arch/x86/include/asm/uaccess.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_X86_UACCESS_H
   3 #define _ASM_X86_UACCESS_H
   4 /*
   5  * User space memory access functions
   6  */
   7 #include <linux/compiler.h>
   8 #include <linux/kasan-checks.h>
   9 #include <linux/string.h>
  10 #include <asm/asm.h>
  11 #include <asm/page.h>
  12 #include <asm/smap.h>
  13 #include <asm/extable.h>
  14
  15 /*
  16  * The fs value determines whether argument validity checking should be
  17  * performed or not.  If get_fs() == USER_DS, checking is performed, with
  18  * get_fs() == KERNEL_DS, checking is bypassed.
  19  *
  20  * For historical reasons, these macros are grossly misnamed.
  21  */
  22
  23 #define MAKE_MM_SEG(s)  ((mm_segment_t) { (s) })
  24
  25 #define KERNEL_DS       MAKE_MM_SEG(-1UL)
  26 #define USER_DS         MAKE_MM_SEG(TASK_SIZE_MAX)
  27
  28 #define get_fs()        (current->thread.addr_limit)
  29 static inline void set_fs(mm_segment_t fs)
  30 {
  31         current->thread.addr_limit = fs;
  32         /* On user-mode return, check fs is correct */
  33         set_thread_flag(TIF_FSCHECK);
  34 }
  35
  36 #define segment_eq(a, b)        ((a).seg == (b).seg)
  37 #define user_addr_max() (current->thread.addr_limit.seg)
  38
  39 /*
  40  * Test whether a block of memory is a valid user space address.
  41  * Returns 0 if the range is valid, nonzero otherwise.
  42  */
  43 static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, unsigned long limit)
  44 {
  45         /*
  46          * If we have used "sizeof()" for the size,
  47          * we know it won't overflow the limit (but
  48          * it might overflow the 'addr', so it's
  49          * important to subtract the size from the
  50          * limit, not add it to the address).
  51          */
  52         if (__builtin_constant_p(size))
  53                 return unlikely(addr > limit - size);
  54
  55         /* Arbitrary sizes? Be careful about overflow */
  56         addr += size;
  57         if (unlikely(addr < size))
  58                 return true;
  59         return unlikely(addr > limit);
  60 }
  61
  62 #define __range_not_ok(addr, size, limit)                               \
  63 ({                                                                      \
  64         __chk_user_ptr(addr);                                           \
  65         __chk_range_not_ok((unsigned long __force)(addr), size, limit); \
  66 })
  67
  68 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
  69 static inline bool pagefault_disabled(void);
  70 # define WARN_ON_IN_IRQ()       \
  71         WARN_ON_ONCE(!in_task() && !pagefault_disabled())
  72 #else
  73 # define WARN_ON_IN_IRQ()
  74 #endif
  75
  76 /**
  77  * access_ok - Checks if a user space pointer is valid
  78  * @addr: User space pointer to start of block to check
  79  * @size: Size of block to check
  80  *
  81  * Context: User context only. This function may sleep if pagefaults are
  82  *          enabled.
  83  *
  84  * Checks if a pointer to a block of memory in user space is valid.
  85  *
  86  * Note that, depending on architecture, this function probably just
  87  * checks that the pointer is in the user space range - after calling
  88  * this function, memory access functions may still return -EFAULT.
  89  *
  90  * Return: true (nonzero) if the memory block may be valid, false (zero)
  91  * if it is definitely invalid.
  92  */
  93 #define access_ok(addr, size)                                   \
  94 ({                                                                      \
  95         WARN_ON_IN_IRQ();                                               \
  96         likely(!__range_not_ok(addr, size, user_addr_max()));           \
  97 })
  98
  99 /*
 100  * These are the main single-value transfer routines.  They automatically
 101  * use the right size if we just have the right pointer type.
 102  *
 103  * This gets kind of ugly. We want to return _two_ values in "get_user()"
 104  * and yet we don't want to do any pointers, because that is too much
 105  * of a performance impact. Thus we have a few rather ugly macros here,
 106  * and hide all the ugliness from the user.
 107  *
 108  * The "__xxx" versions of the user access functions are versions that
 109  * do not verify the address space, that must have been done previously
 110  * with a separate "access_ok()" call (this is used when we do multiple
 111  * accesses to the same area of user memory).
