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 the smallest unsigned integer type that can fit a value
 130  * (up to 'long long')
 131  */
 132 #define __inttype(x) __typeof__(                \
 133         __typefits(x,char,                      \
 134           __typefits(x,short,                   \
 135             __typefits(x,int,                   \
 136               __typefits(x,long,0ULL)))))
 137
 138 #define __typefits(x,type,not) \
 139         __builtin_choose_expr(sizeof(x)<=sizeof(type),(unsigned type)0,not)
 140
 141 /**
 142  * get_user - Get a simple variable from user space.
 143  * @x:   Variable to store result.
 144  * @ptr: Source address, in user space.
 145  *
 146  * Context: User context only. This function may sleep if pagefaults are
 147  *          enabled.
 148  *
 149  * This macro copies a single simple variable from user space to kernel
 150  * space.  It supports simple types like char and int, but not larger
 151  * data types like structures or arrays.
 152  *
 153  * @ptr must have pointer-to-simple-variable type, and the result of
 154  * dereferencing @ptr must be assignable to @x without a cast.
 155  *
 156  * Return: zero on success, or -EFAULT on error.
 157  * On error, the variable @x is set to zero.
 158  */
 159 /*
 160  * Careful: we have to cast the result to the type of the pointer
 161  * for sign reasons.
 162  *
 163  * The use of _ASM_DX as the register specifier is a bit of a
 164  * simplification, as gcc only cares about it as the starting point
 165  * and not size: for a 64-bit value it will use %ecx:%edx on 32 bits
 166  * (%ecx being the next register in gcc's x86 register sequence), and
 167  * %rdx on 64 bits.
 168  *
 169  * Clang/LLVM cares about the size of the register, but still wants
 170  * the base register for something that ends up being a pair.
 171  */
 172 #define get_user(x, ptr)                                                \
 173 ({                                                                      \
 174         int __ret_gu;                                                   \
 175         register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX);            \
 176         __chk_user_ptr(ptr);                                            \
 177         might_fault();                                                  \
 178         asm volatile("call __get_user_%P4"                              \
 179                      : "=a" (__ret_gu), "=r" (__val_gu),                \
 180                         ASM_CALL_CONSTRAINT                             \
 181                      : "0" (ptr), "i" (sizeof(*(ptr))));                \
 182         (x) = (__force __typeof__(*(ptr))) __val_gu;                    \
 183         __builtin_expect(__ret_gu, 0);                                  \
 184 })
 185
 186 #define __put_user_x(size, x, ptr, __ret_pu)                    \
 187         asm volatile("call __put_user_" #size : "=a" (__ret_pu) \
 188                      : "0" ((typeof(*(ptr)))(x)), "c" (ptr) : "ebx")
 189
 190
 191
 192 #ifdef CONFIG_X86_32
 193 #define __put_user_goto_u64(x, addr, label)                     \
 194         asm_volatile_goto("\n"                                  \
 195                      "1:        movl %%eax,0(%1)\n"             \
 196                      "2:        movl %%edx,4(%1)\n"             \
 197                      _ASM_EXTABLE_UA(1b, %l2)                   \
 198                      _ASM_EXTABLE_UA(2b, %l2)                   \
 199                      : : "A" (x), "r" (addr)                    \
 200                      : : label)
 201
 202 #define __put_user_x8(x, ptr, __ret_pu)                         \
 203         asm volatile("call __put_user_8" : "=a" (__ret_pu)      \
 204                      : "A" ((typeof(*(ptr)))(x)), "c" (ptr) : "ebx")
 205 #else
 206 #define __put_user_goto_u64(x, ptr, label) \
 207         __put_user_goto(x, ptr, "q", "er", label)
 208 #define __put_user_x8(x, ptr, __ret_pu) __put_user_x(8, x, ptr, __ret_pu)
 209 #endif
 210
 211 extern void __put_user_bad(void);
 212
 213 /*
 214  * Strange magic calling convention: pointer in %ecx,
 215  * value in %eax(:%edx), return value in %eax. clobbers %rbx
 216  */
 217 extern void __put_user_1(void);
 218 extern void __put_user_2(void);
 219 extern void __put_user_4(void);
 220 extern void __put_user_8(void);
 221
 222 /**
 223  * put_user - Write a simple value into user space.
 224  * @x:   Value to copy to user space.
 225  * @ptr: Destination address, in user space.
 226  *
 227  * Context: User context only. This function may sleep if pagefaults are
 228  *          enabled.
