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 49