56                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
  57         else
  58                 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
  59                                 CONFIG_ARM64_UAO));
  60 }
  61
  62 #define segment_eq(a, b)        ((a) == (b))
  63
  64 /*
  65  * Test whether a block of memory is a valid user space address.
  66  * Returns 1 if the range is valid, 0 otherwise.
  67  *
  68  * This is equivalent to the following test:
  69  * (u65)addr + (u65)size <= current->addr_limit
  70  *
  71  * This needs 65-bit arithmetic.
  72  */
  73 #define __range_ok(addr, size)                                          \
  74 ({                                                                      \
  75         unsigned long __addr = (unsigned long)(addr);                   \
  76         unsigned long flag, roksum;                                     \
  77         __chk_user_ptr(addr);                                           \
  78         asm("adds %1, %1, %3; ccmp %1, %4, #2, cc; cset %0, ls"         \
  79                 : "=&r" (flag), "=&r" (roksum)                          \
  80                 : "1" (__addr), "Ir" (size),                            \
  81                   "r" (current_thread_info()->addr_limit)               \
  82                 : "cc");                                                \
  83         flag;                                                           \
  84 })
  85
  86 /*
  87  * When dealing with data aborts, watchpoints, or instruction traps we may end
  88  * up with a tagged userland pointer. Clear the tag to get a sane pointer to
  89  * pass on to access_ok(), for instance.
  90  */
  91 #define untagged_addr(addr)             sign_extend64(addr, 55)
  92
  93 #define access_ok(type, addr, size)     __range_ok(addr, size)
  94 #define user_addr_max                   get_fs
  95
  96 #define _ASM_EXTABLE(from, to)                                          \
  97         "       .pushsection    __ex_table, \"a\"\n"                    \
  98         "       .align          3\n"                                    \
  99         "       .long           (" #from " - .), (" #to " - .)\n"       \
 100         "       .popsection\n"
 101
 102 /*
 103  * User access enabling/disabling.
 104  */
 105 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
 106 static inline void __uaccess_ttbr0_disable(void)
 107 {
 108         unsigned long ttbr;
 109
 110         /* reserved_ttbr0 placed at the end of swapper_pg_dir */
 111         ttbr = read_sysreg(ttbr1_el1) + SWAPPER_DIR_SIZE;
 112         write_sysreg(ttbr, ttbr0_el1);
 113         isb();
 114 }
 115
 116 static inline void __uaccess_ttbr0_enable(void)
 117 {
 118         unsigned long flags;
 119
 120         /*
 121          * Disable interrupts to avoid preemption between reading the 'ttbr0'
 122          * variable and the MSR. A context switch could trigger an ASID
 123          * roll-over and an update of 'ttbr0'.
 124          */
 125         local_irq_save(flags);
 126         write_sysreg(current_thread_info()->ttbr0, ttbr0_el1);
 127         isb();
 128         local_irq_restore(flags);
 129 }
 130
 131 static inline bool uaccess_ttbr0_disable(void)
 132 {
 133         if (!system_uses_ttbr0_pan())
 134                 return false;
 135         __uaccess_ttbr0_disable();
 136         return true;
 137 }
 138
 139 static inline bool uaccess_ttbr0_enable(void)
 140 {
 141         if (!system_uses_ttbr0_pan())
 142                 return false;
 143         __uaccess_ttbr0_enable();
 144         return true;
 145 }
 146 #else
 147 static inline bool uaccess_ttbr0_disable(void)
 148 {
 149         return false;
 150 }
 151
 152 static inline bool uaccess_ttbr0_enable(void)
 153 {
 154         return false;
 155 }
 156 #endif
 157
 158 #define __uaccess_disable(alt)                                          \
 159 do {                                                                    \
 160         if (!uaccess_ttbr0_disable())                                   \
 161                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt,          \
 162                                 CONFIG_ARM64_PAN));                     \
 163 } while (0)
 164
 165 #define __uaccess_enable(alt)                                           \
 166 do {                                                                    \
 167         if (!uaccess_ttbr0_enable())                                    \
 168                 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt,          \
 169                                 CONFIG_ARM64_PAN));                     \
 170 } while (0)
 171
 172 static inline void uaccess_disable(void)
 173 {
 174         __uaccess_disable(ARM64_HAS_PAN);
 175 }
 176
 177 static inline void uaccess_enable(void)
 178 {
 179         __uaccess_enable(ARM64_HAS_PAN);
 180 }
 181
 182 /*
 183  * These functions are no-ops when UAO is present.
 184  */
 185 static inline void uaccess_disable_not_uao(void)
 186 {
 187         __uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
 188 }
 189
 190 static inline void uaccess_enable_not_uao(void)
 191 {
 192         __uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
 193 }
 194
 195 /*
 196  * The "__xxx" versions of the user access functions do not verify the address
 197  * space - it must have been done previously with a separate "access_ok()"
 198  * call.
 199  *
 200  * The "__xxx_error" versions set the third argument to -EFAULT if an error
 201  * occurs, and leave it unchanged on success.
