include/asm-generic/access_ok.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __ASM_GENERIC_ACCESS_OK_H__
   3 #define __ASM_GENERIC_ACCESS_OK_H__
   4
   5 /*
   6  * Checking whether a pointer is valid for user space access.
   7  * These definitions work on most architectures, but overrides can
   8  * be used where necessary.
   9  */
  10
  11 /*
  12  * architectures with compat tasks have a variable TASK_SIZE and should
  13  * override this to a constant.
  14  */
  15 #ifndef TASK_SIZE_MAX
  16 #define TASK_SIZE_MAX                   TASK_SIZE
  17 #endif
  18
  19 #ifndef __access_ok
  20 /*
  21  * 'size' is a compile-time constant for most callers, so optimize for
  22  * this case to turn the check into a single comparison against a constant
  23  * limit and catch all possible overflows.
  24  * On architectures with separate user address space (m68k, s390, parisc,
  25  * sparc64) or those without an MMU, this should always return true.
  26  *
  27  * This version was originally contributed by Jonas Bonn for the
  28  * OpenRISC architecture, and was found to be the most efficient
  29  * for constant 'size' and 'limit' values.
  30  */
  31 static inline int __access_ok(const void __user *ptr, unsigned long size)
  32 {
  33         unsigned long limit = TASK_SIZE_MAX;
  34         unsigned long addr = (unsigned long)ptr;
  35
  36         if (IS_ENABLED(CONFIG_ALTERNATE_USER_ADDRESS_SPACE) ||
  37             !IS_ENABLED(CONFIG_MMU))
  38                 return true;
  39
  40         return (size <= limit) && (addr <= (limit - size));
  41 }
  42 #endif
  43
  44 #ifndef access_ok
  45 #define access_ok(addr, size) likely(__access_ok(addr, size))
  46 #endif
  47
  48 #endif