arch/x86/include/asm/uaccess.h

   1 #ifndef _ASM_X86_UACCESS_H
   2 #define _ASM_X86_UACCESS_H
   3 /*
   4  * User space memory access functions
   5  */
   6 #include <linux/errno.h>
   7 #include <linux/compiler.h>
   8 #include <linux/thread_info.h>
   9 #include <linux/string.h>
  10 #include <asm/asm.h>
  11 #include <asm/page.h>
  12 #include <asm/smap.h>
  13
  14 #define VERIFY_READ 0
  15 #define VERIFY_WRITE 1
  16
  17 /*
  18  * The fs value determines whether argument validity checking should be
  19  * performed or not.  If get_fs() == USER_DS, checking is performed, with
  20  * get_fs() == KERNEL_DS, checking is bypassed.
  21  *
  22  * For historical reasons, these macros are grossly misnamed.
  23  */
  24
  25 #define MAKE_MM_SEG(s)  ((mm_segment_t) { (s) })
  26
  27 #define KERNEL_DS       MAKE_MM_SEG(-1UL)
  28 #define USER_DS         MAKE_MM_SEG(TASK_SIZE_MAX)
  29
  30 #define get_ds()        (KERNEL_DS)
  31 #define get_fs()        (current_thread_info()->addr_limit)
  32 #define set_fs(x)       (current_thread_info()->addr_limit = (x))
  33
  34 #define segment_eq(a, b)        ((a).seg == (b).seg)
  35
  36 #define user_addr_max() (current_thread_info()->addr_limit.seg)
  37 #define __addr_ok(addr)         \
  38         ((unsigned long __force)(addr) < user_addr_max())
  39
  40 /*
  41  * Test whether a block of memory is a valid user space address.
  42  * Returns 0 if the range is valid, nonzero otherwise.
  43  *
  44  * This is equivalent to the following test:
  45  * (u33)addr + (u33)size > (u33)current->addr_limit.seg (u65 for x86_64)
  46  *
  47  * This needs 33-bit (65-bit for x86_64) arithmetic. We have a carry...
  48  */
  49
  50 #define __range_not_ok(addr, size, limit)                               \
  51 ({                                                                      \
  52         unsigned long flag, roksum;                                     \
  53         __chk_user_ptr(addr);                                           \
  54         asm("add %3,%1 ; sbb %0,%0 ; cmp %1,%4 ; sbb $0,%0"             \
  55             : "=&r" (flag), "=r" (roksum)                               \
  56             : "1" (addr), "g" ((long)(size)),                           \
  57               "rm" (limit));                                            \
  58         flag;                                                           \
  59 })
  60
  61 /**
  62  * access_ok: - Checks if a user space pointer is valid
  63  * @type: Type of access: %VERIFY_READ or %VERIFY_WRITE.  Note that
  64  *        %VERIFY_WRITE is a superset of %VERIFY_READ - if it is safe
  65  *        to write to a block, it is always safe to read from it.
  66  * @addr: User space pointer to start of block to check
  67  * @size: Size of block to check
  68  *
  69  * Context: User context only.  This function may sleep.
  70  *
  71  * Checks if a pointer to a block of memory in user space is valid.
  72  *
  73  * Returns true (nonzero) if the memory block may be valid, false (zero)
  74  * if it is definitely invalid.
  75  *
  76  * Note that, depending on architecture, this function probably just
  77  * checks that the pointer is in the user space range - after calling
  78  * this function, memory access functions may still return -EFAULT.
  79  */
  80 #define access_ok(type, addr, size) \
  81         (likely(__range_not_ok(addr, size, user_addr_max()) == 0))
  82
  83 /*
  84  * The exception table consists of pairs of addresses relative to the
  85  * exception table enty itself: the first is the address of an
  86  * instruction that is allowed to fault, and the second is the address
  87  * at which the program should continue.  No registers are modified,
  88  * so it is entirely up to the continuation code to figure out what to
  89  * do.