 202  */
 203 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 204         asm volatile(                                                   \
 205         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 206                         alt_instr " " reg "1, [%2]\n", feature)         \
 207         "2:\n"                                                          \
 208         "       .section .fixup, \"ax\"\n"                              \
 209         "       .align  2\n"                                            \
 210         "3:     mov     %w0, %3\n"                                      \
 211         "       mov     %1, #0\n"                                       \
 212         "       b       2b\n"                                           \
 213         "       .previous\n"                                            \
 214         _ASM_EXTABLE(1b, 3b)                                            \
 215         : "+r" (err), "=&r" (x)                                         \
 216         : "r" (addr), "i" (-EFAULT))
 217
 218 #define __get_user_err(x, ptr, err)                                     \
 219 do {                                                                    \
 220         unsigned long __gu_val;                                         \
 221         __chk_user_ptr(ptr);                                            \
 222         uaccess_enable_not_uao();                                       \
 223         switch (sizeof(*(ptr))) {                                       \
 224         case 1:                                                         \
 225                 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
 226                                (err), ARM64_HAS_UAO);                   \
 227                 break;                                                  \
 228         case 2:                                                         \
 229                 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
 230                                (err), ARM64_HAS_UAO);                   \
 231                 break;                                                  \
 232         case 4:                                                         \
 233                 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),    \
 234                                (err), ARM64_HAS_UAO);                   \
 235                 break;                                                  \
 236         case 8:                                                         \
 237                 __get_user_asm("ldr", "ldtr", "%x",  __gu_val, (ptr),   \
 238                                (err), ARM64_HAS_UAO);                   \
 239                 break;                                                  \
 240         default:                                                        \
 241                 BUILD_BUG();                                            \
 242         }                                                               \
 243         uaccess_disable_not_uao();                                      \
 244         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 245 } while (0)
 246
 247 #define __get_user(x, ptr)                                              \
 248 ({                                                                      \
 249         int __gu_err = 0;                                               \
 250         __get_user_err((x), (ptr), __gu_err);                           \
 251         __gu_err;                                                       \
 252 })
 253
 254 #define __get_user_error(x, ptr, err)                                   \
 255 ({                                                                      \
 256         __get_user_err((x), (ptr), (err));                              \
 257         (void)0;                                                        \
 258 })
 259
 260 #define get_user(x, ptr)                                                \
 261 ({                                                                      \
 262         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 263         might_fault();                                                  \
 264         access_ok(VERIFY_READ, __p, sizeof(*__p)) ?                     \
 265                 __get_user((x), __p) :                                  \
 266                 ((x) = 0, -EFAULT);                                     \
 267 })
 268
 269 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)    \
 270         asm volatile(                                                   \
 271         "1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",                  \
 272                         alt_instr " " reg "1, [%2]\n", feature)         \
 273         "2:\n"                                                          \
 274         "       .section .fixup,\"ax\"\n"                               \
 275         "       .align  2\n"                                            \
 276         "3:     mov     %w0, %3\n"                                      \
 277         "       b       2b\n"                                           \
 278         "       .previous\n"                                            \
 279         _ASM_EXTABLE(1b, 3b)                                            \
 280         : "+r" (err)                                                    \
 281         : "r" (x), "r" (addr), "i" (-EFAULT))
 282
 283 #define __put_user_err(x, ptr, err)                                     \
 284 do {                                                                    \
 285         __typeof__(*(ptr)) __pu_val = (x);                              \
 286         __chk_user_ptr(ptr);                                            \
 287         uaccess_enable_not_uao();                                       \
 288         switch (sizeof(*(ptr))) {                                       \
 289         case 1:                                                         \
 290                 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr),  \
 291                                (err), ARM64_HAS_UAO);                   \
 292                 break;                                                  \
 293         case 2:                                                         \
 294                 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr),  \
 295                                (err), ARM64_HAS_UAO);                   \
 296                 break;                                                  \
 297         case 4:                                                         \
 298                 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr),    \
 299                                (err), ARM64_HAS_UAO);                   \
 300                 break;                                                  \
 301         case 8:                                                         \
 302                 __put_user_asm("str", "sttr", "%x", __pu_val, (ptr),    \
 303                                (err), ARM64_HAS_UAO);                   \
 304                 break;                                                  \
 305         default:                                                        \
 306                 BUILD_BUG();                                            \
 307         }                                                               \
 308         uaccess_disable_not_uao();                                      \
 309 } while (0)
 310
 311 #define __put_user(x, ptr)                                              \
 312 ({                                                                      \
 313         int __pu_err = 0;                                               \
 314         __put_user_err((x), (ptr), __pu_err);                           \
 315         __pu_err;                                                       \
 316 })
 317
 318 #define __put_user_error(x, ptr, err)                                   \
 319 ({                                                                      \
 320         __put_user_err((x), (ptr), (err));                              \
 321         (void)0;                                                        \
 322 })
 323
 324 #define put_user(x, ptr)                                                \
 325 ({                                                                      \
 326         __typeof__(*(ptr)) __user *__p = (ptr);                         \
 327         might_fault();                                                  \
 328         access_ok(VERIFY_WRITE, __p, sizeof(*__p)) ?                    \
 329                 __put_user((x), __p) :                                  \
 330                 -EFAULT;                                                \
 331 })
 332
 333 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 334 #define raw_copy_from_user __arch_copy_from_user
 335 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 336 #define raw_copy_to_user __arch_copy_to_user
 337 extern unsigned long __must_check raw_copy_in_user(void __user *to, const void __user *from, unsigned long n);
 338 extern unsigned long __must_check __clear_user(void __user *addr, unsigned long n);
 339 #define INLINE_COPY_TO_USER
 340 #define INLINE_COPY_FROM_USER
 341
 342 static inline unsigned long __must_check clear_user(void __user *to, unsigned long n)
 343 {
 344         if (access_ok(VERIFY_WRITE, to, n))
 345                 n = __clear_user(to, n);
 346         return n;
 347 }
 348
 349 extern long strncpy_from_user(char *dest, const char __user *src, long count);
 350
 351 extern __must_check long strnlen_user(const char __user *str, long n);
 352
 353 #endif /* __ASM_UACCESS_H */