 112  */
 113
 114 extern int __get_user_1(void);
 115 extern int __get_user_2(void);
 116 extern int __get_user_4(void);
 117 extern int __get_user_8(void);
 118 extern int __get_user_bad(void);
 119
 120 #define __uaccess_begin() stac()
 121 #define __uaccess_end()   clac()
 122 #define __uaccess_begin_nospec()        \
 123 ({                                      \
 124         stac();                         \
 125         barrier_nospec();               \
 126 })
 127
 128 /*
 129  * This is a type: either unsigned long, if the argument fits into
 130  * that type, or otherwise unsigned long long.
 131  */
 132 #define __inttype(x) \
 133 __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
 134
 135 /**
 136  * get_user - Get a simple variable from user space.
 137  * @x:   Variable to store result.
 138  * @ptr: Source address, in user space.
 139  *
 140  * Context: User context only. This function may sleep if pagefaults are
 141  *          enabled.
 142  *
 143  * This macro copies a single simple variable from user space to kernel
 144  * space.  It supports simple types like char and int, but not larger
 145  * data types like structures or arrays.
 146  *
 147  * @ptr must have pointer-to-simple-variable type, and the result of
 148  * dereferencing @ptr must be assignable to @x without a cast.
 149  *
 150  * Return: zero on success, or -EFAULT on error.
 151  * On error, the variable @x is set to zero.
 152  */
 153 /*
 154  * Careful: we have to cast the result to the type of the pointer
 155  * for sign reasons.
 156  *
 157  * The use of _ASM_DX as the register specifier is a bit of a
 158  * simplification, as gcc only cares about it as the starting point
 159  * and not size: for a 64-bit value it will use %ecx:%edx on 32 bits
 160  * (%ecx being the next register in gcc's x86 register sequence), and
 161  * %rdx on 64 bits.
 162  *
 163  * Clang/LLVM cares about the size of the register, but still wants
 164  * the base register for something that ends up being a pair.
 165  */
 166 #define get_user(x, ptr)                                                \
 167 ({                                                                      \
 168         int __ret_gu;                                                   \
 169         register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX);            \
 170         __chk_user_ptr(ptr);                                            \
 171         might_fault();                                                  \
 172         asm volatile("call __get_user_%P4"                              \
 173                      : "=a" (__ret_gu), "=r" (__val_gu),                \
 174                         ASM_CALL_CONSTRAINT                             \
 175                      : "0" (ptr), "i" (sizeof(*(ptr))));                \
 176         (x) = (__force __typeof__(*(ptr))) __val_gu;                    \
 177         __builtin_expect(__ret_gu, 0);                                  \
 178 })
 179
 180 #define __put_user_x(size, x, ptr, __ret_pu)                    \
 181         asm volatile("call __put_user_" #size : "=a" (__ret_pu) \
 182                      : "0" ((typeof(*(ptr)))(x)), "c" (ptr) : "ebx")
 183
 184
 185
 186 #ifdef CONFIG_X86_32
 187 #define __put_user_goto_u64(x, addr, label)                     \
 188         asm_volatile_goto("\n"                                  \
 189                      "1:        movl %%eax,0(%1)\n"             \
 190                      "2:        movl %%edx,4(%1)\n"             \
 191                      _ASM_EXTABLE_UA(1b, %l2)                   \
 192                      _ASM_EXTABLE_UA(2b, %l2)                   \
 193                      : : "A" (x), "r" (addr)                    \
 194                      : : label)
 195
 196 #define __put_user_x8(x, ptr, __ret_pu)                         \
 197         asm volatile("call __put_user_8" : "=a" (__ret_pu)      \
 198                      : "A" ((typeof(*(ptr)))(x)), "c" (ptr) : "ebx")
 199 #else
 200 #define __put_user_goto_u64(x, ptr, label) \
 201         __put_user_goto(x, ptr, "q", "er", label)
 202 #define __put_user_x8(x, ptr, __ret_pu) __put_user_x(8, x, ptr, __ret_pu)
 203 #endif
 204
 205 extern void __put_user_bad(void);
 206
 207 /*
 208  * Strange magic calling convention: pointer in %ecx,
 209  * value in %eax(:%edx), return value in %eax. clobbers %rbx
 210  */
 211 extern void __put_user_1(void);
 212 extern void __put_user_2(void);
 213 extern void __put_user_4(void);
 214 extern void __put_user_8(void);
 215
 216 /**
 217  * put_user - Write a simple value into user space.