  90  *
  91  * All the routines below use bits of fixup code that are out of line
  92  * with the main instruction path.  This means when everything is well,
  93  * we don't even have to jump over them.  Further, they do not intrude
  94  * on our cache or tlb entries.
  95  */
  96
  97 struct exception_table_entry {
  98         int insn, fixup;
  99 };
 100 /* This is not the generic standard exception_table_entry format */
 101 #define ARCH_HAS_SORT_EXTABLE
 102 #define ARCH_HAS_SEARCH_EXTABLE
 103
 104 extern int fixup_exception(struct pt_regs *regs);
 105 extern int early_fixup_exception(unsigned long *ip);
 106
 107 /*
 108  * These are the main single-value transfer routines.  They automatically
 109  * use the right size if we just have the right pointer type.
 110  *
 111  * This gets kind of ugly. We want to return _two_ values in "get_user()"
 112  * and yet we don't want to do any pointers, because that is too much
 113  * of a performance impact. Thus we have a few rather ugly macros here,
 114  * and hide all the ugliness from the user.
 115  *
 116  * The "__xxx" versions of the user access functions are versions that
 117  * do not verify the address space, that must have been done previously
 118  * with a separate "access_ok()" call (this is used when we do multiple
 119  * accesses to the same area of user memory).
 120  */
 121
 122 extern int __get_user_1(void);
 123 extern int __get_user_2(void);
 124 extern int __get_user_4(void);
 125 extern int __get_user_8(void);
 126 extern int __get_user_bad(void);
 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.
 141  *
 142  * This macro copies a single simple variable from user space to kernel
 143  * space.  It supports simple types like char and int, but not larger
 144  * data types like structures or arrays.
 145  *
 146  * @ptr must have pointer-to-simple-variable type, and the result of
 147  * dereferencing @ptr must be assignable to @x without a cast.
 148  *
 149  * Returns zero on success, or -EFAULT on error.
 150  * On error, the variable @x is set to zero.
 151  */
 152 /*
 153  * Careful: we have to cast the result to the type of the pointer
 154  * for sign reasons.
 155  *
 156  * The use of _ASM_DX as the register specifier is a bit of a
 157  * simplification, as gcc only cares about it as the starting point
 158  * and not size: for a 64-bit value it will use %ecx:%edx on 32 bits
 159  * (%ecx being the next register in gcc's x86 register sequence), and
 160  * %rdx on 64 bits.
 161  *
 162  * Clang/LLVM cares about the size of the register, but still wants
 163  * the base register for something that ends up being a pair.
 164  */
 165 #define get_user(x, ptr)                                                \
 166 ({                                                                      \
 167         int __ret_gu;                                                   \
 168         register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX);            \
 169         __chk_user_ptr(ptr);                                            \
 170         might_fault();                                                  \
 171         asm volatile("call __get_user_%P3"                              \
 172                      : "=a" (__ret_gu), "=r" (__val_gu)                 \
 173                      : "0" (ptr), "i" (sizeof(*(ptr))));                \
 174         (x) = (__typeof__(*(ptr))) __val_gu;                            \
 175         __ret_gu;                                                       \
 176 })
 177
 178 #define __put_user_x(size, x, ptr, __ret_pu)                    \
 179         asm volatile("call __put_user_" #size : "=a" (__ret_pu) \
 180                      : "0" ((typeof(*(ptr)))(x)), "c" (ptr) : "ebx")
 181
 182
 183
 184 #ifdef CONFIG_X86_32
 185 #define __put_user_asm_u64(x, addr, err, errret)                        \
 186         asm volatile(ASM_STAC "\n"                                      \
 187                      "1:        movl %%eax,0(%2)\n"                     \
 188                      "2:        movl %%edx,4(%2)\n"                     \
 189                      "3: " ASM_CLAC "\n"                                \
 190                      ".section .fixup,\"ax\"\n"                         \
 191                      "4:        movl %3,%0\n"                           \
 192                      "  jmp 3b\n"                                       \
 193                      ".previous\n"                                      \
 194                      _ASM_EXTABLE(1b, 4b)                               \
 195                      _ASM_EXTABLE(2b, 4b)                               \
 196                      : "=r" (err)                                       \
 197                      : "A" (x), "r" (addr), "i" (errret), "0" (err))
 198
 199 #define __put_user_asm_ex_u64(x, addr)                                  \
 200         asm volatile(ASM_STAC "\n"                                      \