 229  *
 230  * This macro copies a single simple value from kernel space to user
 231  * space.  It supports simple types like char and int, but not larger
 232  * data types like structures or arrays.
 233  *
 234  * @ptr must have pointer-to-simple-variable type, and @x must be assignable
 235  * to the result of dereferencing @ptr.
 236  *
 237  * Return: zero on success, or -EFAULT on error.
 238  */
 239 #define put_user(x, ptr)                                        \
 240 ({                                                              \
 241         int __ret_pu;                                           \
 242         __typeof__(*(ptr)) __pu_val;                            \
 243         __chk_user_ptr(ptr);                                    \
 244         might_fault();                                          \
 245         __pu_val = x;                                           \
 246         switch (sizeof(*(ptr))) {                               \
 247         case 1:                                                 \
 248                 __put_user_x(1, __pu_val, ptr, __ret_pu);       \
 249                 break;                                          \
 250         case 2:                                                 \
 251                 __put_user_x(2, __pu_val, ptr, __ret_pu);       \
 252                 break;                                          \
 253         case 4:                                                 \
 254                 __put_user_x(4, __pu_val, ptr, __ret_pu);       \
 255                 break;                                          \
 256         case 8:                                                 \
 257                 __put_user_x8(__pu_val, ptr, __ret_pu);         \
 258                 break;                                          \
 259         default:                                                \
 260                 __put_user_x(X, __pu_val, ptr, __ret_pu);       \
 261                 break;                                          \
 262         }                                                       \
 263         __builtin_expect(__ret_pu, 0);                          \
 264 })
 265
 266 #define __put_user_size(x, ptr, size, label)                            \
 267 do {                                                                    \
 268         __chk_user_ptr(ptr);                                            \
 269         switch (size) {                                                 \
 270         case 1:                                                         \
 271                 __put_user_goto(x, ptr, "b", "iq", label);              \
 272                 break;                                                  \
 273         case 2:                                                         \
 274                 __put_user_goto(x, ptr, "w", "ir", label);              \
 275                 break;                                                  \
 276         case 4:                                                         \
 277                 __put_user_goto(x, ptr, "l", "ir", label);              \
 278                 break;                                                  \
 279         case 8:                                                         \
 280                 __put_user_goto_u64(x, ptr, label);                     \
 281                 break;                                                  \
 282         default:                                                        \
 283                 __put_user_bad();                                       \
 284         }                                                               \
 285 } while (0)
 286
 287 #ifdef CONFIG_X86_32
 288 #define __get_user_asm_u64(x, ptr, retval)                              \
 289 ({                                                                      \
 290         __typeof__(ptr) __ptr = (ptr);                                  \
 291         asm volatile("\n"                                               \
 292                      "1:        movl %[lowbits],%%eax\n"                \
 293                      "2:        movl %[highbits],%%edx\n"               \
 294                      "3:\n"                                             \
 295                      ".section .fixup,\"ax\"\n"                         \
 296                      "4:        mov %[efault],%[errout]\n"              \
 297                      "  xorl %%eax,%%eax\n"                             \
 298                      "  xorl %%edx,%%edx\n"                             \
 299                      "  jmp 3b\n"                                       \
 300                      ".previous\n"                                      \
 301                      _ASM_EXTABLE_UA(1b, 4b)                            \
 302                      _ASM_EXTABLE_UA(2b, 4b)                            \
 303                      : [errout] "=r" (retval),                          \
 304                        [output] "=&A"(x)                                \
 305                      : [lowbits] "m" (__m(__ptr)),                      \
 306                        [highbits] "m" __m(((u32 __user *)(__ptr)) + 1), \
 307                        [efault] "i" (-EFAULT), "0" (retval));           \
 308 })
 309
 310 #else
 311 #define __get_user_asm_u64(x, ptr, retval) \
 312          __get_user_asm(x, ptr, retval, "q", "=r")
 313 #endif
 314
 315 #define __get_user_size(x, ptr, size, retval)                           \
 316 do {                                                                    \
 317         retval = 0;                                                     \
 318         __chk_user_ptr(ptr);                                            \
 319         switch (size) {                                                 \
 320         case 1:                                                         \
 321                 __get_user_asm(x, ptr, retval, "b", "=q");              \
 322                 break;                                                  \