 218  * @x:   Value to copy to user space.
 219  * @ptr: Destination address, in user space.
 220  *
 221  * Context: User context only. This function may sleep if pagefaults are
 222  *          enabled.
 223  *
 224  * This macro copies a single simple value from kernel space to user
 225  * space.  It supports simple types like char and int, but not larger
 226  * data types like structures or arrays.
 227  *
 228  * @ptr must have pointer-to-simple-variable type, and @x must be assignable
 229  * to the result of dereferencing @ptr.
 230  *
 231  * Return: zero on success, or -EFAULT on error.
 232  */
 233 #define put_user(x, ptr)                                        \
 234 ({                                                              \
 235         int __ret_pu;                                           \
 236         __typeof__(*(ptr)) __pu_val;                            \
 237         __chk_user_ptr(ptr);                                    \
 238         might_fault();                                          \
 239         __pu_val = x;                                           \
 240         switch (sizeof(*(ptr))) {                               \
 241         case 1:                                                 \
 242                 __put_user_x(1, __pu_val, ptr, __ret_pu);       \
 243                 break;                                          \
 244         case 2:                                                 \
 245                 __put_user_x(2, __pu_val, ptr, __ret_pu);       \
 246                 break;                                          \
 247         case 4:                                                 \
 248                 __put_user_x(4, __pu_val, ptr, __ret_pu);       \
 249                 break;                                          \
 250         case 8:                                                 \
 251                 __put_user_x8(__pu_val, ptr, __ret_pu);         \
 252                 break;                                          \
 253         default:                                                \
 254                 __put_user_x(X, __pu_val, ptr, __ret_pu);       \
 255                 break;                                          \
 256         }                                                       \
 257         __builtin_expect(__ret_pu, 0);                          \
 258 })
 259
 260 #define __put_user_size(x, ptr, size, label)                            \
 261 do {                                                                    \
 262         __chk_user_ptr(ptr);                                            \
 263         switch (size) {                                                 \
 264         case 1:                                                         \
 265                 __put_user_goto(x, ptr, "b", "iq", label);              \
 266                 break;                                                  \
 267         case 2:                                                         \
 268                 __put_user_goto(x, ptr, "w", "ir", label);              \
 269                 break;                                                  \
 270         case 4:                                                         \
 271                 __put_user_goto(x, ptr, "l", "ir", label);              \
 272                 break;                                                  \
 273         case 8:                                                         \
 274                 __put_user_goto_u64(x, ptr, label);                     \
 275                 break;                                                  \
 276         default:                                                        \
 277                 __put_user_bad();                                       \
 278         }                                                               \
 279 } while (0)
 280
 281 #ifdef CONFIG_X86_32
 282 #define __get_user_asm_u64(x, ptr, retval)                              \
 283 ({                                                                      \
 284         __typeof__(ptr) __ptr = (ptr);                                  \
 285         asm volatile("\n"                                               \
 286                      "1:        movl %2,%%eax\n"                        \
 287                      "2:        movl %3,%%edx\n"                        \
 288                      "3:\n"                                             \
 289                      ".section .fixup,\"ax\"\n"                         \
 290                      "4:        mov %4,%0\n"                            \
 291                      "  xorl %%eax,%%eax\n"                             \
 292                      "  xorl %%edx,%%edx\n"                             \
 293                      "  jmp 3b\n"                                       \
 294                      ".previous\n"                                      \
 295                      _ASM_EXTABLE_UA(1b, 4b)                            \
 296                      _ASM_EXTABLE_UA(2b, 4b)                            \
 297                      : "=r" (retval), "=&A"(x)                          \
 298                      : "m" (__m(__ptr)), "m" __m(((u32 __user *)(__ptr)) + 1),  \
 299                        "i" (-EFAULT), "0" (retval));                    \
 300 })
 301
 302 #else
 303 #define __get_user_asm_u64(x, ptr, retval) \
 304          __get_user_asm(x, ptr, retval, "q", "", "=r")
 305 #endif
 306
 307 #define __get_user_size(x, ptr, size, retval)                           \
 308 do {                                                                    \
 309         retval = 0;                                                     \