 201                      "1:        movl %%eax,0(%1)\n"                     \
 202                      "2:        movl %%edx,4(%1)\n"                     \
 203                      "3: " ASM_CLAC "\n"                                \
 204                      _ASM_EXTABLE_EX(1b, 2b)                            \
 205                      _ASM_EXTABLE_EX(2b, 3b)                            \
 206                      : : "A" (x), "r" (addr))
 207
 208 #define __put_user_x8(x, ptr, __ret_pu)                         \
 209         asm volatile("call __put_user_8" : "=a" (__ret_pu)      \
 210                      : "A" ((typeof(*(ptr)))(x)), "c" (ptr) : "ebx")
 211 #else
 212 #define __put_user_asm_u64(x, ptr, retval, errret) \
 213         __put_user_asm(x, ptr, retval, "q", "", "er", errret)
 214 #define __put_user_asm_ex_u64(x, addr)  \
 215         __put_user_asm_ex(x, addr, "q", "", "er")
 216 #define __put_user_x8(x, ptr, __ret_pu) __put_user_x(8, x, ptr, __ret_pu)
 217 #endif
 218
 219 extern void __put_user_bad(void);
 220
 221 /*
 222  * Strange magic calling convention: pointer in %ecx,
 223  * value in %eax(:%edx), return value in %eax. clobbers %rbx
 224  */
 225 extern void __put_user_1(void);
 226 extern void __put_user_2(void);
 227 extern void __put_user_4(void);
 228 extern void __put_user_8(void);
 229
 230 /**
 231  * put_user: - Write a simple value into user space.
 232  * @x:   Value to copy to user space.
 233  * @ptr: Destination address, in user space.
 234  *
 235  * Context: User context only.  This function may sleep.
 236  *
 237  * This macro copies a single simple value from kernel space to user
 238  * space.  It supports simple types like char and int, but not larger
 239  * data types like structures or arrays.
 240  *
 241  * @ptr must have pointer-to-simple-variable type, and @x must be assignable
 242  * to the result of dereferencing @ptr.
 243  *
 244  * Returns zero on success, or -EFAULT on error.
 245  */
 246 #define put_user(x, ptr)                                        \
 247 ({                                                              \
 248         int __ret_pu;                                           \
 249         __typeof__(*(ptr)) __pu_val;                            \
 250         __chk_user_ptr(ptr);                                    \
 251         might_fault();                                          \
 252         __pu_val = x;                                           \
 253         switch (sizeof(*(ptr))) {                               \
 254         case 1:                                                 \
 255                 __put_user_x(1, __pu_val, ptr, __ret_pu);       \
 256                 break;                                          \
 257         case 2:                                                 \
 258                 __put_user_x(2, __pu_val, ptr, __ret_pu);       \
 259                 break;                                          \
 260         case 4:                                                 \
 261                 __put_user_x(4, __pu_val, ptr, __ret_pu);       \
 262                 break;                                          \
 263         case 8:                                                 \
 264                 __put_user_x8(__pu_val, ptr, __ret_pu);         \
 265                 break;                                          \
 266         default:                                                \
 267                 __put_user_x(X, __pu_val, ptr, __ret_pu);       \
 268                 break;                                          \
 269         }                                                       \
 270         __ret_pu;                                               \
 271 })
 272
 273 #define __put_user_size(x, ptr, size, retval, errret)                   \
 274 do {                                                                    \
 275         retval = 0;                                                     \
 276         __chk_user_ptr(ptr);                                            \
 277         switch (size) {                                                 \
 278         case 1:                                                         \
 279                 __put_user_asm(x, ptr, retval, "b", "b", "iq", errret); \
 280                 break;                                                  \
 281         case 2:                                                         \
 282                 __put_user_asm(x, ptr, retval, "w", "w", "ir", errret); \
 283                 break;                                                  \
 284         case 4:                                                         \
 285                 __put_user_asm(x, ptr, retval, "l", "k", "ir", errret); \
 286                 break;                                                  \
 287         case 8:                                                         \
 288                 __put_user_asm_u64((__typeof__(*ptr))(x), ptr, retval,  \