 323         case 2:                                                         \
 324                 __get_user_asm(x, ptr, retval, "w", "=r");              \
 325                 break;                                                  \
 326         case 4:                                                         \
 327                 __get_user_asm(x, ptr, retval, "l", "=r");              \
 328                 break;                                                  \
 329         case 8:                                                         \
 330                 __get_user_asm_u64(x, ptr, retval);                     \
 331                 break;                                                  \
 332         default:                                                        \
 333                 (x) = __get_user_bad();                                 \
 334         }                                                               \
 335 } while (0)
 336
 337 #define __get_user_asm(x, addr, err, itype, ltype)                      \
 338         asm volatile("\n"                                               \
 339                      "1:        mov"itype" %[umem],%[output]\n"         \
 340                      "2:\n"                                             \
 341                      ".section .fixup,\"ax\"\n"                         \
 342                      "3:        mov %[efault],%[errout]\n"              \
 343                      "  xor"itype" %[output],%[output]\n"               \
 344                      "  jmp 2b\n"                                       \
 345                      ".previous\n"                                      \
 346                      _ASM_EXTABLE_UA(1b, 3b)                            \
 347                      : [errout] "=r" (err),                             \
 348                        [output] ltype(x)                                \
 349                      : [umem] "m" (__m(addr)),                          \
 350                        [efault] "i" (-EFAULT), "0" (err))
 351
 352 #define __put_user_nocheck(x, ptr, size)                        \
 353 ({                                                              \
 354         __label__ __pu_label;                                   \
 355         int __pu_err = -EFAULT;                                 \
 356         __typeof__(*(ptr)) __pu_val = (x);                      \
 357         __typeof__(ptr) __pu_ptr = (ptr);                       \
 358         __typeof__(size) __pu_size = (size);                    \
 359         __uaccess_begin();                                      \
 360         __put_user_size(__pu_val, __pu_ptr, __pu_size, __pu_label);     \
 361         __pu_err = 0;                                           \
 362 __pu_label:                                                     \
 363         __uaccess_end();                                        \
 364         __builtin_expect(__pu_err, 0);                          \
 365 })
 366
 367 #define __get_user_nocheck(x, ptr, size)                                \
 368 ({                                                                      \
 369         int __gu_err;                                                   \
 370         __inttype(*(ptr)) __gu_val;                                     \
 371         __typeof__(ptr) __gu_ptr = (ptr);                               \
 372         __typeof__(size) __gu_size = (size);                            \
 373         __uaccess_begin_nospec();                                       \
 374         __get_user_size(__gu_val, __gu_ptr, __gu_size, __gu_err);       \
 375         __uaccess_end();                                                \
 376         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 377         __builtin_expect(__gu_err, 0);                                  \
 378 })
 379
 380 /* FIXME: this hack is definitely wrong -AK */
 381 struct __large_struct { unsigned long buf[100]; };
 382 #define __m(x) (*(struct __large_struct __user *)(x))
 383
 384 /*
 385  * Tell gcc we read from memory instead of writing: this is because
 386  * we do not write to any memory gcc knows about, so there are no
 387  * aliasing issues.
 388  */
 389 #define __put_user_goto(x, addr, itype, ltype, label)                   \
 390         asm_volatile_goto("\n"                                          \
 391                 "1:     mov"itype" %0,%1\n"                             \
 392                 _ASM_EXTABLE_UA(1b, %l2)                                \
 393                 : : ltype(x), "m" (__m(addr))                           \
 394                 : : label)
 395
 396 /**
 397  * __get_user - Get a simple variable from user space, with less checking.
 398  * @x:   Variable to store result.
 399  * @ptr: Source address, in user space.
 400  *
 401  * Context: User context only. This function may sleep if pagefaults are
 402  *          enabled.
 403  *
 404  * This macro copies a single simple variable from user space to kernel
 405  * space.  It supports simple types like char and int, but not larger
 406  * data types like structures or arrays.
 407  *
 408  * @ptr must have pointer-to-simple-variable type, and the result of
 409  * dereferencing @ptr must be assignable to @x without a cast.
 410  *
 411  * Caller must check the pointer with access_ok() before calling this
 412  * function.
 413  *
 414  * Return: zero on success, or -EFAULT on error.
 415  * On error, the variable @x is set to zero.
 416  */
 417
 418 #define __get_user(x, ptr)                                              \
 419         __get_user_nocheck((x), (ptr), sizeof(*(ptr)))
 420
 421 /**
 422  * __put_user - Write a simple value into user space, with less checking.
 423  * @x:   Value to copy to user space.
 424  * @ptr: Destination address, in user space.
 425  *
 426  * Context: User context only. This function may sleep if pagefaults are
 427  *          enabled.
 428  *
 429  * This macro copies a single simple value from kernel space to user
 430  * space.  It supports simple types like char and int, but not larger
 431  * data types like structures or arrays.