 310         __chk_user_ptr(ptr);                                            \
 311         switch (size) {                                                 \
 312         case 1:                                                         \
 313                 __get_user_asm(x, ptr, retval, "b", "b", "=q");         \
 314                 break;                                                  \
 315         case 2:                                                         \
 316                 __get_user_asm(x, ptr, retval, "w", "w", "=r");         \
 317                 break;                                                  \
 318         case 4:                                                         \
 319                 __get_user_asm(x, ptr, retval, "l", "k", "=r");         \
 320                 break;                                                  \
 321         case 8:                                                         \
 322                 __get_user_asm_u64(x, ptr, retval);                     \
 323                 break;                                                  \
 324         default:                                                        \
 325                 (x) = __get_user_bad();                                 \
 326         }                                                               \
 327 } while (0)
 328
 329 #define __get_user_asm(x, addr, err, itype, rtype, ltype)               \
 330         asm volatile("\n"                                               \
 331                      "1:        mov"itype" %2,%"rtype"1\n"              \
 332                      "2:\n"                                             \
 333                      ".section .fixup,\"ax\"\n"                         \
 334                      "3:        mov %3,%0\n"                            \
 335                      "  xor"itype" %"rtype"1,%"rtype"1\n"               \
 336                      "  jmp 2b\n"                                       \
 337                      ".previous\n"                                      \
 338                      _ASM_EXTABLE_UA(1b, 3b)                            \
 339                      : "=r" (err), ltype(x)                             \
 340                      : "m" (__m(addr)), "i" (-EFAULT), "0" (err))
 341
 342 #define __put_user_nocheck(x, ptr, size)                        \
 343 ({                                                              \
 344         __label__ __pu_label;                                   \
 345         int __pu_err = -EFAULT;                                 \
 346         __typeof__(*(ptr)) __pu_val = (x);                      \
 347         __typeof__(ptr) __pu_ptr = (ptr);                       \
 348         __typeof__(size) __pu_size = (size);                    \
 349         __uaccess_begin();                                      \
 350         __put_user_size(__pu_val, __pu_ptr, __pu_size, __pu_label);     \
 351         __pu_err = 0;                                           \
 352 __pu_label:                                                     \
 353         __uaccess_end();                                        \
 354         __builtin_expect(__pu_err, 0);                          \
 355 })
 356
 357 #define __get_user_nocheck(x, ptr, size)                                \
 358 ({                                                                      \
 359         int __gu_err;                                                   \
 360         __inttype(*(ptr)) __gu_val;                                     \
 361         __typeof__(ptr) __gu_ptr = (ptr);                               \
 362         __typeof__(size) __gu_size = (size);                            \
 363         __uaccess_begin_nospec();                                       \
 364         __get_user_size(__gu_val, __gu_ptr, __gu_size, __gu_err);       \
 365         __uaccess_end();                                                \
 366         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 367         __builtin_expect(__gu_err, 0);                                  \
 368 })
 369
 370 /* FIXME: this hack is definitely wrong -AK */
 371 struct __large_struct { unsigned long buf[100]; };
 372 #define __m(x) (*(struct __large_struct __user *)(x))
 373
 374 /*
 375  * Tell gcc we read from memory instead of writing: this is because
 376  * we do not write to any memory gcc knows about, so there are no
 377  * aliasing issues.
 378  */
 379 #define __put_user_goto(x, addr, itype, ltype, label)                   \
 380         asm_volatile_goto("\n"                                          \
 381                 "1:     mov"itype" %0,%1\n"                             \
 382                 _ASM_EXTABLE_UA(1b, %l2)                                \
 383                 : : ltype(x), "m" (__m(addr))                           \
 384                 : : label)
 385
 386 /**
 387  * __get_user - Get a simple variable from user space, with less checking.
 388  * @x:   Variable to store result.
 389  * @ptr: Source address, in user space.
 390  *
 391  * Context: User context only. This function may sleep if pagefaults are
 392  *          enabled.
 393  *
 394  * This macro copies a single simple variable from user space to kernel
 395  * space.  It supports simple types like char and int, but not larger
 396  * data types like structures or arrays.
 397  *
 398  * @ptr must have pointer-to-simple-variable type, and the result of
 399  * dereferencing @ptr must be assignable to @x without a cast.
 400  *
 401  * Caller must check the pointer with access_ok() before calling this
 402  * function.
 403  *
 404  * Return: zero on success, or -EFAULT on error.
 405  * On error, the variable @x is set to zero.