 289                                    errret);                             \
 290                 break;                                                  \
 291         default:                                                        \
 292                 __put_user_bad();                                       \
 293         }                                                               \
 294 } while (0)
 295
 296 #define __put_user_size_ex(x, ptr, size)                                \
 297 do {                                                                    \
 298         __chk_user_ptr(ptr);                                            \
 299         switch (size) {                                                 \
 300         case 1:                                                         \
 301                 __put_user_asm_ex(x, ptr, "b", "b", "iq");              \
 302                 break;                                                  \
 303         case 2:                                                         \
 304                 __put_user_asm_ex(x, ptr, "w", "w", "ir");              \
 305                 break;                                                  \
 306         case 4:                                                         \
 307                 __put_user_asm_ex(x, ptr, "l", "k", "ir");              \
 308                 break;                                                  \
 309         case 8:                                                         \
 310                 __put_user_asm_ex_u64((__typeof__(*ptr))(x), ptr);      \
 311                 break;                                                  \
 312         default:                                                        \
 313                 __put_user_bad();                                       \
 314         }                                                               \
 315 } while (0)
 316
 317 #ifdef CONFIG_X86_32
 318 #define __get_user_asm_u64(x, ptr, retval, errret)      (x) = __get_user_bad()
 319 #define __get_user_asm_ex_u64(x, ptr)                   (x) = __get_user_bad()
 320 #else
 321 #define __get_user_asm_u64(x, ptr, retval, errret) \
 322          __get_user_asm(x, ptr, retval, "q", "", "=r", errret)
 323 #define __get_user_asm_ex_u64(x, ptr) \
 324          __get_user_asm_ex(x, ptr, "q", "", "=r")
 325 #endif
 326
 327 #define __get_user_size(x, ptr, size, retval, errret)                   \
 328 do {                                                                    \
 329         retval = 0;                                                     \
 330         __chk_user_ptr(ptr);                                            \
 331         switch (size) {                                                 \
 332         case 1:                                                         \
 333                 __get_user_asm(x, ptr, retval, "b", "b", "=q", errret); \
 334                 break;                                                  \
 335         case 2:                                                         \
 336                 __get_user_asm(x, ptr, retval, "w", "w", "=r", errret); \
 337                 break;                                                  \
 338         case 4:                                                         \
 339                 __get_user_asm(x, ptr, retval, "l", "k", "=r", errret); \
 340                 break;                                                  \
 341         case 8:                                                         \
 342                 __get_user_asm_u64(x, ptr, retval, errret);             \
 343                 break;                                                  \
 344         default:                                                        \
 345                 (x) = __get_user_bad();                                 \
 346         }                                                               \
 347 } while (0)
 348
 349 #define __get_user_asm(x, addr, err, itype, rtype, ltype, errret)       \
 350         asm volatile(ASM_STAC "\n"                                      \
 351                      "1:        mov"itype" %2,%"rtype"1\n"              \
 352                      "2: " ASM_CLAC "\n"                                \
 353                      ".section .fixup,\"ax\"\n"                         \
 354                      "3:        mov %3,%0\n"                            \
 355                      "  xor"itype" %"rtype"1,%"rtype"1\n"               \
 356                      "  jmp 2b\n"                                       \
 357                      ".previous\n"                                      \
 358                      _ASM_EXTABLE(1b, 3b)                               \
 359                      : "=r" (err), ltype(x)                             \
 360                      : "m" (__m(addr)), "i" (errret), "0" (err))
 361
 362 #define __get_user_size_ex(x, ptr, size)                                \