 432  *
 433  * @ptr must have pointer-to-simple-variable type, and @x must be assignable
 434  * to the result of dereferencing @ptr.
 435  *
 436  * Caller must check the pointer with access_ok() before calling this
 437  * function.
 438  *
 439  * Return: zero on success, or -EFAULT on error.
 440  */
 441
 442 #define __put_user(x, ptr)                                              \
 443         __put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))
 444
 445 extern unsigned long
 446 copy_from_user_nmi(void *to, const void __user *from, unsigned long n);
 447 extern __must_check long
 448 strncpy_from_user(char *dst, const char __user *src, long count);
 449
 450 extern __must_check long strnlen_user(const char __user *str, long n);
 451
 452 unsigned long __must_check clear_user(void __user *mem, unsigned long len);
 453 unsigned long __must_check __clear_user(void __user *mem, unsigned long len);
 454
 455 /*
 456  * movsl can be slow when source and dest are not both 8-byte aligned
 457  */
 458 #ifdef CONFIG_X86_INTEL_USERCOPY
 459 extern struct movsl_mask {
 460         int mask;
 461 } ____cacheline_aligned_in_smp movsl_mask;
 462 #endif
 463
 464 #define ARCH_HAS_NOCACHE_UACCESS 1
 465
 466 #ifdef CONFIG_X86_32
 467 # include <asm/uaccess_32.h>
 468 #else
 469 # include <asm/uaccess_64.h>
 470 #endif
 471
 472 /*
 473  * The "unsafe" user accesses aren't really "unsafe", but the naming
 474  * is a big fat warning: you have to not only do the access_ok()
 475  * checking before using them, but you have to surround them with the
 476  * user_access_begin/end() pair.
 477  */
 478 static __must_check __always_inline bool user_access_begin(const void __user *ptr, size_t len)
 479 {
 480         if (unlikely(!access_ok(ptr,len)))
 481                 return 0;
 482         __uaccess_begin_nospec();
 483         return 1;
 484 }
 485 #define user_access_begin(a,b)  user_access_begin(a,b)
 486 #define user_access_end()       __uaccess_end()
 487
 488 #define user_access_save()      smap_save()
 489 #define user_access_restore(x)  smap_restore(x)
 490
 491 #define unsafe_put_user(x, ptr, label)  \
 492         __put_user_size((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)), label)
 493
 494 #define unsafe_get_user(x, ptr, err_label)                                      \
 495 do {                                                                            \
 496         int __gu_err;                                                           \
 497         __inttype(*(ptr)) __gu_val;                                             \
 498         __get_user_size(__gu_val, (ptr), sizeof(*(ptr)), __gu_err);             \
 499         (x) = (__force __typeof__(*(ptr)))__gu_val;                             \
 500         if (unlikely(__gu_err)) goto err_label;                                 \
 501 } while (0)
 502
 503 /*
 504  * We want the unsafe accessors to always be inlined and use
 505  * the error labels - thus the macro games.
 506  */
 507 #define unsafe_copy_loop(dst, src, len, type, label)                            \
 508         while (len >= sizeof(type)) {                                           \
 509                 unsafe_put_user(*(type *)(src),(type __user *)(dst),label);     \
 510                 dst += sizeof(type);                                            \
 511                 src += sizeof(type);                                            \
 512                 len -= sizeof(type);                                            \
 513         }
 514
 515 #define unsafe_copy_to_user(_dst,_src,_len,label)                       \
 516 do {                                                                    \
 517         char __user *__ucu_dst = (_dst);                                \
 518         const char *__ucu_src = (_src);                                 \
 519         size_t __ucu_len = (_len);                                      \
 520         unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u64, label);  \
 521         unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u32, label);  \
 522         unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u16, label);  \
 523         unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u8, label);   \
 524 } while (0)
 525
 526 #define HAVE_GET_KERNEL_NOFAULT
 527
 528 #define __get_kernel_nofault(dst, src, type, err_label)                 \
 529 do {                                                                    \
 530         int __kr_err;                                                   \
 531                                                                         \
 532         __get_user_size(*((type *)(dst)), (__force type __user *)(src), \
 533                         sizeof(type), __kr_err);                        \
 534         if (unlikely(__kr_err))                                         \
 535                 goto err_label;                                         \
 536 } while (0)
 537
 538 #define __put_kernel_nofault(dst, src, type, err_label)                 \
 539         __put_user_size(*((type *)(src)), (__force type __user *)(dst), \
 540                         sizeof(type), err_label)
 541
 542 #endif /* _ASM_X86_UACCESS_H */
 543