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