 363 do {                                                                    \
 364         __chk_user_ptr(ptr);                                            \
 365         switch (size) {                                                 \
 366         case 1:                                                         \
 367                 __get_user_asm_ex(x, ptr, "b", "b", "=q");              \
 368                 break;                                                  \
 369         case 2:                                                         \
 370                 __get_user_asm_ex(x, ptr, "w", "w", "=r");              \
 371                 break;                                                  \
 372         case 4:                                                         \
 373                 __get_user_asm_ex(x, ptr, "l", "k", "=r");              \
 374                 break;                                                  \
 375         case 8:                                                         \
 376                 __get_user_asm_ex_u64(x, ptr);                          \
 377                 break;                                                  \
 378         default:                                                        \
 379                 (x) = __get_user_bad();                                 \
 380         }                                                               \
 381 } while (0)
 382
 383 #define __get_user_asm_ex(x, addr, itype, rtype, ltype)                 \
 384         asm volatile("1:        mov"itype" %1,%"rtype"0\n"              \
 385                      "2:\n"                                             \
 386                      _ASM_EXTABLE_EX(1b, 2b)                            \
 387                      : ltype(x) : "m" (__m(addr)))
 388
 389 #define __put_user_nocheck(x, ptr, size)                        \
 390 ({                                                              \
 391         int __pu_err;                                           \
 392         __put_user_size((x), (ptr), (size), __pu_err, -EFAULT); \
 393         __pu_err;                                               \
 394 })
 395
 396 #define __get_user_nocheck(x, ptr, size)                                \
 397 ({                                                                      \
 398         int __gu_err;                                                   \
 399         unsigned long __gu_val;                                         \
 400         __get_user_size(__gu_val, (ptr), (size), __gu_err, -EFAULT);    \
 401         (x) = (__force __typeof__(*(ptr)))__gu_val;                     \
 402         __gu_err;                                                       \
 403 })
 404
 405 /* FIXME: this hack is definitely wrong -AK */
 406 struct __large_struct { unsigned long buf[100]; };
 407 #define __m(x) (*(struct __large_struct __user *)(x))
 408
 409 /*
 410  * Tell gcc we read from memory instead of writing: this is because
 411  * we do not write to any memory gcc knows about, so there are no
 412  * aliasing issues.
 413  */
 414 #define __put_user_asm(x, addr, err, itype, rtype, ltype, errret)       \
 415         asm volatile(ASM_STAC "\n"                                      \
 416                      "1:        mov"itype" %"rtype"1,%2\n"              \
 417                      "2: " ASM_CLAC "\n"                                \
 418                      ".section .fixup,\"ax\"\n"                         \
 419                      "3:        mov %3,%0\n"                            \
 420                      "  jmp 2b\n"                                       \
 421                      ".previous\n"                                      \
 422                      _ASM_EXTABLE(1b, 3b)                               \
 423                      : "=r"(err)                                        \
 424                      : ltype(x), "m" (__m(addr)), "i" (errret), "0" (err))
 425
 426 #define __put_user_asm_ex(x, addr, itype, rtype, ltype)                 \
 427         asm volatile("1:        mov"itype" %"rtype"0,%1\n"              \
 428                      "2:\n"                                             \
 429                      _ASM_EXTABLE_EX(1b, 2b)                            \
 430                      : : ltype(x), "m" (__m(addr)))
 431
 432 /*
 433  * uaccess_try and catch
 434  */
 435 #define uaccess_try     do {                                            \
 436         current_thread_info()->uaccess_err = 0;                         \
 437         stac();                                                         \
 438         barrier();
 439
 440 #define uaccess_catch(err)                                              \
 441         clac();                                                         \
 442         (err) |= (current_thread_info()->uaccess_err ? -EFAULT : 0);    \
 443 } while (0)
 444
 445 /**
 446  * __get_user: - Get a simple variable from user space, with less checking.