 406  */
 407
 408 #define __get_user(x, ptr)                                              \
 409         __get_user_nocheck((x), (ptr), sizeof(*(ptr)))
 410
 411 /**
 412  * __put_user - Write a simple value into user space, with less checking.
 413  * @x:   Value to copy to user space.
 414  * @ptr: Destination address, in user space.
 415  *
 416  * Context: User context only. This function may sleep if pagefaults are
 417  *          enabled.
 418  *
 419  * This macro copies a single simple value from kernel space to user
 420  * space.  It supports simple types like char and int, but not larger
 421  * data types like structures or arrays.
 422  *
 423  * @ptr must have pointer-to-simple-variable type, and @x must be assignable
 424  * to the result of dereferencing @ptr.
 425  *
 426  * Caller must check the pointer with access_ok() before calling this
 427  * function.
 428  *
 429  * Return: zero on success, or -EFAULT on error.
 430  */
 431
 432 #define __put_user(x, ptr)                                              \
 433         __put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))
 434
 435 extern unsigned long
 436 copy_from_user_nmi(void *to, const void __user *from, unsigned long n);
 437 extern __must_check long
 438 strncpy_from_user(char *dst, const char __user *src, long count);
 439
 440 extern __must_check long strnlen_user(const char __user *str, long n);
 441
 442 unsigned long __must_check clear_user(void __user *mem, unsigned long len);
 443 unsigned long __must_check __clear_user(void __user *mem, unsigned long len);
 444
 445 /*
 446  * movsl can be slow when source and dest are not both 8-byte aligned
 447  */
 448 #ifdef CONFIG_X86_INTEL_USERCOPY
 449 extern struct movsl_mask {
 450         int mask;
 451 } ____cacheline_aligned_in_smp movsl_mask;
 452 #endif
 453
 454 #define ARCH_HAS_NOCACHE_UACCESS 1
 455
 456 #ifdef CONFIG_X86_32
 457 # include <asm/uaccess_32.h>
 458 #else
 459 # include <asm/uaccess_64.h>
 460 #endif
 461
 462 /*
 463  * The "unsafe" user accesses aren't really "unsafe", but the naming
 464  * is a big fat warning: you have to not only do the access_ok()
 465  * checking before using them, but you have to surround them with the
 466  * user_access_begin/end() pair.
 467  */
 468 static __must_check __always_inline bool user_access_begin(const void __user *ptr, size_t len)
 469 {
 470         if (unlikely(!access_ok(ptr,len)))
 471                 return 0;
 472         __uaccess_begin_nospec();
 473         return 1;
 474 }
 475 #define user_access_begin(a,b)  user_access_begin(a,b)
 476 #define user_access_end()       __uaccess_end()
 477
 478 #define user_access_save()      smap_save()
 479 #define user_access_restore(x)  smap_restore(x)
 480
 481 #define unsafe_put_user(x, ptr, label)  \
 482         __put_user_size((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)), label)
 483
 484 #define unsafe_get_user(x, ptr, err_label)                                      \
 485 do {                                                                            \
 486         int __gu_err;                                                           \
 487         __inttype(*(ptr)) __gu_val;                                             \
 488         __get_user_size(__gu_val, (ptr), sizeof(*(ptr)), __gu_err);             \
 489         (x) = (__force __typeof__(*(ptr)))__gu_val;                             \
 490         if (unlikely(__gu_err)) goto err_label;                                 \
 491 } while (0)
 492
 493 /*
 494  * We want the unsafe accessors to always be inlined and use
 495  * the error labels - thus the macro games.
 496  */
 497 #define unsafe_copy_loop(dst, src, len, type, label)                    \
 498         while (len >= sizeof(type)) {                                   \
 499                 unsafe_put_user(*(type *)src,(type __user *)dst,label); \
 500                 dst += sizeof(type);                                    \
 501                 src += sizeof(type);                                    \
 502                 len -= sizeof(type);                                    \
 503         }
 504
 505 #define unsafe_copy_to_user(_dst,_src,_len,label)                       \
 506 do {                                                                    \
 507         char __user *__ucu_dst = (_dst);                                \
 508         const char *__ucu_src = (_src);                                 \
 509         size_t __ucu_len = (_len);                                      \
 510         unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u64, label);  \
 511         unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u32, label);  \
 512         unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u16, label);  \
 513         unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u8, label);   \
 514 } while (0)
 515
 516 #endif /* _ASM_X86_UACCESS_H */
 517