 447  * @x:   Variable to store result.
 448  * @ptr: Source address, in user space.
 449  *
 450  * Context: User context only.  This function may sleep.
 451  *
 452  * This macro copies a single simple variable from user space to kernel
 453  * space.  It supports simple types like char and int, but not larger
 454  * data types like structures or arrays.
 455  *
 456  * @ptr must have pointer-to-simple-variable type, and the result of
 457  * dereferencing @ptr must be assignable to @x without a cast.
 458  *
 459  * Caller must check the pointer with access_ok() before calling this
 460  * function.
 461  *
 462  * Returns zero on success, or -EFAULT on error.
 463  * On error, the variable @x is set to zero.
 464  */
 465
 466 #define __get_user(x, ptr)                                              \
 467         __get_user_nocheck((x), (ptr), sizeof(*(ptr)))
 468
 469 /**
 470  * __put_user: - Write a simple value into user space, with less checking.
 471  * @x:   Value to copy to user space.
 472  * @ptr: Destination address, in user space.
 473  *
 474  * Context: User context only.  This function may sleep.
 475  *
 476  * This macro copies a single simple value from kernel space to user
 477  * space.  It supports simple types like char and int, but not larger
 478  * data types like structures or arrays.
 479  *
 480  * @ptr must have pointer-to-simple-variable type, and @x must be assignable
 481  * to the result of dereferencing @ptr.
 482  *
 483  * Caller must check the pointer with access_ok() before calling this
 484  * function.
 485  *
 486  * Returns zero on success, or -EFAULT on error.
 487  */
 488
 489 #define __put_user(x, ptr)                                              \
 490         __put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))
 491
 492 #define __get_user_unaligned __get_user
 493 #define __put_user_unaligned __put_user
 494
 495 /*
 496  * {get|put}_user_try and catch
 497  *
 498  * get_user_try {
 499  *      get_user_ex(...);
 500  * } get_user_catch(err)
 501  */
 502 #define get_user_try            uaccess_try
 503 #define get_user_catch(err)     uaccess_catch(err)
 504
 505 #define get_user_ex(x, ptr)     do {                                    \
 506         unsigned long __gue_val;                                        \
 507         __get_user_size_ex((__gue_val), (ptr), (sizeof(*(ptr))));       \
 508         (x) = (__force __typeof__(*(ptr)))__gue_val;                    \
 509 } while (0)
 510
 511 #define put_user_try            uaccess_try
 512 #define put_user_catch(err)     uaccess_catch(err)
 513
 514 #define put_user_ex(x, ptr)                                             \
 515         __put_user_size_ex((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))
 516
 517 extern unsigned long
 518 copy_from_user_nmi(void *to, const void __user *from, unsigned long n);
 519 extern __must_check long
 520 strncpy_from_user(char *dst, const char __user *src, long count);
 521
 522 extern __must_check long strlen_user(const char __user *str);
 523 extern __must_check long strnlen_user(const char __user *str, long n);
 524
 525 unsigned long __must_check clear_user(void __user *mem, unsigned long len);
 526 unsigned long __must_check __clear_user(void __user *mem, unsigned long len);
 527
 528 /*
 529  * movsl can be slow when source and dest are not both 8-byte aligned
 530  */
 531 #ifdef CONFIG_X86_INTEL_USERCOPY
 532 extern struct movsl_mask {
 533         int mask;
 534 } ____cacheline_aligned_in_smp movsl_mask;
 535 #endif
 536
 537 #define ARCH_HAS_NOCACHE_UACCESS 1
 538
 539 #ifdef CONFIG_X86_32
 540 # include <asm/uaccess_32.h>
 541 #else
 542 # include <asm/uaccess_64.h>
 543 #endif
 544
 545 unsigned long __must_check _copy_from_user(void *to, const void __user *from,
 546                                            unsigned n);
 547 unsigned long __must_check _copy_to_user(void __user *to, const void *from,
 548                                          unsigned n);
 549
 550 #ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
 551 # define copy_user_diag __compiletime_error
 552 #else
 553 # define copy_user_diag __compiletime_warning
 554 #endif
 555
 556 extern void copy_user_diag("copy_from_user() buffer size is too small")
 557 copy_from_user_overflow(void);
 558 extern void copy_user_diag("copy_to_user() buffer size is too small")
 559 copy_to_user_overflow(void) __asm__("copy_from_user_overflow");
 560
 561 #undef copy_user_diag
 562
 563 #ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
 564
 565 extern void
 566 __compiletime_warning("copy_from_user() buffer size is not provably correct")
 567 __copy_from_user_overflow(void) __asm__("copy_from_user_overflow");
 568 #define __copy_from_user_overflow(size, count) __copy_from_user_overflow()
 569
 570 extern void
 571 __compiletime_warning("copy_to_user() buffer size is not provably correct")
 572 __copy_to_user_overflow(void) __asm__("copy_from_user_overflow");
 573 #define __copy_to_user_overflow(size, count) __copy_to_user_overflow()
 574
 575 #else
 576
 577 static inline void
 578 __copy_from_user_overflow(int size, unsigned long count)
 579 {
 580         WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count);
 581 }
 582
 583 #define __copy_to_user_overflow __copy_from_user_overflow
 584
 585 #endif
 586
 587 static inline unsigned long __must_check
 588 copy_from_user(void *to, const void __user *from, unsigned long n)
 589 {
 590         int sz = __compiletime_object_size(to);
 591
 592         might_fault();
 593
 594         /*
 595          * While we would like to have the compiler do the checking for us
 596          * even in the non-constant size case, any false positives there are
 597          * a problem (especially when DEBUG_STRICT_USER_COPY_CHECKS, but even
 598          * without - the [hopefully] dangerous looking nature of the warning
 599          * would make people go look at the respecitive call sites over and
 600          * over again just to find that there's no problem).
 601          *
 602          * And there are cases where it's just not realistic for the compiler
 603          * to prove the count to be in range. For example when multiple call
 604          * sites of a helper function - perhaps in different source files -
 605          * all doing proper range checking, yet the helper function not doing
 606          * so again.
 607          *
 608          * Therefore limit the compile time checking to the constant size
 609          * case, and do only runtime checking for non-constant sizes.
 610          */
 611
 612         if (likely(sz < 0 || sz >= n))
 613                 n = _copy_from_user(to, from, n);
 614         else if(__builtin_constant_p(n))
 615                 copy_from_user_overflow();
 616         else
 617                 __copy_from_user_overflow(sz, n);
 618
 619         return n;
 620 }
 621
 622 static inline unsigned long __must_check
 623 copy_to_user(void __user *to, const void *from, unsigned long n)
 624 {
 625         int sz = __compiletime_object_size(from);
 626
 627         might_fault();
 628
 629         /* See the comment in copy_from_user() above. */
 630         if (likely(sz < 0 || sz >= n))
 631                 n = _copy_to_user(to, from, n);
 632         else if(__builtin_constant_p(n))
 633                 copy_to_user_overflow();
 634         else
 635                 __copy_to_user_overflow(sz, n);
 636
 637         return n;
 638 }
 639
 640 #undef __copy_from_user_overflow
 641 #undef __copy_to_user_overflow
 642
 643 #endif /* _ASM_X86_UACCESS_H */
 644